Powder coating compositions containing photothermally active materials, coated substrates, and methods of coating substrates

Abstract

Disclosed are powder coating compositions comprising a film-forming component and optionally a crosslinker and a photothermally active material capable of generating sufficient heat upon exposure to a photothermal zone for at least 1 femtosecond at an intensity of 0.1 W / cm2 to 108 W / cm2 to form a continuous film. Also disclosed are coatings formed from the powder coating compositions and methods of using the powder coating compositions.

Description

POWDER COATING COMPOSITIONS CONTAINING PHOTOTHERMALLY ACTIVE MATERIALS, COATED SUBSTRATES, AND METHODS OF COATING SUBSTRATESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application Serial No. 63 / 621,025, filed January 15, 2024, entitled “Powder Coating Compositions Containing Photothermally Active Materials, Coated Substrates, And Methods of Coating Substrates”, which is incorporated herein in its entirety.FIELD

[0002] Powder coating compositions containing photothermally active materials are disclosed.BACKGROUND

[0003] The coatings industries, including the industrial, aerospace coatings, and automotive industries, including the after-market and refinish coating industries, have demonstrated a desire for cure-on-demand products.SUMMARY

[0004] Disclosed herein is a powder coating composition comprising: a film-forming component and optionally a crosslinker; and a photothermally active material capable of generating sufficient heat upon exposure to a photothermal zone for at least 1 femtosecond at an intensity of 0.1 W / cm2to 108W / cm2to form a continuous film.

[0005] Also disclosed is a method of forming a coating on a surface of a substrate, comprising: applying the powder coating composition of any preceding claims to the surface; and exposing the powder coating composition to photothermal radiation; wherein the photothermal radiation sufficiently excites the photothermally active material to form a continuous film; and wherein (i) the film-forming resin is reflective or transparent to electromagnetic radiation of the photothermal zone, and (ii) the substrate is reflective or transparent to electromagnetic radiation of the photothermal zone.

[0006] Also disclosed is a method of repairing or replacing an existing coating formed from the compositions of any of claims 1 to 10 on a substrate, comprising exposing the coating to sufficient photothermal radiation to cause the coating to reflow and self-heal.

[0007] Also disclosed is a method of repairing or replacing an existing coating on a substrate, comprising: applying the powder coating composition of any of claims 1 to 10 to the substrate; and exposing the coating to sufficient photothermal radiation to form a continuous film to repair or replace the existing coating.

[0008] Also disclosed is a method of restoring or coating a surface of an article in the field comprising: mechanically or chemically preparing the surface; applying the powder coating composition of any of claims 1 to 10 to the surface; and exposing the coating to sufficient photothermal radiation to form a continuous film.DETAILED DESCRIPTION

[0009] Disclosed herein is a powder coating composition comprising a film-foiming resin and a photothermally active material capable of generating sufficient heat upon exposure to a photothermal zone for at least 1 femtosecond at an intensity of 0.1 W / cm2to 108W / cm2to form a continuous coating. As used herein, a “powder coating composition” refers to any coating composition in the form of a co-reactable solid in particulate form which may be substantially free, essentially free, or completely free of water and / or solvent. The powder coating composition may be a thermoplastic powder coating composition or a thermoset powder coating composition.

[0010] As used herein, a “photothermal zone” refers to the portion of the electromagnetic spectrum extending from 380 nm to 1500 nm.

[0011] As used herein, the term “continuous coating,” when used with respect to a thermoplastic powder coating, refers to a powder coating in which the powder particles are melted or flowed in the absence of any chemical reaction. As used herein, a “thermoplastic” powder coating composition refers to a powder coating composition in which there is no change in Mw upon exposure to the photothermal zone. As used herein, the term “continuous coating,” when used with respect to a thermoset powder coating, refers to a cured powder coating. As used herein, a “thermoset” powder coating composition refers to a powder coating composition in which there is an increase in Mw upon exposure to the photothermal zone. As used herein, the term “cure,” “cured,” “curing,” and the like mean that the components that form the composition are crosslinked (i.e., interact and / or react) to form a coating or a bond. The composition begins to cure when the components of the composition are mixed, resulting in the reaction of the reactive functional groups of the components of the composition. “Coating” as used hereinincludes films, layers and the like. The powder coating composition may comprise a pho to thermally active material.

[0012] Photothermally active materials generate heat upon exposure to the photothermal zone for at least 1 femtosecond at an intensity of 0.1 W / cm2to 108W / cm2, typically due to strong light absorption properties coupled with weak light emission properties, giving rise to a strong photothermal effect. Generally, a 1.5 mil (38.1 micrometers) thick dry film powder coating composition can be cured through its thickness to a tack-free state upon exposure to the photothermal zone. The typical duration of exposure of the photothermally active materials to the photothermal zone may be at least 1 femtosecond, such as at least 1 microsecond, such as at least 1 minute, such as at least 1 hour, such as up to days, such as up to 48 hours, such as up to 36 hours, such as up to 24 hours. An intensity of 0.1 W / cm2to 108W / cm2of the dry powder film is typical. Particular exposure conditions are dependent upon the identity of the photothermally active material, i.e., the known light wavelength and intensity for maximum heat emission for a given photothermally active material. As used herein, “generate heat” means the relaxation of electrons from an excited state to a ground state via vibrational relaxation (non- radiative decay).

[0013] Photothermally active materials that may be used in the powder coating compositions disclosed herein include boron nitride, silicon nitride, silicon dioxide, silicon carbide, aluminum nitride, boron arsenide, aluminum oxide, magnesium oxide, dead burned magnesium oxide, beryllium oxide, titanium oxide, zinc oxide, nickel oxide, copper oxide, tin oxide, aluminum oxide (i.e., aluminum trihydrate), magnesium hydroxide, agate, emery, ceramic microspheres, diamond, and combinations thereof.

