High-reliability fast-curing UV adhesive for outer layer protection of power battery, preparation method therefor and use thereof

Abstract

A high-reliability fast-curing UV adhesive for outer layer protection of a power battery, a preparation method therefor, and a use thereof. The UV adhesive contains an acrylate oligomer, a monofunctional acrylate monomer, a bifunctional acrylate monomer, a trifunctional acrylate monomer, an acrylate monomer containing an acidic functional group, a photoinitiator, and an optional additive, wherein the acrylate oligomer simultaneously contains dibasic acid-modified bisphenol A epoxy acrylate, tetrafunctional branched polyester acrylate, and polyurethane acrylate with polyester diol as a backbone. The resulting UV adhesive has a high curing rate, can be cured by means of an LED, is suitable for a high-precision ink-jet process, meets reliability requirements, such as insulation, voltage resistance, boiling resistance in water, and salt spray resistance, and bonding strength requirements, can replace a PET blue film as an insulating protective layer for outer layer packaging of a power battery, and leaves room for lightweight battery design.

Description

A high-reliability fast-curing UV adhesive for power battery outer layer protection, and its preparation method and application

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the Patent Office of China on October 19, 2023, with application number 2023113558956 and entitled “A high-reliability fast-curing UV adhesive for outer layer protection of power batteries, its preparation method and application”, the entire contents of which are incorporated into this application by reference. Technical Field

[0003] The present invention belongs to the field of UV adhesives, and in particular relates to a high-reliability fast-curing UV adhesive for protecting the outer layer of a power battery, and a preparation method and application thereof. Background Art

[0004] Since the new energy vehicle industry has become a focal point, reforms and innovations have been underway across various related technological fields. While striving to enhance performance, these efforts have also focused on high efficiency, environmental protection, energy conservation, and emission reduction. Power battery packaging and integration are crucial components, demanding high production efficiency, excellent yield, low cost, safety, reliability, and volume utilization, all while ensuring widespread adoption. Excellent insulation protection within the power battery outer packaging can enhance safety and reliability, thereby reducing the risk of leakage caused by external corrosion. It also improves volume utilization, leaving room for future battery integration upgrades and helping designers achieve lightweighting goals. Traditional battery cell outer packaging relies primarily on PET blue film, which is bonded to the aluminum core with glue. This method is complex, inefficient, and energy-intensive, failing to meet energy-efficiency and environmental requirements. Furthermore, due to limitations in glue performance and application techniques, it cannot always ensure a complete bond between the blue film and the aluminum core, leading to hollowing and bubbles, a high risk of failure, and hindering the development of lightweight batteries.

[0005] Considering the reliability and energy efficiency required for actual end-use applications, the current improved packaging protection solution is the inkjet process. In this process, UV adhesive is sprayed onto the outer layer of the battery cell and then cured using a UV light source to create an insulating protective layer. This replaces PET blue film as the outer protective layer for the battery cell, leaving ample design space for lightweight battery development. Based on the inkjet process and performance requirements, UV adhesive must simultaneously meet the basic reliability requirements of insulation voltage resistance, boiling water resistance, and salt spray resistance, as well as the bonding strength requirements, while also ensuring rapid curing. However, due to the limited viscosity of UV adhesive, the atomized spray process has unstable product quality, low adhesive utilization, and high waste. Furthermore, the adhesive cures at a moderate speed, making it unsuitable for the more energy-efficient LED curing process. Furthermore, due to formulation limitations, UV adhesive exhibits poor bonding strength and reliability, and unsatisfactory results in aging tests such as boiling water resistance and salt spray resistance, failing to meet increasingly stringent market requirements. Therefore, how to obtain UV glue that has high reliability such as insulation resistance, water boiling resistance, salt spray resistance, high bonding strength and can be quickly cured for the outer layer protection of power batteries has become an urgent problem to be solved.

[0006] Summary of the Invention

[0007] The purpose of the present invention is to overcome the defects of the existing UV glue for outer protection of power batteries, such as poor reliability in insulation pressure resistance, boiling water resistance, salt spray resistance, and bonding strength, and general curing speed, and to provide a UV glue that has high reliability such as insulation pressure resistance, boiling water resistance, salt spray resistance, high bonding strength and can be cured quickly, as well as a preparation method thereof, and its application in the insulation protection of the outer packaging of power battery cells.

[0008] After in-depth research, the inventors of the present invention discovered that a UV adhesive insulation protective layer with a skeleton structure constructed from three prepolymers: dibasic acid-modified bisphenol A epoxy acrylate, tetrafunctional branched polyester acrylate, and polyurethane acrylate with a polyether diol as the main chain, has high reliability such as insulation voltage resistance, boiling water resistance, and salt spray resistance, as well as high bonding strength and the ability to cure quickly. The reasons are speculated to be: the main chain segment of dibasic acid modified bisphenol A epoxy acrylate contains a benzene ring structure, which constitutes the rigid part of the skeleton structure of the UV glue insulating protective layer, giving the UV glue excellent hardness, tensile strength, high temperature resistance and aging resistance; the chain length of dibasic acid modified bisphenol A epoxy acrylate is longer, and this specific structure can reduce the curing volume shrinkage and internal stress, thereby improving its bonding effect on the aluminum layer of the battery core; due to the low polarity of the dibasic acid fatty chain structure in dibasic acid modified bisphenol A epoxy acrylate, its hydrophobicity is enhanced, ensuring the reliability of the cured UV glue insulating protective layer such as boiling resistance and salt spray resistance; in addition, the ether bond structure is introduced through the ring-opening reaction of dibasic acid modified bisphenol A epoxy acrylate to reduce the molecular internal rotation barrier, thereby reducing the viscosity and increasing the glue output to adapt to the inkjet process. The increased concentration of acrylic double bonds in tetrafunctional branched polyester acrylates significantly enhances photocuring reactivity, significantly increasing the overall photocuring speed of UV adhesives and facilitating LED curing. Furthermore, the curing of tetrafunctional oligomers forms a three-dimensional cross-linked network. This dense structure effectively enhances the adhesive layer's water barrier and wear resistance. The high content of polar ester bonds also improves pigment wetting and dispersion, enhancing the interfacial adhesion between the UV adhesive and the aluminum material in the battery core. Polyurethane acrylates, with a polyester diol backbone, offer low viscosity and excellent flexibility after curing, forming the flexible component of the insulating protective layer's skeleton. The urethane bonds in their backbone structure enable intermolecular hydrogen bonding, mitigating curing shrinkage stress and improving adhesion to the aluminum material in the battery core. They also provide cushioning properties to the adhesive layer, ensuring overall toughness and increasing bending and impact resistance, effectively improving insulation and voltage withstand performance.

[0009] After in-depth research, the inventors of the present invention also found that by simultaneously introducing a specific ratio of monofunctional acrylate monomer, difunctional acrylate monomer, trifunctional acrylate monomer and acrylate monomer containing acidic functional groups into UV adhesive, the resulting UV adhesive has better performance. The reasons are speculated to be: if a benzene ring is introduced into a monofunctional acrylate monomer, a conjugated system can be formed with the acrylate double bond, the acrylate double bond is activated, the reaction activity is enhanced, and rapid curing can be achieved even with low light energy, which is suitable for more energy-saving and efficient LED curing; if a bridge group or a bicyclodiene group is introduced into a monofunctional acrylate monomer, the steric hindrance can be increased, and the water-resistant, waterproof, and insulating voltage-resistant properties of the UV adhesive layer can be improved; the difunctional acrylate monomer can increase the density of the adhesive layer, and improve the hardness and wear resistance of the adhesive layer; the trifunctional acrylate monomer uses three reactive groups as cross-linking points to connect the various acrylate oligomers and acrylate monomers, so that the system forms a dense and stable three-dimensional network structure, thereby further enhancing its water resistance and wear resistance; the acidic group in the middle section of the acrylate monomer molecule containing an acidic functional group can improve the adhesion of the adhesive layer to the aluminum layer of the battery core, thereby enhancing the bonding strength of the UV adhesive.

