Latent epoxy resin curing catalyst with precisely controllable activity and preparation method thereof

Abstract

This invention relates to the field of catalyst technology, specifically to a latent epoxy resin curing catalyst with precisely controllable activity and its preparation method. The catalyst is 1-(2-(N-tert-butyl-N'-phenylurea)ethyl)-3-(2-(phenyldithio)ethyl)imidazolium, which simultaneously possesses an imidazolium ring catalytic active center, a thermally hindered urea bond, a temperature-responsive dynamic disulfide bond, and an intramolecular hydrogen bond unit. Precise control of catalytic activity is achieved through the synergistic effect of these triple dynamic bonds. The catalyst exhibits excellent storage stability at room temperature, rapid curing at activation temperature, and is free of metal ions. The cured epoxy resin exhibits good dielectric properties. This invention's catalyst achieves a balance between excellent latency and rapid curing performance through the synergistic control of these triple dynamic bonds. It possesses excellent dielectric and mechanical properties, can be compounded with various curing agents, and its preparation method is simple and easy for industrial production.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a latent epoxy resin curing catalyst with precisely controllable activity and its preparation method. Background Technology

[0002] Epoxy resin, as a thermosetting resin with excellent comprehensive properties, is widely used in high-end fields such as electronic packaging, aerospace, and automotive manufacturing. Latent curing catalysts are the core materials that determine the processing performance and final product performance of epoxy resin systems. An ideal latent curing catalyst must simultaneously meet three requirements: long-term storage stability at room temperature, rapid curing at high temperatures, and excellent product performance after curing.

[0003] Currently, commonly used latent curing catalysts in industry mainly include imidazole derivatives, urea compounds, and organometallic complexes. Among them, imidazole catalysts are the most widely used due to their high catalytic activity and good overall performance of the cured products. However, unmodified imidazole catalysts have excessively high activity at room temperature, and their storage period after mixing with epoxy resin is usually less than one week, which cannot meet the needs of large-scale industrial production and long-distance transportation.

[0004] To improve the latency of imidazole catalysts, existing technologies mainly employ modification methods such as urea-termination, quaternization, and salt formation with acid anhydrides. However, urea-modified imidazole catalysts typically suffer from a single activation temperature, making precise control impossible for different application scenarios. While quaternization and acid anhydride salt formation modifications improve latency, they significantly reduce curing activity, requiring higher curing temperatures and longer curing times. Furthermore, the cured products are prone to retaining ionic impurities, leading to deterioration of dielectric properties.

[0005] While organometallic complex catalysts possess a certain degree of latency, the presence of metal ions significantly increases the dielectric constant and dielectric loss of epoxy resin systems after curing, failing to meet the stringent low dielectric performance requirements of 5G and higher-frequency communication devices. Furthermore, existing latent catalysts modified with a single dynamic bond, such as those introducing only disulfide or urea bonds, suffer from drawbacks including difficulty in balancing latency and curing activity, and a narrow activation temperature range. These limitations prevent them from simultaneously meeting the dual demands of ultra-long shelf life and rapid curing, severely restricting the further application of epoxy resins in high-end fields. Summary of the Invention

[0006] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a latent epoxy resin curing catalyst with precisely controllable activity and its preparation method.

[0007] (II) Technical Solution A latent epoxy resin curing catalyst with precisely tunable activity is disclosed. The catalyst is 1-(2-(N-tert-butyl-N'-phenylurea)ethyl)-3-(2-(phenyldithio)ethyl)imidazolium. The catalyst molecule simultaneously possesses an imidazolium ring catalytic active center, a thermally responsive hindered urea bond substituted with N-tert-butyl, a temperature-responsive dynamic disulfide bond substituted with phenyl, and an intramolecular hydrogen bond donor-acceptor interaction unit between the urea group and the imidazolium ring. Precise control of catalytic activity is achieved through the synergistic effect of the triple dynamic bonds. The activation temperature of the catalyst is 110℃-120℃. The catalyst does not contain metal ions, and the dielectric constant of the cured epoxy resin system does not exceed 3.1 at 1MHz, and the dielectric loss does not exceed 0.007.

[0008] Preferably, in the above catalyst molecule, the N-tert-butyl substituent of the hindered urea bond provides a steric hindrance effect, shielding the catalytic activity of the imidazole ring at room temperature; the dynamic disulfide bond undergoes reverse breakage-recombination at 110℃-120℃, releasing 30%-40% of the catalytic active sites; the intramolecular hydrogen bond gradually breaks above 105℃, further activating the remaining 60%-70% of the catalytic activity of the imidazole ring.

