GB2036031A

GB2036031A - High Solids Coating Composition

Info

Publication number: GB2036031A
Application number: GB7849605A
Authority: GB
Original assignee: Ford Motor Co Ltd; Ford Motor Co
Current assignee: Ford Motor Co Ltd; Ford Motor Co
Priority date: 1977-12-27
Filing date: 1978-12-21
Publication date: 1980-06-25
Also published as: FR2413450A1; IT7852420A0; CA1124430A; JPS5495637A; FR2413450B1; JPS5544112B2; DE2855847A1; IT1192318B; GB2036031B; DE2855847C2

Abstract

A fast curing, high solids coating composition for use as an automotive topcoat and which upon curing forms a hard, glossy, durable coating exhibiting excellent resistance to solvents and water contains greater than about 60 percent by weight of nonvolatile solids and, exclusive of pigments, solvents and other nonreactive components, consists essentially of: (A) a film-forming copolymer selected from monofunctional copolymers bearing pendant epoxy functionality and bifunctional copolymers bearing hydroxy functionality and pendant epoxy functionality, said copolymers have a number average molecular weight (Mn) of between 1500 and 10,000 and a glass transition temperature (Tg) of between -25 DEG and 70 DEG C.; (B) at least one mono- or diester of phosphoric acid; (C) an amino resin crosslinking agent; and (D) optionally a hydroxy functional additive. The organophosphate ester is included in the composition in an amount sufficient to provide between 0.67 and 1.4 acid equivalents for each epoxide equivalent of the copolymer (A), and the amino resin crosslinking agent is included in the composition in an amount sufficient to provide at least about 0.67 equivalents of nitrogen crosslinking functionality for each hydroxyl equivalent included in the composition (i) as a hydroxyl group on said optional hydroxy functional additive, (ii) as a hydroxyl group on said film-forming copolymer or (iii) as a result of esterification of the pendant epoxy functionality of said film-forming copolymer during curing of the composition.

Description

SPECIFICATION High Solids Coating Composition Adapted for Use as Automotive Topcoat This invention is related to a fast curing, high solids, thermosetting coating composition. More particularly, the invention relates to a polymeric, high solids, fast curing coating composition adapted to provide an automotive topcoat which demonstrates hardness, high gloss, outstanding durability and excellent resistance to solvents and water. Still more particularly, this invention relates to a fast curing, high solids, thermosetting coating composition adapted to be used as an automotive topcoat wherein the topcoat includes metallic flake as a pigment.

Because of increasingly strict solvent emissions regulations in recent years, low solvent emission paints have become very desirable. A number of high solids paint compositions have been proposed to meet these low solvent emission requirements. However, many of these compositions are deficient because of difficulty in application, slow curing rates, lack of flexibility, poor durability and low solvent and water resistance. Many of the proposed compositions have been particularly deficient as automotive topcoats, particularly when the topcoat is to include metallic flake as a pigment.

The deficiency in compositions including metallic flake results from undesired reorientation of the metallic flake during application and curing of the coating. The flake reorientation results primarily because of the very low viscosity resins used in the paint compositions to accommodate high solids.

The low thixotropy is not sufficient to immobilize the flakes which tend to redistribute themselves to show "reverse flop" and nonuniform distribution.

The coating compositions of this invention combine the above-discussed desired properties and low application viscosity with rapid cure so as to overcome deficiencies of previously proposed high solids materials and thereby achieve a high solids coating composition particularly adapted for automotive topcoats and still more particularly adapted for automotive topcoats including metallic flake as a pigment.

The thermosetting coating compositions of this invention contain greater than about 60 percent by weight of nonvolatile solids, preferably greater than about 70 percent by weight, and is capable of curing rapidly at a low temperature. The composition, exclusive of pigments, solvents and other nonreactive components, consists essentially of:: (A) an epoxy functional film-forming polymer selected from monofunctional copolymers bearing pendent epoxy functionality or bifunctional copolymers bearing both pendent epoxy and hydroxy functionality, said copolymers having a number average molecular weight (Mn) of between about 1 500 and about 10,000, preferably between about 2000 and about 6000, and a glass transition temperature (Tg) of between about -250C. and about 700 C., preferably between about --100C. and about 500C.; (B) at least one organophosphate ester having the formula:

wherein n=l to 2 and R is selected from alkyl, cycloalkyl, or aryl groups; (C) an amino resin crosslinking agent; and (D) up to about 45 weight percent based on the total weight of (A), (B), (C) and (D) of a hydroxy functional additive having a number average molecular weight (Mn) of between about 1 50 and about 6000, preferably between about 400 and about 2500.

The organophosphate ester is included in the composition in an amount sufficient to provide between about .67 and about 1.4 equivalents, preferably between about .8 and about 1 equivalents, of acid functionality for each equivalent of pendent epoxy functionality of the copolymer. The amino resin crosslinking agent is included in the composition in an amount sufficient to provide at least about 0.67, preferably between about .75 and about 3.75 equivalents, of nitrogen crosslinking functionality for each equivalent of hydroxy functionality included in the composition either (i) a hydroxy group on the copolymer; (ii) a hydroxyl group on the optional hydroxy functional additive or (iii) as a result of esterification of the pendent epoxy functionality of the copolymer during cure of the coating composition.In addition, the high solids coating composition of the invention may include additives such as catalysts, antioxidants, U.V. absorbers, flow control or wetting agents, antistatic agents, pigments, plasticizers, solvents, etc.

U.S. Patents 3,960,979 and 4,018,848 to Khanna teach high solids coating compositions adapted for use as a can coating material. The compositions consists essentially of (i) aromatic epoxide compositions having two or more epoxy groups on an epoxy resin which has a molecular weight not exceeding 2500; (ii) an amino crosslinking agent; (iii) an inorganic or organic monomeric or polymeric acid which acts as a reactive catalyst; and (iv) a flexibilizing polyol.

The compositions of Khanna have the advantage of quick reaction and low application viscosity, but lack durability, and, therefore, do not weather well. This is, in part, because of the presence of ether linkages in the aromatic epoxides. As such, the compositions of Khanna are not desirable for use as automotive topcoats. The Khanna patents describe the compositions as a low cure system. However, when considering the specific teachings of the patents one finds that the composition includes an excess of epoxide resin, apparently with the purpose of "killing off" excess catalyst after completion of the curing reaction. Excess epoxy resin in the composition remains uncured at the low temperature bake range of the baking temperatures disclosed, not giving a complete cure and desirable hardness, durability or solvent resistance.If heated to higher temperatures, as called for in the examples, the excess epoxy does react with excess hydroxy functionality to give still further ether linkages. These ether linkages so obtained have a further deleterious effect on durability and make the materials particularly unsuitable for use as automotive topcoats. Also, the necessary high bake temperatures to achieve the utilization of this excess epoxy makes the composition undesirable from an energy point of view because of the high baking temperatures required. Still further, because the epoxy/catalyst reaction occurs in early stages of the cure, thus "killing off" the catalyst, the melamine-hydroxy curing reaction must proceed substantially without benefit of catalysis. The curing reaction thus proceeds slowly and requires the high temperatures of the Khanna examples.

The high solids coating compositions of this invention overcome disadvantages of prior art high solids compositions, including those of Khanna, to provide a system which is particularly suitable for those applications requiring high gloss, hardness, durability, and high solvent and water resistance as well as a fast cure rate at low temperatures, e.g., from about 750C to about 1500 C, preferably from about 11 00C to about 1300 C. The desirable characteristics of the coating compositions of this invention result from the carefully controlled admixture of the particular components to achieve substantially complete utilization of reactant functionality in a fast and efficient manner.

Each of the components of the high solids coating compositions, the amounts of each of the components required to achieve the desired results of the invention and a method for applying the composition are described hereinafter in greater detail.

Epoxy Functional Film-forming Polymer As mentioned above, the epoxy functional film-forming material of the compositions of the invention may be selected from monofunctional copolymers bearing pendent epoxy functionality or bifunctional copolymers bearing both pendent epoxy functionality and hydroxy functionality. These film-forming copolymers, which are a principal material in the high solids coating compositions of this invention, may be prepared by conventional free radical induced polymerization of suitable unsaturated monomers. The term "copolymer" as used herein means a copolymer of two or more different monomers.

The copolymers used in the high solids coating compositions of this invention have a number average molecular weight (Mn) of between about 1 500 and about 10,000, preferably between about 2,000 and about 6,000, and a glass transition temperature (Tg) of between about -250C. and about 700 C., preferably between about -1 00C. and about 500 C.

