Fluorine-containing copolymer composition and crosslinked rubber article

Abstract

Provided are: a fluorine-containing copolymer composition capable of forming a crosslinked rubber article in which weight reduction after a lapse of a prescribed time is suppressed when used for a long time in a plasma irradiation environment; and a crosslinked rubber article in which weight reduction is suppressed. A fluorine-containing copolymer composition contains: a fluorine-containing copolymer (A) having a unit based on tetrafluoroethylene and a unit based on perfluoro(alkyl vinyl ether); a fluorine-containing copolymer (B) that is different from the fluorine-containing copolymer (A), has a unit based on a monomer having at least one functional group selected from the group consisting of a carboxyl groups and a group represented by formula (X), a unit based on tetrafluoroethylene, and a unit based on perfluoro(alkyl vinyl ether), and has a D90 particle diameter of 4.0 μm or less; and a crosslinking agent.

Description

Fluorine-containing copolymer composition, crosslinked rubber article

[0001] The present invention relates to a fluorine-containing copolymer composition and a crosslinked rubber article.

[0002] Crosslinked rubber articles obtained by crosslinking a fluorine-containing copolymer are widely used as sealing materials (e.g., O-rings, packings, oil seals, gaskets, etc.) and cushioning materials in the fields of vehicles, ships, aircraft, general machinery, construction, etc. Patent Document 1 discloses a composition containing a specific fluorine-containing copolymer as a method for producing a composition used for such crosslinked rubber articles.

[0003] International Publication No. 2021 / 210502

[0004] In recent years, there has been a demand in various fields for improved performance of crosslinked rubber articles, and specifically, there has been a demand for a fluorocopolymer composition capable of forming a crosslinked rubber article that is suppressed in weight loss after a predetermined time has elapsed when used for a long period of time in a plasma irradiation environment. In response to this demand, the present inventors evaluated a crosslinked rubber article formed using a fluorocopolymer composition as described in Patent Document 1, and found that it was difficult to suppress the weight loss after the predetermined time has elapsed.

[0005] An object of the present invention is to provide a fluorocopolymer composition capable of forming a crosslinked rubber article that is suppressed in weight loss after a predetermined time has elapsed when used for a long period of time in a plasma irradiation environment, and a crosslinked rubber article.

[0006] As a result of extensive investigations, the present inventors have found that the above-mentioned problems can be solved by the following constitution. [1] A fluorocopolymer composition comprising: a fluorocopolymer (A) having units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether); a fluorocopolymer (B) which is a fluorocopolymer different from the fluorocopolymer (A) and which has units based on a monomer having at least one functional group selected from the group consisting of a carboxy group and a group represented by formula (X), units based on tetrafluoroethylene, and units based on perfluoro(alkyl vinyl ether), and which has a particle size D90 of 4.0 μm or less; and a crosslinking agent. Formula (X) *-CO-O-CO-* In formula (X), * represents a bonding position. [2] The fluorine-containing copolymer composition according to [1], wherein the fluorine-containing copolymer (A) further has units having a nitrile group, and the content of the units having a nitrile group is 0.05 to 5.0 mol % based on all units of the fluorine-containing copolymer (A), the content of the units based on tetrafluoroethylene is 59.0 to 79.95 mol % based on all units of the fluorine-containing copolymer (A), and the content of the units based on perfluoro(alkyl vinyl ether) is 20.0 to 40.95 mol % based on all units of the fluorine-containing copolymer (A). [3] The fluorine-containing copolymer composition according to [1] or [2], wherein the content of units based on a monomer having at least one functional group selected from the group consisting of a carboxy group and a group represented by the formula (X) is 0.01 to 3.0 mol % relative to all units of the fluorine-containing copolymer (B), the content of units based on tetrafluoroethylene is 90 to 99.89 mol % relative to all units of the fluorine-containing copolymer (B), and the content of units based on perfluoro(alkyl vinyl ether) is 0.1 to 9.99 mol % relative to all units of the fluorine-containing copolymer (B). [4] The fluorine-containing copolymer composition according to any one of [1] to [3], wherein the content of the fluorine-containing copolymer (B) is 50 parts by mass or less relative to 100 parts by mass of the fluorine-containing copolymer (A).[5] The fluorine-containing copolymer composition according to any one of [1] to [4], wherein the crosslinking agent is a compound having two or more amino groups, and the content of the crosslinking agent is 0.3 to 10 parts by mass per 100 parts by mass of the fluorine-containing copolymer (A). [6] The fluorine-containing copolymer composition according to any one of [1] to [5], wherein the fluorine-containing copolymer (B) has a bulk density of 0.25 g / mL or less. [7] A fluorine-containing copolymer composition comprising: a fluorine-containing copolymer (A) having units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether); a fluorine-containing copolymer (B) which is a fluorine-containing copolymer different from the fluorine-containing copolymer (A), and which has units based on a monomer having at least one functional group selected from the group consisting of a carboxy group and a group represented by formula (X), units based on tetrafluoroethylene, and units based on perfluoro(alkyl vinyl ether); and a crosslinking agent, wherein the T of the fluorine-containing copolymer composition in a vulcanization test at 180°C in accordance with JIS K6296 is ９０is 10 minutes or less. Formula (X): *-CO-O-CO-* In formula (X), * represents a bonding site. [8] The fluorine-containing copolymer composition according to [7], wherein the fluorine-containing copolymer (A) has units having a nitrile group, and the content of the units having a nitrile group is 0.05 to 5.0 mol % based on all units of the fluorine-containing copolymer (A), the content of the units based on tetrafluoroethylene is 59.0 to 79.95 mol % based on all units of the fluorine-containing copolymer (A), and the content of the units based on perfluoro(alkyl vinyl ether) is 20.0 to 40.95 mol % based on all units of the fluorine-containing copolymer (A). [9] The fluorine-containing copolymer composition according to [7] or [8], wherein the content of units based on a monomer having at least one functional group selected from the group consisting of a carboxy group and a group represented by formula (X) described later is 0.01 to 3.0 mol % relative to all units of said fluorine-containing copolymer (B), the content of units based on tetrafluoroethylene is 90 to 99.89 mol % relative to all units of said fluorine-containing copolymer (B), and the content of units based on perfluoro(alkyl vinyl ether) is 0.1 to 9.99 mol % relative to all units of said fluorine-containing copolymer (B).

