Sealing member

Abstract

Provided is a sealing member that can suppress occurrence of cracks and the like during demolding in a die molding process and that has excellent resistance to copper contamination.　The sealing member includes a crosslinked product of a rubber composition containing components (A) to (E), wherein the ethylene content of component (A) is 50 mass% or more, and the content of component (B) is 30 to 90 parts by mass, the content of component (D) is 0.5 to 10 parts by mass, and the content of component (E) is 3 to 10 parts by mass, with respect to 100 parts by mass of component (A).　(A) At least one of an ethylene-propylene-diene rubber and an ethylene-butene-diene rubber　(B) Silica　(C) Organic peroxide　(D) Benzimidazole-based antioxidant　(E) Zinc oxide

Description

Sealing material

[0001] The present invention relates to a sealing member made of a crosslinked rubber composition.

[0002] Various types of sealing members are used in various devices such as electronic devices to ensure their waterproofness, etc. For example, wire sealing members that function to prevent the intrusion of water and the like are used inside the housing of connectors used in wire harnesses for automobiles, etc. (see, for example, Patent Document 1, etc.).

[0003] Such a wire seal member is made of a cylindrical body having a through hole for inserting a wire, and is formed with multiple protrusions that protrude radially outward to provide waterproofing. For example, as shown in Fig. 1, the wire seal member has a substantially cylindrical small diameter portion 1 and a large diameter portion 2 having multiple protrusions and grooves that protrude radially outward, and waterproofing is ensured by forming multiple protrusions (2a, etc.) and grooves (2d, etc.).

[0004] Japanese Patent Application Publication No. 05-258802

[0005] Sealing members, such as the aforementioned wire sealing member, often require complex and precise shapes, raising concerns about cracks and deformation during demolding during the molding process. Furthermore, because sealing members are used in a wide variety of products and are often in contact with metal components, there are concerns about deterioration due to redox reactions. Deterioration due to "copper contamination" caused by contact between the sealing member and copper is particularly serious. Therefore, the present invention provides a sealing member that can suppress the occurrence of cracks and other defects during demolding during the molding process, and also suppresses deterioration due to copper contamination.

[0006] As a result of extensive research, the present inventors have found that in a sealing member made of a crosslinked product of a rubber composition containing (A) at least one of ethylene-propylene-diene rubber and ethylene-butene-diene rubber, (B) silica, (C) an organic peroxide, (D) a benzimidazole-based antioxidant, and (E) zinc oxide, by setting the ethylene content of component (A) within a specific range and setting the contents of other components relative to component (A) within respective specific ranges, it is possible to suppress the occurrence of cracks and the like when releasing from the mold in a molding step, and further to suppress deterioration due to copper contamination.

[0007] The gist of the present invention is the following [1] to

[10] . [1] A sealing member comprising a crosslinked product of a rubber composition containing the following components (A) to (E), wherein the ethylene content of component (A) is 50% by mass or more, and the content of component (B) is 30 to 90 parts by mass, the content of component (D) is 0.5 to 10 parts by mass, and the content of component (E) is 3 to 10 parts by mass, relative to 100 parts by mass of component (A): (A) at least one of ethylene-propylene-diene rubber and ethylene-butene-diene rubber; (B) silica; (C) an organic peroxide; (D) a benzimidazole-based antioxidant; and (E) zinc oxide. [2] The sealing member according to [1], wherein the ethylene content of component (A) is 60% by mass or more. [3] The sealing member according to [1] or [2], wherein the content of the component (B) is 50 to 90 parts by mass per 100 parts by mass of the component (A). [4] The BET specific surface area of ​​the component (B) is 30 to 250 m 2 / g. [5] The sealing member according to any one of [1] to [4], wherein the mass ratio (E / D) of the component (E) to the component (D) is 0.5 to 10. [6] The sealing member according to any one of [1] to [5], further containing erucic amide. [7] The sealing member according to [6], wherein the content of the erucic amide is 1 to 15 parts by mass per 100 parts by mass of the component (A). [8] The sealing member according to any one of [1] to [7], wherein the diene component of the ethylene-propylene-diene rubber (A) is 5-vinyl-2-norbornene. [9] The sealing member according to any one of [1] to [8], wherein the sealing member is a wire sealing member having a plurality of protrusions protruding radially outward.

[10] The sealing member according to any one of [1] to [9], which contains a zinc salt of 2-mercaptobenzimidazole as the component (D), and the content of the zinc salt of 2-mercaptobenzimidazole is 0.5 to 10 parts by mass and the content of the component (E) is 0 to 10 parts by mass per 100 parts by mass of the component (A).

