Batch-wise Dyeing
ð All cellulosic materials can be dyed with reactive dyes by batch-wise
dyeing methods, also known as the exhaust method.
ð The
dyeing process generally consists of three stages:
1) Exhaustion
of dye molecules from a bath containing common salt or Glauber’s salt (neutral condition)
2) For
further uptake of dye molecules and the reaction of absorbed dye with fibre
(chemical) enhanced by adding an alkali.
3) Finally,
electrolyte, alkali and unfixed dye have been removed from dyed material by
rinsing and soaping.
Dyeing
Procedure on Jigger/Winch
·
Chlorotriazinyl dyes
ð For
both dye ranges (dichlorotriazinyl and monochlorotriazinyl), the procedure
follows the sequence:
|
Dichlorotriazinyl
dyes (M-Brands) |
Monochlorotriazinyl
dyes (H-Brands) |
|
ð Load the
machine with material and water |
ð Load the
machine with material and water |
|
ð Adjust the temperature
of the bath |
ð Adjust the temperature
of the bath |
|
ð Check pH (not
to exceed 7) and adjust with dilute acetic acid |
ð Check pH (not
to exceed 7) and adjust with dilute acetic acid. |
|
ð Start at 30˚C |
ð Start at 50˚C |
|
ð Add dye
solution over 5 min |
ð Add dye
solution over 5 min |
|
ð In the next hour,
add salt in three portions at intervals of 10-15 min |
ð In the next 40
min, add salt in three portions at intervals of 10 min ð Raise the
temperature at the time of the second addition ð Rate of rising must be lower than 2˚C/min ð So, the bath
can reach 80˚C temperature in 20-30 min |
|
ð 15 min after
salt addition, add 1/10th of required soda ash over 5 min |
ð After 15 min, last salt addition and slowly add soda ash over 15 min |
|
ð After a further
15 min, add the remaining soda ash and continue dyeing for 30-45 min |
ð Continue dyeing
at 80˚C for 30-60 min |
|
ð Check the sample; if it’s ok; rinse/soap |
ð Check the sample; if it’s ok; rinse/soap |
ð Dyeing
recipe and condition
|
|
M-Brands (2.0-4.0 % shade) |
H-Brands (2.0-4.0 % shade) |
|
Starting temperature
(˚C) |
30 |
40 |
|
Dyeing without
salt addition (min) |
25 |
25 |
|
Salt (GPL) |
40 |
75 |
|
Salt treatment
(min) |
45 |
60 |
|
Salt treatment
temperature (˚C) |
40-45 |
75-85 |
|
Na2CO3
(GPL) (soda ash) |
8 |
8 |
|
NaOH (GPL)
(Caustic soda) |
- |
2 |
|
Fixation
temperature (˚C) |
40-45 |
70-80 |
|
Fixation time
(min) |
45 |
45 |
|
Washing |
Thorough and repeated |
Moderate |
·
H-E dyes
ð Fabric
is pretreated with acetic acid (0.5-1.0 GPL) at room temperature to adjust pH 5.5-6.5.
ð Start
at room temperature with dye in two parts. At the same time, add salt and raise
the temperature slowly.
ð Run
the fabric for two turns.
ð During the third turn in salt, increase the temperature to 80-85˚C. Add alkali.
ð After the fourth turn, take the sample. If it’s ok, then rinse/soap.
ð During
dyeing, pH must be maintained at 10.8 - 11.3 throughout the fixation time at 85˚C.
ð Dyeing
can be processed by any of the following methods:
a) Addition
of salt by parts
b) Salt
at start
c) All
in
d) Migration
technique
e) Isothermal
technique
Dyeing
Cycle
a) For addition of salt by parts
c) For All in
d) For Migration technique
e) For Isothermal technique
References
1) Jaysynth
Dyechem Ltd (2009) ‘Reactive HE dyeing manual’, Mumbai, India
2) J.
N. Chakraborty, Fundamentals and Practices in colouration of Textiles, Woodhead
Publishing India Pvt Ltd (2010)
3)
Clifford Preston, The Dyeing of
Cellulosic Fibres, Dyers’ Compnay Publicaion Trust (1986)
