Fu-containing composite

Abstract

To provide a fluorine-containing copolymer excellent in extrusion moldability which can obtain a molded article excellent in mold followability and obtain a molded article which is excellent in wear resistance at 65°C, ozone resistance, solvent crack resistance. low air permeability, creep resistance and tensile creep resistance properties at 140°C and is less likely to elute fluorine ions into a chemical liquid.SOLUTION: There is provided a fluorine-containing copolymer containing a tetrafluoroethylene unit, a hexafluoropropylene unit and a perfluoro (ethyl vinyl ether) unit, wherein the content of the hexafluoropropylene unit is 9.5 to 11.6 mass% based on the total monomer units, the content of the perfluoro (ethyl vinyl ether) unit is 1.2 to 2.9 mass% based on the total monomer units, the melt flow rate at 372°C is 19.0 to 28.0 g / 10 min and the total number of -CF2H, a carbonyl group-containing terminal group, -CF=CF2 and -CH2OH is 90 or less per main-chain carbon number of 106.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to fluorine-containing copolymers. [Background technology]

[0002] Patent Document 1 describes a partially crystalline copolymer containing tetrafluoroethylene and hexafluoropropylene in amounts corresponding to about 2.8 to 5.3 HFPI, characterized in that it is polymerized and isolated in the absence of added alkali metal salts, has a melt flow rate in the range of about 30 ± 3 g / 10 min, and has about 50 or fewer unstable end groups. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication 2006-528274 [Overview of the project] [Problems that the invention aims to solve]

[0004] The present disclosure aims to provide a fluorine-containing copolymer that exhibits excellent extrusion moldability, yields molded articles with excellent mold conformability, and furthermore, yields molded articles with excellent abrasion resistance at 65°C, ozone resistance, solvent crack resistance, low air permeability, creep resistance, and tensile creep resistance at 140°C, and that are less likely to leach fluoride ions into chemical solutions. [Means for solving the problem]

[0005] According to this disclosure, a fluorine-containing copolymer containing tetrafluoroethylene units, hexafluoropropylene units, and perfluoro(ethyl vinyl ether) units, wherein the content of hexafluoropropylene units is 9.5 to 11.6% by mass relative to the total monomer units, the content of perfluoro(ethyl vinyl ether) units is 1.2 to 2.9% by mass relative to the total monomer units, the melt flow rate at 372°C is 19.0 to 28.0 g / 10 min, and the total number of -CF2H, carbonyl group-containing terminal groups, -CF=CF2, and -CH2OH is 10 carbon atoms in the main chain. 6 A fluorine-containing copolymer is provided, having 90 or fewer fluorine atoms per unit.

[0006] The content of hexafluoropropylene units is preferably 10.1 to 11.5% by mass relative to the total monomer units. The perfluoro(ethyl vinyl ether) unit content is preferably 1.3 to 2.1% by mass relative to the total monomer units. The melt flow rate at 372°C is preferably 20.0 to 27.0 g / 10 min.

[0007] Furthermore, according to this disclosure, an injection-molded article containing the above-mentioned fluorine-containing copolymer is provided.

[0008] Furthermore, this disclosure provides a coated wire comprising a coating layer containing the above-mentioned fluorine-containing copolymer.

[0009] Furthermore, according to this disclosure, there is a molded article containing the above-mentioned fluorine-containing copolymer, wherein the molded article is a sheet for hot press processing, a protective film, a release film, a tube, a film, or a wire coating. [Effects of the Invention]

[0010] According to the present disclosure, there is provided a fluorine-containing copolymer excellent in extrusion moldability, from which a molded article excellent in mold following property can be obtained. Furthermore, there is provided a fluorine-containing copolymer excellent in wear resistance at 65°C, ozone resistance, solvent crack resistance, low air permeability, creep resistance, and tensile creep property at 140°C, and from which a molded article in which fluorine ions are hardly eluted into a chemical solution can be obtained.

Mode for Carrying Out the Invention

[0011] Hereinafter, specific embodiments of the present disclosure will be described in detail, but the present disclosure is not limited to the following embodiments.

[0012] The fluorine-containing copolymer of the present disclosure contains tetrafluoroethylene (TFE) units, hexafluoropropylene (HFP) units, and perfluoro(ethyl vinyl ether) (PEVE) units.

[0013] In hot press molding, a processing resin sheet is heated to be softened, and pressure is applied to the sheet from both sides with a mold to obtain a molded article having a desired shape. Therefore, the processing sheet used for hot press molding is required to have properties that it is easily deformed during softening and can follow the shape of the mold. At the same time, the obtained molded article is required to be hardly deformed easily by compression or tension and hardly worn, and no crack occurs even when it comes into contact with ozone or a chemical solution. Furthermore, it is preferable to select a material that can easily manufacture the processing resin sheet itself.

[0014] It has been found that by appropriately adjusting the content of HFP and PEVE units, the melt flow rate, and the number of functional groups in a fluorine-containing copolymer containing TFE units, HFP units, and PEVE units, the extrusion pressure at the fluorine-containing copolymer site decreases, while the load deflection rate at high temperatures increases remarkably, resulting in a fluorine-containing copolymer with a highly balanced extrudeability and mold conformability. Furthermore, molded articles obtained from such fluorine-containing copolymers exhibit excellent abrasion resistance at 65°C, ozone resistance, solvent crack resistance, low air permeability, creep resistance, and tensile creep resistance at 140°C. Therefore, molded articles obtained from such fluorine-containing copolymers are resistant to wear even with repeated use and are resistant to crushing under pressure, making them suitable for use as release films. In addition, molded articles obtained from such fluorine-containing copolymers are resistant to wear and crushing, have excellent durability against ozonated water and hydrogen peroxide, and also exhibit excellent gas barrier properties, making them suitable for use as protective films.

[0015] The fluorine-containing copolymers of this disclosure are melt-processable fluororesins. Melt-processability means that the polymer can be melted and processed using conventional processing equipment such as extruders and injection molding machines.

[0016] The HFP unit content of the fluorine-containing copolymer is 9.5 to 11.6% by mass relative to the total monomer units, preferably 9.6% by mass or more, more preferably 9.7% by mass or more, even more preferably 9.8% by mass or more, still more preferably 9.9% by mass or more, particularly preferably 10.0% by mass or more, most preferably 10.1% by mass or more, preferably 11.5% by mass or less, more preferably 11.2% by mass or less, even more preferably 11.1% by mass or less, particularly preferably 11.0% by mass or less, and most preferably 10.9% by mass or less. If the HFP unit content is too low, a molded article with excellent mold conformability cannot be obtained, and a molded article with excellent 65°C abrasion resistance, ozone resistance, and solvent crack resistance cannot be obtained. If the HFP unit content is too high, a molded article with excellent mold conformability cannot be obtained.

[0017] The PEVE unit content of the fluorine-containing copolymer is 1.2 to 2.9% by mass relative to the total monomer units, preferably 1.3% by mass or more, preferably 2.7% by mass or less, more preferably 2.6% by mass or less, even more preferably 2.5% by mass or less, still more preferably 2.4% by mass or less, especially more preferably 2.3% by mass or less, particularly preferably 2.2% by mass or less, and most preferably 2.1% by mass or less. By having the PEVE unit content within the above range, a molded article with excellent mold conformability can be obtained, and furthermore, a molded article with excellent 65°C abrasion resistance, ozone resistance, solvent crack resistance, low air permeability, creep resistance, and 140°C tensile creep resistance can be obtained. If the PEVE unit content is too low, a molded article with excellent mold conformability cannot be obtained, and a molded article with excellent 65°C abrasion resistance, ozone resistance, and solvent crack resistance cannot be obtained.

[0018] The content of the TFE unit in the fluorine-containing copolymer is preferably 85.5% by mass or more, more preferably 85.7% by mass or more, still more preferably 86.0% by mass or more, yet still more preferably 86.2% by mass or more, particularly preferably 86.4% by mass or more, preferably 89.3% by mass or less, more preferably 89.0% by mass or less, still more preferably 88.9% by mass or less, yet still more preferably 88.8% by mass or less, particularly preferably 88.7% by mass or less, and most preferably 88.6% by mass or less, based on all monomer units. Also, the content of the TFE unit may be selected such that the total content of the HFP unit, PEVE unit, TFE unit, and other monomer units is 100% by mass.

[0019] The fluorine-containing copolymer of the present disclosure may be a copolymer containing only the above three monomer units, or a copolymer containing the above three monomer units and other monomer units, as long as it contains the above three monomer units.

[0020] Other monomers are not particularly limited as long as they are monomers copolymerizable with TFE, HFP, and PEVE, and may be fluoromonomers or non-fluorine-containing monomers.

[0021] Examples of fluoromonomers include chlorotrifluoroethylene, vinyl fluoride, vinylidene fluoride, trifluoroethylene, hexafluoroisobutylene, CH2 = CZ 1 (CF2) n Z 2 (where Z 1 is H or F, Z 2 is H, F, or Cl, and n is an integer from 1 to 10), a monomer represented by CF2 = CF - ORf 1 (where Rf 1 is a perfluoroalkyl group having 1 to 8 carbon atoms), perfluoro(alkyl vinyl ether) [PAVE] (excluding PEVE) represented by CF2 = CF - O - CH2 - Rf 2 (where Rf 2Preferably, is at least one selected from the group consisting of alkyl perfluorovinyl ether derivatives represented by perfluoroalkyl groups having 1 to 5 carbon atoms, perfluoro-2,2-dimethyl-1,3-dioxol [PDD], and perfluoro-2-methylene-4-methyl-1,3-dioxolane [PMD].

