MXPA98001599A - Internal agent to avoid the formation of crateres for compositions used in catodi electroscreatments - Google Patents

Abstract

The present invention relates to an improved, aqueous, cathodic electrocoating composition having an epoxy and amine adduct binder and a blocked polyisocyanate-based crosslinking agent, wherein the improvement consists in the incorporation of an agent which avoids the formation of crystals, which is a polyoxyalkylene diamine having a number average molecular weight of about 700 to 5,000, making it react with the epoxy resin of an epoxy and amine adduct, wherein the ratio of amine equivalent to epoxy, the amine groups of the polyoxyalkylene diamine, to the epoxy groups of the epoxy resin of the epoxy and amine adduct, is in the range of 0.01-0.90 to 1, and the resultant epoxy and amine adduct has an average molecular weight in number from approximately 1,500 to 20,000, where the previous molecular weights are determined by Gel Permeation Chromatography (CPG), using polystyrene as the or stand

Description

INTERNAL AGENT TO AVOID THE FORMATION OF CRATTERS, FOR COMPOSITIONS USED IN CATHODIC ELECTROSCREATMENTS FIELD OF THE INVENTION The present invention is directed to a composition for cathode-electrode stretching, and in particular to a cathodic electrocoating composition containing an agent to prevent the formation of craters, which is incorporated directly into the resin for the formation of the cathodic film and which it significantly reduces the craters and improves the uniformity of the ectrodeposited films of the invention.

BACKGROUND OF THE INVENTION The coating of electrically conductive substrates, by means of an electrodeposition process, also called electrocoating process, is an important and well-known industrial process. Electrodeposition of sizes, on metal substrates REF .: 26748 automotices, is widely used in the automotive industry. In this process, a conductive article, such as a car body or autopart, is immersed in a bath of a coating composition of an aqueous emulsion of a polymer for film formation, and the article acts as an electrode in the electrodeposition process. An electric current is passed between the article and a counter electrode that is in electrical contact with the coating composition, until a coating of desired thickness is deposited on the article. In a cathodic electrocoating process, the article to be coated is the cathode and the counter electrode is the anode. Compositions of film-forming resins used in the bath of a typical cathodic electrodeposition process are also well known in the art. These resins are typically made of polyepoxy resins that have been elongated in their chain and then the adduct is formed to include amine groups in the resin. Amine groups are typically introduced through a reaction of the resin with an amine compound. These resins are mixed with a crosslinking agent and then neutralized to form an emulsion in water which is usually referred to as the main emulsion. The main emulsion is combined with a paste of pigments, coalescing solvents, water, and other additives to form an electrocoating bath. The electrocoating bath is placed in an insulated tank containing the anode. The article to be coated is the cathode and is passed through the tank containing the bath for electrodeposition. The thickness of the coating that is deposited on the article that is elect rorrevi s t i endo, is a function of the characteristics of the bath, of the electrical characteristics of operation of the tank, of the immersion time, and the like. The resulting coated article is removed from the bath and rinsed with deionized water. The coating remaining on the article is typically cured in an oven at a temperature sufficient to form a crosslinked finish on the article.

Compositions for cathodic electrocoating, resin compositions, coating baths and cathodic electrodeposition processes are described in Jarabe et al, US Patent No. 3,922,253 issued November 25, 1975; Wismer et al, U.S. Patent No. 4,419,467 issued December 6, 1983; Belanger, U.S. Patent No. 4,137,140 issued January 30, 1979 and Wismer, and U.S. Patent No. 4,468,307 issued August 25, 1984. A continuing problem with compositions for cathodic electrocoating has been the presence of craters and other imperfections. in the finished already cured. Typically, an anti-crater additive or agent is added to the electrocoating composition to form a smooth, uniform, crater-free finish. The anti-crater additives are presented in Chung et al, US Pat. No. 5, 356,960 issued October 18, 1994 and in the Moriarity et al patents, US Patent No. 4,420,574, issued December 13, 1983, US Patent No. 4,423,166 issued December 27, 1983 and US Patent No. 4,432,850 , issued February 21, 1984. However, when an anti-crater additive is used, in an electrocoating composition, which is baked or baked, in a gas-fired oven, indirectly, or in an electric oven, after electrodeposition In metallic substrate, such as the bodywork of a car or truck, the anti-crater additives described by these references, migrate easily to the surface of the electrodeposited coating, during baking. Any of the sizing compositions, which contain polymeric melamine-based crosslinking agents, applied on that surface, adhere poorly to the electrodeposited coating and cause a failure in the adhesion of a topcoat applied on that sizing. It would be desirable to remove the anti-crater additive from the composition and chemically incorporate the additive directly into the film formation of the resin for the electrocoating composition. This would significantly reduce and possibly stop the migration to the surface of the additive, and would not adversely affect other properties of the electrocoat bath, such as the deposition power of the bath or the curing of the deposited coating, or the properties of the resulting finish film.

