Solvent-free UV (ultraviolet) dielectric insulation protective coating as well as preparation method and application thereof

Abstract

The invention provides a solvent-free UV dielectric insulation protective coating as well as a preparation method and application thereof. The high-surface-energy and high-glass-transition-temperature UV-curable coating is prepared by combining flexible modified polyurethane acrylate, flexible acrylate, rigid acrylate with high glass transition temperature, a high-functionality acrylate cross-linking agent, methyl methacrylate with high dilutability and high glass transition temperature as well as a plurality of photoinitiators, auxiliaries, pigment and filler powder and the like. The invention relates to a dielectric insulation protective coating with high adhesive force. The prepared coating is a solvent-free 100% solid single component, is complete in mixing and dissolving, convenient to construct, high in light curing energy utilization rate, high in production efficiency and suitable for large-scale automatic large-scale flow line production, and compared with PSA back glue used for a traditional PET blue film, the outer surface of the coating has higher surface energy, and the coating has the advantages of being high in light curing energy utilization rate and high in production efficiency. And the film has considerable dielectric insulation performance and good edge covering protection performance, and meets the development requirements of a higher charging voltage platform of a fast-charging electric vehicle in the future.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, relates to insulating protective coatings, and particularly relates to a solvent-free UV dielectric insulating protective coating that can replace the blue film of electric vehicle power batteries, and its preparation method and application. It belongs to a dielectric insulating protective coating with high surface energy and high adhesion obtained by combining flexible modified polyurethane acrylate, flexible acrylate, rigid acrylate with high glass transition temperature, high functionality acrylate crosslinking agent, highly diluting methyl methacrylate with high glass transition temperature, and numerous photoinitiators, additives, pigment and filler powders, etc. Background Art

[0002] The battery packs, battery cores, side walls, cooling plates and other battery components of electric vehicle power batteries need to be dielectrically insulated to prevent short circuits and improve the safety and durability of use. Traditionally, PET (polyethylene terephthalate) blue film is used. Although the equipment investment cost and material cost of PET blue film are relatively low, the automation difficulty is relatively high, which is suitable for small batch production. In addition, the PSA back adhesive force of PET blue film is limited, only 0.5 - 2 MPa. At the same time, the structural adhesive used externally to bond other battery cores also has an adhesive force of only 2.0 - 3.5 MPa. The PSA back adhesive is prone to cohesive failure, resulting in the peeling off of the PET blue film from the battery shell. For the PET blue film external structural adhesive that bonds other battery cores, due to the low surface energy of the PET blue film, interfacial failure and cracking are likely to occur, which will directly affect the safety performance of the power battery. Therefore, it may be limited to applications that do not require high structural adhesion.

[0003] With the substantial increase in the working voltage and energy density of power batteries, the probability of arc insulation breakdown between battery cores has greatly increased, and the relatively easy peeling off of the PET blue film cannot meet the insulation protection safety requirements of future battery cores.

[0004] In order to solve the problem of poor internal and external adhesion performance of the PET blue film, powder coatings and solvent-based coatings have been tried to replace the PET blue film. However, solvent-based coatings are not environmentally friendly, and powder coatings require high-temperature long-time curing, while power batteries are not suitable for a long-time high-temperature curing environment. Summary of the Invention

[0005] To solve the above problems, the present invention provides a solvent-free UV dielectric insulation protective coating, a preparation method thereof, and an application. The solvent-free UV dielectric insulation protective coating provided by the present invention is a dielectric insulation protective coating with high surface energy and high adhesion, which is obtained by combining flexible modified polyurethane acrylate, flexible acrylate, high glass transition temperature rigid acrylate, high functionality acrylate crosslinking agent, high dilution high glass transition temperature methyl methacrylate, and numerous photoinitiators, additives, pigment and filler powders, etc. The coating prepared by the present invention is a solvent-free 100% solid single component, with complete miscibility, convenient construction, high photo-curing energy utilization rate, high production efficiency, and can be applied to large-scale automated mass production lines.

