Dyeing process of azoic dyes perform by three stages,
1) Naphtholation
2) Diazotisation
Now for the each of discussion they are described below:
1 ) Naphtholation:
Naphthols are insoluble in water and they converted into
water soluble compound by treating with alkali
…………………………..
This salt solution is used for the impregnation of fabric.
2 ) Diazotisation:
A base containing amino group (-NH2) reacts with
NaNO2 ( Sodium Nitrite )
to form a solution of diazonium chloride of that base in
presence of excess HCl at O - 5°C
temperature.
…………………….
3 ) Coupling:
The impregnation material is treated in a bath containing
diazonium solution to carry out coupling and thus color is produced inside the
fabric. here PH maintaining is important.
