METHOD OF OBTAINING CHITOSAN Russian patent published in 2015 - IPC C08B37/08 

FIELD: chemistry.

SUBSTANCE: invention relates to obtaining chitosan. The method includes preliminary processing of a natural chitin-containing raw material for the separation from it of the material, which is not enriched with chitin by processing with a weak sodium hydroxide solution with the further separation and washing of the chitin-containing raw material. After that, the chitin-containing raw material is demineralised by submerging into a 0.5-2 M solution of hydrochloric acid at a temperature from 20°C to 30°C for 0.5-2 hours, the raw material is separated, washed for 0.5-2 hours and then separated from washing water. Then, the demineralised chitin-containing raw material is subjected to deproteinisation by processing in a 1-10% sodium hydroxide solution for 4-24 hours at a temperature from 60°C to 80°C, the deproteinised raw material is separated, washed for 0.5-2 hours and separated from washing water. After that, residual water is separated from the chitin raw material and the latter is submerged into a deacetylating 40-50% sodium hydroxide solution with carrying out deacetylation at a temperature from 90°C to 110°C for 1-3 hours. Then, the obtained chitosan biopolymer is separated from the deacetylating solution, washed and separated from washing water. Residual water is separated from the chitosan biopolymer. The biopolymer is dried in air at a temperature not higher than 65°C until the moisture content in the biopolymer reduces to less than 10 wt %. The obtained chitosan is characterised by the deacetylation degree of 80% or higher, protein content less than 0.3%, ash content less than 0.2% and moisture content less than 10%.

EFFECT: invention makes it possible to obtain chitosan of a medical purification degree and does not require additional bleaching stages.

12 cl, 7 dwg, 3 tbl, 1 ex