A polyamide composite film and its preparation method and application

Abstract

The present invention provides a polyamide composite membrane and its preparation method and application, it is characterized in that the dimer ratio measured by GC-MS is 0.95%-1.25%, and the yellow index is 3.5-9.8. The preparation method includes 1) mixing polyfunctional amine and polyfunctional carboxylic acid with water to obtain an aqueous phase solution; 2) mixing polyfunctional acyl chloride and acid amine condensation reagent with a non-polar solvent to obtain an oil phase solution; 3) coating the aqueous phase solution on a base film, then contacting the oil phase solution to carry out interfacial polymerization to obtain a polyamide layer; 4) adding the polyamide layer to a diazotizing agent aqueous solution to carry out a diazotization reaction to generate a diazonium salt, then adding it to water, using acid to adjust the pH to 2-6 for hydrolysis reaction, and obtaining a polyamide composite membrane. The preparation method of the present invention is simple, and the prepared polyamide composite membrane has a higher salt rejection rate and nitrate radical removal rate, and can be used for fluid selective filtration and desalination, and has a good prospect for industrialization.

Description

Technical Field

[0001] The invention belongs to the technical field of membranes and relates to a polyamide composite membrane and a preparation method and application thereof. Background Art

[0002] Polyamide composite membranes are often used in fluid filtration membranes. A typical application is the preparation of reverse osmosis membranes published by Cadotte et al. in US4277344. Porous polysulfone is used as the support layer. The membrane is first soaked in an aqueous polyamine solution, generally containing m-phenylenediamine, isophthalic acid, piperazine, aliphatic amines, polyetheramines, etc., and then coated with an alkane solution of polyacyl chlorides, generally containing isophthalic acid chloride, isophthalic acid chloride, terephthalic acid chloride, etc., to obtain an ultra-thin polyamide layer through interfacial polymerization. This functional layer only allows water molecules to pass through, while salt ions are retained. It is widely used in seawater desalination, brackish water desalination, sewage treatment and other fields.

[0003] The National Standard for Drinking Water Quality (GB 5749-2022) has strict restrictions on the nitrate content in drinking water, requiring it to be less than 10 ppm. Excessive nitrate content in natural water bodies can also lead to eutrophication and affect aquatic organisms and their ecosystems. The Comprehensive Sewage Discharge Standard (GB 8978-1996) has strict restrictions on total nitrogen and ammonia nitrogen in sewage, respectively. Nitrate is the remaining part of the total nitrogen after removing ammonia nitrogen. At present, there are two main methods for removing nitrate from water bodies: physical and chemical methods and biological methods. Reverse osmosis filtration to remove nitrate belongs to the physical and chemical method. The removal rate of nitrate ions by existing polyamide composite membranes is generally around 95%, which cannot reach a removal rate of more than 99% similar to that of sodium chloride. Through modification of polyacrylic acid pre-coating, it can be increased to more than 99% (Chen Yong et al., 2015, Research on the Enhanced Treatment of Nitrate Nitrogen in Wastewater by Reverse Osmosis Pre-coating Membrane, Environmental Science and Technology, 28(5), 12-15). The additional coating process has high requirements for existing production equipment, and a method for improving the nitrate removal rate that is compatible with existing equipment is needed.

[0004] The method of using a diazotizing agent to improve the flux of a composite membrane was first seen in US4888116 and was improved in CN102781560, further improving the boron removal performance and water permeability. However, additional steps were introduced, including the step of contacting the separation layer with a primary amino compound and the step of contacting the separation layer with a reagent that reacts with a diazonium salt or its derivatives. The operation was complicated and production control was difficult. Its guiding significance lies in using the yellow index as a characterization indicator of the reaction degree of the separation layer. The larger the yellow index, the higher the degree of coupling reaction of the diazonium salt. CN105848765 introduces a trialkyl phosphate compound into the aqueous phase and / or oil phase, and then performs a diazotization reaction. The response ratio of the 212m / z and 237m / z fragments in the flame ionization detector in the pyrolysis GC-MS results of the obtained separation layer at 650°C is used as an indicator of the relative conversion rate of the separation layer. A higher dimer ratio indicates the presence of more low-branched network structures and a greater water flux. The theory of this scheme is based on first obtaining a more open polyamide network and then refining the pore structure through a diazotization reaction. This scheme also has strict requirements for the control of the diazotization reaction, and production control is difficult.

[0005] Majamaa et al. pointed out in Pioneering demineralized and desalinated water cost reduction with innovative brackish water RO membrane technology, Desalination and Water Treatment, 51:4-6, 1151-1160 that compared with the brackish water reverse osmosis membrane developed in 1990, the commercial reverse osmosis membrane launched in 2012 not only increased the sodium chloride rejection rate from 99.5% to 99.7%, but also increased the flux from 51LMH to 70LMH, and the nitrate rejection rate from 95% to 99%. It can be seen that improving these three properties at the same time is a problem that people in this field are working hard to solve. Summary of the Invention

[0006] In view of the above-mentioned deficiencies in the prior art, the present invention aims to provide a polyamide composite membrane and a method for preparing the same. The polyamide composite membrane of the present invention has both high salt rejection and nitrate removal rates and can be used for selective filtration and desalination of fluids.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a polyamide composite membrane having a polyamide separation layer on a porous support layer, wherein the polyamide separation layer has the following characteristics:

[0009] a) using GC-MS (gas chromatography-mass spectrometry) to measure the ratio of the integrated areas of the response signals of the dimer structure represented by formula I and the dimer structure represented by formula II when pyrolyzed at 650° C. to be 0.95-1.25%, preferably 1.00-1.1%,

[0010]

[0011] b) Yellowness index is 3.5-9.8, preferably 5.0-8.0.

[0012] The present invention also provides a method for preparing a polyamide composite membrane, which can be used to prepare the above-mentioned polyamide composite membrane, and the preparation method comprises the following steps:

[0013] 1) mixing a polyfunctional amine, a polyfunctional carboxylic acid and water to obtain an aqueous solution;

[0014] 2) mixing a polyfunctional acyl chloride, an acid amine condensation reagent and a non-polar solvent to obtain an oil phase solution;

[0015] 3) coating the aqueous solution on the base film, and then contacting it with the oil phase solution to perform interfacial polymerization to obtain a polyamide layer;

[0016] 4) adding the polyamide layer to a diazotizing agent aqueous solution to carry out a diazotization reaction to generate a diazonium salt, then adding the layer to water, adjusting the pH to 2-6 with an acid, and carrying out a hydrolysis reaction at 20-70° C. to obtain a polyamide composite membrane.

[0017] In step 1) of the present invention, the functionality of the polyfunctional amine is 2-4; the polyfunctional amine is selected from one or more of aromatic polyamines and aliphatic polyamines, the aromatic polyamine is selected from one or more of m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene, and the aliphatic polyamine is selected from one or more of ethylenediamine, piperazine, diethylenetriamine, and triethylenetetramine; the polyfunctional amine is preferably m-phenylenediamine;

[0018] The concentration of the polyfunctional amine in the aqueous solution is 1-8 wt %, preferably 1.5-3 wt %.