BRIEF DESCRIPTION OF THE INVENTION In the present invention there is disclosed an improved, aqueous, cathodic electrocoat composition having a binder of an epoxy amine adduct and a crosslinking agent based on blocked polyisocyanate; wherein the improvement is the incorporation of an anti-crater agent which is a poxy ioxy to the qui lendi amine having a number average molecular weight of from about 700 to 5,000, making it react with the epoxy resin of the epyoxyamine adduct; wherein the ratio of equivalence of amine to epoxy, of the amine groups of the poxioxyalkylene dioxide, to epoxy of the epoxy resin of the epoxy and amine adduct, is within the range of 0.01-0.90 to 1 and the adduct of The resulting epoxy and amine has a number average molecular weight of about 1,500 to 20,000; wherein the above molecular weights are determined by Gel Permeation Chromatography (CPG) using polystyrene as the standard or standard.

DETAILED DESCRIPTION OF THE INVENTION The anti-crater agent is incorporated in the epoxy and amine adduct, which is the film-forming component of the electrocoating composition, by reacting the polyoxyalkylene amide with the epoxy resin component used in the adduct. The anti-crater agent is part of the film-forming component of the electrocoating composition, and can not migrate to the surface, during baking, and cause problems of adhesion failure, but additionally functions as an anti-crater agent and provides an anti-cracking agent. Smooth and uniform finish when baked. Since the anti-crater agent is an integral part of the epoxy and amine adduct, it is stable in the electrocoat composition and in the electrocoat coating bath, for prolonged periods of time and significantly reduces, and often eliminates, craters in the coatings ect. if they are finished and smooth and uniform finishes are formed. In addition, the anti-crater agent improves the control of rheology and improves the protection of the edges of an electrodeposited finish. The amount of anti-crater agent, used in the epoxy and amine adduct, is relatively small and is used in an amine to epoxy equivalence ratio, from the amine groups, to the epoxy groups, from about 0.01-0.90 to 1, and preferably in a ratio of about 0.01-0.2 to 1. The anti-crater agent of a 1-oxy-1-alkylamine is added with the constituents of the epoxy-amine adduct and the constituents are reacted at a temperature of about 50 to 130 ° C. for a time of about 1 to 5 hours, to form an adduct having a number average molecular weight of about 1,500 to 20,000, determined as described above. The polyoxyalkylamino amine used to form the anticrater agent has from 2 to 4 carbon atoms in the alkylene group and is preferably a polyoxypropylene lendiamine having a number average molecular weight of from about 230 to 3,000, preferably from 1,500 to 2,500 such as the Jeffamine D-2000MR which has a number average molecular weight of approximately 2,000 available from Huntsman Corporation. Another polyoxyalkylene diamine that can be used is polyoxyethylene glycol having a similar molecular weight. Approximately 0.01 to 8% by weight, based on the weight of epoxy amine, of an epoxy silane, can be incorporated into the adduct to improve the properties of rust protection; preferably about 2 to 6% by weight of the epoxy silane is used. The typical epoxy silanes are the glycidoxy alkylalcoxysi lanes that have the formula H2C CH CH2 or (CH2) p- (SOR) 3 wherein R is methyl, ethyl, or a mixture of methyl and ethyl, and n is an integer from 1 to 3. Typical silanes are gamma-glycidoxypropyltrimethoxysilane, gamma-glycidoxyethyltrimethoxysilane, gamma-glycoxymethyl 11-imexy yes laño, the gamma-glycidoxymethyltriethoxysilane, the gamma-glycidoxyethyltriethoxysilane, the gamma-glycoidoxypropyl 1 trietoxylamino. Gamma-glycidoxypropyl trimethoxysilane is preferred to form a high quality anti-crater agent. Other useful glycidyl alkylakoxysilanes are beta- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane. The epoxy and amine adduct is the reaction product of an epoxide resin of a polyglycidyl ether and a polyphenol, and an amine. The resulting epoxy and amine adduct has reactive amine and epoxy groups. The epoxy resin which is a polyepoxyhydroxy ether resin, has a 1,2-epoxy equivalency of about two or more, ie, a polyepoxide having on an average basis, two or more epoxy groups per molecule. The preferred polyepoxides are the cyclic polyl ethers of cyclic polyols. Particularly preferred are the polyglycidyl ethers of the polyhydric phenols such as bisphenol A. These polyepoxides can be produced by the etherification of polyhydric phenols with the epihalohydrin or dihalohydrin, such as epichlorohydrin or dichlorohydrin, in the presence of alkali. Examples of polyhydric phenols are 2, bi s - (4-hydroxy pheni 1) ethane, 2-methyl-1, 1-bis- (4-hydroxy phenyl) propane, 2,2-bis- (4-hydroxy) -3 butylphenyl tertiary) propane, 1,1-bis- (4-hydroxy phenol) ethane, bis- (2-hydroxynaphthyl) ethane, 1,5-dihydroxy-3-napht to ene or the like. In addition to the polyhydric phenols, other cyclic polyols may be used in the preparation of the polyether ethers and cyclic polyol derivatives. Examples of other cyclic polyols would be alicyclic polyols, particularly cycloaliphatic polyols, such as 1,2-bis- (hydroxymethyl) cyclohexane, 1,3-bi s- (hydroxymethyl) cyclohexane, 1,2-cyclohexanediol, 1.4, cyclohexandium 1 and hydrogenated bisphenol A. The polyepoxides have molecular weights of at least 200 and preferably molecular weights that are in the range of 200 to 3,000, and more preferably of about 340 to 2,000. The polyepoxy resin chain can be extended, for example, with any of the aforementioned polyhydric phenols such as bisphenol A and ethoxylated bisphenol A and preferably a combination of these phenols. It is also possible to lengthen the polyepoxide