Document NEMXxv7o3rQYZ89gVeLynNQoD

United States Patent iw] Troy [ii] Patent Number: 4,590,235 [45] Date of Patent: May 20, 1986 [54] DUAL-LAYEH COATING CONTAINING ALUMINUM-FLAKE PIGMENT AND COATED ARTICLE [75] Inventor: Daniel J. Troy, Wilmington, Del. [73] Assignee: E. I. Du Pont de Nemours and Company, Wilmington, Del. [21] Appl. No.: 721,215 [22] Filed: Apr. 8,1985 [63] Related U.S. Application Data Continuation of Ser. No. 612,658, May 21, 1984, aban doned, which is a continuation of Ser. No. 420,510, Sep. 20, 1982, abandoned, which is a continuation-inpart of Ser. No. 80,084, Sep. 28, 1979, Pat. No. 4,359,504. [51] Int. CL4...........................C08K 3/08; C08K 5/56; C08K 7/06; C08K 5/07 [52] U.S. Cl. ....................................... 524/439; 524/88; 524/364; 524/512; 524/523; 524/539; 524/560; 524/604 [58] Field of Search............... 524/439, 441, 512, 539, 524/604 [56] References Cited U.S. PATENT DOCUMENTS 3,932,347 1/1976 Camelon et al........................ 524/441 3,941,731 3/1976 Camelon et al........................ 524/441 Primary Examiner--Herbert J. Lifiing Attorney, Agent, or Firm--Donald W. Huntley [57] ABSTRACT A high-solids enamel coating on a substrate can give metallic glamor comparable to that imparted by con ventional lacquer coatings containing metallic-flakes when the amount of metallic flake pigment in the enamel coating composition is increased over conven tional amounts with a proportional increase in the amount of chromatic pigments. 7 Claims, No Drawings N36788 4,590,235 12 having a weight-average molecular weight of DUAL-LAYER COATING CONTAINING 500-10000; and ALUMINUM-FLAKE PIGMENT AND COATED (2) a solvent for the binder constituents in an amount ARTICLE of no more than 100% by weight of the binder, CROSS REFERENCE TO RELATED APPLICATIONS 5 wherein the improvement is characterized in that the metallic-flake pigment is present in the base layer in an amount of 6-24% by weight, based on the weight of the This is a continuation ofapplication Ser. No. 612,658, binder constituents of the base layer, and the chromatic filed May 21,1984, now abandoned, which is a continu pigment is present in an amount sufficient with the ation of application Ser. No. 420,510, filed Sept. 20, 10 amount of the metallic-flake pigment to give the dual 1982, now abandoned, which is a continuation-in-part of layer coating a flake orientation index of at least 40. U.S. application Ser, No. 080,084, filed Sept. 28, 1979, now U.S. Pat. No. 4,359,504. DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THIS INVENTION 15 The improved dual-layer, high solids, pigmented 1. Field 6f The Invention coating composition of this invention achieves metallic This invention is related to dual-layer high-solids glamor of a high quality which has heretofore not been enamel coating systems containing aluminum-flake pig produced in high-solids enamel systems. Metallic ment which, when applied to a substrate and dried, glamor is seen to an observer examining a coated sub result in coatings having excellent metallic glamor. 20 strate as a progressive darkening of the apparent color 2. Description Of The Prior Art as the observer's viewing angle shifts from the normal. Metallic glamor in the coating art refers to the prop This effect results from an orientation of a great major erty of a metallic-pigmented coating that causes the ity of the metallic flakes in the coating to positions intensity of light reflected from idle coated substrate to within very small angles of the coating surface. vary markedly according to the angle from which it is 25 It is well known in the art that this preferred flake observed. This aesthetic property, which is particularly orientation is largely produced by shrinkage of the coat desired in automotive finishes, is largely the result of a ing in a direction normal to the substrate that occurs as non-random orientation of the metallic flakes in the the volatile components of the coating composition dried coating, with most of the flakes positioned practi cally parallel to the coating surface. Heretofore, such orientation has been normally achieved only