Composition containing fluoropolymer and aprotic solvent, method for producing fluoropolymer, fluoropolymer solution, method for producing mixture of fluoromonomer and aprotic solvent, and method for producing fluoropolymer

Abstract

To provide a method for producing a fluorine-containing polymer which suppresses the generation of fluoride ions during polymerization, a composition containing a fluorine-containing polymer and an aprotic solvent and having a low fluoride ion content, a fluorine-containing polymer having a low fluoride ion content and the like.SOLUTION: There is provided a composition containing a fluorine-containing polymer (A) and an aprotic solvent (B), wherein the composition contains 0.01 to 500 mass ppm of fluoride ions, the fluorine-containing polymer (A) contains, as its main component, a constitutional unit represented by formula (A1), formula (A2) or formula (A3) and the aprotic solvent (B) is at least one solvent selected from the group consisting of a perfluoroaromatic compound, a perfluorotrialkylamine, a perfluoroalkane, a hydrofluorocarbon, a fluoro cyclic ether, a hydrofluoroether and an olefin compound containing at least one chlorine atom.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a composition containing a fluorinated polymer and an aprotic solvent having a low fluoride ion content, a method for producing a fluorinated polymer and a fluorinated polymer solution, a method for producing a mixture of a fluorinated monomer and an aprotic solvent, a method for producing a fluorinated polymer, etc. [Background technology]

[0002] A fluoropolymer containing a structural unit having a cyclic structure is produced by polymerizing a fluoromonomer having a cyclic structure with an etheric oxygen atom as a ring-constituting element. For example, Patent Document 1 describes a method for producing a fluororesin, which is characterized by having a precipitation polymerization step in which precipitation polymerization is carried out in the presence of a monomer, a radical polymerization initiator, and an organic solvent with a water content in the reaction system of 1000 mass ppm or less. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-122068 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors have found that in the process for producing a fluoropolymer described in Patent Document 1, a large amount of fluoride ions are generated during monomer polymerization and these fluoride ions remain in the fluoropolymer, causing problems such as corrosion of the production equipment and a reduction in the weight of the fluoropolymer during heat treatment. The objectives of the present disclosure are to provide a method for producing a fluoropolymer in which generation of fluoride ions during polymerization is suppressed; a composition containing a fluoropolymer and an aprotic solvent and having a low fluoride ion content; a fluoropolymer having a low fluoride ion content: a method for producing the fluoropolymer; a method for producing a liquid having a low fluoride ion content by dissolving a fluoropolymer (A) produced by polymerization of a monomer in an aprotic solvent (B) in an aprotic solvent (B); a method for producing a mixture containing a fluoropolymer and an aprotic solvent and having a low fluoride ion content, etc. [Means for solving the problem]

[0005] The present disclosure encompasses, for example, the following aspects. Section 1. A composition comprising a fluoropolymer (A) and an aprotic solvent (B), The composition contains 0.01 to 500 ppm by mass of fluoride ions, The fluoropolymer (A) is Formula (A1) [ka] [In the formula, R 1 represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group. A structural unit represented by Formula (A2) [ka] [In the formula, R 2 ~R 5 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] A structural unit represented by the formula: Formula (A3) [ka] [In the formula, R 6 ~R 9each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The main component is a structural unit represented by The aprotic solvent (B) is at least one solvent selected from the group consisting of perfluoroaromatic compounds, perfluorotrialkylamines, perfluoroalkanes, hydrofluorocarbons, fluorocyclic ethers, hydrofluoroethers, and olefin compounds containing at least one chlorine atom; composition. Section 2. Item 2. The composition according to item 1, wherein the aprotic solvent (B) is at least one solvent selected from the group consisting of perfluoroalkanes, hydrofluorocarbons, and hydrofluoroethers. Section 3. Item 3. The composition according to item 1 or 2, wherein the fluoropolymer (A) contains, as a main component, a structural unit represented by any one of the following formulas (A1-1) to (A3-2): [ka] Section 4. The fluoropolymer (A) is represented by the formula (A3-1): [ka] Item 4. The composition according to item 3, comprising as a main component a structural unit represented by the formula: Section 5. The fluoropolymer (A) is represented by the formula (A3): [ka] [In the formula, R 6 ~R 9 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The main component is a structural unit represented by The fluoropolymer (A) is dissolved in the aprotic solvent (B). Item 3. The composition according to item 1 or 2. Section 6. The fluoropolymer (A) is represented by the formula (A3): [ka] [In the formula, R 6 ~R 9 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The main component is a structural unit represented by The fluoropolymer (A) is a solid or semi-solid. Item 3. The composition according to item 1 or 2. Section 7. Item 5. The composition according to item 4, further comprising a compound represented by the following formula (C) in an amount of 0.01 to 10% by mass based on the mass of the composition: [ka] Section 8. 8. The composition according to any one of items 1 to 7, wherein the composition contains fluoride ions at a concentration of 100 to 400 ppm by mass. Section 9. The composition according to any one of items 1 to 8, wherein the aprotic solvent (B) is at least one selected from the group consisting of CF3CF2CF2CF2OCH3 and (CF3)2CFCF2OCH3, hexafluorobenzene, 1,1,1,3,3,3-hexafluoro-2-methoxypropane, perfluorohexane, CF3CH2OCF2CHF2, or 1,1,2,2,3,3,4-heptafluorocyclopentane. Section 10. The composition contains a fluoride ion at a concentration of 100 to 400 ppm by mass; The fluoropolymer (A) is represented by the formula (A3-1): [ka] The main component is a structural unit represented by The composition according to item 1, wherein the aprotic solvent (B) is at least one selected from the group consisting of CF3CF2CF2CF2OCH3 and (CF3)2CFCF2OCH3, hexafluorobenzene, 1,1,1,3,3,3-hexafluoro-2-methoxypropane, perfluorohexane, CF3CH2OCF2CHF2, or 1,1,2,2,3,3,4-heptafluorocyclopentane. Section 11. A fluoropolymer (A), Contains 0.01 to 100 ppm by mass of fluoride ions, The fluoropolymer (A) is Formula (A1) [ka] [In the formula, R 1 represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group. A structural unit represented by Formula (A2) [ka] [In the formula, R 2 ~R 5 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] A structural unit represented by the formula: Formula (A3) [ka] [In the formula, R 6 ~R 9 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] Contains as a main component a structural unit represented by Fluorine-containing polymer (A). Section 12. Item 12. The fluoropolymer (A) according to item 11, comprising, as a main component, a structural unit represented by any one of the following formulas (A1-1) to (A3-2): [ka] Section 13. The fluoropolymer (A) is represented by the formula (A3-1): [ka] Item 13. The fluoropolymer (A) according to item 12, comprising as a main component a structural unit represented by the following formula: Section 14. 14. The fluoropolymer according to any one of items 11 to 13, wherein the fluoropolymer (A) contains 10 to 80 ppm by mass of fluoride ions. Section 15. A method for producing a fluoropolymer (A) solution in which a fluoropolymer (A) produced by a polymerization reaction is dissolved in the aprotic solvent (B), the method comprising the steps of: polymerizing the monomer (M) in a mixture of the monomer (M) and the aprotic solvent (B), the method comprising the steps of: The solution contains 0.01 to 500 ppm by mass of fluoride ions, The mixture contains 0.05 to 300 ppm by mass of fluoride ions, The monomer (M) is Formula (M1) [ka] [In the formula, R 1 represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group. A compound represented by the formula: Formula (M2) [ka] [In the formula, R 2 ~R 5 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] or Formula (M3) [ka] [In the formula, R 6 ~R 9 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The compound represented by the formula: The fluoropolymer (A) is Formula (A1) [ka] [In the formula, R 1 represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group. A structural unit represented by Formula (A2) [ka] [In the formula, R 2 ~R 5 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] A structural unit represented by the formula: Formula (A3) [ka] [In the formula, R 6 ~R 9 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The main component is a structural unit represented by The aprotic solvent (B) is at least one solvent selected from the group consisting of perfluoroaromatic compounds, perfluorotrialkylamines, perfluoroalkanes, hydrofluorocarbons, fluorocyclic ethers, hydrofluoroethers, and olefin compounds containing at least one chlorine atom; Manufacturing method. Section 16. Item 12. The method for producing a fluoropolymer (A) solution according to Item 11, wherein the aprotic solvent (B) is at least one solvent selected from the group consisting of perfluoroalkanes, hydrofluorocarbons, and hydrofluoroethers. Section 17. The monomer (M) contains a compound represented by any one of the following formulas (M1-1) to (M3-2): [ka] The fluoropolymer (A) contains, as a main component, a structural unit represented by any one of the following formulas (A1-1) to (A3-2): [ka] Item 17. A method for producing a fluoropolymer (A) solution according to item 15 or 16. Section 18. The monomer (M) is represented by the formula (M3-1): [ka] The compound represented by the formula: The fluoropolymer (A) is represented by the formula (A3-1): [ka] Item 18. The method for producing a solution of a fluoropolymer (A) according to item 17, comprising as a main component a constitutional unit represented by the following formula: Section 19. Item 19. The method for producing a solution of a fluoropolymer (A) according to item 18, wherein the solution of the fluoropolymer (A) contains 0.01 to 10 mass % of a compound represented by formula (C). [ka] Section 20. 20. The method for producing a fluorinated polymer (A) solution according to any one of items 15 to 19, wherein the aprotic solvent (B) is at least one selected from the group consisting of CF3CF2CF2CF2OCH3 and (CF3)2CFCF2OCH3, hexafluorobenzene, 1,1,1,3,3,3-hexafluoro-2-methoxypropane, or perfluorohexane. Section 21. 21. The method for producing a solution of a fluoropolymer (A) according to any one of items 15 to 20, wherein the solution contains 100 to 400 ppm by mass of fluoride ions, and the mixture contains 0.05 to 150 ppm by mass of fluoride ions. Section 22. The solution contains 100 to 400 ppm by mass of fluoride ions, The mixture contains 0.05 to 150 ppm by mass of fluoride ions, The monomer (M) is represented by the formula (M3-1): [ka] The compound represented by the formula: The fluoropolymer (A) is represented by the formula (A3-1): [ka] The main component is a structural unit represented by Item 16. The method for producing a fluorinated polymer (A) solution according to Item 15, wherein the aprotic solvent (B) is at least one selected from the group consisting of CF3CF2CF2CF2OCH3 and (CF3)2CFCF2OCH3, hexafluorobenzene, 1,1,1,3,3,3-hexafluoro-2-methoxypropane, or perfluorohexane.

