MXPA96001423A - Method of coating of multiples ca - Google Patents

Abstract

The present invention relates to a method for preparing a coating comprising the steps of: 1) applying to a substrate a first curable coating composition comprising two components that are reactive with one another to form urethane linkages, the composition further comprising a third component that includes one or more epoxy groups, 2) cure the first curable coating composition to form a cured coating, 3) apply a second curable coating composition on the surface of the coating of step (2), and 4) cure the second curab coating composition

Description

METHOD OF COATING OF MULTIPLE LAYERS Field of the Invention This invention relates to coatings and, in particular to a method for preparing a multilayer coating composition using a urethane crosslinked coating.

BACKGROUND OF THE INVENTION Coating compositions are often viewed in thermoplastics and thermosetting compositions. The thermoplastic coating compositions utilize high molecular weight polymers dispersed in an organic or aqueous solvent. After the coating is applied to a layer, the solvent is removed and the polymers are stabilized to form a film. The curable or curable coating compositions use two components that are reactive under certain conditions of cure. The reactive groups in these components are referred to as "functional groups". After the composition containing these components is applied, the coated substrate is subjected to curing conditions, whereby the functional groups react and form a film of a crosslinked matrix. Various combinations of functional groups in the art have been used for curable coating compositions. A widely used combination uses OH-functional groups and the alkylol groups on aminoplast resins. These functional groups react to form ether bridges in the crosslinked coating. Another combination uses acid functional groups and epoxy functional groups, which react to form ester bridges in the crosslinked coating. Curable coating compositions that are cured through the formation of urethane bridges in the crosslinked coating have also been used in the art. Urethane links are often desirable because of their durability, resistance to attack by various agents in the environment, impact resistance and other physical properties such as stress release. Urethane bridges can be formed by various combinations of functional groups, such as OH functional groups and functional isocyanate groups, carbamate groups and aminoplast resins, or cyclic carbonate groups and amino groups. In many coating applications, it is often necessary to apply an additional coating over a cured coating. This can be done to achieve certain visual or physical properties, or it may be necessary to repair areas where the cured coating has been damaged or where coating defects exist. The areas in need of repair are usually identified by visual inspection of the coated surface, which can be aided by mechanical inspection aids or known electronics. In these cases, it is important that the coating applied on the cured coating has adequate adhesion to the cured coating. Even if the cured coating is smoothed before the application of the additional coating, the adhesion factor is still an interest with respect to the overlying areas towards the coating surface without sand. The inter-coat adhesion may be of particular interest with respect to cured urethane coatings. Accordingly, the present invention is directed towards said curable coating composition having good adhesion properties between coatings.

SUMMARY OF THE INVENTION Therefore, the present invention provides a method for preparing a multilayer coating. The method of the invention comprises the steps of: (1) applying on a substrate a first curable coating composition comprising two components q reactive with each other to form urethane linkages and a third component including one or more groups ei, (2) curing the first curable coating composition to form a cured veneer, (3) applying a second curable coating composition on the coating surface of step (2), and (4) curing the second coating composition. curable DESCRIPTION OF THE PREFERRED EMBODIMENTS Various component combinations can be used which are reactive with each other to form urethane linkages in the composition of step (1) in accordance with the present invention. As used herein, the term "urethane linkage" refers to an eniacs in the matrix of a cured coating having the formula: wherein R is H, substituted or unsubstituted alkyl of preference of 1 to 5 carbon atoms, or substituted or unsubstituted cycloalkyl of preferably up to 6 carbon atoms in the anion. One of these combinations uses a to-functional carbamate material as one of the components. ? A variety of carbamate-functional materials are used. These include materials described in WO 94/10211 and EU.A. 5, 356, CG9, the disclosures of which are incorporated herein by reference. A carbamate-functional polymer can be used as the carbamate-functional material in the practice of the present invention. The carbamate-functional polymer components used in the composition of the invention can be prepared in a variety of ways. One way of preparing such polymers is to prepare an acrylic monomer having a carbamate functionality in the ester potion of the monomer. These monomers are well known in the art and are described, for example, in United States Patents 3,479,328, 3,674,838, 4,126,747, 4,279,833 and 4,340.49, the teachings of which are incorporated herein by reference. One method of synthesis involves the reaction of a hydroxy ester with urea to form the carbamy loxi carboxy 1 ato (ie, carboxylic acid-modified acyl). Another synthetic method reacts an ester of alpha, beta-unsaturated acid with a hydroxy-bamate ester to form the carbamy loxycarboxylate. Yet another technique involves the formation of a hydroxyalkyl carbamate by reacting a primary or secondary amine or diamine with a cyclic carbonate such as ethylene carbonate. The hydroxyl group in the hydroxy-1-carbamate is then esterified by reaction with acrylic or methacrylic acid to form the monomer. Other methods for preparing acrylic monomers modified with carbamate are described in the art and may also be used. The acrylic monomer can then be polymerized together with other ethylenically unsaturated monomers, if desired, by techniques well known in the art. An alternative route for preparing carbamate functional polymers is to react an already formed polymer such as an acrylic polymer with another component to form a bamate-functional group attached to the polymer structure, as disclosed in U.S. Patent 4,753,532, whose disclosure is incorporated herein by reference, a technique for the preparation of carbamate-functional polymers involves the thermal decomposition of urea (to release ammonia and HCO) in the presence of anhydroxy-functional acrylic polymer to form a carbamate-acrylic polymer. functional. Another technique involves reacting the hydroxyl group of a hydroxyalkyl carbamate with the isocyanate group of an acrylic or vinyl isocyanate functional monomer to form the carbamate-functional acrylic. Acrylics and soci-functional acrylics are known in the art and are described, for example, in U.S. Patent 4,301,257, the disclosure of which is incorporated herein by reference. Isocyanate vinyl monomers are well known in the art and include -tetramet i lysis unsaturated isocyanate (sold by American (R) Cyanamid as TMI;). Another technique is to react the cyclic carbonate group in a cyclic carbonate-functional acrylic with ammonia in order to form an acrylic carbamate function.