[0019] In step 1) of the present invention, the functionality of the multifunctional carboxylic acid is not less than 3, preferably 3-4; and the multifunctional carboxylic acid is selected from one or more of trimesic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, tetrahydrofuran-2,3,4,5-tetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, benzene-1,2,4,5-tetracarboxylic acid, 1,2,3,4-cyclobutanetetracarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, and ethylenediaminetetraacetic acid, preferably trimesic acid;

[0020] The concentration of the multifunctional carboxylic acid in the aqueous solution is 0.08-2 wt %, preferably 0.2-1.0 wt %.

[0021] In step 2) of the present invention, the functionality of the multifunctional acyl chloride is not less than 2, preferably 2-3, and is selected from one or more of terephthaloyl chloride, isophthaloyl chloride, naphthalene dicarboxylic acid chloride, trimesoyl chloride, 1,3,5-cyclohexanetricarboxylic acid chloride, 1,2,4-cyclobutanetricarboxylic acid chloride, etc., preferably trimesoyl chloride;

[0022] The concentration of the polyfunctional acid chloride in the oil phase solution is 0.08-0.6 wt %, preferably 0.1-0.4 wt %.

[0023] In step 2) of the present invention, the acid-amine condensation reagent is selected from one or more of anhydride compounds, carbodiimide compounds, Burgess reagent compounds, benzotriazolium salts, pentafluorophenol compounds, azide compounds, triazine compounds, and acyl chloride compounds;

[0024] Preferably, the acid anhydride compound is selected from n-propylphosphonic anhydride, the carbodiimide compound is selected from dicyclohexylcarbodiimide and N,N'-diisopropylcarbodiimide, the Burgess reagent compound is selected from (methoxycarbonylsulfamoyl)triethylammonium hydroxide, and the benzotriazolium salt is selected from benzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate, azabenzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate, Fluorophosphate, the pentafluorophenol compound is selected from pentafluorophenol, pentafluorophenyl diphenyl phosphate, 4-nitrobenzenesulfonic acid pentafluorophenyl ester, bis(pentafluorophenyl) carbonate, the azide compound is selected from 2,4,6-triisopropylbenzenesulfonyl azide, the triazine compound is selected from 2-chloro-4,6-dimethoxy-1,3,5-triazine, and the acyl chloride compound is selected from diphenylphosphinyl chloride and 2,4,6-triisopropylbenzenesulfonyl chloride;

[0025] The concentration of the acid-amine condensation agent in the oil phase solution is 0.002-0.2 wt %, preferably 0.02-0.1 wt %.

[0026] In step 2) of the present invention, the non-polar solvent is selected from one or more of C6-C12 linear alkanes, C6-C12 isomeric alkanes, and C6-C12 aromatic solvents; preferably, the linear alkanes are selected from hexane, octane, nonane, and decane; the isomeric alkanes are selected from Isopar E, Isopar G, and Isopar L; and the aromatic solvent is selected from toluene, xylene, and trimethylbenzene; the non-polar solvent is more preferably Isopar G.

[0027] In the present invention, the ratio of the mass concentration of the polyfunctional amine in the aqueous solution in step 1) to the mass concentration of the polyfunctional acyl chloride in the oil solution in step 2) is preferably 10-40:1, preferably 15-30:1.

[0028] In the present invention, the coating method in step 3) is selected from dip coating, slit coating, spray coating or flow coating.

[0029] In the present invention, the interfacial polymerization reaction in step 3) is carried out at room temperature, preferably 20-30° C., and for 0.5-5 min, preferably 1-2 min.

[0030] Preferably, the aqueous phase solution is coated on the base film to remove excess aqueous phase, and then contacted with the oil phase solution to perform an interfacial polymerization reaction; after the interfacial reaction is completed, the excess oil phase is removed and then the next reaction is carried out, wherein the excess oil phase can be removed by conventional air knife, water knife or oven methods, preferably by oven method, the oven temperature is preferably 50-110°C, and the drying time is 20-120s; the membrane after removing the oil phase is then washed with water to remove the residual aqueous phase and oil phase solution.

[0031] In the present invention, in the interfacial polymerization reaction of step 3), in order to regulate the reaction rate and the properties of the final product, the temperature of the solvent phase participating in the reaction can be changed to control the interfacial polymerization reaction time. Auxiliary agents such as acid binding agents (such as sodium hydroxide, camphorsulfonic acid and triethylamine salts), solubilizers (such as toluene), complexing agents (such as phosphate compounds), humectants (such as glycerol), etc. can also be added to the reaction; the above-mentioned auxiliary agents can be added to the aqueous phase solution or the oil phase solution, and their types and amounts are conventionally selected in the art and are not specifically limited in the present invention;

[0032] Preferably, the aqueous solution of the embodiment of the present invention adopts a solution that, based on the total mass of the aqueous solution being 100%, its composition may further include 1-6 wt % of camphorsulfonic acid and 0.5-3 wt % of triethylamine.

[0033] In the present invention, the base membrane in step 3) is selected from a non-woven fabric-supported porous support membrane, comprising a non-woven fabric layer and a porous support layer;

[0034] The non-woven fabric layer is selected from polyester non-woven fabric, with a thickness of 80-110 μm and an air permeability of 0.5-2.5 cm 3 / cm 2 / s (test method refers to JIS L 109-A);

[0035] The porous support layer has a thickness of 30-60 μm and a surface pore size of about 10-50 nm, and its polymer material is selected from one or more of polysulfone, polyethersulfone, polyphenylsulfone, polyphenylene sulfide, polyphenylene ether, polyphenylene sulfide sulfone, polyamide, polyimide, polyester, vinyl polymer, and cellulose polymer; preferably, the vinyl polymer is selected from polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile, etc., and the cellulose polymer is selected from cellulose acetate, cellulose nitrocellulose, etc.; more preferably, it is polysulfone.

[0036] The base membrane used in the present invention is a product disclosed in the prior art and can be purchased or made by oneself. The present invention has no special requirements for its source. For example, the commercially available product US050 membrane of Zhongke Ruiyang Membrane Technology (Beijing) Co., Ltd. can be used; for example, for self-production, reference can be made to the literature Wang Yushuang et al. Preparation and research of reverse osmosis membrane base membrane. Petrochemical Applications, 2019, 38(12):4, "Base membrane regulation and its influence on composite membrane structure and performance" Tian Xinxia's 2015 doctoral dissertation at Tianjin University.

[0037] Preferably, the porous support layer can be obtained by wet phase conversion to obtain an asymmetric pore structure. In some examples, the specific preparation method of the base membrane of the present invention is:

[0038] The polymer is dissolved in a polar solvent to obtain a polymer solution with a concentration of 15-20 wt%, which is then degassed and filtered, coated on a non-woven fabric, and then immersed in pure water to complete curing at room temperature (curing temperature is 5-30° C., preferably 10-25° C.), and then rinsed to obtain a porous support layer;

[0039] The polar solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, preferably N,N-dimethylformamide; optionally, the polar solvent may further include a porogen, ethylene glycol methyl ether, water, polyethylene glycol, and the like.