[10] The fluorine-containing copolymer composition according to any one of [7] to [9], wherein the content of said fluorine-containing copolymer (B) is 50 parts by mass or less relative to 100 parts by mass of said fluorine-containing copolymer (A).

[11] The fluorocopolymer composition according to any one of [7] to

[10] , wherein the crosslinking agent is a compound having two or more amino groups, and the content of the crosslinking agent is 0.3 to 10 parts by mass per 100 parts by mass of the fluorocopolymer (A).

[12] The fluorocopolymer composition according to any one of [7] to

[11] , wherein the fluorocopolymer (B) has a bulk density of 0.25 g / mL or less.

[13] A crosslinked rubber article obtained from the fluorocopolymer composition according to any one of [1] to

[12] .

[0007] According to the present invention, it is possible to provide a fluorocopolymer composition capable of forming a crosslinked rubber article that is suppressed from losing weight after a predetermined time has elapsed when used for a long period of time in a plasma irradiation environment, and the crosslinked rubber article.

[0008] The meanings of terms used in the present invention are as follows. A numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits. A "unit" is a collective term for an atomic group derived from one molecule of the monomer that is formed directly by polymerizing the monomer, and an atomic group obtained by chemically converting a part of the atomic group. A "unit based on a monomer" will hereinafter also be simply referred to as a "unit." A "rubber" means a rubber that exhibits properties defined by JIS K 6200:2008, and is distinguished from a "resin."

[0009] [Fluorocopolymer Composition (First Embodiment)] The fluorine-containing copolymer composition of the first embodiment of the present invention (hereinafter also referred to as "the present composition 1") comprises: a fluorine-containing copolymer (A) having units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether); a fluorine-containing copolymer (B) which is a fluorine-containing copolymer different from the fluorine-containing copolymer (A), which has units based on a monomer having at least one functional group selected from the group consisting of a carboxy group and a group represented by formula (X), units based on tetrafluoroethylene, and units based on perfluoro(alkyl vinyl ether), and which has a particle size D90 of 4.0 μm or less; and a crosslinking agent.

[0010] When a crosslinked rubber article obtained using this composition 1 is used for a long period of time in a plasma irradiation environment, weight loss after a predetermined time has been suppressed (hereinafter also referred to as the "effect of the present invention"). The details of the reason for this are not clear, but it is presumed to be due to the following reasons. A characteristic feature of this composition 1 is, for example, that the particle diameter D90 of the fluorine-containing copolymer (B) is 4.0 μm or less. When a fluorine-containing copolymer (B) with such a controlled particle diameter D90 is contained, the fluorine-containing copolymer (B) can be uniformly dispersed in the resulting crosslinked rubber article, and it is presumed that the desired effect of the present invention is achieved. Other particle diameters include particle diameter D10 and particle diameter D50 (median diameter), but it has been found that the particle diameter D90 in particular has a strong influence on the effect of the present invention.

[0011] The effects of the present invention can be evaluated, for example, using the weight loss rate (mass% / hour (h)) as an index. The weight loss rate (mass% / hour (h)) can be measured, for example, by the method described in the Examples. The weight loss rate (mass% / hour (h), Category A) from the start of plasma treatment to 1.5 hours is preferably 2.150 or less, more preferably 2.125 or less. The weight loss rate (mass% / hour (h), Category B) from 1.5 hours to 3.0 hours from the start of plasma treatment is preferably 2.150 or less, more preferably 2.120 or less. The weight loss rate (mass% / hour (h), Category C) from 3.0 hours to 6.0 hours from the start of plasma treatment is preferably 2.040 or less, more preferably 2.038 or less. When the weight loss rate (mass% / hour (h)) is within the above range, the occurrence of malfunctions in the device can be suppressed when using an apparatus incorporating the crosslinked rubber article of the present invention. Furthermore, the occurrence of defects due to particles can be suppressed when manufacturing semiconductor products, etc., using an apparatus incorporating the crosslinked rubber article of the present invention. In particular, it is preferable that category C is within the above range.

[0012] <Fluorine-containing copolymer (A)> The present composition 1 contains a fluorine-containing copolymer (A). The fluorine-containing copolymer (A) has units based on tetrafluoroethylene (hereinafter also referred to as "TFE") and units based on perfluoro(alkyl vinyl ether) (hereinafter also referred to as "PAVE"). The fluorine-containing copolymer (A) itself does not completely return to its original shape when stretched, but exhibits the property that its ability to return to its original shape is strengthened by crosslinking, that is, it exhibits the properties of a rubber.

[0013] The content of TFE units is preferably from 60.0 to 80.0 mol %, more preferably from 59.0 to 79.95 mol %, and even more preferably from 64.0 to 72.0 mol %, based on all units in the fluorine-containing copolymer (A).

[0014] The PAVE unit is a unit based on perfluoro(alkyl vinyl ether). From the viewpoint of excellent polymerization reactivity and rubber physical properties, the PAVE is preferably a monomer represented by formula (1): CF ２ =CF-O-R ｆ２ (1) In formula (1), R ｆ２ represents a perfluoroalkyl group having 1 to 10 carbon atoms. ｆ２ From the viewpoint of better polymerization reactivity, the number of carbon atoms in the perfluoroalkyl group is preferably 1 to 8, more preferably 1 to 6, even more preferably 1 to 5, and particularly preferably 1 to 3. The perfluoroalkyl group may be linear or branched.

[0015] Specific examples of PAVE include perfluoro(methyl vinyl ether) (hereinafter also referred to as "PMVE"), perfluoro(ethyl vinyl ether) (hereinafter also referred to as "PEVE"), and perfluoro(propyl vinyl ether) (hereinafter also referred to as "PPVE"), with PMVE or PPVE being preferred.

[0016] In order to obtain crosslinked rubber articles with better elasticity, the content of PAVE units is preferably from 20.0 to 40.95 mol%, more preferably from 20.0 to 37.0 mol%, and even more preferably from 27.0 to 33.0 mol%, based on all units of the fluorocopolymer (A). The suitable content is similar when PMVE or PPVE is used as PAVE.

[0017] The fluorine-containing copolymer (A) contains a monomer having a nitrile group (hereinafter referred to as "R ＣＮ It is preferable that the unit is based on R ＣＮ In order to obtain a more excellent effect of the present invention, it is preferable that the monomer further contains a fluorine atom, and the monomer represented by formula (2) is more preferable. １１ R １２ =CR １３ -R １４ -CN (2) In formula (2), R １１ , R １２ and R １３ R each independently represents a hydrogen atom, a fluorine atom, or a methyl group. １４ represents 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.

