A method for preparing a polyimide resin solution

Abstract

This invention provides a method for preparing a PMR type polyimide resin solution, comprising: using a large-group alcohol solvent as an esterification agent and a mixed solvent system of dimethyl carbonate and amides as a reaction medium, to obtain a polyimide resin solution via a PMR (monomer-reactant polymerization) method. The solvent system used in this invention can dissolve a variety of rigid monomers, the resin has a high temperature resistance rating, and the obtained resin solution can be stored at room temperature for a long time.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and particularly relates to a method for preparing a polyimide resin solution. Background Technology

[0002] Thermosetting polyimide (PI) resin, as the resin with the highest heat resistance (long-term operating temperature 280–450℃), has gradually become the most important matrix resin in the field of advanced resin-based composites (APCs) due to its excellent thermal oxidation stability, dielectric properties, good mechanical properties, and molding processability. Traditional PMR-type polyimide resin solutions use lower alcohols (methanol or ethanol) as the reaction medium to form a high-solids-content, low-viscosity monomer mixture solution; a typical example is PMR-15 developed by NASA. This type of resin solution has some technical drawbacks: 1) Poor solubility of lower alcohols, making it impossible to prepare rigid-structure resin solutions, resulting in a lower resin temperature resistance. 2) Poor room temperature stability; the resin solution generally precipitates within four weeks, severely affecting the shelf life of the resin and prepreg, causing problems in the manufacture of composite materials. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a method for preparing a polyimide resin solution. The preparation method provided by the present invention uses dimethyl carbonate as the main solvent and isopropanol, trifluoroisopropanol, n-butanol or isobutanol as esterification reagents. The prepared resin solution system has good stability and long storage period at room temperature. At the same time, the prepared polyimide resin cured product has a higher temperature resistance rating.

[0004] This invention provides a method for preparing a polyimide resin solution, comprising:

[0005] Aromatic dianhydride, end-capping agent monohydric anhydride and alcohol are reacted in the first solvent to obtain an esterification solution;

[0006] The solvent was removed from the esterification solution to obtain an aromatic diester and a capping agent monoester.

[0007] The aromatic diester and the capping agent monoester are reacted with the aromatic diamine in a second solvent to obtain a polyimide resin solution.

[0008] Preferably, the ratio of the number of moles of the alcohol to the total number of moles of anhydride groups in the aromatic dianhydride and the capping agent monohydric anhydride is (1-5):1.

[0009] Preferably, the molar ratio of the aromatic diester, aromatic diamine, and capping agent monoester is n:(n+1):2, where n>0.

[0010] Preferably, the alcohol is selected from any one or more of isopropanol, trifluoroisopropanol, n-butanol and isobutanol.

[0011] Preferably, the first solvent is selected from any one or more of dioxane, ethylene glycol dimethyl ether, acetone and tetrahydrofuran.

[0012] Preferably, the second solvent is a mixture of dimethyl carbonate and an amide solvent.

[0013] Preferably, the amide solvent is selected from N,N-dimethylacetamide and / or N,N-dimethylformamide.

[0014] Preferably, the mass ratio of dimethyl carbonate to amide solvent is (1-9):1.

[0015] Preferably, the temperature of the first reaction is 50–100°C;

[0016] The temperature of the second reaction is 90–120°C.

[0017] This invention uses dimethyl carbonate as the main solvent and isopropanol, trifluoroisopropanol, n-butanol, or isobutanol as esterification agents to obtain esterified monomers with large-scale groups. This effectively suppresses side reactions between monomers, thereby significantly improving the room temperature stability of the resin solution. Compared with dimethyl carbonate alone, the mixed solvent used in this invention has superior solubility, allowing for the preparation of polyimide resins with more rigid monomers, while also greatly extending the resin's shelf life. The resin solution system obtained by this invention has the advantages of diverse structural designs and long room temperature storage life. The cured polyimide resin prepared by this invention exhibits excellent heat resistance, superior to traditional PMR-type resin solution systems using lower alcohols (methanol or ethanol) as solvents. Attached Figure Description

[0018] Figure 1 The viscosity change curve of the resin solution prepared in Example 1 of this invention;

[0019] Figure 2 The thermogravimetric curve of the resin cured product prepared in Example 1 of the present invention in air;

[0020] Figure 3 The glass transition temperature curve of the resin cured product prepared in Example 1 of the present invention. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 instances that are improved or modified by those skilled in the art are within the scope of protection of the present invention. It should be understood that the embodiments of the present invention are only used to illustrate the technical effects of the present invention, and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the methods used in the embodiments are conventional methods.

