Multicycle single-shade high-temperature dyeing on polyester with dispersant free disperse dyes dissolved in the presence of surfactants



The repeated high-temperature dyeing of a given shade and intensity on polyester with three dispersant-free disperse dyes dissolved in the presence of a mixture comprising an anionic and a nonionic surfactant is described. Dyeing was performed on a laboratory dyeing apparatus, the spent liquor being recycled 19 times in the case of the first dye, and nine times each for dye two and three. The dyeings were checked for levelness, reproducibility of intensity, shade and brightness, and fastness properties. The fastness properties were compared with those of conventional high-temperature dyeings. A simple spectrophotometric method was devised to determine the dye concentration in the spent liquors. Equations to optimise the dyeing process are derived, advantages and disadvantages of the new dyeing method are discussed.