Rubber composition, fluorinated elastomer, sealing material and method for storing rubber composition

Abstract

To provide a rubber composition excellent in storage characteristics.SOLUTION: Disclosed is a rubber composition containing (a) a crosslinking reactive fluorine rubber and / or a crosslinking reactive perfluoro rubber, (b) a crosslinking agent, and (c) a compound containing a phenolic hydroxy group, wherein the crosslinking agent contains at least a compound represented by formula (1) (in formula (1), A represents a single bond, - O -, an alkylene group or a fluorinated alkylene group). R1, R2, and R3 are each independently hydrogen, fluoro, alkyl, or fluoroalkyl. However, at least one of R1, R2, and R3 is a fluoride atom or a fluoroalkyl group. ) Rubber Composition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The disclosure in this application relates to a rubber composition having excellent storage properties, a fluorine-containing elastomer obtained by crosslinking the rubber composition, a sealing material, and a method for storing the rubber composition. [Background technology]

[0002] Fluorine-containing elastomers are mainly used for sealing materials that require plasma resistance. For example, Patent Document 1 describes a composition containing a perfluoroelastomer, 55 to 75 parts by weight of carbon black per 100 parts by weight of the perfluoroelastomer, and a crosslinking agent represented by the following formula (1): [ka] [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7066010 Summary of the Invention [Problem to be solved by the invention]

[0004] A fluorine-containing elastomer such as a sealing member is formed by molding and crosslinking the rubber composition (hereinafter, this may be referred to as a "molded product"). Incidentally, in preparation for the occurrence of unexpected defective products, the rubber composition before crosslinking after the materials have been kneaded may be separated from the production line and stored. Since the separated and stored rubber composition before crosslinking (hereinafter, this may be referred to as a "storage product") is prepared in preparation for the occurrence of unexpected defective products, it is desirable that the separated rubber composition deteriorates little for about three months, preferably about six months, at room temperature.

[0005] The properties required for molded products vary depending on the user. For example, when carbon black is used to adjust the hardness, the molded product will be black, but in some cases, users may require a non-black molded product. However, the present inventors have newly discovered that when the compound represented by the above formula (1) is used as a crosslinking agent without using carbon black, a problem occurs in that the storage properties (pot life) of the stored product are deteriorated.

[0006] The present invention has been disclosed in order to solve the above-mentioned problems. As a result of intensive research, the present inventors have newly discovered that when the compound represented by formula (1) is used as a crosslinking agent, the deterioration of storage properties of stored products caused by the compound represented by formula (1) can be suppressed by using the compound in combination with a compound containing a phenolic hydroxy group.

[0007] That is, an object of the disclosure of the present application is to provide a rubber composition, a fluorine-containing elastomer, a sealing material, and a method for storing a rubber composition, which have excellent storage properties. [Means for solving the problem]

[0008] The disclosure of the present application relates to a rubber composition, a fluorine-containing elastomer, a sealing material, and a method for storing a rubber composition, which are shown below.

[0009] (1)(a) a cross-linkable reactive fluororubber and / or a cross-linkable reactive perfluororubber, (b) a cross-linking agent; (c) a compound containing a phenolic hydroxy group; A rubber composition comprising: The crosslinking agent contains at least a compound represented by the following formula (1): [ka] (In formula (1), A is a single bond, —O—, an alkylene group, or a fluorinated alkylene group. R 1 ,R 2 ,R 3are each independently a hydrogen atom, a fluorine atom, an alkyl group, or a fluoroalkyl group, provided that R 1 ,R 2 ,R 3 At least one of is a fluorine atom or a fluorinated alkyl group. Rubber composition. (2) The compound containing a phenolic hydroxy group is dibutylhydroxytoluene. The rubber composition according to (1) above. (3) per 100 parts by weight of the component (a), 0.5 to 20% by weight of the compound represented by formula (1), The dibutylhydroxytoluene is 0.005 to 1% by weight, Included The rubber composition according to (2) above. (4) Further containing 30% by weight or less of an acid acceptor relative to 100 parts by weight of the component (a). The rubber composition according to any one of (1) to (3) above. (5) Further containing a filler The rubber composition according to any one of (1) to (4) above. (6) The torque change rate after storage at 60°C for 22 days is less than -32.6%. The rubber composition according to any one of (1) to (5) above. (7) A fluorine-containing elastomer obtained by crosslinking the rubber composition according to any one of (1) to (6) above. (8) A sealing material comprising the fluorine-containing elastomer described in (7) above. (9) The compression set when heated at 250°C for 336 hours is less than 80%. The fluorine-containing elastomer according to (7) above. (10) A method for storing the rubber composition according to any one of (1) to (6) above, The storage method comprises: a kneading step of kneading the rubber composition; a separating step of separating the kneaded rubber composition; a storage step of storing the rubber composition separated in the separation step; Storage methods, including: [Effects of the Invention]

[0010] By using the rubber composition disclosed in the present application, it is possible to suppress deterioration of storage properties of stored items caused by the compound represented by the above formula (1). [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a graph showing the correlation between the torque reduction rate when a rubber composition is stored at room temperature and when it is stored at 60°C. DETAILED DESCRIPTION OF THE INVENTION

[0012] The rubber composition, the fluorine-containing elastomer, the sealing material, and the method for storing the rubber composition disclosed in the present application will be described in detail below.

