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

Abstract

Provided is a fluorine-containing copolymer composition, etc., with which it is possible to obtain a crosslinked rubber article that has low compression set and is unlikely to break even when used for a long period of time in a compressed state at high temperatures of 325°C or higher. This fluorine-containing copolymer composition contains a fluorine-containing copolymer (A) that has a unit based on a nitrile-group-containing monomer and a unit based on tetrafluoroethylene, and a crosslinking agent (B) that has two or more amino groups. The amount of units based on the nitrile-group-containing monomer is at least 0.80 mol% and less than 1.00 mol% in 100 mol% of all the monomer units in the fluorine-containing copolymer (A), and the amount of the crosslinking agent (B) is 0.80-1.30 parts by mass per 100 parts by mass of the fluorine-containing copolymer (A).

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 excellent heat resistance 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] Crosslinked rubber articles obtained by crosslinking a fluorine-containing copolymer are excellent in heat resistance, chemical resistance, oil resistance, weather resistance, etc., and are therefore widely used as sealing materials (e.g., O-rings, packings, oil seals, gaskets), cushioning materials, etc. in the fields of vehicles, ships, aircraft, general machinery, construction, etc.

[0003] For example, Patent Document 1 discloses a fluorine-containing copolymer having units based on tetrafluoroethylene, units based on perfluoro(alkyl vinyl ether), units based on a monomer having a fluorine atom and two or more polymerizable unsaturated bonds, and units based on a monomer having a nitrile group and a fluorine atom, wherein the storage modulus of the fluorine-containing copolymer at frequencies of 0.3 rad / s and 0.03 rad / s determined by dynamic viscoelasticity measurement at 140°C is G' ０．３ and G' ０．０３ In this case, G' ０．３ / G' ０．０３

[0006] Patent Document 2 discloses a fluorine-containing copolymer composition comprising a fluorine-containing copolymer (A) having units having nitrile groups and units based on tetrafluoroethylene, a fluorine-containing copolymer (B) having units having at least one functional group selected from the group consisting of a group having a carbonyl group, a hydroxy group, an epoxy group, and an isocyanate group, and units based on tetrafluoroethylene, and a crosslinking agent. Patent Document 3 discloses a fluorine-containing copolymer composition comprising a fluorine-containing copolymer having nitrile groups, a phosphorus compound having a melting point of 60°C or less, and a crosslinking agent.

[0004] International Publication No. 2022 / 220180 International Publication No. 2021 / 210502 International Publication No. 2021 / 210503

[0005] Crosslinked rubber articles obtained from the compositions described in Patent Documents 1 to 3 have excellent heat resistance. However, in recent years, there has been a demand for even greater heat resistance. For example, there is a demand for crosslinked rubber articles that have small compression set and are less likely to crack even when used in a compressed state at high temperatures of 325°C or higher for long periods of time.

[0006] 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 gives a crosslinked rubber article which has small compression set and is resistant to cracking even when used in a compressed state at a high temperature of 325°C or higher for a long period of time, a method for producing the same, and a crosslinked rubber article obtainable from the fluorocopolymer composition and a method for producing the same.

[0007] The present invention is based on the finding that a crosslinked rubber article obtained by crosslinking a fluorocopolymer composition which contains a fluorocopolymer having a specific amount of specific monomer units and which contains a specific type of crosslinking agent in a specific ratio relative to the fluorocopolymer has small compression set and is resistant to cracking even when used for a long period of time in a compressed state at a high temperature of 325°C or above 325°C.

[0008] The present invention is as follows: [1] A fluorine-containing copolymer composition comprising: a fluorine-containing copolymer (A) having units based on a monomer having a nitrile group and units based on tetrafluoroethylene; and a crosslinking agent (B) having two or more amino groups, wherein the content of units based on the monomer having a nitrile group in 100 mol % of all monomer units in the fluorine-containing copolymer (A) is 0.80 mol % or more and less than 1.00 mol %, and the content of the crosslinking agent (B) is 0.80 to 1.30 parts by mass per 100 parts by mass of the fluorine-containing copolymer (A). [2] The fluorine-containing copolymer composition according to the above [1], wherein the fluorine-containing copolymer (A) has units based on perfluoro(alkyl vinyl ether), the content of the units based on tetrafluoroethylene in 100 mol% of all monomer units of the fluorine-containing copolymer (A) is 67.0 mol% or more and less than 71.5 mol%, and the content of the units based on perfluoro(alkyl vinyl ether) in 100 mol% of all monomer units of the fluorine-containing copolymer (A) is 27.0 to 32.0 mol%. [3] The fluorine-containing copolymer (A) has a carboxy terminal group, and the fluorine-containing copolymer (A) has a carboxy terminal group in the range of 2210 to 2700 cm in the spectrum obtained by measuring the fluorine-containing copolymer (A) by infrared spectroscopy. －１ 1700 to 1850 cm for the integrated peak intensity of absorbance at －１ The fluorine-containing copolymer composition according to the above [1] or [2], wherein the ratio of integrated peak intensities of absorbance at 1000 ppm or less is 0.7 or more. [4] The fluorine-containing copolymer composition according to any of the above [1] to [3], wherein the crosslinking agent (B) is 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane. [5] The fluorine-containing copolymer composition according to any of the above [1] to [4], which contains a filler (C). [6] The fluorine-containing copolymer composition according to the above [5], wherein the content of the filler (C) is 1 to 20 parts by mass per 100 parts by mass of the fluorine-containing copolymer (A). [7] The fluorine-containing copolymer composition according to the above [5] or [6], wherein the filler (C) is carbon black. [8] The fluorine-containing copolymer composition according to the above [5] or [6], wherein the torque difference (M Ｈ -M ＬThe fluorocopolymer composition according to any one of the above [1] to [7], wherein the maximum torque M in the fluorocopolymer composition is 60 to 90 dN·m. [Measurement method: measured in accordance with JIS K6296-1:2023 using a crosslinking property measuring machine under the conditions of a measurement temperature of 180°C, a measurement time of 30 minutes, a vibration frequency of 100 cpm, and an angle of 3.00 deg.] Ｈ and the minimum value M Ｌ and measuring the crosslinking agent (B).] [9] A method for producing the fluorine-containing copolymer composition according to any one of the above [1] to [8], which comprises kneading the fluorine-containing copolymer (A) and the crosslinking agent (B).

[10] A crosslinked rubber article obtained by crosslinking the fluorine-containing copolymer (A) in the fluorine-containing copolymer composition according to any one of the above [1] to [8].

[11] A method for producing a crosslinked rubber article, which comprises crosslinking the fluorine-containing copolymer (A) in the fluorine-containing copolymer composition according to any one of the above [1] to [8].