[0040] In the present invention, the diazotizing agent in step 4) is nitrous acid. Since nitrous acid is unstable at room temperature, it is preferably prepared by mixing an alkali metal salt of nitrous acid (such as sodium nitrite or potassium nitrite) with an inorganic acid (such as hydrochloric acid, sulfuric acid or phosphoric acid).

[0041] In the aqueous solution of the diazotizing agent, the concentration of the alkali metal salt of nitrous acid is 0.1-0.4 wt %, and the pH value is 1.5-3.5 after adding the inorganic acid.

[0042] In the present invention, the diazotization reaction in step 4) is carried out at a temperature of 4-35°C, preferably 20-30°C, and for a time of 30-200s, preferably 60-120s;

[0043] In the present invention, the acid used to adjust the pH in step 4) is selected from organic acids and / or inorganic acids, the organic acid is selected from citric acid, p-toluenesulfonic acid, tartaric acid, preferably citric acid, and the inorganic acid is selected from hydrochloric acid, sulfuric acid, phosphoric acid, preferably sulfuric acid.

[0044] In the present invention, the hydrolysis reaction in step 4) is carried out at a temperature of 20-70° C., preferably 40-60° C., for a time of 30-200 s, preferably 60-120 s; and the pH value of the system is adjusted to 2-6 by acid during the hydrolysis reaction.

[0045] In the present invention, after the hydrolysis reaction in step 4) is completed, a drying process is further included. The obtained wet film is moisturized with a moisturizer (such as glycerol) and then dried in an oven to obtain a dry film, i.e., a polyamide composite film product.

[0046] The method for preparing the polyamide composite membrane of the present invention first prepares a polyamide layer (1) having a relatively compact network structure, then obtains a diazonium salt (2) through a diazotization reaction, and then obtains a more open pore structure (3) by hydrolyzing most of the diazonium salt. Finally, a polyamide composite membrane with excellent performance and simple production control is obtained. The reaction mechanism can be explained with reference to the following formula:

[0047]

[0048] (1) Polyamide network after interfacial polymerization

[0049]

[0050] (2) Polyamide network after diazotization reaction

[0051]

[0052] (3) Polyamide network after hydrolysis of diazonium salt

[0053] The polyamide composite membrane of the present invention, by characterizing the dimer ratio, can be seen that the polyamide layer of this solution is more compact, and by characterizing the yellow index, it can be seen that most of the diazonium salt of the present invention is hydrolyzed, and a small amount of cross-linked network with extended conjugated structure is generated.

[0054] In the prior art, due to the residual large amount of carboxyl on the polyamide composite film surface, acid amine condensation reagent is mainly used for polyamide surface carboxyl activation, and other chemical structures of grafting are modified, and the application method that acid amine condensation reagent is directly added in interfacial polymerization reaction is not reported, the inventor studies and finds that its main reason is that what participate in reaction in interfacial polymerization is acyl chloride and amine, carboxylic acid functional group is due to the hydrolysis generation of acyl chloride, and the interfacial polymerization reaction of acyl chloride and amine is just stopped in very short time (1-2 minute), and condensation reagent is too late to complete the activation of carboxyl and thus plays a role. The inventor, by concentrating on research, returns to the acid amine condensation reagent kind by special limitation, and coordinates to add multifunctional carboxylic acid compound in water phase, can effectively solve this problem. The present invention, by being directly applied to acid amine condensation reagent in interfacial polymerization reaction process, can generate the polyamide network that crosslinking degree is higher, its main mechanism is by the introduction of condensation reagent, activation carboxylate radical, makes it possible to complete dehydration with amine group under relatively mild conditions to form amide bond. On the other hand, the present invention also reconstructs a polyamide structure with a more uniform pore size distribution through a diazotization reaction, so that the final polyamide composite membrane not only has a larger water production capacity but also a higher desalination rate. It was unexpectedly found that the obtained membrane also has a significantly improved nitrate removal rate.

[0055] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0056] In the present invention, an acid-amine condensation reagent is first mixed with an oil solution of a polyfunctional acid chloride, and a polyfunctional carboxylic acid is pre-mixed with an aqueous solution of a polyfunctional amine. The reaction is then carried out to form a polyamide layer, which is then diazotized and hydrolyzed to obtain a polyamide composite membrane. The preparation method is simple, and the resulting polyamide composite membrane not only has a higher water yield, but also a higher salt rejection rate and a high nitrate removal rate, suggesting promising prospects for industrialization. DETAILED DESCRIPTION

[0057] In order to better understand the technical solutions of the present invention, the present invention is further described below with reference to the following embodiments, but the present invention is not limited to the following embodiments.

[0058] 1. In the various embodiments and comparative examples of the present invention, the main raw materials were obtained from the following sources. Unless otherwise specified, they were purchased from common commercial sources:

[0059] Polysulfone was purchased from Shanghai Kaiyin Chemical Co., Ltd., and its agent is BASF of Germany, model Ultrason S6010 polysulfone;

[0060] Polyester non-woven fabric (thickness 90μm, air permeability 2.1cm 3 / cm 2 / s), purchased from Xinyan (Shanghai) New Material Technology Co., Ltd., which is the agent of Japan Awa Paper KS7709 non-woven fabric;

[0061] A polysulfone-based membrane is prepared by dissolving polysulfone in N,N-dimethylformamide to prepare a solution containing 18 wt% solids. The polysulfone solution is coated on the surface of a non-woven fabric using a 250-μm-thick wet film preparation apparatus. After the non-woven fabric is exposed to air for 4-5 seconds, the non-woven fabric is immersed in pure water at room temperature. After immersion for 5 minutes, the phase inversion is completed. The polysulfone-based membrane that has completed the phase inversion is immersed in pure water at room temperature. The water is changed every 2 hours. After the residual solvent is thoroughly washed off, a polysulfone-based membrane with a porous support layer supported by the non-woven fabric is obtained (the porous support layer has a thickness of 50 μm and a surface pore size of approximately 30 nm). The membrane is then cut and set aside.

[0062] Pentafluorophenyl 4-nitrobenzenesulfonate, 2-chloro-4,6-dimethoxy-1,3,5-triazine, 2,4,6-triisopropylbenzenesulfonyl chloride, pentafluorophenol 2,4,6-triisopropylbenzenesulfonyl azide, and bis(pentafluorophenyl) carbonate were purchased from Suzhou Haofan Biotechnology Co., Ltd.

[0063] Pentafluorophenyl diphenyl phosphate was purchased from Shanghai Haohong Biopharmaceutical Technology Co., Ltd.;

[0064] 1-Propylphosphonic anhydride and diphenylphosphinic chloride were purchased from Chengdu Best Reagent Co., Ltd.;

[0065] Unless otherwise specified, the remaining reagents were purchased from Tokyo Chemical Industry (Shanghai) Co., Ltd. and were reagent grade raw materials.

