One-component epoxy composition structural adhesive and preparation method thereof

Abstract

This invention relates to the field of structural adhesives, and particularly to a one-component epoxy structural adhesive and its preparation method. The one-component epoxy structural adhesive comprises, as a raw material, epoxy resin, toughening agent, curing agent, accelerator, silane coupling agent, defoamer, reinforcing agent, and inorganic filler. The one-component epoxy structural adhesive obtained by this invention exhibits high and durable adhesive strength to engineering plastics such as PBT, PA, and LCP, as well as metal terminals. After curing, the adhesive layer possesses excellent flexibility and resistance to thermal shock, safely withstanding the high temperatures of reflow soldering processes. As a one-component product, it must also possess excellent room temperature storage stability and rapid curing characteristics to meet the dual requirements of modern electronics manufacturing for material performance and process efficiency.

Description

Technical Field

[0001] This invention relates to the field of structural adhesive materials, and in particular to a one-component epoxy composition structural adhesive and its preparation method. Background Technology

[0002] In the electronics industry, connectors are key components for achieving electrical connections and signal transmission. Their long-term reliable sealing is crucial for preventing the intrusion of moisture, dust, and other media, ensuring the stable operation of electronic products in complex environments. Among various sealing materials, epoxy adhesives are widely used due to their excellent bonding strength, hardness, and chemical resistance.

[0003] However, traditional epoxy structural adhesives exhibit significant performance problems when used for sealing modern high-density, miniaturized electronic connectors. For example, epoxy resins suffer from inherent brittleness and insufficient thermal shock resistance. The dense cross-linked network of cured epoxy resin results in high internal stress, leading to high brittleness and poor toughness. Connectors often undergo lead-free reflow soldering after assembly, which involves high peak temperatures. Furthermore, the enormous thermal stress generated during the subsequent rapid heating and cooling cycles cannot be effectively absorbed and dissipated by the brittle adhesive layer, easily causing internal cracking or debonding at the substrate interface, leading to complete seal failure. Secondly, connector shells are often made of non-polar or weakly polar engineering plastics, such as polybutylene terephthalate (PBT), nylon (PA), and liquid crystal polymers (LCP). Traditional epoxy adhesives have limited adhesion to these plastic surfaces, resulting in insufficient bond strength and susceptibility to peeling failure, directly impacting seal reliability.

[0004] Finally, while two-component epoxy adhesives can achieve a longer pot life by selecting a curing agent, they require precise on-site mixing, which leads to problems such as uneven mixing, introduction of air bubbles, cumbersome operation, and material waste, making them unsuitable for high-efficiency, automated electronic assembly lines. On the other hand, single-component epoxy adhesives must ensure a sufficiently long shelf life at room temperature or slightly higher temperatures to meet warehousing and transportation requirements, while also needing to cure quickly and completely upon heating to meet production efficiency. Currently, it is difficult to strike a balance between performance and application effectiveness in existing technologies.

[0005] To address the aforementioned issues, existing technologies have proposed several improvement solutions, but all have limitations. For example, Chinese patent application CN110128982B uses carboxyl-terminated liquid nitrile rubber to toughen epoxy resin, aiming to maintain high strength while improving toughness and mechanical properties. However, this patent explicitly states a two-component mixed system. For achieving efficient connector sealing, its ease of operation, efficiency, and overall performance are inferior to a single-component system. Furthermore, the introduction of liquid nitrile rubber significantly reduces strength and heat resistance. Chinese patent application CN111117542B uses a flexible resin as an additive to improve the elasticity and high-temperature resistance of the adhesive, enabling the adhesive to maintain good flexibility even at temperatures as high as 265°C. However, it focuses on addressing the process requirements of high-temperature reflow soldering. Although it has adhesion to various substrates and good sealing and waterproofing performance, the flexible epoxy resin itself has a high viscosity, requiring the addition of reactive diluents to reduce viscosity, which leads to a significant deterioration in storage properties. Summary of the Invention

[0006] Therefore, there is an urgent need in this field to develop a new type of one-component epoxy structural adhesive that can provide high and long-lasting bonding strength to engineering plastics such as PBT, PA, and LCP, as well as metal terminals. The cured adhesive layer should also possess excellent flexibility and resistance to thermal shock, be able to withstand the high temperatures of reflow soldering, and, as a one-component product, exhibit excellent room temperature storage stability and rapid curing characteristics to meet the dual requirements of modern electronics manufacturing for material performance and process efficiency.

