POLYESTER GRAFT COPOLYMERS AND FLEXIBLE COATING COMPOSITIONS COMPRISING SAME

Abstract: Hydroxy functional polyester graft copolymers are prov­ ided. The copolymer is crosslinkable by hydroxy-reactive crosslinking agent and, in particular, is suitable for use in thermosetting coating compositions adapted to form a flex­ ible cured coating over a variety of substrates, such as metal and plastic. The copolymer has a number average molecular weight between about 1000 and about 15,000, has a hydroxyl number between about 30 and about 300, and is the reaction product of carbon-carbon double bond-reactive mono­ ethylenically unsaturated monomer with hydroxy functional carbon-carbon double bond-bearing branched polyester macromer. The macromer is the reaction product of (i) epoxy acrylate having the formula: with (ii) hydroxy functional polyester reactant containing 0-10 urethane linkages per molecule.

Description: POLYESTER GRAFT COPOLYMERS. FLEXIBLE COATING COMPOSITIONS COMPRISING SAME AND BRANCHED POLYESTER MACROMERS FOR PREPARING SAME Technical Field This invention relates to resins and flexible coating compositions comprising same which have excellent adherence to metal and plastic and possess superior weathering properties. More particularly, the invention relates to hydroxy functional polyester graft copolymers and to coating compositions comprising same. Background Recently, there has been interest in the use of resilient coating materials for areas which are subject to mechanical shock, such as automobile bumpers, moldings and front ends. To maintain the desired appearance for a protective coating on a motor vehicle body panel or like application, any such coating must have certain properties, such as a high degree of extensibility, impact resistance, and resistance to cracking and degradation under severe environmental conditions such as low temperature and high humidity. Conventional coatings, including those heretofore employed on rubber and similar extensible objects, do not have the required combination of properties. Generally, compositions that are flexible enough to be applied over both metal and plastic substrates have rather poor weatherability, appearance, and/or overall durability. U.S. Patent 3,882,189 and U.S. Patent 3.962.522 are exemplary of numerous patents which describe flexible coating compositions, wherein the resin comprises polyurethane modified polyesters formed by reacting 'y-sonyarate with polyester polyols These resins are cured with amine-aldehyde crosslinkers. It is taught tne-ein, that the presence of the urethane groups in the primer significantly contributes to the flexibility as wI1 as improved weathering properties, gloss, and abrasion resistance of the coating. Such coatings. Icwever, are not of an overall quality to meet certain applications, particularly automotive applications. Accordingly, it is an object of the present invention to provide novel polyester graft copolymers and solvent based1 thermosetting coating compositions comprising same, suitable to produce flexible cured coatings with good adhesion over diverse substrates including metal and plastic. In this regard, it is a particular object of the invention to provide such flexible coating compositions at sufficiently low Volatile Organic Content (VOC) to aid in meeting governmental emissions guidelines and yet which can be applied to a substrate by spraying or other known methods. It is another object of the invention to provide a composition which will form a coating on a substrate, which coating has advantageous physical properties including. for example, humidity and solvent resistance, flexibility and corrosion protection for the underlying substrate. Additional aspects and advantages of the invention will be apparent from the following description thereof. Disclosure of the Invention According to the present invention, a novel, non-gel led, hydroxy functional polyester graft copolymer is provided. The copolymer is crosslinkable by hydroxy-reactive crosslinking agent and, in particular, is suitable for use in thermosetting coating compositions adapted to form a flexible cured coating over a variety of substrates, such as metal and plastic. The copolymer of the invention has a number average molecular weight between about 1000 and about 15,000, has a hydroxyl number between about 30 and about 300, and is the reaction product of carbon-carbon double bond-reactive monoethylenically unsaturated monomer with hydroxy functional carbon-carbon double bond-bearing branched polyester macromer. This reaction is performed under free radical polymerization reaction conditions and the monomer bears substantially no functionality which would be substantially reaCtive with the hydroxy functionality of the macromer.under such reaction conditions. The macromer is the reaction product of (i) epoxy acrylate having the formula: EMI3.1 where R preferably is H or alkyl of 1 to about 7 carbons and R' is a hydrocarbon linking moiety, preferably alkyl or COO(CH2)n, n being 0 to about 7, with (ii) hydroxy functional polyester reactant containing 0-10 urethane linkages per molecule. According to the coating composition aspect of the invention, the aforesaid copolymer is employed with polyfunctional, hydroxy-reactive crosslinkinq agent selected from aminoplast crosslinking agent, polyisocyanate crosslinking agent, blocked polyisocyanate crosslinking agent comprising at least two isocyanate groups blocked by reaction with active hydrogen bearing blocking agent, and any compatible mixture thereof. The crosslinking agent is included in an amount sufficient to provide, at a cure temperature of the composition, between about 0.5 and about 1.6 hydroxy-reactive groups per hydroxy group contributed by the hydroxy functional polyester graft copolymer. The coating compositions of the invention can be formulated as either one component coating compositions or two component coating compositions. Typically, unblocked polyisocyanate crosslinking agent is employed in two component compositions in view of its reactivity. A composition of the invention can be formulated, for example, as a one component primer. typically employing blocked polyisocyanate or aminoplast crosslinking agent, as a one component topcoat, preferably employing aminoplast crosslinking agent, or as a two component coating, typically employing polyisocyanate crosslinking agent. Also, the polyester graft copolymer of the invention can be formulated as a pigmented base coat, typically a one component composition, for a base coat/clear coat system such as are known for use as automotive finishes. It also can be formulated as the clear coat thereof, either as a one component or a -two component composition. Advantageously, the flexible coatings of the invention possess superior weathering properties as well as excellent adhesion to metal and plastic, thus making them well suited for use as coatings on, for example, various motor vehicle components. The ability to use the same coating composition on metal and plastic components in motor vehicle production offers distinct commercial advantages, particular in terms of production efficiency. Additionally, because these coatings can be employed on metal as well as plastic components, the problem of color matching, which must be resolved when using different coatings on metal and plastic parts which are to be in proximity to one another, is eliminated. These and additional features and advantages of the invention will be better understood in view of the following detailed disclosure. DETAILED DESCRIPTION OF THE INVENTION The resin of the invention is a novel, hydroxy functional polyester graft copolymer of number average molecular weight (Mn) between about 1,000 and about 15,000, preferably between about 1,000 and about 4.000, and having a hydroxyl number between about 30 and about 300. preferably between about 50 and about 150. The resin is optionally urethaue-modified, more specifically, containing about 0-10 urethane linkages per molecule. Preferably, the resin contains about 0-5 urethane linkages per molecule. As disclosed above, the resin is the reaction product of carbon-carbon double bond-reactive monoethylenically unsaturated monomer with certain hydroxy functional carbon-carbon double bond-bearing branched polyester macromer. Each of these reactants is discussed below in greater detail. Carbon-Carbon Double Bond-Reactive Monoethylinically Unsaturated Monomer Numerous carbon-carbon double bond-reactive monoethylenically unsaturated monomers suitable for making the polyester graft copolymer are known to the skilled of the art. Included are many which are commercially available and many which will be readily apparent in view of te present disclosure. The choice of monomer reactant employed in making the polyester graft copolymer will depend to a large extent upon the particular application intended for the resin or for the coating composition in which the resin is to be used. Examples of suitable monoethylenically unsaturated monomers include, for example. vinyl aromatic hydrocarbons such as styrene, alpha methyl styrene, and vinyl toluene, vinyl acetate, vinyl chloride, and the like. Preferred monomers are acrylate monomers. Numerous acrylate monomers suitable