A high-temperature-resistant polyimide resin and a preparation method thereof

Abstract

This invention relates to the field of polyimide resins, specifically to a high-temperature resistant polyimide resin and its preparation method, which addresses the problems of poor high-temperature dimensional stability, low thermal decomposition temperature, and insufficient long-term heat resistance of traditional polyimides. The method involves adding anhydrous N,N-dimethylacetamide and piperidinyl aromatic diamine to a three-necked flask and stirring, then adding 2,3,6,7-anthracite dianhydride and stirring again. Toluene is then added, and the mixture is heated to remove water. After cooling, the mixture is poured into deionized water for precipitation, filtered under reduced pressure, washed, dried, pulverized, and then placed in a mold for gradient hot pressing. After heat treatment and cooling demolding, the high-temperature resistant polyimide resin is obtained. This high-temperature resistant polyimide resin exhibits excellent high-temperature resistance and mechanical strength.

Description

Technical Field

[0001] This invention relates to the field of polyimide resins, and more specifically to a high-temperature resistant polyimide resin and its preparation method. Background Technology

[0002] With the rapid development of high-tech fields such as flexible electronics, high-frequency communication, optical display, and high-end insulating packaging, the market's requirements for the comprehensive performance of high-temperature resistant polymer materials are constantly increasing. Polyimide resin, with its excellent thermal stability, mechanical properties, chemical corrosion resistance, and insulation properties, has become a core representative of high-end functional polymer materials and is widely used in key fields such as aerospace, microelectronics, flexible circuit boards, and optical devices.

[0003] Traditional fully aromatic polyimides are mostly prepared by polymerization of conventional monomers such as pyromellitic dianhydride and 4,4'-diaminodiphenyl ether. Although they possess a certain degree of heat resistance, the strong aromatic conjugated structure and tight molecular chain stacking of the molecular chains not only easily form intermolecular charge transfer complexes, resulting in dark colors and low light transmittance, but also fail to meet the requirements for transparent optical devices. In addition, traditional polyimides generally suffer from insufficient high-temperature dimensional stability and difficulty in meeting long-term high-temperature resistance standards, leading to significant limitations in their overall applications.

[0004] Therefore, developing a high-temperature resistant polyimide resin with excellent comprehensive performance and outstanding high-temperature thermal stability is of great practical significance for expanding the industrial application of polyimide in high-end optoelectronics, high-frequency electronics and other fields with stringent requirements for high-temperature resistance. Summary of the Invention

[0005] In order to overcome the above-mentioned technical problems, the purpose of this invention is to provide a high-temperature resistant polyimide resin and its preparation method.

[0006] The objective of this invention can be achieved through the following technical solutions: In a first aspect, this application provides a high-temperature resistant polyimide resin, comprising the following components in parts by weight: Piperidinyl aromatic diamine 4.7-9.4 parts, 2,3,6,7-anthracite dianhydride 3.3-6.6 parts, anhydrous N,N-dimethylacetamide 73-146 parts, and toluene 8-16 parts; The piperidinyl aromatic diamine is prepared by the following steps: Step a1: Add nitric acid and concentrated sulfuric acid to a round-bottom flask, stir for 10-12 min under ice bath conditions at a stirring rate of 300-400 r / min, add 4-phenylpiperidine in 3 batches, allow to rise naturally to room temperature, stir and react for 7-7.2 h, pour the reaction solution into 5℃ ice water to precipitate solid, filter, wash the filter cake with deionized water until the filtrate is neutral, recrystallize with ethanol, and then place it in a vacuum drying oven and dry at 55-60℃ for 24-25 h to obtain the first intermediate; .

[0007] Step a2: Add the first intermediate, 4-fluoronitrobenzene, anhydrous potassium carbonate, and N,N-dimethylformamide to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Purge with nitrogen for protection and stir for 30-32 min at 55-60℃ and a stirring rate of 300-400 r / min. Then raise the temperature to 115-120℃ and continue the reaction for 12-13 h. After the reaction is complete, cool to room temperature, pour the reaction solution into deionized water, stir to precipitate crystals, filter, wash 3-5 times with 60℃ hot distilled water, and then place in a vacuum drying oven and dry at 55-60℃ for 24-25 h to obtain the second intermediate. .

