Methods of curing a powder coating composition

Abstract

Disclosed are methods of curing a powder coating composition. The method includes exposing the powder coating composition to electromagnetic radiation generated by a laser for a period of time sufficient to cure the powder coating composition. The powder coating composition may include a resin, a crosslinker, and a photothermally active material. Also disclosed are substrates comprising a coating formed from the powder coating composition cured by the disclosed methods.

Description

METHODS OF CURING A POWDER COATING COMPOSITIONCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Application No. 63 / 687,906, filed on August 28, 2024, and entitled “Powder Coating Compositions Containing Photothermally Active Materials, Coated Substrates, and Methods of Coating Substrates,” incorporated herein in its entirety.FIELD

[0002] Methods of curing a powder coating composition arc disclosed.BACKGROUND

[0003] Multiple industries, including industrial, aerospace, and automotive industries, have demonstrated a desire for cure-on-demand products.SUMMARY

[0004] Disclosed are methods of curing a powder coating composition, comprising exposing the powder coating composition to electromagnetic radiation generated by a laser to cure the powder coating composition; wherein the powder coating composition comprises a filmforming material and a crosslinker.

[0005] Also disclosed are substrates comprising a powder coating formed from a powder coating composition cured by the disclosed methods.DETAILED DESCRIPTION

[0006] Disclosed herein are methods of curing a powder coating composition comprising exposing the composition to electromagnetic radiation generated by a laser and / or an LED to cure the powder coating composition.

[0007] As described in more detail below, the powder coating composition may comprise (a) a film-forming material and (b) a crosslinker.Electromagnetic Radiation and Laser

[0008] Exposure of any of the compositions disclosed herein to electromagnetic radiation (“EMR”) may cure the compositions disclosed herein. As used herein, “electromagnetic radiation” refers to a form of energy that includes visible light and near infrared (“nIR”) light. The EMR may be generated by a laser and / or a light emitting diode (“LED”). As used herein, “visible light” refers to EMR with wavelengths in the range of 380 nm to 750 nm which isvisible to the human eye. As used herein, “near infrared light” refers to EMR with wavelengths in the range of greater than 750 nm to 2,500 nm.

[0009] The EMR may have a wavelength of at least 300 nm, such as at least 350 nm, such as at least 380 nm, such as at least 400 nm, such as at least 450 nm, such as at least 500 nm, such as at least 550 nm, such as at least 600 nm, such as at least 700 nm, such as at least 800 nm, such as at least 900 nm, such as at least 925 nm, such as at least 950 nm, such as at least 960 nm.

[0010] The EMR may have a wavelength of no more than 1,500 nm, such as no more than 1,250 nm, such as no more than 1,080 nm, such as no more than 1,000 nm, such as no more than 985 nm, such as no more than 980 nm, such as no more than 810 nm, such as no more than 530 nm, such as no more than 450 nm.

[0011] The EMR may have a wavelength of 300 nm to 1 ,500 nm, such as 300 nm to 1,000 nm, such as 300 nm to 980 nm, such as 300 nm to 810 nm, such as 300 nm to 530 nm, such as 300 nm to 450 nm, such as 380 nm to 1,500 nm, such as 380 nm to 1,000 nm, such as 380 nm to 980 nm, such as 380 nm to 810 nm, such as 380 nm to 530 nm, such as 380 nm to 450 nm, such as 400 nm to 1,500 nm, such as 400 nm to 1,250 nm, such as 400 nm to 1,000 nm, such as 400 nm to 980 nm, such as 450 nm to 1,500 nm, such as 450 nm to 1,250 nm, such as 450 nm to 1,000 nm, such as 450 nm to 980 nm, such as 500 nm to 1,500 nm, such as 500 nm to 1,250 nm, such as 500 nm to 1,000 nm, such as 500 nm to 980 nm, such as 550 nm to 1,500 nm, such as 550 nm to 1,250 nm, such as 550 nm to 1,000 nm, such as 550 nm to 980 nm, such as 600 nm to 1,500 nm, such as 600 nm to 1,250 nm, such as 600 nm to 1,000 nm, such as 600 nm to 980 nm, such as 700 nm to 1,500 nm, such as 700 nm to 1,250 nm, such as 7000 nm to 1,000 nm, such as 700 nm to 980 nm, such as 800 nm to 1,500 nm, such as 800 nm to 1,250 nm, such as 800 nm to 1,000 nm, such as 800 nm to 980 nm, such as 900 nm to 1,500 nm, such as 900 nm to 1,250 nm, such as 900 nm to 1,080 nm, such as 900 nm to 1,000 nm, such as 900 nm to 980 nm, such as 925 nm to 1,500 nm, such as 925 nm to 1,250 nm, such as 925 nm to 1,000 nm, such as 925 nm to 980 nm, such as 950 nm to 1,500 nm, such as 950 nm to 1,250 nm, such as 950 nm to 1,000 nm, such as 950 nm to 980 nm, such as 960 nm to 985 nm.

[0012] The EMR may be generated as a continuous wave, a quasi-continuous wave, and / or a pulsed wave. As used herein, “continuous wave,” when used with respect to EMR, refers to a constant, uninterrupted beam of light as long as the laser is powered and having a duty cycle of 100%. As used herein, “quasi-continuous wave,” when used with respect to EMR,refers to a series of pulses of light beams with intervals of no emission and having a duty cycle of greater than 50% to less than 100%. As used herein, “pulsed wave,” when used with respect to EMR, refers to a series of pulses of light beams with a duration of femtoseconds to milliseconds separated by intervals of no emission and having a duty cycle of greater than 0% to 50%. As used herein, “duty cycle” refers to the percentage of time that light is actively emitted by laser during a given period of operation. Duty cycle may be calculated according to the following formula: Duty Cycle (D) = (Pulse Duration) / (Pulse Period) * 100%, where “pulse duration” is the time interval during which the laser emits light in one pulse, wherein “pulse period” is the total time interval of one cycle including the pulse duration plus the off time (when the laser is not emitting light). The person skilled in the art of laser technologies will understand that the selection of duty cycle impacts thermal management and power output and must be compatible with the cure chemistry and the substrate to which the composition is applied.

[0013] The EMR may be directional. As used herein, the term “directional,” when used with respect to the EMR, refers to light that is emitted in a single direction.

[0014] The EMR may be monochromatic light from the visible domain to the nearinfrared domain. As used herein, the term “monochromatic” refers to light having a narrow bandwidth (+ / - 25 nm) at a nominal wavelength or frequency.

[0015] The EMR may be polychromatic light from the visible domain to the nearinfrared domain. As used herein, the term “polychromatic” refers to a light having primarily two or more wavelengths or frequencies.

[0016] The EMR may be coherent. As used herein, the term “coherent,” when used with respect to the EMR, means that the photons of the light wave oscillate at the same frequency and whose wavelengths are in the same phase.

[0017] The laser may be defocused. As used herein, “defocused,” when used with respect to a laser, refers to a manipulation by optics of a light beam generated by the laser to result in a divergent light beam of a predetermined shape (i.e., a non-Gaussian and / or wide-area light beam), such as a light beam having a substantially rectangular shape, a substantially square shape, and the like.

[0018] The laser may generate EMR that is diffuse, divergent, and / or collimated. As used herein, “diffuse,” when used with respect to EMR, refers to light that is scattered by molecules, particles, or surfaces before reaching its destination. As used herein, “divergent,”when used with respect to EMR, refers to a light beam that spreads out or expands as it propagates away from the light source. The diameter of a divergent EMR light beam increases with distance from the source. As used herein, “collimated,” when used with respect to EMR, refers to a plurality of light rays that are parallel or substantially parallel, resulting in a beam that does not diverge or converge over a specified distance, i.e., the beam maintains a substantially constant diameter and direction over a specified distance.

[0019] Suitable examples of a laser include a solid-state laser, a gas laser, a semiconductor (diode) laser, a fiber laser, a dye laser, and / or a high harmonic generation laser (such as a frequency-doubled or a frequency-tripled laser).

[0020] Suitable examples of a solid-state laser include a neodymium-doped yttrium aluminum garnet (ND:YAG) laser, a ruby laser, a titanium-doped sapphire (Ti:Sapphire) laser, a neodymium-doped yttrium orthovanadate (Nd:YVO4) laser, and / or an erbium-doped yttrium aluminum garnet (Er:YAG) laser.

[0021] Suitable examples of a gas laser include a helium-neon (He-Ne) laser, a carbon dioxide (CO2) laser, an argon ion laser, a nitrogen laser, and / or an excimer laser such as KrF, ArF, and the like.

[0022] Suitable examples of a semiconductor (diode) laser include an edge-emitting laser diode, a vertical-cavity surface-emitting laser (VCSEL), a quantum cascade laser, a distributed feedback (DFB) laser, and / or a distributed bragg reflector (DBR) laser. Suitable materials used to produce NIR diode lasers include gallium arsenide (GaAs), indium gallium arsenide phosphide (InGaAsP) on an indium phosphide (InP) substrate, and / or indium gallium arsenide (InGaAs) on GaAs or InP.

[0023] Suitable examples of a fiber laser include an ytterbium-doped fiber laser, an erbium-doped fiber laser, a thulium-doped fiber laser, a holmium-doped fiber laser, and / or a Raman fiber laser.

[0024] Suitable examples of a dye laser include a rhodamine 6G dye laser, a coumarin dye laser, a stilbene dye laser, a pyrromethene dye laser, and / or a DCM dye laser.

