Preparation and purification of cellulose ethers

Claim 1

IN A METHOD OF PREPARING ETHERS OF POLYSACCHARIDES BY REACTING AN ALKALI METAL POLYSACCHARIDE SELECTED FROM THE CLASS OF SODIUM STARCH, SODIUM CELLULOSE, POTASSIUM STARCH AND POTASSIUM CELLULOSE WITH AT LEAST ONE MEMBER SELECTED FROM THE GROUP CONSISTING OF A. A C1-C4 ALKYL MONOCHLORIDE, B. C2-C4 VICINAL EPOXIDE, AND C. A C2-C4 MONOCHLOROCARBOXYLIC ACID OR ALKALI METAL SALT THEREOF, IN THE PRESENCE OF A LIQUID ORGANIC DILUENT AT A TEMPERATURE OF FROM ABOUT 50* TO 155*C AND THEREAFTER NEUTRALIZING EXCESS ALKALI, CROSS-LINKING THE ETHERIFIED POLYSACCHARIDE AND WASHING IT WITH WATER, THE IMPROVEMENT COMPRISING, A. USING AS THE ORGANIC DILUENT A LIQUID CONTAINING FROM ABOUT 20 TO 100 PERCENT BY WEIGHT OF A HYDROCARBON HAVING A BOILING POINT OF FROM ABOUT 60 TO ABOUT 155*C AND FROM 80 TO 0 PERCENT BY WEIGHT OF A C3 TO C4 KETONE OR A C3 TO C6 SECONDARY OR TERTIARY MONOHYDRIC ALKANOL, THE WEIGHT RATIO OF DILUENT TO POLYSACCHARIDE BEING FROM ABOUT 8 TO ABOUT 14 TO 1. B. REMOVING AT LEAST A PORTION OF THE WATER AND VOLATILE HYDROXYL CONTAINING BY-PRODUCTS FROM THE NEUTRALIZED REACTION MIXTURE BY AZEOTROPIC DISTILLATION, C. CROSSLINKING THE ETHERIFIED POLYSACCHARIDE IN THE PRESENCE OF THE LIQUID DILUENT WITH FROM ABOUR 0.2 TO ABOUT 10 WEIGHT PERCENT BASED ON THE POLYSACCHARIDE OF AN UNSUBSTITUTED MONOALDEHYDE HAVING 1 TO 6 C ATOMS OR AN UNSUBSSTITUTED DIALDEHYDE OF FROM 2 TO 6C ATOMS AT A PH OF FROM ABOUT 2-6, AND D. WASHING THE CROSSLINKED PRODUCT WITH WATER AT A TEMPERTURE OF FROM ABOUT 0* TO ABOUT 30*C.