Fluorine-containing copolymer composition, method for producing same, crosslinked rubber article, and method for producing same

Abstract

This fluorine-containing copolymer composition contains a fluorine-containing copolymer and silicon carbide. The silicon carbide contains silicon carbide with an alpha-crystal lattice, and the content of the alpha-crystal lattice is 50% or more with respect to 100% of the total crystal lattices in the silicon carbide.

Description

Fluorine-containing copolymer composition and method for producing the same, crosslinked rubber article and method for producing the same

[0001] The present invention relates to a fluorocopolymer composition and a method for producing the same, and a crosslinked rubber article and a method for producing the same, and in particular to a fluorocopolymer composition which can give a crosslinked rubber article having improved resistance to plasma treatment and a method for producing the same, as well as a crosslinked rubber article obtained from the fluorocopolymer composition and a method for producing the same.

[0002] In semiconductor manufacturing processes, CVD equipment and etching equipment are used in processes for forming insulating films and thin metal wiring films, and in such equipment, sealants are used to seal various connecting parts and movable parts. Crosslinked rubber (so-called fluororubber) articles obtained by crosslinking a fluorine-containing copolymer composition are sometimes used as the sealants, from the viewpoint of excellent heat resistance, chemical resistance, oil resistance, weather resistance, etc. Furthermore, since the sealants are exposed to plasmas of various gases during the manufacturing process, they are required to be resistant to plasma treatment.

[0003] For example, Patent Document 1 describes a crosslinkable fluorine-containing elastomer and a polymer having a bulk density of 0.15 g / cm ３ A molded article obtained by crosslinking a crosslinkable fluorine-containing elastomer composition containing the following silicon carbide particles is ２ Plasma treatment and O ２ / CF ４ It is disclosed to be resistant to plasma treatment.

[0004] Furthermore, for example, Patent Document 2 discloses that a fluororubber molded article made from a crosslinkable elastomer composition containing a crosslinkable elastomer (e.g., a copolymer of tetrafluoroethylene and perfluoro(alkyl vinyl ether)) and a non-oxide ceramic filler (e.g., silicon carbide) whose surface is oxidized, is O ２ and NF ３ It is disclosed that the material has plasma resistance of 1000 .mu.m or more.

[0005] Furthermore, for example, Patent Document 3 discloses that a molded article made of a crosslinkable elastomer composition containing 100 parts by weight of a crosslinkable elastomer (for example, a copolymer of tetrafluoroethylene and perfluoro(alkyl vinyl ether)) and 1 to 50 parts by weight of a filler made of a non-oxide ceramic (for example, a carbide or nitride) is NF ３ Plasma treatment and O ３ It is disclosed to be resistant to treatment.

[0006] Patent Document 1: JP-T-2012-509975A International Publication No. 2019 / 078238 Japanese Patent Application Laid-Open No. 2009-30064

[0007] However, it cannot necessarily be said that the molded articles obtained from the compositions described in Patent Documents 1 to 3 have sufficiently improved resistance to plasma treatment.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fluorocopolymer composition which can give crosslinked rubber articles having improved resistance to plasma treatment, a method for producing the same, and a crosslinked rubber article obtainable from the fluorocopolymer composition and a method for producing the same.

[0009] The present invention relates to a method for manufacturing a crosslinked rubber article obtained from a fluorocopolymer composition comprising a fluorocopolymer and silicon carbide, the silicon carbide having a specific α-type crystal lattice, which can be subjected to plasma treatment, particularly O ２ and N ２ / NF ３ The present invention is based on the discovery that the resistance to plasma treatment using silicon carbide-based gases is improved. Although the detailed mechanism by which the resistance to plasma treatment is improved is unknown, it is speculated that the wide band gap and crystalline anisotropy of silicon carbide with an α-type crystal lattice contribute to this.

[0010] The present invention is as follows. [1] A fluorine-containing copolymer composition comprising a fluorine-containing copolymer and silicon carbide, wherein the silicon carbide comprises silicon carbide of an α-type crystal lattice, and the content of the α-type crystal lattice is 50% or more, relative to 100% of all crystal lattices in the silicon carbide. [2] The fluorine-containing copolymer composition according to [1] above, wherein the silicon carbide has a particle size d50 of 60 μm or less. [3] The fluorine-containing copolymer composition according to [1] or [2] above, wherein the silicon carbide of an α-type crystal lattice is at least one type selected from the group consisting of 6H—SiC and 4H—SiC. [4] The fluorine-containing copolymer composition according to [3] above, wherein the silicon carbide of an α-type crystal lattice is 6H—SiC. [5] The fluorine-containing copolymer composition according to any of [1] to [4] above, wherein the content of the silicon carbide is 1 to 100 parts by mass, relative to 100 parts by mass of the fluorine-containing copolymer. [6] The fluorine-containing copolymer composition according to any of [1] to [5] above, wherein the fluorine-containing copolymer has units based on tetrafluoroethylene (TFE) and units based on perfluoroalkyl vinyl ether (PAVE). [7] The fluorine-containing copolymer composition according to [6] above, wherein the content of units based on tetrafluoroethylene (TFE) is 50 to 90 mol % based on all units based on monomers constituting the fluorine-containing copolymer, and the content of units based on perfluoroalkyl vinyl ether (PAVE) is 10 to 50 mol % based on all units based on monomers constituting the fluorine-containing copolymer. [8] The fluorine-containing copolymer composition according to any of [1] to [7] above, wherein the fluorine-containing copolymer contains units based on at least one monomer selected from the group consisting of: units based on a monomer having two or more polymerizable unsaturated bonds, units based on a monomer having at least one atom selected from the group consisting of a chlorine atom, a bromine atom, and an iodine atom, and units based on a monomer having a nitrile group. [9] The fluorine-containing copolymer composition according to any one of the above [1] to [8], further comprising a crosslinking agent, wherein the crosslinking agent is at least one selected from the group consisting of organic peroxides and amines.

[10] The fluorine-containing copolymer composition according to any one of the above [1] to [9], further comprising a crosslinking aid, wherein the crosslinking aid is at least one kind selected from the group consisting of compounds having two or more unsaturated bonds.

[11] A crosslinked rubber article obtained by crosslinking the fluorine-containing copolymer in the fluorine-containing copolymer composition according to any one of the above [1] to

[10] .

[12] A method for producing the fluorine-containing copolymer composition according to any one of the above [1] to

[10] , comprising kneading the fluorine-containing copolymer with the silicon carbide.

[13] A method for producing the crosslinked rubber article according to the above

[11] , comprising primarily heating the fluorine-containing copolymer composition at 100 to 400°C for 1 second to 24 hours, and, after the primary heating, secondary heating at 80 to 400°C for 30 minutes to 48 hours.

[0011] According to the present invention, there can be provided a fluorocopolymer composition which can give crosslinked rubber articles having improved resistance to plasma treatment, a method for producing the same, and a crosslinked rubber article obtainable from the fluorocopolymer composition and a method for producing the same.

[0012] The present invention will be described in detail below. In this specification, preferred definitions may be adopted arbitrarily, and combinations of preferred definitions are considered more preferable. In this specification, the term "XX to YY" for a numerical range means "XX or more and YY or less." In this specification, the lower and upper limits of preferred numerical ranges (e.g., ranges of content, etc.) described in stages can be independently combined. For example, a description of "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to obtain "10 to 60." Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in the Examples. "Room temperature" means 20 to 25°C. The term "unit" collectively refers to an atomic group derived from one molecule of the monomer formed directly by polymerization of the monomer, and an atomic group obtained by chemically converting a portion of the atomic group. Hereinafter, "units based on a monomer" may also be simply referred to as "units." "Rubber" means a rubber exhibiting properties defined by JIS K 6200:2008, and is distinguished from "resin." "Melting point" means the temperature corresponding to the maximum value of the melting peak measured by differential scanning calorimetry (DSC). ２ and N ２ / NF ３ "Resistance to plasma treatment of silicon carbide-based gases" may be simply referred to as "plasma resistance". In this specification, "silicon carbide of an α crystal lattice" may be simply referred to as "α-SiC", and "silicon carbide of a β crystal lattice" may be simply referred to as "β-SiC". In this specification, the content (mol%) of each unit in the fluorinated copolymer was calculated by nuclear magnetic resonance (NMR) analysis, as described in the Examples section. In this specification, the content (mass%) of iodine atoms in the fluorinated copolymer was calculated, as described in the Examples section, using an apparatus combining an automatic sample combustion apparatus, ion chromatograph pretreatment device (manufactured by Mitsubishi Chemical Analytech Co., Ltd., Model AQF-100), and an ion chromatograph.

[0013] [Fluorocopolymer Composition] The fluorine-containing copolymer composition according to an embodiment of the present invention (hereinafter may be simply referred to as "the fluorine-containing copolymer composition of the present embodiment") is not particularly limited as long as it contains a fluorine-containing copolymer and silicon carbide, and may or may not contain a crosslinking agent, a crosslinking aid, other components, and the like, as necessary.

[0014] <Fluorine-containing copolymer> The fluorine-containing copolymer is not particularly limited, and for example, it can be one that has no melting point or one that has a melting point, and it is preferred that it has no melting point.In addition, when a differential scanning calorimeter is used with the fluorine-containing copolymer as a sample, it is preferred that the fluorine-containing copolymer has a melting peak (ΔH) of 4.5 J / g or less.Specifically, the method for measuring the melting peak (ΔH) can be exemplified by weighing 5 mg of sample into an aluminum pan, and heating it from 20 ° C. to 360 ° C. at a temperature rising rate of 10 ° C. / min using a Hitachi DSC600 under an air atmosphere.The fluorine-containing copolymer can be exemplified by (a) a copolymer having tetrafluoroethylene (hereinafter sometimes simply referred to as "TFE") units and perfluoro(alkyl vinyl ether) (hereinafter sometimes simply referred to as "PAVE") units, (b) a copolymer having vinylidene fluoride (hereinafter sometimes simply referred to as "VdF") units, etc. These may be used alone or in combination of two or more. Among these, (a) a copolymer having TFE units and PAVE units is preferred from the viewpoint of heat resistance and chemical resistance.