[0025] Any suitable laser diode configuration may be used. For example, the laser diode configuration may comprise a single diode, a diode laser bar, and / or a diode laser stack. As used herein, a “single diode” laser refers to a single semiconductor device in which a diode pumped with electrical current creates lasing conditions at the diode’s junction. Single diodes may beelectrically connected such that the decline or failure of any one diode does not affect the output of the still-operational diodes. As used herein, a “diode laser bar” refers to an array of single diodes positioned side-by-side on a single semiconductor chip. A diode laser bar may comprise, for example, 10 to 50 emitters spaced apart, such as 100 pm to 200 pm apart, and connected in parallel or in series. As used herein, a “diode laser stack” refers to an assembly of multiple diode laser bars stacked vertically or arranged in arrays. A diode laser stack may comprise, for example, 5 or more diode laser bars, such as up to 20 diodes, such as up to 300 diodes, such as more than 300 diodes.

[0026] The diode laser stack may be coupled, such as pigtail-coupled, to more than one fiber or may be configured as a bundle of fibers. As used herein, “pigtail-coupled” refers to a laser diode that permanently connected to an optical fiber, forming a single unit. Fibers may comprise multi-mode fibers with core diameters of, for example, 100 pm to 600 pm or larger.

[0027] The laser may have a wall plug efficiency of at least 30 percent, such as at least 50 percent, such as at least 60 percent, such as at least 80 percent, such as 30 percent to 80 percent, such as 50 percent to 80 percent, such as 60 percent to 80 percent, such as 30 percent to 50 percent. As used herein, “wall plug efficiency” refers to a ratio of usable output power to the total electrical power consumed from the wall outlet; it measures how effectively electrical power from a wall outlet is converted into usable power.

[0028] Adaptive optics may be used to enhance the capabilities of the laser and / or LED, such as those useful for tailoring focal intensity and wide-area distribution of the EMR.

[0029] A laser and / or an LED may be used to cure coatings over a variety of types of substrate surfaces having a range of surface areas, including a vehicle, such as an automobile, a tractor, a trailer, or an aerospace vehicle, an aerospace structure such as a wing, a skin, and / or a fuselage of an aerospace vehicle, a body in white (that is, the stage before painting in automobile manufacturing in which a car body's frame has been joined together), an appliance or a part thereof, a roof, a door, a ship, a large and / or fixed object or structure such as a bridge, a building, an off-shore platform and the like, and parts of any of the foregoing. As used herein, “fixed” when used with respect to an object or a structure refers to an object or a structure that is designed to remain stationary. The laser optionally may include a fiber amplifier to boost the power generated by the laser.

[0030] The laser and / or LED may be coupled with a temperature sensor and / or an IR sensor to control coating temperature, ramp rate, substrate temperature, and the like. Suitable sensors include a pyrometer, an infrared camera, a thermocouple, and other types of sensors that send information to control feedback loops known to those skilled in the art to control coating temperature, ramp rate, substrate temperature, and the like.

[0031] EMR may be generated by an industrial-sized laser or LED equipment, such as equipment configured for use in a laboratory or on a production line. Accordingly, the methods disclosed herein may be used in laboratory or industrial settings.

[0032] EMR may be generated by a portable laser and / or LED, a hand-held laser and / or LED, a fixed laser and / or LED. Accordingly, the methods disclosed herein may be used in the field, on an existing structure or vehicle, on a fixed structure, and / or as part of a production line for coating substrates.

[0033] EMR may be generated by a robotically guided laser and / or LED.Photothermally Active Materials

[0034] Optionally, the composition may comprise a photothermally active material. As used herein, a “photothermally active material” refers to a material whose presence in a composition reduces by at least 5% the total energy density required to ramp and maintain the composition at a temperature setpoint compared to the total energy density required to ramp and maintain the same composition that does not include the material at the temperature setpoint. As used herein, “total energy density” is calculated according to Equation 1;Equation 1, where Etot = total energy density in J / cm2; to = time zero or start of heating cycle; tmax = time to end of heating cycle, wherein the time from to to tmaxincludes ramp time to a temperature setpoint and hold time at the temperature setpoint (in seconds); %P - the percentage of laser power used in the recorded time interval (as recorded using LASCON Process Manager software by Dr. Mergenthaler GmbH & Co. KG, as part of the controller of the laser system; Lp = laser power, 4500 W; At - 0.02 seconds between recorded data points, ; and A = the projection area of the laser output, 400 cm2. As used herein, “temperature setpoint” refers to a preset temperature to which the coating is ramped and at which the coating is maintained overthe heating cycle. Temperature setpoint may be measured using an infrared thermometer or similar device to measure the temperature of the coating. Temperatures from the infrared thermometer may be read by the controller described above to adjust the EMR generated by the laser system over the heating cycle to ramp or maintain the coating temperature at the temperature setpoint.

[0035] The photothermally active material may be a solid, a neat liquid, a solid dissolved in an aqueous or organic solvent, a dry powder, a solid dispersed in an aqueous or organic solvent, or dispersed in an organic medium that is non-volatile such as a plasticizer or a reactive diluent.

[0036] The photothermally active material that may be used in the 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; aluminum trihydrate; manganese dioxide; magnesium hydroxide; agate; emery; ceramic microspheres; metakaolin; and / or diamond.

[0037] The photothermally active material that may be used in the compositions disclosed herein also include diatomaceous earth; clay, such as kaolin, bentonite, and halloysite; talc; mica; leucophyllite; lazurite; and / or silica, such as precipitated silica, pyrogenic silica and silica gel, sulfur containing sodium silicates, cristobalite, wollastonite, feldspar, leucophyllite, chamotte, perlite, glass powder and flake, quartz, metal and mixed metal silicate, such as aluminum silicate, barium silicate, barium copper silicate, calcium copper silicate, and sulfur containing sodium silicate, and / or other inorganic silicate and derivates such as orthosilicate, such as lithium orthosilicate and / or inorganic phosphosilicate.

[0038] The photothermally active material that may be used in the compositions disclosed herein also include lime; iron oxide such as hematite, magnetite and siderite; chromium oxide; hydrated chromium oxide; chromium trioxide; antimony trioxide; antimony pentoxide; antimony tin oxide; indium tin oxide; cerium oxide; titanium dioxide, such as rutile and anatase titanium dioxide; tungsten oxide; doped tungsten oxides having the formula MxWCh such as CsWCh; reduced tungsten oxide such as violet tungsten oxide; tungstate; tungsten bronzes; vanadium oxide; cupric carbonate hydroxide; copper hydroxide; layered double hydroxide such as hydrotalcite; titanium nitride; and / or organic quaterrylene.

[0039] The photothermally active material that may be used in the compositions disclosed herein also include calcium carbonate; dolomite; huntite; and / or hydromagnesite.

[0040] The photothermally active material that may be used in the compositions disclosed herein also include zinc chromate; zinc tetraoxy chromate; barium chromate; lead chromate; strontium chromate; and / or other inorganic chromates.

[0041] The photothermally active material that may be used in the compositions disclosed herein also include barium sulfate and / or barium manganate sulfate.

[0042] The photothermally active material that may be used in the compositions disclosed herein also include carbon black; graphite; graphene; and / or graphenic carbon particles. Graphene may be a thermal graphene such as turbostatic thermal graphene. Graphene may be in the form of commercially available nanoparticles such as exfoliated graphite. Graphenic 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.

[0043] 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. The average number of stacked layers may be 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 graphenic 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- AB AB AB stacking. Alternatively, the graphenic carbon particles may be in the form of nanotubes. The particles typically do not have a spheroidal or equiaxed morphology.

[0044] The photothermally active material that may be used in the compositions disclosed herein also includes cadmium sulfide; cadmium selenide; and / or cadmium sulfoselenide.

[0045] The photothermally active material that may be used in the compositions disclosed herein also include cobalt stannate; cobalt phosphate; and / or cobalt aluminate.

[0046] The photothermally active material that may be used in the compositions disclosed herein also include copper pigment such as copper phthalocyanine, copper / zinc pigment; zinc pigment; bronze pigment; gold bronze pigment; ferric hexacyanoferrate; lithopone; and YInMn blue pigment (yttrium, indium, and manganese pigment); metal flake pigment such as zinc flake; metal effect pigment; and / or inorganic effect pigment.

[0047] The photothermally active material that may be used in the compositions disclosed herein also include phosphate such as chrome phosphate, phosphite, and phosphonate, inorganic phosphate, polyphosphate, orthophosphate, and / or pyrophosphate such as manganese ammonium pyrophosphate.

[0048] The photothermally active material may also include a micronized rubber compound.

[0049] The photothermally active material may be a conjugated material, a dye, a solubilized pigment, and / or a pigment dispersion. As used herein, a “conjugated compound” refers to a compound having two double bonds separated by a single bond, for example two carbon-carbon double bonds with a single carbon-carbon bond between them. Suitable examples of conjugated materials include catechol violet and / or xylenol orange. A suitable example of a solubilized pigment includes Astrad-IS PCN Blue. Suitable examples of dyes include cyanine dyes, phthalocyanine dyes, porphyrin dyes, and / or boron dipyrrin dyes.

[0050] The photothermally active material may comprise carbon black, graphene, silicone carbide, tungsten oxide, and / or doped tungsten oxide.

[0051] Any combination of the foregoing photothermally active materials disclosed herein above also may be used in the compositions disclosed herein. For example, the photothermally active material may comprise a single photothermal material or may comprise two or more different types of photothermal material.

[0052] The photothermally active material may be soluble or may be in a particulate form.

[0053] Optionally, a photothermally active material of any average particle size can be used in the compositions disclosed herein, provided that the photothermally active material generates sufficient heat for curing to take place when the composition is exposed to EMR. 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 number 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 number 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 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, nanosheets, nanospheres, powders, flakes, microspheres, high aspect ratio materials, and irregularly shaped particles of appropriate size. Number average particle size may be measured by methods known to those skilled in the art, for example, using a scanning electron microscope (SEM).