[0022] CH2=CZ 1 (CF2) n Z 2 The monomers represented by CH2=CFCF3, CH2=CH-C4F9, and CH2=CH-C6F are examples of this monomer. 13 Examples include CH2=CF-C3F6H.

[0023] CF2 = CF - ORf 1 Examples of perfluoro(alkyl vinyl ethers) represented by this formula include CF2=CF-OCF3 and CF2=CF-OCF2CF2CF3.

[0024] Examples of fluorine-free monomers include hydrocarbon monomers copolymerizable with TFE, HFP, and PEVE. Examples of hydrocarbon monomers include alkenes such as ethylene, propylene, butylene, and isobutylene; alkyl vinyl ethers such as ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, and cyclohexyl vinyl ether; vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl isobutyrate, vinyl valerate, vinyl pivalate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl versatate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl benzoate, p-t-butylbenzoate, vinyl cyclohexanecarboxylate, vinyl monochlorovinyl acetate, and vinyl adipate. Examples include vinyl esters such as vinyl acrylate, vinyl methacrylate, vinyl crotate, vinyl sorbate, vinyl cinnamate, vinyl undecylenate, vinyl hydroxyacetate, vinyl hydroxypropionate, vinyl hydroxybutyrate, vinyl hydroxyvalerate, vinyl hydroxyisobutyrate, and vinyl hydroxycyclohexanecarboxylate; alkyl allyl ethers such as ethyl allyl ether, propyl allyl ether, butyl allyl ether, isobutyl allyl ether, and cyclohexyl allyl ether; and alkyl allyl esters such as ethyl allyl ester, propyl allyl ester, butyl allyl ester, isobutyl allyl ester, and cyclohexyl allyl ester.

[0025] Examples of fluorine-free monomers include functional group-containing hydrocarbon monomers copolymerizable with TFE, HFP, and PEVE. Examples of functional group-containing hydrocarbon monomers include hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, hydroxyisobutyl vinyl ether, and hydroxycyclohexyl vinyl ether; fluorine-free monomers having a glycidyl group such as glycidyl vinyl ether and glycidyl allyl ether; fluorine-free monomers having an amino group such as aminoalkyl vinyl ether and aminoalkyl allyl ether; fluorine-free monomers having an amide group such as (meth)acrylamide and methylolacrylamide; bromine-containing olefins, iodine-containing olefins, bromine-containing vinyl ethers, and iodine-containing vinyl ethers; and fluorine-free monomers having a nitrile group.

[0026] The content of other monomer units in the fluorine-containing copolymer of this disclosure is preferably 0 to 3.8% by mass, more preferably 1.1% by mass or less, even more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less, relative to the total monomer units.

[0027] The melt flow rate (MFR) of the fluorine-containing copolymer is 19.0 to 28.0 g / 10 min, preferably 20.0 g / 10 min or more, more preferably 23.0 g / 10 min or more, even more preferably 24.0 g / 10 min or more, particularly preferably 25.0 g / 10 min or more, preferably 27.9 g / 10 min or less, more preferably 27.5 g / 10 min or less, and even more preferably 27.0 g / 10 min or less. If the MFR is too low, it is not possible to obtain a fluorine-containing copolymer with excellent extrusion moldability and a molded article with excellent low air permeability. If the MFR is too high, it is not possible to obtain a molded article with excellent mold conformability and a molded article with excellent 65°C abrasion resistance, ozone resistance, and solvent crack resistance.

[0028] In this disclosure, the melt flow rate is a value obtained in accordance with ASTM D-1238, using a melt indexer G-01 (manufactured by Toyo Seiki Seisakusho Co., Ltd.) at 372°C and under a 5kg load, as the mass of polymer flowing out of a die with an inner diameter of 2 mm and a length of 8 mm per 10 minutes (g / 10 min).

[0029] MFR can be adjusted by adjusting the type and amount of polymerization initiator and chain transfer agent used when polymerizing monomers.

[0030] Fluorine-containing copolymer with 10 carbon atoms in the main chain 6 The total number of -CF2H, carbonyl group-containing terminal groups, -CF=CF2, and -CH2OH per individual is 90 or less. The total number of these functional groups is, in order of preference, 80 or less, 70 or less, 60 or less, 50 or less, 40 or less, 30 or less, 25 or less, and less than 21. By having the total number of these functional groups within the above range, it is possible to obtain a molded article that does not easily leach fluoride ions into chemical solutions such as hydrogen peroxide.

[0031] Carbonyl group-containing terminal groups include, for example, -COF, -COOH, -COOR (where R is an alkyl group), -CONH2, and -O(C=O)OR (where R is an alkyl group). The type of alkyl group (R) in -COOR and -O(C=O)OR is determined by the polymerization initiator, chain transfer agent, etc., used in the production of the fluorine-containing copolymer, and is, for example, an alkyl group having 1 to 6 carbon atoms, such as -CH3.

[0032] Infrared spectroscopy can be used to identify the types of functional groups and measure their number.

[0033] The number of functional groups is specifically measured by the following method. First, the fluorine-containing copolymer is molded by cold pressing to produce a film with a thickness of 0.25 to 0.30 mm. This film is analyzed by Fourier transform infrared spectroscopy to obtain the infrared absorption spectrum of the fluorine-containing copolymer, and a difference spectrum is obtained from this spectrum to the base spectrum where the copolymer is completely fluorinated and no functional groups are present. From the absorption peaks of specific functional groups appearing in this difference spectrum, the number of carbon atoms in the fluorine-containing copolymer (1 × 10) is determined according to the following formula (A). 6 Calculate the number of functional units N per individual.

[0034] N = I × K / t (A) I: Absorbance K: Correction coefficient t: Film thickness (mm)

[0035] For reference, Table 1 shows the absorption frequency, molar extinction coefficient, and correction factor for several functional groups. The molar extinction coefficient was determined from FT-IR measurement data of a small molecule model compound. [Table 1]

[0036] The absorption frequencies of -CH2CF2H, -CH2COF, -CH2COOH, -CH2COOCH3, and -CH2CONH2 are tens of kaiser (cm) from the absorption frequencies of -CF2H, -COF, -COOH free and -COOH bonded, -COOCH3, and -CONH2, respectively, as shown in the table. -1 ) It will become lower.

[0037] For example, the number of functional groups in -COF is the absorption frequency of 1883 cm⁻¹ due to -CF₂COF. -1 The number of functional groups determined from the absorption peak and the absorption frequency of 1840 cm² due to -CH2COF -1 This is the sum of the number of functional groups determined from the absorption peaks.

[0038] Furthermore, the number of -CF2H groups was determined using a nuclear magnetic resonance spectrometer, with the measurement temperature set to (polymer melting point + 20)°C. 19 It can also be determined by performing F-NMR measurements and deriving the peak integral value of the -CF2H group.

[0039] Functional groups such as the -CF2H group are functional groups present at the ends of the main chain or side chains of the fluorine-containing copolymer, as well as functional groups present within the main chain or side chains. These functional groups are introduced into the fluorine-containing copolymer, for example, by chain transfer agents or polymerization initiators used in the production of the fluorine-containing copolymer. For example, if an alcohol is used as a chain transfer agent, or if a peroxide having the -CH2OH structure is used as a polymerization initiator, -CH2OH is introduced to the ends of the main chain of the fluorine-containing copolymer. Alternatively, the above functional groups can be introduced to the ends of the side chains of the fluorine-containing copolymer by polymerizing monomers having functional groups.

[0040] By subjecting a fluorine-containing copolymer having such functional groups to treatments such as wet heat treatment or fluorination treatment, a fluorine-containing copolymer having a number of functional groups within the above range can be obtained. The fluorine-containing copolymer of this disclosure is preferably subjected to wet heat treatment or fluorination treatment, and more preferably to fluorination treatment. The fluorine-containing copolymer of this disclosure is also preferably present with -CF3 terminal groups.

[0041] The melting point of the fluorine-containing copolymer is preferably 220 to 290°C, and more preferably 240 to 280°C. Having the melting point within this range results in superior mold conformability, and allows for the production of molded articles with superior abrasion resistance at 65°C, ozone resistance, solvent crack resistance, low air permeability, creep resistance, and tensile creep resistance at 140°C.

[0042] In this disclosure, the melting point can be measured using a differential scanning calorimetry (DSC).

[0043] The air permeability coefficient of the fluorine-containing copolymer is preferably 370 cm⁻¹. 3 ·mm / (m 2The humidity is less than or equal to 24h·atm. The fluorine-containing copolymers of this disclosure have excellent low air permeability due to the appropriate adjustment of HFP and PEVE unit content, melt flow rate (MFR), and number of functional groups.

[0044] In this disclosure, the air permeability coefficient can be measured under the conditions of a test temperature of 70°C and a test humidity of 0%RH. The specific measurement of the air permeability coefficient can be carried out by the method described in the examples.

[0045] The fluorine-containing copolymers of this disclosure exhibit a fluoride ion elution amount of 4.0 ppm or less, more preferably 3.0 ppm or less, and more preferably 2.8 ppm or less, on a mass basis, in immersion tests in hydrogen peroxide. Because the fluorine-containing copolymers of this disclosure exhibit a low fluoride ion elution amount into hydrogen peroxide, they can be said to have excellent durability against hydrogen peroxide.

[0046] In this disclosure, the hydrogen peroxide immersion test can be performed by preparing a test piece using a fluorine-containing copolymer, having a weight equivalent to 10 molded pieces (15 mm × 15 mm × 0.2 mm), and placing a polypropylene bottle containing the test piece and 15 g of 3% by mass hydrogen peroxide aqueous solution into a constant temperature bath at 95°C for 20 hours.

