An end-amidated hyperbranched benzoxazine hybrid epoxy paste and a method of making the same

Abstract

The application discloses an end-amide hyperbranched benzoxazine hybrid epoxy paste adhesive and a preparation method thereof, relates to the technical field of adhesives, and aims at solving the problems of high linear expansion, high dielectricity and poor temperature resistance of existing epoxy adhesives. The epoxy paste adhesive is prepared from the following raw materials: a multifunctional epoxy resin, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, an end-amide hyperbranched benzoxazine resin, a toughening agent, nano silicon dioxide particles, a coupling agent and a curing agent. The end-amide hyperbranched benzoxazine resin, the multifunctional epoxy resin, the bisphenol A type epoxy resin and the bisphenol F type epoxy resin are added into a reaction kettle, heated, and stirred to obtain a premix; the toughening agent, the nano silicon dioxide particles and the coupling agent are added into the premix after cooling, and stirred to obtain an intermediate product; the curing agent is added into the intermediate product and uniformly mixed at room temperature, so that the epoxy paste adhesive is obtained. The adhesive can be used in the fields of aerospace, high-frequency communication, power electronics and semiconductor packaging.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, specifically to a terminal amide-group hyperbranched benzoxazine hybrid epoxy paste and its preparation method. Background Technology

[0002] Epoxy adhesives possess excellent bond strength, good processability, various curing temperatures, different forms (such as films, liquids, solvent-free pastes, single-component and two-component adhesives), and diverse properties, making them one of the most important classes of adhesive materials in the aerospace field. Pure epoxy resin systems, after curing, exhibit high crosslinking density and high internal stress, but also suffer from drawbacks such as brittleness, poor heat resistance, poor weather resistance, and a high coefficient of linear expansion, affecting their practical application performance. Therefore, developing an epoxy adhesive that combines low linear expansion, low dielectric properties, and excellent high-temperature resistance has significant social value.

[0003] Benzoxazine resins are a class of phenolic resins with unique properties such as excellent heat resistance, flame retardancy, and flexibility in molecular design. Furthermore, they require no catalyst during curing, exhibit zero volume shrinkage, and show no release of small molecules. Therefore, they are widely used in the modification of epoxy resins. Hyperbranched polymers, with their high degree of branching and three-dimensional spherical structures, possess properties such as low melt viscosity, good solubility, and a large number of terminal active groups, making them highly valuable in composite materials, polymer processing, surface modification, and many other fields.

[0004] Existing technologies have extensively reported on the use of hyperbranched benzoxazine blends with other resins in polymer composites and other fields. Application number CN122326151A discloses a low-density, high-temperature, creep-resistant benzoxazine hybrid epoxy paste and its preparation method. Although the benzoxazine used has an amide structure and possesses excellent characteristics such as low density, high temperature resistance, and creep resistance, introducing weakly bonded amide bonds into the polymer chain carries the risk of oxidative breakage at high temperatures, leading to polymer thermal decomposition. Furthermore, it does not address reducing the linear expansion coefficient and dielectric constant of the adhesive. CN120289789A discloses an allyl hyperbranched benzoxazine for toughening bismaleimide resins. While it exhibits good tensile strength, flexural strength, and heat resistance, it primarily focuses on the bulk modification of the resin and does not address research on low linear expansion and low dielectric constant, nor does it address its application in the field of structural adhesives. CN107383300A discloses a method for synthesizing diamine-triphenol type hyperbranched polybenzoxazine, but its structure does not include a trifluoroacetamide structure, and it also does not focus on the application of benzoxazine in epoxy resin modification, or on the research of materials in the field of low linear expansion and low dielectric properties. Furthermore, CN105694756A discloses a heat-resistant benzoxazine structural adhesive film, which has a long shelf life, high adhesive strength, and high-temperature resistance. However, it does not address the linear expansion phenomenon of the adhesive during the heat curing process, or its dielectric properties. Moreover, the adhesive film does not have the good coatability of a paste adhesive, and it has significant shortcomings in bonding irregular structures. Summary of the Invention

[0005] The present invention aims to solve the problems of high linear expansion, high dielectric constant and poor temperature resistance of existing epoxy adhesives, and provides a terminal amide group hyperbranched benzoxazine hybrid epoxy paste and its preparation method.

