WO2022003566A1

WO2022003566A1 - Nonwoven material and mask made therewith

Info

Publication number: WO2022003566A1
Application number: PCT/IB2021/055820
Authority: WO
Inventors: Behnam Pourdeyhimi
Original assignee: North Carolina State University
Priority date: 2020-06-30
Filing date: 2021-06-29
Publication date: 2022-01-06

Abstract

The disclosure relates to a mask configured to cover the nose and mouth of a user including a multi-layer nonwoven fabric, the nonwoven fabric including at least one layer of a spunbond material that includes at least partially fibrillated bicomponent filaments formed from bicomponent filaments having an external fiber component and an internal fiber component, wherein the external fiber component at least partially enwraps the internal fiber component; and wherein the external fiber component is 5% to 25 wt.% of the bicomponent filament.

Description

NONWOVEN MATERIAL AND MASK MADE THEREWITH

FIELD OF THE INVENTION

The present invention relates to a nonwoven material suitable for use in personal protective equipment.

BACKGROUND OF THE INVENTION

Synthetic fibers are widely used in a number of diverse applications to provide stronger, thinner, and lighter weight products. Synthetic thermoplastic fibers are typically thermos-formable and thus are particularly attractive for the manufacture of nonwoven fabrics, either alone or in combination with other non-thermoplastic fibers (such as cotton, wool, and wood pulp, for example). Nonwoven fabrics, in turn, are widely used as components of a variety of articles, including without limitation absorbent personal care products, such as diapers, incontinence pads, feminine hygiene products, and the like; medical products, such as surgical drapes, sterile wraps, and the like; filtration devices; interlinings; wipes; furniture and bedding construction; apparel; insulation; packaging materials; and others.

The coronavirus (COVID-19) global pandemic has caused a global shortage of medical supplies, and in particular, a shortage of various forms of personal protective equipment (PPEs) used by first responders and healthcare providers. The most significant challenge in this domain is the shortage of facemasks.

There are various types of facemasks available on the market. The N95 or N99 masks are among are the most well-known, and are typically referred to as respirators. Surgical masks are also facemasks, but they have drastically different properties from respirators. N95 and N99 respirators and surgical masks are PPEs used to protect the wearer from airborne particles.

The N95 and N99 respirators are regulated by the Centers for Disease Control and Prevention (CDC), the National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA) and must adhere to the strict performance guidelines estabhshed by these organizations. N95 and N99 respirator filters need to have a filtration efficiency of more than 95% of 0.3- micron particles tested at a flow rate of 85 liters per minute for the respirator and 32 L/min for flat sheets (if the face velocity is adequate for determining the efficiency in a respirator). It is desirable that the pressure drop across these masks be less than 60 Pascals for the base filter. When the actual mask is tested, the pressure drops can be much higher and can reach 100 to 200 Pascals or more depending on construction, surface area, and the properties of the meltblown filter used.

A surgical mask is a loose-fitting, disposable device that creates a physical barrier between the mouth and nose of the wearer and potential contaminants in the immediate environment. These are often referred to as facemasks, although not all facemasks are regulated as surgical masks. Unlike the N95 respirators, the edges of the surgical mask are not designed to form a seal around the nose and mouth. These are single-use, disposable respiratoiy protective devices used and worn by healthcare personnel during procedures to protect both the patient and healthcare personnel from the transfer of microorganisms, body fluids, and particulate material. Surgical masks are tested for particle filtration, bacteria capture, and splash resistance.

The technology used in almost all masks for filtration is a polypropylene (PP) meltblown fabric that is electrostatically charged. A nonwoven filter medium that uses a combination of mechanical structure and electret charge provides a means of achieving high initial efficiency and sustained high efficiency. Meltblown PP fabrics are rather fragile and cannot be reused, laundered, or re-sterilized due to potential loss of charge and structural damage. They are often protected by layers of PP spunbond nonwovens made up of larger fibers that protect the meltblown filter layer.

The supply chain to produce these masks includes meltblown fabric manufacturers, spunbond fabric manufacturers, and mask converters who convert the meltblown and spunbond fabrics into masks. Very few companies are vertically integrated to produce both the base materials and the masks. One of the primary challenges in the US and globally due to the pandemic is insufficient converting capacity for making masks. The relative fragility of PP meltblown fabric is a complicating factor as only certain types of automated converting machines can work with such materials. There is a continuing need for improved types of filtration material for use in making personal protective equipment.

SUMMARY OF THE INVENTION

The disclosure provides a mask configured to cover the nose and mouth of a user comprising a multi-layer nonwoven fabric, the nonwoven fabric comprising at least one layer of a spunbond material comprising at least partially fibrillated bicomponent filaments formed from bicomponent filaments having an external fiber component and an internal fiber component, wherein the external fiber component at least partially enwraps the internal fiber component; and wherein the external fiber component is 5% to 25 wt.% of the bicomponent filament. In some embodiments, the mask of the present disclosure combines strong filtration efficiency performance with relatively low pressure drop levels, and offers a construction that is less complex than many conventional masks.

The disclosure includes, without limitation, the following embodiments.

Embodiment 1: A mask configured to cover the nose and mouth of a user comprising a multi-layer nonwoven fabric, the nonwoven fabric comprising at least one layer of a spunbond material comprising at least partially fibrillated bicomponent filaments formed from bicomponent filaments having an external fiber component and an internal fiber component, wherein the external fiber component at least partially enwraps the internal fiber component; and wherein the external fiber component is 5% to 25 wt.% of the bicomponent filament.

Embodiment 2: The mask of Embodiment 1, wherein the internal fiber component and the external fiber component comprise different thermoplastic polymers selected from the list consisting of polyesters, polyamides, thermoplastic copolyetherester elastomers, polyolefins, polyacrylates, and thermoplastic liquid crystalline polymers. Embodiment 3 : The mask of any one of Embodiments 1-2, wherein the internal fiber component comprises a polyolefin such as polypropylene (PP) or polyethylene (PE) and the external fiber component comprises a polyester such as poly lactic acid (PLA) or polyethylene terephthalate (PET), or the internal fiber component comprises a polyester such as poly lactic acid (PLA) or polyethylene terephthalate (PET), and the external fiber component comprises a polyolefin such as polypropylene (PP) or polyethylene (PE).

Embodiment 4: The mask of any one of Embodiments 1-3, comprising multiple layers of the spunbond material, each layer having a basis weight of about 150 gsm or less with a combined spunbond basis weight of about 225 gsm or greater.

Embodiment 5: The mask of any one of Embodiments 1-4, wherein the combined spunbond basis weight is about 250 gsm or greater.