[0010] In summary, a high-reliability, fast-curing UV adhesive is prepared by compounding three prepolymers: dibasic acid-modified bisphenol A epoxy acrylate, a tetrafunctional branched polyester acrylate, and a polyurethane acrylate with a polyester diol backbone. Furthermore, a specific ratio of monofunctional acrylate monomers, difunctional acrylate monomers, trifunctional acrylate monomers, and acrylate monomers containing acidic functional groups is introduced. This adhesive layer exhibits excellent insulation, voltage resistance, boiling water resistance, and salt spray resistance, as well as high bond strength and fast curing properties. This completes the present invention.

[0011] Specifically, the present invention provides a high-reliability fast-curing UV adhesive, which contains an acrylate oligomer, a monofunctional acrylate monomer, a difunctional acrylate monomer, a trifunctional acrylate monomer, an acrylate monomer containing an acidic functional group, a photoinitiator and an optional auxiliary agent; the acrylate oligomer also contains dibasic acid-modified bisphenol A epoxy acrylate, a tetrafunctional branched polyester acrylate and a polyurethane acrylate with a polyether diol as the main chain.

[0012] In a preferred embodiment, the content of the acrylate oligomer is 20-50%, the content of the monofunctional acrylate monomer is 30-55%, the content of the difunctional acrylate monomer is 5-15%, the content of the trifunctional acrylate monomer is 3-10%, the content of the acrylate monomer containing an acidic functional group is 0.5-5%, the content of the photoinitiator is 5-12%, and the content of the auxiliary agent is 0.02-2%.

[0013] In a preferred embodiment, the mass ratio of dibasic acid modified bisphenol A epoxy acrylate, tetrafunctional branched polyester acrylate and polyurethane acrylate with polyester diol as the main chain in the acrylate oligomer is 1:(0.3-0.9):(0.2-0.6).

[0014] In a preferred embodiment, the dibasic acid-modified bisphenol A epoxy acrylate has a structure shown in formula (I):

[0015] In formula (I), R1 is C1-C 10 An alkylene group, R2 has a structure represented by formula (II), and n is 1-10.

[0016] In a preferred embodiment, the dibasic acid modified bisphenol A epoxy acrylate is prepared according to the following method: bisphenol A epoxy resin, acrylic acid and aliphatic dibasic acid are subjected to a ring-opening reaction to obtain dibasic acid modified bisphenol A epoxy acrylate having a structure shown in formula (I).

[0017] In a preferred embodiment, in the preparation method of the dibasic acid modified bisphenol A epoxy acrylate, the general formula of the aliphatic dibasic acid is HOOC-R1-COOH, wherein R1 is selected from C1-C 10 of alkylene.

[0018] In a preferred embodiment, in the preparation method of the dibasic acid-modified bisphenol A epoxy acrylate, the molar ratio of the bisphenol A epoxy resin to acrylic acid is 1:(0.8-1).

[0019] In a preferred embodiment, in the preparation method of the dibasic acid-modified bisphenol A epoxy acrylate, the molar ratio of the bisphenol A epoxy resin to the aliphatic dibasic acid is 1:(0.35-0.55).

[0020] In a preferred embodiment, in the above-mentioned method for preparing dibasic acid-modified bisphenol A epoxy acrylate, the conditions of the ring-opening reaction include a temperature of 90-120° C. and a time of 1-10 h.

[0021] In a preferred embodiment, the tetrafunctional branched polyester acrylate has a main chain structure represented by formula (III) and four acrylate functional group structures represented by formula (III′):

[0022] In formula (III), R3 and R4 are each independently substituted or unsubstituted C1-C 10 The alkylene group is alkylene, and m is 1-10.

[0023] In a preferred embodiment, the polyurethane acrylate with polyester diol as the main chain has a structure shown in formula (IV):

[0024] In formula (IV), R5 and R6 are each independently C1-C 10 of alkylene.

[0025] In a preferred embodiment, the monofunctional acrylate monomer contains a benzene ring-containing acrylate monomer, a bridge group-containing acrylate monomer, and a bicyclodiene group-containing acrylate monomer.

[0026] In a preferred embodiment, the benzene ring-containing acrylate monomer is at least one selected from 2-phenoxyethyl acrylate, 4-ethylphenyl acrylate, 3,5-dihydroxyphenol methacrylate and benzyl acrylate.

[0027] In a preferred embodiment, the bridge group-containing acrylic acid ester monomer is selected from at least one of isobornyl acrylate, 3-isobornylcyclohexyl acrylate and isobornyl methacrylate.

[0028] In a preferred embodiment, the bicycloalkadienyl-containing acrylate monomer is at least one selected from the group consisting of bicyclopentenyl acrylate, bicyclopentenyl ethoxylated acrylate, and bicyclopentenyl methacrylate.

[0029] In a preferred embodiment, the difunctional acrylate monomer is at least one selected from tricyclodecane dimethanol diacrylate, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate and ethoxylated bisphenol A diacrylate.

[0030] In a preferred embodiment, the trifunctional acrylate monomer is at least one selected from ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate and tris(2-hydroxyethyl)isocyanuric acid triacrylate.

[0031] In a preferred embodiment, the acrylate monomer containing an acidic functional group is a phosphate acrylate and / or a carboxylic acid group-containing acrylate.

[0032] In a preferred embodiment, the photoinitiator is a combination of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-methyl-2-(4-morpholinyl)-4'-(methylthio)propiophenone and 2-isopropylthioxanthone.

[0033] In a preferred embodiment, the mass ratio of the 2-methyl-2-(4-morpholinyl)-4'-(methylthio)propiophenone to the 2-isopropylthioxanthone is (2-4):1.

[0034] In a preferred embodiment, the mass ratio of the sum of the 2,4,6-trimethylbenzoyldiphenylphosphine oxide and the 2-isopropylthioxanthone is (8-18):1.

[0035] In a preferred embodiment, the auxiliary agent is selected from at least one of a pigment, a leveling agent, a dispersant, a grinding agent and a diluent.

[0036] The present invention also provides a method for preparing a high-reliability fast-curing UV adhesive, which comprises uniformly mixing an acrylate oligomer, a monofunctional acrylate monomer, a difunctional acrylate monomer, a trifunctional acrylate monomer, an acrylate monomer containing an acidic functional group, a photoinitiator, and an optional auxiliary agent to obtain a high-reliability fast-curing UV adhesive.

[0037] In a preferred embodiment, the mixing method comprises the following steps:

[0038] S1. Evenly mix the trifunctional acrylate monomer, the pigment, and the dispersant to obtain a color paste premix;

[0039] S2. uniformly mixing a monofunctional acrylate monomer, a difunctional acrylate monomer, a trifunctional acrylate monomer, an acrylate monomer containing an acidic functional group, a photoinitiator, and a leveling agent to obtain a pretreated material;

[0040] S3. Evenly mix the color paste premix obtained in S1, the pretreated material obtained in S2, and the acrylate oligomer to obtain the high-reliability fast-curing UV adhesive.

[0041] In addition, the present invention also provides the application of high-reliability fast-curing UV glue in the insulation protection of the outer packaging of power battery cells.

