White car rims after powder coating
Application

Compounding systems for powder coatings

Thermoset powder coatings can be functional and/or decorative

Nowadays, powder coatings are generally understood to be thermoset powder coating, which is applied to surfaces via electrostatic application. With a burn-in and consequent crosslinking process, the surfaces receive their specific properties. These include both functional and decorative functions.

A huge color range of matt, semi-gloss and high-gloss colors, metallic effects, textures and soft-touch colors is available. The functional features range from antibacterial properties to corrosion protection. The major applications are general metal coating, household appliances, facade, furniture and car coating.

Polymer powder coatings have been used since the middle of the 20th century. Initially in the fluidized bed sintering process for which the component to be coated was preheated and immersed in a bath of swirled powder coating particles.

Here, high coating thicknesses of up to 500μm arose and arise up to current times. Initially, mostly thermoplastic plastics were used. During the 1960s, thermoset materials came to the fore step-by-step: epoxy, epoxy polyester (hybrid), polyester/PRIMID, polyester/TGIC, polyurethane as well as acrylate-based preparations.

Typical areas of application

Grey switch box prepared with powder coating compound coating
Granulate for powder coating, manufactured in a compounding system for powder coatings
Red granulate for powder coating, manufactured in a compounding system for powder coatings
Powder for powder coating the colors red, yellow and blue
Building facade clad with powder-coated panels.
Violet granulate for powder coating, manufactured on a compounding system for powder coatings
Mit Pulverlack beschichtete Küche als Beispiel für die Pulverlack-Compoundierung.
Red powder for powder coating, manufactured in a compounding system for powder coatings
Autofelge beschichtet mit Pulverlack, der mit einer Compoundier-Maschine für Pulverlack hergestellt wurde.
Blue powder for powder coating, manufactured on a compounding system for powder coatings

In addition to the excellent coating properties, powder coatings can play numerous further trump cards: this means that you can fully do without solvents (with VOC and others).

This is clearly noticeable in the application, utilisation rate (up to 95%) and the environmental and energy-relevant aspects of the entire process in comparison to alternative systems. The clearly defined coating thickness in a coating process denotes a further positive aspect.

The development trends of new conductive network technologies (e.g. UV), low burn-in temperatures, thinner coating thicknesses and a widening of the substrate range (glass, wood, plastics) must be named. Moreover, customized formulations with correspondingly small batch sizes are becoming more important.

Further insights into our options for the paint and coating industry

Benefits

BUSS compounding systems offer the following specific benefits

Multi-flight BUSS compounders achieve intensive mixing with a low overall specific energy input. This is because there is a high number of mixing cycles, optimally tailored to the respective process zone. The energy is almost exclusively introduced mechanically (dissipated) as shear energy in the compounding line.

The energy required for melting is introduced almost exclusively mechanically (dissipative) as shear energy.

The self-cleaning guarantees that the materials do not adhere to the surfaces, overheat and degrade. Therefore, it ensures that no impurities are caused which would influence product quality. The BUSS Co-Kneader achieves this via its oscillating and simultaneously rotary screw movement: all kneading flight surfaces clean themselves consequently on the stationary kneading pins in the housing. This effects continuous cleaning and at the same time conveying of the product.

The processing of a wide range of formulations with the same screw configuration can be a challenge. The BUSS Co-Kneader technology is meanwhile known for this specific capability. Thanks to a processing length which normally is only half as long as for comparable systems, moderate and adaptable shear rates and the large flexibility when designing screw configuration.

The separate execution of compounding in the BUSS Co-Kneader and pressure build-up in the discharge unit enables processing at low pressures and temperatures. Thus, the configuration of application-specific screw geometries in each process zone can guarantee an optimized temperature profile in each process zone.

Thanks to the hinged BUSS Co-Kneader housing design with a unique opening angle of 120°, optimum access to the process components is guaranteed. This enables easy adaptation of the screw geometry within a few minutes without removal of the screw shaft or housing, guaranteeing fast product changes, top availability and therefore higher profits.

Compounding requirements

for powder coatings

Powder coatings are produced in a compounding system in the solid phase by premixing the weighed-in components such as basic polymer, additives, pigments and fillers. The powder mixture is dosed to the BUSS Co-Kneader in the BUSS compounding system and compounded in the melt phase. The melt is then fed to a cooling device, e.g. a cooling belt, rolled out and crushed into chips in a shredder. These are ground and sifted for exact particle size distribution.

Outstanding dispersive and distributive mixing processes at low product temperatures, which are significantly below crosslinking temperatures of the basic polymers, are crucial for compounding. The BUSS Co-Kneader can demonstrate its specific abilities outstandingly in these applications: the enormously high number of mixing cycles at moderate, constant shear rates allows top mixing efficiency and therefore product quality with maximum throughput.

The proven shaft geometries cover a wide application range. The modular process configuration system allows simultaneous simple adjustments.

The hinged BUSS Co-Kneader housing assures fast access, ease final cleaning in case of extreme colour changes and high availability. The widely supported BUSS process expertise makes the BUSS Co-Kneader the first choice for compounding powder coating and has provided top investment security for over 60 years.

Typical plant layout

Discover our PCS Co-Kneader Series

BUSS Co-Kneaders

worldwide

Our patented Co-Kneaders are used worldwide nowadays, supporting our customers in the production of coatings. Using BUSS compounding systems, our customers can master all the demanding requirements for powder coating compounding.

World map with an overview of the BUSS Co-Kneaders used for powder coating compounding

Number of Co-Kneaders used for powder coating compounding

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PCS Co-Kneader

Powder Coating Fact Sheet

In response to the increased requirements in the preparation of powder coatings, BUSS has succeeded in significantly surpassing the performance of the previous models in every respect with the new PCS series.

Plant and System Solutions

Custom compounding systems from BUSS: tailor-made concepts, integration of all components, precise assembly, and smooth commissioning. Comprehensive expertise results in sustainable compounding solutions for a wide range of material applications.