From the middle of the last century roll coating development, are mainly roller coating. The production of aluminum trim coil is made by the precision coating machine, which uniformly spreads the same thickness coating on the surface of the preprocessed aluminum trim coil, and uniformly enters the oven with the exhaust device, and roasts and solidifies by the infrared or hot air circulation. A complete roller coating film with a certain thickness is obtained by cross-linking the film at a specific temperature.
Roller coating is the carrier of coating roller. Coating roller forms a wet film with a certain thickness on the surface of coating roller. The coating roller contacts with the coated object in the process of rotation to coat the coating surface. Roller coating is suitable for metal sheet coating, especially for high-speed coating of metal sheet. Roller coating requires good leveling, wetting and adhesion, a certain degree of hardness, flexibility and wear resistance, as well as good weather and stain resistance, baking and curing into film speed. Roller coating has the following characteristics:
With high-speed automatic painting operation, the painting speed is fast and the production efficiency is high. The linear speed is generally above 60m/min, and the highest is up to 244 m/min.
Paint does not produce fog, paint use rate close to 100%;
The film thickness can be controlled accurately and uniformly.
May be positive, reverse at the same time coating.
But the roller only ADAPTS to the plane coating, does not adapt to other forms of coating. Because the roller applicator adopts the unified paint circulation transportation and recovery system, the amount of paint input is large, which is not suitable for multi-variety and small-batch production. The coating is transferred to the coated surface by wet film on the surface of the coating roller, the solvent is volatile, the coating viscosity is easy to change in the process of roller coating, if the process conditions are not controlled properly, the film is easy to produce roller mark.
Baking coatings generally belong to thermosetting coatings (except for roller fluorocarbon coating). In a broad sense, the paint that must be baked to a specified temperature before it can be interlinked into a film is called baking paint. The baked coating is more rigid in molecular structure and superior in hardness, mechanical strength, durability and acid and alkali resistance.
Baking coatings are classified into two types according to baking temperature. Baking temperature at 100 ~ 150 ℃ for medium temperature baking coating; Baking temperature greater than 150 ℃ for high temperature baking paint. At present, aluminum coil coating is used for high – temperature baking paint.
After deep processing, products exposed to the outdoors for a long time are exposed to the wind, rain and rain, especially under the irradiation of ultraviolet light, which makes the coating fade and aging and decompose. In order to meet the requirements of the weather resistance of aluminum coils, the organic baking coating PVDF fluorocarbon coating with super weather resistance can be adopted.