Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1995-09-29
1998-05-26
Henderson, Christopher
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525262, 525263, 525265, C08F26502
Patent
active
057565864
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a vulcanizable rubber composition comprising an ethylenically unsaturated nitrile-conjugated diene copolymer rubber, and more particularly to a vulcanizable rubber composition which can provide a vulcanized rubber having excellent heat resistance and oil resistance and moreover stably exhibiting high tensile strength without being affected by kneading conditions.
The vulcanizable rubber composition according to the present invention is suitable for use in, particularly, fields of which high tensile stress or tensile strength is required, for example, as a rubber material for toothed belts, V-belts, packings, hoses, rubber rolls and the like.
BACKGROUND ART
It has heretofore been known that when the zinc salt of methacrylic acid, such as zinc dimethacrylate or basic zinc methacrylate, is compounded into an ethylenically unsaturated nitrile-conjugated diene copolymer rubber, and the rubber is vulcanized with an organic peroxide, a vulcanized rubber excellent in various physical properties such as tensile strength can be obtained. The zinc salt of methacrylic acid may be compounded either in the form of the salt itself prepared in advance or by compounding methacrylic acid and a zinc compound (zinc oxide, zinc carbonate, zinc hydroxide or the like) into the copolymer rubber and reacting them in the rubber, thereby forming the salt.
For example, Japanese Patent Application Laid-Open No. 306441/1989 has disclosed that a vulcanizable rubber composition obtained by compounding methacrylic acid, a zinc compound and an organic peroxide into an ethylenically unsaturated nitrile-conjugated diene copolymer rubber provides a vulcanized rubber having high tensile strength. Japanese Patent Application Laid-Open No. 306443/1989 has disclosed that a vulcanizable rubber composition obtained by compounding methacrylic acid, a zinc compound and an organic peroxide into an ethylenically unsaturated nitrile-conjugated diene copolymer rubber containing conjugated diene units in an amount of at most 30 wt. % provides a vulcanized rubber exhibiting extremely high tensile strength compared with the conventional rubbers.
However, the conventional vulcanizable rubber compositions obtained by blending methacrylic acid, a zinc compound and an organic peroxide with an ethylenically unsaturated nitrile-conjugated diene copolymer rubber has involved a problem that they cannot provide vulcanized rubbers having sufficiently high tensile stress.
When a rubber material is used in a belt, hose or the like, it must have high tensile stress. In particular, a rubber material having high tensile stress together with properties such as excellent heat resistance, oil resistance, tensile strength and processability is required for the application to various toothed belts driven under a high load. A toothed belt is generally formed from a surface coating layer composed of canvas or the like, a rubber layer for forming and holding a toothed part (tooth form), and a reinforcing cord (core) embedded in the rubber layer, and is used as a power transmission means. The toothed belt suffers high stress at the root of each tooth when transmitting the power in mesh with a pulley. In order to withstand this high stress, the tensile stress of the rubber layer which forms and holds the toothed part must be made high.
In general, as an example of a method for enhancing the tensile stress of rubber, may be mentioned a method in which the compounding proportion of a reinforcing material for the rubber, such as carbon black or silica is increased to improve the hardness of the resulting vulcanized rubber. In this case, however, the viscosity of an unvulcanized rubber becomes too high, resulting in deteriorated processability.
Examples of other methods for enhancing the tensile stress of rubber include a method in which the amount of a vulcanizing agent is increased, and a method in which a crosslinking aid such as triallyl isocyanulate or trimethylolpropane triacrylate is added. However, these methods involve probl
REFERENCES:
patent: 4056269 (1977-11-01), Pollitt
Nakajima Kazuyoshi
Nishimura Koichi
Saito Yoshiomi
Serizawa Yasuaki
Tanaka Atsushi
Henderson Christopher
Nippon Zeon Co. Ltd.
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