MXPA00011549A - A process for forming a two-coat electrodeposited composite coating, the composite coating and chip resistant electrodeposited coating composition - Google Patents

Abstract

A process for applying two electrodeposited coatings, one on top of the other, to an electrically conductive substrate is provided. An electrically conductive first coating is applied to provide for corrosion resistance and a second polyurethane-based coating is applied to the first coating to provide chip resistance. Also, aqueous dispersions of the polyurethane coating compositions are disclosed.

Description

A PROCEDURE FOR THE FORMATION OF A COMPOSITE COATED ELECTRODEPOSITATED COATING OF TWO LAYERS, THE COMPOSITE COATING AND A COMPOSITION OF ELECTRODEPOSITE COATING RESISTANT TO DESCAMATION BACKGROUND The present invention is directed to a method for electrodepositing a composite coating of two layers onto a substrate, wherein the first electrodeposited coating protects against corrosion and the second electrodeposited coating protects against desquamation of the deposited compound. Multilayer coating compounds find their use in various industries, including re-coating and / or painting of various motor vehicles. In several of these industries and in the automotive industry, in particular, there may be from 2 to 6 or more coating layers in the multilayer coating compositions. These coating layers can serve to protect the substrate and / or provide a decorative finish. Multilayer coating compositions for metal substrates such as those in the automobile industry have involved electrodeposition coatings as an initial resinous coating layer to protect the metal substrate from corrosion. Coatings by cationic electrodeposition have become the coatings of choice for protection against corrosion. Electrodeposition has become increasingly important in the coatings industry, since, in comparison with non-electrophoretic coating media, electrodeposition offers a greater use of paint, a remarkable protection against corrosion, Low environmental pollution and a highly automated procedure.

In the art, the application of two layers by the electrodeposition process is known. For example, in US Pat. 4,988,420, 4,840,715 and 5,275,707, different types of electroconductive pigments are added to a first electrodeposited resinous acrylic coating and a second electrodeposition coating is applied onto the first conductive electrodeposited acrylic coating. Typically, these second electrodeposition coatings have been applied for durability and decorative purposes. In addition, in multilayer coating compositions for motor vehicles, another coating layer that may be present is a spray-applied desiccation coating layer. Said layer protects the surface of the substrates from the loss of paint by desquamation when the substrate of the vehicle is hit with solid residues, such as gravel and stones. The technique for achieving peeling resistance thanks to spray applied primer coatings has postulated that reducing the difference in impact energy between multiple coating layers would improve the resistance to peeling of the coating. This is in particular the situation for those coating layers with an excessive difference in hardness between them. This reduction in the difference would reduce delamination between the coatings, such as between the sublayer and an intermediate layer and an upper layer or a sublayer and an intermediate layer. In U.S. Pat. No. 5,674,560, this difference is reduced through a polyolefin type of peel-resistant primer that is applied by spraying onto an electrodeposited cationic or anionic film prior to the application of a soft intermediate polyester film. It has been described that the difference in impact energy difference is maximized when the polyolefin primer is applied over the softer anionic electrodeposited film, contrary to a cationic electrodeposited film. Therefore, even though the technique recognizes that cationic electrodeposited coatings provide better corrosion resistance than anionic electrodeposited coatingsOther improvements in the peeling resistance in a multilayer coating system may be at odds with, or involve sacrifice of, some of the corrosion resistance using the electrodeposited anionic coating for protection against corrosion. It is an object of the present invention to provide a method and system for obtaining better multiple setbacks with good peeling resistance while protecting against corrosion, while at the same time providing efficiency in terms of application and indicted. These include a greater use of paint, low environmental pollution and a highly automated procedure. COMPENDIUM OF THE INVENTION The present invention provides a method for electrocoating conductive substrates with two electrodeposited layers, consisting of the following steps: (a) electrodeposition on the substrate of an electrically conductive coating that is deposited from a composition consisting of an ionic resin curable and an electrically conductive pigment; (b) at least partial cure of the electrodeposited coating to make the coating electrically conductive; (c) electrodeposition of a second coating on the electrically conductive coating of step (b), the second coating being deposited from a composition consisting of a polyurethane ion curable resin containing a polymeric segment derived from a hydrogen-containing polymer active and having a glass transition temperature of 0 ° C or less and a number average molecular weight of 400 to 4,000; (d) curing the second coating of step (c). An article coated by the method of the invention is also presented. Also provided is an aqueous electrodepositable composition consisting of a curable polyurethane resin containing ionic salt groups dispersed in an aqueous medium, which is the reaction product: (a) a polyisocyanate and (b) a polymer containing active hydrogen and having a glass transition temperature of 0 ° C or less and a number average molecular weight of 400 to 4,000. DETAILED DESCRIPTION OF THE INVENTION The numerical values in the various ranges specified in this application, unless expressly indicated otherwise, are given as approximations, as if the minimum and maximum values within the ranges indicated were both preceded by the word "approximate". In this way, slight variations above and below the established ranges can be used to achieve substantially the same results as with the values within the ranges. In addition, the description of these ranges is intended to be a continuous range that includes all the values between the minimum and maximum values. The first step of the process of the invention is the electrodeposition of an electrically conductive coating on the surface of an electrically conductive substrate. The coating is deposited from a composition containing a curable ionic resin and an electrically conductive pigment. The composition may be an anionic electrodepositable composition or a cationic electrodepositable composition, which is preferred. The anionic and cationic electrodepositable compositions which can be used are those which provide a high deposition power and a good resistance to corrosion. These compositions are well known in the art. Examples of suitable ionic resins for use in anionic electrodepositable coating compositions are polymers containing carboxylic acids base-solubilized such as the reaction product or adduct of a drying oil or a semi-fatty acid ester with an acid or dicarboxylic anhydride and the reaction product of an unsaturated fatty acid, acid or anhydride ester and any additional unsaturated modifying material which still react with polyol. Also suitable are the at least partially neutralized interpolymers of hydroxyalkyl esters of unsaturated carboxylic acids, unsaturated carboxylic acid and at least one other ethylenically unsaturated monomer. Yet another suitable electrodepositable resin consists of an alkyd-aminoplast carrier, that is, a vehicle containing an alkyd resin and an amine-aldehyde resin. Still another anionic electrodepositable resin composition consists of mixed esters of a resinous polyol. These compositions are described in detail in Pat. USA No. 3,749,657, in col. 9, lines 1 to 75, and in col. 10, lines 1 to 13, all of which are incorporated herein by reference. Other acid-functional polymers, such as polyepoxide phosphate or phosphatic acrylic polymers, can also be used, as is well known to those skilled in the art. Examples of ionic resins suitable for use in cationic electrodepositable coating compositions include resins containing amine salt groups., such as the reaction products solubilized in acid of polyepoxides and primary or secondary amines, such as those described in Pat. USA Nos. 3,663,389, 3,984,299, 3,947,338 and 3,947,339. Normally, these resins containing saline amine groups are used in combination with a blocked isocyanate curing agent. The isocyanate can be completely blocked, as described in Pat. USA No. 3,984,299 mentioned above, or the isocyanate can be partially blocked and reacted with the resin backbone, as described in Pat. USA No. 3,947,338. In addition, one-component compositions can be used, as described in Pat. USA No. 4,134,866 and DE-OS No. 2,707,405, as a film-forming resin. In addition to the epoxy-amine reaction products, film-forming resins can also be selected from cationic acrylic resins such as those described in US Pat. USA No. 3,455,806 and 3,928,157. In addition to resins containing saline amine groups, resins containing salt groups of quaternary ammonium can also be used. Examples of these resins are those that are formed by reaction of an organic polyepoxide with a tertiary amine salt. Said resins are described in Pat. USA No. 3,962,165, 3,975,346 and 4,001,101. Examples of other cationic resins are resins containing saline groups of ternary sulfonium and resins containing saline groups of quaternary phosphonium, such as those described in US Pat. USA No. 3,793,278 and 3,984,922, respectively. In addition, film-forming resins that cure by transesterification can be used, as described in European Application No. 12463. In addition, cationic compositions prepared from Mannich bases, such as those described in Pat. USA No. 4,134,932.

