A post-treatment system for fluoropolymers

Abstract

This invention discloses a post-processing system for fluoropolymers. The system comprises an electro-adsorption liquid device, a continuous negative pressure jet flash evaporator, and a spray dryer connected in sequence. The fluoropolymer emulsion is treated by the electro-adsorption liquid device to remove residual initiator decomposition fragments, and then conveyed to the continuous negative pressure jet flash evaporator for flash concentration to obtain a concentrated fluoropolymer slurry. This slurry is then spray-dried in the spray dryer to produce resin powder. The fluoropolymer is obtained by polymerization of reactants including monomers and an initiator. The post-processing flow provided by this invention is simple and can further reduce the amount of residual impurities in the fluoropolymer and improve its heat resistance and processing performance.

Description

Technical Field

[0001] This invention relates to the field of fluoropolymers, and more specifically to a post-processing system for fluoropolymers. Background Technology

[0002] Common polymerization methods for fluoropolymer production include emulsion polymerization and suspension polymerization, both batch polymerization methods. Emulsion polymerization is a relatively efficient method for preparing fluoropolymers. During emulsion polymerization, emulsifiers such as perfluorooctanoate (PFOA) and anti-sticking agents such as paraffin wax are added. In post-processing, coagulants are added to break up the emulsion. These substances have a significant impact on the properties of the product. The residual additive content in the product should be as low as possible, ideally zero, because residual additives have a significant negative impact on the heat resistance and stability of fluoropolymers. For example, Chinese patent CN1526742A proposes that to prepare highly heat-stable polyvinylidene fluoride (PVDF), the residual surfactant content in the resin powder should be controlled below 300 ppm and the residual paraffin wax content below 200 ppm.

[0003] To reduce residual additives in fluoropolymers and improve the heat stability and processing performance of the products, existing technologies often employ the following methods:

[0004] Chinese patent CN116410375A discloses a method for preparing a large-particle-size polyvinylidene fluoride emulsion. An ionic strength regulator is slowly added during the polymerization process to obtain an emulsion with a particle size of not less than 300 nm, thereby producing polyvinylidene fluoride powder with very low impurity residue.

[0005] Chinese patent CN117304377A discloses a method for improving the heat resistance of polyvinylidene fluoride (PVDF), which involves adding a small amount of ammonium bicarbonate, ammonium carbonate, or dipotassium hydrogen phosphate to the washed resin slurry. The resulting PVDF exhibits excellent resistance to high-temperature yellowing and superior mechanical properties.

[0006] Chinese patent CN104271614A discloses a method for mitigating the thermochromic discoloration of polyvinylidene fluoride (PVDF), which involves adjusting the pH of the aqueous polymer dispersion to above 8.5 and exposing it to an oxygen source. This method requires the use of oxygen or ozone generators.

[0007] By adopting the above-mentioned technical methods, the residual amount of additives in the polyvinylidene fluoride product can be reduced, but it is still impossible to reduce it to zero. The heat resistance stability and processing application performance of the product will be affected by impurities to some extent. Summary of the Invention

[0008] The purpose of this invention is to provide a post-processing system for fluoropolymers. This system has a simple post-processing process and can further reduce the amount of impurities remaining in the fluoropolymer and improve its heat resistance processing performance.

[0009] The technical solution provided by this invention is as follows:

[0010] A post-processing system for fluoropolymers includes an electro-adsorption liquid device, a continuous negative pressure jet flash tank, and a spray dryer connected in sequence. The fluoropolymer emulsion is passed through the electro-adsorption liquid device to remove residual initiator decomposition fragments, and then conveyed to the continuous negative pressure jet flash tank for flash concentration to obtain a concentrated fluoropolymer slurry. The slurry is then spray-dried in the spray dryer to produce resin powder. The fluoropolymer is obtained by polymerization of reactants including monomers and initiators.

[0011] The reactants undergo soap-free emulsion polymerization in a polymerization reactor to obtain a fluoropolymer product. The fluoropolymer product is then separated by a gas-liquid separator to obtain a fluoropolymer emulsion and unreacted monomers. The fluoropolymer emulsion is then transported to an electro-adsorption liquid device. The polymerization reactor does not contain paraffin or surfactants.

