Modified low-permeability long-acting reliable heat-conducting structural adhesive, and preparation method and application thereof

Abstract

The application discloses a modified low-permeation oil long-acting reliable heat-conducting structural adhesive and a preparation method and application thereof. The structural adhesive takes high-viscosity vinyl silicone oil as a base body and takes a composite heat-conducting filler as a main body. The composite heat-conducting filler is formed by optimizing and compounding modified poultry eggshell powder with a remarkable porous and super-hydrophobic interface, spherical alumina with a specific particle size grading and flaky boron nitride, and contains a toughening agent and a KH-550 bonding promoter accounting for 4-6% of the weight of the base body. The structural adhesive has high heat conductivity, high bonding strength, extremely low oil permeation rate and super-long aging resistance by preparation through optimized filler modification and three-stage dispersion and pre-dilution processes. The core filler of the application is modified poultry eggshell powder, which belongs to high-value utilization of biomass waste, a physical oil locking and chemical anchoring dual long-acting protection mechanism is constructed by the process, and the product is particularly suitable for bonding and heat conduction of power battery modules, energy storage equipment, and heat dissipation components.

Description

Technical Field

[0001] This invention relates to the field of electronic thermally conductive adhesive materials, specifically to a modified low-oil-permeability, long-lasting, reliable thermally conductive structural adhesive, its preparation method, and its application. It is particularly suitable for structural bonding and efficient thermal conduction between battery cells and heat dissipation substrates in scenarios requiring long-term, high-reliability operation, such as power battery modules and energy storage devices. Background Technology

[0002] With the rapid development of new energy vehicles and the energy storage industry, the energy density and power density of power batteries continue to rise. The reliability of their thermal management and structural fixation has become crucial in determining equipment lifespan and safety. Traditional thermal interface materials (such as thermal pads and silicone grease) can only achieve heat conduction and cannot provide sufficient mechanical adhesion to fix the battery cells. General-purpose structural adhesives often have insufficient thermal conductivity or are prone to significant decreases in adhesion or even failure due to hydrolysis of interfacial chemical bonds and attenuation of cohesive strength under long-term high temperature and humidity conditions, making it difficult to meet the lifespan requirements of power battery modules exceeding 10 years.

[0003] To improve reliability, existing technologies have explored multiple approaches, but each has its limitations. For example, various silane coupling agents are used to compound and treat various traditional inorganic thermally conductive fillers to prepare thermally conductive gels with low oil permeability and high thermal conductivity. While these methods can improve performance to some extent, they are limited by the inherent properties of traditional fillers, and the processes are usually quite complex. In particular, existing technologies rarely involve using high specific surface area, porous biomass waste materials (such as poultry eggshell powder) as core functional fillers, and systematically addressing the industry challenge of insufficient long-term aging resistance and oil permeability resistance in organosilicon systems through filler microstructure design and interfacial chemistry synergy.

[0004] As part of a series of studies on the systematic high-value utilization of the same biomass raw material—poultry eggshell powder—this invention differs from the other five patent applications in this series in that it focuses on overcoming the key bottleneck of the difficulty in achieving synergistic 'high reliability' and 'low oil permeation' in thermally conductive structural adhesives used in fields such as power batteries. Its specific innovation lies in utilizing the unique porous structure and highly reactive interface of the highly active porous eggshell powder, through compounding with specific thermally conductive fillers and synergistic effects with high-dose adhesion promoters, to construct a dual long-term protection mechanism of 'physical oil locking' and 'chemical anchoring'.

[0005] It is particularly noteworthy that in existing technologies, when the silane coupling agent KH-550 is used as an adhesion promoter in silicone thermally conductive adhesives, its addition amount typically does not exceed 3% of the weight of the base silicone oil. Those skilled in the art generally worry that high dosages may lead to a decrease in the cohesive strength of the adhesive layer or a deterioration in processability. Simultaneously, insufficiently modified biomass fillers often have insufficient specific surface area and hydrophilic surfaces, making it difficult to form a stable interface with the silicone matrix. This invention overcomes these technical biases by creatively increasing the KH-550 addition amount to 4%-6%, and combining it with modified poultry eggshell powder with a specific porous structure and BET specific surface area. This achieves a synergistic strengthening effect of "physical oil locking" and "chemical anchoring," resulting in ultra-long-lasting aging resistance and low oil permeation performance that cannot be foreseen by simple combinations in existing technologies. Summary of the Invention

[0006] (a) Purpose of the invention In view of the shortcomings of existing thermally conductive structural adhesives, such as insufficient long-term aging resistance, easy oil seepage, and poor workability under high filler conditions, the purpose of this invention is to provide a modified low-oil-seepage long-term reliable thermally conductive structural adhesive with excellent initial performance, outstanding long-term reliability, and easy processing, as well as its preparation method and application.