The resins for which the present invention is particularly effective are the positively charged resins containing primary and / or secondary amine groups. Said resins are described in Pat. USA Nos. 3,663,389, 3,947,339 and 4,116,900. In the Pat. USA No. 3,947,339, a polyketimine derivative of a polyamine such as diethylene triamine or triethylene tetraamine reacts with a polyepoxide. When the reaction product is neutralized with acid and dispersed in water, primary amine groups are generated. In addition, equivalent products are formed when the polyepoxide reacts with an excess of polyamines, such as diethylene triamine and triethylene tetraamine, and excess polyamine under vacuum is removed from the reaction mixture. Said products are described in Pat. USA Nos. 3,663,389 and 4,116,900. Electrodepositable compositions such as those described in U.S. Pat. No. 5,767,191, which contain oleic acid and abietic acid, and in US Pat. No. 4,891,111, which contain alkylated polyether. The electrodepositable ionic resin described above is present in the electroreversing composition in amounts of about 1 to about 60 weight percent, preferably about 5 to about 25 based on the total weight of the electrodeposition bath. The electrocoating compositions are in the form of an aqueous dispersion. It is believed that the term "dispersion" is a transparent, translucent or opaque two-phase resinous system in which the resin is in the disperse phase and the water is in the continuous phase. The average particle size of the resinous phase is generally less than 1.0 and usually less than 0.5 microns, preferably less than 0.15 microns. The concentration of the resinous phase in the aqueous medium is at least 1 and usually from about 2 to about 60 weight percent based on the total weight of the aqueous dispersion. The ion electrodepositable compositions contain an electroconductive pigment to make the resulting coating electroconductive. In general, carbon blacks may be any or a mixture of carbon blacks ranging from those known as higher conductive carbon blacks, ie those having a BET surface area greater than 500 m2 / gram and an adsorption number DBP (determined according to ASTM D2414-93) of 200 to 600 ml / 100 g, up to those with lower DBP numbers, in the order of 30 to 120 ml / 100 grams, such as those with DBP numbers of 40 to 80 ml / 100 grams. Examples of commercially available carbon blacks include Cabot Monarch ™ 1300, Cabot XC-72R, Black Pearls 2000 and Vulcan XC 72, sold by Cabot Corporation; Acheson Electrodag ™ 230, sold by Ac e-son Colloids Co .; Columbian Raven ™ 3500, sold by Colum-bian Coal Co., and Printex ™ XE 2, Printex 200, Printex L and Printex L6, sold by DeGussa Corporation, Pigments Group. Carbon blacks suitable in Pat. USA No. 5,733,962. It is also possible to use electrically conductive silica pigments. Examples include "Aerosil 200", sold by Japan Aerosil Co., Ltd., and "Syloid 161", "Syloid 244", "Syloid 308", "Syloid 404" and "Syloid 978", manufactured by Fuji Davison Co ., Ltd. Mixtures of different electroconductive pigments can be used. The amount of electroconductive pigment in the electrodepositable composition may vary depending on the specific type of pigment used, but the level needs to be effective to obtain an electrodeposited coating with a conductivity greater than or equal to 10"12 mhos / cm. In another way, the electrodeposited coating must have a resistivity less than or equal to 1012 ohms-cm, preferably a resistance less than or equal to 108 ohms at typical film thicknesses or thicknesses for electrodeposited coatings., so that, with curing or partial curing, the coating becomes electroconductive. Preferably, the curing is done by heating to a temperature of at least 120 ° C (248 ° F). Typically, the electroconductive pigment content in the electrodepositable composition is from 5 to 25 weight percent based on the total solids of the electrodeposition composition. Most electroconductive substrates, especially metal substrates such as steel, zinc, aluminum, copper, magnesium or similar and galvanized metals such as any galvanized steel and the like, either hot-dip galvanized or electrogalvanized or galvanized by another electroplating method , they can be coated with the electrodepositable compositions. Steel substrates are preferred. It is usual to pretreat the substrate with a phosphate conversion coating, typically a zinc phosphate conversion coating, followed by a wash that seals the conversion coating. The pretreatments are well known to those skilled in the art. Examples of suitable pretreatment compositions are described in US Pat. 4,793,867 and 5,588,989. In the method of applying an electrically conductive coating, the aqueous dispersion of the electrodepositable composition is placed in contact with an electrically conductive anode and cathode. When an electric current passes between the anode and the cathode, an adherent film of the electrodepositable composition will be deposited in a substantially continuous manner at the anode or the cathode depending on whether the composition is anionic or cationically electrodepositable. Electrodeposition is usually carried out at a constant voltage in the range of about 1 volt to several thousand volts, typically between 50 and 500 volts. The current density is typically between about 1.0 amp and 15 amps per square foot (10.8 to 161.5 amps per square meter). After electrodeposition, the coating is at least partially cured, typically by heating. Temperatures usually range from 200 ° F to 400 ° F (93.3 ° C to 204.4 ° C), preferably 300 ° F to 375 ° F (149 ° C) 191 sC) for a period of time that varies between 10 and 60 minutes. The thickness of the resulting film is usually about 10 to 50 microns. The heating or baking of the electrodepositable coating can also be carried out by means of infrared radiation ("IR"). In general, there are three IR categories. These categories are: close to IR (short wavelength), which has a peak wavelength of 0.75 to 2.5 microns ("μ") (750 to 2,500 nanometers); IR intermediate (mean wavelength), which has a peak wavelength of 2.5 to 4 μ (2,500 to 4,000 nanometers), and far IR (long wavelength), which has a peak wavelength of 4 to 1,000 μ (4,000 to 100,000 nanometers). Any of these IR categories, or any combination thereof, or all of them, can be used for heating to at least partially cure the coating. The curing can be carried out selectively. At least one predetermined area of the first electrodeposited coating composition is heated by IR, for example the exterior surfaces of an automobile body, where said predetermined area is to be coated with the second electrodepositable coating composition. The inner surfaces of the electrorevealed substrate are not exposed to the IR and, as a result, the first electroplated coating is not cured on the inner surfaces and does not become electroconductive. Hence, the deposition of the second electrodeposited coating layer is only on the outer surfaces, which are electrically conductive. With this treatment, substrates such as a car body have the first conductive electrodeposited coating cured on the outer surfaces and the first electrodeposited non-conductive and uncured coating on the inner surfaces. By applying the second electrodeposited coating and curing both electrodeposited coatings, the exterior surface of the automotive body will have both the electrodeposited first and second coatings and good resistance to corrosion and desquamation where it is most needed. The inner surface will have only the first electrodeposited coating and resistance to corrosion, but not resistance to desquamation. As interior surfaces will not be exposed to road debris, resistance to desquamation is not needed. When using IR heating with complex shapes, such as automobile bodies, it is preferable to dry the coated substrate with the first electrodeposited coating composition for 2 to 20 minutes in a standard oven, such as a convection oven, electric or powered with gas before exposing the electro-dressed substrate to the IRs. The drying step can be at a temperature sufficient to remove water, but not sufficient to cure the coating, so that it becomes conductive. In general, the temperature is lower than 120 ° C. IR heating can be performed for 10 seconds to 2 hours, usually for 5 to 20 minutes. Temperatures range from over 120 ° C to 220 ° C (248 ° F to 428 ° F) and, preferably, from 130 ° C to 190 ° C (266 ° F to 374 ° F). After application of the electroconductive coating, a second coating is electrodeposited on the first coating. The second coating is deposited from a composition consisting of a curable ionic polyurethane resin, which contains a polymeric segment derived from a polymer containing active hydrogen and having a glass transition temperature of 0 ° C or less and a number average molecular weight of 400-4,000. When the first electrodeposited coating provides resistance to corrosion, the second electrodeposited coating provides resistance to desquamation. The ionic polyurethane resin can be anionic or cationic, but is preferably cationic, and the composition is cationically electrodepositable. The polyurethane will have a molecular weight (Mn) of less than 100,000, preferably less than 50,000 and, more preferably, from 10,000 to 40,000. The polyurethane also has active hydrogen functionality, i.e. primary or secondary hydroxyl or amine, and typically has an active hydrogen equivalent weight of 800 to 2,500 grams per equivalent. By the term "polyurethane", as used herein, the meaning is intended to include polyurethanes, as well as polyureas and poly (urethane-ureas). The molecular weight of the polyurethane and other polymeric materials used in the practice of the invention is determined by gel permeation chromatography using a polystyrene standard. Suitable polyisocyanates used to prepare the polyurethanes include those having aliphatic, cycloaliphatic, araliphatic and / or aromatically bound isocyanate groups. Preferably, the polyisocyanate is aliphatic or cycloaliphatic.

