Preparation of cellulose esters

Claim 1

IN A PORCESS FOR THE PREPARATION OF CELLULOSE ACETATE FROM CELLULOSIC MATERIAL WHEREIN THE ESTERIFICATION PROCEEDS RAPIDLY, THE STEPS WHICH COMPRISES SUBJECTING THE CELLULOSIC MATERIAL TO A MULTI-STAGE PRETREATMENT PRIOR TO ESTERIFICATION, ONE STAGE OF SAID PRETREATMENT COMPRISING THE ADDITION TO THE CELLULOSIC MATERIAL OF A LOWER ALIPHATIC ACID AND ANOTHER STAGE OF SAID PRETREATMENT COMPRISING THE ADDITION TO THE CELLULOSIC MATERIAL CONTAINING THE LOWER ALIPHATIC ACID CONA FURTHER QUANTITY OF A LOWER ALIPHATIC ACID CONTAINING FROM ABOUT 5 TO 15 PARTS BY WEIGHT OF AN ESTERIFICATION CATALYST FOR EACH 100 PARTS BY WEIGHT OF CELLULOSIC MATERIAL WITHOUT DISPLACING ANY OF THE LOWER ALIPHATIC ACID CONTAINED IN THE CELLULOSIC MATERIAL, AND ESTERIFYING THE PRETREATED CELLULOSIC MATERIAL WITH ACETIC ANHYDRIDE WITHOUT A PERIOD OF LESS THAN ABOUT 15 MINUTES AFTER THE ADDITION THERETO OF THE FURTHER QUANTITY OF LOWER ALIPHATIC ACID CONTAINING THE ESTERIFICATION CATALYST.