Preparation Of Liquid Alkali And Its Application In Reactive Dyeing

In this work, the preparation of liquid alkali used as a substitute of soda ash for thefixation of reactive dyes was investigated, and its application characteristics werediscussed. The aim of this study was to solve the problems caused by the use of soda ash asan alkaline fixation agent during the process of reactive dyeing. This study included thefollowing aspects: selection of alkali donors and buffer components, pH and buffercapacity of conventional alkalis and liquid alkali, effect of alkalis on color depth of dyedfabrics and diffusion ability of dyes. Finally, the optimum composition of liquid alkali wasgiven as follows: potassium hydroxide, potassium carbonate, sodium silicate andtriethanolamine.In order to obtain the optimum conditions of liquid alkali applied to reactiveimmersion dyeing, the dosages of liquid alkali and sodium chloride as well as fixation timewere tested as compared to the application of conventional alkali, and the color depth ofdyed fabrics was used as the evaluation standard. In addition, the changes in pH of dyebathin the presence of alkali, pH of residual dyebath and washing solution, color fastness ofdyeings, and cost of dyeing process were also discussed.The optimum pad dyeing process was determined through the investigation about theinfluence of baking temperature, baking time, liquid alkali dosage, and sodium chloridedosage on the apparent color depth of dyed fabrics. Furthermore, the color characteristicsand the color fastness to rubbing of the dyed fabrics with the uses of liquid alkali andconventional alkali were compared.Liquid alkali was also applied to the cold pad-batch reactive dyeing of cotton fabricswere carried out. The depencence of apparent color depth, color hue, and rubbing colorfastness of dyed fabrics on batching time, liquid alkali, urea and sodium chloride dosageswas discussed, and compared with that of the conventional dyeing. The results showed that the use of liquid alkali as an alternative to soda ash exhibitedthe fixation effect close to that of soda ash, and had the advantage of low application cost.