A high-temperature resistant polyimide, its preparation method and application

Abstract

The present invention discloses a high-temperature resistant polyimide, its preparation method and application, belonging to the technical field of material chemistry. In the molecular structure of the high-temperature resistant polyimide of the present invention, there are simultaneously sulfone groups, carbonyl groups and rigid aromatic hydrocarbon units. The unique molecular structure endows it with high heat resistance while significantly improving the toughness and heat resistance of the bismaleimide resin composite material, and has broad application prospects in the fields of aerospace, precision machinery, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of material chemistry, and specifically relates to a high-temperature resistant polyimide and its preparation method and application. Background Art

[0002] Bismaleimide resin (BMI) has excellent properties such as good high-temperature resistance, radiation resistance, moisture resistance, low moisture absorption rate, and small thermal expansion coefficient, and thus is widely used in industrial fields such as aerospace, machinery, and electronics. However, the unmodified bismaleimide resin has disadvantages of poor toughness and poor impact resistance after curing, and cannot be directly used as the resin matrix of advanced composite materials. Therefore, it is necessary to toughen and modify it. At present, the methods for toughening and modifying bismaleimide mainly include: (1) synthesis and modification of new BMI by internal chain extension; (2) copolymerization toughening modification with allyl series compounds; (3) rubber blending toughening modification; (4) thermoplastic resin blending toughening modification; (5) nano-particle toughening modification, etc. Among these modification methods, thermoplastic resin toughening can improve the toughness of BMI resin without reducing the mechanical properties and heat resistance of the resin, so it has been widely used in the field of bismaleimide resin composites. In particular, the bismaleimide resin toughened by thermoplastic polyimide is widely used in aerospace composite structural parts.

[0003] Carbon fiber reinforced bismaleimide resin composite material is a multi-phase complex system. The performance of the system is not only related to the structural properties of the resin matrix and reinforcing fibers themselves, but also greatly related to the interface between the resin matrix and fiber reinforcement, and the interfacial interaction between the thermoplastic polyimide toughening agent and the bismaleimide resin. Increasing the interfacial interaction force between the thermoplastic polyimide resin and the bismaleimide resin can effectively improve the toughness of the carbon fiber bismaleimide resin composite material, especially improve the compressive strength after impact of the carbon fiber bismaleimide resin composite material.

[0004] Therefore, there is an urgent need to provide a thermoplastic polyimide with high temperature resistance and good interfacial interaction force with the bismaleimide resin matrix to meet the requirements of high impact toughness of bismaleimide resin composites in the aerospace field. Summary of the Invention

[0005] The present invention provides a high-temperature resistant polyimide and its preparation method and application. The polyimide of the present invention has a unique molecular chain structure, enabling it to have good interfacial interaction with the bismaleimide resin matrix. The rigid aromatic carbon-hydrogen unit endows it with high heat resistance (glass transition temperature (Tg) higher than 310 °C). Using it to toughen the bismaleimide resin matrix can improve the heat resistance and toughness of the bismaleimide resin simultaneously.

[0006] The present invention first provides a high-temperature resistant polyimide, and the molecular chain of the high-temperature resistant polyimide includes repeating units represented by formula (I) and formula (II);

[0007]

[0008] Among them, Ar1 is a tetravalent aromatic hydrocarbon group, and its structural formula is any one of formula (A) and (B) or a mixture of the two in any proportion;

[0009]

[0010] Ar2 is a tetravalent aromatic hydrocarbon group, and its structural formula is as shown in formula (C);

[0011]

[0012] Ar3 is a divalent aromatic hydrocarbon group, and its structural formula is any one, two or three of formula (D) to (J);

[0013]

[0014] Both m and n are integers from 20 to 500;

[0015] The molar ratio of the repeating units represented by formula (I) and formula (II) is from 20:1 to 1:20.

