Study On Improving Fixation Of Monochlorotriazine Reactive Dyes On Silk Fabric By Using Tertiary Amines

Silk has always been considered as noble and graceful fiber for its high quality ever since it was used by human beings. However, low wash fastness is one main disadvantage of silk dyeings. Reactive dyes have a wide color range and excellent color fastness and are the only type of dyes which can form covalent bond with the silk fiber. Thus the application of reactive dyes to silk fabrics may be the best way to improve the wash fastness of silk dyeings.During the conventional dyeing process of silk with monochlorotriazine reactive dyes, the building and breaking of dye-fiber bond take place at the same time due to the relatively high temperature and pH value. It was reported that hydrolysis of the dye-fiber bond was the main reason for the low fixation of monochlorotriazine reactive dyes on silk fiber. Therefore, tertiary amines, which can react with reactive dyes and form quaternary amine dyes to enhance the activity and thus make dyeing feasible in a mild condition, are able to decrease the extent of hydrolysis.In the present work, three common tertiary amines-nicotinic acid, iso-nicotinic acid and pyridine were selected as catalysts in the dyeing of silk with monochlorotriazine reactive dyes, and the optimal dyeing temperature, pH value, dyeing time and catalyst concentration were determined. The experimental result indicates that fixation can be improved to a certain extent by applying those selected tertiary-base catalysts, meanwhile, sound fastness can be achieved so that the performance of the dyed fabric can meet the practical demand. Furthermore, the addition of catalysts can reduce the dyeing and fixing time and therefore, save the energy consumed in the dying process. Finally, a neutral dyeing bath was beneficial to decrease the damage of fabric strength.Furthermore, HPLC (High Performance Liquid Chromatography) was also used to test the activity of reactive dye Red K-2G with different tertiary amines. By comparing the effect of different tertiary amines on improving the dyeing fixation and the percentages of reactive dyes converting to quaternary amine dyes, a conclusion can be reached that the reactivity between dyes and tertiary amines mainly affect the fixation of reactive dyes on silk in a catalyzed dyeing process. Due to the character of tertiary amines, most of the catalysts would remain in the dye bath and thus lead to waste of reagent. So the feasibility of recycling of the dye bath was investigated in the experiment and the result shows that dye bath can be reused for once or twice for different tertiary amines.At the end of the experiment, the three tertiary amines were used as catalysts for reactive dyes on cellulose dyeing. The experimental result indicates that compared with conventional dyeing of cellulose with reactive dye, tertiary amines improve the dyeing fixation of silk in an alkali condition whereas show no obvious effect under a neutral condition.