An aqueous emulsion latex-derived rubbery copolymer prepared by free radical polymerizing 100 parts by weight of a mixture comprising about 60 to about 95 weight percent of a diene selected from 1,3-butadiene and isoprene and, correspondingly, about 40 to about 5 weight percent of a comonomer selected from styrene and acrylonitrile, in the presence of about 2 to about 6 weight percent of a soap which comprises about 50 to about 100 weight percent of the sodium or potassium salt of an anhydride modified resin backbone characterized by having a softening point in the range of about 45.degree. to about 100.degree. C having a basic resin backbone of piperylene and methyl branched monoolefins.