UNIAXIALLY SHRINKABLE BIAXIALLY ORIENTED POLYPROPYLENE FILM WITH HDPE SKIN

摘要

A UNIAXIALLY HEAT-SHRINKABLE, BIAXIALLY ORIENTED, MULTILAYER FILM HAVING A POLYPROPYLENE-CONTAINING CORE LAYER COMPRISING AT LEAST 70 WT OF SAID MULTILAYER FILM AND AT LEAST ONE POLYOLEFIN-CONTAINING SKIN LAYER ADJACENT SAID CORE LAYER IS PREPARED BY BIAXIALLY ORIENTING A COEXTRUDATE AND THEREAFTER ORIENTING SAID COEXTRUDATE BY STRETCHING 10 TO 40 IN THE MACHINE DIRECTION. THE CORE LAYER CONTAINS ISOTACTIC POLYPROPYLENE AND A MODIFIER WHICH REDUCES THE CRYSTALLINITY OF THE POLYPROPYLENE BY INCREASING CHAIN IMPERFECTIONS OR REDUCING ISOTACTICITY OF THE POLYPROPYLENE-CONTAINING CORE. SUCH MODIFIERS CAN BE SELECTED FROM THE GROUP CONSISTING OF ATACTIC POLYPROPYLENE, SYNDIOTACTIC POLYPROPYLENE, ETHYLENE-PROPYLENE COPOLYMER, PROPYLENE-BUTENE-1 COPOLYMER, ETHYLENE-PROPYLENE-BUTENE-1 TERPOLYMER, AND LINEAR LOW DENSITY POLYETHYLENE. THE SKIN LAYER CAN BE HIGH DENSITY POLYETHYLENE ON BOTH SIDES OR HIGH DENSITY POLYETHYLENE ON ONE SIDE AND ISOTACTIC POLYPROPYLENE ON THE OTHER SIDE.