[0047] The fluorine-containing copolymers of this disclosure can be produced by any polymerization method, such as bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization. In these polymerization methods, conditions such as temperature and pressure, polymerization initiators, chain transfer agents, solvents, and other additives can be appropriately set according to the desired composition and amount of the fluorine-containing copolymer.

[0048] As polymerization initiators, oil-soluble radical polymerization initiators or water-soluble radical initiators can be used.

[0049] The oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, for example, Dialkyl peroxycarbonates such as dinormal propyl peroxydicarbonate, diisopropyl peroxydicarbonate, and disec-butyl peroxydicarbonate; Peroxy esters such as t-butyl peroxyisobutyrate and t-butyl peroxypivalate; Dialkyl peroxides such as di-t-butyl peroxide; Di[fluoro(or fluorochloro)acyl]peroxides; These are some typical examples.

[0050] Examples of di[fluoro(or fluorochloro)acyl]peroxides include diacylperoxides represented as [(RfCOO)-]2 (where Rf is a perfluoroalkyl group, an ω-hydroperfluoroalkyl group, or a fluorochloroalkyl group).

[0051] Examples of di[fluoro(or fluorochloro)acyl]peroxides include di(ω-hydro-dodecafluorohexanoyl)peroxide, di(ω-hydro-tetradecafluoroheptanoyl)peroxide, di(ω-hydro-hexadecafluorononanoyl)peroxide, di(perfluorobutyryl)peroxide, di(perfluoropareryl)peroxide, di(perfluorohexanoyl)peroxide, di(perfluoroheptanoyl)peroxide, di(perfluorooctanoyl)peroxide, di(perfluorononanoyl)peroxide, di(ω-chloro-hexafluorobutyryl)peroxide, di(ω-chloro-decafluorohexanoyl)peroxide, Examples include di(ω-chloro-tetradecafluorooctanoyl) peroxide, ω-hydrodecafluoroheptanoyl-ω-hydrohexadecafluorononanoyl-peroxide, ω-chlorohexafluorobutyl-ω-chlorodecafluorohexanoyl-peroxide, ω-hydrodecafluoroheptanoyl-perfluorobutyl-peroxide, di(dichloropentafluorobutanoyl) peroxide, di(trichlorooctafluorohexanoyl) peroxide, di(tetrachloroundafluorooctanoyl) peroxide, di(pentachlorotetradecafluorodecanoyl) peroxide, and di(undachlorotriacontafluorodocosanoyl) peroxide.

[0052] The water-soluble radical polymerization initiator may be a known water-soluble peroxide, such as ammonium salts, potassium salts, or sodium salts of persulfuric acid, perborate, perchloric acid, superphosphate, or percarbonate, as well as t-butyl permalate and t-butyl hydroperoxide. A reducing agent such as sulfites may also be included, and the amount used may be 0.1 to 20 times the amount of the peroxide.

[0053] Using an oil-soluble radical polymerization initiator as a polymerization initiator is preferable because it avoids the formation of -COF and -COOH, and the total number of -COF and -COOH in the fluorine-containing copolymer can be easily adjusted to the above-mentioned range. Furthermore, using an oil-soluble radical polymerization initiator tends to facilitate the adjustment of the total number of -CF2H, carbonyl group-containing end groups, -CF=CF2, and -CH2OH to the above-mentioned range. In particular, it is preferable to produce the fluorine-containing copolymer by suspension polymerization using an oil-soluble radical polymerization initiator. As the oil-soluble radical polymerization initiator, at least one selected from the group consisting of dialkyl peroxycarbonates and di[fluoro(or fluorochloro)acyl]peroxides is preferred, and at least one selected from the group consisting of dinormalpropyl peroxydicarbonate, diisopropyl peroxydicarbonate, and di(ω-hydro-dodecafluoroheptanoyl)peroxide is more preferred.

[0054] Examples of chain transfer agents include hydrocarbons such as ethane, isopentane, n-hexane, and cyclohexane; aromatics such as toluene and xylene; ketones such as acetone; acetic acid esters such as ethyl acetate and butyl acetate; alcohols such as methanol, ethanol, and 2,2,2-trifluoroethanol; mercaptans such as methyl mercaptan; halogenated hydrocarbons such as carbon tetrachloride, chloroform, methylene chloride, and methyl chloride; and 3-fluorobenzotrifluoride. The amount added may vary depending on the magnitude of the chain transfer constant of the compound used, but is usually used in the range of 0.01 to 20 parts by mass per 100 parts by mass of solvent.

[0055] For example, when dialkyl peroxycarbonates, di[fluoro(or fluorochloro)acyl]peroxides, etc. are used as polymerization initiators, the molecular weight of the resulting fluorine-containing copolymer may become too high, making it difficult to adjust to the desired melt flow rate. However, the molecular weight can be adjusted using a chain transfer agent. In particular, it is preferable to produce fluorine-containing copolymers by suspension polymerization using a chain transfer agent such as alcohols and an oil-soluble radical polymerization initiator.

[0056] Examples of solvents include water, a mixed solvent of water and alcohol, etc. Furthermore, the monomer used in the polymerization of the fluorine-containing copolymer according to this disclosure can also be used as the solvent.

[0057] In suspension polymerization, a fluorinated solvent may be used in addition to water. Examples of fluorinated solvents include hydrochlorofluoroalkanes such as CH3CClF2, CH3CCl2F, CF3CF2CCl2H, and CF2ClCF2CFHCl; chlorofluoroalkanes such as CF2ClCFClCF2CF3 and CF3CFClCFClCF3; and perfluoroalkanes such as perfluorocyclobutane, CF3CF2CF2CF3, CF3CF2CF2CF2CF3, and CF3CF2CF2CF2CF2CF3, with perfluoroalkanes being preferred. From the viewpoint of suspension properties and economy, the amount of fluorinated solvent used is preferably 10 to 100 parts by mass per 100 parts by mass of solvent.

[0058] The polymerization temperature is not particularly limited and may be between 0 and 100°C. Furthermore, when the polymerization initiator is used, such as when dialkyl peroxycarbonates or di[fluoro(or fluorochloro)acyl]peroxides, and the decomposition rate of the polymerization initiator is too fast, it is preferable to adopt a relatively low polymerization temperature, such as one in the range of 0 to 35°C.

[0059] The polymerization pressure is determined appropriately depending on other polymerization conditions such as the type and amount of solvent used, vapor pressure, and polymerization temperature, but is usually between 0 and 9.8 MPaG. Preferably, the polymerization pressure is 0.1 to 5 MPaG, more preferably 0.5 to 2 MPaG, and even more preferably 0.5 to 1.5 MPaG. Furthermore, increasing the polymerization pressure to 1.5 MPaG or higher can improve production efficiency.

[0060] Additives used in polymerization include, for example, suspension stabilizers. The suspension stabilizer is not particularly limited as long as it is conventionally known; methylcellulose, polyvinyl alcohol, etc., can be used. Using a suspension stabilizer ensures that the suspended particles generated by the polymerization reaction are stably dispersed in the aqueous medium. Therefore, even when using a SUS (stainless steel) reaction vessel without anti-adhesion treatment such as glass lining, the suspended particles are less likely to adhere to the vessel. Consequently, a reaction vessel capable of withstanding high pressure can be used, enabling polymerization under high pressure and improving production efficiency. In contrast, when polymerization is performed without a suspension stabilizer, using a SUS reaction vessel without anti-adhesion treatment may result in the adhesion of suspended particles, potentially reducing production efficiency. The concentration of the suspension stabilizer in the aqueous medium can be appropriately adjusted depending on the conditions.

[0061] If an aqueous dispersion containing a fluoropolymer is obtained by the polymerization reaction, the fluorine-containing copolymer contained in the aqueous dispersion may be coagulated, washed, and dried to recover the dried fluoropolymer. Alternatively, if the fluorine-containing copolymer is obtained as a slurry by the polymerization reaction, the slurry may be removed from the reaction vessel, washed, and dried to recover the dried fluoropolymer. By drying, the fluorine-containing copolymer can be recovered in powder form.

[0062] The fluorine-containing copolymer obtained by polymerization may be formed into pellets. There are no particular limitations on the molding method for forming pellets, and conventionally known methods can be used. For example, one method involves melt-extruding the fluorine-containing copolymer using a single-screw extruder, twin-screw extruder, or tandem extruder, and then cutting it to a predetermined length to form pellets. The extrusion temperature during melt-extrusion needs to be varied depending on the melt viscosity of the fluorine-containing copolymer and the manufacturing method, and is preferably between the melting point of the fluorine-containing copolymer + 20°C and the melting point of the fluorine-containing copolymer + 140°C. There are no particular limitations on the cutting method of the fluorine-containing copolymer, and conventionally known methods such as strand cutting, hot cutting, underwater cutting, and sheet cutting can be used. The obtained pellets may be heated to remove volatile components (degassing treatment). The obtained pellets may also be treated by contacting them with hot water at 30-200°C, steam at 100-200°C, or hot air at 40-200°C.

[0063] The fluorine-containing copolymer obtained by polymerization may be heated to a temperature of 100°C or higher in the presence of air and water (wet heat treatment). A method of wet heat treatment includes, for example, using an extruder to melt and extrude the fluorine-containing copolymer obtained by polymerization while supplying air and water. Wet heat treatment can convert thermally unstable functional groups such as -COF and -COOH in the fluorine-containing copolymer to the relatively thermally stable -CF2H, and the total number of -CF2H, carbonyl group-containing end groups, -CF=CF2, and -CH2OH in the fluorine-containing copolymer can be easily adjusted to the aforementioned range. In addition to air and water, heating the fluorine-containing copolymer in the presence of an alkali metal salt can accelerate the conversion reaction to -CF2H. However, it should be noted that depending on the application of the fluorine-containing copolymer, contamination by alkali metal salts should be avoided.

