Preparation method of battery pack sealant

Abstract

The invention relates to a preparation method of a battery pack sealant, and belongs to the technical field of adhesive preparation, and the preparation method comprises the following steps: S1, under protective gas, heating and adding 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, polysiloxane containing double bond end hydroxyalkyl and an initiator at 90-110 DEG C, and devolatilizing to obtain an intermediate; dehydrating, adding diisocyanate and a catalyst, and reacting to obtain a prepolymer; dropwise adding glycidyl for blocking until an isocyanate peak disappears to obtain a modifier; s2, carrying out vacuum dispersion on 100 parts of matrix resin, 15-40 parts of a modifier, 100-300 parts of an insulating heat-conducting filler and 1-5 parts of a coupling agent to obtain a component A; s3, taking 20-50 parts of a curing agent as a component B; s4, uniformly mixing A and B, primarily curing at room temperature, and heating and curing to obtain the sealant, the sealant solves the problem that a traditional additive flame retardant is easy to migrate and separate out, and the battery pack sealant is endowed with long-acting and stable flame-retardant safety performance.

Description

Technical Field

[0001] This invention relates to the field of adhesive preparation, specifically a method for preparing a battery pack sealant. Background Technology

[0002] Linear polyolefins are widely used in polymer packaging materials and film preparation due to their excellent chemical stability and mechanical properties. However, from the perspective of the inherent properties of the matrix resin, there are still many shortcomings in their use as battery pack sealants and high-requirement film materials. Traditional additive flame retardants are prone to migration and precipitation, and the cured resin often has defects such as high brittleness and susceptibility to internal stress failure. In addition, physical blending modification often leads to phase separation due to insufficient compatibility, resulting in decreased material transparency and sacrifice of impact toughness. While conventional chemical crosslinking modification can improve melt strength, it is very easy to generate uncontrollable microgels, which seriously damage the material's appearance and mechanical properties. To overcome the limitations of the aforementioned materials, polymer modification is considered an effective way to compensate for inherent defects and comprehensively optimize overall performance. The core of this method lies in the precise control of chemical structure: by introducing hybrid flexible segments and intrinsic flame-retardant groups into the molecular backbone to reconstruct the crosslinking network. This can not only significantly improve the problem of easy brittleness after material curing, but also enable it to obtain a long-lasting flame-retardant effect and excellent buffering energy absorption characteristics. Currently, effective methods for preparing such high-performance composite materials include in-situ construction and cross-linking curing. The main approach to solving this technical bottleneck is to synthesize hybrid multifunctional modifiers and perform deep covalent cross-linking with the matrix resin to form a micro-phase-separated island-structure interpenetrating network. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a battery pack sealant to solve the problems mentioned in the background art.

[0004] The technical solution of this invention includes: S1, preparation of a phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier: (1) Under a protective gas atmosphere, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was mixed with a carbon-carbon double bond-terminated hydroxyl alkyl polysiloxane, a free radical initiator was added, and an addition reaction was carried out under heating conditions. After the reaction was completed, the volatiles were removed by vacuum treatment to obtain a phosphorus-containing silicon diol intermediate. (2) The phosphorus-containing silicon diol intermediate is subjected to vacuum dehydration treatment, cooled to 50-60°C and diisocyanate and catalyst are added, and the reaction is carried out under heating conditions to obtain a prepolymer with terminal isocyanate groups. (3) Cool the system containing the prepolymer with the terminal isocyanate group, slowly add glycidyl ether at a rate of 1 to 3 drops / second to carry out the end-capping reaction, keep the reaction at the temperature until the characteristic absorption peak of the isocyanate group in the infrared spectrum disappears, and obtain the phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier. Preparation of S2 and A components: By weight, 100 parts of the matrix resin, 15 to 40 parts of the phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier obtained in step S1, 100 to 300 parts of the insulating and thermally conductive filler, and 1 to 5 parts of the silane coupling agent are added to a stirring device and dispersed and mixed at high speed under vacuum conditions to obtain component A. Preparation of S3 and B components: Weigh 20 to 50 parts by weight of the curing agent as component B; S4. Crosslinking and curing: Mix component A and component B evenly, perform initial curing at room temperature and subsequent curing with heat to obtain the battery pack sealant.

[0005] Further, in step (1) of step S1, the molar ratio of the PH bond in the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to the carbon-carbon double-bonded terminal hydroxyl alkyl polysiloxane in step (1) is 1:1, that is, the molar ratio of the PH bond to the C=C double bond is 1:1; the reaction temperature under the heating conditions is 90-110℃; and the protective gas atmosphere is a nitrogen atmosphere.

[0006] Further, in step (1) of step S1, the hydroxyl-terminated polysiloxane containing carbon-carbon double bonds is a hydroxypropyl silicone oil with vinyl-containing side chains; the free radical initiator is azobisisobutyronitrile.

