One of the most important inventions in the fields of textile dyes that were made in the 20th Century was VAT Dye. These chemically complex, water insoluble dyes need to be first reduced to the leuco form by dissolving them in an alkaline solution of sodium hydrosulfite, before they can be used for coloring various materials. The production process of these dyes is quite complex, mainly due to their complex chemical structures. That is why even though these indigo based, dyes form one of the most ancient class of dyes, they now are largely produced synthetically to meet industry requirements.
Vat dyes have a unique working mechanism and are suitable for coloring a wide range of materials including, cotton, wool and other fabrics. However, the application of VAT dye is much more complex as compared to direct dyes or reactive dyes. The process is a combination of several smaller processes including oxidation, reduction, pH control etc. It is also important to be aware of the right quantities of caustic soda and sodium hydrosulfite required for the proper reduction of the dyestuff.
These dyes are generally sold in the form of pigments. It is necessary for the buyers to be aware of the dissolution and other coloring related properties of these dyes, as these characteristics can be easily affected by the particle size of the dye. The dyeing properties might also be affected by the different chemical structures of the dyes, which also play an important role in determining the stability of the dye towards excessive reduction and excessive oxidation, its substantivity as well as its rate of diffusion into and out of the target material.
It is possible to get vast shades of bright colors with the help of VAT dyes. These dyes are also washfast and lightfast and it is rare to find these properties in any other class of dyes. The one drawback that these dyes suffer from is slightly poor rubbing fastness, which can be controlled by applying special treatment to the target material. However, Vat dye is not considered suitable for use for home dyers as they are slightly difficult to work with. Irrespective of that, these dyes are preferred for dyeing specific types of industrial yarns, terry cloth, industrial work clothing and shirting fabrics. Moreover, they are the only dyes that do not exhibit any serious changes in shade when exposed to topical, cellulose reactive and flame retardant finishes.
Royce is a fully diversified international company which was founded in 1929 to manufacture chemicals for textile industry.
