Water-based coating

Abstract

We provide coating systems. [Solution] A coating system, a composite article formed from the coating system, and a method for forming the composite article are provided herein. In an embodiment, the coating system comprises an aqueous primer composition containing an acrylic latex resin and a two-part aqueous clear coat composition. The two-part aqueous clear coat composition comprises a clear coat binder part and a clear coat crosslinking agent part. The clear coat binder part comprises a water-dilutable hydroxyl-functional (meth)acrylate copolymer. The clear coat crosslinking agent part comprises a polyisocyanate compound having a pendant-NCO group. A cured film of the aqueous clear coat composition having a thickness of 67.5 μm placed on a substrate and a cured film of the aqueous primer composition having a thickness of 20 μm exhibits a popping density of less than approximately 3 pops per square centimeter, as measured by visual observation with the naked eye at a distance of 30 cm under a fluorescent light source.

Description

[Technical Field]

[0001] This disclosure generally relates to aqueous coating systems comprising a plurality of aqueous coating compositions, composite articles formed from coating compositions, and methods for forming composite articles. More specifically, this disclosure relates to aqueous coating systems that can be used to form composite articles in which surface defects exhibited after curing of all layers are minimized. [Background technology]

[0002] Coating systems are used in a variety of applications, including automotive refinishing. A typical coating system includes multiple coating compositions, often selected from primer compositions, sealant compositions, basecoat compositions, tie compositions, and / or clearcoat compositions. When each composition is applied to a substrate or a previously formed layer, a layer corresponding to each composition is formed. Multiple layers are used because each layer provides specific benefits. The clearcoat or topcoat layer provides benefits such as protecting the substrate and undercoat from scratch, chemical damage, or environmental damage. Undercoats, such as primers, surfacers, sealants, or basecoat layers, also provide benefits commonly known in the field of coating systems. Primer layers provide benefits such as promoting adhesion between the substrate surface and subsequent coating layers, and enhancing the overall physical properties of the coating system (e.g., corrosion resistance and / or impact strength). Sanding surfacers allow for application and sanding to achieve a very smooth layer to which subsequent layers can be applied. Sealant layers provide a barrier that can prevent the upper layer from being absorbed by other undercoats. The base coat layer contributes to the color or other visual effects of the coating system. Historically, coating compositions used in coating systems, particularly clear coat layers, primers, surfacers, or sealant layers, are solvent-based and therefore contain a considerable amount of volatile organic compounds (VOCs). However, due to environmental concerns, there is a regulatory movement to reduce the levels of such VOCs in coating systems, especially in applications such as automotive refinishing coatings. One method to reduce VOC content is to use "high solids" coating compositions, in which the amount of organic solvent relative to non-volatile components in the coating composition is reduced. However, reducing the amount of organic solvent in the coating composition increases the viscosity of the coating composition, resulting in poor flow properties and making application and / or leveling of the composition difficult.

[0003] Another method for reducing the VOC content of coating systems is to use aqueous coating compositions. Aqueous coating compositions contain minimal amounts of VOCs but do not impair the flow properties of the composition (thus avoiding any difficulties in application and / or leveling). However, after applying an aqueous composition to a substrate to form a layer, water often has to be removed for proper crosslinking and curing to occur. Because water has a higher boiling point than many common organic solvents, it is more difficult to remove by flash drying than many common organic solvents, and water generally has to be removed by a heat drying process under certain conditions of temperature, humidity, and air movement. Some water often remains in the layer after heat drying (or may be reabsorbed into the substrate when the next aqueous layer is applied). As mentioned above, it is typically desirable to have multiple coating layers on the substrate. When multiple aqueous layers are formed on top of each other, especially if one of the substrate layers contains isocyanate, water trapped within the substrate layer may react with the isocyanate in that layer itself, or with isocyanate that has diffused downwards from the upper layer or evaporated upwards from the substrate layer, if present. Also, if the clear coat contains isocyanate, water trapped within the substrate layer may later diffuse into the upper clear coat layer and react with the isocyanate. The reaction between isocyanate and water forms carbon dioxide. This formed carbon dioxide is released during the curing of the upper layer, resulting in surface defects called "pops" (e.g., pinholes, bubbles, depressions, etc.) in the upper layer. Such surface defects, especially in the clear coat layer, impair the aesthetic appeal and protective properties of the coating.

[0004] Surface defects are most likely to occur when both the clear coat layer and the undercoat are formed from aqueous compositions. Water remaining in the clear coat layer formed from an aqueous clear coat composition tends to diffuse into the undercoat, especially if the undercoat is also formed from an aqueous composition and is not completely dry. Such undercoats have a high affinity for water, making it impossible to perform typical repair techniques for surface defects, such as sanding, on the clear coat. Water trapped within the coating system can also degrade the appearance of the clear coat, causing texture formation and fuzzing. The incidence of surface defects also tends to increase with increasing film build, i.e., as the thickness of the layers formed from aqueous coating compositions increases. For a layer to effectively protect the substrate and / or perform other functions, each layer often needs to be at least a certain thickness. Increasing the thickness of the aqueous layer to improve the effectiveness of the layer can lead to an increase in the incidence of surface defects. [Overview of the project]

[0005] Therefore, it is desirable to provide a coating system comprising multiple aqueous coating compositions that can be applied sequentially to a substrate to form a sufficiently thick upper layer that is effective in protecting the substrate, while minimizing surface defects exhibited after the curing of all layers (attributable to the considerable amount of water present in each layer). Furthermore, other desirable properties and features of this disclosure will become apparent from the embodiments for carrying out the subsequent invention and the appended claims in relation to the accompanying drawings and this background art. This summary is provided to introduce a selection of simplified concepts for which the invention will be further described in the embodiments for carrying it out. This summary is not intended to identify the main or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. A coating system, a composite article formed from the coating system, and a method for forming the composite article are provided herein. In embodiments, the coating system comprises an aqueous primer composition and a two-part aqueous clear coat composition. The aqueous primer composition comprises an acrylic latex resin. The two-part aqueous clear coat composition comprises a clear coat binder part and a clear coat crosslinking agent part. The clear coat binder part comprises a water-dilutable hydroxyl-functional (meth)acrylate copolymer. The clear coat crosslinking agent part comprises a polyisocyanate compound having a pendant-NCO group. The molar ratio of active hydrogen atoms to -NCO groups in the aqueous clear coat composition is about 1:5 to about 5:1. A cured film of an aqueous clear coat composition having a thickness of 67.5 μm on a cured film of an aqueous primer composition having a thickness of 20 μm placed on a substrate exhibits a popping density of less than about 3 pops per square centimeter, as measured by visual observation with the naked eye at a distance of 30 cm under a fluorescent light source. [Modes for carrying out the invention]

[0006] The embodiments for carrying out the invention described below are merely illustrative and are not intended to limit the Disclosure or its uses and applications. Furthermore, they are not intended to be bound by the aforementioned background art or any theory presented in the embodiments for carrying out the invention described below. Provided herein are a coating system comprising multiple aqueous coating compositions, a composite article formed from the coating compositions, and a method for forming the composite article. The coating system comprises an aqueous primer composition and a two-part aqueous clear coat composition, as described in more detail below. In accordance with this disclosure, the coating system contemplated herein minimizes surface defects exhibited after curing of all layers without impairing other properties of the coating system by reducing the thickness of the layers. More specifically, based on the chemical properties of the aqueous primer composition and the two-part aqueous clear coat composition, a coating system is provided which exhibits a popping density of less than approximately 3 pops per square centimeter, given that the cured film of the clear coat composition has a thickness of 67.5 μm and the cured film of the aqueous primer composition has a thickness of 20 μm. Such performance has not been achieved with existing aqueous coating systems.

[0007] Where used herein and unless otherwise specified or evident from the context, the term “approximately” is understood to mean within the range normally acceptable in the art, measured using standard measuring devices for a given measurement, for example, within two standard deviations of the mean for a particular measuring device. “Approximately” can also be understood as within 10%, 5%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the specified value. Alternatively, “approximately” can also be understood to imply the exact value of the specified value. Unless otherwise evident from the context, all numerical values ​​provided herein are modified by the term “approximately.” As used herein, "solids content" refers to the mass percentage of non-volatile components in a composition, based on the total mass of the resin or composition after all solvents and / or volatile components have been removed from the resin or composition. When used here, the molecular weight of the polymer is measured by gel permeation chromatography (GPC) using a polystyrene calibration standard, according to ASTM 3536. As used herein, "acid value (acid value or acid number)" is a measure of the amount of free acid present in a compound. The acid value is the number of milligrams of potassium hydroxide (mg KOH / g) required to neutralize the free acid present in 1 gram of the substance. All of the measured acid values provided herein were determined in accordance with ASTM D974-22.

[0008] As used herein, "hydroxyl value" or "OH value" is defined as the mass of potassium hydroxide in milligrams required to neutralize acetic acid when taking up the acetylation of 1 gram of a chemical substance containing free hydroxyl groups. When specified, the hydroxyl value is analyzed in accordance with the standard test method ASTM D4274-11. As used herein, the calculated glass transition temperature (Tg) of a polymer is given by the Fox equation: 1 / T g,ポリマー ≈Σ i w i / T g,i (where T g,ポリマー and T g,i are the glass transition temperatures of the polymer and component monomer (i), respectively, and w i is the mass fraction of component i) is calculated by. The glass transition temperature of a particular homopolymer can be found in published literature. As used herein, the minimum film formation temperature (MFFT) refers to the lowest temperature required for an aqueous polymer dispersion to coalesce into a thin film upon application to a substrate. Here, the MFFT is determined in accordance with ASTM D2354-98 using BAR-90 from Rhopoint Industries.

