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Abstract

An elastomeric butadiene copolymer prepared by a process which comprises copolymerizing butadiene, a polyvinyl aromatic compound and optionally styrene in a hydrocarbon solvent in the presence of an organolithium polymerization initiator and subjecting the resulting copolymer having lithium at the polymer end or ends to a coupling reaction with a trifunctional or tetrafunctional coupling agent, said butadiene copolymer satisfying the following conditions: (a) the content of styrene is at most 50% by weight, (b) the content of vinyl bonds in the butadiene portion is from 10 to 90% by weight, (c) the molecular weight distribution curve obtained by a high performance liquid chromatography has at least three peaks, and 5 to 60% by weight of all the polymer chains have a molecular weight which is at least 5 times the molecular weight in terms of standard polystyrene corresponding to the peak appearing on the lowest molecular weight side of the high performance liquid chromatogram, and (d) the Mooney viscosity (ML.sub.1+4, 100.degree. C.) is from 30 to 200. The butadiene copolymer has an improved processability with excellent resilience, wet grip property, abrasion resistance and mechanical properties, and is suitable for tire use.

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