Vat dyes are usually water-insoluble dyes that can be chemically reduced in the presence of base to form a water-soluble and colorless leuco form of the dye, which is then appl ied to the fiber. Vat dyes can be readily applied to cellulosic fibers and most synthetic fibers, but care must be taken in applying the dyes to protein fibers due to the high basicity of the leuco dye solution which can damage protein fibers.
The dyes are usually indigoids (such as indigo) or anthraquinone derivatives and applied at low (30 °_60 °) temperatures. After application of the leuco form of the vat dye, the dye is reoxidized on the fabric by oxygen in the air or through treatment of the dyed fabric with a mild oxidizing agent. The vat dyes are reasonably colorfast if poorly held surface dye has been removed.
Stable sulfate esters of reduced leuco forms of vat dyes are available which do not require prior chemical reduction before application.
The dyes are usually indigoids (such as indigo) or anthraquinone derivatives and applied at low (30 °_60 °) temperatures. After application of the leuco form of the vat dye, the dye is reoxidized on the fabric by oxygen in the air or through treatment of the dyed fabric with a mild oxidizing agent. The vat dyes are reasonably colorfast if poorly held surface dye has been removed.
Stable sulfate esters of reduced leuco forms of vat dyes are available which do not require prior chemical reduction before application.
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