The monomers used to prepare the monofunctional copolymers include between about 10 and about 30 weight percent of one or more monoethylenically unsaturated monomers bearing glycidyl functionality. These monoethylenically unsaturated monomers may be glycidyl ethers or glycidyl esters.

Preferably, however, the epoxy functional monomers are glycidyl esters of monoethylenically unsaturated carboxylic acids, e.g., glycidyl acrylate or glycidyl methacrylate. These monomers provide the copolymer with its pendent epoxy functionality.

The monomers used to prepare the bifunctional copolymers useful in compositions of the invention include between about 5 and about 25 weight percent of one or more of the glycidyl functional copolymers discussed above and between about 5 and about 25 weight percent of one or more monoethylenically unsaturated monomers bearing hydroxy functionality, with the total of the monoethylenically unsaturated monomers bearing either epoxy or hydroxy functionality being not greater than about 30 weight percent of the monomers in the copolymer.

The monoethylenically unsaturated hydroxy functional monomers which provide the bifunctional copolymer with its hydroxy functionality may be selected from a long list of hydroxy functional monomers. Preferably, however, the hydroxy functional monomers are acrylates and may be selected from the group consisting of, but not limited to, the following esters of acrylic or methacrylic acid and aliphatic alcohols: 2-hydroxy-ethyl acrylate; 3-chloro-2-hydroxypropyl acrylate; 2-hydroxy-1 - methylethyl acrylate; 2-hydroxypropyl acrylate; 3-hydroxypropyl acrylate; 2,3 dihydroxypropyl acrylate; 2-hydroxybutyl acrylate; 4-hydroxybutyl acrylate; diethyleneglycol acrylate; 5-hydroxypentyl acrylate; 6-hydroxy-ethyl acrylate; triethylenegiycol acrylate; 7-hydroxy-heptyl acrylate; 2-hydroxymethyl methacrylate; 3-chloro-2-hydroxypropyl methacrylate; 2-hydroxy - 1 -methylethyl methacrylate; 2hydroxpropyl methacrylate; 3-hydroxypropyl methacrylate; 2,3 dihydroxypropyl methacrylate, 2hydroxybutyl methacrylate; 4-hydroxybutyl methacrylate; 3,4 dihydroxy-butyl methacrylate; 5hydroxypentyl methacrylate; 6-hydroxyhexyl methacrylate; 1 ,3-dimethyl-3-hydroxybutyl methacrylate; 5,6 dihydroxyhexyl methacrylate; and 7-hydroxyheptyl methacrylate.

Although one of ordinary skill in the art will recognize the many different hydroxy bearing monomers, including those listed above could be employed, the preferred hydroxy functional monomers for use in the bifunctional copolymer of the invention are C-C7 hydroxy alkyl acrylates and/or C6-C8 hydroxy alkyl methacrylates, i.e., esters of C2-C3 dihydric alcohols and acrylic or methacrylic acids.

The remainder of the monomers forming the epoxy functional film-forming polymer, i.e., between about 90 and about 70 weight percent of the monomers of the copolymer are other monoethylenically unsaturated monomers. These monoethylenically unsaturated monomers are preferably alpha-beta olefinically unsaturated monomers, i.e., monomers bearing olefinic unsaturation between the two carbon atoms in the alpha and beta positions with respect to the terminus of an aliphatic carbon-tocarbon chain.

Among the alpha-beta olefinically unsaturated monomers which may be employed are acrylates (meaning esters of either acrylic or methacrylic acids) as well as mixtures of acrylates and vinyl hydrocarbons. Preferably, in excess of 50 weight percent of the total of the copolymer monomers are esters of C1-C12 monohydric alcohols and acrylic or methacrylic acids, e.g., methylmethacrylate, ethylacrylate, butylacrylate, butyl methacrylate, hexylacrylate, 2-ethyl hexylacrylate, lauryl methacrylate, etc. Among the monovinyl hydrocarbons suitable for use in forming the copolymers are those containing 8 to 12 carbon atoms and including styrene, alpha-methylstyrene, vinyl tolene, tbutylstyrene and chlorostyrene. When such monovinyl hydrocarbons are employed, they should constitute less than 50 weight percent of the copolymer.Other monomers such as vinyl chloride, acrylonitrile, methacrylonitrile, and vinyl acetate may be included in the copolymer as modifying monomers. However, when employed, these modifying monomers should constitute only up to about 30 weight percent of the monomers in the copolymer.

In preparing the mono functional or bifunctional copolymers, the monomers bearing the desired epoxy and hydroxy functionality and the remaining monoethylenically unsaturated monomers are mixed and reacted by conventional free radical initiated polymerization in such proportions as to obtain the copolymer desired. A large number of free radical initiators are known to the art and are suitable for the purpose. These include: benzoyl peroxide; lauryl peroxide; t-butylhydroxy peroxide; acetylcyclohexane; sulfonyl peroxide; diisobutyryl peroxide; di-(2-ethyl hexyl) peroxydicarbonate; diisopropylperoxydicarbonate; t-butyl peroxypivalate; decanoyl peroxide, azobis(2-methylpropionitrile), etc. The polymerization is preferably carried out in solution using a solvent in which the epoxy functional copolymer is soluble.Included among the suitable solvents are toluene, xylene, dioxane, butanone, etc. If the epoxy functional copolymer is prepared in solution, the solid copolymer can be precipitated by pouring the solution at a slow rate into a nonsolvent for the copolymer such as hexane, octane, or water under suitable agitation conditions.

The mono- or bifunctional copolymers useful in the compositions of this invention can also be prepared by emulsion polymerization, suspension polymerization, bulk polymerization, or combinations thereof, or still other suitable methods. In these methods of preparing copolymers, chain transfer agents may be required to control molecular weight of the copolymer to a desired range. When chain transfer agents are used, care must be taken so they do not decrease the shelf stability of the composition by causing premature chemical reactions.

Organophosphate Ester A second essential component of the high solids coatings of this invention is an organophosphate mono- or diester or a mixture of such mono- and diesters. Such organophosphate esters are preferably formed by esterification of phosphoric acid or its anhydrides or by controlled hydrolysis of alkyl, cycloalkyl or aryl halophosphates. Organo-phosphate esters useful in the compositions of the invention are those having the formula:

wherein n=1 to 2 and R is selected from alkyl, cycloalkyl or aryl groups. Preferably, the mono- or diesters are alkyl esters and the hydrocarbon substituent may be in such cases any alkyl group including, but not limited to methyl, ethyl, butyl, amyl, 2-ethylhexyl, lauryl, stearyl, etc. The most preferred alkyl groups contain 2 to 6 carbon atoms and are primary straight chain radicals.

The organophosphate ester components of the high solids coating composition of the invention is a reactive catalyst which allows the composition to cure rapidly at a low temperature. The acid functionality of the mono- or diester or mixture of such esters reacts with the pendent epoxy functionality of the epoxy functional film-former to form an ester and a hydroxyl group. It is this hydroxyl functionality which crosslinks with the amino resin crosslinking agent. It is critical to achieving the desired results of the high solids coating compositions of this invention, i.e., in making them suitable for use as automotive topcoats, that the amount of organophosphate ester be sufficient to convert substantially all of the epoxy functionality on the copolymer to the desired hydroxy functionality by esterification reaction.Therefore, the organophosphate ester is included in the composition in an amount sufficient to provide between about .67 and about 1.4 equivalents, preferably between about .8 and about 1 equivalents, of acid functionality for each equivalent of pendent epoxy functionality on the copolymer. As will be noted from the equivalent amount stated above, the amount of organophosphate ester acid functionality need not be in stoichiometric amounts to the epoxy functionality. This is because during curing of the high solids coating composition, residual water present in the composition hydrolyzes some of the esterified product back to acid and this hydrolyzed product, in turn, reacts with additional epoxy functionality.

Amino Resin Crosslinking Agent A third essential component of the high solids paint compositions of this invention is an amino resin crosslinking agent. Amino crosslinking agents suitable for crosslinking hydroxy functional bearing materials are well known in the art. Typically, these crosslinking materials are products of reactions or melamine, or urea with formaldehyde and various alcohols containing up to and including 4 carbon atoms. Preferably, the amino crosslinking agents useful in this invention are amine-aldehyde resins such as condensation products of formaldehyde with melamine, substituted melamine, urea, benzoguanamine or substituted benzoguanamine. Preferred members of this class are methylated melamine-formaldehyde resins such as hexamethoxymethylmelamine.These liquid crosslinking agents have substantially 100 percent nonvolatile content as measured by the foil method at 450C. for 45 minutes. For the purposes of the invention it should be recognized that it is important not to introduce extraneous diluents that would lower the final solids content of the coating.