[0007] Further, in step (2) of step S1, the vacuum dehydration treatment is performed under vacuum at 110°C for 2 hours; the cooling is performed at 60°C; the molar ratio of the hydroxyl groups in the phosphorus-containing silicon diol intermediate to the isocyanate groups in the diisocyanate is 1:2.05 to 1:2.2; and the temperature of the heat preservation reaction under the heating conditions is 75 to 85°C.

[0008] Further, in step (2) of step S1, the diisocyanate is isophorone diisocyanate; the catalyst is an organic bismuth catalyst or a dibutyltin dilaurate catalyst.

[0009] Further, in step (3) of step S1, the system is cooled to 50-60°C; the molar ratio of the hydroxyl groups in the glycidyl ether to the remaining isocyanate groups in the prepolymer with terminal isocyanate groups is 1:1; and the reaction temperature is controlled not to exceed 65°C during the end-capping reaction.

[0010] Further, in step S2, the vacuum degree of the vacuum condition is ≤-0.09MPa; the matrix resin is selected from at least one of bisphenol A type epoxy resin or bisphenol F type epoxy resin.

[0011] Furthermore, in step S2, the insulating thermally conductive filler is surface-treated spherical alumina, and the content of water-extractable ions in the insulating thermally conductive filler is less than 800 ppm.

[0012] Further, in step S3, the curing agent is selected from at least one of modified fatty amine, polyether amine or liquid acid anhydride; in step S4, the curing condition after heating is curing at 80°C for 2 hours.

[0013] This invention provides an improved method for preparing a battery pack sealant, which, compared with the prior art, has the following improvements and advantages: 1. This invention introduces the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide structure into a phosphorus-containing silicon diol intermediate through a specific addition reaction, ultimately preparing a phosphorus-containing silicon hybrid polyurethane-epoxy multifunctional modifier. This structural design allows the flame-retardant components to be firmly bonded to the molecular chain in the form of chemical bonds, and introduces active groups that can crosslink with the matrix resin through glycidyl end-capping. During crosslinking and curing, the modifier can form a dense network with the matrix resin and curing agent, solving the problems of easy migration and precipitation of traditional additive flame retardants, and endowing the battery pack sealant with long-lasting and stable flame-retardant safety performance. 2. The multifunctional modifier of the present invention cleverly introduces hydroxyl-terminated polysiloxane and diisocyanate during the synthesis process; the polysiloxane segments endow the material with excellent high and low temperature resistance and low surface energy, while the polyurethane structure provides excellent flexibility; the introduction of these two flexible structures effectively overcomes the defect of high brittleness after curing of traditional matrix resins, so that the final sealant has excellent toughness and shock absorption capacity, and can effectively absorb and alleviate the thermal stress and mechanical stress generated by the battery pack in daily operation; 3. During the preparation process, a large amount of surface-treated spherical alumina is added to the formula as an insulating and thermally conductive filler. This not only ensures that the sealant has high thermal conductivity and can quickly dissipate the heat generated during battery operation, but also that the filler has extremely low water-extractable ion content. This characteristic greatly avoids the risk of leakage or short circuit caused by free ions in the electric field environment, ensuring the insulation reliability and corrosion resistance of the sealant in the complex electrical environment inside the battery pack. 4. The preparation method of this invention precisely controls the molecular structure of the prepolymer and multifunctional modifier through rigorous processes such as stepwise temperature control, vacuum dehydration, and slow dropwise addition of end-capping agents. The addition of silane coupling agents can significantly improve the compatibility between the insulating and thermally conductive filler and the matrix resin, and enhance the adhesion between the sealant and the battery pack shell and the cell interface. After initial curing at room temperature and subsequent curing with heat, the final product perfectly combines multiple excellent properties such as high flame retardancy, high thermal conductivity, high insulation, high flexibility, and strong adhesion. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0015] Example 1

