CN110621386B

CN110621386B - Filter media comprising adhesive and/or oleophobic Properties

Info

Publication number: CN110621386B
Application number: CN201880030782.XA
Authority: CN
Inventors: 苏达卡尔·贾加纳坦; 道格拉斯·M·吉蒙; 嘉利·刘
Original assignee: Hollingsworth and Vose Co
Current assignee: Hollingsworth and Vose Co
Priority date: 2017-03-28
Filing date: 2018-03-28
Publication date: 2022-01-25
Anticipated expiration: 2038-03-28
Also published as: CN114470971A; EP3600601A4; EP3600601A1; CN114470971B; WO2018183481A1; CN110621386A; CN117982986A

Abstract

Articles and methods relating to filter media are generally provided. In certain embodiments, the filter media includes at least a first layer, a second layer, and a binder resin disposed between the first layer and the second layer. In some embodiments, the first layer may be a pre-filter layer or a support layer. The second layer may, for example, comprise fibers formed by a solution spinning process and/or may comprise fine fibers. In some embodiments, the binder resin may be present in relatively low amounts and/or may have a low glass transition temperature. The filter media as a whole may have one or more advantageous properties including one or more of high stiffness, high bond strength between the first and second layers, high gamma, and/or low increase in air resistance after being subjected to IPA vapor discharge. The filter media may be, for example, a HEPA filter and/or an ULPA filter.

Description

Filter media comprising adhesive and/or oleophobic Properties

Technical Field

The present invention relates generally to filter media and, more particularly, to filter media that include a binder and/or have oleophobic properties.

Background

Filter media can be used to remove contaminants in a variety of applications. Depending on the application, the filter media may be designed to have different performance characteristics. For example, the filter media may be designed to have performance characteristics suitable for HEPA and/or ULPA applications.

In general, the filter media may be formed from a fiber web. For example, the web may comprise components such as synthetic fibers. The fiber web provides a porous structure that allows fluid (e.g., air) to flow through the filter media. Contaminant particles contained within the fluid may be trapped on the web. Filter media characteristics, such as fiber diameter and basis weight, affect filter performance including filtration efficiency, dust holding capacity, and resistance to fluid flow through the filter.

While there are many types of filter media for filtering particulates from air, improvements in the physical and/or performance characteristics of the filter media (e.g., strength, air resistance, efficiency, and high dust holding capacity) would be beneficial.

Disclosure of Invention

Filter media and related components and methods associated therewith are provided.

In one set of embodiments, a filter media is provided. In some embodiments, a filter media includes a first layer; a second layer, wherein the second layer is formed from fibers having an average fiber diameter of less than 1 micron; and an adhesive between the first layer and the second layer, wherein the first layer is bonded to the second layer by the adhesive. The stiffness of the filter media is greater than or equal to 200 mg. The bond strength between the first layer and the second layer is greater than or equal to 150 g/inch ². The filter media exhibits a gamma value of greater than or equal to 18 at the most penetrable particle size.

In some embodiments, a filter media includes a first layer; a second layer, wherein the second layer is formed from fibers having an average fiber diameter of less than 1 micron; and an adhesive between the first layer and the second layer. The first layer is bonded to the second layer by an adhesive. The adhesive comprises a solvent-based resin comprising a polymer having a glass transition temperature of less than or equal to 24 ℃.

In some embodiments, a filter media includes a first layer; a second layer, wherein the second layer is in the form of fibers having an average fiber diameter of less than 1 micronForming; and an adhesive between the first layer and the second layer. The adhesive between the first and second layers is present in an amount less than 10 gsm. The first layer is bonded to the second layer by an adhesive. The bond strength between the first layer and the second layer is greater than or equal to 150 g/inch². The filter media exhibits less than a 50% increase in air resistance after subjecting the filter media to the IPA vapor discharge as compared to the filter media prior to the IPA vapor discharge.

In some embodiments, the filter media includes first and second layers, and an adhesive between the first and second layers. The first layer is bonded to the second layer by an adhesive. The second layer is formed of fibers having an average fiber diameter of less than 1 micron. At least one of the first layer and the second layer has an oil rating of greater than or equal to 1. The bond strength between the first layer and the second layer is greater than or equal to 150 g/inch ². The filter media has a stiffness of greater than or equal to 200mg, wherein the stiffness is measured in the machine direction or the cross direction.

In some embodiments, the filter media includes first and second layers, and an adhesive between the first and second layers. The first layer is bonded to the second layer by an adhesive. The first layer comprises fibers. The second layer is a film layer. At least one of the first layer and the second layer has an oil rating of greater than or equal to 1. The bond strength between the first layer and the second layer is greater than or equal to 150 g/inch². The filter media has a stiffness of greater than or equal to 200mg, wherein the stiffness is measured in the machine direction or the cross direction.

In some embodiments, the filter media includes a first layer and a second layer. The second layer is formed of fibers having an average fiber diameter of less than 1 micron. At least one of the first layer and the second layer has an oil rating of greater than or equal to 1. The filter media has a stiffness of greater than or equal to 200mg, wherein the stiffness is measured in the machine direction or the cross direction. The filter medium has a density of greater than or equal to 4.5g/m²Pressure drop at DOP oil loading of less than or equal to 50mm H₂O。

In some embodiments, the filter media includes a first layer and a second layer. The first layer comprises fibers. The second layer is a film layer. Oil of at least one of the first and second layers The rank is greater than or equal to 1. The filter media has a stiffness of greater than or equal to 200mg, wherein the stiffness is measured in the machine direction or the cross direction. The filter medium has a density of greater than or equal to 4.5g/m²Pressure drop at DOP oil loading of less than or equal to 50mm H₂O。

In some embodiments, the filter media includes a first layer and a second layer. The second layer is formed of fibers having an average fiber diameter of less than 1 micron. At least one of the first layer and the second layer has an oil rating of greater than or equal to 1. The filter media has a stiffness of greater than or equal to 200mg, wherein the stiffness is measured in the machine direction or the cross direction. The filter medium has a density of greater than or equal to 4.5g/m²Is greater than or equal to 10.

In some embodiments, the filter media includes a first layer and a second layer. The first layer comprises fibers. The second layer is a film layer. At least one of the first layer and the second layer has an oil rating of greater than or equal to 1. The filter media has a stiffness of greater than or equal to 200mg, wherein the stiffness is measured in the machine direction or the cross direction. The filter medium has a density of greater than or equal to 4.5g/m²Is greater than or equal to 10.

In another set of embodiments, a method is provided. In some embodiments, a method of making a filter media includes spraying a composition comprising a solvent-based binder resin and a crosslinker onto a first layer to form a binder coated first layer, performing a solvent-based spinning process to deposit fibers on the binder coated first layer, wherein the fibers have an average fiber diameter of less than 1 micron and form a second layer; and laminating the second layer to the third layer such that the third layer is disposed on an opposite side of the second layer from the first layer.

In some embodiments as described above and/or herein, the efficiency of the filter media according to standard EN1822:2009 is greater than 95%.

In some embodiments as described above and herein, the efficiency of the filter media according to standard EN1822:2009 may be greater than 99.95%.

In some embodiments as described above and/or herein, the efficiency of the filter media according to standard EN1822:2009 is greater than 99.995%.

In some embodiments as described above and/or herein, the efficiency of the filter media according to standard EN1822:2009 is greater than 99.9995%.

In some embodiments as described above and/or herein, the efficiency of the filter medium according to standard EN1822:2009 is greater than 99.99995%.

In some embodiments as described above and/or herein, the efficiency of the filter media according to standard EN1822:2009 is greater than 99.999995%.

In some embodiments as described above and/or herein, the efficiency of the filter media according to standard EN1822:2009 is greater than 99.9999995%.

In some embodiments as described above and herein, the fibers of the second layer are solvent spun fibers.

In some embodiments as described above and herein, the fibers of the second layer are electrospun fibers or centrifugally spun fibers.

In some embodiments as described above and herein, the second layer is a main filtration layer.

In some embodiments, the filter media further comprises a third layer, as described above and herein.

In some embodiments as described above and herein, the first layer is a wet laid layer.

In some embodiments as described above and herein, the first layer is a meltblown layer.

In some embodiments as described above and herein, the first layer is an electrically charged meltblown layer.

In some embodiments as described above and herein, the first layer is a support layer.

In some embodiments as described above and herein, the first layer is a pre-filter layer.

In some embodiments as described above and herein, the third layer is a meltblown layer.

In some embodiments as described above and herein, the third layer is a wet laid layer.

In some embodiments as described above and herein, the third layer is a pre-filter layer.

In some embodiments as described above and herein, the third layer is a support layer.

In some embodiments as described above and herein, the third layer is an electrically charged meltblown layer.

In some embodiments as described above and herein, the third layer is added in-line.

In some embodiments as described above and herein, the binder comprises water.

In some embodiments as described above and herein, the adhesive comprises a crosslinking agent.

In some embodiments as described above and herein, the glass transition temperature of the adhesive is greater than or equal to-150 ℃.

In some embodiments as described above and herein, the adhesive between the second layer and the third layer is present in an amount of less than 10 gsm.

In some embodiments as described above and herein, the filter media further comprises a fourth layer.

In some embodiments as described above and herein, the fibers of the fourth layer are solvent spun fibers.

In some embodiments as described above and herein, the fibers of the fourth layer are electrospun fibers, centrifugally spun fibers.

In some embodiments as described above and herein, the fourth layer is a main filtration layer.

In some embodiments as described above and herein, the filter media further comprises a fifth layer.

In some embodiments as described above and herein, the fifth layer is a meltblown layer.

In some embodiments as described above and herein, the fifth layer is a pre-filter layer.

In some embodiments as described above and herein, the gamma value at MPPS after exposure to IPA vapor is greater than or equal to 14.

In some embodiments as described above and herein, the first layer is a surface modification layer.

In some embodiments as described above and herein, the second layer is a surface modification layer.

In some embodiments as described above and herein, the third layer is a surface modification layer.

In some embodiments as described above and herein, the surface modification of at least one of the first layer, the second layer, and the third layer is performed by a chemical deposition technique.

In some embodiments as described above and herein, the surface modification of at least one of the first layer, the second layer, and the third layer is performed by plasma enhanced chemical vapor deposition.

In some embodiments as described above and herein, the surface modification of at least one of the first layer, the second layer, and the third layer is performed by electron beam assisted radiation curing.

In some embodiments as described above and herein, the surface modification of at least one of the first layer, the second layer, and the third layer is performed by a physical deposition technique.

In some embodiments as described above and herein, the surface modification of at least one of the first, second and third layers is performed by powder coating.

In some embodiments as described above and herein, the first layer further comprises an oleophobic component.

In some embodiments as described above and herein, the second layer further comprises an oleophobic component.

In some embodiments as described above and herein, the third layer further comprises an oleophobic component.

In some embodiments as described above and herein, the oleophobic ingredient of at least one of the first layer, the second layer, and the third layer is a layer deposited by a chemical deposition technique.

In some embodiments as described above and herein, the oleophobic ingredient of at least one of the first layer, the second layer, and the third layer is a layer deposited by plasma enhanced chemical vapor deposition.

In some embodiments as described above and herein, the oleophobic component of at least one of the first layer, the second layer, and the third layer is a layer deposited by electron beam assisted radiation curing.

In some embodiments as described above and herein, the oleophobic ingredient of at least one of the first layer, the second layer, and the third layer is a layer deposited by a physical deposition technique.

In some embodiments as described above and herein, the oleophobic component of at least one of the first layer, the second layer, and the third layer is a layer deposited by powder coating.

In some embodiments as described above and herein, the oleophobic component comprises an oleophobic resin.

In some embodiments as described above and herein, the oleophobic component includes an oleophobic additive.

In some embodiments as described above and herein, the oil grade of the first layer is greater than or equal to 1.

In some embodiments as described above and herein, the oil grade of the second layer is greater than or equal to 1.

In some embodiments as described above and herein, the oil grade of the layer furthest upstream is greater than or equal to 1.

In some embodiments as described above and herein, the filter media is at greater than or equal to 4.5g/m²(ii) DOP oil loading of less than or equal to 0.5%, less than or equal to 0.05%, less than or equal to 0.005%, less than or equal to 0.0005%, less than or equal to 0.00005%, or less than or equal to 0.000005% DOP penetration at MPPS.

In some embodiments as described above and herein, the oleophobic component comprises a polymer.

In some embodiments as described above and herein, the oleophobic component includes an organofluorine.

In some embodiments as described above and herein, the oleophobic component includes one or more of a wax, a silicone, a corn-based polymer, and a nanoparticle material.

In some embodiments as described above and herein, the first layer comprises fibers and an oil phobic component, and the oil phobic component is in the form of a coating disposed on one or more of the fibers within the first layer.

In some embodiments as described above and herein, the coating at least partially surrounds the one or more fibers within the first layer.

In some embodiments as described above and herein, the filter media has a stiffness in the machine direction of greater than or equal to 300 mg.

In some embodiments as described above and herein, the filter media has a basis weight of less than or equal to 150g/m²。

In some embodiments as described above and herein, the filter media is pleated and the pleat height is greater than or equal to 10mm and less than or equal to 510 mm.

In some embodiments as described above and herein, the filter media is pleated and has a pleat density of greater than or equal to 6 pleats per 100mm and less than or equal to 100 pleats per 100 mm.

In some embodiments as described above and herein, the stiffness is measured in the cross direction.

In some embodiments as described above and herein, the stiffness is measured in the machine direction.

Other advantages and novel features of the invention will become apparent from the following detailed description of various non-limiting embodiments of the invention when considered in conjunction with the drawings. In the event that the present specification and a document incorporated by reference contain conflicting and/or inconsistent disclosure, the present specification shall control. If two or more documents incorporated by reference contain disclosures that are conflicting and/or inconsistent with respect to each other, the document with the effective date shall control.

Drawings

Non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, which are schematic and are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention. In the drawings:

fig. 1A illustrates a filter media including two layers according to some embodiments;

FIG. 1B illustrates a filter media comprising an oleophobic component according to some embodiments;

FIG. 1C shows a filter media including a coating layer;

FIG. 1D illustrates a filter media including three layers according to some embodiments;

fig. 1E illustrates a filter media including five layers according to some embodiments;

figures 2A through 2C illustrate a method of forming a three-layer media according to some embodiments;

FIG. 3 illustrates a lamination process for forming a filter media according to some embodiments;

4A-4C illustrate filter media that may be formed using the process shown in FIG. 3, according to some embodiments;

figure 5 illustrates MPPS penetration as a function of oil loading for a filter media according to some embodiments;

FIG. 6 illustrates a pressure drop as a function of oil loading for a filter media according to some embodiments; and

fig. 7 shows gamma as a function of oil loading for filter media according to some embodiments.

Detailed Description

Articles and methods relating to filter media are generally provided. In certain embodiments, the filter media includes at least a first layer, a second layer, and a binder resin disposed between the first layer and the second layer. In some embodiments, the first layer may be a pre-filter layer or a support layer. The second layer may, for example, comprise fibers formed by a solution spinning process and/or may comprise fine fibers. In some embodiments, the binder resin may be present in relatively low amounts and/or may have a low glass transition temperature. The filter media as a whole may have one or more advantageous properties including one or more of high stiffness, high bond strength between the first and second layers, high gamma values, and/or low increase in air resistance after being subjected to IPA vapor discharge. The filter media may be, for example, a HEPA filter media and/or an ULPA filter media.

In some embodiments, the filter media may include one or more layers having oleophobic properties. For example, one or more layers may comprise an oleophobic component as described herein, such as an oleophobic additive or oleophobic coating, and/or may have an oil rating greater than or equal to 1. In some embodiments, the layer or layers having oleophobic properties (e.g., the layer or layers comprising the oleophobic component, the layer or layers having an oil grade greater than or equal to 1) can impart one or more benefits to the filter media as a whole, such as low pressure drop at high oil loadings, high gamma at high oil loadings, and/or low penetration at high oil loadings. One or more of these characteristics may be beneficial in applications where the filter media is disposed in an environment having a medium or high ambient oil level. For example, the filter media may be used in cleanrooms (e.g., pharmaceutical cleanrooms, electronic cleanrooms, cleanrooms for integrated circuit manufacturing), gas turbines (e.g., offshore gas turbines), indoor air purifiers, face masks, vacuum cleaners, paint spray booths, and/or for filtering oily aerosols. In some embodiments, the filter media having the layer or layers with oleophobic properties (e.g., the layer or layers comprising the oleophobic component, the layer or layers having an oil grade greater than or equal to 1) can be a HEPA filter, an ULPA filter, and/or an HVAC filter. Other types of filter media are also possible.

Methods for making the filter media described herein are also provided. In some embodiments, the manufacture of the filter media may include spraying a composition including a binder resin onto the first layer to form a binder coated first layer, and performing a solvent-based spinning process to deposit fibers forming the second layer on the binder coated first layer. The second layer may be a solvent spun layer, such as an electrospun layer. In some embodiments, the second layer may be laminated to the third layer such that the third layer is disposed on a side of the second layer opposite the first layer. Other configurations and methods of joining or forming the first, second and third layers are also possible.

Fig. 1A depicts a filter media 100 according to certain embodiments of the present invention. The filter media 100 includes a first layer 110 and a second layer 120. In some embodiments, and as described in more detail below, the first layer is a support layer or a pre-filter layer. The second layer may be a main filtration layer. The main filtration layer may, for example, have a higher efficiency than one or more other layers of the media. For example, in some cases, the main filtration layer is a fine fiber layer, such as a layer formed by a solvent-based spinning process. In some embodiments, an adhesive resin is present between the first layer and the second layer. An adhesive resin may be used to bond the first layer to the second layer. In some embodiments, the binder resin may be present in relatively small amounts between the first layer and the second layer, but the bond between the first layer and the second layer may be relatively strong (e.g., bond strength greater than or equal to 150 g/inch) ²). The properties of the layers (e.g., pre-filter layer, support layer, and main filter layer) and the adhesive are described in more detail below.

As described herein, in some embodiments, one or more layers of the filter media can have oleophobic properties, such as including an oleophobic component and/or having an oil grade of greater than or equal to 1 (e.g., one or more of the first, second, third, and fourth layers can include an oleophobic component and/or have an oil grade of greater than or equal to 1). For example, the layer can comprise an oleophobic ingredient as described herein. In some embodiments, the oleophobic component can be present within the layer, for example, in the form of an additive dispersed throughout the layer and/or in the form of a coating disposed on the one or more fibers within the layer (e.g., a conformal coating of the one or more fibers within the layer, a coating at least partially surrounding the one or more fibers within the layer). In some embodiments, the oleophobic component can be present as a component of a coating layer disposed on a surface of a layer of the filter media. In some cases, the layer or layers may be surface-modified layers, e.g., layers in which at least a portion of the surface of the layer has been modified. For example, the surface of the layer or layers may be subjected to one or more processes to modify the surface, such as roughening the surface of the layer or layers and/or depositing an oleophobic component on the surface of the layer or layers. In some embodiments, the surface modification layer may have a higher oil grade than an otherwise equivalent layer that is not a surface modification layer.

FIG. 1B shows one non-limiting example of a filter media 101 in which first layer 110 includes an oleophobic component 115. In FIG. 1B, the oleophobic component is present within the first layer, and the oleophobic component and the first layer together comprise a single layer.

In some embodiments, one or more layers of the filter media may include a coating layer comprising an oleophobic component. The coating layer may be disposed on a surface of the layer of filter media. FIG. 1C illustrates one non-limiting example of a filter media 102 in which a first layer 110 includes an oleophobic component 115 in the form of a coating layer 116 disposed on a surface 112 of the first layer. In some embodiments, a layer of a filter media may include both an oleophobic component within the layer (e.g., in the form of an additive, in the form of a coating on one or more fibers within the layer) and a coating layer that includes the oleophobic component (the same or different from the oleophobic component within the layer). One non-limiting example of a filter media having this configuration is a filter media including an oleophobic coating and a fluorocarbon melt additive.

In some embodiments of filter elements including a filter media including at least one layer having oleophobic properties, the layer having oleophobic properties can be disposed upstream of one or more other layers of the filter media (e.g., it can be disposed near an inlet of the filter element). In some embodiments, the layer may include a coating layer comprising an oleophobic component, and the coating layer may be disposed on an upstream side of the layer. For example, for a filter media such as in fig. 1C, the first layer 110 can be disposed upstream of the second layer 120 in the filter element, and the coating layer 116 can be disposed on the upstream surface 112 of the first layer. Other configurations are also described in more detail below.

In some embodiments, a single layer within the filter media may include the oleophobic component (e.g., one of the first layer, the second layer, the pre-filter layer, or the main filter layer may include the oleophobic component). In some embodiments, two or more layers of the filter media may comprise an oleophobic component (e.g., at least two of the first layer, the second layer, the pre-filter layer, and the main filter layer may comprise the oleophobic component). In some embodiments, each layer of the filter media can comprise an oleophobic component.

It is to be understood that the filter media may optionally further include additional layers, such as a third layer, a fourth layer, and/or a fifth layer, and the like. In some embodiments, one or more layers (e.g., a first layer, a second layer, a third layer, a fourth layer, a fifth layer) may be added using an in-line process. It should also be understood that the orientation of the filter media 100 (as well as the other filter media described herein) relative to the fluid flowing through the filter media or within the filter element may generally be selected as desired. In some embodiments, the first layer 110 is downstream of the second layer 120 (e.g., in a filter element). In other embodiments, the first layer 110 is upstream of the second layer 120 (e.g., in a filter element).

In some embodiments, the layer having oleophobic properties (e.g., a layer comprising an oleophobic component, a layer having an oil grade of greater than or equal to 1, a surface modification layer) can be the layer furthest upstream in the filter element or a layer disposed on the inlet side of the filter element. In other embodiments, the layer having oleophobic properties (e.g., a layer comprising an oleophobic component, a layer having an oil grade greater than or equal to 1, a surface modification layer) can be one or more layers downstream of the most upstream layer in the filter element or downstream of the layer disposed on the inlet side.

In some embodiments, the filter media may include at least three layers, as exemplarily shown in fig. 1D. The filter medium 102 includesOne layer 110, a second layer 120, and a third layer 130. In some embodiments, the third layer may be a support layer or a pre-filter layer. For example, in one set of embodiments, the first layer can be a support layer and the third layer can be a pre-filter layer. In another set of embodiments, the first layer may be a pre-filter layer and the third layer may be a support layer. In some embodiments, an adhesive resin is present between the second layer and the third layer. An adhesive resin may be used to bond the second layer to the third layer. In some embodiments, the binder resin may be present in relatively small amounts between the second layer and the third layer, but the bond between the second layer and the third layer may be relatively strong (e.g., bond strength greater than or equal to 150 g/inch) ²)。

In some cases, each layer of the filter media has different characteristics and filtration characteristics that, when combined, result in the desired overall filtration performance, e.g., as compared to a filter media having a single layer structure. For example, in one set of embodiments, the third layer 130 is a pre-filter layer and the second layer 120 is a main filter layer. In some embodiments, as described further below, the pre-filter layer may be formed using coarser fibers and, thus, may have a lower fluid flow resistance than the main filter layer. The main filter layer may contain finer fibers and have a higher fluid flow resistance than the pre-filter layer. Thus, the main filter layer may generally capture particles of smaller size than the pre-filter layer.

As described above, each layer of the filter media may have different properties. For example, the first and second layers may comprise fibers having different characteristics (e.g., fiber diameter, fiber composition, and fiber length). Fibers having different characteristics may be made of one material (e.g., by using different process conditions) or different materials (e.g., different types of fibers).

In some embodiments, the filter media may include more than one layer of the same type. For example, the filter may include two pre-filter layers, two support layers, and/or two main filter layers. FIG. 1E depicts one non-limiting example of an embodiment in which the filter media includes at least one pre-filter layer, at least one support layer, and two main filtration layers. As shown in the figures, filter media 104 includes a first layer 110, a second layer 120, a third layer 130, a fourth layer 140, and a fifth layer 150. In some embodiments, the third layer is a pre-filter layer, and both the second layer and the fourth layer are main filter layers. In some embodiments, one but not both of the third layer and the fifth layer is a support layer and the other is a pre-filter layer. For example, in one embodiment, the fifth layer 150 is a support layer that functions as a cover or protective layer, e.g., when the fifth layer is disposed downstream of other layers in the filter element. In some cases, the fifth layer may also serve as an efficiency layer. In some embodiments, the third layer and the fifth layer are both support layers. It should be understood that the figure is non-limiting, and that the filter media may include other numbers and types of layers, the layers may be positioned in a different order (e.g., two layers of the same type may be directly adjacent to each other, each layer of the filter media may be different, the filter media may not have a symmetrical configuration, and/or the filter media may include six, seven, or more layers.

As used herein, when a layer is referred to as being "on" or "adjacent" another layer, it can be directly on or adjacent the layer, or intervening layers may also be present. A layer "directly on," directly adjacent to, "or in" contact with "another layer means that there are no intervening layers present.

Certain embodiments relate to methods for making filter media. An exemplary method for making a filter media is shown in fig. 2A through 2C. In fig. 2A, an adhesive 290 is deposited (e.g., sprayed) on the first layer 210. The first layer may be a pre-filter layer or a support layer. In some embodiments, the binder may have a glass transition temperature of less than or equal to 25 ℃ and greater than or equal to-150 ℃ and/or may be a solvent-based resin, as described in more detail below. In some embodiments, the adhesive may comprise a solvent that at least partially evaporates from the adhesive-based resin during or after deposition of the adhesive on the first layer. In some embodiments, the solvent may be water or another solvent.

In some embodiments, the binder resin may undergo crosslinking after the binder is deposited on the first layer. Such a process may allow for the deposition of an adhesive using a method suitable for applying a liquid (e.g., spraying), while also having good properties consistent with a solid after the deposition process is complete (e.g., lack of flow upon exposure to isopropyl alcohol vapor).

In some embodiments, spraying the adhesive may allow a relatively small amount of adhesive to be deposited on the first layer as compared to other methods for depositing the adhesive. Spraying may include passing the adhesive through any suitable nozzle (e.g., an air atomization nozzle, an ultrasonic nozzle, a piezo nozzle, etc.). Other spray parameters (e.g., distance between the nozzle and the first layer, air pressure applied to the adhesive during spraying, size of the nozzle, etc.) may be selected as desired to control the amount of adhesive deposited on the first layer and other parameters.

After spraying the binder onto the first layer, a second layer 220 (e.g., a fine fiber layer) may be formed on the layer 210 by performing a solvent-based spinning process, as exemplarily shown in fig. 2B. Non-limiting examples of solvent spinning processes include electrospinning processes (e.g., solvent electrospinning) or centrifugal spinning processes. In some embodiments, the solvent-based spinning process may result in the formation of fibers having an average fiber diameter of less than 1 micron. In some embodiments, the second layer may be a main filtration layer.

In some embodiments, the use of a solvent-based resin may reduce the conductivity of the substrate (e.g., the first layer) on which the resin is deposited and/or may facilitate adhesion and/or uniform deposition of the second layer (e.g., by a solvent spinning process).

In some embodiments, a third layer may be laminated on the second layer. For example, an adhesive may be deposited (e.g., sprayed) on the second layer 220, and then the second and third layers may be joined. The adhesive may increase the bond strength between the second layer and the third layer. Optionally, an adhesive may be deposited (e.g., sprayed) on the third layer prior to laminating the third layer to the second layer. The resulting media is exemplarily shown in fig. 2C, where a third layer 230 is laminated to the second layer 220 and directly adjacent to the second layer 220. In some embodiments, the third layer is a pre-filter layer or a support layer. For example, in some embodiments where the first layer is a pre-filter layer and the second layer is a main filter layer, the third layer may be a support layer. In embodiments where the first layer is a support layer and the second layer is a main filtration layer, the third layer may be a pre-filtration layer.

In some embodiments, after laminating two or more layers together, the filter media may be subjected to one or more treatment steps. For example, the filter media may be subjected to a step in which increased heat is applied, such as by a felt dryer drum, by an air dryer, by calendar rolls, and/or by a flat bed laminator. In some embodiments, the filter media may be subjected to two or more such steps in sequence (e.g., the filter media may be passed through a felt drying cylinder and then through an air dryer). The increased heat may help evaporate any solvent remaining in the filter media prior to this step.

