MXPA98004918A - Coating compositions of aqueous compounds polyurea - Google Patents

Abstract

Aqueous single-component coating compositions are disclosed which contain as a primary binder component a polyurea, which is the reaction product of: (a) a polymer component containing at least one polymer based on olefinically unsaturated compounds and containing reactive groups or isocyanate consisting of primary amino groups and / or secondary amino groups, with the possible additional presence of hydroxyl groups, and (b) a polyisocyanate component containing polyisocyanate groups in sufficient quantities to provide an equivalent NCO / NH ratio of about 0.5: 1 to 1

Description

COATING COMPOSITIONS OF AQUEOUS COMPOUNDS POLYUREA POLYUREA BACKGROUND OF THE INVENTION This invention relates to aqueous coating compositions based on dispersions of polyurea polymers formed from isocyanates and aminoacrylates. More specifically, it relates to obtaining said compositions in the form of a single packaging, while avoiding mass gelling. It is generally desirable to use water-based coatings in place of coatings based on organic solvents due to environmental considerations. However, the use of water instead of organic solvents in coating compositions based on polyisocyanates containing free isocyanate groups has been impeded by the fact that the isocyanate groups react not only with isocyanate-reactive groups in the intended cross-linking reaction , but also with water. Therefore, in a composition which includes a polyisocyanate, isocyanate-reactive groups and water, the isocyanate / water reaction takes place with the formation of urea and carbon dioxide. Not only is this reaction not capable of achieving the intended cross-linking of the isocyanate-reactive groups, but it also results in gasification or foaming of the composition due to the formation of carbon dioxide. Various attempts have been made in the prior art to stabilize aqueous isocyanate compositions against unwanted side reaction with water. It was described in U.S. Pat. No. 5,075,370 that it is possible to produce aqueous two-component polyurethane coating compositions using neutralized polyhydroxy polymers containing acid groups, ie polyhydroxypoly acrylates, as dispersing agents for polyisocyanates containing free isocyanate groups. The polyisocyanates containing free isocyanate groups are emulsified in the aqueous solution or dispersion of anionic polymer. It is said that the coating compositions according to that patent have a shelf life of several hours and cure by the reaction of isocyanate / hydroxyl groups to form polyurethane bonds. In the U.S. Patent Application Copendent and Commonly Owned, Serial No. 08 / 357,488, filed December 16, 1994, two-component aqueous based coating compositions based on amino acrylates and isocyanates, which are relatively free of collateral reactions with water, are described and claimed. and they react to form polyureas. It would be desirable to have said composition in a stable single packaging form to avoid the drawback of mixing the two components at the site of use. However, mixing a polyamine with a polyisocyanate in a single package usually results in a relatively rapid reaction at room temperature, so that gelation occurs and the mixture soon becomes unusable as a coating composition. Therefore, it has been considered necessary to sell said coatings as two separate packages that are mixed immediately before use. EP-A-0661320 discloses aqueous one-component coating compositions consisting of a (meth) acrylic copolymer having amino and hydroxyl functionality and a polyisocyanate crosslinker. The polyisocyanates useful in these single component coating compositions are those having two or more isocyanate blocked groups per molecule; in other words, the polyisocyanates employed in this patent do not contain free isocyanate groups.

SUMMARY OF THE INVENTION The present invention is directed to aqueous coating compositions of a single package containing as a primary binder component polyureas which are the result of the mixture of aminopolymers and isocyanates. Aminopolymers consist of the polymerization products of olefinically unsaturated compounds, including compounds containing primary amine groups and / or secondary amine groups. Optionally, other isocyanate-reactive groups, such as hydroxyl groups, may be additionally present in the monomers from which the aminopolymer is synthesized. Preferably, the aminopolymer is an amino acrylate. The polyisocyanate compounds that are mixed with the aminopolymer contain a plurality of isocyanate groups. Surprisingly, it has been found that, in certain circumstances, said mixture can be stable and substantially avoid mass gelling in a single package. At the same time, these compositions dry at a very rapid rate when applied to a substrate. Consequently, they are particularly useful as primer-smoothing coatings for automobiles, for example, because they can be sanded for a short time after application. In the stable compositions of a single pack of the present invention, the relative amounts of the polyisocyanate and the aminopolymer are such that the NCO / NH equivalent ratio is less than 1: 1. Preferably, the ratio is also at least 