Fifth, it must be soaped at high temperature.

This is because, during the soaping process, the floating dye remaining on the fabric is simultaneously affected by two forces. First, it comes from the affinity of the dye to the fiber, which has a tendency to adhere; second, it comes from the hydrophilicity of the dye's strong water-soluble group-S03Na, which has a tendency to dissolve. Increasing the soaping temperature can effectively improve the water solubility of the floating dye and reduce the adhesion of the dye, so that the floating dye on the fiber can dissolve and fall more quickly and improve the soaping effect.

Soaping at high temperature (95°C) under neutral conditions, there is no need to worry that the dye on the fiber will fall off too much. Because the dye chemically bonded to the fiber has become a part of the cellulose molecular chain, it has good binding fastness. Some manufacturers use soaping at 60-70°C because they are worried that there will be a lot of color fading after soaping, which will cause changes in shade. This will definitely not guarantee the color fastness.

Color fading by soaping is normal, because the color absorption rate of reactive dyes is always higher than the color fixation rate, and the unfixed dyes and hydrolyzed dyes should be washed down to the maximum extent. If there is too much color fading after soaping, it must be checked from the aspects of color absorption of semi-finished products, level dyeing and penetration of dyeing, sufficiency of dye fixation, acidity and alkalinity of soaping liquid, etc., and cannot be soaped at low temperature. to make up for.

Color fixation if necessary

The production practice shows that, even after washing and soaping, some floating dyes on the fibers of the dyed products of reactive dyes still have some residues. The fastness to washing and soaping is often very poor, and at this time it is generally necessary to fix the color.

The commonly used color fixing agent or cross-linking agent, after entering the fiber, on the one hand, has an ionic bond with the dye on the fiber (fixed dye and unfixed dye), and the water-soluble group of the dye is blocked to reduce its water solubility. On the other hand, it will produce cross-linking between fibers and dyes. Therefore, after the dyed matter is treated with a color-fixing agent, the dye is not easy to fall off in the wet fastness test, and even if it falls into water, the staining on the white cloth is less, so the soaping fastness of the colored cloth can be significantly improved. Wet iron fastness.