Making powder coatings is a multi-step process
essentially composed of batching, premixing, extrusion and particle size reduction. It can be described as being semi-continuous because it begins as a batch process (weighing and pre-mixing) but evolves into a continuous process (extrusion and milling).
Basically, a compilation of somewhat dissimilar materials are blended, melted, cooled and then pulverized. Two major types of mixing are accomplished in successful processing. The resins, additives and pigments are distributed among themselves to create a consistent blend. Uniform mixing affords a consistent appearance and performance of the finished coating, while inconsistent mixing results in variable gloss, smoothness and quite possibly poor durability. It is therefore essential to achieve an adequate distribution of the raw materials.
Manufacturing powder coatings
also involves dispersing pigments throughout the resin system, which entails the de-agglomeration of the pigment. Most pigments naturally exist as agglomerates. The powder manufacturing process, and more specifically the extrusion process, endeavors to disperse these agglomerates to achieve a more consistent and intense color. Incomplete pigment dispersion results in uncontrolled color consistency. Finally, the particle size of the extrudate must be reduced from flakes to a particle size distribution usable with the customer's application equipment.