Thermally conductive dielectric coating

Abstract

A curable liquid coating composition that can be sprayed on a substrate to form a thin, pinhole-free, thermally conductive dielectric coating that exhibits an improved combination of dielectric strength and improved thermal conductivity, wherein the composition comprises an organic resin, a reactive diluent, a thermally conductive filler, a dispersant, an initiator, and an additive selected from the group consisting of organic solvents, accelerators, and rheology modifiers; also provided are methods of making compositions, coatings, and substrates comprising a curable or cured thermally conductive dielectric coating, as well as articles comprising a curable or cured coating of the composition.

Description

Technical Field

[0001] This invention relates to a curable liquid coating composition for depositing a thermally conductive dielectric coating on a substrate, an intermediate comprising a substrate having a curable, optionally dry, coating composition layer deposited thereon, an adhesive layer of the cured thermally conductive dielectric coating composition on the substrate, a coated substrate, and a method for producing said composition, coating, coating, and coated substrate. Background Technology

[0002] Electrical components are typically electrically insulated by applying a high dielectric strength material. While dielectric materials provide electrical insulation, they are generally not conducive to heat dissipation and can be thermally insulating. In many electrical components, particularly for vehicle OEMs, there is a strong need for faster heat dissipation from battery operation to improve the driving range and battery pack life of battery-powered vehicles. Common battery insulation in such vehicles is primarily achieved through powder coatings or the use of plastic insulating wraps or films; neither of these adequately addresses the heat dissipation requirements. The disadvantages of powder coatings include the need for high-temperature curing, such as 175-205°C for 10-15 minutes plus the time required for the component to reach its curing temperature (approximately 30 minutes). Powder coatings are typically thick and use multiple layers to ensure a pinhole-free film. Therefore, powder coatings have the added disadvantages of undesirably increased weight and high thermal resistance, while plastic wraps require complex handling and processing for installation, and long-term reliability and delamination risks are concerns.

[0003] Therefore, there is a need to develop dielectric coatings that promote heat dissipation, particularly for battery cooling systems, prismatic cells, cold plates, power inverters, buses, and chargers. There is also a need to develop improved dielectric coatings that provide good electrical insulation at low film thicknesses to reduce weight, applied through less complex processes and using less time and energy. Therefore, there is a need for a thermally conductive dielectric coating that can be applied defect-free at a thickness thinner than previously available for vehicles, possessing a combination of improved dielectric strength and improved thermal conductivity or low thermal resistance. Summary of the Invention

[0004] According to various aspects of the invention, a curable liquid coating composition, a substrate having a curable, optionally dryable coating composition layer deposited thereon, and a cured polymer thermally conductive dielectric coating on the substrate and the coated substrate, solves one or more of the aforementioned disadvantages or needs and exhibits high dielectric strength, heat dissipation and good electrical insulation, as further described herein.

[0005] Various embodiments of curable liquid coating compositions may comprise or consist essentially of the following: organic resins, such as polyester resins; reactive diluents; thermally conductive fillers; dispersants; initiators; and additives selected from organic solvents, accelerators, rheology modifiers (optionally surface-modified) (also referred to herein as thixotropic agents). Optionally, such compositions may also contain additives such as deaerators, coupling agents, defoamers, pigments and dyes, plasticizers, flexibleizers, flame retardants, impact modifiers / toughening agents, fillers, flow control agents, adhesion promoters, inhibitors, antioxidants, non-reactive diluents, extenders, or other auxiliaries. In some embodiments, the curable liquid coating composition is formaldehyde-free.

[0006] Various embodiments of the invention have been described throughout this disclosure, including:

[0007] Implementation Scheme 1: A curable liquid coating composition comprising: (a) Polyester resin; (b) Reactive diluents; (c) Thermally conductive filler; (d) Dispersant; (e) Initiator; and (f) An optional promoter, different from the initiator; The polyester resin is selected from unsaturated polyester resins, which may preferably include vinyl ester resins, and more preferably epoxy vinyl ester resins, such as epoxy acrylates and epoxy methacrylates, and combinations thereof.

[0008] The curable liquid coating composition may further comprise at least one additive, preferably selected from organic solvents, accelerators, rheology modifiers (optionally surface-modified) (also referred to herein as thixotropic agents). The curable liquid coating composition may also contain degassing agents, coupling agents, defoamers, pigments and dyes, plasticizers, flexibility agents, flame retardants, impact modifiers / toughening agents, fillers other than (c), flow control agents, adhesion promoters, inhibitors, antioxidants, non-reactive diluents, extenders, or other additives. In some aspects of this embodiment, the curable liquid composition is formaldehyde-free.

[0009] Implementation Scheme 2: The curable liquid coating composition of Implementation Scheme 1 is further characterized in that the components are, or contain, the following, given in weight %: (a) One or more unsaturated polyester resins, preferably vinyl ester resins, preferably epoxy vinyl ester resins, such as epoxy acrylates and epoxy methacrylates, and combinations thereof, preferably present in the range of 10% to 95%, preferably 25% to 50%; (b) A free radical reactive diluent, preferably present in the range of 10% to 95%, preferably 25% to 50%; (c) Thermally conductive fillers, such as boron nitride, alumina, and aluminum trihydrate, are preferably present in the range of 5% to 50%, preferably 10% to 30%; (d) Dispersant, preferably present in the range of 0.1% to 2.0%; (e) an initiator, preferably present in the range of 0.1% to 5%; (f) An accelerator, different from the initiator, is preferably present in the range of 0% to 1%; (g) Organic solvent, preferably present in the range of 0.5% to 20%; (h) at least one additive selected from rheology modifiers, adhesion promoters, flexibility agents and plasticizers, each preferably present in the range of 0% to 5%. (i) Degassing agents and / or defoamers, preferably present in the range of 0% to 2.0%; The wt.% of each component is relative to the total weight of the composition, and the total amount of the components does not exceed 100 wt.%.

[0010] Implementation Scheme 3: A curable liquid coating composition according to any one of the disclosed embodiments above, wherein, relative to the total weight of the composition, (a) the unsaturated polyester resin, preferably a vinyl ester resin, preferably an epoxy vinyl ester resin, such as epoxy acrylate and epoxy methacrylate, and combinations thereof, are present in the following ranges: 10 wt.% to 15 wt.%, 15 wt.% to 20 wt.%, 20 wt.% to 25 wt.%, 25 wt.% to 30 wt.%, 30 wt.% to 35 wt.%, 35 wt.% to 40 wt.%. wt.%, 40wt.% to 45wt.%, 45wt.% to 50wt.%, 50wt.% to 55wt.%, 55wt.% to 60wt.%, 60wt.% to 65wt.%, 65wt.% to 70wt.%, 70wt.% to 75wt.%, 75wt.% to 80wt.%, 80wt.% to 85wt.%, 85% to 90%; 90% to 95%, or any combination of two or more of the foregoing ranges, such as 25wt.% to 50wt.%, or any of the foregoing values.

[0011] Implementation Scheme 4: A curable liquid coating composition according to any one of the disclosed embodiments above, wherein, relative to the total weight of the composition, (b) the free radical reactive diluent is present in the following ranges: 10 wt.% to 15 wt.%, 15 wt.% to 20 wt.%, 20 wt.% to 25 wt.%, 25 wt.% to 30 wt.%, 30 wt.% to 35 wt.%, 35 wt.% to 40 wt.%, 40 wt.% to 45 wt.%, 45 wt.% to 50wt.%, 50wt.% to 55wt.%, 55wt.% to 60wt.%, 60wt.% to 65wt.%, 65wt.% to 70wt.%, 70wt.% to 75wt.%, 75wt.% to 80wt.%, 80wt.% to 85wt.%, 85% to 90%; 90% to 95%, or any combination of two or more of the foregoing ranges, such as 25wt.% to 50wt.%, or any of the foregoing values.

[0012] Implementation Scheme 5: A curable liquid coating composition according to any one of the above-disclosed embodiments, wherein, relative to the total weight of the composition, (c) the thermally conductive filler, preferably comprising boron nitride filler, is present in the following ranges: 5 wt.% to 10%, 10 wt.% to 15 wt.%, 15 wt.% to 20 wt.%, 20 wt.% to 25 wt.%, 25 wt.% to 30 wt.%, 30 wt.% to 35 wt.%, 35 wt.% to 40 wt.%, 40 wt.% to 45 wt.%, 45 wt.% to 50 wt.%, or any combination of two or more of the foregoing ranges, for example, 10 wt.% to 30 wt.%, or any one of the foregoing values.

[0013] Implementation Scheme 6: The curable liquid coating composition disclosed in any one of the above embodiments, wherein (d) the dispersant is present in the following range relative to the total weight of the composition: 0.1 wt.% to 0.2 wt.%, 0.2 wt.% to 0.3 wt.%, 0.3 wt.% to 0.4 wt.%, 0.4 wt.% to 0.5 wt.%, 0.5 wt.% to 0.6 wt.%, 0.6% to 0.7 wt.%, 0.7 wt.% to 0.8 wt.%, 0.8 wt.% to 0.9 wt.%, 0.9 wt.% to 1.0 wt.%, 1. 0 wt.% to 1.1 wt.%, 1.1 wt.% to 1.2 wt.%, 1.2 wt.% to 1.3 wt.%, 1.3 wt.% to 1.4 wt.%, 1.4 wt.% to 1.5 wt.%, 1.5 wt.% to 1.6 wt.%, 1.6 wt.% to 1.7 wt.%, 1.7 wt.% to 1.8 wt.%, 1.8 wt.% to 1.9 wt.%, 1.9 wt.% to 2.0 wt.%, or any combination of two or more of the foregoing ranges, such as 0.5 wt.% to 1.2 wt.%, or any of the foregoing values.

[0014] Implementation Scheme 7: A curable liquid coating composition according to any one of the disclosed embodiments above, wherein, relative to the total weight of the composition, (e) the initiator is present in the following amounts, preferably independently in increasing order: at least about 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, 1.0 wt.%, 1.1 wt.%, 1.2 wt.%, 1.3 wt.%, 1.4 wt.%, 1.5 wt.%, 1.6 wt.%, 1.7 wt.%, 1. 8 wt.% or 1.9 wt.%, and preferably present in the following amounts, independently in ascending order: 6.0 wt.%, 5.5 wt.%, 5.25 wt.%, 5.0 wt.%, 4.9 wt.%, 4.8 wt.%, 4.7 wt.%, 4.6 wt.%, 4.5 wt.%, 4.4 wt.%, 4.3 wt.%, 4.2 wt.%, 4.1 wt.%, 4.0 wt.%, 3.9 wt.%, 3.8 wt.%, 3.7 wt.%, 3.6 wt.%, 3.5 wt.%, 3.4 wt.%, 3.3 wt.%, 3.2 wt.%, 3.1 wt.%. wt.%, 3.0 wt.%, 2.9 wt.%, 2.8 wt.%, 2.7 wt.%, 2.6 wt.%, 2.5 wt.%, 2.4 wt.%, 2.3 wt.%, 2.2 wt.%, 2.1 wt.%, 2.0 wt.% or 1.95 wt.%.