[0009] As used here, "particle size" refers to the longest axis of a particle. For a generally spherical particle, the longest axis is the diameter. The term "average volume particle size" (Dv50) refers to a particle size where 50% of the sampled particles have a volume greater than the given Dv50 value, and 50% of the sampled particles have a volume less than the given Dv50 value. Particle size is determined here by laser diffraction using Anton Paar's Particle Size Analyzer (PSA) Litesizer 500, in accordance with ASTM 5861-07 (2017). As used herein, a "multipart composition" is a composition comprising at least two parts that are stored in separate containers until use due to their reactivity with each other. A "two-part composition" is a multipart composition having two parts. The parts are mixed together before or during application of the composition to form a film. After the parts are mixed, they react to form bonds, typically without requiring additional activation, thereby forming a polymer network. Heat may be applied to accelerate the reaction between the parts.

[0010] As used herein, "aqueous composition" means a composition in which the solvent or carrier fluid for the composition mainly consists of water. This may mean that water constitutes about 30% to about 100% by mass, or about 60% to about 95% by mass, or about 70% to about 90% by mass of the liquid solvent in the composition. As used herein, "water-dilutable polymer" refers to a polymer that exists in water in the form of particles, which are dispersed or suspended and stable against aggregation when further diluted with water. In contrast to water-soluble polymers, a diluted solution of a water-dilutable polymer (approximately 1 g / L) exhibits scattering when analyzed using dynamic light scattering or any other technique known in the field of particle analysis. As used herein, "curing" of an aqueous coating composition refers to the formation of a coating on a substrate through the reaction of components in the coating composition. Curing may include crosslinking reactions. Curing may further include evaporation (drying) of water (and cosolvents, if present) from the composition, and aggregation of fine particles or dispersed phases of the composition. Curing may be carried out under ambient conditions or by deliberate exposure to heat and / or irradiation. The degree of curing may be partial or complete.

[0011] As used herein, “ethylenically unsaturated monomer” refers to any monomer containing a terminal double bond that can be polymerized under the normal conditions of free radical polymerization or addition polymerization. As used herein, "active hydrogen atom" refers to a hydrogen atom that exhibits activity according to the Zerewitinoff test. Active hydrogen atoms may originate from hydroxyl, thiol, primary amine, secondary amine, or carboxyl groups. As used here, "(meth)acrylic" is an abbreviation for "acrylic" and / or "methacrylic." Therefore, the term "(meth)acrylate" collectively refers to acrylate and methacrylate. Where used herein, "coating thickness" refers to the total amount of coating applied to a surface, expressed as a measured thickness of the coating after drying. "Film thickness" refers to a measured thickness of a single layer. Film thickness is measured using a Fischer coating thickness gauge, DUALSCOPE FMP40. The coating system provided herein comprises an aqueous primer composition and an aqueous clear coat composition, as described in more detail below. A cured film of an aqueous clear coat composition having a thickness of 67.5 μm, placed on a substrate and cured on an aqueous primer composition having a thickness of 20 μm, exhibits a popping density of less than approximately 3 pops per square centimeter, as measured by visual observation with the naked eye at a distance of 30 cm under a fluorescent light source.

[0012] Aqueous clear coat compositions are included in coating systems to provide protection for substrates and undercoats, and to impart a desired appearance or visual effect. The aqueous clear coat composition is a two-part aqueous clear coat composition comprising a clear coat binder part and a clear coat crosslinking agent part. The clear coat binder part is a component containing a water-dilutable hydroxyl-functional (meth)acrylate copolymer that crosslinks during curing to form a clear coat layer. The free hydroxyl groups of the water-dilutable hydroxyl-functional (meth)acrylate copolymer can react under certain conditions to form crosslinks. Crosslinking contributes to the solidification of the aqueous clear coat composition, forming a clear coat layer. The clear coat crosslinking agent part contains a polyisocyanate compound having pendant-NCO groups that promotes crosslinking of the copolymer. Due to the chemical properties of the water-dilutable hydroxyl-functional (meth)acrylate copolymer in the aqueous clear coat composition, the polyisocyanate compound emulsifies rapidly, minimizing the reaction between residual isocyanate and water, and thus minimizing popping of the clear coat layer after curing of the aqueous clear coat composition.

[0013] In the embodiment, the water-dilutable hydroxyl-functional (meth)acrylate copolymer present in the clear coat binder part of the two-part aqueous clear coat composition has a glass transition temperature of about 20°C to about 50°C, or about 30°C to about 50°C, or about 36°C to about 50°C, calculated using the Fox formula. Water-dilutable hydroxyl-functional (meth)acrylate copolymer having a glass transition temperature within the given range can contribute to the effective drying of the aqueous clear coat composition and / or the durability of the cured film of the clear coat composition. In the embodiment, the water-dilutable hydroxyl-functional (meth)acrylate copolymer has a hydroxyl value of about 110 mg KOH / g to about 160 mg KOH / g, or about 110 mg KOH / g to about 140 mg KOH / g, as analyzed according to the standard test method ASTM D4274-11. The hydroxyl value affects the degree of crosslinking during the curing of the aqueous clear coat composition. In the embodiments, the water-dilutable hydroxyl-functional (meth)acrylate copolymer has an acid value of about 20 mg KOH / g to about 40 mg KOH / g, or about 20 mg KOH / g to about 28 mg KOH / g, as determined according to ASTM D974-22. In the embodiments, the water-dilutable hydroxyl-functional (meth)acrylate copolymer has a mass-average molecular weight of about 10,000 daltons to about 30,000 daltons, or about 10,000 daltons to about 20,000 daltons, as measured by gel permeation chromatography (GPC) using a polystyrene calibration standard, according to ASTM 3536.

[0014] Water-dilutable hydroxyl-functional (meth)acrylate copolymers are reaction products of monomers in a monomer mixture. The types of monomers present in the monomer mixture can affect the appearance, popping performance, and durability of the cured film of the aqueous clear coat composition. Polymerization of component monomers is conventionally carried out by free radical solution polymerization. Two-step free radical solution polymerization (e.g., asymmetric feed polymerization) may be used. In an embodiment, the monomer mixture contains (i) a hydroxyl-functionalized adduct of a monoepoxy ester and an unsaturated carboxylic acid. Typically, the adduct is formed by a nucleophilic addition reaction of a monoepoxy ester and an acid to form a hydroxyalkyl ester. This acid-catalyzed ring-opening reaction conventionally requires a catalyst. The catalyst can be selected from a tertiary amine, a quaternary ammonium compound, and / or a transition metal compound. The monoepoxy ester of the reactant is typically a glycidyl ester derived from an aliphatic saturated monocarboxylic acid having a tertiary or quaternary carbon atom at the alpha position. In an embodiment, the monoepoxy ester of the reactant is a glycidyl ester of a saturated α,α-dialkylalkane-monocarboxylic acid having 5 to 13 carbon atoms or 9 to 11 carbon atoms in the acid molecule. The acid-functionalized compound of the reactant can be an aliphatic unsaturated monocarboxylic acid, for example, an α,β-monoethylenically unsaturated monocarboxylic acid, a C1-C6 alkyl half ester of an α,β-monoethylenically unsaturated dicarboxylic acid, or a C1-C6 alkyl ester of an α,β-monoethylenically unsaturated tricarboxylic acid having one free carboxylic acid group. In an embodiment, the acid-functionalized component of the reactant is (meth)acrylic acid. In an embodiment, monomer (i) is present in the monomer mixture in an amount of about 10% to about 80%, or about 20% to about 60%, or about 30% to about 60% by mass based on the total mass of the monomers in the mixture.

[0015] In an embodiment, the monomer mixture contains (ii) a hydroxyl-functionalized unsaturated monomer different from monomer (i). Monomer (ii) can be selected from hydroxyalkyl esters having a primary or secondary hydroxyl group derived from an α,β-monoethylenically unsaturated monocarboxylic acid. For example, the monomer can be selected from hydroxyalkyl esters derived from acrylic acid, methacrylic acid, crotonic acid, or isocrotonic acid. In an embodiment, monomer component (ii) includes a hydroxyl (meth)acrylate monomer represented by the formula HMA. H2C=CG a CO2R h (HMA) Ga However, if R is hydrogen, halogen, or methyl, h C1-C 18 It is hydroxyl. In embodiments, monomer component (ii) may be selected from hydroxyethyl (meth)acrylate, 1-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 1-hydroxybutyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-hydroxybutyl (meth)acrylate. In embodiments, monomer (ii) is present in the monomer mixture in an amount of about 0% to about 40% by mass, or about 10% to about 30% by mass, or about 10% to about 25% by mass, or about 10% to about 20% by mass, based on the total mass of monomers in the mixture.

[0016] In the embodiment, the monomer mixture contains (iii) an unsaturated acid-functional monomer different from monomers (i) and (ii). With respect to the (iii) unsaturated acid-functional monomer, in the embodiment, the monomer is selected from ethylenically unsaturated carboxylic acids, ethylenically unsaturated sulfonic acids, vinylphosphonic acids, and mixtures thereof. Suitable ethylenically unsaturated sulfonic acids include, for example, vinylsulfonic acid, styrenesulfonic acid, or acrylamidemethylpropanesulfonic acid. In the embodiment, monomer component (iii) includes an ethylenically unsaturated carboxylic acid selected from α,β-monoethylenically unsaturated monocarboxylic acid, α,β-monoethylenically unsaturated dicarboxylic acid, C1-C6 alkyl half-ester of α,β-monoethylenically unsaturated dicarboxylic acid, α,β-monoethylenically unsaturated tricarboxylic acid, C1-C6 alkyl ester of α,β-monoethylenically unsaturated tricarboxylic acid having at least one free carboxylic acid group, or mixtures thereof. In the embodiment, monomer component (iii) comprises an ethylenically unsaturated carboxylic acid selected from methacrylic acid, acrylic acid, itaconic acid, maleic acid, aconitic acid, crotonic acid, fumaric acid, or a mixture thereof. In the embodiment, monomer (iii) is present in the monomer mixture in an amount of about 1% to about 8% by mass, or about 2% to about 6% by mass, or about 2% to about 5% by mass, or about 2% to about 4% by mass, based on the total mass of monomers in the mixture.

