Solvent-resistant polyimide film, method for preparing same, and use thereof

Abstract

The present application relates to a kind of solvent-resistant polyimide film and its preparation method and application, including the following steps: (1) diamine monomer and dianhydride monomer are reacted in the presence of catalyst and first solvent, obtain polyimide;The diamine monomer includes carboxyl-containing diamine monomer;(2) polyimide is dissolved in second solvent to form first polyimide solution, after film formation, phase inversion treatment is carried out, and intermediate film is obtained, and the intermediate film is treated in the organic solution containing metal ions, and support bottom film is obtained;(3) the polyimide is dissolved in third solvent to form second polyimide solution, and is coated on the support bottom film, after drying, it is treated by the organic solution containing metal ions, and the solvent-resistant microporous polyimide film is obtained.The polyimide film prepared by the above method has excellent solvent resistance, and has good hydrophobicity and good permeability to hydrocarbon solvents, and has good application prospect in the field of light crude oil separation.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, specifically to a solvent-resistant polyimide film, its preparation method, and its application. Background Technology

[0002] Separating liquid hydrocarbon mixtures is a challenging engineering task, requiring significant energy consumption in industrial applications to process and successfully separate complex mixtures. Crude oil separation and purification accounts for approximately 3% of global industrial energy consumption. While thermal distillation can fractionate light crude oil based on different boiling points, this energy-intensive process is inconsistent with sustainable development principles. Membrane separation technology offers advantages such as low energy consumption and high efficiency, promising to promote the sustainable development of crude oil fractionation. However, "compact" organic solvent nanofiltration membranes for light crude oil separation are relatively scarce, primarily because most polymer membranes are prone to swelling during separation, resulting in extremely low separation efficiency. Widely used polyimide materials, such as… It readily swells in hydrocarbon solvents, leading to low separation efficiency. Although commercially available polyamide-imide... Due to their high thermal, mechanical, and chemical stability, they are currently widely used in gas separation. However, their extremely high solvent stability results in very low swelling ratios, leading to poor permeability, which is not conducive to large-scale industrial development. Therefore, since commercial membranes cannot achieve good separation efficiency, many new membrane materials for the separation of light crude oil have been developed in recent years.

[0003] The structure of light crude oil separation membranes should possess the following characteristics: (1) the ultra-thin separation layer of the microporous polymer membrane ensures high solvent flux; (2) the hydrophobic polymer facilitates the wetting and permeation of light crude oil onto the membrane; and (3) the membrane's resistance to swelling maintains stable separation performance. Considering these design principles, the formidable challenge of separating light crude oil through membrane technology places higher demands on the design of new materials for this purpose.

[0004] To address the aforementioned issues, existing technologies employ various methods to prepare different membranes, aiming to improve their swelling resistance, physicochemical stability, and crude oil separation efficiency. For example, US20190276454A1 discloses a series of spirocyclic microporous polymers linked by N-aryl bonds. The flexible molecular chains, coupled with strong intermolecular hydrogen bonds, create unconnected microporous structures, resulting in excellent swelling resistance in organic solvents. The dependence of SBAD performance on pore structure and dynamic motion allows for the expansion of fractionation of complex mixtures and can be converted into real crude oil fractions. WO2022123497A1 discloses a PTA-OH asymmetric membrane with an ultrathin selective layer prepared by thermal crosslinking. The selective layer, controlled at a thickness of 10 nm, possesses sub-nanometer channels, suitable for separating hydrocarbons, and addresses solvent resistance and aging issues. US20230140883A1 discloses a novel membrane suitable for separation applications, a method for manufacturing the membrane, and its use in a range of separation applications. Hydrophobic polyamide nanomembranes were prepared by self-assembled vesicle interfacial polymerization. These polyamide nanomembranes provided hydrophobic liquid transport rates more than 100 times faster than traditional hydrophilic nanomembranes. In the fractionation of light crude oil, by controlling the film thickness to ~10 nm, the permeability was an order of magnitude higher than that of the most advanced hydrophobic membranes currently available, while maintaining similar size and type of separation. This high permeability expands the potential for using ultrathin nanomembranes in crude oil fractionation. However, the preparation methods for these ultrathin nanomembranes are complex, have poor reproducibility, and the excessively thin separation membrane layers exhibit poor long-term stability during use, making industrial production and practical applications difficult.

[0005] Currently, polyamide membranes prepared via interfacial polymerization exhibit ultrathin separation layers and highly cross-linked structures, demonstrating excellent separation performance in water treatment. However, the inherent hydrophilicity of polyamide membranes results in low permeability in the separation of oily solvents such as hydrocarbons. Fluorination and hydrophobic modification of monomers have become an important strategy to improve the permeability of OSN and OSRO membranes. However, traditional polyamide membranes still exhibit low solvent permeability due to their highly cross-linked structure. Therefore, there is an urgent need for a membrane material with good swelling resistance and excellent permeability and high selectivity for light crude oil. Summary of the Invention

[0006] To address the problems of existing membrane materials used for crude oil separation, such as difficulty in balancing separation efficiency and permeability, and poor long-term stability, this invention provides a solvent-resistant polyimide membrane, its preparation method, and its application in the separation of light crude oil. This solvent-resistant polyimide membrane has high throughput and can effectively separate organic molecules of different molecular weights. Furthermore, the membrane exhibits good physicochemical stability and has promising application prospects in the field of light crude oil separation.