[0013] In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. Furthermore, in this specification, numerical values, numerical ranges, and qualitative expressions (e.g., expressions such as "same" and "the same") are to be interpreted as indicating numerical values, numerical ranges, and properties that include errors generally accepted in the technical field.

[0014] (Embodiment of rubber composition) The rubber composition according to the embodiment contains (a) a cross-linkable reactive fluororubber and / or a cross-linkable reactive perfluororubber, (b) a cross-linking agent, and (c) a compound containing a phenolic hydroxy group. The cross-linking agent contains at least a compound represented by the following formula (1). Each component will be described in detail below. [ka]

[0015] <(a) Component> First, the component (a), cross-linkable reactive fluororubber (hereinafter sometimes referred to as "FKM") and / or cross-linkable reactive perfluororubber (hereinafter sometimes referred to as "FFKM"), will be described. When FKM and FFKM are collectively referred to as "fluorine-containing cross-linkable reactive rubber," they may be simply referred to as "fluorine-containing cross-linkable rubber."

[0016] "Crosslinking reactive" means a fluorine-containing rubber that can be crosslinked by a crosslinking reaction. The fluorine-containing crosslinking reactive rubber may contain, for example, a repeating unit derived from a fluorine-containing monomer. The fluorine-containing crosslinking reactive rubber may contain a repeating unit derived from one or more types of fluorine-containing monomers.

[0017] Examples of the fluorine-containing monomer include tetrafluoroethylene (TFE) represented by the following formula (a-1) and hexafluoropropylene (HFP) represented by the following formula (a-2). CF2=CF2(a-1) CF2=CFCF3(a-2)

[0018] Further, examples of the fluorine-containing monomer include perfluoroolefins having one ethylene-type unsaturated bond, preferably at a terminal position. Specific examples include perfluoroalkyl vinyl ethers (PAVEs) represented by the following formula (a-3), perfluorooxyalkyl vinyl ethers represented by the following formula (a-4), and perfluorovinyl ethers represented by the following formula (a-5).

[0019] CF2=CFOR f1 (a-3) (In formula (a-3), R f1 is a perfluoroalkyl having 1 to 6 carbon atoms, such as trifluoromethyl or pentafluoropropyl.

[0020] CF2=CFOR f2 (a-4) (In formula (a-4), R f2is a perfluorooxyalkyl having 1 to 12 carbon atoms and containing one or more ether groups, such as perfluoro-2-propoxypropyl.

[0021] CF2=CFOCF2OR f3 (a-5) (In formula (a-5), R f3 is a straight-chain or branched perfluoroalkyl having 2 to 6 carbon atoms, a cyclic perfluoroalkyl having 5,6 carbon atoms, or a straight-chain or branched perfluorooxyalkyl having 2 to 6 carbon atoms and containing 1 to 3 oxygen atoms.

[0022] In one embodiment, the perfluorovinyl ether represented by formula (a-5) is represented by the following formula (a-6) or formula (a-7): The perfluorovinyl ether represented by formula (a-6) may be referred to as "MOVE1", and the perfluorovinyl ether represented by formula (a-7) may be referred to as "MOVE2".

[0023] CF2 = CFOCF2OCF2CF3 (a-6) CF2 = CFOCF2OCF2CF2OCF3 (a-7) In one embodiment, the fluorine-containing crosslinkable reactive rubber may be a copolymer containing repeating units derived from one or more fluorine-containing monomers selected from the group consisting of formula (a-1) and formula (a-2) and repeating units derived from one or more fluorine-containing monomers (comonomers) selected from the group consisting of formula (a-3) to formula (a-5).

[0024] The composition (molar ratio) of the fluorine-containing monomer used to produce the fluorine-containing crosslinkable reactive rubber is not particularly limited.

[0025] In one embodiment, the fluorine-containing crosslinkable reactive rubber is produced using 50 to 85 mol % of one or more fluorine-containing monomers selected from the group consisting of formula (a-1) and formula (a-2), and 15 to 50 mol % of one or more fluorine-containing monomers selected from the group consisting of formula (a-3) to formula (a-5).

[0026] In one embodiment, the fluorine-containing crosslinkable reactive rubber is produced using 50 to 85 mol % of TFE and 15 to 50 mol % of PAVE.

