Rubber composition, rubber crosslinked body and brake sealing components

Abstract

To provide a rubber composition providing a rubber crosslinked body with a reduced amount of a solvent extract.SOLUTION: There is provided a rubber composition which comprises: a component A: an ethylene-propylene-diene rubber; and a component B: a polyolefin compound having a melting point of 70 to 100°C and containing one or more unsaturated bonds in the molecule.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition, a crosslinked rubber product, and a brake sealing component. [Background technology]

[0002] Ethylene-propylene-diene rubber (EPDM) is used in a wide range of applications, including automotive parts. When using crosslinked rubber products primarily composed of EPDM for applications such as automotive brake cups, they are required to have high hardness. Therefore, various rubber compositions primarily composed of EPDM that can provide crosslinked rubber products with high hardness have been proposed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 60-262842 Summary of the Invention [Problem to be solved by the invention]

[0004] As disclosed in Patent Document 1, when increasing the hardness of a cross-linked rubber product mainly composed of EPDM, it has been common practice to incorporate a liquid softener (such as liquid polybutadiene) to improve the processability of the rubber composition before cross-linking. However, according to the findings of the present inventors, in order to incorporate a liquid softener to improve the processability of the rubber composition, it is necessary to increase the amount incorporated. The present inventors' investigations have newly revealed that when such a rubber composition is cross-linked to produce a cross-linked rubber product, the amount of solvent extractables increases.

[0005] An object of one aspect of the present invention is to provide a rubber composition that gives a cross-linked rubber product having a reduced amount of solvent extractables. [Means for solving the problem]

[0006] In order to solve the above problems, a rubber composition according to one embodiment of the present invention contains the following Component A and Component B: Component A: ethylene propylene diene rubber; Component B: A polyolefin compound having a melting point of 70 to 100°C and having one or more unsaturated bonds in the molecule. [Effects of the Invention]

[0007] According to one aspect of the present invention, there is provided a rubber composition that gives a crosslinked rubber product having a reduced amount of solvent extractables. DETAILED DESCRIPTION OF THE INVENTION

[0008] However, the present invention is not limited to the following embodiments and various modifications may be made within the scope of the claims. Embodiments that combine technical means described in different embodiments are also included in the technical scope of the present invention.

[0009] Unless otherwise specified in this specification, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B." In this specification, ethylene propylene diene rubber is sometimes abbreviated as "EPDM."

[0010] [1. Components contained in rubber composition] A rubber composition according to one embodiment of the present invention comprises component A: ethylene-propylene-diene rubber; and component B: a polyolefin compound having a melting point of 70 to 100°C and one or more unsaturated bonds in the molecule. The rubber composition may also contain additives other than those described above. Each of these components may be used alone or in combination of two or more. Each component will be described in detail below.

[0011] [1.1. Component A: Ethylene-propylene-diene rubber] Component A is ethylene-propylene-diene rubber (EPDM), a rubber obtained by copolymerizing ethylene, propylene, and diene monomers.

[0012] Examples of diene monomers constituting component A include linear dienes and cyclic dienes. Examples of linear dienes include 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 1,4-heptadiene, 2-methyl-1,5-hexadiene, 1,4-octadiene, 1,6-octadiene, 1,7-octadiene, 6-methyl-1,5-heptadiene, and 7-methyl-1,6-octadiene. Examples of cyclic dienes include cyclohexadiene, cyclooctadiene, dicyclopentadiene, alkyldicyclopentadiene, methyltetrahydroindene, 5-vinylnorbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-n-propylidene-2-norbornene, 5-isopropylidene-2-norbornene, 5-(2-methyl-2-butenyl)-2-norbornene, and 6-chloromethyl-5-isopropenyl-2-norbornene. Among these, 5-ethylidene-2-norbornene is preferred because of its fast crosslinking rate and excellent balance of physical properties of the crosslinked product.

[0013] The lower limit of the content of ethylene-derived units in Component A may be 30% by weight or more or 40% by weight or more, based on 100% by weight of the weight of Component A. The upper limit of the content of ethylene-derived units in Component A may be 85% by weight or less or 80% by weight or less, based on 100% by weight of the weight of Component A.

[0014] From the viewpoint of improving the low-temperature properties of the obtained cross-linked rubber product, the upper limit of the content of ethylene-derived units in Component A is preferably 58% by weight or less, 55% by weight or less, or 52% by weight or less, where the weight of Component A is 100% by weight.

