What are Dyeing Auxiliaries?
Dyeing auxiliaries are chemical substance which enables a processing operation in preparation, dyeing, printing or finishing to be carried out more effectively. During dyeing process, it helps to enhance the dye’s performance, improve fabric quality, and achieve uniform coloration. To attain high-quality dyeings, proper dyeing auxiliaries should be precisely used. Dyeing auxiliaries are specially used for washing and dying during the production process. Main functions of dyeing auxiliaries to prepare the substrate for coloration, to stabilize the application medium, to increase the fastness properties of dyeing, to modify the substrates etc. Besides, dyeing auxiliaries are essential for optimizing dye uptake, ensuring color fastness, and facilitating specific effects. In this article I will give a list of dyeing auxiliaries and their classification, functions and uses in dyeing.
Functions of Dyeing Auxiliaries:
Major functions of auxiliaries during dyeing are point out below.
- Improving the efficiency of the pre-treatment processes for subsequent dyeing.
- Enhancing the extent of dye uptake and fixation.
- Ensuring the stability of the dyeing bath as well as compatibility of its ingredients.
- Modifying the textile substrate and/or avoiding its damage.
- Upgrading the fastness properties of the obtained dyeings.
- Minimizing the environmental impacts of textile wet processing, especially dyeing.
Classification of Dyeing Auxiliaries:
- Non-surfactants Auxiliaries
- Surfactants Auxiliaries
A. Non-surfactants Auxiliaries:
Simple electrolytes, acids and bases, both inorganic and organic. E.g., sodium chloride, sodium acetate, sulphuric acid, acetic acid and sodium carbonate, together with complex salts (such as sodium dichromate, copper (II) sulphate, sodium ethylenediaminetetra-acetate, sodium hexametaphosphate), oxidizing agents are.
- Oxidising agents (hydrogen peroxide, sodium chlorite)
- Reducing agents (sodium dithionite, sodium sulphide).
Anionic polyelectrolytes such as sodium alginate or carboxymethylcellulose, used mainly as thickening agents and migration inhibitors, also fall within the class of non-surfactants; So too do sorption accelerants such as ophenylphenol, butanol and methylnaphthalene, although they normally require an emulsifier to stabilize them in aqueous media. Fluorescent brightening agents (FBAs) form another large class of non-surfactant auxiliaries.
Here are some dyeing auxiliaries that are not surfactants:
Sequestering agents, oxidizing agents, reducing agents, dye fixing agents, pH regulators (buffering agents), Carriers and optical brighteners etc.
B. Surfactants Auxiliaries:
Organic in nature and more complex structures ‘an agent, soluble or dispersible in a liquid, which reduces the surface tension of the liquid’. In coloration processes this reduction in surface tension usually takes place at a liquid/liquid or liquid/solid interface, although liquid/gas interfaces are also occasionally important.
Here are some examples of surfactant dyeing auxiliaries:
Detergents, dispersing agents, emulsifiers, leveling agents, softeners, and antistatic agents.
List of Dyeing Auxiliaries and Their Uses:
- Sequestering agent
- Lubricants / Anticreasant.
- Peroxide killer
- Levelling agent.
- Wetting and penetrating agents.
- Sequestering, Dispersing and Levelling agent for reactive dyeing.
- Salt/Electrolyte
- Carrier
- Stabilizers
- pH Control and buffer system.
- Desizing agent
- Scouring agent
- Bleaching agent
- Dispersing agent
- Anti-pilling agent
- Antifoaming agent
- After-washing agents.
- Stripping agents.
- Yarn lubricant
- Mercerising agent
- Dyefixing agent
- Optical brightener.
- Soaping agent / Washing off agent.
- Softening agent
Uses and functions of important dyeing auxiliaries are given below:
1. Sequestering Agents:
Sequestering agents are very important auxiliaries in dyeing. It is used to remove hardness of water. Common sequestering agents are orthophosphate, orthosilicate and phosphates. The most effective sequestering agent in dyeing is ethylene diamine tetraacetic acid (EDTA). These are available in powder form. Resotext 600S, Heptol-EMG, Heptol-DBL are few brands of commercial sequestering agents.
2. Dispersing Agents:
The dispersing agents are an organic compound which performs many functions in dying. The main function of a dispersing agent is to prevent agglomeration of individual dye particles during dyeing. It assists the process dye particle size reduction and helps to solubilize dye particle i.e. dispersing agents increase solubility of disperse dye in water. Dispersant WS, Dadamol V, Hispogal, Licol OI, Sarcol NS etc are the example of dispersing agents.
