초록 ▼

Disclosed is a multi-layer, heat shrinkable, thermoplastic packaging film which can be heat sealed to itself to provide strong seals at pasteurizing temperatures. The preferred film has four layers including, in order, a sealing surface layer comprising a blend of propylene-ethylene copolymer and (b

Disclosed is a multi-layer, heat shrinkable, thermoplastic packaging film which can be heat sealed to itself to provide strong seals at pasteurizing temperatures. The preferred film has four layers including, in order, a sealing surface layer comprising a blend of propylene-ethylene copolymer and (butene-1)-ethylene copolymer, a layer comprising ethylene-vinyl acetate copolymer which may be cross-linked to further increase high temperature strength of the film as desired; a relatively gas impermeable layer comprising a copolymer of vinylidene chloride; and, a surface layer of the same blend as the sealing layer. Receptacles such as end seal and side seal bags can be made from the film at a faster rate than with prior art films and these receptacles have the high temperature seal qualities of propylene polymers and the hot water shrink capabilities of ethylene polymers.

대표청구항 ▼

A multi-layer, heat shrinkable, thermoplastic packaging film which will produce heat selas having improved seal strength immediately after initially being heat sealed to itself comprising: (a) a first or surface layer consisting essentially of a blend wherein one constituent of the blend is selected

A multi-layer, heat shrinkable, thermoplastic packaging film which will produce heat selas having improved seal strength immediately after initially being heat sealed to itself comprising: (a) a first or surface layer consisting essentially of a blend wherein one constituent of the blend is selected from the group consisting of propylene homopolymers and copolymers and the other constituent of the blend is selected from the group consisting of butene-1 homopolymers and copolymers; (b) a second layer comprising a polymer selected from the group consisting of ethylene homoplymers and copolymers, said layer being heat shrinkable; (c) a third or low gas transmission layer comprising a polymer selected from the group consisting of vinylidene chloride copolymers and hydrolyzed ethylene-vinyl acetate copolymers; and, (d) a fourth or outer surface layer comprising a blend selected from the group of blends as specified for the first layer. A process for making a multi-layer, heat shrinkable, thermoplastic packaging film which will produce heat seals having improved seal strength immediately after being heat sealed to itself comprising the steps of: (a) coextruding first and second polymeric layers, the first layer consisting essentially of a blend selected from the group consisting of (1) propylene homopolymers and copolymers and (2) butene-1 polymers and copolymers and the second layer comprising a polymer selected from the group consisting of ethylene polymers and copolymers; (b) irradiating said coextruded layers to a dosage level of at least 2 MR; and, (c) after the irradiation step has been completed, joining a third layer of polymeric material to the second layer and a fourth layer to the third layer.