Two-component polyurethane structural adhesive and preparation method thereof

Abstract

The invention relates to the technical field of polyurethane structural adhesives, in particular to a two-component polyurethane structural adhesive and a preparation method thereof. Comprising a component A and a component B. The component A comprises, by weight, 70-130 parts of polyether polyol, 1-5 parts of a chain extender, 5-10 parts of a flame retardant, 6-12 parts of a first dewatering agent, 3-5 parts of a thixotropic agent, 0.06-1 part of a catalyst and 110-200 parts of a modified heat-conducting filler. The component B is prepared from 70 to 130 parts of polyurethane prepolymer, 0.5 to 2 parts of second dewatering agent and 110 to 200 parts of modified heat-conducting filler; the technical problems that in the prior art, a polyurethane system adhesive is serious in cohesive strength attenuation under the working condition of 80 DEG C and low in high-temperature shear strength retention rate are solved by providing the double-component polyurethane structural adhesive.

Description

Technical Field

[0001] This invention relates to the field of polyurethane structural adhesives, and in particular to a two-component polyurethane structural adhesive and its preparation method. Background Technology

[0002] Against the backdrop of the new energy vehicle industry's accelerated transformation towards high-quality development, power batteries, as core components, are undergoing dual technological innovations in integration and performance optimization. With the industry's new energy vehicle penetration rate expected to exceed 41% in the first quarter of 2025, the large-scale application of module-less technologies such as CTP / CTC / CTB has significantly improved battery pack integration, and adhesives have evolved from traditional auxiliary materials into a core structural medium determining system reliability.

[0003] Current technological iterations exhibit two key characteristics: First, structural adhesives need to replace metal connectors (reducing weight by 30%-40%) while achieving a synergistic effect of high shear strength (≥8MPa), V0 flame retardancy, and lightweight (density ≤1.5g / cm³); Second, with battery energy density exceeding 360Wh / kg, the internal temperature gradient of the cell is 2-3 times larger than in traditional designs, impacting the thermal conductivity of the adhesive material (≥1.5W / m³). The CTP (Chip-to-Pack) architecture places more stringent requirements on heat resistance and high-temperature stability. Market data shows that the CTP architecture has increased the amount of adhesive used per vehicle to over 5 kg, an increase of more than 400% compared to the module era.

[0004] However, existing polyurethane adhesives suffer from severe cohesive strength degradation and low high-temperature shear strength retention at 80°C, which limits the thermal management efficiency of high-energy-density batteries. To meet the requirements of advanced systems such as solid-state batteries for interfacial stress management, there is an urgent need to develop a thermally conductive polyurethane structural adhesive that is low-density and retains ≥60% of its high-temperature shear strength without compromising thermal conductivity and flame retardant properties. Summary of the Invention

[0005] The purpose of this invention is to provide a two-component polyurethane structural adhesive and its preparation method. By proposing a two-component polyurethane structural adhesive, the technical problems of severe cohesive strength attenuation and low high-temperature shear strength retention rate of polyurethane adhesives in the prior art are solved.

[0006] This invention provides a two-component polyurethane structural adhesive, comprising component A and component B, wherein, by weight parts, Component A includes 70-130 parts of polyether polyol, 1-5 parts of chain extender, 5-10 parts of flame retardant, 6-12 parts of primary dehydrating agent, 3-5 parts of thixotropic agent, 0.06-1 parts of catalyst, and 110-200 parts of modified thermally conductive filler. Component B comprises 70-130 parts of polyurethane prepolymer, 0.5-2 parts of second dehydrating agent, and 110-200 parts of modified thermally conductive filler.

[0007] Preferably, the modified thermally conductive filler is obtained by surface treatment of the thermally conductive filler with liquid N-phenylamino-POSS; The thermally conductive filler comprises aluminum hydroxide and nano-silicon carbide whiskers, with a mass ratio of aluminum hydroxide to nano-silicon carbide whiskers of 1.2:1; The modifier is 0.15%-0.6% of the mass of the thermally conductive filler.

