Fluorine-free photocuring insulating protective coating as well as preparation method and application thereof

Abstract

The invention discloses a fluoride-free photocuring insulating protective coating as well as a preparation method and application thereof, and relates to the technical field of high-voltage insulating protection and green high polymer materials for power batteries of new energy automobiles. The fluoride-free light-cured insulating protective coating disclosed by the invention is prepared from the following raw materials in parts by mass: 40 to 80 parts of polyfunctional polyurethane acrylate prepolymer, 10 to 40 parts of carbonate modified acrylate monomer, 5 to 15 parts of reactive lithium salt monomer, 10 to 20 parts of filler and 3 to 5 parts of photoinitiator. The polyfunctional polyurethane acrylate prepolymer is prepared by reacting polycaprolactone glycol, vinyl carbonate modified glycol, isophorone diisocyanate and a hydroxyl-containing polyfunctional acrylate monomer in the presence of a catalyst and a polymerization inhibitor. The fluorine-free photocuring insulating protective coating disclosed by the invention is low in PFAS content, and has relatively good pressure resistance, electrolyte resistance and mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of high-voltage insulation protection and green polymer materials technology for power batteries of new energy vehicles, and particularly to a fluorine-free photocurable insulating protective coating and its preparation method and application. Background Technology

[0002] In the field of insulating and protective coatings for power batteries of new energy vehicles, fluorinated insulating and protective coatings have excellent oxidation resistance and electrolyte resistance, but their high fluorine content makes them prone to producing PFAS and have poor environmental performance. However, in existing fluorine-free insulating and protective coatings, such as Chinese patent application CN102314959A, although a fluorine-free electrode surface insulating coating with a withstand voltage of about 3000V is achieved, it relies solely on inorganic fillers such as Al2O3 and SiO2 and binders, lacking a molecular-level electrolyte-resistant structural design. This results in severe blistering and softening after immersion in electrolyte for 10-30 minutes, and large-area cracking after an 8J impact, failing to meet the high-voltage and high-temperature service requirements of the battery pack. Other fluorine-free patent applications, such as CN102569680A, disclose a thermal insulation layer using fillers such as Al2O3 and BN, which improves thermal insulation but still lacks the comprehensive performance of electrolyte immersion resistance and mechanical impact resistance.

[0003] Therefore, there is an urgent need for a fluorine-free photocurable insulating and protective coating, its preparation method, and its application, in order to overcome the shortcomings of existing technologies. Summary of the Invention

[0004] In view of the above problems, the purpose of this invention is to provide a fluorine-free photocurable insulating protective coating, its preparation method and application. The fluorine-free photocurable insulating protective coating has a low PFAS content and good voltage resistance, electrolyte resistance and mechanical properties.

[0005] To achieve the above objectives, the first aspect of the present invention provides a fluorine-free photocurable insulating and protective coating, wherein the raw materials for preparation, by weight, include 40-80 parts of multifunctional polyurethane acrylate prepolymer, 10-40 parts of carbonate-modified acrylate monomer, 5-15 parts of reactive lithium salt monomer, 10-20 parts of filler and 3-5 parts of photoinitiator. Multifunctional polyurethane acrylate prepolymers are prepared by reacting polycaprolactone diol, vinyl carbonate-modified diol, isophorone diisocyanate, and hydroxyl-containing multifunctional acrylate monomers under the conditions of a catalyst and a polymerization inhibitor.

[0006] Compared with the prior art, the fluorine-free photocurable insulating and protective coating of the present invention has at least the following beneficial effects: (1) The raw materials for preparing the multifunctional polyurethane acrylate prepolymer of the present invention include polycaprolactone diol and vinyl carbonate modified diol. Cyclic carbonate groups and polycaprolactone flexible segments can be introduced into the prepolymer chain segments. The cyclic carbonate groups can improve the compatibility of the coating with carbonate electrolytes and make it less prone to foaming and swelling in the electrolyte, thereby improving the electrolyte resistance of the coating. The introduction of polycaprolactone flexible segments can give the coating better toughness, thereby improving its mechanical properties. The combination of the two can further improve the initial pressure resistance of the coating.

