CN116234675A - Method for preparing high-quality immobilized active medium lump material and extruder - Google Patents

Abstract

A method and extruder for making carbon blocks using polyvinylidene fluoride (PVDF) as a binder and an absorbent such as activated carbon and the like are disclosed.

Description

Method for preparing high-quality immobilized active medium lump material and extruder

Technical Field

The present invention relates to a method and extruder for making blocks of active media using polyvinylidene fluoride (PVDF) as a binder and active media such as activated carbon.

Background

Immobilized active media blocks, also known as blocks or carbon blocks or monoliths, have been used well as filters for water filtration applications to remove chlorine, taste, odor and other suspended or dissolved contaminants, such as microorganisms and heavy metals, from drinking water. These blocks can also be used in other applications such as wastewater filtration, chemical reaction catalysts, electrodes for batteries and supercapacitors, transportation, storage, separation, cleaning of liquids and gases, etc.

These blocks are typically made from active media particles or fibers such as activated carbon, graphite, molecular sieves, metals and derivatives, bactericides, heavy metal removers, and the like. These blocks also contain one or more binders, such as polymeric binders, that allow for the interconnection between the active media particles. The polymeric binder can be composed of almost any thermoplastic material, including polyolefins such as polyethylene, polypropylene, and the like; polyethylene such as polyvinyl chloride, polyvinyl fluoride, polyvinylidene chloride, polyvinylidene fluoride, and the like; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and the like; polyamides, and the like. Among these materials, polyethylene and polyester are most widely used in the market place.

There are two main methods for preparing the block. One by sintering/compression molding and the other by continuous extrusion techniques. Extrusion is generally considered to be a more cost effective way of producing blocks.

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The introduction of a series of PVDF polymer binders into the brick industry has proven to have the advantages of reduced binder loading, improved adhesion to active media particles (especially fine particles), and the like. In the case of a water filtration application,the PVDF polymer binder can also improve the performance of removing pollutants such as chlorine, heavy metals and the like. PVDF polymer binders also improve the performance of other block applications such as gas transport, storage, separation and cleaning.

The blocks of the present invention comprise a PVDF polymer binder. PVDF polymer binders include single PVDF polymers, blends of two or more PVDF polymers, and blends of PVDF polymers with other polymers such as polyethylene, polyesters, and polyamides.

When one or more PVDF polymer binders are incorporated into the composition of the block, it is generally not permissible to directly replace them in the processes and equipment used for conventional blocks made from polyethylene and polyester binders. Thus, it is challenging for end users to apply PVDF polymer binders in their products, especially for those users who use extrusion techniques to make blocks.

The present invention relates to an inventive extruder for solving extrusion problems in the manufacture of blocks containing active media particles (e.g., activated carbon) and PVDF polymer binder, thereby improving the convenience and throughput of the extrusion process, as well as the quality and performance of the block.

Typical problems encountered in extruding blocks using PVDF polymer binders include: 1) feeding the particulate blend of active medium and PVDF binder into the extruder barrel, 2) incomplete curing of the binder, and 3) locking of the brick into the barrel results in plugging of the extruder barrel. The feeding problem of the material particle blend is mainly related to the flow of the powder material, whereas PVDF binders tend to impair the flow of the whole powder blend due to their small sub-micron discrete particle size.

Incomplete curing of the blocks is typically due to the fact that the PVDF polymer binder typically has a higher melting temperature than the PE and polyester binders, with temperatures in the range of 110 to 180 ℃. Refers to the bonding of the active medium particles by the binder by curing. Blocks made using PVDF polymers typically require higher temperatures and/or stay in the heating zone of the extruder for longer periods of time. This may result in a partially cured block, for example, when using an extruder of the type having an unthreaded short heating zone as described in WO1992017327 A2.

The problem of extruder barrel blockage is typically due to the high friction of the block against the extruder barrel wall. This problem occurs particularly on blocks containing small active media particles of less than 100 microns, preferably less than 20 microns, most preferably less than 10 microns. PVDF polymer binders are mainly used for such blocks, such as activated carbon blocks for health function filters, which remove heavy metals using small active media particles. The blocks containing PVDF polymer binder also present a sticking problem because the binder loading is low, typically less than 20%, preferably less than 16%. This is because the polymeric binder acts as a lubricant, helping to minimize friction with the extruder walls.

US 2016/012389 A1 and WO2014055473A2 teach methods for making activated carbon block filters using a thermoplastic binder (PVDF) as the binder, and making the filters by compression molding/sintering techniques or by extrusion.

WO1992017327A2 describes the use of an extrusion process to form a solid composite article. An extruder is disclosed for producing blocks from a blend of activated carbon and polyethylene binder. PVDF is not mentioned as a possible binder. Koslow teaches an extruder having a short unthreaded heating zone in the barrel, wherein the heating zone is shorter than the die (cooling) zone. It also discloses that the longer heating zone is not functional because it results in greater friction of the block with the extruder barrel wall, thereby causing barrel blockage.

The extruder described in WO1992017327A2 is not well suited for blocks containing PVDF polymer binder. Because of the relatively high melting temperature of PVDF polymer, between 110 degrees celsius and 180 degrees celsius, short unthreaded heating zones typically do not provide sufficient heat transfer to fully cure the block containing PVDF polymer binder. Thus, the use of such extruders is limited to very low extrusion rates.

