ELASTOMER FILM, METHOD AND APPARATUS FOR PRODUCING SAME AND COMPOSITE FILM CONTAINING SAME

摘要

An elastomer film of a thermoplastic elastomer composition comprising 30-70 weight % of an ethylene-propylene-diene copolymer and 70-30 weight % of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 5-30 weight % and a melt index of 0.2-25 g/10 minutes, the elastomer film having a thickness of 10-6 .mu.m, and a draw ratio expressed by a heat shrinkage ratio at 50.degree.C which is 5-35% in an MD direction and 525% in a TD direction, a ratio of the draw ratio in an MD direction to the draw ratio in a TD direction being 3 or less, is produced by an air-cooled inflation method comprising the steps of (a) extruding the thermoplastic elastomer composition from an annular die at a temperature of 170.degree.C or lower; (b) taking up a bubble of the elastomer film such that a neck portion of the bubble is 1.0-4.0 times as long as a diameter of the annular die; (c) cooling the neck portion to a temperature of 120.degree.C or lower by a cooling air ejected from a first cooling ring disposed near the annular die; (d) drawing the bubble both in an MD direction and in a TD direction in a bubble transition portion between the neck portion and a frost line, while lowering the temperature of the bubble in the frost line to 45.degree.C or lower; (e) cooling the bubble to a temperature of 35.degree.C or lower by a cooling air ejected from a second cooling ring disposed above the frost line; and (f) cooling the bubble to a temperature of 30.degree.C or lowerby a cooling air ejected from a third cooling ring disposed slightly above the second cooling ring, whereby the bubble is not subsequently drawn.