HK1137015B - Multi-layer composites formed from compositions having improved adhesion - Google Patents

Description

Multilayer composite formed from a composition having improved adhesion

Technical Field

The present invention relates to a multilayer composite of two or more polymer layers, at least one of which is formed from a thermosetting composition. The composite comprises at least a first polymer layer formed on a substrate and a second polymer layer formed over at least a portion of the first polymer layer. The present invention also relates to thermosetting coating compositions for forming the multilayer composites and improving the interlayer adhesion of the multilayer composites.

Background

As a prime finish for numerous consumer products including, for example, automotive vehicles, color-plus-clear (color-plus-clear) coating systems have become increasingly popular which involve applying a colored or pigmented base coat to a substrate and then applying a clear or clear coat over the base coat. Color-plus-clear coating systems have excellent appearance properties such as gloss and distinctness of image, which are attributed largely to the clearcoat. These color-plus-clear coating systems have become popular for use in automotive, aerospace applications, floor coverings such as tile and wood flooring, packaging coatings, and the like.

Typical automotive coating systems may include sequential application of an electrodeposition primer (primer), a primer surfacer (primer surface), a color-providing basecoat (base coat), and a clear topcoat. In addition, adhesive coatings or layers, such as windshield adhesives, trim adhesives (trim adhesives) and molding adhesives (molding adhesives), and structural adhesives, are sometimes applied to the cured topcoat. In the manufacture of these multi-layer composite coatings, it is necessary that the different layers have acceptable interlayer adhesion.

On commercial automotive coating lines during application of the coating system, certain parts of the coating line may experience occasional process problems, for example, where the color coat applicator fails, or where the curing oven experiences a failure where the temperature is not within specification. In these instances of failure of the clear coat application system, some automotive manufacturers may choose to fully cure the applied color coat, then reapply the color coat over the fully cured color coat, and then apply the clear coat. In these cases, a fully cured color coating may have poor intercoat adhesion with a subsequently applied color coating, even though the composition may be the same.

In addition, during assembly, the applied color-plus-clear coating may contain surface defects on the clear coating surface that require repair. Some automotive manufacturers may choose to remove the defect and recoat the repaired area with the same clear coat composition. In this case, the cured clear coat layer must have excellent intercoat adhesion to the subsequently applied clear coat layer. However, some clearcoats are known to have poor intercoat adhesion with a subsequently applied repair clearcoat once cured.

In addition, windshields and other parts such as decorative molded articles are generally fixed to vehicle bodies with an adhesive material, which is generally a moisture-curable material containing a polymer having an isocyanate group. The Motor Vehicle Safety Standard (MVSS) requires that these adhesives have complete adhesion to both the windshield and the coated substrate to which they are applied. These adhesive articles adhere well to many cured topcoat compositions used to coat vehicles such as automobiles. However, it is known that these adhesive materials often do not adhere completely to some topcoats, such as those formed from coating compositions based on urethane and/or urea containing polymers. This necessitates the application of a primer coating to the cured urethane and/or urea-based topcoat prior to application of the windshield adhesive to ensure compliance with the automotive safety standards described above. The use of the above primer coatings has proven effective, but the application of the primer coating adds an extra and expensive step to the windshield and/or trim installation process.

In view of the foregoing, there is a need in the coatings industry for coating compositions having improved intercoat or interlayer adhesion.

It has now been found that certain adhesion promoters having surface activation properties provide coating compositions containing the adhesion promoter with a solubility parameter that is sufficiently different from the solubility parameter of a similar coating composition that does not contain the adhesion promoter; the adhesion promoter is distributed to the surface area of the resulting coating. This may result in a greater concentration of adhesion promoter in the surface region compared to the concentration in the interior or bulk region of the coating. This dispensing effect of the adhesion promoter can significantly improve its effectiveness in promoting adhesion of a coating containing the adhesion promoter to a subsequently applied coating and to a substrate to which it is applied.

Summary of The Invention

The present invention relates to a multilayer composite of two or more polymeric layers at least one of which is formed from a thermosetting composition. The composite comprises at least a first polymer layer formed on a substrate and a second polymer layer formed over at least a portion of the first polymer layer, wherein the first polymer layer and the second polymer layer have poor interlayer adhesion in the absence of a boron-containing compound. The improvement comprises including an adhesion promoter in one or both of the first and second polymer layers in an amount sufficient to improve interlayer adhesion between the first polymer layer and the second polymer layer. The adhesion promoter is derived from: (i) boric acid or an equivalent thereof, (ii) an ester having two or more terminal hydroxyl groups derived at least in part from a 1, 3-polyol, the equivalent ratio of boric acid or an equivalent thereof to hydroxyl groups being greater than 0.1: 1 and the equivalent ratio of 1, 3-polyol to acid being greater than 2: 1.

The present invention also relates to thermosetting compositions comprising (a) a film-forming polymer having reactive functional groups; (B) a curing agent having a functional group reactive with the functional group of the polymer (A); and (C) an adhesion promoter as described above.

Detailed description of the preferred embodiments

Other than in the examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

Moreover, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include all sub-ranges between the recited minimum value of 1 and the recited maximum value of 10 (inclusive), i.e., sub-ranges having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10.

As used herein in the specification and claims, "boric acid equivalent" refers to any of a variety of boron-containing compounds capable of hydrolyzing in aqueous media to form boric acid. Specific but non-limiting examples of boric acid equivalents include boron oxides, such as B₂O₃(ii) a Borates, such as those obtained by the reaction of boric acid with an alcohol or phenol, for example trimethyl borate, triethyl borate and triphenyl borate.

Additional non-limiting examples of boronic acid equivalents may include other amino-containing boronic acid esters and tertiary amine salts of boronic acids. These boron-containing compounds include, but are not limited to, 2- (. beta. -dimethylaminoisopropoxy) -4, 5-dimethyl-1, 3, 2-dioxaborolan and 2- (. beta. -diethylaminoethoxy) -4, 4, 6-trimethyl-1, 3, 2-dioxaborolan.

Boric acid equivalents may also include borate metal salts (i.e., metal borates) so long as these metal borates can readily dissociate in aqueous media to form boric acid. Examples of suitable metal borates include, for example, calcium borate, potassium borates such as potassium metaborate and potassium tetraborate.

The ester used in the present invention is a substance containing at least one ester bond and may be a monoester or a polyester having two or more terminal hydroxyl groups derived from the reaction of a mono-or polybasic acid with a polyhydric alcohol at least a part of which is a 1, 3-polyhydric alcohol. Useful monocarboxylic acids include those containing at least 6 contiguous carbon atoms (contiguous carbon atoms), or from 7 to 18 contiguous carbon atoms.

Non-limiting examples of suitable monocarboxylic acids include heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, n-undecanoic acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, isostearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, dihydroxystearic acid, ricinoleic acid, and isomers and mixtures thereof.

In one non-limiting embodiment, the ester-containing material is a polyester. The polyesters may be prepared by known methods from the condensation of polyhydric alcohols and polycarboxylic acids. Suitable polycarboxylic acids include those containing from 4 to 40 contiguous carbon atoms and from 2 to 3 carboxylic acid groups. Non-limiting examples include succinic acid, adipic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, cyclohexanedicarboxylic acid, phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, and trimellitic acid, and aliphatic carboxylic acids such as those available as EMPOL 1008, EMPOL 1010, and priol 1013. In addition to the polycarboxylic acids mentioned above, functional equivalents of the acids, for example their anhydrides if present or lower alkyl esters of the acids such as the methyl esters, may also be used.

The polyols useful in the present invention may include alkylene polyols containing 2 to 16 carbon atoms such as, but not limited to, ethylene glycol, diethylene glycol, neopentyl glycol, 1, 4-butanediol, and 1, 6-hexanediol. At least a portion of the polyol is a 1, 3-polyol, such as trimethylolpropane, pentaerythritol, ditrimethylolpropane and dipentaerythritol.

The esterification reaction is carried out according to techniques well known to those skilled in the art of polymer chemistry, and a detailed discussion is believed unnecessary. Generally, the reaction may be carried out by combining the ingredients and heating to a temperature of about 160 ℃ to about 230 ℃. More details of the esterification process are disclosed in column 3, lines 4-20 and lines 39-45 of U.S. patent 5,468,802.

The ester may be reacted with boric acid or an equivalent thereof under condensation reaction conditions well known in the art. For example, mixing boric acid or boric acid equivalent with a hydroxy functional polyester and removing water by distillation either directly or in combination with a solvent. Other methods for preparing boronic esters can be found in Kirk-Othmer "Encyclopedia of Chemical Technology", 4 th edition, volume 4, page 416; john Wiley and sons; 1992.

additionally, it is understood that the boron ester may be formed in situ. That is, the composition forming one or both of the first and second polymer layers may comprise, as separate components, boric acid and/or an equivalent thereof and an ester-containing material, such as a hydroxy-functional polyester, as separate hydroxy-functional groups. The adhesion promoter may then be formed by forming a reaction product within the composition at ambient temperature or as the composition undergoes a curing reaction at elevated temperatures. In this case, the composition may comprise the reaction product together with boric acid or an equivalent thereof and an ester-containing material as separate components.

The amount of boric acid or equivalent and hydroxy-functional ester used in the adhesion promoter can vary. In alternative non-limiting embodiments, the amount of boric acid or equivalent thereof and hydroxyl groups can be greater than 0.1: 1, alternatively at least 0.2: 1, alternatively 0.3 to 1.25: 1 on an equivalent basis. An equivalent ratio of less than 0.2: 1 can result in poor intercoat adhesion. Ratios greater than 1.25: 1 can be used, but no further benefit is observed at such greater ratios.

