Polymeric film

Abstract

a film formed from a copolyme of ethylene and at least one mono-.alpha.-olefine has a combination of impact strength and stiffness which is such that the function ##EQU1## IS AT LEAST 750. The function is preferably at least 1000 and may be several thousands. The film may also have a high tear strength and good tensile strength.The copolymer from which the film is formed is preferably one in which the comonomer contains at least 5 carbon atoms; the comonomer conveniently contains not more than 12 carbon atoms. The comonomer content of the polymer is typically in the range from 6.5 up to 30%, by weight.The film can be produced by a tubular film technique using a temperature of 170.degree.-300.degree. C, a circumferential expansion of 1.2 to 10.0 times and a draw down of 2.5 to 50 times. The production of the polymeric film can include extruding the ethylene copolymer through an annular dye, maintaining the dye temperature in the range from 170.degree.-300.degree. C, blowing the exudate to give a circumferential expansion of from 1.2 up to 10.0 times and drawing the exudate to give a draw down of from 2.5 up to 50 times.

Description