Method of making high quality fixed active media logs and extruder

Abstract

Disclosed herein are methods of making high quality immobilized active media pellets and an extruder, wherein the extruder for making pellets of active media and PVDF polymer binder comprises an extrusion barrel comprising a threaded heating zone and an unthreaded forming zone, the unthreaded forming zone comprising a cooling section, the heating zone being longer than the forming zone, in the unthreaded forming zone, the inner diameter "D" of the extrusion barrel increases from D1 to D2, the change in diameter from D1 to 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 between 20:1 and 5:4; the method for extruding pellets of active media and PVDF polymer binder comprises the steps of providing a PVDF polymer binder comprising a PVDF polymer and an active media, feeding the PVDF polymer binder and the active media to the above extruder, and extruding the resulting PVDF polymer binder and active media blend to form immobilized media pellets. The present invention does not clog the extrusion barrel when making pellets comprising a PVDF polymer binder.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method and an extruder for making active media blocks using an active agent (e.g., activated carbon) and a polyvinylidene fluoride (PVDF) as a binder. BACKGROUND

[0002] Fixed active media blocks (also referred to as blocks or carbon blocks or monoliths) have been well used as filters in water filtration applications to remove chlorine, taste, odors and other suspended or dissolved contaminants such as microorganisms and heavy metals from drinking water. Blocks can also be used in other applications such as wastewater filtration, catalysts for chemical reactions, electrodes for batteries and supercapacitors, transport, storage, separation, cleaning of liquids and gases, etc.

[0003] The blocks are typically made from active media particles or fibers such as activated carbon, graphite, molecular sieves, metals and their derivatives, germicides, heavy metal removers, etc. These blocks also contain one or more binders such as polymeric binders that can achieve interlinking between the active media particles. The polymeric binders can be composed of almost any thermoplastic material including: polyolefins such as polyethylene, polypropylene, etc.; vinyl polymers such as polyvinyl chloride, polyvinyl fluoride, polyvinylidene chloride, polyvinylidene fluoride, etc.; polyesters such as polyethylene terephthalate, polybutylene terephthalate, etc.; polyamides, etc. Among these materials, polyethylene and polyesters are the most widely used in the market.

[0004] There are two main ways to make blocks. One is by sintering / molding and the other is by continuous extrusion technology. Extrusion is generally considered to be a more economical way to produce blocks.

[0005] Arkema has introduced its Kynar® series of PVDF polymeric binders into the block industry and has shown many advantages such as, for example, reducing binder loading, improving adhesion to active media particles (especially to fine particles). In water filtration applications, the PVDF polymeric binders also provide improved performance in removing contaminants such as chlorine and heavy metals. The PVDF polymeric binders also bring performance improvements in other block applications such as, for example, gas transport, storage, separation and cleaning.

[0006] The blocks of the present invention contain PVDF polymeric binders. The PVDF polymeric binders include a single PVDF polymer, a blend of two or more PVDF polymers, a blend of a PVDF polymer with other polymers such as, for example, polyethylene, polyesters and polyamides.

[0007] When one or more PVDF polymer binders are incorporated into a block composition, they are typically not allowed to be directly substituted in the process and equipment used for traditional blocks made from polyethylene and polyester binders. Therefore, it is challenging for end users to apply PVDF polymer binders to their products, especially for blocks made using extrusion technology.

[0008] The present invention relates to the inventive extruder to solve the extrusion problems in manufacturing blocks containing active media particles (e.g., activated carbon and PVDF polymer binder), improving the simplicity and yield of the extrusion process, and the quality and performance of the blocks.

[0009] The conventional problems encountered during the extrusion of blocks using PVDF polymer binders include: 1) incomplete curing of the binder, and 2) clogging of the extrusion barrel when the blocks lock up inside the barrel.

[0010] Incomplete curing of the blocks is typically due to the fact that the melting temperature of the PVDF polymer binder is typically higher than the melting temperature of PE and polyester binders, and ranges from 110°C to 180°C. By curing, we mean the binding of the active media particles by the binder. Blocks made using PVDF polymers typically require higher temperature and / or longer residence time in the heated zone of the extruder. This results in partially cured blocks, for example, when using extruder types with short heating zones that are not threaded, as described in WO1992017327A2.

[0011] The clogging problem of the extrusion barrel is typically due to the high friction of the blocks against the walls of the extrusion barrel. This problem occurs especially for 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 widely used for such blocks, for example, in the case of activated carbon blocks for health claim filters, which use small active media particles to remove heavy metals. The clogging problem also occurs for blocks containing PVDF polymer binders due to the low binder loading, typically less than 20%, preferably less than 16%. This is because the polymer binder acts as a lubricant and helps to reduce the friction against the walls of the extruder.

[0012] US2016 / 0121249A1 and WO2014055473A2 teach the use of a thermoplastic binder (PVDF) as a binder in the preparation of activated carbon block filters by compression molding / sintering technology or by extrusion, and teach the method of preparing said filters. There is no mention or enumeration of the extruder design that can successfully extrude blocks containing PVDF polymer binders.