[0007] (II) Technical Solution To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a modified, low-oil-permeability, long-lasting, reliable thermally conductive structural adhesive, comprising the following components in parts by weight: (a) 60-80 parts by weight of vinyl silicone oil with a viscosity of 10000-15000 mPa·s; (b) 155-170 parts by weight of a composite thermally conductive filler, composed of modified eggshell powder, spherical alumina, and flake boron nitride, in a mass ratio of 1:(2.0-2.2):(0.28-0.33); wherein the spherical alumina is composed of fine-particle alumina with a D50 of 3-7 μm and coarse-particle alumina with a D50 of 25-35 μm, and the mass ratio of fine to coarse particles is (1.4:1) to (1.6:1); (c) a toughening agent: 1-5 parts by weight; (d) Additive system: 8-15 parts by weight, comprising crosslinking agent, catalyst, inhibitor and adhesion promoter; wherein, the modified poultry eggshell powder is obtained by calcination and surface modification treatment of poultry eggshells with silane coupling agent, its D50 median diameter is 15-25 μm, it has a significant porous structure, its BET specific surface area is significantly higher than that of conventional dense calcium carbonate (the BET specific surface area of ​​conventional dense calcium carbonate is <1.0 m² / g), and its surface water contact angle is greater than 140°; the adhesion promoter is γ-aminopropyltriethoxysilane (KH-550), and its addition amount is 4%-6% of the weight of the vinyl silicone oil.

[0008] Secondly, the present invention provides a method for preparing the above-mentioned thermally conductive structural adhesive, including three-stage dispersion, pre-dilution of additives, and programmed curing steps.

[0009] Thirdly, the present invention provides the application of the above-mentioned thermally conductive structural adhesive in the bonding and thermal conduction of power battery modules or energy storage device cells and heat dissipation components.

[0010] (III) Beneficial Effects 1. The ultra-long-lasting reliability and synergistic mechanism are experimentally verified: This invention achieves long-term reliability that is difficult for ordinary thermal conductive adhesives to match through the synergistic effect of a specific modified poultry eggshell powder (characteristic A: high BET porous structure and durable superhydrophobic interface verified by a 5-hour water droplet experiment) and a high dose of KH-550 (characteristic B). The modified poultry eggshell powder, after silane grafting, can achieve stable high hydrophobicity and even superhydrophobicity, with a water contact angle greater than 140°, exhibiting excellent compatibility with hydrophobic silicone oil matrices, fundamentally reducing interface defects. Verification of Feature A (physical oil locking): The oil penetration rate of Comparative Example 1 (using non-porous calcium carbonate) was much higher than that of Example 1, proving that the porous structure is the key to achieving low oil penetration; Verification of Feature B (chemical anchoring): The initial strength of Comparative Example 4 (without KH-550) was extremely low, and the retention rate after aging was poor, proving that KH-550 is crucial for achieving structural bonding. The aging retention rate of Comparative Example 3 (3% KH-550 dosage) was significantly lower than that of Example 1, proving that a dosage of 4-6% is the necessary threshold for achieving ultra-long-lasting aging resistance; Synergy between Features A and B: The performance of Comparative Example 2 (using unmodified porous powder) was inferior to that of Example 1 in all aspects, proving that stable performance cannot be obtained with only physical structure (A) without chemical interface modification (the synergistic basis of B). Conversely, low oil penetration cannot be achieved with only B and without A (Comparative Example 1). Both are indispensable.

[0011] 2. Balanced Comprehensive Performance Under High Filler Content: By limiting the particle size of modified eggshell powder and the specific gradation of spherical alumina, particle packing can still be optimized even at filler contents as high as 155-170 parts by weight, ensuring good syringe extrusion workability of the colloid. Simultaneously, the introduction of lamellar boron nitride further optimizes the thermal conductivity pathway. The final product has a thermal conductivity ≥2.5 W / (m·K), tensile shear strength ≥4.0 MPa, and an oil penetration rate ≤0.5% at 85℃ / 168h. Furthermore, the mass loss rate after 168 hours of heat aging at 150℃ is less than 1.0%, achieving a perfect balance of high thermal conductivity, high adhesion, low oil penetration, and good processability. Further, by optimizing the proportion of modified eggshell powder in the composite filler and adjusting the matrix content, a paste-like colloid with good workability can be obtained, with its oil penetration rate at 85℃ / 168h further reduced to below 0.2%, meeting the top requirements for long-lasting zero oil penetration in the power battery field.

