Patent ID: 6303233
Filing Date: 2001-10-16
Classification: B32B,Y10S,Y10T

Abstract:
A uniaxially heat-shrinkable, biaxially oriented, multilayer film having a polypropylene-containing core layer and at least one polyolefin-containing skin layer adjacent said core layer,said core layer comprising isotactic polypropylene, a modifier which reduces the crystallinity of the polypropylene-containing core layer and a nucleating agent,wherein said modifier is selected from the group consisting of atactic polypropylene, syndiotactic polypropylene, ethylene-propylene copolymer, propylene-butene-1 copolymer, ethylene-propylene-butene-1 terpolymer, polybutene-1, and linear low density polyethylene,further wherein said film is capable of greater than 15% shrinkage at 100.degree. C. to 145.degree. C. in a first direction with +/-5% stability in a second direction substantially perpendicular to said first direction and said nucleating agent is present in said core layer in an amount, based upon the entire weight of said core layer, sufficient to improve the long-term dimensional stability of said multilayer film,and still further wherein said film exhibits improved long-term dimensional stability by having a reduced rate of shrinkage, said rate of shrinkage being determined by measuring the shrinkage at a temperature of 60.degree. C. and expressing the rate of shrinkage as a slope of a line plotting percentage shrinkage versus logarithinic time, wherein the rate of shrinkage of said film is less than the rate of shrinkage of an identical film without said nucleating agent.