Fluorine-containing copolymer composition, crosslinkable composition and crosslinked rubber article

Abstract

Provided are: a fluorine-containing copolymer composition able to yield a crosslinkable composition which can, when combined with a crosslinking agent, form a crosslinked rubber article that is unlikely to adhere to a target object; and a crosslinked rubber article that is unlikely to adhere to a target object. This fluorine-containing copolymer composition contains: a fluorine-containing copolymer (A) having a unit derived from tetrafluoroethylene and a unit derived from a perfluoro(alkyl vinyl ether); and a fluorine-containing copolymer (B) which is different from the fluorine-containing copolymer (A) and has a unit derived from a monomer having at least one type of functional group selected from the group consisting of a carboxylic group and a group represented by formula (X), a unit derived from tetrafluoroethylene and a unit derived from a perfluoro(alkyl vinyl ether). The fluorine-containing copolymer composition has a prescribed storage elastic modulus.　Formula (X): ＊-CO-O-CO-＊. In formula (X), ＊ denotes a bonding position.

Description

Fluorine-containing copolymer composition, crosslinkable composition, and crosslinked rubber article

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

[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) and cushioning materials in the fields of vehicles, ships, aircraft, general machinery, construction, etc. Patent Document 1 discloses a crosslinkable composition containing a predetermined fluorine-containing copolymer as a crosslinkable composition used to obtain such crosslinked rubber articles.

[0003] International Publication No. 2021 / 210502

[0004] The present inventors have studied the properties of the composition described in Patent Document 1 and found that a crosslinked rubber article formed from the composition tends to adhere to an object, and that this needs to be improved. For example, when a crosslinked rubber article obtained from the composition described in Patent Document 1 is used as an O-ring for a semiconductor device, if the O-ring tends to adhere to a movable member such as a door or lid of the semiconductor device, problems arise in that the movable member becomes difficult to move, such as making it difficult to open the door.

[0005] An object of the present invention is to provide a fluorine-containing copolymer composition that can be obtained by combining a crosslinkable composition capable of forming a crosslinked rubber article that is less likely to adhere to an object with a crosslinking agent. Another object of the present invention is to provide the crosslinkable composition and the crosslinked rubber article.

[0006] As a result of extensive investigation, the present inventors have found that the above-mentioned problems can be solved by the following configuration.

[0007] (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); and a fluorine-containing copolymer (B) which is a fluorine-containing copolymer different from the fluorine-containing copolymer (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 the formula (X) described later, units based on tetrafluoroethylene, and units based on perfluoro(alkyl vinyl ether), wherein a measurement sample composed of the fluorine-containing copolymer (A) and the fluorine-containing copolymer (B) has a storage modulus at 100°C of 650 kPa or less, the measurement sample being the same as the mass ratio of the content of the fluorine-containing copolymer (B) to the content of the fluorine-containing copolymer (A) in the measurement sample. (2) The fluorine-containing copolymer composition according to (1), wherein the fluorine-containing copolymer (A) contains units having a nitrile group, and the content of the units having a nitrile group is 0.14 mol % or more and less than 0.7 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 formula (X), which are contained in the fluorine-containing copolymer (B), is 0.01 to 3 mol % based on all units of the fluorine-containing copolymer (B), the content of units based on tetrafluoroethylene is 90 to 99.89 mol % based on 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 % based on all units of the fluorine-containing copolymer (B). (4) The fluorine-containing copolymer composition according to any of (1) to (3), further comprising a compound represented by formula (9) described below. (5) The fluorine-containing copolymer composition according to (4), wherein the content of the compound represented by formula (9) is 0.1 to 5 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), further comprising a phosphorus compound having a melting point of 60°C or lower. (7) The fluorine-containing copolymer composition according to (6), wherein the content of the phosphorus compound is 0.2 to 5 parts by mass per 100 parts by mass of the fluorine-containing copolymer (A). (8) The fluorine-containing copolymer composition according to any one of (1) to (7), wherein the content of the fluorine-containing copolymer (B) is 2 to 50 parts by mass per 100 parts by mass of the fluorine-containing copolymer (A). (9) A crosslinkable composition comprising the fluorine-containing copolymer composition according to any one of (1) to (8), and further a crosslinking agent. (10) The crosslinkable composition according to (9), wherein the crosslinking agent is a compound having two or more amino groups. (11) The crosslinkable composition according to (9) or (10), wherein 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). (12) A crosslinkable 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) described below, units based on tetrafluoroethylene, and units based on perfluoro(alkyl vinyl ether); and a crosslinking agent, wherein a crosslinked rubber article obtained from the crosslinkable composition has a recovery of less than 80% in a recovery force test after being compressed at 200°C for 70 hours in a 25% compressed state. Formula (X): *-CO-O-CO-* In formula (X), * represents a bonding position. (13) A crosslinkable rubber article obtained from the crosslinkable composition according to any of (9) to (12).

[0008] According to the present invention, there is provided a fluorine-containing copolymer composition that can be obtained by combining a crosslinkable composition capable of forming a crosslinked rubber article that is less likely to adhere to an object with a crosslinking agent. The present invention also provides the crosslinkable composition and the crosslinked rubber article.

[0009] The meanings of terms used in the present invention are as follows. "Unit" is a collective term for 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, "unit based on a monomer" will also be simply referred to as "unit." "Rubber" refers to a rubber exhibiting properties defined by JIS K 6200:2008 and is distinguished from "resin." "Melting point" refers to the temperature corresponding to the maximum value of the melting peak measured by differential scanning calorimetry (DSC). "Boiling point" refers to a value measured according to the equilibrium reflux boiling point test method, specifically, JIS K2233:2017, 8.1. When a pressure is listed after the boiling point, the listed boiling point is a value measured under that pressure. Unless otherwise specified, the value measured according to the above-mentioned JIS K2233:2017, 8.1 method is a value converted to a boiling point at 760 mmHg. (Meth)acrylate is a general term for acrylate and methacrylate, and (meth)acryloyl is a general term for acryloyl and methacryloyl.

