Process for preparing soluble alkali metal salts of cellulose sulfate using chlorosulfuric acid and pyridine

The present invention provides a process for the preparation of water soluble alkali metal salts of cellulose sulfate having a degree of substitution ranging from 1 to 3 and viscosity of 1 percent aqueous solution in excess of 20 centipoises (cps). The process involves the use of chlorosulfuric acid as a sulfonating agent in the presence of pyridine used as a solvent in reaction. The important steps of the process for preparation of the water soluble salts include presoaking of the cellulose in pyridine followed by washing the pyridine salt with an alcohol such as methanol and reacting saturated alkali metal bicarbonate or carbonate solutions with the sulfonated cellulose.