[0007] (2) The multifunctional polyurethane acrylate prepolymer (hereinafter referred to as prepolymer) with special structure of the present invention is compounded with carbonate-modified acrylate monomer, reactive lithium salt monomer and filler. The prepolymer can work with carbonate-modified acrylate monomer to construct a highly cross-linked organic skeleton, so that the coating does not bulge or soften after being immersed in electrolyte for 30 days, and the withstand voltage decrease is less than 5% after immersion in electrolyte. The reactive lithium salt monomer can be chemically bonded to the cross-linked network during photocuring and can form a lithium-ion-rich thin layer at the interface between the coating and the electrode, effectively suppressing the accumulation of space charge, thereby synergistically improving its electrolyte resistance. The addition of filler can make the coating have excellent wear resistance and can work synergistically with prepolymer to improve its impact resistance.

[0008] In summary, the coating of the present invention does not contain fluorine and has a low PFAS content. Furthermore, by compounding a multifunctional polyurethane acrylate prepolymer with a special structure with carbonate-modified acrylate monomers, reactive lithium salt monomers, and fillers, the components generate a synergistic effect through covalent bonding, hydrogen bonding, and microscopic interpenetrating networks, thereby effectively improving the coating's pressure resistance, electrolyte resistance, and mechanical properties.

[0009] Furthermore, the raw materials for preparing the multifunctional polyurethane acrylate prepolymer of the present invention include 800-1200 parts by weight of polycaprolactone diol, 150-600 parts by weight of vinyl carbonate modified diol, 500-1000 parts by weight of isophorone diisocyanate, 350-750 parts by weight of hydroxyl-containing multifunctional acrylate monomer, 0.5-2.0 parts by weight of catalyst, and 0.8-2.5 parts by weight of polymerization inhibitor.

[0010] Furthermore, the vinyl carbonate-modified diol of the present invention is prepared by reacting vinylene carbonate and polyethylene glycol under alkaline catalyst conditions.

[0011] Furthermore, the hydroxyl-containing multifunctional acrylate monomer of the present invention is selected from at least one of pentaerythritol triacrylate monohydroxy ester and dipentaerythritol pentaacrylate monohydroxy ester.

[0012] Furthermore, the carbonate-modified acrylate monomer of the present invention is selected from at least one of vinylene carbonate-modified diacrylate, vinylene carbonate-caprolactone co-modified diacrylate, and cyclic carbonate-modified tetraacrylate.

[0013] Furthermore, the reactive lithium salt monomer of the present invention is selected from at least one of lithium bis(oxalato)borate-acrylate and lithium phosphate-acrylate.

[0014] Furthermore, the filler of the present invention is selected from at least one of alumina, boron nitride, and silicon dioxide.

[0015] Furthermore, the photoinitiator of the present invention is selected from at least one of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0016] A second aspect of the present invention provides a method for preparing the aforementioned fluorine-free photocurable insulating and protective coating, comprising: (1) Preparation of multifunctional polyurethane acrylate prepolymer Under a protective atmosphere, the formulated amounts of polycaprolactone diol, vinyl carbonate-modified diol, isophorone diisocyanate, and catalyst are heated and reacted until the mass percentage of -NCO is 4.0%~6.0%. After cooling, a hydroxyl-containing polyfunctional acrylate monomer is added, and the reaction continues until the infrared detection of the -NCO peak completely disappears. After adding a polymerization inhibitor, the product is discharged, which is a polyfunctional polyurethane acrylate prepolymer. (2) Preparation of fluorine-free photocurable insulating and protective coating Mix the multifunctional polyurethane acrylate prepolymer, carbonate-modified acrylate monomer, reactive lithium salt monomer, filler and photoinitiator in the specified amounts until homogeneous.

[0017] The third aspect of the present invention provides the application of the aforementioned fluorine-free photocurable insulating and protective coating or the fluorine-free photocurable insulating and protective coating prepared according to the aforementioned method for preparing the fluorine-free photocurable insulating and protective coating in the power battery of a new energy vehicle. Detailed Implementation

[0018] To effectively address the critical industry challenge of ensuring that key components within 800-1500V high-voltage power battery packs simultaneously require "high insulation and withstand voltage + impact and abrasion resistance + resistance to electrolyte leakage and corrosion" in complex working environments, while being completely fluorine-free to meet the EU PFAS ban, the latest REACH revision, RoHS 2.0, and the strictest environmental requirements of the automotive industry, this invention provides a fluorine-free photocurable insulating protective coating. This coating contains <1ppm of PFAS, cures rapidly, and the initial withstand voltage of the cured insulating protective coating is greater than 3500V (leakage current <1mA). It does not bubble or crack after 24 hours of immersion in electrolyte, and its withstand voltage performance decreases by 5% after immersion. It withstands 8J impact without cracking and remains ≥2800V after 1000 cycles of a 1kg load.

