WO2025064081A1

WO2025064081A1 - Aqueous dispersions of particles, film-forming compositions and multi-layer coated substrates prepared therefrom, and methods of improving adhesion/cohesion of coating layers in multi-layer coated substrates

Info

Publication number: WO2025064081A1
Application number: PCT/US2024/042002
Authority: WO
Inventors: Paul Hubert LAMERS; Wolfgang Klaeger; Jose CAMERANO; Chad Alan Landis; Steven V. Barancyk; Francesco Ciaccio
Original assignee: PPG Industries Ohio Inc
Current assignee: PPG Industries Ohio Inc
Priority date: 2023-09-22
Filing date: 2024-08-13
Publication date: 2025-03-27
Anticipated expiration: 2026-03-22
Also published as: IT202300019572A1

Abstract

The present disclosure provides aqueous dispersions of hydroxyl functional core-shell particles. The particle core comprises a (meth)acrylic polymer and the shell comprises a polyurethane polymer. The mass ratio of the core to the shell ranges from 20:80 to 80:20. The shell has a hydroxyl value of 1 to 40 mg KOH/g and an acid value of 10 to 60 mg KOH/g. The polyurethane is prepared from: (a) a first prepolymer having a polymerizable ethylenically unsaturated group at one end and an active hydrogen-functional group at an opposite end thereof; (b) a second prepolymer having a polymerizable ethylenically unsaturated group at each end thereof; and (c) a third prepolymer having an active hydrogen-functional group at each end thereof. Also provided are waterborne curable film-forming compositions, multilayer coated substrates, and methods of improving adhesion between and/or cohesion of coating layers on a substrate.

Description

AQUEOUS DISPERSIONS OF PARTICLES, FILM-FORMING COMPOSITIONS AND MULTI-LAYER COATED SUBSTRATES PREPARED THEREFROM, AND METHODS OF IMPROVING ADHESION/COHESION OF COATING LAYERS IN MULTI-LAYER COATED SUBSTRATES

FIELD OF THE DISCLOSURE

[0001] The present disclosure relates to aqueous dispersions of particles having a core-shell morphology, aqueous curable film-forming compositions and multi-layer coated substrates prepared therefrom, and methods of improving adhesion between coating layers and/or cohesion of coating layers on a substrate.

BACKGROUND OF THE DISCLOSURE

[0002] In the automotive industry, a typical multilayer coating stack applied to a substrate includes an electrodeposited protective layer, optionally a primer and/or sealer, and one or more aesthetic topcoats such as a colored basecoat and transparent, usually colorless clearcoat. Occasionally, particularly when the medium of adjacently-applied coating layers is different (solventborne vs. waterborne/aqueous), intercoat adhesion between layers and/or cohesion of one or more layers may be compromised. Similarly, newer sealant compositions on the market, developed to be low VOC to meet environmental regulatory requirements, often contain alkylphthalates as non-volatile diluents. These alkylphthalates can migrate within the multilayer coating stack and negatively impact intercoat adhesion properties.

[0003] It would be desirable to provide aqueous dispersions of particles and waterborne coating compositions prepared therefrom that may be used to prepare multilayer coated substrates, with improved adhesion between coating layers and/or improved cohesion of coating layers.

SUMMARY OF THE DISCLOSURE

[0004] The present disclosure is directed to aqueous dispersions comprising particles having a core-shell morphology and having hydroxyl functional groups. The core of the particles comprises a (meth)acrylic functional polymer and the shell of the particles comprises a polyurethane polymer prepared from a polyurethane prepolymer and having a hydroxyl value of 1 to 40 mg KOH/g, or 1 to 30 mg KOH/g, or 1 to 20 mg KOH/g, or 1 to 15 mg KOH/g, or 1 to 10 mg KOH/g, and an acid value of 10 to 60 mg KOH/g. The polyurethane prepolymer comprises:

(a) 20 to 60 percent by weight, or 20 to 50 percent by weight, of a first prepolymer having a terminal, polymerizable ethylenically unsaturated group at one end of the first prepolymer and an active hydrogen-functional group at an opposite end of the first prepolymer, based on the total weight of the polyurethane prepolymer;

(b) 20 to 80 percent by weight, or 20 to 60 percent by weight, or 20 to 40 percent by weight, or 30 to 80 percent by weight, or 30 to 60 percent by weight, or 30 to 40 percent by weight of a second prepolymer having a terminal, polymerizable ethylenically unsaturated group at each end of the second prepolymer, based on the total weight of the polyurethane prepolymer; and

(c) 1 to 30 percent by weight, or 1 to 20 percent by weight, or 1 to 10, percent by weight, or 10 to 30 percent by weight, or 10 to 20 percent by weight of a third prepolymer having a terminal, active hydrogen-functional group at each end of the third prepolymer, based on the total weight of the polyurethane prepolymer; the mass ratio of the core to the shell ranging from 20:80 to 80:20, or from 20:80 to 70:30, or from 20:80 to 60:40.

[0005] The present disclosure is further directed to waterborne, curable film-forming compositions comprising a) the aqueous dispersion described above; b) a crosslinking agent; and c) a water dispersible polymer that comprises functional groups that are reactive with the crosslinking agent b).

[0006] Also provided are multilayer coated substrates comprising:

A) a substrate;

B) first coating composition applied to a surface of the substrate, forming a first coating on the substrate;

C) a basecoat composition applied on top of the first coating; and

D) a clearcoat composition applied on top of the basecoat composition; wherein the composition C) comprises the waterborne curable film-forming composition described above.

[0007] Additionally provided are methods of improving adhesive properties between a basecoat coating layer and a coating layer directly in contact with the basecoat coating layer on a substrate, and/or improving cohesive properties within a basecoat coating layer on a substrate, comprising: A) applying a first coating composition to a surface of the substrate, forming a first coating on the substrate;

B) applying a basecoat composition on top of the first coating; and

C) applying a clearcoat composition on top of the basecoat composition; wherein the basecoat composition comprises the waterborne curable film-forming composition described above.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0008] Other than in the operating examples, or unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages such as those for amounts of materials, times and temperatures of reaction, ratios of amounts, values for molecular weight (whether number average molecular weight (“M_n”) or weight average molecular weight (“M_w”)), and others in the following portion of the specification may be read as if prefaced by the word “about” even though the term “about” may not expressly appear with the value, amount or range. 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 disclosure. 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. [0009] Also, regarding molecular weights, whether number average (M_n) or weight average (M_w), these quantities are determined by gel permeation chromatography using polystyrene as standards as is well known to those skilled in the art and such as is discussed in U.S. Patent No. 4,739,019, at column 4, lines 2-45.

[0010] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Furthermore, when numerical ranges of varying scope are set forth herein, it is contemplated that any combination of these values inclusive of the recited values may be used. [0011] Plural referents as used herein encompass singular and vice versa. For example, while the disclosure has been described in terms of "a" polyurethane prepolymer, mixtures of such resins can be used, and often are used, as described.

[0012] Any numeric references to amounts, unless otherwise specified, are "by weight". The term “equivalent weight” is a calculated value based on the relative amounts of the various ingredients used in making the specified material and is based on the solids of the specified material. The relative amounts are those that result in the theoretical weight in grams of the material, like a polymer, produced from the ingredients and give a theoretical number of the particular functional group that is present in the resulting polymer. The theoretical polymer weight is divided by the theoretical number of equivalents of functional groups to give the equivalent weight. For example, urethane equivalent weight is based on the equivalents of urethane groups in the polyurethane material.

[0013] As used in the following description and claims, the following terms have the meanings indicated below:

[0014] As used herein, the term “polymer” is meant to refer to both homopolymers and copolymers; the prefix “poly” refers to two or more.

[0015] As used herein, the terms “thermosetting” and “curable” can be used interchangeably and refer to resins that “set” irreversibly upon curing or crosslinking, wherein the polymer chains of the polymeric components are joined together by covalent bonds. This property is usually associated with a crosslinking reaction of the composition constituents often induced, for example, by heat or radiation. See Hawley, Gessner G., The Condensed Chemical Dictionary, Ninth Edition., page 856; Surface Coatings, vol. 2, Oil and Colour Chemists' Association, Australia, TAFE Educational Books (1974). Curing or crosslinking reactions may be carried out under ambient conditions, or elevated temperature conditions, such as 80°C to 140°C. By ambient conditions is meant that the coating undergoes a thermosetting reaction without the aid of heat or other energy, for example, without baking in an oven, use of forced air, or the like. Usually ambient temperature ranges from 60 to 90 °F (15.6 to 32.2 °C), such as a typical room temperature, 72°F (22.2°C). Once cured or crosslinked, a thermosetting resin will not melt upon the application of heat and is insoluble in solvents. As used in this specification and the appended claims, the articles "a," "an," and "the" include plural referents, and are used interchangeably with the terms “at least one” and “one or more”, unless expressly and unequivocally limited to one referent.