[0013] WO 1992017327 A2 describes the formation of solid composite articles using an extrusion process. An extruder is disclosed to produce a briquette from a blend of activated carbon and a polyolefin binder. PVDF is not mentioned as a possible binder. Koslow teaches an extruder with a short, unthreaded heating zone in the barrel, where the heating zone is shorter than the die (cooling) zone. It further teaches that a longer heating zone would not work because it results in higher friction of the briquette with the barrel wall, causing plugging of the barrel.

[0014] The extruder described in WO 1992017327 A2 is not well suited for briquettes containing a PVDF polymer binder. The short, unthreaded heating zone generally does not provide sufficient heat transfer to fully solidify briquettes containing a PVDF polymer binder, as PVDF polymers have a relatively high melt temperature of 110°C to 180°C. Thus, the use of this extruder is limited to very low extrusion rates.

[0015] The plugging or jamming problem of briquettes containing a PVDF polymer binder generally occurs in all existing extruder designs, including those described in WO 9217327 A2 and those with longer and / or threaded heating zones. Plugging associated with briquettes containing a PVDF polymer binder can occur due to the low binder loading of less than 30%, preferably less than 18%, most preferably less than 12%, as the low binder loading corresponds to a high content of activated media particles and can result in higher friction with the extruder barrel. In addition, many applications (e.g., high-end CTO water filters and water filters with health claims) require high briquette densities of more than 0.55 g / cm 3 , preferably more than 0.65 g / cm 3 , most preferably more than 0.75 g / cm 3 . In addition, the briquette generally contains more than 10%, preferably more than 20%, more preferably more than 30% of fine activated media particles that are less than 100 microns, preferably less than 50 microns, most preferably less than 10 microns. Higher briquette densities and the proportion of fine activated media particles also increase the friction with the extruder barrel, which can lead to plugging problems.

[0016] Standard extruders, similar to Figure 1 those shown, have a feed zone that is threaded and generally equipped with a feeder that relies on gravity to feed material from a hopper to the barrel.

[0017] There remains a problem in extruding briquettes containing a PVDF polymer binder, in that the briquette is only partially solidified and / or the extruder barrel is jammed with the briquette inside when using various existing extrusion equipment.

[0018] Applicants have now designed a novel extruder that combines a barrel with a threaded heating zone and a shaped zone in which the diameter of the barrel changes so that it is not constant throughout the zone. With this novel extruder design, the process of making a briquette containing a PVDF polymer binder is improved so that the extrusion barrel does not clog. SUMMARY

[0019] The present invention relates to a manufacturing process and an extruder, and more particularly to an extrusion process and an extruder for producing high quality briquette products from an active media (e.g. activated carbon particles) and a polyvinylidene fluoride polymer binder.

[0020] Some aspects of the present disclosure:

[0021] Aspect 1. An extruder for making a briquette of an active media and a PVDF polymer binder comprising an extrusion barrel comprising a threaded heating zone and an unthreaded shaped zone, the unthreaded shaped zone comprising a cooling section,

[0022] wherein the heating zone is longer than the shaped zone,

[0023] wherein in the unthreaded shaped zone, the internal diameter D of the extrusion barrel increases from Di to D2, wherein the diameter change from Di to D2 is between 0.2% and 1.0%,

[0024] wherein the ratio of the heating zone length to the shaped zone length is 20:1 to 5:4.

[0025] Aspect 2. The extruder of aspect 1, wherein the diameter increases from Di to D2 in the shaped zone by 0.2% to 0.9%, preferably 0.35% to 0.70%.

[0026] Aspect 3. The extruder of aspect 1, wherein the diameter increases from Di to D2 by 0.4% to 0.65%.

[0027] Aspect 4. The extruder of any one of aspects 1 to 3, wherein the diameter change from Di to D2 occurs over 10% to 100% of the length of the shaped zone, preferably 30% to 85% of the length, preferably 40% to 75% of the length.

[0028] Aspect 5. The extruder of aspects 1 to 4, wherein the ratio of the heating zone length to the shaped zone length is preferably 10:1 to 5:4.

[0029] Aspect 6. The extruder of any one of aspects 1 to 6, 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.

[0030] Aspect 7. The extruder of any one of aspects 1 to 7, wherein the shaping zone is 0.01 to 1 meter long, preferably 0.02 to 0.5 meter long.

[0031] Aspect 8. The extruder of any one of aspects 1 to 7, wherein the shaping zone is 0.05 to 0.2 meter long, preferably 0.05 to 0.15 meter long.

[0032] Aspect 9. The extruder of any one of aspects 1 to 8, wherein the cooling section is 0.01 to 1 meter long, preferably 0.02 to 0.5 meter long.

[0033] Aspect 10. The extruder of any one of aspects 1 to 8, wherein the cooling section is 0.05 to 0.2 meter long, preferably 0.05 to 0.15 meter long.

[0034] Aspect 11. The extruder of any one of aspects 1 to 8, wherein the cooling section length is 20% to 100%, preferably 50% to 99% of the shaping zone length.

