An electric cell ultraviolet light curing insulation ink using polyurethane acrylate

Abstract

The present application relates to a kind of battery cell ultraviolet curing insulating ink and its preparation method, the present application provides an ink, it includes self-made polyurethane acrylate, single official high Tg UV monomer, single official hydrophobic UV monomer, multi-official UV monomer, photoinitiator, thiol, phosphate monomer etc..By self-made specific structure polyurethane acrylate and long carbon chain hydrophobic monomer compound, while ensuring low viscosity suitable for inkjet printing, effectively reduce the shrinkage stress of curing;Utilize the synergistic effect of thiol and phosphate monomer, significantly improve the adhesion to aluminum substrate and solve the oxygen inhibition defect when 395nm LED curing.The obtained coating has high flexibility, high insulation and excellent resistance to electrolyte, high and low temperature impact resistance, can be widely used in the shell insulation protection of power battery cell.

Description

Technical Field

[0001] This invention belongs to the field of insulating materials technology, and particularly relates to a self-made polyurethane acrylate and an ultraviolet (UV) cured insulating ink for battery cells using the polyurethane acrylate. Background Technology

[0002] As the "heart" of new energy vehicles, the safety, reliability, and lifespan of power batteries directly determine the performance and market acceptance of the entire vehicle. The insulation protection of the battery cell casing is the first line of defense to ensure the safety of the battery system and prevent fatal failures such as short circuits and leakage.

[0003] Traditionally, the industry commonly uses polyethylene terephthalate (PET) blue film to insulate and protect battery cell casings through manual or semi-automatic wrapping. However, this PET blue film process has several inherent drawbacks: low production efficiency, poor consistency, easy lifting of edges and corners, existence of blind spots, and low material utilization. Furthermore, with the structural changes of next-generation power batteries, cells can be directly bonded to the PACK cover or vehicle chassis, further increasing the requirements for adhesive shear strength. The limited adhesive performance of the PSA backing of the blue film poses a challenge to the insulation reliability of using the PET blue film process for cell casing insulation protection under high-voltage platforms.

[0004] Compared to blue film, the adhesion performance of the coating formed on the surface of the battery cell using powder coating technology is greatly improved. However, because the density of the powder coating is relatively low, a very thick coating is required to achieve good insulation and withstand voltage effects. Moreover, powder coating needs to be baked at a temperature above 150°C for a long time, which is inefficient and energy-intensive.

[0005] UV spraying can meet the requirements and is highly efficient, but it has problems such as low material utilization, serious waste, VOCs, and odor.

[0006] Against this backdrop, inkjet printing of UV insulating inks has emerged and is widely considered an ideal alternative to traditional PET blue film processes. This technology integrates the flexibility of digital printing, the precision of materials science, and the efficiency of photochemistry, exhibiting a series of comprehensive advantages such as high adhesion, excellent insulation, superior weather resistance, near-zero VOC emissions, high production efficiency, high automation, and high material utilization. However, inkjet printing requires low ink viscosity, often requiring very little resin and mostly monomers. A large amount of monomers leads to significant shrinkage after curing, easily causing stress concentration and affecting performance. Furthermore, relatively low-viscosity inks have higher dissolved oxygen levels, which can easily lead to low surface hardness or even stickiness under 395nm LED curing due to oxygen inhibition.

[0007] Therefore, in view of the shortcomings of the existing technology, there is an urgent need to develop a new type of UV-curable insulating ink for battery cells. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a self-made polyurethane acrylate and a cell UV-curable insulating ink using the polyurethane acrylate.

[0009] This polyurethane acrylate is prepared by the addition polymerization reaction of isocyanate and polyol in the following molar ratios, followed by end-capping with an end-capping agent:

[0010] Isocyanate:Polyol = (2.0~2.5):1;

[0011] The polyol is composed of a first polyol and a second polyol, with a molar ratio of (0.1–0.9):(0.9–0.1).

[0012] The first polyol is selected from any one of the following: polytetrahydrofuran ether diol, polybutadiene diol, polycarbonate diol, and organosilicon-modified polyether polyol;

[0013] The second polyol is selected from any one of the following: polypropylene glycol, polycaprolactone glycol;

[0014] The isocyanate is any one of the following: toluene diisocyanate (TDI), methylene diphenyl diisocyanate (MDI), hydrogenated MDI (HMDI), xylylene diisocyanate (XDI), trimethylhexamethylene diisocyanate (TMDI), isophorone diisocyanate (IPDI), or hexamethylene diisocyanate (HDI).

[0015] As a preferred option:

[0016] The polyol is composed of polytetrahydrofuran ether diol and polypropylene glycol;

[0017] Alternatively, the polyol may be composed of polybutadiene diols and polypropylene glycol;

[0018] Alternatively, polyols may be composed of polycarbonate diols and polypropylene glycol;

[0019] Alternatively, the polyol may be composed of organosilicon-modified polyether polyol and polypropylene glycol;

[0020] Alternatively, the polyol may be composed of polytetrahydrofuran ether diol and polycaprolactone diol;

[0021] Alternatively, the polyol may be composed of polybutadiene diol and polycaprolactone diol;

[0022] Alternatively, the polyol may be composed of polycarbonate diol and polycaprolactone diol;

[0023] Alternatively, the polyol may be composed of organosilicon-modified polyether polyol and polycaprolactone diol.

[0024] A method for preparing polyurethane acrylate includes the following steps:

[0025] Step 1, Prepolymerization reaction: Mix the first polyol and the second polyol with isocyanate at 40-60°C for 15-60 minutes; then add the catalyst dropwise, controlling the reaction temperature below 75°C. After the catalyst is added, heat the mixture to 60-85°C and react for 2-4 hours, monitoring the content of isocyanate groups (NCO value); the catalyst is an organometallic compound or an organic amine compound.

[0026] Step 2, polymerization inhibition treatment: Cool down to 60-70℃, add a portion of polymerization inhibitor, the amount of polymerization inhibitor added is 30-80% of the total amount, stir for 10 minutes; the polymerization inhibitor is 2,6-di-tert-butyl-4-methylphenol or p-hydroxyanisole (4-Methoxyphenol, MEHQ).

