Crosslinked rubber article and composition

Abstract

This crosslinked rubber article comprises a crosslinked body obtained by crosslinking a fluorine-containing elastomer, wherein the volume swelling rate, which represents the volume change rate after immersion relative to the volume before immersion when immersed in CF3(CF2)5CH2CH3 at 25°C for 70 hours, is greater than 66.0%.

Description

Crosslinked rubber articles and compositions

[0001] This disclosure relates to crosslinked rubber articles and compositions.

[0002] Cross-linked rubber products are used in a variety of industrial fields and applications due to their excellent heat resistance, chemical resistance, flame retardancy, and weather resistance.

[0003] For example, Patent Document 1 discloses a perfluoroelastomer sealant in which the weight loss rate of the sealant measured under specific conditions is 1% by weight or less, and the adhesion strength, as well as contamination, corrosion, and discoloration of the contact surface with the sealant, are improved.

[0004] Patent Document 2 discloses a fluorine-containing elastic copolymer composition for use as a paint or adhesive, which has excellent solubility in solvents, is easy to remove the solvent from, the solvent is readily available, and the additives are dispersed without applying excessive shear force.

[0005] International Publication No. 2005 / 028547, International Publication No. 2019 / 073934

[0006] However, there is a need to develop new crosslinked rubber articles with properties more suitable for desired applications. This disclosure is made in view of the above, and relates to a crosslinked rubber article that maintains rubber properties while also exhibiting excellent adhesion to polyethylene, and a composition from which such a crosslinked rubber article can be obtained.

[0007] This disclosure includes the following aspects: <1> A crosslinked body comprising a fluorine-containing elastomer, CF ３ (CF ２ ) ５ CH ２ CH ３The volume swelling ratio, which represents the change rate of the volume after immersion with respect to the volume before immersion when immersed at 25°C for 70 hours, is greater than 66.0%, a crosslinked rubber article. <2> The fluorine-containing elastomer contains a structural unit based on tetrafluoroethylene and a structural unit based on perfluoroalkyl vinyl ether, the crosslinked rubber article according to <1>. <3> The crosslinked body contains a structure based on a peroxide, the crosslinked rubber article according to <1> or <2>. <4> The crosslinked body contains a structure based on a compound having two or more allyl groups in one molecule, the crosslinked rubber article according to any one of <1> to <3>. <5> Further containing a filler, the crosslinked rubber article according to any one of <1> to <4>. <6> Further containing a fatty acid metal salt, the crosslinked rubber article according to any one of <1> to <5>. <7> Substantially free of an emulsifier having a fluorine atom, the crosslinked rubber article according to any one of <1> to <6>. <8> Further, a part or all of the surface has CF ３ (CF ２ ) ５ CH ２ CH ３ attached thereto, the crosslinked rubber article according to any one of <1> to <7>. <9> The density when immersed in CF ３ (CF ２ ) ５ CH ２ CH ３ at 25°C for 70 hours is 1.82 g / cm ３ or less, the crosslinked rubber article according to any one of <1> to <8>. <10> An O-ring, the crosslinked rubber article according to any one of <1> to <9>. <11> Containing a fluorine-containing elastomer having an iodine atom and a crosslinking agent, and the iodine crosslinking efficiency calculated by the following formula (5) is 5.0 or more when the fluorine-containing elastomer is crosslinked. Composition. Iodine crosslinking efficiency (ppm / dN·m) = [iodine content] / [M Ｈ - M Ｌ …(5) [In formula (5), [iodine content] represents the content (ppm by mass) of iodine atoms with respect to the mass of the fluorine-containing elastomer. M Ｈ is the maximum value (dN·m) of the torque in the crosslinking curve of the composition showing the relationship between torque and time. MＬ This is the minimum torque (dN·m) in the crosslinking curve. ] <12> The composition according to <11>, wherein the fluorine-containing elastomer comprises a structural unit based on tetrafluoroethylene and a structural unit based on perfluoroalkyl vinyl ether. <13> The composition according to <11> or <12>, substantially free of an emulsifier having a fluorine atom.

[0008] According to this disclosure, a crosslinked rubber article that maintains rubber properties while also exhibiting excellent adhesion to polyethylene, and a composition for obtaining the said crosslinked rubber article are provided.

[0009] One embodiment of this disclosure is described in detail below. However, this disclosure is not limited to the embodiment described below. In the following disclosure, the components (including elemental steps, etc.) are not essential unless otherwise explicitly stated. The same applies to numerical values ​​and their ranges, and do not limit this disclosure.

[0010] In this disclosure, numerical ranges indicated using "~" include the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages in this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Also, in numerical ranges described in this disclosure, the upper or lower limit of that range may be replaced with the values ​​shown in the examples. In this disclosure, each component may contain multiple types of the corresponding substance. If multiple types of the substance corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple types of substances present in the composition, unless otherwise specified. In this disclosure, each component may contain multiple types of particles. If multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for the mixture of the multiple types of particles present in the composition, unless otherwise specified. In this disclosure, "elastomer" means a material exhibiting the properties defined in JIS K 6200:2008 (ISO 1382:2012), and is distinguished from "resin."

[0011] ≪Cross-linked rubber articles≫ The cross-linked rubber articles of this disclosure include a cross-linked body formed by cross-linking a fluorine-containing elastomer, CF ３ (CF ２ ) ５ CH ２ CH ３ When immersed at 25°C for 70 hours, the volume swelling rate, which represents the percentage change in volume after immersion relative to the volume before immersion, is greater than 66.0%.

[0012] The crosslinked rubber articles disclosed herein are CF ３ (CF ２ ) ５ CH ２ CH ３ When immersed at 25°C for 70 hours, the volume swelling rate, which represents the percentage change in volume after immersion relative to the volume before immersion, is greater than 66.0%. In other words, the crosslinked rubber article of this disclosure has a low crosslink density, and the crosslinked rubber article is CF ３ (CF ２ ) ５ CH ２ CH ３ When immersed in, more CF ３ (CF ２ ) ５ CH ２ CH ３ It is easy for foreign matter and impurities to penetrate into the cross-linked rubber article, causing the cross-linked rubber article to swell, and the volume swelling rate becomes greater than 66.0%. Furthermore, surprisingly, the cross-linked rubber article of this disclosure exhibits excellent adhesion to polyethylene while maintaining rubber properties (more specifically, low variation in compression set), and is suitable, for example, as a sealing material. In addition, the cross-linked rubber article of this disclosure is treated with CF to remove foreign matter and impurities adhering to its surface. ３ (CF ２ ) ５ CH ２ CH ３ The surface can be cleaned using a cleaning agent, and the product can be temporarily placed on a polyethylene sheet or the like before use. In this case, the cross-linked rubber article of this disclosure, after being cleaned and swollen, maintains its rubber properties while also exhibiting excellent adhesion to polyethylene.

[0013] In this disclosure, "excellent adhesiveness" means that the material exhibits excellent adhesion in adhesive strength tests and also has excellent peelability. In other words, the crosslinked rubber articles of this disclosure that exhibit excellent adhesiveness to polyethylene can easily adhere to polyethylene and can also be easily peeled off.

[0014] <Crosslinked material> The crosslinked rubber articles of this disclosure include a crosslinked material obtained by crosslinking a fluorine-containing elastomer. The crosslinked material may be a single material or a combination of two or more materials. The crosslinked fluorine-containing elastomer may be a single material or two or more materials.

[0015] [Fluorine-containing elastomers] (Constituent units) From the viewpoint of excellent chemical resistance, electrical insulation, and steam resistance, fluorine-containing elastomers preferably contain constituent units based on at least one monomer selected from the group consisting of tetrafluoroethylene (hereinafter also referred to as "TFE"), fluorine-containing vinyl ether, vinylidene fluoride (hereinafter also referred to as "VdF"), and hexafluoropropylene (hereinafter also referred to as "HFP"). Furthermore, fluorine-containing elastomers may also contain constituent units based on a monomer of propylene (hereinafter also referred to as "Pr").

[0016] From the viewpoint of excellent polymerization reactivity, fluorine-containing vinyl ethers are preferably compounds represented by the following formula (1): CX １１ X １２ = CX １３ -O-(CX) １４ X １５ ) ｍ１ -L １ - (CX １６ X １７ ) ｎ１ -A １ ...(1) In formula (1), X １１ ~X １７ Each of these is independently a hydrogen atom, a fluorine atom, or a fluoroalkyl group, and X １１ ~X １７ At least one of them is a fluorine atom or a fluoroalkyl group, m1 is an integer from 1 to 10, n1 is an integer from 0 to 10, L １ A is a single bond or a divalent linking group.１ This is an ionic group, a salt of an ionic group, a hydrogen atom, or a fluorine atom.

[0017] X １１ ~X １７ A fluorine atom is preferred.

[0018] m1 is preferably 1 to 6, and more preferably 1 to 3. n1 is preferably 0.

[0019] L １ The divalent linking groups represented by are alkylene groups, -CH=CH-, -C≡C-, -O-, -S-, -C(=O)-, -C(=O)O-, -OC(=O)-, and -CONR １１ -, -NR １２ C(=O)- and combinations thereof are preferred. １１ and R １２ Each of these is independently either a hydrogen atom or an alkyl group. １ A single bond is preferred.

[0020] A １ The ionic group represented by may be an anionic group or a cationic group. An anionic group is, for example, -SO ３ H, -OSO ３ H, -P(=O)(OH) ２ , -OP(=O)(OH) ２ Alternatively, -C(=O)OH can be used. Examples of cationic groups include ammonium groups, pyridinium groups, pyrrolidinium groups, and amino groups. A １ Hydrogen atoms or fluorine atoms are preferred.

[0021] Among these, fluorine-containing vinyl ethers are preferred, specifically compounds represented by the following formula (1A): CF ２ =CF-O-R ｆ１ ...(1A) In formula (1A), R ｆ１ R represents a fluoroalkyl group having 1 to 10 carbon atoms. ｆ１ From the viewpoint of superior polymerization reactivity, the number of carbon atoms is preferably 1 to 8, more preferably 1 to 6, even more preferably 1 to 5, and particularly preferably 1 to 3. The fluoroalkyl group may be linear or branched, and a perfluoroalkyl group is preferred.

[0022] Of the fluorinated vinyl ethers, perfluoroalkyl vinyl ethers are preferred.

