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A Term Paper on LYOCELL FIBRE (Manufacturing process and properties) TTL 715 Submitted To Dr. Manjeet Jassal Submitted By: Patanjal Kumar (2011TTF2509) Department of Textile Technology Indian Institute of Technology, New Delhi 1 Contents: 1. Abstract 2. Introduction 3. Lyocell manufacturing process 4. Optimization of cellulose dissolution stage in Lyocell process 5. Computer modelling of the lyocell fibre spinning 6. Lyocell fibre properties(Kinetic study of moisture sorption, swelling behavior of lyocell fiber, etc) 7. Uses of Lyocell Fibre(Lyocell precursor for carbon fibre etc) 8. Recent developments & trends in Lyocell process 9. Referances 2 1 ABSTRACT For the majority of the last century, commercial routes to regenerated cellulose fibres have coped with the difficulties of making a good cellulose solution by using an easy to dissolve derivative (e.g. xanthate in the case of viscose rayon) or complex (e.g. cuprammonium rayon). Advanced cellulosic fibres are defined as those made from a process involving direct dissolution of cellulose. The first examples of such fibres have now been generically designated as lyocell fibres to distinguish them from rayons, and the first commercial lyocell fibre is Courtaulds' Tencel. Some main characteristics of lyocell fibers are that they are soft, absorbent, and very strong when wet or dry, and resistant to wrinkles; lyocell fabric can be machine- or hand-washed or drycleaned, it drapes well, and it can be dyed many colors, and can simulate a variety of textures. In order to develop a commercially viable lyocell production process, it is essential to maximise spinning stability. This requires a good understanding of the fundamental factors that influence fibre formation. Lyocell fibers belong to the new generation of regenerated cellulose fibers produced by on environmentally clean process. Their supramolecular structure is different from the conventional regenerated cellulose fibers what explains their different sorption properties. 3 2 INTRODUCTION Lyocell lots of ideas concerning innovation, fashion and also environmental arguments exist. These topics are mganfed as important in the whole process All these points ere also arguments in spinning. There is less energy required per kg of yam pduced in comparison to cotton. The quantity of raw material for the same production is less than in the case of cotton. Processing of Lyocell in spinning does not muire special efforts, if the fibre and the machines are optimised. Looking to the future shows a big potential for further growth.Whether the need is denim for casual looks or sueded silk- like ensembles for evening wear, lyocell can create the right look and the right fabric. In 1996, lyocell became the first new generic fiber group in 30 years to be approved by the Federal Trade Commission. Since then, lyocell has realized increasing visibility and acceptance in the apparel market, especially in designer and better priced garments. Its versatility and desirable properties provide many advantages, both functional and aesthetic. Lyocell was developed by Courtaulds Fibers (now Acordis Cellulosic Fibers), an international supplier of rayon. It entered the consumer market in 1991. The properties and production processes were unique enough for the Federal Trade Commission to designate it as a separate fiber group. The trade name for lyocell produced by Acordis is Tencel . Lenzing Fibers, another major manufacturer of rayon, has also entered the lyocell market. This product is marketed as Lenzing lyocell. An improved fiber, in terms of performance and properties, lyocell is also friendly to the environment. Virtually all of the chemicals used in the production process are reclaimed. The resulting fiber, lyocell, is both biodegradable and recyclable. Lyocell is a manufactured fiber, but it is not synthetic. It is made from wood pulp harvested from tree farms for this purpose. Because it is made from a plant material, it is cellulosic and possesses many properties of other cellulose fibers, such as cotton, linen, ramie, and rayon another manufactured but non-synthetic fiber. In many ways, lyocell is more similar to cotton than it is to rayon. Like other cellulosic fibers, it is breathable, absorbent, and generally comfortable to wear. In fact, lyocell is more absorbent than cotton and silk, but less so than wool, linen, and rayon. It can take high ironing temperatures, but like other cellulosics will scorch, not melt, if burned, and is susceptible to mildew and damage by silverfish. Cellulosic fibers are not resilient, which means they wrinkle. Lyocell has moderate resiliency. It does not wrinkle as badly as rayon, cotton, or linen, and some wrinkles will fall out if the garment is hung in a warm moist area, such as a bathroom after a hot shower. A light pressing will renew the appearance, if needed. Also, slight