Research On Applications Of Urea And Its Alternatives In Reactive Printing

Reactive dye is one of the most important dyes for the printing of cellulose fibers. Aggregation between reactive dyes easy happens because of large dosage of dye and low bath ratio in reactive dyeing, it lead to poor solubility of the dye, and affects the printing effects, so urea is generally added to increase the solubility of the dye, the permeability of dye solution and the fixation ratio. However, ammonia compounds from the decomposition of urea in the wastewater will accelerate the growth of algae, and affect the ecological environment. In order to reduce the pollution to the environment, the printing process control and urea alternatives application are adopted. The studies of two-phase printing process, increaseing wetting apparatus in the steaming box and urea alternatives to some extent contribute to the reduction of the urea consumption, while the mechanisms are not clear and printing effects are not ideal. Therefore, the study of effects of additives on dye aggregation state in the solution play a guiding role for finding urea alternative.In this paper, the effects of environmental factors on the reactive dye aggregation degree were investigated by determining the viscosityies of the dye solutions, and the solubility of a dye in a certain solution was measured to confirm the dye aggregation state studied in the viscosity method. The effects of homemade cosolvent and several common additives on reactive printing products were studied, the comparison of the nitrogen content in printing wastewater was considered to evaluate the possibility of additives.The determinations of melting point of the mixture of additives and dyes were performed with the aim at exploring the roles of additives in the steaming process.The viscosity related to the concentration of dye solution, the viscosity of solution increased and decreased with the rising of dye concentration and temperature respectively, when dye solution concentration was lower than50g/L, while dramatically increasing trend of viscosity was shown with over concentration50g/L, the dye ions tended to congregate. Dissolution and aggregation of reactive dye in solution related to pH values. The additives as TM-1, urea, glycerol and caprolactam were listed in order of descending viscositiest. Very little influence of sodium dodecyl benzene sulfonate(SDBS) surfactant and non-ionic surfactant(AEO-9) on the dye aggregation were observed. Na2SO4had a significant impact on high concentration dye solution even at a low concentration.The dye solubilities were improved to varying degrees after adding the four additives. TM-1exhibited the best effect, while little effects of caprolactam and glycerol were discovered. The solubility of reactive dye first increased and then decreased with the increase of alkaline agent: sodium carbonate is better than sodium bicarbonate. Electrolyte significantly reduced the dye solubility.In reactive dye printing, urea and TM-1printed fabric showed higher K/S and lower permeability, and the nitrogen content in printing wastewater from TM-1was significantly lower than that of urea. The printing effects of caprolactam and glycerol were poorer. All the printing fabric exhibited good fastness to washing and rubbing that can meet the requirements of normal production.The melting point of the mixture of TM-1and dye was lower than that of urea, mixtures melt at low temperature, which was beneficial to diffusion of dye in fiber and reaction to fibre, therefore achieving good fixation effect.