[0054] Optionally, the particles of photothermally active materials have a number average primary particle size of no more than 500 nanometers, such as no more than 50 nanometers, or no more than 2 nanometers. Number average particle size may be measured by methods known to those skilled in the art, for example, using SEM. As used herein, the term “primary particle size” refers to the smallest diameter sphere that will completely enclose an individual particle as opposed to an agglomeration of two or more individual particles.

[0055] The powder coating compositions may comprise the photothermally active material in an amount of at least 0.001 percent by weight based on total weight of the powder coating composition, such as at least 0.01 percent by weight, such as at least 0.1 percent by weight, such as at least 1 percent by weight. The coating powder coating compositions may comprise the photothermally active material in an amount of no more than 10 percent by weight based on total weight of the powder coating composition, such as no more than 5 percent byweight, such as no more than 1 percent by weight. The powder coating composition may comprise the photothcrmally active material in an amount of 0.001 percent by weight to 10 percent by weight based on total weight of the powder coating composition, such as 0.01 percent by weight to 5 percent by weight, such as 0.1 percent by weight to 5 percent by weight, such as 0.1 percent by weight to 1 percent by weight, such as 0.001 percent by weight to 1 percent by weight, such as 0.001 percent by weight to 0.1 percent by weight.FILM-FORMING MATERIALS AND CROSSLINKERS

[0056] The powder coating compositions disclosed herein may comprise a film-forming material. The powder coating composition optionally may further comprise a crosslinker. 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. As used herein, the term “thermoplastic” refers to a component that can be softened or melted when heated and hardened when cooled. As used herein, the term “thermoset” refers to a composition that permanently hardens through a reactive process which may become insoluble, infusible, and / or unable to melt at elevated temperatures. The powder composition may, upon cure, form a continuous coating on a surface of a substrate.

[0057] The film-forming material 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 materials 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.

[0058] The powder coating composition optionally may further comprise a crosslinker. Non-limiting examples of crosslinkers include a phenol, a triglycidyl isocyanurate, a betahydroxy (alkyl) amide, an alkylated carbamate, a (meth) acrylate, a salt of a polycarboxylic acidwith cyclic amidine, o-tolyl biguanide, an isocyanate, a blocked isocyanate, a polyacid, an anhydride, an organometallic acid-functional material, a polyaminc, a polyamide, an aminoplast, a carbodiimide, an oxazoline, and combinations thereof.

[0059] The powder coating composition may comprise the film-forming material in an amount of at least 40 percent by weight based on total weight of the powder coating composition, such as at least 50 percent by weight. The powder coating composition may comprise the film- forming material in an amount of no more than 90 percent by weight based on total weight of the powder coating composition, such as no more than 75 percent by weight. The powder coating composition may comprise the film-forming material in an amount of 40 percent by weight to 90 percent by weight, such as 50 percent by weight to 75 percent by weight.

[0060] The powder coating composition optionally may comprise the crosslinker in an amount of at least 3 percent by weight based on total weight of the powder coating composition, such as at least 10 percent by weight. The powder coating composition optionally may comprise the crosslinker in an amount of no more than 97 percent by weight based on total weight of the powder coating composition, such as no more than 90 percent by weight. The powder coating composition optionally may comprise the crosslinker in an amount of 3 percent by weight to 97 percent by weight based on total weight of the powder coating composition, such as 10 percent by weight to 90 percent by weight.Additives, Catalysts, and Fillers

[0061] The compositions disclosed herein optionally may comprise an additive in amounts known to those skilled in the art. Such additives include a rheology modifier, a dispersant, a thermoplastic polymer, a surface active agent, a flame retardant, a corrosion inhibitor, a UV stabilizer, a colorant, a tint, a plasticizer, an adhesion promoter, an antioxidant, a silane, a silane terminated polymer, a silyl terminated polymer, a moisture scavenger, an outgassing additive, a degassing additive, a flow additive, a leveling additive, and / or a wax.

[0062] As used herein, the term “plasticizer” refers to a molecule or a compound that does not have a functional group capable of reacting with a functional group(s) on molecules or compounds in a powder coating composition and that is added to the powder coating composition to decrease viscosity, decrease glass transition temperature (Tg), and impart flexibility.

[0063] The powder coating composition may comprise the additive in an amount of at least 0.1 percent by weight based on total weight of the composition, such as at least 1 percent by weight. The powder coating composition may comprise the additive in an amount of no more than 20 percent by weight based on total weight of the powder coating composition, such as no more than 15 percent by weight. The powder coating composition may comprise the additive in an amount of 0.1 percent by weight to 20 percent by weight based on total weight of the powder coating composition, such as 1 percent by weight to 15 percent by weight.

[0064] The compositions disclosed herein optionally may comprise a catalyst. Suitable catalysts include a phosphonium compound, a quaternary ammonium halide compound, an amine compound, an imidazole compound, a sulfonium compound, a compound comprising a transition metal and / or post-transition metal, or any combination thereof that increases the reaction rate between acid and epoxy functionality.

[0065] A “phosphonium compound” refers to a salt comprising a phosphonium cation. Non-limiting examples of phosphonium compounds include tetrabutylphosphonium hydroxide and tetrabutylphosphonium bromide.

[0066] A “quaternary ammonium halide compound” refers a salt comprising a quaternary ammonium cation and a halogen anion. Non-limiting examples of quaternary ammonium halide compounds include dodecyltrimethylammonium chloride, benzyltrimethylammonium chloride, benzyldimethyloctylammonium chloride, and hexadecyltrimethylammonium bromide.

[0067] An “amine compound” refers to a compound comprising one or more primary, secondary, and / or tertiary amines. Non-limiting examples of amine compounds include 1,4- diazabicyclo[2.2.2]octane, l,8-diazabicyclo[5.4.0]undec-7-ene, coco alkyl amine, benzyl diemethyl amine, and 1,1,3,3-tetramethylguanidine.

[0068] An “imidazole compound” refers to a compound comprising a substituted heterocyclic imidazole structure. Non-limiting examples of imidazole compounds include 1- methyl imidazole and 2-methyl imidazole.

[0069] A “sulfonium compound” refers to a salt comprising a sulfonium cation. A nonlimiting example of a sulfonium compound is trimethylsulfonium iodide.

[0070] A “compound comprising a transition metal” refers to a compound comprising an element from one of Groups 3-12 (International Union of Pure and Applied Chemistry (IUPAC)) of the periodic table of the chemical elements, and a “compound comprising post-transitionmetal” refers to a compound comprising a post-transition metal element from one of Groups 13 and 14 (International Union of Pure and Applied Chemistry (IUPAC)) of the periodic table of the chemical elements. Non-limiting examples of compounds comprising a transition metal include non diammonium dihydroxy bis(lactate(2-)-Ol,O2) titanate (2-), and zinc octoate. Non-limiting examples of compounds comprising a post-transition metal include stannous 2-ethylhexoate and tin(II) oxalate.

[0071] Other suitable catalysts include a Lewis base, an ammonium salt, a cyclic amidine, a Lewis acid complex, an amino-phenol, a metal oxide, a peroxide, a sulfonic acid, a solfonamide,

[0072] Any combination of catalysts may be used.

[0073] The powder coating composition may comprise the catalyst in an amount of at least 0.1 percent by weight based on total weight of the composition, such as at least 1 percent by weight. The powder coating composition may comprise the catalyst in an amount of no more than 20 percent by weight based on total weight of the powder coating composition, such as no more than 15 percent by weight. The powder coating composition may comprise the catalyst in an amount of 0.1 percent by weight to 20 percent by weight based on total weight of the powder coating composition, such as 1 percent by weight to 15 percent by weight.

[0074] The compositions disclosed herein optionally may comprise a filler.

[0075] The powder coating composition may comprise a filler. Suitable examples of filler useful in the powder coating composition include barium sulfate, aluminum hydroxide, mica, wollastonite, calcium carbonate, glass microspheres, clay, aluminum silicate, magnesium silicate, silica, and / or nepheline syenite.

[0076] The powder coating composition may comprise the filler, if present at all, in an amount of at least 1 percent by weight based on total solids weight, such as at least 5 percent by weight. The powder coating composition may comprise the filler, if present at all, in an amount of no more than 60 percent by weight based on total solids weight, such as no more than 30 percent by weight. The powder coating composition may comprise the filler, if present at all, in an amount of 1 percent by weight to 60 percent by weight based on total solids weight, such as 5 percent by weight to 30 percent by weight.Powder Coating Compositions

[0077] The powder coating composition may be substantially free, essentially free, or completely free of a photopolymerizable initiator.

[0078] The powder coating composition may be formulated as a sealant composition, an adhesive composition, a gap filler composition, a pottant composition, and / or a prepreg.

[0079] The powder coating composition may be formulated as a composition suitable for molding, casting, extrusion, and / or machining.

[0080] The powder coating composition may be formulated as a one-component composition, a two-component composition, or a higher-component composition.

[0081] As used herein, a “IK” or “one-component” powder coating composition, is a composition in which all the ingredients may be premixed and stored and wherein the reactive components do not readily react at ambient or slightly thermal conditions, for example, temperatures greater than ambient and less than 60°C. One-component powder coating compositions may cure upon exposure to EMR and / or may react at an accelerated rate upon exposure to EMR compared to a reaction rate in the absence of EMR. In the absence of such exposure, the composition will remain largely uncured.

[0082] The powder coating compositions disclosed herein may be formulated as a IK composition comprising, consisting essentially of, or consisting of a film-forming material and optionally a photothermally active material, a crosslinker, a catalyst, an additive, and / or a filler.

