Cationic dye

Cationic dyes are dyes that can dissociate into positively charged colored ions in aqueous solution. They act to form a salt with a negative group on the fiber molecule, firmly attached to the fiber, and dye the fiber. Cationic dyes are one of the basic dyes and have been successfully developed on the basis of basic dyes. However, unlike the dyeing principle of basic dyes, cationic dyes combine the cations with the acidic groups of the third monomer in acrylic fibers. The fiber is dyed, so the fastness is high, but it is easy to cause uneven dyeing. Therefore, a retarder is often added to the dyeing to improve the dyeing performance. Cationic dyes are special dyes for acrylic fiber dyeing. In addition, they can also be used for dyeing and printing of modified polyester and nylon. Mainly used for dyeing polyacrylonitrile fibers. So far, the old varieties are still referred to as basic dyes, and the new varieties are called cationic dyes. Cationic dyes include azo dyes, triarylmethane dyes, anthraquinone dyes, and heterocyclic compounds. It is generally used that the cationic portion of the dye body having a mercapto group forms a salt with hydrochloric acid (or sulfuric acid), and the cation at this time is mostly an N+ ion. This dye is water-soluble, has a stronger affinity than acrylic fiber, and has high fastness. On the other hand, it is not easy to migrate once dyed, resulting in poor leveling. For this purpose, a retarder can be added. There are two ways of connecting the color-conjugated system of cationic dyes with sulfhydryl groups. One of them is a conjugated type. These dyes have bright color and strong coloring power, and have the advantages of basic dyes, such as: methine dyes, three Benzene dye, azo methine dye. The second is that the conjugated system and the sulfhydryl group are separated by a spacer group (that is, the positive charge is fixed on the nitrogen atom of the quaternary ammonium salt), and the dyes have better color vividness and tinting strength than the conjugated type. However, it is excellent in light resistance and heat resistance, and is mostly used for dyeing in light colors, such as an anthraquinone dye or an azo dye. Since the dye has a strong affinity for the interaction of the dye cation affinity with the anionic group introduced into the fiber, the fastness of dyeing is high, but the dye having a high dyeing concentration is difficult to migrate to a portion having a low dyeing concentration, and thus it is easy. A defect that causes uneven dyeing. Cationic dyes are now mostly used for the dyeing of polyester fibers and acrylic fibers. If an acidic group is introduced into the diacetate fiber and the vinyl chloride fiber, it can also be used for dyeing. For certain blended products, when cationic dyes are used, they can be dyed with a carrier or dyed at a high temperature. For some blends (such as polyester fibers and wool fibers), a combination of cationic dyes, acid dyes, direct dyes, reactive dyes, and the like is used for dyeing. In this case, precipitation and tarification occur, and an anti-precipitation agent can be used. Recently, a dispersive cationic dye suitable for such a blend has been developed, that is, a cationic dye and a phosphomolybdic acid, a specific complex, or a condensate of a naphthalenesulfonic acid and a formaldehyde solution, and a salt of lignosulfonic acid or the like. to make. If the dye starts to rise in temperature, the cation slowly dissociates and can be used in combination with a cationic dye such as an acid dye, a direct dye or a reactive dye. There are many types of cationic dyes, and the preparation methods vary. For example, the methine dye and the azo methine dye are prepared by a condensation reaction of an aromatic aldehyde with an active methylene group and an aromatic amine, or a condensation reaction of an aromatic diazonium salt with an active methylene group. Azomethine dyes are generally prepared by azo coupling reactions. Triphenylmethane dyes utilize the condensation of aromatic aldehydes and aromatic amines. A pyridazine dye is a condensation of an aromatic nitroso compound with an aminophenol. But usually it is the formation of hydrochloride, sulfate.