PROCESS FOR PREPARING AN ESTER OF A CELLULOSE ETHER IN THE PRESENCE OF AN ALKALI METAL CARBOXYLATE

摘要

Two or more esters of a cellulose ether, each having the same ether and ester substituents but different weight average molecular weights are prepared in a process which comprises the steps of esterifying a cellulose ether with (i) an aliphatic monocarboxylic acid anhydride or (ii) a dicarboxylic acid anhydride or (iii) a combination of an aliphatic monocarboxylic acid anhydride and a dicarboxylic acid anhydride in the presence of an alkali metal carboxylate in two or more separate reactions, wherein in each reaction a different molar ratio [alkali metal carboxylate/anhydroglucose units of cellulose ether] is used to produce esters of the cellulose ether of different weight average molecular weights.

主权项

1. A process for preparing two or more esters of a cellulose ether, each having the same ether and ester substituents but different weight average molecular weights comprising the steps of
esterifying a cellulose ether being a hydroxypropyl methylcellulose with succinic anhydride and acetic anhydride in the presence of an alkali metal carboxylate and in the presence of an aliphatic carboxylic acid in two or more separate reactions, wherein in each reaction a different molar ratio [alkali metal carboxylate/anhydroglucose units of cellulose ether] is used to produce esters of the cellulose ether of different weight average molecular weights, wherein in each reaction the molar ratio [alkali metal carboxylate/anhydroglucose units of cellulose ether] is at least [0.3/1.0] different from the molar ratio in the other reaction(s).