[0014] Photothermally active materials that may be used in the powder coating compositions disclosed herein also include diatomaceous earth, clays, such as kaolin and, bentonite, halloysite, talcs, mica, leucophyllite, lazurite, silica, such as precipitated silica, pyrogenic silica and silica gel, sulfur containing sodium silicates, cristabolite, wollastonite, feldspar, leucophyllite, chamotte, perlite, glass powders and flakes, quartz, metal and mixed metal silicates, such as aluminum silicates, barium silicates, barium copper silicates, calcium copper silicates, and sulfur containing sodium silicates, other inorganic silicates and derivates such as orthosilicates, such as lithium orthosilicate, inorganic phosphosilicates, and combinations thereof.

[0015] Photothermally active materials that may be used in the powder coating compositions disclosed herein also include lime, iron oxides such as hematite, magnetite and siderite, chromium oxide, hydrated chromium oxide, chromium trioxide, antimony trioxide, antimony pentoxide, cerium oxides, titanium dioxide, such as rutile and anatase titanium dioxides, vanadium oxide, cupric carbonate hydroxide and copper hydroxide, layered double hydroxides such as hydrotalcite, and combinations thereof.

[0016] Photothermally active materials that may be used in the powder coating compositions disclosed herein also include calcium carbonate, dolomite, huntite, hydromagnesite, and combinations thereof.

[0017] Photothermally active materials that may be used in the powder coating compositions disclosed herein also include zinc chromate, zinc tetraoxy chromate, barium chromate, lead chromate, strontium chromate, other inorganic chromates, and combinations thereof.

[0018] Photothermally active materials that may be used in the powder coating compositions disclosed herein also include barium sulfate, barium manganate sulfate, and combinations thereof.

[0019] Photothermally active materials that may be used in the powder coating compositions disclosed herein also include carbon black, graphite, graphene, grapheme carbon particles, and combinations thereof. Graphene may be in the form of commercially available nanoparticles such as exfoliated graphite. Grapheme carbon particles (i) may be thermally produced from a hydrocarbon precursor material capable of forming a two-carbon-fragment species or a hydrocarbon material comprising methane introduced into a thermal zone at a temperature of greater than 3,500°C, (ii) may have an average aspect ratio of greater than 3:1, (iii) may have a BET specific surface area of greater than 70 m2 / g, and / or (iv) may have a Raman spectroscopy 2D / G peak ratio of at least 0.9:1. Graphenic carbon particles may be produced by methods such as those disclosed in U.S. Patent No. 8,486,363 and U.S. Patent No. 8,486,364, each incorporated herein by reference in its entirety.

[0020] As used herein, the term “graphenic carbon particles” means carbon particles having structures comprising one or more layers of one-atom-thick planar sheets of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. The average number of stacked layers may be less than 100, for example, less than 50. In certain embodiments, theaverage number of stacked layers is 30 or less, such as 20 or less, 10 or less, or, in some cases, 5 or less. The average number of stacked layers may be greater than 2, for example, greater than 3, or greater than 4. At least a portion of the grapheme carbon particles may be in the form of platelets that are substantially curved, curled, creased or buckled. The graphenic carbon nanoparticles may be turbostatic, i.e., adjacent stacked atom layers do not exhibit ordered AB Bernal stacking associated with conventional exfoliated graphene, but rather exhibit disordered or non-ABABAB stacking. Alternatively, the graphenic carbon particles may be in the form of nanotubes. The particles typically do not have a spheroidal or equiaxed morphology.

[0021] Photothermally active materials that may be used in the powder coating compositions disclosed herein also include cadmium sulfide, cadmium selenide, cadmium sulfoselinide, and combinations thereof.

[0022] Photothermally active materials that may be used in the powder coating compositions disclosed herein also include cobalt stannate, cobalt phosphate, cobalt aluminates, and combinations thereof.

[0023] Photothermally active materials that may be used in the powder coating compositions disclosed herein also include copper pigments, copper / zinc pigments, zinc pigments, bronze pigments, gold bronze pigments, ferric hexacyanoferrate, lithopone, and YinMn blue, metal flake pigments such as zinc flakes, metal effect pigments, inorganic effect pigments, and combinations thereof.

[0024] Photothermally active materials that may be used in the powder coating compositions disclosed herein also include phosphates such as chrome phosphate, phosphites and phosphonates, inorganic phosphates, polyphosphates and orthophosphates, pyrophosphates such as manganic ammonium pyrophosphate, and combinations thereof.

[0025] Photothermally active materials may also include various micronized rubber compounds.

[0026] Any combination of the foregoing photothermally active materials disclosed hereinabove also may be used in the powder coating compositions disclosed herein.

[0027] A photothermally active material of any average particle size can be used according to the present invention, provided it generates sufficient heat for curing to take place when the curable powder coating composition is exposed to photothermal radiation. For example, the photothermally active material may be micron sized, such as at least 0.5 microns,such as at least 1 micron, such as no more than 50 microns, such as no more than 15 microns, such as 0.5 to 50 microns, such as 1 to 15 microns, with size based on average particle size. Alternatively, the photothermally active material may be nano sized, such as at least 10 nanometers, such as no more than 499 nanometers, such as no more than 100 nanometers, such as 10 nanometers to 499 nanometers, such as 10 nanometers to 100 nanometers, with size based on average particle size. It will be appreciated that these particle sizes refer to the particle size of the photothermally active material at the time of incorporation into the curable film-forming composition. Various coating preparation methods may result in the particles agglomerating, which could increase average particle size, or shearing or other action that can reduce average particle size. Thus, the photothermally active material may be present in the form of particles such as microparticles and / or nanoparticles such as nanowires, nanorods, nanoplatelets, nanospheres, powders, flakes, microspheres, high aspect ratio materials, and irregularly shaped particles of appropriate size.

[0028] Often the particles of photothermally active material have an average primary particle size of no more than 500 nanometers, such as no more than 50 nanometers, or no more than 2 nanometers, as determined by visually examining a micrograph of a transmission electron microscopy (“TEM”) image, measuring the diameter of the particles in the image, and calculating the average primary particle size of the measured particles based on magnification of the TEM image. One of ordinary skill in the art will understand how to prepare such a TEM image and determine the primary particle size based on the magnification. The primary particle size of a particle refers to the smallest diameter sphere that will completely enclose the particle. As used herein, the term “primary particle size” refers to the size of an individual particle as opposed to an agglomeration of two or more individual particles.

