Patent ID: 7026471

Claim:
A purification method of hydroxypropylmethyl cellulose phthalate from a hydroxypropylmethyl cellulose phthalate reaction product mixture obtained by reacting hydroxypropylmethyl cellulose, alkali acetate, phthalic anhydride and alkali chlorate in acetic acid solvent, wherein, after said reaction is completed, 2–4 wt. %, based on a 1 wt. % solution of hydroxypropylmethyl cellulose, of selected from the group consisting of a fluidization solvent water or C 1 –C 5 low alcohol is added and stirred, and the product is sprayed into 10–20 wt. %, based on a 1 wt. % solution of hydroxypropylmethyl cellulose, of water through a spray nozzle whose air or nitrogen gas pressurization speed is 3–8 L/min, and then stirred, filtered and dried.