[0019] Specifically, the fluorine-free photocurable insulating and protective coating of the present invention, by weight, comprises 40-80 parts of multifunctional polyurethane acrylate prepolymer, 10-40 parts of carbonate-modified acrylate monomer, 5-15 parts of reactive lithium salt monomer, 10-20 parts of filler and 3-5 parts of photoinitiator.

[0020] The mass fractions of the multifunctional polyurethane acrylate prepolymer can be, but are not limited to, 40, 45, 50, 55, 60, 65, 70, 75, or 80 parts. Specifically, the multifunctional polyurethane acrylate prepolymer can be a hexafunctional polyurethane acrylate prepolymer or an octafunctional polyurethane acrylate prepolymer, but is not limited to these. The multifunctional polyurethane acrylate prepolymer is prepared by reacting polycaprolactone diol, vinyl carbonate-modified diol, isophorone diisocyanate, and hydroxyl-containing multifunctional acrylate monomers under the conditions of a catalyst and a polymerization inhibitor. Specifically, the raw materials for preparing multifunctional polyurethane acrylate prepolymers include 800-1200 parts by weight of polycaprolactone diol, 150-600 parts by weight of vinyl carbonate modified diol, 500-1000 parts by weight of isophorone diisocyanate, 350-750 parts by weight of hydroxyl-containing multifunctional acrylate monomers, 0.5-2.0 parts by weight of catalyst, and 0.8-2.5 parts by weight of polymerization inhibitor.

[0021] The mass fractions of polycaprolactone diol may be, but are not limited to, 800, 850, 900, 950, 1000, 1050, 1100, 1150, or 1200 parts. The molecular weight of polycaprolactone diol is 500-4000. The mass fractions of vinyl carbonate-modified diol may be, but are not limited to, 150, 200, 250, 300, 350, 400, 450, 500, 550, or 600 parts. Vinyl carbonate modified glycol is prepared by reacting vinylene carbonate and polyethylene glycol under alkaline catalyst conditions. The molar ratio of vinylene carbonate to polyethylene glycol can be 1:1 to 1.1, the molecular weight of polyethylene glycol is 200 to 400 g / mol, the alkaline catalyst can be 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), the reaction temperature can be 60 to 80℃, and the reaction time can be 4 to 8 h. Specifically, the reaction temperature can be, but is not limited to, 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, 78℃, and 80℃; the reaction time can be, but is not limited to, 4 h, 5 h, 6 h, 7 h, and 8 h. The mass fractions of isophorone diisocyanate may be, but are not limited to, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, or 1000 parts. The mass fractions of hydroxyl-containing polyfunctional acrylate monomers may be, but are not limited to, 350, 400, 450, 500, 550, 600, 650, 700, or 750 parts. The hydroxyl-containing polyfunctional acrylate monomers are selected from at least one of pentaerythritol triacrylate monohydroxy ester and dipentaerythritol pentaacrylate monohydroxy ester. The mass fractions of the catalyst may be, but are not limited to, 0.5, 0.8, 1.0, 1.2, 1.4, 1.5, 1.6, 1.8, or 2.0 parts. The catalyst may specifically be an organotin catalyst. The mass fraction of the polymerization inhibitor can be, but is not limited to, 0.8 parts, 1.0 parts, 1.2 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.8 parts, 2.0 parts, 2.3 parts, or 2.5 parts. Specifically, the polymerization inhibitor can be hydroquinone monomethyl ether.

[0022] The mass fractions of carbonate-modified acrylate monomers can be, but are not limited to, 10, 15, 20, 25, 30, 35, or 40 parts. The carbonate-modified acrylate monomers are selected from at least one of vinylene carbonate-modified diacrylates, vinylene carbonate-caprolactone co-modified diacrylates, and cyclic carbonate-modified tetraacrylates. Specifically, vinylene carbonate-modified diacrylates are prepared by reacting vinylene carbonate and hydroxyethyl acrylate under the catalysis of p-toluenesulfonic acid or methanesulfonic acid, wherein the molar ratio of vinylene carbonate to hydroxyethyl acrylate can be 1:2, the catalytic reaction temperature can be 120-140°C, and the catalytic reaction time can be 8-12 hours. Vinylene carbonate-caprolactone co-modified diacrylates are prepared by first ring-opening copolymerization of vinylene carbonate and ε-caprolactone, followed by esterification with acrylate. Cyclic carbonate-modified tetraacrylate is prepared by reacting pentaerythritol with 4-chloromethyl-1,3-dioxolane-2-one in a potassium carbonate / DMF system, followed by azeotropic esterification with acrylic acid. The reaction temperature in the potassium carbonate / DMF system can be 80~100℃, and the reaction time can be 12~18h.

