Method and extruder for preparing high-quality blocks of immobilized active media

Abstract

A method and extruder for producing carbon blocks using poly(vinylidene fluoride) (PVDF) as a binder and an adsorbent such as activated carbon is disclosed.

Description

Technical Field

[0001] The present invention relates to a method and an extruder for producing blocks of an active medium using poly(vinylidene fluoride) (PVDF) as a binder and an active medium such as activated carbon.

Background Art

[0002] Blocks of immobilized active media, also called blocks, carbon blocks, or monoliths, are established 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. Blocks are also used in other applications such as wastewater filtration, catalysts for chemical reactions, electrodes for batteries and supercapacitors, and the transport, storage, separation, and washing of liquids and gases.

[0003] Blocks are usually made of active medium particles or fibers such as activated carbon, graphite, molecular sieves, metals and derivatives, bactericides, and heavy metal removers. Blocks also contain one or more binders such as polymer binders that enable the interconnectedness between the particles of the active medium. The polymer binder can be composed of almost any thermoplastic material including: polyolefins such as polyethylene and polypropylene; polyvinyls such as polyvinyl chloride, polyvinyl fluoride, polyvinylidene chloride, and polyvinylidene fluoride; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyamides, etc. Among these materials, polyethylene and polyester are the most widely used in the market.

[0004] There are mainly two methods for producing blocks. One is by sintering and compression molding, and the other is by continuous extrusion technology. Extrusion is considered to be a more cost-effective method for producing blocks.

[0005] Arkema has introduced its Kyblock® series of PVDF polymer binders to the block industry, demonstrating advantages such as reduced binder requirements and improved adhesion to active medium particles, particularly fine particles. In water filtration applications, PVDF polymer binders also improve the removal of contaminants such as chlorine and heavy metals. PVDF polymer binders also deliver improved performance in other block applications, including gas transport, storage, separation, and washing.

[0006] The block of the present invention comprises a PVDF polymer binder. The PVDF polymer binder includes a single PVDF polymer, a blend of two or more PVDF polymers, and a blend of a PVDF polymer with other polymers such as polyethylene, polyester, and polyamide.

[0007] When one or more PVDF polymer binders are incorporated into a block composition, they typically do not allow for drop-in replacement in the processes and equipment used for conventional blocks made with polyethylene and polyester binders. Therefore, it is difficult for end-users, especially those who manufacture blocks using extrusion technology, to incorporate PVDF polymer binders into their products.

[0008] This invention relates to an innovative extruder that solves the extrusion problems when manufacturing blocks containing activated medium particles such as activated carbon or PVDF polymer binders, and improves the ease and throughput of the extrusion process, as well as the quality and performance of the blocks.

[0009] Common problems encountered during block extrusion using PVDF polymer binders include: 1) feeding the particle blend of the active medium and PVDF binder into the extruder barrel; 2) incomplete curing of the binder; and 3) clogging of the extruder barrel (block locking in the barrel). Problems with feeding the particle blend of the material are largely related to the flow of the powder material, and because PVDF binders have a small submicron discrete particle size, they tend to impair the flow of the overall powder blend.

[0010] Incomplete curing of blocks is typically due to the fact that the melting temperature of PVDF polymer binders is generally higher than that of PE and polyester binders, ranging from 110°C to 180°C. Curing means that the active medium particles are bound together by the binder. Blocks produced using PVDF polymers usually require higher temperatures and / or longer residence times in the extruder's heating zone. This can result in partially cured blocks when using extruders with short, non-flying heating zones, such as those described in International Publication No. 1992 / 0173272.

[0011] Extruder barrel clogging problems are typically caused by high friction of the block against the extruder barrel walls. This problem occurs particularly with blocks containing small active medium particles, less than 100 microns, preferably less than 20 microns, and most preferably less than 10 microns. PVDF polymer binders are primarily used in such blocks, for example, in activated carbon blocks for health-claiming filters that use small active medium particles for heavy metal removal. Clogging problems also occur with blocks containing PVDF polymer binders, as the binder content is typically less than 20%, preferably less than 16%. This is because the polymer binder acts as a lubricant, helping to minimize friction with the extruder walls.

[0012] U.S. Patent Application Publication No. 2016 / 0121249 and International Publication No. 2014 / 055473 teach the use of a thermoplastic binder (PVDF) as a binder in the preparation of activated carbon block filters, and a method for preparing them by compression molding / sintering techniques or extrusion.

[0013] International Publication No. 1992 / 017327 describes the use of an extrusion process to form solid composite articles. An extruder for producing blocks from a blend of activated carbon and polyethylene binder is disclosed. PVDF is not mentioned as a candidate binder. Koslow teaches an extruder with a short non-fly heating zone in the barrel, where the heating zone is shorter than the die (cooling) zone. He also teaches that making the heating zone longer is not functional because it increases friction between the extruder barrel wall and the block, causing the barrel to clog.

[0014] The extruder described in International Publication No. 1992 / 017327 is not well-suited for blocks containing PVDF polymer binders. Because the melting temperature of PVDF polymers is relatively high (110°C–180°C), short, non-flying heating zones typically do not provide sufficient heat transfer to fully cure blocks containing PVDF polymer binders. Therefore, the use of such an extruder is limited to very low extrusion speeds.

