STRETCHED AND VOIDED POLYMERIC FILM

摘要

There is described a simultaneously oriented polyolefinic (e.g. polypropylene) film comprising particles in at least one layer thereof, said particles incompatible with said layer to cause the initiation of voids therein when the cast polyolefin is stretched simultaneously in both the MD and TD, and where the particles comprise: (i) particles having a mean aspect ratio x/y of at least 2 (e.g. long and thin) and a mean size of the longest particle dimension greater than about 3 microns (preferably about 6 microns); and/or (ii) particles having a mean aspect ratio of about 1 (e.g. spherical or boulder-like), with a narrow size distribution, a mean particle size of from about 3 to about 10 microns, (preferably about 6 microns), and which are substantially free of particles above about 12 microns in size and optionally also substantially free of particles below about 3 microns in size. Preferred BOPP films are further characterised in that ratio of at least one of the following properties measured in the MD with respect to TD is: (a) tensile strength of above 0.5; (b) elongation at break of below 2.0; (c) Young's modulus of at least 0.7; and/or (d) shrinkage of at least 0.45,. the TD shrinkage being other than zero.