Preparation method of low-gas-yield easy-to-form thermosetting polyimide resin

Abstract

The invention belongs to the technical field of resin synthesis, and discloses a low-gas-yield easy-to-form thermosetting polyimide resin preparation method which comprises the following specific steps: step 1, providing dianhydride, diamine, an end-capping reagent, an organic solvent, a dehydrating agent and a precipitating agent; 2, respectively adding dianhydride and diamine into the reaction kettles, stirring and dissolving the dianhydride and the diamine in the organic solvent, and respectively and correspondingly forming an anhydride solution and a diamine solution; 3, under the ice-water bath condition, gradually adding the anhydride solution into the diamine solution, and reacting for 2-3 hours; step 4, gradually adding an end-capping reagent into the solution obtained by the reaction in the step 3, and continuously reacting for 6-8 hours under the ice-water bath condition until the viscosity of the solution is increased and the color is turned into yellow red; the aromatic / special group dianhydride diamine and the phenylacetylene end-capping reagent are subjected to polycondensation, and imidization control and molecular weight adjustment are combined, so that the prepared resin has high heat resistance, formability, high strength and toughness and low gas yield.

Description

Technical Field

[0001] This invention belongs to the field of resin synthesis technology, and more specifically, relates to a method for preparing a low-gas-yield, easily moldable thermosetting polyimide resin. Background Technology

[0002] Thermosetting polyimide resins are irreplaceable in the manufacture of high-temperature components in the aerospace field due to their excellent high-temperature resistance (Tg > 400℃) and mechanical strength. For example, aircraft engine parts need to maintain structural integrity in extreme environments above 400℃. However, traditional polyimide resins have the following significant drawbacks:

[0003] 1. High viscosity leads to poor processability: The high melt viscosity of the resin (>5000 cp.s) makes it difficult to uniformly wet the fiber reinforcement, resulting in weak interfacial bonding of the composite material. Furthermore, the high viscosity increases the molding difficulty of complex components, limiting its application in precision parts.

[0004] 2. Incomplete imidization leads to high gas production: Resins synthesized by traditional processes are often imide prepolymers (non-ring-closed polyimides) with a large number of residual carboxyl groups (-COOH) and amino groups (-NH2). These active groups decompose during curing to produce volatile gases (such as H2O and CO2), which increases the porosity of the composite material and causes the flexural strength at 400℃ to drop sharply to 23 MPa.

[0005] Third, it is difficult to balance high-temperature performance and processability: Existing technologies enhance heat resistance by increasing molecular weight, but sacrifice melt flowability. If the imidization process is simplified, although the viscosity is reduced to 378 cp.s, the degree of imidization is insufficient (Td=484℃), resulting in a tensile strength of only 178 MPa at 400℃.

[0006] Therefore, the present invention provides a method for preparing a low-gas-production, easily moldable thermosetting polyimide resin. Summary of the Invention

[0007] In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a method for preparing a low-gas-production, easily moldable thermosetting polyimide resin. By selecting aromatic / special group dianhydride diamine and phenylacetylene end-capping agent for polycondensation, combined with imidization control and molecular weight adjustment, the resin is prepared with high heat resistance, easy molding, high strength and toughness, and low gas production.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A method for preparing a low-gas-production, easily moldable thermosetting polyimide resin includes the following specific steps:

[0010] Step 1: Provide dianhydride, diamine, capping agent, organic solvent, dehydrating agent, and precipitant;

[0011] Step 2: The dianhydride and the diamine are respectively added to each reaction vessel and stirred to dissolve in the organic solvent, thereby forming the dianhydride solution and the diamine solution respectively.

[0012] Step 3: Under ice-water bath conditions, gradually add the acid anhydride solution to the diamine solution and react for 2-3 hours;

[0013] Step 4: Gradually add the capping agent to the solution obtained in Step 3, and continue to react under ice-water bath conditions for 6-8 hours until the viscosity of the solution increases and the color changes to yellow-red.

[0014] Step 5: Add the dehydrating agent to the solution obtained in Step 4, start heating to 150-160℃ and heat under reflux for 14-16 hours to complete the imidization reaction and obtain imidized polyimide resin.

[0015] Step 6: After cooling the polyimide resin solution obtained in Step 5, pour it into a precipitant to precipitate. After washing, filtration and drying, solid thermosetting polyimide resin powder is obtained.

