METHODS OF MAKING THICK, HIGHLY ORIENTED, OPAQUE, LOW-DENSITY, MICROPOROUS POLYOLEFIN FILMS AND THE FILMS MADE THEREBY

摘要

A method of making a polyolefin film in accordance with this invention includes the steps of: blending a propylene block copolymer with a beta nucleating agent; extruding a film layer from the blend and providing a total area draw ratio in excess of 20, where at least one part of the stretching occurs at < 120°C, for forming the film with a density no greater than 0.40g/cm³ and a thickness greater than 160 gauge. The film also constitutes a part of this invention.