[0064] The fluorine-containing copolymer obtained by polymerization may be subjected to fluorination treatment. From the viewpoint of obtaining a molded article that does not easily leach fluoride ions into chemical solutions such as hydrogen peroxide, it is preferable to fluorinate the fluorine-containing copolymer. Fluorination treatment can be carried out by contacting an unfluorinated fluorine-containing copolymer with a fluorine-containing compound. Fluorination treatment can convert thermally unstable functional groups such as -COOH, -COOCH3, -CH2OH, -COF, -CF=CF2, and -CONH2, as well as thermally relatively stable functional groups such as -CF2H, into the thermally extremely stable -CF3. As a result, the total number of -CF2H, carbonyl group-containing terminal groups, -CF=CF2, and -CH2OH in the fluorine-containing copolymer can be easily adjusted to the above-mentioned range.

[0065] The fluorine-containing compound is not particularly limited, but examples include fluorine radical sources that generate fluorine radicals under fluorination treatment conditions. Examples of the above fluorine radical sources include F2 gas, CoF3, AgF2, UF6, OF2, N2F2, CF3OF, and halogenated fluorides (e.g., IF5, ClF3).

[0066] Fluorine radical sources such as F2 gas may be at 100% concentration, but for safety reasons, it is preferable to mix them with an inert gas and dilute them to 5-50% by mass, and more preferably to 15-30% by mass. Examples of the inert gas include nitrogen gas, helium gas, and argon gas, but nitrogen gas is preferred for economic reasons.

[0067] The conditions for the fluorination treatment are not particularly limited, and the fluorine-containing copolymer may be brought into contact with the fluorine-containing compound in a molten state. However, it is usually carried out at a temperature below the melting point of the fluorine-containing copolymer, preferably 20 to 220°C, and more preferably 100 to 200°C. The above fluorination treatment is generally carried out for 1 to 30 hours, preferably 5 to 25 hours. The fluorination treatment is preferably carried out by bringing the unfluorinated fluorine-containing copolymer into contact with fluorine gas (F2 gas).

[0068] A composition may be obtained by mixing the fluorine-containing copolymer of this disclosure with other components as needed. Examples of other components include fillers, plasticizers, processing aids, mold release agents, pigments, flame retardants, lubricants, light stabilizers, weather stabilizers, conductive agents, antistatic agents, ultraviolet absorbers, antioxidants, foaming agents, fragrances, oils, softeners, and hydrofluoricating agents.

[0069] Examples of fillers include silica, kaolin, clay, organic clay, talc, mica, alumina, calcium carbonate, calcium terephthalate, titanium dioxide, calcium phosphate, calcium fluoride, lithium fluoride, cross-linked polystyrene, potassium titanate, carbon, boron nitride, carbon nanotubes, and glass fibers. Examples of conductive agents include carbon black. Examples of plasticizers include dioctyl phthalate and pentaerythritol. Examples of processing aids include carnauba wax, sulfone compounds, low molecular weight polyethylene, and fluorine-based aids. Examples of dehydrofluoridating agents include organonium and amidines.

[0070] Furthermore, other polymers besides the fluorine-containing copolymers described above may be used as the other components. Examples of other polymers include fluororesins other than the fluorine-containing copolymers described above, fluororubber, and non-fluorinated polymers.

[0071] Examples of methods for producing the above composition include a method of dry mixing the fluorine-containing copolymer and other components, or a method of pre-mixing the fluorine-containing copolymer and other components in a mixer and then melt-kneading them in a kneader, melt extruder, etc.

[0072] The fluorine-containing copolymers or compositions described above can be used as processing aids, molding materials, etc., but are preferably used as molding materials. Aqueous dispersions, solutions, suspensions, and copolymer / solvent systems of the fluorine-containing copolymers described above are also available and can be used as coatings, for sealing, impregnation, or film casting. However, since the fluorine-containing copolymers described above have the properties described above, they are preferably used as molding materials.

[0073] A molded article may be obtained by molding the fluorine-containing copolymer or the above composition according to this disclosure.

[0074] The method for molding the above-mentioned fluorine-containing copolymer or composition is not particularly limited and includes injection molding, extrusion molding, compression molding, blow molding, transfer molding, roto molding, roto lining molding, etc. Among the molding methods, extrusion molding, compression molding, injection molding, or transfer molding are preferred, and injection molding, extrusion molding, or transfer molding are more preferred, with injection molding being even more preferred, as they allow for the production of molded articles with high productivity. In other words, the molded article is preferably an extruded article, a compressed article, an injection-molded article, or a transfer-molded article, and is more preferably an injection-molded article, with injection molding being even more preferred, as they allow for the production of molded articles with high productivity. By molding the fluorine-containing copolymer of this disclosure by injection molding, a beautiful molded article can be obtained.

[0075] Examples of molded articles containing the fluorine-containing copolymer of this disclosure include nuts, bolts, fittings, films, bottles, gaskets, wire insulation, tubes, hoses, pipes, valves, seats, seals, packings, tanks, rollers, containers, cocks, connectors, filter housings, filter cages, flow meters, pumps, wafer carriers, wafer boxes, and the like.

[0076] The fluorine-containing copolymers, compositions, or molded articles of this disclosure can be used, for example, in the following applications. Food packaging films, lining materials for fluid transfer lines used in food manufacturing processes, packings, sealing materials, sheets, and other fluid transfer components for food manufacturing equipment; Chemical stoppers, packaging films, lining materials, packings, sealing materials, sheets, and other chemical liquid transfer components used in pharmaceutical manufacturing processes; Internal lining material for chemical tanks and piping in chemical plants and semiconductor factories; O-rings, tubes, gaskets, valve cores, hoses, seals, etc. used in the fuel systems and peripheral equipment of automobiles; fuel transfer components such as hoses and seals used in the automatic transmission systems of automobiles; Carburetor flange gaskets, shaft seals, valve stem seals, sealing materials, hoses, etc. used in automobile engines and peripheral equipment; other automotive components such as automobile brake hoses, air conditioning hoses, radiator hoses, and wire insulation materials; Chemical transfer components for semiconductor equipment, such as O-rings, tubes, packings, valve cores, hoses, sealing materials, rolls, gaskets, diaphragms, and fittings for semiconductor manufacturing equipment; Painting and ink-related components for painting equipment, such as paint rolls, hoses, tubes, and ink containers; Tubes or hoses for food and beverages, belts, gaskets, fittings and other components for transporting food and beverages, food packaging materials, glass cooking equipment; Tubes, hoses, and other components for transporting waste liquids; Components for transporting high-temperature liquids, such as tubes and hoses; Steam piping components such as tubes and hoses for steam piping; Corrosion-preventive tapes for pipes, such as tapes used to wrap around pipes on ship decks; Various coating materials such as wire coatings, optical fiber coatings, transparent surface coatings and backing materials for the light incident side surface of photovoltaic elements in solar cells; Sliding components of diaphragm pumps, such as diaphragms and various packings; Agricultural films, weather-resistant covers for various roofing materials and side walls; Interior materials used in the construction field, and coatings for glass such as non-combustible fire-resistant safety glass; Lining materials such as laminated steel sheets used in the home appliance sector;

[0077] Other fuel transfer components used in the fuel system of the above-mentioned automobile include fuel hoses, filler hoses, and evaporator hoses. These fuel transfer components can also be used as fuel transfer components for sour-resistant gasoline, alcohol-resistant fuels, and fuels containing gasoline additives such as methyl tert-butyl ether and amines.

[0078] The chemical stoppers and packaging films for the above-mentioned chemicals have excellent chemical resistance to acids and other substances. Furthermore, corrosion-resistant tapes wrapped around chemical plant piping can also be used as chemical liquid transfer components.

[0079] Examples of the above-mentioned molded products include automobile radiator tanks, chemical tanks, bellows, spacers, rollers, gasoline tanks, waste liquid transport containers, high-temperature liquid transport containers, and fishing and aquaculture tanks.

[0080] The above-mentioned molded products also include components used in automobiles such as bumpers, door trims, instrument panels, food processing equipment, cooking equipment, water- and oil-repellent glass, lighting-related equipment, display panels and housings for office automation equipment, illuminated signs, displays, liquid crystal displays, mobile phones, printed circuit boards, electrical and electronic components, general merchandise, trash cans, bathtubs, unit baths, ventilation fans, and lighting frames.

[0081] The molded articles containing the fluorine-containing copolymer of this disclosure exhibit excellent mold conformability and superior abrasion resistance at 65°C, ozone resistance, solvent crack resistance, low air permeability, creep resistance, and tensile creep resistance at 140°C. Therefore, they can be suitably used for sheets for hot press processing, protective films, release films, tubes, films, or wire coatings.

[0082] Molded articles containing the fluorine-containing copolymer of this disclosure can be suitably used as compressible members such as gaskets and packings. The compressible member of this disclosure may be a gasket or a packing.

[0083] The size and shape of the compressible member of this disclosure may be set as appropriate depending on the application and are not particularly limited. The shape of the compressible member of this disclosure may be, for example, annular. Furthermore, the compressible member of this disclosure may have a circular, oval, or rounded-corner quadrilateral shape in plan view and have a through hole in its center.

[0084] The compressible member of this disclosure is preferably used as a component for constituting a non-aqueous electrolyte battery. The compressible member of this disclosure is particularly suitable as a component used in contact with the non-aqueous electrolyte in a non-aqueous electrolyte battery. That is, the compressible member of this disclosure may have a liquid-contacting surface with the non-aqueous electrolyte in a non-aqueous electrolyte battery.