[0008] Step a3: Add the second intermediate and anhydrous ethanol to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and constant pressure dropping funnel. Purge with nitrogen for protection and stir for 10-12 min at a temperature of 25-30℃ and a stirring rate of 300-400 r / min. Wet the palladium-carbon catalyst with ethanol and add it to the system. Then raise the temperature to 65-70℃ and stir for 30-32 min. Then add hydrazine hydrate dropwise while stirring, controlling the dropping rate to 1-2 drops / s. Continue the reaction for 8-8.2 h. After the reaction is complete, filter while hot. Allow the filtrate to cool naturally to room temperature. Pour the reaction solution into deionized water, stir to precipitate crystals, filter, wash 2-3 times with ice water, and then place in a vacuum drying oven at a temperature of 55-60℃ for 24-25 h to obtain piperidinyl aromatic diamine.

[0009] .

[0010] In a preferred embodiment of the present invention, the ratio of nitric acid, concentrated sulfuric acid and 4-phenylpiperidine used in step a1 is 80-120 mL: 20-30 mL: 25-37 g.

[0011] In a preferred embodiment of the present invention, the mass fraction of nitric acid in step a1 is 65%; and the mass fraction of concentrated sulfuric acid is 98%.

[0012] In a preferred embodiment of the present invention, the ratio of the first intermediate, 4-fluoronitrobenzene, anhydrous potassium carbonate and N,N-dimethylformamide in step a2 is 50-60 mmol: 50-60 mmol: 52-62 mmol: 150-180 mL.

[0013] In a preferred embodiment of the present invention, the ratio of the second intermediate, anhydrous ethanol, palladium on carbon catalyst and hydrazine hydrate in step a3 is 30-40 mmol: 120-160 mL: 0.4-0.5 g: 15-20 mL.

[0014] In a preferred embodiment of the present invention, the mass fraction of hydrazine hydrate in step a3 is 80%.

[0015] In a preferred embodiment of the present invention, the mass fraction of palladium in the palladium-carbon catalyst in step a3 is 10%.

[0016] Secondly, this application provides a method for preparing a high-temperature resistant polyimide resin, comprising the following steps: Step 1: Weigh out 4.7-9.4 parts by weight of piperidinyl aromatic diamine, 3.3-6.6 parts by weight of 2,3,6,7-anthracite dianhydride, 73-146 parts by weight of anhydrous N,N-dimethylacetamide, and 8-16 parts by weight of toluene, and set aside. Step 2: Add anhydrous N,N-dimethylacetamide and piperidinyl aromatic diamine to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Purge with nitrogen for protection and stir for 15-20 minutes at 25-30℃ and a stirring rate of 300-400 r / min. Add 2,3,6,7-anthracite dianhydride in three batches, 15 minutes apart. After the addition is complete, stir at 25℃ for 12-13 hours. Add toluene, assemble a water separator, and remove water by heating to 155-160℃ under nitrogen protection for 4-4.2 hours. Then, heat to 170-180℃ and hold for 2-2.2 hours. The reaction proceeds... After cooling to room temperature, the product is poured into deionized water for precipitation, filtered under reduced pressure, and the filter cake is collected. The filter cake is first washed with deionized water until the filtrate is neutral, and then transferred to a vacuum drying oven and dried at 75-80℃ for 12-13 hours. It is then pulverized with a grinder and placed in a mold for gradient hot pressing. First, it is held at 280℃ and 2MPa for 10-12 minutes, then heated to 320-350℃ and 3-5MPa for 20-30 minutes. After natural cooling and demolding, it is heat-treated at 300-320℃ for 60-65 minutes to obtain high-temperature resistant polyimide resin.

