There are three method of dyeing with azoic dyes:-
1) Batch/Discontinuous
method
2) Semi
continuous method
3) Continuous
method
1 ) Discontinuous dyeing method with Azoic Dyes in Jigger:
The discontinuous methods of dyeing with azoic dye in Jigger
machine can be described as below:
i.
At first the fabric is passed through water.
ii.
Then it is impregnated in Naphthol solution
containing caustic soda, wetting agent, protective colloid, formaldehyde(if
require) and common salt.
iii.
Then the Naphtholated fabric is wound on a
roller.
iv.
In another bath base, NaNO2 and HCl
are taken to carry out diazotization reaction at low temperature.
v.
Then the Naphtholated fabric is immersed in that
cold diaznium liquor and there the developing of colour occurs by coupling
reaction.
vi.
After dyeing
Ø
It is treated with 3ml/lit HCl
Ø
Rinsed with cold water
Ø
Soap washed with 2gm/lit soap and 1gm/lit soda
at boil
Ø
Again rinsed with cold water
2 ) Semi-continuous dyeing method:
In this method the following sequence is maintained:
i.
Naphtholation in padding mangle
ii.
Drying
iii.
Developing color in Jigger
iv.
After treatment
OR,
i.
Naphtholation in Jigger
ii.
Drying
iii.
Developing color in padding mangle
iv.
After treatment
3 ) Continuous dyeing method:
i.
At first fabric is Naphtholation in padding
mangle ( 3 bowl padding mangle is used )
ii.
Then the Naphtholated fabric is passed through a
dryer ( two types of dryer : 1 ) Hot air dryer
and 2) float dryer )
iii.
Then the dried fabric is padded with base
solution. Here color is developed.
iv.
Then the padded fabric is drief by air dryer.
v.
Then the dried fabric is treated with acid to
neutralize excess bases.
vi.
Then soap solution wash – hot wash and cold wash
is performed one after another.
vii.
Then the rinsed fabric is dried in a dryer.
viii.
Then it is passed through a finishing bath (for
example to add optical brightening agent )
ix.
Then it is passed through a stenter machine to
keep its required width. Then the fabric is Calendered.