Esterification of viscose fibres with orthophosphoric acid and study of their physicochemical and mechanical properties

Esterification of viscose fibres with aqueous solutions of orthophosphoric acid and urea at different ratios of components was investigated. It was shown that in phosphorylation of cellulose with these solutions, one-substituted cellulose phosphates are formed and a side process of formation of cellulose carbamates takes place together with accumulation of phosphate groups. A decrease was found in the mechanical strength of the phosphorylated cellulose preparations and the degree was a function of the concentration of orthophosphoric acid and urea as the phosphorylating solution. Phosphorus-containing viscose fibres (up to 0.5 mmole/g of phosphate groups) obtained in solutions of orthophosphoric acid and urea with a 0.25–0.63 and 3.33–4.17 M concentration have the most satisfactory mechanical properties and stability in phosphate buffer with pH 7.5. __________ Translated from Khimicheskie Volokna, No. 1, pp. 26–30, January—February, 2007.