[0042] The high-reliability, fast-curing UV adhesive provided by the present invention has low viscosity and good fluidity, and is suitable for inkjet processes with high precision and high utilization rate; the curing speed is fast, and it can also be cured in the long-wave light band, taking into account both surface drying and deep curing, and is suitable for energy-saving and efficient LED curing processes; the cured adhesive layer has high hardness and is resistant to bending, which reduces the impact of external force damage on the battery cell; the insulation pressure resistance is good, and the adhesive layer is not easily broken down by voltage, which provides significant leakage and interruption protection for the battery cell; the adhesive layer has dense cross-linking and a stable molecular structure, and can still maintain excellent insulation protection after aging tests such as water boiling test and salt spray test. Compared with traditional PET blue film protection, the high-reliability, fast-curing UV adhesive protection provided by the present invention simplifies the process and avoids process defects caused by lamination. It also improves the bonding strength and insulation pressure resistance, water boiling resistance, salt spray resistance and other reliability of UV adhesive used in high-precision inkjet processes. In summary, the UV adhesive provided in this application has low viscosity and fast curing speed. It can use more energy-saving and efficient LED curing and adapt to high-precision inkjet technology. At the same time, it meets the reliability requirements and bonding strength requirements such as insulation pressure resistance, boiling water resistance, and salt spray resistance. It can replace PET blue film as the insulating protective layer of the outer packaging of power batteries, and reserves sufficient design space for lightweight batteries. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is further illustrated and described below through specific implementation methods.

[0044] The high-reliability fast-curing UV adhesive provided by the present invention contains acrylate oligomers, monofunctional acrylate monomers, difunctional acrylate monomers, trifunctional acrylate monomers, acrylate monomers containing acidic functional groups, photoinitiators, and optional auxiliary agents. Wherein, in terms of weight percentage, the content of the acrylate oligomer is 20-50%, such as 20%, 25%, 30%, 35%, 40%, 45%, 50% or any value therebetween; the content of the monofunctional acrylate monomer is 30-55%, such as 30%, 35%, 40%, 45%, 50%, 55% or any value therebetween; the content of the difunctional acrylate monomer is 5-15%, such as 5%, 7%, 9%, 11%, 13%, 15% or any value therebetween; the content of the trifunctional acrylate monomer is 3-10%, such as 3%, 4%, 5%, 6%, 8%, 9%, 10%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, 210%, 220%, 230%, 240%, 250%, 260%, 270%, 280%, 290%, 300%, 310%, 310%, 320%, 330%, 340%, 350%, 360%, 370%, 380%, 390%, 40 ... %, 6%, 7%, 8%, 9%, 10% or any value therebetween; the content of the acrylate monomer containing an acidic functional group is 0.5-5%, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or any value therebetween; the content of the photoinitiator is 5-12%, such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12% or any value therebetween; the content of the auxiliary agent is 0.02-2%, such as 0.02%, 0.2%, 0.5%, 1%, 1.5%, 2% or any value therebetween.

[0045] In the present invention, the acrylate oligomer contains dibasic acid-modified bisphenol A epoxy acrylate, tetrafunctional branched polyester acrylate, and polyurethane acrylate with a polyester diol as the main chain. The mass ratio of the dibasic acid-modified bisphenol A epoxy acrylate to the tetrafunctional branched polyester acrylate is preferably 1:(0.3-0.9), such as 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, or any value therebetween; and the mass ratio of the dibasic acid-modified bisphenol A epoxy acrylate to the polyurethane acrylate with a polyester diol as the main chain is preferably 1:(0.2-0.6), such as 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, or any value therebetween.

[0046] In the present invention, the dibasic acid-modified bisphenol A epoxy acrylate preferably has a structure shown in formula (I):

[0047] In formula (I), R1 is C1-C 10 wherein R2 has a structure shown in formula (II), and n is 1-10. 10Specific examples of the alkylene group include, but are not limited to, methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, or nonylene.

[0048] In the present invention, the dibasic acid modified bisphenol A epoxy acrylate can be obtained commercially or prepared according to various methods well known in the art. In a preferred embodiment, the dibasic acid modified bisphenol A epoxy acrylate is preferably prepared according to the following method: bisphenol A type epoxy resin, acrylic acid and aliphatic dibasic acid are subjected to a ring-opening reaction to obtain the dibasic acid modified bisphenol A epoxy acrylate with a structure shown in formula (I). Wherein, the molar ratio of the bisphenol A type epoxy resin and acrylic acid is preferably 1: (0.8-1), such as 1: 0.8, 1: 0.85, 1: 0.9, 1: 0.95, 1: 1 or any value therebetween. The molar ratio of the bisphenol A type epoxy resin and aliphatic dibasic acid is preferably 1: (0.35-0.55), such as 1: 0.35, 1: 0.4, 1: 0.45, 1: 0.5, 1: 0.55 or any value therebetween. The conditions of the ring-opening reaction include a temperature of preferably 90-120°C, such as 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C or any value thereof; a time of 1-10h, such as h, 2h, 4h, 6h, 8h, 10h or any value therebetween. The present invention has no particular limitation on the type of aliphatic dibasic acid, as long as it can form an ether bond structure by ring-opening reaction with bisphenol A epoxy resin. The general formula of the aliphatic dibasic acid is HOOC-R1-COOH, where R1 is C1-C 10 The C1-C 10 Specific examples of the alkylene group include, but are not limited to, at least one of glutaric acid, adipic acid, pimelic acid, suberic acid, and azelaic acid.

[0049] In the present invention, the tetrafunctional branched polyester acrylate preferably has a main chain structure represented by formula (III) and four acrylate functional group structures represented by formula (III′):

[0050] In formula (III), R3 and R4 are each independently substituted or unsubstituted C1-C 10 wherein m is 1-10. wherein the acrylate functional group structure may be located entirely at the end group of the tetrafunctional branched polyester acrylate, or entirely at the side group of the tetrafunctional branched polyester acrylate, or partially at the end group and partially at the side group. 10Specific examples of alkylene include, but are not limited to, methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, or nonylene. m can be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0051] In the present invention, the tetrafunctional branched polyester acrylate can be prepared by various existing methods or can be commercially obtained, such as at least one of 6320 produced by Changxing Chemical Industry (China) Co., Ltd. (hereinafter referred to as Changxing), EBECRYL 657 and EBECRYL 800 produced by Allnex Resins (China) Co., Ltd., and GU9400Y and GU9600Z produced by Guojing Chemical Co., Ltd.

[0052] In the present invention, the polyurethane acrylate with polyester diol as the main chain has a structure shown in formula (IV):

[0053] In formula (IV), R5 and R6 are each independently C1-C 10 wherein the C1-C 10 Specific examples of the alkylene group include, but are not limited to, methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, or nonylene.

[0054] In the present invention, the polyurethane acrylate with polyester diol as the main chain can be prepared by various existing methods, or can be purchased commercially, such as Shanghai Yinzhu Industrial Co., Ltd. (abbreviated as Yinzhu) Y-5656 (having the structure shown in formula (IV)).

[0055] In the present invention, the monofunctional acrylate monomers include a benzene ring-containing acrylate monomer, a bridge group-containing acrylate monomer, and a bicycloalkadienyl-containing acrylate monomer. Specific examples of the benzene ring-containing acrylate monomers include, but are not limited to, at least one of 2-phenoxyethyl acrylate, 4-ethylphenyl acrylate, 3,5-dihydroxyphenol methacrylate, and benzyl acrylate. Specific examples of the bridge group-containing acrylate monomers include, but are not limited to, at least one of isobornyl acrylate, 3-isobornylcyclohexyl acrylate, and isobornyl methacrylate. Specific examples of the bicycloalkadienyl-containing acrylate monomers include, but are not limited to, at least one of biscyclopentenyl acrylate, biscyclopentenyl ethoxylated acrylate, and biscyclopentenyl methacrylate. Among monofunctional acrylate monomers, those containing benzene rings have low viscosity and strong dilution capacity. Due to their special structure, the benzene ring and the acrylate double bond form a conjugated system, resulting in strong electron delocalization, activated acrylate double bonds, and very strong reactivity. In practical applications, this is reflected in their ability to rapidly cure even under low light energy, making UV adhesives adaptable to LED curing and high-precision inkjet processes. Furthermore, acrylate monomers containing bridge groups and bicyclodiene groups have low polarity, and the three-dimensional ring structures of the bridge groups and bicyclodiene groups have large steric hindrance, which is beneficial for improving the water-resistant, waterproof, and dielectric strength of the UV adhesive layer. They can also reduce the curing volume shrinkage of the UV adhesive and reduce the internal stress caused by curing shrinkage, thereby improving the adhesion of the UV adhesive to the outer layer of the aluminum material of the battery cell. This structure provides considerable toughness and cushioning properties, improving the bending and impact resistance of the UV adhesive layer. When the battery cell is damaged by external forces, the adhesive layer will not break and lose its protective function of dielectric strength. Preferably, the monofunctional acrylate monomer is a combination of a benzene ring-containing acrylate monomer, a bridge group-containing acrylate monomer and a bicyclodiene group-containing acrylate monomer. The resulting UV adhesive has more excellent insulation withstand voltage, aging resistance and mechanical properties.

