High-insulation and high-flame-retardant polyimide material and preparation method thereof

Abstract

This invention relates to the field of polymer materials and discloses a highly insulating and highly flame-retardant polyimide material and its preparation method. The polyimide material comprises: a bismaleimide monomer, 4,4-diaminodiphenyl disulfide, modified halloysite nanotubes, a modified epoxidized silicon-containing intermediate, and an organic solvent. The bismaleimide monomer is prepared by ring-opening addition of maleic anhydride and 1,5-naphthyldiamine, followed by dehydration and cyclization of maleic acid. The modified halloysite nanotubes are prepared by in-situ reduction of silver nitrate, polyvinylpyrrolidone, ethylene glycol, and sodium chloride to modify the surface of the halloysite nanotubes with silver nanowires. The modified epoxidized silicon-containing intermediate is prepared by reacting an epoxidized silicon-containing intermediate prepared by reacting phenyltris(dimethylsiloxane)silane with allyl glycidyl ether with 1-pyrene butyric acid. The polyimide material prepared by this invention possesses excellent mechanical properties, high temperature resistance, thermal conductivity, hydrophobicity, and flame retardancy.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a highly insulating and highly flame-retardant polyimide material and its preparation method. Background Technology

[0002] Polyimide, as a high-performance polymer, has been widely used in electronics, communication equipment, integrated circuit packaging, military equipment manufacturing, and aerospace due to its advantages such as low density, high strength, high insulation, easy processing and molding, and chemical corrosion resistance. However, the random orientation and entanglement of polyimide molecular chains, the distance between molecular chains, and the presence of impurities lead to a significant reduction in phonon scattering and mean free path, resulting in low thermal conductivity. While filling the polyimide matrix with high thermal conductivity fillers can improve its thermal conductivity to some extent, the interface problem between the filler and the polymer matrix not only affects the thermal conductivity enhancement effect of the filler but may also lead to a significant decrease in the mechanical properties of the composite material, thus failing to fully utilize the mechanical property advantages of polyimide. At the same time, due to the high melting point, high solution viscosity, and difficult processing of polyimide, the introduced thermally conductive filler is difficult to form an efficient and continuous thermal conduction path, limiting the improvement of thermal conductivity. In addition, existing polyimide materials have poor water molecule barrier properties, and with the rapid development of high technology, the high temperature resistance and flame retardancy of traditional polyimide materials can no longer meet current market demands, thus limiting their application scope. Summary of the Invention

[0003] To address the shortcomings mentioned in the background art, the present invention aims to provide a highly insulating and highly flame-retardant polyimide material and its preparation method, thereby producing a polyimide material with excellent mechanical properties, high temperature resistance, thermal conductivity, hydrophobic properties, and flame-retardant properties.

[0004] The objective of this invention can be achieved through the following technical solutions: A highly insulating and highly flame-retardant polyimide material comprises the following components in parts by weight: 31-45 parts of bismaleimide monomer, 24-35 parts of 4,4-diaminodiphenyl disulfide, 0.5-1.2 parts of modified halloysite nanotubes, 3-7 parts of modified epoxidized silicon-containing intermediate, and 95-120 parts of organic solvent; The bismaleimide monomer is prepared by the ring-opening addition reaction of maleic anhydride and 1,5-naphthyldiamine to prepare maleamic acid intermediate, and then the maleamic acid intermediate is dehydrated and cyclized. The modified halloysite nanotubes were prepared by using γ-aminopropyltriethoxysilane and succinic anhydride to prepare carboxylated halloysite nanotubes, and then using silver nitrate as the silver source, polyvinylpyrrolidone as the dispersant, ethylene glycol as the solvent and reducing agent, and sodium chloride as the control agent, and modifying the surface of the halloysite nanotubes with silver nanowires by in-situ reduction method. The modified epoxidized silicon-containing intermediate is prepared by hydrosilylation reaction of phenyltris(dimethylsiloxane)silane with allyl glycidyl ether, and then prepared by ring-opening reaction of 1-pyrene butyric acid with the epoxidized silicon-containing intermediate.