[0009] According to the present invention, there are provided a fluorocopolymer composition which gives a crosslinked rubber article which has small compression set and is resistant to cracking even when used in a compressed state at 325°C or a high temperature exceeding 325°C for a long period of time, a method for producing the same, and a crosslinked rubber article obtainable from the fluorocopolymer composition and a method for producing the same.

[0010] 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 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). 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.

[0011] [Fluorocopolymer Composition] The fluorine-containing copolymer composition according to an embodiment of the present invention (hereinafter sometimes simply referred to as "the fluorine-containing copolymer composition of the present embodiment") comprises a fluorine-containing copolymer (A) having units based on a monomer having a nitrile group and units based on tetrafluoroethylene, and a crosslinking agent (B) having two or more amino groups, wherein the content of units based on the monomer having a nitrile group in 100 mol% of all monomer units in the fluorine-containing copolymer (A) is 0.80 mol% or more and less than 1.00 mol%, and the content of the crosslinking agent (B) is 0.80 to 1.30 parts by mass per 100 parts by mass of the fluorine-containing copolymer (A).

[0012] According to the fluorine-containing copolymer composition of this embodiment, a crosslinked rubber article can be obtained which has small compression set and is resistant to cracking even when used for a long period of time in a compressed state at a high temperature of 325° C. or higher than 325° C. Incidentally, "having small compression set and being resistant to cracking even when used for a long period of time in a compressed state at a high temperature of 325° C. or higher than 325° C." is sometimes simply referred to as "excellent heat resistance."

[0013] Although the details of why the fluorine-containing copolymer composition of this embodiment allows for the production of crosslinked rubber articles with excellent heat resistance are unknown, it is presumed to be as follows. The fluorine-containing copolymer composition of this embodiment has the following combination of features: (i) the content of units based on monomers having nitrile groups, in 100 mol% of all monomer units of the fluorine-containing copolymer (A), is 0.80 mol% or more and less than 1.00 mol%; and (ii) the content of the crosslinking agent (B) having two or more amino groups is 0.80 to 1.30 parts by mass per 100 parts by mass of the fluorine-containing copolymer (A). The combination of features (i) and (ii) makes it possible to make the crosslink density uniform when the nitrile groups and the crosslinking agent (B) are crosslinked, thereby reducing the occurrence of excessive stress concentration and shear force, and thereby reducing the probability of molecular chain breakage while maintaining rubber elasticity. As a result, it is believed that a crosslinked rubber article can be obtained that has small compression set and is less likely to crack, even when used in a compressed state at high temperatures of 325°C or higher for a long period of time.

[0014] The fluorine-containing copolymer composition of the present embodiment is not particularly limited as long as it contains the fluorine-containing copolymer (A) and the crosslinking agent (B), and may or may not contain a filler (C), a crosslinking aid, other components, and the like, as necessary.

[0015] <Fluorocopolymer (A)> The fluorine-containing copolymer (A) has units based on a monomer having a nitrile group and tetrafluoroethylene (hereinafter sometimes simply referred to as "TFE") units.

[0016] The content of fluorine-containing copolymer (A) relative to the total mass of the fluorine-containing copolymer composition is not particularly limited, but from the viewpoint of heat resistance it is preferably 60.00 to 98.70 mass%, more preferably 65.00 to 98.30 mass%, and particularly preferably 70.00 to 98.00 mass%. The content of fluorine-containing copolymer (A) relative to the total mass of polymers contained in the fluorine-containing copolymer composition is not particularly limited, but from the viewpoint of heat resistance it is preferably 80 to 100 mass%, more preferably 90 to 100 mass%, and particularly preferably 95 to 100 mass%.

[0017] (Units Based on Monomer Having Nitrile Group) The fluorine-containing copolymer (A) contains a monomer having a nitrile group (hereinafter simply referred to as "R ＣＮ It has units based on the 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 (1). １１ R １２ =CR １３ -R １４ -CN...General formula (1)

[0018] In general formula (1), 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. １４ R may or may not have an unsaturated bond, but from the viewpoint of heat resistance, it is preferable that it does not have an unsaturated bond.１４ The 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 is preferably 1 to 3, more preferably 1 or 2, from the viewpoints of reactivity and availability.

[0019] Specific examples of the monomer represented by general formula (1) 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.

[0020] From the viewpoint of obtaining crosslinked rubber articles having excellent heat resistance, the content of units based on the monomer having a nitrile group in 100 mol% of all monomer units in the fluorine-containing copolymer (A) is 0.80 mol% or more and less than 1.00 mol%. From this viewpoint, the content is preferably 0.80 to 0.95 mol%, more preferably 0.85 to 0.95 mol%, particularly preferably 0.85 to 0.93 mol%, and even more preferably 0.85 to 0.90 mol%.

[0021] (Unit based on TFE) TFE is CF ２ =CF２ The content of the tetrafluoroethylene-based units (TFE units) in 100 mol% of all monomer units in the fluorocopolymer (A) is preferably 67.0 mol% or more and less than 71.5 mol%. When the TFE units are 67.0 mol% or more, heat resistance is improved. When the TFE units are less than 71.5 mol%, crosslinked rubber articles with high rigidity can be obtained. From these viewpoints, the content of the TFE units in 100 mol% of all monomer units in the fluorocopolymer (A) is more preferably 67.0 to 70.5 mol%, particularly preferably 67.0 to 70.0 mol%.

[0022] The total content of units based on the monomer having a nitrile group and units based on tetrafluoroethylene in 100 mol% of all monomer units in the fluorine-containing copolymer (A) is, from the viewpoint of obtaining crosslinked rubber articles excellent in heat resistance, preferably at least 67.8 mol% and less than 72.5 mol%, more preferably from 67.8 to 71.0 mol%, particularly preferably from 67.0 to 70.0 mol%.

[0023] (PAVE-based units) The fluorine-containing copolymer (A) may or may not have units (PAVE units) based on perfluoro(alkyl vinyl ether) (hereinafter, sometimes simply referred to as "PAVE"), but it is preferable that it has such units. As the PAVE, a monomer represented by the following general formula (2) is preferred: CF ２ =CF-O-R ｆ１ ...General formula (2) In general formula (2), R ｆ１ is a perfluoroalkyl group having 1 to 10 carbon atoms. ｆ１ The number of carbon atoms in the group 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.

[0024] Specific examples of PAVE include the following (i) to (iv): (i) CF ２ = CFOCF ３ (ii) CF: Perfluoro(methyl vinyl ether) (hereinafter, sometimes simply referred to as "PMVE"). ２ = CFOCF２ CF ３ : Perfluoro(ethyl vinyl ether) (iii) CF ２ = CFOCF ２ CF ２ CF ３ (iv) CF: Perfluoro(propyl vinyl ether) (hereinafter, sometimes simply referred to as "PPVE"). ２ = CFOCF ２ CF ２ CF ２ CF ３ 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.