[0029] The amount of photothermally active material used in the curable powder coating composition can vary. For example, the powder coating composition can comprise at least 0.001 percent by weight photothermally active material based on total weight of the powder coating composition, such as at least 0.01 percent by weight, such as at least 0.02 percent by weight, such as at least 0.05 percent by weight. The powder coating composition can comprise no more than 55 percent by weight photothermally active material based on total weight of the powder coating composition. The powder coating composition can comprise 0.001 percent by weight to55 percent by weight photothermally active material based on total weight of the powder coating composition.

[0030] The powder coating compositions disclosed herein may comprise a film-forming resin and optionally a crosslinker.

[0031] The film-forming resin may be transparent to the electromagnetic radiation of the photothermal zone.

[0032] The film- forming resin may be reflective of the electromagnetic radiation of the photothermal zone.

[0033] The film- forming resin may comprise a (meth)acrylate, a polyurethane, a polyester, a polyamide, a polyether, a polysiloxane, an epoxy, a vinyl, copolymers of any of the foregoing, and combinations thereof. As used herein, “(meth) acrylate” and like terms refers both to the acrylate and the corresponding methacrylate. The film-forming resins may comprise any of a variety of functional groups including, but not limited to, a carboxylic acid group, an amine group, an epoxide group, a hydroxyl group, a thiol group, a carbamate group, an amide group, a urea group, an isocyanate group, an ethylenically unsaturated group, and combinations thereof. As used herein, “ethylenically unsaturated” refers to a group having a carbon-carbon double bond. Non-limiting examples of ethylenically unsaturated groups include, but are not limited to, (meth)acrylate groups, vinyl groups, and combinations thereof.

[0034] The film-forming resin may not be curable by photothermal radiation. That is, the film-forming resin may be substantially free of functionality that would allow the film-forming resin to cure or crosslink upon exposure to the photothermal zone, as would be seen, for example, with UV curable coatings. “Substantially free” in this context means that there is not a sufficient amount of the functionality to effect cure by exposure to the photothermal zone.

[0035] The film-forming resin may be present in the powder coating composition in an amount of at least 35 percent by weight based on total weight of the powder coating composition, such as at least 45 percent by weight. The film-forming resin may be present in the powder coating composition in an amount of no more than 99.999 percent by weight based on total weight of the powder coating composition. The film-forming resin may be present in the powder coating composition in an amount of 35 percent by weight to 99.999 percent by weight based on total weight of the film-forming resin, such as 45 percent by weight to 99.999 percent by weight.

[0036] Non-limiting examples of crosslinkers include a phenol, a triglycidyl isocyanurate, a beta-hydroxy (alkyl) amide, an alkylated carbamate, a (meth)acrylate, a salt of a polycarboxylic acid with cyclic amidine, o-tolyl biguanide, an isocyanate, a blocked isocyanate, a polyacid, an anhydride, an organometallic acid-functional material, a polyamine, a polyamide, an aminoplast, a carbodiimide, an oxazoline, and combinations thereof.

[0037] The crosslinker optionally may be present in the powder coating composition in an amount of up to 40 percent by weight based on total weight of the powder coating composition, such as at least 10 percent by weight, such as 10 percent by weight to 40 percent by weight.

[0038] The powder coating composition may be prepared by mixing the previously described film-forming resin and optionally the photothermally active material and / or the crosslinker. Alternatively, the photothermally active material may be post-added following the grinding, sorting, and / or classification described below. The components may be mixed such that a homogenous mixture is formed. The components can be mixed using art-recognized techniques and equipment such as with a Prism high speed mixer for example. When a solid coating composition is formed, the homogenous mixture is next melted and further mixed. The mixture can be melted with a twin screw extruder, single screw extruder, or a similar apparatus known in the ail. During the melting process, the temperatures may be chosen to melt mix the solid homogenous mixture without curing the mixture. The homogenous mixture can be melt mixed in a twin screw extruder with zones set to a temperature of 75°C to 140°C, 75°C to 125°C, such as 85°C to 115°C, or at 100°C.

[0039] After melt mixing, the mixture may be cooled and re- solidified. The re-solidified mixture may then be ground such as in a milling process to form a solid particulate curable powder coating composition. The re-solidified mixture can be ground to any desired particle size. For example, the re-solidified mixture can be ground to an average particle size of at least 10 microns or at least 20 microns and up to 130 microns as determined with a Beckman-Coulter LS™ 13 320 Laser Diffraction Particle Size Analyzer following the instructions described in the Beckman-Coulter LS™ 13 320 manual. Further, the particle size range of the total amount of particles in a sample used to determine the average particle size can comprise a range of from 1 micron to 200 microns, or from 5 microns to 180 microns, or from 10 microns to 150 microns, which is also determined with a Beckman-Coulter LS™ 13 320 Laser Diffraction Particle SizeAnalyzer following the instructions described in the Beckman-Coulter LS™ 13 320 manual. Particles may be sorted using a classifier according to methods known to those skilled in the art.

[0040] Also disclosed is a method of forming a coating on a surface of a substrate. Any of the powder coating compositions described herein may be applied to a portion of the substrate surface, and the powder coating composition may be exposed to photothermal radiation. The photothermal radiation may sufficiently excite the photothermally active material to form a continuous film on the substrate surface.

[0041] The methods disclosed herein may be used to repair or replace an existing coating on a substrate. The existing coating may be formed from any of the powder coating compositions described herein. The existing coating may be exposed to sufficient photothermal radiation to cause the coating to reflow and self-heal.

[0042] Also disclosed herein are methods of repairing or replacing an existing coating on a substrate. Any of the powder coating compositions described herein may be applied to the substrate, such as to a damaged portion of an existing coating on the substrate. The powder coating composition may be applied to a substrate surface to replace an existing coating. The powder coating composition may be exposed to sufficient photothermal radiation to form a continuous film to repair or replace the existing coating.