[0027] In one embodiment, the fluorine-containing cross-linked reactive rubber is produced using 50 to 85 mol % of TFE and 15 to 50 mol % of MOVE, where "MOVE" is one or more selected from the group consisting of MOVE1 and MOVE2.

[0028] In one embodiment, the fluorine-containing crosslinkable reactive rubber may or may not contain units derived from vinylidene fluoride.

[0029] In this specification, FKM refers to the above-mentioned fluorine-containing crosslinkable reactive rubber, which contains hydrogen in its chemical structure. Examples of FKM include fluororubbers (FKM) such as vinylidene fluoride / hexafluoropropylene copolymer (binary FKM), vinylidene fluoride / hexafluoropropylene / tetrafluoroethylene copolymer (ternary FKM), vinylidene fluoride / hexafluoropropylene / perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene / propylene copolymer, hexafluoropropylene / ethylene copolymer, tetrafluoroethylene / ethylene / perfluoroalkyl vinyl ether copolymer, and vinylidene fluoride / 2,3,3,3-tetrafluoropropylene. However, FKM is not limited to these.

[0030] In this specification, FFKM refers to the above-mentioned fluorine-containing cross-linking reactive rubber that does not contain hydrogen in its chemical structure. Examples of FFKM include perfluororubbers such as tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (FFKM), but are not limited thereto.

[0031] FKM is inexpensive and has a certain degree of plasma resistance and heat resistance. On the other hand, FFKM is more expensive than FKM, but has higher plasma resistance than FKM. Therefore, depending on the properties required for the molded product, only FKM may be used, only FFKM may be used, or a mixture of FKM and FFKM may be used. When a mixture of FKM and FFKM is used, there are no particular restrictions on the blending ratio, which may be adjusted appropriately depending on the required plasma resistance properties, etc.

[0032] In one embodiment, the fluorine-containing crosslinkable reactive rubber may or may not contain a unit derived from a fluoroolefin having 3 to 8 carbon atoms containing iodine and / or bromine. When the fluorine-containing crosslinkable reactive rubber contains such a unit, it preferably contains iodine and / or bromine, more preferably iodine, as a radical attack site during crosslinking (curing). Fluorine-containing crosslinkable reactive rubbers that can be cured with peroxides are described, for example, in JP 2006-9010 A. When the fluorine-containing crosslinkable reactive rubber contains such a unit, it generally contains 0.001 to 5% by weight, preferably 0.01 to 2.5% by weight, of the total polymer weight of iodine. The iodine atoms may be present along the chain and / or at the terminal positions of the fluorine-containing crosslinkable reactive rubber.

[0033] <(b) Ingredients> The crosslinking agent, which is the component (b), contains at least a compound represented by the following formula (1). JPEG2026011055000005.jpg23119

[0034] In the above formula (1), A is a single bond, —O—, an alkylene group, or a fluorinated alkylene group, preferably a single bond, an alkylene group, or a fluorinated alkylene group, and more preferably a fluorinated alkylene group.

[0035] The alkylene group of the alkylene group or fluorinated alkylene group may be linear or branched, and preferably has 1 to 15 carbon atoms (more preferably 2 to 8 carbon atoms, and even more preferably 3 to 6 carbon atoms). The fluorinated alkylene group may be a group in which the alkylene group is partially or completely fluorinated, and is preferably a perfluoroalkylene group.

[0036] Examples of the alkylene group include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, and a peptylene group.

[0037] In the above formula (1), R 1 ,R 2 ,R 3 are each independently a hydrogen atom, a fluorine atom, an alkyl group, or a fluoroalkyl group, provided that R 1 ,R 2 ,R 3 At least one of the groups is a fluorine atom or a fluorinated alkyl group.

[0038] The alkyl group of the alkyl group or fluorinated alkyl group may be linear or branched, and preferably has 1 to 15 carbon atoms (more preferably 1 to 6 carbon atoms, and even more preferably 1 to 4 carbon atoms). The fluorinated alkyl group may be a group in which the alkyl group is partially or completely fluorinated, and is preferably a perfluoroalkyl group.

[0039] Examples of the alkyl group include a methyl group, an ethyl group, and a propyl group.

[0040] R 1 ,R 2 ,R 3 are preferably each independently a hydrogen atom or a fluorine atom.

[0041] -CR 1 =CR 2 R 3 Examples of the groups include the following: [ka]

[0042] In the above formula (1), A and -CR 1 =CR 2 R3 may be at any of the ortho, meta or para positions, but is preferably at the para position, and A and two -CR 1 =CR 2 R 3 However, it is more preferable that both are in the para position.

[0043] Specific examples of the compound represented by the formula (1) include compounds represented by the following formulas (2) to (4). [ka] In the above formula, R 1 ,R 2 ,R 3 is the same as above. t is preferably 1 to 15 (more preferably 2 to 8, and even more preferably 3 to 6).

