Types of cationic dyes.-Nantong Longrun Chemical Co., Ltd

Cationic dyes can be classified according to two classifications: application properties and chemical structure type. According to the application performance, China classifies the existing dyes into normal, X-type and M-type. According to the chemical structure, they are classified into two types: isolated and conjugated, depending on the composition of the cationic charge in the dye molecule and the conjugate of the dye chromophore.

(1) Isolated cationic dyes: The positive charge in the dye molecule is connected to the conjugate system of the dye chromophore through the isolation group, and the positive charge is fixed on the nitrogen atom of the quaternary ammonium salt. Cationic dyestuffs are characterised by a slightly lower amount of colour giving and a less vibrant colour light, but are resistant to heat, sunlight, acids and alkalis, and have good stability. For example, Cationic Red GTL (C.I. Basic Red 18 (C.I. 11085) (English name Cationic Red GTL) has the following structural formula:

Cationic Red GTL is a dark red powder, soluble in water, dark red, reddish orange in concentrated sulphuric acid, red when diluted, acrylic dyed dark red. Adopting N-ethyl aniline hydroxyethylation, chlorination, ammoniation; 2-chloro-4-nitroaniline diazotisation coupled with the above ammonia, and then methylation, filtration, drying to produce. It is used for the printing and dyeing of acrylic and its blended fabrics, and can also be used for the dyeing of modified acrylic and polyester, and the printing of acetate fabrics.

(2) Conjugated cationic dyestuffs: The positive charge in the dye molecule is part of the conjugated system of the dye chromophore, and the positive charge is not fixed on a certain atom, but can be shifted. These dyes are characterised by bright colours and high colouring power, but medium fastness to sunlight. For example, Cationic Yellow X-6G (C.I. 48056) (English name Catinic Yellow X-6G) has the following structural formula:

Cationic Yellow X-6G is brownish-yellow powder, slightly soluble in cold and hot water, bright greenish-yellow in acrylic dyeing. It is produced by condensing 1,3,3-trimethylindoline acetaldehyde with p-aminoanisole, filtered and dried. It is used for the printing and dyeing of acrylic and its blended fabrics, and can also be used for the printing of acetate fibre, PVC fibre and modified acrylic fibre.