Multiple intermediate coats are applied in one spray booth and are applied "wet-on-wet". It is necessary to pay attention to their paintability and solve the following problems.
(1) Fusion of paint mist Due to the different functions of anti-cracking paint, interior color paint, pearlescent paint, and black paint for window frames, the resins used are also different. Coupled with different suppliers, during the multiple spraying process, a large amount of paint mist landed on the surface of the car body, resulting in the problem of difficult fusion. Difficulty in miscibility detracts from the appearance of the topcoat. The coatings used should be easily soluble, and there are more requirements for the storage stability and coating conditions of the coatings, so as not to affect the appearance.
(2) Anti-sagging, air-bubble porous coating and coating "sag, air bubble" limit thickness, about 40-50μm. Generally, when using the "wet-on-wet" process to apply coatings for different purposes, it is difficult to adhere, and "sagging" and "bubble holes" occur when the coating is thick, which cannot However, in fact, the film thickness of the recoated part exceeds "50μm" in many cases. Nowadays, depending on the diversification and the suppression of the curing reaction speed of the resin, it is possible to exceed 30μm and the critical film thickness.
(3) Shrinkage cavity resistance After the intermediate coating, special black coating is carried out on the window frame. Extra black paint is an acrylic resin paint, and the surface tension of the primer paint is different from that of the "shrinkage cavity". Therefore, it is necessary to rely on surface conditioners and the like to prevent shrinkage cavities.