[0018] R ＣＮ From the viewpoint of excellent polymerization reactivity of R １１ , R １２ and R １３ is preferably a fluorine atom or a hydrogen atom, and R １１ , R １２ and R １３ are more preferably fluorine atoms or hydrogen atoms, and in view of the superior mold releasability and heat resistance of the crosslinked rubber article, R １１ , R １２ and R １３ More preferably, all of R are fluorine atoms. １４ R may be linear, branched, or cyclic, and is preferably linear or branched. １４ The number of carbon atoms in R is preferably 2 to 8, more preferably 3 to 7, still more preferably 4 to 7, and particularly preferably 4 to 6. １４ R may have an etheric oxygen atom, and preferably has an etheric oxygen atom in order to provide crosslinked rubber articles with better rubber physical properties. １４ The number of etheric oxygen atoms in is preferably 1 to 3, and more preferably 1 or 2.

[0019] Specific examples of the monomer represented by formula (2) include CF ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ CN (hereinafter also referred to as "8CNVE") 、 CF ２ = CFO (CF ２ ) ５ CN (hereinafter also referred to as "MV5CN"), CF ２ = CFOCF ２ CF ２ CF ２ OCF (CF ３ ) CN and CF ２ = CFO (CF ２ ) ３ CN is exemplified, and 8CNVE or MV5CN is preferred in that the crosslinked rubber article has better mold releasability and heat resistance.

[0020] R ＣＮ The content of the units is preferably from 0.05 to 5.0 mol %, more preferably from 0.1 to 3.0 mol %, and even more preferably from 0.2 to 1.5 mol %, based on all units in the fluorine-containing copolymer (A), since the effects of the present invention are more excellent.

[0021] The fluorine-containing copolymer (A) may have units based on monomers other than those mentioned above (hereinafter also referred to as "other monomers"). Specific examples of other monomers include vinylidene fluoride (hereinafter also referred to as "VdF"), hexafluoropropylene (hereinafter also referred to as "HFP"), chlorotrifluoroethylene, a monomer having two or more polymerizable unsaturated bonds (hereinafter also referred to as "BO"), a monomer represented by formula (6), ethylene, propylene, and a monomer having a halogen atom (hereinafter also referred to as "monomer having another halogen atom"). Specific examples of monomers having another halogen atom include bromotrifluoroethylene and iodotrifluoroethylene.

[0022] The BO unit is a unit based on a monomer having two or more polymerizable unsaturated bonds. Specific examples of the polymerizable unsaturated bond include a carbon atom-carbon atom double bond (C═C) and a carbon atom-carbon atom triple bond (C≡C). The number of polymerizable unsaturated bonds in BO is preferably 2 to 6, more preferably 2 or 3, and even more preferably 2, in terms of superior polymerization reactivity. BO preferably further contains a fluorine atom in terms of reducing the compression set of the crosslinked rubber article at high temperatures.

[0023] BO is preferably a monomer represented by formula (3): (CR ３１ R ３２ =CR ３３ ) ａ３ R ３４ (3) In formula (3), R ３１ , R ３２ and R ３３ each independently represents a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. a3 represents an integer of 2 to 6. R 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. ３１ , multiple R ３２ and multiple R ３３ a3 is preferably 2 or 3, and more preferably 2.

[0024] Since the polymerization reactivity of BO is superior, R ３１ , R ３２ and R ３３ is preferably a fluorine atom or a hydrogen atom, and R ３１ , R ３２ and R ３３ In terms of the heat resistance and chemical resistance of the crosslinked rubber article, R ３１ , R ３２ and R ３３ More preferably, all of R are fluorine atoms. ３４R may be linear, branched, or 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 R may have an etheric oxygen atom, and preferably has an etheric oxygen atom in order to provide crosslinked rubber articles with better rubber physical properties. ３４ The number of etheric oxygen atoms in R is preferably 1 to 6, more preferably 1 to 3, and even more 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.

[0025] Of the monomers represented by formula (3), specific examples of suitable monomers include a monomer represented by formula (4) and a monomer represented by formula (5).

[0026] (CF ２ =CF) ２ R ４１ (4) In formula (4), R ４１ represents a divalent perfluorohydrocarbon group having 2 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.

[0027] Specific examples of the monomer represented by formula (4) include CF ２ = CFO (CF ２ ) ２ OCF = CF ２ , C.F. ２ = CFO (CF ２ ) ３ OCF = CF ２ , C.F. ２ = CFO (CF ２ ) ４ OCF = CF ２ , C.F. ２ = CFO (CF ２ ) ６ OCF = CF ２、 CF ２ = CFO (CF ２ ) ８ OCF = CF ２ , C.F.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 =CFO CF 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 =CFO CF ２ CF(CF ３ )O(CF ２ ) ２ OCF(CF ３ )CF ２ OCF = CF ２ , and, CF ２ =CFO CF ２ CF ２ O(CF ２ O) ２ CF ２ CF ２ OCF = CF ２ include, CF ２ =CFO(CF ２ ) ３ OCF = CF ２ , or, CF ２ =CFO(CF ２ ) ４ OCF = CF ２ is preferred.

[0028] (CH ２ =CH) ２ R ５１ (5) In formula (5), R ５１represents a divalent perfluorohydrocarbon group having 2 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.

[0029] Specific examples of the monomer represented by formula (5) include CH ２ =CH(CF ２ ) ２ CH=CH ２ , C.H. ２ =CH(CF ２ ) ４ CH=CH ２ , and C.H. ２ =CH(CF ２ ) ６ CH=CH ２ and CH ２ =CH(CF ２ ) ６ CH=CH ２ is preferred.

[0030] When BO is copolymerized, the polymerizable double bond at the end of BO reacts during the polymerization to give a fluorine-containing copolymer (A) having a branched chain.

[0031] CF ２ =CF-O-R ｆ６ (6) In formula (6), R ｆ６ represents a perfluoroalkyl group having 1 to 8 carbon atoms and containing 1 to 5 etheric oxygen atoms. ｆ６ The number of carbon atoms is preferably 1 to 6, and more preferably 1 to 5.

[0032] Specific examples of the monomer represented by formula (6) include perfluoro(3,6-dioxa-1-heptene), perfluoro(3,6-dioxa-1-octene), and perfluoro(5-methyl-3,6-dioxa-1-nonene).

