Rubber compositions, fluorinated elastomers, sealing materials, and methods for storing rubber compositions

Abstract

[Problem] The problem is to provide a rubber composition with excellent storage properties. [Solution] A rubber composition comprising: (a) a crosslinking reactive fluororubber and / or a crosslinking reactive perfluororubber, (b) a crosslinking agent, and (c) a compound containing a phenolic hydroxyl group, wherein the aforementioned crosslinking agent comprises at least a compound represented by the following formula (1); (in formula (1), A is a single bond, -O-, alkylene, or fluorinated alkylene. R1, R2, and R3 are each independently a hydrogen atom, a fluorine atom, an alkyl group, or a fluorinated alkyl group. However, at least one of R1, R2, and R3 is a fluorine atom or a fluorinated alkyl group).

Description

[Technical Field]

[0001] The disclosure of this case relates to a rubber composition with excellent storage properties, a fluorinated elastomer obtained by crosslinking the rubber composition, a sealing material, and a method for storing the rubber composition. [Previous Technology]

[0002] Fluorinated elastomers are mainly used in sealing materials requiring plasma resistance. For example, Patent Document 1 describes a composition comprising a perfluoroelastomer, 55 to 75 parts by weight of carbon black relative to 100 parts by weight of the aforementioned perfluoroelastomer, and a crosslinking agent represented by the following formula (1). [Chemistry 1] [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent No. 7066010 [Summary of the Invention]

[0004] [Problem to be Solved by the Invention] By molding and crosslinking a rubber composition, a fluorinated elastomer (hereinafter sometimes referred to as "molded article") such as a sealing component can be formed. Furthermore, to prevent the occurrence of sudden defective products, the rubber composition before crosslinking after material mixing is sometimes separated from the manufacturing line and stored. The separated rubber composition before crosslinking (hereinafter sometimes referred to as "stored product") is intended to prevent the occurrence of sudden defective products; therefore, it is desirable that the separated rubber composition exhibits less deterioration, generally about 3 months at room temperature, preferably about 6 months.

[0005] Furthermore, the properties required for molded articles vary from user to user. For example, if carbon black is used to adjust the hardness, the molded article becomes black, but sometimes users also require non-black molded articles. However, the inventors have recently discovered that when the compound represented by the above formula (1) is used as a crosslinking agent and carbon black is not used in combination, the storage properties (shelf life) of the stored article deteriorate.

[0006] This disclosure was made to solve the above-mentioned problem. After conducting in-depth research, the inventors have made a new discovery that when the compound represented by the above formula (1) is used as a crosslinking agent, the deterioration of the storage properties of the stored product caused by the compound represented by the above formula (1) can be suppressed by using it in combination with a compound containing a phenolic hydroxyl group.

[0007] That is, the purpose of this disclosure is to provide rubber compositions, fluorinated elastomers, sealing materials, and methods for storing rubber compositions with excellent storage properties.

[0008] [Means for solving the problem] The disclosure of this case is as follows, concerning rubber composition, fluorinated elastomer, sealing material, and method of storing rubber composition.

[0009] (1) A rubber composition comprising: (a) a crosslinking reactive fluororubber and / or a crosslinking reactive perfluororubber, (b) a crosslinking agent, and (c) a compound containing a phenolic hydroxyl group, wherein the aforementioned crosslinking agent comprises at least a compound represented by the following formula (1). [Chemistry 2] (In formula (1), A is a single bond, -O-, alkylene, or fluorinated alkylene. R1, R2, and R3 are each independently a hydrogen atom, a fluorine atom, an alkyl group, or a fluorinated alkyl group. However, at least one of R1, R2, and R3 is a fluorine atom or a fluorinated alkyl group.) (2) The rubber composition as described in (1) above, wherein the aforementioned compound containing a phenolic hydroxyl group is butylated hydroxytoluene. (3) The rubber composition described in (2) above, wherein, relative to 100 parts by weight of component (a) above, it comprises: 0.5 to 20% by weight of the compound represented by formula (1) above, and 0.005 to 1% by weight of the dibutylhydroxytoluene above. (4) The rubber composition described in any of (1) to (3) above, wherein, relative to 100 parts by weight of component (a) above, it further comprises 30% or less of an acid-receiving agent. (5) The rubber composition described in any of (1) to (4) above, further comprises a filler material. (6) The rubber composition described in any of (1) to (5) above, wherein, after being stored at 60°C for 22 days, the torque change rate is less than -32.6%. (7) A fluorinated elastomer obtained by crosslinking the rubber composition described in any of (1) to (6) above. (8) A sealing material comprising the fluorinated elastomer described in (7) above. (9) The fluorinated elastomer described in (7) above, wherein the compression set after heating at 250°C for 336 hours is less than 80%. (10) A storage method for the rubber composition described in any one of (1) to (6) above, the storage method comprising: a mixing step of mixing the aforementioned rubber composition, a separation step of separating the mixed rubber composition, and a storage step of storing the separated rubber composition.

