Fluorine-containing polymer production method, fluorine-containing polymer, injection molded body, coated electric wire, and molded body

Abstract

The present invention addresses the problem of providing: a fluorine-containing polymer production method for producing a fluorine-containing polymer that makes it possible to form a molded body having excellent ozone resistance; a fluorine-containing polymer that makes it possible to form a molded body having excellent ozone resistance; an injection molded body; a coated electric wire; and a molded body.　A fluorine-containing polymer production method according to the present invention comprises: polymerizing tetrafluoroethylene and perfluoro(alkyl allyl ether) in a reaction system that contains water having an electrical resistivity of 15.0 MΩ⋅cm or more and substantially does not contain any fluorine-containing emulsifier or sulfate ions, thereby obtaining a fluorine-containing polymer; and subjecting the fluorine-containing polymer to a fluorination treatment.

Description

Method for producing fluorine-containing polymers, fluorine-containing polymers, injection-molded articles, coated electric wires, molded articles

[0001] The present invention relates to a method for producing a fluorine-containing polymer, a fluorine-containing polymer, an injection-molded article, a coated electric wire, and a molded article.

[0002] A copolymer of tetrafluoroethylene and perfluoro(alkylallyl ether) is known as a fluororesin that is excellent in mechanical, chemical, and electrical properties, and is also melt-processable. The use of such materials with excellent properties is expected to contribute to the realization of Goal 12 of the United Nations' Sustainable Development Goals (SDGs), "Responsible Consumption and Production," as it leads to a longer product lifecycle and, consequently, a reduction in waste. Patent Document 1 discloses a copolymer comprising tetrafluoroethylene units and predetermined perfluoro(alkylallyl ether) units and having a melt flow index within a predetermined range.

[0003] Patent No. 6829203

[0004] Recently, when using molded bodies made of fluorine-containing polymers as piping materials for semiconductor manufacturing equipment, there is a demand for even greater ozone resistance in these molded bodies. The present inventors evaluated a molded body formed using a fluorine-containing polymer described in Patent Document 1 and found that there is room for further improvement in the ozone resistance of the molded body.

[0005] The present invention has been made in view of the above problems and aims to provide a method for producing a fluorine-containing polymer that can form a molded article with excellent ozone resistance. The present invention also aims to provide a fluorine-containing polymer that can form a molded article with excellent ozone resistance, an injection-molded article, a coated wire, and a molded article.

[0006] As a result of diligent research into the above-mentioned problems, the present inventors have discovered that by polymerizing tetrafluoroethylene and perfluoro(alkylallyl ether) in a reaction system containing water with an electrical resistivity of 15.0 MΩ·cm or more, and substantially free of both fluorine-containing emulsifiers and sulfate ions, and then fluorinating the resulting fluorine-containing polymer, a fluorine-containing polymer can be obtained that can form molded articles with excellent ozone resistance, leading to the present invention.

[0007] In other words, the inventors have found that the above problems can be solved by the following configurations: [1] A method for producing a fluorine-containing polymer, characterized by polymerizing tetrafluoroethylene and perfluoro(alkylallyl ether) in a reaction system containing water with an electrical resistivity of 15.0 MΩ·cm or more, and substantially free of both a fluorine-containing emulsifier and sulfate ions, to obtain a fluorine-containing polymer, and then performing a fluorination treatment on the fluorine-containing polymer. [2] The method for producing a fluorine-containing polymer according to [1], wherein the reaction system further contains methanol. [3] The method for producing a fluorine-containing polymer according to [1] or [2], wherein the reaction system further contains a fluorine-based solvent. [4] The method for producing a fluorine-containing polymer according to [3], wherein the amount of the fluorine-based solvent added to the reaction system is 1 to 70% by mass relative to the amount of water added. [5] The method for producing a fluorine-containing polymer according to any one of [1] to [4], wherein the reaction system further contains an oil-soluble radical initiator. [6] A method for producing a fluorine-containing polymer according to any one of [1] to [5], wherein the content of the fluorine-containing emulsifier and the content of the sulfate ions are each 10 ppm by mass or less with respect to the total mass of the reaction system. [7] A fluorine-containing polymer having units based on tetrafluoroethylene and units based on perfluoro(alkylallyl ether), wherein -CF=CF ２ , -CF ２ H, -COF, -COOH, -COOCH ３ , -CONH ２ and -CH ２ The total number of OH functional groups is equal to the number of carbon atoms in the main chain of the above fluorine-containing polymer. ６A fluorine-containing polymer characterized by having fewer than 150 units per cell and a metal ion elution amount of 100 ppb by mass or less relative to the total mass of the fluorine-containing polymer. [8] The fluorine-containing polymer according to [6], which is substantially free of a fluorine-containing emulsifier. [9] The fluorine-containing polymer according to [7] or [8], wherein the content of the units based on perfluoro(alkyl allyl ether) is 0.2 to 5.0 mol% relative to the total units of the fluorine-containing polymer.

[10] The fluorine-containing polymer according to any one of [7] to [9], wherein the melt flow rate of the fluorine-containing polymer measured under conditions of 372°C in accordance with ASTM D1238 is 0.5 to 100.0 g / 10 min.

[11] The fluorine-containing polymer according to any one of [8] to

[10] , wherein the content of the fluorine-containing emulsifier is 10 ppm by mass or less relative to the total mass of the fluorine-containing polymer.

[12] An injection-molded article characterized by being obtained by injection molding a fluorine-containing polymer produced by a method for producing a fluorine-containing polymer described in any of [1] to [6], or a fluorine-containing polymer described in any of [7] to

[11] .

[13] A coated electric wire comprising a core wire and a coating layer provided around the core wire, wherein the coating layer is obtained by molding a fluorine-containing polymer produced by a method for producing a fluorine-containing polymer described in any of [1] to [6], or a fluorine-containing polymer described in any of [7] to

[11] .

[14] A molded article obtained by molding a fluorine-containing polymer produced by a method for producing a fluorine-containing polymer described in any of [1] to [6], or a fluorine-containing polymer described in any of [7] to

[11] , wherein the molded article is a microtube, a container, a piping member, or an electric wire coating material.

[0008] According to the present invention, a method for producing a fluorine-containing polymer that can form molded articles with excellent ozone resistance can be provided. Furthermore, according to the present invention, a fluorine-containing polymer that can form molded articles with excellent ozone resistance, an injection-molded article, a coated wire, and a molded article can be provided.

[0009] The meanings of the terms in this specification are as follows. A numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In the numerical ranges described step by step in this specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced by the upper limit value or the lower limit value of the numerical range described in other step-by-step descriptions. Also, in the numerical ranges described in this specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced by the value shown in the examples. In this specification, each component may be used alone as one kind of the substance corresponding to each component, or two or more kinds may be used in combination. Here, when two or more kinds of substances are used in combination for each component, the content of that component refers to the total content of the substances used in combination, unless otherwise specified. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, the term "step" is not construed as only an independent step, and even if it cannot be clearly distinguished from other steps, as long as the intended purpose of that step is achieved, it is included in this term.

[0010] "Unit" is a general term for an atomic group directly formed by polymerization of monomers and derived from one molecule of the above monomers, and an atomic group obtained by chemically converting a part of the above atomic group. In the following, in some cases, the unit derived from each monomer is denoted by a name obtained by adding "unit" to the monomer name.

[0011] "Specific functional group" means a functional group included in the group consisting of -CF=CF ２ , -CF ２ H, -COF, -COOH, -COOCH ３ , -CONH ２ and -CH ２ OH. Also, "number of functional groups" means the total number of specific functional groups possessed by the fluorine-containing polymer, unless otherwise specified. "Solvent" means a substance that is liquid at 25°C and 1013 hPa. The pressure in this specification is absolute pressure.

[0012] [First Embodiment: Method for Producing Fluorine-Containing Polymers] The method for producing fluorine-containing polymers according to the first embodiment of the present invention (hereinafter also referred to as "this production method") involves polymerizing tetrafluoroethylene (hereinafter also referred to as "TFE") and perfluoro(alkylallyl ether) (hereinafter also referred to as "PAAE") in a reaction system containing water with an electrical resistivity of 15.0 MΩ·cm or more, and substantially free of both a fluorine-containing emulsifier and sulfate ions, to obtain a fluorine-containing polymer, and then performing a fluorination treatment on the obtained fluorine-containing polymer.

