Low-temperature curing adhesion promoters and primers for substrates

Abstract

Disclosed are low-temperature curing adhesion promoters and primers for substrates, in the form of aqueous coatings or dry powder coatings, combining polyolefins with resins. The aqueous coatings are prepared by mixing a dry solid-powder composition containing polyolefins and a resin containing a curing agent / crosslinking agent with water. The aqueous coatings are applied to substrates such as thermoplastic olefins to make the substrate conductive for electrostatic painting or further processing.

Description

Technical Field

[0001] This application claims the priority and any other benefits of U.S. Provisional Application No. 63 / 501,778, filed on May 12, 2023, and the entire content thereof is incorporated herein by reference.

[0002] Disclosed are adhesion promoters and primers for a substrate surface that can cure at less than 100 °C, preferably less than 95 °C, and most preferably between 90 °C and 80 °C. In particular, the present invention relates to low-temperature curing adhesion promoters and primers that are in the form of an aqueous coating or a dry powder coating and are applied to a substrate surface and cure within the range of 80 °C to 100 °C.

[0003] Background Coatings are an essential element in protecting base materials and products (each called a "substrate") from corrosion, acid etching, oxidation, and surface damage. In most cases, coatings also give the substrate a desirable appearance using color and / or a smooth or textured surface.

[0004] Substrates that can be coated include metals (e.g., aluminum, steel, copper, brass), plastics (e.g., polycarbonate ("PC"), polypropylene ("PP"), acrylic, thermoplastic olefin ("TPO"), sheet molding compounds also known as sheet molding composites ("SMC"), reaction injection molded urethane ("RIM urethane"), polyvinyl chloride ("PVC"), polyethylene terephthalate ("PET"), polycarbonate / polyethylene terephthalate ("PC / PET"), polyamine ("P"), glass, ceramics, wood, medium density fiberboard ("MDF"), and composites such as polymer matrix composites ("PMC"), metal matrix composites ("MMC"), ceramic matrix composites ("CMC"), carbon matrix composites ("CAMC"), etc., including a wide range of materials used in various industries. In addition, substrates used in the electronics industry, such as silicon, can also be coated.

[0005] Coatings can be applied in either a wet or dry state. Wet coatings are primarily applied using solvent-based systems to improve coating efficiency, which is the efficiency of paint transfer to the substrate. However, solvent-based coatings contain materials that are harmful to the environment, such as halogen-containing solvents, including, for example, hazardous air pollutants ("HAPs") as defined in the list issued by the U.S. Environmental Protection Agency ("EPA"), defined volatile organic compounds ("VOCs"), such as those defined by the European Commission in the VOC Solvents Emission Directive 1999 / 13 / EC as "any organic compounds having a vapor pressure of 0.01 kPa or greater at 293.15 K, as well as some creosotes," and sometimes halogen-containing materials such as halogen-containing solvents, including methylene chloride, carbon tetrachloride, chloroform, perchloroethylene, trichloroethylene, trichlorotrifluoroethane, and 1,1,1-trichloroethane, all of which are harmful to the environment and are subject to increasing government regulations to eliminate their use. Generally, halogenated compounds (referred to herein as halogens) include organic molecules containing at least one halogen atom selected from chlorine, fluorine, bromine, and iodine. The halogen astatine is rare, and tennessine does not exist naturally. Halogens can be used to modify polymers (resins) for the purpose of producing modified adhesion promoters for plastics made of polypropylene ("PP") and / or polyethylene. Attempts to reduce these toxic substances include aqueous liquid coating systems and dry powder coating systems. Unfortunately, most current aqueous coating systems still contain small percentages of HAPs and VOCs. Liquid coating systems have advantages as their resin systems have been developed to lower their curing temperatures in an attempt to reduce CO2 emissions caused by the thermosetting process. Some liquid coating systems can cure in a low temperature range of 80°C to 90°C, reducing reliance on the use of fossil fuel energy. Most governments are demanding mandatory remediation of curing liquid coating emissions to eliminate HAPs and VOC emissions.This restoration is achieved by oxidation equipment using one of the following: regenerative thermal oxidation (RTO), thermal recovery oxidation ("TRO"), or catalytic thermal recovery oxidation ("CRO"), all of which have high acquisition costs and high natural gas consumption and costs. CROs operate at temperatures of 315°C to 479°C, while RTOs and TROs use high temperatures of 900°C to remove VOCs. Their use of large amounts of natural gas results in significant CO2 emissions, often negating the benefits of reduced natural gas consumption from low-temperature curing coatings. A liquid coating system that eliminates all HAPs, VOCs, and halogens, while reducing natural gas use and its CO2 emissions for curing, thereby eliminating the need for oxidation equipment, would be ideal.

[0006] Powder coating systems ("powder coatings") were developed to avoid the use of solvents, thereby reducing or eliminating HAPs and VOCs. Powder coating is a conventional method for applying decorative or protective finishes to substrates. The coating is a dry powder that is electrostatically applied to the surface of the substrate and then heat-cured. A wide range of materials can be powder coated, including metals (e.g., steel, aluminum, brass, copper), plastics (e.g., PVC, PC, PP, PC / PET, P), wood, and MDF. In addition, substrates used in the electronics industry, such as silicon, can also be coated.

[0007] Certain substrates, when exposed to high temperatures, exhibit multiple defects and challenges, including deformation and poor degassing in castings (steel, aluminum, etc.), thermoformed products, and other plastics; therefore, it may be necessary to lower the curing temperature to maintain the shape and condition of the substrate. Available powder coatings cure at temperatures above 100°C. Currently, only a few powder coatings with a low thermosetting temperature threshold of 100°C are available on the market (see International Publications 2011 / 138432 and 2017 / 029350). The most common commercially available low-curing powder coatings typically cure at temperatures above 115°C. However, despite this low curing range, these powder coatings are excluded from a large number of heat-sensitive substrates, primarily plastics, thus necessitating the use of liquid coatings, which result in harmful emissions.

[0008] Certain substrates (such as low surface energy substrates) present problems with paint adhesion that require modification or addition of adhesion-promoting functions. Powder coatings require a conductive or heated substrate for the powder coating to adhere to the substrate. Numerous plastic substrates, such as TPO, have low surface energy and high resistivity, which will require an adhesion promoter for liquid or powder coatings to adhere to these plastic substrates. Other substrates require lower curing conditions due to their chemical composition, which results in a softer material and therefore requires a lower E-modulus that cannot maintain or retain its shape / form.

[0009] With its highly desirable properties such as moldability, flexibility, and durability, TPO and TPO-based substrates, aided by the use of recycled materials and low cost, have become widely accepted as a material of choice for many automotive applications, including, to name a few, automotive instrument panels, bumpers and body panels, dashboards, cup holders, and other automotive parts such as door covers. TPO is also used as roofing material, window frames, office furniture, and other industrial parts. TPO is a blend containing thermoplastic olefins (e.g., PP, PE, block copolymer polypropylene), elastomers (e.g., ethylene propylene rubber, ethylene propylene diene rubber, ethylene octene, ethylbenzene, styrene ethylene butadiene styrene), and optional fillers (e.g., talc, fiberglass, carbon fiber, calcium carbonate). In addition to being a strong and durable material, TPO is also resistant to ultraviolet ("UV") radiation and extreme temperatures.

[0010] The global automotive industry is the largest user of plastics, primarily TPO, and its use is increasing as the demand for improved gasoline efficiency or lighter weight in hybrid or electric vehicles grows. The demand for lighter plastics from automakers has placed further pressure on plastics manufacturers to develop lighter plastics. Lighter plastics are developed by increasing the melt flow index ("MFI") (also known as the melt flow rate ("MFR")) of the plastic to meet mold design requirements. Increasing the MFI helps speed up plastic molding and improve production capacity, while also helping to lighten parts by reducing the thickness of molded parts. However, the paint acceptability of plastics is inversely proportional to the increase in MFI, making it more difficult to paint plastics as the MFI increases. These new formulations for lighter plastics make it extremely difficult for current adhesion promoter technologies to keep up with the demand for ultra-low curing coatings.

