Solvent resistant filter membrane and its application in solution polymerization of butadiene rubber to reduce gel

Abstract

This invention discloses a solvent-resistant filter membrane and its application in the degelation process of cis-butadiene rubber solution polymerization, belonging to the fields of polymer materials technology and chemical separation. The filter membrane, from bottom to top, comprises a pretreated nonwoven fabric, a polyetherimide base layer, and a polyimide selective layer. The preparation method includes raw material pretreatment, polyetherimide base layer preparation, in-situ generation of the polyimide selective layer, and post-treatment. Performance optimization is achieved through amine ring-opening crosslinking, interfacial polymerization doping with perfluorodecyl mercaptan, cyclohexane pre-expansion, and trifluoroacetic anhydride post-treatment. It is applied to multiple nodes in the cis-butadiene rubber solution polymerization process. This invention constructs a stable filter membrane structure through multi-dimensional innovative methods, solving problems such as insufficient solvent resistance, easy interlayer peeling, and poor anti-fouling of traditional filter membranes. It achieves efficient retention of gel particles and catalyst residues, significantly reduces the rubber gel content, and maintains long-term stable operation, adapting to stringent process requirements.

Description

Technical Field

[0001] This invention relates to the fields of polymer materials technology and chemical separation, and particularly to solvent-resistant filter membranes and their application in the degelation process of cis-butadiene rubber solution polymerization. Background Technology

[0002] Butadiene rubber is an important synthetic rubber. Its solution polymerization process typically uses butadiene as the monomer and is carried out in organic solvents such as hexane and benzene under the action of catalysts such as alkyl aluminum-nickel systems. During the polymerization process, catalyst impurities and polymerization byproducts easily form gel particles, leading to a decline in the performance of rubber products, blockage of production equipment, and reduced production efficiency and product qualification rate. Therefore, there is an urgent need for specialized filter membranes resistant to polymerization solvents such as cyclohexane to remove gels.

[0003] Existing solutions mainly use traditional polymer filter membranes such as polyamide and polyvinylidene fluoride, or improve solvent resistance through simple cross-linking modification. Some solutions attempt to build a dense selective layer on the surface of the support layer to enhance the retention effect.

[0004] However, existing technologies have significant shortcomings: traditional filter membranes are prone to swelling and dissolving in highly polar organic solvents, resulting in poor long-term operational stability; single crosslinking modification is difficult to balance solvent resistance and permeation flux, easily leading to a "seesaw" effect; the filter membrane lacks compatibility with the polymerization system, and the surface is prone to adsorption of rubber segments, causing contamination and blockage; the support layer and the selective layer have weak bonding, making them prone to delamination and detachment; and the wide pore size distribution makes it impossible to accurately trap gel particles, making it difficult to meet the stringent requirements of the butadiene rubber polymerization process. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a solvent-resistant filter membrane and its application in the degelation process of cis-butadiene rubber solution polymerization.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a solvent-resistant filter membrane includes the following steps:

[0008] S1. Raw material pretreatment:

[0009] Immerse the nonwoven fabric in a 5-10 wt% polyvinyl alcohol solution for 5-15 minutes, control the liquid volume with a precision roller, dry in an oven at 80-100℃ for 5-10 minutes, crush and screen the polyetherimide resin, wash three times with anhydrous ethanol, and dry.

[0010] After immersing the nonwoven fabric in a polyvinyl alcohol solution, the polyvinyl alcohol molecular chains are firmly adsorbed onto the fiber surface through hydrogen bonds and van der Waals forces. Precision rollers control the liquid flow, ensuring a thin and uniform polyvinyl alcohol modified layer is formed, avoiding excessive clogging of the nonwoven fabric's macroporous structure. Subsequently, drying at 80-100℃ not only removes moisture but also induces crystallization and physical cross-linking of the polyvinyl alcohol molecular chains, thus forming a robust, hydrophilic transition layer on the nonwoven fabric fibers. This polyvinyl alcohol layer serves a dual purpose: First, it significantly improves the compatibility between the nonwoven fabric and the subsequent polyetherimide casting solution. The hydroxyl groups on the polyvinyl alcohol interact well with the solvent and polyetherimide, allowing the polyetherimide base layer to be tightly anchored to the nonwoven fabric, preventing interlayer delamination in organic solvent environments. Second, it effectively smooths the rough and uneven surface of the nonwoven fabric, providing an ideal substrate for scraping an ultra-thin, defect-free polyetherimide resin base layer.

[0011] The purpose of crushing and sieving the polyetherimide resin to a specific particle size is to obtain the maximum and uniform specific surface area during dissolution, ensuring that the polyetherimide particles can dissolve quickly and synchronously to form a uniform casting solution without undissolved particles. This is a prerequisite for obtaining a structurally uniform substrate. The purpose of washing with anhydrous ethanol is as a mild Soxhlet extraction to remove catalysts, low molecular weight oligomers and other small molecule additives remaining in the resin during synthesis and granulation. If these impurities are not removed, they will become uncontrollable pore-forming sites or defect origins during phase transformation, severely weakening the mechanical integrity of the substrate and causing the membrane structure to collapse due to impurity dissolution in long-term solvent resistance tests.

[0012] The aforementioned pretreatment, by enhancing interfacial adhesion, improving substrate flatness, and ensuring raw material purity and uniformity, collectively endows the filter membrane with excellent solvent resistance, constructing a firmly bonded, defect-free underlying structure capable of resisting long-term erosion and swelling stress from polymerization solvents such as alkanes and aromatics. This provides the most reliable skeletal support for the precise polyimide selective layer above. In the polybutadiene rubber solution polymerization degelatinization process, this stability directly translates into sustained separation accuracy and an ultra-long service life. The pretreatment prevents interlayer delamination and structural degradation, ensuring that the filter membrane's retention rate of catalyst fragments and gel particles remains consistently stable. Simultaneously, the pure raw materials prevent secondary contamination of the polymerization system by impurity leaching from the membrane itself.

[0013] S2, Preparation of polyetherimide base layer:

[0014] Pretreated polyetherimide resin, polyethylene glycol, nano-SiO2 and N,N-dimethylacetamide were mixed and stirred at 80℃ for 6 hours, vacuum degassing was performed for 12 hours, and the film was scraped onto a nonwoven fabric support using a film scraper. The film was then immersed in a pure water coagulation bath at 18℃ for 24 hours, and then immersed in a 5wt% ethanol solution of 1,6-hexanediamine at 70℃ for 4 hours. The film was washed three times with ethanol and water, and then vacuum dried at 130℃ for 12 hours.