[0016] The present invention also provides a preparation method of the high-temperature resistant polyimide, comprising the following steps:

[0017] (1) Under an inert atmosphere, mix the aromatic dianhydride monomer with a polar aprotic solvent, then dropwise add the aromatic diisocyanate to the above solution, and keep the temperature for reaction after dropping; finally, add a catalyst, raise the temperature and continue the reaction to obtain a polyimide solution;

[0018] (2) Cool the polyimide solution to room temperature, then disperse it in an organic solvent, collect the precipitate, and dry it to obtain the high-temperature resistant polyimide.

[0019] In the above preparation method, in step (1), the aromatic dianhydride monomer is selected from two or three of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride and 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, and includes 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride;

[0020] The polar aprotic solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide;

[0021] The aromatic diisocyanate is selected from any two or three of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane diisocyanate, 4,4'-diisocyanate diphenyl ether, m-phenylene diisocyanate, p-phenylene diisocyanate, 9,9-bis(4-isocyanatophenyl)-9H-fluorene;

[0022] Specifically, the aromatic diisocyanate is selected from any one of the following: (1) diphenylmethane diisocyanate and 2,4-toluene diisocyanate; (2) diphenylmethane diisocyanate, 2,4-toluene diisocyanate and 2,6-toluene diisocyanate; (3) 2,4-toluene diisocyanate and m-phenylene diisocyanate; (4) 2,4-toluene diisocyanate and 4,4'-diisocyanate diphenyl ether; (5) 9,9-bis(4-isocyanatophenyl)-9H-fluorene and 4,4'-diisocyanate diphenyl ether;

[0023] The catalyst is selected from at least one of triethylamine, tripropylamine, triisopropylamine, pyridine and isoquinoline;

[0024] In step (2), the organic solvent is selected from at least one of methanol, ethanol, acetone, butanone, tetrahydrofuran and deionized water.

[0025] In the above preparation method, the molar ratio of the aromatic diisocyanate to the aromatic dianhydride monomer is 0.97-1.03:1;

[0026] Specifically, the molar ratio of the aromatic diisocyanate to the aromatic dianhydride monomer is 0.99-1.03:1;

[0027] The addition amount of the catalyst is 10-150 mL of the catalyst per mole of the aromatic dianhydride monomer.

[0028] In the above preparation method, in step (1), the inert atmosphere is a nitrogen atmosphere or an argon atmosphere;

[0029] The temperature of the solution when the aromatic diisocyanate is added dropwise is 60-85 °C; the aromatic diisocyanate is added dropwise within 4-12 h;

[0030] The temperature of the heat preservation reaction is 60-85 °C, and the time is 1-2 h;

[0031] After the aromatic diisocyanate is added dropwise, the polar aprotic solvent is added to make the solid content of the solution 10%-40%, and then the heat preservation reaction is carried out;

[0032] The temperature of the continued reaction after heating is 86-100 °C, and the time is 8-24 h.

[0033] In the above preparation method, in step (2), the drying is vacuum drying, and the drying program is 80°C - 2h, 150°C - 2h, 180°C - 4h, 200°C - 1h.

[0034] In step (2), there is also a step of washing after collecting the precipitate; there is also a step of pulverizing after the drying.

[0035] The high-temperature resistant polyimide prepared by the above preparation method.

[0036] The application of adding the high-temperature resistant polyimide alone to the polymer matrix or adding it to the polymer matrix after being compounded with other toughening agents to prepare a toughened high molecular material also belongs to the protection scope of the present invention.

[0037] Specifically, the other toughening agents are common toughening agents in the art, such as at least one of polyether ketone, polyether sulfone, and polysulfone.

[0038] In the above application, the polymer matrix is a bismaleimide resin, an epoxy resin, or a phenolic resin; specifically, it can be a bismaleimide resin.

