PURPOSE: To obtain a cellulose acetate having excellent moldability by removing a low-molecular-weight component therefrom by wishing with a solvent having a specified solubility parameter so that the washed product may have a specified molecular weight distribution, a specified average degree of acetylation and a specified viscosity-average degree of polymerization.
CONSTITUTION: A cellulose is pretreated to be actionted with acetic acid, specified amounts of sulfuric acid, acetic anhydride and acetic acid are added to the preactivated cellulose, and the entire mixture is subjected to an esterification reaction. After the reaction, the reaction mixture is neutralized with magnesium acetate and saponified and aged under heating to prepare a cellulose acetate such as cellulose triacetate. A low-molecular-weight component is eluted and removed from the cellulose acetate by washing it under agitation with a solvent selected from among esters, ketones, ethers and organic acids, such as methyl acetate, methyl ethyl ketone and formic acid, having a solubility parameter δof 7-12.5 to obtain a cellulose acetate having a molecular weight distribution Mw/Mn of 1.2-1.7, an average degree of acetylation of 52-62.5% and a viscosity- average degree of polymerization of 290-400.
OKANO TOSHINORI
TANIGUCHI HIROKI
KIYOSE ATSUNOBU
SHIMAMOTO SHU
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