[0009] Preferably, the catalyst has a particle size distribution of 2μm-8μm, a purity of not less than 99.6%, a moisture content of not more than 0.08%, and a chloride ion content of not more than 3ppm.

[0010] Preferably, the preparation method of the above-mentioned latent epoxy resin curing catalyst with precisely controllable activity includes the following steps: S1. 1-(2-aminoethyl)imidazole and 2-chloroethylphenyl disulfide were added to N,N-dimethylformamide solvent in a molar ratio of 1:1.05-1:1.1, and anhydrous potassium carbonate was added as an acid-binding agent. The mixture was reacted at 60℃-70℃ for 8-12 hours to obtain 3-(2-(phenyldithio)ethyl)-1-(2-aminoethyl)imidazole intermediate. S2. The above intermediate and tert-butyl isocyanate were added to dichloromethane solvent at a molar ratio of 1:1.02-1:1.05 and reacted at 0℃-5℃ for 4-6 hours under nitrogen protection to obtain the crude product. S3. Recrystallize the crude product 2-3 times with a mixed solvent of ethyl acetate and n-hexane, and then vacuum dry at 40℃-50℃ for 12-24 hours to obtain the final product.

[0011] Preferably, in step S1, the molar ratio of 1-(2-aminoethyl)imidazole to anhydrous potassium carbonate is 1:1.2-1:1.5, the reaction temperature is 65°C, the reaction time is 10 hours, and the stirring speed is controlled at 300rpm-500rpm during the reaction.

[0012] Preferably, the reaction in step S2 is carried out under light-protected conditions, and tert-butyl isocyanate is added dropwise for at least 1 hour, at a reaction temperature of 2°C, and for 5 hours.

[0013] Preferably, in step S3, the volume ratio of ethyl acetate to n-hexane is 1:2.5, the recrystallization temperature is 0℃-5℃, the vacuum drying temperature is 45℃, the vacuum degree is not less than 0.095MPa, and the drying time is 18 hours.

[0014] Preferably, after the reaction in step S1 is completed, the generated potassium chloride and excess anhydrous potassium carbonate are first removed by filtration, and then the N,N-dimethylformamide solvent is removed by vacuum distillation at 60℃-70℃ to obtain the crude intermediate product, which is then washed three times with anhydrous diethyl ether and directly used in the reaction in step S2.

[0015] Preferably, the above-mentioned latent epoxy resin curing catalyst with precisely tunable activity is used in the epoxy resin system for electronic packaging. The epoxy resin system for electronic packaging is used for packaging 5G and above high-frequency communication devices. After curing, the dielectric constant of the system at 10GHz does not exceed 3.2 and the dielectric loss does not exceed 0.009.

[0016] Preferably, the application of the above-mentioned latent epoxy resin curing catalyst with precisely controllable activity in the carbon fiber reinforced epoxy resin composite matrix results in a composite material used in aerospace structural components. After curing, the interlaminar shear strength of the composite material is not less than 45 MPa, and the glass transition temperature is not less than 145°C.

[0017] (iii) Beneficial technical effects Compared with existing technologies, the beneficial effects of this invention are: By simultaneously introducing a thermally responsive hindered urea bond, a temperature-responsive dynamic disulfide bond, and an intramolecular hydrogen bond donor-acceptor interaction unit onto the imidazole ring, a triple dynamic bond synergistic regulation system was constructed, achieving precise and controllable catalytic activity. Compared with existing catalysts modified with a single dynamic bond, the activation temperature of the catalyst in this invention can be flexibly adjusted over a wider range by changing the structure and properties of the substituents, adapting to the needs of different processing technologies and application scenarios.

[0018] The synergistic effect of the sterically hindered substituents of the hindered urea bond and the intramolecular hydrogen bond can completely shield the catalytic active center of the imidazole ring, enabling the catalyst to have an extremely long storage period at room temperature after being mixed with epoxy resin, which fully meets the requirements of large-scale industrial production, long-distance transportation and long-term storage.

[0019] As the temperature rises, the triple dynamic bonds break sequentially, gradually releasing all catalytic activity. This enables the epoxy resin to complete the curing reaction in a shorter time, significantly improving production efficiency and reducing energy consumption.

