Processable tetrafluoroethylene copolymer

Abstract

Disclosed is a melt processible fluoropolymer composition comprising TFE, VDF and 1-3 mole % of a fluorinated ether. Also disclosed is a method of preparing the polymer.

Description

Technical Field

[0001] The present invention relates to a copolymer of tetrafluoroethylene (TFE), vinylidene fluoride (VDF) and a fluorinated ether. The composition can be processed by conventional means into wires, cables, films and any other parts or articles by thermoplastic forming processes. The resulting articles have both high temperature and low temperature resistance and are resistant to thermal stress cracking. Background Art

[0002] Thermoplastic polymers having high temperature and low temperature resistance as well as high chemical and weather resistance are desirable in a variety of applications such as wires and cables, films, coatings, battery separators or adhesives, and pipes. For applications that require melt processing, it would be a great advantage if the processing temperature and viscosity were within reasonable ranges such that the material could be processed by common and well-known methods such as extrusion (films, wires, etc.), injection molding, blow molding, and 3D printing. Poly(vinylidene fluoride) (PVDF) exhibits very good weather resistance and processability, but is limited in terms of low temperature and high temperature performance.

[0003] It is well known that poly(tetrafluoroethylene) (PTFE) and PTFE-based copolymers have high and low temperature properties, but generally exhibit poor melt processability or are difficult to melt process. In addition, it is known that low molecular weight PTFE fails (cracks) when subjected to both mechanical stress and thermal stress. There is a need for fluoropolymers that are easy to process, resistant to high / low temperatures, and resistant to thermal stress cracking.

[0004] Stress cracking is a phenomenon in polymer materials where external factors (solvents, heat, light, etc.) acting on the polymer cause brittle failure at strains or stresses far below the yield point.

[0005] U.S. Patent No. 3,235,537 discloses a solid polymer for curable resins consisting of 2 - 50 mol% perfluoroalkyl perfluorovinyl ether units, 10 - 85% VDF, and 3 - 80% (–CFX-CFY–) repeating units, but does not discuss viscosity or molecular weight control, processing, or stress crack resistance.

[0006] Japanese Publication JP 2004 - 219579 of Mitsubishi Rayon teaches that optical fibers and cables have 1 - 30 mass% of VDF, 30 - 85% of TFE, and 3 - 40% of a fluoro vinyl compound represented by CF2=CF-(OCF2CF(CF3))a-O-Rf2, and a refractive index of 1.335 to 1.370. Rf2 is a C1 - C8 alkyl, fluoroalkyl, alkoxyalkyl, or fluoroalkoxyalkyl, and a is an integer from 0 to 3. The polymer is used as an outer coating for optical fibers.

[0007] Document US8997797 discloses a fluororesin which comprises TFE, VDF and another ethylenically unsaturated monomer having a storage modulus of 60 - 400 MPa at 170°C. US8997797 requires a minimum amount of 55 mol% of TFE. SUMMARY OF THE INVENTION

[0008] The present invention relates to a copolymer of tetrafluoroethylene (TFE), vinylidene fluoride (VDF) and a fluorinated ether. Preferably, the fluorinated ether is a perfluoroalkyl vinyl ether, such as perfluoropropyl vinyl ether (PPVE). The composition can be processed by conventional means into wires, cables, films and any other parts or articles by thermoplastic forming processes. The resulting articles have both high temperature resistance and low temperature resistance, and have resistance to thermal stress cracking. The polymers of the present invention have a high melting temperature (above 175°C) and low temperature impact resistance below -80°C.

[0009] The polymer comprises 39.5 - 57.0 mol% TFE, 42.0 - 57.5 mol% VDF and 1.0 - 3.0 mol% fluorinated vinyl ether. The polymer is melt processable and exhibits stress crack resistance measured by melt rheology and the methods described herein.

[0010] ASPECTS OF THE INVENTION

[0011] Aspect 1 A fluoropolymer composition comprising 39.5 - 57.0 mol% TFE, 42.0 - 57.5 mol% VDF and 1.0 - 3.0 mol% fluorinated ether, wherein the composition is melt processable.

