Azoic Dyes



The dyes which contain insoluble azo group(-N=N-) are known as azoic dyes. These dyes are not found in ready-made form. They dyes are produced through an in-situ process which created colored material directly on the fabric by a reaction between two compounds namely
1.      Diazo compound or diazo base
2.      Coupling compound i.e. Naphthol
Azoic dye is one type of ingrain dyes .e. it is produced during dyeing process inside the fibre. The general reaction of azoic dye formation is given below:
          R-N=N-Cl + R`-ONa                      R-N=N-R`
Diazo compound     Naphthol                        Azoic color
The diazo compound is very often said fast base or diazonium salt of fast base.
The colored substance formed from essential colorless compound is insoluble in water and the washing fastness of this shade is excellent. But it has poor rubbing fastness. Johann Peter Griess of German discovered the diazotized reaction and subsequent reactions of a diazotized reaction in 1858. This discovery was the foundation stone for the immerse edifice of azo dyes. He found that Premuline can be diazotized on the fiber which afterward takes part in couple reaction with an aromatic hydroxyl or amino compound to give a new dye of greater wet fastness.the oldest application of this method was in the dyeing of para red. This para red was produced by coupling diazotized p-notro aniline with β-naphthol. the formation of an insoluble azoic pigment was first patented by Thomas and Holliday in 1880.


Properties of Azoic Dyes    click here

Azo Dyes     click here

Azoic Dyes      click here

Chemistry of dyeing with Azoic Dyes       click here

Sequence of operation for dyeing with Azoic dyes       click here

Method of dyeing with Azoic Dye        click here

Color performance of Azoic dyeing         click here

Problem in dyeing with azoic color         click here

Protein fibres are not dyed with Azoic dyes       click here