Dyeing Performance of a Synthesized and Ultrafiltrated Bifunctional Reactive Dye with Two Vinylsulfone Groups on Cotton Fabrics

The objective of this study is to investigate the performance of the ultrafiltration process as a purification method on the dyeing properties of a newly synthesized homobifunctional reactive dye. This is a green–blue reactive dye with two vinylsulfone groups. Namely, several properties, such as exhaustion, substantivity, fixation, time to half dyeing, migration index, light fastness, and the effect of metal salts, were studied thoroughly. It was proven that the processed bifunctional reactive dye shows higher exhaustion, substantivity, and dye-uptake values than the untreated one. It was found that the dye fixation is higher for the ultrafiltrated (92%) compared to the non-ultrafiltrated (85%) dye, while the migration index is slightly lower. It is indicated that, due to the possible chemical affinity between the dye and the substrate, a stronger retention is noticed for the treated dye. All in all, high fixation and substantivity lead to higher dye valorization and result in less hydrolyzed waste dyestuff, leading to less water and organic liquid waste at an industrial scale. The effect of metal salts addition (Fe3+, Co2+ and Cu2+) was studied as well, for comparison reasons, but it was found to be unnecessary. It is proven by the property values calculated that the overall process is valuable, since lower dyebath concentrations are required for satisfactory results. Thus, in large-scale dyeings, the ultrafiltration process can be proven to be valuable for environmental protection reasons.