The problem of clogging or locking of blocks containing PVDF polymer binder tends to occur in all existing extruder designs, including those described in WO9217327A2, as well as those with longer and/or threaded heating zonesAnd (5) discharging the machine. Blocking of the blocks containing PVDF polymer binder may occur due to low binder loadings, below 30%, preferably below 18%, most preferably below 12%, because of the low binder loadings translating into high levels of active media particles and higher friction with the extruder barrel. In addition, many applications such as high-end CTO water filters and health function water filters require more than 0.55g/cm ³ Preferably greater than 0.65, most preferably greater than 0.75. In addition, such blocks typically contain greater than 10%, preferably greater than 20%, more preferably greater than 30%, of fine active medium particles less than 100 microns, preferably less than 50 microns, and most preferably less than 10 microns. Higher bulk densities and fractions of fine active medium particles also lead to increased friction with the extruder barrel, leading to plugging problems.

A standard extruder similar to that shown in fig. 1 has a screw-threaded feed zone and is typically equipped with a feeder that relies on gravity to convey material from a feeder hopper (hoper) to the barrel. The particulate blend of active medium and polymeric binder contains at least 2wt% of fine particles of active material and/or polymeric binder, often with poor flowability. Poor flowability results in uneven feed to the extruder. The fine particles have a particle size of less than 50 microns, preferably less than 20 microns, and most preferably less than 10 microns (10 microns and above as tested by a Ro-tap sieve shaker, less than 10 microns as tested by a Microtrac particle analyzer). The PVDF binder may contain at least 20%, preferably at least 50% and up to 100% of fine particles. The active media particles may contain fine particles, particularly in high-end filtration applications, it is important to maximize the accessible surface area of the media. Typical fine particles of the active medium include "activated carbon fines", metal reducing agents, bactericides, and the like.

Problems remain in extruding blocks containing PVDF polymer binder, i.e., inconsistent continuous feeding of the blend of active medium and PVDF binder, only partially cured blocks, and/or blocked blocks with locked extruder barrels when using various existing extrusion equipment.

The applicant has now devised a new extruder which combines a barrel with a screw-threaded heating zone and a forming zone, wherein the diameter of the barrel is modified such that it is not constant throughout the zone. By this novel extruder design, the process for making blocks containing PVDF polymer binder is improved without the extruder barrel clogging.

Disclosure of Invention

The present invention relates to a process and extruder for making, and more particularly to an extrusion process and extruder for producing high quality block products made from a poly (vinylidene fluoride) polymer binder and an active medium such as activated carbon particles.

Disclosure of Invention

Aspect 1. An extruder for making a block of active medium and PVDF polymer binder, comprising an extruder barrel comprising a threaded heating zone and an unthreaded forming zone, the unthreaded forming zone comprising a cooling section,

wherein the heating area is longer than the forming area,

wherein in the unthreaded forming zone, the inner diameter "D" of the barrel is from D ₁ Increase to D ₂ Wherein D is ₁ And D ₂ The diameter of (c) varies between 0.2% and 1.0%,

wherein the ratio of the heating zone length to the forming zone length is from 20:1 to 5:4.

Aspect 2 the extruder of aspect 1, wherein the diameter in the molding zone is from D ₁ To D ₂ The increase is 0.2-0.9%, preferably 0.35% -0.70%.

Aspect 3 the extruder of aspect 1, wherein the diameter is from D ₁ To D ₂ The increase is 0.4% -0.65%.

Aspect 4 the extruder of any one of aspects 1-3, wherein D ₁ To D ₂ The diameter change of (c) occurs over 10% to 100% of the length of the forming zone, preferably over 30% to 85% of the length, preferably over 40% to 75% of the length.

Aspect 5 the extruder of any one of aspects 1-4, wherein the ratio of the heating zone length to the shaping zone length is preferably 10:1-5:4.

Aspect 6 the extruder of any one of aspects 1-6, wherein the heating zone is 0.25-2.0 meters long, preferably 0.5-1.5 meters long, and comprises 1-10 heating sections.

Aspect 7 the extruder of any one of aspects 1-7, wherein the shaping zone is 0.01-1 meter long, preferably 0.02-0.5 meter long.

Aspect 8 the extruder of any one of aspects 1-7, wherein the shaping zone is 0.05-0.2 meters long, preferably 0.05-0.15 meters long.

Aspect 9 the extruder of any one of aspects 1-8, wherein the cooling section is 0.01-1 meter long, preferably 0.02-0.5 meter long.

Aspect 10 the extruder of any one of aspects 1-8, wherein the cooling section is 0.05-0.2 meters long, preferably 0.05-0.15 meters long.

The extruder of any one of aspects 1-8, wherein the cooling zone length comprises 20 to 100%, preferably 50 to 99% of the molding zone length.

Aspect 12 the extruder of any one of aspects 1-11, wherein the inside diameter "D" of the barrel in the screw zone ₁ "1 cm to 50cm, preferably 3cm to 25cm.

Aspect 13 the extruder of any one of aspects 1-11, wherein an inside diameter "D" of the barrel in the screw zone ₁ "1 cm to 25cm, preferably 3cm to 6cm.

Aspect 14 the extruder of any one of aspects 1-13, wherein the extruder further comprises a feeder hopper comprising a spiral reamer (auger).

Aspect 15 the extruder of any one of aspects 1-14, wherein the extruder further comprises an external back pressure device.