[0015] The problem of block clogging, or adhesion, of blocks containing PVDF polymer binders tends to occur in all existing extruder designs, including the extruder described in International Publication No. 92 / 17327 and extruder designs with longer heating zones and / or flight heating zones. Block clogging of PVDF polymer binders can occur because the binder content is less than 30%, preferably less than 18%, and most preferably less than 12%. This is because a lower binder content results in a higher content of active medium particles, leading to increased friction with the extruder barrel. Furthermore, in many applications such as high-end CTO water filters and health-claiming water filters, 0.55 g / cm³ is used. 3A high block density is required, exceeding 0.65, preferably exceeding 0.75. Furthermore, such blocks typically contain more than 10%, preferably more than 20%, and more preferably more than 30%, of fine active medium particles less than 100 microns, preferably less than 50 microns, and most preferably less than 10 microns. Both higher block density and a higher proportion of fine active medium particles contribute to increased friction with the extruder barrel, which can lead to clogging problems.

[0016] A typical extruder, as shown in Figure 1, has a flight feed zone and is equipped with a feeder that typically uses gravity to feed the material from the feeder hopper to the barrel. Particle blends of the active medium and polymer binder, containing at least 2 wt% of active material and / or polymer binder fine particles, tend to have poor flowability. Poor flow results in uneven feeding to the extruder. The particle size of the fine particles is less than 50 microns, preferably less than 20 microns, and most preferably less than 10 microns (tested by a rotap sieve vibrator if 10 microns or more, and by a microtrac particle analyzer if less than 10 microns). PVDF binders can contain at least 20%, preferably at least 50%, and up to 100% fine particles. Fine particles may be included in the active medium particles, especially in high-end filtration applications where maximizing the accessible surface area of ​​the medium is important. Typical fine particles in the active medium include "activated carbon fine particles," metal reducing agents, and bactericides. [Overview of the Initiative] [Problems that the invention aims to solve]

[0017] Extruding blocks containing PVDF polymer binders still presents challenges. With various existing extruders, the continuous supply of the active medium-PVDF binder blend is unstable, resulting in partially cured blocks or blocks becoming trapped inside, clogging the extruder barrel. [Means for solving the problem]

[0018] The applicants designed a novel extruder that combines a barrel, a flight heating zone, and a forming zone where the diameter of the barrel changes so that it is not constant throughout the zone. Such a novel extruder design improves the process of manufacturing blocks containing a PVDF polymer binder and prevents the extruder barrel from clogging.

[0019] The present invention relates to a preparation method and an extruder for manufacturing high-quality block products made from a poly(vinylidene fluoride) polymer binder and an active medium such as activated carbon particles, more specifically, to an extrusion process and an extruder.

[0020] Embodiments of the present invention Aspect 1. An extruder for making a block of an active medium and a PVDF polymer binder, comprising an extruder barrel including a flight heating zone and a non-flight forming zone, wherein the non-flight forming zone includes a cooling section, the heating zone is longer than the forming zone, the inner diameter "D" of the extruder barrel increases from D1 to D2 in the non-flight forming zone, where the change in diameter between D1 and D2 is between 0.2% and 1.0%, the ratio of the length of the heating zone to the length of the forming zone is 20:1 to 5:4, Extruder.

[0021] Aspect 2. The extruder according to Aspect 1, wherein the increase in diameter from D1 to D2 in the forming zone is 0.2 to 0.9%, preferably 0.35 to 0.70%.

[0022] Aspect 3. The extruder according to Aspect 1, wherein the increase in diameter from D1 to D2 is 0.4 to 0.65%.

[0023] Aspect 4. The extruder according to any one of Aspects 1 to 3, wherein the change in diameter from D1 to D2 exists over 10% to 100%, preferably 30% to 85%, preferably 40% to 75% of the length of the forming zone.

[0024] Aspect 5. The ratio of the length of the heating zone to the length of the forming belt is preferably 10:1 to 5:4. The extruder according to any one of Aspects 1 to 4.

[0025] Aspect 6. The heating zone has a length of 0.25 to 2.0 meters, preferably a length of 0.5 to 1.5 meters, and includes 1 to 10 heating sections. The extruder according to any one of Aspects 1 to 6.

[0026] Aspect 7. The length of the forming belt is 0.01 to 1 meter, preferably 0.02 to 0.5 meter. The extruder according to any one of Aspects 1 to 7.

[0027] Aspect 8. The length of the forming belt is 0.05 to 0.2 meter, preferably 0.05 to 0.15 meter. The extruder according to any one of Aspects 1 to 7.

[0028] Aspect 9. The length of the cooling section is 0.01 to 1 meter, preferably 0.02 to 0.5 meter. The extruder according to any one of Aspects 1 to 8.

[0029] Aspect 10. The length of the cooling section is 0.05 to 0.2 meter, preferably 0.05 to 0.15 meter. The extruder according to any one of Aspects 1 to 8.

[0030] Aspect 11. The cooling section constitutes 20 to 100%, preferably 50 to 99% of the forming belt in terms of length. The extruder according to any one of Aspects 1 to 8.

[0031] Aspect 12. The inner diameter "D1" of the barrel in the flight zone is 1 cm to 50 cm, more preferably 3 cm to 25 cm. The extruder according to any one of Aspects 1 to 11.

[0032] Aspect 13. The inner diameter "D1" of the barrel in the flight zone is 1 cm to 25 cm, preferably 3 cm to 6 cm. The extruder according to any one of Aspects 1 to 11.

