JP2003128842A - Rubber composition and vulcanizate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vulcanizate excellent in ozone resistance, resistance to flexural fatigue and oil resistance. SOLUTION: The vulcanizate is prepared by vulcanizing a rubber composition comprising 50-79 wt.% of an α,β-ethylenically unsaturated nitrile/conjugated diene copolymer rubber (A) having a number average molecular weight of 50,000-150,000, 1-30 wt.% of an α,β-ethylenically unsaturated nitrile/conjugated diene copolymer rubber (B) having a number average molecular weight of 1,000-20,000, and 14-49 wt.% of an ethylene/α-olefin copolymer rubber (C).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composition which is a material of a vulcanizate excellent in ozone resistance, flex fatigue resistance and oil resistance, and a vulcanizate thereof.

[0002]

2. Description of the Related Art Conventionally, chloroprene rubber has been widely used as a rubber material having both oil resistance and ozone resistance. However, since chloroprene rubber contains chlorine, alternative materials have been demanded to prevent the occurrence of environmental problems.

As an alternative material to chloroprene rubber, α,
A rubber composition of a β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber and an ethylene-α-olefin copolymer rubber has been investigated. However, even if only these two rubbers were kneaded, they were not compatible, and as a result, the vulcanizates obtained were excellent in ozone resistance but inferior in mechanical strength and bending fatigue. Therefore, it has been proposed to add chlorinated polyethylene to the composition of the α, β-ethylenically unsaturated nitrile-conjugated diene rubber and the ethylene-propylene copolymer rubber (JP-A-59-199737).
Issue). When this composition is vulcanized, a vulcanizate having excellent mechanical strength can be obtained, but the bending fatigue resistance is insufficient,
Further, since it is a material containing chlorine, it may cause environmental problems.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a vulcanized product having excellent ozone resistance, flex fatigue resistance and oil resistance.

[0005]

Means for Solving the Problems As a result of intensive studies to achieve the above objects, the present inventors have found that two kinds of α, β-ethylenically unsaturated nitrile-conjugated diene copolymer rubbers having different molecular weights and ethylene are used. It was found that the vulcanized product of the rubber composition of the α-olefin copolymer rubber is excellent in ozone resistance, bending fatigue resistance and oil resistance, and based on this finding, the present invention has been completed. .

Thus, according to the present invention, the number average molecular weight is 5
50,000 to 150,000 α, β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber (A) 50 to 79
%, Α-β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber (B) having a number average molecular weight of 1,000 to 20,000 and 1 to 30% by weight and an ethylene-α-olefin copolymer rubber ( C) A rubber composition containing 14 to 49% by weight and a vulcanized product obtained by vulcanizing the rubber composition are provided.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The α, β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber (A) (hereinafter referred to as rubber (A)) used in the present invention has a number average molecular weight of 50,000.
˜150,000, which is a rubber obtained by copolymerizing an α, β-ethylenically unsaturated nitrile monomer and a conjugated diene monomer.

The rubber (A) has a number average molecular weight of 50,000 to 150,000, preferably 6 in terms of polystyrene by gel permeation chromatography.
10,000-120,000, more preferably 70,000
00 to 100,000. If the molecular weight is too small, the mechanical strength will be poor, and if it is too large, the processability as a molding material will be poor.

The content of α, β-ethylenically unsaturated nitrile monomer in the rubber (A) is preferably 25 to 60% by weight, more preferably 28 to 50% by weight, particularly preferably 33 to 45% by weight. Is. If the α, β-ethylenically unsaturated nitrile monomer content is too low, the vulcanizate may have poor oil resistance, and if it is too high, the vulcanizate may have poor mechanical strength at high temperatures. Examples of the α, β-ethylenically unsaturated nitrile monomer include acrylonitrile and methacrylonitrile, and acrylonitrile is preferable.

Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene and 1,3-pentadiene.
-Butadiene is preferred.

