Abstract
Viscosities of three cellulose acetate flakes (acetyl contents, 60. 6, 57. 3 and 51.1%) in the mixed solvents of methylene chloride-methanol at 18% concentration at 25°C were measured by falling ball method, and the effects of the methanol contents (1_??_50%) in the mixed solvents upon the viscosities of these concentrated solutions of cellulose acetate differing in the acetyl contents were investigated.
It was found that the methanol contents have the marked influences on the solution viscosities and there are the definite methanol contents for each sample that give the minimum viscosities values.
The higher the acetyl contents of cellulose acetate, the smaller the amounts of methanol corresponding to the minimum viscosities and also the less markedly the changes of viscosities near the minimum values.
These phenomena are briefly discussed with referrence to the behavior of the intrinsic viscosities of various kinds of cellulose acetate in these mixed solvents systems previously reported by one of the authors1).