[0035] Aspect 12. The extruder of any one of aspects 1 to 11, wherein the inner diameter D1 of the barrel in the unthreaded zone is 1 cm to 50 cm, preferably 3 cm to 25 cm.

[0036] Aspect 13. The extruder of any one of aspects 1 to 11, wherein the inner diameter D1 of the barrel in the unthreaded zone is 1 cm to 25 cm, preferably 3 cm to 6 cm.

[0037] Aspect 14. A method for extruding a briquette of active media and a PVDF polymer binder, the method comprising the steps of: providing a PVDF polymer binder comprising a PVDF polymer and an active media, feeding the PVDF polymer binder and the active media to an extruder as described in aspect 1, and extruding the resulting PVDF polymer binder and active media blend to form a fixed media briquette.

[0038] Aspect 15. A method of extruding a carbon briquette, the method comprising the steps of:

[0039] a. providing a PVDF polymer binder and an active media,

[0040] b. providing an extruder comprising an extrusion barrel, the extrusion barrel comprising a threaded heating zone and an unthreaded shaping zone, the shaping zone comprising a cooling section, wherein the ratio of the length of the heating zone to the length of the shaping zone is 20:1 to 5:4, wherein in the shaping zone, the inner diameter D of the extrusion barrel increases from D1 to D2, wherein the diameter change from D1 to D2 is 0.2% to 0.9%,

[0041] c. feeding the PVDF polymer binder and the active media to an extruder,

[0042] d. extruding the PVDF polymer binder and the active media to form a monolith of the media.

[0043] Aspect 16. The method of aspect 14 or 15, wherein the PVDF polymer binder containing PVDF polymer and the active media are blended prior to feeding to the extruder.

[0044] Aspect 17. The method of any one of aspects 14 to 16, wherein the heating zone temperature is from 20°C below the binder melt temperature to 80°C above the binder melt temperature.

[0045] Aspect 18. The method of any one of aspects 14 to 16, wherein the heating zone temperature is from 130°C to 260°C, preferably from 170°C to 230°C.

[0046] Aspect 19. The method of any one of aspects 14 to 18, wherein the binder comprises a VDF / HFP copolymer having a melt viscosity of from 5 to 80 kP, preferably from 15 to 50 kP.

[0047] Aspect 20. The method of any one of aspects 14 to 19, wherein the PVDF polymer contains from 5 to 20 wt% HFP.

[0048] Aspect 21. The method of any one of aspects 14 to 20, wherein the PVDF polymer contains discrete PVDF polymer particles having a size (as average discrete particle size) of from 50 to 500 nm and agglomerates of the discrete polymer particles having a size of from 1 micron to 150 microns, preferably from 3 microns to 50 microns, as measured by electron scanning microscopy.

[0049] Aspect 22. The method of any one of aspects 14 to 21, wherein the active media comprises activated carbon.

[0050] Aspect 23. The method of any one of aspects 14 to 22, wherein the binder comprises from 1 to 30 wt%, preferably from 1 to 10 wt%, based on the total weight of the binder and the active media.

[0051] Aspect 24. The method of any one of aspects 14 to 23, wherein the monolith of the active media and the PVDF polymer binder has a density of at most 0.95 g / cm3, preferably from 0.50 to 0.90 g / cm3, more preferably from 0.65 to 0.85 g / cm3. 3 3 3

[0052] ​​​Aspect 25. The method of any one of aspects 14 to 24, wherein the extruder produces the logs of active media and PVDF polymeric binder at a rate of 0.5 cm to 50 cm per minute, preferably 0.5 to 30 cm per minute.

[0053] Aspect 26. The method of any one of aspects 14 to 25, wherein the heating zone is 0.25 to 1 meter long, preferably 0.5 to 1.5 meters long,

[0054] wherein the shaping zone is 0.075 to 0.20 meters long, the cooling section comprises 27% to 72% of the shaping zone, and the swell from D1 to D2 along the extrusion barrel is 0.3% to 0.7%. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 : Schematic of an existing extrusion barrel, optionally equipped with an internal solid rod to produce hollow cylinder logs. The barrel consists of three zones: a feed zone, a heating zone, and a shaping zone including a cooling section. The feed zone is not heated, threaded, located directly below the feed mill hopper, and ends at the edge of the hopper. The heating zone is threaded and longer than the unthreaded shaping zone. The heating zone begins at the edge of the feed hopper until the end of the threaded section. In a standard extruder, the diameter of the feed zone, heating zone, and shaping zone is constant along the entire length of the barrel. The shaping zone is unthreaded and typically does not have heating elements. The shaping zone begins at the end of the threaded section and extends to the end of the barrel. The shaping zone typically includes a cooling section in which cooling elements are used.