[0010] [Fluorocopolymer Composition] The fluorine-containing copolymer composition of the present invention (hereinafter also referred to as "the composition") comprises a fluorine-containing copolymer (A) (hereinafter also referred to as "copolymer (A)") having units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether), and a fluorine-containing copolymer (B) (hereinafter also referred to as "copolymer (B)") which is a fluorine-containing copolymer different from copolymer (A) and has units based on a monomer having a carboxy group and at least one functional group selected from the group consisting of groups represented by formula (X) described below, units based on tetrafluoroethylene, and units based on perfluoro(alkyl vinyl ether). Furthermore, the composition has a storage modulus at 100°C of 650 kPa or less. Crosslinked rubber articles obtained using a crosslinkable composition containing the composition and a crosslinking agent are less likely to adhere to a target object. The present inventors have found that the above-mentioned storage modulus is related to the adhesion of crosslinked rubber articles obtained from a crosslinkable composition containing the composition and a crosslinking agent to a target object. In other words, it has been found that when the storage modulus is equal to or less than a predetermined value, a crosslinked rubber article obtained from a crosslinkable composition containing the present composition and a crosslinking agent is less likely to adhere to a target object. While the details of why this correlation occurs are unclear, it is speculated that the storage modulus is related to the dispersion state of copolymer (A) and copolymer (B). Furthermore, it is thought that the dispersion state makes the resulting crosslinked rubber article more likely to shrink during heating and cooling treatments. Therefore, when the dispersion state exhibits the storage modulus of the predetermined value, when a crosslinked rubber article obtained from a crosslinkable composition containing the present composition and a crosslinking agent is subjected to a heating or cooling treatment similar to the use conditions of an O-ring or the like, the crosslinked rubber article is more likely to shrink, resulting in a reduced contact area between the crosslinked rubber article and the target object, making the crosslinked rubber article less likely to adhere.

[0011] <Copolymer (A)> The present composition contains copolymer (A). Copolymer (A) is a polymer having units based on tetrafluoroethylene (hereinafter also referred to as "TFE") and units based on perfluoro(alkyl vinyl ether) (hereinafter also referred to as "PAVE"). Copolymer (A) itself does not completely return to its original shape when stretched, but its tendency to return to its original shape is strengthened by crosslinking, i.e., it exhibits rubber properties. In order to achieve better effects of the present invention, copolymer (A) preferably has a unit having a nitrile group in addition to units based on TFE monomer and units based on PAVE monomer. In order to achieve better effects of the present invention, copolymer (A) preferably does not have a unit 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 below.

[0012] 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 ｆ１ (1) In formula (1), R ｆ１ represents a perfluoroalkyl group having 1 to 10 carbon atoms. ｆ１ 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.

[0013] 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"), and among these, PMVE and PPVE are preferred.

[0014] The unit having a nitrile group is a monomer having a nitrile group (hereinafter referred to as "R ＣＮ It is also called ". ") It is a unit based on R ＣＮIn terms of achieving better effects of the present invention, it is preferable that CR has a fluorine atom, and it is particularly preferable that CR is a monomer represented by formula (2). ２１ R ２２ =CR ２３ -R ２４ -CN (2) In formula (2), R ２１ , R ２２ and R ２３ each independently represents a hydrogen atom, a fluorine atom, or a methyl group; R ２４ 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.

[0015] R ＣＮ From the viewpoint of excellent polymerization reactivity of R ２１ , R ２２ , R ２３ is preferably a fluorine atom or a hydrogen atom, and R ２１ , R ２２ , R ２３ It is more preferred that all of R are fluorine atoms or all of R are hydrogen atoms, and in view of the superior mold releasability and heat resistance of the crosslinked rubber article, １１ , R １２ , R １３ It is particularly preferred that all of R are fluorine atoms. ２４ R may be linear, branched, or cyclic, and is preferably linear or branched. ２４ The number of carbon atoms in R is preferably 2 to 8, more preferably 3 to 7, even more preferably 3 to 6, and particularly preferably 3 to 5. ２４ Although R may or may not have an etheric oxygen atom, it is preferable that R has an etheric oxygen atom, since the crosslinkable composition containing the present composition and a crosslinking agent provides a crosslinked rubber article with better rubber physical properties. ２４ The number of etheric oxygen atoms in is preferably 1 to 3, and particularly preferably 1 or 2.

[0016] Specific examples of the monomer represented by formula (2) include CF ２ = CFOCF ２ CF (CF ３ ) OCF２ CF ２ CN (hereinafter 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, CF ２ = CFO (CF ２ ) ３ CN, and 8CNVE and MV5CN are preferred in that they provide crosslinked rubber articles with better mold releasability and heat resistance.

[0017] The 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 the following formula (6), ethylene, and propylene. Other monomers that may be mentioned include monomers having halogen atoms (hereinafter also referred to as "monomers having other halogen atoms") (e.g., bromotrifluoroethylene, iodotrifluoroethylene).

[0018] 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 particularly preferably 2, which provides better polymerization reactivity. BO preferably further contains a fluorine atom.

[0019] BO is preferably a monomer represented by formula (3): (CR ３１ R ３２ =CR ３３ ) ａ３ R ３４ (3) In formula (3), R３１ , 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.

[0020] Since the polymerization reactivity of BO is superior, R ３１ , R ３２ , R ３３ is preferably a fluorine atom or a hydrogen atom, and R ３１ , R ３２ , R ３３ It is more preferable that all of R are fluorine atoms or hydrogen atoms, and from the viewpoint of the heat resistance and chemical resistance of the crosslinked rubber article, ３１ , R ３２ , R ３３ It is particularly preferred that all of R are fluorine atoms. ３４ R may be linear, branched, or cyclic, preferably linear or branched, and particularly 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.

[0021] 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).

[0022] (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.

[0023] 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 (hereinafter referred to as "C3DVE"), CF 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 , C.F. ２ = CFO (CF ２ ) ２ O(CF(CF ３ )CF ２ O) ２ CF = CF ２ , C.F. ２ = CFOCF ２ O (CF ２ CF ２ O) ２ CF = CF ２ , C.F. ２ = CFO (CF２ O) ３ O(CF(CF ３ )CF ２ O) ２ CF = CF ２ , C.F. ２ = CFOCF ２ CF (CF ３ ) O(CF ２ ) ２ OCF (CF ３ )CF ２ OCF = CF ２ , C.F. ２ = CFOCF ２ CF ２ O (CF ２ O) ２ CF ２ CF ２ OCF = CF ２ Among the monomers represented by formula (4), a more preferred specific example of the monomer is CF ２ = CFO (CF ２ ) ３ OCF = CF ２ , C.F. ２ = CFO (CF ２ ) ４ OCF = CF ２ Examples include:

[0024] (CH ２ =CH) ２ R ５１ (5) In formula (5), R ５１ 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.

[0025] 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 , C.H. ２ =CH(CF ２ ) ６ CH=CH ２Among the monomers represented by formula (5), specific examples of more preferred monomers include CH ２ =CH(CF ２ ) ６ CH=CH ２ Examples include:

[0026] When BO is copolymerized, the polymerizable double bond at the end of BO reacts during the polymerization to give a copolymer (A) having a branched chain.

[0027] Equation (6) is as follows: 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 particularly preferably 1 to 5.

[0028] 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).

