This pp elaborates the reactive Dyeing of cotton knitted fabrics.

1. DYEING OF
KNITTED COTTON
FABRIC

2. DEFINITION
Dyeing is a process of imparting color to the fabric and
increase the aesthetic value of it.
There are many techniques of dyeing both natural fiber
and manmade fibers using different types of dye stuffs
with different chemistry and method of application.
Among those methods, exhaust dyeing method is
very common for dyeing cotton and cotton blended
knitted fabric.

3. it is batch dyeing process in which certain weight of
fabric is dyed in a rope/open width form with a dye
migration or exhaustion from the dye liquor to the fabric
with the help of exhausting chemical either by fabric
circulation only or by both fabric and liquor
circulation.
the dyeing parameters are basically determined by the
type of fiber and the nature of the dyes and chemicals
used.
most commonly reactive dyes and disperse dyes are used
to dye cotton and polyester fibers in exhaust dyeing.

4. METHODS OF REACTIVE DYEING AND
PARAMETERS ON JET
reactive (cotton):
ISOTHERMAL(migration 60°C fixation 60°c)
MIGRATION(migration80°C,fixation60),
TURQUESE DYEING (migration 95°c/80°c,fixation
80°c).
machine settings
speed:200-250m/min
 nozzle pressure(70%),circulation(70%)
pick up (200%)
cycle time 2 min .

5. Addition of electrolyte and other chemicals
Electrolytes increase the substantively of reactive
dyes, Hence improve the bath exhaustion.
Common salt may reduce the dye staff solubility
,therefore, for some dyestuffs which have higher
molecular weight like reactive torques(phatalocynic)
and blue(like bezactiv blue s –fr150 we use glauber
salt.
It is common to use sequestrates along with the
dye to protect dyes stuff coagulation and patchy
dyeing.

6. CONTI..
Fixation of reactive dyes is most important part of
dyeing and is achieved at higher PH (10.8-11.5).
Mild alkali (soda ash) or mixed alkali (soda ash
and caustic) are use to achieve the alkali PH.
Fixation has to be done with gradual increase of the
dye bath PH. Rapid increase in PH result in unlevel
dyeing
20-30 min progressive dosing 30-45 min holding
time with out fabric stoppage is recommended for
unlevel dyeing.

7. Conti…
Generally reactive dyeing will take place at different
temperatures based on the nature of the dyes.
The first group of dyes will be migrated at 60°c above
this T, there will be hydrolysis. Bifunctional dyes can
be dyed at both 60 and 80 °c and fix at 60 °c.
The other group of dyes migrate at 80 °c, this dyes
relatively have high molecular weight and need higher
temperature to migrate and fix at 60 °c.
Turquoise dyes are high molecular dyes and mostly
dyed at 95 °c, even though can be done at 80 °c with
longer dyeing time and fix at 80 °c.

8. DYES AND CHEMICAL
PREPARATION
Dye stuff and salt dissolve in hot water. Depending on the
nature of the shade, the addition to the machine can be by
dosing or transfer (from stock tank or addition tank)
Dye dissolution :80 °C for 5 min with high capacity stirrer.
Salt can be transfer but for sensitive shades it should be
dosed in two or three portions in 15 minutes.
Common salt can be transferred to the machine in in
partially soluble state to the machines.
Glaubber salt should not dissolve at temperature less
than 60⁰c, it forms crystal which will hinder the transfer
to the machine, but common salt can dissolve at cold.
Stock solution of salt is crucial measure to prevent salt
crystallization.

9. Conti..
Soda should be dissolved at cold and after dissolution
it should be dosed to the machine minimum in thirty
minutes.
In machine which don’t have dosing mechanism, 20 %
addition of alkali at dye start would be better.
 Hot and concentrated dye solution should not be
left unattended for long time.
 Urea is used to improve the solubility of reactive s
dyes and should not be added to temperature less
than 50 oc.

10. Dry salt transfer

11. Addition tanks

12. CHECKING POINTS AFTER DYEING.
The required shade and pH need to be checked after
soda holding time.
Small piece of fabric should be washed in hot water
using soap for 10 mins.
PH after fixation (10.8-11.5).
the above check points help us to make corrections
before draining the dye bath.

13. AFTER TREATMENT PROCESS
It is a process in which fabric neutralization, soaping
and fixing of some dye ruminants on the fabric takes
place .
Add 2 gpl of acetic acid and hold @60⁰c for 10 min.
Add 1 gpl of soap /detergent and hold 98 ⁰c for 10
min.(can be done once or twice).
Second neutralizing 0.2 gpl acetic acid for 5 min at cold.
Finally fixing of unfixed dyes left on the fabric for
good wash fastness.(o.5% owf of fixing agent).
Any foaming should be removed before unloading
fabric and the final ph should be neutral.
Finally during unloading good arrangements need to
be done for following processes.

14. Temperature –time graph of
migration
40
A
40
B
40
C
80
D
80
E
60
F
60
G
60
H
60
I
60
j
60
k
98
l
98
m
70
n
0
20
40
60
80
100
120
Time

15. TEMP VS TIME TRAPH OF ISOTHERMAL
DYEING PROGRAM
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
Temprature(⁰c)
Time(min)

16. TURQUEZE SHADE DYEING GRAPH
0
20
40
60
80
100
120
10 20 30 40 50 60 70 80 90 100 110 120 130 140
TEMPRATUREIN⁰C
TIME IN MIN

17. Settings

18. Dyes and chemicals used in dyeing
4.4. Chemicals that need special care while using
Acetic acid
Hydrogen peroxide
Urea
Caustic soda
Soda ash
Ammonium sulphate
Sodium hydrosulphite
Sulfuric acid
Sodium sulphate

19. Necessary safety materials in dye house
Safety shoe,
working cloth,
mouse max,
Eye goggle,
Glove, Apron
Water flasher.
Material safety data sheets.