[0039] Finally, the present invention also provides the application of the above high-temperature resistant polyimide in the fields of aerospace or precision machinery.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The polyimide provided by the present invention combines sulfonyl groups, carbonyl groups, and rigid aromatic hydrocarbon units into the same molecular structure, endowing the polyimide with high-temperature resistance and good interfacial interaction with the resin matrix, and improving the toughness of the composite material;

[0042] (2) The preparation method of the polyimide provided by the present invention adopts the route of acid anhydride and isocyanate; this method has mild reaction conditions and a relatively low reaction temperature; no dehydrating agent (such as toluene, xylene, etc.) is required during the reaction, and only CO2 is produced during the reaction, meeting the requirements of environmental protection; moreover, the prices of isocyanates such as toluene diisocyanate and diphenylmethane diisocyanate are much lower than those of diamine monomers with corresponding structures, greatly reducing the synthesis cost; therefore, the preparation method of this polyimide is suitable for large-scale production and has good application prospects. Specific Embodiments

[0043] The following further describes the present invention in detail in combination with specific embodiments. The examples given are only for clarifying the present invention, rather than limiting the scope of the present invention.

[0044] The experimental methods in the following examples are all conventional methods unless otherwise specified.

[0045] In the quantitative tests in the following examples, three repeated experiments were set up, and the results were averaged.

[0046] The materials, reagents, etc. used in the following examples can be obtained from commercial sources without special instructions.

[0047] The test methods used in the following examples are as follows:

[0048] Differential scanning calorimetry was carried out according to the method specified in GB / T 19466.2-2004, and the heating rate was 10 °C / min.

[0049] The CAI of the composite material was measured according to Boeing standard BSS-7260, the impact energy was 4.45 J / mm, the ply sequence was [45 / 0 / -45 / 90]4s, and the specimen size was 150×100×5 mm 3 。

[0050] The glass transition temperature of the composite material was tested using a dynamic thermomechanical analyzer (DMA), and the specimen size was 60 mm×10×3 mm 3 ,with a heating rate of 5 °C / min and a frequency of 1 Hz.

[0051] Example 1

[0052] Into a 2500 mL dry three-necked flask equipped with mechanical stirring, a nitrogen inlet and a thermometer, 64.05 g (0.1988 mol) of 3,3’,4,4’-benzophenone tetracarboxylic dianhydride, 71.26 g (0.1988 mol) of 3,3’,4,4’-diphenylsulfone tetracarboxylic dianhydride and 1185 g of N,N-dimethylacetamide were added, and stirred under nitrogen protection until completely dissolved. The temperature was raised to 75 °C, and 25.02 g (0.1000 mol) of diphenylmethane diisocyanate and 52.25 g (0.3000 mol) of 2,4-toluene diisocyanate were added dropwise to the above solution within 10 h. After the addition was completed, 20 g of N,N-dimethylacetamide was added to rinse the dropping funnel to make the solid content of the solution 15 wt%, and the reaction was carried out at a constant temperature for 2 h. 24 mL of triethylamine catalyst was added to the above solution, and the temperature was raised to 90 °C and reacted for 20 h to obtain a polyimide solution;

[0053] Cooled to room temperature, then the above polyimide solution was dispersed in 5000 g of absolute ethanol, the precipitate was collected, washed, and dried in vacuo. The drying procedure was 80 °C - 2 h, 150 °C - 2 h, 180 °C - 4 h, 200 °C - 1 h, and then pulverized. Finally, 176.17 g of light yellow polyimide resin powder was obtained, and the yield was 99.2%. The Tg measured by differential scanning calorimetry was 315.7 °C.

