Cresidine sulfonic acid

FD C Red 40 is made from diazotized cresidine sulfonic acid (4-amino-5-methoxy-2-toluenesulfonic acid) and Schaeffer s acid. Acid Red 337 is made from diazotized o-aminobenzotrifluoride and Gamma Acid. The coupling in this case is acidic, and the resulting dye is used for the coloration of nylon. 

Other commercially important direct oranges iaclude Direct Orange 26 (66) (R = H) (2 mol aniline coupled to 6,6 -ureylenebis-l-naphthol-3-sulfonic acid), and Direct Orange 72 (67) which is obtained by phosgenatiag two moles of 7-amiQO-l,3-naphthalenedisulfonic acid coupled to cresidine [120-71 -8]. 

Currently PMC, USA is a key manufacturer (approx. 600 tpa). Japan used to manufacture this item. However, currently, Japan is importing the material mostly as p-cresidine-or /io-sulfonic acid from both China and India. Two or three Chinese companies are producing the material and they offer very low price. p-Cresidine is also sold as p-cresidine vinyl sul-fones (pCVS). World demand is estimated at around 1800 tpa. 

The Colour Index (up to June 1991) lists 21 direct violets with disclosed chemical constitutions. Commercially important are Cl Direct Violet 9 [6227-14-1] (79) (Cl 27885) (sulfanilic acid coupled to cresidine followed by alkaline coupling to IV-phenyl J-acid) and Cl Direct Violet 66 [6798-05-4] (80) (Cl 29120) (a copper complex of 2-amino-l-phenol-4-sulfonamide (2 mol) coupled to 6,6,-iminobis- l-naphthol-3-sulfonic acid). 

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