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CN-122003476-A - Thermally conductive dielectric coating

CN122003476ACN 122003476 ACN122003476 ACN 122003476ACN-122003476-A

Abstract

A curable liquid coating composition sprayable onto a substrate to form a thin, pinhole-free thermally conductive dielectric coating exhibiting a combination of improved 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 an organic solvent, an accelerator, and a rheology modifier, methods of preparing compositions, coatings, and substrates comprising the curable or cured thermally conductive dielectric coating, and articles comprising the curable or cured coatings of the composition are also provided.

Inventors

  • DU LIBIN
  • YANG ZHIGI
  • G.T. Donaldson
  • M. A. Little Murphy
  • MUELLER LOTHAR KURT

Assignees

  • 汉高股份有限及两合公司

Dates

Publication Date
20260508
Application Date
20240916
Priority Date
20230922

Claims (20)

  1. 1. A curable liquid coating composition for forming a heat dissipating dielectric coating comprising the following components: (a) A polyester resin; (b) A reactive diluent; (c) A thermally conductive filler; (d) A dispersing agent; (e) Initiator, and (F) Optionally, a promoter different from the initiator; wherein the polyester resin (a) is selected from unsaturated polyester resins, desirably vinyl ester resins, preferably epoxy vinyl ester resins, such as epoxy acrylates and epoxy methacrylates, and combinations thereof.
  2. 2. The curable liquid coating composition of claim 1 further characterized in that the component comprises, consists essentially of, or consists of, in weight percent: (a) Unsaturated polyester resins, preferably epoxy vinyl ester resins, such as epoxy acrylates and epoxy methacrylates, and combinations thereof, desirably present in the range of 10% to 95%, preferably 25% to 50%; (b) The free radical reactive diluent is desirably present in the range of 10% to 95%, preferably 25% to 50%; (c) Thermally conductive fillers, such as boron nitride, alumina, aluminum trihydrate, desirably present in the range of 5% to 50%, preferably 10% to 30%; (d) A dispersant desirably present in the range of 0.1% to 2.0%; (e) An initiator desirably present in the range of 0.1% to 5.0%; (f) Accelerators other than the initiator are desirably present in the range of 0% to 3%; (g) An organic solvent desirably present in the range of 0.5% to 20%; (h) At least one additive selected from the group consisting of rheology modifiers, adhesion promoters, flexibilizers, and plasticizers, each desirably present in a range of 0% to 5%; (i) Deaerators and/or defoamers, desirably present in the range of 0% to 2.0%; wherein the weight% of each component is relative to the total weight of the composition and the total amount of the components is no more than 100 weight%.
  3. 3. The curable liquid coating composition of 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 a range of 10 to 95 weight percent, relative to the total weight of the composition.
  4. 4. The curable liquid coating composition of claim 1, wherein component (b) the free radical reactive diluent is present in a range of 10 wt% to 95 wt%, relative to the total weight of the composition.
  5. 5. The curable liquid coating composition according to claim 1, wherein component (c) the thermally conductive filler, preferably comprising a boron nitride filler, is present in the range of 5 to 50 wt%, relative to the total weight of the composition.
  6. 6. The curable liquid coating composition of claim 1, wherein component (d) the dispersant is present in a range of 0.2 wt% to 1.9 wt% relative to the total weight of the composition.
  7. 7. The curable liquid coating composition of claim 1, wherein component (e) the initiator is present in a range of 0.1 wt% to 5.0 wt% relative to the total weight of the composition.
  8. 8. The curable liquid coating composition of claim 1, wherein component (f) the accelerator other than the initiator is present in a range of 0.05 wt% to 1.0 wt% relative to the total weight of the composition.
  9. 9. The curable liquid coating composition of claim 1, wherein component (g) the organic solvent is present in a range of 1 wt% to 20 wt%, relative to the total weight of the composition.
  10. 10. The curable liquid coating composition of claim 1, wherein component (h) the additive is present in an amount ranging from 0.1 wt% to 5.0 wt% relative to the total weight of the composition.
  11. 11. The curable liquid coating composition of claim 10, wherein the additive comprises a rheology modifier present in a range of 0.1% to 5% relative to the total weight of the composition.
  12. 12. The curable liquid coating composition of claim 1, wherein the pliable agent is present in a range of 0.1% to 5% relative to the total weight of the composition.
  13. 13. The curable liquid coating composition of claim 1, wherein the plasticizer is present in the range of 0.1% -5.0% relative to the total weight of the composition.
  14. 14. The curable liquid coating composition of claim 1, wherein component (i) the degassing and/or defoaming agent is each present in the range of 0.1 to 2.0 wt%, desirably 0.3 to 0.7 wt%, relative to the total weight of the composition.
  15. 15. The curable liquid coating composition of claim 1, wherein component (a) comprises a mixture of two different unsaturated polyester resins comprising an epoxy vinyl ester resin and component (c) the thermally conductive filler comprises boron nitride in platelet form, at least a portion of the boron nitride being hexagonal boron nitride.
  16. 16. The curable liquid coating composition of claim 1, wherein component (a) comprises a mixture of an 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 silicone adhesion promoter.
  17. 17. The curable liquid coating composition of claim 1, wherein component (c) the thermally conductive filler comprises hexagonal boron nitride, the composition further comprising a calcium carbonate extender filler.
  18. 18. A cured dielectric heat sink coating deposited on a metal surface comprising a cured coating formed by contacting a metal surface with the curable liquid coating composition of any one of claims 1-17 and drying the composition on the metal surface, wherein the cured coating has a thermal resistance per mil coating thickness of less than about 0.080K/W.
  19. 19. The cured dielectric heat sink coating of claim 18, further comprising a conversion coating disposed between the metal surface and the cured dielectric heat sink coating.
  20. 20. The cured dielectric heat sink coating of claim 18 having a dielectric strength of the coating greater than about 80kV/mm thickness.