with lowsolids lacquer or enamel coating systems which, al though of excellent quality, have relatively high solvent 30 evaporate. In conventional solution lacquer systems, for example, this shrinkage accounts for a 66% loss in thick ness during solvent evaporation. In high-solids enamel systems, defined for purposes of this invention as coat content. Coating compositions in which the solvent ings containing no more than 50% by weight of solvent, content is low, usually 50% by weight of the composi 35 based on binder and solvent, the shrinkage can be as low tion or less, are normally enamel systems. These high- as 28%, and the desired leveling action on the flake is solids enamel systems, however, have been unable to diminished. achieve high-quality metallic glamor. The current envi Metallic-flake pigments are usually present in coating ronmental emphasis on solvent reduction highlights the compositions in an amoupt of about 0.5-2.5% by continued need for a high-solids coating system which 40 weight, based on the weight of the binder. Automotive provides metallic glamor comparable to that of the lacquer systems. topcoats, for example, also have a significant amount of chromatic pigment, the amount often varying accord ing to the desired color. The usual levels of flake pig SUMMARY OF THE INVENTION mentation, however, have been unable to reproduce the The present invention provides an article having a 45 metallic glamor in high-solids enamels that has been substrate coated with an improved dual-layer high-sol achieved with lacquer coatings or low-solids enamels. It ids enamel coating of the kind wherein the coating has now been found, however, that high-solids enamel comprises coating systems of the kind having a pigmented base (A) a cured base layer produced from a composition layer overlaid with an unpigmented top layer can having 50 achieve the desired metallic glamor when the amounts (1) binder constituents consisting essentially of a first of both metallic-flake pigment and chromatic pigment film-forming material and a crosslinker for the in the base layer are increased by a factor of about 3-15 film-forming material wherein the film-forming over the amounts of such pigments normally used in a material is selected from the group consisting of particular metallic color system. acrylic resins, polyester resins, and alkyd resins 55 The present invention contemplates that the metallic having a weight-average molecular weight of flake be present in the pigmented base layer in an 500-10000; amount of about 6-24% by weight, based on the weight (2) a solvent for the binder constituents in an amount of the binder of the base layer. Preferably 10-20% by of no more than 100% by weight ofthe binder; and weight of flake is present. To impart the desired metal (3) chromatic and metallic-flake pigments; 60 lic glamor, the chromatic pigments must be present in and (B) a cured transparent top layer, deposited on said base an amount sufficient to hide the substrate with a color intensity that can appear dark enough, at viewing angles layer, produced from a composition having shifted from the normal, to provide the necessary con (1) binder constituents consisting essentially of a sec trast. Usually the chromatic pigment is present in the ond film-forming material and crosslinker for the 65 base layer in this invention in an amount of 0.5-85% by film-forming material wherein the film-forming weight based on the weight of the binder of the base material is selected from the group consisting of layer. The exact amount depends somewhat on the acrylic resins, alkyd resins, and polyester resins degree of transparency of the coating at various load- DUP050302148 4,590,235 ings of the chromatic pigment, which is in turn depen containing 16-20% by weight of aluminum flake and dent on the color of the pigment. about 5% by weight of blue chromatic pigment (both Metallic glamor can be objectively measured with a based on weight of binder of pigmented base layer), special goniophotometer using the following geometri exhibits a flake orientation index of 49. This coating has cal arrangement. A coated test panel