MULTILAYER COATINGS AND METHODS FOR PREPARING THEM

Abstract

A multilayer coating system includes: a first basecoat layer formed from a first coating composition including a free polyisocyanate having a weight average molecular weight of less than 600 g / mol and polymeric core-shell particles with hydroxyl functionality, wherein an amount of the free polyisocyanate having a weight average molecular weight of less than 600 g / mol is 3.5% by weight or more; a second basecoat layer formed from a second coating composition including polymeric core-shell particles with carboxylic acid functionality; and a topcoat layer formed from a coating composition including a free polyisocyanate and a film-forming resin reactive with the free polyisocyanate.

Description

MULTILAYER COATINGS AND METHODS FOR PREPARING THEM FIELD OF INVENTION

[0001] The present invention relates to multilayer coatings that can be applied to substrates, such as automotive substrates, and methods for preparing and applying such coatings. BACKGROUND OF THE INVENTION

[0002] Coatings are applied to a wide variety of substrates to provide color and other visual effects, corrosion resistance, abrasion resistance, chemical resistance, and the like. Furthermore, various types of coatings, such as those applied to automotive substrates including vehicles and motorcycles, can be formed from compositions that can be baked and formed at low curing temperatures. Because these compositions can be baked at low curing temperatures, they have proven useful for forming multilayer coatings, which often include a topcoat applied over the basecoat layers.Accordingly, an objective of the present invention is to provide multilayer coatings that can be dehydrated and cured at comparatively low temperatures to form coatings that have diverse properties, thereby reducing costs and increasing the efficiency of coating processes, such as in the automotive industry, for example. BRIEF DESCRIPTION OF THE INVENTION

[0003] The present invention relates to a multilayer coating system comprising: (a) a first base coating layer formed from a first coating composition comprising at least one free polyisocyanate having a weight average molecular weight of less than 600 g / mol and polymeric core-shell particles with hydroxyl functionality, wherein each of a polymeric core and a polymeric shell of the core-shell particles with hydroxyl functionality independently comprises an addition polymer derived from ethylenically unsaturated monomers and an amount of the free polyisocyanate having a weight average molecular weight of less than 600 g / mol is 3.5% by weight or more, depending on the total resin solids of the first coating composition;(b) a second basecoat layer applied over at least a portion of the first basecoat layer, wherein the second basecoat layer is formed from a second coating composition comprising polymeric core-shell particles with carboxylic acid functionality, wherein a polymeric core of the core-shell particles with carboxylic acid functionality includes an addition polymer derived from ethylenically unsaturated monomers and a polymeric shell of the core-shell particles with carboxylic acid functionality includes urethane linkages and groups with carboxylic acid functionality; and (c) a topcoat layer applied over at least a portion of the second basecoat layer, wherein the topcoat layer is formed from a coating composition including a free polyisocyanate and a film-forming resin reactive with the free polyisocyanate.

[0004] The present invention also relates to a process for coating a substrate with a multilayer coating comprising: (i) depositing a first coating composition onto at least a portion of the substrate, wherein the first coating composition includes at least one free polyisocyanate having a weight-average molecular weight of less than 600 g / mol and polymeric core-shell particles with hydroxyl functionality, wherein each of a polymeric core and a polymeric shell of the core-shell particles with hydroxyl functionality independently comprises an addition polymer derived from ethylenically unsaturated monomers and wherein an amount of the free polyisocyanate having a weight-average molecular weight of less than 600 g / mol is 3.5% by weight or more, depending on the total resin solids of the first coating composition;(ii) depositing a second coating composition directly onto at least a portion of the first coating composition (1) after the first coating composition is dehydrated or (2) before the first coating composition is dehydrated, wherein the second coating composition includes polymeric core-shell particles with carboxylic acid functionality, wherein a polymeric core of the core-shell particles with carboxylic acid functionality includes an addition polymer derived from ethylenically unsaturated monomers and a polymeric shell of the core-shell particles with carboxylic acid functionality includes urethane linkages and groups with carboxylic acid functionality; (iii) dehydrating: (a) the second coating composition after (ii)(1); or (b) simultaneously the first coating composition and the second coating composition after (ii)(2);and (iv) depositing a topcoat composition onto at least a portion of the second dehydrated basecoat composition, wherein the topcoat composition includes a free polyisocyanate and at least one film-forming resin reactive with the free polyisocyanate.; DETAILED DESCRIPTION OF THE INVENTION

[0005] For the purposes of the following detailed description, it is understood that the invention may assume various variations and alternative step sequences, except where expressly stated otherwise. Furthermore, apart from any operational example, or where otherwise indicated, it is understood that all numbers expressing, for example, quantities of ingredients used in the specification and the claims are modified in all cases by the expression "around". Accordingly, unless otherwise stated, the numerical parameters stated in the following specification and the appended claims are approximations that may vary depending on the properties desired to be obtained with the present invention.At a minimum, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be interpreted at least in light of the number of significant digits reported and by applying customary rounding techniques.

[0006] Although the numerical parameters and ranges that define the broad scope of the invention are approximations, the numerical values ​​stated in the specific examples are reported as accurately as possible. However, any numerical value inherently contains certain errors that necessarily result from the standard variation found in their respective test measurements.

[0007] Furthermore, it should be understood that any numerical range listed herein is intended to include all subranges within it. For example, a range from 1 to 10 is intended to include all subranges between (and inclusive of) the minimum value of 1 and the maximum value of 10; that is, it has a minimum value equal to or greater than 1 and a maximum value equal to or less than 10.

[0008] In this application, the use of the singular includes the plural and the plural includes the singular, unless specifically stated otherwise. Furthermore, in this application, the use of "or" means "and / or" unless specifically stated otherwise, although "and / or" may be used explicitly in certain cases. Additionally, in this application, the use of "a" means at least one, unless specifically stated otherwise. For example, "a core-shell particle," "a free polyisocyanate," and the like refer to one or more of any of these elements.

[0009] The present invention relates to a multilayer coating comprising at least a first base coat, a second base coat, and a top coat. A base coat refers to a coating that is deposited over a primer and / or directly onto a substrate, optionally including components ML / a / ZUZZ / UU l uu l (such as pigments) that impact color and / or provide other visual effects. A finish refers to a top coating that is deposited over another coating layer, such as a base coat, to provide a protective and / or decorative layer.

[0010] The first base coating layer can be formed from a coating composition comprising a free polyisocyanate and at least one type of polymeric core-shell particles.

[0011] As used herein, a free polyisocyanate refers to polyisocyanates in which at least some of the groups with isocyanate functionality (also referred to herein as NCO groups) are not blocked. Non-limiting examples of free isocyanates include any of the following compounds in which the NCO groups are not blocked: aliphatic polyisocyanates; aromatic polyisocyanates; cycloaliphatic polyisocyanates; heterocyclic polyisocyanates; monomeric polyisocyanates; polymeric polyisocyanates; adducts thereof, such as isocyanurates thereof and / or biurets thereof; a urethdione; and mixtures thereof.

[0012] Non-limiting examples of free polyisocyanates include the following compounds in which the NCO groups are not blocked: isophorone diisocyanate (IPDI), dicyclohexylmethane 4,4'diisocyanate (H12MDI), cyclohexyl diisocyanate (CHDI), m-tetramethylxylylene diisocyanate (m-TMXDI), p-tetramethylxylylene diisocyanate (p-TMXDI), ethylene diisocyanate, 1,2-propane diisocyanate, 1,3-propane diisocyanate, 1,6-hexane diisocyanate (hexamethylene diisocyanate or HDI), 1,4-butylene diisocyanate, Usina diisocyanate, 1,4-methylene bis-(cyclohexyl isocyanate), toluene diisocyanate (TDI), m-xylylene diisocyanate (MXDI), p-xylylene diisocyanate, 4-chloro-l,3-phenylene diisocyanate, 1,5-tetrahydro-naphthalene diisocyanate, 4,4'dibenzyl diisocyanate, 1,2,4-benzene triisocyanate, xylylene diisocyanate (XDI), trimethylene diisocyanate, tetramethylene-l,4-disocyanate, pentamethylene-1,5-diisocyanate, hexamethylene diisocyanate, 1,2-propylene diisocyanate,1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,2,4-trimethylhexamethylene-1,6-d-isocyanate, 2,6-diisocyanate natomethyl lea proate, lysine ester triisocyanate, lysine methyl ester diisocyanate, 1,4,8-octane triisocyanate, 1,6,11-undecane triisocyanate, 1,8-diisocyanato-4-methyloctane diisocyanate, 1,3,6-hexane triisocyanate, 2,5,7-trmethyloctane diisocyanato-5-methyloctane diisocyanate, 1,3-Cyclopentane, 1,4-Cyclohexane diisocyanate, 1,3-Cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 2,4-methylcyclohexane diisocyanate, 2,6-methylcyclohexane diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, norbornane diisocyanate, 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanatocyclohexane, 2-(3-isocyanatopropyl)-2,5-d(isocyanatometyl)-bccyclo[2.2.1]heptane, 2(3-isocyanatopropyl)-2,6-di(isocyanatomethyl)bcicle[2.2.1]heptane, 3-(3-isocyanatopropyl)-2,5di(isocyanatomethyl)-bcyle[2.2.1]heptane, 5-(2-¡soc¡anatoet¡l)-2-¡soc¡anatomethyl-3-(3-¡soc¡anatoprop¡l)IVIA / a / ZUZZ / UU l U» l bicyclo[2.2.1]heptane, 6-(2-¡soc¡anatoet¡l)-2-isoc¡anatomethyl-3-(3-¡soc¡anatopropy)bicyclo[2.2.1]heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)b-c-cyclo[2.2.1]heptane, 6-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)bicyclo[2.2.1]heptane, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, ω,ω'-d-isocyanato-1,4-diethylbencene, 1,3-bis(1-isocyanato-1-methylethyl)bencene, 1,4-bis(1-isocyanato-1-methylethyl)bencene, 1,3,5-triisocyanatomethylbencene, 1,4-isocyanato-1-methyl ... m-phenylene, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'toluidine, 4,4'-diphenyl ether diisocyanate,triphenylmethan-4,4',4-triisocyanate, 1,3,5-triisocyanate benzene, 2,4,6-triisocyanate toluene, 4,4'-diphenylmethane-2,2',5,5'-tetra¡socyanate, diphenyl methan-2,4'diisocyanate, diisocyanate 3,3'-dimethyl-4,4'-diphenylene, dodecan-1,12-diisocyanate, cyclobutan-1,3-diisocyanate, biphenyl diisocyanate, bis(isocyanate ethyl)furnamate, toluene-2,4-diisocyanate, hexahydrotoluene-2,4-diisocyanate, toluene-2,6-diisocyanate, hexahydrotoluene-2,6-diisocyanate; hexahydrophenylen-1,3-diisocyanate, hexahydrophenylen-1,4-diisocyanate, perhydrodiphenylmethane-2,4'-diisocyanate, perhydrodiphenylmethane-4,4'-diisocyanate, isocyanurates thereof (such as isocyanurate trimers), adducts thereof, biurets thereof, mixtures thereof and combinations thereof.

