Patent ID: 8337901

Claim:
Method for the production of regio-selective substituted cellulose sulfate (CS) characterized by a combination of the following steps: a) swelling of native cellulose in a polar aprotic solvent; b) addition of a sulfating reagent and an acetylating reagent, for the simultaneous esterification and distribution of acetate groups and sulfate groups along and between the polymer chains; c) directly followed by a complete neutralization with a base, whereby the sulfate without cleaving the acetyl group is transferred into a sodium salt of the cellulose acetate sulfate (SCS), whereby the directly following neutralization also avoids cleavage of acetate groups and consequently the degradation of the cellulose chains; and d) subsequent precipitation, deacetylation, washing and drying of the SCS, whereby the SCS is characterized by a solution viscosity, which is greater than 10 mPas at a concentration of 1% in water.