[0017] In the embodiment, the monomer mixture contains a (meth)acrylate monomer represented by formula (iv) MA. H2C=CG a CO2R a (MA) In the formula MA, G a R is hydrogen, halogen, or methyl. a This is a C1-C18 alkyl, C2-C18 heteroalkyl, C3-C18 cycloalkyl, C2-C8 heterocycloalkyl, C2-C8 alkenyl, or C2-C8 alkynyl. In the embodiment, R aThese are C1-C18 alkyl or C3-C18 cycloalkyl. Examples of (meth)acrylate monomers conforming to formula MA include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, and 4-tert-butyl acrylate. Examples include chlorohexyl (meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate, dihydrodicyclopentanedienyl (meth)acrylate, ethylene glycol monomethyl ether (meth)acrylate, ethylene glycol monoethyl ether (meth)acrylate, ethylene glycol monododecyl ether (meth)acrylate, diethylene glycol monomethyl ether (meth)acrylate, trifluoroethyl (meth)acrylate, and perfluorooctyl (meth)acrylate. In embodiments, monomer component (iv) includes a (meth)acrylate monomer that, when homopolymerized, yields a homopolymer having a glass transition temperature (Tg) greater than about 30°C. In embodiments, monomer (iv) is present in the monomer mixture in an amount of about 20% to about 60% by mass, or about 25% to about 50% by mass, based on the total mass of monomers in the mixture.

[0018] In the embodiment, the monomer mixture contains (v) at least one vinyl aromatic monomer different from monomers (i) to (iv). In the embodiment, monomer component (v) is of formula (VA) [ka] (In the formula, R 1 is H or C1-C4 alkyl, and each R 2(where n is independently hydrogen or a C1-C4 alkyl group, Ar is an unsubstituted phenyl group or a phenyl group substituted with 1 to 5 substituents, each substituent independently a halogen or a C1-C4 alkyl group, and n is an integer from 0 to 4) It contains a vinyl aromatic monomer. In the embodiment, R 1 is H or methyl, and each R 2 n is independently H or methyl, Ar is unsubstituted phenyl or phenyl substituted with 1 to 5 substituents, each substituent independently is a halogen or a C1-C4 alkyl, and n is 0 or 1. In embodiments, monomer component (v) is selected from styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-tert-butylstyrene, 4-tert-butylstyrene, 2-chlorostyrene, 4-chlorostyrene, or a combination thereof. In embodiments, monomer (v) is present in the monomer mixture in an amount of about 0% to about 20% by mass, or about 0% to about 15% by mass, or about 4% to about 14% by mass, based on the total mass of the monomer mixture.

[0019] In the embodiment, the monomer mixture contains at least one polymerizable unsaturated monomer different from (vi)(i) to (v). With respect to at least one polymerizable unsaturated monomer different from (vi)(i) to (v), in the embodiment, monomer component (vi) is selected from aromatic (meth)acrylate monomers, (meth)acrylate-functionalized oligomers, nitrogen (N-)-functionalized ethylenically unsaturated monomers, silane-functionalized ethylenically unsaturated monomers, such as methacrylateoxypropyltri(C1-C5)alkoxysilane and vinyltri(C1-C5)alkoxysilane, acetoacetyl-functionalized unsaturated monomers, such as acetoacetoxyethyl methacrylate, vinyl esters, vinyl and vinylidene halides, vinyl ethers, alkyl vinyl ketones, cycloalkyl vinyl ketones, heterocyclic aliphatic vinyl compounds, poly(meth)acrylates of alkane polyols, poly(meth)acrylates of oxyalkane polyols, poly(C2-C3)alkylene glycol di(meth)acrylate, or combinations thereof. Suitable aromatic (meth)acrylate monomers include formula AII: H2C=CG b CO2R b (AII) (In the formula, G b R is hydrogen, halogen, or methyl, b (These are C6-C18 aryl, C1-C9 heteroaryl, C7-C18 alkoxyaryl, C7-C18 alkaryl, or C7-C18 aralkyl.) Examples of monomers represented by include: In the embodiment, monomer (vi) is present in the monomer mixture in an amount of about 0% to about 70% by mass, or about 1% to about 20% by mass. In the embodiment, the water-dilutable hydroxyl-functional (meth)acrylate copolymer is present in the clear coat binder part in an amount of about 20% to about 60% by mass, or about 35% to about 55% by mass, based on the total mass of the clear coat binder part.

[0020] In embodiments, the clear coat binder part further comprises a non-aromatic polyester having active hydrogen groups. The presence of polyester in the clear coat binder part can improve the appearance, durability, and / or chemical stability of the cured film of the aqueous clear coat composition. In embodiments, the non-aromatic polyester has a number-average molecular weight (Mn) of about 500 to about 5000 daltons, or about 500 to about 1500 daltons, an acid value of about 0 to about 30 mg KOH / g, a hydroxyl value of about 100 to about 600 mg KOH / g, or about 250 to about 400 mg KOH / g, and about 2 to about 8, or about 4 to about 8 calculated hydroxyl functional groups. In the embodiment, the non-aromatic polyester is prepared by polycondensation of a hydroxyl-functional component, a carboxyl-functional component, and optionally a hydroxycarboxylic acid component. The polycondensation reaction can be exemplified by a stoichiometric excess of hydroxyl groups relative to the carboxyl groups. For example, the stoichiometric excess of hydroxyl groups relative to the carboxyl groups may be about 5 mol% to about 40 mol%, or about 5 mol% to about 35 mol%, or about 5 mol% to about 30 mol%, or about 5 mol% to about 25 mol%. In the embodiment, the hydroxyl functional component includes, based on the total mass of the hydroxyl functional component, a polyol having 3 to 6 hydroxyl groups in an amount of about 75% to about 100% by mass, or about 80% to about 100% by mass, or about 90% to about 100% by mass, or about 95% to about 100% by mass, and a diol in an amount of about 0% to about 25% by mass, or about 0% to about 20% by mass, or about 0% to about 10% by mass, or about 0% to about 5% by mass. In the embodiment, the carboxyl functional component includes, based on the total mass of the carboxyl functional component, a dicarboxylic acid in an amount of about 75% to about 100% by mass, or about 80% to about 100% by mass, or about 90% to about 100% by mass, and a monocarboxylic acid in an amount of about 0% to about 25% by mass, or about 0% to about 20% by mass, or about 0% to about 10% by mass.

[0021] In the embodiment, the non-aromatic polyester is present in the clear coat binder part in an amount of about 0% to about 20% by mass, or about 0% to about 10% by mass, or about 0% to about 5% by mass, based on the total mass of the clear coat binder part. In the embodiment, the mass ratio of the hydroxyl-functional (meth)acrylate copolymer to the non-aromatic polyester is about 100:1 to about 100:35, or about 100:5 to about 100:25, or about 100:5 to about 100:20, or about 100:5 to about 100:15. In embodiments, the clear coat binder part further comprises a nonpolymer polyol. As used herein, “polyol” refers to any compound having two or more hydroxyl groups. Thus, the term “polyol” is intended to encompass diols, triols, and compounds containing four or more hydroxyl groups. The inclusion of a nonpolymer polyol can contribute to the moisture resistance of the aqueous clear coat composition and can also contribute to the effective mixing of the clear coat binder part and the clear coat crosslinking agent part when they are combined. In embodiments, the nonpolymer polyol has a mass-average molecular weight of less than about 300 daltons and water solubility of less than about 6 g per 100 ml of water at 20°C. In embodiments, the nonpolymer polyol is selected from 2-ethylhexane-1,3-diol, 2-butyl-2-ethyl-1,3-propanediol, or a combination thereof. Nonpolymeric polyols may be present in the clear coat binder part in amounts of approximately 0% to 5% by mass, or approximately 0% to 5% by mass, or approximately 0% to 2% by mass, or approximately 0% to 1.5% by mass, based on the total mass of the clear coat binder part.

[0022] The clear coat crosslinking agent part comprises a polyisocyanate compound having a pendant-NCO group. The clear coat crosslinking agent part may contain only one polyisocyanate compound, or it may contain two or more polyisocyanate compounds. Suitable polyisocyanates include aliphatic, alicyclic, aromatic, and heterocyclic isocyanates, their dimers and trimers, and combinations thereof. In the embodiment, the molar ratio of active hydrogen atoms to -NCO groups in the aqueous clear coat composition is about 1:5 to about 5:1, or about 1:3 to about 3:1, or about 1:2 to about 2:1, or about 1:1.5 to about 1.5:1.

[0023] A aqueous primer composition is any aqueous coating composition that can be applied to a substrate before the application of an aqueous clear coat composition, or to a coating layer placed on a substrate. The coating system provided herein may contain only one aqueous primer composition, or two or more aqueous primer compositions. Aqueous primer compositions are provided for a variety of reasons, depending on the type of application and the intended role of the composition. After the application and curing of the coating system, the layer formed from the aqueous primer composition can provide protection to the substrate, form a smooth layer on which other layers can be placed, prevent absorption of the substrate by the upper layer, enhance adhesion between layers in the coating system, or provide a desired visual effect. Aqueous primer compositions may be, for example, surfacer compositions, sealant compositions, primer compositions, base coat compositions, or tie-layer compositions.

