AU3890000A

AU3890000A - High solid epoxy, melamine and isocyanate compositions

Info

Publication number: AU3890000A
Application number: AU38900/00A
Authority: AU
Inventors: Isao Nagata; Sape Kewsi Quashie; Peter William Uhlianuk; Donald A. White
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1999-03-17
Filing date: 2000-03-16
Publication date: 2000-10-04
Anticipated expiration: 2020-03-16
Also published as: AU773223B2; CA2361302A1; EP1233992A1; BR0010382A; KR20020000781A; WO2000055231A1; CN1344285A; CN1152901C; JP2003525966A; NZ514217A

Description

WO 00/55231 PCT/USOO/06960 TITLE HIGH SOLID EPOXY, MELAMINE AND ISOCYANATE COMPOSITIONS 5 BACKGROUND OF INVENTION The present invention generally relates to high solids low VOC (volatile organic component) coating compositions and more particularly to low VOC clear coating compositions suited for multi-layered coatings used in automotive OEM and refinish applications. 10 Basecoat-clearcoat systems have found wide acceptance in the past decade as automotive finishes. Continuing effort has been directed to such coating systems to improve the overall appearance, the clarity of the topcoat, and the resistance to deterioration. Further effort has been directed to the development of coating compositions having low volatile organic content (VOC). A continuing need 15 exists for clear coating formulations which provide an outstanding balance of performance characteristics after application, particularly solvent and mar and etch resistance. Examples of compositions used to form a protective coatings include those disclosed in U.S. Patent No. 4,533,716 (Okoshi et al.). These compositions are 20 prepared using a triazine-type resin formed by a co-condensation reaction with formaldehyde, a polyol, and as required a monohydric alcohol. The polyols used in the condensation reaction may be prepared by an esterification reaction between higher fatty acids and epoxy compounds having a number average molecular weight of 174 to 4,000. The polyols used in the 4,533,716 invention do not include epoxy 25 compounds. The 4,533,716 coating compositions are disclosed to include a triazine type resin and a polyisocianate. The present invention is directed to a clear coating composition comprising isocyanate, melamine, and epoxy components wherein the isocyanate component comprises an aliphatic polyisocyanate having on an average 2 to 6 30 isocyanate functionalities. The present invention is also directed to a method of producing a clear coating on a substrate comprising: applying a layer of a clear coating composition comprising isocyanate ,melamine, and epoxy components wherein the isocyanate component comprises an aliphatic

