A process for producing an esterified cellulose ether can be efficiently be produced by reacting a moist cellulose ether having a water content of at least 10 percent, based on the weight of the moist cellulose ether, with an aliphatic monocarboxylic acid anhydride, a dicarboxylic acid anhydride or a combination thereof. Further improvements in efficiency and reduction in process steps are achieved in a process for producing an esterified cellulose ether which comprises the steps of a) reacting cellulose with an alkaline material to produce alkali cellulose, b) reacting the produced alkali cellulose with one or more etherifying agents and washing the produced cellulose ether to obtain a moist cellulose ether having a water content of at least 10 weight percent, and c) reacting the moist cellulose ether with an aliphatic monocarboxylic acid anhydride and/or a dicarboxylic acid anhydride and with a depolymerizing agent.

A process for producing an esterified cellulose ether comprises the step of reacting a cellulose ether with an aliphatic monocarboxylic acid anhydride and/or a dicarboxylic acid anhydride and with a depolymerizing agent, wherein the cellulose ether has an initial viscosity of at least 500 mPa.Math.s, measured as a 2 weight-% solution in water at 20° C., and the reaction of the cellulose ether with the aliphatic monocarboxylic acid anhydride and/or the dicarboxylic acid anhydride and with the depolymerizing agent is conducted simultaneously or in sequence in one reaction device.

A process for producing a cellulose ether acetate succinate comprises the step of reacting a cellulose ether with acetic anhydride, succinic anhydride and an depolymerizing agent, wherein the cellulose ether has an initial viscosity of at least 50 mPa-s, measured as a 2 weight-% solution in water at 20° C., and the reaction of the cellulose ether with acetic anhydride, succinic anhydride and the depolymerizing agent is conducted simultaneously or in sequence in one reaction device.

Esterified cellulose ethers which have i) as ester groups aliphatic monovalent acyl groups or groups of the formula —C(O)—R—COOA or a combination of aliphatic monovalent acyl groups and groups of the formula —C(O)—R—COOA, wherein R is a divalent aliphatic or aromatic hydrocarbon group and A is hydrogen or a cation, and ii) a content of not more than 0.85 weight percent acetone-insoluble esterified cellulose ether particles, when the esterified cellulose ether is present in a mixture of 12.5 weight parts of esterified cellulose ether and 87.5 weight parts of acetone at 21° C., the weight percent acetone-insoluble esterified cellulose ether particles being based on the total weight of the esterified cellulose ether, wherein iii) not more than 14 percent of the acetone-insoluble esterified cellulose ether particles have a particle size of more than 90 micrometers.

Esterified cellulose ethers which have i) as ester groups aliphatic monovalent acyl groups or groups of the formula —C(O)—R—COOA or a combination of aliphatic monovalent acyl groups and groups of the formula —C(O)—R—COOA, wherein R is a divalent aliphatic or aromatic hydrocarbon group and A is hydrogen or a cation, and ii) a content of not more than 0.85 weight percent acetone-insoluble esterified cellulose ether particles, when the esterified cellulose ether is present in a mixture of 12.5 weight parts of esterified cellulose ether and 87.5 weight parts of acetone at 21° C., the weight percent acetone-insoluble esterified cellulose ether particles being based on the total weight of the esterified cellulose ether, wherein iii) not more than 14 percent of the acetone-insoluble esterified cellulose ether particles have a particle size of more than 90 micrometers.

Provided are hypromellose acetate succinate (HPMCAS) which exhibits high solubility and can suppress generation of undissolved materials when dissolved in a solvent; an HPMCAS-containing composition; and a method for producing the HPMCAS. More specifically, provided are HPMCAS having a ratio of 2-position MS to 3-position MS of 1.2 or less, wherein the 2-position MS means a molar substitution of hydroxypropyl group by which a hydrogen atom of a hydroxyl group on 2-position carbon of each glucose unit of the HPMCAS has been directly replaced, and the 3-position MS means a molar substitution of hydroxypropyl group by which a hydrogen atom of a hydroxyl group on 3-position carbon of each glucose unit of the HPMCAS has been directly replaced; a composition comprising the HPMCAS and a solvent; and the method for producing the HPMCAS.

Provided are hypromellose acetate succinate (HPMCAS) which exhibits high solubility and can suppress generation of undissolved materials when dissolved in a solvent; an HPMCAS-containing composition; and a method for producing the HPMCAS. More specifically, provided are HPMCAS having a ratio of 2-position MS to 3-position MS of 1.2 or less, wherein the 2-position MS means a molar substitution of hydroxypropyl group by which a hydrogen atom of a hydroxyl group on 2-position carbon of each glucose unit of the HPMCAS has been directly replaced, and the 3-position MS means a molar substitution of hydroxypropyl group by which a hydrogen atom of a hydroxyl group on 3-position carbon of each glucose unit of the HPMCAS has been directly replaced; a composition comprising the HPMCAS and a solvent; and the method for producing the HPMCAS.

Provided are a drug-containing particle capable of suppressing dissolution of a drug in the oral cavity to suppress an unpleasant taste thereof and having excellent dissolution of the drug in the digestive tract after passing through the oral cavity; a method for preparing the drug-containing particle; a coating composition used for preparing the drug-containing particle; and a solid preparation having the drug-containing particle. More specifically, provided are a coating composition having 100 parts by weight of a cellulose-based enteric base and 50 parts by weight or less of a water-soluble cellulose ether; a drug-containing particle having a drug-containing core and a coat portion obtained by coating the core with the coating composition; a solid preparation having the drug-containing particle; and a method for preparing a drug-containing particle having a step of coating the drug-containing core with the coating composition.

Provided are a drug-containing particle capable of suppressing dissolution of a drug in the oral cavity to suppress an unpleasant taste thereof and having excellent dissolution of the drug in the digestive tract after passing through the oral cavity; a method for preparing the drug-containing particle; a coating composition used for preparing the drug-containing particle; and a solid preparation having the drug-containing particle. More specifically, provided are a coating composition having 100 parts by weight of a cellulose-based enteric base and 50 parts by weight or less of a water-soluble cellulose ether; a drug-containing particle having a drug-containing core and a coat portion obtained by coating the core with the coating composition; a solid preparation having the drug-containing particle; and a method for preparing a drug-containing particle having a step of coating the drug-containing core with the coating composition.

Provided are a drug-containing particle capable of suppressing dissolution of a drug in the oral cavity to suppress an unpleasant taste thereof and having excellent dissolution of the drug in the digestive tract after passing through the oral cavity; a method for preparing the drug-containing particle; a coating composition used for preparing the drug-containing particle; and a solid preparation having the drug-containing particle. More specifically, provided are a coating composition having 100 parts by weight of a cellulose-based enteric base and 50 parts by weight or less of a water-soluble cellulose ether; a drug-containing particle having a drug-containing core and a coat portion obtained by coating the core with the coating composition; a solid preparation having the drug-containing particle; and a method for preparing a drug-containing particle having a step of coating the drug-containing core with the coating composition.