[0024] The aqueous primer composition contains an acrylic latex resin. The use of an acrylic latex resin in the aqueous primer composition allows water to be released more quickly during the curing of the primer layer formed from the aqueous primer composition, preventing water from re-penetrating the primer layer from the subsequently applied aqueous composition. In embodiments, the aqueous primer composition is an aqueous surfacer composition. Applying the aqueous surfacer composition, curing the resulting layer, and sanding the resulting layer provides a smooth layer on which other layers can be uniformly applied. The aqueous surfacer composition includes a surfacer underlayer part. In embodiments, the aqueous surfacer composition is a two-part composition further comprising a surfacer crosslinking agent part. The surfacer underlayer part is a component containing a polymer that "solidifies" during curing to form, for example, a substantially crosslinked polymer film. The surfacer underlayer part includes a core-shell latex comprising a core copolymer and a shell copolymer. The core copolymer and shell copolymer have pendant carbonyl groups. The carbonyl groups of the copolymers can react under certain conditions to form crosslinks. Crosslinking contributes to the solidification of the aqueous surfacer composition, forming a surfacer coating layer. The surfacer crosslinking agent part can promote the crosslinking of the core-shell latex copolymer.

[0025] As used herein, the term “core-shell latex copolymer” refers to a latex copolymer produced by a stepwise polymerization process having at least two polymerization steps. In one step, an emulsion polymerization process is carried out to produce a “core” copolymer. In another step, an emulsion polymerization process is carried out to form a “shell” copolymer. In embodiments, the core copolymer is synthesized in a free radical emulsion polymerization step that precedes the step of synthesizing the shell copolymer by free radical emulsion polymerization. The shell copolymer is typically formed in the presence of particles of the core copolymer in these embodiments. In other embodiments, typically, if the core copolymer is more hydrophobic than the shell copolymer, the free radical emulsion polymerization step of the shell copolymer may precede the free radical emulsion polymerization step of the core copolymer. In embodiments, additional polymerization steps may be carried out relative to the core-forming and shell-forming steps. Exemplary additional polymerization steps may be carried out before the core-forming step, between the core polymerization step and the shell polymerization step, or after the shell polymerization step.

[0026] In the embodiment, the core copolymer accounts for at least about 10% by mass, or about 10% to about 70% by mass, or about 10% to about 60% by mass, of the total mass of the monomer components in the core-shell latex copolymer. In the embodiment, the calculated Tg of the core copolymer is at least about 20°C higher, or at least about 30°C higher, than the calculated Tg of the shell copolymer. In the embodiment, the core polymer has a higher glass transition temperature (Tg) than the shell polymer. In the embodiment, the core polymer has a calculated Tg of about 20°C to about 80°C, or about -30°C to about 80°C, or about 40°C to about 80°C. In the embodiment, the shell copolymer has a calculated Tg of about -30°C to about 30°C, or about -30°C to about 15°C, or about -25°C to about 10°C. In the embodiment, the core-shell latex copolymer has a calculated Tg of about -20 to about 40°C. In the embodiment, the core-shell latex copolymer has a minimum film formation temperature of less than about 45°C, less than about 40°C, less than about 35°C, or less than about 30°C, without the presence of any binder or solvent. In the embodiment, the core-shell latex copolymer has an average volume particle size (dv50) of about 10 nm to about 1000 nm, or about 50 nm to about 500 nm, or about 50 nm to about 400 nm, as measured using laser diffraction according to ASTM 5861-07 (2017).

[0027] In embodiments, the pendant carbonyl groups of the core polymer and shell polymer are selected from keto groups, aldehyde groups, or combinations thereof. As used herein, the term “keto group” refers to a group in which a carbonyl group is bonded to two carbon atoms. A keto group can be represented by the formula R2C=O (wherein neither R is H). In embodiments, the core polymer and / or shell polymer also have an isocyanate-reactive group. In embodiments, the isocyanate-reactive group is selected from a hydroxyl group, an amine group, or combinations thereof. In embodiments, each of the core copolymer and shell copolymer is formed from a (meth)acrylate monomer represented by the above formula MA. In embodiments, each of the core copolymer and shell copolymer is formed from a vinyl aromatic monomer, optionally a monomer having at least two (meth)acrylate groups, a monomer having an allyl group and a (meth)acrylate group, and / or a hydroxyl-functionalized ethylenically unsaturated monomer. In the embodiment, the core copolymer and / or shell copolymer is formed from carbonyl-functionalized ethylenically unsaturated monomers. With respect to the (meth)acrylate monomer represented by formula MA, in the embodiment, the monomer is formula MA1: H2C=CG a CO2R a1 (MA1) (In the formula, G a R is hydrogen, halogen, or methyl, a1 (These are C1-C18 alkyl, C2-C18 heteroalkyl, C3-C18 cycloalkyl, C2-C8 heterocycloalkyl, C2-C8 alkenyl, or C2-C8 alkynyl.) It is represented by the formula MA2: H2C=CG a CO2Ra 2 (MA2) (In the formula, G a R is hydrogen, halogen, or methyl, a2(These are C6-C18 aryl, C1-C9 heteroaryl, C7-C18 alkoxyaryl, C7-C18 alkaryl, or C7-C18 aralkyl.) It is represented by [this].

[0028] With respect to vinyl aromatic monomers, in embodiments, vinyl aromatic monomers are represented by the formula (VA) defined above. In embodiments, vinyl aromatic monomers are selected from styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-tert-butylstyrene, 4-tert-butylstyrene, 2-chlorostyrene, 4-chlorostyrene, or combinations thereof. In the embodiment, the monomer having at least two (meth)acrylate groups is given by formula DA1: H2C=C(R m )-C(O)O-(R n O) p -O(O)CC(R m )=CH2(DA1) (In the formula, each R m Each is independently H or CH3, and each R n (These are independently C2-C4 alkylenes, and p is an integer between 1 and 8.) This is represented by [the formula shown]. In embodiments, the monomer is selected from tetraethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, or a combination thereof.

[0029] Suitable hydroxyl-functionalized ethylenically unsaturated monomers that can be used in the synthesis of core-shell latex copolymers include hydroxyalkyl esters having primary or secondary hydroxyl groups, derived from α,β-monoethylenically unsaturated monocarboxylic acids. Examples of these include hydroxyalkyl esters derived from acrylic acid, methacrylic acid, crotonic acid, or isocrotonic acid. Hydroxyl-functionalized ethylenically unsaturated monomers may be present in the core-shell latex copolymer in amounts of about 70% to about 100% by mass, or about 80% to about 100% by mass, or about 90% to about 100% by mass, based on the total mass of the hydroxyl-functionalized ethylenically unsaturated monomers. In the embodiment, the core-shell latex copolymer may be present in the surface-surface-inner part in an amount of about 5% to about 100% by mass, or about 10% to about 90% by mass, or about 15% to about 80% by mass, or about 30% to about 75% by mass, based on the total mass of the surface-surface-inner part.

[0030] In embodiments, the surface binder part further comprises an additional copolymer distinct from the core-shell latex polymer. The presence of the additional copolymer in the surface binder part may affect the crosslinking density of the cured film of the aqueous surfacer composition. The additional copolymer may also contribute to the stability of the cured film of the aqueous surfacer composition and / or the adhesion of the cured film of the aqueous surfacer composition to the substrate or other coating layer. The additional copolymer may contain functional groups that can participate in the crosslinking reaction. In embodiments, the additional copolymer is reactive to hydrazide groups. In embodiments, the additional copolymer is a water-dilutable hydroxyl-functional (meth)acrylate copolymer. In embodiments, the water-dilutable hydroxyl-functional (meth)acrylate copolymer has the characteristics described above with respect to a water-dilutable hydroxyl-functional (meth)acrylate copolymer present in the clear coat binder part. In the embodiment, the water-dilutable hydroxyl-functional (meth)acrylate copolymer is present in the surfacer buffer part in an amount of about 5% to about 70% by mass, or about 10% to about 50% by mass, based on the total mass of the surfacer buffer part.

[0031] In some embodiments, the surfacer underlayer part further comprises a polyhydrazide compound. Alternatively, the hydrazide compound can be provided separately as an additional surfacer part, distinct from the surfacer underlayer part and the surfacer crosslinking agent part. The polyhydrazide compound is reactive with pendant carbonyl groups in the core polymer and the shell copolymer. The polyhydrazide may also be reactive with additional copolymers other than the core-shell latex copolymer. The polyhydrazide compound is particularly suitable for reaction with keto groups. By including the polyhydrazide compound in the surfacer underlayer part, a double crosslinking reaction can occur when the surfacer underlayer part and the surfacer crosslinking agent part are combined (a polyhydrazide / carbonyl crosslinking reaction and an isocyanate / isocyanate-reactive group crosslinking reaction). The double crosslinking reaction accelerates the film formation process and contributes to the hardness of the coating layer obtained after curing. Furthermore, when a polyhydrazide compound is included in the aqueous surfacer composition, the crosslinking reaction can be initiated with less polyisocyanate addition than is required when the polyhydrazide compound is absent. Minimizing the amount of isocyanate present in the composition reduces the risk of popping in the coating system after all layers have cured.

[0032] In the embodiment, the polyhydrazide compound is a compound of at least two of the formula -C(=O)-NH-N(R h )(R i )(wherein, R h and R i The hydrazide group has independently H or C1-C12 alkyl. In embodiments, such a hydrazide group has a larger group, for example, of the formula -LC(=O)NH-N(R h )(R i)(wherein L is a divalent linking group selected from -O-, -NH-, C1-C18 alkylene, C2-C18 alkenylene, C3-C18 cycloalkylene, or C6-C18 arylene). In embodiments, the polyhydrazide has 2 to 5 hydrazide functional groups, or 2 to 4 hydrazide functional groups. The polyhydrazide can be polymer, nonpolymer, or a combination thereof. Examples of nonpolymer polyhydrazides include hydrazide derivatives of aliphatic, alicyclic, or aromatic polycarboxylic acids. In embodiments, the polyhydrazide is of the formula H2N-N(H)-C(O)-L 1 -C(O)-N(H)-NH2 (where L 1 is a covalent bond, C1-C 18 Alkylene, C2-C 18 Alkenylene, C3-C 18 Cycloalkylene, or C6-C 18 It is a dihydrazide having a divalent linking group selected from allylenes.

