Composition for pneumatic tires

摘要

A composition for pneumatic tires including more than 30% of star shaped styrene-butadiene copolymers by solution polymerization with or without one or more types of natural rubbers or diene series synthetic rubbers. The composition value X of the solution polymerization star shaped SBR is obtained by the following equation. wherein BR is the butadiene component and the vinyl content is the content of 1, 2 bonded butadiene in butadiene component. The value X falls in the range of the lower limit of 26 to the upper limit of 39. And the coupling efficiency of the solution polymerization star shaped SBR is more than 40%.