is positioned hori- 5 the same binder composition and binder-solvent ratio as zontally within the goniophotometer with the coated the above conventional high-solids enamel, but the pig side facing up. The light from a circular, concentrated mentation level, flake and chromatic in the base layer is light source is collimated by a lens and is directed to strike the panel at a small angle, typically 22.5, from the normal. The light beam reflected from the surface of the panel is directed by a second lens, at unity magnifi cation, through a circular aperture having approxi i0 increased by a factor of 12. The metallic-flake pigments used in the present in vention can be any of the conventional flat metallic flakes. Examples are aluminum flakes, nickel flakes, tin mately the same diameter as the light source. A photo flakes, silver flakes, chromium flakes, stainless steel cell is positioned at a distance of about 6-10 aperture flakes, gold flakes, copper flakes, or combinations of diameters behind the aperture and is of sufficient size to 15 these. Preferred are aluminum flakes of the kind de intercept all light reflected from the panel through the scribed, for example, in U.S. Pat. No. 2,662,027. aperture. The panel can be rotated to different viewing The chromatic pigments can be any of the conven angles about an axis that is defined as the intersection of tional pigments used in coating compositions. Examples the plane of the panel and the plane defined by the beam are iron oxide; metal hydroxides; sulfides; sulfates, car of light incident to and reflected from the panel in its 20 bonates; carbon black; phthalocyanine blues and greens; original horizontal position. It has been found particu organo reds, and other organic dyes. larly useful to measure the intensity of the reflected The pigments, both chromatic and metallic-flake, can light at two different panel positions, when the panel be introduced into the coating composition by first has been rotated to positions of +10 and -|-60 from its forming a pigment concentrate or mill base with the initial horizontal position. 25 film-forming resin, or with polymers compatible with The goniophotometer gives unitless numerical read the film-forming resin, used in the binder of the base ings known as luminous reflectance (G) for each angle layer. The metallic-flake pigment concentrate or mill from which the panel is viewed. The photocell is cali base is preferably prepared by prolonged stirring with brated, with respect to the light source, to indicate a the polymeric portion of the concentrate or mill base. luminous reflectance of 100 for a nonmetallic, mattesurfaced, perfect white viewed at any angle setting. Nonmetallic coatings gives equivalent reflectance read ings from any angle of view. In a coating having good metallic glamor, the reflec tance measured at 10 will be greater than that mea 30 The chromatic pigment concentrate or mill base can be formed by conventional techniques such as sand grind ing, ball milling, attritor grinding, or two-roll milling, to disperse the pigment in the vehicle. The pigment con centrate or mill base is then blended with the binder sured at 60. The reflectance at a given angle A is 35 material in amounts appropriate to give the desired related to another visual characteristic known as light pigmentation levels. ness (L) through the equation The binder constituents of the two layers of the dual- layer enamel coating can be the same or different. Al /( )=2S.29G(^*)i--18.83 though the improvements of the present invention, im- 40 parted by the higher levels of metallic-flake pigments, Goniophotometry, reflectance, and lightness are gener would be evident in any binder system (film-forming ally explained in The Measurement ofAppearance, Hun resins and cross-linker), it is preferred that the binder ter, R. S., John Wiley and Sons, New York 1975. systems have film-forming resins selected from the An objective characterization of the metallic glamor, group of acrylic, alkyd, and polyester resins. the flake orientation index (F.O.I.), is in turn expressed 45 The acrylic resins useful as the film-forming resins in as a function of the lightness of the coating at 10" and this invention are hydroxyl-functional copolymers hav 60, The mathematical expression is ing a weight average molecular weight of about 500-10000 determined by gel permeation chromatogra L 2f .o .i = 10 [too-) - <)]/ f t/un + z.