Patent ID: 6511747
Filing Date: 2003-01-28
Classification: B60C,C08G,D01F,Y10T

Abstract:
A polyethylene naphthalate fiber prepared by a method comprising the steps of:(A) melt-spinning a solid-phase polymerized polyethylene-2,6-naphthalate chip, composed of 95 mol % or more of ethylene-2,6-naphthalate units as the recurring unit, and having a manganese content of 30 to 70 ppm, an antimony content of 180 to 300 ppm and an intrinsic viscosity of 0.90 to 1.00, through a spinneret to a spinning draft ratio ranging from 400 to 900 to form a molten spun yarn, (B) rapid-cooling and solidifying the spun yarn by passing it through a solidification zone, (C) withdrawing the solidified yarn at such a rate that an undrawn yarn having a birefringence of 0.005 to 0.025 is formed, and (D) subjecting the undrawn yarn to a multi-stage-drawing process to a total draw ratio of 6.5 or more to obtain a fiber, wherein the temperature of the second drawing stage is maintained in the range of 150 to 180Â° C.; said fiber having (1) an intrinsic viscosity of 0.70 to 0.77, (2) a tenacity of at least 9.5 g/d, (3) an elongation of at least 9.5%, (4) a birefringence of at least 0.45, (5) a density of 1.355 to 1.368, (6) a melting point of 270 to 275Â° C., and (7) a shrinkage of 2 to 3%.