Clean dyeing of cotton fabrics by cross-linking reactive dyes with fiber macromolecular chains

Increasing dye utilization, shortening the process and reducing the discharge of colored wastewater are the keys to clean dyeing and finishing of fabrics. In this study, we report a clean dyeing process. The process improved the dye utilization and achieved wrinkle-finishing and dyeing in the same bath by enhancing cross-linking of dyes with fiber macromolecular chains. It was observed by SEM that the cross-section of the dyed fibers showed round or oval shape, and the mid-cavities were reduced or even disappeared. The swelling rate of the fibers and cellulase degradation experiments showed that the dyes formed stable cross-linking structures with the macromolecular chains. Furthermore, differences in the structure of reactive dyes affected the optimal reaction conditions between the dyes and the fibers. Compared to conventional processes, the K/S, color fixation rate, and wrinkle recovery angle of dyed fabrics with different dyes were significantly improved. This illustrated the superiority of this process and the applicability of different structural dyes. Compared to traditional processes, the process saved 29.6 % of dyes and 16.7 % of alkalis. Importantly, the process could save 200 % of water, 9.5 KW·h of energy consumption and 61.6 m3 of saturated steam. Ultimately, this process could save 7.22 $ of the cost of dyeing 1 kg of fabric. The concentration of dyes in the dyeing wastewater was significantly reduced. In summary, the clean process has good economic and environmental benefits.