Under what circumstances will the color difference problem occur
1. Paint. Due to the uneven mixing of the paint or the large difference in the viscosity of the paint in different barrels, the paint extends from the feed port side to the return port direction in the material tray, and a color difference band appears. In addition, change the color of the paint. The special ratio has a large color contrast. Due to the unclean cleaning and pollution, the color difference is caused.
2. Substrate. The size of the spangles on the substrate is different, and many small pits of different sizes are formed at the grain boundary, which affects the color difference of the board surface, especially for light colors. It is better to choose no spangle or small spangle substrate.
3. Chemical coating treatment. Improper chemical coating process results in too thick chemical coating film, insufficient plate temperature after drying, or damage to the coating roller body, resulting in the formation of macular patches after drying, resulting in color difference of color coated plates, especially light colors.
4. Film thickness. The film thickness stability has a great influence on the color difference of the color-coated board. The adjustment of film thickness is mainly through: coating viscosity, adjusting the gap between the sticking roll and the coating roll of the roll coater, changing the roll speed of the coating roll and the sticking roll, adjusting the coating roll and the strip steel support roll. pressure.
5. PMT. PMT represents the peak temperature the strip needs to reach when the coating is fully cured. The stability of PMT has a great influence on the color difference of color-coated boards. The adjustment of PMT is mainly through: the change of strip steel specification will cause the change of PMT, the high or low local temperature will affect the PMT, the uneven thickness of the substrate, the change of PMT, and the change of temperature in the furnace due to seasonal changes.
6. Cooling water. Atomization cooling, the cooling water is not replaced in time, when the volatiles of the organic solvent in the furnace gas are cooled and condensed, and the cooling water is brought to the board surface, after being squeezed by the squeeze roller, it will cause color difference on the board surface. During production, the cooling water should be properly overflowed to allow the condensed volatiles to overflow and remove in time to avoid color difference on the board surface.