for preparing the hydroxy functional polyester graft copolymer are known to the skilled of the art and include many which are commercially available and which will be readily apparent in view of the present disclosure. As noted above. the choice of monomer reactant employed in preparing the resin of the invention will depend to a large extent upon the particular application intended for the resin or for the-composition in which the resin is used. Suitable hydroxy-substituted alkyl(meth)acrylates (where Palkyl(meth)acrylates means, in the alternative, alkylacrylates and alkylmethacrylates) which can be employed comprise members selected from the group consisting of the following esters of acrylic or methacrylic acid and C2-C12 aliphatic glycols: 2-hydroxy ethyl acrylate; 3-chloro-2-hydroxypropyl acrylate; 2-hydroxy-l-methylethyl acrylate; 2-hydroxypropyl acrylate; 3-hydroxypropyl acrylate; 2,3-dihydroxypropyl acrylate; 2-hydroxybutyl acrylate; 4-hydroxybutyl acrylate; diethyleneglycol acrylate; 5-hydroxypentyl acrylate; 6-hydroxyhexyl acrylate; triethyleneglycol acrylate, 7-hydroxyheptyl acrylate; 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-substituted alkyl(meth)acrylates including those listed above could be employed. the preferred hydroxy functional monomers for use in the resin of this invention are hydroxy-substituted alkyl acrylates and methacrylates having a total of 5 to 7 carbon atoms. i.e., esters of C2-C3 dihydric alcohols and acrylic or methacrylic acids. such as hydroxyethyl methacrylate, hydroxyethyl acrylate. hydroxypropyl methacrylate and hydroxypropyl acrylate. Most preferably, the hydroxy-substituted alkyl(meth)acrylate monomer comprises a compound of the formula: EMI7.1 wherein R1 is hydrogen or methyl and R2 and R are independently selected from the group consisting of hydrogen and alkyl of from 1 to 6 carbon atoms. Illustrative of these particularly suitable hydroxy-substituted alkyl(meth)acrylate monomers are 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate and 2-hydroxy-l-methylhexyl acrylate. Suitable non-hydroxy substituted alkyl(meth)acrylate monomers which may be employed are (meth)acrylates (as before, meaning esters of either acrylic or methacrylic acids) as well as mixtures of acrylates and vinyl hydrocarbons. Preferred non-hydroxy substituted monomers are esters of C1-C12 monohydric alcohols and acrylic or methacrylic acids, e.g., methylmethacrylate, ethylacrylate. butylacrylate, butyl-methacrylate, hexylacrylate, 2-ethylhexylacrylate, lauryl-methacrylate. glycidyl methacrylate, and the like. Particularly preferred non-hydroxy substituted monomers are compounds selected from the group consisting of monomers of the formula: EMI8.1 wherein is alkyl of from 1 to 6 carbon atoms and 5 R5 is hydrogen or methyl. Particularly preferred are butyl acrylate. butyl methacrylate arid methyl methacrylate. The aforesaid monovinyl aromatic hydrocarbons, preferably containing from 8 to 12 carbon atoms, including styrene, alpha-methyl styrene. vinyl toluene, butyl styrene, chlorostyrene and the like, when employed, will generally be present in an amount of from about 5 to 95 weight percent, preferably from about 5 to 25 weight percent of the total monoethylenically unsaturated monomer. In addition. other suitable monoethylenically unsaturated monomers such as vinyl chloride, acrylonitrile, methacrylonitrile. vinyl acetate, acrylic acid and methacrylic acid also may be employed. In the case of acrylic acid, when employed. this monomer will generally be present in an amount from about 2 to 5 weight percent of the total monomer mixture. The remaining above-mentioned monomers will generally be used in an amount of from 3 to 10 weight percent of the monomer mixture. when employed. Hydroxy Functional Carbon-Carbon Double Bond-Bearing Branched Polyester Macromer The hydroxy functional polyester macromer is reacted with the above described monoethylenically unsaturated monomer according to any of various methods well known to the skilled of the art, which methods will be apparent in view of the present disclosure. Specifically, the macromer and the monomer are employed in a weight ratio of from about 90:10 to about 40:60, more preferably from about 75:25 to about 50:50, respectively. Preferably, all double bonds of the macromer are reacted with monomer double bonds. It will be apparent that the resulting resin will be hydroxy functional by virtue of the macromer hydroxyl groups and the monomer hydroxyl groups (if any). Suitable reaction conditions will be apparent to the skilled of the art and, generally, will include a solvent system and reaction temperature favoring free radical polymerization reaction. The hydroxy functional polyester macromer is the reaction product of any of certain epoxy acrylate with any of certain hydroxy functional polyester. Each of these reactants is discussed below in greater detail. Epoxy Acrylate Epoxy acrylate reactants suitable for reaction with hydroxy functional polyester in making the polyester macromer of the invention are those according to the formula: EMI9.1 wherein R preferably is hydrogen or alkyl of 1 to about 7 carbons and R is a hydrocarbon linking moiety. preferably alkyl or COO(CH2)n, n being 0 to about 7. Numerous such epoxy acrylates are well known to the skilled of the art and include many which are commercially available or readily prepared according to known methods. The choice of epoxy acrylate employed in preparing the polyester macromer will depend largely upon the particular application intended for the final resin or composition comprising the resin. Preferred epoxy acrylates include. for example. glycidyl acrylate, glycidyl methacrylate and a mixture thereof. Hydroxy Functional Polyester The hydroxy functional polyester has a number average molecular weight (Mn) preferably between about 1,000 and about 10.000, more preferably between about 1,000 and about 3,000, and has a hydroxyl number preferably between about 30 and about 300. more preferably between about 50 and about 150. As discussed further below, the polyester preferably, but not necessarily. is urethane modified. that is. bears urethane linkages in the polyester backbone. Suitable hydroxy functional polyesters. both urethane modified and unmodified, are known to the skilled of the art and will be apparent in view of the present disclosure. Such compounds can be prepared according to known methods which also will be apparent in view of the present disclosure. The choice of polyester reactant will depend to a large extent upon the particular application intended for the final resin or composition in which such resin is used. The epoxy acrylate and polyester are reacted together according to known methods and reaction conditions. Typically. these two reactants are employed in molar ratio of about 2:1 to about 1:2, more preferably about 1:1. More generally, the epoxy acrylate is used in an amount insufficient to yield a gelled reaction product. Also. the epoxy acrylate reactant is used in an amount insufficient to react with all of the hydroxy functionality of the polyester, since the reaction product, the branched polyester macromer, must have hydroxy functionality to react with the crosslinking agent during cure. In preparing the macromer a catalyst should be employed for the reaction between the epoxy functionality of the epoxy acrylate and the hydroxy functionality of the polyester. Suitable catalysts for this reaction are known and include commercially available catalysts, such as sulfonic acid catalyst, for example CG 21-746 (trademark) available from Ciba Geigy Corp., Ardsley, N.Y., and phosphine catlaysts, for example Shell 1201 (trademark; Shell Chemical Co.). Additional suitable catalysts will be apparent in view of the present disclosure. It is also preferred to employ an agent to inhibit polymerization reaction of the carbon-carbon double bonds of the epoxy acrylate reactant. Suitable inhibiting agents are well known and include, for example, hydroquinone and others which will be apparent in view of this disclosure. One suitable class of polyester reactants comprises the reaction products of polyol with dicarboxylic acid or an anhydride thereof and most preferably such polyesters are oligomeric polyesters. Preferably, the diacid is selected from the group consisting of saturated and unsaturated, cyclic and acyclic aliphatic dicarboxylic acids, aromatic dicarboxylic acids. and suitable anhydrides thereof. Preferred dicarboxylic acids ate the C6-C36 acids. which include, for example, adipic, azelaic, sebasic, dodecane dicarboxylic acid, and cyclohexanedicarboxylic acid and dimer acids. More preferably, the dicarboxylic acids employed are aliphatic dicarboxylic acids, most preferably additionally being linear, for example, adipic. azelaic, dimer5 and dodecanoic. Also suitable for use as diacid are blocked dicarboxylic acids such as dimethyl-l,4-cycohexanedicarboxylate. Mixtures of suitable diacids and/or their anhydrides may also be used as the dicarboxylic acid component in this invention. Numerous suitable polyols for use in making the hydroxy functional polyester are known to the skilled of the art and will be readily apparent in view of the present disclosure. Included are many commercially