[0043] In any of the methods disclosed herein, the substrate may be mechanically or chemically prepared using techniques known to those skilled in the art of powder coating compositions.

[0044] Photothermal radiation may be generated by industrial- sized laser or LED equipment, such as that configured for use in a laboratory or on a production line. Accordingly, the methods disclosed herein may be used in laboratory or industrial settings.

[0045] Photothermal radiation may be generated by a portable and / or hand-held device. Accordingly, the methods disclosed herein may be used in the field or on an existing structure or vehicle.

[0046] The film-forming resin may not be curable by exposure to photothermal radiation.

[0047] The film- forming resin may be reflective or transparent to electromagnetic radiation of the photothermal zone.

[0048] The substrate may be reflective or transparent to electromagnetic radiation of the photothermal zone.

[0049] Upon exposure of the powder coating composition to photothermal radiation, at least 50 percent of the energy generated in the photothermal zone may be absorbed by the photothermally active material as measured by UV Vis spectroscopy.

[0050] When the composition of the present invention is exposed to the photothermal zone, sufficient heat is generated by the photothermally active material to effect cure of the curable composition. The heat generated by the photothermally active material enables the formation of a bond between reactive functional groups. For example, photothermal particles exhibit surface plasmon resonance when irradiated with light in a known range of wavelengths and intensities, causing a transient and localized (on a molecular scale) generation of heat that promotes chemical reaction between the functional groups on the other components of the curable film-forming composition. In materials demonstrating surface plasmon resonance, the origin of photothermal heat is absorption of light by the surface plasmon resonance (SPR) of the metal particles, which excites a collective oscillation of electrons that quickly (femtoseconds) dephase, transferring energy as heat. The system reaches peak temperature on the picosecond timescale, and then transfers thermal energy away from the particles, elevating the temperature of the local molecular environment, but leaving the bulk temperature of the composition largely unperturbed. The rapid cooling of the particles provides a possible means for retaining species transiently generated (i.e., the crosslinked coating) at high temperatures. In other words, there is no time for the reaction to reverse itself because the heat is dissipated.

[0051] Exposure of the powder coating composition to photothermal radiation eliminates the need to heat the substrate in an oven to melt the film-forming resin and / or to effectuate cure of the film-forming resin as is required in conventional methods of applying powder coating compositions to substrate surfaces. Upon exposure of the substrate coated with the present coatings to photothermal radiation, the heat generated by the photothermally active material may be localized and sufficient to melt the film-forming resin and / or to effectuate cure while maintaining the temperature of the substrate and / or the film-forming resin substantially constant, i.e., without substantially increasing the temperature of the substrate itself and / or without heating the film-forming resin. Exposure to photothermal radiation may prevent the substrate from heating above its heat deflection temperature. For example, the substrate may not be heated above 120 C, such as 100 C, such as 80°C, such as 60°C, such as 40°C. The substrate may not be heated above ambient temperature. Accordingly, the present disclosure allows for reducedenergy consumption and may also allow for the use of powder coatings on temperature sensitive substrates - that is, substrates that cannot withstand the heat at which powder coatings arc conventionally cured.

[0052] The coated substrate may be exposed to photothermal radiation at a wavelength and intensity and for a duration sufficient to cure the powder coating composition. Photothermal radiation used to cure the powder coating composition may have wavelengths.

[0053] The powder coating composition may be exposed to photothermal radiation in the photothermal zone or to any subset of spectra within the portion of the electromagnetic spectrum defined hereinabove as the photothermal zone. That is, the powder coating composition may be exposed to light in the photothermal radiation in the photothermal zone, including the visible spectrum, including light having wavelengths such as 380 nm to less than 810 nm, such as 380 nm to 530 nm, such as 380 nm to 450 nm.

[0054] Photothermal radiation may be applied at an intensity of 0.1 W / cm2to 108W / cm2and / or for a time of at least 1 femtosecond, such as at least 1 microsecond, such as at least 1 minute, such as at least 1 hour, such as at least 1 day.

[0055] The photothermal radiation may be generated by a laser and / or a light emitting diode (LED). The laser may comprise a gas laser, a solid-state laser, a fiber laser, a liquid laser, a semi-conductor laser, or combinations thereof.

[0056] A duration of applying the photothermal radiation may be at least 1 femtosecond, such as at least 1 microsecond, such as at least 1 minute, such as at least 1 hour, such as at least 1 day, such as up to 48 hours.

[0057] The photothermal radiation may be generated in a pulsed wave and / or as a continuous wave.

[0058] The powder coating compositions can be applied by any means standard in the art, such as spraying, electrostatic spraying, a fluidized bed process, and the like. After the powder coating compositions are applied to a substrate, the compositions can be cured or at least partially cured such as with a photothermal radiation to form a partially cured or cured coating.

[0059] The powder coating compositions disclosed herein can also be applied in multiple applications over a substrate. For instance, a first powder coating composition can be applied over at least a portion of a substrate. A second powder coating composition can be applied over at least a portion of the first coating composition. The first powder coating composition canoptionally be cured or at least partially cured before applying the second powder coating composition. Alternatively, the second powder coating composition can be applied over at least a portion of the first coating composition. The first and second coating composition can then be cured together at the same time. The powder coating compositions can be cured with any of the methods previously described.

[0060] Coatings formed from a single powder coating composition can be applied at any desired dry film thickness. For example, the dry film thickness may be at least a 1.5 mil (38.1 micrometers), such as at least 2 mils (50.8 microns), such as at least 3 mils (76.2 microns), such as at least 4 mils (101.6 microns), such as at least 5 mils (127 microns), such as at least 6 mils (152.4 microns), such as at least 8 mils (203.2 microns), such as at least 10 mils (254 microns), such as at least 12 mils (304.8 microns), such as at least 20 mils (508 microns), such as at least 40 mils (1,016 microns). For example, the dry film thickness may be less than 40 mils (1,016 microns), such as less than 20 mils (508 microns), such as less than 12 mils (304.8 microns), less than 10 mils (254 microns), less than 8 mils (203.2 microns), or less than 6 mils (152.4 microns), or less 5 mils (127 microns), or less than 4 mils (101.6 microns), or less than 3 mils (76.2 microns), or less than 2 mils (50.8 microns). It is appreciated that, when multiple powder coating compositions are applied, each composition can be applied to separately provide any of the previously described dry film thicknesses. For instance, when two separate powder coating compositions are applied, each individual powder coating composition can be applied at any of the previously described dry film thicknesses.