Acrylated cyclic carbonate-functional polymers are known in the art and are described, for example, in U.S. Patent 2,979,514, the disclosure of which is incorporated herein by reference. A preferred approach is a transcarbam 1 ation or reaction of transesterification of a hydroxy-functional polymer with an alky carbamate or hydroxyacyl carbamate.

A more difficult, but feasible, way of preparing the polymer would be to transester the acrylate polymer with a hydroxyalkyl carbamate. Other polymers can also be used. For example, a carbamate-functional polyurethane can be prepared as described in United States Patent Application Serial No. 08 / 093,169, the disclosure of which is incorporated herein by reference. A carbamate-functional polyester can be prepared as described in JP 51/4124, the disclosure of which is incorporated in the proposal by reference. The carbamate-functional polymers can have a molecular weight of 1000-20,000 and, preferably, of 4000-60C0. The molecular weight as used herein means the weight-average molecular weight and can be determined by the GPC method using a standard of polystyrene. The polymer content of the polymer, at a molecular weight per equivalent of carbamate functionality, will generally be between 200 and 1500, and preferably between 300 and 500. A class of carbamate-functional polymer component can be represented by randomly repeating units. in accordance with the following formula: In the previous formula, R represents H or CH-. R "represents H, alkyl, preferably 1 to 6 carbon atoms or cycloalkyl, preferably up to 6 carbine atoms in the ring. It should be understood that the terms alkyl and cycloalkyl should include alkyl and substituted cycloalkio, such as the cycloalkyl substituted with halogen. The substitutes that will have an adverse impact on the properties of the cured material, however, should be avoided. For example, the ether linkages are thought to be susceptible to hydrolysis and should be avoided in locations that would place the ether link in the crosslinked matrix. The values x and y represent percentages by weight, with x being 10 to 90% and preferably 40 to 60% e and xing 90 to 10% and preferably 50 to 40%. In the above formula, A represents repeating units derived from one or more ethylenically unsaturated monomers. These monomers for copolymerization with acrylic monomers are known in the art. They include alkyl esters of acrylic or methacrylic acid, e.g., eti lacri lato, buti lacri l or 2-ethe lhexi lacri lato, buti lmetacri lato, i sodeci Imetacri lato, hydrolyte lmetacri lato, hidroxipropi lacri lato and the like; and vinyl monomers such as mtetramethiisocyanate, lime-insoluted isocyanate (sold by American Cyana id as TMI1-1 ^), styrene, nitroluene and the like. L represents a divalent linking group, preferably an aliphatic of 1 to 8 carbon atoms, a cycloaliphatic linking group of 6 to 10 carbon atoms. Examples of L include - (CH2J-, - (CHg ^ »" (CH2 ^ 4 and ° semsJan "have a preferred mode, -L- is represented by -C00-L1- where L 'is a divalent linking group. this way, in a preferred embodiment of the invention, the carbamate-functional polymer component is represented by random repetitive units in accordance with the following formula: o o In this formula, R., R2, A, x and y are as defined in the foregoing. L 'can be an aliphatic diva lens linking group, preferably 1 to 8 carbon atoms, e.g., - (CH -) - (CH2) -, - (CH ^)., And the like, or a divalent cycloaliphatic linking group, preferably up to 3 carbon atoms, v.gr cyclohexyl and the like. However, other divalent linking groups can be used, depending on the technique used to prepare the polymer. For example, if hydroxyalkylcarbamate adduct is added to an isocyanate-functional acrylic polymer, the linking group L 'would include an urethane-NHC-o-chain as a residue of the isocyanate group. Carbamate-functional materials of lower molecular weight, such as oligomeric and non-polymeric materials may well be used in the practice of the present invention. These compounds can be prepared in a variety of ways. One way of preparing said carbamate-functional is to react an alcohol ('alcohol' is defined herein with one or more OH groups) with a urea to form a com pound with carbamate group (s). This reaction is achieved by heating a mixture of alcohol and urea. Another technique is the reaction of a polyol with a monoisocyanate (e.g., meth i 1 isocyanate) to form a compound with multiple secondary carbamate groups or to react an alcohol with cyanic acid to form a compound with primary group 9s) carbamate (i.e., unsubstituted carbamates). This reaction is also carried out under heat, preferably in the presence of a catalyst as is known in the art. The carbamates can also be prepared by reaction of an alcohol with phosgene and then ammonia to form a compound having primary group s) carbamate, or by reaction of a polyol with phosgene and then a primary amine to form a compound having secondary carbamate groups. Another approach is to react an isocyanate (e.g., HDI, IPDI) with a co-position such as hydroxypropyl carbamate to form an isocyanate derivative capped with carbamate. Finally, the carbamates can be prepared by a transfer approach in which an alcohol or hydroxylalkylcarbamate is reacted with an alkyl carbamate (e.g., ethylcarbamate, ethylcarbamate, butylcarbamate) to form a compound containing a primary carba_ group. This reaction is carried out under heat, preferably in the presence of a catalyst such as a metal organ catalyst (e.g., dibutyltin dilaurate) Other techniques for preparing carbamates are also known in the art and they are described, for example, in P. Adams and F. Baron, "Esters of Carba ic Acid", Chemical Revie, v.65, 1965 Various alcohols can be used in the preparation of carbamate compounds useful in the practice of the invention. They generally have from 1 to 160 carbon atoms, preferably 1-60 carbon atoms and can be monofunctional or polyfunctional (preferably a functionality of 2 to 3), aliphatic, aromatic or cycloaliphatic, they can contain only OH groups, or they may contain more heteroatom OH groups such as 0, S, Si, N, P and other groups such as group ester, ether groups, ammonium groups or unsaturated sites Examples of useful alcohols include 1, 6-hexanediol-, 1, 2-hexanediol, 2-eti 1 - 1, 3-hexanediol, ethyl-pro pi 1- 1, 5-pentanediol, 2-methyl-1 -2, 4-pentanediol, 2, 2, -trimeti i-1,3-pentanediol, 2, 4, 7, 9-tetramethyl-5-decin-4,7-diol, 1,3-dihydroxy-c-tone dimer, 2-buten-1,4-dioi, pentotenol, dimethyl Itartrate, pent etiolglgol, dimeti 1 si 1 i idipropanol and 2,2'-thioethanol. Another approach is to react an isocyanate (preferably a diisocyanate, e.g., HDI, IPDI) with a compound such as hydroxypropyl carbamate to form a polyisocyanate derivative capped with carbamate as described in the application of U.S. Patent Serial No. 08 / 098,176. The polyisocyanate can be an aliphatic polyisocyanate, including a cycloalkyl isocyanate or an aromatic polyisocyanate. Useful aliphatic polyisocyanates include diisocyanates such as ethylene diisocyanate, 1,2-diisocyanatopropane, 1,3-diisocyanatopropans, 1,6-diisocyanatohexane, 1,4-butylene diisocyanate, lysine diisocyanate, 1, 4 methy len-bis- (cyclohexy-1-iso cyanate) and isophorone diisocyanate. Useful aromatic diisocyanates and aliphatic diisocyanates include the various isomers of toluene diisocyanate, meta-xi lendi isocyanate and para-xi lendi isocyanate, also 4-chloro-1,3-phenylene diisocyanate, diisocyanate of 1.5. -tetrahydro-naphthalene, 4,4'-d-benzyl diisocyanate and 1,4-benzene tris-isocyanate can be used. In addition, the various diisocyanate isomers of a. fa, alpha, to lfa ', to fa' -tetrameti lxi leño can be used. Also useful (R) isocyanate biurets such as DESM0DUR '100 from obay. In one embodiment of the invention, polyisocyanate is reacted with a compound containing an isocyanate reactive group and a carbamate group, e.g., a hydroxyalkyl ester such as hydroxypropyl carbamate or hydroxyethyl carbamate. Al ternatively, the polyisocyanate can be added with substitutes having the ability to form carbamate groups after