Polyurethane modified polyimide foam thermal insulation material, preparation method and application

Abstract

The invention relates to the technical field of thermal insulation materials, in particular to a polyurethane modified polyimide foam thermal insulation material, a preparation method and application, the thermal conductivity is 0.029 W / (m.K)-0.032 W / (m.K), the density is 0.04 g / cm < 3 >-0.053 g / cm < 3 >, the strength is 0.26 MPa-0. 36 MPa, the flame retardant grade is UL 94 V-0, and the polyurethane modified polyimide foam thermal insulation material has excellent thermal insulation performance and meets the thermal management requirement of a new energy system; the flame retardance is enhanced, and the safety of new energy equipment is improved; the material has the advantages of light weight, balance of mechanical strength and adaptability to complex application environments, and polyurethane modification not only improves the flexibility of the material, but also keeps higher mechanical strength and impact resistance, so that the material has the advantages of light weight and balance of strength. The polyurethane modified polyimide foam material has excellent heat insulation and flame retardant properties, and is suitable for being popularized and applied to the fields of new energy automobiles, energy storage systems and building heat insulation.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal insulation materials, and in particular to a polyurethane-modified polyimide foam thermal insulation material, a preparation method and an application thereof. Background Art

[0002] Polyurethane and polyimide foams are widely used as thermal insulation materials. Due to its lightweight, excellent thermal insulation, and low cost, polyurethane foam is widely used in home insulation, construction, and home appliances. However, polyurethane has limited heat resistance, and its operating temperature is typically between 80°C and 120°C. Above this temperature, polyurethane gradually loses its mechanical strength and thermal insulation properties and easily decomposes. Furthermore, polyurethane has poor flame retardancy and is easily flammable. These characteristics significantly limit its application in high-temperature environments.

[0003] Polyimide foam is a high-temperature resistant material that maintains its physical properties in environments above 300°C, making it valuable for applications in extreme temperatures such as aerospace, defense, and military applications. Furthermore, polyimide foam possesses strong flame retardancy and low thermal conductivity, significantly inhibiting heat conduction. However, the complex preparation process, high cost, and difficulty in processing polyimide foam, coupled with its lack of toughness, hinder its further expansion into other applications.

[0004] In summary, it is particularly important to design a thermal insulation foam material with excellent comprehensive performance to solve the above problems and promote its application in new energy vehicles, energy storage systems, building insulation and other fields. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the above shortcomings and provide a polyurethane-modified polyimide foam insulation material, preparation method and application, which has excellent thermal insulation performance, a balance between lightweight and mechanical strength, and flame retardancy, and can meet the requirements of new energy vehicles, energy storage systems, building insulation and other fields for thermal insulation foam materials with higher comprehensive performance.

[0006] In order to solve the above technical problems, the technical solution of the present invention is: a polyurethane modified polyimide foam insulation material, the polyurethane modified polyimide foam insulation material: Thermal conductivity 0.029W / (m·K)-0.032W / (m·K), density 0.04g / cm 3 -0.053g / cm 3 , strength is 0.26MPa-0.36MPa, flame retardant grade UL 94 V-0.

[0007] A method for preparing a polyurethane-modified polyimide foam thermal insulation material comprises the following steps: Step S1: dissolving pyromellitic anhydride in a polar solvent, stirring at room temperature until completely dissolved, then adding ethylenediamine to the mixed solution and continuing to stir to obtain a polyamic acid solution; Step S2: adding additives and a crosslinking enhancer to the polyamic acid solution in sequence, mixing them uniformly under stirring, then adding a polymerization initiator, continuing stirring, and transferring the mixture to a reactor, performing a polymerization reaction under heating to obtain a polymer solution; Step S3: increasing the temperature of the polymer solution at a set heating rate, maintaining the temperature at 150° C.-180° C. for 2 h-3 h for dehydration cyclization reaction, partially converting the polymer solution into polyimide, and then slowly cooling the temperature to room temperature to obtain a partially imidized polymer solution; Step S4: slowly adding the isocyanate solution dropwise to the partially imidized polymer solution, performing a cross-linking reaction under stirring and heating conditions to form a polyurethane cross-linked network, thereby obtaining a partially imidized polymer solution containing a polyurethane cross-linked structure; Step S5: adding a blowing agent to the partially imidized polymer solution containing a polyurethane cross-linked structure to obtain a foaming mixture, then transferring the foaming mixture into a mold, and allowing it to stand and solidify at room temperature to obtain a preliminarily solidified foam material; Step S6: placing the preliminarily cured foam material in a vacuum drying oven and continuing to cure under set temperature and pressure conditions to obtain a polyurethane-modified polyimide foam insulation material through high-temperature imidization and microporous structure stabilization.

