Methods of Dyeing cotton with Various Reactive dye brands:
Application on cotton fabric by various dyes-
Among these five, below is the explanation of the fifth method.
Explanation-
(5) Vinyl Sulphone-based reactive dyes (VS brand dyes) -
Introduction -These dyes, which mostly get into the dyeing and printing of cotton fabrics, are supported by the reactive group vinyl sulphone.
Principles of using VS dyes to colour cotton- Reactive dyes called VS dyes have a sulphate-ethyl Sulphone group as a part of their compounds.
The dyes become reactive within the presence of alkali, taking the shape of vinyl sulphone, which chemically interacts with the hydroxyl of cellulose to form an ether bond.
Chemical reactions in dyeing -
In this reaction, the reactive dye is supplied as beta sulphate ethyl Sulphone. This group changes to the vinyl Sulphone group in the presence of Alkali.
The VS dye reacts with cellulose (cotton fibre) as follows:
Properties of VS dyes -
(2) excellent brightness;
(3) outstanding versatility;
(4) facile washing of the unfixed dyestuff thanks to the moderate substantivity of the dyes; and
(5) excellent all-around fastness of the dyes.
Water usage - Use soft or softened water and keep one's distance from alkalinity, especially while dissolving colours. when there's access to water.
Sequestering agents like sodium hexametaphosphate should be accustomed to soften it.
The pH range for the water used for dyeing should be between 6 and seven. the subsequent procedures are also wont to rectify acidity or alkalinity when the pH value is outside of those ranges:
pH of water | Chemical for neutralise water |
Alkaline water | Neutralise with sodium or potassium dihydrogen phosphate or acetic acid |
Acidic water | Neutralise with Sodium bicarbonate or soda ash |
Dyeing procedure -
To get satisfactory results the preparation of the cotton material before dyeing is most vital. The goods should be scoured and Bleached to form highly absorbent SNF and free from any alkalinity or acidity.
(B) Preparation of dye solution -
The dyestuff is formed into a smooth paste with cold water and dissolved by adding plight at a temperature of 80°C.
(C) Dyeing cycle for VS dyes is given below in the figure-
(ii) make sure that its pH is simply below 7
(iii) Adjust pH with carboxylic acid if necessary
(iv) Enter the fabric and run it in the bath for five minutes
(v) Add pre-dissolved dyes and continue dyeing for 10 minutes
(vi) Raise the temperature and add the salt in two portions, the first portion after 5 minutes of temperature rise and therefore the second portion after 10 minutes of dyeing.
Continue dyeing for an additional 5 minutes till the temperature reaches 60°C.
(vii) Dye for 10 minutes at 60°C after the last salt addition.
(viii) Add pre-dissolved alkali in two portions in 10 minutes if sodium carbonate is employed as alkali, this should be added over 10 minutes. If a mixture of soda and hydrated oxide is employed the premixture should be added over a quarter-hour.
(ix) Dye for an additional 60 to 90 minutes after Alkali addition.
(x) Drop the bathtub and wash.
The table below indicates the quantities of salt and Alkali and also the dyeing conditions to be used for dyeing cellulosic fibres with VS dyes. It may be noted that the dyeing also can be dispensed at 40°C, the quantity of Alkali used and the final stretch of dyeing being markedly different from the dyeing at 60°C.
 |
| Dyeing cycle for reactive VS brand dyes |
Liquor ratio | 1:20 to 1:30 | |
Dyeing temperature | 60°C | 40°C |
Glaubers salt(gpl) | 50 gpl | 50 |
Trisodium phosphate (gpl) | 5 to 10 gpl | 10 to 15 |
Soda ash (gpl) | 5 gpl | 5 gpl |
Caustic soda 72°Tw | 1 gpl | 2 to 3 gpl |
Dyeing period in minutes after Alkali addition | 60 to 90 gpl | 90 gpl |
(D)Washing off and Soaping -
To achieve optimum fastness properties, the unfixed dyestuff must be thoroughly washed off after completion of the dyeing. This step is achieved as follows-
(i) The material is rinsed in cold water and then neutralised with containing 2 cc/litre ethanoic acid.
(ii)This is followed by a rinse in predicament. The material is then soaped at the boil in a very bath containing a neutral detergent.
Alkaline Soaping of vinyl Sulphone dyed material isn't advisable because it undergoes hydrolysis as shown below-
Reaction -
Process steps for Washing off with reactive VS dyed goods
Questions -
- Which methods are used for the reactive dyeing process?
- Describe Vinyl Sulphone (VS) based reactive dyes process.
- What is the dyeing process for Vinyl Sulphone (VS) based reactive dyes?
- Which sequence does the Vinyl Sulphone (VS) base 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
(N.d.). Textilelearner.net. from https://textilelearner.net/reactive-dyes-classification-dyeing-mechanism/
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)