[0015] The preparation and degassing of the casting solution are the stages that lay the foundation for the microstructure: pretreated polyetherimide resin, porogen polyethylene glycol, nano-SiO2 and solvent N,N-dimethylacetamide are mixed and stirred at 80°C to form a thermodynamically homogeneous solution. In this system, the solution is dissolved by the solvent, while polyethylene glycol, as a hydrophilic polymer, forms a homogeneous system with polyetherimide resin / solvent. However, its affinity for water is much stronger than that of polyetherimide resin. Nano-SiO2 is uniformly dispersed in the solution as an inorganic filler. Subsequent vacuum degassing is crucial, as it removes the gas entrained by stirring and prevents the formation of macroscopic defects such as pinholes in the subsequent film formation.

[0016] The casting process and phase transformation are dynamic processes that form porous structures: After the casting solution is coated onto a pretreated nonwoven fabric, it is immediately immersed in a pure water coagulation bath at 18°C. At this time, the solvent and water undergo rapid bidirectional diffusion. Water penetrates the casting solution, while the solvent seeps out. This exchange causes the originally homogeneous casting solution to undergo liquid-liquid phase separation, separating into a polyetherimide resin-rich phase and a polyetherimide resin-poor phase. The rich phase will form the membrane skeleton, while the poor phase will form pores. The presence of polyethylene glycol exacerbates this phase separation, and due to its hydrophilicity, it rapidly migrates to the aqueous phase under the influence of water, leaving additional pores. At the same time, nano-SiO2 is fixed by the solidified polyetherimide resin skeleton, playing a role in physical reinforcement and regulating the pore structure. Finally, the polyetherimide resin-rich phase solidifies, forming an initial base film with finger-like macropores at the bottom and micropores on the surface.

[0017] Then, chemical crosslinking is the decisive step in giving the base layer excellent solvent resistance: the base film after phase inversion is immersed in an ethanol solution of 1,6-hexanediamine and heated, and a key amine-opening ring-crosslinking reaction occurs. The nitrogen atom on a primary amino group acts as a nucleophile and attacks a carbonyl carbon atom on the imide ring, causing the bond between the carbonyl carbon and nitrogen to break. The imide ring opens, and the crosslinking agent molecule is connected to the polyetherimide chain through the newly formed amide bond. At the same time, a negative charge is generated on the original imide nitrogen atom. The negative charge will take a proton from the solvent or system and form an amide group with the carbon-oxygen double bond in the original ring. The primary amino group of ethylenediamine has high reactivity and can undergo a ring-opening reaction with the five-membered ring of another polyetherimide to covalently connect different polyetherimide molecular chains.

[0018]

[0019] The aforementioned crosslinking reaction initially creates a three-dimensional network structure, which greatly restricts the free movement of polyetherimide molecular chains in organic solvents, thereby fundamentally inhibiting swelling. This transforms the base film from a material that can be partially dissolved or severely swollen by strong solvents into a solvent-resistant skeleton that is dimensionally stable in alkanes and aromatics and has a very high mechanical strength retention rate. Finally, the washing and drying steps aim to thoroughly remove residual porogens, unreacted crosslinking agents, and byproducts from the system, ensuring the purity and long-term stability of the membrane. Vacuum drying at 130°C further promotes the completion of the crosslinking reaction and removes moisture, thus stabilizing the membrane structure.

[0020] Preparation of S3, polyimide selective layer:

[0021] Aqueous phase was prepared by mixing pyromellitic triamine, tris(2-aminoethyl)amine and deionized water, and oil phase was prepared by mixing pyromellitic trimethylol chloride, perfluorodecyl mercaptan and n-hexane. The base film was fixed and poured into the aqueous phase solution. After standing for 3 min for adsorption, excess liquid was removed with a rubber roller. An equal volume of oil phase solution was poured in and the film was discharged after reacting for 60 s. The wet film was transferred to a vacuum oven at 110 °C and heat-treated for 20 min. It was then rinsed with n-hexane and ethanol and vacuum dried at 70 °C for 4 h to complete the preparation of the polyimide selective layer.

[0022] The preparation and adsorption of the aqueous and oil phases are prerequisites for the formation of the separation layer: pyromellitic triamine and tris(2-aminoethyl)amine are dissolved in water, and the two together serve as aqueous phase monomers. When the aqueous solution comes into contact with the hydrophilic base membrane, these amine monomers are adsorbed and fill the surface micropores of the base membrane through capillary forces and hydrogen bonding. Then, excess liquid is removed with a rubber roller to precisely control the position of the interfacial reaction, prevent bulk polymerization in the aqueous liquid layer, and ensure the formation of an ultrathin separation layer.

[0023] When the oil phase containing trimesoyl chloride and perfluorodecyl mercaptan is poured in, the reaction occurs instantaneously at the oil-water interface. Tritrisoyl chloride dissolved in hexane rapidly diffuses to the interface and undergoes a Schottten-Baumann reaction with the amine monomer adsorbed on the surface of the base film. The amine monomer in the aqueous phase has a lone pair of electrons on its nitrogen atom, which acts as a strong nucleophile and attacks the carbonyl carbon atom on the acyl chloride molecule in the oil phase. This carbonyl carbon exhibits a significant positive charge due to the connection between the strongly electronegative oxygen and chlorine atoms, making it highly susceptible to nucleophilic attack. The resulting negatively charged tetrahedral intermediate is very unstable and will quickly eliminate a chloride ion and rehybridize to form a more stable carbon-oxygen double bond (C=O). Finally, the amine molecule is covalently linked to the acyl chloride molecule through the newly formed amide bond (-CO-NH-) to form a polyamide film.

[0024]

[0025] Meanwhile, the terminal thiol group of perfluorodecyl thiol in the oil phase reacts with the unreacted acyl chloride group in the polyamide network. The sulfur atom in the thiol molecule, due to its lone pair electrons, acts as a nucleophile and attacks the partially positively charged carbonyl carbon atom in the acyl chloride functional group. The unstable tetrahedral intermediate quickly eliminates one molecule of hydrogen chloride to form a stable thioester bond, thereby firmly anchoring its long-chain perfluoroalkyl group to the surface of the separation layer and the orifice.

[0026]

[0027] Heat treatment imidization is a key post-curing step. The wet film is heat-treated under vacuum at 110°C to promote the completion of the cross-linking reaction and make the separation layer network more compact. Rinsing and drying aim to thoroughly remove unreacted monomers, byproduct hydrochloric acid, and physically adsorbed impurities to obtain a pure and stable final product.