Examples of aliphatic and cycloaliphatic polyisocyanates include 4,4-methylenebis-cyclohexyl diisocyanate (hydrogenated DIM), hexamethylene diisocyanate (DIH), isophorone diisocyanate (DIIF), methylenbis (cyclohexyl isocyanate) and cyclohexylene diisocyanate (hydrogenated DIX). ). Examples of aromatic polyisocyanates include toluene diisocyanate (DIT) (ie, 2,4-toluene diisocyanate, 2,6-tolylene diisocyanate or a mixture of these), diphenylmethane-4,4-diisocyanate (DIM). ), naphtha-len-1, 5-diisocyanate (DIN), 3, 3-dimethyl-4, 4-biphenylene diisocyanate (DITO), crude DIT (ie, a mixture of DIT and an oligomer thereof), polyisocyanate of polymethylene polyphenyl, crude DIM (ie, a mixture of DIM and an oligomer thereof), xylylene diisocyanate (DIX) and phenylene diisocyanate. Suitable are polyisocyanate derivatives prepared from hexamethylene diisocyanate, 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane ("DIIF"), including isocyanurates, and / or 4,4'-bis (isocyanatocyclohexyl) methane The amount of polyisocyanate used to make the polyurethanes is typically from 10 to 60, preferably from 20 to 50 percent by weight, based on the total weight of the reagents used to make the polyurethane. The material containing active hydrogen for the reaction with the polyisocyanate to form the cationic or anionic polyurethane consists of one or more polymers containing active hydrogen. These materials preferably have an average functionality of active hydrogen ranging from about 2 to 8, preferably from about 2 to 4, and a number average molecular weight in a range preferably from about 400 to 10,000, more preferably from 400 to 4,000, and a glass transition temperature ("Tg") of 0 ° C or less. Polyether polyols are preferred. The term "active hydrogen" means those groups that are reactive with isocyanates, as determined by the Zerewitnoff test, as described in the JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol. 49, page 3181 (1927). Preferably, the active hydrogens are hydroxyl, primary amine and secondary amine. Tg for many polyethers is available in the literature. Also useful in the determination of Tg is the Clash-Berg method, described in Advances in Poiyurethane Technology, Burst et al., Wiley & Sons, 1968, pages 88ff. Examples of polyether polyols are polyalkylene ether polyols, which include those having the following structural formula: where the substituent R is hydrogen or lower alkyl containing from 1 to 5 carbon atoms, including mixed substituents, and n is typically from 5 to 200. They include poly (oxytetramethylene) glycols, poly (oxyethylene) glycols, poly (oxy) -1, 2-propylene) glycols and the reaction products of ethylene glycol with a mixture of 1,2-propylene oxide and ethylene oxide. These materials are obtained by the polymerization of alkylene oxides, such as ethylene oxide, propylene oxide and tetrahydrofuran. In addition, polyethers obtained from the oxyalkylation of various polyols may be used, for example, diols such as 1,6-hexanediol or higher polyols such as trimethylolpropane and sorbitol. A commonly used oxyalkylation method is by reacting a polyol with alkylene oxide, such as ethylene or propylene oxide, in the presence of an acidic or basic catalyst. Examples of other polyethers containing active hydrogen are polyoxyalkylene polyamines. The preferred polyoxyalkylenepolyamines are those of structure: H R I H2N - CH - CH20 C - CH2 - O - CH2 - CH - NH2 1 I R R n where R can be the same or different and is selected from the class consisting of hydrogen and lower alkyl radicals of 1 to 6 carbon atoms and n represents an integer from about 1 to 50, preferably from 1 to 35. A series is described of said polyoxyalkylene polyamines in more detail in Pat. USA No. 3,236,895, column 2, lines 40-72; methods of preparing the polyoxyalkylenepolyamines are illustrated in the patent in Examples 4, 5, 6 and 8-12, in columns 4 to 9 thereof; the aforementioned portions of Pat. USA No. 3,236,895, here incorporated by reference. Mixed polyoxyalkylene polyamines, ie, those in which the oxyalkylene group can be selected from more than one moiety, can be used. Examples would be mixed polyoxyethylene propylene polyamines, such as those having the following structural formula: H CH, i HaN - CH - CH3. OC - CHj 0CHa - CHJm - OCH2 CH-NH2 I I CH, CH3 where n + m is equal to 1 to 50, preferably 1 to 35; m is equal to 1 to 49, preferably 1 to 34, and n is equal to 1 to 34. In addition to the aforementioned polyoxyalkylene polyamines, the polyoxyalkylene polyamine derivatives may also be usable. Examples of suitable derivatives are aminoalkylene derivatives, which are prepared by reacting polyoxyalkylene polyamines, such as those mentioned above, with acrylonitrile, followed by hydrogenation of the reaction product. An example of a suitable derivative would be that of the following structural formula: where R and n have the meanings given above. Therefore, in the practice of the invention, when the expression "polyoxyalkylene polyamines" is used, what is meant is polyamines containing both oxyalkylene groups and at least two amine groups, preferably primary amine groups, per molecule. It is considered that primary amines are monofunctional. Preferred polyethers containing active hydrogen are polyoxytetramethylene, also known as polytetrahydrofuran, and mixed polyoxypropylenediamine or polyoxyethylene propylene diamine.

