Polyamide composite membrane and method for preparing same

Abstract

This specification discloses a polyamide composite membrane and a method for preparing the same. The preparation method includes the following steps: (1) mixing a halogen-containing polyfunctional amine, a polyfunctional amine, and water to obtain an aqueous solution; (2) mixing an amino-protecting reagent, a polyfunctional acyl chloride, and a nonpolar solvent to obtain an oil-phase solution; (3) coating the aqueous solution on a base film and then contacting it with the oil-phase solution to undergo interfacial polymerization to obtain a polyamide composite membrane; (4) placing the polyamide composite membrane in an amino-deprotecting solution to remove the amino-protecting reagent; and (5) adding the polyamide composite membrane from which the protecting reagent has been removed to an aqueous diazotizing reagent solution to undergo diazotization to produce a diazonium salt, which is then coupled under alkaline conditions to obtain a polyamide composite membrane. The preparation method is simple, and the resulting polyamide composite membrane has advantages such as significantly improved water generation, stable salt rejection, and resistance to oil contamination, making it suitable for industrial use.

Description

[Technical Field]

[0001] The present application relates to the field of membranes, for example, polyamide composite membranes and methods for their preparation. [Background technology]

[0002] Polyamide composite membranes are often used in fluid filtration. A typical application is the production of reverse osmosis membranes, as disclosed by Cadotte et al. in US Pat. No. 4,277,344. This involves first immersing a porous polysulfone support membrane in an aqueous polyamine solution (typically containing m-phenylenediamine, 1,3,5-triaminobenzene, piperazine, aliphatic amines, polyetheramines, etc.) and then coating it with an alkane solution of a polybasic acid chloride (typically containing trimesoyl chloride, isophthaloyl dichloride, terephthaloyl chloride, etc.), resulting in an ultrathin polyamide layer via an interfacial polymerization reaction. This functional layer allows only water molecules to pass through while blocking salt ions, and is widely used in fields such as seawater desalination, brackish water desalination, and sewage treatment.

[0003] Over time, fouling accumulates on the surface of polyamide membranes, inevitably reducing their water production. Oil contamination is a common contaminant found in industrial wastewater. CN101432058B synthesized hydrophilic polyethylene oxide molecular brush copolymers and grafted them onto the surface of polyamide membranes to improve their oil fouling resistance. However, the molecular brush synthesis process is complex, and the resulting coating significantly impacts the water production of polyamide membranes. The water production of sheets coated with the molecular brushes was reduced by 50%. Therefore, improving oil fouling resistance without compromising permeation flux is an urgent issue.

[0004] The use of diazotization agents to improve the chlorine resistance and permeation flux of composite membranes was first described in US Pat. No. 4,888,116 and subsequently improved in CN. 102,781,560, further improving boron rejection and water permeability. However, the introduction of additional steps, including contacting the separation layer with a primary amine compound and a reagent that reacts with a diazonium salt or its derivatives, makes the process more complex and production management more difficult. Its guiding principle lies in the use of the yellowness index as an indicator of the degree of reaction of the separation layer; a higher yellowness index indicates a higher degree of diazonium salt coupling reaction. CN. 105,848,765 introduces a trialkyl phosphate compound into the aqueous and / or oil phase, followed by diazotization. The resulting separation layer is subjected to pyrolysis GC-MS at 650°C, and the response ratio of the 212 m / z and 237 m / z fragments in a flame ionization detector is used as an indicator of the relative conversion rate of the separation layer. The higher the dimer ratio, the more low-branched the network structure, which indicates a higher water permeation flux. The theory behind this method is to first obtain a more open polyamide network, and then further refine the pore structure through the diazotization reaction. This method also has strict requirements for controlling the diazotization reaction, making production management more difficult.

[0005] The direct application of halogen-substituted polyamines and amino-protecting reagents to interfacial polymerization reactions has not been reported in the literature. The main reasons for this are that the halogen-substituted membranes become more hydrophobic, resulting in a loss of membrane permeation flux; and the introduction of amino-protecting reagents into interfacial polymerization results in some ammonia reacting with acyl chloride and becoming unable to crosslink, resulting in capping of polyamide chains, which reduces the crosslinking degree of the polymer, and impairs the salt rejection rate of the sheet. Summary of the Invention [Problem to be solved by the invention]

[0006] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0007] The present invention provides an improved polyamide composite membrane and a method for preparing the same, which has excellent permeation flux, salt rejection, and oil fouling resistance, and can be used for fluid filtration and desalination.