[0007] Specifically, the present invention provides the following technical solutions:

[0008] The first aspect of this invention provides a method for preparing a solvent-resistant microporous polyimide film, comprising the following steps:

[0009] (1) A diamine monomer and a dianhydride monomer are reacted in the presence of a catalyst and a first solvent to obtain a polyimide; wherein the diamine monomer comprises a carboxyl-containing diamine monomer;

[0010] (2) The polyimide is dissolved in a second solvent to form a first polyimide solution with a concentration of 10wt%-50wt%. The first polyimide solution is formed into a film and then subjected to phase inversion treatment to obtain an intermediate film. The intermediate film is then treated with an organic solution containing divalent and / or polyvalent metal ions. After the first crosslinking reaction, a supporting substrate film is obtained.

[0011] (3) The polyimide is dissolved in a third solvent to form a second polyimide solution with a concentration of 0.01wt%-5wt%. The second polyimide solution is coated on at least one side of the supporting substrate. After drying, a polyimide modification layer is formed. Then, the polyimide modification layer is treated with an organic solution containing divalent and / or polyvalent metal ions. After a second crosslinking reaction, the solvent-resistant microporous polyimide film is obtained.

[0012] This invention introduces carboxyl-containing diamine monomers to include carboxyl groups in the prepared polyimide segments. An intermediate membrane is formed through a phase transition of the carboxyl-containing polyimide. The carboxyl groups in the different polyimide segments of this intermediate membrane can coordinate with divalent or polyvalent metal ions to achieve crosslinking, thereby effectively improving the solvent resistance of the formed polyimide membrane. The prepared solvent-resistant polyimide membrane is used as a supporting substrate. By controlling the concentration of a carboxyl-containing polyimide organic solution, a suitable concentration of carboxyl-containing polyimide organic solution is coated onto the supporting substrate and crosslinked with metal ions to form a modification layer of suitable thickness and density. The microporous polyimide film prepared by the above method not only has excellent solvent resistance and physicochemical stability but also exhibits good separation ability for low molecular weight hydrocarbon solvents, making it suitable for the separation of light crude oil.

[0013] Further, in step (1), the carboxyl diamine monomer is selected from at least one monomer with the structural formula NH2-R”-NH2, wherein R” is selected from one of the following structural formulas:

[0014]

[0015] In the above structural formula, the "—" connected to the benzene ring represents a covalent bond connecting the benzene ring and the amine group.

[0016] Further, in step (1), the diamine monomer further comprises at least one carboxyl-free diamine monomer, wherein the carboxyl-free diamine monomer is selected from at least one monomer with the structural formula NH2-R'-NH2, wherein R' is selected from one of the following structural formulas:

[0017]

[0018] In the above structural formula, the "—" connected to the benzene ring represents a covalent bond connecting the benzene ring and the amine group.

[0019] Further, in step (1), the dianhydride monomer is selected from at least one structural formula. The monomer, wherein R is selected from one of the following structural formulas:

[0020]

[0021] In the above structural formula, the "—" connected to the benzene ring represents a covalent bond connecting the benzene ring and the carbonyl group.

[0022] In some preferred embodiments, R in the dianhydride monomer structure is selected from one of the following structural formulas:

[0023]

[0024] More preferably, the diamine monomer and / or the dianhydride monomer contain fluorine atoms to improve the oleophilicity of the prepared support substrate and modification layer, which is beneficial to improving the permeability of oily solvents.

[0025] Further, in step (1), the molar ratio of the diamine monomer to the dianhydride monomer is 1:1; preferably, the molar percentage of the carboxyl-containing diamine monomer in the diamine monomer is 1%-99%, for example, 5%, 10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, etc., including but not limited to the molar percentages listed above. This invention simultaneously introduces carboxyl-containing and carboxyl-free diamine monomers, and regulates the density of coordination crosslinking points between the intermediate membrane and metal ions by controlling the ratio of their addition, thereby enabling the polyimide membrane after coordination crosslinking to possess both excellent solvent resistance and high membrane flux.

[0026] Further, in step (1), the first solvent includes m-cresol and / or N-methylpyrrolidone, and preferably, the boiling point of the first solvent is greater than the reaction temperature.

[0027] Furthermore, the reaction temperature is preferably 160-230℃, and the reaction time is preferably 5-10h.

[0028] In some preferred embodiments, the diamine monomer is first dissolved in a first solvent, and then the dianhydride monomer is added in batches to form a reaction system with a total solid content of 100-500 g / L.