[0012] Aspect 2 The fluoropolymer composition according to aspect 1, wherein the fluorinated ether is selected from the group consisting of perfluoromethyl vinyl ether (PMVE), perfluoroethyl vinyl ether (PEVE), perfluoropropyl vinyl ether (PPVE), perfluoroisopropyl vinyl ether (PiPVE) and perfluoro-2-propoxypropyl vinyl ether.

[0013] Aspect 3 The fluoropolymer composition according to aspect 1, wherein the ether comprises PPVE.

[0014] Aspect 4 The fluoropolymer composition according to any one of aspects 1 - 3, wherein the fluoropolymer has no thermal stress cracking behavior at temperatures up to 150°C at strains up to 7%.

[0015] Aspect 5 The fluoropolymer composition according to any one of aspects 1 - 4, wherein the melt viscosity of the fluoropolymer is measured at 260°C and 100 s -1 to be 1 - 20 kP, preferably 5 - 19 kP.

[0016] Aspect 6. The fluoropolymer composition according to any one of Aspects 1-5, wherein the melting point of the fluoropolymer is 170-220 °C, preferably 180-210 °C, more preferably 185-209 °C.

[0017] Aspect 7. The fluoropolymer composition according to any one of Aspects 1-6, wherein, as measured by the IZOD impact test, the fluoropolymer has an impact resistance greater than 100 J / m at as low as -80 °C, preferably greater than 250 J / m, more preferably greater than 500 J / m.

[0018] Aspect 8. The fluoropolymer composition according to any one of Aspects 1-7, wherein the fluoropolymer is melt-processable by extrusion, injection molding or compression molding.

[0019] Aspect 9. The fluoropolymer composition according to Aspect 1, the fluoropolymer composition comprising 51.7-56.0 mol% TFE, 42.5–45.5 mol% VDF and 1.5-2.8 mol% PPVE, wherein the melt viscosity is 10-16 kP.

[0020] Aspect 10. A method for synthesizing a melt-processable fluoropolymer composition, comprising the steps of: providing TFE monomer, VDF monomer and fluorinated vinyl ether monomer; initiating polymerization in the presence of a chain transfer agent, wherein the amount of CTA is 0.01-0.5 mol%, preferably 0.01-0.4 mol%, most preferably 0.01-0.3 mol%, based on the total moles of monomers used in the polymerization process, the fluoropolymer composition comprising 39.5–57.0 mol% TFE, 42.0-57.5 mol% VDF and 1.0–3.0 mol% fluorinated vinyl ether.

[0021] Aspect 11. The method according to Aspect 10, wherein the polymerization is carried out in a pressure range of 0.5 MPa - 5.0 MPa.

[0022] Aspect 12. The method according to Aspect 10 or 11, wherein the polymerization is carried out in a temperature range of 25 °C - 125 °C.

[0023] Aspect 13. The method according to Aspect 10, wherein the polymerization is carried out in a pressure range of 0.5 MPa - 3.0 MPa.

[0024] Aspect 14. The method according to Aspect 10 or 13, wherein the polymerization is carried out in a temperature range of 50 °C - 120 °C.

[0025] Aspect 15 The method according to any one of aspects 10-14, wherein the fluorinated ether is selected from the group consisting of perfluoromethyl vinyl ether (PMVE), perfluoroethyl vinyl ether (PEVE), perfluoropropyl vinyl ether (PPVE), perfluoroisopropyl vinyl ether (PiPVE), and perfluoro-2-propoxypropyl vinyl ether.

[0026] Aspect 16 The method according to any one of aspects 10-15, wherein the chain transfer agent ether is selected from the group consisting of oxygen-containing organic compounds that can be used as chain transfer agents, such as alcohols, carbonates, ketones, esters, and ethers; halogenated hydrocarbons and hydrogen-containing halogenated hydrocarbons, such as chlorohydrocarbons, hydrochlorofluorocarbons, chlorofluorocarbons, and hydrochlorofluorocarbons; ethane and propane.

