A bismaleimide-modified epoxy resin and a method for preparing the same

Abstract

The application discloses a bismaleimide modified epoxy resin and a preparation method thereof, relates to the technical field of epoxy resins, and is prepared from bismaleimide, an epoxy resin, a compounded curing agent, a compounded accelerator, a modifier and a composite solvent. The application adopts allylated bismaleimide to modify the molecular structure, effectively improves the compatibility of the bismaleimide and the epoxy resin, and significantly improves the heat resistance. A composite curing system and an efficient accelerator are selected to reduce the process energy consumption. The modified core-shell rubber particle modifier is introduced into the epoxy resin system, which can significantly improve the toughness and impact resistance of the composite material. Meanwhile, the allyl POSS added in the modified core-shell rubber particle can effectively improve the thermal stability and the flame retardance of the resin. The application of the composite solvent can promote the dissolution, balance the viscosity and the volatilization speed. The resin system is particularly suitable for high-end fields such as 5G high-frequency copper-clad plates and aerospace thermal protection coatings.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin technology, specifically to a bismaleimide modified epoxy resin and its preparation method. Background Technology

[0002] As a high-molecular polymer, epoxy resin (EP) possesses characteristics such as convenient curing, strong adhesion, low shrinkage, good chemical resistance, and excellent electrical insulation. It can be used as a matrix resin in coatings, adhesives, castings, molding materials, and fiber-reinforced composites, and is widely applied in numerous industries including transportation, aerospace, machinery and electronics, machinery manufacturing, construction, and chemical corrosion protection, making it an indispensable basic material. With the widespread application of epoxy resin in various sectors of the national economy, epoxy resin composites need to withstand higher temperature conditions. However, epoxy resin is flammable, brittle, has poor resistance to damp heat, and produces dense smoke and molten droplets during combustion, which significantly limits its application in high-tech fields such as aerospace and electronics. People have increasingly higher requirements for its flame retardancy and heat resistance; therefore, EP modification has become a current hot research topic.

[0003] Bismaleimide resin (BMI), also widely used in aerospace, machinery, and electronics, possesses excellent high-temperature resistance, damp-heat resistance, electrical insulation, and flame retardancy. It is commonly used as a resin matrix for advanced composite materials and high-temperature insulating materials. However, its processing performance is relatively poor. High monomer melting point, high crosslinking density of cured products, and high brittleness are major obstacles hindering BMI from meeting high-tech requirements and expanding into new application areas.

[0004] To address the aforementioned problems, this invention provides a bismaleimide-modified epoxy resin and its preparation method. By using BMI as a modifier for epoxy resin (EP), bismaleimide is copolymerized with epoxy resin to modify the epoxy resin, potentially yielding a product that combines the advantages of both. Summary of the Invention

[0005] The purpose of this invention is to provide a bismaleimide modified epoxy resin and its preparation method to solve the problems raised in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a bismaleimide-modified epoxy resin, comprising the following steps:

[0008] Step S1: Under nitrogen protection, the epoxy resin and modifier are mixed evenly, heated to 110-130℃, stirred for 40-60 min, bismaleimide is added, the temperature is raised to 130-150℃, and kept at the temperature for 40-60 min to form a homogeneous system.

[0009] Step S2: Cool the homogeneous system in S1 to 75-85℃, add the composite solvent, stir and filter to obtain the adhesive solution;

[0010] Step S3: Mix the adhesive, compound curing agent, and compound accelerator from S2, keep warm for 30-60 minutes, and then cool down to obtain a bismaleimide modified epoxy resin.

[0011] In a more optimized manner, in step S1, the raw material composition of the homogeneous system, by weight, is: 15-25 parts epoxy resin, 15-30 parts modifier, and 40-50 parts bismaleimide.

[0012] More preferably, the epoxy resin is one or more of the following: furan epoxy resin, tetraglycidylamine type epoxy resin, bisphenol A type epoxy resin, and flame-retardant epoxy resin; the bismaleimide (BMI) is replaced by allylated bismaleimide, which is obtained by introducing an allyloxy group onto the aromatic ring of BMI; the modifier is one or more of the following: core-shell rubber particles, carboxyl-terminated nitrile butadiene rubber, and siloxane modifier.