[0056] Figure 2 : Schematic of an extrusion barrel of the present invention, optionally equipped with an internal solid rod to produce hollow cylinder logs. The barrel consists of three zones: a feed zone, a heating zone, and a shaping zone including a cooling section. The schematic shows the heating zone and the shaping zone. The feed zone (not shown) is not threaded and is typically not heated, but it can be heated. The heating zone is threaded and equipped with heating elements, which are preferably located on the outer surface of the barrel. The shaping zone is not threaded and is typically not heated. The cooling section in the shaping zone is equipped with cooling elements. The cooling elements are preferably located on the outer surface of the barrel. In the shaping zone, the inner barrel diameter D varies along the length of the barrel such that the final inner barrel diameter (D2) at the exit of the cooling section is greater than the initial inner barrel diameter (D1) at the beginning of the unthreaded zone. The inner barrel diameter D can vary gradually along the entire length of the unthreaded zone, or it can vary in increments. The heating zone is the longest zone in the barrel. DETAILED DESCRIPTION

[0057] All references listed in this application are incorporated herein by reference. All percentages in these compositions are by weight unless otherwise specified. Combinations of the different elements / elements described herein are also considered to be part of this application.

[0058] As used herein, "interconnected" means that the active media particles or fibers are permanently bound together by polymer binder particles without completely coating their surfaces. In the so-called "cured" process, the binder softens and adheres to the active media particles at specific discrete points to create an ordered porous structure. The monolith prepared by the method of the present application is porous. The monolith allows fluid to flow through the interconnected particles or fibers and the fluid is directly exposed to their surfaces, which facilitates adsorption of components of the fluid to the active media. Because the polymer binder adheres to the active media particles only at discrete points, less polymer binder is used to accomplish the interconnection compared to a binder coated to the active media.

[0059] An extruder is disclosed for making a monolith of active media and PVDF binder.

[0060] A method is disclosed for extruding a monolith of active media and PVDF binder using the extruder of the present application.

[0061] The present disclosure describes the extrusion of a monolith of active media (e.g., activated carbon) utilizing PVDF as a binder. The extruder has a novel barrel design that is improved over existing extrusion barrels used to produce monoliths. The novel extruder of the present application allows for the successful extrusion of a monolith of active media and PVDF binder where the monolith does not lock up in the barrel in a jamming event.

[0062] The present disclosure describes an improved extruder scheme for extruding a fixed active media monolith where the extrusion barrel is improved in the shaping zone such that the improved inner diameter (D2) at the barrel exit is greater than the inner diameter (D1) in the threading zone or at the beginning of the threading zone.

[0063] Extrusion apparatus

[0064] The improved extrusion barrel is comprised of three zones: 1) a feed zone, 2) a heating zone, and 3) a shaping zone that includes a cooling section.

[0065] The feed zone is threaded and is generally unheated, receives material from the feeder and brings the material into the heating zone. The heating zone is threaded, has heating elements and is the longest zone in the extrusion barrel to ensure adequate heat transfer and to complete the consolidation of the billet. The forming zone is unthreaded, it is generally unheated although parts of it can optionally be heated. In the forming zone, the cooling section is unthreaded and is equipped with cooling elements. The extrusion barrel changes in the forming zone such that the changed internal diameter (D2) at the end of the forming zone is greater than the internal diameter (D1) at the beginning of the forming zone, as shown in Figure 2 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, preferably 8:1 to 6:4.

[0066] The absolute length of the extrusion barrel and of each barrel zone will depend on the thickness of the billet. For example, the thickness of a solid cylindrical billet is the outer diameter of the billet, the thickness of a hollow cylindrical billet is defined as the difference between the outer diameter and the inner diameter of the billet.

[0067] The feed zone is 0.1 to 1 meter long, preferably 0.2 to 0.5 meters long.

[0068] The heating zone is longer than the forming zone and can be 0.25 to 2 meters long, preferably 0.5 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 elements can be set to room temperature to 300°C, and is generally 20°C below the melting temperature of the binder to 80°C above the melting temperature of the binder. The temperature of each element can be controlled independently.

[0069] The forming zone can be 0.01 to 1 meter long, or 0.02 to 0.7 meters long, preferably 0.05 to 0.5 meters long. The cooling section in the forming zone can be 0.01 to 1 meter long, preferably 0.02 to 0.5 meters long or 0.05 to 0.20 meters long, even more preferably 0.05 to 0.15 meters long. The cooling section is equipped with one or more cooling elements. The cooling elements can contain a cooling fluid, such as water or other coolant, which can optionally be chilled. The temperature of the cooling fluid can be 90°C to -20°C, preferably 35°C to 0°C.