[0033] When the fluorine-containing copolymer (A) contains other monomer units, the content of the other monomer units is preferably from 0.01 to 20 mol %, more preferably from 0.5 to 10 mol %, and even more preferably from 1 to 5 mol %, based on the total units of the fluorine-containing copolymer (A), from the viewpoint of excellent rubber physical properties of the crosslinked rubber article.

[0034] The fluorine-containing copolymer (A) is preferably a fully fluorinated fluorine-containing copolymer, since the effects of the present invention are more excellent. "Fully fluorinated fluorine-containing copolymer" refers to a fluorine-containing copolymer that does not substantially contain hydrogen atoms bonded to carbon atoms, has fluorine atoms in place of those hydrogen atoms, and has a main chain consisting of a chain of carbon atoms. The side chain of the fully fluorinated fluorine-containing copolymer may have a polyvalent atom other than carbon atoms, and the polyvalent atom is preferably an oxygen atom. "Substantially not containing hydrogen atoms" means that the content of hydrogen atoms in the fully fluorinated fluorine-containing copolymer is 0.5% by mass or less, preferably 0.1% by mass or less, more preferably 0.07% by mass or less, and even more preferably 0.05% by mass or less. When the content of hydrogen atoms is within the above range, good heat resistance or chemical resistance is likely to be obtained.

[0035] The fluorine-containing copolymer (A) may contain iodine atoms. In this case, it is preferable that the fluorine-containing copolymer (A) has an iodine atom at the end of the polymer chain. Examples of the iodine atom include iodine atoms derived from an iodine compound that functions as a chain transfer agent, as described below, and iodine atoms in units based on a monomer having an iodine atom among other halogen-containing monomers such as iodotrifluoroethylene, as described above. Iodine atoms derived from an iodine compound that functions as a chain transfer agent are preferred. When the fluorine-containing copolymer (A) contains iodine atoms, the content of the iodine atoms is preferably 0.01 to 5.0% by mass, more preferably 0.05 to 2.0% by mass, and even more preferably 0.05 to 1.0% by mass, relative to the total mass of the fluorine-containing copolymer (A). When the iodine atom content is within the above range, the crosslinking reactivity of the fluorine-containing copolymer (A) is improved, and the mechanical properties of the crosslinked rubber article are excellent.

[0036] The content of the fluorine-containing copolymer (A) is preferably from 55 to 95 mass %, more preferably from 65 to 90 mass %, and even more preferably from 75 to 85 mass %, based on the total mass of the present composition 1.

[0037] An example of the method for producing the fluorine-containing copolymer (A) is a method in which the above-mentioned monomers are copolymerized in the presence of a radical polymerization initiator.

[0038] The radical polymerization initiator is preferably a water-soluble polymerization initiator or a redox polymerization initiator. Specific examples of water-soluble polymerization initiators include persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate, and organic polymerization initiators such as disuccinic acid peroxide and azobisisobutylamidine dihydrochloride. Persulfates are preferred, and ammonium persulfate is more preferred. Examples of redox polymerization initiators include polymerization initiators that combine persulfates with a reducing agent. 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 redox polymerization initiators include alkali metal salts of persulfate such as ammonium persulfate, sodium persulfate, and potassium persulfate, with ammonium persulfate being preferred. Specific examples of reducing agents to be combined with persulfates include thiosulfates, sulfites, hydrogen sulfites, pyrosulfites, and hydroxymethanesulfinates. Hydroxymethanesulfinates are preferred, and sodium hydroxymethanesulfinate is more preferred.

[0039] 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). ２ Specific 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 iodine compound, an iodine compound having a perfluoroalkylene group is preferred, and 1,4-diiodoperfluorobutane is more preferred. When the above-mentioned monomers are copolymerized in the presence of these iodine compounds, iodine atoms can be introduced into the fluorine-containing copolymer (A).

[0040] For details of the components other than those mentioned above used in producing 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.

[0041] <Fluorine-containing copolymer (B)> The present composition 1 contains a fluorine-containing copolymer (B). The fluorine-containing copolymer (B) is a fluorine-containing copolymer different from the fluorine-containing copolymer (A), and has units having at least one functional group selected from the group consisting of a carboxy group and a group represented by formula (X) (hereinafter also referred to as "specific functional group"), TFE units, and units based on PAVE. In other words, the fluorine-containing copolymer (B) has units having a specific functional group, TFE units, and PAVE units.

[0042] The specific functional group may be either or both of a carboxy group and a group represented by formula (X): Formula (X) *-CO-O-CO-* In formula (X), * represents a bonding position. The unit having a specific functional group is a monomer having a specific functional group (hereinafter referred to as "R Ｘ It is preferable that the unit is based on R. Ｘ R may have a plurality of specific functional groups. Ｘ When R has a plurality of specific functional groups, the types of the specific functional groups may be the same or different. Ｘ Since R is used as a monomer, it has a polymerizable unsaturated bond. Specific examples of the polymerizable unsaturated bond are as described above. Ｘ is preferably a compound having one specific functional group and one polymerizable unsaturated bond.

[0043] Examples of monomers having a carboxy group include acid anhydrides of unsaturated dicarboxylic acids such as itaconic anhydride (hereinafter also referred to as "IAH"), citraconic anhydride (hereinafter also referred to as "CAH"), 5-norbornene-2,3-dicarboxylic anhydride (also known as himic anhydride, hereinafter also referred to as "NAH"), and maleic anhydride. As the group containing the group represented by formula (X), a group formed by removing one hydrogen atom from an acid anhydride is preferred. Examples of monomers having a group represented by formula (X) include acid anhydrides of unsaturated dicarboxylic acids such as itaconic anhydride (hereinafter also referred to as "IAH"), citraconic anhydride (hereinafter also referred to as "CAH"), 5-norbornene-2,3-dicarboxylic anhydride (also known as himic anhydride, hereinafter also referred to as "NAH"), and maleic anhydride.

[0044] From the viewpoint of reactivity with the nitrile group that the fluorine-containing copolymer (A) may have, R Ｘ preferably contains a monomer having a group represented by formula (X), and from the viewpoint of facilitating the production of the fluorinated copolymer (B), more preferably contains at least one selected from the group consisting of IAH, CAH and NAH, further preferably contains NAH, and particularly preferably NAH. Ｘ may be used alone or in combination of two or more.

[0045] The TFE units and PAVE units contained in the fluorocopolymer (B) are the same as the TFE units and PAVE units contained in the fluorocopolymer (A), respectively.

