BIAXIALLY HIGHLY ORIENTED POLYPROPYLENE FILM, PROCESS FOR ITS PRODUCTION AND USE THEREOF

摘要

The disclosed biaxially oriented propylene polymer film contains, in its single ply (or, if it is a multi-ply film, in its base ply) a low molecular weight resin, and the film has improved stretchability and other desirable physical properties, even though the propylene polymer of the sole or base ply is preferably a homopolymer. The n-heptane-insoluble fraction of the film has a chain isotaxy index, measured by means of l3C-NMR spectroscopy, of at least 85 to 94%. The sole or base ply contains less than 10% by weight of resin. The film is stretched in such a way that the product of tensile strength in the longitudinal and transverse direction is greater than 50,000 (N/mm2)2. The film is made by, amongother steps, carrying out the orientation in the longitudinal and transverse directions such that the product of the longitudinal stretching ratio and the transverse stretching ratio is