0.5: 1. If the aminopolymer also includes hydroxyl groups, as is eventually allowed, these ratios are related to the equivalent ratio NCO / (NH + OH). The use of polyisocyanates having no more than two NCO functional groups has also been important for the present invention. With a greater number of isocyanate groups per molecule, it is difficult to avoid premature gelation. In the preferred embodiments, higher functional isocyanates are used, but the excess isocyanate groups are defunctionalized by reaction with a compound containing an isocyanate-reactive group, such as an amine or a hydroxyl group. It is further advantageous to use as a defunctionalizing agent a compound which also contains non-isocyanate groups which have the ability to contribute to the crosslinking of the coating composition during drying (for example, silanes). To prepare the compositions of the present invention, the aminopolymer is first solubilized in water by acid neutralization of the amino groups. The polyisocyanate is then emulsified in the aqueous dispersion of the aminopolymer, with or without the aid of a surfactant. This initiates the reaction of the polyisocyanate with the aminopolymer to form urea linkages. It is also believed that some reaction of the polyisocyanate with water occurs. Surprisingly, it has been found that gelation of these mixed components can be avoided under the practice of the present invention, thereby allowing the coating to be supplied in a single package. Not only is the mixture surprisingly stable, but it also dries very quickly when applied to a substrate, where the coalescence of the polymer particles begins by evaporation of the liquid medium. The rapid drying speed favors the use of this coating, for example, as primer-smoothing in automotive applications, since the ability to sand soon after applying the coating is desirable in said application. DETAILED DESCRIPTION The aminopolymers contained in the coatings of the present invention are synthesized in the known manner from olefinically unsaturated monomers containing primary and / or secondary amino groups. These amino groups serve as sites for partial neutralization by an acid to form cationic aqueous dispersions, at the same time as as curing sites for reaction with the isocyanate to form urea linkages. Optionally, the aminopolymers can also include hydroxyl groups, which, after curing with the isocyanate groups, form urethane linkages. Polymers containing amino groups have a number average molecular weight (Mn), determined by gel permeation chromatography, of from about 500 to 50,000, preferably from about 1,000 to 10,000. The amine content of the aminopolymer is preferably 0, 05 to 2.70 milliequivalents per gram, more preferably 0.25 to 1.62 milliequivalents per gram. After the copolymerization, the amino groups are at least partially neutralized with an acid for inversion in the aqueous medium as a cationic polymer. In a particularly preferred embodiment, the cationic groups are secondary amino groups that have been neutralized with acetic acid. The amino polymer component of the coating composition of the present invention is provided in an aqueous medium in amounts of 10 to 50 percent by weight of resin solids, preferably 20 to 40 percent by weight, and has a pH value from 4 to 6, preferably from 5 to 5.5. Depending on the molecular weight of the polymers and their content in cationic groups, the aqueous systems containing the polymers can be colloidal dispersions or molecular solutions. The amino groups contained in the copolymer are used for the purpose of forming salts by means of acid groups which completely or partially neutralize the amino groups. In general, amino comonomers are used in amounts of about 1 to 50 percent by weight, preferably in amounts of about 5 to 30 percent by weight, based on the total weight of monomers used. In principle, amino monomers suitable for use in the copolymerization of the aminopolymers can be any olefinically unsaturated polymerizable compound containing at least one primary or secondary amine group, for example amino acrylates and aminomethacrylates, such as tert-butylaminoethyl methacrylate or metaisopropenyl-a , α-dimethylbenzylamine. Amine groups can also be obtained by reaction of acidic polymers with aziridines, such as ethyleneimine, or by reaction of blocked epoxy and ketimines, as well as other known techniques for adding amine functionality to the polymers. Hydroxyl-containing monomers are not necessary in the present invention, but, when used, they can be included in the monomer mixture in amounts such that the comonomers containing hydroxyl groups are used in amounts of about 0 to 30 percent. by weight, preferably 0 to 10 percent by weight, based on the total weight of monomers used to copolymerize the aminopolymer. Suitable monomers containing hydroxyl groups include, in particular, hydroxyalkyl esters of acrylic acid or methacrylic acid, preferably containing from 2 to 4 carbon atoms in the alkyl radical, such as 2-hydroxyethyl acrylate or methacrylate, or 2 or 3-hydroxypropyl methacrylate, the isomeric hydroxybutyl acrylates or methacrylates and mixtures of said monomers. The third group of olefinically unsaturated monomers that