[0015] Implementation Scheme 8: A curable liquid coating composition according to any one of the disclosed embodiments above, wherein, relative to the total weight of the composition, (f) an accelerator different from the initiator is present in the following amounts, preferably independently in increasing order: at least about 0.01 wt.%, 0.02 wt.%, 0.02 wt.% to 0.03 wt.%, 0.03 wt.% to 0.04 wt.%, 0.04 wt.% to 0.05 wt.%, 0.05 wt.% to 0.06 wt.%, 0.06 wt.% to 0.07 wt.%, 0.07 wt.% to 0.08 wt.%, 0.08 wt.% to 0.09 wt.% 0.09 wt.% to 0.10 wt.%, and preferably present independently in increasing order as follows: not exceeding about 3.0 wt.%, 2.9 wt.%, 2.8 wt.%, 2.7 wt.%, 2.6 wt.%, 2.5 wt.%, 2.4 wt.%, 2.3 wt.%, 2.2 wt.%, 2.1 wt.%, 2.0 wt.%, 1.9 wt.%, 1.8 wt.%, 1.7 wt.%, 1.6 wt.%, 1.5 wt.%, 1.4 wt.%, 1.3 wt.%, 1.2 wt.%, 1.1 wt.%, 1.0 wt.%, 0.9 wt.%, 0.8 wt.%. wt.%, 0.7 wt.%, 0.6 wt.%, 0.5 wt.%, 0.4 wt.%, 0.3 wt.%, 0.2 wt.%, 0.175 wt.%, 0.15 wt.%, or any combination of two or more of the foregoing ranges, such as 0.3 wt.% to 0.8 wt.%, or any of the foregoing values.

[0016] Embodiment 9: A curable liquid coating composition according to any one of the disclosed embodiments above, wherein the organic solvent (g) is present in the following ranges relative to the total weight of the composition: 0.5 wt.% to 1 wt.%, 1 wt.% to 2 wt.%, 2 wt.% to 3 wt.%, 3 wt.% to 4 wt.%, 4 wt.% to 5 wt.%, 5 wt.% to 6 wt.%, 6 wt.% to 7 wt.%, 7 wt.% to 8 wt.%, 8 wt.% to 9 wt.%, and 9 wt.% to 10 wt.%. %, 10wt.% to 11wt.%, 11wt.% to 12wt.%, 12wt.% to 13wt.%, 13wt.% to 14wt.%, 14wt.% to 15wt.%, 15wt.% to 16wt.%, 16wt.% to 17wt.%, 17wt.% to 18wt.%, 18wt.% to 19wt.%, 19wt.% to 20wt.%, or any combination of two or more of the foregoing ranges, such as 0.5wt.% to 1.2wt.%, or any of the foregoing values.

[0017] Embodiment 10: A curable liquid coating composition according to any one of the disclosed embodiments above, wherein, relative to the total weight of the composition, (h) the additive is present in the following amounts: 0.1 wt.% to 0.2 wt.%, 0.2 wt.% to 0.3 wt.%, 0.3 wt.% to 0.4 wt.%, 0.4 wt.% to 0.5 wt.%, 0.5 wt.% to 0.6 wt.%, 0.6% to 0.7 wt.%, 0.7 wt.% to 0.8 wt.%, 0.8 wt.% to 0.9 wt.%, 0.9 wt.% to 1.0 wt.%, 1.0 wt.% to 1.1 wt.%, 1.1 wt.% to 1.2 wt.%, 1.2 wt.% to 1.3 wt.%, 1.3 wt.% to 1.4 wt.%, 1.4 wt.% to 1.5 wt.%, 1.5 wt.% to 1.6 wt.%, 1.6 wt.% to 1.7 wt.%, 1.7 wt.% to 1.8 wt.%, 1.8 wt.% to 1.9 wt.%, 1.9 wt.% to 2.0 wt.%, 2.1 wt.% to 2.2 wt.%, 2.2 wt.% to 2.3 wt.%, 2.3 wt.% to 2.4 wt.%, 2.4 wt.% to 2.5 wt.% 2.5 wt.% to 2.6 wt.%, 2.6 wt.% to 2.7 wt.%, 2.7 wt.% to 2.8 wt.%, 2.8 wt.% to 2.9 wt.%, 2.9 wt.% to 3.0 wt.%, 3.1 wt.% to 3.2 wt.%, 3.2 wt.% to 3.3 wt.%, 3.3 wt.% to 3.4 wt.%, 3.4 wt.% to 3.5 wt.%, 3.5 wt.% to 3.6 wt.%, 3.6 wt.% to 3.7 wt.%, 3.7 wt.% to 3.8 wt.%, 3.8 wt.% to 3.9 wt.%, 3.9 wt.%. % to 4.0 wt.%, 4.0 wt.% to 4.1 wt.%, 4.1 wt.% to 4.2 wt.%, 4.2 wt.% to 4.3 wt.%, 4.3 wt.% to 4.4 wt.%, 4.4 wt.% to 4.5 wt.%, 4.5 wt.% to 4.6 wt.%, 4.6 wt.% to 4.7 wt.%, 4.7 wt.% to 4.8 wt.%, 4.8 wt.% to 4.9 wt.%, 4.9 wt.% to 5.0 wt.%, or any combination of two or more of the foregoing ranges, such as 0.3 wt.% to 0.7 wt.%, or any of the foregoing values.

[0018] Implementation Scheme 11: The curable liquid coating composition of Implementation Scheme 10, wherein the additive comprises a rheology modifier present in any of the above embodiments in the range of 0.05% to 5%.

[0019] Implementation Scheme 12: A curable liquid curable coating composition according to any one of the disclosed embodiments above, wherein, relative to the total weight of the composition, (i) the degassing agent and / or defoamer are each present in the following ranges: 0.1 wt.% to 0.2 wt.%, 0.2 wt.% to 0.3 wt.%, 0.3 wt.% to 0.4 wt.%, 0.4 wt.% to 0.5 wt.%, 0.5 wt.% to 0.6 wt.%, 0.6 wt.% to 0.7 wt.%, 0.7 wt.% to 0.8 wt.%, 0.8 wt.% to 0.9 wt.%, 0.9 wt.%. Up to 1.0 wt.%, 1.0 wt.% to 1.1 wt.%, 1.1 wt.% to 1.2 wt.%, 1.2 wt.% to 1.3 wt.%, 1.3 wt.% to 1.4 wt.%, 1.4 wt.% to 1.5 wt.%, 1.5 wt.% to 1.6 wt.%, 1.6 wt.% to 1.7 wt.%, 1.7 wt.% to 1.8 wt.%, 1.8 wt.% to 1.9 wt.%, 1.9 wt.% to 2.0 wt.%, or any combination of two or more of the foregoing ranges, such as 0.3 wt.% to 0.7 wt.%, or any of the foregoing values.

[0020] For a variety of reasons, it is preferred that the curable liquid coating compositions disclosed herein, the uncured layer (optionally dried) of the deposited coating composition, and the cured thermally conductive dielectric coating can be prepared without certain components, i.e., without certain materials, whether added or generated in situ, except for a small amount of contaminants; or can be substantially free of certain components used in the prior art for similar purposes. Specifically, according to at least some embodiments of the invention, each of the following components, in increasing order of preference, independently for each of the preferred minimized components listed below, contains no more than 1.0%, 0.5%, 0.35%, 0.10%, 0.08%, 0.04%, 0.02%, 0.01%, 0.001%, or 0.0002%, more preferably in g / L, and more preferably in ppm, each of the following components: free bisphenol A, halogenated epoxy resin, nonylphenol, toluene, xylene, copper. Gold, silver, oxidizing agents such as peroxides and peroxy acids, permanganates, perchlorates, chlorates, chlorites, hypochlorites, perborates, hexavalent chromium, sulfuric acid and sulfates, nitric acid and nitrate ions; and fluorine, formaldehyde, formamide, hydroxylamine, cyanide, cyanate esters; solid particles of polymer / boron nitride composites, such as thermosetting polymer / BN particles and / or thermoplastic polymer / BN particles; dissolved or soluble boron substances, such as borax, borates; strontium; and / or free halide ions, such as fluoride ions, chloride ions, bromide ions, or iodide ions.

[0021] As used herein, “dielectric coating” refers to an electrically insulating coating. As will be described in further detail herein, the dielectric coating of embodiments of the present invention maintains electrical insulation, i.e., is practically non-conductive, preferably non-conductive, as measured by a HypotMAX 7720 or Ikonix 3865 and according to ASTM D 149-09 Hipot testing.

[0022] As used herein, the term "polymer" refers to an oligomer (IUPAC 1.2 (1996) defines an oligomer as a molecule "having properties that change significantly with the removal of one or more units"). For clarity, embodiments of the oligomers described herein are desirable to have (preferably in ascending order) more than about 3, 4, 5, or 6 up to about 500, 100, 50, 25, 15, or 10 monomer units or at least 500, 750, 800, 900, or 1000 Daltons, preferably less than 5000, 4000, 3000, or 2000 Daltons, homopolymers (e.g., prepared from a single monomeric substance), copolymers (e.g., prepared from at least two monomeric substances), and graft polymers. The terms "resin" and "polymer" are used interchangeably. Furthermore, the term "crosslinker" refers to a molecule containing two or more functional groups that can react with other functional groups normally present on a polymer and are capable of linking two or more polymer molecules by chemical bonds.

[0023] The transitional terms “comprising,” “substantially consisting of,” and “consisting of” are intended to indicate their generally accepted meanings in the patent dictionary; for those embodiments provided as “substantially consisting of,” the essential and novel feature is the ease of operation of the method or composition / system to provide a composition that exhibits the claimed functional features using only those listed components.

[0024] In this disclosure, the singular forms “a,” “an,” and “the” include plural references, and references to a particular numerical value include at least that particular value unless the context clearly indicates otherwise. Thus, for example, a reference to “compound” is a reference to one or more such compounds and their equivalents known to those skilled in the art, and so on. Furthermore, when indicating that a chemical moiety “may be” X, Y, or Z, this usage is not necessarily intended to exclude other options for that moiety; for example, the statement that a moiety “may be alkyl, aryl, or amino” does not necessarily exclude other options for that moiety, such as halogens, aralkyls, etc.

[0025] Throughout this specification, unless explicitly stated otherwise: percentages, “parts” and ratios are by weight or mass; unless otherwise stated, molecular weight (MW) is weight-average molecular weight; the word “molar” means “gram-molar”, and the word itself and all its grammatical variations can be used for any chemical substance defined by all types and quantities of atoms present therein, whether the substance is ionic, neutral, unstable, hypothetical, or actually a stable neutral substance with well-defined molecules.

[0026] It should be understood that, for clarity, certain features of this disclosure described herein in the context of separate embodiments may also be provided in combination in a single embodiment. That is, unless obviously incompatible or specifically excluded, each individual embodiment is considered to be combinable with any other embodiment, and such combination is another embodiment. Conversely, for brevity, the various features of this disclosure described herein in the context of a single embodiment may also be provided separately or in any sub-combination. Finally, while an embodiment may be described as part of a series of steps or a more general structure, each said step may also be considered an independent embodiment that can be combined with other embodiments.

