Sealing material

Abstract

To provide a seal member that can reduce generation of cracks and the like at the time of mold release in a molding step while exhibiting superior resistance to copper contamination.SOLUTION: There is provided a seal member formed of a crosslinked product of a rubber composition containing the following components (A) to (E), wherein the component (A) has an ethylene content of 50 mass% or more, the amount of the component (B) is 30 to 90 pts.mass relative to 100 pts.mass of the component (A), the amount of the component (D) is 0.5 to 10 pts.mass, and the amount of the component (E) is 3 to 10 pts.mass: (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.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Various types of sealing members are used in various devices such as electronic equipment 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 housings of connectors used in wire harnesses for automobiles, etc. (See, for example, Patent Document 1, etc.).

[0003] Such a wire seal member consists of a cylindrical body with 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 with multiple protrusions and grooves that protrude radially outward, and waterproofing is ensured by forming multiple protrusions (2a, etc.) and grooves (2d, etc.). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 05-258802 Summary of the Invention [Problem to be solved by the invention]

[0005] Sealing components such as the wire sealing component mentioned above are often required to have complex and precise shapes, and there are concerns that cracks or deformations may occur when the components are released from the mold during the molding process. Furthermore, because sealing materials 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, and deterioration due to "copper damage" caused by contact between sealing materials and copper is particularly serious. Therefore, an object of the present invention is to provide a sealing member that can suppress the occurrence of cracks and the like when the mold is released in the molding process, and further, can suppress deterioration due to copper contamination. [Means for solving the problem]

[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 specific ranges, the occurrence of cracks and the like at the time of demolding in a molding process can be suppressed, and further, deterioration due to copper contamination can also be suppressed.

[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, per 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 antioxidants. (E) Zinc oxide. [2] The sealing member according to [1], wherein the ethylene content of the 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 above component (B) is 30 to 250 m 2 The sealing member according to any one of [1] to [3], wherein the value is / 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 acid amide. [7] The sealing member according to [6], wherein the content of the erucamide 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 seal member according to any one of [1] to [8], wherein the seal member is a wire seal 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). [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0009] [Figure 1] 10A and 10B are diagrams illustrating an example of a wire seal member. DETAILED DESCRIPTION OF THE INVENTION

[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 "major component" means the component that accounts for the largest amount in the target substance, and is typically 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, or 95 to 100% by mass.

[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 containing components (A) to (E) (hereinafter sometimes referred to as "the rubber composition"), in which the ethylene content of component (A) is 50 mass% or more, and the content of component (B) is 30 to 90 mass parts, the content of component (D) is 0.5 to 10 mass parts, and the content of component (E) is 3 to 10 mass parts, per 100 mass parts 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 antioxidants. (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 that can ensure the performance of sealing members, and that also incorporates a white reinforcing material as a reinforcing material from the perspective of enhancing design (coloring freedom), etc. During this research and development, it was discovered that in formulations that combine EPDM or the like with white reinforcing materials, the interaction between the polymer chains (hydrophobic) of EPDM or the like and particles (hydrophilic) of silica or the like is weak, resulting in a low modulus at high temperatures (e.g., mold molding temperatures of 170°C or the like), making it difficult to suppress cracking and deformation during demolding in the mold molding process. Furthermore, during this research and development, it was discovered that there were issues with copper contamination resistance, for example, because the white reinforcing material does not function 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 not only prevents cracking and deformation during demolding in the molding process, but also has excellent copper contamination resistance.

[0015] Although the reasons why this sealing member exhibits the above-mentioned excellent effects are not entirely clear, the inventors believe that the interaction between EPDM, etc., with 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 and contributing to improved suppression of cracks and other problems 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 resistance to copper contamination.

[0016] Furthermore, the use of silica, a white reinforcing material, in this seal member enhances the design (coloring freedom) of the seal member, making it highly useful in that it can be easily colored to the 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 has an ethylene content of 50 mass% or more in component (A), and relative to 100 mass parts of component (A), the content of component (B) is 30 to 90 mass parts, the content of component (D) is 0.5 to 10 mass parts, and the content of component (E) is 3 to 10 mass parts. The rubber composition is suitable as a rubber composition for molding seal members, and is particularly useful as a rubber composition for molding wire seal members. (A) At least one of ethylene-propylene-diene rubber (EPDM) and ethylene-butene-diene rubber (EBT). (B) Silica. (C) Organic peroxide. (D) Benzimidazole antioxidants. (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, while EBT is obtained by copolymerizing ethylene, butene, and a diene component. These may be used alone or in combination.