[0016] The terms “aqueous” and “waterborne” are used herein interchangeably and refer to a composition in a liquid medium comprising at least 50 weight % water, based on the total weight of the liquid medium. Such liquid mediums can, for example, comprise at least 60 weight % water, or at least 70 weight % water, or at least 80 weight % water, or at least 90 weight % water, or at least 95% water, up to 100 weight% water, based on the total weight of the liquid medium. The dispersions disclosed herein are aqueous and the liquid medium may further contain organic solvents such as glycol ethers in minor amounts.

[0017] The various examples of the present disclosure as presented herein are each understood to be non-limiting with respect to the scope of the disclosure.

[0018] The term “reactive” refers to a functional group capable of undergoing a chemical reaction with itself and/or other functional groups spontaneously or upon the application of heat or in the presence of a catalyst or by any other means known to those skilled in the art.

[0019] The particles in the disclosed aqueous dispersions are typically polymeric and have a core-shell morphology and hydroxyl functional groups. The core of the particles comprise a (meth)acrylic functional polymer prepared from a (meth)acrylic functional monomer, and the shell of the particles comprises a polyurethane polymer.

[0020] The core (interior domain) and shell (surface domain) polymers may be covalently bonded to each other, and the particles are typically formed by emulsion polymerization in an aqueous medium. The shell polymer may be designed to be more polar than the core by including functional groups such as hydroxyl and acid groups. The shell polymer is a polyurethane typically formed from polyisocyanates and polyols, including acid functional polyols, which may be present in an amount sufficient to allow for dispersion of the polymeric particles in an aqueous medium. Exemplary polymerization methods are demonstrated in the Examples below.

[0021] The mass ratio of the core to the shell in a particle typically ranges from 20:80 to 80:20, or from 20:80 to 70:30, or from 20:80 to 60:40, such as from 20:80 to 40:60. For example, the mass ratio of the core to the shell (core:shell) may be 20:80, or 30:70, or 40:60, or 50:50, or 60:40, or 70:30, or 80:20. [0022] The shell of the particles comprises a polyurethane polymer as noted, often containing acid functional groups. The shell is prepared from a polyurethane prepolymer and has a hydroxyl value of 1 to 40 mg KOH/g, or 1 to 30 mg KOH/g, or 1 to 20 mg KOH/g, or 1 to 15 mg KOH/g, or 1 to 10 mg KOH/g, and an acid value of 10 to 60 mg KOH/g. Polyurethane prepolymers and polymers are prepared by reacting polyols with a polyisocyanate as described below.

[0023] Suitable polyols include ethylene glycol, propylene glycol, butylene glycol, 1 ,6- hexane diol, neopentyl glycol, diethylene glycol, glycerol, trimethylol propane, sorbitol, and pentaerythritol. Polyols having dual functionality such as dimethylol propionic acid and 12-hydroxystearic acid are also suitable, to incorporate acid functional groups into the resulting polyurethane. Polymeric polyols such as polycarbonate polyols, acrylic, polyester, and/or polyether polyols may also be used. Examples of suitable polyether polyols that may be used include, for example, poly(oxytetramethylene) glycols; poly(oxyethylene) glycols; poly(oxy-1 ,2-propylene) glycols; poly(tetrahydrofuran); the reaction products of ethylene glycol with a mixture of 1 ,2-propylene oxide and ethylene oxide. The reaction products obtained by the polymerization of ethylene oxide, propylene oxide and tetrahydrofuran, and mixtures of polyols, are also suitable. Such polymeric polyols may additionally have acid functional groups. Usually a combination of polyols, including at least one polyol having dual functionality, is used.

[0024] The polyisocyanates used to prepare the polyurethanes can be aliphatic or aromatic, or a mixture of the two. Diisocyanates are most often used, although higher polyisocyanates can be used in place of or in combination with diisocyanates. Examples of suitable aromatic diisocyanates are 4,4'-diphenylmethane diisocyanate; 1 ,3-phenylene diisocyanate; 1 ,4-phenylene diisocyanate; alpha, alpha-xylylene diisocyanate; and toluene diisocyanate. Examples of suitable aliphatic diisocyanates are straight chain aliphatic diisocyanates such as 1 ,4-tetramethylene diisocyanate and 1 ,6-hexamethylene diisocyanate. Also, cycloaliphatic diisocyanates can be employed. Examples include isophorone diisocyanate, 1 ,4-cyclohexyl diisocyanate, and 4,4'-methylene-bis-(cyclohexyl isocyanate). Examples of suitable higher polyisocyanates are 1 ,2,4-benzene triisocyanate and polymethylene polyphenyl isocyanate.

[0025] Often the OH/NCO equivalent ratio is less than 1 :1 so that free isocyanate groups are present in the intermediate isocyanate prepolymer, allowing for reaction with an active hydrogen (usually hydroxyl) functional, ethylenically unsaturated monomer such as one or more of hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate, hydroxybutyl(meth)acrylate, polyethylene glycol ester of (meth)acrylic acid, polypropylene glycol ester of (meth)acrylic acid, the reaction product of (meth)acrylic acid and the glycidyl ester of neopentanoic and/or neodecanoic acid, the reaction product of hydroxyethyl(meth)acrylate and the glycidyl ester of neopentanoic and/or neodecanoic acid, and the reaction product of hydroxypropyl(meth)acrylate and the glycidyl ester of neopentanoic and/or neodecanoic acid, Such a reaction between the free isocyanate groups and the active hydrogen functional group provides a terminal, polymerizable ethylenically unsaturated group at one or both ends of the prepolymer. The free isocyanate end groups may alternatively be reacted with polyols, such as 2-methyl- 1 ,3-propanediol, to produce a urethane shell with a plurality of curable chain-end hydroxyl groups. Usually, the polyurethane prepolymer comprises a mixture of prepolymers, having 1 ) a terminal, polymerizable ethylenically unsaturated group at one end of the molecule and an active hydrogen-functional group at an opposite end; 2) a terminal, polymerizable ethylenically unsaturated group at each end of the molecule; and/or 3) an active hydrogen functional group at each end of the molecule. Often, the polyurethane prepolymer comprises:

(c) 1 to 30 percent by weight, or 1 to 20 percent by weight, or 1 to 10, percent by weight, or 10 to 30 percent by weight, or 10 to 20 percent by weight of a third prepolymer having a terminal, active hydrogen-functional group at each end of the third prepolymer, based on the total weight of the polyurethane prepolymer. In a particular example, the polyurethane prepolymer comprises 20 to 50 percent by weight of the first prepolymer, 20 to 80 percent by weight of the second prepolymer, and 1 to 30 percent by weight of the third prepolymer. It is understood that the sum of the percents by weight of (a), (b), and (c) equals 100.

[0026] As noted above, the polyurethanes can be prepared with unreacted carboxylic acid groups, which upon neutralization with bases such as amines allows for dispersion into aqueous medium. Neutralization of acid groups on the polymer may be done using, for example, inorganic bases such as ammonium hydroxide or amines such as dimethylethanolamine, diisopropanolamine, triethylamine, and the like. Effective dispersion techniques may include high shear mixing such as by homogenization, emulsification by use of an emulsifier, use of rotor I stator mixers, Cowles dispersers, or mixing a small volume of material with a conventional stirrer at a high agitation rate.

[0027] Ethylenically unsaturated monomers used to prepare the core of the particles may include hydrophobic monomers such as n-butyl (meth)acrylate, isobutyl (meth)acrylate, lauryl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, and t-butyl (meth)acrylate, usually together with one or more other polymerizable ethylenically unsaturated monomers. As used herein, "hydrophobic monomer” refers to a monomer that is "substantially insoluble" in water. By "substantially insoluble" in water is meant that a monomer has a solubility in distilled water of less than 6 g/100 g at 25°C, determined by placing 3 g of water and 0.18 g of monomer in a test tube at 25°C and shaking the test tube. On visual examination, if two distinct layers form, the monomer is considered to be hydrophobic. If a cloudy solution forms, the turbidity of the mixture is measured using a turbidimeter or nephelometer (for example, Hach Model 2100AN, Hach Company, Loveland, Colo.). A reading of greater than 10 nephelometric turbidity units (NTU) indicates that the monomer is considered to be hydrophobic.