[0013] More preferably, the modifier is selected as modified core-shell rubber particles, and the modified core-shell rubber particles are prepared by:

[0014] 1) Disperse the dried core-shell rubber particles in toluene aqueous solvent, add γ-mercaptopropyltrimethoxysilane, stir at 450-550 rpm for 30-50 min, and distill under reduced pressure to obtain core-shell rubber particles with silane coupling agent coated on the surface.

[0015] 2) Disperse core-shell rubber particles coated with silane coupling agent in a mixed solvent and ultrasonically disperse for 30-40 min. Under nitrogen protection and in the dark, add photoinitiator and stir for 20-30 min. Add allyl POSS, heat to 50-70℃, and mechanically stir at 300 rpm for 30-40 min. Transfer to a quartz reactor and irradiate in a UV curing machine under a nitrogen atmosphere at a wavelength of 365 nm and a light intensity of 10 mW / cm² for 4-6 min. Centrifuge at 8000 rpm for 10 min, wash, and vacuum dry for 10-12 hours to obtain modified core-shell rubber particles.

[0016] More optimally, by weight, the raw material composition of the core-shell rubber particles coated with silane coupling agent is: 10 parts core-shell rubber particles, 50 parts toluene aqueous solvent, and 0.5 parts γ-mercaptopropyltrimethoxysilane; the raw material composition of the modified core-shell rubber particles is: 3 parts allyl POSS, 0.3 parts photoinitiator, 60 parts mixed solvent, and 10 parts core-shell rubber particles coated with silane coupling agent; the mixed solvent is obtained by mixing acetone and N,N-dimethylformamide at a mass ratio of 7:3; the toluene aqueous solvent is obtained by mixing toluene and water at a volume ratio of 9:1.

[0017] In a more optimized manner, in step S2, the mass ratio of the homogeneous system to the composite solvent in the adhesive solution is (3-4):(6-7).

[0018] The optimal mass ratio of epoxy resin, compound curing agent, and compound accelerator is (15-25):(8-12):(1-2).

[0019] In a more optimized manner, in step S2, the composite solvent is prepared by mixing acetone and N,N-dimethylformamide in a mass ratio of 7:3.

[0020] In a more optimized manner, in step S3, the compound curing agent is composed of a curing agent and a viscosity-reducing auxiliary curing agent in a mass ratio of 7:3; the curing agent is one or more of diaminodiphenyl sulfone, phthalic anhydride, and methyltetrahydrophthalic anhydride, and the viscosity-reducing auxiliary curing agent is methylnadic anhydride.

[0021] Ideally, the particle size of the curing agent is 40-50 μm.

[0022] More optimally, the compound accelerator is composed of an accelerator and an auxiliary accelerator in a mass ratio of 3:1; the accelerator is one or more of 2-ethyl-4-methyl-imidazole, tertiary amine, and dicyandiamide, and the auxiliary accelerator is a urea accelerator.

[0023] The present invention will now be described in more detail. The present invention relates to a bismaleimide-modified epoxy resin and its preparation method.

[0024] In this technical solution, the bismaleimide is replaced by allylated BMI, a product with better reactivity and currently available on the market. The allylated BMI improves its copolymerization ability with epoxy resin by introducing allyl groups onto the nitrogen atom or aromatic ring, while also providing flexible chain segments to enhance toughness. The reaction between the modifier and epoxy resin is carried out in stages with temperature control. A low-temperature pre-reaction is performed first, followed by the addition of BMI. This ensures a complete reaction and prevents excessively high temperatures or prolonged reaction times, which could cause the epoxy resin crosslinks to form a gel-like structure.

[0025] In this invention, modified core-shell rubber particles are used as modifiers, and silane coupling agents are added to bridge the particles and resin. POSS increases the interfacial crosslinking density, and the rigid cage-like skeleton improves the heat resistance and mechanical strength of the material. At the same time, the flexibility and reactivity of allyl groups are used to achieve efficient bonding with the polymer. In addition, allyl POSS provides UV curing sites, and photoinitiators trigger rapid molding.