[0008] Preferably, the method for preparing the polyurethane prepolymer is as follows: Polycarbonate diol is added to a reaction vessel, heated to 100-110℃, stirred and dehydrated under a vacuum of 0.1MPa for 2-3 hours, cooled to 60℃, and protected with nitrogen. Diphenylmethane diisocyanate is added, heated to 70-75℃, and reacted for 3-4 hours to obtain polyurethane prepolymer.

[0009] Preferably, the polyether polyol is one or more of polypropylene glycol, polyglycerol, polytetrahydrofuran ether diol, or bisphenol A polyoxypropylene ether; and the chain extender is one or more of 1,4-butanediol, 1,5-pentanediol, or 1,6-hexanediol.

[0010] Preferably, the flame retardant is one or more of TCPP, TCEP, or DMMP.

[0011] Preferably, the first dehydrating agent is one or more of 4A molecular sieve powder, anhydrous calcium chloride, or anhydrous calcium carbonate.

[0012] Preferably, the thixotropic agent is one or more of fumed silica, organobentonite, or polyamide wax.

[0013] Preferably, the catalyst is one or more of the following: tin-based catalysts, organozinc catalysts, or organobismuth catalysts.

[0014] Preferably, the second dehydrating agent is one or both of isocyanates or oxazolidines.

[0015] The present invention provides a method for preparing a two-component polyurethane structural adhesive as described in any of the above, comprising the following steps: Aluminum hydroxide and nano-silicon carbide were mixed at a mass ratio of 1.2:1. After stirring evenly, a modifier was added and mixed evenly to obtain a modified thermally conductive filler. Polyol, chain extender, flame retardant, first dehydrating agent, thixotropic agent and modified thermally conductive filler are added to the reactor, heated to 100-110℃, stirred and dehydrated for 2 hours under vacuum of 0.1MPa, cooled to 60℃, catalyst is added, and stirred and degassed for 30 minutes under vacuum of 0.1MPa to obtain component A. Polyurethane prepolymer and modified thermally conductive filler were added to a reactor and stirred evenly. Then, a second dehydrating agent was added and stirred and degassed for 1 hour under a vacuum of 0.1 MPa to obtain component B. After mixing component A and component B at a volume ratio of 1:1, a two-component polyurethane structural adhesive is obtained.

[0016] The two-component polyurethane structural adhesive provided by this invention has the following advantages compared with the prior art: 1. The two-component polyurethane structural adhesive proposed in this invention uses a composite system of aluminum hydroxide and nano-silicon carbide whiskers as thermally conductive fillers. Through the synergistic effect of the high thermal conductivity of nano-silicon carbide and the barrier effect of aluminum hydroxide, a high thermal conductivity is achieved with a relatively low filler content, while simultaneously controlling the density of the structural adhesive to 1.6 g / cm³. 3 Within a certain range, it meets the requirements for lightweight power battery packs.

[0017] 2. The two-component polyurethane structural adhesive proposed in this invention uses liquid N-phenylamino-POSS as a functional modifier. Liquid N-phenylamino-POSS has a nanocage-like silicon-oxygen skeleton (an octahedral structure composed of Si-O-Si bonds) and eight peripheral benzene ring groups to form an organic-inorganic hybrid system. Liquid N-phenylamino-POSS treats the surface of the thermally conductive filler, uniformly coating the surface of the thermally conductive filler, achieving molecular-level dispersion and effectively inhibiting the agglomeration of the thermally conductive filler. Compared with traditional powdered POSS, the dispersion uniformity is improved. It is precisely because of the liquid properties of N-phenylamino-POSS and the directional bonding between its amino groups and isocyanates that the thermal stability of the polymer backbone is significantly improved, and the shear strength retention rate at 80°C reaches more than 60%.