[0023] The mass fractions of the reactive lithium salt monomer can be, but are not limited to, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 parts. The reactive lithium salt monomer is selected from at least one of lithium bis(oxalato)borate-acrylate and lithium phosphate-acrylate. Specifically, lithium bis(oxalato)borate-acrylate is prepared by esterification of lithium bis(oxalato)borate (LiBOB) with 2-hydroxyethyl acrylate under anhydrous conditions. Lithium phosphate-acrylate is prepared by reacting phosphorus trichloride with hydroxyethyl acrylate to generate bis(acryloyloxyethyl)phosphochloride, followed by reaction with excess lithium hydroxide or lithium carbonate. The reaction temperature of phosphorus trichloride with hydroxyethyl acrylate can be 0–5°C, and the reaction temperature with excess lithium hydroxide or lithium carbonate can be 25–40°C, with a reaction time of 6–10 h.

[0024] The mass fraction of the filler can be, but is not limited to, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 parts. The filler is selected from at least one of alumina, boron nitride, and silica. Alumina, boron nitride, or silica fillers can be uniformly dispersed in the coating system of this invention and form an island-reinforcing phase, giving the coating better hardness and wear resistance, and can synergistically work with the prepolymer of this invention to further improve its impact resistance.

[0025] The photoinitiator may be, but is not limited to, 3 parts, 3.5 parts, 4 parts, 4.5 parts, or 5 parts by mass. The photoinitiator is selected from at least one of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) and 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173). Preferably, the photoinitiator is a combination of TPO and 1173, and the mass ratio of TPO to 1173 may be 1 to 1.5:1. Specifically, the mass ratio of TPO to 1173 may be, but is not limited to, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, or 1.5:1.

[0026] The preparation method of the fluorine-free photocurable insulating and protective coating of the present invention includes the following steps: (1) Preparation of multifunctional polyurethane acrylate prepolymer Under a protective atmosphere, the formulated amounts of polycaprolactone diol, vinyl carbonate-modified diol, isophorone diisocyanate, and catalyst are reacted at 70-75°C until the mass percentage of -NCO is 4.0%-6.0%. After cooling to 45-55°C, a hydroxyl-containing polyfunctional acrylate monomer is added, and the reaction continues until the infrared detection of the -NCO peak completely disappears. After adding a polymerization inhibitor, the product is discharged, which is the polyfunctional polyurethane acrylate prepolymer. (2) Preparation of fluorine-free photocurable insulating and protective coating Mix the multifunctional polyurethane acrylate prepolymer, carbonate-modified acrylate monomer, reactive lithium salt monomer, filler and photoinitiator in the specified amounts until homogeneous.

[0027] To better illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below with reference to specific embodiments. It should be noted that the methods described below are further explanations of this invention and should not be construed as limiting it.

[0028] The raw materials used in the embodiments and comparative examples of the present invention are described below.

[0029] Vinylene carbonate modified diacrylate: Vinylene carbonate and hydroxyethyl acrylate are mixed at a molar ratio of 1:2 and subjected to a ring-opening addition esterification reaction at 130°C for 10 h under the catalysis of p-toluenesulfonic acid. After removing excess alcohol by vacuum distillation, a colorless to pale yellow viscous liquid is obtained, which is vinylene carbonate modified diacrylate.

[0030] Vinylene carbonate-caprolactone co-modified diacrylate: 400g vinylene carbonate, 800g ε-caprolactone, and 8g DBU were added to a reaction flask and reacted at 80℃ under nitrogen protection for 6h to obtain a hydroxyl-terminated intermediate. Subsequently, 350g acrylic acid, 500g methyl methacrylate, 12g p-toluenesulfonic acid, and 1.2g MEHQ were added, and the mixture was azeotropically esterified with water at 130℃ for 10h. After alkali washing, water washing, and desolventization under reduced pressure, a pale yellow transparent liquid was obtained, which is the vinylene carbonate-caprolactone co-modified diacrylate.

