Sealing material and method for manufacturing the same

Abstract

One aspect of the present invention relates to a sealing material or a method for producing the sealing material, the sealing material being an object obtained by crosslinking, with radiation, an elastomer composition which comprises one or more crosslinkable fluoroelastomers (A) that are not perfluoroelastomers, a crosslinking agent, and a crosslinking aid, wherein the fluoroelastomers (A) include a crosslinkable fluoroelastomer (A1) that has a fluorine content of 66-68 mass% and is not a perfluroelastomer.

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a sealing material or a method for manufacturing a sealing material. [Background technology]

[0002] Conventionally, sealing materials have been widely used in various applications. Among these applications, an example of an application of a sealing material that places the greatest load on the sealing material is a sealing material used in semiconductor manufacturing equipment, etc.

[0003] Crosslinkable fluoroelastomers are used as such sealing materials because they can provide sealing materials with excellent plasma resistance and radical resistance. Such sealing materials made of crosslinkable fluoroelastomers are usually prepared by blending additives such as a crosslinking agent and a crosslinking aid with the crosslinkable fluoroelastomer to obtain an elastomer composition, which is then molded and crosslinked. In particular, in terms of plasma resistance and sealing properties of the resulting sealing material, the crosslinking process includes a step of irradiating with radiation (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-131656 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, when an additive is blended with a crosslinkable fluoroelastomer to prepare an elastomer composition, the components in the elastomer composition must be uniformly mixed in order to produce a sealing material exhibiting desired physical properties from the elastomer composition. However, when conventional crosslinkable fluoroelastomers are used, particularly when liquid or oily components are used, it takes a long time to prepare such a uniform elastomer composition, and there is room for improvement in this regard.

[0006] Furthermore, when a sealing material is formed from the prepared elastomer composition with high productivity, the elastomer composition is usually formed into a sheet by a separating process. This separating process is usually carried out by passing the elastomer composition between rolls. However, when a conventional elastomer composition is used, the elastomer composition is not easily caught between the rolls or does not wind properly around the rolls, making it difficult to form into a sheet (poor separating ability). Therefore, conventional elastomer compositions have room for improvement in terms of moldability.

[0007] Furthermore, sealing materials formed from conventional elastomer compositions have room for improvement in terms of properties as sealing materials, such as tensile strength and elongation at break.

[0008] An embodiment of the present invention provides a sealing material that can be produced with good moldability, has excellent sealing properties, and has high tensile strength and elongation at break. [Means for solving the problem]

[0009] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following configuration examples, and have completed the present invention. An example of the configuration of the present invention is as follows.

[0010] [1] A sealing material which is a radiation-crosslinked product of an elastomer composition containing a crosslinkable fluoroelastomer (A) other than a perfluoroelastomer, a crosslinking agent, and a crosslinking aid, The fluoroelastomer (A) contains a crosslinkable fluoroelastomer (A1) other than a perfluoroelastomer having a fluorine content in the range of 66 to 68 mass%. Sealing material.

[0011] [2] The sealing material according to [1], wherein the fluoroelastomer (A) is a peroxide-crosslinkable fluoroelastomer.

[0012] [3] The sealing material according to [1] or [2], wherein the elastomer composition contains at least one ethylenically unsaturated bond-containing compound selected from a perfluoro-skeleton compound having an ethylenically unsaturated bond and a siloxane-skeleton compound having an ethylenically unsaturated bond.

[0013] [4] The sealing material according to any one of [1] to [3], wherein the content of the filler is 5 parts by mass or less per 100 parts by mass of the fluoroelastomer (A).

[0014] [5] A method for producing a sealing material, comprising a step of irradiating an elastomer composition containing a crosslinkable fluoroelastomer (A) other than a perfluoroelastomer, a crosslinking agent, and a crosslinking aid, wherein the fluoroelastomer (A) contains a crosslinkable fluoroelastomer (A1) other than a perfluoroelastomer having a fluorine content in the range of 66 to 68 mass%, or a crosslinked product of the elastomer composition. [Effects of the Invention]

[0015] According to one embodiment of the present invention, a sealing material can be provided that can be produced with good moldability, has excellent sealing properties (small compression set), and has high tensile strength and elongation at break. Specifically, a uniform elastomer composition can be produced in a short time, and a sealing material that has excellent sealing properties and high tensile strength and elongation at break can be provided from an elastomer composition that has excellent moldability, particularly extrusion properties. Furthermore, according to one embodiment of the present invention, it is possible to obtain a sealing material that is excellent in balance with respect to hardness, tensile strength, elongation at break, and tensile stress at 100% elongation (100% Mo), and further has excellent plasma resistance (radical resistance), crack resistance, compression set, etc. Therefore, the sealing material can be suitably used as a sealing material for semiconductor manufacturing equipment and a sealing material for plasma processing equipment. DETAILED DESCRIPTION OF THE INVENTION

[0016] <Sealing material> A sealing material according to one embodiment of the present invention (hereinafter also referred to as "the sealing material") is a radiation-crosslinked product of an elastomer composition (hereinafter also referred to as "the composition") containing a crosslinkable fluoroelastomer (A) other than a perfluoroelastomer, a crosslinking agent, and a crosslinking aid, wherein the fluoroelastomer (A) contains a crosslinkable fluoroelastomer (A1) other than a perfluoroelastomer having a fluorine content in the range of 66 to 68 mass%. Specific examples of the radiation-crosslinked product of the present composition include the present composition itself and a radiation-crosslinked product obtained by a method including a step of irradiating a crosslinked product of the present composition (e.g., a crosslinked product obtained by thermally crosslinking the present composition) with radiation.

[0017] The sealing material can be used, for example, as gaskets or packing for various components, and because it exhibits the above-mentioned effects in particular, it can be suitably used for semiconductor manufacturing equipment and plasma processing equipment, particularly for driving parts such as gate valves used at the openings of plasma processing chamber units. The shape and other properties of the sealing material may be appropriately selected depending on the intended use.

[0018] The present sealing material does not contain the filler, but can have the following physical properties. The Shore A hardness (type A durometer hardness) of the present sealing material measured in accordance with JIS K 6253:2012 is preferably 60 or more. The tensile strength of the present sealing material measured in accordance with JIS K 6251:2017 is preferably 10 MPa or more. The elongation at break of the sealing material measured in accordance with JIS K 6251:2017 is preferably 130% or more. The 100% modulus of the present sealing material measured in accordance with JIS K 6251:2017 is preferably 3.5 MPa or more. The compression set of the sealing material measured in accordance with JIS K 6262:2013 is preferably 35% or less.