[0018] 3. The two-component polyurethane structural adhesive proposed in this invention, after liquid N-phenylamino-POSS is incorporated into the polymer backbone, the nanocage structure in N-phenylamino-POSS delays thermal decomposition through a physical barrier effect, and its benzene ring groups help promote char formation. Together with the endothermic decomposition products of aluminum hydroxide (alumina, water vapor), phosphorus-containing free radicals generated by the decomposition of liquid flame retardants, etc., a multi-level flame retardant synergistic effect is formed in the gas phase and condensed phase, giving the structural adhesive superior flame retardancy. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention provides a two-component polyurethane structural adhesive, comprising component A and component B, wherein, by weight parts, Component A includes 70-130 parts of polyether polyol, 1-5 parts of chain extender, 5-10 parts of flame retardant, 6-12 parts of primary dehydrating agent, 3-5 parts of thixotropic agent, 0.06-1 parts of catalyst, and 110-200 parts of modified thermally conductive filler. Component B comprises 70-130 parts of polyurethane prepolymer, 0.5-2 parts of second dehydrating agent, and 110-200 parts of modified thermally conductive filler.

[0021] Specifically, the modified thermally conductive filler is obtained by surface treatment of the thermally conductive filler with liquid N-phenylamino-POSS; The thermally conductive filler comprises aluminum hydroxide and nano-silicon carbide whiskers, with a mass ratio of aluminum hydroxide to nano-silicon carbide whiskers of 1.2:1; The modifier is 0.15%-0.6% of the mass of the thermally conductive filler.

[0022] Specifically, the method for preparing the polyurethane prepolymer is as follows: Polycarbonate diol is added to a reaction vessel, heated to 100-110℃, stirred and dehydrated under a vacuum of 0.1MPa for 2-3 hours, cooled to 60℃, and protected with nitrogen. Diphenylmethane diisocyanate is added, heated to 70-75℃, and reacted for 3-4 hours to obtain polyurethane prepolymer.

[0023] Specifically, the polyether polyol is one or more of polypropylene glycol, polyglycerol, polytetrahydrofuran ether diol, or bisphenol A polyoxypropylene ether; the chain extender is one or more of 1,4-butanediol, 1,5-pentanediol, or 1,6-hexanediol.

[0024] Specifically, the flame retardant is one or more of TCPP, TCEP, or DMMP.

[0025] Specifically, the first dehydrating agent is one or more of 4A molecular sieve powder, anhydrous calcium chloride, or anhydrous calcium carbonate.

[0026] Specifically, the thixotropic agent is one or more of fumed silica, organobentonite, or polyamide wax.

[0027] Specifically, the catalyst is one or more of the following: tin-based catalysts, organozinc catalysts, or organobismuth catalysts.

[0028] Specifically, the second dehydrating agent is one or both of isocyanates or oxazolidines.

[0029] The present invention provides a method for preparing a two-component polyurethane structural adhesive as described in any of the above, comprising the following steps: Aluminum hydroxide and nano-silicon carbide were mixed at a mass ratio of 1.2:1. After stirring evenly, a modifier was added and mixed evenly to obtain a modified thermally conductive filler. Polyol, chain extender, flame retardant, first dehydrating agent, thixotropic agent and modified thermally conductive filler are added to the reactor, heated to 100-110℃, stirred and dehydrated for 2 hours under vacuum of 0.1MPa, cooled to 60℃, catalyst is added, and stirred and degassed for 30 minutes under vacuum of 0.1MPa to obtain component A. Polyurethane prepolymer and modified thermally conductive filler were added to a reactor and stirred evenly. Then, a second dehydrating agent was added and stirred and degassed for 1 hour under a vacuum of 0.1 MPa to obtain component B. After mixing component A and component B at a volume ratio of 1:1, a two-component polyurethane structural adhesive is obtained.

[0030] The thermally conductive filler of this invention employs a composite system of aluminum hydroxide and nano-silicon carbide whiskers. Through the synergistic effect of the high thermal conductivity of nano-silicon carbide and the barrier effect of aluminum hydroxide, a high thermal conductivity is achieved with a relatively low filler content, while simultaneously controlling the density of the structural adhesive to 1.6 g / cm³. 3 Within a certain range, it meets the requirements for lightweight power battery packs.

