GB1121579A - Process for heat treating ªß-lactone polyester fibres - Google Patents

Abstract

1,121,579. Heat treating #-lactone polyester fibres. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. 21 Dec., 1966, No. 57220/66. Heading B5B. A #-lactone polyester is melt extruded to form filaments, the freshly extruded molten filaments are drawn in a zone heated to a temperature above the polyester crystallization temperature to a diameter of between ¢ to about <SP>1</SP>/ 40 of the diameter at which the filaments were extruded, the filaments are then quickly cooled to a temperature below their crystallization temperature to obtain unstretched filaments, the filaments are then stretched to at least 4.5 times their original length and the starting filaments obtained as above are then given a heat treatment at a temperature of at least 120‹ C. e.g. at 190‹ C at constant length: The fibre may have been prepared from a #-lactone polyester having an intrinsic viscosity between about 2 and 4 dl/g. The polyester may be a polymer of an α, α-di-alkyl-#-propiolactone wherein the alkyl groups each have 1-4 carbon atoms, e.g. α, α-dimethyl-#-propiolactone, (pivalolactone). The starting filaments may be heated at a temperature between 125 and 200‹ C. e.g. in water under pressure or in saturated steam at a temperature between 125 and 160‹ C. or in a dry hot gas at a temperature between 150 and 200‹ C. The heat treatment may be applied for a period of time ranging from a fraction of a second at higher temperatures, such as at 195‹ C., up to several hours, e.g. ¢-2 hours or more at lower temperatures. The filaments may be heated at constant length, with limited shrinkage, or free of tension. They are preferably heated under such conditions that their residual shrinkage is not more than 5%, determined at 180‹ C. This may be effected by boiling off the filaments at constant length for ¢ hour at 100‹ C. followed by saturated steam treatment for 1 hour at 120- 130‹ C. allowing free shrinkage, or by heating free of tension in dry air for 5 minutes at 150‹ C. The heat treatment may be carried out in one or more stages, e.g. first at a temperature below 100‹ C. (preferably in saturated steam at 125-160‹ C.), and the filaments after being converted into fabric form may be given a final heat treatment at a temperature of at least 170‹ C.