TWO COMPONENT COATING COMPOSITION OF AN ANHYDRIDE CONTAINING POLYMER AND A GLYCIDYL COMPONENT

Abstract: A coating composition useful for a finish for automobiles and trucks in which the film forming binder contains two reactive binder components of (a) an acryl polymer having at least two anhydride groups and having a weight average molecular weight of about 2,000-50,000 and (b) a component having at least two reactive glycidyl groups and the composition contains a catalyst.

Description: TITLE Two Component Coating Composition of an Anhydride Containing Polymer and a Glycidyl Cooonent This invention is related to a two component coating composition. There are a wide variety of two component coating compositions available for finishing substrates. Typically with these compositions, the components are mixed together before application and then the resulting composition is applied by conventional techniques such as spraying and the composition is cured at ambient temperatures or can be cured at elevated temperatures. These compositions are used to refinish automobiles and trucks. paint structures such as bridges and buildings. paint appliances, metal cabinets and the like. Representative of such compositions are shown in the following patents: Maroon et al. U.S. Patent 4.452.948 issued June 5, 1984. A two component composition is taught in which one component has at least two free carboxyl groups and a second component has anhydride groups. Hovever, finishes formed from such a composition generally have moisture sensitivity and under high humidity conditions which are common for automobiles and trucks whiten and blister. Gordon et al. U.S. Patent 4,507,411, issued March 26. 1985 shows a two component composition of a functionalized polymeric component and glycidyl component that in the presence of an amine. alcohol, ketimine. acetal or oxazolidine cures at ambient temperatures. However, the compositions disclosed are not useful for finishes for automobiles and trucks. European Patent Application 0.123.793 shows a two component composition in which one component has an anhydride ring that is opened with an amine and has a second component that contains glycidyl groups. Finishes formed from such compositions are not useful for automobiles and trucks since the finishes vhiten and blister on exposure to high humidity conditions and exhibit recoat lifting when repaired within several days after the finish has been applied. There is a need for a coating composition that cures at ambient temperatures and provides a high quality finish that is useful as an exterior finish or refinish for automobiles and trucks that has excellent adhesion to the substrate to which it is applied. good outdoor weatherability and humidity resistance and an excellent appearance. SUMMARY OF THE INVENTION A coating composition containing 20-801 by weight of two reactive binder components and 80-20S by weight of an organic carrier; the binder contains (a) an acrylic polymer having at least two anhydride groups and having a weight average molecular weight of about 2.000-50.000 and (b) a component having at least two reactive glycidyl groups and the composition contains about 0.1-5% by weight. based on the weight of the binder. of a catalyst. DETAILED DESCRIPTION OF THE INVENTION The film forming binder of the coating composition of this invention contains components that are mixed together before application. The film forming binder content of the composition is about 20-80t by weight of an organic carrier which usually is a solvent for the binder. The composition forms an excellent clear coating over colored pigmented finishes. The coating has good adhesion to the pigmented finish. has excellent humidity resistance and is weatherable and durable. The composition is useful for finishing and refinshing the exterior of automobiles and trucks and the composition can be pigmented and form a colored finish. Also. the composition can be used over flexible substrates used in automobiles and trucks such as filler panels. side panels, fender extensions. oldings and other trim parts. The composition also can be pigmented to form a colored finish. These pigmented compositions are useful as exterior original equipment and refinish coatings for automobiles and trucks. as maintenance coatings for tanks. bridges. buildings such as factories and oil refineries and as industrial