A rubbery polymer comprising: (a) butyl acrylate or a mixture of butyl acrylate and 2-ethylhexyl acrylate, (b) at least one member selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate, and ethyl acrylate, (c) acrylonitrile, (d) styrene, (e) a half ester maleate soap, and (f) a crosslinking agent selected from allyl methacrylate, and mixtures of allyl methacrylate with glycidyl methacrylate, trimethylolpropanetrimethyl acrylate, dicyclopentenyloxyethyl methacrylate and divinylbenzene.