Embodiment 6: The mask of any one of Embodiments 1-5, further comprising at least one layer of meltblown nonwoven material having a basis weight of about 60 gsm or less.

Embodiment 7: The mask of any one of Embodiments 1-6, wherein the multi-layer nonwoven fabric has no more than three layers of nonwoven material.

Embodiment 8: The mask of any one of Embodiments 1-7, wherein the multi-layer nonwoven fabric has no more than two layers of nonwoven material.

Embodiment 9: The mask of any one of Embodiments 1-8, wherein the multi-layer nonwoven fabric consists of only the following specified layers of nonwoven material with no other nonwoven layers affixed thereto: (i) two layers of the spunbond material, each layer of spunbond material having a basis weight of about 100 to about 150 gsm with a combined spunbond basis weight of about 225 gsm or greater; or (ii) one or two layers of the spunbond material, each layer of spunbond material having a basis weight of about 100 to about 150 gsm, and a layer of meltblown nonwoven material having a basis weight of about 60 gsm or less.

Embodiment 10: The mask of any one of Embodiments 1-9, wherein the multi-layer nonwoven fabric has a filtration efficiency of about 95% or higher, measured according to the test set forth in 42 CFR Part 84 and NIOSH Procedure No. TEB-APR-STP-0059 at a flow rate of 60 L/min and a sample area of 100 cm².

Embodiment 11 : The mask of any one of Embodiments 1-10, wherein the multi-layer nonwoven fabric has a pressure drop in the range of about 60 Pa or less at a flow rate of 60 L/min and a sample area of 100 cm 2.

Embodiment 12: The mask of any one of Embodiments 1-11, in the form of a surgical mask or a respirator.

Embodiment 13 : The mask of any one of Embodiments 1-12, wherein any layer of the spunbond material further comprises monocomponent fibers mixed therein, such as monocomponent polyolefin fibers (e.g., polyethylene or polypropylene).

These and other features, aspects, and advantages of the present disclosure will be apparent from a reading of the following detailed description together with the accompanying figures, which are briefly described below. The present disclosure includes any combination of two, three, four or more features or elements set forth in this disclosure, regardless of whether such features or elements are expressly combined or otherwise recited in a specific example implementation described herein. This disclosure is intended to be read holistically such that any separable features or elements of the disclosure, in any of its aspects and example implementations, should be viewed as combinable, unless the context of the disclosure clearly dictates otherwise.

It will therefore be appreciated that this brief summary is provided merely for purposes of summarizing some example implementations so as to provide a basic understanding of some aspects of the disclosure. Accordingly, it will be appreciated that the above described example implementations are merely examples and should not be construed to narrow the scope or spirit of the disclosure in any way. Other example implementations, aspects and advantages will become apparent from the following detailed description taken in conjunction with the accompanying figures which illustrate, by way of example, the principles of some described example implementations.

DESCRIPTION OF THE DRAWINGS

Having thus described the present disclosure in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

FIG. 1 is a cross-sectional view of a multi-layer example embodiment of a nonwoven material according to the disclosure;

FIG. 2 shows an islands-in the sea bicomponent fiber;

FIG. 3 depicts a typical bicomponent spunbonding process;

FIG. 4 shows a typical process for hydroentangling;

FIG. 5 is a schematic drawing of a typical meltblowing process;

FIG. 6 is an illustration of an example embodiment of a surgical mask made using the nonwoven material according to the disclosure;

FIG. 7 is an illustration of an example embodiment of a respirator made using the nonwoven material according to the disclosure;

FIG. 8 is an illustration of an example embodiment of a reusable respirator with a replaceable filter made using the nonwoven material according to the disclosure;

FIG. 9 is an SEM image of a nonwoven material made as described in the Experimental section.;

FIG. 10 A graphically illustrates pressure drop overtime and FIG. 10B graphically illustrates filtration efficiency over time for a first embodiment of the present disclosure;

FIG. 11 A graphically illustrates pressure drop over time and FIG. 1 IB graphically illustrates filtration efficiency over time for a second embodiment of the present disclosure;

FIG. 12A graphically illustrates pressure drop over time and FIG. 12B graphically illustrates filtration efficiency over time for a third embodiment of the present disclosure;

FIG. 13A graphically illustrates pressure drop over time and FIG. 13B graphically illustrates filtration efficiency over time for a fourth embodiment of the present disclosure; FIG. 14A graphically illustrates pressure drop over time and FIG. 14B graphically illustrates filtration efficiency over time for a fifth embodiment of the present disclosure;

FIG. 15A graphically illustrates pressure drop over time and FIG. 15B graphically illustrates filtration efficiency over time for a sixth embodiment of the present disclosure;

FIG. 16A graphically illustrates pressure drop over time and FIG. 16B graphically illustrates filtration efficiency over time for a seventh embodiment of the present disclosure; and

FIG. 17A graphically illustrates pressure drop over time and FIG. 17B graphically illustrates filtration efficiency over time for an eighth embodiment of the present disclosure.

DETAILED DESCRIPTION

The present invention now will be described more fully hereinafter. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. As used in this specification and the claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Directional terms, such as “forward,” “rearward,” “front,” “back,” “right,” “left,” “upwardly,” “downwardly,” and the like are words of convenience and are not to be construed as limiting terms.

As used herein, the term “fiber” is defined as a basic element of nonwovens which has a high aspect ratio of, for example, at least about 100 times. In addition, “filaments/continuous filaments” are continuous fibers of extremely long lengths that possess a very high aspect ratio. “Staple fibers” are cut lengths from continuous filaments. Therefore, as used herein, the term “fiber” is intended to include fibers, filaments, continuous filaments, staple fibers, and the like. The term “multicomponent fibers” refers to fibers that comprise two or more components that are different by physical or chemical nature, including bicomponent fibers.

The term “nonwoven” as used herein in reference to fibrous materials, webs, mats, batts, or sheets refers to fibrous structures in which fibers are aligned in an undefined or random orientation. The nonwoven fibers are initially presented as unbound fibers or filaments, which may be natural or man-made. An important step in the manufacturing of nonwovens involves binding the various fibers or filaments together. The manner in which the fibers or filaments are bound can vary, and include thermal, mechanical and chemical techniques that are selected in part based on the desired characteristics of the final product. Nonwoven fabrics or webs have been formed from many processes, which include carding, meltblowing, spunbonding, and air or wet laying processes.

