DYEING PROPERTIES OF POLYESTER MICROFIBERS

Sorption isotherms and dyeing rates of purified disperse dyes on polyester microfibers (fineness of 0.25-1.0 denier) from water have been measured at 95 degrees C. The isotherms are curved and well described in terms of the dual-mode sorption model: Nernst-type partitioning and Langmuir sorption are concurrently operative. The effect of a diffusional boundary layer on the dyeing rate is small under the conditions; the microfibers were dyed in the form of a bulky two-ply yarn in a well stirred bath. Dyeing rates of a commercial dye are also measured at 110 and 130 degrees C. For dyeing of a 0.32d fiber at 130 degrees C, the amount of dye sorbed by the fibers attains a maximum value at an early stage and then decreases gradually. This phenomenon is explained in terms of the aqueous solubility of very fine dye particles. The relation between dye sorption behavior and the fine structure of the microfibers is discussed.