Patent ID: 8318913
Filing Date: 2012-11-27
Classification: C08B

Abstract:
1. A process for the manufacture of chitosan from a naturally occurring chitin source comprises the following steps: (i) an initial pretreatment (“PTRT”) step carried out prior to step (a) below in order to remove non-chitin rich organic material from the naturally occurring chitin source by treating the chitin source with a mild PTRT sodium hydroxide solution for a PTRT time period and under conditions of time and temperature, to remove non-chitin organic material from the chitin source, and then separating the resulting pretreated chitin source from the PTRT sodium hydroxide solution, and washing the pretreated chitin source for a PTRT wash period sufficient to remove therefrom sodium hydroxide; (a) the naturally occurring chitin source is obtained from initial step (i) demineralized by immersing it in a demineralization (“DMIN”) hydrochloric acid solution of from about 0.5 to about 2 M at a temperature of from about 20° C. to about 30° C. and for a DMIN time period of from about 0.5 to about 2 hours to demineralize the chitin source, and then separating the resulting demineralized chitin source from the acid solution, washing the chitin source in a DMIN wash water for a DMIN wash period of from about 0.5 to about 2 hours to remove the hydrochloric acid and calcium salts therefrom, and then separating the demineralized chitin source from the DMIN wash water; (b) subjecting the demineralized chitin source to deproteination (“DPRO”) by treating the demineralized chitin source in a DPRO sodium hydroxide solution containing from about 1% to about 10% w/w NaOH for a DPRO time period of from about 4 to about 24 hours and at a temperature of from about 60° C. to about 80° C. to deproteinize the demineralized chitin source, and then separating the resulting demineralized and deproteinized chitin source from the deproteination sodium hydroxide solution, washing the separated demineralized and deproteinized chitin source in a DPRO wash water for a DPRO wash period of from about 0.5 to about 2 hours to remove the sodium hydroxide from the demineralized and deproteinized chitin source, and then separating the demineralized and deproteinized chitin source from the deproteination wash water; (c) separating residual water from the chitin source obtained in step (b); (d) immersing the chitin source obtained from step (b) into a sodium hydroxide deacetylation (“DEAC”) solution containing from about 40% to about 50% w/w NaOH and carrying out deacetylation at a temperature of from about 90° C. to about 110° C. and for a DEAC time period of from about 1 to about 3 hours to convert acetyl groups of the chitin source obtained from step (c) to amine groups, to thereby form a chitosan biopolymer having d-glucosamine as the monomer of the chitin biopolymer, then separating the resulting chitosan biopolymer from the DEAC solution and washing the separated chitosan biopolymer in a DEAC wash water for a DEAC wash period sufficient to remove sodium hydroxide from the chitosan polymer, and then separating the chitosan biopolymer from the DEAC wash water; and (e) residual water is then separated from the chitosan biopolymer which is then dried in air at a temperature of not more than about 65° C. for a drying time period sufficient to reduce the moisture content of the chitosan biopolymer to below about 10% by weight to provide a medical-grade quality chitosan.