Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Patent
1997-09-30
1999-02-09
Gorgos, Kathryn L.
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
428416, 204488, 427409, C25D 1306
Patent
active
058691987
DESCRIPTION:
BRIEF SUMMARY
This application is the national phase of international application PCT/EP96/01316, filed Mar. 26, 1996 which designated the U.S.
FIELD OF THE INVENTION
This invention relates to a process for the production of multi-layer coatings.
BACKGROUND OF THE INVENTION
Current mass production automobile coatings consist for the most part of a base lacquer/clear lacquer covering coating which is applied to a body which has been electrophoretically primed and coated with primer surfacer. In the course of this procedure, the base lacquer and the clear lacquer are preferably applied wet-into-wet, i.e. after a ventilation period, optionally with heating, and after the subsequent application of a clear lacquer, the base lacquer is stoved jointly with the latter. Processes which serve to reduce further stoving steps have also become known, in which the electrophoretically deposited primer coat and the primer surfacer coat are applied by the wet-into-wet method, as described in DE-A-41 26 476 or EP-A-0 595 186 for example. The primer surfacer coats have to be applied to give a dry film thickness of 30 .mu.m or more, which is customary for primer surfacer lacquers.
The procedure according to DE-A-41 26 476 and EP-A-0 595 186 is subject to restrictions as regards the composition of the primer surfacer coats which are applied wet-into-wet, i.e. it is not possible to use any desired primer surfacer coating media. Furthermore, the properties of the electro-dip lacquer material and of the primer surfacer material have to be matched to each other.
It is known from EP-A-0 265 363 that a previously stoved, cataphoretically deposited primer coat can be provided with a two-coat base lacquer/clear lacquer covering coat by the wet-into-wet method. The primer surfacer coat is dispensed with. An effect which is problematical, however, is that stone impact damage to motor vehicles coated by this process is particularly conspicuous, since on stone impact the primer coat is exposed due to the debonding of the covering lacquer. Whilst protection from corrosion is still in fact ensured, the visual impression cannot be tolerated, however.
For reasons of rationalisation and savings in material, there is a desire for a reduction in the coating thickness of the lacquer structure for the coating of motor vehicles, but without this resulting in significant losses in the overall level of properties thereof.
SUMMARY OF THE INVENTION
The object of this invention is to provide a process for the production of multi-layer coatings, particularly motor vehicle coatings, which have an overall level of properties comparable with the prior art but with a reduced coating thickness of the lacquer structure as a whole, which process minimises the expense of matching the individual lacquer coats to each other and which can be carried out with as few stoving steps as possible.
This object has surprisingly been achieved by a process for the multi-layer coating of electrically conductive substrates by the electrophoretic deposition of a first coating layer comprising an electrophoretically depositable aqueous coating medium, and the subsequent application of further coating layers, which is characterised in that a second coating layer comprising a first colour- and/or effect-imparting base lacquer coating medium is applied wet-into-wet to the first coating layer obtained by electrophoretic deposition, and the first and second coating layers thus obtained are stoved jointly, whereupon a third coating layer comprising a second colour- and/or effect-imparting base lacquer coating medium is applied and a fourth coating layer comprising a clear lacquer coating medium is applied wet-into-wet thereto and the third and fourth coating layers are stoved jointly, wherein the total dry coat thickness (the sum of the coat thicknesses) of the second and third coating layers produced from the base lacquer coating media is between 15 and 40 .mu.m, preferably between 20 and 35 .mu.m, and the proportion of the second coating layer is between 20 and 50%, preferably between 25
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Dobert Jurgen
Erne Marcus
Kimpel Matthias
Klein Klausjorg
Gorgos Kathryn L.
Herberts Gesellschaft mit beschrankter Haftung
Mayekar Kishor
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