Japan Synthetic Rubber Co., Ltd.

Bridgestone Tire Company Limited

Yoshito Yoshimura

Noboru Oshima

Isamu Shimizu

Seisuke Tomita

Tatsuo Fujimaki

Yasumasa Takeuchi

Mitsuhiko Sakakibara

Kazuo Yamamoto

Shinsuke Yamaguchi

Akira Tsuji

Noboru Ohshima

Tomoharu Yamada

Kunihiko Muramori

A branched styrene-butadiene copolymer and a pneumatic tire using the same as a tread base rubber are disclosed. This copolymer is produced by coupling an active styrene-butadiene copolymer anion, which is obtained by polymerizing styrene and butadiene in a hydrocarbon solvent in the presence of ether or a tertiary amine and an initiator of an organolithium compound, with a tin halide compound. In the copolymer, the ratio of branched copolymer connected with tin-butadienyl bond is at least 20% by weight, and the content of bound styrene is not less than 3% by weight but less than 25% by weight, and the content of vinyl bond in butadiene portion is not less than 30% but less than 50%.

Tire tread comprised of branched styrene-butadiene copolymers

An alkenyl aromatic compound-conjugated diene block copolymer having a combined alkenyl aromatic compound content of 25-95% by weight, characterized in that said copolymer is represented by the formula,

Alkenyl aromatic compound-conjugated diene block copolymer and process

A butadiene-base polymer containing a branched polymer through tin-carbon bond and a process for producing the same are disclosed. The butadiene-base polymer is produced by polymerizing 1,3-butadiene alone or 1,3-butadiene and aromatic vinyl compound in a hydrocarbon solvent in the presence of a Lewis base using an organolithium compound as an initiator and then coupling with a tin halide, and satisfies the following requirements:

Butadiene-base polymer and a process for producing the same

Branched styrene-butadiene copolymers and pneumatic tires using the same

A styrene-butadiene copolymer having a high styrene content is disclosed, which is obtained by polymerizing styrene and butadiene in a hydrocarbon solvent in the presence of an organolithium compound and, if necessary, a Lewis base and then coupling with a tin halide compound. This copolymer contains in its main chain at least 30 wt % of polymer having a tin-carbon bond and has a bound styrene content of more than 25 wt % but not more than 60 wt % and a content of vinyl bond in butadiene portion of not less than 30% but less than 50%.

Styrene-butadiene copolymers with high styrene content

High vinyl polybutadiene or styrene-butadiene copolymer obtained by polymerizing 1,3-butadiene alone or with styrene in a hydrocarbon solvent using an organolithium compound as an initiator and coupling the resulting polymer, characterized in that

High vinyl polybutadiene or styrene-butadiene copolymer

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Yokkaichi, Japan

Yoshito Yoshimura