[0013] Other non-limiting examples of free polyisocyanates are free polymeric polyisocyanates, which include the following compounds in which at least some of the isocyanate functional groups are not blocked: polymeric HDI, polymeric MDI, polymeric isophorone diisocyanate, and the like. Free polymeric polyisocyanate may have a weight-average molecular weight of less than 600 g / mol.

[0014] It is observed that one or more, such as at least two or at least three, different free polyisocyanates may be used in the coating composition that forms the first base coating layer. According to the present invention, at least one of the free polyisocyanates forming the coating composition of the first base coating layer has a weight-average molecular weight of less than 600 g / mol. The amount of free polyisocyanate having a weight-average molecular weight of less than 600 g / mol in the coating composition that forms the first base coating layer is 3.5% by weight or more, or 3.6% by weight or more, or 4% by weight or more, or 4.5% by weight or more, or 5% by weight or more, depending on the total resin solids of the coating composition that forms the first base coating layer.Free polyisocyanate having a weight-average molecular weight of less than 600 g / mol may also comprise less than 20% by weight, or 15% by weight or less, or 10% by weight or less, or 8% by weight or less, depending on the total resin solids of the coating composition that forms the first base coating layer. Free polyisocyanate having a weight-average molecular weight of less. ML / a / ZUZZ / UU l UU l of 600 g / mol may comprise an amount that varies from, for example, 3.5% by weight or more to less than 20% by weight, or 3.5% by weight or more to less than 10% by weight or less, or 3.5% by weight or more to less than 8% by weight or less, depending on the total resin solids of the coating composition that forms the first base coating layer.

[0015] Weight average molecular weight is determined by gel permeation chromatography relative to 800 to 900,000 Da linear polystyrene standards using a Waters 2695 separation module with a Waters 2414 differential refractometer (RI detector), manufactured by Waters Corporation (Milford, MA). Tetrahydrofuran (THF) is used as the eluent at a flow rate of 1 mL min⁻¹, and two PLGEL MIXED-C columns (300 x 7.5 mm), manufactured by Agilent Technologies (Santa Clara, CA), are used for separation at 25°C.

[0016] The free polyisocyanates used in the composition forming the first basecoat layer may also comprise more than 9.5 wt% or more than 12 wt% of a urethdione dimer, depending on the total weight of resin solids of all the free polyisocyanate in the coating composition forming the first basecoat layer. The free polyisocyanates used in the composition forming the first basecoat layer may also comprise up to 50 wt%, or up to 45 wt%, or up to 40 wt% of a urethdione dimer, depending on the total weight of resin solids of all the free polyisocyanate in the coating composition forming the first basecoat layer. The free polyisocyanates used in the composition that forms the first base coating layer may also comprise an amount that varies from more than 9.5% by weight to 50% by weight, or from more than 9.5% by weight to 40% by weight, or from more than 9.5 wt% to 30 wt% or 12 wt% to 30 wt% of a urethdione dimer, depending on the total weight of resin solids of all free polyisocyanate in the coating composition that forms the first base coating layer. The urethdione dimer may have a weight-average molecular weight of less than 600 g / mol.

[0017] The amount of urethdione dimer can be determined by gel permeation chromatography, using the specified polystyrene standard and apparatus described above, when the urethdione dimer is the only free, low-molecular-weight (400-700 g / mol) isocyanate in the composition, as a person of intermediate skill would understand. The amount of urethdione dimer can be determined by NMR spectroscopy when the urethdione dimer is not the only free, low-molecular-weight isocyanate in the composition, as a person of intermediate skill would understand.

[0018] It was found that the above-described amounts of free polyisocyanates having a weight-average molecular weight of less than 600 g / mol and the amounts of urethdione dimer-based polyisocyanate used to form the first basecoat layer can provide improved properties to the first basecoat layer and the multilayer coating described in more detail herein. For example, it was found that the first basecoat layer comprising the above-described polyisocyanates provides improved moisture resistance and durability to the final multilayer coating.

[0019] As indicated, the coating composition forming the first base coating layer also comprises at least one type, or at least two different types, of polymeric core-shell particles. As used herein, a core-shell particle in which the core is at least partially encapsulated by the shell refers to a particle comprising (i) at least one first material or materials forming the center of the particle (i.e., the core) and (ii) at least one second material or materials (i.e., the shell) forming a layer over at least a portion of the surface of the first materials (i.e., the core). Core-shell particles may have various shapes (or morphologies) and sizes. For example, core-shell particles may have generally spherical, cubic, sheet-like, polyhedral, or acicular (elongated or fibrous) morphologies.Core-shelled particles can also have an average particle size of 30 to 300 nanometers, 40 to 200 nanometers, or 50 to 150 nanometers. As used herein, average particle size refers to volume-average particle size. The average particle size can be determined, for example, using a ZETASIZER 3000HS, manufactured by Malvern Instruments (Worcestershire, UK), according to the instructions in the ZETASIZER 3000HS manual.

[0020] As indicated, core-shell particles comprise a polymeric core as well as a polymeric shell. A polymeric core means that the core of the core-shell particle comprises one or more polymers, and a polymeric shell means that the shell of the core-shell particle comprises one or more polymers. As used herein, a polymer refers to oligomers and homopolymers (e.g., prepared from a single monomeric species), copolymers (e.g., prepared from at least two monomeric species), and graft polymers. The term resin is used interchangeably with the term polymer.

[0021] A non-limiting example of a core-shell particle that can be used with the first coating composition includes polymeric core-shell particles with hydroxyl functionality, wherein each polymeric core and polymeric shell of the hydroxyl-functional core-shell particles independently comprise an addition polymer derived from ethylenically unsaturated monomers. As used herein, ethylenically unsaturated refers to a group having at least one carbon-carbon double bond. Non-limiting examples of ethylenically unsaturated groups include, but are not limited to, (meth)acrylate groups, vinyl groups, and combinations thereof. As used herein, the term (meth)acrylate refers to both methacrylate and acrylate.

[0022] Specific non-limiting examples of ethylenically unsaturated monomers that can be used to form core-shell particles with hydroxyl functionality include, but are not limited to, (meth)acrylic acid alkyl esters, (meth)acrylic acid hydroxyalkyl esters, ethylenically unsaturated monomers containing an acid group, aromatic vinyl monomers, and combinations thereof.

[0023] Non-limiting examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, ethylhexyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, glycidyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, and combinations thereof. The alkyl group of (meth)acrylic acid alkyl esters may optionally be substituted with functional groups other than hydroxyl groups, for example, as in acetoacetoxyethyl (meth)acrylate or acetoacetoxypropyl (meth)acrylate. Furthermore, the monomer composition may include monomers having at least two ethylenically unsaturated groups.Examples include vinyl(meth)acrylate, alkyl diesters of di(meth)acrylate formed from the condensation of two equivalents of (meth)acrylic acid, such as, for example, ethylene glycol di(meth)acrylate. Alkyl diesters of di(meth)acrylate formed from C2-24 diols, such as butanediol and hexandiol, can also be used.

[0024] Non-limiting examples of hydroxyalkyl esters of (meth)acrylic acid include hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and combinations thereof.

[0025] Non-limiting examples of ethylenically unsaturated monomers containing an acid group include (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, aspartic acid, melic acid, mercaptosuccinic acid, and combinations thereof.

[0026] Non-limiting examples of aromatic vinyl monomers include styrene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, vinyl naphthalene, vinyl toluene, aromatic divinyl monomers such as divinyl benzene, and combinations thereof.

[0027] The polymer core and polymer shell of the core-shell particles are also prepared to provide a hydrophilic polymer shell with improved water dispersibility / stability and a hydrophobic polymer core. As used herein, the term hydrophilic refers to polymers, monomers, and other materials that have an affinity for water and will disperse or dissolve in water or other aqueous media. Typically, hydrophilic materials, such as hydrophilic polymers, have water-dispersible groups. A water-dispersible group refers to a group that has or is formed from one or more hydrophilic functional groups that have an affinity for water and that help disperse a compound, such as a polymer, in water or other aqueous media.As used herein, the term hydrophobic refers to polymers, monomers, and other materials that lack affinity for water or other aqueous media and tend to repel, not dissolve or disperse in, and / or not wett by water or other aqueous media. Hydrophobic materials, such as hydrophobic polymers, are often free of water-dispersible groups.

[0028] Therefore, the polymeric shell may comprise hydrophilic water-dispersible groups, while the polymeric core may be free of hydrophilic water-dispersible groups. The hydrophilic water-dispersible groups may increase the water dispersibility / stability of the polymeric shell in an aqueous medium such that the polymeric shell at least partially encapsulates the hydrophobic core.

[0029] As described above, water-dispersible groups comprise one or more hydrophilic functional groups. For example, polymers forming the hydrophilic polymer shell may comprise ionic or ionizable groups, including hydroxyl groups, and optionally groups with carboxylic acid functionality or salts thereof. Carboxylic acid functional groups can be at least partially neutralized (i.e., at least 30% of the total neutralization equivalent) by a base, such as a volatile amine, to form a salt group. The neutralization of the acid-functional polymer can be theoretically determined based on the equivalence of the amine (or other base) divided by the equivalence of the acid (of the acid-functional polymer). A volatile amine refers to an amine compound having an initial boiling point less than or equal to 250°C as measured at a standard atmospheric pressure of 101.3 kPa.Examples of suitable volatile amines include ammonia, dimethylamine, trimethylamine, monoethanolamine, and dimethylethanolamine. It is appreciated that the amines can evaporate during coating formation to expose the carboxylic acid functional groups and allow them to undergo further reactions. Other, non-limiting examples of water-dispersible groups include polyoxyalkylene groups, such as those found in polyethylene / propylene glycol materials.

[0030] It is observed that the core-shell particles with hydroxyl functionality are obtained from at least ethylenically unsaturated monomers with hydroxyl functionality and ethylenically unsaturated monomers that are free of water-dispersible groups. Furthermore, the polymeric shell of the core-shell particles with hydroxyl functionality comprises the hydroxyl functional groups, while the polymeric core may be free of hydroxyl functional groups or have a low number of hydroxyl functional groups compared to the number of hydroxyl functional groups in the shell.

[0031] In addition, the polymeric coating of the core-coat particles The polymeric core-shell particles with hydroxyl functionality of the first coating composition can be obtained from components comprising more than 10 wt% of an ethylenically unsaturated monomer with hydroxyl functionality, or more than 25 wt% of an ethylenically unsaturated monomer with hydroxyl functionality, or more than 35 wt% of an ethylenically unsaturated monomer with hydroxyl functionality, depending on the total weight of the components forming the polymeric shell. The polymeric shell of the polymeric core-shell particles with hydroxyl functionality of the first coating composition can be obtained from components comprising up to 45 wt% of an ethylenically unsaturated monomer with hydroxyl functionality, or up to 40 wt% of an ethylenically unsaturated monomer with hydroxyl functionality, depending on the total weight of the components forming the polymeric shell.The polymeric coating of the hydroxyl-functional polymeric core-coat particles of the first coating composition can be obtained from components comprising an amount ranging from 20% by weight to 40% by weight of an ethylenically unsaturated monomer with hydroxyl functionality, depending on the total weight of the components forming the polymeric coating.