[0027] Step 3, End-capping reaction: Add the end-capping agent in 2-3 portions, controlling the reaction temperature at 60-85℃, and stop the reaction after 2-4 hours; the end-capping agent is hydroxy acrylate;

[0028] Step 4, Post-processing: Cool to 60-75℃, add the remaining polymerization inhibitor, the amount of polymerization inhibitor added is 20-70% of the total amount, stir for 10-30 minutes, and discharge.

[0029] Preferably, the method specifically includes the following steps:

[0030] Step 1, Prepolymerization reaction: The first and second polyols are mixed with isocyanate at 50-55°C and 300 rpm for 30 minutes; then the catalyst is added dropwise in 2-3 batches, and the reaction temperature is controlled at 70-75°C and the mixture is stirred at 300 rpm for 2.5 hours. After the catalyst is added, the mixture is heated to 60-85°C and reacted for 2-4 hours, monitoring the content of isocyanate groups (NCO value); the catalyst is an organometallic compound or an organic amine compound.

[0031] Step 2, polymerization inhibition treatment: Cool down to 60-65℃, add a portion of polymerization inhibitor, the amount of polymerization inhibitor added is 30-80% of the total amount, and stir at 300 rpm for 10 minutes; the polymerization inhibitor is 2,6-di-tert-butyl-4-methylphenol or p-hydroxyanisole (4-Methoxyphenol, MEHQ).

[0032] Step 3, End-capping reaction: Add the end-capping agent in 2-3 portions, controlling the reaction temperature at 60-85℃, and stop the reaction after 2-4 hours; the end-capping agent is hydroxy acrylate;

[0033] Step 4, Post-processing: Cool to 60-65℃, add the remaining polymerization inhibitor, the amount of polymerization inhibitor added is 20-70% of the total amount, rotate and stir at 300 rpm for 2.5 hours, and then discharge.

[0034] As a preferred option:

[0035] When the catalyst is an organometallic compound, at least one of the following shall be selected: stannous octoate, dibutyltin dilaurate, bismuth 2-ethylhexanoate, bismuth neodecanoate, zirconium neodecanoate, and zirconium 2-ethylhexanoate.

[0036] When the catalyst is an organic amine compound, at least one of the following shall be selected: triethylenediamine, tetramethylbutanediamine, or triethylenediamine;

[0037] The capping agent is selected from at least one of the following: hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate.

[0038] A UV-curable insulating ink for battery cells made of polyurethane acrylate using the above method comprises the following raw materials in parts by weight:

[0039] 15-40 parts by weight of polyurethane acrylate

[0040] Monofunctional (meth)acrylate monomers with alicyclic structures (monofunctional high Tg UV monomers) 20-60 parts by weight.

[0041] Hydrophobic monofunctional (meth)acrylate monomer (monofunctional hydrophobic UV monomer) 5-30 parts by weight

[0042] Multifunctional (meth)acrylate monomer (multifunctional UV monomer) 1-15 parts by weight,

[0043] 2 to 10 parts by weight of coloring paste with a particle size D99 (the particle size corresponding to a cumulative volume distribution of 99%) ≤ 500 nm;

[0044] 1-8 parts by weight of photoinitiator;

[0045] Thiols: 0.5–15 parts by weight;

[0046] 1-10 parts by weight of phosphate ester monomer;

[0047] Stabilizer 0.05-0.5 parts by weight;

[0048] Leveling agent 0.05-0.5 parts by weight;

[0049] Defoamer 0-0.05 parts by weight;

[0050] The stabilizer is 2,6-di-tert-butyl-p-cresol (BHT) or monoethyl ether of hydroquinone (MEHQ).

[0051] Monofunctional (meth)acrylate monomers with alicyclic structures have a glass transition temperature greater than 50 °C.

[0052] As a preferred option:

[0053] The monofunctional (meth)acrylate monomer with an alicyclic structure is selected from at least one of the following: isobornyl acrylate, isobornyl methacrylate, dicyclopentenyl acrylate, dicyclopentenyl methacrylate, cyclohexyl methacrylate, 4-tert-butylcyclohexyl acrylate.

[0054] The hydrophobic monofunctional (meth)acrylate monomer is selected from at least one of the following: 3,3,5-trimethylcyclohexyl acrylate, dodecanoic acid acrylate (lauric acid acrylate), isodecyl acrylate, isononyl acrylate, tetradecyl acrylate, tetradecyl methacrylate, hexadecyl acrylate, octadecyl acrylate, hexadecyl methacrylate, octadecyl acrylate, benzyl acrylate;

[0055] The multifunctional (meth)acrylate monomer is selected from at least one of the following: neopentyl glycol diacrylate, tricyclodecanedimethyl diacrylate, 1,4-dioxane-2,5-dimethyl diacrylate, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, 1,4-butanediol diacrylate, 1,9-nonanediol dimethacrylate, tricyclodecanedimethyl dimethacrylate, tri(2-hydroxyethyl)isocyanurate triacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate.

[0056] The photoinitiator is selected from at least one of the following: 2-isopropylthioxanthone (ITX), 2,4-diethylthioxanthone (DETX), 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TPO), ethyl 2,4,6-trimethylbenzoyl phenylphosphonate (TPO-L), 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide (TMO), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (819), 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone (369), 2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)-1-butanone (379), and ethyl 4-dimethylaminobenzoate (EDB).

[0057] The thiol is selected from at least one of the following: pentaerythritol tetrakis(3-mercaptopropionic acid), trimethylolpropane tris(3-mercaptopropionic acid), pentaerythritol tetrakis(3-mercaptobutyric acid), and 1,4-butanedithiol.

[0058] The phosphate monomer may be selected from any of the following: trifunctional acrylate phosphate (i.e., SR9051NS), 2-hydroxyethyl methacrylate phosphate (i.e., EM39), or trifunctional methacrylate phosphate resin (i.e., Uniclil R9107);

[0059] The leveling agent is polyether-modified polydimethylsiloxane (also known as BYK333);

[0060] The defoamer is a polyolefin-based non-silicone defoamer (such as BYK1790).