[0083] As used herein, the term “two-component” or “2K” refers to a composition in which the reactive components readily associate to form an interaction or react to form a bond (physically or chemically), i.e., cure, without activation. Two-component compositions may be exposed to EMR as described herein. As used herein, “reactive components” refer to components of the final composition containing the film-forming material.

[0084] The powder coating compositions disclosed herein may be formulated as a 2K composition comprising, consisting essentially of, or consisting of: a first component comprising, consisting essentially of, or consisting of a film-forming material; and a second component comprising, consisting essentially of, or consisting of a cross-linker, a photothermally active material, a catalyst, an additive, and / or a filler. The first component optionally may further comprise a photothermally active material, a catalyst, an additive, and / or a filler as longas the optional ingredients do not react with the film-forming material. The first and second components may be mixed immediately prior to use.

[0085] The powder coating composition may be agitated manually or mechanically to homogenize the ingredients using art-recognized techniques and equipment such as, for example, using a Prism high speed mixer. The photothermally active material may be formed as pail of the homogenized mixture or may post-added following the grinding, sorting, and classification described below.

[0086] After mixing to form a homogenous mixture, the mixture is 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, 75 °C to 125°C, such as 85°C to 115°C, or at 100°C.

[0087] 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 powder coating composition. The re-solidified mixture can be ground to any desired particle size.

[0088] For example, the particles of the re-solidified mixture may have an average particle size of at least 10 microns, such as at least 20 microns, such as at least 25 microns, such as no more than 200 microns, such as no more than 150 microns, such as no more than 100 microns, such as no more than 50 microns. For example, the re-solidified mixture may have an average particle size of 10 microns to 200 microns, such as 20 microns to 150 microns, such as 20 microns to 100 microns, such as 25 microns to 50 microns. Particle size may be measured using a laser diffraction particle size analyzer such as, for example, a Beckman-Coulter LS™ 13 320 Laser Diffraction Particle Size Analyzer.

[0089] For example, the particles of the re-solidified mixture may have a D50 of at least 15 microns, such as at least 20 microns, such as no more than 40 microns, such as no more than 35 microns. As used herein the term “D50” means the point in the size distribution in which 50 percent or more of the total volume of material in the sample is contained. For example, a D50 of 15 microns means that 50 percent of the particles of the sample have a size of 15 microns or smaller as measured using a laser diffraction particle size analyzer.

[0090] Particles may be sorted using a classifier according to methods known to those skilled in the art.Methods and Cured Coatings

[0091] Disclosed herein are methods of curing any of the powder coating compositions described above.

[0092] The powder coating may be, for example, a sealant, an adhesive, a gap filler, a pottant, and / or a prepreg.

[0093] The powder coating compositions may be applied alone or as part of a system that can be deposited in a number of different ways onto a number of different substrates. Accordingly, disclosed herein are methods for treating a substrate comprising, or consisting essentially of, or consisting of, contacting a surface of the substrate with any of the powder coating compositions disclosed herein and exposing the powder coating composition to a EMR generated by a laser and / or an LED as described above.

[0094] Substrates may be moved manually or via a conveyer to a powder application booth or area. Powder coating compositions may be applied using a spray gun which imparts a positive or negative charge onto the powder particles. The skilled artisan will appreciate that any of a variety of types of spray guns can be used, including a corona charging spray gun or a tribo charging spray gun. In other non-limiting examples, the powder coating may be applied via fluidized bed application, electrostatic fluidized bed application, hot dip coating, electrophoretic deposition, rotary bell spraying, or magnetic brush coating. In some cases, to encourage a powder coating to stick to the substrate, the substrate may be heated, or the substrate may be coated with a conductive primer.

[0095] Powder coating compositions may be applied in different environments such as a spray booth, a hangar, a paint shop, or a clean room based on need to protect the powder coating composition from airborne contaminants. Spray booths can be maintained to keep constant temperature and humidity. Enclosures may be used in hangar operations to help with cleanliness. Coating repair or application may take place in remote locations lacking booths, hangars, or portable enclosures.

[0096] The method comprises exposing the powder coating composition to EMR generated by a laser and / or an LED to cure the powder coating composition. Such methods may cure the composition to form a coating. The EMR, laser, and / or LED may be any of thosedescribed above. For example, the compositions disclosed herein may be applied to a substrate surface and cured as described herein to form a coating.

[0097] The methods may comprise exposing the powder coating compositions to EMR for at least 1 minute, such as at least 3 minutes, such as at least 5 minutes, such as at least 7 minutes, such as at least 10 minutes to cure the composition. For example, the method may comprise exposing the powder coating composition to EMR with a ramp rate from ambient to a temperature setpoint of at least 191°C and held at the temperature setpoint for at least 10 minutes to cure the composition. For example, the method may comprise exposing the powder coating composition to EMR with a ramp rate from ambient to a temperature setpoint of at least 200°C and then held at the temperature setpoint of at least for at least 1 minute to cure the composition.

[0098] 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 1.0 mil (25.4 micrometers), such as 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), such as at least 45 mils (1,143 microns). For example, the dry film thickness may be less than 45 mils (1,143 microns), such as 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).

[0099] The methods may comprise exposing the compositions to EMR at an intensity of at least 0.01 W / cm2, such as at least 0.1 W / cm2, such as at least 0.2 W / cm2. The methods may comprise exposing the compositions to EMR at an intensity of no more than 108W / cm2, such as no more than 106W / cm2, such as no more than 104W / cm2, such as no more than 102W / cm2, such as no more than 15 W / cm2, such as no more than 12 W / cm2. The methods may comprise exposing the compositions to EMR at an intensity of 0.01 W / cm2to 108W / cm2, such as 0.1 W / cm2to 106W / cm2, such as 0.1 W / cm2to 104W / cm2, such as 0.1 W / cm2to 102W / cm2, such as 0.1 W / cm2to 15 W / cm2, such as 0.2 W / cm2to 12 W / cm2.

[0100] The methods disclosed herein may further comprise cleaning, deoxidizing, and / or degreasing the substrate surface. Suitable methods of cleaning include solvent-wiping, alkaline cleaning, mechanical cleaning and / or abrasion such as by blasting, sandpaper, and the like, ultrasonic cleaning, plasma cleaning or etching, and the like, as understood by those skilled in the art of substrate protection.

[0101] Methods of powder coating a substrate may utilize a conveyer having a speed set such that the substrate remains in contact with the various treatment chemicals for times known to those skilled in the art. Optional rinse steps and drying steps may be included in the methods of treatment.

[0102] The methods disclosed herein may further comprise coating the substrate surface with a coating composition in addition to the powder coating composition. That is, the methods may further comprise treating the substrate surface with a pretreatment composition and / or coating the substrate surface with an electrodepositable coating composition, a primer coating composition, a basecoat coating composition, a topcoat coating composition, and the like, as understood by those skilled in the art of substrate protection. That is, “contacting a surface of the substrate” encompasses contacting a surface of a substrate that has been treated with other coatings, as described herein.

[0103] The methods disclosed herein may comprise applying a powder coating composition as described herein to a damaged portion of a substate surface, and exposing the powder coating composition to EMR generated by a laser and / or an LED as described herein. Optionally, the surface may comprise a pre-existing coating, and the pre-existing coating may be partially removed prior the applying.

[0104] The methods disclosed herein may exclude heating the substrate (i) prior to and / or following applying the composition to a surface of the substrate and / or (ii) prior to and / or following exposing the composition to EMR.

[0105] The methods disclosed herein may be performed using a portable and / or handheld laser, as described above. As such, the methods may be performed in the field and / or on existing structures.

[0106] The methods disclosed herein may be performed using an industrial-sized laser or LED equipment, as described above. As such, the methods may be performed in a laboratory and / or industrial setting.

[0107] The methods disclosed herein may be performed using a robotically guided laser and / or LED.

[0108] The methods disclosed herein may maintain the temperature of the composition, for example, without heating the substrate above its heat deflection temperature. As used herein, “heat deflection temperature” refers to the temperature at which a material’s properties are compromised. For example, the substrate may be heated up to 60°C, such as up to 80°C, such as up to 100 C, such as up to 120°C. The temperature of the substrate may not increase following the exposure to EMR, for example, the substrate may not be heated above ambient temperature. Accordingly, the present disclosure allows for reduced energy consumption and may also allow for the use of coatings on temperature sensitive substrates.

[0109] It was surprisingly discovered that the methods disclosed herein may cure a powder coating composition.

[0110] It was surprisingly discovered that exposure of the compositions disclosed herein to EMR generated by a diode laser and having a wavelength of 900 nm to 1,080 nm, such as 960 nm to 985 nm, may cure the composition upon exposure to the EMR held at a temperature setpoint of at least 191°C for at least 10 minutes. It also was surprisingly discovered that exposure of the compositions disclosed herein to EMR generated by a diode laser and having a wavelength of 900 nm to 1,080 nm, such as 960 nm to 985 nm, may cure the composition upon exposure to the EMR held at a temperature setpoint of at least 200°C for at least 1 minute, such as at least 3 minutes, such as at least 5 minutes, such as at least 7 minutes. Coatings formed by curing powder coating compositions according to such methods had good performance as demonstrated by MEK resistance. As such, neither laser-exposure nor inclusion of photothermally active materials in the powder coating composition negatively impacted performance of samples.