[0025] The content of units based on perfluoro(alkyl vinyl ether) (PAVE units) in 100 mol% of all monomer units in the fluorine-containing copolymer (A) is not particularly limited, but from the viewpoint of heat resistance and chemical resistance, it is preferably from 27.0 to 32.0 mol%, more preferably from 29.0 to 32.0 mol%, particularly preferably from 29.5 to 32.0 mol%.

[0026] The total content of units based on the monomer having a nitrile group, units based on tetrafluoroethylene and units based on PAVE in 100 mol% of all monomer units in the fluorine-containing copolymer (A) is, from the viewpoint of obtaining crosslinked rubber articles having excellent heat resistance, preferably from 75 to 100 mol%, more preferably from 80 to 100 mol%, even more preferably from 90 to 100 mol%, and particularly preferably from 95 to 100 mol%, and may be from 98 to 100 mol%, 99 to 100 mol% or even 100 mol%.

[0027] (Units Based on Other Monomers) The fluorine-containing copolymer (A) may or may not have units other than units based on a monomer having a nitrile group, TFE units, and PAVE units. Monomers other than a monomer having a nitrile group, TFE, and PAVE may be simply referred to as "other monomers." Furthermore, units other than units based on a monomer having a nitrile group, TFE units, and PAVE units may be simply referred to as "units based on other monomers" or "other units." Specific examples of units based on other monomers include vinylidene fluoride (hereinafter sometimes simply referred to as "VdF") units, units based on a monomer having two or more polymerizable unsaturated bonds, units based on a monomer represented by the following general formula (3) (hereinafter sometimes simply referred to as "formula (3) units"), units based on hexafluoropropylene (hereinafter sometimes simply referred to as "HFP units"), and units based on chlorotrifluoroethylene. These may be used alone or in combination of two or more.

[0028] The total content of units based on other monomers in all units constituting the fluorine-containing copolymer (A) is not particularly limited, but from the viewpoint of heat resistance and chemical resistance, it is preferably 0 to 20 mol %, more preferably 0 to 10 mol %, particularly preferably 0 to 1 mol %. It is most preferable that the copolymer (A) does not contain units based on other monomers.

[0029] -Copolymer having VdF units- VdF is CF ２ =CH ２ It is a monomer represented by the formula:

[0030] The proportion of VdF units in all units constituting the fluorinated copolymer (A) is not particularly limited, but from the viewpoint of suppressing sticking, it is preferably from 0.1 to 5 mol %, more preferably from 0.1 to 3 mol %, particularly preferably from 0.1 to 1 mol %.

[0031] -Units Based on Monomers Having Two or More Polymerizable Unsaturated Bonds- The units based on monomers having two or more polymerizable unsaturated bonds preferably contain a fluorine atom, and are preferably units based on fluorine-containing monomers having two or more polymerizable unsaturated bonds. 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 produce 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 (4) is preferred, since the fluorine-containing copolymer (A) has excellent rubber properties when made into a crosslinked rubber article:

[0032] (CR ３１ R ３２ =CR ３３ ) ａ３ R ３４ ... General formula (4) In general formula (4), 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 of the perfluorohydrocarbon group or between the carbon-carbon bonds. In general formula (4), a3 represents an integer of 2 to 6, preferably 2 or 3, and more preferably 2. In general formula (4), 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.

[0033] R ３１ , R３２ , 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.

[0034] Specific preferred examples of the monomer represented by formula (4) include a monomer represented by general formula (4-1) and a monomer represented by general formula (4-2).

[0035] (CF ２ =CF) ２ R ４１ ... General formula (4-1) In general formula (4-1), 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 (4-1) 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 = CF２ :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) ３ O(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 ２As the monomer represented by the general formula (4-1), C3DVE and C4DVE are preferred since they provide even better rubber properties when the fluorocopolymer composition is made into a crosslinked rubber article.

[0036] (CH ２ =CH) ２ R ５１ ... General formula (4-2) In general formula (4-2), 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 (4-2) 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 (4-2), C6-DV is preferred.

[0037] The proportion of units based on a fluorine-containing monomer having two or more polymerizable unsaturated bonds among all units constituting the fluorine-containing copolymer (A) is not particularly limited, but from the viewpoint of heat resistance, it is preferably from 0.1 to 5 mol %, more preferably from 0.3 to 3 mol %, particularly preferably from 0.3 to 1 mol %.

[0038] -Formula (3) Unit- General formula (3) is as follows: CF ２ =CF-O-R ｆ４ ...General formula (3) In general formula (3), R ｆ４ is a group having an etheric oxygen atom between the carbon-carbon bond of a perfluorohydrocarbon group having 1 to 8 carbon atoms. ｆ４The 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 (3) include the following. The description after the formula is the abbreviation for the compound. These may be used alone or in combination of two or more. 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 (A) is made into a crosslinked rubber article.

[0039] The proportion of units of formula (3) in all units constituting the fluorine-containing copolymer (A) is not particularly limited, but from the viewpoint of excellent low-temperature properties, it is preferably from 0.1 to 5 mol %, more preferably from 0.1 to 3 mol %, particularly preferably 0.1 to 1 mol %.

[0040] - Units Based on Monomer Other Than the Above - The fluorine-containing copolymer (A) may have units based on a monomer other than the above. Examples of the other monomer 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 and the like (perfluoroalkyl)ethylenes. Specific examples of the non-fluorine-containing monomer 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. The content of units based on other monomers other than those mentioned above in all units constituting the fluorine-containing copolymer (A) is not particularly limited, but from the viewpoint of excellent heat resistance and chemical resistance, it is preferably 0.1 to 1 mol %, more preferably 0.1 to 0.5 mol %, and particularly preferably 0.1 to 0.3 mol %.

[0041] 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 (A). 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 (5) and compound B represented by general formula (6).

[0042] CR ２１ R ２２ =CR ２３ R ２４ ...General formula (5) CR ２１ R ２２ -R ２５ -CR ２３ R ２４ ...General Formula (6) 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 is an alkyl group, a group having an etheric oxygen atom at the terminal of an alkyl group or between carbon-carbon bonds, a fluoroalkyl group, or a group having an etheric oxygen atom at the terminal of a fluoroalkyl group or between carbon-carbon bonds. ２４ may have at least one of a chlorine atom, a bromine atom, and an iodine atom. ２４ R in general formula (6) 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, a group having an etheric oxygen atom at the terminal of an alkyl group or between carbon-carbon bonds, a fluoroalkyl group, a group having an etheric oxygen atom at the terminal of a fluoroalkyl group or between carbon-carbon bonds. R ２５may have at least one of a chlorine atom, a bromine atom, and an iodine atom. ２５ may be linear or branched.

