METHOD FOR ULTRAFILTERING ELECTRODEPOSITION PAINT

PURPOSE:To increase the recovery rate of electrodeposition paint and to reduce the load of treatment of waste water by doubly arranging membranes for ultrafiltration so that a fluid filtered with the inner membrane is filtered again with the outer membrane whose graduated mol.wt. is equal to or lower than that of the inner membrane. CONSTITUTION:When electrodeposition paint is recovered by ultrafiltration, membranes 7, 8 for ultrafiltration are doubly arranged. A sample fluid is first passed through the inner membrane 7 to carry out first ultrafiltration. The resulting filtrate is passed through the outer membrane 8 whose fractionated mol.wt. is equal to or lower than that of the inner membrane 7. By the two-step ultrafiltration, a filtrate having a low solid content is obtd. Pressure applied to pass the fluid through the inner membrane 7 can be utilized as pressure required to pass the resulting filtrate through the outer membrane 8.