Fachdokumente Online der Landesanstalt für Umwelt Baden-Württemberg

zur LUBW   zum Ministerium für Umwelt, Klima und Energiewirtschaft   zum Ministerium für Ländlichen Raum und Verbraucherschutz   zum Ministerium für Verkehr und Infrastruktur  

Summary

For the reduction of the environmental impacts and the costs in the woodworking industry the increase of the material efficiencies is of most importance [1][2]. The common used compressed air atomizers implement values of 20 - 50 %, depending on the constructive design. The consequences are lacquer wastes, emissions and refuse disposal costs. For the increase of the material efficiencies in the wood industry also oversprayrecyclingtechnologies are in use. For many applications, in which two-component lacquers are used or a frequent lacquer color change system is necessary, have to be found new ways to the increase of the material efficiencies.

The use of powder coatings on wood has been realised only in few cases, due to the application available powder coating systems and the necessary curing conditions.

A success-promising application is the implementation of effective high rotation atomizers for the electrostatic coating of timber materials.

During the AIF project (No. 10820 N/1) "Development of technical measures for the application of electrostatic painting procedures for plastic parts " (01.09.1996 to 31.05.1998) the following concept for the electrostatic lacquer finish of plastic parts has been developed [ 3 ]:

The electrostatic charge, given to the paint particles during the lacquer process, exhausts when moistening the workpiece surface with laquer by the wetpaintfilm. This procedure can be supported by additional measures (e.g. gas and pressing electrodes, workpiece carrier of nonconductor materials, conductive, grounded deposit of the workpieces and a increased ambient air humidity during the lacquer process). The target of this feasibility study was to check the implementation of this concept for the timber industry, referring to the AIF-project.

The substantial measures examined in the study referred to the variation of the grounding dynamics in connection with a variable parameter-adjustment of the spraysystem. Furthermore two different installation types were simulated bymeans of variation of the workpiece carrier construction

  1. Flat part coatingsystem with beltconveyor
  2. Coatingsystem with hanging conveyor

Resulting from this, the material efficiencies (AWG) with the application of electrostatic high rotation atomizers showed an increase of up to 35% in the comparison of the results of a HVLP system. With an open beltconveyor construction a material efficiency of approx. 93% was achieved. The max. achieved AWG of a HVLP system was situated in contrast to this with only 60%.

In a further test series the contamination inclination of the electrostatic application was pointed out as a function of different system parameters.

Therefore a reequipment from systems which were presently in use with metal housing, is to be implemented by sufficient isolation with plastic material (30 mm strong).

For the woodworking industry the process engineering bases and optimization to the advancement with the devices and systems, supplied to the application of electrostatic high rotation bells, should be regenerated in a subsequent project in the form of recommendations and application strategies.

 


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