The main factors affecting the precipitation of electrophoretic paint liquid in general are:
1. The entry of impurity ions with homogenous or heterogeneous impurity ions is bound to react with the charged resin of the coating to form some complexes or precipitates. The formation of these materials destroys the original electrophoretic properties and stability of the coating.
The sources of impurity ions are as follows:
(1) Impurity ions inherent in the coating itself;
(2) Impurities brought in the preparation of electrophoretic paint liquid;
(3) impurities that are not thoroughly brought in by the pre-treatment washing;
(4) impurities brought in by the dirty water when the pretreatment water is washed;
(5) impurity ions generated by the dissolution of the phosphate film;
(6) Impurity ions generated by the dissolution of the anode. From the above analysis, it can be known that the quality of the pretreatment of the coating should be strictly checked. This is not only necessary to improve the quality of the product, but also to maintain the stability of the electrophoretic paint. At the same time, from the above analysis, it can be explained how important the quality of pure water and the choice of phosphating solution (supporting).
2. Solvent In order to make the electrophoretic coating have good dispersibility and water solubility, the coating original paint often contains a certain proportion of organic solvent. In normal production, the consumption of organic solvents is replenished in time as the refinishing work progresses. However, if the production is not normal or the temperature is too high, the solvent consumption (volatilization) is too fast and cannot be replenished in time, and the working lacquer will change when the content is reduced below the lower limit, which makes the coating film thin and serious. At the same time, the resin in the paint liquid is coagulated or precipitated. Therefore, in the tank management process, the manager should pay attention to the change of the solvent content in the electrophoretic paint liquid, and if necessary, carry out solvent content analysis and timely supplement the relevant amount of solvent.
3, temperature, various coatings have a range of adaptation to temperature. An increase or decrease in temperature accelerates or slows down the electrodeposition process, causing the film to thicken or thin. If the temperature of the paint rises too high, the solvent will evaporate too quickly, which will easily cause the paint to condense and precipitate. In order to keep the paint temperature in a relatively constant temperature state, a thermostat is required.
4. The solid content of the solid paint liquid not only affects the quality of the product coating, but also a factor that affects the stability of the paint liquid. If the solid content of the paint liquid is too low, the viscosity is lowered, which promotes the precipitation of the paint liquid. Of course, too high solids are not enough, because the coating is too high, the entrainment increases after the swimming, the loss increases, the coating utilization is reduced, and the cost is increased.
5, cycle agitation In the production process, managers must always pay attention to the circulation of the electrophoretic paint is good, some instrument pressure (such as filters, ultrafilter) is normal. Ensure that the paint liquid is cycled 4-6 times per hour, and the flow rate of the bottom paint liquid is about twice the flow rate of the liquid paint liquid. Do not make the electrophoresis tank form a dead angle. Do not stop mixing unless it is special.
1. The entry of impurity ions with homogenous or heterogeneous impurity ions is bound to react with the charged resin of the coating to form some complexes or precipitates. The formation of these materials destroys the original electrophoretic properties and stability of the coating.
The sources of impurity ions are as follows:
(1) Impurity ions inherent in the coating itself;
(2) Impurities brought in the preparation of electrophoretic paint liquid;
(3) impurities that are not thoroughly brought in by the pre-treatment washing;
(4) impurities brought in by the dirty water when the pretreatment water is washed;
(5) impurity ions generated by the dissolution of the phosphate film;
(6) Impurity ions generated by the dissolution of the anode. From the above analysis, it can be known that the quality of the pretreatment of the coating should be strictly checked. This is not only necessary to improve the quality of the product, but also to maintain the stability of the electrophoretic paint. At the same time, from the above analysis, it can be explained how important the quality of pure water and the choice of phosphating solution (supporting).
2. Solvent In order to make the electrophoretic coating have good dispersibility and water solubility, the coating original paint often contains a certain proportion of organic solvent. In normal production, the consumption of organic solvents is replenished in time as the refinishing work progresses. However, if the production is not normal or the temperature is too high, the solvent consumption (volatilization) is too fast and cannot be replenished in time, and the working lacquer will change when the content is reduced below the lower limit, which makes the coating film thin and serious. At the same time, the resin in the paint liquid is coagulated or precipitated. Therefore, in the tank management process, the manager should pay attention to the change of the solvent content in the electrophoretic paint liquid, and if necessary, carry out solvent content analysis and timely supplement the relevant amount of solvent.
3, temperature, various coatings have a range of adaptation to temperature. An increase or decrease in temperature accelerates or slows down the electrodeposition process, causing the film to thicken or thin. If the temperature of the paint rises too high, the solvent will evaporate too quickly, which will easily cause the paint to condense and precipitate. In order to keep the paint temperature in a relatively constant temperature state, a thermostat is required.
4. The solid content of the solid paint liquid not only affects the quality of the product coating, but also a factor that affects the stability of the paint liquid. If the solid content of the paint liquid is too low, the viscosity is lowered, which promotes the precipitation of the paint liquid. Of course, too high solids are not enough, because the coating is too high, the entrainment increases after the swimming, the loss increases, the coating utilization is reduced, and the cost is increased.
5, cycle agitation In the production process, managers must always pay attention to the circulation of the electrophoretic paint is good, some instrument pressure (such as filters, ultrafilter) is normal. Ensure that the paint liquid is cycled 4-6 times per hour, and the flow rate of the bottom paint liquid is about twice the flow rate of the liquid paint liquid. Do not make the electrophoresis tank form a dead angle. Do not stop mixing unless it is special.
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