[0007] This invention application provides a single-component epoxy structural adhesive, comprising 100 parts by weight, and the raw materials include: 20-35 parts epoxy resin, 5-15 parts toughening agent, 2-5 parts curing agent, 1-5 parts accelerator, 0.2-1 part pigment, 1.2-2 parts silane coupling agent, 0.2-0.5 parts fumed silica, 0.5-2 parts leveling agent, 0.2-0.4 parts defoamer, 5-10 parts reinforcing agent, and inorganic filler to make up to 100 parts.

[0008] In a preferred embodiment, the epoxy resin is a combination of bisphenol F epoxy resin and AG-80 tetrafunctional epoxy resin.

[0009] In a preferred embodiment, the mass ratio of the bisphenol F epoxy resin to the AG-80 tetrafunctional epoxy resin is (6~8):(2~4).

[0010] A more preferred embodiment is that the mass ratio of the bisphenol F epoxy resin to the AG-80 tetrafunctional epoxy resin is (7~8):(2~3).

[0011] In a preferred embodiment, the epoxy equivalent of the bisphenol F epoxy resin is 160~210 g / eq.

[0012] In a more preferred embodiment, the epoxy equivalent of the bisphenol F epoxy resin is 170~190 g / eq.

[0013] A more preferred embodiment is that the bisphenol F epoxy resin is NPEF-170, manufactured by Nan Ya Plastics.

[0014] In a preferred embodiment, the epoxy equivalent of the AG-80 tetrafunctional epoxy resin is 100~130 g / eq.

[0015] In a more preferred embodiment, the epoxy equivalent of the AG-80 tetrafunctional epoxy resin is 110~120 g / eq.

[0016] In a preferred embodiment, the toughening agent is a combination of a core-shell structured polymer resin and a modified polyurethane resin.

[0017] In a preferred embodiment, the mass ratio of the core-shell structure polymer resin to the modified polyurethane resin is (4~9):(3~5.5).

[0018] In a more preferred embodiment, the mass ratio of the core-shell structure polymer resin to the modified polyurethane resin is (8~9):(3.3~4).

[0019] In a preferred embodiment, the core-shell structure polymer resin is MX-154, manufactured by Kanekachi, Japan.

[0020] In a preferred embodiment, the modified polyurethane resin is QR-9466, Japanese Aidi Technology, or HCE-7174, Shandong Hengchuang New Materials.

[0021] In a preferred embodiment, the modified polyurethane resin is a combination of QR-9466 and HCE-7174 in a mass ratio of (1.5~2):(1~1.5).

[0022] In a preferred embodiment, the curing agent is at least one of dicyandiamide curing agents.

[0023] In a preferred embodiment, the average D50 particle size of the dicyandiamide curing agent is 4~10μm.

[0024] In a more preferred embodiment, the average D50 particle size of the dicyandiamide curing agent is 4~8μm.

[0025] In a preferred embodiment, the accelerator is a modified amine accelerator or an organic guanidine accelerator.

[0026] In a preferred embodiment, the organic guanidine promoter is tetramethylguanidine.

[0027] A more preferred embodiment is that the accelerator is a modified amine accelerator.

[0028] In a preferred embodiment, the modified amine accelerator is PN-40, Ajinomoto (Japan) and / or FXR-1030, Fuji Chemical (Japan).

[0029] A more preferred embodiment is that the modified amine accelerator is PN-40.

[0030] The epoxy resin, composite toughening agent, and latent curing system used in this application together constitute a stable material system, which systematically solves the key problems of traditional single-component epoxy adhesives in connector sealing applications, such as insufficient toughness, poor adhesion to plastics, weak thermal shock resistance, and difficulty in balancing storage stability and curing speed.

[0031] By combining high epoxy resin with a composite toughening system, a strong and tough continuous phase and a dispersed elastic phase are simultaneously constructed in the curing network. Furthermore, the combination of ultrafine dicyandiamide curing agent and specific accelerators further balances the chemical inertness at room temperature and the rapid curing activity after heating.