[0029] Furthermore, in step (1), during the reaction process, the water generated in the reaction is removed by toluene azeotropic dehydration, thereby promoting the reaction.

[0030] Further, in step (2), the second solvent includes one or more of m-cresol, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and tetrahydrofuran to dissolve the polyimide.

[0031] Further, in step (2), the first polyimide solution is formed into a film using a method for preparing a flat sheet film, specifically as follows: the polyimide is fully dissolved in a second solvent, stirred, and then allowed to stand or vacuum-removed to remove bubbles; the first polyimide solution after the above treatment is coated onto a nonwoven fabric on a fixed glass plate using a doctor blade to form a uniform and bubble-free film, with a film thickness of 100-300 μm on the substrate surface; then the glass plate with the film is transferred to a coagulation bath for phase inversion, and an intermediate film is obtained after the phase inversion is complete; preferably, the coating is carried out at a temperature of 20-30℃ and a humidity of 10%-80%, and the solvent for the phase inversion treatment includes water and / or ethanol.

[0032] Further, in step (2), the divalent metal ions include Cu. 2+ Zn 2+ Ni 2+ Co 2+ Mg 2+ Ca 2+ One or more of the following, wherein the multivalent metal ions include Fe 3+ Al 3+ La 3+ One or more of them.

[0033] Further, in step (2), the organic solution containing divalent and / or polyvalent metal ions is prepared by dissolving the corresponding metal salt in an organic solvent. Preferably, the organic solvent is selected from one or more of methanol, ethanol, isopropanol, and acetone.

[0034] In some preferred embodiments, the organic solution containing divalent and / or polyvalent metal ions is a methanol solution of copper nitrate.

[0035] Further, in step (2), the concentration of the organic solution containing divalent and / or polyvalent metal ions is preferably 0.1-1 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, etc., including but not limited to the concentration values ​​listed above.

[0036] Furthermore, in step (2), the temperature of the first crosslinking reaction is preferably 30-60°C, and the time is preferably 24-48h. The carboxyl groups in the different polyimide segments contained in the intermediate film can be coordinated with divalent or polyvalent metal ions to achieve crosslinking.

[0037] Further, in step (3), the concentration of the second polyimide solution is preferably 0.1wt%-1wt%, such as 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, etc., including but not limited to the concentration values ​​listed above. The concentration of the second polyimide solution will affect the pore size of the supporting substrate and the thickness of the prepared modification layer. If the concentration of the second polyimide solution is too low, when coated on the surface of the supporting substrate, the second polyimide solution will easily penetrate into the interior of the supporting substrate and block the permeation channels of the substrate, affecting the permeation flux of the solvent; however, at the same time, the concentration of the second polyimide solution should not be too high. In order to ensure the integrity of the modification layer, using a second polyimide solution with an excessively high concentration to prepare the modification layer will result in an excessively thick modification layer, thereby affecting the permeation flux of the solvent. Therefore, to improve separation efficiency while ensuring separation effect, a second polymer solution of appropriate concentration is needed to prepare the modification layer, preferably 0.1wt%-1wt%, more preferably 0.5wt%.

[0038] Further, in step (3), the coating method includes spin coating, specifically: dissolving the polyimide in a third solvent, removing insoluble impurities with a PTFE filter with a pore size of 0.45 μm to obtain a uniform second polyimide organic solution; flatly attaching the support substrate to the silicon wafer, air-drying it in the air, placing the silicon wafer on the vacuum chuck of the spin coater, rapidly dripping the second polymer organic solution onto the support substrate, and rotating it in a specific program under a N2 atmosphere; preferably, the spin coating speed is 2000-6000 rpm.

[0039] Further, in step (3), the divalent metal ions include Cu. 2+ Zn 2+ Ni 2+ Co 2+ Mg 2+ Ca2+ One or more of the following, wherein the multivalent metal ions include Fe 3+ Al 3+ La 3+ One or more of them.

[0040] Further, in step (3), the concentration of the organic solution containing divalent and / or polyvalent metal ions is preferably 0.1-1 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, etc., including but not limited to the concentration values ​​listed above.

[0041] Furthermore, in step (3), the temperature of the second crosslinking reaction is preferably 30-60°C, and the time is preferably 24-48h.

[0042] The second aspect of the present invention provides a solvent-resistant microporous polyimide film prepared by the preparation method described in the first aspect, the solvent-resistant microporous polyimide film comprising a supporting substrate and a metal ion crosslinked carboxylated polyimide modification layer modified on at least one side of the supporting substrate;

[0043] Both the supporting substrate and the metal ion-crosslinked carboxylated polyimide modified layer contain several polyimide polymer segments that are coordinated and crosslinked with metal ions.

[0044] Furthermore, the polyimide polymer chain segment includes a first repeating unit and a second repeating unit, and the ratio of the degree of polymerization of the first repeating unit to the second repeating unit is (1-99):(1-99); the first repeating unit includes a polycondensation unit formed by a carboxyl-containing diamine monomer and a dianhydride monomer, and the second repeating unit includes a polycondensation unit formed by a carboxyl-free diamine monomer and a dianhydride monomer.