[0012] For soap-free emulsion polymerization, surfactants, anti-sticking agents such as paraffin, are not used in the soap-free emulsion polymerization reaction.

[0013] The reactants undergo emulsion polymerization in a polymerization reactor to obtain a fluoropolymer emulsion. The fluoropolymer emulsion is washed with water and then transported to an electro-adsorption liquid device. The polymerization reactor contains paraffin.

[0014] For batch polymerization reactions, since the reaction raw materials include paraffin, a water washing process is required to remove paraffin, surfactants, and initiator fragments.

[0015] The monomer is selected from vinylidene fluoride or vinyl fluoride, the initiator is selected from persulfate or azobisisobutyramidine hydrochloride, and the amount of initiator is 0.005 wt% to 0.1 wt% of the total weight of the reaction raw materials.

[0016] The persulfate is selected from sodium persulfate or potassium persulfate.

[0017] Preferably, the reaction raw materials include modified monomers and / or chain transfer agents.

[0018] The modified monomer is selected from at least one of hexafluoropropylene, pentafluoropropylene, tetrafluoropropylene, trifluoropropylene, perfluorobutene, hexafluorobutadiene, hexafluoroisobutylene, trifluoroethylene, trifluorochloroethylene, perfluoroalkyl vinyl ether, or tetrafluoroethylene. The chain transfer agent is a commonly used chain transfer agent in the fluoropolymer field, preferably selected from at least one of HCFC-21, HCFC-22, HCFC-123, HCFC-225, HFC-4310, butene, isobutylene, or propylene. The amount of the chain transfer agent used is 0.005 wt% to 0.5 wt% of the total weight of the reactants.

[0019] The polymerization reaction temperature is 90℃~125℃, preferably 100~115℃; the polymerization pressure of the vinylidene fluoride is 2.0MPa~8.0MPa, preferably 4.0MPa~6.0MPa; the polymerization pressure of the vinyl fluoride is 15.0MPa~30.0MPa, preferably 20.0MPa~25.0MPa.

[0020] The electro-adsorption liquid device includes a liquid processing unit consisting of one or more conductive plates arranged side by side inside the housing and electrode plates fixed to the conductive plates. The conductive plates at both ends are connected to the power receiving posts, which are connected to a variable polarity DC power supply via wires (to power the electrode plates). The cavity between two adjacent electrode plates is connected to the liquid inlet and outlet of the housing. When the fluoropolymer emulsion flows through the cavity via the liquid inlet and outlet, residual initiator decomposition fragments are removed.

[0021] The continuous negative pressure jet flash tank includes a cylinder, a stirring device, a vacuum vaporization extraction device, and a Venturi jet device. The stirring device is arranged inside the cylinder, and the Venturi jet device is arranged at the bottom of the cylinder. The fluoropolymer emulsion enters the continuous negative pressure jet flash tank through the Venturi jet device. The vacuum vaporization extraction device is connected to a vacuum pump system.

[0022] The spray dryer performs spray drying at temperatures ranging from 120°C to 180°C.

[0023] The inlet temperature of the spray dryer is 130℃~160℃, and the outlet temperature of the spray dryer is 60℃~75℃.

[0024] The particle size D(1.0) of the resin powder is <30μm; when the fluoropolymer is polyvinylidene fluoride, the yellowing index of the polyvinylidene fluoride resin is <6; when the fluoropolymer is polyvinyl fluoride, the yellowing index of the polyvinyl fluoride film prepared by biaxial stretching is <3 when tested at 85℃ and 85RH DH3000.

[0025] The residual surfactant content of the resin powder is <25 ppb.