[0010] [Effects of the Invention] By using the rubber composition disclosed in this case, the deterioration of the storage properties of the stored product caused by the compound represented by the above formula (1) can be suppressed.

Implementation Method

[0012] The following details the rubber composition, fluorinated elastomer, sealing material, and storage method of the rubber composition disclosed in this case.

[0013] It is worth noting that, in this specification, the numerical range indicated by "~" means a range that includes the values ​​described before and after "~" as the lower and upper limits. Furthermore, in this specification, expressions regarding numerical values, numerical ranges, and qualitative terms (e.g., "same," "identical," etc.) are interpreted as representing numerical values, numerical ranges, and properties that are generally permissible in the art.

[0014] (Embodiments of the rubber composition) The rubber composition according to the embodiments includes (a) a crosslinking reactive fluororubber and / or a crosslinking reactive perfluororubber, (b) a crosslinking agent, and (c) a compound containing a phenolic hydroxyl group. Thus, the crosslinking agent includes at least a compound represented by the following formula (1). Each component is described in detail below. [Chemistry 3]

[0015] <Regarding component (a)> First, the description refers to crosslinking reactive fluororubber (hereinafter sometimes referred to as "FKM") and / or crosslinking reactive perfluororubber (hereinafter sometimes referred to as "FFKM"), which are components (a). It is worth noting that in the case of being collectively referred to as FKM and FFKM, it is sometimes simply referred to as "fluorinated crosslinking reactive rubber".

[0016] The term "crosslinking reactivity" refers to fluorinated rubber that can be crosslinked through a crosslinking reaction. Fluorinated crosslinking reactive rubber may, for example, contain repeating units derived from fluorinated monomers. Fluorinated crosslinking reactive rubber may contain repeating units derived from one or more fluorinated monomers.

[0017] As fluorinated monomers, examples include tetrafluoroethylene (TFE) represented by formula (a-1) below, and hexafluoropropylene (HFP) represented by formula (a-2) below. CF2=CF2 (a-1) CF2=CFCF3 (a-2)

[0018] Furthermore, as a fluorinated monomer, it includes, for example, a perfluoroolefin, preferably having an ethylene-type unsaturated bond at the terminal position. Specific examples include perfluoroalkyl vinyl ethers (PAVE) represented by formula (a-3), perfluorooxyalkyl vinyl ethers represented by formula (a-4), and perfluorovinyl ethers represented by formula (a-5).

[0019] CF2=CFORf1 (a-3) (In formula (a-3), Rf1 is a perfluoroalkyl group having 1 to 6 carbon atoms, for example, trifluoromethyl or pentafluoropropyl.)

[0020] CF2=CFORf2 (a-4) (In formula (a-4), there is a perfluoroalkyl group with 1 to 12 carbon atoms containing an ether group with Rf2 of 1 or more, for example, perfluoro-2-propoxypropyl.)

[0021] CF2=CFOCF2ORf3 (a-5) (In formula (a-5), Rf3 is a straight-chain or branched perfluoroalkyl group with 2 to 6 carbon atoms, a cyclic perfluoroalkyl group with 5 or 6 carbon atoms, or a straight-chain or branched perfluorooxyalkyl group with 2 to 6 carbon atoms containing 1 to 3 oxygen atoms.)

[0022] In one embodiment, the perfluorovinyl ether represented by formula (a-5) is represented by formula (a-6) or formula (a-7) below. It is worth noting that the perfluorovinyl ether represented by formula (a-6) is sometimes referred to as "MOVE1" and the perfluorovinyl ether represented by formula (a-7) is referred to as "MOVE2".

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

[0024] There are no particular limitations on the composition (molar ratio) of the fluorinated monomers used to manufacture fluorinated crosslinking reactive rubber.

[0025] In one embodiment, the fluorinated crosslinking reactive rubber can be manufactured using 50 to 85 mol% of one or more fluorinated monomers selected from the group consisting of formulas (a-1) and (a-2) and 15 to 50 mol% of one or more fluorinated monomers selected from the group consisting of formulas (a-3) to (a-5).

