Trisazo dyes

The trisazo dyes include in particular blue, green, and black grades. Diamines used are 4,4 -diaminobenzanilide (DABA) and 4,4 -diaminodiphenylaminc-2-sul-fonic acid (DADPS). The most important synthetic principle in this range is the type K i — Di- K2 — D2. The sequence of the three couplings depends on the nature of the components. 

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. 

Direct Black 150, 32010 [6897-38-7] (15), is produced by double (alkaline) coupling of bis-diazotized 4,4 -diaminodiphenylamine-2-sulfonic acid to y acid and subsequent single coupling to m -phenylenediamine. 

Among the trisazo dyes, series coupling of the type D— Mi- M2— K is also of importance. This group contains a number of dyes with good to veiy good general fastness properties. 

Anilinesulfonic acids are chiefly used as starting component D, naphthylamine and Cleve acids as middle components Mi and M2, and I acid, its /V-phenyl derivatives, H acid, 2-amino-8-hydroxynaphthalene-6-sulfonic acid (y acid), and their derivatives as final component K. This type mainly possesses blue and green shades. Example C. I. DirectBlue 78, 34200 (16) [2503-73-3], 

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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 ... 

Direct Blue 218 had reported sales of 623 t valued at 4.4 million ia 1987. It is produced from Direct Blue 15 (76) by metallizing and elimination of methyl groups from the methoxide to form the copper complex. Direct Blue 15 (76) is prepared by coupling o-dianisidine [119-90-4] to two moles of H-acid (4-amiQO-5-hydroxy-2,7-naphthalenedisulfonic acid) under alkaline pH conditions. Other important direct blues iaclude Direct Blue 80 (74), (9-dianisidine coupled to two moles of R-acid (3-hydroxy-2,7-naphthalenedisulfonic acid [148-75-4]) followed by metallizing to form a bis copper complex, and Direct Blue 22 (77), an asymmetrical disazo dye, prepared by coupling o-dianisidine to Chicago acid [82-47-3] and 2-naphthol. Direct Blue 75 (78) is an example of a trisazo dye represented as metanilic acid — 1,6-Q.eve s acid — 1,6-Q.eve s acid — (alb) Ai-phenyl J-acid. 

Tris(tribromoneopentyl) phosphate, 11 492 Tris(tribromophenyl) triazine, 11 467 Tris- 1-phenylethylcarbamate chiral stationary phase, 6 88t Tris-3,5-dichlorophenylcarbamate chiral stationary phase, 6 88t Tris-3,5-dimethylphenylcarbamate chiral stationary phase, 6 88t Trisaccahrides, 4 697 Trisanyl, 4 358t Trisaturates, 10 813 Trisazo dyes, 9 363... 

Numerous linear diamines, such as many of those in the survey mentioned above, have been evaluated as potential replacements for benzidine, an inexpensive and highly versatile intermediate that was banned in the 1970s because it posed a carcinogenic threat. Two trisazo dyes have been synthesised recently using 4,4, diaminodiphenyl thioether instead of the benzidine component of Cl Direct Black 38 (3.112 X = Y = NH2) and Cl Direct Green 1 (3.112 X = OH, Y = H). These new dyes exhibited higher substantivity and fastness to washing than the two traditional products on cellulosic fibres [119]. 

A further extension to the trisazo dyes on the principle of series coupling D—>Mr M2— M3— K offers no advantages, because the intermediate isolation that is frequently necessary leads to yield losses, and a chain extension is therefore ruled out on economic grounds. This is also reflected in the number of poly-azo dyes listed in the Colour Index [5], Although 78 tetrakisazo dyes with eleven different synthesis principles are listed, only 14 dyes with five and more azo groups are mentioned, two of which are specified with eight azo groups. 

In the manufacture of trisazo dyes, good yield and purity during final coupling are often obtained only in the presence of pyridine or other bases as coupling accelerators [10], Intermediate isolation and separation of impurities prior to continuation of coupling are also frequently necessary. 

With aromatic diamines and triamines as the diazo components, cationic substantive disazo and trisazo dyes (e.g., 16 [62073-65-8]) are obtained, which are suitable for bulk dyeing of paper [47],... 

Since such light fast, direct dyes are usually trisazo dyes, a possible structure is synthesized from 2-naphthylamine-4,8-disulfonic acid, o-naphthylamine, Cleve acid, and y acid (acid coupling). 

Aniline-2,5-disulfonic acid, the preparation of which is described above, is used as a starting material for azo dyes, especially disazo and trisazo dyes of the type of Sirius light blue (see page 279). 

Disazo and trisazo dyes (containing two and three azo groups, respectively) can be treated with COClj to give mostly red or brown shades. For example. Direct Red 80 (4.18 C.I. No. 35780) is prepared by treating (4.19) with phosgene [992a] ... 

Polyazo Dyes. Azo dyes can be made with three, four, or more azo linkages. Those with three (trisazo) and four (tetrakisazo) are quite common. An example of a trisazo dye for cotton is Direct Black 80. It is made by the following sequence p-aminoacetanilide is diazotized and coupled alkaline to Gamma Acid, the acetyl group is removed by hydrolysis, and the resulting diamine is tetrazotized and coupled with 1,6 Cleve s Acid to Gamma Acid (alkaline). 

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