US 4,225,407 AGranted

Cathodic electrodeposition of polymers onto a conductive surface

AssigneeThe Dow Chemical Company

InventorsEarl H. Wagener, Ritchie A. Wessling, Dale S. Gibbs

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Abstract

A method for electrodeposition of an organic material on an electroconductive surface comprising placing the electroconductive surface to be coated in contact with an aqueous dispersion containing a water-insoluble, essentially electrically nonconductive, film-forming, organic polymer as cation-active particles wherein the cation-activity is provided at least predominantly by reducible nitrogen-containing cations and passing an electric current from an electrode through the latex to the electroconductive surface in such a direction that the electroconductive surface is negatively charged, i.e., becomes a cathode in an electrophoretic cell. By use of alternating current, both electrodes become coated with an adherent coating of polymer.

Claims15

Dependent claims

A method for applying an adherent, hydrophobic, smooth, uniform coating to an object having an electroconductive surface comprising:

(1) immersing the object in a coating bath comprising an aqueous dispersion of cationactive particles of water-insoluble, essentially electrically non-conductive, organic, film-forming polymer wherein the cationactivity is provided at least predominantly by reducible nitrogen-containing cations having polarographic half-wave reduction potentials at 25.degree. C. more positive than -1.8 volts measured at a dropping mercury electrode referred to a saturated calomel electrode;
the quantity of said reducible nitrogen-containing cations being from about 0.02 milliequivalent to about 0.6 milliequivalent per gram of polymer;
said aqueous dispersion having a pH from about 2 to about 12 and having a conductivity of from about 300 micromhos to about 3,500 micromhos per centimeter as measured at 25.degree. C. and 10 percent solids;
and wherein any cations of water-soluble salts having electrode potentials more negative than -2.40 volts referred to a standard hydrogen electrode are limited to concentrations from 0 to less than 0.002 normal;
(2) passing an electric current through said bath sufficient to effect deposition of a coating of said polymer on the object by providing a difference of electrical potential of from about 100 volts to about 5,000 volts between the object and an electrode that is
(a) spaced apart from said object;
(b) in electrical contact with said bath;
and
(c) electrically positive in relation to said object;
said coating which is deposited continuing to be adherent in the presence of water after the difference of electrical potential is discontinued;
with the proviso that when the potential is applied for short, intermittent times, the potential is from about 200 volts to about 5,000 volts.

8 more elements

A method for coating an electrically conductive surface with a water-insoluble, adherent, essentially electrically non-conductive, organic, film-forming polymer comprising providing an aqueous dispersion of the polymer as cation-active particles wherein the cation-activity is provided at least predominantly by a reducible nitrogen-containing cation, the quantity of said reducible nitrogen-containing cations being from about 0.02 milliequivalent to about 0.6 milliequivalent per gram of polymer;

said dispersion having a pH from about 2 to about 12 and having a conductivity of from about 300 micromhos to about 3,500 micromhos per centimeter as measured at 25.degree. C. and 10 percent solids and wherein any cations of water-soluble salts having electrode potentials more negative than -2.40 volts referred to a standard hydrogen electrode are limited to concentrations from 0 to less than 0.002 normal, using the dispersion as a bath in an electrophoretic cell comprising an anode and a cathode wherein at least a part of the surface of said cathode comprises the surface to be coated, connecting said anode and said cathode to a source of electromotive potential of from about 100 volts to about 5,000 volts, applying said potential across said anode and said cathode to pass an electric current through the dispersion and thereby to electrodeposit said polymer in the form of a smooth, uniform, adherent coating on at least a part of said cathode surface;
said reducible nitrogen-containing cation having a polarographic half-wave reduction potential at 25.degree. C. more positive than -1.8 volts measured at a dropping mercury electrode referred to a saturated calomel electrode and being quaternized pyridinium, quinolinium, isoquinolinium, phthalazinium, benzimidazolium, benzothiazolium, benzotriazolium ions or activated acyclic quaternized nitrogen ions;
with the proviso that when the potential is applied for short, intermittent times, the potential is from 200 volts to about 5,000 volts.

Dependencies are inferred from the claim text.

Facts

Application: 06/026,720Filed 4 Apr 1979 · continuation in part
Priority: 29 Aug 1973
Granted: 30 Sep 1980
Term ends: Not estimatedThe source records don’t support an estimate.

Classification4 codes

C25D 13/22
Electrophoretic coating characterised by the process: servicing or operating apparatus or multistep processes
C09D 5/44
Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced ; Filling pastes: for…
C25D
Processes for the electrolytic or electrophoretic production of coatings
C09D
Coating compositions