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WO 00/55231 PCTIUSOO/06960 polyisocyanate having on an average 2 to 6 isocyanate functionalities, and curing the layer into the clear coating. One of the advantages of the present invention is its low VOC, significantly below the current guidelines of Environment Protection Agency (EPA) 5 of the United States. Another advantage is etch and mar resistance of the coating resulting from the coating composition of the present invention. Yet another advantage is the clarity of the coating resulting from the coating composition of the present invention. 10 As used herein: "Two-pack coating composition" means a thermoset coating composition comprising two components stored in separate containers. These containers are typically sealed to increase the shelf life of the components of the coating composition. The components are mixed prior to use to form a pot mix. The pot mix 15 has a limited potlife typically of minutes (5 minutes to 45 minutes) to a few hours (4 hours to 6 hours). The pot mix is applied as a layer of desired thickness on a substrate surface, such as an autobody. After application, the layer is cured under ambient conditions or cure-baked at elevated temperatures to form a coating on the substrate surface having desired coating properties, such as high gloss, mar-resistance 20 and resistance to environmental etching. "Low VOC coating composition" means a coating composition that includes less then 0.48 kilograms of organic solvent per liter (4 pounds per gallon) of the composition, as determined under the procedure provided in ASTM D3960. "High solids composition" means a coating composition having solid 25 component in the range of from 65 to 100 percent and preferably greater than 70 percent, all in weight percentages based on the total weight of the composition. "Clear coating composition" means a clear coating composition that produces upon cure, a clear coating having DOI (distinctness of image) and 200 gloss of more than 70. 30 "Polymer solids" or "Composition solids" means a polymer or composition in its dry state. "Aliphatic" as employed herein includes aliphatic and cycloaliphatic materials. "Crosslinkable" means that the individual components of the adduct contain 35 functionality which react within the composition of the invention to give a coating of good appearance, durability, hardness and mar resistance. 2 WO 00/55231 PCT/USOO/06960 Applicants have unexpectedly discovered that contrary to conventional approaches used in typical thermoset coating compositions, i.e., those involving a film forming polymer and crosslinking component, a very viable route lies in a combination of what would traditionally be considered crosslinking agents for 5 producing a unique low VOC high solids clear coating composition which provides coatings with superior properties, such as mar and etch resistance. The clear coating composition includes isocyanate, melamine, and epoxy components. The isocyanate component includes an aliphatic polyisocyanate having on an average 2 to 6, preferably 2.5 to 6 and more preferably 3 to 4 isocyanate 10 functionalities. The coating composition includes in the range of from 35 percent to 70 percent, preferably in the range of from 40 percent to 65 percent and more preferably in the range of from 45 percent to 60 percent of the aliphatic polyisocyanate, the percentages being in weight percentages based on the total weight of composition solids. 15 Examples of suitable aliphatic polyisocyanates include aliphatic or cycloaliphatic di-, tri- or tetra-isocyanates, which may or may not be ethylenically unsaturated, such as 1,2-propylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, 2,3-butylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, 2,2,4-trimethyl hexamethylene diisocyanate, 20 dodecamethylene diisocyanate, 1,3-cyclopentane diisocyanate, 1,2-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, 4-methyl-1,3 diisocyanatocyclohexane, trans-vinylidene diisocyanate, dicyclohexylmethane-4,4' diisocyanate, 3,3'-dimethyl-dicyclohexylmethane4,4'-diisocyanate, meta tetramethylxylylene diisocyanate, polyisocyanates having isocyanaurate structural 25 units such as the isocyanurate of hexamethylene diisocyanate and isocyanurate of isophorone diisocyanate, the adduct of 2 moles of a diisocyanate, such as hexamethylene diisocyanate, uretidiones of hexamethylene diisocyanate, uretidiones of isophorone diisocyanate or isophorone diisocyanate, and one mole of a diol such as ethylene glycol, the adduct of 3 moles of hexamethylene diisocyanate and 1 mole of 30 water (available under the trademark Desmodur N of Bayer Corporation, Pittsburgh, Pennsylvania or Tolonate HDT-LV from Rhodia Co., Cranbury, NJ.). If desired, the isocyanate funtionalities of the polymeric isocyanate may be capped with a monomeric alcohol, isopropanol or isobutanol to prevent premature crosslinking in a one-pack composition. Some suitable monomeric alcohols include methanol, ethanol, 35 propanol, butanol and hexanol. 