The relative amounts of polyol and acid used to form the ester can vary. In one non-limiting embodiment, the amount of polyol and acid may be greater than 1: 1 in terms of an equivalent ratio of hydroxyl groups to acid. In another embodiment, the equivalent ratio of 1, 3-polyol to acid may be greater than 2: 1, or at least 3: 1. If the equivalent ratio of the 1, 3-polyol to the acid is 2: 1 or less, the adhesion between the coatings may be poor.

While not wishing to be bound by any theory, it is believed that the polyester is a surfactant that causes the boron to migrate to the surface region of the polymer layer that contains the adhesion promoter and where it is most effective in promoting interlayer adhesion. It is also believed that the use of boric acid in the absence of the polyester is not effective as an adhesion promoter.

In one embodiment, the present invention is directed to a multilayer composite of two or more polymeric layers at least one of which is formed from a thermoset composition. The composite comprises a first polymer layer formed on a substrate and a second polymer layer formed over at least a portion of the first polymer layer, wherein the first polymer layer and the second polymer layer have poor interlayer adhesion in the absence of an adhesion promoter. The inclusion of an adhesion promoter in a sufficient amount in one or both of the first and second polymer layers can improve the interlayer adhesion of the first and second polymer layers.

In one non-limiting embodiment, the first polymeric layer may include a primer surfacer coating and the second polymeric layer may include a color enhancing basecoat layer to which a clear top coat is subsequently applied. In another embodiment, the first polymer layer can include an electrodepositable primer coating and the second polymer layer can include a primer-surfacer coating to which an appearance-enhancing monocoat (monocoat) or color-plus-clear coating system is subsequently applied. In another embodiment, the first polymer layer can comprise a clear coat (e.g., a clear coat in a color-plus-clear coat system) and the second polymer layer can comprise a repair clear coat or can comprise an adhesive layer applied to a portion (e.g., the periphery) of the clear coat such as, but not limited to, a windshield trim adhesive.

The substrate on which the first polymer layer is formed may comprise a variety of known materials. Non-limiting examples may include metal or elastomeric substrates. In one embodiment of the present invention, the first polymer layer may comprise an electrodepositable primer coating applied to a metal substrate. In another embodiment, the substrate can comprise a metal substrate having an electrodepositable primer layer deposited thereon and optionally a primer-surfacer coating deposited over the electrodepositable primer. In this case, the first polymeric layer may comprise, for example, a colored base coat deposited over the electrodeposited primer or the primer surfacer, and the second polymeric layer may comprise a substantially pigment-free clear coat formed over the colored base coat.

In one embodiment of the present invention, the substrate may comprise a metal substrate. Examples of suitable metal substrates may include ferrous and non-ferrous metals. Suitable ferrous metals include iron, steel, and alloys thereof. Non-limiting examples of useful steel materials include cold rolled steel, galvanized (i.e., galvanized) steel, electrogalvanized steel, stainless steel, pickled steel,Andzinc-aluminum alloys coated on steel, and combinations thereof. Useful non-ferrous metals include aluminum, zinc, magnesium, and alloys thereof. Can also makeA combination or composite of ferrous and non-ferrous metals.

In another embodiment of the present invention, the substrate may comprise an elastomeric substrate. Suitable elastomeric substrates may include any of the thermoplastic or thermoset synthetic materials known in the art. Non-limiting examples of suitable soft elastomeric substrate materials include polyethylene, polypropylene, thermoplastic polyolefins ("TPOs"), acrylonitrile-butadiene-styrene ("ABS") copolymers, ethylene propylene diene terpolymer ("EPDM") rubbers, reaction injection molded polyurethanes ("RIM"), and thermoplastic polyurethanes ("TPU").

When the substrates are used as parts for manufacturing automobiles, including but not limited to automobiles, trucks and tractors, they may have any shape and may be selected from the group consisting of the metal and/or flexible substrates described above. Typical shapes of body parts may include body side molding, fenders, bumpers, hoods, and automotive trim.

In the absence of an adhesion promoter, the first polymer layer and the second polymer layer may have poor interlayer adhesion. That is, in the absence of a boron-containing compound in both the first polymer layer and the second polymer layer, the two layers have poor interlayer (i.e., intercoat) adhesion. As used herein, "poor interlayer adhesion" means that the second polymer layer will have delamination or loss of adhesion to the first polymer layer sufficient to produce a rating of 3 or less as determined by ASTM-D3359-97 method B using the rating scale specified therein.

In one embodiment of the present invention, an adhesion promoter may be included in one or both of the first polymer layer and the second polymer layer in an amount sufficient to improve interlayer adhesion between the first polymer layer and the second polymer layer. The adhesion promoter may be present in the first polymer layer only, the second polymer layer only, or both the first polymer layer and the second polymer layer.

In further embodiments, an adhesion promoter, such as a boron-containing compound, may be present in any of the polymer layers comprising the substrate over at least a portion of which the first polymer layer is formed, and any of the polymer layers that may be subsequently formed over at least a portion of the second polymer layer.

At least one of the first and second polymer layers is formed from a thermosetting composition.

In one embodiment of the invention, both the first polymer layer and the second polymer layer are formed from a thermosetting composition. In another embodiment, the thermosetting composition comprises a curable coating composition as described below.

As used herein, "thermosetting composition" refers to a composition that is irreversibly fixed after curing or crosslinking, wherein the polymer chains of the polymer components are linked together by covalent bonds. This property is generally associated with crosslinking reactions of the composition ingredients, often caused by heat or radiation.

In the present invention, a thermosetting composition, for example, a curable coating composition, comprises (a) a film-forming polymer having a reactive functional group, (B) a curing agent having a functional group reactive with the functional group of (a), and (C) an adhesion promoter.

In alternative non-limiting embodiments, the adhesion promoter may be present in the composition in an amount sufficient to provide a boron content of at least 0.001 wt%, alternatively at least 0.025 wt%, alternatively at least 0.05 wt%, alternatively at least 0.10 wt%, based on the total weight of resin solids present in the composition. In further embodiments, the adhesion promoter is present in an amount of 30 wt% or less, alternatively less than 25 wt%, alternatively less than 15 wt%, based on the total weight of resin solids.

The film-forming polymer may be selected from the group consisting of polyether polymers, polyester polymers, acrylic polymers, silicon-based polymers, polyepoxide polymers, polyurethane polymers, and combinations thereof.

The film-forming polymer has reactive functional groups that may be selected from: hydroxyl, carboxylic acid, isocyanate, blocked isocyanate, primary amine, secondary amine, amide, urethane, urea, epoxy and compatible mixtures thereof.

"compatible mixtures thereof" means functional groups that do not react with each other at room temperature. For example, hydroxyl and free isocyanate groups would not be compatible mixtures. However, the hydroxyl and carbamate will be compatible mixtures.

Suitable film-forming polymers for use as the film-forming polymer (a) containing reactive functional groups in the present invention may include any of a variety of functional polymers known in the art. Non-limiting examples may include, but are not limited to, hydroxyl-containing polymers such as acrylic polyols, polyester polyols, polyurethane polyols, polyether polyols, and mixtures thereof. In one embodiment of the invention, the film-forming polymer may be an acrylic polyol having a hydroxyl equivalent weight of 100-1000 grams per equivalent solids, or 150-500 grams per equivalent solids.

Suitable hydroxyl and/or carboxyl group-containing acrylic polymers can be prepared by conventional methods known in the art. In one embodiment, these polymers may be prepared from polymerizable ethylenically unsaturated monomers, which may be copolymers of (meth) acrylic acid and/or hydroxyalkyl (meth) acrylates with one or more other polymerizable ethylenically unsaturated monomers such as alkyl (meth) acrylates including methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl acrylate, and vinyl aromatic compounds such as styrene, alpha-methylstyrene, and vinyl toluene. As used herein, "(meth) acrylate" and similar terms are intended to include both acrylates and methacrylates.

In another embodiment of the present invention, the acrylic polymer may be prepared from ethylenically unsaturated β -hydroxy ester functional monomers. The monomer may be derived from the reaction of an ethylenically unsaturated acid functional monomer (such as a monocarboxylic acid, for example acrylic acid) with an epoxy compound which does not participate in free radical initiated polymerization with the unsaturated acid monomer. Non-limiting examples of these epoxy compounds may include glycidyl ethers and esters. Suitable glycidyl ethers may include glycidyl ethers of alcohols and phenols, such as, but not limited to, butyl glycidyl ether, octyl glycidyl ether, phenyl glycidyl ether, and mixtures thereof. Suitable glycidyl esters can include those available under the tradename CARDURA E from Shell Chemical Company and GLYDEXX-10 from Exxon Chemical Company. The beta-hydroxy ester functional monomer may be prepared from ethylenically unsaturated epoxy functional monomers, such as glycidyl (meth) acrylate and allyl glycidyl ether, and saturated carboxylic acids, such as saturated monocarboxylic acids, e.g., isostearic acid.

Epoxy functionality can be introduced into polymers made from polymerizable ethylenically unsaturated monomers by copolymerizing monomers containing oxirane groups, such as glycidyl (meth) acrylate and allyl glycidyl ether, with other polymerizable ethylenically unsaturated monomers, such as those described above. The preparation of the epoxy-functional acrylic polymer is described in detail in columns 3-6 of U.S. Pat. No. 4,001,156, incorporated herein by reference.