(6oi phy. The copolymers are primarily of alkyl methacry 50 lates and hydroxyalkyl acrylates or methacrylates, but may contain other monomers copolymerizable there with. The denominator of this expression is a normalizing The alkyl methacrylates useful in such resins contain tvearl.muesef-mopr iarilcl acollyatidnegtserhmavininegd to the produce equal F.O.I. same metallic glamor, 55 1-18 carbon _a_to. ms in..th.e alkyl group. Typical _a_re regardless ofthe color of the coating. It accounts for the .. J*. ' . * ' color intensity of the coating and the ability of the coat rylate, hexyl methacrylate, 2-ethylhexyl methacrylate, ing to hide the substrate, both dependent on the amount nonyl methacrylate, lauryl methacrylate, stearyl meth of chromatic pigment. An index of at least 40, prefera acrylate, cyclohexyl methacrylate, isodecyl methacry- bly 45, is desirable. 50 late, propyl methacrylate, phenyl methacrylate, and By way of comparison, commercial solution lacquer isobomyl methacrylate. systems that have visually acceptable metallic glamor The hydroxy-functional monomers useful in the co exhibit an F.O.I. of about 50. When the same flake-to- polymer are hydroxy-alkyl esters of acrylic or meth- binder and chromatic pigment-to-binder weight ratios acrylic acid having 2-10 carbon atoms in the alkyl as used in this lacquer system are used in a conventional 65 group. Preferred, however, are esters having 2-4 car- high-solids enamel system, the coating exhibits an unac bon atoms in the alkyl group with the hydroxyl group in ceptably low F.O.I. of 29. A most preferred embodi the beta position. Examples are 2-hydroxy ethyl acry ment of the present invention, a blue metallic coating late, 2-hydroxy propyl acrylate, 2-hydroxy butyl acry- DUP050302149 4,590,235 56 late, 2-hydroxy ethyl methacrylate, 2-hydroxy propyl The polybasic acids that are used generally are dicar- methacrylate, and 2-hydroxy butyl methacrylate. boxylic acids having the general formula The other monomers that can be copolymerized with the alkyl methacrylates and hydroxy-alkyl acrylates and methacrylates to form copolymers useful in this inven 5 tion. are vinyl acetate; olefins such as ethylene, propy oo II II HO--C--R--C--OH lene, and the like; conjugated dienes having 4-10 carbon atoms; aromatic hydrocarbons having vinylene groups, wherein R is alkylene, vinylene, aromatic, carboxylic, such as styrene; alkyl maleates; and alkyl esters of or heterocyclic. Anhydrides or dialkyl esters of these acrylic acid having 2-18 carbon atoms in the alkyl 10 acids can also be used. Examples of such acids are glu- group. Small amounts of ethylenically unsaturated car taric, adipic, pimelic, succinic, maleic, itaconic, boxylic acids can also be present, such as acrylic acid, phthalic, isophthalic, terephthalic, cumidic, hexahydro- methacrylic acid, crotonic acid, maleic acid, itaconic phthalic, tetrahydroththalic, and the like. acid, and the like. The polyols that can be used are, for example, any of Crosslinking agents used with the hydroxyl-func 15 the various diols such as ethylene glycol; propylene tional copolymers can be aminoplast resins or organic glycol; 1,3 propane diol; 1,2-butanediol, 2,3 butane diol; polyisocyanates. Preferred ate aminoplasts such as al- and 1,4 butanedipl. Triols, such as glycerine, or other koxymethyl melamines, higher functional alcohols can also be used. The diols The aminoplasts are the alkylated products of amino are preferred. resins, the latter prepared by the condensation of at least 20 The crosslinker used with these alkyd resins can be one aldehyde with at least one of urea, N,-N'- any of the aminoplasts or organic polyisocyanates de ethyleneurea, dicyandiamide, and an aminotriazine such scribed earlier. As with the acrylic resins, from about as a melamine or a guanamine. Among the aldehydes 5-50% by weight of the crosstinker, based on the com that can be used are formaldehyde and its revertable bined weights ofthe crosslinker and alkyd resin, ae used polymers, acetaldehyde, crotonaldehyde, and acrolein. 