[0022] This invention provides a method for preparing a polyimide resin solution, comprising:

[0023] Aromatic dianhydride, end-capping agent monohydric anhydride and alcohol are reacted in the first solvent to obtain an esterification solution;

[0024] The solvent was removed from the esterification solution to obtain an aromatic diester and a capping agent monoester.

[0025] The aromatic diester and the capping agent monoester are reacted with the aromatic diamine in a second solvent to obtain a polyimide resin solution.

[0026] In this invention, the aromatic dianhydride is preferably selected from 2,3,3',4'-biphenyl dianhydride (3,4'-BPDA), 2,3,2',3'-biphenyl dianhydride (3,3'-BPDA), 3,4,3',4'-biphenyl dianhydride (4,4'-BPDA), 2,3,3',4'-diphenoxy ether dianhydride (3,4'-ODPA), 2,3,2',3'-diphenoxy ether dianhydride (3,3'-ODPA), 3,4,3', The dianhydride is any one or a combination of two or more of the following: 4,4'-ODPA, 3,4,3',4'-BTDA, 2,3,3',4'-BTDA, 2,3,2',3'-BTDA, PMDA, MPDA, 6FDA, and fluorene dianhydride, and is not limited thereto.

[0027] In this invention, the end-capping agent monohydric anhydride is preferably selected from any one or more of 4-phenylethynylbenzene monohydric anhydride, 3-phenylethynylbenzene monohydric anhydride, and 5-norbornene-2,3-monohydric anhydride.

[0028] In this invention, the alcohol preferably includes any one or more of isopropanol, trifluoroisopropanol, n-butanol and isobutanol.

[0029] In this invention, the first solvent is preferably selected from any one or more of dioxane, ethylene glycol dimethyl ether, acetone and tetrahydrofuran.

[0030] In this invention, the ratio of the number of moles of the alcohol to the total number of moles of anhydride groups in the aromatic dianhydride and the capping agent monohydric anhydride is preferably (1-5):1, more preferably (2-4):1, and most preferably 3:1.

[0031] In this invention, the ratio of the mass of the first solvent to the total mass of the aromatic dianhydride and the capping agent monohydric anhydride is preferably (0.25-1.5):1, more preferably (0.5-1.2):1, and most preferably (0.8-1):1.

[0032] In this invention, the first reaction is preferably carried out under an inert protective atmosphere; the inert protective atmosphere preferably includes nitrogen and / or argon.

[0033] In this invention, the temperature of the first reaction is preferably 50-100°C, more preferably 60-90°C, and most preferably 75°C; the time of the first reaction is preferably 4-15 hours, more preferably 5-14 hours, and most preferably 8-11 hours.

[0034] In this invention, the solvent removal method is preferably vacuum distillation to remove the solvent.

[0035] In this invention, the temperature for descaling the solvent is preferably 30-90°C, more preferably 40-80°C, and most preferably 60°C; the time for descaling the solvent is preferably 2-10 hours, more preferably 3-9 hours, and most preferably 5-7 hours.

[0036] In this invention, the aromatic diamine is preferably selected from any one or a combination of two or more of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), 3,4'-diaminodiphenyl ether (3,4'-ODA), 1,3-bis(3-aminophenoxy)benzene (1,3,3-APB), 1,3-bis(4-aminophenoxy)benzene (1,3,4-APB), 4,4'-diaminodiphenylmethane (MDA), 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (TFODA), 2,2'-bismethyl-4,4'-diaminobiphenyl (DMBZ), 3,3'-bismethyl-4,4'-diaminodiphenylmethane (DMMDA), m-phenylenediamine (m-PDA), p-phenylenediamine (p-PDA), and 9,9-bis(4-aminophenyl)fluorene (FDA), but is not limited thereto.

[0037] In this invention, the second solvent is preferably a mixture of dimethyl carbonate and an amide solvent.

[0038] In this invention, the amide solvent is preferably selected from N,N-dimethylacetamide and / or N,N-dimethylformamide.

