An interpenetrating network polyamide membrane, its preparation method and use

Abstract

The application provides an interpenetrating network polyamide membrane and a preparation method and application thereof, and the preparation method comprises the following steps: (1) reacting polyether amine, a bisphenol compound and formaldehyde to obtain a polyamine monomer containing a benzoxazine structural unit; (2) performing interfacial polymerization reaction on a base film by using the polyamine monomer in step (1) and acyl chloride to obtain a polyamide separation layer containing a benzoxazine structural unit; and (3) heating the polyamide separation layer in step (2) to make the benzoxazine structural unit in the polyamide separation layer undergo ring-opening polymerization reaction to obtain the interpenetrating network polyamide membrane. The polyamide membrane preparation method is simple, the prepared interpenetrating network polyamide membrane with polybenzoxazine and polyamide has the advantages of good selective permeability, greatly improved acid and alkali resistance, chlorine resistance and mechanical scratch resistance, and has a good industrialization prospect.

Description

Technical Field

[0001] This invention belongs to the field of membrane technology and relates to an interpenetrating polyamide membrane, its preparation method, and its application. Background Technology

[0002] Polyamide membranes are commonly used in fluid filtration. A typical application is the reverse osmosis membrane preparation disclosed by Cadotte et al. in US4277344. This method uses porous polysulfone as a support layer. The membrane is first immersed in an aqueous polyamine solution, typically containing m-phenylenediamine, pyromellitic triamine, piperazine, aliphatic amines, polyetheramines, etc. Then, an alkane solution of polyacrylamide chlorides, typically containing pyromellitic tricarboxylic acid chloride, isophthaloyl chloride, terephthaloyl chloride, etc., is coated on. An ultrathin polyamide layer is obtained through interfacial polymerization. This functional layer allows only water molecules to pass through, while salt ions are retained. It is widely used in seawater desalination, brackish water desalination, and wastewater treatment.

[0003] However, existing polyamide membranes are difficult to tolerate residual chlorine, with a chlorine tolerance generally around 500 ppmh (Suez product technical manual), requiring the influent residual chlorine content to be less than 0.1 ppm. They also cannot operate stably in extreme acidic or alkaline environments; the typical long-term operating pH range is 2-10, and the short-term cleaning pH range is 1-13 (refer to Lanxess Lewabrane technical manual). Because residual chlorine is oxidizing, it attacks the amide bonds in polyamide, and under acidic or alkaline conditions, these bonds are easily hydrolyzed. Both factors lead to amide bond breakage and polymer degradation, causing the polyamide membrane to lose its desalination function.

[0004] According to literature reports (Liu Zhen et al., Research progress on chlorine resistance and chlorination remediation of reverse osmosis membranes, Membrane Science and Technology, 2019, Vol. 39, No. 2, pp. 123-134), the research on chlorine-resistant polyamide membranes mainly involves physical and chemical modification. Physical modification includes PVA coating and the addition of nanomaterials such as graphene oxide; chemical modification includes benzene ring modification (introducing strong electron-withdrawing groups into the benzene ring), amide bond modification (steric hindrance effect and sacrificial protecting groups), and a combination of multiple mechanisms (physical coatings with sacrificial protecting groups). The research on acid and alkali resistant membranes mainly utilizes chemical structures that are more stable under acid and alkali conditions. For example, the cyanochloromethcathinone monomer used in the article "Preparation of acid-resistant nanofiltration membranes by interfacial polymerization using polytriazineamine as a precursor" published by Zeng Yong et al. in the 2017 issue of *Membrane Science* (pp. 225-233), and the sulfonamide polymer used in CN103260731B.

[0005] Currently, most polyamide interpenetrating polymer (IPP) membranes are achieved by introducing another polymer during the interfacial polymerization process. For example, Li Lingbo (Preparation and Performance Study of PA / PDMS Crosslinked Hybrid Solvent-Resistant Nanofiltration Membranes, 2013, Zhengzhou University, Master's Thesis) added hydroxyl-terminated polymethyl-3,3,3-trifluoropropylsiloxane (PDMS) to an oil phase solution of trimesoyl chloride during interfacial polymerization, using polyethyleneimine (PEI) as the aqueous phase, to obtain an IPP-PDMS membrane on a polyacrylonitrile (PAN) base membrane. This material achieved a PEG600 rejection rate of over 90% but a PEG400 rejection rate of only about 60%, indicating that directly introducing modified macromolecules before interfacial polymerization makes it difficult to obtain membrane materials with high rejection rates for small molecules, such as PEG400.

[0006] After long-term operation, polyamide membranes inevitably accumulate dirt on their surface, leading to a decrease in water production. Therefore, after a period of operation, chemical cleaning with acid or alkali is necessary to restore normal water production. Typically, after chemical cleaning, localized hydrolysis of the polyamide material leads to a decrease in desalination rate, thus affecting the membrane's lifespan. CN103492060A describes a double-coated base membrane that yielded a polyamide separation layer with a standard deviation of less than 2 nm and an average thickness of 14-22 nm. This material was subjected to 20 alternating immersions in sulfuric acid solution (pH=1) and sodium hydroxide solution (pH=13). The lowest salt permeation ratio before and after membrane testing was 1.12, still showing a significant decrease.

[0007] In addition to the aforementioned chlorine resistance and acid / alkali resistance, existing polyamide membranes also have shortcomings in terms of resistance to mechanical scratches. During the processing of spiral wound membrane elements, the polyamide membrane sheet is stacked layer by layer with the concentrate and desalination separators and then wound around the central tube. During this process, the polyamide membrane inevitably rubs against the rough separators. To avoid defects caused by friction during processing and a decrease in the desalination rate, a polyvinyl alcohol (PVA) protective layer is often applied to the polyamide surface during membrane processing. As mentioned in US10112154, while PVA can protect the polyamide from scratches, it significantly reduces the membrane flux. To avoid this drawback, this patent uses polyvinylpyrrolidone (PVP) as a protective layer, which protects the membrane from scratches without sacrificing flux. However, the introduction of this protective layer requires additional coating equipment, increasing process complexity and production costs. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing an interpenetrating network polyamide membrane and its preparation method. The interpenetrating network polyamide membrane of this invention possesses excellent resistance to acids, alkalis, and chlorine, as well as resistance to mechanical scratches, and can be used for selective filtration to remove divalent salts and macromolecular organic matter.