coatings for appliances. metal cabinets. shelves and the like. Preferably, the coating composition has a high solids content and contains about 40-70% by weight binder and 30-60t by weight of organic solvent. The binder of the composition contains about 50-90% by weight of acrylic polymer containing at least two anhydride groups and 5-50% by weight of a glycidyl containing component. The acrylic polymer containing has a weight average molecular weight of about 2,000-50.000 determined by gel permeation chromatography using polymethyl methacrylate as a standard and preferably. has a weight average molecular weight of 4,000-25,000. The acrylic polymer is prepared by conventional techniques in which the monomers. solvent. and conventional catalysts such as t-butyl perbenzoate are charged into a polymerization vessel and heated to about 75-2000C for about 0.5-6 hours to form the polymer. The acrylic polymer is formed by polymerizing monomers of alkyl methacrylates, or alkyl acrylates or mixtures thereof, where the alkyl groups have 1-12 carbon atoms and ethylenically unsaturated anhydrides. Optionally. the acrylic polymer can contain other components such as styrene, amethyl styrene, acrylonitrile. methacrylonitrile in amounts of about 0.1-508 by weight. Typical alkyl acrylates and methacrylates that can be used to form the acrylic polymer are as follows: methyl methacrylate, ethyl methacrylate, propyl methacrylate butyl methacrylate. pentyl methacrylate, heryl methacrylate, octyl nethacrylate decyl methacrylate. lauryl methacrylate. methyl acrylate, ethyl acrylate, propyl acrylate. butyl acrylate. octyl acrylate. nonyl acrylate. decyl acrylate. lauryl acrylate and the like. Other components that can be used to form the acrylic polymer are acrylamide, methacrylamide. acrylo alkoxy silanes such as. gamma methacryloyl propyl trimethoxy silane. Also the acrylic polymer can contain about 0.1-SS by weight of an ethylenically unsaturated acid such as acrylic acid, methacrylic acid. itaconic acid. maleic acid and the like. Typically useful ethylenically unsaturated anhydrides are as follows: itaconic anhydride. maleic anhydride and isobutenyl succinic anhydride. Preferred acrylic polymers are as follows: methyl methacrylatelbutyl acrylate/itaconic anhydride. butyl acrylate/styrene/maleic anhydride/maleic acid, methyl methacrylate/butyl acrylate/itaconic anhydride. The following amine containing monomers can be used in the acrylic polymer to eliminate the use of the amine catalyst: vinyl pyridine, alkyl amino ethyl methacrylater diethyl amino ethyl acrylate. dimethyl amino ethyl methacrylate, dimethyl amino ethyl acrylate, tertiary butyl amino ethyl methacrylate, ethyl methyl amino ethyl methacrylate. ethyl methyl amino ethyl acrylate and the like. The glycidyl component contains at least two glycidyl groups and can be an oligomer or a polymer. Typical glycidyl components are as follows: sorbitol polyglycidyl ether, mannitol polyglycidyl ether. pentaerythritol polyglycidyl ether, glycerol polyglycidyl ether. low molecular weight epoxy resins such as epoxy resins of epichlorohydrin and bisphenol A., diglycidyl esters of polyols. polyglycidyl ethers of isocyanurates. such as WDenecol" EX301 from Nagase. Sorbitol polyglycidyl ether is preferred since it forms a high quality finish. Glycidyl methacrylate or acrylate containing acrylic polymers can be used such as random and block polymers of glycidyl methacrylate/butyl methacrylate. The block polymers can be prepared by anionic polymerization or by group transfer polymerization. Typical solvents used to prepare the acrylic polymer and used as a diluent for the coating composition are as follows: toluene, xylene, butyl acetate, ethyl benzene. higher boiling aromatic hydrocarbons. amyl acetate. ethyl acetate, propyl acetate. ethylene or propylene glycol mono alkyl ether acetates. About 0.01-5% by weight, based on the weight of the binder of the coating composition, of a catalyst is added to enhance curing of the composition. Typical catalysts are as follows: triethlene diamine. dialkyl alkanol amines such as dimethyl ethanolamine. diethyl ethanol amine, dibutyl ethanol amine, diethyl hexanol amine and the like, lithium tertiary butoxide, tri(dimethylaminomethyl) phenol, bis(dimethylamio)propan-2-ol. N.N.N1,N1-tetramethylethylenediamine, N,methyl- diethanolamine, N,N-dimethyl-1,3-propanediamine and