[0015] The content of the fluorine-containing copolymer relative to the total mass of the fluorine-containing copolymer composition is not particularly limited, but from the viewpoint of heat resistance and chemical resistance, it is preferably from 60.00 to 99.70 mass%, more preferably from 65.00 to 99.30 mass%, particularly preferably from 70.00 to 99.00 mass%.

[0016] As the fluorine-containing copolymer, from the viewpoint of promoting the crosslinking reaction during the production of crosslinked rubber articles, preferred examples include copolymers containing units based on at least one monomer selected from the group consisting of units based on a monomer having two or more polymerizable unsaturated bonds; units based on a monomer having at least one atom selected from the group consisting of chlorine atoms, bromine atoms, and iodine atoms; and units based on a monomer having a nitrile group.The unit based on a monomer having at least one atom selected from the group consisting of chlorine atoms, bromine atoms, and iodine atoms is not particularly limited as long as it can be made to contain a unit having at least one of the above atoms in the fluorine-containing copolymer, and examples thereof include units obtained by copolymerizing a monomer having at least one of the above atoms, and units obtained by introducing at least one of the above atoms into a unit at the main chain terminal using a chain transfer agent described below.These may be used alone or in combination of two or more.

[0017] (a) Copolymer Having TFE Units and PAVE Units) TFE is CF ２ =CF ２ The proportion of TFE units in all units constituting the fluorine-containing copolymer is not particularly limited, but from the viewpoint of heat resistance and chemical resistance, it is preferably from 50 to 90 mol %, more preferably from 55 to 80 mol %, particularly preferably from 60 to 75 mol %.

[0018] As the PAVE, a monomer represented by the following general formula (3) is preferred: CF ２ =CF-O-R ｆ１ ...General formula (3) In general formula (3), R ｆ１ is a perfluoroalkyl group having 1 to 10 carbon atoms. ｆ１ The number of carbon atoms is not particularly limited as long as it is 1 to 10, but is preferably 1 to 8, more preferably 1 to 6, and particularly preferably 1 to 5. Specific examples of PAVE include (i) CF ２ = CFOCF ３ (ii) Perfluoro(methyl vinyl ether) (hereinafter, sometimes simply referred to as "PMVE"), (ii) CF ２ = CFOCF２ CF ３ (iii) CF ２ = CFOCF ２ CF ２ CF ３ (iv) Perfluoro(propyl vinyl ether) (hereinafter, sometimes simply referred to as "PPVE"), (iv) CF ２ = CFOCF ２ CF ２ CF ２ CF ３ and the like. These may be used alone or in combination of two or more. Among these, PMVE and PPVE are preferred from the viewpoints of reactivity and availability. The proportion of PAVE units in all units constituting the fluorocopolymer is not particularly limited, but from the viewpoints of heat resistance and chemical resistance, it is preferably 10 to 50 mol%, more preferably 20 to 40 mol%, and particularly preferably 25 to 35 mol%. Whether the PAVE is PMVE, PEVE, or PPVE, or whether a mixture of two or more of these is used, the suitable proportion is the same. The total content of TFE units and PAVE units in all units constituting the fluorocopolymer is not particularly limited, but from the viewpoints of heat resistance and chemical resistance, it is preferably 79 to 100 mol%, more preferably 89 to 100 mol%, and particularly preferably 95 to 100 mol%.

[0019] Specific examples of (a) copolymers having TFE units and PAVE units include (i) copolymers having TFE units, PAVE units, and at least one selected from the group consisting of chlorine atoms, bromine atoms, and iodine atoms at the ends and / or in the chain, (ii) copolymers having TFE units, PAVE units, C3DVE units, C4DVE units, C4-DV units, or C6-DV units described below, and at least one of chlorine atoms, bromine atoms, and iodine atoms at the ends and / or in the chain, (iii) copolymers having TFE units, PAVE units, and 8CNVE units or MV5CN units described below, and (iv) copolymers having TFE units, PAVE units, C3DVE units, C4DVE units, C4-DV units, or C6-DV units described below, and 8CNVE units or MV5CN units described below.

[0020] (b) Copolymer Having VdF Units) VdF is a copolymer of CF ２ =CH ２ (b) Specific examples of the copolymer having VdF units include (i) a copolymer having VdF units and units based on hexafluoropropylene (hereinafter, sometimes simply referred to as "HFP units"), (ii) a copolymer having VdF units, HFP units, and TFE units, and (iii) a copolymer having VdF units, PMVE units, and HFP units.

[0021] The proportion of VdF units in all units constituting the fluorinated copolymer is not particularly limited, but from the viewpoint of suppressing sticking, it is preferably from 40 to 90 mol %, more preferably from 45 to 85 mol %, particularly preferably from 50 to 80 mol %.

[0022] (Units based on other monomers) The fluorine-containing copolymer may have units other than TFE units, PAVE units and VdF units, and specific examples thereof include units based on a monomer having two or more polymerizable unsaturated bonds, units based on a monomer having a nitrile group, units based on a monomer represented by the following general formula (5) (hereinafter, sometimes simply referred to as "formula (5) units"), HFP units, units based on chlorotrifluoroethylene, etc. These may be used alone or in combination of two or more. Among these, from the viewpoint of heat resistance, units based on a monomer having two or more polymerizable unsaturated bonds and units based on a monomer having a nitrile group are preferred.

[0023] -Units Based on Monomers Having Two or More Polymerizable Unsaturated Bonds- It is preferable that the fluorine-containing copolymer further contains units based on monomers having two or more polymerizable unsaturated bonds. The units based on monomers having two or more polymerizable unsaturated bonds are not particularly limited, but from the viewpoint of achieving better effects of the present invention, those containing a fluorine atom are preferred, and units based on fluorine-containing monomers having two or more polymerizable unsaturated bonds are preferred. When units based on fluorine-containing monomers having two or more polymerizable unsaturated bonds are copolymerized, the polymerizable double bonds at the ends of the units based on fluorine-containing monomers having two or more polymerizable unsaturated bonds react during polymerization to obtain a copolymer having a branched chain. Examples of polymerizable unsaturated bonds include carbon-carbon double bonds (C=C) and triple bonds (C≡C). These may be used alone or in combination of two or more. Among these, double bonds are preferred from the viewpoint of heat resistance. The number of polymerizable unsaturated bonds is not particularly limited, but from the viewpoint of heat resistance, it is preferably 2 to 6, more preferably 2 or 3, and particularly preferably 2. As the fluorine-containing monomer having two or more polymerizable unsaturated bonds, a compound represented by the following general formula (2) is preferred, from the viewpoint of excellent rubber properties when the fluorine-containing copolymer is made into a crosslinked rubber article.

[0024] (CR ３１ R ３２ =CR ３３ ) ａ３ R ３４...General formula (2) In general formula (2), R ３１ , R ３２ and R ３３ each independently represents a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ３４ represents a trivalent perfluorohydrocarbon group having 1 to 10 carbon atoms, or a group having an etheric oxygen atom at the end or between the carbon-carbon bonds of the perfluorohydrocarbon group. In general formula (2), a3 represents an integer of 2 to 6, preferably 2 or 3, and more preferably 2. In general formula (2), multiple R ３１ , multiple R ３２ , and a plurality of R ３３ may be the same or different from each other, and are preferably the same from each other.

[0025] R ３１ , R ３２ , R ３３ R is preferably a fluorine atom or a hydrogen atom in view of superior polymerization reactivity of a fluorine-containing monomer having two or more polymerizable unsaturated bonds, more preferably all fluorine atoms or all hydrogen atoms, and particularly preferably all fluorine atoms in view of the heat resistance and chemical resistance of the crosslinked rubber article. ３４ R may be any of linear, branched, and cyclic, preferably linear or branched, and more preferably linear. ３４ The number of carbon atoms in R is preferably 2 to 10, more preferably 3 to 8, even more preferably 3 to 6, and particularly preferably 3 to 5. ３４ Although R may or may not have an etheric oxygen atom, it is preferable that R has an etheric oxygen atom in view of better crosslinking reactivity and rubber physical properties. ３４ The number of etheric oxygen atoms in R is preferably 1 to 6, more preferably 1 to 3, and particularly preferably 1 or 2. ３４ The etheric oxygen atom in R ３４ It is preferred that the nucleotide sequence is located at the end of the nucleotide sequence.

[0026] Specific preferred examples of the monomer represented by formula (2) include a monomer represented by general formula (2-1) and a monomer represented by general formula (2-2).

[0027] (CF ２ =CF) ２ R ４１ ...General formula (2-1) In general formula (2-1), R ４１ represents a divalent perfluorohydrocarbon group having 2 to 10 carbon atoms, or a group having an etheric oxygen atom at the end of the perfluorohydrocarbon group or between the carbon-carbon bonds. Specific examples of the monomer represented by general formula (2-1) include the following. The description after the formula is the abbreviation for the compound. One type may be used alone, or two or more types may be used. CF ２ = CFO (CF ２ ) ２ OCF = CF ２ CF ２ = CFO (CF ２ ) ３ OCF = CF ２ : C3DVE CF ２ = CFO (CF ２ ) ４ OCF = CF ２ : C4DVE CF ２ = CFO (CF ２ ) ６ OCF = CF ２ CF ２ = CFO (CF ２ ) ８ OCF = CF ２ CF ２ = CFO (CF ２ ) ２ OCF (CF ３ )CF ２ OCF = CF ２ CF ２ = CFO (CF ２ ) ２ O(CF(CF ３ )CF ２ O) ２ CF = CF ２ CF ２ = CFOCF ２ O (CF ２ CF ２ O) ２ CF = CF ２ CF ２ = CFO (CF ２ O) ３O(CF(CF ３ )CF ２ O) ２ CF = CF ２ CF ２ = CFOCF ２ CF (CF ３ ) O(CF ２ ) ２ OCF (CF ３ )CF ２ OCF = CF ２ CF ２ = CFOCF ２ CF ２ O (CF ２ O) ２ CF ２ CF ２ OCF = CF ２ As the monomer represented by the general formula (2-1), C3DVE and C4DVE are preferred since they provide even better rubber physical properties when the fluorocopolymer composition is made into a crosslinked rubber article.

