MXPA99001647A - Electrodepositable coating compositions and method for improved cure response - Google Patents

Abstract

An improved electrodepositable composition is provided comprising:(a) an active hydrogen-containing cationic resin electrodepositable on a cathode;(b) a capped polyisocyanate curing agent;and (c)an organotin-containing catalyst. The improvement comprises the addition to the electrodepositable composition of a water immiscible acid functional compound having a hydrocarbon chain of at least 5 carbon atoms like abietic acid and natural sources thereof. A preferred acid functional compound is abietic acid. The composition provides improved cure response and appearance properties when electrodeposited over conductive substrates.

Description

ELECTRODEPOSITABLE COATING COMPOSITIONS AND METHOD FOR A BETTER CURING RESPONSE FIELD OF THE INVENTION The present invention relates to electrodepositable cationic compositions and their use in electrodeposition. BACKGROUND OF THE INVENTION The application of an electro-deposition coating involves the deposition of a film-forming composition on an electrically conductive substrate under the influence of an applied electrical potential. Electrodeposition has gained importance in the coatings industry, since, compared to non-electrophoretic coating methods, electrodeposition provides superior paint utilization, remarkable corrosion resistance and low environmental contamination. The first attempts at commercial electrodeposition processes used anionic electrodeposition, where the workpiece that was being coated served as the anode. However, in 1972, cationic electrodeposition was introduced commercially. Since then, cationic electrodeposition has become increasingly popular and is currently the most prevalent method of electrodeposition. Globally, more than 80 percent of all manufactured engine vehicles receive a primer coating by cationic electrodeposition. Many cationic electrodeposition compositions used today are based on resins containing active hydrogen derived from a polyepoxide and a capped polyisocyanate curing agent. These cationic electrodeposition compositions contain organic tin catalysts, such as dibutyltin oxide, to activate the curing of the electrodeposition composition. Due to cost and environmental considerations, the levels of these tin catalysts remain low. The organotin catalysts are relatively inexpensive and appear in the ultrafiltrate of the electrodeposition baths, which can present waste disposal problems. However, low levels of catalysts can reduce the curing response of a coating composition, providing weaker properties than desired in the cured film. The appearance of the cured film may also be affected. In the PCT Patent Application WO 96/12771, the presence of an acid-functional compound immiscible in water with a hydrocarbon chain of at least 5 carbon atoms in the electrodepositable composition was described. Said electrodepositable composition demonstrates a higher curing response at low levels of organotin catalyst, without loss of properties of the cured film, including moisture resistance, adhesion and appearance. It would further be desirable to have an electrodepositable composition demonstrating reduced breakage on wet substrates and, additionally, improving adhesion to bare electrogalvanized substrates. COMPENDIUM OF THE INVENTION According to the present invention, an improved electrodepositable composition and an electrodeposition method using the composition are provided. The electrodepositable composition consists of (a) a cationic resin containing electrodepositable active hydrogen on a cathode, (b) a capped polyisocyanate curing agent and (c) an organotin-containing catalyst. The improvement consists in the addition to the electrodepositable composition of at least one water-immiscible acid-functional compound having a hydrocarbon chain of at least 5 carbon atoms, selected from the group of abietic acid and natural sources of abietic acid. The acid-functional compound immiscible with water is preferably polycyclic. DETAILED DESCRIPTION The cationic resin of the present invention is preferably derived from a polyepoxide and can be prepared by reacting together a polyepoxide and a material containing polyhydroxyl groups, selected from materials containing alcoholic hydroxyl groups and materials containing phenolic hydroxyl groups, to prolong the chain or increase the molecular weight of polyepoxide. The reaction product can then react with a cationic salt group primer to produce the cationic resin. A polyepoxide with prolonged chain is typically prepared as follows: the polyepoxide and the material containing polyhydroxyl groups react with each other in a net manner or in the presence of an inert organic solvent, such as a ketone, including methyl isobutyl ketone and methylamyl ketone, aromatics such as toluene and xylene and glycol ethers such as diethylene glycol dimethyl ether. The reaction is typically carried out at a temperature of about 80 ° C to 160 ° C, for about 30 to 180 minutes, until a resinous reaction product containing epoxy groups is obtained. The equivalent ratio of the reactants, ie, epoxy: aterial containing polyhydroxyl groups, is typically from about 1.00: 0.50 to 1.00: 2.00.

