Uniaxially shrinkable biaxially oriented polypropylene film and its method of preparation

Abstract

A uniaxially heat-shrinkable, biaxially oriented, multilayer film having a polypropylene-containing core layer comprising at least 70 wt % of said multilayer film and at least one polyolefin-containing skin layer adjacent said core layer is prepared by biaxially orienting a coextrudate and thereafter orienting said coextrudate by stretching 10 to 40% in the machine direction. The core layer contains isotactic polypropylene and a modifier which reduces the crystallinity of the polypropylene by increasing chain imperfections or reducing isotacticity of the polypropylene-containing core. Such modifiers can be selected from the group consisting of atactic polypropylene, syndiotactic polypropylene, ethylene-propylene copolymer, propylene-butylene copolymer, ethylene-propylene-butylene terpolymer, and linear low density polyethylene. The skin layer can be selected from the group consisting of polypropylene, ethylene-propylene copolymer, polyethylene, and ethylene-propylene-butylene terpolymer.

Dependencies are inferred from the claim text.