Authors: Sujal Sandeep Patani, Soham Koik, Pakshal Porwal, Darshan Ganesh Shahane
Guided by: Prof. Dr. Y.M. Indi
Institution: D.K.T.E. Society’s Textile and Engineering Institute, Ichalkaranji
Highlight/Abstract:
This article investigates the potential of directly dyeing 100% cotton fabric for dark shades using reactive dyes without undergoing conventional pre-treatment processes like scouring, bleaching, and mercerization. The process utilizes cationization of cotton fabric with keratin hydrolysate, aiming to save energy, time, and reduce production costs while maintaining color brilliancy. A comparison between the cationized dyeing process and the conventional dyeing process is also presented, focusing on washing and rubbing fastness.
Introduction
In the textile industry, traditional dyeing processes for cotton fabrics often require several preparatory steps, including scouring, bleaching, and mercerization, which consume significant amounts of energy and water. With increasing concerns regarding environmental sustainability and energy conservation, there is a growing need to explore alternative methods that reduce water and energy consumption, while still achieving high-quality results.
One promising method for achieving this goal is the cationization of cotton fabric. Cationization refers to the process of modifying cotton fibers to carry positive charges on their surface, which can interact more easily with negatively charged dye molecules, especially reactive dyes. This article explores the possibility of directly dyeing cotton fabric for dark shades using reactive dyes through the cationization of cotton with keratin hydrolysate, thereby eliminating the need for intermediate pre-treatment processes.
Objective
The primary objective of this study is to examine whether it is feasible to directly dye 100% cotton fabric for dark shades using reactive dyes without the need for scouring, bleaching, and mercerization. The key aims of this modified dyeing process are:
- To analyze the washing and rubbing fastness of cationized cotton fabric and compare them to samples dyed via conventional methods.
- To minimize the use of intermediate pre-treatment processes.
- To reduce energy consumption and production costs.
- To achieve a similar brilliancy of dark shades as conventional methods.
The study is driven by the need to conserve water and energy, as well as reduce overall production costs in textile manufacturing.
Methodology
Cationization of Cotton with Keratin Hydrolysate
Cotton fibers are primarily made up of cellulose, which contains hydroxyl groups (-OH) that are reactive and can form bonds with other molecules. Keratin hydrolysate, derived from wool, contains positively charged amino groups (-NH₃⁺ or -NR₄⁺), which can bond with the negatively charged hydroxyl groups on cotton fibers. The ionic interaction between these positively charged keratin hydrolysate molecules and the negatively charged cellulose fibers leads to the formation of a cationic cotton fiber, which is more receptive to anionic dyes such as reactive dyes.
The cationization reaction can be described as follows:
Cellulose-OH + Keratin-NH₃⁺ → Cellulose-O-NH₃⁺
This reaction results in a modified cotton fiber with a positive charge on its surface, making it more suitable for binding with anionic dyes.
Dyeing of Cationized Cotton
Once the cotton is cationized, it can be dyed with reactive dyes, which typically carry a negative charge due to the presence of sulfonate (-SO₃⁻) or carboxyl (-COO⁻) groups. The positive charge on the cationized cotton fibers attracts the negatively charged dye molecules, resulting in electrostatic interactions between the fiber and the dye. This interaction forms an ionic bond between the cotton fiber and the dye.
The dyeing reaction can be described as:
Cellulose-O-NH₃⁺ + Anionic Dye-SO₃⁻ → Cellulose-O-Dye (ionic bond)
This reaction ensures that the dye is effectively fixed onto the cotton fibers, achieving a stable and durable color.
Extraction of Keratin Hydrolysate
Keratin hydrolysate is extracted from wool by treating it with caustic soda (NaOH) under controlled conditions. The extraction process involves hydrolyzing the keratin protein, breaking it into smaller peptides, which can then be modified to carry cationic groups. The extraction process is optimized for maximum yield by adjusting parameters such as temperature, extraction time, and the concentration of caustic soda.
The optimal conditions for keratin extraction were determined using a Taguchi design of experiments, which tested different combinations of temperature, time, and concentration. After extraction, the keratin hydrolysate solution was filtered and stored for use in the cationization process.
Results and Discussion
Fastness Properties
After dyeing the cationized cotton samples with reactive dyes, several fastness properties were tested, including washing and rubbing fastness. The results were compared to conventional cotton dyeing methods that involved scouring, bleaching, and mercerization.
The washing fastness of the cationized cotton samples was found to be comparable to the conventional samples, with minimal color fading or bleeding. Similarly, the rubbing fastness of the cationized samples was also satisfactory, demonstrating that the modified dyeing process did not compromise the durability of the fabric.
Color Brilliancy
The color brilliancy of the dark shades achieved through cationization was evaluated in comparison with the conventional method. The results indicated that the cationized cotton samples exhibited similar color depth and brilliancy to those produced through conventional dyeing processes. This suggests that cationization can effectively facilitate the direct dyeing of cotton fabric without sacrificing color quality.
Environmental and Economic Benefits
One of the significant advantages of the cationization process is the reduction in the need for intermediate pre-treatment steps. Traditional cotton dyeing processes require scouring, bleaching, and mercerization, which consume large amounts of water and energy. By eliminating these steps, the cationization process reduces water and energy consumption, leading to environmental and economic benefits.
Additionally, the cationization process can help reduce the cost of production by minimizing the number of chemical treatments and reducing the need for salt, which is often used in conventional dyeing processes. This saltless dyeing process not only saves on chemical costs but also helps mitigate the environmental impact of salt discharge into wastewater.
Conclusion
The study successfully demonstrates that it is possible to directly dye 100% cotton fabric for dark shades using reactive dyes through the cationization of cotton with keratin hydrolysate. The cationized cotton fabric exhibited comparable washing and rubbing fastness to conventionally dyed fabrics, while maintaining similar color brilliancy. Furthermore, the process offers significant environmental and economic advantages by reducing water and energy consumption, as well as eliminating the need for intermediate pre-treatment steps.
This research opens up new possibilities for energy-efficient, cost-effective, and environmentally sustainable dyeing processes in the textile industry. Future studies could explore the scalability of the process and its applicability to a wider range of dyeing applications.
