Volker Rekowski

Manufacture of Powder Coatings by Spraying of Gas-Enriched Melts

An alternative process for the manufacture of powder coatings was developed. The continuously operated process is applicable to new (low-melting and fast-reacting) and conventional powder coating systems and allows to produce coatings with improved properties. The process uses the solubility of compressed gases in melts of coating polymers at pressures up to 220 bar. The single components of a powder coating mixture are melted in separated tanks and are dosed to a static mixer by means of high-pressure pumps. In the mixer the melts are homogenized and simultaneously compressed carbon dioxide is dissolved. The so-formed solution is depressurized directly afterwards over a nozzle into a spray tower. Thereby, the melt is atomized into fine droplets and cooled by the expanding gas. The droplets reach the solidification point of the melt and fine solid particles are formed. The particle size, particle size distribution and the morphology of the powders could be adjusted by the operating parameters of the plant.