| 摘要 |
PROBLEM TO BE SOLVED: To provide partially oriented undrawn polyester fibers which are produced from a polyester mainly using a titanium catalyst, inhibit the expansion of crystal sizes in orientation crystallinity, especially hardly form the irregularity of fineness in a one step spinning process in a spinning rate region of 2,000 to 4,000 m/min, and are excellent in the dyed irregularity of drawn fibers obtained in the subsequent drawing process; and to provide a false-twisted yarn obtained from the same. SOLUTION: The partially oriented undrawn polyester fibers are characterized by including a polyester composition composed of a polyester (PES), a metal atom, and a phosphonic acid compound, wherein the PES is a polyester which has an intrinsic viscosity of≥0.55 dL/g and≥90 mol% of whose whole repeating units are ethylene terephthalate units, having a double refractive index of 0.03 to 0.07, having a fiber structure having crystal sizes of≤45 angstrom, having a polyester-soluble titanium atom content of 3 to 30 mmol% as Ti metal atoms per the total repeating units constituting PES, has the content of one or more metal atoms selected from the group consisting of manganese, magnesium and zinc in an amount of 10 to 1,000 mmol% per the total repeating units constituting PES, having an antimony element content of <15 mass ppm based on the polyester composition, and containing phenylphophosnic acid in a range satisfying a constant numerical expression. The false-twisted yarn is obtained from the same. COPYRIGHT: (C)2011,JPO&INPIT
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