Polyimide aerogel coating material as well as preparation method and application thereof

Abstract

The invention belongs to the field of polymer composite materials, and relates to a polyimide aerogel coating material as well as a preparation method and application thereof. The invention provides a preparation method of a polyimide solution, which comprises the following steps: efficiently and quickly carrying out a catalyst-free thiol-alkynyl click polymerization reaction on a dithiol monomer and a diyne monomer under mild conditions to construct a uniform polymer network and obtain a high-uniformity polyimide dilute solution; and then forming a three-dimensional porous aerogel structure through coating, solvent exchange and normal-pressure drying. The prepared aerogel coating material can be used as an aerogel composite coating, a fireproof heat insulation fabric, a heat preservation fireproof coating, a heat management interface material and the like to be applied to the fields of new energy, special protective clothing, building heat insulation and fire prevention, electromagnetic shielding and the like. According to the method, the production process is simplified, the application range of the polyimide aerogel coating in a multifunctional composite material is widened, and the continuous production process of the polyimide aerogel coating is promoted.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of high polymer composite materials, and relates to a polyimide aerogel coating material as well as a preparation method and application thereof. BACKGROUND

[0002] Polyimide is a high-performance polymer material, which has excellent thermal stability, excellent mechanical properties, good chemical resistance and low dielectric constant, and is widely used in aerospace, insulation and advanced composite materials and other fields. Aerogel is a material with a nano-porous network structure, and its characteristics include low density, low thermal conductivity, high specific surface area and high porosity, but its large brittleness and low strength limit its application. Polyimide aerogel combines the excellent performance of polyimide and the nano-porous structure of aerogel, which overcomes the brittleness problem of traditional inorganic aerogel while retaining the light weight and thermal insulation properties. When coated on the surface of a substrate in the form of a coating, the substrate can be endowed with special properties such as super-insulation, high-temperature resistance and lightweight.

[0003] Polyimide has poor solubility due to its strong molecular chain rigidity and large force, which makes it difficult to form a stable solution and limits its application in some fields such as solution spinning and coating preparation. The existing technology usually first prepares a polyamide acid solution, and then obtains polyimide through imidization reaction, but the polyamide acid solution is prone to deterioration. CN120665288A discloses a colorless transparent high-temperature-resistant polyimide material and a preparation method thereof, which needs to first prepare a polyimide powder, and then dissolve it in a solvent to obtain a polyimide solution, which has a complex process. CN120518863A has a complex preparation process, which needs to first prepare a polyamide acid solution, then imidize, obtain a powder and then dissolve it. However, the above methods not only have a long process flow and high energy consumption, but also the final solution often has a very high viscosity due to the tight entanglement of polymer molecular chains. Whether it is the instability of the polyamide acid route or the high viscosity problem in the route of first preparing a powder and then dissolving, the polyimide solution prepared therefrom faces challenges such as uneven coating and low production efficiency when performing industrial coating process. On the other hand, the preparation of polyimide aerogel material usually relies on supercritical drying method and freeze-drying method, which have complex process and high cost, and are difficult to realize large-scale production, limiting the actual application.

[0004] Therefore, it is necessary to develop a synthesis method that can directly and efficiently prepare a polyimide solution with excellent solubility, low viscosity and high stability, to solve the problems existing in the prior art SUMMARY

[0005] In view of the problems and deficiencies of the prior art, the present application provides a preparation method of a polyimide aerogel coating material. The present application shortens the reaction time through click chemistry, and the polyimide aerogel composite material is prepared through normal pressure drying, which is simple in process and quickly constructs a three-dimensional network structure.

[0006] The first aspect of the present application provides a preparation method of a polyimide solution, comprising the following steps: S1. Preparation of a dithiol monomer and a diacetylene monomer, step S1 comprising step S11 and step S12; S11. Preparation of a dithiol monomer: imidization reaction of a dianhydride monomer and a thiol-containing monomer in an organic solvent, cooling, precipitation, filtration, washing and vacuum drying after reaction to obtain a dithiol monomer; S12. Preparation of a diacetylene monomer: imidization reaction of a dianhydride monomer and an acetylene-containing monomer in an organic solvent, cooling, precipitation, filtration, washing and vacuum drying after reaction to obtain a diacetylene monomer; S2. Preparation of a polyimide solution: under an inert atmosphere, the dithiol monomer and the diacetylene monomer prepared in step S1 are dissolved in a reaction solvent, mixed and stirred to perform a thiol-acetylene click polymerization reaction without a catalyst to obtain a polyimide solution; The order of step S11 and step S12 is not limited.

