Low temperature non-aqueous dyeing of wool fiber with reactive dyes: A sustainable and eco-friendly method

Conventional wool dyeing usually performed at a boiling point, often destroys the wool structure, consumes plenty energy and water. Aiming at realizing the sustainable cleaning coloration of wool dyeing and keeping the excellent natural quality of wool fiber, a green dyeing technology, non-aqueous dyeing, has been successfully applied. The effect of acid-pretreatment on the reactive dye adsorption behaviors was explored and optimized the dyeing parameters by the design of experiments as well as a single factor screening way. The results demonstrate that acid-pretreatment improved the dye exhaustion rate to 99.79 % effectively by lowering the pH value of wool fiber and increased the dye fixation rate from 75.33 % to 86.93 % by enlarging the dyeing channel. Additionally, the factors that affected wool dyeing were analyzed, approving additional acetic acid had the most significant effect on the wool dyeing. The optimal wool dyeing condition included 1 % on the weight of fiber (o.w.f) acetic acid indicating low-temperature wool dyeing was achieved by this non-aqueous dyeing system at 85 °C for 60min. Furthermore, a higher color depth, constant mechanical properties, good rubbing fastness, and soaping fastness were obtained by this dyeing method. Compared with conventional dyeing, 24.28% energy consumption, 32.50% water usage, and 31.36% wastewater were reduced by this dyeing method. Therefore, sustainable non-aqueous dyeing technology is eco-friendly and has the potential to protect the wool structure from being damaged in the dyeing process.