ZYKLISCHES VERFAHREN ZUR HERSTELLUNG ALKALISCHER LOESUNGEN VON CELLULOSECARBAMAT

摘要

The present invention concerns a cyclic process for producing an alkali aqueous solution of cellulose carbamate, for precipitating the cellulose carbamate from the alkali solution and for recovering and recycling the remaining chemicals. The process comprises the following steps: (a) an alkali solution of cellulose carbamate is prepared by dissolving cellulose carbamate in an aqueous solution of sodium hydroxide, (b) the solution obtained in step (a) is contacted with a precipitation aqueous solution containing sodium carbonate, whereby the cellulose carbamate is precipitated and can be removed, (c) from the solution in step (b) sodium carbonate is crystallized and is returned to the precipitant solution in step (b), and (d) mother liquor containing sodium hydroxide, obtained, i.e. remaining from, step (c), is returned to step (a) for dissolving cellulose carbamate. The crystallizing in step (c) is accomplished in two or several steps by cooling.