Cationic dyes are dyes that can be dissociated into positively charged ions in aqueous solution. They can interact with the negative groups on the fiber molecules to form salts, which can be further firmly attached to the fibers, thereby staining the fibers. Cationic dyes have been successfully developed based on alkaline dyes. The stained principle of cationic dyes is to dye the fibers by combining their cations with acidic groups in the third monomer of acrylon, thereby resulting in high fastness. Cationic dyes are originally used in the dyeing of silk, leather, paper and cotton, as well as the production of ink and copying paper in the office supplies industry. With the development of synthetic fibers, the importance of cationic dyes for dyeing textiles has greatly increased.
Dyeing of synthetic fibers: Mechanism of dyeing synthetic fibers by cationic dyes has been proposed: The cationic chromophore is first absorbed by the fiber surface with negative electricity and then diffuses into the interior of fiber at an elevated temperature; it binds to the active acid groups, but the number of which is limited, so its accessibility depends on temperature and fiber composition. Therefore, the dyeing characteristics of cationic dyes are determined by affinity and diffusibility. Cationic dyes are also used to dye polyacrylonitrile fibers during spinning.
Dyeing of paper, leather, and other substrates: Cationic dyes exhibit good affinity for negatively charged wood pulp and unbleached pulp grades. Cationic dyes are chosen because of their brilliance and intensity, which makes them particularly useful for recycled paper grades. Several cationic dyes linked with substantial moieties, such as urea or triazine, are particularly effective for bleached lignin-free pulp grades. Cationic dyes are the first synthetic organic dyes used to dye leather and originally used for the dyeing of vegetable tanning leathers. Because of their color strength, cationic dyes are also used in the office supplies industry to produce ink, typewriter ribbons, and copying paper. The colorless derivatives of cationic dyes can be applied in the manufacture of carbonless paper and special paper for thermal printers.