[0032] On the other hand, the combined effect of the aforementioned raw materials enables the adhesive to exhibit superior overall technical performance, effectively absorbing and dispersing the enormous thermal stress generated by thermal cycling and reflow soldering processes, thereby preventing adhesive layer cracking or interface delamination. Simultaneously, the entire system maintains excellent storage stability at room temperature, while rapidly and thoroughly curing during application heating, perfectly meeting the stringent requirements of automated electronic assembly production for both material reliability and process convenience.

[0033] In a preferred embodiment, the pigment is at least one of black pigment, red pigment, blue pigment, and green pigment.

[0034] A more preferred embodiment is that the pigment is a black pigment or a red pigment.

[0035] In a preferred embodiment, the silane coupling agent is at least one selected from γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0036] A more preferred embodiment is that the silane coupling agent is γ-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane.

[0037] A more preferred embodiment is γ-aminopropyltriethoxysilane, wherein the silane coupling agent is γ-aminopropyltriethoxysilane.

[0038] In a preferred embodiment, the fumed silica is HDK® H18, manufactured by Wacker Chemie AG, Germany.

[0039] In a preferred embodiment, the leveling agent is at least one of BYK-333, BYK-354, BYK-358N, and Tego 410.

[0040] In a more preferred embodiment, the leveling agent is BYK-333 or BYK-358N.

[0041] A more preferred embodiment is that the leveling agent is BYK-358N.

[0042] In a preferred embodiment, the defoamer is at least one of BYK-066N, BYK-088, BYK-024, BYK-028, and BYK-1788.

[0043] A more preferred embodiment is that the defoamer is BYK-066N or BYK-088.

[0044] In a preferred embodiment, the mass ratio of the epoxy resin to the reinforcing agent is (25~32):(7~10).

[0045] In a preferred embodiment, the mass ratio of the epoxy resin to the reinforcing agent is (28~30):(8.2~9).

[0046] In a preferred embodiment, the reinforcing agent is a combination of hyperbranched polyester and glycerol borate.

[0047] In a preferred embodiment, the mass ratio of the hyperbranched polyester to the glycerol borate ester is (6~9):(1.5~2).

[0048] In a more preferred embodiment, the mass ratio of the hyperbranched polyester to the glycerol borate ester is (7~8):(1.6~1.8).

[0049] In a preferred embodiment, the hyperbranched polyester is Boltorn H20, manufactured by Perstorp in Sweden.

[0050] The reinforcing agent scheme adopted in this application constructs covalent cross-linking points in the epoxy curing network by introducing a specific combination of hyperbranched polymer and glycerol borate compound. This scheme enables the dynamic bonds of the material to break and recombine when subjected to thermal stress, thereby efficiently dissipating energy, significantly improving its intrinsic toughness, and further enhancing stress transmission and dispersion efficiency with a three-dimensional structure.

[0051] On the other hand, this compounding scheme fundamentally optimizes the crack resistance of the colloid without compromising the storage stability and processability of the system. Their combined effect enables the final product to maintain the complete colloid structure and strong interface adhesion even after undergoing severe thermal cycling or high-temperature reflow soldering processes, thereby ensuring the long-term reliable sealing performance of the connector in harsh environments.

[0052] In a preferred embodiment, the inorganic filler is at least one of silicon micro powder, molten silicon micro powder, aluminum hydroxide, or calcium carbonate.

[0053] In a more preferred embodiment, the inorganic filler is silica powder or calcium carbonate.

[0054] In a more preferred embodiment, the inorganic filler is silica powder.

[0055] In a preferred embodiment, the average D50 particle size of the inorganic filler is 5~15μm.

[0056] In a more preferred embodiment, the average D50 particle size of the inorganic filler is 5~10μm.

