Polyamide composite membrane and method for producing the same

Abstract

The present application relates to a kind of polyamide composite film containing interlayer and its preparation method, comprising: polyborosiloxane-based porous polymer substrate, modified polyimide interlayer, polyamide separation layer;Porous polymer substrate surface is loaded with modified polyimide interlayer, and modified polyimide interlayer surface is loaded with polyamide separation layer.The polyborosiloxane-based porous polymer substrate of the present application has better compatibility between modified polyimide interlayer, which helps to reduce interface defects, improve the overall performance of film, not only this, polyborosiloxane-based porous polymer substrate also has self-healing characteristics, after being damaged, can repair the broken connection without external stimulus (such as light and heat), realize the substrate self-repairing.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, specifically to a polyamide composite membrane and its preparation method. Background Technology

[0002] Polyamide composite membranes are functional materials that play a crucial role in membrane separation technology, widely used in water treatment, food processing, and pharmaceutical manufacturing. Their preparation typically involves coating one or more polymer films onto a porous support material (substrate), with the polyamide skin acting as the separation layer and undertaking the primary separation task. The polyamide skin is highly favored due to its excellent chemical stability, mechanical strength, and separation performance. However, the preparation and performance optimization of polyamide composite membranes is a complex process involving the selection of various materials and the control of process parameters. Among these, the selection of the intermediate layer material plays a vital role in improving the adhesion between the polyamide skin and the substrate, enhancing the membrane's antifouling properties, and improving its mechanical strength.

[0003] Existing polyamide composite films have the following disadvantages during use:

[0004] (1) The chemical properties of the intermediate layer material differ greatly from those of the substrate material and the polyamide skin:

[0005] In the preparation of polyamide composite membranes, the selection of the intermediate layer material is often constrained by various factors, such as compatibility with the substrate material, adhesion to the polyamide skin, and its own chemical stability. However, due to the significant differences in chemical properties between the intermediate layer, the substrate, and the polyamide skin, the interfacial adhesion between the membrane layers is often weak, making delamination or peeling easy to occur, thus affecting the overall performance and stability of the membrane.

[0006] (2) Poor resistance to pollution:

[0007] Polyamide composite membranes are susceptible to fouling by various contaminants during use, such as organic matter, inorganic salts, and microorganisms. These contaminants can adhere to the membrane surface or clog the membrane pores, leading to decreased membrane permeability and reduced separation efficiency. Although some polyamide composite membranes with better antifouling properties have been developed, insufficient antifouling resistance still exists, especially when treating complex wastewater or high-concentration pollutants.

[0008] (3) The polymer substrate is easily damaged:

[0009] The substrate of polyamide composite membranes is typically made of polymer materials, such as polysulfone and polyethersulfone. While these polymer substrates possess a certain degree of mechanical strength and chemical stability, they are still susceptible to damage from various factors during long-term use, such as chemical corrosion and physical abrasion. Damage to the substrate can lead to a decline in the overall performance of the membrane, and may even cause the membrane to rupture or fail.

[0010] Therefore, we propose a polyamide composite film with an intermediate layer and its preparation method to solve the problems of large differences in chemical properties between the intermediate layer material and the substrate material and the polyamide skin, poor anti-fouling properties, and easy damage to the polymer substrate. Summary of the Invention

[0011] The purpose of this invention is to overcome the shortcomings of the prior art, adapt to practical needs, and provide a polyamide composite film with an intermediate layer and its preparation method, so as to solve the problems of large differences in chemical properties between the intermediate layer material and the substrate material and the polyamide skin layer, poor anti-fouling properties, and easy damage to the polymer substrate in the current polyamide composite film.

[0012] To achieve the objectives of this invention, the technical solution adopted is as follows:

[0013] A polyamide composite membrane with an intermediate layer includes: a polyborosiloxane-based porous polymer substrate, a modified polyimide intermediate layer, and a polyamide separation layer;

[0014] The porous polymer substrate has a modified polyimide interlayer loaded on its surface, and the modified polyimide interlayer has a polyamide separation layer loaded on its surface.

[0015] In this invention, the modified polyimide interlayer is prepared from a polyimide resin with added inorganic nanoparticles;

[0016] Preferably, the inorganic nanoparticles are selected from at least one of TiO2, ZrO2, Al2O3, SiO2, graphene, graphene oxide, and graphene quantum dots, and the size of the inorganic nanoparticles is preferably 1-100 nm, more preferably 10-60 nm.