[0027] Aspect 17 The method according to any one of aspects 10-16, wherein the vinyl ether includes PPVE, and the CTA contains 0.01-0.5 mol% of ethyl acetate based on the total moles of monomers.

[0028] Aspect 18 The method according to aspect 10, wherein the amount of the CTA is 0.01-0.5 mol% based on the total moles of monomers used in the polymerization process, the fluoropolymer composition contains 51.7-56.0 mol% of TFE, 42.5-45.5 mol% of VDF, and 1.5-2.8 mol% of PPVE, the polymerization is carried out in a pressure range of 0.5-3.0 MPa and a temperature range of 50°C - 120°C, and the melt viscosity of the fluoropolymer is 10-16 kP.

[0029] Aspect 19 A manufactured article comprising the polymer according to any one of aspects 1-9.

[0030] Aspect 20 The article according to aspect 19, wherein the article is selected from the group consisting of wire, cable, greenhouse film, building film, coating, battery adhesive, battery separator or coating, marine pipeline, dielectric film, piezoelectric film and sensor, pyroelectric film and sensor, chemical processing film, polymer processing aid, and automotive tubing, preferably wire and cable. Detailed Description

[0031] In the context of this application, unless otherwise specified, all viscosities are melt viscosities measured at a temperature of 260°C and a shear rate of 100 s -1 Specifically, the melt viscosity can be measured using a Dynisco LCR 7000 capillary rheometer. Using ASTM method D-3835, the measurement is carried out at 260°C, the shear rate is 10-3000 s -1 , and the viscosity is recorded at 100 s -1 .

[0032] Differential scanning calorimetry (DSC) was used to determine the melting point of the polymers of the present invention. The DSC was run at a heating / cooling rate of 10 °C / min. The generated ΔH was defined as the endothermic area in the heat flow curve during the second heating (T m ) or the exothermic area during the first cooling (T c ) integrated and then divided by the heating rate and the sample mass.

[0033] Thermal stress cracking was determined by molding 3 mm thick rectangular copolymer strips, pre-soaking them for 30 minutes at the test temperature, applying stress by bending to a known radius, and then visually inspecting for cracks at each time point. Failure was quantified by the proportion of parts that broke within a given time. The results reported herein were reported as simply pass or fail. Pass indicated that the polymer parts did not crack after three days of testing, and fail indicated that at least one part showed cracks within the three days of testing. More specifically, the parts were molded to be 3 mm thick, 10 cm long, and 1 cm wide. The outer diameter for enclosing them for testing was 2 cm, the strain calculated on the outer polymer surface was 7%, and the test temperature was 150 °C.

[0034] The materials described herein are melt-processable semi-crystalline thermoplastic polymers. Melt-processable herein means that the polymer can be melt-formed (e.g., by an extruder or an injection molding machine) and then cooled to provide a formed article while maintaining its shape without cracking. In addition, as determined by the above capillary rheometry, a melt viscosity equal to or higher than 21 kP at 260 °C and 100 s -1 is not melt-processable.

[0035] Solid-state fluorine NMR analysis was used to determine the chemical composition. Using powder samples loaded into 2.5 mm Bruker zirconia rotors, 19F solid-state spectra could be obtained at room temperature at a spinning speed of 30 kHz on a Bruker AVIII 300WB (7.05T) spectrometer equipped with a 2.5 mm CP MAS probe. To suppress background noise, the 19F spectrum of an empty rotor could be subtracted from the sample spectrum. 19 19F solid-state spectra. To suppress background noise, the 19F spectrum of an empty rotor could be subtracted from the sample spectrum. 19 19F spectrum.

[0036] The composition is a melt-processable fluoropolymer composition comprising 39.5 - 57.0 mol% TFE, 42.0 - 57.5 mol% VDF, and 1.0 - 3.0 mol% fluorinated ether. When more than one ether is used, the total mol% of the ether present in the polymer is 1 - 3 mol%. Preferably, the ether includes perfluoropropyl vinyl ether (PPVE).

