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 f ast-reacting) and conventional powder coating systems and allows to produce coatings with improved properties. The process uses the solubility of comp ressed gases in melts of coating polymers at pressures up to 220 bar. The s ingle 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 mix er the melts are homogenized and simultaneously compressed carbon dioxide i s dissolved. The so-formed solution is depressurized directly afterwards ov er a nozzle into a spray tower. Thereby, the melt is atomized into fine dro plets and cooled by the expanding gas. The droplets reach the solidificatio n point of the melt and fine solid particles are formed. The particle size. particle size distribution and the morphology of the powders could be adju sted by the operating parameters of the plant.