The polyepoxide preferably has at least two 1,2-epoxy groups. In general, the epoxide equivalent weight of the polyepoxide will vary between 100 and about 2000, typically between about 180 and 500. The epoxy compounds can be saturated or unsaturated, cyclic or acyclic, aliphatic, alicyclic, aromatic or heterocyclic. They may contain substituents, such as halogen, hydroxyl and ether groups. Examples of polyepoxides are those having a 1,2-epoxy equivalence greater than one and, preferably, about two; that is, polyepoxides that have, on average, two epoxide groups per molecule. Preferred polyepoxides are polyglycidyl ethers of polyhydric alcohols, such as cyclic polyols. Particularly preferred are the polyglycidyl ethers of polyhydric phenols, such as Bisphenol A. These polyepoxides can be produced by etherification of polyhydric phenols with an epihalohydrin or dihalohydrin, such as epichlorohydrin or dichlorohydrin, in the presence of alkali. In addition to the polyhydric phenols, other cyclic polyols can be used in the preparation of the polyglycidyl ethers of cyclic polyols. Examples of other cyclic polyols include alicyclic polyols, particularly cycloaliphatic polyols, such as 1,2-cyclohexanediol and 1,2-bis (hydroxymethyl) cyclohexane. Preferred polyepoxides have equivalent epoxide weights ranging from about 180 to 2000, preferably from about 186 to 1200. Acrylic polymers containing epoxy groups can also be used. These polymers typically have an epoxy equivalent weight ranging from about 750 to 2000. Examples of materials containing polyhydroxyl groups used to prolong the chain or increase the molecular weight of the polyepoxide (i.e., through the hydroxyl-epoxy reaction) are include materials containing alcoholic hydroxyl groups and materials containing phenolic hydroxyl groups. Examples of materials containing alcoholic hydroxyl groups are simple polyols, such as neopentyl glycol; polyester polyols, such as those described in US Pat. No. 4,148,772; polyether polyols, such as those described in US Pat. 4,468,307, and the urethanediols, such as those described in U.S. Pat. No. 4,931,157. Examples of materials containing phenolic hydroxyl groups are polyhydric phenols, such as Bisphenol A, phloroglucinol, catechol and resorcinol. Mixtures of materials containing alcoholic hydroxyl groups and materials containing phenolic hydroxyl groups can also be used. Bisphenol A is preferred. The active hydrogens associated with the cationic resin include any active hydrogen that is reactive with isocyanates within the temperature range of about 93 to 204 °, preferably about 121 to 177 ° C. Typically, the active hydrogens are selected from the group consisting of aliphatic hydroxyl and primary and secondary amino, including mixed groups, such as hydroxyl and primary amino. Preferably, the cationic resin will have an active hydrogen content of about 1 to 4 milliequivalents, more preferably about 2 to 3 milliequivalents, of active hydrogen per gram of resin solids. The resin contains cationic salt groups, which are preferably incorporated into the resin molecule as follows. The reaction resin product prepared as described above is still reacted with a primer of cationic salt groups. By "cationic salt group primer" is meant a material which is reactive with epoxy groups and which can be acidified before, during or after the reaction with the epoxy groups to form cationic salt groups. Examples of suitable materials include amines, such as primary or secondary amines, which can be acidified after reaction with the epoxy groups to form amine salt groups, or tertiary amines, which can be acidified before the reaction with the epoxy groups and which, after the reaction with the epoxy groups, form saline groups of quaternary ammonium. Examples of other cationic salt group primers are sulfides, which can be mixed with acid prior to reaction with the epoxy groups and form saline groups of ternary sulfonium after subsequent reaction with the epoxy groups. When amines are used as cationic salt primers, monoamines are preferred and hydroxyl-containing amines are particularly preferred. Polyamines can be used, but they are not recommended due to the tendency to gel the resin. Tertiary amines and secondary to primary amines are preferred, since the primary amines are polyfunctional with respect to the epoxy groups and have a greater tendency to gel the reaction mixture. If polyamines or primary amines are used, they must be used in a substantial stoichiometric excess with respect to the epoxy functionality of the polyepoxide, to avoid gelation, and the excess amine must be removed from the reaction mixture by vacuum purification or other technique at the end of the reaction. Epoxy can be added to the amine to ensure excess amine. Examples of hydroxyl-containing amines are alkanolamines, dialkanolamines, trialkanolamines, alkylalcanolamines and aralkylalkanolamines containing from 1 to 18 carbon atoms, preferably 1 to 6 carbon atoms, in each of the alkanol, alkyl and aryl groups. Specific examples include ethanolamine, N-methylethanolamine, diethanolamine, N-phenylethanolamine, N, N-dimethylethanolamine, N-methyldiethanolamine, triethanolamine and N- (2-hydroxyethyl) piperazine. Amines such as mono-, di- and trialkylamines and mixed aryl-alkylamines which do not contain hydroxyl groups or amines substituted with non-hydroxyl groups, which do not adversely affect the reaction between the amine and the epoxy can also be used. Specific examples include ethylamine, methylethylamine, triethylamine, N-benzyldimethylamine, dicocoamine and N, N-dimethylcyclohexylamine. Mixtures of the amines mentioned above can also be used. The reaction of a primary and / or secondary amine with the polyepoxide takes place after the mixture of the amine and the polyepoxide. The amine can be added to the polyepoxide or vice versa .. The reaction can be carried out in a neat form or in the presence of a suitable solvent, such as methyl isobutyl ketone, xylene or 1-methoxy-2-propanol. The reaction is generally exothermic and it may be desired to cool. However, it can be heated to a moderate temperature of about 50 to 150 ° C to accelerate the reaction. The reaction product of the primary and / or secondary amine and the polyepoxide is made cationic and dispersible in water by at least partial neutralization with an acid. Suitable acids include organic and inorganic acids, such as formic acid, acetic acid, lactic acid, phosphoric acid and sulfamic acid. By "sulfamic acid" is meant sulfamic acid itself or derivatives thereof, that is, an acid of the formula: R I H - N - S03H where R is hydrogen or an alkyl group of 1 to 4 carbon atoms. Sulfamic acid is preferred. Mixtures of the aforementioned acids can also be used. The degree of neutralization varies with the particular reaction product involved. However, acid must be used to disperse the electrodepositable composition in water. Typically, the amount of acid used provides at least 20 percent of the total total neutralization. An excess of acid in excess of the amount required for 100 percent total neutralization can also be used. In the reaction of a tertiary amine with a polyepoxide, the tertiary amine can pre-react with the neutralizing acid to form the amine salt and then react the amine salt with the polyepoxide to form a resin containing quaternary salt groups. The reaction is carried out by mixing the amine salt with the polyepoxide in water. Typically, the water is present in an amount ranging from about 1.75 to about 20 weight percent, based on the solids of the total reaction mixture. By forming the resin containing quaternary ammonium salt groups, the reaction temperature can vary between the lowest temperature at which the reaction proceeds, generally the room temperature or slightly above it, and a maximum temperature of about 100 ° C. (at atmospheric pressure). At higher pressures, higher reaction temperatures can be used. Preferably, the temperature of the reaction is in the range of about 60 to 100 ° C. Solvents can be used, such as a sterically blocked ester, ether or ketone sterically blocked, but its use is not necessary. In addition to the primary, secondary and tertiary amines described above, a portion of the amine that reacts with the pooliepoxide may be a ketimine of a polyamine, such as described in US Pat. No. 4,104,147, column 6, line 23 to column 7, line 23. The ketimine groups are decomposed by dispersing the amine-epoxy resin reaction product in water. In addition to resins containing amine salts and quaternary ammonium salt groups, cationic resins containing ternary sulfonium groups can be used in the composition of the present invention. Examples of these resins and their method of preparation are described in US Pat. No. 3,793,278 to DeBona and 3,959,106 to Bosso et al. The degree of formation of cationic salt groups must be such that, when the resin is mixed with an aqueous medium and other components, a stable dispersion of the electrodepositable composition is formed. "Stable dispersion" means one that does not settle or that is easily redispersible if some sedimentation occurs. Moreover, the dispersion must have a sufficient cationic character so that the dispersed resin particles migrate towards a cathode and are electrodeposited on it when an electric potential is established between an anode and a cathode immersed in the aqueous dispersion. In general, the cationic resin in the electrodepositable composition of the present invention contains from about 0.1 to 3.0, preferably from about 0.1 to 0.7, milliequivalents of cationic salt group per gram of resin solids. The cationic resin is preferably non-gelled, with a number average molecular weight varying between about 2,000 and about 15,000, preferably between about 5,000 and about 10,000. By "non-gelled" is meant that the resin is substantially free of crosslinking and, prior to the formation of cationic salt groups, the resin has a measurable intrinsic viscosity when dissolved in a suitable solvent. In contrast, a gelled resin, having an essentially infinite molecular weight, would have an intrinsic viscosity too high to be measured. The electrodepositable composition of the present invention also contains a capped polyisocyanate curing agent. The curing agent polyisocyanate can be a fully capped polyisocyanate substantially free of free isocyanate groups, or may be partially capped and reacted with the skeleton of the resin, as described in US Pat. 3,984,299. The polyisocyanate can be an aliphatic or aromatic polyisocyanate or a mixture of the two. Diisocyanates are preferred, although higher polyisocyanates can be used in place of, or in combination with, diisocyanates. 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-benzene triisocyanate and polymethylene polyphenyl isocyanate, and isocyanate prepolymers, for example reaction products, can also be used. of polyisocyanates with polyols, such as neopentyl glycol and trimethylolpropane, or with polymeric polyols, such as polycaprolactone diols and triols (ratio of equivalents NCO / OH greater than one) A mixture of diphenylmethane-4,4'-diisocyanate is preferred and polymethylenepolyphenyl isocyanate Any suitable aliphatic, cycloaliphatic or aromatic alkylmonoalcohol can be used as the filler for the polyisocyanate in the composition of the present invention, including, for example, lower aliphatic alcohols such as methanol, ethanol and n-butanol; cycloaliphatic alcohols such as cyclohexanol; aromatic alkyl alcohols such as phenylcarbinol and methylphenylcarbinol. The 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. Diethylene glycol butyl ether is preferred among the glycol ethers. Other suitable capping agents include oximes, such as methyl ethyl ketoxime, acetone oxime and cyclohexanone oxime, and lactam, such as epsilon-caprolac-tama. The curing agent polyisocyanate is normally present in the electrodepositable composition in an amount ranging from about 5 to 60 weight percent, preferably about 50 to 50 weight percent, based on the total weight of the resin solids. Organotin catalysts are also present in the electrodepositable composition of the present invention, preferably in the form of a dispersion. Catalysts, which are often solids, are typically dispersed in a conventional pigment grinding vehicle, such as those described in US Pat. 4,0007,154, by a grinding or milling process. The catalysts are typically used in amounts of about 0.05 to 1 weight percent tin based on the weight of the resin solids. Suitable catalysts include dioctyltin oxide and dibutyltin oxide. At low levels of organic tin in conventional systems, the appearance of the cured coating can be a problem. The presence of the acid-functional compound in the electrodepositable composition allows the use of relatively low levels of organic tin catalyst, ie, from about 0.05 to 0.5 weight percent tin based on the weight of the Resin solids, with good curing response and good appearance properties. The acid-functional compound added to the electrodepositable composition of the present invention is immiscible in water, so that it can be electrodepositable on the cathode, and has a hydrocarbon chain (excluding the carbon atoms associated with the acid functionality, ie the group carboxyl) of at least 5 carbon atoms. The acid-functional compound may be monocarboxylic-functional acid or may contain more than one acid-functional group. The hydrocarbon chain of the acid-functional compound can be aliphatic or aromatic, can be saturated or unsaturated and can be branched, linear or cyclic, including polycyclic. The hydrocarbon chain of the acid-functional compound may also be substituted. Examples of substituents include hydroxyl groups. Suitable polycyclic carboxylic acids useful as an acid-functional compound immiscible in water with a hydrocarbon chain length of at least 5 carbon atoms include abietic acid, which is preferred, as are the natural sources of the abietic acid. Natural sources of abietic acid of varying purity include gomorresin, wood rosin and resin oil rosin. The abietic acid can be used in its natural form or can be purified using techniques known to those skilled in the art before being added to the electrodepositable composition of the present invention. For example, dihydroabietic acid and dehydroabietic acid can be used in mixtures of both and with abietic acid. In its natural form as a rosin or rosin acid, the abietic acid may be present with isomeric forms, such as levoprimaric and resin of the pimaric type having a phenanthrene nucleus. Natural sources may also include the oleoresin material with the presence of some or all of the turpentine oils or distillates.