[0039] In this invention, the mass ratio of dimethyl carbonate to amide solvent is preferably (1-9):1, more preferably (2-8):1, and most preferably (4-6):1.

[0040] In this invention, the molar ratio of the aromatic diester, the aromatic diamine and the capping agent monoester is preferably n:(n+1):2, n>0, more preferably (1-4):(2-5):2, and most preferably (2-3):(3-4):2.

[0041] In this invention, the ratio of the mass of the second solvent to the total mass of the aromatic diester, the capping agent monoester, and the aromatic diamine is preferably (1-2):1, more preferably (1.2-1.8):1, and most preferably (1.4-1.6):1.

[0042] In this invention, the temperature of the second reaction is preferably 90-110°C, more preferably 95-105°C, and most preferably 100°C; the time of the second reaction is preferably 0.5-2 hours, more preferably 1-1.5 hours, and most preferably 1.25 hours.

[0043] In this invention, the first reaction and the second reaction are preferably carried out under the same inert protective atmosphere.

[0044] This invention uses dimethyl carbonate as the main solvent and isopropanol, trifluoroisopropanol, n-butanol, or isobutanol as esterification agents to obtain esterified monomers with large-scale groups. This effectively suppresses side reactions between monomers, thereby significantly improving the room temperature stability of the resin solution. Compared with pure dimethyl carbonate solvent, the mixed solvent used in this invention has superior solubility, allowing for the preparation of polyimide resins with higher temperature resistance using monomers with greater rigidity, and greatly extending the resin's shelf life. The resin solution system obtained by this invention has the advantages of diverse structural designs and long room temperature storage life, while the cured polyimide resin prepared also exhibits excellent heat resistance.

[0045] Example 1

[0046] Under nitrogen protection, 6 kg of 3,4'-biphenyl dianhydride, 4 kg of 4,4'-biphenyl dianhydride, 8.4 kg of 4-phenylethynylbenzene monohydric anhydride and 15 kg of isobutanol were added to 18.4 kg of dioxane and reacted at 100 °C for 12 hours to obtain an esterified solution.

[0047] The obtained esterification solution was subjected to reduced pressure evaporation at 75°C for 14 hours to remove the solvent, yielding 9.0 kg of 3,4'-biphenyl diester, 6 kg of 4,4'-biphenyl diester, and 10.9 kg of 4-phenylethynylbenzene monoester.

[0048] The obtained 3,4'-biphenyl diester, 4,4'-biphenyl diester, 4-phenylethynylbenzene monoester, and 16.3 kg of 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl were added to 42.2 kg of mixed solvent and reacted at 100 °C for 1.5 hours to obtain a PMR type polyimide resin solution; the mass ratio of dimethyl carbonate to N,N-dimethylformamide in the mixed solvent was 8:1.

[0049] The viscosity of the resin solution prepared in Example 1 of this invention was tested using a high-temperature rheometer in flow mode at room temperature. The test results are as follows: Figure 1 As shown, by Figure 1 It can be seen that the viscosity of the resin solution fluctuates little within 12 weeks, indicating that the solution has good room temperature stability.

[0050] The thermogravimetric analysis (TGA) method specified in GB / T 27761-2011 "Test Method for Weight Loss and Residual Weight of Thermogravimetric Analyzer" was used to conduct a thermogravimetric analysis on the resin solution prepared in Example 1 of this invention, which formed a cured resin in air. The temperature at which the air mass loss was 5% was measured. The test results are as follows: Figure 2 As shown, by Figure 2 It is known that the 5% thermal weight loss temperature of the resin cured product in air is 550℃.

[0051] The glass transition temperature of the resin solution prepared in Example 1 of this invention was determined using the dynamic mechanical analysis test method specified in Chapter 7 of GB / T 22567-2008 "Test Method for Determination of Glass Transition Temperature of Electrical Insulating Materials". The test results are as follows: Figure 3 As shown, by Figure 3 It is known that the glass transition temperature of the cured resin is 480℃.

[0052] Example 2

[0053] Under nitrogen protection, 5.0 kg of 3,4'-benzophenone dianhydride, 7.7 kg of 4-phenylethynylbenzene monohydric anhydride and 4.6 kg of isobutanol were added to 6.4 kg of dioxane and reacted at 60 °C for 5 hours to obtain an esterified solution.

