Tackified polyethylene layers in stretch/cling films
AssigneeExxon Chemical Patents Inc.
InventorsPatrick Brant, Paul M. German
Life of this patent
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Abstract
A thermoplastic film is provided which is especially suited for use in stretch/cling applications such as, for example, the bundling, packaging and unitizing of foods and other goods. The film comprises a cling layer comprising a polyethylene, preferably low density polyethylene (LLDPE) and a compatible tackifier. The LLDPE has a density of from about 0.87 to about 0.92 g/cc, a melt index of from about 1 to about 30 dg/min and a ratio of weight average molecular weight to number average molecular weight (M.sub.w /M.sub.n) less than about 6. The blend has a glass transition temperature of about 0.degree. C. or less. The film may be a one-sided cling film having a polyolefin slip layer opposite the cling layer.
Claims23
A stretch/wrap thermoplastic film, comprising:
- a cling layer comprising a blend of (i) polyethylene having a density of from about 0.87 to about 0.92 g/cc, a melt index of from about 0.1 to about 30 dg/min, and a ratio of weight average molecular weight to number average molecular weight (M.sub.w /M.sub.n) less than about 6, and (ii) a compatible hydrogenated cycloaliphatic hydrocarbon tackifier, said blend having a glass transition temperature of about -20.degree. C. to about 0.degree. C., said tackifier having a Tg of between about -50.degree. C. to about 50.degree. C.
A stretch/wrap thermoplastic film, comprising:
- a cling layer comprising a blend of linear low density polyethylene and from about 1 to about 30 weight percent of a compatible tackifier, said blend having a glass transition temperature less than about 0.degree. C.;
- said polyethylene having a density of from about 0.89 to about 0.905 g/cc, a melt index of from about 0.1 to about 30 dg/min, a ratio of weight average molecular weight to number average molecular weight (M.sub.w /M.sub.n) less than about 3 and less than about 1 percent cold hexane solubles;
- said tackifier having a glass transition temperature of between about -50.degree. C. to about 50.degree. C. wherein less than about 10 percent of hydrogen in said tackifier is aromatic;
- and
- a polypropylene slip layer opposite said cling layer essentially free of said tackifier.
A process for producing a thermoplastic film having a cling layer opposite a second layer, comprising the steps of:
- blending a linear low density polyethylene with a compatible aliphatic hydrocarbon tackifier to obtain a blend having a glass transition temperature of about 0.degree. C. or less, said polyethylene comprising a copolymer of ethylene and an .alpha.-olefin having from 3 to about 12 carbon atoms and having a density of from about 0.87 to about 0.92 g/cc, a melt index of from about 0.1 to about 30 dg/min, and a ratio of weight average molecular weight to number average molecular weight (M.sub.w /M.sub.n) less than about 6;
- and
- coextruding said blend with polypropylene to form a stretch/wrap film having a cling layer comprising said blend and a slip layer of said polypropylene.
Dependencies are inferred from the claim text.