3 WO 00/55231 PCT/USOO/06960 Some other suitable blockers include lactams, oximes, malonic esters, alkylacetoacetates, triazoles, pyrazoles (e.g. dimethyl pyrazole), phenols and amines. Compositions of the present invention include one or more melamine. A melamine used in the present invention includes, in part, alkylated melamine-formaldehyde 5 resin. The alkylated melamine formaldehyde resin maybe partially or fully alkylated. As examples of partially alkylated melamines, Cymel 1158 Cymel 324, Cymen 327 (from Cytec Ind., from West Paterson, NJ), Resimine BM 9539 (from Solutia, Inc., St. Louis, Mo.) can be mentioned. As examples of fully aklykated melamines, Cymel 350, and Cymel 301 (from Cytec Co., from Cytec. Ind., West Paterson, NJ) and 10 Resimine 764 (from Solutia Inc., St. Louis, Mo.) can be mentioned. A composition of the present invention may comprise from about 10 weight percent to about 40 weight percent of a melamine, preferably from about 15 weight percent to 35 weight percent of a melamine. Compositions of the present invention include one or more oligomeric 15 epoxy compounds, preferably containing at least two epoxy functionalities. Suitable oligomeric epoxy compounds containing a hydroxy functionalily or (OH) group used in the practice of the present invention include, among others, sorbitol polyglycidyl ether such as DCE 358 (form Dixie Chemical Co., Houston, TX), diglycerol polyglycidy ether such as Denacol EX 421 (from Nagase Cehmical Co., Hyogo, 20 Japan), glycerol polyglycidyl ether such as Denacol Ex 313 and EX 314 (from Nagase Chemical Co., Hyogo, Japan), and triglycidyl tris(2-hydroxyethyl) isocyanurate such as Denacol EX 421 (from Nagase Chemical Co., Hyogo, Japan). Suitable oligomeric epoxy compounds which typically do not contain significant hydroxy functionality used in the practice of the present invention include, among 25 others, di- and polyglycidyl ethers of polycarboxylic acid and di- and polyglycidyl ester of acids such as Araldite CY 184 (from Ciba-Geigy, Brewster, N.Y.), cycloaliphatic epoxide such as ERL 4221 (from Union Carbide, Danbury, CT), and polyglycol diepoxide such as DER 736 (from Dow Chemical Co., Midland, MI). A composition of the present invention comprises from about 10 weight percent to 30 about 40 weight percent of an eopxy compound, preferably from about 15 weight percent to 35 weight percent of an epoxy compound. The coating composition preferably includes one or more catalysts to enhance crosslinking of the components on curing. A preferable catalyst is an organotin catalyst such as dibutyltin dilaurate, 35 dibutyltin diacetate, dibutyltin oxide, and dibutyltin bis(acetoacetate) in an amount of generally ranges from 0.001 percent to 1.0 percent, preferably from 0.01 percent to 4 WO 00/55231 PCT/US0O/06960 0.5 percent and more preferably from 0.05 percent to 0.2 percent, the percentages being in weight percentages based on the total weight of composition solids. In addition, the above coating composition can include other suitable catalysts, such as conventional acid catalysts, for example blocked or unblocked 5 phosphoric acid and sulfonic acid in an amount ranging from 0.1 percent to 2 percent, preferably in the range of from 0.2 percent to 1.0 percent. As examples of such acid catalysts, phenyl acid phosphate, butyl acid phosphate, octyl acid phosphate, dodecylbenzenesulfonic acid, para-toluenesulfonic acid and dinonylnaphthalene sulfonic acid, which are optionally blocked with amines such as dimethyl oxazolidine 10 and 2-amino-2-methyl- 1- propanol can be mentioned. The coating composition of the present invention, which is formulated into high solids coating systems may also contain at least one organic solvent typically selected from the group consisting of aromatic hydrocarbons, such as, petroleum naphtha or xylenes; ketones, such as, methyl amyl ketone, methyl isobutyl 15 ketone, methyl ethyl ketone or acetone; esters, such as, butyl acetate or hexyl acetate; and glycol ether esters. such as propylene glycol monomethyl ether acetate. The amount of organic solvent added depends upon the desired solids level as well as the desired amount of VOC of the composition. If desired, the organic solvent may be added to both components of the binder. The amount of organic solvent used results 20 in the composition having a VOC of less than 0.48 kilogram/liter (4 pounds per gallon), preferably in the range of 0.1 kilogram/liter to 0.4 kilogram/liter (1 pound to 3 pounds per gallon) of an organic solvent per liter of the composition. The coating composition of the present invention may also contain conventional additives, such as, stabilizers, and rheology control agents, flow agents, 25 and toughening agents. Such additional additives will, of course, depend on the intended use of the coating composition. Any additives that would adversely effect the clarity of the cured coating will not be included as the composition is used as a clear coating. The foregoing additives may be added to either component or both, depending upon the intended use of the coating composition. 30 To improve weatherability of the clear finish of the coating composition, about 0.1-5%, by weight, based on the weight of the composition solids, of an ultraviolet light stabilizer or a combination of ultraviolet light stabilizers may be added. These stabilizers include ultraviolet light absorbers, screeners, quenchers and specific hindered amine light stabilizers. Also, about 0.1-5% by weight, based on the 35 weight of the composition solids, of an antioxidant can be added. Typical ultraviolet light stabilizers that are useful include benzophenones, such as 5 WO 00/55231 PCT/USOO/06960 hydroxydodecyclbenzo-phenone, 2