the reaction with the finished poly nicotinate compound. For example, the polyisocyanate can be reacted with a compound-since it has an active hydrogen group (2 g, hydroxyl) and a cyclic carbonate group (e.g., the reaction product of g 1 cidol). and CO), and the cyclic carbonate groups are then reacted with ammonia to form the carbamate functional groups. Alternatively, the polyisocyanate can be reacted with an active hydrogen group (e.g., hydroxyl) and an epoxy group and, then with CO to convert the epoxy to cyclic carbonate and the cyclic carbonate groups are then reacted with ammonia to form the carbamate functional groups. Another synthetic method is to first react isocyanate groups in a polyisocyanate with a compound having a group that is reactive with isocyanate and also a functional non-N group. This adduct is then reacted with a compound comprising at least one carbamate group or group that can be converted to carbamate and at least one group reactive with non-functional NCO groups. Examples of non-NC0 functional groups include carboxyl, epoxy, hydroxyl, amino. For example, an OH-functional adduct (which can be formed by reacting a p-isocyanate with an amino alcohol) can be reacted with the oxygen of a C00 portion of the carbamate group or an alkyl carbamate or with the methylol group of methylalacri-lamide ( H0-CH2-NH-C0-CH = CH2). In the case of the C00 group in an alkylcarbamate, the hydroxyl group in the polyurethane is subjected to a tranesterification with the group C00, resulting in the carbamate group being attached to the polyurethane. In the case of methyl acrylamide, the unsaturated double bond is then reacted with peroxide to form an epoxy group. The epoxy groups are then reacted with CO 2 to form cyclic carbonate groups, which are converted to carbamate groups by reaction with ammonia. Alternatively, an acid-functional polyisocyanate (which can be formed by reaction of a polyisocyanate with an acid hydroxy-functional boxyl) can be reacted with acetic anhydride to generate an anhydride-fused tri-isocyanurate which can then be reacted with a hydroxyalkylcarbamate. The polyisocyanates described above are adducts with compounds containing a carbamate group or group that can be converted into carbamate and a group that is reactive with the NC0- or non-NCO-functional group in the polyisocyanate. Compounds containing carbamate which can be adducted to the NCO groups of a diisocyanate or isocyanurate are preferably carbons containing active hydrogen such as hydroxyalkylcarbamates (e.g., hydroxypropyl carbamate or hydroxyethylcarbamate). Compounds containing groups that can be converted to carbamate and groups that are reactive with NCO include cyclic carbonate compounds containing active hydrogen convertible to carbamate by reaction with ammonia (e.g., the reaction product of glycidol and CO), ethers of monogl icidi lo i ^ /. Q r. , (R) Cardura Ev) convertible to carbamate by reaction with C02 and then ammonia and esters of onogl icide (e.g., the reaction product of a carboxylic acid and epichlorohydrin) converted to carbamate by reaction with C02 and then ammonia, allyl alcohole where the alcohol group is reactive with NCO and the double bond can be converted to carbamate by reaction with pe rioxide, and vinyl esters where the ester group is reactive with NCO and the vinyl group can be converted to carbamate mediant reaction with peroxide, leugo C02 and then ammonia. The non-polymeric or oligomeric carbamate-functional compounds will generally have a molecular weight of 75-2000 and preferably 75-1500. As used in this, pe so molecualr means weight average molecular weight. The molecular weight can be determined by the GPC method. A number of materials such as the component can be used to react with carbamate to form a urethane linkage as defined above. These include melamine formaldehyde resin (including polymeric monomeric melamine resin and partially or fully alkylated melamine resin), urea resins (e.g., methylol ureas such as urea formaldehyde resin, alkoxy ureas such as resin). of butylated formaldehyde urea), polyanhydrides (e.g., polysuccinic anhydride), phenol / formaldehyde adducts and poly isi loxanes (e.g., trimethoxy si loxane). Aminoplast resin such as melamine formaldehyde resin or urea formaldehyde resin are especially preferred. Even more preferred are anneaptan resins wherein one or more of the amino nitrogens is substituted with a carbamate group for use in a process with a curing temperature of less than 150QC, as described in U.S. Pat. 5,330,328. Another combination of components that can be used to form urethane linkages in the practice of the present invention uses a polyisocyanate as one of the components. The polyisocyanate can be an aliphatic polyisocyanate including a cycloaliphatic polyisocyanate or an aromatic polyisocyanate. Useful aliphatic polysaccharides include aliphatic diisocyanates such as ethylene diisocyanate, 1,2-diis cyanate propane, 1,3-diisocyanatopropane, 1,6-diisocyanatohexane, 1,4-butyl lendi isocyanate, lysine diisocyanate, 1,4-methylene bis (cyclohexy-1-isocyanate) and isophorone diisocyanate. Useful aromatic diisocyanates and araliphatic diisocyanates include various isomers of toluene diisocyanate, meta-xi lendi isocyanate para-xiiendi isocyanate, also 4-chloro-1,3-phenylene diisocyanate, diisocyanate of 1.5. tetrahydro-naphthalene, 4,4'-diisocyanate-dibenzyl and 1,4-benzene tri-isocyanate may be used. In addition, the various diisocyanate isomers of a lfa, alpha, alpha ', fa' -tetramethylloxy can be used. Also useful as the isocyanate are isocyanurates such as DESMODUR () 3300 from Miles, Inc. and isocyanate biurets such as DESMODUR ( No. 100 of Miles, Inc. Polyisocyanates may not be blocked, in which case the coating composition should be used as a 2K, ie, the reactive components combined shortly before application, or may be blocked. Any known blocking agents, such as oximes, may be used. the polyisocyanates can be reacted with any one of a number of active hydrogen-containing components to form urethane linkages. Functional groups that have active hydrogen are well known in the art. Such groups include, for example, hydroxyl groups, amino groups, thiol groups, hydrazide groups and activated methylene groups. The active hydrogen component for reacting with the polyisocyanate can be polymeric, oligoeric or non-polymeric. In a preferred embodiment, the component is polymeric. Useful polymer resins include, for example, acrylic polymers, modified acrylic polymers, polyesters, polyepoxides, polycarbonates, polyurethanes, polyesters, polyimides and polysiloxanes, all of which are well known in the art. Preferably, the component is a polymeric polyester or oligomer or an acrylic, modified acrylic. More preferably, the component is an acrylic polymer or oligomer resin. In a preferred embodiment of the invention, the compound for reacting with polyisocyanate is an acrylic resin, which may be a polymer or oligomer. The acrylic or oligomeric polymer preferably has an olecular weight of from 500 to 1,000,000, and more preferably from 1,500 to 50,000. As used herein, "molecular weight" refers to the weight average molecular weight, which can be determined by the GPC method using a polystyrene standard. Acrylic polymers and oligomers are well known in the art and can be prepared from monomers such as methacrylate, acrylic acid, methacrylic acid, methyl methacrylate, butyl methacrylate, cyclohexyl methacrylate and the like. The active hydrogeological functional groups, eg, hydroxyl, can be incorporated into the ester portion of the acrylic monomer. * For example, the hydroxy-functional acrylic monomers which can be used to form such resins include hydroxyethyl acrylate, hydroxybutyl lacrylate, hydroxyethylmethacrylate, hydroxypropyl lacrylate, and the like. The amino functional acrylic moieties would include t-butylaminoeti lme crilate and t-buti laminoeti lacri lato. Other acrylic monomers having active hydrogen functional groups in the ester moiety of the monomer also fall within the branch's expertise. Modified acrylics can also be used.