[0017] Preferably, the modified polyimide interlayer is modified by doping with inorganic nanoparticles to improve its weather resistance, heat resistance, and chemical resistance, and to match the substrate material.

[0018] The present invention also provides a method for preparing the above-mentioned polyamide composite film containing an intermediate layer, comprising the following steps:

[0019] S1. Substrate preparation: Dissolve polyborosiloxane in a solvent to form a polyborosiloxane solution. Coat the polyborosiloxane solution evenly on the carrier, then dry it at 60-80℃ for 2-4 hours, and then cure it at 100-150℃ for 8-12 hours to form a polyborosiloxane porous polymer substrate.

[0020] S2. Inorganic nanoparticle dispersion: Inorganic nanoparticles are mixed with solvent and stirred for about 1-2 hours. The stirring speed is controlled at 500-1000 rpm to disperse them evenly and obtain a dispersion. The dispersion is added to the polyimide resin solution to form a polyimide resin solution containing inorganic nanoparticles.

[0021] S3. Preparation of modified polyimide interlayer: A polyimide resin solution containing inorganic nanoparticles is uniformly coated onto a polyborosiloxane alkyl porous polymer substrate by methods such as coating or scraping. A nanoparticle-modified polyimide interlayer is formed by appropriate drying and curing processes.

[0022] S4. Preparation of polyamide separation layer: The polyamide separation layer material is uniformly coated on the modified polyimide intermediate layer using a specific coating technique to obtain the coated composite film.

[0023] S5. Composite film curing: The coated composite film is cured at high temperature for about 0.5-12 hours, with the temperature controlled at 60-180℃.

[0024] S6. Post-processing: Perform necessary post-processing on the cured composite film, such as cutting, trimming, and cleaning. If necessary, the composite film can also be subjected to performance testing and quality inspection.

[0025] Preferably, the solvents in S1 and S2 independently include at least one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), tetrahydrofuran, dichloromethane, water, methanol, ethanol, and isopropanol.

[0026] Preferably, the carrier in S1 can be an inorganic carrier or an organic polymer carrier, such as a porous alumina membrane, a polysulfone ultrafiltration membrane, or a polyvinylidene fluoride microfiltration membrane.

[0027] Preferably, the molecular weight of the polyborosiloxane is 20,000-100,000 g / mol.

[0028] Preferably, the concentration range of the polyborosiloxane solution is 5-50 wt%, more preferably 10-30 wt%, and even more preferably 15-25 wt%.

[0029] Preferably, the coating thickness of the polyborosiloxane on the carrier is 5-100 μm.

[0030] Preferably, the concentration of the S2 dispersion is 0.5-10 wt%, more preferably 1-5 wt%.

[0031] Preferably, the mass ratio of the inorganic nanoparticles to the polyimide resin is 2:100 to 30:100, more preferably 10:100 to 20:100.

[0032] Preferably, the polyimide resin has a molecular weight of 50,000 to 200,000 g / mol.

[0033] Preferably, the concentration of the polyimide resin solution is 2-40 wt%, more preferably 10-30 wt%.

[0034] Preferably, in step S3, the modified polyimide intermediate layer is formed by drying at 50-75°C for 1-3 hours and then curing at 90-140°C for 5-9 hours, and the thickness of the modified polyimide intermediate layer is 20-180 μm, preferably 100-150 μm.

[0035] Preferably, the polyamide separation layer material in S4 is a polyamide solution;

[0036] Preferably, the polyamide molecular weight of the polyamide solution is 2000-500000 g / mol;

[0037] Preferably, the concentration of the polyamide solution is 2-75 wt%, more preferably 20-35 wt%.

[0038] Preferably, the solvent of the polyamide solution includes at least one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), tetrahydrofuran, dichloromethane, water, methanol, ethanol, and isopropanol.

[0039] Preferably, the specific coating technique in S4 is one of dip coating, spray coating or blade coating, and the coating thickness is 5-100μm, preferably 10-40μm, the drying temperature is 60-100℃, and the drying time is 10-60min.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1. The inorganic nanoparticles in this invention can act as bridges, enhancing the interfacial bonding between the intermediate layer and the substrate / polyamide skin through chemical bonding or physical adsorption. This helps reduce delamination or peeling between membrane layers, improving the overall stability and durability of the membrane. Furthermore, the inorganic nanoparticles possess excellent antifouling properties, such as hydrophilicity and antibacterial properties. Their addition endows the polyamide composite membrane with better antifouling capabilities, reducing the adhesion and accumulation of pollutants on the membrane surface, thus solving the problem of polyamide composite membranes being easily contaminated by various pollutants (such as organic matter, inorganic salts, and microorganisms) during use.

