METHOD FOR PRODUCING LOW-MODULUS HIGH-ELASTIC RECOVERY POLYESTER FILAMENT

摘要

PROBLEM TO BE SOLVED: To provide a method for producing a polyester filament by which a low-modulus and high-elastic recovery filament of a polyester such as PBT and PTT can be wound without causing tightening of winding when winding the polyester filament, and defect of unwinding, yarn break and fluff are not caused when unwinding the package for subjecting the package to a drawing step or a post-processing step. SOLUTION: This method for producing the low-modulus and high-elastic recovery polyester filament having <=50 cN/dtex initial modulus and >=50% recovery after 15% elongation comprises attaching a spinning oil to the yarn just after being cooled and solidified after melt spinning so that the swelling degree represented by the following formula (1) [swelling degree (SW) (%)]=[(E2-E1)/E1]×100 [wherein E1 is an elongation by the natural drawing of an unoiled yarn (undrawn yarn); and E2 is the elongation by the natural drawing of an oiled yarn (undrawn yarn)] may be >=5%.