Controlled cure coating compositions

Abstract

Coating compositions that include one or more polyurethane resins containing thiol functional groups and dispersible groups; one or more crosslinkers that include functional groups reactive with the thiol functional groups; a basic catalyst; and a volatile acid. Methods of making and using such coating compositions are also disclosed.

Description

CONTROLLED CURE COATING COMPOSITIONSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to the following U.S. Provisional Patent Applications filed under 35 U.S.C. § 119: 63 / 656,264 filed March 14, 2024, titled “High Solids Coating Composition,” 63 / 565,239 filed March 14, 2024, titled “Controlled Cure Coating Compositions,” and 63 / 767,190 filed March 5, 2025, titled “Emulsifiable Resins,” all of which are incorporated herein by reference.FIELD

[0002] This disclosure generally relates to controlling the cure rate of coating compositions for application to a substrate, methods of forming coating layers and systems therefor.BACKGROUND

[0003] Coatings can be applied to a wide variety of substrates to provide color and other visual effects, corrosion resistance, abrasion resistance, chemical resistance, and the like. In addition, various types of coatings, such as coatings applied to packaging, automotive and a wide variety of substrates, can be formed from compositions that can be baked and formed at relatively low cure temperatures, for example 20 °C to 80 °C.SUMMARY

[0004] The present disclosure is directed to coating compositions that include one or more polyurethane resins containing thiol functional groups and dispersible groups; one or more crosslinkers that include functional groups reactive with the thiol functional groups in the polyurethane resin; a basic catalyst; and a volatile acid. Methods of making and using such coating compositions are also disclosed.DETAILED DESCRIPTION

[0005] For the purposes of the following detailed description, it is to be understood that the disclosure may assume various alternative variations and step sequences, except where expressly specified to the contrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of ingredients used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the present disclosure. At the very least, and not as an attempt tolimit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.I. Definitions

[0006] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard variation found in their respective testing measurements.

[0007] Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of “1 to 10” is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10.

[0008] In this application, the use of the singular includes the plural and plural encompasses the singular, unless specifically stated otherwise. In addition, in this application, the use of “or” means “and / or” unless specifically stated otherwise, even though “and / or” may be explicitly used in certain instances. Further, in this application, the use of “a” or “an” means “at least one” unless specifically stated otherwise. For example, “a” polymer, “an” acid, and the like refer to one or more of any of these items.

[0009] Unless otherwise indicated, ambient conditions of temperature and pressure are ambient temperature (20-25 °C, such as 23 °C) and standard pressure of 101.3 kPa (1 atm) at a relative humidity in the air of 35% to 75%, such as 55%.

[0010] “Acid value,” when used herein, indicates a quantified acidity of a given chemical substance based on the milligrams (mg) of potassium hydroxide (KOH) required to neutralize the acidic constituents in 1 gram of the non-volatile components and can be determined according to ASTM D4662-15.

[0011] As used herein, “actinic radiation” refers to electromagnetic radiation capable of initiating photochemical reactions, such as, without limitation, UVB and UVC radiation (ISO- 315 nm) and near-UV radiant energy in the 320-380 nm (or 400 nm) range.

[0012] As used herein, the term “active hydrogen” refers to the hydrogen of primary or secondary amine functional groups, thiol functional groups and / or hydroxyl functional groups.

[0013] As used herein, the term “ASTM” refers to publications of ASTM International, West Conshohocken, PA.

[0014] As used herein, the terms “backbone” and “polymer backbone” refer to the main chain of monomeric repeat units making up the main chain of a polymer.

[0015] As used herein, unless otherwise indicated, the terms “base” and “basic” refer to a substance that can neutralize an acid by reacting with hydrogen ions.

[0016] As used herein, the term “basecoat” refers to a coating layer that is applied onto a primer coat, another basecoat layer; and / or directly onto a substrate, optionally including components (such as colorants) that impact the color and / or provide other visual impact. A clearcoat may be applied over the basecoat layer.

[0017] As used herein the term “clearcoat” refers to a coating layer that is at least substantially transparent, tinted or fully transparent and often does not include a colorant. The term “substantially transparent” refers to a coating, wherein a surface beyond the coating layer is at least partially visible to the naked eye when viewed through the coating. The term “fully transparent” refers to a coating, wherein a surface beyond the coating layer is completely visible to the naked eye when viewed through the coating.

[0018] As used herein, the term “coating” refers to the finished product resulting from applying one or more coating compositions to a substrate and forming the coating, as a nonlimiting example by curing. A primer coat, basecoat or color coat layer and clear coat layer can comprise part of a coating. As used herein, the term “coating layer” is used to refer to the result of applying one or more coating compositions on a substrate in one or more applications of such one or more coating compositions. As a nonlimiting example, a single coating layer, referred to as a “color coat” or “topcoat” can be used to provide the function of both a basecoat and a clearcoat and can comprise the result of two or more applications of a color coat coating composition.

[0019] As used herein, the term “colorant” refers to any substance that imparts color and / or other opacity and / or other visual effect to a coating composition and can include, without limitation dyes and pigments.

[0020] As used herein, the transitional term “comprising” (and other comparable terms, e.g., “containing” and “including”) is “open-ended” and open to the inclusion of unspecified matter. Although described in terms of “comprising,” the terms “consisting essentially of’ and “consisting of’ are also within the scope of the disclosure.

[0021] As used herein, the terms “crosslinker” and “crosslinking agent,” used interchangeably, refers to a molecule or polymer containing functional groups that are reactive with the crosslinking-functional group of the polymers and / or resins in the coating composition.

[0022] As used herein, the term “crosslinking-functional group" and similar terms refer to functional groups that are positioned in the backbone of a polymer, often, in a group pendant from the backbone of the polymer, terminally positioned on the backbone of the polymer, or combinations thereof, wherein such functional groups are capable of reacting with other crosslinking-functional groups or separate crosslinking agents during curing to produce a crosslinked coating.

[0023] As used herein, the terms “curable”, “cure”, and the like, as used in connection with a coating composition, refer to at least a portion of the components that make up the coating composition are polymerizable and / or crosslinkable, via a condensation reaction, when, as a nonlimiting example, exposed to higher temperatures or ultraviolet radiation.

[0024] As used herein, the term “dispersible group” refers to a group in a molecule that allows the molecule to spread out evenly in a solvent or continuous phase while not necessarily completely merging with the solvent or continuous phase under ambient conditions. A nonlimiting example of a “dispersible group” is a “water soluble group,” which refers to a group that allows the molecule to dissolve and merge in water to form a homogenous solution under ambient conditions.

[0025] As used herein the term “dye” refers to a colored substance, in many cases an organic compound, that can chemically bond to a substrate or another component in a coating composition.

[0026] As used herein the term “electron- withdrawing group” and similar terms refer to a group that reduces electron density in adjacent atoms in a molecule through the carbon atom it is bonded to.

[0027] As used herein the term “epoxy” refers to a molecule that includes one or more glycidyl or oxirane groups.

[0028] As used herein, the term “film-forming” materials refers to film-forming constituents of a coating composition and can include polymers, resins, crosslinking materials, or any combination thereof that are film-forming constituents of the coating composition. Film-forming materials can be dried or cured, as nonlimiting examples, by exposure to elevated temperatures (for example, above 40 °C), actinic radiation or under ambient conditions.

[0029] As used herein, the term “hydroxyl functional compound” refers to an organic compound containing one or more hydroxyl (-OH) groups.

[0030] As used herein, the term “Isocyanate Reactive Compound” refers to a molecule that includes at least one group, such as, without limitation, hydroxyl, primary or secondary amine and / or thiol, that is reactive with an isocyanate group.

[0031] Unless otherwise indicated, as used herein, the term "molecular weight" refers to a weight average molecular weight as determined by gel permeation chromatography (GPC) using appropriate polystyrene standards. If a number average molecular weight is specified, the weight is determined in the same GPC manner, while calculating a number average from the thus obtained polymer molecular weight distribution data. “Number average molecular weight” refers to the total weight of a material divided by the number of molecules in the material and can be determined using gel permeation chromatography. Unless otherwise noted, “weight average molecular weight,” and “number average molecular weight” are in units of g / mol.

[0032] As used herein, the term “monocoat” refers to a coating layer, which can be a single coating layer, such as a topcoat, used to finish a surface of a substrate and not followed by the application of another coating layer, such as a clearcoat.

[0033] As used herein the term “monomer” refers to a molecule that can react together with other monomer molecules, through polymerization processes, to form a larger polymer chain or three-dimensional network.

[0034] As used herein the terms “multi component”, “multi- K” and “multi-pack” refers to a coating composition that includes a first component that contains crosslinkable resins, a second component that contains crosslinking agents and additional components that may or may not contain crosslinkable resins or crosslinking agents, where the components are maintained separately until just prior to use. The crosslinkable resins and crosslinking agents are capable of reacting when combined to form a thermoset composition. When the multi component coating composition does not include additional components, it is a two-component or 2-K coating composition.

[0035] As used herein, the term “NCO Functional Prepolymer” refers to a polymeric intermediate used to make the polyurethane resins described herein containing at least one terminal isocyanate (NCO) group.

[0036] As used herein, the term “olefinic group” refers to one or more pairs of carbon atoms linked by a double bond in a compound containing hydrogen and carbon.

[0037] As used herein the terms “one component”, “1-K” and “1-pack” refer to a coating composition where all of the coating components are maintained in the same package after manufacture, during shipping and storage and are maintained in the same container after manufacture, during storage, and the like, and may remain stable (not substantially react or gel) for longer than 1 month at conditions of 40-120°F (4-49 °C) at 0-95% relative humidity, such as longer than 3 months, longer than 6 months, longer than 9 months, or longer than 12 months.

[0038] As used herein, the term “organic solvent” refers to carbon-based substances capable of dissolving or dispersing other substances.

