To provide a preparation method of a polymer solution wherein a metal oxide particle is suspended, which serves as a raw material of a porous film showing high permeability to pure water.
In the preparation method of the polymer solution wherein the metal oxide particle is suspended, a polymer component and a metal salt other than an alkali metal salt are added to and mixed in a mixed solvent. The mixed solvent used here comprises 90-99.9 mass% polar organic solvent having a boiling point of ≥110°C and compatibility with water and 10-0.1 mass% water. The preparation method comprises a step wherein the polymer component is mixed with the mixed solvent and subsequently heated at a temperature not higher than the boiling point of the polar organic solvent contained in the mixed solvent and a step wherein the metal salt other than the alkali metal salt is added and heated at a temperature not higher than the boiling point of the polar organic solvent contained in the mixed solvent.
Takahiko Mizobe
Shinji Mochida
Yoshitsune Kazumasa