Combination of wet fixation and drying treatments to improve dye fixation onto spray-dyed cotton fabric.

The conventional dyeing process requires a substantial amount of auxiliaries and water, which leaches hazardous colored effluents to the environment. Herein, a newly developed sustainable spray dyeing system has been proposed for cotton fabric in the presence of reactive dyes, which has the potential to minimize the textile dyeing industries environmental impact in terms of water consumption and save significant energy. The results suggest that fresh dye solution can be mixed with an alkali solution before spray dyeing to avoid the reactive dye hydrolysis phenomenon. After that, drying at 60-100 °C, wet fixation treating for 1-6 min, and combined treatments (wet fixation + drying) were sequentially investigated and then dye fixation percentages were around 63-65%, 52-70%, and above 80%, respectively. Following this, fixation conditions were optimized using L16 orthogonal designs, including wet fixation time, temperature, dye concentration, and pH with four levels where the "larger-the-better" function was selected to maximize the dye fixation rate. Additionally, the color uniformity and wash and rubbing fastnesses were at an acceptable level when both treatments were applied. Finally, the dyes were hydrolyzed after wet fixation, and the hydrolysis percentages were enhanced after the drying process.