Methods of Dyeing cotton with Various Reactive dye brands:
Application on cotton fabric by various dyes-
(2) Hot brand reactive dyes (MCT)
(3) High Exhaust brand reactive dyes
(4) ME brand reactive dyes
(5) Vinyl Sulphone (VS) based reactive dyes
Among these five, below is the explanation of the first method.
Explanations -
(1) Cold brand reactive dyes:
Application:
Dyeing with salt followed by alkali which is followed by after treatment
The application of reactive dyes involves the following steps -
(ii) Chemically reacting the dye with the fibre in the presence of an alkali eg. Sodium carbonate (Na2CO3), trisodium phosphate (Na3PO4), caustic soda (NaOH) etc.
(iii) After treatment of the reactive dyed cotton material (Soaping, washing etc).
Chemical reactions in dyeing :
Where,
D - Dye
R - Reactive (functional) groups
Dyeing procedure :
(i) Preparation of cotton for dyeing (RFD):
Bleached material prepared for dyeing must be free from Alkali. Where necessary, treat it in an exceeding liquor containing 0.5 to 1.0 a part of carboxylic acid (30%) per 1000 parts of water before adding a dye solution.
This prevents premature localised fixation and improves levelling of the dyes.
(ii) Preparation of dye solution:
The M brand dye powder is pasted with cold water and dissolved by adding water at 50°C. The required quantity of water is then added with stirring to dissolve the dyestuff.
(iii) Dyeing:
Adjust the dye bath pH to six.5 to 7.0 with carboxylic acid and using the acceptable liquor ratio work the fabric for 10 minutes at temperature. After a quarter-hour add pre-dissolved common salt or salt and dye for one more half-hour Add pre-dissolved alkali (soda ash) and continue dyeing for an additional half-hour and so drain the dye bath. As stated earlier the salt and alkali are also added in two portions
The quantities of salt and sodium carbonate for various liquor ratios are given below in table-
Depth of shade | Salt | Soda ash and MLR | |||
1:5 | 1:10 | 1:20 | 1:30 | ||
Up to 0.5% | 30 gpl | 5 gpl | 5 gpl | 3 gpl | 2 gpl |
0.5 to 2 % | 40 gpl | 10 gpl | 5 gpl | 4 gpl | 2 gpl |
2 to 4 % | 50 gpl | 15 gpl | 10 gpl | 8 gpl | 4 gpl |
Above 4.0% | 60 gpl | 20 gpl | 10 gpl | 10 gpl | 5 gpl |
(iv) Washing off:
After dying, wash the fabric well for optimal fastness. Ten minutes are spent washing the fabric in cold running water.
(v) After treatment:
(a) Wash the dyed material freed from soap first with plight, then with cold water, and so treat it with 1 to 2 GPL of neutral soap at the boil for a quarter-hour.
(b) After treating the soaping material for 10 minutes with 1 to 1.5 GPL of softening agents, dry it.
This final step is optional and is a wrap-up ( A dye-fixing agent is also applied before this step, if necessary) Figures depict the dyeing cycle and also the process flow sheet.
 |
| Dyeing cycle for reactive M brand |
Sequence -
Scoured or Bleached yarn
↓
Enter goods in blank bath
↓
Add dissolved dye & dye for 15 minutes
↓
Add dissolved common salt in 2 portions to dye Bath and dye for 10 minutes each
Bath and dye For 15 minutes each
↓
Dyeing continues for 20 to 30 minutes
↓
Squeeze and wash
↓
Soap at the boil and wash
↓
Softening or dye-fixing treatment (if required)
↓
Squeeze and dry
Questions -
Which methods are used for the reactive dyeing process?
Describe the Cold brand reactive dyes (DCT) method.
What is the dyeing process for DCT reactive dyes?
Which sequence does the DCT Reactive dyeing process follow?
References
Ahmed, S. (2014, September 29). Reactive dyes - classification. TextileTuts. https://textiletuts.com/reactive-dyes/
Chakraborty, J. N. (2010). Waste-water problem in textile industry. In Fundamentals and Practices in Colouration of Textiles (pp. 381–408). Elsevier.
Clark, M. (2011). Handbook of textile and industrial dyeing: Principles, processes and types of dyes (Matthew Clark, Ed.). Woodhead Publishing.
No title. (n.d.). Acs.org. from https://cen.acs.org/articles/96/i29/new-textile-dyeing-methods-make.html
Patwary, E. M. Z. (2012, February 18). Reactive dyes. Textile Fashion Study; Engr. Mohammad Zillane Patwary. https://textilefashionstudy.com/reactive-dyes-definition-classification-properties-and-influencing-factors/
Sayed, A. (n.d.). Why reactive dye is so called? Blogspot.com. from https://textileapex.blogspot.com/2013/11/reactive-dye.html
What are Reactive Dyes? Types of Reactive Dyes. (n.d.). Meghmaniglobal.com. from https://www.meghmaniglobal.com/what-are-reactive-dyes-types-of-reactive-dyes/
Continue reading,
Part 2 Classification of Reactive dyes
Part 3 The reaction of MCT and DCT of reactive dyes
Part 4 General Factors affecting the results of reactive dyeing
Part 5 Reactive dyeing method - DCT
Part 6 Bifunctional systems of reactive dyes
Part 7 Development of reactive dyes
Part 8 Reactive dyes on Silk and nylon with their application
Part 9 Industrial applications of reactive dyes
Part 10 After treatment of reactive dyes
Writer - Rushikesh Patil (Textile Engineer)
