Cellulosic fibres and fabric processing

D CIECHANSKA, Institute of Chemical Fibres, Poland and P NOUSIAINEN, Tampere University of 

In order to evaluate sustainability of products and processes, the life cycle assessment (LCA) concept is a method for industry to understand, manage and reduce the environmental, health and resource consumption impacts associated with processes, products and activities.Due to the well-known environmental impacts of cotton and its further chemical processing, LCA evaluations have been used to develop the sustainability of man-made fibres, as well. In the case of cellulosic fibres based on cellulose polymers produced by photosynthesis, biodegradability can be seen as a benefit to fit the criteria of sustainability. 

Methods of biological utilisation of polyester/cellulose textile blends are based exclusively on the application of cellulolytic enzymes, like cellulases, catalysing the hydrolytic degradation of cellulose to a sugar mixture like glucose or ceUobiose. The recovered polyester components were tested to be recycled in the melt process.  

Microbial synthesis of ceUulosic fibres affords the opportunity of obtaining products with unique properties suitable for practical application in medicine and the electronics industry. For synthesis of modified bacterial cellulose, the Acetobacter subsp. strains have been applied. The selection of suitable polyaminosaccharide modifiers allows the production of bacterial cellulose characterised by valuable mechanical, electro-acoustic and biological properties. Practical applications of this ceUulosic composite material for manufacture of novel wound-heaUng dressings as well as diaphragms for loudspeakers have been tested.  

Strategy based on environmental requirements and laws, where the company s strategy is based on observance of environmental laws and other requirements. 

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Cellulosic fibres and fabric processing Microbial synthesis of cellulosic fibres... 

Most fibres made from regenerated cellulose such as viscose, lyocell, and Celsol are characterised by stiffness as well as a fuzzy and uneven surface that makes fabrics susceptible to pilling, even over a short period of use. In order to modify the surface properties of cellulosic fibres and fabrics and to improve their quality biotechnological approaches based on specialised enzymes are widely used. Finishing processes, employing cellulases and xylanases, can replace a number of mechanical and chemical operations, which have been applied until now to improve comfort and quality of fibres and textiles. The principle of enzyme action in the finishing process is controlled hydrolysis of cellulose, in which impurities and fuzz are removed from the surface of fibres, without decreasing their mechanical tenacity or the elasticity of the fabric. 

Essentially nonionic soil-release agents comprise polyesters, polyamides, polyurethanes, polyepoxides and polyacetals. These have been used mainly on polyester and polyester/ cellulosic fabrics, either crosslinked to effect insolubilisation (if necessary) or by surface adsorption at relatively low temperature. Polyester soil-release finishes have been most important, particularly for polyester fibres and their blends with cellulosic fibres. These finishes, however, have much lower relative molecular mass (1000 to 100 000) than polyester fibres and hence contain a greater proportion of hydrophilic hydroxy groups. They have been particularly useful for application in laundering processes. These essentially nonionic polymers may be given anionic character by copolymerising with, for example, the carboxylated polymers mentioned earlier these hybrid types are generally applied with durable press finishes. 

The CAV for a particular process is dependent on fibre type and fabric construction and absorbency. A finish application below the CAV may result in a non-uniform speckled treatment, while an application above the CAV could lead to finish migration. Cellulosic fibres, becanse of their inherent hydrophilicity, have CAVs in the range of 35 0 % wet pickup. Hydrophobic fibres like polyester can have CAVs of less than 5 %, allowing much lower wet pickups than hydrophilic fibres. 

CONDENSOL FN was specially developed for the moist cross-linking process. This catalyst consists of inorganic acids and organic compounds. It is very suitable for fabrics composed of cellulosic fibres, alone and in blends with synthetics. 

In tropical countries like India synthetic fibres blended with cellulosic fibres fabrics are very popular due to their excellent combination of aesthetic properties and easy care properties. Thus, bleaching of blended fibre fabrics before further processing is an important step. Many of the preparatory processes used for natural and synthetic fibres have little or no application in preparation of blended fibre fabircs. 

Cellulosic fibres, especially cotton, are pretreated with alkali. After rinsing off, a certain amount of residual alkali usually remains in the fabric and this is often distributed unevenly. - This can lead to faults in subsequent processes where alkali interferes, for example with acid-catalysed finishes (easy-care, water-, oil-and soil-repeUent, stretch finish). Another problem caused by alkali is alkali spots. 

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