[0045] Furthermore, the polyimide polymer segments include the following general structural formula:

[0046]

[0047] Where m is any integer from 10 to 1000, n is any integer from 10 to 1000, and m:n = (1-99):(1-99).

[0048] In some preferred embodiments, the intermediate film and / or the polyimide modified layer are treated with a copper-ion-containing organic solution, causing the polyimide polymer segments contained in the intermediate film and / or the polyimide modified layer to coordinate with copper ions, with R" as For example, a supporting substrate film or a polyimide modified layer with metal ion crosslinking and carboxylation is formed with the following crosslinking structure:

[0049]

[0050] Furthermore, the thickness of the supporting substrate is 200-300 μm, and the thickness of the metal ion crosslinked carboxylated polyimide modification layer is 100-120 nm. This ultra-thin coating thickness provides excellent permeability to organic solvents.

[0051] Furthermore, the water contact angle of the solvent-resistant microporous polyimide film is 80°-100°.

[0052] Furthermore, the solvent-resistant microporous polyimide film has a molecular weight cutoff of 170 Da with a retention rate of not less than 80%.

[0053] The third aspect of the present invention provides an application of the solvent-resistant microporous polyimide film described in the second aspect in the separation of toluene / triisopropylbenzene or light crude oil.

[0054] Furthermore, the solvent-resistant microporous polyimide film has a toluene flux of 0.05-1 Lm. -2 h -1 bar -1 The rejection rate for triisopropylbenzene is 80%-99%. By applying pressure or increasing temperature, the membrane flux of the solvent-resistant microporous polyimide film can be further increased, while the rejection rate will decrease slightly.

[0055] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0056] 1. This invention provides a solvent-resistant microporous polyimide film. It utilizes the coordination crosslinking between metal ions and carboxylated polyimide to form a support substrate film with both excellent solvent resistance and high throughput. By setting a metal ion crosslinked carboxylated polyimide modification layer with appropriate thickness and density on the support substrate film, a microporous polyimide film with a hierarchical pore structure is formed. This film not only has excellent solvent resistance but also maintains a high membrane flux for hydrocarbon solvents and exhibits good separation performance in toluene / triisopropylbenzene separation and light crude oil separation.

[0057] 2. The solvent-resistant microporous polyimide membrane provided by this invention has a simple and easy-to-operate preparation process, strong controllability and good repeatability, and is suitable for large-scale production. Moreover, the prepared solvent-resistant microporous polyimide membrane has both high membrane flux and good separation performance for hydrocarbon solvents. It maintains a stable membrane flux and rejection rate of target analytes throughout the continuous 144-hour test period, showing good long-term stability. It has good application prospects in the separation of toluene / triisopropylbenzene or light crude oil. Attached Figure Description

[0058] Figure 1 This is a schematic diagram of the synthetic route for preparing carboxyl-containing polyimide copolymers in Examples 1-6 of the present invention;

[0059] Figure 2 The NMR spectra of the carboxyl-containing polyimide copolymers prepared in Examples 1, 5, and 6 of this invention are shown.

[0060] Figure 3 The contact angle diagrams are shown for the solvent-resistant microporous polyimide films prepared in Examples 1, 5, and 6 of this invention with water, diiodomethane, and toluene.

[0061] Figure 4 The graphs show the p-toluene flux and triisopropylbenzene rejection properties of the solvent-resistant microporous polyimide films prepared in Examples 1, 5, and 6 of this invention before and after the second crosslinking.

[0062] Figure 5 The FT-ICR MS spectra of the solvent-resistant microporous polyimide film prepared in Example 5 of this invention are obtained from the raw material (undiluted crude oil) and permeate collected in the crude oil separation experiment. Detailed Implementation

[0063] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. "Comprising" or "containing" as used herein means that it may include or contain other components in addition to the stated components. "Comprising" or "containing" as used herein may also be replaced with the closed form "is" or "consisting of".

[0064] The present invention will be further described below with reference to specific embodiments and accompanying drawings, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0065] The English designations of the materials involved in this invention have the following meanings in Chinese: DABA is 3,5-diaminobenzoic acid; 6FDA is 4,4'-(hexafluoroisopropene)phthalic anhydride; tmPDA is 2,3,5,6-tetramethyl-1,4-phenylenediamine; pPDA is 1,4-phenylenediamine; TBDN is 3,9-dinitro-4,10-dimethyl-6H,12H-5,11-methylenedibenzo[b,f][1,5]diazopentane. TBDA is 3,9-diamino-4,10-dimethyl-6H,12H-5,11-methylenedibenzo[b,f][1,5]diaza-octanoic acid; NMP is ultra-dry N-methylpyrrolidone; THF is tetrahydrofuran; Toluene is toluene; DMF is N,N'-dimethylformamide; Acetone is acetone; Methanol is methanol; TIPB is triisopropylbenzene; Pristane is norpropane; nC 22 H 46 It is n-dodecane; p-xylene is p-xylene; o-xylene is o-xylene; isooctane is isooctane; mesitylene is mesitylene; 1-methylnaphthalene is methylnaphthalene.