[0029] The content of TFE units is preferably 60 to 68 mol%, more preferably 62 to 67%, particularly preferably 63 to 67 mol%, and most preferably 64 to 66 mol%, based on the total units of copolymer (A), from the viewpoint of more excellent effects of the present invention. Furthermore, when the content of TFE units is within the above-mentioned range, the storage modulus at 100°C of the fluorine-containing copolymer composition is easily adjusted to 650 kPa or less. The content of PAVE units is preferably 32 to 40 mol%, more preferably 33 to 38 mol%, particularly preferably 33 to 37 mol%, and most preferably 34 to 36 mol%, based on the total units of copolymer (A), from the viewpoint of more excellent effects of the present invention. When PMVE or PPVE is used as PAVE, the suitable content is similar. When copolymer (A) is R ＣＮWhen the fluorine-containing copolymer contains other monomer units, the content thereof is preferably from 0.05 to 5 mol %, more preferably from 0.1 to 3 mol %, and particularly preferably from 0.2 to 1.5 mol %, based on all units of the copolymer (A), from the viewpoint of more excellent effects of the present invention. When the fluorine-containing copolymer contains other monomer units, the content thereof is preferably from 0.01 to 20 mol %, more preferably from 0.5 to 10 mol %, and particularly preferably from 1 to 5 mol %, based on all units of the fluorine-containing copolymer, from the viewpoint of more excellent effects of the present invention.

[0030] In the fluorine-containing copolymer (A), R ＣＮ The content of the unit is preferably 0.14 mol % or more and less than 0.7 mol % based on the total units of the copolymer (A).

[0031] The copolymer (A) is preferably a perfluoropolymer in view of the superior effects of the present invention. Here, "perfluoropolymer" refers to a polymer that does not substantially contain hydrogen atoms bonded to carbon atoms, has fluorine atoms instead of those hydrogen atoms, and has a main chain consisting of a chain of carbon atoms. The side chain of the perfluoropolymer may have polyvalent atoms other than carbon atoms, and oxygen atoms are preferred as the polyvalent atoms. Here, "substantially does not contain hydrogen atoms" means that the content of hydrogen atoms in the perfluoropolymer is 0.5% by mass or less, preferably 0.1% by mass or less, more preferably 0.07% by mass or less, and particularly 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.

[0032] The copolymer (A) may contain an iodine atom. In this case, it is preferable that the copolymer (A) has an iodine atom at the end of the polymer chain. Examples of the iodine atom include an iodine atom derived from an iodine compound that functions as a chain transfer agent, as described below, and an iodine atom in a unit based on an iodine atom-containing monomer among other halogen-containing monomers such as iodotrifluoroethylene. An iodine atom derived from an iodine compound that functions as a chain transfer agent is preferred. When the copolymer (A) contains iodine atoms, the content is preferably 0.01 to 5.0 mass%, more preferably 0.05 to 2.0 mass%, and particularly preferably 0.05 to 1.0 mass%, relative to the total mass of the copolymer (A). When the iodine atom content is within the above range, the crosslinking reactivity of the copolymer (A) is improved, resulting in excellent mechanical properties of crosslinked rubber articles.

[0033] The content of the copolymer (A) is preferably from 60 to 99 mass %, more preferably from 70 to 95 mass %, particularly preferably from 80 to 90 mass %, based on the total mass of the composition.

[0034] (Method for Producing Copolymer (A)) One example of a method for producing copolymer (A) is a method in which the above-mentioned monomers are copolymerized in the presence of a radical polymerization initiator.

[0035] As the radical polymerization initiator, a water-soluble polymerization initiator or a redox polymerization initiator is preferred. 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. Among these, persulfates are preferred, with ammonium persulfate being particularly preferred. Examples of redox polymerization initiators include polymerization initiators combining persulfates with a reducing agent. Among these, polymerization initiators capable of polymerizing each monomer at a polymerization temperature in the range of 0 to 85°C are preferred. Specific examples of persulfates constituting the redox polymerization initiator 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, with sodium hydroxymethanesulfinate being particularly preferred.

[0036] In the method for producing the copolymer (A), the above-mentioned monomers may be copolymerized in the presence of a chain transfer agent together with a radical polymerization initiator. The chain transfer agent is preferably an iodine compound 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, with 1,4-diiodoperfluorobutane being particularly preferred. When the above-mentioned monomers are copolymerized in the presence of these iodine compounds, iodine atoms can be introduced into the copolymer (A).

[0037] For details of the components other than those described above used in producing the copolymer (A) and the production method, reference can be made to the method described in paragraphs 0019 to 0034 of WO 2010 / 082633.

[0038] <Copolymer (B)> The present composition contains copolymer (B). Copolymer (B) is a monomer (hereinafter, also referred to as "R Ｘ "). It is a polymer having units based on the above-mentioned formula (X), TFE units, and PAVE units. Formula (X) *-CO-O-CO-* In formula (X), * represents a bonding position.

[0039] 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 is used as a monomer and therefore 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.

[0040] Examples of the monomer having a carboxy group include unsaturated dicarboxylic acids such as itaconic acid, citraconic acid, 5-norbornene-2,3-dicarboxylic acid, and maleic acid, unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, and CF ２ =CFOR ｆｘ CO ２ H (however, R ｆｘ is a perfluoroalkylene group having 1 to 10 carbon atoms which may have an etheric oxygen atom. The group containing the group represented by formula (X) is preferably a group formed by removing one hydrogen atom from an acid anhydride. 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.

[0041] R Ｘ In view of reactivity with the nitrile group of the copolymer (A), R is preferably a monomer having a group represented by formula (X). Among them, in view of facilitating production of the copolymer (B), it is more preferable that R contains at least one selected from the group consisting of IAH, CAH and NAH, and it is particularly preferable that R contains NAH. Ｘ may be used alone or in combination of two or more.

[0042] Specific examples and preferred embodiments of the PAVE units contained in copolymer (B) are the same as those of the PAVE units in copolymer (A).

[0043] Copolymer (B) may contain 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 copolymer (A).

[0044] The copolymer (B) may have a specific functional group as a main chain terminal group. Such a functional group can be introduced by appropriately selecting a radical polymerization initiator, a chain transfer agent, etc., used in the production of the copolymer (B).

[0045] 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 particularly preferably 0.05 to 1 mol%, based on the total units of the 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. Furthermore, the content of TFE units is preferably 90 to 99.89 mol%, more preferably 95 to 99.47 mol%, and particularly preferably 96 to 98.95 mol%, based on the total units of the copolymer (B), from the viewpoint of more excellent effects of the present invention. Furthermore, the content of PAVE units is preferably 0.1 to 9.99 mol%, more preferably 0.5 to 4.97 mol%, and particularly preferably 1 to 3.95 mol%, based on the total units of the 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.

[0046] The content of copolymer (B) is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 25 parts by mass or less, and particularly preferably 20 parts by mass or less, relative to 100 parts by mass of copolymer (A), from the viewpoint of more excellent effects of the present invention. The content of copolymer (B) is preferably 0.5 parts by mass or more, more preferably 2 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more, relative to 100 parts by mass of copolymer (A), from the viewpoint of more excellent effects of the present invention. Furthermore, when the content of copolymer (B) is within the above-mentioned range, it is easy to adjust the storage modulus at 100 ° C. of the fluorine-containing copolymer composition to 650 kPa or less.