[0027] Except in the operational embodiments, or where otherwise indicated, all figures used herein to represent the amount of an ingredient, reaction conditions, or defining parameters of an ingredient should be understood to be modified by the term “about” in all cases. When a value is expressed as an approximation by using the antecedent “about”, it should be understood that the particular value forms another embodiment. As used herein, “about X” (where X is a numerical value) preferably refers to ±10% of the value, including end values. Furthermore, when the term “about” precedes a range, it should be understood that the term modifies the listed end points and all points included in the range. For example, the phrase “about 1-10” should be understood to mean “about 1 to about 10” and “about x”, where x refers to any value between 1 and 10. Where applicable, all ranges are inclusive and composable. For example, when listing a range of “1 to 5”, the listed range should be interpreted to include ranges “1 to 4”, “1 to 3”, “1-2”, “1-2 & 4-5”, “1-3 & 5”, etc. Furthermore, when a list of alternatives is provided affirmatively, such a list can be interpreted as meaning that any alternative can be excluded, for example, by negative limitations in the claims. For instance, when the range “1 to 5” is stated, the stated range can be interpreted as including cases where any one of 1, 2, 3, 4, or 5 is negatively excluded; thus, the statement “1 to 5” can be interpreted as “1 and 3-5, but not 2”, or simply “not including 2.” In another instance, when a list of possible alternatives including “hydrogen, alkyl, and aryl” is provided, the enumerated list can be interpreted as including cases where any one of “hydrogen, alkyl, and aryl” is negatively excluded; thus, the enumeration of “hydrogen, alkyl, and aryl” can be interpreted as “hydrogen and aryl, but not alkyl”, or simply “not alkyl.”

[0028] This section provides a general overview of the present disclosure, rather than a complete disclosure of its entire scope or all features, aspects, or objectives. These and other features and advantages of the present disclosure will become more apparent to those skilled in the art from the detailed description of preferred embodiments. The accompanying drawings are described below. Attached Figure Description

[0029] Figure 1 A field emission scanning electron microscope (FESEM) image of a cross-section of a corner portion of a panel sample taken from an aluminum 3003 alloy battery cell container (commonly referred to as a square battery box) is shown, indicating the metal of the container, the cured thermally conductive dielectric coating adhered thereto, and the measured thickness of the cured coating at the corner portion.

[0030] Figure 2 It shows Figure 1Field emission scanning electron microscopy (FESEM) image of a cross-section of the left end portion of the panel sample, showing the metal of the container, the cured thermally conductive dielectric coating adhered thereto, and a marker indicating the measured thickness of the cured coating at the left end portion.

[0031] Figure 3 It shows Figure 1 A field emission scanning electron microscope (FESEM) image of a cross-section of the left middle portion of the panel sample, showing the metal of the container, the cured thermally conductive dielectric coating adhered to it, and a marker indicating the measured thickness of the cured coating at the left middle portion.

[0032] Figure 4 It shows Figure 1 Field emission scanning electron microscopy (FESEM) image of a cross-section of the right end portion of the panel sample, showing the metal of the container, the cured thermally conductive dielectric coating adhered thereto, and a marker indicating the measured thickness of the cured coating at the right end portion.

[0033] Figure 5 It shows Figure 1 Field emission scanning electron microscopy (FESEM) image of a cross-section of the right middle portion of the panel sample, showing the metal of the container, the cured thermally conductive dielectric coating adhered thereto, and a marker indicating the measured thickness of the cured coating at the right middle portion. Detailed Implementation

[0034] This disclosure can be more readily understood by referring to the following description, which is taken in conjunction with the appended summary, drawings, and embodiments (all of which form part of this disclosure). For the purposes of the following detailed description, it should be understood that the invention may take various alternative variations and sequences of steps unless expressly specified to the contrary. It should be understood that the invention is not limited to the specific products, methods, conditions, or parameters described and / or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to limit the claimed invention.

[0035] The present invention, as described herein, provides an improved dielectric coating that promotes heat dissipation, particularly for vehicle battery systems. The cured thermally conductive dielectric coating according to the invention provides good electrical insulation at low film thicknesses to reduce weight. The chemical properties of the coating composition provide a coating with better heat dissipation than other dielectric coatings at similar coating weights. The cured coating structure and low film thickness work synergistically to better transfer and dissipate heat from the substrate.

[0036] Deposition methods for dielectric coatings are also better suited for large-scale production lines, applied through less complex processes and using less time and energy, such as by spraying and / or printing.

[0037] As described above, an embodiment of the present invention is a curable liquid coating composition comprising: (a) Polyester resin; (b) Reactive diluents; (c) Thermally conductive filler; (d) Dispersant; (e) Initiator; and (f) An optional promoter that is different from the initiator; The polyester resin may include unsaturated polyester resins, preferably vinyl ester resins, and most preferably epoxy vinyl ester resins, such as epoxy acrylates and epoxy methacrylates, and combinations thereof.

[0038] The following provides a further description of the embodiments and components of the present invention. Polyester resin

[0039] Generally, various polyester resins, preferably polyester resins having one, two, or more unsaturated sites, are suitable as (a) the polyester resin used in the compositions of the present invention. Non-limiting examples include unsaturated polyester resins, such as vinyl ester resins; desired unsaturated polyester resins include epoxy vinyl esters, such as epoxy acrylates and epoxy methacrylates. These resins have one or more olefinic unsaturated sites, preferably at least about two C=C functional groups per molecule, and may have other functional groups. Some suitable polyester resins may have an acid value of about 0 to 50, 7 to 35, or 14 to 20 mg KOH / g.

[0040] Representative unsaturated polyester resins are described in U.S. Patent Nos. 4,742,121, 5,567,767, 5,571,863, 5,688,867, 5,777,053, 5,874,503 and 6,063,864, and PCT Publications WO94107674 A1, WO 00123495 A1 and WO 031101918 D, which are incorporated herein by reference.

[0041] Polyester resins can be prepared by the condensation of one or more carboxylic acids (e.g., mono-, di-, or polyfunctional unsaturated or saturated carboxylic acids) or their derivatives (e.g., acid anhydrides, C, alkyl esters, etc.) with one or more alcohols (including monofunctional, difunctional, and polyfunctional alcohols). The carboxylic acids or derivatives can be, for example, a mixture of unsaturated carboxylic acids or derivatives and saturated carboxylic acids or derivatives.

[0042] Unsaturated carboxylic acids or their derivatives may, for example, have about 3 to about 12, about 3 to about 8, or about 4 to about 6 carbon atoms. Representative unsaturated carboxylic acids and their derivatives include maleic acid, fumaric acid, chloromaleic acid, itaconic acid, citraconic acid, methylene glutaric acid, mesoconic acid, acrylic acid, methacrylic acid, and their esters or anhydrides. Desired unsaturated carboxylic acids and their derivatives include maleic acid, fumaric acid, fumarates, and their anhydrides. Unsaturated carboxylic acids or their derivatives may, for example, be present in amounts of about 20 to about 90 mol%, about 35 to about 75 mol%, or about 50 to about 65 mol% of the acid or acid derivative used to prepare unsaturated polyester resins. Saturated carboxylic acids and their derivatives may, for example, have about 8 to about 18, about 8 to about 15, or about 8 to about 12 carbon atoms. Representative saturated carboxylic acids and their derivatives can be aromatic, aliphatic, or combinations thereof, and include succinic acid, glutaric acid, d-methylglutaric acid, adipic acid, sebacic acid, pimelic acid, phthalic anhydride, phthalic acid, isophthalic acid, terephthalic acid, dihydrophthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid or anhydride, tetrachlorophthalic acid, chlorobacteric acid or anhydride, dodecanedicarboxylic acid, nadic anhydride, cis-5-norbornene-2,3-dicarboxylic acid or anhydride, dimethyl-2,6-cycloalkyldicarboxylic acid ester, dimethyl-2,6-cycloalkyldicarboxylic acid, cycloalkyldicarboxylic acid or anhydride, and 1,4-cyclohexanedicarboxylic acid. Other representative carboxylic acids include ethylhexanoic acid, propionic acid, benzene-1,2,4-tricarboxylic acid, benzoic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, and their anhydrides. Representative aromatic saturated carboxylic acids include phthalic acid, isophthalic acid, and their derivatives. Representative aliphatic saturated carboxylic acids include 1,4-cyclohexanedicarboxylic acid, hexahydrophthalic acid, adipic acid, and their derivatives. Saturated carboxylic acids or their derivatives may be present, for example, in amounts of about 10 to about 80 mol%, about 25 to about 65 mol%, or about 35 to about 50 mol% of the acid or acid derivative used in the preparation of unsaturated polyester resins. Furthermore, aromatic carboxylic acids may be present, for example, in amounts of 0 to 100%, 0 to about 50%, or 0 to about 25% of the saturated acid or acid derivative used in the preparation of unsaturated polyester resins, and aliphatic carboxylic acids may be present, for example, in amounts of 0 to 100%, about 50 to 100%, or about 75 to 100% of the saturated acid or acid derivative used in the preparation of unsaturated polyester resins.

[0043] Representative alcohols used in the preparation of unsaturated polyester resins include alkyl glycols and oxaalkyl glycols, such as ethylene glycol, 1,2-propanediol, propane-3-diol, 1,3-butanediol, butene-1,4-diol, hexane-1,6-diol, diethylene glycol, triethylene glycol, polyethylene glycol, cyclohexane-1,2-diol, 2,2-bis-(p-hydroxycyclohexyl)-propane, 5-norbornene-2,2-dihydroxymethyl, 2,3-norbornene diol, cyclohexanediol, etc. Alcohols with neo-structures are preferred, such as 1,2-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethylheptanediol, 2,2-dimethyloctanediol, 2,2-dimethyl-1,3-propanediol (also known as neopentylene glycol), pentaerythritol, dipentaerythritol, tripentaerythritol, trimethylolpropane, di-trimethylolpropane, 2,2,4-trimethyl-1,3-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, and 3-hydroxy-2,2-dimethylpropyl-3-hydroxy-2,2-dimethylpropane (dimetphyrolpanate). Monofunctional alcohols can also be used to prepare unsaturated polyester resins. Representative monofunctional alcohols include benzyl alcohol, cyclohexanol, 2-ethylhexanol, 2-cyclohexylethanol, 2,2-dimethyl-1-propanol, and lauryl alcohol. When using monofunctional alcohols, the amount may be, for example, less than about 10 mol% or less than about 5 mol% of the alcohol used to prepare unsaturated polyester resins.

[0044] Unsaturated polyester resins can be prepared using esterification technology catalysts (e.g., esterification or transesterification catalysts) familiar to those skilled in the art. The esterification process typically proceeds until the polyester reaches an acid value corresponding to the desired molecular weight. For example, the final acid value can be from about 7 to about 30, the number-average molecular weight (Mn) can be from about 800 to about 3600, and the weight-average molecular weight (Mw) can be from about 1,300 to about 11,000. The acid value can be reduced by increasing the reaction temperature, conducting the reaction for a longer time, or by adding an acid neutralizer familiar to those skilled in the art.

[0045] Unsaturated polyester resins can also be formed by reacting a low-weight polyester (i.e., an ester oligomer chain containing a small number of repeating ester units) having a weight-average molecular weight of about 200 to about 4000 with a diisocyanate and a hydroxyalkyl (meth)acrylate to provide a polyurethane acrylate with terminal vinyl groups, as described in WO2006091446A1. The polyurethane acrylate resin can be used as is or blended with other unsaturated polyester resins such as aliphatic or aromatic unsaturated polyester resins.

[0046] In some embodiments, the unsaturated polyester resin is reacted with a reactive diluent such as styrene monomer using a free radical initiator. The double bonds on the polyester and the side-chain double bonds on the styrene diluent provide pathways for chain extension and crosslinking.