shrinkage is typical in lyocell garments. Stability, overall, is similar to that of silk and better than cotton or linen. Lyocell has strength and durability. It is the strongest cellulosic fiber when dry, even stronger than cotton or linen and is stronger than cotton when wet. Lyocell is much stronger than rayon when wet. This property of 4 high wet strength usually determines the extent to which fabrics can be machine washed successfully (see Care below). Other desirable properties of lyocell are its luster and soft drape which makes it an aesthetically pleasing fiber. Since it is a manufactured fiber, the diameter and length of fibers can be varied. Lyocell can be made into microfibers (very fine fibers), offering depth and body to fabrics combined with luxurious drape. Short staple length fibers give a cotton-like look to fabrics. Long filament fibers are successful in silk-like end uses. Lyocell blends well with other fibers including wool, silk, rayon, cotton, linen, nylon, and polyester. It successfully takes many finishes, both functional and those designed to achieve different surface effects, and dyes easily. Overall, lyocell is a versatile fiber with many desirable properties. Lyocell was initially marketed as and can generally be found in high end and designer apparel. Production costs are greater than for cotton, making lyocell more expensive in finished garments. However, as production increases and costs decrease, expect to see more lyocell in moderately priced apparel. Lyocells soft drape and luxurious hand make it very desirable in womens fashion garments as well as mens shirts, particularly apparel traditionally made from silk. Other lyocell end uses include denim, chino, and chambray casual wear. Look for these fabrics in 100% lyocell as well as in blends with cotton, rayon, or polyester. Tencel lyocell gabardines take water resistant finishes for coatings. Other fabrics successfully made from lyocell include jerseyknits, which exhibit a soft hand and luster. As lyocell becomes more available and manufacturers gain experience handling it, look for more varieties of fabrics including knits of all types, leotards and hosiery, velvets, velours, and corduroys. Look for Tencel lyocell blended with Tactel nylon in which the Tactel is on the surface for durability and wind and water resistance, while the Tencel has greater exposure on the backing surface for warmth, absorbency, and comfort. Blends with wool and wool with Lycra spandex and Tencel have been successful. Blends of lyocell with cotton, linen, and rayon, will continue to be available, especially for spring, summer, and fall fashions. In addition, blends with silk and rayon are common, especially in lightweight silky fabrics including those with sueded surfaces. 5 3. Lyocell manufacturing process The Lyocell fibre spinning process is a dry-wet spinning process, and the process of fibre formation can be studied separately in the air gap and in the coagulation bath. The spinning dope, i.e. the cellulose N-methyl-morpholine-N-oxide monohydrate (NMMO-MH) solution, can be melted and solidified repeatedly without any change in its composition. The mass transfer between filament and the environment in the air gap can be neglected. That is why the spinning process in the air gap can be considered as melt spinning. The simulation of the melt spinning process is well known. Any chemical reaction occurs in the coagulation bath, and cellulose is transformed to the solid state by diffusion of the solvent from the filament formed to the coagulation bath and water or diluted NMMO/water from the coagulation bath to the fibre. Therefore, the Lyocell spinning process in the coagulation bath can be considered as a wet spinning process without any chemical reaction. However, the dependencies between the particular parameters of the spinning process are complex, and experiments aiming at obtaining optimal conditions are long-lasting and expensive. The disposition of a theoretical model and appropriate software would improve the optimisation process. The cellulose Lyocell fibre spinning process can be divided into two processes, a dry spinning process in the air gap, and a wet spinning process in the coagulation bath . Hardwood logs are chipped into squares about the size of postage stamps. The chips are digested chemically, to remove the lignin and to soften them enough to 6 be mechanically milled to a wet pulp.This pulp may be bleached. Then it is dried into a continuous sheet and rolled onto spools. At this stage, it has the consistency of thick posterboard paper. The roll of cellulose weighs some 500 lb (227 kg). The waste liquor may be reworked to produce tall oil, used to make alkyd resins. At the Lyocell mill, rolls of pulp are broken into one-inch squares and dissolved in Nmethylmorpholine N-oxide, giving a solution called "dope." The filtered cellulose solution is then pumped