[0028] Other useful alkyl esters of acrylic acid or methacrylic acid that may be used to prepare the core of the particles include aliphatic alkyl esters containing from 1 to 30, and usually 4 to 18 carbon atoms in the alkyl group. When used, they are usually in combination with one or more of the above hydrophobic monomers. Non-limiting examples include methyl (meth)acrylate, ethyl (meth)acrylate, and n-propyl (meth)acrylate. Suitable other copolymerizable ethylenically unsaturated monomers include vinyl aromatic compounds such as styrene and vinyl toluene. Hydroxyl functional ethylenically unsaturated monomers such as hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate may also be used in amounts that do not significantly adversely affect the hydrophobicity of the core.

[0029] Usually the core of the particles is prepared from a reaction mixture comprising 20 to 100 percent by weight, or 40 to 100 percent by weight, or 60 to 100 percent by weight, or 80 to 100 percent by weight n-butyl (meth)acrylate, based on the total weight of the reaction mixture. As such, the core of the particles may comprise 20 to 100 percent by weight, or 40 to 100 percent by weight, or 60 to 100 percent by weight, or 80 to 100 percent by weight residues of n-butyl (meth)acrylate, based on the total weight of the core. By “residue” is meant the moiety remaining after reaction (e. g., polymerization) of a reactant such as a monomer. In a particular example, the reaction mixture consists essentially of butyl acrylate and the core is a homopolymer of butyl acrylate.

[0030] The particles in the aqueous dispersions of the present disclosure typically have an average particle size of 10 to 300 nm, such that they would be considered nanoparticles. Particle size may be determined from among the numerous techniques known in the art, such as the method described below. The particle size is measured with a Malvern Zetasizer, which is a high performance two angle particle size analyzer for the enhanced detection of aggregates and measurement of small or dilute samples, and samples at very low or high concentration using dynamic light scattering. Typical applications of dynamic light scattering are the characterization of particles, emulsions or molecules, which have been dispersed or dissolved in a liquid. The Brownian motion of particles or molecules in suspension causes laser light to be scattered at different intensities. Analysis of these intensity fluctuations yields the velocity of the Brownian motion and hence the particle size using the Stokes-Einstein relationship. The reported particle sizes for all examples are the Z average mean value.

[0031] The aqueous dispersions described herein may be used to prepare waterborne curable film-forming compositions. Such compositions may comprise: a) an aqueous dispersion as described herein; b) a crosslinking agent; and c) a water dispersible polymer that comprises functional groups that are reactive with the crosslinking agent b).

[0032] The aqueous dispersion a) is typically present in the curable film-forming composition in an amount of 5 to 40, or 5 to 30, or 5 to 20, or 10 to 40, or 10 to 30, or 10 to 20 percent by weight, based on the total weight of the curable film-forming composition.

[0033] Suitable crosslinking agents b) include, for example, aminoplasts, polyisocyanates, including blocked isocyanates, polyepoxides, and polycarbodiimides.

[0034] Useful aminoplasts can be obtained from the condensation reaction of formaldehyde with an amine or amide. Nonlimiting examples of amines or amides include melamine, urea and benzoguanamine.

[0035] Although condensation products obtained from the reaction of alcohols and formaldehyde with melamine, urea or benzoguanamine are most common, condensates with other amines or amides can be used. Formaldehyde is the most commonly used aldehyde, but other aldehydes such as acetaldehyde, crotonaldehyde, and benzaldehyde can also be used.

[0036] The aminoplast can contain imino and methylol groups. In certain instances, at least a portion of the methylol groups can be etherified with an alcohol to modify the cure response. Any monohydric alcohol like methanol, ethanol, n-butyl alcohol, isobutanol, and hexanol can be employed for this purpose. Nonlimiting examples of suitable aminoplast resins are commercially available from Cytec Industries, Inc. under the trademark CYMEL® and from Solutia, Inc. under the trademark RESIMENE®.

[0037] Other crosslinking agents suitable for use include polyisocyanate crosslinking agents. As used herein, the term ''polyisocyanate'' is intended to include blocked (or capped) polyisocyanates as well as unblocked polyisocyanates. The polyisocyanate can be aliphatic, aromatic, or a mixture thereof. Although higher polyisocyanates such as isocyanurates of diisocyanates are often used, diisocyanates can also be used. Mixtures of polyisocyanate crosslinking agents can be used.

[0038] Polyisocyanates that may be utilized as crosslinking agents can be prepared from a variety of isocyanate-containing materials. Examples of suitable polyisocyanates include the following diisocyanates and trimers prepared therefrom: toluene diisocyanate, 4,4'-methylene-bis(cyclohexyl isocyanate), isophorone diisocyanate, an isomeric mixture of 2,2,4- and 2,4,4-trimethyl hexamethylene diisocyanate, 1 ,6-hexamethylene diisocyanate, tetramethyl xylylene diisocyanate and 4,4'-diphenylmethylene diisocyanate. Isocyanate prepolymers, for example reaction products of polyisocyanates with polyols also can be used. The polyisocyanate crosslinking agent is usually water emulsifiable or dispersible for use in the waterborne curable film-forming compositions of the present disclosure.

[0039] If the polyisocyanate is to be blocked or capped, any suitable aliphatic, cycloaliphatic, or aromatic alkyl monoalcohol or phenolic compound known to those skilled in the art can be used as a capping agent for the polyisocyanate. Examples of isocyanate blocking agents include various phenolic compounds, for example, phenol, thiophenol, chlorophenol, methyl thiophenol, ethyl phenol, t-butylphenol, ethyl thiophenol, nitrophenol, cresol, xylenol, resorcinol, hydroxy benzoic acid or an ester thereof, or 2,5-di-tert-butyl-4-hydroxytoluene; polycyclic aromatic hydrocarbons, for example pyrene methanol; alcohols such as ethanol, methanol, propanol, isopropanol, butanol, tert-butanol, tert-pentanol, tert-butanethiol, tert-hexanol, propargyl alcohol, 2- chloroethanol, omega-hydroperfluoroalcohols, 1 ,3-dichloro-2-propanol, n-amyl alcohol, t-amyl alcohol, lauryl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, methoxymethanol, glycolic acid, glycolic acid esters, lactic acid, lactic acid esters, methylol urea, methylol melamine, diacetone alcohol, ethylene chlorohydrin, ethylene bromohydrin, 1 ,3-dichloro-2-propanol, co-hydroperfluoro-alcohol, or acetocyanohydrin; aromatic amines such as diphenylamine, diphenyl naphthyl amine or xylidine; imides such as succinic acid imide or phthalic acid imide; active methylene compounds such as acetoacetic acid esters, acetyl acetone or malonic acid diesters; mercaptans such as 2-mercaptobenzothiazole or tert-dodecyl mercaptan; pyrazoles such as 3,5-dimethylpyrazole, lactams such as epsilon-caprolactam, delta- valerolactam, gamma-butyrolactam or beta-propyllactam; imines such as ethylene imine; urea compounds such as urea, thiourea or diethylene urea; oximes such as acetoxime, methylethyl-ketone oxime, or cyclohexanone oxime; diaryl compounds such as carbazole, phenyl naphthyl amine or N-phenyl xylidine; bisulfates; and borates. Mixtures comprising at least one of the foregoing blocking agents can also be employed.

[0040] Polyepoxides are suitable curing agents for polymers having carboxylic acid groups and/or amine groups. Examples of suitable polyepoxides include low molecular weight polyepoxides such as 3,4-epoxycyclohexylmethyl 3,4- epoxycyclohexanecarboxylate and bis(3,4-epoxy-6-methylcyclohexyl-methyl) adipate. Higher molecular weight polyepoxides, including the polyglycidyl ethers of polyhydric phenols and alcohols, are also suitable as crosslinking agents.

[0041] Suitable carbodiimide crosslinkers include an aliphatic and/or cycloaliphatic dinitrogen analogue of carbonic acid of the generalized structure: RN=C=NRi where R and Ri are independently aliphatic or cycloaliphatic groups. The aliphatic groups can comprise 1 -6 carbon atoms. Examples include dibutyl carbodiimide and dicyclohexyl carbodiimide. Oligomeric or polymeric carbodiimide crosslinkers can also be used. Examples of such materials are disclosed in US 2009/0246393A1 .

[0042] The preparation of water dispersible carbodiimide crosslinkers is well known in the art. Suitable water dispersible carbodiimide crosslinkers can be prepared by incorporating minor amounts of an amine, such as dimethyl aminopropylamine, and an alkyl sulfonate or sulfate into the carbodiimide structure. Suitable water dispersible carbodiimides can also be prepared by incorporating polyethylene oxide or polypropylene oxide into the carbodiimide structure.

[0043] Suitable carbodiimides are commercially available. For example, UCARLINK XL-29SE, XL-20 is commercially available from Union Carbide and CARBODILITE V- 02-L2 is commercially available from Nisshinbo Industries, Inc.

