Azo Dyes

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azo dyes

[′a·zō ‚dīz]
(organic chemistry)
Widely used commercial dyestuffs derived from amino compounds, with the ‒N‒ chromophore group; can be made as acid, basic, direct, or mordant dyes.

Azo Dyes

 

organic dyes whose molecules contain one or several azo groups—N=N—which connect aromatic radicals. Depending on the number of such groups, the dyes are called mono-, dis-, tris-, or polyazo dyes. Usually, azo dyes contain substituted or unsubstituted NH2 and OH groups in

the aromatic nucleus and also NO2, CI, SOH3H, COOH, and others. The presence of acid groups ensures the water solubility of the dyes.

Synthesis of azo dyes is achieved by combining aromatic diazo compounds ArN2Cl with phenols, aromatic amines, and their derivatives. For example, see above.

Usually, a dye is precipitated from a sodium chloride solution, dried, and then pulverized.

The simplest monoazo dyes are usually yellow, orange, or red in color. An increase in the number of azo groups, a substitution of phenyl radicals with naphthyl radicals, and an increase in the number of oxy- and amino- groups will intensify the color. Depending on their structure and the character of their interaction with textiles, azo dyes are divided into several groups: basic, acid, direct, mordant, ice-color, active, and others. Basic dyes contain NH2 groups; acid dyes, usually one or several sulfo groups. The latter are used in dyeing silk and wool. Large amounts of direct azo dyes are produced for use in coloring cotton fabrics; usually these are polyazo dyes based on benzidine and α-naphthylamine and its sulfo acids. With Fe3+, Cr3+, and other ions, mordant azo dyes form insoluble complexes on the fiber which are well retained. The formation of dye-fiber chemical bonds is characteristic of the active azo dyes. These azo dyes, in production since 1952, not only afford beautiful tints but also are outstanding in their resistance to water and other processing agents. Ice colors are obtained directly on fabrics. Some azo dyes in a fine-dispersion state are used in polygraphy and the paint and varnish industry. Azo dyes are used mainly for coloring textiles but also for coloring leather, paper, rubber, and certain plastics.

REFERENCES

Chekalin, M. A. Khimiia i tekhnologiia organicheskikh krasitelei. Moscow, 1956.
Chekalin, M. A., B. V. Passet, and B. A. Ioffe. Tekhnologiia organicheskikh krasitelei i promezhutochnykh produktov. Leningrad, 1972.
References in periodicals archive ?
The first step in the synthesis of azo dyes is the conversion of amine compounds into diazonium salts.
Spectrophotometric determination of persulfate by oxidative decolorization of azo dyes for wastewater treatment.
Compared to cyanine and azo dyes found in the majority of CD-Rs on the market, the company continues, phthalocyanine dye lasts significantly longer when subjected to the harmful effects of UV light, heat, and humidity.
photochemical oxidation of reactive azo dye with UV-H2O2 process, Dyes pigm, 62: 269-275.
Effect: A synthetic azo dye, it appears to cause allergic reactions particularly among those who are aspirin intolerant.
Many countries have banned the use of azo dyes in foods aimed at children - but these are still being used here.
The patented AZO dye, which has been optimized for Verbatim/MKM's LTH media, features the same proven reliability, stability and longevity that have made the Verbatim/MKM brand a trusted name in CD-R and DVD-/+R media around the globe.
The decolorization and mineralization of Acid Orange 6 azo dye in aqueous solution by advanced oxidation processes: A comparative study.
E104 Quinoline yellow An azo dye found in smoked haddock and Scotch eggs.
The patented AZO dye used in the recording layer of Verbatim BD-R LTH Type media provides a unique combination of features that range from increased sensitivity to laser light -- the key requirement for optimized recording performance, to control the heat interference between consecutive recorded marks for substantially less jitter and reduced degradation of recording marks.
Kinetics analysis for the photocatalytic degradation of single and binary azo dye solutions:
In this research, the two catalysts In2O3/SnO2/ZnO and SnO2/In2O3/ZnO were firstly synthesized, and then they were used in the degradation of an azo dye (light brown solantine) that exists in the wastewater of textile industry.