[0037] Fluorinated ethers include, but are not limited to, fluorinated or perfluorinated vinyl ethers, such as perfluoromethyl vinyl ether (PMVE), perfluoroethyl vinyl ether (PEVE), perfluoropropyl vinyl ether (PPVE), perfluoroisopropyl vinyl ether (PiPVE), perfluoro-2-propoxypropyl vinyl ether, perfluorobutyl vinyl ether (PBVE), longer-chain perfluorinated vinyl ethers, and combinations thereof.

[0038] The fluorinated vinyl ether is preferably represented by CF2=CF-(OCF2CF(CF3))a-O-R. R is a C1-C8 alkyl, fluoroalkyl, alkoxyalkyl, or fluoroalkoxyalkyl, and a is an integer from 0 to 3. The fluorinated vinyl ether can have one of the following formulas: CF2=CF-O-(CH2)n-(CF2)m-(CF3), where n and m are integers from 0 to 3; CF2=CF-O-(CH2)n-(CH3), where n is an integer from 0 to 3; CF2=CF-O-(CF2)n-O-CF3, where n is an integer from 0 to 3.

[0039] The copolymer of the present invention has an impact resistance at -80°C greater than 100 J / m, greater than 250 J / m, greater than 500 J / m, measured by the IZOD impact test ASTM D256.

[0040] The copolymer of the present invention exhibits stress crack resistance determined by the method described herein.

[0041] The melting point of the copolymer of the present invention is between 170 and 220°C, preferably between 180 and 210°C, as determined by DSC.

[0042] The copolymer of the present invention is generally insoluble in solvents commonly used for PVDF copolymers at ambient temperature. These solvents include polar aprotic solvents such as dimethyl sulfoxide, N-methylpyrrolidone (NMP), N,N'-dimethylformamide (DMF), N,N'-dimethylacetamide (DMAc); ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK); and ethers such as tetrahydrofuran (THF) and methyl tert-butyl ether (MTBE). The copolymer of the present invention is generally also insoluble in solvents in which PVDF and PVDF copolymers are also insoluble, such as water and aqueous solutions, fatty alcohols, alkanes and aromatic hydrocarbons, and chlorinated aliphatic and aromatic solvents.

[0043] Polymerization

[0044] The TFE / VDF / ether polymers of the present invention are synthesized at 0.01 - 0.5 mol% chain transfer agent (CTA) (based on the total moles of monomer chain transfer agent (CTA)) relative to the total monomers used in the polymerization. In order to obtain the polymers of the present invention, the presence of both a fluorinated ether and a CTA is required in the polymerization reaction. The polymers of the present invention are melt processable and have stress crack resistance.

[0045] The copolymer is prepared by emulsion polymerization or suspension polymerization known in the art and described in US8765890B2, which is incorporated herein by reference. For emulsion polymerization, as is known in the art, a pressure range of 0.5 MPa - 5.0 MPa, a temperature range of 25 °C - 125 °C, and an initiator system consisting of inorganic peroxides, redox systems, and organic peroxides are typically employed. When the TFE / VDF comonomer pair is the major component in the structure, the reactivity ratio is such that the monomers are randomly distributed throughout the resulting polymer backbone, thereby forming a uniform composition throughout the material.

[0046] A general procedure for the polymerization reaction is as follows: Purify tetrafluoroethylene (TFE) through an activated carbon bed and mix it by recycling with vinylidene fluoride (VDF) in a holding tank in the desired ratio. The reactor is charged with the required amount of deionized water and surfactant. Deoxygenate the water feed by pressurizing the reactor with nitrogen, hold it under pressure (e.g., for at least 5 minutes) and stir, then vent to 0 psig. This cycle can be repeated. Inject the chain transfer agent (CTA) into the reactor together with a specified amount of fluorinated ether. Stir, heat, and pressurize the reactor contents with the TFE / VDF mixture. Add an initiator to initiate the polymerization. Then add the TFE / VDF mixture to maintain the pressure. Add additional aliquots of the initiator solution to keep the monomers being absorbed at the desired rate. The reaction is completed when a specified amount of the TFE / VDF mixture is added to the reaction, at which point the TFE / VDF mixture feed is stopped and the pressure is allowed to drop on its own. Cool the reaction to room temperature, vent, and the product is discharged through the bottom port of the reactor. The solids content of the latex product is determined by drying a known mass of the latex to a constant weight and then calculating the percentage of solids in the latex product using the mass difference.

