Research on the Application of Acrylic Resin in Metal Effect Powder Coatings

                                                                                                Paint industry:
abstract
Abstract: Based on more than 20 years of industry experience, the author of this article has accumulated examples of the application of acrylic powder and metal powder coatings, and proposed the formula design concept of acrylic metal powder, especially in the new way of modifying metal paint powder. Some key points in its formula design, cost, manufacturing, and spray application were elaborated. This brief introduction aims to provide some reference for the future application of acrylic acid. I believe that driven by the needs of customers and the market, the vast number of powder coating R&D personnel have enriched the surface effects of metal effect powder coatings through the use of acrylic systems.

Introduction to Metal Powder Coatings and Acrylic Powder Systems
As two "high-value" products in the powder coating industry, metal effect powder coatings and acrylic powder coatings have always shown a high and handsome image in the market. In recent years, domestic enterprises have made rapid progress in metal effect powder coating technology, and acrylic powder coatings are also increasingly used in the domestic powder coating market.
Metal powder coating is a solid powder coating composed of resin, curing agent, pigment, filler, and additives. Through bonding and other processes, effect pigments such as aluminum powder and pearl are bonded to the powder coating, resulting in a coating with a metallic texture and colorful effects. This product is mainly used for surface protection and decoration of steel substrates, aluminum and aluminum alloy substrates, and other metal substrates. The core of its formula design and production process lies in meeting customers' needs for metal effect appearance and stable on-site construction.
Acrylic powder coating is a thermosetting powder coating composed of acrylic resin, curing agent, pigment, filler, and additives. Thermosetting acrylic resin is a type of acrylic resin obtained by copolymerizing acrylic monomers containing active functional groups, with the main chain being acrylic acid and the side chains carrying active functional groups. The acrylic ester group has a glycidyl ester (epoxy group) or hydroxyl and carboxyl functional groups. Acrylic resin is synthesized using monomers such as acrylic acid, methacrylic acid, and esters. In these monomers, in addition to double bonds used for addition polymerization reactions, some monomers also carry reactive groups such as hydroxyl, carboxyl, glycidyl, and acylamino groups. Due to the presence of these reactive functional groups, acrylic resin carries reactive functional groups and can undergo cross-linking and curing reactions with curing agents to form films.

Application testing of acrylic resin in powder coatings
2.1 Design Ideas
Metal effect powder coatings are mainly made by the combination of base powder and metal pigments to produce products with good effects and stable construction. Setting aside the binding process, the core of the formula is the design of the base powder and the selection of metal pigments. Based on years of experience, the author has summarized that the base powder should meet the dispersion and arrangement requirements of metal pigments, and highlight the effect of metal pigments together with the base color.
In summary, the base powder needs to provide a transparent coating, strong wettability, and excellent leveling. Through practical application, acrylic powder coatings have shown excellent performance in these aspects, with good wetting and layout adaptability to metal pigments, while maintaining excellent leveling properties.
The testing direction uses GMA acrylic resin+DDDA powder system as the base powder, mixed with aluminum powder and pearl pigment of different particle sizes for spraying, and compares the surface differences of the coating film.
2.2 Preparation and Testing Results of Acrylic Metal Powder Effect Powder
Testing the dispersibility of aluminum powder in a transparent system: Pure silver metal powder made by adding aluminum powder to transparent powder, especially silver glitter aluminum powder, is a mainstream product in the market. We chose three base powder systems: polyester/TGIC, polyester/epoxy, and acrylic/DDDA, and combined them with an acrylic+polyester system. Mix 5% PCR212 and 2% powder 8550 separately, and compare their metallic effect and coating appearance.
From the formula in the table above, it can be seen that compared to conventional polyester/TGIC and polyester epoxy coatings, there is no cloud like phenomenon caused by general pigments, nor is there a significant color difference with film thickness. But we also found that there are significant differences in film thickness or color variations in areas such as the flow angle of the workpiece.
Compared to polyester or polyester epoxy systems, the metallic effect produced by acrylic systems is much more transparent and shimmering. In silver glitter systems, the metallic texture and angular shimmer are very prominent, and the arrangement of aluminum powder in the base powder is relatively neat. In the fine silver system, the overall surface is oily and the aluminum powder is arranged inside the coating. This metallic texture is closer to the effect of paint overlay.
Due to the cost of the acrylic acid system, we also developed a composite system of polyester and acrylic acid. Due to time constraints, many indicators of the two may differ significantly. When the acrylic acid ratio is less than 20%, the overall surface is poor. When the acrylic acid ratio reaches nearly half, there is also a similar metallic effect to acrylic acid. At present, we have only conducted dry touch tests. In the future, we can try to conduct tests using both internal extrusion systems to find a balance between cost and metallic texture.
Testing the dispersion effect of semi transparent base powder on metal pigments: From the previous experiment, it was found that the acrylic system has superior arrangement and wetting properties for aluminum powder. Therefore, we can use organic pigments to make some semi transparent materials, such as semi transparent red, semi transparent yellow, semi transparent blue, etc., and compare them with the polyester TGIC system. Mix these semi transparent powders with aluminum powder. Comparing the polishing and coloring effects of aluminum powder, due to the poor dispersion of pigments in the acrylic system, the base powder process needs to be adjusted to ensure that the pigments can be fully dispersed.

