Process for the preparation of methylhydroxyalkylcellulose

摘要

Industrial preparation of methylhydroxyalkyl cellulose (I), from cellulose present in alkali with chloromethane and hydroxyalkyl composition, comprises spraying the cellulose with aqueous alkali hydroxide solution and a suspension containing chloromethane into an autoclave; optionally adding hydroxyalkyl solution; adding alkali hydroxide; adding chloromethane; and isolating, washing and drying the obtained product. Industrial preparation of methylhydroxyalkyl cellulose (I), from cellulose present in alkali with chloromethane and hydroxyalkyl composition, comprises (A) spraying the cellulose with aqueous alkali hydroxide solution and a suspension containing 20-50 wt.% of chloromethane into an autoclave so that the alkalized cellulose reacts with the chloromethane; (B) optionally adding one or more hydroxyalkyl solution at above 60[deg]C; (C) adding alkali hydroxide with greater stoichiometric value of at least +0.1 related to the chloromethane added in the step (a); (D) optionally adding one or more hydroxyalkyl solution at temperature higher than 60[deg]C and reacting for at least 20 minutes; (E) adding chloromethane with greater stoichiometric value of at least +0.2, related to the alkali hydroxide used in steps (a and c); (F) optionally adding further alkali hydroxide and reacting at 60-110[deg]C; and (G) distilling the suspension with the remaining chloromethane and isolating, washing and drying the obtained product.