An epoxy-based hyperbranched polysiloxane modified aqueous polyimide material and a method for preparing the same

Abstract

This invention discloses an epoxy-modified hyperbranched polysiloxane-modified aqueous polyimide material and its preparation method, belonging to the field of polymer materials technology. The invention involves mixing deionized water, a nitrogen-containing Lewis base, and a diamine monomer, and adding a dianhydride monomer to the aqueous system to prepare a polyamic acid salt precursor solution. Subsequently, epoxy-modified hyperbranched polysiloxane is added to the precursor solution for physical blending to obtain a homogeneous system. The epoxy-modified hyperbranched polysiloxane-modified aqueous polyimide material is then prepared by programmed temperature thermal imidization. The epoxy-modified hyperbranched polysiloxane-modified aqueous polyimide material prepared by this invention exhibits significant improvements in heat resistance, dielectric properties, breakdown resistance, and high-temperature capacitance stability. Furthermore, the preparation method is environmentally friendly and suitable for high-temperature, high-power applications such as new energy vehicles, photovoltaic inverters, and aerospace.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to an epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material and its preparation method. Background Technology

[0002] Polyimide materials are widely used in aerospace, new energy vehicles, power electronics, photovoltaic inverters, and high-temperature insulation due to their excellent high-temperature resistance, mechanical properties, chemical stability, and electrical insulation properties. Especially under high-temperature, high-electric-field, and complex service environments, polyimide materials can maintain stable overall performance over long periods, making them one of the most widely used high-performance engineering plastics and electrical insulation materials.

[0003] However, existing polyimide materials are typically prepared using solution-based processes with polar aprotic organic solvents such as N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide as the reaction medium. These organic solvents are expensive, have high recycling costs, and pose environmental pollution and health risks, which is inconsistent with the development direction of green manufacturing and sustainable development. Therefore, the preparation of polyimide materials using aqueous systems has gradually become an important research direction in this field.

[0004] To address the technical need for aqueous synthesis of polyimides, Chinese patent CN119390980A describes a process where blocked diisocyanate and tetracarboxylic dianhydride are added to water, along with a salt-forming agent, to induce a polymerization reaction and obtain a polyimide solution. By replacing the traditional diamine monomer with blocked diisocyanate units, aqueous synthesis of polyimides is achieved. The polyimide material prepared by this method exhibits excellent mechanical properties, with mechanical and heat resistance properties approaching those of oil-based polyimides, thus enriching the molecular structure types of waterborne polyimides.

[0005] Chinese patent CN112321829B uses water as the reaction medium to carry out a polycondensation reaction between a diamine monomer and an acyl chloride or acid anhydride compound in an aqueous system. By controlling the reaction conditions, a polyamide-imide resin solution is prepared, realizing the construction of polyimide structural units in an aqueous system. This method avoids the use of traditional polar aprotic organic solvents, giving the resulting material both certain heat resistance and mechanical properties, and improving the feasibility of preparing polyimide materials in an aqueous system.

[0006] Chinese patent CN112694614A also uses water as the reaction medium, carrying out a polycondensation reaction between diamine monomers and dianhydride monomers in an aqueous system. The aqueous synthesis of polyimide is achieved by controlling the reaction temperature in stages. This method does not use organic solvents or additional catalysts during the preparation process, reducing the environmental burden and verifying the feasibility of directly synthesizing polyimide materials in an aqueous system. It provides a new technical route for the green preparation of waterborne polyimide materials.

[0007] However, the polyimide materials prepared by the above-mentioned aqueous phase preparation methods are mostly linear molecular structures with limited inter-chain forces and low cross-linking density. Under high temperature or strong electric field conditions, chain segment movement and local structural defect expansion are likely to occur. Their heat resistance, dielectric properties, breakdown resistance and long-term service stability still need to be further improved, making it difficult to meet the ever-increasing application requirements of high-temperature and high-power-density insulation materials in fields such as new energy vehicles, power electronics and aerospace. Summary of the Invention