[0016] A method for preparing a battery pack sealant, comprising the following steps: S1, preparation of a phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier: (1) Under a protective gas atmosphere, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was mixed with a carbon-carbon double bond-terminated hydroxyl alkyl polysiloxane, a free radical initiator was added, and an addition reaction was carried out under heating conditions. After the reaction was completed, the volatiles were removed by vacuum treatment to obtain a phosphorus-containing silicon diol intermediate. In this embodiment, the protective gas atmosphere is set to nitrogen atmosphere. By weight, 21.6 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are mixed with 200 parts of carbon-carbon double-bonded hydroxyl-terminated polysiloxane, i.e., vinyl-terminated hydroxypropyl silicone oil, so that the molar ratio of the PH bond in 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to the C=C double bond in the vinyl-terminated hydroxypropyl silicone oil is strictly controlled to be 1:1. 0.5 parts of the free radical initiator azobisisobutyronitrile are added. The reaction temperature under heating conditions is set to 90°C, and the addition reaction time is 4 hours to ensure that the phosphorus-carbon addition reaction starts smoothly under a low heat load and avoids side reactions caused by kinetic mismatch. This step introduces intrinsic halogen-free flame-retardant groups into the polysiloxane side chain through in-situ construction, endowing the phosphorus-containing silicon diol intermediate with an extremely low glass transition temperature and high hydrophobicity, laying the foundation for the low-temperature toughness and moisture-blocking ability of the subsequent network structure. (2) The phosphorus-containing silicon diol intermediate was subjected to vacuum dehydration treatment, then cooled and diisocyanate and catalyst were added. The reaction was carried out under heating conditions to obtain a prepolymer with terminal isocyanate groups. In this stage, the vacuum dehydration process was set to be carried out at 110°C for 2 hours to remove trace amounts of moisture and prevent it from unintentionally consuming isocyanate groups. Subsequently, the system was cooled to 60°C, and 45.5 parts of isophorone diisocyanate and 0.1 parts of organic bismuth catalyst were added. The molar ratio of hydroxyl groups in the phosphorus-containing silicon diol intermediate to isocyanate groups in the isophorone diisocyanate was set to 1:2.05. The temperature of the heat preservation reaction under heating conditions is set at 75°C and the heat preservation reaction time is 3 hours. The design of this stoichiometric ratio and temperature critical threshold can effectively control the cascade mechanism of polyurethane prepolymer chain extension, so that the urethane bonds are evenly distributed in the macromolecular skeleton. The urethane bonds use their strong hydrogen bonding to provide polar adhesive force for the final colloid and act as stress buffers. (3) Cool down the system of prepolymer containing terminal isocyanate groups, slowly add glycidyl ether at a rate of 1-3 drops / second to carry out the end-capping reaction, keep the reaction at the temperature until the characteristic absorption peak of the isocyanate group in the infrared spectrum disappears, and obtain phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier. After the system is cooled to 50°C, 7.8 parts of glycidyl ether are slowly added dropwise. The molar ratio of the hydroxyl groups in the glycidyl ether to the remaining isocyanate groups in the prepolymer with terminal isocyanate groups is controlled at 1:1. The reaction temperature is controlled at 50°C during the end-capping reaction. This thermal hysteresis effect control strategy aims to prevent the epoxy groups from undergoing unintended ring-opening self-polymerization at high temperatures. When infrared spectroscopy monitoring showed that the characteristic absorption peak of the isocyanate group completely disappeared, it marked the successful synthesis of the phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier. The yield of the modifier was measured to be 98%, and the epoxy equivalent was 1428 g / eq. This multifunctional modifier under specific technical conditions achieved deep integration of rigid epoxy and flexible phosphorus-silicon polyurethane within the same molecular framework. Preparation of S2 and A components: By weight, 100 parts of the matrix resin, 15 parts of the phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier prepared according to step S1, 100 parts of the insulating and thermally conductive filler, and 1 part of the silane coupling agent are added to a stirring device and dispersed and mixed at high speed under vacuum conditions to obtain component A. In this embodiment, the matrix resin is bisphenol A type epoxy resin, the insulating and thermally conductive filler is surface-treated spherical alumina with a water extractable ion content of 500 ppm, the silane coupling agent is γ-glycidoxypropyltrimethoxysilane, and the vacuum degree is controlled at -0.095 MPa to eliminate microbubbles in the system and destroy matrix agglomeration. The ratio of low content of phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier to insulating and thermally conductive filler is intended to verify the interfacial wetting and intrinsic flame retardant performance of the system under basic load. Preparation of S3 and B components: Weigh 20 parts of curing agent by weight as component B; The curing agent is a modified fatty amine. This low-ratio curing agent is precisely matched to the epoxy equivalent in component A to ensure the integrity of the crosslinking network. S4. Crosslinking and curing: Mix component A and component B evenly, allow for initial curing at room temperature and subsequent curing with heat to obtain the battery pack sealant. The initial curing condition at room temperature is to allow the colloid to stand at 25°C for 4 hours until the surface of the colloid loses its fluidity and becomes non-sticky. The curing condition after heating is set to cure at 80°C for 2 hours. Under this heat-driven condition, the terminal epoxy groups of the phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier undergo deep covalent cross-linking with the matrix resin and curing agent to form a micro-phase-separated island structure interpenetrating network, which effectively dissipates the thermal expansion internal stress between dissimilar substrates. Example 2

