Adhesive composition and adhesive tape for bonding PC (Polycarbonate) insulating sheet of battery cell

Abstract

The invention discloses an adhesive composition and an adhesive tape for bonding a PC (Polycarbonate) insulating sheet of a battery cell. The composition comprises an acrylate copolymer, an isocyanate-based acrylate monomer modified acrylate oligomer and an auxiliary agent. The oligomer is synthesized from a rigid monomer containing a double-ring structure, a silane coupling agent and an isocyanate-based acrylate monomer, the rigid structure can effectively inhibit slippage of a copolymer molecular chain at a high temperature, cohesion strength is improved, and isocyanate groups (-NCO) are polymerized on the oligomer molecular chain, so that the high-temperature-resistant performance of the oligomer is improved. When the TDI is reacted with-COOH and-OH in the acrylate copolymer,-NCO is dispersed more uniformly, molecular-level crosslinking of oligomer-glue can be formed, the bonding failure problems of non-uniform crosslinking, overlarge stress, fragility and the like caused by single addition of the TDI are solved, and the interface bonding force and the damp-heat aging resistance are enhanced.

Description

Technical Field

[0001] This invention relates to the field of adhesive materials, and in particular to an adhesive composition and tape for bonding PC insulating sheets for battery cells. Background Technology

[0002] With the rapid development of the new energy vehicle market, battery safety has also attracted much attention. In cell design, engineers bond PC insulating sheets to the bottom of the cell. PC insulating sheets have excellent electrical insulation properties, effectively isolating the cell from other components of the battery pack, preventing leakage and short circuits. They also have good flame retardant properties (reaching V-0 or V-2 rating under UL94 standard), are not easily combustible at high temperatures, and can quickly self-extinguish when burning, reducing flame spread. They also have a certain degree of strength and flexibility, providing buffer protection for the cell during vehicle operation, reducing the impact of vibration and shock on the cell, while preventing the bottom of the cell from being scratched by hard objects. They can resist the corrosion of chemicals such as electrolytes inside the battery, and can withstand a certain range of high temperatures, maintaining stable performance even when heat is generated during battery charging and discharging, and are not easily deformed or damaged. In practical applications, the PC insulating sheet at the bottom of the battery cell mainly serves as insulation and protection, with low requirements for structural strength. Using structural adhesives for bonding involves long curing times and relatively complex operations, which is not conducive to large-scale automated production. Acrylic pressure-sensitive adhesives, on the other hand, have adjustable tack within a certain range, effectively adapting to the bonding requirements between the PC insulating film and the bottom of the battery cell. This ensures a strong bond without damaging the battery cell during subsequent maintenance or replacement due to excessive viscosity, and also offers excellent aging resistance. However, the PC insulating film at the bottom of the battery cell generally has a high roughness, with the rough surface roughness approaching 6µmRa. Furthermore, the PC sheet is prone to moisture generation under high temperature and humidity conditions, and vibrations during vehicle operation can easily affect the bonding, leading to adhesion failure. Commercially available ordinary acrylic double-sided tape, at 80℃, has a peel strength (GB / T2792-2014) < 1500gf / 25mm and a shear and pull-out strength (GB / T...). (7124-2021) 0.1-0.6MPa, pull-out shear strength after aging <2.5MPa, cannot guarantee high peel, shear and pull-out strength of the double-sided tape bonded to the PC surface at temperatures of 80℃ and above and after aging. Therefore, it is particularly important to develop a double-sided tape that has excellent high-temperature, high-peel, high-pull-out, high-shear strength and aging resistance for PC surfaces. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an adhesive composition and tape for bonding PC insulating sheets of battery cells, addressing the shortcomings of the prior art.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an adhesive composition for bonding PC insulating sheets of battery cells, comprising the following raw material components by weight: 70-150 parts of acrylate copolymer, 10-15 parts of acrylate oligomer, and 20-30 parts of additives. The raw materials for preparing the acrylate copolymer include, by weight, 40-70 parts of soft monomer, 15-30 parts of hard monomer, 3-5 parts of functional monomer, 0.5-1 part of initiator, 0.1-1 part of chain transfer agent, and 100-200 parts of organic solvent. The raw materials for preparing the acrylate oligomers include, by weight, 100 parts of a mixture of vinyl cyclic monomers and chain monomers, 8-20 parts of isocyanate-based acrylate monomers, 1-3 parts of chain transfer agent, 100-200 parts of organic solvent, 0.3-1 parts of initiator, and 0.8-2 parts of silane coupling agent. The molecular weight of the acrylate oligomer is 4000-15000 g / mol.