can be used for the copolymerization of the aminopolymer are olefinically unsaturated compounds that do not contain amino or hydroxyl groups. These compounds include esters of acrylic acid or methacrylic acid containing from 1 to 18, preferably from 1 to 8, carbon atoms in the alcohol radical, such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-acrylate, propyl, n-butyl acrylate, 2-ethylhexyl acrylate, n-stearyl acrylate and acrylates or methacrylates containing tertiary amines and the methacrylates corresponding to these acrylates. Also included are styrene, alkyl-substituted styrenes, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl stearate and mixtures of said monomers. The monomers of this third group are used in amounts of 50 to 90 weight percent, preferably of about 40 to 80 weight percent, based on the total weight of the monomers used. The aminopolymers can be produced by standard polymerization procedures. The polymers are preferably produced in organic solvent. The polymerization reaction is initiated by free radicals when the monomer mixture is added together with an initiator mixture over a period of about 1 to 10 hours, preferably about 3 to 6 hours, at room temperature. Then, more initiator may be added eventually to bring the polymerization to a conversion of at least 99 percent. Suitable solvents for the aminopolymer are characterized by their solubility towards the polymer and their ability to be azeotropically distilled for inversion to the aqueous medium. These may include alcohols, such as ethanol, propanol and butanol; aromatic hydrocarbons, such as benzene, toluene, xylene and chloroben-ceno; esters, such as ethyl acetate, butyl acetate, methyl glycol acetate, ethyl glycol acetate and methoxypropyl acetate; ethers, such as butyl glycol, tetrahydrofuran, dioxane and ethyl glycol ether; ketones, such as acetone and methyl ethyl ketone; halogen-containing solvents, such as methylene chloride and trichloro onofluoroethane, and mixtures of these solvents. The polymerization can be initiated by commercially available primers for this purpose. In general, the copolymerization reaction takes place at temperatures in the previously established range, preferably at a temperature of about 50 ° to 160 ° C, at atmospheric pressure. The exact polymerization temperature is determined by the type of initiator and solvent used. The initiators are used in amounts of about 0.05 to 10 percent by weight, based on the total amount of monomers. Suitable initiators include aliphatic azo compounds, such as azoisobutyronitrile, and peroxides, such as dibenzoyl peroxide, t-butyl perpivalate, t-butyl per-2-ethylhexanoate, t-butyl perbenzoate, t-butyl hydroperoxide, di-t-butyl peroxide, eumeno hydroperoxide and dicyclohexyl peroxydicarbonate and dibenzyl. The molecular weight of the polymers can be regulated by standard regulators, such as n-dodecylmer-captan, diisopropylxanthogen disulfide, (methylenetrimethylolpropane) xanthogen and thioglycol disulfide. They are added in amounts of up to about 10 weight percent, based on the monomer mixture. Upon completion of the polymerization, the aminopolymers are converted to an aqueous solution or dispersion. An acid is introduced into the polymerization solution, followed by the addition of water. The organic solvent is then removed by azeotropic distillation. Fugitive acids are preferred for neutralization, i.e., those escaping from the coating upon drying, thus avoiding interference with drying. Fugitive acids are generally organic acids, among which acetic acid, propionic acid, lactic acid and trifluoroacetic acid are preferred. However, within the broad aspects of the invention, mineral acids could also be employed, such as carbonic acid, phosphoric acid and sulfuric acid, of which fugitive carbonic acid is preferred. Other organic acids and minerals are well known in the art and can be used for neutralization in the present invention. The polyisocyanate employed in the coating compositions of the present invention may be any polyisocyanate containing aliphatic, cycloaliphatic, araliphatic and / or aromatically bound isocyanate groups which is liquid at room temperature. The polyisocyanate can be made to be compatible with the aqueous composition in various ways, including modifying the polyisocyanate itself to be water dispersible or water reducible. Example 5 is an illustration of said approach. However, preferred embodiments employed polyisocyanates in combination with a separate emulsifier. The polyisocyanate used as starting material in the present invention is preferably a polyisocyanate compound or mixture of polyisocyanate compounds exclusively containing aliphatic and / or cycloaliphatically isocyanate groups and having an average NCO functionality of about 2.0 to 5.0 per molecule . For use in the coating composition, however, the isocyanate functionality is preferably reduced to an average of no more than 2.0 per molecule, as will be described here below. If necessary, the polyisocyanates can be used in admixture with small amounts of inert solvents to reduce the viscosity. However, the maximum amount in which said solvent is used is such that the coating compositions contain at most 20 weight percent