[0066] Example 1

[0067] This embodiment relates to the preparation of a solvent-resistant microporous polyimide film Cu-c-tmPDA, as detailed below:

[0068] (1) Preparation of carboxyl-containing polyimide copolymer c-tmPDA:

[0069] DABA (0.02 mol) and diamine monomer tmPDA (0.03 mol) were dissolved in 120 mL of ultra-dry NMP under a nitrogen atmosphere, followed by the addition of dianhydride monomer 6FDA (0.05 mol) solid. The mixture was then stirred in a three-necked flask for 24 hours, at room temperature, where the amino and anhydride groups formed polyamic acid through nucleophilic substitution. Subsequently, a water separator and reflux condenser were attached to the three-necked flask, and 20 mL of anhydrous toluene was added to both the flask and the water separator. The reaction temperature was gradually increased to 200 °C, and the reaction was continued for 5-10 hours until the solution gradually became viscous. Simultaneously, water was continuously generated and collected in the water separator. The viscous reaction solution was then poured into 2000 mL of anhydrous methanol to precipitate the solution.

[0070] The collected solid polyimide was washed three times in anhydrous methanol, followed by methanol replacement with ethanol. Finally, the solid was placed in a 60°C forced-air oven to remove most of the ethanol, and then transferred to a 150°C vacuum oven for drying for 24 hours. The resulting carboxyl-containing polyimide copolymer was named c-tmPDA.

[0071] (2) Preparation of the supporting substrate:

[0072] c-tmPDA was dissolved in DMF at a mass percentage of 20 wt% to obtain a first polymer solution with a c-tmPDA mass fraction of 20 wt%. The first polymer solution was stirred uniformly until completely dissolved and then allowed to stand overnight to remove bubbles, thereby obtaining a uniform casting solution.

[0073] At room temperature with a humidity of 30-40%, the casting solution was cast onto a flat nonwoven fabric using a height-adjustable casting tool (250 μm in height). The membrane was immediately immersed in deionized water for phase inversion. After 3 hours, the membrane was transferred to another fresh water bath and soaked for 24 hours to complete phase separation, yielding an intermediate membrane.

[0074] The intermediate membrane was immersed in anhydrous methanol to replace the deionized water inside the membrane; a 0.1 mol / L copper nitrate methanol solution was prepared, and the intermediate membrane was immersed in a Cu(NO3)2 methanol solution in a 40°C water bath for 24 hours. The carboxyl-functionalized c-tmPDA polyimide membrane was crosslinked with metal ions to obtain a supporting substrate membrane (thickness of 200-300 μm); the supporting substrate membrane was washed with methanol to remove residual crosslinking agent, and finally stored in fresh methanol for later use.

[0075] (3) Preparation of solvent-resistant microporous polyimide films:

[0076] c-tmPDA was dissolved in THF solvent at a mass percentage of 0.5 wt%. Insoluble impurities were then removed using a PTFE filter with a pore size of 0.45 μm, resulting in a homogeneous second polymer solution. After air-drying the substrate in air for 2 hours, it was smoothly applied to a silicon wafer. The wafer was then placed on the vacuum chuck of a spin coater, and the 0.5 wt% second polymer solution was rapidly dropped onto the substrate. The wafer was then rotated at a programmed speed of 5000 rpm for 40 seconds in a nitrogen atmosphere.

[0077] After the polyimide film dries, it is immersed in a Cu(NO3)2 methanol solution at 40°C for 24 hours to allow the polymer on the coating to coordinate and crosslink with copper ions, forming a 100-120 nm thick metal ion crosslinked carboxylated polyimide modification layer. Then, the film is washed with methanol to remove residual crosslinking agent, yielding a solvent-resistant microporous polyimide film Cu-c-tmPDA.

[0078] Example 2

[0079] This embodiment relates to the preparation of a solvent-resistant microporous polyimide film Cu-c-tmPDA. The only difference from Example 1 is that the concentration of the second polymer solution is 0.05 wt%, and the rest of the operations are the same, thus obtaining the corresponding solvent-resistant microporous polyimide film Cu-c-tmPDA.

[0080] Example 3

[0081] This embodiment relates to the preparation of a solvent-resistant microporous polyimide film Cu-c-tmPDA. The only difference from Example 1 is that the concentration of the second polymer solution is 0.1 wt%, and the rest of the operations are the same, and the corresponding solvent-resistant microporous polyimide film Cu-c-tmPDA is prepared.

[0082] Example 4

[0083] This embodiment relates to the preparation of a solvent-resistant microporous polyimide film Cu-c-tmPDA. The only difference from Example 1 is that the concentration of the second polymer solution is 1 wt%, and the rest of the operations are the same, and the corresponding solvent-resistant microporous polyimide film Cu-c-tmPDA is prepared.