through spinnerets, devices used with a variety of manmade fibers. The spinneret is pierced with small holes rather like a showerhead; when the solution is forced through it, long strands of fiber come out. The fibers are then immersed in another solution of amine oxide, diluted this time, which sets the fiber strands. Then they are washed with de-mineralized water. The Lyocell fiber next passes to a drying area, where the water is evaporated from it. The strands then pass to a finishingarea, where a lubricant, which may be a soap or silicone or other agent depending on the future use of the fiber, is applied. This step is basically a detangler, prior to carding and spinning into yarn. The dried, finished fibers are at this stage in a form called tow, a large untwisted bundle of continuous lengths of filament. The bundles of tow are taken to a crimper, a machine that compresses the fiber, giving it texture and bulk. The crimped fiber is carded by mechanical carders, which perform an action like combing, to separate and order the strands. The carded strands are cut and baled for shipment to a fabric mill. The entire manufacturing process, from unrolling the raw cellulose to baling the fiber, takes about two hours. After this, the Lyocell may be processed in many ways. It may be spun with another fiber, such as cotton or wool. The resulting yarn can be woven or knitted like any other fabric, and given a variety of finishes, from soft and suede-like to silky. The amine oxide used to dissolve the cellulose and set the fiber after spinning is recycled. 98% of the amine oxide is typically recovered. Since there is little waste product, this process is relatively eco-friendly. However, it uses a substantial amount of energy, and uses an organic solvent of petrochemical origin. After the fiber is created it is provided to manufacturers for weaving into fabric, then the fabric is used to create garments. Manufacturers may use environmentally unfriendly or chemical treatments to overcome the natural reluctance of the fiber to take dye and to overcome its natural pilling tendency. Although the closed-loop manufacturing process makes Lyocell inherently the most ecofriendly of the naturally regenerating fibers, different fabric and garment manufacturers vary in this respect. 7 4. Optimization of cellulose dissolution stage in Lyocell process The worldwide interest to modify cellulose by means of lyocell process has increased strongly in the last 5 years. Today raw cellulose, regardless of its origin, is available as low cost feed material. It can be processed into staple fibers, filaments and films. The core of the lyocell processing technology is the dissolution besides the spinning step. Parallel to viscose and cotton, lyocell fibers show a progressive acceptance from the market. The relatively simple adjustment of the properties of the lyocell fibers ensures the provision of qualitative characteristics that previously could not be reached with viscose fibers. The good skin compatibility as well as the high dry and wet tear strength open new and long-range future opportunities for the cellulose fibers. List AG, Arisdorf Switzerland further optimized the cellulose dissolution technology, which was introduced in 1992. This succeeded the production of excellent spinning solution qualities, produced from a variety of low cost raw materials. The technology fulfils the current high safety standards. In order to increase the application of the lyocell process, it seems necessary to further optimize the dissolution step of Cellulose in NMMO. The optimization aims to improve the economy of the process through the application of a cost-efficient technology. Reviewing the known processing technologies to date, it is apparent that besides the industrially implemented specialized thin film processing technology, the new List dissolution technology is also available. This technology was developed in close collaboration with the Institute for Textile and Plastic Research (TITK, in Rudolstadt/Germany). In 1998 Alceru GmbH (Rudolstadt/Germany) and Grasim Industries Ltd. (Nagda/India) implemented the process on a pilot scale with a production capacity in the range of 300-400 tons fibers/year. The cellulose dissolution in NMMO takes place in a thick-layer kneader of the type List Discotherm B Conti Fiber. The raw materials cellulose and NMMO are homogeneously mixed in the agitated chamber of the kneader and processed to the final cellulose spinning solution. In 2000 pilot units of the 3rd generation were installed in the China Textile University (Shanghai/PR China) and in Fraunhofer Institut f r Angewandte Polymerforschung (Golm/Germany). Both units have a processing capacity of 50 tons cellulose/year. The dissolution technology of the 3rd generation aimed mainly for the optimization of the quality of the spinning solution. In the foreground were the following: a) use