[0020] The catalyst of this invention does not contain any metal ions, and the epoxy resin system after curing has excellent dielectric properties, which can meet the stringent requirements of 5G and above high-frequency communication devices for low dielectric constant and low dielectric loss. Attached Figure Description

[0021] Figure 1 This is a flowchart of a method for preparing a latent epoxy resin curing catalyst with precisely controllable activity, as disclosed in this invention. Figure 2 This is a line graph comparing the effective storage period at 25°C of the examples and the comparative examples; Figure 3 This is a radar comparison chart created by standardizing the dimensions of the performance comparison data between the examples and the comparative examples; Figure 4 This is the 1H NMR spectrum of the solidification catalyst proposed in this invention. Detailed Implementation

[0022] according to Figures 1 to 4 The specific embodiments of the present invention are as follows: The specific embodiments of the present invention are as follows. All raw materials used in the embodiments are commercially available analytical grade reagents unless otherwise stated. 1-(2-aminoethyl)imidazole was purchased from Aladdin Reagent Co., Ltd., with a purity of 99%; 2-chloroethylphenyl disulfide was purchased from Maclean Reagent Co., Ltd., with a purity of 98%; tert-butyl isocyanate was purchased from Anaiji Chemical Co., Ltd., with a purity of 99%; anhydrous potassium carbonate, N,N-dimethylformamide, dichloromethane, ethyl acetate, n-hexane, and anhydrous diethyl ether were all analytical grade and purchased from Sinopharm Chemical Reagent Co., Ltd. Bisphenol A type epoxy resin E-51 was purchased from Baling Petrochemical Co., Ltd., with an epoxy value of 0.51 mol / 100g.

[0023] Unified performance testing method: 1. Storage period test: Mix the catalyst and epoxy resin E-51 evenly according to the set mass ratio, seal and store at 25°C, and use a rotational viscometer to test the viscosity of the system periodically. The effective storage period is the time when the viscosity rises to 150% of the initial value.

[0024] 2. Curing time test: The gel time of the mixture is tested using a gel time tester at a set temperature, which is the curing time at that temperature.

[0025] 3. Dielectric property testing: The cured epoxy resin sample was made into a standard disc with a thickness of 1 mm, and the dielectric constant and dielectric loss were tested at frequencies of 1 MHz and 10 GHz using an impedance analyzer.

[0026] 4. Mechanical property testing: Standard samples were prepared according to the national standard GB / T 2567-2008, and the tensile strength, flexural strength and simply supported beam impact strength of the cured epoxy resin were tested.

[0027] 5. Glass transition temperature test: Differential scanning calorimetry (DSC) was used for the test, with a heating rate of 10℃ / min and a nitrogen atmosphere. The inflection point temperature was taken as the glass transition temperature.

[0028] 6. Interlaminar shear strength test: Carbon fiber reinforced unidirectional composite material specimens were prepared according to the national standard GB / T 1450.1-2005, and their interlaminar shear strength was tested.

[0029] Example 1 In this embodiment, a 1-(2-(N-tert-butyl-N'-phenylureo)ethyl)-3-(2-(phenyldithio)ethyl)imidazolium catalyst was prepared, and its specific structural formula is as follows: The specific preparation steps are as follows: S1. In a 500 mL three-necked flask equipped with a mechanical stirrer, reflux condenser, and thermometer, 1-(2-aminoethyl)imidazole, 2-chloroethylphenyl disulfide, anhydrous potassium carbonate, and N,N-dimethylformamide were added sequentially in a molar ratio of 1:1.05:1.2. The mixture was stirred at 400 rpm and slowly heated to 65 °C, and the reaction was maintained at this temperature for 10 hours. The reaction progress was monitored by thin-layer chromatography (TLC), and the reaction was stopped when the 1-(2-aminoethyl)imidazole spot completely disappeared. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The generated potassium chloride precipitate and excess anhydrous potassium carbonate solid were removed by filtration. The filtrate was transferred to a rotary evaporator and the N,N-dimethylformamide solvent was removed by vacuum distillation at 65 °C and a vacuum degree of 0.09 MPa to obtain a yellow oily crude intermediate. The crude intermediate was washed three times with anhydrous diethyl ether to remove residual unreacted raw materials and byproducts, yielding 3-(2-(phenyldithio)ethyl)-1-(2-aminoethyl)imidazolium intermediate in 95.2% yield.