A copolymerizable monomer other than the α, β-ethylenically unsaturated nitrile monomer and the conjugated diene monomer is copolymerized within a range that does not substantially impair the effects of the present invention. You may. Examples of such a monomer include a non-conjugated diene monomer, an α-olefin monomer, a fluorine-containing vinyl monomer, a fluorine-free aromatic vinyl monomer, α,
Examples include β-ethylenically unsaturated monocarboxylic acid, α, β-ethylenically unsaturated polycarboxylic acid, and anhydrides thereof. The non-conjugated diene-based monomer preferably has 5 to 12 carbon atoms, and is 1,4-pentadiene,
Examples include 1,4-hexadiene, vinyl norbornene, dicyclopentadiene and the like. As the α-olefin, those having 2 to 12 carbon atoms are preferable, and ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1
-Hexene, 1-octene and the like are exemplified. Examples of the fluorine-containing vinyl-based monomer include fluoroethyl vinyl ether, fluoropropyl vinyl ether, o-trifluoromethyl styrene, vinyl pentafluorobenzoate,
Examples thereof include difluoroethylene and tetrafluoroethylene. As the fluorine-free aromatic vinyl-based monomer,
Examples thereof include styrene, α-methylstyrene, vinylpyridine and the like. Examples of the α, β-ethylenically unsaturated monocarboxylic acid include acrylic acid and methacrylic acid. Examples of the α, β-ethylenically unsaturated polycarboxylic acid include itaconic acid, fumaric acid, maleic acid and the like. Examples of the α, β-ethylenically unsaturated polycarboxylic acid anhydride include itaconic anhydride and maleic anhydride.

In addition to these, a copolymerizable antiaging agent may be copolymerized. As a copolymerizable anti-aging agent, N
-(4-anilinophenyl) acrylamide, N- (4
-Anilinophenyl) methacrylamide, N- (4-anilinophenyl) cinnamamide, N- (4-anilinophenyl) crotonamide, N-phenyl-4- (3-
Vinylbenzyloxy) aniline, N-phenyl-4-
(4-vinylbenzyloxy) aniline and the like can be mentioned.

The method for producing the rubber (A) is not particularly limited, and the polymerization may be performed by a known method. Usually, they are copolymerized by an emulsion polymerization method. When the rubber (A) is produced by an emulsion polymerization method, it is carried out at 0 to 50 ° C. in a reactor from which oxygen has been removed. Monomers, emulsifiers, initiators, molecular weight regulators, etc. are added and reacted. Monomers, emulsifiers and the like may be added in total before the reaction starts, or may be arbitrarily added after the reaction starts. A coagulant is added to the emulsion polymerization liquid containing the rubber (A) to coagulate the rubber (A), washed as necessary, dried and recovered.

Low molecular weight α, β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber used in the present invention (B)
(Hereinafter referred to as rubber (B)) has a number average molecular weight of 100
It is a rubber of 0 to 20,000, which is a rubber obtained by copolymerizing an α, β-ethylenically unsaturated nitrile monomer and a conjugated diene monomer.

The number average molecular weight of the rubber (B) is preferably 2,000 to 10,000, more preferably 3,000 to 7,000 in terms of polystyrene equivalent by gel permeation chromatography. If the molecular weight is too small, the mechanical strength will be poor, and if it is too large, the processability and bending fatigue as a molding material will be poor.

The content of α, β-ethylenically unsaturated nitrile monomer in the rubber (B) is preferably 15 to 60% by weight, more preferably 25 to 50% by weight, particularly preferably 30 to 45% by weight. Is. If the α, β-ethylenically unsaturated nitrile monomer content is too low, the vulcanizate may have poor oil resistance and mechanical strength, and if it is too high, the vulcanizate may have poor mechanical strength at high temperatures. is there. The α, β-ethylenically unsaturated nitrile-based monomer, the conjugated diene monomer, and the monomer copolymerizable with these, which is used as necessary, are those described as the monomer used for the rubber (A). Can be used, and the preferred monomers are also the same.