[0057] A method for preparing a single-component epoxy structural adhesive includes the following steps: S1: Mix a portion of silane coupling agent with anhydrous ethanol, stir evenly, adjust the pH with dilute acetic acid, and let stand at room temperature to obtain a pretreatment solution for later use. Then, add inorganic filler to a high-speed heating mixer. While stirring, spray the pretreatment solution onto the surface of the agitated inorganic filler. After completion, heat up and mix at high speed. After heat preservation, obtain the pretreated inorganic filler; S2: Add epoxy resin, toughening agent, pretreated inorganic filler, and remaining silane coupling agent to a planetary mixer. Stir and mix at 15~20Hz revolution and 30~35Hz rotation, and evacuate the vacuum until evenly mixed. After stopping stirring, break the vacuum; S3: Add the remaining raw materials, evacuate the vacuum at room temperature and stir at 20~25Hz revolution and 35~40Hz rotation until the material is a uniform paste and the air bubbles are evenly removed. Stop stirring and slowly break the vacuum. Discharge the material into an air-isolated container to obtain the epoxy structural adhesive.

[0058] The preferred embodiment of the method for preparing the single-component epoxy structural adhesive includes the following steps: S1: Mixing 40-50 wt% of silane coupling agent with anhydrous ethanol at a ratio of 1:(10-12), stirring until homogeneous, adjusting the pH to 4.5-5 with dilute acetic acid, and then allowing it to stand at room temperature for 30-35 minutes to obtain a pretreatment solution for later use. Then, adding the inorganic filler to a high-speed heating mixer and stirring at 200-300 rpm, spraying the pretreatment solution onto the surface of the agitated inorganic filler for 5-10 minutes, and then heating to 90-95℃ and mixing at 400-500 rpm for 50-60 minutes to obtain the pretreated inorganic filler; S2: Epoxy resin, toughening agent, pretreated inorganic filler, and remaining silane coupling agent are added to a planetary mixer. The mixture is stirred at 15-20 Hz and 30-35 Hz for 15-20 minutes, and then evacuated to -0.098 MPa. After the mixture is homogeneous, stirring is stopped and the vacuum is broken. S3: Add the remaining raw materials, evacuate to -0.098 MPa at a temperature range of 25-30°C, and stir. The mixture is stirred at 20-25 Hz and 35-40 Hz for 20-30 minutes, until the material is a uniform paste and the air bubbles are evenly removed. Stirring is stopped and the vacuum is slowly broken. The material is discharged into an airtight container to obtain the epoxy structural adhesive.

[0059] The beneficial effects of this application are:

[0060] 1. The single-component epoxy structural adhesive finally obtained in this application, with a high epoxy value resin as the base and a comprehensive compound toughening agent, significantly improves the adhesion of the structural adhesive to engineering plastics such as PBT, PA and LCP, as well as metal ends, effectively ensuring the sealing integrity of the structural adhesive in practical applications.

[0061] 2. The composite toughening agent added in this application, in conjunction with the epoxy composite resin, forms a stable bonding structure and elastomer phase within the epoxy composite structural adhesive system. This effectively absorbs and disperses internal stress caused by thermal mismatch, maintaining good application quality during thermal shock cycles and significantly reducing phenomena such as adhesive cracking and bond interface peeling. On the other hand, the cured adhesive layer maintains a high glass transition temperature and thermal decomposition temperature, effectively avoiding softening, blistering, and cracking during reflow soldering.

[0062] 3. The epoxy structural adhesive obtained in this application is a single-component product with a latent curing system based on ultrafine dicyandiamide curing agent and specific accelerator. It has a high curing start temperature and is stable at room temperature. Its storage period at 40°C is generally greater than 45 days, which is suitable for automated dispensing. This greatly improves production efficiency and avoids the quality risks caused by uneven mixing of two-component products.

[0063] 4. The epoxy resin, composite toughening agent and latent curing system used in this application together constitute a stable material system, which systematically solves the key problems of insufficient toughness, poor adhesion to plastics, weak thermal shock resistance and difficulty in balancing storage stability and curing speed in traditional single-component epoxy adhesives in connector sealing applications.

[0064] 5. The reinforcing agent compounding scheme adopted in this application fundamentally optimizes the crack resistance of the colloid without compromising the storage stability and processability of the system. Their combined effect enables the final product to maintain the complete adhesive layer structure and strong interface adhesion after undergoing severe thermal cycling or high-temperature reflow soldering processes, thereby ensuring the long-term reliable sealing performance of the connector in harsh environments. Detailed Implementation

[0065] Unless otherwise specified, some of the raw materials used in the specific embodiments of this application are sourced from:

[0066] The bisphenol F epoxy resin is NPEF-170, with an epoxy equivalent of 170 g / eq, from Nan Ya Plastics.