[0028] (CH ２ =CH) ２ R ５１ ...General formula (2-2) In general formula (2-2), R ５１ represents a divalent perfluorohydrocarbon group having 2 to 10 carbon atoms, or a group having an etheric oxygen atom at the end of the perfluorohydrocarbon group or between the carbon-carbon bonds. Specific examples of the monomer represented by general formula (2-2) include the following. The description after the formula is the abbreviation for the compound. One type may be used alone, or two or more types may be used. CH ２ =CH(CF ２ ) ２ CH=CH ２ CH ２ =CH(CF ２ ) ４ CH=CH ２ : C4-DV CH ２ =CH(CF ２ ) ６ CH=CH ２ : C6-DV As the monomer represented by the general formula (2-2), C6-DV is preferred.

[0029] Among all units constituting the fluorine-containing copolymer, the proportion of units based on a fluorine-containing monomer having two or more polymerizable unsaturated bonds is not particularly limited, but from the viewpoint of heat resistance, it is preferably 0.01 to 1.00 mol%, more preferably 0.05 to 0.50 mol%, and particularly preferably 0.10 to 0.30 mol%. When the proportion of units based on a fluorine-containing monomer having two or more polymerizable unsaturated bonds is equal to or greater than the lower limit of the above range, the crosslinking reactivity is excellent, and the crosslinked rubber article after crosslinking has better tensile strength and compression set at high temperatures. When it is equal to or less than the upper limit of the above range, cracking can be further reduced while maintaining the excellent physical properties of the crosslinked rubber article after crosslinking.

[0030] -Units based on a monomer having a nitrile group- The fluorine-containing copolymer contains a monomer having a nitrile group (hereinafter simply referred to as "R ＣＮ It is preferable that the copolymer further has a unit based on R ＣＮ In terms of achieving better effects of the present invention, it is preferable that CR has a fluorine atom, and more preferable that CR is a unit based on a monomer represented by general formula (4). １１ R １２ =CR １３ -R １４ -CN...General formula (4) In general formula (4), R １１ , R １２ and R １３ are each independently a hydrogen atom, a fluorine atom, or a methyl group, and R １４ R is a divalent perfluorohydrocarbon group having 1 to 10 carbon atoms, or a group having an etheric oxygen atom at the end or between the carbon-carbon bonds of the perfluorohydrocarbon group. １１ , R １２ and R １３ As for R ＣＮ In view of excellent polymerization reactivity of R, fluorine atoms or hydrogen atoms are preferred, all fluorine atoms or all hydrogen atoms are more preferred, and in view of excellent mold releasability and heat resistance of the crosslinked rubber article, all fluorine atoms are particularly preferred. １４ R may be linear, branched, or cyclic, but is preferably linear or branched. １４The number of carbon atoms in R is not particularly limited, but from the viewpoints of reactivity and availability, it is preferably 2 to 8, more preferably 3 to 7, even more preferably 3 to 6, and particularly preferably 3 to 5. １４ R may or may not have an etheric oxygen atom, but preferably has an etheric oxygen atom in order to obtain better rubber properties. １４ The number of etheric oxygen atoms in is not particularly limited, but from the viewpoints of reactivity and availability, it is preferably 1 to 3, more preferably 1 or 2. Specific examples of the monomer represented by general formula (4) include the following. The description after the formula is the abbreviation of the compound. These may be used alone or in combination of two or more. CF ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ CN:8CNVE CF ２ = CFO (CF ２ ) ５ CN:MV5CN CF ２ = CFOCF ２ CF ２ CF ２ OCF (CF ３ ) CN CF ２ = CFO (CF ２ ) ３ Among these, 8CNVE and MV5CN are preferred because they provide crosslinked rubber articles with better mold releasability and heat resistance.

[0031] The proportion of units based on monomers having a nitrile group among all units constituting the fluorinated copolymer is not particularly limited, but from the viewpoint of crosslinking reactivity and heat resistance, it is preferably from 0.01 to 2.00 mol %, more preferably from 0.05 to 1.00 mol %, particularly preferably from 0.10 to 0.60 mol %.

[0032] -Formula (5) Unit- General formula (5) is as follows: CF ２ =CF-O-R ｆ４ ...General formula (5) In general formula (5), R ｆ４ is a perfluoroalkyl group containing an etheric oxygen atom and having 1 to 8 carbon atoms.ｆ４ The number of carbon atoms is preferably 1 to 7, more preferably 1 to 6, in terms of excellent low-temperature properties. Specific examples of the monomer represented by general formula (5) include the following. The description after the formula is the abbreviation for the compound. One type may be used alone, or two or more types may be used. CF ２ =CF-OCF ２ CF ２ -OCF ２ -OCF ２ -OCF ２ -OCF ２ -OCF ３ : C9PEVE CF ２ =CF-OCF ２ CF ２ -OCF ２ -OCF ２ -OCF ３ : C7PEVE CF ２ =CF-OCF ２ CF ２ -OCF ２ CF ２ -OCF ２ CF ３ : EEAVE CF ２ =CF-OCF ２ -OCF ３ CF ２ =CF-OCF ２ -OCF ２ CF ３ CF ２ =CF-O(CF ２ CF (CF ３ ) O) ２ CF ２ CF ２ CF ３ CF ２ =CF-OCF ２ -OCF ２ -OCF ３ Among these, C9PEVE, C7PEVE and EEAVE are preferred because they provide better low-temperature properties when the fluorocopolymer is made into a crosslinked rubber article.

[0033] When the fluorine-containing copolymer has units of formula (5), the proportion of units of formula (5) in all units constituting the fluorine-containing copolymer is not particularly limited, but from the viewpoint of excellent low-temperature properties, it is preferably from 1 to 57 mol %, more preferably from 2 to 30 mol %, particularly preferably from 2 to 20 mol %.

[0034] - Units Based on Monomers Other Than the Above - The fluorine-containing copolymer may have units based on monomers other than those mentioned above. Examples of the other monomers include other fluorine-containing monomers and non-fluorine-containing monomers. Specific examples of the other fluorine-containing monomers include vinyl fluoride; pentafluoropropylene; perfluorocyclobutene; CH ２ = CHCF ３ , C.H. ２ = CHCF ２ CF ３ , C.H. ２ = CHCF ２ CF ２ CF ３ , C.H. ２ = CHCF ２ CF ２ CF ２ CF ３ , C.H. ２ = CHCF ２ CF ２ CF ２ CF ２ CF ３ Specific examples of non-fluorine-containing monomers include α-olefins such as isobutylene and pentene, vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether and butyl vinyl ether, and vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate and vinyl caprylate.

[0035] When the fluorine-containing copolymer has units based on other monomers other than the above, the content of the units based on other monomers other than the above in all units constituting the fluorine-containing copolymer is not particularly limited, but from the viewpoint of excellent heat resistance and chemical resistance, it is preferably from 0.001 to 2.00 mol %, more preferably from 0.01 to 1.00 mol %, particularly preferably 0.01 to 0.50 mol %.

[0036] As the other monomer, a monomer having at least one atom selected from the group consisting of a chlorine atom, a bromine atom, and an iodine atom may be used. When a monomer having at least one atom selected from the group consisting of a chlorine atom, a bromine atom, and an iodine atom is copolymerized, at least one of a chlorine atom, a bromine atom, and an iodine atom can be introduced into the side chain of the fluorine-containing copolymer. Suitable examples of the monomer having at least one of a chlorine atom, a bromine atom, and an iodine atom include compound A represented by general formula (6) and compound B represented by general formula (7). CR ２１ R ２２ =CR ２３ R ２４ ...General formula (6) CR ２１ R ２２ -R ２５ -CR ２３ R ２４ ...General Formula (7) where Compound A and Compound B have one or more chlorine atoms, bromine atoms, and iodine atoms. ２１ , R ２２ , and R ２３ are each independently a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom. ２４ R is an alkyl group, an alkyl group having an etheric oxygen, a fluoroalkyl group, or a fluoroalkyl group having an etheric oxygen. ２４ may have at least one of a chlorine atom, a bromine atom, and an iodine atom. ２４ R in general formula (7) may be linear or branched. ２５ is a group having one or more polymerizable unsaturated bonds. The polymerizable unsaturated bond may be bonded to an alkyl group, an alkyl group having an etheric oxygen, a fluoroalkyl group, or a fluoroalkyl group having an etheric oxygen. ２５ may have at least one of a chlorine atom, a bromine atom, and an iodine atom. ２５may be linear or branched. Specific examples of the monomer having a bromine atom include bromotrifluoroethylene, 4-bromo-3,3,4,4-tetrafluorobutene-1, vinyl bromide, 1-bromo-2,2-difluoroethylene, perfluoroallyl bromide, 4-bromo-1,1,2-trifluorobutene-1, 4-bromo-1,1,3,3,4,4-hexafluorobutene, 4-bromo-3-chloro-1,1,3,4,4-pentafluorobutene, 6-bromo-5,5,6,6-tetrafluorohexene, 4-bromoperfluorobutene-1, 3,3-difluoroallyl bromide, 2-bromo-perfluoroethyl perfluorovinyl ether, CF ２ = CFOCF ２ CF ２ CF ２ OCF ２ CF ２ Br, CF ２ BrCF ２ O-CF=CF ２ , C.H. ３ OCF=CFBr, CF ３ CH ２ OCF=CFBr and the like. These may be used alone or in combination of two or more. Specific examples of the monomer having an iodine atom include iodoethylene, 4-iodo-3,3,4,4-tetrafluoro-1-butene, 2-iodo-1,1,2,2-tetrafluoro-1-vinyloxyethane, 2-iodoethyl vinyl ether, allyl iodide, 1,1,2,3,3,3-hexafluoro-2-iodo-1-(perfluorovinyloxy)propane, 3,3,4,5,5,5-hexafluoro-4-iodopentene, iodotrifluoroethylene, 2-iodoperfluoro(ethyl vinyl ether), CF ２ = CFOCF(CF ３ )CF ２ OCF ２ CF ２ CH ２ I, CF ２ = CFOCF ２ CF ２ CH ２ I, CH ２ = CHCF ２ CF ２I, etc. These may be used alone, or two or more types may be used. Specific examples of monomers having an iodine atom and a bromine atom include 3-bromo-4-iodoperfluorobutene-1, 2-bromo-4-iodoperfluorobutene-1, etc. These may be used alone, or two or more types may be used.

