Lyocell

The precise effects obtained are dependent on the fabric quality, the type of cellulase enzyme and the application conditions, but no mechanical forces are involved in removal of the fibrils. The process has attracted considerable attention and is now one of the main methods of defibrillating lyocell fabrics [94,101-114]. Simultaneous treatment with cellulase and protease enzymes has been applied to the biofinishing of wool/cotton blends [115]. 

Lyocell A papermaking process, based on dissolving wood pulp in N-methyl morpholine. Developed by Courtaulds, but the subject of a patent dispute with Lenzing, Austria, since 1993. Courtaulds has a plant in Mobile, AL, and Lenzing has one in Heiligenkreuz, Austria. 

Coupling sugar, 23 480 Courtaulds lyocell process, 11 266-267, 267-269. See also Samuel Courtauld Co., Ltd. 

Lyocell process, environmental issues related to, 22 279-280. See also Courtaulds lyocell process Lyondell s process, 23 345 Lyophilic colloids, 7 283-284 Lyophilization, 28 716 Lyotropic liquid crystalline polyesters,... 

Textured semiconductor surfaces, 14 847 Textured yarn, 11 178 Texture mapping technique, 10 339-341 of lyocell fibers, 11 271 Texturing... 

Fig. 11 Cellulose (beech sulfite pulp) dissolved in NMMO (Lyocell dope). Left DSco and differential MWD of the starting pulp, molecular weights of DP = 50 and DP = 200 are indicated by vertical dashed lines. Right Time course of the overall carbonyl content for three selected molecular weight ranges. Reprinted with permission from Biomacromolecules (2002) 4 743. Copyright (2002) American Chemical Society...

As an example using NMMO solution, the spinning of fibers consisting of blends of cellulose with cationic starch was investigated for the purpose of improving moisture absorbability, dyeability, and enzymatic degradability compared with standard Lyocell fibers [69]. 

Later the same research group claimed that, in the first step of the in situ synthesis scheme, ionic functional groups as such are not necessary for the introduction of ferrous ions into a cellulose matrix [161,162], This suggestion was made based on a comparative study of ferrite synthesis between a case with anionically modified cellulose materials and the other case with non-ionic cellulose gels, which included a never-dried bacterial cellulose (BC) membrane and a never-dried cellulose wet-spun filament or cast film (Lyocell) using N-methylmorpholin-N-oxide as the solvent. SPM proper-... 

The first section covers the chemistry of cellulose solutions in an amine N-oxide solvent (NMMO), the so-called Lyocell chemistry, as encountered in the industrial production of cellulosic Lyocell material. The system is characterized by high reaction temperatures, the presence of a strong oxidant and high complexity by multiple (homolytic and heterolytic) parallel reactions. Trapping was used to address the questions that reactive intermediates are present in Lyocell solutions and are responsible for the observed side-reactions and degradation processes of both solvent and solute. 

N-McLhylmorpholine-N-oxidc monohydrate, a tertiary, aliphatic amine N-oxide, is able to dissolve cellulose directly, i.e. without chemical derivatization, which is used on an industrial scale as the basis of the Lyocell process [ 1, 2], This technology only requires a comparatively low number of process steps compared for instance to traditional viscose production. Cellulose material - mainly fibers - are directly obtained from the cellulose solution in NMMO no chemical derivatization, such as alkalization and xanthation for rayon fibers, is required [3]. The main advantage of the Lyocell process lies in its environmental compatibility very few process chemicals are applied, and in the idealized case NMMO and water are completely recycled, which is also an important economic factor. Even in industrial production systems NMMO recovery is greater than 99%. Thus, compared with cotton and viscose the Lyocell process pertains a significantly lower specific environmental challenge [4]. Today, Lyocell fibers are produced on an industrial scale, and other cellulosic products, such as films, beads, membranes and filaments, are also currently being developed or are already produced commercially. 

It was our aim to study the chemistry of NMMO and Lyocell solutions in order to put the prevention of undesired side-effects on a more scientific foundation [8,9]. The improved understanding of the individual chemical processes in Lyocell solutions today allows an accurate deduction of the different tasks of optimum Lyocell stabilizers. The question of which reactive intermediates are involved in the degradation processes of both NMMO as the solvent and cellulose as the solute was a key issue in the studies of Lyocell chemistry. 

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