[0047] The epoxy vinyl esters used in this invention are typically derived from epoxy resins, wherein the ethylene oxide group has been reacted to generate functional groups having side-chain double bonds. Desiredly, modification of the epoxy resin is achieved by reacting the ethylene oxide group with α-β-unsaturated acrylates, such as acrylates, thereby generating acrylic (double bond) end groups. For example, bisphenol A can react with methacrylic acid to form epoxy methacrylates.

[0048] Examples of suitable epoxy resins include bisphenol A epoxy resins, alicyclic epoxy resins, epoxy phenolic varnishes, and epoxy cresol phenolic varnishes.

[0049] Typically, vinyl ester resin compositions can be prepared by dissolving the vinyl ester in a suitable compatible diluent to facilitate processing, curing, and provide excellent mechanical properties. Such compatible diluents may include, for example, styrene, chlorostyrene, vinyltoluene, α-methylstyrene, diallyl phthalate, triallyl cyanurate, acrylates, and methacrylates, such as bisphenol A epoxy diacrylate and trimethylpropane triacrylate, as well as divinylbenzene. Styrene and mono-, di-, and tri-(meth)acrylates are preferred compatible diluents. However, the resin can also be dissolved in a non-reactive diluent, such as acetone, when a low application viscosity is required, or when properties obtainable with pure resin alone are desired.

[0050] The vinyl ester resin of the present invention is known in the art and can be prepared by an addition reaction between an olefinically unsaturated monocarboxylic acid and an epoxy resin, wherein the epoxy resin has a plurality of ethylene oxide groups that react with acids and R groups that do not participate in the reaction, wherein R can be selected, for example, alkylene, cycloalkylene, arylene, arylene, oxyaryl, oxyaryl, and cycloalkylene esters. Methods for preparing vinyl ester resins suitable for use in this invention include those disclosed in U.S. Patent No. 3,256,226 to Fekete et al., and Nos. 3,317,465 to Doyle et al., 3,345,401 to May, 3,373,221 to May, 3,377,406 to Newey et al., 3,432,478 to May, 3,548,030 to Jernigan, and Nos. 3,564,074 to Swisser et al., 3,634,542 to Dowd et al., and 3,637,618 to May, which are incorporated herein by reference.

[0051] Typically, the vinyl ester resins of this invention are prepared using suitable catalysts, such as tertiary amines, phosphine, alkali metal salts, or onium salts. Suitable components for several vinyl ester resins include, but are not limited to, bisphenol A epoxy resins and phenolic varnish epoxy resins reacted with unsaturated acids such as acrylic acid and methacrylic acid and their derivatives.

[0052] Increased variety of vinyl ester resins can be obtained by selecting unsaturated monomer diluents as described below, which can be combined with and copolymerized with vinyl ester resins. Preferred vinyl ester resins for use in this invention are bisphenol A (BPA)-epoxy vinyl ester resins. These resins can be used in the resin compositions of this invention, with or without reactive diluents, such as co-reactive monomers like styrene.

[0053] BPA-epoxy vinyl ester resins offer processing properties similar to ambient temperature-cured polyester systems, but exhibit excellent physical properties similar to cured epoxy systems upon curing. Therefore, the desired properties of these two different thermosetting resins can be combined into a single resin system.

[0054] Polyester resins can be co-cured with free radical initiators and reactive diluents such as styrene monomers. The double bonds in the polyester backbone and the side chain double bonds in the styrene monomers provide pathways for chain growth and crosslinking. Reactive diluent

[0055] Desiredly, one or more reactive diluents can be used to reduce the viscosity of the composition and can at least partially replace the solvent. Typically, the reactive diluent copolymerizes with the resin during the curing process and is incorporated into the coating. The one or more reactive diluents can be monofunctional, polyfunctional, or a mixture thereof, and monofunctional diluents can be selected to increase the ductility of the cured coating, while polyfunctional diluents can be selected to increase the crosslinking density of the cured coating. In some embodiments, the reactive diluent is preferably one or more free radical reactive diluents capable of participating in free radical polymerization reactions; non-limiting examples are compounds having olefinic unsaturation. Representative examples include substituted and unsubstituted styrene, methyl methacrylate (MMA), and monofunctional, difunctional, and polyfunctional esters of unsaturated monofunctional acids (e.g., acrylic acid and methacrylic acid) with alcohols or polyols having 1 to about 18 carbon atoms; and monofunctional, difunctional, and polyfunctional esters of unsaturated monofunctional alcohols with carboxylic acids having 1 to about 18 carbon atoms or derivatives thereof. Other suitable reactive diluents include, for example, acrylates, methacrylates, phthalates such as diallyl phthalate, triallyl cyanurate, vinyl ethers, etc.

[0056] Representative acrylates and methacrylates include butanediol dimethacrylate, trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate (EGDMA), polyethylene glycol dimethacrylate (PEGDMA), polypropylene glycol dimethacrylate (PPGDMA), trimethylolpropane trimethacrylate (TMPMA), tetramethylolpropane trimethacrylate, dipropylene glycol dimethacrylate, isodecyl methacrylate, 1,3-butanediol dimethacrylate, 2-hydroxyethyl methacrylate (2-HEMA), 1,6-hexanediol dimethacrylate (HDODMA), triethylene glycol dimethacrylate (TEGDMA), acetoacetoxyethyl methacrylate (AAEM), and their acrylate counterparts.

[0057] Mixtures of reactive diluents may be used. Preferred reactive diluents include styrene, methyl methacrylate, TMPTMA, vinyltoluene, p-tert-butylstyrene, p-methylstyrene, EGDMA, 2-HEMA, and mixtures thereof. The reactive diluent may, for example, comprise about 5 to about 60 wt.%, about 10 to about 50 wt.%, or about 20 to about 40 wt.% of the coating composition. Thermally conductive boron nitride filler

[0058] The thermally conductive filler (c) comprises boron nitride, preferably hexagonal BN. Hexagonal boron nitride (“h-BN”) is an inert, lubricating ceramic material having a graphite-like, plate-like hexagonal crystal structure. In one embodiment, the invention relates to a mixture of at least two different boron nitride materials that provides synergistic effects, such as improved performance. The different boron nitride powder materials are selected from plate-like and non-plate-like forms. Non-plate-like boron nitride is defined herein as any boron nitride other than plate-like boron nitride. For example, non-plate-like boron nitride powder materials may comprise boron nitride agglomerates composed of boron nitride plates. Agglomerates of boron nitride powder materials may have spherical or irregular shapes and different sizes from each other. Other non-plate-like boron nitride powder materials include, but are not limited to, partially crystalline boron nitride, amorphous boron nitride, and nano-boron nitride powder materials with different properties (including but not limited to surface area, size, aspect ratio, density). According to one embodiment, the two different boron nitride powder materials may be two different spherical agglomerates of boron nitride powder materials with different particle sizes.

[0059] To aid in reactant viscosity control, the thermally conductive ceramic particles can have a specific particle size distribution within a controlled aspect ratio range. Therefore, the particle size can be between 0.01 and 100 micrometers. In another embodiment, the thermally conductive ceramic particles can have an average particle size of 0.01-100 micrometers or between 1 and 25 micrometers. The aspect ratio of spherical, rod-shaped, or plate-shaped particles can preferably be 1-50 or 1-10.

[0060] In one embodiment, one of the two different BN powder materials comprises crystalline or partially crystalline boron nitride particles prepared by methods known in the art, in the form of agglomerated boron nitride or flake boron nitride. These may include spherical BN particles. In a preferred embodiment, the BN powder material comprises flakes, preferably at least 50%, 60%, or 70% flakes.

[0061] In one embodiment, the particle size distribution having a D50 can range from about 1, 1.2, 1.4, 1.6, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 micrometers to about 10.0, 9.5, 9.0, 8.5, 8.0, 7.5, 7.0, 6.5, or 6.0 micrometers. In another embodiment, the BN particles have a particle size distribution having a D90 in the particle size range of 12-25, 14-24, or 16-22 micrometers. The particle size distribution can be measured by dispersion in ethanol using laser scattering (e.g., Mastersizer 2000).

[0062] The surface area of ​​BN flake powder material is expected to be less than 20 m². 2 / g, and the surface area can be as low as less than 3.0m². 2 / g. Preferably, the surface area and aspect ratio are selected such that the filler does not excessively increase the viscosity and the particles do not extend beyond the surface of the cured coating.

[0063] Optionally, the thermally conductive filler may comprise ceramic particles selected from a variety of non-hexagonal boron nitride (BN) materials, which provide thermal conductivity at the loading concentrations described herein. Examples of thermally conductive ceramic particle materials include alumina, aluminum nitride, boron nitride, beryllium oxide, zinc oxide, titanium dioxide, magnesium oxide, and combinations thereof. Such particles impart significant thermal conductivity to the coatings of the present invention and enhance their dielectric strength. Co-fillers such as alumina, alumina trihydrate (ATH), or calcium carbonate may be used in the coating composition to replace a portion of the boron nitride, provided that the performance tests described herein do not unacceptably degrade. Wetting and dispersing agents

[0064] The compositions of the present invention contain wetting and dispersing agents, which are added to reduce the agglomeration and sedimentation of inorganic fillers, particularly BN and silica fillers, in the coating composition.

[0065] A key performance criterion for wetting and dispersing agents (d) is their ability to inhibit the thickening effect of inorganic fillers in coating compositions. Excessive thickening of the coating composition before application to a substrate can negatively impact sprayability, the surface roughness of the cured coating, and cause air pockets to remain within the coating. Wetting and dispersing agents (d) are components containing one or more groups X that have an affinity for fillers, and thus can covalently, ionicly, and / or through physical adsorption to bind to the filler surface. Wetting and dispersing agents also contribute to the stabilization of filler particles and prevent agglomeration, which would otherwise lead to solid sedimentation and thus a non-uniform product. One or more groups Y in the wetting and dispersing agent (d) that ensure compatibility with the surrounding medium typically play a role in this stabilization.

[0066] The suitable wetting and dispersing agent (d) used is preferably a relatively high molecular weight wetting and dispersing agent (d), more particularly a polymeric wetting and dispersing agent (d). The suitable functional polymer preferably has a number average molecular weight (Mn) of at least 400 g / mol, more preferably at least 800 g / mol, and more preferably at least 2000 g / mol. The maximum molecular weight Mn is effectively 100,000 g / mol, preferably 50,000 g / mol, and more preferably 25,000 g / mol. In one embodiment, the wetting and dispersing agent can be in the range of at least 2000 g / mol to 50,000 g / mol. The number average molecular weight can be determined by gel permeation chromatography relative to a polystyrene standard.

[0067] More specifically, the wetting and dispersing agent (d) used according to the present invention may be selected from linear or branched polymers and copolymers that are compatible with the surrounding medium and functional groups and / or groups having filler affinity. Examples of lubricants and dispersants include alkylammonium salts of polymers and copolymers, polymers and copolymers having acidic groups, comb-shaped and block copolymers, such as block copolymers with basic groups having filler affinity, optionally modified acrylate block copolymers, optionally modified polyurethanes, optionally modified and / or optionally salt-forming polyamines, epoxide-amine adducts, phosphate esters, especially phosphate esters of polyethers, polyesters and polyether-esters, basic or acidic ethoxylates, such as acidic 1,2-dicarboxylic anhydride monoesters of alkoxylated monoamines or polyamines or alkoxylated monoalcohols, reaction products of unsaturated fatty acids with maleic anhydride and / or mono-, di- and polyamines; and amino alcohols, and unsaturated 1,2-dicarboxylic acids and their anhydrides and their salts and their reaction products with alcohols and / or amines; polymers and copolymers having fatty acid residues, optionally modified polyacrylates, such as transesterified polyacrylates, optionally modified polyesters, such as acid-functionalized and / or amino-functionalized polyesters, polyphosphate esters, and mixtures thereof.