[0019] <Crosslinkable fluoroelastomer (A) other than perfluoroelastomer> The elastomer (A) is not particularly limited as long as it includes a crosslinkable fluoroelastomer (A1) other than perfluoroelastomers having a fluorine content in the range of 66 to 68 mass %. The elastomer (A) may be used alone or in combination of two or more kinds, and the elastomer (A1) may be used alone or in combination of two or more kinds. In the present invention, "elastomer" and "rubber" have the same meaning and there is no particular distinction between them.

[0020] The elastomer (A) may contain a crosslinkable fluoroelastomer other than a perfluoroelastomer (hereinafter also referred to as "elastomer (A2)") other than the elastomer (A1), and preferably contains the elastomer (A2) from the viewpoint that a sealing material having excellent chemical resistance such as plasma resistance and chemical resistance can be easily obtained. When the elastomer (A) contains the elastomer (A2), one type of the elastomer (A2) may be used, or two or more types of the elastomer (A2) may be used.

[0021] The elastomer (A) is also called unvulcanized fluororubber, and examples of crosslinked types include peroxide crosslinking, polyol crosslinking, amine crosslinking, radiation crosslinking, etc. Among these, peroxide-crosslinkable fluoroelastomers are preferred, since they do not require the use of an acid acceptor that can generate particles in a plasma atmosphere, etc., and there is no risk of generating particles during use of the resulting sealing material.

[0022] Specific examples of the elastomer (A) include fluoroelastomers (FKM), tetrafluoroethylene-propylene elastomers (FEPM), and fluorine-containing thermoplastic elastomers (e.g., elastomers containing at least one type of elastomeric polymer chain segment and at least one type of non-elastomeric polymer chain segment, at least one of which is a fluorine-containing polymer chain segment).

[0023] The elastomer (A) is preferably an elastomer that can provide a sealing material that is resistant to plasma (plasma etching treatment) used in various semiconductor dry processes, and more preferably FKM, which has relatively good plasma resistance and excellent sealing properties. FKM is also preferred because it is inexpensive and versatile.

[0024] The elastomer (A) may be synthesized by a conventionally known method or may be a commercially available product, such as "Dai-el" manufactured by Daikin Industries, Ltd., "Viton" manufactured by Chemours, "Dyneon" manufactured by 3M, or "Technoflon" manufactured by Solvay.

[0025] The fluorine content of the elastomer (A1) is 66 to 68 mass %. The fluorine content of the elastomer (A2) is not particularly limited as long as it is in a range other than 66 to 68% by mass. However, from the viewpoint of easily obtaining a sealing material having excellent chemical resistance such as plasma resistance and chemical resistance, the fluorine content is preferably 69% by mass or more, more preferably 70% by mass or more, and more preferably 73% by mass or less, and even more preferably 71% by mass or less. By using at least two elastomers having a fluorine content within the above range, a uniform elastomer composition can be prepared in a short time, an elastomer composition with excellent moldability can be easily obtained, and a sealing material with a well-balanced excellent hardness, tensile strength, elongation at break, and 100% Mo can be easily obtained. The fluorine content is 19 F-NMR and 1It can be measured or calculated by elemental analysis of fluorine using 1H-NMR or mass spectrometry (MS spectrometry). The fluorine content in the present invention is a value rounded off to the nearest whole number.

[0026] The Mooney viscosity of the elastomer (A) is preferably 10 or more, more preferably 15 or more, even more preferably 20 or more, and preferably 140 or less, more preferably 120 or less, even more preferably 80 or less, particularly preferably 60 or less. When the Mooney viscosity of the elastomer (A) is within the above range, an elastomer composition having excellent moldability, particularly excellent extrusion property, can be easily obtained. The Mooney viscosity in this specification refers to the Mooney viscosity (ML1+10) at 121° C. measured in accordance with ASTM D 1646.

[0027] In one embodiment of the elastomer (A2), it is preferable to use an elastomer (A2-1) having a Mooney viscosity in the range of preferably 40 to 140, more preferably 40 to 120, and even more preferably 40 to 60, and an elastomer (A2-2) having a Mooney viscosity in the range of preferably 10 or more and less than 40, more preferably 10 to 30. The use of the elastomers (A2-1) and (A2-2) is preferred because it provides a better balance between the normal physical properties of the resulting sealing material, such as hardness, tensile strength, elongation at break, and 100% Mo, and the physical properties of the elastomer composition, such as moldability, particularly extrusion property.

[0028] When the elastomers (A2-1) and (A2-2) are used as the elastomer (A2), the content of the elastomer (A2-1) is preferably 20 to 80% by mass relative to the total of these (100% by mass). It is preferable that the content of the elastomer (A2-1) is within the above range, because the normal physical properties of the resulting sealing material, such as hardness, tensile strength, elongation at break, and 100% Mo, and the physical properties of the elastomer composition, such as moldability, particularly extrusion property, are better balanced and excellent.

[0029] When the elastomer (A) consists solely of the elastomer (A1), the content of the elastomer (A1) in the solid content of the composition is preferably 50% by mass or more, more preferably 70% by mass or more, and preferably 97% by mass or less, more preferably 95% by mass or less. When the content of the elastomer (A1) is within the above range, a sealing material excellent in sealing properties, moldability and chemical resistance can be easily obtained. In this specification, the solid content refers to components other than the solvent.

[0030] When the elastomer (A) contains the elastomer (A2), the content of the elastomer (A1) in the solid content of the composition is preferably 2% by mass or more, more preferably 5% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less. When the content of the elastomer (A1) is within the above range, a sealing material having a good balance between moldability and chemical resistance can be easily obtained.

[0031] Furthermore, when the elastomer (A) contains the elastomer (A2), the content of the elastomer (A2) in the solid content of the composition is preferably 40% by mass or more, more preferably 50% by mass or more, and preferably 95% by mass or less, more preferably 85% by mass or less. When the content of the elastomer (A2) is within the above range, a sealing material having excellent chemical resistance such as plasma resistance and chemical resistance can be easily obtained.