[0061] Preferably, the colorant is blue, red, or gold.

[0062] A method for preparing and applying the above-mentioned UV-curable insulating ink for battery cells includes the following steps:

[0063] Step 1: Add polyurethane acrylate, monofunctional (meth)acrylate monomer with alicyclic structure, hydrophobic monofunctional (meth)acrylate monomer, polyfunctional (meth)acrylate monomer and photoinitiator to the material tank, and disperse at 20-50 ℃ and 200-1500 rpm for 30-120 min until the photoinitiator is completely dissolved.

[0064] Step 2: Add coloring paste with a particle size D99≤500 nm, phosphate monomer, stabilizer, leveling agent and defoamer to the material tank, and disperse for 30-60 min at 20-50 ℃ and 200-1500 rpm.

[0065] Step 3: Add mercaptan to the material tank and disperse it for 30-60 minutes at 20-50 ℃ and 200-1500 rpm to obtain the dispersed ink.

[0066] Step 4, Filtration: Filter the dispersed ink using a polypropylene (PP) or polyethylene (PE) filter membrane with a pore size of 0.5 μm to obtain the filtered ink, ensuring that the particle size D99 of the filtered ink is <1 μm.

[0067] Step 5, Printing and Curing: The filtered ink is inkjet printed onto an aluminum substrate that has undergone laser treatment and plasma treatment. The ink-printed layer is cured using a 395 nm wavelength LED lamp. The ink layer is then pre-cured and finally cured using a 2-spray, 2-pre-curing, and final-curing process. The final coating thickness of the ink layer is controlled between 70 and 150 μm. The pre-curing energy is 200–1000 mJ / cm², and the final curing energy is 20000–30000 mJ / cm².

[0068] As a preferred option:

[0069] In steps 1 to 3, the dispersion conditions are 30–45 °C and 800–1200 rpm for 30–60 min.

[0070] The final ink layer has a coating thickness of 100–120 μm;

[0071] The aluminum substrate is 3003H14 aluminum shell.

[0072] The beneficial effects of this invention are:

[0073] By self-synthesizing a polyurethane acrylate with a specific structure and compounding it with long-chain hydrophobic monomers, the volume shrinkage rate during the curing process is effectively reduced while ensuring the ink has low viscosity (suitable for high-precision inkjet printing). This design successfully overcomes the interfacial stress concentration problem caused by excessive monomers in traditional inkjet inks, giving the coating excellent flexibility and impact resistance, enabling it to adapt to the deformation of the battery cell during charging and discharging and to withstand alternating high and low temperature conditions.

[0074] The introduction of a compound system of thiol and phosphate ester monomers not only serves as an active diluent to adjust viscosity, but more importantly, significantly enhances the chemical bonding ability between the ink and the aluminum substrate (such as 3003H14 aluminum shell). Combined with the high adhesion properties of the self-made resin, it effectively solves the problems of adhesion failure and edge warping of traditional PET blue film adhesives under high temperature and humidity environments, ensuring the structural integrity of the insulation layer during long-term service.

[0075] To address the common defects in the curing process of 395nm LED light sources, such as surface stickiness and insufficient hardness caused by oxygen inhibition, this invention achieves rapid deep curing in an air atmosphere through the combination of the free radical chain transfer mechanism of thiol and a specific photoinitiator system. This not only eliminates the surface oxygen inhibition layer, ensuring high hardness and insulation withstand voltage performance of the coating surface, but also significantly reduces curing energy consumption and improves production line cycle time.

[0076] By introducing high-Tg alicyclic monomers to construct a dense cross-linked network, combined with a stable resin matrix, the coating exhibits excellent resistance to electrolytes, acids, alkalis, and salt spray corrosion. This multi-layered protection mechanism effectively blocks external moisture erosion and internal chemical penetration, significantly improving the safety and cycle life of the power battery in complex operating environments. Attached Figure Description

[0077] Figure 1 This is a flowchart illustrating the preparation route of the polyurethane acrylate of the present invention. Detailed Implementation

[0078] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0079] Example 1

[0080] like Figure 1 As shown, a method for preparing polyurethane acrylate includes the following steps ( Figure 1 In this context, R represents isocyanate, R1 and R2 are the first and second polyols, and R3 is the capping agent.

[0081] Step 1, Prepolymerization: The first polyol (0.1 mol polytetrahydrofuran ether diol (PTMG 2000)) and the second polyol (0.1 mol polypropylene glycol (PPG 2000)) are mixed with isocyanate (0.215 mol isophorone diisocyanate (IPDI)) at 50 °C and 300 rpm for 30 minutes. Then, catalyst AC802 is added dropwise in 2-3 batches (150 ppm for the first addition, controlling the reaction temperature below 75 °C; 350 ppm for the second addition; after the addition is complete, the reaction temperature is controlled below 75 °C; timing begins when the temperature reaches 75±1 °C, and the mixture is stirred at 300 rpm for 2.5 h). After the catalyst addition is complete, the mixture is heated to 60-85 °C and reacted for 2-4 hours, monitoring the isocyanate group content (NCO value).

[0082] Step 2, Polymerization Inhibition Treatment: Cool to 60 ℃, add 200 ppm of polymerization inhibitor (p-hydroxyanisole MEHQ), and stir at 300 rpm for 10 minutes.

[0083] Step 3, End-capping reaction: Add the end-capping agent (0.2323 mol of hydroxyethyl acrylate HEA) in 3 portions, control the reaction temperature below 75 ℃, start timing when the temperature reaches 75±1 ℃, and stop the reaction after 2.5 h;

[0084] Step 4, Post-processing: Cool to 75 ℃, add the remaining polymerization inhibitor (300 ppm MEHQ), stir at 300 rpm for 20 min, discharge, and obtain the self-made polyurethane acrylate SSPU01.