[0111] Additionally, it was surprisingly and unexpectedly discovered that powder coating compositions comprising a photothermally active material required a reduced total energy density to cure the powder coating composition compared to the same powder coating composition that did not include a photothermally active material. That is, on a white substrate, the powder coating compositions disclosed herein comprising a photothermally active material required a reduced total energy density to ramp and maintain the powder coating composition at a temperature setpoint compared to the total energy density required to ramp and maintain thesame powder coating composition that did not include a photothermally active material at the temperature setpoint. For example, powder coating compositions deposited on a white substrate, when exposed to an EMR having a wavelength of 900 nm to 1,080 nm, such as 960 nm to 985 nm, the total energy density required to ramp and maintain the composition at a temperature of 191°C for 10 minutes was less than 2,100 J / cm2, such as less than 2,000 J / cm2, such as less than 1,100 J / cm2, such as less than 700 J / cm2.

[0112] It was also surprisingly and unexpectedly discovered the total energy density required to ramp and maintain the powder coating compositions disclosed herein, deposited on a white substrate and exposed to an EMR having a wavelength of 900 nm to 1,080 nm, such as 960 nm to 985 nm, at a temperature setpoint of 191°C for at least 10 minutes was reduced by at least 5%, such as by at least 10%, such as by at least 50%, such as by at least 70% compared to total energy density required to ramp and maintain the same composition that did not include a photothermally active material at the temperature setpoint for at least 10 minutes.

[0113] It was also surprisingly and unexpectedly discovered that powder coating compositions deposited onto a black substrate and exposed to an EMR having a wavelength of 900 nm to 1,080 nm, such as 960 nm to 985 nm, required a lower total energy density to ramp and maintain the composition at a temperature of 191°C for 10 minutes compared to the same powder coating deposited onto a white substrate and exposed to the same EMR at 191°C for 10 minutes. For example, powder coating compositions deposited on a black substrate, when exposed to an EMR having a wavelength of 900 nm to 1,080 nm, such as 960 nm to 985 nm, the total energy density required to ramp and maintain the composition at a temperature of 191°C for 10 minutes was less than 700 J / cm2. That is, the total energy density required to ramp and maintain the powder coating compositions deposited on a black substrate, when exposed to an EMR having a wavelength of 900 nm to 1,080 nm, such as 960 nm to 985 nm, the total energy density required to ramp and maintain the composition at a temperature of 191°C for 10 minutes was reduced by at least 60%, such as by at least 65%, such as by at least 70% compared to the total energy density required to ramp and maintain the same powder coating composition at a temperature of 191°C for 10 minutes deposited on a white substrate.

[0114] Notably, in contrast to a white substrate, inclusion of a photothermally active material in the powder coating composition did not affect the total energy density required toramp and maintain the same powder coating composition at a temperature of 191 °C for 10 minutes deposited on a black substrate.

[0115] It was also surprisingly and unexpectedly discovered that thicker powder coatings applied to a white substrate having a lower concentration of photothermally active material resulted in lower total energy density required to maintain a powder coating composition temperature of 191°C for 10 minutes, while increasing the amount of photothermally active material had a minimal impact on total energy density required to maintain a powder coating composition temperature of 191°C for 10 minutes.

[0116] It was also surprisingly and unexpectedly discovered that inclusion of catalyst or blocked isocyanate in the powder coating composition decreased the time to cure as measured by MEK resistance.

[0117] These results surprisingly and unexpectedly demonstrated that exposure of compositions to EMR generated by a laser and / or an LED may provide cure on demand for the disclosed compositions without negatively impacting mechanical properties of the resulting coating. As used herein, ‘cure on demand’ refers to a composition whose cure rate and / or degree of cure, as measured by MEK double rubs, can be accelerated by exposing the composition to EMR having a wavelength of 900 nm to 1,080 nm, such as 965 nm to 985 nm.Substrates

[0118] Substrates useful for the methods disclosed herein 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 such as fuel tanks, packaging substrates, pressurized cabins, architectural substrates, aircraft and aerospace components, batteries and battery components, bus bars, metal wires, electrical and aviation equipment, structural joints and rivets, caps, 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 such as environmental control systems, frames, tanks, cords, wires, a rail car, furniture, appliances, apparel, a bulkhead, pipes, transformers, toolboxes, grills, medical equipment, doors, windows, a well, cabinets, pylons, electronics and electronic components including housings and circuit boards, glass, sports equipment, including golf balls,large and / or fixed objects such as stadiums, buildings, bridges, containers such as a food and beverage containers, and the like.

[0119] “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 carts, 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 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.

[0120] 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.

[0121] 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, cadmium plated 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 zinc-aluminum 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.

[0122] Non-metallic substrates include polymeric, plastic, 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, 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 carbon fiber-epoxy composites, 3-D printed polymers and composites, synthetic fibers and the like, such as those available as Kevlar® materials. The shape of the substrate can be in the form of a sheet, plate, bar’, rod, or any shape desired.

[0123] 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 mechanically and / or chemically treated, such as alkaline cleaned, deoxidized, mechanically cleaned and / or abraded, 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.Definitions

[0124] For purposes of this detailed description, it is to be understood that the disclosure may assume alternative variations, except where expressly specified to the contrary.

[0125] The numerical values set forth in the 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.

[0126] Also, 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.

[0127] 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, or ingredients. As used herein, “consisting of’ is understood in the context of this application to exclude the presence of any unspecified element, material, or ingredient. As used herein, “consisting essentially of’ is understood in the context of this application to include the specified elements, materials, or ingredients and those that do not materially affect the basic and novel characteristics of what is being described.

[0128] 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.

[0129] 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 intervening coating layers or films of the same or different composition located between the composition and the substrate surface.

[0130] As used herein, a “composition” or a “coating composition” refers to a solution, mixture, or a dispersion that can produce a coating on a substrate surface. “Coating” as used herein includes films, layers and the like.

[0131] As used herein, a “powder coating composition” refers to a mixture in the form of a powder.

[0132] As used herein, the term “sealant” refers to a coating that can resist atmospheric conditions, such as moisture and temperature, and at least partially block the transmission of materials, such as water, fuel, liquids, and gases. The powder coating compositions disclosed herein may be useful, for example, as aerospace sealants and linings for fuel tanks.

[0133] As used herein, a “gap filler composition” refers to a coating composition that forms a gap filler in its cured state.

[0134] As used herein, a “gap filler” refers to a coating that fills a gap between two substrates to eliminate air voids, such as filling a crack, a hole, or a butt joint. As used herein, “butt joint” refers to a joint formed by two surfaces abutting at right angles.

[0135] As used herein, an “adhesive composition” refers to a coating composition that forms an adhesive in its cured state.

[0136] As used herein, an “adhesive” refers to a coating that produces a load-bearing joint.

[0137] As used herein, a “pottant composition” refers to a composition that, when cured, forms a pottant.

[0138] As used herein, a “pottant” refers to an encapsulant.

[0139] As used herein, a “pre-preg” refers to a composition pre-impregnating reinforcement fibers prior to cure.

[0140] As used herein, “ambient” conditions generally refer to room temperature (e.g., 23 °C) and humidity conditions or temperature and humidity conditions that arc 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, while slightly thermal conditions are temperatures that are slightly above ambient temperature, but are generally below the curing temperature for the composition (i.e., in other words, at temperatures and humidity conditions below which the reactive components will readily react and cure, e.g., > 40°C and less than 220°C at 20% to 80% relative humidity).

[0141] As used herein, the term “cure,” “curing,” and similar terms, means that the components that form the composition begin to crosslink (i.e., interact and / or react) to form a coating or a bond. In the case of a IK composition, the composition begins to cure when the powder coating composition is exposed to EMR. In the case of a 2K composition, 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 and / or the physical interaction of the components of the composition.

[0142] As used herein, “polymer” refers to oligomers, homopolymers, and copolymers.

[0143] As used herein, a dash (“ — ”) that is not between two letters or symbols is used to indicate a point of bonding for a substituent or between two atoms. For example, — CONHorefers to an amide functional group that is bonded to another chemical moiety through the carbon atom.

[0144] As used herein, “alkoxy” refers to a — OR group where R is alkyl or aromatic as defined herein. Non-limiting examples of alkoxy groups include methoxy, ethoxy, n-propoxy, isopropoxy, and n-butoxy.

[0145] As used herein, “alkyl” refers to an aliphatic hydrocarbon group which may be straight or branched. Branched means that one or more alkyl groups such as methyl, ethyl or propyl, are attached to a linear alkyl chain. “Alkyl” may be unsubstituted or optionally substituted by one or more substituents which may be the same or different, each substituent being independently selected from the group consisting of halo, alkyl, aryl, cycloalkyl, cyano, hydroxy, alkoxy, alkylthio, amino, — NH(alkyl), — NH(cycloalkyl), — N(alkyl)2, carboxy and — C(O)O-alkyl. Non-limiting examples of suitable alkyl groups include methyl, ethyl, n-propyl, isopropyl and t-butyl.

[0146] 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 0.05% 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 0.01% 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.

[0147] In view of the foregoing description the present disclosure thus relates to the following Aspects 1 to 103 without being limited thereto.

[0148] Aspect 1. A method of curing a powder coating composition comprising: exposing the powder coating composition to electromagnetic radiation (EMR) generated by a laser and / or a light emitting diode (LED) to cure the powder coating composition; wherein the composition comprises (a) a film-forming material and (b) optionally a crosslinker.

[0149] Aspect 2. A method of curing a powder coating composition, comprising: exposing the powder coating composition to electromagnetic radiation (EMR) generated by a defocused laser to cure the powder coating composition; wherein the composition comprises (a) a film-forming material and (b) optionally a crosslinker.

[0150] Aspect 3. The method of aspect 1 or aspect 2, wherein the EMR comprises visible light and / or near infrared light.

[0151] Aspect 4. The method of any of the preceding aspects, wherein the EMR comprises a wavelength of at least 300 nm, such as at least 900 nm.

[0152] Aspect 5. The method of any of the preceding aspects, wherein the EMR comprises a wavelength of at least 960 nm.

