| abstract |
A rubber composition which can be used for tires or the like. The rubber composition comprises a high-molecular-weight polymer component which contains bound styrene in an amount not greater than 30% by weight, is a styrene-buta- diene copolymer or a conjugated diene polymer such as poly-butadiene, and has a weight-average molecular weight of at least 30 x 10 4 ; and a low-molecular-weight polymer component which contains bound styrene in an amount not greater than 30% by weight, is a styrene-butadiene copolymer or a conju- gated diene polymer such as polybutadiene, and has a weight-average molecular weight of from 0.2 x 10 4 to 8 x 10 4 . The rubber composition contains 30 parts by weight of the low-molecular-weight polymer component relative to 100 parts by weight of the high-molecular-weight polymer component. The ratio between the amount of bound styrene and the vinyl linkage content falls within specific ranges. When the vulcanized rubber composition was extracted by chloroform, an amount of the extract is not less than 15 % by weight of the low-molecular-weight polymer component. |