[0013] This manufacturing method makes it possible to produce fluorine-containing polymers capable of forming molded articles with excellent ozone resistance. Although the detailed reasons for this are not yet clear, it is presumed to be due to the following: In this manufacturing method, TFE and PAAE are polymerized in a reaction system containing water with an electrical resistivity of 15.0 MΩ·cm or higher, thus enabling the production of fluorine-containing polymers with a lower metal content. Furthermore, when a fluorine-containing polymer contains sulfate ions, it is thought that metal ions may leach from components in contact with the fluorine-containing polymer in the polymerization reactor used to produce the polymer, as well as from components in equipment used to form molded articles, such as kneaders used for melt-kneading the fluorine-containing polymer, thereby increasing the metal content in the fluorine-containing polymer. In contrast, since the reaction system in this manufacturing method substantially does not contain sulfate ions, the metal content in the fluorine-containing polymer is suppressed. Thus, it is presumed that using a fluorine-containing polymer with a lower metal content results in the formation of molded articles with excellent ozone resistance. It has also been found that fluorine-containing emulsifiers contained in the fluorine-containing polymer may affect the ozone resistance of the molded articles. In this manufacturing method, TFE and PAAE are polymerized in a reaction system that is substantially free of fluorine-containing emulsifiers. Therefore, it is possible to produce a fluorine-containing polymer that does not contain fluorine-containing emulsifiers, and it is presumed that molded articles with excellent ozone resistance can be formed using this fluorine-containing polymer. Furthermore, by performing a fluorination treatment after polymerizing TFE and PAAE, the number of specific functional groups in the fluorine-containing polymer can be reduced, and the oxidative decomposition of these specific functional groups by ozone can be suppressed, thus it is presumed that molded articles with excellent ozone resistance can be formed.

[0014] The manufacturing method will be described in detail below. In this specification, a reaction system containing water with an electrical resistivity of 15.0 MΩ·cm or more, and substantially free of both fluorine-containing emulsifiers and sulfate ions, is also referred to as a "specific reaction system," and the step of polymerizing TFE and PAAE in the specific reaction system to obtain a fluorine-containing polymer is also referred to as the "polymerization step." Furthermore, the fluorine-containing polymer obtained by the polymerization step, before fluorination treatment, is also referred to as the "untreated polymer."

[0015] <Polymerization Process> In the polymerization process of this manufacturing method, a fluorine-containing polymer (untreated polymer) is obtained by polymerizing monomers containing TFE and PAAE in a specific reaction system containing water with an electrical resistivity of 15.0 MΩ·cm or more. Polymerization methods for polymerizing monomers in the specific reaction system include solution polymerization, suspension polymerization, and emulsion polymerization, with solution polymerization being preferred.

[0016] In the polymerization process, monomers containing at least TFE and PAAE are used for polymerization of the fluorine-containing polymer. The monomer represented by the following formula (1) is preferred as the PAAE: CF ２ = CF - CF ２ -O-Rf (1) In formula (1), Rf represents a perfluoroalkyl group having 1 to 10 carbon atoms. The perfluoroalkyl group represented by Rf may have an etheric oxygen atom between carbon atoms. The number of carbon atoms in the perfluoroalkyl group represented by Rf is preferably 1 to 8, more preferably 1 to 6, even more preferably 1 to 5, and particularly preferably 1 to 3, in terms of superior polymerization reactivity. The perfluoroalkyl group may be linear or branched. When the perfluoroalkyl group has an etheric oxygen atom between carbon atoms, the number of etheric oxygen atoms is preferably 1 to 3, more preferably 1 or 2. It is preferable that the perfluoroalkyl group does not have an etheric oxygen atom. Specific examples of PAAEs include perfluoro(methyl allyl ether), perfluoro(ethyl allyl ether), and perfluoro(propyl allyl ether).

[0017] The ratio of the amount of TFE added to the amount of PAAE added to the specific reaction system during the polymerization process is appropriately adjusted depending on the composition of the target fluorine-containing polymer. For example, the amount of TFE added to the total amount of TFE and PAAE added is preferably 5 to 50% by mass, and more preferably 10 to 45% by mass. In this manufacturing method, the "amount added" of components such as monomers during the polymerization process refers to the total amount of the component added to the specific reaction system during the polymerization process, and does not refer to the amount of the component present in the specific reaction system at any given moment. For example, when TFE is added to the specific reaction system continuously or intermittently, the total amount of TFE added to the specific reaction system during the polymerization process is considered the amount of TFE added. In addition, in this specification, "total mass of the reaction system (or specific reaction system)" refers to the total amount of all components added to the reaction system (or specific reaction system) during the polymerization process.

[0018] In the polymerization process, other monomers polymerizable with TFE and PAAE may be used in addition to TFE and PAAE, and the fluorine-containing polymer obtained by the polymerization process may have units based on other monomers. Examples of other monomers include ethylene, perfluoro(alkyl vinyl ether) (PAVE), vinylidene fluoride (VdF), hexafluoropropylene (HFP), and CX. １ X ２ = CX ３ (CF ２ ) ｎ X ４ (In the formula, X １ , X ２ and X ３ Each of these independently represents either a hydrogen atom or a fluorine atom, and X ４ ) represents a hydrogen atom, a fluorine atom, or a chlorine atom, and n represents an integer from 1 to 10. ) Monomers represented by CF ２ = CF - OCH ２ -Rf ２ (wherein, Rf ２) represents a perfluoroalkyl group having 1 to 5 carbon atoms. Examples of monomers include those represented by ). PAVE is preferred as another monomer. When other monomers are used in the polymerization process, the amount of other monomers added to the specific reaction system is preferably less than 20.0% by mass, and more preferably less than 10.0% by mass, relative to the total amount of monomers added to the specific reaction system. When PAVE is used as another monomer in the polymerization process, the amount of PAVE added to the specific reaction system is preferably less than 20.0% by mass, preferably 1.0 to 10.0% by mass, and more preferably 3.0 to 7.0% by mass, relative to the total amount of monomers added to the specific reaction system.

[0019] In the polymerization process, the total amount of TFE and PAAE added to the specific reaction system is preferably 80.0 to 100.0% by mass, and more preferably 90 to 100.0% by mass, relative to the total amount of monomers added to the specific reaction system. In the polymerization process, it is preferable not to use the other monomers mentioned above for polymerization of the fluorine-containing polymer, and instead to polymerize a fluorine-containing polymer consisting of TFE and PAAE. In this case, the total content of TFE units and PAAE units relative to the total units contained in the fluorine-containing polymer obtained by the polymerization process is 100.0% by mass.

[0020] The specific reaction system includes water with an electrical resistivity of 15.0 MΩ·cm or higher. Electrical resistivity is also called "specific resistivity," and its unit is "MΩ·cm." The electrical resistivity of water can be obtained by measuring the electrical resistivity of water at 25°C using a highly sensitive resistivity measuring device for ultrapure water. The electrical resistivity of water can be adjusted by the content of conductive components such as metal components and metal ions contained in the water.

[0021] The electrical resistivity of the water contained in the specific reaction system is preferably 16.0 MΩ·cm or higher, in that it is possible to form a molded body with superior ozone resistance. The electrical resistivity of the water may be, for example, 20.0 MΩ·cm or lower. The water content in the specific reaction system may be, for example, 5 to 80% by mass, and preferably 15 to 70% by mass, relative to the total mass of the specific reaction system.

[0022] The specified reaction system is substantially free of fluorine-containing emulsifiers. In this specification, "substantially free of fluorine-containing emulsifiers" means that the content of fluorine-containing emulsifiers is 10 ppm by mass or less relative to the total mass of the reaction system. Preferably, the content of fluorine-containing emulsifiers is 1 ppm by mass or less, and more preferably 0.1 ppm by mass or less, relative to the total mass of the specified reaction system. Furthermore, it is also preferable that the content of fluorine-containing emulsifiers in the specified reaction system is below the quantification limit of the measurement method described later.

[0023] The amount of fluorine-containing emulsifier in the reaction system can be calculated from the composition and amount of raw materials used in the preparation of the reaction system. A reaction system prepared without the addition of fluorine-containing emulsifier can be said to be substantially free of fluorine-containing emulsifier. Furthermore, the amount of fluorine-containing emulsifier in the reaction system can also be measured by performing LC-MS analysis using the reaction system as the object of measurement instead of the extract, in the method for measuring the amount of fluorine-containing emulsifier in fluorine-containing polymers described in the examples below.

[0024] Examples of fluorine-containing emulsifiers include the compound represented by formula (S1) and the compound represented by formula (S2). F-(CF ２ ) ｎ１ -COOM Ｓ (S1) F-(CF ２ ) ｎ２ -SO ３ M Ｓ (S2) In equations (S1) and (S2), M Ｓ These are hydrogen atoms, metal atoms, and NR ４ , represents an imidazolium group which may have substituents, a pyridinium group which may have substituents, or a phosphonium group which may have substituents. R may be the same or different, and represents a hydrogen atom or an organic group having 1 to 10 carbon atoms.