[0054] Example 2

[0055] Into a 2500 mL dry three-necked flask equipped with mechanical stirring, a nitrogen inlet and a thermometer, add 51.24 g (0.1590 mol) of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 12.81 g (0.0398 mol) of 2,3,3',4'-benzophenone tetracarboxylic dianhydride, 71.26 g (0.1988 mol) of 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride and 830 g of N,N-dimethylformamide. Stir under nitrogen protection until completely dissolved. Heat up to 75 °C, and dropwise add 25.02 g (0.1000 mol) of diphenylmethane diisocyanate, 41.80 g (0.2400 mol) of 2,4-toluene diisocyanate and 10.45 g (0.0600 mol) of 2,6-toluene diisocyanate into the above solution within 12 h. After the dropping is completed, add 20 g of N,N-dimethylformamide to rinse the dropping funnel to make the solid content of the solution 20 wt%, and keep the temperature for reaction for 1.5 h. Add 32 mL of pyridine catalyst to the reaction system, heat up to 95 °C and react for 24 h to obtain a polyimide solution;

[0056] Cool to room temperature, then disperse the above polyimide solution into 5000 g of acetone, collect the precipitate, wash it, and dry it under vacuum. The drying procedure is 80 °C - 2 h, 150 °C - 2 h, 180 °C - 4 h, 200 °C - 1 h, and then pulverize it. Finally, 174.93 g of light yellow polyimide resin powder is obtained with a yield of 98.5%. The Tg measured by differential scanning calorimetry is 314.4 °C.

[0057] Example 3

[0058] Into a 2500 mL dry three-necked flask equipped with mechanical stirring, a nitrogen inlet and a thermometer, add 112.09 g (0.3478 mol) of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 17.81 g (0.0497 mol) of 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride and 1758 g of N-methylpyrrolidone. Stir under nitrogen protection until completely dissolved. Heat up to 85 °C, and dropwise add 50.44 g (0.2896 mol) of 2,4-toluene diisocyanate and 17.20 g (0.1074 mol) of m-phenylene diisocyanate into the above solution within 4 h. After the dropping is completed, add 20 g of N-methylpyrrolidone to rinse the dropping funnel to make the solid content of the solution 10 wt%, and keep the temperature for reaction for 1 h. Add 4.2 mL of tripropylamine catalyst to the reaction system, heat up to 100 °C and react for 20 h to obtain a polyimide solution;

[0059] Cool to room temperature, then disperse the above polyimide solution into 5000 g of methanol, collect the precipitate, wash it, and dry it under vacuum. The drying procedure is 80°C - 2 h, 150°C - 2 h, 180°C - 4 h, 200°C - 1 h, then pulverize it. Finally, 161.42 g of light yellow polyimide resin is obtained, with a yield of 99.3%. The Tg measured by differential scanning calorimetry is 318.7°C.

[0060] Example 4

[0061] Into a 1000 mL dry three-necked flask equipped with mechanical stirring, a nitrogen inlet, and a thermometer, add 6.40 g (0.0199 mol) of 3,3’,4,4’-benzophenone tetracarboxylic dianhydride, 142.52 g (0.3978 mol) of 3,3’,4,4’-diphenylsulfone tetracarboxylic dianhydride monomer, and 327 g of N-methylpyrrolidone. Stir under nitrogen protection until completely dissolved. Heat up to 60°C, and dropwise add 57.19 g (0.3284 mol) of 2,4-toluene diisocyanate and 25.22 g (0.1 mol) of 4,4’-diisocyanate diphenyl ether into the above solution within 6 h. After the dropping is completed, add 20 g of N-methylpyrrolidone to rinse the dropping funnel to make the solid content of the solution 40 wt%, and keep the temperature for reaction for 1.5 h. Add 62 mL of triisopropylamine catalyst to the reaction system, heat up to 95°C and react for 8 h to obtain a polyimide solution;

[0062] Cool to room temperature, then disperse the above polyimide solution into 5000 g of methyl ethyl ketone, collect the precipitate, wash it, and dry it under vacuum. The drying procedure is 80°C - 2 h, 150°C - 2 h, 180°C - 4 h, 200°C - 1 h, then pulverize it. Finally, 192.23 g of light yellow polyimide resin powder is obtained, with a yield of 98.9%. The Tg measured by differential scanning calorimetry is 312.6°C.