[0006] This invention provides an amide-terminated hyperbranched benzoxazine hybrid epoxy paste, which is prepared from the following raw materials in parts by weight: 35-50 parts of multifunctional epoxy resin, 25-45 parts of bisphenol A type epoxy resin, 15-25 parts of bisphenol F type epoxy resin, 18-45 parts of amide-terminated hyperbranched benzoxazine resin, 12-24 parts of toughening agent, 5-15 parts of nano silica particles, 0.5-1.5 parts of coupling agent, and 12-30 parts of curing agent;

[0007] The molecular structural formula of the terminal amide group hyperbranched benzoxazine resin is:

[0008] or

[0009] A mixture of one or two of them in any proportion.

[0010] Furthermore, the multifunctional epoxy resin is one or a mixture of several of AFG-90, TDE-85, AG80, and AG70.

[0011] Furthermore, the bisphenol A type epoxy resin is one or a mixture of several of E55, E54, E51, and E44.

[0012] Furthermore, the bisphenol F type epoxy resin is one or a mixture of two of CYDF-170 and CYDF-180.

[0013] Furthermore, the toughening agent is a core-shell toughening particle. The core-shell toughening particle is one or more of polybutadiene-polymethyl methacrylate, polybutadiene-polystyrene, polybutyl acrylate-polymethyl methacrylate, and polybutyl acrylate-polystyrene.

[0014] Furthermore, the particle size of the nano-silica particles is 10~200 nm.

[0015] Furthermore, the coupling agent is one or a mixture of several of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-mercaptopropyltriethoxysilane.

[0016] Further, the curing agent is 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenylmethane, 4,4'-methylenebis(2-ethyl)aniline, or dicyandiamine.

[0017] This invention also provides a method for preparing a terminal amide-group hyperbranched benzoxazine hybrid epoxy paste, comprising the following steps:

[0018] Step 1: Weigh the following raw materials according to the following weight proportions: 35-50 parts of multifunctional epoxy resin, 25-45 parts of bisphenol A type epoxy resin, 15-25 parts of bisphenol F type epoxy resin, 18-45 parts of amide-terminated hyperbranched benzoxazine resin, 12-24 parts of toughening agent, 5-15 parts of nano silica particles, 0.5-1.5 parts of coupling agent, and 12-30 parts of curing agent;

[0019] Step 2: Add the terminal amide group hyperbranched benzoxazine resin, multifunctional epoxy resin, bisphenol A type epoxy resin, and bisphenol F type epoxy resin to a reactor equipped with a heating and stirring device, heat to 110℃~130℃, stir and mix to obtain a homogeneous hybrid resin premix; then cool to 100℃~110℃, add toughening agent, nano silica particles and coupling agent, stir and mix to obtain an intermediate product;

[0020] Step 3: Add curing agent to intermediate product and mix evenly at room temperature to obtain low linear expansion, low dielectric and high temperature resistant terminal amide group hyperbranched benzoxazine hybrid epoxy paste.

[0021] The beneficial effects of this invention are:

[0022] 1. This invention constructs a polymer network unit with synergistic and mutually reinforcing effects by compounding terminal amide-group hyperbranched benzoxazine resin with multifunctional epoxy resins, bisphenol A type epoxy resins, and bisphenol F type epoxy resins. Specifically, the amide groups, epoxy groups, amino groups, and hydroxyl groups formed by ring-opening of benzoxazine react with each other, and the amide groups can also promote the curing of the amino and epoxy groups, while the hydroxyl groups formed by epoxy ring-opening promote the ring-opening of benzoxazine. This invention optimizes thermal expansion characteristics and dielectric properties by controlling the amount of each component to balance the temperature resistance and toughness of the hybrid resin.