[0061] Also disclosed is a substrate comprising a coating layer applied from any of the powder coating compositions described herein.

[0062] The substrate coated with the powder coating composition may be selected from a wide variety of substrates and combinations thereof. Non-limiting examples of substrates include vehicles including automotive substrates, industrial substrates, marine substrates and components such as ships, vessels, and on-shore and off-shore installations, storage tanks, packaging substrates, architectural substrates, aerocraft and aerospace components, bus bars, metal wires, copper or aluminum conductors, nickel conductors, wood flooring and furniture, fasteners, coiled metals, heat exchangers, vents, an extrusion, roofing, walls, wheels, grates, belts, conveyors, grain or seed silos, wire mesh, bolts or nuts, a screen or grid, HVAC equipment, frames, tanks, cords, wires, a rail car, furniture, appliances, apparel, a bulkhead,pipes, transformers, toolboxes, grills, medical equipment, doors, windows, a well, cabinets, pylons, munitions, missiles, electronics and electronic components including housings and circuit boards, glass, sports equipment, including golf balls, stadiums, buildings, bridges, containers such as a food and beverage containers, and the like.

[0063] The substrates, including any of the substrates previously described, can be metallic or non-metallic. Metallic substrates may include both flexible and rigid metal substrates such as tin, iron, steel, and alloys thereof. Non-limiting examples of useful steel materials include cold rolled steel, nickel plated cold rolled steel, hot rolled steel, galvanized (zinc coated) steel, electrogalvanized steel, hot-dipped galvanized steel, galvannealed steel, zinc compounds, zinc alloys, galvalume, steel plated with zinc alloy, stainless steel, pickled steel, zinc-aluminum- magnesium alloy coated steel, aluminum plated steel, aluminum alloy plated steel, steel coated with a zinc-aluminum alloy, or combinations thereof. Metallic substrates may include zincaluminum alloys, aluminum, aluminum alloys, magnesium, magnesium alloys, nickel, nickel plating, bronze, tinplate, clad, titanium, brass, copper, silver, gold, 3-D printed metals, cast or forged metals and alloys, or combinations thereof. Aluminum alloys, such as those, for example, of the 1XXX, 2XXX, 3XXX, 4XXX, 5XXX, 6XXX, 7XXX, or 8XXX series as well as clad aluminum alloys and cast aluminum alloys, such as those, for example, of the A356, 1XX.X, 2XX.X, 3XX.X, 4XX.X, 5XX.X, 6XX.X, 7XX.X, or 8XX.X series also may be used as the substrate. The substrate also may comprise, for example, magnesium, such as magnesium alloys of the AZ31B, AZ91C, AM60B, or EV31A series, titanium and / or titanium alloys, such as those of grades 1-36 including H grade variants, copper and copper alloys, or other non-ferrous metals, as well as alloys of these materials.

[0064] Non-metallic substrates include polymeric, plastic, polyester, polyolefin, polyamide, cellulosic, polystyrene, polyacrylic, polyfethylene naphthalate), polypropylene, polyethylene, nylon, EVOH, polylactic acid, other “green” polymeric substrates, poly (ethyleneterephthalate) (PET), polycarbonate, engineering polymers such as poly(etheretherketone) (PEEK), polycarbonate acrylobutadiene styrene (PC / ABS), polyamide, wood, veneer, wood composite, particle board, medium density fiberboard, cement, stone, glass, paper, cardboard, textiles, leather both synthetic and natural, composite substrates such as fiberglass composites or carbon fiber composites such as fiberglass -epoxy composites or carbonfiber-epoxy composites, 3-D printed polymers and composites, and the like. The shape of the substrate can be in the form of a sheet, plate, bar, rod or any shape desired.

[0065] “Vehicle” as used herein refers to in its broadest sense all types of vehicles, such as, but not limited to, cars, trucks, buses, tractors, harvesters, heavy duty equipment, vans, golf calls, motorcycles, bicycles, railcars, subway cars, airplanes, drones, VTOLs, helicopters, ships, vessels, boats of all sizes and the like. A vehicle can include civilian, commercial and military aircraft and or land vehicles, such as those listed above and those used in land-based defense (tanks, armored vehicles and the like). A vehicle can include autonomous and / or unmanned vehicles.

[0066] It will also be appreciated that the substrates of the present disclosure can form a part of a structure. The powder coating compositions of the present disclosure can be used in any article of manufacture, such as a vehicle or a structure. “Structure” as used herein refers to a any part of a building, stadium, bridge, transportation infrastructure, oil rig, oil platform, water tower, power line tower, support structures, wind turbines, storage tanks, nuclear plants, walls, piers, docks, levees, dams, shipping containers, trailers, and any metal structure that is exposed to a corrosive environment.

[0067] Because the source of photothermal radiation can be portable (handheld) a portion of a structure can be coated in the field and / or on existing structures.

[0068] The substrate may comprise a bare substrate or the substrate may undergo various treatments prior to application of the powder coating composition. For instance, the substrate can be alkaline cleaned, deoxidized, mechanically cleaned, ultrasonically cleaned, solvent wiped, roughened, plasma cleaned or etched, exposed to chemical vapor deposition, treated with an adhesion promoter, plated, anodized, annealed, cladded, or any combination thereof prior to application of the powder coating composition. The substrate can be treated using any of the previously described methods prior to application of the powder coating composition such as by dipping the substrate in a cleaner and / or deoxidizer bath prior to applying the powder coating composition. The substrate can also be plated prior to applying the powder coating composition. As used herein, “plating” refers to depositing a metal over a surface of the substrate.