[0042] 2. The polyborosilicate porous polymer substrate of this invention has excellent chemical stability and can resist the erosion of various chemicals, thereby protecting the polyamide composite film from the effects of chemical corrosion. At the same time, the polyborosilicate porous polymer substrate and the modified polyimide interlayer have better compatibility, which helps to reduce interface defects and improve the overall performance of the film. Moreover, the polyborosilicate porous polymer substrate has self-healing properties. After being damaged, it can repair the broken connections without external stimulation (such as light and heat), realizing the self-repair of the substrate.

[0043] 3. In this invention, polyimide is modified with nanomaterials to improve its weather resistance, heat resistance, chemical resistance and other properties, so that it can be better matched with the substrate material. By matching with a chemical structure and properties that are more similar to the polyamide skin, better compatibility and bonding force are provided. Detailed Implementation

[0044] The present invention will be further described below with reference to embodiments.

[0045] Main raw material sources:

[0046] Polyborosiloxane: Jiangxi Nann New Materials Co., Ltd., molecular weight: 50000g / mol;

[0047] Polyimide resin: Qinyang Tianyi Chemical Co., Ltd., 705-292A;

[0048] Polyamide: Shanghai Huzheng Biotechnology Co., Ltd.

[0049] Example 1

[0050] A method for preparing a polyamide composite film containing an intermediate layer includes the following steps:

[0051] S1. Substrate preparation: Polyborosiloxane is dissolved in DMF to form a polymer solution with a solid content of 20wt%. The obtained polymer solution is then uniformly coated on a porous alumina film with an average pore size of 0.23μm and a thickness of 75μm. The film is then dried at 70℃ for 3h and cured at 130℃ for 10h to form a polyborosiloxane porous polymer substrate.

[0052] S2. Inorganic nanoparticle dispersion: SiO2 nanoparticles with an average particle size of 20 nm were uniformly dispersed in ethanol at a content of 0.5 wt% and stirred continuously at 750 rpm for 1.5 h. Then, they were slowly added to a DMF solution of polyimide resin with a solid content of 18%, wherein the mass ratio of SiO2 nanoparticles to polyimide resin was 10:100.

[0053] S3. Preparation of modified polyimide interlayer: A polyimide resin solution containing inorganic nanoparticles is uniformly coated onto a polyborosiloxane alkyl porous polymer substrate by spraying, then dried at 75°C for 2 hours, and then cured at 120°C for 8 hours to form a modified polyimide interlayer with a thickness of 120 μm.

[0054] S4. Preparation of polyamide separation layer: A 21 wt% NMP solution of polyamide is uniformly coated onto the modified polyimide intermediate layer by spraying. The coating thickness is 20 μm, the drying temperature is 75℃, and the drying time is 45 min to ensure the uniformity and integrity of the separation layer.

[0055] S5. Composite film curing: The coated composite film is cured at high temperature for 10 hours, and the temperature is controlled at 150℃.

[0056] S6. Post-processing: Use a laser cutter to cut the composite film into 75mm diameter circular pieces, and carefully measure and mark to ensure accuracy; then, remove burrs and trim the shape to make the edges smooth; finally, rinse the surface three times with anhydrous ethanol to ensure no residue, and let it air dry in a dry and ventilated environment for later use.

[0057] Example 2

[0058] A method for preparing a polyamide composite film containing an intermediate layer includes the following steps:

[0059] S1. Substrate preparation: Polyborosiloxane is dissolved in DMAc to form a polymer solution with a solid content of 25 wt%. The obtained polymer solution is then uniformly coated on a polysulfone ultrafiltration membrane with a thickness of 100 μm. After drying at 70 °C for 3 h, it is then cured at 130 °C for 10 h to form a polyborosiloxane porous polymer substrate.

[0060] S2. Inorganic nanoparticle dispersion: Graphene nanoparticles with an average particle size of 53 nm were uniformly dispersed in ethanol at a content of 1.0 wt%, and stirred continuously at 750 rpm for 1.5 h. Then, they were slowly added to a DMF solution of polyimide resin with a solid content of 20 wt%, wherein the mass ratio of graphene nanoparticles to polyimide resin was 18:100.