[0046] The fluorine-containing copolymer (B) may have units based on monomers other than those mentioned above (hereinafter also referred to as "other monomers"). Specific examples and preferred embodiments of the other monomers are the same as those of the other monomers in the fluorine-containing copolymer (A).

[0047] The fluorine-containing copolymer (B) may further have a specific functional group as a main chain terminal group. The specific functional group as a main chain terminal group can be introduced by a radical polymerization initiator, a chain transfer agent, etc. used in the production of the fluorine-containing copolymer (B).

[0048] The fluorine-containing copolymer (B) is in the form of particles. That is, the fluorine-containing copolymer (B) is in the form of fluorine-containing copolymer (B) particles. The particle diameter D90 of the fluorine-containing copolymer (B) is 4.0 μm or less, preferably 3.5 μm or less, more preferably 3.0 μm or less. The lower limit is preferably 1.0 μm or more, more preferably 2.0 μm or more. The particle diameter D90 of the fluorine-containing copolymer (B) is the volume-based cumulative 90% diameter (D90) determined by a laser diffraction / scattering method. That is, the particle size distribution is measured by a laser diffraction / scattering method, a cumulative curve is determined with the total volume of the particle population as 100%, and the particle diameter is the point on the cumulative curve where the cumulative volume is 90%. Methods for controlling the particle diameter D90 of the fluorine-containing copolymer (B) include, for example, pulverization and classification.

[0049] The bulk density of the fluorine-containing copolymer (B) is preferably 0.50 g / mL or less, more preferably 0.30 g / mL or less, and even more preferably 0.25 g / mL or less. The lower limit is preferably 0.01 g / mL or more, more preferably 0.10 g / mL or more. The bulk density can be measured, for example, by the method shown in the Examples section.

[0050] The content of the units having a specific functional group is preferably 0.01 to 3 mol%, more preferably 0.03 to 2 mol%, and even more preferably 0.05 to 1 mol%, based on all units of the fluorine-containing copolymer (B), from the viewpoint of more excellent effects of the present invention. The preferred range is similar when NAH is used as the unit having a specific functional group. The content of TFE units is preferably 90 to 99.89 mol%, more preferably 95 to 99.47 mol%, and even more preferably 96 to 98.95 mol%, based on all units of the fluorine-containing copolymer (B), from the viewpoint of more excellent effects of the present invention. The content of PAVE units is preferably 0.1 to 9.99 mol%, more preferably 0.5 to 4.97 mol%, and even more preferably 1 to 3.95 mol%, based on all units of the fluorine-containing copolymer (B), from the viewpoint of more excellent effects of the present invention. The preferred range is similar when PPVE units are used as PAVE units.

[0051] The content of fluorine-containing copolymer (B) is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less, per 100 parts by mass of fluorine-containing copolymer (A), from the viewpoint of better effects of the present invention. The content of fluorine-containing copolymer (B) is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 7 parts by mass or more, per 100 parts by mass of fluorine-containing copolymer (A). The content of fluorine-containing copolymer (B) is preferably 1 to 40% by mass, more preferably 1 to 30% by mass, and even more preferably 1 to 20% by mass, per total mass of composition 1.

[0052] An example of the method for producing the fluorine-containing copolymer (B) is a method in which the above-mentioned monomers are copolymerized in the presence of a radical polymerization initiator, the details of which are as described in WO 2016 / 017801.

[0053] <Crosslinking Agent> The present composition 1 contains a crosslinking agent. Specific examples of the crosslinking agent include organic peroxides and compounds having two or more amino groups (hereinafter also referred to as "polyamine compounds"). Polyamine compounds are preferred because they have excellent crosslinkability for the fluorocopolymer (A) and can give crosslinked rubber articles with smaller compression set under high temperature and high compression.

[0054] The polyamine compound may be a compound in which a hydrogen atom of an aliphatic hydrocarbon is substituted with an amino group, or a compound in which a hydrogen atom of an aromatic hydrocarbon is substituted with an amino group, but from the viewpoint of achieving better effects of the present invention, a compound in which a hydrogen atom of an aromatic hydrocarbon is substituted with an amino group is preferred. The polyamine compound preferably contains a fluorine atom. This improves compatibility with the fluorine-containing copolymer (A), thereby enabling a crosslinked rubber article to be obtained that has a smaller compression set under high temperature and high compression.

[0055] Specific examples of polyamine compounds 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 also 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. BOAP is preferred because it provides better effects for the present invention.

[0056] The content of the crosslinking agent is preferably from 0.3 to 10 parts by mass, more preferably from 0.3 to 5 parts by mass, and even more preferably from 0.5 to 3 parts by mass, per 100 parts by mass of the fluorine-containing copolymer (A).

[0057] <Other Components> The present composition 1 may contain other components in addition to those described above. Specific examples of other components include acid acceptors (for example, fatty acid esters, fatty acid metal salts, and oxides of divalent metals (magnesium oxide, calcium oxide, zinc oxide, lead oxide, etc.)), fillers and reinforcing materials (for example, carbon black, barium sulfate, calcium metasilicate, calcium carbonate, titanium oxide, silicon dioxide, fluorine-containing copolymers other than the fluorine-containing copolymer (A) and the fluorine-containing copolymer (B) (for example, tetrafluoroethylene-fluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and ethylene-tetrafluoroethylene copolymer), polytetrafluoroethylene (PTFE), aromatic polyesters, polyamideimides and thermoplastic polyimides, clay, and talc), scorch retarders (for example, 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 (for example, 18-crown-6), and mold release agents (for example, sodium stearate).

[0058] When the present composition 1 contains other components, the total content of the other components is preferably from 0.1 to 30 parts by mass, more preferably from 1 to 15 parts by mass, and even more preferably from 3 to 5 parts by mass, per 100 parts by mass of the fluorinated copolymer (A).

[0059] The T value of this composition 1 in the vulcanization test at 180°C in accordance with JIS K6296 ９０ The lower limit is preferably 1 minute or more. ９０ The measurement method may be, for example, the measurement method shown in the Examples section.

[0060] The method for producing the present composition 1 includes a method of mixing the above-mentioned components. The components can be mixed using a rubber mixing device such as a roll, kneader, Banbury mixer, or extruder. Alternatively, the mixture obtained by mixing the above-mentioned components may be molded. 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 onto a substrate or the like.

