Low Temperature Cure Coating Composition

Abstract

A coating composition includes: an aqueous medium; first core-shell particles dispersed in the aqueous medium, where the first core-shell particles include (i) keto and/or aldo functional groups, (ii) a polymeric shell including carboxylic acid functional groups and urethane linkages, and (iii) a polymeric core at least partially encapsulated by the polymeric shell, where the polymeric shell and/or the polymeric core may comprise the keto and/or aldo functional groups; second core-shell particles dispersed in the aqueous medium, where the second core-shell particles are different from the first core-shell particles and include (a) a polymeric shell including carboxylic acid functional groups and hydroxyl groups, and (b) a polymeric core including hydroxyl functional groups and which is at least partially encapsulated by the polymeric shell; a first crosslinker including a polyhydrazide reactive with the first core-shell particles; and a second crosslinker reactive with the first and second core-shell particles.

Claims

1. A coating composition, comprising: an aqueous medium; first core-shell particles dispersed in the aqueous medium, wherein the first core-shell particles comprise (i) keto and/or aldo functional groups, (ii) a polymeric shell comprising carboxylic acid functional groups and urethane linkages, and (iii) a polymeric core at least partially encapsulated by the polymeric shell, wherein the polymeric shell and/or the polymeric core may comprise the keto and/or aldo functional groups; second core-shell particles dispersed in the aqueous medium, wherein the second core-shell particles are different from the first core-shell particles and comprise (a) a polymeric shell comprising carboxylic acid functional groups and hydroxyl groups, and (b) a polymeric core comprising hydroxyl functional groups and which is at least partially encapsulated by the polymeric shell; a first crosslinker comprising a polyhydrazide reactive with the first core-shell particles; and a second crosslinker reactive with the first core-shell particles and the second core-shell particles, wherein the polymeric core of the first and second core-shell particles are covalently bonded to at least a portion of the corresponding polymeric shell.

2. The coating composition of claim 1, wherein the polymeric core and polymeric shell of the second core-shell particles comprise an addition polymer derived from ethylenically unsaturated monomers, and wherein the addition polymer comprises hydroxyl functional groups and carboxylic acid functional groups.

3. The coating composition of claim 2, wherein the addition polymer of the polymeric core is crosslinked.

4. The coating composition of claim 1, wherein the polymeric core of the second core-shell particles is free of carboxylic acid functional groups.

5. The coating composition of claim 1, wherein the keto and/or aldo functional groups of the first core-shell particles are formed on the polymeric shell.

6. The coating composition of claim 5, wherein the first core-shell particles are obtained from reactants comprising: a polyurethane prepolymer comprising an isocyanate functional group, an ethylenically unsaturated group, and carboxylic acid functional groups; ethylenically unsaturated monomers different from the polyurethane prepolymer; and a Michael Addition reaction product of ethylenically unsaturated monomers comprising a keto and/or aldo functional group, and a compound comprising at least two amino groups.

7. The coating composition of claim 1, wherein the keto and/or aldo functional groups of the first core-shell particles are formed on the polymeric core.

8. The coating composition of claim 7, wherein the first core-shell particles are obtained from reactants comprising: ethylenically unsaturated monomers, wherein at least one of the ethylenically unsaturated monomers comprises keto and/or aldo functional groups; and a polyurethane prepolymer comprising an isocyanate functional group, an ethylenically unsaturated group, and carboxylic acid functional groups.

9. The coating composition of claim 1, wherein the polyhydrazide comprises a non-polymeric polyhydrazide, a polymeric polyhydrazide, or a combination thereof.

10. The coating composition of claim 9, wherein the polymeric polyhydrazide comprises a polyurethane comprising at least two hydrazide functional groups.

11. The coating composition of claim 9, wherein the polymeric polyhydrazide comprises core-shell particles comprising (1) a polymeric core at least partially encapsulated by (2) a polymeric shell comprising hydrazide functional groups, wherein the polymeric core is covalently bonded to at least a portion of the polymeric shell.

12. The coating composition of claim 11, wherein the polymeric polyhydrazide core-shell particles are obtained from reactants comprising: a polyurethane prepolymer comprising an isocyanate functional group and an ethylenically unsaturated group; hydrazine and/or non-polymeric polyhydrazides; and ethylenically unsaturated monomers different from the polyurethane prepolymer and the hydrazine and/or non-polymeric polyhydrazides.

13. The coating composition of claim 1, wherein a weight ratio of the first core-shell particles to the second core-shell particles is from 1:1 to 5:1.

14. The coating composition of claim 1, wherein the second crosslinker comprises a carbodiimide.

15. The coating composition of claim 1, further comprising a non-core-shell particle hydroxyl functional film-forming resin.

