Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-04-07
2002-08-20
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C204S501000, C204S502000, C204S504000, C204S505000, C523S414000, C523S415000, C525S438000, C525S443000
Reexamination Certificate
active
06437055
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to coating compositions and, more particularly, to electrodepositable coating compositions providing improved chip resistance and edge coverage and/or reduced cratering.
BACKGROUND OF THE INVENTION
Electrodepositable coatings have become the coatings of choice for corrosion protection for metal substrates, such as those used in the automobile industry. Electrodeposition processes provide higher paint utilization, outstanding corrosion protection, low environmental contamination, and a highly automated process compared to conventional non-electrophoretic coating methods.
The electrodeposition process involves immersing an electroconductive substrate into a bath of an aqueous electrocoating composition, the substrate serving as a charged electrode in an electrical circuit comprising the electrode and an oppositely charged counter-electrode. Sufficient electrical current is applied between the electrodes to deposit a substantially continuous, adherent film of the electrocoating composition onto the surface of the electroconductive substrate.
U.S. Pat. Nos. 4,148,772 and 4,104,147 disclose electrocoating compositions including polyepoxides chain extended with polyester polyols. Reaction occurs by the alcoholic primary hydroxyl of the polyester polyol opening the epoxide ring forming an ether linkage and a secondary hydroxyl group (U.S. Pat. No. 4,148,772 at column 3, lines 33-35). The chain extended polyepoxides are reacted with a secondary amine and made dispersible in water with acid.
U.S. Pat. No. 4,536,558 discloses electrodepositable resins which are prepared by reacting polyepoxides with polycarboxylic acids to produce chain extended polyepoxides. The chain extended polyepoxides are then reacted with secondary amines or, optionally, with blends of secondary amines with minor amounts of primary amines, care being taken to avoid gelation.
A problem associated with conventional electrodeposition processes is poor coating coverage at the edges of the coated substrate. The coating thickness at the substrate edges tends to be relatively thinner than that of the non-edge portions of the substrate, which can result in the early onset of corrosion at the substrate edges. Additionally, poor flow characteristics of the coating composition may result in pits or craters formed in the coating.
U.S. Pat. No. 5,096,556 discloses a cationic polyepoxide-amine reaction product and a polyepoxide crosslinking agent which are dispersed in water and heated to crosslink to form a cationic microgel dispersion. The dispersion can be combined with ungelled cationic resins to form an aqueous resinous dispersion suitable for electrodeposition which enhances edge coverage.
An object of the present invention is to provide a composition and process for the production of coatings with improved edge coverage and chip resistance and reduced cratering tendency while additionally providing efficiencies in application and processing, such as improved flow control and/or improved solvent resistance.
SUMMARY OF THE INVENTION
The present invention provides a curable coating composition which comprises an at least partially gelled reaction product prepared from reactants comprising: (a) an epoxy functional material and (b) a polyoxyalkylene polyamine.
Another aspect of the present invention is a curable coating composition comprising an at least partially gelled ionic reaction product prepared from reactants comprising: (a) an epoxy functional polyester and (b) an amine-functional material.
A curable coating composition is provided which comprises an at least partially gelled ionic reaction product prepared from reactants comprising an epoxy functional polyester and a primary amine, wherein the reactants are essentially free of secondary amines.
A coated substrate of the invention has on at least a portion of a surface thereof a coating deposited from a coating composition which comprises: (A) a curable, at least partially gelled reaction product prepared from reactants comprising (i) an epoxy functional polyester; and (ii) a polyoxyalkylene polyamine; and (B) a curing agent.
Another coated substrate of the present invention has on at least a portion of a surface thereof a coating deposited from a coating composition which comprises: (A) an at least partially gelled ionic reaction product prepared from reactants comprising: (i) an epoxy functional polyester prepared from reactants comprising: (1) the reaction product of a polyol and a polycarboxylic acid or anhydrides thereof; and (2) an epoxy functional material; and (ii) an amine-functional material; and (B) a curing agent.
Another aspect of the present invention is a coated substrate having on at least a portion of a surface thereof a coating deposited from a coating composition which comprises an at least partially gelled ionic reaction product prepared from reactants comprising an epoxy functional polyester and a primary amine, wherein the reactants are essentially free of secondary amines.
A method of electrocoating an electrically conductive surface of the present invention comprises passing electric current between an anode and a cathode to cause an electrodepositable coating composition to deposit upon the electrically conductive surface, wherein the coating composition comprises an at least partially gelled reaction product prepared from reactants comprising: (i) an epoxy functional polyester; and (ii) a polyoxyalkylene polyamine.
Another method of electrocoating an electrically conductive surface according to the present invention comprises passing electric current between an anode and a cathode to cause an electrodepositable coating composition to deposit upon the electrically conductive surface, wherein the coating composition comprises an at least partially gelled ionic reaction product prepared from reactants comprising: (i) an epoxy functional polyester prepared from reactants comprising (1) the reaction product of a polyol and a polycarboxylic acid or anhydrides thereof, and (2) an epoxy functional material; and (ii) an amine-functional material.
Yet another method of electrocoating an electrically conductive surface according to the present invention comprises passing electric current between an anode and a cathode to cause an electrodepositable coating composition to deposit upon the electrically conductive surface, wherein the coating composition comprises an at least partially gelled ionic reaction product prepared from reactants comprising an epoxy functional polyester and a primary amine, and wherein the reactants are essentially free of secondary amines.
Yet another method of electrocoating an electrically conductive surface according to the present invention comprises passing electric current between an anode and a cathode, and sequentially depositing first and second electrodepositable coating compositions to form a first coating and a second coating on the electrically conductive surface, wherein the first coating composition comprises an electrically conductive material, and wherein the second coating composition comprises an at least partially gelled reaction product prepared from reactants comprising: (i) an epoxy functional polyester; and (ii) a polyoxyalkylene polyamine.
A still further method of coating a substrate comprises providing a substrate and applying a coating composition upon at least a portion of the substrate, the coating composition comprising an at least partially gelled reaction product prepared from reactants comprising an epoxy functional polyester and a polyoxyalkylene polyamine.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about”. Also, as used herein, the term “polymer” is meant to refer to oligomers and both homopolymers and copolymers. Additionally, any numeric reference to amounts, unless otherwise
Moriarity Thomas C.
Webster, Jr. Geoffrey R.
Altman Deborah M.
PPG Industries Ohio Inc.
Sellers Robert E. L.
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