The method for producing the rubber (B) is not particularly limited, and it may be copolymerized by a known method. Generally, they are copolymerized by an emulsion polymerization method. When the rubber (B) is produced by the emulsion polymerization method, the rubber (A) is prepared by the emulsion polymerization method except that the amount of the molecular weight modifier and the preferable range of the α, β-ethylenically unsaturated nitrile monomer content are different. The same method as in the case of manufacturing can be adopted.

A mixture consisting of only rubber (A) and rubber (B) in the amount ratio contained in the rubber composition of the present invention is dissolved in a mixed solvent of tetrahydrofuran and water under the following constant conditions. The pH when measured is preferably 2 to 7, and more preferably 3 to 5.
If this pH value is too small, the vulcanization rate will be slow and the metal contamination property may be inferior. On the contrary, if it is too high, the bending fatigue property may be inferior. This pH value is a value measured 2 minutes after the completion of dropping, by adding an electrode of a pH meter to a solution prepared by dissolving 6 g of a rubber polymer in 100 g of tetrahydrofuran, dropping 2 ml of distilled water with stirring. The rubber (A) and the rubber (B) depending on the amount ratio in the rubber composition of the present invention described below.
It is sufficient that the pH measured by the above-mentioned measuring method becomes a value within the above-mentioned preferable range when the above are mixed, and the pH measured by the above-mentioned measuring method of the rubber (A) and the rubber (B) is not particularly limited. However, the pH measured by the above measuring method for each is preferably in the range of 2 to 7.
More preferably, it is in the range of -5. When both are in such a range, it is possible to reduce the variation in the pH measured by the above-mentioned measuring method due to the variation in the compounding ratio of the two when preparing the rubber composition of the present invention, and to facilitate the preparation. Become.

The pH value of the mixture of the rubber (A) and the rubber (B) is adjusted by the type and amount of the monomer units contained in the substances contained in these rubbers or the structure thereof. In order to attain the above preferable pH range, it is necessary that the rubber (A) and the rubber (B) contain an acidic substance, or a monomer unit showing acidity is contained in the structure. . Acidic substances include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid; organic acids such as acetic acid, citric acid and succinic acid; strong acid salts such as aluminum sulfate and aluminum chloride; a mixture of calcium chloride and sulfuric acid; magnesium sulfate. And a combination of a neutral acid such as a mixture of hydrochloric acid and a strong acid; and the like. All acidic substances function as a coagulant in emulsion polymerization. Further, as the monomer unit showing acidity to be contained in the rubber structure, α, β-ethylenically unsaturated monocarboxylic acid unit,
α, β-ethylenically unsaturated polycarboxylic acid unit, α, β
-Ethylenically unsaturated polycarboxylic acid anhydride units and the like. In the case of emulsion polymerization, if a coagulant showing alkalinity is used in the recovery treatment, the pH measured by the above measuring method becomes alkaline even if the rubber (A) or the rubber (B) contains a monomer unit showing acidity. May be. Therefore, it is preferable to use the above acidic substance as the coagulant.

The pH according to the above measuring method changes depending on the combination of the type and amount of the acidic substance and the monomer unit showing acidity. In order to adjust the rubber (A) and the rubber (B) within the preferable pH range as described above, it is necessary to determine polymerization conditions, coagulation treatment conditions and post-treatment conditions as necessary by preliminary experiments and the like.

The ethylene-α-olefin copolymer rubber (C) (hereinafter referred to as rubber (C)) used in the present invention comprises ethylene, α-olefin and, if necessary, a monomer copolymerizable therewith. It is a copolymerized rubber.

The number average molecular weight of the rubber (C) is preferably 50,000 to 200,000, more preferably 60,000 to 150,000, and particularly preferably, in terms of polystyrene equivalent by gel permeation chromatography. It is 70,000-120,000. If the molecular weight is too small, the vulcanizate will be inferior in mechanical strength, and if it is too large, it will be inferior in processability as a molding material.

The content of α-olefin units in the rubber (C) is preferably 1 to 50% by weight, more preferably 3 to 4%.
It is 0% by weight, particularly preferably 5 to 30% by weight. α-
If the olefin unit content is too low, the vulcanizate may have a problem of poor mechanical strength, and if it is too high, it may have a problem of poor cold resistance.