[0061] [Fluorocopolymer composition (second embodiment)] A fluorocopolymer composition of a second embodiment of the present invention (hereinafter also referred to as "composition 2") is a fluorocopolymer composition comprising: a fluorocopolymer (A) having units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether); a fluorocopolymer (B) which is a fluorocopolymer different from the fluorocopolymer (A) and has units based on a monomer having at least one functional group selected from the group consisting of a carboxy group and a group represented by formula (X), units based on tetrafluoroethylene, and units based on perfluoro(alkyl vinyl ether); and a crosslinking agent, wherein the T vulcanization of the fluorocopolymer composition in a vulcanization test at 180°C in accordance with JIS K6296 is ９０ is 10 minutes or less. Note that the types and contents of the various components, the physical properties of the composition, and other elements in the second embodiment are as described in the first embodiment above, and the preferred embodiments are the same. Note that the particle size D90 of the fluorocopolymer (B) in the second embodiment is not limited to 4.0 μm or less, and is preferably 4.0 μm or less. Although the details of why the configuration of composition 2 provides the desired effect are unclear, it is thought that shortening the time for crosslinking composition 2 shortens the time that composition 2 is exposed to heat, making thermal degradation less likely to occur, thereby increasing the heat resistance of the crosslinked product and achieving the desired effect.

[0062] [Crosslinked Rubber Article] The crosslinked rubber article of the present invention is a rubber article obtained by crosslinking the fluorocopolymer (A) in the present composition described above (hereinafter, "present composition 1" and "present composition 2" will also be collectively referred to simply as "present composition"). As a method for crosslinking the fluorocopolymer (A) in the present composition, a method in which the present composition is crosslinked by heating the present composition is preferred. Specific examples of crosslinking methods by heating include hot press crosslinking, steam crosslinking, injection molding crosslinking, hot air crosslinking, molten salt crosslinking, fluidized bed crosslinking, and funnel crosslinking. The heating conditions are preferably 100 to 400°C for 1 second to 24 hours.

[0063] The crosslinked rubber obtained by heating the composition (first crosslinking) may be further heated to cause second crosslinking. By performing second crosslinking, the mechanical properties, compression set, and other properties of the crosslinked rubber can be stabilized or improved. The heating conditions for performing second crosslinking are preferably 80 to 350°C for 30 minutes to 48 hours.

[0064] As a crosslinking method other than crosslinking the fluorine-containing copolymer (A) by heating, there can be mentioned a method in which the present composition is irradiated with radiation to crosslink the fluorine-containing copolymer (A). Specific examples of the radiation to be irradiated include electron beams and ultraviolet rays.

[0065] <Applications> Crosslinked rubber articles are suitable for materials such as O-rings, sheets, gaskets, oil seals, diaphragms, and V-rings. The present invention can also be applied to heat-resistant and chemical-resistant sealing materials, heat-resistant and oil-resistant sealing materials, wire coating materials, sealing materials for semiconductor manufacturing equipment, sealing materials for liquid crystal display panel manufacturing equipment, sealing materials for light-emitting diode manufacturing equipment, corrosion-resistant rubber coating materials, sealing materials for urea-resistant greases, and the like, rubber coating materials, 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 greases, etc.), 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, etc.), circuit 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.

[0066] The present invention will be described in detail below with reference to examples. Example 1 is an embodiment, and Examples 2 to 4 are comparative examples. However, the present invention is not limited to these examples.

[0067] [Measurement of Composition of Fluorine-Containing Copolymer] The content (mol %) of each unit in the fluorine-containing copolymer (A-1) described below was １９ The content (mol %) of each unit in the fluorinated copolymers (B-1) and (C-1) to (C-3) described below was calculated by melt NMR analysis and fluorine content analysis. However, the content of NAH units was calculated by the following infrared absorption spectroscopy.

[0068] [Infrared absorption spectroscopy analysis] The fluorine-containing copolymers (B-1) and (C-1) to (C-3) described below were each press-molded to obtain a 200 μm film. In the infrared absorption spectrum, the absorption peaks in the NAH-based units in the fluorine-containing copolymers (B-1) and (C-1) to (C-3) were all at 1778 cm －１ The absorbance of the absorption peak was measured, and the molar extinction coefficient of NAH was 20810 mol－１ ・l・cm －１ was used to determine the proportion of units based on NAH in each of the fluorine-containing copolymers (B-1) and (C-1) to (C-3).

[0069] [Particle diameter D90] Each of the fluorine-containing copolymers (B-1) and (C-1) to (C-3) described below was dispersed in isopropyl alcohol to prepare a dispersion (solid content concentration: 0.5% by mass), and the particle diameter D90 of the fluorine-containing copolymer (B-1) and the like in the dispersion was measured using a laser diffraction / scattering particle size distribution analyzer (LMS-2000e, manufactured by Seishin Enterprise Co., Ltd.).

[0070] [Bulk Density] The bulk density of the fluorine-containing copolymer (B-1) and the like was measured using an A.B.D powder property measuring instrument (ABD-100 model) manufactured by Tsutsui Scientific Instruments Co., Ltd. and a 100 mL sample container. Specifically, the fluorine-containing copolymer (B-1) was supplied to each sample container so that the sample container was filled within 30 to 60 seconds, the fluorine-containing copolymer (B-1) that formed a mound above the top of the sample container was leveled off with a spatula, the fluorine-containing copolymer (B-1) adhering to the periphery of the sample container was brushed off, and the mass of sample container 1 filled with the fluorine-containing copolymer (B-1) was measured using an electronic balance. The mass of empty sample container 2 was also measured. Next, the density (g / mL) was calculated from the value obtained by subtracting the mass of sample container 2 from the mass of sample container 1, and this value was taken as the bulk density (g / mL).

[0071] [T ９０ Each fluorine-containing copolymer composition described below was processed into a sheet having a thickness of 3 mm and then cut into 10 g pieces to obtain cut pieces. The obtained cut pieces were sandwiched between two polyester films (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 under the following conditions: measurement device: PREMER RPA (manufactured by Alpha Technologies), die shape: D0380, 180°C, 20 minutes, 100 cpm, angle: 3.00 deg. The minimum value of the obtained torque was set to 0% and the maximum value of the torque was set to 100%, and the processing time at which 90% of the torque value was obtained was defined as T９０ It was decided.

