JP2003221467A - Rubber composition, vulcanizable rubber composition, and vulcanized rubber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vulcanized rubber of a copolymeric rubber containing nitrile groups which is excellent in general physical properties and little in compression set. <P>SOLUTION: One to 50 pts.wt. of an oxide or hydroxide (C) of a metal belonging to the group II of the periodic table is incorporated to a masterbatch containing 100 pts.wt. of a copolymer rubber (A) having nitrile groups and having an iodine value of 100 or less and 3-100 pts.wt. of a metal salt of an α,β-ethylenic unsaturated carboxylic acid (B) to obtain a rubber composition. To this rubber composition, an organic peroxide (D) of 0.1-10 pts.wt. is further mixed, and the mixture is subjected to vulcanization. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a nitrile group-containing copolymer rubber vulcanizate having excellent mechanical properties and a small compression set, and a rubber composition used as the material.

[0002]

As a rubber material having excellent heat resistance and oil resistance, a hydrogenated acrylonitrile-butadiene copolymer rubber obtained by hydrogenating an acrylonitrile-butadiene copolymer rubber is known. In order to reduce the variation in tensile strength of this vulcanized product, a zinc compound, α, β-ethylenically unsaturated carboxylic acid and a metal compound of Group 2 of the periodic table may be blended and vulcanized with an organic peroxide. Proposed (W
O94 / 22947). The zinc compound and α, β-ethylenically unsaturated carboxylic acid react in rubber to produce α, β-
It produces an ethylenically unsaturated carboxylic acid zinc salt and improves the mechanical properties of hydrogenated acrylonitrile-butadiene copolymer rubber. However, this vulcanized product may have a large compression set.

[0003]

An object of the present invention is to provide a nitrile group-containing copolymer rubber vulcanizate having excellent mechanical properties and a small compression set and a nitrile group-containing copolymer rubber composition used as the material. To do.

[0004]

Means for Solving the Problems The inventors of the present invention have made earnest studies to achieve the above-mentioned object, and as a result, consisted of hydrogenated acrylonitrile-butadiene copolymer rubber and α, β-ethylenically unsaturated carboxylic acid zinc salt. It was found that a vulcanized product has excellent mechanical properties and a small compression set by preparing a masterbatch and adding a metal compound of Group 2 of the periodic table to the masterbatch to prepare a rubber composition. The present invention has been completed based on this finding.

Thus, according to the present invention, as the first invention, 100 parts by weight of a nitrile group-containing copolymer rubber (A) having an iodine value of 100 or less and α, β-ethylenically unsaturated carboxylic acid metal salt (B). Provided is a rubber composition comprising a masterbatch containing 3 to 100 parts by weight and 1 to 50 parts by weight of an oxide or hydroxide (C) of a metal of Group 2 of the periodic table. As a second invention, a vulcanizability obtained by further adding 0.1 to 10 parts by weight of an organic peroxide (D) to 100 parts by weight of the nitrile group-containing copolymer rubber (A) in the rubber composition. A rubber composition is provided. Further, as a third invention, there is provided a vulcanized product obtained by vulcanizing the vulcanizable rubber composition.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber composition of the present invention comprises 100 parts by weight of a nitrile group-containing copolymer rubber (A) having an iodine value of 100 or less and α, β-ethylenically unsaturated carboxylic acid metal salt (B) 3 to. A masterbatch containing 100 parts by weight was added to an oxide or hydroxide (C) 1 to 50 of a metal of Group 2 of the periodic table.
A rubber composition containing 1 part by weight.

The nitrile group-containing copolymer rubber (A) used in the present invention is a rubber obtained by copolymerizing an α, β-ethylenically unsaturated nitrile monomer with another monomer and has an iodine value of Is 100 or less.

Examples of the α, β-ethylenically unsaturated nitrile monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, and the like.
Acrylonitrile is preferred. The content of the α, β-ethylenically unsaturated nitrile monomer in the nitrile group-containing copolymer rubber (A) is preferably 10 to 60% by weight, more preferably 12 to 55% by weight, particularly preferably 15 to It is 50% by weight. If the α, β-ethylenically unsaturated nitrile monomer content is too low, the oil resistance of the vulcanizate may be poor,
On the other hand, if the amount is too large, the cold resistance may be poor.