[0043] 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, and 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, etc. These may be used alone or in combination of two or more.

[0044] 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 ２ These may be used alone or in combination of two or more.

[0045] Specific examples of the monomer 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 in combination of two or more.

[0046] <Content ratio of carboxy terminal group> When the fluorocopolymer (A) has a carboxy terminal group, and the fluorocopolymer (A) has a carboxy terminal group, the content ratio of the fluorocopolymer (A) in the region between 2210 and 2700 cm in the spectrum obtained by measuring the fluorocopolymer (A) by infrared spectroscopy －１ 1700 to 1850 cm for the integrated peak intensity of absorbance at －１It is preferable that the ratio of the integrated peak intensities of absorbance at 1000 kJ / min is 0.7 or more. In other words, the content ratio of carboxy terminal groups in the fluorocopolymer (A) measured by infrared spectroscopy is preferably 0.7 or more. When the content ratio of carboxy terminal groups is 0.7 or more, the polarity of the molecular terminals of the fluorocopolymer is increased, thereby improving adhesion to the crosslinking agent and filler. As a result, the vulcanization efficiency is improved, and the heat resistance of the crosslinked rubber article is improved. Furthermore, it is preferable that the content ratio of carboxy terminal groups is 5.0 or less. When the content of carboxy terminal groups is 5.0 or less, decomposition of the fluorocopolymer (A) due to the carboxy terminal groups when exposed to high temperatures is reduced. The content ratio of carboxy terminal groups is preferably 0.7 to 2.0, more preferably 0.7 to 1.0, and even more preferably 0.7 to 0.9. The carboxylic acid content ratio may be more than 0.7, and the carboxy terminal group content ratio may be more than 0.7 and not more than 2.0, more than 0.7 and not more than 1.0, or more than 0.7 and not more than 0.9. In particular, the fluorine-containing copolymer composition according to this embodiment has the following combination of structures: (i) the content of units based on monomers having a nitrile group is 0.80 mol% or more and less than 1.00 mol% in 100 mol% of all monomer units of the fluorine-containing copolymer (A); and (ii) the content of the crosslinking agent (B) having two or more amino groups is 0.80 to 1.30 parts by mass per 100 parts by mass of the fluorine-containing copolymer (A). It is thought that some intermolecular interaction due to the above combination of structures improves the adhesion between the fluorine-containing copolymer (A) and the crosslinking agent due to the carboxy terminal groups, and improves the reaction efficiency with the crosslinking agent. Therefore, it is believed that by having the above-mentioned configurations (i) and (ii) and by adjusting the content of carboxy terminal groups in the fluorocopolymer (A) to 0.7 or more, preferably 0.7 to 5.0, more preferably 0.7 to 2.0, and even more preferably 0.7 to 1.4, it is possible to obtain a crosslinked rubber article having excellent heat resistance.

[0047] <<Method for producing fluorine-containing copolymer (A)>> One example of a method for producing the fluorine-containing copolymer (A) is a method of copolymerizing the above-mentioned monomers in the presence of a radical polymerization initiator. When the above-mentioned monomers are copolymerized in the presence of a radical polymerization initiator, a radical reaction caused by the radical polymerization initiator generates carboxyl terminal groups at the ends of the polymer. Note that the content of carboxyl terminal groups in the fluorine-containing copolymer (A) tends to increase as the ratio of the radical polymerization initiator to the fluorine-containing copolymer (A) increases. As the radical polymerization initiator, a water-soluble polymerization initiator, a redox polymerization initiator, etc. are preferred.

[0048] Specific examples of the water-soluble polymerization initiator include persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate, and organic polymerization initiators such as disuccinic acid peroxide and azobisisobutylamidine dihydrochloride. Among these, persulfates are preferred, and ammonium persulfate is more preferred.

[0049] Examples of redox polymerization initiators include polymerization initiators that combine persulfates and reducing agents. Among these, polymerization initiators that can polymerize each monomer at a polymerization temperature in the range of 0 to 85°C are preferred. Specific examples of persulfates that constitute the redox polymerization initiator include alkali metal salts of persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate, with ammonium persulfate being preferred. Specific examples of reducing agents that can be combined with persulfates include thiosulfates, sulfites, hydrogen sulfites, pyrosulfites, and hydroxymethanesulfinates, with hydroxymethanesulfinates being preferred and sodium hydroxymethanesulfinate being particularly preferred.

[0050] In the method for producing the fluorine-containing copolymer (A), the above-mentioned monomers may be copolymerized together with a radical polymerization initiator in the presence of a chain transfer agent. The chain transfer agent is preferably an iodine compound, and is represented by the formula RI ２ In the above formula, R represents an alkylene group or a perfluoroalkylene group having 3 or more carbon atoms (preferably 3 to 8 carbon atoms). ２Specific examples of the iodo compound represented by the formula (I) include 1,3-diiodopropane, 1,4-diiodobutane, 1,6-diiodohexane, 1,8-diiodooctane, 1,3-diiodoperfluoropropane, 1,4-diiodoperfluorobutane, 1,6-diiodoperfluorohexane, and 1,8-diiodoperfluorooctane. As the iodo compound, an iodo compound having a perfluoroalkylene group is preferred, with 1,4-diiodoperfluorobutane being particularly preferred. By copolymerizing the above-mentioned monomers in the presence of these iodine compounds, iodine atoms can be introduced into the fluorine-containing copolymer (A). For details of the components other than those mentioned above used in the production of the fluorine-containing copolymer (A) and the production method, reference can be made to the method described in paragraphs 0019 to 0034 of WO 2010 / 082633.

[0051] <Crosslinking agent (B)> The fluorocopolymer composition of the present embodiment contains a crosslinking agent (B) having two or more amino groups. Thereby, the fluorocopolymer (A) is crosslinked by the crosslinking agent (B), and a crosslinked rubber article having excellent heat resistance can be obtained. Specific examples of the crosslinking agent (B) having two or more amino groups 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.

[0052] From the viewpoint of heat resistance, the content of crosslinking agent (B) is 0.80 to 1.30 parts by mass relative to 100 parts by mass of fluorocopolymer (A). The content of crosslinking agent (B) is preferably 0.80 to 1.25 parts by mass, more preferably 0.80 to 1.22 parts by mass, and particularly preferably 0.80 to 1.20 parts by mass relative to 100 parts by mass of fluorocopolymer (A). When the blending amount of the crosslinking agent is within the above range, the crosslinked rubber article will have an excellent balance between strength and elongation.