[0084] Example 5

[0085] This embodiment relates to the preparation of a solvent-resistant microporous polyimide film Cu-c-pPDA. The only difference from Example 1 is that an equimolar amount of diamine monomer pPDA is used to replace the diamine monomer tmPDA in Example 1. All other operations are the same, and the corresponding solvent-resistant microporous polyimide film Cu-c-pPDA is prepared. The film thickness is 100-120 nm.

[0086] Example 6

[0087] This embodiment relates to the preparation of a solvent-resistant microporous polyimide film Cu-c-TBDA. The only difference from Example 1 is that an equimolar amount of diamine monomer TBDA is used to replace the diamine monomer tmPDA in Example 1. All other operations are the same, and the corresponding solvent-resistant microporous polyimide film Cu-c-TBDA is prepared. The film thickness is 100-120 nm.

[0088] Comparative Example 1

[0089] This comparative example relates to the preparation of a polyimide film c-tmPDA. The only difference from Example 1 is that step (3) does not include the step of soaking in a methanol solution of Cu(NO3)2. All other operations are the same, and the corresponding polyimide film c-tmPDA is prepared.

[0090] Comparative Example 2

[0091] This comparative example relates to the preparation of a polyimide film c-pPDA. The only difference from Example 2 is that step (3) does not include the step of soaking in a methanol solution of Cu(NO3)2. All other operations are the same, and the corresponding polyimide film c-pPDA is prepared.

[0092] Comparative Example 3

[0093] This comparative example relates to the preparation of a polyimide film c-TBDA. The only difference from Example 2 is that step (3) does not include the step of soaking in a methanol solution of Cu(NO3)2. All other operations are the same, and the corresponding polyimide film c-TBDA is prepared.

[0094] Comparative Example 4

[0095] This comparative example relates to the preparation of a solvent-resistant polyimide film. The only difference from Example 1 is the supporting substrate. The supporting substrate used in this comparative example was prepared as follows: a substrate film was prepared using commercially available P84 polyimide and then immersed in a 0.2 g / mL hexamethylenediamine isopropanol solution for crosslinking at room temperature for 12 h to obtain the supporting substrate used in this comparative example. All other operations were the same, and the corresponding solvent-resistant polyimide film was prepared.

[0096] Performance testing

[0097] The solvent-resistant microporous polyimide films prepared in the above embodiments and the polyimide films prepared in the comparative examples were tested for one or more of the following: hydrophobicity, solvent resistance, stability, and separation performance of p-toluene / triisopropylbenzene and light crude oil.

[0098] (1) Effect of the concentration of the second polymer solution on the separation performance of the prepared solvent-resistant microporous polyimide film Cu-c-tmPDA

[0099] Using toluene as a solvent, a 1 mol% triisopropylbenzene (TIPB) toluene solution was prepared as the separation target. The permeation flux and separation performance of the solvent-resistant polyimide membranes prepared in Examples 1-4 were tested using a dead-end filter under a high pressure of 30 bar. The results are shown in Table 1.

[0100] Table 1

[0101]

[0102] Table 1 shows that the solvent-resistant microporous polyimide films (Cu-c-tmPDA) prepared from different concentrations of the second polymer solution all exhibited good TIPB retention effects, but there were significant differences in toluene flux. Specifically, as the concentration of the second polymer solution increased, the toluene flux first increased and then decreased, reaching its highest value at 0.5 wt%, while the toluene flux at a concentration of 0.05 wt% was only 0.05 L / m³. -2 h -1 bar -1 It is speculated that the low concentration of the second polymer solution, when coated on the surface of the supporting substrate, easily seeps into the substrate and blocks its permeation channels, thus significantly reducing the toluene flux. Furthermore, as the concentration increases, the film thickness increases, leading to a further decrease in permeation flux. Therefore, to effectively separate toluene / TIPB while improving separation efficiency, a suitable concentration of the second polymer solution is needed to prepare the modification layer, preferably 0.1 wt%-1 wt%, more preferably 0.5 wt%.

[0103] (2) The effect of the type of support substrate on the separation performance of solvent-resistant polyimide membranes

[0104] Using toluene as a solvent, a 1 mol% triisopropylbenzene (TIPB) toluene solution was prepared as the separation target. The permeation flux and separation performance of the solvent-resistant polyimide membranes prepared in Example 1 and Comparative Example 4 were tested using a dead-end filter under a high pressure of 30 bar. The results are shown in Table 2.

[0105] Table 2

[0106]

[0107] As shown in Table 2, the only difference between the solvent-resistant polyimide films prepared in Example 1 and Comparative Example 4 is the type of supporting substrate. Comparative Example 4 obtained a solvent-resistant polyimide film by preparing a metal ion crosslinked carboxylated polyimide modification layer on the surface of a P84 polyimide film crosslinked with ethylenediamine. The permeation flux of the polyimide film was tested with toluene as a solvent, and the permeation flux was 0, so it could not be used to separate toluene / TIPB.