[0023] Examples of perfluoroalkyl vinyl ethers (hereinafter also referred to as "PAVE") include perfluoromethyl vinyl ether (hereinafter also referred to as "PMVE"), perfluoroethyl vinyl ether (hereinafter also referred to as "PEVE"), and perfluoropropyl vinyl ether (hereinafter also referred to as "PPVE"). From the viewpoint of excellent polymerization reactivity, PMVE or PPVE is preferred as PAVE, and PMVE is more preferred.

[0024] In other words, it is preferable that the fluorine-containing elastomer contains structural units based on at least one monomer selected from the group consisting of TFE, PAVE, VdF, and HFP. From the viewpoint of excellent heat resistance, chemical resistance, electrical insulation, and steam resistance, it is more preferable that the fluorine-containing elastomer contains structural units based on at least one monomer selected from the group consisting of TFE, PAVE, and VdF, even more preferable that it contains structural units based on at least one monomer selected from the group consisting of TFE and PAVE, and particularly preferable that it contains structural units based on monomers of TFE and PAVE.

[0025] The fluorine-containing elastomer is preferably a TFE / PAVE copolymer (i.e., FFKM), a TFE / Pr copolymer (i.e., a binary FEPM), a TFE / Pr / VdF copolymer (i.e., a ternary FEPM), a TFE / HFP / VdF copolymer (i.e., a ternary FKM), or an HFP / VdF copolymer (i.e., a binary FKM).

[0026] The copolymerization composition of TFE / PAVE copolymers is preferably a molar ratio of TFE-based constituent units to PAVE-based constituent units of 80 / 20 to 20 / 80. The copolymerization composition of TFE / Pr copolymers is preferably a molar ratio of TFE-based constituent units to Pr-based constituent units of 80 / 20 to 20 / 80. The copolymerization composition of TFE / Pr / VdF copolymers is preferably a molar ratio of TFE-based constituent units to Pr-based constituent units to VdF-based constituent units of 50 / 20 / 30 to 10 / 40 / 50. The copolymerization composition of TFE / HFP / VdF copolymers is preferably a molar ratio of TFE-based constituent units to HFP-based constituent units to VdF-based constituent units of 10 / 10 / 80 to 30 / 20 / 50. The copolymerization composition of the HFP / VdF copolymer is preferably one in which the molar ratio of HFP-based constituent units to VdF-based constituent units is 5 / 95 to 40 / 60.

[0027] From the viewpoint of excellent chemical resistance, electrical insulation, and steam resistance, the total content of constituent units based on TFE, fluorinated vinyl ether, VdF, and HFP is preferably 30 to 100 mol%, more preferably 40 to 95 mol%, and even more preferably 50 to 90 mol% relative to the total amount of fluorinated elastomer.

[0028] When the fluorine-containing elastomer contains constituent units based on TFE, fluorine-containing vinyl ether, VdF, or HFP, the content of each of the constituent units based on TFE, fluorine-containing vinyl ether, VdF, or HFP is preferably 10 to 100 mol%, more preferably 10 to 90 mol%, and more preferably 20 to 80 mol% relative to the total amount of the fluorine-containing elastomer.

[0029] The fluorine-containing elastomer may contain a structural unit based on a monomer other than TFE, fluorine-containing vinyl ether, VdF, and HFP. Examples of the other monomers include α-olefins such as ethylene and butene (e.g., Pr), vinyl ethers such as methyl vinyl ether and ethyl vinyl ether, and a monomer having two or more polymerizable unsaturated bonds (hereinafter also referred to as "BO"). The other monomers may be used alone or in combination of two or more. The content of the structural unit based on the other monomers is preferably 0 to 50 mol%, preferably 0 to 30 mol%, and more preferably 0 to 15 mol% based on the total amount of the fluorine-containing elastomer.

[0030] BO is 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 polymerizable unsaturated bond is preferably a carbon atom-carbon atom double bond (C═C). The number of polymerizable unsaturated bonds in BO is preferably 2 to 6, more preferably 2 or 3, and still more preferably 2 from the viewpoint of more excellent polymerization reactivity. BO preferably further has a fluorine atom from the viewpoint of smaller compression set of the crosslinked rubber article at high temperature.

[0031] BO is preferably a monomer represented by the following formula (2) from the viewpoint of more excellent mold release property of the crosslinked rubber article. (CR ２１ R ２２ ═CR ２３ −) ｍ２ R ２４ …(2) In formula (2), R ２１ to R ２３ are each independently a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group, m2 is an integer of 2 to 6, R ２４ is a perfluorohydrocarbon group having 1 to 10 carbon atoms with m2 valences, or a group having an etheric oxygen atom at the terminal or between carbon-carbon bonds of the perfluorohydrocarbon group, a plurality of R ２１ , a plurality of R ２２ , and a plurality of R ２３They may be the same as or different from each other, and it is preferable that they are the same as each other. m2 is preferably 2 or 3, and more preferably 2.

[0032] From the viewpoint of more excellent polymerization reactivity of BO, R ２１ ~R ２３ is preferably a fluorine atom or a hydrogen atom, and R ２１ ~R ２３ are all preferably fluorine atoms or R ２１ ~R ２３ are all more preferably hydrogen atoms, and from the viewpoint of more excellent mold release property of the crosslinked rubber article, R ２１ ~R ２３ are all more preferably fluorine atoms. R ２４ may be linear, branched, or cyclic, is preferably linear or branched, and more preferably linear. The number of carbon atoms of R ２４ is preferably 2 to 8, more preferably 3 to 7, still more preferably 3 to 6, and particularly preferably 3 to 5. R ２４ may or may not have an etheric oxygen atom, and from the viewpoint of more excellent crosslinking reactivity and rubber physical properties, it preferably has an etheric oxygen atom. The number of etheric oxygen atoms in R ２４ is preferably 1 to 6, more preferably 1 to 3, and still more preferably 1 or 2. The etheric oxygen atom in R ２４ is preferably present at the end of R ２４ .

[0033] Among the monomers represented by the formula (2), specific examples of suitable monomers include the monomer represented by the following formula (2A) and the monomer represented by the following formula (2B).

[0034] (CF ２ =CF−) ２ R ２５ ...(2A) In the formula (2A), R ２５ is a divalent perfluorohydrocarbon group having 1 to 10 carbon atoms, or a group having an etheric oxygen atom at the end or between carbon-carbon bonds of the perfluorohydrocarbon group.

[0035] (CH ２ =CH−) ２ R２６ ...(2B) In formula (2B), R ２６ This refers to a divalent perfluorohydrocarbon 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 perfluorohydrocarbon group.

[0036] A concrete example of a monomer represented by formula (2A) is CF ２ = CFO (CF ２ ) ２ OCF = CF ２ CF ２ = CFO (CF ２ ) ３ OCF = CF ２ CF ２ = CFO (CF ２ ) ４ OCF = CF ２ CF ２ = CFO (CF ２ ) ６ OCF = CF ２、 CF ２ = CFO (CF ２ ) ８ OCF = CF ２ CF ２ = CFO (CF ２ ) ２ OCF (CF ３ ) CF ２ OCF = CF ２ CF ２ = CFO (CF ２ ) ２ O(CF(CF ３ ) CF ２ O) ２ CF = CF ２ CF ２ = CFOCF ２ O(CF) ２ CF ２ O) ２ CF = CF ２ CF ２ = CFO (CF ２ O) ３ O(CF(CF ３ ) CF ２ O) ２ CF = CF ２ CF ２ = CFOCF ２ CF (CF ３) O (CF ２ ) ２ OCF (CF ３ ) CF ２ OCF = CF ２ , and CF ２ = CFOCF ２ CF ２ O(CF) ２ O) ２ CF ２ CF ２ OCF = CF ２ Examples include: Among the monomers represented by formula (2A), a more suitable specific example of a monomer is CF ２ = CFO (CF ２ ) ３ OCF = CF ２ (Hereafter also referred to as "C3DVE"), and CF ２ = CFO (CF ２ ) ４ OCF = CF ２ (Hereafter, this will also be referred to as "C4DVE") is one example.

[0037] A concrete example of a monomer represented by formula (2B) is CH ２ =CH(CF ２ ) ２ CH=CH ２ ,CH ２ =CH(CF ２ ) ４ CH=CH ２ , and CH ２ =CH(CF ２ ) ６ CH=CH ２ Examples include CH ２ =CH(CF ２ ) ６ CH=CH ２ (Hereafter, this will also be referred to as "C6DV") is one example.

[0038] In particular, BO is preferably C3DVE or C4DVE.

[0039] (Crosslinkable Groups) Fluorine-containing elastomers preferably have structural units based on monomers having crosslinkable groups. The crosslinkable groups function as crosslinking points. The crosslinkable groups are not particularly limited as long as they are functional groups that can be crosslinked by a crosslinking reaction, and examples include cyano groups (or nitrile groups), polymerizable unsaturated bonds, chlorine atoms, bromine atoms, and iodine atoms, with iodine atoms being preferred. Fluorine-containing elastomers preferably have structural units based on monomers having the above-mentioned crosslinkable groups at least one of the terminal and side chains, and more preferably at the terminals. When producing fluorine-containing elastomers, structural units based on monomers having crosslinkable groups can be introduced by polymerization using monomers having crosslinkable groups. Alternatively, during polymerization, monomers may be polymerized using a chain transfer agent having crosslinkable groups.

[0040] As monomers having a crosslinking group, monomers having a crosslinking group that, when crosslinked, has halogen atoms (preferably iodine atoms) as crosslinking sites are preferred. Examples of monomers having a crosslinking group include iodine or bromine-containing monomers represented by the following formula (3A), and monomers represented by the following formula (3B), which may be used individually or in any combination.

[0041] CX ３１ ２ = CX ３１ -R ｆ３ CHR ３１ X ３２ ...(3A) In formula (3A), X ３１ Each of these is independently a hydrogen atom, a fluorine atom, or -CH₂ ３ And R ３１ is a hydrogen atom or -CH ３ X ３２ is an iodine atom or a bromine atom, R ｆ３ This is a fluoroalkylene group, a perfluoroalkylene group, a fluoropolyoxyalkylene group, or a perfluoropolyoxyalkylene group, and may contain an ether-bonded oxygen atom.

[0042] CF ２ = CFO (CF ２ CF (CF ３ )O)ｍ３ - (CF ２ ) ｎ３ -X ３３ …(3B) In equation (3B), m3 is an integer from 0 to 5, n3 is an integer from 1 to 3, X ３３ This is a cyano group, a carboxyl group, an alkoxycarbonyl group, or a bromine atom.