[0067] AG-80 tetrafunctional epoxy resin, epoxy equivalent of 115 g / eq, Jiangsu Jufeng Chemical.

[0068] The core-shell structured polymer resin is MX-154, manufactured by Kanekachi, Japan.

[0069] Modified polyurethane resin QR-9466, from Idico Japan.

[0070] Modified polyurethane resin HCE-7174, Shandong Hengchuang New Materials.

[0071] Amicure CG-1400F, a dicyandiamide curing agent with an average particle size of 7.5 μm (D50), is manufactured by Evonik Industries, Germany.

[0072] Modified amine accelerator PN-40, from Ajinomoto, Japan.

[0073] Modified amine accelerator FXR-1030, Fuji Chemicals, Japan.

[0074] Organic guanidine accelerator (tetramethylguanidine), Jiangsu Jufeng Chemical.

[0075] Dyhard UR500, a substituted urea accelerator, is produced by Complex Chemistry (Shanghai).

[0076] Black paste, Jiasheng (Shanghai) New Materials.

[0077] Fumed silica HDK H18, Wacker Chemie, Germany.

[0078] Hyperbranched polyester Boltorn H20, Perstorp, Sweden.

[0079] Glyceryl borate ester, industrial grade, Wuhan Huaxiang Kejie Biotechnology.

[0080] Example 1

[0081] A one-component epoxy structural adhesive, comprising 100 parts by weight, includes the following raw materials: 29.75 parts epoxy resin, 12.25 parts toughening agent, 2.8 parts curing agent, 1.75 parts accelerator, 0.35 parts pigment, 1.35 parts silane coupling agent, 0.35 parts fumed silica, 0.8 parts leveling agent, 0.2 parts defoamer, 8.6 parts reinforcing agent, and inorganic filler to make up to 100 parts.

[0082] The epoxy resin is a combination of bisphenol F epoxy resin NPEF-170 and AG-80 tetrafunctional epoxy resin in a mass ratio of 7:3.

[0083] The toughening agent is a combination of core-shell structured polymer resin MX-154 and modified polyurethane resin in a mass ratio of 8.75:3.5.

[0084] The modified polyurethane resin is a combination of modified polyurethane resin QR-9466 and modified polyurethane resin HCE-7174 in a mass ratio of 2:1.

[0085] The curing agent is dicyandiamide curing agent Amicure CG-1400F.

[0086] The accelerator is modified amine accelerator PN-40.

[0087] The pigment is a black color paste; the silane coupling agent is γ-aminopropyltriethoxysilane; the leveling agent is BYK-358N; and the defoamer is BYK-066N.

[0088] The fumed silica is HDK H18.

[0089] The reinforcing agent is a combination of hyperbranched polyester Boltorn H20 and glyceryl borate ester in a mass ratio of 7.2:1.8.

[0090] The inorganic filler is silica powder with an average D50 particle size of 8.6 μm.

[0091] A method for preparing a single-component epoxy structural adhesive includes the following steps: 45 wt% of a silane coupling agent and anhydrous ethanol are mixed at a ratio of 1:10, stirred until homogeneous, and then the pH is adjusted to 5 with dilute acetic acid. The mixture is then allowed to stand at room temperature for 30 minutes to obtain a pretreatment solution. Inorganic fillers are then added to a high-speed heating mixer and stirred at 240 rpm. The pretreatment solution is sprayed onto the surface of the agitated inorganic fillers for 10 minutes. After completion, the temperature is raised to 95°C and mixed at 450 rpm for 60 minutes to obtain the pretreated inorganic filler. S2: Epoxy resin, toughening agent, and... Pretreated inorganic fillers and remaining silane coupling agents are added to a planetary mixer and stirred at 15 Hz revolution and 30 Hz rotation for 20 minutes. Vacuum is then applied to -0.098 MPa. After uniform mixing, stirring is stopped and the vacuum is broken. S3: Other remaining raw materials are added, and vacuum is applied to -0.098 MPa at a temperature range of 25 to 30°C. Stirring is carried out at 20 Hz revolution and 40 Hz rotation for 25 minutes. When the material is a uniform paste and the air bubbles are uniformly removed, stirring is stopped and the vacuum is slowly broken. The material is discharged into an air-isolated container to obtain the epoxy structural adhesive.

