Viscose process, rayon

Its early commercial success owed much to the flammabUity disadvantages of the Chardoimet process, but competition from the viscose process led to its decline for aU but the finest filament products. The process is stiU used, most notably by Asahi in Japan where sales of artificial sHk and medical disposable fabrics provide a worthwhile income. However, its relatively high cost, associated with the cotton fiber starting point, prevented it from reaching the large scale of manufacture achieved by the viscose rayon process. 

The oldest and most widely practiced cellulose regeneration technology of the derivatizing solvent-type is the viscose rayon process. It is based, in part, on the discovery in 1857 by Cross, Bevin, and Beadle of the dissolution of sulfidized cellulose in alkali. Viscose fibers are by far the most important cellulose regenerates, amounting to an annual fiber production of 2.5 X 10 t worldwide [13,74]. 

Process diagram of the viscose rayon process (Adopted from Woodings [74])... 

The process of cellulose regeneration in the form of lyocell fibers is significantly simpler than that of the viscose rayon process. It is illustrated in O Fig. 16. A solution containing 14% cellulose, 10% water, and 76% NMMO plus stabilizers is extruded at a temperature slightly above 100 °C into an aqueous NMMO-bath from which cellulose is precipitated [74,75]. The extrusion has been described as a melt-spinning process that has recently made it possible to manufacture cellulosic self-bonded meltblown nonwovens as well [76]. 

Alternatives to alkaline solutions of carbon disulfide are combinations of formaldehyde and DMSO various alkyl silanes, and urea and alkali. The latter is currently being promoted for industrial applications. It is known under the term carbamate process. The carbamate process has advantages over the viscose rayon process while being able to use the same process technology. 

In the viscose rayon process, still used today, cellulose is digested in a concentrated solution of NaOH to convert the —OH groups to —O Na ionic groups. Reac-... 

Basically, all methods for producing rayon filaments or fibers depend on solubilizing cellulose, then reshaping it into long-fibered products by extrusion through the small holes of a spinnerette, immediately followed by conversion into solid cellulose. Although there are a number of ways in which this can be done, the viscose rayon process is by far the most important and widely practiced. 

Figure 14.37, shows a block scheme of the viscose/rayon process from the spinning stage to production of the final viscose/rayon material. In this process, two types of surfactant process additives are introduced, i.e. spin bath additives and lubricant finishing additives. 

Figure 14.36. Block scheme of the viscose/rayon process, up to and including the spinner stage, showing the general process conditions and typical addition points for the surfactants...

Godet Roller used in the viscose rayon process to guide rayon tow, when using pairs rotating at different speeds, will impart differential stretch to fiber. 

Xanthate zan- that (1831) n. A sodium salt of a dithiocarbonic acid ester, in particular the one formed in the viscose-rayon process by the reaction between sodium hydroxide cellulose and carbon disulfide and having the structure shown below, called cellulose xanthate or viscose. The viscose is subsequently precipitated, filtered, extruded as... 

Xanthate n zan- that n (1831) A sodium salt of a dithiocarbonic acid ester, in particular the one formed in the viscose-rayon process by the reaction between sodium hydroxide cellulose and carbon disulfide and having the structure shown below, called cellulose xanthate or viscose. The viscose is subsequently precipitated, filtered, extruded as filaments into dilute sulfuric acid, washed, and dried to make viscose that be spun into Rayon fabric, and extruded thin sheets are called Cellophane . (Kadolph SJJ, Langford AL (2001) Textiles. Pearson Education, New York Ash M, Ash I (1982-1983) Encyclopedia of Plastics, Polymers, and Resins, Vols. I-in. Chemical Publishing, New York). 

The first commercial-scale production of a manufactured fiber was achieved by a French chemist, Count Hilaire de Chardonnet. In 1884 his fabrics made of artificial silk caused a sensation at the Paris Exhibition. Two years later he built the first commercial rayon plant at Besangon, France, and secured his fame as the father of the rayon industry. However, the artificial silk invented by Chardonnet was based on cellulose nitrate, and its flammability limited its applications. In 1892 the viscose rayon process was invented by Charles F. Cross, Edward J. Bevan, and Clayton Beadle in England, and became the basis for the regenerated cellulose fiber industry. 

Uses Emulsifier dispersant textile dyeing assistant antistat in plastics, viscose rayon processing adjuvant in systemic herbicides and pesticides emulsifier in quat, ammonium formulations Properties Solid/liq, HLB 10,0 100% cone. 

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