Application Of Biocompatible Cationic Reagents In Salt-free Dyeing

The cationization of cotton can improve the affinity between the reactive dyes and the cotton,therefore it could improve the dye exhaustion and fixation.With this method,salt pollution in the dyeing process of reactive dyes was eliminated and color pollution was reduced.In this study,3-chloro-2-hydroxypropyltrimethylammonium chloride(CHPTAC) and betaine were used as cationic agents to cationize cotton.These two cationic agents were both biocompatible and green agents.In this study,a two-bath pad-bake process was designed to separate the usage of CHPTAC and alkali in two baths,and relatively low reaction temperature and short reaction time were investigated for preparation of cationic cotton to avoid reagent migration to the great extent.Experiments showed that 8.0%(o.w.bath) of the reagent,1:1 of molar ratio of sodium hydroxide to the reagent,60℃and 6min of baking temperature and time were selected for cationization and the obtained cationic cotton was suitable for application in salt-free reactive dyeing.Thus the recycle of CHPTAC and continuous processing of preparation of cationic fabrics could be realized,which will increase cationization efficiency and reduce environmental impact.With this method,the dye exhaustion and fixation were near or higher than that of the traditional method,and the fastness properties of the dyes and the mechanical strehgth of the dyed fibers were both good.Moreover,X-ray diffraction(XRD) and scanning electronic microscopy(SEM) were used to evaluate the structure properties of the fibers,and the results showed the structure of cotton was almost not affected after cationization process.In this study,the effects of the concentrations of betaine and dicyandiamide on exhaustion of reactive dyes were studied.And the optimal conditions of cationization were determined.Experiments showed that 6.0%(o.w.bath) betaine,6.0%(o.w.bath) dicyandiamide,120℃and 4min of baking temperature and time were selected for cationization and the obtained cationic cotton was suitable for application in salt-free reactive dyeing.Under the conditions,the color strength(K/S) and fastness properties of the dyes were closed to that of the tradional method.Moreover,the adsorption behavoir of the cationic cotton was studied.The dyeing of cationic cotton was showed to follow Langmuir-type adsorption at specific sites.XRD and SEM showed the structure of cotton was almost not affected after cationization process.