In some embodiments, applying heat to the filter media may include exposing the filter media to an environment having a temperature greater than or equal to 40 ℃, greater than or equal to 60 ℃, greater than or equal to 80 ℃, or greater than or equal to 100 ℃ (e.g., the interior of a drying cylinder, the interior of an air dryer, the interior of a calendar roll, the interior of a flat bed laminator). In some embodiments, applying heat to the filter media may include exposing the filter media to an environment (e.g., the interior of a drying cylinder, the interior of an air dryer, the interior of a calendar roll, the interior of a flat bed laminator) having a temperature of less than or equal to 120 ℃, less than or equal to 100 ℃, less than or equal to 80 ℃, or less than or equal to 60 ℃. Combinations of the above ranges are also possible (e.g., greater than or equal to 40 ℃ and less than or equal to 120 ℃). Other ranges are also possible.

In some embodiments, applying heat to the filter media can include passing the filter media through a heated environment (e.g., the interior of a drying cylinder, the interior of an air dryer, the interior of a calender roll, the interior of a flat bed laminator) at a rate of greater than or equal to 0.1 m/minute, greater than or equal to 0.2 m/minute, greater than or equal to 0.5 m/minute, greater than or equal to 1 m/minute, greater than or equal to 2 m/minute, greater than or equal to 5 m/minute, greater than or equal to 10 m/minute, or greater than or equal to 20 m/minute. In some embodiments, applying heat to the filter media can include passing the filter media through a heated environment (e.g., the interior of a drying cylinder, the interior of an air dryer, the interior of a calender roll, the interior of a flat bed laminator) at a rate of less than or equal to 40 m/minute, less than or equal to 20 m/minute, less than or equal to 10 m/minute, less than or equal to 5 m/minute, less than or equal to 2 m/minute, less than or equal to 1 m/minute, less than or equal to 0.5 m/minute, or less than or equal to 0.2 m/minute. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 m/min and less than or equal to 40 m/min). Other ranges are also possible.

In some embodiments, one or more of the steps depicted in fig. 2A-2C may be repeated in the process of forming the filter media. For example, the binder may be deposited (e.g., sprayed) on both sides of the first layer and/or the layers may be formed on each side of the first layer by a solvent spinning process, such as an electrospinning process or a centrifugal spinning process. In some embodiments, the layers may be laminated to both the top and bottom of the filter media. It is to be understood that these steps may occur sequentially (e.g., the steps depicted in fig. 2A-2C may be performed on one side of the first layer, then on the opposite side of the first layer) or simultaneously (the first layer may be coated with adhesive on both the top and bottom sides, then the steps depicted in fig. 2B-2C may be performed simultaneously on both sides of the first layer). In some embodiments, five, nine, thirteen or more layers of filter media may be constructed in this manner.

In embodiments where one or more layers are added to the filter media, the process for adding the layers may be an on-line process or an off-line process. For example, in some embodiments, one or more layers (e.g., a first layer, a second layer, a third layer, a fourth layer, a fifth layer) may be added using an in-line process associated with the system shown in fig. 3. That is, the filter media may be manufactured on a manufacturing line, and two or more of the processes described herein may occur on the same manufacturing line. Suitable processes that can be performed in-line include lamination, spraying adhesive onto the layers, and gravure processes (e.g., hot melt gravure processes). In some embodiments, the online may include fewer unwinding and rewinding processes than offline processes.

As described above, in some embodiments, one or more layers may be pre-filter layers. For example, in some embodiments, the first layer is a pre-filter layer. In some embodiments, the third layer is a pre-filter layer. In certain embodiments, both the third layer and the fifth layer are pre-filter layers. The characteristics of the pre-filter layer will be described in more detail below.

References herein to a pre-filter layer or layers should be understood to refer independently to each pre-filter layer in the filter media (if any pre-filter layer is present at all). That is, each pre-filter layer present may independently have any or none of the properties described herein. In some embodiments, two or more pre-filter layers in a filter media may have similar compositions and/or characteristics. In other embodiments, each pre-filter layer in the filter media may have a different composition and/or characteristics.

In embodiments where the filter media includes at least one pre-filter layer (e.g., first layer, third layer), the fibers in the pre-filter layer or layers may have any suitable average diameter. In some embodiments, the fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) have an average diameter of greater than or equal to 0.1 microns, greater than or equal to 0.2 microns, greater than or equal to 0.5 microns, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 5 microns, greater than or equal to 10 microns, greater than or equal to 20 microns, greater than or equal to 40 microns, or greater than or equal to 60 microns. In some embodiments, the fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) have an average diameter of less than or equal to 75 microns, less than or equal to 60 microns, less than or equal to 40 microns, less than or equal to 20 microns, less than or equal to 10 microns, less than or equal to 5 microns, less than or equal to 2 microns, less than or equal to 1 micron, less than or equal to 0.5 microns, or less than or equal to 0.2 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 microns and less than or equal to 75 microns, greater than or equal to 0.5 microns and less than or equal to 40 microns, or greater than or equal to 0.5 microns and less than or equal to 2 microns). Other ranges are also possible.

In some embodiments where the filter media includes at least one pre-filter layer (e.g., first layer, third layer, fifth layer), the pre-filter layer can comprise continuous fibers. The continuous fibers can have any suitable average length. In some embodiments, the average length of the continuous fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be greater than or equal to 1 inch, greater than or equal to 2 inches, greater than or equal to 5 inches, greater than or equal to 10 inches, greater than or equal to 20 inches, greater than or equal to 50 inches, greater than or equal to 100 inches, greater than or equal to 200 inches, or greater than or equal to 500 inches. In some embodiments, the average length of the continuous fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 1000 inches, less than or equal to 500 inches, less than or equal to 200 inches, less than or equal to 100 inches, less than or equal to 50 inches, less than or equal to 20 inches, less than or equal to 10 inches, or less than or equal to 5 inches. Combinations of the above characteristics are also possible (e.g., greater than or equal to 5 inches and less than or equal to 1000 inches). Other ranges are also possible.

In other embodiments where the filter media includes at least one pre-filter layer (e.g., first layer, third layer, fifth layer), the pre-filter layer may comprise staple fibers. The staple fibers may have any suitable average length. In some embodiments, the average length of the staple fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) can be greater than or equal to 0.3mm, greater than or equal to 0.5mm, greater than or equal to 1mm, greater than or equal to 2mm, greater than or equal to 5mm, greater than or equal to 10mm, greater than or equal to 20mm, or greater than or equal to 50 mm. In some embodiments, the average length of the staple fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 100mm, less than or equal to 50mm, less than or equal to 20mm, less than or equal to 10mm, less than or equal to 5mm, less than or equal to 2mm, less than or equal to 1mm, or less than or equal to 0.5 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.3mm and less than or equal to 100mm, or greater than or equal to 1mm and less than or equal to 50 mm). Other ranges are also possible.

In some embodiments of filter media including at least one pre-filter layer (e.g., first layer, third layer, fifth layer), the pre-filter layer or layers may comprise fiber types such as synthetic fibers, glass fibers, and/or cellulose fibers. In some cases, the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may comprise a relatively high weight percentage of synthetic fibers (e.g., 100 wt%). For example, the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may comprise synthetic fibers formed from a melt-blown process, a melt-spun process, a centrifugal spinning process, electrospinning, wet-laying, dry-laying, or an air-laying process. In some cases, the synthetic fibers may be continuous, as described further below. In some embodiments, the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may contain relatively few or no glass fibers. In other embodiments, the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may comprise a relatively high weight percentage of glass fibers (e.g., 100 wt%).

In some embodiments, the filter media may include at least one pre-filter layer (e.g., a first layer, a third layer, a fifth layer), and at least one of the pre-filter layers present may comprise synthetic fibers. The synthetic fibers can have a relatively small average fiber diameter (e.g., less than or equal to about 2 microns). For example, the average diameter of the synthetic fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to about 2 microns (e.g., about 0.5 microns to about 1.0 microns). In some embodiments, the synthetic fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) can be continuous fibers formed by any suitable process (e.g., melt-blown, melt-spun, electrospun (e.g., melt-electrospun, solvent-electrospun), centrifugal-spun, wet-laid, dry-laid, or air-laid processes). In certain embodiments, the synthetic fibers may be formed by an electrospinning process. In other embodiments, the synthetic fibers may be discontinuous. In some embodiments, all of the fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) are synthetic fibers.

The synthetic fibers may comprise any suitable type of synthetic polymer. Examples of suitable synthetic fibers include polyesters (e.g., polyethylene terephthalate, polybutylene terephthalate), polycarbonates, polyamides (e.g., various nylon polymers), polyaramides, polyimides, polyethylenes, polypropylenes, polyetheretherketones, polyolefins, acrylics, polyvinyl alcohols, regenerated cellulose (e.g., synthetic celluloses such as lyocell, rayon), polyacrylonitrile, polyvinylidene fluoride (PVDF), copolymers of polyethylene and PVDF, polyethersulfones, and combinations thereof. In some embodiments, the synthetic fibers are organic polymer fibers. Synthetic fibers can also include multicomponent fibers (i.e., fibers having multiple components such as bicomponent fibers). In some cases, the synthetic fibers can include meltblown fibers, meltspun fibers, electrospun (e.g., melt electrospun, solvent electrospun) fibers, or centrifugally spun fibers, which can be formed from polymers (e.g., polyesters, polypropylenes) described herein. In some embodiments, the synthetic fibers may be electrospun fibers. When present, the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may also comprise a combination of more than one type of synthetic fibers. It should be understood that other types of synthetic fiber types may also be used.

In some embodiments, the synthetic fibers of one or more pre-filter layers (e.g., the first layer, the third layer, the fifth layer, if present) can have an average diameter of, for example, greater than or equal to about 0.1 microns, greater than or equal to about 0.3 microns, greater than or equal to about 0.5 microns, greater than or equal to about 1 micron, greater than or equal to about 2 microns, greater than or equal to about 3 microns, greater than or equal to about 4 microns, greater than or equal to about 5 microns, greater than or equal to about 8 microns, greater than or equal to about 10 microns, greater than or equal to about 12 microns, greater than or equal to about 15 microns, or greater than or equal to about 20 microns. In some cases, the synthetic fibers can have an average diameter of less than or equal to about 30 microns, less than or equal to about 20 microns, less than or equal to about 15 microns, less than or equal to about 10 microns, less than or equal to about 7 microns, less than or equal to about 5 microns, less than or equal to about 4 microns, less than or equal to about 1.5 microns, less than or equal to about 1 micron, less than or equal to about 0.8 microns, or less than or equal to about 0.5 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to about 1 micron and less than or equal to about 5 microns). Other values of average fiber diameter are also possible. The average diameter of the fibers can be determined, for example, by scanning electron microscopy.

In some cases, the synthetic fibers (if present) can be continuous (e.g., meltblown fibers, spunbond fibers, electrospun fibers, centrifugally spun fibers, etc.). The above provides the length of the continuous fibers. In other embodiments, the synthetic fibers (if present) are not continuous (e.g., staple fibers). The above provides the length of the staple fiber. Continuous fibers are made by "continuous" fiber forming processes (e.g., meltblown processes, spunbond processes, electrospinning processes, or centrifugal spinning processes) and typically have a longer length than non-continuous fibers. Discontinuous fibers are staple fibers that are typically cut (e.g., from filaments) or formed into discontinuous discrete fibers to have a particular length or range of lengths.

In embodiments where the filter media includes at least one pre-filter layer (e.g., first layer, third layer, fifth layer) comprising synthetic fibers, the synthetic fibers may form any suitable portion of the layer. In some embodiments, the wt% of the synthetic fibers in the pre-filter layer (e.g., first layer, third layer, fifth layer) may be greater than or equal to 0 wt%, greater than or equal to 10 wt%, greater than or equal to 20 wt%, greater than or equal to 30 wt%, greater than or equal to 40 wt%, greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 70 wt%, greater than or equal to 80 wt%, or greater than or equal to 90 wt%. In some embodiments, the wt% of the synthetic fibers in the pre-filter layer (e.g., first layer, third layer, fifth layer) may be less than or equal to 100 wt%, less than or equal to 90 wt%, less than or equal to 80 wt%, less than or equal to 70 wt%, less than or equal to 60 wt%, less than or equal to 50 wt%, less than or equal to 40 wt%, less than or equal to 30 wt%, less than or equal to 20 wt%, or less than or equal to 10 wt%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 100 wt%, or greater than or equal to 10 wt% and less than or equal to 100 wt%). Other ranges are also possible. In some embodiments, the wt% of the synthetic fibers in the pre-filter layer (e.g., first layer, third layer, fifth layer) may be 100 wt%.

In some embodiments, the filter media may include at least one pre-filter layer (e.g., first layer, third layer, fifth layer), and at least one of the pre-filter layers present may comprise bicomponent fibers. The bicomponent fibers may comprise a thermoplastic polymer. The components of the bicomponent fiber may have different melting temperatures. For example, the fiber may comprise a core and a sheath, wherein the sheath has an activation temperature that is lower than the melting temperature of the core. This causes the sheath to melt before the core, allowing the sheath to bond to other fibers in the layer while the core maintains its structural integrity. The core/sheath bonding fibers may be coaxial or non-coaxial. Other exemplary bicomponent fibers may include split fiber, side-by-side fiber, and/or "islands-in-the-sea" fiber.

In some embodiments, the bicomponent fibers (if present) may have an average length of at least about 0.1mm, at least about 0.5mm, at least about 1.0mm, at least about 1.5mm, at least about 2.0mm, at least about 3.0mm, at least about 4.0mm, at least about 5.0mm, at least about 6.0mm, at least about 7.0mm, at least about 8.0mm, at least about 9.0mm, at least about 10.0mm, at least about 12.0mm, at least about 15.0 mm; and/or less than or equal to about 15.0mm, less than or equal to about 12.0mm, less than or equal to about 10.0mm, less than or equal to about 5.0mm, less than or equal to about 4.0mm, less than or equal to about 1.0mm, less than or equal to about 0.5mm, or less than or equal to about 0.1 mm. Combinations of the above ranges are also possible (e.g., at least about 1.0mm and less than or equal to about 4.0 mm). Other values of average fiber length are also possible.

In embodiments where the filter media includes at least one pre-filter layer (e.g., first layer, third layer, fifth layer) comprising bicomponent fibers, the bicomponent fibers may form any suitable portion of the layer. In some embodiments, the wt% of the bicomponent fibers in the pre-filter layer or layers may be greater than or equal to 0 wt%, greater than or equal to 2.5 wt%, greater than or equal to 5 wt%, greater than or equal to 7.5 wt%, greater than or equal to 10 wt%, greater than or equal to 15 wt%, greater than or equal to 20 wt%, greater than or equal to 25 wt%, greater than or equal to 30 wt%, greater than or equal to 35 wt%, greater than or equal to 40 wt%, or greater than or equal to 45 wt%. In some embodiments, the wt% of the bicomponent fibers in the pre-filter layer or layers may be less than or equal to 50 wt%, less than or equal to 45 wt%, less than or equal to 40 wt%, less than or equal to 35 wt%, less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, less than or equal to 15 wt%, less than or equal to 10 wt%, less than or equal to 7.5 wt%, less than or equal to 5 wt%, or less than or equal to 2.5 wt%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 50 wt%, or greater than or equal to 0 wt% and less than or equal to 10 wt%). Other ranges are also possible.

In some embodiments, the filter media may include at least one pre-filter layer (e.g., first layer, third layer, fifth layer), and at least one of the pre-filter layers present may comprise one or more cellulosic fibers, such as softwood fibers, hardwood fibers, a mixture of hardwood fibers and softwood fibers, regenerated cellulosic fibers, and/or mechanical pulp fibers (e.g., groundwood, chemically treated mechanical pulp, and thermo-mechanical pulp).

The average diameter of the cellulose fibers in one or more pre-filter layers (i.e., in embodiments that include at least one pre-filter layer (e.g., first layer, third layer, fifth layer)) can be, for example, greater than or equal to about 1 micron, greater than or equal to about 2 microns, greater than or equal to about 3 microns, greater than or equal to about 4 microns, greater than or equal to about 5 microns, greater than or equal to about 8 microns, greater than or equal to about 10 microns, greater than or equal to about 15 microns, greater than or equal to about 20 microns, greater than or equal to about 30 microns, or greater than or equal to about 40 microns. In some cases, the average diameter of the cellulosic fibers can be less than or equal to about 50 microns, less than or equal to about 40 microns, less than or equal to about 30 microns, less than or equal to about 20 microns, less than or equal to about 15 microns, less than or equal to about 10 microns, less than or equal to about 7 microns, less than or equal to about 5 microns, less than or equal to about 4 microns, or less than or equal to about 2 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to about 1 micron and less than or equal to about 5 microns). Other values of average fiber diameter are also possible.

In some embodiments, the cellulosic fibers (if present) may have an average length. For example, in some embodiments, the average length of the cellulosic fibers may be greater than or equal to about 0.5mm, greater than or equal to about 1mm, greater than or equal to about 2mm, greater than or equal to about 3mm, greater than or equal to about 4mm, greater than or equal to about 5mm, greater than or equal to about 6mm, or greater than or equal to about 8 mm. In some cases, the average length of the cellulosic fibers may be less than or equal to about 10mm, less than or equal to about 8mm, less than or equal to about 6mm, less than or equal to about 4mm, less than or equal to about 2mm, or less than or equal to about 1 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to about 1mm and less than or equal to about 3 mm). Other values of average fiber length are also possible.

In embodiments where the filter media includes at least one pre-filter layer (e.g., first layer, third layer, fifth layer) comprising cellulose fibers, the cellulose fibers may form any suitable portion of the layer. In some embodiments, the wt% of the cellulose fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be greater than or equal to 0 wt%, greater than or equal to 10 wt%, greater than or equal to 20 wt%, greater than or equal to 30 wt%, greater than or equal to 40 wt%, greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 70 wt%, greater than or equal to 80 wt%, or greater than or equal to 90 wt%. In some embodiments, the wt% of the cellulose fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 100 wt%, less than or equal to 90 wt%, less than or equal to 80 wt%, less than or equal to 70 wt%, less than or equal to 60 wt%, less than or equal to 50 wt%, less than or equal to 40 wt%, less than or equal to 30 wt%, less than or equal to 20 wt%, or less than or equal to 10 wt%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 100 wt%, or greater than or equal to 0 wt% and less than or equal to 80 wt%). Other ranges are also possible. In some embodiments, the wt% of the cellulose fibers in the pre-filter layer (e.g., first layer, third layer, fifth layer) may be 100 wt%.

In some embodiments, the filter media may include one or more pre-filter layers (e.g., a first layer, a third layer, a fifth layer), and at least one pre-filter layer may comprise fibrillated fibers. As known to those of ordinary skill in the art, fibrillated fibers include parent fibers that branch into smaller diameter fibrils, which in some cases may further branch into fibrils of even smaller diameters, where further branching is also possible. The branched nature of the fibrils results in a layer and/or web having a high surface area, and may increase the number of contact points between the fibrillated fibers and other fibers in the web. Such an increase in the points of contact between the fibrillated fibers of the web and other fibers and/or components may contribute to the mechanical properties (e.g., flexibility, strength) and/or filtration performance properties of the reinforcement layer and/or fiber web.

In some embodiments, the parent fibers (if present) may have an average diameter in the micron or submicron range. For example, the average diameter of the parent fiber can be greater than or equal to about 0.5 microns, greater than or equal to about 1 micron, greater than or equal to about 5 microns, greater than or equal to about 10 microns, greater than or equal to about 20 microns, greater than or equal to about 30 microns, greater than or equal to about 40 microns, greater than or equal to about 50 microns, greater than or equal to about 60 microns, or greater than or equal to about 70 microns. In some embodiments, the average diameter of the parent fiber may be less than or equal to about 75 microns, less than or equal to about 55 microns, less than or equal to about 35 microns, less than or equal to about 25 microns, less than or equal to about 15 microns, less than or equal to about 10 microns, less than or equal to about 5 microns, less than or equal to about 2 microns, or less than or equal to about 0.5 microns. Combinations of the above ranges are also possible (e.g., the average diameter of the parent fiber is greater than or equal to about 1 micron and less than or equal to about 25 microns). Other ranges are also possible.

The average diameter of the fibrils (if present) is generally smaller than the average diameter of the parent fiber. Depending on the average diameter of the parent fiber, in some embodiments, the average diameter of the fibrils may be less than or equal to about 25 microns, less than or equal to about 20 microns, less than or equal to about 10 microns, less than or equal to about 5 microns, less than or equal to about 1 micron, less than or equal to about 0.5 microns, less than or equal to about 0.1 microns, less than or equal to about 0.05 microns, or less than or equal to about 0.01 microns. In some embodiments, the fibrils may have an average diameter of greater than or equal to about 0.003 microns, greater than or equal to about 0.01 microns, greater than or equal to about 0.05 microns, greater than or equal to about 0.1 microns, greater than or equal to about 0.5 microns, greater than or equal to about 1 micron, greater than or equal to about 5 microns, greater than or equal to about 10 microns, or greater than or equal to about 20 microns. Combinations of the above ranges are also possible (e.g., the average diameter of the fibrils is greater than or equal to about 0.01 microns and less than or equal to about 20 microns). Other ranges are also possible.

In some embodiments, the average length of the fibrillated fibers, if present, may be less than or equal to about 10mm, less than or equal to about 8mm, less than or equal to about 6mm, less than or equal to about 5mm, less than or equal to about 4mm, less than or equal to about 3mm, or less than or equal to about 2 mm. In certain embodiments, the average length of the fibrillated fibers may be greater than or equal to about 1mm, greater than or equal to about 2mm, greater than or equal to about 4mm, greater than or equal to about 5mm, greater than or equal to about 6mm, or greater than or equal to about 8 mm. Combinations of the above ranges are also possible (e.g., the average length of the fibrillated fibers is greater than or equal to about 4mm and less than about 6 mm). Other ranges are also possible. The average length of the fibrillated fibers refers to the average length of the parent fibers from one end of the parent fibers to the opposite end. In some embodiments, the maximum average length of the fibrillated fibers falls within the above ranges. The maximum average length refers to the average of the maximum dimension along one axis of the fibrillated fibers (including parent fibers and fibrils). It is to be understood that in certain embodiments, the fibers and fibrils can have dimensions outside of the ranges described above.

The level of fibrillation of the fibrillated fibers, if present, may be measured according to any number of suitable methods. For example, the level of fibrillation can be measured according to the Canadian Standard Freeness (CSF) test, which is specified by TAPPI test method T227Om 09 Freeness of the pulp. This test may provide an average CSF value. In some embodiments, the average CSF value of the fibrillated fibers may vary between about 10mL to about 750 mL. In certain embodiments, the fibrillated fibers used in the pre-filter layer or layers may have an average CSF value of greater than or equal to about 10mL, greater than or equal to about 50mL, greater than or equal to about 100mL, greater than or equal to about 200mL, greater than or equal to about 400mL, greater than or equal to about 600mL, or greater than or equal to about 700 mL. In some embodiments, the average CSF value of the fibrillated fibers may be less than or equal to about 800mL, less than or equal to about 600mL, less than or equal to about 400mL, less than or equal to about 200mL, less than or equal to about 100mL, or less than or equal to about 50 mL. Combinations of the above ranges are also possible (e.g., the average CSF value of the fibrillated fibers is greater than or equal to about 10mL and less than or equal to about 300 mL). Other ranges are also possible. The average CSF value of the fibrillated fibers may be based on one type of fibrillated fiber or more than one type fibrillated fiber.

In embodiments where the filter media includes at least one pre-filter layer (e.g., first layer, third layer, fifth layer) comprising fibrillated fibers, the fibrillated fibers may comprise any suitable portion of the layer. In some embodiments, the wt% of fibrillated fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be greater than or equal to 0 wt%, greater than or equal to 10 wt%, greater than or equal to 25 wt%, greater than or equal to 50 wt%, greater than or equal to 75 wt%, or greater than or equal to 90 wt%. In some embodiments, the wt% of fibrillated fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 100 wt%, less than or equal to 90 wt%, less than or equal to 75 wt%, less than or equal to 50 wt%, less than or equal to 25 wt%, or less than or equal to 10 wt%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 100 wt%, or greater than or equal to 0 wt% and less than or equal to 75 wt%). Other ranges are also possible. In some embodiments, the wt% of fibrillated fibers in a pre-filter layer (e.g., first layer, third layer, fifth layer) may be 100 wt%.

In some embodiments, the filter media may include at least one pre-filter layer (e.g., a first layer, a third layer, a fifth layer) comprising glass fibers (e.g., microglass fibers, chopped strand glass fibers, or a combination thereof).

The average diameter of the glass fibers (if present) can be, for example, less than or equal to about 30 microns, less than or equal to about 25 microns, less than or equal to about 15 microns, less than or equal to about 12 microns, less than or equal to about 10 microns, less than or equal to about 9 microns, less than or equal to about 7 microns, less than or equal to about 5 microns, less than or equal to about 3 microns, or less than or equal to about 1 micron. In some cases, the glass fibers can have an average fiber diameter of greater than or equal to about 0.1 microns, greater than or equal to about 0.3 microns, greater than or equal to about 1 micron, greater than or equal to about 3 microns, or greater than or equal to about 7 microns, greater than or equal to about 9 microns, greater than or equal to about 11 microns, or greater than or equal to about 20 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to about 0.1 microns and less than or equal to about 9 microns). Other values of average fiber diameter are also possible.

In some embodiments, the average length of the microglass fibers (if present) may be less than or equal to about 10mm, less than or equal to about 8mm, less than or equal to about 6mm, less than or equal to about 5mm, less than or equal to about 4mm, less than or equal to about 3mm, or less than or equal to about 2 mm. In certain embodiments, the average length of the microglass fibers may be greater than or equal to about 1mm, greater than or equal to about 2mm, greater than or equal to about 4mm, greater than or equal to about 5mm, greater than or equal to about 6mm, or greater than or equal to about 8 mm. Combinations of the above ranges are also possible (e.g., the average length of the microglass fibers is greater than or equal to about 4mm and less than about 6 mm). Other ranges are also possible.

Generally, the chopped glass fibers (if present) may have an average fiber diameter greater than the diameter of the microglass fibers. In some embodiments, the chopped glass fibers may have a length in the range of about 0.125 inches to about 1 inch (e.g., about 0.25 inches or about 0.5 inches). In some embodiments, the chopped glass fibers may have an average length of less than or equal to about 1 inch, less than or equal to about 0.8 inch, less than or equal to about 0.6 inch, less than or equal to about 0.5 inch, less than or equal to about 0.4 inch, less than or equal to about 0.3 inch, or less than or equal to about 0.2 inch. In certain embodiments, the chopped glass fibers may have an average length of greater than or equal to about 0.125 inches, greater than or equal to about 0.2 inches, greater than or equal to about 0.4 inches, greater than or equal to about 0.5 inches, greater than or equal to about 0.6 inches, or greater than or equal to about 0.8 inches. Combinations of the above ranges are also possible (e.g., the chopped glass fibers have an average length of greater than or equal to about 0.125 inches and less than about 1 inch). Other ranges are also possible.

In some embodiments, the filter media can include at least one pre-filter layer (e.g., a first layer, a third layer, a fifth layer), and the layer can include any suitable amount of glass fibers. In some embodiments, the wt% of the fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be greater than or equal to 0 wt%, greater than or equal to 10 wt%, greater than or equal to 20 wt%, greater than or equal to 30 wt%, greater than or equal to 40 wt%, greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 70 wt%, greater than or equal to 80 wt%, greater than or equal to 90 wt%, or greater than or equal to 95 wt%. In some embodiments, the weight% of the fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 100 weight%, less than or equal to 95 weight%, less than or equal to 90 weight%, less than or equal to 80 weight%, less than or equal to 70 weight%, less than or equal to 60 weight%, less than or equal to 50 weight%, less than or equal to 40 weight%, less than or equal to 30 weight%, less than or equal to 20 weight%, or less than or equal to 10 weight%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 100 wt%, or greater than or equal to 0 wt% and less than or equal to 95 wt%). Other ranges are also possible. In some embodiments, the wt% of glass fibers in the pre-filter layer (e.g., first layer, third layer, fifth layer) may be 100 wt%.

