What are the requirements for dye performance in cold pad batch dyeing?

1 The salt and alkali resistance of dyes should be high in solubility and stability. Because high-concentration electrolytes have a strong "salting-out effect" on the solubility of dyes, the solubility of the dyes will be greatly reduced, causing the dyes to separate out from the dyeing solution to produce poly-dyeing, Precipitation, resulting in color spots.

2 The hydrolysis resistance and stability of each color matching combination of the dyes should be similar, and the hydrolysis resistance stability should be good. The active groups of reactive dyes are prone to hydrolysis in alkali-containing solutions and lose their dyeing ability. The dye liquor of cold pad-batch dyeing has strong alkalinity, and the inconsistent hydrolysis resistance stability of the color-matching combination dyes is prone to color difference between the head and the tail or the color difference between the rolls.

3 The directness of the dye is not easy to be too high, and the directness of the color matching components is similar. The dye and the salt-alkali bath in the cold pad batch dyeing solution are compared to the traditional two-phase method rolling, drying and steaming the dyeing solution to the cellulose fiber. The directness is high, and the front and back (dark and light) color differences are likely to occur during the padding process.

4 Dyes have stronger reactivity with cellulose fibers, due to the low temperature (about 25°C) during the stacking process of cold pad dyeing for slow fixation: Although the pH value of the dyeing solution is higher, the dyes have stronger reactivity with fibers. Inter-(bonding) reaction to obtain high color fixation depth.

5 When mixing colors, select dyes with similar dye ratio shift values. The dye ratio shift value is small, and the dye affinity is larger, and the dyeing speed is faster; the dye affinity is small when the ratio shift value is small, and the dyeing speed is slow. , Make corrections during production.