[0044] Specific examples of the compound represented by the above formula (1) include the following compounds: These compounds can be synthesized, for example, by referring to WO2016 / 017187. [ka] [ka]

[0045] The crosslinking agent may be one of the compounds listed above, or two or more may be used in combination. There is no particular restriction on the lower limit of the amount of crosslinking agent added, as long as it is an amount that can crosslink the component (a). Examples of lower limits based on 100 parts by weight of component (a) include, but are not limited to, 0.5% by weight or more, 1.0% by weight or more, 1.5% by weight or more, 2.0% by weight or more, 2.5% by weight or more, 3.0% by weight or more, 3.5% by weight or more, 4.0% by weight or more, 4.5% by weight or more, and 5.0% by weight or more. On the other hand, the greater the amount of crosslinking agent added, the more improved the steam resistance and heat resistance. However, if the amount is too much, the composition may become hard. Therefore, although not limited thereto, examples of the upper limit relative to 100 parts by weight of component (a) include 20% by weight or less, 19% by weight or less, 18% by weight or less, 17% by weight or less, 16% by weight or less, 15% by weight or less, 14% by weight or less, 13% by weight or less, 12% by weight or less, 11% by weight or less, and 10% by weight or less.

[0046] The rubber composition according to the embodiment may contain at least the compound represented by formula (1) as a crosslinking agent, and may contain other crosslinking agents. Examples of crosslinking agents other than the compound represented by formula (1) include, but are not limited to, triallyl isocyanurate. When the compound represented by formula (1) is used in combination with other crosslinking agents, the amount of the crosslinking agent used in combination should be the amount of the crosslinking agent described above.

[0047] <(c) Component> The compound containing a phenolic hydroxy group (hereinafter, sometimes referred to as "compound C"), which is component (c), is not particularly limited as long as its use in combination with the compound represented by formula (1) suppresses deterioration of the storage properties of the stored product caused by the compound represented by formula (1). Examples of the compound include, but are not limited to, compounds containing two phenolic hydroxy groups and compounds containing one phenolic hydroxy group.

[0048] An example of a compound containing two phenolic hydroxy groups is a compound represented by the following formula (2). [ka]

[0049] R in the above formula (2) 1 , R 2 are each independently a hydrogen atom, an organic group having 1 to 12 carbon atoms, or a fluorine-containing organic group having 1 to 12 carbon atoms. The organic group having 1 to 12 carbon atoms and the fluorine-containing organic group having 1 to 12 carbon atoms may be linear, branched, or cyclic, and may or may not contain an unsaturated bond. 1 ,R 2 When one of R is bonded to the basic skeleton of formula (2) via an unsaturated bond, 1 ,R 2 The other is not included.

[0050] Examples of the compound represented by formula (2) include, but are not limited to, bisphenol A, bisphenol AF, bisphenol AP, bisphenol C, bisphenol F, and the like.

[0051] An example of the compound containing one phenolic hydroxy group is a compound represented by the following formula (3). [ka]

[0052] R in the above formula (3) 1 , R 2 , R 3 are each independently a hydrogen atom, an organic group having 1 to 12 carbon atoms, or a fluorine-containing organic group having 1 to 12 carbon atoms. The organic group having 1 to 12 carbon atoms and the fluorine-containing organic group having 1 to 12 carbon atoms may be linear, branched, or cyclic, and may or may not contain an unsaturated bond. Furthermore, the organic group having 1 to 12 carbon atoms and the fluorine-containing organic group having 1 to 12 carbon atoms may contain a carboxylic acid derivative.

[0053] Examples of the compound represented by formula (3) include, but are not limited to, dibutylhydroxytoluene (BHT), phenol, p-cresol, m-cresol, o-cresol, p-phenylphenol, m-phenylphenol, o-phenylphenol, allylphenol, p-hydroxybenzoic acid, and methyl p-hydroxybenzoate. There are no particular limitations on the amount of compound C added, as long as it is within a range that can prevent deterioration of the storage properties of the stored product. Examples of the amount of compound C added, but not limited to, based on 100 parts by weight of component (a), include lower limits of 0.005% by weight or more, 0.0075% by weight or more, 0.01% by weight or more, 0.015% by weight or more, 0.02% by weight or more, 0.025% by weight or more, 0.03% by weight or more, 0.035% by weight or more, 0.04% by weight or more, and 0.045% by weight or more. On the other hand, as shown in the examples below, increasing the compound C content increases T90 (the time required to reach 90% of MH (maximum torque)), which is an indicator of rubber molding time. In other words, the production cycle becomes longer, which reduces production efficiency and increases costs. Therefore, the upper limit of compound C may be set from a cost perspective rather than a technical perspective. Examples of upper limits, based on 100 parts by weight of component (a), include, but are not limited to, 1% by weight or less, 0.9% by weight or less, 0.8% by weight or less, 0.7% by weight or less, 0.6% by weight or less, 0.5% by weight or less, 0.4% by weight or less, 0.3% by weight or less, 0.2% by weight or less, and 0.1% by weight or less. It is believed that the combined use of compound C and the compound represented by formula (1) suppresses deterioration of storage properties of stored products due to the compound represented by formula (1) because compound C functions as an antioxidant and scorch retarder by capturing radicals.

