Finishing lyocell

Viscose In principle all the treatments effective on cotton should be effective on viscose as well. However, the delicate viscose libers cannot withstand the harsh finishing processes, and are rarely treated with a finish. However, Lyocell (Coutaulds) can be treated with Pyrovatex CP (Ciba) to produce FR Lyocell.55 The work at Bolton has shown that this fiber being more reactive than cotton needed only half the normal amount of this FR treatment applied to cotton cellulose to produce an equivalent degree of flame resistance. 

Demanding and sophisticated customers as well as fashion designers are looking for new effects. Some of them have been discussed in the chapter on novel finishes, for example anti-odour and protective finishes, wellness finishes that release fragrances or cosmetics and medical finishes that deliver drugs. Additionally, cellulase finishing, especially on microviscose or lyocell fibres, enables novel... 

A range of novel structures and finishing components have been developed and fully characterised by using commercial and relatively inexpensive medical-grade fibres such as bleached cotton, bleached viscose, bleached lyocell, and other natural, biodegradable and non-toxic fibres and finishing components by using conventional materials, equipment, and chemicals. 

N/inm. Composites reinforced with lyocell 6.7 and lyocell 15.0 multilayer webs reached values of 36 N/mm and 28 N/mm respectively. For the needle felt reinforced composites clear reinforcement effects were determined (lyocell 1.3-PLA = 63 N/ mm, lyocell 6.7-PLA = 61 N/mm and lyocell 15.0-PLA = 57 N/mm ). These results lead to the assumption that the kind of the semi-finished product has a clear influence on the mechanical characteristics of the composites produced by the compression molding technique CP-1. This effect could be attributed to a more homogeneous fiber distribution in the PLA matrix due to the additional needling process and the lower thickness of the needle felts compared to the multilayer webs. It is assumed that the lower thickness lead already in the pre-heating phase to a better heat conductivity and drying in the press. 

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. 

Limiting the scope for yarn movements by setting the fabric. Unlike synthetics, lyocell fabrics are not thermoplastic and so cannot be set with heat. However, there are wet finishing treatments that can fix yams so that they will retain a memory of their crease-free state. Resin treatments help in this respect but caustic setting is particularly relevant for lyocell. 

Conventional liquor jet machines will always be problematical because the fabric rope does not move sufficiently in running on the machine and uncontrolled localised fibrillation can develop. We have seen the introduction of air jet technology to help in rope re-orientation and hence with fibrillation control, together with the introduction of new processing routes to reduce the high cost of lyocell piece finishing. Fabric behaviour understanding has... 

Studies of lyocell fabrics processed with conventional open width techniques demonstrate the virtues of lyocell with low-cost production techniques and have shown the excellent easy care performance that lyocell can deliver in combination with resin finishing. The softness, fluidity and drape characteristics shine through even without fibrillation. 

The acceptance of lyocell by the garment processing industry was relatively straightforward as they were already used to enzyme systems for indigo denim. (It is also interesting to note that cellulase enzymes were only introduced for textiles in the mid-1980s so prior to that lyocell would have been impossible to process to a controlled fibrillated finish.)... 

As with any fabric, chemical finishing is an important aspect of the process and this is especially true when considering the finishing of open-width processed lyocell fabrics. In such processing, resination is the method of controlling fibrillation. If too little resin is fixed then fabrics will fibrillate on subsequent washing, too much and physical performance deteriorates. It is also important to include appropriate softeners and auxiliary products into the chemical finish so that performance and handle are appropriate to the customer s requirements. 

Rencheng T, Jianping Z, Shiying M. Lyocell textile dyeing and finishing technology. Beijing China Textile Press 2001. p. 28—29. 

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