[0009] This invention provides a method for preparing an interpenetrating polyamide network film, comprising the following steps:

[0010] (1) Polyamine monomers containing benzoxazine structural units were obtained by reacting polyetheramine, bisphenol compounds and formaldehyde.

[0011] (2) The polyamine monomer and acyl chloride from step (1) are subjected to interfacial polymerization on the base film to obtain a polyamide separation layer containing benzoxazine structural units;

[0012] (3) Heating the polyamide separation layer in step (2) causes the benzoxazine structural units therein to undergo ring-opening polymerization to obtain an interpenetrating network polyamide film.

[0013] In step (1) of the present invention, the polyetheramine is a polyether containing two or more, preferably 2-3 primary amine groups, wherein the polyether chain is obtained by ring-opening homopolymerization or copolymerization using ethylene oxide and / or propylene oxide as raw materials, and can be a linear polyether or a branched polyether.

[0014] Preferably, the polyetheramine has the structure described in Formula 1:

[0015]

[0016] In the formula, x takes values ​​from 2 to 100, preferably from 2 to 70; such as Huntsman's JEFFAMINE D series;

[0017] Preferably, the polyetheramine has the structure described in Formula 2:

[0018]

[0019] In the formula, x takes values ​​from 1 to 10, preferably 1 to 6; y takes values ​​from 2 to 50, preferably 2 to 40; z takes values ​​from 1 to 10, preferably 1 to 6; such as Huntsman's JEFFAMINE ED series;

[0020] Preferably, the polyetheramine has the structure described in Formula 3:

[0021]

[0022] In the formula, x takes the value of 2-5, preferably 2 or 3; such as Huntsman's JEFFAMINE EDR series;

[0023] Preferably, the polyetheramine has the structure described in Formula 4:

[0024]

[0025] In the formula, x takes the value of 4-90, preferably 5-85; y takes the value of 4-90, preferably 5-85; z takes the value of 4-90, preferably 5-85; n takes the value of 0-3, preferably 0 or 1; R is selected from hydrogen atom, methyl or ethyl; such as Huntsman's JEFFAMINE T series.

[0026] In step (1) of this invention, the bisphenol compound has the structure shown in Formula 5:

[0027]

[0028] In the formula, R is selected from one of methylene, ethyl, isopropyl, butyl, hexafluoroisopropyl, thioether, sulfone, phenethyl, and trimethylcyclohexyl, preferably methylene, isopropyl, or sulfone;

[0029] Preferably, the bisphenol compound is any one or a combination of at least two of bisphenol A, bisphenol F, and bisphenol S.

[0030] In step (1) of this invention, the formaldehyde is selected from formaldehyde aqueous solution or paraformaldehyde, preferably paraformaldehyde; the concentration range of the formaldehyde aqueous solution is 10-37 wt%.

[0031] In step (1) of the present invention, the molar ratio of the polyetheramine, bisphenol compound and formaldehyde is 2.02-2.5:1:3.8-4.3, preferably 2.05-2.15:1:3.9-4.2;

[0032] In step (1) of this invention, the reaction is carried out in a solvent environment, and the solvent is selected from any one or a combination of at least two of alcohol ethers and aromatic solvents; preferably, the alcohol ethers are selected from any one or a combination of two of dioxane, ethylene glycol methyl ether, etc., and the aromatic solvents are selected from any one or a combination of two of toluene, xylene, etc.; the solvent is preferably toluene;

[0033] Preferably, the amount of solvent used is 70-90% wt, based on the total mass of the reaction system being 100%.

[0034] In step (1) of the present invention, the reaction temperature is 70-105℃, preferably 80-100℃, such as 90℃, and the reaction time is 4-12h, preferably 6-10h, such as 8h.

[0035] In step (1) of the present invention, the reaction, after the reaction is completed, also includes post-processing such as solvent removal and washing, and cooling to room temperature. The post-processing is a conventional operation in the art, and the present invention does not have any special requirements. In some examples, rotary evaporation is preferred to remove the solvent and the product is washed with n-hexane.

[0036] In step (1) of this invention, the polyamine monomer containing benzoxazine structural units prepared has the structure shown in Formula 6:

[0037]

[0038] In Formula 6 above: R is the same as in Formula 5, that is, selected from one of methylene, ethyl, isopropyl, butyl, hexafluoroisopropyl, thioether, sulfone, phenethyl, trimethylcyclohexyl, preferably methylene, isopropyl or sulfone; PAO represents a polyether chain, which is introduced from the polyether amine raw material in step (1); R1 is selected from hydrogen or primary amine.

[0039] In step (2) of the present invention, the polyamine monomer is preferably dissolved in a polar solvent to prepare a solution for use. The polar solvent is preferably such as methanol or water. Considering cost and safety, it is more preferable to dissolve it in water to prepare an aqueous solution for use. The concentration range of the polyamine dissolved in the aqueous solution is 0.1-20%wt, preferably 0.5-8%wt.

[0040] Preferably, when the polyamine monomer is prepared as an aqueous solution, a water-soluble solvent can be added simultaneously to the aqueous solution of the polyamine monomer to improve its solubility in water. The water-soluble solvent is selected from any one or a combination of at least two of alcohol solvents, alcohol ether solvents, and polar organic solvents. The alcohol solvent is preferably any one or a combination of at least two of methanol, ethanol, and isopropanol. The alcohol ether solvent is preferably any one or a combination of at least two of ethylene glycol methyl ether, ethylene glycol dimethyl ether, and propylene glycol methyl ether. The polar organic solvent is preferably any one or a combination of at least two of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and acetone. More preferably, the mass ratio of the water-soluble solvent to water is 1:3.3-100.

[0041] In step (2) of this invention, the acyl chloride is selected from difunctional or trifunctional acyl chlorides. The difunctional acyl chloride is selected from any one or a combination of at least two of terephthaloyl chloride, isophthaloyl chloride, and naphthaloyl chloride. The trifunctional acyl chloride is selected from any one or a combination of at least two of trimesoyl chloride, 1,3,5-cyclohexanetricarboxylic acid chloride, and 1,2,4-cyclobutanetricarboxylic acid chloride. The difunctional or trifunctional acyl chloride can be used alone or in combination. Considering availability and ease of operation, the acyl chloride is preferably trimesoyl chloride.

