VISCOSITY CHARACTERISTICS OF CELLULOSE SOLUTIONS IN LIQUID SULFUR DIOXIDE

Previous work in this series has shown the preparation of cellulose-liq. SO2 solution in the presence of amine1) and a few properties of solutions under various conditions have also been reported2).The present work was undertaken to investigate the effects of amines for viscosities of cellulose solutions. Diethylamine, triethylamine and piperidine were employed as dissolving aid for cellulose. Viscosities of the solutions were measured with capillary viscometer specially designed for liquid SO2.In the above examination, it was observed that the reduced or intrinsic viscosities of the cellulose solutions containing ethylamine or piperidine were higher than those in which containing triethylamine. The solutions using free secondary amines became more viscous with increase of amine concentration and became less viscous by adding amine hydrochlorides. The similar phenomenon was observed on gelatinizing temperature of the cellulose solutions using secondary amines.Meanwhile, the viscosity of cellulose solution using triethylamine was scarcely effected by the concentration of amine or by the addition of amine hydrochloride. The solution (cellulose 0.15g, triethylamine 0.1 mol, liq. SO2 100ml at 20°C) was not gelatinized even at -60°C, though the solution of the same composition prepared with diethylamine was gelatinized at -14°C.Consequently, in view of the above facts the most reasonable conclusion to be drawn from available data is that the viscosity behaviors of the cellulose-SO2 solutions prepared with secondary amine are quite different from those of which prepared with tertiary amine. Secondary amine has N-H bonding in its structure (R2NH), and it is a well known fact that the hydrogen atom which directly combined with nitrogen atom is markedly active in liq. SO2. Therefore, in the case of using secondary amine as dissolving aid, the evidence thus obtained supports the suggestion that the cellulose molecule dispersed with amine-SO2 complex into the liq. SO2 is liable to form the intramolecular linkage by hydrogen bonding and the secondary amine-SO2 complex may promote such an interaction in liq. SO2.