[0005] Preferably, the method for preparing the bismaleimide monomer includes the following steps: I. Take maleic anhydride in a reactor and dissolve it in acetone solvent by stirring. Then, add a mixed solution of 1,5-naphthyldiamine and acetone under high-speed magnetic stirring. Stir well at room temperature for 5-7 hours. After the reaction is completed, filter, wash and dry to prepare maleamic acid intermediate. II. Disperse the maleamic acid intermediate in acetone solvent, then add zinc acetate catalyst, triethylamine and acetic anhydride dehydrating agent. After stirring and dispersing evenly, heat to 55~65℃ and continue the reaction for 4~5 hours. Then, mix the reaction product with ice water under stirring to produce a precipitate. After standing and precipitating, pour off the supernatant, wash, filter and dry to prepare the bismaleimide monomer.

[0006] Preferably, the molar ratio of maleic anhydride and 1,5-naphthyldiamine in step I is 2~2.1:1.

[0007] Preferably, in step II, the addition ratio of maleic acid intermediate, zinc acetate, triethylamine and acetic anhydride is 17.5~18g: 1.5~2g: 2.5~3.5mL: 11~11.5mL.

[0008] Preferably, the method for preparing the modified halloysite nanotubes includes the following steps: ① Halloysite nanotubes were dispersed in N,N-dimethylformamide, sonicated, and then deionized water was added to obtain a suspension. γ-aminopropyltriethoxysilane, succinic anhydride and N,N-dimethylformamide were placed in a reactor and stirred at 70~95℃ for 2~5h. Then the suspension was added and stirred for 4~6h. After the reaction was completed, the mixture was centrifuged, washed and dried to prepare carboxylated halloysite nanotubes. ② Carboxylated halloysite nanotubes, polyvinylpyrrolidone, and ethylene glycol were placed in a reactor and ultrasonically dispersed to obtain a dispersion. Silver nitrate was dissolved in ethylene glycol and added to the dispersion. The mixture was magnetically stirred at room temperature for 4-8 minutes. Then, sodium chloride was added and stirring was continued for 2-3 minutes. The reaction mixture was transferred to a high-pressure reactor and reacted at 145-155℃ for 2.5-3 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified halloysite nanotubes.

[0009] Preferably, in step ②, the mass ratio of carboxylated halloysite nanotubes, polyvinylpyrrolidone, silver nitrate, and sodium chloride is 0.1g:0.055~0.06g:0.075~0.08g:0.01mg.

[0010] Preferably, the method for preparing the modified epoxidized silicon-containing intermediate includes the following steps: (1) Take phenyltris(dimethylsiloxane)silane in a reactor, stir and heat to 105~110℃, keep warm for 25~30min, then cool down to 100~105℃, then add chloroplatinic acid catalyst, and at the same time add allyl glycidyl ether dropwise within 1h. After the dropwise addition is completed, place it at 105~110℃ for 3~4h to react. After the reaction is completed, prepare the epoxidized silicon-containing intermediate. (2) Take the epoxidized silicon-containing intermediate and N,N-dimethylformamide in a reactor, stir and mix them, then add 1-pyrene butyric acid and tetrabutylammonium bromide. Under nitrogen protection, react at 95~100℃ for 2~4h. After the reaction is completed, add the reaction liquid dropwise to hot water to obtain the crude product, then redissolve it in tetrahydrofuran, repeat the above precipitation-dissolution process, and finally vacuum dry to prepare the modified epoxidized silicon-containing intermediate.

[0011] Preferably, in step (1), the molar ratio of phenyltris(dimethylsiloxane)silane to allyl glycidyl ether is 1:3 to 3.5; and in step (2), the molar ratio of epoxidized silicon-containing intermediate to 1-pyrene butyric acid is 1:1 to 1.2.

[0012] The preparation method of the high-insulation and high-flame-retardant polyimide material as described above includes the following steps: a modified halloysite nanotube is dispersed in an organic solvent to prepare a suspension; bismaleimide monomer and 4,4-diaminodiphenyl disulfide are added to the suspension respectively; the mixture is refluxed at 70-80°C and stirred for 7-9 hours; then a modified epoxidized silicon-containing intermediate is added and stirred for 0.5-1 hours; excess solvent is removed and the mixture is cured; then it is naturally cooled to room temperature to obtain the high-insulation and high-flame-retardant polyimide material.

