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Textile Dyes » Dyes for Cellulose Fibers » Azoic or Naphthol Dyes
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The name AZO has been derived from the word azote and it meant nitrogen in the ancient time in French. In Greek, a means not and zoe means to live.
Azoic Dyes are also called as Azoic or Nepthol Dyes. These AZO Dyes consist a group i.e. called AZO group having two nitrogen atoms and this group (covalent bond) connects atomic ring compounds. The two Nitrogen atoms are bonded with each other and form -N=N- as part of their molecular structure. Azoic Dyes are found mainly in three colors and these are red, brown and yellow. Aromatic amines are the chemicals from which these dyes are manufactured.

Classification of Nepthol Dyes

Azoic Dyes are classified either according to the fibers for which these can be used economically or the methods by which these dyes are applied.

Formation of Azoic Dyes

These dyes cannot be applied directly on the fibers as dyes. Actually, these dyes are produced within the fibers itself. For this production, first the fiber is impregnated with one component of these dyes and then the fiber is treated in another component of these dyes. In this way the AZO dyes are formed. This specialty makes these dyes very fast to washing within the fabric market.

When these dyes are used upon the cellulose fabric then initially this fabric starts to suffer from poor rub fastness. This is due to the deposition of the free pigments on the surface of the fabric. This problem can be rectified by boiling the fabric in soap.

Azoic Dyeing Process

AZO Dyeing Process is such a process in which the insoluble azoic dye is produced on the or within the fiber. By treating a fiber with diazoic and coupling components, this process can be achieved. After adjusting the dye bath conditions appropriately, the two above mentioned components react. From this reaction the required insoluble AZO dye is produced. This is a unique technique. The required color can be changed by altering of the diazoic and coupling components.


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