[0006] After UV curing, the coating prepared by the present invention has a bonding strength with the battery core far higher than that of the PSA adhesive used in traditional PET blue films. At the same time, due to the higher surface energy of the outer surface of the coating than that of the PET blue film, it can be firmly bonded to other battery pack components through structural adhesive, without the potential risk of the PET blue film PSA cohesive failure and the outer structural adhesive shedding, resulting in the blue film peeling off the battery core assembly and the battery pack. At the same time, it has dielectric insulation performance and edge coverage protection performance comparable to those of the PET blue film. Compared with the working voltage platform of less than 400V of the PET blue film, it can be applied to power batteries with a voltage platform greater than 800V and higher energy density, fully meeting the development requirements of higher charging voltage platforms for future fast-charging electric vehicles.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a solvent-free UV dielectric insulation protective coating, and the solvent-free UV dielectric insulation protective coating comprises, by weight: 30-50 parts by weight of acrylate monomer, 15-40 parts by weight of organosilicon-modified polyurethane acrylate, polyester polyurethane acrylate or polyether polyurethane acrylate prepolymer, 5-10 parts by weight of high functionality acrylate crosslinking agent, 1-5 parts by weight of photoinitiator, 2-10 parts by weight of adhesion promoter, 0.5-2 parts by weight of acid remover, 1-5 parts by weight of wetting, dispersing and defoaming agent, 5-10 parts by weight of insulating powder, 5-10 parts by weight of heat-conducting filler and 0.5-3 parts by weight of pigment.

[0009] In the present invention, the UV dielectric insulation protective coating is a solvent-free system, which can reduce at least 60% of the energy loss compared with the traditional curing process. It can form a film and cure quickly under UV light radiation, with higher production efficiency and production quantity. It is easy to construct on an assembly line, and has excellent dielectric properties, breakdown strength, dielectric constant, volume resistivity, and dissipation factor between the positive and negative electrodes, which can significantly improve the safety and efficiency of the battery. Excellent adhesion and flexibility can cope with the mechanical stress and temperature changes generated during battery operation. Low energy consumption, fast curing, and construction convenience enable automated assembly line production (scalability and large-scale production). The solvent-free and environmentally friendly working environment can also better control the accuracy and speed of the production process.

[0010] The UV dielectric insulation coating can make up for the shortcomings of the blue film's cohesive failure and low adhesion to the inner aluminum shell of the inner battery cell and the external thermally conductive adhesive. At the same time, it is equivalent to the blue film in terms of insulation, edge coverage, and production efficiency (the sharp edges can be covered and the required breakdown voltage can be achieved by spraying the edge twice to make the film thickness greater than 100 microns). The specific advantages are as follows: The UV dielectric insulation protective coating is a solvent-free 100% solids content acrylate-based coating, which fully meets the national environmental protection requirements; The UV dielectric insulation protective coating uses a photocuring method, and the light source can be a Heraeus F300 microwave-free UV lamp equipped with an H-type lamp tube or a special mercury lamp, which can complete more than 90% of the curing depth within dozens of seconds; The UV dielectric insulation protective coating is sprayed using a relatively common HVLP gravity spray gun, and the equipment and process have automation and general properties; When the wet film thickness of the UV dielectric insulation protective coating is greater than 100 microns, the breakdown voltage is higher than the passing standard insulation requirement of 6 kV for the cooling plate assembly; The highly efficient thermally conductive gap filler can improve the thermal conductivity of the cured coating and achieve the best balance with the dielectric insulation protection performance, high adhesion, and the fastest production efficiency.

[0011] Therefore, developing an excellent UV dielectric insulation protective coating for electric vehicle power batteries, especially with more prominent energy utilization rate, production speed, and battery insulation protection efficiency, has great research significance.

[0012] As a preferred embodiment of the present invention, the acrylate monomer is an acrylate reactive diluent, and the acrylate reactive diluent includes methyl methacrylate, methyl acrylate, cyclohexyl acrylate, cyclohexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate, hexyl acrylate, hexyl methacrylate, decyl acrylate, decyl methacrylate, isodecyl acrylate, isodecyl methacrylate, norbornene acrylate, norbornene methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, or stearyl methacrylate.