[0092] Example 2

[0093] A one-component epoxy structural adhesive, comprising 100 parts by weight, includes the following raw materials: 29.75 parts epoxy resin, 12.25 parts toughening agent, 2.8 parts curing agent, 1.75 parts accelerator, 0.35 parts pigment, 1.35 parts silane coupling agent, 0.35 parts fumed silica, 0.8 parts leveling agent, 0.2 parts defoamer, 8.6 parts reinforcing agent, and inorganic filler to make up to 100 parts.

[0094] The toughening agent is a combination of core-shell structured polymer resin MX-154 and modified polyurethane resin, with a mass ratio of 8.25:4.

[0095] The modified polyurethane resin is a combination of modified polyurethane resin QR-9466 and modified polyurethane resin HCE-7174 in a mass ratio of 1.8:1.2.

[0096] The remaining implementation schemes are consistent with Example 1.

[0097] Example 3

[0098] A one-component epoxy structural adhesive, comprising 100 parts by weight, includes the following raw materials: 29.75 parts epoxy resin, 12.25 parts toughening agent, 2.8 parts curing agent, 1.75 parts accelerator, 0.35 parts pigment, 1.35 parts silane coupling agent, 0.35 parts fumed silica, 0.8 parts leveling agent, 0.2 parts defoamer, 8.6 parts reinforcing agent, and inorganic filler to make up to 100 parts.

[0099] The reinforcing agent is a combination of hyperbranched polyester Boltorn H20 and glyceryl borate ester in a mass ratio of 7.4:1.6.

[0100] The modified amine accelerator is FXR-1030.

[0101] The remaining implementation schemes are consistent with Example 1.

[0102] Example 4

[0103] A one-component epoxy structural adhesive, comprising 100 parts by weight, comprising: 30.85 parts epoxy resin, 12.25 parts toughening agent, 2.8 parts curing agent, 1.75 parts accelerator, 0.35 parts pigment, 1.35 parts silane coupling agent, 0.35 parts fumed silica, 0.8 parts leveling agent, 0.2 parts defoamer, 7.5 parts reinforcing agent, and inorganic filler to make up to 100 parts.

[0104] The accelerator is an organic guanidine accelerator, specifically tetramethylguanidine.

[0105] The remaining implementation schemes are consistent with Example 1.

[0106] Comparative Example 1

[0107] A one-component epoxy structural adhesive, comprising 100 parts by weight, includes the following raw materials: 29.75 parts epoxy resin, 12.25 parts toughening agent, 2.8 parts curing agent, 1.75 parts accelerator, 0.35 parts pigment, 1.35 parts silane coupling agent, 0.35 parts fumed silica, 0.8 parts leveling agent, 0.2 parts defoamer, 8.6 parts reinforcing agent, and inorganic filler to make up to 100 parts.

[0108] The toughening agent is MX-154, a core-shell structured polymer resin.

[0109] The remaining implementation methods are the same as in Example 1.

[0110] Comparative Example 2

[0111] A one-component epoxy structural adhesive, comprising 100 parts by weight, includes the following raw materials: 29.75 parts epoxy resin, 12.25 parts toughening agent, 2.8 parts curing agent, 1.75 parts accelerator, 0.35 parts pigment, 1.35 parts silane coupling agent, 0.35 parts fumed silica, 0.8 parts leveling agent, 0.2 parts defoamer, 8.6 parts reinforcing agent, and inorganic filler to make up to 100 parts.

[0112] The accelerator is the substituted urea accelerator Dyhard UR500.

[0113] The remaining implementation methods are the same as in Example 1.

[0114] Comparative Example 3

[0115] A one-component epoxy structural adhesive, comprising 100 parts by weight, includes the following raw materials: 35 parts epoxy resin, 12.25 parts toughening agent, 2.8 parts curing agent, 1.75 parts accelerator, 0.35 parts pigment, 1.35 parts silane coupling agent, 0.35 parts fumed silica, 0.8 parts leveling agent, 0.2 parts defoamer, 3.35 parts reinforcing agent, and inorganic filler to bring the total to 100 parts.