[0017] The beneficial effects of this invention are: This invention discloses a high-temperature resistant polyimide resin and its preparation method. The method involves adding anhydrous N,N-dimethylacetamide and piperidinyl aromatic diamine to a three-necked flask and stirring. Then, 2,3,6,7-anthracite dianhydride is added and stirred. Toluene is added, and the mixture is heated to remove water. After cooling, the resin is poured into deionized water for precipitation, filtered under reduced pressure, washed, dried, and pulverized. The precipitate is then placed in a mold for gradient hot pressing, held at the temperature, cooled, demolded, and heat-treated to obtain the high-temperature resistant polyimide resin. Piperidinyl aromatic diamine can improve the resin's solubility and transparency, reduce the dielectric constant and molecular chain packing density, and endow the material with superior comprehensive processing and functional properties while ensuring the high-temperature resistance and mechanical strength of the polyimide resin. The high-temperature resistant polyimide resin exhibits excellent high-temperature resistance and mechanical strength. In the preparation of high-temperature resistant polyimide resin, a piperidinyl aromatic diamine was first prepared. Firstly, 4-phenylpiperidine underwent aromatic ring electrophilic nitration in a mixed acid system of nitric acid and concentrated sulfuric acid, introducing a nitro group onto the benzene ring to obtain a mononitro-substituted first intermediate. Then, the piperidinium nitrogen of the first intermediate acted as a nucleophile, reacting with 4-fluoronitrobenzene in an aromatic nucleophilic substitution reaction, where the fluorine atom was replaced by a piperidinyl group, introducing a second nitro group into the molecule to obtain a dinitro second intermediate. Subsequently, using palladium on carbon as a catalyst and hydrazine hydrate as a reducing agent, the two nitro groups were simultaneously reduced to amino groups by heating in ethanol, finally yielding the piperidinyl aromatic diamine. Piperidine, an alicyclic nitrogen-containing heterocyclic, non-planar, flexible structure, combined with the rigid framework of the aromatic diamine, allows for the synthesis of polymers such as polyimides that retain the excellent heat resistance and mechanical strength of the aromatic structure while significantly reducing the molecular chain packing density, weakening the intermolecular charge transfer complexation effect, and exhibiting steric hindrance from the piperidinyl side groups. The curved structure significantly disrupts the regularity and crystallinity of polymer molecular chains, greatly improving the material's solubility in conventional organic solvents and significantly reducing the difficulty of thin film preparation and solution coating processes. Constructed with 2,3,6,7-anthracite tetracarboxylic dianhydride as the aromatic rigid framework and piperidinyl aromatic diamine as the functional monomer, the synergistic combination of anthracene-based fused-ring aromatic structures and piperidinium polar heterocycles and alicyclic structures achieves extremely low dielectric constant, low dielectric loss, low water absorption, and excellent insulation. It also possesses good high-temperature resistance, aging resistance, and dimensional thermal stability, making it perfectly suited for high-frequency and high-speed substrates, flexible display substrates, chip insulating packaging, high-frequency circuit boards, and other high-end electronic fields with stringent dielectric and insulation requirements. The nitrogen-containing piperidinium heterocycles also impart certain flame retardancy, chemical corrosion resistance, and adhesion properties to the material, enhancing the bonding force between the thin film and the substrate, and broadening its application potential in optoelectronic coatings, functional separation membranes, and weather-resistant insulating materials. Detailed Implementation

[0018] 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.

[0019] Example 1: This example describes a method for preparing a high-temperature resistant polyimide resin, comprising the following steps: Step S1: Add 80 mL of 65% nitric acid and 20 mL of 98% concentrated sulfuric acid to a round-bottom flask. Stir for 10 min at 300 r / min under ice bath conditions. Add 25 g of 4-phenylpiperidine in three portions. Allow the mixture to rise naturally to room temperature and stir for 7 h. Pour the reaction solution into 5°C ice water to precipitate a solid. Filter the solid and wash the filter cake with deionized water until the filtrate is neutral. Recrystallize the solid with ethanol and then place it in a vacuum drying oven at 55°C for 24 h to obtain the first intermediate. Step S2: 50 mmol of the first intermediate, 50 mmol of 4-fluoronitrobenzene, 52 mmol of anhydrous potassium carbonate and 150 mL of N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Nitrogen gas was introduced for protection. The mixture was stirred at 55 °C and 300 r / min for 30 min. Then the temperature was raised to 115 °C and the reaction was continued for 12 h. After the reaction was completed, the mixture was cooled to room temperature. The reaction solution was poured into deionized water, stirred to precipitate crystals, filtered, washed three times with hot distilled water at 60 °C, and then placed in a vacuum drying oven and dried at 55 °C for 24 h to obtain the second intermediate. Step S3: 30 mmol of the second intermediate and 120 mL of anhydrous ethanol were added to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube and constant pressure dropping funnel. Nitrogen gas was introduced for protection. The mixture was stirred for 10 min at 25 °C and a stirring rate of 300 r / min. 0.4 g of palladium-on-carbon catalyst (the mass fraction of palladium in the palladium-on-carbon catalyst was 10%) was moistened with ethanol and added to the system. The temperature was then raised to 65 °C and stirred for 30 min. Then, 15 mL of 80% hydrazine hydrate was added dropwise while stirring, with the dropping rate controlled at 1 drop / s. The reaction was continued for 8 h. After the reaction was completed, the mixture was filtered while hot. The filtrate was allowed to cool naturally to room temperature. The reaction solution was poured into deionized water, stirred to precipitate crystals, filtered, washed twice with ice water, and then placed in a vacuum drying oven and dried at 55 °C for 24 h to obtain piperidinyl aromatic diamine. Step S4: Weigh out 4.7 parts by weight of piperidinyl aromatic diamine, 3.3 parts by weight of 2,3,6,7-anthracite dianhydride, 73 parts by weight of anhydrous N,N-dimethylacetamide and 8 parts by weight of toluene, and set aside. Step S5: Anhydrous N,N-dimethylacetamide and piperidinyl aromatic diamine were added to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Nitrogen gas was introduced for protection, and the mixture was stirred for 15 minutes at 25°C and a stirring rate of 300 r / min. 2,3,6,7-anthracite dianhydride was added in three batches, with 15-minute intervals between each addition. After the additions were complete, the mixture was stirred for 12 hours at 25°C. Toluene was then added, and a water separator was installed. Under nitrogen protection, the mixture was heated to 155°C for 4 hours to remove water, followed by a heating to 170°C and holding for 2 hours. The reaction was then complete. After cooling to room temperature, the mixture was poured into deionized water for precipitation, filtered under reduced pressure, and the filter cake was collected. The filter cake was first washed with deionized water until the filtrate was neutral, and then transferred to a vacuum drying oven and dried at 75°C for 12 hours. It was then pulverized with a grinder and placed in a mold for gradient hot pressing. The mold was first held at 280°C and 2MPa for 10 minutes, then heated to 320°C and 3MPa and held for 20 minutes. After natural cooling and demolding, it was heat-treated at 300°C for 60 minutes to obtain high-temperature resistant polyimide resin.

