Patent ID: 7316848

Claim:
A multilayer, heat-sealable film including at least a first layer and a second heat-sealable layer, said second layer having a first surface adhered to said first layer and a second, opposed surface intended to be heat sealed to another surface, said first layer comprising a mixture of a polypropylene and a second polymer immiscible in said polypropylene, to provide a weakened interface between the first layer and the second heat-sealable layer, said polypropylene constituting over 50% by weight of the mixture, said second layer being free of polybutylene and being formed predominantly of polymers selected from the group consisting of propylene-ethylene copolymers, ethylene-propylene-butene-1 terpolymers and propylene-butene-1 copolymers wherein the propylene in the copolymers and terpolymers constitute over 50%, by weight, of such copolymers and terpolymers, said film with said second opposed surface of said heat-sealable layer heat sealed to said another surface having a peel strength of less than 250 g/in. with peel separation taking place at the interface between the second layer and the first layer and/or through said first layer, said peel strength being less than the peel strength of the second, opposed surface of said heat-sealable layer to said another surface to thereby maintain the seal integrity between said second heat-sealable layer and said another surface.