[0011] Automotive original equipment manufacturers ("OEMs") and suppliers of painted parts require the use of electrostatic spraying equipment for coating application in certain situations. The higher transfer efficiency of electrostatic spraying results in a higher coating rate, less overspray, and lower VOC and HAP emissions. This requires that the substrate surface being coated has a sufficiently low surface electrical resistivity to allow the electrostatic process to function. Metals inherently have low surface electrical resistivity, but other substrates such as TPO and other plastics are poorly paintable due to their low surface energy and / or high surface electrical resistivity. Therefore, processes have been developed to modify substrates such as TPO so that they can be electroplated.

[0012] To coat substrates with low surface energy and / or high surface electrical resistivity using an electrostatic sprayer, these high-surface-resistivity materials require (i) application of a conductive adhesion promoter and primer / coating, or (ii) flame treatment before applying a decorative coating followed by application of a conductive primer. Unfortunately, both options involve several problems associated with their use.

[0013] Conductive adhesion promoters / primers / coatings solve the problem of paint adhesion to thermoplastic olefin substrates, but they are accompanied by serious environmental and safety challenges. Conductive adhesion promoters face compatibility challenges between modified polyolefins that enable adhesion to TPO and co-resins that enable subsequent layers to adhere to the adhesion promoter / primer. In this invention, co-resins are also referred to as resins. Modified polyolefins are typically soluble in hydrocarbon solvents (e.g., toluene, xylene) but typically insoluble in oxygen-containing solvents (i.e., alcohols, ketones, esters, ethers, glycol ethers, etc., such as butyl acetate, which contains carbon, hydrogen, and oxygen atoms in its chemical structure). Co-resins are typically soluble in oxygen-containing solvents (e.g., butyl acetate) but typically insoluble in hydrocarbon solvents (e.g., toluene, xylene). Based on this incompatibility, i.e., resins and co-resins that are insoluble in the same solvent when used herein, the act of mixing and stabilizing modified polyolefins and co-resins has proven challenging.

[0014] Modified polyolefins currently on the market for use in conductive adhesion promoters include (i) halogenated chlorine-modified polyolefins (also defined as chlorinated polyolefins ("CPO")), (ii) maleic anhydride-modified polyolefins, and (iii) acrylic-modified polyolefins. While CPO and acrylic-modified polyolefins help resolve incompatibility between polyolefins and co-resins in adhesion promoters, they come at the expense of gasoline resistance and raise environmental concerns. Halogenated organic compounds such as CPO are persistent organic pollutants ("POPs") that are resistant to environmental degradation by chemical, biological, and photodegradation processes, reflecting the non-reactivity of carbon-chlorine bonds to hydrolysis and photodegradation. Due to its high lipophilicity, CPO bioaccumulates in adipose tissue. For these reasons, non-chlorine-modified polyolefins ("non-CPO"), such as maleic anhydride-modified polyolefins, are preferred. In addition to being more environmentally friendly than CPO, non-CPO generally offers improved gasoline resistance. However, non-CPO has even greater co-resin incompatibility than CPO, which has limited its use considerably. Furthermore, the use of modified polyolefins is limited to high-molecular-weight compounds that meet gasoline resistance standards. Large amounts of hydrocarbon solvents, such as toluene and xylene, are required to dissolve such high-molecular-weight CPOs or non-CPOs.

[0015] Toluene and xylene are VOCs and are on the US Environmental Protection Agency's HAP list; toluene and halogens are restricted chemicals within the European Union. Furthermore, both toluene and xylene have high electrical resistivity, leading to dangerous static charge buildup when added to batches or during spray application. This static charge buildup can result in sparks and potentially lead to fire. The situation is further exacerbated by the fact that toluene has an extremely low flash point (i.e., 4°C). Moreover, conductive adhesion promoters often need to be cured at temperatures above 120°C. In addition to the aforementioned high curing temperatures, the VOCs and HAPs inherent in these materials consume additional energy and generate significant greenhouse gases through the use of expensive oxidation equipment (i.e., RTO, CRO, or TRO) that often require temperatures of 760°C to 900°C to achieve 95% to 99% efficiency. Achieving high curing temperatures requires considerable energy, unfavorably increasing both the time and cost of producing the cured coating. Based on problems associated with existing conductive adhesion promoters, a method was developed involving flame treatment of TPO substrates before applying decorative coatings, followed by the application of a conductive primer. Rapid application of high heat to the TPO surface breaks surface molecular chains and adds polar functional groups. Flame treatment also burns off dust, fibers, oil, and other surface contaminants. However, flame treatment lacks robustness and does not make non-conductive TPO substrates conductive, although conductivity is necessary for the subsequent electrostatic application of the coating layer. Furthermore, flame treatment requires a large amount of energy, resulting in the generation of greenhouse gases through the combustion of natural gas.

[0016] Flame technology involves passing a blue flame of natural gas over a substrate, thereby generating oxygen in the flame. 2Functional groups are formed by reactive species such as radical anions, OH radicals, or hydroperoxy radicals, which then react with the substrate surface, providing oxygen to the substrate and allowing the coating to bind to oxygen acceptors. Because the increase in oxygen surface content is limited to a few nanometers below the surface and the increase in surface tension time is limited, the coating must be applied immediately after the flame process. In addition to significant CO2 emissions and the costly use of natural gas, the flame method requires very precise coating of uneven, non-uniform surfaces to ensure proper surface preparation. This technique requires considerable investment in robotic equipment and ongoing software engineering, as the dimensions and surface characteristics of the parts change with each new part, leading to equipment wear. After flame treatment preparation of the substrate, a primer coating is then applied to the substrate.

[0017] The benefits of using TPO and other types of substrates are so great that their use is expanding despite coating issues. The object of the present invention is to mitigate or overcome one or more of the difficulties associated with the prior art. It has been found that a solid-powder composition can be produced by compounding polyolefins and co-resins that are incompatible based on their respective solubility. The solid-powder composition can be applied in powder form or mixed with water to prepare an aqueous coating comprising a polyolefin having a low melting temperature, a co-resin having a low curing temperature, a curing agent, optionally a conductive agent, and one or more wetting agents, pigments, additives, and fillers. The powder composition or aqueous coating can be applied to many types of substrates, including plastics such as TPO and other substrates with low surface energy nonconductive surfaces, resin transfer molded substrates, and reaction injection molded substrates, to improve paint adhesion. Aqueous coatings avoid the use of organic solvents and halogenated materials and therefore offer a more environmentally friendly alternative to existing adhesion promoters, primers, and coatings. The compositions and methods for preparing the solid-powder compositions, as well as the aqueous coatings, do not involve the use of environmentally hazardous solvents, halogens, or flame treatments to prepare the substrate surface for coating. The compositions and methods for preparing the solid-powder compositions involve curing at temperatures below 100°C, resulting in less energy, time, and cost required to achieve the cured coating.

[0018] The present invention provides an optimal low-curing-temperature liquid aqueous coating system and / or dry powder coating system for pre-treating plastics to accept paint, and simultaneously provides a primer layer for subsequent base and top coating layers. The present invention offers the advantages of being non-toxic, VOC-free, HAP-free, and reducing CO2 emissions, and does not utilize halogens to achieve its purpose of producing a receptive, primer-coated substrate. The present invention also offers significant cost reductions by reducing or eliminating the need for oxidation equipment, and processing cost reductions by eliminating one of the two initial pre-treatment steps by combining surface pre-treatment and application of the prime coating layer into a single process.