solvent, based on the amount of water and any solvent that may still be present in the dispersions or polymer solutions. Suitable solvents for the polyisocyanates include aromatic hydrocarbons such as solvent naphtha, acetates or the solvents indicated as suitable for the polymerization of the aminopolymer, to the exclusion of alcohol solvents. Suitable polyisocyanates include those containing aromatic isocyanate or (cyclo) linked groups, with (cyclo) aliphatic polyisocyanates being particularly preferred. Particularly suitable are the polyisocyanates based on 1,6-hexamethylene diisocyanate, 1-isocyanato-3, 3, 5-trimethyl-5-isocyanato-methylcyclohexane (DIIF) and / or bis (isocyanatocyclohexyl) methane, particularly those based on diisocyanate 1,6-hexamethylene. Other suitable polyisocyanates based on these diisocyanates can include the biuret, urethane, uretdione and / or isocyanurate derivatives of these diisocyanates, which, after their production, have been released in a known manner, preferably by distillation, from the excess starting diisocyanate to a residual content of less than 0.5 weight percent. The aliphatic polyisocyanates for use in accordance with the invention include hexamethylene-based biuret polyisocyanates, which are based on mixtures of N, N ', N "-tris (6-isocyanatohexyl) biuret with small amounts of their higher homologs.These polyisocyanates can be obtained by means of the processes according to US Patent Nos. 3,124,605, 3,358,010, 3,903,126, 3,903,127 or 3,976,622. Cyclic trimers of 1,6-hexamethylene diisocyanate are also preferred. they correspond to the criteria mentioned above, which can be obtained according to US Pat. No. 4,324,879 and which are based on N, N ', N "-tris (6-isocyanatohexyl) isocyanurate in admixture with small amounts of their superior counterparts. The aromatic polyisocyanates which can be used according to the invention, but which are less preferred, are based on 2,4-diisocyanatoto-luene or commercial mixtures thereof with 2,6-diisocyanato-toluene, or are based on 4,4 '- diisocyanatodiphenylmethane or its mixtures with its isomers and / or higher homologs. Aromatic polyisocyanates of this type include the urethane isocyanates obtained by reacting excess amounts of 2,4-diisocyanatotoluene with polyhydric alcohols, such as trimethylolpropane, and then removing the excess unreacted diisocyanate by distillation. Other aromatic polyisocyanates include the trimers of the aforementioned monomeric diisocyanates, which have also been liberated from the excess of monomeric diisocyanates, preferably by distillation, after their production. Although polyisocyanates having more than two isocyanate functional groups are preferred as starting materials, it has been found desirable to partially react some of the isocyanate functionality before adding the polyisocyanate to the coating compositions of the present invention. With an isocyanate functionality greater than 2, it is difficult to avoid premature gelling of the coating composition. The excess of isocyanate groups is defunctionalized by reaction with a compound containing an isocyanate-reactive group such as an amine or a hydroxyl group. Optionally, the defunctionalizing compound may also contain groups other than the isocyanates that have the ability to contribute to the crosslinking of the coating composition during curing. One type of said compounds are the aminosilanes. To prepare ready-to-use coating compositions, the polyisocyanate component is emulsified in the aqueous dispersion of the aminopolymer. The dissolved or dispersed polymer simultaneously serves as an emulsifier for the added polyisocyanate. Eventually, the dispersion of the polyisocyanate can be aided by a separate surfactant. The mixture can be made by simple stirring at room temperature. The amount of the polyisocyanate component is selected to obtain an equivalent NCO: NH ratio. { or NCO equivalent ratio: (NH + OH) if the hydroxyl functionality is present), based on the isocyanate groups of component (b) and primary and secondary amino groups and hydroxyl groups of component (a), of less than 1: 1, preferably at least 0.5: 1. The ratio depends on the isocyanate used in particular. For the purposes of the present invention, a primary amino group is considered to be an equivalent of two and a secondary amino group is considered to be an equivalent of one. Therefore, NH in these ratios represents equivalents of hydrogen amine. Additives typically employed in coating technology can be incorporated into the coating composition of the present invention. The additives include foam inhibitors, leveling aids, pigments, dispersion aids for pigments, etc. and are preferably introduced initially into component (a). The coating compositions according to the invention thus obtained are suitable for virtually any application where high performance with rapid drying is desired. They are particularly useful for coating metal surfaces and various plastic surfaces such as primers-smoothing (ie, a coating typically applied directly on an electrodeposited primer before applying a colored coating.) The invention is further illustrated, but without intending to limit it, by the following examples, in which all parts and