[0023] 2. The amide-terminated hyperbranched benzoxazine resin used in this invention contains highly branched side chains and a large number of terminal amide functional groups. Due to the absence of chain entanglement in its molecular structure, the hyperbranched structure results in lower viscosity in the polymer solution or melt. This low viscosity characteristic gives the hyperbranched polymer better flowability during processing, which helps reduce processing temperature and energy consumption. Under heating, the terminal amide functional groups react with the epoxy resin; the proton hydrogen on the amino group attacks the epoxy group, causing the benzoxazine to be hybridized and grafted into the epoxy resin structure. Furthermore, the amide structure of benzoxazine promotes the curing reaction between the amine curing agent and the epoxy resin. These three factors synergistically promote each other, achieving a ternary copolymerization effect. This not only significantly reduces the curing temperature of benzoxazine but also enables cross-linking and curing among the three components, greatly improving the overall performance of the hybrid resin. Tests showed that, compared with adhesives without terminal amide-group hyperbranched benzoxazine resin, under the same curing conditions of 120℃ / 2h + 150℃ / 2h, adhesives with terminal amide-group hyperbranched benzoxazine resin exhibited higher bond strength, with a room temperature shear strength greater than 28 MPa and a 90° peel strength greater than 4 kN / m.

[0024] 3. This invention introduces a trifluoroacetylamino group at the end of the hyperbranched benzoxazine. The fluorine (F) element in its molecular structure reduces the polarity of the molecule, thereby lowering the dielectric constant of the resin. Furthermore, the hyperbranched polymer possesses numerous branching points and branched structures, with a molecular structure approximating a three-dimensional sphere or quasi-sphere. This structure results in a large number of holes and voids within the polymer molecule, thus imparting low dielectric properties. In addition, the terminal amide bond readily forms hydrogen bonds with the matrix resin, thereby inhibiting the orientation polarization of polar groups under an electric field, which could further reduce the dielectric constant. The unique molecular design can further enhance the thermal stability of the adhesive.

[0025] 4. In this invention, the hyperbranched benzoxazine molecules interweave to form numerous nanoscale cavities, while the thermal stress transmission path is dispersed by a large number of branching points. This reduces the curing volume shrinkage rate of the resin by absorbing deformation energy and avoiding stress accumulation. Simultaneously, the amide-terminated hyperbranched benzoxazine possesses both amide-terminal groups compatible with nano-silica particles and chain segments compatible with epoxy resins, significantly reducing stress concentration at the interface between the inorganic filler and the matrix resin. The hyperbranched structure and the introduction of amide-terminated groups effectively reduce the coefficient of thermal expansion of the epoxy paste.

[0026] This invention achieves a comprehensive performance improvement in adhesives through multi-component synergistic design. The paste-like adhesive possesses multiple characteristics, including low linear expansion, low dielectric constant, high temperature resistance, and high bond strength, meeting the stringent requirements of lightweight, high reliability, and long lifespan for structural bonding materials in high-end fields such as aerospace and rail transportation. This invention is applicable to structural bonding needs in multiple high-end fields, including aerospace, high-frequency communications, power electronics, and advanced semiconductor packaging. Detailed Implementation

[0027] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0028] Specific Implementation Method 1: The amide-terminated hyperbranched benzoxazine hybrid epoxy paste of this implementation method is prepared from the following raw materials in parts by weight: 35-50 parts of multifunctional epoxy resin, 25-45 parts of bisphenol A type epoxy resin, 15-25 parts of bisphenol F type epoxy resin, 18-45 parts of amide-terminated hyperbranched benzoxazine resin, 12-24 parts of toughening agent, 5-15 parts of nano silica particles, 0.5-1.5 parts of coupling agent, and 12-30 parts of curing agent;

[0029] The molecular structural formula of the terminal amide group hyperbranched benzoxazine resin is:

[0030] or

[0031] A mixture of one or two of them in any proportion.

[0032] Specific Implementation Method Two: The multifunctional epoxy resin described in this implementation method is one or a mixture of several of AFG-90, TDE-85, AG80, and AG70. Other steps and parameters are the same as in Specific Implementation Method One.

[0033] Specific Implementation Method 3: The bisphenol A type epoxy resin described in this implementation method is one or a mixture of several of E55, E54, E51, and E44. Other steps and parameters are the same as in Specific Implementation Method 1 or 2.