[0070] In the forming zone, the inside diameter D of the barrel can vary such that the final inside 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 to 1.007 times, the initial inside diameter at the beginning of the forming zone. The gradient change in the inside diameter D can occur only in the forming zone. The change can occur over 10% to 100% of the length of the forming zone, preferably 30% to 85% of the length, preferably 40% to 75% of the length, more preferably 50% to 70% of the length, and can occur in a continuous manner or in one or more steps. The percentage is calculated as the ratio of the length of the varying section to the total length of the forming zone (including the cooling section). The length of the varying section is measured from the point at which the inside diameter first changes in the forming zone to the barrel end at the exit of the cooling section. The gradient change allows for compensation of the shrinkage of the die and release of the pressure built up in the die, which shrinks more than the polymer binder and active medium being extruded. After the gradient change is complete, the final inside diameter at the end of the forming zone (D2) is greater than the initial inside diameter at the beginning of the forming zone (D1). The overall increase in the inside diameter from D1 to D2 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 increase is calculated as follows:

[0071] Increase in D % = 100 * (D2 - D1) / D1

[0072] The inside diameter D1 in the threading zone is preferably 1 cm to 50 cm, more preferably 3 cm to 25 cm. D1 can be up to 100 cm or more. D1 can be 1 cm to 25 cm, or 3 cm to 6 cm, or 4 cm to 5 cm. In the case of a hollow structure, the typical inside diameter of the hollow in the structure is 0.5 cm to 45 cm, more preferably 1 cm to 15 cm, or 1 cm to 10 cm.

[0073] In one exemplary embodiment, the inside diameter D1 of the threading zone is 4.35 cm and varies with a gradient of 0.5% increase to an inside diameter D2 of 4.372 cm at the exit of the cooling section.

[0074] Additionally, the type of extruder can also be equipped with an external device that can stop the block from exiting, thus helping to create back pressure to densify the block. This can be achieved by slowing down the extrusion speed with a conventional puller used in the plastics industry, placing a weight in front of the extrudate, or using a simple device consisting of a spring and a finger piece (also known as a donut) to grab the block and exert a pressure proportional to the spring constant of the spring. There are other devices that create back pressure to help densify the block that can 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 internal diameter of the heating zone to create material buildup. In this case, the internal diameter of the barrel at the end of the heating zone is smaller than the internal diameter of the barrel at the beginning of the heating zone.

[0075] Additionally, a feed device, known as a feeder, is typically used in conjunction with the extruder. The feed device includes a hopper that takes a supply of material and feeds the material to the extruder at a steady rate.

[0076] Finally, the extruder can also be provided with an inline block cutter that helps to cut the extruded block into a specific length.

[0077] The novel and inventive design of the extruder solves the problem of clogging when making blocks containing a PVDF polymer binder. The novel extruder design also ensures complete curing of the block. Thus, the present invention provides a block maker with a high productivity and consistent method of making immobilized active media blocks.

[0078] The extruder of the present invention is designed to extrude blocks containing an active media and a PVDF polymer binder.

[0079] Binder

[0080] The binder in the blocks produced using the extruder of the present invention includes a polyvinylidene fluoride (PVDF) polymer binder. The PVDF polymer binder can include a single PVDF polymer, a blend of two or more PVDF polymers, a blend of a PVDF polymer with other polymers (e.g., polyethylene, polyesters, and or any other thermoplastic polymer). In some embodiments, the PVDF polymer binder is a blend of a PVDF binder with other polymers, with PVDF being the major component of the overall binder, containing greater than 50% of the PVDF polymer based on the total polymer binder. In some embodiments, PVDF is not the major component and can be as low as 10% of the total binder content in the block. The PVDF polymer is a polyvinylidene homopolymer or a copolymer of polyvinylidene with 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.

[0081] Preferred PVDF copolymers include copolymers containing at least 50 mole percent, preferably at least 75 mole percent, more preferably at least 80 mole percent, even more preferably at least 85 mole percent of vinylidene fluoride (VDF) copolymerized with one or more comonomers selected from the group consisting of tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, hexafluoropropylene (HFP), fluoroethylene, pentafluoropropylene, tetrafluoropropylene, trifluoropropylene, perfluoromethylvinyl ether, perfluoropropylvinyl ether, (meth)acrylic acid, (meth)acrylic acid esters, and any other monomer that readily copolymerizes with vinylidene fluoride. The comonomer is preferably hexafluoropropylene.

[0082] In one embodiment, the vinylidene fluoride polymer contains up to 30 weight percent, preferably up to 25 weight percent, more preferably up to 15 weight percent of HFP units and 70 weight percent or more, preferably 75 weight percent or more, more preferably 85 weight percent or more of VDF units. The PVDF polymer can have from 0 to 30 weight percent, preferably from 5 to 20 weight percent of HFP units.

[0083] The PVDF used in the present application is generally prepared by aqueous radical emulsion polymerization using methods known in the art - however, suspension polymerization, solution polymerization, and supercritical CO2 polymerization processes can also be used. Preferably, the PVDF is produced by emulsion polymerization.

[0084] The surfactants used in the polymerization can 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 application is free of fluorosurfactants, and no fluorosurfactants are used in any part of the polymerization. Non-fluorinated surfactants useful in PVDF polymerization can be ionic and non-ionic, including but not limited to: 3-allyloxy-2-hydroxy-1-propane sulfonate, polyvinyl phosphonic acid, polyacrylic acid, polyvinyl sulfonic acid and salts thereof, polyethylene glycol and / or polypropylene glycol and block copolymers thereof, alkyl phosphonate esters, and siloxane based surfactants. In one embodiment, the emulsion polymerization is conducted in the absence of any surfactant.