[0026] The present invention also provides a post-treatment method for fluoropolymers using the above-described system, the method comprising:

[0027] The monomers and initiator undergo polymerization in a polymerization reactor to obtain fluoropolymer products. The fluoropolymer products are separated by a gas-liquid separator, and the separated fluoropolymer emulsion is passed through an electro-adsorption liquid device to remove residual initiator ion fragments. The fluoropolymer emulsion is then passed through a continuous negative pressure jet flash tank, where the liquid water in the emulsion is atomized into fine droplets and rapidly extracted from the flash tank under vacuum, achieving a rapid increase in the solids content of the slurry. The concentrated fluoropolymer slurry is then spray-dried to produce resin powder.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] The post-processing system for fluoropolymers provided by this invention can produce vinylidene fluoride or vinyl fluoride polymers with extremely low impurity content after removing residual initiator decomposition fragments via electro-adsorption, concentrating by negative pressure jet flash evaporation, and then directly spray-drying into resin powder. While ensuring the high-temperature heat resistance of the vinylidene fluoride or vinyl fluoride polymer, the particle size D (1.0) of the resin powder is controlled below 30 μm, exhibiting excellent high-speed self-dispersing construction performance. The obtained vinylidene fluoride or vinyl fluoride polymer can meet the application requirements of various coatings or film materials; and the post-processing process is simple. Especially for fluoropolymers prepared by soap-free emulsion polymerization, the polymerization process does not use surfactants, anti-sticking agents such as paraffin, etc., eliminating unit operations such as cooling, dewaxing, demulsification, and washing, greatly simplifying the post-processing process and eliminating wastewater discharge. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a post-treatment system for fluoropolymers;

[0031] Figure 2 This is a schematic diagram of a polymerization and post-processing system for a fluoropolymer.

[0032] Among them, 1. polymerization reactor, 2. gas-liquid separator, 3. electro-adsorption liquid device, 4. negative pressure jet flash tank, 5. slurry tank, 6. spray dryer, 11. flow meter, 12. metering pump, 13. heat exchanger, 14. gas-liquid mixer, 15. first stirring motor, 16. second stirring motor. Detailed Implementation

[0033] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0034] Example 1

[0035] The structure of the post-processing system for fluoropolymers provided in this embodiment is as follows: Figure 1 As shown, the system includes, in sequence, an electro-adsorption liquid device 3, a continuous negative pressure jet flash evaporator 4, a slurry tank 5, and a spray dryer 6. The process for post-processing fluoropolymers using the above system includes:

[0036] The fluoropolymer is removed by an electro-adsorption liquid device 3 to remove residual initiator decomposition fragments, and then transported to a continuous negative pressure jet flash tank 4. Under the action of the second stirring motor 16, it is flash concentrated to obtain a concentrated fluoropolymer slurry, which is then transported to a slurry tank 5 via an overflow line, and then spray dried by a spray dryer 6 to produce resin powder.

[0037] The electro-adsorption liquid device 3 includes a liquid processing unit consisting of one or more conductive plates arranged side by side inside the housing and electrode plates fixed on the conductive plates. The conductive plates at both ends are connected to the power receiving posts, which are connected to a variable polarity DC power supply through wires. The cavity between two adjacent electrode plates is connected to the liquid inlet and outlet of the housing. When the fluoropolymer emulsion flows through the cavity through the liquid inlet and outlet, residual initiator decomposition fragments are removed.

[0038] The continuous negative pressure jet flash evaporator 4 includes a cylinder, a stirring device, a vacuum vaporization extraction device, and a Venturi jet device. The stirring device is located inside the cylinder, and the Venturi jet device is located at the bottom of the cylinder. The fluoropolymer emulsion enters the continuous negative pressure jet flash evaporator through the Venturi jet device and is flash-concentrated by the vacuum vaporization extraction device under the action of the stirring device. The vacuum vaporization extraction device is connected to a vacuum pump system.

[0039] Example 2

[0040] For the polymerization of fluoropolymers via soap-free emulsion polymerization, the structure of the polymerization and post-processing system for fluoropolymers is as follows: Figure 2 As shown, the system includes a polymerization reactor 1, a gas-liquid separator 2, an electro-adsorption liquid device 3, a continuous negative pressure jet flash evaporator 4, a slurry tank 5, and a spray dryer 6 connected in sequence. The process for polymerizing and post-processing fluoropolymers using the above system includes:

[0041] During the polymerization reaction stage, the initiator and pure water enter the heat exchanger 13 through the flow meter 11 and the metering pump 12 respectively to be heated to the set temperature. The polymer monomer enters the gas-liquid mixer 14 through the flow meter 11 and the metering pump 12 to be fully mixed with the pure water and the initiator and then enters the polymerization reactor 1. Under the action of the first stirring motor 15, a soap-free emulsion polymerization reaction is carried out to obtain the fluoropolymer product.