[0085] Non-aqueous electrolyte batteries are not particularly limited as long as they contain a non-aqueous electrolyte, and examples include lithium-ion secondary batteries and lithium-ion capacitors. Furthermore, components constituting a non-aqueous electrolyte battery include sealing members and insulating members.

[0086] The above non-aqueous electrolyte is not particularly limited, but one or more known solvents such as propylene carbonate, ethylene carbonate, butylene carbonate, γ-butyl lactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate can be used. The non-aqueous electrolyte battery may further include an electrolyte. The above electrolyte is not particularly limited, but LiClO4, LiAsF6, LiPF6, LiBF4, LiCl, LiBr, CH3SO3Li, CF3SO3Li, cesium carbonate, etc. can be used.

[0087] The compressible members of this disclosure can be suitably used, for example, as sealing members such as sealing gaskets and sealing packings, and insulating members such as insulating gaskets and insulating packings. Sealing members are members used to prevent leakage of liquid or gas or intrusion of liquid or gas from the outside. Insulating members are members used to insulate electricity. The compressible members of this disclosure may be members used for both sealing and insulating purposes.

[0088] The compressible member of this disclosure can be suitably used as a sealing member or insulating member for non-aqueous electrolyte batteries. Furthermore, since the compressible member of this disclosure contains the above-mentioned fluorine-containing copolymer, it has excellent insulating properties. Therefore, when the compressible member of this disclosure is used as an insulating member, it adheres firmly to two or more conductive members, preventing short circuits for a long period of time.

[0089] The fluorine-containing copolymer of this disclosure can be suitably used as a material for forming wire coatings. A coated wire having a coating layer containing the fluorine-containing copolymer of this disclosure exhibits excellent electrical properties because its outer diameter hardly fluctuates.

[0090] The insulated wire comprises a core wire and a coating layer provided around the core wire and containing the fluorine-containing copolymer of the present disclosure. For example, the coating layer can be an extruded body obtained by melt-extruding the fluorine-containing copolymer of the present disclosure onto the core wire. The insulated wire is suitable for LAN cables (Eathernet cables), high-frequency transmission cables, flat cables, heat-resistant cables, etc., and is particularly suitable for transmission cables such as LAN cables (Eathernet cables) and high-frequency transmission cables.

[0091] For the core wire material, metal conductor materials such as copper and aluminum can be used. The core wire is preferably 0.02 to 3 mm in diameter. The core wire diameter is more preferably 0.04 mm or more, even more preferably 0.05 mm or more, and particularly preferably 0.1 mm or more. The core wire diameter is more preferably 2 mm or less.

[0092] Specific examples of core wires include, for instance, AWG-46 (solid copper wire with a diameter of 40 micrometers), AWG-26 (solid copper wire with a diameter of 404 micrometers), AWG-24 (solid copper wire with a diameter of 510 micrometers), AWG-22 (solid copper wire with a diameter of 635 micrometers), etc.

[0093] The thickness of the coating layer is preferably 0.1 to 3.0 mm. A thickness of 2.0 mm or less is also preferable.

[0094] Coaxial cables are an example of high-frequency transmission cables. Coaxial cables generally have a structure in which an inner conductor, an insulating coating layer, an outer conductor layer, and a protective coating layer are laminated in order from the core to the outer periphery. The molded article containing the fluorine-containing copolymer of this disclosure can be suitably used as an insulating coating layer containing the fluorine-containing copolymer. The thickness of each layer in the above structure is not particularly limited, but typically the inner conductor has a diameter of about 0.1 to 3 mm, the insulating coating layer has a thickness of about 0.3 to 3 mm, the outer conductor layer has a thickness of about 0.5 to 10 mm, and the protective coating layer has a thickness of about 0.5 to 2 mm.

[0095] The coating layer may contain air bubbles, and it is preferable that the air bubbles are uniformly distributed within the coating layer.

[0096] The average bubble diameter is not limited, but is preferably 60 μm or less, more preferably 45 μm or less, even more preferably 35 μm or less, even more preferably 30 μm or less, particularly preferably 25 μm or less, and especially preferably 23 μm or less. Furthermore, the average bubble diameter is preferably 0.1 μm or more, and more preferably 1 μm or more. The average bubble diameter can be determined by taking an electron microscope image of the wire cross-section, calculating the diameter of each bubble through image processing, and averaging the results.

[0097] The coating layer may have a foaming rate of 20% or more. More preferably 30% or more, even more preferably 33% or more, and even more preferably 35% or more. There is no particular upper limit, but for example, it is 80%. The upper limit of the foaming rate may be 60%. The foaming rate is calculated as ((specific gravity of the wire coating material - specific gravity of the coating layer) / specific gravity of the wire coating material) × 100. The foaming rate can be appropriately adjusted according to the application, for example by adjusting the amount of gas inserted into the extruder as described later, or by selecting the type of gas to dissolve.

[0098] The insulated wire may have another layer between the core wire and the insulated layer, and may have yet another layer (outer layer) around the insulated layer. If the insulated layer contains air bubbles, the wire of this disclosure may have a two-layer structure (skin-foam) with a non-foamed layer inserted between the core wire and the insulated layer, a two-layer structure (foam-skin) with a non-foamed layer covering the outer layer, or a three-layer structure (skin-foam-skin) with a non-foamed layer covering the outer layer of the skin-foam. The non-foamed layer is not particularly limited and may be a resin layer made of TFE / HFP copolymer, TFE / PAVE copolymer, TFE / ethylene copolymer, vinylidene fluoride polymer, polyolefin resin such as polyethylene [PE], or resin such as polyvinyl chloride [PVC].

[0099] Insulated wires can be manufactured, for example, by using an extruder to heat a fluorine-containing copolymer, extruding the molten fluorine-containing copolymer onto a core wire, and forming an insulated layer.

[0100] In forming the coating layer, the fluorine-containing copolymer can be heated, and while the copolymer is molten, a gas can be introduced into the fluorine-containing copolymer to form the coating layer containing bubbles. Examples of gases that can be used include chlorodifluoromethane, nitrogen, carbon dioxide, or mixtures thereof. The gas may be introduced as a pressurized gas into the heated fluorine-containing copolymer, or it may be generated by mixing a chemical blowing agent into the fluorine-containing copolymer. The gas dissolves in the molten fluorine-containing copolymer.

[0101] Furthermore, the fluorine-containing copolymer of this disclosure can be suitably used as a material for high-frequency signal transmission products.

[0102] The above-mentioned high-frequency signal transmission products are not particularly limited as long as they are products used for transmitting high-frequency signals, and include (1) molded boards such as insulating boards for high-frequency circuits, insulating materials for connecting components, and printed circuit boards, (2) molded bodies such as bases for high-frequency vacuum tubes and antenna covers, and (3) insulated wires such as coaxial cables and LAN cables. The above-mentioned high-frequency signal transmission products can be suitably used in equipment that utilizes microwaves, particularly microwaves in the 3 to 30 GHz range, such as satellite communication equipment and mobile phone base stations.

[0103] In the above-mentioned high-frequency signal transmission product, the fluorine-containing copolymer of this disclosure can be suitably used as an insulator due to its low dielectric loss tangent.

[0104] As the molded plate in (1) above, a printed circuit board is preferred because it provides good electrical characteristics. The printed circuit board is not particularly limited, but examples include printed circuit boards for electronic circuits in mobile phones, various computers, communication equipment, etc. As the molded body in (2) above, an antenna cover is preferred because it has low dielectric loss.

[0105] The fluorine-containing copolymers of this disclosure can be suitably used in films.

[0106] The film of this disclosure is useful as a release film. The release film can be manufactured by molding the fluorine-containing copolymer of this disclosure by melt extrusion, calendering, press molding, casting, etc. From the viewpoint of obtaining a uniform thin film, the release film can be manufactured by melt extrusion.

[0107] The film of this disclosure can be applied to the surface of rolls used in office automation equipment. Furthermore, the fluorine-containing copolymer of this disclosure can be formed into the required shape by extrusion molding, compression molding, press molding, etc., to form sheets, films, or tubes, and used as a surface material for office automation equipment rolls or belts. In particular, thin-walled tubes and films can be manufactured by melt extrusion molding.

[0108] The fluorine-containing copolymers of this disclosure can be suitably used in tubes, bottles, and the like.

[0109] Although embodiments have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of the claims. [Examples]

[0110] Next, embodiments of the present disclosure will be described with reference to examples, but the present disclosure is not limited to such embodiments.

[0111] Each value in the examples was measured by the following method.

[0112] (Content in monomer units) The content of each monomer unit of the fluorine-containing copolymer was measured using an NMR analyzer (e.g., Bruker BioSpin AVANCE300 high-temperature probe) or an infrared absorption analyzer (PerkinElmer Spectrum One).

[0113] (Melt Flow Rate (MFR)) The MFR of the fluorine-containing copolymer was determined in accordance with ASTM D-1238 by measuring the mass (g / 10 min) of polymer flowing out of a die with an inner diameter of 2 mm and a length of 8 mm per 10 minutes using a melt indexer G-01 (manufactured by Toyo Seiki Seisakusho Co., Ltd.) at 372°C under a 5 kg load.

[0114] (Number of -CF2H) The number of -CF2H groups in a fluorine-containing copolymer was determined using a nuclear magnetic resonance spectrometer AVANCE-300 (Bruker BioSpin) at a measurement temperature of (polymer melting point + 20°C). 19 The peak integral value of the -CF2H group was determined by performing 1F-NMR measurements.