[0054] The obtained esterification solution was subjected to reduced pressure evaporation at 80°C for 3 hours to remove the solvent, yielding 7.3 kg of 3,4'-benzophenone diester and 10.0 kg of 4-phenylethynylbenzene monoester.

[0055] The obtained 3,4'-benzophenone diester, 4-phenylethynylbenzene monoester and 6.8 kg of 4,4'-diamino-2,2'-dimethylbiphenyl were added to 28.9 kg of mixed solvent and reacted at 95 °C for 1 hour to obtain a PMR type polyimide resin solution; the mass ratio of dimethyl carbonate to N,N-dimethylacetamide in the mixed solvent was 2:1.

[0056] The resin solution prepared in Example 2 of this invention was tested according to the method of Example 1. The stability period of the resin solution was greater than 24 weeks, the 5% thermal weight loss temperature of the cured resin in air was 500°C, and the glass transition temperature of the cured resin was 466°C.

[0057] Example 3

[0058] Under argon protection, 10.0 kg of 3,4'-biphenyl dianhydride, 8.4 kg of 3-phenylethynylbenzene monohydric anhydride and 15 kg of n-butanol were added to 22.1 kg of ethylene glycol dimethyl ether, and the mixture was reacted at 75 °C for 10 hours to obtain an esterified solution.

[0059] The obtained esterification solution was subjected to reduced pressure evaporation at 70°C for 6 hours to remove the solvent, yielding 15 kg of 3,4'-biphenyl diester and 10.9 kg of 3-phenylethynylbenzene monoester.

[0060] The obtained 3,4'-biphenyl diester, 3-phenylethynylbenzene monoester, and 16.3 kg of 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl were added to 63.3 kg of mixed solvent and reacted at 100 °C for 1.25 hours to obtain a PMR type polyimide resin solution; the mass ratio of dimethyl carbonate to N,N-dimethylformamide in the mixed solvent was 5:1.

[0061] Example 4

[0062] Under nitrogen protection, 10.0 kg of 3,4'-biphenyl dianhydride, 8.4 kg of 4-phenylethynylbenzene monohydric anhydride and 24.5 kg of isopropanol were added to 18.4 kg of tetrahydrofuran, and the mixture was reacted at 50 °C for 15 hours to obtain an esterified solution.

[0063] The obtained esterification solution was subjected to reduced pressure evaporation at 40°C for 10 hours to remove the solvent, yielding 12 kg of 3,4'-biphenyl diester and 10.4 kg of 4-phenylethynylbenzene monoester.

[0064] The obtained 3,4'-biphenyl diester, 4-phenylethynylbenzene monoester, and 16.3 kg of 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl were added to 77.4 kg of mixed solvent and reacted at 95 °C for 2 hours to obtain a PMR type polyimide resin solution; the mass ratio of dimethyl carbonate to N,N-dimethylformamide in the mixed solvent was 1:1.

[0065] According to the method of Example 1, the resin solution prepared in Example 4 of the present invention has a stability period of more than 24 weeks, the 5% thermal weight loss temperature of the resin curing product in air is 485°C, and the glass transition temperature of the resin curing product is 370°C.

[0066] Example 5

[0067] Under nitrogen protection, 10.0 kg of 4,4'-benzophenone dianhydride, 5.1 kg of 4-phenylethynylbenzene monohydric anhydride and 24.8 kg of isopropanol were added to 14 kg of acetone and reacted at 55 °C for 9 hours to obtain an esterification solution.

[0068] The obtained esterification solution was subjected to reduced pressure evaporation at 30°C for 7 hours to remove the solvent, yielding 11.9 kg of 4,4'-benzophenone diester and 6.3 kg of 4-phenylethynylbenzene monoester.

[0069] The obtained 4,4'-benzophenone diester, 4-phenylethynylbenzene monoester and 4.5 kg m-phenylenediamine were added to 36.3 kg of mixed solvent and reacted at 105 °C for 1.5 hours to obtain a PMR type polyimide resin solution; the mass ratio of dimethyl carbonate and N,N-dimethylacetamide in the mixed solvent was 9:1.