[0028] S4. Post-processing:

[0029] After the polyimide selective layer is generated in situ on the polyetherimide base layer, it is placed in cyclohexane and kept for 48-72 hours. During this period, a trace amount of trifluoroacetic anhydride is added in portions. The membrane is washed with ethanol, vacuum dried for 12 hours, and then hot-pressed for 30 seconds in a flatbed hot press to calibrate the pore size, thus obtaining the finished filter membrane.

[0030] Immersing the composite membrane in cyclohexane serves primarily for solvent pre-swelling and activation. Cyclohexane, as the actual solvent in the polymerization process, allows the newly formed polyimide selective layer molecular chains to relax and swell appropriately, ensuring thermodynamic stability before use and preventing performance fluctuations during operation. During this process, trifluoroacetic anhydride, added in stages, dissolves in the cyclohexane and diffuses into the swollen polymer network. As a highly efficient acylation and dehydrating agent, trifluoroacetic anhydride reacts with residual amide groups or terminal amino groups in the selective layer polymer. Its reaction with amino groups is particularly important, generating more stable and hydrophobic trifluoroacetyl groups while removing polar sites prone to hydrogen bonding.

[0031]

[0032] This process optimizes the chemical structure of the separation layer at the molecular scale. On the one hand, by introducing a large trifluoromethyl group, it significantly improves the crosslinking density and hydrophobicity of the separation layer, thereby making a qualitative leap in its solvent resistance. On the other hand, it reduces the chemical polarity of the membrane surface, which can effectively reduce the adsorption of cis-butadiene rubber molecular chains and endow the membrane with inherent antifouling properties.

[0033] Ethanol washing and vacuum drying aim to completely terminate the reaction and remove residual reaction byproducts and solvents, ensuring the purity and structural stability of the membrane. Finally, by hot pressing on a flat plate, pressure is applied at a temperature higher than the polymer's glass transition temperature but lower than its melting point. The polyimide selective layer undergoes slight thermoplastic deformation, effectively shrinking those excessively large or loosely structured pores formed during interfacial polymerization. This makes the pore size distribution of the entire separation layer narrower and more uniform, thereby ensuring more precise and reliable retention of gel particles and catalyst agglomerates.

[0034] Preferably, the polyetherimide base layer has a thickness of 30-50 μm, the polyimide selective layer has a thickness of 0.1-0.5 μm, the finished filter membrane has a thickness of 130-250 μm, and the pore size has a diameter of 30-500 nm.

[0035] Preferably, the solvent-resistant filter membrane is installed at one or more of the following process nodes to filter the material:

[0036] The point between catalyst preparation and entry into the aging tank;

[0037] The point between catalyst aging and entry into the polymerization reactor;

[0038] The node after the polymerization reaction and before the adhesive enters the subsequent processing unit.

[0039] The solvent-resistant filter membrane prepared by the method proposed in this invention can be used at various stages of the cis-butadiene rubber solution polymerization process, including after catalyst preparation, aging, and polymerization reaction. It effectively traps micron-sized gel particles and nano-sized catalyst residues in the solution, allowing the purified polymerization liquid to enter subsequent processes. This significantly reduces the gel content in the final product from the source, effectively eliminating "fish-eye" defects. At the same time, its excellent solvent resistance and anti-fouling properties ensure long-term stability and high throughput in strong organic solvent environments such as cyclohexane.

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

[0041] 1. This invention innovatively employs a hexamethylenediamine ethanol solution to chemically crosslink a polyetherimide substrate, leveraging the ring-opening covalent linkage mechanism of the imide ring to overcome the limitations of traditional substrates' insufficient solvent resistance. The primary amino group of hexamethylenediamine acts as a nucleophile, attacking the carbonyl group of the imide ring, causing different polyetherimide molecular chains to be covalently linked through amide bonds, forming a stable three-dimensional network. This greatly restricts the free movement of molecular chains and fundamentally inhibits solvent swelling. Simultaneously, nano-SiO2 and polyethylene glycol in the casting solution synergistically regulate the pore structure, balancing mechanical strength and permeability, enabling the substrate to maintain dimensional stability and structural integrity in alkane and aromatic solvents over a long period.

[0042] 2. This invention introduces perfluorodecyl mercaptan into the oil phase, combining it with the Schotten-Baumann reaction and the thioester bond anchoring mechanism to solve the problem of poor antifouling performance of traditional selective layers. Perfluorodecyl mercaptan reacts with unreacted acyl chloride groups in the polyamide network via its thiol groups, anchoring long-chain perfluoroalkyl groups to the surface of the separation layer. Utilizing the low surface energy of fluorocarbon chains, it reduces the adsorption of rubber segments. Simultaneously, the aqueous monomers, composed of pyromellitic triamine and tris(2-aminoethyl)amine, increase the crosslinking density of the selective layer. Imidization via heat treatment at 110°C further enhances the structural compactness, achieving efficient retention of gel particles and catalyst residues.

[0043] 3. This invention innovatively employs a combination of cyclohexane pre-expansion and trace amounts of trifluoroacetic anhydride post-treatment, along with molecular chain relaxation and acylation modification mechanisms, to simultaneously improve solvent resistance and retention accuracy. Cyclohexane pre-expansion brings the selective layer molecular chains to a thermodynamically stable state, preventing performance fluctuations during operation. Trifluoroacetic anhydride, as an acylation agent, reacts with residual amino groups to generate more hydrophobic trifluoroacetyl groups, increasing crosslinking density and solvent resistance, while simultaneously reducing surface polarity and enhancing anti-fouling properties. Subsequent hot-pressing calibration of the pore size concentrates it within the 30-500 nm range, ensuring precise and reliable retention accuracy, perfectly suited to the gel degelatinization process requirements of cis-butadiene rubber. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the solvent-resistant filter membrane produced by the present invention;

[0045] Figure 2 The image shows the 1H NMR spectrum of the polyetherimide crosslinked with 1,6-hexanediamine according to the present invention. Detailed Implementation

[0046] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0047] Example 1: A method for preparing a solvent-resistant filter membrane, comprising the following steps:

[0048] S1. Raw material pretreatment:

[0049] The nonwoven fabric is immersed in a 7wt% polyvinyl alcohol solution for 5-15 minutes, the liquid volume is controlled by a precision roller, and it is dried in an oven at 90℃ for 5-10 minutes. The polyetherimide resin is crushed and screened, washed three times with anhydrous ethanol, and then dried.