[0068] Polyisocyanate-based polymer wetting and dispersing agents (d) can be prepared by addition reactions of monohydroxy compounds, diisocyanate functional compounds, and compounds having tertiary amino groups onto existing NCO groups of polyisocyanates containing isocyanurate, biuret, carbamate, and / or urethane groups. Amine-based wetting and dispersing agents (d) can be obtained using amine salts (salting) of amine functional compounds prepared with acids.

[0069] The following group of wetting and dispersing agents (d) exhibit particularly good effects in the compositions of the present invention: (a) reaction products of unsaturated fatty acids with maleic anhydride and / or monoamines, diamines and polyamines, amino alcohols, and (b) unsaturated 1,2-dicarboxylic acids and their anhydrides and salts and their reaction products with alcohols and / or amines, unsaturated polyamine amides and their salts, and lower molecular weight acidic polyesters.

[0070] These types of wetting and dispersing agents (d) are commercially available products, such as BYK-Chemie from Wesel, under the trade names BYK-220 S, BYK-P 9908, BYK-9076, BYK-9077, BYK-P 104, BYK-P 104 S, BYK-P 105, BYK-W 9010, BYK-W 920, BYK-W 935, BYK-W 940, BYK-W 960, BYK-W 965, BYK-W 966, BYK-W 975, BYK-W 980, BYK-W 990, BYK-W 995, and BYK-W 996 and the trade name groups BYKUMEN, BYKJET, LACTIMON, ANTI-TERRA, and DISPERBYK. When low levels of volatile organic compounds, particularly organic solvents, are required, the above-mentioned commercially available products are desirable as solvent-free active materials, preferably free of volatile components. Initiator

[0071] Initiators can be added to the curable liquid coating composition when applied to the surface, such as by mixing part A and part B in a spray gun. Alternatively, a potential initiator can be included in the curable liquid coating composition provided to the end user and activated during application. Representative initiators include free radical generators such as peroxides (e.g., benzoyl peroxide, methyl ethyl ketone peroxide (also known as 2-butanone peroxide); cumene hydroperoxide, etc.), azoalkane catalysts, and commercially available initiators or catalysts such as Luperox. TM DDM9 and DHD9 catalysts (from Arkema), HIGH POINT TM 90 catalyst (from Chemtura) and CADOX TML50a catalyst (from Akzo Nobel). Representative radiation-activated or thermally activated initiators or catalysts include IRGACURE. TM 819 initiator (from Ciba Specialty Chemicals) and cumene hydroperoxide. When used, the amount of initiator or catalyst may be, for example, about 0.1 to about 5.0 wt.%, 0.2 to 4.0 wt.%, 0.5 to about 3.0 wt.%, about 1 to about 2.5 wt.%, or about 1.2 to about 2 wt.% of the weight of the unsaturated polyester resin. Accelerator

[0072] Another component that may be present is one or more accelerators, different from the initiator. Representative accelerators for curable liquid coating compositions are electron-donating substances that facilitate the decomposition of the initiator or catalyst and promote or accelerate the curing of the curable liquid coating composition at relatively low temperatures, such as from about 0 to about 30°C. Representative accelerators include metal compounds (e.g., cobalt, manganese, potassium, iron, vanadium, copper, and aluminum salts of organic acids); amines (e.g., dimethylaniline, diethylaniline, phenyldiethanolamine, dimethyl-p-toluidine, and 2-aminopyridine); Lewis acids (e.g., boron fluoride dihydrate and ferric chloride); bases (e.g., tetramethylammonium hydroxide); quaternary ammonium salts (e.g., trimethylbenzylammonium chloride and tetrahydroxymethylphosphonium chloride); sulfur compounds (e.g., dodecyl mercaptan and 2-mercaptoethanol); dimethylacetoacetamide; ethyl acetoacetate; methyl acetoacetate, and mixtures thereof. For example, cobalt salts of organic acids can be used to promote the low-temperature decomposition of peroxide catalysts and the curing of the disclosed curable liquid coating compositions. Preferred accelerators include metal salts of organic acids as described above, particularly cobalt alkylates, such as cobalt 2-ethylhexanoate, cobalt octanoate, potassium octanoate, dimethyl acetoacetamide, ethyl acetoacetate, methyl acetoacetate, and mixtures thereof. Accelerators are typically used in amounts of about 0.03 to about 3 wt.%, or about 0.05 to about 2 wt.%, or 0.1 to about 1 wt.% of the curable liquid coating composition. Inhibitors

[0073] Another desirable component that may be present is an inhibitor. One or more inhibitors help extend or maintain the shelf life of the uncured curable liquid coating composition by inhibiting premature polymerization. Suitable inhibitors may include free radical inhibitors and / or scavengers, such as quinones (e.g., hydroquinone (HQ), methyl hydroquinone (THQ), mono-tert-butyl hydroquinone (MTBHQ), di-tert-butyl hydroquinone (DTBHQ), naphthoquinone (NQ), and monomethyl ether hydroquinone (MEHQ)), butylated hydroxytoluene (BHT), tert-butylcatechol (TBC), etc. Inhibitors may be present, for example, in amounts of about 0.01 to about 0.5 wt.%, about 0.01 to about 0.3 wt.%, or about 0.01 to about 0.1 wt.% of the curable liquid coating composition. organic solvents

[0074] Optional organic solvents added to components can be used to reduce the viscosity of coating compositions. Added solvents, such as butyl acetate or acetone, are distinct from incidental solvents contained in the raw materials and incorporated into the coating composition along with the raw materials. Examples of incidental solvents contained in the raw materials include mineral oil and naphtha. As used herein, solvent refers to chemicals (except in trace amounts) that are removed during the manufacturing process but not incorporated into the final product. rheology modifiers

[0075] Optional rheology modifiers can be used to control the viscosity characteristics, bulk and hold-up characteristics of vinyl ester resins by imparting thixotropy to the vinyl ester resin composition. Suitable examples include modified and unmodified pyrolytic (fumed) amorphous silica or synthetic amorphous silica, preferably alkaline or hydrophobically modified silica. In one embodiment, the rheology modifier can be produced by combining an unsaturated polyester resin with fumed silica. Preferably, the rheology modifier is selected from those having one or more of the following properties: 150 to 210 m 2 / g BET surface area; SiO2 content greater than or equal to 98.5 wt.%; and NaO content less than or equal to 0.5 wt.%. These types of rheology modifiers are available as commercially available products, such as Cab-O-Sil M-5 (a fumed silica product manufactured by Cabot Corporation) and Aerosil®, which is commercially available from Evonik Operations GmbH. Adhesion promoter

[0076] Optional adhesive promoters may be included in the compositions of the present invention to improve adhesion to metal substrates, such as cross-cut adhesion and moisture resistance. Organosilane compounds may be used to promote adhesion, improve strength, and provide enhanced resistance to moisture conditions. Other known adhesive promoters include organotitanates, organochromium, and zirconium complexes.

[0077] In some embodiments, an adhesion promoter is used, and the adhesion promoter may include silanes, such as epoxy resins, vinyl / acrylate / methacrylate functionalized silanes, such as Dynasylan products, and some polyester-based products, such as TEGO Addbond products, all available from Evonik Operations GmbH; and organophosphates, such as HEMA-phosphates.

[0078] Examples of silane coupling agents include, but are not limited to, aminosilanes such as γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-(aminoethyl)-γ-aminopropyltrimethyldimethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane; epoxysilanes such as -(3,4-epoxycyclohexyl)-ethyltrimethoxysilane, γ-epoxypropoxypropyltrimethoxysilane, and γ-epoxypropoxypropyltriethoxysilane; vinylsilanes such as vinyltri(-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane; hexamethyldisilazane; and γ-mercaptopropyltrimethoxysilane.

[0079] Examples of titanate coupling agents include, but are not limited to, tetraisopropoxytitanium, tetra-n-butoxytitanium, tetrabutyl titanate dimer, tetrastearyl titanate, acetylacetone titanium, titanium lactate, tetraoctyl glycol titanate, titanium lactate, and tetrastearyloxytitanium. Flexing agent

[0080] Optional component flexibility agents may be included in embodiments of the invention. Suitable examples of flexibility agents include methyl methacrylate-butadiene-styrene (MBS) and similar rubbers, one example being Clearstrength XT-100, available from Arkema Inc.; and polysulfide resins, such as Thioplast resin, available from Nouryon Chemicals LLC. plasticizer

[0081] In certain embodiments of the invention, optional plasticizers may be used to increase the flexibility and toughness of the cured dielectric coating. Increased toughness of the dielectric coating can reduce cracking and contribute to longer battery life, particularly in batteries used in mobile vehicles. Examples of optional plasticizers include phthalates, benzoates, dibenzoates, phthalates, naphthalene sulfonates, trimellitates, adipates, sebacic acid esters, maleates, sulfonamides, organophosphates, and polybutene. Degassing agent

[0082] Another component that may be present is one or more air-releasing agents, also known as degassing agents. Air-releasing agents help release air from the curable liquid coating composition before it fully cures, thereby reducing air entrainment, which can lead to weaknesses or porosity. Typical air-releasing agents include silicone or non-silicone materials, including solutions of polyalkylene ethers and / or polyolefins in petroleum distillates, silicone degassing agents, acrylic polymers, hydrophobic solids, and mineral oil-based paraffins. Commercially available air-releasing agents include BYK-066, BYK-077, BYK-500, BYK-501, BYK-515, and BYK-555 degassing agents (from BYK-Chemie USA, Inc.). When used, the air-releasing dosage can be, for example, up to about 1.5 wt.%, up to about 1 wt.%, or about 0.1 to about 0.5 wt.% of the curable liquid coating composition. filler or extender

[0083] In addition to the thermally conductive filler in component (c), the curable liquid coating may optionally contain an extender filler different from the thermally conductive filler, such as clay, ground limestone, mica, talc, aluminum trihydrate, barium sulfate, precipitated silica, or silica different from the rheology modifier. The extender filler may also contribute to imparting thixotropic properties to the curable liquid coating of the present invention. While it must be emphasized that the curable liquid coating composition of the present invention containing the rheology modifier described above can be produced without additional extender fillers without diminishing its performance, such additional fillers may still be added if necessary. These amounts of such fillers are not limited, although they are typically added in amounts from about 5 to about 40 wt% of the curable liquid coating composition.

[0084] In some embodiments of the curable liquid coating of the present invention, which can come into contact with moisture or aqueous materials in the environment of use, the curable liquid coating composition is preferably sufficiently free of extender fillers that readily undergo chemical or physical reactions (e.g., swelling, dissolution, or hydration) with moisture or aqueous materials. In this way, the cured coating does not exhibit whitening, delamination, or failure after prolonged contact with moisture or aqueous materials. In this case, typical extender fillers include chopped or ground glass fibers, talc, silica, titanium dioxide, wollastonite, mica, alumina trihydrate, clay, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, and barium sulfate. While small amounts of water-sensitive extender fillers are permissible, it is preferably no more than about 2 wt.%, more preferably no more than about 1 wt.%, including no more than 0.8, 0.5, 0.3, and 0.1 wt.% of water-sensitive extender fillers in the curable liquid coating composition. Other additives

[0085] As described above, curable liquid coating compositions may contain a number of other optional additives, such as coupling agents, defoamers, pigments and dyes, plasticizers, flame retardants, chelate-modified epoxy resins, auxiliary impact modifiers / toughening agents, fillers, flow control agents, antioxidants, non-reactive diluents, extenders, or other additives.