[0085] Example 2

[0086] like Figure 1 As shown, a method for preparing polyurethane acrylate includes the following steps ( Figure 1 In this context, R represents isocyanate, R1 and R2 are the first and second polyols, and R3 is the capping agent.

[0087] Step 1, Prepolymerization: The first polyol (0.15 mol polytetrahydrofuran ether diol (PTMG 1000)) and the second polyol (0.05 mol polycaprolactone diol (PCL 1000)) were mixed with isocyanate (0.22 mol dicyclohexylmethane diisocyanate (HMDI)) at 55 °C and 300 rpm for 50 minutes. Then, catalyst AC83 was added dropwise in 2-3 batches (200 ppm for the first addition, controlling the reaction temperature below 70 °C; 300 ppm for the second addition; after the addition was completed, the reaction temperature was controlled below 70 °C; timing was started when the temperature reached 70±1 °C, and the mixture was stirred at 300 rpm for 3 hours). After the catalyst addition was completed, the mixture was heated to 60-85 °C and reacted for 2-4 hours, monitoring the isocyanate group content (NCO value).

[0088] Step 2, Polymerization Inhibition Treatment: Cool to 60 ℃, add 250 ppm of polymerization inhibitor (p-hydroxyanisole MEHQ), and stir at 300 rpm for 10 minutes.

[0089] Step 3, End-capping reaction: Add the end-capping agent (0.2424 mol of hydroxypropyl acrylate HPA) in 3 portions, control the reaction temperature below 70 ℃, start timing when the temperature is 70±1 ℃, and stop the reaction after 3 h;

[0090] Step 4, Post-processing: Cool to 75 ℃, add the remaining polymerization inhibitor (250 ppm MEHQ), stir at 300 rpm for 20 min, discharge, and obtain the self-made polyurethane acrylate SSPU02.

[0091] Example 3

[0092] like Figure 1 As shown, a method for preparing polyurethane acrylate includes the following steps:

[0093] Step 1, Prepolymerization: The first polyol (0.02 mol polybutadiene glycol (LPBD 2000)) and the second polyol (0.18 mol polypropylene glycol (PPG 2000)) were mixed with isocyanate (0.21 mol hexamethylene diisocyanate (HDI)) at 55 °C and 300 rpm for 40 minutes. Then, the catalyst (dibutyltin dilaurate DBTDL) was added dropwise in 2-3 batches (100 ppm for the first addition, controlling the reaction temperature below 75 °C; 400 ppm for the second addition; after the addition was completed, the reaction temperature was controlled below 75 °C; timing was started when the temperature reached 75±1 °C, and the mixture was stirred at 300 rpm for 2 hours). After the catalyst addition was completed, the mixture was heated to 60-85 °C and reacted for 2-4 hours, monitoring the isocyanate group content (NCO value).

[0094] Step 2, Polymerization Inhibition Treatment: Cool to 65 ℃, add 300 ppm of polymerization inhibitor (p-hydroxyanisole MEHQ), and stir at 300 rpm for 15 minutes.

[0095] Step 3, End-capping reaction: At 65℃, add the end-capping agent (0.222 mol of hydroxybutyl acrylate HBA) in 3 portions, controlling the reaction temperature below 75℃. Start timing when the temperature reaches 75±1℃, and stop the reaction after 3 hours.

[0096] Step 4, Post-processing: Cool to 75 ℃, add the remaining polymerization inhibitor (200 ppm MEHQ), stir at 300 rpm for 15 min, discharge, and obtain the self-made polyurethane acrylate SSPU03.

[0097] Example 4

[0098] A method for preparing and applying a UV-curable insulating ink for battery cells includes the following steps:

[0099] Step 1: Add polyurethane acrylate, monofunctional high Tg UV monomer, monofunctional hydrophobic UV monomer, multifunctional UV monomer and photoinitiator to the container and disperse at 40 ℃ and 1000 rpm for 60 min until the photoinitiator is completely dissolved.

[0100] Step 2: Add 3 parts of color paste (nano UV blue color paste, diluted with UV monomer IBOA, HDDA, or DPGDA) with a particle size D99≤500 nm, phosphate monomer SR9051, stabilizer 2,6-di-tert-butyl-p-cresol (BHT), leveling agent BYK333, and defoamer BYK1790 to the material tank, and disperse for 40 min at 40 ℃ and 1000 rpm.

[0101] Step 3: Add pentaerythritol tetrakis(3-mercaptopropionic acid) to the material tank and disperse it at 40 ℃ and 1000 rpm for 40 min to obtain the dispersed ink.

[0102] The proportions of raw materials used in steps 1 to 3 are as follows:

[0103] Polyurethane acrylate (SSPU01) 30 parts by weight

[0104] Isoborneol acrylate (IBOA) (monofunctional high Tg UV monomer) 35 parts by weight

[0105] Isodecyl acrylate (IDA) (monofunctional hydrophobic UV monomer) 15 parts by weight

[0106] 1,6-Hexanediol diacrylate (HDDA) (polyfunctional UV monomer) 10 parts by weight

[0107] Three parts by weight of coloring paste with a particle size D99 (the particle size corresponding to a cumulative volume distribution of 99%) ≤ 500 nm;

[0108] 1 part by weight of 2-isopropylthioxanthone (ITX), 1 part by weight of 2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)-1-butanone (i.e., 379), and 1.5 parts by weight of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (i.e., 819);

[0109] 0.9 parts by weight of pentaerythritol tetrakis(3-mercaptopropionic acid) ester;

[0110] Phosphate monomer SR9051, 2 parts by weight;

[0111] Stabilizer 2,6-di-tert-butyl-p-cresol (BHT) 0.1 parts by weight;

[0112] Leveling agent BYK333 0.4 parts by weight;

[0113] Defoamer BYK1790 0.1 parts by weight;

[0114] Step 4, Filtration: Filter the dispersed ink using a polypropylene (PP) filter membrane with a pore size of 0.5 μm to obtain the filtered ink, ensuring that the particle size D99 of the filtered ink is <1 μm.