[0044] The amount of the crosslinking agent b) in the curable film-forming composition generally ranges from 5 to 75 percent by weight based on the total weight of resin solids in the curable film-forming composition. For example, the minimum amount of crosslinking agent may be at least 5 percent by weight, often at least 10 percent by weight and more often, at least 15 percent by weight. The maximum amount of crosslinking agent may be 75 percent by weight, more often 60 percent by weight, or 50 percent by weight. Ranges of crosslinking agent may include, for example, 5 to 50 percent by weight, 5 to 60 percent by weight, 10 to 50 percent by weight, 10 to 60 percent by weight, 10 to 75 percent by weight, 15 to 50 percent by weight, 15 to 60 percent by weight, and 15 to 75 percent by weight. As used herein “based on the total weight of resin solids” or “based on the total weight of organic binder solids” (used interchangeably) of the composition means that the amount of the component added during the formation of the composition is based upon the total weight of the resin solids (non-volatiles) of the film forming materials, including crosslinkers and polymers present during the formation of the composition, but not including any water, solvent, or any additive solids such as hindered amine stabilizers, photoinitiators, pigments including extender pigments and fillers, flow modifiers, catalysts, and UV light absorbers.

[0045] The waterborne curable film-forming composition further comprises a third component c) a water dispersible polymer that comprises functional groups that are reactive with the crosslinking agent b). For example, the water dispersible polymer c) may comprise a polyurethane such as an aqueous dispersion of polyurethaneacrylate, or other core-shell particles (different from the particles in the dispersion a)), a vinyl polymer, a polyether, a polyepoxide, an acrylic polymer and/or polyester polymer.

[0046] Suitable acrylic compounds include copolymers of one or more alkyl esters of acrylic acid or methacrylic acid, optionally together with one or more other polymerizable ethylenically unsaturated monomers. Useful alkyl esters of acrylic acid or methacrylic acid include aliphatic alkyl esters containing from 1 to 30, and often 4 to 18 carbon atoms in the alkyl group. Non-limiting examples include methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethyl acrylate, butyl acrylate, and 2-ethyl hexyl acrylate. Suitable other copolymerizable ethylenically unsaturated monomers include vinyl aromatic compounds such as styrene and vinyl toluene; nitriles such as acrylonitrile and methacrylonitrile; vinyl and vinylidene halides such as vinyl chloride and vinylidene fluoride and vinyl esters such as vinyl acetate.

[0047] The water dispersible polymer c) can include hydroxyl functional groups, which are often incorporated into the polymer by including one or more hydroxyl functional monomers in the reactants used to produce the copolymer. Useful hydroxyl functional monomers include hydroxyalkyl acrylates and methacrylates, typically having 2 to 4 carbon atoms in the hydroxyalkyl group, such as hydroxyethyl acrylate, hydroxypropyl acrylate, 4-hydroxybutyl acrylate, hydroxy functional adducts of caprolactone and hydroxyalkyl acrylates, and corresponding methacrylates, as well as the beta-hydroxy ester functional monomers described below. The acrylic polymer can also be prepared with N-(alkoxymethyl)acrylamides and N-(alkoxymethyl)methacrylamides.

[0048] Beta-hydroxy ester functional monomers can be prepared from ethylenically unsaturated, epoxy functional monomers and carboxylic acids having from 13 to 20 carbon atoms, or from ethylenically unsaturated acid functional monomers and epoxy compounds containing at least 5 carbon atoms which are not polymerizable with the ethylenically unsaturated acid functional monomer. [0049] Useful ethylenically unsaturated, epoxy functional monomers used to prepare the beta-hydroxy ester functional monomers include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, methallyl glycidyl ether, 1 :1 (molar) adducts of ethylenically unsaturated monoisocyanates with hydroxy functional monoepoxides such as glycidol, and glycidyl esters of polymerizable polycarboxylic acids such as maleic acid. (Note: these epoxy functional monomers may also be used to prepare epoxy functional acrylic polymers.) Examples of carboxylic acids include saturated monocarboxylic acids such as isostearic acid and aromatic unsaturated carboxylic acids.

[0050] Useful ethylenically unsaturated acid functional monomers used to prepare the beta-hydroxy ester functional monomers or to provide acid functionality to the acrylic polymer include monocarboxylic acids such as acrylic acid, methacrylic acid, cratonic acid; dicarboxylic acids such as itaconic acid, maleic acid and fumaric acid; and monoesters of dicarboxylic acids such as monobutyl maleate and monobutyl itaconate. The ethylenically unsaturated acid functional monomer and epoxy compound are typically reacted in a 1 :1 equivalent ratio. The epoxy compound does not contain ethylenic unsaturation that would participate in free radical-initiated polymerization with the unsaturated acid functional monomer. Useful epoxy compounds include 1 ,2-pentene oxide, styrene oxide and glycidyl esters or ethers, often containing from 8 to 30 carbon atoms, such as butyl glycidyl ether, octyl glycidyl ether, phenyl glycidyl ether and para-(tertiary butyl) phenyl glycidyl ether. Particular glycidyl esters include those of the structure:

\ o / where R is a hydrocarbon radical containing from 4 to 26 carbon atoms. Typically, R is a branched hydrocarbon group having from 8 to 10 carbon atoms, such as neopentanoate, neoheptanoate or neodecanoate. Suitable glycidyl esters of carboxylic acids include VERSATIC ACID 11 and CARDURA E, each of which is commercially available from Shell Chemical Co.

[0051] Carbamate functional groups can be included in the acrylic polymer by copolymerizing the acrylic monomers with a carbamate functional vinyl monomer, such as a carbamate functional alkyl ester of methacrylic acid, or by reacting a hydroxyl functional acrylic polymer with a low molecular weight carbamate functional material, such as can be derived from an alcohol or glycol ether, via a transcarbamoylation reaction. Alternatively, carbamate functionality may be introduced into the acrylic polymer by reacting a hydroxyl functional acrylic polymer with a low molecular weight carbamate functional material, such as can be derived from an alcohol or glycol ether, via a transcarbamoylation reaction. In this reaction, a low molecular weight carbamate functional material derived from an alcohol or glycol ether is reacted with the hydroxyl groups of the acrylic polyol, yielding a carbamate functional acrylic polymer and the original alcohol or glycol ether. The low molecular weight carbamate functional material derived from an alcohol or glycol ether may be prepared by reacting the alcohol or glycol ether with urea in the presence of a catalyst. Suitable alcohols include lower molecular weight aliphatic, cycloaliphatic, and aromatic alcohols such as methanol, ethanol, propanol, butanol, cyclohexanol, 2- ethylhexanol, and 3-methylbutanol. Suitable glycol ethers include ethylene glycol methyl ether and propylene glycol methyl ether. Propylene glycol methyl ether and methanol are most often used. Other carbamate functional monomers as known to those skilled in the art may also be used.

[0052] Amide functionality may be introduced to the acrylic polymer by using suitably functional monomers in the preparation of the polymer, or by converting other functional groups to amido- groups using techniques known to those skilled in the art. Likewise, other functional groups may be incorporated as desired using suitably functional monomers if available or conversion reactions as necessary.

[0053] Acrylic polymers can be prepared via aqueous emulsion polymerization techniques and used directly in the preparation of aqueous coating compositions. More often, the acrylic polymers are prepared via organic solution polymerization with groups capable of salt formation such as acid or amine groups, and upon neutralization of these groups with a base or acid, the polymers can be dispersed into aqueous medium. Generally, any method of producing such polymers that is known to those skilled in the art utilizing art recognized amounts of monomers can be used. [0054] As noted above, the water dispersible polymer c) may additionally or alternatively comprise a polyester polymer. Such polymers may be prepared in a known manner by condensation of polyhydric alcohols and polycarboxylic acids. Suitable polyhydric alcohols include, but are not limited to, ethylene glycol, propylene glycol, butylene glycol, 1 ,6-hexylene glycol, neopentyl glycol, diethylene glycol, glycerol, trimethylol propane, and pentaerythritol. Suitable polycarboxylic acids include, but are not limited to, succinic acid, adipic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, and trimellitic acid. Besides the polycarboxylic acids mentioned above, functional equivalents of the acids such as anhydrides where they exist or lower alkyl esters of the acids such as the methyl esters may be used.

[0055] Carbamate functional groups may be incorporated into the polyester by first forming a hydroxyalkyl carbamate which can be reacted with the polyacids and polyols used in forming the polyester. The hydroxyalkyl carbamate is condensed with acid functionality on the polymer, yielding terminal carbamate functionality. Carbamate functional groups may also be incorporated into the polyester by reacting terminal hydroxyl groups on the polyester with a low molecular weight carbamate functional material via a transcarbamoylation process, or by reacting isocyanic acid with a hydroxyl functional polyester.