[0008] The technical problem solved by this invention is to provide an epoxy-modified hyperbranched polysiloxane-modified aqueous polyimide material, which effectively improves mechanical properties, high-temperature resistance, and puncture resistance under high-temperature conditions. Another technical problem to be solved by this invention is to provide a method for preparing epoxy-modified hyperbranched polysiloxane-modified aqueous polyimide material. This method modifies the polyimide synthesized by the aqueous phase method by introducing epoxy-modified hyperbranched polysiloxane to improve the overall performance of the material and meet the application requirements of high-temperature and high-power fields.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing an epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material includes the following steps:

[0011] 1) Mix and stir deionized water, nitrogen-containing Lewis base and diamine monomer to obtain an aqueous reaction system;

[0012] 2) Add dianhydride monomer to the aqueous reaction system obtained in step 1), and carry out polymerization under stirring conditions to obtain a polyamic acid salt precursor solution;

[0013] 3) Add the epoxy-based hyperbranched polysiloxane to the polyamic acid salt precursor solution obtained in step 2) for physical blending to obtain a uniformly dispersed modified aqueous solution system;

[0014] 4) The modified aqueous solution system obtained in step 3) is subjected to thermal imidization treatment by programmed temperature rise to prepare epoxy hyperbranched polysiloxane modified aqueous polyimide material.

[0015] Further, in step 1), the nitrogen-containing Lewis base is selected from one or more of 1-methylimidazole, 2-methylimidazole, 1,2-dimethylimidazole, N,N-dimethylethylamine, trimethylamine, triethylamine, 2-methylpyridine, 4-methylpyridine, 4-aminopyridine, and 4-dimethylaminopyridine; the diamine monomer is selected from one or more of p-phenylenediamine, 4,4'-diaminodiphenyl ether, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 4,4'-diaminophenyl sulfone, 4,4'-diaminobenzoylaniline, 2-(4-aminophenyl)-5-aminobenzimidazole, trifluoromethyldiaminobiphenyl, and 2,2-bis(4-aminophenyl)hexafluoropropane.

[0016] Furthermore, in step 1), the reaction temperature is 0~90℃ and the reaction time is 0.5~12h.

[0017] Further, in step 2), the dianhydride monomer is selected from one or more of the following: pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-oxobisphthalic anhydride, hexafluoroisopropylphthalic anhydride, 3,3,4,4-diphenylsulfone tetracarboxylic dianhydride, and 4,4'-(4,4'-isopropyldiphenoxy)phthalic anhydride.

[0018] Furthermore, in step 2), the reaction temperature is 0~90℃ and the reaction time is 2~12h.

[0019] Furthermore, in steps 1) to 2), the molar ratio of the nitrogen-containing Lewis base, the diamine monomer, and the dianhydride monomer is 1 to 8: 1: 0.9 to 1.1.

[0020] Further, in step 3), the mass percentage of the epoxy-based hyperbranched polysiloxane is 1wt%~50wt%; the general structural formula of the epoxy-based hyperbranched polysiloxane is:

[0021] ;

[0022] Where R is H, -CH3, , , .

[0023] Furthermore, in step 3), the blending temperature is 0~100℃ and the blending time is 2~24h.

[0024] Furthermore, in step 4), the programmed temperature is 30~350℃, and the programmed heating rate is 0.5℃~20℃ / min.

[0025] Furthermore, the epoxy-modified hyperbranched polysiloxane-modified aqueous polyimide material prepared by the aforementioned method is an epoxy-modified hyperbranched polysiloxane-modified aqueous polyimide material.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) The present invention modifies aqueous polyimide by introducing epoxy hyperbranched polysiloxane, and the resulting material is effectively improved in terms of mechanical properties, high temperature resistance and puncture resistance under high temperature conditions.

[0028] (2) This invention uses an aqueous system to prepare polyimide materials, avoiding the use of polar aprotic organic solvents, thus achieving a green, environmentally friendly, and process-controllable polyimide material preparation process. Furthermore, addressing the issues of existing aqueous-phase polyimide materials having mostly linear molecular structures and low crosslinking density, resulting in insufficient heat resistance, dielectric properties, and breakdown resistance under high temperature and strong electric field conditions, this invention modifies the aqueous-phase synthesized polyimide by introducing epoxy-based hyperbranched polysiloxanes to improve the overall performance of the material and meet the application requirements in high-temperature and high-power fields.