[0070] Example 6

[0071] Under argon protection, 10.0 kg of 4,4'-diphenyl ether dianhydride, 2.1 kg of norbornene monohydric anhydride and 9.2 kg of isopropanol were added to 3.1 kg of dioxane and reacted at 100 °C for 11 hours to obtain an esterified solution.

[0072] The obtained esterification solution was subjected to reduced pressure evaporation at 90°C for 9 hours to remove the solvent, yielding 13.9 kg of 4,4'-diphenyl ether diester and 2.9 kg of norbornene monoester.

[0073] The obtained 4,4'-diphenyl ether diester, norbornene monoester and 7.7 kg of diaminodiphenylmethane were added to 48.9 kg of mixed solvent and reacted at 110 °C for 2 hours to obtain a PMR type polyimide resin solution; the mass ratio of dimethyl carbonate and N,N-dimethylformamide in the mixed solvent was 7:1.

[0074] Example 7

[0075] Under nitrogen protection, 10 kg of 3,4'-diphenyl ether dianhydride, 1.3 kg of norbornene monohydric anhydride and 16 kg of isobutanol were added to 13.6 kg of ethylene glycol dimethyl ether and reacted at 85 °C for 8 hours to obtain an esterified solution.

[0076] The obtained esterification solution was subjected to reduced pressure evaporation at 85°C for 9 hours to remove the solvent, yielding 14.8 kg of 3,4'-diphenyl ether diester and 1.9 kg of norbornene monoester.

[0077] The obtained 3,4'-diphenyl ether diester, norbornene monoester, and 12.2 kg of 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether were added to 40.5 kg of mixed solvent and reacted at 105 °C for 0.5 hours to obtain a PMR type polyimide resin solution; the mass ratio of dimethyl carbonate to N,N-dimethylacetamide in the mixed solvent was 1:1.

[0078] Example 8

[0079] Under argon protection, 10.0 kg of 4,4'-biphenyl dianhydride, 8.4 kg of 4-phenylethynylbenzene monohydric anhydride and 23.0 kg of trifluoroisopropanol were added to 23.9 kg of tetrahydrofuran, and the mixture was reacted at 60 °C for 15 hours to obtain an esterified solution.

[0080] The obtained esterification solution was subjected to reduced pressure evaporation at 70°C for 8 hours to remove the solvent, yielding 13.9 kg of 4,4'-biphenyl diester and 12.3 kg of 4-phenylethynylbenzene monoester.

[0081] The obtained 4,4'-biphenyl diester, 4-phenylethynylbenzene monoester and 10.1 kg of 3,4'-diaminodiphenyl ether were added to 54.5 kg of mixed solvent and reacted at 90 °C for 0.5 hours to obtain a PMR type polyimide resin solution; the mass ratio of dimethyl carbonate and N,N-dimethylformamide in the mixed solvent was 5:1.

[0082] Example 9

[0083] Under argon protection, 7.9 kg of 4,4'-biphenyl dianhydride, 3.7 kg of 4,4'-benzophenone dianhydride, 19.2 kg of 4-phenylethynylbenzene monohydric anhydride and 22.8 kg of n-butanol were added to 15.4 kg of ethylene glycol dimethyl ether and reacted at 100 °C for 9 hours to obtain an esterified solution.

[0084] The obtained esterification solution was subjected to reduced pressure evaporation at 80°C for 8 hours to remove the solvent, yielding 11.9 kg of 4,4'-biphenyl diester, 5.4 kg of 4,4'-benzophenone diester, and 24.9 kg of 4-phenylethynylbenzene monoester.

[0085] The obtained 4,4'-biphenyl diester, 4,4'-benzophenone diester, 4-phenylethynylbenzene monoester, 17.3 kg of 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl, and 2.5 kg of p-phenylenediamine were added to 62 kg of mixed solvent and reacted at 100 °C for 1.75 hours to obtain a PMR type polyimide resin solution; the mass ratio of dimethyl carbonate to N,N-dimethylacetamide in the mixed solvent was 7:1.

[0086] According to the method of Example 1, the resin solution prepared in Example 9 of the present invention has a stability period of more than 8 weeks, the 5% thermal weight loss temperature of the resin curing product in air is 560°C, and the glass transition temperature of the resin curing product is 490°C.

