A low chemical consumption cationization and salt-free dyeing process for cotton fabrics by reusing polyallylamine modification bath.

Cationic polymers have been used in the cationization of cotton fabrics for salt-free dyeing, but commonly used polymers are limited by their high molecular weight and low adsorption efficiency, leading to high dosage or complex modification conditions. In this study, polyallylamine with low molecular weight was found to be an efficient cationic agent for cotton modification and the modified fabrics can be salt-free dyed with different kinds of reactive dyes after the optimization of the modification process. Furthermore, the modification bath was reused by replenishing a small amount of cationic agent and adjusting the pH to the original level. The results showed that all the salt-free dyed cotton fabrics had excellent performance when the fabrics were modified with a 2 g L polyallylamine solution at pH 12 for 1 h. During five consecutive bath reusing cycles, the elemental nitrogen content, zeta potential, and salt-free dyeing performance of the modified cotton fabrics were relatively stable, all the uptakes of C.I. reactive red 24 were >75 %, and all the K/S values of the dyed fabrics were higher than 11, much greater than that of conventional dyeing (about 6). In addition, compared with the conventional dyeing process and the salt-free dyeing with the bath-unreused route, the bath-reused and salt-free dyeing process reduces by 98.36 % and 62.31 % chemicals consumption per kilogram of dyed cotton fabric, respectively. This work provides a low-pollution process for salt-free dyeing of cationic cotton fabrics and provides a reference for improving the utilization efficiency of the cationic agent.