METHOD FOR CONTINUOUS MANUFACTURE OF MICROCRYSTALLINE CHITOSAN

摘要

In a method for continuous manufacture of microcrystalline chitosan by precipitation of chitosan from its aqueous solutions in organic or inorganic acid, or their salts, the chitosan solution in an aqueous acid solution, especially in acetic acid, with polymer concentration not lower than 0.01 wt%, preferably with polymer concentration within 0.1-2.0 wt%, is continuously introduced into a reactor together with an alkaline solution, such as an aqueous solution of an alkaline metal hydroxide or a salt thereof having a concentration ranging from 0.1 to 20.0 wt%. The chitosan solution is introduced into the reactor with a rate within a range of 0.1-20 volume parts per 1 hour and 1 reactor volume part, and the alkaline solution is introduced into a reactor with a rate ranging from 0.1 to 10.0 volume parts per 1 hour and 1 reactor volume part to obtain a mixture pH of equal to or higher than 7. The microcrystalline chitosan dispersion having said pH is simultaneously taken off from the reactor by a continuous system with a rate suitable to keep a constant reaction mixture volume in the reactor, and the microcrystalline chitosan dispersion is collected in a compensation tank and is continuously purified, especially by continuous water washing or by ultrafiltration method. The purified microcrystalline chitosan is finally concentrated to obtain a polymer content of 0.5-10.0 wt% and dried by some well-known method.