[0039] As used herein, the term “pigment” refers to a colored material, often an inorganic compound, that is completely or nearly insoluble in a solvent at ambient conditions.

[0040] As used herein, “Polyol” refers to a compound having two or more hydroxyl groups, such as two, three or four hydroxyl groups.

[0041] As used herein the prefix “poly” refers to two or more. As a nonlimiting example, a polyisocyanate refers to a compound that includes two or more isocyanate groups and a polyol refers to a compound that includes two or more hydroxyl groups.

[0042] As used herein, the term “polyisocyanate” refers to compound having two or more isocyanate groups, such as two, three or four isocyanate groups and can include blocked (or capped) polyisocyanates as well as unblocked polyisocyanates.

[0043] As used herein, the term “polymer” includes homopolymers (formed from one monomer) and copolymers that are formed from two or more different monomers or that comprise two or more distinct repeat units. Further, the term "polymer" includes prepolymers, and oligomers.

[0044] As used herein, “precision application” refers to applying a coating composition to a substrate using a high efficiency applicator that can enable a coating composition to be applied over at least a portion of a substrate without overspray, as a nonlimiting example, with greater than 85% transfer efficiency.

[0045] As used herein, the term “primer coat” refers to an undercoating layer that can be applied onto a substrate in order to prepare the surface for application of a protective or decorative coating composition.

[0046] As used herein, “resin solids” refers to the non-volatile, organic components that make up the binder or film-forming components of the composition, excluding inorganic components such as pigments and fillers. As used herein, a weight percentage based on “resin solids” refers to an amount of a component based on a total weight of the binder or film-forming components of a composition.

[0047] As used herein, the term “solids” refers to the non-volatile portion of a composition.

[0048] As used herein, the term “substrate” refers to an article surface to be coated and can refer to a coating layer has been previously disposed on an article, which is also considered a substrate.

[0049] As used herein, the term “thermosetting” means a polymer or resin that has functional groups that react with functional groups in a crosslinking agent or another polymer or moleculeto form a network material, irreversibly transforming the “soft” polymer to a more rigid form. Thermosetting in many cases refers to resins that “set” irreversibly upon curing or crosslinking, wherein the polymer chains of the resins are joined together by covalent bonds. Once cured or crosslinked, a thermosetting resin will not melt upon the application of heat and is insoluble in solvents.

[0050] As used herein the term “thermoplastic” refers to polymers and resins that are not joined by covalent bonds and, thereby, can undergo liquid flow upon heating and can be soluble in certain solvents.

[0051] As used herein the term “topcoat” refers to an uppermost coating that is deposited over another coating layer, such as a basecoat, to provide a protective and / or decorative layer.

[0052] As used herein, the term “total solids” or “solids” or “solids content” refers to the solids content as determined in accordance with ASTM D2369--20.

[0053] As used herein the terms “two component”, “2-K” and “2-pack” refers to a coating composition that includes a first component that contains a crosslinkable resins and a second component that contains crosslinking agents, where the first and the second components are maintained separately until just prior to use. The crosslinkable resins and crosslinking agents are capable of reacting when combined to form a thermoset composition.

[0054] As used herein, the term “vehicle” is used in its broadest sense and includes all types of vehicles, such as but not limited to cars, mini vans, SUVs (sports utility vehicle), trucks, semitrucks; tractors, buses, vans, golf carts, motorcycles, bicycles, railroad cars, trailers, ATVs (all- terrain vehicle); pickup trucks; heavy duty movers, such as, bulldozers, mobile cranes and earth movers; aircraft; boats; ships; and other modes of transport including, but not limited to all types of aircraft, spacecraft, watercraft, and ground vehicles.

[0055] As used herein, the term “volatile” refers to materials that are readily vaporizable (have a have a vapor pressure of at least 1 mm Hg) under ambient and / or cure conditions.

[0056] As used herein, the term “water dispersible group” refers to a group in a molecule that allows the molecule to spread out evenly in water while not necessarily completely merging with water under ambient conditions. A subset of “water dispersible group” is “water soluble group,” which refers to a group that allows the molecule to dissolve and merge in water to form a homogenous solution under ambient conditions.

[0057] As used herein, the phrase “wt. %” refers to weight percent.

[0058] The present disclosure is directed to coating compositions that include one or more polyurethane resins containing thiol functional groups and dispersible groups; one or more crosslinkers that include functional groups reactive with the thiol functional groups; a basiccatalyst; and a volatile acid. The volatile acid, such as the amount used, can control the rate that the coating compositions cure. The particular acid employed can vary depending on the cure conditions to be employed.II. Polyurethane Resin

[0059] Polyurethanes of the present disclosure and methods of preparing them are well known in the art. The polyurethane can be prepared by reacting an isocyanate reactive compound, such as, without limitation, hydroxyl functional compounds, thiol or mercapto functional compounds, and / or primary or secondary amines, with a polyisocyanate such that the NCO to isocyanate reactive group ratio is greater than 1:1 to generate an NCO functional prepolymer. The terminal isocyanates may then be reacted to generate terminal thiol (-SH) groups. The thiol functional polyurethane polymers can then be used in a curable composition. Optionally, the thiol functional polyurethane may be dissolved or dispersed in water prior to or during use in a curable composition.

[0060] The polyurethane resin may have a number average molecular weight (Mn) from 400, 500, 1000 to 2000, 3000, 4000, or within any range using any two of the foregoing values as endpoints, such as 400 to 4000, 500 to 3000, or 1000 to 2000, as determined by gel permeation chromatography using polystyrene standards.A. NCO Functional Prepolymer

[0061] The NCO functional prepolymer can be formed from an active hydrogen containing compound and an excess of polyisocyanate. The NCO functional prepolymer of the present disclosure may be a polyurethane, a polyurea, poly(thiourethane), and / or a combination thereof. The polyurethane can be formed from a polyol and an excess of polyisocyanate in a first stage to form a prepolymer. The polyurea can be formed from a polyamine and an excess of polyisocyanate in a first stage to form a prepolymer. The poly(thiourethane) can be formed from molecules having one or more mercapto or thiol groups and an excess of polyisocyanate in a first stage to form a prepolymer. The NCO prepolymer can be formed from a combination of polyol, polyamine, polythiol, and / or compounds that contain two different active hydrogens with excess isocyanate. The NCO functional prepolymer can be prepared using any combination of reactants recited above. The prepolymer may then be further modified with a nontertiary amine, polyether, mercapto or thiol compound, and / or acid containing compound to form the polyurethane resin according to this disclosure.i. Polyisocyanate

[0062] The NCO functional prepolymer of the present disclosure may be derived from a polyisocyanate, such as a diisocyanate, and as a nonlimiting example, reactive with a polyol and / or an acid containing hydroxy functional compound and / or other isocyanate reactive compounds.

[0063] Suitable polyisocyanates may be aliphatic, aromatic, cycloaliphatic or heterocyclic isocyanates. Suitable aliphatic isocyanates may include trimethylene, tetramethylene, pentamethylene, hexamethylene, 1,2-propylene, 1,2-butylene, 2,3-butylene and 1,3-butylene diisocyanates; the cycloalkylene compounds such as 1,3-cyclopentane, 1 ,4-cyclohexane, 1,2- cyclohexane diisocyanates and isophorone diisocyanates; the aromatic compounds such as m- phenylene, p-phenylene, 4,4’-diphenyl, 1,5 -naphthalene and 1,4-naphthalene diisocyanates; the aliphatic-aromatic compounds such as 4,4’-diphenylene methane, 2,4- or 2,6-tolylene, or mixtures thereof, 4,4'-toluidine, tetramethyl xylylene, and xylylene diisocyanates; the nuclear- substituted aromatic compounds such as dianisidine diisocyanate, 4,4'-diphenylether diisocyanate and chlorodiphenylene diisocyanate; the triisocyanates such as triphenyl methane- 4,4’,4"-triisocyanate, 1,3,5-triisocyanato benzene, hexamethylene diisocyanate isocyanurate trimer, and 2,4,6-triisocyanato toluene; and the tetraisocyanates such as 4,4'-dimethyldiphenyl methane-2,2',5,5'-tetraisocyanate; the polymerized polyisocyanates such as tolylene diisocyanate dimers and trimers, and the like.

[0064] Suitable diisocyanates also include diisocyanates having a single aromatic or cycloaliphatic ring such as isophorone diisocyanate (IPDI), tetramethyl xylene diisocyanate (TMXD1), 4,4’ -methylene dicyclohexyl diisocyanate (H12MD1), 1 ,6-hexamethylene diisocyanate (HDI), l,3-bis(isocyanato methyl)cyclohexane, l,5-diisocyanato-2-methylpentane, 1 ,6-diisocyanato-2,2,4-trimethylhexane, 1 ,6-diisocyanato-2,4,4-trimethylhexane, 1 ,4- diisocyanatobutanone, tri-methyl-hexamethylene diisocyanate, 1,8-diisocyanatooctane, 1,12- diisocyanatododecane, 1 ,8-diisocyanto-2,4-dimethyloctane, l,4-bis(isocyanato methyl)cyclohexane, trans- 1 ,4-cyclohexylene diisocyanate, and 2,4-diisocyanato-l -methyl cyclohexane.

[0065] Other suitable aliphatic diisocyanates may also include, methyl-2,6- diisocyanatohexanoate, bis(isocyanatomethyl)cyclohexane, 1,3- bis(isocyanatomethyl)cyclohexane, 2,5(6)-bis(isocyanatomethyl)cyclo[2.2. 1. Jheptane, 1,3,3- trimethyl- 1 -(isocyanatomethyl)-5 -isocyanatocyclohexane, octahydro-4,7 -methano-lH- indenedimethyl diisocyanate, and l,l’-methylenebis(4-isocyanatocyclohexane).