[0116] The remaining implementation methods are the same as in Example 1.

[0117] Comparative Example 4

[0118] A one-component epoxy structural adhesive, comprising 100 parts by weight, includes the following raw materials: 29.75 parts epoxy resin, 12.25 parts toughening agent, 2.8 parts curing agent, 1.75 parts accelerator, 0.35 parts pigment, 1.35 parts silane coupling agent, 0.35 parts fumed silica, 0.8 parts leveling agent, 0.2 parts defoamer, 8.6 parts reinforcing agent, and inorganic filler to make up to 100 parts.

[0119] The toughening agent is a combination of core-shell structured polymer resin MX-154 and modified polyurethane resin HCE-7174, with a mass ratio of 11.25:1.

[0120] The remaining implementation methods are the same as in Example 1.

[0121] Comparative Example 5

[0122] A one-component epoxy structural adhesive, comprising 100 parts by weight, includes the following raw materials: 29.75 parts epoxy resin, 12.25 parts toughening agent, 2.8 parts curing agent, 1.75 parts accelerator, 0.35 parts pigment, 1.35 parts silane coupling agent, 0.35 parts fumed silica, 0.8 parts leveling agent, 0.2 parts defoamer, 8.6 parts reinforcing agent, and inorganic filler to make up to 100 parts.

[0123] The reinforcing agent is a combination of hyperbranched polyester Boltorn H20 and glyceryl borate ester, with a mass ratio of 8.5:0.5.

[0124] The remaining implementation methods are the same as in Example 1.

[0125] Performance evaluation test

[0126] The structural adhesives prepared in the examples and comparative examples were cured at 140°C for 30 minutes, and corresponding samples were prepared for testing.

[0127] 1. Tensile shear strength: According to GB / T 7124-2008 standard, the strength of PA66 bonded to PA66 and the shear strength after thermal shock aging were tested. Thermal shock aging conditions: -40℃~105℃, switching time ≤3min, both hot and cold temperatures are maintained for 1h, 10 cycles are performed, and the tensile shear strength before and after thermal shock aging are recorded. The average value of 10 tests is recorded in Table 1.

[0128] 2. Simulated reflow soldering appearance test: After the structural adhesive has cured, the sample is placed in a 260℃ oven for 10 minutes, then allowed to return to room temperature. This process is repeated 5 times. The appearance of the adhesive is observed for cracking or peeling. If any cracking or peeling occurs, the sample is considered unqualified. Otherwise, if no cracking or peeling occurs, the sample is considered qualified. 100 samples are tested for each example and comparative example. The final pass rate is recorded in Table 1.

[0129] 3. Storage stability: The structural adhesives prepared in the examples and comparative examples were placed in a constant temperature oven at 40±1℃, and the specific time (days) required for the viscosity to double was recorded. The results are recorded in Table 1.

[0130] Table 1 Performance Test Results 1

[0131]

[0132] 4. Sealing: Using a standard ceramic encapsulation shell with a through hole, the structural adhesive prepared in the examples and comparative examples was potted into the gap between the pins and the shell hole wall according to the process requirements, and cured under the same conditions (140℃ for 30 min). The internal cavity of the encapsulation shell was filled with helium as a tracer gas, and a helium mass spectrometer was used to detect leaks at 5.0 × 10⁻⁶ m / s. 5Under a helium atmosphere of Pa, the outer surface of the package was inspected using a spray gun method. The flow rate of helium leaking from the inside through the sealant layer was measured. The sealed test piece was first subjected to 100 temperature cycles from -55℃ to 125℃, and then the above test was performed. The helium leakage rate after thermal shock was recorded in Table 2.

[0133] 5. Environmental tolerance: The samples of the examples and comparative examples were placed in a constant temperature and humidity test chamber at 85±2℃ and 90±2% RH for 1000h of continuous aging. After aging, the samples were restored at 23±2℃ and 50±5% RH for 24h. Then, tensile shear strength tests were performed according to performance test 1. The results were taken as the strength retention rate. Strength retention rate (%) = (strength after aging / initial strength) × 100%. The results were recorded in Table 2.