[0017] A method for preparing a battery pack sealant, comprising the following steps: S1, preparation of a phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier: (1) Under a protective gas atmosphere, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is mixed with a carbon-carbon double bond-terminated hydroxyl alkyl polysiloxane, a free radical initiator is added, and an addition reaction is carried out under heating conditions for 2 to 6 hours. After the reaction is completed, the volatiles are removed by vacuum treatment to obtain a phosphorus-containing silicon diol intermediate. In this embodiment, the protective gas atmosphere is set to nitrogen atmosphere. By weight, 21.6 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are mixed with 200 parts of carbon-carbon double bond-containing terminal hydroxyalkyl polysiloxane, i.e., vinyl-containing terminal hydroxypropyl silicone oil. The molar ratio of the PH bond in 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to the C=C double bond in the vinyl-containing terminal hydroxypropyl silicone oil is strictly controlled to be 1:1. 0.5 parts of free radical initiator azobisisobutyronitrile are added. The reaction temperature under heating conditions is set to 90°C, and the addition reaction time is 4 hours to ensure that the phosphorus-carbon addition reaction starts smoothly under a low heat load and avoids side reactions caused by kinetic mismatch. This step introduces intrinsic halogen-free flame-retardant groups into the polysiloxane side chain through in-situ construction, endowing the phosphorus-containing silicon diol intermediate with an extremely low glass transition temperature and high hydrophobicity, laying the foundation for the low-temperature toughness and moisture-blocking ability of the subsequent network structure. (2) The phosphorus-containing silicon diol intermediate was subjected to vacuum dehydration treatment, then cooled and diisocyanate and catalyst were added. The reaction was carried out under heating conditions to obtain a prepolymer with terminal isocyanate groups. In this stage, the vacuum dehydration process was set at 110°C for 2 hours to remove trace amounts of moisture and prevent it from unintendedly consuming isocyanate groups. Subsequently, the system was cooled to 60°C, and 45.5 parts of isophorone diisocyanate and 0.1 parts of organic bismuth catalyst were added. The molar ratio of hydroxyl groups in the phosphorus-containing silicon diol intermediate to isocyanate groups in isophorone diisocyanate was set to 1:2.05. The holding temperature under heating conditions was set to 75°C, and the holding time was 3 hours. This stoichiometric ratio and temperature critical threshold design can effectively control the cascade mechanism of polyurethane prepolymer chain extension, so that urethane bonds are uniformly distributed in the macromolecular backbone. The urethane bonds utilize their strong hydrogen bonding to provide polar adhesive force for the final colloid and act as stress buffers. (3) Cool down the system of prepolymer containing terminal isocyanate groups, slowly add glycidyl ether to carry out the end-capping reaction, keep the reaction at the temperature until the characteristic absorption peak of the isocyanate group in the infrared spectrum disappears, and obtain phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier. In the addition reaction stage, 21.6 parts by weight of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were mixed with 200 parts by weight of vinyl-terminated hydroxypropyl silicone oil, and 0.6 parts by weight of azobisisobutyronitrile were added. The reaction temperature under heating conditions was increased to 100°C, and the addition reaction time was 3.5 hours to moderately accelerate the kinetic conversion. In the heat preservation reaction, 47 parts of isophorone diisocyanate and 0.12 parts of organic bismuth catalyst were added. The molar ratio of hydroxyl groups in the phosphorus-containing silicon diol intermediate to isocyanate groups in the diisocyanate was adjusted to 1:2.12. The heat preservation reaction temperature under heating conditions was set to 80°C and the heat preservation reaction time was 2.5 hours. This fine adjustment of the stoichiometric ratio was intended to optimize the molecular weight distribution of the prepolymer with terminal isocyanate groups, so that it could provide more balanced flexible buffer segments in the subsequent interpenetrating network. After the system was cooled, 8.9 parts of glycidyl were added dropwise to carry out the end-capping reaction. The yield of the phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier prepared in this step was determined to be 97%, and the final epoxy equivalent was 1450 g / eq. Meanwhile, the matrix resin was replaced with bisphenol F type epoxy resin, which utilizes its lower initial viscosity to adapt to the increased amount of insulating and thermally conductive filler (up to 200 parts). γ-aminopropyltriethoxysilane was selected as the silane coupling agent to ensure the fluidity of the colloid during multidimensional arrangement filling and its penetration ability at the interface of dissimilar substrates. A modified aliphatic amine with an active hydrogen equivalent of 56.1 g / eq was selected as the curing agent. Based on the total epoxy equivalent of component A (0.623 eq), approximately 35 parts of curing agent were required for precise matching. Components A and B were mixed evenly and allowed to stand at 25°C for 3.5 hours for initial curing until the colloid surface lost its fluidity and became non-sticky. Then, it was cured at 80°C for 2 hours. Example 3