[0029] (3) The preparation method of the present invention is simple and environmentally friendly, which is conducive to expanding the application of aqueous polyimide film materials in high-temperature and high-power application fields such as new energy vehicles, photovoltaic inverters and aerospace. Attached Figure Description

[0030] Figure 1 This is a photograph of the epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material prepared in Example 1 of this application.

[0031] Figure 2 The infrared spectra of the epoxy-based hyperbranched polysiloxane-modified aqueous polyimide materials prepared in Examples 1-4 and Comparative Example 1 of this application are shown below.

[0032] Figure 3 The X-ray photoelectron spectra of the epoxy-based hyperbranched polysiloxane-modified aqueous polyimide materials prepared in Example 2 and Comparative Example 1 of this application are shown. Detailed Implementation

[0033] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, and it should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0034] In the following examples, the epoxy hyperbranched polysiloxane (EPHPSi) used was prepared using the method disclosed in CN112898586A. The preparation method is as follows: 0.1 mol of methyltrimethoxysiloxane, 1 mol of γ-glycidyl etheroxypropyltrimethoxysilane, and 30 wt% anhydrous methanol were added to a 500 mL three-necked flask equipped with a mechanical stirrer and a condenser. The mixture was stirred at 0°C for 4 h to achieve homogeneity. 0.55 mol of water and 0.1 wt% hydrochloric acid were slowly added dropwise to the reaction system. The reaction temperature was 0°C and the reaction time was 24 h. The solvent was removed by vacuum distillation at 40°C and a pressure of -0.1 MPa for 3 h to obtain EPHPSi.

[0035] Example 1

[0036] A method for preparing an epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material includes the following steps:

[0037] (1) In a 500mL three-necked flask equipped with a mechanical stirrer and a condenser, add 385g of deionized water, 0.40mol of 1,2-dimethylimidazole and 0.05mol of 2,2′-dimethyl-4,4′-diaminobiphenyl, and mix and stir at 0℃ for 12h under nitrogen protection to obtain an aqueous reaction system.

[0038] (2) Add 0.055 mol of hexafluoroisopropylphthalic anhydride to the aqueous reaction system obtained in step (1), and stir continuously at 0°C for 12 h to carry out the aqueous polymerization reaction and obtain the polyamic acid salt precursor solution.

[0039] (3) Add 5 wt% epoxy hyperbranched polysiloxane to the polyamic acid salt precursor solution and perform physical mixing and stirring at 0°C for 24 h to obtain a uniformly dispersed modified aqueous solution system.

[0040] (4) The modified aqueous solution system obtained in step (3) is cast into a film and placed in a forced-air drying oven. The film is subjected to programmed heating thermal imidization treatment at a heating rate of 1℃ / min within the range of 30℃~350℃. Finally, epoxy hyperbranched polysiloxane modified aqueous polyimide material is prepared, denoted as W-PI. EPHPSi -5%.

[0041] Depend on Figure 1 As shown in the physical images of the homogeneous solution of epoxy-modified hyperbranched polysiloxane-modified aqueous polyamic acid salt precursor and the aqueous polyimide material obtained after thermal imidization, the precursor solution is pale yellow, the system is homogeneous and transparent, the viscosity is moderate, and it has good film-forming properties and processing performance.

[0042] Example 2

[0043] A method for preparing an epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material includes the following steps:

[0044] (1) In a 500mL three-necked flask equipped with a mechanical stirrer and a condenser, add 385g of deionized water, 0.05mol of 1-methylimidazole and 0.05mol of p-phenylenediamine. Mix and stir at 0℃ for 12h under nitrogen protection to obtain an aqueous reaction system.

[0045] (2) Add 0.045 mol of pyromellitic anhydride to the aqueous reaction system obtained in step (1), and stir continuously at 90°C for 2 h to carry out aqueous polymerization reaction to obtain polyamic acid salt precursor solution.