In some embodiments, the filter media may include at least one pre-filter layer (e.g., a first layer, a third layer, a fifth layer), and the pre-filter layer or layers may include one or more additives. In some embodiments, the additive may include a wax, such as acrawax. In some embodiments, the weight% of the wax in the pre-filter layer or layers may be greater than or equal to 0 weight%, greater than or equal to 0.1 weight%, greater than or equal to 0.2 weight%, greater than or equal to 0.5 weight%, greater than or equal to 1 weight%, or greater than or equal to 2 weight%. In some embodiments, the weight% of the wax in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 4 weight%, less than or equal to 2 weight%, less than or equal to 1 weight%, less than or equal to 0.5 weight%, less than or equal to 0.2 weight%, or less than or equal to 0.1 weight%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 10 wt%, or greater than or equal to 0.5 wt% and less than or equal to 4 wt%). Other ranges are also possible.

In some embodiments, the additive (if present) may include a stearate (e.g., magnesium stearate, calcium stearate). In some embodiments, the weight% of magnesium stearate in the pre-filter layer (e.g., first layer, third layer, fifth layer) may be greater than or equal to 0 weight%, greater than or equal to 0.1 weight%, greater than or equal to 0.2 weight%, greater than or equal to 0.5 weight%, greater than or equal to 1 weight%, or greater than or equal to 2 weight%. In some embodiments, the weight% of magnesium stearate in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 4 weight%, less than or equal to 2 weight%, less than or equal to 1 weight%, less than or equal to 0.5 weight%, less than or equal to 0.2 weight%, or less than or equal to 0.1 weight%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 10 wt%, or greater than or equal to 0.5 wt% and less than or equal to 4 wt%). Other ranges are also possible.

In embodiments where the filter media includes at least one pre-filter layer (e.g., first layer, third layer, fifth layer), the pre-filter layer or layers may have With any suitable basis weight. In some embodiments, the basis weight of the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) can be greater than or equal to 0.2g/m²0.5g/m or more²Greater than or equal to 1g/m²Greater than or equal to 2g/m²Greater than or equal to 3g/m²Greater than or equal to 5g/m²Greater than or equal to 10g/m²Greater than or equal to 20g/m²Greater than or equal to 40g/m²Or greater than or equal to 100g/m². In some embodiments, the basis weight of the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) can be less than or equal to 150g/m²Less than or equal to 100g/m²Less than or equal to 40g/m²Less than or equal to 20g/m²Less than or equal to 10g/m²Less than or equal to 5g/m²Less than or equal to 2g/m²Less than or equal to 1g/m²Or less than or equal to 0.5g/m². Combinations of the above ranges are also possible (e.g., greater than or equal to 0.2 g/m)²And less than or equal to 150g/m²0.5g/m or more²And less than or equal to 40g/m²Or greater than or equal to 3g/m²And less than or equal to 40g/m²). Other ranges are also possible. The basis weight may be determined according to standard ISO 536.

In some embodiments where the filter media includes at least one pre-filter layer (e.g., first layer, third layer, fifth layer), the thickness of the pre-filter layer or layers may be greater than or equal to 0.02mm, greater than or equal to 0.05mm, greater than or equal to 0.1mm, greater than or equal to 0.2mm, greater than or equal to 0.5mm, greater than or equal to 1mm, or greater than or equal to 2 mm. In some embodiments, the thickness of the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) can be less than or equal to 5mm, less than or equal to 2mm, less than or equal to 1mm, less than or equal to 0.5mm, less than or equal to 0.2mm, less than or equal to 0.1mm, or less than or equal to 0.05 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.02mm and less than or equal to 5mm, or greater than or equal to 0.1mm and less than or equal to 1 mm). Other ranges are also possible. The thickness of the pre-filter layer or layers may be determined according to standard ISO 534 at 50 kPa.

In some embodiments where the filter media includes at least one pre-filter layer (e.g., first layer, third layer, fifth layer), the pre-filter layer or layers can have a mean flow pore size of greater than or equal to 0.5 microns, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 4 microns, greater than or equal to 10 microns, greater than or equal to 20 microns, greater than or equal to 50 microns, or greater than or equal to 70 microns. In some embodiments, the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) can have a mean flow pore size of less than or equal to 100 microns, less than or equal to 70 microns, less than or equal to 50 microns, less than or equal to 20 microns, less than or equal to 10 microns, less than or equal to 4 microns, less than or equal to 2 microns, or less than or equal to 1 micron. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.5 micrometers and less than or equal to 100 micrometers, greater than or equal to 1 micrometer and less than or equal to 70 micrometers, or greater than or equal to 0.5 micrometers and less than or equal to 4 micrometers). Other ranges are also possible. The mean flow pore diameter can be determined according to the standard ASTM F316-03.

In some embodiments, the filter media may include one or more pre-filter layers (e.g., a first layer, a third layer, a fifth layer), and the pressure drop across the pre-filter layer or layers may be greater than or equal to 0.1mm H₂O, 0.2mm H or more₂O, 0.6mmH or more₂O, 1mm H or more₂O, 2mm H or more₂O, greater than or equal to 5mmH₂O, 10mm H or more₂O, or 25mm H or more₂And O. In some embodiments, the pressure drop across the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 50mm H₂O, less than or equal to 25mm H₂O, less than or equal to 10mm H₂O, less than or equal to 5mm H₂O, less than or equal to 2mm H₂O, less than or equal toAt 1mm H₂O, less than or equal to 0.6mm H₂O, or 0.2mm H or less₂And O. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1mm H₂O is less than or equal to 50mm H₂O, or 0.6mm H or more₂O is less than or equal to 25mm H₂O). Other ranges are also possible. Pressure drop can be determined using ASTM D2986-91.

In some embodiments, the filter media may include one or more pre-filter layers, and the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may have an air permeability greater than or equal to 2 feet ³Minute/foot²(CFM), greater than or equal to 4CFM, greater than or equal to 8CFM, greater than or equal to 10CFM, greater than or equal to 20CFM, greater than or equal to 50CFM, greater than or equal to 100CFM, greater than or equal to 300CFM, greater than or equal to 500CFM, or greater than or equal to 1000 CFM. In some embodiments, the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) can have an air permeability of less than or equal to 1400CFM, less than or equal to 1000CFM, less than or equal to 500CFM, less than or equal to 300CFM, less than or equal to 100CFM, less than or equal to 50CFM, less than or equal to 20CFM, less than or equal to 10CFM, less than or equal to 8CFM, or less than or equal to 4 CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 2CFM and less than or equal to 1400CFM, or greater than or equal to 8CFM and less than or equal to 300 CFM). Other ranges are also possible. Air permeability may be determined using TAPPI method T251.

In some embodiments, the filter media can include one or more pre-filter layers, and the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) can have a solidity of greater than or equal to 0.001, greater than or equal to 0.0025, greater than or equal to 0.005, greater than or equal to 0.01, greater than or equal to 0.025, greater than or equal to 0.05, greater than or equal to 0.1, greater than or equal to 0.25, greater than or equal to 0.5, greater than or equal to 1, greater than or equal to 2.5, greater than or equal to 5, greater than or equal to 10, or greater than or equal to 25. In some embodiments, the solidity of the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) can be less than or equal to 50, less than or equal to 25, less than or equal to 10, less than or equal to 5, less than or equal to 2.5, less than or equal to 1, less than or equal to 0.5, less than or equal to 0.25, less than or equal to 0.1, less than or equal to 0.05, less than or equal to 0.025, less than or equal to 0.01, less than or equal to 0.005, or less than or equal to 0.0025. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.001 and less than or equal to 50, or greater than or equal to 0.01 and less than or equal to 25). Other ranges are also possible. Solidity can be determined by using the following formula: solidity [ basis weight/(fiber density thickness) ]. 100. Basis weight and thickness may be determined as described herein. Porosity can be derived from solidity based on the following equation: solidity (%) 100-porosity (%). The fiber density is equal to the average density of the material or materials forming the fiber, which is typically specified by the fiber manufacturer. The average density is obtained by dividing the total mass of fibers within the filter by the total volume of fibers within the pre-filter, where the total volume of fibers within the pre-filter is the sum of the ratio of the mass of each fiber type to the density of each fiber type.

In some embodiments, the filter media can include one or more pre-filter layers, and the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) can have a dioctyl phthalate (DOP) particle efficiency of greater than or equal to 20%, greater than or equal to 25%, greater than or equal to 30%, greater than or equal to 35%, greater than or equal to 40%, greater than or equal to 45%, greater than or equal to 50%, greater than or equal to 55%, greater than or equal to 60%, greater than or equal to 65%, greater than or equal to 70%, greater than or equal to 75%, greater than or equal to 80%, greater than or equal to 85%, greater than or equal to 90%, greater than or equal to 95%, greater than or equal to 97%, greater than or equal to 99%, or greater than or equal to 99.5%. In some embodiments, the DOP particle efficiency of the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) can be less than or equal to 99.5%, less than or equal to 99%, less than or equal to 97%, less than or equal to 95%, less than or equal to 90%, less than or equal to 85%, less than or equal to 80%, less than or equal to 70%, less than or equal to 60%, less than or equal to 50%, less than or equal to 40%, or less than or equal to 30%. Combinations of the above ranges are also possible (e.g., greater than or equal to 20% and less than or equal to 80%). Other ranges are also possible. DOP particle efficiency can be measured by blowing DOP particles through a pre-filter layer or layers (e.g., first layer, third layer, fifth layer) and measuring the percentage of particles that penetrate the layers. The percentage may be determined as follows: based on EN1822:2009 standard for Most Penetrating Particle Size (MPPS) DOP particles, a TSI 3160 automated filter test unit from TSI, inc, equipped with a DOP generator for DOP aerosol testing was used, and particles produced by the particle generator with average diameter varying from 0.02 to 0.3 microns were used. The penetration was measured at a face velocity of 2.0 cm/sec under continuous loading of DOP particles.

In some embodiments, the pre-filter layer (e.g., first layer, third layer, fifth layer) is electrically charged. The charge may be induced on the pre-filter layer by a charging process (e.g., an electrostatic charging process, a triboelectric charging process, or a hydrodynamic charging process). In other embodiments, the pre-filter layer (e.g., first layer, third layer, fifth layer) is uncharged.

In some embodiments, the pre-filter layer (e.g., first layer, third layer, fifth layer) is flame retardant or comprises one or more flame retardant components. For example, the pre-filter layer may include flame retardant fibers, flame retardant binders, flame retardant coatings, and/or flame retardant additives (e.g., flame retardant particles, flame retardant flakes). The flame retardant component may be introduced during manufacture (e.g., during a melt blowing process, a melt spinning process, an electrospinning process, a centrifugal spinning process, a wet-laid process, a dry-laid process, or an air-laid process) or may be added to the binder.

As described above, in some embodiments, one or more layers of the filter media may be a main filtration layer. For example, in some embodiments, the second layer may be a pre-filter layer. In other embodiments, both the second layer and the fourth layer are main filtration layers. The main filtration layer may, for example, have a higher efficiency than one or more other layers of the media. The properties of the main filter layer will be described in more detail herein.

References herein to the main filtration layer or layers should be understood to refer independently to each main filtration layer in the filter media (if any main filtration layer is actually present). That is, each main filter layer present may independently have any or none of the characteristics described below. In some embodiments, two or more main filtration layers in a filter media may have similar compositions and/or characteristics. In other embodiments, each main filtration layer in the filter media may have a different composition and/or characteristics.

In some embodiments that include at least one main filtration layer (e.g., second layer, fourth layer), the main filtration layer or layers (e.g., second layer, fourth layer) can be a solvent spun layer or layers, such as an electrospun (e.g., solvent-electrospun) layer or layers, or a spun layer or layers. As used herein, a layer is a solvent spun layer if the layer is formed during a solvent spinning process, or if the layer comprises solvent spun fibers.

In some embodiments, the filter media may include at least one main filtration layer, and the main filtration layer or layers (e.g., second layer, fourth layer) may comprise synthetic fibers. Non-limiting examples of suitable synthetic fibers include nylon, poly (vinylidene fluoride), poly (acrylonitrile), poly (ether sulfone), and polyurea. In some embodiments, the filter media may comprise a blend of: wherein one or more components of the blend is a synthetic fiber (e.g., a blend comprising at least one type of synthetic fiber, a blend comprising at least two types of synthetic fiber, or a blend comprising three or more types of synthetic fiber). In some embodiments, the main filtration layer or layers (e.g., second layer, fourth layer, if present) may comprise a relatively high amount of nylon fibers (e.g., up to 100 weight percent nylon fibers). In some embodiments, one or more of the synthetic fibers may be continuous fibers. For example, in some embodiments, the main filtration layer (e.g., second layer, fourth layer) comprises 100% continuous synthetic fibers (e.g., 100% solvent spun fibers such as 100% electrospun fibers).

In embodiments where the filter media includes at least one main filtration layer, the fibers in the main filtration layer or layers (e.g., second layer, fourth layer) can have any suitable average diameter. In some embodiments, the average diameter of the fibers in the main filtration layer (e.g., second layer, fourth layer) is greater than or equal to 20nm, greater than or equal to 40nm, greater than or equal to 100nm, greater than or equal to 200nm, greater than or equal to 300nm, or greater than or equal to 500 nm. In some embodiments, the fibers in the main filtration layer or layers (e.g., second layer, fourth layer) have an average diameter of less than or equal to 1000nm, less than or equal to 500nm, less than or equal to 300nm, less than or equal to 200nm, less than or equal to 100nm, or less than or equal to 40 nm. Combinations of the above ranges are also possible (e.g., greater than or equal to 20nm and less than or equal to 1000nm, greater than or equal to 40nm and less than or equal to 500nm, or greater than or equal to 40nm and less than or equal to 300 nm). Other ranges are also possible.

In some embodiments where the filter media includes at least one main filtration layer, the fibers within the main filtration layer (e.g., second layer, fourth layer) may have any suitable average length. In some embodiments, the average length of the fibers in the main filtration layer or layers (e.g., second layer, fourth layer) may be greater than or equal to 1 inch, greater than or equal to 2 inches, greater than or equal to 5 inches, greater than or equal to 10 inches, greater than or equal to 20 inches, greater than or equal to 50 inches, greater than or equal to 100 inches, greater than or equal to 200 inches, or greater than or equal to 500 inches. In some embodiments, the average length of the fibers in the main filtration layer or layers (e.g., second layer, fourth layer) may be less than or equal to 1000 inches, less than or equal to 500 inches, less than or equal to 200 inches, less than or equal to 100 inches, less than or equal to 50 inches, less than or equal to 20 inches, less than or equal to 10 inches, or less than or equal to 5 inches. Combinations of the above characteristics are also possible (e.g., greater than or equal to 5 inches and less than or equal to 1000 inches). Other ranges are also possible. In some embodiments, the fibers within the main filtration layer (e.g., second layer, fourth layer) may be or may comprise continuous fibers.

In some embodiments, the filter media may include at least one main filtration layer, and the main filtration layer or layers (e.g., second layer, fourth layer) may include one or more additives. In some embodiments, the additive may include a charge additive, such as sodium chloride. In some embodiments, the weight% of sodium chloride of the main filtration layer or layers (e.g., second layer, fourth layer) can be greater than or equal to 0 weight%, greater than or equal to 2 weight%, greater than or equal to 4 weight%, greater than or equal to 6 weight%, or greater than or equal to 8 weight%. In some embodiments, the weight% of sodium chloride of the main filtration layer or layers (e.g., second layer, fourth layer) can be less than or equal to 10 weight%, less than or equal to 8 weight%, less than or equal to 6 weight%, less than or equal to 4 weight%, or less than or equal to 2 weight%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 10 wt%). Other ranges are also possible.

In some embodiments, the additive may include a UV protectant. In some embodiments, the weight% of the UV protectant of the main filtration layer or layers (e.g., second layer, fourth layer) can be greater than or equal to 0 weight%, greater than or equal to 2 weight%, greater than or equal to 4 weight%, greater than or equal to 6 weight%, or greater than or equal to 8 weight%. In some embodiments, the weight% of the UV protectant of the main filtration layer or layers (e.g., second layer, fourth layer) can be less than or equal to 10 weight%, less than or equal to 8 weight%, less than or equal to 6 weight%, less than or equal to 4 weight%, or less than or equal to 2 weight%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 10 wt%). Other ranges are also possible.

In some embodiments, the additive may include an antioxidant. In some embodiments, the weight% of antioxidant of the main filtration layer or layers (e.g., second layer, fourth layer) may be greater than or equal to 0 weight%, greater than or equal to 2 weight%, greater than or equal to 4 weight%, greater than or equal to 6 weight%, or greater than or equal to 8 weight%. In some embodiments, the weight% of antioxidant of the main filtration layer or layers (e.g., second layer, fourth layer) may be less than or equal to 10 weight%, less than or equal to 8 weight%, less than or equal to 6 weight%, less than or equal to 4 weight%, or less than or equal to 2 weight%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 10 wt%). Other ranges are also possible.

In embodiments where the filter media includes at least one main filtration layer, the main filtration layer or layers (e.g., second layer, fourth layer) can have any suitable basis weight. In some embodiments, the basis weight of the main filtration layer (e.g., second layer, fourth layer) can be greater than or equal to 0.01g/m²0.03g/m or more ²0.05g/m or more²0.1g/m or more²0.3g/m or more²0.5g/m or more²Greater than or equal to 1g/m²Greater than or equal to 3g/m²Greater than or equal to 5g/m²Greater than or equal to 10g/m²Or greater than or equal to 30g/m². In some embodiments, the basis weight of the main filtration layer (e.g., second layer, fourth layer) can be less than or equal to 40g/m²Less than or equal to 30g/m²Less than or equal to 10g/m²Less than or equal to 5g/m²Less than or equal to 3g/m²Less than or equal to 1g/m²Less than or equal to 0.5g/m²Less than or equal to 0.3g/m²Less than or equal to 0.1g/m²0.05g/m or less²Or less than or equal to 0.03g/m². Combinations of the above ranges are also possible(e.g., greater than or equal to 0.01 g/m)²And less than or equal to 40g/m²0.03g/m or more²And less than or equal to 30g/m²Or 0.01g/m or more²And is less than or equal to 5g/m²). Other ranges are also possible. The basis weight may be determined according to standard ISO 536.

In some embodiments in which the filter media includes at least one main filtration layer, the thickness of the main filtration layer or layers (e.g., second layer, fourth layer) can be greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 5 microns, greater than or equal to 10 microns, greater than or equal to 20 microns, greater than or equal to 50 microns, greater than or equal to 100 microns, greater than or equal to 200 microns, greater than or equal to 500 microns, greater than or equal to 1000 microns, greater than or equal to 2000 microns, greater than or equal to 3000 microns, or greater than or equal to 4000 microns. In some embodiments, the thickness may be less than or equal to 5000 micrometers, less than or equal to 4000 micrometers, less than or equal to 3000 micrometers, less than or equal to 2000 micrometers, less than or equal to 1000 micrometers, less than or equal to 500 micrometers, less than or equal to 200 micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, less than or equal to 20 micrometers, less than or equal to 10 micrometers, less than or equal to 5 micrometers, or less than or equal to 2 micrometers. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 micron and less than or equal to 5000 microns, greater than or equal to 5 microns and less than or equal to 1000 microns, or greater than or equal to 10 microns and less than or equal to 500 microns). Other ranges are also possible. The thickness of the main filter layer or layers can be determined by using SEM cross-sectional imaging.

In some embodiments, the filter media can include one or more main filtration layers, and the solidity of the main filtration layer or layers (e.g., second layer, fourth layer) can be greater than or equal to 0.001, greater than or equal to 0.0025, greater than or equal to 0.005, greater than or equal to 0.01, greater than or equal to 0.025, greater than or equal to 0.05, greater than or equal to 0.1, greater than or equal to 0.25, greater than or equal to 0.5, greater than or equal to 1, greater than or equal to 2.5, greater than or equal to 5, greater than or equal to 10, or greater than or equal to 25. In some embodiments, the solidity of the main filtration layer or layers (e.g., second layer, fourth layer) can be less than or equal to 50, less than or equal to 25, less than or equal to 10, less than or equal to 5, less than or equal to 2.5, less than or equal to 1, less than or equal to 0.5, less than or equal to 0.25, less than or equal to 0.1, less than or equal to 0.05, less than or equal to 0.025, less than or equal to 0.01, less than or equal to 0.005, or less than or equal to 0.0025. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.001 and less than or equal to 50, or greater than or equal to 0.01 and less than or equal to 25). Other ranges are also possible.

In some embodiments, the filter media may include one or more main filtration layers, and the pressure drop across the main filtration layer or layers (e.g., second layer, fourth layer) may be greater than or equal to 0.5mm H₂O, 0.75mm H or more₂O, 1mm H or more₂O, 2.5mm H or more₂O, 5mm H or more₂O, greater than or equal to 7.5mm H₂O, 10mm H or more₂O, 25mm H or more₂O, or 50mmH or more₂And O. In some embodiments, the pressure drop across the main filtration layer or layers (e.g., second layer, fourth layer) may be less than or equal to 100mm H₂O, 75mm H or less₂O, less than or equal to 50mm H₂O, less than or equal to 25mm H₂O, less than or equal to 10mm H₂O, less than or equal to 7.5mm H₂O, less than or equal to 5mm H₂O, less than or equal to 2.5mm H₂O, less than or equal to 1mm H₂O, or 0.75mm H or less₂And O. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.5mm H₂O is less than or equal to 100mm H₂O, or 1mm H or more₂O is less than or equal to 75mm H₂O). Other ranges are also possible. Pressure drop can be determined using ASTM D2986-91.

In some embodiments, one or more layers may be film layers (e.g., extruded film layers, molded film layers, non-fibrous film layers, synthetic film layers). In these embodiments, the membrane layer may act as a main filtration layer. It should be understood that while the description herein generally focuses on filter media that includes a fibrous layer (e.g., a fibrous main filtration layer), the description above and herein also applies to filter media that includes one or more membrane main filtration layers. In some embodiments, the film layer does not comprise fibers (e.g., it is non-fibrous). The membrane layer may be disposed at any suitable location in the filter media. For example, in some embodiments, the second layer and/or the fourth layer is a film layer. The properties of the film layer will be described in more detail below.

References herein to a membrane layer or layers should be understood to refer independently to each membrane layer in a filter media (if any are present at all). That is, each film layer present may independently have any or none of the characteristics described below. In some embodiments, two or more membrane layers in a filter media may have similar compositions and/or characteristics. In other embodiments, each membrane layer in the filter media may have a different composition and/or characteristics.

In general, any suitable material may be used to form the layers (e.g., second layer, fourth layer). Suitable materials include synthetic materials such as Polytetrafluoroethylene (PTFE) (e.g., expanded or unexpanded polytetrafluoroethylene), polyvinylidene fluoride (PVDF), polyethylene (e.g., linear low density polyethylene, ultra high molecular weight polyethylene), polypropylene, polycarbonate, polyester, nitrocellulose mixed esters, polyethersulfone, cellulose acetate, polyimide, polyvinylidene fluoride, polyacrylonitrile, polysulfone, polyethersulfone, and polyamide (e.g., nylon), among others. In some embodiments, the membrane layer may comprise a fluorinated polymer, such as PVDF or PTFE.

When present, the film layer (e.g., second layer, fourth layer) can be a monolayer film or a multilayer film. In embodiments using a multilayer film, the different layers may have different compositions. Generally, the film layer may be formed by suitable methods known in the art.

When present, the film layer (e.g., second layer, fourth layer) has a plurality of pores. The pores allow the passage of fluids while the contaminating particles are trapped on the membrane layer. In some embodiments, the membrane layer may have a mean flow pore size of greater than or equal to about 0.1 microns, greater than or equal to about 0.15 microns, greater than or equal to about 0.2 microns, greater than or equal to about 0.5 microns, greater than or equal to about 1 micron, greater than or equal to about 10 microns, greater than or equal to about 20 microns, greater than or equal to about 30 microns, or greater than or equal to about 40 microns. In some cases, the membrane layer can have a mean flow pore size of less than or equal to about 50 microns, less than or equal to about 40 microns, less than or equal to about 30 microns, less than or equal to about 20 microns, less than or equal to about 15 microns, less than or equal to about 10 microns, less than or equal to about 5 microns, less than or equal to about 2 microns, or less than or equal to about 1 micron. Combinations of the above ranges are also possible (e.g., greater than or equal to about 0.1 microns and less than or equal to about 50 microns, greater than or equal to about 0.5 microns and less than or equal to about 40 microns). Other values of the average pore size are also possible. The mean flow pore diameter can be determined according to the standard ASTM F316-08 method B, BS 6140.

As described above, in some embodiments, one or more layers may be support layers. The support layer may be used to support one or more other layers of media, such as a main filtration layer. In some cases, the support layer may be used to protect and/or cover one or more other layers of the media, such as a main filtration layer. For example, in some embodiments, the third layer is a support layer. In some embodiments, the first layer is a support layer. In certain embodiments, the fifth layer is a support layer. The characteristics of the support layer will be described in more detail below.

Reference herein to a support layer or layers should be understood to refer independently to each support layer in the filter media (if any support layer is present at all). That is, each support layer present may independently have any or none of the characteristics described below. In some embodiments, two or more support layers in a filter media may have similar compositions and/or characteristics. In other embodiments, the support layers in the filter media may have different compositions and/or characteristics.

In some embodiments that include at least one support layer, the support layer or layers (e.g., first layer, third layer, fifth layer) can be a wet-laid layer. That is, in some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) may be formed by a wet-laid process. In other embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) can be a non-wet-laid layer. That is, in some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) may be formed by a non-wet-laid process (e.g., an air-laid process, a carding process, a spinning process (e.g., a spunbond process)). In some embodiments, the support layer or layers may be a spunbond layer, or a layer formed by a spunbond process.

In some embodiments, the filter media may include one or more support layers, and the support layer or layers (e.g., first layer, third layer, fifth layer) may comprise synthetic fibers. The synthetic fibers may comprise any suitable type of synthetic polymer. Examples of suitable synthetic fibers include polyesters (e.g., polyethylene terephthalate, polybutylene terephthalate), polycarbonates, polyamides (e.g., various nylon polymers), polyaramides, polyimides, polyethylenes, polypropylenes, polyetheretherketones, polyolefins, acrylics, polyvinyl alcohols, regenerated cellulose (e.g., synthetic celluloses such as lyocell, rayon), polyacrylonitrile, polyvinylidene fluoride (PVDF), copolymers of polyethylene and PVDF, polyethersulfones, and combinations thereof. In some embodiments, the synthetic fibers are organic polymer fibers. Synthetic fibers can also include multicomponent fibers (i.e., fibers having multiple components such as bicomponent fibers). In some cases, the synthetic fibers can include meltblown fibers, meltspun fibers, electrospun (e.g., melt electrospun, solvent electrospun) fibers, or centrifugally spun fibers, which can be formed from polymers (e.g., polyesters, polypropylenes) described herein. In some embodiments, the synthetic fibers may be staple fibers. In some embodiments, the synthetic fibers may be fibers that include a flame retardant. The filter media, and each layer within the filter media, may also include a combination of more than one type of synthetic fiber. It should be understood that other types of synthetic fibers may also be used.

In some embodiments, the filter media may include a support layer or layers (e.g., a first layer, a third layer, a fifth layer), and the support layer or layers may include flame retardant fibers and/or fibers containing flame retardants. In some embodiments, the fibers containing the flame retardant may be synthetic fibers. Generally, the total weight percent of coarse diameter fibers and/or fine diameter fibers, as described below, may include fibers that include flame retardants (e.g., flame retardant fibers).

In some embodiments, the filter media may include at least one support layer, and the support layer or layers may comprise coarse synthetic fibers. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) can comprise coarse synthetic fibers having an average diameter of greater than or equal to 4 microns, greater than or equal to 7 microns, greater than or equal to 10 microns, greater than or equal to 15 microns, greater than or equal to 17 microns, greater than or equal to 20 microns, greater than or equal to 25 microns, greater than or equal to 30 microns, greater than or equal to 35 microns, greater than or equal to 40 microns, greater than or equal to 45 microns, greater than or equal to 50 microns, or greater than or equal to 55 microns. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) can comprise coarse synthetic fibers having an average diameter of less than or equal to 60 microns, less than or equal to 55 microns, less than or equal to 50 microns, less than or equal to 45 microns, less than or equal to 40 microns, less than or equal to 35 microns, less than or equal to 30 microns, less than or equal to 25 microns, less than or equal to 20 microns, less than or equal to 17 microns, less than or equal to 15 microns, less than or equal to 10 microns, or less than or equal to 7 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 4 microns and less than or equal to 60 microns, greater than or equal to 7 microns and less than or equal to 40 microns, greater than or equal to 10 microns and less than or equal to 60 microns, or greater than or equal to 17 microns and less than or equal to 35 microns). Other ranges are also possible.