As used herein, the terms “hydroentangle” or “hydroentangling” refers to a process by which a high velocity water jet or even an air jet is forced through a web of fibers causing them to become randomly entangled. Hydroentanglement can also be used to impart images, patterns, or other surface effects to a nonwoven fabric by, for example, hydroentangling the fibers on a three-dimensional image transfer device such as that disclosed in U. S. Pat. No. 5,098,764 to Bassett et al. or a foraminous member such as that disclosed in U.S. Pat. No. 5,895,623 to Trokhan et al., both fully incorporated herein by reference for their teachings of hydroentanglement.

Nonwoven Fabric

The fibers utilized to form the nonwoven fabrics of the present disclosure can vary, and include fibers having any type of cross-section, including, but not limited to, circular, rectangular, square, oval, triangular, and multiloba! In certain embodiments, the fibers can have one or more void spaces, wherein the void spaces can have, for example, circular, rectangular, square, oval, triangular, or multilobal cross- sections. The fibers may be selected from single-component or monocomponent (i.e., uniform in composition throughout the fiber) or multicomponent fiber types (e.g., bicomponent) including, but not limited to, fibers having a sheath/core structure and fibers having an islands-in-the-sea structure, as well as fibers having a side-by-side, segmented pie, segmented cross, segmented ribbon, or tipped multilobal cross- sections. In certain embodiments, the fabrics of the invention will include both monocomponent and multicomponent fibers, and will also typically include more than one type of polymer, either different grades of the same polymer or different polymer types. Nonwoven fabrics and methods for nonwoven production that can be adapted for use in the present disclosure are described in US App! No. 16/855,723 filed on April 22, 2020, as well as in US Pat. Nos. 7,981,226 to Pourdeyhimi et al; 7,883,772 to Pourdeyhimi et a!; 7,981,336 to Pourdeyhimi, and 8,349,232 to Pourdeyhimi et a!, all of which are incorporated by reference herein.

The nonwoven fabrics described herein are well-suited for use in personal protective equipment, particularly such equipment used as a breathing barrier. In certain embodiments, one of the benefits of using the material of the present disclosure is the ability to use a broader range of converters to construct protective equipment from the nonwoven material. For example, unlike conventional polypropylene meltblown materials typically used in masks, the spunbond nonwoven material described herein is durable enough to be converted into masks by cutting and sewing, which opens up the possibility of using many converters in the industry that do not normally form masks or other filtration equipment.

When used in a mask, in certain applications, the nonwoven material can be used as a single layer of spunbond material due to the relatively high degree of durability of the nonwoven material compared to many mask materials. In other embodiments, the nonwoven material is used as part of a multi-layer structure. For example, an example multi-layer structure is shown in FIG. 1, which illustrates a nonwoven material 10 comprising an optional inner layer 16 sandwiched between two outer layers, 12 and 14. In certain embodiments of the present disclosure, the multi-layer nonwoven structure can include two layers or three layers, with example configurations including nonwovens with two or three spunbond layers, as well as nonwovens including two or three layers that include both a spunbond layer (or two spunbond layers) and a meltblown layer. Where multiple layers are utilized, the layers can be combined and affixed together using known techniques, such as through stitching or by means of thermal bonding. Certain embodiments of the nonwoven fabric have a filtration efficiency of about 80% or higher, or about 85% or higher or about 90% or higher or about 95% or higher or about 98% or higher or about 99% or higher (e.g., about 90% to about 99% or about 95% to about 99%), measuring according to the test set forth in the Experimental section herein. Example ranges of pressure drop for certain example embodiments of the nonwoven fabric include about 50 Pa or less or about 45 Pa or less or about 40 Pa or less or about 35 Pa or less, such as a range of about 10 to about 50 Pa or about 20 to about 40 Pa, measured at a flow rate of 60 L/min and a sample area of 100 cm². Such pressure drop can be measured as set forth in the Experimental section herein, and the above values can be, for example, the initial pressure drop recorded in the described test in the Experimental section (i.e., initial pressure recorded during the loading test (NIOSH Procedure No. TEB-APR-STP-0059)).

Spunbond Laver

The nonwoven fabric of the disclosure will typically include one or more layers of spunbond material comprising bicomponent fibers that have been partially or fully fibrillated. Such structures provide strong filtration efficiency performance at relatively low pressure drop levels. As used herein, “fibrillation” or “fibrillate” refer to at least partially breaking down a nonwoven web comprising the bicomponent fibers into fibrils through application of mechanical energy, resulting in at least partial separation and intertwining of the internal and external components of the bicomponent fibers. Confirmation of at least partial fibrillation of a nonwoven web of bicomponent fibers can be accomplished by visual inspection of Scanning Electron Microscopy (SEM) micrographs. Although not bound by a particular theory of operation, it is also believed that the fibrillation can impart a certain level of electrostatic charge to the nonwoven structure in certain embodiments, which may enhance filtration efficiency. Advantageously, certain embodiments of the spunbond nonwoven structure can be cut and sewn, which enables the use of a wider range of manufacturers to convert the nonwoven material into a mask structure. In addition, advantageous embodiments of the spunbond nonwoven material can be reused and re-sterilized by ozone, peroxide, and the like.

Prior to fibrillation, the bicomponent filaments include an external fiber component and an internal fiber component, wherein the external fiber component enwraps the internal fiber component. In some embodiments, the external fiber component only partially enwraps the internal fiber component, leaving at least part of the internal fiber component exposed. For example, the bicomponent fiber can be an islands-in- the-sea bicomponent filament having multiple internal fiber components and an external fiber component. FIG. 2 shows a typical islands-in-the-sea bicomponent filament. The “islands” internal fiber components are enwrapped in the “sea” external fiber component.

In certain embodiments, the bicomponent filament comprises an island-in-the-sea fiber having from 2 to about 1000 islands (internal components). In certain embodiments, the bicomponent filament has from about 5 to about 400 islands, such as from about 10 to about 200 islands or about 20 to about 100 islands or about 30 to about 40 islands. In certain embodiments, the internal or external fiber component can comprise a thermoplastic polymer selected from the group consisting of polyesters, polyamides, thermoplastic copolyetherester elastomers, polyolefins, polyacrylates, and thermoplastic liquid crystalline polymers. In certain embodiments, the internal or external fiber component can comprise a thermoplastic polymer selected from the group consisting of nylon 6, nylon 6/6, nylon 6,6/6, nylon 6/10, nylon 6/11, nylon 6/12, nylon 11, nylon 12, polypropylene or polyethylene, polyesters, co-polyesters or other similar thermoplastic polymers. It is desirable to have internal and external fiber components that are not compatible; that is, the two components have minimal affinity for bonding to or sticking to one another. Example bicomponent fibers include those comprising a polyester such as poly lactic acid (PLA) or polyethylene terephthalate (PET) as the external or sea component and a polyolefin such as polypropylene (PP) as the internal or island component.