[0086] The curable liquid coating composition of the present invention may contain one or more additional thermally conductive fillers. Examples of thermally conductive fillers include alumina (Al₂O₃), aluminum nitride (AlN), magnesium oxide (MgO), zinc oxide (ZnO), silicon nitride (Si₃N₄), aluminum powder, and graphite, etc.; any combination of these or similar thermally conductive fillers is acceptable as long as they do not unduly interfere with the benefits of the dielectric and thermal conductivity properties of the present invention. Fillers of different forms having the same chemical composition, such as crystals, nanotubes, sheets, amorphous materials, etc., may also be used. When the curable liquid coating composition contains additional thermally conductive fillers, the content of the thermally conductive filler is 5 wt.% or more, preferably 10 wt.% or more, more preferably 15 wt.% or more, based on the curable liquid coating composition. The content of the additional thermally conductive filler is 45 wt.% or less, preferably 35 wt.% or less, more preferably 25 wt.% or less, based on the curable liquid coating composition.

[0087] Examples of flame retardants include antimony oxides, halogenated hydrocarbons, halogenated esters, halogenated ethers, brominated flame retardants, and halogen-free compounds such as organophosphorus compounds, organonitrogen compounds, and intumescent flame retardants.

[0088] Examples of antioxidants include sodium sulfite, sodium metabisulfite, sodium bisulfite, sodium thiosulfate, and dibutylphenol.

[0089] Examples of UV stabilizers include benzophenone, benzotriazole, substituted acrylates, aryl esters, and compounds containing nickel or cobalt salts.

[0090] Examples of coupling agents include chromium(III) compounds, silane coupling agents, titanate coupling agents, zirconium coupling agents, magnesium coupling agents, and tin coupling agents.

[0091] Examples of pigments or dyes include chromates, sulfates, silicates, borates, molybdates, phosphates, vanadates, cyanates, sulfides, azo pigments, phthalocyanine pigments, anthraquinones, indigo, quinacridones, and dioxazine dyes. Various embodiments of the invention are described throughout this disclosure. In each embodiment described herein, the curable liquid coating composition is preferably a two-part coating composition, wherein the two parts are mixed together for a sufficient period of time prior to application, or optionally mixed together in the nozzle during or immediately prior to application. The preparation of two-component compositions is a conventional method to prevent premature reaction of the reactive components of the composition. Typically, part A comprises a resin and other components that react with an initiator, as well as suitable carriers, additives, and auxiliaries; and part B comprises an initiator and any carrier or additive suitable for packaging with the initiator. Those skilled in the art will understand that embodiments listing all components together describe mixtures of parts A & B, as well as two-part compositions comprising parts A and B prior to combination.

[0092] In some embodiments, the curable liquid organic-based coating composition may be a two-component composition comprising portions A and B, which are combined immediately before application. Therefore, the invention extends to a two-part package providing separate reservoirs for portions A and B. Portion A typically contains a resin, solvent, and additives, as well as other components that react with portion B at ambient temperature; while portion B typically contains one or more initiators that promote the reaction of both portions upon combination, and may contain other components that react with portion A. As described above, portions A and B are mixed together to form a curable liquid coating composition for deposition. This disclosure may also include single-component compositions that provide at least some of the benefits of the invention, wherein the reaction of the combined components is prevented or slowed down by known means, such as reversible blocking of initiators, resins, and / or accelerators.

[0093] Methods for depositing layers of curable coating compositions can include spraying, printing, dipping, applicator deposition, and other known processes. Curable liquid coating compositions can be applied, for example, to the surface of all articles using conventional techniques, such that parts (e.g., vehicle parts or components, cooling devices, etc.) are completely encapsulated by, for example, dipping or spraying, with spraying application being preferred for this purpose. Alternatively, the curable liquid coating composition can be applied to specific portions of the part using any number of masking or printing methods known in the art. In some embodiments, the curable liquid coating composition desirably has a viscosity suitable for spraying and / or printing, and the presence of zero or optionally low solvent content, which facilitates the deposition of a thin, void-free coating, thereby providing complete substrate edge coverage through the uncured deposited coating composition layer. Low solvent content can be, for example (preferably in ascending order), less than 50, 40, 30, 20, 15, 10, 8, 6, 4, 2, or 1 wt.%, more preferably values ​​expressed in grams per liter or mg per liter.

[0094] After optional drying or solvent flash evaporation, the uncured layer can be cured or transported and / or incorporated into an assembly, and then cured. The cured, preferably cross-linked, composition thus forms a thermally conductive dielectric layer, typically in the form of a coating adhered to a substrate. Preferred curing methods include thermal and / or photochemical radiation, such as UV, as described herein.

[0095] The deposition of curable liquid organic-based coating compositions can produce a void-free, cured thin coating that provides continuous coverage at the edges of the substrate and good overall electrical insulation. The cured coating can have a thickness of about 1.75, 2.0, 2.5 to about 3.0, 3.5, 4 mils (meaning one-thousandth of an inch), or about 40, 50, 65 to about 75, 90, or 100 micrometers (also referred to herein as “μm” and “micrometer”). In contrast, cured UV and powder coatings require thicknesses greater than 5 mils (>127 μm) to greater than 10 mils (>254 μm) to provide a void-free cured coating that covers the substrate edges with the necessary thickness and has no bare spots to achieve electrical insulation. Substrates containing the cured coating according to the invention are expected not to exhibit visible edge effects, such as excessive thickness at the edges or a frame effect, even at the lower coating thicknesses described above; these defects are typically present in contrast coatings.

[0096] As measured and described herein, the cured dielectric coatings according to various aspects of the invention provide rapid heat dissipation and good electrical insulation with high dielectric strength. Rapid heat dissipation is evaluated by testing the thermal conductivity and thermal resistance of the cured coating. The cured dielectric coatings according to the invention exhibit high thermal conductivity and / or low thermal resistance as measured according to ASTM D5470, thus facilitating heat dissipation. In some embodiments, the cured dielectric coatings of the invention exhibit thermal conductivity greater than about 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, or 0.55 W / mK (preferably in ascending order).

[0097] Embodiments of the cured dielectric coating of the present invention also exhibit low thermal resistance per mil coating thickness, wherein the amount is less than about 0.080, 0.077, 0.075, 0.074, 0.072, 0.070, 0.068, 0.066, 0.064, 0.062, 0.060, 0.059, 0.058, 0.057, 0.056, 0.055, 0.054, 0.053, 0.052, 0.051, 0.0515, 0.050, 0.049, 0.048, 0.047, 0.046, or 0.045 K / W per mil coating thickness. In contrast, Comparative Example 1 has a thermal resistance of 0.191 K / W / mil coating thickness, which is more than 2.5 times greater than the thermal resistance of the most insulating coating of the present invention. According to some embodiments of the invention, thermal resistances as low as 0.05, 0.06, 0.08, 0.16, and 0.17 K / W can be achieved with coating thicknesses ranging from about 1.1 to about 3 mils. For example, a thicker coating of the invention has a thermal resistance of 0.39 K / W at 7 mils and only 0.8 K / W at a thickness of 10.8 mils. In contrast, Comparative Example 1 exhibits significantly better thermal insulation, with a thermal resistance of 1.13 K / W at 5.9 mils and 1.53 K / W at 8 mils.

[0098] The electrical insulation of the cured coating of the present invention is considered to be good, wherein the coating conducts very little, preferably not, at a dielectric withstand voltage greater than 2.0 kV, preferably greater than 3.0 kV, preferably greater than 4.0 kV, and most preferably greater than 5 kV, as measured by HypotMAX 7720 or Ikonix 3865 and according to ASTM D 149-09 Hipot test.

[0099] Cured dielectric coatings can be used in applications requiring heat dissipation and electrical insulation. They are suitable for high-energy-density power generation or storage where significant amounts of heat can be generated during operation, such as in battery packs in automobiles or aircraft. Cured dielectric coatings with high dielectric strength and high thermal conductivity are advantageous as electrical insulation in battery pack operation, where effective heat dissipation is crucial for battery safety and lifespan. Cured dielectric coatings also provide additional protection against corrosion and abrasion during vehicle operation, where environmental factors such as water condensation, contaminants, vibration, etc., can damage the underlying substrate.

[0100] The applied coating can be air-dried, heat-cured, or a combination thereof at relatively low temperatures (e.g., above ambient temperature, meaning about 20-35°C). For example, in some embodiments, curing can occur in the range of about 10°C to 130°C, preferably (in ascending order) at least about 15, 20, or 25°C, and (in ascending order) not exceeding about 130, 125, 120, 115, 110, 105, 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, or 30°C, or various combinations of curing steps. In a preferred embodiment, the applied coating can be cured at temperatures ranging from ambient temperature to about 65°C, providing significant energy savings compared to the typical curing temperature of about 200°C for powder coatings. In some preferred embodiments, the applied coating can undergo a combination of curing steps: 1) a first curing step lasting 7-30 minutes at the aforementioned temperature, and 2) a second curing step involving heat treatment lasting 7-30 minutes at a temperature, for example, about 110 to 130°C, still providing significant energy savings compared to curing a typical powder coating. The curing duration can be adjusted to provide sufficient time for complete curing of the coating, preferably the total time for each curing step (preferably in ascending order) is at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 minutes, and (preferably in ascending order) does not exceed about 60, 55, 50, 45, 40, 35, 30, 25, 20, or 15 minutes. Void test:

[0101] Electrical insulation testing of cured coatings to reveal coating voids, which may include exposed edges, pinholes, and low-thickness areas on the substrate, can be performed using a "Hipot test," derived from the term "high-potential test." In a Hipot test, a high voltage is applied directly to the component with the cured coating under test. The test voltage is typically much higher than the normal operating voltage of the part to stress the dielectric properties of the coating under test. This test is designed to detect current leakage caused by defects in the insulating cured coating, such as pinholes, cracks, voids, and even low-coating-weight areas. Breakdown in the insulating coating causes current to flow through the test point of the Hipot tester, i.e., current leakage. Hipot testing of cured coatings according to the invention shows no voids, even around corners and edges of the coated substrate, indicating that the edges are equally protected. Electrical insulation test

[0102] Electrical insulation properties are confirmed as “good,” meaning that no current is allowed to flow through the test sample using a high-voltage test (“Hipot test”), which detects current flow when a selected voltage is applied over a specific time period. “Dielectric withstand voltage” is the voltage that a dielectric material (insulator) will withstand without current flowing through it, i.e., the maximum voltage at which little or no current flows (as determined by test results). Desiredly, the electrical insulation properties of the cured dielectric coating according to the invention can exhibit dielectric withstand voltages greater than about 2.0, 2.5, 3.0, 3.5, 4.0, 4.2, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, or 5.5 kV, preferably in increasing order, as measured according to the ASTM D 149-09 Hipot test. Alternatively, the dielectric withstand voltage can be increased in a stepwise manner, and the amount of current allowed to flow through the test sample (also known as current leakage) is recorded in microamperes (μA). The unaged cured coating according to the invention typically limits current leakage at 3.5 kV and 5.0 kV to as low as zero μA to about 5.0 μA. Dielectric strength

[0103] Dielectric strength is a measure of the electrical strength of a material that acts as an insulator. It is defined as the maximum voltage required to induce dielectric breakdown through the material and is expressed in volts per unit thickness. Breakdown typically manifests as electrical burn-through or insulator decomposition. Higher dielectric strength indicates better insulator quality. This measurement allows for performance comparisons between different materials used at varying coating thicknesses. Ideally, cured dielectric coatings should exhibit dielectric strengths greater than approximately 80, 90, 100, 120, 130, 140, 150, or 160 kV / mm thickness (e.g., approximately 1.5, 2, 2.5, 3.0, 3.5, or 4.0 kV / mil thickness) (preferably in ascending order).