[0016] As a further preferred technical solution of the present invention, the dianhydride includes aromatic dianhydride, which is selected from at least one of bisphenol A type diether dianhydride, pyromellitic anhydride, biphenyl anhydride, ketone anhydride or ether anhydride;

[0017] The diamine includes an aromatic diamine selected from at least one of 4,4'-diaminodiphenyl ether, p-phenylenediamine, 9,9-bis(4-aminophenyl)fluorene, or biphenyl diamine.

[0018] As a further preferred technical solution of the present invention, the dianhydride further includes a dianhydride containing a special group, wherein the dianhydride containing the special group is hexafluorodianhydride;

[0019] The diamine also includes diamines containing special groups, wherein the diamine containing special groups is a naphthalene-containing diamine.

[0020] As a further preferred technical solution of the present invention, the molar ratio of each component of dianhydride, diamine and capping agent is: dianhydride 5-7 mol, diamine 5-7 mol and capping agent 1-2 mol.

[0021] The weight ratio of the organic solvent, dehydrating agent, and precipitant is as follows: 5-10 kg of organic solvent, 1.5-3 kg of dehydrating agent, and 5-8 times the weight of the polyimide resin solution obtained in step 5.

[0022] The capping agent is a monofunctional acid anhydride containing unsaturated double bonds.

[0023] As a further preferred technical solution of the present invention, the molar ratio of aromatic dianhydride to dianhydride containing special groups in the dianhydride is (3-5):1, and the molar ratio of aromatic diamine to diamine containing special groups in the diamine is (2-4):1.

[0024] As a further preferred embodiment of the present invention, the naphthalene-containing diamine is selected from at least one of 1,5-naphthyldiamine or 2,2'-binaphth-4,4'-diamine;

[0025] The biphenyl anhydride is selected from at least one of 2,3',3,4'-biphenyltetracarboxylic acid dianhydride or 3,3',4,4'-biphenyltetracarboxylic acid dianhydride;

[0026] The ketone anhydrides include 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride;

[0027] The ether anhydride is selected from at least one of 4,4'-biphenyl ether dianhydride, 4,4'-terephthalodioxydiphthalic anhydride, or 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride.

[0028] As a further preferred technical solution of the present invention, the capping agent is phenylacetylene-phthalic anhydride;

[0029] The organic solvent is selected from at least one of dimethylformamide, dimethylacetamide, or N-methylpyrrolidone;

[0030] The dehydrating agent is toluene;

[0031] The precipitant is deionized water.

[0032] As a further preferred technical solution of the present invention, the imidization reaction is carried out at 150-160°C, and the degree of imidization is 95%-99%, so as to reduce the amount of gas generated during the curing process.

[0033] As a further preferred technical solution of the present invention, the minimum melt viscosity of the solid thermosetting polyimide resin is less than 800 cp.s and the glass transition temperature is greater than 400°C.

[0034] As a further preferred technical solution of the present invention, the polyimide resin prepared by the method, after being made into a composite material, has a room temperature flexural strength greater than 700 MPa and a tensile strength greater than 450 MPa.

[0035] The bending strength is greater than 300 MPa and the tensile strength is greater than 280 MPa at 400℃.

[0036] As described above, the method for preparing a low-gas-production, easily moldable thermosetting polyimide resin provided by the present invention has the following beneficial effects:

[0037] 1. The present invention utilizes the above-mentioned method for preparing a low-gas-production, easily moldable thermosetting polyimide resin. Compared with the prior art, it selects diacid anhydride and diamine polycondensation reaction with aromatic and special groups, which increases the resin's temperature resistance and improves its solubility. At the same time, the chain ends are capped with phenylacetylene-phthalic anhydride to increase the crosslinking density, and the Tg after complete curing is >400℃.

[0038] 2. The present invention utilizes the above-mentioned method for preparing a low-gas-production, easily moldable thermosetting polyimide resin. Compared with the prior art, by adjusting the process and the amount of end-capping agent, the molecular weight of the synthesized resin can be controlled. The resin is soluble in polar solvents at room temperature, and the minimum melt viscosity is <800cp.s, exhibiting excellent molding processability.