In embodiments where the filter media includes at least one support layer (e.g., first layer, third layer, fifth layer) and the support layer or layers comprise coarse synthetic fibers, the average length of the coarse synthetic fibers in the support layer or layers can be any suitable value. In some embodiments, the average length of the coarse synthetic fibers in the support layer or layers (e.g., first layer, third layer, fifth layer) is greater than or equal to 3mm, greater than or equal to 6mm, greater than or equal to 10mm, greater than or equal to 20mm, greater than or equal to 50mm, greater than or equal to 100mm, greater than or equal to 200mm, greater than or equal to 500mm, greater than or equal to 1000mm, greater than or equal to 2000mm, greater than or equal to 5000mm, greater than or equal to 10000mm, or greater than or equal to 20000 mm. In some embodiments, the average length of the coarse synthetic fibers in the support layer or layers (e.g., first layer, third layer, fifth layer) is less than or equal to 25400mm, less than or equal to 20000mm, less than or equal to 10000mm, less than or equal to 5000mm, less than or equal to 2000mm, less than or equal to 1000mm, less than or equal to 500mm, less than or equal to 200mm, less than or equal to 100mm, less than or equal to 50mm, less than or equal to 20mm, or less than or equal to 10mm, less than or equal to 6 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 3mm and less than or equal to 25400mm, or greater than or equal to 6mm and less than or equal to 25400 mm). Other ranges are also possible. In some embodiments, the coarse synthetic fibers are continuous fibers. In other embodiments, the coarse synthetic fibers are discontinuous fibers (e.g., staple fibers).

In some embodiments where the filter media includes a support layer or layers (e.g., first layer, third layer, fifth layer) having coarse synthetic fibers, the weight% of the coarse synthetic fibers in the support layer (e.g., first layer, third layer, fifth layer) can be greater than or equal to 1 weight%, greater than or equal to 2 weight%, greater than or equal to 5 weight%, greater than or equal to 10 weight%, greater than or equal to 20 weight%, greater than or equal to 30 weight%, greater than or equal to 50 weight%, greater than or equal to 70 weight%, or greater than or equal to 90 weight%. In some embodiments, the weight% of the coarse synthetic fibers in the support layer (e.g., first layer, third layer, fifth layer) may be less than or equal to 100 weight%, less than or equal to 90 weight%, less than or equal to 70 weight%, less than or equal to 50 weight%, less than or equal to 30 weight%, less than or equal to 20 weight%, less than or equal to 10 weight%, less than or equal to 5 weight%, or less than or equal to 2 weight%. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 wt% and less than or equal to 100 wt%, greater than or equal to 10 wt% and less than or equal to 100 wt%, or greater than or equal to 30 wt% and less than or equal to 100 wt%). Other ranges are also possible. In some embodiments, the wt% of the coarse synthetic fibers in the support layer (e.g., first layer, third layer, fifth layer) may be 100 wt%.

In some embodiments, the filter media may include a support layer or layers (e.g., a first layer, a third layer, a fifth layer), and the support layer or layers may comprise fine synthetic fibers. In such embodiments, the average diameter of the fine synthetic fibers can be any suitable value. In embodiments comprising both fine and coarse synthetic fibers, the fine synthetic fibers may have an average diameter that is less than the average diameter of the coarse synthetic fibers present in the support layer or layers. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) can comprise fine synthetic fibers having an average diameter of greater than or equal to 1 micron, greater than or equal to 1.5 microns, greater than or equal to 2.5 microns, greater than or equal to 5 microns, greater than or equal to 7.5 microns, greater than or equal to 10 microns, greater than or equal to 12.5 microns, greater than or equal to 15 microns, or greater than or equal to 17.5 microns. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) can comprise fine synthetic fibers having an average diameter of less than or equal to 20 microns, less than or equal to 17.5 microns, less than or equal to 15 microns, less than or equal to 12.5 microns, less than or equal to 10 microns, less than or equal to 7.5 microns, less than or equal to 5 microns, less than or equal to 2.5 microns, or less than or equal to 1.5 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 micron and less than or equal to 20 microns, or greater than or equal to 1.5 microns and less than or equal to 10 microns). Other ranges are also possible.

In embodiments where the filter media includes at least one support layer (e.g., a first layer, a third layer, a fifth layer) and the support layer or layers comprise fine synthetic fibers, the average length of the fine synthetic fibers in the support layer or layers can be any suitable value. In some embodiments, the fine synthetic fibers in the support layer or layers (e.g., first layer, third layer, fifth layer) have an average length of greater than or equal to 3mm, greater than or equal to 6mm, greater than or equal to 9mm, greater than or equal to 12mm, greater than or equal to 15mm, greater than or equal to 18mm, greater than or equal to 21mm, greater than or equal to 24mm, greater than or equal to 27mm, greater than or equal to 50mm, greater than or equal to 100mm, greater than or equal to 200mm, greater than or equal to 500mm, greater than or equal to 1000mm, greater than or equal to 2000mm, greater than or equal to 5000mm, greater than or equal to 10000mm, or greater than or equal to 20000 mm. In some embodiments, the fine synthetic fibers in the support layer or layers have an average length of less than or equal to 25400mm, less than or equal to 20000mm, less than or equal to 10000mm, less than or equal to 5000mm, less than or equal to 2000mm, less than or equal to 1000mm, less than or equal to 500mm, less than or equal to 200mm, less than or equal to 100mm, less than or equal to 50mm, less than or equal to 30mm, less than or equal to 27mm, less than or equal to 24mm, less than or equal to 21mm, less than or equal to 18mm, less than or equal to 15mm, less than or equal to 12mm, less than or equal to 9mm, or less than or equal to 6 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 3mm and less than or equal to 25400mm, greater than or equal to 6mm and less than or equal to 25400mm, greater than or equal to 3mm and less than or equal to 30mm, or greater than or equal to 6mm and less than or equal to 12 mm). Other ranges are also possible. In some embodiments, the fine synthetic fibers are continuous fibers (e.g., fibers formed by a melt blown or spunbond process). In other embodiments, the fine synthetic fibers are discontinuous fibers (e.g., staple fibers). In some embodiments where the filter media includes a support layer or layers having fine synthetic fibers, the weight% of the fine synthetic fibers in the support layer or layers (e.g., first layer, third layer, fifth layer) can be greater than or equal to 0 weight%, greater than or equal to 5 weight%, greater than or equal to 10 weight%, greater than or equal to 15 weight%, greater than or equal to 20 weight%, greater than or equal to 25 weight%, greater than or equal to 30 weight%, greater than or equal to 35 weight%, or greater than or equal to 40 weight%, greater than or equal to 45 weight%. In some embodiments, the weight% of the fine synthetic fibers in the support layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 50 weight%, less than or equal to 45 weight%, less than or equal to 40 weight%, less than or equal to 35 weight%, less than or equal to 30 weight%, less than or equal to 25 weight%, less than or equal to 20 weight%, less than or equal to 15 weight%, less than or equal to 10 weight%, or less than or equal to 5 weight%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 50 wt%, or greater than or equal to 1 wt% and less than or equal to 30 wt%). Other ranges are also possible.

In some embodiments, the filter media may include a support layer or layers (e.g., a first layer, a third layer, a fifth layer), and the support layer or layers may comprise binder fibers. Generally, bonding fibers (if present) may be used for the fibers in the tie layer. In some embodiments, the binding fibers comprise a polymer having a lower melting point than one or more of the major components (e.g., certain fibers) in the layer. The binder fibers may be monocomponent (e.g., polyethylene fibers, copolyester fibers) or multicomponent (e.g., bicomponent fibers). For example, the binding fibers may be bicomponent fibers. The bicomponent fibers may comprise a thermoplastic polymer. The components of the bicomponent fiber may have different melting temperatures. For example, the fiber may comprise a core and a sheath, wherein the sheath has an activation temperature that is lower than the melting temperature of the core. This causes the sheath to melt before the core, allowing the sheath to bond to other fibers in the layer while the core maintains its structural integrity. The core/sheath bonding fibers may be coaxial or non-coaxial. Other exemplary bicomponent fibers may include split fiber, side-by-side fiber, and/or "islands-in-the-sea" fiber. Generally, the total weight percent of coarse diameter fibers and/or fine diameter fibers may include binding fibers.

In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) can comprise binder fibers having an average diameter of greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 5 microns, greater than or equal to 10 microns, greater than or equal to 15 microns, greater than or equal to 20 microns, or greater than or equal to 25 microns. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) can comprise binder fibers having an average diameter of less than or equal to 30 microns, less than or equal to 25 microns, less than or equal to 20 microns, less than or equal to 15 microns, less than or equal to 10 microns, less than or equal to 5 microns, or less than or equal to 2 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 micron and less than or equal to 30 microns, or greater than or equal to 2 microns and less than or equal to 20 microns). Other ranges are also possible.

In embodiments where the filter media includes at least one support layer (e.g., a first layer, a third layer, a fifth layer) and the support layer or layers comprise binder fibers, the average length of the binder fibers in the support layer or layers can be any suitable value. In some embodiments, the average length of the binding fibers in the support layer or layers (e.g., first layer, third layer, fifth layer) is greater than or equal to 3mm, greater than or equal to 6mm, greater than or equal to 9mm, greater than or equal to 12mm, greater than or equal to 15mm, greater than or equal to 18mm, greater than or equal to 21mm, greater than or equal to 24mm, or greater than or equal to 27 mm. In some embodiments, the average length of the binding fibers in the support layer or layers (e.g., first layer, third layer, fifth layer) is less than or equal to 30mm, less than or equal to 27mm, less than or equal to 24mm, less than or equal to 21mm, less than or equal to 18mm, less than or equal to 15mm, less than or equal to 12mm, less than or equal to 9mm, or less than or equal to 6 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 3mm and less than or equal to 30mm, or greater than or equal to 6mm and less than or equal to 12 mm). Other ranges are also possible.

In some embodiments where the filter media includes a support layer or layers (e.g., first layer, third layer, fifth layer) having binding fibers, the weight% of the binding fibers in the support layer or layers can be greater than or equal to 0 weight%, greater than or equal to 5 weight%, greater than or equal to 10 weight%, greater than or equal to 15 weight%, greater than or equal to 20 weight%, greater than or equal to 25 weight%, greater than or equal to 30 weight%, greater than or equal to 40 weight%, greater than or equal to 50 weight%, greater than or equal to 60 weight%, greater than or equal to 70 weight%, or greater than or equal to 80 weight%. In some embodiments, the weight% of the binding fibers in the support layer or layers (e.g., first layer, third layer, fifth layer) can be less than or equal to 90 weight%, less than or equal to 80 weight%, less than or equal to 70 weight%, less than or equal to 60 weight%, less than or equal to 50 weight%, less than or equal to 40 weight%, less than or equal to 30 weight%, less than or equal to 25 weight%, less than or equal to 20 weight%, less than or equal to 15 weight%, less than or equal to 10 weight%, or less than or equal to 5 weight%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 90 wt%, or greater than or equal to 10 wt% and less than or equal to 30 wt%). Other ranges are also possible.

In some embodiments, the filter media may include one or more support layers (e.g., a first layer, a third layer, a fifth layer), and the support layer or layers may comprise one or more binder resins. In general, a binder resin may be used for the fibers in the junction layer. In general, the binder resin may have any suitable composition. For example, the binder resin may include a thermoplastic resin (e.g., acrylic, polyvinyl acetate, polyester, polyamide), a thermosetting resin (e.g., epoxy, phenol), or a combination thereof. In some cases, the binder resin includes one or more of a vinyl acetate resin, an epoxy resin, a polyester resin, a copolyester resin, a polyvinyl alcohol resin, an acrylic resin (e.g., a styrene acrylic resin), and a phenol resin. Other resins are also possible. In some such embodiments, the resin may comprise a polymer resin comprising a covalently attached flame retardant.

The resin, if present, may be added to the fibers in any suitable manner, including for example, in a wet state. In some embodiments, the resin coats the fibers and serves to adhere the fibers to each other to promote adhesion between the fibers. The fibers may be coated using any suitable method and apparatus, for example, using curtain coating, gravure coating, melt coating, dip coating, knife roll coating, spin coating, or the like. In some embodiments, the binder precipitates when added to the fiber blend. Any suitable precipitating agent (e.g., epichlorohydrin) may be provided to the fibers as appropriate, for example, by injection into the blend. In some embodiments, the resin, when added to the fibers, is added in a manner such that one or more layers or the entire filter media are impregnated with the resin (e.g., the resin permeates the monolith). In a multilayer web, the resin may be added to each layer separately before the layers are combined, or the resin may be added to the layers after the layers are combined. In some embodiments, the resin is added to the fibers while in a dry state, for example, by spraying or saturated impregnation, or any of the above methods. In other embodiments, the resin is added to the wet layer.

In certain embodiments, a binder may be present in the layer, and the binder may include both binding fibers and a binder resin.

In some embodiments, the filter media can include one or more support layers (e.g., first layer, third layer, fifth layer), and the weight% of the binder resin in the support layer or layers (e.g., first layer, third layer, fifth layer) can be greater than or equal to 0 weight%, greater than or equal to 5 weight%, greater than or equal to 10 weight%, greater than or equal to 15 weight%, greater than or equal to 20 weight%, greater than or equal to 25 weight%, greater than or equal to 30 weight%, greater than or equal to 40 weight%, greater than or equal to 50 weight%, greater than or equal to 60 weight%, greater than or equal to 70 weight%, or greater than or equal to 80 weight%. In some embodiments, the weight% of the binder resin in the support layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 90 weight%, less than or equal to 80 weight%, less than or equal to 70 weight%, less than or equal to 60 weight%, less than or equal to 50 weight%, less than or equal to 40 weight%, less than or equal to 30 weight%, less than or equal to 25 weight%, less than or equal to 20 weight%, less than or equal to 15 weight%, less than or equal to 10 weight%, or less than or equal to 5 weight%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 90 wt%, or greater than or equal to 10 wt% and less than or equal to 30 wt%). Other ranges are also possible.

In some embodiments, the filter media can include at least one support layer, and the support layer or layers (e.g., first layer, third layer, fifth layer) can include one or more additives. In some embodiments, the additive may include, for example, one or more of an antimicrobial additive, an antifungal additive, a UV protectant, an antioxidant, or other components. In some embodiments, the weight% of the additive of the support layer or layers (e.g., first layer, third layer, fifth layer) can be greater than or equal to 0 weight%, greater than or equal to 2 weight%, greater than or equal to 4 weight%, greater than or equal to 6 weight%, or greater than or equal to 8 weight%. In some embodiments, the weight% of the additive of the support layer or layers (e.g., first layer, third layer, fifth layer) can be less than or equal to 10 weight%, less than or equal to 8 weight%, less than or equal to 6 weight%, less than or equal to 4 weight%, or less than or equal to 2 weight%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 10 wt%). Other ranges are also possible. Each additive may be added independently of each other in one or more of the above ranges.

In some embodiments where the filter media comprises at least one support layer (e.g., first layer, third layer, fifth layer), the thickness of the support layer or layers (e.g., first layer, third layer, fifth layer) can be greater than or equal to 0.05mm, greater than or equal to 0.1mm, greater than or equal to 0.25mm, greater than or equal to 0.38mm, greater than or equal to 0.5mm, greater than or equal to 1mm, greater than or equal to 2mm, or greater than or equal to 3 mm. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) can have a thickness of less than or equal to 5mm, less than or equal to 3mm, less than or equal to 2mm, less than or equal to 1mm, less than or equal to 0.5mm, less than or equal to 0.38mm, less than or equal to 0.25mm, or less than or equal to 0.1 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.25mm and less than or equal to 2mm, greater than or equal to 0.38mm and less than or equal to 1mm, greater than or equal to 0.05mm and less than or equal to 5mm, or greater than or equal to 0.1mm and less than or equal to 3 mm). Other ranges are also possible. The thickness of the support layer or layers may be determined according to standard ISO 534 at 50 kPa.

In embodiments where the filter media includes at least one support layer (e.g., first layer, third layer, fifth layer), the support layer or layers can have any suitable basis weight. In some embodiments, the basis weight of the support layer or layers (e.g., first layer, third layer, fifth layer) can be greater than or equal to 10g/m²Greater than or equal to 20g/m²Greater than or equal to 35g/m²Greater than or equal to 40g/m²80g/m or more²Greater than or equal to 120g/m²Greater than or equal to 150g/m²Greater than or equal to 200g/m²Or greater than or equal to 250g/m². In some embodiments, the basis weight of the support layer or layers (e.g., first layer, third layer, fifth layer) can be less than or equal to 300g/m²Less than or equal to 250g/m²Less than or equal to 200g/m²Less than or equal to 150g/m²Less than or equal to 120g/m²Less than or equal to 80g/m²Less than or equal to 40g/m²Less than or equal to 35g/m²Or less than or equal to 20g/m². Combinations of the above ranges are also possible (e.g., greater than or equal to 10 g/m)²And less than or equal to 300g/m²Greater than or equal to 10g/m²And less than or equal to 150g/m²Greater than or equal to 20g/m²And less than or equal to 200g/m ²Greater than or equal to 40g/m²And is less than or equal to 120g/m²Or greater than or equal to 35g/m²And less than or equal to 80g/m²). Other ranges are also possible. The basis weight may be determined according to standard ISO 536.

In some embodiments where the filter media comprises at least one support layer (e.g., first layer, third layer, fifth layer), the support layer or layers (e.g., first layer, third layer, fifth layer) can have a mean flow pore size of greater than or equal to 20 microns, greater than or equal to 50 microns, greater than or equal to 70 microns, greater than or equal to 100 microns, greater than or equal to 150 microns, greater than or equal to 200 microns, or greater than or equal to 250 microns. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) can have a mean flow pore size of less than or equal to 300 microns, less than or equal to 250 microns, less than or equal to 200 microns, less than or equal to 150 microns, less than or equal to 100 microns, less than or equal to 70 microns, or less than or equal to 50 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 20 micrometers and less than or equal to 300 micrometers, or greater than or equal to 50 micrometers and less than or equal to 150 micrometers). Other ranges are also possible. The mean flow pore diameter can be determined according to the standard ASTM F316-03.

In some embodiments, the filter media can include one or more support layers (e.g., first layer, third layer, fifth layer), and the air permeability of the support layer or layers (e.g., first layer, third layer, fifth layer) can be greater than or equal to 10CFM, greater than or equal to 20CFM, greater than or equal to 50CFM, greater than or equal to 75CFM, greater than or equal to 100CFM, greater than or equal to 200CFM, greater than or equal to 500CFM, greater than or equal to 800CFM, or greater than or equal to 1000 CFM. In some embodiments, the air permeability of the support layer or layers may be less than or equal to 1400CFM, less than or equal to 1000CFM, less than or equal to 800CFM, less than or equal to 500CFM, less than or equal to 200CFM, less than or equal to 100CFM, less than or equal to 75CFM, less than or equal to 50CFM, or less than or equal to 20 CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 10CFM and less than or equal to 1400CFM, greater than or equal to 20CFM and less than or equal to 500CFM, greater than or equal to 50CFM and less than or equal to 800CFM, or greater than or equal to 200CFM and less than or equal to 500 CFM). Other ranges are also possible. Air permeability may be determined using TAPPI method T251.

In some embodiments where the filter media comprises a support layer or layers (e.g., first layer, third layer, fifth layer), the support layer or layers may be capable of removing particulates at certain efficiency levels as measured by EN1822:2009 standard as described herein. In some embodiments, the efficiency of the support layer can be greater than or equal to 20%, greater than or equal to 25%, greater than or equal to 30%, greater than or equal to 35%, greater than or equal to 40%, greater than or equal to 45%, greater than or equal to 50%, greater than or equal to 55%, greater than or equal to 60%, greater than or equal to 65%, greater than or equal to 70%, greater than or equal to 75%, greater than or equal to 80%, greater than or equal to 85%, greater than or equal to 90%, greater than or equal to 95%, greater than or equal to 97%, greater than or equal to 99%, or greater than or equal to 99.5%. In some embodiments, the efficiency of the support layer or layers (e.g., first layer, third layer, fifth layer) can be less than or equal to 99.5%, less than or equal to 99%, less than or equal to 97%, less than or equal to 95%, less than or equal to 90%, less than or equal to 85%, less than or equal to 80%, less than or equal to 70%, less than or equal to 60%, less than or equal to 50%, less than or equal to 40%, or less than or equal to 30%. Combinations of the above ranges are also possible (e.g., greater than or equal to 20% and less than or equal to 80%). In embodiments where both a support layer and a main filtration layer are present in the filter media, the main filtration layer may have a higher efficiency than the efficiency of the support layer.

In some embodiments, the support layer (e.g., first layer, third layer, fifth layer) is flame retardant or comprises one or more flame retardant components. For example, the support layer may comprise flame retardant fibers, flame retardant binders, flame retardant coatings, and/or flame retardant additives (e.g., flame retardant particles, flame retardant flakes). The flame retardant component may be introduced during manufacture (e.g., during a melt blowing process, a melt spinning process, an electrospinning process, a centrifugal spinning process, a wet-laid process, a dry-laid process, or an air-laid process) or may be added to the binder.

In embodiments where the filter media includes a support layer or layers (e.g., first layer, third layer, fifth layer), the support layer or layers can have any suitable dry tensile strength in the cross direction. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) have a dry tensile strength in the cross direction of greater than or equal to 1 lb/inch, greater than or equal to 2 lb/inch, greater than or equal to 4 lb/inch, greater than or equal to 6 lb/inch, greater than or equal to 8 lb/inch, greater than or equal to 10 lb/inch, greater than or equal to 12 lb/inch, greater than or equal to 15 lb/inch, or greater than or equal to 17 lb/inch. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) have a dry tensile strength in the cross direction of less than or equal to 20 lbs/inch, less than or equal to 17 lbs/inch, less than or equal to 15 lbs/inch, less than or equal to 12 lbs/inch, less than or equal to 10 lbs/inch, less than or equal to 8 lbs/inch, less than or equal to 6 lbs/inch, less than or equal to 4 lbs/inch, or less than or equal to 2 lbs/inch. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 lb/inch and less than or equal to 20 lb/inch, or greater than or equal to 6 lb/inch and less than or equal to 15 lb/inch). Other ranges are also possible. The dry tensile strength in the cross machine direction can be determined according to standard T494 om-96 using a test span of 4 inches and a jaw separation speed of 1 inch/minute.

In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) have a dry tensile strength in the machine direction of greater than or equal to 2 lbs/inch, greater than or equal to 5 lbs/inch, greater than or equal to 10 lbs/inch, greater than or equal to 15 lbs/inch, greater than or equal to 20 lbs/inch, greater than or equal to 25 lbs/inch, greater than or equal to 30 lbs/inch, greater than or equal to 35 lbs/inch, greater than or equal to 40 lbs/inch, greater than or equal to 45 lbs/inch, greater than or equal to 50 lbs/inch, or greater than or equal to 55 lbs/inch. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) have a dry tensile strength in the machine direction of less than or equal to 60 lbs/inch, less than or equal to 55 lbs/inch, less than or equal to 50 lbs/inch, less than or equal to 45 lbs/inch, less than or equal to 40 lbs/inch, less than or equal to 35 lbs/inch, less than or equal to 30 lbs/inch, less than or equal to 25 lbs/inch, less than or equal to 20 lbs/inch, less than or equal to 15 lbs/inch, less than or equal to 10 lbs/inch, or less than or equal to 5 lbs/inch. Combinations of the above ranges are also possible (e.g., greater than or equal to 2 lbs/inch and less than or equal to 60 lbs/inch, or greater than or equal to 10 lbs/inch and less than or equal to 40 lbs/inch). Other ranges are also possible. The dry tensile strength in the machine direction can be determined according to standard T494om-96 using a test span of 4 inches and a jaw separation speed of 1 inch/minute.

In some embodiments where the filter media includes at least one support layer (e.g., first layer, third layer, fifth layer), the dry mullen burst strength of the support layer or layers (e.g., first layer, third layer, fifth layer) can be greater than or equal to 20psi, greater than or equal to 30psi, greater than or equal to 50psi, greater than or equal to 75psi, greater than or equal to 100psi, greater than or equal to 125psi, greater than or equal to 150psi, greater than or equal to 175psi, greater than or equal to 200psi, or greater than or equal to 225 psi. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) has a dry mullen burst strength of less than or equal to 250psi, less than or equal to 225psi, less than or equal to 200psi, less than or equal to 175psi, less than or equal to 150psi, less than or equal to 125psi, less than or equal to 100psi, less than or equal to 75psi, less than or equal to 50psi, or less than or equal to 30 psi. Combinations of the above ranges are also possible (e.g., greater than or equal to 20psi and less than or equal to 250psi, or greater than or equal to 30psi and less than or equal to 150 psi). Other ranges are also possible. The dry Marlon burst strength can be determined according to the standard T403 om-91.

In embodiments where the filter media includes at least one support layer (e.g., first layer, third layer, fifth layer), the support layer or layers can have any suitable Gurley stiffness. Stiffness may be measured in the machine direction, or it may be measured in the cross direction. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) has a Gurley stiffness in the cross direction of greater than or equal to 10mg, greater than or equal to 20mg, greater than or equal to 50mg, greater than or equal to 100mg, greater than or equal to 200mg, greater than or equal to 500mg, greater than or equal to 1000mg, or greater than or equal to 2000 mg. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) has a Gurley stiffness in the cross direction of less than or equal to 3500mg, less than or equal to 2000mg, less than or equal to 1000mg, less than or equal to 500mg, less than or equal to 200mg, less than or equal to 100mg, less than or equal to 50mg, or less than or equal to 20 mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 10mg and less than or equal to 3500mg, or greater than or equal to 200mg and less than or equal to 1000 mg). Other ranges are also possible. Stiffness can be determined according to TAPPI T543 om-94 using Gurley stiffness (bending resistance) reported in mm (corresponding to gu).

In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) has a Gurley stiffness in the machine direction of greater than or equal to 150mg, greater than or equal to 200mg, greater than or equal to 350mg, greater than or equal to 500mg, greater than or equal to 1000mg, greater than or equal to 1500mg, greater than or equal to 2000mg, greater than or equal to 2500mg, or greater than or equal to 3000 mg. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) has a Gurley stiffness in the machine direction of less than or equal to 3500mg, less than or equal to 3000mg, less than or equal to 2500mg, less than or equal to 2000mg, less than or equal to 1500mg, less than or equal to 1000mg, less than or equal to 500mg, less than or equal to 350mg, or less than or equal to 200 mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 150mg and less than or equal to 3500mg, greater than or equal to 200mg and less than or equal to 2000mg, or greater than or equal to 350mg and less than or equal to 2000 mg). Other ranges are also possible. Stiffness can be determined according to TAPPI T543 om-94 using Gurley stiffness (bending resistance) reported in mm (corresponding to gu).

As described above, in some embodiments, an adhesive may be present in the filter media at one or more locations (e.g., between the first layer and the second layer, and/or between the second layer and the third layer, etc.). References herein to an adhesive without specifying the location of the adhesive should be understood to refer to the adhesive being present independently at each location in the filter media (if the adhesive is indeed present at any location). That is, at each location where an adhesive is present, the adhesive present there may or may not independently have any or none of the characteristics described below. In some embodiments, two or more locations in the filter media where the binder is present may comprise binders having similar compositions and/or properties. In other embodiments, each binder present in the filter media may have a different composition and/or characteristics.

In some embodiments, the binder or binders may be a solvent-based binder resin. As used herein, a solvent-based binder resin is a binder that is capable of undergoing a liquid to solid transition upon evaporation of the solvent from the resin. The solvent-based binder resin may be applied while in a liquid state. Subsequently, the solvent present can be evaporated to produce a solid binder. Thus, solvent-based adhesives may be considered distinct from hot melt adhesives that do not contain volatile solvents (e.g., solvents that evaporate under normal operating conditions) and typically undergo a liquid-to-solid transition when the adhesive cools.