[0104] The benefits of using the coating compositions of embodiments of the present invention to form a dielectric coating may include, but are not limited to: - The ease of preparation and application of coating compositions reduces the cost of specialized equipment and additional steps: for example, the compositions of the present invention allow the use of standard or low-shear mixing instead of high-shear mixing; reduce or eliminate complex filler grinding steps; facilitate simple application using techniques such as spraying or printing; and allow for optional transport and handling of uncured coated substrates; - Single-layer deposition provides a thin coating with continuous edge coverage, avoiding multiple deposition steps in the preferred embodiment, see the accompanying drawings; - Compared to known powders and other coatings, embodiments of the present invention offer effectively faster curing times. UV curing times can range from approximately 2 to 200 seconds. As described herein, lower temperature baking below 100°C can last from 1 minute to 90 minutes, particularly 10, 30, 60, or 70 minutes. In some embodiments, the applied coating can be cured at ambient temperature or at temperatures in the range of approximately 20-65°C, providing significant energy savings compared to the typical curing temperature of approximately 200°C for powder coatings. - The cured dielectric coating provides electrical insulation greater than 2.0, 3.0, 3.5, 4.0, 4.5 or 5.0 kV and reduced thermal retention; - The cured dielectric coating exhibits high thermal conductivity and / or low thermal resistance as measured according to ASTM D5470, thus aiding in heat dissipation. In some embodiments, the cured dielectric coating of the present invention exhibits a thermal conductivity greater than about 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, or 0.55 W / mK, preferably in increasing order, which is significantly superior to a powder coating of 0.20 W / mK.

[0105] Throughout this document, it should be recognized that the description relates to compositions and methods of preparing and using said compositions. That is, in cases where this disclosure describes or claims features or embodiments associated with a composition or a method of preparing or using the composition, it should be understood that such description or claims are intended to extend to embodiments in each of these contexts (i.e., compositions, methods of preparation, and methods of use).

[0106] The invention is further defined in the following embodiments. It should be understood that while these embodiments illustrate preferred embodiments of the invention, they are given by way of illustration only and should not be construed as limiting the appended claims. Based on the foregoing discussion and these embodiments, those skilled in the art can determine the essential features of the invention, and various changes and modifications can be made to adapt it to various uses and conditions without departing from its spirit and scope. In particular, the following embodiments are intended to supplement, rather than replace or supersede, the preceding description. Example

[0107] The following examples provide experimental methods for preparing and testing liquid coating compositions for depositing thermally conductive dielectric coatings on substrates, their uncured and cured properties, and performance. While each example disclosed in the specification is intended to provide a specific individual embodiment of the composition, preparation method, and use, none of the examples is intended to be considered a limitation on the more general embodiments described herein.

[0108] In the following examples, efforts have been made to ensure the accuracy of the figures used (e.g., quantities, temperatures, etc.), but some experimental errors and biases should be considered. Unless otherwise specified, temperatures are in °C, ambient temperatures are approximately 22 °C, and pressures are at or near atmospheric pressure. High-shear mixing is not required unless otherwise specified. Test method:

[0109] Unless otherwise stated herein, the liquid coating composition of the examples is sprayed onto a commercially available metal test panel and cured as described below. The cured dielectric coating adhered to the metal test panel is tested according to the following standard test methods: - Dielectric withstand voltage strength / HiPot test: ASTM D149-09 - Thermal conductivity: ASTM D5470 - Thermal resistance: ASTM D5470 - Adhesive / Cross-marking: ASTM D3359. Example 1: Styrene-containing formulation

[0110] Add the ingredients listed in Part A of Table 1 sequentially to a mixing container. Then, mix the mixture for 3 minutes at 2000 RPM using a planetary centrifugal mixer to prepare Part A. Add Part B to Part A with stirring for 1 minute and transfer to an HVLP spray gun. Apply the coatings of the compositions in Table 1 to 6061 aluminum plates at different layer thicknesses and bake in an oven at 65°C for 30 minutes to produce cured coatings with thicknesses ranging from 2.8 mils to 8.0 mils (0.071 mm to 0.203 mm). Table 1: Polyester / Styrene, Formulation of Example 1 2,2,4-Trimethyl-1,3-pentanediol diisobutyrate

[0111] The 6061 aluminum plate with the cured dielectric coating of Example 1 was tested according to the test method disclosed above, and the following results were obtained: - Thermal conductivity: The cured coated 6061 aluminum plate exhibits a thermal conductivity of 0.56 watts per meter (W / mK). - Thermal resistance: The cured coated 6061 aluminum plate exhibits a thermal resistance of 0.16 Kelvin / W (K / W) at a cured coating thickness of 2.8 mils and 0.45 K / W at a cured coating thickness of 7.9 mils. - Dielectric withstand voltage: 6061 aluminum plates with cured coating thicknesses of 4 mils (approximately 0.10 mm) and 8 mils (approximately 0.20 mm) can withstand 5000 volts for 2 minutes. Example 2: Styrene-free formulation

[0112] Add the ingredients listed in Part A of Table 2 sequentially to the mixing container. Then, use a planetary centrifugal mixer to mix the mixture at 2000 RPM for 3 minutes to prepare Part A. Add Part B to Part A with stirring for 1 minute and transfer to an HVLP spray gun. Apply coatings of varying thicknesses to 6061 aluminum panels and bake in an oven at 65°C for 30 minutes. Table 2: Polyester / acrylate / BN, no styrene, Formulation of Example 2

[0113] After baking, the dielectric coating of Example 2 was tested as described in Example 1, and the results are as follows:

[0114] Dielectric withstand voltage: 6061 aluminum plates with coating thicknesses of 2.3 mil, 3.5 mil, and 7.5 mil withstand 5000 volts for 2 minutes. The thermal conductivity of the coating is 0.54 W / mK, and the thermal resistance is 0.17 K / W at 2.2 mil, 0.44 K / W at 6.3 mil, and 0.80 K / W at 10.8 mil. Example 3: Styrene-free formulation with mixed fillers

[0115] Add the ingredients listed in Part A of Table 3 sequentially to the mixing container. Then, use a planetary centrifugal mixer to mix the mixture at 2000 RPM for 3 minutes to prepare Part A. Add Part B to Part A with stirring for 1 minute and transfer to an HVLP spray gun. Apply coatings of varying thicknesses to 6061 aluminum panels and bake in an oven at 65°C for 30 minutes. Table 3: Polyester / acrylate / BN / CaCO3, no styrene, formulation of Example 3

[0116] After baking, the dielectric coating of Example 3 was tested as described in Example 1, and the results are as follows: the thermal conductivity of the coating is 0.70 W / mK, the thermal resistance at 4.1 mils is 0.23 K / W, the thermal resistance at 7.0 mils is 0.39 K / W, and the thermal resistance at 9.3 mils is 0.53 K / W.

[0117] Dielectric withstand voltage: 6061 aluminum plate with a coating thickness of 4.0 mils withstands 5000 volts for 2 minutes. Example 4 (Comparative Example): Comparative Example 1

[0118] Add the ingredients listed in Part A of Table 4 sequentially to the mixing container. Then, use a planetary centrifugal mixer to mix the mixture at 2000 RPM for 3 minutes to prepare Part A. Stir Part B into Part A for 1 minute and transfer to an HVLP spray gun. Apply coatings of varying thicknesses to 6061 aluminum panels and bake in an oven at 65°C for 30 minutes. Table 4: Comparative Example 1 formulation, styrene-free formulation, with alumina filler

[0119] After baking, the dielectric coating of Comparative Example 1 was tested as described in Example 1, and the results are as follows: the thermal conductivity of the coating is 0.21 W / mK, the thermal resistance at 3.5 mils is 0.67 K / W, the thermal resistance at 5.9 mils is 1.13 K / W, and the thermal resistance at 8.0 mils is 1.53 K / W.

[0120] Dielectric withstand voltage: 6061 aluminum panels with a coating thickness of 2.5 mils cannot withstand 3500 volts, while coatings with thicknesses of 4.5 mils and 8.5 mils delaminate from the panel (catastrophic failure). Example 5: Styrene-containing formulation with a mixed resin system

[0121] Add the ingredients listed in Part A of Table 5 sequentially to a mixing container. Then stir the mixture overnight at 600 RPM on a magnetic stir plate to prepare Part A. Stir Part B into Part A for 1 minute and transfer to an HVLP spray gun. Apply coatings of varying thicknesses to 5052 aluminum panels and bake in an oven at 65°C for 30 minutes, followed by baking at 125°C for 30 minutes. Table 5. Epoxy Resin / Styrene / Acrylic Ester / BN, Formulation of Example 5 The manufacturer describes it as containing a small amount of catalyst primer.

[0122] After baking, the dielectric coating of Example 5 was tested as described in Example 1, and the results are as follows: the thermal conductivity of the coating is 0.61 W / mK, the thermal resistance is 0.06 K / W at 1.2 mils, 0.08 K / W at 1.6 mils, and 0.23 K / W at 4.3 mils. Dielectric withstand voltage: 5052 aluminum plates with coating thicknesses of 2.1, 3.2, and 4.5 mils withstood a 3500V test for 2 minutes and a 5000V test for 2 minutes, respectively, with a leakage current of 0.0 to 0.1 μA.

[0123] Humidity aging test: The coated panels were aged for 1,000 hours in a Thermotron chamber maintained at 85°C and 85% relative humidity. After aging, the cross-cut adhesion and dielectric withstand voltage of the coated panels were tested according to the test method disclosed above. The results are as follows: All aged coated panels maintained cross-cut adhesion and passed the 5000V dielectric withstand test for 2 minutes, with leakage current ranging from 0.7 to 2.0μA.

[0124] Another sample of the composition from Example 5 was applied to an aluminum 3003 square battery case and baked in an oven at 65°C for 30 minutes, followed by baking at 125°C for 10 minutes, and then fully cured in a shorter time. Painted aluminum plates from the coated battery cell cases were prepared for metallurgical cross-sectional analysis according to AM 530. The equipment / method used was a Hitachi SU5000 field emission scanning electron microscope with EDAX energy dispersive X-ray atomizer (EDX-AM 530). Cross-sectional sample preparation: The components were mounted in epoxy resin with conductive filler. The epoxy-mounted cut plates were ground and polished using a Beuhler Beta Grinder-Polisher according to analytical method A-530. The epoxy base was mounted to an aluminum stage with copper tape and examined by SEM / EDS at 15 keV in low vacuum mode using a backscattered electron detector.