[0108] (3) Effect of diamine monomer type on hydrophobic properties of polyimide film

[0109] The water contact angles of different polyimide films prepared with different diamine monomers in Examples 1, 5, and 6 were measured using a hydrophobicity angle meter. The test results are shown in Table 3 below.

[0110] Table 3

[0111] Test Case polyimide film Water contact angle (°) Example 1 Cu-c-tmPDA 89.0 Example 5 Cu-c-pPDA 82.5 Example 6 Cu-c-TBDA 81.9

[0112] As shown in Table 3, the solvent-resistant microporous polyimide films prepared by this invention all exhibit good hydrophobicity, and... Figure 3 It can be seen that the contact angle between solvent-resistant microporous polyimide films and organic solvents such as diiodomethane and toluene is much smaller than that with water.

[0113] (4) Tests on the absorption rate and absorption amount of toluene by different polyimide films

[0114] Toluene was dropped onto the surface of the polyimide film to be tested, and the time for complete absorption was recorded and measured. Additionally, the polyimide film to be tested was immersed in toluene for seven consecutive days, and the mass change of the film was calculated to represent the absorption amount. The test results are shown in Table 4 below.

[0115] Table 4

[0116] Test Case polyimide film Complete absorption time (s) Absorption Example 1 Cu-c-tmPDA 18 9.5％ Example 5 Cu-c-pPDA 63 15.4％ Example 6 Cu-c-TBDA 30 9.3％ Comparative Example 1 c-tmPDA Continuous absorption for 7 days 43.6％ Comparative Example 2 c-pPDA Continuous absorption for 7 days 31.2％ Comparative Example 3 c-TBDA Continuous absorption for 7 days 39.7％

[0117] As shown in Table 4, the solvent-resistant microporous polyimide film prepared in this invention absorbs little toluene and can quickly reach saturation, exhibiting good solvent resistance and structural stability. In contrast, the polyimide films with uncrosslinked metal ion coordination layers on the surface of the supporting substrate prepared in Comparative Examples 1-3 continuously absorb toluene for up to seven days, and the absorption amount is much higher than that of the solvent-resistant microporous polyimide films prepared in Examples 1, 5, and 6.

[0118] (5) Testing of the separation performance of different separation membranes for toluene / triisopropylbenzene

[0119] A 1 mol% triisopropylbenzene (TIPB) toluene solution was prepared as the separation target. The permeation flux and separation performance of the polyimide membrane were tested using a dead-end filter under a high pressure of 30 bar, and compared with existing technologies. The results are shown in Table 5.

[0120] Table 5

[0121]

[0122]

[0123] Literature 1: KAThompson, R.Mathias, D.Kim, J.Kim, N.Rangnekar, JRJohnson, SJHoy, I.Bechis, A.Tarzia, KEJelfs, BAMcCool, AGLivingston, RPLively, MMGFinn, N-Aryl-linked spirocyclic polymers for membrane separations of complex hydrocarbon mixtures.Science 369,310-315(2020);

[0124] Document 2: HYJang, JRJohnson, Y.Ma, R.Mathias, DABhandari, RPLively, Torlon(R)hollow fiber membranes for organic solvent reverse osmosisseparation of complex aromatic hydrocarbonmixtures.AIChE J.65,e16757(2019).

[0125] Table 5 shows that among the series of separation membranes disclosed in the literature for separating toluene / TIPB, the membranes with high toluene flux have low TIPB rejection rates, all less than 60%; while the membranes with TIPB rejection rates reaching 91% are... Its flux for p-toluene is only 0.01 L / m³. -2 h -1 bar -1 The separation efficiency is extremely low. However, the solvent-resistant microporous polyimide films prepared in Examples 1, 5, and 6 of this invention can combine high toluene throughput with high TIPB rejection rate. Moreover, after 144 hours of continuous testing, the TIPB rejection rate of the solvent-resistant microporous polyimide films did not decrease significantly, demonstrating good and stable separation performance.

[0126] (6) Testing of the separation performance of different polyimide films for toluene / triisopropylbenzene at different temperatures

[0127] The separation performance of the toluene / TIPB mixed solvent was tested at 25℃ and 75℃, respectively. The test results are shown in Table 6 below:

[0128] Table 6

[0129]

[0130]

[0131] As shown in Table 6, the toluene permeation flux of the solvent-resistant microporous polyimide film prepared in this invention increases significantly with increasing temperature, while the TIPB rejection rate decreases slightly. This improvement in solvent permeability at high temperatures is beneficial to the separation efficiency in actual industrial processes.