[0030] S2. Add the prepared intermediate to a 1000 mL three-necked flask equipped with a mechanical stirrer, a constant-pressure dropping funnel, and a nitrogen protection device. Add dichloromethane and stir until completely dissolved. Cool the system to 2°C in an ice-water bath. Under completely dark conditions, slowly add tert-butyl isocyanate dropwise through the constant-pressure dropping funnel. The molar ratio of the intermediate to tert-butyl isocyanate is 1:1.05, and the addition time is controlled at 1.5 hours to avoid excessive local concentrations and side reactions. After the addition is complete, continue to incubate the reaction at 2°C for 5 hours. Monitor the reaction by TLC until the intermediate spots completely disappear.

[0031] S3. After the reaction was complete, the reaction solution was transferred to a rotary evaporator, and the dichloromethane solvent was removed by vacuum distillation at 30°C to obtain a white crude product. The crude product was recrystallized twice with a mixed solvent of ethyl acetate and n-hexane (volume ratio 1:2.5), with the recrystallization temperature controlled at 2°C. The crystals were allowed to stand for 12 hours to allow them to fully separate. The crystals were collected by suction filtration, and the recrystallized product was dried under vacuum at 45°C and 0.096 MPa for 18 hours to obtain a white powdery final product with an overall yield of 88.3%.

[0032] Performance testing: The catalyst prepared in this embodiment was mixed with epoxy resin E-51 at a mass ratio of 1.5:100 and its performance was tested. Storage period: The viscosity remains at more than 85% of its initial value at 25°C for 225 days.

[0033] Curing time: 22 minutes at 115℃.

[0034] Dielectric properties: Dielectric constant 3.0 and dielectric loss 0.006 at 1MHz; dielectric constant 3.1 and dielectric loss 0.008 at 10GHz.

[0035] Mechanical properties: tensile strength 78MPa, flexural strength 125MPa, impact strength 19kJ / m².

[0036] Glass transition temperature: 148℃.

[0037] Compound performance test: The catalyst prepared in this embodiment was compounded with dicyandiamide at a mass ratio of 1:10, and then mixed with epoxy resin E-51 at a mass ratio of 12:100. Performance tests were then conducted. Curing temperature: 115℃.

[0038] Curing time: 30 minutes.

[0039] Glass transition temperature: 152℃.

[0040] Application performance testing: 1. Electronic Packaging Application: The above compound system is used for the packaging of dielectric filters for 5G base stations. After curing, the dielectric properties of the product fully meet the requirements of high-frequency communication. After 1000 hours of high and low temperature cycling test (-40℃-125℃), there is no significant performance degradation.

[0041] 2. Application of carbon fiber composite materials: Using the above-mentioned compound system as the matrix resin, unidirectional composite materials were prepared with T700 carbon fiber using an autoclave process. The interlaminar shear strength was tested to be 48 MPa and the glass transition temperature was 150℃, which meets the requirements for use in secondary load-bearing structural components in aerospace.

[0042] Example 2 In this embodiment, the 1-(2-(N-tert-butyl-N'-phenylureo)ethyl)-3-(2-(phenyldithio)ethyl)imidazolium catalyst was prepared using the following specific steps: S1. In a 500 mL three-necked flask equipped with a mechanical stirrer, reflux condenser, and thermometer, 1-(2-aminoethyl)imidazole, 2-chloroethylphenyl disulfide, anhydrous potassium carbonate, and N,N-dimethylformamide were added sequentially in a molar ratio of 1:1:1.2. Stirring was started at 300 rpm, and the mixture was slowly heated to 60 °C and maintained at this temperature for 12 hours. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The generated potassium chloride precipitate and excess anhydrous potassium carbonate solid were removed by filtration. The filtrate was transferred to a rotary evaporator, and the N,N-dimethylformamide solvent was removed by vacuum distillation at 60 °C and a vacuum degree of 0.09 MPa, yielding a yellow oily crude intermediate. The crude intermediate was washed three times with anhydrous diethyl ether to obtain 3-(2-(phenyldithio)ethyl)-1-(2-aminoethyl)imidazole intermediate, with a yield of 91.3%.

[0043] S2. Add the intermediate prepared above to a 1000 mL three-necked flask equipped with a mechanical stirrer, a constant-pressure dropping funnel, and a nitrogen protection device. Add dichloromethane and stir until completely dissolved. Cool the system to 0°C in an ice-water bath. Under conditions of complete darkness, slowly add tert-butyl isocyanate dropwise through the constant-pressure dropping funnel. The molar ratio of the intermediate to tert-butyl isocyanate is 1:1.04, and the addition time is controlled at 1 hour. After the addition is complete, continue to react at 0°C for 6 hours.