[0085] The latex polymer binder is typically made into a powder form by spray drying, coagulation, or other known processes to produce a dry powder. The powder shape and particle size can be altered by any known process, for example, milling.

[0086] The average discrete particle size of the discrete PVDF binder particles is typically in the range of 5 nm to 700 nm, preferably 50 nm to 500 nm, more preferably 100 nm to 300 nm. In some cases, the discrete polymer particles can be agglomerated into groups of 1 micron to 150 microns, 3 microns to 50 microns, preferably 5 microns to 15 microns. It has been found that some of these agglomerates can de-agglomerate into discrete particles or fibrils during processing into the article. Some of the binder particles are discrete particles and remain as discrete particles in the formed block article. During processing into the block article, the particles bring the active media into abutment and provide interconnection.

[0087] It is important to use as little binder as possible to hold the active material together, as this can leave more surface area of the active media exposed for interaction with a fluid, for example, during a filtration or adsorption process. One advantage of the PVDF polymer is that it has a very high specific gravity of at least about 1.75 g / cm3 3 , preferably at least about 1.77 g / cm3 3 . Thus, the low weight percent of binder required represents an even lower volume percent.

[0088] The molecular weight of the PVDF polymer is not particularly limited. It is preferred to have a higher molecular weight to, in some cases, help the binder not to flow into the active media to contaminate the high surface area of the activated carbon. The melt viscosity of the polymer is preferably 1 to 100 kiloPoise (kP), preferably 5 to 80 kP, 5 to 60 kP, most preferably 15 to 50 kP. The melt viscosity of the polymer is measured according to ASTM D383 by capillary rheometer at 232°C and 100 sec"1.

[0089] Active media

[0090] The active media used are those known for use in block products. The block products can be used for filtration, for example, water filtration, or can be used for transport, storage, separation, cleaning of fluids (gases or liquids) by selection of the appropriate active media. The active media particles are not particularly limited. Examples of active media include, but are not limited to, powder particles or fibers of activated carbon, graphite, molecular sieves, metals and derivatives, biocides and heavy metal removers, and combinations thereof. One preferred active media is activated carbon.

[0091] The active media particles of the present invention typically range in size from 0.1 microns to 3000 microns in diameter, 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, for example, some particles having an average particle size of less than 100 microns and some particles having an average particle size of greater than 200 microns. The active media particles can also be in the form of fibers having a diameter of 0.1 micron to 250 microns, with the ratio of length to width being essentially unlimited. The fibers are preferably chopped to a length of no more than 5 mm.

[0092] The active media fibers or powders should have sufficient thermal conductivity to allow for heating of the powder mixture. In addition, the melting point of the particles and fibers must be sufficiently higher than the melting point of the PVDF polymer binder during the extrusion process to prevent the material from melting and creating a continuous molten phase, but rather to create the typically desired multiphase system.

[0093] Process

[0094] The PVDF polymer binder and active media are blended and processed. The PVDF polymer binder is typically in the form of a powder, which can be dry blended with the active media. Preferably, from 0.5 to 35 weight percent, preferably from 1 to 30 weight percent, more preferably from 3 to 25 weight percent of the PVDF polymer binder is used in the briquette product, based on the total weight of the active media and PVDF polymer binder. The total percentage of PVDF can be from 1 weight percent to 10 weight percent, based on the total weight of the active media and PVDF polymer binder.

[0095] In cases where very dense briquettes are desired, the extrusion process can be performed at higher pressures. The extrusion process is performed in a manner that produces softened polymer binder particles, but not to the extent that they melt and flow to the extent that they contact other polymer particles and form agglomerates or a continuous layer. To be effective in the intended end use, the polymer binder remains as discrete polymer particles that bind the active media particles into an interconnected web for good permeability. Solvents that dissolve the binder are not used in the present invention, because in a solvent system, the individual polymer particles no longer exist, as the particles would dissolve and form a continuous coating on the active media particles. The continuous coating reduces the amount of active surface area for fluid interaction with the active particles, and can reduce their overall effectiveness.

[0096] The active media and polymer binder are formed into a briquette product in an extrusion process. The briquettes of the present invention are formed by an extrusion process. A conventional extrusion process for carbon briquettes is described in US 5,331,037. US 5,331,037 describes the use of an extruder with a short, unthreaded heated barrel to extrude briquettes made with a polyethylene binder. PVDF is not mentioned as a possible binder.

[0097] The polymer binder / active media composite of the present invention is typically dry blended with other additives (e.g., processing aids) and extruded. Continuous extrusion under heat, pressure, and shear can produce an infinite length three-dimensional profile, multi-phase structure. A continuous web of binder-bonded active media particles at points of stress is formed under the conditions of the extruder.

