Rubber composition for tire tread

Abstract

A rubber composition comprising 40 to 100 parts by weight of carbon black per 100 parts by weight of a rubber component, (a) the rubber composition being characterized in that the rubber component contains, in 100 parts by weight thereof, at least 20 parts by weight of a block copolymer prepared by solution polymerization and comprising one unit of butadiene rubber portion and one unit of random-copolymerized styrene-butadiene rubber portion, the butadiene rubber portion having a vinyl content of 15 to 50%, the styrene-butadiene rubber portion having a vinyl content of 20 to 70% and a styrene content of 30 to 60%, the block copolymer having in its entirety a vinyl content of 15 to 60% and a styrene content of 5 to 30% at least 40% of the copolymer being coupled with a tin compound so that the coupled copolymer has a butadiene rubber terminal, the coupled copolymer having only a single Tg at a temperature of up to -60.degree. C., 0 to 80 parts by weight of natural rubber, synthetic polyisoprene rubber, synthetic polybutadiene rubber, synthetic styrene-butadiene rubber, modified products of thers rubbers, or mixtures thereof; (b) the rubber composition being further characterized in that the carbon black has a specific surface area value (N.sub.2 SA) withinthe range of 75 ot 105 as determiend by the nitrogen adsorption method and is at least 15 in the difference between N.sub.2 SA and the iodine adsorption value (IA) thereof, up to 5 in the difference between N.sub.2 SA and the specific surface area valve (CTAB) thereof as determined by the cetyltrimethylammonium bromide adsorption method, 90 to 110 in tint strength and up to -3 in the measured tint strength minus the calculated tint stength (.DELTA.tint).

Dependencies are inferred from the claim text.