| 摘要 |
PURPOSE: A polyethylene naphthalate fiber is provided which is characterized by having high tenacity and improved physical properties, making it possible to produce a treated cord having excellent dimensional stability and tenacity, and being useful for a reinforcement of rubber product such as a tire and a belt. CONSTITUTION: The polyethylene naphthalate fiber is characterized by 0.70-0.77 of inherent viscosity, at least 9.5g/d of tenacity, at least 9.5% of elongation, at least 0.45 of birefringence ratio, 1.355-1.368 of density, 270-275deg.C of melting point and 2-3% of shrinking percentage. The polyethylene naphthalate fiber is obtained by a process containing the steps of: preparing solid-state polymerized polyethylene-2,6-naphthalate chip containing at least 95mol% of ethylene-2,6-naphthalate unit, 30-70ppm of manganese and 180-300ppm of antimony and having 0.90-1.00 of inherent viscosity; melt-spinning the chip in a draft ratio of 400-900 to manufacture yarn; passing the yarn(4) through a cooling zone(3) to solidify; winding on a proper spinning velocity to manufacture an undrawn yarn having 0.005-0.025 of birefringence ratio; and then drawing the wound yarn at 150-180deg.C of drawing temperature to produce the yarn having at least 6.5 of the total draw ratio. |