chain with a polyether or polyester polyol, which improves flow and coalescence. Typical, useful chain extenders are polyols such as polycaprolactone diols such as the Tone 200MR series available from Union Carbide Corporation and the ethoxylated Bisphenol A such as SYNFAC 8009MR available from Milliken Chemical Company. Examples of polyether polyols and conditions for elongation of chains are described in U.S. Patent No. 4,468,307. Examples of polyether polyols for elongation of the chains are described in Marchetti et al, US Patent No. 4,148,772, issued April 10, 1979. The amines used to prepare the epoxy and amine adduct, can be primary or secondary amines , or mixtures thereof. Preferred amines are the monoamines, particularly the hydroxyl-containing amines, such as the alkanolamines, dialkanolamines, trial, canolamines, alkylalkanolamines, arylalcanol amines and the arylalkanolamines, which contain from 2 to 18 carbon atoms in the aryl, alkyl chains. , and aril. Typically, useful amines include ethanolamine, methylethanolamine, N-methylethanolamine, diethanolamine, N-phylmetal, and the like. Other amines that can be used are presented in US Pat. No. 4,419,467 which is incorporated herein by reference. The cathodic binder of the epoxy and amine adduct, and the blocked isocyanate, are the main resinous ingredients in the electrocoating composition and are usually present in amounts of about 30 to 50% by weight solids of the composition. The binder is neutralized with an acid to form a water soluble product. The typically useful acids are lactic acid, acetic acid, formic acid, sulfamic acid, alkaline phonic acids such as methanesulfonic acids and the like. To form an electrocoating bath, the solids of the electrocoating composition are generally reduced with an aqueous medium for the desired solids in the bath. In the composition for electrocoating a crosslinking agent based on blocked polyisocyanate is used. Preferred crosslinking agents, for the above adduct, are also well known in the prior art. These are aliphatic, cycloaliphatic, and aromatic isocyanates, such as hexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexamethylenediisocyanate, toluene diisocyanate, diisocyanate of me ti léndi f eni lo, diisocyanate of me t il endi feni lo polymeric, and the like. These isocyanates are pre-reacted with a blocking agent such as oxy es, alcohols, or caprolact amas, which block the isocyanate functionality, i.e., functionality for crosslinking. By heating the blocking agents separately, a reactive isocyanate group is provided and cross-linking occurs. Isocyanate-based crosslinkers and blocking agents are well known in the prior art and are also described in U.S. Patent No. 4,419,467 mentioned above. In addition to the binder resin described above, the electrocoating composition usually contains a pigment that is incorporated into the composition in the form of a pigment paste. The pigment paste is prepared by grinding or dispersing a pigment in a grinding vehicle, as well as optional ingredients such as wetting agents, surfactants, and defoamers. Any of the pigment grinding vehicles, which are well known in the art, can be used, or the anti-crater agent of this invention can also be used. After grinding, the particle size of the pigment should be as small as practical, and in general, the particle size is about 6-8, using a calibrator for Hegman milling. Pigments that can be used in this invention include titanium dioxide, basic lead silicate, strontium chromate, carbon black, iron oxide, clay and the like. Pigments with high surface areas and high oil absorbencies should be used judiciously because they may have an undesirable effect on the coalescence and flow of the electrodeposited coating. The weight ratio of the pigment to the binder is also important and should preferably be less than 0.5: 1, more preferably less than 0.4: 1, and usually from about 0.2 to 0.4: 1. It has been found that higher binder-to-binder ratios adversely affect coalescence and flow. The electrocoat compositions of the invention may contain optional ingredients such as wetting agents, surfactants, defoamers and the like. Examples of surfactants and wetting agents include alkyl imidazolines such as those available from Ciba-Geigy Industrial Chemical as "Amine C", acetylenic alcohols available from Air Products and Chemicals as "Surfynol 104". These optional ingredients, when present, constitute from about 0.1 to 20% by weight of the binding solids of the composition. Optionally, plasticizers can be used to promote the flow. Examples of useful plasticizers are water-immiscible, high-boiling materials, such as ethylene or propylene oxide adducts, nonyl phenols or bisphenol A. Plasticizers are typically used at levels of about 0.1 to 15% by weight of resin solids. The electrocoat coating composition of this invention is an aqueous dispersion. The term "dispersion" as used within the context of this invention, it is believed to be a binder, resinous, aqueous, translucent or opaque system, of two phases, in which the binder is in the dispersed phase and the water is the continuous phase. The diameter of the average particle size, of the binder phase, is about 0.1 to 10 microns, preferably less than 5 microns. The concentrations of the binder in the aqueous medium are generally not critical, but ordinarily the main portion of the aqueous dispersion is water. the aqueous dispersion usually contains from about 3 to 50%, preferably from 5 to 40%, by weight of solids of the binder. The aqueous binder concentrates, which are to be further diluted with water when added to an electrocoating bath, generally have a binder solids range of 10 to 30% by weight. The following example illustrates the invention. All parts and percentages are on a weight basis unless otherwise indicated.