[0066] The polyurethane may be derived from a mixture comprising a polyisocyanate in an amount from 20 wt. %, or from 25 wt. %, or from 30 wt. % to 40 wt. %, or 50 wt. %, or 55 wt. %, or within any range using any two of the foregoing values as endpoints, such as from 20 wt. % to 55 wt. %, such as from 25 wt. % to 50 wt. %, or from 30 wt. % to 40 wt. %, where wt. % is based on total resin solids.

[0067] When forming the prepolymer, the molar ratio of isocyanate functional groups of the polyisocyanate to isocyanate reactive groups of the acid containing polyol and / or the isocyanate reactive groups of the non-acid containing polyol may be greater than 1. ii. Isocyanate Reactive Compounds

[0068] The NCO functional prepolymer of the present disclosure may be formed from an isocyanate reactive compound, such as primary or secondary amine functional compounds, thiol functional compounds, hydroxyl functional compounds reactive with an isocyanate of the NCO functional prepolymer. The hydroxyl functional compound may be, without limitation, hydroxyl functional polyesters, polycarbonates, polyethers, polyether amines, such as those available under the trade name Jeffamine available from Huntsman International LLC, or acrylic polymers. Thiol functional compounds can include, without limitation, C2-C20 alkyl dithiols, such as dodecanedithiol.

[0069] The hydroxyl groups of the hydroxyl functional compound may be connected by a bridging group selected from: an alkylene group; an alkenylene group; an alkynylene group; or an arylene group. The hydroxyl functional compound may lack acid groups, such as a non-acid containing polyol.

[0070] Hydroxyl functional compounds include, but are not limited to the following: alkylene glycols, such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, hexylene glycol, polyethylene glycol, polypropylene glycol and neopentyl glycol; hydrogenated bisphenol A; cyclohexanediol; propanediols including 1,2-propanediol, 1,3-propanediol, butyl ethyl propanediol, 2-methyl-l,3-propanediol, and 2-ethyl-2-butyl-l,3-propanediol; butanediols including 1 ,4-butanediol, 1,3 -butanediol, and 2-ethyl-l,4-butanediol; pentanediols including trimethyl pentanediol and 2-methylpentanediol; cyclohexanedimethanol; hexanediols including 1,6-hexanediol, caprolactonediol (such as the reaction product of epsilon-capro lactone and ethylene glycol), hydroxyalkylated bisphenols; polyether glycols, such as poly(oxytetramethylene) glycol and polytetrahydrofuran; trimethylol propane; pentaerythritol; di-pentaery thritol; trimethylol ethane; trimethylol butane; dimethylol cyclohexane; glycerol and the like or combinations thereof.

[0071] The hydroxyl functional compound may be a non-acid containing polyol, meaning the polyol lacks acid groups.

[0072] Hydroxy functional polyesters, poly (meth) acrylates, and polycarbonates may be suitable hydroxyl functional compounds reactive with the polyisocyanate in the formation of the polyurethane resin. As used herein and as will be understood by one skilled in art the term "(meth)acrylate" denotes both the acrylate and the corresponding (meth) acrylate. The poly(meth)acrylate can be any suitable poly(meth)acrylate and mixtures thereof. The poly(meth)acrylate may include di(meth)acrylate, tri(meth)acrylate, tetra(meth)acrylate, and / or one or more other ethylenically unsaturated radically polymerizable monomers. Mixtures of poly(meth)acrylate monomers may also be used, including mixtures of mono, di, tri, and / or tetra (meth)acrylate.

[0073] Hydroxy functional compounds include, but are not limited to the following: ethylene glycol; 1,2-propane diol; 1,3 -propane diol; 1,2-butandiol; 1,3-butandiol; 1,4-butandiol; but-2-ene 1,4-diol; 2,3-butane diol; 2-methyl 1,3-propane diol; 2,2'-dimethyl 1,3 -propanediol (neopentyl glycol); 1,5 pentane diol; 3-methyl 1,5-pentanediol; 2,4-diethyl 1,5-pentane diol; 1,6-hexane diol; 2-ethyl 1,3-hexane diol; diethylene glycol; triethylene glycol; dipropylene glycol; tripropylene glycol; 2,2,4-trimethyl pentane 1,3-diol; 1,4 cyclohexane dimethanol; tricyclodecane dimethanol; 2,2,4,4-tetramethyl cyclobutane 1,3-diol; isosorbide; 1,4- cyclohexane diol; l,l'-isopropylidene-bis (4-cyclohexanol); and mixtures thereof.

[0074] Suitable hydroxy functional compounds may include poly ether diols such as Terathane® 250 and Terathane® 650 available from Invista or the PolyTHF® polyether diols available from BASF.

[0075] The polyurethane may include an amount of a hydroxyl functional compound from 15 wt. %, 20 wt. %, 25 wt. % to 30 wt. %, 35 wt. %, 40 wt. %, or within any range using any two of the foregoing values as endpoints, such as 15 wt. % to 40 wt. %, 20 wt. % to 35 wt. %, or 25 wt. % to 30 wt. %, where wt. % is based on total resin solids.B. Polyurethanes containing thiol functional groups

[0076] The polyurethane resins of the present disclosure contain thiol functional groups. Poly thiol or mercapto compounds as well as compounds that include both thiol or mercapto groups and hydroxy functional groups may be suitable compounds that can be reactive with isocyanate groups of the NCO functional prepolymer in the formation of the polyurethane resin.

[0077] Suitable poly thiol or poly mercapto compounds may include, without limitation, C2- C20 alkyl dithiols, such as dodecanedi thiol, trimethylolpropane tris(2-mercaptoacetate), trimethylolpropane tris(2-mercaptopropionate), 1,8- dimercapto-3,6-dioxaoctane, thiolterminated polyethers, pentaerythritol-tetrakis-3-mercapto propionate, pentaerythritol-tetrakis-2- mercapto acetate, 2,3-bis((2-mercaptoethyl)thio)-l-propanethiol, 2,3-dithio (2-mercapto)-l- propane mercaptan and thiol-terminated polyethers.

[0078] Suitable compounds that include both thiol or mercapto groups and hydroxy functional groups may include, without limitation, dithiothreitol; thiol and hydroxy functional polyesters, poly(meth)acrylates, and polycarbonates; 2,3-dimercapto - 1 - propanol, and compounds according to the formula:(HS)x-R1y-(OH)zwhere R1can be a C2 , such as C3 or C<, to C20 linear, branched or cyclic, aliphatic and / or aromatic group or a polymeric backbone that can include O, N and / or S hetero atoms, where y is from 1 to 100, such as 1 to 50 or 1 to 25; x can be from 1 to 50, such as 1 to 30 or 1 to 20 or 1 to 10 or 1 to 5, where the SH group is bonded to a carbon atom; and z can be from 0 to 60, such as 1 to 40 or 1 to 30 or 1 to 20 or 1 to 10 or 1 to 5, where the OH group is bonded to a carbon atom.

[0079] The polyurethane containing thiol functional groups may be derived from a mixture comprising an amount of compounds that include thiol or mercapto groups of from 15 wt. %, such as from 20 wt. %, or from 25 wt. % to 30 wt. %, such as 35 wt. %, or 40 wt. %, or 50 wt. %, or 60 wt. %, or 70 wt. % or within any range using any two of the foregoing values as endpoints, such as from 15 wt. % to 70 wt. %, such as from 20 wt. % to 60 wt. %, or from 25 wt. % to 50 wt. %, where wt. % is based on total resin solids.C. Ionic Polyurethane Resin

[0080] When the polyurethane resin contains thiol functional groups and ionic dispersible groups according to this disclosure, the polyurethane can be prepared by reacting an isocyanate reactive compound, such as a hydroxyl functional polyester, polycarbonate, polyether, and / or acrylic polymer; polyhydroxy compound or poly hydroxy carboxylic acid with a polyisocyanate such that the NCO / isocyanate reactive group ratio is greater than 1:1 to generate an NCO functional prepolymer. Acid groups can be introduced, as a nonlimiting example, by using a poly hydroxy carboxylic acid, such as an acid containing diol. The terminal isocyanates can then be reacted with a thiol containing compound to produce a terminal SH functional polymer. The acid functional polyurethane polymers may be neutralized with a tertiary alkylated amine prior to and / or after contact with water to provide water dispersibility.

[0081] The polyurethane resin of the present disclosure can include an acid containing polyol reactive with the polyisocyanate. The acid containing polyol may include, without limitation, dimethanol propionic acid, 2,2-bis(hydroxymethyl)butyric acid, tartaric acid, 3,5-dihydroxybenzoic acid, ascorbic acid and its isomers, and any acid derivatives of the polyols described herein.

[0082] When the ionic polyurethane resin includes acid functionality, the acid value of the resin may be determined using a Metrohm 798 MPT Titrino automatic titrator, manufactured by Metrohm AG, according to ASTM D4662-15. The value may be then divided by the content of total solids to result in acid value on solids. The active hydrogen containing resin can have an acid value on solids greater than 8 mg KOH / g, greater than 25 mg KOH / g, greater than 50 mg KOH / g, greater than 60 mg KOH / g, greater than 70 mg KOH / g, greater than 75 mg KOH / g to greater than 80 mg KOH / g, greater than 85 mg KOH / g, greater than 90 mg KOH / g, greater than 100 mg KOH / g, on solids, or within any range using any two of the foregoing values as endpoints, such as 10 mg KOH / g to 100 mg KOH / g , 25 mg KOH / g to 90 mg KOH / g, 50 mg KOH / g to 85 mg KOH / g, or 60 mg KOH / g to 80 mg KOH / g.

[0083] The ionic polyurethane resin may be derived from a mixture comprising an amount of acid containing polyol of from 5 wt. %, such as from 10 wt. %, or from 15 wt. % to 20 wt. %, or 25 wt. %, or 30 wt. %, or within any range using any two of the foregoing values as endpoints, such as from 5 wt. % to 30 wt. %, or from 10 wt. % to 25 wt. %, or from 15 wt. % to 20 wt. %, where wt. % is based on total resin solids.