Carbamate functionality may be introduced into polymers made from polymerizable ethylenically unsaturated monomers by copolymerizing, for example, the above-described ethylenically unsaturated monomers with carbamate-functional vinyl monomers, such as carbamate-functional alkyl esters of methacrylic acid. Useful carbamate-functional alkyl esters can be made by reacting, for example, a hydroxyalkyl carbamate (such as the reaction product of ammonia and ethylene or propylene carbonate) with methacrylic anhydride. Other useful carbamate-functional vinyl monomers include, for example, the reaction product of hydroxyethyl methacrylate, isophorone diisocyanate, and hydroxypropyl carbamate; or a reaction product of hydroxypropyl methacrylate, isophorone diisocyanate, and methanol. Other urethane-functional vinyl monomers may be used, such as the reaction product of isocyanic acid (HNCO) with a hydroxy-functional acrylic or methacrylic monomer, such as hydroxyethyl acrylate, and those described in U.S. patent 3,479,328, which is incorporated herein by reference.

Carbamate functionality can also be incorporated into the acrylic polymer by reacting a hydroxy-functional acrylic polymer with a low molecular weight alkyl carbamate, such as methyl carbamate. Pendant carbamate groups can also be introduced into acrylic polymers by a "transamination" reaction in which a hydroxy-functional acrylic polymer is reacted with a low molecular weight carbamate derived from an alcohol or glycol ether. The carbamate groups are exchanged with hydroxyl groups, yielding a carbamate-functional acrylic polymer and the original alcohol or glycol ether. Additionally, a hydroxyl functional acrylic polymer may be reacted with an isocyanate to provide pendant urethane groups. Likewise, a hydroxyl functional acrylic polymer may be reacted with urea to provide pendant carbamate groups.

Polymers made from polymerizable ethylenically unsaturated monomers can be prepared by solution polymerization techniques well known to those skilled in the art in the presence of a suitable catalyst such as an organic peroxide or azo compound, for example benzoyl peroxide or N, N-azobisisobutyronitrile. The polymerization may be carried out in an organic solution in which the monomer is soluble by techniques conventional in the art. In other embodiments, these polymers may be prepared by aqueous emulsion or dispersion polymerization techniques well known in the art. The ratio of reactants and reaction conditions are selected to produce an acrylic polymer having the desired pendant functionality.

In one embodiment of the present invention, polyester polymers may be used as film-forming polymers in the coating compositions of the present invention. Suitable polyester polymers may include condensation products of polyols and polycarboxylic acids. Non-limiting examples of the polyol may include ethylene glycol, neopentyl glycol, trimethylolpropane, pentaerythritol, and mixtures thereof. Non-limiting examples of polycarboxylic acids may include adipic acid, 1, 4-cyclohexyldicarboxylic acid, hexahydrophthalic acid, and mixtures thereof. In addition to the polycarboxylic acids described above, functional equivalents of the acids, such as anhydrides thereof if present or lower alkyl esters (such as the methyl esters) of the acids, may also be used. In addition, small amounts of monocarboxylic acids such as stearic acid may be used. The ratio of reactants and reaction conditions are selected to produce a polyester polymer having the desired pendant functionality, i.e., carboxyl or hydroxyl functionality.

In one non-limiting embodiment, hydroxyl-containing polyesters can be made by reacting an anhydride of a dicarboxylic acid (such as hexahydrophthalic anhydride) with a diol (such as neopentyl glycol) in a 1: 2 molar ratio. Where enhanced air drying is desired, suitable drying oil fatty acids may be used and include those derived from linseed oil, soya oil, tall oil, dehydrated castor oil or tung oil.

The carbamate-functional polyester may be prepared using conventional methods known in the art. In one embodiment, these polyesters may be made by first forming a hydroxyalkyl carbamate, which may be reacted with the polyacid and polyol used to form the polyester. In an alternative embodiment, terminal carbamate functionality may be incorporated into the polyester via transcarbamylation, by reacting isocyanic acid with a hydroxyl functional polyester, or by reacting a hydroxyl functional polyester with urea. Non-limiting examples of preparing suitable carbamate-functional polyesters may include those described in U.S. patent 5,593,733, column 2, line 40 to column 4, line 9, incorporated herein by reference.

In one embodiment of the present invention, polyurethane polymers containing terminal isocyanate or hydroxyl groups can be used as polymer (d) in the coating composition of the present invention. Polyurethane polyols or NCO-terminated polyurethanes can be used. These materials can be prepared by reacting a polyol including a polymer polyol with a polyisocyanate. Polyureas containing terminal isocyanate or primary and/or secondary amine groups can also be used. These materials can be prepared by reacting polyamines, including polymeric polyamines, with polyisocyanates. The hydroxyl/isocyanate or amine/isocyanate equivalent ratio can be adjusted and the reaction conditions selected to obtain the desired end groups. Non-limiting examples of suitable polyisocyanates can include those described in U.S. Pat. No. 4,046,729, column 5, line 26 to column 6, line 28, incorporated herein by reference. Non-limiting examples of suitable polyols include those described in U.S. Pat. No. 4,046,729, column 7, line 52-column 10, line 35, incorporated herein by reference. Non-limiting examples of suitable polyamines include those described in U.S. Pat. No. 4,046,729, column 6, line 61-column 7, line 32 and U.S. Pat. No. 3,799,854, column 3, lines 13-50, incorporated herein by reference.

Carbamate functional groups can be incorporated into the polyurethane polymer by a variety of methods known in the art. In one embodiment, a polyisocyanate may be reacted with a polyester having hydroxyl functionality and containing pendant urethane groups. In another embodiment, the polyurethane may be prepared by reacting a polyisocyanate with a polyester polyol and a hydroxyalkyl carbamate or isocyanic acid as separate reactants. Non-limiting examples of suitable polyisocyanates can include, but are not limited to, aromatic isocyanates such as 4, 4' -diphenylmethane diisocyanate, 1, 3-phenylene diisocyanate, and toluene diisocyanate, and aliphatic polyisocyanates such as 1, 4-tetramethylene diisocyanate and 1, 6-hexamethylene diisocyanate. In one embodiment, cycloaliphatic diisocyanates such as 1, 4-cyclohexyl diisocyanate and isophorone diisocyanate can be used.

Non-limiting examples of suitable polyether polyols may include polyalkylene ether polyols, such as those having the following structural formula (VII) or (VIII): (VII)Or (VIII)Wherein the substituent R is hydrogenOr lower alkyl containing 1 to 5 carbon atoms, including mixed substituents, n has a value of 2 to 6, and m has a value of 8 to 100 or more. In one embodiment, the polyalkylene ether polyol may include poly (oxytetramethylene) glycol, poly (oxytetraethylene) glycol, poly (oxy-1, 2-propylene) glycol, poly (oxy-1, 2-butylene) glycol, and mixtures thereof.

In one embodiment, the polyether polyol may be formed from the alkoxylation of a plurality of polyols. Non-limiting examples of suitable polyols may include glycols such as ethylene glycol, 1, 6-hexanediol, bisphenol a, and the like, or other higher polyols such as trimethylolpropane, pentaerythritol, and the like. Higher functionality polyols which may be used as described may be made by conventional methods known in the art, for example by alkoxylation of compounds such as sucrose or sorbitol. In one embodiment, the alkoxylation process may include the reaction of a polyol with an alkylene oxide, such as propylene oxide or ethylene oxide, in the presence of an acidic or basic catalyst. Specific examples of polyethers can include those sold under the names TERATHANE and TERACOL available from E.I. Du Pont de Nemours and Company, Inc.

In alternative embodiments, the polymers having reactive functional groups useful in the coating compositions of the present invention have a weight average molecular weight (Mw) of 1000-.

In further embodiments, polymers containing hydroxyl and/or carbamate functional groups may be used.

In another embodiment, polyepoxides, such as those described below with respect to curing agent (B), may be used.

In alternative embodiments, the polymer having reactive functional groups may be present in the thermosetting composition in an amount of at least 20 wt%, alternatively at least 30 wt%, alternatively at least 40 wt%, based on the weight of total resin solids in the coating composition. In further embodiments, the polymer having reactive functional groups may be present in the thermosetting composition of the invention in an amount of 80 wt% or less, or 70 wt% or less, or 60 wt% or less, based on the weight of total resin solids in the coating composition. The polymer having reactive functional groups may be present in the thermosetting composition of the invention in an amount ranging between any combination of these values, including the recited values.

The curing agent used in the present invention has functional groups that are reactive with the functional groups of the film-forming polymer.

The curing agent may be selected from a wide variety of materials known in the art. Non-limiting examples may include aminoplast resins, polyisocyanates, blocked isocyanates, polyepoxides, polyacids, anhydrides, amines, polyols, and mixtures thereof. In one embodiment, the curing agent may be selected from aminoplast resins and polyisocyanates.

Aminoplast resins can act as curing agents for hydroxyl, carboxylic acid and carbamate functional groups containing materials and are well known in the art. Aminoplasts can be obtained by a variety of conventional techniques. In one embodiment, aminoplasts can be prepared from the condensation reaction of formaldehyde with an amine or amide. Non-limiting examples of amines or amides may include melamine, urea, or benzoguanamine. In further embodiments, condensates with other amines or amides may be used; for example, aldehyde condensates of glycoluril, which produce high melting point crystalline products that can be used in powder coatings. In alternative embodiments, the aldehyde may be formaldehyde, acetaldehyde, crotonaldehyde, benzaldehyde, and mixtures thereof. In another embodiment, formaldehyde may be used.

