Chemistry: electrical and wave energy – Processes and products – Electrophoresis or electro-osmosis processes and electrolyte...
Patent
1995-12-19
1998-06-02
Gorgos, Kathryn L.
Chemistry: electrical and wave energy
Processes and products
Electrophoresis or electro-osmosis processes and electrolyte...
204501, 204502, 204504, 204505, 204506, C25D 1306, C09D 544
Patent
active
057593728
DESCRIPTION:
BRIEF SUMMARY
This is a national stage application of PCT/EP94/01863, filed Jun. 8, 1994.
The invention relates to aqueous electrodeposition coating materials which contain cathodically depositable synthetic resins and to a method of coating electrically conductive substrates, in which electrodeposition coating material, material, and
Electrodeposition coating materials containing cathodically depositable synthetic resins, and the above-described cathodic electrodeposition coating method in which the electrodeposition coating materials containing cathodically depositable synthetic resins are used, have been known for a long time and are widely employed for the automatic coating of mass products, in particular for the automatic finishing of vehicle bodies, especially motor vehicle bodies (see in this context, for example, Glasurit Handbuch Lacke und Farbe, Curt R. Vincentz Verlag, Hanover, 1984, pages 374-384 and pages 457-462, and also DE-A-35 18 732, DE-A-35 18 770, EP-A-40 090, EP-A-12 463, EP-A-259 181, EP-A-433 783 and EP-A-262 069).
During the coating of electrically conductive substrates using the cathodic electrodeposition coating method, the problem which occurs is that the edges of the substrate to be coated are only coated with a coating layer of inadequate thickness. One of the consequences of this is that the edges of the coated substrate have an increased susceptibility to corrosion in comparison with the flat areas of the coated substrate. In order to solve this problem it is recommended, in EP-A-259 181, to add to the electrodeposition coating material polymer microparticles which have a softening point which is at least 10.degree. C. above the bath temperature, a solubility parameter which differs by not more than 1.0 from the solubility parameter of the cathodically depositable synthetic resin, a refractive index which differs by 0.02-0.3 from the refractive index of the cathodically depositable synthetic resin or a crosslinking density of 0.01-5.05 mmol/g. According to EP-A-433 783 polymer microparticles of crosslinked urea-aldehyde, triazine-aldehyde or phenol-aldehyde resins or polymer particles of noncrosslinked (meth)acrylonitrile homo- or copolymers should be added to the electrodeposition coating materials.
The addition of the polymer microparticles described in EP-A-259 181 and EP-A-433 783 to electrodeposition coating materials leads in some cases to an improvement in the edge coverage. Despite the improved edge coverage, however, the anticorrosion effect of the deposited electrodeposition coating films at the edge is inadequate. Moreover, the addition of the polymer microparticles described in EP-A-259 181 and EP-A-433 783 has the disadvantageous consequences of reducing the stability of the electrodeposition coating material (occurrence of sedimentation in the electrodeposition coating material), of impairing the adhesion to the substrate and/or to coating layers applied subsequently, of severely impairing the flow and of reducing the anticorrosion effect of the deposited electrodeposition coating films.
The object of the present invention consists in the provision of aqueous electrodeposition coating materials which contain cathodically depositable synthetic resins and give coating films having properties which are improved with respect to the prior art. With the aqueous electrodeposition coating materials, containing cathodically depositable synthetic resins, which are provided it should be possible, in particular, to coat electrically conductive substrates using the cathodic electrodeposition coating method and to obtain coating films which give good coverage of the edges of the coated substrate and which exhibit at least some of the above-described disadvantages of the prior art either not at all or only to a reduced extent.
This object is surprisingly achieved by the provision of aqueous electrodeposition coating materials which contain cathodically depositable synthetic resins, which are characterized in that they contain a reaction product (A) and a polymerization initiator (B) which f
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Jouck Walter
Ott Gunther
Reuter Hardy
BASF Lacke & Farben AG
Gorgos Kathryn L.
Leader William T.
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