Description

Thermally conductive dielectric coating Technical Field The present invention relates to a curable liquid coating composition for depositing a thermally conductive dielectric coating on a substrate, an intermediate comprising a substrate having deposited thereon a layer of a curable, optionally dried, coating composition, an adhesion layer of the cured thermally conductive dielectric coating composition on a substrate, a coated substrate and a method of producing the composition, the coating and the coated substrate. Background Electrical components are typically electrically insulated by the application of high dielectric strength materials. While dielectric materials provide electrical insulation, they are generally inconvenient for dissipating heat and can be thermally insulating. In many electrical components, particularly for vehicle OEMs, faster heat dissipation from battery operation is highly desirable to improve the range of battery powered vehicles and the life of the battery pack. The usual battery insulation in such vehicles is mainly by applying powder coatings or using plastic insulating wraps or films, which do not adequately meet the heat dissipation requirements. The disadvantage of powder coatings is the need for high temperatures for curing, for example 175-205 ℃ for 10-15 minutes plus the warm-up time (about 30 minutes) for the part to reach the curing temperature. Powder coatings are typically thick and multiple coatings are employed to ensure a pinhole free film. Thus, powder coatings have the additional disadvantage of undesirably increasing weight and high thermal resistance, while plastic packaging requires complex handling and processing to install, and long-term reliability and delamination risk are problems. It is therefore desirable to develop dielectric coatings that promote heat dissipation, particularly for battery cooling systems, prismatic batteries (PRISMATIC CELLS), cold plates, power inverters, bus bars, and chargers. It is also desirable to develop improved dielectric coatings that provide good electrical insulation at low film thicknesses to reduce weight, that are applied by less complex processes and that use less time and energy. Accordingly, there is a need for a thermally conductive dielectric coating that can be applied defect-free at a coating thickness that is thinner than previously available for use in vehicles, the thermally conductive coating having a combination of improved dielectric strength and improved thermal conductivity or low thermal resistance. Disclosure of Invention In accordance with aspects of the present invention, a curable liquid coating composition, a substrate having a layer of curable, optionally dried, coating composition deposited thereon, and a cured polymeric thermally conductive dielectric coating and coated substrate on the substrate address one or more of the above-described drawbacks or needs, and exhibit high dielectric strength, heat dissipation, and good electrical insulation, as further described herein. Various embodiments of the curable liquid coating composition may comprise or consist essentially of or consist of an organic resin, such as a polyester resin, a reactive diluent, a thermally conductive filler, a dispersant, an initiator, and an additive selected from the group consisting of 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 (de-aerator), coupling agents, defoamers, pigments and dyes, plasticizers, flexibilizers (flexibilizers), flame retardants, impact modifiers/tougheners (toughening agents), fillers, flow control agents, adhesion promoters, inhibitors, antioxidants, nonreactive diluents, extenders (extenders) or other adjuvants. In certain embodiments, the curable liquid coating composition is formaldehyde-free. Various embodiments of the present invention are described throughout this disclosure, including: embodiment 1a curable liquid coating composition comprising: (a) A polyester resin; (b) A reactive diluent; (c) A thermally conductive filler; (d) A dispersing agent; (e) Initiator, and (F) Optionally, a promoter different from the initiator; Wherein the polyester resin is selected from unsaturated polyester resins, which desirably may comprise a vinyl ester resin, preferably an epoxy vinyl ester resin, such as epoxy acrylate and epoxy methacrylate, and combinations thereof. The curable liquid coating composition may further comprise at least one additive, preferably selected from organic solvents, accelerators, rheology modifiers (which optionally may be surface modified) (also referred to herein as thixotropic agents). The curable liquid coating composition may also contain deaerators, coupling agents, defoamers, pigments and dyes, plasticizers, flexibilizers, flame retardants, impact modifiers/tougheners, other fillers than (c), flow control agent