BIAXIALLY ORIENTED POLYPROPYLENE FILM HAVING GOOD TEAR RESISTANCE

摘要

PROBLEM TO BE SOLVED: To provide a biaxially stretched polypropylene film excellent in tear resistance. SOLUTION: In a biaxially stretched polypropylene film having at least one base layer containing polypropylene, the average isotactic block length of polypropylene molecules between two structureal carbon chain defects exceeds 40 as a statistical average and the n-heptane insoluble fraction of polypropylene measured by a<13> C-NMR spectral method has at least 95% of a carbon chain isotactic index. The ratio of a wt. average mol.wt. Mw to a number average mol.wt. Mn is below 4 and the n-heptane soluble fraction of polypropylene is below 1% and the tear resistance in the longitudinal direction of the film is larger than 15N/mm (film thickness) and that in the lateral direction thereof is larger than 15N/mm (film thickness).