[0084] When the dispersible groups of the polyurethane resins include ionic groups, the polyurethane resins may also include nonionic groups. When the polyurethane resins include both ionic groups and nonionic groups the ratio of ionic groups to nonionic groups can be from 80:20 to 5:95, such as 60:40 to 10:90, 50:50 to 15:85, or 65:35 to 20:80.D. Nonionic Polyurethane Resin

[0085] As a nonlimiting example, the polyurethane resin containing thiol functional groups and nonionic dispersible groups can be prepared by first reacting an isocyanate reactive compound, such as a hydroxyl functional compound, with a polyisocyanate such that the NCO / isocyanate reactive group ratio is greater than 1:1 to generate an NCO functional prepolymer. The terminal isocyanates can then be reacted with a polythiol or polymercapto compound to produce a terminal SH functional polymer.

[0086] When the dispersible groups include nonionic groups, the dispersible groups can include polyalkylene oxide groups. The polyalkylene oxide groups can include poly(ethylene oxide), poly (propylene oxide) and / or copolymers of ethylene oxide and propylene oxide.

[0087] Suitable nonionic hydroxy functional compounds may include Methoxypolyethylene Glycol 350, 550, and / or 750 available from Dow (Midland, MI, USA). Suitable nonionichydroxy functional compounds may also include Methoxypolyethylene Glycol 2000 available from Dow (Midland, MI, USA) and / or butoxypropylene glycol..

[0088] The nonionic polyurethane resin may be derived from a mixture comprising an amount of nonionic hydroxy functional compound of from 5 wt. %, 10 wt. %, 15 wt. % to 20 wt. %, 25 wt. %, 30 wt. %, 40 wt. % or within any range using any two of the foregoing values as endpoints, such as 5 wt. % to 40 wt. %, 5 wt. % to 30 wt. %, 10 wt. % to 25 wt. %, or 15 wt. % to 20 wt. %, where wt. % is based on total resin solids.

[0089] When the dispersible groups of the polyurethane resins include nonionic groups, it may also include ionic groups. When the polyurethane resins include both nonionic groups and ionic groups the ratio of nonionic groups to ionic groups can be from 80:20 to 5:95, such as from 60:40 to 10:90, or from 50:50 to 15:85, or from 65:35 to 20:80.

[0090] The polyurethane resins can be present in the coating composition as an aqueous dispersion.E. Blends of Ionic and Nonionic Polyurethane Resins

[0091] The polyurethane resins in the coating compositions disclosed herein can include blends and / or other combinations of ionic polyurethane resins and nonionic polyurethane resins as described above. When blends or other combinations are used, the ratio of ionic polyurethane resins to nonionic polyurethane resins, defined by the ratio of ionic groups to nonionic groups can be from 95:5 to 5:95, such as from 80:20 to 5:95, or from 60:40 to 10:90, or from 50:50 to 15:85, or from 65:35 to 20:80.

[0092] When the polyurethane resins include blends of polyurethane resins containing nonionic groups and polyurethane resins containing ionic groups the polyurethane resins can be used at a weight ratio of from 1:20 to 20:1, such as from 1:4 to 20: 1, or from 1:3 to 10:1, or from 1 :2 to 10:1 or from 1:2 to 8:1 polyurethane resins containing nonionic groups to polyurethane resins containing ionic groups.III. Crosslinker

[0093] The crosslinker includes functional groups reactive with functional groups in the polyurethane resins. The crosslinker can include any of the crosslinkers known in the art to react with the functionality of the resins used in the coating compositions. The functional groups in the crosslinker can include, without limitation, epoxy, olefinic groups and isocyanate functional groups. The crosslinker can be reactive with the thiol functional groups in the polyurethane resin.A. Olefinic crosslinker

[0094] When the functional groups in the crosslinker include olefinic groups, the crosslinker can include, as nonlimiting examples, (meth)acrylic esters of a molecule containing two or more hydroxyl groups, (meth)acrylic amides of a molecule containing an amine and two or more hydroxyl groups, allylic ethers of a molecule containing two or more hydroxyl groups, (meth)acryloyl-functional polyaddition polymers, polyurethanes, and polyesters.

[0095] When the crosslinker includes olefinic groups that are thiol-reactive the crosslinker can include, without limitation, any compound containing two or more olefinically unsaturated groups, with the olefinically unsaturated groups containing at least one electron-withdrawing functionality linked to a carbon atom of the unsaturated bond.

[0096] When the functional groups in the crosslinker include olefinic groups, the molar ratio of thiol groups to olefinic groups can be from 1:3 to 3: 1 such as 1:2 to 2: 1 or 1:1.5 to 1.5:1.

[0097] The coating composition can include an olefinic crosslinker in an amount of from 15 wt. %, 30 wt. %, 40 wt. %, to 50 wt. %, 60 wt. %, 70 wt. %, or within any range using any two of the foregoing values as endpoints, such as 15 wt. % to 70 wt. %, 30 wt. % to 60 wt. %, or 40 wt. % to 50 wt. %, where wt. % is based on the total weight of the coating composition.B. Epoxy Crosslinker

[0098] The crosslinker can include an epoxy group that is reactive with functional groups in the polyurethane resin to form a crosslinked composition. Suitable epoxy group containing compounds may include, without limitation, compounds having two or more epoxy groups in the molecule, such as, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6- hexanediol diglycidyl ether, glycerol, polyglycidyl ether, hydrogenated bisphenol A diglycidyl ether and derivatives thereof, bisphenol F diglycidyl ether and derivatives thereof, trimethyl propane polyglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, and polypropylene glycol diglycidyl ether.

[0099] Other epoxy group containing compounds include, without limitation, epoxy functional polymers, such as those derived from one or more of ethylenically unsaturated monomers containing epoxy groups, such as glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether.

[0100] The curable composition may include a molar ratio of thiol groups (such as from the polyurethane resin) to epoxy groups of from 0.25:1.75, 0.5:1.5 to 0.75:1.25, 1:1, 0.75:1, 0.5:1 or any ratio within the range of the foregoing ratios.

[0101] The coating composition can have an epoxy crosslinker in an amount of from 15 wt. %, such as from 30 wt. %, or from 40 wt. %, to 50 wt. %, or 60 wt. %, or 70 wt. %, or within any range using any two of the foregoing values as endpoints, such as from 15 wt. % to 70 wt.%, or from 30 wt. % to 60 wt. %, or from 40 wt. % to 50 wt. %, where wt. % is based on the total weight of the coating composition.C. Isocyanate Crosslinker

[0102] The crosslinker can include an isocyanate that is reactive with functional groups in the polyurethane resin to form a crosslinked composition. Nonlimiting examples of a suitable compound which contains isocyanate groups include isocyanates and blocked isocyanates. Suitable compounds with an effective number of isocyanate groups suitable for use as crosslinkers in the coating compositions include, without limitation, any isocyanate known from polyurethane chemistry such as described above such as the isocyanurate trimer of 1,6- diisocyanatohexane, the isocyanurate trimer of isophorone diisocyanate, the uretdione dimer of 1,6-diisocyanatohexane, the biuret of 1,6-diisocyanatohexane, the allophanate of 1,6- diisocyanatohexane, and mixtures thereof.

[0103] The curable composition may include a molar ratio of thiol groups (such as from the polyurethane resin) to isocyanate groups of the crosslinker from 0.25: 1.75, 0.5:1.5 to 0.75:1.25, 1 :1, 0.75: 1, 0.5:1 or any ratio within the range of the foregoing ratios.

[0104] The coating composition can have an isocyanate crosslinker in an amount of from 15 wt. %, such as from 30 wt. %, or from 40 wt. %, to 50 wt. %, or 60 wt. %, or 70 wt. %, or within any range using any two of the foregoing values as endpoints, such as 15 wt. % to 70 wt. %, or from 30 wt. % to 60 wt. %, or from 40 wt. % to 50 wt. %, where wt. % is based on the total weight of the coating composition.IV. Basic catalyst

[0105] Any suitable basic catalyst can be used in the present coating composition. Suitable basic catalysts include, without limitation, include primary, secondary, and / or tertiary amines, such as triethyl amine and aldimine.

[0106] When the basic catalyst includes an amine, the amine can include, without limitation, a tertiary amine, tetramethyl guanidine, 1,4-dihydropyrimidines, l,8-diaza-bicyclo[5.4.0]undec- 7-ene, l,4-diaza-bicyclo[2.2.2]octane and 2-alkyl-N-alkyl imidazolines.

[0107] The coating composition can include the catalyst in an amount of from 0. 1 wt. %, such as from 0.5 wt. %, or from 1 wt. %, to 5 wt. %, or 4.5 wt. %, or 4 wt. %, or within any range using any two of the foregoing values as endpoints, such as from 0.1 wt. % to 5 wt. %, or from 0. 1 wt. % to 4.5 wt. %, or from 0.5 wt. % to 4 wt. %, where wt. % is based on the total weight of the coating composition.V. Volatile Acid

[0108] Any suitable volatile acid can be used in the coating composition. Volatile acids can have a vapor pressure of at least 1 mm Hg, such as at least 1.5 mm Hg or at least 1.65 mm Hg at 25 °C for ambient cure coating compositions and have at least the same vapor pressure at higher cure temperatures when such temperatures are employed. Suitable volatile acids include, without limitation, those containing carboxylic acid groups, sulfonic acid groups or sulfamic acid groups. When the volatile acid includes a carboxylic acid group, the volatile acid can include, without limitation, C1-C5 carboxylic acids, such as formic acid, acetic acid, propionic acid, lactic acid, isobutyric acid, n-butyric acid and isovaleric acid when an ambient cure temperature is employed. Volatile acids for use at ambient cure temperatures are volatile at ambient temperatures and can act to control the rate of cure at ambient temperatures.

