Commonly used pastes such as starches are carbohydrates containing a large amount of hydroxyl groups. It can bond with reactive dyes to reduce the amount of color. Moreover, this product has a low dissolution bottom and is difficult to clean. When the fabric is in a wet state, it often causes phenomena such as bleed and take-up, seriously affecting the physical properties of the printing paste and reducing the quality of the printing paste.
Although the chemical structure of sodium alginate also contains hydroxyl groups, all of them are secondary hydroxyl groups, and the dye binding ability is low. In addition, sodium alginate is anionic and has a repellent effect on anionic reactive dyes. Therefore, it is substantially impossible to bond with a reactive dye, so it is a suitable paste for a reactive dye.
However, it should be noted that sodium alginate and calcium ions in hard water can precipitate and reduce their flow enthalpies. The paste containing calcium alginate can react with reactive dyes under neutral and weak alkaline conditions. Can produce insoluble substances. To this end, it is necessary to add complexing agents such as sodium hexametaphosphate and sodium metaphosphate to prevent this phenomenon from occurring.
Reprinted from: China Printing and Dyeing Network