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4 -dihydroxybenzophenone; triazoles, such as 2 phenyl-4-(2'-4'-dihydroxybenzoyl)triazoles; and triazines, such as 3,5-dialkyl-4 hydroxyphenyl derivatives of triazine and triazoles such as 2 -(benzotriazole-2-yl) 4,6-bis(methylethyl- 1 -phenyl ethyl)phenol, 2-(3-hydroxy-3,5'-di-tert amyl phenyl) 5 benzotriazole, 2-(3',5'-bis( 1,1 -dimethylpropyl)-2'-hydroxyphenyl)-2H-benzotriazole, benzenepropanoic acid, 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy ,C7-9-branched alkyl esters, and 2-(3',5'-bis(1-methyl-i -phenylethyl)-2' hydroxyphenyl)benzotriazole. Typical hindered amine light stabilizers are bis(2,2,6,6 10 tetramethylpiperidinyl)sebacate, bis(N-methyl-2,2,6,6 tetramethylpiperidinyl)sebacate and bis(N-octyloxy-2,2,6,6 tetramethylpiperidynyl)sebacate. Particularly useful blend of ultraviolet light absorbers and hindered amine light stabilizers is bis(N-octyloxy-2,2,6,6 tetramethylpiperidynyl)sebacate and benzenepropanoic acid, 3-(2H-benzotriazol-2 15 yl)-5-(1,1-dimethylethyl)-4-hydroxy-,C7-9-branched alkyl esters. The coating composition of the present invention optionally contains, in the range of 0.5 weight percent to 15 weight percnt, preferably 1 weight percent to 10 weight percent of polyhydroxy functional compounds such as polycarbonate polyol (formula shown in the example), 2-ethyl-1,3-hexanediol, polycaprolactone triol, and 20 the adduct of epsilon caprolactone and 1,3,5-tris( 2-hydroxyethyl) cyanuric acid, all percentages being based on the total weight composition solids. The coating composition of the present invention optionally contains in the range of from 0.5 percent to 30 percent, preferably in the range of from 1 percent to 20 percent, stabilized crossslinked polymer particles, non-aqueous dispersion 25 (NAD) ( as described in detail in U.S. Patent 4,960,828), all percentages being based on the total weight of composition solids. The clear coating composition of the present invention may be supplied in the form of a two-pack coating composition in which a first pack includes the polyisocyanate and a second-pack includes the melamine, epoxy compounds and 30 other additives. Generally, the first and the second pack are stored in separate containers and mixed before use. The containers are preferrably sealed air tight to prevent reactions during storage. Alternatively, when the isocyanate funtionalities of the polyisocyanate 35 are blocked, all components of the composition can be stored in the same containers in the form of a one-pack coating composition. 6 WO 00/55231 PCTUSOO/06960 In use, the first-pack of the two-pack coating composition containing the polyisocyanate and the second-pack containing the melamine, epoxy compounds, and other additiaves are mixed just prior to use for about 1 to 15 minutes before use to form a pot mix, which has limited pot life, in range of from 5 minutes to 6 hours, 5 before it becomes too viscous to permit application through conventional application systems, such as spraying. Alternatively, the first pack and the second pack are mixed together at the plural spray gun with or without electrostastics, before applied to a substrate. Other methods of applications include roller coating, dipping or brushing and other conventional application methods. The layer of the coating composition 10 then cures under ambient conditions or preferably at higher temperatures in the range of 80-160*C for 10 minutes to 3 hours, preferably in the range of 20 minutes to 1 hour to form a coating on the substrate having the desired coating properties. When the one-pack coating composition containing the blocked polyisocyanate is used, a layer thereof applied over a substrate using aforedescribed 15 application techniques, is cured at a baking temperature in the range of from 80*C to 200*C, preferably in the range of 80*C to 160*C, for about 10 to 60 minutes It is understtood that actual baking temperature would vary depending upon the catalyst and the amount thereof, thickness of the layer being cured, the blocked isocyanate functionalities and the melamine utilized in the coating composition. The use of the 20 foregoing baking step is particularly useful under Original Equipment Manufature (OEM) condition. It is understood that the actual curing time depends upon catalyst type and amount, the thickness of the applied layer and on the presence or absence of any suitable drying devices, such as, fans that assist in continuously flowing air over the 25 coated substrate to accelerate the cure rate. Generally, a clearcoat layer having a thickness in the range of from 25 micrometers to 75 micrometers applied over a metal substrate, such as automotive body which is often precoated with other coating layers