Since rosin is a complex mixture of fused ring monocarboxylic acids, mainly of twenty carbon atoms and a small amount of non-acidic components, where the resin acid molecule has the double bonds and the carboxylic acid group, it can be use any derivative that maintains the carboxylic acid group. For example, derivatives of oleoresin and rosin can be used. A suitable example of resin oil containing abietic acid and which can be used is Unitol NCY partially hydrogenated resin oil, from Union Camp, Savannah, Georgia. The acid-functional compound can be incorporated into the electrodepositable composition in various ways. It can be added to the final reaction mixture of the main vehicle, ie, the resin containing active hydrogen, just before solubilization with water and acid as described above. Alternatively, it can be added to a partially solubilized resin maintained at a level of solids high enough to be sheared in the final composition. By "partially solubilized" it is meant that the resin is totally neutralized with respect to the acid functionality, but only partially dissolved in water, ie, diluted. Additionally, it can be co-dispersed with polyepoxide-polyoxyalkylenepolyamine-modifying anti-voiding resins such as those described in US Pat. No. 4,423,166. It can also be dispersed in a conventional vehicle for pigment grinding, such as those described in US Pat. 4,007,154, by a grinding or milling process, and can be a component of a pigment paste. The acid-functional compound is added to, and is present in, the electrodepositable composition in the form of an acid, i.e., which is not formed in situ by the decomposition or hydrolysis of a metal salt or catalyst. The acid-functional compound is added to the electrodepositable composition as a compound containing free acid-functional groups. Moreover, the acid-functional compound does not react in the cationic resin backbone, ie, to form an epoxy ester during the epoxy extension reaction, nor does it serve in any substantial measure to solubilize the main vehicle. Although we do not intend to be bound by any theory, we believe that, due to the immiscibility of the acid-functional compounds, they are not well protonated and, therefore, do not solubilize the main vehicle as do the specific acids, such as sulfamic acid, lactic, etc., mentioned above, which are added in order to solubilize the main vehicle. The acid-functional compound is normally present in the electrodepositable composition in an amount ranging from about 0.1 to 3.0 weight percent, based on the weight of the resin solids of the main vehicle, i.e. cationic resin containing active hydrogen and the curing polyisocyanate curing agent, preferably from about 0.4 to 1.5 weight percent, based on the weight of the resin solids of the main vehicle. The electrodepositable composition may optionally contain a coalescing solvent, such as hydrocarbons, alcohols, esters, ethers and ketones. Examples of preferred coalescing solvents are alcohols, including polyols, such as isopropanol, butanol, 2-ethylhexanol, ethylene glycol and propylene glycol; ethers, such as the monobutyl and monohexyl ethers of ethylene glycol, and ketones, such as methyl isobutyl ketone and isophorone. The coalescing solvent is normally present in an amount of up to about 40 weight percent, preferably in a range of about 0.05 to 25 weight percent, based on the total weight of the electrodepositable composition. The electrodepositable composition of the present invention can also contain pigments and various other possible additives, such as plasticizers, surfactants, wetting agents, defoamers and anti-cavitation agents. Examples of suitable surfactants and wetting agents include alkylimidazolines, such as those obtainable from Geigy Industrial Chemicals as GEIGY AMINE C, and acetylenic alcohols, which can be obtained from Air Products and Chemicals as SURFYNOL. Examples of defoamers include a hydrocarbon containing inert diatomaceous earth, which can be obtained from Crucible Materials Corp. as FOAMKILL 63. Examples of anti-cavitation agents are the polyepoxide-polyoxyalkylenepolyamine reaction products, such as those described in the patent. USA No. 4,423,166. These eventual components, when present, are typically used in an amount of up to 30 weight percent, typically from about 1 to 20 weight percent, based on the weight of the resin solids. Suitable pigments include, for example, iron oxides, lead oxides, strontium chromate, carbon black, carbon powder, titanium dioxide, talc, clay, silica, lead silicate and barium sulfate, as well as pigments. dyes, such as cadmium yellow, cadmium red, chromium yellow and the like. The pigment content of the aqueous dispersion, generally expressed as the ratio of pigment to resin (or pigment to binder) (P / L), is usually about 0.05: 1 to 1: 1 The composition of the present invention, which contains the cationic resin, the cured polyisocyanate curing agent, the catalyst, the acid-functional compound and the optional additives mentioned above, is used in an electrodeposition process in the form of an aqueous dispersion. By "dispersion" is meant a transparent, translucent or opaque two-phase aqueous resinous system, in which the resin, pigment and water-insoluble materials are in the dispersed phase, while water and water-soluble materials are in the dispersed phase. they constitute the continuous phase. The dispersed phase has an average particle size of less than about 10 microns, preferably less than 5 microns. The aqueous dispersion preferably contains at least about 0.05 and, typically, about 0.05 to 50 weight percent resin solids, depending on the particular end use of the dispersion. The addition of the acid-functional compound to the electrodepositable composition of the present invention improves the curing response of the composition and reduces breakage on wet substrates, when used in an electrocoating process. By this it is understood that the temperature range for curing the electrodepositable composition of the present invention may be from about 310 to 325 ° F (154.5 to 162.7 ° C), as opposed to 325 to 340 ° F (162 , 7 to 171, 1 ° C) for conventional electrodepositable compositions at conventional levels of organotin catalyst, ie, about 0.5 to 1.0 weight percent tin based on the weight of resin solids. The composition of the present invention also demonstrates better curing response, as measured by solvent resistance when cured at infra-baking temperatures (about 310 ° F, 154.5 ° C), compared to conventional electrodepositable compositions without the acid-functional compound, once again at optimized levels of organotin catalyst. Moreover, the curing speed is improved, i.e., at a given temperature, a deposited film of the present invention cures faster than a comparable film without the acid-functional compound, as measured by the speed of weight loss of a film deposited during baking. Alternatively, the amount of organotin catalyst can be reduced while maintaining curing at normal temperatures. The addition of the acid functional compound to the electrodepositable composition of the present invention also improves the appearance of the composition when used in an electrocoating process. Cationic electrodeposition compositions are conventionally formulated with lead, either as a pigment or as a soluble lead salt. When these compositions also contain low levels of organotin catalysts, i.e., about 0.05 to 0.5 weight percent tin based on the weight of the total resin solids, the cured films deposited exhibit a " hairy "or of. bristling type, particularly with the aging of the electrodeposition bath. The addition of the acid-functional compound to the electrodepositable composition according to the present invention improves the appearance of the cured electrodeposited films, eliminating the downy appearance even with low levels of organotin catalyst in the composition. The addition of the preferred acid-functional compound, abietic acid, to the electrodepositable composition similarly improves curing and appearance, while maintaining the moisture resistance and saline solutions of the composition when used as a coating on an electrogalvanized substrate. In the electrodeposition process, the aqueous dispersion is contacted with an electrically conductive anode and cathode. By passing an electric current between the anode and the cathode, while in contwith the aqueous dispersion, an adherent film of the electrodepositable composition will be deposited in a substantially continuous manner on the cathode. The film will contain the resin containing ve hydrogen, the cured polyisocyanate curing agent, the tin catalyst, the acid-functional compound and the optional additives of the non-aqueous phase of the dispersion. 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 usually between about 1.0 amps and 15 amps per square foot (10.8 to 161.5 amps per square meter) and tends to decrease rapidly during the electro-deposition process, which indicates the formation of a self-insulating continuous film. Any electroconductive substrate, especially metal substrates such as steel, zinc, aluminum, copper, magnesium or the like, can be coated with the electrodepositable composition of the present invention. Steel substrates are preferred. It is customary to pretreat the substrate with a phosphate conversion coating, typically zinc phosphate conversion, followed by a wash that seals the conversion coating. After the deposition, the coating is heated to cure the deposited composition. The heating or curing operation is normally performed at a temperature in the range of 250 to 400 ° F (121.1 to 204, 4 ° C), preferably 300 to 340 ° F (148.8 to 171, 1 ° C). ), 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 invention will still be described in relation to the following examples. Unless otherwise indicated, all parts and percentages are by weight. Comparative Example I Comparative Examples IA to 1-0 illustrate the effect of the addition of various water-immiscible acid-functional compounds to a cationic electrodepositable composition according to the present invention, as compared to the effect of various non-acid-functional compounds added to a cationic electrodepositable composition. COMPARATIVE EXAMPLE I-A (Control) This comparative example describes the preparation of a cationic electrodeposition bath containing no additive. A main vehicle (i.e., the cationic resin containing ve hydrogen and cured polyisocyanate curing agent) was prepared with the following components: Bisphenol A polyglycidyl ether, from Shell Oil and Chemical Co. 2 The capped polyisocyanate crosslinker was prepared with the following mix of components: a A mixture of diphenyl-4,4'-diisocyanate and polyphenyl polyisocyanate, which can be obtained from Miles, Inc. as MONDUR MR. The polyisocyanate, the MIBC and the DLDBE were charged to a reaction flask under a nitrogen atmosphere. 2- (2-Butoxyethoxy) ethanol was slowly added, allowing the reaction mixture to produce an exotherm at a temperature between 45 and 50 ° C. Upon completion of the addition, the reaction mixture was maintained at 50 ° C for 30 minutes. 2-Butoxyethanol was then added and the mixture was allowed to exotherm to 110 ° C and was held there until infrared analysis indicated complete isocyanate consumption. 3 Dicetimine derived from diethylenetriamine and methyl isobutyl ketone (MIBC) (73% solids in MIBC). A reaction vessel was charged with EPON 828, Bisphenol A-ethylene oxide adduct, Bisphenol A and MIBC. This mixture was heated under a blanket of nitrogen at 125 ° C. The ethyltri-phenylphosphonium iodide was then added and the reaction mixture was allowed to produce an exotherm at a temperature of about 145 ° C. The reaction was maintained at 145 ° C for two hours and the equivalent weight of epoxy was determined. At this point, the crosslinker, the diketimine and the N-methylethanolamine were added in succession. The reaction mixture produced exotherm and then a temperature of 132 ° C was established and maintained for one hour. The resin mixture was dispersed (1684 parts) in aqueous medium by adding it to a mixture of 38.34 parts of sulfamic acid and 1220.99 parts of deionized water. The dispersion was again diluted with 657.63 parts of deionized water and 666.28 parts of deionized water stepwise and purified in vacuo to remove the organic solvent and obtain a dispersion having a solids content of 41.2 percent. and a particle size of 984 Angstroms. A cationic electrodeposition bath was prepared from the following components: 1 An aqueous dispersion of a flexibilizer-agent for flow control was prepared, generally in accordance with US Pat. N °. 4,423,166, for use with the electrodepositable composition. The flexibilizer-agent for flow control was prepared from a polyepoxide (EPON 828) and a polyoxyalkylenepolyamine (JEFFAMINE D-2000, Texaco Chemical Co.). The flexibilizer-agent was dispersed to control the flow in aqueous medium with the aid of lactic acid and the dispersion had a resin solids content of 36.2%. 2 The reaction product of 2 moles of diethylene glycol butyl ether and 1 mole of formaldehyde, prepared as generally described in U.S. Pat. No. 4,891,111. 3 A cationic microgel prepared as described, in general, in Examples A and B of US Pat. No. 5,096,556, with the exception that acetic acid was used in place of lactic acid to disperse the soap of Example A, ethylene glycol butyl ether was used in place of MIBC as solvent in the soap of Example A and solution was added. of EPON 828 after purification, better than before, in Example B. The resin had a final solids content of 18.3%. 4 A pigment paste marketed by PPG Industries Inc., containing 27.2% titanium dioxide, 1.4% carbon black, 15.9% aluminum silicate, 5.7% basic lead silicate and 3.8% dibutyltin oxide. Comparative Examples I-B to I-O Main vehicles and electrodeposition baths were prepared as described, in general, in Comparative Example I-A; however, several acid-functional compounds or non-acid-functional compounds immiscible in water, as indicated in Table I below, were added to the reaction mixture of the cationic main vehicle, at 1% on the resin solids of the vehicle main, after the exotherm, and was maintained one hour at 132 ° C, as described in the method of preparation of the previous main vehicle. The bathrooms for the previous examples, including the control, were ultrafiltered, eliminating 20% of the total weight of the bath as ultrafiltrate and replacing the ultrafiltrate with deionized water. Steel panels pre-treated with zinc phosphate were immersed in the baths and electrorevealed with the electrodepositable compositions at 275 volts for 2 min. , at a bath temperature of 87-95 ° F (30.5-35 ° C). After washing with deionized water, the panels were baked for 30 minutes at 310 ° F (154.5 ° C), 325 ° F (162.7 ° C) or 340 ° F (171.1 ° C). The resulting film formations were approximately 0.9 mils (22.9 microns). The cured coatings were evaluated in terms of their appearance, measured by the surface profile (RA) described below, and in terms of the curing response, measured by acetone resistance and cure rate (ATG). In the following Table I the results are given. Table I 1 Data obtained from the coated panels in bathrooms aged for two (2) weeks. The relative roughness of the coating surface is measured with a Surfanalyzer, Model 21-9010-01, Federal Products, Inc. The given number is the average roughness, or the average vertical distance of any point on the surface from a given center line by a style that moves across the surface, expressed in micro-strips. The lower numbers indicate a greater smoothness. These data were obtained from panels cured for 30 minutes at 340 ° P (171, 1 ° C). 2 A saturated acetone cloth was firmly rubbed across the surface of the cured coating. The given number is the number of double rubs required to expose the metal surface. These were obtained from panels cured for 30 minutes at 310 ° F (154.5 ° C). 3 Thermogravimetric analysis: the weight loss of a cured coating is monitored against time for thirty (30) minutes at 325 ° F (162.7 ° C). The linear portion of the graph of the rate of change of the weight loss rate versus time is recorded, expressed as percentage of weight loss per minute2 times 103 (% weight loss / min2 x 103). The higher the values, the faster the weight loss and the faster the curing speed. The data in Table I indicate that all the acid-functional compounds studied tend to improve curing, while other long-chain materials and highly unsaturated materials do not significantly improve curing. By increasing the total number of carbons in the hydrocarbon chain of the acid-functional compound, the appearance of the cured coating tends to improve. Comparative Example II The following comparative examples (II-A to II-C) illustrate the effect of the addition of various levels of a water-immiscible, functional acid compound to a cationic electrodepositable composition according to the present invention. Electrodeposition baths were prepared and steel panels pre-treated with zinc phosphate were coated and cured as in Example I. In the following Table II the results are given.