In one embodiment, the aminoplast resin may comprise methylol groups, and in another embodiment, at least a portion of the methylol groups may be etherified with an alcohol to alter the cure response. Any monohydric alcohol may be used for this purpose including, but not limited to, methanol, ethanol, n-butanol, isobutanol, and hexanol.

Suitable aminoplast resinsMay include, for example, those available from cytec industries, incAnd from Solutia, incThose that are commercially available.

In one embodiment, a polyisocyanate may be used as the curing agent. The term "polyisocyanate" as used herein is intended to include blocked (or blocked) isocyanates as well as unblocked (poly) isocyanates. The polyisocyanate may be an aliphatic or aromatic polyisocyanate, or a mixture thereof. Non-limiting examples can include mixtures of diisocyanates, higher polyisocyanates such as isocyanurates of diisocyanates, combinations of higher polyisocyanates and diisocyanates, isocyanate prepolymers such as the reaction product of a polyisocyanate and a polyol, and polyisocyanate curatives.

In one embodiment, where the polyisocyanate is blocked or blocked, any suitable aliphatic, cycloaliphatic, or aromatic alkyl monoalcohol known to those skilled in the art may be used as the blocking agent for the polyisocyanate. Other non-limiting examples of suitable blocking agents may include oximes and lactams.

In one embodiment, curing agents comprising blocked isocyanate compounds, such as the tricarbamoyltriazine compounds described in detail in U.S. patent 5,084,541, may be used. The tricarbamoyltriazine compounds may be used in combination with aminoplast curatives and may be used in relatively small amounts as compared to the aminoplast, for example, but not limited to, a weight ratio of 15-40 aminoplast to 1 tricarbamoyltriazine.

In one embodiment of the present invention, an anhydride may be used as the curing agent for the hydroxyl functional group-containing material. Suitable anhydrides may be selected from those known in the art. Non-limiting examples of anhydrides can include those having at least two carboxylic anhydride groups per molecule, which can be derived from a monomer mixture comprising an ethylenically unsaturated carboxylic anhydride and a vinyl comonomer (such as, but not limited to, styrene, alpha-methylstyrene, vinyltoluene, and the like). Non-limiting examples of suitable ethylenically unsaturated carboxylic acid anhydrides can include maleic anhydride, citraconic anhydride, and itaconic anhydride. In another embodiment, the anhydride may be an anhydride adduct of a diene polymer, such as a maleated polybutadiene or a maleated butadiene copolymer, such as a butadiene/styrene copolymer. These and other suitable anhydride curing agents are described in U.S. Pat. No. 4,798,746 column 10, lines 16-50; and us patent 4,732,790 column 3 lines 41-57.

In one embodiment of the present invention, a polyepoxide may be used as a curing agent for a carboxylic acid functional group containing material. Polyepoxides suitable for use are well known in the art. Non-limiting examples may include polyglycidyl esters (e.g., acrylic from glycidyl methacrylate), polyglycidyl ethers of polyhydric phenols and aliphatic alcohols that can be made by etherification of a polyhydric phenol, or an aliphatic alcohol with an epihalohydrin (such as epichlorohydrin) in the presence of a base, or mixtures thereof. These and other suitable polyepoxides are described in U.S. patent 4,681,811, column 5, lines 33-58.

Suitable curing agents for epoxy-functional materials may include polyacid curing agents such as acid group-containing acrylic polymers made from ethylenically unsaturated monomers containing at least one carboxylic acid group and at least one ethylenically unsaturated monomer free of carboxylic acid groups. In one embodiment, the acid functional acrylic polymer may have an acid number of 30 to 150. In another embodiment, polyesters containing acid functionality may be used. The above polyacid curing agents are described in more detail in U.S. patent 4,681,811, column 6, line 45-column 9, line 54.

In one embodiment of the present invention, a polyol may be used as a curing agent for the isocyanate functional group-containing material. The polyol may be selected from substances having two or more hydroxyl groups per molecule, which are different from component (b) when it is a polyol. Non-limiting examples of the foregoing may include polyalkylene ether polyols, including thioethers; polyester polyols including polyhydroxy polyester amides; and a hydroxyl group-containing polycaprolactone and a hydroxyl group-containing acrylic copolymer. Other non-limiting examples may include polyether polyols formed from the alkoxylation of a variety of polyols, for example, diols such as ethylene glycol, 1, 6-hexanediol, bisphenol a, and the like, or higher polyols such as trimethylolpropane, pentaerythritol, and the like; and a polyester polyol; and mixtures thereof. These and other suitable polyol curatives are described in U.S. Pat. No. 4,046,729 at column 7, line 52-column 8, line 9; column 8, line 29-column 9, line 66; and us patent 3,919,315, column 2, line 64-column 3, line 33.

In another embodiment, a polyamine may be used as the curing agent for the isocyanate functional group containing material. Non-limiting examples of suitable polyamine curing agents can include primary or secondary diamines or polyamines in which the groups attached to the nitrogen atoms can be saturated or unsaturated, aliphatic, cycloaliphatic, aromatic-substituted aliphatic, aliphatic-substituted aromatic, and heterocyclic. Non-limiting examples of suitable aliphatic and cycloaliphatic diamines may include 1, 2-ethylenediamine, 1, 2-propylenediamine, 1, 8-octanediamine, isophoronediamine, propane-2, 2-cyclohexylamine, and the like. Non-limiting examples of suitable aromatic diamines may include phenylenediamine and toluenediamine, such as o-phenylenediamine and p-toluenediamine. These and other suitable polyamines are described in detail in U.S. Pat. No. 4,046,729 at column 6, line 61-column 7, line 26.

Various mixtures of curing agents may be used. In one embodiment, the thermosetting composition may be formulated as a one-part composition in which a curing agent such as an aminoplast resin and/or a blocked isocyanate compound such as those described above is mixed with the other composition components. The one-component composition can be kept storage-stable in the as-formulated state. In an alternative embodiment, the composition may be formulated as a two-component composition, wherein a polyisocyanate curing agent such as those described above may be added to a pre-formed mixture of the other composition components just prior to application. The pre-formed mixture may contain curing agents such as aminoplast resins and/or blocked isocyanate compounds such as those described above.

In alternative embodiments, the curing agent may be present in the coating composition in an amount of from 5 to 65, or from 10 to 45 weight percent, based on the total weight of resin solids in the composition.

The curable composition of the present invention may be dissolved or dispersed in a diluent, such as an organic solvent, water, or a mixture thereof. In further embodiments, the composition may be in the form of solid particles, such as a powder composition in the form of a dry powder or a powder slurry in water. Non-limiting examples of suitable organic solvents may include alcohols, such as butanol; ketones, such as methyl amyl ketone; aromatic hydrocarbons such as xylene; glycol ethers such as ethylene glycol monobutyl ether; esters; other solvents; and mixtures thereof.

In the diluent-based composition, the diluent may be present in an amount of 5 to 80 wt%, alternatively 30 to 50 wt%, based on the total weight of the resin solids and diluent. In alternative embodiments, the above-described compositions may have a total solids content of 40 to 100 wt%, alternatively 40 to 75 wt%, based on the total weight of the composition.

In further embodiments, additional components may be present in the composition. These additional components may include, but are not limited to, catalysts, pigments, fillers, toughening agents, plasticizers, surfactants, thixotropic agents, rheology control modifiers, air release agents, organic cosolvents, flow control agents, hindered amine light stabilizers, antioxidants, UV light absorbers, similar additives, and mixtures or combinations thereof. In one embodiment, these additional ingredients, when present, are used in an amount up to 40 wt%, based on the total weight of the composition.

In one embodiment, the present invention is directed to a multilayer composite coating wherein the first curable coating composition comprises a color-imparting colored basecoat composition and the second curable composition comprises a substantially pigment-free clearcoat composition.

As used herein, "substantially pigment-free clear coating composition" refers to a coating composition that forms a clear coating. These compositions are sufficiently free of pigments or particles so as not to seriously compromise the optical properties of the resulting coating. As used herein, "clear" means that the cured coating has a BYK haze index of less than 50 as measured with a BYK/haze glossmeter.

The pigment-containing coating composition may be selected from any of the coloring compositions used in the paint industry. In one embodiment, the pigmented coating composition may include a primer coating composition, such as a pigmented thermosetting weldable primer coating composition, for example under the trade nameCommercially available are electrodepositable coating compositions such as ED-5000, primer surfacer coating compositions such as GPX45379, color-providing basecoat layers such as HWB-9517 and ODCT-6373, all available from PPG industries, Inc. of Pittsburgh, Pennsylvania. Non-limiting examples of pigments that may be used in the above-described undercoat layer may include titanium dioxide, iron oxide, organic pigments, and inorganic pigments such as phthalocyanine blue, as well as metallic pigments such as aluminum flakes and metal oxide-coated mica. Other non-limiting examples of tinting compositions may include adhesive compositions such as those used as automotive windshield adhesives, such as BETASEAL 15625 from Essex Specialty Products.

The substantially pigment-free transparent curable coating composition used in the present invention may include any of the pigment-free coatings known in the art. In one embodiment, the pigment-free coating may comprise a clearcoat used in color-plus-clearcoat systems for the automotive industry. Non-limiting examples may include TKU1050AR, ODCT-8000 and under the DIAMOND trade nameAndall of which are commercially available from PPG Industries, inc.