[0087] Example 10

[0088] Under nitrogen protection, 7.9 kg of 4,4'-biphenyl dianhydride, 3.7 kg of 4,4'-benzophenone dianhydride, 19.2 kg of 4-phenylethynylbenzene monohydric anhydride and 11.4 kg of n-butanol were added to 30.8 kg of dioxane and reacted at 90 °C for 12 hours to obtain an esterified solution.

[0089] The obtained esterification solution was subjected to reduced pressure evaporation at 90°C for 10 hours to remove the solvent, yielding 11.9 kg of 4,4'-biphenyl diester, 5.4 kg of 4,4'-benzophenone diester, and 24.9 kg of 4-phenylethynylbenzene monoester.

[0090] The obtained 4,4'-biphenyl diester, 4,4'-benzophenone diester, 4-phenylethynylbenzene monoester, 17.3 kg of 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl, and 2.5 kg of m-phenylenediamine were added to 74.4 kg of mixed solvent and reacted at 105 °C for 2 hours to obtain a PMR type polyimide resin solution; the mass ratio of dimethyl carbonate to N,N-dimethylformamide in the mixed solvent was 4:1.

[0091] According to the method of Example 1, the resin solution prepared in Example 10 of the present invention has a stability period of more than 10 weeks, the 5% thermal weight loss temperature of the cured resin in air is 551°C, and the glass transition temperature of the cured resin is 480°C.

[0092] Comparative Example 1

[0093] The PMR-15 resin was tested according to the method in Example 1. The test results showed that the solution stability period (at room temperature) was less than 4 weeks, the 5% thermal weight loss temperature was 450°C, and the glass transition temperature was 343°C.

[0094] As can be seen from the above embodiments, the present invention uses dimethyl carbonate as the main solvent, making the resin solution safer and more environmentally friendly. The present invention utilizes isopropanol, trifluoroisopropanol, n-butanol, or isobutanol as esterification reagents to obtain esterified monomers with large-scale groups, effectively suppressing side reactions between monomers and thus effectively improving the room temperature stability of the resin solution. Compared with simple dimethyl carbonate solvent, the mixed solvent used in the present invention has superior solubility, significantly extending the resin's shelf life, and allowing the use of monomers with greater rigidity to prepare polyimide resins with higher temperature resistance ratings. The resin solution system obtained by the present invention has the advantages of diverse structural designs, safety and environmental friendliness, and long room temperature storage period, while the cured polyimide resin prepared also has excellent heat resistance.

[0095] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1.A method for preparing a polyimide resin solution, comprising: performing a first reaction of an aromatic dianhydride, a blocking agent monomeric anhydride and an alcohol in a first solvent to obtain an esterification solution; the alcohol is selected from any one or more of isopropyl alcohol, trifluoroisopropyl alcohol, n-butyl alcohol and isobutyl alcohol; the blocking agent monomeric anhydride is selected from any one or more of 4-phenylacetylenyl benzene monomeric anhydride, 3-phenylacetylenyl benzene monomeric anhydride and 5-norbornene-2, 3-monomeric anhydride; removing solvent from the esterification solution to obtain an aromatic diester and a blocking agent monoester; performing a second reaction of the aromatic diester and the blocking agent monoester with an aromatic diamine in a second solvent to obtain the polyimide resin solution; the second solvent is a mixed solvent of dimethyl carbonate and an amide solvent; the mass ratio of the dimethyl carbonate and the amide solvent is (1-9) : 1; the ratio of the number of moles of the alcohol to the number of moles of total anhydride groups in the aromatic dianhydride and the blocking agent monomeric anhydride is (1-5) : 1; the molar ratio of the aromatic diester, the aromatic diamine and the blocking agent monoester is n: (n+1) : 2, n > 0; the first solvent is selected from any one or more of dioxane, ethylene glycol dimethyl ether, acetone and tetrahydrofuran; the amide solvent is selected from N, N-dimethylacetamide and / or N, N-dimethylformamide; the temperature of the first reaction is 50-100℃; and the temperature of the second reaction is 90-120℃. ​ ​ ​ ​ ​ ​ 2. The method of claim 1, wherein, ​ 3. The method of claim 1, wherein, ​ 4. The method of claim 1, wherein, ​ 5. The method of claim 1, wherein, ​ 6. The method of claim 1, wherein, ​ 7. The method of claim 1, wherein, ​

Images