The extruder of aspect 15, wherein the external backpressure device is selected from the group consisting of: a retractor (puller), a weight (weight), or a donut device (donut device) consisting of a spring and finger attached to a block.

Aspect 17. A method for extruding a block of active medium and PVDF polymer binder, the method comprising the steps of: providing a PVDF polymer binder and an active medium comprising a PVDF polymer, feeding the PVDF polymer binder and the active medium to the extruder of any one of aspects 1 to 14, and extruding the resulting PVDF polymer binder and active medium blend to form a fixed media block.

Aspect 18. A method for extruding a carbon block, the method comprising:

a PVDF polymer binder and an active medium are provided,

providing an extruder comprising an extruder barrel comprising a threaded heating zone and an unthreaded forming zone, the forming zone comprising a cooling zone, wherein the ratio of the heating zone length to the forming zone length is from 20:1 to 5:4, wherein in the forming zone the internal diameter "D" of the extruder barrel increases from D1 to D2, wherein the diameter of D1 to D2 varies from 0.2% to 0.9%,

the PVDF polymer binder and active medium are fed to an extruder,

the PVDF polymer binder and the active medium are extruded to form a fixed medium block.

Aspect 19. The method of aspects 17 or 18, wherein the PVDF polymer binder containing PVDF polymer and the active media are blended prior to feeding to the extruder.

The method of any one of aspects 17 to 19, wherein the heating zone temperature is from 20 ℃ below the binder melting temperature to 80 ℃ above the binder melting temperature.

The process of any one of aspects 17 to 19 wherein the heating zone temperature is 130-260 ℃, preferably 170-230 ℃.

Aspect 22 the method of any one of aspects 17 to 21, wherein the binder comprises a VDF/HFP copolymer having a melt viscosity of 5 to 80kP, preferably 15 to 50 kP.

Aspect 23 the method of any one of aspects 17 to 22, wherein the PVDF polymer contains 5 to 20 wt% HFP.

The method of any one of aspects 17 to 23, wherein the combination of the active medium and the polymeric binder contains at least 2% or more by weight of fine particles.

Aspect 25 the method of any one of aspects 17 to 24, wherein the PVDF polymer contains discrete PVDF polymer particles having a size (in terms of average discrete particle size) of 50 to 500nm and agglomerates of discrete polymer particles having a size of 1 to 150 microns, preferably 3 to 50 microns, as measured by electron scanning microscopy.

The method of any one of aspects 17 to 25, wherein the PVDF polymer binder comprises at least 20%, preferably at least 50%, up to 100% by weight of fine particles.

Aspect 27 the method of any one of aspects 17 to 26, wherein the sorbent (sorbent) comprises activated carbon.

The method of any one of aspects 17 to 27, wherein the binder comprises 1 to 30 wt%, preferably 1 to 10 wt%, based on the total weight of binder and sorbent.

Aspect 29 the method of any one of aspects 17 to 28, wherein the density of the active medium and the bulk of the PVDF polymer binder is at most 0.95g/cm ³ Preferably 0.50 to 0.90g/cm ³ More preferably 0.65 to 0.85g/cm ³ 。

Aspect 30 the method of any one of aspects 17 to 29, wherein the extruder produces the block of active medium and PVDF polymer binder at a rate of 0.5cm to 50cm extruded block per minute, preferably 0.5 to 30cm extruded block per minute.

Aspect 31 the method of any one of aspects 17-30, wherein the heating zone is 0.25 to 2 meters long, preferably 0.5 to 1.5 meters long,

wherein the forming zone is 0.075 to 0.20 meters long, the cooling zone comprises 27% to 72% of the forming zone, and the expansion ratio along the extrusion barrel from D1 to D2 is 0.3% to 0.7%.

Aspect 32 the method of any one of aspects 17-31, further comprising applying a back pressure to the extruded block.

Drawings

Fig. 1 is a schematic view of a prior art extrusion barrel optionally equipped with an internal solid rod to create a hollow cylindrical block. The cartridge consists of three zones, namely a feed zone, a heating zone and a forming zone comprising a cooling zone. The feed zone was unheated and threaded, located directly below the feeder hopper, and terminated at the edge of the hopper. The heated zone is threaded and is longer than the unthreaded forming zone. The heating zone starts from the edge of the feed hopper to the end of the screw-threaded section. In standard extruders, the diameters of the feed zone, heating zone and forming zone are constant along the entire length of the barrel. The shaped region is unthreaded and typically has no heating element. The forming zone extends from the end of the unthreaded section to the end of the barrel. The forming zone typically includes a cooling section in which cooling elements are used.

Fig. 2 is a schematic view of an extrusion barrel of the present invention optionally equipped with an internal solid rod to create a hollow cylindrical block. The cartridge consists of three zones, namely a feed zone, a heating zone and a forming zone comprising a cooling zone. The schematic shows the heating zone and the forming zone. The feed zone (not shown) is unthreaded and typically is not heated, but may be heated. The heating zone is threaded and is equipped with a heating element, preferably located on the outer surface of the cartridge. The forming zone is unthreaded and is typically not heated. The cooling section in the forming zone is equipped with cooling elements. The cooling element is preferably located on the outer surface of the cartridge. In the forming zone, the barrel inner diameter "D" varies along the barrel length such that the final barrel inner diameter (D ₂ ) Is greater than the initial inside diameter (D ₁ ). The inner barrel diameter "D" may vary gradually along the entire length of the unthreaded area, or may vary incrementally. The heating zone is the longest zone in the cartridge.