Particularly preferred crosslinking agents are the amino resins sold by American Cyanamid under the trademark "Cymel". In particular, Cymel 301, Cymel 303 and Cymel 11 56, which are alkylated melamine-formaldehyde resins, are useful in the compositions of this invention.

The amino resin materials function as a crosslinking agent in the composition of the invention by reacting with (i) any hydroxy functionality which may be present on the epoxy functional film-former, (ii) hydroxy functionality created by esterification of the pendent epoxy functionality on the epoxy functional copolymer and (iii) hydroxy functionality on the hydroxy functional additive if such material is included in the composition.

In order to achieve the outstanding properties which make these coating compositions particularly useful as automotive topcoat materials, it is essential that the amount of amino crosslinking agent be sufficient to substantially completely crosslink the hydroxy functionality in the coating composition.

Therefore, the amino resin crosslinking agent should be included in the composition in an amount sufficient to provide at least about 0.67 equivalents, preferably between about .75 and about 3.75 equivalents, of nitrogen crosslinking functionality for each equivalent of hydroxy functionality included in the composition either (i) as a hydroxyl group on the epoxy functional film-formers, (ii) as a hydroxyl group on the optional hydroxy functional additive or (iii) as a result of esterification of the pendent epoxy functionality of the epoxy functional film-former during cure of the coating composition.

Optional Hydroxy Functional Additive Additional hydroxy functionality other than that present on the film-former or that achieved by esterification of pendent epoxy functionality of the epoxy functional copolymer may be achieved by adding a hydroxy functional additive in amounts up to about 30 weight percent based on the total of the three above discussed components and the hydroxy functional additive itself. Such a material serves to provide additional hydroxy functional additives so as to provide a more intimate crosslinked structure in the final cured product. The hydroxy functional additives useful in the composition are preferably selected from various polyols having a number average molecular weight (Mn) of between about 1 50 and about 6,000, preferably between about 400 and about 2500. As used herein the term polyol means a compound having two or more hydroxyl groups.

The polyols useful in the invention preferably are selected from the group consisting of: (i) hydroxy functional polyesters; (ii) hydroxy functional polyethers; (iii) hydroxy functional oligoesters, (iv) monomeric polyols; (v) hydroxy functional copolymers produced by free radical polymerization of monoethylenically unsaturated monomers, one of which bears hydroxy functionality and which is included in the copolymer in an amount ranging from about 2.5 to about 30 weight percent, and (vi) mixtures of (i)-(v).

The hydroxy functional polyesters useful in the invention are preferably fully saturated products prepared from aliphatic dibasic acids containing 2-20 carbon atoms, such as succinic acid, glutaric acid, adipic acid, azelaic acid, etc., and short chain glycols of up to and including 21 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 1 ,3-propylene glycol, 1 2-butylene glycol, 1 ,3-butylene glycol, 1 ,4-butylene glycol, neopentyl glycol, 1 4-cyclohexane dimethanol, 1,6-hexamethylene glycol and 2-ethyl-2-methyl-1 ,3 propane diol. The molecular weight of these materials ranges from about 200 to about 2500 and the hydroxyl number ranges from about 30 to about 230. The hydroxyl number is defined as the number of milligrams of potassium hydroxide needed for each gram of sample to neutralize the acetic acid generated during the reaction between the polyol and excess acetic anhydride. The polyester polyols utilized in the invention are low melting, soft waxy solids which are easily maintained in the molten state.

Among preferred polyesters are products derived from the esterification of ethylene glycol and 1,4 butane diol with adipic acid, ethylene glycol and 1,2 propylene glycol with adipic acid, azelaic acid and sebacic acid copolyester diols and mixtures thereof.

Among useful polyether diols are polytetramethylene ether glycol, polyethylene glycol, polypropylene glycol and the like.

The hydroxy functional oligoesters useful as hydroxy functional additives in the compositions of the invention are oligoesters preferably having a molecular weight of between about 1 50 and about 3000. Such oligoesters may be selected from the group consisting of: (1) oligoesters prepared by reacting a dicarboxylic acid with a monoepoxide such as an alkylene oxide; (ii) oligoesters prepared by reacting a polyepoxide with a monocarboxylic acid; and (iii) oligoesters prepared by reacting a hydroxy functional monocarboxylic acid with either a mono- or polyepoxide.

The oligoester prepared by reacting a dicarboxylic acid with an alkylene oxide is a low molecular weight adduct which has a narrow molecular weight distribution when compared to similar compositions made by normal polyester manufacturing techniques. The adduct is prepared by reacting a dibasic carboxylic acid with alkylene oxides, preferably ethylene oxide or propylene oxide, in the presence of a catalyst. Preferred dicarboxylic acids are C6-C12 aliphatic acids such as adipic acid, azelaic acids, sebacic acid or dodecane dicarboxylic acid. Mixtures of these acids or mixtures of the aliphatic dicarboxylic acids with aromatic dicarboxylic acids also yield suitable hydroxy functional oligoesters.

The preparation of oligoesters from carboxylic acids and polyepoxides is well known and is described, for example, in U.S. Patents 2,456,408 and 2,653,141. Numerous hydroxy functional oligoesters within this general category will be apparent to those skilled in the art.

The third type of hydroxy functional oligoester, i.e., those prepared by reaction of a hydroxy functional monocarboxylic acid with an epoxide is described in U.S. Patent 3,404,018. While the epoxides employed in accordance with the teachings of that patent are polyepoxides, oligoesters may be prepared in a similar manner to that described therein by employing a monoepoxide, such as an alkylene oxide, and a hydroxy functional monocarboxylic acid as described therein. Numerous monoepoxide materials suitable for this purpose will be apparent to those skilled in the art.

Among the numerous monomeric polyols which may be employed as the hydroxy functional additive are the various short chain glycols of up to and including 21 carbon atoms which are useful in preparing the hydroxy functional polyesters discussed above. Other conventional polyhydric alcohols such as glycerols and sugar alcohols are also among the numerous monomeric polyols which will be apparent to those skilled in the art.

The hydroxy bearing copolymer useful as the hydroxy functional additive may be formed from monoethylenically unsaturated monomers, with between about 2.5 and about 30 weight percent bearing hydroxyl functionality.

The long list of hydroxy functional monomers which may be employed in these hydroxy functional copolymers includes, but is not limited to, the following esters of acrylic or methacrylic acid and aliphatic alcohols: 2-hydroxyethyl acrylate; 3-chloro-2-hydroxypropyl acrylate; 2-hydroxy-1 - methylethyl acrylate; 2-hydroxypropyl acrylate; 3-hydroxy-propyl acrylate; 2,3 dihydroxypropyl 'acrylate; 2-hydroxy-butyl acrylate; 4-hydroxybutyl acrylate; diethylene-glycol acrylate; 5-hydroxypentyl acrylate; 6-hydroxyhexyl acrylate; triethyleneglycol acrylate; 7-hydroxyheptyl acrylate; 2 hydroxymethyl methacrylate; 3-ch loro-2-hydroxypropyl methacrylate; 2-hydroxy- 1 -methylethyl methacrylate; 2-hydroxypropyl methacrylate; 3-hydroxypropyl methacrylate; 2,3 dihydroxypropyl methacrylate, 2-hydroxybutyl methacrylate; 4-hydroxybutyl methacrylate; 3,4 dihydroxybutyl methacrylate; 5-hydroxypentyl methacrylate; 6-hydroxyhexyl methacrylate; 1,3-dimethyl-3 hydroxybutyl methacrylate; 5,6 dihydroxyhexyl methacrylate; and 7-hydroxyheptyl methacrylate.

Although one of ordinary skill in the art will recognize that many different hydroxy bearing monomers, including those listed above could be employed, the preferred hydroxy functional monomers for use in the hydroxy functional resin of the invention are C5-C7 hydroxy alkyl acrylates and/or C6-C8 hydroxy alkyl methacrylates, i.e., esters of C2-C3 dihydric alcohols and acrylic or methacrylic acids.