percentages are by weight, unless otherwise specified EXAMPLE 1 The initial charge and the following feeds were used in the preparation of the secondary-functional aqueous amine acrylic polymer by a solution polymerization Components Parts by weight Initial charge Isopropanol 130,, 0 Feeding 1 Isopropanol 113,, 0 N-Butyl acrylate 69,, 2 Methyl methacrylate 153,, 0 Tert-butylaminoethyl methacrylate 73,, 0 Styrene 69, , 2 VAZO® 671 18,, 2 Feeding 2 Glacial acetic acid 17,, 7 Feeding 3 Deionized water 1085, , Initiator 2, 2 '-azobis (2-methylbutanonitrile), commercially available from E.I. du Pont de Nemours and Company, Wilmington, Dela are. The initial charge was heated in a reactor with stirring at reflux temperature (80 ° C). Feed 1 was then added continuously over a period of 3 hours. Upon completion of Feed 1, the reaction mixture was refluxed for 3 hours. The resulting acrylic polymer had a total solids content of 61.7 percent, determined at 110 ° C for one hour, and a number average molecular weight of 4792, determined CPG using polystyrene as the standard. Next, Feed 2 was added over five minutes at room temperature with stirring. After the addition of Feed 2 was complete, Feed 3 was added over 30 minutes, while the reaction mixture was heated for azeotropic distillation of isopropanol. When the distillation temperature reached 99 ° C, the distillation was continued for about an additional hour and then the reaction mixture was cooled to room temperature. The total distillate collected was 550.6 grams. The final aqueous dispersion had a solids content of 32.6 percent, determined at 110 ° C for one hour, and a pH of 5.25. EXAMPLE 2 The initial charge and the following feeds were used in the preparation of secondary-functional aqueous amine acrylic polymer by a solution polymerization technique. Components Parts by weight Initial charge Isopropanol 650.0 Feeding 1 Isopropanol 565.0 n-Butyl acrylate 273.5 Methyl methacrylate 783.5 Tert-butylaminoethyl methacrylate 364.5 Styrene 401.0 VAZO1"67 91.0 Feeding 2 Glacial acetic acid 88.5 Feeding 3 Deionized water 5425.0 The initial charge was heated in a reactor with stirring at reflux temperature (81 ° C.) Feed 1 was then added continuously over a period of 3 hours. When the Feeding is completed 1, the reaction mixture was kept under reflux for 3 hours. The resulting acrylic polymer had a total solids content of 59.8 percent, determined at 110 ° C for one hour, and a number average molecular weight of 4833, determined CPG using polystyrene as the standard. After polymerization, Feed 2 was added over 10 minutes at room temperature with stirring. After the addition of Feed 2 was completed, Feed 3 was added over 15 minutes. The reaction mixture was heated for azeotropic distillation of isopropanol. When the distillation temperature reached 99-100 ° C, the distillation was continued for two more hours and the reaction mixture was then cooled to room temperature. The total distillate collected was 2545 grams. After filtration, the final aqueous dispersion had a solids content of 31.5 percent and a pH of 5.32. EXAMPLE 3 The secondary functional amine aqueous acrylic polymer was prepared according to the method of Example 1. The resulting dispersion had a total solids content of 29.7 percent, determined at 110 ° C for one hour, and a pH of 5, 25 EXAMPLE 4 The initial charge and the following feeds were used in the preparation of a secondary functional aqueous amine acrylic polymer by solution polymerization. Components Parts by weight Initial charge EXXATE® 9001 718.2 Feed 1 EXXATE 900 792.6 VAZO-67 254.4 Feed 2 n-Butyl acrylate 762.0 Methyl methacrylate 2179.2 Tert-butylaminoethyl methacrylate 1012.8 Styrene 1116.0 Power 3 EXXATE 900 72.0 Feed 4 EXXATE 900 72.0 1 C9 alkyl acetate from Exxon Chemical Compan. The initial charge was heated in a reactor with stirring at a temperature of 140 ° C under a blanket of nitrogen. Food 1 and Feed 2 were added substantially continuously over a period of 3 hours. Upon completion of Feeding 1 and 2, the addition funnels were washed with Feeds 3 and 4 and the reaction mixture was refluxed for 3 hours. The resulting acrylic polymer had a total solids content of -77.1 percent, determined at 110 ° C for one hour. After the polymerization, 3.100 grams of the prepared polymer solution was placed in a suitable reaction vessel for vacuum distillation and heated to about 150 ° C. When the temperature reached 150 ° C, the distillation of EXXATE 900 was started by applying vacuum. After 2 hours of distillation under 24 to 29 inches of mercury vacuum at a temperature of 148 to 150 ° C, 319.3 grams of total distillate were collected.

The distilled polymer (523.6 grams) was added at 150 ° C to 1018.6 grams of deionized water containing 26.2 grams of glacial acetic acid, at 80 ° C, with stirring, over 20 minutes. The dispersion was cooled to room temperature and filtered through a 10 micron filter bag. The resulting dispersion had a total solids content of 28.4 percent, determined at 110 ° C for one hour, and a pH of 4.91. The following example describes the preparation of a cationic resin reducible in isocyanate water that can be used to crosslink the aminopolyacrylates of the previous examples.