[0026] The epoxy resin mentioned in step S1 of the present invention is one or more of the following: furan epoxy resin, tetraglycidylamine type epoxy resin, bisphenol A type epoxy resin, and flame-retardant epoxy resin; more preferably, the epoxy resin is selected from bisphenol A type epoxy resin or furan epoxy resin.

[0027] Secondly, due to the high volatility of acetone and methyl ethyl ketone (MEK), the adhesive solution is prone to poor storage stability. The composite solvent is a mixture of acetone and N,N-dimethylformamide in a 7:3 ratio, which reduces VOC emissions. DMF improves BMI solubility, and the composite solvent balances viscosity and evaporation rate. Filtering through a 400-mesh sieve removes bubbles and impurities, and ultrasonic dispersion at 40kHz ensures uniform dispersion of POSS. Because N,N-dimethylformamide has a high boiling point, it must be handled in a fume hood to avoid inhalation.

[0028] In addition, a compound curing agent and a compound accelerator are used to ensure that BMI and epoxy cure simultaneously. The curing agent is one or more of diaminodiphenyl sulfone, phthalic anhydride, and methyltetrahydrophthalic anhydride; more optimally, it is a mixture of a main curing agent and a viscosity-reducing auxiliary curing agent in a 7:3 ratio, wherein the viscosity-reducing auxiliary curing agent is methylnadic anhydride.

[0029] Ideally, the curing agent should be ground into powder in advance to achieve a particle size ≤50μm in order to accelerate dissolution.

[0030] The accelerator is one or more of 2-ethyl-4-methyl-imidazole, tertiary amine, and dicyandiamide, more preferably, the accelerator used in the experiment of the present invention is a mixture of 1.5 parts of dicyandiamide and 0.5 parts of auxiliary accelerator, wherein the auxiliary accelerator is a urea accelerator.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] This invention relates to a bismaleimide-modified epoxy resin prepared from allylated bismaleimide (BMI), epoxy resin, a compound curing agent, a compound accelerator, a modifier, and a compound solvent. This transforms traditional thermosetting resins into next-generation materials characterized by "high toughness, ultra-heat resistance, and low pollution." Traditional BMI has poor compatibility with epoxy resin and a high curing temperature, limiting its application in high-end electronic packaging. The allylated BMI used in this invention shortens the dissolution time, significantly improving heat resistance. Untreated core-shell rubber particles tend to agglomerate in the resin matrix, leading to decreased interfacial bonding and limiting their maximum reinforcing effect. Introducing modified core-shell rubber particles into the epoxy resin system significantly improves the toughness and impact resistance of the composite material. Through multi-stage modification, including precise control of the core-shell structure, silane coupling agent interfacial modification, and the addition of allyl POSS, not only is the dispersion problem of nanoparticles solved, but also a synergistic improvement in the overall performance of the material is achieved, demonstrating its outstanding application potential in high-tech fields such as aerospace structural adhesives and 5G high-frequency electronic packaging.

[0033] Meanwhile, the addition of allyl POSS to the modified core-shell rubber particles can significantly improve the compatibility between bismaleimide (BMI) and epoxy resin, and the rigidity of Si8O 12 The cage-like skeleton can effectively improve the thermal stability and flame retardancy of the resin, giving the cured product both super heat resistance and high toughness. The flexible segments of allyl BMI and the rigid cage structure of POSS synergistically optimize the crosslinking network, improve mechanical and dielectric properties, increase impact strength, and achieve UL94 V-0 flame retardancy by promoting char formation.

[0034] Using a 7:3 composite solvent of acetone and DMF, DMF promotes the stretching of BMI molecular chains, increases crosslinking density, balances viscosity and evaporation rate, and promotes dissolution, making it suitable for complex molding processes. The resin system of this invention is particularly suitable for high-end applications such as 5G high-frequency copper-clad laminates and aerospace thermal protection coatings. It offers low repair costs, high thermal stability, excellent dynamic mechanical properties, good high-temperature performance, and simultaneous V-0 flame retardancy, addressing industry pain points related to high temperatures, damage, and combustion. Its comprehensive performance meets the needs of high-end applications such as 5G high-frequency copper-clad laminates and can be widely used in aerospace, aviation, and electronics fields. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0036] Example 1: A method for preparing a bismaleimide modified epoxy resin, the steps of which are as follows:

[0037] Step S1: Under nitrogen protection, the epoxy resin and modifier are mixed evenly, heated to 110°C, stirred for 60 min, bismaleimide is added, the temperature is raised to 130°C, and kept at that temperature for 40 min to form a homogeneous system.