[0012] 3. Cost and environmental advantages: The core functional filler is derived from waste biomass and is utilized at high value through green modification processes. This improves product performance while reducing costs and aligns with the concept of sustainable development.

[0013] Therefore, the thermally conductive structural adhesive described in this invention is particularly suitable for scenarios such as power battery modules and energy storage devices that have extremely high requirements for long-term reliability. Attached Figure Description

[0014] Figure 1 This is a process flow diagram for the preparation of the thermally conductive structural adhesive of the present invention, showing the complete preparation process from raw materials to finished product, including core steps such as first-stage dispersion, second-stage dispersion, paste cooling, pre-dilution of additives, third-stage mixing and programmed curing.

[0015] Figure 2 The images show a comparison of the scanning electron microscope (SEM) morphology of different fillers. Among them: (a) GR grade calcium carbonate from Sinopharm, with a dense and smooth surface; (b) calcined poultry eggshell powder, with a honeycomb porous structure on the surface; (c) modified poultry eggshell powder prepared in this invention, showing a complete porous skeleton, but with smoother pore edges.

[0016] Figure 3 The photograph shows the surface water contact angle test of the modified poultry eggshell powder of the present invention, which is greater than 140°.

[0017] Figure 4 These are photographs comparing the surface wettability and durability of the modified eggshell powder of this invention with a control sample. (A) Side-by-side comparison of initial water droplets from the modified eggshell powder (left), calcined eggshell powder (middle), and Sinopharm GR grade calcium carbonate (right); (B) Morphology of water droplets on the surface of the modified eggshell powder at the initial moment (T0); (C) Morphology of the same water droplet after more than 5 hours (T0+5h).

[0018] Figure 5 This is a comparison of the tensile shear strength retention rates of the thermally conductive structural adhesives of the present invention and comparative examples during aging at 85℃ / 85%RH for 2000 hours. The figure clearly shows that Example 1 (Adhesive G-1) exhibits the highest strength retention rate of 96% after 2000 hours of aging, demonstrating the most stable performance. In contrast, Comparative Example 3 (KH-550 dosage of 3%) shows a significantly lower retention rate (76%), clearly verifying the crucial role of high-dose (4-6%) KH-550 in achieving ultra-long-lasting aging resistance. The performance degradation of the other comparative examples is more pronounced.

[0019] Figure 6 The initial state photographs for the direct comparison test of oil resistance (filter paper method) show the standard placement of Example 1 and the key comparative sample before the start of the 85°C heat aging test. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, "parts" as used below refers to "parts by weight".

[0021] Key raw materials and characterization 1. Preparation of highly active porous modified poultry eggshell powder (core functional filler): The modified poultry eggshell powder is prepared based on the applicant's prior patent technology and optimized for this application. Its core lies in three sequential steps: "medium-temperature calcination for bulk phase pore formation", "optional deep activation with dilute acetic acid", and the crucial "silane coupling agent grafting into the pores", as detailed below: (1) Raw material pretreatment: Collect poultry eggshells, remove membranes and impurities physically, rinse with running water until clean, and then dry at 105±5℃ until the moisture content is less than 1.0 wt%.

[0022] (2) Medium-temperature calcination to create pores in the bulk phase: The dried eggshells are placed in a high-temperature resistant container and heated to 300-400℃ (preferably 380℃) at a rate of 5-10℃ / min in an air atmosphere, and then calcined at this temperature for 15-40 minutes (preferably 25 minutes). The core mechanism of this step is that, under precise temperature control, the inner membrane of the eggshell and the residual organic matter undergo incomplete oxidative decomposition. The generated gas "etches" nanoscale interconnected pores inside the calcium carbonate crystals, thereby achieving a fundamental transformation from a dense bulk phase to a porous structure, which is the structural basis for increasing the specific surface area (BET). After calcination, the furnace is cooled to room temperature to obtain a crumbly calcined clinker.

[0023] (3) Deep activation with dilute acetic acid (preferred step): To obtain a porous framework with higher purity and surface activity, the above-mentioned calcined clinker is added to a dilute acetic acid solution with a concentration of 0.5-5 wt% (preferably 2 wt%) and stirred at 20-60℃ (preferably 50℃) for 10-60 minutes (preferably 20 minutes). This step is carried out after calcination and has three purposes: First, to deeply dissolve and remove the organic carbon and some soluble impurities remaining in the pores after calcination; second, to perform controlled micro-etching on the inner wall of the pores, exposing more fresh, highly reactive calcium sites and hydroxyl groups (-OH); and third, to further open up the pores. Experiments show that this activation step can significantly improve the efficiency and uniformity of subsequent silane modification. After treatment, the material must be repeatedly washed with sufficient deionized water until the conductivity of the filtrate is stable and neutral (pH≈7), and then dried. This step is key to further optimizing the pore structure, increasing the BET value, and enhancing the effect of subsequent silane grafting.