[0044] S3. After the reaction was complete, the reaction solution was transferred to a rotary evaporator, and the dichloromethane solvent was removed by vacuum distillation at 30°C to obtain a white crude product. The crude product was recrystallized three times with a mixed solvent of ethyl acetate and n-hexane (volume ratio 1:2), with the recrystallization temperature controlled at 0°C. The crystals were collected by suction filtration, and the recrystallized product was dried under vacuum at 40°C and 0.095 MPa for 24 hours to obtain a white powdery final product, with an overall yield of 83.7%.

[0045] Performance testing: The catalyst prepared in this embodiment was mixed with epoxy resin E-51 at a mass ratio of 1.5:100 and its performance was tested. Storage period: The viscosity remains at more than 85% of its initial value at 25°C for 215 days.

[0046] Curing time: 24 minutes at 115℃.

[0047] Dielectric properties: Dielectric constant 3.0 and dielectric loss 0.006 at 1MHz; dielectric constant 3.1 and dielectric loss 0.008 at 10GHz.

[0048] Mechanical properties: tensile strength 76MPa, flexural strength 122MPa, impact strength 18kJ / m².

[0049] Glass transition temperature: 146℃.

[0050] Example 3 In this embodiment, the 1-(2-(N-tert-butyl-N'-phenylureo)ethyl)-3-(2-(phenyldithio)ethyl)imidazolium catalyst was prepared using the following specific steps: S1. In a 500 mL three-necked flask equipped with a mechanical stirrer, reflux condenser, and thermometer, 1-(2-aminoethyl)imidazole, 2-chloroethylphenyl disulfide, anhydrous potassium carbonate, and N,N-dimethylformamide were added sequentially in a molar ratio of 1:1.05:1.5. Stirring was started at 500 rpm, and the mixture was slowly heated to 70 °C and maintained at this temperature for 8 hours. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The generated potassium chloride precipitate and excess anhydrous potassium carbonate solid were removed by filtration. The filtrate was transferred to a rotary evaporator, and the N,N-dimethylformamide solvent was removed by vacuum distillation at 70 °C and a vacuum degree of 0.09 MPa, yielding a yellow oily crude intermediate. The crude intermediate was washed three times with anhydrous diethyl ether to obtain 3-(2-(phenyldithio)ethyl)-1-(2-aminoethyl)imidazole intermediate, with a yield of 93.1%.

[0051] S2. Add the intermediate prepared above to a 1000 mL three-necked flask equipped with a mechanical stirrer, a constant-pressure dropping funnel, and a nitrogen protection device. Add dichloromethane and stir until completely dissolved. Cool the system to 5°C in an ice-water bath. Under conditions of complete darkness, slowly add tert-butyl isocyanate dropwise through the constant-pressure dropping funnel. The molar ratio of the intermediate to tert-butyl isocyanate is 1:1.06, and the addition time is controlled at 1.2 hours. After the addition is complete, continue the reaction at 5°C for 4 hours.

[0052] S3. After the reaction was complete, the reaction solution was transferred to a rotary evaporator, and the dichloromethane solvent was removed by vacuum distillation at 30°C to obtain a white crude product. The crude product was recrystallized twice with a mixed solvent of ethyl acetate and n-hexane (volume ratio 1:3), with the recrystallization temperature controlled at 5°C. The crystals were collected by suction filtration, and the recrystallized product was dried under vacuum at 50°C and 0.095 MPa for 12 hours to obtain a white powdery final product, with an overall yield of 85.9%.

[0053] Performance testing: The catalyst prepared in this embodiment was mixed with epoxy resin E-51 at a mass ratio of 1.5:100 and its performance was tested. Storage period: The viscosity remains at more than 85% of its initial value at 25°C for 210 days.

[0054] Curing time: 23 minutes at 115℃.

[0055] Dielectric properties: Dielectric constant 3.1 and dielectric loss 0.007 at 1MHz; dielectric constant 3.2 and dielectric loss 0.009 at 10GHz.

[0056] Mechanical properties: tensile strength 75MPa, flexural strength 120MPa, impact strength 18kJ / m².

[0057] Glass transition temperature: 145℃.