[0038] Step S2: Cool the homogeneous system in S1 to 80°C, add the composite solvent, stir and filter to obtain the adhesive solution;

[0039] Step S3: Mix the adhesive, compound curing agent, and compound accelerator from S2, keep warm for 50 minutes, and then cool down to obtain a bismaleimide modified epoxy resin.

[0040] The raw material composition of the homogeneous system, by weight, is: 20 parts bisphenol A type epoxy resin, 20 parts modified core-shell rubber particles, and 40 parts allylated bismaleimide.

[0041] The composite solvent is prepared by mixing acetone and N,N-dimethylformamide in a mass ratio of 7:3; the mass ratio of the homogeneous system to the composite solvent in the adhesive solution is 3:7.

[0042] The compound curing agent is composed of diaminodiphenyl sulfone and methylnadic anhydride in a mass ratio of 7:3; the compound accelerator is composed of dicyandiamide and urea accelerator in a mass ratio of 3:1.

[0043] In the preparation of the bismaleimide modified epoxy resin, the mass ratio of epoxy resin, compound curing agent, and compound accelerator is 20:9:1.2.

[0044] The modifier is selected from modified core-shell rubber particles, and the modified core-shell rubber particles are prepared as follows:

[0045] 1) Disperse the dried core-shell rubber particles in toluene aqueous solvent, add γ-mercaptopropyltrimethoxysilane, stir at 500 rpm for 40 min, and distill under reduced pressure to obtain core-shell rubber particles with silane coupling agent coated on the surface.

[0046] 2) Disperse core-shell rubber particles coated with silane coupling agent in a mixed solvent and ultrasonically disperse for 30 min. Under nitrogen protection and in the dark, add photoinitiator and stir for 25 min. Add allyl POSS, heat to 50℃, and mechanically stir at 300 rpm for 30 min. Transfer to a quartz reactor and irradiate in a UV curing machine under a nitrogen atmosphere at a wavelength of 365 nm and a light intensity of 10 mW / cm² for 5 min. Centrifuge at 8000 rpm for 10 min, wash, and vacuum dry for 11 hours to obtain modified core-shell rubber particles.

[0047] More optimally, by weight, the raw material composition of the core-shell rubber particles coated with silane coupling agent is: 10 parts core-shell rubber particles, 50 parts toluene aqueous solvent, and 0.5 parts γ-mercaptopropyltrimethoxysilane; the raw material composition of the modified core-shell rubber particles is: 3 parts allyl POSS, 0.3 parts photoinitiator, 60 parts mixed solvent, and 10 parts core-shell rubber particles coated with silane coupling agent; the mixed solvent is obtained by mixing acetone and N,N-dimethylformamide at a mass ratio of 7:3; the toluene aqueous solvent is obtained by mixing toluene and water at a volume ratio of 9:1.

[0048] Example 2: A method for preparing a bismaleimide modified epoxy resin, the steps of which are as follows:

[0049] Step S1: Under nitrogen protection, the epoxy resin and modifier are mixed evenly, heated to 120°C, stirred for 50 min, bismaleimide is added, the temperature is raised to 130°C, and kept at that temperature for 60 min to form a homogeneous system.

[0050] Step S2: Cool the homogeneous system in S1 to 75°C, add the composite solvent, stir and filter to obtain the adhesive solution;

[0051] Step S3: Mix the adhesive, compound curing agent, and compound accelerator from S2, keep warm for 40 minutes, and then cool down to obtain a bismaleimide modified epoxy resin.

[0052] The raw material composition of the homogeneous system, by weight, is: 17 parts bisphenol A type epoxy resin, 25 parts modified core-shell rubber particles, and 45 parts allylated bismaleimide.

