The main cause of powder coating agglomeration
Here, considering the external factors, the temperature of the environment is higher than 30 degrees; from the analysis of the composition of the powder coating, the glass transition temperature of the resin is lower than 60°C, and the leveling agent and brightening agent in the formula are excessive, and the powder coating There are more ultra-fine powders. The following is a brief description of some commonly used anti-caking methods of powder coatings from these aspects.
Selection of raw materials
Adjust the resin curing dosage and the ratio of pigments and fillers, and select a base material with a higher glass transition temperature of the resin and curing agent composition. The choice of polyester resin is very important. For example, terephthalic acid in the monomer has better anti-agglomeration and weather resistance than phthalic acid. In actual use, agglomeration of polyester resin is often found. The proportion of filler in the agglomeration formula is large, and the possibility of powder agglomeration becomes less.
In the formulation design process, try to add as little as possible or no additives that affect the glass transition temperature and storage stability, such as adding less leveling agents, wax-type matting agents and accelerators.
Adding the anti-caking agent to improve the looseness of the powder coating by internal addition, reducing the angle of repose of the powder coating and making the powder less likely to agglomerate. After adding, the affinity and cohesion between the film-forming substances in the powder coating can be adjusted to improve the anti-caking force of the powder coating. The agglomeration temperature improves the storage stability of the powder coating and the flowability of the dry powder; in addition, when the electrostatic powder is sprayed, the powder coating is not easy to block the spray gun. Hubei Laisi Chemical New Material Co., Ltd. dry powder flow agent 445 belongs to this category of additives.
Production process control
The extruded flakes should be cooled to room temperature and then sealed, and 10% of the space should be reserved; the crushing environment should be controlled at room temperature within 30 degrees, humidity below 70%, and cooling and dehumidification are required for upwards; if it does not affect the coating Under the premise, the particle size of the powder can be adjusted to be coarse. There are many ultra-fine powders in the powder. In the environment of high temperature and high humidity, powder clusters are prone to appear during spraying.
Requirements for transportation and storage
During storage and transportation, powder coatings will agglomerate due to moisture absorption in the air or due to pressure and elevated ambient temperature. Therefore, the transportation or warehouse storage temperature should not exceed 40 degrees. Of course, do not squeeze excessive weight.