[0033] In the embodiment, the polyhydrazide compound is present in the surfacer buffer part in an amount of about 0.1% to about 30% by mass, or about 0.5% to about 15% by mass, or about 1% to about 10% by mass, based on the total mass of the aqueous surfacer composition. In the embodiment, the molar ratio of hydrazide groups to carbonyl groups in the aqueous surfacer composition is about 1:5 to about 5:1, or about 1:3 to about 3:1, or about 1:2 to about 2:1. In embodiments, the surfacer buffer part further comprises a surfactant. The surfactant may be selected from anionic surfactants, nonionic surfactants, amphoteric surfactants, cationic surfactants, reactive surfactants, or combinations thereof. In embodiments, the surfacer buffer part further comprises additional additives selected from polymer stabilizers, emulsifiers, buffers, inorganic electrolytes, biocides, defoamers, and / or pH adjusters. The surfacer crosslinking agent part contains the polyisocyanate compounds described above with respect to the clear coat crosslinking agent part. The surfacer crosslinking agent part may contain only one polyisocyanate compound, or it may contain two or more polyisocyanate compounds. The polyisocyanate compound may be present in the surfacer crosslinking agent part in an amount of about 30% to about 90% by mass, or about 40% to about 80% by mass, based on the total mass of the surfacer crosslinking agent part. The surfacer crosslinking agent part may further contain additional crosslinking agents different from the polyisocyanate compounds.

[0034] In the embodiment, the aqueous substrate composition is an aqueous encapsulant composition. After application of the aqueous encapsulant composition and curing of the resulting encapsulant layer, the encapsulant layer can protect the substrate and prevent chemicals from diffusing into and out of the substrate and / or the upper coating layer. The encapsulant layer can also provide a layer having uniform surface energy across its surface. In the embodiment, the aqueous encapsulant composition comprises a core-crosslinked acrylic latex resin, which is core-shell latex-free, and a polyurethane comprising a hydroxyl-functionalized reaction product of a polyol containing a polyisocyanate and a polycarbonate diol. As used herein, “core-crosslinked structure” means that the acrylic latex resin is characterized by a crosslinked structure obtained by using olefinic polyunsaturated monomers at all stages of emulsion polymerization. Thus, the structure of the acrylic latex resin is fully crosslinked as a result of the formation process prior to curing any composition containing the acrylic latex resin. In the embodiment, the aqueous primer composition is an aqueous basecoat composition. In the embodiment, the aqueous basecoat composition contains a compound that imparts color and / or visual effect. The aqueous basecoat composition is known in the art and can be used to form a basecoat layer.

[0035] The composite articles provided herein are formed from the coating systems provided herein. The composite articles include a substrate, a primer layer placed on the substrate, and a clear coat layer placed on the primer layer. The substrate is provided as a surface or object requiring protection by coating. The substrate may be selected from a variety of materials, such as metal, plastic, glass, or wood. The substrate may be an object or surface such as a structural wall, kitchen utensils, or automotive parts. In embodiments, the substrate may be coated by electrodeposition. For the purposes of this description, “substrate” includes any electrodeposition or other pretreatment present on the substrate prior to the formation of the primer layer on the substrate. There may be only one underlayer, or there may be two or more underlayers. The underlayer placed on the substrate may cover the entire surface of the substrate, or it may cover only a portion of the surface of the substrate. The underlayer may cover only one surface of the substrate, or it may cover multiple surfaces of the substrate. The underlayer is formed from an aqueous underlayer composition containing an acrylic latex resin, as described above. The thickness of the layer affects the performance parameters. A greater thickness generally provides stronger protection for the substrate, but a greater thickness can also lead to the formation and release of carbon dioxide from the reaction of isocyanate with water, resulting in more popping or surface defects. In embodiments, the underlayer is a surfacer layer with a thickness of about 30 μm to about 200 μm, or about 35 μm to about 130 μm. In embodiments, the underlayer is a sealant layer with a thickness of about 10 μm to about 30 μm, or about 15 μm to about 25 μm. In this embodiment, the underlayer is a primer layer having a film thickness of approximately 30 μm to approximately 180 μm, or approximately 40 μm to approximately 150 μm.

[0036] The clear coat layer is placed on top of the substrate layer. The clear coat layer may cover the entire surface of the substrate layer, or it may cover only a portion of the surface of the substrate layer. The clear coat layer is formed from the two-part aqueous clear coat composition described above. In the embodiment, the clear coat layer has a film thickness of about 30 μm to about 100 μm, or about 30 μm to about 90 μm, or about 40 μm to about 90 μm. In embodiments, the composite article includes a surfacer layer disposed on a substrate, a sealant layer disposed on the surfacer layer, a base coat layer disposed on the sealant layer, and a clear coat layer disposed on the base coat layer. The composite article may further include a tie layer disposed on the base coat layer and below the clear coat layer. In embodiments, a primer layer is also present. The primer layer may be disposed on the substrate and below the surfacer layer. In embodiments, either the surfacer layer or the sealant layer may be absent. In embodiments, the composite article does not contain any layers formed from a solvent-based coating composition.

[0037] The coating systems and composite articles provided herein are characterized by the performance parameters of the cured layer formed from the aqueous coating composition on a substrate. Specifically, a cured film of an aqueous clear coat composition having a thickness of 67.5 μm on a cured film of an aqueous undercoat composition having a thickness of 20 μm placed on a substrate exhibits a popping density of less than approximately 3 pops per square centimeter, or less than approximately 2.5 pops per square centimeter, or less than approximately 2.2 pops per square centimeter, or about 0 to about 2.2 pops per square centimeter, as measured by visual observation with the naked eye at a distance of 30 cm under a fluorescent light source. The stated performance can be achieved under various conditions. For example, the stated performance can be achieved by flash-drying the film for 5 to 15 minutes, and then curing it for 30 minutes in an oven preheated to a heating drying temperature of about 60°C at an airflow rate of about 35 m / min to about 55 m / min. The performance described can also be achieved by flash-drying the film for 5 to 15 minutes, then curing it for 30 minutes in an oven set to a heating and drying temperature of approximately 60°C without preheating, with the temperature gradually increasing over a period of approximately 7 to 10 minutes, and with an airflow of approximately 10 to 25 meters per minute. The performance described can also be achieved by air-drying the film, for example, overnight.

[0038] In the embodiment, a cured film of an aqueous clear coat composition having a thickness of 67.5 μm, placed on a cured film of an aqueous primer composition having a thickness of 20 μm on a substrate, exhibits a popping density of less than about 0.1 pops per square centimeter, or about 0 to about 0.1 pops per square centimeter. The stated performance can be achieved under various conditions as described above. In particular, the stated performance can be achieved when the film is flash-dried for 5 to 15 minutes, then cured for 30 minutes in an oven set to a heating drying temperature of about 60°C without preheating, with the temperature increased over a period of about 7 to about 10 minutes, and the airflow is about 10 m / min to about 25 m / min. In the embodiment, a cured film of an aqueous clear coat composition having a thickness of 67.5 μm, placed on a cured film of an aqueous primer composition having a thickness of 120 μm on a substrate, exhibits a popping density of less than approximately 3 pops per square centimeter, or less than approximately 2.5 pops per square centimeter, or less than approximately 2.2 pops per square centimeter, or about 0 to about 2.2 pops per square centimeter, as measured by visual observation with the naked eye at a distance of 30 cm under a fluorescent light source. In particular, the performance described can be achieved in embodiments where the aqueous primer composition is an aqueous surfacer composition. The performance described can be achieved under various conditions as described above.

[0039] In the embodiment, a cured film of an aqueous clear coat composition having a thickness of 67.5 μm, placed on a cured film of an aqueous primer composition having a thickness of 120 μm on a substrate under commercially available spray booth conditions, exhibits a popping density of less than about 0.1 pops per square centimeter, or about 0 to about 0.1 pops per square centimeter. In particular, the stated performance can be achieved in embodiments where the aqueous primer composition is an aqueous surfacer composition. The stated performance can be achieved under a variety of conditions as described above. In particular, the stated performance can be achieved when the film is flash-dried for 5 to 15 minutes, then cured for 30 minutes in an oven set to a heating drying temperature of about 60°C without preheating, with the temperature increased over a period of about 7 to about 10 minutes, and the airflow is about 10 m / min to about 25 m / min. As used herein, “popping density” refers to the number of pops present per square centimeter of surface area of ​​a clear coat layer. “Pop” refers to a surface defect resulting from the formation of carbon dioxide within the layer and subsequent eruption of carbon dioxide. The resulting pops may take the form of bubbles, depressions, indentations, or other surface defects. For the purposes of this disclosure, the popping density is measured by visually observing a 1cm × 8cm surface area of ​​the clear coat layer at a distance of 30cm under a fluorescent light source. The number of pops in that area is counted, and the number of pops is divided by the observed area (Popping Density = Number of Pops / 8cm). 2 In this embodiment, three separate regions of the coating layer are observed to determine the popping density of each region, and the average popping density across the three regions is reported (average popping density = (popping density of region 1 + popping density of region 2 + popping density of region 3) / 3).

[0040] The stated popping density of less than approximately 3 pops per square centimeter may not be achievable with existing aqueous coating systems when the cured film of the aqueous clear coat composition has a thickness of 67.5 μm and the cured film of the underlying aqueous substrate composition has a thickness of 20 μm. As explained above, multilayer aqueous coating systems tend to exhibit an unacceptable amount of popping, resulting from the reaction of water and isocyanate within the layers to form carbon dioxide, which "pops" out from the coating surface. As the thickness of each aqueous layer increases, the layers have a larger volume, creating the potential for more water and isocyanate to remain within the layers, thus tending to increase the number of popping instances. In many existing aqueous coating systems, the thickness of the aqueous layers should be less than the stated thickness to achieve a popping density of less than approximately 3 pops per square centimeter. Thinner coating systems do not provide the same level of protection to the substrate as thicker coating systems.