[0020] Example 2: This example describes a method for preparing a high-temperature resistant polyimide resin, comprising the following steps: Step S1: Add 100 mL of 65% nitric acid and 25 mL of 98% concentrated sulfuric acid to a round-bottom flask. Stir for 11 min at 350 r / min under ice bath conditions. Add 31 g of 4-phenylpiperidine in three portions. Allow the mixture to rise naturally to room temperature and stir for 7.1 h. Pour the reaction solution into 5°C ice water to precipitate a solid. Filter the solid and wash the filter cake with deionized water until the filtrate is neutral. Recrystallize the solid with ethanol and then place it in a vacuum drying oven at 57°C for 24.5 h to obtain the first intermediate. Step S2: 55 mmol of the first intermediate, 55 mmol of 4-fluoronitrobenzene, 57 mmol of anhydrous potassium carbonate and 165 mL of N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Nitrogen gas was introduced for protection. The mixture was stirred at 57 °C and 350 r / min for 31 min. Then the temperature was raised to 117 °C and the reaction was continued for 12.5 h. After the reaction was completed, the mixture was cooled to room temperature. The reaction solution was poured into deionized water, stirred to precipitate crystals, filtered, washed 4 times with hot distilled water at 60 °C, and then placed in a vacuum drying oven and dried at 57 °C for 24.5 h to obtain the second intermediate. Step S3: 35 mmol of the second intermediate and 140 mL of anhydrous ethanol were added to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and constant pressure dropping funnel. Nitrogen gas was introduced for protection, and the mixture was stirred for 11 min at 27 °C and a stirring rate of 350 r / min. 0.45 g of palladium-on-carbon catalyst (the mass fraction of palladium in the palladium-on-carbon catalyst was 10%) was moistened with ethanol and added to the system. The temperature was then raised to 67 °C and stirred for 31 min. Then, 17 mL of 80% hydrazine hydrate was added dropwise while stirring, with the dropping rate controlled at 1 drop / s. The reaction was continued for 8.1 h. After the reaction was completed, the mixture was filtered while hot. The filtrate was allowed to cool naturally to room temperature. The reaction solution was poured into deionized water, stirred to precipitate crystals, filtered, washed twice with ice water, and then placed in a vacuum drying oven and dried at 57 °C for 24.5 h to obtain piperidinyl aromatic diamine. Step S4: Weigh out 7 parts by weight of piperidinyl aromatic diamine, 50 parts by weight of 2,3,6,7-anthracite dianhydride, 110 parts by weight of anhydrous N,N-dimethylacetamide and 12 parts by weight of toluene, and set aside. Step S5: Anhydrous N,N-dimethylacetamide and piperidinyl aromatic diamine were added to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Nitrogen gas was introduced for protection, and the mixture was stirred for 17 minutes at 27°C and a stirring rate of 350 r / min. 2,3,6,7-Anthracene tetracarboxylic dianhydride was added in three batches, with 15-minute intervals between each addition. After the additions were complete, the mixture was stirred for 12.5 hours at 25°C. Toluene was then added, and a water separator was installed. Under nitrogen protection, the mixture was heated to 157°C for 4.1 hours to remove water, followed by a heating to 175°C and holding at that temperature for 2.1 hours. The reaction proceeded as planned. After cooling to room temperature, the mixture was poured into deionized water for precipitation, filtered under reduced pressure, and the filter cake was collected. The filter cake was first washed with deionized water until the filtrate was neutral, and then transferred to a vacuum drying oven and dried at 77°C for 12.5 hours. It was then pulverized with a grinder and placed in a mold for gradient hot pressing. The mold was first held at 280°C and 2MPa for 11 minutes, then heated to 330°C and 4MPa and held for 25 minutes. After natural cooling and demolding, the mixture was heat-treated at 310°C for 63 minutes to obtain high-temperature resistant polyimide resin.