For the oxyethylene-propylene mixed groups in the polyether segment, it is preferred that the oxypropylene content be at least 60 weight percent, more preferably at least 70 weight percent and, more preferably, at least 80 weight percent of the polyether segment. The polyether segment can be derived from a single polyether polyol or polyamine or various mixtures thereof. Preferred are mixtures of polyether polyols, such as polyoxytetramethylene diol, and polyether polyamines, such as polyoxypropylene diamine, in weight ratios of 0.5-10: 1, preferably 1 to 7: 1. In addition to polyethers containing active hydrogen, other materials containing active hydrogen may react with the polyisocyanate to give the white segment. Examples include polycarbonate diols, polyester diols, hydroxyl-containing polydiene polymers, hydroxyl-containing acrylic polymers and mixtures thereof. Examples of polyester polyols and hydroxyl-containing acrylic polymers are disclosed in US Pat. No. 3,962,522 and 4,034,017, respectively. Examples of polycarbonate polyols are described in US Pat. No. 4,692,383, in col. 1, line 58 to col. 4, line 14. Examples of hydroxyl-containing polydiene polymers are disclosed in US Pat. No. 5,863,646, col. 2, lines 11-54. These polymeric polyols will have number average molecular weights of from 400 to 10,000. The amount of the active hydrogen-containing polymer that is used to prepare the polyurethane is at least 30, preferably at least 35, and more preferably 35 to 50 percent by weight based on the total weight of the polymers. reagents used to prepare the polyurethane. Low molecular weight polyols, such as those having two to four hydroxyl groups and molecular weights of less than 400, preferably less than 250 and, usually, between 62 and 250, as reagents for the preparation of the polyurethane may also be included. Specific examples include alkylene diols having 1 to 10 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 1,4-butane diol, trimethylolpropane, glycerol, pentaerythritol and sorbitol. Examples of other low molecular weight polyols are the ether polyols, such as diethylene glycol and ethoxylated bisphenol A. The low molecular weight polyols are used in amounts of up to 30 weight percent, preferably from 0.5 to 10 weight percent, based on the weight of the reagents used to prepare the polyurethane. The prepolymer also has ionizable groups, which can be ionized to solubilize the polymer in water. For the purposes of this invention, the term "ionizable" means a group capable of being ionized, that is, capable of dissociating into ions or charging electrically. For cationic polyurethanes, the ionisable moiety is typically a tertiary amine group that can be incorporated into the polyurethane by reaction with an active hydrogen-containing compound. The amine is neutralized with acid to form the amine salt groups. Such compounds include aminoalcohols, such as dimethylaminoethanol, dimethylaminopropanol, aminopropyldiethanolamine, diethylaminopropylamin, hydroxyalkylmorpholine such as hydroxyethylmorpholine and hydroxyalkylpiperazine such as hydroxyethylpiperazine and the like and mixtures thereof. The amount of amine introduced into the polymer is typically sufficient to give 0.1 to 1, preferably 0.2 to 0.5, milliequivalents (meq) of amine per gram of resin solids, as determined by titration. For the anionic polyurethane, the ionizable moiety is an acid group that is typically incorporated into the polyurethane by reaction with a compound containing active hydrogen. The acid is neutralized with base to form the saline carboxylate group. Examples of anionic groups are -0S03 ~, -COO ", -0P03 =, -S020 ~, -P00" and P03 ~, with COO being preferred. "Suitable materials for introducing acidic groups into the anionic polyurethane are hydroxyl and aromatic acids. Caprocarboxylic acids Specific examples include dimethylolpropionic acid, which is preferred, glycolic acid and lactic acid Other examples of compounds containing active hydrogens and acid groups are aminocarboxylic acids, aminohydroxycarboxylic acids, sulfonic acids, hydroxysulfonic acids and the amino sulfonic acids, examples include oxaluric acid, anilidoacetic acid, glycine, 6-aminocaprylic acid, the reaction product of ethanolamine and acrylic acid, hydroxyethylpropionic acid, 2-hydroxyethanesulfonic acid and sulfanilic acid. amino acids should be used in the presence of base, such as potassium hydroxide or a tertiary amine.The amount of acid incorporated into the The polymer is typically sufficient to give the polymer 0.1 to 1, preferably 0.2 to 0.5, meq of acid per gram of resin solids, as determined by titration. The amine or acid groups are neutralized with acid and base, respectively. The neutralization may vary between 0.1 and 1.0, preferably between 0.4 and 0.8, of the total theoretical neutralization equivalents. For cationic polyurethanes, suitable organic neutralizing agents are acetic acid, hydroxyacetic acid, propionic acid, lactic acid, formic acid, tartaric acid, sulfamic acid and dimethylolpropionic acid, which is preferred, as well as inorganic acids, such as sulfuric acid, hydrochloric acid and phosphoric acid. For anionic polyurethanes, suitable neutralizing agents include inorganic and organic bases such as sodium hydroxide, potassium hydroxide, ammonia and amines. Suitable amines include alkane-lamines, such as monoethanolamine, diethanolamine, dimethylaminoethanol, triethanolamine, diisopropanolamine, triisopropanolamine and the like.; alkylamines, such as diethylamine, triethylamine, diisopropylamine, tributylamine and the like; trimethylamine, diethylmethylamine, methyldiethanolamine, triethanolamine and the like. The appropriate amount of the neutralizing agent is about 0.1 to 1.0 times, preferably 0.4 to 0.8 times, the total theoretical neutralization equivalents. To achieve optimum peel resistance and durability, the polyurethane is curable or thermosettable. As such, it is used with a curing or crosslinking agent, such as a blocked or blocked isocyanate, which is preferred for cationic compositions, or an aminoplast, which is preferred for anionic compositions. The polyisocyanate can be completely topped essentially free of isocyanate groups and be present as an independent component, or it can be partially capped and react with hydroxyl or amine groups on the backbone of the polyurethane. Examples of suitable polyisocyanates and fillers are those described in US Pat. No. 3,947,339. When the crosslinking agent contains free isocyanate groups, the film-forming composition is preferably a two-pack composition (one package contains the cross-linking agent and the other contains the hydroxyl-functional polymer) in order to maintain storage stability. In U.S. Pat. No. 3,984,299, fully capped polyisocyanates are described. The polyisocyanate can be an aliphatic, cycloaliphatic or an aromatic polyisocyanate or a mixture of the two. Diisocyanates are preferred, although higher polyisocyanates can be used in place of, or in combination with, the diisocyanates. Aliphatic or cycloaliphatic polyisocyanates are preferred. Examples of suitable aliphatic diisocyanates are straight-chain aliphatic diisocyanates, such as 1,4-tetramethylene diisocyanate and 1,6-hexamethylene diisocyanate. In addition, cycloaliphatic diisocyanates can be employed. Examples include isophorone diisocyanate and 4,4'-methylenebis (cyclohexyl isocyanate). Examples of suitable aromatic diisocyanates are p-phenylene diisocyanate, diphenylmethane-4,4'-diisocyanate and 2,4- or 2,6-toluene diisocyanate. Examples of suitable higher polyisocyanates are triphenylmethane-4,4 ', 4"-triisocyanate, 1,4,4-benzene triisocyanate and polymethylene polyphenyl isocyanate, and biurets and isocyanurates of diisocyanates, including mixtures thereof, are also suitable. the isocyanurate of hexamethylene diisocyanate, the biuret of hexamethylene diisocyanate and the isocyanurate of isophorone diisocyanate Isocyanate prepolymers can also be used, for example the reaction products of polyisocyanates with polyols such as neopentyl glycol and trimethylolpropane, or with polymer polyols , such as polycaprolactone diols and triols (NCO / OH equivalent ratio greater than one) Any aliphatic, cycloaliphatic or aromatic alkyl monoalcohol or phenolic compound suitable as a quenching agent for the crosslinking polyisocyanate crosslinking agent in the composition of the present invention can be used. tion, including, for example, lower aliphatic alcohols res, such as methanol, ethanol and n-butanol; cycloaliphatic alcohols, such as cyclohexanol; aromatic alkyl alcohols, such as phenylcarbinol and methylphenylcarbinol, and phenolic compounds such as the phenol itself and substituted phenols where the substituents do not affect the coating operations, such as cresol and nitrophenol. Glycol ethers can also be used as finishing agents. Suitable glycol ethers include ethylene glycol butyl ether, diethylene glycol butyl ether, ethylene glycol methyl ether, and propylene glycol methyl ether. Other suitable fillers include oxi-mas, such as methyl ethyl ketoxime, acetone oxime and cyclohexa-none oxime; lactams, such as epsilon-caprolactam, and amylas, such as dibutylamine. The crosslinking agent is typically present in the thermosetting compositions of the present invention in an amount of at least 10 percent by weight, preferably at least 15 percent by weight, based on the total weight of resin solids in the composition. The crosslinking agent is also typically present in the composition in an amount of less than 60 weight percent, preferably less than 50 weight percent and, more preferably, less than 40 weight percent, based on weight total resin solids of the composition. The amount of crosslinking agent present in the thermosettable composition of the present invention can range between any combination of these values, including the values quoted. The equivalent ratio of hydroxyl groups in the polymer to reactive functional groups in the crosslinking agent is typically in the range of 1: 0.5 to 1.5, preferably 1.0 to 1.5. The aminoplasts are obtained from the reaction of formaldehyde with an amine or amide. The most common amines or amides are melamine, urea or benzoguanamine, and are preferred. However, condensates can be used with other amines or amides; for example, condensates of glycoluri-aldehyde, which give a crystalline product of high melting point useful in powder coatings. While the aldehyde used is most frequently formaldehyde, other aldehydes may be used, such as acetaldehyde, crotonaldehyde and benzaldehyde. The aminoplast contains methylol groups and, preferably, at least a portion of these groups are etherified with an alcohol to modify the curing response. Any monohydric alcohol can be used for this purpose, including methanol, ethanol, butanol, isobutanol and hexa-nol. Preferably, the aminoplastics used are condensates of melamine-, urea-, glycoluril- or benzogua-na-formaldehyde etherified with an alcohol containing from one to four carbon atoms. The aminoplast is present in the electrodepositable composition in amounts of 5 to 60, preferably 15 to 50, weight percent based on the weight of resin solids. Normally, the thermosetting composition will preferably also contain catalysts to accelerate the curing of the crosslinking agent with reactive groups in the polymer (s). Suitable catalysts for the curing of the aminoplast include acids such as the acid phosphates and sulphonic acid or a substituted sulphonic acid. Examples include dodecylbenzenesulfonic acid, paratoluenesulfonic acid and the like. Suitable catalysts for the curing of the isocyanate include organotin compounds, such as dibutyltin oxide, dioctyltin oxide, dibutyltin dilaurate, and the like. The catalyst is normally present in an amount of about 0.05 to about 5.0 weight percent, preferably about 0.08 to about 2.0 weight percent, based on the total weight of solids of resin in the thermosetting composition.

Possible ingredients, such as pigments, may be present in the polyurethane compositions. Particularly suitable pigments include concealing pigments, such as titanium dioxide, zinc oxide, antimony oxide, etc., and organic or inorganic UV-opacifying pigments, such as iron oxide, red or transparent yellow iron oxide, black of carbon, phthalocyanine blue and the like. The pigments may be present in amounts of up to 35 parts by weight or less based on 100 parts by weight of total solids of the electrodepositable composition. Other optional ingredients are antioxidants, UV absorbers and light stabilizers of blocked amines, such as, for example, blocked phenols, benzophenones, benzotriazoles, triazoles, triazines, benzoates, piperidinyl compounds and mixtures thereof. These ingredients are typically added in amounts of up to about 2% by weight based on the total weight of resin solids of the electrodepositable composition. Other possible ingredients include co-solvents, coalescence aids, defoamers, plasticizers, bactericides and the like. Aqueous cationic or anionic polyurethane dispersions are typically electrodeposited onto the electroconductive coating from a plastics-plating bath having a solids content of 5 to 50 weight percent. The bath temperature is normally about 15 ° C to 35 ° C. The voltage is from 100 to 400 V (charging voltage) using the substrate with the electroconductive coating as the cathode in the case of the cationic polyurethane or as the anode in the case of the anionic polyurethane. The thickness of the film of the electrodeposited coating is not particularly restricted and can vary greatly depending on the application of the finished product, etc. However, the thickness is usually between 3 and 70 microns, particularly 15 to 35 microns, in terms of the thickness of the cured film. The baking and curing temperature of the coating film is usually from 100 ° C to 250 ° C and, preferably, from 140 ° C to 200 ° C. As mentioned above in the case of the selective application of the second electroplate by using IR baking of the first electrodeposited coating, heating or baking after the application of the second electrocoat can cure both the first and the second electrolayer on surfaces not exposed to heating or baking with IR. In addition, baking can complete the curing of the first electrolayer that was exposed to IR and jacket with the second electrolayer. EXAMPLES A cationic electrodepositable composition for protection against corrosion, which results in a conductive coating for a substrate, was prepared from the materials described below in Example 1. These include the blocked polyisocyanate crosslinker prepared according to Example IA and the electrodepositable cationic primer resin which, together with the blocked polyisocyanate, constitutes the main vehicle of the composition prepared in Example IB. The electrodepositable cationic composition was prepared according to Example 1C. Example 1, Part A; Isocyanate Crosslinker A blocked polyisocyanate crosslinker was prepared from the following materials: 1 polymeric DIM, which can be purchased from DOW CHEMICAL Company, Michigan, under the trade name PAPI 2940. Polyisocyanate and methyl isobutyl ketone were charged into a reaction flask under a nitrogen atmosphere and heated to 80 ° C. Trimethylolpropane was then added and the mixture was heated to 105 ° C and maintained for 30 minutes. The mixture was cooled to 65 ° C and dibutyltin dilaurate and 2- (2-butoxyethoxy) ethanol were slowly added, allowing the reaction to produce an exotherm to a temperature between 80 and 100 ° C and remained there until the Infrared indicated that there was no NCO left without reacting. Example 1, Part B; Cationic primer electrodeposition vehicle A cationic aqueous carrier was prepared with the following materials. All parts and percentages are by weight, unless otherwise indicated. 2 Bisphenol A polyglycidyl ether, which can be purchased from Shell Oil and Chemical Co., Houston, Texas. 3 Prepared with materials according to US Pat. No. 4,468,307 (Wismer et al.). 4 Dicetimine derived from diethylenetriamine and methyl isobutyl ketone (73% solids in methyl isobutyl ketone). The EPON 828, the bisphenol A-ethylene oxide adduct, the bisphenol A and the methyl isobutyl ketone were charged to a reaction vessel and heated under a nitrogen atmosphere at 125 ° C. Ethyltriphenylphospho-nium iodide was added and the reaction mixture was allowed to produce an exotherm to about 145 ° C. The reaction was maintained at a temperature of 145 ° C for two hours and an epoxy equivalent was obtained. The epoxy equivalent is usually stopped along with the desired epoxy equivalent weight. At this point, the crosslinker, the diketimine and the N-methylethanolamine were successively added. The mixture was allowed to produce an exotherm and then a temperature of 130 ° C was established and the mixture was maintained for one hour at 130 ° C. The resin mixture (6,000 parts) was dispersed in aqueous medium by adding it to a mixture of 154.62 parts of sulfamic acid and 3339.88 parts of deionized water. After stirring for 30 minutes, Emersol 210 oleic acid was added in an amount of 55.20 parts and the dispersion was stirred for an additional 30 minutes. The Emersol 210 can be purchased from Henkel Corp., Emery Division, Cincinnati, Ohio. The dispersion was further diluted with 1,909.94 parts of deionized water, 1,273.29 parts of deionized water and 2,345.54 parts of deionized water stepwise and purified in vacuo to remove the organic solvent and obtain a dispersion having a solids content of 44.78 percent and a particle size of 860 Angstroms. Example 1, Part C: Preparation of Cationic Electrolayer Primer A cationic electrodeposition coating was prepared with the following materials. All parts and percentages are by weight, unless otherwise indicated.