[0034] Specific Embodiment Four: The bisphenol F type epoxy resin described in this embodiment is one or a mixture of two of CYDF-170 and CYDF-180. Other steps and parameters are the same as in Specific Embodiments One to Three.

[0035] Specific Implementation Method 5: The toughening agent described in this implementation method is a core-shell toughening particle. Other steps and parameters are the same as in Specific Implementation Methods 1 to 4.

[0036] Specific Implementation Method Six: The core-shell toughening particles described in this implementation method are one or more of polybutadiene-polymethyl methacrylate, polybutadiene-polystyrene, polybutyl acrylate-polymethyl methacrylate, and polybutyl acrylate-polystyrene. Other steps and parameters are the same as in Specific Implementation Method Five.

[0037] Specific Implementation Method Seven: The particle size of the nano-silica particles described in this implementation method is 10~200 nm. Other steps and parameters are the same as in Specific Implementation Methods One to Six.

[0038] Specific Embodiment Eight: The coupling agent described in this embodiment is one or a mixture of several of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-mercaptopropyltriethoxysilane. Other steps and parameters are the same as in any one of Specific Embodiments One to Seven.

[0039] Specific Embodiment Nine: The curing agent in this embodiment is 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenylmethane, 4,4'-methylenebis(2-ethyl)aniline, or dicyandiamine. Other steps and parameters are the same as in Specific Embodiments One to Eight.

[0040] Specific Implementation Method 10: The preparation method of the terminal amide group hyperbranched benzoxazine hybrid epoxy paste in this implementation method includes the following steps:

[0041] Step 1: Weigh the following raw materials according to the following weight proportions: 35-50 parts of multifunctional epoxy resin, 25-45 parts of bisphenol A type epoxy resin, 15-25 parts of bisphenol F type epoxy resin, 18-45 parts of amide-terminated hyperbranched benzoxazine resin, 12-24 parts of toughening agent, 5-15 parts of nano silica particles, 0.5-1.5 parts of coupling agent, and 12-30 parts of curing agent;

[0042] Step 2: Add the terminal amide group hyperbranched benzoxazine resin, multifunctional epoxy resin, bisphenol A type epoxy resin, and bisphenol F type epoxy resin to a reactor equipped with a heating and stirring device, heat to 110℃~130℃, stir and mix to obtain a homogeneous hybrid resin premix; then cool to 100℃~110℃, add toughening agent, nano silica particles and coupling agent, stir and mix to obtain an intermediate product;

[0043] Step 3: Add curing agent to intermediate product and mix evenly at room temperature to obtain low linear expansion, low dielectric and high temperature resistant terminal amide group hyperbranched benzoxazine hybrid epoxy paste.

[0044] The embodiments of the present invention will be described in detail below. The following embodiments are implemented based on the technical solution of the present invention, and detailed implementation schemes and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0045] Example 1:

[0046] The preparation method of the terminal amide group hyperbranched benzoxazine hybrid epoxy paste in this embodiment is specifically carried out according to the following steps:

[0047] Step 1: Weigh out the following components by weight: 40 parts of multifunctional epoxy resin, 35 parts of bisphenol A type epoxy resin, 20 parts of bisphenol F type epoxy resin, 30 parts of amide-terminated hyperbranched benzoxazine resin, 20 parts of toughening agent, 10 parts of nano silica particles, 1.2 parts of coupling agent, and 20 parts of curing agent.

[0048] The molecular structural formula of the terminal amide group hyperbranched benzoxazine resin is as follows:

[0049] .

[0050] The multifunctional epoxy resin is AG80, the bisphenol A type epoxy resin is E51, the bisphenol F type epoxy resin is CYDF-170, the toughening agent is core-shell toughening particles, the particle size of the nano silica particles is 50 nm, the coupling agent is γ-aminopropyltrimethoxysilane, and the curing agent is 4,4'-methylenebis(2-ethyl)aniline.