[0063] Example 5

[0064] Into a 1000 mL dry three-necked flask equipped with mechanical stirring, a nitrogen inlet and a thermometer, 6.40 g (0.0199 mol) of 3,3’,4,4’-benzophenone tetracarboxylic dianhydride, 128.27 g (0.3580 mol) of 3,3’,4,4’-diphenylsulfone tetracarboxylic dianhydride and 374 g of dimethyl sulfoxide were added. Under nitrogen protection, it was stirred until completely dissolved. The temperature was raised to 70 °C, and 43.54 g (0.2500 mol) of 2,4-toluene diisocyanate and 33.75 g (0.1338 mol) of 4,4’-diisocyanate diphenyl ether were added dropwise to the above solution within 10 h. After the addition was completed, 20 g of dimethyl sulfoxide was added to rinse the dropping funnel to make the solid content of the solution 35 wt%, and the reaction was carried out at a constant temperature for 2 h. 31 mL of pyridine catalyst was added to the reaction system, and the temperature was raised to 86 °C and reacted for 12 h to obtain a polyimide solution;

[0065] It was cooled to room temperature, and then the above polyimide solution was dispersed in 5000 g of deionized water. The precipitate was collected, washed, and dried in vacuo. The drying procedure was 80 °C - 2 h, 150 °C - 2 h, 180 °C - 4 h, 200 °C - 1 h, and then pulverized. Finally, 177.09 g of light yellow polyimide resin powder was obtained with a yield of 99.2%. The Tg measured by differential scanning calorimetry was 313.7 °C.

[0066] Example 6

[0067] Into a 1000 mL dry three-necked flask equipped with mechanical stirring, a nitrogen inlet and a thermometer, 128.1 g (0.3975 mol) of 3,3’,4,4’-benzophenone tetracarboxylic dianhydride, 14.25 g (0.0398 mol) of 3,3’,4,4’-diphenylsulfone tetracarboxylic dianhydride and 1128 g of N,N-dimethylformamide were added. Under nitrogen protection, it was stirred until completely dissolved. The temperature was raised to 80 °C, and 94.34 g (0.2356 mol) of 9,9-bis(4-isocyanatophenyl)-9H-fluorene (Angene international limited, AGN-PC-02GNSR) and 50.44 g (0.2000 mol) of 4,4’-diisocyanate diphenyl ether were added dropwise to the above solution within 10 h. After the addition was completed, 20 g of N,N-dimethylformamide was added to rinse the dropping funnel to make the solid content of the solution 20 wt%, and the reaction was carried out at a constant temperature for 1 h. 39.8 mL of isoquinoline catalyst was added to the reaction system, and the temperature was raised to 92 °C and reacted for 24 h to obtain a polyimide solution;

[0068] Cool to room temperature, then disperse the above polyimide solution in 5000 g of tetrahydrofuran, collect the precipitate, wash it, and dry it under vacuum. The drying procedure is 80°C - 2 h, 150°C - 2 h, 180°C - 4 h, 200°C - 1 h, and then pulverize it. Finally, 245.66 g of light yellow polyimide resin powder is obtained with a yield of 98.8%. The Tg measured by differential scanning calorimetry is 324.9°C.

[0069] Comparative Example 1

[0070] Add 128.1 g (0.3975 mol) of 3,3',4,4'-benzophenone tetracarboxylic dianhydride and 802 g of N,N-dimethylacetamide to a 2500 mL dry three-necked flask equipped with a mechanical stirrer, a nitrogen inlet, and a thermometer. Stir under nitrogen protection until completely dissolved. Heat up to 75°C, and dropwise add 25.22 g (0.1000 mol) of 4,4'-diisocyanatodiphenyl ether and 52.25 g (0.3000 mol) of 2,4-toluene diisocyanate into the above solution within 7 h. After the addition is complete, add 20 g of N,N-dimethylacetamide to rinse the dropping funnel to make the solid content of the solution 20 wt%, and keep the temperature for reaction for 2 h. Add 32 mL of triethylamine catalyst to the reaction system, heat up to 95°C, and react for 18 h to obtain a polyimide solution;