[0013] As a preferred embodiment of the present invention, the acrylate reaction diluent is one or a mixture of more of norbornene acrylate, isooctyl acrylate, and methyl methacrylate.

[0014] As a preferred embodiment of the present invention, the high-functional acrylate crosslinking agent includes dipentaerythritol hexaacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triethoxy triacrylate, pentaerythritol triacrylate, or pentaerythritol tetraacrylate.

[0015] As a preferred embodiment of the present invention, the photoinitiator is a UV-activated photoinitiator, and the photoinitiator includes benzophenone, 1-hydroxycyclohexyl phenyl ketone, benzoin dimethyl ether, benzoin methyl ether, 2,2-dimethoxy-phenylacetophenone, monoacylphosphine oxide, bisacylphosphine oxide, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, hexaarylbiimidazole, 2-methyl-2-(4-morpholinyl)-1-[4-(methylthio)phenyl]-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, bis(2,6-dimethoxybenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone, diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, triarylsulfonium hexafluoroantimonate, triarylsulfonium hexafluorophosphate, or phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0016] As a preferred embodiment of the present invention, the adhesion promoter includes glycidyl methacrylate, 2-hydroxyethyl methacrylate phosphate, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, methyl methacrylate, or methacryloxypropyltrimethoxysilane.

[0017] As a preferred embodiment of the present invention, the acid scavenger includes zinc phosphate, zinc oxide, and zinc molybdate; the thermal conductive gap filler includes a composition of metal oxides, metal nitrides, and silicon carbide ceramic materials, wherein the metal oxides include alumina, magnesia, zinc oxide, or nickel oxide, and the metal nitrides include aluminum nitride, silicon nitride, or boron nitride.

[0018] In a second aspect, the present invention provides a method for preparing the above solvent-free UV dielectric insulation protective coating, and the preparation method includes the following steps:

[0019] 1) Weigh acrylate monomers. Under no light radiation and at a temperature below 30 °C, successively add a photoinitiator, an adhesion promoter, and a wetting, dispersing, and defoaming agent. Evacuate and stir evenly until there are no bubbles and no powder, then stop evacuating. Respectively add a high-viscosity organosilicon-modified polyurethane acrylate, a polyester polyurethane acrylate, or a polyether polyurethane acrylate prepolymer, and a high-functional acrylate crosslinking agent. Stir and heat until evenly dispersed to obtain a solvent-free UV dielectric insulation protective coating.

[0020] As a preferred embodiment of the present invention, after adding the high-viscosity organosilicon-modified polyurethane acrylate, the polyester polyurethane acrylate, or the polyether polyurethane acrylate prepolymer, and the high-functional acrylate crosslinking agent, stir and heat to 48 - 52 °C.

[0021] In a third aspect, the present invention provides the application of the above-mentioned solvent-free UV dielectric insulation protective coating on an electric vehicle power battery. The coating obtained after curing the UV dielectric insulation protective coating has no pinholes and bubbles formed, and has good coverage on the side edge of the cell aluminum shell. The dry film thickness of the UV dielectric insulation protective coating is 25 - 200 microns.

[0022] The solvent-free UV dielectric insulation protective coating of the present invention is a 100% solid coating. It can be coated onto the cell aluminum shell or other external metal packaging materials (aluminum metal) of the battery pack components by spraying, brushing, or dipping, and then exposed to a UV radiation environment for curing into a film. This is carried out in a UV radiation environment of a mercury lamp. The cured coating is a product of a UV-activated free radical cross-linking reaction of acrylate. The cured coating has no pinholes and bubbles formed, and has good coverage on the side edge of the cell aluminum shell; if the dry film thickness is greater than 100 microns, it can withstand a breakdown voltage of 5 - 10 kV. For the adhesion aging test, it can be carried out in a double 85 environment of 85 °C and 85% relative humidity for up to 1000 hours. Detailed Embodiments

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0024] The present invention provides a solvent-free UV dielectric insulation protective coating, a preparation method thereof and an application. The solvent-free UV dielectric insulation protective coating provided by the present invention is a dielectric insulation protective coating with high surface energy and high adhesion, which is obtained by combining flexible modified polyurethane acrylate, flexible acrylate, rigid acrylate with high glass transition temperature, high functionality acrylate crosslinking agent, highly dilutable methyl methacrylate with high glass transition temperature, and numerous photoinitiators, additives and pigment and filler powders. The coating prepared by the present invention is a solvent-free 100% solid single component, which is completely miscible, convenient for construction, has high photo-curing energy utilization rate and high production efficiency, and is applicable to large-scale automated production lines.

