PURPOSE: To obtain high-tenacity and highly shrinkable polyester fibers of stable quality without deteriorating shrinkage stress nor causing the process trouble, etc., by drawing undrawn polyester yarns having an intrinsic viscosity within a specified range under specific conditions in many stages.
CONSTITUTION: An undrawn polyester yarn (Y) having 0.55W0.95 intrinsic viscosity [η] is drawn between a feed roll 1 at 80W95°C and a draw roll 2 at a lower temperature than the feed roll 1 and ordinary temperature or above, and then drawn between draw roll 2 and a taking off roll 3 at ordinary temperature. The ratio of the draw ratio in the first stage to the total draw ratio [(the first draw ratio-1)/(the total draw ratio-1)×100] is set within (-4.0×10[η]+3.9× 10)W(1.0×102[η]-3.0) range, and the total draw ratio is set within (-9×10-1 [η]+4.0)W(2.5[η]+2.5) range. Thus, the aimed high-tenacity and highly shrinkable polyester yarns having ≥4.0g/denier and ≥18% shrinkage in boiling water are stably obtained.
YOKOI NORIAKI
NAGAI TAKEYA