of raw cellulose of different origin b) production of spinning solution of constant and high quality c) minimization of the gel formation in the spinning solution filter. For safety reasons the List cellulose dissolving technology preferably operates at temperatures lower than 100 C. A major advantage of the low operating temperature and product temperature is the minimization of the discoloration of 8 NMMO and the maximization of its recovery. The large hold-up of the dissolver provides enough buffer capacity to regulate process fluctuation, if it should occur. Hence, the spinning solution is directly discharged from the kneader in the filter and the spinning pump. A new development project between TITK and List aims for further improvements of the technology. It will result in the 4th generation of the cellulose dissolution by means of List technology. List developed a process simulation program for supporting the design and optimization of the process. Furthermore, pilot and full scale process data can be fitted. Fitting and interpreting pilot-scale data, the simulation leads to the optimum design of the full scale unit. Using fullscale data the simulation delivers information about the flexibility of the process and the reserves of the plant. The basis for the process simulation are the mass and energy balance, equipment characteristic values, caloric properties of the components, shear effects as function of product properties and equipment specific geometric characteristics. Taking into account the stringent process safety demands, which are fulfilled through the selection of adequate construction material and the limitation of the operating temperatures, the technology was optimized to produce excellent spinning solutions from practically any cellulose, regardless of its origin. Through the optimization of the dissolution process and of the kneader it is possible to produce spinning solutions of very good quality without pre-treatment (activation) of the raw cellulose. The spinning solution can be used for the production of fibers, filaments and films. The really compact technology can optimally be regulated and controlled. It is characterized by its flexibility and easy adaptation on process conditions and product compositions. Low operating temperatures and the short residence time of the processed product minimize the recuperation and rectification costs of NMMO and contribute to the maximization of the economy of this technology. The integration of the continuous preparation of the cellulose dope in a List Co- Rotating-Processor Conti rounds off the optimization of this technology. List is currently negotiating the extension of the field of application of this technology with new partners 9 5. Computer modelling of the lyocell fibre spinning The spinning process of Lyocell fibres in the air gap can be considered as a melt spinning process. For a steady-state process of melt spinning, the following equations are well known but should be recalled as the basis for performing the measurements and calculations discussed below: Mass continuity equation Moment a balance equation Energy balance equation Rheological constitutive equation where v, d, and T are the velocity, diameter and temperature of the running filament respectively (they are functions of the distance x from the spinneret along the spinning path); F is the tensile force acting on the filament at the given distance x; , Cp, and e are the density, heat capacity, and apparent elongation viscosity of the cellulose NMMO-MH solutions respectively (all are functions of temperature and concentration of cellulose in the dope). If the concentration is fixed, , Cp, and e are functions of temperature. The data of density, heat capacity and elongational viscosityare unknown for cellulose solutions in NMMO-MH. Thus the density was measured by dilatometry, the heat capacity by the DSC method, and the elongational viscosity by using the non-isothermal spinning method for obtaining the parameters necessary to calculate the elongational viscosity values of the dope for different temperatures. With all the data, the average diffusion coefficient of NNMO in the Lyocell fibre spinning process can be calculated and combined with Fick s second law; also, the time during which the NMMO content attained its equilibrium state in the coagulation bath can be predicted. This information helps optimisation of the spinning conditions for a given fibre spinning problem. 10 To develop a commercially viable lyocell production process, it is essential to maximise spinning stability.To consider when optimising fibre production process 1. 2. 3. 4. 