Process for the preparation of blown film

Claim 1

Process for the preparation highly oriented blown film from polymer composition, said process comprising: melting (1) a polyethylene homopolymer having a density 910-940 kg/m 3 , or (2) a copolymer of ethylene with up to 10% by weight of a polar comonomer, or (3) mixtures of (1) and (2), or (4) mixtures of (1) and (2) with up to 50% by weight of polyethylene with a density less than 940 kg/m 3 , copolymers of ethylene with C 3 to C 15 alkene monomer, or propylene; (5) mixtures of at least 70% by weight polyethylene homo- and/or copolymers having a density of 910-940 kg/m 3 with low density polyethylene copolymers (density less than 940 kg/m 3 ), high density of polyethylene (with a density in excess of 940 kg/m 3 ) and/or polypropylene; the polymer having a melt index of from 7-25 dg/min; extruding said molten polymer through an annular die and forming a balloon film product of said polymer by force of a gas applied to an opening in said die, said annular die having a die gap of at least 2 mm, and the molten polymer having a temperature below 160° C. at said die gap; and cooling, flattening and rolling up said balloon; wherein said film product exhibits an X-ray diffraction analysis of the 110 reflection band having (a) a maximum to minimum intensity ratio of at least 20, and (b) angle α of at most 20° between the average orientation direction of the polymer molecules and the film extrusion direction.