Detailed Description

All references listed herein are incorporated by reference. All percentages in the composition are weight percentages unless otherwise indicated. Combinations of the different elements described herein are also considered to be part of the present invention.

As used herein, "interconnectivity" means that the active media particles or fibers are permanently bonded together by the polymeric binder particles without completely coating the surfaces thereof. In a so-called "curing" process, the binder softens and adheres to the active media particles at specific discrete points to create an ordered porous structure. The blocks prepared by the process of the present invention are porous. The block allows fluid to flow through the interconnected particles or fibers and the fluid is directly exposed to its surface, facilitating adsorption of the components of the fluid onto the active medium. Because the polymeric binder adheres to the active media particles only at discrete points, less polymeric binder is used to complete the interconnection than is applied to the active media.

An extruder is disclosed for preparing a block of active medium and PVDF binder.

A method of extruding a block of active medium and PVDF binder using the extruder of the present invention is disclosed.

The present invention provides for extruding blocks of an active medium (e.g., activated carbon) using PVDF as a binder. The extruder has a new barrel design that is an improvement over existing extrusion barrels used to produce blocks. The novel extruder of the present invention allows for successful extrusion of the active medium and PVDF binder slugs, where the slugs do not lock into the barrel in the event of a blockage.

The invention provides an improvement of an extruder for extruding blocks of immobilized active medium, wherein an extrusion barrel is improved in a forming zone such that an improved inner diameter (D ₂ ) Is greater than the internal diameter (D ₁ )。

Extrusion apparatus

The improved extruder barrel comprises three zones, 1) a feed zone, 2) a heating zone, and 3) a forming zone comprising a cooling zone.

The feed zone is threaded, typically without heating, which receives material from the feeder and brings the material into the heating zone. The heating zone is threaded, has a heating element, and is the longest zone in the barrel to ensure adequateAnd complete the block curing. The forming zone is unthreaded, it is typically not heated, although portions thereof may optionally be heated. In the forming zone, the cooling section is unthreaded and equipped with cooling elements. The barrel is modified in the forming zone such that the modified inner diameter (D ₂ ) Is greater than the inner diameter (D) ₁ ) As shown in fig. 2. The ratio of the length of the heating zone to the length of the shaping zone is preferably from 20:1 to 5:4, preferably from 10:1 to 5:4, preferably from 8:1 to 6:4.

The absolute length of the extrusion barrel and barrel zones will depend on the thickness of the block. For example, the thickness of a solid cylindrical block is the outside diameter of the block, and the thickness of a hollow cylindrical block is defined as the difference between the outside diameter of the block minus the inside diameter.

The feed zone is from 0.1 to 1 meter long, preferably from 0.2 to 0.5 meter long.

The heating zone is longer than the forming zone and may be from 0.25 meters to 2 meters long, preferably from 0.5 meters to 1.5 meters long. It is equipped with 1 to 10 heating elements, preferably 3 to 5 heating elements. The temperature of the heating element may be set to a room ambient temperature to 300 ℃ and is typically 20 ℃ below the adhesive melting temperature to 80 ℃ above the adhesive melting temperature. The temperature of each element can be independently controlled.

The forming zone may be from 0.01 to 1 meter, or from 0.02 to 0.7 meters, preferably from 0.05 to 0.5 meters long. The cooling section in the forming zone may be from 0.01 to 1 meter long, preferably from 0.02 to 0.5 meter or from 0.05 to 0.20 meter, even more preferably from 0.05 to 0.15 meter. The cooling section is equipped with one or more cooling elements. The cooling element may contain a cooling fluid, such as water or other coolant, which may optionally be frozen. The temperature of the cooling fluid is from 90 ℃ to-20 ℃, preferably from 35 ℃ to 0 ℃.

In the forming zone, the inner barrel diameter "D" may be varied such that the final barrel inner diameter at the end of the forming zone is 1.002 to 1.01 times, or 1.002 to 1.009 times, preferably 1.003 to 1.007 times, most preferably 1.004-1.007 times the initial barrel inner diameter at the beginning of the forming zone. The gradient of the cylinder inner diameter D may occur only in the forming zone. The improvementThe variation may occur over 10% to 100% of the length of the forming zone, preferably over 30% to 85% of the length, preferably over 40% to 75% of the length, more preferably over 50% to 70%, and may occur in a continuous manner or in one or more steps. The percentage is calculated as the ratio of the total length of the change section to the total length of the forming zone (including the cooling section). The measurement range of the length of the variation section is: starting from the point in the forming zone where the inner diameter of the barrel first changes, until the end of the barrel at the outlet of the cooling section. The gradient change allows compensation for the shrinkage of the die and release of the pressure build up in the die where the metal alloy is used to shrink more than the extruded polymeric binder and active medium. After the gradient change is completed, the final inside diameter of the barrel at the end of the forming zone (D ₂ ) Is greater than the initial inside diameter (D ₁ )。D ₁ To D ₂ The overall increase in the inside diameter of the cartridge is 0.2% to 1.0%, preferably 0.2% to 0.9%, preferably 0.35% to 0.7%, most preferably 0.4% to 0.65%. The percentage of growth is calculated as follows:

increase% of d= 100 x (D ₂ -D ₁ )/D ₁

Barrel inside diameter D in the threaded zone ₁ Preferably 1cm to 50cm, more preferably 3cm to 25cm. D (D) ₁ And may be up to 100cm or more. D (D) ₁ May be 1cm to 25cm, or 3cm to 6cm, or 4cm to 5cm. In the case of hollow structures, the typical internal diameter of the hollow in the structure is from 0.5cm to 45cm, more preferably from 1cm to 15cm, or from 1cm to 10cm.