[0134] Table 2 Performance Test Results 2

[0135]

[0136] Analysis of Test Results: Tables 1 and 2 show that Examples 1-4 of this application, by employing the corresponding technical solutions defined in this application, utilize composite toughening agents in conjunction with epoxy composite resins to form a stable connecting structure and elastomer phase within the epoxy composition structural adhesive system. This effectively absorbs and disperses internal stress caused by thermal mismatch, maintaining good application quality during thermal shock cycles and significantly reducing phenomena such as adhesive cracking and bonding interface peeling. Furthermore, the epoxy resin, composite toughening agent, and latent curing system used together constitute a stable material system, systematically solving key problems of traditional single-component epoxy adhesives in connector sealing applications, such as insufficient toughness, poor adhesion to plastics, weak thermal shock resistance, and difficulty in balancing storage stability and curing speed. Comparative Examples 1-5, however, employ different technical solutions than those defined in this application, resulting in a significant decrease in the effectiveness of their respective technologies within the system. Consequently, the overall comprehensive performance of the single-component epoxy composition structural adhesive declines, showing a significant deviation from Examples 1-4.

Claims

1. A one-component epoxy structural adhesive, characterized in that: The total weight is 100 parts, and the raw materials include: 20-35 parts epoxy resin, 5-15 parts toughening agent, 2-5 parts curing agent, 1-5 parts accelerator, 0.2-1 part pigment, 1.2-2 parts silane coupling agent, 0.2-0.5 parts fumed silica, 0.5-2 parts leveling agent, 0.2-0.4 parts defoamer, 5-10 parts reinforcing agent, and inorganic filler to make up to 100 parts; The epoxy resin is a combination of bisphenol F epoxy resin and AG-80 tetrafunctional epoxy resin, with a mass ratio of (6~8):(2~4). The toughening agent is a combination of core-shell structured polymer resin and modified polyurethane resin, with a mass ratio of (4~9):(3~5.5). The accelerator is a modified amine accelerator or an organic guanidine accelerator; The reinforcing agent is a combination of hyperbranched polyester and glycerol borate ester in a mass ratio of (6~9):(1.5~2). The curing agent is at least one of dicyandiamide curing agents; The average D50 particle size of the dicyandiamide curing agent is 4~10μm.

2. The single-component epoxy structural adhesive according to claim 1, characterized in that: The epoxy equivalent of the bisphenol F epoxy resin is 160~210 g / eq.

3. The single-component epoxy structural adhesive according to claim 2, characterized in that: The epoxy equivalent of the AG-80 tetrafunctional epoxy resin is 100~130 g / eq.

4. The single-component epoxy structural adhesive according to claim 3, characterized in that: The silane coupling agent is at least one selected from γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

5. The single-component epoxy structural adhesive according to claim 4, characterized in that: The leveling agent is at least one of BYK-333, BYK-354, BYK-358N, and Tego 410.

6. The single-component epoxy structural adhesive according to claim 5, characterized in that: The inorganic filler is at least one of silicon micro powder, molten silicon micro powder, aluminum hydroxide, or calcium carbonate.

7. The single-component epoxy structural adhesive according to claim 6, characterized in that: The average D50 particle size of the inorganic filler is 5~15μm.

8. A method for preparing a single-component epoxy structural adhesive according to any one of claims 1 to 7, characterized in that: Includes the following steps: S1: Mix part of the silane coupling agent with anhydrous ethanol, stir evenly, adjust the pH with dilute acetic acid and let stand at room temperature to obtain a pretreatment solution for later use. Then add the inorganic filler to a high-speed heating mixer. While stirring, spray the pretreatment solution onto the surface of the turning inorganic filler. After completion, heat up and mix at high speed. After keeping warm, the pretreated inorganic filler is obtained. S2: Add epoxy resin, toughening agent, pretreated inorganic filler, and remaining silane coupling agent to a planetary mixer, rotate at 15~20Hz and 30~35Hz to mix, and then evacuate the vacuum until the mixture is uniform. After mixing, stop stirring and then break the vacuum. S3: Add the remaining raw materials, evacuate the vacuum at room temperature and stir, rotate at 20~25Hz and 35~40Hz until the material is a uniform paste and the air bubbles are uniformly removed. Stop stirring and slowly break the vacuum. Discharge the material into an airtight container to obtain the epoxy structural adhesive.

Images