Leuco Esters of Vat Dyes on Cellulosic Fibers

The leuco esters of vat dyes are anthraquinoid or indigoid vat dyes (Section 3.4) that have been made water soluble by reduction and esterification of the hydroxyl groups with sulfuric acid. These dyes are used mainly for dyeing high-quality articles of cellulose fibers in light colors and polyester-cellulose blends to moderate depths of shade [58], [59, p. 568], 

The advantages of dyeing with the leuco esters of vat dyes are not only good levelness and penetration but also the excellent fastness of vat dyes. The low affinity of the leuco ester for the cotton fiber and the relatively high dye costs are obstacles to wide application. After application to the fiber, the ester is hydro- 

Batch Dyeing. Because of the low substantivity of leuco esters of vat dyes for cellulose, batch processes (exhaustion processes) are rather unimportant. 

Continuous processes yield more favorable dye yields [60], The most important dyeing methods are  

As a result of their high price, low substantivity, and toxicological problems during production, the importance of the leuco esters of vat dyes is decreasing. They can be replaced easily by pigment coloring or by reactive or vat dyes. 

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