In the nitrile group-containing copolymer rubber (A), the monomer to be copolymerized with the α, β-ethylenically unsaturated nitrile monomer is a conjugated diene monomer or a non-conjugated diene monomer. Examples thereof include a body and α-olefin. Examples of the conjugated diene-based monomer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene, and 1,3-butadiene is preferable. The non-conjugated diene-based monomer preferably has 5 to 12 carbon atoms, and examples thereof include 1,4-pentadiene, 1,4-hexadiene, vinylnorbornene, and dicyclopentadiene. The α-olefin preferably has 2 to 12 carbon atoms and is exemplified by ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and the like. Furthermore, aromatic vinyl monomers, fluorine-containing vinyl monomers, α, β-ethylenically unsaturated monocarboxylic acids, α, β
-Ethylenically unsaturated polycarboxylic acid or anhydride thereof,
A copolymerizable antiaging agent or the like may be copolymerized.

Examples of the aromatic vinyl type monomer include
Examples thereof include styrene, α-methylstyrene, vinylpyridine and the like. Examples of the fluorine-containing vinyl-based monomer include fluoroethyl vinyl ether, fluoropropyl vinyl ether, o-trifluoromethylstyrene, vinyl pentafluorobenzoate, difluoroethylene, tetrafluoroethylene 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. α, β-
Examples of the ethylenically unsaturated polycarboxylic acid anhydride include itaconic anhydride, maleic anhydride and the like. Examples of the copolymerizable antiaging agent include 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.

The iodine value of the nitrile group-containing copolymer rubber (A) is 100 or less, preferably 80 or less, more preferably 60 or less. If the iodine value is too large, the heat resistance will be poor.

When the α, β-ethylenically unsaturated nitrile monomer and the conjugated diene monomer are copolymerized, the iodine value is often large. If the iodine value is high,
The iodine value may be lowered by hydrogenating the carbon-carbon unsaturated bond of the copolymer rubber (A) by a known method. The hydrogenation method is not particularly limited, and a known method may be used.

The Mooney viscosity ML _{1 + 4} , (100 ° C.) of the nitrile group-containing copolymer rubber (A) is preferably 10 to 3
00, more preferably 20 to 250, particularly preferably 3
It is 0 to 200. If the Mooney viscosity is too low, the mechanical properties of the vulcanizate may be inferior, and if too high, the processability may be inferior.

The α, β-ethylenically unsaturated carboxylic acid constituting the α, β-ethylenically unsaturated carboxylic acid metal salt (B) used in the present invention has at least a monovalent free carboxyl group. . For example, α, β-ethylenically unsaturated monocarboxylic acid, α, β-ethylenically unsaturated dicarboxylic acid, α, β-ethylenically unsaturated dicarboxylic acid monoester, etc. are exemplified. Examples of the α, β-ethylenically unsaturated monocarboxylic acid include acrylic acid, methacrylic acid, crotonic acid, and 3-butenoic acid. α,
Examples of the β-ethylenically unsaturated dicarboxylic acid include maleic acid, fumaric acid and itaconic acid. α, β-
Examples of the ethylenic saturated dicarboxylic acid monoester include monomethyl maleate, monoethyl maleate, monomethyl itaconate and monoethyl itaconate. Among these, α, β-ethylenically unsaturated carboxylic acids having no ester group are preferable, α, β-ethylenically unsaturated monocarboxylic acids are more preferable, and methacrylic acid is preferable from the viewpoint of strength characteristics of the vulcanizate. Particularly preferred.

The metal constituting the α, β-ethylenically unsaturated carboxylic acid metal salt (B) is preferably zinc, magnesium, calcium, barium, titanium, chromium, from the viewpoint of strength characteristics of the vulcanized product. Examples thereof include iron, cobalt, nickel, aluminum, tin and lead, more preferably zinc, magnesium, calcium and aluminum, further preferably zinc, magnesium, calcium and aluminum, particularly preferably zinc. Reacting with α, β-ethylenically unsaturated carboxylic acid, α, β-ethylenically unsaturated carboxylic acid metal salt (B)
A metal compound may be reacted as long as it forms Examples of such a metal compound include oxides, hydroxides and carbonates of the above-mentioned metals, particularly zinc oxide,
Zinc carbonate is preferred.