[0056] In the present invention, the difunctional acrylate monomer is preferably selected from at least one of tricyclodecane dimethanol diacrylate, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, and ethoxylated bisphenol A diacrylate. This difunctional acrylate monomer can increase the density, hardness, and wear resistance of the adhesive layer, effectively protecting the battery cells from scratches during transportation and assembly. When tricyclodecane dimethanol diacrylate is the preferred difunctional acrylate monomer, due to its three-dimensional cyclic structure, the corresponding UV adhesive also exhibits low shrinkage, a high glass transition temperature, and aging resistance.

[0057] In the present invention, specific examples of the trifunctional acrylate monomer include, but are not limited to, at least one of ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, and tris(2-hydroxyethyl)isocyanurate triacrylate. The trifunctional acrylate monomer uses three reactive groups as crosslinking points to connect various acrylate oligomers and acrylate monomers, so that the system forms a dense and stable three-dimensional network structure, thereby enhancing its tensile strength, flexural strength, and wear resistance. When the trifunctional acrylate monomer is preferably ethoxylated trimethylolpropane triacrylate, due to the introduction of ethoxy groups with smaller internal rotation barriers, the corresponding UV adhesive can improve the flexibility of the macromolecule after curing, play a role in reducing curing shrinkage, and thus improve the bonding strength. It can also improve the dispersion and packaging of the system for the pigment, thereby increasing the storage stability of the liquid adhesive, and is less likely to cause sedimentation, stratification, and other problems when placed at room temperature.

[0058] In the present invention, the acidic acrylate monomer is preferably a phosphate acrylate and / or a carboxylic acid acrylate. This acidic acrylate monomer can improve the adhesion and bonding strength of the adhesive layer to the aluminum layer of the battery core, increase the hardness and density of the adhesive layer, and enhance the pressure resistance of the UV adhesive.

[0059] The type of the photoinitiator in the present invention is not particularly limited, as long as it can initiate an unsaturated double bond to achieve a free radical polymerization reaction, preferably a combination of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-methyl-2-(4-morpholinyl)-4'-(methylthio)propiophenone and 2-isopropylthioxanthone. Wherein, the mass ratio of the 2-methyl-2-(4-morpholinyl)-4'-(methylthio)propiophenone and the 2-isopropylthioxanthone is preferably (2-4):1, such as 2:1, 2.5:1, 3:1, 3.5:1, 4:1 or any value therebetween; the mass ratio of the 2,4,6-trimethylbenzoyldiphenylphosphine oxide to the 2-isopropylthioxanthone is preferably (8-18):1, such as 8:1, 10:1, 12:1, 14:1, 16:1, 18:1 or any value therebetween. After in-depth research, the inventors of the present invention found that the photoinitiator has light absorption ability in the ultraviolet light region (250-420nm) and the visible light region ((400-800nm). After absorbing light energy, the initiator molecule transitions from the ground state to the excited singlet state, and then can continue to transition to the excited triplet state. At this time, the molecular structure is unstable and will split to produce active free radicals, thereby initiating polymerization of the acrylic double bond. In the present invention, considering that the UV glue needs to adapt to the LED curing process, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO) photoinitiator with an absorption wavelength of up to 420nm is selected, and the dosage is increased to increase the concentration of the photoinitiator molecules in the system, so that the outer layer of UV glue in contact with the air has a higher concentration of active free radicals when illuminated, thereby This overcomes the problem of free radical cleavage during curing, which is caused by oxygen in the air passivating the photoinitiator and causing it to lose its activity, thereby accelerating surface curing and drying. Furthermore, the combination of 2-methyl-2-(4-morpholinyl)-4'-(methylthio)propiophenone (907) and 2-isopropylthioxanthone (ITX) is a classic photoinitiator combination suitable for colored systems. The two complement each other in terms of absorption bands, and the 2-isopropylthioxanthone photoinitiator also has a sensitizing effect, enhancing the light absorption capacity of the initiation system and reducing the effect of pigment absorption on the curing of the adhesive layer. With the synergistic effect of the three initiators, UV adhesives have extremely high curing efficiency and are no longer limited by the high-energy consumption mercury lamp curing process. Even with the more energy-efficient and efficient LED curing, a high degree of curing can be achieved.

[0060] In the present invention, specific examples of the additive include, but are not limited to, at least one of a pigment, a leveling agent, a dispersant, an abrasive, and a diluent. The inventors of the present invention have discovered that using Tego 410 as a leveling agent helps reduce surface tension, improve surface smoothness and flatness, and avoid pinholes and uneven surface defects. Furthermore, using BYKJET-9150 as a dispersant offers excellent compatibility with UV adhesive systems, and the active groups on the chain segments adsorb onto the pigment through intermolecular forces, helping to stably disperse the pigment in the UV adhesive, improving the storage stability of the UV adhesive and preventing problems such as sedimentation and delamination.

[0061] The present invention also provides a method for preparing a high-reliability, fast-curing UV adhesive, comprising uniformly mixing an acrylate oligomer, a monofunctional acrylate monomer, a difunctional acrylate monomer, a trifunctional acrylate monomer, an acrylate monomer containing an acidic functional group, a photoinitiator, and an optional auxiliary agent to obtain a high-reliability, fast-curing UV adhesive. The mixing method may be to add all the raw materials simultaneously and then mix them together, or to add some of the raw materials in any order and then add the remaining raw materials and continue mixing, without particular limitation.

[0062] In the present invention, the mixing method preferably includes the following steps:

[0063] S1. Evenly mix the trifunctional acrylate monomer, the pigment, and the dispersant to obtain a color paste premix;

[0064] S2. uniformly mixing a monofunctional acrylate monomer, a difunctional acrylate monomer, a trifunctional acrylate monomer, an acrylate monomer containing an acidic functional group, a photoinitiator, and a leveling agent to obtain a pretreated material;

[0065] S3. Evenly mix the color paste premix obtained in S1, the pretreated material obtained in S2, and the acrylate oligomer to obtain the high-reliability fast-curing UV adhesive.

[0066] In addition, the present invention also provides the application of high-reliability fast-curing UV glue in the insulation protection of the outer packaging of power battery cells.

[0067] The present invention will be further described below with reference to specific examples and comparative examples. Unless otherwise specified, the parts in the following examples and comparative examples are parts by weight.

[0068] Preparation Example 1

[0069] This preparation example provides a preparation method of dibasic acid modified bisphenol A epoxy acrylate

[0070] 39 g of bisphenol A epoxy resin (E51), 7.41 g of acrylic acid (AA), and 7.74 g of adipic acid (Ada) were placed in a three-necked flask, and then 0.6 g of triphenylphosphine (PPh3) and 0.08 g of para-methoxyphenol (MEHQ) were added. After the addition, the temperature was stirred and controlled from 25°C to 95°C in about 3 hours. After maintaining for 1 hour, the temperature was raised to 105°C. The acid value was tested every half hour until the acid value reached 1 mg·KOH / g, thereby obtaining dibasic acid-modified bisphenol A epoxy acrylate.