[0008] According to the present invention, a sealing member having excellent moldability and resistance to copper contamination can be provided. Specifically, the sealing member of the present invention can suppress the occurrence of cracks and the like during demolding in a molding process, and further suppress deterioration due to copper contamination.

[0009] 10A and 10B are diagrams illustrating an example of a wire seal member.

[0010] Next, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments.

[0011] In this specification, the term "main component" means the component that accounts for the largest amount in the target substance, and typically accounts for 30% by mass or more of the target substance, preferably 50% by mass or more, and more preferably 60% by mass or more, and may be, for example, 70 to 100% by mass, 80 to 100% by mass, 90 to 100% by mass, 95 to 100% by mass, etc.

[0012] A sealing member according to one embodiment of the present invention (hereinafter sometimes referred to as "the sealing member") is a sealing member made of a crosslinked product of a rubber composition (hereinafter sometimes referred to as "the rubber composition") containing components (A) to (E), wherein the ethylene content of component (A) is 50% by mass or more, and the content of component (B) is 30 to 90 parts by mass, the content of component (D) is 0.5 to 10 parts by mass, and the content of component (E) is 3 to 10 parts by mass, relative to 100 parts by mass of component (A). (A) at least one of ethylene-propylene-diene rubber (EPDM) and ethylene-butene-diene rubber (EBT). (B) silica. (C) organic peroxide. (D) benzimidazole-based antioxidant. (E) zinc oxide.

[0013] The present inventors have embarked on research and development of a rubber composition that incorporates, among various rubber components, EPDM and EBT (hereinafter sometimes referred to as "EPDM, etc.") as a rubber material capable of ensuring the performance of sealing members, and that also incorporates a white reinforcing material as a reinforcing material from the perspective of enhancing design (coloring flexibility). During this research and development process, it was discovered that formulations incorporating EPDM, etc., and the white reinforcing material have low modulus at high temperatures (e.g., molding temperatures of 170°C, etc.) due to weak interactions between polymer chains (hydrophobic) such as EPDM and particles (hydrophilic) such as silica, making it difficult to suppress cracking and deformation during demolding during the molding process. Furthermore, during this research and development process, it was discovered that copper contamination resistance is problematic due to, for example, the white reinforcing material not functioning as a radical scavenger.

[0014] In light of the above circumstances, the inventors of the present invention have conducted further research and discovered that by blending components (A) to (E) in specific proportions, it is possible to achieve both high moldability and high resistance to copper contamination. This sealing member can suppress cracking and deformation during demolding in the molding process and also has excellent resistance to copper contamination.

[0015] Although the reason why this sealing member exhibits the above-mentioned excellent effects is not entirely clear, the inventors believe that the interaction between an EPDM having an ethylene content of 50% by mass or more and a specific amount of silica increases the modulus at high temperatures, and furthermore, the interaction between the benzimidazole-based antioxidant and zinc oxide suppresses the crosslinking inhibitory effect, allowing the modulus to be maintained at a high level at high temperatures, contributing to an improved effect of suppressing cracks during demolding. On the other hand, the interaction between the benzimidazole-based antioxidant and zinc oxide promotes the passivation effect of the copper surface, resulting in particularly excellent copper contamination resistance.

[0016] Furthermore, the use of silica as a white reinforcing material in this seal member allows for enhanced design flexibility (coloring freedom), making it highly useful in that it can be easily colored to any desired color to suit various applications and needs.

[0017] Each component constituting the rubber composition will be described below, but the components are not limited to the following.

[0018] The rubber composition is suitable as a rubber composition for molding a seal member, and is particularly useful as a rubber composition for molding a wire seal member. The rubber composition has an ethylene content of 50% by mass or more in component (A), and the content of component (B) is 30 to 90 parts by mass, the content of component (D) is 0.5 to 10 parts by mass, and the content of component (E) is 3 to 10 parts by mass, per 100 parts by mass of component (A). The rubber composition contains (A) at least one of ethylene-propylene-diene rubber (EPDM) and ethylene-butene-diene rubber (EBT). (B) silica. (C) an organic peroxide. (D) a benzimidazole-based antioxidant. (E) zinc oxide.

[0019] (A) At least one of ethylene-propylene-diene rubber and ethylene-butene-diene rubber As component (A), at least one of ethylene-propylene-diene rubber (EPDM) and ethylene-butene-diene rubber (EBT) is used. EPDM is obtained by copolymerizing ethylene, propylene, and a diene component, and EBT is obtained by copolymerizing ethylene, butene, and a diene component. These may be used alone or in combination of two or more.