[0056] Other functional groups such as amine, amide, thiol, urea, and the like may be incorporated into the polyester as desired using suitably functional reactants if available, or conversion reactions as necessary to yield the desired functional groups. Such techniques are known to those skilled in the art.

[0057] Examples of polyether polyols are polyalkylene ether polyols which include those having the following structural formula:

(i)

or (ii)

where the substituent Ri is hydrogen or lower alkyl containing from 1 to 5 carbon atoms including mixed substituents, and n is typically from 2 to 6 and m is from 8 to 100 or higher. Included are poly(oxytetramethylene) glycols, poly(oxytetraethylene) glycols, poly(oxy-1 ,2-propylene) glycols, and poly(oxy-1 ,2-butylene) glycols.

[0058] Also useful are polyether polyols formed from oxyalkylation of various polyols, for example, diols such as ethylene glycol, 1 ,6-hexanediol, Bisphenol A and the like, or other higher polyols such as trimethylolpropane, pentaerythritol, and the like. Polyols of higher functionality which can be utilized as indicated can be made, for instance, by oxyalkylation of compounds such as sucrose or sorbitol. One commonly utilized oxyalkylation method is reaction of a polyol with an alkylene oxide, for example, propylene or ethylene oxide, in the presence of an acidic or basic catalyst. Particular polyethers include those sold under the names TERATHANE and TERACOL, available from Invista, and POLYMEG, available from Lyondell Chemical Co.

[0059] Pendant carbamate functional groups may be incorporated into the polyethers by a transcarbamoylation reaction. Other functional groups such as acid, amine, epoxide, amide, thiol, and urea may be incorporated into the polyether as desired using suitably functional reactants if available, or conversion reactions as necessary to yield the desired functional groups. Examples of suitable amine functional polyethers include those sold under the name JEFFAMINE, such as JEFFAMINE D2000, a polyether functional diamine available from Huntsman Corporation.

[0060] Suitable epoxy functional polymers for use as the water dispersible polymer c) may include a polyepoxide chain extended by reacting together a polyepoxide and a polyhydroxyl group-containing material selected from alcoholic hydroxyl group- containing materials and phenolic hydroxyl group-containing materials to chain extend or build the molecular weight of the polyepoxide.

[0061] A chain extended polyepoxide is typically prepared by reacting together the polyepoxide and polyhydroxyl group-containing material neat or in the presence of an inert organic solvent such as a ketone, including methyl isobutyl ketone and methyl amyl ketone, aromatics such as toluene and xylene, and glycol ethers such as the dimethyl ether of diethylene glycol. The reaction is usually conducted at a temperature of 80°C to 160°C for 30 to 180 minutes until an epoxy group-containing resinous reaction product is obtained.

[0062] The equivalent ratio of reactants; i. e., epoxy:polyhydroxyl group-containing material is typically from 1 .00:0.75 to 1 .00:2.00. [0063] The polyepoxide by definition has at least two 1 ,2-epoxy groups. In general the epoxide equivalent weight of the polyepoxide will range from 100 to 2000, typically from 180 to 500. The epoxy compounds may be saturated or unsaturated, cyclic or acyclic, aliphatic, alicyclic, aromatic or heterocyclic. They may contain substituents such as halogen, hydroxyl, and ether groups.

[0064] Examples of polyepoxides are those having a 1 ,2-epoxy equivalency greater than one and usually two; that is, polyepoxides which have on average two epoxide groups per molecule. The most commonly used polyepoxides are polyglycidyl ethers of cyclic polyols, for example, polyglycidyl ethers of polyhydric phenols such as Bisphenol A, resorcinol, hydroquinone, benzenedimethanol, phloroglucinol, and catechol; or polyglycidyl ethers of polyhydric alcohols such as alicyclic polyols, particularly cycloaliphatic polyols such as 1 ,2-cyclohexane diol, 1 ,4-cyclohexane diol, 2,2-bis(4-hydroxycyclohexyl)propane, 1 ,1 -bis(4-hydroxycyclohexyl)ethane, 2-methyl- 1 , 1 -bis(4-hydroxycyclohexyl)propane, 2,2-bis(4-hydroxy-3- tertiarybutylcyclohexyl)propane, 1 ,3-bis(hydroxymethyl)cyclohexane and 1 ,2- bis(hydroxymethyl)cyclohexane. Examples of aliphatic polyols include, inter alia, trimethylpentanediol and neopentyl glycol.

[0065] Polyhydroxyl group-containing materials used to chain extend or increase the molecular weight of the polyepoxide may additionally be polymeric polyols such as any of those disclosed above. The water dispersible polymer c) may comprise epoxy resins such as diglycidyl ethers of Bisphenol A, Bisphenol F, glycerol, novolacs, and the like. Exemplary suitable polyepoxides are described in U.S. Patent No. 4,681 ,811 at column 5, lines 33 to 58.

[0066] Epoxy functional water dispersible polymers may alternatively be (meth)acrylic polymers prepared with epoxy functional monomers such as glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, and methallyl glycidyl ether. Polyesters, polyurethanes, or polyamides prepared with glycidyl alcohols or glycidyl amines, or reacted with an epihalohydrin are also suitable epoxy functional resins. Epoxide functional groups may be incorporated into a resin by reacting hydroxyl groups on the resin with an epihalohydrin or dihalohydrin such as epichlorohydrin or dichlorohydrin in the presence of alkali.

[0067] The water dispersible polymer c) is often added to the waterborne curable filmforming composition in the form of an aqueous emulsion (latex) of the polymer. [0068] The water dispersible polymer c) is usually present in the waterborne curable film-forming composition in an amount of 5 to 85 percent by weight based on the total weight of resin solids in the curable film-forming composition. For example, the minimum amount of water dispersible polymer c) may be at least 5 percent by weight, often at least 20 percent by weight and more often, at least 40 percent by weight. The maximum amount of water dispersible polymer c) may be 85 percent by weight, more often 75 percent by weight, or 70 percent by weight. Ranges of water dispersible polymer c) may include, for example, 5 to 75 percent by weight, 5 to 70 percent by weight, 20 to 85 percent by weight, 20 to 75 percent by weight, 20 to 70 percent by weight, 40 to 85 percent by weight, 40 to 75 percent by weight, and 40 to 70 percent by weight, based on the total weight of resin solids in the curable film-forming composition.

[0069] The waterborne curable film-forming compositions of the present disclosure may contain additional ingredients conventionally used in coating compositions. Optional ingredients such as, for example, plasticizers, surfactants, thixotropic agents, anti-gassing agents, organic cosolvents, flow controllers, anti-oxidants, UV light absorbers and similar additives conventional in the art may be included in the composition. These ingredients are typically present at up to 40% by weight based on the total weight of resin solids.

[0070] The waterborne curable film-forming composition described above are suitable for use in multilayer coated substrates, which may comprise:

A) a substrate;

B) a first coating composition applied to a surface of the substrate, forming a first coating on the substrate;

C) a basecoat composition applied on top of the first coating; and

D) a clearcoat composition applied on top of the basecoat composition. The composition C) comprises a waterborne curable film-forming composition described above.

[0071] Non-metallic substrates A) include polymeric, plastic, polyester, polyolefin, polyamide, cellulosic, polystyrene, polyacrylic, polyethylene naphthalate), polypropylene, polyethylene, nylon, EVOH, poly(lactic acid), other “green” polymeric substrates, polyethylene terephthalate) (“PET”), polycarbonate, polycarbonate acrylonitrile butadiene styrene (“PC/ABS”), polyamide, polymer composites and the like. Car parts typically formed from thermoplastic and thermoset materials include bumpers and trim.

[0072] The metal substrates used in the present disclosure include ferrous metals, non-ferrous metals and combinations thereof. Suitable ferrous metals include iron, steel, and alloys thereof. Non-limiting examples of useful steel materials include cold rolled steel, pickled steel, steel surface-treated with any of zinc metal, zinc compounds and zinc alloys (including electrogalvanized steel, hot-dipped galvanized steel, GALVANNEAL steel, and steel plated with zinc alloy,) and/or zinc-iron alloys. Also, aluminum, aluminum alloys, zinc-aluminum alloys such as GALFAN, GALVALUME, aluminum plated steel and aluminum alloy plated steel substrates may be used, as well as magnesium metal, titanium metal, and alloys thereof. Steel substrates (such as cold rolled steel or any of the steel substrates listed above) coated with a weldable, zinc-rich or iron phosphide-rich organic coating are also suitable for use in the present disclosure. Such weldable coating compositions are disclosed in U. S. Patent Nos. 4,157,924 and 4,186,036. Cold rolled steel is also suitable when pretreated with an appropriate solution known in the art, such as a metal phosphate solution, an aqueous solution containing at least one Group 11 IB or IVB metal, an organophosphate solution, an organophosphonate solution, and combinations thereof, as discussed below.