[0071] Cool to room temperature, disperse the above polyimide solution in 5000 g of acetone, collect the precipitate, wash it, and dry it under vacuum. The drying procedure is 80°C - 2 h, 150°C - 2 h, 180°C - 4 h, 200°C - 1 h, and then pulverize it. Finally, 169.57 g of light yellow polyimide resin powder is obtained with a yield of 99.4%. The Tg measured by differential scanning calorimetry is 315.0°C.

[0072] Example 7

[0073] Weigh 50 kg of N,N'-(4,4'-methylenediphenyl)bismaleimide, 50 kg of N,N'-(4-methyl-1,3-methylene)bismaleimide, 70 kg of diallylbisphenol A, 2 kg of bisphenol F epoxy resin (Nanya, NPEF-170), and 40 kg of the polyimide resin powder prepared in Example 1. Mix the weighed bismaleimide resins (N,N'-(4,4'-methylenediphenyl)bismaleimide and N,N'-(4-methyl-1,3-methylene)bismaleimide) with diallylbisphenol A and bisphenol F epoxy resin evenly, and then keep them at 120 °C for pre-polymerization for 30 min. Continuously add the polyimide resin powder prepared in Example 1 and stir at high speed to make the resin mixture evenly stirred. Cool it to room temperature to obtain a toughened bismaleimide resin matrix for prepreg. Coat the above bismaleimide resin matrix and compound it with Toray T700SC carbon fiber (Toray Industries, Inc., T700SC carbon fiber) to make a prepreg. The resin content of this hot-melt prepreg is 38 wt%, and it has good drapability and adhesiveness. After curing at 180 °C / 3 h and 210 °C / 6 h, the post-impact compression strength of the composite material is tested to be 322 MPa, and the glass transition temperature of the composite material is tested by dynamic thermomechanical analysis (DMA) to be 285.5 °C.

[0074] Example 8

[0075] Weigh 50 kg of N,N'-(4,4'-methylenediphenyl)bismaleimide, 50 kg of N,N'-(4-methyl-1,3-methylene)bismaleimide, 70 kg of diallylbisphenol A, 2 kg of bisphenol F epoxy resin (Nanya, NPEF-170), and 40 kg of the polyimide resin powder prepared in Example 2. Mix the weighed bismaleimide resins (N,N'-(4,4'-methylenediphenyl)bismaleimide and N,N'-(4-methyl-1,3-methylene)bismaleimide) with diallylbisphenol A and bisphenol F epoxy resin evenly, and then keep them at 120 °C for pre-polymerization for 30 min. Continuously add the polyimide resin powder prepared in Example 2 and stir at high speed to make the resin mixture evenly stirred. Cool it to room temperature to obtain a toughened bismaleimide resin matrix for prepreg. Coat the above bismaleimide resin matrix and pre-impregnate and compound it with Toray T700SC carbon fiber (Toray Industries, Inc., T700SC carbon fiber) to make a prepreg. The resin content of this hot-melt prepreg is 38 wt%, and it has good drapability and adhesiveness. After curing at 180 °C / 3 h and 210 °C / 6 h, the post-impact compression strength of the composite material is tested to be 272 MPa, and the glass transition temperature of the composite material is tested by dynamic thermomechanical analysis (DMA) to be 283.2 °C.