[0008] Furthermore, in step S1, the amount of pyromellitic anhydride is 2 parts to 50 parts, and the amount of ethylenediamine is 0.5 parts to 15 parts; Pyromellitic anhydride and ethylenediamine are replaced by phthalic acid and 2,2-dimethyl-1,3-propylenediamine; The polar solvent is N,N-dimethylacetamide, N-methylpyrrolidone or N,N-dimethylformamide; the dosage is 100 parts; Heat to 60-100°C, reaction time 2-3 hours, stirring speed 100-300 rpm.

[0009] Furthermore, in step S2, the additive is one of methacrylic acid, ethylacrylic acid, propylacrylic acid, methylbutenoic acid, ethylbutenoic acid, propylbutenoic acid, methylpentenoic acid, ethylpentenoic acid, and propylpentenoic acid; the amount is 0.5 parts to 10 parts; The cross-linking enhancer is one of hydroxyethyl methacrylate, hydroxyethyl ethyl acrylate, propyl hydroxyethyl acrylate, hydroxyethyl methyl crotonate, hydroxyethyl ethyl crotonate, propyl hydroxyethyl crotonate, hydroxyethyl methyl pentenoate, hydroxyethyl ethyl pentenoate, and hydroxyethyl propyl pentenoate; the amount used is 0.5 parts to 15 parts; The polymerization initiator is benzoyl peroxide or azobisisobutyronitrile, and the amount used is 0.5 parts to 10 parts.

[0010] Furthermore, in step S2, the polymerization reaction temperature is 60°C-100°C, the reaction time is 2h-3h, and the stirring speed is 100rpm-300rpm.

[0011] Furthermore, in step S3, the heating rate is 2°C / min-5°C / min, and the cooling rate is 1°C / min-3°C / min.

[0012] Further, in step S4, the isocyanate solution is composed of 300-800 parts of isocyanate and 100 parts of polar solvent, wherein the isocyanate is toluene diisocyanate or diphenylmethane-4,4'-diisocyanate; In step S4, the isocyanate solution is added at a rate of 1 mL / min-5 mL / min, the amount added is 30 parts-80 parts, the reaction temperature is 70°C-90°C, the stirring time is 1 h-2 h, and the stirring speed is 100 rpm-300 rpm.

[0013] Furthermore, in step S5, the foaming agent is distilled water or deionized water, and the added amount is 3 parts to 10 parts.

[0014] Furthermore, in step S6, the preliminarily cured foam material is placed in a vacuum drying oven and cured at 10Pa-50Pa and 200°C for 1h-2h, and then cured at 10Pa-50Pa and 250°C for 2h-3h.

[0015] A polyurethane-modified polyimide foam thermal insulation material is used in new energy vehicles, energy storage systems, and building insulation.

[0016] The present invention adopts the above technical solution, which has the following advantages compared with the prior art: 1. Excellent thermal insulation performance to meet the thermal management requirements of new energy systems Polyurethane-modified polyimide foam has lower thermal conductivity, ranging from 0.029W / (m·K) to 0.032W / (m·K), providing excellent thermal insulation. This is particularly critical in new energy applications such as power battery systems and energy storage systems, helping to reduce heat conduction, ensuring stable operation of the system under extreme temperature conditions, and effectively extending the service life of batteries and electronic components.