such as electrocoat, primer and basecoat; cures in 20 to 60 minutes at at about 80'C to 160'C. 30 7 WO 00/55231 PCTIUSOO/06960 Testing Procedures The following test procedures were used for generating data reported in the examples below: Test Test Method Dry film thickness ASTM D1400 Appearance ASTM D523, VISUAL 20* Gloss ASTM D523 DOI ASTM D5767 Tukon Hardness ASTM D1474 Mar resistance ASTM D5178 Percent solids ASTM D2369 5 EXAMPLE The following non-limiting examples will further illustrate the invention. All parts, percentages, ratios, etc., in the examples are by weight unless otherwise indicated. The following abbreviations listed in Table 1 are used throughout. The 10 examples below are carried out using standard techniques, which are well known and routine to those skilled in the art, except where otherwise described in detail. These examples are illustrative, but do not limit the invention. DEFINITIONS 15 ARALDITE CY 184 Oligoeric, Epoxy Resin, 100% Solid (Ciba-Geigy, Brewster, NY) CYMEL 1158 Polymeric Melamine, 80% Solid (Cytec Co., West Paterson, NJ) TINUVIN 384 Ultraviolet Light Screener, 100% Solid (Ciba-Geigy, Tarrytown, NY) TINUVIN 292 Hindered Amino Light Stabilizer (Ciba Geigy, Tarrytown, NY) 8 WO 00/55231 PCTUSOO/06960 BYK 301 Dibutyltin Dilaurate Catalyst (from Air Products, Allentown, Phenyl Acid Phosphate Catalyst (from Albright & Wson Co., Glen Allen, VA) 2-Ethylhexyl Acetate Solvent (from Eastman Chemical Co.,Kingsport, TN) TOLONATE HDT-LV Isocyanate Timer, 100% Solid (from Rhodia Inc., Cranbury, NJ) CYMEL 350 Monomeric Melamine 100% Solid (Cytec Co. West Paterson, NJ) ERL 4221 Oligomeric Epoxy resin, 100% solid (Union Carbide, Danbury, CT) Dodecylbenzenesulfonic acid salt Catalyst (Kings Industry, Norwork, CT) amionethyl-proponol DER 736 Oligomeric Epoxy Resin, 100% solid (Dow Chemical Co. Midland, MI) Synthesis Example 1 Synthesis of polycarbonate PL 10 15 A 5 liter round bottom flask was fitted with stirrer, condenser, heating mantle, thermometer, and Dean Stark trap. To the reactor were charged 402.5 gin 5 tromethylolpropane, 501.6 gmC neopentyaglycol, 567.2 gm 1,6-hexanediol, 1063.2 gn diethylcarbonate, and 0.2 gm dibutyltindilaurate (all available from Aldrich Chemicals, Milwaukee, WI). The mixture was slowly heated under agitation until ethanol began to distill off at approximately 1A20C. Temperature was allowed to slowly increase to 140'C. Distillation continued at 140'C for a total of 16 hours until 10 829.3 gm ethanol were removed. The material was then cooled and 89.8 gm methylamyl ketone was added. The reaction yielded 1,707.2 grams of polycarbonate polyol at 94.2% weight percent solids. 9 WO 00/55231 PCT/USOO/06960 Protective Coating Example 1 Part A was prepared by combining the following ingredients: 20 parts of ARALDITE CY 184; 25 parts of CYMEL 1158; 2.0 parts of TINUVIN 384; 1.5 parats of TINUVIN 292; 0.68 parts of a solution comprising 10 weight percent of 5 BYK 301 in propylene monoetheyl ether acetate; 5.0 parts of a solution of 1 weight percent of dibutyltin dilaurate in butyl acetate; 0.67 parts of a solution of 75 weight percent of phenyl acid phosphate in butanol; 2.0 parts of PL1015, and 5.26 parts of 2 ethylhexyl acetate. This mixture was then combined with 54.7 parts of TOLONATE HDT-LV as a part B to form a clear composition. 10 Separately, a steel substrate, which had been precoated with electrocoat and primer was coated with a conventional waterborne bascoat to a thickness of 15 micron and prebaked at 82*C for 10 minutes. Then, the above clear composition was sprayed over the above prebaked waterborne basecoat and baked at 140'C for 30 minutes. 15 The substrate was cooled and Protective Coating 1 was tested. Characteristics of Protective Coating 1 are illustrated in Table 1 as compared to a characteristics of Control Protective Coating (conventional 2K isocyanate/acrylic polyol clear composition which had been prepared similarly). 10 WO 00/55231 PCT/USOO/06960 TABLE 1 CHARACTERISTICS OF PROTECTIVE COATINGS sample Protective Coating 1 ontrol Coating [acrylic polyol/iso) % Solid 85.6 53.0 VOC (lbs/gal) 1.29 3.9 #4 Ford spray viscosity (sec) 100 30 Gloss (20 deg.) 95 89 DOI 97 97 Tukon hardness(Knoop) 13.3 11.1 Cleveland humidity (96 hour @ 60 C) Tape adhesion No failure No failure Blister No No Boiling water resistance (3h) Tape adhesion No failure No failure blister No No Gravel @ -20 deg. C 7 6 (Note 1) Percent gloss retention after 96 91 dry mar (note 2) Min. temp.(C) without spot 65 60 of synthetic acid rain soln. Note1) Rating based on 1-10 with 10 best Note 2) Gloss retention after 10 rubbing cycles using an abrasive material 5 As shown in Table 1, Clearcoat Example 1 clearly showed good appearance at very low VOC and gave good physical properties. 