In one exemplary embodiment, the barrel inner diameter D of the threaded zone ₁ 4.35cm and a 0.5% incremental gradient to a barrel inner diameter D at the outlet of the 4.372cm cooling section ₂ 。

Furthermore, this type of extruder may also be equipped with external means that can prevent the block from exiting the extruder, thereby helping to create back pressure to densify the block. This can be achieved by: the extrusion speed is slowed down with conventional retractors used in the plastics industry, weights are placed before the extrudate, or simple devices consisting of springs and fingers (also known as donuts) are used to grasp the block and apply a pressure proportional to the spring constant of the springs. There are other means of creating back pressure to assist in the densification of the block that may be used in conjunction with the extruder of the present invention to create a denser carbon block. Internal design modifications can also be made to densify the block, including changing the inside diameter of the heating zone to create a build-up of material. In this case, the barrel inner diameter at the end of the heating zone is smaller than the barrel inner diameter at the beginning of the heating zone.

Furthermore, a feeding device called feeder is often used in combination with an extruder. The feed apparatus includes a hopper that takes a mass of material and feeds the material to an extruder at a steady rate. They consist of a hopper that absorbs a large amount of material and feeds it into the extruder at a steady rate. However, due to poor flowability, typical feeder hoppers have problems with continuous feeding of a particulate blend of active medium and polymeric binder, which particles contain at least 2wt% or more of fine particles of active material and/or polymeric binder. We have now found that this problem can be eliminated by adding a helical reamer within the feeder hopper, which helps to agitate the powder to achieve a consistent feed.

Finally, the extruder may also be provided with an inline lump-cutter that helps cut the extruded lump into specific lengths.

The novel inventive design of the extruder solves the problem of clogging when preparing blocks containing PVDF polymer binder. The novel extruder design also improves the consistency of the continuous feed in the extruder barrel, ensuring complete curing of the block. Accordingly, the present invention provides a high throughput and consistent method for block manufacturers to prepare fixed active media blocks.

The extruder of the present invention is designed to extrude a block containing the active medium and PVDF polymer binder.

Adhesive agent

The binder in the blocks produced using the extruder of the present invention comprises a polyvinylidene fluoride PVDF polymer binder. The PVDF polymer binder may include a single PVDF polymer, a blend of two or more PVDF polymers, a blend of PVDF polymers with other polymers (e.g., polyethylene, polyester, and or any other thermoplastic polymer). In some embodiments, the PVDF polymer binder is a blend of PVDF binder with other polymers, PVDF being the major component of the overall binder, containing greater than 50% PVDF polymer based on the total polymer binder. In some embodiments, PVDF is not the major component and may be as low as 10% of the total binder content in the block. The PVDF polymer is a vinylidene fluoride homopolymer or a copolymer of vinylidene fluoride and one or more comonomers. The copolymer has a lower melting temperature and modulus than the homopolymer. The lower melting temperature of the binder helps to alleviate the problem of extruder lock-up.

Preferred PVDF copolymers include copolymers containing at least 50 mole%, preferably at least 75 mole%, more preferably at least 80 mole%, even more preferably at least 85 mole% vinylidene fluoride (VDF), wherein the vinylidene fluoride (VDF) is copolymerized with one or more comonomers selected from the group consisting of: tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, hexafluoropropylene (HFP), vinyl fluoride, pentafluoropropene, tetrafluoropropene, trifluoropropene, perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, (meth) acrylic acid esters, and any other monomer that is easily copolymerizable with vinylidene fluoride. The comonomer is preferably hexafluoropropylene.

In one embodiment, the vinylidene fluoride polymer contains up to 30 wt%, preferably up to 25 wt%, more preferably up to 15 wt% HFP units and 70 wt% or more, preferably 75 wt% or more, more preferably 85 wt% or more VDF units. The PVDF polymer may have 0 to 30 wt%, preferably 5 to 20 wt% HFP units.

PVDF used in the present invention is typically prepared by methods known in the art using aqueous radical emulsion polymerization-although suspension polymerization, solution polymerization and supercritical CO may also be used ₂ And (3) a polymerization process. Preferably, PVDF is produced by emulsion polymerization.

The surfactant used in the polymerization may be any surfactant known in the art to be useful in PVDF emulsion polymerization, including perfluorinated, partially fluorinated, and non-fluorinated surfactants. Preferably, the PVDF emulsion of the present invention is fluorosurfactant-free and no fluorosurfactant is used in any portion of the polymerization. Non-fluorinated surfactants useful in PVDF polymerization may be ionic and nonionic, including but not limited to: 3-allyloxy-2-hydroxy-1-propane sulfonate, polyvinylphosphonic acid, polyacrylic acid, polyvinylsulfonic acid and salts thereof, polyethylene glycol and/or polypropylene glycol and block copolymers thereof, alkyl phosphonates and siloxane-based surfactants. In one embodiment, the emulsion polymerization is performed in the absence of any surfactant.

Latex polymer binders are typically made into powder form by spray drying, coagulation or other known processes to produce a dry powder. The powder shape and particle size may be changed by any known process (e.g., milling).