16. A substrate at least partially coated with a coating formed from the coating composition of claim 1.

17. A multi-layer coating, comprising: a first basecoat layer to be applied over at least a portion of a substrate which is formed from a first basecoat composition; and a second basecoat layer applied over at least a portion of the first basecoat composition and which is formed from a second basecoat composition, wherein the first basecoat composition and/or the second basecoat composition comprises: an aqueous medium; first core-shell particles dispersed in the aqueous medium, wherein the first core-shell particles comprise (i) keto and/or aldo functional groups, (ii) a polymeric shell comprising carboxylic acid functional groups and urethane linkages, and (iii) a polymeric core at least partially encapsulated by the polymeric shell, wherein the polymeric shell and/or the polymeric core may comprise the keto and/or aldo functional groups; second core-shell particles dispersed in the aqueous medium, wherein the second core-shell particles are different from the first core-shell particles and comprise (a) a polymeric shell comprising carboxylic acid functional groups and hydroxyl groups, and (b) a polymeric core comprising hydroxyl functional groups and which is at least partially encapsulated by the polymeric shell; a first crosslinker comprising a polyhydrazide reactive with the first core-shell particles; and a second crosslinker reactive with the first core-shell particles and the second core-shell particles, wherein the polymeric core of the first and second core-shell particles are covalently bonded to at least a portion of the corresponding polymeric shell.

18. The multi-layer coating of claim 17, further comprising a primer coating layer directly to be applied over at least a portion of the substrate, such that the primer coating layer is positioned between the first basecoat layer and the substrate.

19. The multi-layer coating of claim 17, wherein the polymeric core and polymeric shell of the second core-shell particles comprise an addition polymer derived from ethylenically unsaturated monomers, and wherein the addition polymer comprises hydroxyl functional groups and carboxylic acid functional groups.

20. The multi-layer coating of claim 17, wherein the keto and/or aldo functional groups of the first core-shell particles of the first basecoat composition are formed on the polymeric shell or the polymeric core; and wherein the keto and/or aldo functional groups of the first core-shell particles of the second basecoat composition are formed on: (1) the polymeric core when the keto and/or aldo functional groups of the first core-shell particles of the first basecoat composition are formed on the polymeric shell; or (2) the polymeric shell when the keto and/or aldo functional groups of the first core-shell particles of the first basecoat composition are formed on the polymeric core.

21. The multi-layer coating of claim 20, wherein the core-shell particles having the keto and/or aldo functional groups formed on the polymeric shell are obtained from reactants comprising: a polyurethane prepolymer comprising an isocyanate functional group, an ethylenically unsaturated group, and carboxylic acid functional groups; ethylenically unsaturated monomers different from the polyurethane prepolymer; and a Michael Addition reaction product of ethylenically unsaturated monomers comprising a keto and/or aldo functional group, and a compound comprising at least two amino groups.

22. The multi-layer coating of claim 20, wherein the core-shell particles having the keto and/or aldo functional groups formed on the polymeric core are obtained from reactants comprising: ethylenically unsaturated monomers, wherein at least one of the ethylenically unsaturated monomers comprises keto and/or aldo functional groups; and a polyurethane prepolymer comprising an isocyanate functional group, an ethylenically unsaturated group, and carboxylic acid functional groups.

23. The multi-layer coating of claim 17, wherein the polyhydrazide of the first basecoat composition and the second basecoat composition each independently comprise a non-polymeric polyhydrazide, a polymeric polyhydrazide, or a combination thereof.

24. The multi-layer coating of claim 23, wherein the polymeric polyhydrazide comprises a polyurethane comprising at least two hydrazide functional groups.

25. The multi-layer coating of claim 23, wherein the polymeric polyhydrazide comprises core-shell particles comprising (1) a polymeric core at least partially encapsulated by (2) a polymeric shell comprising hydrazide functional groups, wherein the polymeric core is covalently bonded to at least a portion of the polymeric shell.

26. The multi-layer coating of claim 25, wherein the polymeric polyhydrazide core-shell particles are obtained from reactants comprising: a polyurethane prepolymer comprising an isocyanate functional group and an ethylenically unsaturated group; hydrazine and/or non-polymeric polyhydrazides; and ethylenically unsaturated monomers different from the polyurethane prepolymer and the hydrazine and/or non-polymeric polyhydrazides.

27. The multi-layer coating of claim 23, wherein the first basecoat composition comprises a polymeric polyhydrazide and a non-polymeric polyhydrazide.

28. The multi-layer coating of claim 17, wherein the second crosslinker of the first basecoat composition and the second basecoat composition each independently comprise a carbodiimide.

29. The multi-layer coating of claim 17, wherein the second basecoat composition further comprises a non-core-shell particle hydroxyl functional film-forming resin.