[0073] The substrate may alternatively comprise more than one metal or metal alloy in that the substrate may be a combination of two or more metal substrates assembled together such as hot-dipped galvanized steel assembled with aluminum substrates. The substrate may alternatively comprise a composite material such as a fiberglass composite. It is desirable to have a coating system which can be applied to both metal and non-metal parts. The substrate may comprise part of a vehicle. "Vehicle" is used herein in its broadest sense and includes all types of vehicles, such as but not limited to airplanes, helicopters, cars, trucks, buses, vans, golf carts, motorcycles, bicycles, railroad cars, tanks and the like. It will be appreciated that the portion of the vehicle that is coated according to the present disclosure may vary depending on why the coating is being used.

[0074] The shape of the substrate can be in the form of a sheet, plate, bar, rod or any shape desired, but it is usually in the form of an automobile part, such as a body, door, fender, hood or bumper. The thickness of the substrate can vary as desired. [0075] The substrates to be used may be bare substrates. By “bare” is meant a virgin substrate that has not been treated with (or has been stripped of) any pretreatment compositions such as conventional phosphating baths, heavy metal rinses, etc. Additionally, bare metal substrates being used in the present disclosure may be a cut edge of a substrate that is otherwise treated and/or coated over the rest of its surface. Alternatively, the substrates may undergo one or more treatment steps known in the art prior to the application of the curable film-forming composition.

[0076] Before depositing any coating compositions upon the surface of the substrate, it is common practice, though not necessary, to remove foreign matter from the surface by thoroughly stripping, cleaning and degreasing the surface. Such cleaning typically takes place after forming the substrate (stamping, welding, etc.) into an end-use shape. The surface of the substrate can be cleaned by physical or chemical means, or both, such as mechanically abrading the surface (e. g., sanding) or cleaning/degreasing with commercially available alkaline or acidic cleaning agents which are well known to those skilled in the art, such as sodium metasilicate and sodium hydroxide. A non-limiting example of a cleaning agent is CHEMKLEEN 163, an alkaline-based cleaner commercially available from PPG Industries, Inc.

[0077] A metal substrate may optionally be pretreated with any suitable solution known in the art, such as a metal phosphate solution, an aqueous solution containing at least one Group IIIB or IVB metal, an organophosphate solution, an organophosphonate solution, and combinations thereof. The pretreatment solutions may be essentially free of environmentally detrimental heavy metals such as chromium and nickel. Suitable phosphate conversion coating compositions may be any of those known in the art that are free of heavy metals. Examples include zinc phosphate, which is used most often, iron phosphate, manganese phosphate, calcium phosphate, magnesium phosphate, cobalt phosphate, zinc-iron phosphate, zincmanganese phosphate, zinc-calcium phosphate, and layers of other types, which may contain one or more multivalent cations. Phosphating compositions are known to those skilled in the art and are described in U. S. Patents 4,941 ,930, 5,238,506, and 5,653,790.

[0078] The IIIB or IVB transition metals and rare earth metals referred to herein are those elements included in such groups in the CAS Periodic Table of the Elements as is shown, for example, in the Handbook of Chemistry and Physics, 63rd Edition (1983). [0079] Typical group I IIB and IVB transition metal compounds and rare earth metal compounds are compounds of zirconium, titanium, hafnium, yttrium and cerium and mixtures thereof. Typical zirconium compounds may be selected from hexafluorozirconic acid, alkali metal and ammonium salts thereof, ammonium zirconium carbonate, zirconyl nitrate, zirconium carboxylates and zirconium hydroxy carboxylates such as hydrofluorozirconic acid, zirconium acetate, zirconium oxalate, ammonium zirconium glycolate, ammonium zirconium lactate, ammonium zirconium citrate, and mixtures thereof. Hexafluorozirconic acid is used most often. An example of a titanium compound is fluorotitanic acid and its salts. An example of a hafnium compound is hafnium nitrate. An example of a yttrium compound is yttrium nitrate. An example of a cerium compound is cerous nitrate.

[0080] Typical compositions to be used in the pretreatment step include non- conductive organophosphate and organophosphonate pretreatment compositions such as those disclosed in U. S. Patents 5,294,265 and 5,306,526. Such organophosphate or organophosphonate pretreatments are available commercially from PPG under the name NUPAL®.

[0081] The multi-layer coated substrates of the present disclosure further comprise B) a first coating composition applied to a surface of the substrate, forming a first coating. The composition B) may comprise a single electrocoat layer serving as a protective layer, a primer composition applied directly to the metal substrate without an intervening electrocoat layer, and/or a sealer composition (e. g., a seam sealer) applied directly to the metal substrate or over an electrocoat and/or primer composition. For example, the composition B) may comprise an electrocoat composition applied to a surface of the substrate and a primer composition applied on top of the electrocoat layer. The composition B) may be any conventional electrocoat composition, primer composition, and/or sealer composition known in the art.

[0082] In the process of electrodeposition, the metal substrate being coated, serving as an electrode, and an electrically conductive counter electrode are placed in contact with an ionic, electrodepositable (“electrocoat”) composition. Upon passage of an electric current between the electrode and counter electrode while they are in contact with the electrocoat composition, an adherent film of the electrocoat composition will deposit in a substantially continuous manner on the metal substrate. Typically, the electrocoat composition is cationic. [0083] Electrodeposition is usually carried out at a constant voltage in the range of from 1 volt to several thousand volts, typically between 50 and 500 volts. Current density is usually between 1 .0 ampere and 15 amperes per square foot (10.8 to 161 .5 amperes per square meter) and tends to decrease quickly during the electrodeposition process, indicating formation of a continuous self-insulating film.

[0084] After electrodeposition, the coated substrate is heated to cure the deposited composition. The heating or curing operation is usually carried out at a temperature in the range of from 250 to 450²F (121.1 to 232.2²C), often 300 to 450°F (148.9 to 232.2°C), more often 300 to 400°F (148.9 to 204.4°C) for a period of time sufficient to effect cure of the composition, typically ranging from 10 to 60 minutes. The thickness of the resultant film is usually from 10 to 50 microns.

[0085] Additionally or alternatively, a primer composition different from the electrocoat composition may be used to form the first coating. Again, any primers known in the art may be suitable; an example of a commercially available primer is HP78224EH, available from PPG.

[0086] A sealer composition, or sealant, is typically applied around and inside the doors, hood, trunk, and front dash, and onto the exterior and interior of metal joints and outer area of the back wheel well of a vehicle during OEM; application of the sealant prevents air and water ingress and inhibits rust formation. Commercially available sealer compositions include BETAFILL 55 and BETAMATE 65, both available from Dow Automotive Systems.

[0087] A basecoat composition C) may then be applied to the first coating. The basecoat composition typically comprises a waterborne curable film-forming composition of the present disclosure.

[0088] As a basecoat, the waterborne curable film-forming composition typically includes a colorant for aesthetic purposes. As used herein, the term “colorant” means any substance that imparts color and/or other opacity and/or other visual effect to the composition. The colorant can be added to the coating in any suitable form, such as discrete particles, dispersions, solutions and/or flakes. A single colorant or a mixture of two or more colorants can be used in the coatings of the present disclosure.

[0089] Example colorants include pigments, dyes and tints, such as those used in the paint industry and/or listed in the Dry Color Manufacturers Association (DCMA), as well as special effect compositions. A colorant may include, for example, a finely divided solid powder that is insoluble but wettable under the conditions of use. A colorant can be organic or inorganic and can be agglomerated or non-agglomerated. Colorants can be incorporated into the coatings by grinding or simple mixing. Colorants can be incorporated by grinding into the coating by use of a grind vehicle, the use of which will be familiar to one skilled in the art.

[0090] Example pigments and/or pigment compositions include, but are not limited to, carbazole dioxazine crude pigment, azo, monoazo, disazo, naphthol AS, salt type (lakes), benzimidazolone, condensation, metal complex, isoindolinone, isoindoline and polycyclic phthalocyanine, quinacridone, perylene, perinone, diketopyrrolo pyrrole, thioindigo, anthraquinone, indanthrone, anthrapyrimidine, flavanthrone, pyranthrone, anthanthrone, dioxazine, triarylcarbonium, quinophthalone pigments, diketo pyrrolo pyrrole red (“DPPBO red”), titanium dioxide, carbon black and mixtures thereof. The terms "pigment" and "colored filler" can be used interchangeably.