During fibrillation, the external fiber component, or sea, is fractured. Thus, the sea component can remain in the finished nonwoven fabric instead of being removed by dissolving or other methods. Leaving the sea component in the finished nonwoven fabric has multiple advantages, including reducing the cost of production and being more environmentally sound because solvents are not needed to dissolve the sea.

The compatibility between the fiber components is measured by the chi factor (c) or the solubility parameter of the two polymers used. At the temperatures at which the polymers are processed, there can be chemical interactions between the two polymers, which can affect the interface between the polymer components.

In the bicomponent filament, the external fiber component typically comprises from about 5%-30% by weight of the total fiber for ease of fibrillation. In some embodiments, the external component is less than about 20% by weight of the total fiber. In one embodiment, the external component is about 10% or about 15% by weight of the total fiber. In other embodiments, the external fiber component is about 5%- 10%, 6%-10%, 7%-10%, 8%-10%, 9%-10%, 5%-15%, 6%-15%, 7%-15%, 8%-15%, 9%-15%, 10%-15%, 11%-15%, 12%-15%, 13%-15%, 14%-15%, 15%, 5%-25%, 10%-25%, 15%-25%, or 15%-30%by weight of the total fiber.

In certain embodiments, the external sea component does not entirely enwrap the internal islands components. In certain embodiments, for example when the sea component is less than 20% by weight of the total fiber, the sea forms a thin barrier between the islands due to the low amount of external sea component. This increases the ease of fibrillation. In certain embodiments, the sea enwraps the islands less than 90%. In certain embodiments, the sea enwraps the islands less than 75%, less than 70%, less than 65%, less than 60%, less than 55%, less than 50%, from 1% to 90%, 10% to 90%, 20% to 90%, 30% to 90%, 40% to 90%, 50% to 90%, 60% to 90%, 70% to 90%, or 80% to 90%.

The spunbond material can contain other components, such as monocomponent fibers intermixed with the bicomponent fibers as set forth, for example, in US Pat. No. 7,981,336 to Pourdeyhimi, which is incorporated by reference herein.

The bicomponent fibers, which typically have a filament size of between about 10 to about 100 microns, are formed into a nonwoven using a spunbonding process. FIG. 3 shows an example of a typical bicomponent filament spunbonding process. Polymer is fed from a hopper into an extruder. The polymer is heated in the extruder, melting the polymer. The polymer can be mixed with additives in the extruder. The molten polymer passes through a filter and into a pump. The polymer then moves into the spin pack which contains a spinneret. The spinneret has holes that form the molten polymer into fibers or filaments. Quench air cools the polymer, causing the polymer to solidify. In attenuation, the polymer filaments are stretched, orienting the molecules in the polymer.

In the exemplary process shown in FIG. 3, the polymer filaments are deposited on a forming belt to form a web. The web then passes through a compaction roll and a calender, which bonds the filaments together to form a fabric. Bonding methods used in spunbonding processes can include hydroentangling, needlepunching, thermal bonding, and other methods.

For purposes of the present disclosure, it is advantageous for the bonding process to include hydroentangling, which also causes fibrillation within the nonwoven web. FIG. 4 shows a typical process for hydroentangling. FIG. 4 shows a drum entangler using two drums and four injectors. A pre-wet injector/manifold may be used as well, and there may be more drums and injectors used. In some embodiments, the surface of the drum used in hydroentangling is smooth to enhance separation of the fibrils after fibrillation.

Typically, the fibrillation process utilizes hydro energy for fibrillating the external fiber component. The hydro energy used for fibrillation is also sufficient for hydroentangling the set of bicomponent filaments/fibers. The hydroentanglement process typically occurs after the bicomponent filaments/fibers have been positioned onto a belt carrier in the form of a web. The process produces micro-denier fibers which can be from 0.1 and 5 microns in diameter. In certain embodiments, the diameter is from 0.1 and 0.5 microns, 0.5 and 1 microns, 1 and 1.5 microns, 1.5 and 2 microns, 2 and 2.5 microns, 2.5 and 3 microns, 3 and 3.5 microns, 3.5 and 4 microns, 4 and 4.5 microns, 4.5 and 5 microns, 0.1 and 1 microns, 0.1 and 2 microns, 0.1 and 3 microns, 0.1 and 4 microns, 1 and 5 microns, 2 and 5 microns 3 and 5 microns, or 4 and 5 microns.

The web or the nonwoven fabric can be exposed to one or more hydroentangling manifolds to fibrillate and hydroentangle the fiber components. The web or nonwoven fabric can have a first surface and a second surface. In certain embodiments, the first surface is exposed to water pressure from one or more hydroentangling manifolds. In other embodiments, the first surface and second surface are exposed to water pressure from one or more hydroentangling manifolds. The one or more hydroentangling manifolds can have a water pressure from 10 bars to 1000 bars. Example water pressure used for hydroentanglement can be from 10 bars and 500 bars. In certain embodiments, the water pressure used for hydroentanglement is from 10 bars to 100 bars, 10 bars to 200 bars, 10 bars to 300 bars, 10 bars to 400 bars, 10 bars to 600 bars, 100 bars to 200 bars, 300 bars to 400 bars, 500 bars to 600 bars, 600 bars to 700 bars, 700 bars to 800 bars, 800 bars to 900 bars, 900 bars to 1000 bars, or 500 bars to 1000 bars. In certain embodiments, the water pressure used for hydroentanglement is from 10 bars to 300 bars. In additional embodiments, a series of injectors or manifolds are used, and the pressure is gradually increased. In certain embodiments, the hydroentangling manifold water jets are spaced at least 1200 microns away from each other. In some other examples, the water jets are spaced from 1200 microns to 4800 microns apart, e.g., from 1200 microns to 1800 microns, 1200 microns to 2400 microns, 1800 microns to 2400 microns, 1800 microns to 2400 microns, or 2400 microns to 4800 microns apart. Each water jet spacing pertains to one manifold. In certain embodiments, for the disclosed method, 3, 4, 5, or 6 manifolds can be used. In other embodiments, more than 6 manifolds can be used.

