Powder Coatings Production Celebrating Automated Powder Handling

Author / Editor: Walter Sonntag* / M.A. Manja Wühr

Powder coatings technology dates back to the 1960s, when pure epoxy systems were first used. These had very slow curing times, due to the raw materials in use at the time, and this restricted their areas of application considerably. Nowadays, however, a much wider variety of suitable raw materials is available. This makes it possible to vary the optical and mechanical properties of the coatings. Proven modern materials handling systems improve the economics of coating powders, both in production and in application.

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Dosing systems from Azo are well suited for powder handling.
Dosing systems from Azo are well suited for powder handling.
(Picture: AZO, © Lukas Gojda- Fotolia, [M]-Sahlmüller)

Unlike every other coating technology, powder coatings require no solvents. The coating powders on which the process is based are organic materials that are generally extremely plastic. According to Wikipedia, the main areas of application for coating powders are general metal coating (35%), household appliances (21%), fascia signs (20%), furniture coating (13%), and automotive paintwork (8%). Some 1.1 million tonnes of coating powder were used throughout the world in 2006; one-third of this total was sold in Europe, one-third in Asia, and the remaining third was equally divided between North America and the rest of the world. In Europe, powder coatings made up about ten percent of the total market for coatings.

In the manufacture of coating powders, the first stage after checking the incoming raw materials is to weigh bulk quantities automatically into the mixing container. Small quantities of ingredients, on the other hand, are generally pre-weighed at a manual weighing station before being added to the bulk mix. Weighing is followed by mixing, typically in an overhead mixer that can be discharged under gravity. The homogeneous mixture is fed to an extruder, followed by cooling and rough crushing. In the final phase of the process, the coating powder is ground to a specific particle size, and screened to ensure consistency.

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There is still substantial potential for automation in the production of coating powders, certainly as far as the feeding of raw materials is concerned. Specialist solutions are the obvious choice for receiving and storing raw materials in powder form, particularly since they have already proven themselves repeatedly in the manufacture of coating powders.

An example is the automation of handling systems for titanium dioxide, which because of its very fine particle size is traditionally a difficult material. The use of special silo discharge systems purpose-designed for titanium dioxide results in reliable silo discharge and stable conveying. Choosing the right material of construction, with a high-grade surface finish, helps to prevent caking.

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