Acid-catalyzed, hydrolytic depolymerization of cellulose ethers to low-viscosity products useful e.g. for coating drugs, carried out in pressure filter vessel allowing separation, purification and drying in same apparatus

摘要

Acid-catalyzed, hydrolytic depolymerization of cellulose ethers (I), with subsequent separation and optionally purification and drying of the product (A) at the same location, is carried out in a closed, pressure and acid resistant, heatable vessel provided with a stirrer and a filter element between an inlet and outlet. Acid-catalyzed, hydrolytic depolymerization of cellulose ethers (I), with subsequent separation and optionally purification and drying of the product (A) at the same location, is carried out in a closed, pressure and acid resistant, heatable vessel provided with a stirrer and a filter element between an inlet and outlet. (I) is supplied via the inlet in the form of acidic slurry and is depolymerized, under stirring and optionally under pressure, at a temperature above the flocculation temperature of (A), while being kept separate from the filter element. When depolymerization is complete, the mixture is neutralized by addition of alkali and optionally aggregate, then (by opening the outlet) contacted with the filter element under application of shear force and/or external pressure so that the filtrate is separated. The obtained (A) is optionally purified by applying and removing water (optionally mixed with organic suspending agent(s)) one or more times; and optionally dried by application of vacuum or introduction of gas. An Independent claim is also included for the use of an enameled pressure filter, provided with an inlet, outlet, heating mantle, stirred, solids outlet and filter bed (where all non-enameled parts are of acid-resistant material), for depolymerization of (I).