The average discrete particle size of the discrete PVDF binder particles is typically from 5nm to 700nm, preferably from 50nm to 500nm, more preferably from 100nm to 300nm. In some cases, the discrete polymer particles may be agglomerated into clusters of 1 micron to 150 microns, agglomerates of 3 microns to 50 microns, preferably 5 microns to 15 microns. It has been found that some of these agglomerates can deagglomerate into discrete particles or fibrils during processing into an article. Some of the binder particles are discrete particles and remain as discrete particles in the formed block article. During processing into a bulk article, the particles abut the active medium together and provide interconnection.

It is important that as little binder as possible is used to hold the active materials together, as this can expose more surface area of the active medium for interaction with the fluid, for example during filtration or adsorption processes. One advantage of the PVDF polymer is that it has a weight of at least about 1.75g/cm ³ Preferably at least about 1.77g/cm ³ Is a very high specific gravity. Thus, the low weight percentage of binder required represents an even lower volume percentage.

Molecular weight of PVDF Polymer does not existThe method is particularly limited. The higher molecular weight is preferred to help the binder not to flow into the active medium to contaminate the high surface area of the activated carbon under certain conditions. The melt viscosity of the polymer is preferably 1 to 100 kilopoise (kP), preferably 5 to 80 kilopoise, 5 to 60 kilopoise, most preferably 15 to 50 kilopoise. Melt viscosity of the Polymer according to ASTM D383, at 232℃and 100 seconds by capillary rheometry ^-1 And (5) measuring.

Active medium

The active media used are those known for block products. The block product may be used for filtration, e.g., water filtration, or may be used for transportation, storage, separation, cleaning of fluids (gas or liquid) by selecting the appropriate active medium. The active medium particles are not particularly limited. Examples of active media include, but are not limited to, activated carbon, graphite, molecular sieves, metals and derivatives, bactericides and heavy metal removers, and combinations thereof. One preferred active medium is activated carbon.

The size of the active media particle diameter of the present invention generally ranges from 0.1 microns to 3000 microns, preferably from 1 micron to 500 microns, and most preferably from 5 microns to 100 microns. In certain embodiments, the active media particles have a multimodal particle size distribution, e.g., some particles have an average particle size of less than 100 microns and some particles have an average particle size of greater than 200 microns. The active media particles may also be in the form of fibers having diameters of 0.1 microns to 250 microns with a length to width ratio that is substantially unlimited. The fibres are preferably chopped to a length of no more than 5mm.

The active medium fibers or powders should have sufficient thermal conductivity to allow for heating of the powder mixture. Furthermore, during extrusion, the melting point of the particles and fibers must be sufficiently higher than that of the PVDF polymer binder to prevent melting of the material and to produce a continuous molten phase, but to produce the usual desired multiphase system.

Process for producing a solid-state image sensor

The PVDF polymer binder and active medium are blended and processed. PVDF polymer binders are typically in powder form, which can be dry blended with the active medium. Preferably, 0.5 to 35 wt%, preferably 1 to 30 wt%, more preferably 3 to 25 wt% of PVDF polymer binder is used in the block product, based on the total weight of active medium and PVDF polymer binder. The total weight percent of PVDF may be 1 to 10 weight percent based on the total weight of the active medium and PVDF polymer binder.

In the case where very dense blocks are desired, extrusion processing can be performed at higher pressures. The extrusion process is carried out as follows: the softened polymer binder particles are created, but not melted and flowed to the extent that they contact other polymer particles and form agglomerates or continuous layers. In order to be effective in the intended end use, the polymeric binder remains as discrete polymeric particles that bind the active media particles into an interconnected network to achieve good permeability. The solvent that dissolves the binder is not used in the present invention because in the solvent system the individual polymer particles are no longer present because the particles will dissolve and form a continuous coating on the surface of the active medium particles. The continuous coating reduces the amount of activated surface area for fluid to active particle interactions and may reduce its overall effectiveness.

The active medium and the polymeric binder are formed into a block article in an extrusion process. The blocks of the present invention are formed by an extrusion process. Conventional extrusion processes for carbon blocks are described in US 5,331,037.US 5,331,037 describes an extruder using a barrel with a short unthreaded heating zone for extruding blocks made with a polyethylene binder. PVDF is not mentioned as a possible binder.

The polymeric binder/active medium composites of the present invention are typically dry blended and extruded, optionally with other additives (e.g., processing aids). Continuous extrusion under heat, pressure and shear can produce three-dimensional contoured multiphase structures of infinite length. A continuous web of binder and active media particles bonded at a force point is formed under extruder conditions.

Extrusion processes can produce continuous block structures of any desired diameter and length. Lengths of one centimeter to several hundred meters can be obtained with suitable preparation equipment. The continuous solid block may then be cut to the desired final length. The block may be solid or hollow. The typical outer diameter of the block is preferably from 1cm to 50cm, more preferably from 3cm to 25cm, although structures up to 100cm or even larger in diameter can be produced with appropriately sized dies. In the case of hollow structures, the typical inner diameter is from 0.5cm to 45cm, more preferably from 1cm to 15cm, or from 1cm to 10cm.

