Process for making alkali metal salt of carboxymethylcellulose

Claim 1

A TWO-STAGE CONTINUOUS PROCESS FOR THE PREPARATION OF A WATER-SOLUBLE ALKALI METAL SALT OF CARBOXYMETHYLCELLULOSE IN WHICH THE FIRST STAGE INVOLVES THE PREPARATION OF ALKALI CELLULOSE AND THE SECOND STAGE INVOLVES THE ETHERIFICATION OF THE ALKALI CELLULOSE, SAID FIRST STAGE COMPRISING MIXING INTIMATELY AND THROUGHLY A COMMINUTED CELLULOSE WITH A LOWER ALKANOL HAVING FROM 2 TO 4 CARBON ATOMS AND AQUEOUS ALKALI, EXTRUD9ING THE RESULTANT MASS UNDER PRESSURE THROUGH A DIE, AND THEREAFTER STEEPING THE EXTRUDED MATERIAL FOR A PERIOD OF AT LEAST ABOUT 10 MINUTES, SAID SECOND STAGE COMPRISING INTIMATELY AND THOROUGHLY MIXING THE PRODUCT FROM THE FIRST STAGE WITH MONOCHLOROACETIC ACID, EXTRUDING THE RESULTANT MASS UNDER PRESSURE THROUGH A DIE, AND THEREAFTER AGING THE EXTRUDED MATERIAL FOR A PERIOD OF AT LEAST ABOUT ONE-HALF HOUR, THE AMOUNT OF WATER PRESENT THROUGHOUT SAID PROCESS BEING IN THE RANGE OF ABOUT 0.4 TO 1.2 PARTS BY WEIGHT PER PART OF CELLULOSE, AT LEAST ABOUT 75% OF THE WATER BEING PRESENT DURING THE FIRST STAGE, THE AMOUNT OF ALKANOL PRESENT THROUGHOUT SAID PROCESS BEING IN THE RANGE OF ABOUT 1.0 TO 2.5 PARTS BY WEIGHT PET PART OF CELLULOSE, AT LEAST 35% OF THE ALKANOL BEING PRESENT DURING THE FIRST STAGE, THE WEIGHT RATIO OF ALKALI ADDED DURING THE FIRST STAGE TO MONOCHLOROACETIC ACID ADDED DURING THE SECOND STAGE BEING IN THE RANGE OF ABOUT 0.86 TO 1.25 PARTS OF ALKALI PER PART OF MONOCHLOROACETIC ACID, AND THE MOLE RATIO OF MONOCHLOROACETIC ACID TO ANHYDROGLUCOSE UNITS OF SAID CELLULOSE BEING LESS THAN ABOUT 1.5:1.