[0041] While not bound by any particular theory, it is believed that a specific combination of a water-dilutable hydroxyl-functional (meth)acrylate copolymer and a polyisocyanate compound in an aqueous clear coat composition allows the polyisocyanate compound to emulsify rapidly, minimizing the amount of polyisocyanate remaining in the layer. Therefore, it is thought that the reaction of any remaining isocyanate with water trapped in the layer to form carbon dioxide, which can cause popping on the surface of the clear coat layer, is suppressed. In the embodiment, a multilayer coating comprising a cured film of an aqueous clear coat composition and a cured undercoat film of an aqueous undercoat composition is evaluated by a cross-cut tape test using the standard methods ASTM D2247-92 and ASTM D3359-92A, and exhibits at least equivalent wet adhesion performance to that of a multilayer coating comprising a cured film of a solvent-based clear coat composition and a cured undercoat film of a solvent-based undercoat composition. In the embodiment, a multilayer coating comprising a cured film of an aqueous clear coat composition and a cured undercoat film of an aqueous undercoat composition is evaluated using a BYK® wave-scan Orange Peel Meter, and exhibits at least equivalent appearance characteristics to those of a multilayer coating comprising a cured film of a solvent-based clear coat composition and a cured undercoat film of a solvent-based undercoat composition.

[0042] A method for forming a composite article is also provided herein. This method includes the steps of: applying an aqueous primer composition containing an acrylic latex resin to a substrate to form a primer layer on the substrate; applying an aqueous clear coat composition to the primer layer to form a clear coat layer on the primer layer; and curing the primer layer and the clear coat layer. In embodiments, if the aqueous primer composition is a multi-part composition, the parts of the aqueous primer composition are combined and mixed before applying the aqueous primer composition to the substrate. In embodiments, the clear coat binder part and the clear coat crosslinking agent part of a two-part aqueous clear coat composition are combined and mixed before applying the aqueous clear coat composition onto the aqueous primer layer. The steps of applying the aqueous primer composition and applying the aqueous clear coat composition may include any known application method. For example, the aqueous primer composition may be applied by spraying, brushing, rolling, sprinkling, or dipping. The aqueous primer composition and the aqueous clear coat composition may be applied using the same method, or alternatively, the aqueous primer composition and the aqueous clear coat composition may be applied using different methods. The step of curing the resulting primer and clear coat layers may include air drying, flash drying, heat drying, or any other known curing method. Air drying may be carried out at a temperature of about 25°C for a period of about 15 minutes to about 24 hours, or about 1 hour to about 12 hours. Flash drying may be carried out for a period of about 5 minutes to about 15 minutes. The film may be flash dried and then heat dried. Heat drying may be carried out at a temperature of about 40°C to about 80°C, or about 50°C to about 70°C, for a period of about 15 minutes to about 2 hours, or about 15 minutes to about 1 hour. The primer and clear coat layers may be cured simultaneously (i.e., wet-on-wet application), or alternatively, the primer and clear coat layers may be cured sequentially. In embodiments, the primer is cured before applying the aqueous clear coat composition. [Examples]

[0043] (Examples 1-3 and Comparative Example 1) Two water-dilutable hydroxyl-functional (meth)acrylate copolymer resins were prepared. Resin 1 was prepared according to the synthesis example in U.S. Patent Application No. 63 / 624,392. Resin 2 was prepared according to European Patent No. 1784463. The properties of Resin 1 and Resin 2 are shown in Table 1 below.

[0044] [Table 1]

[0045] In Table 1, Tg is the glass transition temperature in degrees Celsius, calculated using the Fox formula. The OH value is the hydroxyl value analyzed according to the standard test method ASTM D4274-11. The acid value is determined according to ASTM D974-22. The solids content is the mass percentage based on the total mass of the resin. The molecular weight is the mass-average molecular weight in Dalton, measured by gel permeation chromatography (GPC) using a polystyrene calibration standard, according to ASTM 3536. Next, a 2-part (2k) clear coat composition (clear coat 1 and clear coat 2) was prepared. First, parts A and B were prepared according to Table 2 below.

[0046] [Table 2]

[0047] [Table 3]

[0048] The percentages in Table 2 represent the mass percentage of each component, based on the total mass of the deionized (DI) water diluent, which is made by adding both Part A and Part B to reach a total of 100%. For both Clear Coat 1 and Clear Coat 2, Part B was added to Part A and mixed until uniform. Then, DI water diluent was added to each mixture, and each mixture was mixed again to form the clear coat composition. Next, an electrodeposited panel was obtained. In Examples 1 and 2, the aqueous clear coat compositions Clear Coat 1 and Clear Coat 2 described above were spray-applied onto the electrodeposited panel, respectively, to form a clear coat layer having a thickness of 67.5 μm. The clear coat layer was flash-dried for 10 minutes, and then heat-dried for 30 minutes in an oven preheated to 60°C with an airflow rate in the range of 35 to 55 meters per minute.

[0049] In Example 3, an aqueous sealant composition available from Spies Hecker® GmbH under the trademark name Permahyd® 5650 was spray-applied to an electrodeposited panel to form a sealant layer with a thickness of 20 μm. The sealant layer was air-dried. Next, a commercially available aqueous metallic blue basecoat composition was spray-applied onto the sealant layer to form a basecoat layer with a thickness of 15 μm. The basecoat layer was flash-dried at a temperature of 25°C for 30 minutes. Next, the above-mentioned clearcoat 2, which is an aqueous clearcoat composition, was spray-applied onto the basecoat layer to form a clearcoat layer with a thickness of 67.5 μm. The layer was flash-dried for 10 minutes, and then heat-dried in an oven preheated to 60°C at an airflow rate in the range of 35 to 55 meters per minute for 30 minutes. In Comparative Example 1, the procedure of Example 3 was followed, except that a clear coat layer was formed using Clear Coat 1, which is a clear coat composition.

[0050] The popping density of Examples 1-3 and Comparative Example 1 was measured by visually observing a 1cm x 8cm surface area on the surface of the clear coat layer under a fluorescent light source at a distance of 30cm. The number of pops in that area was counted and divided by the observed area (Popping density = Number of pops / 8cm). 2For each example, three separate regions were observed, the popping density of each region was determined, and the average popping density across the three regions was reported (average popping density = (popping density of region 1 + popping density of region 2 + popping density of region 3) / 3). The results are shown in Table 3 below.

[0051] [Table 4]

[0052] For Example 3 and Comparative Example 1, the appearance of the coating system was evaluated by measuring image clarity (DOI), shortwave (SW), longwave (LW), and du (matteness). Specifically, DOI was measured using the ASTM D5767-18 standard test method for instrumental measurement of image clarity (DOI) gloss on coated surfaces. The values ​​obtained by the measurement procedure of this test method range from 0 to 100, with a value of 100 representing perfect DOI (clear image). As the value decreases from 100, the image becomes more distorted. A wave scan was performed using a Wavescan-DOI instrument available from BYK-Gardner GmbH, intended to simulate the visual impression. This instrument provided a laser point source illuminating the sample at a 60° angle. The accompanying detector measured the reflected light intensity at equal but opposite angles. The shortwave signal (structure size <0.6 mm) was separated from the measured signal using a mathematical filtering function. The meter was rolled along the surface, and the optical profile of the surface between two ends of a predetermined distance was measured point by point. The short-term waviness values ​​provided in Table 4 represent the variation in short-wave signal amplitude and are normalized to a unitless value within the range of 0 to 100, where 0 represents the smallest variation (best) and 100 represents the largest variation (worst). Matteness was measured using a Wavescan-DOI instrument available from BYK-Gardner GmbH. A green light-emitting diode (LED) illuminated the sample at an angle of 20°. Diffuse light (produced by surface structures smaller than 0.1 mm in size) was measured by a charge-coupled device (CCD) camera. In operation, the CCD camera analyzes the reflected image of the aperture of the light source. If the coated sample does not have fine microtextures, all the light will be detected within the image of the aperture (Lmax); otherwise, the light will be detected outside (Lscatter). The ratio of these two components (Lscatter / Lmax) is defined as matteness (structural size < 0.1 mm). Since the matteness measurement is relative and not absolute, it is independent of the refractive index and surface curvature. The results are shown in Table 4 below.

[0053] [Table 5] Examples 1-3 and Comparative Example 1 demonstrate that the aqueous clear coat does not exhibit popping in the absence of an aqueous undercoat. When an aqueous undercoat is added, the clear coat composition having resin 1 performs better than the clear coat composition having resin 2 in terms of popping density and appearance characteristics.

[0054] (Example 4) An electrodeposited panel was obtained. In Example 4, an aqueous sanding surfacer (surfacer 1) containing an aliphatic polyisocyanate, as described in Japanese Patent Application No. 63 / 709,854, was spray-applied to the coating panel to form a surfacer layer with a thickness of 75 μm. The surfacer layer was air-dried overnight in a room at a temperature of 25°C. Next, an aqueous metallic black basecoat was spray-applied onto the surfacer layer to form a basecoat layer with a thickness of 15 μm. The basecoat layer was air-dried. Next, the above-mentioned clearcoat 1, which is an aqueous clearcoat composition, was spray-applied onto the basecoat layer to form a clearcoat layer with a thickness of 52 μm. The layer was flash-dried for 10 minutes, and then heated and dried for 30 minutes in an oven set to 60°C and heated from room temperature to 60°C, at an airflow rate in the range of 10 to 25 meters per minute. (Comparative Example 2) In Comparative Example 2, a commercially available solvent-based sanding surfacer was spray-applied onto the coating panel to form a surfacer layer with a thickness of 75 μm. The surfacer layer was air-dried overnight in a room at a temperature of 25°C. Next, a metallic black aqueous basecoat was spray-applied onto the surfacer layer to form a basecoat layer with a thickness of 15 μm. The basecoat layer was air-dried. Then, the above-mentioned clearcoat 1, which is an aqueous clearcoat composition, was spray-applied onto the basecoat layer to form a clearcoat layer with a thickness of 52 μm. The layer was flash-dried for 10 minutes, and then heat-dried for 30 minutes in an oven preheated to 60°C at an airflow rate in the range of 35 to 55 meters per minute. For each of Example 4 and Comparative Example 2, the popping density was evaluated in the same manner as described above for Examples 1 to 3. The results are shown in Table 7 below.