[0076] Example 9

[0077] Weigh 50 kg of N,N'-(4,4'-methylenediphenyl)bismaleimide, 50 kg of N,N'-(4-methyl-1,3-methylene)bismaleimide, 70 kg of diallylbisphenol A, 2 kg of bisphenol F type epoxy resin (Nanya, NPEF-170), and 40 kg of the polyimide resin powder prepared in Example 4. Mix the weighed bismaleimide resins (N,N'-(4,4'-methylenediphenyl)bismaleimide and N,N'-(4-methyl-1,3-methylene)bismaleimide) with diallylbisphenol A and bisphenol F epoxy resin evenly, then keep them at 120 °C for pre-polymerization for 30 min. Continuously add the polyimide resin powder prepared in Example 4 and stir at high speed to make the resin mixture evenly stirred. Cool to room temperature to obtain a toughened bismaleimide resin matrix for prepreg. Coat the above bismaleimide resin matrix and pre-impregnate and compound it with Toray T700SC carbon fiber (Toray Industries, Inc., T700SC carbon fiber) to make a prepreg. The resin content of this hot-melt prepreg is 38 wt%, and it has good drapability and adhesiveness. After curing, the compressive strength after impact of the composite material is tested to be 282 MPa, and the glass transition temperature of the composite material is tested by dynamic thermomechanical analysis (DMA) to be 281.6 °C.

[0078] Example 10

[0079] Weigh 50 kg of N,N'-(4,4'-methylenediphenyl)bismaleimide, 50 kg of N,N'-(4-methyl-1,3-methylene)bismaleimide, 70 kg of diallylbisphenol A, 2 kg of bisphenol F type epoxy resin (Nanya, NPEF-170), and 40 kg of the polyimide resin powder prepared in Example 5. Mix the weighed bismaleimide resins (N,N'-(4,4'-methylenediphenyl)bismaleimide and N,N'-(4-methyl-1,3-methylene)bismaleimide) with diallylbisphenol A and bisphenol F epoxy resin evenly, then keep them at 120 °C for pre-polymerization for 30 min. Continuously add the polyimide resin powder prepared in Example 5 and stir at high speed to make the resin mixture evenly stirred. Cool to room temperature to obtain a toughened bismaleimide resin matrix for prepreg. Coat the above bismaleimide resin matrix and pre-impregnate and compound it with Toray T700SC carbon fiber (Toray Industries, Inc., T700SC carbon fiber) to make a prepreg. The resin content of this hot-melt prepreg is 38 wt%, and it has good drapability and adhesiveness. After curing, the compressive strength after impact of the composite material is tested to be 265 MPa, and the glass transition temperature of the composite material is tested by dynamic thermomechanical analysis (DMA) to be 282.1 °C.

[0080] Comparative Example 2

[0081] Weigh 50 kg of N,N'-(4,4'-methylenediphenyl)bismaleimide, 50 kg of N,N'-(4-methyl-1,3-phenylene)bismaleimide, 70 kg of diallylbisphenol A, 2 kg of bisphenol F type epoxy resin (Nanya, NPEF-170), and 40 kg of polyimide resin powder prepared in Comparative Example 1. Mix the weighed bismaleimide resins (N,N'-(4,4'-methylenediphenyl)bismaleimide and N,N'-(4-methyl-1,3-phenylene)bismaleimide) with diallylbisphenol A and bisphenol F epoxy resin evenly, and then keep them at 120 °C for pre-polymerization for 30 min. Continuously add the polyimide resin powder prepared in Comparative Example 1 and stir at high speed to make the resin mixture evenly stirred. Cool to room temperature to obtain a toughened bismaleimide resin matrix for prepreg. Coat the above bismaleimide resin matrix and pre-impregnate and compound it with Toray T700SC carbon fiber (Toray Industries, Inc., T700SC carbon fiber) to make a prepreg. The resin content of this hot-melt prepreg is 38 wt%, and it has good drapability and adhesiveness. After curing, the compressive strength after impact of the composite material is tested to be 194 MPa, and the glass transition temperature of the composite material is tested by dynamic thermomechanical analysis (DMA) to be 273.2 °C.

