Viscose rayon batch process

The widely different and varied design of present-day viscose rayon plants makes it impractical to describe all of the facilities for making rayon. However, because the chemistry of the process is common to all viscose fiber production, a brief outline of the principal methods will help to consolidate the understanding of how rayon is made. The basic steps of viscose rayon manufacture are outlined schematically in Figure 10.62. Basically, there are two types of process technology, batch and continuous. Pulp is supplied normally in bales of a predetermined weight and sheet size or in rolls. 

FIGURE 10.62 Conventional batch process for viscose rayon manufacture (schematic). (Courtesy of John Wiley Sons, New York.)... 

Rayon. Virtually all current commercial production of man-made cellulosic fibers uses the viscose process, or some modification of it (19,20) (Fig. 1). The basis for this process is the formation of a metastable, water-soluble derivative from which cellulose can be regenerated after the filament is formed. Similar technology is used to manufacture cellophane film. Traditionally the process, as outlined in the following, is a batch operation involving discrete steps more recently semlcontinuous or continuous systems have been developed. 

Several other machines for producing viscose continuously have appeared in the patent literature. Since Richter obtained a patent in 1932 [241], inventors such as Seaman [242], Yasui et al. [243], Von Kohorn [244], and Treiber [245] all claim success in making the several stages in the viscose process on a continuous basis. (Except for the CBX and Contisulf units mentioned before, successful full-rayon-plant operation of the others has not yet been attained.) Most rayon producers, however, prefer batch xanthation in large churns. 

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