l-dimethylamino-2-propanol. The catalyst need not be added to the coating composition. After an article is coated, the article is passed into a chamber containing catalyst vapors. Dimethylethanol amine is a catalyst that can be vaporized and used to cure the composition. Also, to achieve curing. the catalyst can be sprayed with the coating composition using a dual spray gun. Generally, the composition is applied by conventional techniques such as spraying and electrostatic spraying. The resulting coating can be dried and cured at ambient temperatures or can be cured at elevated temperatures of 60 to 2000C. At ambient temperatures, the coating dries to a tack free condition in about 180 minutes and in about 24 hours the coating is substantially cured. In about 5-7 days. the coating is completely cured. Coatings are applied to form a finish about 0.5-5 silts thick, and preferably 1-2 nails thick. The finish has excellent gloss, good adhesion to substrate and excellent weatherability. To improve weatherability of the clear finish of the coating composition. about 0.1-5%, by weight, based on the weight of the binder, of an ultraviolet light stabilizer or a combination of ultraviolet light stabilizers can 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 weight of the binder, of an antioxidant can be added. Typical ultraviolet light stabilizers that are useful are as follows: Benzophenones such as hydroxydodecyclbenzo- phenone, 2.4-dihydroxybenzophenone, hydroxy-benzo phenones containing sulfonic acid groups. 2,4 dihydroxy-3',5'-di-t-butylbenzophenone, 2,2' .4'- trihydroxybenzophenone esters of dicarboxylic acids, 2-hydroxy-4-acryloxyethoxybenzophenone, aliphatic mono-esters of 2,2' .4-trihydroxy-4'-alkoxybenzophenone, 2-bydroxy-4-methoxy-2 '-carboxybenzophenone; ; Triazoles such as 2-phenyl-4-(2'-4'-dihydroxybenzoyl)triazoles, substituted benzotriazoles such as hydroxyphenyltriazoles such as 2-(2 'hydroxy-5 '-methyphenyl) benzotriazole, 2-(2'hydroxyphenyl)benzo-triazole, 2- (2' -hydroxy-5 '-octylphenyl )naphthotriazole; Triazines such as 3,5-dialkyl-4-hydroxyphenyl derivatives of triazine, sulfur-containing derivatives of dialkyl-4-hydroxyphenyltriazines, hydroxyphenyl-1.3,5-triazines and such triazines containing sulfonic acid groups. aryl-1.3,5-triazines. orthohydroxyaryl-s-triazine; Benzoates such as dibenzoate of diphenylolpropane, t-butyl benzoate of diphenylolpropane, nonyl phenyl benzoate. octyl phenyl benzoate, resorcinol dibenzoate. Other ultraviolet light stabilizers that can be used include lower alkyl thiomethylene-containing phenols, substituted benzenes such as 1,3-bis(2'hydroxybenzoyl)benzene. metal derivatives of 3, 5.-di-t-butyll-4-hydroxyphenylpropionic acid. asymmetrical oxalic acid diarylamides, alkylhydroxyphenylthioalkanoic acid esters, dialkylhydroxyphenylalkanoic acid esters of di- and tri- pentaerythritol, phenyl- and naphthlenesubstituted oxalic acid diamides, xethyl-ss-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, a,a' -bis (2-hydroxy-phenyl)diisopropylbenzene, 3,5' -dibromo-2 '-hydroxy-acetophenone. ester derivatives of 4,4-bis(4 '-hydroxy-phenyl)pentaonic acid wherein there is at least one unsubstituted position ortho to the aromatic hydroxyl groups, organophosphorus sulfides such as bis(diphenyl-phosphinothioyl)monosulfide and bis(diphenyl-phosphinothioyl)disulfide, 4-benzoyl-6- (dialkylhydroxybenzyl)resorcinol, bis (3-hydroxy-4-benzoylphenoxy)diphenylsilane. bis (3-hydroxy-4-benzoylphenoxy)dialkylsilane, 1,8-naphthalimides. a-cyano-S.B-diphenylacrylic acid derivatives. bis(2-benzoxazolyl)alkanes. bis(2-naphthoxazolyl)alkanes, methylene malonitriles containing aryl and heterocyclic substitutes, alkylenebis (dithio)carbamate, 4-benzoyl-3-hydroxyphenoxyethyl acrylate, 4-benzoyl-3-hydroxyphenoxyethyl methacrylate, aryl or alkyl-substituted acrylonitriles, 3-methyl-5-isopropylphenyl-6-hydroxycourmarone, 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8triaza- spiro(4. 5 )decanol-2,4-dione. Particularly useful ultraviolet light stabilizers that can be used are hindered amines of piperidyl derivatives such as those disclosed in Xurayama et al.. U.S. Patent 4,061,616, issued December 6, 1977, column 2, line 65, through column 4, line 2, and nickel compounds such as (l-phenyl-3-methyl-4-decanoylpyrazolate(5) i-Ni, bistphenyldithiocarbamato]-Ni(II), and others listed in the above Patent. column 8, line 44 through line 55. The following blend of ultraviolet light stabilizers can be used: 2-t2'-hydroxy-3',5'-1(1-1-dimethyl-propyl)phenylZbeXzo- triazole and bs-t4-(1,2,2.6,6-pentamethylpiperidyll 2-butyl-2-E (3. 