The basecoat composition may be applied to the substrate by any conventional coating technique, such as brushing, spraying, dipping, or flow coating. Spray techniques and equipment for air spraying, airless spraying, and electrostatic spraying in either manual or automated methods may be used, as is known in the art.

In alternative embodiments, the film thickness of the primer layer formed on the substrate during application of the primer layer to the substrate may be from 0.1 to 5 mils, alternatively from 0.1 to 1 mil, alternatively from 0.4 mils.

After forming the base coat film on the substrate, the base coat may be cured, or a drying step may be performed in which the solvent is removed from the base coat film by heating or air drying for a time, and then the clear coat layer is applied. Suitable drying conditions may depend on the particular basecoat composition and, if the composition is aqueous, the ambient humidity. In one embodiment, drying times of 1 to 15 minutes at temperatures of 75 ° to 200 ° F (21 ° to 93 ℃) may be used.

The clear or clear topcoat composition can be applied to the basecoat by any conventional coating technique including, but not limited to, compressed air spraying, electrostatic spraying, and manual or automated methods. The clear top coat can be applied to the cured basecoat or to the dried basecoat prior to curing of the basecoat. In the latter case, the two coatings may then be heated to cure the two coatings simultaneously. In one embodiment, the curing conditions may be from 50 ° F to 475 ° F (10 ℃ to 246 ℃) for from 1 to 30 minutes. In another embodiment, the clear coat thickness (dry film thickness) may be 1 to 6 mils.

In one embodiment, the present invention is directed to a method of repairing a multi-layer composite coating comprising a basecoat formed from a film-forming basecoat composition on a substrate and a first topcoat deposited over at least a portion of the basecoat, the first topcoat formed from a first film-forming topcoat composition comprising any of the foregoing coating compositions, the method comprising locating a defective composite coating region, applying a repair topcoat film-forming composition to the defective region after the defective region has been prepared for repair. The refinish topcoat film-forming composition may comprise the same or different film-forming composition as the first topcoat film-forming composition. The defect area may be any coating imperfection that cannot be wiped off, such as but not limited to dirt particles in the coating surface. The defective area may be scratched or sanded to remove the coating blemish described above. In repairs made according to the method of the present invention, the first topcoat may provide excellent intercoat adhesion with a subsequently applied repair topcoat.

The coating composition of the present invention can provide a cured coating having excellent intercoat or interlayer adhesion to a subsequently applied coating. In one embodiment, any of the foregoing substantially pigment-free coating compositions can be applied as a clear coat in a color-plus-clear coating system as described above. If the cured coating system is damaged resulting in surface defects, it may be necessary to prepare the damaged area for repair with a subsequently applied clearcoat composition. The coating composition of the present invention can provide excellent intercoat adhesion between the first clear coat layer and the subsequently applied repair clear coat layer. When used as a topcoat composition, the coating composition of the present invention also provides excellent interlayer adhesion between the cured topcoat and the subsequently applied windshield adhesive without the intermediate step of applying an adhesion promoting primer.

The following examples illustrate the invention and should not be construed as limiting the invention to the details thereof. All parts and percentages in the examples, as well as throughout the specification, are by weight unless otherwise indicated.

Examples

The following examples show the preparation of a variety of hydroxyl functional polyesters having terminal hydroxyl groups. The polyester is then reacted with boric acid to form the adhesion promoter.

Adhesion promoters were then formulated into the thermosetting compositions used to prepare the multilayer composites and the composites were evaluated for interlayer adhesion. The polyesters of examples D to K are in accordance with the invention. For comparison, the polyesters of examples A, B, C and L to O were prepared. The polyesters of examples A, B and C contained no or insufficient borate content. The polyesters of examples L to O contain no or insufficient amounts of 1, 3-polyol. Examples D through J show the preparation of polyesters from a variety of polycarboxylic acids and polyols with sufficient borate content and sufficient 1, 3-polyol content. Example K shows the preparation of a monoester made from a monocarboxylic acid and a 1, 3-polyol (3: 1 OH/COOH equivalent ratio) at sufficient borate content.Example A, comparison

A polyester was prepared from the following ingredients as follows:

composition (I)	Parts by weight (gram)
		Adipic acid	438.0
Trimethylolpropane	792.0
		Butyl Stannoic acid	1.20
Phosphoric acid triphenyl ester	1.20
		Propylene glycol methyl ether1	500.0

¹DOWANOL PM from Dow Chemical Co

The polyester polymer was prepared in a four-necked round bottom flask equipped with a thermometer, mechanical stirrer, condenser, dry nitrogen sparge, and heating mantle. The first four ingredients were heated to a temperature of 200 ℃ and stirred in a flaskThe stirring was continued until about 97 g of distillate was collected and the acid number dropped below 1.5. The mass was then cooled to a temperature of 130 ℃ and propylene glycol methyl ether was added. The final product was a liquid with a nonvolatile content of 70% (measured at 110 ℃ for 1 hour), a hydroxyl number 571 by weight of solid, and a weight average molecular weight 1548 as determined by gel permeation chromatography.Example B, comparison

A borated polyester was prepared as described below from the following ingredients (B/OH equivalent ratio 0.05: 1):

composition (I)	Parts by weight (gram)
		Polyester of example A	386.5
Boric acid	2.6
		DOWANOL PM	901.2

The resin was prepared in a 2L flask equipped with a dean stark trap, temperature controller, stirrer and reflux condenser. The components are combined in the reactor with N₂And (6) flushing. The mixture was warmed to reflux with stirring and maintained at reflux for 1 hour. 751.9g of distillate were then removed and the reaction was cooled to ambient temperature. The resulting liquid resin was 46.7% solids (measured at 110 ℃ C., 1 hour).Example C, comparison

A borated polyester was prepared as described below from the following ingredients (B/OH equivalent ratio 0.1: 1):

composition (I)	Parts by weight (gram)
		Polyester of example A	386.2
Boric acid	5.2
		DOWANOL PM	901.2

The resin was prepared in a 2L flask equipped with a dean stark trap, temperature controller, stirrer and reflux condenser. The components are combined in the reactor with N₂And (6) flushing. The mixture was warmed to reflux with stirring and maintained at reflux for 1 hour. 751.9g of distillate were then removed and the reaction was cooled to ambient temperature. The resulting liquid resin was 46.7% solids (measured at 110 ℃ C., 1 hour).Example D

A borated polyester was prepared as described below from the following ingredients (B/OH equivalent ratio 0.3: 1):

composition (I)	Parts by weight (gram)
		Polyester of example A	115.1
Boric acid	4.6
		DOWANOL PM	207.6

The resin was prepared in a 1L flask equipped with a dean stark trap, temperature controller, stirrer and reflux condenser. The components are combined in the reactor with N₂And (6) flushing. The mixture was warmed to reflux with stirring and maintained at reflux for 1 hour. 225.7g of distillate was then removed and the reaction was allowed to cool to ambient temperature. The resulting liquid resin was 45.8% solids (measured at 110 ℃ C., 1 hour).Example E

A borated polyester was prepared as described below from the following ingredients (B/OH equivalent ratio 0.6: 1):

composition (I)	Parts by weight (gram)
		Polyester of example A	115.4
Boric acid	270.8
		DOWANOL PM	9.3

The resin was prepared in a 1L flask equipped with a dean stark trap, temperature controller, stirrer and reflux condenser. The components are combined in the reactor with N₂And (6) flushing. The mixture was warmed to reflux with stirring and maintained at reflux for 1 hour. 225.4g of distillate was then removed and the reaction was allowed to cool to ambient temperature. The resulting liquid resin was 41.9% solids (measured at 110 ℃ C., 1 hour).Example F

A borated polyester was prepared as described below from the following ingredients (B/OH equivalent ratio 1: 1):

composition (I)	Parts by weight (gram)
		Polyester of example A	617.9
Boric acid	82.4
		DOWANOL PM	1441.5

The resin was prepared in a 2L flask equipped with a dean stark trap, temperature controller, stirrer and reflux condenser. The components are combined in the reactor with N₂And (6) flushing. The mixture was warmed to reflux with stirring and maintained at reflux for 1 hour. 1240.8g of distillate were then removed and the reaction was cooled to ambient temperature. The resulting liquid resin was 48.5% solids (measured at 110 ℃ C., 1 hour).Example G

A polyester was prepared from the following ingredients as follows:

composition (I)	Parts by weight (gram)
		EMPOL 10081	678.6
Adipic acid	174.7
		Trimethylolpropane	631.8
Butyl Stannoic acid	1.41
		Phosphoric acid triphenyl ester	1.41
Propylene glycol methyl ether	598.5

¹Dimer diacid from Cognis (dimeridiaced)

The polyester polymer was prepared in a four-necked round bottom flask equipped with a thermometer, mechanical stirrer, condenser, dry nitrogen sparge, and heating mantle. The first four ingredients were heated to a temperature of 200 ℃ and stirred in the flask until about 77 grams of distillate was collected and the acid number dropped below 1.5. The mass was then cooled to a temperature of 130 ℃ and propylene glycol methyl ether acetate was added. The final product was a liquid with a nonvolatile content of 70% (measured at 110 ℃ for 1 hour), a hydroxyl number of 383 by weight of solid and a weight average molecular weight of 3651 as determined by gel permeation chromatography.