The α, β-ethylenically unsaturated carboxylic acid metal salt (B) is added to the nitrile group-containing copolymer rubber (A) by α, β
A β-ethylenically unsaturated carboxylic acid and the above metal or metal compound are blended and reacted with each other in a nitrile group-containing copolymer rubber (A) at the time of producing a rubber composition to form a metal salt (B). You may let me. The metal salt (B) produced by such a method is preferable because it becomes fine and easily dispersed. Examples of the metal compound used to generate the metal salt (B) include oxides, hydroxides and carbonates of the above metals, and zinc oxide and zinc carbonate are particularly preferable.

In the nitrile group-containing copolymer rubber (A), α,
When the β-ethylenically unsaturated carboxylic acid is mixed with a metal or a metal compound to produce the α, β-ethylenically unsaturated carboxylic acid metal salt (B), the α, β-ethylenically unsaturated carboxylic acid is used. The amount of metal or metal compound is 0.5 to 3.2 mol, preferably 0.
7-2.5 mol is blended and reacted. If the amount of the metal or the metal compound is too small or too large, the α, β-ethylenically unsaturated carboxylic acid becomes difficult to react with the metal or the metal compound. However, when zinc oxide, zinc carbonate, zinc hydroxide, or the like is used as the metal compound, they function as a vulcanization accelerator alone as a compounding agent for rubber. Therefore, even if the upper limit of the above range is exceeded, depending on the compounding composition. May not cause problems.

The metal salt (B) is preferably fine as long as it does not cause a handling problem, and the content of particles having a particle diameter of 20 μm or more is preferably 5% or less. For that purpose, when the metal salt (B) is blended with the nitrile group-containing rubber (A), a metal salt is used, and when the metal salt (B) is produced with the nitrile group-containing rubber (A), a metal compound, It may be finely divided by a method such as classification with an air classifier or a sieve classifier.

The masterbatch used in the present invention comprises 100 parts by weight of a nitrile group-containing copolymer rubber (A) having an iodine value of 100 or less and 3 to 100 parts by weight of an α, β-ethylenically unsaturated carboxylic acid metal salt (B). It preferably contains 10 to 80 parts by weight, more preferably 25 to 70 parts by weight. If the content is too small, the mechanical properties of the vulcanizate will be inferior, and if too large, kneading will be difficult.

In the masterbatch, it is necessary that the α, β-ethylenically unsaturated carboxylic acid metal salt (B) is sufficiently dispersed in the nitrile group-containing copolymer rubber (A). In the evaluation of the dispersity of carbon black defined as the B method of ASTM D-2663-69, when α, β-ethylenically unsaturated carboxylic acid metal salt (B) is used instead of carbon black, the rubber composition is The dispersity of the product is preferably A to G rank, more preferably A to E.
Rank, particularly preferably A to C ranks. α, β-
When the ethylenically unsaturated carboxylic acid metal salt (B) is not sufficiently dispersed, the compression set of the vulcanized product may increase.

When blending the oxide or hydroxide (C) of a metal of Group 2 of the Periodic Table into the masterbatch, the α, β-ethylenically unsaturated carboxylic acid metal salt ( It is sufficient that B) is dispersed in the nitrile group-containing copolymer rubber (A). For example, when preparing a masterbatch by kneading, it is not necessary to interrupt the kneading, take out the masterbatch, and mix again the oxide or hydroxide (C) of a metal of Group 2 of the periodic table.
In such a case, kneading for preparation as a masterbatch may be continuously mixed with an oxide or hydroxide (C) of a metal of Group 2 of the periodic table and kneading.

The oxide or hydroxide (C) of the Group 2 metal of the periodic table used in the present invention is a Group 2 metal oxide such as calcium oxide, barium oxide or strontium oxide;
Group 2 metal hydroxides such as calcium hydroxide, barium hydroxide, and strontium hydroxide; A Group 2 metal hydroxide is preferable, and calcium hydroxide is particularly preferable.

The particle size of the oxide or hydroxide (C) of Group 2 metal of the periodic table is preferably 1 to 20 μm, more preferably 3 to 17 μm, and particularly preferably 5 to 15 μm. If the particle size is too small, production may be difficult, and if it is too large, the mechanical properties may be poor.

