Cellulose sulfate preparation

Cellulose sulfates can be prepared by using a variety of reagent combinations (Table 9-4). The active agent is sulfur trioxide (S03), present in fuming sulfuric acid or generated according to the following acid-base equilibrium between sulfuric acid molecules ... 

TABLE 9-4. Suitable Reagents for Preparing Cellulose Sulfate... 

Cellulose sulfates are appealing water soluble polymers even at low DS. Cellulose sulfation, however, is complicated by serious chain degradative side reactions. Cellulose sulfation has been carried out using chlorosulfonic acid, sulfuric acid, or sulfur trioxide. At low degrees of substitution (DS 0.2 to 0.3), cellulose sulfates are used in oil well drilling, foodstuffs, cosmetics, and pharmaceuticals. The preparation of cellulose sulfates for symplex capsules can... 

Preferential binding in PEC formation between PDADMAC and mixtures of Na lignosulfonate and Na cellulose sulfate or Na carboxymethylcellulose was studied in [64] in relation to the ionic strength by preparative ultracentrifugation and an analysis of the supernatants by UV spectroscopy. 

Methylation is no longer carried out with dimethyl sulfate, which was previously used. The resulting sodium chloride is rinsed away with water. The product is then spin-dried to a water content of 55-60% and subsequently homogenized and compacted in a screw extender. Ethyl cellulose is prepared in a manner analogous to that used for ethyl chloride and the reaction is taken to 2.1-2.6 ethoxy groups per glucose unit. The products serve as finishing materials in the textile industry as well as for paint bases and injection-molded articles. 

Table 1. Preparation of Cellulose Sulfate Using H2SO4...

There are numerous synthetic strategies available for preparing cellulose sulfates with a wide range of properties. 

Solubility. Cellulose sulfate and cellulose phosphate can be either water-soluble or water-swellable depending on the conditions used during preparation vide supra). Cellulose nitrate and some cellulose sulfonates are generally more hydrophobic and are typically soluble in organic solvents. In general, the level of esterification of cellulose directly impacts the solubility of the product in various solvents and solvent blends. 

Cellulose sulfate, in particular C6 sulfates, can be used for preparing polyanion-polycation complexes for pervaporation membranes (43 5). 

Cellulose sulfates and phosphates are water-soluble derivatives prepared by reactions of alcohol/water/organic diluent mixtures of sulfuric or phosphoric acids. Phosphate derivatives are flame retardant but have not been commercialized (72). 

Sulfation of jute cellulose with chlorosulfonic acid in pyridine at 30 °C gave partially water-soluble cellulose sulfate with a degree of substitution of 1.56. Water-soluble sodium cellulose sulfates containing 1-3 sulfate groups were prepared by treatment of cellulose with the reagent in pyridine followed by reaction with sodium carbonate. ... 

Inorganic esters of cellulose, sulfates, phosphates and borates have also been reported. Cellulose sulfate is unstable in the free acid form. Cellulose phosphate prepared by reaction of phosphoric add with cellulose is flame retardant but has found little utility. Reactions of boric acid and borates with cellulose gave products that were not stable in the presence of water and were rapidly hydrolyzed. 

Fig. 7. Combined sulfur during preparation of cellulose acetate hydrolysis of sulfate and esters (6). Acetylation schedule A, mixer charged with linters and acetic acid B, minor portion of catalyst added C, began cooling to 18°C D, acetic anhydride added and continued cooling to 16°C E, significant portion...

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