EXAMPLES The following emulsions were prepared 1-4 and each one was formulated in a bath for electrocoating.

Emulsion 1 (Control) The following ingredients were charged to a suitable reaction vessel: 953 parts of Epon 828NR (epoxy resin of diglycidyl ether of bisphenol A, having an epoxy equivalent weight, 188); 274 parts of bisphenol A, 343 parts of ethoxylated bisphenol A, having an equivalent weight of hydroxy, of 248 (Synfac 8009NR from Milliken Company), 2 parts of dimethyl-ilbenzylamine and 83 parts of xylene. The resulting reaction mixture was heated to 160 ° C under a blanket of nitrogen and kept at this temperature for one hour. 3 parts of dimethyl-il-benzylamine were added and the mixture was maintained at 147 ° C until an epoxy equivalent weight of 1.050 was obtained. 1,371 parts of a blocked isocyanate-based crosslinker solution (75% solids, blocked with methanol, ethanol and diethylene glycol monobutyl ether with an equivalent ratio of 1: 1: 1.32 of diisocyanate of me ti lendi feni polymeric, PAPI 2027), 105 parts of diketimine (reaction product of diethylenetriamine and methylisobutyl ketone at 72.7% solids) and 90 parts of methylethanolamine. The resulting mixture was maintained at 120 ° C for one hour. The resulting resin was emulsified in 94 parts of 88% aqueous lactic acid solution and 4.208 parts of deionized water. The emulsion was extracted to remove the organic solvent and the resulting emulsion had a solids content of 36%.