[0054] The rubber composition disclosed in the present application can suppress deterioration of storage characteristics of stored products caused by the compound represented by formula (1). In other words, it exhibits the effect of excellent storage characteristics. In this specification, "storage characteristics" refers to the rate of torque change of a rubber composition when stored at 60°C for 22 days, based on the torque of the rubber composition immediately after dispensing (storage day 0). In this specification, "capable of suppressing deterioration of storage characteristics" means that the rate of torque change is less than -32.6%. If the torque drops significantly, the crosslink density decreases, which may result in molding defects (such as poor shape and sticking to the mold) and insufficient heat resistance. However, if the rate of torque change is less than -32.6%, the likelihood of molding defects and poor heat resistance is reduced. There are no particular restrictions on the storage characteristics as long as the rate of torque change is less than -32.6%, but a smaller rate of torque change is preferable. Without being limited thereto, the torque change rate of the rubber composition when stored at 60°C for 22 days may be less than -30%, less than -28%, less than -26%, less than -24%, less than -22%, less than -20%, less than -18%, less than -16%, less than -14%, less than -12%, less than -10%, less than -8%, less than -6%, less than -4%, less than -2%, etc.

[0055] <Optional Additional Components That May Be Included in the Rubber Composition> Next, optional additional components that may be contained in the rubber composition will be described. (d) Acid acceptor The rubber composition may contain an acid acceptor. The acid acceptor is not particularly limited as long as it is one commonly used in the art, and examples thereof include primary amines, secondary amines, tertiary amines, and inorganic acid acceptors. Specific examples of primary amines, secondary amines, and tertiary amines include melamine cyanurate (MC), melamine, 1,4-diazabicyclo[2.2.2]octane (DABCO), 1,8-diazabicyclo[5.4.0]undec-7-ene, and 2,2,6,6-tetramethyl-4-piperidone. Specific examples of inorganic acid acceptors include zinc(II) oxide, calcium(II) oxide, and magnesium(II) oxide.

[0056] As shown in the examples below, when the amount of compound C is small, the addition of an acid acceptor improves the storage properties of the stored product. The amount of acid acceptor added is not particularly limited as long as it improves the storage properties of the stored product. Examples of the amount of acid acceptor added, based on 100 parts by weight of component (a), include, but are not limited to, 30% by weight or less, 28% by weight or less, 26% by weight or less, 24% by weight or less, 22% by weight or less, 20% by weight or less, 18% by weight or less, 16% by weight or less, 14% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 6% by weight or less, 4% by weight or less, 2% by weight or less, 1% by weight or less, 0.8% by weight or less, and 0.6% by weight or less. While compound C improves the storage properties of the rubber composition, it also scavenges radicals generated from peroxides during molding, inhibiting the crosslinking reaction. Therefore, using a large amount of compound C may result in molding defects. When compound C and an acid acceptor are used in combination, a small amount of compound C is used to improve the storage properties of the rubber composition, and the reduced amount of compound C can synergistically reduce the possibility of molding defects.

[0057] (e) Co-crosslinking agent The rubber composition may contain a co-crosslinking agent. Known co-crosslinking agents for crosslinking fluorine-based elastomers can be used. Examples include triallyl isocyanurate (TAIC), triallyl cyanurate, triallyl trimellitate, N,N'-m-phenylenedimaleimide, and trimethylolpropane trimethacrylate. Other acrylate and methacrylate monomers can also be used. TAIC is a liquid. TAIC may be used as is, or in a mixed form (e.g., TAICWH-60) with a powder such as silica to facilitate mixing with other components. In this case, the TAIC component in the mixed form functions as a co-crosslinking agent, and the powder component such as silica functions as a filler, as described below. Liquid co-crosslinking agents other than TAIC may also be used in a mixed form.

[0058] Furthermore, as the co-crosslinking agent, a compound represented by the following formula (e-1) and / or a compound represented by the following formula (e-2) may be used. [ka] (In formula (e-1), A is a single bond, -O-, -S-, a heteroatom-containing group, a linear or branched alkylene group, a cycloalkylene group, or an arylene group, and in these groups, no hydrogen atoms are substituted with fluorine atoms, or some or all of the hydrogen atoms are substituted with fluorine atoms. R 1 , R 2 , R 3 and R 4 are each independently a hydrogen atom, a fluorine atom, an alkyl group, a fluoroalkyl group, or a substituted or unsubstituted aryl group. 1 are the same or different. 2 are the same or different. 3 are the same or different. 4 are the same or different. R 1 , R 2 and R 3 At least one of the groups is a fluorine atom or a group containing a fluorine atom. m is an integer of 1 to 5. n is an integer of 1 to 5.