[0025] Furthermore, the specific reaction system is substantially free of sulfate ions. Substantially free of sulfate ions means that the sulfate ion content is 10 ppm by mass or less relative to the total mass of the reaction system. Preferably, the sulfate ion content is 1 ppm by mass or less, and more preferably 0.1 ppm by mass or less, relative to the total mass of the specific reaction system. It is also preferable that the sulfate ion content in the specific reaction system is below the quantification limit of the measurement method described later.

[0026] The sulfate ion content in the reaction system can be calculated from the composition and amount of raw materials used in its preparation. If sulfate ions are not used in the polymerization process, the reaction system can be said to be substantially sulfate-free. Furthermore, the sulfate ion content in the reaction system can also be quantified by ion chromatography.

[0027] In the polymerization step of this manufacturing method, the specific reaction system may include, in addition to monomers containing TFE and PAAE and water with an electrical resistivity of 15.0 MΩ·cm or more, a polymerization initiator, a polymerization medium other than water, and a chain transfer agent.

[0028] In the polymerization process, it is preferable to polymerize the monomer in a specific reaction system further containing a polymerization initiator. The polymerization initiator is preferably a radical polymerization initiator with a half-life of 10 hours and a temperature of 0 to 100°C, and more preferably a radical polymerization initiator with the above temperature of 20 to 90°C. Specific examples of polymerization initiators include the various polymerization initiators exemplified in International Publication No. 2013 / 015202.

[0029] Polymerization initiators include oil-soluble radical initiators, water-soluble radical initiators, and water-soluble redox catalysts. Oil-soluble radical initiators include oil-soluble organic peroxides such as heptafluorobutyroyl peroxide (PFB), tert-butyl peroxypivalate, and diisopropyl peroxydicarbonate. Water-soluble radical initiators include water-soluble organic peroxides such as disuccinic acid peroxide, bisglutaric acid peroxide, and tert-butyl hydroperoxide (hereinafter also referred to as "TBHP"). Water-soluble redox catalysts include combinations of oxidizing agents such as bromate or its salts, chloric acid or its salts, persulfuric acid or its salts, permanganic acid or its salts, and hydrogen peroxide, and reducing agents such as sulfurous acid or its salts, bisulfite or its salts, thiosulfuric acid or its salts, and organic acids. Oil-soluble radical initiators or water-soluble radical initiators are preferred as polymerization initiators, with oil-soluble radical initiators being more preferred and oil-soluble organic peroxides being even more preferred in that they allow for more efficient production of fluorine-containing polymers.

[0030] The polymerization initiator may be used alone or in combination of two or more types. The amount of polymerization initiator added in the polymerization process is preferably 0.01 to 0.9 parts by mass, and more preferably 0.05 to 0.5 parts by mass, per 100 parts by mass of monomer added.

[0031] The specific reaction system may further contain a polymerization medium other than water. Examples of other polymerization mediums include organic solvents. Fluorine-based solvents such as perfluorocarbons, hydrofluorocarbons, and hydrofluoroethers can be used as organic solvents. Specific examples of organic solvents include the polymerization media exemplified in International Publication No. 2013 / 015202.

[0032] Other polymerization media may be used alone or in combination of two or more. When a particular reaction system contains other polymerization media (e.g., a fluorinated solvent), the amount of other polymerization media added is preferably 1 to 70% by mass, and more preferably 3 to 60% by mass, relative to the amount of water added, in terms of suspendability and economic efficiency. The amount of polymerization media added in the polymerization step is preferably 3 times or more by mass relative to the amount of monomer added, more preferably 5 times or more, and preferably 20 times or less, and more preferably 17 times or less. The amount of polymerization media added is the sum of the amounts of water and other polymerization media added when other polymerization media are used, and is the amount of water added when other polymerization media are not used.

[0033] The specific reaction system preferably further contains a chain transfer agent. Suitable chain transfer agents include alcohols such as methanol, ethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoropropanol, 1,1,1,3,3,3-hexafluoroisopropanol and 2,2,3,3,3-pentafluoropropanol, which have a large chain transfer constant and require only small amounts; hydrocarbons such as n-pentane, n-hexane and cyclohexane; and CF ２ H ２ Hydrofluorocarbons such as acetone; ketones such as methyl mercaptan; esters such as methyl acetate and ethyl acetate; and ethers such as diethyl ether and methyl ethyl ether are preferred. Among these, at least one selected from the group consisting of alcohols, hydrocarbons, and hydrofluorocarbons is preferred, at least one selected from the group consisting of alcohols and hydrocarbons is more preferred, and alcohols are even more preferred, in terms of having a higher chain transfer constant and high stability of the terminal groups of the fluorine-containing polymer. As for alcohols, methanol or ethanol is preferred, and methanol is more preferred in terms of reactivity and availability. Two or more chain transfer agents may be used. The amount of chain transfer agent added is preferably 0.001 times or more by mass ratio of the amount of monomer added, more preferably 0.005 times or more, preferably 5 times or less, and more preferably 4 times or less.

[0034] The polymerization temperature is preferably 15 to 90°C, more preferably 20 to 80°C, and even more preferably 25 to 70°C. If the polymerization temperature is 15°C or higher, excellent polymerizability can be obtained. If the polymerization temperature is 90°C or lower, the productivity of the fluorine-containing polymer can be improved. The polymerization pressure is preferably 0.5 to 3.0 MPa, and more preferably 0.9 to 2.5 MPa. The polymerization time is preferably 1 to 12 hours.

[0035] If polymerization yields an aqueous dispersion containing the untreated polymer, the untreated polymer can be recovered by coagulating the fluorine-containing polymer in the aqueous dispersion, washing, and drying. Alternatively, if polymerization yields the untreated polymer as a slurry, the untreated polymer can be recovered by removing the slurry from the reaction vessel, washing, and drying.

[0036] <Fluorination Treatment> In this manufacturing method, the untreated polymer obtained in the polymerization step is subjected to fluorination treatment. Fluorination treatment removes the -COOH and -COOCH groups present in the untreated polymer. ３ ien-CH ２ OH, -COF, -CF=CF ２ , -CONH ２ and -CF ２ A specific functional group consisting of H, -CF ３ This allows for conversion to a specific functional group, thereby reducing the number of functional groups in the fluorinated polymer and allowing for adjustment of the number of functional groups in the fluorinated polymer. Examples of fluorination treatments include contacting an untreated polymer with a fluorine-containing compound. The untreated polymer to be fluorinated may be in powder, pellet, or granular form.

[0037] Examples of fluorine-containing compounds include fluorine radical sources that generate fluorine radicals under fluorination treatment conditions. Examples of the above-mentioned fluorine radical source include F ２ Gas, N ２ F ２ Also, halogen fluorides (for example, IF ５ and CLF ３ Examples include F. ２ The concentration of fluorine radical sources such as gases may be 100% by volume. In terms of safety, F ２It is preferable to use a mixed gas obtained by diluting the gas with an inert gas so that the gas concentration is 5 to 50 volume percent (more preferably 15 to 30 volume percent). Examples of the inert gas include nitrogen gas, helium gas, and argon gas, and nitrogen gas is preferred from an economic standpoint.

[0038] The treatment temperature in the fluorination treatment is preferably below the melting point of the fluorine-containing polymer, more preferably 20 to 240°C, and even more preferably 100 to 235°C. The fluorination treatment may be carried out by bringing a molten copolymer into contact with a fluorine-containing compound. A specific method of the fluorination treatment is, for example, to place a shelf on which copolymer pellets are placed inside an oven and heat the inside of the oven with F ２ One method involves filling the column with gas or a mixed gas and heating it for a certain period of time. Another method involves heating a flow-through column packed with copolymer pellets while flowing gas or the mixed gas through the column for a certain period of time. The processing time for the fluorination treatment is appropriately changed depending on the number of functional groups in the untreated polymer before fluorination, the number of functional groups to be used, and the fluorination treatment method, but is, for example, 0.5 to 30 hours, with 1 to 24 hours being preferred.

[0039] <Fluorine-containing polymer> The fluorine-containing polymer obtained by this manufacturing method contains at least TFE units and PAAE units.

[0040] The TFE unit content is preferably 95.0 to 99.5 mol%, more preferably 95.5 to 99.5 mol%, and even more preferably 96.0 to 99.5 mol%, relative to the total units contained in the fluorine-containing polymer.

[0041] The PAAE unit content is preferably 0.2 to 5.0 mol%, more preferably 0.2 to 3.0 mol%, even more preferably 0.3 to 2.0 mol%, and particularly preferably 0.5 to 2.0 mol%, relative to the total units contained in the fluorine-containing polymer. The fluorine-containing polymer may contain two or more types of PAAE units. When the fluorine-containing polymer contains two or more types of PAAE units, it means that the total content of the two or more types of PAAE units is within the above range. Preferred PAAE units include units based on the compounds listed as preferred examples of PAAEs to be polymerized in the polymerization process.

