Design, synthesis and application of easy wash-off reactive dyes

New dyes that not only give good fixation levels but also relatively low substantivity in the hydrolysed form were the targets of this research. Our approach involved lowering the substantivity of the hydrolysed dye by reducing the planarity that is required for dyes to have high substantivity on cotton. In this regard, bifunctional bis-dichlorotriazine (bis-DCT) and tetrafunctional bis-monochlorotriazine/ bis-sulphatoethyl sulphone [bis-(MCT/SES)] reactive dyes were made, using selected diaminobiphenyls. Bis-DCT bifunctional reactive dyes were applied to cotton by a pad-batch method, while bis-(MCT/SES) tetrafunctional reactive dyes were applied to cotton by a pad-dry-cure. Following dye application, it was found that the resultant hydrolysed dyes easily washed off the fibre surface and that the dyed cotton fabrics had colour fastness to rubbing and laundering properties that were comparable with the commercial prototypes used in this study. However, it is also apparent that the combination of relatively low water solubility and large molecular size has an adverse effect on fibre penetration.