11 WO 00/55231 PCTIUSOO/06960 Protective Coating Example 2 Protective Coating 2 was prepared as follows: Parts A was prepared by combining 22.0 parts of ARALDITE CY 184, 25.0 parts of CYMEL 1158, 2.0 parts of TINUVIN 384, 1.5 parts of TINUVIN 292, 0.68 parts of a solution of 10 weight 5 percent of BYK 301 in propylene ethyl ether acetate, 5.0 parts of a solution of 1 weight percent dibutyltin dilaurate in butyl acetate, 0.67 parts of a solution of 75 weight percent of phenyl acid phosphate in butanol and 5.26 parts of 2-ethylhexyl acetate. The above part A mixture was then combined with 54.7 parts of TOLONATE HDT-LV as a part B to form a clear composition. The composition had 10 a solid content of 85.6 weight percent, and a volatile organic compounds concentration of 1.29 lbs/gal. (0.15 Kg/liter). The composition was then sprayed over a conventional silver metallic waterborne basecoat which had been applied to the similar substrate as described in Example 1 and prebaked at 82*C for 10 minutes, and baked at 140*C for 30 minutes 15 similar to Example 1. The coating exhibited gloss 95, DOI 95 and Tukon hardness 11.3. Protective Coating Example 3. Protective Coating 3 was prepared as follows: Part A was prepared by 20 mixng 20.0 parts of ARALDITE CY 184, 12.5 parts of CYMEL 1158, 10.0 parts of CYMEL 350, 2.0 parts of TINUVIN 384, 1.5 parts of TINUVIN 292, 0.68 parts of a solution of 10 weight percent of BYK 301 in propylene monoetheyl ether acetate, 0.5 parts of a solution of 10 weight percent of dibutyltin dilaurate in Butyl acetate, 0.67 parts of a solution of 75 weight percent of phenyl acid phosphate in butanol, 2.0 parts 25 of PL1015 and 10.26 parts of 2-ethylhexyl acetate. This part A mixture was then combined with 54.7 parts of TOLONATE HDT-LV as part B to form a clear composition. The clear composition had a solid content of 87.1 weight percent, and a volatile organic compounds concentration of 1.18 lbs/gal. (0.14 Kg/liter). The composition was then sprayed over a conventional silver metallic 30 waterborne basecoat which had been applied to the similar substrate as described in Example 1 and prebaked at 82*C for 10 minutes, and baked at 140*C for 30 minutes similar to Example 1. The coating exhibited gloss 94, DOI 94 and Tukon hardness 11.4. 12 WO 00/55231 PCT/USOO/06960 Protective Coating Example 4 Protective Coating 4 was prepared as follows: Part A was prepared by mixing 20 parts of ERL 4221, 25 parts of CYMEL 1158, 2.0 parts of TINUVIN 384, 1.5 parts of TINUVIN 292, 0.68 parts of a solution of 10 weight percent of BYK 301 5 in propylene monoethyl ether acetate, 0.5 parts of a solution of 10 weight percent dibutyltin dilaurate in butyl acetate, 1.4 parts of dodecylbenzenesulfonic acid salt of amionethylpropanol, 2.0 parts of PL 1015, and 5.26 parts of 2-ethylhexyl acetate. This part A mixture was then combined with 54.7 parts of TOLONATE HDT-LV as a part B to form a clear composition. The clear composition had a solid content of 10 88.44 weight percent, and a volatile organic compounds concentration of 1.05 lbs/gal (0.12 Kg/liter]. The composition was then sprayed over a conventional silver metallic waterborne basecoat which had been applied to the similar substrate as described in Example 1 and prebaked at 82*C for 10 minutes, and baked at 140*C for 30 minutes 15 similar to Example 1. The coating exhibited gloss 90, DOI 90 and Tukon hardness 4.6. Protective Coating Example 5 Protective Coating 5 was prepared as follows: Part A was prepared by 20 mixing 20.0 parts of DER 736 20.0 parts of CYMEL 350, 2.0 parts of TINUVIN 384, 1.5 parts of TINUVIN 292, 0.68 parts of a solution of 10 weight percent BYK 301 in propylene monoetheyl ether acetate, 6.0 parts of the salt of dodecylbenzenesulfonic acid and diethanolamine, 4.2 parts of PL1015 and 6.75 parts of 2-Ethylhexyl Acetate. This part A mixture was then combined with 52.5 parts of TOLONATE 25 HDT-LV as a part B to form a clear composition. The composition had solid content of 88.0 weight percent, and a volatile organic compounds concentration of 1.09 lbs/gal.(0.13 Kilograms/liter). The composition was then sprayed over a conventional silver metallic waterborne basecoat which had been applied to the similar substrate as described in 30 Example 1 and prebaked at 82*C for 10 minutes, and baked at 140'C for 30 minutes similar to Example 1. The coating exhibited gloss 87, DOI 90 and Tukon hardness 3.6. The complete disclosures of all patents, patent applications, and publications are incorporated herein by reference as if individually incorporated. 35 Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention, and 13 WO 00/55231 PCT/US00/06960 should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth herein. 14