[0007] Further, in step S1, the dianhydride monomer is an aromatic dianhydride monomer, selected from at least one of a fluoranil type dianhydride, an ether anhydride type dianhydride, a ketone anhydride type dianhydride, a sulfone anhydride type dianhydride, and a biphenyl type dianhydride; In some embodiments, the fluoranil type dianhydride includes hexafluoro dianhydride and derivatives thereof; the ether anhydride type dianhydride includes but is not limited to 4,4'-oxybisphthalic anhydride, bisphenol A type diether dianhydride, 4,4'-p-phenylenediphthalic anhydride and derivatives thereof; the ketone anhydride type dianhydride includes but is not limited to 3,3',4,4'-benzophenone tetracarboxylic dianhydride and derivatives thereof; the sulfone anhydride type dianhydride includes but is not limited to 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride and derivatives thereof; the biphenyl type dianhydride includes but is not limited to pyromellitic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride and derivatives thereof; and preferably hexafluoro dianhydride.

[0008] In one embodiment, in step S1, the thiol-containing monomer is 4-aminothiophenol, and the acetylene-containing monomer is 3-aminophenylacetylene.

[0009] Further, in step S11, the molar ratio of the dianhydride monomer to the thiol-containing monomer is 1:1-1:2, preferably 1:2; Further, in step S12, the molar ratio of the dianhydride monomer to the acetylene-containing monomer is 1:1-1:2, preferably 1:2; In some embodiments, in step S1, the organic solvent is selected from acetic acid and cyclohexane. In some embodiments, in step S1, the reaction temperature is 120-150 °C. In some embodiments, in step S1, the reaction time is 5-10 h. In a preferred embodiment, in step S1, the reaction temperature is 130 °C, and the reaction time is 6 h.

[0010] In some embodiments, in step S1, the vacuum drying temperature is 60-100 °C, and the drying time is 12-20 h.

[0011] In a preferred embodiment, in step S1, the drying temperature is 80 °C, and the drying time is 12 h.

[0012] In some embodiments, in step S2, the molar ratio of the dithiol monomer and the diacetylene monomer is 1:1-1:1.5; preferably 1:1.

[0013] In step S2, the reaction solvent is selected from at least one of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran; preferably N,N-dimethylacetamide.

[0014] In step S2, the stirring speed is 200-400 r / min; the reaction temperature is 25-40 °C, and the reaction time is 5-30 min.

[0015] In an embodiment, in step S2, the stirring speed is 200-400 r / min, preferably 300 r / min.

[0016] In an embodiment, in step S2, the solid content of the polyimide solution is 3%-12 wt.%, preferably 9 wt.%.

[0017] In a preferred embodiment, in step S2, the reaction temperature is 30 °C, and the reaction time is 15 min.

[0018] A second aspect of the present application provides a polyimide solution prepared by the method, the polyimide having the following structural formula: In the formula, n is an integer of 20-1000; Ar in the formula represents a residue of an aromatic dianhydride monomer, which is an aromatic ring structure unit remaining after the monomer reaction; the dianhydride monomer is selected from fluorinated anhydride type dianhydride, ether anhydride type dianhydride, ketone anhydride type dianhydride, sulfone anhydride type dianhydride, and biphenyl type dianhydride.

[0019] The solution of the polyimide has a solid content of 3-12 wt.%.

[0020] The third aspect of the present application provides a polyimide coating material, comprising a polyimide solution and a binder solution; the volume ratio of the polyimide solution to the binder solution in the coating material is 10-15:1, preferably 13:1. Further, the mass ratio of the binder to the solvent in the binder solution is 1:9-15, preferably 1:10.

[0021] In some embodiments, the binder is selected from at least one of polyvinylidene fluoride, phenolic resin, hydroxymethyl cellulose, styrene-butadiene rubber, polyurethane, and acrylic resin; preferably polyvinylidene fluoride. In some embodiments, the solvent of the binder solution is selected from at least one of N,N-dimethylacetamide, N,N-dimethylformamide, tetrahydrofuran, and N-methylpyrrolidone; preferably N,N-dimethylacetamide.

