MEHRSCHICHTIGE, BIAXIAL ORIENTIERTE POLYPROPYLEN-TRENNFOLIE, VERFAHREN ZUR HERSTELLUNG DER FOLIE UND IHRE VERWENDUNG.

摘要

A separating film (I) comprises a base layer of polypropylene (PP) and two outer covering layers of equal thickness, consisting of PP with 0.5-5 (pref. 1-3) wt.% polydiorganosiloxane (II) as anti -adhesive agent. (I) is produced by co-extrusion, biaxially orienting by stretching, and heat-hardening. (II) is a poly-di (1-4C alkyl)-siloxane (esp. -dimethyl-), with viscosity at least 100 (pref. 5000-50,000) mm2/sec. at 25 deg.C. The outer layers contain 1-20 (pref. 3-15) wt.% of an inorganic pigment (III). (I) is 15-20 (pref. 20-40) microns thick, with outer layers 0.5-5 (pref. 1-2) microns thick. Pref. (III) is BaSO4, CaCO3, silicate (e.g. Al), SiO2 or TiO2 of particle size pref. 0.2-2 microns. (I) is pref. stretched by 4 to 7:1 longitudinally and by 7 to 10:1 transversely.