[0066] 2. Testing methods of polyamide membranes in the examples and comparative examples:

[0067] Salt rejection rate and flux test method: refer to the salt rejection rate and flux test method in GB / T32373-2015 "Reverse Osmosis Membrane Test Method", the test liquid temperature is 25 ° C, the pH value is 7.0, the test liquid is 2000ppm sodium chloride aqueous solution, and the test pressure is 1.55MPa.

[0068] Nitrate removal rate test method: Add 150ppm of sodium nitrate to the 2000ppm sodium chloride desalination test solution, and adjust the pH of the test solution to 8. Use the nitrate detection reagent provided with the Hach DR6000 UV spectrophotometer to detect the nitrate ion concentration in the original solution and the permeate. The nitrate removal rate is calculated as follows:

[0069] R 硝酸根 =(1-C 透过液硝酸根 / C 测试液硝酸根 )*100%

[0070] Dimer ratio test method:

[0071] Extraction of polyamide layer: The non-woven fabric and porous support layer of the polyamide composite membrane are peeled off, and the remaining support layer and polyamide layer are soaked in solvent to dissolve the polysulfone and then removed, and the polyamide layer is obtained after filtration. In order to remove the polysulfone as thoroughly as possible, this scheme uses N, N-dimethylformamide (DMF) as a solvent. The sample without the non-woven fabric is added to 80°C DMF and stirred to dissolve the polysulfone. The undissolved polyamide separation layer is obtained by filtration, and methanol is added dropwise to the surface of the polyamide separation layer. If white flocs of polysulfone are precipitated, fresh DMF is used to stir and dissolve them again, filter, and add methanol dropwise to verify until no polysulfone flocs are precipitated. The sample is washed with methanol until the DMF content in the eluent is less than 1ppm. The sample is transferred to a vacuum oven and vacuum dried at 150°C for 24 hours to obtain the polyamide separation layer to be tested.

[0072] Pyrolysis Gas Chromatography-Mass Spectrometry: Fragment peak areas were determined using a Frontier Lab EGA / PY-3030D pyrolyzer coupled with a Shimadzu GCMS-QP2020 GCMS. The column model was DB-5MSUI 30m*0.25mm*0.25μm. The pyrolysis temperature was 650°C, the inlet temperature was 280°C, and the reflux ratio was 50:1. The GC temperature program was: 50°C to 80°C at 5°C / min, 80°C to 300°C at 15°C / min, and then at 300°C for 15 min. Helium was used as the carrier gas at 1 mL / min. The peak areas of fragments 212 m / z and 237 m / z were normalized to the sample weight, and the normalized peak areas were used to determine the ratio of fragments 212 m / z to 237 m / z. The normalized peak area for fragment 212 m / z divided by the sum of the normalized peak areas for all other fragments provides the fraction of that fragment relative to the polyamide, which was used to determine the dimer content reported for the samples in the Examples section.

[0073] Yellowness index test method:

[0074] The non-woven fabric of the polyamide composite membrane is peeled off from the porous support layer, leaving the support layer and the polyamide layer. The polyamide layer is placed face down on a glass plate and the polysulfone is dissolved and removed by immersion in a solvent. Since the residual amine will also develop color after oxidation, in order to remove the polysulfone and free color-developing impurities as fully as possible, this scheme uses N,N-dimethylformamide (DMF) as a solvent. The sample on the glass plate is rinsed with 80°C DMF. Methanol is added dropwise to the surface of the polyamide separation layer to verify whether the polysulfone has been completely removed. If white polysulfone flocs are precipitated, it is rinsed again with fresh 80°C DMF and methanol is added dropwise to verify until no polysulfone flocs are precipitated. The sample is washed with methanol until the DMF content in the eluate is less than 1 ppm. The sample is transferred to a vacuum oven and vacuum dried at 150°C for 24 hours to obtain a glass plate loaded with the polyamide separation layer to be tested. The transmittance is measured by a colorimeter to determine the yellowness index of the separation layer. The colorimeter uses a Hunter Lab VIS. The test method refers to the standard ASTM E313C.

[0075] Example 1

[0076] The steps for preparing the polyamide composite membrane are as follows:

[0077] 1) m-phenylenediamine, trimesic acid, camphorsulfonic acid, triethylamine and water are mixed to obtain an aqueous solution, wherein the concentrations of the components are 4 wt % of m-phenylenediamine, 1 wt % of trimesic acid, 3 wt % of camphorsulfonic acid and 1.5 wt % of triethylamine.

[0078] 2) Trimesoyl chloride, n-propylphosphonic anhydride and Isopar G were mixed to obtain an oil phase solution; the concentrations of the components were 0.15 wt% of trimesoyl chloride and 0.05 wt% of n-propylphosphonic anhydride.

[0079] 3) At room temperature of 20°C, the cut polysulfone base membrane is attached to a plate frame with a size of 10 cm square and a thickness of approximately 8 mm. 20 ml of the aqueous phase solution is poured on the surface of the polysulfone base membrane surrounded by the plate frame. After waiting for 5 minutes, the aqueous phase solution in the plate frame is poured out, and the excess aqueous phase on the surface of the base membrane is squeezed out with a rubber roller. Then, 20 ml of the oil phase solution is poured on the surface of the polysulfone base membrane. The interfacial polymerization reaction is carried out at 25°C for 1 minute, and then the excess oil phase is poured out. The film is placed in a 60°C forced air oven and dried for 1 minute, and then rinsed in pure water to obtain a polyamide layer.

[0080] 4) The polyamide layer was added to a 0.3 wt% sodium nitrite aqueous solution, the pH of the system was adjusted to 2.5 with hydrochloric acid, and a diazotization reaction was carried out at 25°C for 80 seconds to generate a diazonium salt. The polyamide layer was then added to water, the pH was adjusted to 5 with citric acid, and a hydrolysis reaction was carried out at 50°C for 90 seconds. The wet film was removed and moisturized with glycerin, and then placed in an oven for drying to produce a polyamide composite membrane. The performance test results are shown in Table 1.

[0081] Example 2

[0082] The steps for preparing the polyamide composite membrane are as follows:

[0083] 1) m-phenylenediamine, 2-phosphonobutane-1,2,4-tricarboxylic acid, camphorsulfonic acid, triethylamine and water are mixed to obtain an aqueous solution, wherein the concentrations of the components are 1 wt% of m-phenylenediamine, 2 wt% of 2-phosphonobutane-1,2,4-tricarboxylic acid, 6 wt% of camphorsulfonic acid and 3 wt% of triethylamine, respectively.

[0084] 2) Trimesoyl chloride, dicyclohexylcarbodiimide and a non-polar solvent Isopar G are mixed to obtain an oil phase solution; the concentrations of the components are 0.1 wt % of trimesoyl chloride and 0.2 wt % of dicyclohexylcarbodiimide.