[0047] The polymers of the present invention are synthesized using 0.01 - 0.5 mol%, preferably 0.01 - 0.4 mol%, and most preferably 0.01 - 0.25 mol% of a suitable chain transfer agent, based on the total moles of monomers. A chain transfer agent is added during polymerization to adjust the molecular weight of the product. They can be added to the polymerization in a single portion at the start of the reaction, or incrementally or continuously throughout the reaction. The amount and manner of addition of the chain transfer agent depend on the activity of the particular chain transfer agent used, as well as the desired molecular weight of the polymer product. Examples of chain transfer agents useful in the present invention include, but are not limited to, oxygen-containing organic compounds that can act as chain transfer agents, such as alcohols, carbonates, ketones, esters, and ethers; halogenated hydrocarbons and hydrogen halide-containing hydrocarbons, such as chlorocarbons, hydrochlorofluorocarbons, chlorofluorocarbons, and hydrochlorofluorocarbons; ethane and propane. Specific examples of chain transfer agents that can be used include, but are not limited to, hydrocarbons such as ethane, propane, butane, isopentane, n-hexane, and cyclohexane; aromatic compounds such as toluene and xylene; ketones such as acetone; acetate esters such as ethyl acetate and butyl acetate; alcohols such as methanol and ethanol; thiols such as methyl mercaptan; and halogenated hydrocarbons such as carbon tetrachloride, chloroform, dichloromethane, and chloromethane, as well as polyacrylic acid.

[0048] In one embodiment, a melt-processable fluoropolymer composition comprising 39.5 - 57.0 mol% TFE, 42.0 - 57.5 mol% VDF, and 1.0 - 3.0 mol% PPVE is synthesized using 0.01 - 0.5 mol% ethyl acetate (based on the total moles of monomers) as a chain transfer agent.

[0049] As is known in the art, polymerization can be carried out using a fluorinated surfactant or a non-fluorinated surfactant as an emulsifier (US8080621, US8158734 are incorporated herein by reference).

[0050] Use

[0051] The polymers of the present invention can be thermally processed on normal processing equipment used for extruding or molding PVDF copolymers. The polymers of the present invention can be extruded or thermally molded into any desired shape.

[0052] Applications of such polymers may include wire, cable, building films (greenhouses), coatings, battery adhesives, battery separators or coatings, marine pipes, dielectric films, piezoelectric films and sensors, pyroelectric films and sensors, chemical processing films, polymer processing aids, composite material matrices, and sheaths for automotive tubing.

[0053] Examples

[0054] Procedure - Latex Synthesis in a 10L Reactor

[0055] The following procedure is written using poly(tetrafluoroethylene-co-vinylidene fluoride-co-perfluoropropyl vinyl ether) (p(TFE-VDF-PPVE)) as a model copolymer. A person of ordinary skill in the art can use the following examples and application teachings to extend the present invention to other fluoropolymers of the present invention. Table 1 shows the reaction parameters of the examples.