[0043] X ３２ and X ３３ The iodine atom, bromine atom, cyano group, carboxyl group, and alkoxycarbonyl group function as crosslinking points.

[0044] When the crosslinking point is an iodine atom, the monomer having the crosslinking group is preferably perfluoro-1,4-diiodobutane, 1,6-diiodoperfluorohexane, 1,8-diiodoperfluorooctane, or 1,2-diiodoperfluoroethane. When the crosslinking point is a cyano group (or nitrile group), the monomer having the crosslinking group is 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 one example, and from the viewpoint of having better release properties and heat resistance of crosslinked rubber articles, 8CNVE or MV5CN is preferred.

[0045] The content of constituent units based on monomers having crosslinkable groups is preferably 0.1 to 10 mol%, and more preferably 0.3 to 5 mol%, relative to the total amount of the fluorine-containing elastomer.

[0046] From the viewpoint of obtaining crosslinked rubber articles that maintain rubber properties while also exhibiting excellent adhesion to polyethylene, the composition of the fluorine-containing elastomer is preferably such that the constituent units based on PAVE / constituent units based on TFE / constituent units based on monomers having crosslinkable groups = 80 / 20 / 0.1 to 20 / 80 / 10 (molar ratio). The composition of the fluorine-containing elastomer can be analyzed by NMR.

[0047] From the viewpoint of excellent heat resistance, chemical resistance, electrical insulation, and steam resistance, the fluorine content is preferably 50 to 90 mol%, more preferably 55 to 80 mol%, and even more preferably 60 to 70 mol%, based on the total amount of the fluorine-containing elastomer.

[0048] Furthermore, regarding fluorine-containing elastomers, the constituent units, the molar amount of the said constituent units, and the fluorine content are as follows: １９ It can be analyzed by F-NMR analysis and infrared absorption spectroscopy.

[0049] From the viewpoint of obtaining a crosslinked rubber article that maintains rubber properties while also exhibiting excellent adhesion to polyethylene, iodine atoms are preferred as crosslinking points, and the iodine content is preferably 410 ppm by mass or more, more preferably 450 ppm by mass or more, and even more preferably 500 ppm by mass or more, relative to the total amount of the fluorine-containing elastomer. The iodine content is preferably 800 ppm by mass or less, more preferably 700 ppm by mass or less, and even more preferably 650 ppm by mass or less, relative to the total amount of the fluorine-containing elastomer. The iodine content is, for example, 500 to 650 ppm by mass, relative to the total amount of the fluorine-containing elastomer.

[0050] The iodine content can be calculated using a Vanta handheld X-ray fluorescence analyzer and the fundamental parameter method. More specifically, a solid made of fluorine-containing elastomer is heated and pressed to form a 300 μm sheet. The resulting sheet composition is subjected to X-ray fluorescence analysis using a Vanta handheld X-ray fluorescence analyzer (manufactured by EVIDENT), and the iodine content in the solid (fluorine-containing elastomer) is calculated using the fundamental parameter method.

[0051] (Method for producing fluorine-containing elastomers) Conventional known methods can be applied to produce fluorine-containing elastomers, such as emulsion polymerization, solution polymerization, suspension polymerization, and bulk polymerization. Radical polymerization initiators, redox polymerization initiators, heat, or radiation may be used for the initiation reaction. Conventional known methods can be applied to mold the fluorine-containing elastomers, such as compression molding, extrusion molding, transfer molding, and injection molding.

[0052] A method for producing a fluorine-containing elastomer may also be a method of polymerizing each monomer in the presence of a compound represented by the following formula (X) (hereinafter also referred to as "compound (X)") and an aqueous medium, under conditions where a fluorine atom-containing emulsifier is substantially absent (hereinafter also referred to as "method A"). CX １ X ２ = CX ３ -L-Z...(X) In formula (X), １ and X ２ Each of these is independently a hydrogen atom, a chlorine atom, or an alkyl group, and X ３ L is a hydrogen atom or an alkyl group, L is a single bond or a divalent linking group, and Z is an anionic group or a salt of an anionic group.

[0053] Furthermore, in manufacturing method A, by adjusting the amount of monomer units used, etc., CF ３ (CF ２ ) ５ CH ２ CH ３ A fluorine-containing elastomer can be manufactured to obtain a crosslinked rubber article of this disclosure having a volume swelling rate greater than 66.0% when immersed at 25°C for 70 hours, which represents the rate of change in volume after immersion relative to the volume before immersion.

[0054] Specific examples of aqueous media include water and mixed solvents of water and water-soluble organic solvents. Specific examples of water-soluble organic solvents include tert-butanol, propylene glycol, dipropylene glycol, dipropylene glycol monomethyl ether, and tripropylene glycol.

[0055] In formula (X), １and X ２ The alkyl group in this can be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 10, more preferably 1 to 3, and even more preferably 1. １ and X ２ From the viewpoint of increasing the number of particles of the fluorine-containing elastomer, hydrogen atoms are preferred in both cases. In formula (X), X ３ Specific examples and preferred embodiments of alkyl groups in X １ and X ２ The specific examples and preferred embodiments of alkyl groups are the same as in X. ３ From the viewpoint of increasing the number of fluorine-containing elastomer particles, hydrogen atoms are preferred.

[0056] In formula (X), L is a single bond or a divalent linking group. Examples of the above divalent linking groups include alkylene groups, carbonyl groups, ether bonds, thioether bonds, sulfonyl groups, -NH-, and -SiH. ２ -, phenylene group, -CF ２ - and groups formed by combining two or more of these are examples. Examples of groups formed by combining two or more of these include ester bonds, thioester bonds, amide bonds, sulfonamide bonds, combinations of alkylene groups and ether bonds, combinations of alkylene groups and ester bonds, and combinations of alkylene groups and amide bonds. The alkylene group may be linear, branched, or cyclic, with linear or branched being preferred, and branched being more preferred. The number of carbon atoms in the alkylene group can be, for example, 1 to 6, and 1 to 4 is preferred.

[0057] Specific examples of L include single bonds, alkylene groups, ether bonds, ester bonds, * Ｃ -CO-NH-R-* Ｚ Examples include single bonds, alkylene groups having 1 to 6 carbon atoms, and * Ｃ -CO-NH-R-* Ｚ Preferably, a single bond, an alkylene group having 1 to 2 carbon atoms, and * Ｃ -CO-NH-R-* Ｚ This is preferable. Here, * Ｃ * is the bonding site with the carbon atom in formula (X),Ｚ is the bonding site with Z in formula (X), and R is an alkylene group having 1 to 6 carbon atoms.

[0058] In formula (X), Z is an anionic group or a salt of an anionic group. An anionic group is, for example, -SO ３ H, -OSO ３ H, -P(=O)(OH) ２ , -OP(=O)(OH) ２ Alternatively, -COOH can be used. Examples of salts of anionic groups include groups in which the hydrogen ions of the above anionic group are replaced with cations other than hydrogen ions.

[0059] Examples of cations include metal ions, ammonium ions, imidazolium cations, pyrrolidinium cations, pyridinium cations, piperidinium cations, and phosphonium cations. Examples of metal ions include alkali metal ions such as sodium ions, potassium ions, and lithium ions; and alkaline earth metal ions such as calcium ions and magnesium ions.

[0060] Z is -SO ３ M, -OSO ３ M, -P (=O) (OM) ２ , -OP(=O)(OM) ２ Alternatively, -COOM is preferred, and from the viewpoint of productivity, -SO ３ M and -COOM are more preferred, and -SO ３ Na and -COONa are more preferred, and -SO ３ Na is particularly preferred.

[0061] M is a hydrogen atom, a metal atom, N (R Ｍ１ ) ４ or P(R) Ｍ２ ) ４ And R Ｍ１ and R Ｍ２ Each of these is independently a hydrogen atom or a substituent. The metal atom represented by M is preferably a metal atom of Group 1, and more preferably Li, Na, or K. Ｍ１ and R Ｍ２The substituent represented by is preferably a monovalent organic group, more preferably a monovalent hydrocarbon group, and even more preferably an alkyl group or an aromatic hydrocarbon group. The substituent has 1 to 10 carbon atoms. The alkyl group may be linear, branched, or cyclic. The aromatic hydrocarbon group may be monocyclic or polycyclic. A phenyl group is preferred as the aromatic hydrocarbon group.

[0062] Examples of the molecular weight of compound (X) include 70 to 500, and from the viewpoint of dispersion stability, 70 to 450 is preferred, and 100 to 300 is more preferred.

[0063] Specific examples of compound (X) include vinyl sulfonic acid, vinyl phosphonic acid, (meth)acrylic acid, allyl sulfonic acid, allyl phosphonic acid, butenic acid, crotonic acid, vinyl acetate, 2-sulfoethyl methacrylic acid, 4-vinylbenzenesulfonic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, N-tigroylglycine, 6-acrylamidohexanoic acid, 1,1-difluoro-2-methyl-2-[(1-oxo-2-propen-1-yl)amino]-1-propanesulfonic acid, 3-methyl-3-[(2-methyl-1-oxo-2-propen-1-yl)amino]-2-butanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, 2,3-dimethyl-3-[(1-oxo-2-propen-1-yl)amino]-2-butanesulfonic acid, and their salts. Examples of the above-mentioned metal salts include salts of metal atoms represented by M.

[0064] The compound (X) is preferably a vinyl compound having a sulfonic acid group, a phosphonic acid group, or a carboxyl group, an allyl compound having a sulfonic acid group, a phosphonic acid group, or a carboxyl group, (meth)acrylic acid, (meth)acrylamide having a sulfonic acid group, a phosphonic acid group, or a carboxyl group, and metal salts thereof. Vinyl sulfonic acid, sodium vinyl sulfonate, allyl sulfonic acid, sodium allyl sulfonate, 2-acrylamide-2-methyl-1-propanesulfonic acid, sodium 2-acrylamide-2-methyl-1-propanesulfonate (hereinafter also referred to as "NaAAMPS"), 2-methacrylamide-2-methyl-1-propanesulfonic acid, or sodium 2-methacrylamide-2-methyl-1-propanesulfonate. Note that the above "(meth)acrylic acid" is a concept that includes both acrylic acid and methacrylic acid, and the above "(meth)acrylamide" is a concept that includes both acrylamide and methacrylamide.