[0006] Section 23. A method for producing a mixture of a fluoropolymer (A) and an aprotic solvent (B), comprising the steps of: The method comprises a step of mixing a fluoropolymer (A) and an aprotic solvent (B), The mixture contains 0.01 to 500 ppm by mass of fluoride ions, The fluoropolymer (A) is Formula (A1) [ka] [In the formula, R 1 represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group. A structural unit represented by Formula (A2) [ka] [In the formula, R 2 ~R 5 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] A structural unit represented by the formula: Formula (A3) [ka] [In the formula, R 6 ~R 9 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The main component is a structural unit represented by The aprotic solvent (B) is at least one solvent selected from the group consisting of perfluoroaromatic compounds, perfluorotrialkylamines, perfluoroalkanes, hydrofluorocarbons, fluorocyclic ethers, hydrofluoroethers, and olefin compounds containing at least one chlorine atom; A method for producing a mixture of a fluoropolymer (A) and an aprotic solvent (B). Section 24. Item 24. The method for producing a mixture of a fluorinated polymer (A) and an aprotic solvent (B) according to Item 23, wherein the aprotic solvent (B) is at least one solvent selected from the group consisting of perfluoroalkanes, hydrofluorocarbons, and hydrofluoroethers. Section 25. Item 25. The method for producing a mixture of a fluoropolymer (A) and an aprotic solvent (B) according to item 23 or 24, wherein the fluoropolymer (A) contains, as a main component, a constitutional unit represented by any one of the following formulas (A1-1) to (A3-2): [ka] Section 26. The fluoropolymer (A) is represented by the formula (A3-1): [ka] Item 26. A method for producing a mixture of a fluoropolymer (A) and an aprotic solvent (B) according to item 25, comprising as a main component a structural unit represented by the following formula: Section 27. Item 25. The method for producing a mixture of a fluorinated polymer (A) and an aprotic solvent (B) according to Item 23 or 24, wherein in the mixture of a fluorinated polymer (A) and an aprotic solvent (B), the fluorinated polymer (A) contains a constitutional unit represented by the formula (A3) as a main component and is a solid or semi-solid. Section 28. A method for producing a fluoropolymer (A), comprising a polymerization step of polymerizing a monomer (M) in a mixture of the monomer (M) and an aprotic solvent (B), comprising: the fluoropolymer (A) contains 0.01 to 100 ppm by mass of fluoride ions, and the mixture contains 0.05 to 300 ppm by mass of fluoride ions, The monomer (M) is Formula (M1) [ka] [In the formula, R 1 represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group. A compound represented by the formula: Formula (M2) [ka] [In the formula, R 2 ~R5 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] or Formula (M3) [ka] [In the formula, R 6 ~R 9 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The compound represented by the formula: The fluoropolymer (A) is Formula (A1) [ka] [In the formula, R 1 represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group. A structural unit represented by Formula (A2) [ka] [In the formula, R 2 ~R 5 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] A structural unit represented by the formula: Formula (A3) [ka] [In the formula, R 6 ~R 9 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The main component is a structural unit represented by The aprotic solvent (B) is at least one solvent selected from the group consisting of perfluoroaromatic compounds, perfluorotrialkylamines, perfluoroalkanes, hydrofluorocarbons, fluorocyclic ethers, hydrofluoroethers, and olefin compounds containing at least one chlorine atom; Manufacturing method. Section 29. Item 29. The method for producing a fluorinated polymer (A) according to Item 28, wherein the aprotic solvent (B) is at least one solvent selected from the group consisting of perfluoroalkanes, hydrofluorocarbons, and hydrofluoroethers. Section 30. The monomer (M) contains a compound represented by any one of the following formulas (M1-1) to (M3-2): [ka] The fluoropolymer (A) contains, as a main component, a structural unit represented by any one of the following formulas (A1-1) to (A3-2): [ka] Item 30. A method for producing a fluorinated polymer (A) according to item 28 or 29. Section 31. The monomer (M) is represented by the formula (M3-1): [ka] The compound represented by the formula: The fluoropolymer (A) is represented by the formula (A3-1): [ka] Item 31. The method for producing a fluorine-containing polymer (A) according to item 30, comprising as a main component a structural unit represented by the following formula: Section 32. Item 32. The process for producing a fluorinated polymer (A) according to item 31, wherein the monomer (M) contains 0.01 to 10% by mass of a compound represented by formula (C). [ka] Section 33. Item 30. The method for producing a fluoropolymer (A) according to Item 28 or 29, wherein in the polymerization step, the fluoropolymer (A) produced in the polymerization reaction contains a constitutional unit represented by the formula (A3) as a main component and is dissolved in the aprotic solvent (B), or the fluoropolymer (A) produced in the polymerization reaction is a solid or semi-solid in the aprotic solvent (B). Section 34. Item 34. The method for producing a fluoropolymer (A) according to any one of Items 28 to 33, wherein the fluoropolymer (A) contains 10 to 80 ppm by mass of fluoride ions, and the mixture contains 0.05 to 150 ppm by mass of fluoride ions. Section 35. the fluoropolymer (A) contains 10 to 80 ppm by mass of fluoride ions, and the mixture contains 0.05 to 150 ppm by mass of fluoride ions, The monomer (M) is represented by the formula (M3-1): [ka] The compound represented by the formula: The fluoropolymer (A) is represented by the formula (A3-1): [ka] Item 29. The method for producing a fluoropolymer (A) according to item 28, comprising as a main component a structural unit represented by the following formula: Effect of the Invention

[0007] The present disclosure provides a production method for a fluoropolymer in which generation of fluoride ions during polymerization is suppressed, and a composition containing a fluoropolymer and an aprotic solvent having a low fluoride ion content, and can suppress corrosion of production equipment caused by fluoride ions and increased costs for waste liquid treatment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The remainder of the disclosure more particularly exemplifies example embodiments. In several places in this disclosure, guidance is provided through examples, which examples can be used in various combinations. In each instance, the exemplary group can serve as a non-exclusive and representative group. All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety.

[0009] term Unless otherwise specified, the symbols and abbreviations in this specification should be understood to have the meanings commonly used in the technical field to which this disclosure pertains, in accordance with the context of this specification. As used herein, the phrase "comprising" is intended to encompass the phrases "consisting essentially of" and "consisting of." The steps, treatments, or operations described herein may be carried out at room temperature unless otherwise specified. In this specification, room temperature may mean a temperature in the range of 10 to 40°C. In this specification, the notation "Cn-Cm" (wherein n and m are each a number) indicates that the number of carbon atoms is n or more and m or less, as is commonly understood by those skilled in the art. In this specification, the description of a compound can include all stereoisomers (enantiomers, diastereomers, geometric isomers, etc.) unless otherwise specified by a person skilled in the art.

[0010] In this specification, unless otherwise specified, the term "alkyl group" includes linear, branched, and cyclic alkyl groups. The alkyl group may be a linear or branched alkyl group. The alkyl group can have 1 to 12, 1 to 6, 1 to 5, 1 to 4, 1 to 3, 6, 5, 4, 3, 2, or 1 carbon atom(s), for example. Examples of alkyl groups include straight-chain or branched alkyl groups such as methyl, ethyl, propyl (e.g., n-propyl, isopropyl), butyl (e.g., n-butyl, isobutyl, sec-butyl, tert-butyl), pentyl (e.g., n-pentyl, tert-pentyl, neopentyl, isopentyl, sec-pentyl, 3-pentyl), hexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl; and cyclic alkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl.

[0011] In this specification, unless otherwise specified, the term "fluoroalkyl group" includes linear, branched, or cyclic alkyl groups in which at least one hydrogen atom is replaced with a fluorine atom. The fluoroalkyl group may be a linear or branched alkyl group. The fluoroalkyl group can have 1 to 12, 1 to 6, 1 to 5, 1 to 4, 1 to 3, 6, 5, 4, 3, 2, or 1 carbon atom(s). The number of fluorine atoms in the fluoroalkyl group can be 1 or more (for example, 1 to 3, 1 to 5, 1 to 9, 1 to 11, or 1 to the maximum number that can be substituted). The fluoroalkyl group includes a perfluoroalkyl group, which is an alkyl group in which all hydrogen atoms have been replaced with fluorine atoms. Examples of the fluoroalkyl group include methyl having 1 to 3 fluorine atoms, ethyl having 1 to 5 fluorine atoms, propyl having 1 to 7 fluorine atoms (e.g., n-propyl, isopropyl), butyl having 1 to 9 fluorine atoms (e.g., n-butyl, isobutyl, sec-butyl, tert-butyl), pentyl having 1 to 11 fluorine atoms (e.g., n-pentyl, tert-pentyl, neopentyl, isopentyl, sec-pentyl, 3-pentyl), hexyl having 1 to 13 fluorine atoms, heptyl having 1 to 15 fluorine atoms, octyl having 1 to 17 fluorine atoms, nonyl having 1 to 19 fluorine atoms, decyl having 1 to 21 fluorine atoms, undecyl having 1 to 23 fluorine atoms, dodecyl having 1 to 25 fluorine atoms, tridecyl having 1 to 27 fluorine atoms, tetradecyl having 1 to 29 fluorine atoms, and aryl having 1 to 31 fluorines.

[0043] Fluoroalkyl groups include linear or branched C1-C20 fluoroalkyl groups (e.g., C1-C10, C1-C4, C1-C3, etc., preferably C1-C7, more preferably C1-C6 fluoroalkyl groups (preferably perfluoroalkyl groups) such as pentadecyl having a fluorine atom, hexadecyl having 1-33 fluorine atoms, heptadecyl having 1-35 fluorine atoms, octadecyl having 1-37 fluorine atoms, nonadecyl having 1-39 fluorine atoms, and icosyl having 1-41 fluorine atoms; cyclic C3-C10 fluoroalkyl groups (e.g., C3-C6, C4-C6, C3-C5, C5-C6, C4-C8 fluoroalkyl groups) (preferably perfluoroalkyl groups) such as cyclofluoropropyl, cyclofluorobutyl, cyclofluoropentyl, cyclofluorohexyl, cyclofluoroheptyl, cyclofluorooctyl, and fluoroadamantyl. Examples of perfluoroalkyl groups include trifluoromethyl (CF3-), pentafluoroethyl (C2F5-), perfluoropropyl (e.g., CF3CF2CF2-, (CF3)2CF-), perfluorobutyl (e.g., CF3CF2CF2CF2-, (CF3)2CFCF2-, (CF3CF(CF3)CF2-, (CF3)3C-), perfluoropentyl (e.g., CF3CF2CF2CF2CF2-, (CF3)2CFCF2CF2-, CF3CF2CF(CF3)CF2-, CF3CF2CF2CF(CF3)-, CF3C(CF3)2CF2-), and the like. Specific examples of the fluoroalkyl group include the perfluoroalkyl groups exemplified above, a monofluoromethyl group, a difluoromethyl group, a 2,2,2-trifluoroethyl group (CF3CH2-), a tetrafluoropropyl group (e.g., HCF2CF2CH2-), a hexafluoropropyl group (e.g., (CF3)2CH-), and an octafluoropentyl group (e.g., HCF2CF2CF2CF2CH2-).