The compounding amount of the oxide or hydroxide (C) of a metal of Group 2 of the periodic table is 1 to 50 parts by weight, preferably 3 to 3 with respect to 100 parts by weight of the nitrile group-containing copolymer rubber (A).
It is 0 part by weight, more preferably 5 to 20 parts by weight. If the blending amount is too small, the compression set becomes large, and conversely if the blending amount is too large, the mechanical properties become poor.

In the masterbatch and rubber composition of the present invention, compounding agents used for general rubber, for example, reinforcing agents such as carbon black, silica, short fibers; calcium carbonate, clay, talc, calcium silicate. And the like; a plasticizer; a pigment; an antiaging agent; a tackifier; a processing aid; a scorch inhibitor; Further, a rubber or resin other than the nitrile group-containing copolymer rubber (A) may be contained within a range that does not substantially impair the effects of the present invention.

These compounding agents, rubbers or resins may be compounded at the time of preparing the master batch or at the time of preparing the rubber composition (1), but preferably the rubber composition (1).
It is added at the time of preparation.

The vulcanizable rubber composition of the present invention is obtained by adding the nitrile group-containing copolymer rubber (A) 100 to the above rubber composition.
The organic peroxide (D) is added in an amount of 0.1 to 10 parts by weight per part by weight.

The organic peroxide (D) used in the present invention is used as a vulcanizing agent for rubber and is not particularly limited, and conventionally known organic peroxide vulcanizing agents can be used.

Examples of the organic peroxide (D) include dialkyl peroxides, diacyl peroxides, peroxyesters and the like, and dialkyl peroxides are preferable. Examples of the dialkyl peroxides include dicumyl peroxide and di-t-
Butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) -3-hexyne, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 1,3 -Bis (t-butylperoxyisopropyl) benzene and the like. Examples of diacyl peroxides include benzoyl peroxide and isobutyryl peroxide. Examples of peroxyesters include 2,5-dimethyl-2,
5-bis (benzoylperoxy) hexane, t-butylperoxyisopropyl carbonate, etc.) and the like. The compounding amount of the organic peroxide (D) with respect to 100 parts by weight of the nitrile group-containing copolymer rubber (A) is 0.1 to 1
It is 0 part by weight, preferably 0.3 to 7 parts by weight, particularly preferably 0.5 to 5 parts by weight. If the blending amount of the organic peroxide (D) is too small, the vulcanization density decreases and the compression set increases. If the blending amount of the organic peroxide (D) is too large, the rubber elasticity of the vulcanized product may be insufficient.

When an organic peroxide is used as a vulcanizing agent, a vulcanizing aid is usually used together. As the vulcanization aid, triallyl cyanurate, triallyl isocyanurate,
Trimethylolpropane trimethacrylate, N, N '
It is preferable to use -m-phenylene bismaleimide or the like. The vulcanization aid may be used by dispersing it in clay, calcium carbonate, silica or the like to improve the processability of the rubber composition. The type and amount of the vulcanization aid are not particularly limited, and may be determined according to the application of the vulcanized product, required performance, type of vulcanization agent, type of vulcanization aid, and the like.

Further, as a vulcanizing agent, an organic peroxide (D)
And a sulfur-based vulcanizing agent may be used in combination. 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 polysulfide; and the like.

The method for preparing the vulcanizable rubber composition is not particularly limited and may be a general method for preparing the vulcanizable rubber composition. The vulcanizing agent may be added at the time of preparing the master batch or at the time of preparing the rubber composition, but is preferably added at the time of preparing the rubber composition. When compounding the vulcanizing agent or in the subsequent treatment, the vulcanizable rubber composition is prepared in a temperature range where vulcanization is not performed.

The vulcanized product of the present invention is a vulcanized product of the above vulcanizable rubber composition. The method for vulcanizing the rubber composition may be to heat the vulcanizable rubber composition. In general,
Heat after molding or at the same time as molding.

The temperature during vulcanization is preferably 100 to 20.
The temperature is 0 ° C, more preferably 130 to 195 ° C, and particularly preferably 140 to 190 ° 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 varies depending on the vulcanization method, vulcanization temperature, shape, etc., but is preferably 1 minute to 4 hours from the viewpoint of vulcanization density and production efficiency.

