Process of making alpha cellulose from fibrous ligno-cellulose materials, particularly from bagasse

Claim 1

A PROCESS FOR PRODUCING ALPHA CELLULOSE OF HIGH PURITY AND HIGH DEGREE OF POLYMERIZATION FROM BAGASSE AND LIKE FIBROUS LIGNOSE-CELLULOSE MATERIALS COMPRISING DIGESTING BAGASSE IN AN AQUEOUS SOLUTION CONTAINING FROM ABOUT 3 TO ABOUT 4.5% OF SULFUR DIOXIDE IN WHICH THE RATIO OF FREE SULFUR DIOXIDE TO COMBINED SULFUR DIOXIDE IS ABOUT 0.95-1.1 TO 1, ON A WEIGHT BASIS, SAID SULFUR DIOXIDE CONTENT DERIVED FROM MAGNESIUM SULFITE, CALCIUM SULFITE AND SULFUROUS ACID, THE RATION OF MAGNESIUM TO CALCIUM BEING ABOUT 3-5 TO U BASED ON THE OXIDES, SAID DIGESTION CARRIED OUT AT A TEMPERATURE FROM ABOUT 145* TO ABOUT 150* C. FOR ABOUT 3 TO 4 HOURS, THEREAFTER DIGESTING THE RECOVERED BAGASSE FIBERS SUSPENDED IN AN AMOUNT OF ABOUT 5 TO 10% BY WEIGHT OF SAID FIBERS IN AN AQUEOUS NEUTRAL SODIUM SULFITE SOLUTION CONTAINING FROM ABOUT .03 TO ABOUT 0.8% SULFUR DIOXIDE, BY WEIGHT AT A TEMPERATURE BELOW ABOUT 145* C. FOR AT LEAST ABOUT 30 MINUTES AND FOR LESS THAN ABOUT 1 HOUR.