Reacting a polyester with boric acid to form a borated polyester as follows:

composition (I)	Parts by weight (gram)
		Polyester of example G	276.4
DOWANOL PM	433.2
		Boric acid	24.7

The resin was prepared in a 1L flask equipped with a dean stark trap, temperature controller, stirrer and reflux condenser. The components are combined in the reactor with N₂And (6) flushing. The mixture was warmed to reflux with stirring and maintained at reflux for 1 hour. 361.4g of distillate were then removed and the reaction was cooled to ambient temperature. The resulting liquid resin was 53.5% solids (measured at 110 ℃ C., 1 hour).Example H

A polyester was prepared from the following ingredients as follows:

composition (I)	Parts by weight (gram)
		1, 4-cyclohexanedicarboxylic acid	592.5
Trimethylolpropane	909.5
		Butyl Stannoic acid	1.40
Phosphoric acid triphenyl ester	1.40
		Propylene glycol methyl ether	599.6

The polyester polymer was prepared in a four-necked round bottom flask equipped with a thermometer, mechanical stirrer, condenser, dry nitrogen sparge, and heating mantle. The first four ingredients were heated to a temperature of 200 ℃ and stirred in the flask until about 92 grams of distillate was collected and the acid number dropped below 1.5. The mass was then cooled to a temperature of 130 ℃ and butyl acetate was added. The final product was a liquid having a nonvolatile content of 70% (measured at 110 ℃ for 1 hour), a hydroxyl number of 552 by weight of solid and a weight average molecular weight of 2363 as determined by gel permeation chromatography.

Reacting a polyester with boric acid to form a borated polyester as follows:

composition (I)	Parts by weight (gram)
		Polyester of example H	236.1
DOWANOL PM	541.1
		Boric acid	30.9

The resin was prepared in a 2L flask equipped with a dean stark trap, temperature controller, stirrer and reflux condenser. The components are combined in a reactor with N₂And (6) flushing. The mixture was warmed to reflux with stirring and maintained at reflux for 1 hour. 452.9g of distillate were then removed and the reaction was cooled to ambient temperature. The resulting liquid resin was 51.8% solids (measured at 110 ℃ C., 1 hour).Example I

A polyester was prepared from the following ingredients as follows:

composition (I)	Parts by weight (gram)
		EMPOL 1008	1134.1
Trimethylolpropane	528.0
		Butyl Stannoic acid	1.6
Phosphoric acid triphenyl ester	1.6
		Propylene glycol methyl ether	682.8

The polyester polymer was prepared in a four-necked round bottom flask equipped with a thermometer, mechanical stirrer, condenser, dry nitrogen sparge, and heating mantle. The first four ingredients were heated to a temperature of 200 ℃ and stirred in the flask until about 63 grams of distillate was collected and the acid number dropped below 1.5. The mass was then cooled to a temperature of 130 ℃ and butyl acetate was added. The final product was a liquid having a nonvolatile content of 70% (measured at 110 ℃ for 1 hour), a hydroxyl number of 330 by weight of solid and a weight average molecular weight of 4460 as determined by gel permeation chromatography.

Reacting a polyester with boric acid to form a borated polyester as follows:

composition (I)	Parts by weight (gram)
		Polyester of example I	506.2
DOWANOL PM	901.8
		Boric acid	51.5

The resin was prepared in a 2L flask equipped with a dean stark trap, temperature controller, stirrer and reflux condenser. The components are combined in a reactor with N₂And (6) flushing. The mixture was warmed to reflux with stirring and maintained at reflux for 1 hour. 601.6g of distillate was then removed and the reaction was allowed to cool to ambient temperature. The resulting liquid resin was 54.8% solids (measured at 110 ℃ C., 1 hour).Example J

A polyester was prepared from the following ingredients as follows:

composition (I)	Parts by weight (gram)
		Polyester1	203.7
Methylhexahydrophthalic anhydride	84.3
		Neodecanoic acid glycidyl ester	123.4
Dimethyl benzyl amine	1.36
		DOWANOL PM	100

¹Polyesters made from cyclohexanedicarboxylic acid and pentaerythritol 1: 4

The resin was prepared in a 1L flask equipped with a temperature controller, stirrer and reflux condenser. The polyester was added to the reaction flask. With N₂The reaction was flushed and warmed to 60 ℃ with stirring. Methylhexahydrophthalic anhydride was added over 30 minutes and allowed to react for 1 hour with stirring at 60 ℃. The resulting reaction was warmed to 90 ℃ and glycidyl neodecanoate was added over 1 hour. Dimethylbenzylamine was added to the reaction 10 minutes after the addition of glycidyl neodecanoate was started. After the addition is complete, DOWANOL PM is added. The reaction was stirred at 90 ℃ for 13 hours and cooled. The resin properties obtained were 78.9% solids (measured at 110 ℃ C., 1 hour) and 8.9 AV.

Reacting a polyester with boric acid to form a borated polyester as follows:

composition (I)	Parts by weight (gram)
		Polyester of example J	250.6
DOWANOL PM	310.7
		Boric acid	20.6

The resin was prepared in a 1L flask equipped with a dean stark trap, temperature controller, stirrer and reflux condenser. The components are combined in a reactor with N₂And (6) flushing. The mixture was warmed to reflux with stirring and maintained at reflux for 1 hour. 241.2g of distillate were then removed and the reaction was cooled to ambient temperature. The resulting liquid resin was 62.8% solids (measured at 110 ℃ C., 1 hour).Example K

The monoester-containing materials were prepared from the following ingredients as follows

Composition (I)	Parts by weight (gram)
		12-Hydroxystearic acid	453.3
Trimethylolpropane	206.5
		Butyl Stannoic acid	0.9
Phosphoric acid triphenyl ester	0.9

The resin was prepared in a 2L flask equipped with a temperature controller, stirrer, dean stark trap and reflux condenser. The reaction was added to a reaction flask. With N₂The reaction was flushed and slowly warmed to 200 ℃ with stirring. The reaction was held at 200 ℃ for 6 hours during which time 24.4g of water was collected. The reaction was then allowed to cool to ambient temperature and 428g of DOWANOLPM was added. The resulting resin properties were 55.6% solids (measured at 110 ℃ C., 1 hour), Gardner bubble viscosity-A and AV-2 meq/KOHg.

Reacting the monoester with boric acid to form a borated ester as follows:

composition (I)	Parts by weight (gram)
		Polyester of example K	502.3
DOWANOL PM	405.6
		Boric acid	38.6

The resin was prepared in a 1L flask equipped with a dean stark trap, temperature controller, stirrer and reflux condenser.The components are combined in a reactor with N₂And (6) flushing. The mixture was warmed to reflux with stirring and maintained at reflux for 1 hour. 451.1g of distillate were then removed and the reaction was cooled to ambient temperature. The resulting liquid resin was 61.6% solids (measured at 110 ℃ C., 1 hour).Example L, comparison

A polyester was prepared from the following ingredients as follows:

composition (I)	Parts by weight (gram)
		Trimethylolpropane	266
Neopentyl glycol	594
		Trimethylpentanediol	351
Hexahydrophthalic anhydride	1232

Trimethylolpropane, neopentyl glycol, 2, 4-trimethyl-1, 3-pentanediol, hexahydrophthalic anhydride, 8.8 g of butylstannoic acid and 5.4g of triphenyl phosphite are charged into a suitable reaction vessel equipped with a stirrer, a temperature sensor, a steam-heated reflux condenser with a distillation head and nitrogen bubbling. The flask contents were heated to 90 ℃. The contents then underwent an exotherm to 150 ℃. The reaction was then heated to 200 ℃. At which time water began to evolve from the reaction. The temperature of the reaction mixture was raised to 210 ℃ and maintained at that temperature until 146 g of water were distilled off and the acid number of the reaction mixture was 10. The reactor contents were cooled and poured out. The final material had a measured solids of 97% and a hydroxyl number of 139. The resin was then diluted to 69% solids with a 50: 50 blend of Dowanol PM acetate (propylene glycol acetate monomethyl ether from Dow Chemical Co.) and Dowanol PM (propylene glycol monomethyl ether from Dow Chemical Co.).Example M, comparison

As described belowA borated polyester was prepared from the following ingredients:

composition (I)	Parts by weight (gram)
		Polyester of example L	819.2
Boric acid	30.9
		DOWANOL PM	675.8

The resin was prepared in a 2L flask equipped with a dean stark trap, temperature controller, stirrer and reflux condenser. The components are combined in a reactor with N₂And (6) flushing. The mixture was warmed to reflux with stirring and maintained at reflux for 1 hour. 452.2g of distillate was then removed and the reaction was cooled to ambient temperature. The resulting liquid resin was 55.1% solids (measured at 110 ℃ C., 1 hour).Example N comparison

A polyester was prepared from the following ingredients as follows:

composition (I)	Parts by weight (gram)
		PRIPOL 10131	567
1, 6-hexanediol	236
		Butyl Stannoic acid	0.8
Phosphorous acid triphenyl ester	0.8
		Propylene glycol methyl ether	331.5

¹Dimer diacid from Unichema

The polyester polymer was prepared in a four-necked round bottom flask equipped with a thermometer, mechanical stirrer, condenser, dry nitrogen sparge, and heating mantle. The first four ingredients were heated to a temperature of 200 ℃ and stirred in the flask until about 29 grams of distillate was collected and the acid number dropped below 1.5. The mass was then cooled to a temperature of 130 ℃ and butyl acetate was added. The final product was a liquid having a nonvolatile content of 63.9% (measured at 110 ℃ for 1 hour), a hydroxyl number by weight of solids of 144.9, and a weight average molecular weight of 3668 as determined by gel permeation chromatography.