[0032] When the elastomer (A) contains the elastomer (A2), the content of the elastomer (A1) relative to the total content of the elastomers (A1) and (A2) in the composition is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 40% by mass or less, more preferably 35% by mass or less. When the mass ratio of the contents of the elastomers (A1) and (A2) is within the above range, a sealing material having a good balance between moldability and chemical resistance can be easily obtained.

[0033] [FKM] There are no particular limitations on the FKM, but examples include polymers containing hydrogen atoms (carbon-hydrogen bonds) in the polymer main chain, and specifically, it is preferable that the FKM contains structural units derived from vinylidene fluoride.

[0034] The FKM is not particularly limited, but specific examples include vinylidene fluoride-hexafluoropropylene polymers; vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene polymers; vinylidene fluoride-propylene-tetrafluoroethylene polymers; ethylene-tetrafluoroethylene-perfluoroalkyl vinyl ether polymers; and vinylidene fluoride-tetrafluoroethylene-perfluoroalkyl vinyl ether polymers. A suitable example of the perfluoroalkyl vinyl ether is perfluoromethyl vinyl ether.

[0035] Among these, ternary polymers are preferred because of their excellent plasma resistance, heat resistance, chemical resistance, etc., and vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene polymers are more preferred.

[0036] The peroxide-crosslinkable fluoroelastomer preferably has a functional group such as an iodine group, a bromine group, a cyano group, a peroxy group, or an unsaturated group, and more preferably an iodine group or a bromine group from the viewpoint of ease of introduction of the functional group. A fluoroelastomer having an iodine group and / or a bromine group can be obtained, for example, by using one or more saturated or unsaturated iodine- and / or bromine-containing compounds when synthesizing the elastomer.

[0037] Examples of the iodine- and / or bromine-containing compound include compounds represented by the following formula (1) or (2). By using a compound represented by the following formula (1), a fluoroelastomer having an iodine group and / or a bromine group on the side chain can be synthesized, and by using a compound represented by the following formula (2), a fluoroelastomer having an iodine group and / or a bromine group at the end can be synthesized.

[0038] CY 1 2=CY 2 RfX (1) [Y 1 and Y 2 are each independently a fluorine atom, a hydrogen atom or a methyl group, Rf is a linear or branched fluorine-containing alkylene group in which some or all of the hydrogen atoms have been substituted with fluorine atoms, or a group containing an ether bond in part of the fluorine-containing alkylene group, and X is an iodine atom or a bromine atom.

[0039] Specific examples of the compound represented by the formula (1) include the compounds described in WO 2009 / 119409.

[0040] I n Br m R (2) [R is a fluorohydrocarbon group having 1 to 12 carbon atoms, n and m are each independently an integer of 0 to 2, and n+m is 1 or 2.]

[0041] Specific examples of the compound represented by the formula (2) include compounds described in JP-A Nos. 2002-97329 and 2008-56739.

[0042] <Crosslinking agent> The crosslinking agent is not particularly limited, and can be selected from conventionally known crosslinking agents depending on the type of elastomer (A) used. The crosslinking agent may be used alone or in combination of two or more.

[0043] When FKM is used, examples of the crosslinking agent include peroxide-based crosslinking agents, polyamine-based crosslinking agents, polyol-based crosslinking agents, and triazine-based crosslinking agents.

[0044] Among these, peroxide-based crosslinking agents are preferred because they do not require the incorporation of an acid acceptor such as magnesium oxide or calcium hydroxide, which can be a source of particle generation in a plasma atmosphere, and there is no risk of particle generation during use of the resulting sealing material.

[0045] Examples of peroxide-based crosslinking agents include 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, di-t-butyl peroxide, t-butyldicumyl peroxide, benzoyl peroxide, 2,5-dimethyl-2,5-(t-butylperoxy)hexyne-3, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, and t-butylperoxyisopropyl. Examples of peroxybenzoates include propyl carbonate, di-(4-t-butylcyclohexyl) peroxydicarbonate, p-chlorobenzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butyl peroxybenzoate, 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, α,α-bis(t-butylperoxy)-p-diisopropylbenzene, t-butylperoxybenzene, and t-butylperoxymaleic acid. Among these, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, benzoyl peroxide, and α,α'-bis(t-butylperoxy-m-isopropyl)benzene are preferred, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane is more preferred.

[0046] The content of the crosslinking agent in the present composition is preferably 0.2 to 4 parts by mass, more preferably 0.2 to 2.5 parts by mass, per 100 parts by mass of the elastomer (A), from the viewpoints that the crosslinking reaction proceeds sufficiently and a sealing material having a well-balanced excellent properties of hardness, tensile strength, elongation at break, and 100% Mo can be easily obtained.

[0047] <Crosslinking aid> The crosslinking aid is not particularly limited, and a conventionally known crosslinking aid may be selected depending on the type of crosslinking agent. The crosslinking aid may be used alone or in combination of two or more kinds.

[0048] For example, examples of crosslinking aids that can be used when using peroxide-based crosslinking agents include triallyl isocyanurate, triallyl cyanurate, trimethallyl isocyanurate, triallyl formal, triallyl trimellitate, N,N'-m-phenylene bismaleimide, dipropargyl terephthalate, diallyl phthalate, tetraallyl terephthalamide, polyfunctional (meth)acrylates such as ethylene glycol di(meth)acrylate and trimethylolpropane tri(meth)acrylate, and other compounds capable of co-crosslinking by radicals (polyfunctional monomers), metal salts of higher carboxylic acids, polyhydric alcohol (meth)acrylates, and metal (meth)acrylic acid salts. Among these, triallyl isocyanurate is preferred because it has excellent reactivity, excellent heat resistance, and can easily produce a sealing material with high hardness and high modulus.

[0049] The content of the crosslinking aid in the present composition is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 4 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less, per 100 parts by mass of the elastomer (A), from the viewpoints that the crosslinking reaction will proceed sufficiently and a sealing material that is excellent in balance among hardness, tensile strength, elongation at break, and 100% Mo can be easily obtained. In particular, in order to suppress cracks that may occur in the sealing material under a plasma atmosphere or the like, a radiation-crosslinked sealing material (radiation-treated product) is preferred. In this case, a sealing material with higher hardness and higher modulus can be easily obtained without using a filler such as those described below. For this reason, the content of the crosslinking aid in the present composition is preferably 2 parts by mass or more, more preferably 4 parts by mass or more, and preferably 7 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the elastomer (A).

