University of Groningen Liquid crystalline solutions of cellulose in phosphoric acid for preparing cellulose yarns
It was found that superphosphoric acid is an excellent direct solvent for c6llulose. Dissolution is very fast, and liquid crystalline solutions are formed above a cellulose concentration of 7.5 w/w at room temperature; even solutions containing 38 wlw cellulose can be prepared. Phosphoric acid may occur as a monomer (orthophosphoric acid) a dimer (pyrophosphoric acid) an oligomer and even a polymer. The composition of the solvent is expressed in a PzO5concentration. Anhydrous conditions are obtained above a P205 concentration of 74 w/w (superphosphoric acid) The solutions were characterized by determining the clearing temperature, which was found to increase with decreasing water content in the phosphoric acid solvent and to level off under anhydrous conditions. Superphosphoric acid is also capable of dissolving cellulose acetate, ethyl cellulose and chitin, with formation of anisotropic solutions. 3.