[0050] S2, Preparation of polyetherimide base layer:

[0051] Pretreated polyetherimide resin, polyethylene glycol, nano-SiO2 and N,N-dimethylacetamide were mixed in a mass ratio of 20:25:2:50 and stirred at 80℃ for 6 hours. After vacuum degassing for 12 hours, the mixture was coated onto a nonwoven fabric support using a film scraper. The film was then immersed in a pure water coagulation bath at 18℃ for 24 hours, and then immersed in a 5wt% ethanol solution of 1,6-hexanediamine at 70℃ for 4 hours. The film was washed three times with ethanol and water and then vacuum dried at 130℃ for 12 hours.

[0052] Preparation of S3, polyimide selective layer:

[0053] Aqueous phase was prepared by mixing pyromellitic triamine, tris(2-aminoethyl)amine, and deionized water, with pyromellitic triamine having a mass fraction of 1.5 wt% and tris(2-aminoethyl)amine having a mass fraction of 0.5 wt%. Oil phase was prepared by mixing pyromellitic trimethylol chloride, perfluorodecyl mercaptan, and n-hexane, with pyromellitic trimethylol chloride having a mass fraction of 1.0 wt% and perfluorodecyl mercaptan having a mass fraction of 0.015 wt%. The base film was fixed, and the aqueous phase solution was poured in. After standing for 3 min to adsorb, excess liquid was removed with a rubber roller, and an equal volume of oil phase solution was poured in. After reacting for 60 s, the wet film was discharged and transferred to a vacuum oven at 110 °C for heat treatment for 20 min. The film was then rinsed with n-hexane and ethanol and vacuum dried at 70 °C for 4 h to complete the preparation of the polyimide selective layer.

[0054] S4. Post-processing:

[0055] After the polyimide selective layer is generated in situ on the polyetherimide substrate, it is immersed in cyclohexane for 48-72 hours, during which a trace amount of trifluoroacetic anhydride is added in portions. After washing with ethanol, it is vacuum dried for 12 hours and then hot-pressed for 30 seconds in a flatbed hot press to calibrate the pore size, thus obtaining the finished filter membrane.

[0056] Example 2: A method for preparing a solvent-resistant filter membrane, comprising the following steps:

[0057] S1. Raw material pretreatment:

[0058] The nonwoven fabric is immersed in a 7wt% polyvinyl alcohol solution for 5-15 minutes, the liquid volume is controlled by a precision roller, and it is dried in an oven at 90℃ for 5-10 minutes. The polyetherimide resin is crushed and screened, washed three times with anhydrous ethanol, and then dried.

[0059] S2, Preparation of polyetherimide base layer:

[0060] Pretreated polyetherimide resin, polyethylene glycol, nano-SiO2 and N,N-dimethylacetamide were mixed in a mass ratio of 30:25:2:50 and stirred at 80℃ for 6 hours. After vacuum degassing for 12 hours, the mixture was coated onto a nonwoven fabric support using a film scraper. The film was then immersed in a pure water coagulation bath at 18℃ for 24 hours, and then immersed in a 5wt% ethanol solution of 1,6-hexanediamine at 70℃ for 4 hours. The film was washed three times with ethanol and water and then vacuum dried at 130℃ for 12 hours.

[0061] Preparation of S3, polyimide selective layer:

[0062] Aqueous phase was prepared by mixing pyromellitic triamine, tris(2-aminoethyl)amine, and deionized water, with pyromellitic triamine having a mass fraction of 1.5 wt% and tris(2-aminoethyl)amine having a mass fraction of 0.5 wt%. Oil phase was prepared by mixing pyromellitic trimethylol chloride, perfluorodecyl mercaptan, and n-hexane, with pyromellitic trimethylol chloride having a mass fraction of 1.0 wt% and perfluorodecyl mercaptan having a mass fraction of 0.015 wt%. The base film was fixed, and the aqueous phase solution was poured in. After standing for 3 min to adsorb, excess liquid was removed with a rubber roller, and an equal volume of oil phase solution was poured in. After reacting for 60 s, the wet film was discharged and transferred to a vacuum oven at 110 °C for heat treatment for 20 min. The film was then rinsed with n-hexane and ethanol and vacuum dried at 70 °C for 4 h to complete the preparation of the polyimide selective layer.

[0063] S4. Post-processing:

[0064] After the polyimide selective layer is generated in situ on the polyetherimide substrate, it is immersed in cyclohexane for 48-72 hours, during which a trace amount of trifluoroacetic anhydride is added in portions. After washing with ethanol, it is vacuum dried for 12 hours and then hot-pressed for 30 seconds in a flatbed hot press to calibrate the pore size, thus obtaining the finished filter membrane.

[0065] Example 3: A method for preparing a solvent-resistant filter membrane, comprising the following steps:

[0066] S1. Raw material pretreatment:

[0067] The nonwoven fabric is immersed in a 7wt% polyvinyl alcohol solution for 5-15 minutes, the liquid volume is controlled by a precision roller, and it is dried in an oven at 90℃ for 5-10 minutes. The polyetherimide resin is crushed and screened, washed three times with anhydrous ethanol, and then dried.

[0068] S2, Preparation of polyetherimide base layer:

[0069] Pretreated polyetherimide resin, polyethylene glycol, nano-SiO2 and N,N-dimethylacetamide were mixed in a mass ratio of 25:25:2:50 and stirred at 80℃ for 6 hours. After vacuum degassing for 12 hours, the mixture was coated onto a nonwoven fabric support using a film scraper. The film was then immersed in a pure water coagulation bath at 18℃ for 24 hours, and then immersed in a 5wt% ethanol solution of 1,6-hexanediamine at 70℃ for 4 hours. The film was washed three times with ethanol and water and then vacuum dried at 130℃ for 12 hours.

[0070] Preparation of S3, polyimide selective layer:

[0071] Aqueous phase was prepared by mixing pyromellitic triamine, tris(2-aminoethyl)amine, and deionized water, with pyromellitic triamine having a mass fraction of 1.5 wt% and tris(2-aminoethyl)amine having a mass fraction of 0.5 wt%. Oil phase was prepared by mixing pyromellitic trimethylol chloride, perfluorodecyl mercaptan, and n-hexane, with pyromellitic trimethylol chloride having a mass fraction of 1.0 wt% and perfluorodecyl mercaptan having a mass fraction of 0.015 wt%. The base film was fixed, and the aqueous phase solution was poured in. After standing for 3 min to adsorb, excess liquid was removed with a rubber roller, and an equal volume of oil phase solution was poured in. After reacting for 60 s, the wet film was discharged and transferred to a vacuum oven at 110 °C for heat treatment for 20 min. The film was then rinsed with n-hexane and ethanol and vacuum dried at 70 °C for 4 h to complete the preparation of the polyimide selective layer.