Preferred α-olefins are those having 3 to 20 carbon atoms such as 1-propene, isobutylene, 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene.

The rubber (C) may be a copolymer of a monomer copolymerizable with ethylene and α-olefin within a range that does not substantially impair the effects of the present invention. Examples of such a monomer include aromatic vinyl monomers such as styrene, halogen-substituted styrene, and alkyl-substituted styrene;
Diene monomers such as butadiene, 1,4-hexadiene and dicyclopentadiene; cycloolefin monomers such as cyclopentene, cyclohexene and cyclooctene.

The method for producing the rubber (C) is not particularly limited, and it may be copolymerized by a known method, and usually it is produced by solution polymerization.

The rubber composition of the present invention has a rubber (A) content of 50 to 79% by weight, preferably 55 to 75% by weight,
Particularly preferably 60 to 70% by weight, the content of rubber (B) is 1 to 30% by weight, preferably 3 to 23% by weight, particularly preferably 5 to 15% by weight, the content of rubber (C) is 14 to
It contains 49% by weight, preferably 20 to 40% by weight, particularly preferably 25 to 35% by weight. If the amount of the rubber (A) is too small, the vulcanized product may have a problem of poor oil resistance, while if it is too large, it may have a problem of poor ozone resistance. If the amount of the rubber (B) is too small, the vulcanized product may have a problem of inferior bending fatigue. On the contrary, if the amount of the rubber (B) is too large, it may cause a problem of poor mechanical strength. If the amount of the rubber (C) is too small, the vulcanized product may have a problem of poor ozone resistance, and if it is too large, it may have a problem of poor oil resistance.

The rubber composition of the present invention can be made into a vulcanizable rubber composition by blending a vulcanizing agent. Examples of the vulcanizing agent include sulfur-based vulcanizing agents, organic peroxides, polyamine-based vulcanizing agents, and the like.

Examples of the sulfur-based vulcanizing agent include sulfur such as powdered sulfur and precipitated sulfur; 4,4'-dithiomorpholine, tetramethylthiuram disulfide, tetraethylthiuram disulfide, organic sulfur compounds such as polymer polysulfides, and the like. To be

Examples of organic peroxides include dialkyl peroxides, diacyl peroxides and peroxyesters. Examples of the dialkyl peroxide include dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) -3-hexyne and 2,5-dimethyl-.
2,5-di (t-butylperoxy) hexane, 1,3
-Bis (t-butylperoxyisopropyl) benzene and the like. Examples of the diacyl peroxide include benzoyl peroxide and isobutyryl peroxide. 2,5 as peroxyester
-Dimethyl-2,5-bis (benzoylperoxy) hexane, t-butylperoxyisopropyl carbonate, etc.) and the like.

The polyamine-based vulcanizing agent is a compound having two or more amino groups, and a plurality of hydrogen atoms of an aliphatic hydrocarbon or an aromatic hydrocarbon has an amino group or a hydrazide structure,
That is, it has a structure represented by —CONHNH ₂ . Examples of the polyamine-based vulcanizing agent include aliphatic polyvalent amines, aromatic polyvalent amines, compounds having two or more hydrazide structures, and the like. Examples of the aliphatic polyvalent amines include hexamethylenediamine, hexamethylenediamine carbamate, tetramethylenepentamine, hexamethylenediamine-cinnamaldehyde adduct, hexamethylenediamine-dibenzoate salt and the like. As aromatic polyvalent amines, 4,4'-methylenedianiline, 4,4'-oxydiphenylamine, m
-Phenylenediamine, p-phenylenediamine, 4,
4′-methylenebis (o-chloroaniline) and the like can be mentioned. Examples of the compound having two or more hydrazide structures include isophthalic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide and the like.

The amount of the vulcanizing agent used varies depending on the type of the vulcanizing agent, but is generally 0.1 to 10 parts by weight, and more preferably 0.1 to 100 parts by weight of the nitrile group-containing copolymer rubber. 3 to 7 parts by weight, particularly preferably 0.5 to 5 parts by weight. If the amount of the vulcanizing agent used is too small, the crosslinking density may be low and the oil resistance may be poor.

