TW430700B - A polyester fiber and producing the same - Google Patents

Abstract

A polyester fiber composed of a polyester comprising 90 mole% or more of polyethyleneterephthalate repeating unit, in which the single fiber has a W-shaped cross-sectional shape having a flatness value of from 2 to 4 as represented by a quotient obtained by dividing the lone side of the circumscribed quadrilateral of the W-shaped cross section by the short side thereof, is characterized in that the fiber exhibits the characteristic properties satisfying the following conditions (1) and (2): (1) 60% ≦ elongation at break ≦ 200%; (2) 45% ≦ boil-off shrinkage ≦ 70%. The polyester fiber is an improved pre-oriented fiber having characteristics enabling a draw false-twisting at a higher processing speed to produce a false-twist texturized yarn for making a fabric with an excellent water-absorbency. The polyester fiber can be prepared using a spinneret having specifically modified W-shaped orifices by a melt spinning process in which the following conditions are satisfied: (1) maintaining the surface of the spinnerete at a temperature of 285 DEG C or more; (2) cooling the extruded fibers to solidify by blowing a current of cooling air across the running fibers in the direction normal to the open side of the W-shaped orifices arrange over spinneret; (3) applying a finish oil to the fibers in an amount sufficient to form an finish oil film having a thickness of from 0.02 to 0.05 mu m on the surface of the single fiber; and (4) subsequently winding the fiber yarn at a winding speed of from 3,000 m/min. to 4,500 m/min.