| 摘要 |
PROBLEM TO BE SOLVED: To obtain a soft polyester modified cross section fiber having silk-like glass, excellent in stretchability and post processability and useful as a raw material, etc., for inner fields by spinning a specific polyester under specific conditions. SOLUTION: This polyester modified cross section fiber is obtained by extruding a polyester polymer composed substantially of polytrimethylene terephthalate and having 0.5-1.5 intrinsic viscosity [η] from a spinning machine having 250-290 deg.C extrusion temperature and 235-275 deg.C spinning port surface temperature, cooling and solidifying extruded material without carrying out one-sided cooling, winding up the resultant yarn at 2,000 to 5,000 m/min and drawing the wound up yarn in 70-99% maximum draw ratio at 20-70 deg.C drawing temperature. The fiber has >=4 g/d breaking tenacity, >=2.5 g/d strength in yield point, >=15-50% breaking elongation and 1-1.2 unevenness of breaking elongation of fiber represented by formula I and 1.1-1.8 modified cross section degree of fiber represented by formula II [diameter of circumscribed circle is a diameter of smallest circle enclosing whole fiber cross section; diameter of inscribed circle is a diameter of largest circle in the fiber cross section].
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