[0031] This invention utilizes liquid N-phenylamino-POSS as a functional modifier. Liquid N-phenylamino-POSS possesses a nanocage-like silicon-oxygen framework (an octahedral structure composed of Si-O-Si bonds) forming an organic-inorganic hybrid system with eight peripheral benzene ring groups. Liquid N-phenylamino-POSS treats the surface of the thermally conductive filler, uniformly coating it to achieve molecular-level dispersion and effectively inhibit filler agglomeration. Compared to traditional powdered POSS, the dispersion uniformity is improved. Due to the liquid nature of N-phenylamino-POSS and the directional bonding between its amino groups and isocyanates, the thermal stability of the polymer backbone is significantly enhanced, achieving a shear strength retention rate of over 60% at 80°C.

[0032] Furthermore, after liquid N-phenylamino-POSS is incorporated into the polymer backbone, the nanocage structure in N-phenylamino-POSS delays thermal decomposition through a physical barrier effect. Its benzene ring groups help promote char formation. Together with the endothermic decomposition products of aluminum hydroxide (alumina, water vapor) and phosphorus-containing free radicals generated by the decomposition of liquid flame retardants, a multi-level flame-retardant synergistic effect is formed in the gas phase and condensed phase, giving the structural adhesive superior flame retardancy.

[0033] Example 1 The method for preparing a two-component polyurethane structural adhesive provided by the present invention includes the following steps: 101) Mix 550 parts of aluminum hydroxide and 477 parts of nano silicon carbide at a mass ratio of 1.2:1, add to a high-speed mixer and stir until uniform, then add 3 parts of liquid N-phenylamino-POSS, disperse and mix at 2000 rpm for 10 min, and obtain the modified thermally conductive filler after uniform mixing. 102) Add 105 parts of polyether polyol, 1 part of chain extender, 5 parts of flame retardant, 10 parts of first dehydrating agent, 3 parts of thixotropic agent and 160 parts of modified thermally conductive filler to a reactor, heat to 100°C, stir and dehydrate for 2 hours under vacuum of 0.1 MPa, cool to 60°C, add 0.07 parts of catalyst, stir and degas for 30 minutes under vacuum of 0.1 MPa to obtain component A; The polyether polyol in this embodiment comprises 65 parts of bisphenol A polyoxypropylene ether and 40 parts of polypropylene glycol DL-1000D. The chain extender is 1,4-butanediol.

[0034] The flame retardant in this embodiment is TCPP; The first dehydrating agent in this embodiment is 4A molecular sieve powder; In this embodiment, the thixotropic agent is fumed silica; The catalyst in this embodiment is a tin-based catalyst; 103) Add 64 parts of polycarbonate diol to a reactor, heat to 100°C, stir and dehydrate for 2 hours under a vacuum of 0.1 MPa, cool to 60°C, purge with nitrogen for protection, add 100 parts of diphenylmethane diisocyanate, heat to 70°C, react for 3 hours to obtain polyurethane prepolymer; add 110 parts of polyurethane prepolymer and 165 parts of modified thermally conductive filler to a reactor, stir evenly, add 1.5 parts of the second dehydrating agent, stir and degas for 1 hour under a vacuum of 0.1 MPa to obtain component B; The second dehydrating agent in this embodiment is an isocyanate; 104) Mix component A and component B evenly at a volume ratio of 1:1 to obtain a two-component polyurethane structural adhesive.

[0035] The two-component polyurethane structural adhesive obtained in this embodiment was tested for shear strength, density, thermal conductivity, and flame retardant properties. The test results are shown in Table 1.

[0036] Shear strength: Tested according to GB / T 7124-2008. Components A and B were mixed in proportion and then evenly applied to an untreated 3003 aluminum sheet (100mm×25mm×2mm). The bonding method was aluminum-aluminum bonding, and the adhesive layer thickness was 0.2mm. The sample was cured for 7 days at 23±2℃ and 50±5%RH before shear strength testing.

[0037] Density: Tested according to GB / T 13354-1992.

[0038] Thermal conductivity: tested according to GB / T 29313-2012.

[0039] Flame retardant performance: tested according to GB / T 2408-2021.