In some embodiments, hydroentangling can use multiple manifolds where the spacing of the water jets increases or decreases from the first manifold or set of manifolds to the last manifold or set of manifolds. For example, at least 3 manifolds can have jet spacings of at least 1200 microns, where the rest are below 1200 microns. In other embodiments, at least 4, 5, or 6 manifolds can have jets at least 1200 microns apart where the rest are below 1200 microns. In some other embodiments, at least 3, 4, or 5 manifolds can have jet spaced at least 2400 microns apart where the rest are less than 2400 microns apart. In additional embodiments, 6 manifolds can be used with at least three of the water jets being spaced 1200 microns apart, at least two of the water jets being spaced at least 2400 microns apart, and at least one of the water jets being spaced 600 microns apart. In other embodiments, 5 manifolds can be used with at least two of the water jets being spaced 1200 um apart, at least two of the water jets being spaced at least 2400 um apart, and at least one of the water jets being spaced 600 microns apart. In yet other embodiments, 4 manifolds can be used with at least two of the water jets being spaced 1200 um apart and at least two of the water jets being spaced at least 2400 microns apart. In further embodiments, 3 manifolds can be used with at least two of the water jets being spaced 1200 microns apart. This spacing of the manifold jet strips can lead to partial fibrillation of the bicomponent filaments/fibers. The partial fibrillation allows for a low- density material with a low pressure drop while keeping a high efficiency. The structure of the material is made up of fine fibrils and larger fibers. Partial fibrillation can result, for example, in about 50% of the fibers being fibrillated. This can be determined by SEM micrographs. In some examples, from 80% to 10% of the fibers are fibrillated, e.g., 70%, 60%, 50%, 40%, 30%, 20%, or 10%, where any value can form the upper or lower endpoint of a range, can be fibrillated as determined by SEM micrographs.

By at least partially fibrillating the external fiber component, a spunbond nonwoven fabric comprising microfibers or nanofibers can be produced which can be used for construction of masks as set forth in greater detail below. In certain embodiments, the thickness of the spunbond fabric that results from this disclosed method can be from 1 to 2 mm, e.g., from 1 mm to 1.2 mm, from 1 mm to 1.4 mm, from 1.4 mm to 1. 6 mm, from 1.4 mm to 1.8 mm, or 1.4 mm to 2 mm.

In some embodiments, the basis weight of the spunbond nonwoven web used in each spunbond layer is about 200 g/m² or less, about 175 g/m² or less, about 150 g/m² or less, about 125 g/m² or less, about 100 g/m² or less, or about 75 g/m² or less. In certain embodiments, the spunbond nonwoven fabric used in each spunbond layer has a basis weight of about 75 g/m² to about 200 g/m², such as about 100 to about 150 g/m². In certain embodiments, multiple spunbond layers are used in the nonwoven structure, with a total spunbond layer basis weight of about 225 g/m² or greater, about 250 g/m² or greater, about 275 g/m² or greater, or about 300 g/m² or greater. The basis weight of the fabric can be measured, for example, using test methods outlined in ASTM D 3776/D 3776M-09ae2 entitled “Standard Test Method for Mass Per Unit Area (Weight) of Fabric.” This test reports a measure of mass per unit area and is measured and expressed as grams per square meter (i.e., gsm or g/m²).

Meltblown Laver

In certain embodiments, the nonwoven fabrics of the present disclosure can include a meltblown layer. For example, the meltblown layer could comprise a thermoplastic polymer selected from the group consisting of polyesters, polyamides, thermoplastic copolyetherester elastomers, polyolefins, polyacrylates, and thermoplastic liquid crystalline polymers. In certain embodiments, the meltblown layer can comprise a thermoplastic polymer selected from the group consisting of nylon 6, nylon 6/6, nylon 6,6/6, nylon 6/10, nylon 6/11, nylon 6/12, nylon 11, nylon 12, polypropylene or polyethylene, polyesters, co-polyesters or other similar thermoplastic polymers. Certain advantageous embodiments of the meltblown material comprise polypropylene.

Fibers used in meltblown layer of the present disclosure can also include an elastomeric component. “Elastomer” and “elastomeric component,” as used herein, refer to any polymer that exhibits a degree of elasticity (e.g. , capable of returning substantially to its original shape or form after being subjected to stretching or deformation).

Although not limited, the elastomers used in the present disclosure typically are thermoplastic elastomers (TPEs), which generally exhibit some degree of elasticity and can be processed via thermoplastic processing methods (e.g., can be easily reprocessed and remolded). Thermoplastic elastomers can comprise both crystalline (i.e., “hard”) and amorphous (i.e., “soft”) domains and often comprise a blend or copolymer of two or more polymer types. Where the thermoplastic elastomer comprises a copolymer, it may be prepared, for example, by block or graft polymerization techniques. Thermoplastic elastomeric copolymers can, for example, comprise a thermoplastic component and an elastomeric component. In certain copolymeric thermoplastic elastomers, the physical properties of the material can be controlled by varying the ratio of the monomers and/or the lengths of the segments.

Certain exemplary thermoplastic elastomers can be classified as styrenic elastomers (e.g., styrene block copolymers), polyester and copolyester elastomers, polyurethane elastomers, polyamide elastomers, polyolefin blends (TPOs), polyolefins (alloys, plastomers, and elastomers including metallocene polyolefin elastomers), ethylene vinyl acetate elastomers, and thermoplastic vulcanizates. Certain specific elastomers that are useful according to the present invention include, for example, polyisoprene, butadiene rubber, styrene-butadiene rubber, poly(styrene-/>-butadiene-/>-styrene) (SBS), poly (styrene-/ -cthcnc-co-butanc-/ - styrene (SEBS), poly(styrene-/>-isoprene- >-styrene), ethylene propylene diene monomer rubber (EPDM rubber), EPDM rubber/polypropylene (EPDM/PP), polychloroprene, acrylonitrile-butadiene rubber, hydrogenated nitrile rubber, butyl rubber, ethylene-propylene rubber (EPM), silicone rubber, chlorosulfonated polyethylene, polyacrylate rubber, fluorocarbon rubber, chlorinated polyethylene rubber, epichlorohydrin rubber, ethylene-vinylacetate copolymer, styrene-isoprene block copolymer, urethane rubber, and copolymers, blends, and derivatives thereof.