[0072] S4. Post-processing:

[0073] After the polyimide selective layer is generated in situ on the polyetherimide substrate, it is immersed in cyclohexane for 48-72 hours, during which a trace amount of trifluoroacetic anhydride is added in portions. After washing with ethanol, it is vacuum dried for 12 hours and then hot-pressed for 30 seconds in a flatbed hot press to calibrate the pore size, thus obtaining the finished filter membrane.

[0074] Example 4: A method for preparing a solvent-resistant filter membrane, comprising the following steps:

[0075] S1. Raw material pretreatment:

[0076] The nonwoven fabric is immersed in a 7wt% polyvinyl alcohol solution for 5-15 minutes, the liquid volume is controlled by a precision roller, and it is dried in an oven at 90℃ for 5-10 minutes. The polyetherimide resin is crushed and screened, washed three times with anhydrous ethanol, and then dried.

[0077] S2, Preparation of polyetherimide base layer:

[0078] Pretreated polyetherimide resin, polyethylene glycol, nano-SiO2 and N,N-dimethylacetamide were mixed in a mass ratio of 25:25:2:50 and stirred at 80℃ for 6 hours. After vacuum degassing for 12 hours, the mixture was coated onto a nonwoven fabric support using a film scraper. The film was then immersed in a pure water coagulation bath at 18℃ for 24 hours, and then immersed in a 5wt% ethanol solution of 1,6-hexanediamine at 70℃ for 4 hours. The film was washed three times with ethanol and water and then vacuum dried at 130℃ for 12 hours.

[0079] Preparation of S3, polyimide selective layer:

[0080] Aqueous phase was prepared by mixing pyromellitic triamine, tris(2-aminoethyl)amine, and deionized water, with pyromellitic triamine having a mass fraction of 1.5 wt% and tris(2-aminoethyl)amine having a mass fraction of 0.5 wt%. Oil phase was prepared by mixing pyromellitic trimethylol chloride, perfluorodecyl mercaptan, and n-hexane, with pyromellitic trimethylol chloride having a mass fraction of 0.8 wt% and perfluorodecyl mercaptan having a mass fraction of 0.015 wt%. The base film was fixed, and the aqueous phase solution was poured in. After standing for 3 min to adsorb, excess liquid was removed with a rubber roller, and an equal volume of oil phase solution was poured in. After reacting for 60 s, the wet film was discharged and transferred to a vacuum oven at 110 °C for heat treatment for 20 min. The film was then rinsed with n-hexane and ethanol and vacuum dried at 70 °C for 4 h to complete the preparation of the polyimide selective layer.

[0081] S4. Post-processing:

[0082] After the polyimide selective layer is generated in situ on the polyetherimide substrate, it is immersed in cyclohexane for 48-72 hours, during which a trace amount of trifluoroacetic anhydride is added in portions. After washing with ethanol, it is vacuum dried for 12 hours and then hot-pressed for 30 seconds in a flatbed hot press to calibrate the pore size, thus obtaining the finished filter membrane.

[0083] Example 5: A method for preparing a solvent-resistant filter membrane, comprising the following steps:

[0084] S1. Raw material pretreatment:

[0085] The nonwoven fabric is immersed in a 7wt% polyvinyl alcohol solution for 5-15 minutes, the liquid volume is controlled by a precision roller, and it is dried in an oven at 90℃ for 5-10 minutes. The polyetherimide resin is crushed and screened, washed three times with anhydrous ethanol, and then dried.

[0086] S2, Preparation of polyetherimide base layer:

[0087] Pretreated polyetherimide resin, polyethylene glycol, nano-SiO2 and N,N-dimethylacetamide were mixed in a mass ratio of 25:25:2:50 and stirred at 80℃ for 6 hours. After vacuum degassing for 12 hours, the mixture was coated onto a nonwoven fabric support using a film scraper. The film was then immersed in a pure water coagulation bath at 18℃ for 24 hours, and then immersed in a 5wt% ethanol solution of 1,6-hexanediamine at 70℃ for 4 hours. The film was washed three times with ethanol and water and then vacuum dried at 130℃ for 12 hours.

[0088] Preparation of S3, polyimide selective layer:

[0089] Aqueous phase was prepared by mixing pyromellitic triamine, tris(2-aminoethyl)amine, and deionized water, with pyromellitic triamine having a mass fraction of 1.5 wt% and tris(2-aminoethyl)amine having a mass fraction of 0.5 wt%. Oil phase was prepared by mixing pyromellitic trimethylol chloride, perfluorodecyl mercaptan, and n-hexane, with pyromellitic trimethylol chloride having a mass fraction of 1.2 wt% and perfluorodecyl mercaptan having a mass fraction of 0.015 wt%. The base film was fixed, and the aqueous phase solution was poured in. After standing for 3 min to adsorb, excess liquid was removed with a rubber roller, and an equal volume of oil phase solution was poured in. After reacting for 60 s, the wet film was discharged and transferred to a vacuum oven at 110 °C for heat treatment for 20 min. The film was then rinsed with n-hexane and ethanol and vacuum dried at 70 °C for 4 h to complete the preparation of the polyimide selective layer.

[0090] S4. Post-processing:

[0091] After the polyimide selective layer is generated in situ on the polyetherimide substrate, it is immersed in cyclohexane for 48-72 hours, during which a trace amount of trifluoroacetic anhydride is added in portions. After washing with ethanol, it is vacuum dried for 12 hours and then hot-pressed for 30 seconds in a flatbed hot press to calibrate the pore size, thus obtaining the finished filter membrane.

[0092] Comparative Example 1:

[0093] Compared to Example 3, the mass ratio of polyetherimide resin, polyethylene glycol, nano-SiO2 and N,N-dimethylacetamide in Comparative Example 1 was 35:25:2:50.

[0094] Comparative Example 2:

[0095] Compared to Example 3, the mass fraction of pyromellitic methyl chloride in Comparative Example 2 was 0.5 wt%.

[0096] Comparative Example 3:

[0097] Compared to Example 3, the nonwoven fabric in Comparative Example 3 was not treated with polyvinyl alcohol solution.

[0098] Comparative Example 4:

[0099] Compared to Example 3, no nano-SiO2 was added to the polyetherimide base layer in Comparative Example 4.