[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, and 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 above 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 based on the total amount of the rubber composition (100% by mass). The content of component (A) may also be 30 to 70% by mass, 32 to 65% by mass, or 34 to 55% by mass based on the total amount of the rubber composition (100% by mass).

[0026] (B) Silica In this sealing 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] Component (B) is not particularly limited, but wet silica is preferred. Examples of wet silica include wet silica obtained by the neutralization reaction of sodium silicate and mineral acid (precipitated silica synthesized and agglomerated under alkaline conditions, and gel-process silica particles synthesized and agglomerated under acidic conditions); colloidal silica obtained by polymerizing acidic silicic acid in an alkaline state; and sol-gel silica obtained by hydrolysis of an organic silane compound (e.g., alkoxysilane). Among these, precipitated silica is particularly preferred from the viewpoints 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 appropriately set 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 preventing a decrease in modulus due to inhibition of vulcanization, it is preferably from pH 5.5 to 9.0, more preferably from pH 5.5 to 7.5, and even more preferably from pH 6.0 to 7.0. The pH value is determined in accordance with ISO 787-9. Specifically, a suspension of the silica to be tested at a mass fraction of 10% is prepared in water in a glass container, the container is stoppered, and the suspension is vigorously shaken for 1 minute. After allowing to stand for 5 minutes, the stopper is removed, and the pH of the suspension is measured to the nearest 0.1.

[0030] The BET specific surface area of ​​component (B) is not particularly limited, but from the viewpoint of improving the modulus at high temperatures and suppressing cracks during demolding, it is preferably, for example, 30 to 250 m 2 / g is preferable, and 30 to 210m 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 / g, etc. 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 adsorption 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, more preferably 2 to 13 parts by mass, per 100 parts by mass of component (A). The content of component (C) can be appropriately set 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 added so that the ratio is within the above range.

[0036] (D) Benzimidazole-based antioxidants 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 appropriately set 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 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.

[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 appropriately set within the above range, and may be, for example, 3.5 to 9 parts by mass or 4 to 8 parts by mass.

[0040] 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, from the viewpoint of significantly exhibiting the effects of the present invention.

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

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

[0043] Other ingredients 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] (anti-aging agent) Examples of the antioxidant include diphenylamine-based antioxidants, phenylenediamine-based antioxidants, carbamate-based antioxidants, phenol-based antioxidants, phenylamine-based antioxidants, quinoline-based antioxidants, waxes, etc. These may be used alone or in combination of two or more.

[0045] Examples of diphenylamine antioxidants include p-(p-toluenesulfonylamido)diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, octylated diphenylamine, and styrenated diphenylamine. 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 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 component (A).

[0047] (processing aids) 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 the 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, relative to 100 parts by mass of (A).

[0057] (coloring agent) 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 pigments may be used alone or in combination.

[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 aid) Examples of crosslinking aids 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 aid 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, including 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 is, for example, 5 to 50 parts by mass, or 5 to 30 parts by mass, per 100 parts by mass of component (A).

[0061] Furthermore, there is a strong interaction between polymer chains (hydrophobic) such as EPDM and carbon black particles (hydrophobic), which increases the reinforcing properties and thereby improves the moldability of the sealing member. However, the design (coloring freedom) is insufficient, making it difficult to color the desired color. From the viewpoint of enhancing design (coloring freedom), the carbon black content 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). It may be preferable that the composition contains substantially no carbon black, and in some cases it may be preferable that the composition contains no carbon black (0 parts by mass).

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

[0063] 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, but as in other embodiments, it is also possible to blend the zinc salt of 2-mercaptobenzimidazole alone, which also achieves the same effects, improving the modulus and copper staining resistance at high temperatures. In other embodiments, the incorporation of zinc oxide is not excluded, 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 the component (A).

[0065] The content of the (E) zinc oxide 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 (A) component.

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

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

[0068] (Preparation of the rubber composition and crosslinking of the sealing member) The preparation of the 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 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 this sealing material) This sealing material has a high modulus at high temperatures, can suppress the occurrence of cracks during demolding in the molding process, and is also highly resistant to copper contamination, making it highly useful technically. The modulus at high temperature 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 rubber composition and the sealing member) The rubber composition is suitable as a rubber composition for molding seal members, and is particularly useful as a rubber composition for molding wire seal members.