[0026] In one embodiment, the fluorinated crosslinking reactive rubber is manufactured using 50-85 mol% TFE and 15-50 mol% PAVE.

[0027] In one embodiment, the fluorinated crosslinking reactive rubber is manufactured using 50-85 mol% TFE and 15-50 mol% MOVE. Here, "MOVE" is selected from one or more of the group consisting of MOVE1 and MOVE2.

[0028] In one embodiment, the fluorinated crosslinking reactive rubber may or may not contain vinylidene fluoride-derived units.

[0029] In this specification, FKM in the above-mentioned fluorinated crosslinking reactive rubbers means a rubber containing hydrogen in its chemical structure. FKM includes, for example, 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, fluororubber (FKM) of vinylidene fluoride / 2,3,3,3-tetrafluoropropylene, etc., but is not limited to them.

[0030] In this specification, FFKM in the above-mentioned fluorinated crosslinking reactive rubbers means a rubber that does not contain hydrogen in its chemical structure. FFKM includes, for example, perfluororubbers such as tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (FFKM), but is not limited to them.

[0031] FKM is relatively 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. Therefore, depending on the required properties of the molded product, FKM, FFKM, or a mixture of both can be used. It is worth noting that in the case of mixing FKM and FFKM, there is no particular restriction on the mixing ratio; it can be adjusted appropriately according to the required plasma resistance properties, etc.

[0032] In one embodiment, the fluorinated crosslinking reactive rubber may or may not contain units derived from fluoroolefins with 3 to 8 carbon atoms, including iodine and / or bromine. In the case where the fluorinated crosslinking reactive rubber contains the aforementioned units, iodine and / or bromine are preferably included as attack sites for free radicals during crosslinking (curing), and iodine is more preferred. Fluorinated crosslinking reactive rubbers that can be cured by peroxides are, for example, described in Japanese Patent Application Laid-Open No. 2006-9010. In the case where the fluorinated crosslinking reactive rubber contains the aforementioned units, the iodine content is generally 0.001% to 5% by weight relative to the total polymer weight, preferably 0.01% to 2.5% by weight. Iodine atoms may be present on the chain and / or at the terminal positions of the fluorinated crosslinking reactive rubber.

[0033] <About component (b)> The crosslinking agent as component (b) contains at least the compound represented by the following formula (1).

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

[0035] The alkylene or fluorinated alkylene may be straight-chain or branched, preferably with 1 to 15 carbon atoms (more preferably 2 to 8 carbon atoms, and even more preferably 3 to 6 carbon atoms). The alkylene of the fluorinated alkylene may be partially or completely fluorinated. Perfluoroalkylene is preferred.

[0036] Examples of the aforementioned alkylene groups include methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, etc.

[0037] In the above formula (1), R1, R2, and R3 are each independently a hydrogen atom, a fluorine atom, an alkyl group, or a fluorinated alkyl group. However, at least one of R1, R2, and R3 is a fluorine atom or a fluorinated alkyl group.

[0038] The alkyl group of the alkyl or fluorinated alkyl group may be straight-chain or branched, and the number of carbon atoms is preferably 1 to 15 (more preferably 1 to 6, and even more preferably 1 to 4). The alkyl group of the fluorinated alkyl group may be partially or completely fluorinated. Perfluoroalkyl is preferred.

[0039] The aforementioned alkyl group can be exemplified by methyl, ethyl, propyl, etc.

[0040] R1, R2, and R3 are preferably independent hydrogen atoms or fluorine atoms.

[0041] As -CR1=CR2R3, examples include the following groups. [Chemistry 4]

[0042] In the above formula (1), A and -CR1=CR2R3 can be adjacent, intermediate, or opposite, but it is preferred to be opposite, and even more preferably A and 2 -CR1=CR2R3 are opposite.

[0043] Specific examples of compounds represented by the aforementioned formula (1) include compounds represented by the following formulas (2) to (4). [Chemistry 5] In the above formulas, R1, R2, and R3 are the same as those mentioned above. t is preferably 1 to 15 (more preferably 2 to 8, and even more preferably 3 to 6).