[0013] Preferably, the organic solvent is N,N-dimethylformamide or acetone; the curing temperature conditions are 130~135℃ for 3~3.5h and 165~170℃ for 2~2.5h.

[0014] The beneficial effects of this invention are: This invention utilizes a two-step reaction involving the ring-opening addition of maleic anhydride to 1,5-naphthyldiamine and the dehydration and cyclization of maleic acid to prepare a bismaleimide monomer containing a naphthalene ring structure. The rigid, double-fused-ring structure of the naphthalene ring significantly inhibits chain segment thermal motion and increases the material's heat distortion temperature by enhancing the planar rigidity and conjugation effect of the molecular chain. The aromatic ring structure also reduces the water absorption rate of the resin system, which is beneficial for improving the material's high-temperature resistance. Furthermore, this invention utilizes γ-aminopropyltriethoxysilane and succinic anhydride to prepare carboxylated halloysite nanotubes. Then, using silver nitrate as the silver source, polyvinylpyrrolidone as the dispersant, ethylene glycol as the solvent and reducing agent, and sodium chloride as the control agent, an in-situ reduction method is employed to prepare the nanotubes. Modified halloysite nanotubes with silver wires are used in polymer reinforcement and flame retardant modification due to their unique tubular structure, large aspect ratio, excellent strength and thermal stability. Silver wires have a high aspect ratio, excellent thermal conductivity, good dispersibility and interfacial interaction. Carboxylation treatment of halloysite nanotubes can effectively improve their dispersibility, and positively charged silver ions are adsorbed on the surface of halloysite nanotubes in the form of Ag-O bonds, thereby reducing and growing on the surface of halloysite nanotubes, increasing the entanglement between halloysite nanotubes and silver wires. The coexistence of doping and grafting between the two is more conducive to the establishment of a thermally conductive network.

[0015] This invention utilizes a hydrosilylation reaction between phenyltris(dimethylsiloxane)silane and allyl glycidyl ether to prepare an epoxidized silicon-containing intermediate. Then, a ring-opening reaction is performed between 1-pyrene butyric acid and the epoxidized silicon-containing intermediate to prepare a modified epoxidized silicon-containing intermediate with two remaining ungrafted epoxy groups. Using 4,4-diaminodiphenyl disulfide as a curing agent, bismaleimide monomers, and the modified epoxidized silicon-containing intermediate as raw materials, a polyimide material is prepared via Michael addition and epoxy ring-opening reactions. This polyimide material contains flame-retardant N-Si-S synergistic flame-retardant elements in its structure, imparting excellent flame-retardant properties. The introduced pyrene group further enhances its properties. The silicon-oxygen bond (-Si-O-Si-) exhibits excellent hydrophobic and high-temperature resistance properties. Modified halloysite nanotubes also possess certain strength, thermal stability, flame retardancy, and thermal conductivity. Modified halloysite nanotubes are used to prepare polyimide materials via in-situ polymerization. When subjected to external forces, the long linear silver nanowires and short fibrous halloysite nanotubes effectively transfer and diffuse external stress to various parts of the material. Furthermore, the introduction of inorganic rigid materials can resist external stress, providing both reinforcement and toughening. This results in superior mechanical properties, high-temperature resistance, thermal stability, thermal conductivity, and flame retardancy. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1: A method for preparing a bismaleimide monomer includes the following steps: I. Take 10.3g of maleic anhydride in a reactor and stir it thoroughly to dissolve it in 100mL of acetone solvent. Then, under high-speed magnetic stirring, add a mixed solution of 7.9g of 1,5-naphthyldiamine and 50mL of acetone. Stir thoroughly at room temperature for 6h. After the reaction is completed, filter, wash and dry to prepare maleamic acid intermediate. II. Take 17.7g of maleamic acid intermediate and disperse it in 100mL of acetone. Then add 1.8g of zinc acetate catalyst, 3mL of triethylamine and 11.2mL of acetic anhydride dehydrating agent. After stirring and dispersing evenly, heat to 60℃ and continue to react for 5h. Then mix the reaction product with 200mL of ice water under stirring to produce a precipitate. After standing and precipitating, discard the supernatant. After washing, filtering and drying, prepare the bismaleimide monomer.