[0042] In the post-processing stage, the fluoropolymer product is separated into fluoropolymer emulsion and unreacted polymer monomers by gas-liquid separator 2. The fluoropolymer emulsion is then removed by electro-adsorption liquid device 3 to remove residual initiator decomposition fragments, and then transported to continuous negative pressure jet flash tank 4. Under the action of the second stirring motor 16, it is flash concentrated to obtain concentrated fluoropolymer slurry, which is then transported to slurry tank 5 via tank overflow line, and then spray dried by spray dryer 6 to produce resin powder.

[0043] The electro-adsorption liquid device 3 includes a liquid processing unit consisting of one or more conductive plates arranged side by side inside the housing and electrode plates fixed on the conductive plates. The conductive plates at both ends are connected to the power receiving posts, which are connected to a variable polarity DC power supply through wires. The cavity between two adjacent electrode plates is connected to the liquid inlet and outlet of the housing. When the fluoropolymer emulsion flows through the cavity through the liquid inlet and outlet, residual initiator decomposition fragments are removed.

[0044] The continuous negative pressure jet flash evaporator 4 includes a cylinder, a stirring device, a vacuum vaporization extraction device, and a Venturi jet device. The stirring device is located inside the cylinder, and the Venturi jet device is located at the bottom of the cylinder. The fluoropolymer emulsion enters the continuous negative pressure jet flash evaporator through the Venturi jet device and is flash-concentrated by the vacuum vaporization extraction device under the action of the stirring device. The vacuum vaporization extraction device is connected to a vacuum pump system.

[0045] Example 3

[0046] The polymerization reactor 1 used in this embodiment is a 5L Hastelloy reactor. The first stirring motor 15 of the reactor is a magnetically driven stirrer, which adopts a high-absorption, low-shear impeller design.

[0047] Vinylidene fluoride monomer is supplied from a gas cylinder and pumped into polymerization reactor 1. The feed rate is determined by the weight loss of the gas cylinder. The polymerization reaction medium is ultrapure water, which is degassed and stored in a graduated container filled with nitrogen. The feed rate of ultrapure water to polymerization reactor 1 is determined by the weight loss of the container. Potassium persulfate initiator solution, taken from a burette, is pumped into polymerization reactor 1. The feed rate is determined by the volume change observed in the burette. Chain transfer agent HCFC-123 is supplied from a gas cylinder and pumped into polymerization reactor 1. The feed rate is determined by the weight loss of the gas cylinder.

[0048] Polymerization reaction conditions: pure water feed rate of 27.58 g / min, polymerization temperature of 105℃, polymerization pressure of 4.5 MPa, initiator potassium persulfate feed rate of 0.46 g / hr, initiator concentration in reactor of 0.025 wt%, chain transfer agent HCFC-123 feed rate of 1.02 g / hr, and polymerizable monomer vinylidene fluoride feed rate of 6.13 g / min.

[0049] The polymerization reactor 1 is connected to the electroadsorption liquid device 3 and the negative pressure jet flash tank 4 by pressure control valves to maintain the flow of polymer slurry. The monomer vinylidene fluoride is fed into the polymerization reactor 1 at a set feed rate. The ultrapure water feed is heated to a predetermined temperature by a tubular steam heater. After polymerization begins, the temperature control mode of the tubular steam heater is switched to cooling mode to compensate for the heat of polymerization and maintain a constant temperature in the polymerization reactor 1.

[0050] The fluoropolymer product is continuously removed from the polymerization reactor 1 and discharged through a pipe expansion and diameter reduction method. The pressure drops rapidly and the product is transferred to the gas-liquid separator 2. After the fluoropolymer emulsion and unreacted vinylidene fluoride monomer in the fluoropolymer product are separated, the residual initiator decomposition fragments are removed by the electro-adsorption liquid device 3. Then, the product is flash concentrated by the negative pressure jet flash tank 4 and transported to the slurry tank 5 through the tank overflow line. Finally, it is spray dried into resin powder by the spray dryer 6. The collection tank in the spray dryer 6 is periodically emptied to prepare the polymer sample, and the resin powder is weighed.