[0051] Step 2: The weighed multifunctional epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and terminal amide group hyperbranched benzoxazine resin are added to a reactor equipped with a heating and stirring device. The temperature is raised to 120°C, and the mixture is stirred at 1000 r / min for 2 h to obtain a homogeneous hybrid resin. Then the temperature is lowered to 100°C, toughening agent, nano silica particles and coupling agent are added, and the mixture is stirred at 900 r / min for 2 h to obtain an intermediate product.

[0052] Step 3: Add curing agent to the intermediate product obtained in Step 2, and stir and mix at 400 r / min at 50℃ for 1 h to obtain terminal amide group hyperbranched benzoxazine hybrid epoxy paste.

[0053] Example 2:

[0054] The preparation method of the terminal amide group hyperbranched benzoxazine hybrid epoxy paste in this embodiment is specifically carried out according to the following steps:

[0055] Step 1: Weigh out the following components by weight: 40 parts of multifunctional epoxy resin, 40 parts of bisphenol A type epoxy resin, 25 parts of bisphenol F type epoxy resin, 40 parts of amide-terminated hyperbranched benzoxazine resin, 20 parts of toughening agent, 15 parts of nano silica particles, 1.5 parts of coupling agent, and 25 parts of curing agent.

[0056] The molecular structure of the terminal amide group hyperbranched benzoxazine resin is as follows:

[0057] .

[0058] The multifunctional epoxy resin is a mixture of AG80 and AFG90 in a mass ratio of 2:1; the bisphenol A type epoxy resin is a mixture of E51 and E44 in a mass ratio of 1:1; the bisphenol F type epoxy resin is CYDF-180; the toughening agent is core-shell toughening particles; the particle size of the nano silica particles is 50 nm; the coupling agent is γ-mercaptopropyltrimethoxysilane; and the curing agent is a mixture of 4,4'-methylenebis(2-ethyl)aniline and 4,4'-diaminodiphenylmethane in a mass ratio of 1:1.

[0059] Step 2: The weighed multifunctional epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and amide-terminated hyperbranched benzoxazine resin are added to a reactor equipped with a heating and stirring device. The temperature is raised to 130°C, and the mixture is stirred at 1100 r / min for 2 h to obtain a homogeneous hybrid resin. Then the temperature is lowered to 100°C, toughening agent, nano silica particles and coupling agent are added, and the mixture is stirred at 800 r / min for 2 h to obtain an intermediate product.

[0060] Step 3: Add curing agent to the intermediate product obtained in Step 2, and stir and mix at 50°C and 500 r / min for 2 h to obtain terminal amide group hyperbranched benzoxazine hybrid epoxy paste.

[0061] Example 3:

[0062] The preparation method of the terminal amide group hyperbranched benzoxazine hybrid epoxy paste in this embodiment is specifically carried out according to the following steps:

[0063] Step 1: Weigh out the following components by weight: 50 parts of multifunctional epoxy resin, 40 parts of bisphenol A type epoxy resin, 20 parts of bisphenol F type epoxy resin, 45 parts of amide-terminated hyperbranched benzoxazine resin, 24 parts of toughening agent, 15 parts of nano silica particles, 1.5 parts of coupling agent, and 26 parts of curing agent.

[0064] The molecular structure of the terminal amide group hyperbranched benzoxazine resin is as follows:

[0065] and A mixture in a mass ratio of 1:1.

[0066] The multifunctional epoxy resin is a mixture of AG80 and AG70 in a mass ratio of 3:1; the bisphenol A type epoxy resin is a mixture of E51 and E54 in a mass ratio of 2:1; the bisphenol F type epoxy resin is CYDF-170; the toughening agent is core-shell toughening particles; the particle size of the nano silica particles is 50 nm; the coupling agent is γ-glycidoxypropyltrimethoxysilane; and the curing agent is a mixture of 4,4'-methylenebis(2-ethyl)aniline and 4,4'-diaminodiphenyl sulfone in a mass ratio of 2:1.

[0067] Step 2: The weighed multifunctional epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and amide-terminated hyperbranched benzoxazine resin are added to a reactor equipped with a heating and stirring device. The temperature is raised to 120°C, and the mixture is stirred at 1100 r / min for 2.5 h to obtain a homogeneous hybrid resin. Then the temperature is lowered to 100°C, toughening agent, nano silica particles and coupling agent are added, and the mixture is stirred at 1000 r / min for 2 h to obtain an intermediate product.