[0018] Example 2: A method for preparing modified halloysite nanotubes includes the following steps: ① Take 1g of halloysite nanotubes and disperse them in 50mL of N,N-dimethylformamide. After ultrasonic treatment, add 10mL of deionized water to obtain a suspension. Take 1g of γ-aminopropyltriethoxysilane, 0.4g of succinic anhydride and 50mL of N,N-dimethylformamide in a reactor and stir at 80℃ for 3h. Then add the suspension and stir for 5h. After the reaction is completed, centrifuge, wash and dry to prepare carboxylated halloysite nanotubes. ② Take 0.6g of carboxylated halloysite nanotubes, 0.35g of polyvinylpyrrolidone and 30mL of ethylene glycol in a reactor, and disperse them evenly by ultrasonication to obtain a dispersion. Take 0.47g of silver nitrate, dissolve it in 25mL of ethylene glycol and add it to the dispersion. Stir magnetically at room temperature for 5min, then add 0.06mg of sodium chloride and continue stirring for 2min. Transfer the reaction mixture to a high-pressure reactor and react at 150℃ for 3h. After the reaction is completed, filter, wash and dry to prepare modified halloysite nanotubes.

[0019] Example 3 A method for preparing a modified epoxide silicon-containing intermediate includes the following steps: (1) Take 13.4g of phenyltris(dimethylsiloxane)silane in a reactor, stir and heat to 110℃, keep warm for 30min, then cool down to 105℃, and then add 30.5μL of chloroplatinic acid catalyst PT-5000. At the same time, add 16.2g of allyl glycidyl ether dropwise within 1h. After the dropwise addition is completed, place it at 110℃ for 3h. After the reaction is completed, an epoxidized silicon-containing intermediate is prepared. (2) Take 16.8g of epoxidized silicon-containing intermediate and 50mL of N,N-dimethylformamide in a reactor, stir and mix, then add 7.5g of 1-pyrenebutyric acid and 0.8g of tetrabutylammonium bromide. Under nitrogen protection, react at 100℃ for 3h. After the reaction is completed, add the reaction solution dropwise to 300mL of hot water to obtain the crude product. Then redissolve it in tetrahydrofuran and repeat the above precipitation-dissolution process. Finally, vacuum dry to prepare the modified epoxidized silicon-containing intermediate.

[0020] Example 4 A highly insulating and highly flame-retardant polyimide material comprising the following components by weight: 32 parts of bismaleimide monomer prepared in Example 1, 25 parts of 4,4-diaminodiphenyl disulfide, 0.6 parts of modified halloysite nanotubes prepared in Example 2, 3.3 parts of modified epoxidized silicon-containing intermediate prepared in Example 3, and 98 parts of organic solvent N,N-dimethylformamide.

[0021] The preparation method of the above-mentioned highly insulating and highly flame-retardant polyimide material includes the following steps: Modified halloysite nanotubes were dispersed in the organic solvent N,N-dimethylformamide to prepare a suspension. Bismaleimide monomer and 4,4-diaminodiphenyl disulfide were added to the suspension respectively. The mixture was refluxed at 75°C and stirred for 8 hours. Then, modified epoxidized silicon-containing intermediate was added and stirred for 1 hour. Excess solvent was removed and the mixture was cured at 135°C for 3 hours and 170°C for 2 hours. The mixture was then allowed to cool naturally to room temperature to prepare a highly insulating and highly flame-retardant polyimide material.

[0022] Example 5 A highly insulating and highly flame-retardant polyimide material comprising the following components by weight: 38 parts of bismaleimide monomer prepared in Example 1, 30 parts of 4,4-diaminodiphenyl disulfide, 0.9 parts of modified halloysite nanotubes prepared in Example 2, 5.4 parts of modified epoxidized silicon-containing intermediate prepared in Example 3, and 107 parts of organic solvent N,N-dimethylformamide.

