Color coated panels will appear color difference problems in several cases

Aug 16,2023

Under what circumstances will the color difference problem occur on the prepainted board

1 Paint. Due to uneven mixing of paint or large differences in the viscosity of paint in different barrels, the paint extends from the side of the feed port to the reflow port in the material tray, and a color difference band appears. In addition, replace the color of the coating, Terby is a large color contrast, due to unclean cleaning, pollution caused by color difference.

2 Substrate. The different sizes of the substrate zinc flowers form many small pits of different sizes at the grain boundary, which affects the color difference of the plate surface, especially for light colors. It is good to choose zinc-free or small zinc flower substrates.

3 Chemical coating treatment. Improper coating process, resulting in too thick coating film, insufficient temperature of the plate after drying, or the body of the coating roller is injured, and yellowing patches are formed after drying, resulting in color difference of the color coating plate, especially the light color is obvious.

4 Film thickness. The stability of film thickness has a great influence on the color difference of the color coating plate. The adjustment of film thickness mainly by: coating viscosity, adjusting the gap between the sticky roller and the coating roller of the roller coater, changing the roll speed of the coating roller and the sticky roller, and adjusting the pressure between the coating roller and the strip support roller.

5 PMT。 PMT represents the peak temperature required for strip to be reached when the paint is cured. PMT stability has a great influence on the color difference of prepainted plate. The adjustment of PMT is mainly through: strip specification changes will cause PMT changes, local high or low temperature will affect PMT, substrate thickness uneven PMT changes, seasonal changes furnace temperature changes and PMT changes.

6 Cooling water. Atomization cooling, cooling water is not replaced in time, when the volatiles of organic solvents in the furnace gas are cold condensed, as the cooling water is brought to the plate surface, after being squeezed by the squeeze roller, it causes color difference on the plate surface. In production, the cooling water should be properly maintained to overflow, so that the condensed volatiles can be removed in time to avoid causing the color difference of the board surface.