[0005] Preferably, the soft monomer is selected from one or more of isooctyl acrylate, n-butyl acrylate, ethyl acrylate, and lauryl acrylate; The hard monomer is selected from one or more of methyl methacrylate, isobornyl acrylate (IBOA), acrylamide (ACMO), styrene, acrylonitrile, and methyl methacrylate; The functional monomer is selected from one or more of the following: 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, glycidyl methacrylate, acrylamide, N-hydroxymethylacrylamide, vinyltrimethylsiloxane, vinyltriethoxysilane, and acrylic acid. Preferably, the mixture of vinyl cyclic monomers and chain monomers is selected from one or a mixture of two of isobornyl methacrylate and dicyclopentenyl methacrylate with methyl methacrylate; The isocyanate-based acrylate monomers are selected from one of ethyl isocyanate methacrylate (IEM) and ethyl isocyanate acrylate (AOI). The silane coupling agent is selected from one or more of γ-methacryloxypropyltrimethoxysilane (KH570), N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792), γ-aminopropyltriethoxysilane (KH550), and γ-glycidoxypropyltrimethoxysilane (KH560); The chain transfer agent is selected from one or more of dodecyl mercaptoethanol, mercaptoethanol, and tert-dodecyl mercaptoethanol; The antioxidant is selected from 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 264 (butylated hydroxytoluene), with 264 being preferred; The organic solvent is selected from ethyl acetate; Preferably, the mixture of vinyl cyclic monomers and chain monomers is a mixture of methyl methacrylate, dicyclopentenyl methacrylate, isobornyl methacrylate and ethyl isocyanate; wherein the mass ratio of methyl methacrylate: dicyclopentenyl methacrylate: isobornyl methacrylate is 3:3:4. Preferably, the silane coupling agent is a mixture of KH-570 and KH-560 in a mass ratio of 3:2.

[0006] Preferably, the acrylate copolymer is prepared by the following method: S1-1. Under an inert atmosphere, mix 2 / 3 of the total mass of soft monomer, 2 / 3 of the total mass of hard monomer, and 2 / 3 of the total mass of functional monomer evenly, keep warm at 70°C for 1 hour, then add chain transfer and 1 / 4 of the total mass of initiator, and react at 70°C for 2 hours. S1-2, add another 1 / 4 of the total mass of initiator, and use a peristaltic pump to drop the remaining soft monomer, hard monomer and functional monomer, keep at 70°C, and react for 2-3 hours after 1 hour of drop addition; S1-3. Add the remaining initiator, keep the reaction at a constant temperature for 3 hours, cool down, and discharge to obtain the acrylate copolymer.

[0007] Preferably, the acrylate copolymer has a solid content of 35-55%, a molecular weight of 500,000-1,000,000, and a glass transition temperature (Tg) of -60°C to -40°C.

[0008] Preferably, the acrylate oligomers are prepared by the following method: S2-1. Under an inert atmosphere, mix vinyl cyclic monomers and chain monomers, silane coupling agent, chain transfer agent and solvent, heat to 70°C and add 1 / 4 of the total mass of initiator, and react at 70°C for 2 hours. S2-2, then add 3 / 4 of the total mass of initiator, heat to 85℃ and react for 3 hours, then cool down to obtain acrylate oligomer.

[0009] Preferably, the solid content of the acrylate oligomer is 40-50%, and the molecular weight is 4000-15000 g / mol.

[0010] Preferably, the additives comprise, by weight, 8-20 parts of a mixture of rosin resin and terpene phenol resin, 0.5-1.5 parts of curing agent, and 1-2 parts of antioxidant.

[0011] Preferably, the rosin resin and terpene resin mixture is a mixture of terpene phenol resins TP7042 and TP-2040 and rosin pentaerythritol ester PLS in a mass ratio of 3:4:3; Preferably, the curing agent is a mixture of L-75 and aluminum acetylacetonate; This invention provides an adhesive tape for bonding PC insulating sheets to battery cells, which is prepared using the adhesive composition described above and a substrate. The preparation method of this tape includes the following steps: Acrylic ester copolymer, acrylic ester oligomer and additives are mixed evenly to obtain an adhesive composition. The adhesive composition is then evenly coated on release paper and dried. The resulting adhesive layer is then bonded to both sides of a PET substrate to obtain a double-sided adhesive semi-finished product. After curing, the adhesive tape for bonding the PC insulation sheet of the battery cell is obtained.