[0039] 3. The present invention utilizes the above-mentioned method for preparing a low-gas-production, easily moldable thermosetting polyimide resin. Compared with the prior art, the resin has higher mechanical strength. When made into a prepreg and pressed into a composite material, the room temperature flexural strength is >700 MPa, the tensile strength is >450 MPa, the flexural strength at 400℃ is >300 MPa, and the tensile strength is >280 MPa.

[0040] 4. The present invention utilizes the above-mentioned method for preparing a low-gas-production, easily moldable thermosetting polyimide resin. Compared with the prior art, the imidization stage is completed during resin synthesis, the imidization degree is >95%, the gas production during the molding process is small, and no exhaust is required.

[0041] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a flowchart of a method for preparing a low-gas-production, easily moldable thermosetting polyimide resin according to the present invention. Detailed Implementation

[0044] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0045] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art and are not intended to limit the scope of the invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention. Specific structures can be described with reference to the accompanying drawings of the patent application.

[0046] This invention provides a method for preparing a low-gas-production, easily moldable thermosetting polyimide resin. Please refer to [link / reference]. Figure 1 As shown, the specific steps include the following:

[0047] Step 1: Provide dianhydride, diamine, capping agent, organic solvent, dehydrating agent, and precipitant;

[0048] Step 2: The dianhydride and the diamine are respectively added to each reaction vessel and stirred to dissolve in the organic solvent, thereby forming the dianhydride solution and the diamine solution respectively.

[0049] Step 3: Under ice-water bath conditions, gradually add the acid anhydride solution to the diamine solution and react for 2-3 hours;

[0050] Step 4: Gradually add the capping agent to the solution obtained in Step 3, and continue to react under ice-water bath conditions for 6-8 hours until the viscosity of the solution increases and the color changes to yellow-red.

[0051] Step 5: Add the dehydrating agent to the solution obtained in Step 4, start heating to 150-160℃ and heat under reflux for 14-16 hours to complete the imidization reaction and obtain imidized polyimide resin.

[0052] Step 6: After cooling the polyimide resin solution obtained in Step 5, pour it into a precipitant to precipitate. After washing, filtration and drying, solid thermosetting polyimide resin powder is obtained.

[0053] The dianhydride includes aromatic dianhydrides, which are selected from at least one of bisphenol A type diether dianhydride, pyromellitic anhydride, biphenyl anhydride, ketone anhydride, or ether anhydride.

[0054] The diamine includes an aromatic diamine selected from at least one of 4,4'-diaminodiphenyl ether, p-phenylenediamine, 9,9-bis(4-aminophenyl)fluorene, or biphenyl diamine.

[0055] The dianhydride also includes dianhydrides containing special groups, wherein the dianhydride containing special groups is hexafluorodianhydride;

[0056] The diamine also includes diamines containing special groups, wherein the diamine containing special groups is a naphthalene-containing diamine.

[0057] The molar ratio of each component of the dianhydride, diamine and capping agent is: dianhydride 5-7 mol, diamine 5-7 mol and capping agent 1-2 mol;

[0058] The weight ratio of the organic solvent, dehydrating agent, and precipitant is as follows: 5-10 kg of organic solvent, 1.5-3 kg of dehydrating agent, and 5-8 times the weight of the polyimide resin solution obtained in step 5.

[0059] The capping agent is a monofunctional acid anhydride containing unsaturated double bonds.

[0060] The molar ratio of aromatic dianhydride to dianhydride containing special groups in the dianhydride is (3-5):1, and the molar ratio of aromatic diamine to diamine containing special groups in the diamine is (2-4):1.

[0061] The naphthalene-containing diamine is selected from at least one of 1,5-naphthyldiamine or 2,2'-binaphth-4,4'-diamine;

[0062] The biphenyl anhydride is selected from at least one of 2,3',3,4'-biphenyltetracarboxylic acid dianhydride or 3,3',4,4'-biphenyltetracarboxylic acid dianhydride;

[0063] The ketone anhydrides include 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride;

[0064] The ether anhydride is selected from at least one of 4,4'-biphenyl ether dianhydride, 4,4'-terephthalodioxydiphthalic anhydride, or 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride.

[0065] The capping agent is phenylacetyl phthalic anhydride;

[0066] The organic solvent is selected from at least one of dimethylformamide, dimethylacetamide, or N-methylpyrrolidone;

[0067] The dehydrating agent is toluene;

[0068] The precipitant is deionized water.

