The processing sector is undoubtedly the most significant stage in the textile value chain. C.N. Sivaramakrishnan discusses the technologies that are contributing to more sustainable processing.
The Indian textile industry is as diverse as the country is and as complex an entity. There is an organised, decentralised sector and down the line, there are weavers, artisans as well as the farmers. The spectrum of technology is widespread, right from handmade to semi-mechanical and highly sophisticated information- and micro-processor based technologies. The processing sector is undoubtedly the most significant stage in the value chain contributing to the end user an array of properties like easy care and wrinkle free finishes besides aesthetic value addition in terms of colours, motifs and designs. The value addition at this stage is often manifold, with a range of other functional finishes like hydrophilic, stretch-back effect, oil and water repellant, and peace effect, to name a few. Specialty chemicals have played a significant role in the production of fibres and textiles. Awareness of chemical reactions, polymer sciences and understanding complex biochemical reactions have resulted in what we see as a dramatic shift in the minds of a processor.
The tools available to a processor today are plenty and technological positioning of ideas from other streams of sciences converts a modern day scientist into a virtual magician, especially when it comes to polymers. Fibre blends bring in a series of substrates available for any type of application including routine clothing to exotic spacewear suits. Filament or staple yarn properties can be enhanced to get synergistic updates with several available techniques.
Textile manufacturing begins with the production or harvest of raw material. Fibre used in textiles can be harvested from natural sources like wool and cotton or manufactured from regenerative cellulosic materials like rayon acetate or they can be entirely synthetic like polyester and nylon. After the raw, natural or manufactured fibres are shipped from the farm or the chemical plant, they pass through four main stages: yarn production, fabric production, finishing and fabrication.
In yarn production, natural fibres, predominantly cotton and wool, are cleaned, carded or combed and then spun into yarn. Fabric production is the second step. It involves either weaving or knitting. Finishing represents the third step. Fabrics undergo a series of operations like singeing, de-sizing, scouring, bleaching, dyeing, printing, finishing and finally, fabric formation.
Textile processing generates many waste streams, including water-based effluents and air emissions, solids and hazardous wastes. The nature of the waste generated depends on the type of textile facility, processes adopted, technologies operated, type of fibres and chemicals used. Most processes performed in the dye houses cause atmospheric emissions. Gaseous emissions have been identified as the second-greatest pollutant after effluents. Unfortunately, there is no clear data available on air emissions. Most of the published data is based on mass balance calculations and not as direct measurements. Air pollution is the most difficult type of pollution to sample, test and quantify in an audit. Measurement techniques such as direct reading tubes and gas chromatography or mass spectrometry have been used to collect more reliable data.