[0025] The solvent-free UV dielectric insulation protective coating described above comprises, by weight: 30-50 parts by weight of acrylate monomer, 15-40 parts by weight of organosilicon-modified polyurethane acrylate, polyester polyurethane acrylate or polyether polyurethane acrylate prepolymer, 5-10 parts by weight of high functionality acrylate crosslinking agent, 1-5 parts by weight of photoinitiator, 2-10 parts by weight of adhesion promoter, 0.5-2 parts by weight of acid remover, 1-5 parts by weight of wetting, dispersing and defoaming agent, 5-10 parts by weight of insulating powder, 5-10 parts by weight of heat conductive filler and 0.5-3 parts by weight of pigment.

[0026] Preferably, in the present invention, the acrylate monomer comprises various acrylate reactive diluents.

[0027] More preferably, the acrylate reactive diluent includes, but is not limited to, methyl methacrylate, methyl acrylate, cyclohexyl acrylate, cyclohexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate, hexyl acrylate, hexyl methacrylate, decyl acrylate, decyl methacrylate, isodecyl acrylate, isodecyl methacrylate, norbornene acrylate, norbornene methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate or stearyl methacrylate.

[0028] Even more preferably, the acrylate reactive diluent comprises at least one or more of norbornene acrylate, isooctyl acrylate and methyl methacrylate.

[0029] Preferably, the polyurethane acrylate prepolymer comprises one or more of organosilicon-modified polyurethane acrylate, polyester polyurethane acrylate or polyether polyurethane acrylate prepolymer.

[0030] Preferably, the high functionality acrylate crosslinking agent includes, but is not limited to, dipentaerythritol hexaacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triethoxy triacrylate, pentaerythritol triacrylate or pentaerythritol tetraacrylate.

[0031] Most preferably, the high-functional acrylate crosslinking agent is dipentaerythritol hexaacrylate.

[0032] Preferably, the photoinitiator includes various UV-activated photoinitiators.

[0033] More preferably, the photoinitiator includes, but is not limited to, benzophenone, 1-hydroxycyclohexyl phenyl ketone, benzoin dimethyl ether, benzoin methyl ether, 2,2-dimethoxy-phenyl acetophenone, monoacylphosphine oxide, bisacylphosphine oxide, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, hexaarylbiimidazole, 2-methyl-2-(4-morpholinyl)-1-[4-(methylthio)phenyl]-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, bis(2,6-dimethoxybenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone, diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, triarylsulfonium hexafluoroantimonate, triarylsulfonium hexafluorophosphate, or phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0034] Preferably, the adhesion promoter includes, but is not limited to, various types of adhesion promoters such as vinyl, acrylic, methacrylic, mercapto, hydroxy, acid groups such as carboxyl, phosphate, sulfonic acid, zirconate, titanate, silane, etc., and more specifically includes, but is not limited to, acrylic acid, methacrylic acid, functionalized carboxylic acid or phosphate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, dialkoxy zirconate or titanate, vinyltrimethoxysilane, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, glycidyl methacrylate, 2-hydroxyethyl methacrylate phosphate, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, or methacryloxypropyltrimethoxysilane.

[0035] More preferably, the adhesion promoter includes at least one of glycidyl methacrylate, 2-hydroxyethyl methacrylate phosphate, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, methyl methacrylate, and methacryloxypropyltrimethoxysilane.

[0036] Preferably, the acid scavenger includes a zinc acid scavenger.

[0037] More preferably, the acid scavenger includes, but is not limited to, zinc phosphate, zinc oxide, and zinc molybdate.