An aqueous dispersion of a flow-flexibilizing agent was prepared generally according to US Pat. No. 4,423,166 for use in the electrodepositable composition. The flexibilizing agent-flow controller was prepared from a polyepoxide (EPON 828) and a polyoxyalkylenepolyamine (JEFFAMINE D-2000, from Huntsman Corporation, Salt Lake City, Utah.). The flexibilizing agent-flow controller was dispersed in aqueous medium with the aid of lactic acid and the dispersion had a resin solids content of 36.0 percent. 6 A surfactant mixture (85-XS-139) from Air Products and Chemicals, Inc., Allent n, Pennsylvania. 7 A cationic pigment paste (CP639) having an electroconductive carbon black pigment, from PPG Industries, Inc., Pittsburgh, Pennsylvania. The cationic electrodepositable coating composition was prepared by adding the components in the indicated order to a bath-type container for panel coating. The deposition of the composition involved the immersion of a steel panel treated with zinc phosphate, an electrogalvanized one treated with zinc phosphate and one zinc-iron alloy treated with zinc phosphate in the bath and the individual electro-coating of the 180-degree panels. volts for two minutes at 95 ° F (35 ° C) to produce baked film thicknesses of approximately 0.75 milli-inches (19.0 microns). The electrocoated panels were baked for 30 minutes at 365 ° F (185 ° C). Several electrodepositable thermosetting polyurethane coating compositions resistant to desquamation were prepared as shown in the following Examples. Example 2; Part A - Preparation of anionic polyurethane resins Polyurethane anionic resins were prepared with the materials listed in Table 1. All parts and percentages are by weight, unless otherwise indicated. Table 1 8 Polytetrahydrofuran. 9 Polypropylene oxide. 10 Polytetrahydrofuran, molecular weight 1,000, from Great Lakes Chemical, Corp., West Lafayette, Indiana. 11 Polypropylene glycol, molecular weight 1,000, which can be purchased from Arco Chemical Co., of Newton Square, Pennsylvania, as PPG-1025. 12 TS-30, from Perstorp Poiyols, Inc., Toledo, Ohio. Preparation of Example 21 Isophorone diisocyanate (929.1 g, 8.37"eq" equivalents), dibutyl tin dilaurate (0.58 grams "g") and methyl isobutyl ketone (145.6 g) in a round bottom flask. The solution was heated to 50 ° C. At 50 ° C, polyTHF Polymeg'lOOO (1535.4 g, 3.07 eq) and MIBC were added. (402.3 g) dropwise at such a rate that the temperature did not exceed 90 ° C. The reaction was maintained at 72 ° C for 45 minutes after the addition was complete and an isocyanate equivalent weight of 571. Obtained at 72 ° C, dimethylolpropionic acid (162.8 g, 2.43 eq) and MIBC ( 7.5 g) and the reaction was maintained at 90 ° C for an anticipated isocyanate equivalent weight of 1135. To the anticipated equivalent weight ("P. eq"), propylene glycol (95.8 g, 2.52 eq), trimethylolpropane (177 g, 5.21 eq) and MIBC (168.9 g) were added and the reaction was maintained until no more isocyanate remained (determined by IR). In general, polyurethane resins II and III were prepared in a manner similar to that of I. The exceptions were that, for II, Jeffamine D-2000 and pTMP were added more than polyTHF alone. Similarly, for example III, polypropylene glycol, Jeffamine D-2000 and pTMP were added and polyTHF was not added. In addition, for II and III, 1,4-butanediol was added in the preparation of the polyurethane resin. Example 2: Part B - Pigment-dispersing anionic resin The following parts by weight were combined: Material Quantity 1 Polythylene Polymegß200013 131.0 2 Polyester Fomrez * 55-5614 131.0 3 l-methyl-2-pyrrolidinone 160.7 4 Neopentylglycol 10.2 5 Dimethylolpropionic acid 54.1 6 Polyisocyanate Desmodur W15 235.1 13 Poly (tetramethylene ether) glycol, MW = 2,000, from Great Lakes Chemical Corp., West Lafayette, Indiana. 1 Hydroxy finished polyester, number of hydroxyl 56, from Witco Corporation, Endicott, New York. Methylenebis (4-cyclohexyl) diisocyanate, from Bayer Corporation, Pittsburgh, Pennsylvania.