30. The multi-layer coating of claim 17, further comprising a topcoat layer applied over at least a portion of the first or second basecoat layer.

Description

EXAMPLES

[0115] The following examples are presented to demonstrate the general principles of the invention. The invention should not be considered as limited to the specific examples presented. All parts and percentages in the examples are by weight unless otherwise indicated.

Example 1

Preparation of a Latex having Keto Functional Core-Shell Particles

[0116] Part A: A polyurethane was first prepared by charging the following components into a four necked round bottom flask fitted with a thermocouple, mechanical stirrer, and condenser: 538 grams of butyl acrylate, 433 grams of FOMREZ 66-56 (hydroxyl terminated saturated linear polyester polyol, commercially available from Chemtura Corporation (Philadelphia, Pa.)), 433 grams of POLYMEG 2000 polyol (polytetramethylene ether glycol, commercially available from LyondellBasell Industries N.V. (Rotterdam, Netherlands)), 3.1 grams of 2,6-di-tert-butyl 4-methyl phenol, 41.4 grams of hydroxyethyl methacrylate (HEMA), 140 grams of dimethylol propionic acid (DMPA), and 6.3 grams of triethylamine. The mixture was heated to 50 C. and held for 15 minutes. Next, 601.0 grams of isophorone diisocyanate was charged into the flask over 10 minutes, and mixed for 15 minutes. After mixing, 39 grams of butyl acrylate and 1.6 grams of dibutyl tin dilaurate (DBTDL) was charged into the flask and immediate exotherm was observed. After exotherm subsided, the mixture was heated to 90 C. and held for 60 minutes. The mixture was cooled to 70 C. and 538 grams of butyl acrylate and 94.0 grams of hexanediol diacrylate were charged into the flask. The resulting mixture was kept at 60 C. before being dispersed into water.

[0117] Part B: A latex comprising polyurethane-acrylic core-shell particles with urea linkages, urethane linkages, pendant carboxylic acid functionality, and pendant keto functionality on the polyurethane shell was prepared by charging the following components into a four necked round bottom flask fitted with a thermocouple, mechanical stirrer, and condenser: 2400.0 grams of deionized water, 215 grams of diacetone acrylamide, 88 grams of dimethyl ethanolamine, and 50 grams of ethylenediamine. The mixture was heated to 70 C. and held for two hours with an N2 blanket. After heating the mixture, 1925 grams of deionized water and 40 grams of AEROSOL OT-75 (surfactant, commercially available from Cytec Industries (Woodland Park, N.J.)) were charged into the flask and held at 50 C. for 15 minutes. Next, 2600.0 grams of the polyurethane prepared in Part A was dispersed into the flask over 20 minutes and mixed for an additional 15 minutes. A mixture of 7.7 grams of ammonium persulfate and 165 grams of deionized water was then charged into the flask over 15 minutes. The temperature rose from 50 C. to 80 C. due to polymerization exotherm. The mixture was held at 75 C. for an additional hour. After being cooled to 40 C., 1.2 grams of FOAMKILL 649 (non-silicone defoamer, commercially available from Crucible Chemical Company (Greenville, SC)), 25 grams of ACTICIDE MBS (microbiocide formed of a mixture of 1,2-benzisothiazolin-3-one and 2-methyl-4-isothiazolin-3-one, commercially available from Thor GmbH (Speyer, Germany)), and 55 grams of deionized water were charged and mixed for an additional 15 minutes. The resulting latex had a solid content of 38.6% (measured at 110 C. for 1 hour) and an average particle size of 60 nm. The average particle size was determined with a Zetasizer 3000HS following the instructions in the Zetasizer 3000HS manual.

Example 2

Preparation of a Latex having Keto Functional Core-Shell Particles

[0118] Part A: A mixture containing a polyurethane acrylate prepolymer was prepared by adding 270 grams of butyl acrylate (BA), 213.8 grams of hydroxyethyl methacrylate, 242.6 grams of dimethylol propionic acid, 4.1 grams of 2,6-di-tert-butyl 4-methyl phenol, 2.1 grams of triphenyl phosphite, 10.8 grams of triethyl amine and 2.1 grams of dibutyl tin dilaurate to a four-necked round bottom flask fitted with a thermocouple, mechanical stirrer, and condenser and heated to 90 C. to obtain a homogeneous solution. Then 1093.5 grams of polytetrahydrofuran (weight average molecular weight (Mw) of approximately 1000) was added. To this mixture at 90 C., 636.1 grams of isophorone diisocyanate was added over 90 minutes. The isocyanate container was rinsed with 54.0 grams of BA. The reaction mixture was stirred at 90 C. until all the isocyanate groups were reacted. Ethylhexyl acrylate (EHA) (1215 grams) was added and cooled.