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.

Depending on the shape and size of the vulcanized product, the inside may not be vulcanized even if the surface is vulcanized. In such a case, after the vulcanization as described above, the secondary vulcanization that is maintained at a high temperature may be performed.

[0037]

The vulcanizate of the present invention has excellent mechanical properties,
Small compression set.

The use of the vulcanized product of the present invention is not particularly limited,
For example, it can be used not only for industrial products such as seals, rubber belts, rubber rolls and rubber hoses or parts thereof, but also for packers used in oil wells, gas wells, out pre-benders, pipe protectors and the like. Examples of the seal include rotating seals, swinging seals, reciprocating seals, and stationary seals. Examples of motion seals include oil seals, piston seals, and mechanical seals, and examples of stationary seals include O-rings, mental legend seals, and various gaskets. Examples of the rubber belt include a flat belt, a V belt, a V ribbed belt, a round belt, a square belt, and a toothed belt. Examples of the rubber rolls include rolls that are parts of OA equipment such as printing equipment and copying equipment, spinning rolls for spinning, textile processing rolls such as drafting rolls for spinning, bridle rolls, snubber rolls, and steelmaking rolls such as steering rolls. Examples of the rubber hose include a single tube rubber hose, a multi-layer rubber hose, a braided type hose, and a cloth wound type hose. Since the vulcanized product of the present invention has low mechanical strength and low compression set, it is particularly suitable for seal and rubber belt applications.

[0039]

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 evaluation method is as follows.

Tensile Strength and Elongation The prepared vulcanizable rubber composition was vulcanized at 170 ° C. for 20 minutes under a pressing pressure of 10 MPa to obtain a sheet having a thickness of 2 mm. Punch this sheet using a number 3 dumbbell,
A test piece was prepared. Using these test pieces, the tensile strength and elongation of the vulcanized product were measured as mechanical strength according to Japanese Industrial Standard JIS K6251.

Hardness According to JIS K 6253, the hardness of the vulcanized product was measured using a durometer hardness tester type A type.

Using a mold having an inner diameter of 29 mm for compression set and a thickness of 12.5 mm, the vulcanizable rubber composition was heated at 160 ° C. for 25 minutes under a pressure of 10 MP.
It was vulcanized with a to obtain a test piece. The compression set is JIS
According to K 6262, using these test pieces, 25
After holding at 150 ° C for 70 hours in a% compressed state,
After holding for 8 hours, measurement was performed.

Reference Example 1 Nitrile group-containing copolymer rubber A (Zetpol 202
0, manufactured by Zeon Corporation, hydrogenated acrylonitrile-butadiene copolymer rubber, acrylonitrile unit content 36.2
%, Iodine value about 28, Mooney viscosity ML _{1 + 4} , (100
C.) 78) 100 parts, methacrylic acid 15 parts, and zinc oxide a (average particle size 0.5 μm, particles of 20 μm or more and 5% or less) 10 parts were kneaded by a kneader. When the temperature of the rubber in the kneader reached 140 ° C. or higher, the pressure lid of the kneader was moved up and down to remove the reaction product water and
In the evaluation of the dispersity of carbon black defined as the B method of STM D-2663-69, a nitrile group-containing copolymer rubber A / methacrylic acid / zinc oxide in which zinc methacrylate is dispersed to a B rank instead of carbon black. A masterbatch (1) was prepared.

Example 1 Copolymer rubber containing nitrile group A / methacrylic acid / zinc oxide masterbatch (1) 125 parts, carbon black (N7
62 Asahi # 50, manufactured by Asahi Carbon Co., Ltd., 10 parts, Tri- (2
-Ethylhexyl) trimellitate (plasticizer) 6 parts,
4,4 '-(α, α'-dimethylbenzyl) diphenylamine (anti-aging agent) 1 part, 2-mercaptobenzimidazole zinc salt (anti-aging agent) 1 part, 1,3-bis (t
-Butylperoxyisopropyl) benzene 40% product (Vul-cup 40KE, manufactured by Hercules) 6 parts and calcium hydroxide (average particle size 10 µm) 10 parts were roll-kneaded at 50 ° C to prepare a vulcanizable rubber composition. did. Using this vulcanizable rubber composition, each test piece was vulcanized, and normal state physical properties were evaluated and compression set was measured. The results are shown in Table 1.

