Importance

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Abstract

An unbalanced polymeric film has a plurality of adjacent molecularly oriented layers. The first, second, and third layers are molecularly oriented, and are, respectively (1) polypropylene, (2) anhydride modified polypropylene and (3) a barrier layer of either ethylene vinyl alcohol or nylon or a blend of ethylene vinyl alcohol and nylon. A fourth layer is optionally oriented and serves as a heat sealable layer having good adhesion to the barrier layer. In a more sophisticated structure, the fourth layer is oriented and serves an adhesive layer between the barrier layer and a fifth sealant layer. The fifth layer is then optionally oriented. A process for making the films comprises heating the exterior surfaces of the two surface layers to a temperature between 10.degree. and 100.degree. F. below the respective heat sealing temperature of each of the respective surface layers, stretching the so-heated film, annealing the stretched film, and cooling the annealed film.

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First Claim