[0044] Specific examples of compounds represented by formula (1) above include compounds as described below. It is worth noting that such compounds can be synthesized, for example, by referring to WO2016 / 017187. [Chemistry 6][Chemistry 7]

[0045] The crosslinking agent may be a single type from the compounds mentioned above, or a combination of two or more types may be used. There is no particular limitation on the minimum amount of crosslinking agent that can crosslink the components described in (a) above. The minimum amount relative to 100 parts by weight of component (a) includes, but is 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 more crosslinking agent is used, the better the vapor resistance and heat resistance tend to be. However, if too much is used, it may cause hardening. Therefore, relative to 100 parts by weight of component (a), the upper limit includes, but is not limited to, less than 20% by weight, less than 19% by weight, less than 18% by weight, less than 17% by weight, less than 16% by weight, less than 15% by weight, less than 14% by weight, less than 13% by weight, less than 12% by weight, less than 11% by weight, less than 10% by weight, etc.

[0046] The rubber composition involved in the embodiment contains at least the compound represented by formula (1) above as a crosslinking agent, and may also contain other crosslinking agents. Crosslinking agents other than the compound represented by formula (1) include, but are not limited to, triallyl isocyanurate. In the case where the compound represented by formula (1) above is used in combination with other crosslinking agents, the amount of crosslinking agent used is set to the amount of the crosslinking agent mentioned above.

[0047] <Regarding component (c)> The compound containing a phenolic hydroxyl group (hereinafter sometimes referred to as "compound C") that is component (c) is not particularly limited in that it can suppress the deterioration of the storage properties of the stored product caused by the compound represented by formula (1) when used in combination with the compound represented by formula (1). For example, it includes, but is not limited to, compounds containing two phenolic hydroxyl groups and compounds containing one phenolic hydroxyl group.

[0048] A compound containing two phenolic hydroxyl groups includes compounds represented by formula (2) below. [Chemistry 8]

[0049] In the above formula (2), R1 and R2 independently represent any one of a hydrogen atom, an organic group having 1 to 12 carbon atoms, and a fluorinated organic group having 1 to 12 carbon atoms. The organic group having 1 to 12 carbon atoms and the fluorinated organic group having 1 to 12 carbon atoms can also be linear, branched, or cyclic, and may or may not contain unsaturated bonds. It is worth noting that in the case where one of R1 and R2 is bonded to the basic framework of formula (2) by unsaturated bonds, the other one of R1 and R2 is not present.

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

[0051] A compound containing one phenolic hydroxyl group includes compounds represented by the following formula (3). [Chemistry 9]

[0052] In the above formula (3), R1, R2, and R3 independently represent any one of a hydrogen atom, an organic group having 1 to 12 carbon atoms, and a fluorinated organic group having 1 to 12 carbon atoms. The organic group having 1 to 12 carbon atoms and the fluorinated organic group having 1 to 12 carbon atoms can also be linear, branched, or cyclic, and may or may not contain unsaturated bonds. Furthermore, the organic group having 1 to 12 carbon atoms and the fluorinated organic group having 1 to 12 carbon atoms can also contain carboxylic acid derivatives.

[0053] Examples of compounds represented by formula (3) include, but are not limited to, butylated hydroxytoluene (BHT), phenol, p-cresol, m-cresol, o-cresol, p-phenylphenol, m-phenylphenol, o-phenylphenol, allylphenol, p-hydroxybenzoic acid, methyl p-hydroxybenzoate, etc. The amount of compound C is not particularly limited as long as it is within the range that can inhibit the deterioration of the storage properties of the stored product. As a lower limit relative to 100 parts by weight of component (a), it includes, but is not limited to, 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, 0.045% by weight or more, etc. On the other hand, if the amount of compound C is large, as shown in the following examples, the T90 (the time until 90% of MH (maximum torque)) which is an indicator of rubber molding time becomes longer. In other words, the manufacturing cycle becomes longer, thus manufacturing efficiency decreases and costs increase. Therefore, from a cost point of view rather than a technical point of view, an upper limit value for compound C can be set. As an upper limit value relative to 100 parts by weight of component (a), it includes, but is not limited to, less than 1% by weight, less than 0.9% by weight, less than 0.8% by weight, less than 0.7% by weight, less than 0.6% by weight, less than 0.5% by weight, less than 0.4% by weight, less than 0.3% by weight, less than 0.2% by weight, less than 0.1% by weight, etc. It is worth noting that by using compound C together with the compound represented by formula (1), the deterioration of the storage properties of the stored product caused by the compound represented by formula (1) can be suppressed. The reason is speculated to be that compound C functions as an antioxidant or anti-scorching agent by capturing free radicals.