25 in the enamel compositions. The preferred aminoplasts are formed by alkylating Either or both layers of the dual-layer enamel coating the amino resins with from one to six aikanol molecules, of this invention can be produced from a polyester each containing 1-6 carbon atoms. The alkanols can be film-forming material also. Polyester resins used herein straight-chain, branched, or cyclic. The most preferred are prepared by the condensation reaction of polybasic members of this class are the methylated melamine-for 30 acids and polyols. The weight-average molecular maldehyde resins such as hexamethoxymethylmela- weight of these resins, which can be prepared by any of mine. The organic polyisocyanates that can be used as the the conventionally known processes for polyester pro duction, should be about 500-10000, as determined by crosslinker include aliphatic, cycloaliphatic, alkaryl, gel permeation chromatography. aralkyl, heterocyclic, and aryl di- or tri-isocyanates. 35 The polyols used in preparation of the polyesters are Oligomers of these can also be used. Preferred from preferably diols that can be either aliphatic or aromatic. these classes are hexamethylene di-isocyanate or its Suitable diols include ethylene glycol; propylene gly trimer, methylene-bis-(4-cyclohexyl isocyanate), and col; 1,3 propane diol, any of the butanediols; neopentyl isophorone di-isocyanate. glycol; 2,2,4-trimethyl-1,3-pentane diol; 2,2-dietliylpro- The relative amount of cross-linker to film-forming 40 pane-l,3-diok 2-methyl-2-propylpropane-l,3-diol; deca- resin will depend largely on the amount of hydroxyl methylene glycol; dodecamethylene glycol; monoethyl monomer in the copolymer. Normally, however, high ether of glycerine, alpha, beta-alkyl ethers of glycerol, solids enamel compositions have acceptable physical and the like. Triols or other more highly functional and chemical properties when the stoichiometrically polyols can also be used. necessary amount of cross-linker is from 5-50% of the 45 The polybasic acids used are normally dibasic car total binder weight. boxylic acids that are either aliphatic (saturated or not), The alkyd resins which are useful as the film-forming or aromatic. Suitable acids include, for example ma- resins of this invention are well known as including lonic, succinic, glutaric, adipic, pimelic, suberic, azelaic, esterification products having fatty acid or oil constitu sebacic, brasylic, maleic, fumaric, diphenic, tetrachlor- ents. The resins are usually the reaction product of a 50 opbthalic, phthalic, terephthalic, isophthalic, cyclohex fatty acid or its glyceride, a polyol, and a polybasic acid. ane-1,2-dicarboxylic add, p-phenylene diacetic, naph Alternatively, the alcoholosis product of a fatty acid thalene dicarboxytic acid, beta-methyl adipic acid, tri- glyceride and a polyol can first be formed and then methyl adipic acid, and the like. further reacted with a polyol and polybasic acid by Anhydrides, acid chlorides, or dialkyl esters of the well-known methods to produce resins having a weight 55 above acids can also be used. Preferred polyesters are average molecular weight, determined by gel perme formed from both aliphatic and aromatic acids with ation chromatography, of about 500-10000. The alkyd mixtures of polyols. Blends of polyester resins, some resins can be formed from various mixtures of several formed only from polyols and aromatic acids, some different fatty acids, polyols, and polyacids. Formed only from polyols and aliphatic acids, can also The fatty acid glycerides are found in castor oil, de 60 be used. hydrated castor oil, coconut oil, cottonseed oil, peanut Crosslinkers used with the polyester resins can be the oil, tung oil, linseek oil, soya oil, etc. The fatty acids same as those described for the hydroxyl-functional derived from these and like oils are straight-chain acrylic or alkyd systems. monocarboxylic acids having a total of 8 to 12 carbon Although