5. Polymer content & flow properties of spinning solution Production speed Unit productivity (e.g. jet size, filament packing) Design simplification (e.g. Minimise costs, maintenance) Process robustness (ease of operation, resistance to problems/fluctuations The core of the programme is the development of a computer model of the air gap spinning system a) The Air Gap Model b) The single filament model c) The CFD model The Air Gap Model There are three key stages in the development of the air-gap model STAGE 1 is to decide what we need the model to predict. Ideally we would like the model to tell us when filaments will not spin. Rather than trying to construct a theoretical model of spinnability, we have used empirical experiments to define the spinnability of a filament in terms of its environmental variables such as the air temperature and line speed. 11 STAGE 2 is to apply the data on the failure criteria to develop a model of an individual filament that will interact with its environment in an appropriate manner. As will be made clear shortly, we need a model that will predict the exchange of heat, moisture and momentum with its environment. The model must also allow obvious process parameters such as line speed, spinneret hole size, polymer concentration and temperature to be included. As far as possible, model predictions are validated against experiment. STAGE 3 is to incorporate the single filament model into a model that takes account of larger scale features such as air injection systems, the shape and temperature of the jet bodies etc. This is an area that can be treated by conventional computational fluid dynamicspackages (CFD). Again, simulation performance is tested, as far as possible, against practical observation. In the air gap, there are several processes going on: 1. 2. 3. 4. 5. The reduction in temperature of the filament The mass transfer of water across its surface, The acceleration of the material and reduction in its diameter, The orientation of the polymer chains, and The possible crystallization of the cellulose or the cellulose solution Air-gap length has quite a strong effect on the diameter profile. As the air gap is shortened, the die swell is reduced and disappears for an air gap of 10 mm. Whatever the spinneret size and air-gap length, however, all the draw occurs in the air gap 12 6. Lyocell fibre properties (Kinetic study of moisture sorption, swelling behavior of lyocell fiber, etc) Lyocell Fiber Characteristics Soft, strong, absorbent Fibrillated during wet processing to produce special textures Excellent wet strength Wrinkle resistant Very versatile fabric dyable to vibrant colors, with a variety of effects and textures. Can be hand washable Simulates silk, suede, or leather touch Good drapability Biodegradable Lyocell can be either washable or dry-cleanable, depending on the care label. When the proper finish is applied, lyocell can be laundered at home and is highly resistant to shrinkage. Lyocell first went on public sale as a type of rayon in 1991. It shares many properties with other cellulosic fibers such as cotton, linen, ramie and rayon. Some main characteristics of lyocell fibers are that they are soft, absorbent, very strong when wet or dry, and resistant to wrinkles; lyocell fabric can be machine- or hand-washed or drycleaned, it drapes well, and it can be dyed many colors, and can simulate a variety of textures such as suede, leather, and silk . Products made of Lyocell are characterized by their particularly high wearing comfort, their optimum moisture management, their very high wet and dry tenacity, as well as their flowing drape. An important function of textiles is supplying a maximum of wearing comfort to human bodies. Clothing materials should thus have a high moisture retention capacity and high moisture transportation properties to maintain a constant temperature and humidity between skin and fabric. This is based on the fact that the moist fibers can act as a heat reservoir. Moreover, moisture also changes the fiber properties. The moisture uptake causes a swelling of the hygroscopic fibers, which is a dimensional change due to breaking of inter- and intramolecular hydrogen bonds between the cellulose molecules. Not only physical properties such as density, shape, stiffness and crystal structure of the fibers but also mechanical properties, e.g. fiber fiber friction, tensile modulus and breaking stress are altered by water sorption. This strongly affects also the general dyeing behavior of the fibers and the finishing processes of textiles, e.g. resincoating and crosslinking treatments. The lyocell fiber, which is a regenerated cellulosic fiber manufactured by means of N-methyl morpholine-N-oxide dissolution followed by coagulation, has a high crystallinity and fibrillar morphology and offer different characteristics compared to cotton fibers. 