Barrier resins and impact modifiers therefor

Claim 1

An impact modifier composition comprising a graft copolymer of (A) from 20 to 60 weight percent of a superstrate polymer polymerized from a monomer mixture comprising from 50 to 90 weight percent acrylonitrile, from 5 to 28 weight percent of vinylidene aromatic monomer of the formula ##STR2## wherein R 1 is hydrogen, chlorine or methyl and R 2 is a substituted or unsubstituted aromatic radical having from 6 to 10 carbon atoms and from 2 to 25 weight percent of an olefinic ester of the formula ##STR3## and (B) from 80 to 40 weight percent of a substrate polymer having a glass transition temperature of less than -40° C. comprising from 50 to 100 weight percent of a conjugated diene selected from the group consisting of 1,3-butadiene and isoprene, from 50 to 0 weight percent of an ethylenically unsaturated monomer selected from the group consisting of vinylidene aromatic monomer, acrylonitrile, and mixtures thereof, and from 0 to 10 weight percent of olefinic ester, provided that said superstrate polymer is at least about 50 percent grafted onto said substrate polymer.