Desirable properties of the adhesive may include sufficient tack and open time (i.e., the amount of time the adhesive remains tacky after exposure to ambient atmosphere). Without wishing to be bound by theory, the tack of the adhesive may depend on both the glass transition temperature of the adhesive and the molecular weight of any polymeric component of the adhesive. Higher glass transition values and lower molecular weight values can promote enhanced tack, and higher molecular weight values can result in higher cohesion and higher bond strength in the adhesive. In some embodiments, adhesives having a glass transition temperature and/or molecular weight within one or more of the ranges described herein can provide suitable values for both tack and open time. For example, the adhesive may be adapted and arranged to remain tacky for a relatively long period of time (e.g., the adhesive may remain tacky after complete evaporation of any solvent initially present, and/or may be tacky indefinitely when held at room temperature). In some embodiments, the open time of the adhesive may be less than or equal to 24 hours, less than or equal to 12 hours, less than or equal to 6 hours, less than or equal to 1 hour, less than or equal to 30 minutes, less than or equal to 15 minutes, less than or equal to 10 minutes, less than or equal to 5 minutes, less than or equal to 3 minutes, less than or equal to 1 minute, less than or equal to 30 seconds, or less than or equal to 10 seconds. In some embodiments, the open time of the adhesive may be at least 1 second, at least 10 seconds, at least 15 seconds, at least 30 seconds, at least 1 minute, at least 3 minutes, at least 5 minutes, at least 10 minutes, at least 15 minutes, at least 30 minutes, at least 1 hour, at least 6 hours, or at least 12 hours. Combinations of the above ranges are also possible (e.g., at least 1 second and less than or equal to 24 hours). Other values are also possible.

It is also believed that exposure to isopropyl alcohol (IPA) vapors may result in a filter containing the binder resin having a high pressure drop due to the binder being dissolved by IPA vapors, and the presence of a crosslinker in the binder may reduce such dissolution and pressure drop in some embodiments.

As described above, in some embodiments, an adhesive may be present between the first layer and the second layer and/or between other layers of the media (e.g., between the second layer and the third layer). The adhesive may be used to coat one or more layers using the solvent spray method described herein or using any other suitable method. Non-limiting examples of suitable adhesives include acrylates, acrylate copolymers, polyurethanes, polyesters, poly (vinyl alcohol), ethylene-vinyl acetate copolymers, silicone solvents, polyolefins, synthetic and/or natural rubbers, synthetic elastomers, ethylene-acrylic acid copolymers, ethylene-methacrylate copolymers, ethylene-methyl methacrylate copolymers, poly (vinylidene chloride), polyamides, epoxy resins, melamine resins, poly (isobutylene), styrene block copolymers, styrene-butadiene rubbers, aliphatic urethane acrylates, and phenolic resins.

In embodiments where there are three or more layers (e.g., a first layer, a second layer, and a third layer), each interface can comprise an adhesive independently selected from the adhesives described herein. In some embodiments, the adhesive at the first interface (e.g., between the first layer and the second layer) is different than the adhesive at the second interface (e.g., between the second adhesive and the third adhesive). In other embodiments, the adhesive at different interfaces is the same.

In some embodiments, when present, the binder may comprise a crosslinker. In some embodiments, the crosslinking agent is a small molecule (i.e., the crosslinking agent is not a polymer). In some embodiments, the small molecule cross-linking agent is one or more of the following: carbodiimides, isocyanates, aziridines, zirconium compounds (e.g., zirconium carbonate), metal acid esters, metal chelates, multifunctional propylene imines, and amino resins. In some embodiments, the adhesive comprises at least one polymer having one or more active sites capable of reacting with a crosslinker. Non-limiting examples of suitable reactive sites include alcohol groups, carboxylic acid groups, epoxy groups, amine groups, and amine groups.

In some embodiments, the adhesive does not contain a small molecule crosslinker, but the polymer molecules forming the adhesive can undergo self-crosslinking via functional groups attached to the polymer.

In some embodiments, a temperature may be applied to the adhesive to aid in solvent removal and/or to accelerate the rate of crosslinking. In some embodiments, the temperature can be greater than or equal to 24 ℃, greater than or equal to 40 ℃, greater than or equal to 50 ℃, greater than or equal to 60 ℃, greater than or equal to 70 ℃, greater than or equal to 80 ℃, greater than or equal to 90 ℃, greater than or equal to 100 ℃, greater than or equal to 110 ℃, greater than or equal to 120 ℃, greater than or equal to 130 ℃, or greater than or equal to 140 ℃. In some embodiments, the temperature can be less than or equal to 150 ℃, less than or equal to 140 ℃, less than or equal to 130 ℃, less than or equal to 120 ℃, less than or equal to 110 ℃, less than or equal to 100 ℃, less than or equal to 90 ℃, less than or equal to 80 ℃, less than or equal to 70 ℃, less than or equal to 60 ℃, less than or equal to 50 ℃, or less than or equal to 40 ℃. Combinations of the above ranges are also possible (e.g., greater than or equal to 24 ℃ and less than or equal to 150 ℃, or greater than or equal to 24 ℃ and less than or equal to 130 ℃). Other ranges are also possible.

When present, the small molecule crosslinker can constitute any suitable amount of binder. In some embodiments, the wt% of the crosslinking agent relative to the total mass of the binder and crosslinking agent present in a specified location of the filter media (e.g., between two layers, e.g., between a first layer and a second layer, or between a second layer and a third layer) can be greater than or equal to 0.1 wt%, greater than or equal to 0.2 wt%, greater than or equal to 0.5 wt%, greater than or equal to 1 wt%, greater than or equal to 2 wt%, greater than or equal to 5 wt%, greater than or equal to 10 wt%, greater than or equal to 15 wt%, greater than or equal to 20 wt%, or greater than or equal to 25 wt%. In some embodiments, the weight% of the small molecule crosslinker relative to the total mass of binder and crosslinker present in a given location (e.g., between two layers, e.g., between a first layer and a second layer, or between a second layer and a third layer) can be less than or equal to 30 weight%, less than or equal to 25 weight%, less than or equal to 20 weight%, less than or equal to 15 weight%, less than or equal to 10 weight%, less than or equal to 5 weight%, less than or equal to 2 weight%, less than or equal to 1 weight%, less than or equal to 0.5 weight%, or less than or equal to 0.2 weight%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 wt% and less than or equal to 30 wt%, or greater than or equal to 1 wt% and less than or equal to 20 wt%). Other ranges are also possible.

The binder and/or any small molecule crosslinking agent (if present) comprised by the binder may be capable of undergoing a crosslinking reaction at any suitable temperature. In some embodiments, the crosslinking agent may be capable of undergoing a crosslinking reaction at a temperature greater than or equal to 24 ℃, greater than or equal to 40 ℃, greater than or equal to 50 ℃, greater than or equal to 60 ℃, greater than or equal to 70 ℃, greater than or equal to 80 ℃, greater than or equal to 90 ℃, greater than or equal to 100 ℃, greater than or equal to 110 ℃, greater than or equal to 120 ℃, greater than or equal to 130 ℃, or greater than or equal to 140 ℃. In some embodiments, the adhesive and/or any small molecule crosslinker comprised by the adhesive may be capable of undergoing a crosslinking reaction at a temperature of less than or equal to 150 ℃, less than or equal to 140 ℃, less than or equal to 130 ℃, less than or equal to 120 ℃, less than or equal to 110 ℃, less than or equal to 100 ℃, less than or equal to 90 ℃, less than or equal to 80 ℃, less than or equal to 70 ℃, less than or equal to 60 ℃, less than or equal to 50 ℃, or less than or equal to 40 ℃. Combinations of the above ranges are also possible (e.g., greater than or equal to 25 ℃ and less than or equal to 150 ℃, or greater than or equal to 25 ℃ and less than or equal to 130 ℃). Other ranges are also possible.

In some embodiments where an adhesive is present in at least one location in the filter media (e.g., between two layers, such as between a first layer and a second layer, or between a second layer and a third layer), the adhesive or adhesives may comprise a solvent prior to applying the adhesive to the layers. In some embodiments, the binder or binders may be applied to the layer or filter medium while dissolved or suspended in a solvent. Non-limiting examples of suitable solvents include water, hydrocarbon solvents, ketones, aromatic solvents, fluorinated solvents, toluene, heptane, acetone, n-butyl acetate, methyl ethyl ketone, methylene chloride, naphtha, and mineral spirits (mineral spirits).

In some embodiments, the glass transition temperature of the adhesive may be relatively low. In some embodiments, the glass transition temperature of the adhesive can be less than or equal to 60 ℃, less than or equal to 50 ℃, less than or equal to 45 ℃, less than or equal to 40 ℃, less than or equal to 35 ℃, less than or equal to 30 ℃, less than or equal to 24 ℃, less than or equal to 25 ℃, less than or equal to 20 ℃, less than or equal to 15 ℃, less than or equal to 10 ℃, less than or equal to 5 ℃, less than or equal to 0 ℃, less than or equal to-5 deg.C, less than or equal to-10 deg.C, less than or equal to-20 deg.C, less than or equal to-30 deg.C, less than or equal to-40 deg.C, less than or equal to-50 deg.C, less than or equal to-60 deg.C, less than or equal to-70 deg.C, less than or equal to-80 deg.C, less than or equal to-90 deg.C, less than or equal to-100 deg.C, or less than or equal to-110 deg.C. In some embodiments, the glass transition temperature of the adhesive can be greater than or equal to-125 ℃, greater than or equal to-110 ℃, greater than or equal to-100 ℃, greater than or equal to-90 ℃, greater than or equal to-80 ℃, greater than or equal to-70 ℃, greater than or equal to-60 ℃, greater than or equal to-50 ℃, greater than or equal to-40 ℃, greater than or equal to-30 ℃, greater than or equal to-20 ℃, greater than or equal to-10 ℃, greater than or equal to 0 ℃, greater than or equal to 5 ℃, greater than or equal to 10 ℃, greater than or equal to 24 ℃, greater than or equal to 25 ℃, greater than or equal to 40 ℃, or greater than or equal to 50 ℃. Combinations of the above ranges are also possible (e.g., greater than or equal to-125 ℃ and less than or equal to 60 ℃, or greater than or equal to-100 ℃ and less than or equal to 25 ℃). Other ranges are also possible. The glass transition temperature value of the binder can be measured by differential scanning calorimetry.

The molecular weight of the binder can be selected as desired. In some embodiments, the number average molecular weight of the binding agent may be greater than or equal to 10kDa, greater than or equal to 30kDa, greater than or equal to 50kDa, greater than or equal to 100kDa, greater than or equal to 300kDa, greater than or equal to 500kDa, greater than or equal to 1000kDa, greater than or equal to 2000kDa, or greater than or equal to 3000 kDa. In some embodiments, the number average molecular weight of the binding agent may be less than or equal to 5000kDa, less than or equal to 4000kDa, less than or equal to 3000kDa, less than or equal to 1000kDa, less than or equal to 500kDa, less than or equal to 300kDa, less than or equal to 100kDa, less than or equal to 50kDa, or less than or equal to 30 kDa. Combinations of the above ranges are also possible (e.g., greater than or equal to 10kDa and less than or equal to 5000kDa, or greater than or equal to 30kDa and less than or equal to 3000 kDa). Other ranges are also possible. The number average molecular weight can be measured by light scattering.

In embodiments where the filter media comprises an adhesive in any single location (e.g., between two layers, such as between a first layer and a second layer, and/or between a second layer and a third layer), the adhesive or adhesives can have any suitable basis weight at that location. In some embodiments, the basis weight of the adhesive or adhesives at any single location may be greater than or equal to 0.05g/m ²0.1g/m or more²0.2g/m or more²0.5g/m or more²Greater than or equal to 1g/m²Greater than or equal to 2g/m²Or greater than or equal to 5g/m². In some embodiments, the basis weight of the adhesive or adhesives at any single location may be less than or equal to 10g/m²Less than or equal to 5g/m²Less than or equal to 2g/m²Less than or equal to 1g/m²Less than or equal to 0.5g/m²Less than or equal to 0.2g/m²Or less than or equal to 0.1g/m². Combinations of the above ranges are also possible (e.g., greater than or equal to 0.05 g/m)²And less than or equal to 10g/m²Or greater than or equal to 0.1g/m²And is less than or equal to 5g/m²). Other ranges are also possible. The basis weight of the adhesive at any single location may be determined according to standard ISO 536, where the basis weight of the filter media measured prior to applying the adhesive to the location is subtracted from the basis weight measured after applying the adhesive to the location to obtain the basis weight of the adhesive at the location.

In embodiments where the filter media comprises one or more binders, the total amount of binder in the filter media is totalThe weight (i.e., the sum of the basis weights of the adhesive at each location) can be greater than or equal to 0.05g/m ²0.1g/m or more²0.2g/m or more²0.5g/m or more²Greater than or equal to 1g/m²Greater than or equal to 2g/m²Or greater than or equal to 5g/m². In some embodiments, the total basis weight of the binder or binders may be less than or equal to 10g/m²Less than or equal to 5g/m²Less than or equal to 2g/m²Less than or equal to 1g/m²Less than or equal to 0.5g/m²Less than or equal to 0.2g/m²Or less than or equal to 0.1g/m². Combinations of the above ranges are also possible (e.g., greater than or equal to 0.05 g/m)²And less than or equal to 10g/m²Or greater than or equal to 0.1g/m²And is less than or equal to 5g/m²). Other ranges are also possible.

In some embodiments, the filter media may comprise an adhesive in at least one location, and the adhesive may be capable of adhering one layer to another layer (e.g., adhering a first layer to a second layer, and/or adhering a second layer to a third layer) with a relatively large bond strength. In some embodiments, the adhesive or adhesives may adhere the two layers together with the following bond strengths: greater than or equal to 100 g/inch²Greater than or equal to 150 g/inch²Greater than or equal to 200 g/inch ²500 g/inch or more²750 g/inch or more²Greater than or equal to 1000 g/inch²Greater than or equal to 1250 g/inch²Greater than or equal to 1500 g/inch²1750 g/inch or more²Greater than or equal to 2000 g/inch²2250 g/inch or more²2500 g/inch or more²2750 g/inch or more²Greater than or equal to 3000 g/inch²3250 g/inch or more²3500 g/inch or more²3750 g/inch or more²4000 g/inch or more²4250 g/inch or more²4500 g/inch or more²Or greater than or equal to 4750 g/inch². In some embodiments, the adhesive or adhesives may adhere the two layers together with the following bond strengths: less than or equal to 5000 g/inch²4750 g/inch or less²4500 g/inch or less²4250 g/inch or less²4000 g/inch or less²Less than or equal to 3750 g/inch²Less than or equal to 3500 g/inch²3250 g/inch or less²Less than or equal to 3000 g/inch²2750 g/inch or less²Less than or equal to 2500 g/inch²2250 g/inch or less ²Less than or equal to 2000 g/inch²1750 g/inch or less²Less than or equal to 1500 g/inch²1250 g/inch or less²Less than or equal to 1000 g/inch²750 g/inch or less²Less than or equal to 500 g/inch²Less than or equal to 200 g/inch²Or less than or equal to 150 g/inch². Combinations of the above ranges are also possible (e.g., greater than or equal to 100 g/inch)²And less than or equal to 5000 g/inch²Or greater than or equal to 150 g/inch²And less than or equal to 3000 g/inch²). Other ranges are also possible. In some embodiments, the entire filter media generally has an internal bond strength within one or more of the ranges described above. The bond strength of the overall filter media is generally equal to the weakest bond strength between the two layers of the media.

The bond strength (e.g., internal bond strength) between two layers (e.g., between a first layer and a second layer, between a second layer and a third layer) can be determined by using a z-direction peel strength test. In short, the bond strength was determined by mounting a 1 "x 1" sample on a steel block having dimensions of 1 "x 0.5" using double-sided tape. The sample block was mounted on the non-traversing head of the tensile tester with double-sided tape and another steel block of the same size was attached to the traversing head. The traversing head moves down and bonds to the sample on the steel block of the non-traversing head. Sufficient pressure is applied so that the blocks of steel are bonded together via the mounted sample. The traverse head was moved at a traverse speed of 1 "/minute, and the maximum load was obtained from the peak of the stress-strain curve. The bond strength (e.g., internal bond strength) between the two layers is considered to be equal to the maximum load.

As described herein, in certain embodiments, one or more layers (e.g., a first layer, a second layer, a third layer, a pre-filter layer, a main filter layer) may include oleophobic properties, may include an oleophobic component, and/or may be a surface modification layer. In some embodiments, one or more layers may include a coating (e.g., an oleophobic coating, an oleophobic component that is an oleophobic coating) and/or comprise a resin (e.g., an oleophobic resin, an oleophobic component that is an oleophobic resin). The coating process may involve chemical and/or physical deposition techniques. For example, the coating process may include introducing a resin or material (e.g., an oleophobic component that is a resin or material) dispersed in a solvent or solvent mixture into a pre-formed fibrous layer (e.g., a pre-formed web formed by a melt-blown process). As one example, the pre-filter layer may be sprayed with a coating material (e.g., a water-based fluorinated acrylate, such as AGE 550D). Non-limiting examples of coating methods include using vapor deposition (e.g., chemical vapor deposition, physical vapor deposition), layer-by-layer deposition, wax curing, self-assembly, sol-gel processing, slot die coater, gravure coating, wire screen coating, size press coating (e.g., double roll or metered knife size press), film press coating, knife coating, roll-knife coating, air knife coating, roll coating, foam application, reverse roll coating, rod coating, curtain coating, composite coating (champlexcooting), brush coating, Bill-blade coating, short dwell knife coating, lip coating, gate roll press coating, laboratory size press coating, melt coating, dip coating, knife roll coating, spin coating, powder coating, spray coating (e.g., electrospraying), notched roll transfer coating, filler saturation coating, and the like, Saturated immersion, chemical bath deposition and solution deposition. Other coating methods are also possible. The layer having oleophobic properties and/or being a surface modification layer can be charged or uncharged, and it is to be understood that any of the techniques described herein can be used to form a charged or uncharged layer.

In some embodiments, the coating material may be applied to the web using a non-compressive coating technique. The non-compressive coating technique can coat the web while not substantially reducing the thickness of the web. In other embodiments, the resin may be applied to the web using a compression coating technique.

Other techniques include vapor deposition methods. Such methods include Atmospheric Pressure Chemical Vapor Deposition (APCVD), Low Pressure Chemical Vapor Deposition (LPCVD), Metal Organic Chemical Vapor Deposition (MOCVD), Plasma Assisted Chemical Vapor Deposition (PACVD) or Plasma Enhanced Chemical Vapor Deposition (PECVD), Laser Chemical Vapor Deposition (LCVD), photochemical vapor deposition (PCVD), Chemical Vapor Infiltration (CVI), Chemical Beam Epitaxy (CBE), electron beam assisted radiation curing, and atomic layer deposition. In Physical Vapor Deposition (PVD), a thin film (e.g., a thin film comprising an oleophobic component) is deposited by condensing a vaporized form of the desired film material onto a substrate. The method involves physical processes such as high temperature vacuum evaporation followed by condensation, plasma sputter bombardment rather than chemical reaction, electron beam evaporation, molecular beam epitaxy and/or pulsed laser deposition.

In some embodiments, the surfaces of one or more layers (e.g., the surface of the first layer, the surface of the second layer, the surface of the third layer, the surface of the pre-filter layer, the surface of the main filter layer) may be modified with an additive (e.g., an oleophobic component that is an additive such as an oleophobic additive). In some embodiments, one or more layers (e.g., first layer, second layer, third layer, pre-filter layer, main filter layer) may comprise an additive or additives (e.g., an oleophobic component as an additive such as an oleophobic additive). The additives may be functional chemicals added to the polymer/thermoplastic fibers during the melt blowing process, electrospinning process, and/or extrusion process, which may cause the physical and chemical properties on the surface to be different from those of the polymer/thermoplastic fibers themselves after formation. For example, additives may be added to the electrospinning solution used to form one or more of the second layer, fourth layer, and main filtration layer. In some embodiments, the additive may migrate to the surface of the fiber during or after formation of the fiber material (polymer/thermoplastic) such that the surface of the fiber is modified with the additive, wherein the center of the fiber comprises more polymer/thermoplastic material. In some embodiments, one or more additives are included to render the surface of the fiber oleophobic as described herein. For example, the additive may be an oleophobic material as described herein. Non-limiting examples of suitable additives include fluorinated acrylates, fluorosurfactants, oleophobic silicones, fluoropolymers, fluoromonomers, fluorooligomers, and oleophobic polymers.

If present, the additive (e.g., the oleophobic component in the form of an additive) can be present in any suitable form prior to undergoing a melt-blowing, electrospinning or wet-laying procedure or in any suitable form in the fiber after the fiber is formed. For example, in some embodiments, the additive may be in the form of a liquid (e.g., molten) that is mixed with the thermoplastic material prior to or during fiber formation. In some cases, the additives may be in particulate form before, during, or after the fibers are formed. In certain embodiments, particles of the melt additive may be present in the fully formed fibers. In some embodiments, the additive may be a component of the binder, and/or may be added to one or more layers by spraying the layers with a composition comprising the additive. If particulate, the additive may have any suitable morphology (e.g., particles of different shapes and sizes, flakes, spheroids, fibers).

Any suitable size of additive particles (e.g., particles that are the oleophobic component of the additive) can be included with the fiber-forming thermoplastic material to form and/or be present in the fully formed fiber. For example, the particles can have an average particle size (e.g., average diameter or average cross-sectional dimension) of greater than or equal to about 0.002 microns, greater than or equal to about 0.01 microns, greater than or equal to about 0.05 microns, greater than or equal to about 0.1 microns, greater than or equal to about 0.5 microns, greater than or equal to about 1 micron, greater than or equal to about 5 microns, greater than or equal to about 10 microns, greater than or equal to about 20 microns, greater than or equal to about 50 microns, greater than or equal to about 100 microns, or greater than or equal to about 200 microns. The average particle size of the particles can be, for example, less than or equal to about 300 microns, less than or equal to about 200 microns, less than or equal to about 100 microns, less than or equal to about 50 microns, less than or equal to about 30 microns, less than or equal to about 15 microns, less than 10 microns or equal to about 10 microns, less than or equal to about 5 microns, less than or equal to about 1 micron, less than or equal to about 0.1 microns, or less than or equal to about 0.01 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to about 0.01 micrometers and less than or equal to about 10 micrometers). Other ranges are also possible. The average particle size as used herein is measured by dynamic light scattering.

In some embodiments, a material (e.g., an oleophobic component, a precursor that reacts to form the oleophobic component) can undergo a chemical reaction (e.g., polymerization) after being applied to a layer (e.g., a first layer, a second layer, a third layer, a pre-filter layer, a main filter layer). For example, the surface of the layer may be coated with one or more monomers that polymerize after coating. In another example, the surface of the layer may comprise monomers that polymerize after formation of the web due to the melt additive. In some such embodiments, in-line polymerization may be used. In-line polymerization (e.g., in-line ultraviolet polymerization) is a process of curing a monomer or liquid polymer solution on a substrate under conditions sufficient to induce polymerization (e.g., under UV irradiation).

The term "self-assembled monolayer" (SAM) refers to a molecular assembly that can form spontaneously by immersing a suitable substrate in a solution of an active surfactant in an organic solvent to produce an oleophobic surface.

In wax solidification, the layer is immersed in molten Alkyl Ketene Dimer (AKD) heated at 90 ℃ and then dried N at room temperature₂Cooling in a gas atmosphere. AKD undergoes fractal growth as it solidifies and improves the oleophobicity of the substrate.

In some embodiments, the substance used to form the surface modification layer (e.g., the surface modified first layer, the surface modified second layer, the surface modified third layer, the surface modified pre-filter layer, the surface modified main filter layer) or as a component of the surface modification layer (e.g., the oleophobic component, a precursor that reacts to form the oleophobic component) can comprise a small molecule, such as an inorganic or organic oleophobic molecule. Non-limiting examples include hydrocarbons (e.g., CH)₄、C₂H₂、C₂H₄、C₆H₆) Fluorocarbons (e.g., fluoroaliphatic, fluoroaromatic, fluoropolymer, fluorocarbon block copolymer, fluorocarbon acrylate polymer, fluorocarbon methacrylate polymer, fluoroelastomer, fluorosilane, fluorosiloxane, fluoro polyhedral oligomeric silsesquioxane, fluorinated dendrimer, inorganic fluorine compound, CF₄、C₂F₄、C₃F₆、C₃F₈、C₄H₈、C₅H₁₂、C₆F₆、SF₃、SiF₄、BF₃) Silane (e.g. SiH)₄、Si₂H₆、Si₃H₈、Si₄H₁₀) Organosilanes (e.g., methylsilane, dimethylsilane, triethylsilane), siloxanes (e.g., dimethylsiloxane, hexamethyldisiloxane), ZnS, CuSe, InS, CdS, tungsten, silicon carbide, silicon nitride, silicon oxynitride, titanium nitride, carbon, silicon-germanium and hydrophobic acrylic monomers end-capped with alkyl groups and halogenated derivatives thereof (e.g., ethyl 2-ethacrylate, methyl methacrylate, acrylonitrile). In certain embodiments, suitable hydrocarbons for modifying the surface of a layer may have the formula C _xH_yWherein x is an integer of 1 to 10 and y is an integer of 2 to 22. In certain embodiments, a suitable silane for modifying the surface of a layer may have the formula Si_nH_2n+2Wherein any hydrogen may be substituted with a halogen (e.g., Cl, F, Br, I), and wherein n is an integer from 1 to 10. In some embodiments, materials or articles for forming surface modification layersThe substance that is a component of the surface modification layer may comprise one or more of a wax, a silicone, and a corn-based polymer (e.g., zein). In some embodiments, the substance used to form or as a component of the surface modification layer may comprise one or more nanoparticle materials. Other compositions are also possible.

As used herein, "small molecule" refers to a molecule having a relatively low molecular weight, whether naturally occurring or artificially produced (e.g., via chemical synthesis). Typically, the small molecule is an organic compound (i.e., it comprises carbon). Small organic molecules may contain multiple carbon-carbon bonds, stereocenters, and other functional groups (e.g., amines, hydroxyls, carbonyls, and heterocycles, etc.). In certain embodiments, the small molecule has a molecular weight of at most about 1,000g/mol, at most about 900g/mol, at most about 800g/mol, at most about 700g/mol, at most about 600g/mol, at most about 500g/mol, at most about 400g/mol, at most about 300g/mol, at most about 200g/mol, or at most about 100 g/mol. In certain embodiments, the small molecule has a molecular weight of at least about 100g/mol, at least about 200g/mol, at least about 300g/mol, at least about 400g/mol, at least about 500g/mol, at least about 600g/mol, at least about 700g/mol, at least about 800g/mol, or at least about 900g/mol, or at least about 1,000 g/mol. Combinations of the above ranges (e.g., at least about 200g/mol and at most about 500g/mol) are also possible.

In some embodiments, the substance used to form or as a component of the surface modification layer (e.g., the oleophobic component, the precursor that reacts to form the oleophobic component) can include a cross-linking agent (e.g., the surface modified first layer, the surface modified second layer, the surface modified third layer, the surface modified pre-filter layer, the surface modified main filter layer). Non-limiting examples of suitable crosslinking agents include materials having one or more acrylate groups, such as 1, 6-hexanediol diacrylate and alkoxylated cyclohexanedimethanol diacrylate.

In some embodiments, the surface of a layer (e.g., the surface of a first layer, the surface of a second layer, the surface of a third layer, the surface of a pre-filter layer, the surface of a main filter layer) may be modified by roughening the surface or the material on the surface of the layer. In some such cases, the surface modification may be a roughened surface or material. The surface of the layer or the surface roughness of the material on the surface of the layer may be microscopically and/or macroscopically roughened. Non-limiting examples of methods for increasing roughness include modifying the surface with certain fibers, blending fibers with different diameters, and photolithography. In certain embodiments, fibers having different diameters (e.g., staple fibers, continuous fibers) may be mixed or used to increase or decrease surface roughness. In some embodiments, electrospinning can be used to produce an applied surface roughness alone or in combination with other methods (e.g., chemical vapor deposition). In some embodiments, photolithography may be used to roughen the surface. Photolithography includes many different types of surface treatments in which a design is transferred from a master onto a surface.