[0012] In this specification, unless otherwise specified, an "alkoxy group" can be a group represented by RO- [wherein R is an alkyl group]. The alkoxy group includes linear, branched, and cyclic alkoxy groups. The alkoxy group can be a linear or branched alkoxy group. The alkoxy group can have 1 to 12, 1 to 6, 1 to 5, 1 to 4, 1 to 3, 6, 5, 4, 3, 2, or 1 carbon atom. Examples of alkoxy groups can include linear or branched alkoxy groups such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, isopentyloxy, neopentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, and decyloxy, and cyclic alkoxy groups such as cyclopropyloxy, cyclobutyloxy, cyclopentyloxy, cyclohexyloxy, cycloheptyloxy, and cyclooctyloxy.

[0013] In this specification, unless otherwise specified, a "fluoroalkoxy group" is an alkoxy group in which at least one hydrogen atom is replaced with a fluorine atom. The "fluoroalkoxy group" may be a linear or branched fluoroalkoxy group. The fluoroalkoxy group can have 1 to 12, 1 to 6, 1 to 5, 1 to 4, 1 to 3, 6, 5, 4, 3, 2, or 1 carbon atom(s). The number of fluorine atoms in the fluoroalkoxy group can be 1 or more (for example, 1 to 3, 1 to 5, 1 to 9, 1 to 11, or 1 to the maximum number that can be substituted). Fluoroalkoxy groups include perfluoroalkoxy groups. A perfluoroalkoxy group is an alkoxy group in which all of the hydrogen atoms have been substituted with fluorine atoms. Examples of perfluoroalkoxy groups include trifluoromethyloxy (CF3O-), pentafluoroethyloxy (C2F5O-), perfluoropropyloxy (e.g., CF3CF2CF2O-, (CF3)2CFO-), perfluorobutyloxy (e.g., CF3CF2CF2CF2O-, (CF3)2CFCF2O-, (CF3CF(CF3)CF2O-, (CF3)3CO-), perfluoropentyloxy (e.g., CF3CF2CF2CF2CF2O-, (CF3)2CFCF2CF2O-, CF3CF2CF(CF3)CF2O-, CF3CF2CF2CF(CF3)O-, CF3C(CF3)2CF2O-), and the like. Specific examples of fluoroalkoxy groups include the perfluoroalkoxy groups exemplified above, monofluoromethoxy, difluoromethoxy, 2,2,2-trifluoroethyloxy (CFCHO-), tetrafluoropropyloxy (e.g., HCFCFCHO-), hexafluoropropyloxy (e.g., (CF)CHO-), octafluoropentyloxy (e.g., HCFCFCFCFCHO-), and the like.

[0014] composition One embodiment of the present disclosure is a composition containing a fluoropolymer (A) containing a structural unit represented by formula (A1), (A2), or (A3) as a main component, and an aprotic solvent (B). Although this composition contains a fluoropolymer (A), the fluoride ion content is low, for example, 0.01 to 500 ppm by mass. The composition of the present disclosure can be used as a coating liquid for the fluoropolymer (A), and is useful in that it can suppress corrosion and deterioration of the substrate when the coating liquid is applied to a substrate made of glass, metal, or the like to form a coating of the fluoropolymer (A) because of its low fluoride ion content. In addition, the composition of the present disclosure is useful in that it makes it easy to use a container made of glass, metal, or the like as a storage container when storing it. The composition of the present disclosure may contain other components such as a polymerization initiator and impurities that are mixed in during the polymerization process of the fluorine-containing monomer (A).

[0015] Fluorine-containing polymer (A) The fluoropolymer (A) contains, as a main component, a structural unit represented by the following formula (A1), (A2) or (A3).

[0016] Formula (A1) [ka] [In the formula, R 1 represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group. (Herein, also referred to as "structural unit (A1)") represented by the following formula:

[0017] Formula (A2) [ka] [In the formula, R 2 ~R 5 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] (Herein, also referred to as "structural unit (A2)") represented by the following formula:

[0018] Formula (A3) [ka] [In the formula, R 6 ~R 9 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] (Herein, also referred to as "structural unit (A3)") represented by the following formula:

[0019] "Containing a structural unit as a main component" means that the proportion of the structural unit in all structural units in the fluoropolymer (A) is 50 mol% or more. The proportion can be 51 mol% or more, 60 mol% or more, etc., preferably 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 100 mol%. The fluoropolymer (A) includes homopolymers of structural units represented by formula (A1), (A2), or (A3).

[0020] The fluoropolymer (A) may contain one or more types of structural units represented by the formula (A1), (A2) or (A3), preferably one to three types, more preferably one or two types, and particularly preferably one type.

[0021] In the structural unit (A1), R 1 R can be a fluorine atom or a C1-C4 linear or branched perfluoroalkyl group. 1 is preferably a fluorine atom, trifluoromethyl, or perfluoroethyl, more preferably a fluorine atom or trifluoromethyl, particularly preferably a fluorine atom.

[0022] Preferred examples of the structural unit (A1) include a structural unit represented by the following formula (A1-1) (also referred to herein as "structural unit (A1-1)"). [ka]

[0023] In the structural unit (A2), R 2 ~R 5 R can each independently be a fluorine atom, a C1-C3 linear or branched perfluoroalkyl group, or a C1-C3 linear or branched perfluoroalkoxy group. 2 ~R 5 are each independently preferably a fluorine atom, trifluoromethyl, pentafluoroethyl, or trifluoromethoxy, and more preferably a fluorine atom, trifluoromethyl, or trifluoromethoxy.

[0024] A preferred structural unit (A2) is a structural unit represented by the formula (A2): 2 and R 3 each independently represents a fluorine atom, trifluoromethyl, or trifluoromethoxy; R 4 and R 5 are structural units each independently representing a fluorine atom or trifluoromethyl.

[0025] More preferred structural units (A2) are those represented by the formula (A2): 2 represents a fluorine atom, and R 3 represents a fluorine atom, trifluoromethyl, or trifluoromethoxy; R 4 and R 5 are structural units each independently representing a fluorine atom or trifluoromethyl.

[0026] Particularly preferred structural units (A2) are those represented by the formula (A2): 2 represents a fluorine atom, and R 3 represents a fluorine atom or trifluoromethoxy; R 4 and R 5 are structural units each independently representing a fluorine atom or trifluoromethyl.

[0027] Preferred examples of the structural unit (A2) include structural units represented by the following formulas (A2-1) and (A2-2) (also referred to herein as "structural unit (A2-1)" and "structural unit (A2-2)", respectively). [ka]

[0028] In the structural unit (A3), R 6 ~R 9 R can each independently be a fluorine atom, a C1-C3 linear or branched perfluoroalkyl group, or a C1-C3 linear or branched perfluoroalkoxy group. 6 ~R 9 are each independently preferably a fluorine atom, trifluoromethyl, perfluoroethyl, or trifluoromethoxy, and more preferably a fluorine atom, trifluoromethyl, or trifluoromethoxy.

[0029] A preferred structural unit (A3) is a structural unit represented by the formula (A3): 6 ~R 9 are each independently a structural unit representing a fluorine atom or trifluoromethyl.

[0030] More preferred structural units (A3) are those represented by the formula (A3): R 6 ~R 9 represents a fluorine atom, R 6 ~R 8 represents a fluorine atom, and R 9 represents trifluoromethyl; R 6 represents trifluoromethyl, and R 7 ~R 9 represents a fluorine atom, or R 6 and 9 represents trifluoromethyl, and R 7 and R 8 represents a fluorine atom, It is a building block.

[0031] Preferred examples of the structural unit (A3) include structural units represented by the following formulas (A3-1) and (A3-2), respectively (herein, these are also referred to as "structural unit (A3-1)" and "structural unit (A3-2)". [ka]

[0032] The fluoropolymer (A) may contain other structural units in addition to the structural units (A1), (A2), and (A3) contained as main components. The proportion of the other structural units in all structural units in the fluoropolymer (A) may be 50 mol % or less, preferably 20 mol % or less, more preferably 10 mol % or less, and particularly preferably 0 mol %.

[0033] Other structural units include those of the following formula (A11): [ka] [In the formula, R 111 represents a fluorine atom, a C1-C6 perfluoroalkyl group, or a C1-C6 perfluoroalkoxy group. Examples of structural units include, but are not limited to, structural units represented by the following formula (sometimes referred to as "structural unit (A11)" in this specification). For example, the fluoropolymer (A) may be a fluoropolymer having a structural unit (A2-1) and a structural unit represented by the following formula (A11-1): [ka] (sometimes referred to herein as "structural unit (A11-1)").

[0034] R 111 can be a fluorine atom, a linear or branched C1-C6 perfluoroalkyl group, or a linear or branched C1-C6 perfluoroalkoxy group. Preferred R 111 is a fluorine atom, a linear or branched C1-C4 perfluoroalkyl group, or a linear or branched C1-C4 perfluoroalkoxy group. More preferred R 111is a fluorine atom, a linear or branched C1-C3 perfluoroalkyl group, or a linear or branched C1-C3 perfluoroalkoxy group. Particularly preferred R 111 is a fluorine atom or trifluoroalkyl.

[0035] The mass average molecular weight of the fluoropolymer (A) can be, for example, in the range of 5,000 to 1,000,000, 10,000 to 1,000,000, 10,000 to 500,000, or 90,000 to 350,000, preferably in the range of 10,000 to 750,000, more preferably in the range of 40,000 to 500,000, and particularly preferably in the range of 70,000 to 350,000. The lower limit of the mass average molecular weight of the fluoropolymer (A) can be, for example, 5000 or more, preferably 10000 or more, more preferably 40000 or more, and particularly preferably 70000 or more. The upper limit of the mass average molecular weight of the fluoropolymer (A) can be, for example, 1000000 or less, preferably 750000 or less, more preferably 500000 or less, and particularly preferably 350000 or less. The lower limit and the upper limit may be appropriately combined. The mass average molecular weight of the fluoropolymer (A) is a value determined by GPC (gel permeation chromatography) method (particularly the GPC method described in the examples).

[0036] In the composition of the present disclosure, the content of the fluoropolymer (A) relative to the mass of the composition can be 20% by mass or more, preferably in the range of 20 to 65% by mass, more preferably in the range of more than 20 to 65% by mass, and particularly preferably in the range of more than 20 to 50% by mass.

