JP2002293995A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition reduced in modulus anisotropy by improving both the modulus and breaking strength in the anticalender direction of a rubber containing >=50 pts.wt. of a highly saturated ethylenic unsaturated nitrile-conjugated diene rubber <=30 wt.% in conjugated diene unit content. SOLUTION: This rubber composition is obtained by compounding a total of 100 pts.wt. of rubber containing >=50 pts.wt. of a highly saturated ethylenic unsaturated nitrile-conjugated diene rubber <=30 wt.% in conjugated diene unit content with 10-120 pts.wt. of an ethylenic unsaturated carboxylic acid metal salt, 0.5-15 pt(s).wt. of an organic peroxide and 0.01-20 pt(s).wt. of an aromatic carboxylic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in the vulcanizability of a specific rubber composition, and more particularly to an ethylenically unsaturated nitrile-conjugated diene system having a conjugated diene unit content of 30% or less. The present invention relates to a rubber composition having a reduced anisotropy in vulcanization properties inherent in a rubber containing 50 parts by weight or more of a saturated rubber.

[0002]

2. Description of the Related Art Conventionally, stiffness is higher than that of generally used sulfur vulcanizable diene rubber, tan δ is lower,
Focusing on the properties of hydrogenated NBR, which is excellent in heat resistance, weather resistance, and abrasion resistance and has a low unvulcanized viscosity while being hard, has a specific composition of hydrogenated NBR, zinc methacrylate and organic peroxide. It is known that a rubber composition containing the compound is used for a tire member or the like (JP-A-3-188138, JP-A-5-185805, etc.). However, such a rubber composition has much larger anisotropy than general rubber because the contained zinc methacrylate is oriented in the rubber. This property is also a factor that such a rubber composition generates a large modulus, but if the wrong direction is used, the desired strength cannot be exhibited, or cracks easily grow along the grain direction, There may be disadvantages depending on the application used. Therefore, it is desired to increase the tear strength as the modulus in the anti-grain direction increases.

[0003]

Accordingly, in the present invention, a rubber containing 50% by weight or more of an ethylenically unsaturated nitrile-conjugated diene-based highly saturated rubber having a conjugated diene unit content of 30% or less is required. By adding a predetermined amount of aromatic carboxylic acid to a rubber composition containing a fixed amount of a metal salt of an ethylenically unsaturated carboxylic acid and an organic peroxide, the modulus in the reverse direction and the breaking strength are improved. Accordingly, an object of the present invention is to provide a rubber composition having reduced modulus anisotropy.

[0004]

According to the present invention, a total of 100 parts by weight of a rubber containing at least 50 parts by weight of an ethylenically unsaturated nitrile-conjugated diene-based highly saturated rubber having a conjugated diene unit content of 30% or less is provided. To the metal salt of an ethylenically unsaturated carboxylic acid in an amount of 10 to 120 parts by weight, and 0.1 parts of an organic peroxide.
A rubber composition comprising 5 to 15 parts by weight and 0.01 to 20 parts by weight of an aromatic carboxylic acid is provided.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber component used in the rubber composition of the present invention is an ethylenically unsaturated nitrile-conjugated diene-based highly saturated copolymer rubber already known as so-called "hydrogenated NBR", and is composed of acrylonitrile, Copolymers of ethylenically unsaturated nitriles such as acrylonitrile and conjugated dienes such as 1,3-butadiene, isoprene and 1,3-pentadiene, monomers copolymerizable with the above two monomers, for example, , A vinyl aromatic compound, a (meth) acrylic acid, an alkyl (meth) acrylate, an alkoxyalkyl (meth) acrylate, a multi-component copolymer with a cyanoalkyl (meth) acrylate, and specifically,
Acrylonitrile-butadiene copolymer rubber, acrylonitrile-isoprene copolymer rubber, acrylonitrile-butadiene-isoprene copolymer rubber, acrylonitrile-
Butadiene-acrylate copolymer rubber, acrylonitrile-butadiene-acrylate-methacrylic acid copolymer rubber, and the like. These rubbers contain 30 to 60 parts by weight of an ethylenically unsaturated nitrile unit, and contain 30 units of a conjugated diene unit by means such as partial hydrogenation of the conjugated diene unit.
% By weight, preferably 20% by weight or less.

[0006] The rubber component in the rubber composition of the present invention is used for adjusting the physical properties of an ethylenically unsaturated nitrile-conjugated diene-based highly saturated rubber having a conjugated diene unit content of 30% or less. A rubber composition containing 0 to 50 parts by weight of an unvulcanized rubber other than the above may be used. As such an unvulcanized rubber, for example, natural rubber (N
R), isoprene rubber (IR), butadiene rubber (B
R), chloroprene rubber (CR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), styrene-isoprene-styrene block copolymer rubber (SIS), epoxidized natural rubber, trans
-Polyisoprene rubber and the like. Two or more of these unvulcanized rubbers may be used in combination.

