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Temporarily solubilised disperse dyes derived from aminophenyl-4-(β-sulphatoethylsulphone) are exhausted on the polyester fibre mostly in the vinylsulphone form and to a lesser extent as their hydroxyethylsulphone analogues. After dyeing, to remove the unexhausted dyes on the polyester fibre, sulphite anions were added to the dyebath. The vinylsulphone residue of the dye was attacked by the sulphite anion via an addition reaction converting the dye into a soluble derivative, which then had little affinity for the polyester fibre. The effect of sodium sulphite on the conversion of the dye was investigated using HPLC. The wash and rub fastness properties of the dyed fabric aftertreated with sodium sulphite were similar to those obtained with reduction clearing.

Four temporarily solubilised disperse dyes were synthesised. To obtain the optimum application conditions for dispersant‐free polyester dyeing, their conversion rates into insoluble derivatives were measured using HPLC and found to be more dependent on pH than on temperature. The results showed that it was possible to use these dyes in dispersant‐free polyester dyeing for which the optimum application pH was between pH 5 and 6 at which the hydrolysis rate of the dyes was moderate.

Temporarily solubilised disperse dyes derived from aminophenyl‐4‐(β‐sulphatoethylsulphone) have been applied to wool fabric without the use of a levelling agent. By virtue of their characteristic dye structure, excellent levelling properties were observed on wool fabric. Good exhaustion, fixation and fastness test values were also obtained.