[0053] The composite solvent is prepared by mixing acetone and N,N-dimethylformamide in a mass ratio of 7:3; the mass ratio of the homogeneous system to the composite solvent in the adhesive solution is 3.5:6.5.

[0054] The compound curing agent is composed of diaminodiphenyl sulfone and methylnadic anhydride in a mass ratio of 7:3; the compound accelerator is composed of dicyandiamide and urea accelerator in a mass ratio of 3:1.

[0055] In the preparation of the bismaleimide modified epoxy resin, the mass ratio of epoxy resin, compound curing agent, and compound accelerator is 17:8:1.5.

[0056] More preferably, the modifier is selected as modified core-shell rubber particles, and the modified core-shell rubber particles are prepared by:

[0057] 1) Disperse the dried core-shell rubber particles in toluene aqueous solvent, add γ-mercaptopropyltrimethoxysilane, stir at 500 rpm for 50 min, and distill under reduced pressure to obtain core-shell rubber particles with silane coupling agent coated on the surface.

[0058] 2) Disperse core-shell rubber particles coated with silane coupling agent in a mixed solvent and ultrasonically disperse for 30 min. Under nitrogen protection and in the dark, add photoinitiator and stir for 30 min. Add allyl POSS, heat to 60℃, and mechanically stir at 300 rpm for 40 min. Transfer to a quartz reactor and irradiate in a UV curing machine under a nitrogen atmosphere at a wavelength of 365 nm and a light intensity of 10 mW / cm² for 6 min. Centrifuge at 8000 rpm for 10 min, wash, and vacuum dry for 12 hours to obtain modified core-shell rubber particles.

[0059] More optimally, by weight, the raw material composition of the core-shell rubber particles coated with silane coupling agent is: 10 parts core-shell rubber particles, 50 parts toluene aqueous solvent, and 0.5 parts γ-mercaptopropyltrimethoxysilane; the raw material composition of the modified core-shell rubber particles is: 3 parts allyl POSS, 0.3 parts photoinitiator, 60 parts mixed solvent, and 10 parts core-shell rubber particles coated with silane coupling agent; the mixed solvent is obtained by mixing acetone and N,N-dimethylformamide at a mass ratio of 7:3; the toluene aqueous solvent is obtained by mixing toluene and water at a volume ratio of 9:1.

[0060] Example 3: A method for preparing a bismaleimide modified epoxy resin, the steps of which are as follows:

[0061] Step S1: Under nitrogen protection, the epoxy resin and modifier are mixed evenly, heated to 130°C, stirred for 55 min, bismaleimide is added, the temperature is raised to 150°C, and kept at that temperature for 45 min to form a homogeneous system.

[0062] Step S2: Cool the homogeneous system in S1 to 80°C, add the composite solvent, stir and filter to obtain the adhesive solution;

[0063] Step S3: Mix the adhesive, compound curing agent, and compound accelerator from S2, keep warm for 55 minutes, and then cool down to obtain a bismaleimide modified epoxy resin.

[0064] The raw material composition of the homogeneous system, by weight, is: 30 parts bisphenol A type epoxy resin, 25 parts modified core-shell rubber particles, and 50 parts allylated bismaleimide.

[0065] The composite solvent is prepared by mixing acetone and N,N-dimethylformamide in a mass ratio of 7:3; the mass ratio of the homogeneous system to the composite solvent in the adhesive solution is 4:6.

[0066] The compound curing agent is composed of diaminodiphenyl sulfone and methylnadic anhydride in a mass ratio of 7:3; the compound accelerator is composed of dicyandiamide and urea accelerator in a mass ratio of 3:1.

[0067] In the preparation of the bismaleimide modified epoxy resin, the mass ratio of epoxy resin, compound curing agent, and compound accelerator is 30:10:2.0.

[0068] More preferably, the modifier is selected as modified core-shell rubber particles, and the modified core-shell rubber particles are prepared by:

[0069] 1) Disperse the dried core-shell rubber particles in toluene aqueous solvent, add γ-mercaptopropyltrimethoxysilane, stir at 550 rpm for 50 min, and distill under reduced pressure to obtain core-shell rubber particles with silane coupling agent coated on the surface.

