The wash-off of reactive dyes on cellulosic fibres. Part 1: Dichlorotriazinyl dyes on cotton

Abstract

Three dichlorotriazinyl reactive dyes were applied, at 2% omf, to woven cotton and the dyeings then washed-off using tap water, sodium bicarbonate and six commercial surfactants, the latter in both the presence and absence of sodium carbonate. The duration and temperature of wash-off, as well as the concentration of sodium bicarbonate used, were varied and the effects of these variables on both the extent of removal of dye from the dyeings and the wash fastness of the dyeings were determined. The finding that the extent of removal of unfixed dye increased with increasing temperature and duration of wash-off can be attributed to the increasing severity that accompanied an increase in time and temperature of wash-off. Each of the six surfactants alone and sodium carbonate alone was more effective in removing dye than tap water alone; the use of each of the surfactants in conjunction with sodium carbonate resulted in enhanced effectiveness of the surfactants. In terms of the effect of wash-off on the wash-fastness of the dyeings, it was found that dyeings which had been washed-off using tap water only or using each of the six surfactants alone, at each of the temperatures and durations of wash-off, displayed lower wash fastness than those dyeings which had been washed-off using sodium carbonate alone or using the six surfactants in the presence of alkali. However, there was little difference between the six surfactants, when used in both the presence and absence of sodium carbonate, in terms of the level of wash-fastness achieved. It was also evident that, in general, there was no difference in wash fastness between dyeings that had been washed-off using each of three concentrations of sodium carbonate and using each of the six surfactants in conjunction with alkali. From the wash-fastness and dye removal results secured, it appears that the use of surfactants in wash-off is unnecessary and that a wash-off using between 2 and 5 g/l sodium carbonate is sufficient to achieve an adequate level of wash fastness.