Ultrafilter is one of the important equipment in electrophoretic coating, correct use and maintenance is very important to prolong its service life and ensure the application effect.
1) Antifreeze of the ultrafiltration element
In order to prevent the ultrafiltration element from freezing and cracking, an insulation layer can be added outside the complement of the ultrafiltration device, or controlled by a time relay, and the ultrafiltration liquid supply pump should be started regularly for 10 minutes every 30 minutes to prevent freezing. This method is also conducive to the uniformity of the bath liquid.
2) Anti-mold of ultrafiltration tube
After the ultrafiltration technology is applied in the electrophoretic coating process, it is found that the ultrafiltration tube is easy to grow mold in summer. The types of mold include Bacillus, yeast mold and Geotrichum candidum, etc. The mold is attached to the wall of the ultrafiltration tube and affects the permeation. Once the circulating flushing water produces mold, it will make the ultrafiltrate stink. After the mold is brought into the electrophoresis tank, the electrophoretic coating will be decomposed, corrupted and smelly, and the electrophoretic performance will be deteriorated, resulting in the scrapping of the electrophoretic coating solution. At the same time, mold dealers may also plug the flushing nozzles, causing flushing failures.
The reason for the mold growth is that the water-based paint contains a large amount of organic matter, such as dicephexan, dicephexamine, etc., which are rich in nourishment for the mold, especially at 28~30°C, which is more favorable for the growth and reproduction of the mold. condition. At the same time, due to the large number of water outlets of the ultrafiltration membrane, there are many opportunities for the ultrafiltrate to meet the air at an angle, and in the circulating flushing area, if the volume of the water storage tank is large, most of the washing water will be recycled during the washing process, which is beneficial to mold production. reproduction.
For this reason, it is necessary to try to prevent the survival of mold, and the following measures can be taken.
a. When designing the ultrafiltration system, the contact angle between the ultrafiltrate and the air should be reduced, and the volume of the flushing water storage tank in the circulating flushing area should be as small as possible, so as to shorten the recovery period of the flushing water and inhibit the reproduction of mildew.
b. Add an appropriate amount of antifungal agent to the water-based paint to prevent the water-based paint from multiplying. Antifungal agents mainly include sodium pentachlorophenate, α-naphthol and ethyl benzoate.
The principle of adding antifungal agents to electrophoretic coatings is that it is less toxic to the human body and has strong antifungal ability; it has good mutual solubility for electrophoretic coatings; it has little effect on the performance of electrophoretic coatings, such as the conductivity, pH value, and throwing power of coating liquids. , stability and coating appearance, etc.