[0070] 2) Disperse core-shell rubber particles coated with silane coupling agent in a mixed solvent and ultrasonically disperse for 40 min. Under nitrogen protection and in the dark, add photoinitiator and stir for 20 min. Add allyl POSS, heat to 70℃, and mechanically stir at 300 rpm for 35 min. Transfer to a quartz reactor and irradiate in a UV curing machine under a nitrogen atmosphere at a wavelength of 365 nm and a light intensity of 10 mW / cm² for 5 min. Centrifuge at 8000 rpm for 10 min, wash, and vacuum dry for 10 hours to obtain modified core-shell rubber particles.

[0071] More optimally, by weight, the raw material composition of the core-shell rubber particles coated with silane coupling agent is: 10 parts core-shell rubber particles, 50 parts toluene aqueous solvent, and 0.5 parts γ-mercaptopropyltrimethoxysilane; the raw material composition of the modified core-shell rubber particles is: 3 parts allyl POSS, 0.3 parts photoinitiator, 60 parts mixed solvent, and 10 parts core-shell rubber particles coated with silane coupling agent; the mixed solvent is obtained by mixing acetone and N,N-dimethylformamide at a mass ratio of 7:3; the toluene aqueous solvent is obtained by mixing toluene and water at a volume ratio of 9:1.

[0072] Comparative Example 1: Example 2 was used as the control group. In step S1, the modified core-shell rubber particles were replaced with core-shell rubber particles, while other processes were normal.

[0073] Comparative Example 2: Using Example 2 as the control group, in step S1, the modified core-shell rubber particles were replaced with core-shell rubber particles coated with silane coupling agent, and other processes were normal.

[0074] Sources of raw materials used (for illustrative purposes only):

[0075] The raw materials used in this technical solution are all commercially available products: allylated bismaleimide: supplied by Evonik under the trade name Compimide® 796; epoxy resin: bisphenol A type epoxy resin sold by Nan Ya Plastics under the trade name NPEL-128; curing agent: diaminodiphenyl sulfone sold by Wuhan Jiyesheng Chemical Co., Ltd. under the trade name 3,3'-diaminodiphenyl sulfone; viscosity-reducing auxiliary curing agent: methyl nadic anhydride sold by Kandis Chemical (Hubei) Co., Ltd.; accelerator: dicyandiamide sold by AlzChem under the trade name DYHARD® 100SF; auxiliary accelerator: urea accelerator sold by Shikoku Kasei under the trade name UR-300; core-shell rubber particles: supplied by Kaneka under the trade name Kane Ace®. The products sold by MX-125 include: coupling agent (sold by Nanjing Shuguang Chemical under the trade name KH-590), allyl POSS (sold by Qiyue Bio under the trade name allyl-heptacyclopentyl POSS), and photoinitiator (sold by Tianjin Jiuri New Materials under the trade name Jiuri 819); acetone, N,N-dimethylformamide, and toluene, analytical grade, purchased commercially.

[0076] Performance testing: The bismaleimide-modified epoxy resins prepared in the examples and comparative examples were tested:

[0077] The prepared bismaleimide-modified epoxy resin was heated and cured in a mold to obtain a sample.

[0078] (1) Differential scanning calorimetry (DSC)

[0079] Differential scanning calorimetry (DSC) was used, with high-purity indium and zinc standards for temperature and heat flux correction. 8 mg of sample was weighed and placed in an aluminum crucible, with high-purity nitrogen (50 mL / min) as the protective atmosphere. The test procedure was set as follows: first, the temperature was increased from 25 °C to 150 °C at a rate of 10 °C / min to eliminate thermal history; then, it was cooled to 25 °C at a rate of 20 °C / min; finally, the temperature was scanned to 300 °C at a rate of 10 °C / min to analyze the glass transition temperature (Tg).

[0080] (2) Thermogravimetric analysis (TGA)

[0081] A simultaneous thermal analyzer was used, with α-Al₂O₃ as the reference. 10 ± 0.5 mg of sample was weighed and placed in a platinum crucible. The temperature was increased from 25 °C to 800 °C at a rate of 10 °C / min under a high-purity air atmosphere (50 mL / min). The 5% weight loss temperature, a key thermal stability parameter, was analyzed by recording the change in sample mass with temperature. Temperature calibration was performed using standard indium, zinc, and gold samples before testing to ensure an accuracy of ±0.5 °C.