[0055] [Table 6]

[0056] The results in Table 7 show that, when used in combination with an aqueous base coat and an aqueous clear coat, the coating system using aqueous surfacer 1 functions equivalently to the coating system using a solvent-based surfacer. (Examples 5-8) A 2-part (2k) clear coat composition (clear coat 3) was prepared. First, parts A and B were prepared according to Table 5 below.

[0057] [Table 7]

[0058] [Table 8]

[0059] The percentages in Table 5 represent the mass percentage of each component, based on the total mass of the deionized (DI) water diluent, which is made by adding both Part A and Part B to reach a total of 100%. Polyester 1 is a non-aromatic polyester having active hydrogen groups, prepared according to the synthesis example of U.S. Patent Application No. 63 / 624,388. For Clear Coat 3, Part B was added to Part A and mixed until uniform. Then, DI water diluent was added to each mixture, and each mixture was mixed again to form the Clear Coat composition.

[0060] A core-shell latex copolymer (Resin 3) having pendant hydroxyl groups and pendant carbonyl groups was prepared in accordance with Japanese Patent Application No. 63 / 709,857. The monomers used to form the core-shell latex copolymer contained 3.7% by mass of carbonyl-functionalized ethylenically unsaturated monomers based on the total mass of the monomer mixture. The characteristics of Resin 3 were measured as described above for Resin 1 and Resin 2. The core copolymer of Resin 3 had a calculated Tg at 69.5°C, and the shell copolymer of Resin 3 had a calculated Tg at 0.7°C. Resin 3 had an acid value of 0.9 mg KOH / g, a hydroxyl value of 12.2 mg KOH / g, and a solids content of 46.3%. Mill base (Mill base 1) was formed by grinding the components shown in Table 8 together in the amounts shown in Table 8.

[0061] [Table 9]

[0062] The percentages in Table 8 represent the mass percentage of each component, based on the total mass in the mill base. Dispersant 1 is a solution of acrylic resin having an acid value of 106 mg KOH / g. Dispersant 2 is a solution of an acrylic resin having a hydroxyl functional group and an acid value of 44 mg KOH / g. The rust inhibitor additive is a liquid rust inhibitor sold by ICL Performance Products LP under the trademark name Halox® Flash X-150. The nonionic surfactant is a 75% by mass solution of Surfonyl® 104H in ethylene (ethyl) glycol monobutyl ether, which is commercially available from Evonik Industries.

[0063] The components shown in Table 9 were used in the amounts shown in Table 9 to form a black dispersion (black dispersion 1). [Table 10]

[0064] The percentages in Table 9 represent the mass percentage of each component relative to the total mass of the black dispersion. Dispersant 3 is a polymer dispersant commercially available from The Lubrizol Corporation under the trademark name Solsperse® 27000. The nonionic surfactant is a 75% by mass solution of Surfonyl® 104H in ethylene (ethyl) glycol monobutyl ether, which is commercially available from Evonik Industries. To form a black dispersion, all components of Table 9 except carbon black were added to a container and mixed using an air mixer for 15 minutes. Then, without stopping the air mixer, carbon black was added to the container. Mixing was continued for a further 30 minutes. The resulting dispersion was ground using an LMZ mill and then filtered through a 10 μm filter to form black dispersion 1.

[0065] Two aqueous sanding surfacer compositions were prepared, each containing the components shown in Table 10 in the amounts shown in Table 10. [Table 11]

[0066] [Table 12]

[0067] The percentages in Table 10 represent the mass percentage of each component, based on the total mass of both Part A and Part B. To form Surfacer 2 and Surfacer 3 using the components shown in Table 10 above, Resin 3 and dihydrazide adipic acid (ADH) were mixed for 10 minutes in a high-speed mixer-disperser operating at 1000 rpm. Then, Mill Base 1 and Black Dispersion 1 were added and mixed for a further 30 minutes. Next, the components of Part B in Table 10 were added to form the final composition.

[0068] In Example 5, Surfacer 2, a sanding surfacer composition, was spray-applied onto an electrodeposited panel to form a surfacer layer with a thickness of 50 μm. The surfacer layer was air-dried in a room at a temperature of 25°C for 3 hours. The surfacer layer was then sanded. A commercially available metallic blue aqueous basecoat composition was spray-applied onto the surfacer layer to form a basecoat layer with a thickness of 15 μm. The basecoat layer was air-dried. Clearcoat 3, a clearcoat composition, was spray-applied onto the basecoat layer to form a clearcoat layer with a thickness of 55 μm. The clearcoat layer was flash-dried for 10 minutes, and then heat-dried for 30 minutes in an oven set to 60°C and heated from room temperature to 60°C with an airflow rate in the range of 10 to 25 meters per minute.

[0069] In Example 6, the procedure was the same as in Example 5, except that the thickness of the surfacer layer was 100 μm. In Example 7, the procedure of Example 5 was followed, except that a surfacer layer was formed using Surfacer 3, which is a sanding surfacer composition. In Example 8, the procedure was the same as in Example 7, except that the thickness of the surfacer layer was 100 μm.

[0070] (Comparative Examples 3-6) In Comparative Example 3, a commercially available solvent-based sanding surfacer composition was spray-applied onto an electrodeposited panel to form a surfacer layer with a thickness of 50 μm. The surfacer layer was air-dried in a room at a temperature of 25°C for 3 hours. The surfacer layer was then sanded. A commercially available metallic blue aqueous basecoat composition was spray-applied onto the surfacer layer to form a basecoat layer with a thickness of 15 μm. The basecoat layer was air-dried. Clearcoat 3, a clearcoat composition, was spray-applied onto the basecoat layer to form a clearcoat layer with a thickness of 55 μm. The clearcoat layer was flash-dried for 10 minutes, and then heat-dried for 30 minutes in an oven set to 60°C and heated from room temperature to 60°C with an airflow rate in the range of 10 to 25 meters per minute.

[0071] In the case of Comparative Example 4, the procedure was the same as in Comparative Example 3, except that the surfacer layer had a thickness of 100 μm. In Comparative Example 5, the procedure was followed in the same manner as in Comparative Example 3, except that a commercially available solvent-based clear coat composition was used to form the clear coat layer. In Comparative Example 6, the procedure was the same as in Comparative Example 5, except that the surfacer layer had a thickness of 100 μm. For Examples 5-8 and Comparative Examples 3-6, the popping performance was rated as "pass" or "fail." Here, "pass" means that the popping density was less than 0.1 pops per square centimeter, and "fail" means that the popping density was greater than 0.1 pops per square centimeter. The visual characteristics were evaluated by measuring the DOI for Examples 1-3, as described above. The results are shown in Table 11 below.

[0072] [Table 13]

[0073] The results in Table 11 show that an all-aqueous coating system using Clear Coat 2 in combination with Surfacer 2 or Surfacer 3 functions similarly to a system in which the Clear Coat and / or Surfacer are replaced with a solvent-based composition. (Comparative Examples 7-8) Millbase (Millbase 2) was prepared by grinding the components shown in Table 12 together in the amounts shown in Table 12.

[0074] [Table 14]

[0075] A sanding surfacer composition (surfacer 4) was formed using the components shown in Table 13 in the amounts shown in Table 13. [Table 15]

[0076] [Table 16]

[0077] The percentages in Table 13 represent the mass percentage of each component, based on the total mass of both Part A and Part B. To form the composition for Surfacer 4, the components of Part A shown in Table 13 were combined and mixed for 30 minutes in a high-speed mixer-disperser operating at 1000 rpm. The components of Part B shown in Table 13 were blended separately. In Comparative Example 7, Surfacer 4, a sanding surfacer composition, was spray-applied onto an electrodeposited panel to form a surfacer layer. The surfacer film thickness varied from 50 μm to 150 μm between the two ends of the panel. The surfacer layer was flash-dried for 10 minutes, and then heated and dried for 30 minutes in an oven set to 60°C and heated from room temperature to 60°C, with an airflow rate ranging from 10 to 25 meters per minute. In Comparative Example 8, the procedure was the same as in Comparative Example 7, except that a surfacer layer was formed using a commercially available two-part aqueous sanding surfacer based on an isocyanate that reacts with the acrylate dispersion.

[0078] After heat drying, instances of popping were visually observed on the surface of the surfacer layer on each coated panel. In both Comparative Example 7 and Comparative Example 8, the amount of popping per square centimeter increased as the film thickness increased. The film thickness at which popping became visible ("critical film thickness") was recorded for each coated panel. In Comparative Example 7, the critical film thickness was 120 μm. In Comparative Example 8, the critical film thickness was 70 μm. Comparative Examples 7 and 8 demonstrate that Surfacer 4 exhibits better popping performance than commercially available water-based surfacers. (Example 9 and Comparative Example 9) In Example 9, Surfacer 4, a sanding surfacer composition, was spray-applied onto an electrodeposited panel to form a surfacer layer with a thickness of 70 μm. The surfacer layer was then heat-dried for 30 minutes in an oven set to 60°C and heated from room temperature to 60°C, with an airflow rate in the range of 10 to 25 meters per minute. A black aqueous basecoat composition was spray-applied onto the surfacer layer to form a basecoat layer with a thickness of 13 μm. The basecoat layer was air-dried. Then, Clearcoat 3, a clearcoat composition, was spray-applied onto the basecoat layer to form a clearcoat layer with a thickness of 48 μm. The layer was flash-dried for 10 minutes, and then heat-dried for 30 minutes in an oven set to 60°C and heated from room temperature to 60°C, with an airflow rate in the range of 10 to 25 meters per minute.