[0008] After extensive research, the present inventors have found that the above problems can be solved by combining a halogen-substituted polyamine with an amino-protecting reagent and introducing a diazotization crosslinking reaction. On the one hand, the amino-protecting reagent provides a large number of reactive amino sites for the diazotization crosslinking reaction, resulting in a polyamide network with a higher degree of crosslinking. On the other hand, the polyamide structure is reconstructed through the diazotization reaction, and the halogen-substituted polyamine is redistributed within the polymer network. The final polyamide composite membrane not only has a higher water generation rate, but also a higher salt rejection rate and better oil-fouling resistance. [Means for solving the problem]

[0009] The technical solutions adopted in the embodiments of the present application are as follows:

[0010] A polyamide composite membrane having a polyamide separation layer on a porous support layer, the polyamide separation layer having the following characteristics: a) the ratio of the response signal integral area of ​​the dimer structure represented by formula I to the dimer structure represented by formula II when thermally decomposed at 650°C as measured by GC-MS (gas chromatography-mass spectrometry) is 4.5% to 10%, preferably 6 to 8%; TIFF2025541995000001.tif33151b) A yellowness index of 15 to 40, preferably 25 to 35; c) The content of halogen atoms on the surface as measured by XPS is 0.15 to 1 mol %, preferably 0.25 to 0.75 mol %.

[0011] The present embodiment further provides a method for producing a polyamide composite membrane, which can be used to prepare the above-mentioned polyamide composite membrane, and the method includes: Step 1) mixing a halogen atom-containing polyfunctional amine, a polyfunctional amine, and water to obtain an aqueous phase solution; Step 2) mixing an amino-protecting reagent, a polyfunctional acyl chloride, and a non-polar solvent to obtain an oil phase solution; Step 3) of applying the aqueous phase solution onto the base film and then contacting it with the oil phase solution to carry out an interfacial polymerization reaction to obtain a polyamide composite film; Step 4) placing the polyamide composite membrane in an amino deprotection solution to remove the amino protecting reagent; and step 5) adding the polyamide composite membrane from which the amino-protecting reagent has been removed to an aqueous diazotization reagent solution to carry out a diazotization reaction to generate a diazonium salt, which is then coupled under alkaline conditions to obtain a polyamide composite membrane.

[0012] In step 1) of the present application, the polyfunctional amine has a functionality of 2 to 4 and is one or more selected from aromatic polyamines and aliphatic polyamines, the aromatic polyamine is one or more selected from m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene, the aliphatic polyamine is one or more selected from ethylenediamine, piperazine, diethylenetriamine, and triethylenetetramine, and the polyfunctional amine is preferably m-phenylenediamine.

[0013] The concentration of the polyfunctional amine in the aqueous phase solution is 1 to 8 wt %, preferably 1.5 to 3.5 wt %.

[0014] The halogen atom-containing polyfunctional amine may be one or a mixture of two or more thereof, and may be 4-trifluoromethoxy-m-phenylenediamine, 3,5-diaminobenzotrifluoride, 4-chloro-1,3-phenylenediamine, or 5-chloro-1,3-phenylenediamine, and is preferably 4-trifluoromethoxy-m-phenylenediamine; The concentration of the halogen atom-containing polyfunctional amine in the aqueous solution is 0.1 to 3 wt %, preferably 1 to 2.5 wt %.

[0015] In step 2) of the present invention, the polyfunctional acyl chloride has a functionality of 2 or more, preferably 2 to 3, and is one or more selected from terephthaloyl chloride, isophthaloyl dichloride, naphthalene-2,6-dicarboyl chloride, trimesoyl chloride, 1,3,5-cyclohexanetricarbonyl chloride, 1,2,4-cyclobutanetricarbonyl chloride, etc., and is preferably trimesoyl chloride; The concentration of the polyfunctional acyl chloride in the oil phase solution is 0.08 to 0.6 wt %, preferably 0.1 to 0.3 wt %.

[0016] the amino-protecting reagent is one or a mixture of two or more selected from the group consisting of trifluoroacetic anhydride, di-tert-butyl dicarbonate, triphenylmethyl chloride, and 9-fluorenylmethyl chloroformate; The concentration of the amino-protecting reagent in the oil phase solution is 0.01 to 10 wt %, preferably 0.05 to 2 wt %.

