1 Preface

Powder coating is a decorative and protective coating that contains 100% solid content and is dispersed in the form of powder using air as a dispersing medium. It is applied in the form of powder coating (including electrostatic spraying, etc.) and then cured into a film through high-temperature baking. At present, it has become a recognized 4E coating that meets the requirements of high production efficiency, excellent coating performance, ecology, and economy. It has the advantages of energy conservation, environmental protection, durability, high recycling rate, and diversity in color and effect. With the improvement of people's living standards and increasingly strict environmental requirements, powder coating products will be applied to more fields, and the development prospects will become better and better.

With the maturity of production and construction technology in the powder coating industry, the market's requirements for powder performance are also increasing. General powder coatings are difficult to solve the problem of fertilizer edges on sprayed boards or workpieces. Through experiments, the production of anti fertilizer edge household matte powder coatings is studied from the perspective of formula design.

2 Experimental section

2.1 Experimental Equipment

Twin screw extruder SLJ-32, small mixing cylinder GHJ-30, vertical grinder ACM-01, electrostatic spray gun, high temperature electric oven, gel time meter QT-JII, electronic balance, gloss meter, etc.

2.2 Raw Materials

Carboxyl terminated resin 1: acid value 69.8mgKOH/g, viscosity 4850mPa· s/200℃；

Carboxyl terminated resin 2: acid value 71.4mgKOH/g, viscosity 3320Pa· s/200℃；

Carboxyl terminated resin 3: acid value 47.5mgKOH/g, viscosity 4960Pa· s/200℃；

Bisphenol A-type epoxy resin E=0.125, softening point 90 ℃;

Precipitation barium sulfate, leveling agents, and other additives.

2.3 Experimental steps

1. Accurately weigh according to the designed formula, mix thoroughly in a small mixing tank, and then use a twin-screw extruder to extrude and cool the tablets for crushing. After cooling, add a small amount of alumina and grind it in a vertical grinder;

2. Take a portion of the ground powder spray plate, place it in a high-temperature electric oven to bake and solidify, cool it down, observe its appearance, and conduct a series of physical property tests. Take another portion of the powder for gelation time testing and record the data;

3. Repeat the experiment once to ensure the accuracy of the results.

From Table 1, it can be seen that polyester resins with different viscosities and acid values, as well as different resin contents, have a significant impact on the appearance of powder coatings in terms of gloss and leveling effect due to the differences between the adhesives during gelation, and have a greater influence on the powder's resistance to fertilizer edges. Choosing the appropriate resin and reducing the resin content appropriately can shorten the flow time during powder solidification, which is beneficial for obtaining a coating with good anti fertilizer edge. When the baking temperature is high, the melting and flow time of the coating is shorter and the glossiness of the coating is lower for powders with the same formula, which is beneficial for improving the anti fertilizer edge performance of the powder. After adding promotion, the glossiness of the coating is significantly improved due to the accelerated reaction rate, which is not conducive to the production of matte anti fat edge powder. Adding white carbon black or anti fertilizer edge additives can significantly improve the phenomenon of surface fertilizer edge, and when white carbon black and anti fertilizer edge additives are added at the same time, they can have a more prominent effect.

3 Conclusion

With the continuous maturity of powder coating production and construction technology, as well as market demand, some special requirements for powders are also increasing. When making matte anti fertilizer edge powder, the following points should be noted:

1. Choose resins with appropriate acid value and viscosity, as well as matching curing agents, fillers, etc. Some materials such as bentonite can also improve the phenomenon of fertilizer edge after addition, but excessive addition can lead to poor coating leveling, so attention should be paid to controlling the amount added.

2. Controlling the resin content and appropriately increasing the baking temperature are beneficial for obtaining coatings with stable gloss and good anti fat edge effect.

3. When designing the formula, adding an appropriate amount of additives such as anti fertilizer edge additives, white carbon black, or other additives can significantly prevent fertilizer edges.

In summary, improving the fertilizer edge performance of powders requires comprehensive consideration of various aspects, understanding the changes and impacts brought about by different changes, and manufacturing better and more in line with industry development trends powder coating products while meeting market demand.