The materials 1-5 were loaded in the order and quantities indicated in a reaction vessel. The mixture was then heated to 54 ° C. Polyisocyanate Desmodur W and l-methyl-2-pyrrolidinone (19.0) were then added to the reactor at a rate such that the temperature did not exceed 85 ° C. After the addition of the polyisocyanate was completed, butanol (2.7) and dibutyltin dilaurate (0.6) were added to the reactor. The solution was maintained at 85 to 90 ° C until achieving an isocyanate breakdown (<15 units / h, theoretical equivalent weight of isocyanate = 1560). After stopping the isocyanate (NCO) advance, the resin was dispersed in deionized water (992.9), dimethylethanolamine (35.0) and ethylenediamine (15.0) and the dispersion was maintained at 75 ° C for 30 minutes. After 30 minutes, the dispersion was cooled to 50 ° C. At 50 ° C, deionized water (38.8) and propyleneimine were added (6.5). The dispersion was then heated to 60 ° C and maintained at this temperature for four hours before cooling to room temperature. Example 2; Part C - Anionic polyurethane pigment paste Part C; Preparation of neutralized acid catalyst Two formulations of neutralized acid catalyst were prepared. For Example 2, Part Cl (1), an amount of 284.93 grams of Nacure 1051 dinonylnaphthalenesulfonic acid was mixed, which can be purchased as a fifty percent dino-nilnaphthalenesulfonic acid in ethylene glycol monobutyl ether, from King Industries of Norwalk, Connecticut, with 30.32 grams of dimethylethanolamine. This gives a neutralized acid catalyst intermediate with calculated solids of 45.19 weight percent. For Example 2, Part Cl (2), 60.0 grams of dinonylnaphthalenesulfonic acid solution, Nacure 1051, and 6.68 grams of triethylamine were mixed together and diluted with 511.7 grams of deionized water to obtain a dispersion of neutralized catalyst with a solids content of 5.19%. Part CII: Preparation of pigment paste The following two formulations of pigment paste were prepared with the materials mentioned, the amounts being indicated in parts by weight. These materials were mixed with a Cowles blade and then dispersed with conventional equipment for pigment dispersion up to a Hegman reading of 7.5+: 16 Resin prepared with the materials described in Example A of US Pat. 5,530,043 at 100 percent solids. 17th Raven 410 and 17b Raven 1200, both from Columbian Chemical Company, Atlanta, Georgia. ? aa R-900 and 18b R-960-38, both from DuPont de Nemours Company, Delaware. 19 1030-AC-1005, by Cookson Matthey of Jacksonville, Florida. 248-0061, from Sun Chemical, Inc., Linden, New Jersey. For Example CII (1) after dispersion, the dispersion mill was washed with a small amount of deionized water. The resulting pigment paste had a solids content (60 minutes at 110 ° C) of 57.3 percent. Example 2: Part D - Preparation of electrodepositable thermosetting anionic polyurethane formulations The following formulations were prepared using the polyurethane backbones of Example 2, Part A, as indicated in Table 2, crosslinkers and modifiers: Table 2 21 Methoxy / n-butoxy melamine and formaldehyde resins from Cytec Industries Inc., West Patterson, New Jersey. 22 Methylated and ethylated benzoguanamine resins from Cytec Industries Inc. 23 LHT-240, 720 molecular weight polypropylene triol oxide, from Arco Chemical Co. of Newton Square, Pennsylvania. Formulations D1-D4 were prepared using the following "hot mix" procedure: The resin, the crosslinkers and the amine were weighed into a quarter-gallon stainless steel beaker and the beaker was placed in a bath of water maintained at 80 ° C. The mixtures were agitated with an air motor propeller blade and a minimum angle step. Under continuous agitation, 550 grams of deionized water was added slowly to form an aqueous dispersion. After forming the aqueous dispersion, the heat supplied to the water bath was deactivated and the mixtures were allowed to cool. The mixtures were transferred to one gallon open plastic containers and stirred overnight with magnetic stir bars. After stirring overnight to allow the largest of the ketone solvent to evaporate, an additional 3490 grams of de-ionized water was added, along with 75.1 grams of the pigment paste of Example 2, Part CII (1), for complete the electrocoat coating formulations. The calculation of the amount of flexibilizing segment was determined in Table 2 of Example 2, Part D, as follows. The following is added: polytetrahydrofuran, polyether diols, polyether diamines, polyether plasticizers and any known material imparts flexibility to the coating films. For the total resin solids, all the materials that contribute to the resin solids are added, with the proviso that, for the amine-formaldehyde resins Cymel 1123 and Cymel 1135, a weight loss with the curing is estimated. It is estimated that the weight loss for Cymel 1123 and for Cymel 1135 is 20%, which gives them an estimated solids content in a baked film of 80%. As a sample calculation of the flexibilizing segment content, the calculation for Formulation Dl is as follows: Resin solid resin materials: 215 grams Cymel 1135 (20 grams x 0.8) 16 grams Cymel 1123 (15 grams x 0.8) 12 grams Total 243 grams Flexibilizing segments: 215 grams of resin solids x 53.34% Polymeg 100 = 114.7 grams of Polymeg 1000. 114.7 / 243 = 47.2% as amount of flexibilizing segment. The other amounts of flexibilizing segment for the other formulations were calculated in a similar way. The determination of the weight loss with the curing of the amine-formaldehyde resins may depend on many factors, such as the baking program, the amount of acid catalysis and the amount of co-reactants available. However, it can be estimated by the range indicated by the provider of equivalent weight. The equivalent weight of Cymel 1123 is given in a range of 130 to 190 grams per mole of reaction site. The molecular weight of the benzo-guanamine monomer Cymel 1123 is estimated at 391 assuming equal moles of the alkylation alcohols, methanol and ethanol. The calculation of the weight loss for two moles of methanol gives a calculated weight loss of 15.8%. The calculation of the weight loss for two moles of methanol and one mole of ethanol gives a calculated weight loss of 27.4%. The calculations are only gross estimates of how an amine-formaldehyde resin will cure in a particular formulation. An estimate of 20% weight loss is applied for both Cymel 1123 and Cymel 1135 in the examples. Examples 3 and 4 Two electrodepositable thermosetting polyurethane anionic compositions were prepared with the formulations shown in Table 3, where the amounts of the components are given in parts by weight.

Table 3 4 Propoxylated cresol plasticizer from C.P. Hall Company, Chicago, Illinois. Preparation of solvent-free anionic polyurethane formulation For Examples 3 and 4, the components listed in Table 3 were combined in a similar manner, where any difference of Example 4 with respect to Example 3 is indicated in parentheses in the following description. The isophorone diisocyanate, the dibutyltin dilaurate and the MIBC were charged in a reaction vessel. The mixture was heated at 70 ° C (50 ° C) under a blanket of nitrogen with stirring. The POLYMEG® 1000, MIBC, 1,4-butanediol and JEFFAMINE® D2000 were slowly added at a rate that maintained the reaction temperature at 90 ° C or lower. (For Example 4, JEFFAMINE® D2000 was slowly added with a wash of MIBC to the other three materials after combining them at a rate that maintained the temperature below 90 ° C, together with a wash of MIBC and was maintained at 75 ° C for 27 minutes). For Example 3, a MIBC wash was also made following the addition of the JEFFAMINE® D2000 polyamine. The reaction was maintained at 75 ° C for 60 (27) minutes. An equivalent weight (eq.) Of isocyanate of 556 (570) was obtained. Dimethylolpropionic acid was added, followed by a washing with MIBC, and the reaction mixture was heated at 88 ° C. When the p. eq. of isocyanate reached 1185 (1132), propoxylated propylene glycol and trimethylolpropane, for Example 3, or (trimethylolpropane) for Example 4, and MIBC were added to the reaction mixture and washed with MIBC. The reaction mixture was maintained at 100 ° C until the isocyanate was consumed (determined by IR). For Example 3, the reaction mixture was cooled to 93 ° C. For Example 4, the reaction was stopped overnight and heated the next day at 95 ° C. Dimethylethanolamine and either CYMEL® 1123, either CYMEL® 1135 (or, for Example 4, Paraplex WP-1 and CYMEL® 1170) were added and mixed for 10 minutes. For Example 3, the first addition of deionized water was made over one hour and the dispersion was cooled to 60 ° C. This temperature was maintained for 30 minutes before making the second addition of deionized water for 60 minutes, while maintaining a temperature of 60 ° C. For Example 4, the first addition of deionized water was made up to 93% of the above reaction over 34 minutes and the reaction was allowed to mix for 24 minutes. The second addition of deionized water was made over 47 minutes. Both dispersions were purified under vacuum at 60 ° C to remove the solvent. For Example 3, the composition was filtered using diatomaceous earth and adjusted with deionized water to a solids content of 34.1 (35.1% by weight for Example 4). For Example 3, an amount of 953.2 grams of this filtered resin was mixed with 97.63 grams of the pigment paste of Example CII (1) and 2.75 liters of deionized water to complete the formulation of the electrode bath. -Rorrevestment. For Example 4, the electrodepositable composition of anionic polyurethane thermosettable with the polyurethane of Example 4 and the catalyst dispersion of Example 2, Part CI (2) and the pigment plaster of the Axis-pio CII (2) was prepared. This was done under stirring conditions with a magnetic stir bar in a gallon sized plastic container, where an amount of 880.7 grams of the polyurethane resin of Example 4 was diluted with 1.5 liters of water deionized. 24.66 grams of catalyst dispersion of Example 2, Part Cl (2) were also diluted with 100 grams of deionized water and the beaker was washed with additional deionized water. An amount of 70.5 grams of the pigment paste of Example CII (2) was diluted with 50 grams and the beaker was washed with additional deionized water. Deionized water was added to increase the volume of electrocoat bath to 3, 5 liters, completing the formulation. Study of the electrocoating compositions. Steel panels were coated with a conductive priming electrode layer of Example 1, then baked and electrorevealed with the formulations of the baths of Examples 2 and 3. The coated steel panels were pretreated. a zinc-iron galvanizing layer, commonly referred to as electro-zinc-iron, cleaning and phosphating with CHEMFOS C-700 phosphate pretreatment from PPG Industries Inc., Pittsburgh, Pennsylvania. The resulting panels, supplied as part number APR-24526 by ACT Laboratories, Inc., of Hillsdale, Michigan, were coated with the conductive primer composition of Example 1. The panels were coated at 180 volts at 95.5 ° F (35 ° C). , 3 ° C) for 135 seconds, spray-washed with deionized water and baked for 30 minutes at 365 ° F (185 ° C) in a gas oven. A dry film thickness of 0.7 to 0.75 mils (17.8 to 19 microns) resulted. After cooling, these primed panels were coated with the second peel-resistant electrolayers of Examples 2 and 3 at 160 volts and at a temperature of 85 ° F (29 ° C). The coating time, the baking temperature and the film thickness varied between the samples, as shown in Table 4. During the second electrocoating operation, the panels were removed from the electrocoating bath and spray washed with deionized water in the usual way in the electroplastic process. Furthermore, on the front side of the panel, a 0.1% solution of Surfynol GA surfactant was flowed with an "HLB" (Hydrophilic-Lipophilic Balance) of 13+ and a cloud point of the solution of 135 ° F. , 57 ° C (from Air Products and Chemicals Inc.) in deionized water on the newly electrodeposited film. After draining, the panels were baked by two methods: 30 minutes at 300 ° F (149 ° C) in an electrically heated oven and for 30 minutes at 320 ° F (160 ° C) in a gas heated oven. Table 4 summarizes the results of the tests for the defects and the peeling resistance of the films. For the study of peeling resistance, the panels were given an upper coating with NHU-90394 / DCT-3000, a white acrylic-melamine topcoat of the basecoat / clearcoat type from PPG Industries.