[0115] Step 5, Printing and Curing: The filtered ink is inkjet printed onto an aluminum substrate (3003H14 aluminum shell) that has undergone laser treatment and plasma treatment. The ink-printed ink layer is cured using a 395 nm wavelength LED lamp. Then, the ink layer is pre-cured and finally cured using a 2-spray 2-pre-curing and final curing process. The final coating thickness of the ink layer is controlled between 100 and 120 μm. The pre-curing energy is 500 mJ / cm², and the final curing energy is 25000 mJ / cm².

[0116] The ink layer obtained in Example 4 exhibits the following adhesion grades: Grade 0 (adhesion test according to ISO 2409); no cracking or peeling after a 0.5 J drop hammer impact; no cracking or peeling after bending 180° around a 32 mm diameter wire bar; no blistering, cracking, or peeling after 1000 h of double 85 aging; shear strength of 13.9 MPa; pull-out strength of 13.2 MPa; insulation resistance of 15.6 GΩ at 1000 VDC for 60 s; leakage current of 1.2 uA at 5000 VDC for 60 s; no blistering, cracking, or peeling after 1000 h of high and low temperature impact from -40 ℃ to 85 ℃; shear strength of 17.6 MPa; pull-out strength of 16.1 MPa; insulation resistance of 18.6 GΩ at 1000 VDC for 60 s; leakage current of 0.2 uA at 5000 VDC for 60 s; and resistance to blistering, cracking, or peeling after 48 hours of immersion in room temperature electrolyte. After immersion in water at room temperature for 7 days, the coating did not bubble, crack, or peel off. (Lithium battery electrolyte, main components: propylene carbonate, ethylene carbonate, methyl ethyl carbonate, lithium hexafluorophosphate; test conducted at 25 ℃ under non-charged conditions). Adhesion rating: 0. Insulation resistance at 1000VDC for 60 s: 3.7 GΩ. Leakage current at 5000 VDC for 60 s: 7.8 uA. After immersion in water at room temperature for 7 days, the coating did not bubble, crack, or peel off. Adhesion rating: 0. Insulation resistance at 1000 VDC for 60 s: 13.7 GΩ. Leakage current at 5000 VDC for 60 s: 2.6 uA.

[0117] Example 5

[0118] A method for preparing and applying a UV-curable insulating ink for battery cells includes the following steps:

[0119] Step 1: Add polyurethane acrylate, monofunctional high Tg UV monomer, monofunctional hydrophobic UV monomer, multifunctional UV monomer and photoinitiator to the container and disperse at 40 ℃ and 1000 rpm for 60 min until the photoinitiator is completely dissolved.

[0120] Step 2: Add 4 parts of color paste (nano UV blue color paste, diluted with UV monomer IBOA, HDDA, or DPGDA) with a particle size D99≤500 nm, phosphate monomer SR9051, stabilizer p-hydroxyanisole (MEHQ), leveling agent BYK3568, and defoamer TEGO900 to the material tank, and disperse for 30 min at 40 ℃ and 1000 rpm.

[0121] Step 3: Add trimethylolpropane tris(3-mercaptopropionate) to the material tank and disperse it at 40 °C and 1000 rpm for 30 min to obtain the dispersed ink.

[0122] The proportions of raw materials used in steps 1 to 3 are as follows:

[0123] Polyurethane acrylate (SSPU02) 40 parts by weight

[0124] Dicyclopentenyl methacrylate (DCPA) (monofunctional high Tg UV monomer) 20 parts by weight

[0125] Benzyl acrylate (BZA) (monofunctional hydrophobic UV monomer) 25 parts by weight

[0126] Tricyclodecanediethanol dimethacrylate (DCPDA) (polyfunctional UV monomer) 5 parts by weight

[0127] Four parts by weight of coloring paste with a particle size D99 (the particle size corresponding to a cumulative volume distribution of 99%) ≤ 500 nm;

[0128] 2-Isopropylthioxanthone (ITX) 0.7 parts by weight, 2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)-1-butanone (i.e., 379) 0.3 parts by weight, 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide (i.e., TMO) 2 parts by weight;

[0129] Trimethylolpropane tris(3-mercaptopropionate) 1 part by weight;

[0130] 1.5 parts by weight of phosphate monomer SR9051;

[0131] Stabilizer p-hydroxyanisole (MEHQ) 0.1 parts by weight;

[0132] Leveling agent BYK3568 0.3 parts by weight;

[0133] 0.1 parts by weight of defoamer TEGO900;

[0134] Step 4, Filtration: Filter the dispersed ink using a polypropylene (PP) filter membrane with a pore size of 0.5 μm to obtain the filtered ink, ensuring that the particle size D99 of the filtered ink is <1 μm.

[0135] Step 5, Printing and Curing: The filtered ink is inkjet printed onto an aluminum substrate (3003H14 aluminum shell) that has undergone laser treatment and plasma treatment. The ink-printed ink layer is cured using a 395 nm wavelength LED lamp. Then, the ink layer is pre-cured and finally cured using a 2-spray 2-pre-curing and final curing process. The final coating thickness of the ink layer is controlled between 100 and 120 μm. The pre-curing energy is 600 mJ / cm², and the final curing energy is 28000 mJ / cm².

[0136] The ink layer obtained in Example 5 exhibits the following adhesion grades: Grade 0 (adhesion test according to ISO 2409); no cracking or peeling after a 0.5 J drop hammer impact; no cracking or peeling after bending around a 32 mm diameter wire rod 180°; no blistering, cracking, or peeling after 1000 h of double 85 aging; shear strength of 13.8 MPa; pull-out strength of 12.9 MPa; insulation resistance of 16.5 GΩ at 1000 VDC for 60 s; leakage current of 1.7 uA at 5000 VDC for 60 s; no blistering, cracking, or peeling after 1000 h of high and low temperature impact from -40 ℃ to 85 ℃; shear strength of 18.5 MPa; pull-out strength of 15.2 MPa; insulation resistance of 19.8 GΩ at 1000 VDC for 60 s; leakage current of 0.1 uA at 5000 VDC for 60 s; and resistance to blistering, cracking, or peeling after 48 hours of immersion in room temperature electrolyte. After immersion in water at room temperature for 7 days, the coating did not bubble, crack, or peel off. (Lithium battery electrolyte, main components: propylene carbonate, ethylene carbonate, methyl ethyl carbonate, lithium hexafluorophosphate; test conducted at 25 ℃ under non-charged conditions). Adhesion rating: 0. Insulation resistance at 1000 VDC for 60 s: 4.2 GΩ; leakage current at 5000 VDC for 60 s: 6.9 uA. After immersion in water at room temperature for 7 days, the coating did not bubble, crack, or peel off. Adhesion rating: 0. Insulation resistance at 1000 VDC for 60 s: 12.8 GΩ; leakage current at 5000 VDC for 60 s: 1.6 uA.