[0033] Embodiment 14. The extruder according to any one of Embodiments 1 to 13, wherein the extruder further includes a feeder hopper, and the feeder hopper includes an auger.

[0034] Embodiment 15. The extruder according to any one of Embodiments 1 to 14, further comprising an external back pressure device.

[0035] Embodiment 16. The extruder according to Embodiment 15, wherein the external back pressure device is selected from the group consisting of a puller, a weight, or a donut device comprising a spring and fingers attached to the block.

[0036] Embodiment 17. A method for extruding a block of an active medium and a PVDF polymer binder, comprising: providing a PVDF polymer binder comprising a PVDF polymer and an active medium; supplying the PVDF polymer binder and the active medium to an extruder according to any one of Embodiments 1 to 14; and extruding the resulting blend of the PVDF polymer binder and the active medium to form a block of an immobilized medium.

[0037] Embodiment 18. A method for extruding a carbon block, a. Provide PVDF polymer binder and active medium, b. An extruder is provided comprising an extruder barrel, wherein the extruder barrel includes a flight heating zone and a non-flight forming zone, the forming zone includes a cooling section, the ratio of the length of the heating zone to the length of the forming zone is 20:1 to 5:4, and the inner diameter "D" of the extruder barrel increases from D1 to D2 in the forming zone, where the change in diameter between D1 and D2 is between 0.2% and 0.9%. c. The PVDF polymer binder and the active medium are supplied to the extruder. d. Extruding the blend of the PVDF polymer binder and the active medium to form a block of immobilization medium. Methods that include...

[0038] Embodiment 19. The method according to Embodiment 17 or 18, wherein the PVDF polymer binder and active medium, which contain the PVDF polymer, are blended before being supplied to the extruder.

[0039] Embodiment 20. The method according to any one of Embodiments 17 to 19, wherein the temperature of the heating zone ranges from 20°C lower than the melting temperature of the binder to 80°C higher than the melting temperature of the binder.

[0040] Embodiment 21. The method according to any one of Embodiments 17 to 19, wherein the temperature of the heating zone is 130 to 260°C, preferably 170 to 230°C.

[0041] Embodiment 22. The method according to any one of Embodiments 17 to 21, wherein the binder comprises a VDF / HFP copolymer having a melt viscosity of 5 to 80 kP, preferably 15 to 50 kP.

[0042] Embodiment 23. The method according to any one of Embodiments 17 to 22, wherein the PVDF polymer contains 5% to 20% by weight of HFP.

[0043] Embodiment 24. The method according to any one of Embodiments 17 to 23, wherein the combination of the active medium and the polymer binder contains at least 2% by weight of fine particles.

[0044] Embodiment 25. The method according to any one of Embodiments 17 to 24, wherein the PVDF polymer comprises discrete PVDF polymer particles having an average discrete particle size of 50 to 500 nm and aggregates of the discrete polymer particles, the aggregates having a size of 1 to 150 micrometers, preferably 3 to 50 micrometers, when measured with a scanning electron microscope.

[0045] Embodiment 26. The method according to any one of Embodiments 17 to 25, wherein the PVDF polymer binder comprises at least 20%, preferably at least 50%, and up to 100% by weight of fine particles.

[0046] Embodiment 27. The method according to any one of Embodiments 17 to 26, wherein the adsorbent includes activated carbon.

[0047] Embodiment 28. The method according to any one of Embodiments 17 to 27, wherein the binder accounts for 1 to 30 weight percent, preferably 1 to 10 weight percent, based on the total weight of the binder and the adsorbent.

[0048] Embodiment 29. The method according to any one of Embodiments 17 to 28, wherein the block of the active medium and the PVDF polymer binder has a density of up to 0.95 g / cc, preferably 0.50 to 0.90 g / cc, and more preferably 0.65 to 0.85 g / cc.

[0049] Embodiment 30. The method according to any one of Embodiments 17 to 29, wherein the extruder produces blocks of the active medium and PVDF polymer binder at a speed of 0.5 cm to 50 cm per minute, preferably 0.5 to 30 cm / min.

[0050] Embodiment 31. The length of the heating zone is 0.25 to 2 m, preferably 0.5 to 1.5 m. The method according to any one of embodiments 17 to 30, wherein the length of the molding strip is 0.075 to 0.20 meters, the cooling section constitutes 27 to 72% of the molding strip, and the expansion from D1 to D2 along the barrel of the extruder is 0.3% to 0.7%.

[0051] Embodiment 32. The method according to any one of Embodiments 17 to 31, further comprising applying back pressure to the extrusion block. [Brief explanation of the drawing]

