Powder coatings are prepared in a compounding machinery in the solid phase by medium-intensity premixing the weighed-in components including base polymer, additives, pigments and fillers. This mixture is fed in the BUSS compounding machinery to the BUSS Kneader and compounded in the viscous melting phase. The melt is then fed to a cooling conveyor or similar, rolled out into a friable sheet, cooled and broken into chips via a mechanical knibler, and the chips are then ground down to precise grain size distributions or particle sizes.
Decisive for the compounding stage is highly efficient dispersive and distributive mixing at low product temperatures well below the base polymer crosslinking temperatures.
The BUSS Kneader’s specific capabilities really come to the fore in this application: Due to the operating principle of the compounding machinery, the enormous number of mixing cycles at moderate and uniform shear rates enables unsurpassed mixing efficiency and resultant product quality at maximum throughputs. The well-proven screw geometries cover a wide range of applications, and the modular process configuration system enables uncomplicated adaptation. The hinged barrel casing of the BUSS Kneader enables rapid access, easy cleaning prior to extreme colour changes, and high availability.