[0040] Example 2 The method for preparing a two-component polyurethane structural adhesive provided by the present invention includes the following steps: 201) Mix 550 parts of aluminum hydroxide and 477 parts of nano silicon carbide at a mass ratio of 1.2:1, add to a high-speed mixer and stir until uniform, then add 1.5 parts of liquid N-phenylamino-POSS, disperse and mix at 2000 rpm for 10 min, and obtain the modified thermally conductive filler after uniform mixing. 202) Add 130 parts of polyether polyol, 5 parts of chain extender, 10 parts of flame retardant, 12 parts of first dehydrating agent, 5 parts of thixotropic agent and 200 parts of modified thermally conductive filler to a reactor, heat to 110°C, stir and dehydrate for 2 hours under vacuum of 0.1 MPa, cool to 60°C, add 1 part of catalyst, stir and degas for 30 minutes under vacuum of 0.1 MPa to obtain component A; In this embodiment, the polyether polyol is 90 parts of bisphenol A polyoxypropylene ether and 40 parts of polypropylene glycol DL-1000D. The chain extender is 1,5-pentanediol.

[0041] The flame retardant in this embodiment is DMMP; The first dehydrating agent in this embodiment is anhydrous calcium chloride; The thixotropic agent in this embodiment is organic bentonite.

[0042] The catalyst in this embodiment is an organozinc catalyst.

[0043] 203) Add 64 parts of polycarbonate diol to a reactor, heat to 100-110℃, stir and dehydrate for 2 hours under vacuum of 0.1MPa, cool to 60℃, purge with nitrogen for protection, add 100 parts of diphenylmethane diisocyanate, heat to 75℃, react for 4 hours to obtain polyurethane prepolymer; add 130 parts of polyurethane prepolymer and 200 parts of modified thermally conductive filler to a reactor, stir evenly, add 2 parts of second dehydrating agent, stir and degas for 1 hour under vacuum of 0.1MPa to obtain component B; The second dehydrating agent in this embodiment is an oxazolidine-based agent.

[0044] 204) Mix component A and component B evenly at a volume ratio of 1:1 to obtain a two-component polyurethane structural adhesive.

[0045] The two-component polyurethane structural adhesive obtained in this embodiment was tested for shear strength, density, thermal conductivity, and flame retardant properties. The test results are shown in Table 1.

[0046] Shear strength: Tested according to GB / T 7124-2008. Components A and B were mixed in proportion and then evenly applied to an untreated 3003 aluminum sheet (100mm×25mm×2mm). The bonding method was aluminum-aluminum bonding, and the adhesive layer thickness was 0.2mm. The sample was cured for 7 days at 23±2℃ and 50±5%RH before shear strength testing.

[0047] Density: Tested according to GB / T 13354-1992.

[0048] Thermal conductivity: tested according to GB / T 29313-2012.

[0049] Flame retardant performance: tested according to GB / T 2408-2021.

[0050] Example 3 The method for preparing a two-component polyurethane structural adhesive provided by the present invention includes the following steps: 301) Mix 550 parts of aluminum hydroxide and 477 parts of nano silicon carbide at a mass ratio of 1.2:1, add to a high-speed mixer and stir until uniform, then add 6 parts of liquid N-phenylamino-POSS, disperse and mix at 2000 rpm for 10 min, and obtain the modified thermally conductive filler after uniform mixing. 302) Add 70 parts of polyether polyol, 5 parts of chain extender, 10 parts of flame retardant, 6 parts of first dehydrating agent, 5 parts of thixotropic agent and 110 parts of modified thermally conductive filler to a reactor, heat to 105℃, stir and dehydrate for 2 hours under vacuum of 0.1MPa, cool to 60℃, add 0.08 parts of catalyst, stir and degas for 30 minutes under vacuum of 0.1MPa to obtain component A; In this embodiment, the polyether polyol is 30 parts of bisphenol A polyoxypropylene ether and 40 parts of polypropylene glycol DL-1000D. The chain extenders are 1,4-butanediol and 1,6-hexanediol.

[0051] The flame retardants in this embodiment are TCPP and DMMP; The first dehydrating agent in this embodiment is anhydrous calcium carbonate; The thixotropic agent in this embodiment is polyamide wax.

[0052] The catalyst in this embodiment is an organobismuth catalyst.