[0047] The melting point of copolymer (B) is preferably 260 to 320°C, more preferably 280 to 315°C, and particularly preferably 295 to 310°C. When the melting point of copolymer (B) is above the lower limit of the above range, crosslinked rubber articles obtained from a crosslinkable composition containing the present composition containing copolymer (B) and a crosslinking agent have excellent heat resistance. When the melting point is below the upper limit of the above range, crosslinked rubber articles obtained from a crosslinkable composition containing the present composition containing copolymer (B) and a crosslinking agent have excellent processability and excellent surface smoothness. The melting point of copolymer (B) can be adjusted by the type, content, molecular weight, etc. of the units constituting copolymer (B). For example, the melting point of copolymer (B) tends to increase as the proportion of TFE units increases.

[0048] (Method for Producing Copolymer (B)) An example of a method for producing copolymer (B) is a method of copolymerizing the above-mentioned monomers in the presence of a radical polymerization initiator, the details of which are as described in WO 2016 / 017801.

[0049] (Form) The copolymer (B) is preferably contained in the composition in the form of particles. That is, the copolymer (B) is preferably contained in the composition in the form of resin particles containing the copolymer (B). The resin particles may contain a resin other than the copolymer (A) and the copolymer (B) (hereinafter also referred to as "other resins"). Examples of other resins include fluorine-containing copolymers other than the copolymer (A) and the copolymer (B) described below (e.g., tetrafluoroethylene-fluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, etc.), polytetrafluoroethylene, aromatic polyester, polyamideimide, and thermoplastic polyimide. The content of the copolymer (B) in the resin particles is preferably 80 to 100% by mass, more preferably 85 to 100% by mass, even more preferably 90 to 100% by mass, and particularly preferably 100% by mass, based on the total mass of the resin particles.

[0050] The average particle diameter of the resin particles is preferably 0.02 to 50 μm, more preferably 0.02 to 35 μm, and particularly preferably 0.02 to 10 μm, in order to obtain superior effects of the present invention. The average particle diameter of the resin particles is the volume-based cumulative 50% diameter (D50) determined by a laser diffraction / scattering method. That is, the particle size distribution is measured by the laser diffraction / scattering method, a cumulative curve is determined with the total volume of the particle group set to 100%, and the average particle diameter is the particle diameter at the point on the cumulative curve where the cumulative volume is 50%.

[0051] The resin particles can be produced, for example, by the method for producing resin particles and resin powder described in WO 2016 / 017801.

[0052] <Specific phosphorus compound> The present composition preferably contains a phosphorus compound (hereinafter also referred to as "specific phosphorus compound") having a melting point of 60°C or less, from the viewpoint of achieving better effects of the present invention. The melting point of the specific phosphorus compound is 60°C or less, and from the viewpoint of further improving the dispersibility of the specific phosphorus compound and achieving better effects of the present invention, it is preferably 35°C or less, and particularly preferably 20°C or less. Note that the above compounds having melting points below a specific temperature also include compounds that are liquid at 20°C. The boiling point of the specific phosphorus compound is preferably 50°C or more, and more preferably 100°C or more, from the viewpoint of ease of handling.

[0053] The specific phosphorus compound is preferably a phosphine or phosphine oxide having an alkyl group, more preferably a trialkylphosphine or trialkylphosphine oxide, further preferably a compound represented by the following formula (7) or (8), and particularly preferably a compound represented by the following formula (7), in order to further improve the dispersibility of the specific phosphorus compound and to further enhance the effects of the present invention. P(R ７１ ) ３ Formula (7) In formula (7), R ７１ represents a linear or branched alkyl group having 2 to 9 carbon atoms. ７１ may be the same or different, but are preferably the same. ８１ ) ３ Formula (8) In formula (8), R ８１ represents a linear or branched alkyl group having 2 to 9 carbon atoms. ８１ may be the same or different from each other, but are preferably the same from each other.

[0054] R ７１ The number of carbon atoms in the group R is 2 to 9, preferably 4 to 9, and particularly preferably 6 to 8. ７１ are each preferably a linear alkyl group having 2 to 9 carbon atoms. ８１ The number of carbon atoms in each of the three R is 2 to 9, preferably 4 to 9, and particularly preferably 6 to 8. ８１ are each preferably independently a linear alkyl group having 2 to 9 carbon atoms.

[0055] Specific examples of the compound represented by formula (7) include triethylphosphine (melting point -86°C, liquid at 20°C, boiling point 127 to 128°C), tri-n-propylphosphine (melting point unknown, liquid at 20°C, boiling point 72 to 74°C / 12 mmHg), tri-n-butylphosphine (melting point -65°C, liquid at 20°C, boiling point 150°C / 50 mmHg), tri-tert-butylphosphine (melting point 30 to 35°C, liquid or solid at 20°C, boiling point 102°C / 13 mmHg), tri-n-pentylphosphine (melting point unknown, liquid at 20°C, boiling point unknown), tri-n-hexylphosphine (melting point unknown, liquid at 20°C, boiling point 227°C / 50 mmHg), and tri-n-octylphosphine (melting point unknown, liquid at 20°C, boiling point 175°C / 0.3 mmHg). Specific examples of the compound represented by formula (8) include triethylphosphine oxide (melting point 52°C, solid at 20°C), tri-n-propylphosphine oxide (melting point 39°C, solid at 20°C), tri-n-hexylphosphine oxide (melting point 34°C, solid at 20°C), and tri-n-octylphosphine oxide (melting point 52°C, solid at 20°C). Of the specific phosphorus compounds, tri-n-octylphosphine is preferred.

[0056] The content of the specific phosphorus compound is preferably 0.01 parts by mass or more, more preferably 0.10 parts by mass or more, relative to 100 parts by mass of copolymer (A) from the viewpoint of further suppressing cracking in crosslinked rubber articles obtained from a crosslinkable composition containing this composition and a crosslinking agent, and is even more preferably 0.20 parts by mass or more from the viewpoint of excellent releasability of crosslinked rubber articles obtained from a crosslinkable composition containing this composition and a crosslinking agent. The content of the specific phosphorus compound is preferably 5 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1.0 part by mass or less, relative to 100 parts by mass of copolymer (A) from the viewpoint of more excellent effects of the present invention.

[0057] <Compound Represented by Formula (9)> The present composition preferably contains a compound represented by formula (9). ２ C=CH-R ９１ -R ９３ -R ９２ -CH=CH ２ Formula (9) R９１ and R ９２ are each independently CH ２ or CF ２ indicates CH ２ is preferred. ９３ represents a divalent fluorohydrocarbon group having 1 to 10 carbon atoms, or a group having an etheric oxygen atom at the end of the fluorohydrocarbon group or between the carbon-carbon bonds. The fluorohydrocarbon group may be linear, branched, or cyclic, preferably linear or branched, and particularly preferably linear. R ９３ The number of carbon atoms in the group is preferably from 2 to 10, more preferably from 3 to 8, even more preferably from 3 to 6, and particularly preferably from 3 to 5. The fluorohydrocarbon group is preferably a perfluorohydrocarbon group.