available polyols and others which are readily prepared according to known methods. Preferably, the polyol comprises diol and triol in hydroxyl equivalent ratio of from about 4:1 to about 1:4, more preferably from about 3:1 to about 3:2.5, respectively. Suitable diols include, but are not limited to. alkylene glycol. such as butylene glycol. neopentyl glycol, 1,5-pentene glycol, 3-cyclohexene-l,l-dimethylol, and other glycols such as hydrogenated bisphenol A, caprolactone diol (e.g., the reaction product of caprolactone and ethylene glycol), hydroxy alkylated bisphenol, polyether glycols. e.g., poly(oxytetrametilene) glycol, polyester diols, e.g., 2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypro- pionate, and the like. Preferred diols are neopentyl glycol and 2.2-dimethyl-3-hydroxypropyl-2.2-dimethyl 3-hydroxypropionate, the latter material being commercially available as Esterdiol 204 ( trademark; Union Carbide Corp., Danbury, Conn.) The polyol generally should comprise at least about 5 weight percent triol and may consist substantially entirely of triol. The polyol component also may comprise tetrols and higher functionality polyols. but these generally are less preferred. By employing diols in the polyol component in addition to the triols. the flexibility of the coating composition is generally increased. Thus. selection of the polyol component to be used in forming the polyester compositions will be dependent on the particular desired properties and application of the coating composition. When diols are employed in the polyol component. the polyol preferably comprises from about 10 to about 80 weight percent triols and from about 90 to about 20 weight percent diols. Preferred triols are conventional low molecular triols such as 1,2,6-hexanetriol, l,l,l-trimethylolpropane, 3-(2-hydroxypropoxy)-1,2-propanediol and polycaprolactone triols which are commercially available as, for example. Tone-301 (trademark; Union Carbide Corp., Danbury, Conn.). Additional preferred polycaprolatone triols are described in United States Patent 4,165,345, incorporated herein by reference. Suitable tetrols will be apparent and include, for example. pentaerythritol and the like While a number of types of polyols have been mentioned above as suitable for use in making the hydroxy functional polyester reactant. their disclosure is not meant to be limiting. A great many additional suitable diols. triols. etc. are known in the art and selection of other polyols which would be suitable for use would be well within the skill of those in the art in view of this disclosure. The polyol reactant (i.e.. diols. triols and optionally tetrols, etc.) and diacid reactant are combined and reacted. generally in the presence of a catalyst and at elevated temperatures, to produce the aforesaid hydroxy functional polyester. Suitable catalysts for the carboxy/hydroxy condensation reaction include such catalysts as tetraisopropyl titanate. strong acids such as p-toluene phosphonic acid. phosphoric acid. sulfuric acid and materials such as zinc oxide, antimony oxide (Sb2O3). dibutyl tin oxide. hydrated monobutyl tin oxide, and sodium acetate. Other catalysts will be apparent to those skilled in the art in view of this disclosure. The polyol and dicarboxylic acid are reacted preferably in such proportions as to provide a molar equivalent ratio of OH to COOH from about 6:2 to about 6:5, respectively. Sufficient polyol must be used to provide a hydroxy functional polyester product. As noted above, the hydroxy functional polyester is optionally urethane modified and typically nay contain about 1-10 urethane groups per molecule. According to one embodiment of the invention, urethane groups are introduced by reaction of the above-described hydroxy functional polyester with organic diisocyanate. Such reaction is carried out according to known methods. generally in the presence of solvents commonly employed for coating formulations such as toluene. xylene, methyl amyl ketone. and the like. Numerous suitable organic diisocyanates are readily commercially available and will be apparent to the skilled of the art in view of the present disclosure. Suitable diisocyanates include hydrocarbon diisocyanate or substituted hydrocarbon diisocyanate, such as 1.6-hexamethylene diisocyanate, isophorone diisocyanate, p-phenylene diisocyanate, biphenyl diisocyanate, toluene diisocyanate, and 3, 3-dimethyl-4 . 4-biphenylene diisocyanate. While the diisocyanate may be any of a number of aliphatic, cycloaliphatic, and aromatic diisocyanates, it is preferred that the diisocyanate be an aliphatic diisocyanate, suc as 4.4-dicyclohexylmethanediisocyanate. As would be apparent to those skilled in the art, mixtures of various diisocyanates may also be employed as the diisocyanate component used in forming urethane-modified polyester. Typically. the hydroxy functional polyester and diisocyanate are reacted in such proportions as to provide about 4-10 hydroxyl groups per isocyanate group. While urethane modification may be introduced in the manner discussed above. according to an alternative embodiment of the invention the polyol component employed in reaction with dicarboxylic acid comprises urethane modified polyol. In this case. there is no need to react with diisocyanate the polyester reaction product of polyol and dicarboxylic acid. Employing urethane modified polyol is found to provide a final resin. i.e.. a polyester graft copolymer, which is somewhat more flexible than when the urethane groups are introduced by reaction of the polyester with diisocyanate. Suitable urethane modified polyols are commercially available or readily prepared according to known methods. Exemplary urethane modified diols are made by reaction of diol and diisocyanate in a molar ratio of from about 4:1 to about 4:3, preferably from about 2:0.8 to about 2:1.2, more preferably about 2:1. Suitable diols and diisocyanates include those mentioned above. Such ratio of diol to diisocyanate (i.e.. a molar excess of diol) causes the reaction product to be substantially free of unreacted isocyanate groups. This urethane modified diol is then combined with other portions of the polyol reactant (e.g., additional diol, triol. tetrol, etc.) and the dicarboxylic acid reactant. generally at elevated temperature and in the presence of a catalyst (as discussed above) to produce the hydroxy functional polyester. specifically. a hydroxy functional urethane modified polyester. It will be apparent to those skilled in the art, that urethane modified triol. urethane modified tetrols, etc. can be used in addition to or in lieu of urethane modified diol, according to the methods and guidelines discussed above, to provide hydroxy functional urethane modified polyester. Coating Copositions According to another aspect of the invention the above-described hydroxy functional polyester graft copolymer is employed in an organic solvent based thermosetting coating composition together with suitable polyfunctional hydroxy-reactive crosslinking agent. Such crosslinking agent is selected. preferably, from aminoplast crosslinking agents and polyisocyanate crosslinking agents. either blocked or unblocked depending upon the intended application. Coating compositions of the invention can be formulated so as to be suitable for numerous different applications including. particularly, as motor vehicle body panel coatings. Thus, for example. a coating composition of the invention can be formulated as a primer or as a topcoat, such as a basecoat for a basecoat/clearcoat system. a clearcoat for a basecoat/clearcoat system. or as a one-coating topcoat. Moreover, any of these coatings can be formulated as either a one-component (i.e., resin and crosslinker combined) or a two-component (i.e.. resin and crosslinker segregated) coating composition, except that the basecoat of a base/clear system generally would be formulated only as a one-component coating in view of the high pigment content thereof and the mixing and dispersion problems which would result in attempting to add the crosslinking agent at the time of application to a substrate. It is, of course, well known to the skilled of the art to employ unblocked polyisocyanate crosslinking agents generally only in two-component formulations to prevent premature reaction thereof with the hydroxy functional copolymer. Blocked polyisocyanate crosslinkers are employed in one-component coatings, but typically these are employed in primers since the two-component unblocked polyisocyanate coatings of the invention are found generally to provide better surface appearance. The amino resin crosslinking agents also are employed. typically. in one component formulations. In a coating composition intended for use as a high solids basecoat or clear coat of a base/clear automotive coating formulation, typically it is preferred that the polyester graft copolymer have a number average molecular weight (Mn) between about 1.500 and about 3,000, more preferably between about 1,500 and about 2,500. Also. for such use the resin preferably has a hydroxy number between about 50 and about 150. Crosslinking Agent The crosslinking agent is generally included in compositions of the invention in an amount between about 5 and about 60 weight percent, preferably in an amount between about 20 and about 50 weight percent based on the weight of the copolymer and crosslinker combined. Selection of the optimal amount of crosslinking agent to be employed in the coating composition is dependent on the desired properties (e.g., flexibility) of the coating as well as its intended use. and selection of such amount would be within the skill of one in the art. Polyisocyanate crosslinking agents are well known in the art and numerous suitable organic isocyanates having 2 or more reactive isocyanate groups per molecule will be apparent to those skilled in the art. Among the many suitable polyisocyanates are aliphatic, cycloaliphatic and aromatic isocyanate compounds. Representative of the numerous isocyanates which can be employed are (1) aliphatic diisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate. 1.2-propylene diisocyanate, 1,2-butylene diisocyanate. 