PROCESS FOR ACHIEVING HIGHER ORIENTATION IN PARTIALLY ORIENTED YARNS

摘要

Provided is a process for melt spinning a partially oriented yarn of increased birefringence, and hence higher orientation, for a given wind-up speed. The process comprises extruding a molten fiber forming polyester through a shaped orifice to form a molten filamentary material, which is then passed in the direction of its length into a quench zone wherein the filamentary material is contacted with a first gaseous quenching medium. While the filamentary material is still in a deformable state, however, it is passed through a hot zone provided with an atmosphere having a temperature greater than the first gaseous quenching medium and greater than the glass transition temperature of the molten polyester filamentary material. The filamentary material is then withdrawn from the hot zone and contacted with a second gaseous quenching medium at a temperature below the glass transition temperature of the filamentary material until the filamentary material is no longer deformable, after which the filamentary material is withdrawn from the quench zone.