[0046] (3) Add 10 wt% of epoxy hyperbranched polysiloxane to the polyamic acid salt precursor solution and perform physical blending and stirring at 100 °C for 2 h to obtain a uniformly dispersed modified aqueous solution system.

[0047] (4) The modified aqueous solution system obtained in step (3) is cast into a film and placed in a forced-air drying oven. The film is subjected to programmed heating thermal imidization treatment at a heating rate of 10℃ / min within the range of 30℃~350℃ to finally prepare epoxy hyperbranched polysiloxane modified aqueous polyimide material, denoted as W-PI. EPHPSi -10%.

[0048] Example 3

[0049] A method for preparing an epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material includes the following steps:

[0050] (1) In a 500mL three-necked flask equipped with a mechanical stirrer and a condenser, add 385g of deionized water, 0.125mol of N,N-dimethylethylamine and 0.05mol of 4,4'-diaminodiphenyl ether. Mix and stir at 30°C for 8h under nitrogen protection to obtain an aqueous reaction system.

[0051] (2) Add 0.049 mol of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to the aqueous reaction system obtained above, and stir continuously at 30°C for 10 h to carry out aqueous polymerization reaction to obtain polyamic acid salt precursor solution.

[0052] (3) Add 15 wt% epoxy hyperbranched polysiloxane to the polyamic acid salt precursor solution and perform physical mixing and stirring at 30 °C for 12 h to obtain a uniformly dispersed modified aqueous solution system.

[0053] (4) The modified aqueous solution system obtained in step (3) is cast into a film and placed in a forced-air drying oven. The film is subjected to programmed heating thermal imidization treatment at a heating rate of 5℃ / min within the range of 60℃~300℃. Finally, epoxy hyperbranched polysiloxane modified aqueous polyimide material is prepared, denoted as W-PI. EPHPSi -15%.

[0054] Example 4

[0055] A method for preparing an epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material includes the following steps:

[0056] (1) In a 500mL three-necked flask equipped with a mechanical stirrer and a condenser, add 385g of deionized water, 0.125mol of N,N-dimethylethylamine and 0.05mol of 4,4'-diaminodiphenyl ether. Mix and stir at 30°C for 8h under nitrogen protection to obtain an aqueous reaction system.

[0057] (2) Add 0.049 mol of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to the aqueous reaction system obtained in step (1), and stir continuously at 30°C for 10 h to carry out the aqueous polymerization reaction and obtain a polyamic acid salt precursor solution.

[0058] (3) Add 20 wt% of epoxy hyperbranched polysiloxane to the polyamic acid salt precursor solution and perform physical mixing and stirring at 30 °C for 12 h to obtain a uniformly dispersed modified aqueous solution system.

[0059] (4) The modified aqueous solution system obtained in step (3) is cast into a film and placed in a forced-air drying oven. The film is subjected to programmed thermal imidization treatment at a heating rate of 2℃ / min within the range of 60℃~300℃. Finally, epoxy hyperbranched polysiloxane modified aqueous polyimide material is prepared, denoted as W-PI. EPHPSi -20%.

[0060] Example 5

[0061] A method for preparing an epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material includes the following steps:

[0062] (1) In a 500mL three-necked flask equipped with a mechanical stirrer and a condenser, add 385g of deionized water, 0.25mol of triethylamine and 0.05mol of 4,4'-diaminophenyl sulfone, and mix and stir at 70°C for 2h under nitrogen protection to obtain an aqueous reaction system.

[0063] (2) Add 0.051 mol of 3,3',4,4'-benzophenone tetracarboxylic dianhydride to the aqueous reaction system obtained in step (1), and stir continuously at 70°C for 10 h to carry out the aqueous polymerization reaction and obtain a polyamic acid salt precursor solution.

[0064] (3) Add 10 wt% of epoxy hyperbranched polysiloxane to the polyamic acid salt precursor solution and perform physical mixing and stirring at 70 °C for 12 h to obtain a uniformly dispersed modified aqueous solution system.