When a sulfur-based vulcanizing agent is used, a vulcanization accelerator is usually used together. As the vulcanization accelerator, zinc white, sulfenamide-based vulcanization accelerator, guanidine-based vulcanization accelerator,
Examples thereof include thiazole-based vulcanization accelerators, thiuram-based vulcanization accelerators, and dithioate-based vulcanization accelerators. The amount of the vulcanization accelerator used is not particularly limited and may be determined according to the application of the vulcanized product, the required performance, the type of the sulfur vulcanizing agent, the type of the vulcanizing accelerator and the like.

When an organic peroxide is used, a vulcanization aid is usually used together. Examples of the vulcanization aid include triallyl cyanurate, trimethylolpropane trimethacrylate, N, N′-m-phenylene bismaleimide, and the like. These may be used by dispersing in clay, calcium carbonate, silica or the like to improve the processability of the rubber composition. The amount of the vulcanization aid used is not particularly limited and may be determined according to the application of the vulcanized product, the required performance, the type of vulcanization agent, the type of vulcanization aid, and the like.

The rubber composition of the present invention contains a compounding agent used for general rubbers, such as carbon black and a reinforcing agent such as silica, calcium carbonate, etc. within a range that does not substantially impair the effects of the present invention. Clay, talc, filler such as calcium silicate, α, β-unsaturated carboxylic acid metal salt, plasticizer, pigment and the like may be contained. In addition, the α, β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber (A), α,
A rubber or resin other than the β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber (B) and the ethylene-α-olefin copolymer rubber (C) may be contained.

The method for preparing the rubber composition of the present invention is not particularly limited, and it may be prepared by a general method for preparing a rubber composition like other rubber compositions, and may be a closed mixer or an open roll. It can be used and kneaded. Vulcanizing agent, vulcanization aid,
When a vulcanization accelerator or the like is blended, after the blending, the temperature is adjusted so as to be the vulcanization start temperature or lower and the mixture is performed.

The vulcanized product of the present invention is a vulcanized product of the rubber composition of the present invention. The method for vulcanizing the rubber composition is not particularly limited. If necessary, a vulcanization system is added to obtain a vulcanizable rubber composition, which is then heated and vulcanized.

The temperature during vulcanization is preferably 100 to 20.
The temperature is 0 ° C, more preferably 130 to 190 ° C, and particularly preferably 140 to 180 ° C. If the temperature is too low, the vulcanization time may be long and the vulcanization density may be low. If the temperature is too high, molding may be defective.

The vulcanization time depends on the vulcanization method, vulcanization temperature,
Although it depends on the shape and the like, a range of 1 minute or more and 5 hours or less is preferable from the viewpoint of vulcanization density and production efficiency.

Further, depending on the shape and size of the molding, even if the surface is vulcanized, the interior may not be sufficiently vulcanized, so secondary vulcanization may be performed.

The heating method for vulcanization may be appropriately selected from the methods used for vulcanizing rubber such as press heating, steam heating, oven heating and hot air heating.

[0042]

The vulcanized product of the present invention is excellent in ozone resistance, flex fatigue resistance and oil resistance, and has sufficient mechanical strength. The vulcanized product of the present invention is used as an industrial part such as a roll, a hose, a belt and a sealing material, and is suitable as a rubber part for automobiles such as packing, a fuel hose, an air intake hose, an air duct hose, a boot material and an automobile interior member. Is.

[0043]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. Parts and% are, unless otherwise specified,
It is based on weight. The test method and the like were as follows.

The number average molecular weight was measured by gel permeation chromatography using tetrahydrofuran as a solvent as a standard polystyrene conversion value.

Of the normal physical properties of rubber vulcanizates, tensile strength,
For elongation and 100% tensile stress, after producing a sheet-shaped vulcanized product, a dumbbell-shaped No. 3 test piece was punched out, and a tensile speed of 500 was used according to JIS K 6251.
It was measured in mm / min.

