PROCESS FOR PREPARATION OF BIAXIALLY DRAWN LAMINATED FILMS

摘要

A biaxially drawn laminated films having a good oxygen barrier property, a good mechanical strength and high thickness uniformity are made by a process comprising: a first step of forming a substantially amorphous unoriented laminated film comprising a saponified ethylene/vinyl acetate copolymer having an ethylene content of 25 to 45 mole % and a polyamide, and drawing the film in the longitudinal direction at a deformation rate of at least 10,000%/min and a draw ratio of 2.7 to 3.5 at 45 DEG to 65 DEG C. by using a roll drawing machine; a second step of transferring the film drawn at the first step to the transverse drawing-initiating point of a tenter type transverse drawing machine, expanding the width of the film at an angle of not larger than 6 DEG with respect to the central line of the film at least until the mechanically set ratio of the tenter clip distance to the original distance becomes at least 1.4 while maintaining the temperature of the tenter clips at a level lower than the temperature of the film and drawing the film in the transverse direction at an average deformation rate of 2,000 to 10,000%/min and a draw ratio of 3 to 5 under temperature conditions such that, from the transverse drawing-initiating point, the temperature of the film is elevated stepwise so that the temperature of the film is from 70 DEG to 100 DEG C. at the point of termination of the transverse drawing; and a third step of heat-treating the film drawn at the second step at a temperature form 110 DEG C. to the temperature lower by 10 DEG C. than the melting point of the starting polyamide.