[0022] The fourth aspect of the present application provides a polyimide aerogel coating material prepared from the polyimide coating material, comprising a base material and a polyimide aerogel layer, the polyimide aerogel layer being prepared from the polyimide coating material by aging, solvent exchange, and normal pressure drying treatment; In some embodiments, the base material is at least one of a polyolefin separator, a polyimide fiber membrane, a metal foil, a textile, a fiber cloth, a building wall, a building wood, etc.

[0023] Further, the thermal decomposition temperature of the polyimide aerogel layer is 475-480 ℃. Further, the polyimide aerogel layer is formed on one side or both sides of the base material; in the technical solution of the present application, the aerogel layer can be formed on only one side of the base material or aerogel coating layers can be formed on both sides of the base material.

[0024] The fifth aspect of the present application provides a preparation method of the polyimide aerogel coating material, comprising the steps of: forming a wet gel on a base material from the polyimide coating material, and then performing aging, solvent exchange, and drying treatment to prepare the polyimide aerogel coating composite material. Further, the coating methods include but are not limited to blade coating, spin coating, spraying, and dip-coating. Further, the drying methods include at least one of normal pressure drying method, freeze-drying method, and supercritical drying method; preferably normal pressure drying method. In some embodiments, the normal pressure drying temperature is 20-40 ℃, and the drying time is 4-12 h. The normal pressure drying method can be used for continuous production, is the most economical and the fastest.

[0025] In a preferred embodiment, the normal pressure drying temperature is 25 °C, and the time is 12 h.

[0026] Further, the solvent used in the solvent exchange is selected from at least one of methanol, ethanol, acetone, cyclohexane, n-hexane; preferably anhydrous ethanol.

[0027] In some embodiments, the solvent exchange time is 1-15 min, preferably 5 min.

[0028] In some embodiments, the aging time is 1-10 min; preferably 5-10 min, more preferably 10 min.

[0029] The sixth aspect of the present application provides the use of the polyimide solution, the use of the polyimide coating material, or the use of the polyimide aerogel coating material in the fields of new energy, special protective clothing, building thermal insulation and fireproofing, electromagnetic shielding, etc. Further, the prepared aerogel coating material can be used as an aerogel composite coating, a fireproofing and thermal insulation fabric, a thermal insulation and fireproofing coating, a thermal management interface material, etc. Further, it is used for preparing a battery separator, an electromagnetic shielding material, a building energy-saving material, a heat-resistant insulation material.

[0030] In some embodiments, the average pore size of the polyimide aerogel coating material is 75-150 nm.

[0031] In some embodiments, the thermal decomposition temperature of the polyimide aerogel coating material is 475-480 °C.

[0032] The thickness of the polyimide aerogel coating material is about 1-50 μm for a battery separator, about 25-1000 μm for a heat-resistant insulation material, about 0.1-5 mm for an electromagnetic shielding material, about 0.5-10 mm for a thermal insulation and protective material, and about 5-100 mm for a building energy-saving material.

[0033] Advantages Compared with the prior art, the present application has at least the following advantages: (1) The present application first prepares a polyimide dilute solution through thiol-alkyne click polymerization, rapidly constructs a polyimide network under mild reaction conditions, omits the traditional high-temperature imidization process, shortens the reaction time, and does not need a redissolution process, thereby reducing the production energy consumption and the preparation process complexity.

[0034] (2) The polyimide dilute solution developed in the application has excellent coatability, can be attached to the surface of various substrates, and the coating process is simple, and after forming a wet gel, the polyimide aerogel coating composite material can be prepared by aging, solvent exchange, and drying at normal temperature and pressure; compared with the solvent exchange process of dozens of hours required by the traditional process, the solvent exchange time is shortened to only about 5 minutes by virtue of the stable polymer structure, and the production efficiency is greatly improved; (3) The polyimide aerogel coating composite material prepared in the application does not have structural shrinkage or collapse, and the three-dimensional network structure is complete, not only retaining the inherent high-temperature resistance, electrical insulation and other advantages of polyimide, but also having the characteristics of super-low thermal conductivity, low dielectric constant and high porosity of aerogel materials. It has great application potential in the fields of battery separators, electromagnetic shielding, heat protection, building energy saving, heat-resistant insulation and the like; (4) The application realizes the preparation of polyimide aerogel coating material by normal pressure drying method, gets rid of the dependence on expensive and complex supercritical drying and freeze drying equipment, reduces the investment and production cost, and makes continuous industrial production possible. BRIEF DESCRIPTION OF DRAWINGS

