This invention relates to novel compositions comprising regioselectively substituted cellulose esters. One aspect of the invention relates to processes for preparing regioselectively substituted cellulose esters from cellulose dissolved in ionic liquids. Another aspect of the invention relates to the utility of regioselectively substituted cellulose esters in applications such as protective and compensation films for liquid crystalline displays.

The present invention is to provide a cellulose acetate that has a low total degree of acetyl substitution and a degree of acetyl substitution at 6-position that is lower compared to the degrees of acetyl substitution at 2-position and 3-position of a glucose ring, and has excellent water solubility. A cellulose acetate having: a total degree of acetyl substitution of 0.4 or greater and 0.9 or less, a proportion of a degree of acetyl substitution at 6-position in the total degree of acetyl substitution of 0% or greater and 18% or less, and a light transmittance at 660 nm of 5% or greater in 4 wt. % aqueous solution.

The present invention is to provide a cellulose acetate that has a low total degree of acetyl substitution and a degree of acetyl substitution at 6-position that is lower compared to the degrees of acetyl substitution at 2-position and 3-position of a glucose ring, and has excellent water solubility. A cellulose acetate having: a total degree of acetyl substitution of 0.4 or greater and 0.9 or less, a proportion of a degree of acetyl substitution at 6-position in the total degree of acetyl substitution of 0% or greater and 18% or less, and a light transmittance at 660 nm of 5% or greater in 4 wt. % aqueous solution.

Provided is a method for producing hydroxypropyl methylcellulose acetate succinate that can be industrially and efficiently produced and results in particles having controlled pore volume. The method for producing hydroxypropyl methylcellulose acetate succinate includes an esterification reaction step, a precipitation step, a liquid removal step, a pulverizing step, and a drying step, wherein a screw press is used in the liquid removal step.

Provided is a method for producing hydroxypropyl methylcellulose acetate succinate that can be industrially and efficiently produced and results in particles having controlled pore volume. The method for producing hydroxypropyl methylcellulose acetate succinate includes an esterification reaction step, a precipitation step, a liquid removal step, a pulverizing step, and a drying step, wherein a screw press is used in the liquid removal step.