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, ethylidene diisocyanate, butylidene diisocyanate, 4,4t-bistisocyanate hexyl) methane, bis(2-isocyanate-ethyl)fumarate, 2,6-diisocyanate methyl caproate. 2,2,4-(2,4,4)-trimethylhexamethylene diisocyanate, and dimer acid diisocyanates; (2) cycloaliphatic diisocyanates such as 1,3-cyclopentane diisocyanate, 1,4-cyclopentane diisocyanate. 1,2-cyclopentane diisocyanate. and methylcyclohexylene diisocyanate; (3) aromatic diisocyanates such as m-phenylene diisocyanate, p-phenylenediisocyanate, 4.4'-diphenyl diisocyanate; (4) aliphatic/aromatic diisocyanates such as 4.4'-diphenylene methane diisocyanates, 2,4- or 2,6-tolylene diisocyanate. 4,4'-toluidene diisocyanate, 1,4-xylylene diisocyanate; (5) nuclear substituted aromatic compounds such as dianisidine diisocyanate, 4.4'-diphenylether diisocyanate, chiorodiphenylene diisocyanate; (6) triisocyanates such as triphenylmethane-4,4',4"-triisocyanate, 1.3.S-triisocyanate benzene, 2,4.6-triisocyanate toluene: (7) tetraisocyanates such as 4.4'-diphenyl dimethylmethane 2.2' .5.5'-tetraisocyanate; (8) polymerized isocyanates such as tolylene diisocyanate dimers and trimers and the like; and (9) polyisocyanates such as prepolymers derived from a polyol, including polyester polyols or polyester polyols (including polyethers which are reacted with excess polyisocyanates to form isocyanate terminated prepolymers), simple polyols such as glycols (e.g., ethylene glycol, propylene glycol), other polyols such as glycerol, trimethylol propane, hexane triols. pentaerythritol and the like. as well as monoethers. e.g., diethylene glycol. tripropylene glycol and the like, and polyethers, i.e., alkylene oxide condensates of the above. While the polyisocyanate cross linking agent may be any organic polyisocyanate as has been noted above, such crosslinking agents for coating composition to be employed as clear (top) coats are preferably aliphatic and cycloaliphatic polyisocyanates. due to their superior weatherability. Especially preferred for use in clearcoat compositions of the invention are trimerized products of aliphatic diisocyanates such as 1,6-hexamethylene diisocyanate. Still another particularly preferred type of crosslinking agent is a polyisocyanate having a biuret structure. This type of polyisocyanate is well known. as are methods for making the same. Suitable such polyisocyanate crosslinking agents are high molecular weight biurets of 1,6-hexamethylene diisocyanate sold by Mobay Chemical Company under the trademarks Desmodur N and Desmodure L 2291. Exemplary of other biuret type polyisocyanates are those prepared in accordance with U.S. Patent No. 3.976.622 to Wagner et al. Blocked polyisocyanate crosslinking agents are well known to the skilled of the art and many suitable for use in compositions of the invention are commercially available or readily prepared and will be apparent from the present disclosure. More specifically. blocked polyisocyanate crosslinking agents comprise the reaction product of a polyisocyanate, such as those mentioned above, with a blocking agent. that is, an active hydrogen-bearing reactant. Exemplary blocked polyisocyanates are described. for example. in United States patent 4,497,938. which description is incorporated herein by reference. Blocked polyisocyanate cross linking agents are used generally in the same proportions disclosed above for unblocked polyisocyanate crosslinking agents. Amine-aldehyde crosslinking agents suitable for crosslinking hydroxy functional bearing materials are well known in the art. Typically, these cross linking materials are products of reactions of melamine, or urea with formaldehyde and various alcohols containing up to and including 4 carbon atoms. Preferably. the amine-aldehyde crosslinking agents are amine-aldehyde resins such as condensation products of formaldehyde with melamine. substituted melamine, urea. benzoguanamirie or substituted benzoguanamine. Preferred members of this class are methylated melamine-formaldehyde resins such as hexamethoxymethylmelamine. Particularly preferred crosslinkers are the high solids melamine resins which have substantially 95+ percent nonvolatile content. For so-called "high solids" compositions of this invention. it should be recognized that it is important not to introduce extraneous diluents that lower the final solids content of the coating. Other suitable amine-aldehyde crosslinking agents will be apparent to one skilled in the art. Amine-aldehyde cross linking agents are preferred for basecoat compositions of the invention. The amine-aldehyde crosslinking agent is generally included in a basecoat composition in an amount of between about 5 and about 60, preferably between about 20 and about 40 weight percent However, selection of the particular amount of amine-aldehyde crosslinking agent to be employed in any such composition is dependent on the desired properties of the composition as well as its intended use and would be apparent to one skilled in the art. Particularly preferred crosslinking agents are the amino crosslinking agents sold by American Cyanamid under the trademark 'Cymel11. In particular, Cymel 301. 303. 325. 1130, 1156. 1161 and 1168 (trademarks) are alkalated melamine aldehyde resins useful in the compositions of this invention. The crosslinking reactions are catalytically accelerated by acids. One such catalyst. for example. which may be so employed is p-toluene sulfonic acid. which when employed is generally added to the composition in about 0.5% by weight based on the total weight of the polyester graft copolymer and crosslinking agent. Additional Materials Additional materials which may be employed in the coating compositions of this invention include a high molecular weight linear polyurethane which has a number average molecular weight of between about 15,000 and about 40. 000. preferably between about 20,000 and about 30,000. It may be made by reacting one of the above mentioned diisocyanates and diols such as oligoester diol. polycaprolactone diol, polyoxypropylene diol. polyether diols. etc. Suitable high molecular weight linear polyurethane materials are commercially available, for example. as Spenlite L06-30S. (trademark. Spencer-Kellogg, Buffalo, N.Y.). It has been found that these high molecular weight polyurethanes may be employed in metallic flake pigment-bearing topcoat compositions in small amounts. typically up to about 15 weight percent based on the total weight of the polyester graft copolymer and crosslinking agent. to improve the orientation of the metallic flake pigment in the cured coating. It has been found that by including suc linear polyurethane, for example. in a basecoat of a basecoat/clearcoat system. the depth of color and metallic glamour of the system may be improved. Other materials which ay be included in the coating compositions of this invention include, for example. catalysts, antioxidants, U.V. absorbers (for topcoats), solvents, surface modifiers and whitening agents. Solvents used in the coating composition of this invention are those which are commonly used, e.g., to facilitate spray application and high solids content ad include toluene. xylene, methylethyl ketone. acetone. 2-ethoxy-l-ethanol. diacetone alcohol, tetrahydrofuran, ethyl acetate, dimethylsuccinate. dimethylgiutarate. dimethyladipate and mixtures thereof. The solvent in which the polyester graft copolymer is prepared may be employed as a solvent for the composition, thus eliminating the need for drying the resin after preparation, if such is desired. Typical ultraviolet light stabilizers that are useful in topcoat compositions of this invention are benzophenones such as dodecyl oxibenzophenone, 2. 4-dihydroxybenzophenone. hydroxybenzophenones containing sulfonic groups. 2.4-dihydroxy-3' ,5 '-ditertiarybutylbenzophenone. 2,2',4'-trihydroxybenzopheone esters of dicarboxylic acids. 