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Cotton Printing (Reactive Dye)
- Reactive dyes based on vinyl sulphone (SO2-CH=CH2) group are widely used for printing the cotton materials, like bed sheets, pillow covers, lungies etc. as this group can be fixed without steaming, and so most suitable for cottage industries.
- Vinyl sulphone dyes are fixed by padding the printed fabric through sodium silicate (about 106˚ Tw) solution.
- Dichloro (cold brand) and monochloro (hot brand) traizine dyes are fixed due to substitution reaction with the liberation of HCl
- Direct Style:
· Reactive Dye: These are molecules that form a
covalent bond with the cotton fabric molecules, and it is an anionic dye.
· Thickeners: As the reactive dye reacts with
primary hydroxyl groups, gums and starches are not suitable as a thickener.
Therefore, sodium alginate is the best suitable thickener for reactive dye
printing. But in the case of steaming fixation, half-emulsion thickener is
advisable.
· Mild oxidizing agent: Resist Salt L (Ludigol)
· Solvent: Urea, Diethylene glycol,
thiodoethylen glycol
· Hygroscopic agent: Urea, glycerine - It
increases the brightness of the dye and spread the dye evenly in the paste.
Assist the dye fixation and prevent aggregation of the dye.
· Weak alkali: Sodium bicarbonate (NaHCO3)
– for maintain the pH, and also helps in fixation.
· Various methods of printing reactive dyes
depends on the process used for fixation of the dye, and they are
[1] Steaming [2]
Baking or Thermofixing
[3] Flash-ageing [4]
Wet developing
[5] Silicate padding [6]
Air hanging
1) Steaming Process
·
For printing the cotton with reactive dye by
direct style, following paste is used:
Ingredients | Quantity
(Parts) |
Reactive
Dye | 50 |
Water | 290 |
Urea | 180 |
Resist
Salt L | 10 |
Sodium
bicarbonate | 20 |
Sodium
alginate (6%) | 450 |
Total | 1000 |
·
After printing and drying, the fabric is steamed
for 5 – 10 minutes in Rapid ager and for 15 – 20 minutes in a Star ager or
steamed under high pressure at 130˚C for 30 seconds, then rinsed well in cold
water, soaped with 2 gpl non-ionic detergent, rinsed and dried.
·
During steaming sodium bicarbonate decomposes
to give alkaline conditions for fixation of the dye.
2) Baking or Thermo-fixing Process
·
Urea is used in high concentration in this
process.
·
Cold brand reactive dyes are fixed by using
sodium bicarbonate and hot brand reactive dyes are fixed by sodium carbonate.
·
For printing the cotton with reactive dye by
direct style, following paste is used:
Ingredients | Quantity
(Parts) |
Reactive
Dye | 50 |
Water | 375 |
Urea | 200 |
Resist
Salt L | 10 |
Sodium
carbonate (hot brand) Sodium
bicarbonate (cold brand) | 15 |
Sodium
alginate (6%) | 350 |
Total | 1000 |
·
After printing and dyeing, the fabric is
baked or thermo fixed at 150˚C for 5 minutes, soaped with non-ionic detergent
at boil, rinsed and dried.
3) Flash-ageing
Process
·
In this process, the fabric is printed with a
paste which does not contain alkali, and then padded with an alkaline solution.
·
After padding the fabric is steamed in the
wet condition at 140˚C for 30 seconds, which is known as flash-ageing.
·
For printing the cotton with reactive dye by
direct style, following paste is used:
Ingredients | Quantity
(Parts) |
Reactive
Dye | 50 |
Water | 480 |
Urea | 100 |
Resist
Salt L | 10 |
Sodium
alginate (6%) | 360 |
Total | 1000 |
·
After printing and drying, the fabric is
padded with a solution containing:
Ingredients | Quantity
(Parts) |
Caustic
soda (70˚Tw) | 60 |
Sodium
carbonate | 150 |
Potassium
carbonate | 50 |
Common
salt | 100 |
Solution
made with water | 1000 |
·
After padding, the fabric is steamed in the
wet condition at 140˚C for 30 seconds by passing through Festoon ager.
·
The fabric is then washed to remove alkali,
soaped with non-ionic detergent, washed and dried.
4) Wet Development
·
In this process, after printing fabric is
passed through hot alkaline solution at 95˚ to 98˚C for 15 seconds, and
steaming is not done.
·
This process is most suitable for viscose
rayon fabrics.
·
This process can fix 50% more colour than
normal steaming process.
·
For printing the cotton with reactive dye by
direct style, following paste is used:
Ingredients | Quantity
(Parts) |
Reactive
Dye | 50 |
Water | 240 |
Urea | 200 |
Resist
Salt L | 10 |
Sodium
alginate (6%) | 500 |
Total | 1000 |
·
After printing and drying, the fabric is
steamed for 5 minutes at 100 – 102˚C, and then pass through a solution
containing:
Ingredients | Quantity
(Parts) |
Caustic
soda (66˚Tw) | 60 |
Sodium
carbonate | 100 |
Sodium
silicate | 20 |
Common
salt | 150 |
Solution
made with water | 1000 |
·
After passing the fabric from above solution,
fabric is rinsed with cold water first and then with hot water, soaped with
non-ionic detergent, rinsed and dried.
5) Silicate Padding (Pad-Batch) Process
·
Vinyl sulphone based reactive dyes are
majorly printed using this process. The process is most suitable for cottage
industries, as the fixation of dye is done by padding the printed fabric
through sodium silicate solution.