EXAMPLE 5 Isophorone diisocyanate (176.8 grams, 1.6 equivalents) and DESMODUR W (104.8 grams, 0.8 equivalents) were placed in a one-liter, four-necked, round bottom flask. The flask was heated to 60 ° C and a blanket of nitrogen was applied throughout the reaction. Propoxylated n-methyldiethanolamine was carefully mixed (126.7 grams, 0.54 OH equivalents, 0.26 equivalents amine) and methanesulfonic acid (25.0 grams, 0.26 equivalents) and the resulting mixture was slowly added to the flask at 60 ° C through a funnel additional. The flask was maintained at 60 ° C until the isocyanate equivalent weight reached 224. The propoxylated n-methyldiethanolamine was the product of the reaction of p-methylethanolamine (1 mol) with propylene oxide (7 mol). The amino acrylate resins of Examples 1, 2, 3 and 4 were used to formulate aqueous coating compositions of a single package in combination with various isocyanates as indicated in the following Examples A to D. All were stable against premature gelation. and they dried very quickly. In Example A, the isocyanate was self-dispersing, so no emulsifier was needed. Example B used a combination of a trifunctional isocyanate and a nonionic emulsifier. Example C used a combination of a difunctional isocyanate and a nonionic emulsifier. Example D used a combination of a partially defunctionalized isocyanate and a nonionic emulsifier. EXAMPLE A Component Percent by weight Grinding paste: Aminoacrylate from Example 1 16,821 RAVEN8 4101 0.035 MICROTALC9 MP-12-502 7,991 BARIMITE9 XF3 8.254 TI-PURE® R902-384 9,395 SOLSPERSE "270005 0.307 DEE F0ß 97-36 0.053 Deionized water 4,560 DSX -1514® 7 0.292 Add: PROGLYDEF DMM8 0.117 n-Propanol9 0.030 Aminoacrylate from Example 1 18.965 EXXATE9 90010 3.029 Deionized water 22.419 Isocyanate: Cationic isocyanate of Example 5 3.324 EXXATE 900 0.542 Deionized water 3.866 EXAMPLE B Component? IucuI ic CII Jjc &? Grinding paste: Aminoacrylate of Example 2 17,017 RAVEN 410 0.036 MICROTALC MP-12-50 8,271 BARIMITE XF 8,543 TI-PURE R902-38 9,725 SOLSPERSE 27000 0.318 DEE FO 97-3 0.091 Deionized water 6,350 Butyl Acetate CELLOSOLVE® or 0,545 DSX-1514 0,303 Add: PROGLYDE DMM 0.121 n-Propanol 0.031 Aminoacrylate of Example 2 17, 178 EXXATE 900 1,909 Deionized water 24, 994 Isocyanate: DESMODUR® N 320012 1,834 Emulsifier13 0.825 EXXATE 900 1,909 EXAMPLE C Component Percent by weight Grinding paste: Aminoacrylate from Example 3 19, 108 RAVEN 410 0.038 MICROTALC MP-12-50 8,553 BARIMITE XF 8,835 TI-PURE R902-38 10,056 EXXATE 900 2, 123 SOLSPERSE 27000 0.329 DEE FO 97-3 0.094 Deionized water 3,496 DSX-1514 0,313 Add: PROGLYDE DMM 0,117 n-Propanol 0,157 Aminoacrylate of Example 3 26,975 EXXATE 900 2,444 Deionized water 15, 836 Isocyanate: Isophorone diisocyanate 14 1,233 Emulsifier 15 0.411 EXAMPLE D Component Percent by weight Grinding paste: Aminoacrylate of Example 4 22, 608 RAVEN 410 0.042 MICROTALC MP-12-50 9,532 BARIMITE XF 9, 846 TI-PURE R902-38 11,208 SOLSPERSE 27000 0,367 DEE FO 97-3 0.105 Deionized water 4,948 DSX-1514 0.349 Add: n-Propanol 0.175 Deionized water 6.285 Aminoacrylate from Example 4 14,192 EXXATE 900 3,142 Isocyanate: DESMODUR * N 340 O16 3,228 S ILQUEST9 Y- 966917 1,444 Emulsifier18 2,055 1 RAVEN * 410 - Carbon black pigment from Cities Service Co. , Columbian Div., Akron, Ohio. 2 MICROTALC® MP-12-50 - Hydrated magnesium silicate from Whittaker, Clark & Daniel Inc., South Plain-field, New Jersey. 3 BARIMITE XF® - Barium Sulphate from Cyprus Industrial Mineral Co. , Catersville, Georgia. 4 TI-PURE® R902-38 - Pigment of titanium dioxide from E.I. du Pont de Nemours & Co., Wilmington, Delaware. 5 SOLSPERSE® 27000 - Hyperdispersant from ICI Surfactants, Wilmington, Delaware. 6 DEE FO® 97-3 - Ultra Additives Defoamer, Inc., Paterson, New Jersey. 7 DSX-1514 < S > - Thickener from Henkel, Kankakee, Illinois. 8 PROGLYDE® DMM - Solvent, dimethoxyether of dipropylene glycol, from Dow Chemical U.S.A., Chemicals and Performance Products Dept. , Midland, MI. 9 n-Propanol - Solvent from Eastman Chemical Products, Inc., Kingsport, Tennessee. 10 EXXATE8 900 - C9 alkyl acetate solvent from Exxon Chemical Co. , Houston Texas. 1X Butyl Acetate CELLOSOLVE - Solvent Eastman Chemical Products, Inc., Kingsport, Tennessee. 12 DESMODUR® N 3200 - A biuret of hexamethylene diisocyanate from Bayer Corporation, Pittsburgh, Pennsyl-vania. 13 Emulsifier - A nonionic surfactant that has residual isocyanate functionality prepared by the reaction of 75 percent of T-1890 (an isophorone diisocyanate from Huís America, Piscataway, New Jersey) and 25 percent of CARBOWAXF 750 ME (a surfactant) monofunctional polyether from Union Carbide Chemicals and Plastics Co., Charleston, West Virginia) in methyl ethyl ketone and PROGLYDE® DMM (dipropylene glycol di ethoxyether from Dow Chemical Co., Midland, Michigan). Isophorone Diisocyanate - Monomeric Aliphatic Isocyanate from Bayer Corporation, Pittsburgh, PA. 15 Emulsifier - A non-ionic surfactant that does not have residual isocyanate functionality, prepared by reaction of 33.3 weight percent of T-1890, 11.1 weight percent of CARBOWAX® 750ME and 55.6 percent by weight of SOLVACTANT® DMH-7, all supplied at 100% resin solids. 