[0054] The rubber composition disclosed in this case can suppress the deterioration of the storage characteristics of the stored product caused by the compound represented by the above formula (1). In other words, it can achieve excellent storage characteristics. It is worth noting that in this specification, "storage characteristics" means the torque change rate of the rubber composition after storage at 60°C for 22 days, based on the torque of the freshly separated rubber composition (stored product day 0). Therefore, in this specification, suppressing the deterioration of storage characteristics means that the torque change rate is less than -32.6%. If the torque drops sharply, the crosslinking density decreases, which may result in poor molding (poor shape, adhesion to the mold, etc.) or insufficient heat resistance. However, if it is less than -32.6%, the possibility of poor molding or poor heat resistance is reduced. There is no particular limitation that the torque change rate is less than -32.6% for storage characteristics, but the smaller the torque change rate, the better. The torque change rate of the rubber composition after storage at 60℃ for 22 days can also be, but is not limited to, 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] <Regarding optional additives that may also be included in rubber compositions> Next, optional additives that may also be included in rubber compositions will be described. (d) Acid-receiving agents Rubber compositions may also include acid-receiving agents. Acid-receiving agents are generally used in this technical field and are not particularly limited, such as including primary amines, secondary amines, tertiary amines, inorganic acid-receiving agents, etc. Specific examples of any of the primary, secondary, or 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 oxide (II), calcium oxide (II), and magnesium oxide (II).

[0056] As shown in the following examples, when an acid acceptor is added in a small amount of compound C, the storage properties of the product can be improved. The amount of acid acceptor is not particularly limited as long as it is within the range that improves the storage properties of the product. Relative to 100 parts by weight of component (a), this includes, but is 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, 0.6% by weight or less, etc. It is worth noting that while compound C can improve the storage properties of the rubber composition, it also captures free radicals generated by peroxides during molding, thus hindering the crosslinking reaction. Therefore, if a large amount of compound C is used, poor molding may occur. In the case of using compound C with an acid-receiving agent, the storage properties of the rubber composition can be improved with a smaller amount of compound C, and the possibility of molding defects can be reduced due to the reduced amount of compound C.

[0057] (e) The co-crosslinking agent rubber composition may also contain a co-crosslinking agent. Commonly known co-crosslinking agents for fluoroelastomers can be used. Examples include triallyl isocyanurate (TAIC), triallyl cyanurate, triallyl trimellitate, N,N'-m-phenylenediamine, trimethylolpropane trimethacrylate, etc. Other monomers such as acrylate-based and methacrylate-based monomers may also be used. It is worth noting that TAIC is a liquid. TAIC can be used directly as a liquid, but for easier mixing with other components, it can also be used in a mixed form (e.g., TAICWH-60) after being mixed with powders such as silica. In this case, the mixed form of TAIC functions as a co-crosslinking agent, and the powdered component such as silica functions as a filler. Liquid co-crosslinking agents other than TAIC can also be used in mixed forms.

[0058] Also, as a co-crosslinking agent, compounds represented by formula (e-1) and / or compounds represented by formula (e-2) can also be used. [Chemistry 10] (In formula (e-1), A is a single bond, -O-, -S-, a heteroatom-containing group, a straight-chain or branched alkylene, cycloalkylene, or aryl group in which hydrogen atoms are unsubstituted with fluorine atoms, or some or all of the hydrogen atoms are substituted with fluorine atoms. R1, R2, R3, and R4 are each independently a hydrogen atom, a fluorine atom, an alkyl group, a fluorinated alkyl group, or a substituted or unsubstituted aryl group. A plurality of R1s are the same or different. A plurality of R2s are the same or different. A plurality of R3s are the same or different. A plurality of R4s are the same or different. At least one of R1, R2, and R3 is a fluorine atom or a group containing a fluorine atom. m is an integer from 1 to 5. n is an integer from 1 to 5.)

[0059] [Chemistry 11] (In formula (e-2), n and m are 0 or 1 respectively. t is an integer greater than 2. Z is a chain group with a valence of t.)

[0060] It is worth noting that detailed descriptions of the compounds described in formulas (e-1) and (e-2) above are provided in International Publication No. 2021 / 230231. Therefore, the descriptions of formulas (e-1) and (e-2) above are omitted in this specification. The contents described in International Publication No. 2021 / 230231 are incorporated herein by reference. The above-mentioned co-crosslinking agents can be used alone or in combination of two or more.