[0035] The accompanying drawings are included to provide a further understanding of the application, and constitute a part of the specification, and are used to explain the application together with the embodiments of the application, and do not constitute a limitation on the application. In the drawings: Figure 1 It is the preparation flow chart of the polyimide aerogel coating material of example 1; Figure 2 It is the Tyndall effect diagram of the polyimide dilute solution prepared in example 1; Figure 3 It is the scanning electron microscope photo of the polyimide aerogel coating material of example 1; Figure 4 It is the pore size distribution diagram of the polyimide aerogel coating material of example 1; Figure 5 It is the Fourier infrared spectrum of the polyimide aerogel coating material of example 1; Figure 6 It is the thermogravimetric analysis curve of the polyimide aerogel coating material of example 1; Figure 7 It is the composite separator photo of the polyimide aerogel coating material coated on the polyolefin separator of example 1. DETAILED DESCRIPTION

[0036] In order to make the above objectives, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below. In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the concept of the present application, therefore the present application is not limited to the specific embodiments disclosed below. In the following examples, the experimental methods are described, and if not specifically stated, the conventional methods are used; the reagents and instruments, if not specifically stated, can be obtained from commercial channels.

[0037] The present application provides the characterization test results of Example 1, and the same characterization test methods are used in other examples. Those skilled in the art can directly and without doubt determine the content of the embodiments of the present application by the characterization test methods provided by the present application, which will not be described here.

[0038] Example 1: Polyimide aerogel coating material (1) Preparation of dithiol: 6FDA (4.4424 g, 10 mmol) and 4-aminothiophenol (2.5038 g, 20 mmol) were weighed into a round-bottom flask. Then 150 mL of acetic acid and 30 mL of cyclohexane were added to the flask, and a water separator was installed for continuous water removal. The reaction was stirred at 130 °C for 6 h at a speed of 300 r / min, and after cooling to room temperature, it was poured into 500 mL of ice water to precipitate a yellow precipitate. After washing, filtering, and finally drying under vacuum at 80 °C for 12 h, dithiol 6FSH was obtained.

[0039] (2) Preparation of diacetylene monomer: 6FDA (4.4424 g, 10 mmol) and 3-aminophenylacetylene (2.343 g, 20 mmol) were weighed into a round-bottom flask. Then 100 mL of acetic acid and 20 mL of cyclohexane were added to the flask, and a water separator was installed for continuous water removal. The reaction was stirred at 130 °C for 6 h at a speed of 300 r / min, and after cooling to room temperature, it was poured into 500 mL of ice water to precipitate a white precipitate. After washing, filtering, and finally drying under vacuum at 80 °C for 12 h, diacetylene monomer 6FDA-APA was obtained.

[0040] (3) Under nitrogen protection, the dithiol monomer 6FSH (0.8891 g, 1.35 mmol) and the diacetylene monomer 6FDA-APA (0.8674 g, 1.35 mmol) obtained above were added to a three-necked flask and dissolved in 18.9 mL of N,N-dimethylacetamide. The reaction was stirred at 30 °C for 15 min at a magnetic stirring speed of 300 r / min, and a yellow polyimide dilute solution with a solid content of 9 wt.% was obtained.

[0041] (4) The polyimide solution was mixed with a PVDF solution (1.8 g, PVDF:DMAC = 1:10, mass ratio) for 30 min, and then sprayed on both sides of a base material (for example, a polyolefin separator). After aging one side of the separator for 10 min to form a wet gel coating, the above step was repeated to spray the other side. The composite material was placed in an appropriate amount of anhydrous ethanol for solvent exchange for 5 min. Finally, it was taken out and dried at room temperature under normal pressure for 12 h to obtain a polyimide aerogel composite coating material.

[0042] The reaction steps of step (3) are shown in the following figure: the dithiol monomer prepared in step (1) and the diacetylene monomer prepared in step (2) were stirred under nitrogen protection under mild conditions to obtain a yellow polyimide dilute solution.