The remainder of the monomers forming the hydroxy functional copolymer, i.e., between about 90 and about 70 weight percent, are other monoethylenically unsaturated monomers. These monoethylenically unsaturated monomers, as was the case with respect to the epoxy functional copolymer discussed above, are preferably alpha-beta olefinically unsaturated monomers. As was also tjle case with respect to the epoxy functional copolymer, the preferred alpha-beta olefinically unsaturated monomers are acrylates and preferably are employed in excess of 50 weight percent of the total copolymer. Preferred acrylate monomers are esters of C1-C12 monohydric alcohols and acrylic or methacrylic acids.Monovinyl hydrocarbons and other modifying monomers may also be employed in the same proportion as they are employed in the epoxy functional copolymer discussed above.

Other Materials In addition to the above discussed components, other materials may be included in the high solids coating compositions of the invention. These include materials such as catalysts, antioxidants, U.V. absorbers, solvents, surface modifiers and wetting agents as well as pigments. The solvents used in the coating compositions of the invention are those which are commonly used. Typical solvents useful in the coating compositions facilitate spray application at high solids content and include toluene, xylene, methyethyi ketone, acetone, 2-ethoxy-1 -ethanol, 2-butoxy-1 -ethanol, diacetone alcohol, tetrahydrofuran, ethylacetate, dimethyl-succinate, dimethylglutarate, dimethyladipate or mixtures thereof.The solvent in which the epoxy functional copolymer of the coating composition is prepared, may be employed as the solvent for the coating composition thus eliminating the need for drying the epoxy functional copolymer after preparation if such is desired. As mentioned above, the non-volatiie solids content of the high solids coating composition is at least 60 percent and preferably 70 percent or more, thus limiting the amount of solvent included in the composition.

Surface modifiers or wetting agents are common additives for liquid paint compositions. The exact mode of operation of these surface modifiers is not known, but it is thought that their presence contributes to better adhesion of the coating composition to the surface being coated and helps formation of thin coatings, particularly on metal surfaces. These surface modifiers are exemplified by acrylic polymers containing 0.1-10 percent by weight of a copolymerized monoethylenically unsaturated carboxylic acids such as methacrylic acid, acrylic acid or itaconic acid, cellulose acetate butyrate, silicon oils or mixtures thereof. Of course, the choice of surface modifiers or wetting agent is dependent upon the type of surface to be coated and selection of the same is clearly within the skill of the artisan.

The high solids coating composition of the invention also may include pigments. As noted above, the high solids compositions of this invention are particularly useful when the coating composition includes metallic flake as a pigment. The rapid set and curing of the composition eliminates problems associated with redistribution of the metallic flake. The amount of pigment in the high solids coating composition may vary, but preferably is between about 3 and about 45 weight percent based on the total weight of the paint composition. If the pigment is metallic flake, the amount ranges from about 1 to about 7 weight percent.

Application Techniques The high solids coating composition can be applied by conventional methods known to those in the art. These methods include roller coating, spray coating, dipping or brushing and, of course, the particular application technique chosen will depend on the particular substrate to be coated and the environment in which the coating operation is to take place.

A particularly preferred technique for applying the high solids coating compositions, particularly when applying the same to automobiles as topcoats, is spray coating through the nozzle of a spray gun.

High solids paints have in the past caused some difficulty in spray coating techniques because of the high viscosity of the materials and resultant problems in clogging of spray guns. However, because the compositions of this invention demonstrate relatively low viscosity considering the high solids content they can be applied by spray coating techniques.

The invention will be further understood by referring to the following detailed examples. It should be understood that the specific examples are presented by way of illustration and not by way of limitation. Unless otherwise specified, all references to "parts" is intended to mean parts by weight.

Example 1 The following mixture of monomers was used for a polymer synthesis: Wt. (gram) Wit. % Butylmethacrylate 127.5 17 Ethylhexyl acrylate 1 80 24 Glycidyl methacrylate 195 26 Methyl methacrylate 210 28 Styrene 37.5 5 37 grams t-butyl perbenzoate is added to the above monomer mixture the resulting solution added over a period of one hour and 10 minutes to 500 grams of refluxing methyl amyl ketone refluxing methyl amyl ketone under nitrogen. Heating and stirring is continued for half an hour after the addition is complete and then two grams of t-butylperbenzoate are added portionwise. The reaction mixture is refluxed for two more hours and then allowed to cool to room temperature. The calculated Tg of the polymer obtained is 90C and the solution viscosity is 41 Sec. &num;4 Ford cup.

Eighty-three and one third (83-1/3) parts of the above polymer solution and 30 parts of Cymel 301 are dissolved in 25 parts of butyl acetate and 11 parts of butyl acid phosphate (mixture of monobutyl and dibutyl phosphates, equivalent wit. 120) are added to the solution. The resulting formulation is applied to steel test panels by spraying. The panels are baked at 1 300C for 20 minutes to obtain a glossy (82/200) coating with excellent hardness, adhesion and solvent (xylene and methylamyl ketone) resistance. The coating does not show any loss of gloss or adhesion after 14 days exposure in a Cleveland Humidity Chamber.

Example 2 Four parts of aluminum flakes (65% in naphtha) are mixed well with 80 parts of the polymer solution prepared in accordance with Example 1. Thirty (30) parts of Cymel 301 and 25 parts of butyl acetate are added to the above mixture and the resulting material is filtered through a course filtering cloth. Eleven (11) parts of butyl acid phosphate (Eq. wt. 120) are added to the filtrate and the resulting formulation is immediately applied to primed steel test panels by spraying in a three coat application.

The intermediate flash time is one minute and the final flash is five minutes. The panels are baked at 11 00C for 20 minutes to obtain coatings with excellent adhesion and solvent (xylene and methyl ethyl ketone) resistance. These is no apparent aluminum reorientation and the gloss is 62/200C.

Example 3 An epoxy functional copolymer is prepared from the following monomers: Wt. (grams) Wt. % Butyl methacrylate 1 20 1 6 Ethyl hexyl acrylate 142.5 19 Glycidyl methacrylate 195 26 Methyl methacrylate 255 34 Styrene 37.5 5 The polymerization is carried out as outlined in Example 1 by employing 500 grams of methyl amyl ketone and 30 grams of t-butyl perbenzoate. The addition of initiator and the monomer mixture is completed in two hours and the reaction mixture is refluxed for one additional hour. Two grams of the initiator are then added and the reaction mixture refluxed for two hours. The molecular weight is determined by Gel Permeation Chromatography and found to beM=31 68 and Mw/M,=2.15. The Tg of this polymer is calculated to be 200C.Twenty-seven (27) parts of the above polymer solution and ten parts of Cymel 301 are dissolved in eight parts of butyl acetate and 2.8 parts of butyl acid phosphate (mixture of monobutyl and dibutyl phosphates) are added to this solution. The composition is drawn on a steel test panel and baked at 1 300C for 20 minutes. The coating has excellent hardness, adhesion and solvent (xylene and methyl ethyl ketone) resistance.

Example 4 Twenty-seven (27) parts of the polymer described in Example 3, 1 3 parts of Cymel 301 and 5 parts of Acryloid (Registered Trade Mark) OL-42 (Rohm and Haas Chem. Co.) are dissolved in 10 parts of butyl acetate. Three and seven tenths (3.7) parts of butyl acid phosphate (mixture of monobutyl and dibutyl phosphate) is added to the above solution and the resulting formulation drawn on a steel test panel. It is baked at 1 300C for ten minutes to obtain glossy coating with excellent hardness, adhesion and solvent resistance.

Example 5 Ethyl phosphorodichloridate (125 g) is dissolved in 150 ml butyl acetate, placed in a round bottom flask and cooled with an ice water mixture. Cold water (28 g) is added dropwise with stirring and simultaneous vacuum application with a water aspirator. The reaction mixture is stirred under vacuum for three days and then titrated with sodium hydroxide to obtain a monoethyl phosphate solution with acid equivalent weight of 112.

Eighty (80) parts of the polymer solution prepared in Example 1, 10 parts of bis (hydroxypropyl)azelate (product of propylene oxide and azelaic acid) and 35 parts of ethoxymethoxymethyl benzoguanamine (Cymel 1123, American Cyanamid) are dissolved in 25 parts of butyl acetate and 10.1 parts of the above ethyl acid phosphate solution are added to this solution.

The resulting formulation is applied to primed steel panels by spraying and is baked at 1 300C for 20 minutes to obtain hard, glossy coatings with excellent adhesion and solvent resistance.

Example 6 A butyl acetate solution of mono-cyclohexylmethyl phosphate with an equivalent weight of 145 is prepared from cyclohexylmethyl phosphorodichloridate by following the procedure outlined in Example 5.

