Three-layered polypropylene films

Details Three-layered polypropylene films Three-layered polypropylene films

1979-10-01

1980-11-25

Lesmes, George F.

Envelopes, wrappers, and paperboard boxes

Wrapper

Bottle

428215, 428 35, 428516, 229 35R, 229 48T, B32B 702

Patent

active

042353653

ABSTRACT:
This invention relates to a three-layered polypropylene film consisting of a core layer of biaxially oriented polypropylene sandwiched between ethylene-propylene copolymer layers having a different degree of molecular orientation, shown by birefringence, i.e., birefringence of one copolymer layer is different from that of the other copolymer layer. The film thus prepared has not only a good heat sealing property but also a good resistance against "hot-tack", "blocking", and "scratches". The film can be provided by a process wherein one copolymer layer is biaxially stretched, while the other copolymer layer is uniaxially stretched. Three-layered films of this invention are particularly suited for making bags with lap sealed parts, where lap sealing is a heat sealing method characterized by heat sealing one side of a film with the other side of the film.

REFERENCES:
patent: 3508944 (1970-04-01), Henderson
patent: 3540979 (1970-11-01), Hughes
patent: 3620825 (1971-11-01), Lohmann
patent: 3671383 (1972-06-01), Sakata et al.
patent: 3887745 (1975-06-01), Yoshii et al.

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