[0109] When higher cure temperatures, such as from 40 °C to 240 °C, from 45 °C to 210 °C or from 50 °C to 140 °C are used, acids that are volatile at those cure temperatures can be used. As a nonlimiting example of acids that are volatile at higher cure temperatures and can be used include C2 - C22 linear, branched, or cyclic aliphatic or aromatic carboxylic acids that include from 1 to 5, such as from 1 to 4 or from 1 to 3 carboxylic acid groups. Nonlimiting examples of such acids include isononanoic acid, isostearic acid. Volatile acids for use at higher cure temperatures may not be volatile at ambient temperatures but are volatile at the higher cure temperatures and can act to control the rate of cure at those temperatures.

[0110] The coating composition can include the volatile acid in an amount of from 0.01 wt. %, such as from 0.05 wt. %, or from 0. 1 wt. %, to 0.5 wt. %, or 0.45 wt. %, or 0.4 wt. %, or within any range using any two of the foregoing values as endpoints, such as from 0.01 wt. % to 0.5 wt. %, or from 0.01 wt. % to 0.45 wt. %, or from 0.05 wt. % to 0.4 wt. %, where wt. % is based on the total weight of the coating composition.VI. Other Additives

[0111] The present the coating composition can include conventional additives for coating compositions in the art. Such additives include, without limitation, water, stabilizers, flow additives, fillers, plasticizers, antioxidants, hindered amine light stabilizers, UV light absorbers and stabilizers, catalyst blocking agents, colorants (dyes, color pigments, metallics and / or pearls), wax, defoamers, surfactants, rheology modifiers, thixotropic agents, fillers, wetting agents leveling agents, catalysts, grind vehicles, and other customary auxiliaries.

[0112] The coating composition can be water borne or solvent borne. Solvent borne compositions may include any solvent known in the art, i.e., aliphatic and / or aromatic hydrocarbons. Examples include, without limitation, toluene, xylene, butyl acetate, ethyl acetate, acetone, methyl isobutyl ketone, methyl isoamyl ketone, methyl ethyl ketone, ether, etheralcohol, ether ester, hexylglycol, butoxyethanol, 1 -methoxy-propanol-2, 1-ethoxy -propanol-2, 1- propoxy-propanol-2, 1 -butoxy-propanol-2, 1 -isobutoxy-propanol-2, dipropylene glycol monomethyl ether; methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, ethylene glycol, diethylene glycol, dimethyl dipropylene glycol, diacetone alcohol, methylether of diacetone alcohol, ethoxy ethyl propionate, or a mixture of any of these. Water borne means that the volatile content of the composition includes a substantial proportion of water, such as at least 20 wt. %, at least 30 wt. % or at least 40 wt. % based on the total weght of the coating composition; but can also include an organic co-solvent. The co-solvents used in water borne compositions include the same ones as the organic solvents mentioned above.

[0113] The coating compositions described herein can include less than 780 g / 1 of volatile organic compounds (VOC) based on the total composition, such as less than 420 g / 1, or less than 250 g / 1 determined according to the following equation:'S"LActual (where Cd represents the coating density in pounds per gallon; W™ represents the total weight of volatile material as a percent of the total coating weight (pounds); Wwrepresents the weight of water in the coating as a percent of the total coating weight (pounds); and Werepresents the weight of exempt compounds in the coating as a percent of the total coating weight (pounds). Exempt compounds are defined by local regulations if permitted at all. Examples of exempt solvents may include acetone, dimethyl carbonate, methyl acetate, parachlorobenzotrifluoride (Oxsol 100), tert-Butyl acetate, and propylene carbonate. The curable composition of the present disclosure may be entirely free of VOC.VII. Total Solids - Viscosity

[0114] The coating compositions described herein can have a total resin solids of at least 20 wt. %, such as at least 21 wt. %, or at least 22 wt. %, or at least 23 wt. %, or at least 24 wt. %, or at least 25 wt. % and up to 65 wt. %, such as up to 50 wt. %, or up to 45 wt. %, or up to 42 wt. %; or from 20 wt. % to 65 wt. %, such as 20 wt. % to 50 wt. %, or from 21 wt. % to 45 wt. %, or from 22 wt. % to 42 wt. % or from 25 wt. % to 42 wt. % determined as described above.

[0115] The coating compositions described herein can have a viscosity of from 10 to 500 cps, such as from 20 to 100 cps measured using a Cone and Plate Viscometer, such as a CAP 2000 viscometer available from Brookfield (AMETEK Brookfield) at 25 °C, 900rpm using spindle number 1.

[0116] The coating compositions can be one-component, two-component or multi-component compositions. When multi- or two-component compositions are used, one component can include the polyurethane resin, and another component can include the crosslinker. The basic catalyst and volatile acid can be in any component or as a separate component or components.

[0117] The coating compositions described herein can be applied, as a nonlimiting example, by forming a coating layer on at least a portion of a substrate. The method can include applying the present coating composition over at least a portion of the substrate; and exposing the coating composition to a sufficient amount of energy for a sufficient amount of time for the coating composition to cure, such as the reaction of the polyurethane resin and the crosslinker.

[0118] The coating composition can be applied using methods known in the art, such as spray application, draw down, brush application, dip application and / or precision application.

[0119] The substrate described above, can include iron, steel, and aluminum, plastic, wood, composite, glass, synthetic material, paper, leather, and / or another coating layer.

[0120] The coating composition can be cured, without limitation, by exposure to ambient conditions, elevated temperature, and / or actinic radiation.

[0121] When the coating composition is cured by exposure to elevated temperatures the temperature can be from 40 °C to 240 °C, from 45 °C to 210 °C or from 50 °C to 140 °C.

[0122] Not being bound to any particular theory, the cure time can be affected by the volatile acid, which, as a nonlimiting example, can inhibit the cure reaction when it is present, the effect of which subsides as the volatile acid evaporates. The coating composition can have a cure time of from 30 seconds to 24 hours, such as from 1 minute to 12 hours, or from 5 minutes to 8 hours, or from 10 minutes to 4 hours, or from 30 seconds to 10 minutes, or from 45 seconds to 5 minutes at cure temperatures as determined by achieving 100 MEK double rubs (MEKDR) with a rating of 8 or greater as described below.

[0123] As indicated above, the substrate can include a previously applied coating layer. As a nonlimiting example, the present coating composition can become part of a multilayer coating composition. As nonlimiting examples, the present coating composition can be a coating layer applied over a basecoat or a coating layer applied over a primer coat.

[0124] Depending on the particular use intended, the present coating composition can be applied as a topcoat, such as a clearcoat, or it can be applied as a direct gloss topcoat or monocoat.

[0125] Application of the present coating composition can result in a coating layer that has a dry film thickness of from 0.5 pm to 250 pm, such as from 0.5 pm to 200 pm, or from 0.5 pm to 150 pm, or from 0.5 pm to 100 pm, or from 0.5 pm to 75 pm, or from 0.5 pm to 65 pm, or from0.5 pm to 55 pm, or from 0.5 ,um to 52 pm, or from 1 |rm to 250 |rm, or from 1 |im to 200 |rm, or from 1 |im to 100 |rm, or from 1 |im to 65 |im, or from 1 pm to 60 pm, or from 1 |im to 55 pm, or from 5 |im to 250 pm, or from 5 pm to 200 pirn, or from 5 m to 100 pm, or from 5 pm to 65 pm, or from 5 pm to 60 pm or from 5 pm to 55 pm measured according to ASTM D7091- 21.

[0126] The present disclosure also provides a substrate at least partially coated with a coating formed from the coating compositions described above. In particular, the coating composition can be applied to a substrate and cured to form a coating thereover. The coating can be a continuous film formed over at least a portion the substrate.

[0127] The substrate over which the coating composition can be applied includes a wide range of substrates. As a nonlimiting example, the coating composition of the present disclosure can be applied to a vehicle substrate, an industrial substrate, an aerospace substrate, and the like.

[0128] The vehicle substrate can include a component of a vehicle. As a nonlimiting example, the vehicle can include an aerospace substrate (a component of an aerospace vehicle, such as an aircraft such as, for example, airplanes (e.g., private airplanes, and small, medium, or large commercial passenger, freight, and military airplanes), helicopters (e.g., private, commercial, and military helicopters), aerospace vehicles (e.g., rockets and other spacecraft), and the like). The vehicle can also include a ground vehicle such as, for example, animal trailers (e.g., horse trailers), all-terrain vehicles (ATVs), cars, trucks, buses, vans, heavy duty equipment, tractors, golf carts, motorcycles, bicycles, snowmobiles, trains, railroad cars, and the like. The vehicle can also include watercraft such as, for example, ships, boats, hovercrafts, and the like. The vehicle substrate may include a component of the body of the vehicle, such as an automotive hood, door, trunk, roof, and the like; such as an aircraft or spacecraft wing, fuselage, and the like; such as a watercraft hull, and the like.

[0129] The coating composition can be applied over an industrial substrate which can include, without limitation, tools, heavy duty equipment, furniture such as office furniture (e.g., office chairs, desks, filing cabinets, and the like), appliances such as refrigerators, ovens and ranges, dishwashers, microwaves, washing machines, dryers, small appliances (e.g., coffee makers, slow cookers, pressure cookers, blenders, etc.), metallic hardware, extruded metal such as extruded aluminum used in window framing, other indoor and outdoor metallic building materials, and the like.

[0130] The coating composition can be applied over storage tanks, windmills, nuclear plant components, packaging substrates, wood flooring and furniture, apparel, electronic including,but not limited to, housings and circuit boards, glass and transparencies, sports equipment, including golf balls, stadiums, buildings, bridges, and the like.

