Carboxyethyl cellulose ethers

Claim 1

IN A METHOD FOR PRODUCING ALKALI SALTS OF CARBOXYLIC ETHYL CELLULOSE ETHERS WHEREIN CELLULOSE IS REACTED WITH ACRYLONITRILE IN THE PRESENCE OF AN AQUEOUS ALKALI METAL HYDROXIDE AND THE REACTION PRODUCT THEREFROM IS HYDROLYZED TO FORM SAID ALKALI METAL SALTS OF CARBOXYLIC ETHY CELLULOSE ETHERS, THE IMPROVEMENT COMPRISING CARRYING OUT THE REACTION BETWEEN THE ACRYLONITRILE AND CELLUSE IN THE ALKALINE SOLUTION AT A TEMPERATURE BELOW 5*C., STIRRING THE MIXTURE AT ABOUT HALF HOUR INTERVALS OVER A PERIOD OF FROM ONE AND ONEHALF TO TWENTY-FOUR HOURS, SAID STIRRING BEING SUFFICIENTLY MILD SO AS TO PRODUCE AN INTERMEDIATE CYANOETHYL CELLULOSE ETHER PRECIPITATE OF DEGREE OF SUBSTITUTION BETWEEN THE LIMITS OF 0.34 AND 0.75, AND SEPARATING THIS PRECIPITATE FROM ITS MOTHER LIQUOR PRIOR TO THE HYDROLYSIS STEP.