16 DESMODUR8 N 3400 - A trimeric isocyanate of Bayer Corporation, Pittsburgh, Pennsylvania. 17 SILQUEST® Y- 9669 - A inosilane from Osi Specialties, Inc., Sistersville, West Virginia. 18 Emulsifier - A nonionic surfactant that does not have residual isocyanate, prepared by reaction of a 49.46 weight percent of T-1890, 16.49 weight percent of CARBOWAX 750ME, 17.03 weight percent of diethylethanolamine and 17.03 weight percent of SOLVACTANT8 DMH-7 (a nonionic surfactant from Union Carbide), in methyl ethyl ketone and EXXATE® 900. The coating compositions of Examples A to D were prepared in the following manner. In a milling vessel, under a high stirring speed with a Cowles blade, the other components of the milling paste (except the thickener) were sieved.

After stirring for 5 minutes, the Cowles blade was replaced with an Impeller blade and then zircoa beads were added. This mixture was stirred at high speed for one hour, after which the beads were separated from the milling paste. The thickener (DSX-1514) was then added to the grinding paste and stirred at high speed for five minutes, after which the grinding paste was diluted with the addition components. The isocyanate portions of the Examples were prepared and added to the other components as described below. In Example A, the cationic isocyanate of Example 5 was first diluted with EXXATE 900 to 70 weight percent resin solids and then further diluted to 35 percent with deionized water. Because this isocyanate was self-dispersing, no emulsifier was needed in this example. The diluted isocyanate was immediately stirred with moderate agitation in the vessel containing the rest of the components. In Example B, 75 weight percent of DESMODUR N 3200 (at 100% resin solids) was mixed with 25 weight percent solids of the isocyanate emulsifier. This isocyanate package was agitated with moderate agitation in the container containing the rest of the components. In Example C, 75 percent isophorone diisocyanate (100% solids) was mixed with 25 percent isocyanate emulsifier (also at 100% solids). This isocyanate package was stirred with moderate agitation in the container containing the rest of the components. In Example D, DESMODUR N 3400 (100% solids) was mixed with SILQUEST Y-9669 (100% solids) in a ratio of 3 parts of isocyanate to 1 part of amine in equivalents. Then 25 weight percent solids of the emulsifier was added. After an induction of 24 hours, the isocyanate mixture was stirred with moderate agitation in the vessel containing the rest of the components. Each of the coating formulations of Examples A, B, C and D was studied for performance by application on a substrate prepared as follows. The substrates were 32 gauge steel panels with zinc phosphate pretreatment (from Advanced Coating Technologies, Inc., Hillsdale, Michigan; as B952 P60 DIW cold rolled steel, varnish) primed with an epoxy-polyamide metal primer, DP -40 / DP-401 (a metal primer prepared by mixing 1 volume of DP-40 epoxy primer with 1 volume of DP-401 epoxy primer catalyst, both from PPG Industries, Inc., Pittsburgh, Pennsylvania). Substrates primed under ambient conditions were air-dried for at least 1 hour before applying the coatings of the examples. After an induction period of at least 24 hours, each of the compositions of Examples A to D was applied by spraying atomized air at 45 pounds per square inch onto the previously prepared substrates. Each coated substrate was air dried at ambient conditions for 1 hour. Each was then sanded dry with sandpaper P400 (production paper P400-213Q, Imperial Wetordry®, weight "A", 3M, St. Paul, Minnesota) immediately and, if necessary, at each interval successive one hour. The time in which it was observed that the coating of the example was sandable, that is, when it was not soiled on sandpaper, was taken as the minimum time necessary after the application to be sandable. Immediately after each spray application, the remaining portion of the composition of each example, approximately 85 to 100 grams, was sealed in a 1/2 pint container. Each sample container was stored at room temperature for one month, reopened and observed for flowability. The evaluation of the adhesion of the coating of each example to the substrate was carried out by applying tape in ascaradora (2 inches, "232 Masking Tape", from 3M, St. Paul, Minnesota) after a drying time of 1 hour and then tearing it off. An additional adhesion test was performed according to the method established in ASTM D3359, Method B, where the coating of the example was scratched with a Cross Cut Tester Gardner, Model PAT, equipped with a PA-2056 blade, both from Gardco, Pompano Beach, Florida. The lined coatings were subjected to strip removal using Permacel 99 tape after drying the coatings of the examples and were dried for 96 hours, and again after an additional 96 hours, during which they were exposed to 100 degrees F and 100 % moisture . The results of each of these performance tests are indicated in Table 1.