[0037] In the composition of the present disclosure, the fluoropolymer (A) may or may not be dissolved in the aprotic solvent (B). When dissolved, the fluoropolymer (A) may be partially or entirely dissolved, and it is preferable that the entire amount is dissolved. When the fluoropolymer (A) is not partially or entirely dissolved, it may be solid or semi-solid. Examples of semi-solid forms include gel forms (forms in which the fluoropolymer is swollen with the aprotic solvent (B)). In this specification, the solid and semi-solid fluoropolymers (A) are also referred to as the solid material of the fluoropolymer (A) and the semi-solid material of the fluoropolymer (A), respectively.

[0038] In the composition of the present disclosure, an embodiment in which the entire amount of the fluoropolymer (A) is dissolved in the aprotic solvent (B) is also referred to as a "fluoropolymer (A) solution". In addition, in the composition of the present disclosure, an embodiment in which a part or the entire amount of the fluoropolymer (A) is not dissolved in the aprotic solvent (B) and is in a solid or semi-solid form is also referred to as a "mixture of fluoropolymer (A) and aprotic solvent (B)".

[0039] When the fluoropolymer (A) is dissolved in the aprotic solvent (B), it is preferable that the entire amount of the fluoropolymer (A) contained in the composition of the present disclosure is dissolved, but a part of it may be dissolved. When a part of the fluoropolymer (A) is dissolved in the aprotic solvent (B), the undissolved fluoropolymer (A) may be in a solid state or a semi-solid state. An example of a semi-solid state is a gel state.

[0040] The fluoropolymer (A) may contain fluoride ions. When the fluoropolymer (A) contains fluoride ions, the concentration of the fluoride ions in the fluoropolymer (A) may be, for example, 0.01 to 100 ppm by mass, preferably 0.01 to 90 ppm by mass, more preferably 0.01 to 80 ppm by mass, and still more preferably 10 to 80 ppm by mass.

[0041] The fluoropolymer (A) can be synthesized by a known method. For example, it can be synthesized by polymerizing a monomer corresponding to a structural unit of the fluoropolymer. As the polymerization method, radical polymerization, bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. can be used. The method for producing the fluoropolymer (A) of the present disclosure is particularly preferred in that the fluoropolymer (A) can be dissolved in a solvent at a high concentration.

[0042] Aprotic Solvent (B) The composition of the present disclosure contains an aprotic solvent (B). Aprotic solvents are superior to protic solvents in that (1) they have high solubility for fluoropolymers, (2) they have low viscosity and are therefore suitable as polymerization solvents and solvents for forming fluoropolymer films, and (3) they have low reactivity and can suppress unexpected side reactions. The aprotic solvent may be a perfluoroaromatic compound, a perfluorotrialkylamine, a perfluoroalkane, a hydrofluorocarbon, a fluorocyclic ether, a hydrofluoroether, or an olefin compound containing at least one chlorine atom, and may be used alone or in combination of two or more.Preferably, it is at least one solvent selected from the group consisting of perfluoroalkane, hydrofluorocarbon, and hydrofluoroether.More preferably, it is at least one solvent selected from the group consisting of hydrofluorocarbon and hydrofluoroether.

[0043] The perfluoro aromatic compound may have, for example, one or more perfluoroalkyl groups. The aromatic ring of the perfluoro aromatic compound may be at least one ring selected from the group consisting of a benzene ring, a naphthalene ring, and an anthracene ring. The perfluoro aromatic compound may have one or more aromatic rings (e.g., 1, 2, or 3). The perfluoroalkyl group as a substituent is, for example, a linear or branched C1-C6, C1-C5, or C1-C4 perfluoroalkyl group, preferably a linear or branched C1-C3 perfluoroalkyl group, more preferably trifluoromethyl or pentafluoroethyl. The number of the substituents is, for example, 1 to 4, preferably 1 to 3, and more preferably 1 or 2. When there are a plurality of substituents, they may be the same or different. Examples of perfluoroaromatic compounds include perfluorobenzene, perfluorotoluene, perfluoroxylene, and perfluoronaphthalene. Preferred examples of the perfluoroaromatic compound include perfluorobenzene and perfluorotoluene.

[0044] Perfluorotrialkylamine is, for example, an amine substituted with three linear or branched perfluoroalkyl groups. The number of carbon atoms in the perfluoroalkyl groups is, for example, 1 to 10, preferably 1 to 5, and more preferably 1 to 4. The perfluoroalkyl groups may be the same or different, and are preferably the same. Examples of perfluorotrialkylamines include perfluorotrimethylamine, perfluorotriethylamine, perfluorotripropylamine, perfluorotriisopropylamine, perfluorotributylamine, perfluorotrisec-butylamine, perfluorotritert-butylamine, perfluorotripentylamine, perfluorotriisopentylamine, and perfluorotrineopentylamine. Preferred examples of the perfluorotrialkylamine include perfluorotripropylamine and perfluorotributylamine.

[0045] The perfluoroalkane is, for example, a linear, branched, or cyclic C3-C12 (preferably C3-C10, more preferably C3-C6) perfluoroalkane. Examples of perfluoroalkanes include perfluoropentane, perfluoro-2-methylpentane, perfluorohexane, perfluoro-2-methylhexane, perfluoroheptane, perfluorooctane, perfluorononane, perfluorodecane, perfluorocyclohexane, perfluoro(methylcyclohexane), perfluoro(dimethylcyclohexane) (e.g., perfluoro(1,3-dimethylcyclohexane)), and perfluorodecalin. Preferred examples of perfluoroalkanes include perfluoropentane, perfluorohexane, perfluoroheptane, and perfluorooctane.

[0046] The hydrofluorocarbon may be, for example, a C3-C8 hydrofluorocarbon. Examples of hydrofluorocarbons include CF3CH2CF2H, CF3CH2CF2CH3, CF3CHFCHFC2F5, 1,1,2,2,3,3,4-heptafluorocyclopentane, CF3CF2CF2CF2CH2CH3, CF3CF2CF2CF2CF2CHF2, and CF3CF2CF2CF2CF2CF2CF2CH2CH3. Preferred examples of hydrofluorocarbons include CF3CHFCHFC2F5, 1,1,2,2,3,3,4-heptafluorocyclopentane, CF3CH2CF2H, CF3CH2CF2CH3.

[0047] The fluorocyclic ether is, for example, a fluorocyclic ether that may have one or more fluoroalkyl groups. The ring of the fluorocyclic ether may be a 3- to 6-membered ring. The ring of the fluorocyclic ether may have one or more oxygen atoms as ring-constituting atoms. The ring preferably has one or two oxygen atoms, more preferably one oxygen atom. The fluoroalkyl group as a substituent is, for example, a linear or branched C1-C6, C1-C5, or C1-C4 fluoroalkyl group. The preferred fluoroalkyl group is a linear or branched C1-C3 fluoroalkyl group. The preferred fluoroalkyl group is a perfluoroalkyl group, for example, a linear or branched C1-C6, C1-C5, C1-C4, or C1-C3 perfluoroalkyl group. The fluorocyclic ether is preferably a perfluorocyclic ether. The perfluorocyclic ether may have one or more perfluoroalkyl groups. The perfluoroalkyl group may be, for example, a linear or branched C1-C6, C1-C5, or C1-C4 perfluoroalkyl group. The preferred perfluoroalkyl group is a linear or branched C1-C3 perfluoroalkyl group. The number of the substituents is, for example, 1 to 4, preferably 1 to 3, and more preferably 1 or 2. When there are a plurality of substituents, they may be the same or different. Examples of fluorocyclic ethers include perfluorotetrahydrofuran, perfluoro-5-methyltetrahydrofuran, perfluoro-5-ethyltetrahydrofuran, perfluoro-5-propyltetrahydrofuran, perfluoro-5-butyltetrahydrofuran, and perfluorotetrahydropyran. Preferred examples of the fluorocyclic ethers include perfluoro-5-ethyltetrahydrofuran and perfluoro-5-butyltetrahydrofuran.

[0048] Hydrofluoroethers are, for example, fluorine-containing ethers. The global warming potential (GWP) of the hydrofluoroether is preferably not more than 600, more preferably not more than 400, and particularly preferably not more than 300. The lower limit of the global warming potential (GWP) of the hydrofluoroether may be 1 or more, or 5 or more. An example of a hydrofluoroether is CF3CF2CF2CF2OCH 3、 CF3CF2CF(CF3)OCH 3、 CF3CF(CF3)CF2OCH 3、CF3CF2CF2CF2OC2H5, CF3CH2OCF2CHF2, C2F5CF(OCH3)C3F7, (CF3)2CHOCH3, (CF3)2CFOCH3, (CF3)2CFCF2OCH3, (CF3)2CFCF2OCH2CH3, CHF2CF2OCH2CF3, CHF2CF2CH2OCF2CHF2, CF3CHFCF2OCH3, CF3CHFCF2OCF3, trifluoromethyl 1,2,2,2-tetrafluoroethyl ether (HFE-227me), difluoromethyl 1,1,2,2,2-pentafluoroethyl ether (HFE-227mc), trifluoromethyl 1,2,2,2-tetrafluoroethyl ether (HFE-227mc), These include difluoromethyl 1,1,2,2-tetrafluoroethyl ether (HFE-227pc), difluoromethyl 2,2,2-trifluoroethyl ether (HFE-245mf), 2,2-difluoroethyl trifluoromethyl ether (HFE-245pf), 1,1,2,3,3-hexafluoropropyl methyl ether (CF3CHFCF2OCH3), 1,1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (CF3CF2OCH2CF3), and 1,1,1,3,3,3-hexafluoro-2-methoxypropane ((CF3)2CHOCH3). A preferred example of a hydrofluoroether is CF3CF2CF2CF2OCH 3、 These include CF3CF2CF2CF2OC2H5, CF3CH2OCF2CHF2, C2F5CF(OCH3)C3F7, (CF3)2CFCF2OCH3, (CF3)2CFCF2OCH2CH3, 1,1,2,3,3-hexafluoropropyl methyl ether (CF3CHFCF2OCH3), 1,1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (CHF2CF2OCH2CF3), and 1,1,1,3,3,3-hexafluoro-2-methoxypropane ((CF3)2CHOCH3).