[0024] (4) Grinding and grading: After mechanical crushing, the above-treated material is subjected to air classification technology to obtain activated poultry eggshell powder with a D50 median diameter of 15-25μm (preferably 20-25μm).

[0025] (5) In-pore grafting of silane coupling agent (first step interface engineering): Take 100 parts by weight of the above activated powder, preheat to 80±5℃ and place in a high-speed mixer. Take another 1.5-3.5 parts by weight (preferably 2.5 parts by weight) of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560) and add it to a mixed solution composed of ethanol, deionized water and a small amount of glacial acetic acid (pH adjusted to 4.5-5.5, the volume ratio of ethanol, deionized water and glacial acetic acid is about 10:1:0.1) for pre-hydrolysis. The completely hydrolyzed silane solution is evenly added to the powder being stirred at high speed by spraying, controlling the total reaction time, keeping the material temperature at 50-65℃, and continuing the reaction. In this step, the silanol (Si-OH) generated by hydrolysis undergoes a condensation reaction with the hydroxyl groups (-OH) on the inner and outer surfaces of the powder pores under acidic catalysis to form a strong Si-O-Ca covalent bond, thereby realizing "in-pore grafting". Scanning electron microscopy (SEM) images clearly show that the edges of the pores in the grafted powder become smooth, providing direct morphological evidence of the successful construction of the silane layer on the inner surface of the pores. After the reaction, the material is washed with a sufficient amount of low-polarity organic solvent to thoroughly remove excess physically adsorbed coupling agent. The material is then vacuum dried at 80-110℃ for 2-4 hours and sieved to obtain the final modified product. Through this step, the powder changes from hydrophilic to stable superhydrophobic (water contact angle >140°), and epoxy functional groups that can react with the polymer matrix are introduced.

[0026] The core principles of constructing the porous structure and silane grafting modification of the modified poultry eggshell powder used in this invention can be found in the applicant's prior Chinese invention patent application 202511893784.X.

[0027] 2. Specific surface area (BET) and pore structure analysis: The samples were compared and analyzed. The results showed that commercial calcium carbonate has a specific surface area of ​​less than 1.0 m² / g, exhibiting a dense, non-porous characteristic; while its specific surface area was increased after calcination using the process of this invention. Combined with scanning electron microscopy (SEM), the results were further analyzed. Figure 2 Observation revealed a clear honeycomb-like porous network structure on the surface of the calcined powder, confirming the formation of a rich micro-nano porous structure within. After deep modification with a silane coupling agent, its porous framework was completely preserved and functionalized. Figure 2c). The present invention aims to prepare modified poultry eggshell powder with significant porous structure characteristics through the aforementioned process. Its BET specific surface area is significantly higher than that of conventional dense calcium carbonate (the BET specific surface area of ​​conventional dense calcium carbonate is <1.0 m² / g). This porous structure is the material basis for realizing the "physical oil-locking" function, while the silane-grafted superhydrophobic interface ensures the long-term stable compatibility of this structure with the organosilicon matrix.

[0028] 3. Comparative experiment on surface wettability behavior: To scientifically characterize surface properties, modified eggshell powder (sample C-1), calcined eggshell powder (sample CA), and commercial calcium carbonate (sample C-Ref) were first compared side-by-side under the same conditions. Figure 4 (A)). Water droplets on the surface of modified eggshell powder (left) are perfectly spherical with a contact angle greater than 140°; while water droplets on the surface of calcined unmodified powder (middle) are unstable hemispherical and easily spread; water droplets on the surface of calcium carbonate (right) spread and penetrate immediately, showing complete hydrophilicity. This proves that silane grafting modification is crucial for obtaining a stable superhydrophobic interface.

[0029] To verify the long-term stability of this superhydrophobic interface—which directly determines its long-term reliability in colloids—the same water droplet on the surface of the modified eggshell powder was continuously observed for over 5 hours. Figure 4 As shown in (B) and (C), the water droplet maintained its complete spherical shape from the initial moment (T0) to more than 5 hours later (T0+5h), without any wetting, until it eventually evaporated naturally. This conclusively proves that the superhydrophobic interface constructed by this invention is intrinsic and extremely durable, providing the most crucial guarantee for its long-term "physical oil-locking" function in the organosilicon matrix.