[0069] The imidization reaction is carried out at 150-160°C, with an imidization degree of 95%-99%, in order to reduce the amount of gas generated during the curing process.

[0070] The solid thermosetting polyimide resin has a minimum melt viscosity of less than 800 cp.s and a glass transition temperature of greater than 400℃.

[0071] The polyimide resin prepared by the method, after being made into a composite material, has a room temperature flexural strength greater than 700 MPa and a tensile strength greater than 450 MPa.

[0072] The bending strength is greater than 300 MPa and the tensile strength is greater than 280 MPa at 400℃.

[0073] Example 1

[0074] Provide 2 mol of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 1 mol of hexafluorodianhydride, 2 mol of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 1.2 mol of phenylethynylphthalic anhydride, 2.8 mol of p-phenylenediamine, 2.8 mol of 4,4'-diaminodiphenyl ether, 1.5 kg of toluene, 6 kg of dimethylformamide, and 40 kg of deionized water;

[0075] 3,3',4,4'-benzophenone tetracarboxylic dianhydride, hexafluoro dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride and 4 kg of dimethylformamide were added to a reaction vessel according to the specified proportions and stirred to dissolve to obtain an acid anhydride solution;

[0076] Add p-phenylenediamine, 4,4'-diaminodiphenyl ether and 2 kg of dimethylformamide into a reaction vessel according to the specified proportions, and stir to dissolve to obtain a diamine solution;

[0077] The acid anhydride solution was gradually added to the diamine solution, and the reaction was carried out in an ice-water bath for 2-3 hours. Then, phenylethynyl phthalic anhydride was gradually added, and the reaction was carried out in an ice-water bath for 6-8 hours. When the solution had a preliminary viscosity and the color turned yellow-red, 1.5 kg of toluene was added, and the temperature was raised to 150-160℃. The solution was heated under reflux for 14-16 hours to obtain imidized polyimide resin. After the solution cooled, the polyimide resin solution was poured into deionized water to precipitate, washed, filtered, and dried to obtain solid thermosetting polyimide resin powder.

[0078] Example 2

[0079] Provide 2 mol of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 1 mol of hexafluorodianhydride, 2 mol of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2 mol of phenylethynylphthalic anhydride, 3.5 mol of p-phenylenediamine, 3.5 mol of 4,4'-diaminodiphenyl ether, 1.8 kg of toluene, 7 kg of dimethylformamide, and 45 kg of deionized water;

[0080] 3,3',4,4'-benzophenone tetracarboxylic dianhydride, hexafluoro dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride and 4 kg of dimethylformamide were added to a reaction vessel according to the specified proportions and stirred to dissolve to obtain an acid anhydride solution;

[0081] Add p-phenylenediamine, 4,4'-diaminodiphenyl ether and 3 kg of dimethylformamide into a reaction vessel according to the specified proportions, and stir to dissolve to obtain a diamine solution;

[0082] The acid anhydride solution was gradually added to the diamine solution, and the reaction was carried out in an ice-water bath for 2-3 hours. Then, phenylethynyl phthalic anhydride was gradually added, and the reaction was carried out in an ice-water bath for 6-8 hours. When the solution had a preliminary viscosity and the color turned yellow-red, 1.8 kg of toluene was added, and the temperature was raised to 150-160℃. The solution was heated under reflux for 14-16 hours to obtain imidized polyimide resin. After the solution cooled, the polyimide resin solution was poured into deionized water to precipitate, washed, filtered, and dried to obtain solid thermosetting polyimide resin powder.

[0083] Example 3

[0084] Provide 2 mol of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2 mol of 2,3',3,4'-biphenyltetracarboxylic dianhydride, 2 mol of 4,4'-biphenyl ether dianhydride, 2.4 mol of phenylethynylphthalic anhydride, 3.6 mol of p-phenylenediamine, 3.6 mol of 1,5-naphthylenediamine, 2 kg of toluene, 8 kg of dimethylformamide, and 50 kg of deionized water;

[0085] 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride, 2,3',3,4'-biphenyltetracarboxylic acid dianhydride, 4,4'-biphenyl ether dianhydride and 5 kg of dimethylformamide were added to the reaction vessel according to the specified proportions and stirred to dissolve to obtain an acid anhydride solution.

