Disazo

Disazo dyes Disazo yellow pigments Discharge printing Disclosure... 

The monoazo and disazo pigments contain one or more chromophoric groups usually referred to as the azo group. However, it... 

One area which requires special comment is a study (13) which showed that certain diaryUde pigments processed ia polymers above 200°C and particularly above 240°C decompose to give off 3,3 -dichlorobenzidine, an animal carciaogen. As a consequence diaryUde pigments (not, however, condensation disazo pigments) are not recommended for use ia any appHcations where they might be exposed to temperatures exceeding 200°C. 

Chemically, the azo class is subdivided according to the number of azo groups present into mono-, dis-, tris-, tetrakis-, etc. Mono- and disazo dyes are essentially equal in importance, trisazo dyes are less important, and tetrakisazo dyes, except for a few, are much less important. For this reason, substances with more than three azo linkages are generally included under the heading of polyazo dyes. The Colour Index]isX.s the azo dyes as follows ... 

Primary Disazo Dyes. The foHowing dyes are examples of the four types of primary disazo compounds. Their stmctures appear in Figure 3. 

Fastusol Yellow 66 [91-34-9] (25) (Cl Direct YeUow 4 Cl 24890) is a symmetrical primary disazo dye from a tetrazo component (4,4 diamino-2,2 stilbene-disulfonic acid [81-11-8],... 

Amidine Fast Red F [2429-84-7] (26) (Cl Direct Red 1 Cl 22310) is an iinsymmetrical primary disazo dye from a tetrazo component (benzidine... 

Resorcine Brown R [5850-16-8] (27) (Cl Acid Brown 14, Cl 20195) is a symmetrical primary disazo dye with bihmctional coupling component (resorcinol). 

Calcocid Blue Black Ex [1064-48-8] (28) (Cl Acid Black 1 Cl 20470) is an unsymmetrical primary disazo dye with bihmctional coupling component (H-acid). 

Secondary Disazo Dyes. There are about 250 dyes of known constitutions in this group. They are made by diazotizing an aminoazo compound, the amino group of which derives from the original coupling component and coupling it to a suitable intermediate. Intrasil Orange YBLH... 

Miscellaneous Disazo Dyes. Another group of disazo dyes is prepared by condensation of two identical or different aminoazo compounds commonly with phosgene, cyanuric chloride, or fumaryl dichloride, the fragments of which act as blocking groups between chromophores. 

Economically, the most important acid red is Acid Red 151. This disazo dye (39) is obtained by coupling -aminophenylazo)benzenesulfonic acid to 2-naphthol. 

Other disazo dyes with good substantivity and high wet-fastness properties on polyamides are Acid Red 114 (40), made by coupling o-toHdine to phenol which is then coupled to G-acid, followed by reaction of the phenoHc hydroxyl group with -toluenesulfonyl chloride, and Acid Blue 113 (41) (metanilic acid — 1-naphthylamine — 8-anilino-1-naphthalenesulfonic acid). 

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

Dyes with OjO -hydroxycarboxyazo and OjO -hydroxyaminoazo ligands are important for yeUow shades. Anthranilic acid [118-92-3] is used advantageously with various couplers. OjO -Hydroxyaminoazo dyes are also used to obtain green and brown shades. An example is Monochrome Brown EB [3564-15-6] (54) (Cl Mordant Brown 1 Cl 20110) an unsymmetrical primary disazo dye. 

Disazo JMordant Dyes. Examples of disazo dyes are Diamond Alizarine Black SN [3258-74-0] (55) (Cl Mordant Black 25 Cl 21725) and a secondary disazo dye. Diamond Black F [8027-29-0] (56) (Cl Mordant Black 5 Cl 26695). 

Direct dyes are defined as anionic dyes substantive to ceUulosic fibers (cotton, viscose, etc), when applied from an aqueous bath containing an electrolyte. Before the discovery of Congo Red in 1884, only mordanted cotton could be dyed. Congo Red [573-58-0] (62) (Cl Direct Red 28 Cl 22120) a primary symmetrical disazo dye, which is made readily from bisdiazotized benzidine and naphthionic acid [84-86-6] (4-arnino-l-naphthalenesulfonic acid), was the precursor of a most important line of dyes, including all shades, derived from benzidine and its homologues. Today, no benzidine dye is produced because benzidine is carcinogenic. 

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). 

Direct Reds. The principal commercially produced direct reds, with revealed chemistry, are of disazo or polyazo composition (Table 6). Direct Red 81 (68) is manufactured by couplingp- -aminopheny1azo)henzenesu1fonic acid to A/-benzoyl J-acid Other important direct red dyes iaclude those shown ia Figure 5. 

Direct Blues. Direct Blue 86, a phthalocyanine direct dye, represents a small but important segment of the direct dye stmcture groups. The dyes are brilliant greenish blue or turquoise shades. Sales of nearly 2 million were reported in the United States in 1988. Among the disazo blues. Direct Blue 80 (74) and Direct Blue 98 (75) were sold in 152 t and 107 t quantities at an average cost of 2.22 and 1.81/kg, respectively, in 1988. Table 7 and Figure 6 show some direct blues. 

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