[0053] 303) Polycarbonate diol was added to a reactor, heated to 105°C, and stirred for 2 hours under a vacuum of 0.1 MPa to remove water. The temperature was then lowered to 60°C, nitrogen gas was introduced for protection, diphenylmethane diisocyanate was added, and the temperature was raised to 72°C. The reaction was carried out for 3-4 hours to obtain a polyurethane prepolymer. 70 parts of the polyurethane prepolymer and 110 parts of the modified thermally conductive filler were added to a reactor, stirred evenly, and then 0.5 parts of the second dehydrating agent were added. The mixture was stirred for 1 hour under a vacuum of 0.1 MPa to remove bubbles to obtain component B. The second dehydrating agent in this embodiment is one or both of isocyanates or oxazolidines.

[0054] 304) Mix component A and component B evenly at a volume ratio of 1:1 to obtain a two-component polyurethane structural adhesive.

[0055] The two-component polyurethane structural adhesive obtained in this embodiment was tested for shear strength, density, thermal conductivity, and flame retardant properties. The test results are shown in Table 1.

[0056] Shear strength: Tested according to GB / T 7124-2008. Components A and B were mixed in proportion and then evenly applied to an untreated 3003 aluminum sheet (100mm×25mm×2mm). The bonding method was aluminum-aluminum bonding, and the adhesive layer thickness was 0.2mm. The sample was cured for 7 days at 23±2℃ and 50±5%RH before shear strength testing.

[0057] Density: Tested according to GB / T 13354-1992.

[0058] Thermal conductivity: tested according to GB / T 29313-2012.

[0059] Flame retardant performance: tested according to GB / T 2408-2021.

[0060] Example 4 The only difference between this embodiment and Embodiment 1 is that in step 102, the polyether polyol is 65 parts of polyglycerol and 40 parts of polypropylene glycol DL-1000D. The two-component polyurethane structural adhesive obtained in this embodiment was tested for shear strength, density, thermal conductivity and flame retardancy. The test results are shown in Table 1.

[0061] Example 5 The only difference between this embodiment and Embodiment 1 is that in step 102, the polyether polyol is 65 parts of polyglycerol and 40 parts of polypropylene glycol DL-2000D. The two-component polyurethane structural adhesive obtained in this embodiment was tested for shear strength, density, thermal conductivity and flame retardancy. The test results are shown in Table 1.

[0062] Comparative Example 1 The only difference between this comparative example and Example 1 is the absence of the modification step of the thermally conductive filler in step 101. The obtained two-component polyurethane structural adhesive was tested for shear strength, density, thermal conductivity and flame retardancy. The test results are shown in Table 1.

[0063] Comparative Example 2 The only difference between this comparative example and Example 1 is that the modifier in step 101 is silane coupling agent KH-560. The obtained two-component polyurethane structural adhesive was tested for shear strength, density, thermal conductivity and flame retardancy. The test results are shown in Table 1.

[0064] Comparative Example 3 The only difference between this comparative example and Example 1 is that the modifier in step 101 is solid octaphenyl-POSS. The obtained two-component polyurethane structural adhesive was tested for shear strength, density, thermal conductivity and flame retardancy. The test results are shown in Table 1.

[0065] Comparative Example 4 The only difference between this comparative example and Example 1 is that the thermally conductive filler in step 101 is talc. The obtained two-component polyurethane structural adhesive was tested for shear strength, density, thermal conductivity and flame retardant properties. The test results are shown in Table 1.

[0066] Comparative Example 5 The only difference between this comparative example and Example 1 is that the amount of modifier added in step 101 is 7 parts. The obtained two-component polyurethane structural adhesive was tested for shear strength, density, thermal conductivity and flame retardancy. The test results are shown in Table 1.

[0067] Comparative Example 6 The only difference between this comparative example and Example 1 is that the thermally conductive filler in step 101 is only aluminum hydroxide. The obtained two-component polyurethane structural adhesive was tested for shear strength, density, thermal conductivity and flame retardant properties. The test results are shown in Table 1.