5-t-butyl-4-hydroxyphenyl)methyl) propanedioate. The stabilizers can be used in any ratio however, a 1:1 ratio of benzotriazole to propanedioate is preferred. Another useful blend of ultraviolet light stabilizers is 2-(benzotriazole-2-VL) 4.6-bis(methylethyl-l-phenyl ethyl)phenol, and 2(3 hydroxy-3.5'-ditert amyl phenyl) benzotriazole. Generally. when the coating composition of this invention is used as a clear coating. it is applied by conventional spraying techniques, to a color or base coat of an automobile or truck, preferably, electrostatic spraying is used. In an assembly operation, the clear coating usually is applied before the color coat is baked. The coatings are baked at about 110 to 230C for about 20 to 40 minutes. In refinishing automobiles and trucks, the clear coating is applied to a color coat and then can be dried at ambient temperatures or baked to form a clear finish. The resulting clear coat or finish is about 1-5 mils thick preferably 1-2 mils thick and has excellent gloss, good adhesion to the color coat and excellent weatherability. The composition can be pigmented to form a colored finish. About 0.1-50t by weight, based on the weight of the binder, of conventional pigments can be added using conventional techniques in which a mill base containing pigment, dispersant and solvent is first formed. The mill base is then mixed with the composition to form a colored composition. This composition can be applied and cured as shown above. The following examples illustrate the invention. All parts and percentages are on a weight basis unless indicated otherwise. Molecular weights are determined by gel permeation chromatography using polymethyl methacrylate as the standard. Example 1 The following constituents were charged into a reactor equipped with a thermometer, stirrer, dropping funnel, nitrogen induction tube and condenser: Parts Portion 1 BY Weight Xylene 837.0 Portion 2 Methylmethacrylate monomer 585.6 Butylacrylate monomer 878.4 Itaconic anhydride monomer 488.0 Portion 3 t-butyl perbenzoate 94.0 Portion 4 t-butyl perbenzoate 20.0 rylene 100.0 Total 3003.0 Portion 1 was charged into the reactor. covered with nitrogen and heated to its reflux temperature. Portion 2 was premixed and warmed to 450C and portions 2 and 3 were added simultaneously and dropwise to the reactor over a 150 minute period while holding the contents of the reactor at reflux temperatures. Portion 4 was premixed and added over a 30 minute period and then the resulting composition was held at its reflux temperature for an additional hour. The resulting polymer composition had a weight solids content of 69% and the polymer had a Gardner Holdt Viscosity of Z-1. The polymer had a weight average molecular weight of 4500. Coating composition was prepared by thoroughly blending together the following constituents: Parts Portion 1 BY Weight Polymer Composition 43.7 (prepared above) DenecoloEx622 14.3 (Sorbitol polyglycidyl ether) DABC0 (triethylene diamine) 0.9 Butyl acetate 41.1 Total 100.0 The resulting coating composition had a solids content of 458 and a viscosity of 18 seconds measured with a No. 2 Zahn Cup. The coating composition was sprayed onto a primed metal panel coated with a pigmented acrylic lacquer. The composition cured at ambient temperature and provided a clear coat with excellent hardness and adhesion to the lacquer layer. After 24 hours curing at an ambient temperature, a 3 mil thick film of the pigmented acrylic lacquer was applied over the clear coat. No wrinkling or adhesion loss was noted indicating that the clear coat was fully cured in 24 hours. Panels as described above were spray coated with the above composition under ambient temperatures and at a constant 60% relative humidity. The composition was cured at ambient temperatures and after 7 days the resulting clear finish withstood 200 double rubs with methylethyl ketone and withstood four days in a humidity cabinet maintained at 38iC and 100% relative humidity without blistering or whitening of the finish or loss of adhesion of the finish. A second coating composition was prepared by thoroughly blending together the following constituents: Parts Portion 1 BY