[0043] Example 2: Polyimide aerogel coating material The difference between this example and Example 1 is that in step (3), the dithiol monomer 6FSH (1.1855 g, 1.8 mmol) and the diacetylene monomer 6FDA-APA (1.1565 g, 1.8 mmol) are dissolved in 16.1 mL of N,N-dimethylacetamide to obtain a yellow polyimide dilute solution with a solid content of 12 wt.%. The remaining steps and conditions are exactly the same as in Example 1. Example 3: Polyimide aerogel coating material The difference between this example and Example 1 is that in step (3), the stirring reaction time is extended to 30 min to obtain a yellow polyimide dilute solution with a solid content of 9 wt.%. The remaining steps and conditions are exactly the same as in Example 1.

[0044] Example 4: Polyimide aerogel coating material The difference between this example and Example 1 is that the dianhydride monomer used in the preparation of the dithiol and diacetylene monomers is pyromellitic dianhydride (PMDA).

[0045] (1) Preparation of dithiol: PMDA (2.18 g, 10 mmol) and 4-aminothiophenol (2.5038 g, 20 mmol) were weighed into a round-bottom flask. Then 150 mL of acetic acid and 30 mL of cyclohexane were added to the flask, and a water separator was installed for continuous water removal. The reaction was stirred at 130 °C for 6 h at a speed of 300 r / min, and after cooling to room temperature, the yellow precipitate was poured into 500 mL of ice water. After washing and filtering, the final product, dithiol PMSH, was obtained by vacuum drying at 80 °C for 12 h.

[0046] (2) Preparation of diyne monomer: PMDA (2.18 g, 10 mmol) and 3-aminophenylacetylene (2.343 g, 20 mmol) were weighed and added to a round-bottom flask. Then, 100 mL of acetic acid and 20 mL of cyclohexane were added to the flask, and a water separator was installed to continuously remove water. The reaction was stirred at 130 °C for 6 h at a speed of 300 r / min. After cooling to room temperature, the mixture was poured into 500 mL of ice water, and a white precipitate was formed. After washing and filtration, the precipitate was dried under vacuum at 80 °C for 12 h to obtain the diyne monomer PMDA-APA.

[0047] (3) Under nitrogen protection, the dithiol monomer PMSH (0.5838 g, 1.35 mmol) and the diyne monomer PMDA-APA (0.5621 g, 1.35 mmol) obtained above were added to a three-necked flask and dissolved in 12.3 mL of N,N-dimethylacetamide. The mixture was stirred at 30°C for 15 min with a magnetic stirring speed of 300 r / min to obtain a dilute polyimide solution with a solid content of 9 wt.%.

[0048] (4) The polyimide solution and PVDF solution (1.2 g, PVDF:DMAC = 1:10, mass ratio) are thoroughly mixed for 30 min and sprayed onto both sides of the substrate material (taking a polyolefin membrane as an example). After one side of the membrane ages for 10 min to form a wet gel coating, the above steps are repeated to spray the other side. The composite material is placed in an appropriate amount of anhydrous ethanol for solvent exchange for 5 min. Finally, it is taken out and dried at room temperature and normal pressure for 12 h to obtain the polyimide aerogel composite coating material.

[0049] like Figure 1 The diagram shows the preparation flow of the polyimide aerogel coating material in Example 1. This invention first synthesizes alkynyl monomers and thiol monomers, then obtains a polyimide solution via a one-step click chemistry reaction, eliminating the need for a further dissolution step. The obtained polyimide solution is then mixed with a binder solution to prepare a polyimide coating. After the coating forms a wet gel on the substrate surface, the polyimide aerogel composite material is obtained through aging, solvent exchange, and drying. This invention employs a catalyst-free thiol-alkynyl click chemistry reaction, rapidly constructing a polyimide network in a single step under mild conditions, replacing the high-temperature imidization reaction. Simultaneously, the stable polymer network structure reduces the solvent exchange time to approximately 5 minutes, and atmospheric pressure drying replaces supercritical / freeze-drying, achieving efficient and low-cost preparation.

[0050] Structural characterization and performance testing of polyimide aerogel coating materials: like Figure 2The figure shows the Tyndall effect of the dilute solution of polyimide prepared in step (3) of Example 1. The polyimide solution obtained by the reaction shows obvious Tyndall effect under the irradiation of a laser pen, indicating that the polyimide molecules form nanoscale colloidal particles in the solution, and the whole is in a stable solution state. This proves that the click polymerization generates a polyimide solution that is conducive to the subsequent efficient formation of a uniform three-dimensional aerogel network. The dilute solutions of polyimides prepared in Examples 2-4 can also produce the same test effect, which is not shown here.