[0052] [Figure 1]Figure 1 shows a diagram of an existing extruder barrel, optionally equipped with an internal solid rod for producing hollow cylindrical blocks. The barrel consists of three zones: a feed zone, a heating zone, and a forming zone which includes a cooling section. The feed zone is unheated and of the flight type, located directly below the feeder hopper and ending at the end of the hopper. The heating zone is also of the flight type and is longer than the non-flying forming zone. The heating zone starts at the end of the feed hopper and extends to the end of the flight section. In a standard extruder, the diameters of the feed, heating, and forming zones are constant along the entire length of the barrel. The forming zone is non-flying and usually has no heating element. The forming zone starts at the end of the flight section and extends to the end of the barrel. The forming zone typically includes a cooling section which uses a cooling element. [Figure 2] Figure 2 shows an extruder barrel of the present invention, optionally equipped with an internal solid rod for producing hollow cylindrical blocks. The barrel consists of three zones: a feed zone, a heating zone, and a forming zone including a cooling section. The schematic diagram shows the heating zone and the forming zone. The feed zone (not shown) is non-flying and is not normally heated, but can be heated. The heating zone is flying and equipped with heating elements, preferably located on the outer surface of the barrel. The forming zone is non-flying and is not normally heated. The cooling section within the forming zone is equipped with cooling elements, preferably located on the outer surface of the barrel. In the forming zone, the inner diameter of the barrel "D" is changed along the length of the barrel, with the final barrel inner diameter (D2) at the outlet of the cooling section being larger than the initial barrel inner diameter (D1) at the beginning of the non-flying zone. The change in barrel inner diameter "D" can be progressive or stepwise along the entire length of the non-flying zone. The heating zone is the longest zone in the barrel. [Modes for carrying out the invention]

[0053] All references listed herein are incorporated herein by reference. Unless otherwise indicated, all percentages in the compositions are by weight. Different combinations of elements described herein are also considered part of the present invention.

[0054] As used herein, “interconnection” means that active medium particles or fibers are permanently bound together by polymer binder particles without completely coating their surface. During a process called “curing,” the binder softens and adheres the active medium particles to specific discrete points, creating an organized porous structure. Blocks produced by the method of the present invention are porous. The blocks allow fluids to pass through the interconnected particles or fibers, exposing the fluids directly to their surfaces and facilitating the adsorption of fluid components onto the active medium. Because the polymer binder adheres to the active medium particles only at discrete points, the amount of binder used for complete interconnection is less compared to the amount of binder coated onto the active medium.

[0055] An extruder for producing blocks of an active medium and a PVDF binder is disclosed.

[0056] A method for extruding blocks of an active medium and a PVDF binder using the extruder of the present invention is disclosed.

[0057] This invention provides an extrusion method for blocks of an active medium, such as activated carbon, using PVDF as a binder. The extruder employs a new barrel design that has been modified compared to existing extruder barrels used in the production of blocks. The novel extruder of this invention allows for the successful extrusion of blocks of the active medium and PVDF binder, and prevents the blocks from becoming stuck in the barrel when jammed.

[0058] The present invention provides a modification of an extruder for extruding an immobilized active medium block, wherein the extruder barrel is modified in the forming zone, and the modified inner diameter (D2) at the barrel outlet is larger than the inner diameter (D1) at the beginning of the flight zone or non-flight zone.

[0059] Extruder The modified extruder barrel includes a molding strip with three strips: 1) a feed strip, 2) a heating strip, and 3) a cooling section.

[0060] The feed zone is a flying type, normally unheated, receiving material from the feeder and transporting it to the heating zone. The heating zone is a flying type, has heating elements, is the longest zone in the barrel, and ensures proper heat transfer and complete curing of the block. The forming zone is non-flying and normally unheated, although a portion of it can be optionally heated. Within the forming zone, the cooling section is non-flying and equipped with cooling elements. As shown in Figure 2, the extruder barrel is modified at the forming zone, with the modified inner diameter (D2) at the end of the forming zone being larger than the inner diameter (D1) at the beginning of the forming zone. The ratio of the length of the heating zone to the length of the forming zone is preferably 20:1 to 5:4, preferably 10:1 to 5:4, and preferably 8:1 to 6:4.

[0061] The absolute length of the barrel and barrel strip depends on the thickness of the block. For example, the thickness of a solid cylinder block is defined as the outer diameter of the block, while the thickness of a hollow cylinder block is defined as the difference between the outer diameter and the inner diameter of the block.

[0062] The length of the supply strip can be 0.1 to 1 meter, preferably 0.2 to 0.5 meters.

[0063] The heating zone is longer than the molding zone, and can be 0.25 to 2 m in length, preferably 0.5 to 1.5 m in length. It is equipped with 1 to 10 heating elements, preferably 3 to 5 heating elements. The temperature of the heating elements can be set between room temperature and 300°C, typically ranging from 20°C below the binder melting temperature to 80°C above the binder melting temperature. The temperature of each element can be controlled independently.

[0064] The length of the molding strip can be 0.01 to 1 meter, or 0.02 to 0.7 meters, preferably 0.05 to 0.5 meters. The length of the cooling section within the molding strip can be 0.01 to 1 meter, preferably 0.02 to 0.5 meters, or 0.05 to 0.20 meters, more preferably 0.05 to 0.15 meters. The cooling section is equipped with one or more cooling elements. The cooling elements may contain a cooling fluid such as water or other coolants and can be cooled as needed. The temperature of the cooling fluid can be between 90°C and -20°C, preferably between 35°C and 0°C.