[0042] Preferably, the acyl chloride is dissolved in a nonpolar solvent to prepare an oil-phase solution for use. The nonpolar solvent is selected from any one or a combination of at least two of straight-chain alkanes, isoalkanes, and aromatic solvents. The straight-chain alkanes are selected from any one or a combination of at least two of hexane, octane, nonane, decane, etc. The isoalkanes are selected from any one or a combination of at least two of Isopar E, Isopar G, Isopar L, etc. The aromatic solvent is selected from any one or a combination of at least two of toluene, xylene, trimethylbenzene, etc. Considering cost and safety, Isopar G is preferred.

[0043] More preferably, the concentration of the acyl chloride in the oil phase solution is 0.08-2 wt%, preferably 0.1-0.4 wt%.

[0044] In step (2) of the present invention, the mass concentration ratio of the polyamine monomer in the aqueous solution to the acyl chloride in the oil solution is preferably 4-40:1.

[0045] In step (2) of this invention, the base film is selected from polysulfone, polyethersulfone, polyphenylsulfone, polyphenylene sulfide, polyphenylene ether, polyphenylene sulfide sulfone, polyamide, polyimide, polyester, vinyl polymer, and cellulose polymer. The vinyl polymer is selected from polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile, etc., and the cellulose polymer is selected from cellulose acetate, cellulose nitrate, etc. It can be a blend of one or more of these. Considering chemical, mechanical and thermal stability, the base film is preferably polysulfone.

[0046] In step (2) of the present invention, the interfacial polymerization reaction is carried out at room temperature, preferably 20-30°C, for a reaction time of 0.5-5 min, preferably 1-2 min.

[0047] Preferably, in order to regulate the reaction rate and the performance of the final product, the interfacial polymerization reaction can be controlled by changing the temperature of the polar and non-polar solvent phases involved in the reaction, controlling the interfacial polymerization reaction time, and adding phase transfer catalysts (e.g., dodecyltrimethylammonium chloride), acid-binding agents (e.g., sodium hydroxide, camphor sulfonic acid, and triethylamine salt), solubilizers (e.g., toluene), complexing agents (e.g., phosphate esters), humectants (e.g., glycerin), etc. to the formulation. For example, as a preferred embodiment of the present invention, the aqueous phase solution adopted is composed of 0.5-8% polyamine monomer, 1-6% camphor sulfonic acid, 0.5-3% triethylamine, 1-20% water-soluble solvent, and 67-94% water, based on the total mass of the aqueous phase solution of 100%.

[0048] In step (2) of the present invention, the preferred specific operation method for the interfacial polymerization reaction is as follows: pour an aqueous solution containing polyamine monomers onto the surface of the base film, soak for 0.5-5 minutes, squeeze out the excess aqueous solution from the surface of the base film, then pour an oil solution containing acyl chlorides onto the surface of the base film to carry out the interfacial polymerization reaction, and then pour off the excess oil phase to obtain a polyamide separation layer.

[0049] There are no special requirements for the amount of aqueous solution and oil solution used, as long as they can completely immerse the base film; preferably, the volume ratio of aqueous solution to oil solution is 1-4:1.

[0050] In step (2) of this invention, the interfacial polymerization reaction involves not only the condensation reaction of the acyl chloride and the polyamine, but also the hydrolysis reaction of the acyl chloride itself, resulting in a partially cross-linked polyamide. The polymer network retains carboxyl groups obtained from the hydrolysis of the acyl chloride and unreacted amine groups. The polyamide separation layer (i.e., the polyamide separation layer containing benzoxazine structural units) comprises a structure approximately as shown in Formula 7 below.

[0051]

[0052] For clarity, Equation 7 only shows the linear chain segment of the reaction between two acyl chloride functional groups and an amine. In the actual reaction process, the acyl chloride may be randomly hydrolyzed into a carboxyl group.

[0053] In Formula 7 above: R is the same as in Formula 6, that is, selected from one of methylene, ethyl, isopropyl, butyl, hexafluoroisopropyl, thioether, sulfone, phenethyl, and trimethylcyclohexyl, preferably methylene, isopropyl, or sulfone; R1 is the same as in Formula 6, that is, a primary amine group or a hydrogen atom; PAO represents a polyether chain, introduced from the polyetheramine raw material in step (1); when the acyl chloride is a difunctional acyl chloride, R2 is a hydrogen atom, when the acyl chloride is a trifunctional acyl chloride, R2 is the next amide unit, or a carboxyl group; unless otherwise specified, the wavy line in the formula represents that it may be connected to the next structural unit, or a hydrogen atom end cap.

[0054] In step (3) of the present invention, the ring-opening polymerization reaction is carried out at a temperature of 120-160℃, preferably 130-150℃, and for a reaction time of 3-10 min, preferably 5-7 min.

[0055] In step (3) of the present invention, interpenetrating network polyamide is obtained by ring-opening polymerization of the benzoxazine structural unit. In the actual reaction process, the degree of ring-opening of the benzoxazine unit is related to the reaction temperature and time.

[0056] Taking the polyamide separation layer shown in Formula 7 as an example, the interpenetrating network polyamide membrane obtained by the ring-opening polymerization reaction contains a structure roughly as shown in Formula 8. For a clearer illustration, only the structural unit in which benzoxazine undergoes one ring-opening crosslinking is listed.

[0057]

[0058] The method of this invention uses polyetheramine, bisphenol compounds and formaldehyde to synthesize polyamine monomers containing benzoxazine units, and forms an interfacial polymerization reaction to form a polyamide layer. The ring-opening polymerization of benzoxazine is completed under heating conditions to obtain an interpenetrating network of polybenzoxazine and polyamide. This separation layer has the advantages of both polymers: on the one hand, it has the excellent water filtration performance and selective permeability of the polyamide layer; on the other hand, the high degree of crosslinking of polybenzoxazine improves the acid, alkali and chlorine resistance of the polyamide layer. At the same time, the polymer network contains both the soft segments of polyetheramine and the hard segments of polyamide and polybenzoxazine, which greatly improves the product's resistance to mechanical scratches.