[0053] The fluorine-containing copolymer composition of this embodiment has the following constitutional combination: (i) the content of units based on monomers having nitrile groups is 0.80 mol % or more and less than 1.00 mol % in 100 mol % of all monomer units in the fluorine-containing copolymer (A); and (ii) the content of the crosslinking agent (B) having two or more amino groups is 0.80 to 1.30 parts by mass per 100 parts by mass of the fluorine-containing copolymer (A); and it is presumed that when crosslinking occurs with the nitrile groups and the crosslinking agent (B) acting as crosslinking points, the crosslink density is improved without causing excessive stress concentration, and a crosslinked rubber article with high heat resistance can be obtained.

[0054] When the content of units based on monomers having a nitrile group in 100 mol% of all monomer units in the fluorine-containing copolymer (A) is 0.80 mol% or more and less than 1.00 mol%, the content of crosslinking agent (B) is preferably 0.80 to 1.25 parts by mass, more preferably 0.80 to 1.22 parts by mass, and particularly preferably 0.80 to 1.20 parts by mass, relative to 100 parts by mass of the fluorine-containing copolymer (A). When the content of units based on monomers having a nitrile group in 100 mol% of all monomer units in the fluorine-containing copolymer (A) is 0.80 to 0.95 mol%, the content of crosslinking agent (B) is preferably 0.80 to 1.25 parts by mass, more preferably 0.80 to 1.22 parts by mass, and particularly preferably 0.80 to 1.20 parts by mass, relative to 100 parts by mass of the fluorine-containing copolymer (A). For example, the content of units based on monomers having a nitrile group in 100 mol% of all monomer units in the fluorine-containing copolymer (A) may be 0.80 to 0.95 mol%, and the content of crosslinking agent (B) may be 0.80 to 1.25 parts by mass relative to 100 parts by mass of the fluorine-containing copolymer (A). When the content of units based on monomers having a nitrile group in 100 mol% of all monomer units in the fluorine-containing copolymer (A) is 0.85 to 0.95 mol%, the content of crosslinking agent (B) is preferably 0.80 to 1.25 parts by mass, more preferably 0.80 to 1.22 parts by mass, and particularly preferably 0.80 to 1.20 parts by mass relative to 100 parts by mass of the fluorine-containing copolymer (A). For example, the content of units based on monomers having a nitrile group in 100 mol% of all monomer units in the fluorine-containing copolymer (A) may be 0.85 to 0.95 mol%, and the content of crosslinking agent (B) may be 0.80 to 1.22 parts by mass relative to 100 parts by mass of the fluorine-containing copolymer (A). When the content of units based on monomers having a nitrile group in 100 mol% of all monomer units in the fluorine-containing copolymer (A) is 0.85 to 0.90 mol%, the content of crosslinking agent (B) is preferably 0.80 to 1.25 parts by mass, more preferably 0.80 to 1.22 parts by mass, and particularly preferably 0.80 to 1.20 parts by mass relative to 100 parts by mass of the fluorine-containing copolymer (A).For example, the content of units based on a monomer having a nitrile group in 100 mol % of all monomer units in the fluorine-containing copolymer (A) may be 0.85 to 0.90 mol %, and the content of the crosslinking agent (B) may be 0.80 to 1.20 parts by mass per 100 parts by mass of the fluorine-containing copolymer (A).

[0055] <Other Crosslinking Agents> The fluorine-containing copolymer composition of this embodiment may or may not contain other crosslinking agents. However, since the fluorine-containing copolymer composition of this embodiment contains the crosslinking agent (B), it is preferable that it does not contain other crosslinking agents. The other crosslinking agents are used to crosslink the fluorine-containing copolymer (A), and examples thereof include organic peroxides, polyols, triazines, etc. These may be used alone or in combination of two or more. Among these, organic peroxides are preferred from the viewpoint of better crosslinking reactivity of the fluorine-containing copolymer (A), productivity of the crosslinked rubber article, heat resistance of the crosslinked rubber article, and chemical resistance of the crosslinked rubber article.

[0056] The total content of the crosslinking agent (B) and the other crosslinking agents is preferably 0.80 to 1.25 parts by mass, more preferably 0.80 to 1.22 parts by mass, and particularly preferably 0.80 to 1.20 parts by mass, relative to 100 parts by mass of the fluorine-containing copolymer (A). The content of the crosslinking agent (B) in 100% by mass of the total amount of the crosslinking agents contained in the fluorine-containing copolymer composition is preferably 60 to 100% by mass, more preferably 80 to 100% by mass, particularly preferably 90 to 100% by mass, and may even be 100% by mass.

[0057] <Filler (C)> The fluorocopolymer composition may or may not contain a filler (C), but it is preferable that it contain one from the viewpoint of excellent mold release properties. Examples of the filler (C) include carbon black, barium sulfate, calcium metasilicate, calcium carbonate, titanium oxide, silicon dioxide, aromatic polyester, polyamideimide, thermoplastic polyimide, clay, and talc. Of these fillers (C), carbon black is preferred from the viewpoint of excellent mold release properties. In the fluorocopolymer composition, the content of the filler (C) per 100 parts by mass of the fluorocopolymer (A) is not particularly limited, but from the viewpoint of heat resistance and chemical resistance, it is preferably 1 to 20 parts by mass, more preferably 5 to 20 parts by mass, and particularly preferably 10 to 20 parts by mass.

[0058] <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 (A) with an organic peroxide. After the crosslinking reaction is completed, the crosslinking aid bonds to the fluorine-containing copolymer (A) 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.

[0059] When the fluorine-containing copolymer composition contains a crosslinking aid, the mass ratio of the content of crosslinking agent to the content of crosslinking aid in the fluorine-containing copolymer composition (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 order to prevent unreacted crosslinking aid from remaining and to ensure that the crosslinking reaction proceeds 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 (A) is not particularly limited, but is preferably 0.80 to 5.00 parts by mass, more preferably 0.80 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.

[0060] When the fluorine-containing copolymer composition contains a crosslinking aid, the content of the crosslinking aid 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 0.30 to 10.00 mass%, more preferably from 0.30 to 5.00 mass%, particularly preferably from 0.31 to 1.00 mass%.

[0061] <Other Components> The fluorine-containing copolymer composition may or may not contain other components other than those described above, provided that the effects of the present invention are not impaired. Examples of other components include processing aids (for example, acid acceptors such as fatty acid esters (glycerin monooleate, etc.), fatty acid metal salts (sodium stearate, calcium stearate, etc.), divalent metal oxides (magnesium oxide, calcium oxide, zinc oxide, lead oxide, etc.), synthetic waxes (polyethylene wax, etc.), fluorine-containing copolymers other than the above-mentioned fluorine-containing copolymer (A) (hereinafter also referred to as "other fluorine-containing copolymers")), vulcanizing agents, scorch retarders (for example, phenolic hydroxyl group-containing compounds such as bisphenol A, quinones such as hydroquinone, α-methylstyrene dimers such as 2,4-di(3-isopropylphenyl)-4-methyl-1-pentene), crown ethers (for example, 18-crown-6), pigments, etc.