Among the normal physical properties of the vulcanized rubber composition, the hardness was measured by using a durometer hardness type A according to JIS K6253.

The ozone resistance is 80 pp for ozone concentration according to JIS K 6259 by preparing the test piece described in item 4.
It was kept in an environment of hm, temperature of 40 ° C. and elongation of 40%, and the state of crack generation 72 hours and 120 hours after the start of holding was evaluated according to JIS K 62149, Table 1. NC represents that no crack occurs, A-1,
A-2 represents the state of cracks. In A-1 and A-2, A-2 has a larger crack, but
In both cases, the test piece did not break. CUT indicates that the test piece broke due to a crack.

The bending fatigue resistance was evaluated by the number of times of bending at which the test piece was broken, after the test piece was prepared in accordance with JIS K 6260 Section 5.3 and repeated in accordance with Section 5.2.1.

The oil resistance was evaluated in accordance with JIS K6258 by preparing a test piece, immersing the test piece in test oil IRM903 at 100 ° C. for 70 hours, and then evaluating the rate of change in volume before and after the immersion.

Reference Example 1 Monomer mixture (butadiene 67
%, Acrylonitrile 33%) 100 parts, sodium dodecylbenzene sulfonate (emulsifier) 5 parts, sodium sulfate (emulsifier) 0.2 parts, potassium persulfate (polymerization initiator) 0.3 parts and tert-dodecyl mercaptan (molecular weight adjustment) 8 parts of the agent) was charged into an autoclave substituted with nitrogen, reacted at a reaction temperature of 30 ° C. until the conversion rate of the monomer reached 80%, and 0.5 parts of N, N-diethylhydroxylamine was added to the stopper to react. Stopped. Take out the emulsion polymerization reaction liquid, blow steam at 100 ° C.,
280 parts of emulsion polymerization liquid from which unreacted monomers have been removed
% Aluminum sulfate aqueous solution 1000 parts, to solidify the copolymer rubber, and wash the solidified product thoroughly with water,
By drying for an hour, the number average molecular weight of 3,000,
98 parts of α, β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber (B) -1 was obtained. An electrode of a pH meter was placed in a solution prepared by dissolving 6 g of the copolymer rubber in 100 g of tetrahydrofuran, 2 ml of distilled water was added dropwise with stirring, and the pH was measured 2 minutes after the completion of the addition, and it was 4.2.

Reference Examples 2 to 4 12 parts of tert-dodecyl mercaptan and 19 parts
Parts, and 4 parts, except that the same treatment as in Reference Example 1 was carried out to obtain an α, β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber (B) -2 having a number average molecular weight of 10,000.
98 parts, 98 parts of an unsaturated nitrile-conjugated diene-based copolymer rubber-3 having a number average molecular weight of 500, and an average molecular weight of 3,0.
98 parts of unsaturated nitrile-conjugated diene-based copolymer rubber-4 of No. 00 was obtained. An electrode of a pH meter was placed in a solution prepared by dissolving 6 g of these copolymer rubbers in 100 g of tetrahydrofuran, 2 ml of distilled water was added dropwise with stirring, and the pH was measured 2 minutes after the completion of the addition, and all were 4.2. It was