[0100] Comparative Example 5:

[0101] Compared to Example 3, no perfluorodecyl mercaptan was added to the oil phase in Comparative Example 5.

[0102] Comparative Example 6:

[0103] Compared to Example 3, no trifluoroacetic anhydride was added to the cyclohexane-treated filter membrane in Comparative Example 6.

[0104] Comparative Example 7:

[0105] Compared to Example 3, in Comparative Example 7, 1,6-ethylenediamine was not used for initial crosslinking during the preparation of the polyetherimide base layer.

[0106] Performance testing:

[0107] According to the standard test methods in national standards such as GB / T 1690-2010 "Liquid Resistance Test of Vulcanized Rubber", GB / T 32361-2015 "Separation Membrane Pore Size Test Method - Bubble Point and Average Flow Rate Method", GB / T 36138-2018 "Polytetrafluoroethylene Flat Sheet Microfiltration Membrane for Sterilization", GB / T1040.2-2022 "Determination of Tensile Properties of Plastics", and GB / T 6165-2021 "Performance Test of High Efficiency Air Filters", the filter membranes prepared in the above examples and comparative examples were tested for weight loss, dimensional change rate, bubble point pressure, average pore size, tensile strain, tensile strength, elongation at break, pressure drop, and repeatability of filtration efficiency after immersion.

[0108] Table 1 Mechanical test data of filter membranes prepared in each group

[0109]

[0110] Table 2 Performance test data of filter membranes prepared in each group

[0111]

[0112] Data Analysis:

[0113] Figure 1 This is a schematic diagram of the solvent-resistant filter membrane produced by the present invention. The solvent-resistant filter membrane adopts a unique three-layer gradient structure, consisting of a polyimide selective layer, a polyetherimide base layer, and a pre-treated nonwoven fabric from top to bottom. The top polyimide selective layer achieves precise pore size sieving through a rigid, highly cross-linked network, and its surface-grafted perfluoroalkyl molecular brushes further endow it with extreme antifouling properties. The middle polyetherimide base layer serves as a framework, forming a solvent-resistant composite structure through chemical cross-linking, ensuring high throughput through asymmetric channels (finger-like pores and surface micropores). The bottom pre-treated nonwoven fabric achieves strong bonding through interface modification, preventing interlayer delamination under solvent impact. When a solution containing gelled cis-butadiene rubber flows through the membrane surface, micron-sized gel particles are precisely trapped by the selective layer, while the purified solution flows smoothly through the porous structure, ultimately achieving highly efficient gel degreasing.

[0114] Figure 2The image shows the 1H NMR spectrum of the polyetherimide after crosslinking with 1,6-hexanediamine according to the present invention. The aromatic hydrogen peaks of 7.0-8.0 ppm indicate that the aromatic ring skeleton of the polyetherimide was not destroyed after crosslinking with 1,6-hexanediamine. The aliphatic hydrogen peaks of 1.0-4.0 ppm correspond to the characteristic signals of the hexanediamine chain segment, confirming that it successfully participated in the crosslinking reaction and formed a three-dimensional network. Moreover, there are no obvious impurity peaks in each peak, indicating that the product has high purity and the crosslinking process is effective, thus endowing the polyetherimide base layer with a stable solvent-resistant structure.

[0115] According to the data in Tables 1 and 2, the solvent resistance, mechanical properties, and filtration stability of Example 1 are slightly inferior to those of Example 3. The main reason lies in the difference in the raw material ratio of the polyetherimide base layer. In Example 1, the proportion of polyetherimide resin is lower than that in Example 3, resulting in a lower resin concentration in the casting solution. The density of the base layer skeleton formed after phase inversion is insufficient. Although it is cross-linked with 1,6-hexanediamine, the integrity of the three-dimensional network structure is still slightly weak, and there is slightly more solvent penetration between molecular chains during cyclohexane immersion. At the same time, the difference in base layer density is transmitted to the selective layer support effect, resulting in a slightly lower bubble point pressure, a slightly larger pore size, a slightly faster flux decay during long-term filtration, and a slightly lower gel rejection rate.

[0116] Example 2 exhibits solvent resistance and mechanical strength similar to Example 3, with only slightly lower elongation at break and flux retention. This is attributed to the higher proportion of polyetherimide resin. A higher resin concentration results in a denser substrate skeleton, and the three-dimensional network becomes more stable after 1,6-hexanediamine crosslinking. Consequently, the weight loss rate and dimensional change rate are close to the standard sample, and the tensile strength is superior. However, excessively high resin concentration reduces the fluidity of the casting solution, decreases the uniformity of pore distribution within the substrate during coating, and slightly impairs the dispersion of nano-SiO2, leading to reduced substrate toughness and elongation at break. Simultaneously, insufficient pore uniformity results in slightly larger fluctuations in filtration resistance and a slightly lower long-term flux retention.

[0117] Example 3 achieved optimal performance across all aspects thanks to the synergistic optimization of process parameters and raw material ratios throughout the entire process. Polyvinyl alcohol-modified nonwoven fabric ensured strong anchoring of the substrate, while the ratio of polyetherimide, polyethylene glycol, and nano-SiO2 optimized the uniformity of the casting solution. After phase inversion, the substrate formed a rational structure of "finger-like macropores + surface micropores." Fully cross-linked 1,6-hexanediamine constructed a stable three-dimensional network, and perfluorodecylthiol in the selective layer uniformly anchored the substrate to enhance antifouling properties. In post-treatment, trifluoroacetic anhydride cross-linking and hot-pressing calibration precisely controlled the pore size. The synergy of each step achieved a balance between substrate density, selective layer retention accuracy, and antifouling properties, resulting in an optimal match between solvent resistance, mechanical properties, and filtration performance.

[0118] Comparative Example 1 showed significantly inferior performance compared to Example 3. The core issue was the excessively high proportion of polyetherimide resin. The high resin concentration caused a sharp increase in the viscosity of the casting solution, making it difficult to form a homogeneous system during stirring. Vacuum degassing failed to completely remove internal air bubbles, resulting in micro-pinholes and heterogeneous areas in the substrate after coating. During phase inversion, bidirectional diffusion between solvent and water was hindered, leading to disordered pore structure, an increased proportion of macropores, and difficulty in fully penetrating and crosslinking with 1,6-hexanediamine. Defects in the three-dimensional network resulted in significant solvent penetration during cyclohexane immersion, causing a dramatic increase in weight loss and dimensional change rate. These substrate defects resulted in weak adhesion of the selective layer, a wide pore size distribution, and a comprehensive decline in mechanical properties and filtration stability.