[0042] The fluorine-containing polymer may contain units based on other monomers in addition to TFE units and PAAE units. The other monomers are as described above, including preferred embodiments. When the fluorine-containing polymer contains units based on other monomers, the content of these units is preferably less than 4.5 mol%, more preferably less than 2.5 mol%, more preferably less than 1.0 mol%, and particularly preferably less than 0.5 mol%, relative to the total units contained in the fluorine-containing polymer. For example, when the fluorine-containing polymer contains PAVE units in addition to TFE units and PAAE units, the content of PAVE units is preferably 0 to 3.0 mol%, more preferably 0.1 to 2.0 mol%, and even more preferably 0.2 to 1.8 mol%, relative to the total units contained in the fluorine-containing polymer. It is preferable that the fluorine-containing polymer does not contain units based on the other monomers.

[0043] In a fluorinated polymer, the total content of TFE units and PAAE units is preferably 95.5 to 100.0 mol%, more preferably 97.5 to 100.0 mol%, and even more preferably 98.0 to 100.0 mol%, relative to the total units contained in the fluorinated polymer. Preferably, the fluorinated polymer contains only TFE units and PAAE units. In this case, the total content of TFE units and PAAE units is 100.0 mol% relative to the total units contained in the fluorinated polymer.

[0044] The respective contents of TFE units, PAAE units, and other monomer-based units in fluorine-containing polymers are:１９ It can be measured by known methods such as F-NMR (nuclear magnetic resonance analysis).

[0045] (Number of functional groups) Fluorine-containing polymers can form molded articles with superior ozone resistance, and -CF = CF ２ , -CF ２ H, -COF, -COOH, -COOCH ３ , -CONH ２ and -CH ２ The total number of specific functional groups (number of functional groups) in the group consisting of OH is equal to the carbon number of the fluorine-containing polymer. ６ The number of functional groups per unit is preferably less than 150, more preferably less than 50, even more preferably less than 20, and particularly preferably 10 or less. The number of functional groups may be 0.

[0046] Specific functional groups are functional groups present at the ends of the main chain or side chains of the fluorine-containing polymer, and functional groups present in the main chain or side chains. The number of functional groups is the sum of the number of specific functional groups. Specific functional groups are introduced into the fluorine-containing polymer, for example, by chain transfer agents or polymerization initiators used in the production of the fluorine-containing polymer. More specifically, this includes cases where an alcohol is used as a chain transfer agent, or where -CH is used as a polymerization initiator. ２ When using a peroxide having an OH structure, -CH is added to the main chain end of the fluorine-containing polymer. ２ An OH group is introduced. Furthermore, by polymerizing a monomer having a functional group, the above functional group is introduced to the side chain end of the fluorine-containing polymer. Through the above fluorination treatment, the specific functional group is introduced to -CF ３ By converting to terminal groups, the number of functional groups in the fluorinated polymer can be reduced. The number of functional groups in the fluorinated polymer can be adjusted by changing the conditions of the fluorination treatment (e.g., treatment time, etc.).

[0047] Infrared spectroscopy can be used to identify the types of functional groups and measure the number of functional groups in fluorinated polymers. Specifically, the number of functional groups is measured by the following method. First, a fluorinated polymer is molded by hot pressing at 330°C to produce a film with a thickness of 0.30 to 0.35 mm. This film is analyzed by Fourier transform infrared spectroscopy to obtain the infrared absorption spectrum of the fluorinated polymer. Separately, an infrared absorption spectrum (base spectrum) is obtained from a completely fluorinated polymer that does not contain specific functional groups, and the difference spectrum between the infrared absorption spectrum and the base spectrum of the fluorinated polymer is obtained. From the absorption peak of the specific functional group appearing in this difference spectrum, the number of carbon atoms in the fluorinated polymer is determined according to the following formula (A). ６ Calculate the number of functional groups N per individual.

[0048] N = I × K / t (A) I: Absorbance K: Correction factor t: Film thickness (mm)

[0049] Table 1 shows the absorption frequency, molar extinction coefficient, and correction factor for specific functional groups. The molar extinction coefficient of specific functional groups is determined from FT-IR (Fourier transform infrared spectroscopy) measurement data of low-molecular-weight model compounds.

[0050]

[0051] Furthermore, in fluorine-containing polymers, -CH ２ CF ２ H, -CH ２ COF, -CH ２ COOH, -CH ２ COOCH ３ and -CH ２ CONH ２ The absorption frequency is -CF shown in the table. ２ H, -COF, -COOH (free and bonded), -COOCH ３ , and also, -CONH ２ From each absorption frequency, several tens of kaiser (cm －１ ) becomes lower. For example, the number of -COF is -CF ２ The absorption frequency due to COF is 1883 cm⁻¹. －１The number of functional groups determined from the absorption peak, and -CH ２ The absorption frequency due to COF is 1840 cm⁻¹. －１ This is the sum of the number of functional groups determined from the absorption peaks.

[0052] It is preferable that the fluorine-containing polymer is substantially free of fluorine-containing emulsifiers. In this specification, "substantially free of fluorine-containing emulsifiers" means that the content of fluorine-containing emulsifiers is 10 ppm by mass or less relative to the total mass of the fluorine-containing polymer. The content of fluorine-containing emulsifiers in the fluorine-containing polymer is preferably 1 ppm by mass or less, and more preferably 0.1 ppm by mass or less, relative to the total mass of the fluorine-containing polymer. The content of fluorine-containing emulsifiers may be 0 ppb by mass relative to the total mass of the solids.

[0053] The content of fluorinated emulsifiers in fluorinated polymers can be measured by extracting the fluorinated emulsifier-containing components from the fluorinated polymer using an alcohol solvent such as methanol, and then analyzing the extract using a liquid chromatography / mass spectrometry (LC-MS) instrument. A more specific method for measuring the fluorinated emulsifier content in the extract is as follows.

[0054] First, methanol standard solutions are prepared for five or more levels of fluorine-containing emulsifiers, each containing a fluorine-containing emulsifier within the range of 2 to 180 ng / g, using the fluorine-containing emulsifier to be measured. From the concentrations of each standard solution and the integral value of the peak area detected by LC-MS analysis, a straight line passing through the origin and represented by the following equation (A1) is derived by a linear approximation, and the slope a is determined. A = a × x (A1) In equation (A1), A represents the peak area of ​​the detected fluorine-containing emulsifier, and x represents the concentration of the fluorine-containing emulsifier (ng / g) relative to the total mass in the methanol standard solution.

[0055] Next, an extract containing a fluorine-containing emulsifier is prepared from the fluorine-containing polymer using the method described above. Specific examples of the extraction method for extracting a fluorine-containing emulsifier from a fluorine-containing polymer are described in the examples below. The obtained extract is subjected to LC-MS analysis using multiple reaction monitoring (MRM) to determine the peak area of ​​each fluorine-containing emulsifier. Table 2 below shows an example of the measuring instruments and measurement conditions used for LC-MS analysis by MRM. The MRM measurement parameters are appropriately selected according to the fluorine-containing emulsifier being measured. Literature values ​​may be used as MRM measurement parameters, or they may be determined using an LC-MS instrument. When determining MRM measurement parameters using an LC-MS instrument, for example, by selecting product ion search using the LC-MS instrument, inputting the molecular weight of the fluorine-containing emulsifier being measured, and performing precursor ion, precursor adjustment, voltage optimization, and product m / z optimization, the MRM measurement parameters for the target are calculated. As an example, the MRM measurement parameters of compounds contained in fluorine-containing emulsifiers are shown in Tables 3 and 4.

[0056]

[0057]

[0058]

[0059] Next, the amount of fluorine-containing emulsifier of each carbon number contained in the extract is calculated using the following formula (A2): XCm = ACm / a (A2) In formula (A2), XCm represents the amount of fluorine-containing emulsifier of each carbon number contained in the extract (ng / g), ACm represents the peak area of ​​the fluorine-containing emulsifier of each carbon number detected by LC-MS analysis of the extract, and a represents the slope a obtained by formula (A1) above. Note that the limit of quantification in the above LC-MS analysis is approximately 1 ng / g.