[0019] overview In a first embodiment, an aqueous coating for application to a substrate is disclosed, comprising water, a polyolefin having a melting temperature of less than 100°C, a resin having a curing temperature in the range of 80°C to 100°C and / or a melting temperature in the range of 65°C to 90°C, a curing agent, an optional substrate wetting agent, and an optional conductive agent. In a second embodiment, a dry powder coating application to a substrate is disclosed, comprising a dry powder coating comprising a polyolefin having a melting temperature of less than 100°C, a resin having a curing temperature in the range of 80°C to 100°C and / or a melting temperature in the range of 65°C to 90°C, a curing agent, an optional substrate wetting agent (such as SURFYNOL® 104 and others), and an optional conductive agent (such as TUBALL® Matrix 821 and others).

[0020] In one example of Embodiment 1, the substrate is made of a material selected from the group consisting of polymers, metals, carbon fibers, and combinations thereof.

[0021] In another example of Embodiment 1, the substrate is selected from the group consisting of non-conductive low surface energy substrates, thermoplastic olefin substrates, resin transfer molded substrates, and reaction injection molded substrates.

[0022] In another example of Embodiment 1, the substrate wetting agent is present in an amount of 0.1 to 1.5 weight percent of the aqueous coating. A free-flowing powder substrate wetting material, for example, a tetramethyldecinediol gemin surfactant.

[0023] In another example of Embodiment 1, the conductive agent is present in the aqueous coating in an amount of 0.1 to 10 weight percent of the aqueous coating.

[0024] In another example of Embodiment 1, the conductive agent includes single-walled carbon nanotubes.

[0025] In another example of Aspect 1, the polyolefin is a non-halogenated modified polyolefin.

[0026] In another example of Aspect 1, the non-halogenated modified polyolefin is a maleic anhydride modified polyolefin, or the polyolefin is an unmodified polyolefin.

[0027] In another example of Aspect 1, the polyolefin has a melting temperature within the range of 60°C to 90°C.

[0028] In another example of Aspect 1, the resin is an epoxy resin.

[0029] In another example of Aspect 1, the resin has a curing temperature within the range of 80°C to 90°C.

[0030] In another example of Aspect 1, the curing agent is an amine-functional compound, and / or the curing agent has a melting temperature within the range of 65°C to 90°C.

[0031] In another example of Aspect 1, the amine-functional compound is selected from the group consisting of polyamine compounds, aliphatic polyamine compounds, and aromatic amine compounds. The curing agent may also be a polyanhydride compound.

[0032] In another example of Aspect 1, a thermoplastic olefin substrate coated with the aqueous coating according to Aspect 1, wherein the coating of the aqueous coating is cured at a temperature within the range of 60°C to 90°C, is disclosed.

[0033] In another example of Aspect 1, the aqueous coating used to coat the thermoplastic olefin substrate is not composed of materials processed through an extrusion process (i.e., a mixture of dry materials).

[0034] In a second embodiment, a dry or wet composition for coating a substrate is disclosed, comprising a polyolefin having a melting temperature of less than 100°C, a resin having a curing temperature in the range of 80°C to 100°C, a curing agent having a melting temperature in the range of 65°C to 90°C, an optional substrate wetting agent, and an optional conductive agent.

[0035] In one example of embodiment 2, the substrate is made of a material selected from the group consisting of polymers, metals, carbon fibers, or combinations thereof.

[0036] In another example of Embodiment 2, the substrate is selected from the group consisting of non-conductive low surface energy substrates, thermoplastic olefin substrates, resin transfer molded substrates, and reaction injection molded substrates.

[0037] In another example of Embodiment 2, the polyolefin is a non-halogen-modified polyolefin.

[0038] In another example of Embodiment 2, the non-halogenated polyolefin is a maleic anhydride-modified polyolefin.

[0039] In another example of Embodiment 2, the polyolefin has a melting temperature in the range of 60°C to 90°C.

[0040] In another example of Embodiment 2, the resin is an epoxy resin.

[0041] In another example of Embodiment 2, the resin has a curing temperature in the range of 65°C to 97°C.

[0042] In another example of Embodiment 2, the curing agent is present in the composition at a weight of 12 to 40 percent based on the total weight of the composition, and the curing agent is an amine-functional compound.

[0043] In another example of Embodiment 2, the amine-functional compound is selected from the group consisting of polyamine compounds, aliphatic polyamines, and aromatic amine compounds. The curing agent may also be a polyanhydride compound.

[0044] In another example of Embodiment 2, there is a thermoplastic olefin substrate coated with a dry or wet composition cured at a temperature in the range of 60°C to 100°C.

[0045] In another example of Embodiment 2, the dry or wet solid-powder composition coating the thermoplastic olefin does not consist of a material processed through an extrusion process (i.e., a mixture of dry materials).

[0046] A third aspect of the invention discloses a method for preparing an aqueous coating for application to a substrate, comprising: preparing a solid-powder composition comprising a resin having a curing temperature in the range of 80°C to 100°C and a polyolefin having a melting temperature of less than 100°C; extruding the solid-powder composition to prepare an extruder; and combining the extruder with a curing agent and water to prepare an aqueous coating.

[0047] In one example of embodiment 3, the solid-powder composition further comprises at least one of a pigment, a flow regulator, and a degassing agent.

[0048] In another example of Embodiment 3, the method further includes adding a conductive agent to the aqueous coating.

[0049] In another example of Embodiment 3, the method further includes milling the extruded material before the step of combining it with water.

[0050] A fourth aspect discloses a method for preparing a substrate for electrostatic coating, comprising: preparing a solid-powder composition comprising a resin having a curing temperature in the range of 80°C to 100°C and a polyolefin having a melting temperature of less than 100°C; extruding the solid-powder composition to prepare an extruder; combining the extruder with a curing agent and water to prepare an aqueous coating; and preparing a coated substrate by applying the aqueous coating to the substrate.

[0051] In one example of Embodiment 4, the method further includes curing the coated substrate at a temperature in the range of 60°C to 100°C.

[0052] In another example of Embodiment 4, the method further includes applying a finishing coat to the coated substrate by electrostatic coating.

[0053] A fifth aspect discloses a method for preparing a substrate for electrostatic coating, comprising: preparing an aqueous coating containing a conductive agent; applying the aqueous coating to a substrate to prepare a wet substrate; preparing a dry solid-powder composition containing a resin having a curing temperature in the range of 80°C to 100°C, a polyolefin having a melting temperature of less than 100°C, and a curing agent; and applying the dry solid-powder composition to a wet substrate.

[0054] In one example of Embodiment 5, the dry solid-powder composition is prepared as a dry mix without extrusion.

[0055] In another example of Embodiment 5, the method further comprises curing the applied dry solid-powder composition at a temperature in the range of 60°C to 100°C.

[0056] The embodiments described above (or examples of such embodiments) may be provided on their own or in combination with one or more examples of such embodiments or other embodiments discussed above. For example, the first embodiment may be provided on its own or in combination with one or more examples of the first, second, third, fourth, or fifth embodiments discussed above.

[0057] Additional features and advantages are described in the following detailed description and will be readily apparent to those skilled in the art from that description, or will be recognized by carrying out the embodiments described herein, including the following detailed description.

[0058] Detailed explanation The technical terms used herein are for illustrative purposes only and should not be construed as limiting the invention as a whole.

[0059] In this specification, when a range such as 5 to 25 (or 5 to 25) is given, it preferably means at least 5, and individually, preferably 25 or less. In one example, such a range defines at least 5, and individually, independently, 25 or less.