[0012] Preferably, the PET substrate has a thickness of 12 μm, and the two adhesive layers each have a thickness of 19 μm.

[0013] The beneficial effects of this invention are: This invention provides an adhesive composition and tape for bonding PC insulation sheets in battery cells. The composition comprises an acrylate copolymer, an acrylate oligomer modified with isocyanate-based acrylate monomers, and additives. The core innovation of this invention lies in the fact that, through molecular design, the acrylate oligomer undergoes a chemical reaction with the acrylate copolymer, rather than a simple physical blending. Specifically, the oligomer is synthesized from rigid monomers containing bicyclic structures (such as IBOMA, DCPMA, and methyl methacrylate), a silane coupling agent, and isocyanate-based acrylate monomers. Its rigid structure effectively inhibits the slippage of copolymer molecular chains at high temperatures, improving cohesive strength. The isocyanate groups (-NCO) polymerize on the oligomer molecular chains, and when they react with -COOH and -OH in the acrylate copolymer, the -NCO is more evenly dispersed, forming a molecular-level crosslinking of "oligomer-adhesive." This solves the bonding failure problems caused by the single addition of TDI, such as uneven crosslinking, excessive stress, and brittleness, and enhances interfacial bonding strength and resistance to damp heat aging. This invention solves the technical problem of insufficient adhesion strength of ordinary acrylic tape to PC materials under high temperature and high humidity conditions, which leads to tape loss of adhesion and easy bubbling failure. Detailed Implementation

[0014] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0015] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0016] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. For examples where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments whose manufacturers are not specified, they are all commercially available products.

[0017] The present invention provides an adhesive composition for bonding PC insulating sheets of battery cells, comprising the following raw material components by weight: 70-150 parts of acrylate copolymer, 10-15 parts of acrylate oligomer, and 20-30 parts of additives. The raw materials for preparing acrylate copolymers include, by weight: 40-70 parts soft monomer, 15-30 parts hard monomer, 3-5 parts functional monomer, 0.5-1 part initiator, 0.1-1 part chain transfer agent, and 100-200 parts organic solvent. The raw materials for preparing acrylate oligomers include, by weight, 100 parts of a mixture of vinyl cyclic monomers and chain monomers, 8-20 parts of isocyanate-based acrylate monomers, 1-3 parts of chain transfer agent, 100-200 parts of organic solvent, 0.5-2 parts of initiator, and 0.8-2 parts of silane coupling agent. The molecular weight of acrylate oligomers is 4000-15000 g / mol.

[0018] In a preferred embodiment, the soft monomer in the acrylate copolymer is selected from one or more of isooctyl acrylate, n-butyl acrylate, ethyl acrylate, and lauryl acrylate; The hard monomer is selected from one or more of methyl methacrylate, isobornyl acrylate, acrylmorpholine, styrene, acrylonitrile, and methyl acrylate; The functional monomer is selected from one or more of the following: 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, glycidyl methacrylate, acrylamide, N-hydroxymethylacrylamide, vinyltrimethylsiloxane, vinyltriethoxysilane, and acrylic acid. In a preferred embodiment, the mixture of vinyl cyclic monomers and chain monomers is selected from one or two of isobornyl methacrylate and dicyclopentenyl methacrylate, and a mixture of methyl methacrylate. The isocyanate-based acrylate monomers are selected from one of isocyanoethyl methacrylate and isocyanate ethyl acrylate. Silane coupling agents are selected from γ-methacryloyloxypropyltrimethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane; The chain transfer agent is selected from one or more of dodecyl mercaptoethanol, mercaptoethanol, and tert-dodecyl mercaptoethanol; The mixture of vinyl cyclic monomers and chain monomers is a mixture of methyl methacrylate, dicyclopentenyl methacrylate, isobornyl methacrylate and ethyl isocyanate; wherein the mass ratio of methyl methacrylate: dicyclopentenyl methacrylate: isobornyl methacrylate is 3:3:4.

[0019] In a preferred embodiment, the silane coupling agent is a mixture of KH-570 and KH-560 in a mass ratio of 3:2.