[0119] Part B: A polyurethane acrylic latex containing 9 percent by weight diacetone acrylamide (DAAM) and 6 percent by weight of 1,6-hexanediol diacrylate, the percentages by weight being based on total weight of ethylenically unsaturated monomers, was prepared as follows: Sixty-seven (67) grams of Aerosol OT-75 (surfactant from Cytec Industries (Woodland Park, N.J.)), 25.3 grams of ADEKA REASOAP SR-10 (emulsifier from Adeka Corp. (Tokyo, Japan)), 73.8 grams of dimethyl ethanol amine, 1715.7 grams of prepared polyurethane/EHA mixture of Part A, 84.3 grams of 1,6-hexanediol diacrylate, 606.7 grams of methyl methacrylate, 205.6 grams of butyl methacrylate, 252.7 grams of diacetone acrylamide and 4512.0 grams of deionized water were charged to a four-necked round bottom flask fitted with a thermocouple, mechanical stirrer, and condenser and heated to 33 C. to obtain a homogeneous solution. 4.1 grams of t-butylhydroperoxide and 126.4 grams of deionized water was then charged into the flask and mixed for 10 minutes. After that, 4.1 grams of ferrous ammonium sulfate and 2.0 grams of sodium meta bisulfite dissolved in 126.4 grams of deionized water was added over 30 minutes. The reaction mixture was then heated to 65 C. and held at this temperature for 1 hour. After it cooled to 45 C., 29.5 grams of acticide MBS (biocide from Thor GmbH (Speyer, Germany)), 1.52 grams of FOAMKILL 649 (defoamer from Crucible Chemical Co. (Greenville, SC)) and 12.6 grams of deionized water were charged into the flask and mixed for 15 minutes. The resulting latex included core-shell particles and had a solid contents of 38% (measured at 110 C. for 1 hour).

Example 3

Preparation of a Latex having Core-Shell Particles having a Polymeric Shell Comprising Carboxylic Acid Functional Groups and Hydroxyl Functional Groups and a Polymeric Core

[0120] Comprising Hydroxyl Functional Groups

[0121] A latex having core-shell particles was prepared using the components listed in Table 1.

TABLE-US-00001 TABLE 1 Amount Component (grams) Charge A Deionized water 778.0 RHODAPEX AB/20.sup.1 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/20.sup.1 4.58 Methyl methacrylate 222.07 Butyl acrylate 89.3 Hexanediol diacrylate 8.23 Hydroxy ethyl methacrylate 18.14 Charge E Deionized water 74.0 Ammonium persulfate 0.27 Charge F Deionized water 28.6 RHODAPEX AB/20.sup.1 0.66 Methyl methacrylate 8.49 Butyl acrylate 18.57 Methacrylic acid 11.59 Hydroxy ethyl acrylate 12.31 Charge G Deionized water 54.3 Borax decadydrate granular.sup.2 0.44 Ammonium persulfate 0.14 Charge H Deionized water 18.1 Dimethyl ethanol amine 2.9 Charge I Deionized water 14.4 ACTICIDE MBS.sup.3 4.2 .sup.1Anionic surfactant available from Solvay S. A. (Brussels, Belgium) .sup.2Available from American Borate Company (Virginia Beach, VA) .sup.3Microbiocide formed of a mixture of 1,2-benzisothiazolin-3-one and 2-methyl-4-isothiazolin-3-one, commercially available from Thor GmbH (Speyer, Germany)

[0122] Charge A was added to a four-neck round bottom flask equipped with a thermocouple, mechanical stirrer, and condenser. Charge A was heated to 65 C. The reaction mixture was heated to 85 C. and Charge B was added, followed by addition of Charge C and then a hold for 30 minutes. Charges D and E were added over 180 minutes, followed by a hold of 60 minutes. Charges F and G were then added over 90 minutes, followed by a hold of 120 minutes and then cooling to 70 C. At this temperature, Charge H was added over 20 minutes. The product was then cooled to 40 C. and then diluted with Charge I and mixed for 15 minutes. The final product has a solid contents of 25% (measured at 110 C. for 1 hour), Brookfield viscosity of around 40 centipoise measured according to ASTM D2196 at ambient temperature (20 C-27 C.) and pH of 6.6 measured according to ASTM D4584. For measuring pH, the test material is poured into a non-conducting container, the pH electrode is lowered into the sample specimen, and the pH measurement taken. The electrode is removed from the sample specimen, rinsed with solvent, if necessary, then rinsed with deionized water, and returned to its storage vessel.