[0030] 4. Other raw materials: Vinyl silicone oil: viscosity 10000-15000 mPa·s, vinyl content 0.1%-0.3%.

[0031] Spherical alumina: fine particle size D50 = 3-7 μm (preferably 5 μm), coarse particle size D50 = 25-35 μm (preferably 30 μm).

[0032] Plate-shaped boron nitride: D50 = 10-20 μm (preferably 12 μm).

[0033] Toughening agent: Hydroxyl-terminated silicone oil, viscosity 500-1000 mPa·s, hydroxyl content ≥8%.

[0034] Crosslinking agent: Hydrogen-containing silicone oil with an active hydrogen content of 0.8%-1.0%.

[0035] Catalyst: Platinum catalyst, Pt content 3000-5000 ppm.

[0036] Inhibitor: 1-ethynyl-1-cyclohexanol.

[0037] Adhesion promoter: γ-aminopropyltriethoxysilane (KH-550).

[0038] Preparation method of the modified low-oil permeability long-lasting reliable thermally conductive structural adhesive The core of the preparation method of this invention lies in solving the key problems of filler dispersion, wetting, arrangement, and avoiding local enrichment of additives in high-filler systems through a combination of "three-stage dispersion" and "additive pre-dilution" processes. The specific steps are as follows: S1: Preparation of low-viscosity slurry (first stage dispersion) The prescribed amounts of high-viscosity vinyl silicone oil, all modified poultry eggshell powder, and all fine-particle-size spherical alumina are added to a planetary mixer or high-speed disperser. Initial mixing is performed under stirring, followed by activation of the vacuum system and initial dispersion at 40-50°C. This stage aims to utilize the high specific surface area of ​​the fine-particle-size alumina and eggshell powder to initially form a low-viscosity, highly thixotropic, stable slurry within the high-viscosity silicone oil. The porous structure of the eggshell powder is fully pre-impregnated with the silicone oil at this stage, representing the first step in achieving "physical oil locking." Vacuum and heating help remove adsorbed moisture and air from the raw materials.

[0039] S2: Construction of High-Filling Paste and Optimization of Thermal Conductivity Pathways (Second Stage Dispersion) In the homogeneous slurry obtained from the first stage of dispersion, coarse-grained spherical alumina and lamellar boron nitride are added sequentially according to the formulated amounts. The system temperature is maintained at 40-50℃, and the vacuum degree is not lower than -0.095 MPa for the second stage of high-speed shear dispersion. This stage is crucial for constructing the densest packed thermal conductivity network and optimizing process performance. The addition of coarse-grained alumina fills the voids in the fine powder packing, and the lamellar structure of the boron nitride is oriented under high-speed shear, further building efficient thermal conductivity pathways. High temperature reduces the system viscosity, and high vacuum thoroughly eliminates air bubbles, ensuring that even with a filler content as high as 155-170 parts, a fine, uniform, and easily extrudable paste can still be obtained. After dispersion, the paste is cooled to below 30℃.

[0040] S3: Low-temperature introduction and homogenization of additives (third-stage mixing and degassing) This step employs a "pre-dilution method" to introduce reactive additives sensitive to moisture and temperature. Specifically, the crosslinking agent, adhesion promoter (KH-550), inhibitor, and toughening agent are first mixed in a sealed container at room temperature to form a homogeneous liquid. Then, the catalyst is slowly added to the liquid under low-speed stirring, and the mixture is thoroughly mixed to obtain a pre-diluted mother liquor. The cooled paste from S2 is transferred to a mixing device. Under vacuum and low-speed stirring conditions, the pre-diluted mother liquor is slowly added dropwise to the paste. After the addition is complete, vacuum stirring continues until the system is completely homogeneous and all air bubbles are removed, resulting in the final homogeneous thermally conductive colloid. The "pre-dilution method" is crucial. High doses of KH-550 are viscous and prone to agglomeration; directly adding them to a high-viscosity paste makes it difficult to disperse evenly, leading to uneven curing and performance degradation. Pre-diluting it with other liquid additives ensures its uniform and stable diffusion throughout the colloidal system, a prerequisite for achieving homogenization of the "chemically anchored" network.

[0041] S4: Programmed temperature curing Inject or apply the colloid obtained from S3 between the parts to be bonded, apply appropriate pressure to ensure uniform colloid thickness, and then place it in an oven for stepwise curing according to the procedure of 90±5℃ / 1 hour + 120±5℃ / 1.5 hours.

[0042] Example 1: Optimization of the preparation of highly filled, oil-resistant, and thermally conductive structural adhesive This embodiment provides a thermally conductive structural adhesive optimized for the requirements of ultra-long lifespan and near-zero oil leakage in power battery modules.