[0050] The mass ratio of the content of the crosslinking aid to the content of the crosslinking agent in the composition (content of crosslinking aid / content of crosslinking agent) is preferably 4 or more, more preferably 6 or more, and preferably 30 or less, more preferably 20 or less, from the viewpoints that the crosslinking agent can be reacted in just the right amount and a sealing material exhibiting desired physical properties can be easily obtained, and in particular, a sealing material with higher hardness and higher modulus can be easily obtained without using a filler such as those described below.

[0051] <Other ingredients> In addition to the above components, the present composition may contain other components that have been conventionally incorporated into sealing materials, as needed, within the scope of not impairing the effects of the present invention. Examples of such other components include ethylenically unsaturated bond-containing compounds, reactive organosilicon compounds having two or more hydrosilyl groups in the molecule, catalysts, acid acceptors such as magnesium oxide and calcium hydroxide, organic pigments such as anthraquinone pigments, perylene pigments, and dioxazine pigments, plasticizers, processing aids, vulcanization accelerators, antioxidants, antioxidants, inorganic fillers, and organic fillers. The other components may each be used alone or in combination of two or more.

[0052] [Ethylenically unsaturated bond-containing compounds] The present composition preferably contains an ethylenically unsaturated bond-containing compound (hereinafter also referred to as "compound (B)"), since it is possible to easily obtain a sealing material that is excellent in plasma resistance and non-sticky. The compound (B) may be at least one compound selected from the group consisting of a compound (B1) having a perfluoro skeleton and an ethylenically unsaturated bond, and a compound (B2) having a siloxane skeleton and an ethylenically unsaturated bond. Among these, the compound (B) preferably contains the compound (B1) because it is possible to easily obtain a sealing material having better plasma resistance.

[0053] Examples of the ethylenically unsaturated bond include alkenyl groups having 2 to 8 carbon atoms, such as vinyl, methylvinyl, allyl, propenyl, isopropenyl, butenyl, pentenyl, hexenyl, and heptenyl, vinylphenyl, (meth)acryloyl, allyloxy, styryl, and propargyl. Among these, alkenyl groups are preferred, alkenyl groups having 2 to 4 carbon atoms are more preferred, and vinyl groups are particularly preferred. The compound (B) may have two or more types of ethylenically unsaturated bonds.

[0054] Compound (B) may be synthesized by a conventionally known method, or may be a commercially available product, such as "SIFEL" (manufactured by Shin-Etsu Chemical Co., Ltd.). In addition, commercially available products containing compound (B) include one-component and two-component products, and any of these may be used. In addition, commercially available products containing compound (B) include liquid, paste, oil, millable, and the like, and any of these may be used.

[0055] When a commercially available product is used as compound (B), the commercially available product may contain additives such as a reactive organosilicon compound having two or more hydrosilyl groups in the molecule (e.g., organosilicon compounds described in JP-A Nos. 2003-183402 and 11-116684), a catalyst (e.g., the catalysts described in JP-A Nos. 2003-183402 and 11-116684), a filler (e.g., silica), etc., and compound (B) containing these additives may be used.

[0056] When the present composition contains compound (B), the content of compound (B) in the present composition is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 50 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of elastomer (A), from the viewpoints that a uniform elastomer composition can be obtained in a shorter time and a sealing material with better plasma resistance can be easily obtained.

[0057] When the present composition contains the compound (B) and a crosslinking agent, the mass ratio of the content of the compound (B) to the content of the crosslinking agent in the present composition (content of the compound (B) / content of the crosslinking agent) is preferably 1 or more, more preferably 2 or more, and is preferably 20 or less, more preferably 10 or less, from the viewpoint that a sealing material having superior plasma resistance can be easily obtained.

[0058] [Compound (B1)] The compound (B1) is a compound other than the elastomer (A). Examples of the compound (B1) include a compound having a perfluoropolyether structure with an ethylenically unsaturated bond and a compound having a perfluoroalkylene structure with an ethylenically unsaturated bond. Among these, a compound having a perfluoropolyether structure with an ethylenically unsaturated bond (hereinafter also referred to as "compound (B1-1)") is preferred. When the present composition contains a compound (B1), the compound (B1) contained in the present composition may be one type or two or more types.

[0059] ·Compound (B1-1) The compound (B1-1) is preferably a perfluoropolyether having two or more ethylenically unsaturated bonds in one molecule.

[0060] Suitable examples of the compound (B1-1) include the compounds described in JP-A Nos. 2003-183402, 11-116684, 11-116685, and 2015-67737.

[0061] An example of the compound (B1-1) is a compound represented by the following formula (1). Z 1 -(X) p -(Rf-Q) a -Rf-(X) p -Z 2 ···(1)

[0062] X independently represents -CH2-, -CH2O-, -CH2OCH2-, *-Si(R 2 )2-Ph-(Ph: phenylene group), *-Y-NR 1 SO2- or *-Y-NR 1 -CO-(where Y is -CH2- or *-Si(R 2 )2-Ph-. In addition, the * portion is Z 1 or Z 2 ) which binds to Rf is a divalent perfluoropolyether group (divalent perfluorooxyalkylene group). p is independently 0 or 1. a is an integer of 0 or more, preferably an integer of 0 to 10, and more preferably an integer of 0 to 6. Q is a group represented by the following formula (2), (3) or (4).

[0063] R 2is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms, particularly 1 to 8 carbon atoms, and examples thereof include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, hexyl, octyl, and decyl groups; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl groups; alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, and hexenyl groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl groups; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms or the like (e.g., fluorine-substituted alkyl groups such as chloromethyl, chloropropyl, bromoethyl, 3,3,3-trifluoropropyl, and 6,6,6,5,5,4,4,3,3-nonafluorohexyl groups).

[0064] R 1 is a hydrogen atom or the R 2 is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms, particularly 1 to 8 carbon atoms, similar to the groups exemplified as R 2 Examples of the alkyl group include alkyl groups such as a methyl group, an ethyl group, a propyl group, and an isopropyl group; cycloalkyl groups such as a cyclohexyl group; alkenyl groups such as a vinyl group and an allyl group; aryl groups such as a phenyl group and a tolyl group; and groups in which some of the hydrogen atoms of these groups have been substituted with halogen atoms or the like (e.g., fluorine-substituted alkyl groups such as a chloromethyl group, a chloropropyl group, a 3,3,3-trifluoropropyl group, and a 6,6,6,5,5,4,4,3,3-nonafluorohexyl group).