[0032] The ethylenically unsaturated monomer with hydroxyl functionality used to form the hydroxyl-functional polymer core-shell particles of the first coating composition can also be used to form a separate homopolymer to evaluate the Van Krevelen solubility parameter of the polymers formed with the monomer. For example, the homopolymer formed from the ethylenically unsaturated monomer with hydroxyl functionality used to form the hydroxyl-functional polymer core-shell particles, as well as the polymer shell, of the first coating composition may have a Van Krevelen solubility parameter at 298 K of more than 25.0 MPa⁰.⁵ or a solubility parameter at 298 K of more than 26.0 MPa⁰.⁵. The Van Krevelen solubility parameter of a homopolymer is calculated using Synthia implemented in Material Studio 5.0, commercially available from Accelrys, Inc.(San Diego, CA).

[0033] The polymeric coating of the hydroxyl-functional polymer core-coat particles of the first coating composition may comprise at least 5% by weight, at least 10% by weight, or at least 15% by weight of each core-coat particle, depending on the total weight of solids of the core-coat particle. The polymeric coating of the hydroxyl-functional polymer core-coat particles of the first coating composition may comprise up to 30% by weight, up to 25% by weight, or up to 20% by weight of each core-coat particle, depending on the total weight of solids of the core-coat particle. The polymeric coating of the hydroxyl-functional polymer core-coat particles of the first coating composition may further comprise an amount that ML / a / ZUZZ / UU l υυ l varies from 5% by weight to 30% by weight or from 10% by weight to 20% by weight, of each core-shell particle, depending on the total weight of solids of the core-shell particle.

[0034] One or more, even all, for example, of the polymeric core-shell particles with hydroxyl functionality of the first coating composition may comprise a core-to-shell weight ratio of 95:5 to 70:30, or 90:10 to 75:25, or 90:10 to 80:20, or 85:15 to 80:20.

[0035] Core-shell particles with hydroxyl functionality may also comprise additional functional groups. Non-limiting examples of additional functional groups that may be formed in the polymer shell and / or polymer core include amine groups, epoxide groups, carboxylic acid groups, thiol groups, carbamate groups, amide groups, urea groups, isocyanate groups (including blocked isocyanate groups), aldo groups (aldehyde groups), keto groups (ketone groups), ethylenically unsaturated groups, and combinations thereof. For example, the polymer shell may also comprise groups with carboxylic acid functionality in addition to groups with hydroxyl functionality. It is appreciated that the polymer shell, the polymer core, or both may be free of (i.e., do not contain) any of the functional groups described above, such as being free of aldo groups and keto groups.

[0036] The polymer shell is also covalently bonded to at least a portion of the polymer core. For example, the polymer shell can be covalently bonded to the polymer core by reacting at least one functional group in the monomers and / or prepolymers used to form the polymer shell with at least one functional group in the monomers and / or prepolymers used to form the polymer core. The functional groups may include any of the functional groups described above, provided that at least one functional group in the monomers and / or prepolymers used to form the polymer shell is reactive with at least one functional group in the monomers and / or prepolymers used to form the polymer core.For example, the ethylenically unsaturated groups of the monomers and / or prepolymers used to form the polymer shell and core can react with each other to form a chemical bond. As used herein, a prepolymer refers to a polymer precursor capable of further reaction or polymerization by one or more reactive groups to form a higher molecular weight or crosslinked state.

[0037] The polymeric core-shell particles with hydroxyl functionality of the first coating composition may comprise at least 20% by weight, at least 25% by weight, or at least 30% by weight, depending on the total weight of resin solids in the coating composition forming the first base coating layer. The particles of The polymeric core-shell particles with hydroxyl functionality of the first coating composition may also comprise up to 60% by weight, up to 50% by weight, or up to 40% by weight, depending on the total weight of resin solids in the coating composition that forms the first base coating layer. The polymeric core-shell particles with hydroxyl functionality of the first coating composition may further comprise an amount ranging from 20% to 60% by weight, or from 25% to 50% by weight, or from 25% to 40% by weight, or from 30% to 40% by weight, depending on the total weight of resin solids in the coating composition that forms the first base coating layer.

[0038] The core-shell particles of the first coating composition forming the first base coating layer may also be selected from polymeric core-shell particles with carboxylic acid functionality (different from the polymeric core-shell particles with hydroxyl functionality described above) comprising a polymeric core comprising an addition polymer derived from ethylenically unsaturated monomers and a polymeric shell comprising urethane linkages and groups with carboxylic acid functionality. The polymeric shell may also comprise additional linkages including, but not limited to, ester linkages, ether linkages, urea linkages, and combinations thereof.

[0039] As indicated, the polymer shell comprises groups with carboxylic acid functionality. The polymer shell and / or the polymer core may also comprise additional functional groups. Other, non-limiting examples of functional groups that may be formed in the polymer shell and / or the polymer core include amine groups, epoxide groups, hydroxyl groups, thiol groups, carbamate groups, amide groups, urea groups, isocyanate groups (including blocked isocyanate groups), aldo groups, keto groups, ethylenically unsaturated groups, and combinations thereof. For example, the polymer shell may also comprise groups with hydroxyl functionality in addition to groups with carboxylic acid functionality. It is appreciated that the polymer shell, the polymer core, or both may be free of (i.e., do not contain) any of the functional groups described above, such as being free of aldo and keto groups.

[0040] Polymeric core-shell particles with carboxylic acid functionality are prepared from various components. For example, core-shell particles with carboxylic acid functionality can be formed from polyurethane prepolymers with isocyanate functionality, ethylenically unsaturated monomers, polyols, and / or polyamines. Polyurethane prepolymers with isocyanate functionality can be prepared according to any method known in the art, such as by reacting at least one polyisocyanate with one or more compounds having functional groups reactive with the ML / a / ZUZZ / UU l uu l isocyanate functionality of the polyisocyanate. Reactive functional groups can be functional groups containing active hydrogen, such as hydroxyl groups, thiol groups, amine groups, and acid groups, such as carboxylic acid groups. For example, a hydroxyl group can react with an isocyanate group to form a urethane bond. A primary or secondary amine group can react with an isocyanate group to form a urea bond. Examples of suitable compounds that can be used to form polyurethane include, but are not limited to, polyols, polyisocyanates, compounds containing carboxylic acids, such as carboxylic acid-containing diols, polyamines, ethylenically unsaturated components with hydroxyl functionality, such as hydroxyalkyl esters of (meth)acrylic acid, and / or other compounds having reactive functional groups, such as hydroxyl groups, thiol groups, amine groups, and carboxylic acids.

[0041] Non-limiting examples of suitable polyisocyanates and ethylenically unsaturated components with hydroxyl functionality include any of the compounds described above.

[0042] Non-limiting examples of polyols include glycols, polyether polyols, polyester polyols, copolymers thereof, and combinations thereof. Non-limiting examples of low molecular weight glycols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, tetramethylene glycol, hexamethylene glycol, and combinations thereof, as well as other compounds comprising two or more hydroxyl groups and combinations thereof. Non-limiting examples of suitable polyether polyols include polytetrahydrofuran, polyethylene glycol, polypropylene glycol, polybutylene glycol, and combinations thereof.

[0043] Other suitable polyols include, but are not limited to, cyclohexandimethanol, 2-ethyl-1,6-hexanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, trimethylol propane, 1,2,6-hexantriol, glycerol, and combinations thereof.

[0044] Non-limiting examples of acid-containing diols include, but are not limited to, 2,2-bis(hydroxymethyl)propionic acid, also called dimethylolpropionic acid (DMPA), 2,2-bis(hydroxymethyl)butyric acid, also called dimethylolbutanoic acid (DMBA), diphenolic acid, and combinations thereof.

[0045] Suitable polyamines include aliphatic and aromatic compounds comprising two or more amine groups selected from primary and secondary amine groups. Examples include, but are not limited to, diamines such as, for example, ethylenediamine, hexamethylenediamine, 1,2-propandiamine, 2-methyl-1,5-pentamethylenediamine, 2,2,4-trimethyl-1,6-hexandiamine, isophoronediamine, diaminocyclohexane, xylylenediamine, 1,12-diamino-4,9-dioxadodecane, and combinations thereof.

[0046] Core-shell particles with carboxylic acid functionality can have various shapes (or morphologies) and sizes, such as the shapes and sizes The polymers described above are prepared to provide a hydrophilic polymer shell with improved water dispersibility / stability and a hydrophobic polymer core such that the polymer shell at least partially encapsulates the hydrophobic core. Furthermore, the groups with carboxylic acid functionality can be at least partially neutralized (i.e., at least 30% of the total neutralization equivalent) by a base, such as a volatile amine, to form a salt group, as described above. The polymer shell is also covalently bonded to at least a portion of the polymer core, such as by the reaction of ethylenically unsaturated groups of the polymer shell and the polymer core.

[0047] The polymeric core-shell particles with carboxylic acid functionality of the first coating composition may comprise at least 0.1% by weight, or at least 0.5% by weight, or at least 1% by weight, or at least 5% by weight, or at least 10% by weight, depending on the total weight of resin solids in the coating composition forming the first base coating layer. The polymeric core-shell particles with carboxylic acid functionality of the first coating composition may also comprise 20% by weight or less, or 15% by weight or less, or 12% by weight or less, depending on the total weight of resin solids in the coating composition forming the first base coating layer. The polymeric core-shell particles with carboxylic acid functionality of the first coating composition may comprise an amount ranging from 0.1% to 20% by weight, or from 0.5% by weight to 15% by weight or from 1% by weight to 10% by weight, depending on the total weight of resin solids in the coating composition that forms the first base coating layer.

[0048] It is observed that the first coating composition may comprise both types of polymer core-shell particles described above. That is, the first coating composition may comprise at least one or both types of polymer core-shell particles described above.

[0049] The coating composition forming the first base coat layer may further comprise additional materials, including but not limited to additional resins, such as additional film-forming resins. As used herein, a film-forming resin refers to a resin that, when used in a coating composition, can form a continuous, self-supporting film on at least one horizontal surface through dehydration and / or curing. The term dehydration refers to the removal of water and / or other solvents. It is appreciated that dehydration can also produce at least partial curing of a resinous material. The coating composition comprising the additional resin can be dehydrated and / or cured under ambient conditions, by heat, or by other means, such as actinic radiation, as described above. Furthermore, ML / a / ZUZZ / UU l uu l environmental conditions refers to the conditions of the surrounding environment (for example, the temperature, humidity and pressure of the environment or outside environment in which the substrate is located, such as, for example, at a temperature of 23°C and a relative humidity in the air of 35% to 75%).

[0050] The additional resin may include any of a variety of thermoplastic and / or thermoset film-forming resins known in the art. The term thermoset refers to resins that settle irreversibly upon curing or crosslinking, where the polymer chains of the resins are linked by covalent bonds. Once cured or crosslinked, a thermoset resin will not melt upon application of heat and is insoluble in solvents. As noted, the film-forming resin may also include a thermoplastic film-forming resin. The term thermoplastic refers to resins that are not linked by covalent bonds and, therefore, may undergo liquid flow upon heating and may be soluble in certain solvents.

[0051] Non-limiting examples of suitable additional resins include polyurethanes, polyesters such as polyester polyols, polyamides, polyethers, polysiloxanes, fluoropolymers, polysulfides, polythioethers, polyureas, (meth)acrylic resins, epoxy resins, vinyl resins, and combinations thereof. Additional resins may also include particulate and non-particulate resins.

