Coating processes – Applying superposed diverse coating or coating a coated base – Synthetic resin coating
Patent
1997-11-25
1999-06-01
Dudash, Diana
Coating processes
Applying superposed diverse coating or coating a coated base
Synthetic resin coating
427195, 427379, 427409, 427458, B05D 138, B05D 726, B05D 302
Patent
active
059086670
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for preparing a multilayer lacquer coating for conductive, in particular metallic, substrates which is particularly well suited for the lacquer-coating of motor vehicles.
Present-day high-grade lacquers for the assembly-line lacquering of motor vehicles generally comprise an electrophoretically applied anticorrosive primer and subsequent coats which are then applied by spraying and comprise a filler layer and a subsequent layer which is applied for decorative purposes and consists of a colour-giving and/or effect-producing base coat, and a protective clear lacquer coat which seals the surface.
The overall thickness of such motor vehicle lacquers is, in practice, between 90 and 130 .mu.m which is the total produced by a layer thickness of 15 to 25 .mu.m for the primer, 30 to 40 .mu.m for the filler layer, 10 to 25 .mu.m for the base lacquer coat and 30 to 40 .mu.m for the clear lacquer coat. These layer thicknesses are far greater when it is intended to produce lacquer coatings which have a particularly good optical appearance, i.e. with a prominent luster and coating lacquer condition, for example, when lacquer-coating motor vehicles in the upper and luxury classes. The application of a plurality of clear lacquer coats no to a base lacquer coat is described, for example, in DE-A-42 15 070 and DE-A-38 39 905. In such cases, layer thicknesses exceeding 120 .mu.m, for example up to 170 .mu.m, are produced, but this is undesirable for reasons relating to savings in the materials used and to reduction of the mass of the finished vehicle.
The object of the invention is to provide multilayer lacquer coatings, in particular motor vehicle lacquers, which meet the requirements with regard to a prominent luster and coating lacquer condition, without exceeding the standard measure for overall layer thicknesses for motor vehicle lacquer coatings, and without any concomitant disadvantages in the overall level of properties.
It has been found that it was possible to meet this object in a novel manner according to the invention by a process f or producing a multilayer lacquer coating, in which a primer of an electrophoretically depositable aqueous coating agent (1) is electrophoretically applied on to an electrically conductive substrate and is then stoved, whereupon a colour-giving and/or effect-producing base lacquer of an aqueous coating agent (II) is applied and stoved and this coat is then provided with one or more clear lacquer coatings, according to which process will produce an electrically conductive primary coat is used, aqueous coating agent (II) by a process of electrophoretical deposition, coats is about 40 and 80 .mu.m, and about 80 to 110 .mu.m.
Within the framework of the multilayer lacquer coatings according to the invention, a clear lacquer coat having a substantial thickness of 40 to 80 .mu.m, preferably 50 to 60 .mu.m, is provided. This coat is applied on to the stoved base lacquer coat. The clear lacquer coat may comprise one or more layers, the first clear lacquer layer preferably being stoved prior to application of the additional clear lacquer coats. A plurality of clear lacquer coats may be provided to be from the same or from different clear lacquer coating agents.
In the process according to the invention, it is possible to use, as the electrophoretically depositable but different coating agents (I) and (II), anodically or cathodically depositable electro-dipcoats (ETL), which are known per se, to produce the first and the second coating layer, it being imperative that the electrophoretically depositable coating agent (I) contain components which give an adequately low specific resistance to the first coating layer, in the stoved state, for the electrophoretic depositing of a further coating layer of an electrophoretically depositable coating agent (II) which differs from (I), and that the electrophoretically depositable coating agent (II) contain colour-giving and/or effect-producing pigments.
The coating agents (I) and (II) are aqueous coating agents having a
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Blum Joachim
Engel Dieter
Kimpel Matthias
Klein Klausjorg
Kuhhirt Walter
Dudash Diana
Herberts Gesellschaft mit beschrankter Haftung
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