Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1997-05-29
1998-12-22
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524433, C08K 522
Patent
active
058520937
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a vulcanizable rubber composition comprising a highly saturated nitrile copolymer rubber as the base ingredient; a material for a seal used in a dynamic state which material is composed of a vulcanizate of the rubber composition; and a seal used in a dynamic state.
BACKGROUND ART
In general rubber elastomeric materials, especially an acrylonitrile-butadiene copolymer rubber (NBR) is used as materials for seals which are used in a static or dynamic state as parts of automobiles and aircrafts, and in the field of an energy industry and other industries.
The applicant has proposed in Japanese Unexamined Patent Publication 62-230837 a nitrile group-containing highly saturated copolymer rubber, i.e., hydrogenated NBR, as a sealing material characterized in that, when it is used under high-temperature and high-pressure conditions, neither reduction of sealability nor breakage due to compression occurs. The sealing material made of a nitrile group-containing highly saturated copolymer rubber has greatly enhanced heat resistance and tenacity as compared with a sealing material made of NBR, but, when it is used for a long period, a sealing surface especially a rotational or sliding surface is undesirably carbonized to be thereby blackened and further a multiplicity of fine cracks, i.e., heat cracks occur on the rotational or sliding surface. This undesirable carbonization of the rubber sealing surface is believed to be due to the fact that, when the seal is used for a long period, repeated distortion and friction on the rotational or sliding surface cause heat build-up.
To avoid the undesirable carbonization, the following remedies are considered: (1) enhancement of abrasion resistance of a rubber sealing material by incorporation of a reinforcing filler; (2) reduction of friction coefficient, and (3) suppression of heat build-up. When a salient amount of a reinforcing filler such as, for example, carbon black is incorporated, abrasion wear of the rubber sealing material on the rotational or sliding surface can be reduced. However, the friction coefficient increases with the result of enhancement of heat build-up.
It is known that, when a salient amount of a metal oxide such as zinc oxide is incorporated in a rubber elastomeric material, thermal conductivity is increased and thus heat build-up is suppressed. However, the incorporation of a salient amount of a metal oxide such as zinc oxide inevitably reduces compression set of the elastomeric material and the material does not possess good and balanced characteristics required for a sealing material.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a vulcanizable rubber composition which gives a sealing material having good and balanced characteristics and exhibiting a high thermal conductivity, a suppressed heat build-up and a minimized occurrence of heat cracks.
Another object of the present invention is to provide a sealing material used in a dynamic state, which has the above-mentioned characteristics.
As results of an extensive research, the inventors have found that, when the amount of a reinforcing filler such as carbon black incorporated in a nitrile group-containing highly saturated copolymer rubber is smaller than the amount thereof conventionally employed, and in addition, a relatively large amount of a non-reinforcing filler such as zinc oxide or calcium carbonate is incorporated, a vulcanizable rubber composition having improved thermal conductivity and reduced heat build-up as well as good characteristics required for a sealing material can be obtained. Based on this finding, the present invention has been completed. Further, it has been found that a rubber vulcanizate of the vulcanizable rubber composition is characterized in that the friction coefficient is small and the abrasion wear is within a limited range and does not exceed this range, and thus, the vulcanizate is suitable for a sealing material which is used in a dynamic state at a rotational part or sliding part of a se
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Aimura Yoshiaki
Ito Suguru
Michl Paul R.
Nippon Zeon Co. Ltd.
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