[0065] Z 1 and Z 2 are each independently an ethylenically unsaturated bond-containing group, and may be -Si(ethylenically unsaturated bond-containing group)(R')2. The ethylenically unsaturated bond-containing group is preferably a monovalent alkenyl group, more preferably a monovalent alkenyl group having 2 to 4 carbon atoms, and particularly preferably a monovalent vinyl group. R' is independently a substituted or unsubstituted monovalent hydrocarbon group, and specific examples include alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, pentyl, and hexyl; aryl groups such as phenyl, tolyl, and xylyl; and halogenated alkyl groups such as 3-chloropropyl and 3,3,3-trifluoropropyl. Among these, alkyl groups having 1 to 5 carbon atoms are preferred.

[0066] [ka]

[0067] In formulas (2) to (4), X, p, and R 1 represents X, p and R in the formula (1). 1 It is synonymous with R. 3 and R 4 are each independently a substituted or unsubstituted divalent hydrocarbon group which may have one or more atoms selected from oxygen atoms, nitrogen atoms, silicon atoms, and sulfur atoms interposed in the bond, and R in formula (2) 3 and R in Eq. (3) 4 may each independently be a group represented by the following formula (5) or (6):

[0068] [ka]

[0069] In equations (5) and (6), R 5 is a substituted or unsubstituted monovalent hydrocarbon group, and R 6 is a group containing at least one atom selected from carbon atoms, oxygen atoms, nitrogen atoms, silicon atoms and sulfur atoms.

[0070] R 3 and R 4Although there are no particular limitations on the group as long as it is a substituted or unsubstituted divalent hydrocarbon group, divalent hydrocarbon groups having 1 to 20 carbon atoms, and particularly 2 to 12 carbon atoms, are preferred. Specific examples include alkylene groups such as methylene, ethylene, propylene, methylethylene, butylene, and hexamethylene; cycloalkylene groups such as cyclohexylene; arylene groups such as phenylene, tolylene, xylylene, naphthylene, and biphenylene; groups in which some of the hydrogen atoms of these groups have been substituted with halogen atoms or the like; and combinations of these substituted or unsubstituted alkylene and arylene groups.

[0071] -(X) p -(Rf-Q) a -Rf-(X) p - is -(OR 7 ) n -[R 7 represents a perfluoroalkanediyl group, and n represents an integer of 2 or more. 7 may be the same or different.

[0072] R 7 Examples of the perfluoroalkanediyl group represented by the formula (I) include C m F 2m (m is an integer of 2 or more), which may be linear or branched. The number of carbon atoms in the perfluoroalkanediyl group (i.e., m) is, for example, 1 to 10, preferably 2 to 6, more preferably 2 to 4, and particularly preferably 2 to 3.

[0073] n may be 2 or more, for example, 10 or more, preferably 40 or more, and more preferably 70 or more. Also, n is, for example, 300 or less, preferably 200 or less, and more preferably 150 or less.

[0074] -(OR 7 ) n - may be the same group as Rf below.

[0075] The compound represented by the formula (1) is preferably a compound represented by the following formula (1-1). CH2=CH-(X) p -(Rf-Q) a -Rf-(X) p -CH=CH2 (1-1) [The definitions of each symbol in formula (1-1) are the same as those of each symbol in formula (1)]

[0076] The compound represented by the formula (1-1) is preferably a compound in which a is 0, and in this case, it is represented by the following formula (1-1-1). CH2=CH-(X) p -Rf-(X) p -CH=CH2 (1-1-1) [The definitions of each symbol in formula (1-1-1) are the same as those of each symbol in formula (1)]

[0077] Specific examples of Rf include the following groups. -[CF(Z)OCF2] p -(CF2) r -[CF2OCF(Z)] q - (Z is a fluorine atom or —CF3, and p, q, and r are integers satisfying p≧1, q≧1, 2≦p+q≦200, preferably 2≦p+q≦110, and 0≦r≦6.) -CF2CF2OCF2-(CF(CF3)OCF2) s -(CF2) r -(CF2OCF(CF3)) t -CF2OCF2CF2- (r, s, and t are integers satisfying 0≦r≦6, s≧0, t≧0, 0≦s+t≦200, preferably 2≦s+t≦110.) -CF(Z)-(OCF(Z)CF2) u -(OCF2) v -OCF(Z)- (Z is a fluorine atom or —CF3, and u and v are integers satisfying the conditions 1≦u≦100 and 1≦v≦50.) -CF2CF2-[OCF2CF2CF2] w -OCF2CF2- (W is an integer that satisfies 1≦w≦100.)

[0078] [Compound (B2)] The compound (B2) is preferably a polysiloxane having two or more ethylenically unsaturated bonds in one molecule, and more preferably an organopolysiloxane having two or more ethylenically unsaturated bonds in one molecule and having an organic group bonded to a silicon atom. The bonding position of the ethylenically unsaturated bond is not particularly limited. When the present composition contains a compound (B2), the compound (B2) contained in the present composition may be one type or two or more types.

[0079] Examples of the organic group bonded to a silicon atom include the above-mentioned ethylenically unsaturated bond, a linear alkyl group, a branched alkyl group, a cyclic alkyl group, an aryl group, an aralkyl group, and a halogenated alkyl group. Examples of the linear alkyl group include groups having 1 to 20 carbon atoms, preferably 1 to 6 carbon atoms, such as a methyl group, an ethyl group, a propyl group, a hexyl group, an octyl group, and a decyl group. Examples of the branched alkyl group include groups having 1 to 20 carbon atoms, preferably 1 to 6 carbon atoms, such as an isopropyl group, an isobutyl group, a t-butyl group, and a 2-ethylhexyl group. Examples of the cyclic alkyl group include groups having 3 to 20 carbon atoms, such as a cyclopentyl group and a cyclohexyl group. Examples of the aryl group include groups having 6 to 20 carbon atoms, such as a phenyl group and a tolyl group. Examples of the aralkyl group include groups having 7 to 20 carbon atoms, such as a benzyl group, a 2-phenylethyl group, and a 2-methyl-2-phenylethyl group. Examples of halogenated alkyl groups include groups having 1 to 20 carbon atoms, preferably 1 to 6 carbon atoms, such as a 3,3,3-trifluoropropyl group, a 2-(nonafluorobutyl)ethyl group, and a 2-(heptadecafluorooctyl)ethyl group.