[0132] (7) Testing of the separation performance of different polyimide films for multi-component mixed solvents

[0133] Solvent-resistant microporous polyimide films prepared in Examples 1, 5, and 6 respectively resisted solvents such as xylene, trimethylbenzene, isooctane, methylnaphthalene, TIPB, Pristane, and nC. 22 H 46 Separation was performed by mixing the solvent with toluene at a ratio of 1 mol% to prepare mixed solvents. The retention rates for different solvents are shown in Table 7 below:

[0134] Table 7

[0135]

[0136] As shown in Table 7, the solvent-resistant microporous polyimide film prepared in this invention has a good screening effect on hydrocarbon solvents with relatively high molecular weight.

[0137] (8) Testing of crude oil separation performance

[0138] Using light crude oil provided by China Petroleum & Chemical Corporation as raw material, the solvent-resistant microporous polyimide membrane prepared in Example 5 was used to separate the raw material under an applied pressure of 4.0 MPa. The raw material and permeate components were analyzed using FT-ICR MS, and the results are as follows: Figure 5 As shown in the figure, FT-ICR mass spectrometry analysis revealed a significantly lower average mass / charge (m / z) ratio in the molecular weight distribution of the permeate compared to the feedstock. These results confirm the potential of copper-crosslinked membranes for the fractionation of light crude oil.

[0139] The embodiments described above are merely preferred examples to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A process for producing a solvent resistant microporous polyimide film, characterized by, The method comprises the following steps: (1) reacting diamine monomers with dianhydride monomers in the presence of a catalyst and a first solvent to obtain a polyimide; the diamine monomers comprise a carboxyl-containing diamine monomer; The carboxyl-containing diamine monomer is selected from at least one monomer with a structural formula of NH2-R''-NH2, wherein R'' is selected from one of the following structural formulas: ； The diamine monomers further comprise at least one carboxyl-free diamine monomer selected from at least one monomer with a structural formula of NH2-R'-NH2, wherein R' is selected from one of the following structural formulas: ； The dianhydride monomers are selected from at least one monomer of the structure wherein R is selected from one of the following structures: ； (2) dissolving the polyimide in a second solvent to form a first polyimide solution with a concentration of 10 wt%-50 wt%, performing phase inversion treatment on the first polyimide solution after film formation to obtain an intermediate film, and then treating the intermediate film with an organic solution containing divalent and / or multivalent metal ions to obtain a support base film after a first cross-linking reaction; (3) dissolving the polyimide in a third solvent to form a second polyimide solution with a concentration of 0.01 wt%-5 wt%, coating the second polyimide solution on at least one side of the support base film, and then drying to form a polyimide modification layer, and then treating the polyimide modification layer with an organic solution containing divalent and / or multivalent metal ions to obtain the solvent-resistant microporous polyimide film after a second cross-linking reaction.

2. The production method according to claim 1, characterized by, In step (1), the molar proportion of the carboxyl-containing diamine monomer in the diamine monomers is 1%-99%. The reaction temperature is 160-230 ℃.

3. The preparation method according to claim 1, characterized in that, In step (2), at least one of the following features is included: (1) the first polyimide solution is formed into a film by a method for preparing a flat sheet membrane; (2) the solvent for the phase inversion treatment comprises water and / or ethanol; (3) the divalent metal ion comprises one or more of Cu 2+ , Zn 2+ , Ni 2+ , Co 2+ , Mg 2+ , Ca 2+ , and the polyvalent metal ion comprises one or more of Fe 3+ , Al 3+ , La 3+ ; (4) the concentration of the organic solution containing divalent and / or multivalent metal ions is 0.1-1 mol / L; (5) the temperature of the first cross-linking reaction is 30-60 ℃, and the time is 24-48 h.

4. The method of claim 1, wherein, In step (3), the concentration of the second polyimide solution is 0.1 wt%-1 wt%.

5. The preparation method according to claim 1, characterized in that, In step (3), the coating method comprises spin coating, and the spin coating speed is 2000-6000 rpm.

6. The method of claim 1, wherein, In step (3), the divalent metal ions include one or more of Cu 2 + , Zn 2+ , Ni 2+ , Co 2+ , Mg 2+ , Ca 2+ ; and the polyvalent metal ions include one or more of Fe 3+ , Al 3+ , La 3+ . The concentration of the organic solution containing divalent and / or multivalent metal ions is 0.1-1 mol / L; The temperature of the second cross-linking reaction is 30-60 ℃, and the time is 24-48 h.

7. A solvent resistant microporous polyimide film characterized in that, Prepared by the preparation method of any one of claims 1-6; the solvent-resistant microporous polyimide film comprises a support base film and a metal ion cross-linked carboxylated polyimide modification layer modified on at least one side of the support base film; Both the support base film and the metal ion cross-linked carboxylated polyimide modification layer comprise a plurality of polyimide polymer segments coordinated and cross-linked with metal ions.

8. The solvent resistant microporous polyimide film according to claim 7, wherein The thickness of the support base film is 200-300 µm, and the thickness of the metal ion cross-linked carboxylated polyimide modification layer is 100-120 nm.

9. Use of the solvent resistant microporous polyimide film according to claim 7 or 8 for toluene / cumene separation or light crude oil separation.

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