• lene or ethylene with an alpha-olefin having 4 to 18 carbon atoms, or of ethylene or propylene with an acrylic monomer such as acrylic acid, methacrylic acid, acrylonitrile, methacrylonitrile or an ester of acrylic or methacrylic acid and an alkyl or substituted alkyl group having 1 to 16 carbon atoms, for example ethyl acrylate, methyl acrylate or butyl acrylate, or a copolymer with vinyl acetate