[0085] 3) At room temperature of 20°C, the cut polysulfone base membrane is attached to a plate frame with a size of 10 cm square and a thickness of approximately 8 mm. 20 ml of the aqueous phase solution is poured on the surface of the polysulfone base membrane surrounded by the plate frame. After waiting for 5 minutes, the aqueous phase solution in the plate frame is poured out, and the excess aqueous phase on the surface of the base membrane is squeezed out with a rubber roller. Then, 20 ml of the oil phase solution is poured on the surface of the polysulfone base membrane. The interfacial polymerization reaction is carried out at 30°C for 5 minutes, and then the excess oil phase is poured out. The film is placed in a 110°C forced air oven and dried for 2 minutes, and then rinsed in pure water to obtain a polyamide layer.

[0086] 4) The polyamide layer was added to a 0.1 wt% potassium nitrite aqueous solution, the pH of the system was adjusted to 3.5 using sulfuric acid, and a diazotization reaction was carried out at 4°C for 200 seconds to generate a diazonium salt. The polyamide layer was then added to water, and the pH was adjusted to 4 using p-toluenesulfonic acid. A hydrolysis reaction was carried out at 20°C for 200 seconds. The wet film was removed and moisturized with glycerin, and then placed in an oven for drying to produce a polyamide composite membrane. The performance test results are shown in Table 1.

[0087] Example 3

[0088] The steps for preparing the polyamide composite membrane are as follows:

[0089] 1) m-phenylenediamine, tetrahydrofuran-2,3,4,5-tetracarboxylic acid, camphorsulfonic acid, triethylamine and water are mixed to obtain an aqueous solution, wherein the concentrations of the components are 8 wt % of m-phenylenediamine, 0.08 wt % of tetrahydrofuran-2,3,4,5-tetracarboxylic acid, 1 wt % of camphorsulfonic acid and 0.5 wt % of triethylamine.

[0090] 2) Trimesoyl chloride, N,N'-diisopropylcarbodiimide and a non-polar solvent, n-hexane, are mixed to obtain an oil phase solution; the concentrations of the components are 0.6 wt% of trimesoyl chloride and 0.002 wt% of N,N'-diisopropylcarbodiimide.

[0091] 3) At room temperature of 20°C, the cut polysulfone base membrane is attached to a plate frame with a size of 10 cm square and a thickness of approximately 8 mm. 20 ml of the aqueous phase solution is poured on the surface of the polysulfone base membrane surrounded by the plate frame. After waiting for 5 minutes, the aqueous phase solution in the plate frame is poured out, and the excess aqueous phase on the surface of the base membrane is squeezed out with a rubber roller. Then, 20 ml of the oil phase solution is poured on the surface of the polysulfone base membrane. The interfacial polymerization reaction is carried out at 20°C for 0.5 min, and then the excess oil phase is poured out. The film is placed in a 50°C forced air oven and dried for 20 seconds. Then, it is rinsed in pure water to obtain a polyamide layer.

[0092] 4) The polyamide layer was added to a 0.4 wt% sodium nitrite aqueous solution, the pH of the system was adjusted to 1.5 using hydrochloric acid, and a diazotization reaction was carried out at 35°C for 30 seconds to generate a diazonium salt. The polyamide layer was then added to water, the pH was adjusted to 6 using tartaric acid, and a hydrolysis reaction was carried out at 70°C for 30 seconds. The wet film was removed and moisturized with glycerin, and then placed in an oven for drying to produce a polyamide composite membrane. The performance test results are shown in Table 1.

[0093] Example 4

[0094] The preparation method was prepared according to Example 1, except that trimesic acid in the aqueous phase was replaced with 1,2,3,4-cyclopentanetetracarboxylic acid, and the concentrations of the components in the aqueous phase after replacement were 4 wt% of m-phenylenediamine, 1 wt% of 1,2,3,4-cyclopentanetetracarboxylic acid, 3 wt% of camphorsulfonic acid, and 1.5 wt% of triethylamine.

[0095] At the same time, n-propylphosphonic anhydride (acid amine condensation reagent) in the oil phase solution was replaced with (methoxycarbonylsulfamoyl)triethylammonium hydroxide. After the replacement, the concentrations of the components in the oil phase solution were 0.15 wt% of trimesoyl chloride and 0.05 wt% of (methoxycarbonylsulfamoyl)triethylammonium hydroxide.

[0096] The pH value of the diazonium salt hydrolysis was adjusted to 2 using hydrochloric acid. Other operations remained unchanged to prepare a polyamide composite membrane, and the performance test results are shown in Table 1.

[0097] Example 5

[0098] The preparation method was prepared according to Example 2, except that 2-phosphonobutane-1,2,4-tricarboxylic acid in the aqueous phase was replaced with benzene-1,2,4,5-tetracarboxylic acid, and the concentrations of the components in the aqueous phase after replacement were 1 wt% of m-phenylenediamine, 2 wt% of benzene-1,2,4,5-tetracarboxylic acid, 6 wt% of camphorsulfonic acid, and 3 wt% of triethylamine.

[0099] At the same time, dicyclohexylcarbodiimide in the oil phase solution was replaced by benzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate. After the replacement, the concentrations of the components in the oil phase solution were 0.1 wt% of trimesoyl chloride and 0.2 wt% of benzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate.

[0100] The pH of the diazonium salt hydrolysis was adjusted to 3 using sulfuric acid.

[0101] The other operations remained unchanged to prepare a polyamide composite membrane, and the performance test results are shown in Table 1.

[0102] Example 6

[0103] The preparation method was prepared according to Example 2, except that 2-phosphonobutane-1,2,4-tricarboxylic acid in the aqueous phase was replaced with 1,2,3,4-cyclobutanetetracarboxylic acid, and the concentrations of the components in the aqueous phase after replacement were 1 wt% of m-phenylenediamine, 2 wt% of 1,2,3,4-cyclobutanetetracarboxylic acid, 6 wt% of camphorsulfonic acid, and 3 wt% of triethylamine.

[0104] At the same time, dicyclohexylcarbodiimide in the oil phase solution was replaced by azabenzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate, and the non-polar solvent Isopar G was replaced by dodecane. After the replacement, the concentrations of each component in the oil phase solution were 0.1 wt% of trimesoyl chloride and 0.2 wt% of azabenzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate.

[0105] The pH of the diazonium salt hydrolysis was adjusted to 3 using phosphoric acid.

[0106] The other operations remained unchanged to prepare a polyamide composite membrane, and the performance test results are shown in Table 1.

[0107] Example 7

[0108] The preparation method was prepared according to Example 2, except that 2-phosphonobutane-1,2,4-tricarboxylic acid in the aqueous phase was replaced with 1,4,5,8-naphthalenetetracarboxylic acid, and the concentrations of the components in the aqueous phase after replacement were 1 wt% of m-phenylenediamine, 2 wt% of 1,4,5,8-naphthalenetetracarboxylic acid, 6 wt% of camphorsulfonic acid, and 3 wt% of triethylamine.