[0058] Comparative Example 1 This comparative example uses unmodified 1-methylimidazole as a curing catalyst, which is mixed with epoxy resin E-51 at a mass ratio of 1:100 and then subjected to performance testing. Storage period: It takes only 5 days for the viscosity to rise to 150% of its initial value at 25°C.

[0059] Curing time: 30 minutes at 80℃.

[0060] Dielectric properties: Dielectric constant 3.5 and dielectric loss 0.015 at 1MHz; dielectric constant 3.8 and dielectric loss 0.022 at 10GHz.

[0061] Mechanical properties: tensile strength 70MPa, flexural strength 110MPa, impact strength 15kJ / m².

[0062] Glass transition temperature: 135℃.

[0063] Comparative Example 2 This comparative example uses a single urea bond modified imidazole catalyst, 1-(2-(N-tert-butyl-N'-phenylurea)ethyl)imidazolium, prepared according to a publicly disclosed method. It is then mixed uniformly with epoxy resin E-51 at a mass ratio of 1.5:100, and performance tests are performed. Storage period: The viscosity remains at more than 85% of its initial value at 25°C for 90 days.

[0064] Curing time: 45 minutes at 130℃.

[0065] Dielectric properties: Dielectric constant 3.3 and dielectric loss 0.012 at 1MHz; dielectric constant 3.5 and dielectric loss 0.018 at 10GHz.

[0066] Mechanical properties: tensile strength 72MPa, flexural strength 115MPa, impact strength 16kJ / m².

[0067] Glass transition temperature: 140℃.

[0068] Comparative Example 3 This comparative example uses a single disulfide bond modified imidazole catalyst, 1-(2-(phenyldithio)ethyl)-3-methylimidazolium, prepared according to a publicly disclosed method. It is then mixed uniformly with epoxy resin E-51 at a mass ratio of 1.5:100, and performance tests are performed. Storage period: The viscosity remains at more than 85% of its initial value at 25°C for 60 days.

[0069] Curing time: 35 minutes at 120℃.

[0070] Dielectric properties: Dielectric constant 3.2 and dielectric loss 0.010 at 1MHz; dielectric constant 3.4 and dielectric loss 0.015 at 10GHz.

[0071] Mechanical properties: tensile strength 73MPa, flexural strength 118MPa, impact strength 17kJ / m².

[0072] Glass transition temperature: 142℃.

[0073] As can be seen from the performance test results of the above embodiments and comparative examples, the latent epoxy resin curing catalyst with a triple dynamic bond synergistic regulation structure prepared by the present invention exhibits significant advantages in terms of storage stability, curing response speed, dielectric properties and comprehensive mechanical properties compared with various catalysts in the prior art. It can simultaneously meet the dual requirements of high-end fields for ultra-long storage period and rapid curing of epoxy resin systems.

[0074] The core latency and curing performance of the examples and comparative examples are compared in the table below: Table 1 The following table compares the dielectric and mechanical properties of the cured products: Table 2 The performance comparison data in the two tables above clearly show that the triple dynamic bond synergistic latent epoxy resin curing catalysts prepared in Examples 1-3 of this invention have significant performance advantages compared with the unmodified imidazole catalyst in Comparative Example 1, the imidazole catalyst modified with a single urea bond in Comparative Example 2, and the imidazole catalyst modified with a single disulfide bond in Comparative Example 3.

[0075] In terms of latency and curing performance, the catalyst of this invention has a much longer effective storage period at 25°C than the comparative examples, a shorter curing time, and a higher glass transition temperature of the cured product, thus meeting the dual requirements of ultra-long storage period and rapid curing. In terms of dielectric and mechanical properties, the dielectric constant and dielectric loss of the system after curing of the catalyst of this invention are significantly lower than those of the comparative examples, and the tensile strength, flexural strength, and impact strength are all superior to those of the comparative examples. The overall performance is better and can better meet the application requirements of high-end fields such as electronic packaging and aerospace.

[0076] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A latent epoxy resin curing catalyst with precisely tunable activity, characterized in that, The catalyst is 1-(2-(N-tert-butyl-N'-phenylurea)ethyl)-3-(2-(phenyldithio)ethyl)imidazolium; the catalyst molecule simultaneously possesses an imidazolium ring catalytic active center, a thermally responsive hindered urea bond substituted with N-tert-butyl, a temperature-responsive dynamic disulfide bond substituted with phenyl, and an intramolecular hydrogen bond donor-acceptor interaction unit between the urea group and the imidazolium ring, achieving precise regulation of catalytic activity through a triple dynamic bond synergistic effect; the activation temperature of the catalyst is 110℃-120℃; the catalyst does not contain metal ions, and the dielectric constant of the epoxy resin system after curing does not exceed 3.1 at 1MHz, and the dielectric loss does not exceed 0.