[0080] The organic group bonded to the silicon atom is preferably a linear alkyl group, an alkenyl group, or an aryl group, more preferably a linear alkyl group, an alkenyl group, or an aryl group having 1 to 6 carbon atoms, and particularly preferably a methyl group, a vinyl group, or a phenyl group.

[0081] The molecular structure of compound (B2) is not particularly limited, and examples thereof include linear, branched, partially branched linear, and dendritic (dendrimer) structures, with linear and partially branched linear structures being preferred. Compound (B2) may be a single polymer having these molecular structures, a copolymer having these molecular structures, or a mixture of two or more of these polymers.

[0082] Examples of compound (B2) include dimethylpolysiloxanes terminally capped with dimethylvinylsiloxy groups, dimethylpolysiloxanes terminally capped with methylphenylvinylsiloxy groups, dimethylsiloxane-methylphenylsiloxane copolymers terminally capped with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers terminally capped with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers terminally capped with silanol groups, dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers terminally capped with silanol groups, dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers terminally capped with trimethylsiloxy groups, and methyl(3,3,3-trifluoropropyl)polysiloxane terminally capped with dimethylvinylsiloxy groups, and the formula: (CH3)3SiO 1 / 2 Siloxane units represented by the formula: (CH3)2(CH2=CH)SiO 1 / 2 Siloxane units represented by the formula: CH3SiO 3 / 2 Siloxane units represented by the formula: (CH3)2SiO 2 / 2 and a compound represented by the following formula (7).

[0083] [ka] [In formula (7), R1 are each independently an unsubstituted or substituted monovalent hydrocarbon group, and R 2 are independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group, b is an integer of 2 to 100, and a is an integer of 1 to 3. However, in formula (7), R 1 and R 2 At least two of the groups contain the ethylenically unsaturated bond.]

[0084] In formula (7), R 1 are each independently an unsubstituted or substituted monovalent hydrocarbon group, preferably having 1 to 10 carbon atoms, examples of which include the same groups as those exemplified above as the organic group bonded to a silicon atom. Of these, monovalent hydrocarbon groups having 1 to 6 carbon atoms are preferred, and alkenyl groups, aryl groups, and alkyl groups having 1 to 3 carbon atoms are more preferred.

[0085] R in equation (7) 2 Examples of the alkyl group and alkenyl group in the above formula include the same straight-chain alkyl group, branched-chain alkyl group, cyclic alkyl group, and alkenyl group as those exemplified as the organic group bonded to a silicon atom. R in equation (7) 2 Examples of the alkoxyalkyl group in the formula include groups having 2 to 10 carbon atoms, such as a methoxyethyl group and a methoxypropyl group. R in equation (7) 2 Examples of the acyl group in the formula include groups having 2 to 10 carbon atoms, such as an acetyl group and an octanoyl group.

[0086] In the formula (7), b is preferably an integer of 10 to 50, and a is preferably 3.

[0087] [Reactive organosilicon compounds] The reactive organosilicon compound is a compound other than compound (B2), and suitable examples include compounds similar to compounds having two or more hydrosilyl groups in the molecule described in JP-A Nos. 2003-183402 and 11-116684.

[0088] [catalyst] Suitable examples of the catalyst include the same catalysts as those described in JP-A Nos. 2003-183402 and 11-116684.

[0089] [Organic pigments] Suitable examples of the organic pigment include organic pigments similar to those described in International Publication No. 2016 / 043100, Japanese Patent No. 4720501, International Publication No. 2004 / 094527, and the like.

[0090] [Filling material] The inorganic filler and organic filler (hereinafter collectively referred to simply as "filler") are particulate (powder) components other than the crosslinking agent, crosslinking aid and compound (B). Examples of the inorganic filler include carbon black, silica, barium sulfate, titanium oxide, and aluminum oxide. Examples of the organic filler include fluororesins such as PTFE, PFA, FEP, ETFE, and PVDF, polyethylene resins, polyimide resins, silicone resins, and melamine resins.

[0091] When the present sealing material is used in an application where particle generation is a problem, such as in a plasma atmosphere, the content of the filler is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and most preferably 0 part by mass, per 100 parts by mass of the elastomer (A).

[0092] <Method of manufacturing the present composition> The present composition can be produced by mixing (kneading) the elastomer (A), the crosslinking agent, the crosslinking aid, and, if necessary, the other components described above, and preferably by mixing (kneading) the elastomer (A), the crosslinking agent, the crosslinking aid, the compound (B), and, if necessary, the other components described above. The order of mixing the elastomer (A), the crosslinking agent, the crosslinking aid, and the other components is not particularly limited, and they may be mixed (kneaded) sequentially in any order, or may be mixed (kneaded) all at once. However, it is preferable to mix (knead) them sequentially so that each component becomes uniform.

[0093] For the mixing (kneading), a conventionally known mixer (kneader) can be used, and examples thereof include an open roll, a Banbury mixer, a twin-screw roll, and a kneader. Furthermore, during the mixing (kneading) process, the components may be mixed (kneaded) under heating or cooling, as necessary, depending on the mixer (kneader) used.

[0094] <Method of manufacturing the sealing material> The present sealing material can be produced by a method including a step of irradiating the present composition or a crosslinked product thereof with radiation (radiation irradiation step). By including this radiation irradiation step, it is possible to easily obtain a sealing material that is excellent in plasma resistance (radical resistance), crack resistance, compression set, non-stickiness, etc., and that has a well-balanced excellent hardness, tensile strength, elongation at break, and 100% Mo, and it is also possible to easily suppress cracks that may occur in the sealing material in a plasma atmosphere, etc.

[0095] When forming a sealing material from the present composition, it is preferable to carry out a separating step in order to improve the efficiency of the molding operation, reduce the defective rate, etc. This separating step is usually carried out using a roll or the like, and is usually also a step of preliminarily forming the present composition into a sheet.

[0096] The sheet obtained in the separating step is preferably preformed into a desired shape of a sealing material before the crosslinking step or the radiation exposure step. This preforming may involve directly forming the desired sealing material shape from the sheet obtained in the extrusion process, or the sheet obtained in the extrusion process may be cut or extrusion molded into a rope-like shape (which also has the same meaning as a ribbon-like or noodle-like shape), and the resulting rope-like material may be formed into the desired sealing material shape.

[0097] When producing the present sealing material, a crosslinking step is preferably included before the radiation exposure step, and the crosslinking step more preferably includes a primary crosslinking step and a secondary crosslinking step. The crosslinking step is preferably carried out using the desired sealing material shape obtained by the preforming step.

