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US 4,333,968 AGranted
Thermoplastic packaging films with improved heat-seal characteristics
AssigneeMobil Oil Corporation
InventorA. Michael Nahmias
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Abstract
Biaxially oriented polypropylene films are extrusion coated with an ethylene-vinyl acetate copolymer coating to yield a coated film product exhibiting heat-seals which are peelable and which exhibit good heat-seal strengths.
Claims1
A method for producing coated biaxially oriented polypropylene film, said film being adapted for heat sealing in a manner whereby the seal may be peeled apart without damaging the film layers in the seal area, which comprises the sequential steps of:
- a. Extruding a polypropylene base film and orienting said film in the longitudinal direction;
- b. Extrusion coating at least one surface of said oriented film with a single layer of an ethylene-vinyl acetate copolymer coating to form a coated film, said copolymer containing from about 6% up to about 10% by weight vinyl acetate in said copolymer;
- c. Preheating said coated film at a heating rate of above about 5.degree. F. per second and below about 40.degree. F. per second;
- and
- d. Orienting the resultant preheated coated film in the transverse direction.
2 more elements
Dependencies are inferred from the claim text.