W. R. Grace & Co., Cryovac Div.

W. R. Grace & Co., Cryovac Division

Johnnie J Walters

Norman D Bornstein

Henry G Schirmer

Timothy T Oberle

Philip T Voso

Karl N Caldwell

A heat sealing layer is provided for multiply tubular film preferably of the type having an inner shrink layer of an irradiatively cross-linked ethylene vinyl acetate copolymer, a core barrier layer of vinylidene chloride-vinyl chloride copolymer, and an outer abuse layer of an ethylene vinyl acetate copolymer, the sealing layer being melt bonded onto the shrink layer and being composed of a propylene ethylene random copolymer. Heat seals formed in making bags from the improved film demonstrate enhanced high temperature strength and grease resistance. An associated method for making the tubular film is also provided.

Tubular film having sealing layer of propylene ethylene random copolymer

A pasteurizable and/or cook-in shrink film is provided that includes a first or sealing layer of a nonlipophillic polymeric material having a softening point greater than that of the following shrink layer; a second or shrink controlling layer, melt bonded to the first layer, of an ethylene homopolymer or copolymer; a third or adhesive layer, melt bonded to the second layer, of a chemically modified polyethylene being irradiatively cross-linkable and having functional groups with a relatively strong affinity for the following barrier layer; a fourth or barrier layer, melt bonded to the third layer, of a hydrolyzed ethylene-vinyl acetate copolymer; a fifth or adhesive layer as in said third layer, melt bonded to the fourth layer; and a sixth or abuse layer, melt bonded to the fifth layer. An associated method for making the film is also provided that includes full coextrusion and selective irradiation and orientation.

Pasteurizable, cook-in shrink film

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.

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Greer, SC, United States of America

Johnnie J Walters