Table II 1 The indicated amount is the percentage by weight based on the solids of the main vehicle. The data in Table II indicate that the effect of an acid-functional compound on the cure rate (ATG) is proportional to its level. Comparative Example III The following comparative examples (III-A and III-B) illustrate the effect of the addition of a water-immiscible acid-functional compound to a cationic electrodepositable composition containing a polyisocyanate crosslinking agent topped with a "slow" quenching agent. , that is, a quenching agent such as a secondary alcohol that does not readily separate at standard curing temperatures. The compositions were prepared as in Comparative Example I, with the following exception. The crosslinking polyisocyanate topped with the following mixture of components .- was prepared to MONDUR MR. Polyisocyanate, MIBC and DLDBE were charged into a reaction flask under a nitrogen atmosphere. The propylene glycol monomethyl ether was added slowly, allowing the reaction mixture to produce an exotherm at a temperature between 100 and 110 ° C. Upon completion of the addition, the reaction mixture was maintained at 110 ° C, until infrared analysis indicated complete isocyanate consumption. The crosslinker was incorporated into the electrodeposition bath as in Comparative Example I-A, except at 31% solids on solids instead of 34% solids on solids. The electrodepositable composition of the Example Comparative III-A did not contain acid-functional materials, while Comparative Example III-B contained 1% oleic acid by weight, based on the weight of the resin solids of the main vehicle. Electrodeposition baths were prepared and steel panels pre-treated with zinc phosphate were coated and cured as in Comparative Example I, unless otherwise indicated. In the following Table III the results are given. Table III 1 These data were obtained from coated panels cured for 30 minutes at 310 ° F (154.5 ° C). 2 These data were obtained from coated panels cured for 30 minutes at 340 ° F (171, 1 ° C). 3 These data were obtained from coated panels cured for 30 minutes at 325 ° F (162.7 ° C). 4 These data were obtained from coated panels cured for 30 minutes at 340 ° F (171, 1 ° C). The data in Table III indicate that acid-functional compounds improve curing speed (ATG) in a system containing a polyisocyanate crosslinking agent topped with a "slow" quenching agent.

