PURPOSE: To stably produce a thick-and-thin yarn having high quality over a long period by leaving standing an undrawn polyester filament yarn having a specific birefringence for a specific period in relaxed state and subjecting the yarn to drawing and heat-setting processes.
CONSTITUTION: The objective thick-and-thin yarn can be produced by leaving standing an undrawn polyester filament yarn having a birefringence (n) of 20×10-3≤n≤35×10-3 in relaxed state until the yarn satisfies the formula sh=(sh0-sh1)/sh0≥0.04 (sh0 is hot-water shrinkage % of undrawn yarn immediately after spinning and sh1 is hot-water shrinkage % of undrawn yarn after the relaxation treatment), drawing the yarn at a temperature below the glass transition point and a draw ratio smaller than the spontaneous draw ratio and finally heat-setting at ≥110°C.
TANIZAWA HIROTSUNA
NAITO KAZUHIKO
| JPS61275430A | 1986-12-05 | |||
| JPS56107039A | 1981-08-25 |