[0065] (4) The modified aqueous solution system obtained in step (3) is cast into a film and placed in a forced-air drying oven. The film is subjected to programmed thermal imidization treatment at a heating rate of 1℃ / min within the range of 60℃~300℃. Finally, epoxy hyperbranched polysiloxane modified aqueous polyimide material is prepared, denoted as W-PI. EPHPSi -10%.

[0066] Example 6

[0067] A method for preparing an epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material includes the following steps:

[0068] (1) In a 500mL three-necked flask equipped with a mechanical stirrer and a condenser, add 385g of deionized water, 0.25mol of 2-methylpyridine and 0.05mol of 4,4'-diaminobenzoyl aniline, mix and stir at 70℃ for 6h under nitrogen protection to obtain an aqueous reaction system.

[0069] (2) Add 2.55 mol of 4,4'-oxophthalic anhydride to the aqueous reaction system obtained in step (1), and stir continuously at 80°C for 4 h to carry out the aqueous polymerization reaction and obtain the polyamic acid salt precursor solution.

[0070] (3) Add 20 wt% of epoxy hyperbranched polysiloxane to the polyamic acid salt precursor solution and perform physical mixing and stirring at 30 °C for 12 h to obtain a uniformly dispersed modified aqueous solution system.

[0071] (4) The modified aqueous solution system obtained in step (3) is cast into a film and placed in a forced-air drying oven. The film is subjected to programmed thermal imidization treatment at a heating rate of 1℃ / min within the range of 60℃~300℃. Finally, epoxy hyperbranched polysiloxane modified aqueous polyimide material is prepared, denoted as W-PI. EPHPSi -20%.

[0072] Example 7

[0073] A method for preparing an epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material includes the following steps:

[0074] (1) In a 500mL three-necked flask equipped with a mechanical stirrer and a condenser, add 385g of deionized water, 0.15mol of 4-dimethylaminopyridine and 0.05mol of trifluoromethyldiaminobiphenyl. Mix and stir at 50°C for 1h under nitrogen protection to obtain an aqueous reaction system.

[0075] (2) Add 0.049 mol of 4,4'-(4,4'-isopropyldiphenoxy) phthalic anhydride to the aqueous reaction system obtained in step (1), and stir continuously at 60°C for 12 h to carry out the aqueous polymerization reaction and obtain a polyamic acid salt precursor solution.

[0076] (3) Add 1 wt% of epoxy hyperbranched polysiloxane to the polyamic acid salt precursor solution and perform physical blending and stirring at 50°C for 10 h to obtain a uniformly dispersed modified aqueous solution system.

[0077] (4) The modified aqueous solution system obtained in step (3) is cast into a film and placed in a forced-air drying oven. The film is subjected to programmed thermal imidization treatment at a heating rate of 2℃ / min within the range of 60℃~250℃. Finally, epoxy hyperbranched polysiloxane modified aqueous polyimide material is prepared, denoted as W-PI. EPHPSi -1%.

[0078] Example 8

[0079] A method for preparing an epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material includes the following steps:

[0080] (1) In a 500mL three-necked flask equipped with a mechanical stirrer and a condenser, add 385g of deionized water, 0.25mol of trimethylamine and 0.05mol of 2-(4-aminophenyl)-5-aminobenzimidazole. Mix and stir at 30°C for 1h under nitrogen protection to obtain an aqueous reaction system.

[0081] (2) Add 0.05 mol of hexafluoroisopropylphthalic anhydride to the aqueous reaction system obtained in step (1), and stir continuously at 70°C for 5 h to carry out aqueous polymerization reaction to obtain polyamic acid salt precursor solution.

[0082] (3) Add 50 wt% epoxy hyperbranched polysiloxane to the polyamic acid salt precursor solution and perform physical blending and stirring at 70 °C for 6 h to obtain a uniformly dispersed modified aqueous solution system.

[0083] (4) The modified aqueous solution system obtained in step (3) is cast into a film and placed in a forced-air drying oven. The film is subjected to programmed heating thermal imidization treatment at a heating rate of 10℃ / min within the range of 60℃~300℃. Finally, epoxy hyperbranched polysiloxane modified aqueous polyimide material is prepared, denoted as W-PI. EPHPSi -50%.