[0065] The content of compound (X) is preferably 0.1 to 5000 ppm by mass, more preferably 0.2 to 1000 ppm by mass, even more preferably 0.3 to 500 ppm by mass, and particularly preferably 0.5 to 100 ppm by mass, relative to the total amount of the aqueous medium.

[0066] The compound (X) used in manufacturing method A may or may not be copolymerized with each monomer. The fluorine-containing elastomer may or may not contain structural units based on compound (X).

[0067] In manufacturing method A, for example, an aqueous dispersion containing particles of fluorine-containing elastomer is obtained by polymerizing each monomer. The average particle diameter of the fluorine-containing elastomer particles is preferably 500 nm or less, more preferably 300 nm or less, even more preferably 200 nm or less, and particularly preferably 150 nm or less, from the viewpoint of particle dispersion stability. The lower limit is preferably 2 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more. As the average particle diameter of the fluorine-containing elastomer particles, the particle diameter calculated by analyzing the autocorrelation function obtained by dynamic light scattering using the monodisperse cumulant method or D50 (median diameter) can be used. The above D50 is the particle diameter at the point on the cumulative curve where the cumulative volume is 50%, obtained by measuring the particle size distribution by laser diffraction and scattering, setting the total volume of the particle collection to 100%. More detailed methods for measuring the average particle diameter are shown in the Examples section.

[0068] A polymerization initiator may be used in the production of fluorine-containing elastomers. The polymerization initiator used in the production of fluorine-containing elastomers is preferably a water-soluble polymerization initiator, more preferably persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate, more preferably organic polymerization initiators such as disuccinic acid peroxide and azobisisobutylamidine dihydrochloride, even more preferably persulfates, and particularly preferably ammonium persulfate.

[0069] The amount of polymerization initiator used is preferably 0.01 to 5 parts by mass, more preferably 0.01 to 3 parts by mass, and even more preferably 0.01 to 2 parts by mass, relative to the total amount of each monomer.

[0070] When a polymerization initiator is used, it may be added to the reactor all at once or in stages. If added in stages, it may be added in multiple stages or continuously.

[0071] The polymerization temperature is preferably 10 to 95°C, and more preferably 15 to 90°C. The polymerization pressure is preferably 0.5 to 4.0 MPaG, and more preferably 0.6 to 3.5 MPaG. The polymerization time is preferably 90 to 1000 minutes, and more preferably 90 to 800 minutes.

[0072] Fluorine-containing elastomers are preferably those that do not have a melting point. The melting point can be measured using a differential scanning calorimetry (DSC). More detailed methods for measuring the melting point are shown in the Examples section.

[0073] -Emulsifiers- Emulsifiers may be used in the manufacture of fluorine-containing elastomers. From the viewpoint of preventing a decrease in the molecular weight of the manufactured fluorine-containing elastomer, it is preferable to manufacture the fluorine-containing elastomer under conditions in which emulsifiers containing fluorine atoms (hereinafter also referred to as "fluorine-containing emulsifiers") are substantially absent, and it is more preferable to manufacture the fluorine-containing elastomer under conditions in which fluorine-containing emulsifiers and emulsifiers not containing fluorine atoms (hereinafter also referred to as "non-fluorine emulsifiers") (hereinafter, fluorine-containing emulsifiers and non-fluorine emulsifiers are collectively referred to as "emulsifiers") are substantially absent. That is, the composition used in the manufacture of the crosslinked article of this disclosure (hereinafter also referred to as "Composition A") preferably substantially contains no fluorine-containing emulsifiers, and more preferably substantially contains no emulsifiers. Similarly, the crosslinked rubber article of this disclosure preferably substantially contains no fluorine-containing emulsifiers, and more preferably substantially contains no emulsifiers.

[0074] In this disclosure, "substantially absent" or "substantially not contained" means that the amount or content is 10 ppm by mass or less of the total amount, preferably 150 ppb by mass or less, and more preferably 50 ppb by mass or less. The lower limit of the amount or content is 0 ppb by mass. For example, the amount or content of the emulsifier can be measured using a liquid chromatograph-mass spectrometer. More specifically, the method for measuring the amount or content of the emulsifier is shown in the Examples section.

[0075] The above compound (X) and the polymer of compound (X) do not constitute emulsifiers. Therefore, method A is a method of polymerizing each monomer under conditions where emulsifiers are substantially absent.

[0076] If emulsifiers remain in crosslinked rubber articles manufactured using compositions containing fluorine-containing elastomers, there is a risk of contamination of the surrounding environment. Therefore, there is a growing demand to reduce the use of emulsifiers. With manufacturing method A, fluorine-containing elastomers can be obtained under conditions where emulsifiers are substantially absent, and crosslinked rubber articles can be obtained that maintain rubber properties while also exhibiting excellent adhesion to polyethylene.

[0077] Examples of emulsifiers include water-soluble emulsifiers. A water-soluble emulsifier is defined as an emulsifier whose solubility in 1000 g of water at 25°C is 100 mg or more, while a non-water-soluble emulsifier is defined as an emulsifier other than the water-soluble emulsifiers mentioned above. Water-soluble emulsifiers may be either ionic or nonionic. Examples of emulsifiers include those that do not have a carbon-carbon double bond.

[0078] Examples of fluorine-containing emulsifiers include anionic fluorine-containing emulsifiers. Examples of anionic fluorine-containing emulsifiers include fluorine-containing emulsifiers in which the total number of carbon atoms in the portion excluding the anionic group is 20 or less, and fluorine-containing emulsifiers in which the molecular weight of the anionic portion is 800 or less.

[0079] A non-fluorinated emulsifier is an emulsifier that does not contain fluorine atoms and has hydrocarbon groups such as alkyl groups as its hydrophobic portion. It is also possible to substitute the hydrogen atoms of the hydrocarbon groups in a non-fluorinated emulsifier with halogen atoms other than fluorine atoms.

[0080] Examples of non-fluorinated emulsifiers include ionic hydrocarbon emulsifiers and nonionic hydrocarbon emulsifiers.

[0081] Examples of ionic hydrocarbon emulsifiers include anionic hydrocarbon emulsifiers. Anionic hydrocarbon emulsifiers refer to emulsifiers having a negatively charged hydrophilic portion such as a carboxylic acid group, sulfonic acid group, sulfate group, phosphonic acid group, and phosphate group, and a hydrocarbon group such as an alkyl group as a hydrophobic portion. Specific examples of anionic hydrocarbon emulsifiers include sodium dodecyl sulfate, a highly branched C10 tertiary carboxylic acid supplied by Resolution Performance Products as Versatic® 10, sodium linear alkyl polyethersulfonate supplied by BASF as the Avanel® S series, and the sulfosuccinate emulsifier Lankropol® K8300 available from AkzoNobelSurfaceChemistryLLC.

[0082] Nonionic hydrocarbon emulsifiers are emulsifiers that exhibit surface activity without dissociating into ions in water and have hydrocarbon groups such as alkyl groups as hydrophobic portions. Examples of hydrophilic portions of nonionic hydrocarbon emulsifiers include water-soluble functional groups such as polyethylene oxide chains obtained from the polymerization of ethylene oxide. Examples of nonionic hydrocarbon emulsifiers include polyalkylene oxide block copolymers, such as block copolymers having polyethylene oxide and polypropylene oxide.

[0083] Another example of a nonionic hydrocarbon emulsifier is the emulsifier described in paragraphs

[0043] to

[0052] of Japanese Patent Publication No. 2016-537499.

[0084] The emulsifier may contain silicon atoms. Examples of emulsifiers containing silicon atoms include siloxane emulsifiers. Siloxane emulsifiers are hydrocarbon-containing emulsifiers having a siloxane skeleton. Examples of siloxane emulsifiers include those described in U.S. Patent No. 6,841,616 (Wille et al.) and U.S. Patent No. 7,977,438 (Brothers et al.).

[0085] The emulsifier may be a polymer emulsifier. Examples of polymer emulsifiers include polymers obtained by polymerizing monomers having fluorine atoms or monomers not having fluorine atoms. Examples of polymer emulsifiers consisting of polymers obtained by polymerizing monomers having fluorine atoms or monomers not having fluorine atoms include polymers having hydrophilic groups in their side chains. Examples of such polymer emulsifiers include polymers obtained by polymerizing units based on compounds having polymerizable sites and hydrophilic groups. Also, examples include polymers obtained by polymerizing units based on compounds that do not initially have hydrophilic groups but have groups that can become hydrophilic groups, and then undergoing post-treatment such as hydrolysis. It is preferable that the polymer emulsifier is water-soluble.

[0086] - Surfactants - Surfactants may be used in the production of fluorine-containing elastomers. From the viewpoint of preventing a decrease in the molecular weight of the fluorine-containing elastomer produced, it is preferable to produce the fluorine-containing elastomer under conditions where surfactants are substantially absent. That is, composition A used in the production of the crosslinked article of this disclosure is preferably substantially free of surfactants. Similarly, the crosslinked rubber article of this disclosure is also preferably substantially free of surfactants.

[0087] Examples of surfactants include the emulsifiers mentioned above, as well as neutral surfactants (nonionic surfactants), cationic surfactants, anionic surfactants, and amphoteric surfactants.

[0088] The amount or content of surfactants can be measured using LC-MS / MS.

[0089] [Method for producing a crosslinked body] The crosslinked body of this disclosure is obtained by crosslinking a fluorine-containing elastomer. Preferably, the crosslinked body is obtained by crosslinking a fluorine-containing elastomer using composition A which contains a fluorine-containing elastomer. A crosslinking agent may be used for crosslinking, or a crosslinking agent and a crosslinking aid may be used.

[0090] (Composition A) Composition A used in the manufacture of the crosslinked body of the present disclosure comprises a fluorine-containing elastomer. In addition to the fluorine-containing elastomer, Composition A may contain various additives such as crosslinking agents, crosslinking aids, fillers (also called reinforcing agents), processing aids (e.g., mold release agents), metal oxides, plasticizers, colorants, stabilizers, conductivity imparters, thermal conductivity imparters, flexibility imparters, heat resistance improvers, and flame retardants, to the extent that they do not affect the effects of the present disclosure.

[0091] In other words, the crosslinked rubber articles of this disclosure may also contain various additives such as crosslinking agents, crosslinking aids, fillers (also called reinforcing agents), processing aids (e.g., mold release agents), metal oxides, plasticizers, colorants, stabilizers, conductivity imparters, thermal conductivity imparters, flexibility imparters, heat resistance improvers, and flame retardants, or structures based thereon, to the extent that they do not affect the effects of this disclosure.