the preferred film-forming resins for use in atoms. The acids can be saturated or mono- or polyun 65 the present dual-layer enamel systems are hydroxyl- saturated. When the acids are unsaturated, derived from functional acrylic, polyester, or alkyd resins, it is to be the so-called drying oils, crosslinking is also effected understood that any conventionally used film-forming through air oxidation. constituents, with appropriate crosslinkers, can be used. DUP050302150 4,590,235 78 For example, resins that are epoxy-functional can be means, but spraying is preferred. The pigmented base used, crosslinked with a diacid, and conversely, resins layer is first applied to a substrate and preferably cured that are acid-functional can be crosslinked with an to a degree sufficient to effect substantia] solvent evapo epoxy resin. Other variations of the resins are also possi ration and crosslinking. Curing is normally carried out ble. 5 by baking or heating the layer for 10-60 minutes at Each of the coating layers of the present dual-layer 50"-200 C. Before baking, it is often preferable to allow enamel system is formed from a high-solids composition the base layer to flash at room temperature, 23" C., for containing at least 50% by weight ofbinder constituents (film-forming resins and crosslinker) based on the com bined weight of binder and solvent. The solvents that 10 up to 15 minutes. This facilitates the flake orientation. The transparent top layer is applied directly over the can be used are typically organic, inert to the binder base layer, preferably after the base layer is cured. It is constituents, and sufficiently volatile to be easily evapo important that the solvents of the transparent top layer rated during the curing process when the film-forming do not attack the base layer. This attack, or strike-in, resins are completing crosslinking. Specific examples can cause the film-forming resins of the two layers to are toluene, acetone, ethyl acetate, methyl isobutyl 15 combine at the layers' interface, and can destroy the ketone, methylethyl ketone, and ethyl alcohol. Any of desired flake orientation in the base layer. As stated the other conventionally used cycloaliphatic or aro above, it is preferably to cure the base layer such that matic hydrocarbons, esters, ethers, ketones, or alcohols crosslinking occurs to a degree sufficient to make the are also suitable. base layer immune to attack from the solvent in the top The coating compositions can be formulated by con 20 layer. ventional means. For example, the acrylic resins useful After the top layer is applied, baking is carried out as in this invention are typically formed by co-polymeriz- with the base layer, with optional flashing ofthe coating ing the monomers in one of the above inert organic before the bake, to completely cure both layers. The top solvents in the presence of a free-radical forming initia tor. The orosslinking agent and mill base, for the pig mented layer, are then blended into the composition. 25 layer not only provides depth to the coating, enhancing the metallic glamor, but also increases the gloss and The coating composition for either layer or both distinctness-of-image over values obtainable if only a layers can optionally contain an ultraviolet light stabi single pigmented layer were used. The metallic glamor lizer, an antioxidant or both. The ultraviolet light stabi is evident, however, even when no transparent top lizer can be present in an amount of 1-20% by weight, 30 layer is used. based on the weight of the binder; the anti-oxidant can The following Example illustrates the invention. be present in an amount of 0.1-5% by weight, based on the weight of the binder. EXAMPLE Typical ultraviolet light stabilizers are benzophe- Control Coating A nones, triazoles, triazines, benzoates, lower alkyl thi- 35 A conventional acrylic solution lacquer can be pre omethylene-containing phenols, substituted benzenes, pared according to Example 1 of U.S. Pat. No. organophosphorous sulfides, and substituted methylene malontriles. Particularly useful are the hindered amines and nickel compounds shown in U.S. Pat. No. 4,061,616 (Dec. 6, 1977). 