[0023] The preparation method of the above-mentioned highly insulating and highly flame-retardant polyimide material is the same as that in Example 4.

[0024] Example 6 A highly insulating and highly flame-retardant polyimide material comprising the following components by weight: 44 parts of bismaleimide monomer prepared in Example 1, 34 parts of 4,4-diaminodiphenyl disulfide, 1.1 parts of modified halloysite nanotubes prepared in Example 2, 6.5 parts of modified epoxidized silicon-containing intermediate prepared in Example 3, and 115 parts of organic solvent N,N-dimethylformamide.

[0025] The preparation method of the above-mentioned highly insulating and highly flame-retardant polyimide material is the same as that in Example 4.

[0026] Comparative Example 1: A highly insulating and highly flame-retardant polyimide material comprising the following components by weight: 44 parts of 4,4-bismaleimide diphenylmethane, 34 parts of 4,4-diaminodiphenyl disulfide, 1.1 parts of the modified halloysite nanotubes prepared in Example 2, 6.5 parts of the modified epoxidized silicon-containing intermediate prepared in Example 3, and 115 parts of the organic solvent N,N-dimethylformamide.

[0027] The preparation method of the above-mentioned highly insulating and highly flame-retardant polyimide material is the same as that in Example 4.

[0028] Comparative Example 2 A highly insulating and highly flame-retardant polyimide material comprising the following components by weight: 44 parts of bismaleimide monomer prepared in Example 1, 34 parts of 4,4-diaminodiphenyl disulfide, 1.1 parts of halloysite nanotubes, 6.5 parts of modified epoxidized silicon-containing intermediate prepared in Example 3, and 115 parts of organic solvent N,N-dimethylformamide.

[0029] The preparation method of the above-mentioned highly insulating and highly flame-retardant polyimide material is the same as that in Example 4.

[0030] Comparative Example 3: A highly insulating and highly flame-retardant polyimide material comprising the following components by weight: 44 parts of bismaleimide monomer prepared in Example 1, 34 parts of 4,4-diaminodiphenyl disulfide, 1.1 parts of modified halloysite nanotubes prepared in Example 2, 6.5 parts of epoxidized silicon-containing intermediate prepared in Example 3, and 115 parts of organic solvent N,N-dimethylformamide.

[0031] The preparation method of the above-mentioned highly insulating and highly flame-retardant polyimide material is the same as that in Example 4.

[0032] Comparative Example 4: A highly insulating and highly flame-retardant polyimide material comprising the following components by weight: 44 parts of bismaleimide monomer prepared in Example 1, 34 parts of 4,4-diaminodiphenyl disulfide, 1.1 parts of modified halloysite nanotubes prepared in Example 2, 6.5 parts of bisphenol A diglycidyl ether, and 115 parts of the organic solvent N,N-dimethylformamide.

[0033] The preparation method of the above-mentioned highly insulating and highly flame-retardant polyimide material is the same as that in Example 4.

[0034] Performance testing The performance of the polyimide materials prepared in Examples 4-6 and Comparative Examples 1-4 was tested: (1) Mechanical property testing: According to ASTM-D882 standard, tensile strength, Young's modulus and elongation at break were measured at room temperature using a universal testing machine. The tensile rate was 2 mm / min. Each sample was tested more than five times, and the average value was calculated. The data results are shown in Table 1.

[0035] (2) High temperature resistance test: The sample was tested under nitrogen atmosphere using a thermogravimetric analyzer at a heating rate of 10℃ / min to 800℃, and the thermal decomposition temperature T was determined. d5% Thermal decomposition temperature T d30% The data results are shown in Table 1.

[0036] (3) Thermal conductivity test: According to the standard GB / T 10297-2015, the thermal conductivity of the sample was measured using a TC3200 thermal conductivity meter. The sample size was 60mm×60mm. The data results are shown in Table 1.

[0037] (4) Hydrophobicity test: The sample was immersed in deionized water for 12 hours and weighed. The water absorption rate of the sample after immersion was calculated. The sample size was 3cm×4cm. The data results are shown in Table 1.

