DE2747803

An improved process is provided for the formation of a high performance polyester (at least 85 mol percent polyethylene terephthalate) multifilament yarn. The product possesses a high strength (at least 7.5 grams per denier) and an unusually stable internal structure which renders it particularly suited for use in industrial applications at elevated temperatures. The filaments are melt spun and uniformly quenched under relatively high stress conditions (as described) to yield an as-spun filamentary material of relatively high birefringence (+9x10-3 to +70x10-3) which is passed in-line from the quench zone to a first draw zone where it is drawn at a draw ratio of 1.01:1 to 3.0:1, and subsequently is drawn (as described) to achieve at least 85 percent of the maximum draw ratio of the as-spun filamentary material. The resulting filamentary material exhibits unusually low shrinkage and hysteresis characteristics (i.e. work loss characteristics) as well as the high strength chatracteristics. Accordingly, when utilized in the formation of a tire cord and embedded in a rubber matrix a highly stable tire may be formed which exhibits a significantly lesser heat generation upon flexing.