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.

An all-solid-state secondary battery includes a positive electrode active substance layer; a negative electrode active substance layer; and an inorganic solid electrolyte layer, in which at least one of the positive electrode active substance layer, the negative electrode active substance layer, or the inorganic solid electrolyte layer contains an inorganic solid electrolyte having conductivity of ions of metal belonging to Group 1 or 2 of the periodic table and a cellulose polymer.

Provided is an optical film containing a cellulose derivative, the optical film having an in-plane retardation Ro.sub.550 within the range of 120 to 160 nm measured at a wavelength of 550 nm under an atmosphere of a temperature of 23° C. and a relative humidity of 55%, and a ratio Ro.sub.450/Ro.sub.550 within the range of 0.65 to 0.99, Ro.sub.450/Ro.sub.550 being a ratio of an in-plane retardation Ro.sub.450 measured at a wavelength of 450 nm to the in-plane retardation Ro.sub.550 measured at a wavelength of 550 nm, wherein, a substituent of a glucose skeleton in the cellulose derivative satisfies the requirements (a) and (b) which are described in the specification, and the optical film contains a compound A satisfying the following condition defined by Expression (a1) which is described in the specification.

Provided is an optical film containing a cellulose derivative, the optical film having an in-plane retardation Ro.sub.550 within the range of 120 to 160 nm measured at a wavelength of 550 nm under an atmosphere of a temperature of 23° C. and a relative humidity of 55%, and a ratio Ro.sub.450/Ro.sub.550 within the range of 0.65 to 0.99, Ro.sub.450/Ro.sub.550 being a ratio of an in-plane retardation Ro.sub.450 measured at a wavelength of 450 nm to the in-plane retardation Ro.sub.550 measured at a wavelength of 550 nm, wherein, a substituent of a glucose skeleton in the cellulose derivative satisfies the requirements (a) and (b) which are described in the specification, and the optical film contains a compound A satisfying the following condition defined by Expression (a1) which is described in the specification.

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 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.

Provided are a composite for cellulose fiber dispersion that can inexpensively and sufficiently disperse cellulose fibers, particularly nanocellulose, in a hydrophobic resin and a cellulose fiber composition containing the composite. A composite for cellulose fiber dispersion according to the present invention has a structure in which a vinyl polymer is grafted to a cellulose derivative. A cellulose fiber composition according to the present invention contains the composite and cellulose fibers and more specifically also contains an organic solvent, a resin precursor, or a resin.

A biodegradable material and a method for preparing a biodegradable material are provided. The biodegradable material includes a continuous phase and a dispersed phase. The continuous phase includes a polyester, and the dispersed phase includes a modified saccharide oligomer. In particular, the weight ratio of the modified saccharide oligomer to the polyester is from 3:97 to 30:70. The dispersed phase has a maximum diameter of 100 nm to 900 nm.