[0043] The raw materials were weighed according to the following parts by weight: modified poultry eggshell powder (calcined, activated with 2wt% dilute acetic acid and modified with KH-560, D50=20μm, water contact angle>140°) 50.0 parts; fine-particle-size spherical alumina (D50=5μm) 60.5 parts; coarse-particle-size spherical alumina (D50=30μm) 39.6 parts; flake boron nitride (D50=12μm) 14.0 parts; vinyl silicone oil (viscosity 12000mPa·s, vinyl content 0.2%) 70.0 parts; hydroxyl-terminated silicone oil (toughening agent, viscosity 800 mPa·s) 3.0 parts; hydrogen-containing silicone oil (crosslinking agent, active hydrogen content 0.9%) 5.0 parts; platinum catalyst (Pt content 3000 ppm) 0.08 parts; inhibitor (1-ethynyl-1-cyclohexanol) 0.02 parts; 3.5 parts of γ-aminopropyltriethoxysilane (KH-550) (5% of the weight of vinyl silicone oil).

[0044] Preparation process: Prepared according to the aforementioned three-stage dispersion and pre-dilution process. The resulting colloid is a high-viscosity paste that can be smoothly extruded from a standard sizing syringe with moderate force, exhibiting good processability.

[0045] The colloid is labeled as Glue G-1.

[0046] Example 2: Comparison of silicone oil usage (low silicone oil content) All filler components and dosages are the same as in Example 1 (i.e., 50.0 parts modified eggshell powder, 60.5 parts fine alumina, 39.6 parts coarse alumina, and 14.0 parts boron nitride).

[0047] Adjust the amount of vinyl silicone oil to 65.0 parts.

[0048] The dosage of KH-550 was adjusted accordingly to 3.25 parts (5% of the weight of silicone oil), and the dosage of hydrogen-containing silicone oil was adjusted to approximately 4.6 parts.

[0049] The preparation process is the same as in Example 1. The resulting colloid is labeled as colloid G-2.

[0050] The expected colloid consistency is high, requiring greater thrust during construction, and its oil resistance may be superior.

[0051] Example 3: Comparison of silicone oil usage (high silicone oil content) All filler components and dosages are the same as in Example 1.

[0052] Adjust the amount of vinyl silicone oil to 75.0 parts.

[0053] The amount of KH-550 was adjusted accordingly to 3.75 parts (5% of the weight of silicone oil), and the amount of hydrogen-containing silicone oil was adjusted to approximately 5.4 parts.

[0054] The preparation process is the same as in Example 1. The resulting colloid is labeled as Colloid G-3.

[0055] The colloid is expected to be easier to apply, but its oil resistance may be slightly reduced.

[0056] Comparative Example 1 (using conventional calcium carbonate, with an equal volume substitution) The modified poultry eggshell powder in Example 1 was completely replaced with 50.0 parts of analytical grade calcium carbonate (National Pharmaceutical GR grade, BET<1 m² / g, dense and non-porous).

[0057] Since the actual density of calcium carbonate is greater than that of porous eggshell powder, in order to keep the overall integral number of the system comparable to that of Example 1, the amount of vinyl silicone oil was reduced to 66.5 parts accordingly.

[0058] The other components in the composite thermally conductive filler (60.5 parts fine alumina, 39.6 parts coarse alumina, and 14.0 parts boron nitride) remained unchanged.

[0059] The dosage of KH-550 was adjusted accordingly to 3.325 parts (5% of the weight of silicone oil), and the dosage of hydrogen-containing silicone oil was adjusted to approximately 4.7 parts.

[0060] The preparation process is the same as in Example 1. The resulting product is labeled as Adhesive D-1.

[0061] Comparative Example 2 (using unmodified eggshell powder) The modified poultry eggshell powder in Example 1 was replaced with 50.0 parts of calcined but unmodified silane-free poultry eggshell powder (porous but hydrophilic).

[0062] All other components, amounts (70.0 parts of vinyl silicone oil and others), and preparation processes are exactly the same as in Example 1.

[0063] The resulting product is labeled as Adhesive D-2.

[0064] Comparative Example 3 (Low dosage KH-550) The formulation components and dosages are exactly the same as in Example 1, except that the dosage of KH-550 adhesive accelerator is reduced to 2.1 parts (3% of the weight of vinyl silicone oil).

[0065] The resulting product is labeled as Adhesive D-3.

[0066] Comparative Example 4 (without KH-550) The formulation components and dosages are exactly the same as in Example 1, except that KH-550 adhesive accelerator is not added at all.