By utilizing the wettability of acrylic acid and combining it with the metallic texture of aluminum powder, another type of paint like effect can be achieved. Considering the covering power of metallic pigments, the amount of pigment used can also be reduced. After binding the base powder with the desired metallic effect pigment. Secondly, to sublimate the effect of acrylic acid, aluminum powder is uniformly contained in the acrylic film, forming a uniform and transparent semi transparent aluminum coating. The color can achieve various effects such as red, yellow, blue, and green by selecting the type of acrylic acid, and then combined with the metallic effect of the base coat. Mirror silver can form a similar effect to paint, and fine glitter silver can achieve a similar effect to paint. These products have broad development potential in the hub industry, especially in the aftermarket. (Definition of Middle Surface Integration: Based on the acrylic powder coating system, providing a single coating with color to replace the current 2-coating process of color paint and acrylic transparent powder.)

Key points and application prospects in 3 applications
The advantages of acrylic acid in powder applications have brought new effects, but we cannot ignore its disadvantages, which are also key points we need to pay attention to in our daily work. The lack of acrylic acid can cause pollution to other powder systems, and acrylic powder coatings are prone to interference during production and construction applications, with strict requirements for the production and construction environment and conditions. Whether it is the application of paint to powder or topcoat as mentioned earlier, pollution is an unavoidable issue.
In addition, the melt viscosity of acrylic coatings is relatively high, the pigment dispersion is poor, the resin itself has strong rigidity, and the impact strength is slightly worse than other powder coatings. The cost of acrylic acid is high, and its selling price is much higher than other powder coatings, mainly due to the price of resin. We call on domestic acrylic acid production enterprises to improve the cost-effectiveness of acrylic resin suitable for the market through more research and development.
As mentioned at the beginning, the acrylic resin used in this study is the GMA/DDDA curing system. There are many other systems of acrylic acid, and we can make more attempts to compare and find the best combination of performance and cost. How to utilize the advantages of acrylic acid to develop more new products in the future while improving and avoiding its disadvantages through raw materials, formula design, processes, etc. is of paramount importance.

4 Conclusion
In summary, currently, the application of acrylic acid in other coatings or industries is minimal compared to powder coatings, as it is influenced by factors such as usage environment, process, cost, and workpiece equipment. Although acrylic acid chemistry is complex, as powder technicians, we are engaged in the environmental protection industry that is related to green environment. It is our responsibility to improve the expansion, cross-border development and application of the powder coating industry, which is the mission of R&D technicians. The "paint to powder effect" of powder is related to the customer's experience and construction and usage costs. We believe that in the future development of coatings, more industries and customers will recognize the advantages of paint to powder. In this trend, the role of acrylic acid is indispensable. We hope that this comprehensive report can inspire our peers and bring more good products. Thus ushering in a new peak in the powder industry.