Adhesive compositions of a block copolymer and tackifying resin

Claim 1

A pressure sensitive adhesive which comprises a mixture of (a) an unvulcanized elastomeric block copolymer comprised of both non-elastomeric and elastomeric polymer blocks having the general configuration A -- B -- A wherein each A is an independently selected non-elastomeric styrene polymer block having an average molecular weight of 5000 to 30,000 and a glass transition temperature above about 25° C., the total block A content being from about 10 to about 50 percent by weight of the copolymer, and B is an elastomeric conjugated diene polymer block of 1,3-butadiene having an average molecular weight from about 50,000 to about 500,000 and a glass transition temperature below about 10° C., said copolymer having a tensile strenght at 25° C., in excess of about 200 pounds per square inch, prepared by first strength polymerizing sytrene with a lithium-based initiator to a polymer of molecular weight in the range of about 5,000 to about 30,000, followed by adding 1,3-butadiene and additional amounts of styrene to the polymerization mixture, and (b) about 20 to about 80 weight percent of a compatible, thermoplastic tackifying resin containing carbon-to-carbon unsaturation therein, based on the total tackifying resin and block copolymer, and characterized by having a softening point in the range of about 70° C. to about 110° C. consisting essentially of from about 30 to about 55 weight percent units derived from piperylene, from about 20 to about 45 weight percent units derived from 2-methyl-2-butene, from about 20 to about 35 weight percent units derived from dicyclopentadiene and from about 20 to about 35 weight percent units derived from α-methyl styrene prepared by the method which comprises polymerizing said monomers in the presence of aluminum chloride and a solvent selected from aliphatic hydrocarbons and steam stripping the resin product.