[0060] Disclosed herein are solid-powder compositions comprising incompatible polyolefins (the term “incompatible” in relation to blends of polyolefins and resins means that the individual components are virtually insoluble in the same type of solvent or water) and resins, and the use of solid-powder compositions for preparing aqueous coatings to enable coating of substrates, such as low surface energy nonconductive substrate surfaces (e.g., TPO). The term “nonconductive surface” as used in this disclosure refers to a surface having a surface resistivity higher than 10 MΩ (10 megohms as measured by a multimeter). The term “low surface energy surface” as used in this disclosure refers to a surface having a surface energy of less than 35 mN / m (millineutons / meter as measured by a tensile strength meter). The compositions and aqueous coatings can be used to coat substrates other than low surface energy nonconductive substrates, for example, the substrates may include polymers, metals, carbon fibers, or combinations thereof. Other suitable examples of substrates include resin transfer molded substrates and reaction injection molded substrates.

[0061] Based on this incompatibility, blends of polyolefins and resins begin to separate into different layers immediately after being combined in a solvent. This separation renders the mixture unsuitable for commercial use, as the mixture must be constantly stirred to maintain uniform dispersion of the components in the solvent. The disclosed process utilizes extrusion (e.g., a melting and mixing process) or grinding and mixing to formulate the incompatible components (i.e., dry solid modified polyolefins and resins) into a sufficiently homogeneous and stable solid-powder composition. The resulting solid-powder composition is, in certain examples, dispersed in water to prepare an aqueous coating, thus avoiding the use of hydrocarbon solvents (e.g., toluene and xylene) and / or oxygen-containing solvents (e.g., butyl acetate). In other words, the aqueous coating is free of hydrocarbon solvents and / or oxygen-containing solvents.

[0062] The dry solid-powder composition comprises a polyolefin, a resin, a curing agent, and optionally a combination of a wetting agent, a conductive agent, a flow modifier, a degassing agent, a pigment, and / or a filler. The solid-powder composition is preferably curable in a temperature range of 80°C to 100°C. The solid-powder composition has the following preferred formulations shown in Table 1. In Table 1, all values ​​are weight percentages based on the total weight of the solid-powder composition. It should be further understood that the solid-powder compositions disclosed herein do not necessarily have to be composed entirely of components from a single column in Table 1. Such a solid-powder composition may, for example, contain one or more components from the “Most Preferred” column, other components from the “Less Preferred” column, and yet other components from the “Even Less Preferred” column.

[0063] [Table 1]

[0064] The solid-powder composition provides the powder composition necessary for powder coating onto receptive substrates, but it also serves as a precursor for aqueous coatings applied to substrates that typically receive liquid coatings, as well as substrates containing low surface energy nonconductive substrates such as TPO. The solid-powder composition can be stored, for example, at ambient temperature for at least one year. Hereinafter, each of the components from Table 1 above will be described further.

[0065] Solid powder compositions comprise a resin, such as a powder-coating resin, and a powder coating crosslinking agent or curing agent. Herein, the curing agent is sometimes also referred to as the crosslinking agent. Therefore, the curing agent may be added to the composition separately or as a component of the resin used as a starting material. The selection of polyolefins and resins to be included in the solid-powder composition is based on the desired properties of the final coating. Such properties may include Tg (softening point), 60°C high-pressure washer resistance, weather resistance (e.g., ozone resistance, UV resistance), gasoline resistance, and other durability tests required by regulations or customers (e.g., DIN ISO 16575, ISO 11358-1:2022, Daimler DBL 5415, DIN EN ISO 16925 Version B, and the tests in Table 24 of this specification). Powder coating resins and powder coating crosslinking agents and / or curing agents suitable for use in resins have a melting or softening point of 60°C to 100°C. Other examples include powder coating resins and powder coating crosslinkers and / or curing agents that are incompatible with the polyolefins used in solid powder compositions in terms of solubility in a given solvent, as described above. Suitable powder coating resins include acrylic resins, epoxy resins, amine-modified resins, phenolic resins, saturated and unsaturated polyester resins, urea resins, urethane resins, blocked isocyanate resins, and mixtures thereof. Suitable powder coating crosslinkers are accelerators for polyamines, polyamidoamines, and adducts used in conjunction with epoxy resins and acrylic-based oxazoline-functional copolymers. Suitable powder coating curing agents are amine-functional curing agents that may include polyamine compounds, aliphatic polyamines, aliphatic polyanhydrides, aromatic amine compounds, or combinations thereof. Suitable powder coating curing agents are also identified as crosslinkers and curing agents. Such powder coating resins, crosslinkers, and curing agents include those identified below and further listed in Table 2 below. In Table 2, "MR" represents the melting temperature range, DSC represents differential scanning calorimeter readings, and EEW represents epoxy equivalent.

[0066] [Table 2]

[0067] When resins from the group of conventional powder coating resin systems (i.e., polyester / epoxy hybrids) containing epoxy resins are included, the polyolefin is incorporated into the crosslinked three-dimensional matrix as a result.

[0068] A resin comprising a combination of one or more types of resins and one or more types of crosslinking agents and / or curing agents is preferably present in the solid-powder composition in an amount of 50% to 97% by weight, more preferably 60% to 87%, and most preferably 40% to 50% of the total composition. The crosslinking agent and / or curing agent components of a resin that may contain one or more types of crosslinking agents and curing agents are present in the solid-powder composition in an amount of 12% to 40% by weight, more preferably 10% to 45%, and most preferably 5% to 50% of the total composition.

[0069] Polyolefins are provided to facilitate the adhesion of coating compositions to substrates. Polyolefins suitable for use in solid-powder compositions include those having a melting or softening point of 60°C to 100°C and a molecular weight of 60,000 to 90,000 g / mol, and those that are incompatible with the resins used in the solid-powder compositions. Polyolefins used in solid-powder compositions include homopolymers produced from ethylene, propylene, or higher alkylenes, copolymers from two or more such monomers, unmodified polyolefins, and chemically modified polyolefins such as maleic anhydride polyolefins. Preferably, such polyolefins include ADVANTIS 510W, CP 730-1(registered trademark), and CP 164-1(registered trademark) (non-CPO commercially available from Eastman); AUROREN AE 20(registered trademark) and AE-301(registered trademark) (non-CPO commercially available from Nippon Paper Chemical); KOATTRO PB M 8510M(registered trademark) and KOATTRO PB M 8911M(registered trademark) (non-modified polyolefins, butene-1 random copolymers with high ethylene content, commercially available from Lyondell Basel); HARDLEN(registered trademark) series (chlorinated polyolefins modified with maleic anhydride, including HARDLEN CY1321P(registered trademark), HARDLEN CY-9122P(registered trademark), and HARDLEN F2P(registered trademark), commercially available from Toyobo Co., Ltd.); TOYO TAC(registered trademark) series (TOYO TAC PMA-L(registered trademark), TOYO TAC Maleic anhydride-modified polypropylene including PMAKE®, TOYO TAC PMA-KH®, and TOYO TAC PMA-T® (commercially available from Toyobo Co., Ltd.); and CPO including the TRAPYLEN® series (commercially available from Tramaco®, including TRAPYLEN 950S®, TRAPYLEN 911S®, TRAPYLEN 139S®, and TRAPYLEN 145S®).

[0070] When polyolefins contain maleic anhydride polyolefins, a portion of the polyolefin undergoes acidic hydrolysis. These acidic functional groups enable crosslinking between the maleic anhydride polyolefin and the functional groups of the resin, such as epoxy groups.

[0071] Polyolefins are preferably present in the solid-powder composition in an amount of 8% to 50%, more preferably 10% to 30%, and most preferably 14% to 30% by weight of the total composition.