[0059] The interpenetrating network polyamide membrane prepared by the method described above in this invention exhibits excellent selective permeability and can be used for the selective removal of divalent and polyvalent salts (such as MgSO4, AlCl3, etc.) and macromolecular organic matter (such as humic acid, pesticides, etc.) from materials. In particular, it can achieve a retention rate of over 90% for organic matter with a molecular weight less than 400. The interpenetrating network polyamide membrane of this invention is especially suitable for treating two types of materials with the following characteristics: one type contains substances that are destructive to ordinary polyamide materials, such as acids, alkalis, and oxidizing substances, such as acidic wastewater discharged from electroplating, precious metal extraction, and sulfur chemical industries; alkaline wastewater discharged from the paper industry; the recovery of acidic electrolytes during battery recycling; and pure water containing residual chlorine commonly used in the sterile pure water of the pharmaceutical industry. The other type is materials that are prone to membrane fouling, requiring frequent cleaning with acids or alkalis. Using this product can significantly extend the normal operating life of the product.

[0060] The interpenetrating network polyamide membrane of the present invention has excellent acid and alkali resistance. It can operate stably in both acid (such as sulfuric acid) and alkali (such as sodium hydroxide) at a concentration of 10 wt%. After 20 alternating immersions in acid and alkali at pH=1 and pH=13, the salt permeability ratio is less than 1.05.

[0061] The interpenetrating network polyamide membrane of the present invention exhibits excellent chlorine resistance. After immersion at 18,000 ppmh, it can still maintain stable flux and rejection rate, which is a significant improvement compared to the chlorine resistance of traditional polyamide materials at 500 ppmh.

[0062] The interpenetrating network polyamide membrane of the present invention also has mechanical scratch resistance, and after being rubbed by a concentrated water separator, the salt permeability ratio is less than 1.01.

[0063] Compared with existing technologies, the polyamide film preparation method of this invention is simple, and the polyamide film prepared has the advantages of good selective permeability, significantly improved acid and alkali resistance, chlorine resistance and mechanical scratch resistance, and has good prospects for industrialization. Attached Figure Description

[0064] Figure 1 The infrared spectrum of the polyamide film obtained after interfacial polymerization in Example 6;

[0065] Figure 2 The image shows the infrared spectrum of the polyamide film obtained after ring-opening polymerization in Example 6. Detailed Implementation

[0066] To better understand the technical solution of the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0067] I. Sources and brands of main reagents in the examples and comparative examples:

[0068] Polysulfone, purchased from BASF, Germany, Ultrason S6010.

[0069] Non-woven fabric, purchased from Zhejiang Qinglan Membrane Technology Co., Ltd., R80.

[0070] Polyetheramines, D-230, ED-600, EDR-148 and T403, were purchased from Huntsman Corporation, USA.

[0071] Polysulfone-based membrane, preparation method: dissolve polysulfone in N,N-dimethylformamide to prepare a solution with a solid content of 18%. Use a 250-micron thick wet film preparation device to coat the polysulfone solution onto the surface of nonwoven fabric. After staying in the air for 4-5 seconds, immerse the nonwoven fabric in room temperature pure water. After immersion for 5 minutes, the phase inversion is completed. Immerse the polysulfone-based membrane that has completed the phase inversion in room temperature pure water, changing the water every 2 hours. After thoroughly cleaning the residual solvent, cut it for use.

[0072] Unless otherwise specified, all other reagents were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., and are reagent-grade raw materials.

[0073] II. Test methods for polyamide films in the examples and comparative examples:

[0074] Molecular weight cutoff test method: Refer to the polyethylene glycol molecular weight cutoff test method in GB / T32360-2015 "Test Methods for Ultrafiltration Membranes".

[0075] Desalination rate and flux test methods: Refer to the desalination rate and flux test methods in GB / T32373-2015 "Reverse Osmosis Membrane Test Methods". The test solution temperature is 25℃, the pH value is 7.0, the test solution is 2000ppm magnesium sulfate aqueous solution, and the test pressure is 0.49MPa.

[0076] Acid and alkali resistance cycling test method: Place the membrane in a sulfuric acid aqueous solution with pH=1 at 25℃ for 1 hour, then immerse it in a sodium hydroxide aqueous solution with pH=13 for 1 hour. Repeat this operation 20 times, calculate the SP ratio, and compare the change in the membrane's salt permeability before and after immersion. The SP ratio represents the ratio of the membrane's desalination rate before and after acid and alkali immersion. The larger the value, the more significant the performance decline. If the value is 1, it means that the performance has not changed before and after acid and alkali immersion.

[0077] SP ratio = (100 - desalination rate after immersion) / (100 - desalination rate before immersion).

[0078] Acid resistance test method: Place the membrane in a 10wt% sulfuric acid aqueous solution at 25℃ and soak for 18 hours. Then soak and wash with pure water until the pH of the rinse water is 6-7. Compare the membrane flux and desalination rate before and after soaking.

[0079] Alkali resistance test method: Place the membrane in a 10wt% sodium hydroxide aqueous solution at 25℃ and soak for 18 hours. Then soak and wash with pure water until the pH of the rinse water is 7-8. Compare the membrane flux and desalination rate before and after soaking.

[0080] Chlorine resistance test method: The membrane is placed in a 1000ppm available chlorine sodium hypochlorite aqueous solution at 25℃ and soaked for 18 hours. Then it is soaked and rinsed with pure water until the residual chlorine in the rinse water is less than 0.1ppm. The membrane flux and desalination rate are compared before and after soaking.

[0081] Test method for mechanical scratch resistance: Fix a 40cm*50cm polyamide dry membrane sheet face up on the surface of an automatic membrane scraper. Lay a 28mil thick concentrate separator of the same size on the right side of the membrane sheet, and place a glass plate of the same size on top. Place a 100g weight directly above the glass plate. Move the concentrate separator from right to left at a speed of 3cm / second until all separator membranes have evenly swept across the polyamide membrane surface. Compare the flux and desalination rate of the polyamide layer before and after scratching. The membrane sheet with less performance degradation has better scratch resistance.

[0082] NMR characterization method for polyamine monomers containing benzoxazine units: 1 The 1H NMR spectra were obtained using a Bruker AVANCE III instrument at 400 MHz. All samples were dissolved in deuterated chloroform, and tetramethylsilane was used as an internal standard.

