To produce an etherified material having a uniformly etherified substitution degree without blocking in an etherifying process as compared with that of a conventional method for producing a cellulosic derivative.
The etherifying reaction is carried out in the following two stages in a method for etherifying a cellulosic derivative in the presence of an alkali in an organic solvent and water as solvents with an etherifying agent: the first stage: the etherifying reaction in a slurry state at 1:(0.01-0.5):(0.8-10) weight ratio of the cellulosic derivative:water:organic solvent until the etherifying substitution degree attains 1.8-2.1 and the second stage: the etherifying reaction at 1:(0.5-10):(0.8-10) weight ratio of the etherified cellulosic derivative: water:water-miscible organic solvent within the range of 1.8-3.0 of the etherifying substitution degree.
TANIGUCHI ISOKI
OTA ATSUSHI
SHINODA KATSUMI