[0068] Step 3: Add curing agent to the intermediate product obtained in Step 2, and stir and mix at 500 r / min at 45℃ for 2 h to obtain terminal amide group hyperbranched benzoxazine hybrid epoxy paste.

[0069] Comparative Example 1:

[0070] The difference between this comparative example and Example 1 is that no terminal amide group hyperbranched benzoxazine resin is added in step one, while the other components, dosages, steps and parameters are the same as in Example 1.

[0071] Comparative Example 2:

[0072] The difference between this comparative example and Example 1 is that: in step one, terminal amide-group hyperbranched benzoxazine resin is not added; instead, ordinary benzoxazine resin is used, and its molecular structure is:

[0073]

[0074] The other components, dosages, steps, and parameters are the same as in Example 1.

[0075] Comparative Example 3:

[0076] The difference between this comparative example and Example 1 is that: in step one, terminal amide-terminated hyperbranched benzoxazine resin is not added, but terminal hydroxyl-terminated hyperbranched benzoxazine resin is used instead, and its molecular structure is:

[0077]

[0078] The other components, dosages, steps, and parameters are the same as in Example 1.

[0079] Comparative Example 4:

[0080] The difference between this comparative example and Example 1 is that: in step one, the terminal trifluoroacetamide hyperbranched benzoxazine resin is not added, but replaced with terminal acetamide hyperbranched benzoxazine resin, whose molecular structure is:

[0081]

[0082] The other components, dosages, steps, and parameters are the same as in Example 1.

[0083] Comparative Example 5:

[0084] The difference between this comparative example and Example 1 is that no nano-silica particles are added in step one, while the other components, dosages, steps, and parameters are the same as in Example 1.

[0085] Comparative Example 6:

[0086] The difference between this comparative example and Example 1 is that no core-shell toughening particles are added in step one, while the other components, dosages, steps, and parameters are the same as in Example 1.

[0087] The epoxy paste adhesives obtained in Examples 1 to 3 and the adhesives prepared in Comparative Examples 1 to 6 were cured at 120℃ / 2h + 150℃ / 2h and their performance was tested. The results are shown in Table 1.

[0088] The testing standards adopted are as follows:

[0089] (1) Room temperature shear strength: The bonded material is 2A12 aluminum alloy. Before bonding, the surface is subjected to phosphoric acid anodizing treatment. After curing, the test is carried out according to GB / T 7124-2008 standard.

[0090] (2) Peel strength of floating roll: Tested according to GB / T 7122-2025 standard.

[0091] (3) Linear expansion coefficient: The average linear expansion coefficient of the material was measured in accordance with ISO 11359-2:2021 Thermomechanical analysis of plastics (TMA) Part 2: Determination of linear thermal expansion coefficient and glass transition temperature.

[0092] (4) Dielectric constant: Tested in accordance with GB / T 31838.8-2024 standard.

[0093] Table 1 Performance Summary Table

[0094]

[0095] (1) As can be seen from the test results of Examples 1 to 3, the amide-terminated hyperbranched benzoxazine hybrid epoxy paste prepared in this invention, after curing at 120℃ / 3h + 180℃ / 2h, has a room temperature shear strength greater than 28MPa, a 90° peel strength greater than 4.0kN / m, and a 220℃ shear strength greater than 10MPa; the coefficient of thermal expansion of the adhesive resin after curing is only 50 μm•(m•°C). -1 The dielectric constant at 18.3 GHz is below 2.93. It possesses multiple properties including low linear expansion coefficient, low dielectric constant, high room temperature bond strength, and high temperature resistance. This invention achieves precise control of the crosslinked network structure through the precise formulation of terminal amide-group hyperbranched benzoxazine resins, simultaneously meeting the performance requirements of low linear expansion and low dielectric constant.

