| abstract |
A zip fastener made of a monofilament of 200 to 20,000 denier composed of a polymethylene terephthalate containing at least 85 mole % of trimethylene terephthalate, tetramethylene terephthalate or hexamethylene terephthalate as a recurring unit, said monofilament having an intrinsic viscosity of 0.35 to 3.5 and a circularity of not more than 1.01. The monofilament is prepared by melt-extruding the polymethylene terephthalate in the form of a filament, passing the extruded filament through an air gap, passing it through a cooling bath of an inert quenching liquid held at a temperature of about 60 DEG to 100 DEG C., then passing it through a cooling zone at a temperature of below 35 DEG C., and then drawing the filament. |