[0051] The residual emulsifier, residual metal impurities, particle size, and yellowing index of the polymer products prepared in this embodiment were determined.

[0052] No residual sodium perfluorooctanoate (PFOA) emulsifying agent was detected in the polyvinylidene fluoride (PVDF) powder by HPLC-MS / MS. The residual amounts of potassium and sodium ions in the PVDF powder were measured to be 31462 ppb and 15 ppb, respectively, by ICP-MS. The particle size D (1.0) of the PVDF powder was measured to be 28.9 μm by a Malvern Mastersizer 2000 laser particle size analyzer. The PVDF powder was placed in an oven at 250℃ for 30 min and then removed. The yellowness index was measured to be 5.0 by a HunterLab ColorFlex EZ colorimeter.

[0053] Example 4

[0054] The polymerization reactor 1 used in this embodiment is a 5L Hastelloy reactor. The first stirring motor 15 of the reactor is a magnetically driven stirrer, which adopts a high-absorption, low-shear impeller design.

[0055] Vinyl fluoride monomer is supplied from a steel cylinder and pumped into polymerization reactor 1. The feed rate is determined by the weight loss of the steel cylinder. The polymerization reaction medium is ultrapure water, which is degassed and stored in a graduated container filled with nitrogen. The feed rate of ultrapure water to polymerization reactor 1 is determined by the weight loss of the container. Azobisisobutyramidine hydrochloride initiator solution, taken from a burette, is pumped into polymerization reactor 1. The feed rate is determined by the volume change observed in the burette. Chain transfer agent isobutylene is supplied from a steel cylinder and pumped into polymerization reactor 1. The feed rate is determined by the weight loss of the steel cylinder.

[0056] Polymerization reaction conditions: pure water feed rate of 41.63 g / min, polymerization temperature of 105℃, polymerization pressure of 22.5 MPa, initiator azobisisobutyramidine hydrochloride feed rate of 0.274 g / hr, initiator concentration in reactor of 0.015 wt%, chain transfer agent isobutylene feed rate of 0.98 g / hr, and monomer vinyl fluoride feed rate of 9.25 g / min.

[0057] The polymerization reactor 1 is connected to the electroadsorption liquid device 3 and the negative pressure jet flash tank 4 by pressure control valves to maintain the flow of the polymer slurry. The monomer vinyl fluoride is fed into the polymerization reactor 1 at a set feed rate, and the ultrapure water feed is heated to a predetermined temperature using a tubular steam heater. After polymerization begins, the temperature control mode of the tubular steam heater is switched to cooling mode to compensate for the heat of polymerization and maintain a constant temperature in the polymerization reactor 1.

[0058] The fluoropolymer product is continuously removed from the polymerization reactor 1 and discharged through a pipe expansion and diameter reduction method. The pressure drops rapidly and the product is transferred to the gas-liquid separator 2. After the fluoropolymer emulsion and unreacted vinyl fluoride monomer in the fluoropolymer product are separated, the residual initiator decomposition fragments are removed by the electro-adsorption liquid device 3. Then, the product is flash concentrated by the negative pressure jet flash tank 4 and then transported to the slurry tank 5 through the tank overflow line. Finally, it is spray dried into powder by the spray dryer 6. The collection tank in the spray dryer 6 is periodically emptied to prepare the polymer sample, and the resin powder is weighed.

[0059] No residual sodium perfluorooctanoate (PFOA) was detected in the polyvinyl fluoride powder prepared in this embodiment using HPLC-MS / MS. The residual potassium and sodium metal ions in the polyvinyl fluoride powder were measured to be 17 ppb and 13 ppb, respectively, using ICP-MS. The particle size D(1.0) of the polyvinyl fluoride powder was 29.2 μm, as measured by a Malvern Mastersizer 2000 laser particle size analyzer. The yellowing index ΔYI of the film prepared by biaxial stretching of polyvinyl fluoride resin was 0.79.

[0060] Comparative Example 1

[0061] Same as Example 1, except that sodium perfluorooctanoate is added as an emulsifying agent during the polymerization of vinylidene fluoride.

