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
1997-11-19
2000-06-20
Warzel, Mark L.
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...
524526, 525193, 525197, C08L 906, C08L 900
Patent
active
060778997
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for producing a rubber composition superior in the tan .delta. balance of the vulcanizate, more specifically a process for producing a rubber composition useful as a pneumatic tire.
BACKGROUND ART
Improvements have been proposed in the tan .delta. of tire tread rubber for reducing the fuel consumption of a vehicle. Specifically, separate mixing of ingredients and use of terminal-modified rubber have been proposed.
For example, Japanese Examined Patent Publication (Kokoku) No. 5-1298 discloses a rubber composition further improving the impact resilience and tensile strength of a vulcanizate including a conjugated diene polymer having an aromatic tertiary amino group in the terminal portion of the conjugated diene polymer. On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 55-10434 discloses, during the production of a rubber composition for a tire tread comprising blending a starting rubber composed of an amorphous 1,2-polybutadiene and natural rubber and/or polyisoprene rubber (or additionally including a partially conjugated diene rubber) with carbon black, first mixing a starting rubber containing at least 25% by weight of the 1,2-polybutadiene and the carbon black in a specific ratio, then adding and mixing the remaining starting rubber so as to improve the fuel economy and safety of a car.
Further, Japanese Examined Patent Publication (Kokoku) No. 2-129241 proposes the improvement of the tensile strength and abrasion resistance of the vulcanizate by mixing a terminal-modified conjugated diene polymer with carbon black in an organic solvent.
DISCLOSURE OF INVENTION
The above-mentioned method of separate mixture of ingredients, use of terminal-modified rubber, and other technologies, however, had problems such as the only slight effect in a formulation with a large oil and carbon black content and therefore improvements continued to be demanded. In the case of divided mixing, the technique was only effective for specific combinations of rubbers and the range of possible use are limited. Further, when adopting the method of first mixing the terminal-modified rubber and carbon black and then later adding the emulsion polymerized polymer, while the tan .delta. balance was improved, there was still the problem that the abrasion resistance fell.
Accordingly, the objects of the present invention are to provide a rubber composition superior in the tan .delta. balance of the vulcanizate and a process for producing a rubber composition for a tire tread giving a vulcanizate with a superior tan .delta. balance and improved abrasion resistance.
In accordance with the present invention, there is provided a process for producing a rubber composition characterized by comprising mixing 100 parts by weight of (A) a starting rubber composed of 50 to 90 parts by weight of a starting rubber mixture containing 20 to 80% by weight of a terminal-modified and/or coupled diene rubber and 50 to 10 parts by weight of (B) a starting rubber composed of at least one terminal unmodified diene rubber with 50 to 120 parts by weight of a reinforcing agent and 20 to 80 parts by weight of a softening agent to produce the rubber composition, wherein the average glass transition temperature TgA (.degree. C.) of the starting rubber (A) and the average glass transition temperature TgB (.degree. C.) of the starting rubber (B) have the following relationship: amount of the reinforcing agent are mixed at a temperature of at least 135.degree. C., followed by adding the starting rubber (B), the remaining reinforcing agent and the softening agent.
In accordance with the present invention, there is further provided a process for producing a rubber composition characterized by comprising first mixing 20 to 90 parts by weight of (A') a starting diene rubber having a weight average molecular weight Mw(A') in the range of 100,000 to 1,200,000 with 50 to 120 parts by weight of a reinforcing agent, followed by adding 80 to 10 parts by weight of (B') a starting diene rubber
REFERENCES:
patent: 5834552 (1998-11-01), Kawazura et al.
Kaido Hiroyuki
Kawazura Tetsuji
Yatsuyanagi Fumito
The Yokohama Rubber Co. Ltd.
Warzel Mark L.
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