Hot pad-batch dyeing of cotton fabrics using reactive blue-vinyl sulfone dye

Cold pad-batch dyeing of reactive dyes is low energy consumption and a clean dyeing technique. However, the room dyeing temperature requires strongly active base reactive dyes for dye fixation, bringing about the limitation of dye adaptability. Here, we propose a new technology of hot pad-batch dyeing that has the advantages of higher dye fixation and excellent color fastness. Three blue reactive dyers (C.I. Reactive Blue 19, C.I. Reactive Blue 21, C.I. Reactive Blue 203) that contain beta-sulfate ethyl sulfone were used to increase the dye fixation of reactive dyes with cotton fibers. The effects of alkali concentration, dyeing temperature, batching time, and salt concentration on the dyeing performance of cotton fabrics were studied. The effects of post-treatment (soaping and fixation) on the K/S values and color fastness were also investigated. The study showed that the dye fixation rate of the three reactive blue dyes was higher than 87%, and the rubbing and washing color fastness was more than grade 3-4 in the process of hot pad-batch dyeing of cotton fabrics. Furthermore, the dyed cotton fiber was fixed with a fixing agent (polyurethane (PU) and a mixture of PU and an aziridine crosslinker), and the color fastness reached not less than grade 4. Compared with cold pad-batch dyeing, hot pad-batch dyeing has the advantages of higher dye fixation and excellent color fastness for the three reactive blue dyes. Therefore, the dyeing performance of beta-sulfate ethyl sulfone types of blue reactive dyes using hot pad-batch dyeing can effectively reduce the burden of post-treatment and the discharge of dyeing wastewater, and has a good application prospect in the dyeing of cotton fabrics.