[0017] In step 2) of the present application, the non-polar solvent is one or more selected from the group consisting of C6 to C12 linear alkanes, C6 to C12 isoparaffins, and C6 to C12 aromatic solvents. Preferably, the linear alkanes are selected from hexane, octane, nonane, and decane, the isoparaffins are selected from Isopar E, Isopar G, and Isopar L, and the aromatic solvents are selected from toluene, xylene, and trimethylbenzene. The non-polar solvent is more preferably Isopar G.

[0018] In the present application, the ratio of the mass concentration of the polyfunctional amine in the aqueous phase solution in step 1) to the mass concentration of the polyfunctional acyl chloride in the oil phase solution in step 2) is preferably 10 to 40:1, more preferably 15 to 30:1.

[0019] In the present application, the coating method in step 3) is selected from dip coating, slit coating, spray coating, or flow coating.

[0020] In the interfacial polymerization reaction in step 3) of the present invention, the reaction temperature is 20 to 30°C, and the reaction time is 0.5 to 5 minutes, preferably 1 to 2 minutes; Preferably, the aqueous phase solution is applied to a base film, the excess aqueous phase is removed, and then the base film is contacted with an oil phase solution to carry out the interfacial polymerization reaction. After the interfacial polymerization reaction is completed, the excess oil phase is removed and the next step of the reaction begins. Here, the excess oil phase may be removed using a conventional method such as an air knife, water knife, or oven, but is preferably removed using an oven method, with the oven temperature preferably being 50 to 110°C and the drying time being 20 to 120 seconds. The sheet from which the oil phase has been removed is then washed with water to remove the remaining aqueous phase and oil phase solution.

[0021] In the present application, in the interfacial polymerization reaction of step 3), the temperature of the solvent phase involved in the reaction can be changed or the interfacial polymerization reaction time can be controlled to adjust the reaction rate and the performance of the final product. During the reaction, auxiliary agents such as acid binders (e.g., sodium hydroxide, camphorsulfonic acid, and triethylamine salts), solubilizers (e.g., toluene), complexing agents (e.g., phosphate ester compounds), and humectants (e.g., glycerin) can also be added. The above auxiliary agents may be added to the aqueous phase solution or the oil phase solution, and the type and amount used are all within the scope of common practice in the art and are not particularly limited in the present application.

[0022] Preferably, one of the forms adopted for the aqueous phase solution in the examples of the present application is that the total mass of the aqueous phase solution is 100%, and the composition may further include 1 to 6 wt % of camphorsulfonic acid and 0.5 to 3 wt % of triethylamine.

[0023] The base membrane in step 3) of the present invention is selected from a nonwoven-supported porous membrane comprising a nonwoven layer and a porous support layer; The nonwoven fabric layer is preferably a polyester nonwoven fabric, has a thickness of 80 to 110 μm, and preferably has an air permeability of 0.5 to 2.5 cm 3 / cm 2 / s (see JIS L 109-A for test method) The porous support layer has a thickness of 30 to 60 μm and a surface pore size of approximately 10 to 50 nm, and its polymer material is one or more selected from polysulfone, polyethersulfone, polyphenylenesulfone, polyphenylene sulfide, polyphenylene ether, polyphenylene sulfide sulfone, polyamide, polyimide, polyester, vinyl polymer, and cellulose-based polymer, and preferably the vinyl polymer is selected from polyethylene, polypropylene, polyvinyl chloride, and polyacrylonitrile, and the cellulose-based polymer is selected from cellulose acetate and cellulose nitrate, more preferably polysulfone.

[0024] The base membrane used in this application is a product disclosed in the related art and can be obtained by purchasing or self-preparing. This application does not impose any special requirements on its origin. For example, the commercially available US050 sheet from Zhongke Ruiyang Membrane Technology (Beijing) Co., Ltd. can be used. For example, if self-prepared, it can be prepared by referring to the method published in Wang Yushuang et al., "Preparation and Research of Base Membranes for Reverse Osmosis Membranes," Petrochemical Industry Applications, 2019, 38(12):4, "Control of Base Membrane and Its Effect on the Structure and Performance of Composite Membranes," Tian Xinxia's doctoral dissertation, Tianjin University, 2015.

[0025] Preferably, the porous support layer is obtained with an asymmetric pore structure by wet phase transformation, and in some examples, the specific preparation method employed for the base membrane of the present application is as follows.

