L-Amino-8-hydroxynaphthalene-3,6-disulfonic acid

Modified PAN fibres containing aldehyde groups can be used to obtain chemically stained fibres. The chemical addition of dyes can be conducted following two schemes A) The fibres of the above composition are treated with aromatic amines, e.g., l-amino-8-hydroxynaphthalene-3,6-disulfonic acid ( H-acid ), and then azocoupling is carried out with a diazonium salt ... 

An example is C. I. DirectBlack 166, 30026 [57131-19-8] (14). The first step is the acid coupling of 3,3 -diaminobenzanilide to l-amino-8-hydroxynaphthalene-3,6-disulfonic acid (H-acid), followed by alkaline coupling of aniline to the mono-azo dye and finally coupling of the disazo dye to w-phcnylenediaminc. 

A dye component that is used frequently is H acid (l-amino-8-hydroxynaphthalene-3,6-disulfonic acid). Production of this comparatively complex substitution pattern requires a series of different chemical reactions. The known side reactions and subsequent reactions on sulfonation and nitration of the naphthalene system and high-pressure hydrolysis of its substituents reduce the yield of the target product. If, as a consequence, intermediate isolations are unavoidable during the course of the process to prevent a gradual increase in the amount of by-products, additional product losses in mother and wash liquors will occur. Management of the often considerable quantities of solid waste and wastewater is therefore an important consideration in the production of H acid. 

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