[0083] Infrared spectral characterization method for polyamide film materials: A Thermo 470 FTIR instrument was used with an attenuated total reflectance (ATR) accessory, and the spectral resolution was 4 cm⁻¹. -1 The infrared spectrum of the polyamide layer was characterized by superimposing the results of 64 scans.

[0084] Example 1

[0085] Preparation of polyamine monomers (DA) containing benzoxazine units.

[0086] Preparation method: A 30wt% toluene solution was prepared by mixing 2.15 mol of polyetheramine D-230, 3.8 mol of paraformaldehyde, and 1 mol of bisphenol A. The solution was heated to 105 °C and refluxed with stirring for 4 h. After the reaction was completed, the mixture was cooled to room temperature, and the toluene was removed using a rotary evaporator. The product was washed three times with n-hexane. The 1H NMR spectrum results were as follows: 1 NMR (400MHz, CDCl3) δ 1.12 (12H,d), 1.37 (12H,d), 1.72 (6H,s), 3.12 (4H,m), 3.34–3.71 (24H,m), 5.01 (4H,s), 5.11 (4H,d), 6.79 (2H,d), 7.0 (2H,d), 7.06 (2H,m) indicates that the product contains the polyetheramine benzoxazine oligomer DA as shown in the following formula, where x is approximately 2.

[0087]

[0088] Example 2

[0089] Synthesis of polyamine monomers containing benzoxazine units (ED-F)

[0090] Synthesis method: A 10wt% dioxane solution containing 2.02 mol of polyetheramine ED-600, 4.3 mol of formaldehyde in a 10wt% formaldehyde aqueous solution, and 1 mol of bisphenol F was prepared. The mixture was heated to 70℃ and refluxed with stirring for 12 h. After the reaction, the mixture was cooled to room temperature, and the dioxane was removed using a rotary evaporator. The product was washed three times with n-hexane. The 1H NMR spectrum results were as follows: 1 NMR (400MHz, CDCl3) δ 1.12 (30H, d), 3.12 (10H, m), 3.31–3.71 (92H, m), 3.96 (2H, m), 5.01 (4H, m), 5.11 (4H, d), 6.75 (2H, d), 6.93 (2H, d), 6.99 (2H, m) indicates that the product contains a polyetheramine benzoxazine oligomer as shown in the following formula, where y is approximately 9 and x + z is approximately 4.

[0091]

[0092] Example 3

[0093] Synthesis of polyamine monomers containing benzoxazine units (EDR-F)

[0094] Synthesis method: 2.5 mol of polyetheramine EDR-148, a 37 wt% formaldehyde aqueous solution containing 4 mol of formaldehyde, and 1 mol of bisphenol F were mixed to prepare a 20 wt% solid-containing dioxane solution. The mixture was heated to 80 °C and refluxed with stirring for 6 h. After the reaction, the mixture was cooled to room temperature, and the dioxane was removed using a rotary evaporator. The product was washed three times with n-hexane. The 1H NMR spectrum results were as follows: 1 NMR (400MHz, CDCl3) δ 2.51 (4H,t), 3.07 (4H,m), 3.54 (8H,t), 3.60 (4H,t), 3.70 (4H,s), 3.76 (4H,t), 3.96 (2H,s), 5.01 (4H,s), 5.11 (4H,t), 6.75 (2H,d), 6.93 (2H,d), 6.99 (2H,m), indicating that the product contains the polyetheramine benzoxazine oligomer EDR-F as shown in the formula below, where x is approximately 2.

[0095]

[0096] Example 4

[0097] Synthesis of polyamine monomers containing benzoxazine units (TA)

[0098] Synthesis method: 2.15 mol of polyetheramine T-403, a 20 wt% formaldehyde aqueous solution containing 4 mol of formaldehyde, and 1 mol of bisphenol A were mixed to prepare a 20 wt% solid-containing dioxane solution. The mixture was heated to 90 °C and refluxed with stirring for 10 h. After the reaction, the mixture was cooled to room temperature, and the dioxane was removed using a rotary evaporator. The product was washed three times with n-hexane. The 1H NMR spectrum results were as follows: 1 NMR (400MHz, CDCl3) δ 0.9 (6H, t), 1.12 (18H, d), 1.37 (18H, d), 1.52 (4H, m), 1.69–1.72 (10H, m), 2.79 (2H, m), 3.12 (4H, m), 3.34–3.71 (34H, m), 5.01 (4H, s), 5.11 (8H, d), 5.80 (12H, s), 6.79 (2H, d), 7.00 (2H, d), 7.06 (2H, s), indicating that the product contains the polyetheramine benzoxazine oligomer TA as shown in the formula below, where R is ethyl, n = 1, and x + y + z is approximately 5–6.

[0099]

[0100] Example 5

[0101] Synthesis of polyamine monomers containing benzoxazine units (TS)

[0102] Synthesis method: A 20 wt% toluene solution was prepared by mixing 2.05 mol of polyetheramine T-403, 3.9 mol of paraformaldehyde, and 1 mol of bisphenol S. The solution was heated to 100 °C and refluxed with stirring for 8 h. After the reaction was completed, the mixture was cooled to room temperature, and the toluene was removed using a rotary evaporator. The product was washed three times with n-hexane. The 1H NMR spectrum results were as follows: 1 NMR (400MHz, CDCl3) δ 0.9 (6H, t), 1.12 (18H, d), 1.37 (18H, d), 1.52 (4H, m), 1.69-1.72 (4H, m), 2.79 (2H, m), 3.12 (4H, m), 3.34-3.71 (34H, m), 5.01 (4H, s), 5.11 (8H, d), 5.80 (12H, s), 7.04 (2H, d), 7.63 (2H, s), 7.88 (2H, d), indicating that the product contains the polyetheramine benzoxazine oligomer TS as shown in the formula below, where R is ethyl, n = 1, and x + y + z is approximately 5-6.