40 3,823,205, with the exception that the pigment disper sion is made by blending together the following two mill bases: Typical antioxidants are tetra-kis alkylene (di-alkyI hydroxy aryl) alkyl ester alkanes, reaction product of p-amino diphenylamine and glycidyl methacrylate, and alkyl hydroxyphenyi groups bonded through carboalkoxy linkages to a nitrogen atom of a heterocyclic nu 45 cleus containing an imidodicarbonyl group or an imidodithiocarbonyl group. One preferred combination of ultraviolet light stabi lizer and antioxidant is 2-hydroxy-4-dodecyloxy benzophenone or a substituted 2(2'-hydroxyphenyl) benzo- 50 traizole and tetra-kis methylene 3(3',5'-dibutyl-4'- Parts by Weight Mill Base 1. prepared by blending Aluminum Flake Polyinethyl Methacrylate Toluene/Acetone (70/30) 3.2 12.8 25.8 41.8 Mill Base 2, oreoared bv sand grinding Monastral Blue Pigment Polyraethyl Methacrylate Toluene/Acetone (70/30) 0.85 1.45 4.37 hydroxyphenyt) propionate methane. 6.67 The coating compositions for either layer or both layers may optionally contain additives to control rhe ology during and after application ofthe composition to 55 a substrate. Examples of such rheology control agents This lacquer coating has an aluminum flake/binder ratio of 1.5/100 and an aluminum flake/chromatic pig include additives containing fumed silica, such as dis ment weight ratio of 3.75/1.0. The lacquer is thinned to closed in U.S. Pat. No. 4,238,387 to Antonelli et al., and 12% volume solids with a conventional solution lacquer polymer microparticles, such as disclosed in U.S. Pat. thinner and is sprayed onto a primed aluminum panel. Nos. 4,220,679 to Backhouse and 4,180,619 to Mark- m Four coats are applied to the panel, three passes per hlouf. The fumed silica can be present in an amount of coat, allowing a flash oftwo minutes between coats and 1 to 15% by weight, based on the weight of the coating a flash of ten minutes after the last coat is applied. The composition. The polymer microparticles may be pres coating is then baked for 20 minutes at about 155" C. ent in an amount ofat least 10% of the aggregate weight of film-forming polymer and polymer microparticles. 65 Control Coating B Combinations of such additives may also be used. A pigmented high-solids enamel coating is prepared The coating composition of each layer of this inven by conventional means to have the following final com tion can be applied to a substrate by any well-known position: DUP0503021 4,590,235 9 10 coats, two passes per coat, allowing a flash of two min Acrylic Polymer Solution, prepared by conventional means, wherein the polymer solution has a weight solids content of 74%, the polymer is a copolymer of methyl methacrylate, n-butyl acrylate, and 2-hydroxyethyl acrylate having a weight average molecular weight of 3000 and a glass transition temperature of -10 C. Hexamethoxymethylmebraine Methylethyi Ketone Aluminum Flake Figment Monastra! (E^BIue Pigment Parts by Weight 70 30 107.6 1.23 0.33 209.16 utes between coats and a flash of fifteen minutes after the last coat is applied. The coating is then baked for thirty minutes at 71" C. and for thirty additional minutes 5 at 163" C. The flake orientation index of the coatings on each of the three panels is determined using a gonicphotometer as previously described. Control Coating A (a solution lacquer with conventional pigmentation levels) exhibits 10 a flake orientation index of 52. Control Coating B (a high-solids enamel with conventional pigmentation levels) exhibits an index of 29. The dual-layer high-sol ids enamel having pigmentation levels within the range of the present invention exhibits a flake orientation 15 index of 49. I claim: 1. In a high-solids enamel coating composition having The enamel coating has a binder solids content of (1) binder constituents consisting essentially of a film- 65% by weight, based on weight of binder and solvent, and has an aluminum flake/binder weight ratio of 20 forming material and a crosslinker for the filmforming material wherein the film-forming material 1.5/100 and a chromatic pigment/binder weight ratio of is