Isoprene-butadiene diblock rubber

摘要

The subject invention discloses an isoprene-butadiene diblock rubber which is particularly valuable for use in making treads for tires which have improved wear characteristics without compromising traction characteristics or rolling resistance. Said isoprene-butadiene diblock rubber is comprised of (1) a first block which is comprised of repeat units which are derived from 1,3-butadiene and (2) a second block which is comprised of repeat units which are derived from both 1,3-butadiene and isoprene, wherein the repeat units derived from isoprene and 1,3-butadiene in the second block are in an essentially random order, wherein the diblock rubber has a glass transition temperature which is within the range of about -100 DEG C. to about -70 DEG C., and wherein the diblock rubber has a Mooney viscosity which is within the range of about 50 to about 140. In cases where the isoprene-butadiene diblock rubber of this invention is employed in automobile tires it will preferably have a second glass transition temperature which is within the range of about -50 DEG C. to about 0 DEG C. The Mooney viscosity will preferably be within the range of about 80 to about 135 and in the case of oil extended polymers will more preferably be within the range of about 100 to about 130 before oil extension.