[0065] In the forming strip, the barrel inner diameter "D" is changed, and the final barrel inner diameter at the end of the forming strip is 1.002 to 1.01 times, or 1.002 to 1.009 times, preferably 1.003 to 1.007 times, and most preferably 1.004 to 1.007 times, larger than the initial barrel inner diameter at the beginning of the forming strip. The gradual change in the barrel inner diameter D may only exist in the forming strip. The change may exist over a length of 10% to 100%, preferably 30% to 85%, preferably 40% to 75%, more preferably 50% to 70% of the length of the forming strip, and may exist in a continuous manner or in one or more stepwise changes. This percentage is calculated as the ratio of the total length of the changed section to the total length of the forming strip (including the cooling section). The length of the changed section is measured from the point where the barrel inner diameter is first changed in the forming strip to the end of the barrel at the exit of the cooling section. Gradual changes can compensate for the shrinkage of dies using metal alloys that shrink more than the polymer binder or extruded active medium, and release the pressure accumulated within the die. After the gradual changes are complete, the final barrel diameter (D2) at the end of the molding strip is greater than the initial barrel diameter (D1) at the beginning of the molding strip. The overall increase in barrel diameter between D1 and D2 is 0.2% to 1.0%, 0.2% to 0.9%, preferably 0.35% to 0.7%, and most preferably 0.4% to 0.65%. The increase rate is calculated as follows: Increase in D % = 100 × (D2 - D1) / D1

[0066] The inner diameter D1 of the flight band barrel is preferably between 1 cm and 50 cm, more preferably between 3 cm and 25 cm. D1 can be larger than 100 cm. D1 can be between 1 cm and 25 cm, or between 3 cm and 6 cm, or between 4 cm and 5 cm. In the case of a hollow structure, the typical inner diameter of the hollow structure is between 0.5 cm and 45 cm, more preferably between 1 cm and 15 cm or between 1 cm and 10 cm.

[0067] In one exemplary embodiment, the barrel bore diameter D1 of the flight section is 4.35 cm and is changed in a 0.5% incremental progression to a barrel bore diameter D2 of 4.372 cm at the outlet of the cooling section.

[0068] Furthermore, this type of extruder can also be equipped with an external device that can resist the block from coming out of the extruder. This helps to generate back pressure to increase the density of the block. This can be achieved by a puller, a common tool used in the plastics industry, which resists the extrusion speed, by placing a weight in front of the extruder, or by a simple device (also known as a donut) consisting of a spring and fingers that grips the block and applies pressure proportional to the spring constant of the spring. Other means exist to generate back pressure that helps increase the density of the block, which can be used in conjunction with the extruder of the present invention to produce a higher density carbon block. The internal design can also be modified to increase the density of the block, such as by changing the inner diameter of the heating zone to allow material to accumulate. In such cases, the inner diameter of the barrel at the end of the heating zone is smaller than the inner diameter of the barrel at the beginning of the heating zone.

[0069] Furthermore, feeding devices known as feeders are commonly used in combination with extruders. These consist of a hopper that takes in a large amount of material and supplies it to the extruder at a constant rate. However, typical feeder hoppers have poor flow characteristics, making it difficult to consistently feed a particle blend of the active medium and / or polymer binder containing at least 2% by weight or more of the active material and / or polymer binder particles. This problem has been found to be resolved by adding an auger to the feeder hopper, which agitates the powder and allows for a stable feed.

[0070] Finally, the extruder can also be set up with an in-line block cutter to help cut the extruded block to a specific length.

[0071] The novel and innovative design of the extruder solves the clogging problem when manufacturing blocks containing PVDF polymer binders. The new extruder design also improves the consistency of the continuous feed of material within the extruder barrel, ensuring complete curing of the block. Thus, the present invention provides block manufacturers with a highly productive and consistent method for preparing blocks of immobilized active media.

[0072] The extruder of the present invention is designed to extrude a block containing an active medium and a PVDF polymer binder.

[0073] binder The binder in the block produced using the extruder of the present invention comprises a poly(vinylidene fluoride)PVDF polymer binder. The PVDF polymer binder may be a single PVDF polymer, a blend of two or more PVDF polymers, a blend of a PVDF polymer with other polymers such as polyethylene or polyester, or any other thermoplastic polymer. In some embodiments, the PVDF polymer binder is a blend of the PVDF binder with other polymers, where PVDF is the main component of the total binder and contains more than 50% PVDF polymer based on the total polymer binder. In some embodiments, PVDF is not the main component and may be as low as 10% of the total binder content of the block. The PVDF polymer is a homopolymer of vinylidene fluoride, or a copolymer of vinylidene fluoride with one or more comonomers. Copolymers have lower melting temperatures and lower modulus of elasticity compared to homopolymers. The lower melting temperature of the binder reduces the problem of extruder locking.

[0074] Preferred PVDF copolymers include those copolymerized with at least 50 mol%, preferably at least 75 mol%, more preferably at least 80 mol%, and even more preferably at least 85 mol% vinylidene fluoride (VDF) and one or more comonomers selected from the group consisting of: tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, hexafluoropropene (HFP), vinyl fluoride, pentafluoropropene, tetrafluoropropene, trifluoropropene, perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, (meth)acrylic acid, (meth)acrylic acid esters, and any other monomers that readily copolymerize with vinylidene fluoride. The comonomer is preferably hexafluoropropene.

[0075] In one embodiment, the vinylidene fluoride polymer contains up to 30% by weight, preferably up to 25%, more preferably up to 15% HFP units, and 70% or more by weight, preferably 75% or more by weight, more preferably 85% or more VDF units. The PVDF polymer may have 0 to 30% by weight, preferably 5 to 20% by weight HFP units.

[0076] The PVDF used in this invention is generally prepared by means known in the art using aqueous free radical emulsion polymerization, but suspension, solution, and supercritical CO2 polymerization processes may also be used. Preferably, the PVDF is produced by emulsion polymerization.