[0084] Comparative Example 1

[0085] A method for preparing an aqueous polyimide material includes the following steps:

[0086] (1) In a 500mL three-necked flask equipped with a mechanical stirrer and a condenser, add 385g of deionized water, 0.40mol of 1,2-dimethylimidazole and 0.05mol of 2,2′-dimethyl-4,4′-diaminobiphenyl, and mix and stir at 30°C for 1h under nitrogen protection to obtain an aqueous reaction system.

[0087] (2) Add 0.055 mol of hexafluoroisopropylphthalic anhydride to the aqueous reaction system obtained in step (1), and stir continuously at 70°C for 5 h to carry out aqueous polymerization reaction to obtain polyamic acid salt precursor solution.

[0088] (4) The polyamic acid salt precursor solution obtained in step (2) is cast into a film and placed in a forced-air drying oven. The film is subjected to programmed heating thermal imidization treatment at a heating rate of 1℃ / min within the range of 30℃~350℃. Finally, epoxy hyperbranched polysiloxane modified aqueous polyimide material is prepared, denoted as W-PI.

[0089] Depend on Figure 2 The infrared spectra of the epoxy-based hyperbranched polysiloxane-modified aqueous polyimide materials prepared in Examples 1-4 and Comparative Example 1 show that at 1380 cm⁻¹... -1 1720cm -1 and 1770cm -1 The characteristic peaks of CNC stretching vibration in the polyimide structure, as well as the asymmetric and symmetric stretching vibration peaks of C=O in the imide ring, appeared at 1090 cm⁻¹, indicating that a polyimide structure has been successfully formed in the material. Meanwhile, at 1090 cm⁻¹... -1 The presence of a distinct Si-O-Si stretching vibration characteristic peak indicates that epoxy-based hyperbranched polysiloxanes have been successfully introduced into the polyimide system.

[0090] Depend on Figure 3The X-ray photoelectron spectroscopy (XPS) spectra of the epoxy-modified hydropolyimide materials prepared in Example 2 and Comparative Example 1 show that the thin film material exhibits characteristic binding energy peaks of O 1s, N 1s, C 1s, Si 2s, and Si 2p at 532.08 eV, 399.08 eV, 284.08 eV, 152.08 eV, and 101.08 eV, respectively. This indicates that the material contains both polyimide structural elements and silicon-oxygen structural units, demonstrating that epoxy-modified hydropolyimide has been successfully introduced into the hydropolyimide system, thus realizing the preparation of epoxy-modified hydropolyimide materials.

[0091] The epoxy-based hyperbranched polysiloxane-modified aqueous polyimide materials prepared in Examples 1-8 and Comparative Example 1 were subjected to performance tests. The results are shown in Table 1.

[0092] (1) Thermal stability test: The thermal stability of the sample was tested using a thermal analyzer (NETZSCH STA449F3, Germany) under a nitrogen atmosphere. The test temperature range was 100~1000℃, the heating rate was 10℃ / min, and the gas flow rate was 50mL / min.

[0093] (2) Tensile property test: The mechanical properties of the samples were tested using a universal testing machine (Instron 4466, USA) in accordance with GB / T1041, with a tensile rate of 10 mm / min.

[0094] (3) Breakdown strength test: The thin film with gold electrode was immersed in dimethyl silicone oil. The breakdown strength was tested using a ferroelectric material tester (Premier II, Radiant Technology Inc., USA). The test conditions were 200℃ and the test frequency was 10Hz. At least 15 points were measured for each sample, and the values ​​were sorted by size. The middle 10 points were processed by Weibull distribution to obtain the breakdown strength characteristic value.

[0095] (4) Dynamic thermomechanical analysis test: The material was tested using DMA1 (Mettler, Switzerland) in tensile mode, with a temperature range of 100~500℃, a heating rate of 3℃ / min, and a frequency of 1Hz.

