First, in a color-fixing bath where salt and alkali coexist, the dye will have a higher concentration of electrolyte (salt, alkali), a greater salting-out effect, and the occurrence of "elimination reaction" of the active group of ß-hydroxyethyl sulfone sulfate. , the water-solubility of its own plummeted, resulting in different degrees of "coagulation". 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.
Second, 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 loss of soda ash (also electrolyte). When added, the electrolyte concentration increases abruptly, resulting 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).
Third, the fixation rate of medium-temperature reactive dyes is relatively low (60% to 70%), and the dyes have different degrees of "agglomeration" and "sudden dyeing" problems in the fixation stage, so fiber (or The floating rate of dyes on fabrics (including hydrolyzed dyes, semi-hydrolyzed dyes and unhydrolyzed and unfixed dyes) is relatively high, and the requirements for soaping after dyeing are harsh. If soaping is not in place, its dyeing fastness will inevitably be low.