[0058] The content of the compound represented by formula (9) is preferably 0.1 to 5 parts by mass, more preferably 1 to 3 parts by mass, per 100 parts by mass of copolymer (A), in terms of better effects of the present invention.

[0059] <Other Components> The present composition may contain other components in addition to those described above, provided that the effects of the present invention are not impaired. Examples of other components include acid acceptors (e.g., fatty acid esters, fatty acid metal salts, and oxides of divalent metals (magnesium oxide, calcium oxide, zinc oxide, lead oxide, and the like)), fillers and reinforcing materials (e.g., carbon black, barium sulfate, calcium metasilicate, calcium carbonate, titanium oxide, silicon dioxide, fluorine-containing copolymers other than copolymer (A) and copolymer (B) (e.g., tetrafluoroethylene-fluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, and the like), polytetrafluoroethylene (PTFE), aromatic polyesters, polyamideimides and thermoplastic polyimides, clay, and talc), scorch retarders (e.g., phenolic hydroxyl group-containing compounds such as bisphenol A, quinones such as hydroquinone, and α-methylstyrene dimers such as 2,4-di(3-isopropylphenyl)-4-methyl-1-pentene), crown ethers (e.g., 18-crown-6), and mold release agents (e.g., sodium stearate).

[0060] When the present composition contains other components, the total content of the other components is preferably more than 0.1 parts by mass and not more than 30 parts by mass, more preferably 1 to 15 parts by mass, and particularly preferably 3 to 5 parts by mass, per 100 parts by mass of copolymer (A).

[0061] However, the present composition does not contain a crosslinking agent. As will be described later, a crosslinkable composition can be obtained by combining the present composition with a crosslinking agent.

[0062] The composition can be prepared by mixing the above 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 components may be molded. Specific examples of molding methods for the mixture include compression molding, injection molding, extrusion molding, calendar molding, and dissolving the mixture in a solvent and dipping or coating it onto a substrate or the like.

[0063] <Storage Modulus> The composition exhibits a predetermined storage modulus. The measuring device may be a device capable of measuring the storage modulus, such as a PREMER RPA (manufactured by Alpha Technologies, die shape: D0380). The measurement is preferably performed using a sheet of the composition (thickness: approximately 3 mm). The measurement procedure involves holding the sheet of the composition at 100°C, a frequency of 30 cpm, and an amplitude angle of 0.2 deg for 2 minutes, then reducing the amplitude angle to 0.5 deg and increasing the frequency to 10 cpm, 20 cpm, and 50 cpm, and measuring the storage modulus. The storage modulus at a frequency of 50 cpm is the storage modulus of the composition.

[0064] The storage modulus of the composition at 100° C. is 650 kPa or less, and is preferably 50 to 600 kPa, particularly preferably 400 to 600 kPa, in that the effects of the present invention are more excellent.

[0065] [Crosslinkable composition (first embodiment)] The crosslinkable composition of the first embodiment of the present invention (hereinafter also referred to as "the present crosslinkable composition 1") is obtained by combining the present composition with a crosslinking agent. In other words, the present crosslinkable composition 1 is a crosslinkable composition containing the present composition and further a crosslinking agent. The configuration of the present composition is as described above.

[0066] <Crosslinking Agent> Specific examples of the crosslinking agent contained in the present crosslinkable composition 1 include organic peroxides and compounds having two or more amino groups (hereinafter also referred to as "polyamine compounds"). Polyamine compounds are preferred in terms of excellent crosslinkability of the copolymer (A).

[0067] 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. However, in terms of the effects of the present invention being more excellent, 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 copolymer (A).

[0068] 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. Of these, BOAP is preferred because it provides superior effects for the present invention.

[0069] The content of the crosslinking agent in the present crosslinkable composition 1 is preferably 0.3 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, and particularly preferably 0.5 to 3 parts by mass, relative to 100 parts by mass of the copolymer (A). When the content of the crosslinking agent is within the above range, the effects of the present invention are more excellent.

[0070] [Crosslinkable Composition (Second Embodiment)] The crosslinkable composition of the second embodiment of the present invention (hereinafter also referred to as "the present crosslinkable composition 2") contains copolymer (A), copolymer (B), and further a crosslinking agent. Furthermore, in the present crosslinkable composition 2, a crosslinked rubber article obtained from the present crosslinkable composition 2 exhibits a recovery of less than 80% in a recovery force test after being compressed at 200°C for 70 hours under a 25% compression state. The crosslinked rubber article obtained using the present crosslinkable composition 2 is less likely to adhere to the target object. While the details of why the configuration of the present crosslinkable composition 2 achieves a predetermined effect are unclear, if the recovery of a crosslinked rubber article obtained from the present crosslinkable composition 2 containing a predetermined component is less than a predetermined value, the crosslinked rubber article is likely to return to its pre-pressure state when pressure is released. When a crosslinked rubber article exhibiting such characteristics is used in a pressure-sensitive component such as an O-ring, it is likely to return to its original state when pressure is released, thereby reducing the area of ​​contact between the crosslinked rubber article and the target object, thereby reducing adhesion.

[0071] The definitions and preferred embodiments of the copolymer (A), copolymer (B), and crosslinking agent contained in the present crosslinkable composition 2 are the same as those described for the present composition and the present crosslinkable composition 1. The content of copolymer (A) in the present crosslinkable composition 2 is preferably 60 to 99 mass%, more preferably 70 to 95 mass%, and particularly preferably 80 to 90 mass%, relative to the total mass of the present crosslinkable composition 2. The content of copolymer (B) in the present crosslinkable composition 2 is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less, relative to 100 parts by mass of copolymer (A), in terms of achieving better effects of the present invention. The content of copolymer (B) in the present crosslinkable composition 2 is preferably 0.5 parts by mass or more, more preferably 2 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more, relative to 100 parts by mass of copolymer (A), in terms of achieving better effects of the present invention. The content of the crosslinking agent in the present crosslinkable composition 2 is preferably 0.3 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, and particularly preferably 0.5 to 3 parts by mass, relative to 100 parts by mass of the copolymer (A). When the content of the crosslinking agent is within the above range, the effects of the present invention are more excellent.