[0062] Polymerization reaction conditions: pure water feed rate of 27.58 g / min, polymerization temperature of 105℃, polymerization pressure of 4.5 MPa, potassium persulfate initiator feed rate of 0.46 g / hr, initiator concentration in reactor of 0.025 wt%, chain transfer agent HCFC-123 feed rate of 1.02 g / hr, emulsifier sodium perfluorooctanoate, emulsifier concentration in reactor of 0.025 wt%, and polymerizable monomer vinylidene fluoride feed rate of 6.13 g / min.

[0063] The residual amount of sodium perfluorooctanoate (PFOA) emulsifying agent in polyvinylidene fluoride (PVDF) powder was detected to be 909.75 ppm using HPLC-MS / MS. The residual amounts of potassium and sodium metal ions in the resin powder were measured to be 40163 ppb and 47991 ppb, respectively, using ICP-MS. The particle size D (1.0) of PVDF powder was measured to be 27.6 μm using a Malvern Mastersizer 2000 laser particle size analyzer. After being placed in an oven at 250℃ for 30 min, the yellowness index of PVDF powder was measured to be 25.0 using a HunterLabColorFlex EZ colorimeter.

[0064] Comparative Example 2

[0065] Same as Example 2, except that sodium perfluorooctanoate is added as an emulsifying agent during the polymerization of fluoroethylene.

[0066] Polymerization reaction conditions: pure water feed rate was 41.63 g / min, polymerization temperature was 105℃, polymerization pressure was 22.5 MPa, initiator azobisisobutyramidine hydrochloride feed rate was 0.274 g / hr, initiator concentration in reactor was 0.015 wt%, chain transfer agent isobutylene feed rate was 0.98 g / hr, emulsifier was sodium perfluorooctanoate, emulsifier concentration in reactor was 0.025 wt%, and polymerizable monomer vinyl fluoride feed rate was 9.25 g / min.

[0067] The residual amount of sodium perfluorooctanoate (PFOA) emulsifying agent in polyvinyl fluoride (PVC) powder was detected to be 602.48 ppm using HPLC-MS / MS. The residual amounts of potassium and sodium metal ions in the PVC powder were measured to be 13 ppb and 31793 ppb, respectively, using ICP-MS. The particle size D(1.0) of the PVC powder was measured to be 28.2 μm using a Malvern Mastersizer 2000 laser particle size analyzer. The yellowing index ΔYI of the PVC resin film prepared by biaxial stretching was 3.79.

[0068] The polymerization process conditions and resin performance tests for the examples and comparative examples are detailed in Table 1.

[0069] Table 1. Polymerization process conditions and resin performance test data for the examples and comparative examples.

[0070]

[0071]

[0072] Note: Residual amount of sodium perfluorooctanoate emulsifier 1 Test method: The polymer powder sample to be tested was pretreated with extractant, and Soxhlet extraction was performed to obtain the extract. After purification, the residue was detected using a Waters ACQUITY UPLC high-performance liquid chromatography-tandem quadrupole mass spectrometer (HPLC-MS / MS). The mobile phase of the mass spectrometer was chromatographically pure methanol and water, with gradient elution. The chromatographic column was an ACQUITY BEH C18 column with dimensions of 2.1 mm × 50 mm and a diameter of 1.7 μm. The column temperature was 30-50℃, and the flow rate was 0.4 mL / min. The mass spectrometry detection conditions were: ESI ionization mode, MRM (multiple reaction monitoring) mode, and negative ion scanning.

[0073] Metal ion dissolution 2 Take 100g of fluoropolymer resin powder and put it into 100ml of ion extraction solution (20% by mass ultra-high purity nitric acid), soak it at 60℃ for 24h; after cooling, measure the metal ion content by ICP-MS.

[0074] Resin powder particle size 3 Particle size D (1.0) was measured using a Malvern Mastersizer 2000 laser particle size analyzer.

[0075] Yellow Index 4 The polymer powder was placed in aluminum foil, placed in a 250°C oven for half an hour, and then removed. The yellowness index was measured using a HunterLab ColorFlex EZ colorimeter.