Exemplary commercially available thermoplastic elastomers include, but are not limited to, OnFlex™, Versaflex™, Dynaflex™, Dynalloy™, Versalloy™, and Versollan™ from PolyOne™ Corporation (Avon Lake, OH); RTP 1200, 1500, 2700, 2800, 2900, and 6000 Series Elastomers fromRTP Company (Winona, MN); Elastocon 2800, 8000, STK, SMR, CLR, and OF Series TPEs from Elastocon (Rochester, IL); Enflex® and Ensoft® fromEnplast (Turkey); Styroflex® SBS, Elastollan®, and Elasturan® fromBASF (Florham Park, NJ); KratonMD6705, G1643, MD6717, MD6705, G1643 (Kraton Performance Polymers, Inc., Houston, TX); Affinity™, Amplify™, Engage™, Infuse™, Nordel™, and Versify™ from Dow Chemical (Midland, MI); Vistamaxx™, Santoprene™, and Exact™ from ExxonMobil Chemical Company (Houston, TX); Kalrez®, Neoprene, Hytrel®, Surlyn®, Vamac®, and Viton® from DuPont® Chemicals (Wilmington, DE); Pebax® from Arkema (France); Mediprene® and Dryflex® from Elasto (Sweden); Estagrip® and Estane® from Lubrizol Corporation (Wickliffe, OH); Garaflex™, Garathane™, Vythrene™, and Evoprene™ from AlphaGary (Leominster, MA) and Santoprene® from Advanced Elastomer Systems (Newport, CA). Other exemplary elastomeric materials are described, for example, in US2010/0029161 to Pourdeyhimi, which is incorporated herein by reference; see also, US50 5240 to Braun et al. and US5540976 to Shawver et al., and Zapletalova et al., Polyether Based Thermoplastic Polyurethane Melt Blown Nonwovens, Journal of Engineered Fibers and Fabrics, Vol. 1, Issue 1 (2006), which are incorporated herein by reference.

In certain embodiments, the elastomer is a thermoplastic elastomer (TPE), such as a thermoplastic polyurethane elastomer (TPU) or thermoplastic polyester elastomer (TPE-ET). A particularly advantageous TPE-ET is a series of polymers sold under the Hytrel® trade name by DuPont (Wilmington, DE), which are block copolymers consisting of hard crystalline segments of polybutylene terephthalate and soft amorphous segments based on long-chain polyether glycols. Properties of various HYTREL grades are determined by the ratio of hard to soft segments. Particularly advantageous grades of TPE-ET, such as HYTREL, for use in the present disclosure have a shore D hardness in the range of about 45 to about 65D (tested according to ISO 868), such as about 50D to about 60D, and a flexural modulus at 23°C of about 125 MPa to about 350 MPa (tested according to ISO 178), such as about 150 to about 250 MPa.

In certain embodiments, the elastomer can be used in a blend with one or more additional polymers. In such embodiments, it is advantageous for the blend to be at least 90% by weight of the elastomer, such as at least about 95% by weight elastomer. Example blending partners include polyesters, co-polyesters, polyamides, polyolefins, polyacrylates, or thermoplastic liquid crystalline polymers. Specific examples include biodegradable polymers such as polybutylene succinate (PBS), poly (butylene succinate)-co- (butylene carbonate) (PBS-co-BC), polyethylene carbonate (PEC), polyhydroxyalkanoates (PHA) such as polyhydroxybutyrate (PHB), poly(glycolic acid) (PGA), polycaprolactone (PCL), and combinations thereof. In certain advantageous embodiments, the blending partner is a polyolefin, such as polypropylene. The use of a blending partner can be particularly convenient when the blending partner is commercially available as a masterbatch with a desired additive for the nonwoven material, such as charge stabilizers discussed below.

Meltblowing is a process wherein a polymer (or polymers) is melted to a liquid state and extruded through a linear die containing numerous (e.g. , several hundred or more) small orifices. As the polymer is extruded, streams of hot air are rapidly blown at the polymer, rapidly stretching and/or attenuating the extruded polymer streams to form extremely fine filaments. The air streams typically stretch or attenuate the molten polymer by many orders of magnitude. The stretched polymer fibers are collected as a randomly entangled, self -bonded nonwoven web. Meltblowing generally is described, for example, in US3849241 to Butin, which is incorporated herein by reference.

As illustrated in FIG. 5, for example, a high-velocity gas jet impinges upon the polymer as it emerges from the spinneret 4. An extruder 1 can feed a polymer to a first die 3 and through spinneret 4. Air enters from air intake 5 and into the air manifold 2. High pressure air is then used to draw the polymer into a fiber which can be collected on collector 6. The drag force caused by the air attenuates the fiber rapidly, and reduces its diameter as much as a hundred times from the nozzle diameter. Melt blown webs are typically reported to have fibers in the range of 0.1-10 mip. high surface area per unit weight, high insulation value, self-bonding, and high barrier properties yet breathability.

Meltblowing is generally capable of providing fibers with relatively small diameters. Diameter and other properties of meltblown fibers can be tailored by modifying various process parameters (e.g., die design, die capillary size, polymer throughput, air velocity, collector distance, and web handling). Attenuating the air pressure affects fiber size, as higher pressures typically yield finer fibers (e.g., up to about 5 microns, such as about 1-5 microns) and lower pressures yield coarser fibers (e.g., up to about 20 microns, such as about 10-20 microns). In certain embodiments, the nonwoven web comprises meltblown fibers having average diameters of about 20 microns or less, such as about 15 microns or less or about 10 microns or less or about 5 microns or less (e.g., about 1 to about 10 microns or about 1 to about 5 microns in average diameter). By meltblown standards, the use of a relatively large fiber, such as the ranges provided above, can improve breathability of the resulting fabric.

The design of the meltblowing dies can vary. A conventional Exxon-design meltblown technology (i.e., single-row-capillary or impinging-air type die design) has a single row of spinning capillaries with impinging air streams from both sides of the die tip to draw the fibers. The safe operation pressure of this process is less than about 100 bar, for example. The Biax meltblown die technology (i.e., concentric-air design) features multiple rows of spinning nozzles with individual concentric air jets to attenuate the fibers.

It also tolerates high melt pressures at the spinneret and therefore can utilize higher viscosity polymers with a wide operation window. See, e.g., R. Zhao, “Melt Blowing Polyoxy methylene Copolymer,” International Nonwoven Journal, Summer 2005, pp. 19-21 (2005), herein incorporated by reference.

After production of the fibers and deposition of the fibers onto a surface, the meltblown nonwoven web can, in some embodiments, be subjected to some type of bonding (including, but not limited to, thermal fusion or bonding, mechanical entanglement, chemical adhesive, or a combination thereof), although in some embodiments, the web preparation process itself provides the necessary bonding and no further treatment is used. In one embodiment, the nonwoven web is bonded thermally using a calendar or a thru-air oven. In other embodiments, the nonwoven web is subjected to hydroentangling, which is a mechanism used to entangle and bond fibers using hydrodynamic forces. For example, the fibers can be hydroentangled by exposing the nonwoven web to water pressure from one or more hydroentangling manifolds at a water pressure in the range of about 10 bar to about 1000 bar. In some embodiments, needle punching is utilized, wherein needles are used to provide physical entanglement between fibers.