[0103]

[0104] Example 6

[0105] The steps for preparing an interpenetrating polyamide network membrane are as follows:

[0106] At room temperature (20°C), a pre-cut polysulfone-based film was attached to a frame. The frame was a square with sides of 10cm and a thickness of approximately 8mm. 20ml of an aqueous solution containing 4wt% of the DA monomer prepared in Example 1, 6wt% camphor sulfonic acid, 3wt% triethylamine, 20wt% isopropanol, and 67wt% water was poured onto the polysulfone-based film surface enclosed by the frame. After 5 minutes, the aqueous solution within the frame was poured off. Excess aqueous phase on the film surface was removed by squeezing with a rubber roller. Then, 20ml of a 0.1wt% Isopar G solution was poured onto the polysulfone-based film surface to initiate an interfacial polymerization reaction. After 2 minutes, excess oil phase was poured off, yielding a polyamide separation layer. Infrared spectroscopy (e.g., ...) was performed. Figure 1 As shown), at 942cm -1 It contains characteristic peaks of the benzoxazine ring.

[0107] The polyamide separation layer was placed in a forced-air drying oven and heated to 150°C to induce the ring-opening polymerization of the benzoxazine structural units for 5 minutes, completing the reaction and obtaining an interpenetrating polyamide membrane. Its infrared (e.g., Figure 2 (As shown) Test results show that the benzoxazine ring is at 942 cm⁻¹-1 The characteristic peaks are significantly smaller, and the range of 3200-3400 cm⁻¹ is reduced. -1 The significantly stronger hydroxyl peak indicates that ring-opening polymerization has occurred.

[0108] The performance of the diaphragm was tested, and the results are shown in Table 1.

[0109] Example 7

[0110] The steps for preparing an interpenetrating polyamide network membrane are as follows:

[0111] At room temperature (30°C), the cut polysulfone-based membrane was attached to a plate frame. 20 ml of an aqueous solution containing 0.5 wt% of the ED-F monomer prepared in Example 2, 3 wt% camphor sulfonic acid, 1.5 wt% triethylamine, 1 wt% N,N-dimethylformamide, and 94 wt% water was poured onto the surface of the polysulfone-based membrane. After waiting 0.5 minutes, the aqueous solution in the plate frame was poured off, and excess aqueous phase was removed by squeezing with a rubber roller. Then, 10 ml of a 0.1 wt% pyromellitic trichlorohexane solution was poured onto the surface of the polysulfone-based membrane to carry out the interfacial polymerization reaction. After waiting 1 minute, excess oil phase was poured off, and the membrane was placed in a 120°C forced-air oven and heated for 10 minutes to complete the reaction, obtaining an interpenetrating polyamide membrane.

[0112] The performance of the diaphragm was tested, and the results are shown in Table 1.

[0113] Example 8

[0114] The steps for preparing an interpenetrating polyamide network membrane are as follows:

[0115] At room temperature (25°C), the cut polysulfone-based film was attached to a plate frame. 20 ml of an aqueous solution containing 8 wt% of the EDR-F monomer prepared in Example 3, 1 wt% camphor sulfonic acid, 0.5 wt% triethylamine, 4 wt% ethylene glycol methyl ether, and 86.5 wt% water was poured onto the surface of the polysulfone-based film. After waiting for 4 minutes, the aqueous solution in the plate frame was poured off, and excess aqueous phase was removed by squeezing with a rubber roller. Then, 5 ml of an Isopar G solution containing 2 wt% isophthaloyl chloride and 20 wt% toluene was poured onto the surface of the polysulfone-based film to carry out the interfacial polymerization reaction. After waiting for 0.5 minutes, excess oil phase was poured off, and the film was placed in a 130°C forced-air oven and heated for 8 minutes to complete the reaction, obtaining an interpenetrating polyamide membrane.

[0116] The performance of the diaphragm was tested, and the results are shown in Table 1.

[0117] Example 9

[0118] The steps for preparing an interpenetrating polyamide network membrane are as follows:

[0119] At room temperature (25°C), the cut polysulfone-based film was attached to a plate frame. 20 ml of an aqueous solution containing 3.2 wt% TA monomer prepared in Example 4, 6 wt% camphor sulfonic acid, 3 wt% triethylamine, 5 wt% ethanol, and 82.8 wt% water was poured onto the surface of the polysulfone-based film. After waiting for 2 minutes, the aqueous solution in the plate frame was poured off, and excess aqueous phase was removed by squeezing with a rubber roller. Then, 20 ml of a 0.08 wt% Isopar G solution was poured onto the surface of the polysulfone-based film to carry out the interfacial polymerization reaction. After waiting for 5 minutes, excess oil phase was poured off, and the film was placed in a 160°C forced-air oven and heated for 3 minutes to complete the reaction, obtaining an interpenetrating polyamide membrane.

[0120] The performance of the diaphragm was tested, and the results are shown in Table 1.

[0121] Example 10

[0122] The steps for preparing an interpenetrating polyamide network membrane are as follows:

[0123] At room temperature (25°C), the cut polysulfone-based film was attached to a plate frame. 20 ml of an aqueous solution containing 3.5 wt% TS monomer prepared in Example 5, 6 wt% camphor sulfonic acid, 3 wt% triethylamine, 1 wt% N-methylpyrrolidone, and 86.5 wt% water was poured onto the surface of the polysulfone-based film. After waiting for 3 minutes, the aqueous solution in the plate frame was poured off, and excess aqueous phase was removed by squeezing with a rubber roller. Then, 20 ml of a 0.15 wt% Isopar G solution of pyromellitic trimethylol chloride was poured onto the surface of the polysulfone-based film to carry out the interfacial polymerization reaction. After waiting for 3 minutes, excess oil phase was poured off, and the film was placed in a 160°C forced-air oven and heated for 3 minutes to complete the reaction, obtaining an interpenetrating polyamide membrane.

[0124] The performance of the diaphragm was tested, and the results are shown in Table 1.

[0125] Comparative Example 1

[0126] The polyamide membrane was prepared according to the steps in Example 6, except that the post-crosslinking oven heating step was omitted from the polyamide separation layer, while the other conditions remained the same. After obtaining the polyamide separation layer, it was directly used as a membrane product.

[0127] The performance of the diaphragm was tested, and the results are shown in Table 1.