[0072] If desired, pigments are provided to introduce color into the coating. This would be a desirable feature for either quality control or color enhancement. Suitable pigments for use in solid-powder compositions include white pigments (e.g., KRONOS 2300®, CAS No. 13463-67-7®, commercially available from KRONOS®), black pigments (e.g., REGAL 400R®, CAS No. 1333-86-4®, commercially available from CABOT®), conductive grade black pigments (e.g., ENSACO 250G®, CAS No. 1333-86-4®, commercially available from TIMCAL®), yellow pigments (e.g., BAYFERROX 3910®, CAS No. 5127400-1®, commercially available from LANXESS®), red pigments (HOSTAPERM D3G70®, commercially available from CLARIANT®), and blue pigments (e.g., HOSTAPERM B2G 03®, commercially available from CLARIANT®).

[0073] For all colors except black, the pigment is preferably present in the solid-powder composition in an amount of 0% to 25% by weight, more preferably 8% to 20%, and most preferably 9% to 11% of the total composition. When black pigment is used, it is preferably present in an amount of 0% to 10% by weight, more preferably 0.2% to 5%, and most preferably 0.5% to 2% of the total composition.

[0074] If desired, optional flow modifiers are provided to reduce the surface tension of powder particles, prevent coating craters, and reduce orange peel. Suitable flow modifiers used in solid-powder compositions include polyacrylates, polyethers, silicones, and fluorocarbons. Preferably, such flow modifiers include MODAFLOW 6000® (polyalkyl acrylate), commercially available from CYTEC®, RESIFLOW PL200® (acrylic copolymer prepared from 2-ethylhexyl acrylate and butyl acrylate, commercially available from ESTRON®), and POWDERMATE 570FL® (amide-modified polyether oligomer, commercially available from TROY®). To support adhesion, and because the flow of the product is a result of particle size and application method, not just the flow properties of the coating (aqueous coatings can function without a flow modifier), the flow modifier can be reduced to a very low percentage.

[0075] The flow modifier is preferably present in the solid-powder composition in an amount of 0% to 2% by weight, more preferably 0.4% to 1.7%, and most preferably 0.5% to 1.5% of the total composition.

[0076] Optional degassing agents are provided to reduce surface tension and prevent pinholes in the coating. Suitable degassing agents for use in solid-powder compositions include benzoin (CAS No. 119-53-9 (registered trademark), commercially available from ESTRON®), OXYMELT A-2 (registered trademark), -4 (registered trademark), -6 (registered trademark), and -7 (registered trademark) (commercially available from ESTRON®), and POWDERADD 9025 (registered trademark) (a polyolefin wax commercially available from LUBRIZOL®).

[0077] The optional degassing agent is preferably present in the solid-powder composition in an amount of 0% to 2% by weight, more preferably 0.1% to 1%, and most preferably 0.25% to 1% of the total composition.

[0078] Optional defoamers are provided to reduce air trapped in aqueous coatings during handling or mixing. Suitable degassing agents for use in aqueous compositions include BYK-1707®, BYK-012®, and BYK-1711® (all commercially available from BYK®).

[0079] The optional defoaming agent is preferably present in the aqueous composition in an amount of 0% to 2% by weight, more preferably 0.1% to 1%, and most preferably 0.25% to 0.75% by weight of the total composition.

[0080] The curing agent / crosslinking agent / curing agent is preferably a solid aliphatic polyamine adduct acting as a curing agent, crosslinking agent, or curing agent. It may also be an aliphatic polyanhydride. The curing agent exhibits high reactivity and is therefore suitable for use in combination with other curing agents such as Aradur® 835, Aradur® 3086, and Accelerator 2950 (all available from Huntsman). Accelerator 2950® is a low-reactive tertiary amine-based accelerator with a low plasticizing effect. It is commonly used as a co-curing agent when used with polyurethane systems, polyamines, polyamidoamines, and their adducts. It is good for aqueous systems at low temperatures. All three can be used as curing agents, crosslinking agents, or curing agrems. Furthermore, ADDITOL® P 791 (available from Allnex) is a solid aliphatic polyanhydride curing agent for use in glycidyl functional group reactions and can be used as a crosslinking agent / curing agent / curing agent according to the present invention.

[0081] The optional wetting agent may be a conventional surfactant (e.g., SURFYNOL® 104®), a nonionic surfactant commercially available as a powder formulation of surfactants in different solvents or on an inorganic support. As a powder, SURFYNOL® 104 S® is a free-flowing powder surfactant that provides non-yellowing and degassing properties to powder coatings. Another wetting agent tested is SURFYNOL® 440®, a substrate wetting agent with moderate solubility in aqueous systems that provides foam control. It is suitable for aqueous coatings and inks. SURFYNOL® AD-01® is a multifunctional gemini surfactant that combines dynamic wetting and molecular defoaming. SURFYNOL® AD-01® also acts as a bonding agent. Each SURFYNOL® product is available from Evonik.

[0082] The optional wetting agent is preferably present in an amount of 0% to 1.5%, more preferably 0.1% to 1.0%, and most preferably 0.25% to 0.75% by weight of the total composition.

[0083] Optional conductive agents are provided to improve the electrostatic coating efficiency in coatings and, therefore, to make non-conductive substrates conductive for subsequent finishing (i.e., electrostatic painting). Suitable conductive agents used in both solid powder coatings and aqueous coating formulations include conductive grade black pigments (ENSACO 250G from TIMCAL), carbon nanofibers, single-walled nanotubes, multi-walled carbon nanotubes, and dispersions of mixtures thereof. Preferably, such conductive agents include carbon nanotubes such as TUBALL® MATRIX 821 concentrate by OCSiAl. TUBALL® MATRIX 821 has been tested. A concentration of 0.2% wt is recommended, which allows for a surface resistivity of 10⁶ ohms / sq. A uniform distribution of TUBALL® COAT E by OCSiAl in the target formulation further improves electrical conductivity. In aqueous coating formulations, OCSiAL's TUBALL® COAT E H2O 0.4% SDBS is preferably used to prepare the conductive rotationally molded polyethylene (PE) portion, and is mixed with a standard polymer in powder form.

[0084] The conductive agent is preferably present in the solid powder coating and aqueous coating formulations in an amount of 0% to 10% by weight, more preferably 3% to 8%, and most preferably 4% to 6% of the total composition. Optionally, the conductive agent is present in the aqueous coating in an amount of at least 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 8%, or 10% by weight of the total composition. Optionally, the conductive agent is present in the aqueous coating in an amount of 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, or 2% or less by weight of the total composition.

[0085] To prepare a solid-powder composition, each component is weighed and mixed. For example, the components can be weighed on a laboratory scale (e.g., Mettler Toledo DSC 822E) and mechanically mixed using a standard mechanical mixer (e.g., Prism or MIXACO).

[0086] After the initial mixing step, the mixture passes through an extruder (e.g., a Copirion SK 25 double-barrel extruder) (Method 1). In the extrusion process, the mixture is heated to a temperature at least 1°C higher than the melting temperatures of the polyolefin and resin. The polyolefin and resin are blended in the extruder, and the non-molten components (i.e., pigments) are de-aggregated and uniformly distributed in the mixture. The residence time in the extruder is kept to a minimum to prevent premature crosslinking of the co-resin. For example, the residence time in the extruder may be 30 seconds or less. This mixture does not contain a curing agent because the curing temperature of the system may fall below the temperature inside the extruder, causing the extruder to clog and become inoperable.

[0087] Following the extrusion process, the extruded material is cooled. For example, the extruded material may be passed through a chiller roller (BBBA cooler). This cooling prevents chemical crosslinking between the components in the extruded material. The extruded material is then broken down into smaller pieces or chips, which can be stored until ready for use in further processing steps. For example, the extruded material can be passed through a kibbler to produce smaller pieces approximately 2 cm wide x 2 cm long x 1 mm thick. Based on the properties of the components used in the mixture, the extrusion process can be repeated, where the smaller pieces are passed through the extruder one or more times for further formulation.