[0020] The ethylene content of component (A) is 50% by mass or more. If the ethylene content is less than 50% by mass, the modulus at high temperatures tends to decrease and cracks tend to occur during demolding. The ethylene content of component (A) can be appropriately set within the above range, and is preferably, for example, 55% by mass or more, 58% by mass or more, or 60% by mass or more. The upper limit of the ethylene content is not particularly limited, but is, for example, 72% by mass or less.

[0021] The propylene content in component (A) is not particularly limited, but is, for example, 30 to 50 mass%, preferably 30 to 45 mass%, and more preferably 35 to 45 mass%. The butene content in component (A) is also not particularly limited, but is, for example, 30 to 50 mass%, preferably 30 to 45 mass%, and more preferably 35 to 45 mass%.

[0022] The diene component, which is the third component in component (A), is preferably, for example, a diene monomer having 5 to 20 carbon atoms. Specific examples include 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 2,5-dimethyl-1,5-hexadiene, 1,4-octadiene, 1,4-cyclohexadiene, cyclooctadiene, dicyclopentadiene (DCP), 5-ethylidene-2-norbornene (ENB), 5-vinyl-2-norbornene (VNB), 5-butylidene-2-norbornene, 2-methallyl-5-norbornene, and 2-isopropenyl-5-norbornene. Among the diene monomers, 5-vinyl-2-norbornene (VNB) is preferred from the viewpoint of improving the modulus at high temperatures and suppressing cracks during demolding, and ethylene-propylene-VNB rubber is particularly preferred as component (A).

[0023] The diene content in component (A) is not particularly limited, but is, for example, 1 to 15 mass%, preferably 3 to 15 mass%, and more preferably 5 to 12 mass%. The diene content can be set appropriately within the above range, and may be, for example, 1 to 10 mass%, 1 to 6 mass%, or 1 to 3 mass%.

[0024] For example, when the diene component is 5-ethylidene-2-norbornene (ENB), the ENB content is preferably 1 to 15 mass%, 3 to 15 mass%, 3.5 to 12 mass%, 4 to 10 mass%, 5 to 10 mass%, etc. Furthermore, when the diene component is 5-vinyl-2-norbornene (VNB), the ENB content is preferably 1 to 5 mass%, 1 to 4 mass%, 1 to 3 mass%, etc.

[0025] Component (A) constitutes the main rubber component contained in the rubber composition, and its content is usually preferably 30% by mass or more relative to the total amount (100% by mass) of the rubber composition. The content of component (A) may also be 30 to 70% by mass, 32 to 65% by mass, or 34 to 55% by mass, relative to the total amount (100% by mass) of the rubber composition.

[0026] <<(B) Silica>> In the present seal member, (B) silica is particularly used as a white reinforcing material. Examples of silica include wet silica and dry silica. These may be used alone or in combination of two or more.

[0027] The component (B) is not particularly limited, but is preferably wet silica.Examples of wet silica include wet silica obtained by neutralization reaction of sodium silicate and mineral acid (precipitation silica synthesized and aggregated under alkaline conditions, gel silica particles synthesized and aggregated under acidic conditions); colloidal silica obtained by polymerizing acidic silicic acid in an alkaline state; and sol-gel silica obtained by hydrolysis of organic silane compound (for example, alkoxysilane).Among these, precipitation silica is particularly preferred from the viewpoint of improving the modulus at high temperatures and suppressing cracks during demolding.

[0028] The content of component (B) is 30 to 90 parts by mass, preferably 50 to 90 parts by mass, per 100 parts by mass of component (A). If the content is outside this range, the modulus at high temperatures tends to decrease and cracks tend to occur during demolding. The content of component (B) can be set appropriately within the above range, and may be, for example, 40 to 80 parts by mass, 45 to 70 parts by mass, or 50 to 65 parts by mass.

[0029] The pH value of component (B) is not particularly limited, but from the viewpoint of suppressing a decrease in modulus due to vulcanization inhibition, a pH of 5.5 to 9.0 is preferred, a pH of 5.5 to 7.5 is more preferred, and a pH of 6.0 to 7.0 is even more preferred. The pH value can be determined in accordance with ISO 787-9, specifically by preparing a suspension of silica to be tested at a mass fraction of 10% using water in a glass container, stopping the container, shaking vigorously for 1 minute, allowing to stand for 5 minutes, removing the stopper, and measuring the pH of the suspension to the nearest 0.1.

