MANUFACTURE OF HIGH-TENACITY POLYESTER FIBER

PURPOSE:To obtain a polyester fiber having high strength, low elongation and low- heat-shrinkage, under good drawing condition, by carrying out the two-step drawing and heat-treatment of undrawn polyester tow under a specific condition. CONSTITUTION:The first-step drawing of an undrawn polyester tow is carried out by heating the feed roller group and the first draw roller group at 35-55 deg.C, passing the undrawn tow through the hot-water bath under the final roller of the feed roller group, and drawing at the draw ratio DR1. The depth of the two in the bath is selected to 5-40mm., and the length of the tow immersed in the bath is adjusted to satisfy the formula I . Thd drawn tow is subjected to the second-step drawing at a draw ratio DR2 in the stem box placed just after the first draw roller group. The length of the steam box (Z2mm.) is selected to satisfy the formula II. After the second-step drawing, the tow is heat treated with the hot roller group heated at 190-220 deg.C. [The ratio DR1/DR2 satisfies the formula III; X1 and X2 are the denier numbers X10 per 1mm. width of the tow passing through the feed roller group and the first draw roller group, respectively, and x1