[0021] Example 3: This example describes a method for preparing a high-temperature resistant polyimide resin, comprising the following steps: Step S1: Add 120 mL of 65% nitric acid and 30 mL of 98% concentrated sulfuric acid to a round-bottom flask. Stir for 12 min at 400 r / min under ice bath conditions. Add 37 g of 4-phenylpiperidine in three portions. Allow the mixture to rise naturally to room temperature and stir for 7.2 h. Pour the reaction solution into 5°C ice water to precipitate a solid. Filter the solid and wash the filter cake with deionized water until the filtrate is neutral. Recrystallize the solid with ethanol and then place it in a vacuum drying oven at 60°C for 25 h to obtain the first intermediate. Step S2: 60 mmol of the first intermediate, 60 mmol of 4-fluoronitrobenzene, 62 mmol of anhydrous potassium carbonate and 180 mL of N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Nitrogen gas was introduced for protection. The mixture was stirred at 60 °C and 400 r / min for 32 min. Then the temperature was raised to 120 °C and the reaction was continued for 13 h. After the reaction was completed, the mixture was cooled to room temperature. The reaction solution was poured into deionized water, stirred to precipitate crystals, filtered, washed 5 times with hot distilled water at 60 °C, and then placed in a vacuum drying oven and dried at 60 °C for 25 h to obtain the second intermediate. Step S3: 40 mmol of the second intermediate and 160 mL of anhydrous ethanol were added to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube and constant pressure dropping funnel. Nitrogen gas was introduced for protection. The mixture was stirred for 12 min at 30 °C and a stirring rate of 400 r / min. 0.5 g of palladium-on-carbon catalyst (the mass fraction of palladium in the palladium-on-carbon catalyst was 10%) was moistened with ethanol and added to the system. The temperature was then raised to 70 °C and stirred for 32 min. Then, 20 mL of 80% hydrazine hydrate was added dropwise while stirring, with the dropping rate controlled at 2 drops / s. The reaction was continued for 8.2 h. After the reaction was completed, the mixture was filtered while hot. The filtrate was allowed to cool naturally to room temperature. The reaction solution was poured into deionized water, stirred to precipitate crystals, filtered, washed 3 times with ice water, and then placed in a vacuum drying oven and dried at 60 °C for 25 h to obtain piperidinyl aromatic diamine. Step S4: Weigh out 9.4 parts by weight of piperidinyl aromatic diamine, 6.6 parts by weight of 2,3,6,7-anthracite dianhydride, 146 parts by weight of anhydrous N,N-dimethylacetamide and 16 parts by weight of toluene, and set aside. Step S5: Anhydrous N,N-dimethylacetamide and piperidinyl aromatic diamine were added to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Nitrogen gas was introduced for protection, and the mixture was stirred for 20 minutes at 30°C and a stirring rate of 400 r / min. 2,3,6,7-anthracite dianhydride was added in three batches, with 15-minute intervals between each addition. After the additions were complete, the mixture was stirred for 13 hours at 25°C. Toluene was then added, and a water separator was installed. Under nitrogen protection, the mixture was heated to 160°C for 4.2 hours to remove water, followed by a heating to 180°C and holding at that temperature for 2.2 hours. The reaction proceeded as planned. After cooling to room temperature, the mixture was poured into deionized water for precipitation, filtered under reduced pressure, and the filter cake was collected. The filter cake was first washed with deionized water until the filtrate was neutral, and then transferred to a vacuum drying oven and dried at 80°C for 13 hours. It was then pulverized with a grinder and placed in a mold for gradient hot pressing. The mold was first held at 280°C and 2MPa for 12 minutes, then heated to 350°C and 5MPa and held for 30 minutes. After natural cooling and demolding, it was heat-treated at 320°C for 65 minutes to obtain high-temperature resistant polyimide resin.