[0071] Preparation Example 2

[0072] This preparation example provides a preparation method of dibasic acid modified bisphenol A epoxy acrylate

[0073] 39 g of bisphenol A epoxy resin (E51), 7.41 g of acrylic acid (AA), and 7.74 g of adipic acid (Ada) were placed in a three-necked flask, and then 0.6 g of triphenylphosphine (PPh3) and 0.08 g of para-methoxyphenol (MEHQ) were added. After the addition, the temperature was stirred and controlled from 25°C to 95°C in about 3 hours. After maintaining for 2 hours, the temperature was raised to 115°C. The acid value was tested every half hour until the acid value reached 0.5 mg·KOH / g, thereby obtaining dibasic acid-modified bisphenol A epoxy acrylate.

[0074] Preparation Example 3

[0075] This preparation example provides a preparation method of dibasic acid modified bisphenol A epoxy acrylate

[0076] 39 g of bisphenol A epoxy resin (E51), 7.41 g of acrylic acid (AA), and 7.74 g of adipic acid (Ada) were placed in a three-necked flask, and then 0.6 g of triphenylphosphine (PPh3) and 0.08 g of para-methoxyphenol (MEHQ) were added. After the addition, the temperature was stirred and controlled from 25°C to 95°C in about 3 hours. After maintaining for 4 hours, the temperature was raised to 125°C. The acid value was tested every half hour until the acid value reached 0.3 mg·KOH / g, thereby obtaining dibasic acid-modified bisphenol A epoxy acrylate.

[0077] Example 1

[0078] This embodiment provides a method for preparing a high-reliability fast-curing UV adhesive.

[0079] S1. 50 parts of ethoxylated trimethylolpropane triacrylate, 50 parts of trimethylolpropane triacrylate, 5 parts of BYKJET-9150 dispersant, and 18 parts of blue pigment were added to a reactor in sequence, stirred at 1000 rpm until uniformly mixed, and then transferred to a grinding tank. The mixture was ground with 1 mm zirconium oxide beads to a particle size of ≤1 μm, and the material was filtered to obtain a color paste premix;

[0080] S2, 10 parts of benzyl acrylate, 25 parts of isobornyl acrylate, 8 parts of dicyclopentenyl ethoxylated acrylate, 8 parts of tricyclodecane dimethanol diacrylate, 5 parts of ethoxylated trimethylolpropane triacrylate, 1 part of acrylate monomer containing acidic functional group P-2M (Kyoei Co., Ltd.), 6.6 parts of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 1.5 parts of 2-methyl-2-(4-morpholinyl)-4'-(methylthio)propiophenone, 0.5 parts of 2-isopropylthioxanthone and 0.1 parts of Tego 410 leveling agent were added to a reactor and dispersed at a high speed of 500 rpm until completely dissolved to obtain a pretreated material;

[0081] S3. Add 6 parts of the color paste premix to the pretreated material and stir at a speed of 500 rpm until the mixture is evenly mixed; then add 15 parts of the dibasic acid-modified bisphenol A epoxy acrylate prepared in Preparation Example 1, 10 parts of a tetrafunctional branched polyester acrylate (Changxing 6320), and 6 parts of a polyurethane acrylate with a polyester diol as the main chain (brand name: Yinzhu Y-5656), stir at a speed of 1000 rpm until the mixture is evenly mixed, and then filter the material to obtain a high-reliability fast-curing UV adhesive.

[0082] Example 2

[0083] This embodiment provides a method for preparing a high-reliability fast-curing UV adhesive.

[0084] S1. 50 parts of ethoxylated trimethylolpropane triacrylate, 50 parts of trimethylolpropane triacrylate, 5 parts of BYKJET-9150 dispersant, and 18 parts of blue pigment were added to a reactor in sequence, stirred at 1000 rpm until uniformly mixed, and then transferred to a grinding tank. The mixture was ground with 1 mm zirconium oxide beads to a particle size of ≤1 μm, and the material was filtered to obtain a color paste premix;

[0085] S2, 25 parts of benzyl acrylate, 25 parts of isobornyl acrylate, 8 parts of dicyclopentenyl ethoxylated acrylate, 8 parts of tricyclodecane dimethanol diacrylate, 5 parts of ethoxylated trimethylolpropane triacrylate, 1 part of acrylate monomer containing acidic functional group P-2M (Kyoei Co., Ltd.), 6.6 parts of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 1.5 parts of 2-methyl-2-(4-morpholinyl)-4'-(methylthio)propiophenone, 0.5 parts of 2-isopropylthioxanthone and 0.1 parts of Tego 410 leveling agent were added to a reactor and dispersed at a high speed of 500 rpm until completely dissolved to obtain a pretreated material;

[0086] S3. Add 6 parts of the color paste premix to the pretreated material and stir at a speed of 500 rpm until the mixture is uniformly mixed; then add 15 parts of the dibasic acid-modified bisphenol A epoxy acrylate prepared in Preparation Example 1, 10 parts of a tetrafunctional branched polyester acrylate (EBECRYL 657 from Allnex Resins (China) Co., Ltd.), and 6 parts of a polyurethane acrylate with a polyester diol as the main chain (brand name: Yinzhu Y-5656), stir at a speed of 1000 rpm until the mixture is uniformly mixed, and then filter the material to obtain a high-reliability fast-curing UV adhesive.

[0087] Example 3

[0088] This embodiment provides a method for preparing a high-reliability fast-curing UV adhesive.

[0089] S1. 50 parts of ethoxylated trimethylolpropane triacrylate, 50 parts of trimethylolpropane triacrylate, 5 parts of BYKJET-9150 dispersant, and 18 parts of blue pigment were added to a reactor in sequence, stirred at 1000 rpm until uniformly mixed, and then transferred to a grinding tank. The mixture was ground with 1 mm zirconium oxide beads to a particle size of ≤1 μm, and the material was filtered to obtain a color paste premix;

[0090] S2, 25 parts of benzyl acrylate, 25 parts of isobornyl acrylate, 8 parts of dicyclopentenyl acrylate, 8 parts of dicyclopentenyl ethoxylated acrylate, 8 parts of tricyclodecane dimethanol diacrylate, 5 parts of ethoxylated trimethylolpropane triacrylate, 1 part of acrylate monomer containing acidic functional group P-2M (Kyoei Co., Ltd.), 6.6 parts of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 1.5 parts of 2-methyl-2-(4-morpholinyl)-4'-(methylthio)propiophenone, 0.5 parts of 2-isopropylthioxanthone and 0.1 parts of Tego 410 leveling agent were added to a reactor and dispersed at a high speed of 500 rpm until completely dissolved to obtain a pretreated material;

[0091] S3. Add 6 parts of the color paste premix to the pretreated material and stir at a speed of 500 rpm until the mixture is uniformly mixed; then add 15 parts of the dibasic acid-modified bisphenol A epoxy acrylate prepared in Preparation Example 1, 10 parts of a tetrafunctional branched polyester acrylate (EBECRYL 800 of Allnex Resins (China) Co., Ltd.), and 6 parts of a polyurethane acrylate with a polyester diol as the main chain (brand name: Yinzhu Y-5656), stir at a speed of 1000 rpm until the mixture is uniformly mixed, and then filter the material to obtain a high-reliability fast-curing UV adhesive.

[0092] Example 4

[0093] This embodiment provides a method for preparing a high-reliability fast-curing UV adhesive.

