In recent years, the coating industry in our country is in the ascendance, and the total output of the coating also ranks in the forefront of the world, forming a related industrial group, actively promoting the technological revolution and development in the traditional coating field. With the continuous improvement of people's living standards, on the one hand, consumers feel that the high-gloss gloss coating after film reflection is more serious, harmful to people's eyes; On the other hand, consumers' aesthetic concept is more and more inclined to leisure, fashion and personalized. Coupled with booming demand from the country's auto and home appliance industries. These factors have led to a sharp increase in the demand for low-gloss coatings with a soft appearance. At the same time, how to produce coatings with extinction performance has become a problem that the coating industry needs to face. The matting agents commonly used in coatings are as follows:
1, polyethylene wax: wax is used earlier and widely used as a kind of extinction agent, it belongs to the organic suspension type of extinction agent. After the coating construction is completed, with the evaporation of solvent, the wax in the coating is precipitated, and the fine crystals are suspended on the surface of the coating, forming a layer of rough surface that scatters light and plays the role of extinction. The characteristics of wax as a matting agent are easy to use, and can give the film a good feel and water resistance, resistance to moisture and heat, anti-fouling. However, after the formation of wax layer on the coating surface, it will also prevent the evaporation of solvent and the infiltration of oxygen, which will affect the drying and recoating of the coating. The future development trend is to synthesize high molecular wax and silica to achieve better extinction effect.
2, metal soap: metal soap is a kind of extinction agent commonly used in the early days, it is mainly some metal stearate, such as aluminum stearate, zinc stearate, calcium stearate, magnesium stearate and so on. Among them, aluminum stearate is more used. The extinction principle of metal soap is based on its incompatibility with the paint components. It is suspended in the paint with very fine particles, and distributed on the surface of the film when it is formed, so that the surface of the film has microscopic roughness, and the reflection of light on the surface of the film is reduced to achieve the extinction purpose.
3, functional fine material body pigment, such as diatomite, kaolin, fumed silica and so on are special for the functional fine material extinction agent, it belongs to inorganic filling type extinction agent. When the coating is dry, their tiny particles will form a micro-rough surface on the coating surface, reducing the reflection of light to obtain the extinction appearance. The extinction effect of this kind of absorber is restricted by many factors. Taking silica as an example, when it is used as an extinction agent, its pore volume, average particle size and particle size distribution, dry film thickness and whether the particle surface has been treated and other factors will affect its extinction effect. The experimental results show that the extinction performance of silica with larger pore volume, uniform particle size distribution and the matching of particle size and dry film thickness is better.
In addition to the above three types of common matting agent, some dry oil, such as tung oil can also be used as a matting agent in the coating. It mainly uses the high reactivity of conjugated double bonds in tung oil to make the coating surface uneven and achieve extinction effect due to different oxidation and cross-linking speeds on the bottom surface of the coating.