Adsorption kinetics of anionic direct dyes

Reducing effluent staining and minimising broke are significant criteria which can be achieved by an ideal dying process. This can further be optimised by dye application pior to the headbox enabling also last colour correction. Based on this background the adsorption kinetics of anionic direct dyes by dyeing just before the fan pump were analysed. A special dyeing apparatus was constructed to reproduce mill conditions. A selection of 7 dyes with similar structure but different molecular weight and anionic charge was analysed. With these dyes dyeing trials under varying contact times as 5, 15, 30 and 180 seconds were carried out The amount of dye, fixing agent (charge modification), temperature and water hardness was changed. The results provide new information on about substantivity and kinetics of the dye adsorption.