Weight Polymer composition 341.15, (prepared above) DenecoleEx622 114.14 (described above) DABCO (triethylene diamine) 3.53 Dimethylethanolamine 3.53 Butyl acetate 337.65 Total 600.00 The resulting coating composition had a solids content of 45% and a viscosity of about 18 seconds measured with a No. 2 Zahn cup. A 2 mil thick coating of the composition was applied to a glass substrate and cured at ambient temperatures. After 1 day, the Percoz hardness was 250 counts and the film withstood 200 double rubs with methylethyl ketone indicating the coating was fully cured. The coating composition was sprayed onto primed metal panels coated with a while acrylic lacquer. The composition cured at ambient temperatures for 24 hours and no discoloration was noted and adhesion and hardness of the resulting finish excellent. After curing for seven days. the finish withstood four days in a humidity cabinet maintained at 360C and 100S relative humidity without loss of adhesion or blistering of the finish. Also, the finish could be recoated with an acrylic lacquer without wrinkling of the finish. The above coating composition was reforxulated without using an amine or diamine. The resulting composition was sprayed onto a primed metal panel coated with an acrylic lacquer and then placed in a chamber containing dimethyl ethanol amine vapors. The panel was removed from the chamber and allowed to cure at ambient temperatures. The resulting finish was hard and glossy and humidity resistant. Example 2 The following constituents were charged into a reactor equipped as in Example 1: Parts Portion 1 Zz Weight Zylene 450 Portion 2 Butyl acrylate monomer 908 Styrene monomer 708 Maleic anhydride 319 Maleic acid 42 Propylene glycol monomethyl ether 450 t-butyl perbenzoate 53 Portion 3 Xylene 269 t-butyl perbenzoate 9 Total 3208 Portion 1 was charged into the reactor and heated to its reflux temperature. Portion 2 was premixed and slowly added over 3 hours to the reactor while maintaining the contents of the reactor at reflux temperature. Portion 3 was mixed and slowly added to the reactor over a 45 minute period and then the resulting composition vas held at its reflux temperature for an Additional two hours. The resulting polymer composition had a weight solids content of 50% and the polymer had a Gardner Holdt viscosity of V measured at 25'C. The polymer had a weight average molecular weight of 22.000. A coating composition was prepared by thoroughly blending together the following constituents: Parts BY weiqht Polymer composition 53.20 (prepared above) Denecole EX622 15.90 (described in Example 1) DABCO (described in Example 1) 0.85 Butyl acetate 100.05 Total 170.00 The resulting coating composition had a solids content of 25S and a viscosity of 18 seconds measured with a No. 2 Zahn cup. The coating composition was sprayed onto a metal substrate and after 7 days of curing at ambient temperatures the coating had a Percoz hardness of 240, resisted over 150 double rubs with methylethyl ketone. After exposure to a humidity cabinet maintained at 380C and 100S relative humidity, the coating did not whiten, blister or show loss of adhesion. Example 3 The following constituents were charged into a reactor equipped as in Example 1: Parts Portion 1 By Weioht Toluene 304.00 Portion 2 Glycidyl methacrylate 293.2 Butyl methacrylate 195.5 Toluene 23 5 2.2 2-methylbutane nitrile 23.5 Portion 3 Toluene 17.9 2.2 2-methylbutane nitrile 2.9 Total 660.5 Portion 1 was heated to its reflux temperature. Portion 2 vas premixed and slowly added to the reactor over a two hour period while maintaining the contents of the reactor at reflux temperature. Portion 3 was premixed and slowly added over a 20 minute period and the resulting reaction mixture was held at its reflux temperature for an additional 60 minutes. The resulting polymer composition had a weight solids content of 56%. The polymer had a weight average molecular weight of 7.000. A coating composition was prepared by thoroughly blending together the following constituents: Parts BY Weiaht Polymer composition 40.04 (Prepared in Example 1) Polymer composition 28.67 (Prepared above) DABCO (described in Example 1) 0.88 Butyl Acetate 30.41 Total 100.00 The resulting coating composition had a solids content of 45t and a viscosity of 18 seconds measured with a No. 2 Zahn cup. Coatings were sprayed onto petal substrates and cured at