[0069] For purposes of this detailed description, it is to be understood that the disclosure may assume alternative variations and step sequences, except where expressly specified to the contrary. Accordingly, unless indicated to the contrary, the numerical parameters set forth in thefollowing 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 to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0070] 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.

[0071] 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.

[0072] As used herein, “including,” “containing” and like terms are understood in the context of this application to be synonymous with “comprising” and are therefore open-ended and do not exclude the presence of additional undescribed or unrecited elements, materials, ingredients or method steps. As used herein, “consisting of’ is understood in the context of this application to exclude the presence of any unspecified element, ingredient or method step. As used herein, “consisting essentially of’ is understood in the context of this application to include the specified elements, materials, ingredients or method steps “and those that do not materially affect the basic and novel characteristic(s)” of what is being described. As used herein, open- ended terms include closed terms such as consisting essentially of and consisting of.

[0073] In this application, the use of the singular includes the plural and plural encompasses singular, unless specifically stated otherwise. For example, although reference is made herein to “a” photothermally active material, and “a” resin, a combination (i.e., a plurality) of these components may be used.

[0074] 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.

[0075] As used herein, the terms “on,” “onto,” “applied on,” “applied onto,” “formed on,” “deposited on,” “deposited onto,” and the like mean formed, overlaid, deposited, or provided on, but not necessarily in contact with, a substrate surface. For example, a composition “applied onto” a substrate surface does not preclude the presence of one or more other intervening coating layers or films of the same or different composition located between the composition and the substrate surface.

[0076] As further defined herein, ambient conditions generally refer to room temperature (e.g., 23°C) and humidity conditions or temperature and humidity conditions that are typically found in the area in which the composition is applied to a substrate, e.g., at 10°C to 40°C and 5% to 80% relative humidity.

[0077] As used herein, “Mw” refers to the weight average molecular weight, for example the theoretical value as determined by Gel Permeation Chromatography using Waters 2695 separation module with a Waters 410 differential refractometer (RI detector) and polystyrene standards, tetrahydrofuran (THF) used as the eluent at a flow rate of 1 ml min"1, and two PL Gel Mixed C columns used for separation.

[0078] As used herein, “polymer” refers to oligomers, homopolymers, and copolymers.

[0079] As used herein, the term “solvent” refers to a molecule or a compound that is used to lower the viscosity of a resin, volatilizes under ambient conditions, and does not have a reactive functional group capable of reacting with molecules or compounds in a composition.

[0080] As used herein, unless indicated otherwise, the term “substantially free” means that a particular material is not purposefully added to a mixture or composition, respectively, and is only present as an impurity in a trace amount of less than 5% by weight based on a total weight of the mixture or composition, respectively. As used herein, unless indicated otherwise, the term “essentially free” means that a particular material is only present in an amount of less than 2% by weight based on a total weight of the mixture or composition, respectively. As used herein, unless indicated otherwise, the term “completely free” means that a mixture or composition, respectively, does not comprise a particular material, i.e., the mixture or composition comprises 0% by weight of such material.

[0081] In view of the foregoing description the present disclosure thus relates in particular' to the following Aspects 1-34 without being limited thereto.ASPECTS

[0082] 1. A powder coating composition comprising: a film-forming component and optionally a crosslinker; and a photothermally active material capable of generating sufficient heat upon exposure to a photothermal zone for at least 1 femtosecond at an intensity of 0.1 W / cm2to 108W / cm2to form a continuous film.

[0083] 2. The powder coating composition of aspect 1, wherein the photothermal zone comprises the visible spectrum, such as a wavelength of 380 nm to 810 nm, such as 380 nm to 530 nm, such as 380 nm to 450 nm.

[0084] 3. The powder coating composition of aspect 1 or aspect 2, wherein the powder coating composition is formulated as a thermoplastic powder coating composition or a thermoset powder coating composition.

[0085] 4. The powder coating composition of any of the preceding aspects, wherein the film-forming component is transparent to electromagnetic radiation of the photothermal zone.

[0086] 5. The powder coating composition of any of the preceding aspects, wherein the film-forming component is reflective to electromagnetic radiation of the photothermal zone.

[0087] 6. The powder coating composition of any of the preceding aspects, wherein the powder coating composition is substantially free of a photopolymerization initiator.

[0088] 7. The powder coating composition of any of the preceding aspects, wherein the photothermally active material comprises titanium dioxide, carbon black, graphene, and / or grapheme carbon particles.

[0089] 8. The powder coating composition of aspect 7, wherein the graphenic carbon particles (i) are thermally produced from a hydrocarbon precursor material capable of forming a two-carbon-fragment species or a hydrocarbon material comprising methane introduced into a thermal zone at a temperature of greater than 3,500°C, (ii) have an average aspect ratio of greater than 3:1, (iii) have a BET specific surface area of greater than 70 m2 / g, and / or (iv) have a Raman spectroscopy 2D / G peak ratio of at least 0.9:1.

[0090] 9. The curable powder coating composition of any of the preceding aspects, wherein the composition comprises the photothermally active material in an amount of:(a) at least 0.001 percent by weight based on total weight of the composition;(b) no more than 55 percent by weight based on total weight of the composition; and / or(c) 0.001 percent by weight to 55 percent by weight based on total weight of the composition.

[0091] 10. The curable powder coating composition of any of the preceding aspects, wherein the film-forming resin comprises a (meth)acrylate, a polyurethane, a polyester, a polyamide, a polyether, a polysiloxane, an epoxy, a vinyl, copolymers of any of the foregoing, and / or combinations thereof.

[0092] 11. The curable powder coating composition of any of the preceding aspects, wherein the crosslinker comprises a phenol, a triglycidyl isocyanurate, a beta-hydroxy (alkyl) amide, an alkylated carbamate, a (meth)acrylate, a salt of a polycarboxylic acid with cyclic amidine, o-tolyl biguanide, an isocyanate, a blocked isocyanate, a polyacid, an anhydride, an organometallic acid-functional material, a polyamine, a polyamide, an aminoplast, a carbodiimide, and / or an oxazoline.

