| abstract |
PURPOSE:To manufacture the high performance polyimide semipermeable membrane of stable quality by a method in which the polyimide obtained from biphenyl tetracarboxylic acid and an aromatic diamine is dissolved in a phenolic solvent to form a liquid thin membrane and then the thin membrane is coagulated. CONSTITUTION:The polyimide used is obtained by dissolving an aromatic polyimide having 90% or more (based on total constitutional units) a repeating unit of formula I (where R is a divalent aromatic diamine residual group deprived of amino group) as the main chain soluble in a solution of phenolic compound. From a doped solution of the polyimide composition thus obtained, the liquid thin membrane of a flat membrane, hollow yarn, tubular form, etc., is formed by a well known method, and then dipped in a coagulating liquid to manufacture the polyimide semipermeable membrane. |