[0088] After the extruded material is cooled and broken down into smaller pieces, the particle size of the composition is reduced using a grinding device (e.g., a Neuman & Esser ICM 2.4 lab mill) to meet the development requirement (D50 = 35 μm). The particle size is measured using a Malvern Mastersizer, for example, by laser diffraction. The resulting solid-powder composition can be stored until ready for later use.

[0089] Aqueous premixtures are prepared by blending solid-powder compositions in water as described below. Optionally, the water used to blend the solid-powder compositions is deionized water or reverse osmosis ("RO") water. The aqueous premixtures have the following preferred formulations shown in Table 3. In Table 3, all values ​​are weight percentages. It should be further understood that the aqueous premixtures disclosed herein do not necessarily have to derive their entire composition from a single column in Table 1. Such aqueous premixtures may, for example, contain one or more components from the "Most Preferred" column below, other components from the "Less Preferred" column, and yet another component from the "Even Less Preferred" column.

[0090] [Table 3]

[0091] The aqueous premixture is prepared by mixing the solid-powder composition with water and a curing agent that has been pre-ground to a particle size similar to the remaining formulation. The components may be mechanically mixed by a standard mechanical mixer, paint shaker, high-speed dissolver with high-shear blades, or other conventional mixing methods. Optionally, the components may be mixed by a vertical or horizontal wet mill. Optionally, the solid powder components can be pre-ground in a counter-jet mill to reduce the particle size of the powder coating formulation and shorten the grinding time in the wet mill. Excessive mechanical stress in the mill can result in undesirable behavior in terms of curing.

[0092] Next, the particle size of the solid-powder composition in the aqueous premixture is reduced by milling so that the particles have a preferred average value of 3 micrometers and a distribution of 2-5 micrometers (measured by a BYK grinder meter). Optionally, the solid-powder composition is pre-milled using a jet mill. This size of particle is preferable according to the present invention because it remains suspended in the water without further separation. The aqueous premixture remains stable when stored at room temperature.

[0093] Aqueous coatings are prepared by combining an aqueous premixture with a substrate wetting agent and optionally a conductive agent. Optionally, aqueous coatings may additionally contain viscosity modifiers and / or anti-settling agents. Aqueous coatings have the following preferred formulations shown in Table 4. In Table 4, all values ​​are weight percentages based on the total composition. Like powder compositions, aqueous coatings are preferably curable in the temperature range of 80°C to 100°C. It should be further understood that the aqueous coatings disclosed herein do not necessarily have to derive their entire composition from a single column in Table 1. Such aqueous coatings may, for example, contain one or more components from the “Most Preferred” column below, other components from the “Less Preferred” column, and yet other components from the “Even Less Preferred” column.

[0094] [Table 4]

[0095] Aqueous coatings are prepared by blending an aqueous premixture with a substrate wetting agent, an optional conductive agent, an optional viscosity modifier, and an optional anti-settlement agent. The components may be mechanically blended by a standard mechanical mixer, a high-speed dissolver with low-shear blades, or other conventional mixing methods. Aqueous coatings can be applied to any substrate surface, including low surface energy non-conductive substrates (e.g., TPO substrates), so that a subsequent coating layer (depending on the use of the coating as either an adhesion promoter, primer, or coating, e.g., primer, base coat, or top coat) adheres to the substrate or coating, and the subsequent coating layer can be applied using electrostatic spray application. Hereinafter, each of the non-aqueous premixture components from Table 4 above is described further.

[0096] Optional substrate wetting agents are provided to improve wetting and reduce surface tension for coating. Suitable substrate wetting agents used in aqueous coatings include silicone surfactants, polyether-modified siloxanes, and acetylene-based surfactants. Preferably, such substrate wetting agents include BYK 3450® (a silicone surfactant commercially available from BYK) and SURFYNOL 440® or SURFYNOL AD01® or SURFYNOL 104S® (ethoxylated acetylene-based diols commercially available from EVONIK®).

[0097] The substrate wetting agent is preferably present in the aqueous coating in an amount of 0% to 1.5% by weight, more preferably 0.1% to 1%, and most preferably 0.25% to 0.75% of the total composition.

[0098] Optional conductive agents are provided to improve the electrostatic coating efficiency in aqueous coatings and, therefore, to make non-conductive substrates or coatings conductive for subsequent finishing (i.e., electrostatic painting). Suitable conductive agents used in aqueous coatings include conductive grade black pigments, carbon nanofibers, single-walled carbon nanotubes, multi-walled carbon nanotubes, and dispersions of mixtures thereof. Preferably, such conductive agents include TUBALL COAT_E H2O 0.4% (registered trademark) (an aqueous dispersion of single-walled carbon nanotubes commercially available from OCSiAl (registered trademark)) and ENSACO 250G (registered trademark) (a conductive carbon black commercially available from TIMCAL).

[0099] The conductive agent is preferably present in the aqueous coating in an amount of 0% to 10% by weight, more preferably 3% to 8%, and most preferably 4% to 6% of the total composition. Optionally, the conductive agent is present in the aqueous coating in an amount of at least 0.1% to 10% by weight of the total composition. Optionally, the conductive agent is present in the aqueous coating in an amount of 15% to 2% or less by weight of the total composition.

[0100] Optional viscosity modifiers are available to improve the flow-stopping and settling-preventing properties of the coating. Suitable viscosity modifiers for use in aqueous coatings include, for example, modified urea, RHEOBYK-420® (a solution of modified urea commercially available from BYK), and ACRYSOL RM8® (a hydrophobic modified ethoxylated urethane commercially available from DOW).

[0101] Optional viscosity modifiers are preferably present in the aqueous coating in an amount of 0% to 4%, more preferably 0% to 3%, and most preferably 0% to 2% by weight of the total composition.

[0102] If desired, optional anti-settling agents are available to increase the viscosity of the coating. Suitable anti-settling agents for use in aqueous coatings include ANTI-TERRA 250® (a more molecular weight alkylol ammonium salt of an acidic polymer, commercially available from BYK) and TAMOL SN® (a neutral sodium salt of a condensed aryl sulfonic acid, commercially available from DOW).

[0103] The settling inhibitor is preferably present in the aqueous coating in an amount of 0% to 2% by weight, more preferably 0% to 1%, and most preferably 0% to 0.5% of the total composition.

[0104] If desired, optional defoaming agents are available to improve the anti-foaming properties of the coating. Suitable anti-foaming agents for use with aqueous coatings include, for example, BYK-1707® (commercially available from BYK).

[0105] The anti-foaming agent is preferably present in the aqueous coating in an amount of 0% to 2% by weight, more preferably 0% to 1%, and most preferably 0% to 0.5% of the total composition.

[0106] Method 2 does not use an extruder to produce the aqueous coating. In Method 2, an impact classifying mill (Neuman & Esser ICM 2.4) and / or a jet mill (NOLL Grinding) are used to reduce the finely ground powder components according to an average particle size of 3 micrometers and a distribution of 2-5 micrometers, or according to any other particle size required by the customer's requirements. The aqueous coating is further mixed with the components specified according to Table 4.

[0107] Water-based coatings are applied to substrates, including low surface energy nonconductive substrates, by any conventional method, including dipping, brushing, and spraying (SAMES HVOP). For example, a standard spray gun for liquid paints may be used to apply the water-based coating to a nonconductive substrate (e.g., TPO).

[0108] Other non-conductive substrates suitable for use with the aqueous coating compositions disclosed herein include plastic substrates such as any thermoplastic or thermosetting non-conductive substrates. For example, other suitable substrates include, among others, polycarbonate, polyurethane, thermoplastic polyurethane, acrylonitrile butadiene styrene ("ABS"), thermoplastic elastomers, and thermosetting polyesters. The transfer efficiency when spraying the aqueous coating is achieved by the same means as applied to conventional liquid adhesion promoters, i.e., droplets of the material being sprayed are wet and adhere to the substrate upon contact.