[0131] The substrate can be metallic or non-metallic. Metallic substrates include, but are not limited to, tin, steel (including electrogalvanized steel, cold rolled steel, hot-dipped galvanized steel, among others), aluminum, aluminum alloys, zinc-aluminum alloys, steel coated with a zincaluminum alloy, and aluminum plated steel. Non-metallic substrates include polymeric materials, plastic and / or composite material, polyester, polyolefin, polyamide, cellulosic, polystyrene, polyacrylic, poly(ethylene naphthalate), polypropylene, polyethylene, nylon, ethylene vinyl alcohol (EVOH), polylactic acid, other “green” polymeric substrates, poly(ethyleneterephthalate) (PET), polycarbonate, polycarbonate acrylobutadiene styrene (PC / ABS), wood, veneer, wood composite, particle board, medium density fiberboard, cement, stone, glass, paper, cardboard, textiles, leather, both synthetic and natural, and the like. The substrate can include a metal, and / or a plastic and / or composite material, and / or a fibrous material. The fibrous material may comprise a nylon and / or a thermoplastic polyolefin material with continuous strands or chopped carbon fiber. The substrate can be one that has already been treated in some manner, such as to impart visual and / or color effect, a protective pretreatment or other coating layer, and the like.

[0132] The coating composition of the present disclosure can be particularly beneficial when applied to a metallic substrate. The coatings of the present disclosure can be particularly beneficial when applied to metallic substrates that are used to fabricate automotive vehicles, such as cars, trucks, and tractors.

[0133] As a nonlimiting example, the coating composition can be applied to a substrate having multiple components, wherein the coating composition is simultaneously applied to the multiple components and simultaneously cured to form a coating over the multiple components without deforming, distorting, or otherwise degrading any of the components. The components can be parts of a larger whole of the substrate. The components can be separately formed and subsequently arranged together to form the substrate. The components can be integrally formed to form the substrate.

[0134] Non-limiting examples of components of a substrate in the vehicle context include a vehicle body (e.g., made of metal) and a vehicle bumper (e.g., made or plastic) which are separately formed and subsequently arranged to form the substrate of the vehicle. Further examples include a plastic automotive component, such as a bumper or fascia in which the bumper or fascia comprises regions or subcomponents which comprise more than one type of substrate. Further examples include aerospace or industrial components comprising more than one substrate type. It will beappreciated that other such multi-component substrates are contemplated within the context of this disclosure.VIII. Properties of the Cured Composition

[0135] Coating compositions formed as described herein may exhibit resistance to solvents and increased cross-linking density (XLD).A. Solvent Resistance Test

[0136] To test the resistance of the coating composition, a substrate coated with the coating composition may be subjected to a solvent resistance test according to the method described below.

[0137] A solvent resistance test may be performed by placing a test panel on a flat table or other suitable flat, firm surface. A disposable wipe (such as a WypAll L30) is folded to a roughly one inch square dimension in order to test the cured panel for solvent resistance.

[0138] The wipe is saturated with an appropriate solvent, such as methyl ethyl ketone (MEK), for the substrate being tested. The wipe is re-saturated every 25 double rubs.

[0139] The substrate coated with the curable composition is immediately rubbed with the saturated wipe over the test area using a back-and-forth stroke of 2-4 inches.

[0140] The back-and-forth strokes may be continued, counting one “double rub” for each forward and backward motion completed until the bare substrate is exposed in the center of the strip where the rubs are performed or until 100 double rubs are achieved.

[0141] The number of “double rubs” are recorded as the test result. The wipe should be removed and replaced with a new wipe in between each sample tested.

[0142] The curable composition formed using the methods described herein may have a solvent resistance of at least 60 MEK double rubs (MEKDR), at least 70 MEK double rubs, at least 80 MEK double rubs, at least 100 MEK double rubs, with a rating of 8 or greater according to the following scale:B. Coating Hardness

[0143] To test the hardness of a coating composition applied to a plane rigid surface, a Konig Pendulum Hardness Test can be performed as detailed in ASTM D 4386-95. The coating layer of the coating composition formed using the methods described herein may have a Konig Hardness of at least 20 seconds, such as at least 25 seconds, or at least 30 seconds.ASPECTS

[0144] A first aspect of the disclosure is directed to a coating composition, which includes: one or more polyurethane resins that include thiol functional groups and dispersible groups; one or more crosslinkers that include functional groups reactive with the thiol functional groups; a basic catalyst; and a volatile acid.

[0145] A second aspect of the disclosure is directed to a coating composition according to the first aspect, where the dispersible groups include ionic groups and nonionic groups.

[0146] A third aspect of the disclosure is directed to a coating composition according to the second aspect, where the ratio of ionic groups to nonionic groups is from 80:20 to 5:95, such as 60:40 to 10:90, 50:50 to 15:85, or 65:35 to 20:80.

[0147] A fourth aspect of the disclosure is directed to a coating composition according to any preceding aspect, wherein the polyurethane resins include a blend or combination of ionic polyurethane resins and nonionic polyurethane resins having a ratio of ionic groups to nonionic groups of from 80:20 to 5:95, such as 60:40 to 10:90, 50:50 to 15:85, or 65:35 to 20:80.

[0148] A fifth aspect of the disclosure is directed to a coating composition according to any preceding claim, wherein the dispersible groups include ionic groups.

[0149] A sixth aspect of the disclosure is directed to a coating composition according to any preceding aspect, where the dispersible groups include ionic groups that include carboxylate groups.

[0150] A seventh aspect of the disclosure is directed to a coating composition according to any preceding aspect, where the dispersible groups include nonionic groups.

[0151] An eighth aspect of the disclosure is directed to a coating composition according to any preceding aspect, where the dispersible groups include polyalkylene oxide groups.

[0152] A ninth aspect of the disclosure is directed to a coating composition according to any preceding aspect, where the dispersible groups include poly(ethylene oxide), poly (propylene oxide) and / or copolymers of ethylene oxide and propylene oxide.

[0153] A tenth aspect of the disclosure is directed to a coating composition according to any preceding aspect, where the functional groups reactive with the thiol functional groups include olefinic groups, isocyanate groups and / or epoxy groups.

[0154] An eleventh aspect of the disclosure is directed to a coating composition according to the tenth aspect, where the ratio of thiol groups to olefinic groups is from 1:3 to 3:1 such as 1:2 to 2: 1 or 1:1.5 to 1.5: 1.

[0155] A twelfth aspect of the disclosure is directed to a coating composition according to any preceding aspect, where the polyurethane resins are present in the coating composition as an aqueous dispersion.

[0156] A thirteenth aspect of the disclosure is directed to a coating composition according to any preceding aspect, where the crosslinkers includes acrylic esters of a molecule that includes two or more hydroxyl groups.

[0157] A fourteenth aspect of the disclosure is directed to a coating composition according to any preceding aspect, where the basic catalyst includes amines, such as tertiary amines.

[0158] A fifteenth aspect of the disclosure is directed to a coating composition according to any preceding aspect, where the volatile acid includes carboxylic acid groups, sulfonic acid groups or sulfamic acid groups having a vapor pressure of at least 1 mm Hg, such as at least 1.5 mm Hg or at least 1.65 mm Hg at 25 °C or at desired cure temperatures.

[0159] A sixteenth aspect of the disclosure is directed to a coating composition according to the fifteenth aspect, where the desired cure temperature is ambient temperature, such as 23 °C and the volatile acid includes C1-C5 carboxylic acids, such as formic acid, acetic acid, propionic acid, lactic acid, isobutyric acid, n-butyric acid and / or isovaleric acid.

[0160] A seventeenth aspect of the disclosure is directed to a coating composition according to the fifteenth aspect, where the cure temperature is from 40 °C to 240 °C, such as from 45 °C to 210 °C or from 50 °C to 140 °C and the volatile acid includes C2 - C22 linear, branched or cyclic aliphatic or aromatic carboxylic acids that include from 1 to 5, such as from 1 to 4 or from 1 to 3 carboxylic acid groups, such as isononanoic acid and isostearic acid.

[0161] An eighteenth aspect of the disclosure is directed to a coating composition according to any preceding aspect, where the coating composition includes the volatile acid in an amount of from at least 0.01 wt. %, such as at least 0.05 wt. %, or at least 0.1 wt. % and up to 0.5 wt. %, such as up to 0.45 wt. %, or up to 0.4 wt. %, and can be from 0.01 wt. % to 0.5 wt. %, such as from 0.01 wt. % to 0.45 wt. %, or from 0.05 wt. % to 0.4 wt. %, where wt. % is based on the total weight of the coating composition.

[0162] A nineteenth aspect of the disclosure is directed to a coating composition according to any preceding aspect, where the coating composition has a total resin solids of at least 20 wt. %, such as at least 21 wt. %, or at least 22 wt. %, or at least 23 wt. %, or at least 24 wt. %, or at least 25 wt. % and up to 65 wt. %, such as up to 50 wt. %, or up to 45 wt. %, or up to 42 wt. %; or from 20 wt. % to 65 wt. %, such as 20 wt. % to 50 wt. %, or from 21 wt. % to 45 wt. %, or from 22 wt. % to 42 wt. % or from 25 wt. % to 42 wt. % determined according to ASTM D2369-20.

[0163] A twentieth aspect of the disclosure is directed to a coating composition according to any preceding aspect, where the coating composition has a viscosity of from 10 to 500 cps, such as from 20 to 100 cps measured using a Cone and Plate Viscometer at 25 °C at 900rpm.

[0164] A twenty-first aspect of the disclosure is directed to a method of forming a coating layer on at least a portion of a substrate that includes: applying the coating composition according to any preceding aspect over at least a portion of the substrate; and exposing the coating composition to a sufficient amount of energy for a sufficient amount of time for the coating composition to cure.

[0165] A twenty-second aspect of the disclosure is directed to the method of the twenty-first aspect, where the coating composition is applied using a method that includes spray application, draw down, brush application, dip application and / or precision application.

[0166] A twenty-third aspect of the disclosure is directed to the method of either of the twenty-first or twenty-second aspects, where the substrate includes iron, steel, aluminum, plastic, wood, composite, glass, synthetic material, paper, leather, and / or another coating layer.

