REACTIVE DYES – Application (Exhaust Method)

 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

          b) For salt at start

         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)