[0049] The hydrofluoroether may be at least one selected from the group consisting of a compound represented by the following formula (B-1), a compound represented by the following formula (B-2), a compound represented by the following formula (B-3), a compound represented by the following formula (B-4), (CF3)2CHOCH3, (CF3)2CFOCH3, CF3CHFCF2OCH3, C2F5CF(OCH3)C3F7, (CF3)2CFCF2OCH3, (CF3)2CFCF2OCH2CH3, CHF2CF2OCH2CF3, and CF3CHFCF2OCF3. Formula (B-1): F(CF2) p O(CH2) q H (B-1) [In the formula, p is an integer of 1 to 6, and q is an integer of 1 to 4.] Formula (B-2): H(CF2) p O(CF2) q F (B-2) [In the formula, p and q are as defined above.] Formula (B-3): H(CF2) p O(CH2) q H (B-3) [In the formula, p and q are as defined above.] Formula (B-4): X(CF2) p CH2O(CF2) q H (B-4) [In the formula, X represents a fluorine atom or a hydrogen atom, and p and q are as defined above.]

[0050] The hydrofluoroether is represented by the following formula (B-5): R 21 -OR 22 (B-5) [In the formula, R 21 is a straight-chain or branched-chain propyl or butyl group in which one or more hydrogen atoms have been replaced by fluorine atoms; R 22 is methyl or ethyl. The compound represented by formula (B-5) is preferably a compound represented by R 21 is perfluorobutyl, and R22 is methyl or ethyl.

[0051] The olefin compound containing at least one chlorine atom is a C2-C4 (preferably C2-C3) olefin compound containing at least one chlorine atom in its structure. The olefin compound containing at least one chlorine atom is a hydrocarbon having 2 to 4 carbon atoms and having 1 or 2 (preferably 1) double bonds, in which at least one hydrogen atom bonded to a carbon atom is substituted with a chlorine atom. The number of chlorine atoms is from 1 to the maximum substitutable number. The number of chlorine atoms can be, for example, 1, 2, 3, 4, 5, etc. The olefinic compound that contains at least one chlorine atom may also contain at least one (eg, 1, 2, 3, 4, 5, etc.) fluorine atom. Examples of olefinic compounds containing at least one chlorine atom include CH2=CHCl, CHCl=CHCl, CCl2=CHCl, CCl2=CCl2, CF3CH=CHCl, CHF2CF=CHCl, CFH2CF=CHCl, CF3CCl=CFCl, CF2HCl=CFCl, CFH2Cl=CFCl. Preferred examples of olefinic compounds containing at least one chlorine atom include CHCl=CHCl, CHF2CF=CHCl, CF3CH=CHCl, CF3CCl=CFCl.

[0052] The aprotic solvent (B) can be at least one selected from the group consisting of CF3CF2CF2CF2OCH3 and (CF3)2CFCF2OCH3, hexafluorobenzene, 1,1,1,3,3,3-hexafluoro-2-methoxypropane, perfluorohexane, CF3CH2OCF2CHF2, or 1,1,2,2,3,3,4-heptafluorocyclopentane.

[0053] The aprotic solvent (B) can be at least one selected from the group consisting of CF3CF2CF2CF2OCH3 and (CF3)2CFCF2OCH3, hexafluorobenzene, 1,1,1,3,3,3-hexafluoro-2-methoxypropane, or perfluorohexane.

[0054] The global warming potential (GWP) of the aprotic solvent (B) can be 600 or less, 400 or less, etc., preferably 375 or less, more preferably 350 or less, and particularly preferably 0. The lower limit of the global warming potential (GWP) of the aprotic solvent (B) may be 1 or more, or 5 or more.

[0055] In the composition of the present disclosure, the content of the aprotic solvent (B) relative to the mass of the composition can be 80 mass% or less, preferably in the range of 35 to 80 mass%, more preferably in the range of 35 to less than 80 mass%, and particularly preferably in the range of 50 to less than 80 mass%.

[0056] The composition of the present disclosure may contain a compound represented by the following formula (C) (also referred to as compound (C) in this specification). When the composition of the present disclosure contains compound (C), the content thereof may be 0.01 to 10 mass%, preferably 0.01 to 8 mass%, and more preferably 0.01 to 5 mass%, based on the total mass of the composition. [ka]

[0057] Fluoride ion The composition of the present disclosure contains fluoride ions in addition to the fluoropolymer (A) and the aprotic solvent (B). When the monomer is polymerized to produce the fluoropolymer (A), fluoride ions are generated, which cause disadvantages such as corrosion of the production equipment, increased cost of wastewater treatment, or the need for an additional step for removing or reducing the fluoride ions. The composition of the present disclosure has a low fluoride ion concentration, which may be, for example, 0.01 to 500 ppm by mass, and these disadvantages are alleviated. The fluoride ion concentration in the composition of the present disclosure is preferably 0.01 to 400 ppm by mass, more preferably 100 to 400 ppm by mass.

[0058] Other Ingredients The composition of the present disclosure may contain, in addition to the fluoropolymer (A), the aprotic solvent (B), and the fluoride ion, raw material monomers used in the production of the fluoropolymer, oligomers formed from the raw material monomers, a polymerization initiator, impurities derived from the raw materials, etc. The amount of each of the above-mentioned components contained in the composition can be adjusted, for example, by setting the production conditions of the fluoropolymer (A) (e.g., temperature, time, type and amount of raw material monomer, type and amount of solvent, type and amount of polymerization initiator). In addition, the amount of each of the components can be adjusted by purification after the production of the fluoropolymer (A).

[0059] Method for producing fluoropolymer (A) The fluoropolymer (A) can be produced, for example, by a polymerization step of polymerizing the monomer (M) in a mixture of the monomer (M) and the aprotic solvent (B) (also referred to as the "raw material mixture" in this specification). For example, the composition of the present disclosure can be produced by subjecting the raw material monomer (which may be only the monomer (M) or a combination of the monomer (M) and other monomers) and the aprotic solvent (B) containing an optional polymerization initiator to polymerization conditions to polymerize the monomer (M). In one embodiment, the composition of the present disclosure can be produced by mixing the monomer (M) and the aprotic solvent (B) and polymerizing the monomer in the mixture to which a polymerization initiator, other monomers, other components, etc. are added as necessary. The polymerization method may be solution polymerization or precipitation polymerization. In solution polymerization, the fluoropolymer (A) is dissolved in its entirety in the polymerization product liquid. This is one embodiment of the fluoropolymer (A) solution. In the precipitation polymerization, a part or the whole of the fluoropolymer (A) does not dissolve in the polymerization product liquid, and a solid or semi-solid fluoropolymer (A) and a polymerization product liquid are obtained. This is one embodiment of a mixture of the fluoropolymer (A) and the aprotic solvent (B).

[0060] The fluoropolymer (A) may contain fluoride ions at a concentration of 0.01 to 100 ppm by mass, 0.05 to 100 ppm by mass, 0.05 to 90 ppm by mass, or 0.05 to 80 ppm by mass. The fluoride ion content of the fluoropolymer (A) is preferably low. The fluoride ion content in the fluoropolymer (A) is preferably 0.01 to 90 ppm by mass, more preferably 0.01 to 80 ppm by mass, and even more preferably 10 to 80% by mass. In the present disclosure, by using a raw material mixture having a low fluoride ion content, the fluoride ion content of the fluoropolymer (A) produced after polymerization can be reduced.

[0061] In the method for producing a fluoropolymer (A) of the present disclosure, a mixture of a monomer (M) and an aprotic solvent (B) having a low fluoride ion content (also referred to as a "raw material mixture" in this specification) is used, thereby obtaining a fluoropolymer (A) having a low fluoride ion content. For this reason, the polymerization step in the method for producing a fluoropolymer (A) of the present disclosure is suitable as a method for producing a composition of the present disclosure. The fluoride ion content of the raw material mixture is preferably 0.05 to 300 ppm by mass, more preferably 0.05 to 250 ppm by mass, still more preferably 0.05 to 200 ppm by mass, and particularly preferably 0.05 to 150 ppm by mass.

[0062] The fluoride ion content in the aprotic solvent (B) may be, for example, 100 ppm by mass or less, 50 ppm by mass or less, 25 ppm by mass or less, 10 ppm by mass or less, 5 ppm by mass or less, 1 ppm by mass or less, 0.001 to 100 ppm by mass, 0.001 to 50 ppm by mass, 0.001 to 25 ppm by mass, 0.001 to 10 ppm by mass, 0.001 to 5 ppm by mass, 0.001 to 1 ppm by mass, or the like.

[0063] Methods for reducing the fluoride ion concentration in the aprotic solvent (B) include treatments such as adsorption, washing with water, and distillation, with activated carbon adsorption and washing with water being preferred.

[0064] monomer "Monomer (M)" is a monomer corresponding to a structural unit contained as a main component in the fluoropolymer (A). In addition to the monomer (M), other monomers can be used as the monomer. In this specification, a monomer corresponding to a structural unit contained in the fluoropolymer (A) other than the structural unit contained as a main component may be referred to as "another monomer".

[0065] Those skilled in the art will understand that by polymerizing a specific monomer, a fluoropolymer (A) having a structural unit corresponding to this monomer can be obtained. Therefore, those skilled in the art will be able to select an appropriate monomer to produce a desired fluoropolymer (A). For example, monomers corresponding to the structural unit (A1), structural unit (A2), structural unit (A3), structural unit (A1-1), structural unit (A2-1), structural unit (A2-2), structural unit (A3-1), structural unit (A3-2), and structural unit (A11-1) can be monomers represented by the formulas (M1), (M2), (M3), (M1-1), (M2-1), (M2-2), (M3-1), (M3-2), and (M11-1) shown below (which may be referred to herein as "monomer (M1)", "monomer (M2)", "monomer (M3)", "monomer (M1-1)", "monomer (M2-1)", "monomer (M2-2)", "monomer (M3-1)", "monomer (M3-2)," and "monomer (M11-1)," respectively). [ka] [In the formula, R 1 ~R 9 each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.

[0066] R in monomer (M1), monomer (M2), and monomer (M3) 1 ~R 9 In the case of the structural unit (A1), the structural unit (A2), and the structural unit (A3), R 1 ~R 9 The statements made regarding the above are applicable. The monomer (M) can be used alone or in combination of two or more. The monomer (M) can also be used in combination with other monomers. For example, the monomer (M2-1) and the monomer (M11-1) can be combined to produce a fluorine-containing polymer (A) containing the structural unit (A2-1) and the structural unit (A11-1).

