1、 Cause of occurrence

1. The solubility stability of reactive turquoise blue and reactive light yellow in salt and alkali solutions is poor. Once too much or too early salt and soda ash are added, it is easy to produce condensation, which seriously affects the uniform adsorption and diffusion of dyes, resulting in excessive floating color and a decrease in dyeing fastness.

2. The relative molecular weight of reactive turquoise blue is relatively large, lacks linear structure, and has poor diffusion. Especially during the secondary absorption process, due to the fact that the adsorption rate of dyes is much higher than the diffusion rate, more dyes form overlapping piles on the fiber surface. In addition, reactive turquoise blue has weak reactivity, low fixation rate, and more unfixed dyes remain on the fiber, resulting in poor washability and low wet treatment fastness, as well as poor level dyeing and penetration effect.

3. Due to the high sensitivity of reactive light yellow to alkaline agents, the phenomenon of "instant coloring" is severe in the initial stage of secondary absorption. In addition, the fixed dyes have a certain blocking effect on the diffusion of dyes adsorbed on the fiber surface but not fixed, resulting in excessive floating color and affecting wet treatment fastness and levelness.

2、 Prevention and control methods

To improve the wet treatment fastness of dyeing bright green with reactive turquoise blue and reactive light yellow, in terms of dyeing process alone, the following methods can be adopted:

1. Improve the diffusion and penetration effect of dyes, and increase the fixation rate (mainly reactive turquoise blue).

2. Improve the solubility of dyes and prevent dye condensation in the dye solution. When dyeing bright green with reactive turquoise and reactive light yellow, it is not advisable to use pre alkali dyeing method, let alone the dyeing method of adding salt and soda ash at the same time. Otherwise, it can easily cause dye condensation and precipitation (the problem of reactive light yellow is the most prominent), leading to serious dyeing problems.

3. Strengthen post dyeing soaping to reduce the adhesion of floating dyes. Never use the process of "simply soaping first, then fixing the color with a fixing agent". Because in situations where there is a lot of floating color, using a fixing agent to fix the color can improve the washing fastness, but the rubbing fastness is poor, and it can also affect the brightness and light fastness, making it difficult to repair the color after dyeing.

4. Reduce the dye uptake rate during the dyeing process (mainly during the initial stage of alkali addition).

Of course, before dyeing, the fabric should be thoroughly pre-treated, and some of the measures proposed above are based on a uniform and consistent whiteness and wool effect.