[0052] The additional resin may have any of a variety of reactive functional groups, including, but not limited to, carboxylic acid groups, amine groups, epoxide groups, hydroxyl groups, thiol groups, carbamate groups, amide groups, urea groups, isocyanate groups (including blocked isocyanate groups), (meth)acrylate groups, and combinations thereof. Thermoset coating compositions generally comprise a crosslinker, which may be selected from any of the crosslinkers known in the art to react with the functionality of the resins used in the coating compositions. Alternatively, a thermoset film-forming resin may be used that has functional groups that are reactive with each other; in this way, such thermoset resins are self-crosslinking.

[0053] The coating composition forming the first basecoat layer may further include one or more additional crosslinking agents other than free polyisocyanate. As used herein, a crosslinking agent, crosslinker, and the like refer to a molecule comprising two or more functional groups that are reactive with other functional groups and that is capable of linking two or more monomers or polymer molecules by chemical bonds. Non-limiting examples of additional crosslinking agents include polyhydrazides, carbodiimides, polyols, phenolic resins, epoxy resins, beta-hydroxy(alkyl)amide resins, hydroxy(alkyl)urea resins, oxazoline, alkylated carbamate resins, (meth)acrylates, ML / a / ZUZZ / UU l uu l isocyanates, blocked isocyanates, polyacids, anhydrides, organometallic acid functional materials, polyamines, polyamides, aminoplasts, aziridines, and combinations thereof. For example, the coating composition forming the first coating layer may further comprise an aminoplast resin, such as a melamine-formaldehyde resin. The coating compositions of the present invention may also be free of any or all additional film-forming resins and / or crosslinkers, such as polyhydrazides.

[0054] The coating composition forming the first base coating layer may also include other additional materials, such as a colorant. As used herein, colorant refers to any substance that imparts color and / or other opacity and / or other visual effect to the composition. The colorant may be added to the coating in any suitable form, such as particles, dispersions, solutions, and / or separate sheets. A single colorant or a mixture of two or more colorants may be used in the coatings of the present invention.

[0055] Example colorants include pigments (organic or inorganic), dyes, and tinctures, such as those used in the paint industry and / or those listed by 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 may be organic or inorganic and may be agglomerated or non-agglomerated. Colorants may be incorporated into coating compositions with the use of a grinding vehicle, such as an acrylic grinding vehicle, the use of which will be familiar to a person of intermediate skill.

[0056] Example pigments and / or pigment compositions include, but are not limited to, crude carbazole dioxazine pigment, azo, monoazo, diazo, naphthol AS, salt type (sheets), benzimidazolone, isoindolinone, isoindoline and polycyclic phthalocyanine, quinacridone, perylene, perinone, diketopyrrolepyrrole, thioindigo, anthraquinone, indanthrone, anthrapyrimidine, flavantrone, pyrantrone, antantrone, dioxazine, triarylcarbonium, quinophthalone pigments, diketopyrrolepyrrole red (DPPBO red), titanium dioxide, carbon black, and mixtures thereof. The term pigment and the expression colored filler may be used interchangeably.

[0057] Example dyes include, but are not limited to, solvent-based and / or aqueous dyes such as phthalo green or blue, iron oxide, and bismuth vanadate.

[0058] Suitable dyes include, but are not limited to, pigments dispersed in water-miscible or water-based carriers, such as AQUA-CHEM 896, commercially available from Evonik Industries (Essen, Germany), CHARISMA COLORANTS and MAXITONER INDUSTRIAL COLORANTS, commercially available from Accurate Dispersions, a division of ML / a / ZUZZ / UU l uu l Eastman Chemical Company (South Holland, IL).

[0059] The colorant that may be used with the coating composition forming the first basecoat layer may also comprise a special effect composition or pigment. As used herein, a special effect composition or pigment refers to a composition or pigment that interacts with visible light to provide an appearance effect distinct from or apart from a continuous, unchanging color. Example special effect compositions and pigments include those that produce one or more appearance effects, such as reflectance, pearlescence, metallic luster, texture, phosphorescence, fluorescence, photochromism, photosensitivity, thermochromism, goniochromism, and / or color change.Non-limiting examples of special effect compositions may include transparent coated mica and / or synthetic mica, coated silica, coated alumina, aluminum foil, a transparent liquid crystal pigment, a liquid crystal coating, and combinations thereof.

[0060] Other non-limiting examples of additional materials that may be optionally used with the coating composition forming the first base coating layer include plasticizers, abrasion-resistant particles, antioxidants, hindered amine light stabilizers, UV light stabilizers and absorbers, surfactants, flow and surface control agents, thixotropic agents, catalysts, reaction inhibitors, and other common auxiliaries.

[0061] It is noted that the components of the first coating composition described herein are dispersed in an aqueous medium. As used herein, an aqueous medium refers to a liquid medium comprising more than 50% by weight of water, based on the total weight of the liquid medium. Such aqueous liquid media may comprise, for example, at least 60% by weight of water, or at least 70% by weight of water, or at least 80% by weight of water, or at least 90% by weight of water, or at least 95% by weight of water, or 100% by weight of water, based on the total weight of the liquid medium. Solvents, if present, constituting less than 50% by weight of the liquid medium include organic solvents. Non-limiting examples of suitable organic solvents include polar organic solvents, e.g., protic organic solvents such as glycols, glycol ether alcohols, volatile ketones, glycol diethers, esters, and diesters.Other non-limiting examples of organic solvents include aromatic and aliphatic hydrocarbons.

[0062] The first coating composition can be applied directly or indirectly onto at least a portion of the substrate by any standard means in the art, such as spraying, electrostatic spraying, dipping, rolling, brushing, and the like. ινΐΛ / a / zuzz / uu i uu i

[0063] The substrate on which the first coating composition can be applied includes a wide range of substrates. For example, the coating composition of the present invention can be applied to a vehicle substrate, an industrial substrate, an aerospace substrate, and the like.

[0064] A vehicle substrate may include a component of a vehicle. In this disclosure, the term "vehicle" is used in its broadest sense and includes all types of aircraft, spacecraft, watercraft, and land vehicles. For example, a vehicle may include, but is not limited to, an aerospace substrate (a component of an aerospace vehicle, such as an aircraft, including, for example, airplanes (e.g., private airplanes and small, medium, or large airplanes for commercial passenger, cargo, and military use), helicopters (e.g., private, commercial, and military helicopters), aerospace vehicles (e.g., rockets and other types of spacecraft), and the like).The vehicle may also include a land vehicle such as, for example, animal trailers (e.g., horse trailers), all-terrain vehicles (ATTs), automobiles, trucks, buses, vans, heavy-duty equipment, tractors, golf carts, motorcycles, bicycles, snowmobiles, trains, railroad cars, and the like. The vehicle may also include watercraft such as, for example, ships, boats, hovercraft, and the like. The vehicle substrate may include a component of the vehicle body, such as an automotive hood, door, trunk, roof, and the like; an aerospace wing, fuselage, and the like; or a vessel hull and the like.

[0065] The first coating composition can be applied over an industrial substrate which may include tools, heavy-duty equipment, furniture such as office furniture (e.g., office chairs, desks, cabinets and the like), household appliances such as refrigerators, ovens and stoves, dishwashers, microwaves, washing machines, dryers, small household appliances (e.g., coffee makers, slow cookers, pressure cookers, blenders, etc.), metal hardware, extruded metal such as extruded aluminum used in window frames, other interior and exterior metal building materials and the like.

[0066] The first coating composition can be applied to storage tanks, mills, nuclear plant components, packaging substrates, wooden floors and furniture, clothing, electronic components including housings and circuit boards, glass and transparencies, sports equipment including golf balls, stadiums, buildings, bridges and the like.

[0067] The substrate can be metallic or non-metallic. Metallic substrates include, but are not limited to, tin, steel (which includes electrogalvanized steel, cold-rolled steel, ML / a / ZUZZ / UU l uu l hot-dip galvanized steel, among others), aluminum, aluminum alloys, zinc-aluminum alloys, zinc-aluminum alloy-coated steel, and aluminum-clad steel. Non-metallic substrates include polymeric materials, plastic and / or composite materials, polyester, polyolefin, polyamide, cellulosic, polystyrene, polyacrylic, poly(ethylene naphthalate), polypropylene, polyethylene, nylon, ethylene vinyl alcohol (EVOH), polylactic acid, other environmentally friendly polymeric substrates, poly(ethylene terephthalate) (PET), polycarbonate, acrylonitrile butadiene styrene polycarbonate (PC / ABS), wood, mortar, wood composite, particleboard, medium-density fiberboard, cement, stone, glass, paper, cardboard, textiles, both synthetic and natural leather, and the like. The substrate may comprise a metal, a plastic and / or composite material, and / or a fibrous material.The fibrous material may comprise nylon and / or a thermoplastic polyolefin material with continuous strands or chopped carbon fiber. The substrate may be one that has already been treated in some way, such as to impart a visual and / or color effect, a protective pretreatment, or another coating layer, and the like.

[0068] The coatings of the present invention are particularly beneficial when applied to a metallic substrate. For example, the coatings of the present invention are particularly beneficial when applied to metallic substrates used to manufacture vehicles, such as motor vehicles, including cars, trucks, and tractors.

[0069] After applying the first coating composition, the second coating composition may be applied directly over at least a portion of the first coating composition as a wet-on-wet process (i.e., before the dehydration of the first coating composition), or the second coating composition may be applied after the dehydration of the first coating composition. The second coating composition may be applied by any standard means in the art, such as spraying, electrostatic spraying, dipping, rolling, brushing, and the like.

[0070] The second coating composition forming the second base coating layer comprises at least one type, such as at least both types, of the core-shell particles described above. For example, the second coating composition forming the second base coating layer may comprise the polymeric core-shell particles with carboxylic acid functionality described above, comprising a polymeric core comprising an addition polymer derived from ethylenically unsaturated monomers and a polymeric shell comprising urethane linkages and groups with carboxylic acid functionality. It is appreciated that the polymeric core-shell particles with carboxylic acid functionality are obtained from the materials described above and include any ML / a / ZUZZ / UU l uu l of the characteristics described above with respect to polymeric core-shell particles with carboxylic acid functionality. For example, the polymer shell may also comprise groups with hydroxyl functionality in addition to groups with carboxylic acid functionality.

[0071] The polymer core-shell particles with carboxylic acid functionality of the second coating composition may comprise more than 20% by weight, more than 25% by weight, or more than 30% by weight, depending on the total weight of resin solids in the coating composition that forms the second base coating layer. The polymer core-shell particles with carboxylic acid functionality of the second coating composition may also comprise up to 60% by weight, up to 50% by weight, or up to 45% by weight, depending on the total weight of resin solids in the coating composition that forms the second base coating layer.The polymeric core-shell particles with carboxylic acid functionality of the second coating composition may further comprise an amount ranging from 20% to 60% by weight, or from 25% to 50% by weight, or from 30% to 45% by weight, depending on the total weight of resin solids in the coating composition that forms the second base coating layer.