In some embodiments, the roughness of the layer (e.g., roughness of the first layer, roughness of the second layer, roughness of the third layer, roughness of the pre-filter layer, roughness of the main filter layer) may be used to alter the wettability of the layer with respect to a particular fluid. In some cases, the roughness may alter or enhance the wettability of the surface of the layer. In some cases, roughness may be used to enhance the oleophobicity of an intrinsically oleophobic surface. One of ordinary skill in the art will appreciate methods of altering the roughness of the surface of the web.

As described above, in some embodiments, the filter media can include one or more layers having an oil grade of greater than or equal to 1 (e.g., a first layer having an oil grade of greater than or equal to 1, a second layer having an oil grade of greater than or equal to 1, a third layer having an oil grade of greater than or equal to 1, a pre-filter layer having an oil grade of greater than or equal to 1, a main filter layer having an oil grade of greater than or equal to 1, a layer furthest upstream having an oil grade of greater than or equal to 1). The oil grade may be due to fibers within the layer that inherently have an oil grade greater than or equal to 1 (e.g., poly (tetrafluoroethylene) fibers), may be due to surface modification that increases the oil grade of the fibers within the layer having the initially lower oil grade, and/or may be due to an oleophobic component that increases the oil grade of the layer. The layer with the relatively high oil grade may or may not be charged. In some embodiments, the oil grade of one or more layers within the filter media is greater than or equal to 1, greater than or equal to 2, greater than or equal to 3, greater than or equal to 4, greater than or equal to 4.5, greater than or equal to 5, greater than or equal to 5.5, greater than or equal to 6, greater than or equal to 6.5, greater than or equal to 7, or greater than or equal to 7.5. In some embodiments, the oil grade of one or more layers within the filter media is less than or equal to 8, less than or equal to 7.5, less than or equal to 7, less than or equal to 6.5, less than or equal to 6, less than or equal to 5.5, less than or equal to 5, less than or equal to 4.5, less than or equal to 4, less than or equal to 3, or less than or equal to 2. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 and less than or equal to 8, greater than or equal to 1 and less than or equal to 6, or greater than or equal to 5 and less than or equal to 6). Other ranges are also possible.

Oil grades as described herein were determined according to AATCC TM 118(1997) at 23 ℃ and 50% Relative Humidity (RH). Briefly, 5 drops of each test oil (average drop diameter of about 2mm) were placed on five different locations on the surface of the web. A test oil having a maximum oil surface tension that does not wet the surface of the web (e.g., a contact angle with the surface of greater than or equal to 90 degrees) after 30 seconds of contact with the web at 23 ℃ and 50% RH corresponds to an oil grade (listed in table 1). For example, if a test oil with a surface tension of 26.6mN/m does not wet (i.e., has a contact angle with the surface of greater than or equal to 90 degrees) the surface of the web after 30 seconds, but a test oil with a surface tension of 25.4mN/m wets the surface of the web within 30 seconds, the web has an oil rating of 4. As another example, if a test oil with a surface tension of 25.4mN/m does not wet the surface of the web after 30 seconds, but a test oil with a surface tension of 23.8mN/m wets the surface of the web within 30 seconds, the web has an oil rating of 5. As yet another example, if a test oil with a surface tension of 23.8mN/m does not wet the surface of the web after 30 seconds, but a test oil with a surface tension of 21.6mN/m wets the surface of the web within 30 seconds, the web has an oil rating of 6. In some embodiments, if three or more of the five droplets partially wet the surface in a given test (e.g., droplets are formed on the surface, but not rounded droplets), the oil grade is expressed as the closest 0.5 value determined by subtracting 0.5 from the number of test liquids. As an example, if a test oil with a surface tension of 25.4mN/m does not wet the surface of the web after 30 seconds, but a test oil with a surface tension of 23.8mN/m only partially wets the surface of the web within 30 seconds after 30 seconds (e.g., three or more test droplets form droplets that are not rounded droplets on the surface of the web), the web has an oil rating of 5.5.

TABLE 1

In some embodiments, the filter media as a whole may have one or more desired properties. For example, the filter media may be a High Energy Particulate Air (HEPA) or Ultra Low Penetration Air (ULPA) filter. According to EN 1822: 2009, these filters need to remove particulates at efficiency levels greater than 99.95% and 99.9995%, respectively. In some embodiments, the filter media can remove particulates with an efficiency of greater than 95%, greater than 99.995%, or greater than 99.99995%, or up to 99.999995%. In some embodiments, the filter media may be suitable for HVAC applications. That is, the particulate efficiency of the filter media may be greater than or equal to about 10% and less than or equal to about 90%, or greater than or equal to about 35% and less than or equal to about 90%. The HEPA, ULPA, or HVAC filter media may include, for example, a pre-filter layer disposed upstream of a main filter layer and a support layer disposed downstream of the main filter layer. In some embodiments, the HEPA, ULPA, or HVAC filter may include a melt-blown pre-filter layer (e.g., basis weight of, for example, 3 g/m)²To 40g/m²Melt blown polypropylene pre-filter layer), an electrospun main filter layer (e.g., having a basis weight of, for example, 0.01 g/m)²To 5g/m ²Including, for example, 40nm to 300nmNylon electrospun main filtration layer) and a support layer (e.g., having a basis weight of, for example, 35g/m²To 80g/m²A wet laid synthetic support layer). Other types of filter media and efficiencies are also possible. In some embodiments, the filtration media may be a HEPA, ULPA, or HVAC filter and may be one component of a filter element as described in more detail below.

The filter media as a whole may have any suitable stiffness. Stiffness may be measured in the machine direction, or it may be measured in the cross direction. In some embodiments, the filter media has a Gurley stiffness in the cross direction of greater than or equal to 50mg, greater than or equal to 100mg, greater than or equal to 150mg, greater than or equal to 200mg, greater than or equal to 250mg, greater than or equal to 300mg, greater than or equal to 350mg, greater than or equal to 400mg, greater than or equal to 450mg, greater than or equal to 500mg, greater than or equal to 1000mg, greater than or equal to 1500mg, greater than or equal to 2000mg, or greater than or equal to 3000 mg. In some embodiments, the filter media has a Gurley stiffness in the cross direction of less than or equal to 3500mg, less than or equal to 3000mg, less than or equal to 2000mg, less than or equal to 1500mg, less than or equal to 1000mg, less than or equal to 500mg, less than or equal to 450mg, less than or equal to 400mg, less than or equal to 350mg, less than or equal to 300mg, less than or equal to 250mg, less than or equal to 200mg, less than or equal to 150mg, or less than or equal to 100 mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 50mg and less than or equal to 3000mg, or greater than or equal to 100mg and less than or equal to 1500 mg). Other ranges are also possible. Stiffness can be determined according to TAPPI T543 om-94 using Gurley stiffness (bending resistance) reported in mm (corresponding to gu).

In some embodiments, the filter media has a Gurley stiffness in the machine direction of greater than or equal to 100mg, greater than or equal to 150mg, greater than or equal to 200mg, greater than or equal to 250mg, greater than or equal to 300mg, greater than or equal to 350mg, greater than or equal to 400mg, greater than or equal to 450mg, greater than or equal to 350mg, greater than or equal to 500mg, greater than or equal to 1000mg, greater than or equal to 1500mg, greater than or equal to 2000mg, greater than or equal to 2500mg, or greater than or equal to 3000 mg. In some embodiments, the support layer or layers has a Gurley stiffness in the machine direction of less than or equal to 3500mg, less than or equal to 3000mg, less than or equal to 2500mg, less than or equal to 2000mg, less than or equal to 1500mg, less than or equal to 1000mg, less than or equal to 500mg, less than or equal to 350mg, less than or equal to 450mg, less than or equal to 400mg, less than or equal to 350mg, less than or equal to 300mg, less than or equal to 250mg, less than or equal to 200mg, or less than or equal to 150 mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 100mg and less than or equal to 3000mg, or greater than or equal to 150mg and less than or equal to 3000 mg). Other ranges are also possible. Stiffness can be determined according to TAPPI T543 om-94 using Gurley stiffness (bending resistance) reported in mm (corresponding to gu).

Because it may be desirable to rank a filter media or layer based on the relationship between the rate of penetration across the media and the pressure drop, or the particulate efficiency as a function of the pressure drop across the media or web, the filter media may be ranked according to a value known as the gamma value. In general, a higher gamma value indicates better filtration performance, i.e., high particulate efficiency as a function of pressure drop. The gamma value is expressed according to the following formula: gamma (-log)₁₀(MPPS penetration%/100)/pressure drop, mm H₂O) x 100, where MPPS penetration is equal to MPPS penetration as described below and may be measured using EN1822:2009 standard as described below. As described below, γ may be measured before undergoing exposure to IPA vapor or after undergoing exposure to IPA vapor. The MPPS penetration for any given gamma value is the penetration at MPPS measured when that gamma value was measured. Unless otherwise noted, reference to γ should be considered to refer to the γ value measured before the filter media is subjected to exposure to IPA vapor and DOP oil loading. In this case, the relevant MPPS is the MPPS value prior to exposure to IPA vapor discharge and DOP oil loading, and the relevant MPPS penetration value is the MPPS penetration value prior to exposure to IPA vapor discharge and DOP oil loading.

The penetration rate, often expressed as a percentage, is defined as follows: penetration (%) ═ C/C₀) 100, wherein C is in passing through the filterSubsequent particle concentration, C₀Is the concentration of particles before passing through the filter. A typical test for penetration includes blowing dioctyl phthalate (DOP) particles through a filter media or layer and measuring the percentage of particles that penetrate the filter media or layer. Penetration values described herein were determined based on the EN1822:2009 standard for MPPS DOP particles using a TSI 3160 automated filter test unit from TSI, inc, equipped with a dioctyl phthalate generator for DOP aerosol testing. In this test, a set of particles varying in average diameter from 0.04 to 0.3 microns was produced by a particle generator. The instrument measures the penetration value across the filter media (or layer) by determining the DOP particle size at the highest penetration level of the measurement test (i.e., the Most Penetrating Particle Size (MPPS)). Thus, all γ values recited herein refer to the γ value at the most penetrating particle size. All penetration values, and thus the gamma values described herein, were determined as follows: continuous loading with DOP particles and having the upstream face of the layer at 100cm of the web ²The surface area was subjected to a 12 liter/min air flow, resulting in a media face velocity of 2 cm/sec. Particles having sizes of 0.04 microns, 0.08 microns, 0.12 microns, 0.16 microns, 0.2 microns, 0.26 microns, and 0.3 microns with a geometric standard deviation of less than 1.3 are produced, and the filter media is sequentially exposed to the particles of each size. The penetration of the particles was plotted as a function of particle size and the data was fitted with a parabolic function. Then, obtaining the maximum value of the parabolic function; the particle size at the maximum is the Most Penetrating Particle Size (MPPS) and the penetration at the maximum is the penetration at MPPS.

The pressure drop value (e.g., for determining γ) is determined by an air resistance test based on EN1822:2009 standard using a TSI 3160 automated filter test unit from TSI, inc. The instrument measures the pressure drop across the filter media (or layer) when the filter media or layer is subjected to a 5.3 cm/sec face velocity.

The filter media as a whole may have a relatively high gamma value at MPPS (e.g., prior to exposure to IPA vapor discharge). In some embodiments, the filter media has a gamma value at MPPS of greater than or equal to 16, greater than or equal to 18, greater than or equal to 20, greater than or equal to 25, greater than or equal to 50, greater than or equal to 75, greater than or equal to 100, greater than or equal to 125, greater than or equal to 150, greater than or equal to 175, greater than or equal to 200, or greater than or equal to 225. In some embodiments, the filter media has a gamma value at MPPS of less than or equal to 250, less than or equal to 225, less than or equal to 200, less than or equal to 175, less than or equal to 150, less than or equal to 125, less than or equal to 100, less than or equal to 75, less than or equal to 50, less than or equal to 25, less than or equal to 20, or less than or equal to 18. Combinations of the above ranges are also possible (e.g., greater than or equal to 16 and less than or equal to 250, or greater than or equal to 18 and less than or equal to 150). Other ranges are also possible.

The filter media as a whole may have any suitable basis weight. In some embodiments, the basis weight of the filter media can be greater than or equal to 20g/m²Greater than or equal to 40g/m²Greater than or equal to 50g/m²75g/m or more²Greater than or equal to 100g/m²125g/m or more²Greater than or equal to 150g/m²175g/m or more²Greater than or equal to 200g/m²225g/m or more²Greater than or equal to 250g/m²Or 275g/m or more². In some embodiments, the basis weight of the filter media can be less than or equal to 300g/m²275g/m or less²Less than or equal to 250g/m²Less than or equal to 225g/m²Less than or equal to 200g/m²175g/m or less²Less than or equal to 150g/m²125g/m or less²Less than or equal to 100g/m²Less than or equal to 75g/m²Less than or equal to 50g/m²Or less than or equal to 40g/m². Combinations of the above ranges are also possible (e.g., greater than or equal to 20 g/m)²And less than or equal to 300g/m²Or 40g/m or more²And less than or equal to 200g/m²). Other ranges are also possible. The basis weight may be determined according to standard ISO 536.

In some embodiments, the filter media as a whole has a thickness of greater than or equal to 0.075mm, greater than or equal to 0.1mm, greater than or equal to 0.25mm, greater than or equal to 0.5mm, greater than or equal to 0.75mm, greater than or equal to 1mm, or greater than or equal to 2.5 mm. In some embodiments, the filter media has a thickness of less than or equal to 5mm, less than or equal to 2.5mm, less than or equal to 1mm, less than or equal to 0.75mm, less than or equal to 0.5mm, or less than or equal to 0.25 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.075mm and less than or equal to 5mm, or greater than or equal to 0.1mm and less than or equal to 1 mm). Other ranges are also possible. The thickness of the filter medium can be determined according to standard ISO 534 at 50 kPa.

In some embodiments, the average flow pore size of the filter media as a whole can be greater than or equal to 0.1 microns, greater than or equal to 0.2 microns, greater than or equal to 0.5 microns, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 5 microns, greater than or equal to 10 microns, greater than or equal to 20 microns, or greater than or equal to 40 microns. In some embodiments, the filter media can have a mean flow pore size of less than or equal to 60 microns, less than or equal to 40 microns, less than or equal to 20 microns, less than or equal to 10 microns, less than or equal to 5 microns, less than or equal to 2 microns, less than or equal to 1 micron, less than or equal to 0.5 microns, or less than or equal to 0.2 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 microns and less than or equal to 60 microns, or greater than or equal to 0.5 microns and less than or equal to 40 microns). Other ranges are also possible. The mean flow pore diameter can be determined according to the standard ASTM F316-03.

The pressure drop across the filter media can be any suitable value. In some embodiments, the pressure drop across the filter media may be greater than or equal to 0.5mm H₂O, 1mm H or more ₂O, 2mm H or more₂O, 5mm H or more₂O, 10mm H or more₂O, 20mm H or more₂O, 50mm H or more₂O, or greater than or equal to 100mmH₂And O. In some embodiments, across the filter mediaThe pressure drop may be less than or equal to 200mmH₂O, less than or equal to 100mm H₂O, less than or equal to 50mm H₂O, less than or equal to 20mmH₂O, less than or equal to 10mm H₂O, less than or equal to 5mm H₂O, less than or equal to 2mmH₂O, or 1mm H or less₂And O. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.5mm H₂O is less than or equal to 200mm H₂O, or 2mmH or more₂O is less than or equal to 100mm H₂O). Other ranges are also possible. Pressure drop can be determined using ASTM D2986-91.

In some embodiments, the filter media as a whole may perform particularly well after exposure to isopropyl alcohol (IPA) vapor (and, in some cases, before exposure to IPA vapor or oil loads). Such performance characteristics may include: the filter media has a relatively low pressure drop after exposure to IPA vapor, a relatively low change in pressure drop after IPA vapor exposure as compared to the same media prior to IPA vapor exposure, a high gamma value at MPPS after exposure to IPA vapor, and/or a relatively low change in gamma value after IPA vapor exposure as compared to the same media prior to IPA vapor exposure.

Typically, IPA vapor exposure is performed according to ISO 16890-4 standard. The filter media to be tested was cut into 6 inch by 6 inch squares and placed on the shelves of a metal shelf. The metal rack and media were then placed over a container containing at least 250mL 99.9 wt% IPA. After this step, the metal shelf, media and container were placed in a 24 inch by 18 inch by 11 inch chamber. A second container containing 250mL of 99.9 wt% IPA was then placed in the container above the top shelf of the metal shelf and the lid of the chamber was closed and tightly sealed. The device was held at 70 ° F and 50% relative humidity for at least 14 hours, after which the filter media was removed and allowed to dry at room temperature for 1 hour. The filter media characteristics after IPA exposure were then measured.

In some embodiments, the maximum pressure drop of the filter media as a whole after IPA exposure may be greater than or equal to 1mm H₂O, is greater thanOr equal to 3mm H₂O, 5mm H or more₂O, greater than or equal to 7.5mm H₂O, 10mm H or more₂O, 25mm H or more₂O, 50mm H or more₂O, or 75mm H or more₂And O. In some embodiments, the maximum pressure drop of the filter media after IPA exposure may be less than or equal to 100mm H ₂O, 75mm H or less₂O, less than or equal to 50mm H₂O, less than or equal to 25mm H₂O, less than or equal to 10mm H₂O, less than or equal to 7.5mm H₂O, less than or equal to 5mm H₂O, or 3mm H or less₂And O. Combinations of the above ranges are also possible (e.g., greater than or equal to 1mm H₂O is less than or equal to 100mm H₂O, or 3mm H or more₂O is less than or equal to 75mm H₂O). Other ranges are also possible. Pressure drop can be determined using ASTM D2986-91.

In some embodiments, the maximum pressure drop of the filter media after IPA exposure may be quite similar to the maximum pressure drop of the same filter media prior to IPA exposure. In some embodiments, the percent change in the maximum pressure drop of the filter media after IPA exposure may be less than or equal to 50%, less than or equal to 40%, less than or equal to 30%, less than or equal to 25%, less than or equal to 20%, less than or equal to 15%, less than or equal to 10%, or less than or equal to 5%. In some embodiments, the percent change in the maximum pressure drop of the filter media after IPA exposure may be greater than or equal to 0%, greater than or equal to 10%, greater than or equal to 20%, greater than or equal to 30%, or greater than or equal to 40%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% and less than or equal to 50%, or greater than or equal to 0% and less than or equal to 20%). Other ranges are also possible. Pressure drop can be determined using ASTM D2986-91. The percent change in value (e.g., pressure drop) is defined by the following equation: percent change ═ final value) - (initial value) |/(initial value) × 100.

In some embodiments, the filter media may have a relatively high gamma value at MPPS after exposure to IPA vapor. In some embodiments, the gamma value of the filter media at MPPS after exposure to IPA vapor may be greater than or equal to 14, greater than or equal to 18, greater than or equal to 20, greater than or equal to 40, greater than or equal to 60, or greater than or equal to 80. In some embodiments, the gamma value of the filter media at MPPS after exposure to IPA vapor may be less than or equal to 100, less than or equal to 80, less than or equal to 60, less than or equal to 40, less than or equal to 20, or less than or equal to 18. Combinations of the above ranges are also possible (e.g., greater than or equal to 14 and less than or equal to 100, or greater than or equal to 18 and less than or equal to 60). Other values are also possible.

In some embodiments, the gamma value of the filter media as a whole after IPA exposure may be quite similar to the gamma value of the same filter media prior to IPA exposure. In some embodiments, the percent change in the gamma value of the filter media after IPA exposure may be less than or equal to 60%, less than or equal to 50%, less than or equal to 40%, less than or equal to 30%, less than or equal to 25%, less than or equal to 20%, less than or equal to 15%, less than or equal to 10%, or less than or equal to 5%. In some embodiments, the percent change in the gamma value of the filter media after IPA exposure may be greater than or equal to 0%, greater than or equal to 10%, greater than or equal to 20%, greater than or equal to 30%, greater than or equal to 40%, or greater than or equal to 50%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% and less than or equal to 60%, or greater than or equal to 0% and less than or equal to 40%). Other ranges are also possible. The percent change in value (e.g., gamma value) is defined by the following equation: percent change ═ final value) - (initial value) |/(initial value) × 100.

In some embodiments, the filter media as a whole (e.g., a filter media comprising one or more layers having oleophobic properties (e.g., comprising an oleophobic component), one or more layers having an oil grade of greater than or equal to 1, and/or one or more surface modification layers) can perform particularly well after undergoing a DOP oil loading process. Such performance characteristics may include the filter media having a relatively low pressure drop after undergoing the DOP oil loading process, a relatively low change in pressure drop after undergoing the DOP oil loading process as compared to the same media prior to the DOP oil loading process, a relatively low penetration rate at the MPPS after undergoing the DOP oil loading process, a relatively low change in penetration rate at the MPPS after undergoing the DOP oil loading process as compared to the same media prior to the DOP oil loading process, a high gamma value after undergoing the DOP oil loading process, and/or a relatively low change in gamma value after undergoing the DOP oil loading process as compared to the same media prior to the DOP oil loading process.

Typically, the DOP oil loading process is carried out by passing 100cm of filter media²The test area was exposed to a concentration of 80mg/m³To 100mg/m³And an aerosol of DOP particles having a flow rate of 32L/min and a face velocity of 5.32 cm/sec. The DOP particles were produced by a TDA 100P aerosol generator available from Air technologies International and had a median diameter by count of 0.18 microns, a mass mean diameter of 0.3 microns, and a geometric standard deviation of less than 1.6 microns. Depending on the particular test, different filter media characteristics may be determined continuously during DOP oil loading or by pausing DOP oil loading for one or more measurements. For example, the pressure drop across the filter media as a function of DOP oil loading can be measured continuously. As another example, the DOP oil loading or weight of DOP per filter media area at any given pressure drop may be determined by: the pressure drop during DOP oil loading was measured continuously, the oil loading was stopped once the relevant pressure drop was reached, and the filter media was then weighed. Any increase in filter media weight was attributed to DOP oil, so DOP oil loading can be determined by taking the difference between the measured weight and the initial DOP-free filter media. Other parameters (e.g., penetration at MPPS, γ) can also be determined during or after DOP oil loading by taking measurements as described herein.

In some embodiments, the filter media is at greater than or equal to 4.5g/m²Greater than or equal to 5g/m²Greater than or equal to 6g/m²Greater than or equal to 7g/m²Greater than or equal to 8g/m²Greater than or equal to 9g/m²Greater than or equal to 10g/m²Greater than or equal to 11g/m²Greater than or equal to 20g/m²Greater than or equal to 30g/m²Greater than or equal to 40g/m²Greater than or equal to 50g/m²Greater than or equal to 60g/m²Or greater than or equal to 70g/m²The pressure drop at DOP oil loading of can be less than or equal to 50mm H₂And O. In some embodiments, the filter media is at or below 80g/m²Less than or equal to 70g/m²Less than or equal to 60g/m²Less than or equal to 50g/m²Less than or equal to 40g/m²Less than or equal to 30g/m²Less than or equal to 20g/m²Less than or equal to 11g/m²Less than or equal to 10g/m²Less than or equal to 9g/m²Less than or equal to 8g/m²Less than or equal to 7g/m²Or less than or equal to 6g/m²The pressure drop at DOP oil loading of can be less than or equal to 50mm H₂And O. Combinations of the above ranges are also possible (e.g., at greater than or equal to 5 g/m)²And less than or equal to 80g/m²Or greater than or equal to 5g/m²And less than or equal to 11g/m²Pressure drop at DOP oil loading of less than or equal to 50mm H ₂O). Other ranges are also possible.

In some embodiments, the filter media is at greater than or equal to 4.5g/m²Greater than or equal to 5g/m²Greater than or equal to 6g/m²Greater than or equal to 7g/m²Greater than or equal to 8g/m²Greater than or equal to 9g/m²Greater than or equal to 10g/m²Greater than or equal to 11g/m²Greater than or equal to 15g/m²Greater than or equal to 20g/m²Greater than or equal to 25g/m²Greater than or equal to 30g/m²Greater than or equal to 35g/m²Greater than or equal to 40g/m²Greater than or equal to 45g/m²Greater than or equal to 50g/m²Greater than or equal to 55g/m²Greater than or equal to 60g/m²65g/m or more²70g/m or more²Or greater than or equal to 75g/m²Can have a penetration at MPPS of less than or equal to 0.5% at DOP oil loading (e.g., E12 filter media). In some embodiments, the filter media is at or below 80g/m²Less than or equal to 75g/m²Less than or equal to 70g/m²65g/m or less²Less than or equal to 60g/m²55g/m or less²Less than or equal to 50g/m²Less than or equal to 45g/m²Less than or equal to 40g/m²Less than or equal to 35g/m²Less than or equal to 30g/m²Less than or equal to 25g/m²Less than or equal to 20g/m ²Less than or equal to 15g/m²Less than or equal to 12g/m²Less than or equal to 11g/m²Less than or equal to 10g/m²Less than or equal to 9g/m²Less than or equal to 8g/m²Less than or equal to 7g/m²Less than or equal to 6g/m²Or less than or equal to 5g/m²The penetration at MPPS at DOP oil loading of (a) may be less than or equal to 0.5%. Combinations of the above ranges are also possible (e.g., at greater than or equal to 4.5 g/m)²And less than or equal to 80g/m²Or greater than or equal to 4.5g/m²And is less than or equal to 12g/m²Penetration at MPPS of less than or equal to 0.5% at DOP oil loading). Other ranges are also possible. The penetration at MPPS can be measured based on the EN1822:2009 standard for MPPS DOP particles as described above by using a TSI 3160 automated filter test unit from TSI, inc.

In some embodiments, the filter media is at greater than or equal to 4.5g/m²Greater than or equal to 5g/m²Greater than or equal to 6g/m²Greater than or equal to 7g/m²Greater than or equal to 8g/m²Greater than or equal to 9g/m²Greater than or equal to 10g/m²Greater than or equal to 11g/m²Greater than or equal to 15g/m ²Greater than or equal to 20g/m²Greater than or equal to 25g/m²Greater than or equal to 30g/m²Greater than or equal to 35g/m²Greater than or equal to 40g/m²Greater than or equal to 45g/m²Greater than or equal to 50g/m²Greater than or equal to 55g/m²Greater than or equal to 60g/m²65g/m or more²70g/m or more²Or greater than or equal to 75g/m²Can have a penetration at MPPS of less than or equal to 0.05% at DOP oil loading (e.g., H13 filter media). In some embodiments, the filter media is at or below 80g/m²Less than or equal to 75g/m²Less than or equal to 70g/m²65g/m or less²Less than or equal to 60g/m²55g/m or less²Less than or equal to 50g/m²Less than or equal to 45g/m²Less than or equal to 40g/m²Less than or equal to 35g/m²Less than or equal to 30g/m²Less than or equal to 25g/m²Less than or equal to 20g/m²Less than or equal to 15g/m²Less than or equal to 12g/m²Less than or equal to 11g/m²Less than or equal to 10g/m²Less than or equal to 9g/m²Less than or equal to 8g/m²Less than or equal to 7g/m²Less than or equal to 6g/m²Or less than or equal to 5g/m²The penetration at MPPS at DOP oil loading of (a) may be less than or equal to 0.05%. Combinations of the above ranges are also possible (e.g., at greater than or equal to 4.5 g/m) ²And less than or equal to 80g/m²Or greater than or equal to 4.5g/m²And is less than or equal to 12g/m²Penetration at MPPS of less than or equal to 0.05% at DOP oil loading). Other ranges are also possible.