[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 has a substantially cylindrical small-diameter portion 1 and a large-diameter portion 2 having multiple protrusions and grooves protruding radially outward. By forming multiple protrusions (2a, 2b, 2c) and grooves (2d, 2e) in the large-diameter portion 2, this wire seal member effectively prevents the intrusion of water, dust, oil, and the like from the outside. 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 for use around automobile engines and electronic components. [Example]

[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 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.

[0076] <(B) Silica> Silica (b1): Wet silica, BET specific surface area 48m 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): Perkmyl 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 amide> Erucic acid amide (f1): D1008, manufactured by Tokyo Chemical Industry Co., Ltd.

[0082] <Other ingredients> Anti-aging agent: Diphenylamine-based anti-aging agent, B1970, manufactured by Tokyo Chemical Industry Co., Ltd. Processing aids: Stearic acid, Sakura stearate beads, manufactured by Nippon Oil & Fats Co., Ltd. Processing aids: Paraffin 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 to 13, Comparative Examples 1 to 8] The components (A) to (F) were blended in the proportions shown in Table 1 below, and the components listed under "other components" above were blended in proportions of 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 paraffin-based oil per 100 parts by mass of component (A). The above components, excluding component (C), were blended in the above proportions 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℃, M100> A 2 mm thick rubber sheet was prepared using the uncrosslinked rubber composition using a 6-inch mixing roll, and this was then hot pressed at 170°C for 10 minutes to obtain a crosslinked rubber sheet. JIS No. 5 dumbbells were punched out of the rubber sheet to prepare test pieces. The test pieces were left to stand in an atmosphere of 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 when demolded> 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 form a sealing member with the shape shown in Figure 1. The upper mold was then removed, and the upper part of the sealing member (see small diameter part 1 in Figure 1) was pinched with a jig to release it 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 score of "Good" was given if there were no cracks, and a score of "Poor" if there were cracks.

[0086] <Copper contamination resistance test: Presence or absence of copper contamination> A 2 mm thick rubber sheet was prepared using the uncrosslinked rubber composition 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 blackening. The test specimen was visually inspected for blackening; no copper contamination (blackening) was marked "Good," and the presence of copper contamination (blackening) was marked "Poor."

[0087] [Table 1]

[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 demolded in the molding process, and further have good resistance to copper contamination.

[0089] In contrast, in Comparative Example 1, since the component (A) of the present invention was not contained (the ethylene content was less than 50% by mass), the modulus at high temperatures was low and cracks occurred when the mold was released during the molding process. Also, in Comparative Examples 2 and 3, since the content of the component (B) was outside the range specified in the present invention (below the lower limit or above the upper limit), the modulus at high temperatures was low and cracks occurred when the mold was released during the molding process. Furthermore, in Comparative Example 4, since component (B) was not contained but talc was contained, the modulus at high temperatures was low and cracks occurred when the mold was released in the molding step. In addition, in Comparative Examples 5 and 6, since the content of component (D) was outside the range specified in the present invention (below the lower limit or above 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. In addition, in Comparative Examples 7 and 8, since the content of component (E) was outside the range specified in the present invention (below the lower limit or above 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. [Industrial Applicability]

[0090] 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.

Claims

1. A sealing member comprising a crosslinked product of a rubber composition containing the following components (A) to (E): component (A) has an ethylene content of 50% by mass or more, and relative to 100 parts by mass of component (A), the content of component (B) is 50 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. (A) At least one of an ethylene-propylene-diene rubber and an ethylene-butene-diene rubber. (B) Silica. (C) Organic peroxide. (D) Benzimidazole-based antioxidants. (E) Zinc oxide.

2. A sealing member comprising a crosslinked product of a rubber composition containing the following components (A) to (E): The sealing member is a wire sealing member having a plurality of protrusions protruding radially outward, 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 an ethylene-propylene-diene rubber and an ethylene-butene-diene rubber. (B) Silica. (C) Organic peroxide. (D) Benzimidazole-based antioxidants. (E) Zinc oxide.

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

4. The BET specific surface area of ​​the component (B) is 30 to 250 m 2 The sealing member according to claim 1 or 2, wherein the viscosity is 1 / g.

5. 3. The sealing member according to claim 1, 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 claim 1 or 2, further comprising erucamide.

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

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

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