[0086] Add p-phenylenediamine, 1,5-naphthylenediamine and 3 kg of dimethylformamide into a reaction vessel according to the specified proportions, and stir to dissolve to obtain a diamine solution;

[0087] The acid anhydride solution was gradually added to the diamine solution, and the reaction was carried out in an ice-water bath for 2-3 hours. Then, phenylethynyl phthalic anhydride was gradually added, and the reaction was carried out in an ice-water bath for 6-8 hours. When the solution had a preliminary viscosity and the color turned yellow-red, 2 kg of toluene was added, and the temperature was raised to 150-160℃. The solution was heated under reflux for 14-16 hours to obtain imidized polyimide resin. After the solution cooled, the polyimide resin solution was poured into deionized water to precipitate, washed, filtered, and dried to obtain solid thermosetting polyimide resin powder.

[0088] Comparative Example 1 [Without PEPA]

[0089] Provide 2 mol of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 1 mol of hexafluorodianhydride, 2 mol of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2.5 mol of p-phenylenediamine, 2.5 mol of 4,4'-diaminodiphenyl ether, 1.5 kg of toluene, 6 kg of dimethylformamide, and 40 kg of deionized water;

[0090] 3,3',4,4'-benzophenone tetracarboxylic dianhydride, hexafluoro dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride and 4 kg of dimethylformamide were added to a reaction vessel according to the specified proportions and stirred to dissolve to obtain an acid anhydride solution;

[0091] Add p-phenylenediamine, 4,4'-diaminodiphenyl ether and 2 kg of dimethylformamide into a reaction vessel according to the specified proportions, and stir to dissolve to obtain a diamine solution;

[0092] The acid anhydride solution was gradually added to the diamine solution, and the reaction was carried out in an ice-water bath for 6-8 hours. When the solution had a preliminary viscosity and the color turned yellow-red, 1.5 kg of toluene was added, and the temperature was raised to 150-160℃. The mixture was heated under reflux for 14-16 hours to obtain the imidized polyimide resin. After the solution cooled, the polyimide resin solution was poured into deionized water to precipitate, washed, filtered, and dried to obtain solid thermosetting polyimide resin powder.

[0093] Comparative Example 2 [No addition (no imidization)]

[0094] Provide 2 mol of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 1 mol of hexafluorodianhydride, 2 mol of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 1.2 mol of phenylethynylphthalic anhydride, 2.8 mol of p-phenylenediamine, 2.8 mol of 4,4'-diaminodiphenyl ether, 6 kg of dimethylformamide, and 40 kg of deionized water;

[0095] 3,3',4,4'-benzophenone tetracarboxylic dianhydride, hexafluoro dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride and 4 kg of dimethylformamide were added to a reaction vessel according to the specified proportions and stirred to dissolve to obtain an acid anhydride solution;

[0096] Add p-phenylenediamine, 4,4'-diaminodiphenyl ether and 2 kg of dimethylformamide into a reaction vessel according to the specified proportions, and stir to dissolve to obtain a diamine solution;

[0097] The acid anhydride solution was gradually added to the diamine solution, and the reaction was carried out in an ice-water bath for 2-3 hours. Then, phenylacetylene-phthalic anhydride was gradually added, and the reaction was carried out in an ice-water bath for 6-8 hours. When the solution had a preliminary viscosity and the color turned yellow-red, a polyimide resin solution was obtained. After the solution was cooled, the polyimide resin solution was poured into deionized water to precipitate, washed, filtered, and dried to obtain solid thermosetting polyimide resin powder.

[0098] The performance tests of solubility, resin properties and mechanical properties of composite materials were carried out in Examples 1-3 and Comparative Examples 1-2, as shown in Tables 1 to 3.