[0037] The fluorine-containing copolymer preferably has at least one atom selected from the group consisting of a chlorine atom, a bromine atom, and an iodine atom, and particularly preferably has at least one of a chlorine atom, a bromine atom, and an iodine atom at the end of the fluorine-containing copolymer (polymer chain). Here, "end" means both the end of the main chain and the end of the branched chain of the fluorine-containing copolymer. The chlorine atom, bromine atom, and iodine atom include those derived from a compound having at least one of a chlorine atom, a bromine atom, and an iodine atom that functions as a chain transfer agent described below, and those derived from the above-mentioned monomer having at least one of a chlorine atom, a bromine atom, and an iodine atom, and those derived from a compound having at least one of a chlorine atom, a bromine atom, and an iodine atom that functions as a chain transfer agent described below are preferred. When the fluorine-containing copolymer has at least one of a chlorine atom, a bromine atom and an iodine atom, the content of at least one of a chlorine atom, a bromine atom and an iodine atom relative to the total mass of the fluorine-containing copolymer is not particularly limited, but is preferably 0.01 to 5.00% by mass, more preferably 0.03 to 2.00% by mass, particularly preferably 0.05 to 1.00% by mass, in terms of better crosslinking reactivity of the fluorine-containing copolymer and better mechanical properties of the crosslinked rubber article.

[0038] When the fluorine-containing copolymer has at least one of chlorine atoms, bromine atoms, and iodine atoms, the mass ratio of the content of at least one of chlorine atoms, bromine atoms, and iodine atoms to the content of crosslinking agent in the fluorine-containing copolymer composition (content of at least one of chlorine atoms, bromine atoms, and iodine atoms / content of crosslinking agent) is not particularly limited, but is preferably 0.01 to 0.50, more preferably 0.02 to 0.30, and particularly preferably 0.03 to 0.20. When it is equal to or more than the lower limit of the above range, the crosslinking reaction is likely to proceed, and when it is equal to or less than the upper limit of the above range, the hardness is better.

[0039] When the fluorine-containing copolymer has at least one of chlorine atoms, bromine atoms, and iodine atoms, the mass ratio of the content of at least one of chlorine atoms, bromine atoms, and iodine atoms to the content of cross-linking aid in the fluorine-containing copolymer composition (content of at least one of chlorine atoms, bromine atoms, and iodine atoms / content of cross-linking aid) is not particularly limited, but is preferably 0.01 to 0.50, more preferably 0.02 to 0.30, and particularly preferably 0.03 to 0.20. When it is equal to or more than the lower limit of the above range, the cross-linking reaction is likely to proceed, and when it is equal to or less than the upper limit of the above range, the hardness is better.

[0040] <<Method for producing a fluorine-containing copolymer>> An example of the method for producing a fluorine-containing copolymer is a method of copolymerizing the above-mentioned monomers in the presence of a chain transfer agent and a radical polymerization initiator. For details of the method for producing the fluorine-containing copolymer, reference can be made to, for example, paragraphs 0019 to 0034 of WO 2010 / 082633, paragraphs 0027 to 0048 of WO 2018 / 225586, paragraphs 0030 to 0033 of WO 2020 / 184427, and paragraphs 0035 to 0038 of WO 2021 / 210502.

[0041] (Chain transfer agent) The chain transfer agent is preferably a compound having at least one of a chlorine atom, a bromine atom, and an iodine atom. When polymerizing a monomer component, by having a chain transfer agent having at least one of a chlorine atom, a bromine atom, and an iodine atom present in the polymerization system, at least one of a chlorine atom, a bromine atom, and an iodine atom can be introduced into the fluorine-containing copolymer. Note that, when the monomer component is polymerized in the presence of a chain transfer agent, at least one of a chlorine atom, a bromine atom, and an iodine atom can be introduced into the main chain terminal unit of the fluorine-containing copolymer. Examples of chain transfer agents having at least one of a chlorine atom, a bromine atom, and an iodine atom include compound C represented by general formula (8), compound D represented by general formula (9), compound E represented by general formula (10), and compound F represented by general formula (12). R ｆ４ I ２ ...General formula (8) R ｆ５ IBr...General formula (9) R ｆ６ Br ２ ...General formula (10) R ｆ７ Cl ２ ...General formula (12) R in general formulas (8) to (10) and (12) ｆ４ ~R ｆ７ are each independently an alkylene group having 1 to 16 carbon atoms, a fluoroalkylene group, or a skeleton having an aromatic ring, and are preferably an alkylene group or a perfluoroalkylene group having 3 or more carbon atoms (preferably 3 to 8). ｆ４ ~R ｆ７ The alkylene group or fluoroalkylene group of R may be linear or branched. ｆ４ ~R ｆ７ As the alkyl group, a perfluoroalkylene group is preferred.

[0042] Examples of the compound C represented by the general formula (8) include 1,2-diiodoperfluoroethane, 1,3-diiodoperfluoropropane, 1,4-diiodoperfluorobutane (C4DI), 1,5-diiodoperfluoropentane, 1,6-diiodoperfluorohexane, 1,8-diiodoperfluorooctane, 2-iodoperfluoropropane, 1,3-diiodo-2-chloroperfluoropropane, 1,5-diiodo-2,4-dichloroperfluoropentane, 1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane, diiodomethane, 1,2-diiodoethane, 1,3-diiodopropane (1,3-diiodo-n-propane), 1,4-diiodobutane, 1,6-diiodohexane, 1,8-diiodooctane, and (2-iodoethyl)-substituted benzene. These may be used alone or in combination of two or more. Among these, 1,4-diiodoperfluorobutane (C4DI) is preferred from the viewpoints of reactivity and availability.

[0043] Examples of compound D represented by general formula (9) include 1-iodo-4-bromoperfluorobutane, 1-iodo-6-bromoperfluorohexane, 1-iodo-8-bromoperfluoroctane, 1-bromo-2-iodoperfluoroethane, 1-bromo-3-iodoperfluoropropane, 2-bromo-3-iodoperfluorobutane, 3-bromo-4-iodoperfluorobutene-1, 2-bromo-4-iodoperfluorobutene-1, monoiodomonobromo-substituted benzene, and diiodomonobromo-substituted benzene. These may be used alone or in combination of two or more.

[0044] Examples of the compound E represented by the general formula (10) include CF ２ Br ２ , BrCF ２ CF ２ Br, CF ３ CFBrCF ２ Br, CFClBr ２ , BrCF ２ CFClBr, CFBrClCFClBr, BrCF ２ CF ２ CF ２Br, BrCF ２ CFBrOCF ３ and (2-bromoethyl) substituted benzene. These may be used alone or in combination of two or more.

[0045] <Silicon carbide> The silicon carbide contained in the fluorine-containing copolymer composition of the present embodiment is not particularly limited as long as it is silicon carbide containing silicon carbide of an α-type crystal lattice, and may or may not contain silicon carbide of a β-type crystal lattice, amorphous silicon carbide, etc. Furthermore, the silicon carbide may or may not contain impurities within a range that does not impair the effects of the present invention. Known silicon carbides can be used as the silicon carbide. The silicon carbides may be used alone or in combination of two or more.

[0046] The content of silicon carbide in the α-type crystal lattice relative to 100% of the total crystal lattice in silicon carbide is not particularly limited as long as it is 50% or more. However, from the viewpoint of improving plasma resistance and ease of availability, it is preferably 55 to 99%, more preferably 65 to 98%, even more preferably 75 to 96%, and particularly preferably 85 to 94%. When two or more types of silicon carbide are used, the content of silicon carbide in the α-type crystal lattice relative to 100% of the total crystal lattice of all silicon carbides used can be calculated by taking a weighted average of the silicon carbide content of the α-type crystal lattice of each silicon carbide based on the blending amount of two or more types of silicon carbide. The content of silicon carbide in the α-type crystal lattice can be calculated by Rietveld analysis of the X-ray diffraction data of silicon carbide obtained by X-ray diffraction measurement.

[0047] The particle shape of silicon carbide is not particularly limited, and examples thereof include amorphous particles, spheres, whiskers, fibers, plates, and aggregates thereof. These may be used alone or in combination of two or more. Among these, spherical shapes are preferred from the viewpoint of isotropy of physical properties.

[0048] The particle diameter d50 of silicon carbide is not particularly limited, but from the viewpoint of improving plasma resistance, it is preferably 60 μm or less, more preferably 0.01 to 10 μm, even more preferably 0.1 to 5 μm, and particularly preferably 0.2 to 0.5 μm. The "particle diameter d50" here is measured by the method described in the Examples section below.

[0049] The content of silicon carbide per 100 parts by mass of the fluorocopolymer is not particularly limited, but from the viewpoint that when the fluorocopolymer composition is made into a crosslinked rubber article, the rubber physical properties, for example, compression set CS, will be excellent, it is preferably 1 to 100 parts by mass, more preferably 10 to 80 parts by mass, and particularly preferably 20 to 70 parts by mass.

[0050] The specific surface area of ​​silicon carbide is not particularly limited, but from the viewpoint of ensuring voids and suppressing granule collapse, it is preferably 1.18 to 15.00 m ２ / g, more preferably 1.21 to 14.00 m ２ / g, particularly preferably 1.24 to 13.00 m ２ / g. The "specific surface area" herein is a value measured in accordance with JIS Z 8830:2013 using a specific surface area measuring device (model: Macsorb, manufactured by Mountech Co., Ltd.). If the specific surface area of ​​the silicon carbide is known when it is obtained, the known specific surface area can be used.

[0051] The pore diameter of silicon carbide is not particularly limited, but is preferably 0.10 to 5.00 μm from the viewpoint of ensuring voids and suppressing granular collapse. The "pore diameter" here is a value measured using a pore diameter measuring device (model: POREMASTER-60, manufactured by Quantachrome). Note that if the pore diameter is known when the silicon carbide is obtained, the known pore diameter can be used.