[0109] At the same time, dicyclohexylcarbodiimide in the oil phase solution was replaced by pentafluorophenol. After the replacement, the concentrations of the components in the oil phase solution were 0.1 wt % of trimesoyl chloride and 0.2 wt % of pentafluorophenol.

[0110] The other operations remained unchanged to prepare a polyamide composite membrane, and the performance test results are shown in Table 1.

[0111] Example 8

[0112] The preparation method was prepared according to Example 2, except that 2-phosphonobutane-1,2,4-tricarboxylic acid in the aqueous phase was replaced with ethylenediaminetetraacetic acid, and the concentrations of the components in the aqueous phase after replacement were 1 wt% of m-phenylenediamine, 2 wt% of ethylenediaminetetraacetic acid, 6 wt% of camphorsulfonic acid, and 3 wt% of triethylamine.

[0113] At the same time, dicyclohexylcarbodiimide in the oil phase solution was replaced by pentafluorophenyl diphenyl phosphate. After the replacement, the concentrations of the components in the oil phase solution were 0.1 wt % of trimesoyl chloride and 0.2 wt % of pentafluorophenyl diphenyl phosphate.

[0114] The other operations remained unchanged to prepare a polyamide composite membrane, and the performance test results are shown in Table 1.

[0115] Example 9

[0116] The preparation method was prepared according to Example 2, except that 2-phosphonobutane-1,2,4-tricarboxylic acid in the aqueous phase was replaced with trimesic acid, and the concentrations of the components in the aqueous phase after replacement were 1 wt% of m-phenylenediamine, 2 wt% of trimesic acid, 6 wt% of camphorsulfonic acid, and 3 wt% of triethylamine;

[0117] At the same time, dicyclohexylcarbodiimide in the oil phase solution was replaced by pentafluorophenyl 4-nitrobenzenesulfonate. After the replacement, the concentrations of the components in the oil phase solution were 0.1 wt % of trimesoyl chloride and 0.2 wt % of pentafluorophenyl 4-nitrobenzenesulfonate.

[0118] The other operations remained unchanged to prepare a polyamide composite membrane, and the performance test results are shown in Table 1.

[0119] Example 10

[0120] The preparation method was prepared according to Example 1, except that trimesic acid in the aqueous phase was replaced by 2-phosphonobutane-1,2,4-tricarboxylic acid. After replacement, the concentrations of the components in the aqueous phase solution were 4 wt% of m-phenylenediamine, 1 wt% of 2-phosphonobutane-1,2,4-tricarboxylic acid, 3 wt% of camphorsulfonic acid, and 1.5 wt% of triethylamine.

[0121] At the same time, n-propylphosphonic anhydride in the oil phase solution was replaced by bis(pentafluorophenyl) carbonate. After the replacement, the concentrations of the components in the oil phase solution were 0.15 wt % of trimesoyl chloride and 0.05 wt % of bis(pentafluorophenyl) carbonate.

[0122] The other operations remained unchanged to prepare a polyamide composite membrane, and the performance test results are shown in Table 1.

[0123] Example 11

[0124] The preparation method was prepared according to Example 1, except that trimesic acid in the aqueous phase was replaced by tetrahydrofuran-2,3,4,5-tetracarboxylic acid. After replacement, the concentrations of the components in the aqueous phase solution were 4 wt% of m-phenylenediamine, 1 wt% of tetrahydrofuran-2,3,4,5-tetracarboxylic acid, 3 wt% of camphorsulfonic acid, and 1.5 wt% of triethylamine.

[0125] At the same time, n-propylphosphonic anhydride in the oil phase solution was replaced by 2,4,6-triisopropylbenzenesulfonyl azide. After the replacement, the concentrations of the components in the oil phase solution were 0.15 wt % of trimesoyl chloride and 0.05 wt % of 2,4,6-triisopropylbenzenesulfonyl azide.

[0126] The other operations remained unchanged to prepare a polyamide composite membrane, and the performance test results are shown in Table 1.

[0127] Example 12

[0128] The preparation method was prepared according to Example 1, except that trimesic acid in the aqueous phase was replaced by 1,2,3,4-cyclopentanetetracarboxylic acid. After the replacement, the concentrations of the components in the aqueous phase solution were 4 wt% of m-phenylenediamine, 1 wt% of 1,2,3,4-cyclopentanetetracarboxylic acid, 3 wt% of camphorsulfonic acid, and 1.5 wt% of triethylamine.

[0129] At the same time, n-propylphosphonic anhydride in the oil phase solution was replaced by 2-chloro-4,6-dimethoxy-1,3,5-triazine. After the replacement, the concentrations of the components in the oil phase solution were 0.15 wt% of trimesoyl chloride and 0.05 wt% of 2-chloro-4,6-dimethoxy-1,3,5-triazine.

[0130] The other operations remained unchanged to prepare a polyamide composite membrane, and the performance test results are shown in Table 1.

[0131] Example 13

[0132] The preparation method was prepared according to Example 1, except that trimesic acid in the aqueous phase was replaced by benzene-1,2,4,5-tetracarboxylic acid. After replacement, the concentrations of the components in the aqueous phase solution were 4 wt% of m-phenylenediamine, 1 wt% of benzene-1,2,4,5-tetracarboxylic acid, 3 wt% of camphorsulfonic acid, and 1.5 wt% of triethylamine.

[0133] At the same time, n-propylphosphonic anhydride in the oil phase solution was replaced by diphenylphosphinic chloride. After the replacement, the concentrations of the components in the oil phase solution were 0.15 wt % of trimesoyl chloride and 0.05 wt % of diphenylphosphinic chloride.

[0134] The other operations remained unchanged to prepare a polyamide composite membrane, and the performance test results are shown in Table 1.

[0135] Example 14

[0136] The preparation method was prepared according to Example 1, except that trimesic acid in the aqueous phase was replaced by 1,2,3,4-cyclobutanetetracarboxylic acid. After the replacement, the concentrations of the components in the aqueous phase solution were 4 wt% of m-phenylenediamine, 1 wt% of 1,2,3,4-cyclobutanetetracarboxylic acid, 3 wt% of camphorsulfonic acid, and 1.5 wt% of triethylamine.

[0137] At the same time, n-propylphosphonic anhydride in the oil phase solution was replaced by 2,4,6-triisopropylbenzenesulfonyl chloride. After the replacement, the concentrations of the components in the oil phase solution were 0.15 wt % of trimesoyl chloride and 0.05 wt % of 2,4,6-triisopropylbenzenesulfonyl chloride.

[0138] The other operations remained unchanged to prepare a polyamide composite membrane, and the performance test results are shown in Table 1.

[0139] Comparative Example 1

[0140] The preparation method was prepared by referring to Example 1, except that the multifunctional carboxylic acid trimesic acid was not added in step 1) and other operations remained unchanged to prepare a polyamide composite membrane. The performance test results are shown in Table 1.