selected from the group consisting of acrylic 0.4/100. The enamel is sprayed onto a primed aluminum resins, polyester resins, and alkyd resins having a panel in four coats, two passes per coat, allowing a flash weight-average molecular weight of 500-10,000; of two minutes between coats and a flash of thirty min utes after the last coat is applied. The coating is then 25 (2) a solvent for the binder constituents in an amount of no more than 100% by weight of the binder; and baked for thirty minutes at 71" C. and for thirty addi (3) chromatic and metallic-flake pigments; tional minutes at 163" C. the improvement wherein the metallic-flake pigment is Dual-Layer High-Solids Enamel present in the composition in an amount of 10-24% by 1. A pigmented base-layer coating is prepared by 30 weight, based on the weight of the binder constituents, conventional means to have the following composition: and the chromatic pigment is present in an amount sufficient with the amount of the metallic-flake pigment to give acured coating ofthiscomposition a flake orien tation index of at least 40. Parts by Weight 35 2. The composition of claim 1 wherein the film-form Acrylic Polymer Solution (described in Coating B) Hexamethoxymethybnelamine Methylethyi ketone Aluminum Flake Pigment Monastral (g) Blue Pigment 70 30 107.6 14.76 3.96 ing material is a polyester resin. 3. The composition of claim 2 wherein the film-form ing material is a polyester resin that is a mixture of the condensation products of (1) aliphatic diols and ali 40 phatic dibasic acids, and (2) aliphatic diols and aromatic 226.32 dibasic acids, and wherein the crosslinker is an amino- plast This enamel composition has a binder solids content 4. The composition of claim 1 wherein the film-form of 65% by weight, based on weight of binder and sol vent, and has an aluminum flake/binder weight ratio of 45 ing material is an acrylic resin. 5. The composition of claim 4 wherein the film-form 18/100 and a chromatic pigment/binder weight ratio of ing material is a copolymer of an alkyl acrylate, alkyl 4.8/100. methacrylate, and at least one of a hydroxy alkyl acry 2. An unpigmented top-layer coating composition is late and hydroxy alkyl methacrylate, and wherein the prepared as is the base layer but without pigmentation. The pigmented base-layer enamel composition is 50 crosslinker is an aminoplast. 6. The composition ofclaim 1 in which the film-form sprayed onto a primed aluminum panel in one coat, two ing material is an alkyd resin. passes per coat, allowing a flash of 15 minutes after the 7. The composition of claim 6 wherein the film-form coat is applied. The coating is then baked for thirty ing material is an alkyd resin that is the reaction product minutes at 71" C. and for thirty additional minutes at about 93" C. The unpigmented top-layer enamel com position is then sprayed over the base-layer in four 55 of a glyceride of a fatty acid, a diol, and a dicarboxylic acid. ***** 60 DUPO50302152 FINAL FEE & ADVANCED ORDER FOR COPIES OF PATENT & FEE THE STAMP OF THE PATENT OFFICE HEREON ACKNOWLEDGES THE RECEIPT, ON THE DATE INDICATED, OF THE FOLLOWING: ---- TROY SER. NO.: FILE DATE: ALLOWED: FF7498C 721,215 04/08/85 12/11/85 ATTORNEY D. W. h u n t l : * N36788.01 DUP050302153 E. I. DU PONT DE NEMOURS & CO. (INC.) LEGAL DEPARTMENT WILMINGTON, DELAWARE .19898 -22 USr'S DUP050302154 Amendment and Declaration w/certificate of Mailing '' THE STAMP OF THE PATENT OFFICE HEREON ACKNOWLEDGES THE RECEIPT, ON THE DATE INDICATED, OF THE FOLLOWING: DUP050302155 E. I. DU PONT DE NEMOURS & CO. (INC.) LEGAL DEPARTMENT WILMINGTON, DELAWARE 19898 1382 USPS DUP050302156 \ THE STAMP OF THE PATENT OfFICE HEREON ACKNOWLEDGES THE RECEIPT! ON THE DATE INDICATED, OF THE FOLLOWING: . * - t>0 7; 1l 215 Applicant (s> : DANIEL J. TROY.. FF-7498-C Title: IMPROVED DUAL-LAYER COATING CONTAINING ALUMINUM-FLAKE PIGMENT AND COATED ARTICLE Pages of Pages of Spec............. 1.9..... Claims .../..2,- eets of iwtngs none. Oath Declar. X.......... Fee .53 ATTORNEY ... DONALD W DUP050302157 E. I. DU PONT DE NEMOURS & CO. (! NC.) LEGAL DEPARTMENT WILMINGTON, DELAWARE 19898 iW\ oupo503021