Excellent fixation and color fastness of nylon fibers dyed with low-water-soluble reactive dyes based on the reactivity and stability of vinyl sulfone

Reactive dyes in nylon dyeing have been associated with utilization inefficiencies despite their high color fastness. A potential solution to this issue involves combining the benefits of reactive dyes and milling acid dyes to obtain low-water-soluble reactive dyes (LWSRDs), which can stain and fix to nylon fibers under neutral conditions. To identify a suitable functional group for LWSRDs, six model dyes comprising one vinyl sulfone and five monochloro-s-triazines were prepared and reacted with glycine or hydrolyzed to simulate the fixation progress on nylon fibers. The results show that vinyl sulfone exhibited sufficient reactivity with glycine, and similar to 3% hydrolysis over 90 min. Consequently, vinyl sulfone was considered a superior functional group for LWSRDs. Based on these results, four LWSRDs with monofunctional groups were synthesized and used for dyeing nylon 6 microfibers. Notably, these dyes exhibited fixation of >91% and demonstrated exceptional color fastness against washing and rubbing, exceeding grade 4. These results underscore the potential of LWSRDs as highly efficient and effective dyes for nylon, offering a solution to the limitations associated with conventional dyeing techniques.