Dispersant-free disperse dyes for polyester an eco-friendly approach

Disperse dyes contain around 30–60% of dispersing agents as well as dyeing with disperse dyes requires around 2–5 g/L of dispersing agent for faultless dyeing of polyester and other hydrophobic fibres. Dispersing agents are not absorbed by the fibres and a large quantity of dispersing agent creates unavoidable load on the effluent treatment. Dispersant-free disperse dyes seem to have an acceptable solution to this existing problem. These dyes can work in absence of dispersing agents and thus are called as dispersant free disperse dyes. In this work, dispersant-free disperse dyes were synthesised by coupling diazotised p-nitroaniline with the different components like sulfomethylated aniline and m-toluidine. These synthesised dyes were applied successfully on polyester which resulted into uniform dyeing, good build-up and desired colour yield. The dyeing was dependent on the pH and the optimum pH was 5 similar to that employed in conventional polyester dyeing. The fastness properties obtained were good and comparable with the conventional dyes. Whereas the chemical oxygen demand levels of the dispersant-free disperse dyes were much lower than those from commercial disperse dye.