PRODUCTION OF POLYESTER FIBER OF HIGH STRENGTH AS WELL AS OF HIGH THERMAL DIMENSION STABILITY AND CHEMICAL STABILITY

摘要

PURPOSE:An ethylene-terephthalate unit polyester is melt-spun through a spinneret and cooled down, then the resultant yarn is taken out under control of its tension at the solidification point and subjected to specific multiple step drawing and relaxation to produce the titled fiber suitable for use in tire cords, because of its high strength. CONSTITUTION:A polyester which contains ethylene-terephthalate as a main recurring unit and has over 0.7 intrinsic viscosity (measured in a phenol-tetrachloroethane 6:4 mixture solvent at 30 deg.C) is melt-spun at a throughput of less than 3.5g/min/orifice and cooled down with air of 35-80 deg.C. Then, the resultant yarn is taken out under tension of 1.5X107-7.5X107dyne/cm2 at the solidification point and subjected to the first step drawing between the first and the second stress-relievers, as it is passed through a device for fixing the drawing point, using superheated steam up to 400-650 deg.C at a draw ratio D which satisfies equation I [Y is equation II where B is average reflactive index of the extruded yarn X103]. The yarn is further drawn between the second and the third stress-relievers at 180 deg.C- the melting point at a draw ratio of 1.05-1.20, relaxed between the third and the fourth stress-relievers and wound up.