[0094] S1. 50 parts of ethoxylated trimethylolpropane triacrylate, 50 parts of trimethylolpropane triacrylate, 5 parts of BYKJET-9150 dispersant, and 18 parts of blue pigment were added to a reactor in sequence, stirred at 1000 rpm until uniformly mixed, and then transferred to a grinding tank. The mixture was ground with 1 mm zirconium oxide beads to a particle size of ≤1 μm, and the material was filtered to obtain a color paste premix;

[0095] S2, 25 parts of benzyl acrylate, 25 parts of isobornyl acrylate, 8 parts of dicyclopentenyl ethoxylated acrylate, 8 parts of tricyclodecane dimethanol diacrylate, 5 parts of ethoxylated trimethylolpropane triacrylate, 1 part of acrylate monomer containing acidic functional group P-2M (Kyoei Co., Ltd.), 4 parts of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 1.5 parts of 2-methyl-2-(4-morpholinyl)-4'-(methylthio)propiophenone, 0.5 parts of 2-isopropylthioxanthone and 0.1 parts of Tego 410 leveling agent were added to a reactor and dispersed at a high speed of 500 rpm until completely dissolved to obtain a pretreated material;

[0096] S3. Add 6 parts of the color paste premix to the pretreated material and stir at a speed of 500 rpm until the mixture is evenly mixed; then add 15 parts of the dibasic acid-modified bisphenol A epoxy acrylate prepared in Preparation Example 1, 10 parts of a tetrafunctional branched polyester acrylate (GU9400Y from Guojing Chemical Co., Ltd.), and 6 parts of a polyurethane acrylate with a polyester diol as the main chain (brand name: Yinzhu Y-5656), stir at a speed of 1000 rpm until the mixture is evenly mixed, and then filter the material to obtain a high-reliability fast-curing UV adhesive.

[0097] Example 5

[0098] This embodiment provides a method for preparing a high-reliability fast-curing UV adhesive.

[0099] S1. 100 parts of trimethylolpropane triacrylate, 5 parts of BYKJET-9150 dispersant, and 18 parts of blue pigment were added to a reactor in sequence, stirred at 1000 rpm until uniformly mixed, and then transferred to a grinding jar. The mixture was ground with 1 mm zirconium oxide beads to a particle size of ≤1 μm, and the material was filtered to obtain a color paste premix;

[0100] S2, 58 parts of isobornyl acrylate, 8 parts of tricyclodecane dimethanol diacrylate, 5 parts of trimethylolpropane triacrylate, 1 part of acidic functional group-containing acrylate monomer P-2M (Kyoei Co., Ltd.), 6.5 parts of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2 parts of 2-methyl-2-(4-morpholinyl)-4'-(methylthio)propiophenone, 0.5 parts of 2-isopropylthioxanthone and 0.1 parts of Tego 410 leveling agent were added to a reactor and dispersed at a high speed of 500 rpm until completely dissolved to obtain a pretreated material;

[0101] S3. Add 6 parts of the color paste premix to the pretreated material and stir at a speed of 500 rpm until the mixture is evenly mixed; then add 15 parts of the dibasic acid-modified bisphenol A epoxy acrylate prepared in Preparation Example 2, 13.5 parts of a tetrafunctional branched polyester acrylate (GU9600Z from Guojing Chemical Co., Ltd.), and 3 parts of a polyurethane acrylate with a polyester diol as the main chain (brand name: Yinzhu Y-5656), stir at a speed of 1000 rpm until the mixture is evenly mixed, and then filter the material to obtain a high-reliability fast-curing UV adhesive.

[0102] Example 6

[0103] This embodiment provides a method for preparing a high-reliability fast-curing UV adhesive.

[0104] S1. 100 parts of tris(2-hydroxyethyl)isocyanurate triacrylate, 5 parts of BYKJET-9150 dispersant, and 18 parts of blue pigment were added to a reactor in sequence, stirred at 1000 rpm until uniformly mixed, and then transferred to a grinding jar. The mixture was ground with 1 mm zirconium oxide beads to a particle size of ≤1 μm, and the material was filtered to obtain a color paste premix.

[0105] S2, 58 parts of dicyclopentenyl ethoxylated acrylate, 8 parts of ethoxylated bisphenol A diacrylate, 5 parts of tris(2-hydroxyethyl)isocyanurate triacrylate, 1 part of acidic functional group-containing acrylate monomer P-2M (Kyoeisha), 6.6 parts of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 1.5 parts of 2-methyl-2-(4-morpholinyl)-4'-(methylthio)propiophenone, 0.5 parts of 2-isopropylthioxanthone and 0.1 parts of Tego 410 leveling agent were added to a reactor and dispersed at a high speed of 500 rpm until completely dissolved to obtain a pretreated material;

[0106] S3. Add 6 parts of the color paste premix to the pretreated material and stir at a speed of 500 rpm until the mixture is uniformly mixed; then add 15 parts of the dibasic acid-modified bisphenol A epoxy acrylate prepared in Preparation Example 3, 13.5 parts of a tetrafunctional branched polyester acrylate (Changxing 6320), and 3 parts of a polyurethane acrylate with a polyester diol as the main chain (brand name: Yinzhu Y-5656), stir at a speed of 1000 rpm until the mixture is uniformly mixed, and then filter the material to obtain a high-reliability fast-curing UV adhesive.

[0107] Comparative Example 1

[0108] According to Example 3 of patent CN112876949B, a UV-curable leakage protection coating was synthesized, comprising the following components in parts by weight: 20 parts of difunctional fatty acid-modified bisphenol A epoxy acrylate, 15 parts of difunctional poly HDI isocyanate acrylate, 15 parts of hydroxypropyl methacrylate, 15 parts of tetrahydrofuran acrylate, 10 parts of tricyclodecane dimethanol diacrylate, 15 parts of tricyclodecane dimethanol dimethyl diacrylate, 5 parts of propoxylated glycerol triacrylate, 15 parts of pigments and fillers, 5 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2.5 parts of (2,4,6-trimethylbenzoyl) diphenylphosphine oxide, 5 parts of silane coupling agent KH-570, 1.2 parts of dispersant, 0.8 parts of defoaming agent, and 1 part of leveling agent.

[0109] Comparative Example 2

[0110] According to Example 4 of patent CN113881282A, a UV inkjet ink for surface protection of aluminum alloy of power battery was synthesized, comprising the following components in parts by weight: 6 parts of phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 15 parts of polyurethane acrylate, 8 parts of modified epoxy acrylate, 20 parts of cyclotrimethylolpropane formal acrylate, 10 parts of acryloylmorpholine, 25 parts of tetrahydrofuran acrylate, 10 parts of 2-phenoxyethyl acrylate, 20 parts of UV color paste, 5 parts of ethyl acetate, and 2 parts of leveling agent.

[0111] Comparative Example 3

[0112] UV adhesive was prepared according to the method of Example 2, except that the content of the dibasic acid-modified bisphenol A epoxy acrylate prepared in Preparation Example 1 was 31 parts, the content of the tetrafunctional branched polyester acrylate (brand name Changxing 6320) was 0 parts, and the content of the polyurethane acrylate with polyester diol as the main chain (brand name Yinzhu Y-5656) was 0 parts. The other conditions remained unchanged.

[0113] Comparative Example 4

[0114] UV adhesive was prepared according to the method of Example 2, except that the content of the dibasic acid-modified bisphenol A epoxy acrylate prepared in Preparation Example 1 was 0 parts, the content of the tetrafunctional branched polyester acrylate (brand name Changxing 6320) was 31 parts, and the content of the polyurethane acrylate with polyester diol as the main chain (brand name Yinzhu Y-5656) was 0 parts. The other conditions remained unchanged.

[0115] Comparative Example 5

[0116] UV adhesive was prepared according to the method of Example 2, except that the content of the dibasic acid-modified bisphenol A epoxy acrylate prepared in Preparation Example 1 was 0 parts, the content of the tetrafunctional branched polyester acrylate (brand name Changxing 6320) was 0 parts, and the content of the polyurethane acrylate with polyester diol as the main chain (brand name Yinzhu Y-5656) was 31 parts. The other conditions remained unchanged.