An alternative to a single structure is to form two or more structures-a solid rod and one or more hollow block cylinders designed to nest together to form a larger structure. Once the annular or rod-shaped block members are formed, the members can be nested together to create a larger structure. This approach may provide several advantages over extruding a single large structure. Blocks with smaller cross-sectional diameters can be produced at a faster rate than large solid single pass blocks. For each smaller cross-section workpiece, the cooling profile can be better controlled. Another advantage of this concept may be a reduction in the gas diffusion path length through the monolith because the spacing between concentric blocks may serve as a channel for rapid gas flow.

Properties of (C)

The articles formed by the present invention are high quality, strong block structures of active media and binders. The density of the block may be fine tuned, for example, the density may be very high to maximize the amount of active medium and thus the efficiency of the block.

The extruder of the present invention provides a density of up to 0.95g/cm ³ Is a block of (a). Preferably, the density of the block product is from 0.50 to 0.90g/cm ³ More preferably 0.65 to 0.85g/cm ³ 。

The extruder of the present invention provides higher throughput due to reduced friction of the composition particles with the extruder walls. The extruder of the present invention can provide a throughput of extruded blocks of up to 0.5cm to 50cm per minute, preferably up to 1cm to 30cm per minute.

The temperature of the heating zone is typically driven by the softening temperature of the binder, typically 20 ℃ below the melting temperature of the binder to 80 ℃ above the melting temperature of the binder. For example, the temperature is typically 130 ℃ to 260 ℃, and may be 170 ℃ to 230 ℃. Depending on the polymeric binder, the temperature may be lower or higher than these examples.

The novel extruder barrel can continuously extrude fine particles using PVDF polymer binder while minimizing the problem of lock-up encountered with conventional extruders.

Examples

Example 1

The extrusion barrel includes: a1 meter screw-threaded heating zone, a 0.23 meter forming zone having a 0.115 meter cooling section. The initial barrel inner diameter d1=4.35 cm of the screw zone and the final barrel inner diameter d2= 4.372cm (0.5% change) at the extruder outlet. The change in inner diameter may occur along 0.172 meters in the length of the unthreaded forming section. The cartridge is equipped with an inner rod for extruding the hollow cylindrical block. The screw diameter is equal to the inner diameter of the hollow block and the inner diameter id=1.9 cm. The thread clearance was 4cm. (made of CrMoAl).

The preparation comprises 8 wt% of binder

FG-81) and 92 wt.% of activated carbon of 80X 325, jacobi (Jaccobi) company.

The processing conditions are as follows:

the binder and carbon were mixed in a rotating mixer at low speed for 1 hour.

Extrusion conditions of 190 ℃, 200 ℃, 150 ℃, 105 ℃ (T1T 2T 3 and T4);

the density of the resulting block was 0.75g/cm ³ (measured by weight/volume after the block has cooled). The linear velocity of the produced block was 8 cm/min.

The bulk density indicates mechanical strength and shows stability of the process. The extruder was run for 3 hours without any problems (no lock). This is in contrast to the case of running the same lump-forming composition on an extruder with an unmodified barrel of constant inner diameter d1=4.35 cm. Without the barrel modified, the extruder was locked during the first 30 minutes and the block stuck in the barrel.

Example 2

The extruder barrel was the same as in example 1.

The preparation comprises 25 wt% of binder

FG-415) and 75 wt% of activated carbon of 80X 325 size from jacobian.

The processing conditions are as follows:

the binder and carbon were mixed in a rotating mixer at low speed for 1 hour.

Extrusion conditions four heating zones: 170 ℃, 180 ℃, 150 ℃, 105 ℃ (T1T 2T 3 and T4);

the density of the resulting block was 0.8g/cm ³ (measured by weight/volume after the block has cooled). The linear velocity of the produced block was 8 cm/min.

The bulk density indicates mechanical strength and shows stability of the process.

The extruder was run for 3 hours without any problems (no lock). As in example 1, this is in contrast to the unmodified barrel which resulted in extruder lock.

Example 3

Using two different feeders will contain 8% binder (by weight)

FG-81) and 92% (by weight) of activated carbon of 80 x 325 size from jacobian company are fed into the extruder barrel. All binders are considered fine particles, which tend to impair the flow of the overall powder blend in a typical feeder apparatus. In a comparative example using a standard feeder made according to a simple hopper design (no screw reamer), the powder blend feed to the extruder barrel was not uniform. The powder tends to adhere to the hopper walls and itself, resulting in a "stop-and-go" feed profile. In the case of the improvement of the feeder hopper with a spiral reamer, the powder is fed at a constant rate without any inconsistencies. The use of a feeder hopper modified with a helical reamer allows for the inclusion ofIt is critical that more than 2% of the fine particle formulation enter the extruder consistently. Consistent powder feed and use of a modified extruder barrel are necessary to produce a quality carbon block product. />

Claims (32)

1. An extruder for preparing a block of active medium and PVDF polymer binder, comprising an extruder barrel comprising a threaded heating zone and an unthreaded forming zone comprising a cooling section,

wherein the heating area is longer than the forming area,

wherein in the unthreaded forming zone, the inner diameter "D" of the barrel is from D ₁ Increased to D ₂ Wherein D is ₁ To D ₂ The diameter of (c) varies between 0.2% and 1.0%,

wherein the ratio of the heating zone length to the shaping zone length is from 20:1 to 5:4.

2. The extruder of claim 1 wherein the diameter in the forming zone is from D ₁ To D ₂ The increase is 0.2% to 0.9%, preferably 0.35% to 0.70%.