The fibrous webs thus produced can have varying thicknesses. The process parameters can be modified to vary the thickness. For example, in some embodiments, increasing the speed of the moving belt onto which fibers are deposited results in a thinner web. Average thicknesses of the nonwoven webs can vary and, in some embodiments, the web may have an average thickness of about 1 mm or less.

The stiffness of the meltblown structure can be controlled by employing larger diameter fibers and/or a higher basis weight. In some embodiments, the basis weight of the meltblown nonwoven web is about 100 g/m² or less, about 75 g/m² or less, about 65 g/m² or less, about 60 g/m² or less, about 50 g/m² or less, or about 40 g/m² or less. In certain embodiments, the meltblown nonwoven fabric has a basis weight of about 20 g/m² to about 60 g/m², such as about 20 to about 50 g/m² or about 25 to about 35 g/m².

Fiber Additives

In certain embodiments, the nonwoven fabrics of the present disclosure, or portions or layers thereof, are electrostatically charged. Due to conductivity within the material and ionic attacks from the environment, it is possible that this charge will decay after a period of time, which can lead to reduction of filtration efficiency. Accordingly, in certain embodiments, one or more charge stabilizer additives adapted to increase filtration efficiency and enhance longevity of the surface charge of the fabric can be added to one or of the polymers that form the nonwoven material. Example additives include metal salts of fatty acids such as stearic acid (e.g., magnesium, zinc, or aluminum stearate), titanate salts such as alkaline earth metal titanate salts (e.g., barium titanate or perovskite), silicate salts such as tourmaline, and other mineral materials such as perlite. When present, the amount of this type of additive is typically in the range of less than about 10% by weight of the overall fiber composition, such as less than about 7.5% or less than about 5% (e.g., about 0.1 to about 10% by weight or about 0.1 to about 5% by weight).

The polymer composition used to form any of the nonwoven materials noted herein can optionally include other components not adversely affecting the desired properties thereof. Examples include, without limitation, antioxidants, particulates, pigments, and the like. These and other additives can be used in conventional amounts.

Optional Electrostatic Charging

The nonwoven web, or a portion or layer thereof, can be treated to induce an electrostatic charge within the fibrous material, which enhances filtration efficiency of the material. Electric charge can be imparted to the fibers by various methods including, but not limited to, corona charging, tribocharging, hydrocharging, and plasma fluorination. See, for example, the electric charging techniques set forth in US4215682 to Kubik et al.; US4588537 to Klasse et ah; US4798850 to Brown; US5401446 to Tsai et ah; US6119691 to Angadjivand et al.; and US6397458 to Jones et ah, all of which are incorporated by reference herein. In one particular embodiment, the fibrous material is charged using corona charging by treating one or both sides of the nonwoven web with charging bars, such as those available from Simco-Ion, which can be placed close to the surface of the nonwoven web (e.g., about 20 to about 60 mm) and operating at a voltage of about 35 to about 50 kV. The treated nonwoven fabric is electrostatically charged following such treatment, and such materials are sometimes referred to as electret fibrous materials.

Mask Structures

Masks constructed using the nonwoven material of the invention can vary in form and will include surgical masks, disposable respirators, and reusable respirators with replaceable filter cartridges. Typically, a mask according to this aspect of the disclosure will be configured to cover the mouth and nose of a user, and will include one or more bands (typically elastomeric) to temporarily affix the mask to the head of the user. These bands typically encircle the head or encircle the ears of the user.

Surgical masks are typically loosely -fitting and adapted for use as a single-use covering of the nose and mouth. FIG. 6 illustrates a surgical mask 20 according to one embodiment that can include a nonwoven material 22, optionally in pleated form as shown. The surgical mask 20 can further include an edge material 24 stitched or otherwise affixed to the nonwoven material 22 and elastic bands 26 adapted to fit over the ears of the user. The nonwoven material 22 can be a single layer of the spunbond nonwoven material (e.g., a 125 gsm spunbond nonwoven) of the present disclosure or a multi-layer structure such as shown in FIG. 1. Various features of surgical masks that can be combined with the fibrous material of the present disclosure are shown, for example, in US2016/0235136 to Palomo et al., which is incorporated by reference herein.

An N95 mask or N95 respirator is a particulate-filtering facepiece respirator that meets the U.S. National Institute for Occupational Safety and Health (NIOSH) N95 classification of air filtration, meaning that it filters at least 95% of airborne particles. Respirators have been categorized as being "filtering face- pieces" because the mask body itself functions as the filtering mechanism. Unlike respirators that include mask bodies with attachable filter cartridges or insert-molded filter elements, filtering face-piece respirators are designed to have the filter media cover much of the mask body so there is no need for installing or replacing a filter cartridge. These filtering face-piece respirators commonly come in two configurations: molded respirators and flat-fold respirators. Example embodiments of masks of this type that could be produced using the fibrous material of the invention are shown in US2017/0252590 to Angadjivand et al. and US2019/0307185 to Shiva et al., each of which is incorporated by reference herein.

FIG. 7 illustrates a respirator 30 according to one embodiment that can include a nonwoven material 32 and elastic bands 36 adapted to encircle the head of the user. The nonwoven material 32 is typically in the form of a multi-layer structure that includes two or more layers of the spunbond nonwoven material of the present disclosure, such as shown in FIG. 1. In an example embodiment of respirator 30, the nonwoven material is a multi-layer structure comprising at least two layers of the spunbond material of the present disclosure (e.g., each layer having a basis weight of about 150 gsm or less with a combined spunbond basis weight of about 225 gsm or higher), with an optional layer of meltblown material of the present disclosure (e.g., a meltblown having a basis weight of about 60 gsm or less). Although not shown in the illustrated embodiment, respirators can include an exhalation valve to reduce pressure drop during exhalation.

Certain mask bodies are reusable and include attachable filter cartridges or insert-molded filter elements that include replaceable filter materials. The electrostatically charged meltblown elastomer of the present disclosure could be used as the filter material in such mask designs as well. The bodies of such masks are typically constructed of a rubber/elastomeric material or other thermoplastic polymer. In some cases, such mask bodies can be made by injection molding or 3D printing. Reusable mask bodies that can accommodate a filter material are shown, for example, in US2015/0352382 to Jayaraman et ah, which is incorporated by reference herein.

FIG. 8 illustrates a reusable respirator 40 according to one embodiment that can include a molded or printed mask body 42 adapted to cover the mouth and nose of the user, a replaceable filter insert 44 that can include a filter material such as a nonwoven material of the present disclosure, and a cap 46 configured for attachment to the mask body to hold the filter insert in place. Although not shown, the respirator 40 would typically further include elastic bands for affixing the respirator to the head of the user, such as shown in FIGS. 6 and 7.