13 A schematic diagram of direct and indirect moisture sorption onto external surface (1), amorphous regions (2), inner surface of voids (3), and crystallites (4). A mechanism of moisture sorption especially in hydrophilic fiber materials, e.g. cellulosic fibers are comparatively complex because it involves a continuous change of the structure of the fiber owing to swelling. High internal temperature change caused by heat of sorption with large amount of moisture also complicates kinetics of the moisture sorption. Various theories have been proposed and modified since 1893 to describe the sorption mechanisms of individual fiber material. Brunauer et al., derived a model for multi-layer adsorption and Langmuir developed the classical model for adsorption isotherms which is applicable for gases adsorbed in a monolayer on material surfaces. Peirce introduced a model which is based on the assumption of direct and indirect sorption of water molecules on attractive groups of the materials and a theory, in which the interaction between water and the binding sites considers three types of water with different associating strength was proposed by Speakman. Young and Nelson developed a complete sorption desorption theory, starting from the assumption of a distinct behavior of bound and condensed water. Moisture regain and loss on the fibers during sorption and desorption experiments were gravimetrically measured using the automatic moisture sorption analyzer. The swelling behavior of lyocell fiber in alkali solutions and the alkali uptake were investigated as well as their influences on the reaction of sodium-hydroxy-dichlortriazine with lyocell. The uptake of NaOH was increased from 0.69 mmol/g up to 4.63 mmol/g, leading to the enhancement of fiber swelling from 1.01 cm3/g to 2.34 cm3/g when alkali concentration in preliminary alkali treatment was increased from 0.4 mol/l to 8.0 mol/l. The rise in alkali uptake heightened the crosslinking reaction. The fiber swelling was hindered by addition of acetone to alkali solution, resulting in water retention capacity of 0.64 cm3/g in the 37.5% v/v of acetone/water mixture and increase in the reaction yield. The fiber was more swollen in NaOH solution than in KOH though the uptake of NaOH was 5.7-times less than that of KOH. The reaction yield of crosslinking agent in NaOH solution was 9.9-times larger than that in KOH at the same alkali uptake. The abrasion resistance of lyocell fiber was improved by the method used in this work, causing high pillingresistance of lyocell fabric as compared to a conventional method. 14 7. Uses of Lyocell Fibre(Lyocell precursor for carbon fibre etc) Application in separator The fibrillated fibers have a diameters mainly range from 200nm to 2000nm. The fine pore structure can be made when these ultra-fine fibers to be used in papermaking process. The fine pore structure is very important for battery separators. The pore size must be smaller than the particle size of the electrode components, including the electrode active materials and the conducting additives. In practical cases, membranes with 10-20 m average pore sizes have proven adequate to block the penetration of particles since the tortuous structure of the pores assists in blocking the particles from reaching the opposite electrode in Zn/MnO2 battery. The electrolyte is 35-40% KOH liquid in this battery. So the material of the separator of the battery must has a good alkaline resistence, su ch as PVA fiber, viscose fiber and special wood fiber. Tencel fiber also has the same character. The refining Tencel fiber at 450CSF is added into the separator. Tencel fiber can be fibrillated to expose the fibrills with the diameter from 200nm to 2000nm. The optimal SEL is colse to 0.4-0.8 Ws/m for fibrillation in refining process. The fibrillated fiber can be used to the Zn/MnO2 battery separator. The average pore size is 12 m much smaller than the commercial sample and with the porosity 35%. It indicated that the fibrillated Tencel fiber is a good material for alkaline battery separator to control the pore size and thickness and improve the tensile index. Composit materials from Lyocell fabric Lyocell fiber is a new kind of regenerated cellulose fiber and expected to replace the Rayon fiber to be not only used in the textile field but also used in the fields of industry and aerospace after being modified. In this work, the multi-walled carbon nanotubes (MWNTs)/Lyocell composite fibers were prepd. under different draw ratios by dry-wet spinning and their elec. properties, mech. properties, and structure were investigated. It was found that an appropriate amt. of MWNTs could be dispersed homogeneously in the Lyocell matrix and could improve the mech. and thermal properties 15 Use of Lyocell as dehumidification sheets The arrangement protects the dehumidification sheets against delamination of absorbents from its substrate and still provides excellent moisture absorption, even upon impregnation of a high amt. of absorbents.Moisture absorbent comprises fibrillated Lyocell fiber. Use of Lyocell as Blend backing A fabric includes a synthetic leather and a substrate contg. Lyocell. The substrate backs and adheres to the synthetic