[0117] Comparative Example 6

[0118] UV adhesive was prepared according to the method of Example 2, except that no monofunctional acrylate monomer was added to the system, that is, the contents of benzyl acrylate, isobornyl acrylate, and dicyclopentenyl ethoxylated acrylate were all 0 parts, and the other conditions remained unchanged.

[0119] Comparative Example 7

[0120] UV adhesive was prepared according to the method of Example 2, except that no difunctional acrylate monomer was added to the system, that is, the content of tricyclodecane dimethanol diacrylate was 0 parts, and the other conditions remained unchanged.

[0121] Comparative Example 8

[0122] UV adhesive was prepared according to the method of Example 2, except that no trifunctional acrylate monomer was added to the system, that is, the contents of ethoxylated trimethylolpropane triacrylate and trimethylolpropane triacrylate were both 0 parts, and the other conditions remained unchanged.

[0123] Comparative Example 9

[0124] UV adhesive was prepared according to the method of Example 2, except that no acrylate monomer containing an acidic functional group was added to the system, that is, no acrylate monomer containing an acidic functional group P-2M (Kyoei Co., Ltd.) was added, and other conditions remained unchanged.

[0125] Comparative Example 10

[0126] UV adhesive was prepared according to the method of Example 3, except that the tetrafunctional branched polyester acrylate (brand name Changxing 6320) was replaced by the same weight portion of the dibasic acid-modified bisphenol A epoxy acrylate prepared in Preparation Example 1, and the other conditions remained unchanged.

[0127] Test Case

[0128] The above embodiments and comparative examples are compared with the following test results.

[0129] (1) Viscosity test: The viscosity of the UV adhesive obtained in each embodiment and comparative example was tested using a HAAKE MARS40 rotational rheometer, using a No. 52 rotor, a test temperature of 25° C., and a shear rate of 2 s -1 , thereby determining the viscosity (cps) of the UV glue. The results are shown in Table 1.

[0130] (2) LED curing surface dry test: The film thickness of the UV adhesive obtained in each embodiment and comparative example was controlled at 100±5μm, and a 395nm LED was used for pre-curing (200mj / cm 2 *3s), and then use 365nm LED for final curing (1000mj / cm 2 ), the maximum final curing time is 60s, and the surface curing degree is evaluated. Completely dry to the touch is judged as pass, and the surface is sticky as NG. The results are detailed in Table 1.

[0131] (3) Shear Test: Shear sheets were prepared and overlapped, then bonded together using the UV adhesive obtained in each of the Examples and Comparative Examples. The adhesive layer thickness was controlled to be 0.25 mm. The sheets were cured at 80°C for 4 hours. After cooling, a shear strength test was performed in accordance with GBT7124 / ISO4587 at a test temperature of 25°C and a tensile speed of 5 mm / min. The resulting samples were subjected to a double 85 aging test (i.e., aging at 85°C / 85% RH for 1000 hours, the same below) to determine the shear strength (MPa) of the UV adhesive before and after double 85 aging. The results are detailed in Table 1.

[0132] (4) Adhesion test: The UV adhesive samples obtained in each embodiment and comparative example were subjected to adhesion test according to DIN EN ISO 2409 (coating-coating grid cutting test) method before and after double 85 aging test, and the total peeling area at the edge and intersection of the cutting line was divided into: 5B is 0, 4B is 0-5% (including the endpoint of 5%), 3B is 5-15% (excluding the endpoint of 5% but including the endpoint of 15%), 2B is 15-35% (excluding the endpoint of 15% but including the endpoint of 35%), 1B is 35-65% (excluding the endpoint of 35% but including the endpoint of 65%), and 0B is greater than 65%. The results determine that the adhesion is qualified when it is ≥4B, thereby determining the adhesion of the UV adhesive before and after double 85 aging. The results are detailed in Table 1.

[0133] (5) Bending test: The UV adhesive obtained in each embodiment and comparative example was bent 90° on a mandrel with a curvature radius of 32 mm. The surface condition of the adhesive layer was observed. If there were no obvious cracks or damage, it was judged to be pass. If there were cracks or damage, it was judged to be NG. The results are detailed in Table 1.

[0134] (6) Insulation resistance test: The UV adhesive obtained in each embodiment and comparative example was subjected to a double 85 aging test. The samples before and after double 85 aging were tested using a GPT-9803 voltage / insulation resistance tester. The test conditions were adjusted to DC 1000 V, 10 s, and the test was clicked and the test results were read to determine the insulation resistance (MΩ) of the UV adhesive. The results are detailed in Table 1.

[0135] (7) Voltage Withstand Test: The UV adhesive obtained in each embodiment and comparative example was subjected to a double 85 aging test. The samples before and after double 85 aging were tested using a GPT-9803 voltage / insulation resistance tester. The test conditions were adjusted to AC 2230V 60s / DC 4000V 60s. Click the test button and read the test results. A leakage current of ≤0.1mA was judged as pass, and a leakage current of >0.1mA was judged as NG. The results are detailed in Table 1.

[0136] (8) Boiling water resistance test: The UV adhesive samples obtained in each embodiment and comparative example were placed in boiling water for 72 hours, taken out, wiped dry and placed for 1 hour, and tested for adhesion and voltage resistance. If adhesion ≥ 4B and voltage resistance test leakage current ≤ 0.1mA, it was judged as pass; if adhesion < 4B and voltage resistance test leakage current > 0.1MA (any of these phenomena occurred), it was judged as NG. The results are shown in Table 1.

[0137] (9) Electrolyte resistance test: 0.5 g of electrolyte was added to the UV adhesive samples obtained in each embodiment and comparative example, and the samples were baked at 85°C for 2 h. After being taken out, they were wiped dry and left for 1 h. Adhesion test, voltage test and appearance observation were performed. If adhesion ≥ 4B, voltage test leakage current ≤ 0.1 mA, and no obvious wrinkling or falling off in appearance, it was judged as pass. If adhesion < 4B, voltage test leakage current > 0.1 MA, and obvious changes in appearance (any of these phenomena) were found, it was judged as NG. The results are shown in Table 1 for details.

[0138] (10) Salt spray test: The test method refers to the salt spray requirements of GB / T31467.3. Aging experiments are carried out at the severity level (5). Adhesion and withstand voltage are tested. Adhesion ≥ 4B and withstand voltage test leakage current ≤ 0.1mA are judged as pass. Adhesion < 4B and withstand voltage test leakage current > 0.1MA (any of these phenomena occurs) are judged as NG. The results are detailed in Table 1.

[0139] As can be seen from the results in Table 1, the high-reliability fast-curing UV adhesive provided by the present invention has low viscosity (27-37 cps) and fast curing speed. It can use more energy-saving and efficient LED curing and adapt to high-precision inkjet technology. At the same time, it meets the reliability requirements and bonding strength requirements such as insulation pressure resistance, boiling water resistance, and salt spray resistance. It can replace PET blue film as the insulating protective layer of the outer packaging of power battery cells, leaving sufficient design space for lightweight batteries.

[0140] A comparison of Example 2 and Comparative Example 1 shows that the viscosity of the UV adhesive provided by the present invention is between 27 and 37 cps, meeting the requirements of high-precision inkjet processing, while the viscosity of Comparative Example 1 is relatively high and cannot meet the requirements of inkjet processing. Furthermore, the UV adhesive provided by the present invention has a fast curing speed, good surface drying effect, and is suitable for LED curing, while the LED curing effect of Comparative Example 1 is unsatisfactory, and even with increased light energy, it cannot achieve complete surface drying.

