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
1997-10-10
1999-08-17
Cain, Edward J.
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...
524493, 524495, 524496, C08K 300
Patent
active
059394846
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a rubber composition comprising silica and a silane coupling agent and to a pneumatic tire prepared by using the rubber composition, and more particularly, to a rubber composition in which gelation of a polymer due to a silane coupling agent during mixing at high temperatures of 150.degree. C. or more is suppressed such that the reaction of silica and the silane coupling agent proceeds efficiently without a deterioration in workability, and in which low heat buildup property and abrasion resistance are improved, and to a pneumatic tire prepared by using this rubber composition.
BACKGROUND ART
Heretofore, carbon black has been used as a reinforcing filler for rubber because carbon black provides higher reinforcement and more excellent abrasion resistance than other fillers. Recently, because of social requirements to save energy and to save resources, particularly to cut down fuel consumption of automobiles, a decrease in the heat buildup of rubber compositions is also required.
For decreasing the heat buildup of a rubber composition by using carbon black, use of a small amount of carbon black or use of a carbon black having a large particle size is considered. However, it is well known that, in both methods, decreasing heat buildup is in a contradictory relation with improving reinforcement and abrasion resistance of a rubber composition.
On the other hand, silica is known as a filler which provides decreased heat buildup of a rubber composition, and applications for many patents, for example, Japanese Patent Application Laid-Open No. Hei-3-252431, have heretofore been made.
However, silica has a tendency to form agglomerates of particles by hydrogen bonding of a silanol group which is a functional group on the surface. For improving the dispersion of silica particles into rubber, the mixing time must be increased. When dispersion of silica particles into rubber is insufficient, a problem arises in that processability in processes such as extrusion and the like deteriorates due to the increase in the Mooney viscosity.
Moreover, the surfaces of the silica particles are acidic. Therefore, there are problems in that, during vulcanization of the rubber composition, basic substances used as vulcanization accelerators are adsorbed such that vulcanization is not carried out sufficiently, and a sufficient modulus of elasticity is not obtained.
In order to solve these problems, various types of silane coupling agents have been developed. For example, use of a silane coupling agent as a reinforcing material is described in Japanese Patent Application Publication No.Sho-50-29741. However, the use of a silane coupling agent as a reinforcing material is still insufficient for improving fracture properties, workability, and processability of a rubber composition to high standards. Rubber compositions in which a combination of silica and a silane coupling agent is used as a reinforcing material are described in Japanese Patent Application Publication No. Sho-51-20208 and others. However, this method of using a combination of silica and a silane coupling agent as a reinforcing material has a drawback in that flow of the uncured rubber composition is markedly inferior and workability and processability deteriorate, although reinforcement of the rubber composition can be remarkably improved and the fracture properties are improved.
The drawbacks of the conventional technologies in which silane coupling agents are used arise due to the following mechanism. When the mixing temperature of rubber is low, the silanol group on the surface of the silica does not react sufficiently with the silane coupling agent, and as a result, the reinforcing effect is not obtained. Dispersion of the silica into the rubber is also inferior, and this causes deterioration of the low heat buildup property which is the strong point of a rubber composition containing silica. Moreover, some of the alcohol formed by the reaction of the silanol group on the surface of the silica and the silane couplin
REFERENCES:
patent: 4820751 (1989-04-01), Takeshita et al.
Araki Shunji
Yanagisawa Kazuhiro
Bridgestone Corporation
Cain Edward J.
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