Dyeing Process of Cotton Fabric With Sulphur Dyes

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Dyeing process of cotton fabric with sulphur dyes

Dyeing Process of Cotton Fabric With Sulphur Dyes

Sulphur Dyes

Sulphur dyes are highly colored, water-insoluble compounds and have to be converted into Water Soluble substantive forms before application to the textile materials. This conversion is carried out by a treatment with a reducing agent like dilute aqueous Na2S.

Apparatus Required for Dyeing

  • Beaker
  • Glass Rod
  • Cylinder
  • Electric Balance 
  • Thermometer
  • Dryer


Nature of the Sample:

100 % cotton knitted fabric

Objectives of Sulphur Dyeing:

  • To learn about how to cotton fabric dyeing with sulphur dyes
  • To know about sulphur dyes
  • To get an idea about the function of used dyeing chemicals
  • To know how to improve the dyeing process

Function of Used Dyeing Chemicals

Sequestering Agent- To remove the hardness from water

Alkali - It converts oil into water-soluble fatty acid and soap

Salt - It acts as a catalyst that accelerates absorption rate and reduces surface tension. 

Hydrose - It acts as a reducing agent

H2O2 - It helps to insoluble the sulfur dyes

Acetic acid - Helps to keep the solution in an acidic medium to react with dye and fabric

Shade - Provides the desired color.

Working Procedure:

Reduction

The dye was taken in a vessel and mixed well with alkali and added specific amount of water. Specific amount of soda ash is added to neutralize any acid formed in the dyestuff during storage. The quantity of reducing agent depends upon the shade depth and M:L of the bath.

Dyeing

The dye is kept ready with small quantity of the alkali stable and compatible wetting agent, a dye bath stabilizer, sodium sulphide and caustic soda. The dye is then added to the solution after (15-25) minutes. The temperature is then raised to above 180 C and kept above the heater enough time

Oxidation

The oxidation is done to reconvert the leuco compound back to insoluble dye.


Dyeing Recipe:

1. Reduction: 

Sequestering agent - 1cc/L
Hydrose - 3gm/L
NaOH - 3 gm/L
pH- 11 
Temperature - 60 C
Time- 10min
Dyes - 1% (o.w.f)
M:L - 1: 70

2. Dyeing 

Salt - 15 gm/L
Time - 20 min
Temperature - 80 C

3. Oxidation

Sequestering agent - 1cc /L
Acetic acid - 2cc/L
H2O2 - 3cc/L
pH - (4.5-5.5)
Temperature - 80 C
Time - 10 min
M: L - 1:60

Calculation:

Fabric weight = 3.65gm

Weight of water = 3.65*70 (M:L ratio) = 260cc/L

Hydrose = 3*260/1000 = 0.78 gm

NaOH = 3*260/1000 = 0.78gm

Sequestering agent = 1*260 /1000 = 0.26cc/L

Dyes = 1*3.65 /100 (o.w.f) = 0.0.37 gm

Salt = 15*260/1000 = 3.9 gm

Sequestering agent = 3.65*60 (M:L ratio) = 219/1000 = 0.219cc/L

Acetic acid = 2*219/1000 = 0.438 cc/L

H2O2 = 3*219/1000 = 0.657 cc/L

Conclusion: 
From this experiment, we can learn how to dye cotton fabric with sulphur dyes which will helps in our future practical dyeing job life. 

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