| 摘要 |
In one of several methods of producing polybutadiene or a butadiene-styrene copolymer with an organolithium initiator, an organotin compound such as tetraallyltin, tetrabenzyltin and tetraphenyltin is added to the polymerization system in a period of growth of the polymer chain between a time immediately after a start of the polymerization to a time before an end of the polymerization. In another of the methods, tin tetrachloride or tin dichloride is added at an earlier time after a start of the polymerization. A polymer comprising a considerable amount of high molecular weight polymer containing the chain having a tin-carbon linkage is formed. A rubber composition for tires comprises specified amounts of the polymer described above, natural rubber, carbon black and vulcanizing agents. The rubber composition has a small loss factor and excellent fracture properties. The rubber composition provides a tire having excellent wear resistance, low rolling resistance and wet skid resistance without impairing fracture properties. In addition, the rubber composition is inexpensive.
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