Burns, Doane, Swecker & Mathis
Process for the production of semipermeable polybenzimidazole membranes and the resultant product
 A membrane cast in the form of either a hollow filament or a flat film formed of a polybenzimidazole polymer is subjected to an annealing process by contacting the membrane with a non-aqueous annealing medium comprised of a solvent for the polymer and a non-solvent for the polymer. Such an annealing step can advantageously occur at an annealing temperature below about 125.degree. C. (e.g., below 100.degree. C.) These polybenzimidazole membranes find particular utility in reverse osmosis desalination processes. The annealing step of the present invention improves the mechanical and separative properties of the membrane. 
Celanese Corporation
B
B01D
inventional
Donald G. J.
Wang