Twenty-five (25) parts of the polymer solution prepared in Example 3, 13 parts of hexamethoxymethyl melamine (Cymel 301, American Cyanamid), and 5 parts of caprolactone based hydroxyester PCP0300 (Union Carbide) are dissolved in ten (10) parts of butyl acetate. Four and two tenths (4.2) parts of the acid phosphate prepared above is added to the above solution and the resulting formulation is applied to primed steel test panels by spraying. The panels are baked at 1 300C for 20 minutes to obtain coatings with excellent hardness, adhesion, gloss and solvent resistance (xylene and methyl ethyl ketone).

Example 7 The following mixture of monomers is used in a polymer synthesis: Wt.% Butyl methacrylate 25 Glycidyl acrylate 30 Methyl methacrylate 40 Styrene 5 The polymerization is carried out as outlined in Example 1 to obtain a 50% solution of the polymer.

Seventy (70) parts of the polymer solution, 1 5 parts of bis-(hydroxypropyl) azelate (reaction product of propylene oxide and azelaic acid) and 25 parts of hexamethoxymethyl melamine (Cymel 301) are dissolved in 10 parts of butyl acetate. Amyl acid phosphate (mixture of monoalkyl and dialkyl phosphates (13.3 parts)) is added to the above solution and the resulting formulation is applied to primed steel panels by spraying. The panels are baked at 1 300C for 20 minutes to obtain glossy (87/200) coatings with excellent adhesion, hardness and solvent (xylene and methyl ethyl ketone) resistance.

Example 8 A hydroxy acrylic copolymer is prepared from the following monomers: Wt. (grams) Wt. % Butyl methacrylate 1000 50 Hydroxyethyl acrylate 400 20 Methyl methacrylate 400 20 Styrene 200 10 One hundred grams t-butyl perbenzoate is added to the above monomer mixture and the resulting solution is added dropwise over a period of two hours to 1400 grams of refluxing methyl amyl ketone under nitrogen. The heating and stirring is continued for half an hour after the addition is complete and five (5) grams of t-butyl perbenzoate are added portionwise to the reaction mixture. The reaction mixture is refluxed for an additional ninety (90) minutes and then allowed to cool to room temperature.

The molecular weight is determined by Gel Permeation Chromatography: Mn=2540, Mwii n=1 .94.

Forty (40) parts of the above polymer, 45 parts by weight of the glycidyl methacrylate polymer from Example 1 and 31 parts of hexamethoxymethyl melamine (Cymel 301) are dissolved in 20 parts of butyl acetate. 5.3 parts of butyl acid phosphate (mixture of monobutyl and dibutyl phosphates, eq.

wt. 120) is added to the above solution and the resulting formulation is applied to primed steel test panels by spraying. The panels are baked at 1 300C for 20 minutes to obtain glossy coatings with excellent hardness, adhesion and solvent (xylene and methyl ethyl ketone) resistance.

Example 9 Twenty-five (25) parts of polymer from example 3, 25 parts of hydroxy polymer from Example 8 and 25 parts of hexabutoxy-methyl melamine (Cymel 11 56) are dissolved in 1 5 parts of butyl acetate.

Butyl acid phosphate (mixtures of monobutyl and dibutyl phosphates, eq. wt. 120) (3.4 parts) is added to the above solution and the resulting formulation is applied to primed steel panels by spraying. The panels are baked at 1 300C for 20 minutes to obtain glossy coatings with excellent hardness, adhesion and solvent resistance.

Example 10 Thirty (30) parts of glycidyl methacrylate polymer from Example 3, 5 parts of bis-(hydroxypropyl) azelate and 1 5 parts of ethoxymethoxy methyl benzoguanamine (Cymel 1123, American Cyanamid) are dissolved in 10 parts of butyl acetate. 4.4 parts of butyl acid phosphate (mixture of monobutyl and dibutyl phosphates, eq. wt. 120) is added to the above solution and the resulting formulation is applied to primed steel panels by spraying. The panels are baked at 1 300C for 20 minutes to obtain hard, glossy coatings with excellent adhesion and solvent (xylene and methyl ethylketone) resistance.

Example 11 Twenty-five (25) parts of glycidyl methacrylate polymer from Example 1, 20 parts of hydroxy polymer from Example 8, 5 parts of bis-(hydroxypropyl) azelate and 1 7 parts of butoxymethyl glycoluril (Cymel 11 70, American Cyanamid) is dissolved in 1 5 parts of butyl acetate. 3.3 parts of butyl acid phosphate (mixture of monobutyl and dibutyl phosphates, eq. wt 120) is added to the above solution and the resulting formulation is applied to primed steel panels by spraying. The panels are baked at 1 300C for 20 minutes to obtain hard, glossy coatings with excellent adhesion and solvent (xylene and methyl ethyl ketone) resistance.

Example 12 Thirty (30) parts of glycidyl methacrylate polymer from Example 3, 7 parts of Acryloid OL42 (Rohm and Haas Chem. Co.), 25 parts of butoxymethyl urea resin (Beetle (Registered Trade Mark) 80, American Cyanamid) are dissolved in 20 parts of butyl acetate. 4.4 parts of butyl acid phosphate (mixture of monobutyl and dibutyl phosphate, eq. wt. 120) is added to the above solution and the resulting formulation is applied to primed steel panels by spraying. The panels are baked at 1 300C for 20 minutes to obtain a hard glossy coating.

Example 13 The following mixture of monomers is employed in the synthesis of a polymer: Wt. % Allyl glycidyl ether 30 Butyl methacrylate 25 Methyl methacrylate 30 Styrene 1 5 The polymerization is carried out as outlined in Example 3 to obtain a 52% solution of the polymer in methyl amyl ketone.

Thirty-one (31 ) parts of the above polymer, 30 parts of hydroxy polymer from Example 8, and 17 parts of hexamethoxymethyl melamine (Cymel 301, American Cyanamid) are dissolved in 10 parts butyl acetate. 5.1 parts of butyl acid phosphate (mixture of monobutyl and dibutyl phosphates) is added to the above solution and the resulting formulation is applied to primed steel panels by spraying.

The panels are baked at 1 300C for 20 minutes to obtain hard, glossy coatings with excellent adhesion and solvent (xylene and methyl ethyl ketone) resistance.

Example 14 Monophenyl phosphate is prepared from phenyl phosphorodichloridate by following the procedure described in Example 5. The acid equivalent weight of this solution is found to be 144.

Forty (40) parts of the glycidyl methacrylate copolymer from Example 1, 30 parts of the hydroxy polymer from Example 8 and 25 parts of hexamethoxymethyl melamine (Cymel 301) are dissolved in 20 parts of butyl acetate. The phenyl phosphate solution (7.2 parts) is added to the above solution and the resulting formulation is spray applied to primed steel panels by spraying. The panels were baked at 1 300C for 20 minutes to obtain hard, glossy coatings with excellent adhesion and solvent resistance.

Example 15 The following monomers are employed in synthesis of a polymer: wt.% Butyl methacrylate 40 Glycidyl methacrylate 15 Methyl methacrylate 40 Styrene 5 The polymerization is carried out in methyl amyl ketone by employing 1.8% (by wt. of the monomers) of the initiator. The molecular weight from Gel Permeation Chromatography is found to be My=5750 Mw/M,=2.4. The solids content was found to be 54% by weight.

Sixty (60) parts of this polymer solution, 70 parts of polymer from Example 8 and 50 parts hexamethoxymethyl melamine (Cymel 301) were dissolved in 30 parts of butyl acetate. 4.1 parts of butyl acid phosphate (mixture of monobutyl and dibutyl phosphates, eq. wt. 120), is added to the above solution and the resulting formulation is spray applied to primed steel panels. The panels are baked at 1 300C for 20 minutes to obtain coatings with excellent hardness, adhesion and solvent (xylene and methyl ethyl ketone) resistance.

Example 16 Ten parts of 2-ethyl-1, 3-hexane diol and 4 parts of hexamethoxymethyl melamine (Cymel 301) are added to the formulation described in Example 1. The resulting formulation is applied to primed steel panels by spraying in three coats with intermediate flash of one minute and a final flash of five minutes. The panels are baked at 1 200C for 20 minutes to obtain a clear coating with excellent hardness, adhesion, gloss (90/200) and solvent (xylene and methyl ethyl ketone) resistance.

Example 17 The paint formulation described in Example 2 is repeated by employing 6 parts of aluminum flakes and 10.4 parts of butyl acid phosphate. The application and bake conditions are the same as in Example 2. The coating exhibits excellent physical properties.