[0091] Example dyes include, but are not limited to, those that are solvent and/or aqueous based such as acid dyes, azoic dyes, basic dyes, direct dyes, disperse dyes, reactive dyes, solvent dyes, sulfur dyes, mordant dyes, for example, bismuth vanadate, anthraquinone, perylene, aluminum, quinacridone, thiazole, thiazine, azo, indigoid, nitro, nitroso, oxazine, phthalocyanine, quinoline, stilbene, and triphenyl methane.

[0092] Example tints include, but are not limited to, pigments dispersed in waterbased or water miscible carriers such as AQUA-CHEM 896 commercially available from Degussa, Inc., CHARISMA COLORANTS and MAXITONER INDUSTRIAL COLORANTS commercially available from Accurate Dispersions division of Eastman Chemical, Inc.

[0093] As noted above, the colorant can be in the form of a dispersion including, but not limited to, a nanoparticle dispersion. Nanoparticle dispersions can include one or more highly dispersed nanoparticle colorants and/or colorant particles that produce a desired visible color and/or opacity and/or visual effect. Nanoparticle dispersions can include colorants such as pigments or dyes having a particle size of less than 150 nm, such as less than 70 nm, or less than 30 nm. Nanoparticles can be produced by milling stock organic or inorganic pigments with grinding media having a particle size of less than 0.5 mm. Example nanoparticle dispersions and methods for making them are identified in U.S. Patent No. 6,875,800 B2. Nanoparticle dispersions can also be produced by crystallization, precipitation, gas phase condensation, and chemical attrition (i.e., partial dissolution). In order to minimize re-agglomeration of nanoparticles within the coating, a dispersion of resin-coated nanoparticles can be used. As used herein, a “dispersion of resin-coated nanoparticles” refers to a continuous phase in which is dispersed discreet “composite microparticles” that comprise a nanoparticle and a resin coating on the nanoparticle.

[0094] Example special effect compositions that may be used in the basecoat include pigments and/or compositions that produce one or more appearance effects such as reflectance, pearlescence, metallic sheen, phosphorescence, fluorescence, photochromism, photosensitivity, thermochromism, goniochromism and/or colorchange. Additional special effect compositions can provide other perceptible properties, such as reflectivity, opacity or texture. In a non-limiting example, special effect compositions can produce a color shift, such that the color of the coating changes when the coating is viewed at different angles. Example color effect compositions are identified in U.S. Patent No. 6,894,086. Additional color effect compositions can include transparent coated mica and/or synthetic mica, coated silica, coated alumina, a transparent liquid crystal pigment, a liquid crystal coating, and/or any composition wherein interference results from a refractive index differential within the material and not because of the refractive index differential between the surface of the material and the air.

[0095] In general, the colorant can be present in the coating composition in any amount sufficient to impart the desired property, visual and/or color effect. The colorant may comprise from 1 to 65 weight percent of the present compositions, such as from 3 to 40 weight percent or 5 to 35 weight percent, with weight percent based on the total weight of the compositions.

[0096] A clearcoat composition D) is applied on top of the basecoat composition C). The clearcoat composition may be any of those known in the art. A notable improvement in intercoat adhesion at the interface between the basecoat and coating layers directly in contact with the basecoat, such as the clearcoat and/or sealant, has been observed, as well as cohesive properties within a basecoat coating layer on a substrate, when the basecoat comprises a waterborne curable film-forming composition of the present disclosure; for example, when the basecoat comprises a waterborne curable film-forming composition of the present disclosure and the clearcoat comprises a polyisocyanate and a film-forming resin comprising active hydrogen groups reactive with isocyanate. Often the clearcoat is provided as a multipackage (e. g., “2K”) composition.

[0097] Other than the electrocoat, each coating composition (primer, basecoat, etc.) may be applied to the substrate in the preparation of the multilayer coated substrate by known application techniques, such as dipping or immersion, spraying, intermittent spraying, dipping followed by spraying, spraying followed by dipping, brushing, or by roll-coating. Usual spray techniques and equipment for air spraying and electrostatic spraying, either manual or automatic methods, can be used.

[0098] After application of a composition, a film is formed by driving the liquid medium, i. e., water and any organic solvent, out of the film by heating or by an air-drying period. Suitable drying conditions will depend on the particular composition and/or application, but in some instances a drying time of from 5 to 30 minutes at a temperature of room temperature to 100°C will be sufficient. More than one coating layer of each composition may be applied if desired. Usually between coats, the previously applied coat is flashed; that is, exposed to ambient conditions for the desired amount of time. The coating layers may be cured by exposure to a temperature sufficient to effect cure reactions after application of each layer, or the coating layers may be applied in a wet- on-wet process, (i.e. prior to dehydration of the previously-applied coating composition), and all of the layers cured simultaneously in a single curing step. For an automotive OEM cure regimen, cure temperatures of 80°C to 140°C are typical.

[0099] As noted above, an improvement in adhesive properties between a basecoat coating layer and a coating layer directly in contact with the basecoat coating layer (i. e., at the interface between coating layers) on a substrate, and/or an improvement in cohesive properties within a basecoat coating layer on a substrate has been observed when the basecoat comprises a waterborne curable film-forming composition of the present disclosure. Thus, the present disclosure is further drawn to a method of improving adhesive properties between a basecoat coating layer and a coating layer directly in contact with the basecoat coating layer on a substrate, and/or improving cohesive properties within a basecoat coating layer on a substrate, the method comprising:

A) applying a first coating composition as described above to a surface of the substrate, forming a first coating on the substrate; B) applying a basecoat composition on top of the first coating; and

[00100] The following working Examples are intended to further describe and demonstrate the compositions, coated articles, and methods described herein. It is understood that the disclosure of this specification is not necessarily limited to the examples described in this section. Components that are mentioned elsewhere in the specification as suitable alternative materials for use, but which are not demonstrated in the working Examples below, are expected to provide results comparable to their demonstrated counterparts. Unless otherwise indicated, all parts are by weight.

EXAMPLES

Example 1

[00101] A waterborne polyurethane prepolymer was prepared from the following ingredients:

¹ polytetrahydrofuran, available from BASF [00102] To a four-necked reaction flask outfitted with a stirrer, gas inlet, thermometer and condenser was added the contents of Charge 1 and the mixture was heated to 50 °C. After the exotherm subsided, the temp was raised to 85 °C and held for 4 hours or until the reaction mixture achieved an NCO equivalent weight > 1350. Charge 2 was then added rapidly, and the mixture was held for 1 hour or until the isocyanate was no longer observable by infrared spectroscopy. Charge 3 was added and stirred for 5 minutes, then Charge 4 was added and stirred for 5 minutes. 85% of the combined Charge 1 -4 was then reverse-thinned into Charge 5 to produce the dispersion which was not isolated but converted directly in the next Example.

Example 2

[00103] An aqueous dispersion of polyurethane-acrylate polymeric particles was prepared from the following ingredients:

1 Defoamer available from Crucible Chemical CO.

2 Initiator available from ARKEMA

3 Available from Azelis Americas [00104] Charge 1 was sparged with an N2 stream (1 CFM) for 60 minutes to remove dissolve oxygen. Charge 2 was then added and stirred for 10 minutes. The N2 stream was switched to an N2 blanket and Charge 3 was added over ~ 5 minutes. An approximately 12 °C exotherm ensued and stirring was continued. The reaction was then cooled and Charges 4 and 5 were added. The final dispersion had a solids content of 32%, a viscosity of 1040 cps, a pH of 8.7, and a particle size of 60 nm. Theory AV(s) = 19, OH(s) = 5. “Solids”, or “non-volatiles”, include any materials, whether solid or liquid at ambient temperature, that remain after subjecting a 1 -gram sample of the material to 1 10°C for one hour.

Examples 3 to 6

[00105] A series of aqueous dispersions of polyurethane-acrylate polymeric particles (20% by mass acrylic core : 80% by mass polyurethane shell) was prepared by varying the relative mole ratio of the Charge 2 components Hydroxyethyl methacrylate (HEMA) and 2-Methyl-1 ,3-Propanediol (2-MPD) of Example 1 . Variation of these components affected the polyurethane chain-end distribution of graftable moieties (HEMA) and curable moieties (2-MPD) according to the table below.