In some embodiments, the filter media is at greater than or equal to 4.5g/m²Greater than or equal to 5g/m²Greater than or equal to 6g/m²Greater than or equal to 7g/m²Greater than or equal to 8g/m²Greater than or equal to 9g/m²Greater than or equal to 10g/m²Greater than or equal to 11g/m²Greater than or equal to 15g/m²Greater than or equal to 20g/m²Greater than or equal to 25g/m²Greater than or equal to 30g/m²Greater than or equal to 35g/m²Greater than or equal to 40g/m²Greater than or equal to 45g/m²Greater than or equal to 50g/m²Greater than or equal to 55g/m²Greater than or equal to 60g/m²65g/m or more²70g/m or more²Or greater than or equal to 75g/m²Can have a penetration at MPPS of less than or equal to 0.005% (e.g., H14 filter media). In some embodiments, the filter media is at or below 80g/m²Less than or equal to 75g/m²Less than or equal to 70g/m²65g/m or less²Less than or equal to 60g/m²55g/m or less²Less than or equal to 50g/m ²Less than or equal to 45g/m²Less than or equal to 40g/m²Less than or equal to 35g/m²Less than or equal to 30g/m²Less than or equal to 25g/m²Less than or equal to 20g/m²Less than or equal to 15g/m²Less than or equal to 12g/m²Less than or equal to 11g/m²Less than or equal to 10g/m²Less than or equal to 9g/m²Less than or equal to 8g/m²Less than or equal to 7g/m²Less than or equal to 6g/m²Or less than or equal to 5g/m²The penetration at MPPS at DOP oil loading of (a) may be less than or equal to 0.005%. Combinations of the above ranges are also possible (e.g., at greater than or equal to 4.5 g/m)²And less than or equal to 80g/m²Or greater than or equal to 4.5g/m²And is less than or equal to 12g/m²Penetration at MPPS of less than or equal to 0.005%) at DOP oil loading. Other ranges are also possible.

In some embodiments, the filter media is at greater than or equal to 3.5g/m²Greater than or equal to 4g/m²Greater than or equal to 4.5g/m²Greater than or equal to 5g/m²Greater than or equal to 6g/m²Greater than or equal to 7g/m²Greater than or equal to 8g/m²Greater than or equal to 9g/m²Greater than or equal to 10g/m²Greater than or equal to 11g/m²Greater than or equal to 15g/m²Greater than or equal to 20g/m²Greater than or equal to 25g/m ²Greater than or equal to 30g/m²Greater than or equal to 35g/m²Greater than or equal to 40g/m²Greater than or equal to 45g/m²Greater than or equal to 50g/m²Greater than or equal to 55g/m²Greater than or equal to 60g/m²65g/m or more²70g/m or more²Or greater than or equal to 75g/m²Can have a penetration at MPPS of less than or equal to 0.0005% (e.g., U15 filter media). In some embodiments, the filter media is at or below 80g/m²Less than or equal to 75g/m²Less than or equal to 70g/m²65g/m or less²Less than or equal to 60g/m²55g/m or less²Less than or equal to 50g/m²Less than or equal to 45g/m²Less than or equal to 40g/m²Less than or equal to 35g/m²Less than or equal to 30g/m²Less than or equal to 25g/m²Less than or equal to 20g/m²Less than or equal to 15g/m²Less than or equal to 12g/m²Less than or equal to 11g/m²Less than or equal to 10g/m²Less than or equal to 9g/m²Less than or equal to 8g/m²Less than or equal to 7g/m²Less than or equal to 6g/m²Less than or equal to 5g/m²Less than or equal to 4.5g/m²Or less than or equal to 4g/m²The penetration at MPPS at DOP oil loading of (a) may be less than or equal to 0.0005%. Combinations of the above ranges are also possible (e.g., at greater than or equal to 3.5 g/m) ²And less than or equal to 80g/m²Or greater than or equal to 3.5g/m²And is less than or equal to 12g/m²Penetration at MPPS of less than or equal to 0.0005% at DOP oil loading). Other ranges are also possible.

In some embodiments, the filter media is at greater than or equal to 3.5g/m²Greater than or equal to 4g/m²Greater than or equal to 4.5g/m²Greater than or equal to 5g/m²Greater than or equal toAt 6g/m²Greater than or equal to 7g/m²Greater than or equal to 8g/m²Greater than or equal to 9g/m²Greater than or equal to 10g/m²Greater than or equal to 11g/m²Greater than or equal to 15g/m²Greater than or equal to 20g/m²Greater than or equal to 25g/m²Greater than or equal to 30g/m²Greater than or equal to 35g/m²Greater than or equal to 40g/m²Greater than or equal to 45g/m²Greater than or equal to 50g/m²Greater than or equal to 55g/m²Greater than or equal to 60g/m²65g/m or more²70g/m or more²Or greater than or equal to 75g/m²Can have a penetration at MPPS of less than or equal to 0.00005% (e.g., U16 filter media). In some embodiments, the filter media is at or below 80g/m²Less than or equal to 75g/m²Less than or equal to 70g/m²65g/m or less²Less than or equal to 60g/m ²55g/m or less²Less than or equal to 50g/m²Less than or equal to 45g/m²Less than or equal to 40g/m²Less than or equal to 35g/m²Less than or equal to 30g/m²Less than or equal to 25g/m²Less than or equal to 20g/m²Less than or equal to 15g/m²Less than or equal to 12g/m²Less than or equal to 11g/m²Less than or equal to 10g/m²Less than or equal to 9g/m²Less than or equal to 8g/m²Less than or equal to 7g/m²Less than or equal to 6g/m²Less than or equal to 5g/m²Less than or equal to 4.5g/m²Or less than or equal to 4g/m²The penetration at MPPS at DOP oil loading of (a) may be less than or equal to 0.00005%. Combinations of the above ranges are also possible (e.g., at greater than or equal to 3.5 g/m)²And less than or equal to 80g/m²Or greater than or equal to 3.5g/m²And is less than or equal to 12g/m²Penetration at MPPS of less than or equal to 0.00005% at DOP oil loading). Other ranges are also possible.

At one endIn some embodiments, the filter media is at or above 3.5g/m²Greater than or equal to 4g/m²Greater than or equal to 4.5g/m²Greater than or equal to 5g/m²Greater than or equal to 6g/m²Greater than or equal to 7g/m²Greater than or equal to 8g/m²Greater than or equal to 9g/m²Greater than or equal to 10g/m ²Greater than or equal to 11g/m²Greater than or equal to 15g/m²Greater than or equal to 20g/m²Greater than or equal to 25g/m²Greater than or equal to 30g/m²Greater than or equal to 35g/m²Greater than or equal to 40g/m²Greater than or equal to 45g/m²Greater than or equal to 50g/m²Greater than or equal to 55g/m²Greater than or equal to 60g/m²65g/m or more²70g/m or more²Or greater than or equal to 75g/m²Can have a penetration at MPPS of less than or equal to 0.000005% at DOP oil loading (e.g., U17 filter media). In some embodiments, the filter media is at or below 80g/m²Less than or equal to 75g/m²Less than or equal to 70g/m²65g/m or less²Less than or equal to 60g/m²55g/m or less²Less than or equal to 50g/m²Less than or equal to 45g/m²Less than or equal to 40g/m²Less than or equal to 35g/m²Less than or equal to 30g/m²Less than or equal to 25g/m²Less than or equal to 20g/m²Less than or equal to 15g/m²Less than or equal to 12g/m²Less than or equal to 11g/m²Less than or equal to 10g/m²Less than or equal to 9g/m²Less than or equal to 8g/m²Less than or equal to 7g/m²Less than or equal to 6g/m²Less than or equal to 5g/m²Less than or equal to 4.5g/m ²Or less than or equal to 4g/m²The penetration at MPPS at DOP oil loading of (a) may be less than or equal to 0.000005%. Combinations of the above ranges are also possible (e.g., at greater than or equal to 3.5 g/m)²And less than or equal to 80g/m²Or greater than or equal to 3.5g/m²And is less than or equal to 12g/m²Penetration at MPPS of less than or equal to 0.000005% at DOP oil loading). Other ranges are also possible.

In some embodiments, the filter media is at greater than or equal to 4.5g/m²Greater than or equal to 5g/m²Greater than or equal to 6g/m²Greater than or equal to 7g/m²Greater than or equal to 8g/m²Greater than or equal to 9g/m²Or greater than or equal to 10g/m²The DOP oil loading of (a) may have a gamma value of greater than or equal to 8. In some embodiments, the filter media is at less than or equal to 11g/m²Less than or equal to 10g/m²Less than or equal to 9g/m²Less than or equal to 8g/m²Less than or equal to 7g/m²Less than or equal to 6g/m²Or less than or equal to 5g/m²The DOP oil loading of (a) may have a gamma value of greater than or equal to 8. Combinations of the above ranges are also possible (e.g., at greater than or equal to 4.5 g/m)²And less than or equal to 11g/m²A gamma value of greater than or equal to 8) at DOP oil loading. Other ranges are also possible. γ can be determined based on the MPPS penetration rate of the DOP particles as described above.

In some embodiments, the filter media is at greater than or equal to 4.5g/m²Greater than or equal to 5g/m²Greater than or equal to 6g/m²Greater than or equal to 7g/m²Greater than or equal to 8g/m²Greater than or equal to 9g/m²Or greater than or equal to 10g/m²The DOP oil loading of (a) may have a gamma value of greater than or equal to 10. In some embodiments, the filter media is at less than or equal to 11g/m²Less than or equal to 10g/m²Less than or equal to 9g/m²Less than or equal to 8g/m²Less than or equal to 7g/m²Less than or equal to 6g/m²Or less than or equal to 5g/m²The DOP oil loading of (a) may have a gamma value of greater than or equal to 10. Combinations of the above ranges are also possible (e.g., at greater than or equal to 4.5 g/m)²And less than or equal to 11g/m²A gamma value of greater than or equal to 10) at DOP oil loading. Other ranges are also possible. Gamma may beDetermined based on the MPPS penetration of the DOP particles as described above.

In some embodiments, the filter media as a whole may have a PAO loading capacity greater than or equal to 3g/m²Greater than or equal to 5g/m²Greater than or equal to 10g/m²Greater than or equal to 20g/m²Greater than or equal to 50g/m²75g/m or more²Greater than or equal to 100g/m²Or greater than or equal to 150g/m ². In some embodiments, the filter media can have a PAO loading capacity of less than or equal to 200g/m²Less than or equal to 150g/m²Less than or equal to 100g/m²Less than or equal to 75g/m²Less than or equal to 50g/m²Less than or equal to 20g/m²Less than or equal to 10g/m²Or less than or equal to 5g/m². Combinations of the above ranges are also possible (e.g., greater than or equal to 3 g/m)²And less than or equal to 200g/m²Or greater than or equal to 5g/m²And less than or equal to 150g/m²). Other ranges are also possible. The PAO loading capacity of the filter media can be determined by: at 120mg/m³Loading rate of (2) and loading of 491cm with PAO oil at a medium surface speed of 5.3 cm/sec²Until the pressure drop across the filter medium increased by 250 Pa. The PAO particles may be produced by a Laskin nozzle and may have a median diameter of 0.25 microns. PAO load capacity is determined by: the filter media was weighed before and after the test and the measured mass increase was divided by the area of the filter media to obtain the PAO loading capacity per unit area of the filter media.

In some embodiments, the NaCl loading capacity of the filter media as a whole may be greater than or equal to 0.1g/m ²0.3g/m or more²0.5g/m or more²Greater than or equal to 1g/m²Greater than or equal to 2g/m²Greater than or equal to 5g/m²Greater than or equal to 7.5g/m²Greater than or equal to 10g/m²Greater than or equal to 12.5g/m²Greater than or equal to 15g/m²Greater than or equal to 17.5g/m²Is greater thanOr equal to 20g/m²22.5g/m or more²Greater than or equal to 25g/m²Or greater than or equal to 27.5g/m². In some embodiments, the filter media can have a NaCl loading capacity less than or equal to 30g/m²Less than or equal to 27.5g/m²Less than or equal to 25g/m²Less than or equal to 22.5g/m²Less than or equal to 20g/m²Less than or equal to 17.5g/m²Less than or equal to 15g/m²Less than or equal to 12.5g/m²Less than or equal to 10g/m²Less than or equal to 7.5g/m²Less than or equal to 5g/m²Less than or equal to 2g/m²Less than or equal to 1g/m²Less than or equal to 0.5g/m²Or less than or equal to 0.3g/m². Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 g/m)²And less than or equal to 30g/m²Or greater than or equal to 0.3g/m²And less than or equal to 20g/m²). Other ranges are also possible. The NaCl Loading capacity of the filter media can be determined by setting the nominal exposure area to 100cm ²Is exposed to a gas at 15mg/m³And NaCl particles with a median diameter of 0.26 microns at a face velocity of 5.3 cm/sec. NaCl Loading 8130CertiTest from TSI, Inc. equipped with a sodium chloride generator was used^TMAn automated filter test unit. The average particle size produced by the salt particle generator was 0.26 microns mass mean diameter. 8130 operate in a continuous mode with approximately one pressure drop reading per minute. Using a composition containing 15mg/m³100cm of NaCl²A sample of the filter media was tested at a flow rate of 32 liters/minute (face velocity of 5.3 cm/sec) until the pressure drop across the filter media increased by 250 Pa. The NaCl loading capacity was determined as follows: the filter media was weighed before and after the test and the measured mass increase was divided by the area of the filter media to obtain the NaCl loading capacity per unit area of the filter media. In some embodiments, the air permeability of the filter media as a whole can be greater than or equal to 0.6CFM, greater than or equal to 1CFM, greater than or equal to 1.4CFM, greater than or equal to 5CFM, greater than or equal to 10CFM, greater than or equal toOr equal to 20CFM, greater than or equal to 67CFM, greater than or equal to 100CFM, or greater than or equal to 200 CFM. In some embodiments, the air permeability of the filter media may be less than or equal to 260CFM, less than or equal to 200CFM, less than or equal to 100CFM, less than or equal to 67CFM, less than or equal to 20CFM, less than or equal to 10CFM, less than or equal to 5CFM, less than or equal to 1.4CFM, or less than or equal to 1 CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.6CFM and less than or equal to 260CFM, or greater than or equal to 1.4CFM and less than or equal to 67 CFM). Other ranges are also possible. Air permeability may be determined using TAPPI method T251.

The solidity of the filter media as a whole can be any suitable value. In some embodiments, the filter media has a solidity of greater than or equal to 0.0001, greater than or equal to 0.0002, greater than or equal to 0.0005, greater than or equal to 0.001, greater than or equal to 0.002, greater than or equal to 0.005, greater than or equal to 0.01, greater than or equal to 0.02, greater than or equal to 0.05, greater than or equal to 1, greater than or equal to 2, greater than or equal to 5, greater than or equal to 10, or greater than or equal to 25. In some embodiments, the filter media has a solidity of less than or equal to 50, less than or equal to 25, less than or equal to 10, less than or equal to 5, less than or equal to 2, less than or equal to 1, less than or equal to 0.5, less than or equal to 0.2, less than or equal to 0.1, less than or equal to 0.05, less than or equal to 0.02, less than or equal to 0.01, less than or equal to 0.005, less than or equal to 0.002, less than or equal to 0.001, less than or equal to 0.0005, or less than or equal to 0.0002. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.0001 and less than or equal to 50, or greater than or equal to 0.001 and less than or equal to 25). Other ranges are also possible. Solidity can be determined by using the following formula: density [% basis weight/(fiber density thickness) ] + 100. Basis weight and thickness may be determined as described herein. Porosity can be derived from solidity based on the following equation: solidity (%) 100-porosity (%).

In some embodiments, the dry tensile strength of the filter media as a whole in the cross direction can be greater than or equal to 3 lbs/inch, greater than or equal to 4 lbs/inch, greater than or equal to 5 lbs/inch, greater than or equal to 10 lbs/inch, greater than or equal to 15 lbs/inch, greater than or equal to 20 lbs/inch, greater than or equal to 25 lbs/inch, greater than or equal to 30 lbs/inch, greater than or equal to 35 lbs/inch, greater than or equal to 40 lbs/inch, greater than or equal to 45 lbs/inch, greater than or equal to 50 lbs/inch, greater than or equal to 55 lbs/inch, greater than or equal to 60 lbs/inch, greater than or equal to 65 lbs/inch, or greater than or equal to 70 lbs/inch. In some embodiments, the dry tensile strength of the filter media in the cross direction may be less than or equal to 75 lbs/inch, less than or equal to 70 lbs/inch, less than or equal to 65 lbs/inch, less than or equal to 60 lbs/inch, less than or equal to 55 lbs/inch, less than or equal to 50 lbs/inch, less than or equal to 45 lbs/inch, less than or equal to 40 lbs/inch, less than or equal to 35 lbs/inch, less than or equal to 30 lbs/inch, less than or equal to 25 lbs/inch, less than or equal to 20 lbs/inch, less than or equal to 15 lbs/inch, less than or equal to 10 lbs/inch, less than or equal to 5 lbs/inch, or less than or equal to 4 lbs/inch. Combinations of the above ranges are also possible (e.g., greater than or equal to 3 lbs/inch and less than or equal to 75 lbs/inch, or greater than or equal to 4 lbs/inch and less than or equal to 50 lbs/inch). Other ranges are also possible. The dry tensile strength in the cross machine direction can be determined according to standard T494 om-96 using a test span of 4 inches and a jaw separation speed of 1 inch/minute.

In some embodiments, the dry tensile strength of the filter media as a whole in the machine direction can be greater than or equal to 6 lbs/inch, greater than or equal to 10 lbs/inch, greater than or equal to 20 lbs/inch, greater than or equal to 30 lbs/inch, greater than or equal to 40 lbs/inch, greater than or equal to 50 lbs/inch, greater than or equal to 60 lbs/inch, greater than or equal to 70 lbs/inch, greater than or equal to 80 lbs/inch, greater than or equal to 90 lbs/inch, greater than or equal to 100 lbs/inch, greater than or equal to 110 lbs/inch, greater than or equal to 120 lbs/inch, greater than or equal to 130 lbs/inch, or greater than or equal to 140 lbs/inch. In some embodiments, the dry tensile strength of the filter media in the machine direction can be less than or equal to 150 lbs/inch, less than or equal to 140 lbs/inch, less than or equal to 130 lbs/inch, less than or equal to 120 lbs/inch, less than or equal to 110 lbs/inch, less than or equal to 100 lbs/inch, less than or equal to 90 lbs/inch, less than or equal to 80 lbs/inch, less than or equal to 70 lbs/inch, less than or equal to 60 lbs/inch, less than or equal to 50 lbs/inch, less than or equal to 40 lbs/inch, less than or equal to 30 lbs/inch, less than or equal to 20 lbs/inch, or less than or equal to 10 lbs/inch. Combinations of the above ranges are also possible (e.g., greater than or equal to 6 lbs/inch and less than or equal to 150 lbs/inch, or greater than or equal to 10 lbs/inch and less than or equal to 100 lbs/inch). Other ranges are also possible. The dry tensile strength in the machine direction can be determined according to standard T494 om-96 using a test span of 4 inches and a jaw separation speed of 1 inch/minute.

In some embodiments, the wet tensile strength of the filter media as a whole in the cross direction can be greater than or equal to 3 lbs/inch, greater than or equal to 4 lbs/inch, greater than or equal to 5 lbs/inch, greater than or equal to 10 lbs/inch, greater than or equal to 15 lbs/inch, greater than or equal to 20 lbs/inch, greater than or equal to 25 lbs/inch, greater than or equal to 30 lbs/inch, greater than or equal to 35 lbs/inch, greater than or equal to 40 lbs/inch, greater than or equal to 45 lbs/inch, greater than or equal to 50 lbs/inch, greater than or equal to 55 lbs/inch, greater than or equal to 60 lbs/inch, greater than or equal to 65 lbs/inch, or greater than or equal to 70 lbs/inch. In some embodiments, the filter media may have a wet tensile strength in the cross direction of less than or equal to 75 lbs/inch, less than or equal to 70 lbs/inch, less than or equal to 65 lbs/inch, less than or equal to 60 lbs/inch, less than or equal to 55 lbs/inch, less than or equal to 50 lbs/inch, less than or equal to 45 lbs/inch, less than or equal to 40 lbs/inch, less than or equal to 35 lbs/inch, less than or equal to 30 lbs/inch, less than or equal to 25 lbs/inch, less than or equal to 20 lbs/inch, less than or equal to 15 lbs/inch, less than or equal to 10 lbs/inch, less than or equal to 5 lbs/inch, or less than or equal to 4 lbs/inch. Combinations of the above ranges are also possible (e.g., greater than or equal to 3 lbs/inch and less than or equal to 75 lbs/inch, or greater than or equal to 4 lbs/inch and less than or equal to 50 lbs/inch). Other ranges are also possible. The wet tensile strength in the cross direction can be determined according to standard T494 om-96 using a test span of 4 inches and a jaw separation speed of 1 inch/min.

In some embodiments, the wet tensile strength of the filter media as a whole in the machine direction can be greater than or equal to 6 lbs/inch, greater than or equal to 10 lbs/inch, greater than or equal to 20 lbs/inch, greater than or equal to 30 lbs/inch, greater than or equal to 40 lbs/inch, greater than or equal to 50 lbs/inch, greater than or equal to 60 lbs/inch, greater than or equal to 70 lbs/inch, greater than or equal to 80 lbs/inch, greater than or equal to 90 lbs/inch, greater than or equal to 100 lbs/inch, greater than or equal to 110 lbs/inch, greater than or equal to 120 lbs/inch, greater than or equal to 130 lbs/inch, or greater than or equal to 140 lbs/inch. In some embodiments, the filter media may have a wet tensile strength in the machine direction of less than or equal to 150 lbs/inch, less than or equal to 140 lbs/inch, less than or equal to 130 lbs/inch, less than or equal to 120 lbs/inch, less than or equal to 110 lbs/inch, less than or equal to 100 lbs/inch, less than or equal to 90 lbs/inch, less than or equal to 80 lbs/inch, less than or equal to 70 lbs/inch, less than or equal to 60 lbs/inch, less than or equal to 50 lbs/inch, less than or equal to 40 lbs/inch, less than or equal to 30 lbs/inch, less than or equal to 20 lbs/inch, or less than or equal to 10 lbs/inch. Combinations of the above ranges are also possible (e.g., greater than or equal to 6 lbs/inch and less than or equal to 150 lbs/inch, or greater than or equal to 10 lbs/inch and less than or equal to 100 lbs/inch). Other ranges are also possible. The dry tensile strength in the machine direction can be determined according to standard T494 om-96 using a test span of 4 inches and a jaw separation speed of 1 inch/minute.

The dry mullen burst strength of the filter media as a whole may be any suitable value. In some embodiments, the filter media can have a dry mullen burst strength of greater than or equal to 10psi, greater than or equal to 20psi, greater than or equal to 50psi, greater than or equal to 75psi, greater than or equal to 100psi, greater than or equal to 125psi, greater than or equal to 150psi, greater than or equal to 175psi, greater than or equal to 200psi, greater than or equal to 225psi, greater than or equal to 250psi, or greater than or equal to 275 psi. In some embodiments, the filter media can have a dry mullen burst strength of less than or equal to 300psi, less than or equal to 275psi, less than or equal to 250psi, less than or equal to 225psi, less than or equal to 200psi, less than or equal to 175psi, less than or equal to 150psi, less than or equal to 125psi, less than or equal to 100psi, less than or equal to 75psi, less than or equal to 50psi, or less than or equal to 20 psi. Combinations of the above ranges are also possible (e.g., greater than or equal to 10psi and less than or equal to 300psi, or greater than or equal to 20psi and less than or equal to 200 psi). Other ranges are also possible. The dry Marlon burst strength can be determined according to the standard T403 om-91.

The wet mullen burst strength of the filter media as a whole may be any suitable value. In some embodiments, the filter media can have a wet mullen burst strength of greater than or equal to 5psi, greater than or equal to 10psi, greater than or equal to 20psi, greater than or equal to 30psi, greater than or equal to 40psi, greater than or equal to 50psi, greater than or equal to 60psi, greater than or equal to 70psi, greater than or equal to 80psi, greater than or equal to 90psi, greater than or equal to 100psi, greater than or equal to 110psi, greater than or equal to 120psi, greater than or equal to 130psi, greater than or equal to 140psi, greater than or equal to 150psi, greater than or equal to 160psi, greater than or equal to 170psi, greater than or equal to 180psi, or greater than or equal to 190 psi. In some embodiments, the filter media can have a wet mullen burst strength of less than or equal to 200psi, less than or equal to 190psi, less than or equal to 180psi, less than or equal to 170psi, less than or equal to 160psi, less than or equal to 150psi, less than or equal to 140psi, less than or equal to 130psi, less than or equal to 120psi, less than or equal to 110psi, less than or equal to 100psi, less than or equal to 90psi, less than or equal to 80psi, less than or equal to 70psi, less than or equal to 60psi, less than or equal to 50psi, less than or equal to 40psi, less than or equal to 30psi, less than or equal to 20psi, or less than or equal to 10 psi. Combinations of the above ranges are also possible (e.g., greater than or equal to 5psi and less than or equal to 200psi, or greater than or equal to 10psi and less than or equal to 150 psi). Other ranges are also possible. The dry Marlon burst strength can be determined according to the standard T403 om-91.

In some embodiments, the filter media as a whole can have a Gurley stiffness in the cross direction of greater than or equal to 50mg, greater than or equal to 100mg, greater than or equal to 150mg, greater than or equal to 200mg, greater than or equal to 300mg, greater than or equal to 350mg, greater than or equal to 400mg, greater than or equal to 450mg, greater than or equal to 500mg, greater than or equal to 1000mg, greater than or equal to 1500mg, or greater than or equal to 2000 mg. In some embodiments, the filter media can have a Gurley stiffness in the cross direction of less than or equal to 3000mg, less than or equal to 2000mg, less than or equal to 1500mg, less than or equal to 1000mg, less than or equal to 500mg, less than or equal to 450mg, less than or equal to 400mg, less than or equal to 350mg, less than or equal to 300mg, less than or equal to 250mg, less than or equal to 200mg, or less than or equal to 100 mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 50mg and less than or equal to 3000mg, or greater than or equal to 100mg and less than or equal to 3000 mg). Other ranges are also possible. Stiffness can be determined according to TAPPI T543om-94 using Gurley stiffness (bending resistance) reported in mm (corresponding to gu).

In some embodiments, the filter media as a whole can have a Gurley stiffness in the machine direction of greater than or equal to 100mg, greater than or equal to 150mg, greater than or equal to 200mg, greater than or equal to 250mg, greater than or equal to 300mg, greater than or equal to 350mg, greater than or equal to 400mg, greater than or equal to 450mg, greater than or equal to 500mg, greater than or equal to 1000mg, or greater than or equal to 2000 mg. In some embodiments, the filter media can have a Gurley stiffness in the machine direction of less than or equal to 3000mg, less than or equal to 2000mg, less than or equal to 1000mg, less than or equal to 500mg, less than or equal to 450mg, less than or equal to 400mg, less than or equal to 350mg, less than or equal to 300mg, less than or equal to 250mg, less than or equal to 200mg, or less than or equal to 150 mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 100mg and less than or equal to 300mg, or greater than or equal to 150mg and less than or equal to 2000 mg). Other ranges are also possible. Stiffness can be determined according to TAPPI T543om-94 using the Gurley stiffness (bending resistance) reported in mm (corresponding to gu).

In some embodiments, the filter media as a whole is flame retardant and/or comprises one or more flame retardants described herein in one or more layers. For example, the filter media may have a B2 rating according to DIN 4102-1.

In some embodiments, the filter media comprises a first layer and a second layer, and the second layer is formed from fibers having an average fiber diameter of less than 1 micron. An adhesive may be present between the first layer and the second layer, and the first layer may be bonded to the second layer by the adhesive. The filter media can have a stiffness of greater than or equal to 200mg and greater than or equal to 150 g/inch²The strength of the bond between the first layer and the second layer. The filter media may also exhibit a gamma value of greater than or equal to 18 at the most penetrable particle size when tested using a penetration test with 0.02 to 0.3 micron particles traveling at a face velocity of about 2.0 cm/sec and when tested for air resistance at a face velocity of about 5.3 cm/sec.

In some embodiments, a filter media includes a first layer, a second layer formed from fibers having an average fiber diameter of less than 1 micron, and a binder between the first layer and the second layer. The first layer may be bonded to the second layer by an adhesive. The adhesive may comprise a solvent-based resin comprising a polymer having a glass transition temperature of less than or equal to 25 ℃.