[0056] Tetrafluoroethylene (TFE) was purified through an activated carbon bed and mixed by recycling with vinylidene fluoride (VDF) in a specified ratio in a holding tank. A 10 L autoclave equipped with internal cooling coils and mechanical stirring was charged with the required amount of deionized water and 9.0 g (surfactant) perfluoro(2,5-dimethyl-3,6-dioxanonanoic acid). The water feed was deoxygenated by pressurizing the reactor to 60 psig with ultra-pure nitrogen, stirring was maintained at this pressure for 5 minutes, and then the pressure was vented to 0 psig. This cycle was repeated 2 more times. At this time, ethyl acetate (EA) chain transfer agent (CTA) was injected into the reactor together with a specified amount of perfluoropropyl vinyl ether (PPVE). The reactor contents were stirred, heated to 80 °C, and pressurized to 1.4 MPa with the TFE / VDF mixture. Aqueous solutions of 1.0 g of 1.0% potassium persulfate and 1.0% dipotassium hydrogen phosphate (KPS / K2HP) were added using a high-pressure injection pump to initiate the polymerization. Then the TFE / VDF mixture was added in the same ratio as during pressurization to maintain a pressure of 1.4 MPa. Additional aliquots of the KPS / K2HP solution were added to maintain a monomer absorption rate greater than 500 g / hr. The reaction was completed when a specified amount of the TFE / VDF mixture was added to the reactor, at which time the TFE / VDF mixture feed was stopped and the pressure was allowed to drop on its own for 30 minutes. The reactor was cooled to room temperature, vented, and the product was discharged through the bottom port of the reactor. The solids content of the latex product was determined by drying a known mass of the latex to a constant weight and then calculating the percentage of solids in the latex product using the mass difference.

[0057] Each run constitutes a single batch as described in the general procedure, with the material quantities and process parameters as previously described.

[0058] Table 1. Synthesis reaction conditions of poly(TFE-VDF-PPVE)

[0059]

[0060] (*Initiator solution = aqueous solution of 1% potassium persulfate and 1% dipotassium hydrogen phosphate) ( 200 L reactor; 180 g surfactant) (**n / a: no recovered fluid latex; coagulated)

[0061] The melt temperature and melt viscosity were measured as described above.

[0062] Table 2

[0063]

[0064] Compositions with a melt viscosity of 21 or higher are not melt processable.

Claims

1. A fluoropolymer composition comprising 39.5 - 57.0 mol% tetrafluoroethylene, 42.0 - 57.5 mol% vinylidene fluoride and 1.0 - 3.0 mol% fluorinated ether, wherein the melt viscosity of the fluoropolymer is measured at 260 °C and 100 s -1 to be 1 - 20 kP, and the fluoropolymer is melt processable.

2. The fluoropolymer composition according to claim 1, wherein the fluorinated ether is selected from the group consisting of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, perfluoropropyl vinyl ether, perfluoroisopropyl vinyl ether, and perfluoro-2-propoxypropyl vinyl ether.

3. The fluoropolymer composition according to claim 1, wherein the fluorinated ether comprises perfluoroethyl vinyl ether.

4. The fluoropolymer composition according to any one of claims 1-3, wherein the fluoropolymer does not exhibit thermal stress cracking behavior at a temperature up to 150 °C under a strain up to 7%.

5. The fluoropolymer composition according to any one of claims 1-3, wherein the melt viscosity of the fluoropolymer is measured to be 5-19 kP at 260 °C and 100 s -1 under measurement.

6. The fluoropolymer composition according to any one of claims 1-3, wherein the melting point of the fluoropolymer is 170-220 °C.

7. The fluoropolymer composition according to any one of claims 1-3, wherein the melting point of the fluoropolymer is 180-210 °C.

8. The fluoropolymer composition according to any one of claims 1-3, wherein the melting point of the fluoropolymer is 185-209 °C.

9. The fluoropolymer composition according to any one of claims 1-3, wherein the fluoropolymer has an impact resistance greater than 100 J / m at a temperature as low as -80 °C as measured by the IZOD impact test.

10. The fluoropolymer composition according to any one of claims 1-3, wherein the fluoropolymer has an impact resistance greater than 250 J / m at a temperature as low as -80 °C as measured by the IZOD impact test.

11. The fluoropolymer composition according to any one of claims 1-3, wherein the fluoropolymer has an impact resistance greater than 500 J / m at a temperature as low as -80 °C as measured by the IZOD impact test.