[0119] The overall performance of Example 4 was slightly inferior to that of Example 3. The main reason for this was the adjustment of the oil phase monomer concentration during the preparation of the polyimide selective layer. In Example 4, the concentration of trimesoyl chloride was lower than that of the standard sample. Although a selective layer could still be formed through interfacial polymerization, the lower monomer concentration slowed down the polymerization rate and resulted in a slightly lower crosslinking density of the selective layer, leading to a slightly larger pore size and a slightly lower bubble point pressure. However, the raw material ratio of the base layer was the same as that of the standard sample. The 1,6-hexanediamine was fully crosslinked and the nano-SiO2 was evenly dispersed. Therefore, the solvent resistance and mechanical properties were close to those of the standard sample. Only during long-term filtration, due to the slightly poor density of the selective layer, the flux retention rate and retention accuracy decreased slightly, but the overall performance remained at a relatively good level.

[0120] Example 5 exhibits better solvent resistance and retention accuracy than Example 3, with slight fluctuations in mechanical properties. The key difference lies in the increased concentration of monomers in the oil phase. In Example 5, the concentration of trimesoyl chloride is higher than that of the standard sample, increasing the probability of monomer collisions during interfacial polymerization, resulting in a more complete reaction and a higher crosslinking density and denser structure in the selected layer. Consequently, the weight loss and dimensional changes during cyclohexane immersion are smaller, the bubble point pressure is higher, the pore size is smaller, and the retention rate is superior. However, the excessively high monomer concentration slightly intensifies the exothermic polymerization reaction, leading to a slight decrease in the local uniformity of the selected layer and a slightly lower elongation at break. Nevertheless, since the base layer process was not adjusted, the overall mechanical strength remains at a high level, and the long-term filtration stability is excellent.

[0121] The performance of Comparative Example 2 was significantly inferior to that of Example 3. The core problem was the excessively low concentration of monomers in the oil phase during the preparation of the polyimide selective layer. The excessively low concentration of trimesoyl chloride resulted in insufficient interfacial polymerization, leading to an extremely low crosslinking density, a loose structure, and a significantly increased and unevenly distributed pore size in the selected layer. This caused a sharp drop in bubble point pressure and a significant decrease in gel retention rate. At the same time, the loose selective layer could not effectively block solvent penetration, resulting in a significant increase in weight loss and dimensional change rate during cyclohexane immersion. Although the base layer process was consistent with the standard sample, the defects of the selective layer directly affected the overall performance. During long-term filtration, the flux decayed rapidly, and the mechanical properties decreased slightly due to the impact on the bonding force between the selective layer and the base layer. This fully demonstrates the decisive role of monomer concentration in the performance of the selective layer.

[0122] By comparing the performance differences of Examples 3, 4, and 5 with Comparative Example 2, the critical influence of oil phase monomer concentration on filter membrane performance can be clearly seen. Examples 4 and 5, by adjusting the concentration of trimesoyl chloride, slightly fluctuated the crosslinking density of the selective layer compared to the standard sample, thus affecting retention accuracy and solvent resistance. However, their base layer processes were consistent with the standard sample, so their mechanical properties remained at a high level. Comparative Example 2, due to its excessively low oil phase monomer concentration, directly resulted in structural defects in the selective layer. Even with a normal base layer process, the overall performance was significantly reduced. This indicates that filter membrane performance is the synergistic result of base layer support and selective layer separation efficiency. The selective layer monomer concentration directly determines the crosslinking density and structural compactness, which are core factors affecting retention accuracy and solvent resistance, while the base layer process is the foundation for ensuring mechanical properties.

[0123] Comparative Example 3 showed inferior performance compared to Example 3, primarily due to the lack of polyvinyl alcohol (PVA) modification treatment on the nonwoven fabric. The absence of the PVA transition layer significantly reduced the interfacial compatibility between the nonwoven fabric and the polyetherimide substrate. The two relied solely on physical contact for bonding, lacking hydroxyl-mediated hydrogen bonding for anchoring, resulting in weak interlayer adhesion. Simultaneously, the rough surface of the nonwoven fabric was not smoothed, leading to uneven substrate thickness and the formation of microcracks during film application. The 1,6-hexanediamine crosslinking proved insufficient to repair these interfacial defects. This resulted in solvent penetration into the interlayer during cyclohexane immersion, causing delamination, increased weight loss and dimensional change rate, and a significant reduction in substrate mechanical strength due to interfacial defects. Consequently, pore size stability was insufficient during filtration, leading to decreased flux retention and rejection rates.

[0124] The mechanical properties, solvent resistance, and filtration accuracy of Comparative Example 4 were all inferior to those of Example 3. The root cause was the absence of nano-SiO2 in the polyetherimide substrate. Nano-SiO2, as an inorganic filler, forms physical support points in the substrate skeleton, improving its density and resistance to deformation. Without it, the pores are prone to collapse or expansion during phase transformation due to uneven stress, leading to decreased pore structure stability. Simultaneously, the reinforcing effect of nano-SiO2 disappears, weakening the tensile strength and toughness of the substrate. During cyclohexane immersion, the molecular chains are more susceptible to displacement, increasing the degree of swelling. This dual weakening of pore structure and mechanical properties results in lower bubble point pressure, wider pore size distribution, accelerated flux decay during long-term filtration, and decreased retention accuracy.

[0125] The flux retention rate of Comparative Example 5 was significantly lower than that of Example 3, while other properties were similar. The key reason is the absence of perfluorodecyl mercaptan (PFM) in the oil phase. PFM is anchored to the fluorocarbon chains on the selective layer surface via thioester bonds. It can reduce the adsorption of rubber segments by utilizing its low surface energy. Without PFM, the selective layer surface polarity is high, and rubber segments are easily adsorbed onto the membrane surface and pores via hydrogen bonds or van der Waals forces. As filtration proceeds, the adsorbed segments gradually accumulate and clog the pores, leading to a rapid decline in flux and a significant decrease in the 800-hour flux retention rate. However, PFM does not directly affect the cross-linking structure of the substrate and the density of the selective layer, so the changes in solvent resistance, mechanical properties, and gel rejection rate are relatively small.

