| 摘要 |
PROBLEM TO BE SOLVED: To obtain highly oriented and non-drawn polyester fibers having a birefringence in a specific range in good productivity by spinning a polyester containing a specific phosphorous compound at a specific take-off speed. SOLUTION: The highly oriented and non-drawn polyester fibers contain a phosphorous compound of formula I [R1 and R2 are each H or a monovalent organic group; R3 is a divalent organic group; R4 and R5 are each carboxyl, hydroxyl(ester), a hydroxyalkyl, an alkylalkylene glycol, amino or amido] or formula II R1, R3, R4 and R5 are each same as above; R6 is (CH2)n [(n) is 2-4]} in an amount of 20-1,000 ppm as phosphorus atoms, and has a birefringenceδn of 0.015-0.08. The highly oriented and non-drawn polyester fibers are preferably obtained by spinning polyethylene terephthalate at a take-off speed of preferably >=2,000 m/min, more preferably, 3,000-7,000 m/min. The birefringenceδn and a set take-off speed V m/min satisfy the relation: 0.0025×V<=1,000×δn<=0.012×V.
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