2-hydroxy-4-acryloxyethoxybenzophenone, aliphatic monoesters of 2,2',4-trihydroxy-4'-alkoxybenzophenone, 2-hydroxy-4-methoxy-2-carboxybenzophenone, triazoles such as 2-phenyl-4-(2'4'-dihydroxybenzoly)-triazoles, substituted benzotriazoles such as hydroxyphenyltriazoles such as 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxyphenyl)benzotriazole, and 2-(2'-hydroxy-5'-octylphenylinaphthiotriazole. Another type of ultraviolet light stabilizer and one that is particularly preferred for use in the coatings of this invention is that taught in U.S. patent 4,480,084 entitled "Polymeric Light Stabilizers to Kordomenos et al. These stabilizers contain the sterically hindered polyalkylpiperidine radical and at least two primary hydroxyl groups available for reacting with the crosslinking agent. e.g.. amine-aldehyde or polyisocyanate. of the coating composition. Typical antioxidants which may be employed in the coating composition include tetrakis alkylene (di-alkyl hydroxy aryl) alkyl ester alkanes such as tetrakis methylene 3-(3',5'-di-tert-butyl-48-hydroxy- phenyl)proprionate methane (available under the trademark Irganox 1010 from Ciba-Geigy Corp.). Also suitable are the reaction product of p-amino diphenylamine and glycidyl methacrylate, the reaction product of n-hexyl-Nµ-phenyl-p-phenylene diamine and glycidyl methacrylate, pentaerythritol tetrakis(thioglycolate). trimethylol propane tris(thioglycolate). trimethylol ethane tris(thioglycoate). N-(4-anilinophenyl)maleimide, alkylhydroxyphenyl groups bonded through carboalkoxy linkages to nitrogen atom of a heterocyclic nucleus containing an imidodicarbonyl group or an imidodithiocarbonyl group. 3,3-ditertbutyl-4-hydroxy-cinnamonitrile, ethyl-3,5-diterthexyl-4-hydroxy-cinnamate, substituted benzyl esters of beta-substituted (hydroxyphenyl)-propionic acids. bis-(hydroxyphenylalkylene)alkyl isocyanurate compounds. tetrakis hydroxy benzyl phosphonium halides alone or in combination with a dialkylthiodialkanoate, thiodimethylidyne tetrakisphenols alone or in combination with a dialkyl thiodialkanoate or phosphite or phosphonate. dihydrocarbyl-hydroxyphenyl aryl or alkyl phosphonites or phosphonates or phosphates or phosphinites or phosphinates or phosphionites or phosphorothionates or phosphinothionates, diphenyl-bls(3,5-ditertbutyl-4-hydroxyphenoxy)silane, hydrocarbylhydroxyphenyl-dibydrocarbyldithio-carbamates such as 3,5-ditertbutyl-4-hydroxyphenyl dimethyldithiocarbamate and amino benzyl thioether. In one preferred embodiment a baseZclear topcoat system is provided, wherein both the basecoat and the clearcoat comprise a resin and crosslinker composition according to the invention. The basecoat would preferably contain only a benzotriazole U.V. stabilizer such as Tinuvin 328 (trademark. Ciba-Geigy. Ardsley, N.Y.). and the clearcoat would contain a benzotriazole U.V. stabilizer, e.g., Tinuvin 328, the polymeric hindered amine light stabilizer of the aforementioned U.S. patent 4,480.084 to Kordomenos et al and an antioxidant, e.g., Irganox-1010 (trademark; Ciba-Geigy). While preferred combinations of stabilizer6 and antioxidants have bee described. these teachings are not meant to be limiting. Selection of suitable stabilizers and antioxidants is within the skill of one in the art. 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 coating compositions to the surface being coated and helps formation of thin coatings, particularly on metal surfaces. The choice of surface modifiers or wetting agents is dependent upon the type(s) of surface to be coated. Selection of appropriate surface modifiers is well within the skill of the art. Typical of these surface modifiers are polybutyl acrylate and a wide variety of silicon wetting agents which are commercially available. For many applications of the coating compositions of the invention. particularly high solids compositions. it may be desirable to employ flow control additives to provide sag free coatings. Among the many such materials which are known are non-aqueous dispersions (NADaS) such as described by Porter (S. Porter, Jr., and B. N. McBane. U.S. Patent No. 4,025,474, May 24, 1977). These particle dispersions may be included generally in an amount up to 15% by weight of the total composition. Other types of NAD's such as described by D. L. Maker and S. C. Peng (U.S. Patent No. 3.814,721. June 4, 1974) or by S. K. Horvath (U.S. application Serial No. 292,853, filed August 14. 1981) also may be included izk the coating compositions. Coating compositions according to certain embodiments of the invention may contain pigments. Thus, for example. primer compositions and the basecoat of a base/clear system may comprise any of the wide variety of suitable pigments which are known to the art and readily commercially available. Selection of suitable pigments and the amounts of same will depend largely on the intended use and desired properties of the coating. for example. desired color. hiding properties, etc., and is within the skill of those in the art. The coating coinposition can be applied by conventional methods known to those in the art. These methods include roll coating. spray coating. dipping or brushing. The particular application technique chosen will depend upon the particular substrate to be coated and the environment in which the coating operation takes place. Preferred techniques for applying these coating compositions, particularly when applying the same to automobiles, is spray coating through the nozzle of the spray gun. A basecoat, for example. can be applied as a single component by means of a single component spray gun. On the other hand, in spray applying a two component clearcoat composition. the polyester graft copolymer and additives such as pigments. U.V. absorbers. antioxidants and other nonreactive materials are admixed with a solvent. These materials are fed as one component of a two component system into a spray gun which combines the materials as they are sprayed into the automotive substrate. The other material is the polyisocyanate crosslinking agent. which may or may not be cut with a suitable nonreactive solvent. 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 are intended to mean parts by weight. Example I Hydroxy functional oligomeric polyester. more specifically, a urethane modified hydroxy functional oligomeric polyester was prepared according to this example. In a suitable reactor 720g Esterdiol-204 (trademark; Union Carbide, Danbury. Conn.; 2,2-dimethyl-3 hydroxypropyl-2.2-dimethyl-3-hydroxypropionate). 216g trimethylolpropane, 504g adipic acid, and 2g dibutyl tin oxide were charged. The mixture was heated to 3000F and water was distilled off until the acid number dropped below 10. The batch was then thinned with 150 parts xylene. The temperature was lowered to 2000F and 255g Desmodur W (trademark; Mobay Chemical Co., diisocyanate) was added dropwise in a period of two hours. After addition was complete, the mixture was postreacted at 2000F until no NCO group was observed in an IR spectrum. At this point the batch was thinned with 2245g xylene. The final product had A viscosity at 39.4S non-volatiles and and acid number of 2 EMI26.1 Example II Urethane modified hydroxy functional oligomeric polyester was prepared according to this example. In a suitable reactor 10209 Esterdiol-204 (trademark; Union Carbide), 440g trimethylolpropane. 7309 adipic acid, and 3.07g Fascat 4100 (trademark; M & Chemicals, Inc., Rahway. N.J.; catalyst) were charged. The mixture was heated to 300"F ad water was distilled off until the acid number dropped below 10. The batch was then thinned with 228 parts xylene. The temperature was lowered to 2000F and 4389 Desmodur W (trademark; Mobay Chemical Co.) was added dropwise in a period of two hours. After addition was complete, the mixture was postreacted at 2000F until no NCO group was observed in an IR spectrum. At this point the batch was thinned with 1800g xylene. The final product had an I-J viscosity at 55.3% non-volatiles. Example III Hydroxy functional carbon-carbon double bond-bearing branched polyester macromer was prepared according to this example. In a suitable reactor 1085g of the resin from Example I and 911g xylene were charged. The mixture was brought to reflux (300"F) and any water present was stripped out. The temperature was lowered to 2000F and 83mg hydroquinone and 4.13g sulfonic acid catalyst CG 21-746 (trademark; Ciba-Geigy) were added. To this mixture 54g glycidyl methacrylate was added dropwise in a period of 20 minutes. After the end of the addition. the mixture was postreacted at 2000F until no oxirane ring was observed in an IR spectrum. The final product had A viscosity at 37t non-volatiles. ExamPle IV Hydroxy functional carbon-carbon double bond-bearing branched polyester macromer was prepared according to this example. In a suitable reactor 1085g of the resin from Example II and 911g xylene were charged. The mixture was brought to reflux (300 F) and any water present was stripped out. The temperature was lowered to 2000F and 83mg hydroquinone and 4.13g of catalyst Shell 1201 (trademark; Shell Chemical Company; phosphine catalyst) were added. To this mixture 54g glycidyl methacrylate was added dropwise in a period of 20 minutes. After addition was complete, the mixture was postreacted at 200 F until no oxirazie ring was observed in an IR spectrum. The final product had a viscosity of A at 39.by non-volatiles. Example V Hydroxy functional polyester graft copolymer of the invention was prepared according to this example. In a suitable reactor 300g Exxate 700 (trademark; Exxon Chemicals; oxyl heptyl acetate solvent), 136g n-butanol, and 7.2g cumene hydroperoxide were charged. The mixture was brought to reflux (280-3000F). A mixture of 1760g of the resin from Example IV, 242g iso-butylmethacrylate, 24g hydroxyethylacrylate. 