By: Ananya Sharma
Picture this: a world where vibrant and colourful textiles are created without harming the environment. Where water is conserved and energy is saved. This may sound like a dream, but with the use of supercritical CO2 fluid for textile dyeing, it is a reality. The dense and compressed carbon dioxide fluid may seem small, but its impact is mighty. With its ability to dye a wide range of textiles faster and with higher colour yields, it’s like a superhero in the world of dyeing. And the best part? It does all of this while being kind to the planet. So let’s raise a toast to the future of sustainable textiles, where every colour tells a story of innovation and responsibility.
Supercritical CO2 (scCO2) dyeing technique is a highly efficient and environmentally friendly alternative to traditional textile dyeing processes. It allows for the economic production of high-end textile products where uniform through coloration is desired. The process uses minimal water, chemicals, and energy, resulting in reduced environmental impact and lower production costs. The scCO2 dyeing technique also offers precise colour matching and increased colourfastness, making it suitable for a wide range of applications in the textile industry.
Carbon dioxide has been extensively investigated as a non-flammable, environmentally benign, and inexpensive solvent, both as a liquid and in its supercritical state. While water and carbon dioxide are two of the most popular benign solvents, the knowledge of water’s behaviour as a solvent still surpasses that of CO2. However, the benefits of using scCO2 in textile chemical wet processing, based on minimum utilization of water, make it a suitable choice. scCO2 is non-toxic, non-flammable, and widely used in the food and beverage industry. It is supplied in large amounts either from combustion processes or volcanic sources without the need to produce new gas, and it can be recycled in a closed system.
The low viscosity of supercritical fluids and the high diffusion properties of dissolved molecules make scCO2 especially promising for dyeing processes. A supercritical dyeing fluid should easily dissolve solid dyestuffs and penetrate even the smallest pores without the need for vigorous convection procedures. In addition to dyeing, scCO2 has also been explored for other textile processes such as fabric cleaning, finishing, and coating. The development of scCO2 technology in textile processing has the potential to reduce the industry’s environmental impact while also providing economic benefits.
Supercritical carbon dioxide is a substance that can exist in a state where its temperature and pressure exceed its critical points, which are 31 degrees Celsius and 74 bar pressure. At these conditions, carbon dioxide exhibits solvent properties similar to those of liquid hydrocarbons, making it a useful substance for a variety of applications. One such application is dyeing, where the use of supercritical carbon dioxide can offer advantages such as reduced waste and energy consumption. The apparatus used for dyeing in supercritical carbon dioxide includes a vessel with a capacity of 50 mm and a quick release cap for convenience. Additionally, the apparatus features a temperature controller, vessel heater, manometer, and a Varex HPLC carbon dioxide pump. The pump is equipped with a cooler to cool the head of the pump. By using this specialized equipment, researchers and technicians can take advantage of the solvent properties of supercritical carbon dioxide to achieve their dyeing goals. Overall, understanding the critical points of carbon dioxide and utilizing specialized equipment can lead to innovative solutions with this unique substance.
Supercritical fluid based textile dyeing (SCFTD) technology using supercritical carbon dioxide as a solvent has shown great promise in the textile industry. This technology allows for lesser consumption of energy and solvents compared to traditional dyeing methods, making it more environmentally friendly. IIT Bombay has recently developed a fully operational SCFTD prototype plant that can be effectively used by textile industries. The plant has been designed and developed in collaboration with industry partners and is currently housed in the Mumbai-based textile research organization Synthetic and Art Silk Mills Research Association (SASMIRA). The plant is being used for exploratory research on SCF based textile dyeing. A number of successful trials have been conducted using dyes of various colours to check the properties such as dye solubility, dye fixation, and uniformity of deposition on fabric as well as fibre. The results of these trials are expected to help optimize processing conditions and establish the economic viability of this innovative technology. This information will also enable the design of a commercial plant for the textile industry. Overall, SCFTD technology has the potential to revolutionize the textile industry by providing a more sustainable and environmentally friendly method for textile dyeing.
CO2 dyeing technology is gaining popularity among textile companies as a sustainable and environmentally friendly alternative to traditional water-based dyeing methods. Companies such as DyeCoo are leading the way in this field, providing industrial CO2 dyeing equipment and innovative processes that eliminate the need for water in the dyeing process. This technology offers several benefits, including reduced water consumption and wastewater generation, lower energy consumption, and improved product quality. Major brands such as IKEA and Nike have already embraced CO2 dyeing technology, and now, companies in India, including Arvind Mills, are considering adopting this technology to improve their sustainability practices.
The realm of supercritical CO2 dyeing has emerged as a promising innovation that has garnered much attention due to its environmentally friendly attributes. However, as with any novel approach, it is essential to weigh the pros and cons before delving into it. Among the challenges posed by this process are the exceptionally high pressures required, which call for specialized machinery design and significant investments for up-scaling. In addition, paramount importance must be placed on the implementation of safety measures to regulate CO2 concentrations and safeguard the well-being of workers. Furthermore, classical colour measurement techniques may not suffice in capturing the non-additive behavior of dye components. Supercritical CO2 dyeing is also unsuitable for natural fibres, for CO2 lacks the ability to break hydrogen bonds. Lastly, certain types of dyes such as reactive, direct, and acid dyes, may incur damage from the high temperatures and pressures required for the process. Thus, before embarking on supercritical CO2 dyeing in the textile industry, it is imperative to thoroughly ponder over these aspects.
As the world becomes increasingly aware of the impact of industrial practices on the environment, there is a growing need for sustainable alternatives that can help reduce our carbon footprint. Supercritical carbon dioxide dyeing technology is one such innovation that has captured the imagination of the textile industry. By offering a more efficient and environmentally friendly method of dyeing, it has the potential to transform the way we produce textiles. With its numerous advantages and ongoing research efforts to overcome the challenges, the future of supercritical CO2 dyeing looks bright. As we move towards a more sustainable future, this technology could be the game-changer we need to make a significant impact on the world around us. The stage is set for a revolution in the textile industry, and supercritical CO2 dyeing is at the forefront of this change.