3. Wetting and Penetrating Agents:
Wetting agents are used in dye bath to ensure that the entering goods are thoroughly and uniformly wetted with the dye solution. It is also called penetrating agents, since they cause the dye solution to penetrate into the interior of the yarn. Wetting agents reduce the surface tension of water by adsorbing at the liquid-gas interface.
4. Carrier:
Carriers are substances which accelerate the rate of dyeing of disperse dyes on polyester fibre materials when dyed at boil at atmospheric pressure. It is an organic compound which helps to take up dye at lower temperature and pressure over the textile material. Normally disperse dyeing is done in three ways on hydrophobic fibers (synthetic fibres). At the lowest temperature and pressure dyeing method is done with carrier dyeing. This substance is divided into three chemicals groups. Such as:
- Phenolic groups
- Prirnary amines
- Starch
Tumescal BDN, Carrylon GDX, Tumescal OP 45%, Teraux C, Superlene CR etc. are the example of carriers.
5. Stabilizers:
Stabilizers are used to maintain the stability of the dye bath during the dyeing process. They prevent undesirable chemical changes, ensure uniform dye uptake, and improve the overall quality of the dyeing process. Stabilizer PSLT, kappazon H53, STAB, Tinoclarite CBB are some commercial name of stabilizer.
6. Peroxide Killer:
Peroxide is harmful for the material. It is used to destroy the remaining peroxide content. Peroxide killers added at the stage of pre bleaching and also at peroxide bleaching processes.
7. Antifoaming Agent:
It is one type surfactant which is able to reduce or prevent foam. Usually used in dyeing bath and in printing paste to prevent foam generation. Excess foam generation can create adverse effect in processing and product. It also reduces dyeing uptake percentage. Most of antifoaming agents which are more efficient are based on silicones. Fatty alcohol and lower alcohols, cyclohexanols etc., are used as antifoaming agents.
8. Anti-pilling Agent:
Some manmade fiber and blended fiber fabrics can easily form pills in their surface. Anti-pilling agent plays a vital role in reducing the pilling in fabrics.
9. Levelling Agents:
Levelling agent is very important auxiliary in dyeing because it helps to secure level or uniform dyeing. Therefore, levelling agents are added to the dye bath to regulate the process of dyeing and to get uniform results. Levelex-P, Jinleve leve-RSPL, Serabid- MIP, Dyapol XLF, Lubovin-RG-BD are common leveling agents are found in market.
10. Dye Fixing Agents:
Dye fixing agents are a type of dyeing auxiliary used to improve the color fastness of dyed fabrics. The main drawback of direct cotton dyes is that their fastness to washing and soaping is poor. In this case Dye Fixing Agents are added in dye bath to increase fastness properties. Sandofix EC, Tinofix-ECO, Protefix-DPE-568, Jinfix –SR, Optifix-EC are common dye fixing agents.
11. Stripping Agents:
Stripping agents are used to remove unwanted or defective dye from fabrics. These agents are essential for correcting dyeing faults, lightening colors, or preparing fabrics for re-dyeing.
12. Anticreasing Agents:
Crease formation is one of the most unpleasant faults that can occur during the finishing of garments. There is an extensive literature on the mechanism, prevention, and cure of creasing. Because the removal of many types of crease is either impossible or extremely difficult, textile manufacturers always try to prevent them as far as possible. Anticreasing agents act as lubricants which improve the sliding of one part of the textile over another, so that creases formed during movement of the textile open up and disappear more easily.
Conclusion:
Dyeing auxiliaries play a considerable role in the development of textile products, contributing to achievements such as enhanced color fastness, increased functionality, improved mechanical strength, shortened process, reduced energy consumption, and decreased greenhouse gas emissions. The temperature and time controlling are two key factors in dyeing. In order to get satisfactory results during dyeing, dyeing auxiliaries are invariably employed. In this article I have described different types of dyeing auxiliaries and their classification, functions and uses. If you have any query about dyeing auxiliaries please let us know by commenting.
References:
- Physico-chemical Aspects of Textile Coloration by Stephen M. Burkinshaw
- Ji, Y., Li, X., Jin, K. et al. Research Progress and Development Trend of Textile Auxiliaries. Fibers Polym 25, 1569–1601 (2024). https://doi.org/10.1007/s12221-024-00545-0
- Industrial Dyes: Chemistry, Properties, Applications Edited by Klaus Hunger
- Colorants and Auxiliaries (Second Edition) Volume 1 – Colorants Edited by John Shore