[0038] (5) Flame retardant performance test: The flame retardant performance of the sample was evaluated by the top surface burning method using a limiting oxygen index tester. The test was conducted in accordance with GB / T2406.2-2009. The sample size was 80mm×10mm. The data results are shown in Table 1.

[0039] Table 1 Sample performance test results As can be seen from the data in Table 1, the polyimide materials prepared in Examples 4-6 of this invention possess excellent mechanical properties, high-temperature resistance, thermal conductivity, hydrophobicity, and flame retardancy. In Comparative Example 1, where the bismaleimide monomer was replaced in equal amounts with 4,4-bismaleimide diphenylmethane, the measured thermal decomposition temperature and limiting oxygen index were lower than those in Examples 4-6, indicating that the introduction of the bismaleimide monomer is beneficial to improving the high-temperature resistance and flame retardancy of the material. In Comparative Example 2, where no halloysite nanotubes were modified, the measured tensile strength, Young's modulus, elongation, and thermal conductivity were lower than those in Examples 4-6, indicating that the addition of modified halloysite nanotubes improved the mechanical and thermal conductivity of the material to a certain extent. In Example 3, 1-pyrene butyric acid was not used to graft the epoxidized silicon-containing intermediate. The measured thermal decomposition temperature and hydrophobicity were lower than those in Examples 4-6. This is because the introduction of the pyrene group is beneficial to improving the hydrophobicity and high-temperature resistance of the material. In Comparative Example 4, the modified epoxidized silicon-containing intermediate was replaced with an equal amount of bisphenol A diglycidyl ether. The measured thermal decomposition temperature, water contact angle, and limiting oxygen index were lower than those in Examples 4-6. This indicates that the introduction of the modified epoxidized silicon-containing intermediate has improved the hydrophobicity, high-temperature resistance, and flame retardant properties of the material to a certain extent.

[0040] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0041] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A highly insulating and highly flame-retardant polyimide material, characterized in that, It comprises the following components by weight: 31-45 parts of bismaleimide monomer, 24-35 parts of 4,4-diaminodiphenyl disulfide, 0.5-1.2 parts of modified halloysite nanotubes, 3-7 parts of modified epoxidized silicon-containing intermediate, and 95-120 parts of organic solvent. The bismaleimide monomer is prepared by the ring-opening addition reaction of maleic anhydride and 1,5-naphthyldiamine to prepare maleamic acid intermediate, and then the maleamic acid intermediate is dehydrated and cyclized. The modified halloysite nanotubes were prepared by using γ-aminopropyltriethoxysilane and succinic anhydride to prepare carboxylated halloysite nanotubes, and then using silver nitrate as the silver source, polyvinylpyrrolidone as the dispersant, ethylene glycol as the solvent and reducing agent, and sodium chloride as the control agent, and modifying the surface of the halloysite nanotubes with silver nanowires by in-situ reduction method. The modified epoxidized silicon-containing intermediate is prepared by hydrosilylation reaction of phenyltris(dimethylsiloxane)silane with allyl glycidyl ether, and then prepared by ring-opening reaction of 1-pyrene butyric acid with the epoxidized silicon-containing intermediate.

2. The high insulation, high flame retardant polyimide material according to claim 1, wherein, The preparation method of the bismaleimide monomer includes the following steps: I. Take maleic anhydride in a reactor and dissolve it in acetone solvent by stirring. Then, add a mixed solution of 1,5-naphthyldiamine and acetone under high-speed magnetic stirring. Stir well at room temperature for 5-7 hours. After the reaction is completed, filter, wash and dry to prepare maleamic acid intermediate. II. Disperse the maleamic acid intermediate in acetone solvent, then add zinc acetate catalyst, triethylamine and acetic anhydride dehydrating agent. After stirring and dispersing evenly, heat to 55~65℃ and continue the reaction for 4~5 hours. Then, mix the reaction product with ice water under stirring to produce a precipitate. After standing and precipitating, pour off the supernatant, wash, filter and dry to prepare the bismaleimide monomer.