[0026] The polymer is dissolved in a polar solvent to obtain a polymer solution with a concentration of 15 to 20 wt %, which is then degassed and filtered and applied to a nonwoven fabric, which is then immersed in pure water and cured at room temperature (curing temperature: 5 to 30°C, preferably 10 to 25°C), and then rinsed with pure water to obtain a porous support layer.

[0027] The polar solvent is one or more selected from N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, and is preferably N,N-dimethylformamide. Optionally, the polar solvent may include a porogen, ethylene glycol methyl ether, water, polyethylene glycol, and the like.

[0028] In step 4) of the present application, the polyamide composite membrane is placed in an amino deprotection solution to remove the amino protecting reagent, and different amino protecting reagents correspond to different removal steps.

[0029] When the amino-protecting reagent is trifluoroacetic anhydride and 9-fluorenylmethyl chloroformate, the removal solution is an alkaline aqueous solution having a pH in the range of 11.5 to 12.5, and the pH value is adjusted with one or more of sodium hydroxide, sodium carbonate, piperidine, and diethylamine, the removal temperature is 40 to 90°C, and the removal time is 0.5 to 2 minutes; When the amino-protecting reagent is di-tert-butyl dicarbonate and triphenylmethyl chloride, the removal solution is an acidic aqueous solution having a pH in the range of 1 to 2, and the pH value is adjusted with one or more of hydrochloric acid, sulfuric acid, acetic acid, and trifluoroacetic acid. The removal temperature is 60 to 90°C, and the removal time is 0.5 to 2 minutes.

[0030] The diazotization agent in step 5) of the present invention is nitrous acid. Because nitrous acid is unstable at room temperature, it is preferably produced by mixing an alkali metal salt of nitrous acid (e.g., sodium nitrite, potassium nitrite) with an organic acid and / or an inorganic acid. The organic acid is selected from citric acid, p-toluenesulfonic acid, and tartaric acid, preferably citric acid, and the inorganic acid is selected from hydrochloric acid, sulfuric acid, and phosphoric acid, preferably sulfuric acid.

[0031] In the aqueous diazotization reagent solution, the concentration of the alkali metal salt of nitrous acid is 0.1 to 0.4 wt %, and the pH value when an acid is added is 1.5 to 3.5.

[0032] The diazotization reaction in step 5) of the present invention is carried out at a temperature of 4 to 35°C, preferably 20 to 30°C, for a time of 30 to 200 seconds, preferably 60 to 120 seconds.

[0033] The coupling reaction in step 5) of the present invention is carried out at a temperature of 10 to 40°C, preferably 20 to 30°C, for 30 to 200 seconds, preferably 60 to 120 seconds. During the reaction, the pH of the system is adjusted to 8 to 11, preferably 9 to 10, with an alkali. The alkali used for adjusting the pH is selected from organic alkalis and / or inorganic alkalis, and the organic alkali is selected from triethylamine and N,N-dimethylaniline, preferably triethylamine, and the inorganic alkali is selected from sodium carbonate and sodium hydroxide, preferably sodium hydroxide.

[0034] After the coupling reaction of step 5) of the present invention is completed, the method further includes rinsing with pure water and drying, in which the obtained wet sheet is thoroughly rinsed with pure water, moisturized with a moisturizer (e.g., glycerin), and baked in an oven.

[0035] In the polyamide composite membrane of the present invention, characterization of the dimer ratio revealed that the resulting polyamide layer was looser and more sparse; characterization of the yellowness index revealed that most of the diazonium salt of the present invention was involved in coupling to produce a crosslinked network with an extended conjugated structure; and characterization of the halogen atom content in the polyamide layer revealed that hydrophobic halogen atoms were introduced into the polyamide structure.

[0036] In the related art, by properly controlling the dimer ratio and yellowness index, high salt rejection and permeation flux of the sheet can be simultaneously ensured, but in order to obtain good anti-fouling performance, the permeation flux of the sheet must be further sacrificed. After extensive research, the present applicant has unexpectedly discovered that by introducing a halogen-containing polyamine into the aqueous phase and an amino-protecting reagent into the oil phase, a polyamide layer with a relatively open structure, high porosity, and halogen atoms can be obtained. This can be combined with subsequent steps of removing the protecting reagent and a diazotization coupling reaction to reconstruct the polyamide separation layer structure and reduce the pore size, thereby simultaneously improving the permeation flux and salt rejection of the sheet, while significantly improving the anti-fouling effect of the resulting sheet.

