Process for preparing water-soluble cellulose ethers with recovery of sodium hydroxide

Cellulose ethers which contain hydroxyalkyl groups are prepared, with the recovery of sodium hydroxide, by cellulose being etherified with alkylene oxide in a water-containing organic suspension medium in the presence of at least 1.0 mol of sodium hydroxide per mole of anhydroglucose units, the water-containing organic suspension medium being separated off after the etherification reaction is complete, the crude cellulose ether being extracted with a suitable solvent mixture, the lower-boiling organic components being distilled off from the solvent mixture after the extraction, the water-containing organic suspension medium separated off being added to the distillation residue of the solvent mixture to form a multiphase mixture, the bottom phase of the multiphase mixture being separated and the sodium hydroxide present in the bottom phase being reused.