[0082] (3) Vertical burning test:

[0083] The UL94 vertical burning tester was used, and the tests were conducted according to GB / T 2408-2021 "Test Method for Burning Performance of Plastics". The specimens were cut to standard dimensions of 125mm × 13mm × 3mm and vertically fixed to the specimen clamping device. A methane flame (flame height 20mm) was applied to the lower end of the specimen for 10 seconds, and the burning time, whether the dripping material ignited the absorbent cotton, and the self-extinguishing time were recorded. Five specimens were tested in each group, and the V-0, V-1, or V-2 rating was assigned based on the burning behavior.

[0084] (4) Universal testing machine:

[0085] The test was conducted using a universal testing machine according to ASTM D638-14, "Standard Test Method for Tensile Properties of Plastics". Cured resin was injection molded into Type I standard dumbbell-shaped specimens (gauge length 50 mm, width 10 mm, thickness 2 mm), and tested at a tensile rate of 5 mm / min in an environment of 25°C and 50% humidity. The tensile strength (MPa) was calculated.

[0086] (5) Cantilever beam impact test:

[0087] The impact test was conducted using a cantilever beam impact testing machine according to ASTM D256-10, "Standard Test Method for Notched Impact Strength of Plastics". The specimen was machined into a strip shape measuring 63.5 mm × 12.7 mm × 3.2 mm, with a pre-made V-notch of 2.54 mm depth in the center. The pendulum energy was 2.75 J, the impact velocity was 3.5 m / s, and the energy absorbed at fracture was measured to calculate the impact strength (kJ / m²).

[0088] (6) Network Analyzer:

[0089] The tests were conducted using a vector network analyzer according to ASTM D150-18, "Test Methods for Dielectric Properties of Solid Electrical Insulators". Resin samples were prepared as 50 mm diameter, 1 mm thick discs, with gold electrodes sputtered onto their surfaces. The dielectric loss tangent (tanδ) was measured at 10 GHz using the coaxial waveguide method. System errors were calibrated using standard polytetrafluoroethylene (PTFE) samples prior to testing.

[0090] According to the standard IPC-TM-650 analysis and evaluation, the test results are as follows:

[0091] Table 1

[0092]

[0093] The analysis results are as follows:

[0094] The resin curing process was analyzed using DSC differential scanning calorimetry. The glass transition temperature of the resin was determined to be 240-256℃ using the second-order heating method, which is 17-48℃ higher than that of the unmodified system. Thermogravimetric analysis showed that the modified resin had a 5% thermal weight loss temperature of 323-330℃ under a nitrogen atmosphere, which is 43-63℃ higher than that of the traditional product, demonstrating excellent thermal stability. Vertical burning tests on the cured resin showed that its flame retardant performance met the UL94 V-0 standard. After 10 seconds of direct flame exposure, the self-extinguishing time of the sample was ≤5 seconds, with no molten dripping. The tensile properties of the cured resin were tested using a universal testing machine. The tensile strength of the resin reached over 81MPa, significantly improved compared to the unmodified system, demonstrating a balance between high rigidity and moderate toughness. The impact resistance of the resin was tested using a cantilever beam impact tester. The notched impact strength was 22.1-23.4kJ / m², a significant improvement compared to the traditional system, indicating that nano-dispersion effectively inhibited crack propagation. The dielectric properties of the resin at 10 GHz were measured using a vector network analyzer. The dielectric loss (tanδ) was significantly reduced compared to the unmodified system, which meets the requirements of 5G high-frequency copper clad laminates for low signal loss.

[0095] Optimized curing process reduces energy consumption, increases the glass transition temperature of the material to 240-256℃, significantly improves thermal stability, enhances dynamic mechanical properties, maintains good high-temperature performance, and meets the comprehensive performance requirements of high-end applications such as 5G high-frequency copper clad laminates.