[0077] The surfactant used in polymerization may be any surfactant known in the art to be useful for PVDF emulsion polymerization, including perfluorinated, partially fluorinated, and nonfluorinated surfactants. Preferably, the PVDF emulsion of the present invention does not contain fluorinated surfactants, and no fluorinated surfactants are used in any part of the polymerization. Nonfluorinated surfactants useful for PVDF polymerization can have both ionic and nonionic properties and include, but are not limited to, 3-allyloxy-2-hydroxy-1-propanesulfonates, polyvinylphosphonic acids, polyacrylic acids, polyvinylsulfonic acids and their salts, polyethylene glycol and / or polypropylene glycol and their block copolymers, alkylphosphonates and siloxane-based surfactants. In one embodiment, emulsion polymerization is carried out in the absence of surfactants.

[0078] Latex polymer binders are generally reduced to a powder form by spray drying, solidification, or other known processes to produce a dry powder. The shape and particle size of the powder can be altered by any known process, such as grinding.

[0079] Discrete PVDF binder particles generally have an average discrete particle size of 5 to 700 nm, preferably 50 to 500 nm, and more preferably 100 to 300 nm. In some cases, discrete polymer particles may aggregate to form aggregates of 1 to 150 micrometers, or aggregates of 3 to 50 micrometers, preferably 5 to 15 micrometers. Some of these aggregates have been found to decompose into discrete particles or fibrils during processing into articles. Some of the binder particles are discrete particles and remain as discrete particles in the formed block article. During processing into a block article, the particles are adjacent to each other in the active medium and provide interconnection.

[0080] It is important to use only the amount of binder necessary to hold the active material. This exposes a larger surface area of ​​the active medium, which can then be used for interaction with fluids in processes such as filtration and adsorption. One advantage of PVDF polymers is that they have a very high specific gravity of at least about 1.75 g / cc, preferably at least about 1.77 g / cc. Therefore, the weight percentage and volume percentage of the binder required can be even lower.

[0081] The molecular weight of the PVDF polymer is not particularly limited. In some cases, a higher molecular weight is preferable to prevent the binder from flowing into the active medium and contaminating the high surface area of ​​the activated carbon. The melt viscosity of the polymer is preferably 1 to 100 kPoise, preferably 5 to 80 kPoise, 5 to 60 kPa, and most preferably 15 to 50 kPoise. The melt viscosity of the polymer is determined by capillary rheometry at 232°C and 100 s in accordance with ASTM D3835. -1 It is measured at [location / location].

[0082] active medium The active medium used is one known to be used in block products. Block products can be used for filtration, such as water filtration, or for transporting, storing, separating, and washing fluids (gases or liquids) by selecting an appropriate active medium. The active medium particles are not particularly limited. Examples of active mediums include, but are not limited to, powder particles or fibers of activated carbon, graphite, molecular sieves, metals and derivatives, disinfectants, heavy metal removers, and combinations thereof. One preferred active medium is activated carbon.

[0083] The active medium particles of the present invention generally have a size range of 0.1 to 3,000 microns in diameter, preferably 1 to 500 microns, and most preferably 5 to 100 microns. In certain embodiments, the active medium particles have a multimodal particle size distribution, for example, some particles have an average particle size of less than 100 microns, and some particles have an average particle size of more than 200 microns. The active medium particles may also be in the form of fibers with a diameter of 0.1 to 250 microns and an essentially unlimited length-to-width ratio. The fibers are preferably cut to a length of 5 mm or less.

[0084] The active medium fibers or powder must have sufficient thermal conductivity to allow heating of the powder mixture. Furthermore, in the extrusion process, the melting points of the particles and fibers must be sufficiently higher than the melting point of the PVDF polymer binder to prevent both materials from melting and producing a continuous molten phase rather than the usually desirable multiphase system.

[0085] process The PVDF polymer binder and the active medium may be mixed and processed. The PVDF polymer binder is usually in powder form and can be dry blended with the active medium. Preferably, 0.5 to 35, preferably 1 to 30, and more preferably 3 to 25 weight percent of the PVDF polymer binder is used in the block product, based on the total weight of the active medium and the PVDF polymer binder. The weight percentage of PVDF may be 1 to 10 weight percent, based on the total weight of the active medium and the PVDF polymer binder.

[0086] If a very dense block is required, extrusion at higher pressures can be used. The extrusion process is carried out in a manner that softens the polymer binder particles but does not melt and flow them until they come into contact with other polymer particles and form aggregates or continuous layers. To be effective in the intended end application, the polymer binder remains as discrete polymer particles that bind the active medium particles to an interconnected web to obtain good permeability. No solvent is used to dissolve the binder in this invention because, in a solvent system, the particles dissolve and form a continuous coating on the active medium particles, so the individual polymer particles no longer exist. The continuous coating may reduce the amount of activated surface area available for the interaction between the fluid and the active particles, potentially reducing its overall effectiveness.

[0087] The active medium and polymer binder are formed into a block article by an extrusion process. The block of the present invention is formed by an extrusion molding process. A general extrusion process for carbon blocks is described in U.S. Patent No. 5,331,037. U.S. Patent No. 5,331,037 describes extruding a block made of polyethylene binder using an extruder with a barrel having a short non-flight heating zone. PVDF is not mentioned as a candidate binder.

[0088] The polymer binder / active medium composite of the present invention is generally dry-blended with other additives, such as processing aids, as needed, and then extruded. Continuous extrusion under heat, pressure, and shear can generate infinitely long three-dimensional multiphase profile structures. Under the extruder conditions, a continuous web of forced point bonds between the binder and active medium particles is formed.

