| 摘要 |
PROBLEM TO BE SOLVED: To reduce the treatment time and the space for equipment and to obtain a particle which can easily decrease ash content in a washing step by conducting a step of dissolving a reaction product of an alkali cellulose and a hydroxypropylating agent in water and a step of neutralizing the same with an acid successively. SOLUTION: Water is supplied quantitatively while a crude reaction product is quantitatively supplied into a continuous kneader to successively dissolve and an acid is added to the travelling solution at a regulated addition speed such that the acid is equivalent to the amount of caustic soda present in the solution. Desirably, the water inlet is placed very close to the inlet of the crude reaction product and the acid inlet is provided at the place where the crude reaction product is fully dissolved. Preferably, a twin screw type continuous kneader is used. As the hydroxypropyl cellulose with a low degree of substitution, those with the number of moles of substituting hydroxypropoxyl groups per glucose unit (C6H10O5) of 0.1-0.5 are desired.
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