[0076] PVF film yellowing index △YI 5 The yellowing index of the film was tested using DH3000 at 85℃ and 85RH.

Claims

1. A post-treatment system for fluoropolymers, characterized in that, The system includes an electro-adsorption liquid device, a continuous negative pressure jet flash tank, and a spray dryer connected in sequence. The fluoropolymer emulsion is removed by the electro-adsorption liquid device to remove residual initiator decomposition fragments, and then transported to the continuous negative pressure jet flash tank for flash concentration to obtain a concentrated fluoropolymer slurry. The slurry is then spray-dried by the spray dryer to produce resin powder. The fluoropolymer emulsion is obtained by the polymerization reaction of reactants including monomers and initiators.

2. The post-processing system for fluoropolymers according to claim 1, characterized in that, The reactants undergo soap-free emulsion polymerization in a polymerization reactor to obtain a fluoropolymer product. The fluoropolymer product is then separated by a gas-liquid separator to obtain a fluoropolymer emulsion and unreacted monomers. The fluoropolymer emulsion is then transported to an electro-adsorption liquid device. The polymerization reactor does not contain paraffin or surfactants.

3. The post-processing system for fluoropolymers according to claim 1, characterized in that, The reactants undergo emulsion polymerization in a polymerization reactor to obtain a fluoropolymer emulsion. The fluoropolymer emulsion is washed with water and then transported to an electro-adsorption liquid device. The polymerization reactor contains paraffin.

4. The post-processing system for fluoropolymers according to claim 1, characterized in that, The polymerization monomer is selected from vinylidene fluoride or vinyl fluoride, and the initiator is selected from persulfate or azobisisobutyramidine hydrochloride. The amount of initiator is 0.005 wt% to 0.1 wt% of the total weight of the reaction raw materials. The reaction raw materials include modified monomers and / or chain transfer agents. The amount of chain transfer agents is 0.005 wt% to 0.5 wt% of the total weight of the reaction raw materials. The polymerization reaction temperature is 90℃ to 125℃, the polymerization pressure of vinylidene fluoride is 2.0 MPa to 8.0 MPa, and the polymerization pressure of vinyl fluoride is 15.0 MPa to 30.0 MPa.

5. The post-processing system for fluoropolymers according to claim 1, characterized in that, The electro-adsorption liquid device includes a liquid processing unit consisting of one or more conductive plates arranged side by side inside the housing and electrode plates fixed to the conductive plates. The conductive plates at both ends are connected to the electrode terminals, which are connected to a variable polarity DC power supply through wires. The cavity between two adjacent electrode plates is connected to the liquid inlet and outlet of the housing. When the fluoropolymer emulsion flows through the cavity through the liquid inlet and outlet, residual initiator decomposition fragments are removed.

6. The post-processing system for fluoropolymers according to claim 1, characterized in that, The continuous negative pressure jet flash tank includes a cylinder, a stirring device, a vacuum vaporization extraction device, and a Venturi jet device. The stirring device is arranged inside the cylinder, and the Venturi jet device is arranged at the bottom of the cylinder. The fluoropolymer emulsion enters the continuous negative pressure jet flash tank through the Venturi jet device. The vacuum vaporization extraction device is connected to a vacuum pump system.

7. The post-processing system for fluoropolymers according to claim 1, characterized in that, The spray dryer performs spray drying at temperatures ranging from 120°C to 180°C.

8. The post-processing system for fluoropolymers according to claim 1, characterized in that, The inlet temperature of the spray dryer is 130℃~160℃, and the outlet temperature of the spray dryer is 60℃~75℃.

9. The post-processing system for fluoropolymers according to any one of claims 1-8, characterized in that, The particle size D(1.0) of the resin powder is <30μm; when the fluoropolymer is polyvinylidene fluoride, the yellowing index of the polyvinylidene fluoride resin is <6; when the fluoropolymer is polyvinyl fluoride, the yellowing index of the polyvinyl fluoride film prepared by biaxial stretching is <3 when tested at 85℃ and 85RH DH3000.

10. The post-processing system for fluoropolymers according to any one of claims 1-8, characterized in that, The residual surfactant content of the resin powder is <25 ppb.

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