Claims

1. A low VOC clear coating composition comprising isocyanate, epoxy compound and melamine components wherein said isocyanate component comprises 5 an aliphatic polyisocyanate having an average of 2 to 6 isocyanate functionalities.

2. The composition of claim 1 wherein said composition further comprises a catalyst. 10

3. The composition of claim 2 wherein said catalyst is selected from the group consisting of an organotin catalyst, acid catalyst and combinations thereof.

4. The composition of claim 3 wherein said organotin catalyst is selected from the group consisting of dibutylin diacetate, dibutyltin dilaurate, dibutylin oxide, 15 dibutyltin bis(acetoacetate) and combinations thereof.

5. The composition of claim 3, wherein said acid catalyst is selected from the group consisting of phenyl acid phosphate, butyl acid phosphate, octyl acid phosphate, dodecylbenzenesulfonic acid, para-toluenesulfonic acid, 20 dinonylnaphthalenesulfonic acid and combinations thereof.

6. The composition of claim 3 or 5, wherein said acid catalyst is blocked with an amine. 25

7. The composition of claim 6, wherein said amine is dimethyloxazolidine, 2-amino-2-methyl-1-propanol, di(2-hydroxyethyl)amine or a combination thereof.

8. The composition of claim 2,3,4,5 or 6 wherein said composition comprises about 0.001 weight percent to about 3.0 weight percent of catalyst, all 30 percentages based on the total weight of composition solid.