[0092] -Fluorine-containing elastomer- Details of the fluorine-containing elastomer are as described above. The content of the fluorine-containing elastomer relative to the total amount of composition A is preferably 50 to 100% by mass, more preferably 70 to 95% by mass, and even more preferably 80 to 90% by mass.

[0093] -Crosslinking Agents- Examples of crosslinking agents used for crosslinking include polyamine-based crosslinking agents, polyol-based crosslinking agents, peroxide-based crosslinking agents, imidazole-based crosslinking agents, triazine-based crosslinking agents, oxazole-based crosslinking agents, and thiazole-based crosslinking agents. Crosslinking agents may be used individually or in combination of two or more.

[0094] Examples of polyol-based crosslinking agents include polyhydroxy compounds such as bisphenol AF, hydroquinone, bisphenol A, and diaminobisphenol AF. Examples of peroxide-based crosslinking agents include dialkyl peroxides (e.g., di-tert-butyl peroxide, tert-butylcumyl peroxide, dicumyl peroxide, α,α-bis(tert-butylperoxy)-p-diisopropylbenzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (e.g., "Perhexa® 25B"), 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexyn-3, etc.), 1,1-di(tert-butylperoxy)- Examples of peroxides include organic peroxides such as 3,3,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, benzoyl peroxide, tert-butylperoxybenzene, 1,3-bis(tert-butylperoxyisopropyl)benzene (e.g., "Parcadox® 14"), 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, tert-butylperoxymaleic acid, and tert-butylperoxyisopropyl carbonate. Examples of polyamine crosslinking agents include polyamine compounds such as 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. 5833657. Examples of triazine-based crosslinking agents include organotin compounds such as tetraphenyltin and triphenyltin.Examples of oxazole crosslinking agents, imidazole crosslinking agents, and thiazole crosslinking agents include bisdiaminophenyl crosslinking agents, bisaminophenol crosslinking agents, bisaminothiophenol crosslinking agents, bisamidorasone crosslinking agents, and bisamidoxime crosslinking agents.

[0095] From the viewpoint of excellent productivity, heat resistance, and chemical resistance, the crosslinking agent is more preferably a peroxide, and even more preferably an organic peroxide. That is, the crosslinked body of this disclosure preferably includes a structure based on the crosslinking agent, more preferably a structure based on a peroxide, and particularly preferably an organic peroxide. The structure based on a peroxide is an oxide structure, i.e., a residue obtained by removing the ether group from a peroxide, and the structure based on an organic peroxide is a t-butyl oxide structure, i.e., a residue obtained by removing the ether group from an organic peroxide. The content of the crosslinking agent in composition A is preferably 0.001 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, and even more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the fluorine-containing elastomer.

[0096] -Crosslinking Aids- When crosslinking aids are used in addition to crosslinking, the crosslinking efficiency is further increased. Crosslinking aids may be used alone or in combination of two or more. Examples of crosslinking aids used in crosslinking include triallyl cyanurate; triallyl isocyanurate; trimethyl isocyanurate; 1,3,5-triacryloylhexahydro-1,3,5-triazine; triallyl trimellitate; m-phenylenediamine bismaleimide; p-quinone dioxime; p,p'-dibenzoylquinone dioxime; dipropargyl terephthalate; diallyl phthalate; N,N',N'',N'''-tetraallyl terephthalamide; bisolefin compounds such as vinyl group-containing siloxane oligomers (polymethylvinylsiloxane and polymethylphenylvinylsiloxane, etc.); and fluorine-containing aromatic compounds having two or more vinyl or allyl groups bonded to an aromatic ring.

[0097] The crosslinking aid is preferably a polyfunctional compound, preferably a compound having two or more allyl groups in one molecule, more preferably at least one selected from the group consisting of triallyl cyanurate, triallyl isocyanurate, trimethyl isocyanurate, bisolefin-containing compounds, and the aforementioned fluorine-containing aromatic compounds, and even more preferably triallyl isocyanurate. That is, the crosslinked product of this disclosure preferably includes a structure based on a polyfunctional compound, more preferably includes a structure based on a compound having two or more allyl groups in one molecule, even more preferably includes a structure based on a compound having two to four allyl groups in one molecule, and particularly preferably includes a structure based on at least one selected from the group consisting of triallyl isocyanurate and 1,6-divinyl(perfluorohexane).

[0098] The amount of crosslinking aid in composition A is preferably 0.001 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, and even more preferably 1 to 10 parts by mass, per 100 parts by mass of fluorine-containing elastomer.

[0099] -Fillers- Fillers may be used individually or in combination of two or more types. Examples of fillers include carbon materials, polymers, and silicon dioxide-containing materials. Examples of carbon materials include multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon nanofibers, carbon nanobelts, carbon nanohorns, nanographite, fullerenes, graphite, carbon fiber, and carbon black. Examples of polymers include polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polychlorotrifluoroethylene, TFE-ethylene copolymers, TFE-propylene copolymers, and TFE-vinylidene fluoride copolymers. Examples of silicon dioxide-containing materials include Celite and silica. Examples of silica include nanosilica. Examples of other fillers include cellulose nanofibers, barium sulfate, calcium carbonate, titanium dioxide, titanate whiskers, metal nanoparticles, clay, and talc.

[0100] The amount of filler in composition A is preferably 0.1 to 30 parts by mass, more preferably 1 to 20 parts by mass, and even more preferably 5 to 15 parts by mass, per 100 parts by mass of fluorine-containing elastomer.

[0101] -Processing aids- Processing aids may be used individually or in combination of two or more. There are no particular limitations on the processing aids. Examples of processing aids that exhibit lubricant function (i.e., mold release agents) include fatty acid metal salts (stearates such as sodium stearate and calcium stearate), synthetic waxes (polyethylene wax, etc.), and fatty acid esters (glycerin monooleate, etc.).

[0102] The amount of processing aid in composition A is preferably 0.001 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, and even more preferably 0.5 to 5 parts by mass, per 100 parts by mass of fluorine-containing elastomer.

[0103] - Metal Oxides - Metal oxides may be used individually or in combination of two or more. Metal oxides facilitate the crosslinking reaction quickly and reliably. Examples of metal oxides include divalent metal oxides such as magnesium oxide, calcium oxide, zinc oxide, and lead oxide.

[0104] The metal oxide content in composition A is preferably 0.1 to 5.0 parts by mass, more preferably 0.2 to 3.0 parts by mass, and even more preferably 0.5 to 2.0 parts by mass, per 100 parts by mass of fluorine-containing elastomer.

[0105] (Crosslinking Method) Composition A can be prepared by mixing a fluorine-containing elastomer, a crosslinking agent, and any other material using an open roll mixer, Banbury mixer, or kneader. Composition A can also be prepared by using a closed mixer or by co-coagulation from emulsion mixing.

[0106] Composition A used for crosslinking may be further molded after preparation, and conventionally known molding methods can be applied. Examples of molding methods include compression molding, injection molding, extrusion molding, and calendering. It may also be molded by a molding method such as a dip molding method or a coating method using a solution of composition A.

[0107] The method for crosslinking the fluorine-containing elastomer contained in composition A is not particularly limited, but a method of heating the fluorine-containing elastomer is preferred. 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 crosslinking reaction of composition A may be carried out under atmospheric pressure, under pressurized pressure, or under reduced pressure. Preferred heating conditions are 100 to 400°C for 1 second to 24 hours.

[0108] A fluorine-containing elastomer may be heated (i.e., primary crosslinked) to obtain a material that has been further heated to undergo secondary crosslinking. The crosslinked material of this disclosure may be obtained by primary crosslinking or by secondary crosslinking. Secondary crosslinking can stabilize or improve the mechanical properties, compression set, removal of impurities such as volatile components, and other properties of the crosslinked material. The heating conditions for secondary crosslinking are preferably 80 to 350°C for 30 minutes to 48 hours.

[0109] Another crosslinking method besides heating is to irradiate the fluorine-containing elastomer with radiation. Specific examples of radiation used include electron beams and ultraviolet rays.

[0110] <CF ３ (CF ２ ) ５ CH ２ CH ３ Adhesion > The crosslinked rubber articles of this disclosure have CF on part or all of their surface. ３ (CF ２ ) ５ CH ２ CH ３ It is preferable that it is attached. CF ３ (CF ２ ) ５ CH ２ CH ３This is also written as 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorooctane or HFC-76-13sf, and is, for example, Asahi Clean® AC-6000 manufactured by AGC Inc.

[0111] CF applied to part or all of the surface of a cross-linked rubber article. ３ (CF ２ ) ５ CH ２ CH ３ Even when coated, cross-linked rubber articles maintain their rubber properties while also exhibiting excellent adhesion to polyethylene. CF ３ (CF ２ ) ５ CH ２ CH ３ The method of attaching CF to the cross-linked rubber article is not particularly limited, ３ (CF ２ ) ５ CH ２ CH ３ This may also be done by coating, immersion, spraying, or exposure as vapor.

[0112] CF applied to part or all of the surface of a cross-linked rubber article. ３ (CF ２ ) ５ CH ２ CH ３ The presence of this substance can be confirmed by extracting it with methanol and performing gas chromatography.

[0113] <Volume Swelling Rate> The cross-linked rubber articles of this disclosure have a volume swelling rate of CF ３ (CF ２ ) ５ CH ２ CH ３ When immersed in CF for 70 hours at 25°C, the volume swelling rate, which represents the percentage change in volume after immersion relative to the volume before immersion, is greater than 66.0%. More specifically, first, the volume of the cross-linked rubber article before immersion is measured using the Archimedes method with a hydrometer. Next, the cross-linked rubber article is immersed in CF ３ (CF ２ ) ５ CH ２ CH ３The cross-linked rubber article is immersed for 70 hours in (AGC Inc., product name: Asahi Clean® AC-6000). The immersion is carried out in an environment controlled at 25°C and 50% humidity. The volume of the cross-linked rubber article after immersion is measured using the Archimedes method with a hydrometer. The volume swelling rate is then calculated using the following formula (4): Volume swelling rate (%) = {(Volume after immersion - Volume before immersion) / Volume before immersion} × 100 …(4)

[0114] The volume swelling rate of the crosslinked rubber article of this disclosure is greater than 66.0%, preferably 67.0% or more, more preferably 68.0% or more, even more preferably 69.0% or more, particularly preferably 70.0% or more, and most preferably 71.0% or more. The volume swelling rate may also be 200.0% or less, 150.0% or less, 100.0% or less, 90.0% or less, or 80.0% or less. For example, the volume swelling rate of the crosslinked rubber article of this disclosure is greater than 66.0% and 200.0% or less. A method for making the volume swelling rate of the crosslinked rubber article of this disclosure greater than 66.0% is, for example, to further adjust the amount of monomer units used in the above manufacturing method A. More specifically, examples include adding compound (X) at a concentration of 5 to 100 ppm by mass relative to the amount of aqueous medium added, adding an aqueous solution of ammonium persulfate at a concentration of 0.2 to 0.7 mmol / L relative to the amount of aqueous medium added, or adding a fluorine-containing elastomer having an iodine atom at a concentration of 0.03 to 0.2 mol% relative to the amount of monomer added after the start of polymerization.