[0068] Some of the raw material suppliers in the above embodiments are as follows: Bisphenol A polyoxypropylene ether was purchased from Zhejiang Huangma Technology Co., Ltd. Polyether polyol DL-1000D was purchased from Shandong Lanxing Dongda Co., Ltd. The polyether polyol DL-2000D was purchased from Shandong Lanxing Dongda Co., Ltd. Polyglycerol was purchased from Shandong Lanxing Dongda Co., Ltd. The polyether polyol was purchased from Shandong Lanxing Dongda Co., Ltd. 1,4-Butanediol, 1,5-pentanediol or 1,6-hexanediol were all purchased from Sichuan Tianhua Chemical Group Co., Ltd. Flame retardants TCPP, TCEP, and DMMP were all purchased from Hefei Wanran New Materials Technology Co., Ltd. Tin-based catalysts, organozinc catalysts, and organobismuth catalysts were all purchased from Guangzhou Yourun Synthetic Materials Co., Ltd. 4A molecular sieve activated powder was purchased from Jiangxi Xintao Technology Co., Ltd. Fumed silica was purchased from Evonik Specialty Chemicals (Shanghai) Co., Ltd. The isocyanate was purchased from Wanhua Chemical Group Co., Ltd. Polycarbonate diol was purchased from Huizhou Daya Bay Dazhi Fine Chemical Co., Ltd. Silane coupling agent KH-560 was purchased from Hangzhou Jessica Chemical Co., Ltd. Solid cage-type polysilsesquioxane octaphenyl-POSS was purchased from Xi'an Qiyue Biotechnology Co., Ltd. Liquid cage-type polysilsesquioxane N-phenylamino POSS was purchased from Forsmann Technology (Beijing) Co., Ltd. Aluminum hydroxide was purchased from Chinalco Shandong Co., Ltd. The nano-silicon carbide whiskers were purchased from Ningbo Luofei Nanotechnology Co., Ltd.

[0069] Table 1. Performance test results of the two-component polyurethane structural adhesives prepared in the examples and comparative examples.

[0070] From the test results in Table 1, the 80℃ shear strength retention rate of Examples 1 to 5, Comparative Examples 4 and 5 all exceeded 60%, which was significantly higher than that of Comparative Examples 1 to 3.

[0071] Examples 1 to 5, and Comparative Examples 4 and 5, which use liquid N-phenylamino-POSS, show better performance than Comparative Example 1 (without liquid N-phenylamino-POSS), Comparative Example 2 (using conventional silane coupling agent KH-560), and Comparative Example 3 (using solid octaphenyl-POSS). This demonstrates that the introduction of liquid N-phenylamino-POSS is the decisive factor in achieving high-temperature shear strength retention. Its liquid properties and amino functional groups effectively improve the thermal stability of the material by improving filler dispersibility and bonding with the polyurethane backbone.

[0072] Comparative Example 4 used talc as a filler, whose thermal conductivity was much lower than that of Example 1, and its flame retardancy rating was only V-1. Comparative Example 6 used aluminum hydroxide as a single filler; although its other properties were similar to those of Example 1, its thermal conductivity was lower than that of the other examples. The fillers used in Examples 1 to 5 were a composite system of aluminum hydroxide and nano-silicon carbide whiskers, which has high thermal conductivity (≥1.5 W / (m·K)) and a V-0 flame retardancy rating. Therefore, the selection of filler has a crucial impact on the performance of the entire system.

[0073] The room temperature shear strength (10.5 MPa) and 80°C shear strength (6.5 MPa) of Example 5 are slightly lower than those of other examples. This is mainly because the polyether polyol used in Example 5 is polypropylene glycol DL-2000D. The molecular weight, functionality and hydroxyl value of polypropylene glycol DL-2000D are different from those of polypropylene glycol DL-1000D used in Example 1. It can be seen that the type of polyol has a certain impact on the performance. However, the high temperature performance improvement (retention rate of 61.9%) brought about by liquid N-phenylamino-POSS modification is still significant.

[0074] The flame retardant properties of Examples 1 to 5 were significantly improved compared to Comparative Examples 1 and 2. The improved flame retardant properties were due to the aluminum hydroxide / nano silicon carbide whisker composite system and its synergistic effect with POSS and flame retardants.