[0089] The extrusion process can produce continuous block structures of any desired diameter and length. With appropriate manufacturing equipment, lengths from 1 cm to several hundred meters are possible. The continuous solid blocks can then be cut to the desired final length. The blocks may be solid or hollow. The typical outer diameter of the blocks is preferably 1 cm to 50 cm, more preferably 3 cm to 25 cm, however, with the use of appropriately sized dies, structures with larger diameters of up to 100 cm or more can be manufactured. For hollow structures, the typical inner diameter is 0.5 cm to 45 cm, more preferably 1 cm to 15 cm, or 1 cm to 10 cm.

[0090] Instead of a single structure, there is a method of forming two or more structures, namely a solid rod and one or more hollow block cylinders designed to nest together to form a larger structure. Once each annular or rod-shaped block component is formed, the components can be nested to create a larger structure. This process has several advantages compared to extruding a single large structure. Blocks with smaller cross-sectional diameters can be manufactured at a faster rate than manufacturing large, solid single-pass blocks. Cooling profiles can be better controlled for each smaller cross-sectional component. A further advantage of this concept is that the length of the gas diffusion path through the monolith can be shortened because the spacing between concentric blocks can act as channels for rapid gas flow.

[0091] characteristics The articles formed by this invention are high-quality, robust block structures of active medium and binder. The density of the blocks can be finely adjusted. For example, the density can be made very high to maximize the amount of active medium in order to maximize block efficiency.

[0092] The extruder of the present invention provides blocks having a density of up to 0.95 g / cc. Preferably, the density of the block product can be 0.50 to 0.90 g / cc, and more preferably 0.65 to 0.85 g / cc.

[0093] The extruder of the present invention provides higher productivity because friction between the composition particles and the walls of the extruder is reduced. The extruder of the present invention can produce extruded blocks at a rate of up to 0.5 cm to 50 cm per minute, preferably 1 cm to 30 cm per minute.

[0094] The temperature of the heating zone is generally determined by the softening temperature of the binder, typically ranging from 20°C below the binder's melting temperature to 80°C above it. For example, the temperature is generally 130°C to 260°C, and may also be 170°C to 230°C. Depending on the polymer binder, the temperature may be lower or higher than these examples.

[0095] This novel extruder barrel enables continuous extrusion of microparticles using a PVDF polymer binder while minimizing the sticking problems experienced with conventional extruders. [Examples]

[0096] Example 1 The extruder barrel includes a 1m flying heating zone, a 0.23m forming zone, and a 0.115m cooling section. The initial barrel inner diameter of the flying zone is D1 = 4.35cm, and the final barrel inner diameter at the extruder outlet is D2 = 4.372cm (0.5% change). The change in inner diameter occurs along the length of the non-flying forming zone, which is 0.172m. The barrel is equipped with an internal rod for extruding a hollow cylinder block. The diameter of the rod is equal to the inner diameter of the hollow block, with an ID of 1.9cm. The thread gap is 4cm (made of CrMoAl).

[0097] This formulation contains 8% (by weight) of binder (Kyblock® FG-81) and 92% (by weight) of Jaccobi 80 x 325 size activated carbon.

[0098] The process conditions are as follows: A. Mix the binder and carbon in a rotary mixer at low speed for 1 hour. B. Extrusion conditions: 190°C, 200°C, 150°C, 105°C (T1, T2, T3, and T4).

[0099] The resulting block was 0.75 g / cm³ 3 It has a density (measured by weight / volume after the block has cooled). The line speed for manufacturing the block is 8 cm / min.

[0100] Block density indicates mechanical strength and process stability. The extruder operated without problems for 3 hours (no seizing). This is in contrast to when the same block composition was run in an extruder with a non-modified barrel having a constant inner diameter D1 = 4.35 cm. In the case of the non-modified barrel, the extruder seized within the first 30 minutes, and the block clogged the barrel.

[0101] Example 2 The extruder barrel is the same as in Example 1.

[0102] This formulation contains 25% (by weight) of binder (Kyblock® FG-415) and 75% (by weight) of Jaccobi 80 x 325 activated carbon.

[0103] The process conditions are as follows: A. Mix the binder and carbon in a rotary mixer at low speed for 1 hour. B. Extrusion conditions: Four heating zones: 170°C, 180°C, 150°C, 105°C (T1, T2, T3, and T4).

[0104] The resulting block was 0.8 g / cm³ 3 It has a density (measured by weight / volume after the block has cooled). The line speed for manufacturing the block is 8 cm / min.

[0105] Block density indicates mechanical strength and process stability.

[0106] The extruder operated without issue for 3 hours (no seizing occurred). This is in contrast to the case of the unmodified barrel, which caused the extruder to seize, as in Example 1.

[0107] Example 3 A powder blend containing 8% (by weight) binder (Kyblock® FG-81) and 92% (by weight) Jaccobi 80 x 325 activated carbon was fed into an extruder barrel using two different feeders. All binders are considered to be fine particles and tend to disrupt the overall flow of the powder blend in a typical feeder setup. In a comparative example using a standard feeder made with a simple hopper design (no auger), the feeding of the powder blend into the extruder barrel was inconsistent. The powder tended to adhere to both the hopper walls and itself, resulting in a "stop-and-go" feeding profile. When the feeder hopper was modified with an auger, the powder was fed evenly and at a consistent rate. The use of a feeder hopper modified with an auger was key to consistently feeding formulations containing more than 2% fine particles into the extruder. To produce high-quality carbon block products, a combination of consistent powder feeding and the use of an improved extruder barrel is necessary.