[0031] Cyclic vinylene carbonate modified diacrylate: Pentaerythritol and 4-chloromethyl-1,3-dioxolane-2-one were reacted in a potassium carbonate / DMF system at 90°C for 16 h, followed by azeotropic esterification with acrylic acid for 2 h, to obtain a pale yellow viscous liquid, which is cyclic vinylene carbonate modified diacrylate.

[0032] LiBOB-acrylate: prepared by esterification of lithium bis(oxalato)borate with 2-hydroxyethyl acrylate under anhydrous conditions.

[0033] Lithium phosphate ester-acrylate: Phosphorus trichloride and hydroxyethyl acrylate are reacted in anhydrous acetonitrile at 0~5℃ to generate bis(acryloyloxyethyl) phosphate chloride, which is then reacted with excess lithium carbonate in a water / acetonitrile mixed solvent at 33℃ for 8h to obtain a white solid, which is lithium phosphate ester-acrylate.

[0034] Vinyl carbonate modified diol: 1 mol of vinylene carbonate and 1.05 mol of polyethylene glycol (molecular weight 200~400) were reacted at 70℃ for 6 h under DBU catalysis to obtain a vinyl carbonate modified diol with a molecular weight of about 500.

[0035] In the embodiments and comparative examples of the present invention, all other raw materials not described herein are obtained from commercially available sources.

[0036] Example 1 This embodiment provides a fluorine-free photocurable insulating and protective coating. The raw materials, by weight, include 60 parts of hexafunctional polyurethane acrylate prepolymer, 20 parts of vinylene-modified diacrylate, 8 parts of LiBOB-acrylate, and 15 parts of spherical Al₂O₃ (particle size D). V The product consists of 50 parts of a 15μm polyurethane prepolymer and 5 parts of a photoinitiator (TPO:1173=1:1). The hexafunctional polyurethane acrylate prepolymer is prepared from 1000 parts of polycaprolactone diol (molecular weight 1000), 400 parts of vinyl carbonate-modified diol, 800 parts of isophorone diisocyanate, and 500 parts of pentaerythritol triacrylate monohydroxy ester under the conditions of 1 part dibutyltin dilaurate and 1 part hydroquinone monomethyl ether.

[0037] The preparation method of this fluorine-free photocurable insulating and protective coating includes the following steps: (1) Preparation of hexafunctional polyurethane acrylate prepolymer Under a nitrogen atmosphere, the aforementioned amounts of polycaprolactone diol, vinyl carbonate-modified diol, isophorone diisocyanate, and dibutyltin dilaurate were reacted at 75°C until the mass percentage of -NCO was 6.0%. After cooling to 50°C, pentaerythritol triacrylate monohydroxy ester was added, and the reaction continued until the infrared detection of the -NCO peak completely disappeared. Hydroquinone monomethyl ether was added, and the product was discharged to obtain the hexafunctional polyurethane acrylate prepolymer. (2) Preparation of fluorine-free photocurable insulating and protective coating The hexafunctional polyurethane acrylate prepolymer, vinylene carbonate modified diacrylate, LiBOB-acrylate, spherical Al2O3 and photoinitiator in the aforementioned formulations are mixed evenly to obtain a fluorine-free photocurable insulating and protective coating.

[0038] Example 2 This embodiment provides a fluorine-free photocurable insulating and protective coating. The raw materials, by weight, include 55 parts of an octafunctional polyurethane acrylate prepolymer, 20 parts of vinylene carbonate-modified diacrylate, 10 parts of lithium phosphate acrylate, 18 parts of hexagonal boron nitride, and 4 parts of a photoinitiator (TPO:1173=1:1). The octafunctional polyurethane acrylate prepolymer is prepared from 1000 parts of polycaprolactone diol (molecular weight 1000), 400 parts of vinyl carbonate-modified diol, 800 parts of isophorone diisocyanate, and 500 parts of dipentaerythritol pentaacrylate monohydroxy ester under the conditions of 1 part dibutyltin dilaurate and 1 part hydroquinone monomethyl ether.

