Controlled prodn. of cellulose acetate-phosphate or -sulphate mixed ester(s)

摘要

Deacetylation and subsequent esterification of cellulose triacetate (CTA) to produce cellulose acetate-phosphate or -sulphate mixed esters with a defined mol. structure for the anhydroglucose units (AGU) in the C2-, C3- and C6- positions comprises: (i) dissolving the CTA in an aprotic polar solvent and effecting partial deacetylation by addn. of an aq. amine soln. (opt. together with addn. of an org. solvent), the deg. of deacetylation obtd. being determined by variation of time in range 0.5-72 hrs. and temp. 20-100 deg C; and (ii) isolating and drying the prod. and then converting it to the required -phosphate or -sulphate in conventional fashion. Pref. the aprotic solvent used in step (i) is acetone, acetonitrile, N,N-di-Me-acetamide, N,N-DMF, DMSO, hexamethylphosphoric triamide or pyridine. The amine, used at 1-10 mol per mol AGU with the ester in the soln. being at 10-100 mol per mol AGU is of formulae (I) - (III). H2N-R1 (I) H2N-R2-NH2 (II) R3-NH-R4 (III) R1 = 3-8C alkyl or cycloalkyl; R2 = 4-8C alkyl; and R3 and R4 = 1-3C alkyl. Deacetylation is for 1-36 hrs. at 60-80 deg C and the conversion in step (ii) is effected using one of the solvents listed in step (i) and at 20-120 deg C for 0.5-24 hrs..