[0072] The crosslinkable composition 2 may contain components other than the copolymer (A), the copolymer (B), and the crosslinking agent. Examples of such components include the specific phosphorus compound, the compound represented by formula (9), and the above-mentioned "other components" that the composition may contain. The content of the specific phosphorus compound in the crosslinkable composition 2 is preferably 0.01 parts by mass or more, more preferably 0.10 parts by mass or more, relative to 100 parts by mass of the copolymer (A) in order to further suppress the occurrence of cracks in the crosslinked rubber article obtained from the crosslinkable composition 2. The content of the specific phosphorus compound in the crosslinkable composition 2 is preferably 0.20 parts by mass or more, relative to 100 parts by mass of the copolymer (A) in order to further enhance the effects of the present invention. The content of the specific phosphorus compound in the crosslinkable composition 2 is preferably 5 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1.0 part by mass or less, relative to 100 parts by mass of the copolymer (A). The content of the compound represented by formula (9) in the present crosslinkable composition 2 is preferably 0.1 to 5 parts by mass, and more preferably 1 to 3 parts by mass, relative to 100 parts by mass of copolymer (A), in terms of more excellent effects of the present invention. When the present crosslinkable composition 2 contains the above-mentioned "other components," the total content of the other components is preferably more than 0.1 part by mass and not more than 30 parts by mass, more preferably 1 to 15 parts by mass, and particularly preferably 3 to 5 parts by mass, relative to 100 parts by mass of copolymer (A).

[0073] A crosslinked rubber article obtained from this crosslinkable composition 2 was compressed at 25% compression for 70 hours at 200°C, and the recovery rate in a recovery force test was less than 80%. Since the effects of the present invention are more excellent, a recovery rate of 60% or less is preferred, and a recovery rate of 50% or less is particularly preferred. The lower limit of the recovery rate is 0%. The recovery rate varies depending on the content ratio of copolymer (A) and copolymer (B), the content of each unit in copolymer (A) and copolymer (B), and the content and type of crosslinking agent. Specifically, the recovery rate was measured by compressing the crosslinked rubber article in an oven at 200°C for 70 hours at 25% compression using a jig. The sample was then removed from the oven and left at room temperature for 24 hours with the test piece still sandwiched between the jig. The jig was then removed, and the thickness of the test piece was measured after 30 minutes had passed. The recovery rate (%) was calculated using the following formula and evaluated. Recovery (%) = (thickness of test specimen before test - thickness of test specimen after test) ÷ (original thickness of test specimen - thickness of spacer) × 100 The jig and measurement method used above conform to ASTM-D395, except for the time when the jig was removed.

[0074] [Crosslinked Rubber Article] The crosslinked rubber article of the present invention is an article obtained from the above-mentioned crosslinkable composition (hereinafter, "Present Crosslinkable Composition 1" and "Present Crosslinkable Composition 2" will also be collectively referred to simply as "Present Crosslinkable Composition"). As a method for crosslinking the copolymer (A) in the present crosslinkable composition, a method in which the present crosslinkable composition is heated is preferred. Specific examples of crosslinking methods by heating include hot press crosslinking, steam crosslinking, and hot air crosslinking. Any of these methods may be appropriately selected taking into consideration the shape and application of the present crosslinkable composition. The heating conditions are preferably 100 to 400°C for 1 second to 24 hours.

[0075] The crosslinked rubber obtained by heating the crosslinkable 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.

[0076] As a crosslinking method other than crosslinking the present crosslinkable composition by heating, there is a method of crosslinking the present crosslinkable composition by irradiating it with radiation, specific examples of which include electron beams and ultraviolet rays.

[0077] The adhesive strength of the crosslinked rubber article is preferably 23 kgf or less, more preferably 20 kgf or less, and even more preferably 10 kgf or less. When the adhesive strength is 23 kgf or less, the crosslinked rubber article is less likely to adhere to movable members such as doors and lids of semiconductor devices, making it less likely that the movable members will have difficulty moving. The adhesive strength can be measured by the method shown in the Examples.

[0078] <Applications> Crosslinked rubber articles are suitable as materials for O-rings, sheets, gaskets, oil seals, diaphragms, V-rings, and the like. 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 paints, sealing materials for urea-resistant greases, and the like, rubber paints, adhesive rubbers, hoses, tubes, calendered sheets (rolls), sponges, rubber rolls, oil drilling components, heat-dissipating sheets, solution-crosslinked bodies, rubber sponges, bearing seals (urea-resistant grease, 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-proofing agents, vibration-damping agents, sealants, additives for other materials, and toys.

[0079] The present invention will be described in detail below with reference to examples. Examples 4, 5, and 9 are working examples, and Examples 1 to 3, 6 to 8, and 10 are comparative examples. However, the present invention is not limited to these examples. The blending amounts of each component in the tables below are based on mass.

[0080] [Measurement of Composition of Fluorine-Containing Copolymer] The content (mol %) of each unit in the copolymers (A-1) to (A-4) described below was １９The content of propylene units was calculated by F-nuclear magnetic resonance (NMR) analysis. １ H and １３ The content (mol%) of each unit in the copolymer (B-1) described below was calculated by melt NMR analysis and fluorine content analysis. However, the content of the NAH unit was calculated by the following infrared absorption spectroscopy analysis. (Infrared absorption spectroscopy analysis) The copolymer (B-1) described below was press-molded to obtain a 200 μm film. In the infrared absorption spectrum, the absorption peaks of the units based on NAH in the copolymer (B-1) 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 The proportion of units based on NAH in the copolymer (B-1) was determined using the formula:

[0081] [Storage Modulus] A PREMER RPA (manufactured by Alpha Technologies, die shape: D0380) was used as the measuring device. A 3 mm thick sheet-like measurement sample (weight approximately 10 g) was prepared using the fluorine-containing copolymer composition used in each example, and the sheet-like measurement sample was sandwiched between two polyester films (ALFA Technologies PART # F0311-S, 130 mm x 130 mm x 24 μm), and the measurement sample sandwiched between the polyester films was placed on the die. The die temperature was set to 100 ° C. Next, the sheet-like measurement sample was held at 100 ° C., a frequency of 30 cpm, and an amplitude angle of 0.2 deg for 2 minutes, after which the amplitude angle was set to 0.5 deg, and the frequency was increased to 10 cpm, 20 cpm, and 50 cpm, and the storage modulus was measured. The storage modulus at a frequency of 50 cpm was taken as the storage modulus of the fluorine-containing copolymer composition. The results are shown in Table 1 under the column "Storage modulus (kPa)".

[0082] [Recovery] A crosslinked rubber article (an O-ring (size: P-26) described below) was used as a test specimen to measure recoverability. Specifically, the crosslinked rubber article was compressed in an oven at 200°C for 70 hours at 25% compression using a jig, and then the jig holding the test specimen was removed from the oven and left at room temperature for 24 hours with the test specimen still held between the jigs. The test specimen was then removed from the jig, and the thickness of the test specimen was measured after 30 minutes had passed, and the recovery rate was evaluated as recoverability (%). The results are shown in the "Recovery (%)" column in Table 1. Recoverability (%) = (thickness of test specimen before test - thickness of test specimen after test) ÷ (original thickness of test specimen - thickness of spacer) × 100. The jig and measurement method used above conformed to ASTM-D395, except for the time when the jig was removed.