[0072] [Plasma Test] The O-rings produced in each of the examples described below were cut at three locations along the thickness direction so as to divide the outer periphery length into three equal parts to prepare measurement samples. A plasma etcher (CPE-200AHM, manufactured by Sakigake Semiconductor Co., Ltd.) was used, and the gas species were N ２ / NF ３ (NF ３ The plasma treatment was carried out under the conditions of a mixing ratio of 20%, power of 300 W, and pressure of 26 Pa. Each sample was removed after 1.5, 3, and 6 hours of plasma treatment, and its mass (value up to one decimal place) was measured using an Azpro electronic balance (Device name: BCA64I-1SJP, manufactured by Sartorius). Next, the plasma treatment time was divided into 0 to 1.5 hours as Category A, 1.5 to 3.0 hours as Category B, and 3.0 to 6.0 hours as Category C, and the weight loss rate of the sample during each plasma treatment time relative to the mass of the sample before plasma treatment per unit time for each category (mass % / hour (h)) was calculated. For example, if the mass of a sample before plasma treatment is 10.0 g, the mass of the sample after 1.5 hours of plasma treatment is 8.0 g, and the mass of the sample after 3.0 hours of plasma treatment is 5.0 g, the rate of weight loss of the sample during the plasma treatment time relative to the mass of the sample before plasma treatment per unit time in section A is [100 × (10.0 − 8.0) / 10.0] / (1.5) = 13.33 (mass % / h). Also, the rate of weight loss of the sample during the plasma treatment time relative to the mass of the sample before plasma treatment per unit time in sections A+B is [100 × (10.0 − 5.0) / 10.0] / (3.0) = 16.67 (mass % / h), and the rate of weight loss of the sample during section B is 16.67 − 13.33 = 3.34 (mass % / h).

[0073] [Production of Fluorocopolymer (A-1)] A stainless steel pressure reactor having an internal volume of 20 L and equipped with an anchor blade was degassed, and then 7.2 L of ultrapure water and an emulsifier C were added. ２ F ５ OCF ２ CF ２ OCF ２COONH ４ 880 g of a 30% by mass solution of 8CNVE, 7.3 g of 8CNVE, and 15.9 g of a 5% by mass 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 injected into the vessel, and the internal temperature was then raised to 80 ° C. The pressure inside the reactor was 0.90 MPa [gauge]. 28 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 = 26.3:73.3:0.4.

[0074] After the initiation of polymerization, as the polymerization progressed, the monomer was injected as follows. Hereinafter, injecting a monomer after the initiation of polymerization will be referred to as "post-addition," and a monomer injected after the initiation of polymerization will be referred to as "post-added monomer." 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 slow down, a 3% by mass aqueous solution of APS was appropriately added. The total amount of the 3% by 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 mass of the post-added TFE reached 1193 g, the addition of the post-added monomer was stopped, the internal temperature of the reactor 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 mass of each post-added monomer was 1193 g of TFE, 666 g of PMVE, and 66.6 g of 8CNVE, which was converted to a molar ratio of TFE:PMVE:8CNVE = 74.0:25.0:1.0. The latex was added to a 5 mass% aqueous solution of aluminum potassium sulfate, and the fluorine-containing copolymer was coagulated and separated. The fluorine-containing copolymer was filtered, washed with ultrapure water, and dried under vacuum at 50 ° C. to obtain a white fluorine-containing copolymer (A-1). The contents (molar ratio) of the individual units in the resulting fluorine-containing copolymer (A-1) were TFE units:PMVE units:8CNVE units=70.9:28.6:0.5.

[0075] [Fluorine-containing copolymer (B-1)] "Fluorine-containing copolymer (X1-1)" in the Examples section of WO 2016 / 017801 was subjected to primary pulverization using a rotor mill (Fritsch, Rotor Speed ​​Mill P-14), and then subjected to secondary pulverization using a jet mill (Seishin Enterprise Co., Ltd., Single Track Jet Mill FS-4 type) at a pulverization pressure of 0.6 MPa to obtain a resin powder. Furthermore, the obtained resin powder was classified using a high-efficiency precision air classifier (Seishin Enterprise Co., Ltd., Cruseal N-10 type) at a processing speed of 0.4 kg / hr to obtain a fluorine-containing copolymer (B-1). The particle size D90 of the obtained fluorine-containing copolymer (B-1) was 3.0 μm. The molar ratio of each unit in the fluorine-containing copolymer (B-1) was NAH unit:TFE unit:PPVE unit = 0.1:97.9:2.0.

[0076] [Fluorocopolymer (C-1)] "Fluorocopolymer (X1-1)" in the Examples section of WO 2016 / 017801 was pulverized using a jet mill at a pulverization pressure of 0.5 MPa and used as fluorine-containing copolymer (C-1). The particle size D90 of the obtained fluorine-containing copolymer (C-1) was 5.0 μm, and the particle size D50 was 2 to 3 μm. The molar ratio of each unit in the fluorine-containing copolymer (C-1) was NAH unit:TFE unit:PPVE unit=0.1:97.9:2.0.

[0077] [Fluorocopolymer (C-2)] "Fluorocopolymer (X1-1)" in the Examples section of WO 2016 / 017801 was pulverized using a rotor mill to obtain fluorine-containing copolymer (C-2). The particle size D90 of the obtained fluorine-containing copolymer (C-2) was 100 μm. The molar ratio of each unit in fluorine-containing copolymer (C-2) was NAH unit:TFE unit:PPVE unit=0.1:97.9:2.0.

[0078] [Fluorine-containing copolymer (C-3)] "Fluorine-containing copolymer (X1-1)" in the Examples section of WO 2016 / 017801 was pulverized using a jet mill at a pulverization pressure of 0.55 MPa to obtain fluorine-containing copolymer (C-3). The particle diameter D90 of the obtained fluorine-containing copolymer (C-3) was 4.5 μm, and the particle diameter D50 was 1.7 μm. The molar ratio of each unit in the fluorine-containing copolymer (C-3) was NAH unit:TFE unit:PPVE unit=0.1:97.9:2.0.

[0079] Example 1 The components and amounts shown in Table 1 were mixed and kneaded using a two-roll mill at room temperature for 10 minutes to obtain a fluorine-containing copolymer composition. The obtained fluorine-containing copolymer composition was hot-pressed using a hydraulic press (model: SA-301 50T type, manufactured by Tester Sangyo Co., Ltd., ram diameter: 180 mm) under pressing conditions of 180°C for 20 minutes to obtain an O-ring (size: P-26) (primary crosslinking). Then, in a nitrogen atmosphere, the O-ring was heated at 90°C for 2 hours, then heated to 200°C over 2 hours and maintained at that temperature for 4 hours. The temperature was further raised to 305°C over 2 hours and heated at 305°C for 13 hours (secondary crosslinking). The mixture was then cooled to room temperature to obtain the O-ring of Example 1.