These acrylics can be acrylic modified with polyester or acrylic modified with polyurethane as is well known in the industry. Polyester-modified acrylics modified with e-caprolactone are described in U.S. Patent No. 4,546,046 to Etzell et al, the disclosure of which is incorporated herein by reference. Acrylics modified with polyurethane are also known in the industry. They are described, for example, in U.S. Patent 4,584,354, the disclosure of which is incorporated herein by reference. Polyesters having active hydrogen groups such as hydroxyl groups can also be used as the polymer in the composition according to the invention. These p-esters are well known in the art and can be prepared by the polyesterification of organic polycarboxylic acids (e.g., phthalic acid, hexahydrothilic acid, adipic acid, maleic acid) or their anhydrides with organic polyols containing primary or secondary hydroxyl groups (e.g., eti lengl icol, butj lenglicol, neopenti lgl icol). Polyurethanes having active hydrogen functional groups are also well known in the art. They are prepared by means of a chain extension reaction of a polyisocyanate (e.g., diisocyanate of hexe eti log, isophorone diisocyanate, MDI, etc.) and a polyol (eg, 1, 6-exandiol, 1, 4-butandioi, neo-penicillin, tri-eti loipropane). They can be provided with funcinale groups of active hydrogen by plugging the polyuryl chain with an excess of diol, polyamine, amino alcohol or leaving it free. Although the polymeric or igomeric active hydrogen components are often preferred, the non-polymeric active components of lower molecular weight may also be used in some applications, eg, aliphatic polyols (e.g. -hexandiol), hydroxylamines (e.g., nobutanolamine) and the like. The composition of the present invention also purchased from a component that includes one or more epoxide groups. The two are well known in the field. The epoxide can be of the general formula: wherein R1, R2, R3 and R4 are each independently H (with the proviso that at least one of R1-R4 is other than H), an organic radical, which may be polymeric or non-polymeric and may contain unsaturation and / or hetero omos, or one of R1 or R2 together with one of R3 or R4 may form a cyclic ring, which may contain unsaturation and / or heteroatoms. Although essentially any epoxy can be used in the practice of the present invention, the reference epoxy is substantially free of groups that are reactive with either of the two components that are reactive with each other to form urethane linkages. By "substantially freeing" said groups, it is implied that the degree of reaction between any of the two components which are reactive to form urethane bonds and any reactive component in the epoxide is sufficiently low in order to avoid any adverse impact thereto. The desired epoxides on the adhesion properties between layers of the coating, useful epoxides can be prepared from alkaline holes, eg, butanol, trimethylolpropane, by reaction with an epihalohdrine (e.g., epichlorohydride) by the reaction of an allyl group with peroxide, oligo- or polyimic polyepoxides, such as polymers or acrylic oligomers which have glycidi ethacrylate or polyether ethers terminated with epoxy such as diglycidyl ether of bisphenol A (DGEBPA The epoxy polyurethane resins or polyester resins can also be prepared by making the polyurethanes or polyesters reactive. that contain OH group, as they are known in the field, with an epihalohydrin. Epoxides can also be prepared by reacting an isocyanate-terminated component such as monomeric poly nicity or polymer or oligomer with glycidol. Other oxygenated polyepoxides, e.g., epoxy-novolacs, may also be used. In a preferred embodiment, the epoxide is an oligomeric polymers containing acrylic, preferably deriving its epoxy groups from glycidyl methacrylate monomer, 1-chloro-methacrylate, 1-cyclohexyl ether, 1-cyclohexy-1-monoepoxymethacrylate, the epoxide of the cyclopentadienmethacrylate or non-epoxidized butadiene epoxide, more preferably glycidimethacrylate. In another preferred embodiment, both, the epoxy-containing component and one of the components that react to form urethane bonds are acrylic polymers or oligomers. The epoxide is preferably present in the coating composition in an amount of 0.0001 to 0.05 equivalents of epoxy per 100 g of resin. In a preferred embodiment, the composition of the present invention also includes a component, which may be the same or different from any of the other components, comprising one or more acid groups. Any type of acid can be used, including Bronsted or Le is acids. The acids can be inorganic acids (eg, phosphoric), but organic acids are preferred. Various types of organic acids may be used, such as phenolic, cresyl or hydroxy acids (eg citric acid, phenol, cresol, tartaric acid, amino acids), or carboxylic acids, with the carboxylic acids being preferred. Organic acids can be monofunctional or polyfunctional. In a modality, the acid is monofunctional. These monofunctional acids include octanoic acid, benzoic acid, acetic acid, hexanoic acid or benzyl acid.