Example 4

Preparation of a Polyester Polymer

[0123] A polyester was prepared according to Example A1 of EP 1,454,971 B1 as follows: In a reactor equipped with a stirrer, a water separator, and a control unit for the temperature, and the following components were mixed and heated to 185 C.: 1732 grams of TERATHANE (polytetramethylene ether glycol having a number average molecular weight of 650 g/mol, commercially available from DuPont (Wilmington, Del.)), and 307 grams of trimellitic anhydride. Upon reaching a MEQ Acid content of 0.713 mmol/g (acid number =40 mg KOH/g) as measured according to ASTM D1639, the reaction temperature is lowered to 175 C. The reaction is continued until reaching a MEQ Acid content of 0.535 mmol/g (acid number =30 mg KOH/g). For MEQ Acid content, the sample is weighed based off of theoretical acid and is dissolved in 60mL of an 80%/20% blend of THF/1,2-Propanediol. The sample is then titrated by a verified 0.1N KOH in Methanol and the end point is determined by a potentiometric electrode. The resulting MEQ Acid content is calculated by the following equation:

[00001]$\mathrm{MEQ}.Math..Math.\mathrm{Acid}=\frac{\left(T-S\right)*N}{W}$

[0124] where: W=specimen weight in grams, S=volume of the solvent blank, or 0 if no solvent blank determined, T=volume of the sample titration, and N=normality of the standardized potassium hydroxide

[0125] The Gardner-Holdt viscosity of the resin solution at 60% strength in butoxyethanol was V as measured according to ASTM D1545-89. After cooling the polyester melt to 85 C., 552 grams of a 10% aqueous dimethylethanolamine solution was added followed by 2390 grams of deionized water. A finely divided dispersion was formed having a nonvolatile content of 40% and an acid number of 29 mg KOH/g.

Example 5

Preparation of a Polyether Carbamate

[0126] A hydroxy functional polyether carbamate was prepared using the components listed in Table 2.

TABLE-US-00002 TABLE 2 Component Amount (grams) Equivalents JEFFAMINE D 400.sup.4 2000 10 Ethylenecarbonate 968 11 .sup.4Polypropyleneoxide amine from Huntsman Corporation (The Woodlands, Texas)

[0127] Both the ingredients were added to the reaction vessel and heated to 130 C. The reaction mixture was held at this temperature till greater than 90% of the amine was reacted as measured by potentiometric titration of the mixture, in which the mixture was solubilized in acetic acid and titrated with 0.1 N (normal) perchloric acid in glacial acetic acid. The product was slightly yellowish, had a theoretical % weight solids of 100%, and a weight averaged molecular weight (Mw) of 800 as measured by gel permeation chromatography using a polystyrene standard according to ASTM D6579-11 (performed using a Waters 2695 separation module with a Waters 2414 differential refractometer (RI detector); tetrahydrofuran (THF) was used as the eluent at a flow rate of 1 ml/min, and two PLgel Mixed-C (3007.5 mm) columns were used for separation at the room temperature; weight and number average molecular weight of polymeric samples can be measured by gel permeation chromatography relative to linear polystyrene standards of 800 to 900,000 Da).

Example 6

Preparation of a Red Basecoat (B1) Coating Composition

[0128] A red basecoat coating composition was prepared by mixing the components listed in Table 3.

TABLE-US-00003 TABLE 3 Example 6 Components (Parts by Weight) Latex of Example 1 928.46 Adipic Acid Dihydrazide.sup.5 10.45 Polyester Polymer of 178.08 Example 4 BYK 348.sup.6 1.63 BYK 032.sup.7 12.62 Red Tint.sup.8 297.53 Red Tint.sup.9 412.69 Red Tint.sup.10 161.59 Black Tint.sup.11 3.67 Red Tint.sup.12 148.46 White Tint.sup.13 3.05 BYKETOL WS.sup.14 58.50 SURFYNOL 104E.sup.15 26.00 Isopropanol.sup.16 58.50 TALCRON MP1052.sup.17 26.00 50% DMEA.sup.18 7.80 N-butoxypropanol.sup.19 130.00 Deionized Water 120.00 CARBODILITE V-O2-L2.sup.20 261.42 Total 2846.45 .sup.5Crosslinker commercially available from Japan Finechem Company (Tokyo, Japan) .sup.6Additive commercially available from BYK Chemie (Wesel, Germany) .sup.7Additive commercially available from BYK Chemie (Wesel, Germany) .sup.8Red tint paste consisting of 32% BAYFERROX red 140M (Lanxess Corporation (Pittsburgh, PA)) dispersed in 10% acrylic polymer and having a solids content of 45% .sup.9Red tint paste consisting of 12% HOSTAPERM pink E (Clariant Specialty Chemicals (Muttenz, Switzerland)) dispersed in 12% acrylic polymer and having a solids content of 24% .sup.10Red tint paste consisting of 12% PALIOGEN red L-3875 (BASF (Ludwigshafen, Germany)) dispersed in 12% acrylic polymer and having a solids content of 24% .sup.11Black tint paste consisting of 6% carbon black dispersed in 16% acrylic polymer and having a solids content of 26% .sup.12Red tint paste consisting of 13% SICOTRANS Red L2817 (BASF (Ludwigshafen, Germany)) dispersed in 14% acrylic polymer and having a solids content of 32% .sup.13White tint paste consisting of 61% TiO.sub.2 dispersed in 9% acrylic polymer blend and having a solids content of 70% .sup.14Additive commercially available from BYK Chemie (Wesel, Germany) .sup.15Additive commercially available from Air Products & Chemicals (Allentown, PA) .sup.16Solvent commercially available from Dow Chemical Company (Midland, MI) .sup.17Magnesium silicate commercially available from Barretts Minerals Inc. (Helena, MT) .sup.18Dimethylethanolamine 50% aqueous solution .sup.19Solvent commercially available from Dow Chemical Company (Midland, MI) .sup.20Crosslinker commercially available from Nisshinbo Chemical Inc. (Tokyo, Japan)

