MANUFACTURE OF LAMINATED BIAXIALLY ORIENTED FILM

摘要

PURPOSE:To obtain a laminated biaxially oriented film superior in oxygen barrier properties and mechanical strength, by a method wherein an ethylene-vinyl acetate copolymer saponified matter and polyamide are quenched by laminating within an annular die and tubular biaxial orientation is performed under a specific orientation condition. CONSTITUTION:A matter (EVOH) whose ethylene content is 25-45mol% and saponification proof is 98% or higher is used as an ethylene-vinyl acetate copolymer saponification matter. A laminated sheet extruded through an annular die lip and comprised of polyamide, EVOH and the polyamide is quenched by a liquid whose temperature is, for example, 40 deg.C or lower, fed to two pairs of nip roll groups which are positioned at the top and bottom and having different peripheral speeds and biaxially oriented both in length and width simultaneously by pressure of gas enclosed on the inside and adjustment of peripheral speeds of the nip rolls. An annular film is heated at 45-100 deg.C by an annular heter and oriented immediately by 2-5 times within respective ranges of mean deformation rates of 2000-10000%/min. in a flowing direction and a direction meeting at right angles with the flowing direction. Then heat-treated within a temperature range extending from 190 deg.C to a temperature lower by 10 deg.C than the melting point of the polyamide.