[0052] The cumulative pore volume of silicon carbide having a pore diameter of 0.10 to 5.00 μm is not particularly limited, but from the viewpoint of ensuring voids and suppressing granule collapse, it is preferably 0.35 to 1.00 cm ３ / g, more preferably 0.40 to 0.85 cm ３ / g, particularly preferably 0.45 to 0.80 cm ３ / g. The "cumulative pore volume" here is a value measured using a pore size measuring device (model: POREMASTER-60, manufactured by Quantachrome). If the cumulative pore volume is known when the silicon carbide is obtained, the known cumulative pore volume can be used.

[0053] The loose bulk density of silicon carbide is not particularly limited, but from the viewpoint of ensuring voids and suppressing granular collapse, it is preferably 0.30 to 0.70 g / cm ３ , more preferably 0.30 to 0.65 g / cm ３ , particularly preferably 0.30 to 0.60 g / cm ３ Here, the "loose bulk density" is a value measured in accordance with JIS K 5101:2004 using a bulk density measuring device (manufactured by Tsutsui Scientific Instruments Co., Ltd.). If the loose bulk density of the silicon carbide is known at the time of procurement, the known loose bulk density can be used.

[0054] The method for producing silicon carbide is not particularly limited, and known methods can be applied, such as a sublimation recrystallization method (modified Lely process), a vapor phase growth method such as chemical vapor deposition, a liquid phase growth method, or the Acheson process, followed by pulverization, classification, or the like to obtain silicon carbide. One synthesis method may be used alone, or two or more synthesis methods may be used. Among these synthesis methods, the Acheson process is preferred from the viewpoint of productivity.

[0055] The Acheson process is a method of sintering silicon dioxide and a carbon-based material in a reducing atmosphere. The sintering temperature is not particularly limited, but is preferably 2000°C or higher from the viewpoint of increasing the proportion of α-SiC in silicon carbide.

[0056] (Silicon carbide of α-type crystal lattice) Examples of silicon carbide of α-type crystal lattice include 15R-SiC, 6H-SiC, 4H-SiC, 21R-SiC, and 2H-SiC, which are expressed in Ramsdell notation. These may be used alone or in combination of two or more. Among these, from the viewpoint of chemical stability, 6H-SiC and 4H-SiC are preferred, and 6H-SiC is more preferred.

[0057] (β-type crystal lattice silicon carbide) The content of β-type crystal lattice silicon carbide relative to 100% of all crystal lattices in silicon carbide is not particularly limited as long as it is less than 50%, but from the viewpoint of improving plasma resistance, it is preferably 0 to 40%, more preferably 0 to 20%, and particularly preferably 0 to 10%. The content of β-type crystal lattice silicon carbide can be calculated in the same manner as the method for calculating the content of α-type crystal lattice silicon carbide.

[0058] An example of silicon carbide with a β-type crystal lattice is 3C—SiC, which is expressed in the Ramsdell notation.

[0059] (Impurities) The content of impurities relative to the total mass of silicon carbide (100 mass%) is not particularly limited as long as it is within a range that does not impair the effects of the present invention. From the viewpoint of excellent resistance to plasma treatment, however, the content is preferably 30.0 ppm by mass or less, more preferably 10.0 ppm by mass or less, and particularly preferably 5.0 ppm by mass or less.

[0060] Examples of impurities contained in silicon carbide include boron, aluminum, phosphorus, iron, copper, sodium, titanium, and chromium. These may be contained alone or in combination. The boron content of the impurities is a value measured by ICP-AES using the alkali fusion method described in "Technical Letter: Geological Standards by Alkali Fusion / Inductively Coupled Plasma Atomic Emission Spectroscopy" by Shigeru Terashima, Takashi Okai, and Masahiro Taniguchi, Japan Society for Analytical Chemistry, Vol. 47 (1998) No. 7, pp. 451-454. The aluminum, phosphorus, iron, copper, titanium, and chromium content of the impurities are values ​​measured by ICP-AES in accordance with JIS R 1616:2007. The sodium content of the impurities is a value measured by the following method. To 50 mg of the sample to be measured, 2 mL of hydrofluoric acid was added, followed by 20 mL of concentrated hydrochloric acid. The resulting slurry was sealed with a lid and heated to 1100°C in an oven to melt the sample. The resulting solution was diluted with ultrapure water to prepare 50 mL of a measurement sample. The resulting measurement sample was measured under the following conditions. Measurement equipment: CCD multi-ICP optical emission spectrometer (SPECTRO Analytical Instruments) Interference removal gas mode: Ar Measurement method: Radial photometry Measurement method (calibration curve method): A standard solution containing known concentrations of the measurement element, its 2x diluted solution and 10x diluted solution, and a control solution were prepared, and a calibration curve was created by introducing the control solution, 10x diluted solution, 2x diluted solution, and standard solution (mother liquor) into the ICP-AES in this order.

[0061] <Crosslinking Agent> The fluorocopolymer composition of the present embodiment may or may not contain a crosslinking agent. The crosslinking agent is used to crosslink the fluorocopolymer, and examples thereof include organic peroxides, amines, polyols, triazines, etc. These may be used alone or in combination of two or more. Among these, organic peroxides and amines are preferred in terms of the crosslinking reactivity of the fluorocopolymer, the productivity of the crosslinked rubber article, the heat resistance of the crosslinked rubber article, and the chemical resistance of the crosslinked rubber article.

[0062] (Organic Peroxides) Specific examples of organic peroxides include alkyl peroxides, benzoyl peroxide, tert-butylperoxybenzene, 2,5-dimethylhexane-2,5-dihydroperoxide, 1,3-bis(tert-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, tert-butylperoxymaleic acid, tert-butylperoxyisopropyl carbonate, tert-butylcumyl peroxide, dicumyl peroxide, α,α'-bis(tert-butylperoxy)-p-diisopropylbenzene, α,α'-bis(tert-butylperoxy)-m-diisopropylbenzene, 2,5-dimethylhexane-2,5-dihydroxyperoxide, tert-butylperoxymaleic acid, and 2,5-dimethyl-2,5-di(tert-butylperoxy)-3-hexyne. These may be used alone or in combination of two or more. Among these, alkyl peroxides, α,α'-bis(tert-butylperoxy)-p-diisopropylbenzene, and α,α'-bis(tert-butylperoxy)-m-diisopropylbenzene are preferred from the viewpoint of crosslinkability.

[0063] Specific examples of alkyl peroxides include 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, di-tert-butylperoxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, and 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane. These may be used alone or in combination of two or more. Of these, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane is preferred. When the fluorine-containing copolymer composition contains an organic peroxide and further contains a crosslinking aid described below, the crosslinking efficiency becomes higher.

[0064] (Amine) Specific examples of amines include hexamethylenediamine, hexamethylenediamine carbamate, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis(3-amino-4-hydroxyphenyl)propane, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (hereinafter sometimes simply referred to as "BOAP"; also known as bisaminophenol AF), 2,2-bis(3,4-diaminophenyl)propane, 2,2-bis(3,4-diaminophenyl)hexafluoropropane, 2,2-bis(3-amino-4-(N-phenylamino)phenyl)hexafluoropropane, 4,4'-methylenedianiline, m-phenylenediamine, adipic acid dihydrazide, and the compound represented by formula (XII) of Japanese Patent No. 5,833,657. These may be used alone or in combination of two or more. Among these, BOAP is preferred because it provides a more excellent effect of the present invention.

[0065] The content of the crosslinking agent relative to the total mass of the fluorocopolymer composition is not particularly limited, but is preferably from 0.30 to 10.00% by mass, more preferably from 0.30 to 5.00% by mass, and particularly preferably from 0.31 to 1.00% by mass. When the amount of crosslinking agent blended is within the above range, the crosslinked rubber article will have an excellent balance between strength and elongation.

[0066] <Crosslinking Aid (Co-Crosslinking Agent)> The fluorine-containing copolymer composition of this embodiment may or may not contain a crosslinking aid (co-crosslinking agent). The crosslinking aid is preferably used to improve crosslinking efficiency when crosslinking the fluorine-containing copolymer with an organic peroxide. After the crosslinking reaction is completed, the crosslinking aid bonds to the fluorine-containing copolymer and becomes part of the crosslinked structure. The crosslinking aid is preferably a compound having two or more reactive functional groups in the same molecule. Specific examples of the reactive functional group include an unsaturated bond, a halogen atom, an acid anhydride residue, a carboxy group, an amino group, a cyano group, and a hydroxyl group. The multiple reactive functional groups present in the same molecule of the crosslinking aid may be the same or different. Examples of the unsaturated bond include a carbon-carbon double bond-containing group. Specific examples of the carbon-carbon double bond-containing group include alkenyl groups such as a vinyl group, an allyl group, and a methallyl group; unsaturated acyl groups such as an acryloyl group and a methacryloyl group; a maleimide group; and the like. The carbon-carbon double bond-containing group is preferably an alkenyl group having 2 to 4 carbon atoms, more preferably an allyl group.

[0067] Specific examples of the crosslinking aid include compounds represented by the following general formula (11), triallyl cyanurate, triallyl isocyanurate, trimethallyl isocyanurate, 1,3,5-triacryloylhexahydro-1,3,5-triazine, triallyl trimellitate, m-phenylenediamine bismaleimide, p-quinonedioxime, p,p'-dibenzoylquinonedioxime, dipropargyl terephthalate, diallyl phthalate, N,N',N'',N'''-tetraallyl terephthalamide, and vinyl group-containing siloxane oligomers (polymethylvinylsiloxane, polymethylphenylvinylsiloxane, etc.). These may be used alone or in combination of two or more. Among these, from the viewpoint of more excellent crosslinking reactivity, the compound represented by the following general formula (11), triallyl cyanurate, triallyl isocyanurate, and trimethallyl isocyanurate are preferred, the compound represented by the following general formula (11) and triallyl isocyanurate are more preferred, and triallyl isocyanurate is particularly preferred.