[0115] (Number of -COOH, -COOCH3, -CH2OH, -COF, -CF=CF2, and -CONH2 molecules) The dried powders or pellets obtained in the examples and comparative examples were molded by cold pressing to produce films with a thickness of 0.25 to 0.3 mm. These films were scanned 40 times using a Fourier transform infrared spectrometer (FT-IR, Spectrum One, PerkinElmer) and analyzed to obtain infrared absorption spectra. The obtained infrared absorption spectra were compared with the infrared absorption spectra of known films to determine the types of end groups. Furthermore, from the absorption peaks of specific functional groups appearing in the difference spectra between the obtained infrared absorption spectra and the infrared absorption spectra of known films, the carbon atoms in the sample (1 × 10⁶) were identified according to the following formula (A). 6 The number of functional cards N per individual was calculated.

[0116] N = I × K / t (A) I: Absorbance K: Correction coefficient t: Film thickness (mm)

[0117] For reference, Table 2 shows the absorption frequency, molar extinction coefficient, and correction factor for the functional groups in the examples. The molar extinction coefficient was determined from FT-IR measurement data of a low-molecular-weight model compound.

[0118] [Table 2]

[0119] (-OC (=O)OR (number of carbonate groups)) The analysis was performed using the method described in International Publication No. 2019 / 220850. The absorption frequency was 1817 cm⁻¹. -1Except for using a molar extinction coefficient of 170 (l / cm / mol) and a correction factor of 1426, the number of -OC(=O)OR (carbonate groups) was calculated in the same manner as the calculation method for the number of functional groups N.

[0120] (Melting point) The melting point of the fluorine-containing copolymer was determined using a differential scanning calorimeter (product name: X-DSC7000, manufactured by Hitachi High-Tech Science Corporation). The first heating was performed at a heating rate of 10°C / min from 200°C to 350°C, followed by cooling at a cooling rate of 10°C / min from 350°C to 200°C, and then a second heating was performed at a heating rate of 10°C / min from 200°C to 350°C. The melting point was determined from the peak of the melting curve generated during the second heating process.

[0121] Comparative Example 1 945 g of deionized water and 7.8 g of methanol were added to a 4 L autoclave equipped with a stirrer, and the autoclave was thoroughly purged with vacuum nitrogen. Then, the autoclave was degassed under vacuum, and 945 g of HFP and 9.1 g of PEVE were added to the vacuum-filled autoclave, and the autoclave was heated to 30.0 °C. Subsequently, TFE was added until the internal pressure of the autoclave reached 0.920 MPa, and then 14.7 g of 8 mass% di(ω-hydroperfluorohexanoyl) peroxide solution (hereinafter abbreviated as DHP) was added to the autoclave to start polymerization. The internal pressure of the autoclave was set to 0.920 MPa at the start of polymerization, and the set pressure was maintained by continuously adding TFE. 7.88 g of methanol was added 1.5 hours after the start of polymerization. Two hours and four hours after the start of polymerization, 14.7g of DHP was added and the internal pressure was reduced by 0.001MPa. At six hours, 11.3g of DHP was added and the internal pressure was reduced by 0.001MPa. Thereafter, 3.0g of DHP was added every two hours until the reaction was complete, and the internal pressure was reduced by 0.001MPa each time.

[0122] PEVE added 2.6g of TFE when the continuous amount of TFE added reached 190g and 380g, respectively. Additionally, 7.8g of methanol was added to the autoclave when the total amount of TFE added reached 140g. Polymerization was terminated when the total amount of TFE added reached 454g. After polymerization, unreacted TFE and HFP were released to obtain a wet powder. This wet powder was then washed with pure water and dried at 150°C for 10 hours to obtain 518g of dry powder.

[0123] The obtained powder was melt-extruded at 370°C using a 14φ screw extruder (manufactured by Imoto Seisakusho) to obtain copolymer pellets. The HFP content and PEVE content were measured using the obtained pellets by the method described above. The results are shown in Table 3.

[0124] The obtained pellets were degassed in an electric furnace at 200°C for 8 hours, then placed in a portable reactor TVS1 (manufactured by Pressure Glass Industry Co., Ltd.) and heated to 200°C. After vacuuming, F2 gas diluted to 20% by volume with N2 gas was introduced to atmospheric pressure. 0.5 hours after the introduction of F2 gas, the reactor was vacuumed and F2 gas was introduced again. After another 0.5 hours, the reactor was vacuumed again and F2 gas was introduced again. Thereafter, the above operations of introducing F2 gas and vacuuming were continued once every hour, and the reaction was carried out at a temperature of 200°C for 8 hours. After the reaction was completed, the reactor was thoroughly replaced with N2 gas to terminate the fluorination reaction and obtain pellets. Various physical properties were measured using the obtained pellets by the method described above. The results are shown in Table 3.

[0125] Comparative Example 2 Copolymer pellets were obtained in the same manner as in Comparative Example 1, except that the amount of methanol added before polymerization started was changed to 8.1 g, the amount of methanol added in installments after polymerization started was changed to 8.1 g each, the amount of PEVE added before polymerization started was changed to 13.8 g, the amount of PEVE added in installments after polymerization started was changed to 3.9 g each, and the set pressure inside the autoclave before and after polymerization started was changed to 0.926 MPa. The HFP content and PEVE content were measured using the obtained pellets by the method described above. The results are shown in Table 3.

[0126] The obtained pellets were fluorinated in the same manner as in Comparative Example 1. Various physical properties were measured using the obtained pellets according to the method described above. The results are shown in Table 3.

[0127] Comparative Example 3 Copolymer pellets were obtained in the same manner as in Comparative Example 1, except that the amount of methanol added before polymerization started was changed to 4.3 g, the amount of methanol added in installments after polymerization started was changed to 4.3 g each, the amount of PEVE added before polymerization started was changed to 17.0 g, the amount of PEVE added in installments after polymerization started was changed to 5.2 g each, and the set pressure inside the autoclave before and after polymerization started was changed to 0.909 MPa. The HFP content and PEVE content were measured using the obtained pellets by the method described above. The results are shown in Table 3.

[0128] The obtained pellets were fluorinated in the same manner as in Comparative Example 1. Various physical properties were measured using the obtained pellets according to the method described above. The results are shown in Table 3.

[0129] Comparative Example 4 945 g of deionized water and 13.2 g of methanol were added to a 4 L autoclave equipped with a stirrer, and the autoclave was thoroughly purged with vacuum nitrogen. Then, the autoclave was degassed under vacuum, and 945 g of HFP and 27.8 g of PEVE were added to the vacuum-filled autoclave, and the autoclave was heated to 25.5°C. Subsequently, TFE was added until the internal pressure of the autoclave reached 0.927 MPa, and then 29.4 g of 8 mass% di(ω-hydroperfluorohexanoyl) peroxide solution (hereinafter abbreviated as DHP) was added to the autoclave to start polymerization. The internal pressure of the autoclave was set to 0.927 MPa at the start of polymerization, and the set pressure was maintained by continuously adding TFE. 13.2 g of methanol was added 1.5 hours after the start of polymerization. Two hours and four hours after the start of polymerization, 29.4g of DHP was added while the internal pressure was reduced by 0.002MPa. At six hours, 22.6g of DHP was added while the internal pressure was reduced by 0.002MPa. Thereafter, 6.0g of DHP was added every two hours until the reaction was complete, and the internal pressure was reduced by 0.002MPa each time.

[0130] PEVE added 5.2g of TFE when the continuous addition amount of TFE reached 190g and 380g, respectively. Additionally, 13.2g of methanol was added to the autoclave when the total amount of TFE added reached 140g. Polymerization was terminated when the total amount of TFE added reached 454g. After polymerization, unreacted TFE and HFP were released to obtain a wet powder. This wet powder was then washed with pure water and dried at 150°C for 10 hours to obtain 500g of dry powder.

[0131] The obtained powder was melt-extruded at 370°C using a 14φ screw extruder (manufactured by Imoto Seisakusho) to obtain copolymer pellets. The HFP content and PEVE content were measured using the obtained pellets by the method described above. The results are shown in Table 3.

[0132] The obtained pellets were fluorinated in the same manner as in Comparative Example 1. Various physical properties were measured using the obtained pellets according to the method described above. The results are shown in Table 3.

[0133] Comparative Example 5 Copolymer pellets were obtained in the same manner as in Comparative Example 1, except that the amount of methanol added before polymerization started was changed to 4.3 g, the amount of methanol added in installments after polymerization started was changed to 4.3 g each, the amount of PEVE added before polymerization started was changed to 13.1 g, the amount of PEVE added in installments after polymerization started was changed to 4.4 g each, and the set pressure inside the autoclave before and after polymerization started was changed to 0.888 MPa. The HFP content and PEVE content were measured using the obtained pellets by the method described above. The results are shown in Table 3.

[0134] The obtained pellets were fluorinated in the same manner as in Comparative Example 1. Various physical properties were measured using the obtained pellets according to the method described above. The results are shown in Table 3.

[0135] Comparative Example 6 40.25 kg of deionized water and 0.237 kg of methanol were added to a 174 L autoclave equipped with a stirrer, and the autoclave was thoroughly purged with vacuum nitrogen. Then, the autoclave was degassed under vacuum, and 40.25 kg of HFP and 0.45 kg of PPVE were added to the vacuumed autoclave, and the autoclave was heated to 30.0°C. Subsequently, TFE was added until the internal pressure of the autoclave reached 0.897 MPa, and then 0.63 kg of 8 mass% di(ω-hydroperfluorohexanoyl) peroxide solution (hereinafter abbreviated as DHP) was added to the autoclave to start polymerization. The internal pressure of the autoclave was set to 0.897 MPa at the start of polymerization, and the set pressure was maintained by continuously adding TFE. 1.5 hours after the start of polymerization, an additional 0.237 kg of methanol was added. Two hours and four hours after the start of polymerization, 0.63 kg of DHP was added and the internal pressure was reduced by 0.001 MPa. At six hours, 0.48 kg was added and the internal pressure was reduced by 0.001 MPa. Thereafter, 0.13 kg of DHP was added every two hours until the reaction was complete, and the internal pressure was reduced by 0.001 MPa each time.

