Disazo colorants

The situation becomes more complex when two separate diazotisations and azo couplings are required. Four separate strategies leading to disazo colorants may be identified, using the commonly accepted SDC terminology and symbolism, exemplified as follows as strategies (a)-(d). 

Among the acid colors of green, brown, and black shades, three disazo dyes are important Acid Green 20 (42) -nitroaniline------ H-acid... 

Direct Oranges. AU principal commercially produced direct oranges are of disazo or stUbene chemical composition (Table 5). Direct Orange 102 (65) (R = COO Na+ ), is manufactured by first coupling aniline to 6,6 -ureylenebis-l-naphthol-3-sulfonic acid foUowed by a second coupling with /)-aminobenzoic acid [150-13-0]. 6,6 -Ureylenebis-l-naphthol-3-sulfonic acid [134-47-4] is the coupling component in many of the most important direct colors. It is produced by phosgenation of two moles of J-acid (6-ainino-l-naphthol-3-sulfonic acid). 

The most prevalent metal complex dyes for textile and related applications are metal complex azo dyes. Their colors span the entire spectrum although, as described earlier, they tend to give dull shades. They may be 1 1 dye metal complexes or 2 1 complexes and contain mainly one (mono-azo) or two (disazo) azo groups. 

Disazo Black, colorant for plastics, 7 374t Disazo Condensation Orange, pigment for plastics, 7 367t... 

Commercially viable systems for the decolorisation of spent dyebaths can be based on hydrogen peroxide treatment initiated by UV radiation. A representative selection of six disulphonated monoazo acid dyes and two disazo disulphonated types was exposed for various times in a pilot-scale photochemical reactor of this kind. The controlling parameters were dye structure, pH, peroxide dosage and UV light intensity [39]. In a wider survey of the response of various classes of dyes to the combination of UV radiation and hydrogen peroxide, viable candidates for further in-plant treatment trials were the water-soluble reactive, direct, acid and basic classes. On the other hand, water-insoluble colorants such as disperse and vat dyes did not appear to be viable [40]. 

Molecular dimerization, as in the transition from Hansa Yellow to disazo yellow pigments, increases the color strength considerably. A comparison of a Naph-thol AS/disazo condensation pigment pair gives similar results ... 

The paint industry is interested in individual representatives of this class, such as P.Y.128. These are used to color high grade paints, such as automobile (O.E.M) finishes and automotive refinishes. Other types are used in general industrial paints. As a rule, the fastness of disazo condensation pigments to overcoating is good to excellent in some media. The pigments are also used in architectural paints, sometimes also in emulsion paints. 

Various disazo condensation pigments are utilized in decorative printing on laminated plastic sheets. They are also applied in a number of special-purpose media outside the above-mentioned groups, such as oil colors for artists and crayons. 

By exhaustive alkylation of 3-aminophenylpyrazolone compounds, a trimethy-lammonium moiety can be introduced into this coupling component. The disazo dye 7 [86565-98-2] colors paper in orange shades [28],... 

The mono and disazo resorcinol dyes can act as indicators and change color very markedly, depending on pH. Monoazo and disazo varieties are often found as byproducts with higher molecular weight resorcinol dyes. This property makes them less obtrusive on leather. Because of their strong intermolecular forces of attraction, resorcinol dyes are very well fixed on leather, despite their low to medium molecular weight. Their indicator properties are scarcely noticeable, in contrast to the case with textiles. This explains why these dyes are not necessarily suitable for textiles, particularly polyamides. 

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