[0061] (f) The rubber composition involved in the embodiment of the filler material may also include a filler material. The filler material may be any filler material known in the field of fluoroelastomers. Including but not limited to carbon black, silicon dioxide, calcium carbonate, clay, wollastonite, mica, talc, barium sulfate, etc. It is worth noting that the rubber composition involved in the embodiment can solve the problem of this case by using the compound described in formula (1) and compound C together. The rubber composition involved in the embodiment can also add carbon black for coloring or hardness adjustment of the molded article whenever it can solve the problem of this case. That is to say, the rubber composition involved in the embodiment may include or not include carbon black as an essential inventive feature, which includes the compound described in formula (1) and compound C.

[0062] (g) Other components may be any additives other than those described in (d) to (f) above, such as initiators, thickeners, pigments, coupling agents, stabilizers, etc., including dicumyl peroxide, di-tert-butyldicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, etc. The examples of such additives may use materials known in the field of fluoropolymers.

[0063] (Embodiments of Fluorinated Elastomers) The fluorinated elastomers involved in the embodiments can be manufactured by crosslinking the rubber composition of any embodiment disclosed in this application. There are no particular limitations on the conditions for crosslinking the rubber composition (crosslinking conditions). For example, heating the rubber composition at 100–250°C for 10 minutes to 5 hours is sufficient. Typically, as a single crosslinking step, the raw material (rubber composition) is placed in a mold, stamped, and crosslinked simultaneously. A single crosslinking step is, for example, heating at 150–200°C for 5–60 minutes. Then, it is removed from the mold and crosslinked a second time in air or an inert gas atmosphere. A second crosslinking step is, for example, heating at 150–300°C for 1–100 hours. Crosslinking can be performed using an electric furnace or the like. By imparting a thermal process through two crosslinking steps, deformation during use can be prevented. Radiation treatment is not necessarily required during crosslinking; it is preferable to omit radiation treatment. It is worth noting that the rubber composition used in the manufacture of the fluorinated elastomer involved in the embodiments may be stored or not. In this specification, the description of "rubber composition" before crosslinking includes both storage and non-storage.

[0064] (Implemental Forms of Sealing Materials) The sealing materials involved in the embodiments include the fluorinated elastomers involved in any of the embodiments disclosed in this application. The form of the sealing material is not particularly limited, and may include, for example, molded bodies such as gaskets or sealing rings. The application of the sealing material is not particularly limited and can be widely used in various devices; however, the sealing material disclosed in this application has excellent plasma resistance and relatively high hardness, thus it is suitable, for example, as a sealing material for semiconductor manufacturing devices. Semiconductor manufacturing devices include, for example, plasma devices, etching devices, plasma CVD devices, etc.

[0065] (Embodiment of Storage Method) The storage method involved in any embodiment disclosed in this case is a method for storing the rubber composition involved in any embodiment. The storage method includes a mixing step of mixing the rubber composition, a separation step of separating the mixed rubber composition, and a storage step of storing the rubber composition separated by the separation step. The storage step can be performed at room temperature (23±2℃).

[0066] The following examples illustrate the embodiments disclosed in this case, but these examples are merely for illustrative purposes and do not limit or restrict the scope of the invention disclosed in this case.

[0067] [Example] <Materials> The materials used in the examples and comparative examples are as follows. (a) Components (FKM, FFKM) • FKM: DAI-EL G912, manufactured by Daikin Industries, Ltd. • FFKM: AFLAS (registered trademark) Premium PM3000, manufactured by AGC Corporation • FFKM: 3M Japan Co., Ltd. LJ213091 (b) Components (crosslinking agent) • Compound represented by formula (1): The following compound was synthesized by our company. It is worth noting that it is listed as FN-10 in the table below. (c) Components (compounds containing phenolic hydroxyl groups) • BHT: Manufactured by Nacalai Tesque Co., Ltd. 2,6-Di-tert-butyl-p-cresol (d) Components (acid acceptor) • Melamine cyanurate: Manufactured by Nissan Chemical Co., Ltd. MC6000 • Melamine: Manufactured by Nacalai Tesque Co., Ltd. • DABCO: Manufactured by Nacalai Tesque Co., Ltd. Triethylenediamine (e) Components (co-crosslinking agent) • TAIC WH-60: Manufactured by Mitsubishi Chemical Co., Ltd. TAIC WH-60 (f) Components (filler) • AEROSIL R972: Manufactured by AEROSIL Co., Ltd. (g) Components (initiator) • PERHEXA 25B: Manufactured by Nippon Oil Co., Ltd.

[0068] <Preparation of Rubber Composition> A rubber composition is prepared by mixing the materials in the proportions (by weight) shown in Tables 1 to 7 below using an open roller.