[0020] In a preferred embodiment, the acrylate copolymer is prepared by the following method: S1-1. Under an inert atmosphere, mix 2 / 3 of the total mass of soft monomer, 2 / 3 of the total mass of hard monomer, and 2 / 3 of the total mass of functional monomer evenly, keep warm at 70°C for 1 hour, then add chain transfer and 1 / 4 of the total mass of initiator, and react at 70°C for 2 hours. S1-2, add another 1 / 4 of the total mass of initiator, and use a peristaltic pump to drop the remaining mixture of soft monomers, hard monomers and functional monomers. Keep at 70°C, and react for 2-3 hours after 1 hour of drop addition. S1-3. Add the remaining initiator, keep the reaction at a constant temperature for 3 hours, cool down, and discharge to obtain the acrylate copolymer.

[0021] In a preferred embodiment, the acrylate oligomer is prepared by the following method: S2-1. Under an inert atmosphere, mix vinyl cyclic monomers and chain monomers, silane coupling agent, chain transfer agent and solvent, heat to 70°C and add 1 / 4 of the total mass of initiator, and react at 70°C for 2 hours. S2-2, then add 3 / 4 of the total mass of initiator, heat to 85℃ and react for 3 hours, then cool down to obtain acrylate oligomers; In a preferred embodiment, the additives include, by weight: 8-20 parts of a mixture of rosin resin and terpene phenol resin, 0.5-1.5 parts of curing agent, and 1-2 parts of antioxidant.

[0022] In a preferred embodiment, the rosin resin and terpene resin mixture is a mixture of terpene phenol resins TP7042 and TP-2040 and rosin pentaerythritol ester PLS in a mass ratio of 3:4:3. The curing agent is a mixture of L-75 and aluminum acetylacetonate.

[0023] The present invention also provides an adhesive tape for bonding PC insulating sheets of battery cells, which is prepared by using the above adhesive composition and a substrate. The preparation method of the tape includes the following steps: Acrylic ester copolymer, acrylic ester oligomer and additives are mixed evenly to obtain an adhesive composition. The adhesive composition is then evenly coated on release paper and dried. The resulting adhesive layer is then bonded to both sides of a PET substrate to obtain a double-sided adhesive semi-finished product. After curing, it becomes an adhesive tape for bonding PC insulation sheets of battery cells.

[0024] The above is the general concept of the present invention. Based on this, detailed embodiments and comparative examples are provided below to further illustrate the present invention.

[0025] The main sources of raw materials involved in the following examples and comparative examples are as follows: Example 1 An adhesive composition for bonding PC insulating sheets in battery cells comprises the following raw material components in parts by weight: 100 parts of acrylate copolymer, 13 parts of acrylate oligomer, and 26.6 parts of additives; The additives include: 25 parts of a mixture of rosin resin and terpene resin, 1 part of curing agent L-75, 0.1 part of aluminum acetylacetonate, and 0.5 parts of antioxidant 264; The mixture of rosin resin and terpene resin is obtained by mixing terpene phenol resins TP7042 and TP-2040 and rosin pentaerythritol ester PLS in a ratio of 3:4:3, and then diluting with the same mass of solvent to obtain the mixture of rosin resin and terpene resin.

[0026] The raw materials for preparing the acrylate copolymer include, by weight, the following: Soft monomers: 30 parts butyl acrylate, 55 parts isooctyl acrylate, 3 parts functional monomer acrylic acid, 1 part hydroxyethyl acrylate; chain transfer agents: 0.3 parts dodecyl mercaptan, 11 parts methyl acrylate, 0.5 parts initiator 2,2'-azobisisobutyronitrile, 150 parts ethyl acetate.

[0027] The Tg of the acrylate copolymer is approximately -53.05℃.