[0022] Comparative Example 1: This comparative example illustrates a method for preparing a high-temperature resistant polyimide resin, comprising the following steps: Step S1: Add 80 mL of 65% nitric acid and 20 mL of 98% concentrated sulfuric acid to a round-bottom flask. Stir for 10 min at 300 r / min under ice bath conditions. Add 25 g of 4-phenylpiperidine in three portions. Allow the mixture to rise naturally to room temperature and stir for 7 h. Pour the reaction solution into 5°C ice water to precipitate a solid. Filter the solid and wash the filter cake with deionized water until the filtrate is neutral. Recrystallize the solid with ethanol and then place it in a vacuum drying oven at 55°C for 24 h to obtain the first intermediate. Step S2: 50 mmol of the first intermediate, 50 mmol of 4-fluoronitrobenzene, 52 mmol of anhydrous potassium carbonate and 150 mL of N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Nitrogen gas was introduced for protection. The mixture was stirred at 55 °C and 300 r / min for 30 min. Then the temperature was raised to 115 °C and the reaction was continued for 12 h. After the reaction was completed, the mixture was cooled to room temperature. The reaction solution was poured into deionized water, stirred to precipitate crystals, filtered, washed three times with hot distilled water at 60 °C, and then placed in a vacuum drying oven and dried at 55 °C for 24 h to obtain the second intermediate. Step S3: 30 mmol of the second intermediate and 120 mL of anhydrous ethanol were added to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube and constant pressure dropping funnel. Nitrogen gas was introduced for protection. The mixture was stirred for 10 min at 25 °C and a stirring rate of 300 r / min. 0.4 g of palladium-on-carbon catalyst (the mass fraction of palladium in the palladium-on-carbon catalyst was 10%) was moistened with ethanol and added to the system. The temperature was then raised to 65 °C and stirred for 30 min. Then, 15 mL of 80% hydrazine hydrate was added dropwise while stirring, with the dropping rate controlled at 1 drop / s. The reaction was continued for 8 h. After the reaction was completed, the mixture was filtered while hot. The filtrate was allowed to cool naturally to room temperature. The reaction solution was poured into deionized water, stirred to precipitate crystals, filtered, washed twice with ice water, and then placed in a vacuum drying oven and dried at 55 °C for 24 h to obtain piperidinyl aromatic diamine. Step S4: Weigh out 4.7 parts by weight of piperidinyl aromatic diamine, 3.3 parts by weight of pyromellitic dianhydride, 73 parts by weight of anhydrous N,N-dimethylacetamide and 8 parts by weight of toluene, and set aside. Step S5: Anhydrous N,N-dimethylacetamide and piperidinyl aromatic diamine were added to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Nitrogen gas was introduced for protection, and the mixture was stirred for 15 minutes at 25°C and a stirring rate of 300 r / min. Pyromellitic dianhydride was added in three batches, 15 minutes apart. After the addition was complete, the mixture was stirred for 12 hours at 25°C. Toluene was then added, and a water separator was installed. Under nitrogen protection, the mixture was heated to 155°C for 4 hours to remove water, followed by heating to 170°C and holding for 2 hours. After the reaction was complete, the mixture was cooled to... At room temperature, the solution was poured into deionized water for precipitation, filtered under reduced pressure, and the filter cake was collected. The filter cake was first washed with deionized water until the filtrate was neutral, and then transferred to a vacuum drying oven and dried at 75°C for 12 hours. It was then pulverized with a grinder and placed in a mold for gradient hot pressing. The mold was first held at 280°C and 2MPa for 10 minutes, then heated to 320°C and 3MPa and held for 20 minutes. After natural cooling and demolding, it was heat-treated at 300°C for 60 minutes to obtain high-temperature resistant polyimide resin.