[0051] As shown in Figure 3 The figure shows the scanning electron micrograph of the polyimide aerogel coating material of Example 1. The polyimide solution is sprayed onto the substrate material to form a wet gel coating, and then aged, solvent exchanged and dried at normal pressure to obtain a polyimide aerogel coating. As can be seen from the figure, the obtained aerogel has a uniform nanometer porous structure.

[0052] As shown in Figure 4 The figure shows the pore size distribution of the polyimide aerogel coating material of Example 1. The average pore size of the separator is about 135 nm by pore size statistical software analysis.

[0053] As shown in Figure 5 The figure shows the Fourier infrared spectrum of the polyimide aerogel coating material of Example 1. As can be seen from the spectrum, the characteristic absorption peaks of the asymmetric and symmetric vibrations of the C=O of the polyimide are located at 1783 cm -1 and 1722 cm -1 , respectively, and the stretching vibration peak of C-N-C is about 1375 cm -1 , indicating that the five-membered imide ring is incorporated into the polymer backbone, confirming the successful synthesis of the polyimide material.

[0054] As shown in Figure 6 The figure shows the thermogravimetric analysis curve of the polyimide aerogel coating material of Example 1. The mass percentage remains basically 100% between 0-450 ℃, without obvious mass loss, indicating that the residual organic solvent or adsorbed water during the preparation of the material has been completely removed, and the polyimide aerogel coating itself does not decompose significantly before 450 ℃. The mass starts to decrease after 450 ℃, and accelerates to decrease at 475-480 ℃, corresponding to the imide ring rupture of the polyimide backbone. Thus, the thermal decomposition temperature of the material is 475-480 ℃, and the material has strong thermal stability and is suitable for high temperature environment.

[0055] As shown in Figure 7The shown is a large-area composite diaphragm coated with polyimide aerogel coating material based on a polyolefin diaphragm in Example 1. A large-area composite diaphragm with a polyolefin diaphragm as a base film and a polyimide aerogel as a coating, about 50 cm x 40 cm in size, is shown, and the coating surface is observed to be continuous, undamaged and uniformly covered on the base film; the polyimide solution / coating prepared by the application has the process feasibility of large-area coating, which shows that the technical scheme of the application has the potential for large-scale application.

[0056] It should be noted that Examples 2, 3 and 4 can also use the same method as Example 1 to test the performance of the product, and similar technical effects to Example 1 are obtained, which will not be described here.

[0057] In summary, in view of the problems and deficiencies of the prior art, the present application provides a preparation method of a polyimide solution, which is prepared by one-step reaction under mild conditions through click polymerization; and further a polyimide coating material is prepared, which has good coatability, and after forming a wet gel on the base material, a polyimide aerogel layer composite material with a three-dimensional network structure and high porosity can be quickly and conveniently prepared by drying at normal temperature and pressure. The inherent excellent performance of polyimide is retained, and the material has uniform pore structure and excellent thermal performance. The preparation method of the application has mild conditions, high production efficiency and simple process, and does not require complex equipment; it has great application potential in the fields of battery diaphragm, electromagnetic shielding, heat protection, building energy saving, heat-resistant insulation and the like.

[0058] It should be noted that the above examples are only used to illustrate the technical solutions of the application and are not limiting, and although the application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the application, and they should be included in the scope of the application.

Claims

1. A method for preparing a polyimide solution, characterized in that, Includes the following steps: S1. Preparation of dithiol monomer and diyne monomer, step S1 includes step S11 and step S12; S11. Preparation of dithiol monomer: The dianhydride monomer and the mercapto-containing monomer are subjected to an imidization reaction in an organic solvent. After the reaction, the mixture is cooled, precipitated, filtered, washed, and vacuum dried to obtain the dithiol monomer. S12. Preparation of diyne monomer: The dianhydride monomer and the alkynyl group-containing monomer are subjected to an imidization reaction in an organic solvent. After the reaction, the mixture is cooled, precipitated, filtered, washed, and vacuum dried to obtain the diyne monomer. S2. Preparation of polyimide solution: Under an inert atmosphere, the dithiol monomer and diyne monomer obtained in step S1 are dissolved in the reaction solvent, mixed and stirred to carry out a catalyst-free thiol-alkynyl click polymerization reaction to obtain a polyimide solution. The order of steps S11 and S12 is not limited.

