The addition of salt in the dyeing solution enhances the dye uptake. The electrical ions produced by dissolving salt in water can reduce the charge effect during the fiber dyeing process, and therefore have a significant effect on the promotion of basic dyes. Cellulose fibers in the neutral or weakly alkaline dye bath will have surface potentials that can generate a certain mutual charge repulsion with the basic dye anion. After adding the salt electrolyte solution, a large number of positively charged sodium ions bind to the dye anion. The charge neutrality is maintained, which greatly reduces the difficulty in the dyeing process, and can promote the close contact of the fiber surface with the dye molecules, reduce the concentration difference between the dye liquid and the fiber interface, and enhance the printing and dyeing effect of dyes and fibers. The dyeing process can be gradually divided into three stages: adsorption, diffusion, and fixation. In the adsorption stage, it should not be colored too quickly. If electrolytes are added during the adsorption stage, dyestuffs may aggregate and cause uneven dyeing. The addition of electrolytes in the middle can avoid the above mentioned conditions and increase the printing and dyeing rate in the printing and dyeing process.
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