[0128] Comparative Example 2

[0129] The steps for preparing a polyamide film are as follows:

[0130] At room temperature (25°C), the cut polysulfone-based membrane was attached to a plate frame. 20 ml of an aqueous solution containing 1.5 wt% piperazine monomer, 6 wt% camphor sulfonic acid, 3 wt% triethylamine, and 89.5 wt% water was poured onto the surface of the polysulfone-based membrane. After waiting for 5 minutes, the aqueous solution in the plate frame was poured off. Excess aqueous phase was removed by squeezing with a rubber roller. Then, 0.1 wt% Isopar G solution of pyromellitic trimethylol chloride was poured onto the surface of the polysulfone-based membrane. After waiting for 2 minutes, excess oil phase was poured off. The membrane was placed in a 70°C forced-air oven and heated for 10 minutes to complete the reaction, yielding a polyamide nanofiltration membrane.

[0131] The performance of the diaphragm was tested, and the results are shown in Table 1.

[0132] Comparative Example 3

[0133] The steps for preparing the polybenzoxazine membrane are as follows:

[0134] At room temperature (25°C), the cut polysulfone-based membrane is attached to a plate frame. 20 ml of an aqueous solution containing 3.5 wt% TS monomer, 6 wt% camphor sulfonic acid, 3 wt% triethylamine, and 87.5 wt% water is poured onto the surface of the polysulfone-based membrane. After waiting for 5 minutes, the aqueous solution in the plate frame is poured off. Excess aqueous phase is removed by squeezing with a rubber roller. The membrane is then placed in a 160°C forced-air oven and heated for 3 minutes to complete the reaction, yielding an interpenetrating network polybenzoxazine membrane.

[0135] The performance of the diaphragm was tested, and the results are shown in Table 1.

[0136] Comparative Example 4

[0137] To prepare a polybenzoxazine membrane, cashew phenol and γ-aminopropyltriethoxysilane were used as raw materials to replace bisphenol and polyetheramine in Comparative Example 1, respectively, to synthesize benzoxazine monomers. The synthesis process is as described in Example 1.

[0138] Since the amine groups in the raw materials have already participated in the reaction, they cannot continue to react with acyl chloride to generate polyamide, and the product has poor water solubility and cannot undergo interfacial polymerization. Therefore, a separation membrane is prepared by coating. A 1 wt% toluene solution of benzoxazine synthesized in this comparative example is coated on the surface of the polysulfone membrane. After draining, it is placed in a 160°C forced-air oven and heated for 10 minutes to obtain a polybenzoxazine membrane.

[0139] The performance of the diaphragm was tested, and the results are shown in Table 1.

[0140] Comparative Example 5

[0141] To prepare a polybenzoxazine membrane, bisphenol A and 2,5-bistrifluoromethylaniline were used as raw materials to replace bisphenol and polyetheramine in Comparative Example 1, respectively, to synthesize benzoxazine monomers. The synthesis process is as described in Example 1.

[0142] Since the amine groups in the raw materials have already participated in the reaction, they cannot continue to react with acyl chloride to generate polyamide, and the product has poor water solubility and cannot undergo interfacial polymerization. Therefore, a separation membrane is prepared by coating. A 1 wt% toluene solution of benzoxazine synthesized in this comparative example is coated on the surface of the polysulfone membrane. After draining, it is placed in a 160°C forced-air oven and heated for 10 minutes to obtain a polybenzoxazine membrane.

[0143] The performance of the diaphragm was tested, and the results are shown in Table 1.

[0144] Table 1. Diaphragm Performance Test Data

[0145]

Claims

1. A method for preparing an interpenetrating polyamide network film, characterized in that the steps include... include: (1) Polyamine monomers containing benzoxazine structural units were obtained by reacting polyetheramine, bisphenol compounds and formaldehyde; (2) The polyamine monomers from step (1) and acyl chlorides are subjected to interfacial polymerization on the base film to obtain a polyamide separation layer containing benzoxazine structural units; (3) Heating the polyamide separation layer in step (2) causes the benzoxazine structural units therein to undergo ring-opening polymerization to obtain an interpenetrating network polyamide film.

2. The preparation method according to claim 1, characterized in that, In step (1), the polyetheramine is a polyether containing two or more primary amine groups, wherein the polyether chain is obtained by ring-opening homopolymerization or copolymerization using ethylene oxide and / or propylene oxide as raw materials, and can be a linear polyether or a branched polyether.

3. The preparation method according to claim 2, characterized in that, The polyetheramine is a polyether containing 2-3 primary amine groups.

4. The preparation method according to claim 2, characterized in that, The polyetheramine has the structure described in Formula 1: Formula 1 In the formula, x takes values ​​from 2 to 100.

5. The preparation method according to claim 4, characterized in that, x takes values ​​from 2 to 70.

6. The preparation method according to claim 4, characterized in that, The polyetheramine is from Huntsman's JEFFAMINED series.

7. The preparation method according to claim 2, characterized in that, The polyetheramine has the structure described in Formula 2: Formula 2 In the formula, x takes values ​​from 1 to 10, y takes values ​​from 2 to 50, and z takes values ​​from 1 to 10.

8. The preparation method according to claim 7, characterized in that, x takes values ​​from 1 to 6, y takes values ​​from 2 to 40, and z takes values ​​from 1 to 6.

9. The preparation method according to claim 7, characterized in that, The polyetheramine is from Huntsman's JEFFAMINEED series.

10. The preparation method according to claim 2, characterized in that, The polyetheramine has the structure described in Formula 3: Formula 3 In the formula, x takes values ​​from 2 to 5.

11. The preparation method according to claim 10, characterized in that, x can be either 2 or 3.

12. The preparation method according to claim 10, characterized in that, The polyetheramine is from Huntsman's JEFFAMINEEDR series.

13. The preparation method according to claim 2, characterized in that, The polyetheramine has the structure described in Formula 4: Formula 4 In the formula, x takes values ​​from 4 to 90, y takes values ​​from 4 to 90, z takes values ​​from 4 to 90, and n takes values ​​from 0 to 3; R is selected from hydrogen atoms, methyl or ethyl atoms.

14. The preparation method according to claim 13, characterized in that, x takes values ​​from 5 to 85, y takes values ​​from 5 to 85, z takes values ​​from 5 to 85, and n takes values ​​of 0 or 1.

15. The preparation method according to claim 13, characterized in that, The polyetheramine is from Huntsman's JEFFAMINET series.