[0141] From the comparison between Example 2 and Comparative Example 2, it can be seen that the UV adhesive provided by the present invention has high bonding strength. The shear strength after 1000 hours of double 85 aging test is still greater than 10MPa, which can meet the practical application requirements of battery cell bonding. It also has strong adhesion, and there will be no adhesion loss or adhesive layer shedding problems even after long-term aging. In addition, the UV adhesive provided by the present invention has good insulation voltage resistance, water boiling resistance, and salt spray resistance. The insulation resistance value is ≥10GΩ at DC 1000V, exceeding the instrument range, and no obvious voltage failure phenomenon occurs after double 85 aging. After the rigorous test of boiling in boiling water for 72 hours, it can still maintain qualified adhesion and voltage resistance. After electrolyte thermal aging, it can still maintain consistent appearance and adhesion, with no obvious attenuation of insulation performance. After salt spray aging, it still has excellent adhesion to the aluminum layer, which can meet the practical application requirements of battery cell protection. However, the bonding strength of Comparative Example 2 is poor, and after double 85 aging, the leakage current exceeds the standard and even the adhesive layer is broken down. In addition, the test reliability is poor, and the results of aging tests such as insulation withstand voltage, water boiling resistance, and salt spray resistance are not ideal.

[0142] From the comparison between Example 2 and Comparative Examples 3-9, it can be seen that when the UV glue does not simultaneously contain the three prepolymers of dibasic acid-modified bisphenol A epoxy acrylate, tetrafunctional branched polyester acrylate, and polyurethane acrylate with polyester diol as the main chain, monofunctional acrylate monomer, difunctional acrylate monomer, trifunctional acrylate monomer, and acrylate monomer containing an acidic functional group, the prepared UV glue cannot simultaneously meet the reliability requirements such as insulation withstand voltage, boiling water resistance, salt spray resistance, and high bonding strength and fast curing properties.

[0143] From the comparison between Example 3 and Comparative Example 10, it can be seen that the UV glue provided by the present invention can still ensure the integrity of the glue layer when bending with a large curvature, and will not crack or fall off. When the battery cell with this UV glue as the outer wrapping layer undergoes a large deformation, the UV glue layer can still play a role in insulation protection.

[0144] In summary, three prepolymers, namely, dibasic acid-modified bisphenol A epoxy acrylate, tetrafunctional branched polyester acrylate, and polyurethane acrylate with polyester diol as the main chain, are compounded and used. At the same time, a specific proportion of monofunctional acrylate monomer, difunctional acrylate monomer, trifunctional acrylate monomer, and acrylate monomer containing acidic functional groups are introduced to prepare high-reliability fast-curing UV adhesive, which can give the adhesive layer good insulation voltage resistance, boiling water resistance, salt spray resistance and other reliability as well as high bonding strength and fast curing properties.

[0145] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A high reliability fast curing UV adhesive, characterized in that: The high-reliability fast-curing UV adhesive contains acrylate oligomers, monofunctional acrylate monomers, difunctional acrylate monomers, trifunctional acrylate monomers, acrylate monomers containing acidic functional groups, photoinitiators and optional auxiliary agents; the acrylate oligomers also contain dibasic acid-modified bisphenol A epoxy acrylate, tetrafunctional branched polyester acrylate and polyurethane acrylate with polyether diol as the main chain.

2. The high reliability fast curing UV adhesive according to claim 1, characterized in that: In weight percentage, the content of the acrylate oligomer is 20-50%, the content of the monofunctional acrylate monomer is 30-55%, the content of the difunctional acrylate monomer is 5-15%, the content of the trifunctional acrylate monomer is 3-10%, the content of the acrylate monomer containing an acidic functional group is 0.5-5%, the content of the photoinitiator is 5-12%, and the content of the auxiliary agent is 0.02-2%.

3. The high reliability fast curing UV adhesive according to claim 1, characterized in that: The mass ratio of the dibasic acid modified bisphenol A epoxy acrylate, the tetrafunctional branched polyester acrylate and the polyurethane acrylate with polyester diol as the main chain in the acrylate oligomer is 1:(0.3-0.9):(0.2-0.6).

4. The high reliability fast curing UV adhesive according to claim 1, characterized in that: The dibasic acid modified bisphenol A epoxy acrylate has a structure shown in formula (I): In formula (I), R1 is C1-C 10 An alkylene group, R2 has a structure represented by formula (II), and n is 1-10.

5. The high reliability fast curing UV adhesive according to claim 1, characterized in that: The dibasic acid modified bisphenol A epoxy acrylate is prepared according to the following method: bisphenol A type epoxy resin, acrylic acid and aliphatic dibasic acid are subjected to a ring-opening reaction to obtain dibasic acid modified bisphenol A epoxy acrylate having a structure shown in formula (I).

6. The high reliability fast curing UV adhesive according to claim 5, characterized in that: The general formula of the aliphatic dibasic acid is HOOC-R1-COOH, where R1 is C1-C 10 of alkylene.

7. The high reliability fast curing UV adhesive according to claim 5, characterized in that: The molar ratio of the bisphenol A epoxy resin to acrylic acid is 1:(0.8-1); the molar ratio of the bisphenol A epoxy resin to aliphatic dibasic acid is 1:(0.35-0.55).

8. The high reliability fast curing UV adhesive according to claim 5, characterized in that: The conditions of the ring-opening reaction include a temperature of 90-120° C. and a time of 1-10 h.

9. The high reliability fast curing UV adhesive according to claim 1, characterized in that: The tetrafunctional branched polyester acrylate has a main chain structure shown in formula (III) and four acrylate functional group structures shown in formula (III'): In formula (III), R3 and R4 are each independently substituted or unsubstituted C1-C 10 The alkylene group is an alkylene group, and m is 1-10.

10. The high reliability fast curing UV adhesive according to claim 1, characterized in that: The polyurethane acrylate with polyester diol as the main chain has a structure shown in formula (IV): In formula (IV), R5 and R6 are each independently C1-C 10 of alkylene.

11. The high reliability fast curing UV adhesive according to claim 1, characterized in that: The monofunctional acrylate monomers simultaneously contain acrylate monomers containing a benzene ring, acrylate monomers containing a bridge group, and acrylate monomers containing a bicyclic diene group.

12. The high reliability fast curing UV adhesive according to claim 1, characterized in that: The bifunctional acrylate monomer is at least one selected from tricyclodecane dimethanol diacrylate, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate and ethoxylated bisphenol A diacrylate.

13. The high reliability fast curing UV adhesive according to claim 1, characterized in that: The trifunctional acrylate monomer is at least one selected from ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate and tris(2-hydroxyethyl)isocyanuric acid triacrylate.

14. The high reliability fast curing UV adhesive according to claim 1, characterized in that: The photoinitiator is a combination of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-methyl-2-(4-morpholinyl)-4'-(methylthio)propiophenone and 2-isopropylthioxanthone.

15. The high reliability fast curing UV adhesive according to claim 14, characterized in that: The mass ratio of the 2-methyl-2-(4-morpholinyl)-4'-(methylthio)propiophenone to the 2-isopropylthioxanthone is (2-4):

1.

16. The high reliability fast curing UV adhesive according to claim 14, characterized in that: The mass ratio of the 2,4,6-trimethylbenzoyldiphenylphosphine oxide to the 2-isopropylthioxanthone is (8-18):

1.

17. The method for preparing the high-reliability fast-curing UV adhesive according to claim 1, characterized in that: The method comprises uniformly mixing acrylate oligomers, monofunctional acrylate monomers, difunctional acrylate monomers, trifunctional acrylate monomers, acrylate monomers containing acidic functional groups, photoinitiators and optional auxiliary agents to obtain high-reliability fast-curing UV adhesive.

18. Application of the high-reliability fast-curing UV adhesive of claim 1 in the insulation protection of the outer packaging of power battery cells.

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