[0017] 2. Enhanced flame retardancy improves the safety of new energy equipment The inherent flame retardancy of polyimide is retained and further optimized after polyurethane modification, achieving a UL 94 V-0 flame retardancy rating. This is crucial for new energy applications, especially in battery systems and building insulation, where there is a potential risk of thermal runaway. It helps reduce the risk of fire and explosion, improving overall system safety.

[0018] 3. Balance between lightweight and mechanical strength to adapt to complex application environments Polyurethane modification not only improves the flexibility of the material, but also maintains high mechanical strength and impact resistance, with a density of 0.04g / cm 3 -0.053g / cm 3 , with a strength of 0.26MPa-0.36MPa, giving it the advantages of lightweight and balanced strength.

[0019] Polyurethane-modified polyimide foam materials have excellent thermal insulation and flame retardant properties, and are suitable for promotion and application in new energy vehicles, energy storage systems, building insulation and other fields. DETAILED DESCRIPTION

[0020] The specific embodiments of the present invention will be further described below with reference to the examples. It should be noted that the description of these embodiments is intended to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0021] The raw materials and equipment used in the specific embodiments of the present invention are all known products and are obtained by purchasing commercially available products.

[0022] Example 1, a method for preparing a polyurethane-modified polyimide foam thermal insulation material, comprising the following steps: Step S1: At room temperature, add 2.5 g of pyromellitic anhydride to 100 g of N,N-dimethylacetamide and stir until completely dissolved at 200 rpm to obtain a transparent solution. Then, add 0.7 g of ethylenediamine to the transparent solution and heat to 75°C while stirring at 150 rpm for 2 hours to form a polyamic acid solution. Step S2: 2.0 g of methacrylic acid and 4.0 g of hydroxyethyl methacrylate were added to the polyamic acid solution and stirred at 150 rpm until completely dissolved. Then, 1.5 g of benzoyl peroxide was added and stirred at the same speed for 10 min to ensure uniform dissolution. The solution was then transferred to a 500 mL reactor and heated to 60° C. for 2 h, with a stirring rate of 150 rpm, to obtain a transparent and uniform polymer solution. Step S3: raising the reaction temperature to 180° C. at a heating rate of 2° C. / min, maintaining the temperature for 3 h to carry out a dehydration cyclization reaction, partially converting the reaction into polyimide; then, lowering the temperature to 150° C. at a rate of 2° C. / min, maintaining the temperature for 30 min, and finally lowering the temperature to room temperature at a rate of 2° C. / min to obtain a partially imidized polymer solution; Step S4: preparing an 80 vol% isocyanate solution with 520 g of toluene diisocyanate and 100 g of N,N-dimethylacetamide, and adding 45 g of the isocyanate solution dropwise to the partially imidized polymer solution at a rate of 3 mL / min under magnetic stirring at 150 rpm. Simultaneously, the temperature was raised to 80° C. and the reaction was continued for 1 hour to form a polyurethane cross-linked network, thereby obtaining a partially imidized polymer solution containing a polyurethane cross-linked structure. Step S5: Using a pipette, 5.2 g of distilled water was measured and added to the partially imidized polymer solution containing a polyurethane cross-linked structure to initiate a foaming reaction to obtain a foaming mixture. The foaming mixture was then transferred into a metal mold and allowed to stand at room temperature for 2 h to obtain a preliminarily solidified foam material. Step S6: Place the preliminarily cured foam material in a vacuum drying oven, set the temperature to 200°C and the pressure to 10 Pa, continue curing under these conditions for 1 hour, then raise the temperature to 250°C and maintain for 2 hours to complete the final imidization reaction. Through high-temperature imidization and microporous structure stabilization, a polyurethane-modified polyimide foam insulation material is obtained.

[0023] The polyurethane modified polyimide foam insulation material prepared in Example 1 has a density of 0.045 g / cm 3 , strength of 0.3MPa, and has a thermal conductivity of 0.03W / (m·K) and a UL 94 V-0 flame retardant level.

