| 摘要 |
PURPOSE:To obtain the titled yarn having high shrinkage percentage, high shrinkage stress and low change of these properties with time, by successively subjecting polyester undrawn yarn having a specific birefringence ratio to stretching heat treatment and drawing treatment under specific conditions, respectively. CONSTITUTION:Firstly, a fiber-forming polyester having ethylene terephthalate as a main repeating unit is spun at high speed usually at 2,500-4,500m/min spinning speed to give undrawn yarn having very low orientation of 0.025-0.06 birefrigence DELTAn. Then, as the undrawn yarn is stretched at 1-10% stretching ratio, it is heat-treated in a dry state at 150-220 deg.C. Then, the heat-treated, stretched polyester yarn is drawn at 20-80 deg.C, preferably 50-80 deg.C at >=1.3 draw ratio to give the aimed yarn. The stretching, heat treatment, for example, is carried out by bringing the undrawn yarn into contact with a hot plate and a hot roller.
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