Biaxially drawn polyhexamethylene adipamide film and process for producing same

Abstract From the Canadian patent

Disclosed is a biaxially drawn polyhexamethylene adipamide film having a relative viscosity of at least 3.2 as measured at 25°C in aqueous 96% H2SO4 a degree of, crystallinity of from 35% to 45% a birefringence ( .DELTA. n), of not more than 0.006 as determined at any point in its, entire area and an initial modulus of elasticity in tension of at least 230 kg/mm2 as determined in ay direction across substantially its entire area. The film may be produced by a process wherein molten polyhexamethylene adipamide is extruded through a circular die gap and the tubular extrudate is brought in sliding contact with the outer periphery of an inside mandrel, thereby to be cooled which process is …