Formation of Polysaccharide Esters

Cellulose nitrate, with a lower d.s. of 1.9-2.5 is known as pyroxylin (reaction 7.2). This nitrate was used to form the first important commercial plastic known as celluloid, which was formed by mixing pyroxylin with camphor as a plasticizer. The camphor eliminates the explosive properties, but produces a very flammable product. The addition of the pyroxylin/camphor mass in alcohol into molds with heat and pressure gives the formation of celluloid in a desired shape. Pyroxylin is also used in lacquers and films. 

Mixed esters of cellulose acetate and cellulose propionate, and cellulose acetate and cellulose butyrate can be formed by using mixtures of the anhydride of one acid and the acid of the other [4]. These mixed esters (60-65% acetate and 40-35% propionate or butyrate) give improved properties of toughness and shock resistance necessary for injection molding and special-purpose lacquers. 

Polysaccharides react with carbon disulfide and sodium hydroxide to give dithiocarbonic acid esters called xanthates. The polysaccharide, such as cellulose, is first treated with 18% sodium hydroxide to give alkaline cellulose (reaction 7.4). The alkaline cellulose is usually aged several hours to achieve lower d.p. values. It is then reacted with carbon disulfide for 1-3 hr at 20-30°C (reaction 7.4). 

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