[0038] Preferably, the wetting, dispersing, and defoaming aids include, but are not limited to, Disperbyk 2300, Disperbyk 270, BYK 3500, and BYK 141.

[0039] Preferably, the insulating filler includes, but is not limited to, various untreated hydrophilic fumed silica and treated hydrophobic fumed silica.

[0040] Preferably, the thermal conductive gap filler includes, but is not limited to, various metal oxides such as aluminum oxide, magnesium oxide, zinc oxide, nickel oxide, and metal nitrides such as aluminum nitride, silicon nitride, boron nitride, and silicon carbide ceramic materials.

[0041] In the present invention, the structural formula of the silicone-block polyester polyurethane acrylate resin is as follows:

[0042]

[0043] In the formula, A: C5H 10 ; x: 1 - 2; y: 4 - 20; R' is an isocyanate intermediate structure such as IPDI, HI-100, HDI or MDI; R" is a hydrosilylation monomer intermediate structure such as hydroxyethyl allyl ether or hydroxypropyl allyl ether.

[0044] The structural formula of one kind of polyester polyurethane acrylate resin is as follows:

[0045]

[0046] In the formula, R' is an isocyanate intermediate structure such as IPDI, HI-100, HDI or MDI.

[0047] The structural formula of another kind of polyester polyurethane acrylate resin is as follows:

[0048]

[0049] In the formula, R' is an isocyanate intermediate structure such as IPDI, HI-100, HDI or MDI.

[0050] The structural formula of the polyether polyurethane acrylate resin is as follows:

[0051]

[0052] In the formula, n is 1 - 4, and R' is an isocyanate intermediate structure such as IPDI, HI-100, HDI or MDI.

[0053] The solvent-free UV dielectric insulation protective coating of the present invention can replace the blue film of the power battery of electric vehicles. The UV dielectric insulation protective coating is applied to the outer metal packaging material of the cell aluminum shell or other battery pack components, and then exposed to a UV radiation environment for curing into a film (curing is carried out in a UV radiation environment of a mercury lamp). The cured coating is a product of a UV-activated free radical cross-linking reaction of acrylate.

[0054] The coating obtained after curing the UV dielectric insulation protective coating of the present invention has no pinholes and bubbles formed, and has good coverage on the side edge of the aluminum shell of the battery cell. The dry film thickness of the UV dielectric insulation protective coating is 25 - 200 microns. If the dry film thickness is greater than 100 microns, it can withstand a breakdown voltage of 5 - 10 kV.

[0055] The materials of the above battery pack assembly are mainly metal packaging materials, more precisely, aluminum metal packaging materials.

[0056] Example 1

[0057] This example provides a solvent-free UV dielectric insulation protective coating, and its preparation method includes:

[0058] 1) Take 45 g of a combination of norbornene acrylate and isooctyl acrylate (mass ratio 4:1). Under no light radiation and at a temperature below 30 °C, sequentially add 3 g of a photoinitiator (2,2 - dimethoxy - phenylacetophenone), 8 g of an adhesion promoter (glycidyl methacrylate), and a combination of a wetting, dispersing, and defoaming agent (Degussa 2300) (mass ratio 1:1). Vacuumize and stir evenly until there are no bubbles and no powder. Then stop vacuumizing, and respectively add 19.3 g of a combination of high-viscosity organosilicon-modified polyurethane acrylate, polyester polyurethane acrylate, and polyether polyurethane acrylate prepolymers (the viscosity of the prepolymers is generally greater than 6000 and not exceeding 20000 at most. Considering surface energy control to improve the bonding performance of the internal and external adhesives, as well as leveling and adhesion control, the above three prepolymers are in a ratio of 1:3:1), 6.4 g of dipentaerythritol hexaacrylate (the purpose is to crosslink monofunctional acrylate through side chains), and stir and heat to 50 °C until evenly dispersed.

