Yellow pigments diarylide yellows

Diarylamines Diarylide pigments Diarylide yellows Diaryliodomum... 

Two experiments were conducted to study the utility of HPLC in determining aromatic amines in commercial dyes. In the first experiment a benzidine based dye, Direct Blue 6, and a commercial hair dye formulation containing Direct Blue 6 were analyzed for benzidine. In the second experiment a DCB based pigment (diarylide yellow) was analyzed for residual DCB. 

Diarylammes Diarylide pigments Diarylide yellows Diaryliodoruum... 

Diazo pigments diarylide yellows, pyrazolone orange... 

Diarylide Yellows. Diaryhde or disa2o yellow pigments are represented by the foUowiag general stmctural formula ... 

Diarylide yellow pigments, 74 317 79 433 Diaryliodonium salt photoinitiators, 74 270 Diaryliodonium salts, 79 108 photolysis of, 70 414... 

For decades, P.Y.l represented the standard source of yellow for all printing purposes. Today, however, P.Y.l has been replaced in this field by the stronger diarylide yellow pigments. 

P.Y.62 exhibits comparably low tinctorial strength. A 0.5% pigment concentration in HD PE is necessary to produce 1/3 SD colorations (containing 1 % Ti02), compared to the 0.17% pigment concentration required to afford equal depth of shade with the somewhat more reddish diarylide yellow pigment P.Y.13. 

Acetoacetarylides and l-aryl-pyrazolone-5 are the two most common coupling components. The former affords diarylide yellow pigments (Sec. 2.4.1), while the latter produces disazopyrazolone pigments (Sec. 2.4.3). 

The printing ink industry, currently the most important area of application for diarylide yellow pigments, first introduced these products around 1938 in the USA. 

The chemically most simple diarylide yellow pigment is made from bisdiazo-tized 3,3 -dichlorobenzidine and acetoacetanilide. This pigment exhibits high tinctorial strength, a property which is particularly useful for process printing inks, for which other diarylide yellow pigments were later developed. 

Commercially significant diarylide yellow pigments have the following chemical structure ... 

In order to manufacture a diarylide yellow pigment, the diamine, dissolved in hydrochloric acid or sulfuric acid, is bisdiazotized with an aqueous sodium nitrite solution. The resulting diazonium compound is subsequently coupled onto two equivalents of acetoacetarylide. Since a material with a very fine particle size is needed for a fast and complete coupling reaction, the coupling component is prepared by dissolution in an alkaline medium and reprecipitation with an acid, such as acetic acid or hydrochloric acid. Dichlorobenzidine cannot be diazotized stepwise. A lack of sodium nitrite does not produce the monodiazonium compound, but an excess of 3,3 -dichlorodiaminodiphenyl remains. 

Adsorption of e.g. rosin (abietic acid) at the pigment surface may - depending on the concentration of the rosin - reduce or accelerate the crystal growth. The presence of an excess amount of rosin during the production of diarylide yellow pigments of the Pigment Yellow 13 type affords an additional crystal modification, which can be identified by X-ray diffraction spectroscopy [4],... 

Diarylide yellow pigments range in shade from very greenish to extremely reddish yellow. The more greenish types almost exclusively contain 2,2, 5,5 -tetra-chlorobenzidine in place of the otherwise more common 3,3 -dichlorobenzidine. 

Most commercial varieties of diarylide yellow pigments are materials with comparatively fine pigment particles and specific surface areas between 50 and 90 m2/g. 

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