What are the common disadvantages of the daily use of the paint coating of the curtain coater? Orange peel: When the coating film dries and hardens, a partial or all orange peel-like uneven surface occurs on the surface of the coating film.
Drench coater
There are many reasons for orange peel. In summer, it is generally due to the high temperature of the construction environment and the fast volatilization of the solvent, which causes the coating of the curtain coater to dry during the leveling process. It is recommended to add an appropriate amount of slow when mixing the paint. Dry water, reduce the speed of surface drying.
But it should be noted that the slow-drying water should not be added too much, otherwise the gloss of the paint will increase and the drying will slow down, which will affect the later stacking and packaging of the workpieces, and affect the delivery time.
In addition, the high spray viscosity of the curtain coater paint can also cause this phenomenon. Adjusting the appropriate spray viscosity and oil output is also a very critical factor.
Pinholes: The bubbles are enclosed in the wet coating liquid during the coating process. Because the bubbles are difficult to volatilize and escape, the wet coating film and the coated object have poor wettability, and there are small holes on the surface of the coating film. , Spray coating is more prone to pinholes than dip coating and curtain coating, and oily system coatings with excellent wettability have less chance of pinholes.
During defoaming, air bubbles migrate from the bottom of the wet coating film to the surface. Due to the high temperature of the construction environment, the coating film is too thick, and the air bubbles have not been completely separated, the coating film is already dry, so that the path of the bubbles cannot be leveled. The air bubbles cannot escape completely, resulting in pinholes.
At this time, it is necessary to adjust the drying speed of the paint. The addition ratio of the curing agent can be appropriately reduced, and a small amount of slow-drying water should be added. However, the ratio of the curing agent should not be too low to prevent the paint film from drying completely. The film becomes soft and the scratch resistance deteriorates.
Whitening/Whitening: The air humidity is too high, the solvent in the coating film will volatilize and absorb heat, so that the air temperature on the surface of the coating film will decrease and reach the dew point, and the water vapor will condense and penetrate into the coating film, causing the water vapor and the coating film to become milky white. (Partially or fully).