[0098] The primary crosslinking step is preferably a step of heating and pressurizing the desired sealing material shape obtained by the preforming step. Specifically, for example, the preformed material is placed in a mold and crosslinked using a heating press or the like under a pressure of about 2 to 15 MPa at a temperature of, for example, 150 to 200°C for, for example, about 5 to 20 minutes.

[0099] The secondary crosslinking step is preferably a step of heating the molded body obtained in the primary crosslinking step, and specifically includes a step of heating the molded body at normal pressure to reduced pressure using various ovens, preferably a vacuum oven, at a temperature of, for example, 150 to 300°C for 1 to 24 hours, more preferably for 3 to 24 hours. This secondary crosslinking process can accelerate crosslinking, and even if unreacted components remain after the primary crosslinking process, the unreacted components can be decomposed and evaporated, thereby producing a sealing material that emits less gas.

[0100] The radiation to be irradiated in the radiation irradiation step is not particularly limited as long as it can crosslink the elastomer (A), and examples thereof include X-rays, gamma rays, electron beams, proton beams, neutron beams, heavy particle beams, alpha rays, and beta rays. Among these, gamma rays and electron beams are preferred. The radiation to be irradiated may be of one type alone or of two or more types.

[0101] When irradiating with radiation, it is desirable to irradiate with radiation so that the absorbed dose is preferably 1 to 120 kGy, more preferably 20 to 100 kGy. When irradiating with radiation in such an amount, unreacted components that may become particles or released gases can be reduced, and a sealing material excellent in plasma resistance, crack resistance, etc. can be easily obtained without excessively lowering the molecular weight of the elastomer (A). The radiation irradiation step may be carried out in two or more stages by changing the conditions.

[0102] Although irradiation with radiation may be performed in air, the presence of oxygen during irradiation may inhibit the crosslinking reaction, resulting in a decrease in the mechanical strength of the sealing material and the possibility of the surface of the sealing material becoming sticky. For this reason, the radiation irradiation step is preferably performed in an atmosphere of an inert gas such as nitrogen or argon. [Example]

[0103] Next, the present invention will be described in more detail by showing examples, but the present invention is not limited to these examples.

[0104] <Elastomer> The elastomers used in the following examples and comparative examples are as follows: Elastomer (A1-1): Tecnoflon P757 (manufactured by Solvay, fluorine content: 67% by mass) Elastomer (A1-2): Tecnoflon P457 (manufactured by Solvay, fluorine content: 67% by mass) Elastomer (A2-1): Daiel G912 (manufactured by Daikin Industries, Ltd., fluorine content: 71% by mass) Elastomer (A2-2): Tecnoflon P959 (manufactured by Solvay, fluorine content: 70% by mass) Elastomer (A2-3): Tecnoflon P459 (manufactured by Solvay, fluorine content: 70% by mass) Elastomer (A2-4): Tecnoflon PL855 (manufactured by Solvay, fluorine content: 64% by mass) Elastomer (A2-5): Daiel LT302 (manufactured by Daikin Industries, Ltd., fluorine content: 65% by mass)

[0105] [Example 1] 20 parts by mass of elastomer (A1-1), 80 parts by mass of elastomer (A2-2), 1.0 part by mass of SIFEL 8070A (manufactured by Shin-Etsu Chemical Co., Ltd.), 1.0 part by mass of SIFEL 8070B (manufactured by Shin-Etsu Chemical Co., Ltd.), 6.0 parts by mass of TAIC (manufactured by Mitsubishi Chemical Corporation, triallyl isocyanurate), and 0.5 parts by mass of Perhexa 25B (manufactured by NOF Corporation) were sequentially placed in a kneader and kneaded until the current value stabilized, thereby obtaining a block of elastomer composition. At least one of SIFEL 8070A and SIFEL 8070B contains a compound with a perfluoro skeleton having an ethylenically unsaturated bond.

[0106] The total time from the addition of the first component to the kneader until the current value stabilized after the addition of the last component was defined as the kneading time. The results are shown in Table 1. Generally, when kneading is performed using a kneader, the current value stabilizes once the added components are uniformly kneaded, and the point at which the current value stabilizes is often used as a yardstick for determining that a uniform composition has been obtained.

[0107] The obtained bulk elastomer composition was subjected to a separating step (sheet forming step) using rolls (roll gap: 8 mm, temperature: 50°C). In this case, the extrudability was evaluated as follows: if a sheet could be formed from the bulk elastomer composition, the extrudability was rated as "OK"; if the elastomer composition was not caught between the rolls or had poor adhesion to the rolls, and a good extrudable sheet was not obtained, the extrudability was rated as "NG." The results are shown in Table 1.

[0108] The sheet obtained in the extrusion step was press-molded using a compression vacuum press at 170°C for 10 minutes under a pressure of 5 MPa (primary crosslinking), and then the press-molded sheet was heated at 200°C for 16 hours under reduced pressure in a vacuum oven (vacuum degree: 50 Pa) (secondary crosslinking).Then, the secondary crosslinked sheet was irradiated with radiation so that the absorbed dose was 80 kGy, thereby obtaining a molded product. The following physical properties of the obtained molded body were measured in the normal state, and the results are shown in Table 1.

[0109] <Normal physical properties> As normal physical properties, Shore A hardness was measured in accordance with JIS K 6253:2012, and tensile strength, elongation at break, and tensile stress at 100% elongation (100% Mo) were measured in accordance with JIS K 6251:2017.

[0110] [Examples 2 to 6 and Comparative Examples 1 and 2] Various evaluations were carried out in the same manner as in Example 1, except that the elastomers shown in Table 1 were used in the amounts shown in Table 1. The results are shown in Table 1.

[0111] [Table 1]

[0112] In Examples 1 to 6, it took a short time to produce a uniform elastomer composition, and it was found that the elastomer compositions obtained in Examples 1 to 6 had excellent extrudability (sheet formability). In Comparative Examples 1 and 2, it took a long time to produce a uniform elastomer composition, and the elastomer compositions obtained in Comparative Examples 1 and 2 had poor extrudability; specifically, the elastomer compositions were not caught between the rolls or were not properly wound around the rolls, and therefore, a good sheet could not be formed.