[0115] <Density> The cross-linked rubber articles of this disclosure have a density of CF ３ (CF ２ ) ５ CH ２ CH ３ The density after immersion at 25°C for 70 hours is 1.82 g / cm³. ３ The following is preferred. The density of the cross-linked rubber article after immersion can be measured using a hydrometer by the Archimedes method. More specifically, the method for measuring the density of the cross-linked rubber article after immersion is shown in the Examples section.

[0116] The density of the cross-linked rubber article after immersion was 1.82 g / cm³. ３ The following is preferable: 1.81 g / cm³ ３The following is more preferable: The density of the cross-linked rubber article after immersion is 1.60 g / cm³. ３ Above, 1.70g / cm ３ The above, or 1.80 g / cm³ ３ The above is also acceptable. The density of the cross-linked rubber article after immersion is, for example, 1.60 to 1.82 g / cm³. ３ Or 1.80–1.82 g / cm³ ３ That is the case.

[0117] Furthermore, a higher volume swelling rate of the crosslinked rubber article means that the crosslinking density of the crosslinked rubber article is lower, the iodine crosslinking efficiency in composition A and composition B (described later) is higher, and the crosslinked rubber article has superior adhesion to polyethylene while maintaining its rubber properties. The density of the crosslinked rubber article after immersion is 1.82 g / cm³. ３ The following conditions apply: The crosslinked rubber articles of this disclosure have a lower crosslink density and more CF ３ (CF ２ ) ５ CH ２ CH ３ The material penetrates and swells within the cross-linked rubber article, resulting in superior adhesion to polyethylene while maintaining the rubber's properties.

[0118] <Applications> The cross-linked rubber articles of this disclosure are suitable for use as materials for O-rings, sheets, gaskets, oil seals, diaphragms, V-rings, and the like. Furthermore, the crosslinked rubber articles of this disclosure can be applied to heat-resistant and chemical-resistant sealing materials, heat-resistant and oil-resistant sealing materials, wire insulation 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-based greases, etc., rubber paints, adhesive rubber, hoses, tubes, calender sheets (rolls), sponges, rubber rolls, components for oil drilling, heat dissipation sheets, solution crosslinked bodies, rubber sponges, bearing seals (urea-resistant, etc.), linings (chemical-resistant), insulating sheets for automobiles, insulating sheets for electronic equipment, rubber bands for watches, packings for endoscopes (amine-resistant), bellows hoses (processed from calender sheets), packings / valves for water heaters, fenders (marine civil engineering, ships), fibers / nonwoven fabrics (protective clothing, etc.), substrate sealing materials, rubber gloves, stators for single-screw eccentric pumps, components for urea SCR systems, vibration dampers, vibration control agents, sealing materials, additives to other materials, and toys, etc.

[0119] ≪Composition B≫ Composition B of the present disclosure comprises a fluorine-containing elastomer having iodine atoms and a crosslinking agent, wherein the iodine crosslinking efficiency calculated by the following formula (5) when the fluorine-containing elastomer is crosslinked is 5.0 or higher. Iodine crosslinking efficiency (mass ppm / dN·m) = [iodine content] / [M Ｈ -M Ｌ ] ... (5) In formula (5), [iodine content] represents the content of iodine atoms (mass ppm) relative to the mass of the fluorine-containing elastomer. M Ｈ This is the maximum torque (dN·m) in the crosslinking curve of composition B, which shows the relationship between torque and time. Ｌ This is the minimum torque value (dN·m) in the aforementioned bridge curve.

[0120] As described above, the iodine content can be calculated using a Vanta handheld X-ray fluorescence analyzer and the fundamental parameter method.

[0121] M Ｈ and M ＬThis can be measured using a rubber processing tester (RPA). More specifically, the torque (dN·m) is measured according to the method in accordance with JIS K6296-1, under the following conditions: measuring device: PREMER RPA (Alpha Technologies), die shape: D0380, 160°C (test temperature), 20 minutes (crosslinking time), 100 cpm, Angle: 3.00 deg., and the torque-crosslinking time curve is determined. From the obtained torque-crosslinking time curve, the maximum torque value is determined. Ｈ The minimum torque value is M Ｌ Let's assume that.

[0122] The iodine crosslinking efficiency when composition B of the present disclosure is crosslinked may be 5.0 or higher, 5.3 or higher, 5.5 or higher, 5.8 or higher, or 6.0 or higher. The iodine crosslinking efficiency may be 10 or lower, 7.0 or lower, or 6.5 or lower. The iodine crosslinking efficiency when composition B of the present disclosure is crosslinked is, for example, 5.0 to 6.5.

[0123] Furthermore, when composition B is crosslinked, the lower the crosslinking density, the smaller the torque difference, and therefore the higher the iodine crosslinking efficiency. Conversely, the higher the crosslinking density, the larger the torque difference, and therefore the lower the iodine crosslinking efficiency. In other words, the lower the iodine crosslinking efficiency (i.e., the higher the crosslinking density), the more likely composition B is to produce a crosslinked rubber article that maintains rubber properties while also exhibiting excellent adhesion to polyethylene. Moreover, since the iodine crosslinking efficiency of composition B in this disclosure is 5.0 or higher when crosslinked, the hardness is less likely to decrease when used as an O-ring at high temperatures.

[0124] The description of the fluorine-containing elastomer having iodine atoms in Composition B of this disclosure, including definitions, examples, and preferred embodiments, is the same as the description of the fluorine-containing elastomer having iodine atoms as crosslinkable groups among the "fluorine-containing elastomers" described in the above section on "Crosslinked Rubber Articles." That is, the fluorine-containing elastomer having iodine atoms in Composition B of this disclosure is preferably a fluorine-containing elastomer having iodine atoms as crosslinking sites, and is more preferably a fluorine-containing elastomer that includes structural units based on TFE and structural units based on PAVE.

[0125] The description of the emulsifier in Composition B of this disclosure, including definitions, examples, and preferred embodiments, is the same as the description of the emulsifier in the section on "Crosslinked Rubber Articles" above. That is, Composition B of this disclosure preferably contains substantially no emulsifier having a fluorine atom (also known as a fluorine-containing emulsifier), and more preferably contains substantially no emulsifier.

[0126] The fluorine-containing elastomer having an iodine atom in composition B of this disclosure is preferably manufactured under conditions where a fluorine-containing emulsifier is substantially absent, more preferably under conditions where an emulsifier is substantially absent, from the viewpoint of preventing a decrease in the molecular weight of the manufactured fluorine-containing elastomer. In other words, it is more preferably manufactured by manufacturing method A described in the section on "Crosslinked Rubber Articles" above.

[0127] The description of composition B in this disclosure, including definitions, examples, and preferred embodiments, is the same as the description of composition A in this disclosure described in the section on "Crosslinked Rubber Articles" above, except that the fluorine-containing elastomer is a fluorine-containing elastomer having iodine atoms.

[0128] The crosslinked rubber articles of this disclosure may be obtained using composition B of this disclosure, and may include a crosslinked body obtained by crosslinking a fluorine-containing elastomer having iodine atoms contained in composition B.

[0129] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to the following examples unless it exceeds the spirit of the disclosure. Examples 1 and 2 are examples, and Examples 3 and 4 are comparative examples.

[0130] <Preparation of Fluorine-Containing Elastomers> (Fluorine-Containing Elastomer 1) Ultrapure water (1774 g), 50% by mass aqueous solution of sodium 2-acrylamido-2-methyl-1-propanesulfonate (NaAAMPS, corresponding to compound (X)) (15 μL, NaAAMPS is 7.5 mg), PMVE (105 g), and TFE (22 g) were added to a 3.2 L stainless steel pressure reactor, and the temperature was raised to 80°C while stirring at 385 rpm. The reactor pressure at 80°C was 1.4 MPaG. Next, an aqueous solution of ammonium persulfate (2.5% by mass, 11 g) was added and polymerization was started. As polymerization started, the pressure inside the reactor decreased, so TFE was added to maintain a constant pressure. This was repeated, and when the amount of TFE added after polymerization started reached 37 g, 1.7 g of perfluoro-1,4-diiodobutane and 10 g of PMVE were injected under pressure. Subsequently, 10 g of PMVE was injected each time 12 g of TFE was injected. When the amount of TFE added after the start of polymerization reached 133 g, the addition of TFE and PMVE injected after the start of polymerization was stopped, the reactor temperature was cooled to 10°C to stop the polymerization reaction, the remaining gas in the reactor was recovered, and the liquid was drained to obtain aqueous dispersion 1. The total amount of monomers added before the start of polymerization was 22 g of TFE and 105 g of PMVE. The total amount of monomers added after the start of polymerization was 133 g of TFE and 80 g of PMVE. The total amount of TFE added was 155 g, and the total amount of PMVE added was 185 g. The average particle size of the fluorine-containing elastomer 1 particles in aqueous dispersion 1 was 79.6 nm, and the number of particles of fluorine-containing elastomer 1 was 2.6 × 10⁶. １４ The solid content was 12.4% by mass in aqueous dispersion 1, with a solid content of 12.4% by mass. Aqueous dispersion 1 was added to a 3% by mass aqueous nitric acid solution to coagulate, then filtered, and the obtained fluorine-containing elastomer 1 was washed with ultrapure water. After that, it was vacuum dried at 100°C. NMR analysis of the obtained fluorine-containing elastomer 1 showed a PMVE / TFE ratio of 33 / 67 (molar ratio). The iodine content was 637 ppm by mass. Furthermore, fluorine-containing elastomer 1 was FFKM and did not have a melting point.

