PROBLEM TO BE SOLVED: To provide a method capable of washing effectively a mechanical stirring type mixer used for production of a cellulose derivative or the like.SOLUTION: A washing method of a mechanical stirring type mixer has step (I)-step (III) step (I): a step for decompressing a pressure in the mechanical stirring type mixer to 80 kPa or lower step (II): a step for introducing a cleaning fluid into the mixer after the step (I), and stirring under a reduced pressure of 80 kPa or lower and step (III): a step for lowering the pressure in the mixer to an atmospheric pressure after the step (II), and then discharging the cleaning fluid.SELECTED DRAWING: NoneCOPYRIGHT: (C)2018,JPO&INPIT【課題】セルロース誘導体などの製造に用いた機械攪拌式混合機を効果的に洗浄しうる方法を提供する。【解決手段】下記工程(I)~工程(III)を有する機械撹拌式混合機の洗浄方法。 工程(I):機械撹拌式混合機内の圧力を80kPa以下に減圧する工程 工程(II):工程(I)の後に前記混合機内に洗浄液を導入し、80kPa以下の減圧下で撹拌する工程 工程(III):工程(II)の後に前記混合機内の圧力を大気圧とし、次いで、前記洗浄液を排出する工程【選択図】なし