[0068] The general formula (11) is as follows: (CR ６１ R ６２ =CR ６３ ) ２ R ６４ ...General formula (11) In general formula (11), R ６１ , R ６２ , and R ６３ are each independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 5 carbon atoms, or a fluoroalkyl group having 1 to 5 carbon atoms, and R ６４ is a divalent fluorohydrocarbon group having 1 to 18 carbon atoms, or a group having an etheric oxygen atom at the end or between the carbon-carbon bonds of the fluorohydrocarbon group. ６１ , multiple R ６２ , and a plurality of R ６３ may be the same or different from each other. ６１ , R ６２ , and R ６３ When R is an alkyl group or a fluoroalkyl group, it may be linear or branched, but is preferably linear. ６１ , R ６２ , and R ６３ When R is an alkyl group or a fluoroalkyl group, the number of carbon atoms therein is not particularly limited, but is preferably 1 to 5, more preferably 1 to 3, and particularly preferably 1 or 2. ６１ , R ６２ , and R ６３ As for R, it is preferable that all of them are hydrogen atoms, since this has better crosslinking reactivity. ６４ As the fluorohydrocarbon group in R, a perfluorohydrocarbon group is preferred in view of superior heat resistance of the crosslinked rubber article. ６４ R may be any of linear, branched, and cyclic, preferably linear or branched, and more preferably linear. ６４ The number of carbon atoms in R is not particularly limited, but is preferably 1 to 18, more preferably 2 to 8, and particularly preferably 3 to 7. ６４ When R has an etheric oxygen atom, ６４The number of etheric oxygen atoms in R is not particularly limited, but is preferably 1 to 6, more preferably 1 to 3, and particularly preferably 1 or 2. ６４ has an etheric oxygen atom, the etheric oxygen atom is ６４ It is preferred that the nucleotide sequence is located at the end of the nucleotide sequence.

[0069] The compound represented by the general formula (11) is not particularly limited, but from the viewpoint of heat resistance and chemical resistance, C3DVE, C4DVE, CH ２ =CH(CF ２ ) ２ CH=CH ２ , C4-DV, and C6-DV are preferred, with C6-DV being more preferred.

[0070] The content of the crosslinking aid in the fluorocopolymer composition per 100.00 parts by mass of the fluorocopolymer is not particularly limited, but is preferably 0.10 to 10.00 parts by mass, more preferably 0.20 to 5.00 parts by mass, and particularly preferably 0.40 to 2.50 parts by mass. When the amount of the crosslinking aid is within the above range, the crosslinked rubber article will have an excellent balance between strength and elongation.

[0071] In the fluorine-containing copolymer composition, the mass ratio of the content of the crosslinking agent to the content of the crosslinking aid (crosslinking agent content / crosslinking aid content) is not particularly limited, but is preferably 0.2 to 7.0, more preferably 0.4 to 5.0, and particularly preferably 0.5 to 2.0, in terms of preventing unreacted crosslinking aid from remaining and allowing the crosslinking reaction to proceed smoothly. In the fluorine-containing copolymer composition, the total content of the crosslinking agent and crosslinking aid per 100.00 parts by mass of the fluorine-containing copolymer is not particularly limited, but is preferably 0.10 to 5.00 parts by mass, more preferably 0.50 to 4.00 parts by mass, and particularly preferably 0.80 to 3.00 parts by mass. When the total content of the crosslinking agent and crosslinking aid is not less than the lower limit, the hardness of the crosslinked rubber article tends to be excellent. When the total content of the crosslinking agent and crosslinking aid is not more than the upper limit, the crosslinking reactivity is excellent.

[0072] The content of the crosslinking aid relative to the total mass of the fluorinated copolymer composition is not particularly limited, but from the viewpoint of heat resistance and chemical resistance, it is preferably from 0.30 to 10.00 mass%, more preferably from 0.30 to 5.00 mass%, particularly preferably from 0.31 to 1.00 mass%.

[0073] <Other Components> The fluorocopolymer composition may contain other components in addition to those described above, provided that the effects of the present invention are not impaired. Examples of other components include processing aids (e.g., acid acceptors such as fatty acid esters (glycerin monooleate, etc.), fatty acid metal salts (sodium stearate, calcium stearate, etc.), and oxides of divalent metals (magnesium oxide, calcium oxide, zinc oxide, lead oxide, etc.), synthetic waxes (polyethylene wax, etc.), fillers and reinforcing agents (e.g., carbon black, barium sulfate, calcium metasilicate, calcium carbonate, titanium oxide, silicon dioxide, aromatic polyesters, polyamideimides, thermoplastic polyimides, clay, talc, and the fluorine-containing copolymers described below other than the above-mentioned fluorine-containing copolymers having no melting point (hereinafter also referred to as "specific fluorine-containing copolymers")), vulcanizing agents, scorch retarders (e.g., phenolic hydroxyl group-containing compounds such as bisphenol A, quinones such as hydroquinone, and α-methylstyrene dimers such as 2,4-di(3-isopropylphenyl)-4-methyl-1-pentene), crown ethers (e.g., 18-crown-6), and pigments.

[0074] (Specific Fluorine-Containing Copolymer) The specific fluorine-containing copolymer preferably has a melting point. The melting point is a value measured by weighing 5 mg of a sample into an aluminum pan and heating it from 20°C to 360°C at a temperature increase rate of 10°C / min in an air atmosphere using a differential scanning calorimeter (model: DSC600, manufactured by Hitachi High-Tech Science Corporation). The melt flow rate (hereinafter referred to as "MFR") of the specific fluorine-containing copolymer at a temperature 20°C or more higher than the melting point of the specific fluorine-containing copolymer (usually 372°C) is not particularly limited, but is preferably 0.1 to 1000g / 10 min, more preferably 0.5 to 100g / 10 min, even more preferably 1 to 30g / 10 min, and particularly preferably 5 to 20g / 10 min. The specific fluorine-containing copolymer preferably has TFE units. The proportion of TFE units in all units constituting the specific fluorine-containing copolymer is not particularly limited, but from the viewpoint of heat resistance and chemical resistance, it is preferably from more than 90 to 100 mol%, more preferably from 95 to 99 mol%, and particularly preferably from 96 to 98 mol%. An example of the specific fluorine-containing copolymer is "Fluorine-containing copolymer (X1-1)" in the Examples section of WO 2016 / 017801.

[0075] The content of components other than the fluorine-containing copolymer in the fluorine-containing copolymer composition per 100.00 parts by mass of the fluorine-containing copolymer is not particularly limited, but is preferably 0.50 to 50.00 parts by mass, more preferably 1.00 to 40.00 parts by mass, and particularly preferably 2.00 to 30.00 parts by mass. If the content is at least the lower limit of the above range, the hardness of the crosslinked rubber article will be superior, and if it is at most the upper limit of the above range, the transparency of the crosslinked rubber article will be superior.

[0076] The content of other components relative to the total mass of the fluorinated copolymer composition is not particularly limited, but from the viewpoint of heat resistance and chemical resistance, it is preferably from 0.50 to 33.33 mass%, more preferably from 0.99 to 28.57 mass%, particularly preferably from 1.96 to 23.08 mass%.

[0077] [Method for producing a fluorine-containing copolymer composition] The method for producing a fluorine-containing copolymer composition of the present invention is a method for kneading the fluorine-containing copolymer and the silicon carbide. The kneading is achieved by kneading the fluorine-containing copolymer, silicon carbide containing silicon carbide of an α-type crystal lattice, and, if necessary, other components, by a kneading method using a known rubber kneading device such as a two-roll mill, a kneader, a Banbury mixer, or an extruder. After obtaining a mixture by kneading the components, the mixture may be molded. That is, the fluorine-containing copolymer composition may be a molded product. Specific examples of methods for molding the mixture include compression molding, injection molding, extrusion molding, calendar molding, or a method in which the mixture is dissolved in a solvent and molded by dipping or coating.

[0078] [Crosslinked Rubber Article] The crosslinked rubber article of the present invention is obtained by crosslinking the fluorocopolymer in the fluorocopolymer composition of the present invention.

[0079] [Method for producing crosslinked rubber article] The method for producing a crosslinked rubber article of the present invention is a method for producing the crosslinked rubber of the present invention, which involves primarily heating the fluorocopolymer composition at 100 to 400°C for 1 second to 24 hours and, after the primary heating, secondary heating at 80 to 400°C for 30 minutes to 48 hours. The crosslinked rubber article is obtained by crosslinking the fluorocopolymer in the fluorocopolymer composition. Methods for crosslinking the fluorocopolymer in the fluorocopolymer composition include a method in which the fluorocopolymer composition is crosslinked by heating, and a method in which the fluorocopolymer composition is irradiated with ionizing radiation. Specific examples of crosslinking methods by heating include hot press crosslinking, steam crosslinking, and hot air crosslinking. An appropriate method may be selected from these methods taking into consideration the shape and application of the fluorocopolymer composition.

[0080] Examples of the molding method include injection molding, extrusion molding, coextrusion molding, blow molding, compression molding, inflation molding, transfer molding, calendar molding, etc. Examples of the extrusion molding method include a method in which a fluorine-containing copolymer or a fluorine-containing copolymer composition is extruded and molded into the shape of a hose or an electric wire.

[0081] When the fluorine-containing copolymer composition contains an organic peroxide as a crosslinking agent, crosslinking by heating is preferred. A specific method for producing a crosslinked rubber article by thermal crosslinking is, for example, hot press molding. In hot press molding, a heated mold is used, a fluorine-containing copolymer composition is filled into a mold cavity having a desired shape, and the composition is heated to crosslink the composition simultaneously with molding (hot press crosslinking), thereby obtaining a crosslinked rubber article. The heating temperature is not particularly limited, but is preferably 100 to 400°C, more preferably 130 to 220°C, even more preferably 140 to 200°C, and particularly preferably 150 to 180°C. The heating time is not particularly limited, but is preferably 1 second to 24 hours, more preferably 1 minute to 1 hour, and particularly preferably 5 to 40 minutes.

