| 摘要 |
<p>Biaxially oriented polypropylene (BOPP) film with at least one base layer (A) contg. polypropylene (PP) is claimed, in which (a) the isotactic block length between two structural defects is more than 40 (statistical average), (b) the n-heptane-insol. component of the PP has an isotacticity (by <13>C-NMR spectrometry) of at least 95%, (c) the mol. wt. ratio Mw/Mn is less than 4, (d) the PP contains less than 1% n-heptane-soluble component, and (e) the base layer has elastic moduli of more than 2400 and more than 4800 N/mm<2> in the machine (longitudinal) and transverse directions respectively. Also claimed is a process for the prodn. of this BOPP film, by heating, compressing and melting the polymers for the different layers in extruders, combining the different melts, extruding through a sheet die, cooling and compacting the film on a take-off roll, and orienting the film by stretching in the machine direction by a factor of (3:1)-(9:1) and in the transverse direction by a factor of (4:1)- (12:1).</p> |