Ant i Crater Agent Used with Emulsion 1 The anti-crater agent was prepared by charging to a suitable reaction vessel, 2,322 parts by weight of Jeffamine D2000 ™ (polyoxypropylene diamine having a number-average molecular weight of 2,000 and an amine equivalent of 1,000) and 188 parts by weight of Epon 828 ™ were added ( described above) under a nitrogen atmosphere and the resulting mixture was heated to about 90 ° C and then 859 parts by weight of Epon 1001MR (diglycidyl ether of bisphenol A having an epoxy equivalent weight of 500, from Shell Chemical Company) and 345 parts by weight of 2-butoxyethanol. The resulting reaction mixture was dispersed by combining it with 68 parts of acetic acid and 5.345 parts of deionized water. The resulting anti-crater emulsion has a solids content of about 35%.

Emuls ion 2- Containing Agent Antichraters, which has already reacted The following ingredients were charged into a suitable reaction vessel: 953 parts of Epon 828MR (described above); 274 parts of bisphenol A; 343 parts of ethoxylated bisphenol A, having an equivalent weight of hydroxy, of 248 (Synfac 8009MR), 2 parts of dimethybenzylamine and 83 parts of xylene. The reaction mixture -resultant was heated to 160 ° C under a blanket of nitrogen and kept at that temperature for one hour. 3 parts of dimethyl-ilbenzyl sheet were added and the mixture was maintained at 147 ° C until an epoxy equivalent weight of 1.050 was obtained. 1,450 parts of a solution of the blocked isocyanate-based crosslinker (described above), 105 parts of diketimine (described above), 108 parts of Jeffamine D2000MR (described above) and 82 parts of methylethanolamine were added. The resulting mixture was maintained at 120 ° C for 1 hour. The resulting resin was emulsified in 94 parts of 88% aqueous lactic acid solution and 4.363 parts of deionized water. The emulsion was extracted to remove the organic solvent and the resulting emulsion had a solids content of 36%.

Emul s ion -which contains agent Anticyclet that has Reacted, and Siloxane The following ingredients were charged to a suitable reaction vessel: 953 parts of Epon 828MR (described above); 274 parts of bisphenol A; 343 parts of ethoxylated bisphenol A having an equivalent hydroxy weight of 248 (Synfac 8009MR), 2 parts of dimethylenbenzylamine and 83 parts of xylene. The resulting reaction mixture was heated to 160 ° C under a blanket of nitrogen and kept at this temperature for 1 hour. 3 parts of dimethylbenzene sheet were added and the mixture was maintained at 147 ° C until 1 equivalent weight of epoxy of 1 was obtained., 050. 1,484 parts of blocked isocyanate cross-linking solution (described above), 1.05 parts of diketimine (described above), 108 parts of Jeffamine D2000MR (described above) and 82 parts of methylethanolamine were added. The resulting mixture was maintained at 120 ° C for 1 hour. Thirty-eight parts of gamma-glycoxypropyl 1 trimethoxy were added and the mixture was kept at 120 ° C for 10 minutes. The resulting resin was emulsified in 94 parts of 88% aqueous lactic acid solution and 44.671 parts of deionized water. The emulsion was extracted to remove the organic solvent and the resulting emulsion had a solids content of 36%.

Emulsion 4- Containing Anti-Crater Agent that has Reacted, and Siloxane The following ingredients were charged to a suitable reaction vessel: 953 parts of Epon 828MR (described above); 274 parts of bisphenol A; 343 parts of ethoxylated bisphenol A having an equivalent hydroxy weight of 248 (Synfac 8009MR), 2 parts of dimethylbenzene sheet and 83 parts of xylene. The resulting reaction mixture was heated to 160 ° C under a blanket of nitrogen and kept at this temperature for 1 hour. 3 parts of dimethylbenzene sheet were added and the mixture was maintained at 147 ° C until an epoxy equivalent weight of 1.050 was obtained. 1,464 parts of a blocked isocyanate crosslinker solution (described above), 110 parts of diketimine (described above), 44 parts of Jeffamine D2000MR were added. (described above) and 86 parts of methylethanolamine. The resulting mixture was maintained at 120 ° C for one hour. 74 parts of gamma-glycoxypropyl 1 trimethoxy were added and the mixture was kept at 120 ° C for 10 minutes. The resulting resin was emulsified in 113 parts of 88% aqueous lactic acid solution and 4.487 parts of deionized water. The emulsion was extracted to remove the organic solvent and the resulting emulsion had a solids content of 36%.