[0080] Examples 2 to 4 The O-rings of Examples 2 to 4 were obtained in the same manner as in Example 1, except that the fluorine-containing copolymers were changed as shown in the table.

[0081] BOAP: 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, a polyamine compound (crosslinking agent)

[0082]

[0083]

[0084] As shown in the table, it was confirmed that the effects of the present invention can be achieved by using this composition. Specifically, comparing Example 1 and Example 2, the weight loss rate of Example 1 was equivalent to that of Example 2 in Sections A and B, while the weight loss rate of Example 1 was lower than that of Example 2 in Section C. In other words, when the present crosslinked rubber article was used for a long period of time in a plasma irradiation environment, the weight loss rate of Example 1 in Section C after a predetermined time had elapsed was reduced compared to that of Example 2 of the prior art, confirming that the present invention exhibits advantageous effects over the prior art. The effects of the present invention are effects that would be difficult for a person skilled in the art to predict. Furthermore, comparing Example 1 and Example 3, the weight loss rate of Example 1 was lower than that of Example 3 in all Sections A to C. Furthermore, comparing Example 1 and Example 4, the weight loss rate of Example 1 was equivalent to that of Example 2 in Sections A and B, while the weight loss rate of Example 1 in Section C was lower than that of Example 4. The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2023-221261, filed on December 27, 2023, are incorporated herein by reference as the disclosure of the present invention.

Claims

1. A fluorine-containing copolymer composition comprising a fluorine-containing copolymer (A) having units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether); a fluorine-containing copolymer (B) different from the fluorine-containing copolymer (A), having units based on a monomer having at least one functional group selected from the group consisting of a carboxy group and a group represented by formula (X), units based on tetrafluoroethylene, and units based on perfluoro(alkyl vinyl ether), and having a particle size D90 of 4.0 μm or less; and a crosslinking agent. Formula (X): *-CO-O-CO-*, where * represents the bonding position.

2. Further, the fluorine-containing copolymer (A) has units having a nitrile group, the content of the units having a nitrile group is 0.05 to 5.0 mol% based on all the units of the fluorine-containing copolymer (A), the content of the units based on tetrafluoroethylene is 59.0 to 79.95 mol% based on all the units of the fluorine-containing copolymer (A), and the content of the units based on perfluoro(alkyl vinyl ether) is 20.0 to 40.95 mol% based on all the units of the fluorine-containing copolymer (A). The fluorine-containing copolymer composition according to claim 1.

3. The content of the units based on a monomer having at least one functional group selected from the group consisting of a carboxy group and the group represented by formula (X) is 0.01 to 3.0 mol% based on all the units of the fluorine-containing copolymer (B), the content of the units based on tetrafluoroethylene is 90 to 99.89 mol% based on all the units of the fluorine-containing copolymer (B), and the content of the units based on perfluoro(alkyl vinyl ether) is 0.1 to 9.99 mol% based on all the units of the fluorine-containing copolymer (B). The fluorine-containing copolymer composition according to claim 1 or 2.

4. The content of the fluorine-containing copolymer (B) is 50 parts by mass or less with respect to 100 parts by mass of the fluorine-containing copolymer (A). The fluorine-containing copolymer composition according to claim 1 or 2.

5. The crosslinking agent is a compound having two or more amino groups, and the content of the crosslinking agent is 0.3 to 10 parts by mass with respect to 100 parts by mass of the fluorine-containing copolymer (A). The fluorine-containing copolymer composition according to claim 1 or 2.

6. The bulk density of the fluorine-containing copolymer (B) is 0.25 g / mL or less. The fluorine-containing copolymer composition according to claim 1 or 2.

7. A fluorine-containing copolymer composition comprising: a fluorine-containing copolymer (A) having units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether); a fluorine-containing copolymer (B) different from the fluorine-containing copolymer (A), the fluorine-containing copolymer (B) having units based on a monomer having at least one functional group selected from the group consisting of a carboxy group and a group represented by the formula (X), units based on tetrafluoroethylene, and units based on perfluoro(alkyl vinyl ether); and a crosslinking agent, wherein T in the vulcanization test at 180 °C according to JIS K6296 of the fluorine-containing copolymer composition ９０ is 10 minutes or less. Formula (X): *-CO-O-CO-*, where * represents the bonding position.

8. The fluorine-containing copolymer (A) has a unit having a nitrile group, the content of the unit having a nitrile group is 0.05 to 5.0 mol% with respect to all units of the fluorine-containing copolymer (A), and the content of the unit based on tetrafluoroethylene is 59.0 to 79.95 mol% with respect to all units of the fluorine-containing copolymer (A), and the content of the unit based on perfluoro(alkyl vinyl ether) is 20.0 to 40.95 mol% with respect to all units of the fluorine-containing copolymer (A). The fluorine-containing copolymer composition according to claim 7.

9. The content of the unit based on the monomer having at least one functional group selected from the group consisting of the carboxy group and the group represented by the formula (X) is 0.01 to 3.0 mol% with respect to all units of the fluorine-containing copolymer (B), the content of the unit based on tetrafluoroethylene is 90 to 99.89 mol% with respect to all units of the fluorine-containing copolymer (B), and the content of the unit based on perfluoro(alkyl vinyl ether) is 0.1 to 9.99 mol% with respect to all units of the fluorine-containing copolymer (B). The fluorine-containing copolymer composition according to claim 7 or 8.

10. The content of the fluorine-containing copolymer (B) is 50 parts by mass or less with respect to 100 parts by mass of the fluorine-containing copolymer (A). The fluorine-containing copolymer composition according to claim 7 or 8.

11. The crosslinking agent is a compound having two or more amino groups, and the content of the crosslinking agent is 0.3 to 10 parts by mass with respect to 100 parts by mass of the fluorine-containing copolymer (A). The fluorine-containing copolymer composition according to claim 7 or 8.

12. The bulk density of the fluorine-containing copolymer (B) is 0.25 g / mL or less. The fluorine-containing copolymer composition according to claim 7 or 8.

13. A crosslinked rubber article obtained from the fluorine-containing copolymer composition according to claim 1 or 7.

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