50g styrene, 20g acrylic acid and 7.5g t-butylperbenzoate was added dropwise over a period of S hours. The mixture was postreacted at 3009F for 2 hours. The temperature was raised and solvent was distilled off to afford a resin with a viscosity of T-U at 70% non-volatiles. Example VI Hydroxy functional polyester graft copolymer was prepared according to this example. In a suiable reactor 220g xylene and 3.6g cumene hydroperoxide were charged. The temperature was raised to 2700F and a mixture of 892g of the resin from Example III, 121g butylmethacrylate, 12g hydroxypropylmethacrylate, 25g methylmethacrylate, and 3.69 t-butylperbenzoate was added dropwise over a period of 5 hours. The mixture was postreacted at 2700F for 2 hours. The temperature was raised to 300 F and 450g xylene were stripped off. The final product had a J viscosity at 59% non-volatiles and an acid number of 1.13. Example VII Hydroxy functional polyester graft copolymer was prepared according to this example. In a suitable reactor 220g xylene and 3.6g cumene hydroperoxide were charged. The mixture was brought to reflux (3000F) and any water present was stripped out. The temperature was maintained at 2700F and a mixture of 8109 of the resin from Example III, 121g iso-butylmethacrylate, 24g hydroxyethylacrylate, 25g styrene, 12g acrylic acid, and 3.6g t-butylperbenzoate were added dropwise over a period of 4 hours. The mixture was postreacted at 2700F for 2 hours. The temperature was raised to 3000F and xylene was stripped off to afford a resin with a Y viscosity at 47S non-volatiles. Example VIII Hydroxy functional oligomeric polyester was prepared according to this example. In a suitable reactor 720g Esterdiol-204 (trademark: Union Carbide Corp.). 490g Tone 0301 (trademark; Union Carbide Corp.; polycaprolactone triol). 252g adipic acid, 255g phthalic anhydride. and 2g dibutyl tin oxide were charged. The mixture was heated to 3500F and water distilled off until the acid number dropped to 5. The temperature was lowered and the batch was thinned with 571 parts xylene. The temperature was raised to 200"F and 133g Desmodur W (trademark; Mobay Chemical Co.; diisocyanate) was added dropwise over a period of 2 hours. The mixture was postreacted at 2000F until no isocyanate was observed in an IR spectrum (2270 cm The batch was thinned with 1623g xylene to afford a resin with an A viscosity at 42S non-volatiles. Example IX Hydroxy functional acrylate-bearing branched polyester macromer was prepared according to this example. In a suitable reactor 3657g of the resin from Example VIII, 1.3g Shell 1201 catalyst (trademark; Shell Chemical Co.), and 0.13g hydroquinone were charged. The mixture was heated to 1500F and 135g glycidyl methacrylate was added dropwise over a period of 20 minutes. The mixture was postteacted at 1500F until the WPE (weight per epoxy) rose above 1600. The final resin had a viscosity of A at 41S non-volatiles. Example X Hydroxy functional polyester graft copolymer of the invention was prepared according to this example. In a suitable reactor 660g xylene and 10.8g cumene hydroperoxide were charged. The mixture was heated to 270QF and a mixture of 2640 of the resin from Example IX. 363g iso-butylmethacrylate, 36g hydroxyethylacrylate. 75g styrene, 30g acrylic acid, and 10.89 t-butylperbenzoate was added dropwise over a period of 4 hours. The mixture was postreacted at 2700F for 2 hours. The temperature was raised and 1300g solvent were distilled off to afford a resin with a viscosity of T at 66t non-volatiles. Example II Hydroxy functional oligomeric polyester was prepared according to this example. In a suitable reactor 498g triethylene glycol, 719 trimethylol propane. 1979 1,4-cyclohexanedimethanol, 1.83 g Fascat 4100 (trademark; M & Chemicals, Inc.; catalyst), and 0.87g para-toluene sulfonic acid were charged. The mixture was heated to 3000F and water was distilled off until the acid number reached 10.2. The batch was thinned with 148 parts xylene. The temperature was lowered to 2000F and 76g Desmodur W (Trademark; Mobay Chemical Co.; diisocyanate) was added dropwise over a period of 2 hours. After addition was complete. the mixture was postreacted at 2000F until no isocyanate group was observed in an IR spectrum (2270 cm The resin had a T viscosity at 67t non-volatiles. Example XII Hydroxy functional carbon-carbon double bond-bearing branched polyester macromer was made according to this example. In a suitable reactor 700g of the resin from Example XI, 700g xylene. 4.6g Shell 1201 catalyst (trademark; Shell Chemical Cho.), and 0.5g hydroquinone were charged. The mixture was heated to 2000F at which time 43g glycidyl acrylate was added dropwise over a period of 20 minutes. The mixture was postreacted at 2000F until the WPE rose above 1800. The final resin had a viscosity of A at 39S non-volatiles. Example IIII Hydroxy functional polyester graft copolyomer was prepared according to this example. In a suitable reactor were charged 220g xylene and 3.6g cumene hydroperoxide. The temperature was raised to 270"F and a mixture of 846g of the resin from Example XII. 121g butyl methacrylate, 12g hydroxypropylmethacrylate. 25g methyl methacrylate. and 3.6g t-butylperbenzoate was added dropwise over a period of 5 hours. The mixture was postreacted at 2700F for 2 hours. The temperature was raised to 300"F and solvent was stripped off to afford a final product having viscosity of X at 70% non-volatiles. Example XIV Hydroxy functional oligomeric polyester was prepared according to this example. In a suitable reactor 204g Esterdiol-204 (trademark; Union Carbide Corp.; diol), 66g trimethylol propane. 75g dimethyl-1.4-cyclohexanedicarboxylate. 559 adipic acid and 0.76g Fascat 4100 (trademark; M & Chemicals, Inc.; catalyst) were charged. The mixture was headed to 325"F and water was distilled off until the acid number dropped below 10. The batch was thinned with 180 parts xylene. The temperature was lowered to 1800F and 38g isophorone diisocyanate was added dropwise over a period of 2 hours. After addition was complete, the mixture was postreacted at 2000F until no NCO group was observed in -an IR spectrum. The resin had a viscosity of S at 69% non-volatiles. Example XV Hydroxy functional carbon-carbon double bond-bearing branched polyester macromer was prepared according to this example. In a suitable reactor 670g of the resin from Example XIV, 700g xylene, 4.6g Shell 1201 catalyst (trademark; Shell Chemical Co.), and 0.5g hydroquinone were charged. The mixture was heated to at at which time 43g glycidyl methacrylate was added dropwise over a period of 15 minutes. The mixture was postreacted at 2000F until the WPE reached 1890. The final resin had a viscosity of A at 40X non-volatiles. Example XVI Hydroxy functional polyester graft copolymer was prepared according to this example. In a suitable reactor 300g Exxate 700 (trademark; Exxon Chemical, oxylheptylacetate solvent), 136g xylene, and 7.2g cumene hydroperoxide were charged. The mixture was brought to reflux (2900F) and a mixture of 17509 of the resin from Example XV, 242g iso-butylmethacrylate, 24g hydroxyethylacrylate. 50g styrene, 20g acrylic acid, and 7.5g t-butylperbenzoate was added dropwise over a period of 5 hours. The mixture was postreacted at 3100F for 2 hours. The temperature was raised to reflux and solvent was distilled off to afford a final resin with a viscosity of Y-Z at 76% non-volatiles. Example XVII Hydroxy functional carbon-carbon double bond-bearing branched polyester macromer was prepared according to this example. Into a suitable reactor were placed 4B5g triethylene glycol, 719 trimethylol propane, 323g dimethyl-1.4-cyclohexanedicarboxylate. 1.759 dibutyl tin oxide. and 0.87g of a paratoluene sulfonic acid solution (40% active in butanol). The mixture was heated to 3S00F and water was distilled off until -the acid number dropped to below 6. The mixture was cooled to 175OF and 200g xylene. 0.7g Shell 1201 catalyst (trademark; Shell Chemical Co.), and 0.07g hydroquinone were added. To this solution was added dropwise over a period of 15 minutes 73.7g glycidylmethacrylate. The mixture was postreacted at 2100F until the WPE rose above 1500. The resin obtained had a viscosity of A at 62.2S non-volatiles. Example XVIII Into a suitable reactor was charged 340g xylene and 5.2g cumene hydroperoxide. This solution was heated to 2800F. at which time dropwise addition of a mixture of 700g of the resin from Example XVII, l8Bg butylmethacrylate. 