[0062] The content of other components relative to the total mass of the fluorocopolymer composition is not particularly limited, but from the viewpoint of heat resistance and chemical resistance, it is preferably from 0 to 30 mass%, more preferably from 0 to 20 mass%, particularly preferably from 0 to 10 mass%.

[0063] [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 (A) and the crosslinking agent (B). The kneading is achieved by kneading the fluorine-containing copolymer (A), the crosslinking agent (B), 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 then dipped or coated to form a molded product.

[0064] <Torque of Fluorocopolymer Composition> The torque difference (M Ｈ -M Ｌ [Measurement method: The maximum torque M in the fluorocopolymer composition was measured using a crosslinking property measuring device in accordance with JIS K6296-1:2023 under the conditions of a measurement temperature of 180°C, a measurement time of 30 minutes, a vibration frequency of 100 cpm, and an angle of 3.00 deg.] Ｈ and the minimum value M Ｌ Measure the torque difference (M Ｈ -M Ｌ When the torque difference (M) is 60 dN·m or more, a sufficient crosslink density can be ensured, and the compression set at 325°C or more is improved. Ｈ -M Ｌ If the torque difference (M Ｈ -M Ｌ) is preferably 60 to 90 dN·m, more preferably 65 to 85 dN·m, and even more preferably 67 to 83 dN·m.

[0065] The torque M Ｈ The torque M is preferably 68 to 96 dN·m. Ｈ When the torque M is 68 dN·m or more, a sufficient crosslink density can be ensured, and the compression set at 325°C or more is improved. Ｈ If the torque M is 96 dN·m or less, cracking of the test piece can be suppressed at 325°C or higher. Ｈ is preferably 70 to 95 dN·m, more preferably 71 to 90 dN·m, and even more preferably 73 to 89.0 dN·m.

[0066] The torque M Ｌ The torque M is preferably 5.0 to 7.0 dN·m. Ｌ When the torque M is 5.0 dN·m or more, a sufficient crosslink density can be ensured and cracking of the test piece can be suppressed at 325°C or more. Ｌ When the torque M is 7.0 dN·m or less, cracking of the test piece can be suppressed at 325°C or higher. Ｌ is preferably 5.5 to 6.5 dN·m, more preferably 5.7 to 6.3 dN·m, and even more preferably 5.8 to 6.1 dN·m.

[0067] [Crosslinked Rubber Article] The crosslinked rubber article of the present invention is obtained by crosslinking the fluorocopolymer (A) in the fluorocopolymer composition of the present invention.

[0068] [Method for producing crosslinked rubber article] The method for producing a crosslinked rubber article of the present invention is a method for crosslinking the fluorocopolymer (A) in a fluorocopolymer composition. The method for producing a crosslinked rubber article of the present invention is preferably a method in which the fluorocopolymer composition is primarily heated at 100 to 400°C for 1 second to 24 hours, and, after the primary heating, is subsequently secondary heated at 80 to 400°C for 30 minutes to 48 hours. The crosslinked rubber article is obtained by crosslinking the fluorocopolymer (A) in the fluorocopolymer composition. Examples of methods for crosslinking the fluorocopolymer (A) 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.

[0069] 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 (i) a method in which a suspension solution prepared by dissolving and dispersing the fluorine-containing copolymer (A) or the fluorine-containing copolymer composition in a suitable solvent is applied and dried to form a coating film, and (ii) a method in which the fluorine-containing copolymer (A) or the fluorine-containing copolymer composition is extruded and molded into the shape of a hose or an electric wire.

[0070] The fluorocopolymer (A) is preferably crosslinked by heating. Specific examples of methods for producing crosslinked rubber articles by thermal crosslinking include hot press molding. In hot press molding, a heated mold is used, a fluorocopolymer 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.

[0071] 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 350°C, even more preferably 180 to 350°C, and particularly preferably 200 to 320°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.

[0072] 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 irradiation with ionizing radiation, a preferred method is to first mold the fluorine-containing copolymer (A) or the fluorine-containing copolymer composition into a desired shape and then irradiate it with ionizing radiation to crosslink it. The irradiation dose of ionizing radiation is appropriately set and is preferably 1 to 300 kGy, more preferably 10 to 200 kGy.

[0073] <Physical Properties> The compression set CS of the crosslinked rubber article at 325°C for 70 hours is not particularly limited, but is preferably 40% or less, more preferably 25% or less, and particularly preferably 22% or less, in order to ensure that the fluorocopolymer (A) is well crosslinked and that the crosslinked rubber article has excellent shape recovery after pressure. The compression set CS of the crosslinked rubber article at 325°C for 168 hours is not particularly limited, but from the same viewpoint, it is preferably 55% or less, more preferably 39% or less, and particularly preferably 36% or less. The compression set CS of the crosslinked rubber article at 340°C for 70 hours is not particularly limited, but from the same viewpoint, it is preferably 53% or less, more preferably 42% or less, and particularly preferably 39% or less. The compression set CS of the crosslinked rubber article at 340°C for 168 hours is not particularly limited, but from the same viewpoint, it is preferably 80% or less, more preferably 65% ​​or less, and particularly preferably 64% or less. The compression set of the crosslinked rubber article is measured by the method described in the Examples section below.

[0074] <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.

[0075] 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 gist of the present invention. Examples 1 and 2 are examples, and Examples 3 to 8 are comparative examples.

[0076] <Measurement of Composition of Fluorine-Containing Copolymer> The content (mol %) of each unit in Fluorine-Containing Copolymer 1 and Fluorine-Containing Copolymer 2 was measured. １９ The content of propylene units was calculated by F-nuclear magnetic resonance (NMR) analysis. １ H and １３ Calculated from C-nuclear magnetic resonance (NMR) analysis.

[0077] <Identification of carboxyl terminal in fluorine-containing copolymer> The carboxyl terminal group ratio is 1700 to 1850 cm －１ To quantitatively compare the ratio of carboxyl end groups between different samples, the absorbance was measured at 2210-2700 cm －１ The integrated absorbance ratio was normalized by taking the ratio to the integrated absorbance of the fluorocopolymer obtained. The obtained fluorocopolymer was press-molded at 100°C to obtain a sheet. The obtained sheet was measured with a transmission Fourier transform infrared spectrophotometer to obtain an infrared absorption spectrum. The carboxy terminal group amount ratio was calculated from the obtained spectrum.