[0059] [ka] (In formula (e-2), n and m are each 0 or 1. t is an integer of 2 or greater. Z is a t-valent linking group.)

[0060] Detailed descriptions of the compounds described in the above formula (e-1) and formula (e-2) are described in International Publication No. 2021 / 230231. Therefore, in this specification, the description of the above formula (e-1) and formula (e-2) is omitted. The disclosures of International Publication No. 2021 / 230231 are incorporated herein by reference. The above-mentioned co-crosslinking agents may be used alone or in combination of two or more.

[0061] (f) Filler material The rubber composition according to the embodiment may contain a filler. Fillers known in the field of fluorine-based elastomers can be used as the filler. Examples of fillers include, but are not limited to, carbon black, silica, calcium carbonate, clay, wollastonite, mica, talc, and barium sulfate. The problem of the present application is solved by using the compound represented by formula (1) in combination with compound C in the rubber composition according to the embodiment. As long as the problem of the present application is solved, carbon black may be added to the rubber composition according to the embodiment, for example, to color or adjust the hardness of a molded product. In other words, the rubber composition according to the embodiment may or may not contain carbon black, as long as the compound represented by formula (1) and compound C are included as essential features of the invention.

[0062] (g) Other ingredients Examples of optional additional components other than those described in (d) to (f) above include initiators such as dicumyl peroxide, di-t-butylperoxydiisopropylbenzene, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, thickeners, pigments, coupling agents, stabilizers, etc. The optional additional components exemplified above can be materials known in the field of fluorine-based elastomers.

[0063] (Embodiment of Fluorine-Containing Elastomer) The fluorine-containing elastomer according to the embodiment can be produced by crosslinking the rubber composition according to any embodiment disclosed in the present application. The conditions for crosslinking the rubber composition (crosslinking conditions) are not particularly limited. For example, the rubber composition may be heated at 100 to 250°C for 10 minutes to 5 hours. Typically, the raw material (rubber composition) is placed in a mold and crosslinked while being pressed, as the primary crosslinking. The primary crosslinking is performed, for example, by heating at 150 to 200°C for 5 to 60 minutes. The composition is then removed from the mold and subjected to secondary crosslinking in air or an inert gas atmosphere. The secondary crosslinking is performed, for example, by heating at 150 to 300°C for 1 to 100 hours. Crosslinking can be performed using an electric furnace or the like. By providing a thermal history in the secondary crosslinking, deformation during use can be prevented. Radiation treatment is not necessarily required for crosslinking, and it is preferable to omit radiation treatment. The rubber composition used to produce the fluorine-containing elastomer according to the embodiment may or may not have been stored. In this specification, the term "rubber composition" refers to a composition that has been stored or not, provided that it is not yet crosslinked.

[0064] (Embodiment of sealing material) The sealing material according to the embodiment includes a fluorine-containing elastomer according to any of the embodiments disclosed in the present application. The form of the sealing material is not particularly limited, and examples thereof include molded articles such as gaskets and seal rings. The uses of the sealing material are not particularly limited, and the sealing material can be widely applied to various devices. However, the sealing material disclosed in the present application has excellent plasma resistance and can be made relatively hard, and is therefore suitable as a sealing material for, for example, semiconductor manufacturing equipment. Examples of semiconductor manufacturing equipment include plasma equipment, etching equipment, and plasma CVD equipment.

[0065] (Embodiment of storage method) A storage method according to an embodiment is a method for storing a rubber composition according to any of the embodiments disclosed in the present application. The storage method includes a kneading step of kneading the rubber composition, a separating step of separating the kneaded rubber composition, and a storage step of storing the rubber composition separated in the separating step. The storage step may be performed at room temperature (23±2°C).

[0066] The following examples are provided to specifically explain the embodiments disclosed in the present application, but these examples are merely for the purpose of explaining the embodiments and are not intended to limit or restrict the scope of the invention disclosed in the present application. [Example]

