Laminar thermoplastic film constructions
AssigneeMobil Oil Corporation
InventorsEdward M. Bullard, Gregory M. Smith
Life of this patent
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Abstract
Laminar thermoplastic film constructions comprising a layer of low density polyethylene bonded to a layer of a dissimilar polymer blend comprising high density polyethylene and polyethylene copolymers. In particular such copolymers comprise polyethylene copolymerized with another alpha olefin containing from about 3 up to about 15 carbon atoms. Such copolymers are also characterized by being linear, low density polymers having densities which are below about 0.94 grams/cc.
Claims2
A method of forming a laminar film structure comprising, coaxially coextruding in a blown film process from concentric tubular die orifices separate molten streams of:
- (a) at least one layer comprising a general purpose low density polyethylene resin with;
- (b) a second thinner layer comprising a resinous blend of (1) a high density polyethylene and (2) a linear low density polyethylene-alpha-olefin copolymer, wherein said blend contains a major amount of said copolymer;
- merging said streams outside of said die orifices;
- and subjecting said coextruded tubular streams to an internal pressure trapped within the tube so as to effect a blow-up ratio of from about 1.5:3.0:1 and thereafter cooling the molten resins, said low density polyethylene having a thickness on the order of from about 65% up to about 85% of the overall thickness of said laminate.
Dependencies are inferred from the claim text.