[0024] Example 2, a method for preparing a polyurethane-modified polyimide foam insulation material, comprising the following steps: Step S1: At room temperature, add 2.5 g of adipic acid to 100 g of N-methylpyrrolidone and stir until completely dissolved at 300 rpm to obtain a transparent solution. Then, add 2.7 g of hexamethylenediamine to the transparent solution, raise the temperature to 85°C, and continue stirring at 200 rpm for 2 hours to form a polyamic acid solution. Step S2: 2.0 g of methacrylic acid and 4.0 g of hydroxyethyl methacrylate were added to the polyamic acid solution and stirred at 150 rpm until completely dissolved. Then, 1.0 g of azobisisobutyronitrile was added and stirred at the same speed for 10 minutes to ensure uniform dissolution. The solution was then transferred to a 500 mL reactor and heated to 70° C. for 2 hours, with a stirring rate of 150 rpm, to obtain a transparent and uniform polymer solution. Step S3: raising the reaction temperature to 180° C. at a heating rate of 2.5° C. / min, maintaining the temperature for 3 h to carry out a dehydration cyclization reaction, partially converting the reaction into polyimide; then, lowering the temperature to 150° C. at a rate of 2.5° C. / min, maintaining the temperature for 30 min, and finally lowering the temperature to room temperature at a rate of 2.5° C. / min to obtain a partially imidized polymer solution; Step S4: 80.7 vol% isocyanate solution was prepared with 500 g of diphenylmethane-4,4'-diisocyanate and 100 g of N-methylpyrrolidone. Under the action of magnetic stirring at 150 rpm, 53.6 g of the isocyanate solution was dropwise added to the partially imidized polymer solution at a rate of 3 mL / min. The temperature was raised to 85° C. and the reaction was continued for 1 hour to form a polyurethane cross-linked network, thereby obtaining a partially imidized polymer solution containing a polyurethane cross-linked structure. Step S5: Using a pipette, 5 g of deionized water was added to the partially imidized polymer solution containing a polyurethane cross-linked structure to initiate a foaming reaction to obtain a foaming mixture. The foaming mixture was then transferred into a metal mold and allowed to stand at room temperature for 2 h to obtain a preliminarily solidified foam material. Step S6: Place the preliminarily cured foam material in a vacuum drying oven, set the temperature to 200°C and the pressure to 30 Pa, continue curing under these conditions for 1 hour, then raise the temperature to 250°C and maintain for 2 hours to complete the final imidization reaction. Through high-temperature imidization and microporous structure stabilization, a polyurethane-modified polyimide foam insulation material is obtained.

[0025] The polyurethane modified polyimide foam insulation material prepared in Example 2 has a density of 0.05 g / cm 3 , strength of 0.32MPa, thermal conductivity of 0.031W / (m·K) and UL 94 V-0 flame retardancy level.

[0026] Example 3, a method for preparing a polyurethane-modified polyimide foam insulation material, comprising the following steps: Step S1: At room temperature, add 2.5 g of terephthalic acid to 100 g of N,N-dimethylformamide and stir until completely dissolved at 100 rpm to obtain a transparent solution. Then, add 1.4 g of ethylenediamine to the transparent solution, raise the temperature to 80°C, and continue stirring at 200 rpm for 2.5 hours to form a polyamic acid solution. Step S2: 2.0 g of ethyl acrylic acid and 4.0 g of hydroxyethyl ethyl acrylate were added to the polyamic acid solution and stirred at 150 rpm until completely dissolved. Then, 1.0 g of azobisisobutyronitrile was added and stirred at the same speed for 10 min to ensure uniform dissolution. The solution was then transferred to a 500 mL reactor and heated to 65° C. for 2.5 h, with a stirring rate of 150 rpm, to obtain a transparent and uniform polymer solution. Step S3: raising the reaction temperature to 180° C. at a heating rate of 2° C. / min, maintaining the temperature for 3 h to carry out a dehydration cyclization reaction, partially converting the reaction into polyimide; then, lowering the temperature to 155° C. at a rate of 2° C. / min, maintaining the temperature for 35 min, and finally lowering the temperature to room temperature at a rate of 2° C. / min to obtain a partially imidized polymer solution; Step S4: 80.1 vol% isocyanate solution was prepared with 520 g of toluene diisocyanate and 100 g of N,N-dimethylformamide. Under the action of magnetic stirring at 150 rpm, 46.6 g of the isocyanate solution was dropwise added to the partially imidized polymer solution at a rate of 3 mL / min. The temperature was raised to 85° C. and the reaction was continued for 1 h to form a polyurethane cross-linked network, thereby obtaining a partially imidized polymer solution containing a polyurethane cross-linked structure. Step S5: Using a pipette, 5.5 g of distilled water was measured and added to the partially imidized polymer solution containing a polyurethane cross-linked structure to initiate a foaming reaction to obtain a foaming mixture. The foaming mixture was then transferred into a metal mold and allowed to stand at room temperature for 2 h to obtain a preliminarily solidified foam material. Step S6: Place the preliminarily cured foam material in a vacuum drying oven, set the temperature to 200°C and the pressure to 20 Pa, continue curing under these conditions for 1 hour, then raise the temperature to 250°C and maintain for 2 hours to complete the final imidization reaction. Through high-temperature imidization and microporous structure stabilization, a polyurethane-modified polyimide foam insulation material is obtained.