·
The fabric is printed with the paste prepared
as in Flash-ageing process, and after drying the fabric is padded though 106˚
Tw sodium silicate solution at pH 11.4 – 12.
·
After padding the fabric is batched and
stored for 12 – 14 hours and then rinsed, soaped with non-ionic detergent at
boil, rinsed and dried.
6) Air Hanging Process
·
For printing of mercerized cotton or rayon
with cold brand reactive dye, this process is mostly applied.
·
The fabric is padded with 2% sodium carbonate
and dried.
·
After padding the fabric is printed with the
paste prepared as in Steaming process, but without sodium bicarbonate.
·
After printing, the fabric is dried by
hanging in air for several hours in warm, humid atmosphere.
·
Finally, fabric is rinsed, soaped with
non-ionic detergent at boil, rinsed and dried.
ð
White Discharge style:
· For discharge printing, cotton is dye with
some selected procion dyes, which can be discharged easily, and give good
whites on the ground.
· This style for reactive dyed ground is
limited for specific application and so, it is not popular.
· The fabric is dyed with a dischargeable
reactive dye (dischargeability rating 4 – 5) is taken and printed with
discharging agent for white discharge printing.
·
Discharging agent: Rongalite C (Sodium
Sulphoxylate Formaldehyde) (NaHSO2.CH2O.2H2O)
acts as discharging agent. It is not a powerful reducing agent at room
temperature. It is dissolved in cold water, and then boiled to separate
formaldehyde and sodium sulphoxylate, and thus separated sodium sulphoxylate is
the powerful reducing agent.
· Zinc oxide: for obtaining better white
· For obtaining white discharge effect on the
cotton fabric dyed with reactive dye by discharge style, following paste is
used:-
Ingredients | Quantity
(Parts) |
Rongalite
C | 150 |
Cold
water | 50 |
Gum-tragacanth
thickener paste | 625 |
ZnO | 125 |
Sodium
carbonate | 50 |
Total | 1000 |
·
After printing and drying, the fabric is
steamed for 15 minutes in rapid ager at 100 – 102˚C, rinsed well and
dried.
ð
Colour Discharge
style:
· The fabric is dyed with a dischargeable
reactive dye (dischargeability rating 4 – 5) is taken and printed with
discharging agent for Colour discharge printing.
· Discharging agent: Rongalite C (Sodium
Sulphoxylate Formaldehyde) (NaHSO2.CH2O.2H2O)
acts as discharging agent. It is not a powerful reducing agent at room
temperature. It is dissolved in cold water, and then boiled to separate
formaldehyde and sodium sulphoxylate, and thus separated sodium sulphoxylate is
the powerful reducing agent.
· Zinc oxide: for obtaining better white
· For obtaining Colour discharge effect on the
cotton fabric dyed with reactive dye by discharge style, following paste is
used:-
Ingredients | Quantity
(Parts) |
Vat Dye Rongalite
C | 50 100 |
Cold
water | 50 |
Gum-tragacanth
thickener paste | 625 |
ZnO | 125 |
Sodium
carbonate | 50 |
Total | 1000 |
· After printing and drying, the fabric is
steamed for 15 minutes in rapid ager at 100 – 102˚C, rinsed well and dried.
ð
White Resist style:
·
Resist style is more popular than the
discharged style on reactive dye ground.
·
Resisting agent: Citric acid is used as a
resisting agent.
· As acidic environment is not suitable for
development of reactive dye, and so, where citric acid is present reactive dye
will not develop.
· For obtaining white resist effect on the
cotton fabric by resist style, following paste is used:-
Ingredients | Quantity
(Parts) |
Citric
acid | 50 |
Water | 350 |
Acid-resistant
thickener | 600 |
Total | 1000 |
·
After printing and drying, the fabric is
padded with a solution containing:
Ingredients | Quantity
(Parts) |
Reactive
dye (Remazol) | 50 |
Resist
salt L | 10 |
Water
(hot) | 360 |
Sodium
bicarbonate (3%) | 500 |
Acid-resistant
thickener | 80 |
Total | 1000 |
· After padding and drying, the fabric is
steamed for 10 minutes, rinsed, soaped with non-ionic detergent, rinsed and
dried.
ð
Colour Resist style:
·
Coloured resist on reactive dyed ground can
be obtained with solublised vat dyes.
·
The fabric is first padded with the solution
shown below:
Ingredients | Quantity
(Parts) |
Reactive
dye (Remazol) | 30 |
Sodium
chlorate | 10 |
Water
(hot) | 300 |
Lactic
acid | 2 |
Gum-tragacanth
thickener | 50 |
Total
(adjusted with water) | 1000 |
·
Padded fabric is printed with following
paste:
Ingredients | Quantity
(Parts) |
Solublised
vat dye | 50 |
Water | 375 |
Glycine
A | 40 |
Citric
acid | 100 |
Starch-tragacanth
thickener | 400 |
Ammonium
vanadate | 20 |
Alum | 15 |
Total | 1000 |
·
After printing, the fabric is quickly dried,
steamed for developing the solublised vat dye, and then padded through the
solution containing:
Ingredients | Quantity
(Parts) |
Caustic
soda (70˚Tw) | 20 |
Glauber’s
salt | 200 |
Common
salt | 100 |
Total
(adjusted with water) | 1000 |
· Padded fabric is then steamed in wet condition at 140˚C
for 30 seconds, rinsed, soaped with non-ionic detergent at boil, rinsed and
dried.
References:
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