It also improves the acetone resistance and appearance. Comparative Example IV The following comparative examples (IV-A and IV-B) illustrate the effect of adding water-immiscible acid-functional compound to a cationic electrodepositable composition containing dioctyltin oxide instead of dibutyltin oxide, at the same levels of tin, as a catalyst. Comparative Example IV-A This comparative example demonstrates the preparation of a cationic electrodepositable composition containing as a catalyst dioctyltin oxide and no acid-functional compound.

A pigment paste was prepared with the following components: 1 The pigment grinding vehicle was prepared by first preparing a quaternizing agent, followed by reaction of the quaternizing agent with an epoxy resin. The quaternizing agent was prepared as follows: The capped middle toluene diisocyanate of 2-ethylhexanol was added to the DMEA in a suitable reaction vessel at room temperature. The mixture produced exotherm and was stirred for one hour at 80 ° C. The aqueous lactic acid solution was then charged, followed by the addition of 2-butoxyethanol. The reaction mixture was stirred for about one hour at 65 ° C to form the quaternizing agent. The pigment grinding vehicle was prepared as follows: to diglycidyl ether of Bisphenol A, from Shell Oil and Chemical Co. EPON 829 and Bisphenol A were charged under a nitrogen atmosphere in a suitable reactor and heated to 150 to 160 ° C to initiate an exotherm. The reaction mixture was allowed to produce exotherm for one hour at 150 to 160 ° C. The reaction mixture was then cooled to 120 ° C and the capped middle toluene diisocyanate of 2-ethylhexanol was added. The temperature of the reaction mixture was maintained at 110 to 120 ° C for one hour, followed by the addition of 2-butoxyethanol. The reaction mixture was then cooled to 85 to 90 ° C, homogenized and charged with water, followed by the quaternizing agent. The temperature of the reaction mixture was maintained at 80 to 85 ° C until an acid value of about 1 was obtained. The final product had a solids content of about 57.1%. 2 It can be obtained from E. I. Du Pont de Nemours and Co. as R-900. 3 It can be obtained from Engelhard Corp. as ASP-200. 4 Can be obtained from the Columbian division of Cities Service Co. as Raven 410. 5 Obtainable from Eagle-Picher Industries, Inc. as EP202. The pigment paste was milled with sand at a Hegman reading of 7. A cationic electrodeposition bath was prepared with the following components: Comparative Example IV-B This example demonstrates the preparation of a cationic electrodepositable composition containing dioctyltin oxide as a catalyst and an acid-functional compound immiscible in water at 1 weight percent on the solids of the main vehicle. A cationic electrodeposition bath was prepared with the following components: The electrodeposition baths of Comparative Examples IV-A and IV-B were prepared and steel panels pre-treated with zinc phosphate were coated and cured as in Example I. Results are indicated in the following Table IV.