[0067] <Material> The materials used in the examples and comparative examples are as follows. (a) Ingredients (FKM, FFKM) FKM: Daiel G912, manufactured by Daikin Industries, Ltd. FFKM: AFLAS (registered trademark) Premium PM3000, manufactured by AGC Inc. FFKM: 3M Japan Ltd. LJ213091 Component (b) (crosslinking agent) Compound represented by formula (1): The following compound was synthesized in-house. In the table below, it is referred to as FN-10. JPEG2026011055000014.jpg34156(c) component (compound containing a phenolic hydroxy group) BHT: 2,6-di-t-butyl-p-cresol manufactured by Nacalai Tesque, Inc. (d) Component (acid acceptor) Melamine cyanurate: Nissan Chemical Co., Ltd. MC6000 Melamine: Melamine manufactured by Nacalai Tesque, Inc. DABCO: Triethylenediamine manufactured by Nacalai Tesque, Inc. Component (e) (co-crosslinking agent) TAICWH-60: Mitsubishi Chemical Corporation Taik WH-60 (f) Component (filler) Aerosil R972: Nippon Aerosil Co., Ltd. Component (g) (initiator) Perhexa 25B: NOF Corporation

[0068] <Preparation of Rubber Composition> Rubber compositions were prepared by kneading materials in the blending ratios (weight ratios) shown in Tables 1 to 7 below with an open roll.

[0069] The resulting rubber compositions were evaluated as follows. (1) Torque measurement Measurement was carried out under the following conditions using a rubber vulcanization tester (Premier MDR) manufactured by Alpha Technologies. Measurement conditions: 155°C x 30 min ·Angle: 0.5° a: Maximum torque (MAX [dNm]) b: Optimum vulcanization point (T90 [min], time to reach 90% of maximum torque)

[0070] (2) Torque change rate The torque change rate was calculated using the following formula, where the maximum torque measured immediately after dispensing using the method (1) above (storage day 0) was defined as A and the maximum torque measured after storage for a predetermined number of days was defined as B. The storage was carried out at 60°C for 7, 14, and 22 days, and at room temperature for 14, 59, and 92 days. JPEG2026011055000015.jpg2281

[0071] (3) Heat resistance CS% (3-1) Sample preparation method The above-mentioned material was molded at 155°C for 15 minutes and subjected to secondary crosslinking at 160°C for 15 hours to prepare a sample (O-ring). (3-2) Experimental method The obtained O-ring was cut into a length of 30 mm and used as a test specimen. This test specimen was then bolted together with two flat plates using a spacer to compress it by 25% to prepare a fastened assembly. This fastened assembly was then subjected to heat exposure in a gear oven under specified conditions (atmospheric environment, 200, 250°C x 70, 336 hours). The fastened assembly was then removed from the gear oven and opened while still hot. After cooling to room temperature, the wire diameter was measured and the compression set was calculated using the following formula (unit: %). This compression set was taken as heat resistance. Compression set = (initial wire diameter - wire diameter after heat exposure) / (initial wire diameter - spacer thickness) x 100

[0072] [Correlation between storage at room temperature and storage at 60°C] <Example 1, Comparative Example 1> The correlation between the torque reduction rate when the extracted rubber composition was stored at room temperature and when it was stored at 60°C was investigated. The formulation of the rubber composition used in the experiment is shown in Table 1. Tables 2 and 3 show the maximum torque and the rate of change in maximum torque when stored for a specified number of days at room temperature and 60°C. A graph created based on the results in Table 2 is shown in Figure 1. [Table 1] [Table 2] [Table 3]

[0073] As is clear from Tables 2 and 3 and Figure 1, the maximum torque of the extracted rubber composition decreased almost linearly with increasing storage time, whether it was stored at room temperature or at 60°C. The torque decrease rate after 22 days of storage at 60°C was approximately -55%, and as is clear from Figure 1, it took at least 92 days or more for the torque decrease rate after storage at room temperature to exceed -55%. Therefore, it was confirmed that storage of the rubber composition at 60°C for 22 days was equivalent to storage at room temperature for at least three months or more. As mentioned above, it is generally required that extracted rubber compositions can be stored at room temperature for approximately three months. Therefore, in the following experiment, from the perspective of experimental efficiency, the properties of the rubber composition after storage at 60°C for 22 days were examined.

[0074] [Types of cross-linkable reactive rubber and the blending ratio of BHT and acid acceptor] <Examples 2 to 7, Comparative Examples 2 to 3> Rubber compositions were prepared in the same manner as in Example 1, except that the formulations shown in Table 4 below were used, and the torque change rates were examined. The results of the torque change rates are also shown in Table 4. [Table 4]

[0075] As shown in Table 4, in both cases where the fluorine-containing cross-linked reactive rubber was FFKM (Examples 2 to 5) and FKM (Examples 6 to 7), the combined use of the compound represented by formula (1) and BHT improved storage properties compared to Comparative Examples 2 and 3, in which BHT was not used. Compared to FFKM, FKM improved storage properties even with a smaller amount of BHT blended. Furthermore, the results of Examples 2 to 5 confirmed that the greater the amount of BHT blended, the better the storage properties. Furthermore, the results of Examples 4-5 and 6-7 confirmed that the combined use of BHT and an acid acceptor further improved storage properties.