[0015] The lower limit of the content of diene monomer-derived units in Component A may be 0.5% by weight or more or 1% by weight or more, based on 100% by weight of the weight of Component A. The upper limit of the content of ethylene-derived units in Component A may be 20% by weight or less or 15% by weight or less, based on 100% by weight of the weight of Component A.

[0016] The rubber composition may contain a rubber component other than component A. Examples of rubbers other than component A include fluororubber (FKM), natural rubber (NR), styrene-butadiene rubber (SBR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), ethylene-propylene rubber (EPM), urethane rubber (U), ethylene acrylic rubber (AEM), acrylic rubber (ACM), and silicone rubber (Q).

[0017] The rubber component in the rubber composition is preferably composed mainly of component A. In one embodiment, the weight percentage of component A among all rubber components contained in the rubber composition is 70% by weight or more, 80% by weight or more, or 90% by weight or more. In one embodiment, the rubber composition does not contain any rubber component other than component A.

[0018] [1.2. Component B: Polyolefin compound having a melting point of 70 to 100°C and one or more unsaturated bonds in the molecule] Component B is a polyolefin compound having one or more unsaturated bonds in the molecule. Component B has a melting point of 70 to 100°C, and can be said to be solid at room temperature. Alternatively, the melting point of component B is not specified, and it is a polyolefin compound that is solid at room temperature and has one or more unsaturated bonds in the molecule.

[0019] Examples of polyolefin compounds having one or more unsaturated bonds in the molecule include polybutadiene, polybutene, polyisoprene, polyisobutylene, and butyl rubber. In one embodiment, component B is polybutadiene and / or polyisobutylene. In one embodiment, component B is polybutadiene.

[0020] The lower limit of the number average molecular weight of Component B may be 50,000 or more, or 100,000 or more. The upper limit of the number average molecular weight of Component B may be 300,000 or less, or 200,000 or less.

[0021] In an embodiment in which component B is polybutadiene, the lower limit of the 1,2-vinyl bonds contained in the polybutadiene may be 90% or more, where the total number of 1,2-vinyl bonds and 1,4-vinyl bonds is 100%. The upper limit of the 1,2-vinyl bonds contained in the polybutadiene may be 95% or less, where the total number of 1,2-vinyl bonds and 1,4-vinyl bonds is 100%.

[0022] Component B may be modified in the molecular chain or at the molecular chain end. For example, Component B may be a modified polymer into which a reactive group such as a hydroxy group, a carbonyl group, a maleic acid group, or a carboxy group has been introduced. Alternatively, Component B may be an unmodified polymer.

[0023] [1.3. Other Ingredients] The rubber composition may contain components that can be used in the rubber industry in addition to Components A and B. Examples of such components include fillers, metal oxides, plasticizers / softeners, antioxidants / stabilizers, processing aids, crosslinking agents, co-crosslinking agents, crosslinking accelerators, crosslinking accelerator assistants, and crosslinking retarders.

[0024] (filling material) Examples of fillers include carbon black, silica, calcium carbonate, activated calcium carbonate, finely divided talc, finely divided silicic acid, diatomaceous earth, and clay, which may be surface-treated with a silane coupling agent or the like.

[0025] Among these, one or more selected from the group consisting of carbon black, silica, and clay are preferred, with carbon black being more preferred. Examples of carbon black include SAF, ISAF, HAF, FEF, and GPF. Conductive carbon black (acetylene black, ketjen black, etc.) is also included in the carbon black example. Examples of silica include fumed silica, precipitated silica, and crystalline silica. Examples of clay include kaolin, rosewood, aluminum oxide, aluminum silicate, and aluminosilicate.

[0026] (metal oxides) Examples of metal oxides include zinc oxide, magnesium oxide, and iron oxide.

[0027] (Plasticizers / Softeners) Examples of plasticizers include coal tar, mineral oil, fatty oils (castor oil, linseed oil, rapeseed oil, soybean oil, palm oil, etc.), waxes (beeswax, carnauba wax, etc.), higher fatty acids or their salts or esters, naphthenic acid, pine oil, rosin or derivatives thereof, synthetic polymers (terpene resins, petroleum resins, coumarone-indene resins, etc.), ester-based plasticizers (dioctyl phthalate, dioctyl adipate, etc.), microcrystalline wax, poly-α-olefins (liquid polybutadiene, modified liquid polybutadiene, etc.), hydrocarbon-based synthetic lubricating oils, tall oil, sub(factice), and phosphorus-based plasticizers.

