| 摘要 |
PURPOSE:To stably obtain the titled yarn having high orientation and low specific gravity, by subjecting a polyethylene terephthalate having specific viscosity from a spinneret to melt spinning, cooling the yarn by a liquid cooling device at a specific position while regulating liquid temperature, liquid flow rate and take-off speed and taking up. CONSTITUTION:A polyethylene terephthalate polyester having >=0.8 intrinsic viscosity IV is subjected to melt spinning from a spinneret 1, spun yarn 2 is passed through a liquid cooling device set right below the spinneret and cooled. In the operation, distance L (cm) between the spinneret 1 and liquid level 3 of the liquid cooling device satisfies position relationship shown by formula I, liquid flow rate (m/minute) at the end of the liquid cooling device satisfies correlation shown by a formula II in relationship between the liquid flow rate and take-off speed VW(m/minute), the take-off speed VW(m/minute) satisfies correlation shown by formula III in relationship between the take-off speed and extrusion rate V0(m/minute) of the polyester from the spinneret 1, vertical distance H(cm) from the liquid level 3 of the liquid cooling device to the liquid bottom is >=5cm and liquid temperature of the liquid cooling device is <=50 deg.C. The yarn is cooled, take-off by take-up rollers 5 to give the aimed yarn having double refraction index DELTAn satisfying a formula IV and specific gravity SG satisfying a formula V.
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