Example 18 Five (5) parts of polypropylene glycol {PIuracol (Registered Trade Mark) (710, BASF Wyandotte Co.)) and 2 parts of hexamethoxy methyl melamine (Cymel 301) are added to the formulation described in Example 3. The resulting formulation is applied to primed steel test panels by spraying in a three coat application. The panels are baked at 1 300C for 1 5 minutes to obtain coatings with excellent gloss (91/200), adhesion, hardness and solvent resistance.

Example 19 Three hundred fifty (350) grams of titanium dioxide is mixed with 350 parts of Acryloid OL-42 (Rohm and Haas Chemical Co.) and 25 parts of butyl acetate. The above mixture is taken up in a porcelain bottle containing porcelain beads and is put on a roller mill for 1 6 hours. Forty (40) parts of the above mill base is mixed with 28 parts of polymer from Example 1, 5 parts of hydroxy ester Desmophen KL5-2330 (Rohm and Haas Chem. Co.), 11 parts of hexamethoxymethyl melamine (Cymel 301) and 20 parts of butyl acetate. 3.8 parts of butyl acid phosphate (mixture of monobutyl and dibutyl phosphates, eq. wt. 120), is added to the above mixture and the resulting formulation is spray applied to primed steel panels.The panels are baked at 1 200C for 20 minutes to obtain coatings with excellent physical properties.

Example 20 Five hundred (500) parts of titanium dioxide and 250 parts of Ferrite yellow are mixed with 500 parts of Acryloid OL-42 (Rohm and Haas Chem. Co.), 7.8 parts of dispersing agent BYKP 104S ('BYK' is a Registered Trade Mark) (Mellinckrodt) and 200 parts of butyl acetate; the millbase is prepared as described in Example 19. Thirty-five (35) parts of this millbase are mixed with 50 parts of polymer from Example 3, 23 parts of hexamethoxymethyl melamine, 3 parts of 1 ,4-cyclohexamedimethanol and 22 parts of butyl acetate. 6.8 parts of butyl acid phosphate (eq. wt. 120), is added to the above mixture and the resulting formulation spray applied to primed steel panels. The panels are baked 11 50C for 20 minutes to obtain coatings with excellent physical properties.

Example 21 Fifty (50) parts of blue pigment phthalo Blue are mixed with 500 parts of Acryloid OL-42 (Rohm and Haas Chem. Co.) and 44 parts of butyl acetate, the mill base is ground as described in Example 19.

Twenty-five parts of the above mill base are mixed with 41 parts of the polymer solution from Example 3, 6 parts of aluminum flakes (65% in naphtha), 15 parts of bis-(hydroxy-propyl) azelate, 29 parts of hexamethoxymethyl melamine (Cymel 301) and 20 parts butyl acetate. 5.6 parts of butyl acid phosphate (eq. wt. 120) is added to the above mixture and the resulting formulation is spray applied to primed steel panels in four coats with one minute flash time between coats. After five minutes final flash the panels are baked at 1 300 C. for 20 minutes to a blue metallic coating with excellent hardness, adhesion and solvent resistance.

Example 22 In a three-necked, two liter round bottom flask, equipped with a stirrer, a condenser and a dropping funnel, 750 ml. of toluene is brought to reflux under nitrogen. The following mixture of monomers, containing 1 5 grams of 2,2-azobis-(2-methylpropionate) dissolved in 50 ml. acetone, is added dropwise to the refluxing toluene: Wt./grams wt. % Butyl methacrylate 1 50 50 Glycidyl methacrylate 45 1 5 Hydroxypropyl methacrylate 30 10 Methyl methacrylate 60 20 Styrene 15 5 The addition of initiator and monomer solution is completed in three hours.The reaction mixture is refluxed for half an hour more and then a 1 O ml. acetone solution of two grams of the above initiator is added dropwise and the reaction mixture is refluxed for half an hour. Part of the solvent is distilled out to bring the solids content to 66%.

Thirteen (13) parts of the above polymer solution are mixed with three parts of Cymel 301 and the mixture is dissolved in three parts of butyl acetate. One part of butyl acid phosphate (mixture of monobutyl and dibutyl phosphates) is added to the above solution and the mixture is drawn on a steel test panel. The panel is baked at 100 C. for 20 minutes to obtain a glossy (85/200) coating with excellent hardness adhesion and solvent (xylene and methyl ethyl ketone) resistance.

Example 23 Ten (10) parts of the copolymer described in Example 22, seven (7) parts of Cymel 301 and seven (7) parts of polyester Desmophen (Registered Trade Mark) KL5-2330 (Mobay Chem. Co.) are dissolved in eight (8) parts of butyl acetate. One (1) parts of butyl acid phosphate (mixture of monobutyl and dibutyl phosphates) is added to the above solution and the resulting formulation is drawn on a steel test panel. The panel is baked at 100 C. for 20 minutes to obtain a glossy (92/200) coating with excellent hardness, adhesion and solvent (xylene and methyl ethyl ketone) resistance.

Example 24 A copolymer is prepared by following the procedure described in Example 1 in methyl amyl ketone at 1 250C. using the following monomers: Wt.% Butyl methacrylate 50 Ethylhexyl acrylate 10 Glycidyl methacrylate 1 5 Hydroxypropyl methacrylate 10 Methyl methacrylate 10 Styrene 5 t-butyl peroctoate (5.25% of monomers) is used as an initiator and determined solids content of the composition is 66.6% by weight. The calculated Tg of the copolymer is 250C. and the molecular weight from Gel Permeation Chromatography is found to be Mn=4220 and MM,=1.90.

A 'mill base is prepared by dispersing titanium dioxide in the polymer with a high speed Cowl's blade. The composition of the mill base is: 1 5% polymer (100% nonvolatiles), 65% titanium dioxide and 20% methyl amyl ketone. Seventy-two (72) parts of this millbase, 31 parts of the polymer, 12.5 parts of bis-(hydroxypropyl) azelate, 30 parts of Cymel 301 and 29 parts of methyl amyl ketone are taken up in a plastic bottle. Butyl acid phosphate (mixtures of monobutyl and dibutyl phosphates, eq.

wt. 120), 3.6 parts is added to the above mixture and the resulting formulation is applied to both primed and unprimed steel panels by spraying. The panels are baked at 1 300 C. for 20 minutes to obtain hard, glossy coatings with excellent adhesion. The coating has an excellent solvent and humidity resistance.

Example 25 (a) By following the procedure described in Example 24, a copolymer is prepared from the following monomers: Wt.% Butyl methacrylate 60 Glycidyl methacrylate 20 Hydroxyethyl acrylate 10 Styrene 10 The calculated Tg of the polymer is 250C. and solids content is found to be 54.9% by weR ht. The molecular weight by Gel Permeation Chromotography is found to be My=1809 and MW/Mn=2.44.

(b) As described in Example 24, a millbase is prepared from the following materials: Copolymer (a) 21% (100% nonvolatile) Titanium dioxide 61% Methyl amyl ketone 18% Sixty-five (65) parts of this millbase, 26.4 parts of the polymer solution, 12.5 parts of bis (hydroxypropyl) azelate, 31 parts of hexabutoxymethyl melamine (Cymel 1156) and 25 parts of methyl amyl ketone are taken up in a plastic bottle. 7.3 parts of amyl acid phosphate (mixtures of monoamyl and diamyl phosphates eq. wt. 162) is added to the above mixture and the resulting formulation is applied to both primed and unprimed panels by spraying. The panels are baked at 1 300 C. for 20 minutes to obtain hard, glossy coatings with excellent adhesion and solvent resistance.The coating, when put in the Cleveland Humidity Chamber for 14 days, does not show any deterioration in general physical properties.

Example 26 By following the procedure described in Example 22 a copolymer is prepared from the following monomers: wt. % Butyl methacrylate 49 Glycidyl methacrylate 20 Hydroxypropyl methacrylate 10 Methyl methacrylate 1 6 Styrene 5 The calculated Tg of the copolymer is 430C. and solids content is found to be 52%. The molecular weight, by Gel Permeation Chromatography, is found to be Mn,=2906 and Mw/Mn=2.3 1.