[0060] Next, the content of the fluorine-containing emulsifier relative to the total mass of the fluorine-containing polymer (ZCm) is determined using the following formula (A3): ZCm = XCm × ρ1 × La / W1 (A3) In formula (A3), ZCm represents the content of the fluorine-containing emulsifier for each carbon number in the fluorine-containing polymer, ρ1 represents the density of the extraction solvent (e.g., methanol), La represents the volume of the extraction solvent, and W1 represents the mass of the fluorine-containing polymer contained in the extract. The total content of the fluorine-containing emulsifier in the fluorine-containing polymer is determined by summing the content of the fluorine-containing emulsifier for each carbon number (ZCm) obtained from formula (A3).

[0061] (Metal ion elution amount) The amount of metal ions eluted from the fluorine-containing polymer is preferably 250 ppb by mass or less, more preferably 100 ppb by mass or less, and even more preferably 50 ppb by mass or less, relative to the total mass of the fluorine-containing polymer, in order to form a molded article with superior ozone resistance. The amount of metal ions eluted from the fluorine-containing polymer may also be below the detection limit of the measurement method described later.

[0062] In this manufacturing method, monomers are polymerized in a reaction system that is substantially free of both fluorine-containing emulsifiers and sulfate ions, resulting in a fluorine-containing polymer with reduced metal ion elution. Furthermore, by using components with a low metal content in this manufacturing method, a fluorine-containing polymer with even lower metal ion elution can be produced.

[0063] The amount of metal ions eluted from fluorine-containing polymers is determined by quantifying the content of metal ions in a sample solution obtained after immersing the fluorine-containing polymer in hydrochloric acid using an inductively coupled plasma mass spectrometer and the absolute calibration curve method, and then summing up the individual content amounts. The metal ions measured are those of lead (Pb), cadmium (Cd), silver (Ag), zinc (Zn), copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn), chromium (Cr), titanium (Ti), calcium (Ca), potassium (K), aluminum (Al), magnesium (Mg), sodium (Na), and lithium (Li). Details of the method for measuring the amount of metal ions eluted from fluorine-containing polymers are described in the examples below.

[0064] (Melt Flow Rate: MFR) The MFR of a fluorinated polymer is, for example, 0.5 to 100.0 g / 10 min, and is preferably 1.0 to 50.0 g / 10 min, more preferably 3.0 to 45.0 g / 10 min, particularly preferably 3.0 to 25.0 g / 10 min, and very preferably 3.0 to 12.0 g / 10 min, in order to form a molded article with a good balance of folding resistance and flexural strength. A specific example of a method for bringing the MFR of a fluorinated polymer within the above range is to adjust the molecular weight of the fluorinated polymer. The larger the molecular weight of the fluorinated polymer, the smaller the MFR. The MFR of a fluorinated polymer is measured in accordance with ASTM D1238, under conditions of a temperature of 372°C and a load of 5 kg, and represents the mass (g) of the fluorinated polymer flowing out of an orifice with a diameter of 2 mm and a length of 8 mm in 10 minutes.

[0065] (Melting Point) The melting point of the fluorine-containing polymer is preferably 280°C or higher, more preferably 285°C or higher, even more preferably 290°C or higher, and preferably 325°C or lower, more preferably 320°C or lower, and even more preferably 315°C or lower. A specific example of a method to bring the melting point of the fluorine-containing polymer within the above range is to adjust the composition of the fluorine-containing polymer. The melting point of the fluorine-containing polymer is the temperature corresponding to the endothermic peak when the fluorine-containing polymer is heated in an air atmosphere at a rate of 10°C / min using a scanning differential thermal analyzer.

[0066] The fluorine-containing polymer produced by this manufacturing method may take any form, such as powder, pellets, or granules. The powdered fluorine-containing polymer may be primary particles or secondary particles formed by aggregation of primary particles. When the fluorine-containing polymer is in pellet form, a molded product with a diameter or length of 1 to 10 mm is preferred. The shape of the pelletized fluorine-containing polymer is not limited, but it is usually spherical, ellipsoidal, or cylindrical.

[0067] Pelletized fluorine-containing polymers can be molded by conventionally known methods. One method for molding pelletized fluorine-containing polymers is to extrude the fluorine-containing polymer while melting it using a melt kneader such as a single-screw extruder, twin-screw extruder, or tandem extruder, and then cut it to a predetermined length to form pellets. The extrusion temperature in melt extrusion is appropriately changed depending on the melt viscosity of the fluorine-containing polymer and the manufacturing method, but is preferably between +20°C and +140°C above the melting point of the fluorine-containing polymer. Conventional methods such as strand cutting, hot cutting, underwater cutting, and sheet cutting can be used to cut the fluorine-containing polymer.

[0068] The composition containing the fluorine-containing polymer obtained by the polymerization process may also contain other components besides the fluorine-containing polymer. Specific examples of such other components include other resins besides the fluorine-containing polymer, heat stabilizers, antioxidants, colorants, ultraviolet absorbers, fillers, crosslinking agents, crosslinking aids, and organic peroxides. When the above-mentioned other components are present, the content of the other components is preferably 0.0000001 to 5 parts by mass, more preferably 0.0000005 to 3 parts by mass, and even more preferably 0.000001 to 1 part by mass, per 100 parts by mass of the fluorine-containing polymer.

[0069] [Second Embodiment: Fluorine-containing Polymer] The fluorine-containing polymer according to the second embodiment of the present invention (hereinafter also referred to as "this polymer") is a fluorine-containing polymer having TFE units and PAAE units, wherein -CF=CF ２ , -CF ２ H, -COF, -COOH, -COOCH ３ , -CONH ２ and -CH ２ The total number of OH functional groups (number of functional groups) is equal to the number of carbon atoms in the main chain of the fluorine-containing polymer. ６ The number of functional groups per unit is less than 150, and the amount of metal ions eluted is 100 ppb by mass or less relative to the total mass of the fluorine-containing polymer. This polymer, with its functional group count and metal ion elution amount within the above range, can be used to form molded articles with excellent ozone resistance.

[0070] The composition, physical properties, and shape of this polymer are as follows: The number of functional groups is 10 carbon atoms in the main chain of this polymer. ６ Except for having fewer than 150 ions per unit and having a metal ion elution amount of 100 ppb by mass or less relative to the total mass of the polymer, the fluorine-containing polymer obtained by the manufacturing method according to the first embodiment of the present invention is as described, including preferred embodiments.

[0071] [Molded Article] The molded article is obtained by molding a fluorine-containing polymer produced by the manufacturing method according to the first embodiment of the present invention, or a fluorine-containing polymer according to the second embodiment of the present invention. Examples of molded articles include injection-molded articles obtained by injection molding of a fluorine-containing polymer, extruded articles obtained by extrusion molding, blow-molded articles obtained by blow molding, transfer-molded articles obtained by transfer molding, press-molded articles obtained by press molding, rotationally molded articles obtained by rotational molding, and coatings obtained by electrostatic coating. Press-molded articles obtained by press molding of a fluorine-containing polymer are preferred as molded articles. Injection-molded articles of fluorine-containing polymers are also preferred because they can be obtained with a beautiful appearance without corroding the mold used for molding.

[0072] Specific examples of molded products include nuts, bolts, fittings, films, bottles, gaskets, wire insulation materials, tubes, hoses, pipes, valves, seats, seals, packings, tanks, rollers, containers, cocks, connectors, filter housings, filter cages, flow meters, pumps, wafer carriers, and wafer boxes.

[0073] [Applications] The fluorine-containing polymer produced by the manufacturing method according to the first embodiment of the present invention, the fluorine-containing polymer according to the second embodiment of the present invention, and the molded articles can be used for the following applications. Fluid transfer components for food manufacturing equipment, such as food packaging films, lining materials, packings, seals, and sheets for fluid transfer lines used in food manufacturing processes; chemical stoppers, packaging films, lining materials, packings, seals, and sheets for fluid transfer lines used in pharmaceutical manufacturing processes; internal lining materials for chemical tanks and piping in chemical plants or semiconductor factories; O-rings, tubes, packings, valve cores, hoses, and seals used in automobile fuel systems and peripheral equipment, as well as fuel transfer components such as hoses and seals used in automobile automatic transmission systems; carburetor flange gaskets, shaft seals, valve stem seals, seals, and hoses used in automobile engines and peripheral equipment, as well as other automobile components such as automobile brake hoses, air conditioning hoses, radiator hoses, and wire insulation materials; semiconductor components such as O-rings, tubes, packings, valve cores, hoses, seals, rolls, gaskets, diaphragms, and fittings for semiconductor manufacturing equipment. Examples include: chemical liquid transfer components for body equipment; paint and ink components such as paint rolls, hoses, tubes, and ink containers for painting equipment; food and beverage transfer components such as tubes or hoses for food and beverages, hoses, belts, gaskets, and fittings, as well as food packaging materials and glass cooking equipment; waste liquid transport components such as tubes and hoses for waste liquid transport; high-temperature liquid transport components such as tubes and hoses for high-temperature liquid transport; steam piping components such as tubes and hoses for steam piping; corrosion-resistant tapes for piping such as tapes wrapped around piping on ship decks, etc.; various coating materials such as wire coating materials, optical fiber coating materials, transparent surface coating materials and backing materials provided on the light incident side surface of photovoltaic elements of solar cells; sliding components such as diaphragms and various gaskets for diaphragm pumps; agricultural films, fuel cell carrier films, and weather-resistant covers for various roofing materials and side walls, etc.; interior materials used in the building sector, and coating materials for glass such as non-combustible fire-resistant safety glass; lining materials such as laminated steel sheets used in the home appliance sector, etc.