EXPERIMENTAL

Spunbond Preparation

A spunbond web comprising bicomponent islands-in-the-sea fibers having 37 PP islands and a PLA sea (85% PP/15% PLA by weight) was prepared. The spunbond web was partially fibrillated with water jets by using 7 injectors comprising hydroentanglingjet strips with the jets spaced at 2400, 2400, 1200, 1200, 1200, 600 microns apart, with a pre-wet manifold having jets 1200 microns apart. Samples having different basis weights were prepared, including 100, 125, and 150 gsm samples.

A scanning electron microscope (SEM) image with magnification at 340X is provided as FIG. 9 for a 125 gsm sample, which provides visual confirmation of the fibrillation.

Meltblown Preparation

A PP meltblown nonwoven web was formed at a basis weight of 30 gsm. The samples were produced on a Reicofil R4 meltblowing machine where the throughput was kept between 0.3 to 0.5 gram per hole per minute by using a meltblowing die with 45 to 60 holes per inch (300 micron capillary). The die to collector distance was kept constant at 225 mm. The air was 1250 m³ /meter/hour. Filtration Efficiency /Pressure Drop Testing

Samples were tested for filtration efficiency using a test set forth in 42 CFR Part 84 and NIOSH Procedure No. TEB-APR-STP-0059, which was conducted using a Model 8130 Automated Filter Tester manufactured by TSI Incorporated. The test involved challenging the nonwoven material with salt particles having a particle size distribution with count median diameter of 0.075±0.020 pm and a standard geometric deviation not exceeding 1.86 in an aerosol at room temperature (about 25°C) and a relative humidity of about 30%. The NaCl particles were neutralized and each tested material was challenged with a salt particle concentration of not more than 200 mg/m³.

The nonwoven materials were tested as flat sheets as opposed to testing after converting the nonwoven into a mask/respirator. The smallest respirator is 140-150 cm² in surface area and respirators are tested at 85 L/min, which comes to a face velocity of about 10 cm/s. The flat sheet area for the test is only 100 cm². Therefore, the testing was conducted at 60 L/min to achieve the same face velocity of 10 cm/s. Accordingly, it is believed that the data generated will correlate well to test data for masks made of the same material. To be designated an N95 respirator, the minimum filtration efficiency achieved by this test must be

95%, and the filtration efficiency cannot fall below this level at any point during the test. Pressure drop was also determined on the TSI 8130 machine for each material simultaneously.

A series of flat sheets comprising multiple layers of spunbond material were tested, in some cases combined with a layer of the meltblown material. Specifically, the combinations set forth in Table 1 below were tested and the resulting data are set forth in the appended figures also designated below. In the table, “SB” is spunbond and “MB” is meltblown.

Table 1

All of the noted configurations of Table 1, with the exception of Sample A, met the qualifications of an N95 mask (i.e., maintained a filtration efficiency of 95% or greater throughout the test). This suggests that use of the spunbond material of the present disclosure in a layered configuration, and particularly at a total basis weight of greater than 200 gsm, can provide an effective N95 mask material. Sample H met the qualifications of an N99 mask (i.e., maintained a filtration efficiency of 99% or greater throughout the test). This suggests that combinations of the spunbond material of the present disclosure with a meltblown layer in a three-layer structure can provide an effective N99 mask material.

N95 masks must have a max pressure drop of < 343 Pa during inhalation and a max pressure drop of < 245 Pa during exhalation. As shown in the appended figures, all of the two-layer spunbond embodiments

(Samples A-D) of the present disclosure had an initial pressure drop of no more than about 50 Pa and the pressure drop remained below about 200 Pa during the entire test. Even the three-layer spunbond embodiment of Sample E maintained a pressure drop below about 250 Pa. The three-layer spunbond- meltblown-spunbond embodiment of Sample H also maintained a low pressure drop. Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing description. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

CLAIMS:

1. A mask configured to cover the nose and mouth of a user comprising a multi-layer nonwoven fabric, the nonwoven fabric comprising at least one layer of a spunbond material comprising at least partially fibrillated bicomponent filaments formed from bicomponent filaments having an external fiber component and an internal fiber component, wherein the external fiber component at least partially enwraps the internal fiber component; and wherein the external fiber component is 5% to 25 wt.% of the bicomponent filament.

2. The mask of claim 1, wherein the internal fiber component and the external fiber component comprise different thermoplastic polymers selected from the list consisting of polyesters, polyamides, thermoplastic copolyetherester elastomers, polyolefins, polyacrylates, and thermoplastic liquid crystalline polymers.

3. The mask of claim 1, wherein the internal fiber component comprises a polyolefin and the external fiber component comprises a polyester.

4. The mask of claim 1, comprising multiple layers of the spunbond material, each layer having a basis weight of about 150 gsm or less with a combined spunbond basis weight of about 225 gsm or greater.

5. The mask of claim 4, wherein the combined spunbond basis weight is about 250 gsm or greater.

6. The mask of claim 1, further comprising at least one layer of meltblown nonwoven material having a basis weight of about 60 gsm or less.

7. The mask of any one of claims 1 to 6, wherein the multi-layer nonwoven fabric has no more than three layers of nonwoven material.

8. The mask of claim 7, wherein the multi-layer nonwoven fabric has no more than two layers of nonwoven material.

9. The mask of any one of claims 1 to 6, wherein the multi-layer nonwoven fabric consists of only the following specified layers of nonwoven material with no other nonwoven layers affixed thereto: (i) two layers of the spunbond material, each layer of spunbond material having a basis weight of about 100 to about 150 gsm with a combined spunbond basis weight of about 225 gsm or greater; or (ii) one or two layers of the spunbond material, each layer of spunbond material having a basis weight of about 100 to about 150 gsm, and a layer of meltblown nonwoven material having a basis weight of about 60 gsm or less.

10. The mask of any one of claims 1 to 6, wherein the multi-layer nonwoven fabric has a filtration efficiency of about 95% or higher, measured according to the test set forth in 42 CFR Part 84 and NIOSH Procedure No. TEB-APR-STP-0059 at a flow rate of 60 L/min and a sample area of 100 cm².

11. The mask of any one of claims 1 to 6, wherein the multi-layer nonwoven fabric has a pressure drop in the range of about 60 Pa or less at a flow rate of 60 L/min and a sample area of 100 cm².

12. The mask of any previous claim, in the form of a surgical mask or a respirator.