There is provided a method for producing hydroxypropyl methyl cellulose acetate succinate (HPMCAS), including an esterification step of reacting hydroxypropyl methyl cellulose with an acetylating agent and a succinoylating 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 HPMCAS; a precipitation step of precipitating the HPMCAS by mixing the reaction product solution with water to obtain a suspension of the precipitated HPMCAS; and a washing and recovery step of washing the HPMCAS in the suspension and recovering the washed HPMCAS. Further, there is provided HPMCAS having yellowness at 20° C. of 15.0 or less, as determined in a 2% by mass solution of the HPMCAS in a mixed solvent of dichloromethane, methanol and water in a mass ratio of 44:44:10.

There is provided a method for producing hydroxypropyl methyl cellulose acetate succinate (HPMCAS), including an esterification step of reacting hydroxypropyl methyl cellulose with an acetylating agent and a succinoylating 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 HPMCAS; a precipitation step of precipitating the HPMCAS by mixing the reaction product solution with water to obtain a suspension of the precipitated HPMCAS; and a washing and recovery step of washing the HPMCAS in the suspension and recovering the washed HPMCAS. Further, there is provided HPMCAS having yellowness at 20° C. of 15.0 or less, as determined in a 2% by mass solution of the HPMCAS in a mixed solvent of dichloromethane, methanol and water in a mass ratio of 44:44:10.

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.

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.

A cellulose resin formed by substituting hydrogen atoms of hydroxy groups of a cellulose with a long-chain component being a linear saturated aliphatic acyl group having 14 or more carbon atoms and a short-chain component being an acyl group having 2 or 3 carbon atoms, in which a degree of substitution with the long-chain component (DS.sub.Lo) and a degree of substitution with the short-chain component (DS.sub.Sh) satisfy conditional expressions (1) and (2) shown below:
DS.sub.Lo+DS.sub.Sh2.1(1)
4DS.sub.Sh/DS.sub.Lo12(2).

A cellulose resin formed by substituting hydrogen atoms of hydroxy groups of a cellulose with a long-chain component being a linear saturated aliphatic acyl group having 14 or more carbon atoms and a short-chain component being an acyl group having 2 or 3 carbon atoms, in which a degree of substitution with the long-chain component (DS.sub.Lo) and a degree of substitution with the short-chain component (DS.sub.Sh) satisfy conditional expressions (1) and (2) shown below:
DS.sub.Lo+DS.sub.Sh2.1(1)
4DS.sub.Sh/DS.sub.Lo12(2).

A cellulose resin composition comprising a cellulose resin, a high refractive-index organic material and a carbon black, in which the cellulose resin is an acylated cellulose obtained by substituting at least part of hydrogen atoms of hydroxy groups of a cellulose with an acyl group having 2 to 4 carbon atoms, the carbon black is an acidic carbon black, the mass fraction (B/A) of the high refractive-index organic material (B) to the cellulose resin (A) falls within the range of 10/90 to 70/30, and the content of the carbon black (C) relative to the total of the cellulose resin composition falls within the range of 0.05 to 10% by mass.

A cellulose resin composition comprising a cellulose resin, a high refractive-index organic material and a carbon black, in which the cellulose resin is an acylated cellulose obtained by substituting at least part of hydrogen atoms of hydroxy groups of a cellulose with an acyl group having 2 to 4 carbon atoms, the carbon black is an acidic carbon black, the mass fraction (B/A) of the high refractive-index organic material (B) to the cellulose resin (A) falls within the range of 10/90 to 70/30, and the content of the carbon black (C) relative to the total of the cellulose resin composition falls within the range of 0.05 to 10% by mass.

A cellulose ester, wherein, in a structural formula of the following general formula (I), a degree of substitution where X is an acyl group is from 2.91 to 3.0; the acyl group includes benzoyl group (A) optionally having a substituent, and benzoyl group (B) optionally having a substituent different from that of benzoyl group (A); and when the degree of substitution is 3.0, a degree of substitution of benzoyl group (A) is from 1.5 to 2.9, and a degree of substitution of benzoyl group (B) is from 0.1 to 1.5, ##STR00001##
wherein all or some of X represents an acyl group; when some of X represents an acyl group, the remainder represents a group selected from a hydrogen atom and an alkyl group; and n represents an integer of from 20 to 20,000.

A cellulose ester, wherein, in a structural formula of the following general formula (I), a degree of substitution where X is an acyl group is from 2.91 to 3.0; the acyl group includes benzoyl group (A) optionally having a substituent, and benzoyl group (B) optionally having a substituent different from that of benzoyl group (A); and when the degree of substitution is 3.0, a degree of substitution of benzoyl group (A) is from 1.5 to 2.9, and a degree of substitution of benzoyl group (B) is from 0.1 to 1.5, ##STR00001##
wherein all or some of X represents an acyl group; when some of X represents an acyl group, the remainder represents a group selected from a hydrogen atom and an alkyl group; and n represents an integer of from 20 to 20,000.