Cationic dyes can be classified according to two classification methods: application performance and chemical structure type. According to the application performance, China divides the existing dyes into ordinary type, X type and M type. According to the chemical structure, it can be divided into two types: isolated type and conjugated type according to the different composition forms of the conjugated body of the cationic charge and the dye chromophore in the dye molecule.
(1) Isolated cationic dye: The positive charge in the dye molecule is connected by the conjugate system of the spacer and the chromophore of the dye, and the positive charge is fixed on the nitrogen atom of the quaternary ammonium salt. The characteristic of cationic dyes is that the amount of color given is slightly lower, the shade is not very bright, but it is heat-resistant, light-resistant, acid-base resistant, and stable. For example, Cationic Red GTL (C.I. Basic Red 18 (C.I.11085) (English name Cationic Red GTL), its structural formula is as follows:
Cationic Red GTL is dark red powder, soluble in water, dark red, reddish orange in concentrated sulfuric acid, red after dilution, dark red dyed acrylic fiber. N-ethylaniline is hydroxyethylated, chlorinated and aminated; 2-chloro-4-nitroaniline is diazotized and coupled with the above-mentioned amide, then methylated, filtered and dried. Used for the printing and dyeing of acrylic fiber and its blended fabric, and also for the dyeing of modified acrylic fiber and polyester fiber, and the printing of acetate fiber fabric.
(2) Conjugated cationic dye: The positive charge in the dye molecule is a component of the conjugated system of the dye chromophore. The positive charge is not fixed on a certain atom, but can be shifted. This type of dye is characterized by bright color, high tinting strength, but medium light fastness. For example, Cationic Yellow X-6G (C.I.48056) (English name Catinic Yellow X-6G), its structural formula is as follows:
Cationic Yellow X-6G is brown-yellow powder, slightly soluble in cold water and hot water, and dyed acrylic fiber is bright greenish yellow. It is obtained by condensation of 1,3,3-trimethylindoline acetaldehyde and p-aminoanisole, filtration and drying. Used for printing and dyeing of acrylic fiber and its blended fabric, and also for printing of acetate fiber, polyvinyl chloride fiber and modified acrylic fiber.