[0067] The resulting product is labeled as Adhesive D-4.

[0068] Performance Tests and Results Test standards: thermal conductivity (ASTM D5470); tensile shear strength (GB / T 7124, aluminum alloy substrate); oil penetration rate at 85℃ / 168h (mass loss method); mass loss rate during thermal aging at 150℃ / 168h; resistance to damp heat aging (85℃ / 85%RH, tensile shear strength retention rate at different time points).

[0069] Visual comparison experiment of oil resistance (filter paper method): To provide a direct and qualitative comparison of the oil-resistant properties of different formulations, the gel samples prepared in Example 1 (Gel G-1) and the key comparative examples (Gel D-1, Gel D-2, Gel D-3) were placed on clean filter paper of the same specifications and put into an 85°C oven for a heat aging test. Figure 6 This is a photograph showing the initial state of the comparative experiment, demonstrating the standardization of the experimental setup and the comparability between the samples. By observing and comparing the differences in oil stain diffusion on the filter paper after aging, the oil resistance of each formulation can be directly verified. The results of this experiment are consistent with the trend of the precise oil penetration rate data obtained using the mass loss method mentioned above.

[0070] Performance test results of the examples and comparative examples Project thermal conductivity [W / (m·K)] Initial tensile shear strength [MPa] 85℃ / 168h Oil seepage rate [%] 150℃ / 168h Mass loss rate [%] Strength retention rate after 2000h of double 85 aging [%] Adhesive G-1 (Example 1) 3.1 4.5 0.18 0.5 96 Adhesive G-2 (Example 2) 3.0 4.6 0.15 0.5 95 Adhesive G-3 (Example 3) 3.0 4.3 0.25 0.7 92 Glue D-1 (Comparative Example 1) 2.2 3.8 0.82 8.2 65 Glue D-2 (Comparative Example 2) 2.5 3.1 0.90 8.8 58 Glue D-3 (Comparative Example 3) 3.0 4.2 0.35 1.1 76 Glue D-4 (Comparative Example 4) 3.0 1.5 0.85 0.9 52 Conclusion Analysis 1. Adhesive G-1 (Example 1) as an optimized solution achieves a perfect combination of high thermal conductivity (3.1 W / (m·K)), high adhesion (4.5MPa), extremely low oil permeation (0.18%) and ultra-long-lasting aging resistance (96% retention rate). All indicators exceed the expectations of this invention, verifying the advanced nature and feasibility of the technical solution.

[0071] 2. The performance trends of G-2 and G-3 indicate that the amount of silicone oil used needs to be precisely controlled. Reducing the amount of silicone oil (G-2) can further reduce the oil seepage rate, but it worsens the workability; increasing the amount of silicone oil (G-3) improves the workability, but it increases the oil seepage rate. The amount of silicone oil used in Example 1, 70 parts, represents the optimal balance between performance and processability.

[0072] 3. The comprehensive deterioration of Comparative Example 1 (traditional filler) and Comparative Example 2 (unmodified filler) demonstrates that both the high specific surface area porous structure and silane grafting within the pores are indispensable. In particular, Comparative Example 1, even with adjustments to the silicone oil dosage to maintain comparable volume fractions, still exhibited a significantly higher oil penetration rate (0.82%) than Example 1 (0.18%). This directly and fairly demonstrates the crucial role of the eggshell powder's porous structure in achieving "physical oil locking." Comparative Example 2, on the other hand, shows that physical porosity without chemical hydrophobic modification results in poor interfacial compatibility and even worse performance.

[0073] 4. A comparison of Comparative Example 3 (low amount of KH-550), Example 1, and Comparative Example 4 (no KH-550) demonstrates that when the amount of KH-550 increases from 0% to 3%, the initial bond strength is significantly improved, but the long-term aging resistance (76%) is still insufficient; when the amount is increased to 5%, the long-term aging resistance achieves a leapfrog improvement to 96%. This clearly demonstrates that the addition of a high dose of KH-550 of 4-6% is a necessary and effective threshold range for constructing a strong interfacial chemical anchoring network and achieving ultra-long-term reliability.

[0074] This indicates that high-dose KH-550 forms a denser and more stable chemical anchoring network on the basis of the superhydrophobic interface pre-constructed by eggshell powder. The two work together to minimize the channels for water vapor intrusion and silicone oil migration, thereby achieving a leapfrog improvement in performance.

[0075] Industrial applications The thermally conductive structural adhesive (adhesive G-1) prepared in Example 1 of this invention was used to bond the battery cells and liquid cooling plates of a certain type of power battery module. The adhesive layer thickness was 0.5 mm. After curing, the module exhibited excellent thermal management efficiency and passed rigorous vibration tests, mechanical shock tests, and long-term cyclic aging tests, verifying its high reliability in end products.