[0067] The fluoride ion concentration in the monomer (M) may be 0.01 to 1000 ppm by mass, preferably 0.01 to 800 ppm by mass, and more preferably 0.01 to 500 ppm by mass. The monomer (M) is decomposed during storage to generate fluoride ions, and as a result, the fluoride ions may be mixed into the monomer (M). In the present disclosure, the amount of fluoride ions contained in the monomer (M) used for producing the fluorine-containing polymer (A) is reduced in advance to obtain a fluorine-containing polymer (A) having a low fluoride ion concentration. Methods for reducing the fluoride ion concentration in the monomer (M) include treatments such as adsorption, washing, and distillation, and activated carbon adsorption and water washing are preferred. As an example of distillation, a method of treating the monomer (M) at a temperature of 30 to 60° C. and a pressure of 50 to 500 hPa can be mentioned. The adsorption may be, for example, a method in which the monomer (M) is dissolved in a solvent capable of dissolving the monomer (M), such as an aprotic solvent (B), and the resulting monomer solution is treated with an adsorbent in an amount of 1 to 20% by mass relative to the mass of the monomer (M). Examples of the adsorbent include activated carbon, silica gel, activated alumina, and zeolite, and activated carbon is preferred. Examples of the adsorption treatment method include a flow method and a batch method. Examples of the water washing may include a method in which the monomer (M) is dissolved in a solvent capable of dissolving the monomer (M), such as an aprotic solvent (B), and the resulting monomer solution is washed with water, and a method in which the monomer (M) is directly washed with water.

[0068] The type and amount of the other monomer may be appropriately adjusted so that the desired fluoropolymer (A) is formed. The other monomer may be one that forms a fluoroolefin unit by polymerization (e.g., a fluoroolefin). The proportion of the fluoroolefin unit may be 50 mol% or less, preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, and particularly preferably 0 mol% of the total constitutional units constituting the fluoropolymer (A).

[0069] The fluoroolefin unit is a structural unit formed after polymerization of a monomer containing a fluorine atom and a carbon-carbon double bond. The atoms constituting the fluoroolefin unit may be limited to fluorine atoms, halogen atoms other than fluorine atoms, carbon atoms, hydrogen atoms, and oxygen atoms. The atoms constituting the fluoroolefin unit may be only fluorine atoms, halogen atoms other than fluorine atoms, carbon atoms, and hydrogen atoms. The atoms constituting the fluoroolefin unit may be only fluorine atoms, carbon atoms, and hydrogen atoms. The atoms constituting the fluoroolefin unit may be only fluorine atoms and carbon atoms.

[0070] The fluoroolefin unit includes at least one unit selected from the group consisting of fluorine-containing perhaloolefin units, vinylidene fluoride units (-CH2-CF2-), trifluoroethylene units (-CFH-CF2-), pentafluoropropylene units (-CFH-CF(CF3)-, -CF2-CF(CHF2)-), 1,1,1,2-tetrafluoro-2-propylene units (-CH2-CF(CF3)-), and the like.

[0071] The fluorine-containing perhaloolefin unit is a structural unit formed by polymerization of a monomer which contains a fluorine atom and a carbon-carbon double bond and may contain halogen atoms other than fluorine atoms. The fluorine-containing perhaloolefin unit includes at least one selected from the group consisting of a chlorotrifluoroethylene unit (-CFCl-CF2-), a tetrafluoroethylene unit (-CF2-CF2-), a hexafluoropropylene unit (-CF2-CF(CF3)-), a perfluoro(methyl vinyl ether) unit (-CF2-CF(OCF3)-), a perfluoro(ethyl vinyl ether) unit (-CF2-CF(OC2F5)-), a perfluoro(propyl vinyl ether) unit (-CF2-CF(OCF2C2F5)-), a perfluoro(butyl vinyl ether) unit (-CF2-CF(O(CF2)2C2F5)-), and a perfluoro(2,2-dimethyl-1,3-dioxole) unit (-CF-CAF- (wherein A represents a perfluorodioxolane ring formed together with the adjacent carbon atoms shown in the formula, and two trifluoromethyls are bonded to the carbon atom at the 2-position of the dioxolane ring).

[0072] The fluoroolefin unit may include at least one selected from the group consisting of a chlorotrifluoroethylene unit, a tetrafluoroethylene unit, a hexafluoropropylene unit, a perfluoro(methyl vinyl ether) unit, and a perfluoro(propyl vinyl ether) unit.

[0073] Those skilled in the art can understand other monomers corresponding to the structural units constituting the fluoropolymer (A). For example, monomers corresponding to the tetrafluoroethylene unit, the hexafluoropropylene unit, and the vinylidene fluoride unit are tetrafluoroethylene (CF2=CF2), hexafluoropropylene (CF3CF=CF2), and vinylidene fluoride (CH2=CF2), respectively.

[0074] The fluoroolefin (monomer) corresponding to the fluoroolefin unit may be, for example, at least one selected from the group consisting of fluorine-containing perhaloolefin, vinylidene fluoride, trifluoroethylene, pentafluoropropylene, and 1,1,1,2-tetrafluoro-2-propylene. The fluoroolefin may preferably be at least one selected from the group consisting of chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(methyl vinyl ether), and perfluoro(propyl vinyl ether).

[0075] The fluorine-containing perhaloolefin may be at least one selected from the group consisting of chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), perfluoro(propyl vinyl ether), perfluoro(butyl vinyl ether), and perfluoro(2,2-dimethyl-1,3-dioxole).

[0076] Aprotic Solvent (B) In the method for producing the fluoropolymer (A) of the present disclosure, a monomer is polymerized in an aprotic solvent (B). For details of the aprotic solvent (B), the description of the aprotic solvent (B) in the composition of the present disclosure is referred to unless otherwise specified.

[0077] Polymerization initiator In the production method of the present disclosure, a polymerization initiator may be used in the polymerization step. Any polymerization initiator may be used as long as it can polymerize the monomer (M), for example, a radical polymerization initiator. It is preferable that the polymerization initiator does not contain a fluorine element in its structure. It is preferable that the polymerization initiator has a 10-hour half-life temperature within the range of 0°C to 160°C. The polymerization initiator may be used alone or in combination of two or more kinds.

[0078] Preferred examples of the polymerization initiator used in the polymerization step include di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, diisobutyryl peroxide, di(ω-hydro-dodecafluoroheptanoyl) peroxide, di(ω-hydro-hexadecafluorononanoyl) peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydrohexadecafluorononanoyl-peroxide, benzoyl peroxide, bis(2,3,4,5,6-pentafluorobenzoyl) peroxide, tert-butyl peroxypivalate, tert-hexyl peroxypivalate, ammonium persulfate, sodium persulfate, and potassium persulfate. More preferred examples of the polymerization initiator include di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, diisobutyryl peroxide, di(ω-hydro-dodecafluoroheptanoyl) peroxide, benzoyl peroxide, bis(2,3,4,5,6-pentafluorobenzoyl) peroxide, tert-butyl peroxypivalate, tert-hexyl peroxypivalate, and ammonium persulfate.

[0079] Polymerization process to polymerize monomer (M) The amount of monomer (M) used in the polymerization reaction can be appropriately determined depending on the ratio of structural units corresponding to monomer (M) in the desired fluoropolymer (A), etc. For example, it is 50 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 100 mol%, based on the total number of moles of all raw material monomers. When other monomers are used in addition to the monomer (M), the amount of the other monomers can be appropriately determined depending on the ratio of the structural units corresponding to the other monomers in the desired fluoropolymer (A), etc. For example, it is 50 mol% or less, preferably 20 mol% or less, more preferably 10 mol% or less, and particularly preferably 0 mol%, based on the total number of moles of all raw material monomers.

[0080] The amount of the aprotic solvent (B) used in the polymerization reaction can be within a range of 20 to 300 mass%, preferably within a range of 35 to 250 mass%, and more preferably within a range of 50 to 300 mass%, assuming that the amount of the monomer (M) is 100 mass%.

[0081] The amount of the polymerization initiator used in the polymerization reaction may be, for example, within a range of 0.0001 g to 0.05 g per 1 g of all monomers (i.e., the total amount of monomer (M) and other monomers) to be subjected to the reaction, preferably within a range of 0.0001 g to 0.01 g, and more preferably within a range of 0.0005 g to 0.008 g.

[0082] The polymerization reaction can be carried out in the presence or absence of an inert gas, but is preferably carried out in the presence of an inert gas from the viewpoint of further reducing the fluoride ion content of the fluoropolymer (A). Examples of the inert gas include nitrogen, argon, helium, neon, carbon dioxide, etc., preferably nitrogen and argon, and more preferably nitrogen.

[0083] The temperature of the polymerization reaction may be, for example, within the range of -10°C to 160°C, preferably within the range of 0°C to 160°C, and more preferably within the range of 0°C to 100°C. The polymerization reaction may be carried out at a temperature not higher than 20°C higher than the lower boiling point of the monomer (M) corresponding to the structural unit that is the main component of the fluoropolymer (A) and the aprotic solvent, and not higher than 20°C higher than the 10-hour half-life temperature of the polymerization initiator. In this case, the lower limit of the temperature can be, for example, -10°C, and preferably 0°C.

[0084] The reaction time of the polymerization reaction may be preferably within the range of 0.5 to 72 hours, more preferably within the range of 1 to 48 hours, and further preferably within the range of 1 to 30 hours.

[0085] The polymerization reaction can be carried out under reduced pressure, atmospheric pressure, or pressurized conditions. The polymerization reaction is preferably carried out in the presence of an inert gas and under pressurized conditions, from the viewpoint of further reducing the fluoride ion content of the fluoropolymer (A). In this case, the pressurization is preferably 0.05 to 0.2 MPa (gauge pressure).

[0086] The fluoropolymer (A) produced by the polymerization reaction can be isolated or purified, if desired, by a conventional method such as extraction, dissolution, concentration, filtration, precipitation, dehydration, adsorption, chromatography or a combination of these.

[0087] The fluoropolymer (A) produced by the production method of the present disclosure has a low fluoride ion content, and is therefore advantageous in terms of reducing waste liquid treatment costs and reducing corrosion of facilities during subsequent purification.

[0088] The fluoropolymer (A), particularly the fluoropolymer (A3), usually has low solubility in the aprotic solvent (B). For this reason, it has been difficult to obtain a coating agent containing the fluoropolymer (A) at a high concentration for forming a coating film of the fluoropolymer (A). However, the production method of the present disclosure can produce a liquid in which the fluoropolymer (A) is dissolved at a high concentration in the aprotic solvent (B). For example, a liquid can be produced in which the amount of the fluoropolymer (A) dissolved is 20% by mass or more, preferably in the range of 20 to 65% by mass, more preferably in the range of more than 20% by mass to 65% by mass, particularly preferably in the range of more than 20% by mass to 50% by mass, based on the total mass of the fluoropolymer (A) and the aprotic solvent (B). The fluoropolymer (A) may be purified and isolated from the liquid. In another embodiment, the liquid may be used as it is for an application requiring the fluoropolymer (A).