Claims

1. An extruder for producing a block of an active medium and a PVDF polymer binder, wherein the extruder barrel includes a flight heating zone having flights and a non-flight molding zone where the extruder does not have flights, and the non-flight molding zone includes a cooling section. The aforementioned flight heating zone is longer than the aforementioned non-flight forming zone. The inner diameter "D" of the extruder barrel is D in the non-flight molded strip. 1 From D 2 It increases to, and here, D 1 and D 2 The change in diameter is between 0.2% and 1.0%. The ratio of the length of the flight heating zone to the length of the non-flight forming zone is 20:1 to 5:

4. Extruder.

2. Diameter D in the non-flight forming strip 1 From D 2 The extruder according to claim 1, wherein the increase to is 0.2 to 0.9%.

3. Diameter D 1 From D 2 The extruder according to claim 2, wherein the increase to is 0.4% to 0.65%.

4. D 1 from D 2 The change in diameter to D exists over 10% to 100% of the length of the non-flight forming zone, the extruder according to claim 1.

5. The extruder according to claim 1, wherein the ratio of the length of the flight heating zone to the length of the non-flight forming zone is 10:1 to 5:

4.

6. The extruder according to claim 1, wherein the flight heating zone has a length of 0.25 to 2.0 meters and includes 1 to 10 heating sections.

7. The extruder according to claim 1, wherein the length of the non-flight molded strip is 0.01 to 1 meter.

8. The extruder according to claim 1, wherein the length of the non-flight molded strip is 0.05 to 0.2 meters.

9. The extruder according to claim 1, wherein the length of the cooling section is 0.01 to 1 meter.

10. The extruder according to claim 1, wherein the length of the cooling section is 0.05 to 0.2 meters.

11. The extruder according to claim 1, wherein the cooling section constitutes 20 to 100% of the length of the non-flight molded strip.

12. The extruder according to claim 1, wherein the inner diameter "D" of the extruder barrel in the flight heating zone is 1 cm to 50 cm.

13. The extruder according to claim 1, wherein the inner diameter "D" of the extruder barrel in the flight heating zone is 1 cm to 25 cm.

14. The extruder according to claim 1, further comprising a feeder hopper, wherein the feeder hopper includes an auger.

15. The extruder according to claim 1, further comprising an external back pressure device.

16. The extruder according to claim 15, wherein the external back pressure device is selected from the group consisting of a puller, a weight, or a donut device comprising a spring and fingers attached to the block.

17. A method for extruding a block of an active medium and a PVDF polymer binder, comprising: providing a PVDF polymer binder comprising a PVDF polymer and an active medium; supplying the PVDF polymer binder and the active medium to an extruder according to claim 1; and extruding the resulting blend of the PVDF polymer binder and the active medium to form a block of immobilized medium.

18. A method for extruding carbon blocks, We provide PVDF polymer binders and active media. An extruder is provided comprising an extruder barrel, wherein the extruder barrel includes a flight heating zone having flights and a non-flight forming zone where the extruder does not have flights, the non-flight forming zone includes a cooling section, the ratio of the length of the flight heating zone to the length of the non-flight forming zone is 20:1 to 5:4, and the inner diameter "D" of the extruder barrel is D in the non-flight forming zone. 1 From D 2 It increases to, and here, D 1 and D 2 The change in diameter is between 0.2% and 0.9%. The PVDF polymer binder and active medium are supplied to the extruder. The blend of the PVDF polymer binder and the active medium is extruded to form a block of immobilized medium. A method that includes this.

19. The method according to claim 17 or 18, wherein a PVDF polymer binder containing a PVDF polymer and an active medium are blended before being supplied to the extruder.

20. The method according to claim 17 or 18, wherein the temperature of the flight heating zone is between 20°C lower than the melting temperature of the PVDF polymer binder and 80°C higher than the melting temperature of the binder.

21. The method according to claim 17 or 18, wherein the temperature of the flight heating zone is 130 to 260°C.

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

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

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

25. The method according to claim 17 or 18, wherein the PVDF polymer comprises discrete PVDF polymer particles having an average discrete particle size of 50 to 500 nm and aggregates of the discrete PVDF polymer particles, the aggregates having a size of 1 to 150 micrometers when measured with a scanning electron microscope.

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

27. The method according to claim 17 or 18, wherein the activated medium includes activated carbon.

28. The method according to claim 17 or 18, wherein the PVDF polymer binder accounts for 1 to 30 percent by weight based on the total weight of the binder and the active medium.

29. The method according to claim 17 or 18, wherein the block of the active medium and the PVDF polymer binder has a density of up to 0.95 g / cc.

30. The method according to claim 17 or 18, wherein the extruder can produce blocks of the active medium and PVDF polymer binder at an extrusion block rate of 0.5 cm to 50 cm per minute.

31. The length of the aforementioned flight heating zone is 0.25 to 2 m. The length of the non-flight molding strip is 0.075 to 0.20 meters, the cooling section constitutes 27 to 72% of the non-flight molding strip, and D is located along the extruder barrel. 1 From D 2 The method according to claim 17 or 18, wherein the expansion to is 0.3% to 0.7%.

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

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