Hydroxypropyl methyl cellulose acetate succinate, method for producing the same, and composition for hot-melt extrusion

Hydroxypropyl methyl cellulose acetate succinate having a volume fraction of spherical particles from 93.2% to 99.0% relative to all of hydroxypropyl methyl cellulose acetate succinate particles, the all of the hydroxypropyl methyl cellulose acetate succinate particles, being classified, on a basis of dynamic image analysis, into fine particles, spherical particles and fibrous particles;

• the fine particles have a length of fiber of less than 40 μm;
• the spherical particles have a length of 40 μm or more and consist of first and second spherical particles, wherein the first spherical particles have an elongation, which is a ratio of a diameter of fiber to a length of fiber, of 0.5 or more, and the second spherical particle have an elongation of less than 0.5, an aspect ratio, which is a ratio of a minimum Feret diameter to a maximum Feret diameter, of 0.5 or more, and a circularity, which is a ratio of a perimeter (PEQPC) of a circle that has the same area as a projection area of a particle to a real perimeter (Preal) of a particle, of 0.7 or more;
• the fibrous particles consist of long and short fibrous particles;
• the long fibrous particles have a length of fiber of 200 μm or more and an elongation of less than 0.5, and consist of first and second long fibrous particles, wherein the first long fibrous particles have an aspect ratio of less than 0.5, and the second long fibrous particles have an aspect ratio of 0.5 or more and a circularity of less than 0.7;
• and
• the short fibrous particles have a length of fiber of 40 μm or more and less than 200 μm and an elongation of less than 0.5, and consist of first and second short fibrous particles, wherein the first short fibrous particles have an aspect ratio of less than 0.5, and the second short fibrous particles have an aspect ratio of 0.5 or more and a circularity of less than 0.7.