[0061] S3. Preparation of modified polyimide interlayer: A polyimide resin solution containing inorganic nanoparticles is uniformly coated onto a polyborosiloxane alkyl porous polymer substrate by spraying, then dried at 50°C for 1.5 h, and then cured at 120°C for 6 h to form a modified polyimide interlayer with a thickness of 140 μm.

[0062] S4. Preparation of polyamide separation layer: A DMSO solution of polyamide with a concentration of 26 wt% was uniformly coated onto the modified polyimide intermediate layer by spraying. The coating thickness was 20 μm, the drying temperature was 75℃, and the drying time was 45 min to ensure the uniformity and integrity of the separation layer.

[0063] S5. Composite film curing: The coated composite film is cured at high temperature for 10 hours, and the temperature is controlled at 150℃.

[0064] S6. Post-processing: Use a laser cutter to cut the composite film into 75mm diameter circular pieces, and carefully measure and mark to ensure accuracy; then, remove burrs and trim the shape to make the edges smooth; finally, rinse the surface three times with anhydrous ethanol to ensure no residue, and let it air dry in a dry and ventilated environment for later use.

[0065] Example 3

[0066] A method for preparing a polyamide composite film containing an intermediate layer includes the following steps:

[0067] S1. Substrate preparation: Polyborosiloxane is dissolved in DMSO to form a polymer solution with a solid content of 15wt%. The obtained polymer solution is then uniformly coated on a polyvinylidene fluoride microfiltration membrane with a thickness of 15μm. After drying at 70℃ for 3h, it is then cured at 120℃ for 10h to form a polyborosiloxane porous polymer substrate.

[0068] S2. Inorganic nanoparticle dispersion: TiO2 nanoparticles with an average particle size of 40 nm were uniformly dispersed in DMF at a content of 5 wt%, and stirred continuously at 750 rpm for 1.5 h. Then, they were slowly added to a DMF solution of polyimide resin with a solid content of 25%, wherein the mass ratio of TiO2 nanoparticles to polyimide resin was 25:100.

[0069] S3. Preparation of modified polyimide interlayer: A polyimide resin solution containing inorganic nanoparticles is uniformly coated onto a polyborosiloxane alkyl porous polymer substrate by spraying, then dried at 60°C for 2 hours, and then cured at 120°C for 7 hours to form a modified polyimide interlayer with a thickness of 160 μm.

[0070] S4. Preparation of polyamide separation layer: A 30 wt% polyamide DMF solution is uniformly coated onto the modified polyimide intermediate layer by spraying. The coating thickness is 30 μm, the drying temperature is 78℃, and the drying time is 55 min to ensure the uniformity and integrity of the separation layer.

[0071] S5. Composite film curing: The coated composite film is cured at high temperature for 10 hours, and the temperature is controlled at 150℃.

[0072] S6. Post-processing: Use a laser cutter to cut the composite film into 75mm diameter circular pieces, and carefully measure and mark to ensure accuracy; then, remove burrs and trim the shape to make the edges smooth; finally, rinse the surface three times with anhydrous ethanol to ensure no residue, and let it air dry in a dry and ventilated environment for later use.

[0073] Comparative Example 1

[0074] A simplified preparation method for a polyamide composite film containing an intermediate layer (without the addition of inorganic nanoparticles) is described below:

[0075] S1. Substrate preparation: Polyborosiloxane is dissolved in DMF to form a polymer solution with a solid content of 20%. The obtained polymer solution is then uniformly coated on a porous alumina film with an average pore size of 0.23 μm and a thickness of 75 μm. It is then dried at 70°C for 3 h and cured at 130°C for 10 h to form a polyborosiloxane porous polymer substrate.

[0076] S2, (Inorganic nanoparticle dispersion step omitted);

[0077] S3. Preparation of polyimide intermediate layer: A DMF solution of polyimide resin with a solid content of 18% is directly sprayed evenly onto a polyborosilicate porous polymer substrate, then dried at 75°C for 2 hours, and then cured at 120°C for 8 hours to form a polyimide intermediate layer with a thickness of 120 μm.

[0078] S4. Preparation of polyamide separation layer: Same as in Example 1;

[0079] S5. Composite film curing: Same as in Example 1;

[0080] S6. Post-processing: Same as in Example 1.