Preparation of the Agent Used for the Formation of a Quaternary Compound The agent used for the formation of a quaternary compound was prepared by adding 87 parts of di-t-t-anoleamine to 320 parts of toluene diisocyanate semi-cured with ethylhexanol, in the reaction vessel, at room temperature. An exothermic reaction occurred and the reaction mixture was stirred for one hour at 80 ° C. Then 118 parts of aqueous lactic acid solution (75% nonvolatile compound content) were added, followed by the addition of 39 parts of 2-butoxyethane 1. The reaction mixture was maintained for about one hour at 65 ° C. C with constant agitation to form the quaternary compound formation agent.

Preparation of a Vehicle for the Grinding Pigment The vehicle for grinding was prepared by charging 710 parts of Epon 828 MR described above), 0.8 parts of ethyltriphenylphosphide iodide and 290 parts of bisphenol A, in a suitable vessel, under nitrogen blanket, and heated to a temperature between 150 and 160 ° C to initiate an exothermic reaction. The exothermic reaction was continued for about one hour at 150-160 ° C. The reaction mixture was then cooled to 120 ° C and 496 parts of semi-cured toluene diisocyanate were added with 2-ethylhexanol. The temperature of the reaction mixture was maintained at 110-120 ° C for one hour, followed by the addition of 1.095 parts of 2-butoxyethane 1, then the reaction mixture was cooled to 85-90 ° C and 71 parts were added. of deionized water followed by the addition of 496 parts of agent for the formation of quaternary compounds (prepared above). The temperature of the reaction mixture was maintained at 85-90 ° C until an acid value of about 1 was obtained.

Preparation of pigment paste Parts by weight Pigment grinding vehicle (prepared 812 above) Deionised water 1, 660 Titanium dioxide pigment 1,068 Aluminum silicate pigment 212 Lead silicate pigment 92 Carbon black pigment 32 Dibutyltin pigment 124 Total 4, 000 The above ingredients were mixed until a homogeneous mixture was formed in a suitable mixing vessel. They were then dispersed by loading the mixture into a sand mill and then ground until a Hegman reading of seven or greater was obtained.

Preparation of Baths 1-4, for Electroforming The following baths 1-4 for electrocoating were prepared using the above emulsions: The 1-4 electrocoating baths were prepared by mixing the above ingredients. Then each bath was subjected to ultrafiltration. Steel panels, phosphates, were electrified in each bath at a rate of 250 to 310 volts, to obtain a film of 20.3-25.4 microns (0.8-0.9 thousandths of an inch) thick, on each panel. All the electrodevés tido s panels were baked at 182 ° C for 17 minutes in an electric oven. The cratering, initial, was taken as the number of craters on the film. The ASPP exploded crater test was used in each bath. The resistance of the crater was classified according to the following classification scale, from A-E: A - 0-10% defects B - 11-20% defects C - 21-40% defects D - 41-80% defects E - Greater than 80% defects The adhesion of a surface agent to the electrorevented sizing was determined by the application of a sizing containing polymeric melamine (sizing 764DG007 from DuPont) and baked under normal conditions. A standard tape adhesion test was used to measure the adhesion between the sizing surface agent and the electrorevented sizing agent. To measure the corrosion resistance at the edges, one blade was emitted (10 x 20 cm) in each bath, with a coating voltage, which provided a film with a thickness of 0.0216 mm (0.85 mils) ). The coated blades were exposed to a salt spray for 7 days. The number of rust spots was counted by analyzing the blades under a microscope. The results of each of the previous tests are presented in the following table: The results of the previous tests show the following: the resistance to the craters, of each one of the baths, was of A, since there were no craters or defects; the adhesion test, the exploded crater test and the rust stain test on the blades all showed that the electrocoating bath 1, used as a control, containing the additive of the anti-crater agent that had not been previously reacted with the Film-forming components of the electrocoating composition showed poorer adhesion, resistance to bursting craters and formation of rust on the blades, which as in the electrodeposited film, from each of the baths 2-4 wherein the anti-crater agent had previously reacted with the film-forming components of the electrocoating compositions; baths 3 and 4 containing the silane component had improved resistance to bursting craters and improved protection against rust, compared to baths 1 and 2 that did not contain the silane component. It is noted that in relation to this date, the best known method for carrying out the aforementioned invention is that which is clear from the present description of the invention. Having described the invention as above, the content of the following is claimed as property:

Claims (10)

RE IVIND ICAC IONE S

1. An improved, improved, cathodic electrocoat composition having a binder of an epoxy and amine adduct and crosslinking agent based on blocked polyisocyanate; characterized in that the improvement lies in the incorporation of an anti-crater agent consisting of a polyoxyalkylene diamine having a number average molecular weight of from about 700 to 5,000, by reacting the agent with the epoxy resin of the epoxy and amine adduct; wherein the amine to epoxy equivalence ratio of the epoxy-amine adduct is from about 0.01-0.90 to 1 and the resultant epoxy-amine adduct has a number average molecular weight of about 1,500 to 20,000; wherein the molecular weights are determined by Gel Permeation Chromatography (CPG) using polystyrene as the standard or standard.

2. The composition for electrocoating, improved, according to claim 1, characterized in that the polyoxyalkylene diamine is a polyoxy-propylene diamine having a number average molecular weight of about 230-3,000.

3. The composition for electrocoating, improved, according to claim 1, characterized in that it contains approximately 0.01 to 8% by weight, based on the weight of the epoxy and amine adduct, of a glycoxycoalkylene coil if it has reacted with groups amine of the epoxy and amine adduct.

4. The composition for electrocoating, improved, according to claim 3, characterized in that the silane is gamma-glycoprotein 1 trimetoxylamino.

5. The improved electrocoating composition according to claim 1, characterized in that the polyoxyalkylene diamine is the polyoxy-propylene diamine having a number average molecular weight of about 230 to 3,000, and that it is used in an equivalency ratio of amine to epoxy , from about 0.01-0.2 al, and the silane is gamma-glycidoxypropyl trimethoxy if tin in about an amount of 2-6% by weight, based on the weight of the epoxy and amine adduct.

6. The composition for electrocoating, improved, according to claim 1, characterized in that the adduct of epoxy and amine is the reaction product of an epoxy resin of a diglycidyl ether and a polyphenol, elongated with a polyphenol and an ethoxylated polyphenol and also has reacted with an amine.

7. A method for the preparation of a composition for cathodic electrocoating, characterized in that it comprises the following steps in any order in which it can be worked: (a) preparing an epoxy and amine adduct, by reacting an epoxy resin of a diglycidyl ether and a polyphenol which is elongated with a polyphenol and an ethoxylated polyphenol and an amine; (b) reacting the epoxy and amine adduct, with a polyoxyalkylene diamine having a number average molecular weight of about 700 to 5,000, by reacting the agent with the epoxy resin of the epoxy and amine adduct; wherein the equivalence ratio of amine to epoxy, of the amine groups of the polyoxyalkylene diamine, to the epoxy groups of the epoxy and amine adduct, is from about 0.01-0.90 to 1, and the resultant epoxy and amine adduct has a number average molecular weight of about 1,500-20,000; wherein the molecular weights are determined by Gel Permeation Chromatography (CPG), using polystyrene as the standard or standard; (c) preparing a crosslinking agent, based on blocked polyisocyanate; (d) mixing the epoxy and amine adduct of step (b) with the blocked polyisocyanate-based crosslinking agent; (e) neutralizing the epoxy and amine adduct with an organic acid, to form an emulsion; and (f) mixing the emulsion with a pigment paste, to form the composition for electrocoating.

8. The method according to claim 7, characterized in that the polyoxyalkyl ediamine is a polyoxy-propylene diamine having a number average molecular weight of about 230 to 3,000.

9. The method according to claim 7, characterized in that approximately 0.01 to 8% by weight, based on the weight of the epoxy and amine adduct, of a glycidoxy to the 1 to the coxi if 1 year, is reacted with groups amine of the epoxy and amine adduct.

10. The method according to claim 7, characterized in that the polyoxyalkylene diamine is a polyoxypropyl lendiamine having a number average molecular weight of about 230 to 3,000 and is used in an amine to epoxy equivalence of 0.01-0.2 to 1, and about from 2 to 6% by weight, based on the weight of the epoxy and amine adduct, of a glycidoxy-propyl trimethoxy and tin which is reacted with the amine groups of the epoxy and amine adduct.