In some embodiments, a method for making a filter media includes spraying a composition including a solvent-based binder resin and a crosslinker onto a first layer to form a binder coated first layer, performing a solvent-based spinning process to deposit fibers on the binder coated first layer, and laminating a second layer to a third layer such that the third layer is disposed on an opposite side of the second layer from the first layer. The fibers in the second layer may have an average fiber diameter of less than 1 micron and form the second layer.

In some embodiments, the filter media includes a first layer formed from fibers having an average fiber diameter of less than 1 micronA second layer of rice fibers, and an adhesive between the first and second layers. The adhesive between the first and second layers may be present in an amount of less than 10 gsm. The first layer can be bonded to the second layer by an adhesive, and the bond strength between the first layer and the second layer can be greater than or equal to 150 g/inch². The filter media may exhibit less than a 50% increase in air resistance after subjecting the filter media to the IPA vapor discharge as compared to the filter media prior to the IPA vapor discharge.

In some embodiments as described above and herein, the binder comprises water.

In some embodiments, a filter media comprising one or more layers (e.g., a two-layer filter media, a three-layer filter media, a five-layer filter media, which may include, for example, a HEPA filter, an ULPA filter, or an HVAC filter) may be a component of the filter element. That is, the filter media may be incorporated into an article suitable for end-user use. Non-limiting examples of suitable filter elements include flat filters, V-bank filters (including, for example, 1V to 24V), cartridge filters, cylindrical filters, conical filters, and curvilinear filters. The filter element can have any suitable height (e.g., 2 inches to 124 inches for flat panel filters, 4 inches to 124 inches for V-bank filters, 1 inch to 124 inches for cartridge and cylindrical filter media). The filter element may also have any suitable width (2 inches to 124 inches for flat panel filters and 4 inches to 124 inches for V-bank filters). Some filter media (e.g., cartridge filter media, cylindrical filter media) can be characterized by a diameter rather than a width; the diameter of these filter media can be any suitable value (e.g., 1 inch to 124 inches). The filter element typically includes a frame, which may be made of one or more materials (e.g., cardboard, aluminum, steel, alloys, wood, and polymers).

In some embodiments, the filter media described herein may be a component of a filter element and may be pleated. The pleat height and pleat density (the number of pleats per unit length of media) can be selected as desired. In some embodiments, the pleat height can be greater than or equal to 10mm, greater than or equal to 15mm, greater than or equal to 20mm, greater than or equal to 25mm, greater than or equal to 30mm, greater than or equal to 35mm, greater than or equal to 40mm, greater than or equal to 45mm, greater than or equal to 50mm, greater than or equal to 53mm, greater than or equal to 55mm, greater than or equal to 60mm, greater than or equal to 65mm, greater than or equal to 70mm, greater than or equal to 75mm, greater than or equal to 80mm, greater than or equal to 85mm, greater than or equal to 90mm, greater than or equal to 95mm, greater than or equal to 100mm, greater than or equal to 125mm, greater than or equal to 150mm, greater than or equal to 175mm, greater than or equal to 200mm, greater than or equal to 225mm, greater than or equal to 250mm, greater than or equal to 275mm, greater than or equal to 300mm, greater than or equal to 325mm, greater than or equal to 350mm, greater than or equal to 375mm, or equal to 60mm, or equal to, Greater than or equal to 400mm, greater than or equal to 425mm, greater than or equal to 450mm, greater than or equal to 475mm, or greater than or equal to 500 mm. In some embodiments, the pleat height can be less than or equal to 510mm, less than or equal to 500mm, less than or equal to 475mm, less than or equal to 450mm, less than or equal to 425mm, less than or equal to 400mm, less than or equal to 375mm, less than or equal to 350mm, less than or equal to 325mm, less than or equal to 300mm, less than or equal to 275mm, less than or equal to 250mm, less than or equal to 225mm, less than or equal to 200mm, less than or equal to 175mm, less than or equal to 150mm, less than or equal to 125mm, less than or equal to 100mm, less than or equal to 95mm, less than or equal to 90mm, less than or equal to 85mm, less than or equal to 80mm, less than or equal to 75mm, less than or equal to 70mm, less than or equal to 65mm, less than or equal to 60mm, less than or equal to 55mm, less than or equal to 53mm, less than or equal to 50mm, less than or equal to 45mm, less than or equal to 40mm, or equal to 70mm, less than or equal to 225mm, or equal to 70mm, less than or equal to 225mm, less than or equal to 125mm, or equal to, Less than or equal to 35mm, less than or equal to 30mm, less than or equal to 25mm, less than or equal to 20mm, or less than or equal to 15 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 10mm and less than or equal to 510mm, or greater than or equal to 10mm and less than or equal to 100 mm). Other ranges are also possible.

In some embodiments, the filter media may have a pleat density of greater than or equal to 5 pleats per 100mm, greater than or equal to 6 pleats per 100mm, greater than or equal to 10 pleats per 100mm, greater than or equal to 15 pleats per 100mm, greater than or equal to 20 pleats per 100mm, greater than or equal to 25 pleats per 100mm, greater than or equal to 28 pleats per 100mm, greater than or equal to 30 pleats per 100mm, or greater than or equal to 35 pleats per 100 mm. In some embodiments, the filter media may have a pleat density of less than or equal to 40 pleats per 100mm, less than or equal to 35 pleats per 100mm, less than or equal to 30 pleats per 100mm, less than or equal to 28 pleats per 100mm, less than or equal to 25 pleats per 100mm, less than or equal to 20 pleats per 100mm, less than or equal to 15 pleats per 100mm, less than or equal to 10 pleats per 100mm, or less than or equal to 6 pleats per 100 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 5 pleats per 100mm and less than or equal to 100 pleats per 100mm, greater than or equal to 6 pleats per 100mm and less than or equal to 100 pleats per 100mm, greater than or equal to 25 pleats per 100mm and less than or equal to 28 pleats per 100 mm). Other ranges are also possible.

Other pleat heights and pleat densities may also be possible. For example, the filter media in a flat panel filter or V-bank filter may have a pleat height of 1/4 inches to 24 inches, and/or a pleat density of 1 pleat/inch to 50 pleats/inch. As another example, the filter media within a cartridge filter or a conical filter may have a pleat height of 1/4 inches to 24 inches and/or a pleat density of 1/2 pleats/inch to 100 pleats/inch. In some embodiments, the pleats may be separated by pleat separators made of, for example, polymer, glass, aluminum, and/or cotton. In other embodiments, the filter element may lack a pleat separator. The filter media may be wire-backed, or it may be self-supporting.

Example 1

In this example, a five-layer filter media was made in which the layers were laminated together using a solvent-based adhesive.

Fig. 3 illustrates a schematic diagram of a system 300 for forming a filter media described herein. Solvent-based adhesive 310(Super 77, synthetic elastomer dissolved in acetone, cyclohexane, dimethyl glutarate and other petroleum distillates; available from 3M company) was sprayed to a basis weight of 50g/M ²On the first layer (support layer). The basis weight of the adhesive coating is less than 10g/m²(e.g., less than 1 g/m)²). The adhesive coated support layer then enters a spinning unit 320 (e.g., an electrospinning chamber) where a second layer (a nylon main filter layer) is added adjacent to the adhesive. Then, the weight of the additive sprayed with the constant weight of less than 10g/m is laminated through the winding unit 330²(e.g., less than 1 g/m)²) The third layer of adhesive (spunbond pre-filter layer; trade name Reemay 2250) to form a three-layer filter media. The resulting filter media formed during this first pass is shown in fig. 4A and includes a first layer 410, a second layer 420, a third layer 430, and an adhesive 490. Referring back to FIG. 3, then at less than 10g/m²(e.g., less than 1 g/m)²) To the first fixed weightAdhesive 340 was applied to three layers (pre-filter layers) and the three layer filter media was again passed through the spin cell to add a fourth layer (nylon main filter layer) near the opposite side of the third layer. The fifth layer (support layer) was sprayed with adhesive and laminated so that its adhesive coated side was adjacent to the fourth layer to form a five-layer filter media. Fig. 4A through 4C illustrate the resulting structure formed using the system and method described above. The filter media includes a first layer 410, a second layer 420, a third layer 430, a fourth layer 440, a fifth layer 440, and an adhesive 490 (filter media 1).

For comparison purposes, four layers of filter media (filter media 2) were made by hand collating two binderless filter media together, each binderless filter media being made by electrospinning a second layer (main filtration layer) onto a first layer (support layer). Manual finishing was performed after each filter media was wound once. The electrospun main filtration layer of filter media 2 is similar in structure (e.g., fiber diameter, material, and basis weight) to the main filtration layer of filter media 1, and the support layer of filter media 2 is similar in structure (e.g., fiber diameter, material, and basis weight) to the support layer of filter media 2. The spunbond pre-filter layer present in filter medium 1 but not in filter medium 2 does not contribute significantly to the gamma value of filter medium 1 due to its relatively low air resistance and high penetration rate compared to the other layers in the medium.

Filter medium 1 had a higher gamma value (59.1) than filter medium 2(45.1), indicating that the filter medium containing the solvent-based binder formed by the method described in this example was superior to the filter medium containing no binder.

Example 2

This example describes the use of an adhesive comprising a small molecule crosslinker.

By setting the basis weight to 0.2g/m²Is electrospun onto the first layer (support layer) to produce a two-layer filter media.

The adhesive composition was prepared by adding carbodiimide crosslinking agent (Carbodilite E-02; available from Nisshinbo Chemicals) in various amounts (e.g., 0 wt.%, 3 wt.%, or 7 wt.% of crosslinking agent relative to the total weight of the layer) to a waterborne acrylate copolymer adhesive having a glass transition temperature of-30 deg.C (Carbond 1995; available from Lubrizol Corporation).

Adhesive composition (containing both Carbobond 1995 and crosslinker) at 1g/m²Sprayed onto the third layer (polyester spunbond protective layer; trade name Reemay 2250). The adhesive coated third layer was laminated to a two-layer filter media at 80 ℃ and the air resistance of the resulting three-layer filter media was measured. The three-layer filter media was then exposed to IPA vapor as described above, after which the air resistance of the three-layer filter media was measured again. Filter media comprising an adhesive composition containing 0 wt% crosslinker or 3 wt% crosslinker have a significant increase in air resistance after exposure to IPA vapor (3.7 mm H for 0 wt% crosslinker ₂O to 18.8mm H₂O, 3.7mm H for 3% by weight of crosslinker₂O to 9.4mm H₂O). Filter media comprising adhesive compositions containing 7 wt% crosslinker exhibited negligible increase in air resistance (3.3mm H) after IPA vapor exposure₂O to 4.1mm H₂O)。

Example 3

This example describes the manufacture of filter media.

An in-line nozzle system capable of in-line application of adhesive to a filter media layer at several points during the manufacturing process is customized. Using a catalyst having a viscosity of 50g/m²The weighed wet-laid synthetic medium acts as a first layer (support layer) and is passed through the system and sprayed with a binder. The adhesive covered layer was then passed into an electrospinning line to deposit a second layer (nylon electrospun main filtration layer) adjacent to the adhesive. The main filtration layer has a density of 0.25g/m²Basis weight and an average fiber diameter of 100 nm. These two layers were then combined with a third layer (20 g/m) coated with adhesive²Polypropylene meltblown web pre-filter layer) is finished so that the adhesive on the meltblown pre-filter layer is adjacent to the main filter layer. This multi-layer media was passed through a felt dryer that could maintain a surface temperature of 120 ℃. The laminated media was wound into rolls and characterized.

The binder used above was Carbobond 1995 in combination with a Carbodilite crosslinker. Carbond 1995 was prepared at 15 wt.% solids and blended with 10 wt.% wet of Carbodilite E02 crosslinker. The pH of the blend was adjusted to 7 to 8 using potassium hydroxide. At each interface in the final filter media there is 1.03g/m²Is present at 1.03g/m at the interface between the wet laid layer and the main filtration layer²At the interface between the main filtration layer and the meltblown layer, 1.03g/m²The adhesive of (1). )

The three layer main filter made as described above had a density of 343 g/inch²And good bonding of the three layers. These filter media also exhibit other positive properties after exposure to IPA vapor, such as negligible increase in air resistance (17.1mm H)₂O to 17.8mm H₂O), negligible increase in penetration at MPPS (0.0044% to 0.01373%) and relatively high gamma values (22.7).

Example 4

This example describes the manufacture of a filter media as in example 3.

A three-layer filter media was made by using similar procedures as used in example 3.

The first layer (support layer) was 60g/m having a stiffness of 380mg, a machine direction tensile strength of 25.7 lbs/inch, a thickness of 0.016 inch and a dry Marlon strength of 70psi ²A wet laid backing was synthesized.

The second layer (main filtration layer) was made of nylon fibers (electrospun fibers) having an average fiber diameter of about 120 nm.

The third layer (pre-filter layer) has a basis weight of 22g/m²And a melt-blown polypropylene layer having an average fiber diameter of 1.5 microns. The pre-filter layer was also corona charged so that its initial efficiency measured at a face velocity of 5.32 cm/sec for 0.3 micron DOP particles was 8.5% and the IPA vapor discharge efficiency was 65%.

The adhesive formulation is also similar to that used in example 3, except that it has 12.5 wt% solids. Between each pair of layers (i.e., between the support layer and the main filtration layer,and between the main filtration layer and the pre-filtration layer) 0.8g/m²1.6g/m in total for the entire filter medium²The adhesive of (1).

The filter media showed a 9% increase in air resistance after IPA vapor discharge and a gamma value of 18.89 after IPA vapor discharge. The average internal bond strength of the filter media was 189.4 g/inch²。

Example 5

This example presents a comparison of several properties of a filter medium having oleophobic properties (oleophobic coating) with two filter media lacking oleophobic properties (oleophobic coating).

Filter medium 1 is a three-layer filter medium comprising 20g/m ²Melt-blown polypropylene pre-filter layer, 0.25g/m²The main filter layer of the electrostatic spinning nylon is 60g/m²A wet laid polyester and an acrylate support layer. The pre-filter layer was charged by corona discharge to form an electret with a NaCl penetration of 0.3 micron particles of 2.5% and a pressure drop of 2mm H at a face velocity of 5.32 cm/sec₂And O. The main filtration layer had an average fiber diameter of 100 nm. The filter medium 1 was prepared by: spraying an adhesive onto a support layer, passing the support layer coated with the adhesive through an electrospinning unit to form a main filtration layer disposed on the support layer, and then laminating a pre-filtration layer coated with the sprayed adhesive to the support layer coated with the main filtration layer. These steps are performed in-line and do not require an external lamination step.

Filter media 2 is a three-layer filter media comprising 30g/m²A melt blown pre-filter layer and the main filter layer and support layer described above for filter media 1.

Filter media 3 is similar to filter media 1 except that it includes an oleophobic coating on the pre-filter layer that is oil grade 5 to 6. The oleophobic coating is formed on the pre-filter layer prior to laminating the pre-filter layer to the support layer coated with the main filter layer. The oleophobic coating was formed by passing the pre-filter layer through a vacuum plasma chamber containing C6 fluorinated acrylate monomers. During this step, the C6 fluoroacrylate monomers polymerize on the surface of the prefilter layer fibers to form a thin coating layer (e.g., a film). The pre-filter layer is then charged with corona discharge, sprayed with adhesive, and laminated to a support layer coated with a main filter layer as described above for filter media 1.

Table 2 below shows several characteristics of the formed filter media 1, 2 and 3.

TABLE 2

For each filter medium, the following procedure was performed. Make 100cm²The test area was exposed to a concentration of 80mg/m³To 100mg/m³Aerosol of DOP particles of (a). The DOP particles were produced by a TDA 100P aerosol generator available from air technologies International and had a median diameter by count of 0.18 microns, a mass mean diameter of 0.3 microns, and a geometric standard deviation of less than 1.6 microns. During this process, the pressure drop across the filter media is continuously measured. When the pressure drop increased to 4mm H greater than the pressure drop of the formed filter media (which was not exposed to DOP particles)₂O value, the filter media was weighed to determine oil loading and the MPPS penetration of the filter media was measured using a TSI 3160 instrument at a face velocity of 2 cm/sec. The process was repeated with every 4mm H increase in pressure drop₂MPPS penetration rate measurement and oil load measurement are carried out at O time until 55mm H is reached₂The endpoint pressure drop of O.

Fig. 5 shows MPPS penetration of the filter media 1 to 3 as a function of oil loading, fig. 6 shows pressure drop of the filter media 1 to 3 as a function of oil loading, and fig. 7 shows γ of the filter media 1 to 3 as a function of oil loading. For each of these characteristics, filter media 3 exhibited better performance than either filter media 1 or filter media 2 at higher oil loading levels. For example, as shown in FIG. 5, the filter media 3 is at or above 4.5g/m ²Penetration at MPPS of less than or equal to 0.004 at DOP oil loading. FIG. 6 shows that the filter medium 3 is at 4.5g/m or more²Pressure drop at DOP oil loading of less than or equal to 50mm H₂And O. FIG. 7 shows the filter medium 3 at 4.5g/m or more²Is greater than or equal to 10.

While various embodiments of the invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the functions and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings of the present invention is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the scope of the present invention.

All definitions, as defined and used herein, should be understood to take precedence over dictionary definitions, definitions in documents incorporated by reference, and/or general meanings of the defined terms.

Unless explicitly indicated to the contrary, objects modified by no numerical terms as used herein in the specification and claims should be understood to mean "at least one".

The phrase "and/or" as used herein in the specification and claims should be understood to mean "either or both" of the elements so combined, i.e., the elements that are present together in some cases and separately in other cases. Multiple elements listed with "and/or" should be construed in the same manner, i.e., "one or more" of the elements so combined. In addition to the elements specifically identified by the "and/or" clause, other elements may optionally be present, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, when used in conjunction with open-ended language such as "comprising," reference to "a and/or B" may refer in one embodiment to a alone (optionally including elements other than B); may refer to B alone (optionally including elements other than a) in another embodiment; and in yet another embodiment may refer to both a and B (optionally including other elements); and so on.

As used herein in the specification and claims, "or" should be understood to have the same meaning as "and/or" as defined above. For example, when separating items in a list, "or" and/or "should be understood to include, i.e., include, at least one of a plurality of elements or a list of elements, but also include more than one, and optionally include additional unlisted items. To the contrary, terms such as "only one of" or "exactly one of," or "consisting of," when used in a claim, are intended to include a plurality of elements or exactly one element of a list of elements. In general, when preceding an exclusive term (e.g., "any," "one of," "only one of," or "exactly one of"), the term "or" as used herein should only be understood to mean an exclusive alternative (i.e., "one or the other but not both"). "consisting essentially of, when used in a claim, shall have its ordinary meaning as used in the patent law field.

As used herein in the specification and claims, the phrase "at least one," when referring to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but does not necessarily include at least one of each element specifically listed in the list of elements, nor exclude any combination of elements in the list of elements. The definition also allows that elements may optionally be present other than the elements specifically identified in the list of elements referred to by the phrase "at least one," whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, "at least one of a and B" (or, equivalently, "at least one of a or B," or, equivalently "at least one of a and/or B") can refer, in one embodiment, to at least one a, optionally including more than one a, with no B present (and optionally including elements other than B); in another embodiment, it may refer to at least one B, optionally including more than one B, with no a present (and optionally including elements other than a); in yet another embodiment, it may refer to at least one a, optionally including more than one a, and at least one B, optionally including more than one B (and optionally including other elements); and so on.

It will also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or action, the order of the steps or actions of the method need not be limited to the order in which the steps or actions of the method are recited.

In the claims, as well as in the specification above, all transitional phrases such as "comprising," "including," "carrying," "having," "containing," "involving," "holding," "including," and the like are to be understood to be open-ended, i.e., to mean including but not limited to. The transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively, as set forth in section 2111.03 of the patent examination program manual of the U.S. patent office.

Claims

1. A filter media, comprising:

a first layer;

a second layer, wherein the second layer is formed from fibers having an average fiber diameter of less than 1 micron; and

an adhesive between the first layer and the second layer, wherein the first layer is bonded to the second layer by the adhesive,

wherein at least one of the first layer and the second layer has an oil rating of greater than or equal to 1,

Wherein the bond strength between the first layer and the second layer is greater than or equal to 150 g/inch²，

Wherein the filter media has a stiffness of greater than or equal to 200mg, wherein the stiffness is measured in the machine direction or cross direction, an

Wherein the first layer has a mean flow pore size greater than or equal to 0.5 microns and less than or equal to 100 microns.

2. A filter media, comprising:

a first layer, wherein the first layer comprises fibers;

a second layer, wherein the second layer is a film layer; and

3. A filter media, comprising:

a first layer; and

a second layer, wherein the second layer is formed from fibers having an average fiber diameter of less than 1 micron,

wherein the filter media has a stiffness of greater than or equal to 200mg, wherein the stiffness is measured in the machine direction or the cross-machine direction,

wherein the filter media is at greater than or equal to 4.5g/m²Pressure drop at DOP oil loading of less than or equal to 50mm H₂O, and

4. A filter media, comprising:

a first layer, wherein the first layer comprises fibers; and

a second layer, wherein the second layer is a film layer,

5. A filter media, comprising:

a first layer; and

wherein the filter media is at greater than or equal to 4.5g/m²Has a gamma value at the loading of DOP oil of greater than or equal to 10, an

6. A filter media, comprising:

a first layer, wherein the first layer comprises fibers; and

a second layer, wherein the second layer is a film layer,

7. The filter media of any one of claims 1-6, wherein the filter media has an efficiency according to standard EN1822:2009 of greater than 95%.

8. The filter media of any one of claims 1-6, wherein the filter media has an efficiency according to standard EN1822:2009 of greater than 99.95%.

9. The filter medium of any one of claims 1-6, wherein the filter medium has an efficiency according to standard EN1822:2009 of greater than 99.995%.

10. The filter media of any one of claims 1-6, wherein the filter media has an efficiency according to standard EN1822:2009 of greater than 99.9995%.

11. The filter medium of any one of claims 1-6, wherein the filter medium has an efficiency according to standard EN1822:2009 of greater than 99.99995%.

12. The filter medium of any one of claims 1-6, wherein the filter medium has an efficiency according to standard EN1822:2009 of greater than 99.999995%.

13. The filter media of any one of claims 1-6, wherein the filter media has an efficiency according to standard EN1822:2009 of greater than 99.9999995%.

14. The filter media of any of claims 1-6, wherein the fibers of the second layer are solvent spun fibers.

15. The filter media of any of claims 1-6, wherein the fibers of the second layer are electrospun or centrifugally spun fibers.

16. The filter media of any of claims 1-6, wherein the second layer is a main filtration layer.

17. The filter media of any of claims 1-6, wherein the first layer is a wet-laid layer.

18. The filter media of any of claims 1-6, wherein the first layer is a meltblown layer.

19. The filter media of any of claims 1-6, wherein the first layer is an electrically charged meltblown layer.

20. The filter media of any of claims 1-6, wherein the first layer is a support layer.

21. The filter media of any of claims 1-6, wherein the first layer is a pre-filter layer.

22. The filter media of any of claims 1-6, wherein the filter media comprises a third layer.

23. The filter media of claim 22, wherein the third layer is a meltblown layer.

24. The filter media of claim 22, wherein the third layer is a wet-laid layer.

25. The filter media of claim 22, wherein the third layer is a pre-filter layer.

26. The filter media of claim 22, wherein the third layer is a support layer.

27. The filter media of claim 22, wherein the third layer is an electrically charged meltblown layer.

28. The filter media of claim 22, wherein the first layer is a surface modification layer, and/or the second layer is a surface modification layer, and/or the third layer is a surface modification layer.

29. The filter media of claim 28, wherein surface modification of at least one of the first layer, the second layer, and the third layer has been performed by a chemical deposition technique.

30. The filter media of claim 28, wherein surface modification of at least one of the first layer, the second layer, and the third layer has been performed by plasma enhanced chemical vapor deposition.

31. The filter media of claim 28, wherein surface modification of at least one of the first layer, the second layer, and the third layer has been performed by electron beam assisted radiation curing.

32. The filter media of claim 28, wherein surface modification of at least one of the first layer, the second layer, and the third layer has been performed by a physical deposition technique.

33. The filter media of claim 28, wherein the surface modification of at least one of the first layer, the second layer, and the third layer has been performed by powder coating.

34. The filter media of claim 22, wherein the first layer further comprises an oleophobic component, and/or wherein the second layer further comprises an oleophobic component, and/or wherein the third layer further comprises an oleophobic component.

35. The filter media of claim 34, wherein the oil repellent component of at least one of the first, second, and third layers is a layer that has been deposited by a chemical deposition technique.

36. The filter media of claim 34, wherein the oil repellent component of at least one of the first layer, the second layer, and the third layer is a layer that has been deposited by plasma enhanced chemical vapor deposition.

37. The filter media of claim 34, wherein the oil repellent component of at least one of the first, second, and third layers is a layer that has been deposited by electron beam assisted radiation curing.

38. The filter media of claim 34, wherein the oil repellent component of at least one of the first layer, the second layer, and the third layer is a layer that has been deposited by a physical deposition technique.

39. The filter media of claim 34, wherein the oil repellent component of at least one of the first, second, and third layers is a layer that has been deposited by powder coating.

40. The filter media of claim 34, wherein the oleophobic component comprises an oleophobic resin.

41. The filter media of claim 34, wherein the oleophobic component comprises an oleophobic additive.

42. The filter media of any of claims 1-6, wherein the oil grade of the first layer is greater than or equal to 1.

43. The filter media of any of claims 1-6, wherein the oil grade of the second layer is greater than or equal to 1.

44. The filter media of any of claims 1-6, wherein the oil grade of the layer furthest upstream is greater than or equal to 1.

45. The filter media of any of claims 1-6, wherein the filter media is at greater than or equal to 4.5g/m²DOP penetration at MPPS of less than or equal to 0.5% at DOP oil loading.

46. The filter media of any of claims 1-6, wherein the filter media is at greater than or equal to 4.5g/m²DOP penetration at MPPS at DOP oil loading of less than or equal to 0.05%.

47. The filter media of any of claims 1-6, wherein the filter media is at greater than or equal to 4.5g/m²DOP penetration at MPPS of less than or equal to 0.005% at DOP oil loading.

48. The filter media of any of claims 1-6, wherein the filter media is at greater than or equal to 4.5g/m²DOP oil loading at MPPSThe DOP penetration at the lower level is less than or equal to 0.0005%.

49. The filter media of any of claims 1-6, wherein the filter media is at greater than or equal to 4.5g/m²DOP penetration at MPPS of less than or equal to 0.00005% at DOP oil loading.

50. The filter media of any of claims 1-6, wherein the filter media is at greater than or equal to 4.5g/m²DOP penetration at MPPS of less than 0.000005% at DOP oil loading.

51. The filter media of claim 34, wherein the oleophobic component comprises a polymer.

52. The filter media of claim 34, wherein the oleophobic component comprises an organofluorine.

53. The filter media of claim 34, wherein the oleophobic component comprises one or more of a wax, a silicone, a corn-based polymer, and a nanoparticle material.

54. The filter media of any of claims 1-6, wherein the first layer comprises fibers and an oleophobic component, and wherein the oleophobic component is in the form of a coating disposed on one or more fibers within the first layer.

55. The filter media of claim 54, wherein the coating at least partially surrounds one or more fibers within the first layer.

56. The filter media of any of claims 1-6, wherein the filter media has a gamma value greater than or equal to 18.

57. The filter media of any of claims 1-6, wherein the stiffness of the filter media is greater than or equal to 300 mg.

58. The filter media of any of claims 1-6, wherein the filter media has a basis weight of less than or equal to 150g/m²。

59. The filter media of any of claims 1-6, wherein the filter media has a thickness of less than or equal to 1 mm.

60. The filter media of any of claims 1-6, wherein the filter media is pleated and a pleat height is greater than or equal to 10mm and less than or equal to 510 mm.

61. The filter media of any of claims 1-6, wherein the filter media is pleated and has a pleat density of greater than or equal to 6 pleats per 100mm and less than or equal to 100 pleats per 100 mm.

62. The filter media of any one of claims 1-6, wherein the stiffness is measured in the cross direction.

63. The filter media of any one of claims 1-6, wherein the stiffness is measured in the machine direction.

64. A method of using the filter media of any of claims 1-63, comprising filtering a fluid through the filter media of any of claims 1-63.