Verfahren zur Herstellung von Cellulosecarbamat in einem inerten organischen, mit Wasser nicht mischbaren Loesungsmittel

Die vorliegende Erfindung betrifft ein Verfahren zur Herstellung von Cellulosecarbamat in einem organischen Reaktionsmedium mit folgenden Reaktionsschritten: a) in situ-Aktivierung von Cellulose in Gegenwart eines mit Wasser nicht mischbaren organischen Loesungsmittels sowie einer Harnstoff und Natriumhydroxid enthaltenden waessrigen Loesung, b) Abtrennung des Wassers, c) reaktive Umsetzung bei Temperaturen zwischen 120 und 180°C zum Cellulosecarbamat und d) Separation des Cellulosecarbamats vom organischen Reaktionsmedium.

DE 10253672 B UPAB: 20040302 NOVELTY - Production of cellulose carbamate (I) in a series of organic reaction stages comprises (a) in situ-activation of cellulose (II) in the presence of a water-immiscible organic solvent (III) and an aqueous solution containing urea and sodium hydroxide (NaOH; (b) separation of the water; (c) reaction to (I) at 120-180 deg. C; and (d) separation of (I) from (III). USE - The cellulose carbamate (I) is used for producing cellulose moldings, e.g. fibers, films or granules (all claimed). ADVANTAGE - Cellulose carbamate (I) is usually produced by heating a mixture of cellulose and urea, which is as homogeneous as possible, to temperatures above 130 deg. C. Dry heating has problems associated with very poor heat transfer, whilst the existing slurry process requires a separate activation stage. The present process avoids these drawbacks and provides a simpler method of preparing uniformly substituted, readily soluble (I) using slurry technology. A separate activation stage is unnecessary and the entire process is more effective and more environmentally friendly. The (I) obtained has a degree of substitution of 0.3-0.5 and is clearly and completely soluble in 8-10% cooled aqueous sodium hydroxide solution.