[0075] Both Example 3 and Comparative Example 5 exhibited excellent room temperature and high temperature shear strength due to the addition of high amounts of liquid N-phenylamino-POSS, indicating that appropriately increasing the amount of liquid N-phenylamino-POSS is beneficial to improving mechanical properties. However, increasing the amount of N-phenylamino-POSS from 6 parts to 7 parts did not significantly improve performance, suggesting that there is an economically effective optimization range for the amount of POSS added; excessive addition may lead to increased costs with limited performance benefits.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A two-component polyurethane structural adhesive characterized by: Comprise A component and B component, wherein, according to weight fraction, A component includes polyether polyol 70-130 parts, chain extender 1-5 parts, flame retardant 5-10 parts, first water removing agent 6-12 parts, thixotropic agent 3-5 parts, catalyst 0.06-1 parts and modified thermal conductive filler 110-200 parts; B component includes polyurethane prepolymer 70-130 parts, second water removing agent 0.5-2 parts and modified thermal conductive filler 110-200 parts.

2. The two-component polyurethane structural adhesive according to claim 1, wherein: The modified thermal conductive filler is obtained by surface treatment of the thermal conductive filler with liquid N-phenyl amino-POSS; The thermal conductive filler comprises aluminum hydroxide and nano silicon carbide whiskers, and the mass ratio of aluminum hydroxide to nano silicon carbide whiskers is 1.2:1; The modifier is 0.15%-0.6% of the mass of the thermal conductive filler.

3. The two-component polyurethane structural adhesive according to claim 1, characterized in that: The polyurethane prepolymer is prepared by: Adding polycarbonate diol into a reaction kettle, heating to 100-110℃, stirring and dehydrating under the condition of 0.1MPa vacuum for 2-3h, cooling to 60℃, filling with nitrogen protection, adding diphenyl methane diisocyanate, heating to 70-75℃, and reacting for 3-4h to obtain polyurethane prepolymer.

4. The two-component polyurethane structural adhesive according to claim 1, characterized in that: The polyether polyol is one or more of polypropylene glycol, polyglycerol, polytetrahydrofuran ether diol or bisphenol A polyoxypropylene ether; The chain extender is one or more of 1,4-butanediol, 1,5-pentanediol or 1,6-hexanediol.

5. The two-component polyurethane structural adhesive according to claim 1, characterized in that: The flame retardant is one or more of TCPP, TCEP or DMMP.

6. The two-component polyurethane structural adhesive according to claim 1, characterized in that: The first water removing agent is one or more of 4A molecular sieve powder, anhydrous calcium chloride or anhydrous calcium carbonate.

7. The two-component polyurethane structural adhesive according to claim 1, wherein: The thixotropic agent is one or more of fumed silica, organic bentonite or polyamide wax.

8. The two-component polyurethane structural adhesive according to claim 1, characterized in that: The catalyst is one or more of tin-based catalyst, organic zinc-based catalyst or organic bismuth-based catalyst.

9. The two-component polyurethane structural adhesive according to claim 1, characterized in that: The second water removing agent is one or more of isocyanate or oxazolidine.

10. A process for the preparation of a two-component polyurethane structural adhesive based on any one of claims 1-9, characterized by: Comprise the following steps: Mixing aluminum hydroxide and nano silicon carbide according to a mass ratio of 1.2:1, stirring uniformly, adding a modifier, mixing uniformly to obtain a modified thermal conductive filler; Adding polyol, chain extender, flame retardant, first water removing agent, thixotropic agent and modified thermal conductive filler into a reaction kettle, heating to 100-110℃, stirring and dehydrating under the condition of 0.1MPa vacuum for 2h, cooling to 60℃, adding a catalyst, stirring and defoaming under the condition of 0.1MPa vacuum for 30min to obtain A component; Adding polyurethane prepolymer and modified thermal conductive filler into a reaction kettle, stirring uniformly, adding a second water removing agent, stirring and defoaming under the condition of 0.1MPa vacuum for 1h to obtain B component; Mixing A component and B component according to a volume ratio of 1:1 uniformly to obtain a two-component polyurethane structural adhesive.

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