[0082] As can be seen from the above examples and comparative examples, the polyimide provided by the present invention having a sulfone group, a carbonyl group and a rigid aromatic hydrocarbon unit in its molecular structure at the same time has a unique molecular structure that endows it with high heat resistance (Tg>310 °C). At the same time, this molecular structure enhances the interfacial interaction between the polyimide and the resin matrix. When it is added to the bismaleimide matrix resin, compared with the comparative example, the toughness and heat resistance of the bismaleimide resin composite material can be significantly improved.

Claims

1. A high-temperature resistant polyimide, characterized in that: The molecular chain of the high-temperature resistant polyimide includes repeating units shown in Formula (I) and Formula (II); Formula (I) Formula (II) Wherein, Ar1 is a tetravalent aromatic hydrocarbon group, and its structural formula is any one of Formula (A) and (B) or a mixture composed of the two in any proportion; Ar2 is a tetravalent aromatic hydrocarbon group, and its structural formula is as shown in Formula (C); Ar3 is a divalent aromatic hydrocarbon group, and its structural formula is any one, two or three of Formula (D)-(J); Both m and n are integers from 20 to 500; The molar ratio of the repeating units shown in Formula (I) and Formula (II) is from 20:1 to 1:

20.

2. The preparation method of the high-temperature resistant polyimide according to claim 1, comprising the following steps: (1) Under an inert atmosphere, mix the aromatic dianhydride monomer with a polar aprotic solvent, then dropwise add the aromatic diisocyanate to the above solution, and keep the temperature for reaction after the dropping is completed; finally, add a catalyst, raise the temperature and continue the reaction to obtain a polyimide solution; (2) Cool the polyimide solution to room temperature, then disperse it in an organic solvent, collect the precipitate, and dry it to obtain the high-temperature resistant polyimide.

3. The preparation method according to claim 2, wherein: In step (1), the aromatic dianhydride monomer is selected from two or three of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride and 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, and includes 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride; The polar aprotic solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide; The aromatic diisocyanate is selected from any two or three of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane diisocyanate, 4,4'-diisocyanate diphenyl ether, m-phenylene diisocyanate, p-phenylene diisocyanate, 9,9-bis(4-isocyanatophenyl)-9H-fluorene; The catalyst is selected from at least one of triethylamine, tripropylamine, triisopropylamine, pyridine and isoquinoline; In step (2), the organic solvent is selected from at least one of methanol, ethanol, acetone, butanone, tetrahydrofuran and deionized water.

4. The preparation method according to claim 2 or 3, characterized in that: The molar ratio of the aromatic diisocyanate to the aromatic dianhydride monomer is 0.97-1.03:

1. The addition amount of the catalyst is 10-150 mL of catalyst added per mole of the aromatic dianhydride monomer.

5. The preparation method according to claim 2 or 3, characterized in that: In step (1), the inert atmosphere is a nitrogen atmosphere or an argon atmosphere; The temperature of the solution when the aromatic diisocyanate is dropped is 60-85°C; the aromatic diisocyanate is dropped within 4-12 h; The temperature of the heat preservation reaction is 60-85°C, and the time is 1-2 h; After the aromatic diisocyanate is dropped, add the polar aprotic solvent to make the solid content of the solution 10%-40%, and then carry out the heat preservation reaction; The temperature for continuing the reaction after raising the temperature is 86-100°C, and the time is 8-24 h.

6. The preparation method according to claim 2 or 3, characterized in that: In step (2), the drying is vacuum drying, and the drying procedure is 80°C - 2h, 150°C - 2h, 180°C - 4h, 200°C - 1h.

7. Use of the high-temperature resistant polyimide described in claim 1 when added alone to a polymer matrix or when compounded with other toughening agents and then added to a polymer matrix to prepare a toughened high-molecular material.

8. The application according to claim 7, wherein: The polymer matrix is a bismaleimide resin, an epoxy resin or a phenolic resin.

9. The application according to claim 8, wherein: The polymer matrix is a bismaleimide resin.

10. Use of the high-temperature resistant polyimide described in claim 1 in the fields of aerospace or precision machinery.

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