JPH05339426A - Curable rubber composition - Google Patents

Abstract

PURPOSE:To provide the subject composition excellent in tensile strength, flexural fatigue resistance, tear strength, compression set and heat resistance, useful for automotive transmission belts, etc., comprising a specific hydrogenated rubber, unsaturated carboxylic acid metal salt, organic peroxide and sulfur component at specified proportion. CONSTITUTION:The objective composition comprising (A) 10 pts.wt. of a hydrogenated rubber consisting of an ethylenically unsaturated nitrile-conjugated diene copolymer, (B) 10-100 pts.wt. of an unsaturated carboxylic acid metal salt such as lead (meth)acrylate, (C) 0.2-10 pts.wt. of an organic peroxide such as benzoyl peroxide, and (D) 0.4-1.0 pt.wt. of a sulfur component which is more than the organic peroxide in terms of number of moles.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a vulcanizable rubber composition, and more particularly to a vulcanizable rubber composition having excellent strength characteristics and fatigue characteristics.

[0002]

2. Description of the Related Art Conventionally, a toothed belt has been used as, for example, a transmission belt for automobiles, but the life of the toothed belt has been required to be extended with the recent increase in the output of the engine. Then, as a vulcanizable rubber composition whose physical properties have been modified to meet such demands, for example, JP-A 1-3
As disclosed in Japanese Patent No. 11158, by mixing zinc methacrylate and an organic peroxide with a hydrogenated rubber composed of an ethylenically unsaturated nitrile-conjugated diene copolymer, the tensile strength is improved. Something like this has been proposed. The vulcanizable rubber composition contains no sulfur component.

On the other hand, as a general vulcanizable rubber composition, a sulfur component having an equimolar atom to the organic peroxide is added to an existing rubber such as EPR (ethylene propylene rubber) mixed with an organic peroxide. By doing so, it has been conventionally known that the sulfur component acts as a co-crosslinking agent at the time of crosslinking with an organic peroxide so as to improve bending fatigue resistance and tear strength.

[0004]

However, in the former vulcanizable rubber composition, although the tensile strength is excellent, the flexural fatigue resistance and the tear strength are not always satisfactory.

On the other hand, the latter general vulcanizable rubber composition is excellent in bending fatigue resistance and tear strength, but when the amount of sulfur component added increases, compression set and heat resistance decrease, Moreover, since the tensile strength tends to deteriorate, the amount of sulfur component added is naturally limited, and physical properties such as bending fatigue and tear strength are further improved in order to adequately respond to higher engine output. The current situation is that even if you try to do so, you cannot leave it to me.

The present invention has been made in view of the above points, and an object thereof is to add an appropriate amount of a sulfur component to the former vulcanizable rubber composition.
Another object of the present invention is to provide a vulcanizable rubber composition capable of sufficiently improving tensile strength, flexural fatigue resistance, tear strength, compression set and heat resistance.

[0007]

In order to achieve the above object, the solution of the present invention is an ethylenically unsaturated nitrile-
Hydrogenated rubber comprising a conjugated diene copolymer; 100 parts by weight, unsaturated carboxylic acid metal salt; 10 to 100 parts by weight, organic peroxide; 0.2 to 10 parts by weight and sulfur component;
That is, the vulcanizable rubber composition is constituted by containing 4 to 1.0 parts by weight and converting the sulfur component into the number of moles to be more than the organic peroxide.

That is, a hydrogenated rubber comprising an ethylenically unsaturated nitrile-conjugated diene copolymer is an ethylenically unsaturated nitrile such as acrylonitrile or methacrylonitrile, 1,3-butadiene, isoprene, 1,3-
A rubber obtained by adding hydrogen to a copolymer of a conjugated diene such as pentadiene to saturate the double bond present in the conjugated diene monomer unit. For example, a hydrogenated acrylonitrile butadiene rubber obtained by hydrogenating a copolymer of acrylonitrile and 1,3-butadiene (hereinafter referred to as H-
(Abbreviated as NBR). Taking this as an example,
The proportion of acrylonitrile rubber monomer units in H-NBR is 10 to 60% by weight, and the proportion of conjugated diene monomer units is 30% by weight or less by means such as partial hydrogenation. The molecular weight of H-NBR, the glass transition temperature, the hydrogenation rate and the like are not particularly limited, but usually, the hydrogenation rate of the double bond of the conjugated diene monomer unit is 10 to 99%, preferably 80 to 95. % Is good.

The unsaturated carboxylic acid metal salt is an ionic bond between an unsaturated carboxylic acid having a carboxyl group and a metal, and is preferably zinc acrylate or zinc methacrylate. The content of this unsaturated carboxylic acid metal salt is set to 10 to 100 parts by weight with respect to 100 parts by weight of hydrogenated rubber, and the effects as expected below 10 parts by weight and above 100 parts by weight are obtained. Because you cannot do it. Further, the ratio of the hydrogenated rubber to the unsaturated carboxylic acid metal salt is preferably set to 100/100 ≧ hydrogenated rubber / unsaturated carboxylic acid metal salt ≧ 100/25. The reason for setting such a range is that if it is less than 100/25, the strength characteristics are inferior, while if it exceeds 100/100, the bending fatigue resistance and impact resilience are inferior, and the hardness increase is large.