[0082] When using the hot press molding method, it is also preferable to further heat the crosslinked rubber article obtained by hot press crosslinking (sometimes referred to as primary crosslinking or primary heating) in an oven or the like using electricity, hot air, steam, or the like as a heat source to further promote crosslinking (sometimes referred to as secondary crosslinking or secondary heating). The temperature during secondary crosslinking is not particularly limited, but is preferably 80 to 400°C, more preferably 80 to 350°C, even more preferably 150 to 280°C, even more preferably 180 to 260°C, and particularly preferably 200 to 250°C. The secondary crosslinking time is not particularly limited, but is preferably 30 minutes to 48 hours, more preferably 1 hour to 48 hours, and particularly preferably 4 hours to 24 hours. By achieving sufficient secondary crosslinking, the rubber physical properties (mechanical properties, compression set, and other properties) of the crosslinked rubber article are improved. Furthermore, the peroxide residue contained in the crosslinked rubber article is decomposed, volatilized, and reduced. The hot press molding method is preferably applied to the molding of sealing materials, etc.

[0083] Examples of the ionizing radiation in the method of irradiating with ionizing radiation include electron beams, ultraviolet rays, gamma rays, etc. When crosslinking is carried out by irradiating with ionizing radiation, a preferred method is to first mold the fluorine-containing copolymer or fluorine-containing copolymer composition into a desired shape and then irradiate with ionizing radiation to crosslink it. The dose of ionizing radiation is appropriately set and is preferably 1 to 300 kGy, more preferably 10 to 200 kGy.

[0084] <Physical Properties> The tensile strength of the crosslinked rubber article is not particularly limited, but is preferably 1 to 50 MPa, more preferably 10 to 40 MPa, and particularly preferably 15 to 40 MPa, in order to provide superior rubber properties for the crosslinked rubber article. The tensile elongation of the crosslinked rubber article is not particularly limited, but is preferably 100 to 1000%, more preferably 150 to 600%, even more preferably 150 to 500%, and particularly preferably 150 to 400%, in order to provide superior rubber properties. The tensile strength and tensile elongation of the crosslinked rubber article are values ​​measured by a method in accordance with JIS K 6251:2010 (corresponding international standard ISO 37:2005).

[0085] The hardness (Shore-A) of the crosslinked rubber article is not particularly limited, but in terms of excellent rubber properties, it is preferably 55 to 100, more preferably 55 to 90, even more preferably 60 to 85, and particularly preferably 65 to 80. The hardness (Shore-A) of the crosslinked rubber article is a value measured using a type A durometer in accordance with JIS K6253-1:2012 using a plate-shaped molded product (thickness 1 mm) of the crosslinked rubber article.

[0086] The compression set CS of the crosslinked rubber article at 200°C for 70 hours is not particularly limited, but is preferably 70% or less, more preferably 50% or less, and particularly preferably 40% or less, in order that the fluorocopolymer is well crosslinked and the crosslinked rubber article has better shape recovery after pressure is obtained. The compression set of the crosslinked rubber article at 200°C for 70 hours is measured by the method described in the Examples section below.

[0087] <Applications> Crosslinked rubber articles are suitable as materials for O-rings, sheets, gaskets, oil seals, diaphragms, V-rings, and the like. The crosslinked rubber articles can also be used in semiconductor manufacturing equipment parts, heat-resistant and chemical-resistant sealing materials, heat-resistant and oil-resistant sealing materials, wire coating materials, sealing materials for liquid crystal display panel manufacturing equipment, sealing materials for light-emitting diode manufacturing equipment, corrosion-resistant rubber paints, sealing materials for urea-resistant grease, rubber paints, adhesive rubbers, hoses, tubes, calendered sheets (rolls), sponges, rubber rolls, oil drilling components, heat-dissipating sheets, solution-crosslinked products, rubber sponges, bearing seals (urea-resistant grease and the like), linings (chemical-resistant), insulating sheets for automobiles, insulating sheets for electronic devices, rubber bands for watches, endoscope packings (amine-resistant), bellows hoses (processed from calendered sheets), water heater packings / valves, fenders (offshore civil engineering, ships), fibers and nonwoven fabrics (protective clothing and the like), board sealing materials, rubber gloves, stators for uniaxial eccentric screw pumps, parts for urea SCR systems, vibration isolators, vibration dampers, sealants, additives for other materials, and toys. Examples of semiconductor manufacturing equipment parts using crosslinked rubber articles include sealing materials (O-rings, square rings, gaskets, packings, oil seals, bearing seals, lip seals, etc.), tubes, hoses, various rubber rolls, diaphragms, linings, etc. Examples of semiconductor manufacturing equipment include etching equipment (dry etching equipment, plasma etching equipment, reactive ion etching equipment, reactive ion beam etching equipment, sputter etching equipment, ion beam etching equipment, wet etching equipment, ashing equipment, etc.), cleaning equipment (dry etching cleaning equipment, UV / O ３ cleaning equipment, ion beam cleaning equipment, laser beam cleaning equipment, plasma cleaning equipment, gas etching cleaning equipment, extraction cleaning equipment, Soxhlet extraction cleaning equipment, high temperature and high pressure extraction cleaning equipment, microwave extraction cleaning equipment, supercritical extraction cleaning equipment, etc.), exposure equipment (steppers, coater developers, etc.), polishing equipment (CMP equipment, etc.), film formation equipment (CVD equipment, sputtering equipment, etc.), diffusion / ion implantation equipment (oxidation diffusion equipment, ion implantation equipment, etc.), etc.

[0088] The present invention will be specifically described below based on examples, but the present invention is not limited to the following examples, and various modifications are possible within the scope of the present invention. Examples 1 to 3, 9, 11, 13, 15 to 16, and 19 are examples, and Examples 4 to 8, 10, 12, 14, 17 to 18, and 20 are comparative examples.

[0089] <Measurement of Composition of Fluorine-Containing Copolymer> The content (mol %) of each unit in Fluorine-Containing Copolymer 1 and Fluorine-Containing Copolymer 2 was calculated by nuclear magnetic resonance (NMR) analysis. In addition, the content of iodine atoms in the copolymer was calculated using an apparatus combining an automatic sample combustion apparatus, a pretreatment device for ion chromatography (manufactured by Mitsubishi Chemical Analytech Co., Ltd., Model AQF-100), and an ion chromatograph.

[0090] <Compounds Used> Details of the various compounds used and explanations of their abbreviations are shown below: TFE: tetrafluoroethylene PMVE: CF ２ = CFOCF ３ : Perfluoro(methyl vinyl ether) C4DI: 1,4-diiodoperfluorobutane 8CNVE: (CF ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ CN) ・C3DVE:CF ２ = CFO (CF ２ ) ３ OCF = CF ２ P25B: organic peroxide (crosslinking agent), 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, "Perhexa (registered trademark) 25B", manufactured by NOF Corporation TAIC: crosslinking aid (co-crosslinking agent), triallyl isocyanurate, "Taic (registered trademark)", manufactured by Mitsubishi Chemical Corporation BOAP: polyamine compound (crosslinking agent), 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, C ２ F ５ OCF ２ CF ２ OCF ２ COONH ４Disodium hydrogen phosphate dodecahydrate: APS: ammonium persulfate (polymerization initiator) Nitric acid: manufactured by Kanto Chemical Co., Ltd.

[0091] <Silicon carbide used> Details of the various silicon carbides used and explanations of their abbreviations are shown below: SiC1: 90% α-SiC (6H-SiC), specific surface area 4.0 m ２ / g, "Shinano Random GP #10000", manufactured by Shin-Etsu Electric Refining Co., Ltd. SiC2: 88% α-SiC (6H-SiC), loose bulk density 0.48 g / cm ３ , "GC-#40000", manufactured by Fujimi Incorporated Co., Ltd. SiC3: 93% α-SiC (6H-SiC), "GC-#4000", manufactured by Fujimi Incorporated Co., Ltd. SiC4: 97% β-SiC (3C-SiC), specific surface area 20 m ２ / g, "βSiC3000A" manufactured by Superior Graphite ・SiC5: 97% β-SiC (3C-SiC), "NM-SiC", manufactured by Nanomakers Co., Ltd. ・SiC6: 90% β-SiC (3C-SiC) / 10% amorphous, specific surface area 35 m ２ / g, loose bulk density 0.05 g / cm ３ , "NP-SIC-8", manufactured by EM Japan Co., Ltd. SiC7: 90% β-SiC (3C-SiC) / 10% amorphous, specific surface area 60 m ２ / g, loose bulk density 0.05 g / cm ３ , "NP-SiC-9", manufactured by EM Japan Co., Ltd. SiC8: 90% β-SiC (3C-SiC) / 10% amorphous, specific surface area 105 m ２ / g, loose bulk density 0.03 g / cm ３ , "NP-SiC-10", manufactured by EM Japan Co., Ltd. SiC9: 50% α-SiC (6H-SiC) / 40% β-SiC (3C-SiC) / 10% amorphous, "NP-SiC-7", manufactured by EM Japan Co., Ltd. SIC10: 99% β-SiC (3C-SiC) specific surface area 15 m ２ / g, "βSiC220" Superior, manufactured by Graphite