Table IV The data in Table IV indicate that the addition of water-immiscible acid-functional compound to a cationic electrodepositable composition containing dioctyltin oxide clearly improves the cure rate, as shown by the marked increase in the ATG. Comparative Example V The following comparative examples (VA and VB) illustrate the effect of the reaction of an acid-functional compound immiscible in water in the main vehicle, at 1% on the solids of the main vehicle, forming an epoxy ester, in comparison with the post-addition of the acid-functional compound to the electrodepositable cationic composition. Comparative Example V-A This example describes the preparation of a cationic elctrodeposition bath containing 1% oleic acid on the solids of the main vehicle, added to the fully reacted resin. A main vehicle was prepared with the following components: A reaction vessel was charged with EPON 828, the initial charge of Bisphenol A-ethylene oxide adduct, Bisphenol A and the initial charge of MIBC. This mixture was heated under a blanket of nitrogen at 125 ° C. The ethyltriphenylphosphonium iodide was then added and the reaction mixture was allowed to produce an exotherm at a temperature of about 145 ° C. The reaction was maintained at 145 ° C for two hours and the second adduct charge of Bisphenol A-ethylene oxide was added and the equivalent weight of epoxy was determined. At this point, the second charge of MIBC, the crosslinker, the diketimine and the N-methylethanolamine were added successively. The reaction produced an exotherm and then a temperature of 132 ° C was established and maintained for one hour. The resin mixture (1500 parts) was dispersed in aqueous medium by adding it to a mixture of 34.72 parts of sulfamic acid and 1145.23 parts of deionized water. After five minutes, 14.25 parts of oleic acid was added to the high solids dispersion and mixed further for 30 minutes. The dispersion was again diluted with 581.29 parts of deionized water and 603.38 parts of deionized water stepwise and purified under vacuum to remove the organic solvent and achieve a dispersion having a solids content of 42.6 percent. and a particle size of 861 Angstroms. A cationic electrodeposition bath was prepared with the following components: Comparative Example V-B This comparative example describes the preparation of a cationic electrodeposition bath containing 1% oleic acid on the solids of the main vehicle, reacted in the resin during the epoxy extension step. A main vehicle was prepared with the following components: A reaction vessel was charged with EPON 828, Bisphenol A-ethylene oxide adduct, Bisphenol A, oleic acid and MIBC. This mixture was heated under a blanket of nitrogen at 125 ° C. The ethyltriphenylphosphonium iodide was then added and the reaction mixture was allowed to exotherm at a temperature of about 145 ° C. The reaction was maintained at 145 ° C for two hours and the equivalent weight of epoxy was determined. At this point, the crosslinker, the diketimine and the N-methylethanolamine. The reaction mixture produced exotherm and a temperature of 132 ° C was then established and maintained for one hour. The resin mixture was dispersed (1,700 parts) in aqueous medium by adding it to a mixture of 38.31 parts of sulfamic acid and 1,219.38 parts of deionized water. The dispersion was again desalted with 657.26 parts of deionized water and 665.91 parts of deionized water stepwise and purified in vacuo to remove the organic solvent and obtain a dispersion having a solids content of 43.1% by weight. one hundred and one particle size of 870 Angstroms. A cationic electrodeposition bath was prepared as in Example V-A, except for the fact that the main vehicle of Example V-B was used in place of the main vehicle of Example V-A. The electrodeposition baths of Examples V-A and V-B were prepared and steel panels pre-treated with zinc phosphate were coated and cured as in Example I. The results are given in Table V below.

Table V The data in Table V indicate that the post-addition of an acid-functional compound immiscible in water to the electrodepositable cationic composition of Example V provides a better appearance, a better cure and a better curing speed than the reaction of the cationic resin. with the acid-functional compound immiscible in water. Comparative Example VI The following comparative examples (VI-A to VI-G) illustrate the effect of the addition of a water-immiscible acid-functional compound to the cationic electrodepositable composition with respect to the tin catalyst levels required for the appearance and curing Comparative Example VI-A This comparative example describes the preparation of a cationic electrodeposition bath containing 1.45% dibutyltin oxide (ODBE) on the total resin solids (0.69% tin on total resin solids) and without acid-functional compound immiscible in water. A pigment paste with the following components was prepared: The sand pulp was milled at a Hegman reading of 7. A catalyst paste was prepared with the following components: The sand pulp was milled at a Hegman reading of 7. A cationic electrodeposition bath was prepared with the following components: Comparative Example VI-B This comparative example describes the preparation of a cationic electrodeposition bath containing 1.45% ODBE on total resin solids (0.69% tin on total resin solids) and 1% compound acid-functional immiscible in water on solids of the main vehicle. A cationic electrodeposition bath was prepared with the following components: Comparative Example VI-C to VI-G These comparative examples describe the preparation of various cationic electrodeposition baths containing reduced levels of ODBE and 1% acid-functional compound on solids of the main vehicle. The baths were prepared by diluting the bath of Example VI-B, which contained 1.45% ODBE on the total resin solids, with a bath that did not contain ODBE, prepared with the following components: The electrodeposition baths of Comparative Examples VI-A to VI-G were prepared and zinc pre-treated steel panels were coated and cured as in Example I. The results are given in Table VI below.

