In the color-fixing bath where salt and alkali coexist, the dye will be water-soluble due to the high concentration of electrolyte (salt, alkali), the greater salting-out effect, and the occurrence of the "elimination reaction" of the active group of ß-hydroxyethyl sulfone sulfate. The ability to drop sharply, resulting in different degrees of "cohesion". Especially some vinyl sulfone dyes, the performance is more serious. such as C. i. Active Yuanqing 5, C. i. Reactive brilliant blue 19, C. i. Active Turquoise Blue 21 and so on. Excessive degree of "agglomeration" of dyes will inevitably result in uneven color, even color spots and stains, and will also affect the purity of the shade and the fastness of the color.
In the color-fixing stage of adding alkali (especially the initial stage of color-fixing), the dyes in the dye bath will be caused by the rapid occurrence of bonding and fixing reaction, the rapid breaking of the original color absorption balance, and the addition of soda ash (also electrolyte), the electrolyte The sudden increase of the concentration results in different degrees of "sudden dyeing", and the performance of vinylsulfone dyes is particularly prominent. Excessive degree of "sudden dyeing" of dyes will undoubtedly cause obvious or even serious adverse consequences to the dyeing quality (level dyeing effect and dyeing fastness).
The fixation rate of medium-temperature reactive dyes is relatively low (60% to 70%), and the dyes have different degrees of "cohesion" and "sudden dyeing" problems in the fixation stage, so the fiber (or fabric) The floating rate of dyes (including hydrolyzed dyes, semi-hydrolyzed dyes and unhydrolyzed and unfixed dyes) is relatively high, and the requirements for soaping after dyeing are harsh. If the soaping is not in place, the dyeing fastness will inevitably be low.