[0027] The polyurethane modified polyimide foam insulation material prepared in Example 3 has a density of 0.046 g / cm 3 , strength of 0.31MPa, and has a thermal conductivity of 0.03W / (m·K) and a UL 94 V-0 flame retardant level.

[0028] Example 4, a method for preparing a polyurethane-modified polyimide foam insulation material, comprising the following steps: Step S1: At room temperature, add 2.5 g of phthalic acid to 100 g of N-methylpyrrolidone and stir until completely dissolved at 180 rpm to obtain a transparent solution. Then, add 1.5 g of 2,2-dimethyl-1,3-propylenediamine to the transparent solution, raise the temperature to 80°C, and continue stirring at 200 rpm for 3 hours to form a polyamic acid solution. Step S2: 2.0 g of propyl acrylic acid and 4.0 g of propyl hydroxyethyl acrylate were added to the polyamic acid solution and stirred at 200 rpm until completely dissolved. Then, 0.5 g of azobisisobutyronitrile was added and stirred at the same speed for 10 min to ensure uniform dissolution. The solution was then transferred to a 500 mL reactor and heated to 65° C. for 2.5 h, with a stirring rate of 200 rpm, to obtain a transparent and uniform polymer solution. Step S3: raising the reaction temperature to 180° C. at a heating rate of 2° C. / min, maintaining the temperature for 3 h to carry out a dehydration cyclization reaction, partially converting the reaction into polyimide; then, lowering the temperature to 150° C. at a rate of 2° C. / min, maintaining the temperature for 30 min, and finally lowering the temperature to room temperature at a rate of 2° C. / min to obtain a partially imidized polymer solution; Step S4: 80.7 vol% isocyanate solution was prepared with 500 g of diphenylmethane-4,4'-diisocyanate and 100 g of N-methylpyrrolidone. Under the action of magnetic stirring at 180 rpm, 30 g of the isocyanate solution was dropwise added to the partially imidized polymer solution at a rate of 3 mL / min. The temperature was simultaneously raised to 80° C. The reaction was continued for 1.5 h to form a polyurethane cross-linked network, thereby obtaining a partially imidized polymer solution containing a polyurethane cross-linked structure. Step S5: Using a pipette, 5.0 g of distilled water was measured and added to the partially imidized polymer solution containing a polyurethane cross-linked structure to initiate a foaming reaction to obtain a foaming mixture. The foaming mixture was then transferred into a metal mold and allowed to stand at room temperature for 2 h to obtain a preliminarily solidified foam material. Step S6: Place the preliminarily cured foam material in a vacuum drying oven, set the temperature to 200°C and the pressure to 20 Pa, continue curing under these conditions for 1 hour, then raise the temperature to 250°C and maintain for 2 hours to complete the final imidization reaction. Through high-temperature imidization and microporous structure stabilization, a polyurethane-modified polyimide foam insulation material is obtained.

[0029] The polyurethane modified polyimide foam insulation material prepared in Example 4 has a density of 0.04 g / cm 3, strength of 0.26MPa, thermal conductivity of 0.029W / (m·K) and UL 94 V-0 flame retardancy level.