[0089] Method for producing a solution of fluoropolymer (A) The method for producing a fluoropolymer (A) solution includes a polymerization step of polymerizing the monomer (M) in the presence of the monomer (M), optionally a polymerization initiator, and an aprotic solvent (B). The polymerization step is, for example, polymerizing the monomer (M) in a mixture of the monomer (M) and the aprotic solvent (B). The solution may contain 0.01 to 500 ppm by mass of fluoride ions, preferably 0.01 to 400 ppm by mass, and more preferably 100 to 400 ppm by mass. The mixture of the monomer (M) and the aprotic solvent (B) may contain 0.05 to 300 ppm by mass of fluoride ions, preferably 0.05 to 250 ppm by mass, and more preferably 0.05 to 150 ppm by mass.

[0090] When the fluoropolymer (A) is a fluoropolymer (A3), the amount of the fluoropolymer (A3) dissolved relative to the total mass of the fluoropolymer (A3) and the aprotic solvent (B) can be, for example, 20 mass% or more, 30 mass% or more, more than 30 mass% or 31 mass% or more, preferably in the range of 20 to 65 mass%, more than 20 mass% to 65 mass%, or 20 to 50 mass%, more preferably in the range of 30 to 65 mass%, more than 30 mass% to 65 mass%, or 31 to 65 mass%, and particularly preferably in the range of 30 to 50 mass%, more than 30 mass% to 50 mass%, or 31 to 50 mass%.

[0091] When the fluoropolymer (A) is a fluoropolymer (A3) and the aprotic solvent is a non-perfluoro solvent, the amount of the fluoropolymer (A3) dissolved may be less than 20% by mass in addition to the above ranges, and can be, for example, 1% by mass or more, 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, 30% by mass or more, more than 30% by mass, or 31% by mass or more, preferably within the range of 20 to 65% by mass, more than 20% by mass to 65% by mass, or within the range of 20 to 50% by mass, more preferably within the range of 30 to 65% by mass, more than 30% by mass to 65% by mass, or within the range of 31 to 65% by mass, and particularly preferably within the range of 30 to 50% by mass, more than 30% by mass to 50% by mass, or within the range of 31 to 50% by mass.

[0092] In the method for producing a fluoropolymer (A) solution, a solution is obtained in which the fluoropolymer (A) produced by the polymerization reaction is dissolved in the aprotic solvent (B). In this method, for example, the monomer (M) is polymerized in the aprotic solvent (B), and the resulting fluoropolymer (A) is obtained in a state of being dissolved in the polymerization reaction liquid. This method can typically be carried out in the same manner as the method for producing the fluoropolymer (A) described above. Therefore, unless otherwise specified, the description regarding the method for producing the fluoropolymer (A) described above can be applied to the method for producing a fluoropolymer (A) solution. For example, the following items used in the method for producing a fluoropolymer (A) solution can be applied to the items described in the section on the method for producing the fluoropolymer (A). The types, amounts used, and fluoride ion concentrations of the monomer (M), polymerization initiator, aprotic solvent (B), etc.; various conditions of the polymerization reaction; the type, fluoride ion concentration, dissolution concentration, etc. of the obtained fluoropolymer (A).

[0093] Method for producing a mixture of fluoropolymer (A) and aprotic solvent (B) The method for producing a mixture of a fluoropolymer (A) and an aprotic solvent (B) comprises the step of mixing the fluoropolymer (A) and the aprotic solvent (B). The mixture may contain fluoride ions in an amount of 0.01 to 500 ppm by mass, preferably 0.01 to 400 ppm by mass, and more preferably 100 to 400 ppm by mass.

[0094] The step of mixing the fluoropolymer (A) and the aprotic solvent (B) may be a method of mixing the fluoropolymer (A) with the aprotic solvent (B) in an amount equal to or greater than the amount of the aprotic solvent (B) that can dissolve the fluoropolymer (A). The above descriptions regarding the composition and the fluoropolymer (A) are applicable to the method for producing the mixture, unless otherwise specified.

[0095] How to determine fluoride ion concentration The fluoride ion concentration of the fluoropolymer (A) can be determined as follows. Add 5 mL of hexafluorobenzene to 1 g of polymer and heat to dissolve the polymer at 50℃. Add 5 mL of pure water to 5 mL of the resulting solution and stir at room temperature. Separate the resulting aqueous phase and add 4 mL of total ionic strength adjustment buffer to 4 mL of the aqueous phase. Measure the fluoride ion concentration of the resulting solution with an ion meter. Taking into account the dilution rate, the fluoride ion concentration is determined to be 18 times the measured value.

[0096] The fluoride ion concentration of a mixture of monomer and solvent (monomer solution (e.g., raw material mixture)) can be determined as follows. Add 5 mL of pure water to 1 g of the monomer and solvent mixture and stir at room temperature. Separate the resulting aqueous phase, and add 4 mL of total ionic strength adjustment buffer to 4 mL of the aqueous phase. Measure the fluoride ion concentration of the resulting solution with an ion meter. Taking into account the dilution rate, the fluoride ion concentration is determined as 10 times the measured value.

[0097] The fluoride ion concentration of the aprotic solvent (B) can be determined in the same manner as for the monomer-solvent mixture, except that no monomer is used.

[0098] The fluoride ion concentration of the monomer (M) can be determined as follows. A mixed solution of a monomer and a solvent is prepared, and the fluoride ion concentration of the mixed solution is determined by the above-mentioned method. Separately, the fluoride ion concentration of the solvent is determined by the above-mentioned method. The fluoride ion concentration of the monomer is determined by subtracting the fluoride ion concentration of the solvent from the fluoride ion concentration of the mixed solution of the monomer and the solvent.

[0099] The fluoride ion concentration of a composition containing the fluoropolymer (A) and the aprotic solvent (B) (for example, a polymerization liquid of the fluoropolymer (A)) can be determined as follows. Dilute 3 mL of the composition by adding 3 mL of the aprotic solvent (B) contained in the composition. Add 5 mL of pure water to 1 g of the diluted solution and stir at room temperature. Separate the resulting aqueous phase, and add 4 mL of total ionic strength adjustment buffer to 4 mL of the aqueous phase. Measure the fluoride ion concentration of the prepared solution with an ion meter. Taking into account the dilution rate, the fluoride ion concentration is determined by multiplying the measured value by 20.

[0100] The fluoropolymer (A) produced by the production method of the present disclosure can be used in the applications of conventionally known fluoropolymers (A). The fluoropolymer (A) produced by the production method of the present disclosure has a low fluoride ion content, and is therefore advantageous in that it can reduce corrosion of equipment (e.g., refining equipment, melt molding equipment, etc.) used for the fluoropolymer (A) and can suppress the inclusion of foreign matter due to corrosion.

[0101] Although the embodiments have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the claims. EXAMPLES

[0102] Hereinafter, the embodiments of the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited thereto. The fluorine-containing monomers and the like used in the following examples are as follows.

[0103] (raw material monomer) Perfluoro(2-methylene-4-methyl-1,3-dioxolane) (Monomer (M3-1))

[0104] (Polymerization initiator) PFBPO (Bis(2,3,4,5,6-pentafluorobenzoyl) peroxide)

[0105] (Polymerization initiator solution) Polymerization initiator solution (1): Methanol solution containing 50% by mass of NPP (di-n-propyl peroxydicarbonate (10-hour half-life temperature: 40°C))

[0106] (Aprotic Solvents) Novec7100: Mixture of CF3CF2CF2CF2OCH2 and (CF3)2CFCF2OCH3 (3M Japan Limited) Hexafluorobenzene HFMOP: 1,1,1,3,3,3-Hexafluoro-2-methoxypropane (Daikin Industries, Ltd.) FC-72: Perfluorohexane (3M Japan Limited) AE-3000:CF3CH2OCF2CHF2(AGC Inc.) Zeorora H: 1,1,2,2,3,3,4-heptafluorocyclopentane (Zeon Corporation)

[0107] (Method for measuring fluoride ion concentration in a mixture of monomer and solvent (monomer solution)) 5 mL of pure water was added to 1 g of the monomer / solvent mixture and stirred at room temperature. The resulting aqueous phase was separated, and 4 mL of total ionic strength adjustment buffer was added to 4 mL of the aqueous phase. The fluoride ion concentration of the prepared solution was measured with an ion meter. Taking into account the dilution rate, the fluoride ion concentration was determined to be 10 times the measured value.

[0108] (Method for measuring fluoride ion concentration in polymer) 5 mL of hexafluorobenzene was added to 1 g of polymer, and the polymer was heated and dissolved at 50°C. 5 mL of pure water was added to 5 mL of the resulting solution and stirred at room temperature. The resulting aqueous phase was separated, and 4 mL of total ionic strength adjustment buffer was added to 4 mL of the aqueous phase. The fluoride ion concentration of the prepared solution was measured with an ion meter. Taking into account the dilution rate, the fluoride ion concentration was determined to be 18 times the measured value.

[0109] (Method for measuring fluoride ion concentration in polymerization reaction solution) The reaction solution after the polymerization reaction was diluted by adding the same amount of polymerization solvent to 3 mL. In the case of solution polymerization, the reaction solution in which the polymer generated in the polymerization reaction was dissolved (a composition containing a polymer and a solvent) was used as the reaction solution to be diluted, and in the case of precipitation polymerization, the polymerization reaction solution in the mixture of the solid polymer generated in the polymerization reaction and the polymerization reaction solution (a composition containing a polymer and a solvent) was used as the reaction solution to be diluted. 5 mL of pure water was added to 1 g of the diluted solution and stirred at room temperature. The resulting aqueous phase was separated, and 4 mL of total ionic strength adjustment buffer was added to 4 mL of the aqueous phase. The fluoride ion concentration of the prepared solution was measured with an ion meter. Taking into account the dilution rate, the value obtained was 20 times the measured value, which was taken as the concentration of fluoride ions.

[0110] (Whether or not the stainless steel vessel used in the polymerization reaction is corroded) If the inside of the container after the polymerization reaction turned black or gold, it was judged that corrosion had occurred.

[0111] Production Example 1 (Treatment for reducing fluoride ion concentration in monomer (M3-1) solution) 100g of Novec7100 was added to 50g of monomer (M3-1) and stirred. The fluoride ion concentration of the resulting monomer solution was 1500 mass ppm. This monomer solution was treated with 15g of activated carbon to obtain a monomer solution with a fluoride ion concentration of 110 mass ppm. In addition, when this monomer solution was analyzed by gas chromatography, it was found that the compound (C) was contained in an amount of 3.6% relative to the monomer (GC area percentage).