Examples 7-8

Preparation of a Red Basecoat (B2) Coating Composition

[0129] The red basecoat B2 coating composition was prepared by mixing each component in Table 4 in the order listed. A pre-blend was made with the deionized water and LAPONITE RD BYK Chemie (Wesel, Germany) and that mixture was added to the preceding ingredients. An additional pre-blend was made of the n-butoxypropanol, odorless mineral spirits, 2-ethylhexanol, mica, aluminum paste, and aluminum passivation agent and that mixture was added to the preceding ingredients.

TABLE-US-00004 TABLE 4 Example 7 Comp. Example 8 Components (Parts by Weight) (Parts by Weight) Latex of Example 2 1387.40 1646.38 Adipic Acid Dihydrazide.sup.5 18.80 22.31 Polyester Polymer of 494.66 494.66 Example 4 Polyether Carbamate of 22.23 22.23 Example 5 Latex of Example 3 385.44 50% DMEA.sup.18 19.30 14.70 BYK 348.sup.6 2.65 2.65 Red Tint.sup.21 521.15 521.15 Maroon Tint.sup.22 177.05 177.05 Red Tint.sup.23 152.00 152.00 Red Tint.sup.24 41.67 41.67 Black Tint.sup.11 13.35 13.35 White Tint.sup.13 15.03 15.03 Deionized Water 778.55 778.55 LAPONITE RD.sup.25 15.64 15.64 N-butoxypropanol.sup.19 335.00 335.00 Odorless Mineral Spirits.sup.26 73.38 73.38 2-Ethylhexanol.sup.27 89.36 89.36 Mica Pigment.sup.28 40.51 40.51 Aluminum Paste.sup.29 94.42 94.42 Al passivation Agent 116.29 116.29 Deionized Water 342.30 352.00 CARBODILITE V-02-L2.sup.20 363.22 358.23 Total 5499.40 5376.56 .sup.21Red tint paste consisting of 22% SUNFAST Red 254 (Sun Chemical (Troy Hills, NJ)) dispersed in 24% acrylic polymer and having a solids content of 49% .sup.22Maroon tint paste consisting of 21% PERRINDO Maroon 179 (Sun Chemical (Troy Hills, NJ)) dispersed in 10% acrylic polymer and having a solids content of 32% .sup.23Red tint paste consisting of 28% IRGAZIN Rubine L4025 (BASF (Ludwigshafen, Germany)) dispersed in 13% acrylic polymer and having a solids content of 42% .sup.24Red tint paste consisting of 25% KROMA RED Iron Oxide RO 3097 (Huntsman Corporation (The Woodlands, TX)) dispersed in 16% acrylic polymer and having a solids content of 48% .sup.25Sodium lithium magnesium silicate available from BYK Chemie (Wesel, Germany) .sup.26Solvent commercially available from Shell Chemical Company (Houston, TX) .sup.27Solvent commercially available from Dow Chemical Company (Midland, MI) .sup.28IRIODIN 97225 Ultra Rutile Blue Pearl SW available from Merck KGaA (Darnstadt, Germany) .sup.29PALIOCROM Orange L2800 available from BASF (BASF (Ludwigshafen, Germany))

Example 9-10

Forming Coated Panels

[0130] The red B1 and red B2 coating compositions of Examples 6-8 were spray applied in an environment controlled to 70-75 F. (21-24 C.) and 60-65% relative humidity onto 4 inch by 12 inch steel panels that were coated with PPG Electrocoat (ED 6465) commercially available from PPG Industries, Inc. (Pittsburgh, Pa.) as follows. The substrate panels were obtained from ACT Test Panels, LLC (Hillsdale, Mich.). The red B1 coating composition was applied in one coat and then flashed at ambient temperature for 4 minutes. The film thickness was approximately 14 microns. One of the red B2 coating compositions were then applied wet-on-wet over the red B1 composition in two coats, with a 90 second flash between coats, and then flashed at ambient temperature for 4 minutes and then dehydrated for 5 minutes at 80 C. The red B2 film thicknesses were approximately 17 microns.