[0028] The acrylate copolymer was prepared by the following method: S1-1. Under an inert atmosphere (nitrogen protection to eliminate oxygen interference), add 2 / 3 of the total mass of soft monomer, 2 / 3 of the total mass of hard monomer, and 2 / 3 of the total mass of functional monomer to the reactor and stir thoroughly to ensure uniform mixing. Then heat to 70°C and hold for 1 hour. Add chain transfer agent and 1 / 4 of the total mass of initiator 2,2'-azobisisobutyronitrile to start the polymerization reaction and continue stirring for 2 hours. This stage aims to initially establish the polymer chain. S1-2. Add 1 / 4 of the total mass of initiator 2,2'-azobisisobutyronitrile to the above reaction system, and add the remaining soft monomer, hard monomer and functional monomer dropwise using a peristaltic pump for 1 hour. During the dropwise addition, by controlling the dropwise acceleration rate and temperature (maintained at 70°C), the molecular weight distribution of the product can be effectively adjusted, thereby optimizing the material properties. Afterward, maintain this temperature condition and continue the reaction for 3 hours to fully complete the chain growth process. S1-3. After completing the first two steps of the reaction, add the remaining initiator 2,2'-azobisisobutyronitrile to the system, keep the reaction at a high temperature for 3 hours to eliminate residual monomers, so as to promote a deeper polymerization reaction and increase the molecular weight. Cool down and discharge the material to obtain the acrylate copolymer. The raw materials for preparing acrylate oligomers include, by weight, the following: 100 parts of vinyl cyclic and chain monomers (including 30 parts of DCPMA, 30 parts of methyl methacrylate, 40 parts of isobornyl methacrylate, and 11 parts of ethyl isocyanate acrylate AOI), 3 parts of chain transfer agent, 1.5 parts of 2,2'-azobisisobutyronitrile, 0.9 parts of KH570, 0.6 parts of silane coupling agent KH560, and 100 parts of ethyl acetate.

[0029] S2-1. Under an inert atmosphere (nitrogen protection to eliminate oxygen interference), vinyl cyclic monomers and chain monomers, silane coupling agent, chain transfer agent, and solvent are added to another reactor. After heating to 70°C, 1 / 4 of the total mass of initiator 2,2'-azobisisobutyronitrile is added, and the reaction is carried out at 70°C for 2 hours. S2-2, then add 3 / 4 of the total mass of initiator 2,2'-azobisisobutyronitrile, then heat to 85℃, react for 3 hours, cool down, and obtain silane coupling agent modified acrylate oligomer; A tape for bonding PC insulating sheets to battery cells, the preparation method of which includes the following steps: By weight, 100 parts of the acrylate copolymer, 13 parts of the acrylate oligomer, and 26.6 parts of the additives prepared above are mixed evenly to obtain an adhesive composition. The adhesive composition is then evenly coated on two release papers and dried at 110°C for 3 minutes to obtain an adhesive layer with a thickness of 19 μm on both release papers. The obtained adhesive layer is then bonded to both sides of a PET substrate with a thickness of 12 μm to obtain a double-sided adhesive semi-finished product. After curing at 50°C for 48 hours, an adhesive tape for bonding PC insulating sheets of battery cells is obtained.