Table VI The data in Table VI indicates that the appearance of a coating improves when the composition contains an acid-functional compound immiscible with water, for all tested catalyst levels. Curing, measured by acetone resistance, is the same for the composition containing 0.7% ODBE with an acid-functional compound immiscible in water and the composition containing 1.45% ODBE without acid-functional compound . The curing rate, measured by ATG, is slightly better for a composition containing 0.5% of ODBE with an acid-functional compound immiscible in water which for the composition containing 1.45% of ODBE are acidic compound. functional immiscible in water. Comparative Example VII The following examples (VII-A and VII-B) illustrate the effect of the addition of an acid-functional compound immiscible in water to a lead-free cationic electrodepositable priming composition. Comparative Example VII-A This example describes the preparation of a cationic electrodeposition primer bath containing no lead or acid-functional compound immiscible with water. A pigment paste was prepared with the following components: The pigment paste was milled with sand at a Hegman reading of 7. A cationic electrodeposition bath was prepared with the following components: j emp comparing ivo - This example describes the preparation of a cationic electrodeposition primer bath that does not contain lead and contains 1% water-immiscible acid-functional compound on the solids of the main vehicle. A cationic electrodeposition bath was prepared with the following components: Electrodeposition baths of Comparative Examples VII-A and VII-B were prepared and zinc-phosphate pre-treated steel panels were coated and cured as in Example I. The results are given in the following Table VII. Table VII 1 These data were obtained from coated panels cured for 30 minutes at 340 ° F (171, 1 ° C). These data were obtained from coated panels cured for 30 minutes at 310 ° F (154.5 ° C). 3 These data were obtained from coated panels cured for 30 minutes at 325 ° F (162.7 ° C). These data were obtained from coated panels cured for 30 minutes at 340 ° F (171, 1 ° C). The data in Table VII indicate that the addition of water-immiscible acid-functional compounds to electrodepositable, lead-free compositions improves curing, as measured by acetone and ATG resistance, despite the absence of lead as a catalyst. auxiliary isocyanate desmemator. Example VIII This example illustrates gomorresin or natural abietic acid as an acid-functional compound immiscible in water having a hydrocarbon chain of at least 5 carbon atoms. Gomorresine has several unexpected advantages over oleic acid and 0.3% abietic acid over the solids of the main vehicle is similar or better over 0.5% oleic acid over the main vehicle solids in all properties. Example VIII-A This example describes the preparation of a cationic electrodeposition bath containing no additives. A main vehicle was prepared with the following components: 1 The crosslinking polyisocyanate capped was prepared from the following mixture of components: to polymeric DIM which can be obtained from Miles Inc. as MONDUR MR, as indicated in Example I-A. The polyisocyanate, the methyl isobutyl ketone and the dibutyltin dilaurate were charged into a reaction flask under a nitrogen atmosphere. 2- (2-Butoxyethoxy) ethanol was added slowly, allowing the reaction to produce an exotherm to a temperature between 45 and 50 ° C. When the addition is complete, the reaction mixture was maintained at 50 ° C for 30 minutes. Then 2-butoxyethanol was added and the mixture was allowed to produce an exotherm to 110 ° C and was kept there until the infrared analysis indicated that no unreacted NCO remained. 2 Dicetimine derived from diethylenetriamine and methyl isobutyl ketone (73% solids in methyl isobutyl ketone). The EPON 828, the initial charge of Bisphenol A-ethylene oxide adduct and the initial charge of methyl isobutyl ketone in a reaction vessel were charged and heated under a nitrogen atmosphere at 125 ° C. Ethyltriphenylphosphonium iodide was then added and the reaction mixture was allowed to produce an exotherm to about 145 ° C. The reaction was maintained at 145 ° C for 2 hours and the second charge of the Bisphenol A-ethylene oxide adduct was added and one equivalent of epoxy was obtained. The epoxy equivalent usually stays close to the weight of the epoxy target equivalent. At this point, the second charge of methyl isobutyl ketone, the crosslinker, the diketimine and the N-methylethanolamine were successively added. The mixture was allowed to produce an exotherm and a temperature of 125 ° C was then established. The mixture was maintained at 125 ° C for 1 hour. The resin mixture (7,500 parts) was dispersed in aqueous medium by adding it to a mixture of 165.59 parts of sulfamic acid and 4,908.21 parts of deionized water. After 60 minutes, the dispersion was again diluted with 2,794.18 parts of deionized water and 2830.95 parts of deionized water stepwise and purified in vacuo to remove the organic solvent and obtain a dispersion having a solids content. of 42.53 percent a particle size of 830 Angstroms. A cationic electrodeposition bath was prepared with the following components: Example VIII-B This example describes the preparation of a cationic electrodeposition bath containing 0.5% oleic acid on the solids of the main vehicle. A main vehicle was prepared with the following components.

The reaction was carried out as in Example VIII-A, except for the fact that, after the second exotherm, a temperature of 130 ° C was established. The mixture was maintained at 130 ° C for 1 hour. The resin mixture (1600 parts) was dispersed in aqueous medium by adding it to a mixture of 34.17 parts of sulfamic acid and 1052.03 parts of deionized water. After 60 minutes, 7.20 parts of Emersol 210 oleic acid (a commercial grade of oleic acid from the Emery Chemicals Group of the Henkel Corporation) was added to the high solids dispersion and mixed again for 30 minutes. The dispersion was again diluted with 598.53 parts of deionized water and 606.41 parts of deionized water stepwise and purified in vacuo to remove the organic solvent and obtain a dispersion having a solids content of 43.0. percent and a particle size of 948 Angstroms.

A cationic electrodeposition bath was prepared with the following components: Example VIII-C This example describes the preparation of a cationic electrodeposition bath containing 0.5% gomorresin (natural abietic acid) on the solids of the main vehicle. A main vehicle was prepared with the following components: The reaction was carried out as in Example VIII-A, except for the fact that, after the second exotherm, a temperature of 130 ° C was established. The mixture was maintained at 130 ° C for 1 hour. The resin mixture (345.3 parts) was dispersed in aqueous medium by adding it to a mixture of 7.62 parts of sulfamic acid and 227.2 parts of deionized water. After 60 minutes, 1.6 parts of Gum Rosin, which can be obtained from the Colyer Chemical Company, and 1.6 parts of premixed methylisobutyl ketone as a solution to the high solids dispersion were added and re-mixed during 30 minutes . This gomorresin contains 10% neutral materials and 90% rosin acid, of which 90% is abietic acid (and isomers) and 10% is a mixture of dihydroabietic acid and dehydroabietic acid. The dispersion was again diluted with 129.3 parts of deionized water and 109.4 parts of deionized water stepwise and purified in vacuo to remove the organic solvent and obtain a dispersion having a solids content of 40.8 percent. and a particle size of 924 Angstroms. A cationic electrodeposition bath was prepared with the following components: Example VIII-D This example describes the preparation of a cationic electrodeposition bath containing 0.3% gomorresin (natural abietic acid) on the solids of the main vehicle. A main vehicle dispersion was prepared as in Example VIII-C, with a solids content of 41.3 percent and a particle size of 932 Angstroms.

The dispersion differed from that of Example VIII-C in that it contained 0.3% gomorresin on the solids of the main vehicle instead of 0.5%. A cationic electrodeposition bath was prepared with the following components The baths of Examples VIII-A to VIII-D were each ultrafiltered, removing 20% of the total weight of the bath as ultrafiltrate and replacing the ultrafiltrate with deionized water. Electro-coated steel panels pretreated with zinc phosphate and electrogalvanized non-phosphated steel smooth panels with each composition at 275 volts, for 2 minutes, at bath temperatures of 81-86 ° F (27.2-30, 0 ° C). ). After washing with deionized water, the panels were baked for 30 minutes at 310 ° F (154.5 ° C), 325 ° F (162.7 ° C) or 340 ° F (171.1 ° C). The resulting film formations were approximately 0.9 mils (22.9 microns). The cured coatings were measured in terms of appearance, response to curing measured by acetone resistance and Thermogravimetric Analysis (ATG), resistance to moisture on electrogalvanized substrate and resistance to hot saline on electrogalvanized substrate. Table VIII summarizes all the test results.