[0093] 12. The curable powder coating composition of any of the preceding aspects, wherein the composition comprises the crosslinker in an amount of:(a) at least 10 percent by weight based on total weight of the powder coating composition;(b) no more than 40 percent by weight based on total weight of the powder coating composition; and / or(c) 10 percent by weight to 40 percent by weight based on total weight of the powder coating composition.

[0094] 13. The curable powder coating composition of any of the preceding aspects, wherein the composition comprises the film-forming resin in an amount of:(a) at least 35 percent by weight based on total weight of the powder coating composition;(b) no more than 99.999 percent by weight based on total weight of the powder coating composition; and / or(c) 35 percent by weight to 99.999 percent by weight based on total weight of the powder coating composition.

[0095] 14. A method of forming a coating on a surface of a substrate, comprising: applying the powder coating composition of any preceding aspects to the surface; and exposing the powder coating composition to photothermal radiation; wherein the photothermal radiation sufficiently excites the photothermally active material to form a continuous film; and wherein (i) the film-forming resin is reflective or transparent to electromagnetic radiation of the photothermal zone, and (ii) the substrate is reflective or transparent to electromagnetic radiation of the pho to thermal zone.

[0096] 15. A method of repairing or replacing an existing coating formed from the compositions of any of aspects 1 to 13 on a substrate, comprising exposing the coating to sufficient photothermal radiation to cause the coating to reflow and self-heal.

[0097] 16. A method of repairing or replacing an existing coating on a substrate, comprising: applying the powder coating composition of any of aspects 1 to 13 to the substrate; and exposing the coating to sufficient photothermal radiation to form a continuous film to repair or replace the existing coating.

[0098] 17. A method of restoring or coating a surface of an article in the field comprising: mechanically or chemically preparing the surface; applying the powder coating composition of any of aspects 1 to 13 to the surface; and exposing the coating to sufficient photothermal radiation to form a continuous film.

[0099] 18. The method of any of aspects 15 to 17, wherein (i) the film- forming resin is reflective or transparent to electromagnetic radiation of the photothermal zone, and (ii) the substrate is reflective or transparent to electromagnetic radiation of the photothermal zone.

[0100] 19. The method of any of aspects 14 to 18, wherein the pho to thermal radiation is applied at an intensity of 0.1 W / cm2to 108W / cnr and / or for a time of at least 1 femtosecond, such as at least 1 microsecond, such as at least 1 minute, such as at least 1 hour, such as at least 1 day.

[0101] 20. The method of any of aspects 14 to 19, wherein the film-forming resin is not curable by exposure to photothermal radiation.

[0102] 21. The method of any of aspects 14 to 20, wherein the photothermal radiation is generated by a portable device, such as a hand-held device.

[0103] 22. The method of any of aspects 14 to 21, excluding heating the substrate following the applying.

[0104] 23. The method of any of aspects 14 to 22, wherein a temperature of the substrate and / or the film-forming resin does not increase upon the exposing.

[0105] 24. The method of any of aspects 14 to 23, wherein the substrate comprises aluminum and / or an aluminum alloy, copper, a composite such as a carbon fiber epoxy composite or a glass fiber epoxy composite, a temperature sensitive material, plastic, and / or wood.

[0106] 25. The method of any of aspects 14 to 24, wherein the method is performed in the field or on an existing structure or vehicle.

[0107] 26. The method of any of aspects 14 to 25, wherein the photothermal radiation comprises a laser and / or a light emitting diode.

[0108] 27. The method of aspect 26, wherein the laser comprises a gas laser, a solid- state laser, a fiber laser, a liquid laser, a semi-conductor laser, or combinations thereof.

[0109] 28. The method of any of aspects 14 to 27, wherein the photothermal radiation is pulsed.

[0110] 29. The method of any of aspects 14 to 28, wherein the photothermal radiation is continuous.

[0111] 30. The method of any of aspects 14 to 29, wherein the substrate is not heated above its heat deflection temperature.

[0112] 31. The method of any of aspects 14 to 30, wherein the substrate is not heated above 120°C, such as 100 C, such as 80°C, such as 60°C, such as 40°C.

[0113] 32. The method of any of aspects 14 to 31, wherein the substrate is not heated above ambient temperature.

[0114] Illustrating the disclosure are the following examples, which, however, are not to be considered as limiting the disclosure to their details. Unless otherwise indicated, all parts and percentages in the following examples, as well as throughout the specification, are by weight.EXAMPLESTabic 1. Hypothetical Powder Coating Composition

[0115] Hypothetical powder coating compositions may be prepared from the components listed in Table 1. In Example 1, the film-forming resin and optionally the catalyst and / or the crosslinker may be mixed to form a homogenous mixture using a Prism high speed mixer. In Example 2, the film-forming resin and optionally the photothermally active material and / or the crosslinker may be mixed to form a homogenous mixture using a Prism high speed mixer.

[0116] When a solid coating composition is formed from the mixtures of Example 1 or Example 2, the homogenous mixture may be melted and further mixed. The mixture can be melted with a twin screw extruder, single screw extruder, or a similar apparatus known in the art. During the melting process, the temperatures may be chosen to melt mix the solid homogenous mixture without curing the mixture. The homogenous mixture can be melt mixed in a twin screw extruder with zones set to a temperature of 75°C to 140°C.

[0117] After melt mixing, the mixture may be cooled and re- solidified. The re-solidified mixture may then be ground such as in a milling process to form a solid particulate curable powder coating composition. The re-solidified mixture can be ground to any desired particle size. The resulting powder coating composition may be a solid particulate powder coating composition that is free flowing.

[0118] The compositions of Example 1 and Example 2 may be applied to a surface of a substrate.

[0119] The components of Example 1 may be cured by conventional means known to those skilled in the art, such as heating in an oven.