[0018] A method for preparing a battery pack sealant, comprising the following steps: S1, preparation of a phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier: (1) Under a protective gas atmosphere, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was mixed with a carbon-carbon double bond-terminated hydroxyl alkyl polysiloxane, a free radical initiator was added, and an addition reaction was carried out under heating conditions. After the reaction was completed, the volatiles were removed by vacuum treatment to obtain a phosphorus-containing silicon diol intermediate. In this embodiment, the protective gas atmosphere is set to nitrogen atmosphere. By weight, 21.6 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are mixed with 200 parts of carbon-carbon double bond-containing terminal hydroxyalkyl polysiloxane, i.e., vinyl-containing terminal hydroxypropyl silicone oil. The molar ratio of the PH bond in 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to the C=C double bond in the vinyl-containing terminal hydroxypropyl silicone oil is strictly controlled to be 1:1. 0.5 parts of free radical initiator azobisisobutyronitrile are added. The reaction temperature under heating conditions is set to 90°C, and the addition reaction time is 4 hours to ensure that the phosphorus-carbon addition reaction starts smoothly under a low heat load and avoids side reactions caused by kinetic mismatch. This step introduces intrinsic halogen-free flame-retardant groups into the polysiloxane side chain through in-situ construction, endowing the phosphorus-containing silicon diol intermediate with an extremely low glass transition temperature and high hydrophobicity, laying the foundation for the low-temperature toughness and moisture-blocking ability of the subsequent network structure. (2) The phosphorus-containing silicon diol intermediate was subjected to vacuum dehydration treatment, then cooled and diisocyanate and catalyst were added. The reaction was carried out under heating conditions to obtain a prepolymer with terminal isocyanate groups. In this stage, the vacuum dehydration process was set to be carried out at 110°C for 2 hours to remove trace amounts of moisture and prevent it from unintentionally consuming isocyanate groups. Subsequently, the system was cooled to 60°C, and 45.5 parts of isophorone diisocyanate and 0.1 parts of organic bismuth catalyst were added. The molar ratio of hydroxyl groups in the phosphorus-containing silicon diol intermediate to isocyanate groups in the isophorone diisocyanate was set to 1:2.05. The temperature of the heat preservation reaction under heating conditions is set at 75°C and the heat preservation reaction time is 3 hours. The design of this stoichiometric ratio and temperature critical threshold can effectively control the cascade mechanism of polyurethane prepolymer chain extension, so that the urethane bonds are evenly distributed in the macromolecular skeleton. The urethane bonds use their strong hydrogen bonding to provide polar adhesive force for the final colloid and act as stress buffers. (3) Cool down the system of prepolymer containing terminal isocyanate groups, slowly add glycidyl ether to carry out the end-capping reaction, keep the reaction at the temperature until the characteristic absorption peak of the isocyanate group in the infrared spectrum disappears, and obtain phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier. In the addition reaction stage of S1, 21.6 parts by weight of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were mixed with 200 parts by weight of vinyl-terminated hydroxypropyl silicone oil, and 0.8 parts by weight of azobisisobutyronitrile were added. The addition reaction time was 3 hours. In the heat preservation reaction stage, 48.8 parts by weight of isophorone diisocyanate and 0.15 parts by weight of organobismuth catalyst were added. The heat preservation reaction time was 2 hours. In the end-capping reaction step, 10.4 parts of glycidyl ether were slowly added dropwise, and the system temperature was controlled at 60℃. During the end-capping reaction, the reaction temperature was controlled at 65℃, which is close to the thermal stability critical threshold of the epoxy group. This verified the effectiveness of the thermal hysteresis effect control strategy in the higher temperature range. The yield of the phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier prepared in this step was determined to be 98.5%, and the final epoxy equivalent was 1550 g / eq. To address the risks of increased interface defects and internal stress caused by up to 300 parts of insulating and thermally conductive filler, the amount of phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier was increased to a maximum of 40 parts. Bisphenol A type epoxy resin was selected as the matrix resin, KH-560 was selected as the silane coupling agent, and polyetheramine was selected as the curing agent. The polyetheramine utilizes the flexibility of the polyether segments to synergize with the polysiloxane segments in the phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier, thereby strengthening the buffer phase volume of the island structure. This ensures that the colloid maintains long-term durable adhesion to polar substrates such as aluminum alloys and polyimides even under high thermal conductivity requirements. Components A and B were mixed evenly and allowed to stand at 25°C for 3 hours for initial curing until the colloid surface lost its fluidity and became non-sticky. Then, it was cured at 80°C for 2 hours. Example 4

