By adopting the dope dyeing process, less chemicals and energy are needed as the process is short and less waste water is generated, infer Ajay Sardana and Amit Dayal.
Viscose has been a fibre loved by consumers on account of its excellent attributes of comfort, fluid drape and aesthetic appeal. Made from a renewable natural resource, wood pulp, Viscose has been a preferred choice across applications like women’s fashion wear, menswear in blends and home textiles.
Why dope-dyed fibres?
Wet processing, a common step in the textile industry, has the potential to cause a significant impact on the environment and human health. Large amounts of chemicals and dyes are used in the wet processing operations resulting in generation of effluents with a complex chemical composition.
The cellulosic textile industry consumes a large quantity of water in wet processing operations like desizing, scouring, mercerizing, bleaching and dyeing employed during conversion of fibre to fabric.
The last decade has seen a growing concern about environmental issues, which have increased many fold because of increasing industrial pollution, waste problems, effects of global warming, etc. Dope-dyed viscose is the right solution to reduce environmental pollution and waste water discharges in the textile industry.
Benefits of dope-dyed viscose
In order to verify this, a qualitative life-cycle assessment between viscose dope-dyed knitted fabrics versus viscose piece-dyed knitted fabrics has been completed by the North India Textile Research Association (NITRA). It is clear from this independent study by NITRA that:
li>Greenhouse gas emissions are reduced up to 20 per cent by using spun-dyed viscose as compared to the conventional dyeing of viscose
- Waste water generation is reduced up to 10 per cent and a significant reduction is noticed in heavy metal concentrations in the effluent generated by spun-dyed viscose
- By adopting the dope dyeing process, less chemicals and energy are needed as the process is short and less waste water is generated. This enables direct savings on production costs and ensures a substantial reduction of the environmental footprint of the final products.
Dope-dyed viscose based fabrics have better wash and perspiration fastness (rating of 4-5 for both wash & perspiration fastness against rating of 3 for piece-dyed fabrics) against piece-dyed viscose fabrics, though there is no significant difference in rubbing and sublimation fastness.
Apart from the above advantages, on the cost front, dope-dyed Viscose fabric is about Rs 15-20 per kg cheaper compared to piece-dyed viscose fabric.
4. Ease of processing
As the fibre is already dyed, the process of dyeing is completely eliminated leading to the saving of a large amount of resources such as water, energy and chemicals. This results in less loading of effluents into the environment.
In a recent development, China is planning to introduce an environmental tax on printing and dyeing companies. The law, to enter into force on January 1, 2018, will be key to fighting pollution. The law will target enterprises and public institutions that discharge listed pollutants directly into the environment. So, dope-dyed viscose can be very helpful to the manufacturers who are using piece dyeing processes and facing the issues of environmental pollution, shade consistency and cost in their production. Dope-dyed fibre can be a significant part of the solution to all such problems.
Applications of dope-dyed viscose
Dope-dyed viscose applications include dress pants, work wear, uniforms, leggings, knitted tops, thermal wear, carpets and nonwoven wipes. In all these apps, consumers will value the benefits brought about by dope-dyed fibres through their enhanced performance and the conservation of scarce natural resources.
Ajay Sardana is Chief Sustainability Officer, and Amit Dayal is AVP - Textile Research & Application Development Centre with Grasim Industries Ltd., Aditya Birla Group.