[0072] The core-shell particles used in the second coating composition can also be selected from the hydroxyl-functional core-shell particles described above, wherein each polymer core and polymer shell of the hydroxyl-functional core-shell particles independently comprise an addition polymer derived from ethylenically unsaturated monomers. The hydroxyl-functional polymer core-shell particles are obtained from the materials described above and include any of the features described above with respect to the hydroxyl-functional polymer core-shell particles of the first coating composition. For example, the polymer shell can also comprise groups with carboxylic acid functionality in addition to the groups with hydroxyl functionality.

[0073] It is observed that the second coating composition may comprise both types of polymer core-shell particles described above. That is, the second coating composition may comprise at least one or both types of polymer core-shell particles described above.

[0074] The second coating composition may also comprise any of the additional optional resins, crosslinkers, colorants, and / or materials described above. For example, the second coating composition may further comprise a free polyisocyanate and / or an aminoplast, such as a melamine-formaldehyde resin. ML / a / ZUZZ / UU l uu l Alternatively, the second coating composition may be free of any or all of the additional components described above, such as being free of free polyisocyanate or free of an aminoplast, such as a melamine-formaldehyde resin, or free of polyhydrazides. It is noted that the components of the second coating composition described herein are dispersed in an aqueous medium.

[0075] The second coating composition may comprise components that form a one-component composition. A one-component composition is also called a one-container system or 1K system. As used herein, a one-component composition refers to a composition in which all coating components are kept in the same container after manufacturing, during storage, etc. In contrast, a multi-component composition, such as a two-component (2K) or higher composition, has at least two components that are kept in different containers after manufacturing, during storage, etc., prior to application and coating formation on a substrate. Therefore, the second coating composition may be free of components that are generally used to form a multi-component composition, such as being free of free polyisocyanates, for example.It is observed that the first coating composition contains free polyisocyanates and is a multi-component composition, such as a two-component composition (2K).

[0076] A one-component composition generally cures at elevated temperatures, such as 1 to 30 minutes at 250°F to 450°F (121°C to 232°C). However, it was found that the second coating composition can be a one-component composition, but cures at lower temperatures due to the composition of the first coating layer and the topcoat.

[0077] As described above, the first coating composition can be applied directly or indirectly to at least a portion of the substrate, followed by the second coating composition, which is applied directly before or after dehydrating the first coating composition. When the second coating composition is applied before the first coating composition is dehydrated, the first and second coating compositions can be dehydrated simultaneously from room temperature (e.g., 20°C) to 90°C, or from room temperature to 80°C, or from room temperature to 70°C, or from room temperature to 60°C, or from 40°C to 80°C, or from 40°C to 70°C. The coating compositions can be dehydrated at the above temperatures for a period of time of less than 15 minutes, less than 10 minutes, less than 5 minutes, less than 2 minutes, or less than 1 minute.The time period for dehydrating the coating composition is the time period designated for dehydration and does not include the time it takes to transfer and subject the coating composition to another stage, such as a curing stage.

[0078] The second basecoat composition can also be applied directly over at least a portion of the first basecoat layer that has been dehydrated as described above. The second basecoat composition can then be dehydrated from room temperature (e.g., 20°C) to 90°C, or from room temperature to 80°C, or from room temperature to 70°C, or from room temperature to 60°C, or from 40°C to 80°C, or from 40°C to 70°C. The coating compositions can be dehydrated at the above temperatures for a period of time of less than 15 minutes, less than 10 minutes, less than 5 minutes, less than 2 minutes, or less than 1 minute.

[0079] The first and second base coatings taken together after dehydration may have a high solids content. For example, the first and second base coatings taken together after dehydration may comprise a solids content of at least 80% by weight, based on the total weight of the first and second base coatings.

[0080] After dehydrating the second coating composition, the base coatings can be cured at temperatures of 120°C or lower, or 100°C or lower, or 80°C or lower. The terms curable, cured, and the like mean that at least a portion of the resinous materials in a composition is crosslinked or crosslinkable. Curing, or the degree of curing, can be determined by dynamic mechanical thermo-mechanical analysis (DMTA) using an MK III DMTA analyzer, manufactured by Polymer Laboratories (Loughborough, UK), carried out in nitrogen. The degree of curing can be, for example, at least 10%, such as at least 30%, such as at least 50%, such as at least 70%, or at least 90% of full crosslinking as determined by the analysis described above.

[0081] It was discovered that the coatings of the present invention can be formed at lower dehydration / curing temperatures than those typically required for other coatings commonly applied to automotive substrates. As such, the coatings of the present invention help reduce costs and accelerate the overall coating process.

[0082] The multilayer coating also comprises a topcoat that is applied directly over at least a portion of the second basecoat layer before or after the basecoat layers have cured. The topcoat is formed from a coating composition comprising a film-forming resin and a free polyisocyanate reactive with the film-forming resin. It is noted that the coating composition forming the topcoat contains free polyisocyanates and is a multicomponent composition, such as a two-component (2K) composition.

[0083] Film-forming resin, for example, may include any of IVIA / a / 2U22 / UU l U91 the film-forming resins described above. For example, the film-forming resin may comprise a polyol-based film-forming resin. Non-limiting examples of film-forming resins may also include the film-forming resins available in the commercially available product of PPG Industries, Inc. (Pittsburgh, PA) under the trade names CERAMICLEAR.

[0084] It is noted that the free polyisocyanates used in the coating composition that forms the topcoat layer may include any of the polyisocyanates described above. The coating composition that forms the topcoat layer may comprise one or more, such as at least two, different free polyisocyanates.

[0085] The topcoat used with the multilayer coating of the present invention may be a clear topcoat. As used herein, a clear topcoat refers to a coating that is at least substantially transparent or completely transparent. The term substantially transparent refers to a coating in which a surface beyond the coating is at least partially visible to the naked eye when viewed through the coating. The term completely transparent refers to a coating in which a surface beyond the coating is completely visible to the naked eye when viewed through the coating. It is appreciated that the clear topcoat may comprise colorants, such as pigments, provided that the colorants do not interfere with the desired transparency of the clear topcoat.Alternatively, the clear topcoat is free of colorants such as pigments (i.e., pigment-free).

[0086] As indicated, the topcoat can be cured simultaneously with the first and second basecoat layers. For example, the topcoat and basecoat layers can be cured simultaneously at temperatures of 120°C or less, or 100°C or less, or 80°C or less.

[0087] The multilayer coating according to the present invention may also comprise other optional layers, including, but not limited to, additional basecoat layers, as well as a primer coat layer as described above. As used herein, a primer coat layer refers to a sub-coat that can be deposited on a substrate to prepare the surface for the application of a protective or decorative coating system. The primer coat layer can be formed on at least a portion of the substrate, and the first or second basecoat layer can be formed on at least a portion of the primer coat layer. In addition, the additional basecoat layers can be prepared from any of the core-shell particles and other materials described above. The basecoat layers Additional ML / a / ZUZZ / UU l υυ l can be applied, for example, over the first or second base coat before applying the top coat.

[0088] The primer coating layer optionally used with the multilayer coating of the present invention may be formed from a coating composition comprising a film-forming resin, such as a cationic-based resin, an anionic-based resin, and / or any of the additional film-forming resins described above. The coating composition used to form the primer coating composition may also include the crosslinkers, colorants, and other optional materials described above.

[0089] In addition, the primer coating composition may include a corrosion inhibitor. As used herein, a corrosion inhibitor refers to a component such as a material, substance, compound, or complex that reduces the rate or severity of corrosion of a surface on a metal or metal alloy substrate. The corrosion inhibitor may include, among others, an alkali metal component, an alkaline earth metal component, a transition metal component, or combinations thereof. The term alkali metal refers to an element in Group 1 (International Union of Pure and Applied Chemistry (IUPAC) of the periodic table of chemical elements) and includes, for example, cesium (Cs), francium (Fr), lithium (Li), potassium (K), rubidium (Rb), and sodium (Na).The term alkaline earth metal refers to an element in Group 2 (IUPAC) of the periodic table of chemical elements, and includes, for example, barium (Ba), beryllium (Be), calcium (Ca), magnesium (Mg), and strontium (Sr). The term transition metal refers to an element in Groups 3 through 12 (IUPAC) of the periodic table of chemical elements, and includes, for example, titanium (Ti), chromium (Cr), and zinc (Zn), among others.

[0090] Specific non-limiting examples of inorganic components that act as a corrosion inhibitor include magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium phosphate, magnesium silicate, zinc oxide, zinc hydroxide, zinc carbonate, zinc phosphate, zinc silicate, zinc powder, and combinations thereof.

[0091] As indicated, the primer coating composition can be deposited directly onto at least a portion of a substrate prior to the application of the first or second base coating composition and dehydrated and / or cured to form the primer coating layer. The primer coating composition of the present invention can be applied by any standard means in the art, such as electroplating, spraying, electrostatic spraying, dipping, laminating, brushing, and the like. Once the primer coating composition is applied to at least a portion of the substrate, the composition can be dehydrated and / or cured to form the primer coating layer. The primer coating composition can ML / a / ZUZZ / UU l uu l dehydrate and / or cure, for example, at a temperature of 175°C to 205°C to form the primer coating layer.

[0092] It was discovered that the multilayer coatings of the present invention can be formed at lower dehydration / curing temperatures than those typically required for other coatings commonly applied to automotive substrates. As such, the multilayer coatings of the present invention help reduce costs, decrease the amount of coating equipment required, and accelerate the overall coating process.

[0093] The present invention also relates to a process for preparing a multilayer coating. The process includes: forming a first basecoat layer on at least a portion of a substrate by depositing a first coating composition onto at least a portion of the substrate; and forming a second basecoat layer on at least a portion of the first basecoat layer by depositing a second coating composition directly onto at least a portion of: (1) the first basecoat layer after the first coating composition has dehydrated; or (2) the first coating composition before the first basecoat composition has dehydrated. The first and second basecoat compositions can be dehydrated separately or simultaneously and then cured as described above.A topcoat is formed over at least a portion of the second basecoat layer by depositing a finishing composition (for example, directly) onto at least a portion of the second basecoat layer. The basecoat and topcoat layers can be cured simultaneously or separately.

[0094] The substrate may optionally comprise a primer coating layer, and the first base coating layer is applied over at least a portion of the primer coating layer by depositing a first base coating composition directly onto at least a portion of the primer coating layer. The primer coating layer may be formed by depositing a primer coating composition, such as by electrodeposition of an electrodepositable coating composition, onto at least a portion of the substrate before depositing the first base coating composition.

[0095] Multilayer coatings can be applied to any type of substrate as described above, such as, for example, automotive parts in an automotive assembly plant. In some examples, during the application of the multilayer coating in an automotive assembly plant, a metal substrate is optionally first passed to an electrodeposition station where the primer coating composition is electrodeposited onto the metal substrate and dehydrated and / or cured. Then, the first The first base coating composition is applied directly onto the electrodeposited coating layer or, alternatively, directly onto at least a portion of the substrate in a base coating zone comprising one or more coating stations. The base coating zone may be located downstream of and adjacent to an electrodeposition furnace. The first base coating station has one or more conventional applicators, for example, bell or gun applicators, connected to or in flow communication with a source of the first base coating composition. The first base coating composition may be applied, for example, by spraying, onto the substrate by one or more applicators at the first base coating station in one or more spray passes to form a first base coating layer on the substrate.