[0019] A method for preparing a battery pack sealant, comprising the following steps: S1, preparation of a phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier: (1) Under a protective gas atmosphere, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was mixed with a carbon-carbon double bond-terminated hydroxyl alkyl polysiloxane, a free radical initiator was added, and an addition reaction was carried out under heating conditions. After the reaction was completed, the volatiles were removed by vacuum treatment to obtain a phosphorus-containing silicon diol intermediate. In this embodiment, the protective gas atmosphere is set to nitrogen atmosphere. By weight, 21.6 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are mixed with 200 parts of carbon-carbon double bond-containing terminal hydroxyalkyl polysiloxane, i.e., vinyl-containing terminal hydroxypropyl silicone oil. The molar ratio of the PH bond in 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to the C=C double bond in the vinyl-containing terminal hydroxypropyl silicone oil is strictly controlled to be 1:1. 0.5 parts of free radical initiator azobisisobutyronitrile are added. The reaction temperature under heating conditions is set to 90°C, and the addition reaction time is 4 hours to ensure that the phosphorus-carbon addition reaction starts smoothly under a low heat load and avoids side reactions caused by kinetic mismatch. This step introduces intrinsic halogen-free flame-retardant groups into the polysiloxane side chain through in-situ construction, endowing the phosphorus-containing silicon diol intermediate with an extremely low glass transition temperature and high hydrophobicity, laying the foundation for the low-temperature toughness and moisture-blocking ability of the subsequent network structure. (2) The phosphorus-containing silicon diol intermediate was subjected to vacuum dehydration, cooled down and diisocyanate and catalyst were added, and the reaction was carried out under heating conditions to obtain a prepolymer with terminal isocyanate groups. In this stage, the vacuum dehydration process was set to be carried out at 110°C for 2 hours to remove trace amounts of moisture and prevent it from unintentionally consuming isocyanate groups. Subsequently, the system was cooled to 60°C, and 45.5 parts of isophorone diisocyanate and 0.1 parts of organic bismuth catalyst were added. The molar ratio of hydroxyl groups in the phosphorus-containing silicon diol intermediate to isocyanate groups in the isophorone diisocyanate was set to 1:2.05. The temperature of the heat preservation reaction under heating conditions is set at 75°C and the heat preservation reaction time is 3 hours. The design of this stoichiometric ratio and temperature critical threshold can effectively control the cascade mechanism of polyurethane prepolymer chain extension, so that the urethane bonds are evenly distributed in the macromolecular skeleton. The urethane bonds use their strong hydrogen bonding to provide polar adhesive force for the final colloid and act as stress buffers. (3) Cool down the system of prepolymer containing terminal isocyanate groups, slowly add glycidyl ether to carry out the end-capping reaction, keep the reaction at the temperature until the characteristic absorption peak of the isocyanate group in the infrared spectrum disappears, and obtain phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier. The addition reaction stage was heated to 95°C, and the holding reaction stage was held at 78°C. The molar ratio of hydroxyl groups in the phosphorus-silicon diol intermediate to isocyanate groups in the diisocyanate was 1:2.08. This relatively low setting extended the residence time of the in-situ construction reaction, resulting in more ordered formation of urethane bonds and reducing the probability of unexpected molecular chain entanglement caused by local overheating. With 150 parts of insulating and thermally conductive filler, the system demonstrated process adaptability and structural molding stability under mild manufacturing conditions. In order to strictly control the single variable to accurately attribute the effect of the core parameter, the particle size of the matrix resin, insulating and thermally conductive filler, and the types of other raw materials such as surface treatment agent, silane coupling agent and curing agent in this embodiment are completely consistent with those in Example 1. By comparing with Example 1, it can be seen that, under the premise of strictly controlling a single variable, as the amount of modifier increases to 20 parts and the amount of filler increases to 150 parts, the system maintains excellent peel strength while the volume resistivity is further improved. This is accurately attributed to the positive synergistic effect of the increased ratio of modifier and filler on electrical insulation and adhesion. Example 5

[0020] A method for preparing a battery pack sealant, comprising the following steps: S1, preparation of a phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier: (1) Under a protective gas atmosphere, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was mixed with a carbon-carbon double bond-terminated hydroxyl alkyl polysiloxane, a free radical initiator was added, and an addition reaction was carried out under heating conditions. After the reaction was completed, the volatiles were removed by vacuum treatment to obtain a phosphorus-containing silicon diol intermediate. In this embodiment, the protective gas atmosphere is set to nitrogen atmosphere. By weight, 21.6 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are mixed with 200 parts of carbon-carbon double bond-containing terminal hydroxyalkyl polysiloxane, i.e., vinyl-containing terminal hydroxypropyl silicone oil. The molar ratio of the PH bond in 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to the C=C double bond in the vinyl-containing terminal hydroxypropyl silicone oil is strictly controlled to be 1:1. 0.5 parts of free radical initiator azobisisobutyronitrile are added. The reaction temperature under heating conditions is set to 90°C, and the addition reaction time is 4 hours to ensure that the phosphorus-carbon addition reaction starts smoothly under a low heat load and avoids side reactions caused by kinetic mismatch. This step introduces intrinsic halogen-free flame-retardant groups into the polysiloxane side chain through in-situ construction, endowing the phosphorus-containing silicon diol intermediate with an extremely low glass transition temperature and high hydrophobicity, laying the foundation for the low-temperature toughness and moisture-blocking ability of the subsequent network structure. (2) The phosphorus-containing silicon diol intermediate was subjected to vacuum dehydration treatment, then cooled and diisocyanate and catalyst were added. The reaction was carried out under heating conditions to obtain a prepolymer with terminal isocyanate groups. In this stage, the vacuum dehydration process was set to be carried out at 110°C for 2 hours to remove trace amounts of moisture and prevent it from unintentionally consuming isocyanate groups. Subsequently, the system was cooled to 60°C, and 45.5 parts of isophorone diisocyanate and 0.1 parts of organic bismuth catalyst were added. The molar ratio of hydroxyl groups in the phosphorus-containing silicon diol intermediate to isocyanate groups in the isophorone diisocyanate was set to 1:2.05. The temperature of the heat preservation reaction under heating conditions is set at 75°C and the heat preservation reaction time is 3 hours. The design of this stoichiometric ratio and temperature critical threshold can effectively control the cascade mechanism of polyurethane prepolymer chain extension, so that the urethane bonds are evenly distributed in the macromolecular skeleton. The urethane bonds use their strong hydrogen bonding to provide polar adhesive force for the final colloid and act as stress buffers. (3) Cool down the system of prepolymer containing terminal isocyanate groups, slowly add glycidyl ether to carry out the end-capping reaction, keep the reaction at the temperature until the characteristic absorption peak of the isocyanate group in the infrared spectrum disappears, and obtain phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier. This embodiment verifies the kinetic matching degree under relatively high operating parameters; the reaction temperature in the addition reaction stage is set at 105℃ under heating conditions, and the molar ratio of hydroxyl groups in the phosphorus-silicon diol intermediate to isocyanate groups in the diisocyanate reaches 1:2.18 in the heat preservation reaction stage, and the heat preservation reaction temperature is 82℃; the higher excess ratio of isocyanate and temperature accelerate the end-capping preparation process of the prepolymer with terminal isocyanate groups, providing a more active crosslinking precursor for subsequent physical resistance to 250 parts of high-density insulating and thermally conductive filler. Experimental data show that even under the condition of a surge in reaction kinetics, the system can still form a dense interpenetrating network through chemical bonding without phase separation. Similarly, to eliminate the interference of multiple variables, the physical specifications of the matrix resin, insulating and thermally conductive filler, surface treatment agent, silane coupling agent and curing agent in this embodiment are strictly consistent with those in Example 1. Under the control of a single variable, the amount of modifier is further increased to 35 parts to adapt to 250 parts of filler. The test results compared with those of Example 1 and Example 4 show that the peel strength and volume resistivity both show a regular increase, which effectively confirms that after eliminating the interference of changes in the resin matrix and coupling agent type, the increase of the constant value in the core range has a significant effect on the comprehensive performance under thermo-mechanical-humid alternating environment.