[0030] The BET specific surface area of ​​component (B) is not particularly limited, but is preferably 30 to 250 m, for example, from the viewpoint of improving the modulus at high temperatures and suppressing cracks during demolding. 2 / g is preferred, and 30 to 210 m 2 / g, and even more preferably 30 to 170 m 2 The BET specific surface area of ​​component (B) can be appropriately set within the above range, and is not particularly limited, but is, for example, 30 to 150 m 2 / g, 30-100m 2 / g, 30-80m 2 The BET specific surface area of ​​silica can be determined, for example, by degassing a sample at 200°C for 15 minutes and then using a mixed gas (N: 70%, He: 30%) as the adsorbent gas with a BET specific surface area measuring device (Microdata Corporation, 4232-II).

[0031] (C) Organic Peroxide The organic peroxide functions as a cross-linking agent in the sealing member. Examples of the organic peroxide include, but are not limited to, peroxyketals, peroxyesters, dialkyl peroxides, ketone peroxides, diacyl peroxides, and peroxydicarbonates. These may be used alone or in combination.

[0032] Examples of peroxyketals include n-butyl-4,4-di(t-butylperoxy)valerate, 2,2-di(t-butylperoxy)butane, 2,2-di(4,4-di(t-butylperoxy)cyclohexyl)propane, 1,1-di(t-butylperoxy)cyclohexane, 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane, and 1,1-di(t-butylperoxy)-2-methylcyclohexane.

[0033] Examples of peroxyesters include t-butyl peroxybenzoate, t-butyl peroxyacetate, t-hexyl peroxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxy-2-ethylhexyl monocarbonate, t-butyl peroxylaurate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxymaleic acid, and t-hexylperoxyisopropyl monocarbonate.

[0034] Examples of dialkyl peroxides include di(2-t-butylperoxypropyl)benzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-hexyl peroxide, di-t-butyl peroxide, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3.

[0035] The content of component (C) is not particularly limited, but is preferably 1.5 to 14 parts by mass, and more preferably 2 to 13 parts by mass, per 100 parts by mass of component (A). The content of component (C) can be set appropriately within the above range, and may be, for example, 3 to 11 parts by mass, 4 to 10 parts by mass, etc. When a 100% pure active ingredient is not used as component (C), the active ingredient is blended so that the proportion is within the above range.

[0036] (D) Benzimidazole-Based Antiaging Agents Examples of component (D) include 2-mercaptobenzimidazole (MBI), 2-mercapto-5-methylbenzimidazole, 2-mercapto-5-methoxybenzimidazole, 2-mercapto-5-carboxybenzimidazole, 2-mercapto-5-nitrobenzimidazole, 1,3-dihydro-1-phenyl-2H-benzimidazole-2-thione, and metal salts thereof (e.g., 2-mercaptobenzimidazole zinc salt (ZnMBI)). These may be used alone or in combination of two or more.

[0037] The content of component (D) is 0.5 to 10 parts by mass per 100 parts by mass of component (A). If the content is outside this range, the modulus at high temperatures tends to decrease, cracks tend to occur during demolding, or copper contamination resistance tends to decrease. The content of component (D) can be set appropriately within the above range, and may be, for example, 0.5 to 8 parts by mass, 1 to 7 parts by mass, or 1.5 to 5 parts by mass.

[0038] (E) Zinc Oxide Examples of the component (E) include zinc oxide type 1, zinc oxide type 2, zinc oxide type 3, fine zinc oxide, etc. These may be used alone or in combination of two or more types.

[0039] The content of component (E) is 3 to 10 parts by mass per 100 parts by mass of component (A). If the content is outside this range, the modulus at high temperatures tends to decrease, cracks tend to occur during demolding, or copper contamination resistance tends to decrease. The content of component (E) can be set appropriately within the above range, and may be, for example, 3.5 to 9 parts by mass, 4 to 8 parts by mass, etc.

[0040] In order to significantly exhibit the effects of the present invention, the mass ratio of the component (E) to the component (D) ((E) zinc oxide / (D) benzimidazole antioxidant) is preferably 0.5 to 10, more preferably 0.5 to 8, and even more preferably 0.5 to 6.

[0041] (F) Fatty Acid Amide The rubber composition may optionally contain (F) a fatty acid amide. Examples of component (F) include caproic acid amide, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, methylene bisstearic acid amide, and ethylene bisstearic acid amide. These may be used alone or in combination. Among these, erucic acid amide is preferred from the viewpoints of improving the modulus at high temperatures and suppressing cracking during mold release.

[0042] The amount of component (F) is not particularly limited, but is, for example, 0.5 to 30 parts by mass, and preferably 1 to 25 parts by mass, relative to 100 parts by mass of component (A). Alternatively, the amount of component (F) may be 1 to 20 parts by mass, 2 to 15 parts by mass, or 3 to 12 parts by mass.

[0043] <<Other Components>> The rubber composition may contain optional additives other than the components (A) to (F), such as antioxidants, processing aids, silane coupling agents, colorants, plasticizers, crosslinking aids, rubber components, etc., as needed, within the range that does not impair the effects of the present invention. These may be used alone or in combination of two or more.