[0112] Example 1 (Solution Polymerization) In a 300 mL capacity SUS autoclave, 100 g of the monomer (M3-1) solution obtained in Production Example 1 was placed, followed by 0.1 g of the polymerization initiator solution (1). After cooling the autoclave to -78°C, the atmosphere in the system was replaced with nitrogen gas, and nitrogen gas was filled so that the internal pressure was 0.1 MPaG. The system was subjected to a polymerization reaction at 40°C for 24 hours, and a polymer solution (a composition containing a fluoropolymer (A) and an aprotic solvent (B)) in which the produced polymer was dissolved was obtained. The fluoride ion concentration of the polymer solution was measured and shown in Table 1. 100 g of AE-3000 was added to the polymer solution, and then dimethyl carbonate, a poor solvent, was added dropwise. The resulting precipitate was collected by filtration and dried at 120°C to obtain a polymer. The fluoride ion concentration of the polymer was measured and is shown in Table 1. When the state inside the autoclave after the polymerization was visually inspected, no discoloration to black or gold was observed.

[0113] Examples 2 to 4 (Solution Polymerization) The fluoride ion concentration and the presence or absence of corrosion of the polymerization vessel were evaluated in the same manner as in Example 1, except that the solvent was changed to one (hexafluorobenzene, HFMOP, or FC-72) shown in Table 1. The results are shown in Table 1.

[0114] Comparative Example 1 (Solution Polymerization) The fluoride ion concentration and the presence or absence of corrosion of the polymerization vessel were evaluated in the same manner as in Example 1, except that the monomer solution was changed to one before the fluoride ion concentration reduction treatment (fluoride ion concentration was 1500 ppm). The results are shown in Table 1. When the state inside the autoclave after polymerization was visually inspected, discoloration of the material to gold was confirmed.

[0115] Example 5 (Precipitation Polymerization) A monomer (M3-1) solution was obtained in the same manner as in Production Example 1, except that the solvent was changed from Novec7100 to AE-3000. 100 g of this monomer (M3-1) solution was placed in a 300 mL capacity autoclave made of SUS, and then 0.1 g of the polymerization initiator solution (1) was placed. After cooling the autoclave to -78°C, the atmosphere in the system was replaced with nitrogen gas, and nitrogen gas was filled so that the internal pressure was 0.1 MPaG. The mixture was subjected to a polymerization reaction at 40°C for 24 hours, and a polymer mixture (a composition containing a fluoropolymer (A) and an aprotic solvent (B)) in which the produced polymer precipitated was obtained. The fluoride ion concentration in the polymerization reaction solution in the polymer mixture was measured and shown in Table 1. The polymer mixture was collected by filtration and dried at 120° C. to obtain a solid polymer. The fluoride ion concentration of the polymer was measured and is shown in Table 1. When the state inside the autoclave after the polymerization was visually inspected, no discoloration to black or gold was observed.

[0116] Example 6 (Precipitation Polymerization) The fluoride ion concentration and the presence or absence of corrosion of the polymerization vessel were evaluated in the same manner as in Example 5, except that the solvent was changed to Zeorora H. The results are shown in Table 1.

[0117] Comparative Example 2 (Precipitation Polymerization) The fluoride ion concentration and the presence or absence of corrosion of the polymerization vessel were evaluated in the same manner as in Example 5, except that the monomer solution was changed to one before the fluoride ion concentration reduction treatment (fluoride ion concentration was 1500 ppm) and the polymerization initiator solution (1) was changed to a polymerization initiator (PFBPO; 0.1 g). The results are shown in Table 1. When the state inside the autoclave after polymerization was visually inspected, discoloration of the material to gold was confirmed.

[0118] [Table 1]

Claims

1. A method for producing a fluoropolymer (A) solution in which a fluoropolymer (A) produced by a polymerization reaction is dissolved in the aprotic solvent (B), the method comprising the steps of: polymerizing the monomer (M) in a mixture of the monomer (M) and an aprotic solvent (B), the method comprising the steps of: The solution contains 0.01 to 500 ppm by mass of fluoride ions, The mixture contains 0.05 to 300 ppm by mass of fluoride ions, The monomer (M) is Formula (M1) 【Chemistry 1】 [In the formula, R １ represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group. A compound represented by the formula: Formula (M2) 【Chemistry 2】 [In the formula, R ２ ~R ５ each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] or Formula (M3) 【Chemistry 3】 [In the formula, R ６ ~R ９ each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The compound represented by the formula: The fluoropolymer (A) is Formula (A1) 【Chemistry 4】 [In the formula, R １ represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group. A structural unit represented by Formula (A2) 【Chemistry 5】 [In the formula, R ２ ~R ５ each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] A structural unit represented by the formula: Formula (A3) 【Chemistry 6】 [In the formula, R ６ ~R ９ each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The main component is a structural unit represented by The aprotic solvent (B) is at least one solvent selected from the group consisting of perfluoroaromatic compounds, perfluorotrialkylamines, perfluoroalkanes, hydrofluorocarbons, fluorocyclic ethers, hydrofluoroethers, and olefin compounds containing at least one chlorine atom; Manufacturing method.

2. 2. The method for producing a fluoropolymer (A) solution according to claim 1, wherein the aprotic solvent (B) is at least one solvent selected from the group consisting of perfluoroalkanes, hydrofluorocarbons, and hydrofluoroethers.

3. The monomer (M) contains a compound represented by any one of the following formulas (M1-1) to (M3-2): 【Chemistry 7】 The fluoropolymer (A) contains, as a main component, a structural unit represented by any one of the following formulas (A1-1) to (A3-2): 【Chemistry 8】 A process for producing the fluoropolymer (A) solution according to claim 1.

4. The monomer (M) is represented by the formula (M3-1): 【Chemistry 9】 The compound represented by the formula: The fluoropolymer (A) is represented by the formula (A3-1): 【Chemistry 10】 The process for producing a fluoropolymer (A) solution according to claim 3, which contains, as a main component, a structural unit represented by the following formula:

5. The method for producing a fluoropolymer (A) solution according to claim 4, wherein the fluoropolymer (A) solution contains 0.01 to 10 mass % of a compound represented by formula (C). 【Chemistry 11】

6. The aprotic solvent (B) is CF ３ CF ２ CF ２ CF ２ OCH ３ and (CF ３ ) ２ CFCF ２ OCH ３ 2. The method for producing a fluoropolymer (A) solution according to claim 1, wherein the fluoropolymer (A) is at least one selected from the group consisting of:

7. 2. The method for producing a fluoropolymer (A) solution according to claim 1, wherein the solution contains 100 to 400 ppm by mass of fluoride ions, and the mixture contains 0.05 to 150 ppm by mass of fluoride ions.

8. The solution contains 100 to 400 ppm by mass of fluoride ions, The mixture contains 0.05 to 150 ppm by mass of fluoride ions, The monomer (M) is represented by the formula (M3-1): 【Chemistry 12】 The compound represented by the formula: The fluoropolymer (A) is represented by the formula (A3-1): 【Chemistry 13】 The main component is a structural unit represented by The aprotic solvent (B) is CF ３ CF ２ CF ２ CF ２ OCH ３ and (CF ３ ) ２ CFCF ２ OCH ３ 2. The method for producing a fluoropolymer (A) solution according to claim 1, wherein the fluoropolymer (A) is at least one selected from the group consisting of:

9. 1. A process for producing a fluoropolymer (A), comprising a polymerization step of polymerizing a monomer (M) in a mixture of the monomer (M) and an aprotic solvent (B), comprising: the fluoropolymer (A) contains 0.01 to 100 ppm by mass of fluoride ions, and the mixture contains 0.05 to 300 ppm by mass of fluoride ions, The monomer (M) is Formula (M1) 【Chemistry 14】 [In the formula, R １ represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group. A compound represented by the formula: Formula (M2) 【Chemistry 15】 [In the formula, R ２ ~R ５ each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] or Formula (M3) 【Chemistry 16】 [In the formula, R ６ ~R ９ each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The compound represented by the formula: The fluoropolymer (A) is Formula (A1) 【Chemistry 17】 [In the formula, R １ represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group. A structural unit represented by Formula (A2) 【Chemistry 18】 [In the formula, R ２ ~R ５ each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] A structural unit represented by the formula: Formula (A3) 【Chemistry 19】 [In the formula, R ６ ~R ９ each independently represents a fluorine atom, a C1-C5 perfluoroalkyl group, or a C1-C5 perfluoroalkoxy group.] The main component is a structural unit represented by The aprotic solvent (B) is at least one solvent selected from the group consisting of perfluoroaromatic compounds, perfluorotrialkylamines, perfluoroalkanes, hydrofluorocarbons, fluorocyclic ethers, hydrofluoroethers, and olefin compounds containing at least one chlorine atom; Manufacturing method.

10. The process for producing a fluoropolymer (A) according to claim 9, wherein the aprotic solvent (B) is at least one solvent selected from the group consisting of perfluoroalkanes, hydrofluorocarbons, and hydrofluoroethers.

11. The monomer (M) contains a compound represented by any one of the following formulas (M1-1) to (M3-2): 【Chemistry 20】 The fluoropolymer (A) contains, as a main component, a structural unit represented by any one of the following formulas (A1-1) to (A3-2): 【Chemistry 21】 A process for producing the fluoropolymer (A) according to claim 9 or 10.

12. The monomer (M) is represented by the formula (M3-1): 【Chemical 22】 The compound represented by the formula: The fluoropolymer (A) is represented by the formula (A3-1): 【Chemistry 23】 The method for producing a fluoropolymer (A) according to claim 11, which comprises, as a main component, a structural unit represented by the following formula:

13. The process for producing a fluoropolymer (A) according to claim 12, wherein the monomer (M) contains 0.01 to 10 mass % of a compound represented by formula (C). 【Chemistry 24】

14. The method for producing a fluoropolymer (A) according to claim 9 or 10, wherein, in the polymerization step, the fluoropolymer (A) produced in the polymerization reaction contains a constitutional unit represented by the formula (A3) as a main component and is dissolved in the aprotic solvent (B), or the fluoropolymer (A) produced in the polymerization reaction is a solid or semi-solid in the aprotic solvent (B).

15. The method for producing a fluoropolymer (A) according to claim 9, wherein the fluoropolymer (A) contains 10 to 80 ppm by mass of fluoride ions, and the mixture contains 0.05 to 150 ppm by mass of fluoride ions.

16. the fluoropolymer (A) contains 10 to 80 ppm by mass of fluoride ions, and the mixture contains 0.05 to 150 ppm by mass of fluoride ions, The monomer (M) is represented by the formula (M3-1): 【Chemistry 25】 The compound represented by the formula: The fluoropolymer (A) is represented by the formula (A3-1): 【Chemistry 26】 The method for producing a fluoropolymer (A) according to claim 9, which contains, as a main component, a structural unit represented by the following formula:

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