The optional polyacidic acid components can also be used. The organic acid component can be a monomeric acid or an adduct thereof, or it can be a polymeric or oligomeric polyacrylate. For onomeric polyacids, liquid polyethers are usually used. Non-limiting examples of these acids are succinic acid, slutárico acid, adipic acid, azelaic acid, oxalic acid, phthalic acid, iso phthalic acid, hexahydrothylelic acid, methylhexylhydrophthalic acid, maleic acid, chlordenedic acid and the like. The polyacids d higher acid functionality, w. gr. , trimethylic acid, trichilic acid, aconitic acid and the like can also be used. Adducts containing polyacid of higher molecular weight can also be used. Examples of useful polyacid-containing adducts are acid-containing polyesters, acid-containing polyurethanes, acrylics containing the like acid. An example of the polyesters containing acid can be prepared by reacting an excess of a monomeric polyether as described above with a polyol. Alternatively, in a preferred embodiment, a cyclic anhydride (e.g., a 1,2-acid anhydride such as hexahydrophthalic anhydride and alkylahexahydrophthalic anhydride) may be reacted with a polyol, such as 1: 6. -hexandiol, tri eti lolpropane and poly icaprolactone triol to form a polyacid of half ester. Illustrative examples of acid-containing acrylics are copolymers of an ethically unsaturated monomer containing an acid group. The copolymers can be prepared using conventional techniques such as free radical polymerization or anionic polymerization, for example, in a lot or stepwise process, one or more other ethylenically unsaturated monomers containing no acid group can be incorporated into the polymer which It contains acid. Examples of the ethylenically unsaturated monomers containing an acid group may be acrylic acid, methacrylic acid, itaconic acid and maleic acid. Other polymerizable monomers may be alkyl esters of acrylic or methacrylic acid, e.g., eti lacri lato, buti lacri lato, 2-atihaloxy lacrylate, butyl methacrylate, isodecylmethacrylate, hydroxyethylmethacrylate, hydroxypropyl alcohol, lato and the like; V ivore monomers such as styrene vinyl toluene and the like. The monomer copolymers containing groups which will react with the acid groups under the addition reaction conditions should be avoided in order to produce a non-gelled product. Useful anhydrides include monoaryl anhydrides such as alkylahydrophthalic anhydride, wherein the chlyl group has up to 7 carbon atoms, e.g., methylhe hydrophthalic anhydride, succinic anhydride, methylisuccinic anhydride, sodium dodeceni 1 succinic, anhydride octadeceni lsuccinic, phthalic anhydride, tetrahydrophthalic anhydride, nahidridc meti ltetrahi drophthalic anhydride, tatrachlorophthalic anhydride, endomethylenhydrophthalic anhydride, chlordened anhydride, itaconic anhydride, citraconic anhydride and anhydride anhydride. The anhydride can also be polymeric, such as copolymers of maieic anhydride with other ethylenically unsaturated monomers. Said copolymers are preferably formed in the same manner as the acid-containing copolymers previously discussed. The acid component is preferably present in an amount of 0 to 0.5 equivalents of acid per 100 g of resin solids, and more preferably 0.00008 to 0.008 equivalents of acid per 100 g of resin solids. In a preferred embodiment of the invention, one of the components that are curable to form uratane bonds is acrylic resin, and the component that includes one or more epoxy groups is an acrylic epoxy resin. Said epoxyacrylic resin preferably includes one or more of the methacrylate components of lauryl, 2-ethylhexyl lacrylate, 2-ethylhexyl methacrylate, or bu tilacrylate. The epoxy equivalent weight, molecular weight and glass transition temperature of the epoxy-acrylic resin is adjusted by varying the monomer alignment to optimize the function in the particular coating composition by techniques known in the art. A solvent may optionally be used in the coating composition used in the practice of the present invention. Although the composition employed according to the present invention can be used, for example, in the form of substantially solid powder, or a dispersion, it is often desirable that the composition be in a substantially liquid state, which can be achieved with the use of a solvent. It is solvent you must act as a solvnete with respect to all the components in the composition. In general, depending on the solubility of the various components, the solvent can be any organic solvent and / or water. In a preferred embodiment, the solvent is a polar organic solvent. More preferably, the solvent is a polar aliphatic solvent or polar aromatic solvent. Still more preferably, the solvent is a cathone, ester, acetate, aprotic amide, aprotic sulphoxide or aprotic amine Examples of useful solvents include methyl ethyl ketone, methyl isobutyl ketone, m-amyl acetate, ether ethyl acetate, and ethyl acetate. , propylene glycol monomethyl ether acetate, xylene, N-me ti Ipirrol idone or mixtures of aromatic hydrocarbons. In another preferred condition, the solvent is water or a mixture of water with small amounts of cosolvents. The coating composition used in the practice of the invention may include, irrespective of the acid composition described above, a catalyst tai as an acid catalyst to improve the curing reaction. For example, when using a polycarbamate and aminoplast compounds as the components for forming urethane linkages, a strong acid catalyst can be used to improve the curing reaction. These catalysts are known in the art and include, for example, β-toluene sulfonium acid, dinonylnaphthalenedisulfonyl acid, dodecyl benzenesulfonic acid, phenyl acid phosphate, monobutyl maleate, butyl phosphate and hydroxyphosphate ester. The acid catalysts strong with frequent are blocked, v. gr., with an amine. When a polyisocyanate and a polio are used as the components to form urethane linkages, organometallic catalysts, such as stylolate laurate, can be used. Other catalysts which may be useful in the composition of the invention include Lewis acids, zinc salts and aluminum salts. In a preferred embodiment of the invention, the solvent is present in the coating composition in an amount of from about 0.01 weight percent to about 99 weight percent, preferably from about 10 weight percent to about 60 weight percent. percent by weight and, more preferably, from about 30 weight percent to about 50 weight percent. The coating compositions in steps (1) and (3) can be coated on the substrate by any of a number of techniques well known in the art. These include, for example, spray coating, investment coating, roller coating, curtain coating and the like. The substrate can be steel or other metal with imprinter or without primer, glass, wood or plastic. If the substrate is a car body panel, spray coating is preferred. Any additional agents used, for example, surfactants, fillers, stabilizers, wetting agents, dispersing agents, adhesion promoters, UV absorbers, HALS, etc. they can be incorporated into the coating composition While the agents are well known in the above branch, the amount used must be controlled to avoid adversely affecting the coating characteristics. The coating compositions used in the practice of the invention. They can be transparent and can be re-dressed with pigmented paint. When pigmented, the pigment can be any organic or inorganic compounds, or colored materials, fillers, metallic flake or other inorganic materials such as mica or aluminum flake, and other materials of the kind that the industry normally calls pigments. The pigments are usually used in the composition in an amount of 1% to 100%, based on the total solid weight of the components in the coating composition (ie, a ratio of P: B gives 0.1 to 1). ). In a preferred embodiment, the coating composition applied in step (1) according to the invention is the transparent coating of a more transparent colored composite ravastimethane. The coating compositions of b are pigmented useful therewith include any of a number of types well known in the art, and does not require detailed explanation herein. Polymers known in the art to be useful in basecoat compositions include acrylics, vinyls, polyurethanes, polycarbonates, polyesters, aids and poly isi loxanes. Preferred polymers include acrylics and polyurethanes. In a preferred embodiment of the invention, the base coating composition also utilizes a carbamate-functional acrylic polymer. The basecoating polymers can be thermoplastic, but preferably are crosslinkable and comprise one or more types of crosslinkable functional groups. These groups include, for example, hydroxy group, isocyanate, amine, epoxy, acrylate, vinyl, silane and acetoacetate. These groups can be masked or blocked in such a manner that they are unblocked and available for the crosslinking reaction under the conditions. of curing desired, usually elevated temperatures. Useful crosslinkable functional groups include hydroxy, epoxy, acid, anhydride, silane acetoacetate groups. Preferred crosslinkable functional groups include hydroxy functional groups and amino functional groups. The basecoat polymers may be self-crosslinking, or may require a separate crosslinking agent. reactive with the functional groups of the polymer. When the polymer comprises hydroxy functional groups, for example, the crosslinking agent may be a resin of blocked aminoplas, isocyanates and isocyanates (including isocyanurate and functional acid or anhydride crosslinking agents.

