How to solve the problem of coating powder agglomeration in coating powder production?

Considering the internal reasons of powder coatings, the main reason is that the glass transition temperature of powder coatings is low. The reason for the low glass transition temperature of the powder coating is that the glass transition temperature of the resin, curing agent and additives is low, and the main reason is that it is related to the low glass transition temperature of the resin. When the glass transition temperature of the resin is low, the glass transition temperature of the powder coating is also low, which is easy to make the powder coating agglomerate.

In order to solve the problem of agglomeration in the production of powder coatings, first of all, when designing the formulation of powder coatings, it is necessary to select resins, curing agents and additives with high glass transition temperatures, the most important of which is the selection of resins. When choosing a high glass transition temperature When the resin is used, the softening point of this resin is generally low, and the melt viscosity is also high under the curing temperature condition, and the leveling property of the coating film of the powder coating is reduced. In addition, in the powder coating formulation, the leveling agent used is a viscous liquid, and the glass transition temperature of some curing agents is low. When their dosage increases, the glass transition temperature of the powder coating will drop significantly, thus affecting the resistance of the powder coating. Unity. Although the glass transition temperature of the poly resin used in polycool powder coatings is above 60°C, the glass transition temperature of the powder coatings will also drop significantly after the powder coatings are formulated with TGIC and PT910 curing agents. The performance is not as good as the polyhexy epoxy powder coating prepared with polyester resin with a glass transition temperature of 53-58 atm. This is because the curing agent epoxy resin used for polyphenol epoxy powder coatings has little effect on the glass transition temperature of polyphenol epoxy powder coatings.

In order to improve the problem that the powder coating is easy to agglomerate, a loosening agent with anti-agglomeration effect can be added to the powder coating. This loosening agent is added when the powder coating raw materials are premixed. In addition, there is another way to add loosening agent to powder coating semi-finished or finished products. A commonly used loosening agent is fumed silica. It is added in the fine grinding process or in the finished product.

Considering external reasons, the environmental temperature and production process of powder coating production are important factors affecting the aggregation of powder coating products. When the environmental temperature of powder coating production increases, the thermal movement of low-molecular organic compounds in powder coatings will be accelerated. The softening of the low-molecular-weight compounds in the high-molecular compound makes the powder coating easy to agglomerate; and when the temperature of the powder coating itself is too high, it also makes the powder coating easy to agglomerate.

From the perspective of production process, if the molten extrusion mixture is not cooled sufficiently on the cooling rod and cooling belt, the material temperature of the crushed material will be higher; in the process of fine grinding, a large amount of heat is generated by the collision of thousands of materials, Restricted by the ambient temperature conditions, it cannot dissipate heat in time, so that the temperature of the material rises by 2~3°C. In this way, the temperature of the powder coating product may reach above 35°C, or even reach below 40°C. Dissipated, the temperature is always kept high, and the powder coating is agglomerated due to the intense thermal movement of low molecular weight organic and high molecular compounds. In order to make the powder coating not easy to agglomerate, the following measures should be taken.

(1) The material before entering the fine pulverizer is allowed to cool down to room temperature during the tablet cooling and crushing process.

(2) Take cooling measures to reduce the ambient temperature of the household to below 35°C, preferably around 30°C.

(3) Use methods such as central air conditioning, local compartment cooling, or air-conditioning through the suction port of the fine pulverizer, so that the temperature of the powder-uncoated product does not exceed 3 ℃:. When the temperature is higher than this, it is necessary to open the packaging bag of the powder coating product and place it in a room with a lower temperature to lower it to room temperature. After confirming that the powder coating in the bag is not agglomerated, the final packaging is carried out. ; In addition, powder coating products can also be received in an open metal tank first, and then packaged after cooling to temperature. If it is found that the powder coating products in the packing box have agglomerated, it needs to be screened with a vibrating sieve before repacking.