[0096] (2) Combining the technical solutions of the comparative example and Example 1, it can be seen from the data in Table 1 that the terminal amide group hyperbranched benzoxazine resin was omitted in Comparative Example 1. The prepared paste adhesive has relatively low shear strength at 220°C and peel strength at 90°C, and the linear expansion coefficient is greater than 50 μm•(m•°C). -1 Meanwhile, the dielectric constant also reached 3.89. This indicates that the amide-terminated hyperbranched benzoxazine resin is indispensable; otherwise, it would be impossible to obtain a hybrid resin system with low dielectric constant and low linear expansion through hybridization with various epoxy resins.

[0097] (3) Combining the technical solutions of Comparative Example 2 and Example 1, it can be seen from the data in Table 1 that the commercially available ordinary bisphenol A type benzoxazine in Comparative Example 2 replaced the terminal amide group hyperbranched benzoxazine resin of the present invention. Its molecular structure does not contain F element, amide group, or a large number of branched molecular chains. The results show that the dielectric constant of Comparative Example 2 is as high as 3.57, and the 90° peel strength also decreases to 2.9 kN / m, and the temperature resistance also decreases significantly (the shear strength at 220°C is only 7.2 MPa). This shows that the trifluoroacetamide group is the core mechanism of the present invention to promote curing and reduce dielectric properties, and the branched chain containing alkynyl groups plays a role in achieving both rigidity and flexibility. The alkynyl groups polymerize and carbonize at high temperature, which toughens the adhesive without damaging its temperature resistance, proving the uniqueness and irreplaceability of the structural design of the terminal amide group hyperbranched benzoxazine resin of the present invention.

[0098] (4) Combining the technical solutions of Comparative Example 3 and Example 1, it can be seen from the data in Table 1 that the benzoxazine resin without terminal amide groups was not added in Comparative Example 3. The results show that the shear strength at 220℃ is only 7.6 MPa. This indicates that the amide group introduced in this invention plays a role in reducing the curing temperature. The lack of amide functional groups promotes the curing reaction, and according to the curing process of 120℃ / 2h + 150℃ / 2h, the benzoxazine hybrid epoxy paste cannot achieve the ideal shear strength at 220℃. The amide group is the key component for achieving the curing of the paste at 120℃ / 2h + 150℃ / 2h.

[0099] (5) Combining the technical solutions of Comparative Example 4 and Example 1, it can be seen from the data in Table 1 that Comparative Example 4 did not add terminal trifluoroacetamide-terminated hyperbranched benzoxazine resin. The results show that the dielectric constant of the adhesive after curing also reached 3.45. This fully demonstrates that the F atom has a stronger electron-withdrawing effect than other atoms, a larger atomic volume, and a smaller polarization ability of the CF bond, which has the effect of reducing the dielectric constant of the adhesive.

[0100] (6) Combining the technical solutions of Comparative Example 5 and Example 1, it can be seen from the data in Table 1 that no nano-silica particles were added in Comparative Example 5, and the results show that the linear expansion coefficient reached 69 μm•(m•°C). -1 During heating, the material undergoes significant deformation. This indicates that the nano-silica particles introduced in this invention, acting as a functional filler, effectively reduce the linear expansion coefficient. Without this filler, the thermal expansion coefficient increases, leading to greater deformation. This filler is a crucial component for achieving a low linear expansion coefficient in the paste-like adhesive. Further combining the technical solutions of Comparative Examples 2, 5, and 1, the data in Table 1 shows that in Comparative Example 2, replacing the terminal amide-group hyperbranched benzoxazine resin of this invention with commercially available bisphenol A type benzoxazine resulted in a linear expansion coefficient of 56 μm•(m•°C). -1This indicates that the numerous branching points of hyperbranched benzoxazine disperse the stress concentration of the resin during thermal expansion, thereby reducing the curing volume shrinkage rate of the resin. Hyperbranched benzoxazine is a key component for improving the low linear expansion coefficient of paste adhesives.