The coating compositions described herein are subjected to conditions in steps (2) and (4) so as to cure the coating layers. Although various curing methods can be used, thermal curing is preferred. In general, thermal curing is carried out by exposing the coated article to high temperatures provided primarily by sources of radiant heat. The curing temperatures will vary depending on the particular block groups used in the crosslinking agents, however, they generally vary between S2 s C and 177 e C. The curing time will vary depending on the particular cc speakers used and the physical parameters such as the thickness of the layers, however, the typical curing times vary from 15 to 60 minutes. The coating composition to be applied in step (3) according to the invention can be any of the types described above for step (1) or the types described above for pigmented coatings. (.g., acrylic resin OH-functional -i-meia ina, OH-functional urathane resin + pol ii socianato). In a preferred embodiment, the ethane coating composition (3) of the type qua utilizes a carbamate functional component and a component which is reactive therewith, as described above for step (1). In another preferred embodiment, the coating composition of step (1) and the coating composition of step (3) both use the same curing chemistry, preferably carbamate / aminoplast. When the second stage (4) of curing must be a low curing temperature (82dC to 104SC, v.gr for repair at low baking of automobile bodies or repair of finished automobiles), the composition of stage (3) preferably it uses an aminoplast as one of the component in combination with a coreactive component (e.g., an OH = functional component or, more preferably, a carbamate functional component) and an unblocked acid curing catalyst, or an unblocked polyisocyanate component in combination with a coreactive active hydrogen component. The invention is further described in the following examples.