[0078] <Torque difference (M Ｈ -M Ｌ Measurement of Torque (dNm)> The obtained fluorine-containing copolymer composition was cut into 10 g pieces to obtain cut pieces. The obtained cut pieces were sandwiched between two polyester films (manufactured by ALFA Technologies, PART#F0311-S, 130 mm x 130 mm x 24 μm) on both sides of the main surface to obtain a measurement sample. The measurement sample was placed on a die. Next, torque (dNm) was measured using a measurement device (manufactured by Alpha Technologies) under the conditions of 180°C (test temperature), 30 minutes (vulcanization time), vibration frequency 100 cpm, and angle 3.00 deg. in accordance with JIS K6296-1:2023, to obtain a torque-vulcanization time curve. From the obtained torque-vulcanization time curve, the minimum torque value (MＬ ) and the maximum torque (M Ｈ ) and from these values, the torque difference (M Ｈ -M Ｌ ) was calculated.

[0079] <Measurement of Compression Set, etc.> The compression set of the obtained crosslinked rubber article (O-ring) was measured with reference to JIS K 6262:2013. The O-ring (original thickness (wire diameter) of the test piece = 3.5 mm) produced in each example was compressed to a compression ratio of 18% using a compression device. Next, the compression device with the compressed O-ring fixed thereto was placed in an electric furnace and left at 325°C for 70 hours (compression treatment 1), 325°C for 168 hours (compression treatment 2), 340°C for 70 hours (compression treatment 3), or 340°C for 168 hours (compression treatment 4). Thereafter, the compression device was removed from the electric furnace, and the O-ring was immediately removed from the compression device. The removed O-ring was placed in a constant temperature chamber and left at 23°C for 30 minutes. Thereafter, the thickness of the O-ring (thickness after compression treatment) was measured. The test was performed using two test pieces, and the arithmetic average of the measured values ​​of the two test pieces was used. The compression set rate was calculated using the following formula. The closer the compression set rate is to 0%, the better the result is. Compression set rate (%) = {original thickness of test piece (wire diameter) - thickness of test piece 30 minutes after removal from the compression device (thickness after compression treatment)} ÷ (original thickness of test piece - thickness of spacer) x 100 The test pieces were also evaluated for the presence or absence of cracks according to the following criteria: 0 / 2: Neither of the two pieces were cracked. 1 / 2: One of the two pieces was cracked. 2 / 2: Two of the two pieces were cracked.

[0080] <Compounds Used> Details of the various compounds used and explanations of their abbreviations are given below: (1) Monomers TFE: tetrafluoroethylene PMVE: CF ２ = CFOCF ３ : Perfluoro(methyl vinyl ether) ・8CNVE:CF ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２CN (2) Polyamine compound (crosslinking agent) BOAP: 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (3) Emulsifier C ２ F ５ OCF ２ CF ２ OCF ２ COONH ４ (4) Polymerization initiator APS: ammonium persulfate (5) Filler CB: carbon black (manufactured by Cancarb Limited, grade: N990, particle size (D50): 450 nm) (6) pH adjuster disodium hydrogen phosphate dodecahydrate (7) Coagulant nitric acid: manufactured by Kanto Chemical Co., Ltd.

[0081] [Production of Fluorocopolymer] Fluorocopolymers 1 and 2 were produced as follows.

[0082] <Fluorocopolymer 1> A 20 L stainless steel pressure reactor equipped with an anchor blade was degassed, and then 9795 g of ultrapure water and emulsifier C ２ F ５ OCF ２ CF ２ OCF ２ COONH ４ 1194 g of a 30% by mass solution of 8CNVE, 50.0 g of 8CNVE, and 21.5 g of a 5% by mass aqueous solution of disodium hydrogen phosphate dodecahydrate were charged, and the gas phase was purged with nitrogen. While stirring at a speed of 180 rpm using an anchor blade, 118 g of TFE and 545 g of PMVE were injected into the vessel, and the internal temperature was then raised to 80°C. The pressure inside the reactor was 0.90 MPa [gauge]. 100 mL of a 3% by mass aqueous solution of ammonium persulfate (APS) was added to initiate polymerization. The molar ratio of the monomers injected before the start of polymerization (hereinafter also referred to as "initial added monomer") was TFE:PMVE:8CNVE = 23.6:73.6:2.8. After the start of polymerization, as the polymerization progressed, the monomers were injected as follows: Hereinafter, injection of a monomer after the start of polymerization will also be referred to as "post-addition," and a monomer injected after the start of polymerization will also be referred to as "post-added monomer."

[0083] When the reactor pressure dropped to 0.89 MPa [gauge], TFE was injected, and the reactor pressure was increased to 0.90 MPa [gauge]. This was repeated, and every time 153 g of TFE was injected, 10.1 g of 8CNVE and 113 g of PMVE were injected in this order. When the cycle in which the total added mass of TFE reached 1071 g was completed, 153 g of TFE was injected. When the total added mass of TFE added later reached 1224 g, the addition of the post-added monomer was stopped, the reactor temperature was cooled to 10 ° C., and the polymerization reaction was stopped, to obtain a latex containing a fluorine-containing copolymer. The polymerization time was 273 minutes. The total mass of the post-added monomers was 1,224 g for TFE, 791 g for PMVE, and 70.6 g for 8CNVE, which was converted into a molar ratio of TFE:PMVE:8CNVE=71.2:27.7:1.1.

[0084] The latex was added to a 5% by mass aqueous solution of nitric acid, and the fluorocopolymer was coagulated and separated. The fluorocopolymer was filtered, washed with ultrapure water, and dried in vacuum at 100°C to obtain a white fluorocopolymer 1. The content (molar ratio) of each unit in the obtained fluorocopolymer 1 was TFE unit: PMVE unit: 8CNVE unit = 68.6: 30.5: 0.9. The amount of carboxyl end groups in the obtained fluorocopolymer 1 was measured by the above-mentioned method and was found to be 0.88.

[0085] <Fluorocopolymer 2> A 20 L stainless steel pressure reactor equipped with an anchor blade was degassed, and then 7.2 L of ultrapure water and emulsifier C were added. ２ F ５ OCF ２ CF ２ OCF ２ COONH ４880 g of a 30% by weight solution of 8CNVE, 7.3 g of 8CNVE, and 15.9 g of a 5% by weight aqueous solution of disodium hydrogen phosphate dodecahydrate were charged, and the gas phase was replaced with nitrogen. While stirring at a speed of 375 rpm using an anchor blade, 137 g of TFE and 635 g of PMVE were pressurized into the vessel, and the internal temperature was then raised to 80 ° C. The internal pressure of the reactor was 0.90 MPa [gauge]. 28 mL of a 3% by weight aqueous solution of ammonium persulfate (APS) was added to initiate polymerization. The molar ratio of the initially added monomers was TFE:PMVE:8CNVE = 26.3:73.3:0.4.