[0030] Example 2 Unlike Example 1, the ethyl isocyanate acrylate AOI is replaced with isocyanate ethyl methacrylate (IEM). Example 3 Unlike Example 1, the amount of ethyl isocyanate acrylate AOI added was changed to 17 parts. Example 4 Unlike Example 1, the amount of isocyanate methacrylate (IEM) added was changed to 17 parts. Comparative Example 1 Unlike Example 1, the ethyl isocyanate acrylate AOI was removed during the preparation of the acrylate oligomers. Comparative Example 2 Unlike implementation 1, the ethyl isocyanate acrylate AOI is replaced with ethyl acrylate. Comparative Example 3 Unlike Example 1, the amount of ethyl isocyanate acrylate AOI added was changed to 6 parts. Comparative Example 4 Unlike Example 1, the amount of ethyl isocyanate acrylate AOI added was changed to 22 parts. Comparative Example 5 Unlike Example 1, the amount of isocyanate methacrylate (IEM) added was changed to 6 parts. Comparative Example 6 Unlike Example 1, the amount of isocyanate methacrylate (IEM) added was changed to 22 parts. The double-sided adhesive tapes prepared in the examples and comparative examples were subjected to the following performance tests: (1) Measure the 180° peel force at 80℃: Cover one side of the PET double-sided tape with 25um PET, attach it to the PC board, let it stand for 20 minutes, then put it in the oven and heat for 20 minutes before testing. The test speed is 300mm / min. (2) 80℃ tensile and shear performance test: The sample was cut to a size of 12.5mm*12.5mm, attached to the surface of the PC board, and placed in an oven for 20min for testing. The test speed was 50.8mm / min. (3) Pull-out shear test after aging: The sample was attached to the shear plate and the pull-out block, and after standing for 20 minutes, it was placed in an 85℃ / 85% oven for 1000 hours of aging. The sample was then taken out for testing. The test results are shown below: Table 1. Test results of bonding performance of PC boards Item 80°C peel strength gf / 25 mm 80°C shear strength MPa 80°C pull strength MPa aged 1000 h shear strength MPa aged 1000 h pull strength MPa Example 1 1660 0.85 0.92 3.30 3.2 Example 2 1584 0.90 0.80 3.01 2.87 Example 3 1512 0.84 0.81 2.63 2.61 Example 4 1582 0.78 0.69 3.30 3.27 Comparative Example 1 1366 034 0.42 2.01 1.98 Comparative Example 2 1357 0.33 0.41 1.92 1.97 Comparative Example 3 1422 0.46 0.44 2.48 2.43 Comparative Example 4 1470 0.56 0.61 2.38 2.48 Comparative Example 5 1407 0.41 0.40 2.22 2.31 Comparative Example 6 1438 0.58 0.62 2.51 2.47 Commercially available ordinary double-sided tape 1107 0.23 0.36 1.88 2.01 Cut double-sided tape samples to 12.5*12.5mm size and attach them to PC boards. Observe for bulging at 80℃ to further determine the PC gas release resistance. A bulging area >20% is recorded as X (whitening), no bulging is recorded as ✓, and less than 10% bulging is recorded as O. The test results are shown in Table 2 below: Table 2 Lamination phenomenon Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Commercially available ordinary double-sided tape Swelling state ✓ ✓ ✓ ✓ X X O O O O X Based on the above test results: 1. As can be seen from Tables 1 and 2 (Examples 1-4), the present invention constructs an IPN network by reacting acrylate copolymers with isocyanate-based acrylate-modified acrylate oligomers and then adding L-75 and aluminum acetylacetonate for curing and dual crosslinking. This can overcome the problems of traditional adhesives that only add L-75 and aluminum acetylacetonate curing agents, resulting in strong chain rigidity, poor adhesion to PC at high temperatures, and easy embrittlement. It significantly improves the peel strength at 80°C (1660 gf / 25 mm in Example 1).

[0031] 2. Analysis of the experimental data in Tables 1 and 2 (Comparative Example 1 and Comparative Example 2) shows that when unmodified isocyanate-based acrylate oligomers are mixed with acrylate copolymers, no functional groups participate in the reaction; it is a simple physical mixture, which leads to varying degrees of influence on shear strength and peel force. 3. As can be seen from Comparative Examples 3 and 5 in Tables 1 and 2, when the addition amount of AOI and IEM is 6 parts, the peel force and shear strength begin to improve compared to (Comparative Examples 1 and 2). However, because the amount is relatively small, the modified acrylate oligomer and acrylate copolymer have fewer reactive groups and a lighter degree of crosslinking, resulting in a slight improvement in PC adhesion. The PC gas release resistance confirms this view. 4. As can be seen from Tables 1 and 2, using Comparative Examples 4 and 6, when the AOI and IEM addition amounts are 22 parts, the peel force and shear strength show a decreasing trend compared to Examples 1-4. This is because the hydroxyl content in the acrylate copolymer is low, and when the amount of isocyanate acrylate added is large, the reaction cannot be fully completed. Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. An adhesive composition for bonding PC insulating sheets of battery cells, characterized in that, It includes the following raw material components by weight: 70-150 parts of acrylate copolymer, 10-15 parts of acrylate oligomer, and 20-30 parts of additives; The raw materials for preparing the acrylate copolymer include, by weight, 40-70 parts of soft monomer, 15-30 parts of hard monomer, 3-5 parts of functional monomer, 0.5-1 part of initiator, 0.1-1 part of chain transfer agent, and 100-200 parts of organic solvent. The raw materials for preparing the acrylate oligomers include, by weight, 100 parts of a mixture of vinyl cyclic monomers and chain monomers, 8-20 parts of isocyanate-based acrylate monomers, 1-3 parts of chain transfer agent, 100-200 parts of organic solvent, 0.5-2 parts of initiator, and 0.8-2 parts of silane coupling agent. The molecular weight of the acrylate oligomer is 4000-15000 g / mol.

