Common problems and solutions of waterborne paint for furniture
Waterborne paint is a new type of coating material. Its biggest feature is that water replaces the organic solvent in the oily paint as the dispersion medium. Compared with the oily paint, it does not use organic solvent, contains no harmful substances such as benzene, toluene, xylene, formaldehyde, etc., is non-toxic, non irritating, resource saving and more environmentally friendly. In order to have a principled understanding of the performance and construction of waterborne paint, it is necessary to fully understand its film-forming mechanism.
I. different film-forming mechanisms of water-based single and two-component coatings
The water-based coating is mainly composed of water-based resin, pigments and fillers, additives and water. Its film-forming process and solvent coating have completely different mechanisms and are relatively complex, mainly because of the special structure of water-based resin and the existence of water.
After the water-based one component coating is applied on the surface of furniture, the moisture begins to volatilize. With the decrease of water content, the arrangement of dispersed latex particles becomes more and more compact from evacuation. Under the action of capillary pressure and surface tension, the latex particles are extruded and deformed, and then they fuse and diffuse with each other to form a film.
In the process of film formation, the reaction of polyisocyanate and water, the coacervation of polyol and polyisocyanate particles, the reaction of polyol and polyisocyanate and so on will affect the whole drying process of the two-component waterborne coating.
It can be seen that “water” is the lifeblood of water-based paint. What problems will be encountered in the construction process of using water-based paint? Next, we will classify these problems and analyze the causes, and give solutions.
II. Common problems and solutions of waterborne wood paint
1. The paint film is wrinkled or cracked
Problems: under high temperature, the surface of the thick water-based paint film dries rapidly to form a film, while the thick inner layer dries slowly. During the drying process, the flow of the paint produces poor tension, resulting in uneven surface of the final film, i.e. wrinkle; or directly leading to the cracking of the primer film.
Solution: during the construction, do not apply thick paint once, but thin paint several times; at the same time, keep the furniture temperature above 15 ℃ and humidity below 70%, in a well ventilated environment, let the paint film dry normally.
2. Poor adhesion between paint layers
Problems: the direct cause of poor adhesion between layers of paint film is that there is no grinding between base materials or coating during construction, resulting in poor adhesion (because water-based paint is physical film-forming, which depends on surface friction to improve adhesion); the indirect cause is high temperature in summer, and the time required for the interface between wet paint film and dry paint film to form a firm layer is insufficient, so that the adhesion is affected.
Solution: the construction personnel are required to fully polish each layer to enhance the adhesion during construction, and the construction should be arranged in the morning and evening to ensure the internal quality of the product.
3. White paint layer
Problems: it is mainly caused by too much humidity in the construction environment and too thick film during the construction. Because of the high temperature in summer, the air humidity in some areas is relatively high. The surface drying time of the paint layer accelerates with the increase of temperature, but the actual drying time is relatively slow; the painter may ignore the actual drying time in the construction process, and immediately apply another layer of paint after the surface drying of the paint layer, resulting in the phenomenon that the bottom paint layer is not completely dry and the paint layer is white.
Solution: the construction interval shall be well controlled, and the next process construction shall be carried out under the condition that the paint layer is dry.
4. Paint layer flow hanging
Problem: the main cause of the problem is too much water, too thin, too thick painting, or too much air humidity, the paint layer drying slowly, resulting in sagging.
Solution: during construction, pay attention to adding appropriate water to dilute, thin coating for many times, and select low humidity weather for construction.
At present, the automatic equipment is more conducive to the furniture spraying process, so that the enterprise can produce efficiently and quickly, at the same time, it also greatly reduces labor, and is more safe and environmentally friendly. Now, there are more mature machines in the market, such as reciprocating machine, five axis machine, spray machine, vacuum spray machine, etc.
Line vacuum spraying
The paint utilization rate of line vacuum is over 97%, which is about 60% less than that of manual spraying. Meanwhile, during the working process, the atomized paint is recycled in the quasi closed space, without leakage and emission.
Sharp vacuum spraying production line
1. Green environmental protection: vacuum spraying can quickly and evenly adhere the paint to the surface of the line, without waste and pollution;
2. High processing efficiency: shorten the processing cycle of the line, reduce the flow time of the workpiece, and improve the processing efficiency;
3. Wide range of application: vacuum spraying machine can be widely used in the painting of furniture and cabinet, process composite door, door jamb line, skirting line, curtain rod, mirror frame and other products (waterborne paint, UV paint, wood wax oil, preservative).