[0136] Furthermore, PPVE was added in increments of 0.14 kg each time the continuous addition amount of TFE reached 8.1 kg, 16.2 kg, and 24.3 kg. In addition, when the addition amount of TFE reached 6.0 kg and 18.1 kg, 0.237 kg of methanol was added to the autoclave each time. Polymerization was terminated when the addition amount of TFE reached 40.25 kg. After polymerization was complete, unreacted TFE and HFP were released to obtain a wet powder. This wet powder was then washed with pure water and dried at 150°C for 10 hours to obtain 46.6 kg of dry powder.

[0137] The obtained powder was melt-extruded at 370°C using a screw extruder (product name: PCM46, manufactured by Ikegai Co., Ltd.) to obtain copolymer pellets. The HFP content and PPVE content were measured using the obtained pellets by the method described above. The results are shown in Table 3.

[0138] The obtained pellets were degassed in an electric furnace at 200°C for 8 hours, then placed in a vacuum vibration reactor VVD-30 (manufactured by Okawara Seisakusho Co., Ltd.) and heated to 200°C. After vacuuming, F2 gas diluted to 20% by volume with N2 gas was introduced to atmospheric pressure. 0.5 hours after the introduction of F2 gas, the reactor was vacuumed and F2 gas was introduced again. After another 0.5 hours, the reactor was vacuumed again and F2 gas was introduced again. Thereafter, the above operations of introducing F2 gas and vacuuming were continued once every hour, and the reaction was carried out at a temperature of 200°C for 8 hours. After the reaction was completed, the reactor was thoroughly replaced with N2 gas to terminate the fluorination reaction and obtain pellets. Various physical properties were measured using the obtained pellets by the method described above. The results are shown in Table 3.

[0139] Comparative Example 7 Copolymer pellets were obtained in the same manner as in Comparative Example 1, except that the amount of methanol added before polymerization started was changed to 6.2 g, the amount of methanol added in installments after polymerization started was changed to 6.2 g each, the amount of PEVE added before polymerization started was changed to 18.2 g, the amount of PEVE added in installments after polymerization started was changed to 5.2 g each, and the set pressure inside the autoclave before and after polymerization started was changed to 0.926 MPa. The obtained pellets were used without fluorination, and various physical properties were measured using the method described above. The results are shown in Table 3.

[0140] Example 1 Copolymer pellets were obtained in the same manner as in Comparative Example 1, except that the amount of methanol added before polymerization started was changed to 7.0 g, the amount of methanol added in installments after polymerization started was changed to 7.0 g each, the amount of PEVE added before polymerization started was changed to 19.4 g, the amount of PEVE added in installments after polymerization started was changed to 5.4 g each, and the set pressure inside the autoclave before and after polymerization started was changed to 0.929 MPa. The HFP content and PEVE content were measured using the obtained pellets by the method described above. The results are shown in Table 3.

[0141] The obtained pellets were degassed in an electric furnace at 200°C for 72 hours, then placed in a portable reactor TVS1 (manufactured by Pressure Glass Industry Co., Ltd.) and heated to 120°C. After vacuuming, F2 gas diluted to 20% by volume with N2 gas was introduced to atmospheric pressure. 0.5 hours after the introduction of F2 gas, the reactor was vacuumed and F2 gas was introduced again. After another 0.5 hours, the reactor was vacuumed again and F2 gas was introduced again. Thereafter, the above operations of introducing F2 gas and vacuuming were continued once every hour, and the reaction was carried out at a temperature of 120°C for 7 hours. After the reaction was completed, the reactor was thoroughly replaced with N2 gas to terminate the fluorination reaction and obtain pellets. Various physical properties were measured using the obtained pellets by the method described above. The results are shown in Table 3.

[0142] Example 2 Copolymer pellets were obtained in the same manner as in Comparative Example 1, except that the amount of methanol added before polymerization started was changed to 6.0 g, the amount of methanol added in installments after polymerization started was changed to 6.0 g each, the amount of PEVE added before polymerization started was changed to 15.5 g, the amount of PEVE added in installments after polymerization started was changed to 4.7 g each, and the set pressure inside the autoclave before and after polymerization started was changed to 0.912 MPa. The HFP content and PEVE content were measured using the obtained pellets by the method described above. The results are shown in Table 3.

[0143] The obtained pellets were fluorinated in the same manner as in Comparative Example 1. Various physical properties were measured using the obtained pellets according to the method described above. The results are shown in Table 3.

[0144] Example 3 Copolymer pellets were obtained in the same manner as in Comparative Example 1, except that the amount of methanol added before polymerization started was changed to 5.2 g, the amount of methanol added in installments after polymerization started was changed to 5.2 g each, the amount of PEVE added before polymerization started was changed to 10.6 g, the amount of PEVE added in installments after polymerization started was changed to 3.4 g each, and the set pressure inside the autoclave before and after polymerization started was changed to 0.912 MPa. The HFP content and PEVE content were measured using the obtained pellets by the method described above. The results are shown in Table 3.

[0145] The obtained pellets were fluorinated in the same manner as in Comparative Example 1. Various physical properties were measured using the obtained pellets according to the method described above. The results are shown in Table 3.

[0146] [Table 3]

[0147] Table 3, "Other (individual / C10)" 6The notation ")" represents the total number of -COOCH3, -CF=CF2, and -CONH2. In Table 3, "<9" means that the number of -CF2H groups (total) is less than 9. In Table 3, "<6" means that the number of target functional groups (total) is less than 6. In Table 3, "ND" means that a peak sufficient for quantification could not be confirmed for the target functional group.

[0148] Next, the following characteristics were evaluated using the obtained pellets. The results are shown in Table 4.

[0149] (Abrasion test) Using a pellet and heat press molding machine, sheet-like test specimens approximately 0.2 mm thick were prepared, and 10 cm x 10 cm test specimens were cut from them. The prepared test specimens were fixed to the test stand of a Taber abrasion tester (No. 101 Special Taber-type ablation tester, manufactured by Yasuda Seiki Seisakusho Co., Ltd.), and an abrasion test was performed using the Taber abrasion tester under the following conditions: test specimen surface temperature 65°C, load 500 g, abrasion wheel CS-10 (polished 20 times with #240 abrasive paper), and rotation speed 60 rpm. The weight of the test specimen was measured after 1000 rotations, and then measured again after another 5500 rotations of the same test specimen. The amount of abrasion was calculated using the following formula. Wear amount (mg)=M1-M2 M1: Weight of the test specimen after 1000 rotations (mg) M2: Weight of the test specimen after 5500 rotations (mg)

[0150] (Ozone exposure test) A fluorine-containing copolymer was compressed and molded at 350°C under a pressure of 0.5 MPa to produce a 1 mm thick sheet, which was then cut into 10 × 20 mm sections to serve as samples for ozone exposure testing. Ozone gas (ozone / oxygen = 10 / 90 vol%) generated by an ozone generator (product name: SGX-A11MN (modified), manufactured by Sumitomo Seiki Kogyo Co., Ltd.) was connected to a PFA container filled with deionized water. Water vapor was added to the ozone gas by bubbling it through the deionized water, and the sample was exposed to moist ozone gas by passing it through a PFA cell containing the sample at a rate of 0.7 liters / min at room temperature. Eighty days after the start of exposure, the sample was removed, the surface was lightly rinsed with deionized water, and the area from the sample surface to a depth of 5 to 200 μm was observed using a transmission optical microscope at 100x magnification. The area was photographed together with a standard scale, and the 1 mm portion of the sample surface was also photographed. 2 The number of cracks with a length of 10 μm or more per unit area was measured. The evaluation was conducted based on the following criteria. ○: 10 or fewer cracks ×: More than 10 cracks

[0151] (Chemical immersion crack test) A molded body with a thickness of approximately 2 mm was produced using a pellet and heat press molding machine. Three test specimens were obtained by punching out the resulting sheet using a 13.5 mm × 38 mm rectangular dumbbell. A notch was made in the center of the long side of each obtained test specimen using a 19 mm × 0.45 mm blade in accordance with ASTM D1693. Three notched test specimens and 25 g of Tetraglyme were placed in a 100 mL polypropylene bottle and heated in an electric furnace at 150 °C for 20 hours, after which the notched test specimens were removed. The three obtained notched test specimens were mounted in a stress crack test fixture in accordance with ASTM D1693 and heated in an electric furnace at 150 °C for 24 hours, after which the notches and their surroundings were visually observed and the number of cracks was counted. Sheets that did not develop cracks exhibited excellent solvent crack resistance. ○: The number of cracks is 0. ×: The number of cracks is one or more.