[0096] The first basecoat can be dehydrated using a conventional drying device, such as an oven, located downstream and / or adjacent to the second coating station and / or the first coating station. After applying the second basecoat composition, the second basecoat layer can be dehydrated separately if the first basecoat layer has been previously dehydrated. Alternatively, when the second basecoat composition is applied wet-on-wet to the first basecoat composition, both basecoat compositions can be dehydrated simultaneously. The basecoats can then be cured using an oven.

[0097] After the first basecoat composition and the second basecoat composition have been dehydrated and / or cured, the topcoat is applied over the basecoat layers at a finishing station. The finishing station includes one or more conventional applicators, e.g., bell applicators, connected to and in flow communication with a source of the topcoat composition. An oven is located downstream and / or adjacent to the finishing station to dehydrate and / or cure the topcoat composition separately or simultaneously with the basecoats.

[0098] A non-limiting example of an automobile assembly plant for applying a multi-layer coating is described in U.S. Patent No. 8,846,156 in col. 3 line 1 to col. 4, line 43 and Figure 1, which is incorporated herein by reference.

[0099] The present invention also includes the following aspects.

[00100] A first aspect relates to a multilayer coating system comprising: (i) a first base coating layer formed from a first coating composition comprising at least one free polyisocyanate having a weight average molecular weight of less than 600 g / mol and polymeric core-shell particles with hydroxyl functionality, wherein each of a polymeric core and a polymeric shell of the hydroxyl functional core-shell particles independently comprises an addition polymer derived from ethylenically unsaturated monomers and wherein an amount of the free polyisocyanate having a weight average molecular weight of less than 600 g / mol is 3.5% by weight or more, depending on the total resin solids of the first coating composition;(i) a second base coating layer placed over at least a portion of the first base coating layer, wherein the second base coating layer is formed from a second coating composition comprising polymeric core-shell particles with carboxylic acid functionality, wherein a polymeric core of the core-shell particles with carboxylic acid functionality comprises an addition polymer derived from ethylenically unsaturated monomers and a polymeric shell of the core-shell particles with carboxylic acid functionality comprises urethane linkages and groups with carboxylic acid functionality; and (iii) a topcoat layer placed over at least a portion of the second base coating layer, wherein the topcoat layer is formed from a topcoat composition comprising a free polyisocyanate and a film-forming resin reactive with the free polyisocyanate.

[00101] A second aspect relates to the multi-layer coating system according to the first aspect, wherein the free polyisocyanate in the coating composition forming the first base coating layer comprises more than 9.5% by weight of a urethedione dimer, based on the total weight of the resin solids of the first base coating layer.

[00102] A third aspect relates to the multilayer coating system according to the first or second aspects, wherein the polymeric coating of the polymer core-coat particles with hydroxyl functionality of the first coating composition comprises 5 to 30% by weight of the core-coat particles, depending on the total weight of solids of the core-coat particles.

[00103] A fourth aspect relates to the multilayer coating system according to any of the first to third aspects, wherein the polymeric coating of the polymer core-coat particles with hydroxyl functionality of the first coating composition is obtained from components comprising more than 10% by weight of an ethylenically unsaturated monomer with hydroxyl functionality, based on the total weight of the components forming the polymeric coating.

[00104] A fifth aspect relates to the multilayer coating system according to the fourth aspect, wherein a homopolymer formed from the ethylenically unsaturated monomer with hydroxyl functionality has a Van Krevelen solubility parameter at 298K of more than 25.0 MPa0·5. ML / a / ZUZZ / UU l 1

[00105] A sixth aspect relates to the multilayer coating system according to any of aspects one through five, wherein the first coating composition further comprises polymeric core-shell particles with carboxylic acid functionality, wherein a polymeric core of the polymeric core-shell particles with carboxylic acid functionality comprises an addition polymer derived from ethylenically unsaturated monomers and a polymeric shell of the polymeric core-shell particles with carboxylic acid functionality comprises urethane linkages and groups with carboxylic acid functionality.

[00106] A seventh aspect relates to the multilayer coating system according to any of aspects one through six, wherein the first coating composition and / or the second coating composition further comprises an aminoplast resin.

[00107] An eighth aspect relates to the multilayer coating system according to any of aspects one through three, wherein the second coating composition comprises more than 20% by weight of polymeric core-shell particles with carboxylic acid functionality, based on the total resin solids of the second coating composition.

[00108] A ninth aspect relates to the multilayer coating system according to any of aspects one through eight, wherein the second coating composition further comprises polymeric core-shell particles with hydroxyl functionality, wherein each of a polymeric core and a polymeric shell of the polymeric core-shell particles with hydroxyl functionality of the second coating composition independently comprises an addition polymer derived from ethylenically unsaturated monomers.

[00109] A tenth aspect relates to the multilayer coating system in accordance with any of aspects one through nine, wherein the second coating composition further comprises a free polyisocyanate.

[00110] An eleventh aspect relates to the multi-layer coating system in accordance with any of aspects one through ten, wherein each of the first coating composition and the second coating composition independently comprises at least one colorant.

[00111] A twelfth aspect relates to the multilayer coating system according to any of aspects one through eleven, wherein a core-to-shell weight ratio of the core-shell particles with hydroxyl functionality of the first coating composition is 95:5 to 70:30. ML / a / ZUZZ / UU l UU l

[00112] A thirteenth aspect relates to the multi-layer coating system according to any of aspects one through twelve, further comprising a primer coating layer, wherein the first coating layer is placed over at least a portion of the primer coating layer.

[00113] A fourteenth aspect refers to a substrate coated at least partially with the multi-layer coating system in accordance with any of aspects one through thirteen.

[00114] A fifteenth aspect relates to the substrate in accordance with the fourteenth aspect, wherein the substrate comprises at least a portion of an automobile.

[00115] A sixteenth aspect relates to a process for coating a substrate with a multilayer coating comprising: (i) depositing a first coating composition onto at least a portion of the substrate; (ii) depositing a second coating composition directly onto at least a portion of the first coating composition (1) after the first coating composition is dehydrated or (2) before the first coating composition is dehydrated; (iii) dehydrating: (a) the second coating composition after (ii)(1); or (b) simultaneously the first coating composition and the second coating composition after (ii)(2);and (iv) depositing a topcoat composition over at least a portion of the second dehydrated basecoat composition, wherein the first coating composition, the second coating composition and the topcoat composition are defined as in any of aspects 1 to 15.;

[00116] A seventeenth aspect refers to a process in accordance with the sixteenth aspect, wherein the first coating composition is dehydrated prior to the application of the second base coating composition.

[00117] An eighteenth aspect refers to the process in accordance with the sixteenth or seventeenth aspects, wherein the first and second coating compositions are dehydrated simultaneously.

[00118] A nineteenth aspect relates to the process in accordance with any of the sixteenth to eighteenth aspects, wherein, after dehydration, the first and second base coatings together comprise a solids content of at least 80% by weight, based on the total weight of the first and second base coatings.

[00119] A twentieth aspect relates to the process in accordance with any of the sixteenth to nineteenth aspects, further comprising curing the first and second coating compositions at a temperature of 120°C or less.

[00120] A twenty-first aspect relates to the process in accordance with ML / a / ZUZZ / UU l uu l any of the sixteenth to nineteenth aspects, which further comprises curing the first and second coating compositions and the finishing composition simultaneously at a temperature of 120°C or less.

[00121] The following examples are presented to demonstrate the general principles of the invention. The invention should not be considered limited to the specific examples presented. All parts and percentages in the examples are by weight, unless otherwise indicated. EXAMPLE 1 Preparation of a polyurethane-acrylic dispersion

[00122] A polyurethane was first prepared by loading the following components in order into a first reboiler reactor equipped with baffles, a thermocouple, a mechanical stirrer, and a condenser: 698.8 g of butyl acrylate, 32.3 g of 1,4-butanediol, 1500 g of a polyester having a hydroxyl equivalent of 85 (the polyester was prepared by reacting 4.9 parts of maleic anhydride, 22.2 parts of adipic acid, 25.7 parts of isophthalic acid, and 100 parts of 1,6-hexanediol), 193.6 g of dimethylolpropionic acid, 58.4 g of triethylamine, 2.3 g of butylated hydroxytoluene, and 2.3 g of phosphorous acid triphenyl ester. The mixture was heated to 55°C and held for 15 minutes. Next, 522.8 g of isophorone diisocyanate were added to the reactor for 20 minutes. The isocyanate addition funnel was rinsed with 52.3 g of butyl acrylate.The temperature of the reaction mixture was maintained at 90°C until there was no NCO peak by IR characterization, and the reaction mixture was cooled to 60°C.

[00123] A second kettle reactor equipped with baffles, a thermocouple, a mechanical stirrer, and a condenser was charged with 5511.2 g of deionized water and 36.6 g of dimethylethanolamine and heated to 85°C. Then, 95% of the contents of the first kettle reactor were added to the second kettle reactor over a period of 20 minutes. The mixture was maintained at 85°C, and a nitrogen atmosphere was established and maintained in the reactor for the remainder of the reaction. A monomer mixture of 2090 g of butyl acrylate, 216.2 g of hydroxypropyl methacrylate, and 216.2 g of ethylene glycol dimethacrylate was added to the kettle over a period of 20 minutes. Next, 1.3 g of t-butyl hydroperoxide (70%) in 128.6 g of water were added to the reactor and cooled to 30°C, followed by a 30-minute addition of a solution of 5.1 g of sodium metabisulfite and 0.1 g of ferrous ammonium sulfate in 154.2 g of water. The temperature rose exothermically to 65-70°C.When the temperature began to decrease, the reaction set point was changed to 30°C and held for 30 min. The mixture was then cooled to 30°C. ML / a / ZUZZ / UU l uu l

[00124] The resulting dispersion included particles comprising a polyurethane coating covalently bonded to an acrylic core. The final dispersion had a Brookfield viscosity of ~197 centipoise, a pH of 7.79, and a non-volatile content of 46.7%. Brookfield viscosity was measured at 25°C on a Brookfield DV-II+Pro viscometer, manufactured by Brookfield Engineering (Middleboro, MA), with a No. 3 spindle at 100 RPM. Non-volatile content was determined by comparing the initial sample weights with the sample weights after exposure to 110°C for 1 hour. pH was measured at room temperature (20–27°C) using a Fisherbrand Accumet AE150 Benchtop pH meter, manufactured by Thermo Fisher Scientific (Waltham, MA). EXAMPLE 2 Preparation of an acrylic latex

[00125] An acrylic latex was prepared from the components listed in Table 1. Table 1 Component Quantity (grams) Charge A Deionized water 778.0 RHODAPEX AB / 201 2.1 Charge B Butyl acrylate 1.32 Methyl methacrylate 8.92 Methacrylic acid 0.28 Deionized water 11.2 Charge C Deionized water 4.4 Ammonium persulfate 0.1 Charge D Deionized water 189.4 RHODAPEX AB / 201 4.58 Butyl methacrylate 222.2 Acrylamide 9.8 Butyl acrylate 89.3 Ethylene glycol dimethacrylate 8.2 Hydroxyethyl methacrylate 8.2 Charge E Deionized water 74.0 Ammonium persulfate 0.27 Charge F Deionized water 28.6 RHODAPEX AB / 201 0.66 Methyl methacrylate 8.8 Butyl acrylate 19.3 Methacrylic acid 9.9 Hydroxyethyl acrylate 12.9 Charge G Deionized water 54.3 Granulated borax decahydrate 2 0.44 Ammonium persulfate 0.14 Charge H Deionized water 18.1 Dimethylethanolamine 2.9 Charge I Deionized water 14.4 ACTICIDE MBS3 4.2 ινΐΛ / a / zuzz / uu ruar1An anionic surfactant commercially available through Solvay (Brussels, Belgium). 2Borax decahydrate in granular form that is commercially available through American Borate Company (Virginia Beach, VA). 3Microbiocide consisting of a mixture of l,2-benzisothiazolin-3-one and 2-methyl-4-isothiazolin-3-one, available commercially through Thor GmbH (Speyer, Germany).