[0028] Examples of mineral oils include process oil, lubricating oil, paraffin oil, liquid paraffin, petroleum asphalt, and vaseline. Of these, process oil is preferred. Examples of process oils include paraffin-based process oil, naphthenic process oil, and aromatic process oil. Of these, paraffin-based process oil is preferred.

[0029] Examples of higher fatty acids constituting higher fatty acids or their salts or esters include oleic acid, palmitic acid, stearic acid, lauric acid, linoleic acid, abietic acid, erucic acid, myristic acid, arachic acid, lignoceric acid, and ricinoleic acid. The higher fatty acids may be saturated or unsaturated, and preferably contain unsaturated fatty acids. The salts of higher fatty acids are usually metal salts, preferably alkali metal salts or alkaline earth metal salts. Examples of metal salts include lithium salts, potassium salts, sodium salts, barium salts, calcium salts, magnesium salts, aluminum salts, iron salts, and zinc salts. Specific examples of higher fatty acids or their salts include ricinoleic acid, palmitic acid, stearic acid, lauric acid, barium stearate, zinc stearate, and calcium stearate.

[0030] (anti-aging agent / stabilizer) Examples of the antioxidant include amine-based antioxidants, phenol-based antioxidants, and sulfur-based antioxidants.

[0031] Specific examples of amine-based antioxidants include aromatic amines (e.g., phenylbutylamine, N,N-di-2-naphthyl-p-phenylenediamine) and amine ketones. Specific examples of phenol-based antioxidants include monophenols (e.g., dibutylhydroxytoluene), bisphenols, and polyphenols (e.g., tetrakis[methylene(3,5-di-t-butyl-4-hydroxy)hydrocinnamate]methane). Specific examples of sulfur-based antioxidants include thioethers (e.g., bis[2-methyl-4-(3-n-alkylthiopropionyloxy)-5-t-butylphenyl]sulfide), dithiocarbamates (e.g., nickel dibutyldithiocarbamate), thiourea, 2-mercaptobenzoylimidazole, 2-mercaptobenzimidazole, zinc salt of 2-mercaptobenzimidazole, dilauryl thiodipropionate, and distearyl thiodipropionate.

[0032] (processing aids) Examples of processing aids include the higher fatty acids or their salts or esters listed under plasticizers and softeners. Further examples of processing aids include higher fatty acid amides (e.g., oleic acid amide).

[0033] (Crosslinking agent) Examples of cross-linking agents include organic peroxides. Because organic peroxides do not contain sulfur-based compounds, they do not corrode metals (especially silver or copper) that come into contact with the cross-linked rubber. Examples of organic peroxides include t-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane.

[0034] [2. Content of each component in rubber composition] In the rubber composition, the lower limit of the content of Component B is preferably 1 part by weight or more, more preferably 3 parts by weight or more, and even more preferably 5 parts by weight or more, based on 100 parts by weight of the content of Component A. In the rubber composition, the upper limit of the content of Component B is preferably 50 parts by weight or less, more preferably 40 parts by weight or less, and even more preferably 30 parts by weight or less, based on 100 parts by weight of the content of Component A.

[0035] From the viewpoint of improving the hardness of the obtained cross-linked rubber product, the lower limit of the content of Component B is preferably 6 parts by weight or more, and more preferably 7 parts by weight or more, based on 100 parts by weight of the content of Component A. From the viewpoint of improving the mechanical strength of the obtained cross-linked rubber product, the upper limit of the content of Component B is preferably 28 parts by weight or less, more preferably 25 parts by weight or less, even more preferably 23 parts by weight or less, and even more preferably 20 parts by weight or less, based on 100 parts by weight of the content of Component A.

[0036] In the rubber composition, the lower limit of the filler content is preferably 30 parts by weight or more, and more preferably 60 parts by weight or more, based on 100 parts by weight of the content of Component A. In the rubber composition, the upper limit of the filler content is preferably 200 parts by weight or less, more preferably 150 parts by weight or less, and even more preferably 100 parts by weight or less, based on 100 parts by weight of the content of Component A.