Table 4 Multiple numbers represent replication, for example three independent panels. The film defects in these films were a common type of electroplating defect, crater depressions, which were counted. 2G Desquamation resistance using the General Motors Engineering GM9508P Pattern, where the evaluations given are on a scale from 0 to 9, 0 being severely peeling and 9 representing a remarkable resistance to peeling. 27 For the Kugelstoss tests, upside-down panels with an upper layer were stored in a freezer at -20 ° C for at least two hours and then fired with a 3 mm chrome steel ball at a speed of 155 mm. miles per hour (249 km / hour). The ball impacted on the test panel coated at 90 °, or perpendicular to the surface. After removing from the freezer, the lifted and loose portions of the paint system were removed with a sharp tool. The total area of damage was measured and the results were given in square millimeters of damage. 28 For the impact tests with 3 mm balls, the same method was used as with the Kugelstoss tests, except for the fact that steel balls were fired at 3 mm chrome at 75 miles per hour (121 km / h ) and 95 miles per hour (153 km / h). The galvanic bath of Example 4 was applied by electrocoating onto a substrate consisting of 0.74 mils (18.8 microns) of a conductive black electrolayer cured on a phosphating electrozinc-iron steel panel. This electrolayer can be purchased from PPG Industries Inc. By connecting the substrate as an anode, the composition of Example 4 was deposited at 120 volts, at a bath temperature of 85 ° F (29 ° C) and for 50 seconds. After removing the electroplastic bath, it was washed by spraying with deionized water as usual. Moreover, on the front side of the panel, a 0.1% solution of sur-Factants Surfynol GA in deionized water was allowed to flow over the newly electrodeposited film. After draining, the panel was baked for 10 minutes at 200 ° F (93 ° C) in an electric oven, the oven temperature was set at 250 ° F (121 ° C) and the panel was baked for an additional 20 minutes. As a result, a cured coating resistant to solvents, having a film thickness of 1.29 mils (32.8 microns), was produced. After 100 double rubs with a cloth soaked in acetone, only a trace fogging of the cured film was observed. Comparative Examples 1 and 2 The following desquamation tests were made on powder priming paint known in the industry to have an excellent desquamation resistance, PCV-70100, from PPG Industries, Inc. The substrate for the powder coating was Electrozinc-iron with a CHEMFOS 700 / C20 phosphate pretreatment and a chrome wash, also from PPG Industries Inc. After phosphating, the panels were coated with electrocoat ED-8100 (from PPG Industries, Inc.) and then with the dust. The top layer used for the desquamation test is the same as for Examples 2 and 3 above, NHU-90394 / DCT-3000. Since the peeling-resistant coating was not electrodeposited, there was no voltage, no coating temperature and coating time for electrodeposition. After application of the top coat on the desquamation resistant coating, the coatings were baked at 340 ° F (171 ° C) in an electric and gas oven to obtain a film thickness of 3 mils (75 microns). Table 5 shows tests of this type of a peel-resistant coating in said coating system of a spray-applied peeling-resistant coating, of a layer electrodeposited layer and a top layer layer. Table 5 Example 5: Preparation of cationic pigment paste of electrodepositable composition of cationic thermosetting polyurethane for cationic polyurethane Example 5, Part A: Preparation of cationic polyurethane resin. Isophorone diisocyanate (1,200.6 g, 10.82 eq), methyl isobutyl ketone (520.2 g) and dichloroethane dilaurate (0.6 g) were charged in a round background. The mixture was heated at 30 ° C. Trimethylolpropane (125.1 g, 2.80 eq) was then added to the solution. After the addition, the temperature was raised to 73 ° C. Caprolactam (382.9 g, 3.38 eq) and MIBC C40.0 g) were added to the flask. The mixture was maintained at 85 ° C until obtaining a p. eq. of isocyanate (NCO) of 490. Te-9 rethane 650 is a polytetrahydrofuran with a molecular weight of 650 from DuPont. An amount of this PolyTHF (707.9 g, 2.21 eq) and MIBC (275.7 g) were then added to the flask. The addition was made at such a rate that the temperature was maintained below 90 ° C. After completion of the addition, the temperature was allowed to fall below 65 ° C. At 65 ° C, Jeffamide * D2000 (437.0 g, 0.44 eq) and MIBC (40.0 g) were added and the mixture was maintained for 15 minutes. After this maintenance period, a p. eq. of NCO of 1,974. Then diethanolamine (87.0 g, 0.83 eq) and 125 g aminopropyldiethanolamine (125.2 g, 0.77 eq) were added to the reaction mixture. The solution was maintained at 80 ° C until no presence of NCO was detected by IR analysis. After the isocyanate was consumed, 31 g of Surfynol8 GA surfactant (30.7 g) and MIBC (40.0 g) were added and the solution was mixed for 15 minutes. The resin was then dispersed in deionized water (1666.0 g) and dimethylolpropionic acid (82.9 g, 0.62 eq). The resin was re-diluted with deionized water (3,303.0 g), resulting in a final dispersion at 36.5% solids. The dispersion was then purified under vacuum at 60 ° C to remove the solvent. Example 5, Part B The following materials were mixed with a Cowles blade and then dispersed with conventional pigment dispersion equipment until a Hegman reading of 7+ was obtained: 29 Sulfonium-quaternary ammonium type described in US Pat. No. 5,130,004 (PPG Industries, Inc., Johnson &McCollum), with a solids content of 31.2%. 30 See footnote 18a. 31 See footnote 19. 32 See footnote 20. 33 See footnote 17a. The resulting pigment paste had a calculated solids content of 58.4 percent by weight. Example 5 Part C: Electroplated Polyurethane Cationic Composition 1067.9 grams of the resin of Example 5, Part A, were mixed with 105.8 grams of the pigment paste of Example 5, Part B and diluted with water to a volume total of 3.8 liters. Study of the Cationic Polyurethane Electrolayer The same type of steel panel of Examples 2 and 3, electrozinc-phosphatized iron, was electro-coated with the conductive primer of Example 1 and baked for 30 minutes at 365 ° F (185 ° C). ) in a gas oven to obtain a dry film thickness of 0.7 to 0.75 mils (17.8 to 19 microns). A dry film thickness of 0.7 to 0.75 mils (17.8 to 19 microns) was obtained as a result. The coating conditions here were for coating addition and may not be similar to those of the aforementioned examples. After cooling, the primed panel was electro-coated with the cationic polyurethane electroplating bath of Example 5. After the second electroplating operation, the panel was removed from the electroplating bath and spray-washed with deionized water as usual in the process of electrocoating. Moreover, a 0.1% solution of Surfynol GA surfactants in deionized water was flowed on the front side of the panel onto the newly electrocoated film. After draining, the panel was baked for 30 minutes at 350 ° F (111 ° C) in an electric oven. An upper layer was applied with the same top layer system used in Example 3, NHU-90304 / DCT-3000, from PPG Industries Inc. In Table 6, the results of the test are summarized. Table 6 Comparison of the results of the electrodeposited thermosetting anionic polyurethane-resistant peeling coating of Table 4 and the electrodeposited thermosetting cationic polyurethane of Table 6 with the commercial peeling-resistant spray coating of Table 5 indicates that the Electrodeposited coatings may work better than commercial spray coatings. In particular from the results of Table 4, it can be seen that the polyurethane coatings of this invention can give excellent resistance to desquamation. The resistance to impacts at high speeds is higher for the electrodeposited coatings resistant to the desquamation of polyurethane of the present invention than that of a commercialized primer, which means an important improvement. The peeling results with the gravelometer between the electrodeposited and the spray coatings indicated an identical excellent performance, except for a slightly lower, but acceptable performance of the anionic polyurethane without polytetrahydrofuran and with the flexibilizing segment of polypropylene oxide polymer. For the Kugelstoss and impact tests, all electrodeposited coatings with flexibilizing segments of polytetrahydrofuran worked better than the commercial spray peeling resistant coating. The use of polytetrahydrofuran is particularly useful. When the polytetrahydrofuran is omitted, as in Example 2D3 of Table 4, the desquamation resistance, although still valid, decreases, as seen by the greater areas of damage by ball impacts. Specifically, it is desirable that the Kugelstoss test have less than 8 square millimeters of damage. Also the electrodeposited coating with all the polypropylene oxide flexibilizing segments functioned in a manner comparable to that of the commercially available spray peel-resistant composition. The data also show that the inclusion of some polypropylene oxide in the formulation, either forming part of the polymer as in Example 2D2 of Table 2, or added as a free polyol as in Example 2D4 of Table 4, is beneficial for the appearance of the film and for obtaining a reduction in type defects. crater. Therefore, a combination of polytetrahydrofuran and polypropylene oxide in the formulations of this invention provides good resistance to flaking and appearance of the film.