[0023] Comparative Example 2: This comparative example illustrates a method for preparing a high-temperature resistant polyimide resin, comprising the following steps: Step S1: Weigh out 4.7 parts by weight of 4,4'-diaminodiphenyl ether, 3.3 parts by weight of 2,3,6,7-anthracite dianhydride, 73 parts by weight of anhydrous N,N-dimethylacetamide and 8 parts by weight of toluene, and set aside. Step S2: Anhydrous N,N-dimethylacetamide and 4,4'-diaminodiphenyl ether were added to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Nitrogen gas was introduced for protection, and the mixture was stirred for 15 minutes at 25°C and a stirring rate of 300 r / min. 2,3,6,7-anthracite dianhydride was added in three batches, with 15-minute intervals between each addition. After the additions were complete, the mixture was stirred for 12 hours at 25°C. Toluene was then added, and a water separator was installed. Under nitrogen protection, the mixture was heated to 155°C for 4 hours to remove water, followed by a heating to 170°C and holding for 2 hours. The reaction proceeded as planned. After cooling to room temperature, the mixture was poured into deionized water for precipitation, filtered under reduced pressure, and the filter cake was collected. The filter cake was first washed with deionized water until the filtrate was neutral, and then transferred to a vacuum drying oven and dried at 75°C for 12 hours. It was then pulverized with a grinder and placed in a mold for gradient hot pressing. The mold was first held at 280°C and 2MPa for 10 minutes, then heated to 320°C and 3MPa and held for 20 minutes. After natural cooling and demolding, it was heat-treated at 300°C for 60 minutes to obtain high-temperature resistant polyimide resin.

[0024] Comparative Example 3: This comparative example illustrates a method for preparing a high-temperature resistant polyimide resin, comprising the following steps: Step S1: Weigh out 4.7 parts by weight of 4,4'-diaminodiphenyl ether, 3.3 parts by weight of pyromellitic dianhydride, 73 parts by weight of anhydrous N,N-dimethylacetamide, and 8 parts by weight of toluene, and set aside. Step S2: Anhydrous N,N-dimethylacetamide and 4,4'-diaminodiphenyl ether were added to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Nitrogen gas was introduced for protection, and the mixture was stirred for 15 minutes at 25°C and a stirring rate of 300 r / min. Pyromellitic dianhydride was added in three batches, 15 minutes apart. After the addition was complete, the mixture was stirred for 12 hours at 25°C. Toluene was then added, and a water separator was installed. Under nitrogen protection, the mixture was heated to 155°C for 4 hours to remove water, followed by heating to 170°C and holding for 2 hours. After the reaction was complete, the mixture was cooled. The solution was cooled to room temperature, then poured into deionized water for precipitation. The mixture was filtered under reduced pressure, and the filter cake was collected. The filter cake was first washed with deionized water until the filtrate was neutral, then transferred to a vacuum drying oven and dried at 75°C for 12 hours. It was then pulverized using a grinder and placed in a mold for gradient hot pressing. The mold was first held at 280°C and 2MPa for 10 minutes, then heated to 320°C and 3MPa for 20 minutes. After natural cooling and demolding, it was heat-treated at 300°C for 60 minutes to obtain high-temperature resistant polyimide resin.

[0025] Performance testing The high-temperature resistant polyimide resins of Examples 1-3 and Comparative Examples 1-3 were tested according to the following methods; Thermal stability test: Thermogravimetric analysis was used for testing under a nitrogen atmosphere. The heating rate was 10℃ / min, and the test temperature range was 30-800℃. The temperature corresponding to a 5% loss of sample mass was recorded to characterize the resin's resistance to thermal decomposition.

[0026] Glass transition temperature test: Differential scanning calorimetry was used for testing under nitrogen protection at a heating rate of 10℃ / min. The glass transition temperature was determined by the inflection point of the secondary heating curve, which is the upper limit of the material's high-temperature resistance.

[0027] Tensile strength test: The test was conducted in accordance with GB / T 1040.1-2025 "Determination of tensile properties of plastics - Part 1: General". A universal electronic tensile testing machine was used. The specimens were cut into standard strips. The tensile rate was 5 mm / min. The test was conducted at room temperature to characterize the mechanical strength of the material.

