Thick and thin polyamide based fibers, and a production process thereof

Abstract

A material and product excellent in stability in the yarn forming process, small in the color shade contrast due to dyeing, to provide natural irregularity, having microscopic unevenness on the surface of a fabric, to provide dry touch to the eyes and by touch, and good in color fastness are disclosed. The polyamide based fibers of the present invention is a thick and thin yarn in which the unevenness of thickness in the length direction of the polyamide based multifilament is 5 to 20% and in which the standard deviation of the stress at 40% elongation in the stress-strain curve with a sample length of 20 cm is 0.3 g/d or less. The thick and thin yarn can be produced by a process, in which an undrawn polyamide based multifilament of 20.times.10.sup.-3 or less in birefringence .DELTA.n is drawn at a low ratio, comprising the steps of falsely twisting it at a position between a feed roller and a draw roller, drawing from 1.5 to 2.5 times, and thermosetting at 100.degree. C. to 200.degree. C.

Dependencies are inferred from the claim text.