Anhydrous dyeing processes of ramie fiber in liquid ammonia

A real anhydrous liquid ammonia dyeing technique was established that included a cationic modification of the ramie fiber in liquid ammonia, dyeing of the cationic ramie fiber in liquid ammonia, drying to fix the cationic agents and the reactive dyes in the ramie fiber, and washing the cationic ramie fiber and the dyed cationic ramie fiber with liquid ammonia to remove the unfixed chemicals. The zeta potential of the cationic ramie fiber indicated that the cationic groups were successfully grafted on the fiber. The dye exhaustion percentage and the fixation rate improved. The dyed cationic ramie fiber had excellent wash fastness, satisfactory color uniformity, and acceptable breaking strength and breaking elongation rate for spinning. High performance liquid chromatography analysis was used to measure the stability of the dye’s reactive group during the liquid ammonia dyeing and drying. The results showed that the dichlorotriazinyl group was unstable, while the monochlorotriazinyl and vinyl sulfone groups were stable during the liquid ammonia dyeing. The monochlorotriazinyl group and vinyl sulfone groups changed to their non reactive derivatives after drying.