[0081] Performance testing:

[0082] 1. Physical performance testing

[0083] Tensile strength and elongation at break: Refer to the test method for tensile properties of films in GB / T 13022-1991. The test temperature is 25±2℃, the relative humidity is 40%-60%, the tensile speed is 5mm / min, the maximum tensile force at the breaking point is recorded as the tensile strength Rm, and the elongation at the breaking point of the sample is the elongation at break e, and the test results are obtained.

[0084] 2. Chemical stability and compatibility testing

[0085] Solvent resistance: The dried sample was immersed in DMF at 25°C for 24 hours, then removed and thoroughly rinsed with pure water to remove any residue. The sample was then dried at 100°C for 30 minutes. The dry weight before and after immersion in DMF was accurately measured, and the weight loss rate after immersion in DMF was calculated.

[0086] Acid and alkali resistance: The dried sample was soaked in hydrochloric acid solution with pH=2 at 25℃ for 24 hours, then the residue was thoroughly washed with pure water, and then dried at 100℃ for 30 minutes. The dry weight before and after soaking in acid was accurately weighed, and the weight loss after soaking was calculated to characterize the acid resistance of the sample.

[0087] The dried sample was soaked in a sodium hydroxide solution with pH=12 at 25°C for 24 hours, then thoroughly rinsed with pure water to remove any residue, and subsequently dried at 100°C for 30 minutes. The dry weight before and after soaking in alkali was accurately measured, and the weight loss after soaking was calculated to characterize the alkali resistance of the sample.

[0088] Chemical compatibility: The dried sample was immersed in NMP at 60°C for 24 hours, then removed and thoroughly rinsed with pure water to remove any residue. It was then dried at 100°C for 30 minutes. The chemical compatibility was determined by observing whether there was any peeling or detachment between the membrane layers.

[0089] 3. Separation performance test

[0090] Permeation flux and rejection rate: The permeation flux and rejection rate of the membrane were tested using a cross-flow membrane performance evaluation device. The effective area of ​​the membrane was 28.26 cm². 2 The feed temperature is 25℃ and the test pressure is 10 bar (gauge pressure).

[0091] Permeation flux refers to the volume of permeate passing through a unit membrane area per unit time at 10 bar, denoted by J, and is calculated using the following formula:

[0092] J = V / (T × S)

[0093] Where J is the membrane permeation flux, in L / m³.2 •h; V is the volume of exudate in L during the test time; T is the sampling time in h; S is the effective area of ​​the membrane in m². 2 ;

[0094] The conductivity of the exudate and the original solution was measured using a conductivity meter. The retention rate was calculated using the following formula:

[0095] R = (1 - Cp / Cf) × 100%

[0096] Where R refers to the retention rate (%); Cp refers to the eluent concentration (ppm); and Cf refers to the feed concentration (ppm).

[0097] The feed solution was prepared as a 2000ppm MgSO4 solution. Before the formal test, it was pre-pressurized for 0.5h to stabilize the membrane performance, and then the separation performance test was carried out.

[0098] 4. Anti-pollution performance test

[0099] Continuous filtration test: The membrane's antifouling ability is characterized by the flux change after 24 hours of continuous filtration using a 1 g / L bovine serum albumin solution as feed, a feed temperature of 25°C, and a test pressure of 10 bar (gauge pressure). Specifically, the water flux J after 24 hours of continuous filtration is calculated. w With initial water flux J w,0 The ratio, (1-J w / J w,0 The flux decay rate after fouling is used to determine the degree of water flux decay and evaluate the membrane's antifouling performance.

[0100] Cleaning and recovery: After the membrane's antifouling performance test, the membrane surface was cleaned using pure water as the feed solution. The feed temperature was 25℃, the operating pressure was 10 bar, and the cleaning was performed continuously for 30 minutes. The water flux J after cleaning was calculated. w,1 With initial water flux J w,0 The ratio J w,1 / J w,0 The flux recovery rate after cleaning is used to determine the cleaning recovery status after fouling and to evaluate the cleaning recovery capability of the membrane after fouling.

[0101] 5. Self-healing test

[0102] A 5-10 μm scratch was manually made on the surface of the film with a blade. The film was then placed in an 80°C atmosphere and left to stand for 30 minutes. The self-healing of the scratch was observed using an optical microscope. By observing the repair of the scratch width, the self-healing performance of the material can be clearly observed.

[0103] The results of the example and comparative tests are as follows:

[0104] Table 1. Diaphragm Performance Test Data

[0105]

[0106] The embodiments disclosed in this invention are preferred embodiments, but are not limited thereto. Those skilled in the art can easily understand the spirit of this invention based on the above embodiments and make different extensions and variations, but as long as they do not depart from the spirit of this invention, they are all within the protection scope of this invention.

