Biaxially and monoaxially oriented polypropylene cold seal release film
AssigneeBorden, Inc.
InventorAndrew F. Wilkie
Life of this patent
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Abstract
The invention presents a new use for modified polypropylene films, wherein the films are cold sealable for heat sensitive packaging operations. In a preferred embodiment, the film comprises a laminate having at least one cold seal release layer and a cold seal receptive layer such that when the release layer is adjacent a cold seal cohesive on the cold seal receptive layer, the release layer and the cold seal receptive layer exhibit remarkably low adhesion. Typical cold seal materials include natural and synthetic rubber latex cohesives.
Claims22
A component of a packaging laminate film, said component having improved cold seal release properties, which comprises a core layer selected from the group consisting of homopolymer isotactic polypropylene, ethylene-propylene random copolymer, and ethylene-propylene block copolymer, and a cold seal release layer on one side of said core, said laminate having a cold seal cohesive on an outer surface of said laminate on a side of the core opposite said cold seal release layer, wherein said cold seal release layer comprises 50 to 80 weight percent of ethylene-propylene random copolymer, wherein the ethylene content of the random copolymer is 2 to 6 weight percent, and wherein the cold seal release layer further comprises 20 to 50 weight percent of a polybutylene-ethylene copolymer, wherein the ethylene content in the polybutylene-ethylene copolymer is about 0.5 to 2.5 weight percent.
A method of packaging an article, said method comprising providing, as roll stock, a laminate film wherein said film comprises a core layer selected from the group consisting of homopolymer isotactic polypropylene, ethylene-propylene random copolymer, and ethylene-propylene, ethylene-propylene block copolymer, and a cold seal release skin layer comprising 50 to 80 weight percent of ethylene-propylene random copolymer, wherein the ethylene content of the random copolymer is 2 to 6 weight percent, and wherein the skin layer further comprises 20 to 50 weight percent of a polybutyleneethylene copolymer, wherein the ethylene content is at least about 0.5 weight percent, said skin layer, when in roll stock form, being adjacent a cold seal cohesive, wherein said method comprises the steps:
- (a) unrolling the laminate film,
- (b) positioning the laminate film around an article to be packaged, wherein the cold seal cohesive of the film at least partially overlaps itself;
- (c) applying sufficient pressure to the overlapped portion of the film at a temperature below about 150.degree. F. to thereby seal said film to itself.
Dependencies are inferred from the claim text.