Formation of Polysaccharide Ethers

The excess carbon disulfide is removed by vacuum, leaving the sodium salt of cellulose xanthate, which is known as viscose [5-7]. 

Viscose can be forced through fine holes in a spinerette into an acid bath, giving the removal of the xanthate group and the regeneration of cellulose in the form of a fine filament or thread known as rayon. If instead, the viscose is forced through a narrow slit into an acid bath, cellulose is regenerated as a thin, transparent sheet that can be softened with glycerol to make cellophane. 

Ethers can be formed with the alcohol groups of polysaccharides by reacting an alkaline solution or suspension of the polysaccharide with alkyl halides or epoxides [8]. The ethers produce polysaccharide derivatives that are usually soluble in water. This is in contrast to polysaccharide esters, which are usually insoluble in water and soluble in organic solvents. 

Methyl or ethyl ethers can be formed by the reaction of the alkaline polysaccharide with methyl chloride (reaction 7.5), or ethyl chloride at 70-120°C to give d.s. values of 1.2-2.3 [9]. 

Carboxymethyl ethers can be prepared by reaction of alkaline polysaccharide with chloroacetate at 30-80°C to achieve d.s. values of 0.8 to 1.1 [8,10] (reaction 7.6). Carboxymethyl cellulose (CM-cellulose) was first developed in Germany in 1916, and then in 1935, it was found that it improved the performance of synthetic detergents [11]. CM-cellulose has since found wide application in textiles, detergents, foods, pharmaceuticals, cosmetics, oil and gas drilling muds, paper, adhesives, coatings, ceramics, suspending agents, and emulsions [11]. 

---