PURPOSE: To easily obtain the subject fiber having excellent moist-heat resistance and dry-heat deterioration resistance and suitable as a rubber-reinforcing material, etc., by applying an antioxidant to the inner part of a PVA fiber using a specific method and cross-linking exclusively the surface part of the fiber using a specific method.
CONSTITUTION: A PVA polymer having a viscosity-average polymerization degree of ≥3,000 is dissolved in a solvent and the solution is extruded through a nozzle to form a fiber. The fiber is treated with an extraction bath to extract the solvent and an antioxidant is applied to the fiber within a stage from the spinning dope of PVA to the extraction bath. The fiber is dried to hold the antioxidant in an amount of 0.2-3wt.% in the fiber and on the surface of the fiber. Subsequently, a crosslinking agent is applied to the surface of the fiber within a stage before the drying process to immediately before the dry-hot drawing and the fiber is subjected to dry drawing at a total draw ratio of ≥16 to obtain the objective fiber having a gel elastic modulus of 0.1×10-2 to 1.5×10-2g/d, a hot-water breakage temperature of ≥150°C, a yarn strength of ≥15g/d and a strength retention of ≥50% after the heat-treatment at 160°C for 24hr.
SANO HIROFUMI
YOSHIMOCHI TOSHIMI