[0098] Extrusion processing can produce continuous block structures of any desired diameter and length. Lengths from one centimeter to hundreds of meters can be obtained with suitable fabrication equipment. The continuous solid block can then be cut to the desired final length. The block can be solid or hollow. The typical outer diameter of the block is preferably from 1 cm to 50 cm, more preferably from 3 cm to 25 cm - although structures up to 100 cm or even more in diameter can be produced with appropriately sized dies. In the case of hollow structures, the typical inner diameter is from 0.5 cm to 45 cm, more preferably from 1 cm to 15 cm, or from 1 cm to 10 cm.

[0099] An alternative to a single structure is to form two or more structures - solid rods and one or more hollow block cylinders designed to nest together to form a larger structure. Once the individual annular or rod-shaped block components are formed, these components can be nested together to produce a larger structure. This approach can offer several advantages over extruding a single large structure. Blocks with smaller cross-sectional diameters can be produced at a faster rate than a large solid single-pass block. The cooling profile can be better controlled for each smaller cross-sectional piece. Another advantage of this concept can be a reduction in the gas diffusion path length through the monolith, as the spacing between the concentric blocks can act as a channel for rapid gas flow.

[0100] Properties

[0101] The article formed by the present invention is a high quality, robust block structure of active media and binder. The density of the block can be finely tuned, for example, the density can be very high to maximize the amount of active media, thereby maximizing the efficiency of the block.

[0102] The extruder of the present invention provides blocks with a density up to 0.95 g / cm3. 3 Preferably, the density of the block product is from 0.50 to 0.90 g / cm3, 3 more preferably from 0.65 to 0.85 g / cm3. 3 .

[0103] The extruder of the present invention provides higher production capacity due to reduced frictional forces of the composition particles against the walls of the extruder. The extruder of the present invention can provide a throughput of extruded blocks up to 0.5 cm to 50 cm per minute, preferably up to 1 cm to 30 cm per minute.

[0104] The temperature of the heating zone is generally driven by the softening temperature of the binder, typically 20°C below the melting temperature of the binder to 80°C above the melting temperature of the binder. For example, the temperature is typically 130°C to 260°C, and can be 170°C to 230°C. Depending on the polymer binder, the temperature can be lower or higher than these examples.

[0105] The new extrusion barrel allows continuous extrusion of fine particles with PVDF polymer binder while minimizing the problem of jamming encountered with traditional extruders.

[0106] Example

[0107] Example 1

[0108] The extrusion barrel comprises: 1 meter of threaded heating zone, 0.23 meter of shaping zone, the shaping zone having a cooling section of 0.115 meter. The initial barrel inner diameter D1 of the threaded zone = 4.35 cm, and the final barrel inner diameter D2 at the exit of the extruder = 4.372 cm (variation of 0.5%). The variation of the inner diameter can occur along 0.172 meter in the length of the unthreaded shaping zone. The barrel is equipped with an internal rod for extruding a hollow cylindrical bulk. The screw diameter is equal to the inner diameter of the hollow bulk, and the inner diameter ID = 1.9 cm. The thread gap is 4 cm. (made of CrMoAl).

[0109] The formulation comprises 8% by weight of a binder (FG-81) and 92% by weight of activated carbon of size 80 x 325 from the company Jaccobi. FG-81) and 92% by weight of activated carbon of size 80 x 325 from the company Jaccobi.

[0110] The processing conditions are as follows:

[0111] A. The binder and the carbon are mixed in a rotary mixer at low speed for 1 hour.

[0112] B. Extrusion conditions: 190°C, 200°C, 150°C, 105°C (T1, T2, T3 and T4);

[0113] The density of the resulting bulk is 0.75 g / cm3 (measured by weight / volume after cooling of the bulk). The linear speed of production of the bulk is 8 cm / minute. 3

[0114] The bulk density is indicative of the mechanical strength and shows the stability of the process. The extruder runs for 3 hours without any problem (no jamming).

[0115] Example 2

[0116] The extrusion barrel is the same as in example 1.

[0117] ​The formulation contained 25% by weight of a binder (FG-415) and 75% by weight of activated carbon of size 80 x 325 from Jacobi. FG-415) and 75% by weight of activated carbon of size 80 x 325 from Jacobi.

[0118] The processing conditions were as follows:

[0119] A. The binder and carbon were mixed in a rotary mixer for 1 hour at low speed.

[0120] B. Extrusion conditions: four heating zones: 170°C, 180°C, 150°C, 105°C (T1 T2 T3 and T4);

[0121] The density of the resulting briquettes was 0.8 g / cm 3 (measured by weight / volume after cooling of the briquettes). The linear speed of production of the briquettes was 8 cm / min.

[0122] The density of the briquettes is indicative of the mechanical strength and shows the stability of the process.

[0123] The extruder ran for 3 hours without any problems (no lock-up).

Claims

1. An extruder for producing a briquette of active media and a PVDF polymer binder comprising an extrusion barrel comprising a threaded heating zone and an unthreaded forming zone, the unthreaded forming zone comprising a cooling section, wherein the heating zone is longer than the forming zone, wherein in the unthreaded forming zone, the internal diameter D of the extrusion barrel increases from Di to D2, wherein the diameter change from Di to D2 is between 0.2% and 1.0%, wherein the ratio of the length of the heating zone to the length of the forming zone is between 20:1 and 5:

4.