[0113] [Example 7] 30 parts by mass of crosslinkable fluoroelastomer (A1-1), 70 parts by mass of crosslinkable fluoroelastomer (A2-1), 2 parts by mass of SIFEL 3590-N (manufactured by Shin-Etsu Chemical Co., Ltd., one-component liquid type containing a perfluoro skeleton compound having an ethylenically unsaturated bond), 6 parts by mass of TAIC, and 0.5 parts by mass of Perhexa 25B were sequentially placed in a kneader and kneaded until the current value stabilized, thereby obtaining a block elastomer composition. A molded article was obtained in the same manner as in Example 1 using the obtained bulk elastomer composition. The obtained molded body was measured for the above-mentioned normal physical properties and the following plasma resistance. The results are shown in Table 2.

[0114] [Example 8] A block elastomer composition was obtained in the same manner as in Example 7, except that the amount of SIFEL 3590-N used was changed to 10 parts by mass and the amount of Perhexa 25B used was changed to 1 part by mass. A molded article was obtained in the same manner as in Example 1 using the obtained bulk elastomer composition. The obtained molded body was measured for the above-mentioned normal physical properties and the following plasma resistance. The results are shown in Table 2.

[0115] [Example 9] A block elastomer composition was obtained in the same manner as in Example 7, except that the amount of SIFEL 3590-N used was changed to 20 parts by mass and the amount of Perhexa 25B used was changed to 1 part by mass. A molded article was obtained in the same manner as in Example 1 using the obtained bulk elastomer composition. The obtained molded body was measured for the above-mentioned normal physical properties and the following plasma resistance. The results are shown in Table 2.

[0116] [Example 10] A bulk elastomer composition was obtained in the same manner as in Example 7, except that 2 parts by mass of KE-1830 (manufactured by Shin-Etsu Chemical Co., Ltd., one-component liquid type containing a siloxane skeleton compound having an ethylenically unsaturated bond) was used instead of 2 parts by mass of SIFEL 3590-N in Example 7. A molded article was obtained in the same manner as in Example 1 using the obtained bulk elastomer composition. The obtained molded body was measured for the above-mentioned normal physical properties and the following plasma resistance. The results are shown in Table 2.

[0117] <Plasma resistance> Furthermore, the plasma resistance (mass reduction rate) of the obtained molded body was measured. Specifically, the measurement was performed as follows. Using a flat-plate plasma processing device with an electrode diameter of 300 mm and an electrode distance of 50 mm, the obtained compact was irradiated with plasma for 3 hours under conditions of RF 500 W, CF4 gas flow rate 50 sccm, O2 gas flow rate 150 sccm, and vacuum level 1 torr. The obtained molded body was placed 6 cm away from the plasma electrode. Next, the mass of the molded body was measured before and after the test, and the mass loss rate (%) was calculated using the following formula to evaluate plasma resistance. The smaller the mass loss rate, the better the plasma resistance. Mass reduction rate (%) = [(mass of molded body before test - mass of molded body after test) / mass of molded body before test] × 100

[0118] [Table 2]

[0119] [Examples 11 to 12 and Comparative Examples 3 to 7] A block of elastomer composition was obtained in the same manner as in Example 1, except that the elastomers shown in Table 3 were used in the amounts shown in Table 3. The obtained bulk elastomer composition was filled into a mold and press-molded using a compression vacuum press at 170°C for 10 minutes under a pressure of 5 MPa (primary crosslinking), and then the press-molded sheet was heated at 200°C for 16 hours under reduced pressure in a vacuum oven (vacuum degree: 50 Pa) (secondary crosslinking).Then, the secondarily crosslinked sheet was irradiated with radiation to an absorbed dose of 80 kGy, to obtain a molded product. The obtained molded body was measured for the above-mentioned physical properties in the normal state. The results are shown in Table 3.

[0120] [Table 3]

[0121] [Examples 13 to 15] A radiation-induced crosslinked product was prepared in the same manner as in Example 11, except that the elastomers shown in Table 4 were used in the amounts shown in Table 4. However, in Example 15, SIFEL 8070A and SIFEL 8070B were not used.

[0122] [Comparative Examples 8 to 9] A secondary crosslinked body was prepared in the same manner as in Example 11, except that the elastomer shown in Table 4 was used in the amount shown in Table 4 and no radiation was applied.

[0123] <Compression set> In accordance with JIS K 6262:2013, measurement samples (AS214 O-rings) were prepared from the radiation-crosslinked products obtained in Examples 13 to 15 or the secondary crosslinked products obtained in Comparative Examples 8 and 9. The prepared O-rings were compressed by 25% in the thickness direction at 200°C for 70 hours, and then removed from the compression device. 30 minutes later, the thickness of the crosslinked product was measured and the compression set was calculated. The results are shown in Table 4.

[0124] [Table 4]

Claims

1. A sealing material which is a radiation-crosslinked product of an elastomer composition comprising a crosslinkable fluoroelastomer (A) other than a perfluoroelastomer, a crosslinking agent, and a crosslinking aid, The fluoroelastomer (A) comprises a crosslinkable fluoroelastomer (A1) other than perfluoroelastomers having a fluorine content in the range of 66 to 68 mass%, and a crosslinkable fluoroelastomer (A2) other than perfluoroelastomers having a fluorine content in the range of 69 to 73 mass%, Sealing material.

2. 2. The sealing material according to claim 1, wherein the fluoroelastomer (A) is a peroxide-crosslinkable fluoroelastomer.

3. 3. The sealing material according to claim 1, wherein the elastomer composition contains at least one ethylenically unsaturated bond-containing compound selected from the group consisting of a perfluoro-skeleton compound having an ethylenically unsaturated bond and a siloxane-skeleton compound having an ethylenically unsaturated bond.

4. 4. The sealing material according to claim 1, wherein the content of the filler is 5 parts by mass or less per 100 parts by mass of the fluoroelastomer (A).

5. A method for producing a sealing material, comprising: an elastomer composition comprising a crosslinkable fluoroelastomer (A) other than a perfluoroelastomer, a crosslinking agent, and a crosslinking aid, wherein the fluoroelastomer (A) comprises a crosslinkable fluoroelastomer (A1) other than a perfluoroelastomer having a fluorine content in the range of 66 to 68 mass% and a crosslinkable fluoroelastomer (A2) other than a perfluoroelastomer having a fluorine content in the range of 69 to 73 mass%, or a step of irradiating a crosslinked product of the elastomer composition with radiation.

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