[0167] A twenty-fourth aspect of the disclosure is directed to the method of any of the twenty- first through twenty-third aspects, where the coating composition is cured by exposure to ambient conditions, elevated temperature, and / or actinic radiation.

[0168] A twenty-fifth aspect of the disclosure is directed to the method of the twenty-fourth aspect, where the coating composition is cured by exposure to elevated temperatures of from 40 °C to 240 °C, from 45 °C to 210 °C or from 50 °C to 140 °C.

[0169] A twenty-sixth aspect of the disclosure is directed to the method of any of the twenty- first through twenty-fifth aspects, where the coating composition has a cure time of from 30 seconds to 24 hours, such as from 1 minute to 12 hours, or from 5 minutes to 8 hours, or from 10 minutes to 4 hours, or from 30 seconds to 10 minutes, or from 45 seconds to 5 minutes at cure temperatures.

[0170] A twenty-seventh aspect of the disclosure is directed to the method of any of the twenty-first through twenty-sixth aspects, where the coating composition has a cure time that is affected by the amount of acid and basic catalyst present in the coating composition.

[0171] A twenty-eighth aspect of the disclosure is directed to the method of any of the twenty- first through twenty-seventh aspects, where the coating layer is applied over one or more previously applied coating layers and / or is part of a multilayer coating composition.

[0172] A twenty-ninth aspect of the disclosure is directed to the method of any of the twenty- first through twenty-eighth aspects, where the coating layer is applied over a basecoat.

[0173] A thirtieth aspect of the disclosure is directed to the method of any of the twenty-first through twenty-eighth aspects, where the coating layer is applied over a primer coat.

[0174] A thirty-first aspect of the disclosure is directed to the method of any of the twenty- first through twenty-eighth aspects, where the coating layer is a topcoat, such as a clearcoat.

[0175] A thirty-second aspect of the disclosure is directed to the method of any of the twenty- first through twenty-eighth aspects, where the coating layer is a monocoat.

[0176] A thirty-third aspect of the disclosure is directed to the method of any of the twenty- first through thirty-second aspects, where the coating layer has a dry film thickness of from 0.5 pm to 250 pm, such as from 0.5 pm to 200 pm, or from 0.5 pm to 150 pm, or from 0.5 pm to 100 pm, or from 0.5 pm to 75 pm, or from 0.5 pm to 65 pm, or from 0.5 pm to 55 pm, or from 0.5 pm to 52 pm, or from 1 pm to 250 pm, or from 1 pm to 200 pm, or from 1 pm to 100 pm, or from 1 pm to 65 pm, or from 1 pm to 60 pm, or from 1 pm to 55 pm, or from 5 pm to 250 pm, or from 5 pm to 200 pm, or from 5 pm to 100 pm, or from 5 pm to 65 pm, or from 5 pm to 60 pm or from 5 pm to 55 pm measured according to ASTM D7091-21.

[0177] A thirty-fourth aspect of the disclosure is directed to a substrate at least partially coated according to the method of any of the twenty-first through thirty-third aspects.

[0178] A thirty-fifth aspect of the disclosure is directed to the substrate of the thirty-fourth aspect, where the substrate includes a vehicle substrate.EXAMPLES

[0179] Aspects of the present disclosure are further illustrated by reference to the following examples. It will be apparent to those skilled in the art that many modifications, both to materials, and methods, may be practiced without departing from the scope of the disclosure.THIOL EQUIVALENT WEIGHT

[0180] As used herein, “thiol equivalent weight” can be and was determined in the following examples as follows. A sample (0.2-0.6 g) of the thiol terminated polyurethane was dissolved in 1 ml pyridine and 30 ml of a 1: 1 solution by weight of methyl ethyl ketone and toluene. The solution was titrated via colorimetric analysis with 0. 1 N iodine solution until a slight yellow color persisted in the solution. Thiol solid equivalent weight was calculated using the following equation. weight of sample (g) * 1000— - — . — - * % solids ml of titrant * 0.1 N iodine

[0181] The reported thiol equivalent weights are the average of triplicate measurements.EXAMPLE 1 - Polyurethane dispersion PUD-1TABLE 1 Polyurethane dispersion (Ionic Dispersion; PUD-1)'Poly (tetrahydrofuran) polyol available from BASF (Southfield, MI, USA)2Dipropylene glycol dimethyl ether available from Dow (Midland, MI, USA)

[0182] To a four necked reaction flask outfitted with a stirrer, gas inlet, thermometer and condenser was added the contents of Charge 1 as indicated in Table 1. After the exotherm subsided, the temperature was raised to 80 °C and held for 2 hours. Charge 2 was added, andreaction was allowed to exotherm. Once the exotherm subsided the reaction was held at 80 °C until NCO levels were undetectable as measured by infrared spectroscopy. Charge 3 was added. An aqueous dispersion was produced by dispersing 680 g of the resulting material into Charge 4 heated to 60 °C. The final dispersion had a measured solids content of 34.4 wt. %, and measured thiol equivalent weight of 714 g / mol iodine on solids.EXAMPLE 2: Polyurethane dispersion - Non-ionic TABLE 2 Polyurethane dispersion (Non-ionic Dispersion; PUD-2)3Methoxypolyethylene Glycol 350 available from Dow (Midland, MI, USA)4Aliphatic polyisocyanate resin based on hexamethylene diisocyanate available from Covestro (Pittsburgh, PA, USA)5Dipropylene glycol dimethyl ether available from Dow (Midland, MI, USA)

[0183] To a four necked reaction flask outfitted with a stirrer, gas inlet, thermometer and condenser was added the contents of Charge 1 as indicated in Table 2. After the exotherm subsided, the temperature was raised to 80 °C and held for 2 hours. Charge 2 was added followed by Charge 3. The reaction was allowed to exotherm. Once the exotherm subsided the reaction was held at 80 °C until NCO levels were undetectable as measured by infrared spectroscopy. The solventborne resin had a measured solids of 80.5 wt. % and a measured thiol equivalent weight of 441 g / mol iodine on solids. An aqueous dispersion was produced by dispersing 200 grams of material into Charge 4 resulting in a dispersion with a theoretical solids of 40 wt. %.EXAMPLES 3-5: Blends 1, 2, and 3

[0184] Blends of Ionic and Non-ionic resin systems are shown in Table 3. The blends of PUD-1 and PUD-2 were made prior to formulating coatings. The resins were added to a 4 oz glass jar in the amounts in Table 3. Deionized water was used to thin blends to desired solids levels. Mixtures were stirred until homogenous. A milky dispersion was obtained for each example.TABLE 3EXAMPLE 6

[0185] Thiol-acrylate coating formulations were prepared in a 20 mL vial. Coatings were formulated using a 1:1 ratio of thiol equivalents to acrylate equivalents as shown in Table 4. Order of addition for mixing is listed below in the formulation information. Each formulation was drawn down using an 8 mil square bar over an ED7100 e-coated steel panel available from ACT Test Panel technologies (273 Industrial Dr., Hillsdale, MI 49242). The panels were allowed to flash for 10 minutes at ambient conditions then placed in a 60 °C oven for 45 minutes for cure. Panels were allowed to post-cure for 24 hours at ambient conditions and then evaluated for MEK resistance and Kbnig Hardness.TABLE 46Ethoxylated (3) Trimethylolpropane Triacrylate Available from Sartomer (Exton, PA, USA)710 wt. % l,4-diazabicyclo[2.2. 2]octane solution in deionized water8Silicone Surfactant available from BYK-Chemie Gmbh (Wese], Germany)

[0186] The examples indicate that the use of non-ionic resin allows for improved efficacy of catalyst, increasing cure performance and hardness development over purely ionic resin systems as shown by higher Konig hardness and MEKDR Rating of Examples 6-1 to 6-4 as compared to Example 6-5. By adjusting the ratio of non-ionic to ionic resin, a desired balance of cure and viscosity was obtained. Viscosity was determined using a CAP 2000 viscometer available from Brookfield (AMETEK Brookfield) at 25 °C, 900 rpm using spindle number 1.EXAMPLE 7

[0187] Thiol-epoxy coating formulations were prepared in a 20 mL vial. Coatings were formulated using a 1:1 ratio of thiol equivalents to epoxy equivalents as shown in Table 5. Order of addition for mixing is listed below in the formulation information. Each formulation was drawn down using an 8 mil square bar over an ED7100 e-coated steel panel available from ACT Test Panel technologies (273 Industrial Dr., Hillsdale, MI 49242). The panels were allowed to flash at ambient conditions for 10 minutes then placed in a 60 °C oven for 45 minutes. Panels were allowed to post-cure for 24 hours at ambient conditions and then evaluated for MEK resistance and Konig Hardness.TABLE 5710 wt. % l,4-diazabicyclo[2.2. 2]octane Solution in deionized water8Silicone Surfactant available from BYK-Chemie Gmbh (Wesel, Germany)9Sorbitol polyglycidyl ether-based epoxy crosslinker available from Nagase Specialty Materials N. A. LLC (Itasca, IL, USA)

[0188] The use of non-ionic resin allowed for improved efficacy of the catalyst, increasing cure performance and hardness development over purely ionic resin systems as shown by higher Konig hardness and MEKDR rating of Examples 7-1 to 7-4 as compared to Example 7-5. The introduction of non-ionic resins also allowed for an improved viscosity relationship with the viscosity of the blended PUD systems being lower than the non-ionic only system of Example 7- 1 and the viscosity of the blended systems of Examples 7-2 to 7-4 were similar to the viscosity of Example 7-5 or between the viscosity of Examples 7-1 and 7-5. By adjusting the ratio of non- ionic to ionic resin, a desired balance of cure and viscosity was obtained. Viscosity was determined using a CAP 2000 viscometer available from Brookfield (AMETEK Brookfield) at 25 °C, 900 rpm using spindle number 1.EXAMPLE 8

[0189] These examples demonstrate the beneficial use of a volatile acid to delay the cure response using the nonionic polyurethane of Example 2 and an acrylate cure system.TABLE 6710 wt. % l,4-diazabicyclo[2.2. 2]octane Solution in deionized Water8Silicone Surfactant available from BYK-Chemie Gmbh (Wesel, Germany)10Ethoxylated (3) Trimethylolpropane Triacrylate Available from Sartomer (Exton, PA, USA)11Gel time was too short to be able to measure viscosity

[0190] The examples shown in Table 6 were formulated at a 1:1 equivalent ratio of thiol to acrylate. The order of addition was thiol functional resin first then addition of the tri-acrylate monomer and the remaining ingredients except catalyst of initiator. The formula was then stirred until a milky homogeneous mixture was obtained. Then catalyst was added and stirred. Films were applied on ED7100 e-coated steel panel available from ACT Test Panel technologies (273 Industrial Dr., Hillsdale, MI 49242) using an 8 mil square drawdown bar. The films were then baked at 60 °C for 45 minutes. Panels were allowed to post-cure for one hour then tested for MEK resistance and Kbnig hardness.