[0131] After forming the B1 and B2 layers, a 2K isocyanate cured clearcoat was applied over the basecoated panels in two coats with a 90 second flash between coats. The clearcoated panels were allowed to flash for 7 minutes at ambient condition and baked for 30 minutes at 80 C. The film thickness was approximately 50 microns.

[0132] Longwave and shortwave appearance, sag resistance, and hardness properties were tested on the coated panels, and the results are shown in Table 5.

TABLE-US-00005 TABLE 5 BYK Wavescan.sup.30 Layer Longwave Shortwave Sag Example Description Horizontal Vertical Horizontal Vertical Resistance.sup.31 Hardness.sup.32 Example 9 Example 6 B1 2.7 11.8 12.2 12.1 No sag 117 Example 7 B2 Comp. Example 6 B1 3.4 15.9 15.6 16.7 Sag- bottom 107 Example 10 Comp. Example edge build on 8 B2 panel .sup.30Using BYK Wavescan instrument manufactured by BYK Gardner USA (Columbia, MD) where horizontal and vertical are the positions of the coated panels .sup.31Visual observation .sup.32Hardness values were measured in (N/mm2) units using a HM2000 Fischer Microhardness instrument (available from Fischer Technology, Inc. (Windsor, CT)), and hardness was measured one week after application of the multi-layer coatings.

[0133] Lower values in longwave and shortwave, no sag, and higher hardness are more desirable physical properties. The inventive multi-layer coating of Example 9 outperformed the multi-layer coating of Comp. Example 10.

[0134] The present invention thus relates inter alia, without being limited thereto, to the subject matter of the following clauses:

[0135] Clause 1: A coating composition comprising: an aqueous medium; first core-shell particles dispersed in the aqueous medium, wherein the first core-shell particles comprise (i) keto and/or aldo functional groups, (ii) a polymeric shell comprising carboxylic acid functional groups and urethane linkages, and (iii) a polymeric core at least partially encapsulated by the polymeric shell, wherein the polymeric shell and/or the polymeric core may comprise the keto and/or aldo functional groups; second core-shell particles dispersed in the aqueous medium, wherein the second core-shell particles are different from the first core-shell particles and comprise (a) a polymeric shell comprising carboxylic acid functional groups and hydroxyl groups, and (b) a polymeric core comprising hydroxyl functional groups and which is at least partially encapsulated by the polymeric shell; a first crosslinker comprising a polyhydrazide reactive with the first core-shell particles; and a second crosslinker reactive with the first core-shell particles and the second core-shell particles, wherein the polymeric core of the first and second core-shell particles is covalently bonded to at least a portion of the corresponding polymeric shell.

[0136] Clause 2: The coating composition of clause 1, wherein the polymeric core and polymeric shell of the second core-shell particles comprise an addition polymer derived from ethylenically unsaturated monomers, and wherein the addition polymer comprises hydroxyl functional groups and carboxylic acid functional groups.

[0137] Clause 3: The coating composition of clause 2, wherein the addition polymer of the polymeric core is crosslinked.

[0138] Clause 4: The coating composition of any of clause 1, wherein the polymeric core of the second core-shell particles is free of carboxylic acid functional groups.

[0139] Clause 5: The coating composition of any of clauses 1-4, wherein the keto and/or aldo functional groups of the first core-shell particles are formed on the polymeric shell.

[0140] Clause 6: The coating composition of clause 5, wherein the first core-shell particles are obtained from reactants comprising: a polyurethane prepolymer comprising an isocyanate functional group, an ethylenically unsaturated group, and carboxylic acid functional groups;

[0141] ethylenically unsaturated monomers different from the polyurethane prepolymer; and a Michael Addition reaction product of ethylenically unsaturated monomers comprising a keto and/or aldo functional group, and a compound comprising at least two amino groups.

[0142] Clause 7: The coating composition of any of clauses 1-6, wherein the keto and/or aldo functional groups of the first core-shell particles are formed on the polymeric core.

[0143] Clause 8: The coating composition of clause 7, wherein the first core-shell particles are obtained from reactants comprising: ethylenically unsaturated monomers, wherein at least one of the ethylenically unsaturated monomers comprises keto and/or aldo functional groups; and a polyurethane prepolymer comprising an isocyanate functional group, an ethylenically unsaturated group, and carboxylic acid functional groups.

