Heat Sealable And Peelable Film
Published January 8, 2008
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Patented is a multilayer, heat-sealable film including at least a first layer and a second heat-sealable layer. The second layer has a first surface adhered to the first layer and a second, opposed surface is intended to be heat sealed to another surface. The first layer comprises a mixture of a polypropylene and a second polymer immiscible in the polypropylene, to provide a weakened interface between the first layer and the second heat-sealable layer. The polypropylene constitutes more than 50% by weight of the mixture. The second layer is free of polybutylene and is formed predominantly of polymers selected from the group consisting of propylene-ethylene copolymers, ethylene-propylene-butene-1 terpolymers and propylene-butene-1 copolymers. The propylene in the copolymers and terpolymers constitute more than 50%, by weight, of such copolymers and terpolymers. The film with the second opposed surface of the heat-sealable layer is heat sealed to another surface having a peel strength of less than 250 grams per inch. Peel separation takes place at the interface between the second layer and the first layer and/or through the first layer. The peel strength is less than the peel strength of the second, opposed surface of the heat-sealable layer to the other surface. This maintains the seal integrity between the second heat-sealable layer and the other surface.