[0096] Table 1. Performance tests of epoxy-based hyperbranched polysiloxane-modified aqueous polyimide materials prepared in Examples 1-8 and Comparative Example 1

[0097]

[0098] As shown in Table 1, compared with Comparative Example 1, the epoxy-modified hyperbranched polysiloxane-modified aqueous polyimide material prepared in this invention exhibits significant improvements in initial thermal decomposition temperature, tensile strength, characteristic breakdown strength, and glass transition temperature. Specifically, the initial thermal decomposition temperature increased by a maximum of 38.2℃, indicating excellent thermal stability of the modified aqueous polyimide film; the tensile strength increased by a maximum of 37.9%, and the Young's modulus increased by 2.79 GPa, indicating significantly enhanced mechanical properties; at 200℃, the characteristic breakdown strength reached a maximum of 630 MV / m, proving that the material maintains good electrical insulation properties even at high temperatures; furthermore, its glass transition temperature reached 403.5℃, an increase of 11.8℃ compared to Comparative Example 1, reflecting high mechanical rigidity over a wide temperature range and excellent thermomechanical properties.

[0099] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material, characterized in that: Includes the following steps: 1) Mix and stir deionized water, nitrogen-containing Lewis base and diamine monomer to obtain an aqueous reaction system; 2) Add dianhydride monomer to the aqueous reaction system obtained in step 1), and carry out polymerization under stirring conditions to obtain a polyamic acid salt precursor solution; 3) Add the epoxy-based hyperbranched polysiloxane to the polyamic acid salt precursor solution obtained in step 2) for physical blending to obtain a uniformly dispersed modified aqueous solution system; 4) The modified aqueous solution system obtained in step 3) is subjected to thermal imidization treatment by programmed temperature rise to prepare epoxy hyperbranched polysiloxane modified aqueous polyimide material.

2. The method for preparing epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material according to claim 1, characterized in that: In step 1), the nitrogen-containing Lewis base is selected from one or more of 1-methylimidazole, 2-methylimidazole, 1,2-dimethylimidazole, N,N-dimethylethylamine, trimethylamine, triethylamine, 2-methylpyridine, 4-methylpyridine, 4-aminopyridine, and 4-dimethylaminopyridine; the diamine monomer is selected from one or more of p-phenylenediamine, 4,4'-diaminodiphenyl ether, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 4,4'-diaminophenyl sulfone, 4,4'-diaminobenzoylaniline, 2-(4-aminophenyl)-5-aminobenzimidazole, trifluoromethyldiaminobiphenyl, and 2,2-bis(4-aminophenyl)hexafluoropropane.

3. The method for preparing epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material according to claim 1, characterized in that: In step 1), the reaction temperature is 0~90℃ and the reaction time is 0.5~12h.

4. The method for preparing epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material according to claim 1, characterized in that: In step 2), the dianhydride monomer is selected from one or more of the following: pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-oxobisphthalic anhydride, hexafluoroisopropylphthalic anhydride, 3,3,4,4-diphenylsulfone tetracarboxylic dianhydride, and 4,4'-(4,4'-isopropyldiphenoxy)phthalic anhydride.

5. The method for preparing epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material according to claim 1, characterized in that: In step 2), the reaction temperature is 0~90℃ and the reaction time is 2~12h.

6. The method for preparing epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material according to claim 1, characterized in that: In steps 1) to 2), the molar ratio of nitrogen-containing Lewis base, diamine monomer, and dianhydride monomer is 1 to 8:1:0.9 to 1.

1.

7. The method for preparing epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material according to claim 1, characterized in that: In step 3), the mass percentage of the epoxy-based hyperbranched polysiloxane is 1wt%~50wt%; the general structural formula of the epoxy-based hyperbranched polysiloxane is: ； Where R is H, -CH3, , , .

8. The method for preparing epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material according to claim 1, characterized in that: In step 3), the blending temperature is 0~100℃ and the blending time is 2~24h.

9. The method for preparing epoxy-based hyperbranched polysiloxane-modified aqueous polyimide material according to claim 1, characterized in that: In step 4), the programmed temperature is 30~350℃, and the programmed heating rate is 0.5℃~20℃ / min.

10. The epoxy-modified hyperbranched polysiloxane-modified aqueous polyimide material prepared by the preparation method of any one of claims 1 to 9.

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