Example 1 Acrylonitrile-butadiene copolymer rubber (acrylonitrile unit content 40%, number average molecular weight 81,000, 6 g of copolymer rubber dissolved in 100 g of tetrahydrofuran was charged with a pH meter electrode and distilled while stirring. 2 ml of water was added dropwise and the pH measured 2 minutes after the end of the addition was
4.5) 65 parts, α, β-ethylenically unsaturated nitrile-
5 parts of conjugated diene-based copolymer rubber (B) -1, ethylene-
Propylene-conjugated diene rubber (EPT4070, manufactured by Mitsui Chemicals, ethylene unit content 68 mol%, iodine value 22, iodine number average molecular weight 90,000) 30 parts by weight, stearic acid 1 part by weight, zinc oxide (Zinc Hua No. 1, Shodo Kagaku) ) 5 parts by weight, carbon black (Shiest 3, manufactured by Tokai Carbon Co., Ltd.) 40 parts, dibutyldiglycol adipate (Adeka Sizer RS-107, manufactured by Asahi Denka Co., Ltd., plasticizer) 5 parts, naphthenic oil (Sunsen 415, Nippon Sun) Oil company,
5 parts of a softening agent) and 1 part of a diphenylamine derivative (ANTAGE OD, manufactured by Kawaguchi Chemical Co., Ltd., an antiaging agent) were kneaded in Banbury for 5 minutes while controlling at 50 ° C. Then, 1 part of sulfur (passing through 325 mesh), 2 parts of N-cyclohexyl-2-benzothiazolylsulfenamide (vulcanization accelerator), and 0.2 parts of tetraethylthiuram disulfide (vulcanization accelerator) at 50 ° C. Roll kneading was performed to prepare a rubber composition.

This rubber composition was subjected to press vulcanization at 160 ° C. for 20 minutes at a press pressure of 10 MPa to obtain a sheet, and after making each test piece, normal state physical properties were measured and ozone resistance,
The flex fatigue resistance and oil resistance were evaluated. The results are shown in Table 1.
Shown in.

Examples 2 to 6 and Comparative Examples 1 to 8 Rubber compositions were prepared in the same manner as in Example 1 except that the composition of the rubber composition was changed as shown in Table 1 or Table 2. , Test pieces were manufactured, normal state physical properties were measured, and ozone resistance, bending fatigue resistance, and oil resistance were evaluated. In addition, Table 1
Alternatively, Table 2 shows only those which may be changed from the composition of Example 1. Table 1 shows the measurement results and evaluation results.
Or shown in Table 2.

[0055]

[Table 1]

[0056]

[Table 2]

As the rubber, an α, β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber (B) having a small molecular weight is used.
And a large molecular weight α, β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber (A) and ethylene-
Even if the rubber composition containing only the α-olefin copolymer rubber (C) is vulcanized, the obtained vulcanized product is inferior in ozone resistance and flex fatigue resistance (Comparative Examples 1 to 3). A rubber composition containing α, β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber-3 having a number average molecular weight of less than 1,000 in place of the rubber (B) having a number average molecular weight of 1,000 or more. Even if it is vulcanized, the vulcanized product obtained is inferior in flex fatigue resistance (Comparative Example 4). Instead of the rubber (B) having a number average molecular weight of 20,000 or less, an α, β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber having a number average molecular weight of 20,000 or more and less than 50,000 is used-4 Even if the rubber composition containing vulcanization is vulcanized, the obtained vulcanized product is inferior in flex fatigue resistance (Comparative Example 5). Even if a rubber composition containing too much ethylene-α-olefin copolymer rubber (C) is vulcanized, the resulting vulcanizate has poor oil resistance (Comparative Example 6).
Even if a rubber composition containing too little ethylene-α-olefin copolymer rubber (C) is vulcanized, the obtained vulcanized product is inferior in ozone resistance (Comparative Example 7). Even if a rubber composition containing too much rubber (B) having a small molecular weight is vulcanized,
The obtained vulcanized product is inferior in mechanical strength (Comparative Example 8).

On the other hand, when the rubber composition of the present invention is vulcanized, the obtained vulcanized product has sufficient mechanical strength,
Excellent ozone resistance, flex fatigue resistance, and oil resistance (Example 1
~ 6).

Continued front page    F term (reference) 4J002 AC071 AC072 BB053 BB153                       FD01 FD14 GJ02 GM01

Claims (2)

[Claims] 1. A number average molecular weight of 50,000 to 150,0.
00, α, β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber (A) 50 to 79% by weight, number average molecular weight,
1,000 to 20,000 α, β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber (B) 1 to 30% by weight and ethylene-α-olefin copolymer rubber (C)
A rubber composition containing 14 to 49% by weight. 2. A vulcanized product obtained by vulcanizing the rubber composition according to claim 1.