[0037] In the rubber composition, the lower limit of the metal oxide content is preferably 1 part by weight or more, and more preferably 2 parts by weight or more, based on 100 parts by weight of the content of Component A. In the rubber composition, the upper limit of the metal oxide content is preferably 10 parts by weight or less, and more preferably 7 parts by weight or less, based on 100 parts by weight of the content of Component A.

[0038] In the rubber composition, the lower limit of the plasticizer content is preferably more than 0 parts by weight, and more preferably 2 parts by weight or more, based on 100 parts by weight of the content of Component A. In the rubber composition, the upper limit of the plasticizer content is preferably 10 parts by weight or less, and more preferably 8 parts by weight or less, based on 100 parts by weight of the content of Component A.

[0039] In the rubber composition, the lower limit of the content of the crosslinking agent (such as an organic peroxide) is preferably 5 parts by weight or more, based on 100 parts by weight of the content of Component A. In the rubber composition, the upper limit of the content of the crosslinking agent (such as an organic peroxide) is preferably 10 parts by weight or less, based on 100 parts by weight of the content of Component A.

[0040] [3. Cross-linked rubber and its applications] The crosslinked rubber product according to one embodiment of the present invention is obtained by crosslinking the rubber composition according to one embodiment of the present invention. For example, the rubber composition can be produced by kneading the components described in Section [1]. A kneader can be used to knead the components. Examples of kneaders include an open roll, a kneader, a planetarium mixer, a Banbury mixer, and an extruder. The kneading temperature may be 25 to 200°C. The kneading time may be 1 minute to 1 hour.

[0041] A crosslinked rubber product can be produced by curing the rubber composition. The curing temperature may be 120 to 200°C. The curing time may be 10 seconds to 120 minutes. The cured molded product may be further subjected to secondary curing. The secondary curing temperature may be 120 to 250°C. The secondary curing time may be 30 minutes to 4 hours.

[0042] The rubber composition can be molded and crosslinked to form an article. Examples of molding methods include injection molding, transfer molding, casting, compression molding, pressing, and extrusion. In one embodiment, the article is a brake sealing part. Examples of brake sealing parts include brake cups, diaphragms, boots, and piston seals.

[0043] 4. Physical Properties of Rubber Composition and Cross-Linked Rubber Minimum viscosity (M L ) is preferably 0.25 N m or less, more preferably 0.23 N m or less. If the minimum viscosity is within the above range, it can be said that the processability in injection molding and the like is good. The minimum viscosity is the minimum value of torque in the vulcanization curve. In this specification, the vulcanization curve is measured using a vibration vulcanization tester based on JIS K6300-2. For more specific examples of the measurement method, see the examples of this application.

[0044] The lower limit of the Shore A hardness of the crosslinked rubber product is preferably more than 80, more preferably 85 or more. The upper limit of the Shore A hardness of the crosslinked rubber product is preferably 95 or less, more preferably 90 or less. If the Shore A hardness is within the above range, it can be said that the product has sufficient hardness for use as a brake cup or the like. In this specification, the Shore A hardness is measured using a Type A durometer based on JIS K6253. For more specific examples of the measurement method, see the examples of the present application.

[0045] The weight percentage of the solvent extract contained in the crosslinked rubber product is preferably 10% by weight or less, more preferably 7% by weight or less, and even more preferably 5% by weight or less, assuming the weight of the crosslinked rubber product to be 100% by weight. If the weight percentage of the solvent extract is within the above range, fewer components will be eluted upon contact with brake fluid, thereby reducing deterioration of the brake fluid. In this specification, the weight percentage of the solvent extract is measured by Soxhlet extraction based on JIS K6229. In this case, the extraction solvent is hexane, and the extraction time is 8 hours. For more specific examples of the measurement method, see the examples of the present application.

[0046] The tensile strength of the crosslinked rubber product is preferably 15 MPa or more, more preferably 17 MPa or more. If the tensile properties are within the above range, it can be said that the product has sufficient mechanical strength when used as a miniaturized brake component. In this specification, tensile strength is measured by a tensile test based on JIS K6251. For more specific examples of the measurement method, see the examples of this application.