Preparation 1 A coating composition having the following formulation was prepared: Component Parts in Weight Carbamate-functional acrylic resin 129.18 (An acrylic resin having a pro-by-weight molecular weight of about 53 6500, an equivalent carbamate weight of about 450, wherein the source of the carbamate functionality is a repeating unit of carbamate. polymer of the formula: Component Parts in Step Rasimine, (R) '747 melamine resin 13.61 Tinuvin ^ 34SB UVA 3.16 Tinuvin (R) HALE 1.50 Nacure (R) 5225, blocked dodecylbenzenesulfonic acid • with isobutanol 3.00 amyl acetate 23.00 3-ethoxyethyl propionate 2S.00 Preparation 2 Sa prepared a coating composition having a composition identical to Preparation 1 with the addition of 1. parts by weight of an epoxy-functional acrylic polymer quaating a weight average molecular weight of about 20,000 with a monomer alignment ( by weight) of 38.5% glycidyl ethacrylate, 59.5% 2-ethylhexyl lacrylate, 1% styrene and 1% methyl ethacrylate.

Preparation 3 A coating composition having the composition identical to Preparation 2 was prepared with the addition of 0.29 parts by weight of octanoic acid.

EXAMPLE 1 The coating compositions of Preparation 1 Preparation 2 and Preparation 3 were coated on a steel primer with primer as the clearcoat of a base coat / clearcoat composite coating having a pigmented base coating in We used a hydroxy-functional acrylic resin and a melamine resin reticulator. The panels were cured as described below for each of the adhesion tests in layers.

High Bake Repair Test (HBR) The coated panels were cured for 20 minutes at 1329 C and allowed to cool. The panels were then coated with a base coat coating. wet on wet / transprent layer having a transparent layer that was identical to Prep ration 1 and a basecoat composition having the following composition: Component Parts in Weight Acrylic Resin Dispersion 0H = Functioni l? .oo (Acrylic resin having a weight average weight weight of about - 8000 composed of 15 parts by weight of hiriroxieti lacri lato (modified with 30 Component Parts by weight parts by weight of e-caprolactone), 20 tablets by weight of styrene, 16 parts by weight of 2-ethylhexyl lacrylate, 15 parts by weight of n-butyl methacrylate and 3 parts by weight of acrylic acid.) dispersion of microgel acrylic 26. 1 1 melamine resin Resimene, (R ') / 755 1 7. 18 ground black pigment paste 21 .82 Acrylic polymer flow additive 0.15 N-meti Ipirrol idona 1.40 UV and HALS solution 2.88 Acid catalyst blocked Nacure, ('R) 5225 1.62 Ethanol 1.90 n-Butyl acetate 3.27 The panels were cured for 20 minutes at 132 ° C and cooled. The panels were then subjected to an adhesion test as described in ASTM 3359 which involves grating a portion of the coating with a cut pattern and applying and removing pressure-sensitive adhesive tape. The panels were evaluated for pass / fail with a pass representing 10% or less of the second base / clear coating that is removed during the trial and one failure being greater than 10% of the second base / transvestite cover removed during the test.

Intercoat Adhesion Test (ICA) III The panels were processed and tested as described for the HBR test, except that the first basecoat / clearcoat was cured for 20 minutes at 146 SC and the second basecoat / clearcoat was cured for 20 minutes at 127SC Interlayer Adhesion Test (ICA) IV The panels were processed and tested as described for the HBR test, except that the first basecoat / clearcoat was cured for 60 minutes at 146 eC and the second basecoat / clearcoat was He cured for 20 minutes at 127SC. The results are described in Table I below.

Table I Preparation • HBR ICA III ICA I 1 (comparison) Falla Falla Fall 2 (invention) Pasa Pasa Fall 3 (invention) Pasa Pasa Pas Preparation 4 A composition having the following formation was prepared: Component Parts in Deso Hydroxy-Functional Acrylic Resin 135.34 (An acrylic resin having a weight average molecular weight of about-4000, a weight equivalent to hydroxy of air of 310, wherein the source of the hydroxy functional- is a repeating polymer - derivative from hydroxypropyl methacrylate Tinuvin (R) 1130 UVA A.96 Tinuvin (R) 123 HALS 2.36 5% solution of BY (R) 320 6.05 Butyl loyal acetate losolve 14.14 di isobutylketany 7.85 Butyl acetate lcarbitol 13.64 Preparation 5 A composition was prepared having the composition identical to Preparation 1, with the addition of 0.847 parts by weight of the acrylic or functional epoxy polymer of Preparation 2.

Preparation 6 Sa prepared a composition having the composition identical to Preparation 1, with the addition of 2.54 parts by weight of the epoxy functional acrylic polymer of Preparaicon 2.

Pregaeifln 7 A composition having the composition identical to Preparationl was prepared, with the addition of 4.23 parts by weight of the epoxy functional acrylic polymer of Preparation 2.

Preparation 8 A composition having the following formulation was prepared: Component Parts in Weight Isocyanurate diisocyanate of isophorone 97.79 Diisocyanate of isocyanurate of hexamethyl wood 35.06 Di isobuti Icetona 21.65" Ex amp 2 The coating compositions of Preparation 4 were used, Preparation 5, Preparation 6 and Preparation 7 com component "A" of a 2K clear coating composition and was combined with Preparaicon 8 as component "B" and, and was reviewed on a steel panel with primer as the coating. transparent of a basecoat / clearcoat composite having a base layer pigmented in black using an acrylic hydroxy functional resin as a melamine resin crosslinker. The panels were cured for 20 minutes at 129 ° C, cooled and subjected to the following tests. The panels were then subjected to the ICA III, and ICA IV tests as described in the Example by whitening a base coat that was similar to Example 1 and a clear coat that was the same as Preparation 4 for the reverse side. transparent second second / transparent coating. The re-results are shown in Table II below.