The polyester of example N was borated as follows:

composition (I)	Parts by weight (gram)
		Polyester of example N	227
DOWANOL PM	451.1
		Boric acid	20.6

The resin was prepared in a 1L flask equipped with a dean stark trap, temperature controller, stirrer and reflux condenser. The components are combined in a reactor with N₂And (6) flushing. The mixture was warmed to reflux with stirring and maintained at reflux for 1 hour. Then 301.2g of distillate was removed and the reaction was cooled to ambient temperature. The resulting liquid resin was 43.4% solids (measured at 110 ℃ C., 1 hour).Example O, comparison

A polyester was prepared from the following ingredients as follows:

composition (I)	Parts by weight (gram)
		Adipic acid	284.6
1, 6-hexanediol	460
		Butyl Stannoic acid	1.56
Phosphorous acid triphenyl ester	1.56
		Propylene glycol methyl ether	294.5

The polyester polymer was prepared in a four-necked round bottom flask equipped with a thermometer, mechanical stirrer, condenser, dry nitrogen sparge, and heating mantle. The first four ingredients were heated to a temperature of 200 ℃ and stirred in the flask until about 51 grams of distillate was collected and the acid number dropped below 1.5. The mass was then cooled to a temperature of 130 ℃ and butyl acetate was added. The final product was a liquid with a nonvolatile content of 57.3% (measured at 110 ℃ for 1 hour) and a hydroxyl number of 163 by weight of solids.

The polyester of example O was borated as follows:

composition (I)	Parts by weight (gram)
		Polyester of example O	334.4
DOWANOL PM	270.8
		Boric acid	12.4

The resin was prepared in a 1L flask equipped with a dean stark trap, temperature controller, stirrer and reflux condenser. The components are combined in a reactor with N₂And (6) flushing. The mixture was warmed to reflux with stirring and maintained at reflux for 1 hour. 181.3g of distillate was then removed and the reaction was cooled to ambient temperature. The resulting liquid resin was 45.4% solids (measured at 110 ℃ C., 1 hour).Examples 1 to 4

Examples 1-4 are formulated clearcoat compositions. Examples 2, 3 and 4 contained varying amounts of the adhesion promoter of the present invention. Example 1 is a control without adhesion promoter. The coating composition was formulated by first forming a premix and then adding the adhesion promoter as shown in table 1 below.

A premix was prepared by mixing the following components in order with gentle stirring: premix A¹2-butoxyethyl acetate solvent from Union Carbide Corp²Diethylene glycol monobutyl ether available from Union Carbide corp³2- (2-butoxyethoxy) ethyl acetate from Union Carbide Corp⁴UV absorbers from Ciba Specialty Chemicals Corp⁵Sterically hindered amine light stabilizers from Ciba Additives⁶Dodecyl benzene sulfonic acid solution from Chemcentral⁷Melamine formaldehyde resins from Cytec Industries⁸Tris (alkylcarbamoyl) triazines from BASF AG⁹SCA acrylic resin solution from PPG¹⁰Acrylic resin solution from PPG¹¹Melamine-formaldehyde Resins from Nuplex Resins¹²Polyacrylic copolymer solution from Byk Chemie¹³Polyether modified polydimethylsiloxane solution from Byk Chemie¹⁴Viscosity in seconds measured at ambient temperature with a #4FORD flow cup¹⁵Sufficient solvent was added to achieve the desired spray viscosity Table 1

Composition (I)	Example 1 (comparative)	Example 2	Example 3	Example 4
					Control	83.9(44.1)	83.9(44.1)	83.9(44.1)	83.9(44.1)
Acrylic resin1	14.2(9.2)	9.4(6.1)	4.8(3.1)	-
					Resin example ATMP/adipic acid/Borate	-	6.4(3.1)	12.6(6.1)	19.0(9.2)

¹A polymer comprising Cardura E, styrene, hydroxyethyl methacrylate, 2-ethylhexyl acrylate, acrylic acid, Mw about 8000, with a hydroxy EW as solids of 370. The polymer was 65 wt% solids in xylene/SOLVESSO 100 (ex Exxon) at 34/66 weight ratio.

The amount without parentheses is the total weight. The amounts in parentheses are by weight of solids.

Examples 5-18 are also formulated clearcoat compositions. Examples 10-18 are of the invention wherein different amounts of different adhesion promoters of the invention are included in the composition. Examples 5-9 for comparative purposes, different additives outside the scope of the present invention were included in the formulations. In example 5, carbamylated acrylic resin is the additive; example 6 a polyester that is not borated was used. Example 7 the borated form of the polyester of example 6 was used, but with a 1, 3-polyol content below that required by the present invention. Examples 8 and 9 use borated polyesters that do not contain 1, 3-polyols.

The coating composition was formulated by first forming a premix, denoted premix B below, and then adding the adhesion promoter as shown in table 2 below. In each case, the adhesion promoter was added to about 160 parts by weight (88.4 solids) of the premix. Premix B¹Dipropylene glycol monomethyl ether from Dow Chemical Co.²Propylene glycol acetate methyl ether from Dow Chemical Co.³Benzotriazole derivatives from CIBA Additives⁴2- (2 ' -hydroxy-3 ', 5 ' -di-tert-amylphenyl) benzotriazole UV light stabilizers from CIBA Additives⁵A crosslinked polymer dispersion comprising ethylene glycol dimethacrylate, styrene, butyl acrylate, and methyl methacrylate. The dispersion was 31% by weight in oxohexyl acetate (ex exxon chemicals). The number average particle size was 1000 angstroms.⁶A dispersion comprising AEROSIL R812S silica (ex Degussa) and a polymer component comprising hydroxypropyl acrylate, styrene, butyl methacrylate acrylic acid, the polymer component having an Mw of 7000 and a hydroxyl EW, calculated as solids, of 325. The polymer was 67.5 wt% solids in 60/40 weight ratio propylene glycol monoacetate methyl ether/SOLVESSO 100 (ex Exxon).⁷Melamine formaldehyde resins from Solutia Inc⁸Urethane functional polyester resin solution (composition described in US 6,592,999)⁹Sterically hindered amine light stabilizers from Ciba Additives¹⁰Dodecyl benzene sulfonic acid solution from Chemcentral¹¹Flow control agents from DuPont at 62.5% solids Mw about 6700 and Mn about 2600 in xylene¹²Additives from King Industries¹³Viscosity in seconds measured at ambient temperature with a #4FORD flow cupExamples 19 to 24

Examples 19-24 show the effect of increasing borate content in ester-borate adhesion promoters. For all examples, the coating compositions were formulated by adding an adhesion promoter to premix B as shown in table 5 below. In all cases, the adhesion promoter was added to about 160 parts by weight (88.4 solids) of the premix.

Example 19 is a control using an adipic acid-trimethylolpropane polyester without a borate ester. Examples 20 and 21 are comparative examples containing borated hexane at insufficient borate contentA diacid-trimethylolpropane polyester. Examples 22, 23 and 24 are examples of the present invention wherein the borated adipic acid-trimethylolpropane polyester contains sufficient borate content to positively affect adhesion. TABLE 5

Example No. 2Additive agent	19	20	21	22	23	24
							A	23.8(15.3)
B		32.4(15.3)
							C			34.7(15.3)
D				33.3(15.3)
							E					36.5(15.3)
F						31.5(15.3)

The film-forming compositions of examples 1-24 were spray applied to a pigmented basecoat to form a color-plus-clear composite coating over a primed electrocoated steel sheet. The sheet used was a cold-rolled steel sheet (dimensions 4 inches × 12 inches (10.16cm × 30.48 cm)). The panels of examples 1-4 were coated with an ED6060 electrocoat and an 1177225a primer, both from PPG Industries, Inc. For examples 5-24, the panels were coated with ED6230B electrocoat and FCP6519 primer, both from PPG Industries, Inc.

Examples 1-4 utilized a ReflexSilver, silver water-based basecoat from PPG Industries, Inc. Black solvent based acrylic/melamine base coat from PPG Industries, Inc, DCT6373, was used for examples 5-24.

The base coat was automatically sprayed onto the electrocoated and primed steel panels at ambient temperature (about 70F (21 c)). The primer layer is targeted to a dry film thickness of about 0.6 to 0.8 mils (about 15 to 20 microns). The water-based coated panels were dehydrated at 176 ° F (80 ℃) for 10 minutes before applying the clear coat. The solvent-based substrate coated panels were air flashed for only 1-5 minutes at ambient temperature.

