The present invention relates to thermoplastic, water-soluble cellulose derivatives of the general formula 1 in which Cell is the substituted residue of a hydroxyl group on the cellulose chain, A is hydrogen or a hydroxycarboxylic acid residue, B is an ether residue (nullEnullO)n, in which n is 1 to 4, the molar degree of substitution by hydroxycarboxylic acid being between 0 and 1 and the molar degree of substitution of the ether being greater than or equal to 3, E represents C1-C6-alkyl.