[0039] The preparation method of this fluorine-free photocurable insulating and protective coating includes the following steps: (1) Preparation of octafunctional polyurethane acrylate prepolymer Under a nitrogen atmosphere, the aforementioned amounts of polycaprolactone diol, vinyl carbonate-modified diol, isophorone diisocyanate, and dibutyltin dilaurate were reacted at 75°C until the mass percentage of -NCO was 5.0%. After cooling to 50°C, dipentaerythritol pentaacrylate monohydroxy ester was added, and the reaction continued until the infrared detection of the -NCO peak completely disappeared. Hydroquinone monomethyl ether was added, and the product was discharged to obtain the octafunctional polyurethane acrylate prepolymer. (2) Preparation of fluorine-free photocurable insulating and protective coating The aforementioned amounts of octafunctional polyurethane acrylate prepolymer, vinylene carbonate-modified diacrylate, lithium phosphate ester-acrylate, hexagonal boron nitride, and photoinitiator are mixed evenly to obtain a fluorine-free photocurable insulating and protective coating.

[0040] Example 3 This embodiment provides a fluorine-free photocurable insulating and protective coating. The raw materials, by weight, include 65 parts of hexafunctional polyurethane acrylate prepolymer, 18 parts of vinylene carbonate-caprolactone co-modified diacrylate, 12 parts of LiBOB-acrylate, and 12 parts of molten SiO2 (particle size D). V The product consists of 50 parts (20 μm) and 4 parts photoinitiator (TPO:1173=1:1). The hexafunctional polyurethane acrylate prepolymer is prepared from 1000 parts polycaprolactone diol (molecular weight 1000), 400 parts vinyl carbonate-modified diol, 800 parts isophorone diisocyanate, and 500 parts pentaerythritol triacrylate monohydroxy ester under the conditions of 1 part dibutyltin dilaurate and 1 part hydroquinone monomethyl ether.

[0041] The preparation method of this fluorine-free photocurable insulating and protective coating includes the following steps: (1) Preparation of hexafunctional polyurethane acrylate prepolymer This step is the same as in Example 1; (2) Preparation of fluorine-free photocurable insulating and protective coating The hexafunctional polyurethane acrylate prepolymer, vinylene carbonate-caprolactone co-modified diacrylate, LiBOB-acrylate, molten SiO2 and photoinitiator in the aforementioned formulation amounts are mixed evenly to obtain a fluorine-free photocurable insulating and protective coating.

[0042] Example 4 This embodiment provides a fluorine-free photocurable insulating and protective coating. The raw materials, by weight, include 50 parts of an octafunctional polyurethane acrylate prepolymer, 30 parts of cyclic vinylene carbonate-modified diacrylate, 8 parts of lithium phosphate acrylate, and 15 parts of spherical Al₂O₃ (particle size D). V The product consists of 50 parts of a 15μm polyurethane prepolymer and 5 parts of a photoinitiator (TPO:1173=1:1). The octafunctional polyurethane acrylate prepolymer is prepared from 1000 parts of polycaprolactone diol (molecular weight 1000), 400 parts of vinyl carbonate-modified diol, 800 parts of isophorone diisocyanate, and 500 parts of dipentaerythritol pentaacrylate monohydroxy ester under the conditions of 1 part dibutyltin dilaurate and 1 part hydroquinone monomethyl ether.

[0043] The preparation method of this fluorine-free photocurable insulating and protective coating includes the following steps: (1) Preparation of octafunctional polyurethane acrylate prepolymer This step is the same as in Example 2; (2) Preparation of fluorine-free photocurable insulating and protective coating The aforementioned amounts of octafunctional polyurethane acrylate prepolymer, cyclic vinylene carbonate modified diacrylate, lithium phosphate ester-acrylate, spherical Al2O3, and photoinitiator are mixed evenly to obtain a fluorine-free photocurable insulating and protective coating.

[0044] Example 5 This embodiment provides a fluorine-free photocurable insulating and protective coating. The raw materials, by weight, include 70 parts of hexafunctional polyurethane acrylate prepolymer, 20 parts of vinylene carbonate-modified diacrylate, 10 parts of lithium phosphate acrylate, and 15 parts of spherical Al₂O₃ (particle size D). V 50 parts (15 μm) and 4.5 parts photoinitiator (TPO:1173=1.2:1). The multifunctional polyurethane acrylate prepolymer was prepared from 1000 parts polycaprolactone diol (molecular weight 1000), 400 parts vinyl carbonate-modified diol, 800 parts isophorone diisocyanate, and 500 parts pentaerythritol triacrylate monohydroxy ester under the conditions of 1 part dibutyltin dilaurate and 1 part hydroquinone monomethyl ether.