[0021] Comparative Example 1: This comparative example provides a conventional flame-retardant modified battery pack sealant preparation method. Its basic formula and process parameters are consistent with those of Example 2, except that the preparation and addition of the phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier are cancelled and replaced with a mixture of 25 parts of small molecule liquid flame retardant triphenyl phosphate and hydroxyl-terminated silicone oil directly physically blended in component A. This design aims to compare the differences in interface failure and precipitation under long-term thermal shock between the in-situ construction of chemically bonded flame-retardant skeleton in this invention and the traditional physical blending method.

[0022] Comparative Example 2: This comparative example provides a method for preparing a battery pack sealant lacking flexible siloxane segments. Its basic formulation and process parameters are consistent with those of Example 2, except that in step (1) of preparing the S1 phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier, terminal hydroxyl alkyl polysiloxanes containing carbon-carbon double bonds are not used, but instead, equimolar amounts of conventional aliphatic small molecule diols, such as 1,4-butanediol, are used. This design aims to verify the irreplaceable role of polysiloxane segments in imparting extremely low glass transition temperatures and high hydrophobicity to the colloid.

[0023] Verification experiment: To comprehensively evaluate the overall performance of the battery pack sealant prepared in this invention under complex thermo-mechanical-humidity alternating environments, and the synergistic effect brought about by the phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier, the sealant samples prepared in Examples 1 to 5 and Comparative Examples 1 to 2 were systematically tested for reliability, weather resistance and intrinsic flame retardant properties.

[0024] Testing standards: Flame retardant performance testing strictly follows the UL94 standard for vertical flammability rating assessment; weather resistance testing adopts the industry standard double 85 test, that is, continuous aging for 1000 hours in a high temperature and high humidity environment of 85℃ and 85% relative humidity; peel strength testing is performed in accordance with the GB / T2790-1995 standard; volume resistivity testing is measured in accordance with the GB / T1410-2006 standard.

[0025] Specific testing process: In the peel strength test, the prepared battery pack sealant was applied between a standard aluminum alloy plate and a polyimide film substrate. The thickness of the adhesive layer was controlled and cross-linking and curing were completed according to the set curing conditions. Then, the sealant was peeled at a constant rate of 180 degrees on a universal testing machine. The peak load at failure was recorded to characterize the polar adhesive force. In the double 85 test, the cured standard sample was placed in a constant temperature and humidity test chamber. After 1000 hours of aging cycles, the sample was taken out to observe whether there was small molecule VOC precipitation or phase separation on the surface. A high resistance meter was immediately connected to apply DC voltage and the volume resistivity after aging was measured to evaluate the blocking effect of the hydrophobic network on water vapor intrusion. Table 1 Performance test data of Examples 1-5 and Comparative Examples 1-2

