. . . "Examples of other ethylenic unsaturated compounds to be copolymerized with acrylonitrile are vinyl and vinylidene halides, ethylenic unsaturated carboxylic acids and salts thereof, acrylates and methacrylates, vinyl esters, unsaturated hydrocarbon sulfonic acids and salts thereof, vinyl compounds such as styrene and alkylated or halogenated compounds thereof and vinyl compounds containing a basic" .