As described in Example 3, a millbase is prepared with the following composition: Wt.% Titanium dioxide 65 The above copolymer 13 (100% nonvolatile) Methyl amyl ketone 22 Sixty-nine (69) parts of this millbase, 37 parts of the polymer, 1 7.5 parts bis-(hydroxypropyl) azelate, 31 parts ethoxymethoxymethyl benzoguanamine (Cymel 1123, American Cyanamid) and 22 parts of butyl acetate are taken up in a plastic bottle. 4.8 parts of butyl acid phosphate (mixture of monobutyl and dibutyl phosphates, eq. wt. 120) is added to the above mixture and the resulting formulation is applied to primed test panels by spraying. The panels are baked at 11 50C. for 20 minutes to obtain glossy, hard coatings with excellent solvent (xylene and methyl ethyl ketone) resistance.This coating does not show any loss of gloss, adhesion or solvent resistance upon exposure in Cleveiand Humidity Chamber for 14 days.

Example 27 By following the procedure described in Example 21 a copolymer is prepared in refluxing methyl amyl ketone from the following monomers: Wt.% Glycidyl methacrylate 20 Hydroxyethyl acrylate 10 Butyl methacrylate 60 Styrene 10 Two percent (2%) t-butyl peroctoate is used as an initiator. The solids content is found to be 53.6%.

From Gel Permeation Chromatography the molecular weight of the polymer is found to be: Mn=2746 and M;iVin=2.33.

As described in Example 24, a millbase is prepared with the following ingredients: Wt.% Titanium dioxide 56 The above Polymer 26 (100% nonvolatile) Methyl amyl ketone 18 Seventy-one (71) parts of this millbase, 14.6 parts of the polymer, 1 2.5 parts bis-(hydroxypropyl) azelate, 31 parts butoxymethyl glycoluril (Cymel 1170, American Cyanamid) 25 parts of methyl amyl ketone are taken up in a plastic bottle. Butyl acid phosphate (mixture of monobutyl and dibutyl phosphates, eq. wt. 1 20), 4.8 parts, is added to the above mixture and this formulation is applied to primed test panels by spraying. The panels are baked at 1 300C for 20 minutes to obtain glossy, hard coatings with excellent solvent (xylene and methyl ethyl ketone) resistance. The coatings do not show any loss of gloss, adhesion or solvent resistance upon exposure in a Cleveland Humidity Chamber for 14 days.

Example 28 By following the procedure described in Example 22, a copolymer is prepared in refluxing toluene from the following monomers: Wt.% Butyl methacrylate 50 Ethylhexyl acrylate 20 Glycidyl methacrylate 15 Hydroxypropyl methacrylate 10 Styrene 5 One thousand grams of the total monomers, 700 ml of toluene and 50 grams t-butyl peroctoate are used. The calculated Tg of this polymer is 60C and solids content is found to be 59% by weight; Gel Permeation Chromatography shows its molecular weight to be Mn=4337 and MwMn=2.14. and Viscosity of this polymer solution is 1.33 Stokes.

Fifty parts of the above polymer solution, 5 parts of bis-(hydroxypropyl) adipate and 29 parts of butoxymethyl urea resin (Bettle 80, American Cyanamid) are dissolved in 1 5 parts of n-butyl acetate.

3.7 parts of butyl acid phosphate (mixture of monobutyl and dibutyl phosphates, eq. wit. 120), is added to the above solution and the resulting formulation is applied by spraying to primed steel panels. The panels are baked at 1 300C for 20 minutes to obtain coatings with excellent hardness, adhesion, gloss and solvent (xylene and methyl ethyl ketone) resistance.

Example 29 Ethyl phosphorodichloridate, 1 25 g, is dissolved in 1 50 ml butyl acetate, placed in a round bottom flask and cooled with an ice water mixture. Cold water, 28 g, is added dropwise with stirring and simultaneous vacuum application with a water aspirator. The reaction mixture is stirred under vacuum for three days and then titrated with sodium hydroxide to obtain a monoethyl phosphate solution with acid equivalent weight of 112.

Twenty (20) parts of the polymer solution from Example 1, eight (8) parts of hexamethoxymethyl melamine (Cymel 301) and 2 parts of bis-(2-hydroxyethyl) adipate are dissolved in 9 parts of butyl acetate. The ethyl phosphate solution described above, 1.9 parts, is added to the above solution and the resulting formulation is drawn on steel test panels. The panels are baked at 11 00C for 1 5 minutes to obtain a hard, glossy coating with excellent adhesion and solvent (xylene and methyl ethyl ketone) resistance.

Example 30 A butyl acetate solution of mono-cyclohexylmethyl phosphate with acid equivalent weight of 145 is prepared from cyclohexylmethyl phosphorodichloridate by following the procedure outlined in Example 29. The paint is formulated as described in Example 4 by employing 6.5 parts of the above acid phosphate solution,instead of amyl acid phosphate. The paint is applied by spraying to primed steel panels and is baked at 1 200C for 20 minutes to obtain coatings with excellent gloss, hardness, adhesion and solvent (xylene and methyl ethyl ketone) resistance.

Example 31 A hydroxy acrylic copolymer is prepared from the following monomers: Wt. grams Wt. % Butyl methacrylate 1000 50 Hydroxyethyl acrylate 400 20 Methyl methacrylate 400 20 Styrene 200 10 One hundred (100) grams t-butyl perbenzoate is added to the above monomer mixture and the resulting solution is added dropwise over a period of two hours to 1400 grams of refluxing methyl amyl ketone under nitrogen. The heating and stirring is continued for half an hour after the addition is complete and then five grams of t-butyl perbenzoate are added portionwise to the reaction mixture.

The reaction mixture is refluxed for an additional ninety minutes and then allowed to cool to room temperature. The molecular weight is determined by Gel Permeation Chromatography to be M n=2540 and Mwlii,=1.94. n=1.94. Mono-phenyl phosphate is prepared from phenyl phosphorodichloridate by following the procedure described in Example 8. The acid equivalent weight of this solution is found to be 144.

Forty (40) parts of the above hydroxy polymer solution. 40 parts of the polymer solution from Example 21, and 27 parts of hexamethoxymethyl melamine (Cymel 301) are dissolved in 24 parts of butyl acetate. 4.8 parts of the phenyl acid phosphate solution described above is added to the above solution and the resulting formulation applied by spraying to primed steel panels. The panels are baked at 1 300C for 20 minutes to obtain hard, glossy coatings with excellent adhesion and solvent (xylene and methyl ethyl ketone) resistance.

Example 32 By following the procedure described in Example 24, a copolymer is prepared from the following monomers: wt.% Butyl methacrylate 40 Glycidyl acrylate 20 Hydroxypropyl methacrylate 10 Methyl methacrylate 20 Styrene 10 The solids content in methyl amyl ketone is determined to be 55% by weight.

Twenty-five (25) parts of the above polymer and 7 parts of hexamethoxymethyl melamine (Cymel 301) is dissolved in 4 parts of butyl acetate. 2.6 parts of butyl acid phosphate (mixture of monobutyl and dibutyl phosphates, eq. wt. 120) is added to the above solution and resulting formulation is drawn on primed steel panels. The panels are baked at 1 300C for 20 minutes to obtain coating with excellent physical properties.

Example 33 By following the procedure described in Example 22, a copolymer is prepared from the following monomers: Wt.% Allyl glycidyl ether 10 Butyl methacrylate 30 Hydroxypropyl methacrylate 1 5 Methyl methacrylate 25 Styrene 20 Toluene is distilled out to bring the solids level to 59% by weight.

Eighty-five (85) parts of the above polymer, ten (10) parts of a caprolactone based hydroxy ester (PCP0300 from Union Carbide) and 23 parts of hexamethoxymethyl melamine are dissolved in 20 parts of butyl acetate. Butyl acid phosphate (mixture of monobutyl and dibutyl phosphates, eq. wt.

120), 5.3 parts, is added to the above solution and the resulting formulation is applied by spraying on primed steel panels. The panels are baked at 1 300C for 20 minutes to obtain hard, glossy coatings with excellent adhesion and solvent (xylene and methyl ethyl ketone) resistance.

Example 34 Ninety (90) parts of the polymer solution from Example 22 are mixed with 12 parts of aluminum flakes (65% in naphtha) and well dispersed with a camel hair brush. Twenty (20) parts of butyl acetate is added to the above mixture and filtered through a coarse cloth. Thirty (30) parts of hexamethoxy methyl melamine (Cymel 301) and five parts of bis-(hydroxypropyl) azelate are added to the above mixture and it is stirred well. 7.5 parts of butyl acid phosphate (mixture of monobutyl and dibutyl) are added to the above mixture and the resulting formulation spray applied to primed steel panels in three coats. The intermediate flash time is one minute and the final flash is five minutes.The panels are baked at 1 200C for 20 minutes to obtain a silver metallic coating with excellent hardness, adhesion, aluminum control and solvent (xylene and methyl ethyl ketone) resistance.

