| 摘要 |
<p>Disclosed is a biaxially drawn polyhexamethylene adipamide film having a relative viscosity of at least 3.2 as measured at 25 DEG 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 characterized in that polyhexamethylene adipamide having a relative viscosity of from 3.3 to 5.0, as measured at 25 DEG C. in aqueous 96% H2SO4, is used; the tubular extrudate formed therefrom is cooled at a cooling rate (X DEG C./sec.) satisfying the following formula with respect to the relative viscosity of the polymer used, -100x eta rel+1,200<X<-170x eta rel+2,150 at least in the cooling stage in which the tubular extrudate is cooled from 250 DEG C. to 150 DEG C., and; then, the obtained tubular film is concurrently biaxially drawn.</p> |