Claims

1. A polyamide composite film, characterized in that, include: Polyborosiloxane alkyl porous polymer substrate, modified polyimide interlayer, and polyamide separation layer; The porous polymer substrate has a modified polyimide interlayer loaded on its surface, and the modified polyimide interlayer has a polyamide separation layer loaded on its surface. The modified polyimide interlayer is prepared from polyimide resin with added inorganic nanoparticles, wherein the inorganic nanoparticles are selected from at least one of TiO2, ZrO2, Al2O3, SiO2, graphene, graphene oxide, and graphene quantum dots.

2. The polyamide composite film as described in claim 1, characterized in that, The size of inorganic nanoparticles ranges from 1 to 100 nm.

3. A method for preparing a polyamide composite film as described in any one of claims 1-2, characterized in that, Includes the following steps: S1. Substrate preparation: The polyborosiloxane solution is uniformly coated on the carrier, dried, and cured to form a polyborosiloxane porous polymer substrate. S2. Inorganic nanoparticle dispersion: Inorganic nanoparticles are mixed with a solvent to obtain a dispersion, and the dispersion is mixed with a polyimide resin solution to form a polyimide resin solution containing inorganic nanoparticles. S3. Preparation of modified polyimide interlayer: A polyimide resin solution containing inorganic nanoparticles is uniformly coated on a polyborosiloxane alkyl porous polymer substrate, dried, and cured to form a modified polyimide interlayer. S4. Preparation of polyamide separation layer: The polyamide separation layer material is uniformly coated on the modified polyimide intermediate layer to obtain the coated composite film. S5. Composite film curing: Curing the coated composite film; S6. Post-treatment: Perform post-treatment on the cured composite film.

4. The preparation method according to claim 3, characterized in that, The solvents in S1 and S2 each independently include at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, dichloromethane, water, methanol, ethanol, and isopropanol.

5. The preparation method according to claim 3 or 4, characterized in that, The carrier described in S1 is selected from inorganic carriers or organic polymer carriers; The molecular weight of the polyborosiloxane is 20,000-100,000 g / mol; The concentration of the polyborosiloxane solution is 5-50 wt%. The coating thickness of the polyborosiloxane on the carrier is 5-100 μm.

6. The preparation method according to claim 5, characterized in that, The carrier mentioned in S1 is selected from porous alumina membrane, polysulfone ultrafiltration membrane, or polyvinylidene fluoride microfiltration membrane.

7. The preparation method according to claim 5, characterized in that, S1 is dried at 60-80℃ for 2-4 hours and cured at 100-150℃ for 8-12 hours.

8. The preparation method according to claim 3 or 4, characterized in that, The concentration of the S2 dispersion is 0.5-10 wt%.

9. The preparation method according to claim 3 or 4, characterized in that, In S2, the mass ratio of the inorganic nanoparticles to the polyimide resin is 2:100 to 30:100; The molecular weight of the polyimide resin is from 50,000 to 200,000 g / mol; The concentration of the polyimide resin solution is 2-40 wt%.

10. The preparation method according to claim 9, characterized in that, In S2, the mass ratio of the inorganic nanoparticles to the polyimide resin is 10:100 to 20:

100.

11. The preparation method according to claim 3, characterized in that, In S3, drying is carried out at 50-75℃ for 1-3 hours, followed by curing at 90-140℃ for 5-9 hours; the thickness of the modified polyimide interlayer is 20-180 μm.

12. The preparation method according to claim 11, characterized in that, In S3, the thickness of the modified polyimide interlayer is 100–150 μm.

13. The preparation method according to claim 3, characterized in that, The polyamide separation layer material in S4 is a polyamide solution; The concentration of the polyamide solution is 2-75 wt%. The solvent of the polyamide solution includes at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, dichloromethane water, methanol, ethanol, and isopropanol. The coating thickness is 5-100μm, the drying temperature is 60-100℃, and the drying time is 10-60min.

14. The preparation method according to claim 13, characterized in that, In S4, the coating thickness is 10-40 μm.

15. The preparation method according to claim 3, characterized in that, In S5, cure at 60-180℃ for 0.5-12 hours.

16. The preparation method according to claim 3, characterized in that, In S6, the post-processing is selected from cutting, trimming, and cleaning.

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