As a key process widely used in printing, packaging, electronics, energy and other fields, coating technology has developed rapidly with the progress of industrial technology in recent years. Whether it is a battery pole piece, an optical film, or a packaging material, the selection and application of coating technology directly affects the performance and quality of the product. Today, we will talk about several common coating methods, as well as their characteristics and application scenarios.
1. Compression roller coating
Compression roller coating is a common coating method in which the coating solution is transferred to the substrate by the pressure between the rollers. This method is suitable for higher viscosity coatings, and the amount of coating can be controlled by adjusting the gap between the rollers. The advantage of compression roller coating is that it is evenly coated and suitable for large-scale production, but the equipment cost is high and the rheology of the coating is required.
2. Scraper coating
Doctor blade coating is another common coating method, which mainly uses the doctor blade to scrape off excess paint to control the amount of coating. Scraper coating can be divided into several different types, such as air knife coating, comma scraper coating, etc.
(1) Air knife coating
Air knife coating uses a high-pressure air stream to blow away excess paint and is suitable for the production of coated paper. It has the advantage of not being in direct contact with the substrate and is suitable for the application of pressure-sensitive coatings, but the smoothness and gloss of the coating are poor.
（2）Comma scraper
Comma scraperIt is a new type of scraper coating method, which is suitable for coatings with high viscosity and high solid content. It has the advantage that the coating amount is easy to control and the coating accuracy is high, but the rheology of the coating is required.
(3) Wire rod coating
Wire rod coating, also commonly referred to:Wire scraper coating, which is a simple but very effective way to coat. Its core component is a high-precision round steel rod with stainless steel wires wound around it to form grooves of different shapes. The design of these grooves determines the amount of fluid transferred and the thickness of the coating.The working principle of wire scraper coating is to evenly scrape the coating solution on the surface of the substrate through the contact between the scraper and the substrate. The solids content of the coating solution and the diameter of the wire are the main factors affecting the coating amount. The higher the solids content, the greater the coating amount; The larger the wire diameter, the greater the coating weight. Therefore, by adjusting the wire diameter and the solids content of the coating solution, the coating amount can be precisely controlled.
3. Extrusion coating
Extrusion coating is a technique in which molten thermoplastics are extruded through a die to form a film and laminated onto a substrate. This method is suitable for the coating of plastic substrates, and is often used in the production of lithium battery pole pieces and packaging materials. The advantages of extrusion coating are that the coating amount is small, the price is cheap, and the environmental pollution is small, but the accuracy of the equipment is required.
4. Rotary coating
Rotational coating uses the centrifugal force generated by high-speed rotation to evenly spread the coating on the substrate and is suitable for the coating of polymer solutions. This method is widely used in the electronic information industry, such as the coating of flat panel display glass substrates. The advantage of rotary coating is that the coating thickness is uniform, but the coating speed is slower, making it suitable for small-scale production.
5. Curtain coating
Curtain coating is a non-contact coating technique in which the paint flows out of the nozzle to form a continuous film that falls onto the substrate like a curtain. This method is suitable for coating irregular surfaces, with excellent coating quality, simple operation and low cost. The future application of curtain coating is promising, and it may gradually replace air knife coating, especially in the field of inkjet printing materials and flexible packaging materials.
6. Spray coating
Spray coating is also a non-contact coating technique in which the paint is evenly applied to the substrate by means of a high-pressure spray. This method is suitable for high-speed coating operations, with a wide range of coating weights, smooth coating surface, and good hand feel. The advantage of spray coating is that it has low operating costs and is suitable for large-scale production, but it requires high rheology of coatings.
With the advancement of industrial technology, coating technology is developing towards two extremes: on the one hand, battery pole pieces and non-woven coating require very thick coatings; On the other hand, optical thin films and magnetic recording media require very thin coatings, even down to the nanometer level. Therefore, the key to the future development of coating technology is to select the appropriate coating method, strengthen the in-line detection and adjust the rheology of the coating.In addition, as the demand for high-speed coating increases, the rheological properties of coatings become a key factor in determining coating quality. The rheology of the coating affects not only the uniformity of the coating, but also the surface quality of the coating. Therefore, the future coating technology will pay more attention to the rheology research and control of coatings.
As an important process in modern industrial production, the selection and application of coating technology directly affect the performance and quality of products. Whether it is compression roll coating, scraper coating, extrusion coating, rotary coating, each coating method has its own unique advantages and application scenarios. In the future, with the continuous progress of industrial technology, coating technology will develop in the direction of more efficient and more accurate, providing better coating products for all walks of life.
So, the next time you see a sleek wrapper or a high-performance battery, think about the coating technology behind it, which is the "hero behind the scenes"!