[0137] Example 6

[0138] A method for preparing and applying a UV-curable insulating ink for battery cells includes the following steps:

[0139] Step 1: Add polyurethane acrylate, monofunctional high Tg UV monomer, monofunctional hydrophobic UV monomer, multifunctional UV monomer and photoinitiator to the container and disperse at 35 ℃ and 1200 rpm for 50 min until the photoinitiator is completely dissolved.

[0140] Step 2: Add 5 parts of color paste (nano UV blue color paste, diluted with UV monomer IBOA, HDDA, or DPGDA) with a particle size D99≤500 nm, phosphate monomer SR9051, stabilizer 2,6-di-tert-butyl-p-cresol (BHT), leveling agent BYK333, and defoamer BYK1790 to the material tank, and disperse for 30 min at 35 ℃ and 1200 rpm.

[0141] Step 3: Add pentaerythritol tetrakis(3-mercaptopropionic acid) to the material tank and disperse it at 35 ℃ and 1200 rpm for 30 min to obtain the dispersed ink.

[0142] The proportions of raw materials used in steps 1 to 3 are as follows:

[0143] Polyurethane acrylate (SSPU03) 15 parts by weight,

[0144] 4-tert-butylcyclohexyl acrylate (TBCHA) (monofunctional high Tg UV monomer) 35 parts by weight

[0145] Isononyl acrylate (monofunctional hydrophobic UV monomer) 20 parts by weight

[0146] Dipentaerythritol hexaacrylate (DPHA) (polyfunctional UV monomer) 3 parts by weight

[0147] Five parts by weight of coloring paste with a particle size D99 (the particle size corresponding to a cumulative volume distribution of 99%) ≤ 500 nm;

[0148] 2,4-Diethylthioxanthone (DETX) 2 parts by weight, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO-L) 2 parts by weight, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone (369) 1.5 parts by weight;

[0149] 10 parts by weight of pentaerythritol tetra(3-mercaptopropionic acid) ester;

[0150] 1.5 parts by weight of phosphate monomer SR9051;

[0151] Stabilizer 2,6-di-tert-butyl-p-cresol (BHT) 0.1 parts by weight;

[0152] Leveling agent BYK333, 0.3 parts by weight;

[0153] Defoamer BYK1790 0.1 parts by weight;

[0154] Step 4, Filtration: Filter the dispersed ink using a polypropylene (PP) filter membrane with a pore size of 0.5 μm to obtain the filtered ink, ensuring that the particle size D99 of the filtered ink is <1 μm.

[0155] Step 5, Printing and Curing: The filtered ink is inkjet printed onto an aluminum substrate (3003H14 aluminum shell) that has undergone laser treatment and plasma treatment. The ink-printed ink layer is cured using a 395 nm wavelength LED lamp. Then, the ink layer is pre-cured and finally cured using a 2-spray 2-pre-curing and final curing process. The thickness of the final ink layer is controlled between 100 and 120 μm. The pre-curing energy is 300 mJ / cm², and the final curing energy is 20000 mJ / cm².

[0156] The ink layer obtained in Example 6 exhibits the following adhesion grades: Grade 0 (adhesion test according to ISO 2409); no cracking or peeling after a 0.5 J drop hammer impact; no cracking or peeling after bending 180° around a 32 mm diameter wire bar; no blistering, cracking, or peeling after 1000 h of double 85 aging; shear strength of 16.2 MPa; pull-out strength of 15.3 MPa; insulation resistance of 17.1 GΩ at 1000 VDC for 60 s; leakage current of 1.0 uA at 5000 VDC for 60 s; no blistering, cracking, or peeling after 1000 h of high and low temperature impact from -40 ℃ to 85 ℃; shear strength of 18.5 MPa; pull-out strength of 17.7 MPa; insulation resistance of 18.7 GΩ at 1000 VDC for 60 s; leakage current of 0.5 uA at 5000 VDC for 60 s; and resistance to blistering, cracking, or peeling after 48 hours of immersion in room temperature electrolyte. After immersion in water at room temperature for 7 days, the coating did not bubble, crack, or peel off. (Lithium battery electrolyte, main components: propylene carbonate, ethylene carbonate, methyl ethyl carbonate, lithium hexafluorophosphate; test conducted at 25 ℃ under non-charged conditions). Adhesion rating: 0. Insulation resistance at 1000 VDC for 60 s: 5.9 GΩ; leakage current at 5000 VDC for 60 s: 3.3 uA. After immersion in water at room temperature for 7 days, the coating did not bubble, crack, or peel off. Adhesion rating: 0. Insulation resistance at 1000 VDC for 60 s: 16.8 GΩ; leakage current at 5000 VDC for 60 s: 2.2 uA.

[0157] Comparative example:

[0158] The phosphate ester-free ink layer initially exhibited an adhesion grade of 2, which increased to 5 after 1000 hours of double 85 treatment.

[0159] In the mercaptan-free system, the resulting ink layer coating, after being immersed in electrolyte for 48 hours, exhibited an adhesion level of 4.