[0047] [5. Summary] The present invention includes the following aspects. <1> A rubber composition comprising the following components A and B: Component A: ethylene propylene diene rubber; Component B: A polyolefin compound having a melting point of 70 to 100°C and having one or more unsaturated bonds in the molecule. <2> When the content of the component A is 100 parts by weight, the content of the component B is 1 to 50 parts by weight. <1> The rubber composition according to claim 1. <3> The content of ethylene-derived units in the component A is 58% or less, with the weight of the component A being 100% by weight. <1> or <2> The rubber composition according to claim 1. <4> The minimum viscosity of the rubber composition measured with a vibration vulcanization tester is 0.25 N m or less. <1> ~ <3> The rubber composition according to any one of the preceding claims. <5> <1> ~ <4> The rubber composition according to any one of the above items is cured. Crosslinked rubber. <6> Shore A hardness is over 80, <5> The crosslinked rubber product according to claim 1. <7> the weight ratio of the solvent extract when the crosslinked rubber product is subjected to Soxhlet extraction with hexane for 8 hours is 10% by weight or less, assuming the weight of the crosslinked rubber product to be 100% by weight; <5> or <6> The crosslinked rubber product according to claim 1. <8> <5> ~ <7> The crosslinked rubber product according to any one of the preceding claims. Brake sealing parts. <9> brake cup, diaphragm, boot or piston seal, <8> The brake sealing component according to claim 1. [Example]

[0048] [Materials used] Ingredient A EPDM1 (4021, Mitsui Chemicals, Inc., ethylene-derived unit content: 51% by weight) EPDM2 (3091, Mitsui Chemicals, Inc., ethylene-derived unit content: 61% by weight) ●Ingredient B Polybutadiene 1 (RB810, ENEOS Materials Corporation, melting point: 71°C (ASTM D3418)) ●Component B' (Components not corresponding to Component B) Polybutadiene 2 (B-1000, Nippon Soda Co., Ltd., melting point: no data (liquid at 20°C)) ●Filling material Filler 1 (Asahi #70, Asahi Carbon Co., Ltd., black filler) Filler 2 (silica:clay = 20:50 (weight ratio), white filler) Plasticizers Process oil (Diana Process Oil PW-90, Idemitsu Kosan Co., Ltd., paraffin-based process oil) Metal oxides Zinc oxide (Zinc oxide type 2, Sakai Chemical Industry Co., Ltd.) Crosslinking agent Crosslinking agent 1 (Perhexa 25B-40, NOF Corporation, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane) Crosslinking agent 2 (fine sulfur powder 500 Mesh, Hosoi Chemical Industry Co., Ltd.)

[0049] [Examples 1 to 6, Comparative Examples 1 to 3] A crosslinked rubber sheet was prepared according to the following procedure. The crosslinked rubber sheet was used to prepare test pieces for the tests described below. 1. The components listed in Table 1, excluding the crosslinking agent, were kneaded in a kneader. The temperature during kneading was 50 to 150° C. The kneading time was 10 to 30 minutes. 2. A crosslinking agent was added and the mixture was kneaded with an open roll. The temperature during kneading was 20 to 100° C. The kneading time was 5 to 30 minutes. 3. An uncrosslinked rubber sheet was produced from the resulting kneaded product. 4. The uncrosslinked rubber sheet was press-crosslinked at 170°C for 10 minutes. 5. Further, secondary crosslinking was carried out for 1 hour at 180° C. In this way, a crosslinked rubber sheet having a thickness of 2 mm was obtained.

[0050] [Test method] [1.Minimum viscosity] The processability of the rubber composition was evaluated by a vulcanization test. Specifically, the vulcanization characteristics of the rubber composition were measured using a vibration vulcanization tester based on JIS K6300-2, and the minimum viscosity (M L ) was determined. The vulcanization curve is a curve with the vulcanization time on the horizontal axis and the torque on the vertical axis, and the minimum viscosity is the minimum torque value. The test method used was die vulcanization test method A (torsional vibration type flat die vulcanization test). The test conditions were a test temperature of 180°C and a measurement time of 4 minutes.

[0051] [2. Shore A hardness] The Shore A hardness of the crosslinked rubber sheets obtained in step 5 of the Examples and Comparative Examples was measured in accordance with JIS K6253. The specific procedure is as follows. 1. Three 2 mm thick cross-linked rubber sheets were stacked together to form a measurement sample. 2. Measurements were made using a Type A durometer at 23°C and a relative humidity of 50%. The peak value of the durometer was taken as the Shore A hardness.

[0052] [3. Amount of solvent extract] The cross-linked rubber was subjected to Soxhlet extraction in accordance with JIS K6229, and the weight percentage of the solvent extractables in the cross-linked rubber was determined. The specific extraction method used was Method A of the same standard. The extraction conditions were extraction solvent: hexane, extraction time: 8 hours.