leather. A method for producing a fabric includes providing a substrate contg. Lyocell and adhering a synthetic leather to the substrate containing Lyocell. The synthetic leather may be formed of polyurethane or polyvinyl chloride. Lyocell as tyre cord The invention relates to a lyocell raw cord manufacturing method comprising properly regulating twisting tension in a process for manufacturing a lyocell raw cord to control the difference of long diameter and short diameter of the raw cord in a certain range (0.15-0.23). As of 2010 Lyocell is more expensive to produce than cotton or rayon. It is used in many everyday fabrics. Staple fibres are used in clothes such as denim, chino, underwear, casual wear, and towels. Filament fibers are used in items that have a silkier appearance such as women s clothing and men s dress shirts. Lyocell can be blended with a variety of other fibers such as silk, cotton, rayon, polyester, linen, nylon, and wool. Lyocell is also used in conveyor belts, specialty papers and medical dressings. (Textiles, Kadolph & Langford). Tencel is also used for making some brands of baby diaper wipe. 16 8. Recent developments & trends in Lyocell process Dissolution of cellulose with NMMO by microwave heating Microwave heating caused the decrease in the dissolution time and energy consumption.Environmentally friendly microwave heating process was applied to the dissolution of cellulose in Nmethylmorpholine- N-oxide (NMMO) with 105 490W and 2450 MHz microwave energy until the dissolution completed . Recently, a new lyocell process, the Cocel process was devised, which has some characteristic features similar to the Tencel process. The new process dissolves finely powdered cellulose in molten NMMO hydrate within 5 minutes by means of a pasting stage, which causes much less decomposition of cellulose. Method of recovery of aqueous NMMO oxide solution used in production of lyocell fibre A method of recovering an aq. N-methylmorpholine-N-oxide (NMMO) soln. used in prodn. of Lyocell fiber includes: 1. Decoloring the aq. NMMO solution by mixing the same with activated carbon using an agitation blower 2. By alternately energizing and de-energizing the agitation blower to contact the activated carbon 3. aq. NMMO soln. thoroughly in an energy-efficient manner; filtering the aq. NMMO sol decolored through coarse filtration followed by ultrafiltration to remove the activated carbon and impurities from the aq. NMMO solution 17 9. Referances 1. Water accessibilities of man-made cellulosic fibers effects of fiber Characteristics, Satoko Okubayashi1,*, Ulrich J. Griesser2 and Thomas Bechtold1, Cellulose (2005) 12:403 410 2. Optimization of cellulose dissolution stage in lyocell process as origin for different applications, A. Diener, G. Raouzeos, List AG, Arisdorf/Switzerland 3. Lenzinger Berichte, 84 (2005) 103-109, OBSERVATIONS ON LYOCELL FIBRE FORMATION,MJ Hayhurst and Dr AJ Banks,Tencel, Spondon, UK 4. A kinetic study of moisture sorption and desorption on lyocell fibers, Satoko Okubayashia,*, Ulrich J. Griesserb, Thomas Bechtolda, Carbohydrate Polymers 58 (2004) 293 299 . 5. Alkali uptake and swelling behavior of lyocell fiber and their effects on crosslinking reaction, S. Okubayashi* and T. Bechtold, Cellulose (2005) 12:459 467. 6. http://www.fibersource.com/f-tutor/lyocell.htm[19-02-2012 PM 06:11:58] 7. http://en.wikipedia.org/wiki/Lyocell[19-02-2012 PM 06:06:37] 8. http://ohioline.osu.edu/hyg-fact/5000/5572.html[19-02-2012 PM 06:09:18] 9. http://www.fibersource.com/F-Info/More_News/lenzing-050504.htm[19-022012 PM 06:10:06] 10.http://www.lenzing.com/en/fibers/tencel.html[19-02-2012 PM 06:07:53] 11.COMPUTER MODELLING OF THE LYOCELL FIBRE SPINNING PROCESS, Huili Shao, Ruigang Liu, Xuechao Hu, AUTEX Research Journal, Vol. 3, No1, March 2003 AUTEX 12.Continuous cellulose fiber-reinforced cellulose ester composites. II. Fiber surface modification and consolidation conditions, Kevin C. Seavey & Wolfgang G. Glasser, Cellulose 8: 161 169, 2001. 13. Chou, Wen-Tung; Lai, Ming-Yi; Huang, Kun-Shan, From U.S. Pat. Appl. Publ. (2011), US 20110226427 A1 20110922 14.Shojaei, K. M.; Dadashian, F.; Montazer, M.,From Applied Biochemistry and Biotechnology (2012), 166(3), 744-752 15.Yang, Gesheng; Shao, Huili; Hu, Xuechao ,From Fangzhi Xuebao (2011), 32(1), 6-10. 16.Lee, W. S., Jo, S. M., Kang, H. J., Kim, D. B., Park, C. S, U.S. patent no. 5584919) 17.Carbohydrate Polymers 75 (2009) 90 94 18 18.Int. J. Electrochem. Sci., 6 (2011) 4999 5004 19. Choi, Jae Sin From Repub. Korean Kongkae Taeho Kongbo (2011), KR 2011078128 A 20110707) 20.U.S. Pat. Appl. Publ. (2011), US 20110244746 A1 20111006. 21.Tanabe, Kunihiro From Jpn. Kokai Tokkyo Koho (2011), JP 2011183326 A 20110922 22.Lu, Jiang; Zhang, Huihui; Jian, Yihui; Shao, Huili; Hu, Xuechao , From Journal of Applied Polymer Science (2012), 123(2), 956-961) 19

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