[0045] The preparation method of this fluorine-free photocurable insulating and protective coating includes the following steps: (1) Preparation of hexafunctional polyurethane acrylate prepolymer This step is the same as in Example 1; (2) Preparation of fluorine-free photocurable insulating and protective coating The hexafunctional polyurethane acrylate prepolymer, vinylene carbonate modified diacrylate, lithium phosphate ester-acrylate, spherical Al2O3 and photoinitiator in the aforementioned formulation amounts are mixed evenly to obtain a fluorine-free photocurable insulating and protective coating.

[0046] Comparative Example 1 This comparative example provides a fluorine-free photocurable insulating and protective coating. The raw materials, by weight, include 60 parts of hexafunctional polyurethane acrylate prepolymer, 20 parts of vinylene-modified diacrylate, 8 parts of LiBOB-acrylate, and 15 parts of spherical Al₂O₃ (particle size D). V The product contains 50 parts of 15μm and 5 parts of photoinitiator (TPO:1173=1:1). Among them, the hexafunctional polyurethane acrylate prepolymer is a commercially available hexafunctional polyurethane acrylate prepolymer without cyclic carbonate structure (Yinchang New Materials YC6001).

[0047] The preparation method of the fluorine-free photocurable insulating and protective coating includes: mixing commercially available hexafunctional polyurethane acrylate prepolymer, vinylene carbonate modified diacrylate, LiBOB-acrylate, spherical Al2O3 and photoinitiator (TPO:1173=1:1) in the specified amounts to obtain the fluorine-free photocurable insulating and protective coating.

[0048] Comparative Example 2 The difference between this comparative example and Example 1 is that the raw materials for preparing the hexafunctional polyurethane acrylate prepolymer do not contain 1000 parts of polycaprolactone diol, while the rest are the same as in Example 1.

[0049] Comparative Example 3 The difference between this comparative example and Example 1 is that the raw materials for preparing the hexafunctional polyurethane acrylate prepolymer do not contain 400 parts of vinyl carbonate modified diol, while the rest are the same as in Example 1.

[0050] Comparative Example 4 The difference between this comparative example and Example 1 is that 20 parts of vinylene carbonate modified diacrylate are replaced with 20 parts of 1,6-hexanediol diacrylate, while the rest are the same as in Example 1.

[0051] Comparative Example 5 The difference between this comparative example and Example 1 is that 20 parts of vinylene carbonate modified diacrylate are replaced with 20 parts of polyethylene glycol diacrylate, while the rest are the same as in Example 1.

[0052] Comparative Example 6 The difference between this comparative example and Example 1 is that 20 parts of vinylene carbonate modified diacrylate are replaced with 20 parts of ethoxylated trimethylolpropane triacrylate, while the rest are the same as in Example 1.

[0053] Comparative Example 7 The difference between this comparative example and Example 1 is that it does not contain 8 parts of LiBOB-acrylate, while all other aspects are the same as in Example 1.

[0054] The fluorine-free photocurable insulating and protective coatings prepared in Examples 1-5 and Comparative Examples 1-7 were sprayed onto a polyamide substrate and applied using a 405nm LED lamp at 200 mW / cm². 2 Irradiation was performed to form a 100 μm dry film, and the curing time was recorded. The results are shown in Table 1. The protective coatings obtained after curing in Examples 1-5 and Comparative Examples 1-7 were subjected to PFAS, pressure resistance, RCA, impact resistance, and electrolyte resistance tests. The test conditions are as follows, and the test results are shown in Table 1.

[0055] PFAS test: obtained according to UL746G test.

[0056] Withstand voltage performance test: conducted in accordance with GB / T 1408.1-2016 "Test methods for electrical strength of insulating materials - Part 1: Test at power frequency", to test the dielectric strength of the coating.

[0057] Electrolyte resistance test: The protective coatings of the examples and comparative examples were immersed in an electrolyte at 85°C (ethylene carbonate: methyl ethyl carbonate: dimethyl carbonate = 1:2:1, and the concentration of LiPF6 in the electrolyte was 1 mol / L) for 2 hours. The coatings were observed to see if blistering, swelling, or cracking occurred. The coating adhesion was tested by cross-cut test, and then the pressure resistance test was performed.

