Sealable, transparent polyolefinic multilayer film
AssigneeHoechst Aktiengesellschaft
InventorsGunther Crass, Lothar Bothe, Siegfried Janocha
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Abstract
A sealable, transparent polyolefinic multilayer film composed of a polypropylene base layer, a non-sealable surface layer, and a sealable surface layer, and process therefor. The sealable surface layer has a low minimum sealing temperature and is made from a copolymer of propylene and ethylene or butene-1 units and/or a terpolymer of ethylene, propylene and butene-1 units. The non-sealable layer is a combination of a propylene homopolymer, a slip agent, and an anti-blocking agent. The process includes coextruding the three layers, biaxially stretching the coextruded film, and subjecting the non-sealable layer to a corona-discharge treatment.
Claims18
A sealable, transparent polyolefinic multilayer film, comprising:
- a polypropylene base layer;
- a sealable surface layer disposed on one surface of said base layer and comprising an ethylene-propylene-butene-1 terpolymer and a propylene-butene-1 copolymer, corresponding to a content of from about 0.1% to about 7% by weight of ethylene, from about 53% to about 89.9% by weight of propylene and from about 10 to about 40% by weight of butene-1, based on the total weight of the olefin resin composition;
- and
- a non-sealable surface layer disposed on the other surface of said base layer and comprising from about 96.5% to about 99.6% by weight of a propylene homopolymer, from about 0.3% to about 2.5% by weight of a slip agent, and from about 0.1% to about 1.0% by weight of an anti-blocking agent.
A process for preparing a sealable, transparent polyolefinic multilayer film, comprising the steps of:
- coextruding a base layer and a separate surface layer on each side of said base layer to form the multilayer film, one of said surface layers being sealable and the other of said surface layers being non-sealable;
- biaxially stretching said multilayer film in longitudinal and transverse directions;
- and
- subjecting said non-sealable surface layer to a corona-discharge treatment;
- wherein said base layer is a polypropylene, said sealable surface layer comprises an ethylene-propylene-butene-1 terpolymer and a propylene-butene-1 copolymer, corresponding to a content of from about 0.1% to about 7% by weight of ethylene, from about 53% to about 89.9% by weight of propylene and from about 10 to about 40% by weight of butene-1, based on the total weight of the olefin resin composition;
- and said non-sealable surface layer comprise from about 96.5% to about 99.6% by weight of a propylene homopolymer, from about 0.3% to about 2.5% by weight of a slip agent, and from about 0.1% to about 1.0% by weight of an anti-blocking agent.
Dependencies are inferred from the claim text.