TABLE 1 A rating of "Pasa" in SANDING indicates that there was no fouling of the sandpaper due to embedment of the coating in the sand. N.E. or "not applicable" indicates that no further tests were needed. A "Pass" rating on the ADHESION indicates an adhesion greater than 95% of the coating of the example on the substrate (in this case, 100% for each of the Examples). A rating of "Pasa" in FLUIDEZ indicates a coating of the examples that did not exhibit the characteristic of having a non-sprayable viscosity even when diluted with water. The compositions of Examples A to D fulfill all the objectives of rapid drying speed and stability as coatings of a package. However, some of the examples have other characteristics that affect their attractiveness for commercial use. Example A exhibited excellent stability against gelation, but had less than optimal resistance to gas generation and, therefore, is not a preferred embodiment for most applications. It is thought that Example B is an anomalous result because its stability was not reproducible with any other composition that was prepared with an isocyanate having trifunctionality, such as DESMODUR N 3200 used herein. The reason for the stability of Example B is not understood, but it is believed to be the result of the particular amino acrylate used. All other amino acrylates tested in the same combination resulted in unstable, gel-forming compositions. Example C exhibited excellent properties, demonstrating that difunctional isocyanates (such as isophorone diisocyanate) are preferable with respect to the trifunctional isocyanates in the present invention. However, the use of isophorone diisocyanate in many commercial coating situations has environmental drawbacks. For environmental purposes, the use of higher molecular weight isocyanates is preferred. Advantageously, Example D employs a higher molecular weight isocyanate, but avoids the gelation problem appearing with higher isocyanate functionality. Although Example D starts with a trifunctional isocyanate (DESMODUR N 3400), it is partially defunctionalized with an amine compound (SILQUEST Y-9669). An aminosilane compound is used to obtain the additional crosslinking ability of the silane group in Example D, but any amine compound could help the goal of defunctionalizing the excess isocyanate functionality. Instead of an amine, any compound containing a group that is reactive with isocyanate, such as a hydroxy group, could be used.

Claims (10)

1. CLAIMS 1. A single-component coating composition containing as a primary binder component a polyurea in an aqueous medium and consisting of the mixture of: an aqueous polymer dispersion consisting of an aminopolymer produced from olefinically unsaturated compounds and containing isocyanate reagents selected from the group consisting of primary amino groups, secondary amino groups or combinations thereof, wherein at least a portion of said amine groups are neutralized to disperse the polymer in water and a polyisocyanate selected from the group consisting of polyisocyanates which are water-dispersible, polyisocyanates which are reducible in water and polyisocyanates in combination with a non-ionic surfactant, the polyisocyanate of which has unreacted isocyanate groups and has an average functionality of no more than two isocyanate groups per molecule; the polyisocyanate and the aminopolymer being provided to each other in an NCO / NH equivalent ratio of less than 1: 1.
2. 2. The coating composition of claim 1, wherein the equivalent NCO / NH ratio is at least 0.5: 1.
3. 3. The coating composition of claim 1, wherein the aminopolymer is an acrylic polymer.
4. 4. The coating composition of claim 2, wherein the amino group content of the polyacrylate of component (a) is from 0.05 to 2.70 milliequivalents per gram.
5. 5. The coating composition of claim 1, wherein the amino group content of the aminopolymer is from 0.25 to 1.62 milliequivalents per gram.
6. 6. The coating composition of claim 3, wherein the aminopolymer is the reaction product of monomers, of which 1 to 50 weight percent are monomers containing amino groups.
7. The coating composition of claim 2, wherein the aminopolymer is the reaction product of monomers, of which 5 to 30 weight percent are monomers containing amino groups.
8. The coating composition of claim 1, wherein the functionality of the polyisocyanate has been reduced from more than two isocyanate groups per molecule before mixing with the aminopolymer.
9. 9. The coating composition of claim 8, wherein the functionality of the polyisocyanate has been reduced by reaction with a compound containing an amine group or a hydroxyl group. The coating composition of claim 9, wherein the compound used to reduce the isocyanate functionality additionally contains a silane group.