Example 35 Four (4) parts of 1 ,4-cyclohexanedimethanol and two parts of hexamethoxymethyl melamine (Cymel 301) are added to the formulation described in Example 22. The resulting formulation is drawn on primed steel panels; the panels are baked at 1 200C for 20 minutes to obtain hard, glossy coatings with excellent adhesion and solvent (xylene and methyl ethyl ketone) resistance.

Example 36 Eight (8) parts 2-ethyl-I -1 ,3-hexanediol and three (3) parts of hexamethoxymethyl melamine (Cymel 301) are added to the formulation described in Example 3 and the resulting formulation is spray applied to primed steel test panels. The panels are baked at 1 200C for 20 minutes to obtain coatings with excellent physical properties.

Example 37 Three (3) parts of polypropylene glycol (Pluracol P710, BASF Wyndotted Co.) and one (1) parts of hexamethoxymethyl melamine (Cymel 301 > are added to the formulation described in Example 22. The resulting paint composition is drawn on primed steel panels and the panels are baked at 1 250C for 20 minutes to obtain coatings with excellent physical properties.

Example 38 Three hundred fifty (350) grams of titanium dioxide are mixed with three hundred fifty (350) parts of Acryloid OL-42 (Rohm and Haas Chem. Co.) and twenty4ive (25) parts of butyl acetate. The above mixture is taken up in a porcelain bottle containing porcelain beads and put on a roller mill for 1 6 hours.

Thirty-two (32) parts of this millbase are mixed with ten (10) parts of bis-(hydroxypropyl) azelate, thirty (30) parts of polymer solution from Example 22 twenty-five (25) parts of hexamethoxymethyl melamine (Cymel 301) and twenty (20) parts of butyl acetate. 2.7 parts of butyl acid phosphate (eq.

wt. 120) are added to the above mixture and the resulting formulation is applied by spraying to primed steel panels. The panels baked at 1 250C for 20 minutes to obtain coatings with excellent physical properties.

Example 39 Fifty (50) parts of blue pigment Phthalo Blue were mixed with five hundred (500) parts of Acryloid OL-42 (Rohm and Haas Chem. Co.) and forty-four (44) parts of butyl acetate, and the millbase is ground as described in Example 1 7. Twenty-five (25) parts of the above millbase are mixed with forty-two (42) parts of the polymer solution from Example 1, five (5) parts of bis-(hydroxypropyl) azelate, twenty-one (21) parts of Cymel 301, four (4) parts of aluminum flakes (65%) in naphtha) and ten (10) parts of butyl acetate. 3.9 parts of butyl acid phosphate (eq. wt. 120) are added to the above mixture and the resulting formulation is spray applied to primed steel panels in four coats with one minute flash time between coats. After five minutes final flash the panels are baked at 1 300C for 20 minutes to a blue metallic coating with excellent hardness, adhesion and solvent resistance.

In view of this disclosure, many modifications of this invention will be apparent to those skilled in the art. It is intended that all such modifications which fall within the true scope of this invention be included within the terms of the appended claims.

Claims

1. A thermosetting coating composition adapted for low temperature bake applications which contains greater than about 60 percent by weight of nonvolatile solids, and which exclusive of pigments, solvents and other nonreactive components, consists essentially of: (A) an epoxy functional film-forming copolymer selected from (1) monofunctional copolymers bearing pendent epoxy functionality, said copolymers consisting of between about 10 and about 30 weight percent of monoethylenically unsaturated monomers bearing glycidyl functionality and between about 90 and about 70 weight percent of other monoethylenically unsaturated monomers; and (2) bifunctional copolymers bearing hydroxy functionality and pendent epoxy functionality, said copolymer consisting essentially of (i) between about 5 and about 25 weight percent of monoethylenically unsaturated monomers bearing glycidyl functionality and between about 5 and about 25 weight percent of monoethylenically unsaturated monomers bearing hydroxy functionality with the total of said monoethylenically unsaturated monomers bearing either said glycidyl functionality or said hydroxy functionality being not greater than about 30 weight percent of said copolymer, and (ii) between about 90 and about 70 weight percent of other monoethylenically unsaturated monomers; (B) at least one organophosphate ester having the formula:

wherein n=1 to 2 and R is selected from alkyl, cycloalkyl or aryl radicals; (C) an amino resin crosslinking agent; and (D) up to about 45 weight percent based on the total weight of (A), (B), (C) and (D) of a hydroxy functional additive having a number average molecular weight (Mn) of between about 1 50 and about 6000; said organophosphate ester being included in said composition in an amount sufficient to provide between about .67 and about 1.4 equivalents of acid functionality for each equivalent of pendent epoxy functionality on said film-forming copolymer, and said amino resin crosslinking agent being included in said composition in an amount sufficient to provide at least about 0.67 equivalents of nitrogen crosslinking functionality for each equivalent of hydroxy functionality included in said composition (i) as a hydroxyl group on said hydroxy functional additive, (ii) as a hydroxyl group on said film-forming copolymer, or (iii) as a result of esterification of the pendent epoxy functionality of said film-forming copolymer during cure of said coating composition.

2. A composition in accordance with Claim 1 wherein said monoethylenically unsaturated monomers bearing epoxy functionality in said film-forming copolymers are selected from glycidyl esters and glycidyl ethers.

3. A composition in accordance with Claim 2 wherein said monoethylenically unsaturated monomers bearing glycidyl functionality are selected from glycidyl esters of monoethylenically unsaturated carboxylic acids.

4. A composition in accordance with Claim 1 wherein said monoethylenically unsaturated monomers bearing hydroxy functionality in said film-forming copolymers are selected from the group consisting of hydroxyalkyl acrylates formed by the reaction of C2-C5 dihydric alcohols and acrylic or methacrylic acids.

5. A composition in accordance with Claim 1 wherein said other monoethylenically unsaturated monomers in said film-forming copolymers are selected from the group consisting of acrylates or other monoethylenically unsaturated vinyl monomers.

6. A composition in accordance with Claim 5 wherein said acrylate monomers comprise at least about 50 weight percent of the total monomers in said film-forming copolymer and are selected from the group consisting of esters of C1-C12 monohydric alcohols and acrylic or methacrylic acids.

7. A composition in accordance with any one of Claims 1 to 6 wherein said organophosphate ester comprises an alkyl monoester.

8. A composition in accordance with Claim 7, wherein the alkyl group of said organophosphate monoester is a primary straight chain radical containing 2 to 6 carbon atoms.

9. A composition in accordance with any one of Claims 1 to 6 wherein said organophosphate ester comprises an alkyl diester.

1 0. A composition in accordance with Claim 9, wherein at least one alkyl group of said organophosphate diester is a primary straight chain radical containing 2 to 6 carbon atoms.

11. A composition in accordance with any one of Claims 1 to 6 wherein said organophosphate ester is a mixture of alkyl mono- and diesters.

12. A composition in accordance with Claim 11, wherein at least one alkyl group of said organophosphate ester is a primary straight chain radical containing 2 to 6 carbon atoms.

13. A composition in accordance with any one of Claims 1 to 12 wherein said amino resin crosslinking agent is an amine aldehyde resin selected from the group consisting of condensation products of formaldehyde with melamine, substituted melamine, urea, benzoguanamine and substituted benzoguanamine and mixtures of said condensation products, and is included in an amount sufficient to provide between about .75 and about 3.75 equivalents of nitrogen crosslinking functionality per equivalent of hydroxy functionality.

14. A composition in accordance with Claim 1 3 wherein said amine-aldehyde resin is included in an amount sufficient to provide between about .9 and about 1.7 equivalents of nitrogen crosslinking functionality for each equivalent of hydroxy functionality.

1 5. A composition in accordance with any one of Claims 1 to 14 wherein said hydroxy functional additive is a polyol selected from the group consisting of (i) hydroxy functional polyesters, (ii) hydroxy functional polyethers, (iii) hydroxy functional oligoesters, (iv) monomeric polyols, (v) hydroxy functional -copolymers formed from monoethylenically unsaturated monomers, one or more of which bears hydroxyi functionality and which is included in said copolymer in amounts ranging from about 2.5 to about 30 weight percent of said copolymer, and (vi) mixtures of (i)-(v).

1 6. A coating composition in accordance with any one of Claims 1 to 1 5, wherein said organophosphate ester is included in said composition in an amount sufficient to provide between about .8 and about 1 equivalents of acid functionality for each equivalent of pendant epoxy functionality on said film-forming copolymer.

17. A coating composition according to any one of the Examples.