[0076] [Types of acid acceptors] <Examples 8 to 10> Rubber compositions were prepared in the same manner as in Example 1 above, except that the formulations shown in Table 5 below were used, and the torque change rate was measured. The torque change rate results and color tone are also shown in Table 5. For comparison, the results of Example 3 are also shown. [Table 5]

[0077] As shown in Table 5, it was confirmed that the storage properties of the rubber composition were improved by using BHT in combination with any type of acid acceptor. In addition, it was confirmed that in Examples 3 and 8 to 10, the color tone was not black because carbon black was not used, and the color tone of the rubber composition could be adjusted by the type of acid acceptor used.

[0078] [Effects of including an acid acceptor] <Examples 11 and 12> Rubber compositions were prepared in the same manner as in Example 1, except that the formulations shown in Table 6 below were used, and the heat resistance was examined according to the procedure described in "(3) Heat resistance CS%" above. The heat resistance results are also shown in Table 6.

[0079] [Table 6]

[0080] The higher the heat resistance CS [%] value shown in Table 6, the lower the heat resistance, and generally, if it exceeds 80%, the sealability is evaluated as "X." As is clear from Table 6, the heat resistance CS [%] value of Example 12, in which MC6000 as an acid acceptor was added, was lower than the value of Example 11, in which MC6000 was not added. From the above results, it was confirmed that the acid acceptor simultaneously exerts the different effects of improving the storage properties of the rubber composition and improving the heat resistance of the molded article obtained by crosslinking the rubber composition.

[0081] [Relationship between BHT content and T90] Example 13 Rubber compositions were prepared in the same manner as in Example 1, except that the amount of BHT in Example 1 was changed to the weight shown in Table 7, and the T90 [min] was measured. The results of T90 [min] are also shown in Table 7. [Table 7]

[0082] As is clear from Table 7, the T90 time increased as the blending amount of BHT increased. Therefore, it was confirmed that the upper limit of the blending amount of BHT in the rubber composition disclosed in the present application should be appropriately set from the viewpoint of production efficiency, not from the viewpoint of technical aspects. [Industrial Applicability]

[0083] The rubber composition disclosed in the present application has improved storage properties, and therefore, even if a defective product is suddenly produced, molded products can be provided using the same rubber composition lot. Therefore, the rubber composition disclosed in the present application is useful in the sealing material industry, which requires plasma resistance and a predetermined hardness, and in the semiconductor industry, such as in plasma processing equipment and semiconductor manufacturing equipment, which use the sealing material.

Claims

1. (a) a crosslinkable reactive fluororubber and / or a crosslinkable reactive perfluororubber, (b) a cross-linking agent; and (c) a compound containing a phenolic hydroxy group; and A rubber composition comprising: The crosslinking agent contains at least a compound represented by the following formula (1): 【Chemistry 1】 (In formula (1), A is a single bond, —O—, an alkylene group, or a fluorinated alkylene group. R １ , R ２ , R ３ are each independently a hydrogen atom, a fluorine atom, an alkyl group, or a fluorinated alkyl group, provided that R １ , R ２ , R ３ At least one of is a fluorine atom or a fluorinated alkyl group. Rubber composition.

2. The compound containing a phenolic hydroxy group is dibutylhydroxytoluene. The rubber composition according to claim 1.

3. For 100 parts by weight of the component (a), 0.5 to 20% by weight of the compound represented by formula (1), The dibutylhydroxytoluene is 0.005 to 1% by weight, Included The rubber composition according to claim 2.

4. Further containing 30% by weight or less of an acid acceptor relative to 100 parts by weight of the component (a). The rubber composition according to claim 1.

5. Further containing 30% by weight or less of an acid acceptor relative to 100 parts by weight of the component (a). The rubber composition according to claim 2.

6. Further containing 30% by weight or less of an acid acceptor relative to 100 parts by weight of the component (a). The rubber composition according to claim 3.

7. Further containing a filler The rubber composition according to any one of claims 1 to 6.

8. Torque change rate after storage at 60°C for 22 days is less than -32.6% The rubber composition according to any one of claims 1 to 6.

9. A fluorine-containing elastomer obtained by crosslinking the rubber composition according to any one of claims 1 to 6.

10. A fluorine-containing elastomer obtained by crosslinking the rubber composition according to claim 7.

11. A sealing material comprising the fluorine-containing elastomer according to claim 9.

12. A sealing material comprising the fluorine-containing elastomer according to claim 10.

13. Compression set is less than 80% when heated at 250°C for 336 hours The fluorine-containing elastomer according to claim 9.

14. A method for storing the rubber composition according to any one of claims 1 to 6, comprising: The storage method comprises: a kneading step of kneading the rubber composition; a separating step of separating the kneaded rubber composition; a storage step of storing the rubber composition separated in the separation step; Storage methods, including:

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