[0083] [Adhesion] The surface of the O-ring to be used was wiped with water, and the aluminum jig to be used was wiped with acetone. Next, the O-ring was sandwiched between two A6061 plates (aluminum plates) via a spacer (thickness 2.625 mm), compressed at a compression rate of 25%, and left at 200°C for 24 hours. A TABAI inert oven, model IHPS-222, was used as the oven. The sample was removed from the oven and cooled while still compressed at 25%. The pressure was then released, and the sample was left in a constant temperature environment of 23°C and 50% humidity for 24 hours. The aluminum plate was then peeled off using the following equipment and test conditions, and the maximum point load (kgf) was used as the adhesion force. The results are shown in the "Adhesion Force (kgf)" column of Table 1. Test conditions: Peeling speed 5 mm / min. Equipment: Strograph, manufactured by Toyo Seiki Seisakusho Co., Ltd.: STROGRAPH-R2 Load cell: 981N RCT-100KR-AF Range: x 2

[0084] [Production of Copolymer (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 ２ F ５ OCF ２ CF ２ OCF ２ COONH ４880 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.

[0085] 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., the polymerization reaction was stopped, and a latex containing a fluorine-containing copolymer was obtained. The polymerization time was 375 minutes. The total added masses of the post-added monomers were 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 (hereinafter referred to as "copolymer (A-1)"). The content (molar ratio) of each unit in the resulting copolymer (A-1) was TFE unit:PMVE unit:8CNVE unit=70.9:28.6:0.5.

[0086] [Production of Copolymer (A-2)] Copolymer (A-2) was obtained in the same manner as in the above [Production of Copolymer (A-2)] except for changing the amounts of the raw materials used. The content (molar ratio) of each unit in the obtained copolymer (A-2) was TFE unit:PMVE unit:8CNVE unit=64.4:35.1:0.5.

[0087] [Production of Copolymer (A-3)] A stainless steel pressure reactor having an internal volume of 20 L and equipped with an anchor blade was degassed, and then 8.2 L of ultrapure water and C２ F ５ OCF ２ CF ２ OCF ２ COONH ４733 g of a 30% by mass solution of 10.0 g of C3DVE, 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, 198 g of TFE and 454 g of PMVE were pressure-charged into the vessel after the internal temperature reached 80°C. The pressure inside the reactor was 0.90 MPa [gauge]. 40 mL of a 1% by mass aqueous solution of ammonium persulfate was added to initiate polymerization. The molar ratio of the monomers (hereinafter referred to as initial monomers) pressure-charged before the start of polymerization was TFE:PMVE:C3DVE = 41.74:57.64:0.61. As the polymerization progressed, 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 62 g of PMVE was also injected every time 80 g of TFE was injected. In addition, 7.0 g of 1,4-diiodoperfluorobutane was injected into the reactor together with 50 mL of ultrapure water from the ampoule tube when 60 g of TFE was injected. When the total added mass of TFE reached 1,200 g, the addition of the monomer injected after the start of polymerization (hereinafter referred to as "post-added monomer") was stopped, and the internal temperature of the reactor was cooled to 10°C to terminate the polymerization reaction, thereby obtaining a latex containing a fluorine-containing copolymer. The polymerization time was 360 minutes. The total mass of the post-added monomers was 1200 g of TFE and 868 g of PMVE, which was converted to a molar ratio of TFE:PMVE = 68:32. Nitric acid (Kanto Chemical Co., Ltd., special grade) was dissolved in ultrapure water to prepare a 3 mass% aqueous solution of nitric acid. The latex was added to the nitric acid aqueous solution in a TFE / perfluoro(alkyl vinyl ether) copolymer (PFA) container to coagulate the fluorine-containing copolymer. The amount of the nitric acid aqueous solution was 150 parts by mass per 100 parts by mass of the fluorine-containing copolymer in the latex. The coagulated fluorine-containing copolymer was recovered by filtration, poured into ultrapure water in a PFA container, and washed by stirring at 200 rpm for 30 minutes. The amount of ultrapure water was 100 parts by mass per 100 parts by mass of the fluorine-containing copolymer. The above washing was repeated 10 times. The washed fluorocopolymer was recovered by filtration and dried at 50° C. under reduced pressure of 10 kPa to obtain copolymer (A-3).The molar ratio of the individual units in the copolymer (A-3) was TFE units:PMVE units:C3DVE units=69.91:29.96:0.13, and the content of iodine atoms was 0.10% by mass.

[0088] [Production of Copolymer (A-4)] A stainless steel pressure reactor having an internal volume of 2,100 mL and equipped with an anchor blade was degassed, and then 804 g of ultrapure water, C ２ F ５ OCF ２ CF ２ OCF ２ COONH ４80.1 g of a 30% by weight solution of 1,4-diiodoperfluorobutane, 0.72 g of C3DVE, 1.8 g of a 5% by weight aqueous solution of disodium hydrogen phosphate dodecahydrate, and 0.87 g of 1,4-diiodoperfluorobutane were charged, and the gas phase was replaced with nitrogen. While stirring at a speed of 600 rpm using an anchor blade, 13 g of TFE and 65 g of PMVE were pressure-charged into the vessel once the internal temperature reached 80°C. The pressure inside the reactor was 0.90 MPa [gauge]. 20 mL of a 1% by weight aqueous solution of ammonium persulfate was added, and polymerization was initiated. The molar ratio of the monomers (hereinafter referred to as initial monomers) pressure-charged prior to the start of polymerization was TFE:PMVE:C3DVE = 25:75:0.19. As the polymerization progressed, when the reactor internal pressure dropped to 0.89 MPa [gauge], TFE was injected, and the reactor internal pressure was increased to 0.90 MPa [gauge]. This was repeated, and 7 g of PMVE was also injected every time 8 g of TFE was injected. When the total added mass of TFE reached 80 g, the addition of the monomer injected after the start of polymerization (hereinafter referred to as "post-added monomer") was stopped, and the internal temperature of the reactor was cooled to 10 ° C. to terminate the polymerization reaction, thereby obtaining a latex containing a fluorine-containing copolymer. The polymerization time was 185 minutes. The total added mass of the post-added monomers was 80 g of TFE and 63 g of PMVE, which was converted to a molar ratio of TFE:PMVE = 65:35. Nitric acid (manufactured by Kanto Chemical Co., Ltd., special grade) was dissolved in ultrapure water to prepare a 3 mass% aqueous solution of nitric acid. The latex was added to an aqueous nitric acid solution in a TFE / perfluoro(alkyl vinyl ether) copolymer (PFA) container to coagulate the fluorine-containing copolymer. The amount of the aqueous nitric acid solution was 150 parts by mass per 100 parts by mass of the fluorine-containing copolymer in the latex. The coagulated fluorine-containing copolymer was recovered by filtration, poured into ultrapure water in a PFA container, and washed by stirring at 200 rpm for 30 minutes. The amount of ultrapure water was 100 parts by mass per 100 parts by mass of the copolymer. Washing was repeated 10 times. The washed fluorine-containing copolymer was recovered by filtration and dried at 50°C and reduced pressure at 10 kPa to obtain a white copolymer (A-4).The molar ratio of the individual units in the fluorine-containing copolymer (A-4) was TFE units:PMVE units:C3DVE units=65.88:33.94:0.18, and the iodine atom content was 0.15% by mass.

