Process for synthesizing styrene-isoprene rubber

Abstract

The subject invention relates to a technique for synthesizing rubbery copolymers of styrene and isoprene. These rubbery copolymers exhibit an excellent combination of properties for utilization in tire tread rubber compounds. By utilizing these styrene-isoprene rubbers in tire treads, tires having improved wet skid resistance can be built without sacrificing rolling resistance or tread wear characteristics. This invention more specifically discloses a process for the synthesis of styrene-isoprene rubbers which exhibit essentially a single glass transition temperature and which are particularly useful in tire tread rubber compounds, said process comprising copolymerizing a monomer mixture containing from about 2 weight percent to about 15 weight percent styrene monomer and from about 85 weight percent to about 98 weight percent isoprene monomer in an organic solvent in the presence of a catalyst system which is comprised of (a) a lithium initiator and (b) a modifier having the structural formula: ##STR1## wherein n represents an integer within the range of 3 to 6, wherein R represents an alkyl group containing from 1 to about 10 carbon atoms, and wherein the molar ratio of the modifier to the lithium initiator is within the range of 2:1 to 40:1.

Dependencies are inferred from the claim text.