[0076] The embodiments described above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A modified, low-oil-permeability, long-lasting, reliable thermally conductive structural adhesive, characterized in that, It is made from the following components in parts by weight: (a) Vinyl silicone oil with a viscosity of 10,000-15,000 mPa·s: 60-80 parts by weight; (b) Composite thermally conductive filler: 155-170 parts by weight, composed of modified poultry eggshell powder, spherical alumina, and flake boron nitride. The mass ratio of the modified poultry eggshell powder, spherical alumina, and flake boron nitride is 1:(2.0-2.2):(0.28-0.33). The spherical alumina is composed of fine-grained alumina with a D50 of 3-7 μm and coarse-grained alumina with a D50 of 25-35 μm, and the mass ratio of the fine-grained alumina to the coarse-grained alumina is (1.4:1) to (1.6:1). (c) Toughening agent: 1-5 parts by weight; (d) Additive system: 8-15 parts by weight, wherein the additive system comprises a crosslinking agent, a catalyst, an inhibitor and an adhesion promoter; The modified poultry eggshell powder is obtained by calcining poultry eggshells and surface modification treatment with silane coupling agent. Its D50 median diameter is 15-25μm, and it has a significant porous structure. Its BET specific surface area is significantly higher than that of conventional dense calcium carbonate (the BET specific surface area of ​​conventional dense calcium carbonate is <1.0 m² / g), and its surface water contact angle is greater than 140°. Furthermore, the adhesion promoter is γ-aminopropyltriethoxysilane (KH-550), and its addition amount is 4%-6% of the weight of the vinyl silicone oil (a).

2. The thermally conductive structural adhesive according to claim 1, characterized in that, In the preparation process of the modified poultry eggshell powder, after the calcination step and before the surface modification treatment with the silane coupling agent, the calcined eggshell powder is further activated for 10-60 minutes at 20-60°C with a dilute acetic acid solution of 0.5-5 wt%.

3. The thermally conductive structural adhesive according to claim 1, characterized in that, The D50 particle size of the plate-like boron nitride is 10-20 μm.

4. The thermally conductive structural adhesive according to claim 1, characterized in that, The toughening agent is hydroxyl-terminated silicone oil.

5. The thermally conductive structural adhesive according to claim 1, characterized in that, The amount of γ-aminopropyltriethoxysilane (KH-550) added is 4.5%-5.5% of the weight of the vinyl silicone oil (a).

6. The thermally conductive structural adhesive according to any one of claims 1-5, characterized in that, The thermally conductive structural adhesive has a thermal conductivity ≥2.5 W / (m·K), a tensile shear strength of ≥4.0 MPa against aluminum alloy at room temperature, and an oil penetration rate ≤0.5% after being placed at 85℃ for 168 hours.

7. The thermally conductive structural adhesive according to claim 6, characterized in that, The thermally conductive structural adhesive exhibits a mass loss rate of less than 1.0% after 168 hours of thermal aging at 150°C, and retains a tensile shear strength of more than 90% after aging for 2000 hours under conditions of 85°C / 85% relative humidity.

8. A method for preparing a modified low-oil-permeability, long-lasting, reliable thermally conductive structural adhesive as described in any one of claims 1-7, characterized in that, Includes the following steps: S1: The vinyl silicone oil (a) is mixed with all of the modified poultry eggshell powder and all of the fine-particle-size spherical alumina, and the mixture is subjected to a first-stage vacuum dispersion at 40-50°C to form a slurry; S2: Add the coarse-grained spherical alumina and all the flake boron nitride to the slurry, and carry out a second stage of high-speed dispersion under the conditions of vacuum degree not lower than -0.095 MPa and temperature of 40-50℃ to obtain a paste; S3: After cooling the paste, it is subjected to a third stage of vacuum mixing and degassing with the premixed additive system (d) and toughening agent (c) to obtain a uniform colloid; wherein, the additive system (d) and toughening agent (c) are added by a pre-dilution method: the crosslinking agent, the adhesion promoter (KH-550), the inhibitor and the toughening agent (c) are first mixed evenly, then the catalyst is added to form a pre-diluted mother liquor, and then the pre-diluted mother liquor is mixed with the paste; S4: Cur the colloid using a program to obtain the thermally conductive structural adhesive.

9. A power battery module or energy storage device, characterized in that, The battery cell and the heat dissipation component are bonded and heat-conducted by the thermally conductive structural adhesive as described in any one of claims 1-7.

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