[0131] (Fluorine-containing elastomer 2) Aqueous dispersion 2 was obtained using the same procedure as for fluorine-containing elastomer 1, except that the amount of 50% by mass aqueous solution of NaAAMPS added was changed to 30 μL (15 mg of NaAAMPS). The average particle size of the particles of fluorine-containing elastomer 2 in aqueous dispersion 2 was 64.3 nm, and the number of particles of fluorine-containing elastomer 2 was 5.0 × 10⁻⁶. １４ The solid content of aqueous dispersion 2 was 12.4% by mass, with a solid content of 12.4% by mass. Aqueous dispersion 2 was added to a 3% by mass nitric acid aqueous solution to coagulate, then filtered, and the obtained fluorine-containing elastomer 2 was washed with ultrapure water. After that, it was vacuum dried at 100°C. NMR analysis of the obtained fluorine-containing elastomer 2 showed a PMVE / TFE ratio of 33 / 67 (molar ratio). The iodine content was 517 ppm by mass. Furthermore, fluorine-containing elastomer 2 was FFKM and did not have a melting point.

[0132] (Fluorine-containing elastomer 3) Polymerization was started using the same procedure as for fluorine-containing elastomer 1, except that the amount of 50% by mass aqueous solution of NaAAMPS added was changed to 45 μL (22.5 mg of NaAAMPS), and the amount of ammonium persulfate aqueous solution (2.5% by mass) added was changed to 7 g. As polymerization started, the pressure inside the reactor decreased, so TFE was added to maintain a constant pressure. This was repeated, and when the amount of TFE added after polymerization started reached 25 g, 10 g of PMVE was injected. Thereafter, 10 g of PMVE was injected every time 12 g of TFE was injected. When the amount of TFE added after polymerization started reached 325 g, the addition of TFE and PMVE injected after polymerization started was stopped, the reactor temperature was cooled to 10°C to stop the polymerization reaction, the remaining gas in the reactor was recovered, and the liquid was drained to obtain aqueous dispersion 3. The total amount of monomers added before polymerization began was 22 g of TFE and 105 g of PMVE. The total amount of monomers added after polymerization began was 325 g of TFE and 240 g of PMVE. The total amount of TFE added was 347 g, and the total amount of PMVE added was 345 g. The average particle size of the fluorine-containing elastomer 3 particles in the aqueous dispersion 3 was 68.2 nm, and the number of particles of the fluorine-containing elastomer 3 was 9.8 × 10⁶. １４The solid content of aqueous dispersion 3 was 24.9% by mass, with a solid content of 24.9% by mass. Aqueous dispersion 3 was added to a 3% by mass aqueous nitric acid solution to coagulate, then filtered, and the obtained fluorine-containing elastomer 3 was washed with ultrapure water. It was then vacuum-dried at 100°C. NMR analysis of the obtained fluorine-containing elastomer 3 showed a PMVE / TFE ratio of 33 / 67 (molar ratio). The iodine content was 613 ppm by mass. Furthermore, fluorine-containing elastomer 3 was FFKM and had no melting point.

[0133] (Fluorine-containing elastomer 4) After degassing a 2.2 L stainless steel pressure reactor equipped with anchor blades, ultrapure water (980 g) and C as an emulsifier are added. ２ F ５ OCF ２ CF ２ OCF ２ COONH ４A 30% by mass solution of (EEA) (201.7 g) and a 5% by mass aqueous solution of disodium hydrogen phosphate dodecahydrate (2.3 g) were charged, and the gas phase was purged with nitrogen. While stirring at a speed of 600 rpm using an anchor blade, PMVE (54 g) and TFE (11 g) were injected into the container under pressure, and the internal temperature was raised to 80°C. Next, an aqueous solution of APS (0.5% by mass, 13 mL, with 0.06 g of ammonium persulfate) was added, and polymerization was started. As polymerization began, the pressure inside the reactor decreased, so TFE and PMVE were injected under pressure in a molar ratio of 65 / 35, and the pressure was kept constant at 0.9 MPa [gauge]. After 6 g of TFE had been injected under pressure, perfluoro-1,4-diiodobutane (2.0 g) was injected under pressure. After injecting 410 g of TFE and 280 g of PMVE under pressure, the reactor was cooled to terminate the polymerization reaction and obtain fluorine-containing elastomer 4. The polymerization time was 500 minutes. After recovering the gas remaining in the reactor, the liquid was withdrawn. This liquid was designated as aqueous dispersion 4. Aqueous dispersion 4 was a dispersion in which particles containing fluorine-containing elastomer 4 (average particle size 80 nm) were dispersed in an aqueous medium, and the solid content concentration was 38.8% by mass. The above aqueous dispersion 4 was added to 2500 g of 3% by mass nitric acid aqueous solution, and after stirring the mixture, the aggregates were filtered and recovered. The recovered aggregates were washed with 2000 g of ultrapure water at 23°C and vacuum dried at 100°C to obtain rubbery fluorine-containing elastomer 4. Analysis of the obtained fluorine-containing elastomer 4 by NMR revealed that the TFE unit content was 65 mol% of the total unit content of the fluorine-containing elastomer 4, and the PAVE unit (PMVE unit) content was 35 mol% of the total unit content of the fluorine-containing elastomer 4. The iodine content was 406 ppm by mass. Furthermore, the fluorine-containing elastomer 4 was FFKM and did not have a melting point.

[0134] (Measurement of average particle size of fluorine-containing elastomers) Each of the obtained aqueous dispersions was degassed at 25°C for 5 minutes, pressurized with nitrogen gas to 0.2 MPaG, purged, and returned to atmospheric pressure to obtain measurement samples. The average particle size of the obtained measurement samples was measured using a dynamic light scattering particle size distribution analyzer (Otsuka Electronics Co., Ltd., ELSZ) with the number of integration cycles set to 100, and this was taken as the average particle size of the particles in each aqueous dispersion.

[0135] (Proportion of each constituent unit in fluorine-containing elastomer) The proportion of each constituent unit in fluorine-containing elastomer is: １９ This was determined from F-NMR analysis and infrared absorption spectroscopy.

[0136] (Measurement of iodine content in fluorine-containing elastomers) For each of the obtained fluorine-containing elastomers 1 to 4, the solid made of the fluorine-containing elastomer was heated and pressed to form a 300 μm sheet. The obtained sheet compositions were subjected to fluorescent X-ray analysis using a Vanta handheld X-ray fluorescence analyzer (manufactured by EVIDENT), and the iodine content in the solid (fluorine-containing elastomer) was calculated using the fundamental parameter method.

[0137] (Measurement of the melting point of the fluorine-containing elastomer) For each of the obtained aqueous dispersions 1 to 4, the aqueous dispersion was frozen and agglomerated, then filtered to obtain the fluorine-containing elastomer. 5 mg of the obtained fluorine-containing elastomer was weighed into an aluminum pan and heated from 20°C to 360°C in an air atmosphere at a heating rate of 10°C / min using a Hitachi DSC600 to check for the presence or absence of a melting point peak.

[0138] <Production of Composition> The components and proportions shown in Table 1 were mixed and kneaded at room temperature for 10 minutes using a two-roller system to obtain a mixture. The gap between the two roller systems was adjusted, and composition 1, which was processed into a 3 mm thick sheet using the obtained mixture, was obtained. The details of the components other than fluorine-containing elastomer 1 from the components in Table 1 are as follows: Filler: MT Carbon N990, manufactured by Vanderbilt, carbon black Crosslinking aid: TAIC-WH60, manufactured by Mitsubishi Chemical, triallyl isocyanurate 60% by mass silica diluted product Crosslinking agent: Perhexa 25B, manufactured by NOF Corporation, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane Release agent: Nonsal SN-1, manufactured by NOF Corporation, sodium stearate

[0139]

[0140] Compositions 2 to 4 were obtained in the same manner as described above, except that fluorine-containing elastomer 1 was replaced with fluorine-containing elastomers 2 to 4.

[0141] (M Ｈ -M Ｌ Measurement) Each of the obtained compositions 1 to 4 was cut to 10 g to obtain cut pieces. The obtained cut pieces were sandwiched between two polyester films (ALFA Technologies, PART #F0311-S, 130 mm × 130 mm × 24 μm) on both sides of the main surface to obtain a sample for measurement. The sample for measurement was placed on the die. Then, in accordance with JIS K6296-1, the torque (dN・m) was measured under the following conditions: measuring device: PREMER RPA (Alpha Technologies), die shape: D0380, 160°C (test temperature), 20 minutes (crosslinking time), 100 cpm, Angle: 3.00 deg., and the torque-crosslinking time curve was obtained. From the obtained torque-crosslinking time curve, the minimum torque value (M Ｌ ) and the maximum torque (M Ｈ ) seek, M Ｈ -M Ｌ The result was calculated and is shown in Table 5.

[0142] (Calculation of iodine crosslinking efficiency) The iodine crosslinking efficiency was calculated from the following formula (5): Iodine crosslinking efficiency (mass ppm / dN·m) = [iodine content] / [M Ｈ -M Ｌ ] ... (5) In equation (5), [iodine content] represents the content of iodine atoms relative to the mass of the fluorine-containing elastomer (mass ppm). The iodine content was calculated using a Vanta handheld X-ray fluorescence analyzer and the fundamental parameter method. [M Ｈ -M Ｌ ] is the M calculated above Ｈ -M Ｌ The results are shown in Table 5.

[0143] (Measurement of Emulsifier Content) - Preparation of Measurement Samples - Compositions 1 to 4 (solid compositions) obtained were freeze-milled using a freeze mill 6775 (manufactured by SPEX) under the following conditions. Before freeze-milling, 10% by mass of dibutylhydroxytoluene (BHT) was added to the total mass of the composition to obtain a pulverized powder. The freeze-milling conditions were: composition: 3 g, BHT: 0.3 g, Runtime: 5 mins, Rate: 15 cps, Cycle: 3. 2.5 g of the obtained pulverized powder was mixed with 5 mL of methanol and subjected to sonication at 50°C for 2 hours. Centrifugation (5000 rpm, 5 mins) was performed to settle each fluorine-containing elastomer, and the supernatant was used as the extract. The obtained extract was measured by LC / MS / MS. Fluorine-containing emulsifiers and non-fluorine emulsifiers in the extract were measured using a liquid chromatograph-mass spectrometer. Table 2 shows the configuration of the measuring equipment and the LC-MS measurement conditions. Using aqueous solutions of fluorine-containing and non-fluorine emulsifiers of known concentration, aqueous solutions with five or more levels of content were prepared. LC / MS analysis was performed on each aqueous solution with different content levels, and the relationship between the content and the area area corresponding to that content was plotted to create a calibration curve. Using the above calibration curve, the area areas of the LC / MS chromatograms of fluorine-containing and non-fluorine emulsifiers in the extract were converted to the content of fluorine-containing and non-fluorine emulsifiers.