3. The high insulation, high flame retardant polyimide material according to claim 2, wherein, In step I, the molar ratio of maleic anhydride to 1,5-naphthyldiamine is 2~2.1:

1.

4. The high insulation, high flame retardant polyimide material according to claim 2, wherein, In step II, the addition ratio of maleic acid intermediate, zinc acetate, triethylamine and acetic anhydride is 17.5~18g: 1.5~2g: 2.5~3.5mL: 11~11.5mL.

5. The high insulation, high flame retardant polyimide material according to claim 1, wherein, The method for preparing the modified halloysite nanotubes includes the following steps: ① Halloysite nanotubes were dispersed in N,N-dimethylformamide, sonicated, and then deionized water was added to obtain a suspension. γ-aminopropyltriethoxysilane, succinic anhydride and N,N-dimethylformamide were placed in a reactor and stirred at 70~95℃ for 2~5h. Then the suspension was added and stirred for 4~6h. After the reaction was completed, the mixture was centrifuged, washed and dried to prepare carboxylated halloysite nanotubes. ② Carboxylated halloysite nanotubes, polyvinylpyrrolidone, and ethylene glycol were placed in a reactor and ultrasonically dispersed to obtain a dispersion. Silver nitrate was dissolved in ethylene glycol and added to the dispersion. The mixture was magnetically stirred at room temperature for 4-8 minutes. Then, sodium chloride was added and stirring was continued for 2-3 minutes. The reaction mixture was transferred to a high-pressure reactor and reacted at 145-155℃ for 2.5-3 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified halloysite nanotubes.

6. The high insulation, high flame retardant polyimide material according to claim 5, wherein, In step ②, the mass ratio of carboxylated halloysite nanotubes, polyvinylpyrrolidone, silver nitrate, and sodium chloride is 0.1g:0.055~0.06g:0.075~0.08g:0.01mg.

7. The high insulation, high flame retardant polyimide material according to claim 1, wherein, The method for preparing the modified epoxidized silicon-containing intermediate includes the following steps: (1) Take phenyltris(dimethylsiloxane)silane in a reactor, stir and heat to 105~110℃, keep warm for 25~30min, then cool down to 100~105℃, then add chloroplatinic acid catalyst, and at the same time add allyl glycidyl ether dropwise within 1h. After the dropwise addition is completed, place it at 105~110℃ for 3~4h to react. After the reaction is completed, prepare the epoxidized silicon-containing intermediate. (2) Take the epoxidized silicon-containing intermediate and N,N-dimethylformamide in a reactor, stir and mix them, then add 1-pyrene butyric acid and tetrabutylammonium bromide. Under nitrogen protection, react at 95~100℃ for 2~4h. After the reaction is completed, add the reaction liquid dropwise to hot water to obtain the crude product, then redissolve it in tetrahydrofuran, repeat the above precipitation-dissolution process, and finally vacuum dry to prepare the modified epoxidized silicon-containing intermediate.

8. The high-insulation, high-flame-retardant polyimide material according to claim 7, characterized in that, In step (1), the molar ratio of phenyltris(dimethylsiloxane)silane to allyl glycidyl ether is 1:3~3.5; in step (2), the molar ratio of epoxidized silicon-containing intermediate to 1-pyrenebutyric acid is 1:1~1.

2.

9. A method for preparing a highly insulating and highly flame-retardant polyimide material according to any one of claims 1 to 8, characterized in that, Includes the following steps: Modified halloysite nanotubes were dispersed in an organic solvent to prepare a suspension. Bismaleimide monomer and 4,4-diaminodiphenyl disulfide were added to the suspension respectively. The mixture was refluxed at 70-80°C and stirred for 7-9 hours. Then, modified epoxidized silicon-containing intermediate was added and stirred for 0.5-1 hours. Excess solvent was removed and the mixture was cured. The mixture was then naturally cooled to room temperature to prepare a polyimide material with high insulation and high flame retardancy.

10. The method for preparing the highly insulating and highly flame-retardant polyimide material according to claim 9, characterized in that, The organic solvent is N,N-dimethylformamide or acetone; the curing temperature conditions are 130~135℃ for 3~3.5h and 165~170℃ for 2~2.5h.

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