[0144] Clause 9: The coating composition of any of clauses 1-8, wherein the polyhydrazide comprises a non-polymeric polyhydrazide, a polymeric polyhydrazide, or a combination thereof.

[0145] Clause 10: The coating composition of clause 9, wherein the polymeric polyhydrazide comprises a polyurethane comprising at least two hydrazide functional groups.

[0146] Clause 11: The coating composition of clause 9 or 10, wherein the polymeric polyhydrazide comprises core-shell particles comprising (1) a polymeric core at least partially encapsulated by (2) a polymeric shell comprising hydrazide functional groups, wherein the polymeric core is covalently bonded to at least a portion of the polymeric shell.

[0147] Clause 12: The coating composition of clause 11, wherein the polymeric polyhydrazide core-shell particles are obtained from reactants comprising: a polyurethane prepolymer comprising an isocyanate functional group and an ethylenically unsaturated group; hydrazine and/or non-polymeric polyhydrazides; and ethylenically unsaturated monomers ethylenically unsaturated monomers different from the polyurethane prepolymer and the hydrazine and/or non-polymeric polyhydrazides.

[0148] Clause 13: The coating composition of any of clauses 1-12, wherein a weight ratio of the first core-shell particles to the second core-shell particles is from 1:1 to 5:1.

[0149] Clause 14: The coating composition of any of clauses 1-13, wherein the second crosslinker comprises a carbodiimide.

[0150] Clause 15: The coating composition of any of clauses 1-14, further comprising a non-core-shell particle hydroxyl functional film-forming resin.

[0151] Clause 16: A substrate at least partially coated with a coating formed from the coating composition of any of clauses 1-15, such as a multi-layer coating as defined in any one of subsequent clauses 17-26.

[0152] Clause 17: A multi-layer coating comprising: a first basecoat layer to be applied over at least a portion of a substrate which is formed from a first basecoat composition; and a second basecoat layer applied over at least a portion of the first basecoat composition and which is formed from a second basecoat composition, wherein the first basecoat composition and/or the second basecoat composition comprises a coating composition according to any one of clauses 1-15.

[0153] Clause 18: The multi-layer coating of clause 17, further comprising a primer coating layer directly to be applied over at least a portion of the substrate, such that the primer coating layer is positioned between the first basecoat layer and the substrate.

[0154] Clause 19: The multi-layer coating of clause 17 or 18, wherein both the first basecoat composition and the second basecoat composition comprise a coating composition according to any one of clauses 1-15.

[0155] Clause 20: The multi-layer coating of any of clause 19, wherein the keto and/or aldo functional groups of the first core-shell particles of the first basecoat composition are formed on the polymeric shell or the polymeric core; and wherein the keto and/or aldo functional groups of the first core-shell particles of the second basecoat composition are formed on: (1) the polymeric core when the keto and/or aldo functional groups of the first core-shell particles of the first basecoat composition are formed on the polymeric shell; or (2) the polymeric shell when the keto and/or aldo functional groups of the first core-shell particles of the first basecoat composition are formed on the polymeric core.

[0156] Clause 21: The multi-layer coating of clause 20, wherein the core-shell particles having the keto and/or aldo functional groups formed on the polymeric shell are obtained from reactants comprising: a polyurethane prepolymer comprising an isocyanate functional group, an ethylenically unsaturated group, and carboxylic acid functional groups; ethylenically unsaturated monomers different from the polyurethane prepolymer; and a Michael Addition reaction product of ethylenically unsaturated monomers comprising a keto and/or aldo functional group, and a compound comprising at least two amino groups.

[0157] Clause 22: The multi-layer coating of clause 20 or 21, wherein core-shell particles having the keto and/or aldo functional groups formed on the polymeric core are obtained from reactants comprising: ethylenically unsaturated monomers, wherein at least one of the ethylenically unsaturated monomers comprises keto and/or aldo functional groups; and a polyurethane prepolymer comprising an isocyanate functional group, an ethylenically unsaturated group, and carboxylic acid functional groups.

[0158] Clause 23: The multi-layer coating of any of clauses 17-22, wherein the first basecoat composition comprises a polymeric polyhydrazide and a non-polymeric polyhydrazide.

[0159] Clause 24: The multi-layer coating of any of clauses 19-23, wherein the second crosslinker of the first basecoat composition and the second basecoat composition each independently comprise a carbodiimide.

[0160] Clause 25: The multi-layer coating of any of clauses 17-24, wherein the second basecoat composition further comprises a non-core-shell particle hydroxyl functional film-forming resin.

[0161] Clause 26: The multi-layer coating of any of clauses 17-25, further comprising a topcoat layer applied over at least a portion of the first or second basecoat layer.

[0162] Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.