[0058] RCA test: Using an alcohol friction machine, the device is rubbed back and forth 1000 times under a 1kg load at a friction rate of 40 times / min. After the friction is completed, the pressure resistance is tested.

[0059] Impact resistance test: According to GB / T 1732-2020 "Test Method for Impact Resistance of Coating Film", a 1kg hammer was dropped from a height of 80cm to impact the coating sample (impact energy 8J), and the damage to the coating film was observed.

[0060] Table 1 Performance test results of the examples and comparative examples

[0061] The test results are shown in Table 1. As can be seen from the performance test results of the examples and comparative examples, the fluorine-free photocurable insulating protective coating of the present invention has superior overall pressure resistance, electrolyte resistance, abrasion resistance and impact resistance.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A fluorine-free photocurable insulating and protective coating, characterized in that, The raw materials, by mass, include 40-80 parts of multifunctional polyurethane acrylate prepolymer, 10-40 parts of carbonate-modified acrylate monomer, 5-15 parts of reactive lithium salt monomer, 10-20 parts of filler and 3-5 parts of photoinitiator. The multifunctional polyurethane acrylate prepolymer is prepared by reacting polycaprolactone diol, vinyl carbonate-modified diol, isophorone diisocyanate, and hydroxyl-containing multifunctional acrylate monomers under the conditions of a catalyst and a polymerization inhibitor.

2. The fluorine-free photocurable insulating and protective coating according to claim 1, characterized in that, The raw materials for preparing the multifunctional polyurethane acrylate prepolymer include 800-1200 parts by weight of the polycaprolactone diol, 150-600 parts by weight of the vinyl carbonate modified diol, 500-1000 parts by weight of the isophorone diisocyanate, 350-750 parts by weight of the hydroxyl-containing multifunctional acrylate monomer, 0.5-2.0 parts by weight of the catalyst, and 0.8-2.5 parts by weight of the polymerization inhibitor.

3. The fluorine-free photocurable insulating and protective coating according to claim 1 or 2, characterized in that, The vinyl carbonate-modified diol is prepared by reacting vinylene carbonate and polyethylene glycol under alkaline catalyst conditions.

4. The fluorine-free photocurable insulating and protective coating according to claim 1 or 2, characterized in that, The hydroxyl-containing multifunctional acrylate monomer is selected from at least one of pentaerythritol triacrylate monohydroxy ester and dipentaerythritol pentaacrylate monohydroxy ester.

5. The fluorine-free photocurable insulating and protective coating according to claim 1 or 2, characterized in that, The carbonate-modified acrylate monomer is selected from at least one of vinylene carbonate-modified diacrylate, vinylene carbonate-caprolactone co-modified diacrylate, and cyclic carbonate-modified tetraacrylate.

6. The fluorine-free photocurable insulating and protective coating according to claim 1 or 2, characterized in that, The reactive lithium salt monomer is selected from at least one of lithium bis(oxalato)borate-acrylate and lithium phosphate-acrylate.

7. The fluorine-free photocurable insulating and protective coating according to claim 1 or 2, characterized in that, The filler is selected from at least one of alumina, boron nitride and silicon dioxide.

8. The fluorine-free photocurable insulating and protective coating according to claim 1 or 2, characterized in that, The photoinitiator is selected from at least one of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone.

9. A method for preparing a fluorine-free photocurable insulating and protective coating according to any one of claims 1 to 8, characterized in that, include: (1) Preparation of multifunctional polyurethane acrylate prepolymer Under a protective atmosphere, the polycaprolactone diol, the vinyl carbonate-modified diol, the isophorone diisocyanate, and the catalyst in the prescribed amounts are heated and reacted until the mass percentage of -NCO is 4.0%~6.0%. After cooling, the hydroxyl-containing multifunctional acrylate monomer is added, and the reaction continues until the infrared detection -NCO peak completely disappears. After adding the polymerization inhibitor, the product is discharged to obtain the multifunctional polyurethane acrylate prepolymer. (2) Preparation of fluorine-free photocurable insulating and protective coating The multifunctional polyurethane acrylate prepolymer, the carbonate-modified acrylate monomer, the reactive lithium salt monomer, the filler, and the photoinitiator are mixed evenly in the specified amounts.

10. The application of a fluorine-free photocurable insulating and protective coating prepared by any one of claims 1 to 8 or by any one of claims 9 in the power battery of a new energy vehicle.

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