[0160] In summary, the insulating ink of the present invention has the following technical effects:

[0161] By compounding a self-made polyurethane acrylate with a monofunctional hydrophobic monomer, the curing shrinkage rate was significantly reduced while ensuring low viscosity (suitable for inkjet printing). Examples 4-6 show that the coating did not crack or peel after 1000 hours of high and low temperature shock from -40℃ to 85℃, and the shear strength reached 13.8-18.5MPa, effectively solving the problems of large shrinkage and stress concentration caused by the excessively high proportion of low viscosity monomers in traditional inkjet inks.

[0162] The synergistic effect of flexible segments (such as polytetrahydrofuran ether diol and polybutadiene diol) and rigid segments (such as isocyanate) in the self-made polyurethane acrylate, combined with long-chain hydrophobic monomers (such as isodel acrylate and benzyl acrylate), gives the coating both high flexibility and water resistance. In Examples 4-6, the coating still had a grade 0 adhesion after being soaked in water at room temperature for 7 days, and the insulation resistance reached 12.8-16.8 GΩ; after being soaked in electrolyte for 48 hours, there was no bubbling or peeling, and the shear strength retention rate was >90%.

[0163] Introducing monofunctional high-Tg UV monomers with a glass transition temperature >50℃ (such as isobornyl acrylate and dicyclopentenyl acrylate) improves the heat resistance of the coating. In Examples 4-6, after 1000 hours of double 85 aging, the coating showed no blistering or cracking, with an insulation resistance of 15.6–19.8 GΩ at 1000VDC and a leakage current of only 0.1–7.8 μA at 5000VDC, meeting the insulation requirements of high-voltage platforms.

[0164] The combination of thiols (such as pentaerythritol tetrakis(3-mercaptopropionic acid)) with phosphate monomers (SR9051NS) and stabilizers (BHT / MEHQ) effectively inhibits oxygen inhibition during the curing of 395nm LEDs. Comparative examples show that the adhesion of the thiol-free system decreased to grade 4 after electrolyte immersion, and the adhesion of the phosphate monomer-free system decreased to grade 5 after double 85 aging; while the coatings in Examples 4-6 of this invention achieved a surface hardness of over 2H and exhibited no stickiness.

[0165] Deep curing under 395nm LED light is achieved through a synergistic initiation system of photoinitiators (ITX / TPO / 819, etc.) and thiols. In Examples 4-6, after a 2-spray 2-pre-curing + final curing process, the coating exhibits an adhesion rating of 0, shows no cracking under a 0.5J drop hammer impact, and does not peel off after a 180° bend around a 32mm wire bar. It combines insulation, mechanical properties, and weather resistance, making it suitable for insulation protection of power battery cells.

Claims

1. A polyurethane acrylate, characterized in that, It is prepared by the addition polymerization reaction of isocyanate and polyol from raw materials including the following molar ratios, followed by end-capping with an end-capping agent: Isocyanate:Polyol = (2.0~2.5):1; The polyol is composed of a first polyol and a second polyol, and the molar ratio of the first polyol to the second polyol is (0.1-0.9):(0.9-0.1). The first polyol is selected from any one of the following: polytetrahydrofuran ether diol, polybutadiene diol, polycarbonate diol, and organosilicon-modified polyether polyol; The second polyol is selected from any one of the following: polypropylene glycol, polycaprolactone diol; The isocyanate is any one of the following: toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, phenyl dimethylene diisocyanate, 2,2,4-trimethylhexane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate.

2. The polyurethane acrylate according to claim 1, characterized in that: The polyol is composed of polytetrahydrofuran ether diol and polypropylene glycol; Alternatively, the polyol may be composed of polybutadiene diol and polypropylene glycol; Alternatively, the polyol may be composed of polycarbonate diol and polypropylene glycol; Alternatively, the polyol may be composed of organosilicon-modified polyether polyol and polypropylene glycol; Alternatively, the polyol may be composed of polytetrahydrofuran ether diol and polycaprolactone diol; Alternatively, the polyol may be composed of polybutadiene diol and polycaprolactone diol; Alternatively, the polyol may be composed of polycarbonate diol and polycaprolactone diol; Alternatively, the polyol may be composed of organosilicon-modified polyether polyol and polycaprolactone diol.

3. A method for preparing polyurethane acrylate as described in claim 1 or 2, characterized in that, Includes the following steps: Step 1, Prepolymerization reaction: The first polyol and the second polyol are mixed with the isocyanate at 40-60°C for 15-60 minutes; Subsequently, the catalyst was added dropwise, and the reaction temperature was controlled below 75°C. After the catalyst addition was complete, the mixture was heated to 60–85°C and reacted for 2–4 hours, while monitoring the content of isocyanate groups. The catalyst was an organometallic compound or an organic amine compound. Step 2, polymerization inhibition treatment: Cool down to 60-70℃, add a portion of polymerization inhibitor, the amount of the polymerization inhibitor added is 30-80% of the total amount, stir for 10 minutes; the polymerization inhibitor is 2,6-di-tert-butyl-4-methylphenol or p-hydroxyanisole; Step 3, End-capping reaction: Add the end-capping agent in 2-3 portions, controlling the reaction temperature at 60-85℃, and stop the reaction after 2-4 hours; the end-capping agent is hydroxy acrylate; Step 4, Post-processing: Cool to 60-75℃, add the remaining polymerization inhibitor, the amount of the polymerization inhibitor added is 20-70% of the total amount, stir for 10-30 minutes, and discharge.

4. The preparation method according to claim 3, characterized in that, Specifically, the following steps are included: Step 1, Prepolymerization reaction: The first polyol and the second polyol are mixed with the isocyanate at 50-55°C and 300 rpm for 30 minutes; then the catalyst is added dropwise in 2-3 batches, and the reaction temperature is controlled at 70-75°C and the mixture is stirred at 300 rpm for 2.5 hours. After the catalyst addition is complete, the mixture is heated to 60-85°C and reacted for 2-4 hours, monitoring the content of isocyanate groups; the catalyst is an organometallic compound or an organic amine compound; Step 2, polymerization inhibition treatment: Cool down to 60-65℃, add a portion of polymerization inhibitor, the amount of the polymerization inhibitor added is 30-80% of the total amount, and stir at 300 rpm for 10 minutes; the polymerization inhibitor is 2,6-di-tert-butyl-4-methylphenol or p-hydroxyanisole; Step 3, End-capping reaction: Add the end-capping agent in 2-3 portions, controlling the reaction temperature at 60-85℃, and stop the reaction after 2-4 hours; the end-capping agent is hydroxy acrylate; Step 4, Post-processing: Cool to 60-65℃, add the remaining polymerization inhibitor, the amount of the polymerization inhibitor added is 20-70% of the total amount, stir at 300 rpm for 2.5 hours, and then discharge.

