Blends of cyclodiene-containing copolymers and block copolymers having improved high temperature green tensile strength

Claim 1

A process for increasing the green tensile strength of a block copolymer represented by the formula Z(B-A) n wherein A is an essentially homopolymer block of a vinyl aromatic compound and B is selected from the group consisting of an essentially homopolymer block of a conjugated diene having from 4 to 8 carbon atoms and a random copolymer block of said conjugated diene and said vinyl aromatic compound wherein the weight ratio of said vinyl aromatic compound to said conjugated diene is in the approximate range of 1:4 to 4:1, Z is derived from a polyfunctional compound having 3 or 4 reactive sites, and n is an integer having a value of 3 or 4, which comprises incorporating therewith from 5 to 100 parts of a copolymer of cyclodiene per 100 parts of said block copolymer, wherein said copolymer of cyclodiene is prepared by polymerizing a mixture of (1) from 10 to 90 weight percent of a 1,3-cyclodiene compound having from 5 to 20 carbon atoms selected from the group consisting of 1,3-cyclohexadiene and substituted derivatives thereof represented by the formula ##STR4## and 1,3-cyclopentadiene and substituted derivatives thereof represented by the formula ##STR5## wherein in each of the above formulas each R is individually selected from the group consisting of hydrogen, methyl and ethyl, and each R' is individually selected from the group consisting of hydrogen, alkyl having from 1 to 6 carbon atoms, cycloalkyl having from 5 to 6 carbon atoms, phenyl and methylcyclopentyl, and (2) from 90 to 10 weight percent of at least one monomer selected from the group consisting of acyclic conjugated dienes having from 4 to 8 carbon atoms per molecule, vinyl-substituted aromatic compounds having from 8 to 14 carbon atoms per molecule, and mixtures thereof in which the weight ratio of said acyclic conjugated diene to said vinyl aromatic compound is in the approximate range of 99:1 to 1:99.