[0125] FESEM imaging was performed at the corners and on both edges of the panel away from the corners (two regions, the ends and the middle), and the coating thickness was measured, see Table 5a and Figure 1-5 . Table 5a Formulation of Example 5, FESEM measurements of coating thickness

[0126] FESEM imaging revealed a coating thickness on one side similar to that at a corner, while the other side had a thickness greater than that at the corner. As the coating fully cured, FESEM images showed excellent edge coverage and acceptable thickness variation. Example 6: Styrene-containing formulation with mixed resin system and different BN fillers

[0127] Add the ingredients listed in Part A of Table 6 sequentially to a mixing container. Then stir the mixture overnight at 600 RPM on a magnetic stirring plate to prepare Part A. Stir Part B into Part A for 1 minute and transfer to an HVLP spray gun. Apply coatings of varying thicknesses to 5052 aluminum plates and bake in an oven at 65°C for 30 minutes, followed by baking at 125°C for 30 minutes. Table 6. Epoxy / acrylate / styrene, with different BN particles, formulations from Example 6.

[0128] After baking, the dielectric coating of Example 6 was tested as described in Example 1, and the results are as follows: the thermal conductivity of the coating is 0.60 W / mK, the thermal resistance is 0.08 K / W at 1.5 mils, 0.21 K / W at 4.0 mils, and 0.28 K / W at 5.2 mils. Dielectric withstand voltage: 5052 aluminum plates with coating thicknesses of 2.5 and 4.0 mils withstood a 3500V test for 2 minutes and a 5000V test for 2 minutes, respectively, with leakage currents of 0.1 and 0.0 μA.

[0129] Humidity aging test: The coated boards were aged for 1,000 hours in a Thermotron chamber maintained at 85°C and 85% relative humidity. After aging, the cross-cut adhesion and dielectric withstand voltage of the coated boards were tested according to the test method disclosed above. The results are as follows: All aged coated panels maintained cross-cut adhesion and passed the 5000V dielectric withstand test for 2 minutes, with leakage currents of 9.8 and 5.1μA, respectively. Example 7: Styrene-containing formulation on pretreated substrate

[0130] Add the ingredients listed in Part A of Table 7 sequentially to the mixing container. Then stir the mixture overnight at 600 RPM on a magnetic stir plate to prepare Part A. Stir Part B into Part A for 1 minute and transfer the combination of the two into an HVLP spray gun. Table 7. Epoxy / Styrene / Acrylic / BN, Formulations from Example 7 The manufacturer describes it as containing a small amount of catalyst primer.

[0131] In this embodiment, the aluminum 5052 metal substrate panel was pretreated according to the procedure listed in Table 8 below before coating with the liquid dielectric coating composition of Example 7. Bonderite C-AK 6849 is an aqueous alkaline cleaner commercially available from Henkel Corp. Bonderite C-IC SmutGo NC is an acidic deoxidizer commercially available from Henkel Corp. Bonderite M-NT 5200 organic / inorganic conversion coating is commercially available from Henkel Corp. Table 8: Pretreatment test method for aluminum substrate in Example 7

[0132] As shown in Table 8, aluminum 5052 panels that have been pretreated according to pretreatment process A or pretreatment process B are coated with different amounts of the composition in Table 7 using an HVLP spray gun, and then baked in an oven at 65°C for 30 minutes, and then baked at 125°C for 30 minutes to produce dielectric coatings with various film thicknesses as shown in Table 9.

[0133] After baking, the dielectric coating of Example 7, which adhered to the pretreated substrate as described in Example 1, was tested, and the test results are shown in Table 9: Table 9 shows the un-aging test results of the cured dielectric coating of Example 7 on the pretreated substrate.

[0134] The coated boards in Table 9 were then subjected to humidity aging for 1,000 hours in a Thermotron chamber maintained at 85°C and 85% relative humidity. Following humidity aging, the coated boards were tested for cross-cut adhesion and dielectric withstand voltage at 5000 volts according to the test methods disclosed above, with results shown in Table 10. All aged coated boards maintained cross-cut adhesion and passed the dielectric withstand test at 5000 volts for 2 minutes, with leakage currents ranging from 8.1 to 1.1 μA. Table 10: Humidity aging test of the cured dielectric coating of Example 7 on pretreated substrates

[0135] Subsequent testing of the shorter duration of secondary curing in the above embodiments showed acceptable results with 10-30 minute secondary curing. The above exemplary embodiments demonstrate that the coating compositions of the present invention can be used to form a thin, void-free coating with continuous coverage on the edges of a substrate, providing rapid heat dissipation and good electrical insulation with high dielectric strength. Therefore, the cured coating offers significant advantages in high-energy-density power generation or storage applications that generate substantial heat during operation, such as battery packs in vehicles (e.g., automobiles or aircraft). The coating can provide further protection against battery damage during vehicle operation, where water condensation and constant vibration are common sources of corrosion and abrasion. The coating can be air-dried or baked to cure as described above, and can be further cured with UV light in a dual-curing manner.

Claims

1. A curable liquid coating composition for forming a heat-dissipating dielectric coating, comprising the following components: (a) Polyester resin; (b) Reactive diluents; (c) Thermally conductive filler; (d) Dispersant; (e) Initiators; and (f) An optional promoter, different from the initiator; The polyester resin (a) is selected from unsaturated polyester resins, preferably vinyl ester resins, and most preferably epoxy vinyl ester resins, such as epoxy acrylates and epoxy methacrylates, and combinations thereof.

2. The curable liquid coating composition according to claim 1, further characterized in that the components comprise, substantially consist of, or consist of, the following, in weight percent: (a) An unsaturated polyester resin, preferably an epoxy vinyl ester resin, such as epoxy acrylate and epoxy methacrylate, and combinations thereof, is preferably present in the range of 10% to 95%, preferably 25% to 50%; (b) A free radical reactive diluent, preferably present in the range of 10% to 95%, preferably 25% to 50%; (c) Thermally conductive fillers, such as boron nitride, alumina, and aluminum trihydrate, are preferably present in the range of 5% to 50%, and more preferably 10% to 30%; (d) Dispersant, preferably present in the range of 0.1% to 2.0%; (e) An initiator, preferably present in the range of 0.1% to 5.0%; (f) An accelerator, unlike the initiator, is preferably present in the range of 0% to 3%; (g) Organic solvent, preferably present in the range of 0.5% to 20%; (h) At least one additive selected from rheology modifiers, adhesion promoters, flexibility agents and plasticizers, each of which is desired to be present in the range of 0% to 5%; (i) Degassing agents and / or defoamers, preferably present in the range of 0% to 2.0%; The weight percentage of each component is relative to the total weight of the composition, and the total amount of the components does not exceed 100% by weight.

3. The curable liquid coating composition according to claim 2, wherein component (a) the unsaturated polyester resin, epoxy vinyl ester resin, such as epoxy acrylate and epoxy methacrylate, and combinations thereof, are present in the range of 10% to 95% by weight relative to the total weight of the composition.

4. The curable liquid coating composition according to claim 1, wherein component (b) the free radical reactive diluent is present in the range of 10% to 95% by weight relative to the total weight of the composition.

5. The curable liquid coating composition according to claim 1, wherein component (c) the thermally conductive filler, preferably comprising boron nitride filler, is present in the range of 5% to 50% by weight relative to the total weight of the composition.

6. The curable liquid coating composition according to claim 1, wherein component (d) the dispersant is present in the range of 0.2% to 1.9% by weight relative to the total weight of the composition.

7. The curable liquid coating composition according to claim 1, wherein component (e) the initiator is present in the range of 0.1% to 5.0% by weight relative to the total weight of the composition.

8. The curable liquid coating composition according to claim 1, wherein component (f), the accelerator different from the initiator, is present in the range of 0.05% by weight to 1.0% by weight relative to the total weight of the composition.

9. The curable liquid coating composition according to claim 1, wherein the component (g) of the organic solvent is present in the range of 1% to 20% by weight relative to the total weight of the composition.

10. The curable liquid coating composition according to claim 1, wherein the additive in component (h) is present in an amount ranging from 0.1% to 5.0% by weight relative to the total weight of the composition.

11. The curable liquid coating composition of claim 10, wherein the additive comprises a rheology modifier present in the range of 0.1% to 5% relative to the total weight of the composition.

12. The curable liquid coating composition according to claim 1, wherein the flexibility agent is present in the range of 0.1% to 5% relative to the total weight of the composition.

13. The curable liquid coating composition according to claim 1, wherein the plasticizer is present in the range of 0.1% to 5.0% relative to the total weight of the composition.

14. The curable liquid coating composition according to claim 1, wherein the component (i) the degassing agent and / or defoamer are each present in the range of 0.1% to 2.0% by weight, or preferably 0.3% to 0.7% by weight, relative to the total weight of the composition.

15. The curable liquid coating composition according to claim 1, wherein component (a) comprises a mixture of two different unsaturated polyester resins, said unsaturated polyester resins comprising epoxy vinyl ester resin; and component (c) the thermally conductive filler comprises lamellar boron nitride, at least a portion of said boron nitride being hexagonal boron nitride.

16. The curable liquid coating composition according to claim 1, wherein component (a) comprises a mixture of unsaturated polyester resin, methyl methacrylate and triacrylate; component (e) the initiator comprises a peroxide; the accelerator comprising a cobalt composition is present; and component (h) the at least one additive is present as a fumed silica rheology modifier and a siloxane adhesion promoter.

17. The curable liquid coating composition according to claim 1, wherein component (c) the thermally conductive filler comprises hexagonal boron nitride; the composition further comprises calcium carbonate extender filler.

18. A cured dielectric heat-dissipating coating deposited on a metal surface, comprising a cured coating formed by contacting the metal surface with a curable liquid coating composition according to any one of claims 1-17 and drying the composition on the metal surface, wherein the cured coating has a thermal resistance of less than about 0.080 K / W per mil coating thickness.

19. The cured dielectric heat dissipation coating of claim 18, further comprising a conversion coating disposed between the metal surface and the cured dielectric heat dissipation coating.

20. The cured dielectric heat dissipation coating according to claim 18, having a dielectric strength greater than about 80 kV / mm thickness of the coating.

21. The cured dielectric heat dissipation coating according to claim 18, having a thickness of about 40 micrometers, 50 micrometers, 65 micrometers to about 75 micrometers, 90 micrometers or 100 micrometers.

22. A method for increasing heat dissipation and electrical insulation of a metal substrate surface, comprising the following steps: The surface of a metal substrate, preferably a metal casing for electrical components, is brought into contact with the curable liquid coating composition according to any one of claims 1-17, preferably immersed, more preferably sprayed; and The composition is dried in situ, optionally at a temperature in the range of 10°C to 100°C, preferably in the range of about 20-65°C, to form a cured dielectric heat dissipation coating that adheres to the metal substrate.

23. The method of claim 22, further comprising applying a conversion coating to the surface of the metal substrate prior to contacting the metal substrate with the curable liquid coating composition, such that the cured dielectric heat dissipation coating adheres to the conversion coating deposited on the metal substrate.

24. The method of claim 22, wherein the surface of the metal substrate coated with the cured dielectric heat dissipation coating exhibits a dielectric strength greater than about 90 kV / mm thickness.

25. A metal container comprising a surface that has been contacted with a curable liquid coating composition according to any one of claims 1-17.

26. The metal container of claim 25, wherein the surface of the metal substrate coated with the cured dielectric heat-dissipating coating has a thermal conductivity greater than about 0.25, preferably greater than 0.35 watts per meter Kelvin (W / mK).

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