1 Choose the right dye
The color fastness is closely related to the structure of the dye, and the selection of the dye should consider:
① Strong reactivity between dyes and fibers;
②High fixation rate;
③It has better acid-base stability;
④ The bond energy of the covalent bond of the dye-fiber is high, the chemical stability is better, and the bond is not easy to break;
⑤ The ability of antioxidants and reducing agents is better;
⑥ The compatibility and compatibility of color matching dyes are better.
2 Choose the right dyeing process
The dyeing process has a great influence on the color fastness. The selection of the dyeing process can be considered from the following aspects:
a. ① Try to use higher temperature dyeing, such as using medium temperature dye (KN type) dyeing, the dyeing temperature can be increased from 60~65℃ to 75~80℃, and then reduced to 60~65℃, and then add alkali to fix the color;
②Using low temperature weak alkali to fix color;
③The fixing temperature is generally 60~65℃;
④The fixing agent adopts a single soda ash;
⑤ pH is stable at around 11;
⑥ Soda ash is added in stages;
⑦ Use the correct water washing and soaping process. The purpose of soaping is to remove floating color, and the purpose of water washing is to remove the residual alkali agent on the fiber. Washing and soaping should prevent the bonded dyes from breaking, hydrolyzing, and falling off the fibers.
To this end, pay attention to the following points: wash with water before soaping, choose a soaping agent with good washing ability, dispersing ability, emulsifying ability and dirt-carrying ability, it must be at a higher temperature (90 ° C) and under neutral conditions Soap.
b. For special reactive cyan dyes, hydrolysis is accelerated under the condition of salt. R brilliant blue has high directness and is very sensitive to alkali. A special dyeing process is given for these two special dyes, which is different from conventional KN dyes. , for the special Cuilan and Yanlan, different dyeing heating curves and the process of adding saline and alkali are introduced, so it is necessary to avoid the generation of colored flowers and improve the reproducibility.
Fixing and Fixing Treatment Methods
After the reactive dyes are dyed and fixed, although they form covalent bonds with the fibers, there are more or less unfixed dyes on the fibers, especially in the pores of the fibers. In addition, in the application stage, the dyes in the fibers may also break bonds to form hydrolyzed dyes. In the wet state, these dyes will diffuse out of the fibers, causing desorption and reducing color fastness, especially for some dark products. . To this end, after dyeing with reactive dyes or after thorough washing, cotton fabrics are treated with some color-fixing agents for color-fixing treatment.
1 Fixing agent requirements
①Environmental protection, no pollution to the environment;
②After being fixed by the color-fixing agent, it can comprehensively improve the color fastness, including soaping fastness, dry and wet grinding fastness, acid-base perspiration fastness, etc.;
③After fixing by the fixing agent, the color change should be small, the color light of the fabric will not be affected, and the hand feeling will be less affected, which is convenient for production control;
④The color-fixing agent is required to be safe, non-toxic, and does not produce toxic and harmful substances during storage and use.
2 Fixing mechanism
①Using the cationic groups in the molecules of the formaldehyde-free fixing agent and the anionic groups in the dye molecules to form ionic bonds to form precipitation on the fibers, thereby reducing the water solubility of the dyes and improving the soaping fastness and white background of dyed fabrics For color fastness, the more cationic groups in the molecules of the color-fixing agent, the stronger the cationicity, the better the soaping fastness of the fabric after color-fixing.
②Using the film-forming properties of the color-fixing agent, a firm film is formed, and the dye is firmly wrapped on the surface of the fiber, thereby improving the fastness of dyed fabrics, especially the rubbing fastness.
③Using the intermolecular attraction between the fixing agent and fibers and dyes to increase the fixing strength of the fixing agent, thereby improving the dyeing fastness.