[0028] Carbon residue test: Thermogravimetric analysis was used. The test atmosphere was high-purity nitrogen (nitrogen flow rate of 50 mL / min). The heating range was 30-800℃ and the heating rate was 10℃ / min. 10 mg of dried polyimide resin sample was accurately weighed and placed in an alumina crucible. The temperature was increased at a uniform rate according to the set program. The real-time mass change of the sample was recorded. The percentage of the remaining mass at 800℃ relative to the initial mass of the sample is the high-temperature carbon residue of the material.

[0029] The test results are shown in Table 1: .

[0030] Referring to the table above, based on the comparison between Examples 1-3 and Comparative Examples 1-3, it can be seen that the prepared high-temperature resistant polyimide resin has excellent high-temperature resistance and mechanical strength.

[0031] 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.

[0032] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in this application, they should all fall within the protection scope of the present invention.

Claims

1. A high-temperature resistant polyimide resin, characterized in that, Includes the following components by weight: Piperidinyl aromatic diamine 4.7-9.4 parts, 2,3,6,7-anthracite dianhydride 3.3-6.6 parts, anhydrous N,N-dimethylacetamide 73-146 parts, and toluene 8-16 parts; The piperidinyl aromatic diamine is prepared by the following steps: Step a1: Add nitric acid and concentrated sulfuric acid to a round-bottom flask, stir, add 4-phenylpiperidine, raise to room temperature, stir the reaction, pour the reaction solution into ice water to precipitate solid, filter, wash, recrystallize with ethanol, and then dry to obtain the first intermediate; Step a2: Add the first intermediate, 4-fluoronitrobenzene, anhydrous potassium carbonate and N,N-dimethylformamide to a three-necked flask and stir. Then heat up to continue the reaction. Cool down, pour the reaction solution into deionized water, stir to precipitate crystals, filter, wash, and then dry to obtain the second intermediate. Step a3: Add the second intermediate and anhydrous ethanol to a three-necked flask and stir to react. Wet the palladium-carbon catalyst with ethanol and add it to the system. Stir, then add hydrazine hydrate and continue the reaction. Filter while hot, cool, pour the reaction solution into deionized water, stir to precipitate crystals, filter, wash, and then dry to obtain piperidinyl aromatic diamine.

2. The high-temperature resistant polyimide resin according to claim 1, characterized in that, The ratio of nitric acid, concentrated sulfuric acid and 4-phenylpiperidine used in step a1 is 80-120 mL: 20-30 mL: 25-37 g.

3. The high-temperature resistant polyimide resin according to claim 1, characterized in that, In step a2, the ratio of the first intermediate, 4-fluoronitrobenzene, anhydrous potassium carbonate, and N,N-dimethylformamide is 50-60 mmol: 50-60 mmol: 52-62 mmol: 150-180 mL.

4. The high-temperature resistant polyimide resin according to claim 1, characterized in that, In step a3, the ratio of the second intermediate, anhydrous ethanol, palladium on carbon catalyst, and hydrazine hydrate is 30-40 mmol: 120-160 mL: 0.4-0.5 g: 15-20 mL.

5. The high-temperature resistant polyimide resin according to claim 1, characterized in that, The nitric acid in step a1 has a mass fraction of 65%; the concentrated sulfuric acid has a mass fraction of 98%.

6. The high-temperature resistant polyimide resin according to claim 1, characterized in that, The hydrazine hydrate in step a3 has a mass fraction of 80%; the palladium metal in the palladium-on-carbon catalyst has a mass fraction of 10%.

7. A method for preparing a high-temperature resistant polyimide resin, characterized in that, The method for preparing the high-temperature resistant polyimide resin as described in any one of claims 1-6 comprises the following steps: Step 1: Weigh out 4.7-9.4 parts by weight of piperidinyl aromatic diamine, 3.3-6.6 parts by weight of 2,3,6,7-anthracite dianhydride, 73-146 parts by weight of anhydrous N,N-dimethylacetamide, and 8-16 parts by weight of toluene, and set aside. Step 2: Anhydrous N,N-dimethylacetamide and piperidinyl aromatic diamine were added to a three-necked flask and stirred. 2,3,6,7-anthracite dianhydride was added and stirred. Toluene was added, and the mixture was heated to remove water. After heating, the mixture was kept at the same temperature and then cooled. The mixture was then poured into deionized water for precipitation. The mixture was filtered under reduced pressure, and the filter cake was collected, washed, dried, and pulverized. The cake was then placed in a mold for gradient hot pressing, kept at the same temperature, and then kept under pressure. After cooling and demolding, the mixture was heat-treated to obtain high-temperature resistant polyimide resin.