[0109] When applied to substrates containing low surface energy nonconductive materials, aqueous coatings are cured or flashed (a rapid process that allows the freshly sprayed coating to form a film, even though it is not yet fully cured, enabling the application of additional coatings) at ambient temperature or a high temperature, based on the materials selected for the coating. The curing / flash temperature and curing / flash time are based on the temperature, relative humidity, and rate of the air moving over the coated substrate, as well as the sensitivity of the selected subsequent coating to residual water, which is sufficient to dry the coating to a film. The flash time and flash temperature are substantially the same as those for the aqueous basecoat before applying a solvent-based clearcoat, which is a widely known and understood practice in the industry.

[0110] If desired, the coated substrate is then slowly cooled and ready for application of additional coatings and / or finishing layers. The coated substrate can be electrostatically coated with a conventional topcoat or other liquid or powder coating. For example, the finishing layer may be applied by 1K / 1K or 1K / 2K coating. Following the application of the final coating, the coating is cured or flashed at ambient temperature or high temperature before cooling to room temperature.

[0111] In an alternative embodiment, the solid-powder composition is prepared as described above. However, instead of being added to water to prepare an aqueous coating, the solid-powder composition is applied to a substrate containing a low surface energy nonconductive substrate that has been wetted with an aqueous coating, which may or may not contain a conductive agent or other additives for wetting the surface with water (e.g., wetting agents, rheological agents). In this embodiment, water or an aqueous coating is applied to the substrate containing a low surface energy nonconductive substrate (e.g., a TPO substrate) to wet the substrate and make it conductive. The solid-powder composition can then be applied directly to the wetted substrate containing the low surface energy nonconductive substrate (Method 3).

[0112] In alternative embodiments, the solid-powder composition comprises a combination of polyolefin, resin, pigment, flow regulator, and deaeration agent. The solid-powder composition has preferred formulations shown in Table 1. In Table 1, all values ​​are weight percentages. It should be further understood that the solid-powder compositions disclosed herein do not necessarily have to be composed entirely of components from a single column in Table 1. Such solid-powder compositions may, for example, contain one or more components from the “Most Preferred” column, other components from the “Less Preferred” column, and yet other components from the “Even Less Preferred” column. The amounts of each component in the solid-powder composition of the alternative embodiments are the same as the amounts of each component discussed earlier for the first embodiment.

[0113] The solid-powder composition can be stored at ambient temperature for a certain period, for example, at least one year. Each of the components from Table 1 is the same as described above. Each component is weighed and mixed to prepare the solid-powder composition. For example, a standard mechanical mixer (a Prism mixer) can be used to mechanically mix the components.

[0114] After the initial mixing step, the mixture passes through an extruder (Method 1) or through an impact classification mill or jet mill (Method 2). In the extrusion process, the mixture is heated to a temperature higher than the melting points of the polyolefin and resin. The polyolefin and resin are blended in the extruder, and non-molten components (e.g., pigments) are de-aggregated and uniformly distributed in the mixture. The residence time in the extruder is kept to a minimum to prevent premature crosslinking of the co-resin. For example, the residence time in the extruder may be 30 seconds or less.

[0115] Following the extrusion process (Method 1), the extruded material is cooled. For example, the extruded material may be passed through a chiller roller (BBBA cooler). This cooling prevents chemical crosslinking between the components in the extruded material. The extruded material is then broken down into smaller pieces or chips, which can be stored until ready for use in further processing steps. For example, the extruded material can be passed through a kibler to produce smaller pieces approximately 2 cm wide × 2 cm long × 1 mm thick. Based on the properties of the components used in the mixture, the extrusion process can be repeated, where the smaller pieces are passed through the extruder one or more times for further formulation.

[0116] After the extruded material has cooled and broken down into smaller pieces, the particle size of the composition is reduced using a grinding device (e.g., a Neuman & Esser ICM 2.4 lab mill). The particle size is measured using a Mastersizer, e.g., a Malvern Mastersizer. The resulting solid-powder composition can be stored until ready for later use.

[0117] Based on the alternative embodiment, an aqueous coating is applied to a substrate containing a non-conductive substrate before the solid-powder composition in order to make the substrate conductive and wet. The aqueous coating has the following preferred formulations shown in Table 5. In Table 5, all values ​​are weight percentages based on the total composition. It should be further understood that the aqueous coatings disclosed herein do not necessarily have to derive their total composition from a single column in Table 5. Such an aqueous coating may, for example, contain one or more components from the “Most Preferred” column below, other components from the “Less Preferred” column, and yet other components from the “Even Less Preferred” column. Optionally, the amounts of each component in the aqueous coating of the alternative embodiment (i.e., water, substrate wetting agent, conductive agent, viscosity modifier, and anti-settling agent) are the same as the amounts of each component discussed earlier for the first embodiment.

[0118] [Table 5]

[0119] Aqueous coatings are prepared by mixing water with an optional substrate wetting agent, a conductive agent, and optional viscosity modifiers and optional anti-settling agents. The components may be mechanically mixed by a standard mechanical mixer, paint shaker, high-speed dissolver with high-shear blades, or other conventional mixing methods. Optionally, the components may be mixed by a vertical or horizontal wet mill.

[0120] Next, the aqueous coating is applied to a substrate containing low surface energy, such as a non-conductive substrate (e.g., TPO). For example, the aqueous coating may be sprayed in a thin layer onto a low surface energy non-conductive substrate using a standard spray gun used for liquid paints. In another example, the low surface energy non-conductive substrate can be immersed in the aqueous coating, which makes it possible to apply the aqueous coating to complex three-dimensional molded substrates that may be difficult to coat with liquid spray equipment. Regardless of how it is applied, the aqueous coating adheres to substrates containing low surface energy non-conductive materials because it is wet and forms a thin film on the substrate, thus enabling further coating applications.

[0121] Following the application of an aqueous coating to a substrate containing a low surface energy nonconductive substrate, the substrate is wetted with DI or RO water, and a solid-powder composition is applied to the substrate using a conventional powder coating apparatus. The solid-powder composition adheres to the wetted substrate and is then cured or flashed at ambient temperature or high temperature, based on the material selected for the coating. The curing / flash temperature and curing / flash time are based on the temperature, relative humidity, and speed of the air moving over the coated substrate, as well as the selected subsequent coating's sensitivity to residual water, and are sufficient to dry the coating to a film. The flash time and flash temperature are substantially the same as those for the aqueous basecoat before applying a solvent-based clearcoat, which is a widely known and understood practice in the automotive industry.

[0122] Next, the coated substrate is slowly cooled and ready for application of additional coatings and / or finishing layers. Since the coated substrate is now conductive due to the application of the conductive agent in the aqueous coating, the coated substrate can be electrostatically painted with a conventional topcoat or other liquid or powder coating. For example, a finishing layer may be applied by 1K / 1K or 1K / 2K coating. Following the application of the final coating, the coating is cured or flashed at ambient temperature or high temperature before being cooled to room temperature.

[0123] Examples The examples in Table 6 further illustrate various aspects of the disclosed solid-powder compositions and their use in the preparation of aqueous coatings for application to low surface energy nonconductive surfaces. In the following examples, all compositional data are given as weight percentages of the specified components based on the total composition of each example. The coatings prepared in the examples were tested for retention in the gasoline immersion test described herein.

[0124] Example 1 - Preparation of a solid-powder composition for use in aqueous coatings The following solid-powder compositions listed in Table 6 were prepared. All amounts are in weight percentages based on the total weight of the solid-powder composition.

[0125] [Table 6]

[0126] To prepare the solid-powder composition, the components listed in Table 6 were dry-mixed in a mechanical mixer (MIXACO equipment). The solid-powder composition was then melt-mixed by passing it through a twin-screw extruder with a length-to-diameter ratio of at least 19:1 (Method 1), or by fine grinding it using a jet mill (Method 2).