199 hydroxypropylmethacrylate, 399 methyl methacrylate and S.2g t-butylperbenzoate was begun. The time of addition was 5 hours. After addition was complete the mixture was postreacted for 2 hours at 2800F. The resin was then stripped of solvent to afford a resin with a viscosity of Q at 74% non-volatiles. ExamPles XIX-XXIV One and two component coatings within the scope of the invention. useful as the clear coat of a base/clear automotive coating system were formulated according to the compositions shown in Table A. The order of addition was as follows. In the case of one component coatings formulated with Cymel 1130, the resin was mixed with n-butylacetate, a W stabilizer/absorber package, butyl acrylate, methyl amyl ketone. and Tetralin. This mixture was added to a premixed solution of Cymel 1130. blocked acid catalyst, cellosolve acetate, and xylene. The viscosity of the coating was adjusted to 20 sec *4 Ford Cup (800F) with xylene. In the case of two component coatings formulated with an organic polyisocyanate, the resin was mixed with n-butyl acetate. a UV stabilizer/absorber package, butyl acrylate, methyl amyl ketone. and Tetralin. To this mixture the polyisocyanate, predissolved in xylene and cellosolve acetate. was added just before spraying. The viscosity of the coatings was adjusted to 22 sec *4 Ford Cup (80 F) with xylene. TABLE A EXAMPLE COMPOSITION XIX XX XXI XXII XXIII XXIV Resin of Example V 60.8 60.8 60.8 Resin of Example VI 72.3 72.3 72.3 n-butyl acetate 7.2 7.2 7.2 7.2 7.2 7.2 UV stabilizer/absorber packageÚ 13.8 13.8 13.8 13.8 13.8 13.8 Polybutyl acrylate 0.96 0.96 0.96 0.96 0.96 0.96 Methyl amyl ketone 18.18 18.18 18.18 18.18 18.18 18.18 Tetralinê 12 12 12 12 12 12 Xylene 14 14 14 14 14 14 Cellosolve Acetate 1 1 1 1 1 1 Blocked acid catalyst5 0.85 0.85 Cymel 1130 14.1 14.1 14.1 Desmodur L-22-14 22.8 22.8 Desmodur N-33904 22.8 22.8 1. Solution of 25 parts TIN 079L, 8 parts TIN 900, 7 parts TIN 328 (trademarks; Ciba-Geigy) and 60 parts xylene. 2. 1, 2, 3, 4-tetrahydronaphthalene. 3. Trademark; American Cyanamid Company; hexamethoxymelamine crosslinking agent. 4. Trademark; Mobay Chemical Corporation; polyisocyanate crosslinking agent. 5. Nacure 2500X (trademark; King Industries). Examples XXV-XXXII Additional clear coat compositions were formulated as shown in Table B. The components are shown in the order of addition. The compositions were reduced to 22 sec &num;4 Ford Cup (BOOF) with a 60/40 (w/w) blend of Exxate 600 (trademark; Exxon Chemical Co.; solvent) and butyl acetate. TABLE B EXAMPLE COMPOSITION XXV XXVI XXVII XXVIII XXIX XXX XXXI XXXII Resin of Example VII 84.6 84.6 Resin of Example XIII 80.9 56.6 Resin of Example X 86.2 60.3 Resin of Example XVI 74.5 52.1 polybutyl acrylate 1.6 0.76 1.7 0.3 1.7 0.3 1.7 .3 TetralinÚ 5.4 5.4 7.0 4 7.0 4 7.0 4 UV absorber/stabilizer packageê 13.9 13.9 14.4 6.9 14.4 6.9 14.4 6.9 xylene 30 26 26 26 stannous octaoate 0.4 0.45 0.45 0.45 microgel flow control additive 2.5 4.6 4.6 4.6 p-toluene sulfonic acid solution (40% w/w in butanol) 1.14 1.14 1.14 1.14 methanol 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 butanol 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 Desmodur N-33904 28 28 28 28 Cymel 11615 12.6 12.6 12.6 12.6 1. 1, 2, 3, 4-tetrahydronaphthalene. 2. Solution of 25 parts TIN 079L, 8 parts TIN 900, 7 parts TIN 328 (trademarks; Ciba-Geigy) and 60 parts xylene. 3. Prepared according to Examples 1-3 of U.S. Patent 4,425,450. 4. Trademark; Mobay Chemical Co.; polyisocyanate crosslinking agent. 5. Trademark; American Cyanamid Company; hexamethoxymelamine crosslinking agent. Example XXXIII An additional clear coat composition was formulated as shown below. The components were added in the order listed. The composition was reduced to 24 sec *4 Ford Cup (800F) with a 60/40 (w/w) blend of butyl acetate and Exxate 600 (trademark; Exxon Chemical Co.; solvent). 128 gms resin from Example XVIII 22.5g n-butanol 4.5g methanol lOg Tetralin 17.3g UV stabilizer/absorber pkg (See Examples XXlV-XIX) 31.5g Cymel 1130 (trademark; American Cyanamid) 0.75g polybutylacrylate 2.8g p-toluene sulfonic acid solution (40t solution in butanol) 5.5g Acryloid B-82 (trademark; Rohm & Haas Co.) solution (25t in xylene). Examples XXXIV-XXXV Coating compostions according to the invention, specifically, pigmented basecoat compostions adapted for use in a basecoat/clearcoat automotive topcoat system were prepared according to the formulations shown in Table C. The components were admixed in the order listed. The viscosity was reduced to 18 sec *4 Ford Cup (800F) with methyl amyl ketone before spraying. TABLE C EXAMPLE COMPOSITION XXXIV XXXV Resin of Example VI 139.8 Resin of Example X 125 Spenlite LO-6;3051 19.2 19.2 Cymel 11302 52.4 52.4 Cymel 11612 35.2 35.2 Tinuvin-3283 9.6 9.6 PTSA (40s) 2.0 2.0 5000-AR4 123 123 Microgel flow control additive5 96 96 Esterdiol-2046 46 46 cellosolve acetate 19.2 19.2 aluminum stearate 96 96 xylene 15.4 15.4 isopropanol 15.4. 15.4 1. Trademark; Spencer-Kellog, Buffalo, N.Y.; linear polyurethane modifying agent for aluminum pigment orientation. 2. Trademark; American Cyanamid Co., Wayne. N.J.; alkylated melamine crosslinking agent. 3. Trademark; Ciba-Geigy; U.V. absorber. 4. Trademark; Silberline, Lansford. PA.; aluminum paste. S. Prepared according to Examples 1-3 of U.S. Patent 4,425,450. 6. Trademark; Union Carbide Corp.; diol. Examples XXXVI-XXXVII One component enamel compostions were formulated according to the compositions shown in Table D. The order of addition was as follows: The designated resin was mixed with Cymel 1168 (trademark) and Cymel 1130 (trademark) and diluted with denatured ethanol. To this mixture was added a mixture of Bentone 27 gel (trademark; NL Industries; see Example LXVII), the microgel flow control additive and Modarez TMF 25 (trademark; Synthron Corp.) flow control additive. The blocked/unblocked acid catalyst mixture was added followed by the addition of the pigment dispersions. Finally, pine oil and oxvl-hexyl acetate were added and the viscosity of the paint was adjusted to 27 sec &num;4 Ford Cup (BO-F) with Solvesso 100. Bonderite steel panels and plastic panels were sprayed and baked at 250"F for 30 minutes to afford smooth, tough films with excellent flexibility and MEK resistance. TABLE D EXAMPLE COMPOSITION XXXVI XXXVI I Resin of Example ZIII 3497 4071 Cymel 11681 265 555 Cymel 11301 680 537 ethanol 80 80 Bentone 27 gel 2 650 650 Modarez TMF 258 9 9 Microgel flow control additive3 350 350 acid catlyst 450 450 blocked acid catalyst 180 180 Tipure R960HG4 2178 217e yellow iron oxide5 20 20 transparent red iron oxide6 1 1 Cabot Black Pearls 13007 3 pine oil 150 150 oxyl hexyl acetate 150 150 1. Trademark; American Cyanamid Co.; alkylated melamine crosslinking agents. 2. Prepared according to Example LXVII. 3. Prepared according to Examples 1-3 of U.S. Patent 4,425,450. 4. Trademark; E. I. duPont deNemours & Co., Wilmington. Delaware; pigment. 5. Pfizer Chemical Co. 6. Hilton Davis Co. 7. Trademark; Cabot Co.; pigment. 8. Trademark; Synthron Corp.; flow control additive. Examples XXXVIII-LI Base coat/clear coat coating systems according to the present invention were prepared according to these examples. Specifically, the one component base coats and one component clear coats identified in Table E were applied by spraying over metal and plastic substrates. The coatings were cured at 250at for 30 minutes and then tested for flexibility. resistance to methyl ethyl ketone. and resistance to ultra violet light degradation. The test results are shown in Table E. TABLE E One Component Base Coat/One Component Clear Coat Example XXXVIII XXXIX XL XLI XLII XLIII XLIV XLV XLVI XLVII XLVIII XLIX L LI Basecoat of Example XXXIV XXXIV XXXIV XXXIV XXXIV XXXIV XXXIV XXXV XXXV XXXV XXXV XXXV XXXV XXXV Clearcoat of Example XXXIII XXI XXII XXVI XXVIII XXX XXXI XXXIII XXI XXII XXVI XXVIII XXX XXXII Percent elongation 90 70 80 80 75 75 70 80 65 75 75 65 65 60 MEK Resistance good exc exc exc good exc exc exc good exc exc good good good (100 rubs) QUV (1000 hrs.) good exc exc exc good exc exc exc good exc exc good good good 1. "Exc" means: excellent. Examples LI I-LXVI I Base coat/clear coat coating systems according to the present invention were prepared according to these examples. Specifically. the one component base coats and two component clear coats identified in Table F were applied by spraying over metal and plastic substrates. The coatings were cured at 2500F for 30 minutes and then tested for flexibility, resistance to methyl ethyl ketone, and resistance to ultra violet light degradation. The test results are shown in Table F. TABLE F One Component Base Coat/One Component Clear Coat Example LII LIII LIV LV LVI LVII LVIII LIX LX LXI LXII LXIII LXIV LXV LXVI LXVII Basecoat of Example XXXIV XXXIV XXXIV XXXIV XXXIV XXXIV XXXIV XXXIV XXXIV XXXV XXXV XXXV XXXV XXXV XXXV XXXV Clearcoat of Example XIX XX XXIII XXIV XXV XXVII XXIX XXXI XIX XX XXIII XXIV XXV XXVII XXIX XXXI Percent elongation 90 110 120 130 100 95 95 90 85 100 110 110 90 80 85 80 MEK Resistance exc exc exc exc exc exc exc exc exc exc exc exc exc exc exc exc (100 rubs) QUV (1000 hrs.) exc exc exc exc exc exc exc exc exc exc exc exc exc exc exc exc Example SXVIII The organo-clay dispersion employed in certain of the above examples. identified as Bentone 27 gel. was prepared by mixing together in the following order: xylene 686.9 Bentone 27 36.g propylene carbonate 12.g Resimene 7172 240.g 1. Trademark; National Lead Co.; quaternary ammonium bentonite complex. 2. Trademark; Monsanto Chemical Cho. ; alkylated melamine. Industrial Applicability It will be apparent from the foregoing that this invention has industrial applicability as a protective coating. for example on rotor vehicle body panels. and for like applications and provides a flexible. durable coating for metal. plastic and other substrates.

