Anthraquinonoid pigments

Colorants based on the anthraquinone structure are categorized as a subclass of carbonyl colorants. Anthraquinone textile dyes rank second in importance to azo dyes, especially within the vat dye application class. Vat dyes became of interest to the pigment industry because of their insolubility. This insolubility and generally excellent fastness properties inspired investigations into the selection of suitable established anthraquinonoid vat dyes for use as pigments after conversion to a physical form that is appropriate for their applications. Originally this proved difficult, but was eventually achieved following the development of appropriate conditioning after treatment processes. The structural chemistry of the various types of anthraquinonoid pigments in relation to their technical and coloristic performance is discussed. The chapter concludes with an illustrated description of the main synthetic routes and finally with a description of the principal applications of the individual commercial products. Anthraquinonoid pigments are generally regarded as high-performance products, suitable for highly demanding applications, although they tend to be expensive.