TABLE VIII Resistance Resistance to saline solution to moisture5 hot6 TABLE VIII (notes) 1 Before the ultrafiltration, the baths of Examples VIII-A to VIII-D were studied for resistance to breakage defects on wet substrates as follows: Pre-treated steel smooth panel is pre-wetted with zinc phosphate with deionized water and then electrified rapidly with 300 volts for 35 seconds at 95 ° F (35 ° C). The electrocoated panel is baked for 30 minutes at 340 ° F (171 ° C) and observations are made of a tendency to produce areas of vortex, breakage and elevated defects. Break patterns are rated on a scale of 0 to 10, with 10 being the best. 2 These data were obtained from steel panels pre-treated with zinc phosphate and coated, cured for 30 minutes at 340 ° F (171, 1 ° C). 3 These data were obtained from steel panels pretreated with zinc phosphate and coated, cured for 30 minutes at 310 ° F (154.5 ° C). 4 These data were obtained from steel panels pretreated with zinc phosphate and coated, cured at 340 ° F (171, 1 ° C). 5 Panels, on bare electrogalvanized steel, baked at 325 ° F (162.8 ° C) and 350 ° F (176.7 ° C), are exposed to condensation moisture from a bath maintained at 140 ° F (60 ° C) C), in a QCT cabinet supplied by Q-Panel Co., for 24 hours. They are immediately subjected to a cross hatch adhesion test using an instrument with 6 teeth spaced 2 mm apart. The loss of adhesion is then assessed on a scale from 0 = worse to 10 = better. 6 X-striped panels were plated on bare electrogalvanized steel baked at 325 ° F (162.8 ° C) and 350 ° F (176.7 ° C) in 5% NaCl solution at 55 ° C for 120 hours. The panels were removed and washed with water. A blade was used to scrape the loose paint around the scratch. The total width of the scratch loss is measured and recorded as the widest point. Example VIII demonstrates that, in the electrodepositable composition of the present invention, abietic acid or gomorresin are significantly better than oleic acid to prevent breakage on wet substrates and to improve adhesion to a bare electro-galvanized substrate and is the preferred embodiment of the invention with respect to these properties. Gumorresin is significantly better than oleic acid for the appearance and curing response. The example also demonstrates that 0.3% gomorresin on the solids of the main vehicle has effects on the curing response approximately equivalent to 0.5% oleic acid, while still providing further improvement in resistance to defects of break on wet substrate.

Claims (24)

1. CLAIMS 1. In an electrocoating method, an electroconductive substrate that serves as a cathode in an electrical circuit, consisting of said cathode and an anode, submerged in an aqueous electrodepositable composition, containing a cationic resin dispersible in water, which method consists in passing an electric current between the anode and the cathode to cause the electrodepositable composition to deposit on the cathode as a substantially continuous film, and to heat the electrodeposited film at an elevated temperature to cure the film, wherein the electrodepositable composition consists of (a) a resin cationic containing electrodepositable active hydrogen on a cathode, (b) a curing polyisocyanate curing agent and (c) an organotin-containing catalyst; whose improvement consists in the addition to the electrodepositable composition of at least one water-immiscible acid-functional compound having a hydrocarbon chain of at least 5 carbon atoms, selected from the group consisting of abietic acid and natural sources of abietic acid.
2. 2. The method of claim 1, wherein the cationic resin is derived from a polyepoxide.
3. 3. The method of claim 1, wherein the cathode is a steel substrate.
4. 4. The method of claim 2, wherein the polyepoxide is a polyglycidyl ether of a polyhydric alcohol.
5. The method of claim 2, wherein the cationic resin contains saline groups, which are amine salt groups.
6. The method of claim 2, wherein the amine salt groups are derived from basic nitrogen groups neutralized with an acid selected from the group consisting of formic acid, acetic acid, lactic acid, phosphoric acid, sulfamic acid and mixtures thereof.
7. The method of claim 1, wherein the acid-functional compound is gomorresin.
8. The method of claim 1, wherein the acid-functional compound is abietic acid.
9. The method of claim 1, wherein the organotin-containing compound is present in amounts of about 0.05 to 1 percent tin by weight, based on the total weight of the resin solids in the electrodepositable composition .
10. The method of claim 1, wherein the electrodepositable composition contains lead.
11. The method of claim 1, wherein the electrodeposited film is heated to a temperature range of about 300 to 340 ° F (148.8 to 171.1 ° C) to cure the film.
12. The method of claim 1, wherein the addition of acid-functional compound is in an amount ranging from about 0.1 to 3.0 percent by weight, based on the weight of the resin solids of the main vehicle of the cationic resin containing active hydrogen and the curing agent polyisocyanate capped.
13. The method of claim 12, wherein the acid-functional compound is present in an amount ranging from about 0.4 to 1.5 percent by weight, based on the weight of the resin solids of the vehicle is such that a reduced amount of the organotin-containing catalyst is present in amounts of about 0.05 to 0.5 percent tin by weight, based on the weight of the resin solids.
14. The method of claim 1, wherein the acid-functional compound is present by the addition of the acid-functional compound to the electrodepositable composition and wherein the acid-functional compound remains unreacted with the skeleton of the cationic resin of the Cationic resin containing active hydrogen in the electrodepositable composition, to allow the acid-functional compound to increase the curing response when the organotin catalyst activates the curing of the electrodeposition composition.
15. The method of claim 1, wherein the curing agent polyisocyanate is present in an amount ranging from about 5 to 60 weight percent, based on the total weight of the resin solids.
16. 16. The method of claim 15, wherein the curing agent polyisocyanate is present in an amount ranging from about 25 to 50 percent by weight, based on the total weight of the resin solids.
17. 17. In an electrodepositable composition consisting of (a) a cationic resin containing electrodepositable active hydrogen on a cathode, (b) a curing polyisocyanate curing agent and (c) an organotin-containing catalyst, the improvement consisting of the presence in the composition electrodepositable of at least one acid-functional compound immiscible in water having a hydrocarbon chain of at least 5 carbon atoms selected from the group consisting of abietic acid and its natural sources.
18. 18. The electrodepositable composition of claim 17, wherein the cationic resin is derived from a polyepoxide.
19. 19. The electrodepositable composition of claim 18, wherein the polyepoxide is a polyglycidyl ether of a polyhydric alcohol.
20. 20. The electrodepositable composition of claim 18, wherein the cationic resin contains salt groups that are amine salt groups.
21. The electrodepositable composition of claim 20, wherein the amine salt groups are derived from basic nitrogen groups neutralized with an acid selected from the group consisting of formic acid, acetic acid, lactic acid, phosphoric acid, sulfamic acid and mixtures thereof.
22. 22. The electrodepositable composition of claim 1, wherein the organotin catalyst is present in amounts of about 0.05 to 1 percent tin by weight, based on the total weight of resin solids in the electrodepositable composition.
23. 23. The electrodepositable composition of claim 22, further containing lead. The electrodepositable composition of claim 17, which is curable in a temperature range of about 300 to 340 ° F (148.8 to 171.1 ° C).