[0191] The formulations and properties of the coating films are shown in Table 6. The uncatalyzed formula (example 8-1) showed a useful initial viscosity but did not demonstrate any cure on the panel. The addition of an amine catalyst (example 8-2) induced cure, but too quickly for reasonable application. The inclusion of the volatile acid (examples 8-3, 8-4, and 8-5), at a 1 : 1 molar ratio, allowed for an extension of gel time while still delivering cure on the panel. Viscosity was determined using a CAP 2000 viscometer available from Brookfield (AMETEK Brookfield) at 25 °C, 900 rpm using spindle number 1.EXAMPLE 9

[0192] These examples demonstrate the beneficial use of a volatile acid to delay the cure response using the nonionic polyurethane of Example 2 and an epoxy cure system.As shown in Table 7, the examples were formulated at a 1: 1 equivalent ratio of thiol to epoxy. The order of addition was thiol functional resin first then addition of the epoxy monomer. The formula was then stirred until a milky homogeneous mixture was obtained. Then catalyst was added and stirred. Films were applied on ED7100 e-coated steel panel available from ACT Test Panel technologies (273 Industrial Dr., Hillsdale, MI 49242) using an 8 mil square drawdown bar. The films were then baked at 60 °C for 45 minutes. Panels were allowed to post-cure for one hour then tested for MEK resistance and Kbnig hardness.

[0193] As shown in Table 7, the uncatalyzed formula (example 9-1) showed a useful initial viscosity relationship but did not demonstrate any cure on the panel. The addition of an amine catalyst (example 9-2) induced cure, but too quickly for reasonable application, with a short gel time of 10 minutes. The inclusion of the volatile acid (examples 9-3, 9-4, and 9-5), at a 1: 1 molar ratio, allowed for an extension of gel time while still delivering cure on the panel. Viscosity was determined using a CAP 2000 viscometer available from Brookfield (AMETEK Brookfield) at 25 °C, 900 rpm using spindle number 1.

[0194] Whereas particular embodiments of this disclosure have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations ofthe details of the present disclosure can be made without departing from what is defined in the appended claims.TABLE 7710wt. % l,4-diazabicyclo[2.2. 2]octane Solution in deionized Water8Silicone Surfactant available from BYK-Chemie Gmbh (Wesel, Germany)12Sorbitol polyglycidyl ether-based epoxy crosslinker available from Nagase Specialty Materials N. A. LLC (Itasca, IL, USA)

Claims

CLAIMSWe claim:

1. A coating composition, comprising: one or more polyurethane resins comprising thiol functional groups and dispersible groups; one or more crosslinkers comprising functional groups reactive with the thiol functional groups; a basic catalyst; and a volatile acid.

2. The coating composition according to claim 1, wherein the dispersible groups of the polyurethane resins comprise ionic groups and / or nonionic groups, such that when ionic and nonionic groups are present, they are present at a ratio of ionic groups to nonionic groups of from 80:20 to 5:95, such as 60:40 to 10:90, 50:50 to 15:85, or 65:35 to 20:80.

3. The coating composition according to any preceding claim, wherein the polyurethane resins comprise a blend or combination of ionic polyurethane resins and nonionic polyurethane resins having a ratio of ionic groups to nonionic groups of from 80:20 to 5:95, such as 60:40 to 10:90, 50:50 to 15:85, or 65:35 to 20:80.

4. The coating composition according to any preceding claim, wherein the dispersible groups comprise ionic groups comprising carboxylate groups and / or the dispersible groups comprise polyalkylene oxide groups, such as poly(ethylene oxide), poly (propylene oxide) and / or copolymers of ethylene oxide and propylene oxide.

5. The coating composition according to any preceding claim, wherein the functional groups reactive with the thiol functional groups comprise olefinic groups, isocyanate groups and / or epoxy groups, wherein the ratio of thiol groups to functional groups reactive with the thiol functional groups is from 1:3 to 3: 1 such as 1:2 to 2: 1 or 1:1.5 to 1.5: 1.

6. The coating composition according to any preceding claim, wherein the crosslinkers comprise acrylic esters of a molecule comprising two or more hydroxyl groups.

7. The coating composition according to any preceding claim, wherein the basic catalyst comprises amines, such as tertiary amines.

8. The coating composition according to any preceding claim, wherein the volatile acid comprises carboxylic acid groups, sulfonic acid groups or sulfamic acid groups having a vapor pressure of at least 1 mm Hg, such as at least 1.5 mm Hg or at least 1.65 mm Hg at 25 °C or at desired cure temperatures.

9. The coating composition according to claim 15, wherein the desired cure temperature is ambient temperature, such as 23 °C and the volatile acid comprises C1-C5 carboxylic acids, such as formic acid, acetic acid, propionic acid, lactic acid, isobutyric acid, n-butyric acid and / or isovaleric acid; or wherein the desired cure temperature is from 40 °C to 240 °C, such as from 45 °C to 210 °C or from 50 °C to 140 °C and the volatile acid comprises C2 - C22 linear, branched, or cyclic aliphatic or aromatic carboxylic acids that include from 1 to 5, such as from 1 to 4 or from 1 to 3 carboxylic acid groups, such as isononanoic acid and isostearic acid.

10. The coating composition according to any preceding claim, wherein the coating composition comprises the volatile acid in an amount of from at least 0.01 wt. %, such as at least 0.05 wt. %, or at least 0. 1 wt. % and up to 0.5 wt. %, such as up to 0.45 wt. %, or up to 0.4 wt. %, and can be from 0.01 wt. % to 0.5 wt. %, such as from 0.01 wt. % to 0.45 wt. %, or from 0.05 wt. % to 0.4 wt. %, where wt. % is based on the total weight of the coating composition; and / or wherein the coating composition has a total resin solids of at least 20 wt. %, such as at least 21 wt. %, or at least 22 wt. %, or at least 23 wt. %, or at least 24 wt. %, or at least 25 wt. % and up to 65 wt. %, such as up to 50 wt. %, or up to 45 wt. %, or up to 42 wt. %; or from 20 wt. % to 65 wt. %, such as 20 wt. % to 50 wt. %, or from 21 wt. % to 45 wt. %, or from 22 wt. % to 42 wt. % or from 25 wt. % to 42 wt. % determined according to ASTM ASTM D2369-20.

11. A method of forming a coating layer on at least a portion of a substrate comprising: applying the coating composition according to any preceding claim over at least a portion of the substrate; and exposing the coating composition to a sufficient amount of energy for a sufficient amount of time for the coating composition to cure; wherein the coating composition is applied using a method comprising spray application, draw down, brush application, dip application and / or precision application; and wherein the substrate comprises iron, steel, aluminum, plastic, wood, composite, glass, synthetic material, paper, leather, and / or another coating layer.

12. The method according to claim 11, wherein the coating composition is cured by exposure to ambient conditions, elevated temperature and / or actinic radiation; wherein the coating composition is cured by exposure to elevated temperatures of from 40 °C to 240 °C, from 45 °C to 210 °C or from 50 °C to 140 °C; and / orwherein the coating composition has a cure time of from 30 seconds to 24 hours, such as from 1 minute to 12 hours, or from 5 minutes to 8 hours, or from 10 minutes to 4 hours, or from 30 seconds to 10 minutes, or from 45 seconds to 5 minutes at cure temperatures.

13. The method according to either of claims 11 or 12, wherein the coating composition has a cure time that is affected by the amount of acid and basic catalyst present in the coating composition.

14. The method according to any of claims 11 through 13, wherein the coating layer is applied over one or more previously applied coating layers and / or is part of a multilayer coating composition; wherein the coating layer is applied over a basecoat; or wherein the coating layer is applied over a primer coat; or wherein the coating layer is a topcoat, such as a clearcoat.

15. The method according to any of claims 11 through 13, wherein the coating layer is a monocoat.

16. The method according to any of claims 11 through 15, wherein the coating layer has a dry film thickness of from 0.5 pm to 250 pm, such as from 0.5 pm to 200 pm, or from 0.5 pm to 150 pm, or from 0.5 pm to 100 pm, or from 0.5 pm to 75 pm, or from 0.5 pm to 65 pm, or from 0.5 pm to 55 pm, or from 0.5 pm to 52 pm, or from 1 pm to 250 pm, or from 1 pm to 200 pm, or from 1 pm to 100 pm, or from 1 pm to 65 pm, or from 1 pm to 60 pm, or from 1 pm to 55 pm, or from 5 pm to 250 pm, or from 5 pm to 200 pm, or from 5 pm to 100 pm, or from 5 pm to 65 pm, or from 5 pm to 60 pm or from 5 pm to 55 pm measured according to ASTM D7091-21.

17. A substrate at least partially coated according to the method of any of claims 11 through 16.

18. The substrate according to claim 17, wherein the substrate comprises a vehicle substrate.

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