2. The method for preparing the polyimide solution according to claim 1, characterized in that, In step S1, the dianhydride monomer is an aromatic dianhydride monomer, selected from at least one of fluoroanhydride dianhydrides, ether anhydrides, ketoanhydrides, sulfone anhydrides, and biphenyl dianhydrides; and / or, The mercapto-containing monomer is 4-aminothiophenol, and the alkynyl-containing monomer is 3-aminophenylacetylene.

3. The method for preparing the polyimide solution according to claim 1, characterized in that, In step S11, the molar ratio of the dianhydride monomer to the mercapto-containing monomer is 1:1 to 1:2; and / or, In step S12, the molar ratio of the dianhydride monomer to the alkynyl-containing monomer is 1:1-1:2 and / or... In step S1, the organic solvent includes acetic acid and cyclohexane; and / or In step S1, the reaction temperature is 120-150 °C; and / or In step S1, the reaction time is 5-10 h; and / or In step S1, the drying temperature is 60-100 ℃ and the drying time is 12-20 h.

4. The method for preparing the polyimide solution according to claim 1, characterized in that, In step S2, the molar ratio of the dithiol monomer to the diyne monomer is 1:1 to 1:1.5; and / or In step S2, the reaction solvent is selected from at least one of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran; and / or In step S2, the stirring speed is 200-400 r / min; the reaction temperature is 25-40 ℃; and the reaction time is 5-30 min.

5. The polyimide solution prepared by the method according to any one of claims 1-4, characterized in that, The polyimide has the following structural formula: The value of n is an integer between 20 and 1000; Ar in the formula represents the residue of the aromatic dianhydride monomer. The polyimide solution has a solid content of 3%-12 wt.%.

6. A polyimide coating material, characterized in that, Including polyimide solutions and adhesive solutions; The polyimide solution is the polyimide solution according to claim 5 or the polyimide solution prepared by the method according to any one of claims 1-4; The volume ratio of polyimide solution to binder solution in the coating is 10-15:1, preferably 13:1; The mass ratio of the binder to the solvent in the adhesive is 1:9-15, preferably 1:

10.

7. The polyimide coating material according to claim 6, characterized in that, The adhesive is selected from at least one of polyvinylidene fluoride, phenolic resin, hydroxymethyl cellulose, styrene-butadiene rubber, polyurethane, and acrylic resin; and / or, The solvent of the adhesive solution is selected from at least one of N,N-dimethylacetamide, N,N-dimethylformamide, tetrahydrofuran, and N-methylpyrrolidone; preferably N,N-dimethylacetamide.

8. A polyimide aerogel coating material prepared from the polyimide coating material according to any one of claims 6 or 7, characterized in that, It includes a base material and a polyimide aerogel layer, wherein the polyimide aerogel layer is prepared by aging, solvent exchange and atmospheric pressure drying of the polyimide coating material; The substrate material is at least one of the following: polyolefin membrane, polyimide fiber membrane, metal foil, textile, fiber cloth, building wall, building wood, etc. The thermal decomposition temperature of the polyimide aerogel layer is 475-480 ℃; The polyimide aerogel layer is formed on one or both sides of the substrate material.

9. The method for preparing the polyimide aerogel coating material according to claim 8, characterized in that, The process includes the following steps: coating the polyimide coating material onto a substrate material to form a wet gel, followed by aging, solvent exchange, and drying to obtain the polyimide aerogel coating composite material; Coating methods include, but are not limited to, scraping, spin coating, spraying, and dip-coating; The drying method includes at least one of atmospheric pressure drying, freeze drying, and supercritical drying; preferably, it is atmospheric pressure drying: the drying temperature is 20-40 ℃, and the drying time is 4-12 h.

10. The application of the polyimide solution of claim 5, or the application of the polyimide coating of claim 6 or 7, or the application of the polyimide aerogel coating material of claim 8, characterized in that, It is applied in the fields of new energy, special protective clothing, building insulation and fire protection, and electromagnetic shielding.

Images