| 摘要 |
PURPOSE:A polyamide of a specific relative viscosity is melt spun under specific conditions, cooled, treated with a finishing oil, drawn and heat treated to produce the titled fiber with optical birefringences of the fiber and of the inside of fiber cross section in a specific range, thus showing high fatigue resistance in rubber reinforcement. CONSTITUTION:A polyamide with a relative viscosity of higher than 3.50 is subjected to melt spinning under such conditions as satisfying equationI[Q is throughput per each nozzle in g/sec.; D is diameter of nozzle in cm], equation II[Vw is taking-up speed in cm/min.], equation III[T20 is the atmospheric temperature at the position 20mm. beneath from the nozzle surface and 5mm. apart from the yarn in deg.C], equation IV[DELTAn is optical birefringence], and the resultant yarn is cooled, treated with a finishing oil, drawn and heat treated to give the objective fiber in which its optical birefringence inside the fiber cross section satisfies the equation V DELTAnA is optical birefringence at the position where the ratio of the distance from the center r in fiber cross section/ the diameter R of the fiber cross section is 0.9; DELTAnB is the optical birefringence at the position where r/R is 0.0, the optical birefringence of the fiber DELTAn is higher than 50X10<-3> and the strength at break in g/d x(elongation at break in %)<1/2> is no less than 46.0. |