[0044] (Antiaging Agent) Examples of the antiaging agent include diphenylamine-based antiaging agents, phenylenediamine-based antiaging agents, carbamate-based antiaging agents, phenol-based antiaging agents, phenylamine-based antiaging agents, quinoline-based antiaging agents, waxes, etc. These may be used alone or in combination of two or more.

[0045] Examples of diphenylamine-based antioxidants include p-(p-toluenesulfonylamido)diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, octylated diphenylamine, styrenated diphenylamine, etc. Examples of phenylenediamine-based antioxidants include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-β-naphthyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, N-(3-methacryloyloxy-2-hydroxypropyl)-N'-phenyl-p-phenylenediamine, and N-cyclohexyl-N'-phenyl-p-phenylenediamine.

[0046] The content of the antioxidant (excluding the component (D)) is not particularly limited, but is, for example, 0.1 to 4 parts by mass, preferably 0.2 to 3 parts by mass, and more preferably 0.3 to 2 parts by mass, per 100 parts by mass of the component (A).

[0047] (Processing Aid) Examples of processing aids include higher fatty acids such as stearic acid and oleic acid, higher fatty acid salts such as sodium stearate, and higher fatty acid esters such as ethyl oleate. These may be used alone or in combination of two or more. The content of the processing aid is not particularly limited, but is, for example, 0.5 to 10 parts by mass, preferably 0.8 to 8 parts by mass, and more preferably 1 to 5 parts by mass per 100 parts by mass of component (A).

[0048] (Silane Coupling Agent) Examples of the silane coupling agent include mercapto-based silane coupling agents, sulfide-based silane coupling agents, amine-based silane coupling agents, epoxy-based silane coupling agents, vinyl-based silane coupling agents, etc. These may be used alone or in combination of two or more.

[0049] Examples of the mercapto-based silane coupling agent include 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane.

[0050] Examples of sulfide-based silane coupling agents include bis-(3-(triethoxysilyl)-propyl)-disulfide, bis(3-triethoxysilylpropyl)trisulfide, bis-(3-(triethoxysilyl)-propyl)-tetrasulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, and 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide. sulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, and 3-trimethoxysilylpropyl methacrylate monosulfide.

[0051] Examples of amine-based silane coupling agents include 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, and 3-(N-phenyl)aminopropyltrimethoxysilane.

[0052] Examples of epoxy-based silane coupling agents include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, and 3-glycidoxypropylmethyldimethoxysilane.

[0053] Examples of the vinyl-based silane coupling agent include vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(β-methoxyethoxy)silane, vinyldimethylchlorosilane, vinyltrichlorosilane, vinyltriisopropoxysilane, and vinyltris(2-methoxyethoxy)silane.

[0054] The content of the silane coupling agent is not particularly limited, but is, for example, 0.1 to 10 parts by mass, preferably 0.5 to 8 parts by mass, and more preferably 1 to 6 parts by mass, per 100 parts by mass of component (A).

[0055] (Plasticizer) Examples of the plasticizer include adipic acid derivatives, azelaic acid derivatives, sebacic acid derivatives, paraffinic process oils, naphthenic process oils, etc. These may be used alone or in combination of two or more.

[0056] The content of the plasticizer is not particularly limited, but is, for example, 10 to 60 parts by mass, preferably 15 to 55 parts by mass, and more preferably 20 to 45 parts by mass, per 100 parts by mass of (A).

[0057] (Colorant) Examples of colorants include inorganic pigments and organic pigments. Examples of inorganic pigments include titanium dioxide, zinc white, zinc powder, lead zincide, aluminum pigments, lead monoxide, micaceous iron oxide pigments, red lead, white lead, yellow lead, ochre, kaolin, clay, ultramarine, Prussian blue, iron oxide, cyanamide lead, heavy calcium carbonate, zinc chromate, talc, iron yellow, and chalk. Examples of organic pigments include azo pigments such as soluble azo red, monoazo yellow, monoazo red, disazo yellow, and disazo orange, and phthalocyanine pigments such as copper phthalocyanine blue, copper phthalocyanine green, and cobalt phthalocyanine blue. These may be used alone or in combination of two or more.

[0058] The content of the colorant is not particularly limited, but is, for example, 1 to 20 parts by mass, 2 to 18 parts by mass, or 3 to 12 parts by mass relative to 100 parts by mass of (A).

