| 摘要 |
PROBLEM TO BE SOLVED: To obtain a polybutadiene having a high melting temperature and improved syndiotacticity by polymerizing 1,3-butadiene in the presence of a chromium compound soluble in a hydrocarbon solvent, an organomagnesium compound, a cyclic hydrogenphosphorous ester, and a molecular weight modifier. SOLUTION: A chromium compound soluble in a hydrocarbon solvent is combined with an organomagnesium compound in a molar ratio of 2:1 to 50:1 and a cyclic hydrogenphosphorous ester of the formula (wherein R is a 2-20C optionally substituted alkylene or arylene) in a molar ratio of the chromium compound to the ester of 1:5 to 1:25 to obtain a catalyst composition. 1,3-Butadiene is polymerized at -10 to 100 deg.C desirably, 20-90 deg.C in a hydrocarbon solvent in the presence of 0.01-1 pt.wt., desirably, 0.05-0.5 pt.wt., per 100 pts.wt. 1,3-butadiene, molecular weight modifier to obtain a syndiotactic 1,2-polybutadiene having a melting temperature of 120 deg.C or above and a syndiotacticity of 70% or above.
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