Electrodeposition coating materials and a process for coating el

Details Electrodeposition coating materials and a process for coating el Electrodeposition coating materials and a process for coating el

1997-03-13

1999-11-09

Gorgos, Kathryn L.

Chemistry: electrical and wave energy

Processes and products

Electrophoresis or electro-osmosis processes and electrolyte...

204505, 523415, 524901, C25D 1304

Patent

active

059807156

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to cathodically depositable aqueous electrodeposition coating materials and to a process for coating electrically conductive substrates, in which electrodeposition coating material, material, and
Cathodically depositable, aqueous electrodeposition coating materials and the above-described process for coating electrically conductive substrates are known (cf. e.g. EP-B-301 293, DE-A-35 18 732, DE-A-35 18 770, EP-A-4090, EP-A-12 463, EP-A-262 069, U.S. Pat. No. 3,799,854, U.S. Pat. No. 4,031,050, U.S. Pat. No. 4,252,703, U.S. Pat. No. 4,332,711, DE-A-31 08 073, DE-A-27 01 002, EP-A-59 895, DE-A-31 03 642 and DE-A-32 15 891). Cathodic electrodeposition coating using cathodically depositable, aqueous electrodeposition coating materials has become established as a process for the automatic coating of bulky products, in particular vehicle bodies. Advantages of electrodeposition coating using cathodically depositable, aqueous electrodeposition coating materials are, for example, its environmental friendliness (water as solvent), very good material yield and high reliability with extensive automation of plants.
The present invention is based on the object of providing new cathodically depositable, aqueous electrodeposition coating materials which give coats having improved properties, in particular with regard to the formation of runs (runouts, boilouts), sensitivity to drops of water, and bridging.
Interfering runs can be formed if, during the baking process, electrodeposition coating material emerges from, for example, seams and runs down the coated surface. When the substrates present are of complex shape (e.g. V-shaped metal sheets) the emerging electrodeposition coating material may solidify in the form of bridges. In this case, bridging defects are the result. If--prior to the baking process--water or diluted electrodeposition coating material drips onto the electrodeposition coating film which, although not yet baked, has dried superficially, then, in the case of electrodeposition coating films with a high sensitivity to water drops, water-spotting defects can be seen after baking.
It is often attempted to eliminate the defects described above by adding surfactants. However, in many cases the addition of surfactants results in new interfering side-effects, for example the formation of foam and/or delamination of coatungs applied subsequently.
The present invention is based in particular on the object of eliminating as far as possible the defects described above without producing new interfering side-effects, for example the formation of foam and/or delamination of coatings applied subsequently.
This object is surprisingly achieved by adding, to cathodically depositable, aqueous electrodeposition coating materials known per se, particles of wax having a diameter of from 1 to 20 .mu.m. When incorporating the particles of wax into the electrodeposition coating material, those skilled in the art can employ all methods known to them for incorporating particulate additives into electrodeposition coating materials. It is preferred to incorporate the particles of wax in powder form or in the form of a dispersion in water, in a water-miscible organic solvent or in a mixture of water-miscible organic solvents into the pigment paste.


BRIEF DESCRIPTION OF THE DRAWING

The drawing illustrates the configuration of the test specimens used in the examples to demonstrate the advantages provided by the coatings of the invention.


DETAILED DESCRIPTION

In the context of the present invention, the term "wax" is understood to refer to all naturally occurring and synthetic substances having the following properties:
If a substance fails to conform to more than one of these properties, it is no longer a "wax" in the sense of this invention (cf. Ullmanns Enzyklopadie der technischen Chemie [Ullmann's Encyclopedia of Industrial Chemistry]; 4th revised and extended edition; Verlag Chemie; Weinheim; Deerfield Beach, Fla.; Basel, 1983, page 3).
According to the present i

REFERENCES:
patent: 3476668 (1969-11-01), Scheiber et al.
patent: 3869366 (1975-03-01), Suzuki et al.
patent: 4482446 (1984-11-01), Streitberger et al.
patent: 4948678 (1990-08-01), Shindou et al.
patent: 5166255 (1992-11-01), Anderson, Jr. et al.

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