5. The preparation method according to claim 3, characterized in that: When the catalyst is an organometallic compound, at least one of the following shall be selected: stannous octoate, dibutyltin dilaurate, bismuth 2-ethylhexanoate, bismuth neodecanoate, zirconium neodecanoate, and zirconium 2-ethylhexanoate. When the catalyst is an organic amine compound, at least one of the following is selected: triethylenediamine, tetramethylbutanediamine, or triethylenediamine; The capping agent is selected from at least one of the following: hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate.

6. A UV-curable insulating ink for battery cells made of polyurethane acrylate using the method described in claim 3, characterized in that, The raw materials used include the following parts by weight: The polyurethane acrylate is 15-40 parts by weight. 20-60 parts by weight of monofunctional (meth)acrylate monomers with an alicyclic structure. 5-30 parts by weight of hydrophobic monofunctional (meth)acrylate monomers 1-15 parts by weight of multifunctional (meth)acrylate monomers 2-10 parts by weight of coloring paste with particle size D99≤500 nm; 1-8 parts by weight of photoinitiator; Thiols: 0.5–15 parts by weight; 1-10 parts by weight of phosphate ester monomer; Stabilizer 0.05-0.5 parts by weight; Leveling agent 0.05-0.5 parts by weight; Defoamer 0-0.05 parts by weight; The stabilizer is 2,6-di-tert-butyl-p-cresol or hydroquinone monomethyl ether; The glass transition temperature of the monofunctional (meth)acrylate monomer with an alicyclic structure is greater than 50 °C.

7. The UV-curable insulating ink for battery cells according to claim 6, characterized in that: The monofunctional (meth)acrylate monomer having an alicyclic structure is selected from at least one of the following: isobornyl acrylate, isobornyl methacrylate, dicyclopentenyl acrylate, dicyclopentenyl methacrylate, cyclohexyl methacrylate, 4-tert-butylcyclohexyl acrylate. The hydrophobic monofunctional (meth)acrylate monomer is selected from at least one of the following: 3,3,5-trimethylcyclohexyl acrylate, dodecanoic acid acrylate, isodecyl acrylate, isononyl acrylate, tetradecyl acrylate, tetradecyl methacrylate, hexadecyl acrylate, octadecyl acrylate, hexadecyl methacrylate, octadecyl methacrylate, benzyl acrylate; The multifunctional (meth)acrylate monomer is selected from at least one of the following: neopentyl glycol diacrylate, tricyclodecanedimethyl diacrylate, 1,4-dioxane-2,5-dimethyl diacrylate, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, 1,4-butanediol diacrylate, 1,9-nonanediol dimethacrylate, tricyclodecanedimethyl dimethacrylate, tri(2-hydroxyethyl)isocyanurate triacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate. The photoinitiator is selected from at least one of the following: 2-isopropylthioxanthonone, 2,4-diethylthioxanthonone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoyl phenylphosphonate, 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone, 2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)-1-butanone, ethyl 4-dimethylaminobenzoate; The thiol is selected from at least one of the following: pentaerythritol tetrakis(3-mercaptopropionic acid), trimethylolpropane tris(3-mercaptopropionic acid), pentaerythritol tetrakis(3-mercaptobutyric acid), and 1,4-butanedithiol. The phosphate monomer is selected from any one of the following: trifunctional acrylate phosphate, 2-hydroxyethyl methacrylate phosphate, or trifunctional methacrylate phosphate resin; The leveling agent is polyether-modified polydimethylsiloxane; The defoamer is a polyolefin-based non-silicone defoamer.

8. The UV-curable insulating ink for battery cells according to claim 6, characterized in that: The colorant is blue, red, or gold.

9. A method for preparing and applying a UV-curable insulating ink for battery cells as described in any one of 6-8, characterized in that, Includes the following steps: Step 1: Add the polyurethane acrylate, the monofunctional (meth)acrylate monomer with an alicyclic structure, the hydrophobic monofunctional (meth)acrylate monomer, the polyfunctional (meth)acrylate monomer, and the photoinitiator to a container and disperse them at 20–50 °C and 200–1500 rpm for 30–120 min until the photoinitiator is completely dissolved. Step 2: Add the color paste with a particle size D99≤500 nm, the phosphate ester monomer, the stabilizer, the leveling agent, and the defoamer to the material tank, and disperse for 30-60 min at 20-50 ℃ and 200-1500 rpm. Step 3: Add the thiol to the material tank and disperse it for 30-60 minutes at 20-50 °C and 200-1500 rpm to obtain the dispersed ink. Step 4, Filtration: Filter the dispersed ink using a polypropylene or polyethylene filter membrane with a pore size of 0.5 μm to obtain filtered ink, ensuring that the particle size D99 of the filtered ink is <1 μm. Step 5, Printing and Curing: The filtered ink is inkjet printed onto an aluminum substrate that has undergone laser treatment and plasma treatment. The ink-printed ink layer is cured using a 395 nm wavelength LED lamp. The ink layer is then pre-cured and finally cured, and the final coating thickness of the ink layer is controlled between 70 and 150 μm. The pre-curing energy is 200 to 1000 mJ / cm², and the final curing energy is 20000 to 30000 mJ / cm².

10. The preparation and application method according to claim 9, characterized in that: In steps 1 to 3, the dispersion conditions are all 30–45 °C and 800–1200 rpm for 30–60 min. The final ink layer has a coating thickness of 100–120 μm; The aluminum substrate is a 3003H14 aluminum shell.

Images