Patent ID: 11873351

Abstract:
There is provided a method for producing hydroxypropyl methyl cellulose phthalate (HPMCP), including an esterification step of reacting hydroxypropyl methyl cellulose with a carboxybenzoylating agent in the presence of an aliphatic carboxylic acid in a kneader reactor equipped with two or more stirring blades rotating around their own axes and orbitally revolving, to obtain a reaction product solution containing HPMCP; a precipitation step of precipitating the HPMCP by mixing the reaction product solution with water to obtain a suspension of the precipitated HPMCP; and a washing and recovery step of washing the HPMCP in the suspension and recovering the washed HPMCP. Further, there is provided HPMCP having yellowness at 20° C. of 10.0 or less, as determined in a 10% by mass solution of the HPMCP in acetone.