[0074] In particular, the molded body can be suitably used as piping components (e.g., pipes, fittings, gaskets, and packings), tubes (e.g., microtubes), and containers for transferring fluids in semiconductor manufacturing equipment. The molded body can also be suitably used as a wire coating material. A specific example of use is a coated wire comprising a core wire and a coating layer provided around the core wire, the coating layer being made of a molded body obtained by molding the fluorine-containing polymer. A coated wire with the coating layer has excellent electrical properties because the core wire is resistant to corrosion and the outer diameter hardly changes, and is suitably used as a high-frequency transmission cable, flat cable, and heat-resistant cable. Such a coated wire can be manufactured, for example, by melt-extruding a fluorine-containing polymer onto a core wire to form the coating layer.

[0075] Furthermore, the molded body can also be suitably used as a compressible member. A compressible member is a member used in a compressed and deformed state, and its size and shape are appropriately set according to the application. The shape of the compressible member may be, for example, annular. Also, the compressible member may have a circular, oval, or rounded-corner square shape in plan view, and may have a through hole in its center. The compressible member can be used as a piping member for transferring fluids. Furthermore, the compressible member can be used as a member for constituting a non-aqueous electrolyte battery, and is particularly suitable as a member used in contact with the non-aqueous electrolyte in a non-aqueous electrolyte battery. The compressible member can also be suitably used as a sealing member such as sealing gaskets and sealing packings, and as an insulating member 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 member may be a member used for both sealing and insulating purposes.

[0076] The present invention will be described in detail below with reference to examples. Examples 1 to 3, 7 and 8 are examples, and Examples 4 to 6 are comparative examples. However, the present invention is not limited to these examples. Various measurement and evaluation methods are as follows.

[0077] [Measurement] <Composition of fluorine-containing polymer> The content (mol%) of TFE units and PAAE units in the fluorine-containing polymer (or untreated polymer, the same applies hereinafter) obtained in each example is determined by melt １９ This was determined from F-NMR analysis.

[0078] <MFR> For each example of fluorine-containing polymer obtained, a melt indexer (manufactured by Technoseven Co., Ltd.) was used to measure the mass (g) of the fluorine-containing polymer flowing out of an orifice with a diameter of 2 mm and a length of 8 mm for 10 minutes under conditions of a temperature of 372°C and a load of 5 kg, in accordance with ASTM D1238, and this was defined as the MFR (g / 10 min).

[0079] <Number of Functional Groups N> The fluorine-containing polymers obtained in each example were molded by hot pressing at 340°C to produce films with a thickness of 0.30 to 0.35 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. Next, the fluorine-containing polymers obtained in each example were subjected to a fluorination treatment similar to the fluorination treatment performed in Example 1 described below for a long period of time (specifically 20 hours) to completely fluorinate them and prepare separate fluorine-containing polymers for each base that did not contain specific functional groups. Base films were then obtained in the same manner as above. Next, the difference spectrum between the infrared absorption spectrum of the film obtained by molding the fluorine-containing polymers in each example and the base spectrum of the base film was obtained. From the absorption peaks of the specific functional groups appearing in this difference spectrum, for each specific functional group, the number of carbon atoms in the main chain of the fluorine-containing polymer in the sample was determined according to formula (A) above. ６ The total number of specific functional groups per individual (number of functional groups N) was calculated.

[0080] <Metal Ion Elution Amount> The fluorine-containing polymers obtained in each example were pelletized using an extruder and kneader in the following manner. The copolymer was fed into the raw material supply port of a twin-screw extruder and subjected to melt kneading treatment (kneading conditions: cylinder temperature 280-380°C, die temperature 380°C). Next, the obtained molten material was extruded from the die head to form strands. After that, the strands were water-cooled in a cooling water bath and then cut with a pelletizer to obtain pellets. The specific equipment used for pellet production is shown below. Twin-screw extruder: Fully meshed co-rotating twin-screw extruder (φ32, Technovel Co., Ltd. "KZW32T W"). Vacuum degassing device: Water-sealed vacuum pump (Shinko Seiki Co., Ltd. "SW-25AS"). Strand die head: Technovel Co., Ltd. "STD321". Cooling water bath: Technovel Co., Ltd. "SCB250-2000". • Pelletizer: Technovel Corporation's "SCP-302".

[0081] High-purity hydrochloric acid (EL grade) was diluted with ultrapure water to prepare hydrochloric acid with a concentration of 3.6% by mass. A polypropylene container was washed three times with 3.6% by mass hydrochloric acid that had been preheated to 60°C. 10 g of the pellet sample and 20 mL of 3.6% by mass hydrochloric acid were placed in the washed polypropylene container, and the pellet sample was immersed in the hydrochloric acid at 25°C for 7 days. After immersion, the pellet sample was removed from the test solution containing hydrochloric acid, and the amount of metal components contained in the test solution was quantified using an inductively coupled plasma mass spectrometer (ICP-MS, Agilent 8900, manufactured by Agilent Technologies) based on the absolute calibration curve method. ICP-MS was used to quantify the amounts of each metal ion: lead (Pb), cadmium (Cd), silver (Ag), zinc (Zn), copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn), chromium (Cr), titanium (Ti), calcium (Ca), potassium (K), aluminum (Al), magnesium (Mg), sodium (Na), and lithium (Li). The total amount of these metal ions relative to the total mass of the pellet sample was calculated as the metal ion elution amount (unit: mass ppb) of the fluorine-containing polymer. In cases where metal ions of the same element existed with different valencies, the sum of the amounts of each metal ion was used as the elution amount for that element.

[0082] <Content of Fluorine-Containing Emulsifier in Fluorine-Containing Polymers> The fluorine-containing polymers obtained in each example were freeze-dried using a freeze-dried mill "Freezer Mill 6775" (manufactured by SPEX) under the following conditions. Before freeze-driing, 10% by mass of dibutylhydroxytoluene (BHT) was added to the total mass of the fluorine-containing polymer, and the resulting mixture was freeze-dried to obtain a pulverized powder. The freeze-dried conditions were: fluorine-containing polymer: 3 g, BHT: 0.3 g, Run time: 5 mins, Rate: 15 cps, Cycle: 3. 5 mL of methanol was added to 2.5 g of the obtained pulverized powder. The resulting mixture was subjected to sonication at 50°C for 2 hours and centrifugation (5000 rpm, 5 minutes) to settle the fluorine-containing polymer contained in the pulverized powder, and the supernatant was collected as an extract. LC-MS analysis was performed on each extract according to the method described above, and the total amount of fluorine-containing emulsifier in the fluorine-containing polymer obtained in each example was determined.

[0083] <Electrical Resistivity of Water> Using a portable conductivity meter (HI98197, manufactured by Hanna Instruments Japan), the electrical resistivity of the water used in each example was measured at 25°C before being added to the reaction system.

[0084] [Evaluation Test] <Ozone Resistance> The fluorine-containing polymer produced in each example was compression-molded at 340 °C to prepare a sheet with a thickness of 1 mm. The obtained sheet was cut into a size of 10 mm × 20 mm and used as a sample for the ozone exposure test. A test apparatus was prepared in which an ozone generator (trade name: SGX-A11MN (modified), manufactured by Sumitomo Seiki Co., Ltd.), a PFA container filled with ion-exchanged water, and a PFA cell containing the sample were connected in this order. Ozone gas (volume ratio of ozone / oxygen = 10 / 90) generated by the ozone generator was bubbled in ion-exchanged water to add water vapor to the ozone gas. The obtained wet ozone gas was passed through the PFA cell containing the sample at a rate of 0.7 liter / min to expose the sample to the wet ozone gas. In the ozone exposure test, the temperature was maintained at 40 °C and the humidity was maintained at 80% RH. After 180 days from the start of the ozone exposure test, the sample was taken out and the surface of the sample was gently rinsed with ion-exchanged water. Then, the surface of the sample was photographed using a laser microscope, and the number of blisters with a major diameter of 1 μm or more was counted. The major diameter of the blister means the maximum diameter of the blister as viewed from the normal direction of the sample surface. Based on the following evaluation criteria, the ozone resistance of each fluorine-containing polymer was evaluated from the counted number of blisters.