[0030] Example 5, a method for preparing a polyurethane-modified polyimide foam insulation material, comprising the following steps: Step S1: At room temperature, add 3.0 g of pyromellitic anhydride to 100 g of N,N-dimethylacetamide and stir until completely dissolved at 200 rpm to obtain a transparent solution. Then, add 0.9 g of ethylenediamine to the transparent solution, raise the temperature to 80°C, and continue stirring at 200 rpm for 2.5 hours to form a polyamic acid solution. Step S2: 2.5 g of methacrylic acid and 4.0 g of hydroxyethyl ethyl acrylate were added to the polyamic acid solution and stirred at 180 rpm until completely dissolved. Then, 1.5 g of benzoyl peroxide was added and stirred at the same speed for 10 min to ensure uniform dissolution. The solution was then transferred to a 500 mL reactor and heated to 65° C. for 2 h, with a stirring rate of 180 rpm, to obtain a transparent and uniform polymer solution. Step S3: raising the reaction temperature to 180° C. at a heating rate of 2.5° C. / min, maintaining the temperature for 3 h to carry out a dehydration cyclization reaction, partially converting the reaction into polyimide; then, lowering the temperature to 150° C. at a rate of 2.5° C. / min, maintaining the temperature for 30 min, and finally lowering the temperature to room temperature at a rate of 2.5° C. / min to obtain a partially imidized polymer solution; Step S4: preparing a 79.7 vol% isocyanate solution with 510 g of toluene diisocyanate and 100 g of N,N-dimethylacetamide, and adding 35 g of the isocyanate solution dropwise to the partially imidized polymer solution at a rate of 3 mL / min under magnetic stirring at 180 rpm. Simultaneously, the temperature was raised to 80° C. and the reaction was continued for 1.5 h to form a polyurethane cross-linked network, thereby obtaining a partially imidized polymer solution containing a polyurethane cross-linked structure. Step S5: Using a pipette, 5.0 g of distilled water was measured and added to the partially imidized polymer solution containing a polyurethane cross-linked structure to initiate a foaming reaction to obtain a foaming mixture. The foaming mixture was then transferred into a metal mold and allowed to stand at room temperature for 2 h to obtain a preliminarily solidified foam material. Step S6: Place the preliminarily cured foam material in a vacuum drying oven, set the temperature to 200°C and the pressure to 15 Pa, continue curing under these conditions for 1 hour, then raise the temperature to 250°C and maintain for 2 hours to complete the final imidization reaction. Through high-temperature imidization and microporous structure stabilization, a polyurethane-modified polyimide foam insulation material is obtained.

[0031] The polyurethane modified polyimide foam insulation material prepared in Example 5 has a density of 0.053 g / cm 3 , strength of 0.36MPa, thermal conductivity of 0.032W / (m·K) and UL 94 V-0 flame retardancy.

[0032] This example demonstrates the effectiveness of the present invention through experiments. The results show that the foam material of the present invention has good thermal stability and flame retardancy in new energy vehicle battery systems and building insulation panels, providing an excellent thermal insulation and flame retardant material option for the new energy industry.

[0033] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A polyurethane modified polyimide foam insulation material, characterized in that: The polyurethane modified polyimide foam thermal insulation material: Thermal conductivity 0.029W / (m·K)-0.032W / (m·K), density 0.04g / cm 3 -0.053g / cm 3 , strength is 0.26MPa-0.36MPa, flame retardant grade UL 94 V-0.

