GB1192323A - A process for improving the Dyeability of Polyester Filaments - Google Patents

Abstract

1,192,323. Improving dyeability of polyester fibres. E. I. DU PONT DE NEMOURS & CO. 17 Jan., 1969 [17 Jan., 1968], No. 2953/69. Heading B5B. [Also in Division D1] The dyeability of polyester filaments is improved by (a) drawing them in an amorphous state at a temperature above their " apparent minimum crystallization temperature," but below 180‹ C. in order to render them crystalline and to increase their tenacity; (b) relaxing the drawn crystalline filaments at a temperature above 180‹ C.; (c) dimensionally stabilizing the filaments by heating them under tension at a temperature higher than the relaxation temperature and lower than the " filament softening temperature " to further crystallize the filaments, with the proviso that during the stabilization, if the filaments are stretched then the extent of the elongation does not exceed the extent to which the filaments were allowed to relax in step (b). The relaxing temperature is preferably at least 15‹ C. below the stabilizing temperature and the stabilizing temperature preferably does not exceed 235‹ C. The relaxing temperature is preferably within the range 180- 210‹ C., the relaxation being effected with the filaments under tension. The filaments may be heated in step (b) in a free-to-relax state. The stabilizing temperature may be at least 195‹ C. The temperature at which the filaments are drawn is preferably at least 100‹ C., the temperature at which they are relaxed under tension preferably within the range of 180‹ to 210‹ C., and the stabilizing temperature preferably within the range 195‹ to 225‹ C. The filaments may be stabilized at constant length. The polyester may be polyethylene terephthalate, polytrimethylene terephthalate, poly(phexahydroxylene terephthalate), poly(diphenylolpropane isophthalate) or a polyethylene naphthalene dicarboxylate. The expression " apparent minimum crystallization temperature " is defined as the lowest temperature at which a marked rate of density change, which is known to occur simultaneously with crystallization, takes place within six hours. The density may be determined either in air or in silicone oil over a temperature range. The rate of density change alters quite abruptly from no change in 6 hours to a change within minutes when the temperature is increased by only a few degrees near the apparent minimum crystallization temperature. The " filament softening temperature " is regarded as being the same as the " polymer melt temperature " which is defined as the temperature at which a polymer sample becomes molten and leaves a trail when moved across a hot metal surface with moderate pressure.