[0069] The obtained rubber composition was evaluated as follows. (1) Torque was measured using a rubber vulcanization tester (Premier MDR) manufactured by Alpha Technologies under the following conditions. ・Measurement conditions: 155°C × 30 min ・Angle: 0.5° a: Maximum torque (MAX [dNm]) b: Optimal vulcanization point (T90 [min], the time to reach 90% of the maximum torque).

[0070] (2) The torque change rate is calculated by the following formula when the maximum torque of the freshly separated rubber composition (stored item 0 days) measured by the method described in (1) above is defined as A, and the measured value after a specified number of days of storage is defined as B. It is worth noting that the storage room is at 60°C for 7 days, 14 days, and 22 days, and at room temperature for 14 days, 59 days, and 92 days.

[0071] (3)Heat Resistance CS% (3-1) Sample Preparation Method The sample (O-ring) is prepared by molding the above material at 155℃ for 15 minutes and cross-linking at 160℃ for 15 hours twice. (3-2) Experimental Method The obtained O-ring is cut into test pieces with a length of 30 mm. The test pieces are fastened with bolts in two flat plates using spacers to compress 25%. The bond is prepared and exposed to heat in a gear oven under specified conditions (atmospheric environment, 200, 250℃ for 70, 336 hours). Then, the test pieces are removed from the gear oven and opened while the bond is still hot. After cooling to room temperature, the wire diameter is measured and the compression set (unit: %) is calculated using the following formula. This compression set is taken as the heat resistance. Compression Set = (Initial Wire Diameter - Wire Diameter after Heat Exposure) / (Initial Wire Diameter - Spacer Thickness) × 100

[0072] [Regarding the Relationship Between Storage at Room Temperature and Storage at 60°C] <Example 1, Comparative Example 1> The relationship between the torque reduction rate of the separated rubber components after storage at room temperature and after storage at 60°C was examined. The proportions of the rubber components used in the experiment are shown in Table 1. Furthermore, the maximum torque and the rate of change of maximum torque after storage at room temperature and 60°C for a specified number of days are shown in Tables 2 and 3. A graph based on the results in Table 2 is shown in Figure 1. [Table 1][Table 2][Table 3]

[0073] As can be seen from Tables 2 and 3 and Figure 1, the maximum torque of the separated rubber composition decreases slightly linearly with increasing storage days, whether stored at room temperature or at 60°C. Therefore, the torque decrease rate after 22 days of storage at 60°C is approximately -55%, while Figure 1 shows that a torque decrease rate exceeding -55% at room temperature requires at least 92 days. Thus, it can be confirmed that storage of the rubber composition at 60°C for 22 days is equivalent to at least 3 months at room temperature. As mentioned above, the separated rubber composition is generally required to be stored at room temperature for approximately 3 months. Therefore, in the following experiment, from the perspective of experimental efficiency, the characteristics of the rubber composition after 22 days of storage at 60°C are examined.

[0074] 〔Regarding the type of crosslinking reactive rubber and the proportions of BHT and the acid acceptor〕 <Examples 2-7, Comparative Examples 2-3> Rubber compositions were prepared in the same order as in Example 1 above, except that the proportions described in Table 4 below were used, and the torque change rate was tested. The results of the torque change rate are also shown in Table 4. [Table 4]

[0075] As shown in Table 4, in both FFKM (Examples 2-5) and FKM (Examples 6-7), the storage properties of the fluorinated crosslinked reactive rubber were improved by combining the compound described in Formula (1) with BHT, compared to Comparative Examples 2 and 3 which did not use BHT. It is worth noting that FKM improved storage properties even with a smaller amount of BHT compared to FFKM. Furthermore, the results from Examples 2-5 confirmed that the greater the amount of BHT, the better the storage properties. In addition, the results from Examples 4-5 and 6-7 confirmed that the storage properties were further improved by combining BHT with an acid acceptor.

[0076] 〔Regarding the type of acid-receiving agent〕 <Examples 8-10> Rubber compositions were prepared in the same order as in Example 1, except that the proportions described in Table 5 below were used, and the torque change rate was tested. The results of the torque change rate and the color tone are also shown in Table 5. Furthermore, for comparison, the results of Example 3 are also shown. [Table 5]

[0077] As shown in Table 5, it can be confirmed that regardless of the type of acid-receiving agent, the storage properties of the rubber composition can be improved by using it in combination with BHT. Furthermore, it can be confirmed in Examples 3, 8 to 10 that carbon black was not used, so the color did not turn black, and the color of the rubber composition could be adjusted according to the type of acid-receiving agent used.