[0085] (Ozone Resistance Evaluation Criteria) ○: The number of blisters is 10 / mm ２ or less △: The number of blisters is more than 10 / mm ２ and less than 100 / mm ２ ×: The number of blisters is more than 100 / mm ２ and more <00>

[0086] <Flex resistance> In accordance with ASTM D2176, a flex fatigue test was conducted using the MIT method, which is known as a method for evaluating stress crack resistance. The fluoropolymer produced in each example was compression-molded at 340 °C to produce a film with a thickness of 0.23 mm. From the obtained film with a thickness of 0.23 mm, a rectangular test piece with a width of 12.5 mm and a length of 130 mm was cut out. The obtained test piece was attached to a MIT flex fatigue measuring machine (manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the test piece was bent under the conditions of a load of 1.25 kg, a left and right bending angle of 135 degrees each, and a bending frequency of 175 times / min, and the number of bends (flex resistance) until the test piece was cut was measured. The larger the measured flex resistance, the better the flex resistance of the film.

[0087] [Example 1] In a 1.3 L stainless steel pressure reactor, a fluorine-based solvent (trade name: Asahiklin AE3000, chemical formula: CF ３ CH ２ OCF ２ CF ２ H, manufactured by AGC) (24.79 g), CF ２ =CFCF ２ OCF ２ CF ２ CF ３(PFAE) (425.63 g), methanol (32.73 g) as a chain transfer agent, and ultrapure water (612.86 g, electrical resistivity: 18.2 MΩ·cm) were charged and heated to 50°C (polymerization temperature) while stirring at 500 rpm. Next, TFE was injected into the reactor under pressure and the pressure was increased to 1.4 MPaG. Then, a solution of heptafluorobutyroyl peroxide (PFB) in AE3000 (0.06 mass%), which is a polymerization initiator, was added to start polymerization. The polymerization initiator was added continuously until the end of polymerization. As the pressure in the reactor decreased as polymerization started, TFE was added to maintain a constant pressure from the start of polymerization. When the amount of TFE injected under pressure reached 160 g, the reactor was cooled and the polymerization reaction was terminated. In the polymerization reaction of Example 1, neither fluorine-containing emulsifiers nor components containing sulfate ions were used. Therefore, the reaction system in which the polymerization reaction was carried out did not contain fluorine-containing emulsifiers or sulfate ions. After recovering the gas remaining in the reactor, the liquid containing the slurry-like untreated polymer 1 was withdrawn from the reactor. After removing and recovering AE3000 using an evaporator, the untreated polymer 1 and water were separated by filtration, and the obtained untreated polymer 1 was dried at 150°C for 15 hours. The composition of the obtained untreated polymer 1 was TFE units / PFAE units = 98.4 / 1.6 (molar ratio). Furthermore, as a result of measurement using the above measurement method, the MFR of the obtained untreated polymer 1 was 4.0 g / 10 min.

[0088] <Fluorination Treatment> Next, the untreated polymer 1 obtained by the polymerization reaction was subjected to fluorination treatment. The obtained untreated polymer 1 was placed in a vacuum reactor and heated to 210°C. After vacuuming, a mixed gas diluted with nitrogen gas to a fluorine gas concentration of 20% by volume was introduced into the vacuum reactor. The pressure inside the vacuum reactor was set to 1 atm and the temperature inside the vacuum reactor was set to 230°C. Ten hours after the start of introduction of the mixed gas, the inside of the vacuum reactor was thoroughly replaced with nitrogen gas to complete the fluorination treatment and obtain fluorine-containing polymer 1. The composition of the obtained fluorine-containing polymer 1 was TFE units / PFAE units = 98.4 / 1.6 (molar ratio). The MFR, number of functional groups N, amount of metal ion elution, and content of fluorine-containing emulsifier of fluorine-containing polymer 1, measured by the above measurement method, are shown in the table below.

[0089] [Example 2] The polymerization reaction of TFE and PFAE and the fluorination treatment were carried out in the same manner as in Example 1, except that the amount of methanol added was changed from 32.73 g to 56.38 g and the amount of ultrapure water added was changed from 612.86 g to 582.92 g, to obtain fluorine-containing polymer 2. The composition of the obtained fluorine-containing polymer 2 was TFE units / PFAE units = 98.4 / 1.6 (molar ratio). Furthermore, the MFR of the obtained fluorine-containing polymer 2, as measured by the above measurement method, was 27.0 g / 10 min. The number of functional groups N, the amount of metal ions eluted, and the content of fluorine-containing emulsifier of fluorine-containing polymer 2, as measured by the above measurement method, are shown in the table below.

[0090] [Example 3] The polymerization reaction of TFE and PFAE and the fluorination treatment were carried out in the same manner as in Example 1, except that the amount of methanol added was changed from 32.73 g to 48.30 g and the amount of ultrapure water added was changed from 612.86 g to 593.15 g, to obtain fluorine-containing polymer 3. The composition of the obtained fluorine-containing polymer 3 was TFE units / PFAE units = 98.4 / 1.6 (molar ratio). Furthermore, the MFR of the obtained fluorine-containing polymer 2, as measured by the above measurement method, was 14.0 g / 10 min. The number of functional groups N, the amount of metal ions eluted, and the content of fluorine-containing emulsifier of fluorine-containing polymer 3, as measured by the above measurement method, are shown in the table below.

[0091] [Example 4] A fluorine-containing polymer 4 was obtained in the same manner as in Example 1, except that the amount of methanol added was changed from 32.73 g to 46.41 g, the amount of ultrapure water added was changed from 612.86 g to 595.54 g, and the polymerization reaction of TFE and PFAE was carried out, and no fluorination treatment was performed. The composition of the obtained fluorine-containing polymer 4 was TFE units / PFAE units = 98.4 / 1.6 (molar ratio). Furthermore, the MFR of the obtained fluorine-containing polymer 4, as measured by the above measurement method, was 12.0 g / 10 min. The number of functional groups N, the amount of metal ions eluted, and the content of fluorine-containing emulsifier of the fluorine-containing polymer 4, as measured by the above measurement method, are shown in the table below.

[0092] [Example 5] Except for changing the amount of methanol added from 32.73 g to 29.16 g and using 617.38 g of ion-exchanged water (electrical resistivity: 1.0 MΩ·cm) instead of 612.86 g of ultrapure water, the polymerization reaction of TFE and PFAE and the fluorination treatment were carried out in the same manner as in Example 1 to obtain a fluorine-containing polymer 5. The composition of the untreated polymer 5 obtained by the polymerization reaction before fluorination treatment was TFE units / PFAE units = 98.4 / 1.6 (molar ratio). Furthermore, the MFR of the obtained untreated polymer 5, as measured by the above measurement method, was 3.0 g / 10 min. In addition, the composition of the obtained fluorine-containing polymer 5 was TFE units / PFAE units = 98.4 / 1.6 (molar ratio). The MFR, number of functional groups N, amount of metal ions eluted, and content of fluorine-containing emulsifier of the fluorine-containing polymer 5 measured by the above measurement method are shown in the table below.

[0093] [Example 6] In a 1.3 L stainless steel pressure reactor, ion-exchanged water (758 g, electrical resistivity: 1.0 MΩ・cm), PFAE (2.7 g), ethane (0.05 g) as a chain transfer agent, and C as a water-soluble emulsifier containing fluorine atoms. ２ F ５ OCF ２ CF ２ OCF ２ COONH ４A 30% by mass aqueous solution (18 g) was charged and heated to 90°C (polymerization temperature) while stirring at 260 rpm. Next, TFE was injected into the reactor under pressure and the pressure was increased to 0.6 MPaG. Then, ammonium persulfate (0.05 g), which is a polymerization initiator, was added and polymerization was started. As the pressure in the reactor decreased as polymerization started, TFE was added to maintain a constant pressure from the start of polymerization. When the amount of TFE injected under pressure reached 100 g, the reactor was cooled and the polymerization reaction was terminated to obtain untreated polymer 6. The content of the fluorine-containing emulsifier was 0.69% by mass of the total mass of the reaction system, and the content of sulfate ions was 83 ppm by mass of the total mass of the reaction system. The content of each component was calculated from the amount added. After recovering the gas remaining in the reactor, the liquid in a latex state was withdrawn from the reactor and freeze-coagulated. After separating the untreated polymer 6 and water by filtration, it was dried at 150°C for 10 hours. The composition of the obtained untreated polymer 6 was TFE units / PFAE units = 99.5 / 0.5 (molar ratio). Furthermore, the MFR of the obtained untreated polymer 6, as measured by the above measurement method, was 4.5 g / 10 min.

