NYLON 66 FIBER HAVING HIGH STRENGTH AND HIGH FATIGUE RESISTANCE, AND ITS MANUFACTURE

摘要

PURPOSE:To produce the titled fiber having specific physical properties and suitable for tire cord, carpet, etc., by heat-treating and cooling a nylon 66 fiber produced by high-speed spinning, under specific conditions. CONSTITUTION:Nylon 66 fiber spun at a spinning speed of =4,000m/min is heat- treated under the longitudinal tension of 0.5-0.99T (T is tensile strength of the fiber), in an oxygen-free atmosphere at a temperature higher than 240 deg.C and lower than the temperature defined by the formula I [Tm3 is the temperature at which the DSC melting curve determined at the heating rate of 10 deg.C/min returns to the base line; v is speed of the treatment (mm./min)] in a heat-treatment zone having the length l(mm.) of formula II (d is denier; theta is heat-treatment temperature) measured along the fiber axis. The heat-treated fiber is cooled to =-60 deg.C. The absolute value of the temperature gradient in the cooling process is =1,300 deg.C/min. The objective fiber having the temperature Tmax corresponding to the peak (tandelta)max of the mechanical loss tangent of =100 deg.C, the loss tangent peak of 0.06-0.10, and the average birefringence DELTAn(0) of =5.8X10-2 at the core of the fiber can be produced by this process.