[0152] (Air permeability coefficient) Sheet-like test specimens with a thickness of approximately 0.1 mm were prepared using a pellet and heat press molding machine. Using the obtained test specimens, air permeability was measured using a differential pressure gas permeability meter (L100-5000 type gas permeability meter, manufactured by Systech illinois) in accordance with the method described in JIS K7126-1:2006. Permeation area: 50.24 cm² 2 The air permeability values ​​were obtained at a test temperature of 70°C and a test humidity of 0%RH. Using the obtained air permeability values ​​and the thickness of the test specimen, the air permeability coefficient was calculated using the following formula. Air permeability coefficient (cm 3 ·mm / (m 2 24h (atm) = GTR × d GTR: Air permeability (cm) 3 / (m 2 24-hour ATM) d: Test specimen thickness (mm)

[0153] (Deflection under load at 85°C) Using pellets and a heat press molding machine, sheet-like test specimens approximately 4.0 mm thick were prepared. From these, 80 x 10 mm test specimens were cut out and heated in an electric furnace at 85°C for 20 hours. Except for using the obtained test specimens, tests were conducted using a heat distortion tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) in accordance with the method described in JIS KK 7191-1, under the conditions of a test temperature of 30 to 150°C, a heating rate of 120°C / hour, a bending stress of 1.8 MPa, and the flatwise method. The load deflection ratio was calculated using the following formula. Sheets with a large load deflection ratio at 85°C soften and deform easily, indicating excellent mold conformability. Load deflection rate (%) = a² / a¹ × 100 a1: Thickness of the test specimen before testing (mm) a2: Deflection at 85℃ (mm)

[0154] (Creep resistance evaluation) Creep resistance was measured according to the methods described in ASTM D395 or JIS K6262:2013. A molded body with an outer diameter of 13 mm and a height of 8 mm was prepared using a pellet and heat press molding machine. A test specimen with an outer diameter of 13 mm and a height of 6 mm was prepared by cutting the obtained molded body. The prepared test specimen was compressed to a compression deformation rate of 25% at room temperature using a compression device. The compressed test specimen was left in an electric furnace with the compression device fixed in place and left at 40°C for 72 hours. The compression device was removed from the electric furnace, and after cooling to room temperature, the test specimen was removed. After leaving the recovered test specimen at room temperature for 30 minutes, the height of the recovered test specimen was measured and the recovery rate was calculated using the following formula. Restoration rate (%) = (t2 - t1) / t3 × 100 t1: Spacer height (mm) t2: Height of the test specimen removed from the compression device (mm) t3: Height after compression deformation (mm) In the above test, t1 = 4.5 mm and t3 = 1.5 mm.

[0155] (Tensile creep test) Tensile creep strain was measured using a Hitachi High-Tech Science TMA-7100. A sheet approximately 0.1 mm thick was prepared using a pellet and heat press molding machine, and a sample 2 mm wide and 22 mm long was created from the sheet. The sample was mounted on a measuring jig with a jig-to-jig distance of 10 mm. A cross-sectional load of 3.32 N / mm was applied to the sample. 2 A load was applied to the sample, and it was left at 140°C. The displacement (mm) of the sample length was measured from 90 minutes after the start of the test to 450 minutes after the start of the test, and the ratio of the length displacement (mm) to the initial sample length (10 mm) (tensile creep strain (%)) was calculated. Sheets with a small tensile creep strain (%) measured under the conditions of 140°C and 450 minutes are less likely to elongate even when subjected to tensile load for a long time in a high-temperature environment, and have excellent high-temperature tensile creep resistance (140°C).

[0156] (Extrusion pressure) Extrusion pressure was measured using a twin capillary rheometer RHEOGRAPH 25 (Goettfert). A main die with an inner diameter of 1 mm and L / D = 16, and a sub-die with an inner diameter of 1 mm and L / D < 1 were used. Measurement temperature was 302°C, preheating time after pellet loading was 10 minutes, and shear rate was 20 sec. -1 The extrusion pressure was determined by applying a Burgray correction to the cylinder pressure value after extrusion for 10 minutes. Copolymers with low extrusion pressure exhibit excellent moldability, including extrusion and injection molding properties.

[0157] (Immersion test in hydrogen peroxide solution) Using a pellet and heat press molding machine, sheets approximately 0.2 mm thick were prepared, and 15 mm square test specimens were created. Ten test specimens and 15 g of 3% by mass hydrogen peroxide aqueous solution were placed in a 50 mL polypropylene bottle, heated in an electric furnace at 95 °C for 20 hours, and then cooled to room temperature. The test specimens were removed from the hydrogen peroxide aqueous solution, and TISAB solution (10) (manufactured by Kanto Chemical Co., Ltd.) was added to the remaining hydrogen peroxide aqueous solution. The fluoride ion concentration in the resulting hydrogen peroxide aqueous solution was measured using a fluoride ion meter. From the obtained measurement values, the fluoride ion concentration per sheet weight (eluted fluoride ion concentration) was calculated according to the following formula. Eluted fluoride ion concentration (mass ppm) = Measured value (ppm) × Amount of hydrogen peroxide solution (g) / Weight of test specimen (g)

[0158] [Table 4]

Claims

1. A fluorine-containing copolymer containing tetrafluoroethylene units, hexafluoropropylene units, perfluoro(ethyl vinyl ether) units and other monomer units, The hexafluoropropylene unit content is 9.5 to 11.6% by mass relative to the total monomer units. The perfluoro(ethyl vinyl ether) unit content is 1.2 to 2.9% by mass relative to the total monomer units. The content of other monomer units is 0 to 3.8% by mass relative to the total number of monomer units. The content of tetrafluoroethylene units is selected such that the total content of hexafluoropropylene units, perfluoro(ethyl vinyl ether) units, tetrafluoroethylene units, and other monomer units is 100% by mass. The melt flow rate at 372°C is 19.0–27.0 g / 10 min. -CF ２ H, carbonyl group-containing terminal group, -CF=CF ２ and -CH ２ The total number of OH groups is 10 carbon atoms in the main chain. ６ There are 40 or fewer per unit. Fluorine-containing copolymers (excluding fluorine-containing copolymers containing tetrafluoroethylene units, hexafluoropropylene units, and perfluoro(ethyl vinyl ether) units, wherein the hexafluoropropylene unit content is 9.5 to 11.6% by mass relative to the total monomer units, the perfluoro(ethyl vinyl ether) unit content is 1.2 to 2.9% by mass relative to the total monomer units, the tetrafluoroethylene unit content is 85.5 to 89.3% by mass relative to the total monomer units, the melt flow rate at 372°C is 23.0 to 27.0 g / 10 min, and the total number of -CF₂H, carbonyl group-containing end groups, -CF=CF₂, and -CH₂OH is 40 or less per 10⁶ carbon atoms in the main chain).

2. The fluorine-containing copolymer according to claim 1, wherein the content of hexafluoropropylene units is 10.1 to 11.5% by mass relative to the total monomer units.

3. The fluorine-containing copolymer according to claim 1 or 2, wherein the content of perfluoro(ethyl vinyl ether) units is 1.3 to 2.1% by mass relative to the total monomer units.

4. A fluorine-containing copolymer according to any one of claims 1 to 3, wherein the melt flow rate at 372°C is 20.0 to 27.0 g / 10 min.

5. An injection-molded article containing a fluorine-containing copolymer according to any one of claims 1 to 4.

6. A coated electric wire comprising a coating layer containing a fluorine-containing copolymer according to any one of claims 1 to 4.

7. A molded article containing a fluorine-containing copolymer according to any one of claims 1 to 4, wherein the molded article is a sheet for hot press processing, a protective film, a release film, a tube, a film, or a wire coating.

8. A pellet containing a fluorine-containing copolymer, The fluorine-containing copolymer is a fluorine-containing copolymer containing tetrafluoroethylene units, hexafluoropropylene units, perfluoro(ethyl vinyl ether) units and other monomer units, The hexafluoropropylene unit content is 9.5 to 11.6% by mass relative to the total monomer units. The perfluoro(ethyl vinyl ether) unit content is 1.2 to 2.9% by mass relative to the total monomer units. The content of other monomer units is 0 to 3.8% by mass relative to the total number of monomer units. The content of tetrafluoroethylene units is selected such that the total content of hexafluoropropylene units, perfluoro(ethyl vinyl ether) units, tetrafluoroethylene units, and other monomer units is 100% by mass. The melt flow rate at 372°C is 19.0–27.0 g / 10 min. The total number of -CF₂H, carbonyl group-containing terminal groups, -CF=CF₂, and -CH₂OH is 40 or less per 10⁶ carbon atoms in the main chain. pellet.

9. The pellet according to claim 8, wherein the content of hexafluoropropylene units is 10.1 to 11.5% by mass relative to the total monomer units.

10. The pellet according to claim 8 or 9, wherein the content of perfluoro(ethyl vinyl ether) units is 1.3 to 2.1% by mass relative to the total monomer units.

11. The pellet according to any one of claims 8 to 10, wherein the melt flow rate at 372°C is 20.0 to 27.0 g / 10 min.

12. An extruded article containing a fluorine-containing copolymer, The fluorine-containing copolymer is a fluorine-containing copolymer containing tetrafluoroethylene units, hexafluoropropylene units, perfluoro(ethyl vinyl ether) units and other monomer units, The hexafluoropropylene unit content is 9.5 to 11.6% by mass relative to the total monomer units. The perfluoro(ethyl vinyl ether) unit content is 1.2 to 2.9% by mass relative to the total monomer units. The content of other monomer units is 0 to 3.8% by mass relative to the total number of monomer units. The content of tetrafluoroethylene units is selected such that the total content of hexafluoropropylene units, perfluoro(ethyl vinyl ether) units, tetrafluoroethylene units, and other monomer units is 100% by mass. The melt flow rate at 372°C is 19.0–27.0 g / 10 min. The total number of -CF₂H, carbonyl group-containing terminal groups, -CF=CF₂, and -CH₂OH is 40 or less per 10⁶ carbon atoms in the main chain. Extruded product.

13. The extruded article according to claim 12, wherein the content of hexafluoropropylene units is 10.1 to 11.5% by mass relative to the total monomer units.

14. The extruded article according to claim 12 or 13, wherein the content of perfluoro(ethyl vinyl ether) units is 1.3 to 2.1% by mass relative to the total monomer units.

15. An extruded article according to any one of claims 12 to 14, wherein the melt flow rate at 372°C is 20.0 to 27.0 g / 10 min.

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