As the metal salt of the ethylenically unsaturated carboxylic acid to be incorporated in the rubber composition of the present invention, zinc methacrylate is effectively used exclusively, and 10 to 120 parts by weight based on 100 parts by weight of rubber. , Preferably 50 to 80 parts by weight.

The method of mixing the zinc methacrylate into the rubber is not particularly limited, and a mixer such as a roll, a Banbury, a kneader, a single-screw kneader, or a twin-screw kneader usually used in the rubber industry may be used. it can. Also,
In addition to the method of directly mixing zinc methacrylate with the rubber composition of the present invention, first, a zinc compound such as zinc oxide or zinc carbonate is blended with the above-mentioned hydrogenated NBR, and after sufficient dispersion, methacrylic acid is mixed or absorbed. Then, a method of forming zinc methacrylate in the polymer may be adopted, and this method is preferable because a very good dispersion of zinc methacrylate can be obtained. It is also preferable to use a composition in which zinc methacrylate and a zinc compound are previously dispersed in the hydrogenated NBR. Such a composition is available from Nippon Zeon [ZS
C] (trade name) series, for example, ZSC 2022,
ZSC 2030L, ZSC 2295, ZSC 22
95N, ZSC 2298, ZSC 2395, and the like.

[0009] The rubber composition of the present invention is preferably crosslinked with an organic peroxide. As the organic peroxide, those used in ordinary peroxide vulcanization of rubber can be used. Such as dicumyl peroxide,
Di-t-butyl peroxide, t-butylcumyl peroxide, benzoyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne,
2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-mono (t-
Butylperoxy) hexane, α, α′-bis (t-butylperoxy-m-isopropyl) benzene and the like. One or two or more of these organic peroxides are used, and 0.5 to 15 parts by weight based on 100 parts by weight of rubber.
It is preferable to mix them by weight, preferably 0.2 to 8 parts by weight.

As the aromatic carboxylic acid to be added to the rubber composition of the present invention to exert the desired effect, benzoic acid, salicylic acid, phthalic acid, naphthalenecarboxylic acid, naphthalic acid, aminobenzoic acid and the like are used. Of these, benzoic acid is particularly effectively used. The aromatic carboxylic acid is used in an amount of 0.01 to 100 parts by weight of rubber.
It is preferable that the compounding amount be from 20 to 20 parts by weight, preferably from 0.1 to 5 parts by weight.

The rubber composition of the present invention further includes, for example,
Fillers such as carbon black, silica, calcium carbonate, talc, etc .; crosslinking assistants such as triallyl isocyanate, higher esters of methacrylic acid, diallyl phthalate, m-phenylene bismaleide, 1,2-polybutadiene, and other rubber industries Plasticizers, antioxidants, stabilizers, adhesives, resins, processing aids, coloring agents, and the like commonly used in the above.

[0012]

EXAMPLES The present invention will be described below with reference to Examples and Comparative Examples, but it goes without saying that the scope of the present invention is not limited by these Examples.

Preparation of Test Samples A vulcanizing agent was added to a master batch obtained by kneading the components shown in Table 1 except for the cross-linking agent DCP (organic peroxide) in a 1.8 liter closed mixer for 5 minutes. DCP to 8
The rubber composition was obtained by kneading with an inch open roll.
Next, this rubber composition was added in a size of 15 cm × 15 cm × 0.2
After press vulcanization at 170 ° C. for 10 minutes in a metal mold having a diameter of 10 cm, a test piece (rubber sheet) was prepared by cutting in the direction of grain and counter grain.

Test method 1) Tensile strength: Measured in accordance with the test method of JIS K6301 using test samples in the grain and anti-grain directions. 2) Tear strength: Measured according to the test method of JIS K6301 using test samples in the grain and anti-grain directions.

The results are shown in Table 1.

[Table 1]

[0016]

From the results shown in Table 1, it can be seen that the ratio of the tensile strength in the grain direction and the anti-grain direction, that is, the anisotropy, is reduced by blending the aromatic carboxylic acid. Understand. Depending on the blending amount of benzoic acid, the modulus on the low elongation side may decrease, but may show a very large elongation at break. In that case, the tear strength also increased.

Continued on front page F term (reference) 4J002 AC012 AC032 AC062 AC072 AC082 AC092 AC112 BG101 BP012 EF098 EF118 EG046 EJ068 EK037 EK047 EK057 EN068 FD010 FD146 FD147 FD150 FD158

Claims (2)

[Claims] 1. A total of 100 parts by weight of a rubber containing 50 parts by weight or more of an ethylenically unsaturated nitrile-conjugated diene-based highly saturated rubber having a conjugated diene unit content of 30% or less,
A rubber composition comprising 10 to 120 parts by weight of a metal salt of an ethylenically unsaturated carboxylic acid, 0.5 to 15 parts by weight of an organic peroxide, and 0.01 to 20 parts by weight of an aromatic carboxylic acid. 2. The rubber composition according to claim 1, wherein the aromatic carboxylic acid is benzoic acid.