Reduced dye

A vat dye is a type of dye that can be dyed after reduction. They are insoluble in water. The molecule contains two or more carbonyl groups. Under the action of the alkali solution of the powder, the carbonyl group is reduced to a hydroxyl group to dissolve the dye in the alkali solution, so that the dye has an affinity for the cellulose and dyes the fiber, and then passes through the air or the oxidant. Oxidation, and then restored to the original insoluble dye fixed to the fiber. The vat dyes are classified into an anthraquinone dye and an anthraquinone dye according to the structure, among which the anthraquinone dyes are various. The vat dye is the most fast of all dyes, and the chromatogram is complete and the color is bright, which is second only to the basic dye. It can be used for dyeing and printing cotton, linen and viscose. A strong base must be used for the reduction of the vat dye, which is not suitable for the dyeing of protein fibers such as wool and silk, and the leveling property is poor. Therefore, the leuco body of some vat dyes is made into a stable water-soluble sulfate and dyed in water, and then hydrolyzed by dilute acid and reoxidized to a vat to fix on the fiber. Such dye is called soluble reduction. dye. Soluble vat dyes do not use strong alkali in the process, can dye wool, silk and other protein fibers, and the leveling is good, but the price is more expensive, and can only be used to dye medium or light color, difficult to dye dark. The vat dye has a long history. The Han Ma Tomb Ma Wang piled out the linen fabric and dyed with the plant vat dye indigo. Indigo, which is present in the form of a glycoside in plants, is leached with water and can be obtained by fermentation, hydrolysis, and oxidation. From 1870 to 1883, Bayer (AVBayer) analyzed the structure of indigo and synthesized it. In 1890, K. Heumann proposed the industrial production method. In 1897, BASF produced the first indigo dyes. In 1901, BeneBohn developed the important blue quinone vat dye linketone-indanthrene. Later, sulfur sulfonium and reduced green XBN were synthesized. By the 1930s, the basic color of these pigments was complete, and it became a commonly used dye in modern printing and dyeing factories. The vat dyes have various fastnesses. After the successful development of reactive dyes, although some of them are replaced by this dye, it is still a very important dye variety for printing and dyeing cellulose fiber textiles. The vat dye can also be used for vinylon dyeing. Some vat dyes are used as disperse dyes for dyeing polyester fibers.