[0094] Next, the obtained untreated polymer 6 was fluorinated using the same method as described in the <Fluorination Treatment> section of Example 1 to obtain a fluorine-containing polymer 6. The composition of the obtained fluorine-containing polymer 6 was TFE units / PFAE units = 99.5 / 0.5 (molar ratio). The MFR, number of functional groups N, amount of metal ions eluted, and content of fluorine-containing emulsifier of the fluorine-containing polymer 6 measured by the above measurement method are shown in the table below.

[0095] [Example 7] A fluorine-based solvent (product name: Asahi Clean AE3000, chemical formula: CF) is added to a 1.3 L stainless steel pressure reactor. ３ CH ２ OCF ２ CF ２ H, manufactured by AGC Inc. (289.22g), CF ２ = CFCF ２ OCF ２ CF ２ CF ３ (PFAE) (103.82g), CF ２ = CFOCF２ CF ２ CF ３ (PPVE) (30.42 g), methanol (42.06 g) as a chain transfer agent, and ultrapure water (601.1 g, electrical resistivity: 18.2 MΩ・cm) were charged, and the mixture was heated to 50°C (polymerization temperature) while stirring at 500 rpm. Next, TFE was injected into the reactor under pressure, and the pressure was increased to 1.4 MPaG. Then, a solution of heptafluorobutyroyl peroxide (PFB) in AE3000 (0.06 mass%), which is a polymerization initiator, was added to start polymerization. The polymerization initiator was added continuously until the end of polymerization. As the pressure in the reactor decreased as polymerization started, TFE was added to maintain a constant pressure from the start of polymerization. When the amount of TFE injected under pressure reached 160 g, the reactor was cooled and the polymerization reaction was terminated. In the polymerization reaction of Example 7, neither fluorine-containing emulsifiers nor components containing sulfate ions were used. Therefore, the reaction system in which the polymerization reaction was carried out did not contain a fluorine-containing emulsifier or sulfate ions. After recovering the gas remaining in the reactor, the liquid containing the slurry-like untreated polymer 7 was withdrawn from the reactor. After removing and recovering AE3000 using an evaporator, the untreated polymer 7 and water were separated by filtration, and the obtained untreated polymer 7 was dried at 150°C for 15 hours. Thereafter, a fluorination treatment was carried out in the same manner as in Example 1 to obtain a fluorine-containing polymer 7. The composition of the obtained fluorine-containing polymer 7 was TFE units / PFAE units / PPVE units = 98.3 / 0.3 / 1.4 (molar ratio). Furthermore, as a result of measurement using the above measurement method, the MFR of the obtained fluorine-containing polymer 7 was 14.0 g / 10 min. The MFR, number of functional groups N, amount of metal ions eluted, and content of fluorine-containing emulsifier of the fluorine-containing polymer 7 measured using the above measurement method are shown in the table below.

[0096] [Example 8] Fluorine-containing polymer 8 was obtained in the same manner as in Example 7, except that the amount of methanol added was changed from 42.06 g to 6.96 g to carry out the polymerization reaction of TFE, PFAE, and PPVE. The composition of the obtained fluorine-containing polymer 8 was TFE units / PFAE units / PPVE units = 98.3 / 0.3 / 1.4 (molar ratio). Furthermore, the MFR of the obtained fluorine-containing polymer 8, as measured by the above measurement method, was 2.0 g / 10 min. The number of functional groups N, the amount of metal ions eluted, and the content of fluorine-containing emulsifier of the fluorine-containing polymer 8, as measured by the above measurement method, are shown in the table below.

[0097] Table 5 shows the physical properties of the reaction system, the composition of the fluorine-containing polymer, and the evaluation results for each example. In the table, the "Fluorine-containing emulsifier (mass%)" column under "Reaction system" and the "SO ４ ２－ The "(mass ppm)" column shows the content of fluorine-containing emulsifier (unit: mass%) and sulfate ion (unit: mass ppm) relative to the total mass of the reaction system in each example. The "TFE units (mol%)" column and "PFAE units (mol%)" column show the content of TFE units (unit: mol%) and PFAE units (unit: mol%) relative to the total units contained in the fluorine-containing polymer, respectively. "Number of functional groups N (units / 10) ６ The "Number of" column indicates the total number of specific functional groups contained in the fluorine-containing polymer. For example, the notation "<10" in Example 1 indicates that the main chain carbon number of fluorine-containing polymer 1 is 10 ６ This means that the total number of specific functional groups per unit was less than 10, and the notation "150<" in Example 4 refers to the number of carbon atoms in the main chain of the fluorine-containing polymer 4 being 10 ６This means that the total number of specific functional groups per molecule exceeded 150. The "Fluorine-containing emulsifier (mass ppb)" column for "Fluorine-containing polymer" shows the content (mass ppb) of fluorine-containing emulsifier relative to the total mass of the fluorine-containing polymer. Table 6 also shows the amount of metal ions eluted for each metal element and their total amount for each example of fluorine-containing polymer. In each example, the TFE units and PFAE units content of the untreated polymer before fluorination treatment were the same as those content of the fluorine-containing polymer after fluorination treatment.

[0098]

[0099]

[0100] As shown in Table 5 above, it was confirmed that a fluorine-containing polymer obtained by a manufacturing method in which TFE units and PFAE units are polymerized in a reaction system containing water with an electrical resistivity of 15.0 MΩ·cm or more, and substantially free of fluorine-containing emulsifiers and sulfate ions, and the resulting fluorine-containing polymer is subjected to a fluorination treatment, can form molded articles with excellent ozone resistance (Examples 1, 2, 3, 7, and 8).

[0101] Furthermore, the entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2025-019092, filed on February 7, 2025, are incorporated herein by reference as disclosure of the present invention.

Claims

1. A method for producing a fluorine-containing polymer, characterized by polymerizing tetrafluoroethylene and perfluoro(alkylallyl ether) in a reaction system containing water with an electrical resistivity of 15.0 MΩ·cm or more, and substantially free of both a fluorine-containing emulsifier and sulfate ions, to obtain a fluorine-containing polymer, and then performing a fluorination treatment on the fluorine-containing polymer.

2. The method for producing a fluorine-containing polymer according to claim 1, wherein the reaction system further comprises methanol.

3. The method for producing a fluorine-containing polymer according to claim 1 or 2, wherein the reaction system further comprises a fluorine-based solvent.

4. The method for producing a fluorine-containing polymer according to claim 3, wherein the amount of fluorine-based solvent added to the reaction system is 1 to 70% by mass relative to the amount of water added.

5. The method for producing a fluorine-containing polymer according to claim 1 or 2, wherein the reaction system further comprises an oil-soluble radical initiator.

6. The method for producing a fluorine-containing polymer according to claim 1 or 2, wherein the content of the fluorine-containing emulsifier and the content of the sulfate ions are each 10 ppm by mass or less with respect to the total mass of the reaction system.

7. A fluorine-containing polymer having units based on tetrafluoroethylene and units based on perfluoro(alkylallyl ether), wherein -CF=CF ２ , -CF ２ H, -COF, -COOH, -COOCH ３ , -CONH ２ and -CH ２ The total number of OH functional groups is equal to the number of carbon atoms in the main chain of the fluorine-containing polymer. ６ A fluorine-containing polymer characterized by having fewer than 150 ions per unit and a metal ion elution amount of 100 ppb by mass or less relative to the total mass of the fluorine-containing polymer.

8. The fluorine-containing polymer according to claim 7, which is substantially free of fluorine-containing emulsifiers.

9. The fluorine-containing polymer according to claim 7 or 8, wherein the content of the units based on perfluoro(alkylallyl ether) is 0.2 to 5.0 mol% relative to the total units of the fluorine-containing polymer.

10. The fluorine-containing polymer according to claim 7 or 8, wherein the melt flow rate of the fluorine-containing polymer, as measured under conditions of a temperature of 372°C in accordance with ASTM D1238, is 0.5 to 100.0 g / 10 min.

11. The fluorine-containing polymer according to claim 8, wherein the content of the fluorine-containing emulsifier is 10 ppm by mass or less relative to the total mass of the fluorine-containing polymer.

12. An injection-molded article characterized by being obtained by injection molding a fluorine-containing polymer according to claim 7 or 8.

13. A coated electric wire comprising a core wire and a covering layer provided around the core wire, wherein the covering layer is obtained by molding a fluorine-containing polymer as described in claim 7 or 8.

14. A molded article obtained by molding a fluorine-containing polymer according to claim 7 or 8, characterized in that the molded article is a microtube, a container, a piping member, or a wire covering material.

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