[0153] Aspect 6. The method of any of the preceding aspects, wherein the EMR comprises a wavelength of no more than 2,500 nm, such as no more than 1,500 nm.

[0154] Aspect 7. The method of any of the preceding aspects, wherein the EMR comprises a wavelength of no more than 1,080 nm, such as no more than 985 nm.

[0155] Aspect 8. The method of any of aspects 1 to 4 and 6, wherein the EMR comprises a wavelength of 300 nm to 2,500 nm, such as 300 nm to 1,500 nm.

[0156] Aspect 9. The method of any of aspects 1 to 4 and 6 to 8, wherein the EMR comprises a wavelength of 900 nm to 1,080 nm.

[0157] Aspect 10. The method of any of the preceding aspects, wherein the EMR comprises a wavelength of 960 nm to 985 nm.

[0158] Aspect 11. The method of any of the preceding aspects, wherein the EMR is generated as a continuous wave, a quasi-continuous wave, and / or a pulsed wave.

[0159] Aspect 12. The method of any of the preceding aspects, wherein the EMR is directional.

[0160] Aspect 13. The method of any of the preceding aspects, wherein the EMR comprises monochromatic light and / or polychromatic light.

[0161] Aspect 14. The method of any of the preceding aspects, wherein the EMR is coherent.

[0162] Aspect 15. The method of any of aspects 1 and 3 to 14, wherein the laser and / or the LED is defocused.

[0163] Aspect 16. The method of any of the preceding aspects, wherein the laser generates diffuse EMR, divergent EMR, and / or collimated EMR.

[0164] Aspect 17. The method of any of the preceding aspects, wherein the laser comprises a solid-state laser, a gas laser, a semiconductor (diode) laser, a fiber laser, a dye laser, and / or a high harmonic generation laser such as a frequency-doubled or a frequency-tripled laser.

[0165] Aspect 18. The method of any of the preceding aspects, wherein the laser and / or the LED is configured as a single diode, a diode laser bar, and / or a diode laser stack.

[0166] Aspect 19. The method of any of the preceding aspects, wherein the laser has a wall plug efficiency of at least 30 percent, such as at least 50 percent.

[0167] Aspect 20. The method of any of the preceding aspects, wherein the laser has a wall plug efficiency of at least 60 percent, such as at least 80 percent.

[0168] Aspect 21. The method of any aspects 1 to 19, wherein the laser has a wall plug efficiency of 30 percent to 80 percent, such as 50 percent to 80 percent.

[0169] Aspect 22. The method of any of the preceding aspects, wherein the laser has a wall plug efficiency of 60 percent to 80 percent.

[0170] Aspect 23. The method of any of aspects 1 to 19, wherein the laser has a wall plug efficiency of 30 percent to 50 percent.

[0171] Aspect 24. The method of any of the preceding aspects, wherein a unit comprising the laser and / or the LED further comprises adaptive optics such as optics to tailor focal intensity and / or a wide area distribution of the EMR.

[0172] Aspect 25. The method of aspect 24, wherein the unit comprising the laser and / or the LED further comprises an amplifier, a temperature sensor, and / or an IR sensor.

[0173] Aspect 26. The method of aspect 24, wherein the temperature sensor controls a temperature of the composition, a temperature of a substrate, and / or a ramp rate

[0174] Aspect 27. The method of any of the preceding aspects, wherein the laser and / or the LED comprises an industrial-sized laser and / or LED.

[0175] Aspect 28. The method of any of aspects 1 to 26, wherein the laser and / or the LED comprises a portable device and / or a hand-held device.

[0176] Aspect 29. The method of any of the preceding aspects, wherein the composition further comprises a photothermally active material.

[0177] Aspect 30. The method of aspect 29, wherein the photothermally active material comprises carbon black, graphemic carbon particles, silicone carbonate, and / or tungsten oxide.

[0178] Aspect 31. The method of aspect 30, wherein the graphenic carbon particles comprise thermal graphene, such as turbostratic thermal graphene.

[0179] Aspect 32. The method of aspect 30 or aspect 31, 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.

[0180] Aspect 33. The method of any of aspects 29 to 32, wherein the photothermally active material is soluble in an aqueous solvent or an organic solvent and / or is present in a particulate form.

[0181] Aspect 34. The method of any of aspects 29 to 33, wherein the photothermally active material is a solid, a liquid, dissolved in an aqueous or organic solvent, a dry powder, dispersed in an aqueous or organic solvent, or dispersed in an organic medium that is nonvolatile such as a plasticizer or a reactive diluent.

[0182] Aspect 35. The method of any of aspects 29 to 34, wherein the composition comprises the photothermally active material in an amount of at least 0.001 percent by weight based on total weight of the composition, such as at least 0.01 percent by weight.

[0183] Aspect 36. The method of any of aspects 29 to 35, wherein the composition comprises the photothermally active material in an amount of at least 0.1 percent by weight based on total weight of the composition, such as at least 1 percent by weight.

[0184] Aspect 37. The method of any of aspects 29 to 36, wherein the composition comprises the photothermally active material in an amount of no more than 10 percent by weight based on total weight of the composition, such as no more than 5 percent by weight.

[0185] Aspect 38. The method of any of aspects 29 to 37, wherein the composition comprises the photothermally active material in an amount of no more than 1 percent by weight based on total weight of the composition.

[0186] Aspect 39. The method of any of the preceding aspects, wherein the composition comprises the photothermally active material in an amount of 0.001 percent by weight to 10percent by weight based on total weight of the composition, such as 0.01 percent by weight to 5 percent by weight.

[0187] Aspect 40. The method of any of aspects 29 to 34, 36, 37, and 39, wherein the composition comprises the photothermally active material in an amount of 0.1 percent by weight to 5 percent by weight based on total weight of the composition, such as 0.1 percent by weight to 1 percent by weight.

[0188] Aspect 41. The method of any of aspects 29 and 36 to 40, wherein the composition comprises the photothermally active material in an amount of 0.001 percent by weight to 1 percent by weight based on total weight of the composition, such as 0.001 percent by weight to 0.1 percent by weight.

[0189] Aspect 42. The method of any of the preceding aspects, wherein the powder coating composition comprises a thermoplastic powder coating composition.

[0190] Aspect 43. The method of any of aspects 1 to 41, wherein the powder coating composition comprises a thermoset powder coating composition.

[0191] Aspect 44. The method of any of the preceding aspects, wherein the film-forming material 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.

[0192] Aspect 45. The method of any of the preceding aspects, wherein the film-forming material comprises a carboxylic acid functional group, an amine functional group, an epoxide functional group, a hydroxyl functional group, a thiol functional group, a carbamate functional group, an amide functional group, a urea functional group, an isocyanate functional group, and / or an ethylenically unsaturated functional group.

[0193] Aspect 46. The method 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 acidfunctional material, a polyamine, a polyamide, an aminoplast, a carbodiimide, and / or an oxazoline.

[0194] Aspect 47. The method of any of the preceding aspects, wherein the powder coating composition comprises the film-forming material in an amount of at least 40 percent byweight based on total weight of the powder coating composition, such as at least 50 percent by weight.

[0195] Aspect 48. The method of any of the preceding aspects, wherein the powder coating composition comprises the film-forming material in an amount of no more than 90 percent by weight based on total weight of the powder coating composition, such as no more than 75 percent by weight.

[0196] Aspect 49. The method of any of the preceding aspects, wherein the powder coating composition comprises the film-forming material in an amount of 40 percent by weight to 90 percent by weight based on total weight of the powder coating composition, such as 50 percent by weight to 75 percent by weight.

[0197] Aspect 50. The method of any of the preceding aspects, wherein the powder coating composition comprises the crosslinker in an amount of at least 3 percent by weight based on total weight of the powder coating composition, such as at least 10 percent by weight.

[0198] Aspect 51. The method of any of the preceding aspects, wherein the powder coating composition comprises the crosslinker in an amount of no more than 97 percent by weight based on total weight of the powder coating composition, such as no more than 90 percent by weight.

[0199] Aspect 52. The method of any of the preceding aspects, wherein the powder coating composition comprises the crosslinker in an amount of 3 percent by weight to 97 percent by weight based on total weight of the powder coating composition, such as 10 percent by weight to 90 percent by weight.

[0200] Aspect 53. The method of any of the preceding aspects, wherein the powder coating composition further comprises an additive, a catalyst, and / or a filler.

[0201] Aspect 54. The method of aspect 53, wherein the additive comprises a rheology modifier, a dispersant, a thermoplastic polymer, a surface active agent, a flame retardant, a corrosion inhibitor, a UV stabilizer, a colorant, a tint, a plasticizer, an adhesion promoter, an antioxidant, a silane, a silane terminated polymer, a silyl terminated polymer, a moisture scavenger, an outgassing additive, a degassing additive, a flow additive, a leveling additive, and / or a wax.

[0202] Aspect 55. The method of aspect 53 or aspect 54, wherein the powder coating composition comprises the additive in an amount of at least 0.1 percent by weight based on total weight of the composition, such as at least 1 percent by weight.

[0203] Aspect 56. The method of any of aspects 53 to 55, wherein the powder coating composition comprises the additive in an amount of no more than 20 percent by weight based on total weight of the powder coating composition, such as no more than 15 percent by weight.

[0204] Aspect 57. The method of any of aspects 53 to 56, wherein the powder coating composition comprises the additive in an amount of 0.1 percent by weight to 20 percent by weight based on total weight of the powder coating composition, such as 1 percent by weight to 15 percent by weight.

[0205] Aspect 58. The method of any of aspects 53 to 57, wherein the powder coating composition comprises the catalyst in an amount of at least 0.1 percent by weight based on total weight of the composition, such as at least 1 percent by weight.

