| 摘要 |
PROBLEM TO BE SOLVED: To obtain a polybutadiene rubber useful for base tread, sidewall, etc., of a tire by including a specific boiling n-hexane-insoluble component and a boiling n-hexane-soluble component at a specific ratio. SOLUTION: The objective rubber contains (A) 10-25 wt.% component insoluble in boiling n-hexane and composed mainly of 1,2-polybutadiene having a reduced viscosity of 0.5-4 and (B) 90-75 wt.% component soluble in boiling n- hexane and composed mainly of a high-cis polybutadiene satisfying the formula t-cp>4ML (t-cp is viscosity of toluene solution; ML is Mooney viscosity at 100 deg.C). The rubber can be produced by polymerizing butadiene using a catalyst obtained by aging a compound of a group III metal of the periodic table, an alkylaluminum hydride compound and butadiene, etc., and further polymerizing butadiene in the presence of the obtained polymer solution and a syndiotactic 1,2-polymerization catalyst.
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