Table II Preparation ICA III ICA IV 4 + 8 (comparison Failure to 5 + 8 (invention) Pass Failure 6 i- 8 (invention) Pass Fal 7 + 8 (invention) Pass Passes Results of Examples.1 and 2 the addition of the epoxy component to the crosslinking urethane clear coating compositions improved interlayer adhesion aspects as measured by certain adhesion tests between c. Further improvements in interlayer adhesion for certain coating compositions could be achieved by mediant The use of higher amounts of the epoxy component and / or the addition of the acid component The invention has been described in detail with reference to preferred embodiments thereof, It should be understood, however, that variations and modifications can be made within the scope of the invention. it is spirit and scope of the invention.

Claims (29)

1. - A method for preparing a coating comprising the steps of: (1) applying a first curable coating composition on two substrates which comprises two components that are reactive with each other to form urethane bonds, the composition comprising a third component; , which includes one or more epoxy groups, (2) curing the first curable coating composition to form a cured coating, (3) applying a second curable coating composition on the surface of the coating of step 92), and (4) ) curing the second curable coating composition.

2. A method according to claim 1, wherein the component comprising one or more epoxy groups is substantially free of groups that are reactive with any of the two components that are reactive with each other to form urethane bonds.

3. A method according to claim 1, comprising the steps of: (1) applying to a substrate a top coating a first curable coating composition comprising two components that are reactive with each other to form urethane bonds, the composition further comprising a third component comprising one or more epoxy groups, (2) curing the first curable coating composition to form a cured top layer, (2a) identifying the locations of the top layer with no need for repair, 93 ) applying a curable repair coating composition on the surface of the top layer at the locations identified in step (2a), and (4) curing the repair coating composition.

4. A method according to claim 1, wherein the two reactive components are: (A) a component comprising a plurality of active hydrogen groups, and (B) a component comprising a plurality of isocyanate groups.

5. A method of conformance with irradiation 4, wherein the active hydrogen groups are amino group or hydroxy group.

6. A method according to claim 4, wherein the active hydrogen groups are hydroxyl groups.

7. A method according to the claim and wherein the component (A) is an acrylic resin.

8. A method according to claim 4 wherein the component (A) is an acrylic resin.

9. A method according to claim 8, wherein the third component is an acrylic resin.

10. A method according to claim wherein the epoxy groups in the third component are derived from glycidylmethacrylate, glycidi lacrylate, allyl cycidyl ether, cyclohexylmonoepoxymethacrylate, and the epoxide of the cyclopentadienemethacrylate dimer and epoxidized butadiene.

11. A method according to claim 1 wherein the third component is selected from the group consisting of epoxy-containing acrylic resins, epoxy-terminated DGEBPA resin, epoxy novolac resins, polyurethane resin containing epoxy group. , epoxy-containing polyester resins.

12. A method according to claim wherein the third component is selected from the group consisting of epoxy-containing acrylic resins, epoxy-terminated DEBPA resins, epoxy novolac resins, polyurethane resins containing epoxy group, polyester ress containing epoxy group.

13. A method according to claim wherein the component (A) and the third component are each an acrylic resin.

14. A method according to claim wherein the epoxy groups in the third component are derived from gl icidi lmetacri lato.

15. A method according to claim 1, wherein the two reactive components are: (A) a component comprising a plurality of group carbamate, and (B) a component comprising a plurality of groups that are reactive with the carbamate groups in component (A).

16. A method according to claim 1 wherein the component (B) is an aminoplast resin.

17. A method according to claim 1 wherein the component (B) is a melamine resin.

18. A method according to claim 1 wherein the component (A) is a carbamate-functional acrylic resin.

19. A method according to claim 1 wherein the third component is an acrylic resin.

20.- A method of conformity with the reification 19 where the epoxy groups and the third component are derived to partride gl icidi lmetacri lato, glycidyl lactide, ether of 1 to 1 g of sodium, cyclohexymonopoxymethacrylate, the epoxide of the chloropentadienemethacrylate dimer and epoxidized butadiene.

21. A method according to claim 2 wherein the epoxy groups in the third component are derived from the glycidi lmetacri lato.

22. - A method according to claim 1 wherein the third component is selected from the group - consisting of epoxy-containing acrylic resins, epoxy-terminated DGEBPA resins, epoxy novoiaca resins, polyurethane resins containing group epoxy, polyester resins containing epoxy group.

23. A method of conformance with any of the vindications 1-22 wherein the curable coating composition of the eta (1) includes a component, which may be the same as any of the other components, comprising one or more acid groups.

24. A method according to claim wherein the component comprising one or more acid groups is different from the components (A), (B) or (C).

25. A method of compliance with the claim wherein the acid component is an organic acid.

26. A method, according to the claim wherein the organic acid is a monofunctional organic acid.

27. A method according to claim wherein the organic acid is a carboxylic acid.

28. A method according to any of claims 1-22, wherein the coating composition gives curable repair of step (4) comprises a component q has a plurality of carbamate functional groups, a component having a plurality of groups that are reactive with the carbamate groups and, an acid-curing catalyst.

29. A method according to claim wherein the second curable coating composition of step (3) comprises a component that iterates a plurality of functional carbamate g, a component having a plurality of groups that are reactive with the carbamate groups, and an acid-curing catazorant. METHOD OF COATING OF MULTIPLE LAYERS Summary of the Invention A method for preparing a multilayer coating is described. The method comprises the steps of: (1) applying to a substrate a first curable coating composition comprising two components that are reactive with each other to form urethane linkages and a third component that includes one or more epoxide groups. (2) cure the first curable coating composition to form a cured coating, (3) apply a second curable coating composition on the coating surface of step 92), and (4) cure the second curable coating composition.