Electrophoretic coating is a coating method in which the workpiece and corresponding electrodes are placed in a water-soluble coating, connected to a power source, and the physical and chemical effects generated by the electric field are used to evenly precipitate and deposit the resin and pigments in the coating on the surface of the electrode, forming an insoluble paint film.
Ultrafiltration and ultrafiltration devices play an important role in the electrophoretic coating process. Better use and promotion of ED-RO new technology can further improve the utilization rate of electrophoretic coatings and water resources, and significantly reduce the discharge of electrophoretic wastewater. Correctly and effectively use and maintain ultrafiltration equipment to improve the utilization rate of the ultrafiltration system. The purpose of using ultrafiltration cleaning (UF) after electrophoresis is to remove floating paint attached to the surface of the electrophoresis film, improve the appearance quality of the film, and recycle the electrophoresis coating.
Ultrafiltration (UF) is a membrane separation technology. It is a solution separation process driven by the pressure difference on both sides of the UF membrane and based on the principle of mechanical screening. The operating pressure is usually (0.1-0.6) MPa, and the separation pore size is 1nm~0.1 μ m. Intercepted molecular weight is around 500 to 1000000. During the UF process of electrophoretic paint, when the electrophoretic paint comes into contact with the UF film, the solution and inorganic salts can pass through the UF film, while molecules similar in size to resins and pigments cannot pass through and are trapped in the paint solution and transported back to the electrophoretic tank.
Ultrafilter is a key equipment on the electrophoresis coating line, and its main purpose for the electrophoresis line is to obtain deionized water and paint solvent from the electrophoresis tank through UF device, provide washing water for the electrophoresis parts, clean the excess electrophoresis paint attached to the electrophoresis parts, and return it to the electrophoresis tank. This can recycle and utilize the electrophoretic paint brought out on the surface of the workpiece, achieving closed loop circulation, and saving enterprises 30% of the cost of purchasing electrophoretic paint; Secondly, by releasing some of the UF solution, impurities and ions brought into the electrophoresis tank during the painting process can be eliminated, so that the impurity content of the working solution in the electrophoresis tank remains within the specified conductivity and pH range of the process. UF solution can be recycled instead of deionized water as the flushing water for the electrophoresis workpiece, without discharging the electrophoresis paint, avoiding the wastewater treatment load caused by direct cleaning with deionized water and reducing environmental pollution.
Ultrafiltration is used to remove impurities and ions from the working solution of electrophoretic paint, as well as effectively close the cationic and anionic pollution sources brought in, ensuring the stability of the paint solution and the integrity of the paint film. Ultrafiltration (UF) is a membrane filtration separation technology that can purify, separate, or concentrate solutions. The ultrafiltration process can be understood as a screening process related to the size of the membrane pore size. Using the pressure on both sides of the membrane as the driving force and the ultrafiltration membrane as the filtering medium, under a certain pressure, when the solution flows through the membrane surface, only water, inorganic salts, and small molecule substances are allowed to pass through the membrane, while large molecules such as suspended solids, colloids, proteins, and microorganisms in the tissue water pass through to achieve the purpose of solution purification, separation, and concentration. Ultrafiltration is a continuous, low-pressure operation.