2. The method for preparing a polyurethane-modified polyimide foam thermal insulation material according to claim 1, wherein: The following steps are involved: Step S1: dissolving pyromellitic anhydride in a polar solvent, stirring at room temperature until completely dissolved, then adding ethylenediamine to the mixed solution and continuing to stir to obtain a polyamic acid solution; Step S2: adding additives and a crosslinking enhancer to the polyamic acid solution in sequence, mixing them uniformly under stirring, then adding a polymerization initiator, continuing stirring, and transferring the mixture to a reactor, performing a polymerization reaction under heating to obtain a polymer solution; Step S3: increasing the temperature of the polymer solution at a set heating rate, maintaining the temperature at 150° C.-180° C. for 2 h-3 h for dehydration cyclization reaction, partially converting the polymer solution into polyimide, and then slowly cooling the temperature to room temperature to obtain a partially imidized polymer solution; Step S4: slowly adding the isocyanate solution dropwise to the partially imidized polymer solution, performing a cross-linking reaction under stirring and heating conditions to form a polyurethane cross-linked network, thereby obtaining a partially imidized polymer solution containing a polyurethane cross-linked structure; Step S5: adding a blowing agent to the partially imidized polymer solution containing a polyurethane cross-linked structure to obtain a foaming mixture, then transferring the foaming mixture into a mold, and allowing it to stand and solidify at room temperature to obtain a preliminarily solidified foam material; Step S6: placing the preliminarily cured foam material in a vacuum drying oven and continuing to cure under set temperature and pressure conditions to obtain a polyurethane-modified polyimide foam insulation material through high-temperature imidization and microporous structure stabilization.

3. The preparation method according to claim 2, wherein: In step S1, 2 to 50 parts of pyromellitic anhydride and 0.5 to 15 parts of ethylenediamine are used; Pyromellitic anhydride and ethylenediamine are replaced by: terephthalic acid and ethylenediamine, adipic acid and hexamethylenediamine, phthalic acid and 2,2-dimethyl-1,3-propylenediamine; The polar solvent is N,N-dimethylacetamide, N-methylpyrrolidone or N,N-dimethylformamide; the dosage is 100 parts; The temperature was raised to 75-85°C, the reaction time was 2-3 hours, and the stirring speed was 100-300 rpm.

4. The preparation method according to claim 2, wherein: In step S2, the additive is one of methacrylic acid, ethylacrylic acid, propylacrylic acid, methylbutenoic acid, ethylbutenoic acid, propylbutenoic acid, methylpentenoic acid, ethylpentenoic acid, and propylpentenoic acid; the amount used is 0.5 parts to 10 parts; The cross-linking enhancer is one of hydroxyethyl methacrylate, hydroxyethyl ethyl acrylate, propyl hydroxyethyl acrylate, hydroxyethyl methyl crotonate, hydroxyethyl ethyl crotonate, propyl hydroxyethyl crotonate, hydroxyethyl methyl pentenoate, hydroxyethyl ethyl pentenoate, and hydroxyethyl propyl pentenoate; the amount used is 0.5 parts to 15 parts; The polymerization initiator is benzoyl peroxide or azobisisobutyronitrile, and the amount used is 0.5 parts to 10 parts.

5. The preparation method according to claim 2, wherein: In step S2, the polymerization reaction temperature is 60°C-100°C, the reaction time is 2h-3h, and the stirring speed is 100rpm-300rpm.

6. The preparation method according to claim 2, wherein: In step S3, the heating rate is 2°C / min-5°C / min, and the cooling rate is 1°C / min-3°C / min.

7. The preparation method according to claim 2, characterized in that: In step S4, the isocyanate solution is composed of 300-800 parts of isocyanate and 100 parts of polar solvent, wherein the isocyanate is toluene diisocyanate or diphenylmethane-4,4'-diisocyanate; In step S4, the isocyanate solution is added at a rate of 1 mL-5 mL / min, the amount added is 30-80 parts, the reaction temperature is 70°C-90°C, the stirring time is 1 h-2 h, and the stirring speed is 100 rpm-300 rpm.

8. The preparation method according to claim 2, wherein: In step S5, the foaming agent is distilled water or deionized water, and the added amount is 3 parts to 10 parts.

9. The preparation method according to claim 2, wherein: In step S6, the preliminarily cured foam material is placed in a vacuum drying oven and cured at 10 Pa-50 Pa and 200° C. for 1 h-2 h, and then cured at 10 Pa-50 Pa and 250° C. for 2 h-3 h.

10. An application of a polyurethane-modified polyimide foam thermal insulation material, characterized in that: Used in new energy vehicles, energy storage systems and building insulation.