[00126] Charge A was added to a four-necked round-bottom flask equipped with a thermocouple, mechanical stirrer, and condenser. Charge A was heated to 65°C. The reaction mixture was then heated to 85°C, and Charge B was added, followed by the addition of Charge C, and the mixture was held for 30 minutes. Charges D and E were added for 180 minutes, and the mixture was held for 60 minutes. Charges F and G were then added for 90 minutes, and the mixture was held for 120 minutes before cooling to 70°C. When the temperature reached 70°C, Charge H was added for 20 minutes. The mixture was then cooled to 40°C, diluted with Charge I, and mixed for 15 minutes.

[00127] The resulting dispersion included particles comprising an acrylic shell covalently bonded to an acrylic core. The final dispersion had a solids content of 25% (measured at 110°C for 1 hour), a Brookfield viscosity of approximately 40 centipoises, and a pH of 6.6, which were measured according to the procedures described above in Example 1. EXAMPLE 3 Preparation of a polyurethane-acrylic dispersion

[00128] A polyurethane was first prepared by loading the following components in order into a first kettle reactor equipped with baffles, a thermocouple, a mechanical stirrer, and a condenser: 200 g of 2-ethylhexyl acrylate, 158.4 g of hydroxyethyl methacrylate, 811 g of poly(tetramethylene ether) glycol with a number-average molecular weight of 1000 g / mol, 163.2 g of dimethylolpropionic acid, 8.0 g of triethylamine, 1.6 g of dibutyltin dilaurate, and 1.6 g of phosphorous acid triphenyl ester. The mixture was heated to 90°C and held for 15 minutes. Then, 450.8 g of isophorone diisocyanate was loaded into the reactor for 90 minutes. The isocyanate addition funnel was rinsed with 40 g of 2-ethylhexyl acrylate. The temperature of the reaction mixture was maintained at 90°C until no NCO peak was detected by IR characterization.The reaction mixture was cooled to 50°C and then 908 g of 2-ethylhexyl acrylate and 145 g of DOWANOL PM (commercially available through The Dow Chemical Company (Midland, MI)) were added to the mixture before cooling to room temperature.

[00129] A second kettle reactor equipped with baffles, a thermocouple, a mechanical stirrer, and a condenser was charged with 4361 g of deionized water, 124.8 g of OT-75 AEROSOL (surfactant, commercially available through Cytec Industries (Woodland Park, NJ)), 85.6 g of dimethylethanolamine, 568.8 g of methyl methacrylate, 946.9 g of 2-ethylhexyl acrylate, 88.8 g of 1,6-hexenediol diacrylate, and 83% of the contents of the mixture from the first kettle reactor. The mixture was stirred and heated to 33°C. The mixture was maintained at 33°C, a nitrogen atmosphere was established, and it was kept in the reactor for the remainder of the reaction. Next, 2.1 g of t-butyl hydroperoxide (70%) in 120 g of water were added to the reactor, followed by a 30-minute addition of a solution of 3.0 g of sodium metabisulfite and 0.1 g of ferrous ammonium sulfate in 120 g of water. The temperature was raised exothermically to 6570°C.When the temperature began to decrease, the reaction set point was changed to 65°C and held for 30 min. The mixture was then cooled to 30°C.

[00130] The resulting dispersion included particles comprising a polyurethane coating covalently bonded to an acrylic core. The final dispersion had a Brookfield viscosity of ~165 centipoise, a pH of 8.48, and a non-volatile content of 38.1%, which were measured according to the procedures described above in Example 1. EXAMPLE 4 Preparation of a base coating composition

[00131] A gray base coating composition was prepared according to the present invention from the components listed in Table 2. ML / a / ZUZZ / UU l uu l Table 2 Components Parts by weight of component Polyurethane-acrylic dispersion of Example 1 102.87 Acrylic latex of Example 2 128.41 BYK 3484 0.26 BYK 0325 1.60 SURFYNOL 104E6 3.47 50% DMEA7 1.59 Mineral spirits8 2.60 White dye9 27.63 Black dye10 17.63 Yellow dye11 7.86 Urethane diol12 5.22 DOWANOL PnB13 2.60 2-Ethylhexanol 6.08 50% DMEA7 1.13 BYKETOL WS14 6.73 RESIMENE HM260815 7.02 CYMEL 115816 4.27 Deionized water 27.21 ΜΛ / a / ZUZZ / UU l υυ l4Silicone surfactant, commercially available from BYK-Chemie GmbH (Wesel, Germany). 5Foam remover, available commercially through BYK-Chemie GmbH (Wesel, Germany). 6Surfactant, commercially available through Evonik Industries (Essen, Germany). 7. 50% aqueous solution of dimethylethanolamine. 8Solvent, commercially available through Shell Chemical Company (Houston, TX). 9White dye paste formed from 61% TiOz dispersed in 9% acrylic polymer having a solids content of 70% by weight, wherein the acrylic polymer is a copolymer of 17.9% by weight butyl methacrylate, 29.99% by weight styrene, 34.98% by weight butyl acrylate, 8.52% by weight acrylic acid and 8.52% by weight hydroxyethyl acrylate, with a weight average molecular weight of about 100,000 g / mol and a solids content of 27% by weight. 10Black dye paste formed from 6% carbon black dispersed in 18% acrylic polymer and having a solids content of 24% by weight, wherein the acrylic polymer is a copolymer of 17.9% by weight butyl methacrylate, 29.99% by weight styrene, 34.98% by weight butyl acrylate, 8.52% by weight acrylic acid and 8.52% by weight hydroxyethyl acrylate, with a weight average molecular weight of about 100,000 g / mol and a solids content of 27% by weight. 11Yellow dye paste formed from 25% Mapico Yellow 1050A dispersed in 21% acrylic polymer and having a solids content of 46% by weight, wherein the acrylic polymer is a copolymer of 17.9% by weight butyl methacrylate, 29.99% by weight styrene, 34.98% by weight butyl acrylate, 8.52% by weight acrylic acid and 8.52% by weight hydroxyethyl acrylate, with a weight average molecular weight of about 100,000 g / mol and a solids content of 27% by weight. 12Polyurethane diol prepared by reacting 1 mol of JEFFAMINE D-400 (commercially available through Huntsman Corporation (The Woodlands, TX)) with 2 moles of ethylene carbonate at 130°C as described in Example A of U.S. Patent No. 7,288,595, which is incorporated herein by reference. 13N-propylene glycol butyl ether, commercially available through The Dow Chemical Company (Midland, MI). 14Silicone-free surface additive, commercially available through BYK-Chemie GmbH (Wesel, Germany). 15Melamine-formaldehyde resin, available through INEOS (London, UK). 16Butylated melamine-formaldehyde crosslinking agent, available through Allnex (Frankfurt, Germany).

[00132] The components listed in Table 2 were slowly added to a stirring / mixing vessel during mixing. The final coating composition had a pH of 9.1, a coating solids content of 32 wt%, and a viscosity of 90 cp, as measured by the BYK CAP 2000+ viscometer, manufactured by BYK Additives and Instruments (Wesel, Germany), with spindle No. 4 at a shear rate of 1000 s1 and 20°C. EXAMPLE 5 Preparation of a base coating composition

[00133] A silver-based coating composition was prepared according to the present invention from the components listed in Table 3. ML / a / zuzz / uu i υυ i Table 3 Components Parts by weight of component Polyurethane-acrylic dispersion of Example 3 127.0 Acrylic latex of Example 2 158.0 BYK 3484 0.23 BYK 0325 1.96 SURFYNOL 104E6 5.04 50% DMEA7 2.50 Butyl glycol17 5.20 SILVER ULTRA 670418 9.55 Aluminum paste TCR3070A19 12.94 Passive aluminum solution20 8.44 ACEMATT TS10021 1.06 DOWANOL PnB13 3.0 2-Ethylhexanol 14.0 50% DMEA7 1.13 RESIMENE HM260815 11.1 Deionized water 100.21 ινΐΛ / a / zuzz / uu / υυ / 17Monobutyl ether of ethylene glycol, available on the market through BASF (Ludwigshafen, Germany). 18 Silver dollar aluminum pigment, available on the trade through Silberline Manufacturing Co. Inc. (Leven, UK). 19Aluminum paste, available commercially through Toyal America Inc. (Lockport, IL). 20Aluminum passivator solution, comprising a mixture of 35.45 parts of 2-butoxyethanol (commercially available through The Dow Chemical Company (Midland, MI)), 60.25 parts of LUBRIZOL 2062 (commercially available through Lubrizol (Wickliffe, OH)) and 1.30 parts of dimethylethanolamine. 21Untreated thermal silica, available through Evonik Industries (Essen, Germany).

[00134] The components listed in Table 3 were slowly added to a stirring / mixing vessel during mixing. The final coating composition had a pH of 9.1, a coating solids content of 31 wt%, and a viscosity of 70 cp, as measured by the BYK CAP 2000+ viscometer, manufactured by BYK Additives and Instruments (Wesel, Germany), with spindle No. 4 at a shear rate of 1000 s⁻¹ and 20°C. EXAMPLES 6-8 Preparation of polyisocyanate components

[00135] Several polyisocyanate mixtures were prepared with the components listed in Table 4. Table 4 Example BAYHYDUR4017022 (grams) DESMODUR N3300A23 (grams) DESMODUR N340024 (grams) PROGLYDE DMM25 (grams) 6 37.5 12.8 15.7 18 7 30 15.2 18.6 19 8 25 16.7 20.5 21 IVIA / a / ZUZZ / UU l U» l22 Hydrophilically modified aliphatic polyisocyanate based on isophorone diisocyanate (IPDI), commercially available through Covestro (Leverkusen, Germany). 23Aliphatic polyisocyanate (HDI trimer), commercially available through Covestro (Leverkusen, Germany). 24Aliphatic polyisocyanate (HDI urethdione), commercially available through Covestro (Leverkusen, Germany). 25Dimethyl dipropylene glycol ether, commercially available through The Dow Chemical Company (Midland, MI).

[00136] The components in each example in Table 4 were slowly added to a stirring / mixing vessel until a homogeneous solution was obtained at 20°C. The isocyanate mixture of each sample was analyzed using the gel permeation chromatography technique described. EXAMPLE 9 Preparation of a finishing composition

[00137] A finishing composition was prepared from a two-component polyol-polyisocyanate crosslinkable composition based on CERAMICLEAR 2K clear repair coating (commercially available through PPG Industries, Inc. (Pittsburgh, PA)), wherein the polyisocyanate component was replaced with the mixture prepared from the components listed in Table 5. Table 5 DESMODUR N-3300A23 (grams) DESMODUR N-340024 (grams) Namyl acetate (grams) n-Butyl acetate (grams) AROMATIC 10026 (grams) 10% dibutyltin dilaurate in xylene (grams) 27.64 16.92 8 6 4 0.5 26Solvent, commercially available through Shell Chemical Company (Houston, TX).