Each clear coat composition was self-sprayed onto the basecoated panels at ambient temperature with ambient flash between application of the two coats. The clearcoat target is a dry film thickness of 1.6-1.8 mils (about 41-46 microns). All coatings were air flashed at ambient temperature prior to oven treatment. The plates were baked at 285F (141 ℃) for 30 minutes to fully cure the coating. The plates were baked in a horizontal position. To test the recoat adhesion, the panels initially coated with the base coat and clear coat described above were given another base coat and clear coat or just a clear coat. One half of the initial panel was coated with a base coat and a clear coat from each clear coat and the other half of the panel was coated with only a clear coat. To re-coat the panels (1-4) half way, the lower half of the original panel was covered with aluminum foil and then sprayed with a Reflex Silver primer coat automatically as described above. The aluminum foil was removed to give an initial panel with the top half coated with primer and the bottom half still having only the initial coating. The respective clear coat is then sprayed automatically onto the entire panel as described above.Half of the resulting panel was coated with a base coat/clear coat from the initial spray and another base coat/clear coat from the re-spray (B/C// B/C). The other half of the resulting panel was coated with a base coat/clear coat from the initial spray and another clear coat from the re-spray (B/C// C). Coating properties are reported below in tables 3,4 and 6. TABLE 3TABLE 4

Examples	Equivalent ratio of boron to OH	Equivalent ratio of 1, 3-polyol to acid	Initial 20 ° gloss1	DOI2	Adhesive force of fast knife4(% cohesive failure)
						5 (comparison)	-	-	88	97	0
6 (comparison)	0	0.75∶1	88	97	0
						7 (comparison)	1.0	0.75∶1	89	96	0
8 (comparison)	1.0	0	80	90	40
						9 (comparison)	1.0	0	88	95	0
10 (comparison)	0	3∶1	88	95	0
						11	1.0	3∶1	88	92	100
12	1.0	3∶1	88	97	100
						13	1.0	3∶1	86	93	100
14	1.25	3∶1	82	96	100
						15	1.0	3∶1	87	94	100
16	1.25	4∶1	88	97	100
						17	1.0	3∶1	88	97	100
18	1.25	3∶1	78	50	100

TABLE 6

Examples	Equivalent ratio of boron to OH	Equivalent ratio of 1, 3-polyol to acid	Initial 20 ° gloss1	DOI2	Adhesive force of fast knife4(% cohesive failure)
						19 (comparison)	0	3∶1	88	95	0
20 (comparison)	0.05	3∶1	90	94	0
						21 (comparison)	0.10	3∶1	91	91	0
22	0.30	3∶1	89	95	100
						23	0.60	3∶1	89	95	100
24	1.0	3∶1	86	93	100

¹20 ℃ Gloss was measured with a Statistical Novo-Gloss 20 ℃ Gloss meter from Paul N.Gardner Company, Inc²With Hunter Associates Dorigon II^TMDOI meter determination of image sharpness (DOI) measurements³Respread adhesion test Specification (cross-hatch adhesion) -reference US 6,592,999 test Specification for footnote 2 under Table 3³The fast knife test was performed as follows: to test windshield adhesion, a bead of windshield adhesive was applied to the clearcoat surface within 1-4 hours after the final bake (30 minutes at 285 ° F). Betaseal urethane moisture cure windshield adhesive 15625 from Dow Automotive was used. Approximately 5mm by 250mm adhesive beads were placed on the cured color-plus-clear substrate. The adhesive was cured at room temperature (-75F) and 20-50% relative humidity for 72 hours. After 72 hours, the adhesive beads were cut with a razor blade. Cuts were made at 60 ° angles through the adhesive bead at 12mm intervals while pulling back the edge of the adhesive at 180 ° angles. A minimum of 10 cuts were made for each system. The expected results are described as 90-100% Cohesive Failure (CF). Cohesive Failure (CF) occurs when the adhesive bead loses integrity due to cutting and pulling. When a loss of adhesion between the adhesive bead and the clearcoat surface occurred, the cohesive failure rating was 0%.

The results summarized in Table 3 show that the adhesion promoters of the present invention (examples 2, 3 and 4) provide excellent recoat adhesion at different levels (5.8-17.3 wt% solids) without adversely affecting appearance compared to the control containing no adhesion promoter.

The results summarized in Table 4 show that various additives of the present invention (examples 11-18) provide better adhesion than comparative examples (5-10) containing additives outside the scope of the present invention. In examples 11 to 17, the appearance was not adversely affected. However, in example 18, the appearance was adversely affected.

The results summarized in table 6 indicate that the equivalent ratio of boron to hydroxyl groups in the borated polyester should be greater than 0.10.

Although specific embodiments of the invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.

Claims (31)

1. A thermosetting composition comprising:

(a) a film-forming polymer having reactive functional groups,

(b) a curing agent having a functional group reactive with the functional group of (a),

(c) an adhesion promoter derived from:

(i) boric acid or an equivalent thereof, said equivalent being a boron-containing compound capable of hydrolyzing in an aqueous medium to form boric acid, and

(ii) an ester having two or more terminal hydroxyl groups formed from the reaction of a polyacid and a polyol having at least a portion of a 1, 3-polyol;

the equivalent ratio of boric acid or equivalent thereof to hydroxyl groups is greater than 0.1: 1 and the equivalent ratio of 1, 3-polyol to acid is greater than 2: 1.

2. The composition of claim 1 wherein the functional groups of the film-forming polymer are selected from the group consisting of hydroxyl, primary amino, secondary amino, carboxylic acid, epoxy, carbamate, amide, urea, and compatible mixtures thereof.

3. The composition of claim 2 wherein said functional group is selected from the group consisting of hydroxyl, carbamate, and compatible mixtures thereof.

4. The composition of claim 2, wherein the functional group of the curing agent is selected from the group consisting of isocyanates including blocked isocyanates, methylol including methylol ethers, epoxies, carboxylic acids, anhydrides, and compatible mixtures thereof.

5. The composition of claim 3, wherein the curing agent is selected from the group consisting of isocyanates including blocked isocyanates and aminoplasts.

6. The composition of claim 1 wherein (i) is selected from the group consisting of boric acid, boric acid esters, metal borates, and mixtures thereof.

7. The composition of claim 6, wherein (i) is a borate ester having 1 to 6 carbon atoms in the ester group.

8. The composition of claim 7, wherein the borate ester is selected from the group consisting of trimethyl borate, triisopropyl borate, and triphenyl borate.

9. The composition of claim 1 wherein (c) is present in said composition in an amount sufficient to provide a boron content of from 0.001 to 5 weight percent, based on the total weight of resin solids present in said curable composition.

10. The composition of claim 1, wherein (i) and (ii) are present in the curable composition as reaction products.

11. The composition of claim 1, wherein the ester is a polyester.

12. The composition of claim 11 wherein the polyester is formed from the reaction of a polycarboxylic acid or equivalent thereof with a 1, 3-polyol.

13. The composition of claim 1, wherein the 1, 3-polyol is selected from trimethylolpropane and pentaerythritol.

14. A multilayer composite of two or more polymer layers at least one of which is formed from a thermosetting composition, the composite comprising a first polymer layer formed on a substrate and a second polymer layer formed over at least a portion of the first polymer layer, including an adhesion promoter in one or both of the polymer layers in an amount sufficient to improve interlayer adhesion between the first and second polymer layers, wherein the adhesion promoter is derived from:

(i) boric acid or an equivalent thereof, said equivalent being a boron-containing compound capable of hydrolyzing in an aqueous medium to form boric acid,

(ii) an ester having two or more terminal hydroxyl groups formed from the reaction of a polyacid and a polyol having at least a portion of a 1, 3-polyol;

the equivalent ratio of boric acid or equivalent thereof to hydroxyl groups is greater than 0.1: 1 and the equivalent ratio of 1, 3-polyol to acid is greater than 2: 1.

15. The composite of claim 14, wherein one or both of the first polymer layer and the second polymer layer comprises a cured layer formed from the thermosetting composition of any one of claims 1-9 or 11-13.

16. The composite of claim 15, wherein the film-forming polymer (a) comprises at least one polymer selected from the group consisting of acrylic polymers, polyester polymers, polyurethane polymers, and mixtures thereof.

17. The composite of claim 15, wherein the film-forming polymer (a) comprises functional groups selected from the group consisting of hydroxyl, carboxylic acid, primary amine, secondary amine, amide, carbamate, urea, epoxy, and compatible mixtures thereof.

18. The composite of claim 17, wherein the film-forming polymer comprises functional groups selected from hydroxyl groups, urethane groups, and mixtures thereof.

19. The composite of claim 15, wherein the curing agent (b) comprises an aminoplast resin, a polyisocyanate, a blocked polyisocyanate, a polycarboxylic acid, a polyepoxide, and compatible mixtures thereof.

20. The composite of claim 19, wherein the curing agent (b) comprises at least one aminoplast resin and at least one blocked isocyanate compound comprising a tricarbamoyltriazine compound.

21. The composite of claim 14, wherein (i) is selected from the group consisting of boric acid, boric acid esters, metal borates, and mixtures thereof.

22. The composition of claim 14, wherein (i) is a borate ester having 1 to 6 carbon atoms in the ester group.

23. The complex of claim 14, wherein (i) and (ii) are present as reaction products.

24. The composite of claim 14, wherein (i) and (ii) are present in an amount sufficient to provide a boron content of 0.001 to 5 wt% based on the weight of resin solids in the composite.

25. The composite of claim 15, wherein the composite comprises a pigmented polymer layer deposited on a metallic or elastomeric substrate, a substantially pigment-free transparent polymer layer deposited on the pigmented polymer layer, and an adhesive layer deposited on the transparent polymer layer, the transparent polymer layer being the first polymer layer and the adhesive layer being the second polymer layer.

26. The composite of claim 25, wherein the adhesion promoter is present in the transparent polymer layer.

27. The composite of claim 15, wherein the composite comprises a first transparent substantially pigment-free polymer layer deposited on a pigment-containing polymer layer, and a second transparent substantially pigment-free polymer layer deposited on the first transparent polymer layer.

28. The composite of claim 27, wherein the adhesion promoter is present in the first transparent polymer layer.

29. The composite of claim 15, wherein the ester is a polyester.

30. The composite of claim 29, wherein the polyester is formed from the reaction of a polycarboxylic acid or equivalent thereof with a 1, 3-polyol.

31. The composition of claim 14, wherein the 1, 3-polyol is selected from the group consisting of trimethylolpropane and pentaerythritol.