[0026] The test data in Table 1 clearly show that Examples 1 to 5 all achieved the UL94V-0 flame retardant standard without adding free flame retardants, and maintained a flame retardancy rating greater than [value missing] after undergoing rigorous double 85 aging tests. The volume resistivity and excellent interfacial peel strength of the phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier verified the robustness of the modifier under different parameter gradients. Through the comparison of the strict single-variable control group composed of Examples 1, 4 and 5, it was found that as the ratio of modifier to insulating and thermally conductive filler gradually increases in the core range, the volume resistivity and peel strength of the system after aging show a regular and steady increase, which is accurately attributed to the specific performance gain brought about by the adjustment of core parameters and eliminates the interference caused by multivariate coupling. In contrast, Comparative Example 1, which uses physically blended flame retardants, exhibited severe small molecule precipitation after aging, leading to a sharp drop in volume resistivity and a significant decrease in interfacial adhesion. This indicates that physical additions cannot resist phase separation caused by long-term thermal shock. While Comparative Example 2, which lacks polysiloxane segments, maintained flame retardancy, the loss of highly hydrophobic and flexible buffer phases allowed moisture intrusion, resulting in colloid pulverization and degradation, and a significant decrease in adhesion to polar substrates. This invention, by constructing an interpenetrating network structure in situ, successfully achieved a balance between rigid support and stress dissipation, demonstrating an unexpected synergistic effect.

[0027] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a battery pack sealant, characterized in that, The preparation method includes the following steps: S1. Preparation of phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier: (1) Under a protective gas atmosphere, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was mixed with a carbon-carbon double bond-terminated hydroxyl alkyl polysiloxane, a free radical initiator was added, and an addition reaction was carried out under heating conditions. After the reaction was completed, the volatiles were removed by vacuum treatment to obtain a phosphorus-containing silicon diol intermediate. (2) The phosphorus-containing silicon diol intermediate is subjected to vacuum dehydration treatment, cooled to 50-60°C and diisocyanate and catalyst are added, and the reaction is carried out under heating conditions to obtain a prepolymer with terminal isocyanate groups. (3) Cool the system containing the prepolymer with the terminal isocyanate group, slowly add glycidyl ether at a rate of 1 to 3 drops / second to carry out the end-capping reaction, keep the reaction at the temperature until the characteristic absorption peak of the isocyanate group in the infrared spectrum disappears, and obtain the phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier. Preparation of S2 and A components: By weight, 100 parts of the matrix resin, 15 to 40 parts of the phosphorus-silicon hybrid polyurethane-epoxy multifunctional modifier obtained in step S1, 100 to 300 parts of the insulating and thermally conductive filler, and 1 to 5 parts of the silane coupling agent are added to a stirring device and dispersed and mixed at high speed under vacuum conditions to obtain component A. Preparation of S3 and B components: Weigh 20 to 50 parts by weight of the curing agent as component B; S4. Crosslinking and curing: Mix component A and component B evenly, perform initial curing at room temperature and subsequent curing with heat to obtain the battery pack sealant.

2. The method for preparing a battery pack sealant according to claim 1, characterized in that: In step (1) of step S1, the molar ratio of the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to the carbon-carbon double-bonded terminal hydroxyl alkyl polysiloxane is 1:1, that is, the molar ratio of PH bond to C=C double bond is 1:1; the reaction temperature under the heating conditions is 90-110℃; and the protective gas atmosphere is a nitrogen atmosphere.

3. The method for preparing a battery pack sealant according to claim 2, characterized in that: In step (1) of step S1, the carbon-carbon double bond-containing terminal hydroxyalkyl polysiloxane is a vinyl-containing terminal hydroxypropyl silicone oil; the free radical initiator is azobisisobutyronitrile.

4. The method for preparing a battery pack sealant according to claim 1, characterized in that: In step (2) of step S1, the vacuum dehydration treatment is performed at 110°C for 2 hours; the cooling is performed at 60°C; the molar ratio of the hydroxyl groups in the phosphorus-containing silicon diol intermediate to the isocyanate groups in the diisocyanate is 1:2.05 to 1:2.2; and the temperature of the heat preservation reaction under the heating conditions is 75 to 85°C.

5. The method for preparing a battery pack sealant according to claim 4, characterized in that: In step (2) of step S1, the diisocyanate is isophorone diisocyanate; the catalyst is an organic bismuth catalyst or a dibutyltin dilaurate catalyst.

6. The method for preparing a battery pack sealant according to claim 1, characterized in that: In step (3) of step S1, the system is cooled to 50-60°C; the molar ratio of the hydroxyl groups in the glycidyl ether to the remaining isocyanate groups in the prepolymer with terminal isocyanate groups is 1:1; and the reaction temperature is controlled not to exceed 65°C during the end-capping reaction.

7. The method for preparing a battery pack sealant according to claim 1, characterized in that: In step S2, the vacuum degree of the vacuum condition is ≤-0.09MPa; the matrix resin is selected from at least one of bisphenol A type epoxy resin or bisphenol F type epoxy resin.

8. The method for preparing a battery pack sealant according to claim 1, characterized in that: In step S2, the insulating thermally conductive filler is surface-treated spherical alumina, and the content of water-extractable ions in the insulating thermally conductive filler is less than 800 ppm.

9. The method for preparing a battery pack sealant according to claim 1, characterized in that: In step S3, the curing agent is selected from at least one of modified fatty amine, polyether amine or liquid acid anhydride; in step S4, the curing condition after heating is curing at 80°C for 2 hours.

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