Claims: CLkIMS: 1. Hydroxy functional polyester graft copolymer suitable for flexible, thermosetting coating compositions over metal and plastic substrates, which copolymer has number average molecular weight between about 1.000 and about 15,000, has a hydroxyl number between about 30 and about 300. and is the reaction product of carbon-carbon double bond-reactive monoethylenically unsaturated monomer with hydroxy functional carbon-carbon double bond-bearing branched polyester macromer, under free radical polymerization reaction conditions, said monomer bearing substantially no functionality which is substantially reactive with hydroxy functionality of said macromer under said reaction conditions and said macromer being the reaction product of (i) epoxy acrylate having the formula: : EMI47.1 wherein R is hydrogen or C1 to about C7 alkyl. and R' is C1 to about C7 alkyl or COO(CH2)D, n being 0 to about 7. with (ii) hydroxy functional polyester having about 0-10 urethane groups per molecule. 2. The hydroxy functional polyester graft copolymer of claim 1, wherein said epoxy acrylate is selected from the group consisting of glycidyl acrylate, glycidyl methacrylate and a mixture thereof. 3. The hydroxy functional polyester graft copolymer of claim 1. wherein said epoxy acrylate and said hydroxy functional polyester are reacted in approximately 1:1 molar ratio. 4. The hydroxy functional polyester graft copolymer of claim 1, wherein said carbon-carbon double bond-reactive monoethylenically unsaturated monomer consists of acrylate monomers selected from the group consisting of alkylacrylate, alkyl methacrylate, hydroxyalkylacrylate, hydroxyalkyl methacrylate and mixtures thereof. wherein each alkyl and hydroxyalkyl moiety has one to about seven carbons. 5. The hydroxy functional polyester graft copolymer of claim 1. wherein said carbog-carbon double bond-reactive monoethylenically unsaturated monomer consists of monomers selected from the group consisting of acrylic acid, methacrylic acid. styrene, methylacrylate. ethylacrylate, propylacrylate, butylacrylate, methylmethacrylate, ethylmethacrylate, propylmethacrylate, butylmethacrylate, hydroxyethylacrylate, hydroxypropylacrylate. hydroxybutylacrylate. hydroxyethylmethacrylate. hydroxypropylmethacrylate. hydroxybutylmethacrylate. and any mixture thereof. 6. The hydroxy functional polyester graft copolymer of claim 1, wherein said hydroxy functional polyester comprises the reaction product of dicarboxylic acid with polyol comprising at least about 5 percent by weight triol. said dicarboxylic acid being selected from the group consisting of saturated and unsaturated. cyclic and acyclic aliphatic dicarboxylic acids and aromatic dicarboxylic acids suitable anhydrides thereof. and mixtures thereof. 7. The hydroxy functional polyester graft copolymer of claim 6, wherein said dicarboxylic acid is selected from the group consisting of substantially saturated, acyclic. aliphatic dimer acids of about 6-36 carbons. 8. The hydroxy functional polyester graft copolymer of claim 6, wherein said dicarboxylic acid is selected from the group consisting of adipic acid, azelaic acid, sebasic acid, dodecane dicarboxylic acid. phthalic anhydride and any mixture thereof. 9. The hydroxy functional polyester graft copolymer of claim 6, wherein said polyol comprises diol and triol in hydroxy equivalent ratio of from about 4:1 to about 1:4. 10. The hydroxy functional polyester graft copolymer of claim 9, wherein said triol is selected from the groups consisting of trimethylol propane, polycaprolactone triol. and any mixture thereof. 11. The hydroxy functional polyester graft copolymer of claim 9, wherein said diol is aliphatic diol of the general formula HO - R - OH wherein R is a divalent, aliphatic, linking moiety substantially unreactive with said dicarboxylic acid. 12. The hydroxy functional polyester graft copolymer of claim 11, wherein said aliphatic diol has a molecular weight of about 60-500 and is selected from the group consisting of trimethylene glycol. triethylene glycol. 1,4-cyclohexane dimethanol, alkyl substituted or unsubstituted propanediol, butanediol, pentanediol and hexanediol, and a mixture of any of them. 13. The hydroxy functional polyester graft copolymer of claim 9. wherein said diol is selected from the group consisting of alkyl glycol of about 2-7 carbons. and any mixture thereof. 14. The hydroxy functional polyester graft copolymer of claim 6, wherein said hydroxy functional polyester is urethane modified, said polyol comprising the reaction product of organic diisocyanate with polyhydroxy reactant. 15. The hydroxy functional polyester graft copolymer of claim 14, wherein said diisocyanate is selected from the group consisting of phenylene diisocyanate, biphenyl diisocyanate, toluene diisocyanate, isophorone diisocyanate. 3,3'-dimethyl-4,4'-biphenylene diisocyanate, diisocyanatoalkane wherein the alkane moiety has about three to about ten carbons. and a compatible mixture of any of them. 16. The hydroxy functional polyester graft copolymer of claim I. wherein said hydroxy functional polyester is urethane modified, comprising the reaction product of organic diisocyanate with the reaction product of dicarboxylic acid with polyol comprising at least about 5 percent by weight triol. said dicarboxylic acid being selected from the group consisting of saturated and unsaturated, cyclic and acyclic aliphatic dicarboxylic acids. aromatic dicarboxylic acids, suitable anhydrides thereof, and any mixture thereof. 17. The hydroxy functional polyester graft copolymer of claim 16, wherein said dicarboxylic acid is selected from the group consisting of substantially saturated, acyclic, aliphatic dimer acids of about 6-36 carbons. 18. The hydroxy functional polyester graft copolymer of claim 16, wherein said dicarboxylic acid is selected from the group consisting of adipic acid. azelaic acid, sebasic acid, dodecane dicarboxylic acid and any mixture thereof. 19. The hydroxy functional polyester graft copolymer of claim 16, wherein said polyol comprises diol and triol in hydroxy equivalent ratio of from about 4:1 to about 1:4. 20. The hydroxy functional polyester graft copolymer of claim 19, wherein said diol has molecular weight of about 60-500 and is selected from the group consisting of trimethylene glycol, triethylene glycol. 1,4-cyclohexane dimethanol, alkyl substituted or unsubstituted propanediol, butanediol, pentanediol and hexanediol, and a mixture of any of them. 21. The hydroxy functional polyester graft copolymer of claim 19, wherein said triol is selected from the group consisting of trimethylol propane. polycaprolactone triol. and any mixture thereof. 22. Hydroxy functional carbon-carbon double bond-bearing branched polyester macromer consisting of the reaction product of reactants comprising (i) epoxy acrylate having the formula: EMI51.1 wherein R is hydrogen or C1 to about C7 alkyl. and R' is C1 to about C7 alkyl or COO(CH2)n, n being 0 to about 7. with (ii) hydroxy functional polyester reactant having about 0-10 urethane groups per molecule. 23. The hydroxy functional carbon-carbon double bond-bearing branched polyester macromer of claim 22, wherein said hydroxy functional polyester reactant comprises oligomeric polyester having a number average molecular weight between about 1,000 and about 10,000 and a hydroxyl number between about 30 and about 300. 24. The hydroxy functional carbon-carbon double bond-bearing branched polyester macromer of claim 22. wherein said epoxy acrylate consists of glycidyl acrylate. glycidyl methacrylate or a mixture thereof. 25. The hydroxy functional polyester graft copolymer of claim 16, wherein said diisocyanate is selected from the group consisting of phenylene diisocyanate, biphenyl diisocyanate. toluene diisocyanate, isophorone diisocyanate. 3,3'-dimethyl-4,4f-biphenylene diisocyanate, diisocyanatoalkane wherein the alkane moiety has about three to about ten carbons, and a compatible mixture of any of them. 26. A solvent based flexible coating composition, useful as an automotive coating on metal and plastic substrates, comprising: A) hydroxy functional polyester graft copolymer of number average molecular weight between about 1,000 and about 15,000. having a hydroxyl number between about 30 and about 300, and being the reaction product of carbon-carbon double bond-reactive monoethylenically unsaturated monomer with hydroxy functional carbon-carbo double bond-bearing branched polyester macromer. under free radical polymerization reaction conditions, said monomer bearing substantially no functionality which is substantially reactive with hydroxy functionality of said macromer under said reaction conditions, which macromer is the reaction product of (i) epoxy acrylate having the formula: : EMI53.1 wherein R is hydrogen or C1 to about C7 alkyl, and R' is C1 to about C7 alkyl or COO(CII2)n, n being 0 to about 7, with (ii) hydroxy functional polyester having about 0-10 urethane groups per molecule; and B) polyfunctional. hydroxy-reactive crosslinking agent selected from aminoplast crosslinking agent. polyisocyanate crosslinking agent. blocked polyisocyanate crosslinking agent comprising at least two isocyanate groups blocked by reaction with active hydrogen bearing blocking agent. arid a compatible mixture of any of them. said crosslinking agent being included in an amount sufficient to provide. at a cure temperature of said composition, between about 0.5 and about 1.6 hydroxy reactive groups per hydroxy group contributed by said hydroxy functional polyester graft copolymer. 27. A solvent based. one component, high solids enamel topcoat. adapted for application as a flexible coating on metal and plastic substrates, comprising: A) hydroxy functional polyester graft copolymer of number average molecular weight about 1.500 - 3,000, having a hydroxyl number between about 50 and about 150 and about 1-7 urethane linkages per molecule, and being the reaction product of carbon-carbon double bond-reactive monoethylenically unsaturated monomer with carbon-carbon double bond-bearing branched polyester macromer under free radical polymerization reaction conditions, said monomer bearing substantially no functionality which is substantially reactive with hydroxy functionality of said macromer under said reaction conditions, said macromer being the reaction product of glycidyl methacrylate with hydroxy functional oligomeric polyester; and (B) alkylated melamine crosslinking agent. said crosslinking agent being included in an amount sufficient to provide between about 0.5 and about 1.6 hydroxy reactive group per hydroxy group of said polyester graft copolymer.

Inventors: KORDOMENOS, PANAGIOTIS I., RYNTZ, ROSE ANN
Applicants: E.I. DU PONT DE NEMOURS AND COMPANY
Application year: 1986
Main classification: C08F283
IPC codes: C09D151, C08F283, C08F299, C08G18