Coextrusion process for preparing a composite polymer film construction

Claim 1

In a coextrusion process for preparing a composite polymer film construction having polymers in the two surface layers which are fusion-bonded to each other by an intermediate polymer layer in which three polymer streams are fed into three channels of a film die, and the three polymer streams flow into the film die and are extruded to form an extrudate in which the three polymer streams form a film having three fusion-bonded layers, the improvement which consists of employing an ethylene polymer or an isotactic propylene polymer as the polymer to form each of the two surface layers and employing to form the intermediate polymer layer a polymeric composition consisting essentially of an intimate fusion blend of; a. 100 parts by weight of an ionomer resin, and b. about 5 to 900 parts by weight of an alkenyl succinic anhydride; said ionomer resin being a metal salt of an ethylene-acid copolymer which is a copolymer of ethylene and acrylic or methacrylic acid having an acid content of about 1-10 mol % and having a high load melt index of at least about 1.0 and a normal load melt index of up to about 50; and said alkenyl succinic anhydride having the structure: ##STR2## where R is an alkyl group containing about 13 to 49 carbon atoms.