[0059] 2) To prevent moisture from existing in the premixed combination, appropriate vacuumizing can be carried out. Finally, at 50 °C, add 17.5 g of powder materials, including insulating powder, heat-conducting filler, and pigment (the insulating powder is mainly precipitated silica fume, the heat-conducting filler is mainly alumina treated with a coupling agent, and the pigment can be phthalocyanine or ultramarine, with a mass ratio of 10:5:1), 0.8 g of an acid remover (zinc phosphate). After high-speed dispersing for a certain time by a high-speed disperser until uniform, the required solvent-free UV dielectric insulation protective coating is obtained. The obtained coating has a relatively high viscosity and needs to be discharged at 50 °C.

[0060] 3) Spray the obtained coating onto an aluminum plate through a gravity spray gun, and control the wet film thickness to be 80 - 125 microns. Then, at an energy of 1500 mJ / cm 2Under the H-type mercury lamp, the cumulative energy was monitored by an EIT UVICURE PLUS II four-band energy detector. The upper and lower values of the breakdown voltage for a film thickness of 110 microns were 12 kV (ASTM, D3755), and the volume resistivity was 7x10 14 (ASTM D257-14). The adhesion test passed after 1000 hours in a double 85 environment (ISO 2409), and the bending flexibility passed (90-degree folding).

[0061] Example 2

[0062] This example provides a solvent-free UV dielectric insulation protective coating, and its preparation method includes:

[0063] 1) Take 35.9 g of a combination of norbornene acrylate and isooctyl acrylate (mass ratio 3:1), 10 g of methyl methacrylate. Under no light radiation and below 30 °C, successively add 3 g of a photoinitiator (benzoin methyl ether), 10.5 g of an adhesion promoter (2-hydroxyethyl methacrylate phosphate), and a wetting, dispersing, and defoaming agent combination (BYK 3500, mass ratio 1:1). Vacuumize and stir evenly until there are no bubbles and no powder, then stop vacuumizing. Then add 16.9 g of a combination of high-viscosity organosilicon-modified polyurethane acrylate, polyester polyurethane acrylate, and polyether polyurethane acrylate prepolymers (the viscosity of the prepolymers is generally greater than 6000 and not exceeding 20000 at most. Considering surface energy control to improve the adhesion performance of the internal and external adhesives, as well as leveling and adhesion control, the above three prepolymers are in a ratio of 1:3:1), 5.0 g of dipentaerythritol hexaacrylate, and stir and heat to 50 °C until evenly dispersed.

[0064] (2) To prevent moisture from existing in the premixed combination, vacuumization can be appropriately carried out. Finally, at 50 °C, add 14.9 g of powders, including insulating powders, thermal conductive fillers, and pigments (the insulating powder is mainly precipitated silica, the thermal conductive filler is mainly alumina treated with a coupling agent, and the pigment can be phthalocyanine or ultramarine, mass ratio 10:5:1), 3.8 g of an acid scavenger (zinc oxide). After high-speed dispersion by a high-speed disperser for a certain time until uniform, the desired solvent-free UV dielectric insulation protective coating is obtained. The viscosity of the obtained coating is relatively high, and the discharging operation needs to be carried out at 50 °C.

[0065] 3) Spray the obtained coating onto an aluminum plate through a gravity spray gun, and control the wet film thickness to be 80 - 125 microns. Then, under the H-type mercury lamp with an energy of 1500 mJ / cm 2 the cumulative energy was monitored by an EIT UVICURE PLUS II four-band energy detector. The upper and lower values of the breakdown voltage for a film thickness of 110 microns were 11 kV (ASTM, D3755), and the volume resistivity was 5x1014 (ASTM D257-14), passed the adhesion test for 1000 hours in the double 85 environment (ISO 2409), and passed the bending flexibility test (90-degree folding).