[0078] 〔Effects of containing acid-resistant agents〕 <Examples 11-12> Except for the proportions described in Table 6 below, rubber compositions were prepared in the same order as in Example 1 above, and heat resistance was tested in the order described in "(3) Heat resistance CS%" above. The results of heat resistance are also shown in Table 6.

[0079] [Table 6]

[0080] As shown in Table 6, the higher the heat resistance CS [%) value, the lower the heat resistance. Generally, if it exceeds 80%, the sealing performance evaluation becomes ×. It is clear from Table 6 that the heat resistance CS [%) value of Example 12, which includes MC6000 as an acid acceptor, is lower than that of Example 11 without MC6000. From the above results, it can be confirmed that the acid acceptor can simultaneously enhance the storage properties of the rubber composition and improve the heat resistance of the molded article obtained by crosslinking the rubber composition.

[0081] 〔Regarding the Relationship between BHT Ingredient Amount and T90〕 <Example 13> Except that the amount of BHT in Example 1 was changed to the weight shown in Table 7, the rubber composition was prepared in the same order as in Example 1 above, and the T90 [min] was tested. The results of T90 [min] are also shown in Table 7. [Table 7]

[0082] As can be seen from Table 7, the higher the amount of BHT, the longer the T90 time. Therefore, from a manufacturing efficiency point of view rather than a technical point of view, it can be confirmed that an upper limit is appropriately set for the amount of BHT in the rubber composition disclosed in this case.

[0083] [Industrial Application Potential] The storage characteristics of the rubber composition disclosed in this case can be improved, so even in the event of sudden defective products, the same batch of rubber composition can still be used to supply molded products. Therefore, it is very useful for the sealing material industry that requires plasma resistance and specified hardness, and for the semiconductor industry, such as plasma processing equipment or semiconductor manufacturing equipment that use the sealing material. [Simplified Explanation of the Diagram]

[0011] Figure 1 is a graph showing the correlation between the torque reduction rate of the rubber composition after storage at room temperature and after storage at 60°C.

Claims

1. A rubber composition comprising: (a) a crosslinking reactive fluororubber and / or a crosslinking reactive perfluororubber, (b) a crosslinking agent, and (c) a compound containing a phenolic hydroxyl group, wherein the aforementioned crosslinking agent comprises at least a compound represented by the following formula (1); [Chemistry 1] In formula (1), A is a single bond, -O-, alkylene, or fluorinated alkylene; R1, R2, and R3 are each independently a hydrogen atom, a fluorine atom, an alkyl group, or a fluorinated alkyl group; but at least one of R1, R2, and R3 is a fluorine atom or a fluorinated alkyl group.

2. The rubber composition as described in claim 1, wherein, The aforementioned compound containing a phenolic hydroxyl group is butylated hydroxytoluene.

3. The rubber composition as described in claim 2, wherein, Relative to 100 parts by weight of component (a) above, it comprises: 0.5 to 20% by weight of the compound represented by formula (1) above, and 0.005 to 1% by weight of the dibutylhydroxytoluene above.

4. The rubber composition as described in claim 1, wherein, Compared to 100 parts by weight of component (a) above, it further contains less than 30% by weight of an acid-receiving agent.

5. The rubber composition as described in claim 2, wherein, Compared to 100 parts by weight of component (a) above, it further contains less than 30% by weight of an acid-receiving agent.

6. The rubber composition as described in claim 3, wherein, Compared to 100 parts by weight of component (a) above, it further contains less than 30% by weight of an acid-receiving agent.

7. The rubber composition described in any one of claims 1 to 6 further includes filler material.

8. The rubber composition described in any one of claims 1 to 6, wherein, The torque change rate after storage at 60℃ for 22 days is less than -32.6%.

9. A fluorinated elastomer obtained by crosslinking a rubber composition as described in any one of claims 1 to 6.

10. A fluorinated elastomer obtained by crosslinking a rubber composition as described in claim 7.

11. A sealing material comprising a fluorinated elastomer as described in claim 9.

12. A sealing material comprising a fluorinated elastomer as described in claim 10.

13. The fluorinated elastomer as described in claim 9, wherein, The compression set is less than 80% after heating at 250°C for 336 hours.

14. A method for storing the rubber composition described in any one of claims 1 to 6, the method comprising: a mixing step of mixing the aforementioned rubber composition; a separation step of separating the mixed rubber composition; and a storage step of storing the separated rubber composition.

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