[0127] Method 1: The mixing zone temperature was maintained at 85°C to 115°C, and the feeder speed was maintained to generate 60% to 90% torque. The resulting extruded material was then pressed into a sheet and cooled by chiller rolls. The resulting extruded sheet was then crushed into chips by a kibler. The chips were then passed through an air classifying mill to obtain a particle size of approximately 30 μm, or 2 to 5 μm by Method 2 below, and then passed through a vibrating tray sieve to remove all oversized particles.

[0128] Method 2: The chips from Method 1 were processed with a jet mill to prepare particles with a size in the range of 2-5 μm. A counter-jet mill is preferred to achieve a suitable particle size so that the dry blend does not melt or harden during milling due to the flexible components in the powder formulation, and to maintain the temperature below the product's Tg (<35°C).

[0129] Example 2 - Preparation of aqueous premixture The following aqueous premixtures in Table 7 were prepared using the solid-powder composition of Example 1. All amounts are in weight percentages based on the total weight of the aqueous premixture.

[0130] [Table 7]

[0131] An aqueous premixture was prepared by adding the solid-powder composition of Example 1 to deionized water or RO water while mixing in a high-speed disperser equipped with high-shear blades. The aqueous premixture was then passed through a horizontal bead mill (Dispermat SL-250-C1) to produce an aqueous premixture with an average particle size of approximately 3 μm, as determined by a Malvern Mastersizer 3000 particle analyzer.

[0132] Example 3 - Preparation of aqueous coating The following aqueous coatings listed in Table 8 were prepared. All quantities are in weight percentages based on the total weight of the aqueous coating.

[0133] [Table 8]

[0134] An aqueous coating was prepared by adding a substrate wetting agent (Surfynol 104S®) and a conductive agent to an aqueous premixture.

[0135] Example 4 - Application of aqueous coating to a low surface energy nonconductive substrate As prepared in Example 3, an aqueous coating was applied in a single coat using a standard spray gun (SATA minijet® 3000B) to a low surface energy nonconductive TPO substrate, achieving a dry film thickness of 3–5 μm as determined by a Malvern Mastersizer 3000 particle analyzer. The coated substrate was then air-flashed at room temperature for 10 minutes and baked at 90°C (194°F). A 1 K Hydro Iridium Silver (Iridiumsilber) base coat and a 2 K solvent clear coat were applied to the dry film obtained by the aqueous coating. The base coat thickness, as determined by a Malvern Mastersizer 3000 particle analyzer, was approximately 8–12 μm, and the clear coat thickness, as determined by a Malvern Mastersizer 3000 particle analyzer, was approximately 30–40 μm. The base coat was cured at 80°C for 15 minutes, and the clear coat was cured at 80°C for 30 minutes.

[0136] A prepared substrate covered with a film formed by an aqueous coating has its surface cross-hatched according to ASTM D6677 in order to investigate the adhesion of the film to the substrate surface.

[0137] The coated TPO substrate of Example 4 was subjected to a BMW steam jet test (60°C / 65 bar / 60 seconds / distance 13 cm), and no delamination was observed according to the BMW standard (DBL5415), which requires that less than 90% of the delamination be less than 1 mm.

[0138] Samples 87-93 and 100-106 were further tested according to the BMW steam jet test. The results are shown in Table 9 below. Table 9 includes multiple trials of the developed powder formulations according to DIN EN ISO 2409, with a maximum value of 1 indicating a pass in the test. The difference in formulations is that different substrates may require different curing rates, Tg, or other properties that can be achieved with different accelerators / curers. Since the inventors have an epoxy system, products called "Accelerator 2950CH®" and "Accelerator 960-1®," commercially available from Huntsman, are amine adducts and can be used as curers and accelerators. In addition, Sumitomo EPOCROSWS-700® was used to accelerate the curing time. The ability to achieve low-temperature curing in a solvent-free coating system and achieve adequate adhesion while fully meeting the test specifications could not be compared to other materials in the inventors' tests because there were no similar materials to test for comparison.

[0139] [Table 9-1]

[0140] [Table 9-2]

[0141] [Table 10]

[0142] Exemplary embodiments have been described herein. It will be apparent to those skilled in the art that the compositions and methods described above can be modified and altered without departing from the scope of this disclosure. Accordingly, this disclosure is not limited to any particular detail herein, and such modifications and their adaptations are included within the spirit and scope of the appended claims.

Claims

1. A water-based coating for application to a substrate, a. Water and, b. Polyolefins having a melting temperature of less than 100°C, c. A resin having a curing temperature in the range of 80°C to 100°C or a melting temperature in the range of 65°C to 90°C, d. Hardener and e. A selective substrate wetting agent, f. Selective conductive agents and A water-based coating, including

2. The aqueous coating according to claim 1, wherein the substrate is composed of a material selected from the group consisting of polymers, metals, carbon fibers and / or combinations thereof.

3. The aqueous coating according to claim 1, wherein the substrate is selected from the group consisting of a non-conductive low surface energy substrate, a thermoplastic olefin substrate, a resin transfer molded substrate, and a reaction injection molded substrate.

4. The aqueous coating according to claim 1, wherein the substrate wetting agent is present in an amount of 0.1 to 1.5 weight percent of the aqueous coating.

5. The aqueous coating according to claim 1, wherein the conductive agent is present in an amount of 0.1 to 10 weight percent of the aqueous coating.

6. The aqueous coating according to claim 1, wherein the polyolefin is a non-halogen-modified polyolefin.

7. The aqueous coating according to claim 6, wherein the non-halogen-modified polyolefin is a maleic anhydride-modified polyolefin.

8. The aqueous coating according to claim 1, wherein the polyolefin is an unmodified polyolefin.

9. The aqueous coating according to claim 1, wherein the polyolefin has a melting temperature in the range of 60°C to 90°C.

10. The aqueous coating according to claim 1, wherein the resin is an epoxy resin.

11. The aqueous coating according to claim 1, wherein the resin has a curing temperature in the range of 80°C to 90°C.

12. The aqueous coating according to claim 1, wherein the curing agent is an amine-functional compound or an aliphatic polyanhydride, and the curing agent has a melting temperature in the range of 65°C to 90°C.

13. The aqueous coating according to claim 12, wherein the amine-functional compound is selected from the group consisting of polyamine compounds, aliphatic polyamine compounds, and aromatic amine compounds.

14. A thermoplastic olefin substrate coated with the aqueous coating described in claim 1, wherein the aqueous coating is cured at a temperature in the range of 60°C to 90°C.

15. The aqueous coating is a thermoplastic olefin substrate according to claim 15, wherein the aqueous coating does not contain extruded material.

16. A dry solid-powder composition for coating a substrate, a. Polyolefins having a melting temperature of less than 100°C, b. A resin having a curing temperature in the range of 80°C to 100°C, c. A curing agent having a melting temperature in the range of 65°C to 90°C, d. A selective substrate wetting agent, e. Optional conductive agents and A dry solid-powder composition containing the following:

17. The dry solid-powder composition according to claim 16, wherein the polyolefin is a non-halogen-modified polyolefin.

18. The dry solid-powder composition according to claim 16, wherein the polyolefin has a melting temperature in the range of 60°C to 90°C, and the resin has a curing temperature in the range of 80°C to 90°C.

19. The dry solid-powder composition according to claim 16, wherein the curing agent is present in the composition in an amount of 12 to 30 weight percent based on the total weight of the composition, and / or the curing agent is an amine-functional compound or an aliphatic polyanhydride.

20. A thermoplastic olefin substrate coated with the dry solid-powder composition described in claim 16, wherein the coating of the dry solid-powder composition is cured at a temperature in the range of 60°C to 90°C.

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