[0079] In Comparative Example 9, except that the surface layer was formed using the commercially available aqueous surfacer composition described above for Comparative Example 8, the surfacer layer had a thickness of 59 μm and the clear coat layer had a thickness of 46 μm, following the procedure of Example 9. For Example 9 and Comparative Example 9, the popping performance was graded as "pass" or "fail," as described above for Examples 5-8. The external characteristics were evaluated by measuring DOI, LW, SW, and du, as described above for Examples 1-3. Gloss at a 20° angle was also measured using a micro TRI gloss device manufactured by Byk Gardner (Germany). Reflected light was measured at a 20° angle. The results are shown in Table 14 below.

[0080] [Table 17]

[0081] Clear Coat 3 exhibits acceptable popping density and appearance characteristics when combined with various water-based surfacers. This result also indicates that the layer formed from Surfacer 4 has a greater film thickness than the layer formed from commercially available water-based surfacers, while still exhibiting comparable popping performance. While the above-described modes for carrying out the invention have presented at least one exemplary embodiment, it should be recognized that a vast number of variations exist. It should also be recognized that the exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of the Disclosure. Rather, the above-described modes for carrying out the invention provide a convenient roadmap for those skilled in the art to carry out the exemplary embodiments of the Disclosure. It should be understood that various modifications to the function and arrangement of the elements described in the exemplary embodiments may be made without departing from the scope of the Disclosure as stated in the accompanying claims.

Claims

1. It is a coating type, A water-based primer composition containing an acrylic latex resin, It is a two-part aqueous clear coat composition. A clear coat binder part containing a water-dilutable hydroxyl-functionalized (meth)acrylate copolymer, and Clear coat crosslinking agent part containing a polyisocyanate compound having a pendant-NCO group A two-part aqueous clear coat composition containing Includes, The molar ratio of active hydrogen atoms to -NCO groups in the aqueous clear coat composition is approximately 1:5 to approximately 5:

1. A cured film of an aqueous clear coat composition having a thickness of 67.5 μm, placed on a substrate and cured on an aqueous primer composition having a thickness of 20 μm, exhibits a popping density of less than approximately 3 pops per square centimeter, as measured by visual observation with the naked eye at a distance of 30 cm under a fluorescent light source. Coating type.

2. The coating system according to claim 1, wherein the aqueous primer composition is an aqueous sealing material composition.

3. The coating system according to claim 1, wherein the aqueous dilutable hydroxyl-functionalized (meth)acrylate copolymer of the aqueous clear coat composition has a glass transition temperature of about 20°C to about 50°C, calculated using the Fox formula.

4. The coating system according to claim 1, wherein the aqueous dilutable hydroxyl-functionalized (meth)acrylate copolymer of the aqueous clear coat composition has a hydroxyl value of about 110 mg KOH / g to about 160 mg KOH / g as analyzed according to the standard test method ASTM D4274-11.

5. The coating system according to claim 1, wherein the aqueous dilutable hydroxyl-functionalized (meth)acrylate copolymer of the aqueous clear coat composition has an acid value of about 20 mg KOH / g to about 40 mg KOH / g.

6. The coating system according to claim 1, wherein the aqueous dilutable hydroxyl-functional (meth)acrylate copolymer of the aqueous clear coat composition has a mass-average molecular weight of about 10,000 daltons to about 30,000 daltons, as measured by gel permeation chromatography using a polystyrene calibration standard in accordance with ASTM 3536.

7. In the aqueous clear coat composition, the water-dilutable hydroxyl-functional (meth)acrylate copolymer, based on the total mass of monomers, Approximately 20 to 60% by mass of (i) a hydroxyl functional adduct of a monoepoxy ester and an unsaturated carboxylic acid, Approximately 10 to 30% by mass of (ii) a hydroxyl-functionalized unsaturated monomer different from compound (i), Approximately 2 to 6% by mass of (iii) unsaturated acid functional monomers, Approximately 20 to approximately 60% by mass, (iv) formula MA: H 2 C=CG a CO 2 R a (MA) (In the formula, G a is hydrogen, halogen, or methyl, R a is C 1 -C 18 alkyl, C 2 -C 18 heteroalkyl, C 3 -C 18 cycloalkyl, C 2 -C 8 heterocycloalkyl, C 2 -C 8 alkenyl, or C 2 -C 8 (is alkynyl) (Meth)acrylate monomers represented by (v) at least one vinyl aromatic monomer, in an amount of approximately 0 to approximately 15% by mass, Approximately 0 to approximately 20% by mass of at least one polymerizable unsaturated monomer different from (vi)(i) to (v). The coating system according to claim 1, wherein the coating system is a reaction product of monomers in a monomer mixture containing the above.

8. A water-based primer composition, A surfacer buffer part comprising a core-shell latex containing a core copolymer and a shell copolymer, wherein the core copolymer and the shell copolymer have pendant carbonyl groups. The coating system according to claim 1, which is an aqueous surfacer composition containing the following.

9. The coating system according to claim 8, wherein a cured film of an aqueous clear coat composition having a thickness of 67.5 μm, placed on a cured film of an aqueous primer composition having a thickness of 120 μm on a substrate, exhibits a popping density of less than approximately 3 pops per square centimeter, as measured by visual observation with the naked eye at a distance of 30 cm under a fluorescent light source.

10. The coating composition according to claim 8, wherein the surface buffer part further comprises a water-dilutable hydroxyl-functionalized (meth)acrylate copolymer.

11. The coating composition according to claim 8, wherein the surface buffer part further comprises a polyhydrazide compound.

12. The coating composition according to claim 8, wherein the molar ratio of hydrazide groups to carbonyl groups in the aqueous surfacer composition is about 1:5 to about 5:

1.

13. The polyhydrazide compound contains at least two compounds of the formula -C(=O)-NH-N(R h ) (Caution i ) (wherein, R h and R i H or C 1 -C 12 The coating system according to claim 11, having a hydrazide group (which is alkyl).

14. A water-based surfacer composition, Surface crosslinking agent part containing polyisocyanate compounds The coating system according to claim 8, further comprising a two-part composition.

15. Each of the core copolymer and shell copolymer in the aqueous surfacer composition is Formula MA: H 2 C=CG a CO 2 R a (MA) (In the formula, G a is hydrogen, halogen, or methyl, R a C 1 -C 18 Alkyl; C 2 -C 18 Heteroalkyl; C 3 -C 18 Cycloalkyl; C 2 -C 8 Heterocycloalkyl; C 2 -C 8 Alkenil; C 2 -C 8 Alkinyl; C 6 -C 18 Ariel, C 1 -C 9 Heteroaryl, C 7 -C 18 Alkoxyaryl, C 7 -C 18 Alkaline, or C 7 -C 18 (It is Aralkir) The coating system according to claim 8, formed from a (meth)acrylate monomer represented by

16. Each of the core copolymer and shell copolymer in the aqueous surfacer composition is Vinyl aromatic monomer, A monomer having at least two (meth)acrylate groups, A monomer having an allyl group and a (meth)acrylate group, and / or Hydroxyl-functionalized ethylenically unsaturated monomers A coating system according to claim 8, formed from the above.

17. The coating system according to claim 8, wherein the core copolymer and / or shell copolymer in the aqueous surfacer composition is formed from a carbonyl-functionalized ethylenically unsaturated monomer.

18. base material, A base layer formed from an aqueous base composition containing an acrylic latex resin, which is placed on a substrate, and Placed on top of the subsoil layer, A clear coat binder part containing a water-dilutable hydroxyl-functionalized (meth)acrylate copolymer, and Clear coat crosslinking agent part containing a polyisocyanate compound having a pendant-NCO group A clear coat layer formed from a two-part aqueous clear coat composition, including A composite article including, The molar ratio of active hydrogen atoms to -NCO groups in the aqueous clear coat composition is approximately 1:5 to approximately 5:

1. When the base layer has a thickness of 20 μm and the clear coat layer has a thickness of 67.5 μm, the clear coat layer exhibits a pop density of less than approximately 3 pops per square centimeter, as measured by visual observation with the naked eye at a distance of 30 cm under a fluorescent light source. Composite goods.

19. The composite article according to claim 18, which does not contain any layer formed from a solvent-based coating composition.

20. A method for forming a composite article, The step of applying an aqueous primer composition containing an acrylic latex resin to a substrate to form a primer layer placed on the substrate, The step involves applying an aqueous clear coat composition to a substrate to form a clear coat layer placed on top of the substrate. A water-based clear coat composition, A clear coat binder part containing a water-dilutable hydroxyl-functionalized (meth)acrylate copolymer, and Clear coat crosslinking agent part containing a polyisocyanate compound having a pendant-NCO group The aqueous clear coat composition contains such that the molar ratio of active hydrogen atoms to -NCO groups is approximately 1:5 to approximately 5:

1. Steps, and Steps to cure the base layer and the clear coat layer. Includes, Before applying the water-based clear coat composition to the substrate, mix the clear coat binder part and the clear coat crosslinking agent part. When the base layer has a thickness of 20 μm and the clear coat layer has a thickness of 67.5 μm, the clear coat layer exhibits a pop density of less than approximately 3 pops per square centimeter, as measured by visual observation with the naked eye at a distance of 30 cm under a fluorescent light source. method.

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