[0066] Example 3

[0067] This example provides a solvent-free UV dielectric insulation and protection coating, and its preparation method includes:

[0068] Take 40 g of a combination of norbornene acrylate and isooctyl acrylate (mass ratio 4:1). Under no light radiation and at a temperature below 30 °C, sequentially add 3 g of a photoinitiator (1-hydroxycyclohexyl phenyl ketone), 12 g of an adhesion promoter (3-(2,3-epoxypropoxy)propyltrimethoxysilane), and a combination of a wetting, dispersing, and defoaming agent (Degussa 270) (mass ratio 1:1). Evacuate and stir evenly until there are no bubbles and no powder. Then stop evacuating, and respectively add 25 g of a combination of high-viscosity organosilicon-modified polyurethane acrylate, polyester polyurethane acrylate, and polyether polyurethane acrylate prepolymers (the viscosity of the prepolymers is generally greater than 6000 and does not exceed 20000 at most. Considering surface energy control to improve the adhesion performance of the internal and external adhesive, as well as the leveling and adhesion control, the above three prepolymers are in a ratio of 1:4:1), 6.4 g of dipentaerythritol hexaacrylate, and stir and heat to 50 °C until evenly dispersed.

[0069] 2) To prevent moisture from existing in the premixed combination, evacuation can be appropriately carried out. Finally, at 50 °C, add 15.5 g of powders, including insulating powders, heat-conducting fillers, and pigments (the insulating powder is mainly precipitated silica fume, the heat-conducting filler is mainly alumina treated with a coupling agent, and the pigment can be phthalocyanine or ultramarine, with a mass ratio of 10:5:1), 4.5 g of an acid remover (zinc molybdate). After high-speed dispersing for a certain time by a high-speed disperser until it is uniform, the desired solvent-free UV dielectric insulation and protection coating is obtained. The viscosity of the obtained coating is relatively high, and the discharging operation needs to be carried out at 50 °C.

[0070] 3) Spray the obtained coating onto an aluminum plate through a gravity spray gun, and control the wet film thickness to be 80 - 125 μm. Then, under an H-type mercury lamp with an energy of 1500 mJ / cm 2 monitor the cumulative energy through an EIT UVICURE PLUS II four-band energy detector. The upper and lower values of the breakdown voltage for a 110-μm film thickness are 12 kV (ASTM, D3755), and the volume resistivity is 3×10 14 (ASTM D257-14), passed the adhesion test for 1000 hours in the double 85 environment (ISO 2409), and passed the bending flexibility test (90-degree folding).

[0071] The beneficial effects of the present invention are as follows: The coating prepared by the present invention is a solvent-free 100% solid single-component, with complete miscibility, convenient construction, high utilization rate of photocuring energy, high production efficiency, and is applicable to large-scale automated mass production lines. After UV curing, the coating prepared by the present invention has a bonding strength with the battery core far higher than that of the PSA back glue used in traditional PET blue films. At the same time, due to the higher surface energy of the outer surface of the coating compared to PET blue films, it can be firmly bonded to other battery pack components through structural adhesives, eliminating the potential risks of the peeling of the blue film from the battery core component and the battery pack caused by the cohesive failure of the PSA in the PET blue film and the peeling of the outer structural adhesive. At the same time, it has dielectric insulation performance and edge coverage protection performance comparable to those of PET blue films. Compared with the working voltage platform of less than 400V for PET blue films, it can be applied to voltage platforms greater than 800V and power batteries with higher energy density, fully meeting the development requirements of future fast-charging electric vehicles with higher charging voltage platforms.

[0072] The above is only the preferred embodiment of the present invention, and it does not impose any formal or substantial limitations on the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the method of the present invention, several improvements and supplements can still be made, and these improvements and supplements should also be regarded as the protection scope of the present invention. Any equivalent changes, such as minor modifications, decorations, and evolutions made by those skilled in the art who are familiar with this specialty without departing from the spirit and scope of the present invention by using the technical content disclosed above, are all equivalent embodiments of the present invention; at the same time, any equivalent changes, such as modifications, decorations, and evolutions made to the above embodiments based on the essential technology of the present invention, still fall within the scope of the technical solution of the present invention.

Claims

1. A solvent-free UV dielectric insulation protective coating, characterized in that: The solvent-free UV dielectric insulating protective coating comprises, by weight: 30-50 parts by weight of acrylate monomer, 15-40 parts by weight of silicone-modified polyurethane acrylate, polyester polyurethane acrylate or polyether polyurethane acrylate prepolymer, 5-10 parts by weight of high-functionality acrylate crosslinking agent, 1-5 parts by weight of photoinitiator, 2-10 parts by weight of adhesion promoter, 0.5-2 parts by weight of acid scavenger, 1-5 parts by weight of wetting and dispersing defoaming agent, 5-10 parts by weight of insulating powder, 5-10 parts by weight of thermal conductive filler and 0.5-3 parts by weight of pigment.