[0206] Aspect 59. The method of any of aspects 53 to 58, wherein the powder coating composition comprises the catalyst in an amount of no more than 20 percent by weight based on total weight of the powder coating composition, such as no more than 15 percent by weight.

[0207] Aspect 60. The method of any of aspects 53 to 59, wherein the powder coating composition comprises the catalyst in an amount of 0.1 percent by weight to 20 percent by weight based on total weight of the powder coating composition, such as 1 percent by weight to 15 percent by weight.

[0208] Aspect 61. The method of any of aspects 53 to 60, wherein the filler comprises barium sulfate, aluminum hydroxide, mica, wollastonite, calcium carbonate, glass microspheres, clay, aluminum silicate, magnesium silicate, silica, and / or nepheline syenite.

[0209] Aspect 62. The method of any of aspects 53 to 61, wherein the powder coating composition comprises the filler in an amount of at least 1 percent by weight based on total weight of the composition, such as at least 5 percent by weight.

[0210] Aspect 63. The method of any of aspects 53 to 62, wherein the powder coating composition comprises the filler in an amount of no more than 60 percent by weight based on total weight of the powder coating composition, such as no more than 30 percent by weight.

[0211] Aspect 64. The method of any of aspects 53 to 63, wherein the powder coating composition comprises the filler in an amount of 1 percent by weight to 60 percent by weightbased on total weight of the powder coating composition, such as 5 percent by weight to 30 percent by weight.

[0212] Aspect 65. The method of any of the preceding aspects, wherein the powder coating composition is substantially free, essentially free, or completely free of a photopolymerizable initiator.

[0213] Aspect 66. The method of any of the preceding aspects, wherein the powder coating composition is formulated as a sealant composition, an adhesive composition, a gap filler composition, a pottant composition, and / or a prepreg.

[0214] Aspect 67. The method of any of the preceding aspects, wherein the powder coating composition is formulated as a IK composition, a 2K composition, or a higher component composition.

[0215] Aspect 68. The method of any of the preceding aspects, wherein the powder coating composition is in the form of particles having an average particle size of at least 10 microns as measured by laser diffraction, such as at least 20 microns.

[0216] Aspect 69. The method of any of the preceding aspects, wherein the powder coating composition is in the form of particles having an average particle size of no more than 200 microns as measured by laser diffraction, such as no more than 150 microns.

[0217] Aspect 70. The method of any of the preceding aspects, wherein the powder coating composition is in the form of particles having an average particle size of 10 microns to 200 microns as measured by laser diffraction, such as 20 microns to 150 microns.

[0218] Aspect 71. The method of any of the preceding aspects, wherein the powder coating composition is exposed to the EMR for at least 1 minute, such as at least 3 minutes.

[0219] Aspect 72. The method of any of the preceding aspects, wherein the powder coating composition is exposed to EMR for at least 5 minutes, such as at least 7 minutes.

[0220] Aspect 73 The method of any of the preceding aspects, wherein the powder coating composition is exposed to the EMR for at least 10 minutes.

[0221] Aspect 74. The method of any of the preceding aspects, wherein the powder coating composition is exposed to the EMR at an intensity of at least 0.01 W / cm2, such as at least 0.1 W / cm2.

[0222] Aspect 75. The method of any of the preceding aspects, wherein the powder coating composition is exposed to the EMR at an intensity of at least 0.2 W / cm2.

[0223] Aspect 76. The method of any of the preceding aspects, wherein the powder coating composition is exposed to the EMR at an intensity of no more than 108W / cm2, such as no more than 106W / cm2.

[0224] Aspect 77. The method of any of the preceding aspects, wherein the powder coating composition is exposed to the EMR at an intensity of no more than 104W / cm2, such as no more than 102W / cm2.

[0225] Aspect 78. The method of any of the preceding aspects, wherein the powder coating composition is exposed to the EMR at an intensity of no more than 15 W / cm2, such as no more than 12 W / cm2.

[0226] Aspect 79. The method of any of aspects 1 to 77, wherein the powder coating composition is exposed to the EMR at an intensity of 0.01 W / cm2to 108W / cm2, such as 0.1 W / cm2to 106W / cm2.

[0227] Aspect 80. The method of any of aspects 1 to 75 and 77, wherein the powder coating composition is exposed to the EMR at an intensity of 0.1 W / cm2to 104W / cm2, such as 0.1 W / cm2to 102W / cm2.

[0228] Aspect 81. The method of any of aspects 1 to 75 and 78, wherein the powder coating composition is exposed to the EMR at an intensity of 0.1 W / cm2to 15 W / cm2, such as 0.2 W / cm2to 12 W / cm2.

[0229] Aspect 82. The method of any of aspects 26 to 81, comprising applying the powder coating composition to a surface of the substrate.

[0230] Aspect 83. The method of aspect 82, comprising cleaning, degreasing, and / or deoxidizing the substrate surface.

[0231] Aspect 84. The method of any aspect 82 or aspect 83, comprising coating the substrate surface with a coating composition in addition to the powder coating composition such as a pretreatment composition, an electrodepositable coating composition, a primer coating composition, a conductive primer coating composition, a basecoat coating composition, and / or a topcoat coating composition.

[0232] Aspect 85. The method of any of the preceding aspects, wherein the substrate comprises a fixed structure.

[0233] Aspect 86. The method of any of aspects 82 to 85, comprising applying the powder coating composition to a damaged portion of the surface of the substrate.

[0234] Aspect 87. The method of aspect 89, wherein the surface comprises a preexisting coating, and wherein the pre-existing coating is at least partially removed prior to the applying.

[0235] Aspect 88. The method of any of aspects 82 to 87, wherein a temperature of the surface of the substrate does not exceed 121°C upon exposure to EMR.

[0236] Aspect 89. The method of any of aspects 82 to 88, further comprising contacting a surface of a second substrate to the composition such that the composition is between the substrate and the second substrate.

[0237] Aspect 90. The method of any of the preceding aspects, wherein a total energy density of less than 2,100 J / cm2is required to cure the powder coating composition, such as less than 2,000 J / cm2.

[0238] Aspect 91. The method of any of the preceding aspects, wherein a total energy density of less than 1,100 J / cm2is required to cure the powder coating composition, such as less than 700 J / cm2.

[0239] Aspect 92. The method of any of aspects 29 to 91, wherein a total energy density required to cure the powder coating composition was reduced by at least 5% compared to the total energy density required to cure a powder coating composition that does not comprise the photothermally active material, such as reduced by at least 10%.

[0240] Aspect 93. The method of any of aspects 29 to 92, wherein a total energy density required to cure the powder coating composition was reduced by at least 50% compared to the total energy density required to cure a powder coating composition that does not comprise the photothermally active material, such as reduced by at least 70%.

[0241] Aspect 94. The method of any of aspects 82 to 93, wherein the substrate has a black surface, and wherein a total energy density of less than 700 J / cm2is required to cure the coating composition on the black surface.

[0242] Aspect 95. The method of aspect 94, wherein a total energy density required to cure the powder coating composition on the black substrate was reduced by at least 60% compared to the total energy density required to cure the powder coating composition on a substrate having a white surface, such as reduced by at least 65%.

[0243] Aspect 96. The method of aspect 94 or aspect 95, wherein a total energy density required to cure the powder coating composition on the black surface was reduced by at least70% compared to the total energy density required to cure the powder coating composition on the white surface.

[0244] Aspect 97. The method of any of the preceding aspects, wherein the laser is robotically guided.

[0245] Aspect 98. The method of any of aspects 26 to 97, wherein a temperature of the substrate following exposure to the EMR is below a heat deflection temperature of the substrate.

[0246] Aspect 99. A substrate comprising a powder coating formed from a powder coating composition cured by the method of any of the preceding aspects.

[0247] Aspect 100. The substrate of aspect 99, wherein the power coating has a dry film thickness of at least 1.5 mil, such as at least 5 mil.

[0248] Aspect 101. The substrate of aspect 99 or aspect 100, wherein the powder coating has a dry film thickness of no more than 40 mil, such as no more than 20 mil.

[0249] Aspect 102. The substrate of any of aspects 99 to 101, wherein the power coating has a dry film thickness of 1.5 mil to 40 mil, such as 5 mil to 20 mil.

[0250] Aspect 103. The substrate of any of aspects 99 to 102, wherein the powder coating is a sealant, an adhesive, a gap filler, a pottant, and / or a prepreg.

[0251] Illustrating the disclosure are the following examples, which, however, are not to be considered as limiting the disclosure to their details.EXAMPLESTable 1A. Powder Coating Compositions A to F1 C rylcoat 2437 available from Allnex2 Triglycidyl isocyanurate available from HUANGSHAN LINLU COATINGS MATERIALS3 Benzoin available from Miwon Spcialty Chemical Co Ltd4 Resiflow PL200A available from Estron Chemical5 Regal 660 carbon black available from Cabot Corporation6 Graphene nanoparticle available as an aqueous dispersion from Raymor Industries Inc.7 AEROXIDE® Alu C available from Evonik IndustriesTable IB. Powder Coating Compositions G to O8 Microgrit silicon carbide GC2000 available from Micro Abrasives Corporation9 Available from American Elements10 TRONOX® CR-880 available from Tronox11 Blanc Fixe Micro available from Sachtleben Chemie GmbHTabic 1C. Powder Coating Compositions IP to IX

[0252] Each of the components listed in Tables 1A to 1C were weighed in a container and mixed in a Prism high speed mixer for 30 seconds at 3500 RPM to form dry homogeneous mixtures. The mixtures were then melt-mixed in a Werner Pfleiderer 19 mm twin screw extruder and a speed of 500 RPM. The first zone was set at 50°C and the second, third, and fourth zones were set at 100°C. The feed rate was such that a torque of 40-50% was observed on the equipment. The mixtures were dropped onto a set of chill rolls to cool and re- solidify the mixtures into solid chips. The chips were ground in a Mikro ACM®-1 Air Classifying Mill to obtain a particle size of 5 to 150 microns with a mean particle size of 20 to 40 microns measured using a Beckman Coulter LS 13 320 Laser Diffraction Particle Size Analyzer with a TornadoDry System. The resulting powder coating compositions were solid particulate powder coating compositions that were free flowing.

