Patent ID: 6891034

Claim:
A process for preparing alkylhydroxyalkyl cellulose comprising the steps of: a) alkalizing cellulose with an aqueous caustic solution containing from 1.5 to 5.5 equivalents of alkali metal hydroxide per anhydroglucose unit (AGU) of said cellulose, in the presence of a suspension agent which contains alkyl halide in the amount of from (equivalents of alkali metal hydroxide per AGU minus 1.4) to (equivalents of alkali metal hydroxide per AGU plus 0.8); b) reacting the alkalised cellulose of step a) with one or more alkylene oxides at a temperature higher than 65° C.; c) adding alkyl halide, to the product of step b), in an amount of at least the difference between (i) the equivalents of alkyl halide per AGU in step a) and (ii) the equivalents of alkali metal hydroxide added per AGU in step a), provided that the amount of additionally added alkyl halide is at least 0.2 equivalents per AGU; d) isolating alkylhydroxyalkyl cellulose from the reaction mixture of step c); and e) optionally purifying the isolated alkylhydroxyalkyl cellulose.