[0059] (Crosslinking Auxiliary Agent) Examples of crosslinking auxiliary agents include maleimide compounds, triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), ethylene glycol dimethacrylate (EG), amylphenol disulfide polymers, trimethylolpropane trimethacrylate (TMPT), etc. The content of the crosslinking auxiliary is not particularly limited, but is, for example, about 0.1 to 5 parts by mass per 100 parts by mass of component (A).

[0060] The rubber composition may contain carbon black as a reinforcing material. Examples of carbon black include various grades of carbon black such as SAF, ISAF, HAF, MAF, FEF, GPF, SRF, FT, and MT. The amount of carbon black is not particularly limited, but may be, for example, 5 to 50 parts by mass or 5 to 30 parts by mass per 100 parts by mass of component (A).

[0061]

[0013] Note that there is a strong interaction between polymer chains (hydrophobic) such as EPDM and carbon black particles (hydrophobic), and although this increases the reinforcing properties and thereby improves the moldability of the sealing member, the design (coloring freedom) is insufficient, and it is difficult to color the desired color. From the viewpoint of improving the design (coloring freedom), the content of carbon black is preferably 30 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of component (A). In some cases, it may be preferable for the composition to be substantially free of carbon black, and in other cases it may be preferable for the composition to contain no carbon black (0 parts by mass).

[0062] Other Embodiments In another embodiment of the sealing member of the present invention, the rubber composition contains a zinc salt of 2-mercaptobenzimidazole as the component (D), the content of the zinc salt of 2-mercaptobenzimidazole is 0.5 to 10 parts by mass relative to 100 parts by mass of the component (A), and the content of the zinc oxide (E) is 0 to 10 parts by mass relative to 100 parts by mass of the component (A).

[0063] That is, in the embodiment detailed above, the interaction between the benzimidazole antioxidant and zinc oxide produces, for example, a zinc salt of 2-mercaptobenzimidazole, thereby improving the modulus and copper staining resistance at high temperatures. However, as in other embodiments, it is also possible to incorporate a zinc salt of 2-mercaptobenzimidazole alone. In such other embodiments, similar effects are achieved, and the modulus and copper staining resistance at high temperatures can be improved. It should be noted that the incorporation of zinc oxide is not excluded in other embodiments, and a zinc salt of 2-mercaptobenzimidazole and zinc oxide may be used in combination.

[0064] The content of the zinc salt of 2-mercaptobenzimidazole is, for example, preferably 0.5 to 10 parts by mass, and more preferably 0.5 to 8 parts by mass, per 100 parts by mass of component (A).

[0065] The content of the zinc oxide (E) is, for example, preferably 0 to 10 parts by mass, and more preferably 3.5 to 8 parts by mass, per 100 parts by mass of the component (A).

[0066] Another embodiment of the sealing member of the present invention may be, from the same viewpoint, a sealing member comprising a crosslinked product of a rubber composition containing components (A) to (D), in which the ethylene content of component (A) is 50% by mass or more, component (D) is a zinc salt of 2-mercaptobenzimidazole, the content of component (B) is 30 to 90 parts by mass per 100 parts by mass of component (A), and the content of the zinc salt of 2-mercaptobenzimidazole is 0.5 to 10 parts by mass. (A) at least one of an ethylene-propylene-diene rubber and an ethylene-butene-diene rubber. (B) silica. (C) an organic peroxide. (D) a benzimidazole-based antioxidant.

[0067] Commercially available zinc salts of 2-mercaptobenzimidazole include "Suncerer MZ" manufactured by Sanshin Chemical Industry Co., Ltd.

[0068] (Preparation of the Present Rubber Composition, Crosslinking Molding of the Present Seal Member) The preparation of the present rubber composition is not particularly limited, but is carried out by kneading various materials using a kneading machine such as a single-screw extruder, a twin-screw extruder, an open roll, a Banbury mixer, a kneader, etc. The crosslinking molding of the present rubber composition is not particularly limited, but is carried out by a crosslinking step at about 160 to 180°C for about 8 to 15 minutes.

[0069] (Usefulness of the present sealing member) The present sealing member has a high modulus at high temperatures, can suppress the occurrence of cracks and the like during demolding in the molding process, and also has excellent resistance to copper contamination, making it highly technically useful. The modulus at high temperatures is not limited to the following, but is preferably 1.5 MPa or more, and more preferably 1.7 MPa or more, as M100 (100% modulus) based on the measurement method (170°C condition) described in the Examples below.

[0070] (Uses of the Present Rubber Composition and the Present Seal Member) The present rubber composition is suitable as a rubber composition for molding a seal member, and is particularly useful as a rubber composition for molding a wire seal member.