2. The extruder of claim 1, wherein, the diameter increases in the forming zone from Di to D2 by between 0.2% and 0.9%.

3. The extruder of claim 2, wherein, the diameter increases in the forming zone from Di to D2 by between 0.4% and 0.65%.

4. The extruder of claim 1, wherein, the diameter change from Di to D2 occurs over between 10% and 100% of the length of the forming zone.

5. The extruder of claim 4, wherein, the diameter change from Di to D2 occurs over between 30% and 85% of the length of the forming zone.

6. The extruder of claim 1, wherein, the ratio of the length of the heating zone to the length of the forming zone is between 10:1 and 5:

4.

7. The extruder of claim 1, wherein, the heating zone is between 0.25 and 2.0 meters long and comprises between 1 and 10 heating sections.

8. The extruder of claim 7, wherein, the heating zone is between 0.5 and 1.5 meters long.

9. The extruder of claim 1, wherein, the forming zone is between 0.01 and 1 meters long.

10. The extruder of claim 9, wherein, the forming zone is between 0.02 and 0.5 meters long.

11. The extruder of claim 1, wherein, the forming zone is between 0.05 and 0.2 meters long.

12. The extruder of claim 1, wherein, the cooling section is between 0.01 and 1 meters long.

13. The extruder of claim 12, wherein, the cooling section is between 0.05 and 0.2 meters long.

14. The extruder of claim 1, wherein, the length of the cooling section is between 20% and 100% of the length of the forming zone.

15. The extruder of claim 14, wherein, the length of the cooling section is between 50% and 99% of the length of the forming zone.

16. The extruder of claim 1, wherein, the internal diameter D of the extrusion barrel in the unthreaded zone is between 1 cm and 50 cm.

17. The extruder of claim 16, wherein, the internal diameter D of the extrusion barrel in the unthreaded zone is between 3 cm and 25 cm.

18. The extruder of claim 17, wherein, the internal diameter D of the extrusion barrel in the unthreaded zone is between 3 cm and 6 cm.

19. A method for extruding a briquette of active media and a PVDF polymer binder, the method comprising the steps of: providing a PVDF polymer binder comprising a PVDF polymer and active media, feeding the PVDF polymer binder and active media to an extruder as claimed in claim 1, and extruding the resulting PVDF polymer binder and active media blend to form a fixed media briquette.

20. A method of extruding a carbon briquette, the method comprising the steps of: a. providing a PVDF polymer binder comprising a PVDF polymer and active media, b. providing an extruder comprising an extrusion barrel comprising a threaded heating zone and an unthreaded forming zone, the forming zone comprising a cooling section, wherein, the ratio of the length of the heating zone to the length of the forming zone is between 20:1 and 5:4, wherein in the forming zone, the internal diameter D of the extrusion barrel increases from Di to D2, wherein the diameter change from Di to D2 is between 0.2% and 0.9%, c. feeding the PVDF polymer binder and active media to the extruder, d. extruding the PVDF polymer binder and active media to form a fixed media briquette.

21. The method of claim 19 or 20, wherein, The PVDF polymer binder comprising a PVDF polymer and active media are blended prior to being fed to the extruder.

22. The method of claim 19 or 20, wherein, The heating zone temperature is between 20°C below the binder melt temperature and 80°C above the binder melt temperature.

23. The method of claim 19 or 20, wherein, The heating zone temperature is between 130°C and 260°C.

24. The method of claim 23, wherein, The heating zone temperature is between 170°C and 230°C.

25. The method of claim 19 or 20, wherein, The binder comprises a VDF / HFP copolymer having a melt viscosity of between 5 and 80 kP.

26. The method of claim 19 or 20, wherein, The PVDF polymer comprises between 5% and 20% by weight of HFP.

27. The method of claim 19 or 20, wherein, The PVDF polymer contains discrete PVDF polymer particles having an average discrete particle size of 50 to 500 nm and agglomerates of the discrete polymer particles having a size of 1 micron to 150 microns as measured by electron scanning microscopy.

28. The method of claim 27, wherein, The agglomerates have a size of 3 microns to 50 microns as measured by electron scanning microscopy.

29. The method of claim 19 or 20, wherein, The active media includes activated carbon.

30. The method of claim 19 or 20, wherein, The binder comprises 1 to 30 weight percent based on the total weight of the binder and the active media.

31. The method of claim 19 or 20, wherein, The density of the bulk of active medium and PVDF polymer binder is at most 0.95 g / cm 3 .

32. The method of claim 19 or 20, wherein, The extruder produces the chunks of active media and PVDF polymer binder at a rate of 0.5 cm to 50 cm per minute.

33. The method of claim 19 or 20, wherein, The heating zone is 0.25 to 2 meters long, wherein the forming zone is 0.075 to 0.20 meters long, wherein the cooling section comprises 27% to 72% of the forming zone, and wherein the swell ratio from D1 to D2 along the extrusion barrel is 0.3% to 0.7%.

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