[0099] Table 1 Solubility

[0100]

[0101] Table 2 Resin Properties

[0102]

[0103] Table 3 Mechanical properties of composite materials

[0104]

[0105] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing a low-gas-production, easily moldable thermosetting polyimide resin, characterized in that, The specific steps include the following: Step 1: Provide dianhydride, diamine, capping agent, organic solvent, dehydrating agent, and precipitant; Step 2: The dianhydride and the diamine are respectively added to each reaction vessel and stirred to dissolve in the organic solvent, thereby forming the dianhydride solution and the diamine solution respectively. Step 3: Under ice-water bath conditions, gradually add the acid anhydride solution to the diamine solution and react for 2-3 hours; Step 4: Gradually add the capping agent to the solution obtained in Step 3, and continue to react under ice-water bath conditions for 6-8 hours until the viscosity of the solution increases and the color changes to yellow-red. Step 5: Add the dehydrating agent to the solution obtained in Step 4, start heating to 150-160℃ and heat under reflux for 14-16 hours to complete the imidization reaction and obtain imidized polyimide resin. Step 6: After cooling the polyimide resin solution obtained in Step 5, pour it into a precipitant to precipitate. After washing, filtration and drying, solid thermosetting polyimide resin powder is obtained.

2. The method for preparing low-gas-production, easily moldable thermosetting polyimide resin according to claim 1, characterized in that, The dianhydride includes aromatic dianhydrides, which are selected from at least one of bisphenol A type diether dianhydride, pyromellitic anhydride, biphenyl anhydride, ketone anhydride, or ether anhydride. The diamine includes an aromatic diamine selected from at least one of 4,4'-diaminodiphenyl ether, p-phenylenediamine, 9,9-bis(4-aminophenyl)fluorene, or biphenyl diamine.

3. The method for preparing low-gas-production, easily moldable thermosetting polyimide resin according to claim 2, characterized in that, The dianhydride also includes dianhydrides containing special groups, wherein the dianhydride containing special groups is hexafluorodianhydride; The diamine also includes diamines containing special groups, wherein the diamine containing special groups is a naphthalene-containing diamine.

4. The method for preparing low-gas-production, easily moldable thermosetting polyimide resin according to claim 3, characterized in that, The molar ratio of each component of the dianhydride, diamine and end-capping agent is: 5-7 mol of dianhydride, 5-7 mol of diamine and 1-2 mol of end-capping agent; The weight ratio of the organic solvent, dehydrating agent, and precipitant is as follows: 5-10 kg of organic solvent, 1.5-3 kg of dehydrating agent, and 5-8 times the weight of the polyimide resin solution obtained in step 5. The capping agent is a monofunctional acid anhydride containing unsaturated double bonds.

5. The method for preparing low-gas-production, easily moldable thermosetting polyimide resin according to claim 4, characterized in that, The molar ratio of aromatic dianhydride to dianhydride containing special groups in the dianhydride is (3-5):1, and the molar ratio of aromatic diamine to diamine containing special groups in the diamine is (2-4):

1.

6. The method for preparing low-gas-production, easily moldable thermosetting polyimide resin according to claim 3, characterized in that, The naphthalene-containing diamine is selected from at least one of 1,5-naphthyldiamine or 2,2'-binaphth-4,4'-diamine; The biphenyl anhydride is selected from at least one of 2,3',3,4'-biphenyltetracarboxylic acid dianhydride or 3,3',4,4'-biphenyltetracarboxylic acid dianhydride; The ketone anhydrides include 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride; The ether anhydride is selected from at least one of 4,4'-biphenyl ether dianhydride, 4,4'-terephthalodioxydiphthalic anhydride, or 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride.

7. The method for preparing low-gas-production, easily moldable thermosetting polyimide resin according to claim 1, characterized in that, The capping agent is phenylacetyl phthalic anhydride; The organic solvent is selected from at least one of dimethylformamide, dimethylacetamide, or N-methylpyrrolidone; The dehydrating agent is toluene; The precipitant is deionized water.

8. The method for preparing low-gas-production, easily moldable thermosetting polyimide resin according to claim 1, characterized in that, The imidization reaction is carried out at 150-160°C, with an imidization degree of 95%-99%, in order to reduce the amount of gas generated during the curing process.

9. The method for preparing low-gas-production, easily moldable thermosetting polyimide resin according to claim 1, characterized in that, The solid thermosetting polyimide resin has a minimum melt viscosity of less than 800 cp.s and a glass transition temperature of greater than 400℃.

10. The method for preparing low-gas-production, easily moldable thermosetting polyimide resin according to claim 1, characterized in that, The polyimide resin prepared by the method, after being made into a composite material, has a room temperature flexural strength greater than 700 MPa and a tensile strength greater than 450 MPa. The bending strength is greater than 300 MPa and the tensile strength is greater than 280 MPa at 400℃.

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