Abstract: An aqueous emulsion interpolymer composition capable of forming stable films which have excellent protective properties, especially on metallic substrates, good chemical resistance and/or permeability to water vapor, comprising particles suspended in an aqueous solution made by interpolymerizing an acrylic latex seed particle with a vinylidene chloride polymer comprising vinylidene chloride, one or more alkyl acrylates having from 1 to 18 carbon atoms in the alkyl group and/or one or more alkyl methacrylates having 1 to 18 carbon atoms in the alkyl group, one or more aliphatic alpha-beta-unsaturated carboxylic acids, and a copolymerizable surface active agent, the proportion of vinylidene chloride being 65 to 90 parts by weight, the portion of said alkyl acrylates and/or methacrylates being from 2 to 30 parts by weights, the portion of said carboxylic acids being from 0.1 to 20 parts by weight, and the portion of said copolymerizable surface active agent being from 0.1 to 5.0 parts by weight.