[0126] Comparative Example 6 exhibits inferior solvent resistance, antifouling properties, and pore size stability compared to Example 3. The core issue is the absence of trifluoroacetic anhydride during cyclohexane post-treatment. Trifluoroacetic anhydride can react with residual amino groups in the selective layer to generate hydrophobic trifluoroacetyl groups, increasing crosslinking density and hydrophobicity. Without it, the selective layer crosslinking is insufficient, leading to easy relaxation and swelling of the molecular chains in cyclohexane, resulting in increased weight loss and dimensional change rate. Simultaneously, the surface polarity remains unchanged, increasing the adsorption capacity of rubber segments and decreasing flux retention. Furthermore, without the molecular modification effect of trifluoroacetic anhydride, the pore wall stability of the selective layer is insufficient, making it difficult to form a uniform pore size distribution during hot-press calibration, resulting in a slight decrease in retention accuracy.

[0127] Comparative Example 7 exhibited the worst performance across all categories, particularly with a significant decline in solvent resistance and mechanical properties. The root cause was the lack of 1,6-hexanediamine crosslinking in the polyetherimide substrate. The uncrosslinked substrate relies solely on intermolecular forces to maintain its structure, lacking a three-dimensional network formed by covalent bonds. Upon immersion in cyclohexane, the strong free movement of molecular chains easily leads to swelling and even localized dissolution, resulting in a dramatic increase in weight loss and dimensional change rate. Furthermore, the substrate skeleton lacks crosslinking support, causing a sharp decrease in mechanical strength and susceptibility to fracture under tension. Simultaneously, the loose pore structure of the uncrosslinked substrate fails to provide stable support for the selective layer, leading to cracking or detachment of the selective layer, disordered pore size distribution, and a comprehensive deterioration in gel retention and flux retention.

[0128] In summary, the performance data comparison between the examples and comparative examples shows that the superior performance of the solvent-resistant filter membrane of the present invention stems from the synergistic effect of key processes and raw material ratios throughout the entire process. The core conclusions are as follows: First, the modification of non-woven polyvinyl alcohol, the doping of nano-SiO2 in the base layer, and the crosslinking of 1,6-hexanediamine are the foundation for ensuring the stability of the membrane structure. The absence of any one of these steps will lead to a decrease in interlayer bonding force, a weakening of mechanical strength, or a reduction in solvent resistance. Second, the addition of perfluorodecyl mercaptan to the oil phase and the introduction of trifluoroacetic anhydride in the post-treatment are key to improving antifouling properties. These two steps reduce the adsorption of rubber segments through surface chemical modification, and their absence will significantly reduce the flux retention rate. Third, the raw material ratio needs to be precisely controlled. Too high or too low a proportion of polyetherimide resin will disrupt the uniformity of the casting solution, leading to disordered pore structure.

[0129] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A solvent resistant filter membrane, characterized in that, From bottom to top, the layers consist of a pretreated nonwoven fabric, a polyetherimide base layer, and a polyimide selective layer. The preparation steps for the polyimide selective layer are as follows: Aqueous phase was prepared by mixing pyromellitic triamine, tris(2-aminoethyl)amine and deionized water, and oil phase was prepared by mixing pyromellitic trimethylol chloride, perfluorodecyl mercaptan and n-hexane. The base film was fixed and poured into the aqueous phase solution. After standing for 3 min for adsorption, excess liquid was removed with a rubber roller, and an equal volume of oil phase solution was poured in. After reacting for 60 s, the wet film was discharged and transferred to a vacuum oven at 110 °C for heat treatment for 20 min. The film was then rinsed with n-hexane and ethanol and vacuum dried at 70 °C for 4 h to complete the preparation of the polyimide selective layer.

2. The solvent resistant filter membrane of claim 1, wherein, The aqueous phase contains 1-2 wt% pyromellitic triamine, 0-1 wt% tris(2-aminoethyl)amine, and the oil phase contains 0.8-1.2 wt% pyromellitic trimethylol chloride and 0.01-0.02 wt% perfluorodecyl mercaptan.

3. The method of claim 1 or 2, wherein the solvent resistant filter membrane is prepared by the steps of: Includes the following steps: S1. Raw material pretreatment: Immerse the nonwoven fabric in a 5-10 wt% polyvinyl alcohol solution for 5-15 minutes, control the liquid volume with a precision roller, dry in an oven at 80-100℃ for 5-10 minutes, crush and screen the polyetherimide resin, wash three times with anhydrous ethanol, and dry. S2, Preparation of polyetherimide base layer: Pretreated polyetherimide resin, polyethylene glycol, nano-SiO2 and N,N-dimethylacetamide were mixed and stirred at 80℃ for 6 hours, vacuum degassing was performed for 12 hours, and the film was scraped onto a nonwoven fabric support using a film scraper. The film was then immersed in a pure water coagulation bath at 18℃ for 24 hours, and then immersed in a 5wt% ethanol solution of 1,6-hexanediamine at 70℃ for 4 hours. The film was washed three times with ethanol and water, and then vacuum dried at 130℃ for 12 hours. S3, Post-processing: After the polyimide selective layer is generated in situ on the polyetherimide substrate, it is immersed in cyclohexane for 48-72 hours, during which a trace amount of trifluoroacetic anhydride is added in portions. After washing with ethanol, it is vacuum dried for 12 hours and then hot-pressed for 30 seconds in a flatbed hot press to calibrate the pore size, thus obtaining the finished filter membrane.

4. The method of claim 3, wherein the solvent resistant filtration membrane is prepared by the steps of: In S1, the particle size of the polyetherimide resin after crushing is 45-150 μm, and the moisture content after drying is less than 100 ppm.

5. The method for preparing the solvent-resistant filter membrane according to claim 3, characterized in that, The mass ratio of polyetherimide resin, polyethylene glycol, nano-SiO2 and N,N-dimethylacetamide in S2 is 20-30:20-30:2:40-60.

6. The method of claim 3, wherein the solvent resistant filtration membrane is prepared by the steps of: The polyetherimide base layer in S2 has a thickness of 30-50 μm, the polyimide selective layer has a thickness of 0.1-0.5 μm, the finished filter membrane has a thickness of 130-250 μm, and the pore size has a diameter of 30-500 nm.

7. The method of claim 3, wherein the solvent resistant filtration membrane is prepared by the steps of: The total amount of trifluoroacetic anhydride added in S3 accounts for 1-2% of the total mass of the system.

8. Use of the solvent resistant filter membrane according to any one of claims 1 to 2 in a solution polymerization gel reduction process of butadiene, characterized in that, This includes setting the solvent-resistant filter membrane at one or more of the following process nodes to filter materials: The point between catalyst preparation and entry into the aging tank; The point between catalyst aging and entry into the polymerization reactor; The node after the polymerization reaction and before the adhesive enters the subsequent processing unit.

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