Claims (58)

1. An electrocoating method of electrically conductive substrates with two electrodeposited layers, consisting of the following steps: (a) electrodeposition of an electrically conductive coating from a composition consisting of a curable ionic resin and an electroconductive pigment; (b) at least partial cure of the electrodeposited coating to make the coating electrically conductive; (c) electrodeposition of a second coating on the electrically conductive coating of step (b), the second coating being deposited from a composition consisting of a curable ionic polyurethane resin containing a polymeric segment derived from a polymer that contains active hydrogen and having a glass transition temperature of 0 ° C or less and a number average molecular weight of 400-4,000, and (d) curing the second coating of step (c).

2. The process of claim 1, wherein the polyurethane coating is derived from the reaction product of: (a) a polyisocyanate and (b) a polyether containing active hydrogen.

3. The process of claim 2, which contains as another component (c) plus an active hydrogen-containing compound that contains a group that can be converted to an ionic group.

4. The process of claim 3, wherein (c) is a compound containing active hydrogen containing carboxylic acid groups or amino groups.

The method of claim 3, which contains as another component (d) plus, an active hydrogen-containing compound having a molecular weight of less than 400.

6. The process of claim 2, wherein the polyisocyanate is an aliphatic polyisocyanate. or cycloaliphatic.

The method of claim 1, wherein the active hydrogens of the active hydrogen-containing polyether are hydroxyl or primary amine.

The process of claim 1, wherein the active hydrogen containing polyether contains (i) a polyoxytetramethylene diol.

The process of claim 8, wherein the active hydrogen-containing polyether further contains (ii) a polyoxypropylene polyol or a polyoxypropylene polyamine.

The method of claim 9, wherein the weight ratio of (i) to (ii) is 0.5-10: 1.

The process of claim 2, wherein (b) is present in an amount of at least thirty (30) weight percent of the reagents used in the preparation of the polyurethane.

12. The process of claim 6, wherein the polyisocyanate is isophorone diisocyanate, 1,6-hexamethylene diisocyanate and its isocyanurates.

The method of claim 1, wherein the curable polyurethane contains active hydrogens and a curing agent having groups that are reactive with the active hydrogens.

The process of claim 13, wherein the curing agent is an aminoplast or a capped polyisocyanate.

15. The method of claim 1, wherein the second coating contains an opacifying pigment.

16. The method of claim 15, wherein the opacifying pigment is selected from the group consisting of non-transparent iron oxides and transparent iron oxides.

The method of claim 1, wherein the second coating contains a stabilizer against blocked amine light.

18. The process of claim 8, wherein the active hydrogen-containing polyether further contains an oxyalkylated triol.

19. The process of claim 1, wherein the polyurethane resin further contains a derivatized segment of a polymeric polyol selected from polyester polyols and polycarbonate polyols.

The method of claim 1, wherein the electrically conductive coating is deposited from a cationic electrodepositable composition.

21. The method of claim 1, wherein the second coating is deposited from an anionic electrodepositable composition.

22. The method of claim 21, wherein the second coating is deposited from an anionic composition that also contains an aminoplast curing agent.

23. The process of claim 22, wherein the aminoplast is present in an amount of 5 to 50 weight percent based on the weight of the beef solids a.

The method of claim 1, wherein the second coating is deposited from a cationic electrodepositable coating composition.

The method of claim 24, wherein the second coating is derived from a cationic electrodepositable composition containing active hydrogen and further containing a capped polyisocyanate curing agent.

26. The process of claim 25, wherein the polyisocyanate is capped with caprolactam and / or dibutylamine.

27. The process of claim 25, which has an equivalent ratio of NCO / active hydrogen of 1.0 to 1.5: 1.

28. The method of claim 1, wherein the electroconductive coating has a resistivity of less than 1012 ohm-centimeter.

29. The method of claim 1, wherein the electrodeposited coating of step (a) is at least partially cured by radiant heating with infrared.

30. The method of claim 29, wherein infrared radiant heating is directed to a predetermined area of the electrodeposited coating.

The method of claim 30, wherein the substrate is a body for a motor vehicle with internal and external metal surfaces and the electrodeposited coating is partially cured by directing infrared radiant heat to the external metal surfaces coated with the electrodeposited coating, to cure the coating on the outer metallic surface, leaving the electrodeposited coating on the inner surface essentially uncured.

32. The method of claim 31, wherein the infrared heating is done for a time of between 10 seconds and 2 hours.

The method of claim 32, wherein, before the infrared heating, the electrodeposited coating is subjected to heating by convection under conditions sufficient to remove water, but insufficient to produce a conductive coating.

34. The process of claim 1, wherein partial curing is done at a temperature in the range of 120 ° C to 220 ° C (248 ° F-428 ° F).

35. The method of claim 1, wherein the conductive substrate is selected from the group consisting of steel, zinc, aluminum, copper, magnesium, galvanized metals, hot dip galvanized steel and electrogalvanized steel.

36. An electrically conductive substrate coated by the method of claim 1.

37. An aqueous electrodepositable composition consisting of a curable polyurethane resin containing ionic salt groups dispersed in the aqueous medium, which polyurethane is the reaction product of: (a) ) a polyisocyanate and (b) a polymer containing active hydrogen selected from the group consisting of polyalkylene ether polyols, polyoxyalkylene polyamines and mixtures thereof.

38. The aqueous dispersion of claim 37, wherein the polyisocyanate is an aliphatic or cycloaliphatic polyisocyanate.

39. The aqueous dispersion of claim 37, wherein (b) is a polyalkylene ether polyol containing activated hydrogen selected from the group consisting of polyoxytetramethylenediols, polyoxypropylene polyols, polyoxyethylenpolyols and mixtures thereof.

40. The aqueous dispersion of claim 39, wherein (b) consists of a mixture of (i) polyoxytetramethylene diol and (ii) polyoxypropylene polyol or polyoxyalkylene polyamine, wherein the weight ratio of (i) to (ii) is 0 , 5-10: 1.

41. The aqueous dispersion of claim 37, wherein (b) is a polyoxyalkylenepolyamine containing active hydrogen selected from the group consisting of polyoxypropylenedianes and polyoxyethylenepropylenediamines.

42. The aqueous dispersion of claim 37, wherein the polymer (b) containing active hydrogen has a glass transition temperature of 0 ° C or less and a number average molecular weight of 400-4,000.

43. The aqueous dispersion of claim 37, wherein (b) is present in an amount of at least 30 percent by weight based on the weight of the reagents used to prepare the polyurethane.

44. The aqueous dispersion of claim 37, which contains as a third component (c) a compound containing active hydrogen having a molecular weight of less than 400.

45. The aqueous dispersion of claim 37, wherein the polyurethane resin curable has active hydrogen groups and a curing agent having groups that are reactive with the active hydrogens.

46. The aqueous dispersion of claim 37, wherein the curing agent is an aminoplast or a capped polyisocyanate.

47. The aqueous dispersion of claim 46, wherein the capped polyisocyanate is capped with caprolactam and / or dibutylamine.

48. The aqueous dispersion of claim 46, wherein the capped polyisocyanate is integral with the polyurethane backbone.

49. The aqueous dispersion of claim 37, wherein the reagents used to prepare the polyurethane contain an active hydrogen and a group that can be converted to an ionic salt group.

50. The aqueous dispersion of claim 49, wherein the group is carboxylic acid or amine.

51. The aqueous dispersion of claim 37, wherein the curable polyurethane contains saline carboxylate groups and an aminoplast curing agent.

52. The aqueous dispersion of claim 37, which contains an opacifying pigment.

53. The aqueous dispersion of claim 37, which contains a stabilizer against blocked amine light.

54. A cationic aqueous electrodepositable composition consisting of a polyurethane resin containing active hydrogen and having cationic salt groups dispersed in an aqueous medium, the polyurethane being the reaction product of: (a) an aliphatic or cycloaliphatic polyisocyanate, - (b) ) a polyether containing active hydrogen consisting of a mixture of: (i) a polyoxytetramethylene diol and (ii) a polyoxypropylene polyamine; the weight ratio of (i) to (ii) being from 0.5 to 10: 1; (c) an active hydrogen group containing a tertiary amine group, the polyurethane being at least partially neutralized with acid and the dispersion also containing a capped polyisocyanate curing agent.

55. The aqueous dispersion of claim 54, wherein the capped polyisocyanate is capped with caprolac-tama and / or dibutylamine.

56. The aqueous dispersion of claim 54, wherein the capped polyisocyanate is integral with the polyurethane skeleton.

57. The aqueous dispersion of claim 54, having an equivalent hydrogen / isocyanate ratio of 1 to 1.5: 1.

58. The aqueous dispersion of claim 37, having a resin solids content of 5 to 50 weight percent.