[0092] [Production of Fluorocopolymer] Fluorocopolymers 1 and 2 were produced as follows. <Fluorocopolymer 1> A stainless steel pressure reactor having an internal volume of 2,100 mL was degassed, and then 804 g of ultrapure water, C ２ F ５ OCF ２ CF ２ OCF ２ COONH ４80.1 g of a 30% by mass solution of 1.8 g of a 5% by mass aqueous solution of disodium hydrogen phosphate dodecahydrate, 0.72 g of C3DVE, 1.8 g of a 5% by mass aqueous solution of disodium hydrogen phosphate dodecahydrate, and 0.87 g of C4DI were charged, and the gas phase was replaced with nitrogen. While stirring at a speed of 600 rpm, 13 g of TFE and 65 g of PMVE were injected into the vessel when the internal temperature reached 80 ° C. The pressure inside the reactor was 0.90 MPa [gauge]. 20 mL of a 1% by mass aqueous solution of APS was added to initiate polymerization. The molar ratio of the monomers injected before the start of polymerization (hereinafter referred to as initial monomers) was TFE:PMVE:C3DVE = 25:75:0.19. As the polymerization progressed, when the reactor internal pressure dropped to 0.89 MPa [gauge], TFE was injected, and the reactor internal pressure was increased to 0.90 MPa [gauge]. This was repeated, and 7 g of PMVE was also injected every time 8 g of TFE was injected. When the total added mass of TFE reached 80 g, the addition of the monomer injected after the start of polymerization (hereinafter referred to as "post-added monomer") was stopped, and the internal temperature of the reactor was cooled to 10 ° C. to terminate the polymerization reaction, thereby obtaining a latex containing a fluorine-containing copolymer. The polymerization time was 185 minutes. The total added mass of the post-added monomers was 80 g of TFE and 63 g of PMVE, which was converted to a molar ratio of TFE:PMVE = 65:35. Nitric acid was dissolved in ultrapure water to prepare a 3 mass% aqueous solution of nitric acid. The latex was added to an aqueous nitric acid solution in a TFE / PMVE copolymer (PFA) container to coagulate the fluorine-containing copolymer. The amount of the aqueous nitric acid solution was 150 parts by mass relative to 100 parts by mass of the fluorine-containing copolymer in the latex. The coagulated fluorine-containing copolymer was recovered by filtration, poured into ultrapure water in a PFA container, and washed by stirring at 200 rpm for 30 minutes. The amount of ultrapure water was 100 parts by mass relative to 100 parts by mass of the copolymer. Washing was repeated 10 times. The washed fluorine-containing copolymer was recovered by filtration and dried under reduced pressure at 50°C and 10 kPa to obtain a white fluorine-containing copolymer 1. The molar ratio of each unit in the fluorine-containing copolymer 1 was TFE unit:PMVE unit:C3DVE unit = 65.88:33.94:0.18, and the iodine atom content was 0.15% by mass.

[0093] <Fluorocopolymer 2> Fluorocopolymer 2 was obtained by the same production method as for “Copolymer (A-1)” in the examples of WO 2021 / 210502. The contents (molar ratio) of the respective units in the obtained fluorine-containing copolymer 2 were TFE units:PMVE units:8CNVE units=70.90:28.60:0.50.

[0094] Examples 1 to 14 The components and amounts (parts by mass) shown in Table 1 were mixed and kneaded using a two-roll mill at room temperature for 10 minutes to obtain a mixed fluorine-containing copolymer composition. The obtained fluorine-containing copolymer composition was hot-pressed at 150°C for 20 minutes using a hydraulic press (model: SA-301 50T type, manufactured by Tester Sangyo Co., Ltd., ram diameter: 180 mm) to obtain an O-ring (P-26 (standard defined in JIS B2401:2012)) (primary crosslinking). The O-ring was then heated in an oven at 250°C for 4 hours in an air atmosphere (secondary crosslinking). Thereafter, the O-ring was cooled to room temperature to obtain the O-rings that are the crosslinked rubber articles of Examples 1 to 14. The following physical properties were measured using the obtained crosslinked rubber articles. The measurement results are shown in Table 1.

[0095] Examples 15 to 20 The components and amounts (parts by mass) shown in Table 2 were mixed and kneaded using a two-roll mill at room temperature for 10 minutes to obtain a mixed fluorine-containing copolymer composition. The obtained fluorine-containing copolymer composition was hot-pressed at 180°C for 20 minutes using a hydraulic press (model: SA-301 50T type, manufactured by Tester Sangyo Co., Ltd., ram diameter: 180 mm) to obtain an O-ring (P-26 (standard defined in JIS B2401:2012)) (primary crosslinking). The O-ring was then heated in an oven under the following conditions in a nitrogen atmosphere (secondary crosslinking). The secondary crosslinking was performed by heating at 90°C for 2 hours, then increasing the temperature to 200°C over 2 hours, and maintaining it at 200°C for 4 hours. The temperature was then increased to 305°C over 2 hours, and further heating at 305°C for 13 hours. By the above method, the O-rings, which were the crosslinked rubber articles of Examples 15 to 20, were obtained. The following physical properties of the resulting crosslinked rubber article were measured. The measurement results are shown in Table 2.

[0096] [Compression set CS] Measurement was performed with reference to JIS K 6262:2013. The test specimens used were P26 O-rings prepared in each example in accordance with JIS B 2401-1:2012. The O-rings prepared in each example (original thickness (wire diameter) of the test specimen = 3.5 mm) were compressed to a compression rate of 18% using a compression device. The compression device with the compressed O-ring fixed thereto was then placed in an electric furnace and left at 200°C for 70 hours. The compression device was then removed from the electric furnace, the O-ring was immediately removed from the compression device, and the removed O-ring was placed in a constant temperature chamber and left at 23°C for 30 minutes. The thickness of the O-ring (thickness after compression treatment) was measured. The test was performed using two test specimens, and the arithmetic average of the measured values ​​of the two test specimens was used. The results are shown in Tables 1 and 2. The compression set was calculated using the following formula. The closer the compression set rate to 0%, the better. Compression set rate (%) = (original thickness of test piece (wire diameter) - thickness 30 minutes after removing the test piece from the compression device (thickness after compression treatment) ÷ (original thickness of test piece - thickness of spacer) × 100

[0097] [Particle diameter d50] A laser diffraction / scattering particle size distribution analyzer (model: LA-300, manufactured by Horiba, Ltd.) was used to determine the particle diameter (particle diameter d50) at which the cumulative particle volume from the small particle size side in the volume-based cumulative particle size distribution was 50% of the total particle volume. The results are shown in Tables 1 and 2. However, if the median diameter (particle diameter d50) was known at the time of procurement of the silicon carbide, this known median diameter (particle diameter d50) was used.

[0098] [Mass loss rate after plasma treatment] The plasma resistance of a crosslinked rubber article was judged from the mass loss rate (mass %) after plasma treatment. The closer the mass loss rate is to 0 mass %, the better the plasma resistance. Plasma treatment was carried out using a plasma etcher (model: CPE-200AHM, manufactured by Sakigake Semiconductor Co., Ltd.) under the following conditions. The stage temperature rose to a maximum of 155°C due to plasma irradiation. The mass of the measurement sample before and after plasma treatment was measured, and the mass loss rate (mass %) was calculated. The mass was measured to the nearest 0.1 mg using an Azpro electronic balance (device name: BCA64I-1SJP, manufactured by Sartorius). The measurement results are shown in Tables 1 and 2. Plasma treatment conditions: O ２ :Flow rate 30sccm N ２ (80%) / NF ４ (20%): Flow rate 30 sccm Power: 300 W Pressure: 26 Pa Irradiation time: 6 hours

[0099]

[0100]

[0101] As can be seen from the evaluation results shown in Table 1, the crosslinked rubber articles obtained by crosslinking the fluorine-containing copolymer composition of the present invention (Examples 1 to 3, 9, 11, and 13) had a higher O resistance than the crosslinked rubber articles obtained by crosslinking a fluorine-containing copolymer composition other than the present invention (Examples 4 to 8, 10, 12, and 14). ２ and NF ３ As can be seen from the evaluation results shown in Table 2, the crosslinked rubber articles obtained by crosslinking the fluorocopolymer composition of the present invention (Examples 15-16 and 19) had a smaller mass loss after plasma treatment with the O-type gas than the crosslinked rubber articles obtained by crosslinking a fluorocopolymer composition other than the present invention (Examples 17-18 and 20). ２ and NF ３ It was confirmed that the mass loss after plasma treatment of the system gas was small, that is, the plasma resistance was high.

Claims

1. A fluorine-containing copolymer composition comprising a fluorine-containing copolymer and silicon carbide, wherein the silicon carbide has an α-type crystal lattice, and the content of the α-type crystal lattice is 50% or more, relative to 100% of the total crystal lattice in the silicon carbide.

2. The fluorine-containing copolymer composition according to claim 1, wherein the silicon carbide has a particle size d50 of 60 μm or less.

3. The fluorine-containing copolymer composition according to claim 1, wherein said silicon carbide of α-type crystal lattice is at least one type selected from the group consisting of 6H—SiC and 4H—SiC.

4. The fluorine-containing copolymer composition according to claim 3, wherein said silicon carbide of α-type crystal lattice is 6H-SiC.

5. The fluorine-containing copolymer composition according to claim 1, wherein the content of said silicon carbide is 1 to 100 parts by mass per 100 parts by mass of said fluorine-containing copolymer.

6. The fluorine-containing copolymer composition according to claim 1, wherein the fluorine-containing copolymer has units based on tetrafluoroethylene (TFE) and units based on perfluoroalkyl vinyl ether (PAVE).

7. The fluorine-containing copolymer composition according to claim 6, wherein the content of units based on said tetrafluoroethylene (TFE) is 50 to 90 mol % based on all units based on monomers constituting said fluorine-containing copolymer, and the content of units based on said perfluoroalkyl vinyl ether (PAVE) is 10 to 50 mol % based on all units based on monomers constituting said fluorine-containing copolymer.

8. The fluorine-containing copolymer composition according to claim 1, wherein the fluorine-containing copolymer comprises units based on at least one monomer selected from the group consisting of: units based on a monomer having two or more polymerizable unsaturated bonds, units based on a monomer having at least one atom selected from the group consisting of chlorine atoms, bromine atoms and iodine atoms, and units based on a monomer having a nitrile group.

9. The fluorine-containing copolymer composition according to claim 1, further comprising a crosslinking agent, said crosslinking agent being at least one selected from the group consisting of organic peroxides and amines.

10. The fluorine-containing copolymer composition according to claim 1, further comprising a crosslinking aid, said crosslinking aid being at least one kind selected from the group consisting of compounds having two or more unsaturated bonds.

11. A crosslinked rubber article obtained by crosslinking the fluorocopolymer in the fluorocopolymer composition according to any one of claims 1 to 10.

12. A method for producing the fluorine-containing copolymer composition according to any one of claims 1 to 10, comprising kneading said fluorine-containing copolymer and said silicon carbide.

13. A method for producing a crosslinked rubber article according to claim 11, comprising: primary heating the fluorocopolymer composition at 100 to 400°C for 1 second to 24 hours; and, after the primary heating, secondary heating at 80 to 400°C for 30 minutes to 48 hours.