9. The composition of claim 1 further comprises a polyhydroxyl functional compound. 35

10. The composition of claim 9 wherein said polyhydroxyl functional compound is a polycarbonate polyol. 15 WO 00/55231 PCTIUSOO/06960

11. The composition of claim 9 or 10 wherein said polyhydroxyl functional compound comprises from about 0.5 weight percent to about 15 weight percent of the composition. 5

12. The composition of claim 1 further comprises a non-aqueous dispersion resin, stabilized dispersed polymer particles.

13. The composition of claim 1, wherein said epoxy compound is selected 10 from the group consisting of a polyglycidyl ester of an acid, a polyfunctional aliphatic epoxy compound, a cycloaliphatic epoxy compound, a polyfunctional cycloaliphatic epoxy compound or combinations thereof.

14. The composition of claim 1 or 13, wherein said epoxy compound is a di 15 or polyglycidyl ester of a di or polycarboxylic acid.

15. The composition of claim 1, 13 or 14, wherein said epoxy compound comprises from about 10 weight percent to about 40 weight percent of the composition. 20

16. The composition of claim 1, wherein said melamine is a fully alkylated melamine-formaldehyde resin.

17. The composition of claim 1, wherein said melamine is a partially 25 alkylated melamine-formaldehyde resin.

18. The composition of claim 1, 16 or 17, wherein said melamine compound comprises from about 10 weight percent to about 40 weight percent of the composition. 30

19. The composition of claim 1 further comprises ultraviolet light absorbers, light stabilizers of a combination thereof.

20. The composition of claim 1, wherein said aliphatic polyisocyanate is 35 selected from the group consisting of trimers of hexamethylene diisocyanate, 16 WO 00/55231 PCT/USOO/06960 isophome diisocyanate, or meta-tetramethylene diisocyanate and combinations thereof.

21. The composition of claim 1 or 20, wherein said aliphatic polyisocyanate 5 is blocked.

22. The composition of claim 1, 20 or 21, wherein aliphatic polyisocyanate is blocked by reacting with an aliphatic mono-alcohol. 10

23. The composition of claim 1, 20, 21 or 22, wherein said aliphatic polyisocyanate comprises from about 35 weight percent to about 70 weight percent of the composition.

24. The composition of claim 1 further comprises a solvent. 15

25. The composition of claim 1, wherein said composition has a solids content of greater than 65 weight percent.

26. A composition of claim 1, wherein said composition has a solids content 20 of greater than 80 weight percent.

27. An article comprising a substrate having a first and a second major surface and a layer of protective coating, the protective coating comprising a hardened composition of claim 1. 25

28. The article of claim 27, wherein said substrate is selected from the group consisting of metal, plastic, wood and rubber.

29. The article of claim 27, wherein said layer of protective coating has a 30 thickness of about 25 micrometers to about 75 micrometers.

30. The article of claim 27, wherein said layer of protective coating is acid resistant. 35

31. The article of claim 27, wherein said layer of protective coating is transparent. 17 WO 00/55231 PCTIUS0O/06960

32. The article of claim 27, comprising a layer of electrocoat, primer and a layer of basecoat interposed between the substrate and the layer of protective coating. 5

33. A process of making a composition that upon hardening forms a protective coating comprising the steps of: combining an aliphatic polyisocyanate having an average of 2 to 6 isocyanate functionalities an epoxy compound, and melamine. 10

34. A process of making a composition that upon hardening forms a protective coating comprising the steps of : making a first mixture comprising an epoxy, a melamine; making a second mixture comprising an aliphatic polyisocyanate 15 having an average of 2 to 6 isocyanate functionalities; and combining the first and second mixtures wherein said first mixture, second mixture or both mixtures comprise a solvent.

35. The process of claim 34 wherein said first mixture, second mixture or 20 both mixtures contain a solvent.

36. The product produced by the process of claim 34.

37. A process of making an article comprising the steps of: 25 applying a composition comprising an aliphatic polyisocyanate having an average of 2 to 6 isocyanate functionalities, an epoxy compound, and melamine to a substrate; and hardening the composition. 30

38. The process of claim 37 wherein said composition is applied by spraying. 18