2. The adhesive composition for bonding PC insulating sheets of battery cells according to claim 1, characterized in that, The soft monomer in the acrylate copolymer is selected from one or more of isooctyl acrylate, n-butyl acrylate, ethyl acrylate, and lauryl acrylate; The hard monomer is selected from one or more of methyl methacrylate, isobornyl acrylate, acrylmorpholine, styrene, acrylonitrile, and methyl acrylate; The functional monomer is selected from one or more of the following: 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, glycidyl methacrylate, acrylamide, N-hydroxymethylacrylamide, vinyltrimethylsiloxane, vinyltriethoxysilane, and acrylic acid.

3. The adhesive composition for bonding PC insulating sheets of battery cells according to claim 1, characterized in that, The vinyl cyclic monomer and chain monomer mixture is selected from one or two of isobornyl methacrylate and dicyclopentenyl methacrylate and a mixture of methyl methacrylate; The isocyanate-based acrylate monomers are selected from one of isocyanoethyl methacrylate and isocyanate ethyl acrylate. The silane coupling agent is selected from γ-methacryloxypropyltrimethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane; The chain transfer agent is selected from one or more of dodecyl mercaptoethanol, mercaptoethanol, and tert-dodecyl mercaptoethanol.

4. The adhesive composition for bonding PC insulating sheets of battery cells according to claim 3, characterized in that, The mixture of vinyl cyclic monomers and chain monomers is a mixture of methyl methacrylate, dicyclopentenyl methacrylate, isobornyl methacrylate and ethyl isocyanate acrylate. The mass ratio of methyl methacrylate, dicyclopentenyl methacrylate, and isobornyl methacrylate is 3:3:

4.

5. The adhesive composition for bonding PC insulating sheets of battery cells according to claim 3, characterized in that, The silane coupling agent is a mixture of KH-570 and KH-560 in a mass ratio of 3:

2.

6. The adhesive composition for bonding PC insulating sheets of battery cells according to claim 1, characterized in that, The acrylate copolymer is prepared by the following method: S1-1. Under an inert atmosphere, mix 2 / 3 of the total mass of soft monomer, 2 / 3 of the total mass of hard monomer, and 2 / 3 of the total mass of functional monomer evenly, keep warm at 70°C for 1 hour, then add chain transfer and 1 / 4 of the total mass of initiator, and react at 70°C for 2 hours. S1-2, add another 1 / 4 of the total mass of initiator, and use a peristaltic pump to drop the remaining mixture of soft monomers, hard monomers and functional monomers. Keep at 70°C, and react for 2-3 hours after 1 hour of drop addition. S1-3. Add the remaining initiator, keep the reaction at a constant temperature for 3 hours, cool down, and discharge to obtain the acrylate copolymer.

7. The adhesive composition for bonding PC insulating sheets of battery cells according to claim 1, characterized in that, acrylate oligomers were prepared by the following method: S2-1. Under an inert atmosphere, mix vinyl cyclic monomers and chain monomers, silane coupling agent, chain transfer agent and solvent, heat to 70°C and add 1 / 4 of the total mass of initiator, and react at 70°C for 2 hours. S2-2, then add 3 / 4 of the total mass of initiator, heat to 85℃ and react for 3 hours, then cool down to obtain acrylate oligomer.

8. The adhesive composition for bonding PC insulating sheets of battery cells according to claim 1, characterized in that, The additives, by weight, include: 8-20 parts of a mixture of rosin resin and terpene phenol resin, 0.5-1.5 parts of curing agent, and 1-2 parts of antioxidant.

9. The adhesive composition for bonding PC insulating sheets of battery cells according to claim 8, characterized in that, The mixture of rosin resin and terpene resin is a mixture of terpene phenol resins TP7042 and TP-2040 and rosin pentaerythritol ester PLS in a mass ratio of 3:4:

3. The curing agent is selected from a mixture of L-75 and aluminum acetylacetonate.

10. A tape for bonding PC insulating sheets in battery cells, characterized in that, It is prepared using the adhesive composition as described in any one of claims 1-9 and a substrate, and the method for preparing the tape includes the following steps: Acrylic ester copolymer, acrylic ester oligomer and additives are mixed evenly to obtain an adhesive composition. The adhesive composition is then evenly coated on release paper and dried. The resulting adhesive layer is then bonded to both sides of a PET substrate to obtain a double-sided adhesive semi-finished product. After curing, the adhesive tape for bonding the PC insulation sheet of the battery cell is obtained.

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