[0071] This seal member can be used as various seal members such as O-rings and gaskets, but is particularly suitable for use as a wire seal member. As shown in FIG. 1 , the wire seal member is a member having a through hole for inserting a wire (electric wire), and includes a substantially cylindrical small-diameter portion 1 and a large-diameter portion 2 having multiple protrusions and grooves protruding radially outward. This wire seal member effectively prevents the intrusion of water, dust, oil, and the like from the outside by forming multiple protrusions (2a, 2b, 2c) and grooves (2d, 2e) in the large-diameter portion 2. This seal member, like the wire seal member, exhibits particularly excellent performance in molded products that require complex and precise shapes, such as automotive seal members around automobile engines and electronic components.

[0072] Next, examples will be described together with comparative examples. However, the present invention is not limited to these examples. In Table 1, "Et amount" means the ethylene content.

[0073] First, the following materials were prepared.

[0074] <(A) EPDM, EBT (ethylene content 50% by mass or more)> - EPDM (a1): ethylene content 50% by mass, ENB-EPT 3090EM, manufactured by Mitsui Chemicals. - EPDM (a2): ethylene content 60% by mass, ENB-EPT 3091, manufactured by Mitsui Chemicals. - EBT (a3): ethylene content 50% by mass, ENB-EBT K-9330M, manufactured by Mitsui Chemicals. - EPDM (a4): ethylene content 60% by mass, VNB-EPT PX-006M, manufactured by Mitsui Chemicals.

[0075] <(A') EPDM, EBT (ethylene content less than 50% by mass)> EPDM (a'): ethylene content 45% by mass, EPT 4045M, manufactured by Mitsui Chemicals, Inc.

[0076] <(B) Silica> Silica (b1): wet silica, BET specific surface area 48 m 2 / g, pH 6.8, Nipsil EL, manufactured by Tosoh Silica Corporation.

[0077] <(B') White reinforcing material other than silica> Talc (b'): Fuji Talc RS613, manufactured by Fuji Talc Kogyo Co., Ltd.

[0078] <(C) Organic Peroxide> Organic peroxide (c1): Percumyl D-40, manufactured by NOF Corporation.

[0079] <(D) Benzimidazole-based antioxidant> 2-mercaptobenzimidazole (d1): B0055, manufactured by Tokyo Chemical Industry Co., Ltd.

[0080] <(E) Zinc Oxide> Zinc oxide type 2 (e1): manufactured by Mitsui Mining & Smelting Co., Ltd.

[0081] <(F) Fatty Acid Amides> Erucic acid amide (f1): D1008, manufactured by Tokyo Chemical Industry Co., Ltd.

[0082] <Other ingredients> Antiaging agent: diphenylamine-based antiaging agent, B1970, manufactured by Tokyo Chemical Industry Co., Ltd. Processing aid: stearic acid, beads stearate Sakura, manufactured by Nippon Oil & Fats Co., Ltd. Processing aid: paraffin-based oil, Diana Process PW-380, manufactured by Idemitsu Sanko Co., Ltd. Colorant: titanium dioxide, T4017, manufactured by Tokyo Chemical Industry Co., Ltd. Silane coupling agent: V0042, manufactured by Tokyo Chemical Industry Co., Ltd.

[0083] Examples 1-13, Comparative Examples 1-8: Components (A) to (F) were mixed in the proportions shown in Table 1 below. The "Other Components" section included 0.5 parts by mass of a diphenylamine-based antioxidant, 2 parts by mass of stearic acid, 10 parts by mass of titanium dioxide, 2 parts by mass of a silane coupling agent, and 40 parts by mass of paraffinic oil per 100 parts by mass of component (A). The components listed above, excluding component (C), were mixed in the proportions shown above and kneaded in a 1.7 L Banbury mixer. Component (C) was then kneaded using an 8-inch roll to prepare an uncrosslinked rubber composition. The resulting rubber composition was evaluated as follows. The results are shown in Table 1 below.

[0084] <High-Temperature Modulus Test: 170°C, M100> Using an uncrosslinked rubber composition, a 2 mm thick rubber sheet was prepared using a 6-inch mixing roll, and this was subjected to a hot press at 170°C for 10 minutes to obtain a crosslinked rubber sheet. A JIS No. 5 dumbbell was punched out of this rubber sheet to prepare a test specimen. This test specimen was allowed to stand in an atmosphere at 170°C for 10 minutes, and then subjected to a tensile test in accordance with JIS K 6251 to measure the modulus 100 (M100) [MPa].