[0253] The laser unit used for all studies was a Compact Heating and Drying SYS-CD system supplied by IPG Photonics® Corporation (Marlborough, MA) outfitted with a Class I laser, laser wavelength (EMR) of 960 nm to 985 nm (model number DLS-4500-U-ECO) projected onto a 20cm x 20cm area using an enclosure (model number SYSMACDHE000004U). In Examples 1 to 3, the powder coating compositions were exposed to the laser with a 30 second ramp from ambient to 191 °C and then held at 191 °C for 10 minutes. In Example 4, the powder coating compositions were exposed to the laser with a 30 second ramp from ambient to 191 °C and then held at 191°C for either 1 minute, 3 minutes, 5 minutes, or 7 minutes (see Table 5). In Example 5, the powder coating compositions were exposed to the laser with a 30 second ramp from ambient to 200°C and then held at 200°C for either 1 minute, 3 minutes, 5 minutes, or 7 minutes (see Table 6). Dry film thickness was measured using an Elcometer 415 thickness gauge.

[0254] Maximum laser output was 4500W. The total energy density was calculated according to Equation I disclosed above. Data are reported in Tables 2 to 4.Example 1: Impact of Photothermally Active Material in Powder Coating Compositions Applied to a White Substrate

[0255] Powder Compositions 1A - 1R were applied to a white substrate (pretreated steel panels (C700, C59 from ACT) with a cured coating of PCST80118 (a white polyester coating cured with a hydroxy alkyl amide, available from PPG Industries, Inc.) with a Nordson Encore corona gun to a film build of 3 - 5 mils. Powder coating compositions were cured using the laser as described above. Dry film thickness and total energy density were measured as described above and are reported in Table 2.

[0256] Photothermally active material was added in the formulation prior to melt mixing the material (Compositions A to R) or was added after the powder was prepared during a postadd blending process (Compositions 10-1 and 10-2).Table 2. Dry Film Thickness and Total Energy Density of Powder Coating Compositions Applied to a White Substrate (Example 1)

[0257] From the data in Table 2, it can be seen that compositions applied to a white substrate and that included carbon (carbon black and graphene nanoparticles) (Compositions 1A to IF), silicon carbide (Compositions 1G to II), or tungsten oxide (1J to IL) required less total energy density to maintain a temperature of 191°C for 10 minutes than did compositions that did not include a photothermally active material (Compositions IM to 10).Example 2: Impact of Photothermally Active Material in Powder Coating Compositions Applied to a Black SubstrateTable 3. Dry Film Thickness and Total Energy Density of Powder Coating Compositions Applied to a Black Substrate (Example 2)

[0258] Powder coating compositions A to O were applied to a black substrate (C6000CX black clcctrocoat available from ACT) as described above in Example 1. Powder coating compositions were cured using the laser as described above. Dry film thickness and total energy density were measured as described above and are reported in Table 3.

[0259] From the data in Table 3, it can be seen that compositions applied to a black substrate were unaffected by the inclusion of photothermally active materials as demonstrated by the total energy density of Examples 2A to 2L, 2N, and 20 required to maintain a coatingcomposition temperature of 191 °C for 10 minutes, which were all substantially similar. Example 2M required higher total energy density to maintain a coating composition temperature of 191 °C for 10 minutes. The data from Example 1 (Table 2) and Example 2 (Table 3) demonstrate the impact of the color of the substrate on total energy density, with the total energy density required to maintain a coating composition temperature of 191°C for 10 minutes being independent of the inclusion of photothermally active material when the coating composition is applied to a black substrate (see Table 3). In contrast, as demonstrated by the data shown in Table 2, the inclusion of photothermally active material in powder coating compositions applied to a white substrate decreased the total energy density required to maintain a coating composition temperature of 191 °C for 10 minutes.Example 3: Impact of dry film thickness on total energy density of powder coating compositions applied to a white substrate

[0260] Powder coating compositions E and C were applied to a white substrate (pretreated steel panels (C700, C59 from ACT)) with a cured coating of PCST80118 (available from PPG Industries, Inc.) with a Nordson Encore corona gun to a film build of 3 - 5 mils. The powder coating was then exposed to a laser as described in Example 1. Dry film thickness and total energy density were measured as described above. Data are reported in Table 4.Table 4. Dry Film Thickness and Total Energy Density of Powder Coating Compositions Applied to a White Substrate (Example 3)

[0261] As shown by the data reported in Table 4, it was unexpectedly discovered that thicker powder coatings applied to a white substrate having a lower concentration ofphotothermally active material resulted in lower total energy density required to maintain a coating composition temperature of 191 °C for 10 minutes, while increasing the amount of photothermally active material had a minimal impact on total energy density required to required to maintain a coating composition temperature of 191°C for 10 minutes.Example 4: Impact of catalyst or blocked isocyanate on the rate of curing powder coating compositions using a laser

[0262] Coated substrates were prepared as described above in Example 1, except that the powder coating compositions were exposed to the laser with a 30 second ramp from ambient to 191 °C and then held at 191 °C for 1, 3, 5 or 7 minutes as shown in Table 5. Dry film thickness was measured as described above. Coating cure was measured using an MEK double rub test based on ASTM D5402, using a cotton swab saturated with MEK and was used to rub the coating with a uniform force, with each back-and-forth movement of the cotton swab being counted as one double nib. 100 double rubs were completed unless there was a breakthrough to the substrate prior to reaching 100 double rubs. If fewer than 100 double rubs were achieved, that number was recorded. If 100 double nibs were achieved, that was recorded and the area that was tested was given a rating ranked as follows:Untouched (0% surface marred) v si mar (very slight mar) (>0% to 25% surface marred) si mar (slight mar) (>25% to 50% surface marred) mar (marring) (>50% to 75% surface marred) v mar (very high marring (>75% to 100% surface marred)Table 5. Impact of catalyst or blocked isocyanate on the rate of curing powder coating compositions with a laser

[0263] The data reported in Table 5 demonstrate that inclusion of catalyst or blocked isocyanate in the powder coating composition demonstrated MEK resistance at 3 minutes, 5 minutes, and 7 minutes, while compositions that did not include catalyst or blocked isocyanate did not cure until 7 minutes, as measured by MEK resistance. These data demonstrate that inclusion of catalyst or blocked isocyanate accelerated cure time compared to the same composition that did not include catalyst or blocked isocyanate.Example 5: Dry Film Thickness and Cure Rate of Powder Coating Compositions Applied to a White Substrate

[0264] Coated substrates were prepared as described above in Example 1, except that the powder coating compositions were exposed to the laser with a 30 second ramp from ambient to200°C and then held at 200°C for 1 , 3, 5 or 7 minutes as shown in Table 6. Dry film thickness was measured as described above. Coating cure was measured using an MEK double rub test as described above. Data are reported in Table 6.Table 6: Dry Film Thickness and Cure Rate of Powder Coating Compositions Applied to aWhite Substrate (Example 5)

[0265] The data in Table 6 demonstrate that powder coating compositions comprising a variety of film-forming resin types can be cured with exposure to EMR, as demonstrated by the results achieved with the MEK double rub test.

[0266] Whereas specific aspects of the disclosure 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 disclosure which is to be given the full breadth of the claims appended and any and all equivalents thereof.

Claims

We claim:

1. A method of curing a powder coating composition, comprising: exposing the powder coating composition to electromagnetic radiation (EMR) generated by a defocused laser to cure the powder coating composition; wherein the powder coating composition comprises (a) a film-forming material and (b) a crosslinker.

2. The method of claim 1, wherein the laser is a diode laser.

3. The method of claim 1 or claim 2, wherein the EMR comprises a wavelength of 300 nm to 1,500 nm.

4. The method of any of the preceding claims, wherein the EMR comprises a wavelength of 900 nm to 1,080 nm.

5. The method of any of the preceding claims, wherein the EMR comprises a wavelength of 960 nm to 985 nm.

6. The method of any of the preceding claims, wherein the powder coating composition further comprises a photothermally active material.

7. The method of any of the preceding claims, wherein the photothermally active material comprises carbon black, graphemic carbon particles, silicone carbonate, and / or tungsten oxide.

8. The method of claim 6 or claim 7, wherein the powder coating composition comprises the photothermally active material in an amount of 0.001 percent by weight to 10 percent by weight based on total weight of the powder coating composition.

9. The method of any of the preceding claims, wherein a total energy density of less than 2,100 J / cm2is required to cure the powder coating composition.

10. The method of any of claims 6 to 9, wherein a total energy density required to cure the powder coating composition is reduced by at least 5% compared to the total energy density required to cure a powder coating composition that does not comprise the photothermally active material.

11. The method of any of the preceding claims, wherein a total energy density required to cure the powder coating composition deposited on a substrate having a black surface is less than 700 J / cm2.

12. The method of any of the preceding claims, wherein a total energy density required to cure the powder coating composition deposited on a substrate having a black surface is reduced by at least 60% compared to the total energy density required to cure the powder coating composition on a substrate having a white surface.

13. A substrate comprising a powder coating formed from a powder coating composition cured by the method of any of the preceding claims.

14. The substrate of claim 13, wherein the powder coating has a thickness of 1.5 mil to 40 mil.

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