[0053] [4. Tensile test] The cross-linked rubber was subjected to a tensile test based on JIS K6251 to measure the tensile strength and elongation at break. Measurement samples used were No. 3 dumbbell test pieces according to JIS K6251, punched out from the cross-linked rubber sheets obtained in step 5 of the Examples and Comparative Examples.

[0054] [5.TR10] The low-temperature properties of the cross-linked rubber were evaluated by a low-temperature elastic recovery test (TR test). Specifically, the cross-linked rubber was subjected to a low-temperature elastic recovery test based on JIS K6261-4, and a temperature-shrinkage curve was obtained. The temperature at which the shrinkage rate was 10% was defined as TR10.

[0055] 〔result〕 The results are shown in Table 1. [Table 1]

[0056] As can be seen from Table 1, the rubber compositions according to the examples contained both Component A and Component B. These rubber compositions had a low minimum viscosity (e.g., 0.25 N·m or less) and therefore excellent processability. Furthermore, the cross-linked rubber products obtained by cross-linking these rubber compositions had a high Shore A hardness (e.g., greater than 80 points) and a low weight percentage of solvent extractables (e.g., 10.0 wt % or less). In other words, the rubber compositions according to the examples not only provided cross-linked rubber products with excellent processability and high hardness, but also reduced the amount of solvent extractables in the cross-linked rubber products.

[0057] The rubber composition of Comparative Example 1 did not produce a cross-linked rubber product with high hardness and also had poor processability. The rubber composition of Comparative Example 2 improved its processability by increasing the blending amounts of filler and plasticizer, but did not improve its hardness. Thus, in a system that did not blend component B or component B', it was not possible to achieve both a rubber composition with high processability and a cross-linked rubber product with high hardness.

[0058] Comparative Example 3 corresponds to Invention Example 2 of Patent Document 1 (see Table 1 of Patent Document 1). The cross-linked rubber obtained from the rubber composition of Comparative Example 3 had a significantly large amount of solvent extractables. Furthermore, although the rubber composition of Comparative Example 3 contains Component B, it had a high minimum viscosity and could not be said to have sufficient processability.

[0059] Comparing the Examples, the cross-linked rubber product of Example 6 had a relatively low tensile strength compared to the cross-linked rubber products of Examples 1 to 5. Therefore, from the viewpoint of improving the mechanical strength of the cross-linked rubber product, it is even more preferable that the blending amount of Component B is not too large (for example, 28 parts by weight or less, assuming that Component A is 100 parts by weight).

[0060] Similarly, when comparing the Examples, the cross-linked rubber product of Example 2 had a relatively high TR10 compared to the cross-linked rubber products of Examples 1 and 3 to 5. Therefore, from the perspective of improving the low-temperature properties of the cross-linked rubber product, it is preferable that the content of ethylene-derived units in Component A is not too high (for example, 58% by weight or less, where the weight of Component A is 100% by weight). [Industrial Applicability]

[0061] The present invention can be used for sealing parts for brakes, etc.

Claims

1. A rubber composition comprising the following components A and B: Component A: ethylene propylene diene rubber; Component B: A polyolefin compound having a melting point of 70 to 100°C and having one or more unsaturated bonds in the molecule.

2. When the content of the component A is 100 parts by weight, the content of the component B is 1 to 50 parts by weight. The rubber composition according to claim 1.

3. the content of ethylene-derived units in the component A is 58% or less, with the weight of the component A being 100% by weight; The rubber composition according to claim 1.

4. The minimum viscosity of the rubber composition measured with a vibration vulcanization tester is 0.25 N m or less. The rubber composition according to claim 1.

5. A rubber composition obtained by curing the rubber composition according to any one of claims 1 to 4. Crosslinked rubber.

6. Shore A hardness is greater than 80. The crosslinked rubber product according to claim 5.

7. the weight ratio of the solvent extract when the crosslinked rubber product is subjected to Soxhlet extraction with hexane for 8 hours is 10% by weight or less, assuming the weight of the crosslinked rubber product to be 100% by weight; The crosslinked rubber product according to claim 5.

8. The crosslinked rubber product according to claim 5 is contained. Brake sealing parts.

9. brake cup, diaphragm, boot or piston seal, The brake sealing component according to claim 8.

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