Heat resistant heat shrinkable films

Claim 1

A heat shrinkable oriented three layer film, wherein said film comprises a first heat sealable layer of ionomer having two surfaces, a second layer of a vinylidene chloride copolymer having two surfaces, and having one of said surfaces on said second layer on one said surface of said first layer, and a third outer layer on the other said surface of said second layer, the composition of said third layer being a blend of an ionomer and an ethylene vinyl acetate copolymer, the ethylene copolymer content of said blend being no greater than 20% by weight, the vinyl acetate content of said ethylene vinyl acetate copolymer being at least 22%, and the vinyl acetate content of said blend being at least 4.5% by weight, said film having been made by the process of: (a) coextruding a three layer tubular tape having a first inner layer of an ionomer, a second layer of a vinylidene chloride copolymer, and a third layer of a blend of an ionomer and an ethylene vinyl acetate copolymer, wherein the ethylene vinyl acetate copolymer content of said blend is no greater than 20% by weight, the vinyl acetate content of said ethylene vinyl acetate is at least 22%, and the vinyl acetate content of said blend is at least 4.5% by weight; (b) cooling said tape below the crystalline melting temperatures of each of the three layers; (c) reheating said tape to a temperature of about 195° to 205° F.; and (d) orienting said tape to form a film by blowing a bubble in the reheated tape and providing an appropriate draw to the film to provide an oriented film having normally balanced shrink properties, the free shrink of said film at 160° F. being about 20% to 26% and at 180° F. being about 42% to 45%, the shrink force of said film at 160° F. being about 160 to 219 grams per inch and at 180° F. being about 160 to 188 grams per inch.