[0144]

[0145] MRM measurement parameters should be appropriately selected according to the structure of the fluorine-containing and non-fluorine emulsifiers being measured. Literature values ​​can be used for MRM parameters, or they may be calculated using an LC-MS instrument. When determining MRM parameters using an LC-MS instrument, the specific procedure is as follows: Using an LC / MS instrument (Shimadzu Corporation, LCMS-8060NX), select product ion search, input the molecular weights of the fluorine-containing and non-fluorine emulsifiers being measured, and perform precursor ion, precursor adjustment, voltage optimization, and product m / z optimization. The calculated MRM measurement parameters are then used. As an example, the MRM measurement parameters for compounds (S1) and (S2), which are fluorine-containing emulsifiers, are shown in Tables 3-4. Note that in formulas (S1) and (S2), M ＳThese are hydrogen atoms, metal atoms, and NR ４ (R may be the same or different, and represents a hydrogen atom or an organic group having 1 to 10 carbon atoms), optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium. F-(CF ２ ) ｎ４ - COOM Ｓ ...(S1) F-(CF ２ ) ｎ５ -SO ３ M Ｓ ... (S2) However, n4 is an integer between 3 and 17, and n5 is an integer between 4 and 12.

[0146]

[0147]

[0148] -Quantitative determination of fluorine-containing and non-fluorine emulsifiers- Specifically, first, methanol standard solutions of fluorine-containing and non-fluorine emulsifiers with known concentrations of 1 to 180 ng / g were prepared at five different levels. Using a linear approximation from the sample concentration and the integral value of the peak, a was determined using the following formula (A1): A = a × X …(A1) A: Peak area of ​​each emulsifier, X: Concentration of each emulsifier (ng / g)

[0149] Next, the emulsifier content in the extract was calculated using formula (A2). Note that 'a' in formula (A2) refers to the 'a' obtained using formula (A1) above. XCm = ACm / a …(A2) XCm: Emulsifier content in each extract (ng / g) ACm: Peak area of ​​the emulsifier in each extract Note that the limit of quantification in this measurement is 1 ng / g.

[0150] The emulsifier content (ZCm) relative to the total mass of the composition was calculated using the following formula (A3). The results are shown in Table 5. ZCm = XCm × ρ1 × La / W1 …(A3) ZCm: Content of emulsifier contained in the composition ρ1: Density of the extraction solvent (e.g., methanol) La: Volume of the extraction solvent (e.g., 5 mL) W1: Mass of the sample used for extraction (e.g., 2.5 g of composition)

[0151] Furthermore, if the composition is substantially free of emulsifiers, the crosslinked rubber article will also be substantially free of emulsifiers.

[0152] <Preparation of Crosslinked Rubber Articles (Examples 1-4)> Composition 1 was heated and pressed at 160°C for 20 minutes using a hydraulic press (model: SA-301 50T type, manufactured by Tester Sangyo Co., Ltd., ram diameter: 180 mm) to obtain an O-ring (P-26 (standard specified in JIS B2401:2012)) (primary crosslinking). Next, the O-ring was heated in an air atmosphere using an oven at 250°C for 4 hours (secondary crosslinking) to obtain a crosslinked rubber article 1 which is an O-ring.

[0153] Crosslinked rubber articles 2 to 4 were obtained in the same manner as described above, except that composition 1 was changed to compositions 2 to 4.

[0154] (Measurement of volume swelling rate) For the obtained cross-linked rubber articles 1 to 4, the volume swelling rate was measured by the Archimedes method and the following formula (4). More specifically, first, the volume of the cross-linked rubber article before immersion was measured using a hydrometer by the Archimedes method. Next, the cross-linked rubber article was subjected to CF ３ (CF ２ ) ５ CH ２ CH ３ The cross-linked rubber articles were immersed for 70 hours in (AGC Inc., product name: Asahi Clean® AC-6000). The immersion was carried out in an environment controlled at 25°C and 50% humidity. The volume of the cross-linked rubber articles after immersion was measured using the Archimedes method with a hydrometer. The volume swelling rate was then calculated using the following formula (4) (N=2). The results are shown in Table 5. Volume swelling rate (%) = {(Volume after immersion - Volume before immersion) / Volume before immersion} × 100 …(4)

[0155] (Density of cross-linked rubber articles after immersion) For each of the cross-linked rubber articles 1 to 4 obtained, the density of the cross-linked rubber article after immersion was measured using a hydrometer and the Archimedes method.

[0156] (Evaluation of adhesion to polyethylene) For the cross-linked rubber articles 1 to 4 obtained, CF was used to evaluate each of them. ３ (CF ２ ) ５ CH２ CH ３ Nine O-rings were prepared by immersing them in AGC Inc.'s product name: Asahi Clean® AC-6000 for 70 hours. Next, the nine O-rings were arranged in a 3x3 square without any gaps. Then, one polyethylene bag (Taiyo Poly Bag, size: No. 12, manufactured by Nakagawa Seitaikako Co., Ltd.) was placed over the top, and a 100 kg weight was placed on top of it and left for one day. After one day, a peel test was performed by attaching the attached hook to a digital force gauge (FGP-0.2, manufactured by Nidec Corporation) and hooking it onto the opening of the polyethylene bag. The load (N) at that time was used to evaluate the adhesion to polyethylene. The results are shown in Table 5. In addition, for the obtained cross-linked rubber articles 1 and 2, no O-ring residue remained on the polyethylene after the peel test (i.e., after peeling), and the peelability was excellent.

[0157] (Measurement of Compression Set) As an indicator of rubber properties, the compression set (CS) was measured for each of the cross-linked rubber articles 1 to 4, referring to ASTM D395 or JIS K 6262 (2013) (ISO 815-1:2008, ISO 815-2:2008). As test specimens, P26 O-rings conforming to JIS B 2401-1 (2012) (ISO 3601-1:2008) were used. The O-rings prepared in each example (original thickness (wire diameter) of the test specimen = 3.5 mm) were compressed to a compression ratio of 18% using a compression device. Next, the compression device with the compressed O-ring fixed in place was left in an electric furnace at 200°C for 70 hours. After that, the compression device was removed from the electric furnace, the O-ring was immediately removed from the compression device, and the removed O-ring was left in a constant temperature room at 23°C for 30 minutes to measure its thickness (thickness after compression). The test was carried out using 10 O-rings, and the arithmetic mean of the measured values ​​of 6 O-rings was used. The compression set was calculated using the following formula (6). Note that the closer the compression set is to 0%, the smaller the compression set, which is preferable. In addition, the average, deviation, and coefficient of variation (CV value) × 100 of the compression set of the 10 O-rings were calculated. The results are shown in Table 5. Compression set (%) = [(t ０ -t １ ) / (t ０ -t２ )]×100…(6) t ０ : Original thickness (wire diameter) of the O-ring t １ : Thickness of the O-ring 30 minutes after removal from the compression device (thickness after compression treatment) t ２ : Thickness of the spacer

[0158]

[0159] As shown above, in Examples 1 and 2, crosslinked rubber articles that maintain rubber properties while also exhibiting excellent adhesion to polyethylene, and compositions that yield the crosslinked rubber articles were obtained. The excellent adhesion to polyethylene is due to CF ３ (CF ２ ) ５ CH ２ CH ３ By storing the cross-linked rubber articles in polyethylene bags after use in the environment, preventing exposure to air, contamination can be reduced. Furthermore, the cross-linked rubber articles in Examples 1 and 2 showed small variations in compression set.

[0160] Furthermore, the disclosure of Japanese Patent Application No. 2025-009468, filed on January 22, 2025, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

Claims

1. Contains a crosslinked material formed by crosslinking a fluorine-containing elastomer, CF ３ (CF ２ ) ５ CH ２ CH ３ A cross-linked rubber article whose volume swelling rate, which represents the percentage change in volume after immersion relative to the volume before immersion, is greater than 66.0% when immersed at 25°C for 70 hours.

2. The crosslinked rubber article according to claim 1, wherein the fluorine-containing elastomer comprises a structural unit based on tetrafluoroethylene and a structural unit based on perfluoroalkyl vinyl ether.

3. The crosslinked rubber article according to claim 1 or 2, wherein the crosslinked body includes a peroxide-based structure.

4. The crosslinked rubber article according to claim 1 or 2, wherein the crosslinked material comprises a structure based on a compound having two or more allyl groups in one molecule.

5. The crosslinked rubber article according to claim 1 or 2, further comprising a filler.

6. The crosslinked rubber article according to claim 1 or 2, further comprising a fatty acid metal salt.

7. A crosslinked rubber article according to claim 1 or 2, which is substantially free of an emulsifier having a fluorine atom.

8. Further, CF is attached to a part or all of the surface ３ (CF ２ ) ５ CH ２ CH ３ and the crosslinked rubber article according to claim 1 or 2.

9. CF ３ (CF ２ ) ５ CH ２ CH ３ The density after immersion at 25°C for 70 hours is 1.82 g / cm³. ３ The following is the crosslinked rubber article according to claim 1 or 2.

10. The crosslinked rubber article according to claim 1 or 2, which is an O-ring.

11. A composition comprising a fluorine-containing elastomer having iodine atoms and a crosslinking agent, wherein the iodine crosslinking efficiency calculated by the following formula (5) when the fluorine-containing elastomer is crosslinked is 5.0 or higher. Iodine crosslinking efficiency (mass ppm / dN·m) = [iodine content] / [M Ｈ -M Ｌ ] ... (5) [In formula (5), [iodine content] represents the content of iodine atoms (mass ppm) relative to the mass of the fluorine-containing elastomer. M Ｈ This is the maximum torque (dN·m) in the crosslinking curve of the composition, which shows the relationship between torque and time. Ｌ This is the minimum torque value (dN·m) in the aforementioned bridge curve.

12. The composition according to claim 11, wherein the fluorine-containing elastomer comprises a structural unit based on tetrafluoroethylene and a structural unit based on perfluoroalkyl vinyl ether.

13. The composition according to claim 11 or 12, which substantially does not contain an emulsifier having a fluorine atom.

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