[0089] [Production of Copolymer (B-1)] The "fluorine-containing copolymer (X1-1)" in the Examples section of WO 2016 / 017801 was pulverized using a jet mill and used as copolymer (B-1). The molar ratio of each unit in copolymer (B-1) was NAH unit:TFE unit:PPVE unit = 0.1:97.9:2.0. Copolymer (B-1) is a resin particle having a melting point of 310°C and an average particle size (D50) of 2 to 3 μm.

[0090] Examples 1 to 10 The components and amounts (parts by mass) shown in Table 1 were mixed and kneaded for 10 minutes at room temperature using a two-roll mill to obtain a mixed fluorine-containing copolymer composition. Furthermore, the fluorine-containing copolymer composition and a crosslinking agent were mixed using a two-roll mill with the components and amounts shown in Table 1 to obtain a crosslinkable composition. For example, in Example 4, copolymer (A-2), copolymer (B-1), and TOCP were mixed to obtain a fluorine-containing copolymer composition, and this was further mixed with BOAP (crosslinking agent) to obtain a crosslinkable composition. The obtained crosslinkable composition was hot-pressed using a hydraulic press (model: SA-301 50T type, manufactured by Tester Sangyo Co., Ltd., ram diameter: 180 mm) under the following conditions to obtain an O-ring (size: P-26) (primary crosslinking). The primary crosslinking in Examples 1 to 4 and 9 was all performed by hot pressing at 180°C for 20 minutes. The primary crosslinking in Examples 5 to 8 was performed by hot pressing at 150°C for 20 minutes. The primary crosslinking in Example 10 was performed by hot pressing at 170°C for 10 minutes. The O-rings were then heated in an oven under a nitrogen atmosphere under the following conditions (secondary crosslinking). The secondary crosslinking in Examples 1 to 4 and 9 was performed by heating at 90°C for 2 hours, then increasing the temperature to 200°C over 2 hours and holding at 200°C for 4 hours. The secondary crosslinking was performed by further increasing the temperature to 305°C over 2 hours and then heating at 305°C for 13 hours. The secondary crosslinking in Examples 5 to 8 was performed by heating at 250°C for 4 hours. The secondary crosslinking in Example 10 was performed by heating at 200°C for 24 hours. The O-rings were then cooled to room temperature to obtain the O-rings of Examples 1 to 10. The O-rings correspond to crosslinked rubber articles. The above-mentioned physical properties were measured using the obtained O-rings. The measurement results are shown in Table 1.

[0091] The components listed in Table 1, excluding fluorine-containing copolymers (A-1) to (A-4) and (B-1), are summarized below. Copolymer (A-5) (fluorine content 66% by mass, median Mooney viscosity (ML1+10 121°C) of 53, specific gravity 1.83 g / cm ３ , ternary FKM (TFE / VdF / HFP copolymer)) TOCP: manufactured by Hokko Chemical Industry Co., Ltd., tri-n-octylphosphine (liquid at 20°C), specific phosphorus compound C6-DV: manufactured by Tosoh Finechem Co., Ltd., CH ２ =CH-(CF ２) ６ -CH=CH ２ TAIC: Trade name, manufactured by Mitsubishi Chemical Corporation, triallyl isocyanurate. BOAP: 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, polyamine compound (crosslinking agent). P-25B (Perhexa 25B): Trade name, manufactured by NOF Corporation, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, organic peroxide (crosslinking agent).

[0092]

[0093] As shown in the table, it was confirmed that the effects of the present invention can be obtained by using this composition. When the adhesion force of the O-ring is 23 kgf or less, it is difficult for it to adhere to the aluminum plate used in measuring adhesion. The O-ring of Example 10 did not separate from the aluminum plate used in measuring adhesion. This was a similar phenomenon to the O-ring of Example 8. The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2023-221216, filed on December 27, 2023, are hereby incorporated by reference as the disclosure of the specification 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), and 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 formula (X), units based on tetrafluoroethylene, and units based on perfluoro(alkyl vinyl ether), wherein the storage elastic modulus at 100 °C is 650 kPa or less. Formula (X): *-CO-O-CO-*, where * represents the bonding position.

2. The fluorine-containing copolymer composition according to claim 1, wherein the fluorine-containing copolymer (A) has units having a nitrile group, and the content of the units having a nitrile group is 0.14 mol% or more and less than 0.7 mol% based on all the units of the fluorine-containing copolymer (A).

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

4. The fluorine-containing copolymer composition according to claim 1 or 2, further comprising a compound represented by formula (9). H ２ C=CH-R ９１ -R ９３ -R ９２ -CH=CH ２ Formula (9) R ９１ and R ９２ each independently represents CH ２ or CF ２ and R ９３ represents a divalent fluorohydrocarbon group having 1 to 10 carbon atoms, or a group having an etheric oxygen atom at the terminal or between carbon-carbon bonds of the fluorohydrocarbon group.

5. The fluorine-containing copolymer composition according to claim 4, wherein the content of the compound represented by formula (9) is 0.1 to 5 parts by mass with respect to 100 parts by mass of the fluorine-containing copolymer (A).

6. The fluorine-containing copolymer composition according to claim 1 or 2, further comprising a phosphorus compound having a melting point of 60 °C or less.

7. The fluorine-containing copolymer composition according to claim 6, wherein the content of the phosphorus compound is 0.2 to 5 parts by mass with respect to 100 parts by mass of the fluorine-containing copolymer (A).

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

9. A crosslinkable composition comprising the fluorine-containing copolymer composition according to claim 1 and further a crosslinking agent.

10. The crosslinkable composition according to claim 9, wherein the crosslinking agent is a compound having two or more amino groups.

11. The crosslinkable composition according to claim 9, wherein 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).

12. A fluorine-containing copolymer (A) having units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether); a fluorine-containing copolymer 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); a crosslinking agent; a crosslinkable composition, wherein the crosslinkable composition has a recovery property of less than 80% in a recovery force test after compression at 200 °C for 70 hours in a 25% compressed state of a crosslinked rubber article obtained from the crosslinkable composition. Formula (X) *-CO-O-CO- * In formula (X), * represents a bonding position.

13. A crosslinked rubber article obtained from the crosslinkable composition according to claim 9 or 12.

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