16. The preparation method according to claim 1, characterized in that, In step (1), the bisphenol compound has the structure shown in Formula 5: Formula 5 In the formula, R is selected from one of methylene, ethyl, isopropyl, butyl, hexafluoroisopropyl, thioether, sulfone, phenethyl, and trimethylcyclohexyl; and / or The formaldehyde is selected from formaldehyde aqueous solution or paraformaldehyde, and the concentration of the formaldehyde aqueous solution is 10-37 wt%.

17. The preparation method according to claim 16, characterized in that, The bisphenol compound is any one or a combination of at least two of bisphenol A, bisphenol F, and bisphenol S.

18. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of the polyetheramine, bisphenol compound, and formaldehyde is 2.02-2.5:1:3.8-4.3; and / or The reaction is carried out in a solvent environment, wherein the solvent is selected from any one or a combination of at least two of alcohol ethers and aromatic solvents; and / or The reaction is carried out at a temperature of 70-105℃ for a time of 4-12 hours.

19. The preparation method according to claim 18, characterized in that, The molar ratio of the polyetheramine, bisphenol compound and formaldehyde is 2.05-2.15:1:3.9-4.

2.

20. The preparation method according to claim 18, characterized in that, The alcohol ethers are selected from any one or a combination of two of dioxane and ethylene glycol methyl ether, and the aromatic solvents are selected from any one or a combination of two of toluene and xylene.

21. The preparation method according to claim 18, characterized in that, Based on the total mass of the reaction system being 100%, the amount of solvent used is 70-90% wt.

22. The preparation method according to claim 18, characterized in that, The reaction is carried out at a temperature of 80-100℃ for 6-10 hours.

23. The preparation method according to claim 1, characterized in that, In step (2), the polyamine monomer is dissolved in a polar solvent to prepare a solution for use.

24. The preparation method according to claim 23, characterized in that, The polar solvent is selected from methanol and water.

25. The preparation method according to claim 24, characterized in that, The polyamine monomer is dissolved in water to prepare an aqueous solution for use.

26. The preparation method according to claim 25, characterized in that, The concentration of the polyamine in the aqueous solution is 0.1-20%wt.

27. The preparation method according to claim 26, characterized in that, The concentration of the polyamine in the aqueous solution is 0.5-8%wt.

28. The preparation method according to claim 25, characterized in that, When the polyamine monomer is prepared as an aqueous solution, a water-soluble solvent is simultaneously added to the aqueous solution of the polyamine monomer. The water-soluble solvent is selected from any one or a combination of at least two of alcohol solvents, alcohol ether solvents, and polar organic solvents.

29. The preparation method according to claim 28, characterized in that, The alcohol solvent is selected from any one or a combination of at least two of methanol, ethanol, and isopropanol; the alcohol ether solvent is selected from any one or a combination of at least two of ethylene glycol methyl ether, ethylene glycol dimethyl ether, and propylene glycol methyl ether; and the polar organic solvent is selected from any one or a combination of at least two of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and acetone.

30. The preparation method according to claim 28, characterized in that, The mass ratio of the water-soluble solvent to water is 1:3.3-100.

31. The preparation method according to claim 1, characterized in that, In step (2), the acyl chloride is selected from difunctional acyl chloride or trifunctional acyl chloride. Difunctional acyl chloride or trifunctional acyl chloride can be used alone or in combination of two or more.

32. The preparation method according to claim 31, characterized in that, The 2-functional acyl chloride is selected from any one or a combination of at least two of terephthaloyl chloride, isophthaloyl chloride, and naphthaloyl chloride, and the 3-functional acyl chloride is selected from any one or a combination of at least two of pyromellitic tricarboxylic acid chloride, 1,3,5-cyclohexanetricarboxylic acid chloride, and 1,2,4-cyclobutanetricarboxylic acid chloride.

33. The preparation method according to claim 31, characterized in that, The acyl chloride is dissolved in a nonpolar solvent to prepare an oil phase solution for use. The nonpolar solvent is selected from any one or a combination of at least two of the following: straight-chain alkanes, isoalkanes, and aromatic solvents.

34. The preparation method according to claim 33, characterized in that, The straight-chain alkane is selected from any one or a combination of at least two of hexaane, octane, nonane, and decane; the isomeric alkane is selected from any one or a combination of at least two of Isopar E, Isopar G, and Isopar L; and the aromatic solvent is selected from any one or a combination of at least two of toluene, xylene, and trimethylbenzene.

35. The preparation method according to claim 33, characterized in that, The concentration of the acyl chloride in the oil phase solution is 0.08-2 wt%.

36. The preparation method according to claim 35, characterized in that, The concentration of the acyl chloride in the oil phase solution is 0.1-0.4 wt%.

37. The preparation method according to claim 1, characterized in that, In step (2), the base film is selected from polysulfone, polyethersulfone, polyphenylsulfone, polyphenylene sulfide, polyphenylene ether, polyphenylene sulfide sulfone, polyamide, polyimide, polyester, vinyl polymer, cellulose polymer; and / or In step (2), the interfacial polymerization reaction is carried out at room temperature for 0.5-5 min.

38. The preparation method according to claim 37, characterized in that, The vinyl polymer is selected from polyethylene, polypropylene, polyvinyl chloride, and polyacrylonitrile, and the cellulose polymer is selected from cellulose acetate and cellulose nitrate.

39. The preparation method according to claim 37, characterized in that, The interfacial polymerization reaction is carried out at a temperature of 20-30℃ for 1-2 minutes.

40. The preparation method according to claim 37, characterized in that, The mass concentration ratio of polyamine monomer in the aqueous phase solution to acyl chloride in the oil phase solution used for interfacial polymerization is 4-40:

1.

41. The preparation method according to claim 1, characterized in that, In step (3), the ring-opening polymerization reaction is carried out at a temperature of 120-160℃ and a reaction time of 3-10 min.

42. The preparation method according to claim 41, characterized in that, The ring-opening polymerization reaction is carried out at a temperature of 130-150℃ and a reaction time of 5-7 minutes.

43. An interpenetrating network polyamide film prepared by the method of any one of claims 1-42.

44. The use of the interpenetrating network polyamide film prepared by the method of any one of claims 1-42 or the interpenetrating network polyamide film of claim 43.

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