Table 1

[00106] The possible outcomes are polyurethane chains with (a) HEMA moiety at one end and 2-MPD moiety at the other end (“HEMA-OH”); (b) HEMA moieties at both ends (“Bis HEMA”); and (c) 2-MPD moieties at both ends (“Bis DIOL”). Based upon probability theory, the relative amount of these options can be calculated. Example 7

[00107] A waterborne polyurethane was prepared from the following ingredients:

[00108] To a four-necked reaction flask outfitted with a stirrer, gas inlet, thermometer and condenser was added the contents of Charge 1 and the mixture was heated to 50 °C. After the exotherm subsided, the temperature was raised to 85 °C and held for 4 hours or until the reaction mixture achieved an NCO equivalent weight > 1350. Charge 2 was then added rapidly, and the mixture was held for 1 hour or until the isocyanate was no longer observable by infrared spectroscopy. Charge 3 was added and stirred for 5 minutes. A dispersion was produced by adding alternately Charge 4 and Charge 5 to the organic phase. A fine particle dispersion at 30% solids was produced with a theory AV(s) = 24, theory OH(s) = 6. This dispersion was then used to prepare aqueous dispersions of polyurethane-acrylate polymeric particles with core:shell mass ratios of 20:80, 30:70, and 40:60. Example 8

[00109] An aqueous dispersion of polyurethane-acrylate polymeric particles having a core:shell mass ratio of 20:80 was prepared from the following ingredients:

[00110] Charge 1 was sparged with an N2 stream (1 CFM) for 60 minutes to remove dissolve oxygen. Charge 2 was then added and stirred for 10 minutes. The N2 stream was switched to an N2 blanket and Charge 3 was added over ~ 5 minutes. An approximately 12 °C exotherm ensued and stirring was continued. The reaction was then cooled and Charges 4 and 5 were added. The final dispersion had a solids content of 32%, a viscosity of 340 cps, a pH of 8.4 Theory AV(s) = 19, OH(s) = 5.

Example 9

[00111] An aqueous dispersion of polyurethane-acrylate polymeric particles having a core:shell mass ratio of 30:70 was prepared from the following ingredients:

[00112] Charge 1 was sparged with an N2 stream (1 CFM) for 60 minutes to remove dissolve oxygen. Charge 2 was then added and stirred for 10 minutes. The N2 stream was switched to an N2 blanket and Charge 3 was added over ~ 5 minutes. An approximately 17 °C exotherm ensued and stirring was continued. The reaction was then cooled and Charges 4 and 5 were added. The final dispersion had a solids content of 32%, a viscosity of 400 cps, a pH of 8.4. Theory AV(s) = 16, OH(s) = 4.

Example 10

[00113] An aqueous dispersion of polyurethane-acrylate polymeric particles having a core:shell mass ratio of 40:60 was prepared from the following ingredients:

[00114] Charge 1 was sparged with an N2 stream (1 CFM) for 60 minutes to remove dissolve oxygen. Charge 2 was then added and stirred for 10 minutes. The N2 stream was switched to an N2 blanket and Charge 3 was added over ~ 5 minutes. An approximately 24 °C exotherm ensued and stirring was continued. The reaction was then cooled and Charge’s 4 and 5 were added. The final dispersion had a solids content of 32%, a viscosity of 850 cps, a pH of 8.3. Theory AV(s) = 14, OH(s) = 4.

Examples A and B

[00115] Curable film-forming compositions were prepared as colored basecoats, with and without an aqueous dispersion of polymeric particles according to the present disclosure.

¹”Polyester A1 ” as prepared in EP 1454971

²As prepared in United States Patent Number 8,846,156, Example A

³As prepared in United States Patent Number 8,846,156, Example G

⁴Additive from BYK Additives and Instruments.

⁵Additive from BYK Additives and Instruments.

⁶Solvent commercially available from Phillips 66.

⁷Solvent commercially available from Eastman Chemical Company.

⁸Melamine commercially available from Prefere Resins.

⁹Solvent commercially available from Eastman Chemical Company.

¹⁰Solvent commercially available from Dow Chemical Company.

¹¹ Aqueous solution of Laponite RD available from BYK Additives and Instruments

¹²Tint paste prepared from Cinilex DPP Red available from Cinic Chemicals. [00116] The example basecoats were prepared by combining components in the order listed, and were then reduced to Ph of 8.8 and a viscosity of 90 Cp. The basecoats were spray applied over primed electrocoated panels in two coats. The basecoats were flashed for 5 minutes at ambient conditions, then baked in an oven for 10 minutes at 80°C. The basecoats had a dry film thickness of approximately 13- 17 microns. A commercial 2K isocyanate clearcoat was then applied in two coats over the dehydrated basecoat. The clearcoat was flashed for 7 minutes at ambient conditions, then baked for 30 minutes at either 125°C or 140°C. The testing of properties for cure were performed initially at 1 - hour post-bake and then followed up for hardness at 1 day and 6 days. Sections of panels were edge primed and placed in a 63°C water bath for 3 days. The panels were tested by pressure water-jetting in accordance with ISO 16925 (2014), with the difference being that the amplitude of the adhesion loss was measured as a metric.

Table 2

[00117] The multi-layer coated substrate prepared using a waterborne curable filmforming composition of the present disclosure (Example B) demonstrated significantly better adhesion than that of the Comparative Example A, prepared using a waterborne curable film-forming composition that did not contain an aqueous dispersion as disclosed.

[00118] Whereas particular examples of this disclosure 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 disclosure may be made without departing therefrom as defined in the appended claims. Although various examples of the disclosure have been described in terms of "comprising", embodiments consisting essentially of or consisting of are also within the scope of the present disclosure.

Claims

THEREFORE, WE CLAIM:

1. An aqueous dispersion comprising particles having a core-shell morphology and having hydroxyl functional groups, the core of the particles comprising a (meth)acrylic functional polymer, the shell of the particles comprising a polyurethane polymer prepared from a polyurethane prepolymer and having a hydroxyl value of 1 to 40 mg KOH/g, or 1 to 30 mg KOH/g, or 1 to 20 mg KOH/g, or 1 to 15 mg KOH/g, or 1 to 10 mg KOH/g, and an acid value of 10 to 60 mg KOH/g; wherein the polyurethane prepolymer comprises:

2. The aqueous dispersion of claim 1 , wherein the shell of the particles has a hydroxyl value of 1 to 20 mg KOH/g.

3. The aqueous dispersion of claim 1 or 2, wherein the polyurethane prepolymer comprises 20 to 50 percent by weight of the first prepolymer, 20 to 80 percent by weight of the second prepolymer, and 1 to 30 percent by weight of the third prepolymer.

4. The aqueous dispersion of any of claims 1 to 3, wherein the core of the particles comprises residues of n-butyl (meth)acrylate, isobutyl (meth)acrylate, lauryl (meth)acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, styrene, and/or t-butyl (meth)acrylate.

5. The aqueous dispersion of claim 4, wherein the core of the particles comprises 20 to 100 percent by weight, or 40 to 100 percent by weight, or 60 to 100 percent by weight, or 80 to 100 percent by weight residues of n-butyl (meth)acrylate, based on the total weight of the core.

6. The aqueous dispersion of claim 5, wherein the core consists essentially of a homopolymer of n-butyl acrylate.

7. The aqueous dispersion of claim any of claims 1 to 6, wherein the mass ratio of the core to the shell ranges from 20:80 to 30:70.

8. A waterborne curable film-forming composition comprising: a) the aqueous dispersion of any of claims 1 to 7; b) a crosslinking agent; and c) a water dispersible polymer comprising functional groups that are reactive with the crosslinking agent b).

9. The waterborne curable film-forming composition of claim 8, wherein the crosslinking agent b) comprises an aminoplast.

10. The waterborne curable film-forming composition of claim 8 or 9, wherein the water dispersible polymer c) comprises an acrylic polymer and/or polyester polymer comprising hydroxyl functional groups.

11. The waterborne curable film-forming composition of any of claims 8 to 10, wherein the aqueous dispersion a) is present in the curable film-forming composition in an amount of 5 to 40, or 5 to 30, or 5 to 20, or 10 to 40, or 10 to 30, or 10 to 20 percent by weight, based on the total weight of the curable film-forming composition.

12. A multilayer coated substrate comprising:

A) a substrate;

C) a basecoat composition applied on top of the first coating; and

D) a clearcoat composition applied on top of the basecoat composition; wherein the basecoat composition C) comprises the waterborne curable film-forming composition of any of claims 8 to 11 .

13. The multi-layer coated substrate of claim 12, wherein the clearcoat composition D) comprises:

1 ) a polyisocyanate; and

2) a film-forming resin comprising active hydrogen groups reactive with isocyanate.

14. A method of improving adhesive properties between a basecoat coating layer and a coating layer directly in contact with the basecoat coating layer on a substrate, and/or improving cohesive properties within a basecoat coating layer on a substrate, comprising:

A) applying a first coating composition to a surface of the substrate, forming a first coating on the substrate;

B) applying a basecoat composition on top of the first coating; and

C) applying a clearcoat composition on top of the basecoat composition; wherein the basecoat composition comprises the waterborne curable film-forming composition of any of claims 8 to 11 .