[0086] After the initiation of polymerization, as the polymerization progressed, the monomers were injected as follows. When the pressure inside the reactor dropped to 0.89 MPa [gauge], TFE was injected, and the pressure inside the reactor was increased to 0.90 MPa [gauge]. This was repeated, and every time 119.3 g of TFE was injected, 3.7 g of 8CNVE, 74 g of PMVE, and 3.7 g of 8CNVE were injected in this order. When the polymerization rate began to decrease, a 3 mass% aqueous solution of APS was appropriately added. The total amount of the 3 mass% aqueous solution of APS added after the initiation of polymerization was 35 mL. When the cycle was completed, in which the total added mass of TFE reached 1073.7 g, 119.3 g of TFE was injected. When the total added amount of the post-added TFE reached 1193 g, the addition of the post-added monomer was stopped, the reactor internal temperature was cooled to 10 ° C., and the polymerization reaction was stopped to obtain a latex containing a fluorine-containing copolymer. The polymerization time was 375 minutes. The total added amount of each post-added monomer was 1193 g of TFE, 666 g of PMVE, and 66.6 g of 8CNVE, which was converted into a molar ratio of TFE:PMVE:8CNVE=74.0:25.0:1.0.

[0087] The latex was added to a 5% by mass aqueous solution of aluminum potassium sulfate, and the fluorocopolymer was coagulated and separated. The fluorocopolymer was filtered, washed with ultrapure water, and vacuum dried at 50°C to obtain a white fluorocopolymer 2. The content (molar ratio) of each unit in the obtained fluorocopolymer 2 was TFE unit: PMVE unit: 8CNVE unit = 70.9: 28.6: 0.5. The amount of carboxyl end groups in the obtained fluorocopolymer 2 was measured by the above-mentioned method and was found to be 0.66.

[0088] Examples 1 to 8 (1) Production of fluorocopolymer compositions The components shown in Table 1 were mixed in the amounts (parts by mass) shown in Table 1 and kneaded using a two-roll mill at room temperature for 10 minutes to obtain mixed fluorocopolymer compositions. The above-mentioned physical properties were measured using the obtained fluorocopolymer compositions. The measurement results are shown in Table 1.

[0089] (2) Production of Crosslinked Rubber Articles (O-Rings) The obtained fluorine-containing copolymer composition was hot-pressed at 180°C for 30 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). Immediately after molding, the mold releasability was evaluated. A: The O-ring could be removed from the mold. B: The O-ring stuck to the mold and could not be removed. Samples that could not be removed in the mold releasability evaluation were sufficiently cooled, and after the sample had thermally shrunk, they were removed from the mold. Then, the above O-rings were heated in an oven under a nitrogen atmosphere under the following conditions (secondary crosslinking). Conditions for secondary crosslinking After heating at 90°C for 2 hours, the temperature was raised to 200°C over 2 hours and maintained at 200°C for 4 hours. The temperature was then raised to 305°C over 2 hours, and the mixture was further heated at 305°C for 13 hours.

[0090] Thereafter, the O-rings were cooled to room temperature to obtain the O-rings that were the crosslinked rubber articles of Examples 1 to 8. The above-mentioned physical properties were measured using the obtained crosslinked rubber articles. The measurement results are shown in Table 1.

[0091]

[0092] As can be seen from the evaluation results shown in Table 1, the crosslinked rubber articles (Examples 1 and 2) obtained by crosslinking a fluorocopolymer of the fluorocopolymer composition of the present invention had smaller compression sets after compression treatment at high temperatures of 325°C and 340°C and were less likely to crack even after the compression treatment, compared with the crosslinked rubber articles (Examples 3 to 8) obtained by crosslinking a fluorocopolymer of a fluorocopolymer composition other than the present invention.

Claims

1. A fluorine-containing copolymer composition comprising: a fluorine-containing copolymer (A) having units based on a monomer having a nitrile group and units based on tetrafluoroethylene; and a crosslinking agent (B) having two or more amino groups, wherein the content of units based on the monomer having a nitrile group in 100 mol % of all monomer units in said fluorine-containing copolymer (A) is 0.80 mol % or more and less than 1.00 mol %, and the content of said crosslinking agent (B) is 0.80 to 1.30 parts by mass per 100 parts by mass of said fluorine-containing copolymer (A).

2. The fluorine-containing copolymer composition according to claim 1, wherein said fluorine-containing copolymer (A) has units based on perfluoro(alkyl vinyl ether), the content of said units based on tetrafluoroethylene in 100 mol% of all monomer units in said fluorine-containing copolymer (A) is 67.0 mol% or more and less than 71.5 mol%, and the content of said units based on perfluoro(alkyl vinyl ether) in 100 mol% of all monomer units in said fluorine-containing copolymer (A) is 27.0 to 32.0 mol%.

3. The fluorocopolymer (A) has a carboxy terminal group, and the fluorocopolymer (A) has a peak in the range of 2210 to 2700 cm in the spectrum obtained by measuring the fluorocopolymer (A) by infrared spectroscopy. －１ 1700 to 1850 cm for the integrated peak intensity of absorbance at －１ 2. The fluorine-containing copolymer composition according to claim 1, wherein the ratio of integrated peak intensities of absorbance at 4. The fluorine-containing copolymer composition according to claim 1, wherein said crosslinking agent (B) is 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane.

5. The fluorine-containing copolymer composition according to claim 1, which contains a filler (C).

6. The fluorine-containing copolymer composition according to claim 5, wherein the content of said filler (C) is 1 to 20 parts by mass per 100 parts by mass of the fluorine-containing copolymer (A).

7. The fluorine-containing copolymer composition according to claim 6, wherein said filler (C) is carbon black.

8. The torque difference (M Ｈ -M Ｌ The fluorocopolymer composition according to claim 1, wherein the maximum torque M in the fluorocopolymer composition is 60 to 90 dN·m. [Measurement method: measured by a method in accordance with JIS K6296-1:2023 using a crosslinking property measuring machine under the conditions of a measurement temperature of 180°C, a measurement time of 30 minutes, a vibration frequency of 100 cpm, and an angle of 3.00 deg.] Ｈ and the minimum value M Ｌ Measure the following.] 9. A method for producing a fluorine-containing copolymer composition according to any one of claims 1 to 8, which comprises kneading said fluorine-containing copolymer (A) and said crosslinking agent (B).

10. A crosslinked rubber article obtained by crosslinking said fluorocopolymer (A) in the fluorocopolymer composition according to any one of claims 1 to 8.

11. A method for producing a crosslinked rubber article, which comprises crosslinking said fluorocopolymer (A) in the fluorocopolymer composition according to any one of claims 1 to 8.

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