Multilayer high clarity shrink film comprising monovinylarene-conjugated diene copolymer

Abstract

We disclose a shrink film comprising a first layer comprising a monovinylarene-conjugated diene copolymer; a second layer comprising low density polyethylene (LDPE) and linear low density polyethylene (LLDPE); and a third layer comprising a monovinylarene-conjugated diene copolymer; wherein the second layer is disposed between the first layer and the third layer. We also disclose methods of using the shrink film to prepare bundled or fully enclosed groups of objects.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates generally to the field of monovinylarene-conjugated diene block copolymers. More particularly, it concerns multilayer shrink films comprising such copolymers and polyethylenes. [0002] A variety of shrink films have been available for the packaging industry. In bundling a group of objects, a film is wrapped around the group of objects and then heat is applied, typically in a heat tunnel, and the film shrinks, unitizing the contents and providing rigidity and protection during handling. In bundling a group of objects, the film used generally only substantially shrinks in one direction, and thus the ends of bundled packages are only enclosed by the shrinking of the loose film edges, which produces what the industry calls a “bullseye.” Also known is fully enclosing a group of objects, which involves generally the same technique, with a difference in using a film which generally shrinks in both directions. [0003] Films know...

AI Technical Summary

Benefits of technology

[0009] In one embodiment, the present invention relates to a shrink film comprising a first layer comprising a monovinylarene-conjugated diene copolymer; a second layer comprising low density polyethylene (LDPE) and linear low density polyethylene (LLDPE); and a third layer comprising a monovinylarene-conjugated diene copolymer; wherein the second layer is disposed between the first layer and the third layer.

Problems solved by technology

Films known commercially for bundling a group of objects or fully enclosing a group of objects include monolayer polyethylene (PE) films, which have limitations of clarity and gloss due to the nature of the polyethylene molecule.

However, LDPE films do not have sufficient strength and puncture resistance for some packaging applications.

An LDPE+LLDPE film generally has increased strength relative to an LDPE film, but often have reduced clarity and shrink.

The increased strength of an LDPE+LLDPE film has allowed reductions in the thickness of the films, which may improve clarity and reduce film costs, but reduces film stiffness.

While an LDPE+LLDPE+HDPE film does have increased stiffness relative to an LDPE+LLDPE film, it generally has both lower clarity and lower gloss.

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