[0141] Comparative Example 2

[0142] The preparation method was prepared by referring to Example 1, except that in step 1) the polyfunctional carboxylic acid trimesic acid was replaced by acetic acid, and other operations remained unchanged to prepare a polyamide composite membrane. The performance test results are shown in Table 1.

[0143] Comparative Example 3

[0144] The preparation method was prepared by referring to Example 1, except that: in step 1), the multifunctional carboxylic acid trimesic acid was replaced by 1,3-benzenedisulfonic acid disodium salt, and other operations remained unchanged to prepare a polyamide composite membrane. The performance test results are shown in Table 1.

[0145] Comparative Example 4

[0146] The preparation method was prepared by referring to Example 1, except that the acid-amine condensation reagent n-propylphosphonic anhydride was not added in step 2. Other operations remained unchanged to prepare a polyamide composite membrane. The performance test results are shown in Table 1.

[0147] Comparative Example 5

[0148] The preparation method was referred to Example 1, except that the hydrolysis reaction in step 4) was omitted and other operations remained unchanged to prepare a polyamide composite membrane. The performance test results are shown in Table 1.

[0149] Comparative Example 6

[0150] The preparation method was referred to Example 1, except that the entire step 4) was omitted and other operations remained unchanged to prepare a polyamide composite membrane. The performance test results are shown in Table 1.

[0151] Comparative Example 7

[0152] The preparation method was prepared by referring to Example 1, except that the hydrolysis temperature in step 4) was changed to 80°C and other operations remained unchanged to obtain a polyamide composite membrane. The performance test results are shown in Table 1.

[0153] Comparative Example 8

[0154] The preparation method was prepared by referring to Example 1, except that: no multifunctional carboxylic acid was added to the aqueous phase in step 1), no acid-amine condensation reagent was added to the oil phase in step 2), and the entire step 4) was omitted. Other operations remained unchanged to obtain a polyamide composite membrane. The performance test results are shown in Table 1.

[0155] Comparative Example 9

[0156] The preparation method was referred to Example 1, except that no multifunctional carboxylic acid was added to the aqueous phase in step 1) and no acid-amine condensation reagent was added to the oil phase in step 2. Other operations remained unchanged to prepare a polyamide composite membrane. The performance test results are shown in Table 1.

[0157] Table 1 Diaphragm performance test data

[0158] diaphragm Flux LMH Desalination rate% Yellow Index Dimer ratio % Nitrate removal rate% Example 1 116 99.5 8.3 1.04 99.4 Example 2 90 99.6 3..5 0.95 97.7 Example 3 114 99.5 9.8 1.09 98.6 Example 4 115 99.7 6.0 1.04 99.5 Example 5 105 99.5 8.5 1.22 97.2 Example 6 106 99.6 6.8 1.02 99.8 Example 7 99 99.5 8.1 1.10 99.1 Example 8 102 99.5 6.3 1.03 99.9 Example 9 114 99.9 6.4 1.05 99.4 Example 10 120 99.5 8.4 1.25 97.9 Example 11 98 99.7 7.9 1.04 98.6 Example 12 99 99.6 8.0 1.23 97.5 Example 13 108 99.8 4.8 1.08 99.8 Example 14 109 99.7 9.2 1.07 98.6 Comparative Example 1 63 99.2 4.1 1.32 95.1 Comparative Example 2 41 98.1 3.9 0.93 92.3 Comparative Example 3 62 99.2 4.0 1.33 95.2 Comparative Example 4 58 99.5 3.7 1.43 94.7 Comparative Example 5 46 99.6 13.0 0.75 95.5 Comparative Example 6 34 99.7 2.1 0.81 96.1 Comparative Example 7 133 98.6 7.2 1.27 95.7 Comparative Example 8 47 99.3 2.3 1.36 94.2 Comparative Example 9 59 99.5 5.5 1.35 93.6

Claims

1. A method for preparing a polyamide composite membrane, characterized in that: The following steps are involved: 1) mixing a polyfunctional amine, a polyfunctional carboxylic acid and water to obtain an aqueous solution; 2) mixing a polyfunctional acyl chloride, an acid amine condensation reagent and a non-polar solvent to obtain an oil phase solution; 3) coating the aqueous solution on the base film, and then contacting it with the oil phase solution to perform interfacial polymerization to obtain a polyamide layer; 4) adding the polyamide layer to an aqueous solution of a diazotizing agent to carry out a diazotization reaction to generate a diazonium salt, which is then added to water, and the pH is adjusted to 2-6 with an acid, and a hydrolysis reaction is carried out at 20-70° C. to produce a polyamide composite membrane; In step 1), the functionality of the multifunctional carboxylic acid is not less than 3; In step 2), the acid-amine condensation reagent is selected from one or more of anhydride compounds, carbodiimide compounds, Burgess reagent compounds, benzotriazolium salts, pentafluorophenol compounds, azide compounds, triazine compounds, and acyl chloride compounds; The polyamide composite membrane has a polyamide separation layer on a porous support layer, and the characteristics of the polyamide separation layer include: a) using GC-MS, measuring the ratio of the integrated areas of the response signals of the dimer structure represented by formula I and the dimer structure represented by formula II during pyrolysis at 650° C. to be 0.95-1.25%, b) Yellow index is 3.5-9.

8.

2. The preparation method according to claim 1, characterized in that In step 1), the multifunctional amine has a functionality of 2-4 and is selected from one or more of aromatic polyamines and aliphatic polyamines, wherein the aromatic polyamine is selected from one or more of m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene, and the aliphatic polyamine is selected from one or more of ethylenediamine, piperazine, diethylenetriamine, and triethylenetetramine; The concentration of the multifunctional amine in the aqueous solution is 1-8 wt %; In step 1), the functionality of the multifunctional carboxylic acid is 3-4; it is selected from one or more of trimesic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, tetrahydrofuran-2,3,4,5-tetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, benzene-1,2,4,5-tetracarboxylic acid, 1,2,3,4-cyclobutanetetracarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, and ethylenediaminetetraacetic acid; The concentration of the multifunctional carboxylic acid in the aqueous solution is 0.08-2 wt %.

3. The preparation method according to claim 2, characterized in that The multifunctional amine is m-phenylenediamine.

4. The preparation method according to claim 2, characterized in that The concentration of the multifunctional amine in the aqueous solution is 1.5-3 wt %.

5. The preparation method according to claim 2, characterized in that The multifunctional carboxylic acid is trimesic acid.

6. The preparation method according to claim 2, characterized in that The concentration of the multifunctional carboxylic acid in the aqueous solution is 0.2-1.0 wt %.

