Optimization of Salt-Free Reactive Dyeing Process for Cotton with Coconut Oil/Water Dual-Phase Dyeing System

Abstract

In this study, the coconut oil/water dual-phase dyeing system for developing salt-free reactive dyeing process for cotton was established. The selected dyes in this work were hot-dyeing reactive dyes, including C.I. Reactive Red 243, C.I. Reactive Blue 214 and C.I. Reactive Orange 70. A dual-phase dyeing system was performed under various coconut oil to water ratios and a comparative study was conducted on the conventional aqueous-based reactive dyeing in the presence and absence of salt. The results showed that the oil to water ratio of 3:1 imparted the highest colour yields (K/S values) and achieved a superior colour yield to the conventional aqueous-based dyeing. The results also pointed out that better dye fixation could be attained by dyeing cotton with the coconut oil/water dual-phase dyeing process under the optimum conditions. A comparable degree of dye exhaustion was observed for the aqueous-based and the dual-phase dyeing processes, however, the dye fixation was higher for the dual-phase dyeing, indicating less dye hydrolysis in this dyeing system. Consequently, superior colour fastnesses to washing and rubbing were obtained, less dye staining was observed in the case of dual-phase dyeing. A study on reusability of the coconut oil recovered from the spent dyebath for another reactive dyeing cycle was also conducted. The oil from the spent dyebath was directly taken to use without any further purification as a dual-phase medium along with water and the obtained result indicated a reusability potential of coconut oil. From this research, it infers that cleaner reactive dyeing process with the coconut oil/water dual-phase system for cotton could be developed.