[00138] The components in Table 5 were slowly added to a stirring / mixing vessel until a homogeneous solution was obtained at 20°C. The isocyanate mixture was analyzed using the described gel permeation chromatography technique. EXAMPLES 10-12 Preparation of multilayer coatings

[00139] Several multilayer coatings were prepared from the components listed in Table 6. ML / a / ZUZZ / UU l uu l Table 6 Example: Composition of the first base coat Composition of the second base coat Composition of the clear topcoat Component 1 Component 2 Mass ratio of component 1:2 % by weight of free NCO with Mw of less than 600 g / mol27 Part A Part B 10* Example 4 Example 6 5:1 3.0 Example 5 Polyol28 Ex-9 11* Example 4 Example 7 5:1 3.3 Example 5 Polyol28 Ex.9 12 Example 4 Example 8 5:1 3.6 Example 5 Polyol28 Ex-9 27Amount of free polyisocyanate having a weight-average molecular weight of less than 600 g / mol, as a function of the total resin solids in the coating composition. The weight-average molecular weight was determined by gel permeation chromatography relative to 800 to 900,000 Da linear polystyrene standards using a Waters 2695 separation module with a Waters 2414 differential refractometer (RI detector), manufactured by Waters Corporation (Milford, MA). Tetrahydrofuran (THE) was used as the eluent at a flow rate of 1 mL min1, and two PLGEL MIXED-C columns (300 x 7.5 mm), manufactured by Agilent Technologies (Santa Clara, CA), were used for separation at room temperature. 28 CERAMICLEAR 2K-based polyol, commercially available as BMW A-B204134 through PPG Industries, Inc. (Pittsburgh, PA).

[00140] Each multi-layer coating was prepared by spraying the respective first and second basecoat compositions onto 4-inch by 12-inch steel panels that had been previously coated with ED 6465 electrocoating (a commercially available electrocoating from PPG Industries, Inc. (Pittsburgh, Pennsylvania)). The basecoat compositions were applied under controlled ambient conditions of 70–75°F (21–24°C) and 60–65% relative humidity. In addition, the first basecoat was prepared by mixing Component 1 and Component 2 just before spraying and was applied in one coat, then allowed to evaporate at room temperature for five minutes. The film thickness of the first basecoat was 18–20 micrometers.

[00141] Next, the second base coating compositions of each multilayer coating were applied in two layers, with an ambient evaporation of 90 seconds between layers, then evaporated at room temperature for 4 minutes and dehydrated for 7 minutes at 70°C. The film thickness of the second base coatings was 14-16 micrometers.

[00142] After the basecoat layers were formed, the clearcoat was prepared by mixing Part A and Part B and then applied to the basecoat panels in two coats with a 90-second ambient evaporation time between coats. The mixing ratio of Part A to Part B was 2:1 by weight. The coated panels were allowed to evaporate for 10 minutes under ambient conditions and then baked for 30 minutes at 80°C. The dry film thickness of the clearcoats was 50–55 micrometers. The basecoats and clearcoat were sprayed using a Binks Model 95 spray gun, manufactured by Carlisle Fluid Technologies (Scottsdale, AZ), with an automation air pressure of 60 psi. EXAMPLE 13 Evaluation of multilayer coatings

[00143] The image distinction (DOI) of the final films was measured using a BYK Wavescan instrument (manufactured by BYK Gardner USA (Columbia, MD)). The moisture resistance of the final baked films was tested by placing the finished baked panels in a water bath at 63°C for 2 days. The DOI was measured before the moisture test and after removal from the water bath, and recovered at room temperature for 24 hours. The % DOI loss was defined as (DOI at 24 hours of recovery - DOI before moisture) / DOI after moisture. The lower the % DOI loss value, the better the moisture resistance of the multilayer coating.

[00144] The results of the DOI tests are shown in Table 7. Table 7 Example of multilayer coating % DOI loss at 24 hours after moisture test recovery Comparative example 10 38 Comparative example 11 30 Example 12 15

[00145] As shown in Table 7, Example 12, which included a first basecoat prepared with 3.6 wt% of an isocyanate having a weight-average molecular weight of less than 600 g / mol, exhibited a significantly lower % DOI loss compared to Comparative Examples 10 and 11, which included first basecoats prepared with 3.0 wt% and 3.3 wt%, respectively, of an isocyanate having a weight-average molecular weight of less than 600 g / mol. As such, the % DOI loss is correlated with the wt% of isocyanate having a weight-average molecular weight of less than 600 g / mol as a function of the total resin solids in the coating composition that forms the first basecoat layer.

[00146] Although particular embodiments of this invention have been described above for illustrative purposes, it will be evident to persons of average skill that numerous variations of the details of the present invention can be made without departing from the invention as defined in the appended claims.

Claims

1. A multilayer coating system comprising: a first base coating layer formed from a first coating composition comprising at least one free polyisocyanate having a weight average molecular weight of less than 600 g / mol and polymeric core-shell particles with hydroxyl functionality, wherein each of a polymeric core and a polymeric shell of the core-shell particles with hydroxyl functionality independently comprises an addition polymer derived from ethylenically unsaturated monomers and wherein an amount of the free polyisocyanate having a weight average molecular weight of less than 600 g / mol is 3.5% by weight or more, depending on the total resin solids of the first coating composition;a second base coating layer placed over at least a portion of the first base coating layer, wherein the second base coating layer is formed from a second coating composition comprising polymeric core-shell particles with carboxylic acid functionality, wherein a polymeric core of the core-shell particles with carboxylic acid functionality comprises an addition polymer derived from ethylenically unsaturated monomers and a polymeric shell of the core-shell particles with carboxylic acid functionality comprises urethane linkages and groups with carboxylic acid functionality; and a topcoat layer placed over at least a portion of the second base coating layer, wherein the topcoat layer is formed from a coating composition comprising a free polyisocyanate and a film-forming resin reactive with the free polyisocyanate.

2. The multilayer coating system according to claim 1, wherein the free polyisocyanate in the coating composition forming the first base coating layer comprises more than 9.5% by weight of a urethedione dimer, based on the total weight of the resin solids of the first base coating layer.

3. The multilayer coating system according to claim 1 or 2, wherein the polymeric coating of the polymeric core-coat particles with hydroxyl functionality of the first coating composition comprises from 5 to 30% by weight of the core-coat particles, depending on the total weight of solids of the core-coat particles.

4. The multilayer coating system according to any of claims 1 to 3, wherein the polymeric coating of the polymer core-coat particles with hydroxyl functionality of the first coating composition is obtained from components comprising more than 10% by weight of an ethylenically unsaturated monomer with hydroxyl functionality, based on the total weight of the components forming the polymeric coating.

5. The multilayer coating system according to claim 4, wherein a homopolymer formed from the ethylenically unsaturated monomer with hydroxyl functionality has a Van Krevelen solubility parameter at 298K of more than 25.0 MPa0·5.

6. The multilayer coating system according to any of claims 1 to 5, wherein the first coating composition further comprises polymeric core-shell particles with carboxylic acid functionality, wherein a polymeric core of the polymeric core-shell particles with carboxylic acid functionality comprises an addition polymer derived from ethylenically unsaturated monomers and a polymeric shell of the polymeric core-shell particles with carboxylic acid functionality comprises urethane linkages and groups with carboxylic acid functionality.

7. The multilayer coating system according to any of claims 1 to 6, wherein the first coating composition and / or the second coating composition further comprises an aminoplast resin.

8. The multilayer coating system according to any of claims 1 to 7, wherein the second coating composition comprises more than 20% by weight of polymeric core-shell particles with carboxylic acid functionality, based on the total resin solids of the second coating composition.

9. The multilayer coating system according to any of claims 1 to 8, wherein the second coating composition further comprises polymeric core-shell particles with hydroxyl functionality, wherein each of a polymeric core and a polymeric shell of the polymeric core-shell particles with hydroxyl functionality of the second coating composition independently comprises an addition polymer derived from ethylenically unsaturated monomers.

10. The multilayer coating system according to any of claims 1 to 9, wherein the second coating composition further comprises a free polyisocyanate.

11. The multilayer coating system according to any of claims 1 to 10, wherein each of the first coating composition and the second coating composition independently comprises at least one colorant.

12. The multilayer coating system according to any of claims 1 to 11, wherein a core-to-shell weight ratio of the core-shell particles with hydroxyl functionality of the first coating composition is from 95:5 to 70:

30.

13. The multi-layer coating system according to any of claims 1 to 12, further comprising a primer coating layer, wherein the first coating layer is placed over at least a portion of the primer coating layer.

14. A substrate coated at least partially with the multilayer coating system according to any of claims 1 to 13.

15. The substrate according to claim 14, wherein the substrate comprises at least a portion of an automobile.

16. A process for coating a substrate with a multilayer coating comprising: (i) depositing a first coating composition onto at least a portion of the substrate, wherein the first coating composition comprises at least one free polyisocyanate having a weight-average molecular weight of less than 600 g / mol and polymeric core-shell particles with hydroxyl functionality, wherein each of a polymeric core and a polymeric shell of the hydroxyl-functional core-shell particles independently comprises an addition polymer derived from ethylenically unsaturated monomers and wherein an amount of the free polyisocyanate having a weight-average molecular weight of less than 600 g / mol is 3.5% by weight or more, based on the total resin solids of the first coating composition;(i) depositing a second coating composition directly onto at least a portion of the first coating composition (1) after the first coating composition is dehydrated or (2) before the first coating composition is dehydrated, wherein the second coating composition comprises polymeric core-shell particles with carboxylic acid functionality, wherein a polymeric core of the core-shell particles with carboxylic acid functionality comprises an addition polymer derived from ethylenically unsaturated monomers and a polymeric shell of the core-shell particles with carboxylic acid functionality comprises urethane linkages and groups with carboxylic acid functionality; (iii) dehydrating: (a) the second coating composition after (i)(1); or (b) simultaneously the first coating composition and the second coating composition after (ii)(2);and ML / a / ZUZZ / UU l uu l (iv) depositing a topcoat composition onto at least a portion of the second dehydrated basecoat composition, wherein the topcoat composition comprises a free polyisocyanate and at least one film-forming resin reactive with the free polyisocyanate.; 17. The process according to claim 16, wherein the first coating composition is dehydrated prior to the application of the second base coating composition.

18. The process according to claim 16, wherein the first and second coating compositions are dehydrated simultaneously.

19. The process according to any of claims 16 to 18, wherein the first base coating composition and the second base coating composition are dehydrated at a temperature ranging from ambient temperature to 90°C.

20. The process according to any of claims 16 to 19, wherein, after dehydration, the first and second base coatings together comprise a solids content of at least 80% by weight, based on the total weight of the first and second base coatings.

21. The process according to any of claims 16 to 20, further comprising curing the first and second coating compositions at a temperature of 120°C or less.

22. The process according to any of claims 16 to 21, further comprising curing the first and second coating compositions and the finishing composition simultaneously at a temperature of 120°C or less.