7. The preparation method according to claim 1, characterized in that In step 2), the functionality of the multifunctional acyl chloride is 2-3, and the multifunctional acyl chloride is selected from one or more of terephthaloyl chloride, isophthaloyl chloride, naphthalene dicarboxylic acid chloride, trimesoyl chloride, 1,3,5-cyclohexanetricarboxylic acid chloride, and 1,2,4-cyclobutanetricarboxylic acid chloride; The concentration of the multifunctional acyl chloride in the oil phase solution is 0.08-0.6 wt %; In step 2), the acid anhydride compound is selected from n-propylphosphonic anhydride, the carbodiimide compound is selected from dicyclohexylcarbodiimide and N,N'-diisopropylcarbodiimide, the Burgess reagent compound is selected from (methoxycarbonylsulfamoyl)triethylammonium hydroxide, and the benzotriazolium salt is selected from benzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate, azabenzotriazole-N,N,N',N'-tetramethyluronium Hexafluorophosphate, the pentafluorophenol compound is selected from pentafluorophenol, pentafluorophenyl diphenyl phosphate, 4-nitrobenzenesulfonic acid pentafluorophenyl ester, bis(pentafluorophenyl) carbonate, the azide compound is selected from 2,4,6-triisopropylbenzenesulfonyl azide, the triazine compound is selected from 2-chloro-4,6-dimethoxy-1,3,5-triazine, and the acyl chloride compound is selected from diphenylphosphinyl chloride and 2,4,6-triisopropylbenzenesulfonyl chloride; The concentration of the acid-amine condensation agent in the oil phase solution is 0.002-0.2 wt %.

8. The preparation method according to claim 7, characterized in that The multifunctional acid chloride is trimesoyl chloride.

9. The preparation method according to claim 7, characterized in that The concentration of the multifunctional acyl chloride in the oil phase solution is 0.1-0.4 wt %.

10. The preparation method according to claim 7, characterized in that The concentration of the acid-amine condensation agent in the oil phase solution is 0.02-0.1 wt %.

11. The preparation method according to claim 1, characterized in that In step 2), the non-polar solvent is selected from one or more of C6-C12 linear alkanes, C6-C12 isoalkanes, and C6-C12 aromatic solvents; The ratio of the mass concentration of the polyfunctional amine in the aqueous phase solution of step 1) to the mass concentration of the polyfunctional acyl chloride in the oil phase solution of step 2) is 10-40:1; Step 3) The coating method is selected from dip coating, slit coating, spray coating or flow coating.

12. The preparation method according to claim 11, characterized in that The linear alkane is selected from hexane, octane, nonane, and decane; the isomeric alkane is selected from Isopar E, Isopar G, and Isopar L; and the aromatic solvent is selected from toluene, xylene, and trimethylbenzene.

13. The preparation method according to claim 11, characterized in that The non-polar solvent is Isopar G.

14. The preparation method according to claim 11, characterized in that The ratio of the mass concentration of the multifunctional amine in the aqueous phase solution in step 1) to the mass concentration of the multifunctional acyl chloride in the oil phase solution in step 2) is 15-30:

1.

15. The preparation method according to claim 1, characterized in that Step 3) The interfacial polymerization reaction is carried out at room temperature and for 0.5-5 min.

16. The preparation method according to claim 15, characterized in that The interfacial polymerization reaction has a reaction temperature of 20-30° C. and a reaction time of 1-2 minutes.

17. The preparation method according to claim 1, characterized in that Step 3) The aqueous phase solution is coated on the base film to remove excess aqueous phase, and then contacted with the oil phase solution to perform an interfacial polymerization reaction; after the interfacial reaction is completed, the excess oil phase is removed and the next reaction is carried out, wherein the excess oil phase is removed using an air knife, a water knife or an oven method; the membrane after the oil phase is removed is then washed with water to remove the residual aqueous phase and oil phase solution.

18. The preparation method according to claim 17, characterized in that The excess oil phase is removed by an oven method, the oven temperature is 50-110° C., and the drying time is 20-120 seconds.

19. The preparation method according to claim 1, characterized in that In step 3), the interfacial polymerization reaction is added with an auxiliary agent, which is selected from an acid binding agent, a solubilizer, a complexing agent, and a humectant.

20. The preparation method according to claim 19, characterized in that The acid binding agent is selected from sodium hydroxide, camphorsulfonic acid and triethylamine salt; the solubilizing agent is selected from toluene; the complexing agent is selected from phosphate compounds; and the moisturizing agent is selected from glycerol.

21. The preparation method according to claim 1, characterized in that In step 3), based on the total mass of the aqueous phase solution being 100%, the composition includes 1-6 wt % of camphorsulfonic acid and 0.5-3 wt % of triethylamine.

22. The preparation method according to claim 1, characterized in that Step 3) the base membrane is selected from a non-woven fabric supported porous support membrane, comprising a non-woven fabric layer and a porous support layer; The non-woven fabric layer is selected from polyester non-woven fabric with a thickness of 80-110 μm; The porous support layer has a thickness of 30-60 μm and a surface pore size of 10-50 nm, and its polymer material is selected from one or more of polysulfone, polyethersulfone, polyphenylsulfone, polyphenylene sulfide, polyphenylene ether, polyphenylene sulfide sulfone, polyamide, polyimide, polyester, vinyl polymer, and cellulose polymer.

23. The preparation method according to claim 22, characterized in that The non-woven fabric layer is selected from polyester non-woven fabric with an air permeability of 0.5-2.5cm 3 / cm 2 / s.

24. The preparation method according to claim 22, 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.

25. The preparation method according to claim 22, characterized in that The polymer material is polysulfone.

26. The preparation method according to claim 1, characterized in that Step 4) the diazotizing agent is nitrous acid; Step 4) The diazotization reaction is carried out at a temperature of 4-35° C. and a time of 30-200 s.

27. The preparation method according to claim 26, characterized in that The diazotizing agent is prepared by mixing an alkali metal salt of nitrous acid with an inorganic acid.

28. The preparation method according to claim 27, characterized in that In the aqueous solution of the diazotizing agent in step 4), the concentration of the alkali metal salt of nitrous acid is 0.1-0.4 wt %, and the pH value is 1.5-3.5 after adding the inorganic acid.

29. The preparation method according to claim 28, characterized in that The alkali metal salt of nitrous acid is selected from sodium nitrite and potassium nitrite; the inorganic acid is selected from hydrochloric acid, sulfuric acid and phosphoric acid.

30. The preparation method according to claim 26, characterized in that The diazotization reaction is carried out at a temperature of 20-30° C. and for a time of 60-120 seconds.

31. The preparation method according to claim 1, characterized in that The acid used in adjusting the pH in step 4) is selected from organic acids and / or inorganic acids, the organic acid is selected from citric acid, p-toluenesulfonic acid, and tartaric acid, and the inorganic acid is selected from hydrochloric acid, sulfuric acid, and phosphoric acid; Step 4) the hydrolysis reaction is carried out at a temperature of 20-70° C. for 30-200 seconds; the pH value of the system is adjusted to 2-6 by acid during the hydrolysis reaction; Step 4) The hydrolysis reaction is completed and further includes a drying process, wherein the obtained wet film is moisturized with a moisturizer and then placed in an oven for drying.

32. The preparation method according to claim 31, characterized in that The organic acid is citric acid, and the inorganic acid is sulfuric acid.

33. The preparation method according to claim 31, characterized in that The hydrolysis reaction temperature is 40-60° C. and the time is 60-120 seconds.

Images