There are three major defects in the medium temperature reactive dye dip dyeing
1. In the fixing bath where salt and alkali coexist, the dye will have a higher concentration of electrolyte (salt, alkali), the salting-out effect is greater, and the "elimination reaction" of the active group of ß-hydroxyethyl sulfone sulfate will occur. The sudden drop of its own water-soluble capacity produces different degrees of "cohesion". Especially some vinyl sulfone dyes, the performance is getting worse. Such as C. I. Active Yuanqing 5, C. I. Reactive Brilliant Blue 19, C. I. Reactive Turquoise Blue 21 and so on. Too much "cohesion" of the dye will inevitably cause uneven color, even color spots and stains, and also affect the purity of the shade and the fastness of the color.
2. During the alkali fixation stage (especially the initial stage of fixation), the dye in the dye bath will occur immediately due to the bonding fixation reaction, the original color absorption balance will be quickly broken, and the addition of soda ash (also electrolyte) , The abrupt increase of the electrolyte concentration produces different degrees of "sudden dyeing", especially the performance of vinyl sulfone dyes. Too much "sudden dyeing" of the dye will undoubtedly cause obvious or even serious adverse consequences to the dyeing quality (level dyeing effect and dye fastness).
3. The fixation rate of medium-temperature reactive dyes is relatively low (60%～70%). In addition, the dyes have different degrees of "cohesion" and "sudden dyeing" problems in the fixing stage, so the fiber (or fabric ) The floating rate of the dyes (including hydrolyzed dyes, semi-hydrolyzed dyes and unhydrolyzed and unfixed dyes) is high, and the requirements for soaping after dyeing are strict. If the soaping is not in place, the dyeing fastness will inevitably be low.