RUBBER COMPOSITION FOR TIRE TREAD

A rubber composition for tire tread is disclosed, which is prepared by compounding specific amounts of carbon black, white carbon and sulfur in a mixed rubber component of styrene-butadiene copolymer rubber obtained by emulsion polymerization wherein the amount of bound styrene is 30 to 40 wt %, wherein the amount of isolated styrene (S1) based on total bound styrene amount is 58 % or more, and wherein sum of isolated styrene (S1) and styrene chain composed of two styrene units (S2) based on total bound styrene amount is 87.5 % or more, preferably mixed with a styrene-butadiene copolymer rubber obtained by solution polymerization wherein the amount of bound styrene is 10 to 20 wt %, wherein the amount of isolated styrene (S1) based on total bound styrene amount is 80 % or more, and wherein a sum of the bound styrene and bound vinyl amount in butadiene moiety is 70 wt % or less. When used as tire tread, this composition reduces temperature dependence of hardness of the tire tread surface, prevents sticking and adhesion of rubber tailings, and markedly improves driving stability and gripping properties in driving in winter.