[0096] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a bismaleimide-modified epoxy resin, characterized in that, The preparation method involves the following steps: Step S1: Under nitrogen protection, the epoxy resin and modifier are mixed evenly, heated to 110-130℃, stirred for 40-60 min, bismaleimide is added, the temperature is raised to 130-150℃, and kept at the temperature for 40-60 min to form a homogeneous system. Step S2: Cool the homogeneous system in S1 to 75-85℃, add the composite solvent, stir and filter to obtain the adhesive solution; Step S3: Mix the adhesive, compound curing agent, and compound accelerator from S2, keep warm for 30-60 minutes, and then cool down to obtain a bismaleimide modified epoxy resin. In step S1, the raw material composition of the homogeneous system, by weight, is: 15-25 parts epoxy resin, 15-30 parts modifier, and 40-50 parts bismaleimide. The modifier is core-shell rubber particles; The core-shell rubber particles are modified core-shell rubber particles, and the modified core-shell rubber particles are prepared as follows: 1) Disperse the dried core-shell rubber particles in toluene aqueous solvent, add γ-mercaptopropyltrimethoxysilane, stir at 450-550 rpm for 30-50 min, and distill under reduced pressure to obtain core-shell rubber particles with silane coupling agent coated on the surface. 2) Disperse the core-shell rubber particles coated with silane coupling agent in a mixed solvent, ultrasonically disperse for 30-40 min, add photoinitiator under nitrogen protection and in the dark, stir for 20-30 min, add allyl POSS, heat to 50-70℃, mechanically stir for 30-40 min, transfer to a quartz reactor, irradiate in a UV curing machine under nitrogen atmosphere for 4-6 min, centrifuge and wash, vacuum dry for 10-12 hours to obtain modified core-shell rubber particles; The toluene aqueous solvent is obtained by mixing toluene and water at a volume ratio of 9:

1. The bismaleimide is an allylated bismaleimide.

2. The method for preparing a bismaleimide-modified epoxy resin according to claim 1, characterized in that: In step S2, the mass ratio of the homogeneous system to the composite solvent in the adhesive solution is (3-4):(6-7).

3. The method for preparing a bismaleimide-modified epoxy resin according to claim 1, characterized in that: The mass ratio of epoxy resin, compound curing agent, and compound accelerator is (15-25):(8-12):(1-2).

4. The method for preparing a bismaleimide-modified epoxy resin according to claim 1, characterized in that: The epoxy resin is one or a blend of several of the following: furan epoxy resin, tetraglycidylamine type epoxy resin, bisphenol A type epoxy resin, and flame-retardant epoxy resin.

5. The method for preparing a bismaleimide-modified epoxy resin according to claim 1, characterized in that: By weight, the raw material composition of the core-shell rubber particles coated with silane coupling agent is: 10 parts core-shell rubber particles, 50 parts toluene aqueous solvent, and 0.5 parts γ-mercaptopropyltrimethoxysilane; the raw material composition of the modified core-shell rubber particles is: 3 parts allyl POSS, 0.3 parts photoinitiator, 60 parts mixed solvent, and 10 parts core-shell rubber particles coated with silane coupling agent; the mixed solvent is obtained by mixing acetone and N,N-dimethylformamide in a mass ratio of 7:

3.

6. The method for preparing a bismaleimide-modified epoxy resin according to claim 1, characterized in that: The composite solvent is prepared by mixing acetone and N,N-dimethylformamide in a mass ratio of 7:

3.

7. The method for preparing a bismaleimide-modified epoxy resin according to claim 1, characterized in that: The compound curing agent is composed of a curing agent and a viscosity-reducing auxiliary curing agent in a mass ratio of 7:

3. The curing agent is one or more of diaminodiphenyl sulfone, phthalic anhydride, and methyltetrahydrophthalic anhydride, and the viscosity-reducing auxiliary curing agent is methylnadic anhydride. The compound accelerator is composed of an accelerator and an auxiliary accelerator in a mass ratio of 3:

1. The accelerator is one or more of 2-ethyl-4-methyl-imidazolium, tertiary amine, and dicyandiamide, and the auxiliary accelerator is a urea accelerator.

8. A bismaleimide-modified epoxy resin, characterized in that: It is prepared according to any one of claims 1-7.

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