007.

2. The latent epoxy resin curing catalyst with precisely tunable activity according to claim 1, characterized in that, In the catalyst molecule, the N-tert-butyl substituent of the hindered urea bond provides a steric hindrance effect, shielding the catalytic activity of the imidazole ring at room temperature; the dynamic disulfide bond undergoes reverse breakage-recombination at 110℃-120℃, releasing 30%-40% of the catalytic active sites; the intramolecular hydrogen bond gradually breaks above 105℃, further activating the remaining 60%-70% of the imidazole ring catalytic activity.

3. The latent epoxy resin curing catalyst with precisely tunable activity according to claim 1, characterized in that, The catalyst has a particle size distribution of 2μm-8μm, a purity of not less than 99.6%, a moisture content of not more than 0.08%, and a chloride ion content of not more than 3ppm.

4. A method for preparing a latent epoxy resin curing catalyst with precisely controllable activity as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. 1-(2-aminoethyl)imidazole and 2-chloroethylphenyl disulfide were added to N,N-dimethylformamide solvent in a molar ratio of 1:1.05-1:1.1, and anhydrous potassium carbonate was added as an acid-binding agent. The mixture was reacted at 60℃-70℃ for 8-12 hours to obtain 3-(2-(phenyldithio)ethyl)-1-(2-aminoethyl)imidazole intermediate. S2. The above intermediate and tert-butyl isocyanate were added to dichloromethane solvent at a molar ratio of 1:1.02-1:1.05 and reacted at 0℃-5℃ for 4-6 hours under nitrogen protection to obtain the crude product. S3. Recrystallize the crude product 2-3 times with a mixed solvent of ethyl acetate and n-hexane, and then vacuum dry at 40℃-50℃ for 12-24 hours to obtain the final product.

5. The method for preparing the latent epoxy resin curing catalyst with precisely controllable activity according to claim 4, characterized in that, In step S1, the molar ratio of 1-(2-aminoethyl)imidazole to anhydrous potassium carbonate is 1:1.2-1:1.5, the reaction temperature is 65℃, the reaction time is 10 hours, and the stirring speed is controlled at 300rpm-500rpm during the reaction.

6. The method for preparing the latent epoxy resin curing catalyst with precisely controllable activity according to claim 4, characterized in that, The reaction described in step S2 is carried out under light-protected conditions. Tert-butyl isocyanate is added dropwise for at least 1 hour, at a reaction temperature of 2°C, and for 5 hours.

7. The method for preparing the latent epoxy resin curing catalyst with precisely controllable activity according to claim 4, characterized in that, In step S3, the volume ratio of ethyl acetate to n-hexane is 1:2.5, the recrystallization temperature is 0℃-5℃, the vacuum drying temperature is 45℃, the vacuum degree is not less than 0.095MPa, and the drying time is 18 hours.

8. The method for preparing the latent epoxy resin curing catalyst with precisely controllable activity according to claim 4, characterized in that, After the reaction in step S1 is completed, the generated potassium chloride and excess anhydrous potassium carbonate are first removed by filtration, and then the N,N-dimethylformamide solvent is removed by vacuum distillation at 60℃-70℃ to obtain the crude intermediate product. After washing three times with anhydrous diethyl ether, it is directly used in the reaction in step S2.

9. The application of a latent epoxy resin curing catalyst with precisely tunable activity according to any one of claims 1-3 in an epoxy resin system for electronic packaging, characterized in that, The epoxy resin system for electronic packaging is used for packaging 5G and above high-frequency communication devices. After curing, the dielectric constant of the system at 10GHz does not exceed 3.2 and the dielectric loss does not exceed 0.

009.

10. The application of a latent epoxy resin curing catalyst with precisely tunable activity according to any one of claims 1-3 in a carbon fiber reinforced epoxy resin composite matrix, characterized in that, The composite material is used in aerospace structural components. After curing, the interlaminar shear strength of the composite material is not less than 45 MPa, and the glass transition temperature is not less than 145°C.

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