[0085] <<Moldability Test: Presence or Absence of Cracks Upon Demolding>> An uncrosslinked rubber composition was press-filled into a chamber in a mold consisting of an upper mold and a lower mold, and crosslinked at 170°C for 10 minutes to mold a sealing member having the shape shown in Figure 1. The upper mold was then removed, and the upper portion of the sealing member (see small diameter portion 1 in Figure 1) was pinched with a jig and demolded from the lower mold, and the presence or absence of cracks in the sealing member was evaluated. The sealing member was visually inspected for cracks, and a rating of "good" was given if there were no cracks, and a rating of "poor" if there were cracks.

[0086] <<Copper Stain Resistance Test: Presence or Absence of Copper Staining>> Using the uncrosslinked rubber composition, a 2 mm thick rubber sheet was prepared using a 6-inch mixing roll. This was then hot-pressed at 170°C for 10 minutes to obtain a sheet-like test specimen (crosslinked product) (50 mm x 10 mm x 2 mm). The test specimen and a copper plate (50 mm x 10 mm x 0.2 mm) were placed in a compression jig, and the test specimen was compressed by 25% with the test specimen and copper plate in contact. After aging at 160°C for 120 hours, the test specimen was evaluated for the presence or absence of blackening. The test specimen was visually inspected for blackening, and a rating of "good" was given if there was no copper staining (blackening), and a rating of "poor" if there was copper staining (blackening).

[0087]

[0088] From the results in Table 1 above, it was confirmed that the sealing members of the present invention according to the examples have a high modulus at high temperatures, do not crack when released from the mold during the molding process, and further have good resistance to copper contamination.

[0089] In contrast, Comparative Example 1 did not contain the component (A) of the present invention (because the ethylene content was less than 50% by mass), so the modulus at high temperatures was low and cracks occurred during demolding in the molding process. In Comparative Examples 2 and 3, the content of the component (B) was outside the range specified in the present invention (because it was below the lower limit or exceeded the upper limit), so the modulus at high temperatures was low and cracks occurred during demolding in the molding process. In Comparative Example 4, the component (B) was not contained but talc was contained, so the modulus at high temperatures was low and cracks occurred during demolding in the molding process. In Comparative Examples 5 and 6, the content of the component (D) was outside the range specified in the present invention (because it was below the lower limit or exceeded the upper limit), so the modulus at high temperatures was low and cracks occurred during demolding in the molding process, or the copper contamination resistance was poor. In addition, in Comparative Examples 7 and 8, since the content of component (E) was outside the range specified in the present invention (because it was less than the lower limit or more than the upper limit), the modulus at high temperatures was low, cracks occurred during demolding in the molding process, or the resistance to copper contamination was poor.

[0090] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0091] The sealing member of the present invention exhibits particularly excellent performance in molded articles that require complex and precise shapes, such as sealing members for automobiles around engines and electronic components.

[0092] 1... Small diameter portion 2... Large diameter portion 2a... Projection portion 2d... Groove portion

Claims

1. A sealing member comprising a crosslinked product of a rubber composition containing the following components (A) to (E), wherein the ethylene content of component (A) is 50% by mass or more, and the content of component (B) is 30 to 90 parts by mass, the content of component (D) is 0.5 to 10 parts by mass, and the content of component (E) is 3 to 10 parts by mass, per 100 parts by mass of component (A): (A) at least one of ethylene-propylene-diene rubber and ethylene-butene-diene rubber; (B) silica; (C) organic peroxide; (D) benzimidazole-based antioxidant; and (E) zinc oxide.

2. The sealing member according to claim 1, wherein the ethylene content of component (A) is 60% by mass or more.

3. The sealing member according to claim 1 or 2, wherein the content of the component (B) is 50 to 90 parts by mass per 100 parts by mass of the component (A).

4. The BET specific surface area of ​​the above component (B) is 30 to 250 m 2 The sealing member according to any one of claims 1 to 3, wherein the tensile strength is 1 / g.

5. The sealing member according to any one of claims 1 to 4, wherein the mass ratio (E / D) of the component (E) to the component (D) is 0.5 to 10.

6. The sealing member according to any one of claims 1 to 5, further containing erucic acid amide.

7. The sealing member according to claim 6, wherein the content of said erucamide is 1 to 15 parts by mass per 100 parts by mass of said component (A).

8. The sealing member according to any one of claims 1 to 7, wherein the diene component of the ethylene-propylene-diene rubber (A) is 5-vinyl-2-norbornene.

9. A seal member according to any one of claims 1 to 8, wherein the seal member is a wire seal member having a plurality of protrusions that protrude radially outward.

10. A sealing member according to any one of claims 1 to 9, which contains a zinc salt of 2-mercaptobenzimidazole as component (D), and the content of the zinc salt of 2-mercaptobenzimidazole is 0.5 to 10 parts by mass and the content of component (E) is 0 to 10 parts by mass per 100 parts by mass of component (A).

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