Provided are HPMCAS powder having high solubility when dissolved in a solvent and being capable of suppressing generation of undissolved materials; and a method for producing the powder. More specifically, provided is hypromellose acetate succinate powder having an average ratio of L to D of from 2.0 to 3.0, wherein L and D mean maximum and minimum diameters of each particle, respectively. Also provided is a method for producing a hypromellose acetate succinate, comprising the steps of: dissolving hypromellose powder in a solvent, esterifying the dissolved hypromellose with succinic anhydride and acetic anhydride in the presence of a catalyst to obtain a reaction mixture, and mixing the reaction mixture with water to precipitate hypromellose acetate succinate, wherein the reaction mixture just before being mixed with the water has a viscosity of from 100 to 200 Pa.Math.s.

Provided are HPMCAS powder having high solubility when dissolved in a solvent and being capable of suppressing generation of undissolved materials; and a method for producing the powder. More specifically, provided is hypromellose acetate succinate powder having an average ratio of L to D of from 2.0 to 3.0, wherein L and D mean maximum and minimum diameters of each particle, respectively. Also provided is a method for producing a hypromellose acetate succinate, comprising the steps of: dissolving hypromellose powder in a solvent, esterifying the dissolved hypromellose with succinic anhydride and acetic anhydride in the presence of a catalyst to obtain a reaction mixture, and mixing the reaction mixture with water to precipitate hypromellose acetate succinate, wherein the reaction mixture just before being mixed with the water has a viscosity of from 100 to 200 Pa.Math.s.

There are provided HPMCAS (hypromellose acetate succinate) having such a property that a solution of the HPMCAS in a solvent has a controlled viscosity; and a method for producing the HPMCAS. More specifically, provided are HPMCAS having such property that a solution of 10 parts by weight of the HPMCAS in 100 parts by weight of a mixed solvent having a weight ratio of methylene chloride to methanol of 1:1 has a viscosity at 20 C. of 135 mPa.Math.s or less; and a method for producing the HPMCAS including an esterification step of adding acetic anhydride and succinic anhydride to a solution of hypromellose in glacial acetic acid in the presence of sodium acetate to obtain a reaction product mixture, wherein the succinic anhydride is added intermittently, and a precipitation step of mixing the reaction product mixture with water to precipitate the HPMCAS.

There are provided HPMCAS (hypromellose acetate succinate) having such a property that a solution of the HPMCAS in a solvent has a controlled viscosity; and a method for producing the HPMCAS. More specifically, provided are HPMCAS having such property that a solution of 10 parts by weight of the HPMCAS in 100 parts by weight of a mixed solvent having a weight ratio of methylene chloride to methanol of 1:1 has a viscosity at 20 C. of 135 mPa.Math.s or less; and a method for producing the HPMCAS including an esterification step of adding acetic anhydride and succinic anhydride to a solution of hypromellose in glacial acetic acid in the presence of sodium acetate to obtain a reaction product mixture, wherein the succinic anhydride is added intermittently, and a precipitation step of mixing the reaction product mixture with water to precipitate the HPMCAS.

Provided is a polymer material containing at least one kind of a cellulose derivative having (a) an organosilyl group (the organosilyl group having a first aliphatic group, an unsaturated aliphatic group, or an aromatic group), and (b) an acyl group or a second aliphatic group.

Provided is a polymer material containing at least one kind of a cellulose derivative having (a) an organosilyl group (the organosilyl group having a first aliphatic group, an unsaturated aliphatic group, or an aromatic group), and (b) an acyl group or a second aliphatic group.

Provided are HPMCAS powder having high solubility when dissolved in a solvent and being capable of suppressing generation of undissolved materials; and a method for producing the powder. More specifically, provided is hypromellose acetate succinate powder having an average ratio of L to D of from 2.0 to 3.0, wherein L and D mean maximum and minimum diameters of each particle, respectively. Also provided is a method for producing a hypromellose acetate succinate, comprising the steps of: dissolving hypromellose powder in a solvent, esterifying the dissolved hypromellose with succinic anhydride and acetic anhydride in the presence of a catalyst to obtain a reaction mixture, and mixing the reaction mixture with water to precipitate hypromellose acetate succinate, wherein the reaction mixture just before being mixed with the water has a viscosity of from 100 to 200 Pa.Math.s.

Provided are HPMCAS powder having high solubility when dissolved in a solvent and being capable of suppressing generation of undissolved materials; and a method for producing the powder. More specifically, provided is hypromellose acetate succinate powder having an average ratio of L to D of from 2.0 to 3.0, wherein L and D mean maximum and minimum diameters of each particle, respectively. Also provided is a method for producing a hypromellose acetate succinate, comprising the steps of: dissolving hypromellose powder in a solvent, esterifying the dissolved hypromellose with succinic anhydride and acetic anhydride in the presence of a catalyst to obtain a reaction mixture, and mixing the reaction mixture with water to precipitate hypromellose acetate succinate, wherein the reaction mixture just before being mixed with the water has a viscosity of from 100 to 200 Pa.Math.s.

Esterified cellulose ethers which have i) as ester groups aliphatic monovalent acyl groups or a combination of aliphatic monovalent acyl groups and groups of the formula C(O)RCOOA wherein R is a divalent aliphatic or aromatic hydrocarbon group and A is hydrogen or a cation, ii) a weight average molecular weight M.sub.w of from 80,000 Dalton to 220,000 Dalton, iii) a Polydispersity M.sub.w/M.sub.n of from 1.3 to 4.0, and iv) an M.sub.z/M.sub.n of not more than 18.5, when the weight average molecular weight M.sub.w, the number average molecular weight Mn and the z-average molecular weight M.sub.z are measured by SEC-MALLS using as mobile phase a mixture produced from 40 parts by volume of acetonitrile and 60 parts by volume of aqueous buffer containing 50 mM NaH.sub.2PO.sub.4 and 0.1 M NaNO.sub.3. are useful as enteric polymers for pharmaceutical dosage forms.

Esterified cellulose ethers which have i) as ester groups aliphatic monovalent acyl groups or a combination of aliphatic monovalent acyl groups and groups of the formula C(O)RCOOA wherein R is a divalent aliphatic or aromatic hydrocarbon group and A is hydrogen or a cation, ii) a weight average molecular weight M.sub.w of from 80,000 Dalton to 220,000 Dalton, iii) a Polydispersity M.sub.w/M.sub.n of from 1.3 to 4.0, and iv) an M.sub.z/M.sub.n of not more than 18.5, when the weight average molecular weight M.sub.w, the number average molecular weight Mn and the z-average molecular weight M.sub.z are measured by SEC-MALLS using as mobile phase a mixture produced from 40 parts by volume of acetonitrile and 60 parts by volume of aqueous buffer containing 50 mM NaH.sub.2PO.sub.4 and 0.1 M NaNO.sub.3. are useful as enteric polymers for pharmaceutical dosage forms.