ambient temperatures to form a 2 mii thick finish. After curing for 7 days at 25"C, the finishes had a Percoz hardness of 225 counts and resisted 150 double rubs with methyl ethyl ketone. The chip resistance of the finish was acceptable. Example 4 A coating composition was prepared by thoroughly blending together the following constituents: Parts BY Weight Polymer composition (prepared in Example 1) 365.46 AralditeO CY184 102.66 (Glycidyl ester of a diol from Ciba Geigy Corporation) DABCO (described in Example 1) 3.40 Dimethyl ethanol amine 3.40 Butyl acetate 311.50 Tinuvine 328 t2-(2hydroxy-3.5-ditertiary amyl phenol)2-H-benzotriazole) Tinuvine 144 (hindered amine light stabilizer) ¯ 6.79 Total 800.00 The resulting coating composition had a solids content of 45% and a viscosity of 18 seconds measured with a No. 2 Zahn cup. The coating composition was sprayed onto a primed metal panel coated with a pigmented water borne acrylic lacquer. The coating was baked for 30 minutes at 71vC. The resulting finish was about 2 mils thick, had a gloss measured at 20' of 85 and had a general appearance which was rated as excellent. The hardness of the finish was 3.5 knoops and after 7 days the hardness was 6.5 knoops.

Claims: CLAIMS: 1. A coating composition comprising 20-80% by weight of two reactive binder components and 80-20% by weight of an organic liquid carrier; wherein the binder comprises: (a) an acrylic polymer component having at least two anhydride groups and a weight average molecular weight of about 2,000 50,000; (b) a glycidyl component having at least two reactive glycidyl groups and the composition contains about 0.1-5% by weight, based on the weight of the binder of a catalyst. 2. A coating composition according to claim 1 in which the binder comprises about 50-95% by weight of the acrylic polymer component and 5-508 by weight of the glycidyl component. 3. A coating composition. according to claim 1 or claim 2 in which the acrylic polymer comprises polymerised monomers of alkyl methacrylate, alkyl acrylate and ethylenically unsaturated anhydride, wherein the alkyl groups have 1-12 carbon atoms. 4. A coating composition according to claim 3 in which the acrylic polymer contains about 0.1-5% by weight styrene. 5. A coating composition according to claim 1 or claim 2 in which the acrylic polymer is a polymer of styrene, an alkyl acrylate or an alkyl methacrylate and an ethylenically unsaturated anhydride. 6. A coating composition according to any one of the preceding claims in which the glycidyl component comprises a polyglycidyl ether of a polyol. 7. A coating composition according to any one of the preceding claims which comprises 40-70% by weight of binder and 30-60% by weight of organic solvent. 8. A coating composition according to any one of the preceding claims in which the glycidyl component is a polymer of polymerised glycidyl acrylate or glycidyl methacrylate and an alkyl methacrylate, an alkyl acrylate or mixtures thereof in which the alkyl group has 1-12 carbon atoms. 9. A substrate having a base coat comprising a layer of a pigmented coating composition and a topcoat layer firmly adhered to said base layer and comprising a composition as claimed in any one of the preceding claims. 10. A process for forming a cured surface coating on a substrate which comprises applying a layer of a coating composition comprising 20-80% by weight of two reactive binder components and 80-20% by weight of an organic liquid carrier; wherein the binder comprises: (a) an acrylic polymer component having at least two anhydride groups and a weight average molecular weight of about 2,000 50,000; (b) a glycidyl component having at least two reactive glycidyl groups and subjecting the layer to vapors of an amine catalyst until the layer is cured. 11. A coating composition comprising 20-80% by weight of two reactive binder components and 80-20% by weight of an organic liquid carrier; wherein the binder comprises: (a) an acrylic polymer component having at least two anhydride groups and secondary or tertiary amine groups for curing and the polymer having a weight average molecular weight of about 2,000-50,000 and (b) a glycidyl component having at least two glycidyl groups.

Inventors: CORCORAN, PATRICK HENRY
Applicants: E.I. DU PONT DE NEMOURS AND COMPANY
Application year: 1986
Main classification: C09D4
IPC codes: C08G59, C09D133, C09D163, C08L63