The organic peroxide is used as a cross-linking agent for hydrogenated rubber, and examples thereof include benzoyl peroxide, lauroyl peroxide, ditertiary butyl peroxide, acetyl peroxide, tert-butyl peroxybenzoic acid, dicumyl peroxide. , Diazo compounds such as peroxybenzoic acid, tertiary butyl peroxypivalate and azobisisobutyronitrile are preferred. These organic peroxides may be used alone or in combination. The content of this organic peroxide is set to 0.2 to 10 parts by weight with respect to 100 parts by weight of hydrogenated rubber. This is because sufficient rubber elasticity cannot be obtained if it exceeds the area.

The sulfur component is a so-called co-crosslinking agent which is a vulcanizing agent used in combination with organic peroxide vulcanization, and is used in the form of sulfur, a sulfur compound and a mixture of sulfur and a sulfur compound. The content of this sulfur component is 0.4 to 1.0 parts by weight with respect to 100 parts by weight of hydrogenated rubber,
If it is less than 0.4 parts by weight or more than 1.0 parts by weight, the tear strength will decrease. Further, in general, the addition of a sulfur component is accompanied by an increase in compression set, or the addition of a large amount thereof lowers the crosslinking efficiency and promotes a large increase in hardness during heat aging. Although the number of moles is controlled to be equimolar to that of the oxide, in the present invention, the sulfur component is contained in a larger amount than the organic peroxide in terms of moles. In particular, it is preferable to add about 2.5 to 5 times the molar atom of the organic peroxide because the crosslinking effect can be sufficiently exhibited.

In the vulcanizable rubber composition of the present invention, a reinforcing agent such as carbon black and silica, a filler such as calcium carbonate and talc, a cross-linking aid, together with the above components,
Vulcanization accelerator, plasticizer, stabilizer, processing aid, antioxidant,
Various chemicals usually used in the rubber industry, such as colorants, are appropriately blended according to the purpose of use.

[0013]

With the above structure, in the present invention, an organic peroxide and a sulfur component are used together in a hydrogenated rubber as a cross-linking agent, and the sulfur component is added in an amount larger than that of the organic peroxide in terms of moles. Therefore, as compared with the case where a general rubber such as EPR is co-crosslinked, the bending fatigue property is improved, and particularly the tear strength is further improved. In addition, the compression set, heat resistance and tensile strength of general rubber are lowered by the addition of the sulfur component, but they are not reduced in the present invention.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples.

(Example 1) The H-NBR compositions shown in Table 1 were kneaded in a Banbury mixer, and then rolled by a calender roll to give an unvulcanized rubber sheet. It was vulcanized for a minute to obtain a vulcanized rubber sheet. The properties of this vulcanized rubber sheet are shown in Table 1 and FIG.

[0016]

[Table 1] As a result, the bending fatigue resistance and the tear strength were improved as compared with the case where the EPR was co-crosslinked (data in FIG. 2), and the tear strength was further improved. Further, in EPR, compression set, heat resistance and tensile strength were lowered by the addition of the sulfur component, but they were not lowered in the examples of the present invention. And, judging from the above data, the sulfur component is 0.4 ~
It can be seen that the characteristics are excellent at 0.7 parts by weight. This range is about 2.5 to about 0.5 of the organic peroxide in terms of number of moles.
This is equivalent to 5 times the number of moles.

Therefore, the vulcanizable rubber composition of the present invention is useful for producing toothed belts, high-pressure hoses, rolls, anti-vibration rubbers, etc., which are required to have excellent strength characteristics as the engine output increases. Is.

[0018]

As described above, according to the present invention,
Hydrogenated rubber consisting of ethylenically unsaturated nitrile-conjugated diene copolymer; 100 parts by weight, unsaturated carboxylic acid metal salt; 10 to 100 parts by weight, organic peroxide; 0.2 to 10
Parts by weight and sulfur component; 0.4 to 1.0 part by weight, and since the content of the sulfur component was converted to the number of moles to be larger than that of the organic peroxide, tensile strength, flexural fatigue resistance, Tear strength, compression set and heat resistance can be sufficiently improved.

[Brief description of drawings]

FIG. 1 is a data diagram showing the effect of H-NBR mixed with zinc methacrylate on an organic peroxide.

FIG. 2 is a data diagram showing the effect of EPR on organic peroxide.

[Explanation of symbols]

 None

Claims (1)

[Claims] 1. A hydrogenated rubber comprising an ethylenically unsaturated nitrile-conjugated diene copolymer; 100 parts by weight; unsaturated carboxylic acid metal salt; 10 to 100 parts by weight; organic peroxide; 0.2 to 10 Parts by weight and sulfur component; 0.4-1.
A vulcanizable rubber composition containing 0 parts by weight and containing a sulfur component in an amount larger than that of the organic peroxide in terms of number of moles.