2. A solvent-free UV dielectric insulation protective coating according to claim 1, characterized in that: The acrylic acid ester monomer is an acrylic acid ester reactive diluent, and the acrylic acid ester reactive diluent includes methyl methacrylate, methyl acrylate, cyclohexyl acrylate, cyclohexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate, hexyl acrylate, hexyl methacrylate, decyl acrylate, decyl methacrylate, isodecyl acrylate, isodecyl methacrylate, norbornyl acrylate, norbornyl methacrylate, lauryl acrylate, lauryl methacrylate, stearic acid ester or stearic acid ester.

3. A solvent-free UV dielectric insulation protective coating according to claim 2, characterized in that: The acrylic acid ester reactive diluent is a mixture of one or more of norbornyl acrylate, isooctyl acrylate and methyl methacrylate.

4. The solvent-free UV dielectric insulation protective coating according to claim 1, characterized in that: The high-functionality acrylate crosslinking agent includes dipentaerythritol hexaacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triethoxy triacrylate, pentaerythritol triacrylate or pentaerythritol tetraacrylate.

5. The solvent-free UV dielectric insulation protective coating according to claim 1, characterized in that: The photoinitiator is a UV activated photoinitiator, and the photoinitiator includes benzophenone, 1-hydroxycyclohexyl phenyl ketone, benzoin dimethyl ether, benzoin methyl ether, 2,2-dimethoxy-phenyl acetophenone, monoacylphosphine oxide, bisacylphosphine oxide, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, hexaarylbiimidazole, 2-methyl-2-(4-morpholinyl)-1-[4-(methylthio)phenyl] ... ]-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, bis(2,6-dimethoxybenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone, diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, triarylsulfonium hexafluoroantimonate, triarylsulfonium hexafluorophosphate or phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

6. The solvent-free UV dielectric insulation protective coating according to claim 1, characterized in that: The adhesion promoter includes glycidyl methacrylate, 2-hydroxyethyl methacrylate phosphate, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, methyl methacrylate or methacryloxypropyltrimethoxysilane.

7. The solvent-free UV dielectric insulation protective coating according to claim 1, characterized in that: The acid scavenger includes zinc phosphate, zinc oxide and zinc molybdate; the thermal conductive gap filler includes a combination of metal oxide, metal nitride and silicon carbide ceramic material, wherein the metal oxide includes aluminum oxide, magnesium oxide, zinc oxide or nickel oxide, and the metal nitride includes aluminum nitride, silicon nitride or boron nitride.

8. A method for preparing a solvent-free UV dielectric insulation protective coating, characterized in that: The preparation method comprises the following steps: 1) Weighing an acrylate monomer, adding a photoinitiator, an adhesion promoter and a wetting and dispersing defoamer in sequence without light radiation and below 30 degrees Celsius, vacuuming and stirring evenly until there is no bubble and powder, stopping vacuuming, adding high-viscosity silicone-modified polyurethane acrylate, polyester polyurethane acrylate or polyether polyurethane acrylate prepolymer and a high-functionality acrylate crosslinking agent respectively, stirring and heating until uniform dispersion, and preparing a solvent-free UV dielectric insulation protective coating.

9. The method for preparing a solvent-free UV dielectric insulation protective coating according to claim 8, characterized in that: After adding high-viscosity silicone-modified polyurethane acrylate, polyester polyurethane acrylate or polyether polyurethane acrylate prepolymer and high-functionality acrylate crosslinking agent, stir and heat to 48-52°C.

10. An application of a solvent-free UV dielectric insulation protective coating, characterized in that: The solvent-free UV dielectric insulation protective coating is used on electric vehicle power batteries, and the dry film thickness of the UV dielectric insulation protective coating is 25-200 microns.

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