[0101] (7) Based on the technical solution of Comparative Example 6 and Example 1, it can be seen from the data in Table 1 that no core-shell toughening particles were added in Comparative Example 6, and the other components were the same as in Example 1. The results show that the room temperature shear strength of Comparative Example 6 dropped sharply to 24.0 MPa, and the 90° peel strength was only 1.9 kN / m, which was much lower than that of Example 1. This indicates that the lack of core-shell toughening particles in this invention makes it impossible to synergistically toughen with the branched segments in the hyperbranched benzoxazine resin molecular structure with terminal amide groups, resulting in a significant decrease in shear strength and peel strength.

Claims

1. A terminal amide-group hyperbranched benzoxazine hybrid epoxy paste, characterized in that, The terminal amide-group hyperbranched benzoxazine hybrid epoxy paste is prepared from the following raw materials in parts by weight: 35-50 parts of multifunctional epoxy resin, 25-45 parts of bisphenol A type epoxy resin, 15-25 parts of bisphenol F type epoxy resin, 18-45 parts of terminal amide-group hyperbranched benzoxazine resin, 12-24 parts of toughening agent, 5-15 parts of nano silica particles, 0.5-1.5 parts of coupling agent, and 12-30 parts of curing agent; The molecular structural formula of the terminal amide group hyperbranched benzoxazine resin is: or A mixture of one or two of them in any proportion.

2. The amide-terminated hyperbranched benzoxazine hybrid epoxy paste according to claim 1, characterized in that, The multifunctional epoxy resin is one or a mixture of several of AFG-90, TDE-85, AG80, and AG70.

3. The amide-terminated hyperbranched benzoxazine hybrid epoxy paste according to claim 1, characterized in that, The bisphenol A type epoxy resin is one or a mixture of several of E55, E54, E51, and E44.

4. The amide-terminated hyperbranched benzoxazine hybrid epoxy paste according to claim 1, characterized in that, The bisphenol F type epoxy resin is one or a mixture of two of CYDF-170 and CYDF-180.

5. The amide-terminated hyperbranched benzoxazine hybrid epoxy paste according to claim 1, characterized in that, The toughening agent is a core-shell toughening particle.

6. The amide-terminated hyperbranched benzoxazine hybrid epoxy paste according to claim 5, characterized in that, The core-shell toughening particles are one or more of polybutadiene-polymethyl methacrylate, polybutadiene-polystyrene, polybutyl acrylate-polymethyl methacrylate, and polybutyl acrylate-polystyrene.

7. The amide-terminated hyperbranched benzoxazine hybrid epoxy paste according to claim 1, characterized in that, The particle size of the nano-silica particles is 10~200 nm.

8. The amide-terminated hyperbranched benzoxazine hybrid epoxy paste according to claim 1, characterized in that, The coupling agent is one or a mixture of several of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-mercaptopropyltriethoxysilane.

9. The amide-terminated hyperbranched benzoxazine hybrid epoxy paste according to claim 1, characterized in that, The curing agent is 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenylmethane, 4,4'-methylenebis(2-ethyl)aniline, or dicyandiamine.

10. The method for preparing the terminal amide group hyperbranched benzoxazine hybrid epoxy paste as described in claim 1, characterized in that, The method includes the following steps: Step 1: Weigh the following raw materials according to the following weight proportions: 35-50 parts of multifunctional epoxy resin, 25-45 parts of bisphenol A type epoxy resin, 15-25 parts of bisphenol F type epoxy resin, 18-45 parts of amide-terminated hyperbranched benzoxazine resin, 12-24 parts of toughening agent, 5-15 parts of nano silica particles, 0.5-1.5 parts of coupling agent, and 12-30 parts of curing agent; Step 2: Add the terminal amide group hyperbranched benzoxazine resin, multifunctional epoxy resin, bisphenol A type epoxy resin, and bisphenol F type epoxy resin to a reactor equipped with a heating and stirring device, heat to 110℃~130℃, stir and mix to obtain a homogeneous hybrid resin premix; then cool to 100℃~110℃, add toughening agent, nano silica particles and coupling agent, stir and mix to obtain an intermediate product; Step 3: Add curing agent to intermediate product and mix evenly at room temperature to obtain low linear expansion, low dielectric and high temperature resistant terminal amide group hyperbranched benzoxazine hybrid epoxy paste.

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