Example 2 The procedure of Example 1 was repeated except that the amount of calcium hydroxide was changed from 10 parts to 5 parts. The results are shown in Table 1.

Example 3 The procedure of Example 1 was repeated except that the amount of calcium hydroxide was changed from 10 parts to 20 parts. The results are shown in Table 1.

Example 4 The same treatment as in Example 1 was carried out except that calcium oxide was used instead of calcium hydroxide.

Reference Example 2 Nitrile was prepared in the same manner as in Reference Example 1 except that 25 parts of zinc methacrylate (average particle size of 10 μm, particles having a particle size of 20 μm or more and 5% or less) were used instead of 15 parts of methacrylic acid and 10 parts of zinc oxide. A group-containing copolymer rubber / zinc methacrylate masterbatch (2) was prepared.

Example 5 Example 1 except that nitrile group-containing copolymer rubber / methacrylic acid / zinc oxide masterbatch (1) was used in place of nitrile group-containing copolymer rubber A / methacrylic acid / zinc oxide masterbatch (1). The same process was carried out. The results are shown in Table 1.

Comparative Example 1 Nitrile group-containing copolymer rubber A1 instead of the masterbatch
The amount of carbon black is from 10 parts to 50 parts.
The same process as in Example 1 was carried out except that the parts were changed. The results are shown in Table 1.

Comparative Example 2 The same treatment as in Example 1 was carried out except that calcium hydroxide was not used. The results are shown in Table 1.

Comparative Example 3 The same treatment as in Example 1 was carried out except that calcium carbonate was used instead of calcium hydroxide. The results are shown in Table 1.

Comparative Example 4 Instead of the nitrile group-containing copolymer rubber A / methacrylic acid / zinc oxide masterbatch (1), 100 parts of nitrile group-containing copolymer rubber A, 15 parts of methacrylic acid and zinc oxide a
The same process as in Example 1 was carried out except that 10 parts were used. The results are shown in Table 1.

Comparative Example 5 Example 1 was repeated except that 100 parts of nitrile group-containing copolymer rubber A and 25 parts of zinc methacrylate b were used in place of the nitrile group-containing copolymer rubber A / methacrylic acid / zinc oxide masterbatch (1). It processed similarly. The results are shown in Table 1.

[0055]

[Table 1]

The vulcanizate of Comparative Example 1 containing no α, β-ethylenically unsaturated carboxylic acid metal salt (B) has a small elongation and a large tensile stress. The vulcanizates of Comparative Examples 2 and 3 which do not contain the oxide or hydroxide (C) of the Group 2 metal of the periodic table have a large compression set. Comparative Example in which α, β-ethylenically unsaturated carboxylic acid metal salt (B) is dispersed in nitrile group-containing copolymer rubber (A) at the same time as oxide or hydroxide (C) of Group 2 metal of the periodic table No. 4 has a small elongation.
The problem of Comparative Example 5 is that tensile strength and elongation are slightly inferior.

On the other hand, the vulcanized product of the present invention has excellent normal state physical properties and a small compression set.

Continued front page    F-term (reference) 4F070 AA07 AC04 AC13 AC40 AC43                       AC46 AC50 AC56 AC63 AC66                       AE01 AE02 AE03 AE30 FB03                 4J002 AC071 EG016 EK037 EK047                       EK057 EK087

Claims (3)

[Claims] 1. A masterbatch containing 100 parts by weight of a nitrile group-containing copolymer rubber (A) having an iodine value of 100 or less and 3 to 100 parts by weight of an α, β-ethylenically unsaturated carboxylic acid metal salt (B), A rubber composition comprising 1 to 50 parts by weight of an oxide or hydroxide (C) of a Group 2 metal of the periodic table. 2. A vulcanized rubber composition comprising the rubber composition according to claim 1 and 0.1 to 10 parts by weight of an organic peroxide (D) per 100 parts by weight of a nitrile group-containing copolymer rubber (A). Rubber composition. 3. A vulcanized product obtained by vulcanizing the rubber composition according to claim 2.