3. The extruder of claim 2, wherein the diameter is from D ₁ To D ₂ The increase is 0.4% to 0.65%.

4. The extruder of claim 1, wherein D ₁ To D ₂ The diameter change of (c) occurs over 10% to 100% of the length of the forming zone, preferably over 30% to 85% of the length, preferably over 40% to 75% of the length.

5. The extruder of claim 1, wherein the ratio of the heating zone length to the forming zone length is from 10:1 to 5:4.

6. The extruder of claim 1, wherein the heating zone is 0.25 to 2.0 meters long, preferably 0.5 to 1.5 meters long, and comprises 1 to 10 heating sections.

7. The extruder of claim 1, wherein the forming zone is 0.01 to 1 meter long, preferably 0.02 to 0.5 meter long.

8. The extruder of claim 1, wherein the forming zone is 0.05 to 0.2 meters long, preferably 0.05 to 0.15 meters long.

9. The extruder of claim 1, wherein the cooling section is 0.01 to 1 meter long, preferably 0.02 to 0.5 meter long.

10. The extruder of claim 1, wherein the cooling section is 0.05 to 0.2 meters long, preferably 0.05 to 0.15 meters long.

11. An extruder according to claim 1, wherein the cooling zone length is 20% to 100%, preferably 50% to 99% of the length of the forming zone.

12. The extruder of claim 1, wherein the inner diameter "D" of the barrel in the screw zone is 1cm to 50cm, preferably 3cm to 25cm.

13. The extruder of claim 1, wherein the inner diameter "D" of the barrel in the screw zone is 1cm to 25cm, preferably 3cm to 6cm.

14. The extruder of claim 1, wherein the extruder further comprises a feeder hopper comprising a spiral reamer.

15. The extruder of claim 1, wherein the extruder further comprises an external back pressure device.

16. The extruder of claim 15, wherein the external backpressure device is selected from the group consisting of: a retractor, a weight, or a multi-doughnut device consisting of a spring and fingers attached to a block.

17. A method for extruding a block of active medium and PVDF polymer binder, the method comprising the steps of: providing a PVDF polymer binder and an active medium comprising a PVDF polymer, feeding the PVDF polymer binder and the active medium to the extruder of claim 1, and extruding the resulting PVDF polymer binder and active medium blend to form a fixed media block.

18. A method of extruding a carbon block, the method comprising the steps of:

a PVDF polymer binder and an active medium are provided,

providing an extruder comprising an extruder barrel comprising a threaded heating zone and an unthreaded forming zone comprising a cooling zone, wherein the ratio of the heating zone length to the forming zone length is from 20:1 to 5:4, wherein in the forming zone the internal diameter "D" of the extruder barrel is from D ₁ Increased to D ₂ Wherein D is ₁ To D ₂ The diameter variation of (a) is 0.2 to 0.9%,

the PVDF polymer binder and active medium are fed to an extruder,

the PVDF polymer binder and active medium blend is extruded to form a fixed medium block.

19. The method of claim 17 or 18, wherein the PVDF polymer binder containing PVDF polymer and the active media are blended prior to feeding to the extruder.

20. A method as claimed in claim 17 or 18, wherein the heating zone temperature is from 20 ℃ below the binder melting temperature to 80 ℃ above the binder melting temperature.

21. A process according to claim 17 or 18, wherein the heating zone temperature is 130-260 ℃, preferably 170-230 ℃.

22. The method of claim 17 or 18, wherein the binder comprises a VDF/HFP copolymer having a melt viscosity of 5 to 80kP, preferably 15 to 50 kP.

23. The method of claim 17 or 18, wherein the PVDF polymer contains 5 wt.% to 20 wt.% HFP.

24. The method of claim 17 or 18, wherein the combination of active medium and polymeric binder contains at least 2% or more by weight of fine particles.

25. The method of claim 17 or 18, wherein the PVDF polymer contains discrete PVDF polymer particles having an average discrete particle size of 50 to 500nm and agglomerates of discrete polymer particles having a size of 1 to 150 microns, preferably 3 to 50 microns, as measured by electron scanning microscopy.

26. The method of claim 17 or 18, wherein the PVDF polymer binder contains at least 20%, preferably at least 50%, up to 100% by weight of fine particles.

27. The method of claim 17 or 18, wherein the sorbent comprises activated carbon.

28. A method according to claim 17 or 18, wherein the binder comprises 1 to 30 wt%, preferably 1 to 10 wt%, based on the total weight of binder and sorbent.

29. The method of claim 17 or 18, wherein the density of the active medium and the bulk of the PVDF polymer binder is at most 0.95g/cm ³ Preferably 0.50 to 0.90g/cm ³ More preferably 0.65 to 0.85g/cm ³ 。

30. The method of claim 17 or 18, wherein the extruder produces the blocks of active medium and PVDF polymer binder at a rate of 0.5cm to 50cm per minute of extrusion of the blocks, preferably 0.5 to 30cm per minute of extrusion of the blocks.

31. The process according to claim 17 or 18, wherein the heating zone is from 0.25 to 2 meters long, preferably from 0.5 to 1.5 meters long,

wherein the forming zone is 0.075 to 0.20 meters long, the cooling zone comprises 27% to 72% of the forming zone, and is located along the extrusion barrel from D ₁ To D ₂ The expansion ratio of (2) is 0.3% to 0.7%.

32. The method of claim 17 or 18, further comprising applying back pressure to the extruded block.

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