12. The fluoropolymer composition according to any one of claims 1-3, wherein the fluoropolymer is melt-processable by extrusion, injection molding, or compression molding.

13. The fluoropolymer composition according to claim 1, the fluoropolymer composition comprising 51.7-56.0 mol% tetrafluoroethylene, 42.5-45.5 mol% vinylidene fluoride, and 1.5-2.8 mol% perfluoroethyl vinyl ether, wherein the melt viscosity is 10-16 kP.

14. A method for synthesizing a melt-processable fluoropolymer composition, comprising the following steps: Tetrafluoroethylene monomers, vinylidene fluoride monomers, and fluorinated vinyl ether monomers are provided; polymerization is initiated in the presence of a chain transfer agent, wherein the amount of the chain transfer agent is 0.01 - 0.5 mol%, based on the total number of moles of monomers used in the polymerization process, and the fluoropolymer composition contains 39.5 - 57 mol% tetrafluoroethylene, 42 - 57.5 mol% vinylidene fluoride, and 1 - 3 mol% fluorinated vinyl ether, wherein the melt viscosity of the fluoropolymer is measured at 260 °C and 100 s -1 to be 1 - 20 kP.

15. The method according to claim 14, wherein the amount of the chain transfer agent is 0.01-0.4 mol%.

16. The method according to claim 14, wherein the amount of the chain transfer agent is 0.01-0.3 mol%.

17. The method according to claim 14, wherein the polymerization is carried out in a pressure range of 0.5 MPa - 5.0 MPa.

18. The method according to claim 17, wherein the polymerization is carried out in a temperature range of 25 °C - 125 °C.

19. The method according to claim 14, wherein the polymerization is carried out in a pressure range of 0.5 MPa - 3.0 MPa.

20. The method according to claim 19, wherein the polymerization is carried out in a temperature range of 50 °C - 120 °C.

21. The method according to claim 14, wherein the fluorinated vinyl ether is selected from the group consisting of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, perfluoropropyl vinyl ether, perfluoroisopropyl vinyl ether, and perfluoro-2-propoxypropyl vinyl ether.

22. The method according to claim 14, wherein the chain transfer agent is selected from the group consisting of oxygen-containing organic compounds that can be used as chain transfer agents; halogenated hydrocarbons; ethane; and propane.

23. The method according to claim 22, wherein the oxygen-containing organic compound is selected from the group consisting of alcohols, carbonates, ketones, esters, and ethers.

24. The method according to claim 22, wherein the halogenated hydrocarbon is selected from the group consisting of chlorohydrocarbons and chlorofluorohydrocarbons.

25. The method according to claim 22, wherein the halogenated hydrocarbon is selected from the group consisting of hydrochlorohydrocarbons and hydrochlorofluorohydrocarbons.

26. The method according to claim 14, wherein the fluorinated vinyl ether comprises perfluoroethyl vinyl ether, and the chain transfer agent comprises ethyl acetate in an amount of 0.01 to 0.5 mol% based on the total moles of monomers.

27. The method according to claim 14, wherein the fluoropolymer composition comprises 51.7 to 56.0 mol% tetrafluoroethylene, 42.5 to 45.5 mol% vinylidene fluoride, and 1.5 to 2.8 mol% perfluoroethyl vinyl ether, the polymerization is carried out in a pressure range of 0.5 to 3.0 MPa and a temperature range of 50°C to 120°C, and the melt viscosity of the fluoropolymer is 10 to 16 kP.

28. A manufactured article comprising the fluoropolymer composition according to claim 1.

29. The article according to claim 28, wherein the article is selected from the group consisting of wire, cable, greenhouse film, building film, coating, battery adhesive, battery separator or coating, marine pipe, dielectric film, piezoelectric film and sensor, pyroelectric film and sensor, chemical processing film, polymer processing aid, and automotive pipe.

30. The article according to claim 28, wherein the article is selected from the group consisting of wire and cable.

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