[0120] The components of Example 2 may be exposed to light in the photothermal zone for at least 1 femtosecond at an intensity of 0.1 W / cm2to 108W / cm2to form a continuous film.

[0121] It is hypothesized that a powder coating composition that includes photothermally active materials and is exposed to light in the photothermal zone will have at least one of the following: will be cured at least 50 percent of the energy generated in the photothermal zone may be absorbed by the photothermally active material as measured by UV Vis spectroscopy; the film-forming resin will not be curable by exposure to photothermal radiation; the temperature of the substrate and / or the film-forming resin will not increase upon exposing the powder coating composition to light in the photothermal zone; the substrate will not be heated above its heat deflection temperature; the substrate will not be heated above 120 C; and / or the substrate will not be heated above ambient temperature.

[0122] Whereas specific aspects of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.

Claims

We claim:

1. A powder coating composition comprising: a film-forming component and optionally a crosslinker; and a photothermally active material capable of generating sufficient heat upon exposure to a photothermal zone for at least 1 femtosecond at an intensity of 0.1 W / cm2to 108W / cm2to form a continuous film.

2. The powder coating composition of claim 1, wherein the photothermal zone comprises the visible spectrum, such as a wavelength of 380 nm to 810 nm, such as 380 nm to 530 nm, such as 380 nm to 450 nm.

3. The powder coating composition of claim 1 or claim 2, wherein the powder coating composition is formulated as a thermoplastic powder coating composition or a thermoset powder coating composition.

4. The powder coating composition of any of the preceding claims, wherein the filmforming component is transparent to electromagnetic radiation of the photothermal zone or wherein the film-forming component is reflective to electromagnetic radiation of the photothermal zone.

5. The powder coating composition of any of the preceding claims, wherein the powder coating composition is substantially free of a photopolymerization initiator.

6. The powder coating composition of any of the preceding claims, wherein the photothermally active material comprises a metal oxide such as titanium dioxide, carbon black, and / or graphene.

7. The powder coating composition of claim 6, wherein the graphene comprises (i) thermally produced graphenic carbon particles produced from a hydrocarbon precursor material capable of forming a two-carbon-fragment species or a hydrocarbon material comprisingmethane introduced into a thermal zone at a temperature of greater than 3,500°C and / or (ii) thermally produced grapheme carbon particles having an average aspect ratio of greater than 3:1, a BET specific surface area of greater than 70 m2 / g, and a Raman spectroscopy 2D / G peak ratio of at least 0.9:1.

8. The curable powder coating composition of any of the preceding claims, wherein the film-forming resin comprises a (meth)acrylate, a polyurethane, a polyester, a polyamide, a polyether, a polysiloxane, an epoxy, a vinyl, and / or copolymers of any of the foregoing, and / or wherein the crosslinker comprises a phenol, a triglycidyl isocyanurate, a beta-hydroxy (alkyl) amide, an alkylated carbamate, a (meth)acrylate, a salt of a polycarboxylic acid with cyclic amidine, o-tolyl biguanide, an isocyanate, a blocked isocyanate, a polyacid, an anhydride, an organometallic acid-functional material, a polyamine, a polyamide, an aminoplast, a carbodiimide, and / or an oxazoline.

9. A method of forming a coating on a surface of a substrate, comprising: applying the powder coating composition of any preceding claims to the surface; and exposing the powder coating composition to photothermal radiation; wherein the photothermal radiation sufficiently excites the photothermally active material to form a continuous fdm; and wherein (i) the film-forming resin is reflective or transparent to electromagnetic radiation of the photothermal zone, and (ii) the substrate is reflective or transparent to electromagnetic radiation of the pho to thermal zone.

10. A method of repairing or replacing an existing coating formed from the compositions of any of claims 1 to 8 on a substrate, comprising exposing the coating to sufficient photothermal radiation to cause the coating to reflow and self-heal.

11. A method of repairing or replacing an existing coating on a substrate, comprising: applying the powder coating composition of any of claims 1 to 8 to the substrate, andexposing the coating to sufficient photothermal radiation to form a continuous film to repair or replace the existing coating.

12. A method of restoring or coating a surface of an article in the field comprising: mechanically or chemically preparing the surface; applying the powder coating composition of any of claims 1 to 8 to the surface; and exposing the coating to sufficient photothermal radiation to form a continuous film.

13. The method of any of claims 10 to 12, wherein (i) the film-forming resin is reflective or transparent to electromagnetic radiation of the photothermal zone, and (ii) the substrate is reflective or transparent to electromagnetic radiation of the photothermal zone.

14. The method of any of claims 9 to 13, wherein the photothermal radiation is applied at an intensity of 0.1 W / cm2to 108W / cm2and / or for a time of at least 1 femtosecond, such as at least 1 microsecond, such as at least 1 minute, such as at least 1 hour, such as at least 1 day.

15. The method of any of claims 9 to 14, wherein the film- forming resin is not curable by pho to thermal radiation.

16. The method of any of claims 9 to 15, wherein the photothermal radiation is generated by a mobile device and / or a hand-held device.

17. The method of any of claims 9 to 16, excluding heating the substrate following the applying.

18. The method of any of claims 9 to 17, wherein a temperature of the substrate and / or the film-forming resin does not increase upon the exposing.

19. The method of any of claims 9 to 18, wherein the substrate comprises aluminum and / or an aluminum alloy, copper, a composite such as a carbon fiber epoxy composite or a glass fiber epoxy composite, a temperature sensitive material, plastic, and / or wood.

20. The method of any of claims 9 to 19, wherein the method is performed in the field or on an existing structure or vehicle.

21. The method of any of claims 9 to 20, wherein the photothermal radiation comprises a laser and / or a light emitting diode and / or wherein the photothermal radiation is pulsed and / or continuous.

22. The method of any of claims 9 to 21, wherein the substrate (i) is not heated above its heat deflection temperature, (ii) is not heated above 120°C, such as 100°C, such as 80 C, such as 60°C, such as 40°C, and / or (iii) is not heated above ambient temperature.

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