[0037] Compared with the prior art, the technical solutions of the embodiments of the present application have the following beneficial effects:

[0038] In the present embodiment, first, an amino-protecting agent is mixed with an oil solution of a polyfunctional acyl chloride, then a halogen-containing polyamine is mixed uniformly with an aqueous polyfunctional amine solution, and then the mixture is reacted to prepare a polyamide layer. After that, the protecting agent is removed, and the polyamide composite membrane is obtained through diazotization and coupling. The preparation method is simple, and the prepared polyamide composite membrane not only has a higher water generation rate, but also a higher salt rejection rate, and the sheet's oil contamination resistance is greatly improved, which shows promising future industrialization.

[0039] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION OF THE INVENTION

[0040] In order to better understand the technical solutions of the present application, the present application will be further described below with reference to examples, but the present application is not limited to the following examples.

[0041] 1. In each example and comparative example of this application, the origins of the main raw materials are as follows, and unless otherwise specified, all are purchased through general commercial means.

[0042] Polysulfone: Ultrason S6010 polysulfone, model of BASF, Germany, purchased from Shanghai Kaiyin Chemical Co., Ltd., which is represented by Shanghai Kaiyin Chemical Co., Ltd.

[0043] Polyester nonwoven fabric (thickness 90 μm, air permeability 2.1 cm) 3 / cm 2 / s): Nonwoven fabric of model KS7709 from Japan Awa Paper Co., Ltd., purchased from Shinken (Shanghai) New Materials Technology Co., Ltd., which is represented by Shinken (Shanghai) New Materials Technology Co., Ltd.

[0044] Polysulfone membrane: The preparation method is as follows: polysulfone is dissolved in N,N-dimethylformamide to prepare a solution with a solids content of 18 wt%. The polysulfone solution is applied to the surface of a nonwoven fabric using a 250 micron-thick wet film preparation device. After leaving it in the air for 4 to 5 seconds, the nonwoven fabric is immersed in pure water at room temperature for 5 minutes to allow for phase conversion. After the phase conversion is complete, the polysulfone membrane is immersed in pure water at room temperature, with the water changed every 2 hours. After thoroughly washing off any residual solvent, a polysulfone membrane with a nonwoven fabric-supported porous support layer (porous support layer thickness: 50 μm, surface pore size: approximately 30 nm) is obtained, which is then cut into pieces for use.

[0045] 4-Trifluoromethoxy-m-phenylenediamine was purchased from Hangzhou Hi-Rui Chemical Co., Ltd.

[0046] 5-Chloro-1,3-phenylenediamine was purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0047] Unless otherwise noted, all other reagents were reagent-grade raw materials purchased from TCI (Shanghai) Chemical Industry Development Co., Ltd.

[0048] 2. Testing methods for polyamide membranes in the examples and comparative examples Test method for salt rejection and permeation flux: Refer to the test method for salt rejection and permeation flux in GB / T32373-2015 "Test method for reverse osmosis membranes". The test liquid temperature is 25°C, the pH value is 7.0, the test liquid is 1500 ppm sodium chloride aqueous solution, and the test pressure is 1.03 MPa.

[0049] Test method for oil contamination resistance: First, operate the sheet at 25°C, 1.55 MPa in a 2000 ppm sodium chloride aqueous solution, and measure the permeation flux and salt rejection rate. Then, add 100 ppm dodecane and 50 ppm sodium dodecyl sulfate (simulating oil contamination) to the test liquid, and after 100 hours of continuous operation, compare the decrease in permeation flux before and after contamination.

[0050] How to test the dimer ratio: Extraction of the polyamide layer: After peeling off the nonwoven fabric and porous support layer from the polyamide composite membrane, the remaining support layer and polyamide layer are immersed in a solvent to dissolve and remove the polysulfone, followed by filtration to obtain the polyamide layer. To remove the polysulfone as completely as possible, N,N-dimethylformamide (DMF) is used as the solvent. The sample from which the nonwoven fabric has been removed is added to DMF and stirred to dissolve the polysulfone. The resulting solution is filtered to obtain an undissolved polyamide separation layer. Methanol is then added dropwise to the surface of the polyamide separation layer. If white polysulfone flocs are precipitated, fresh DMF is added, followed by stirring and dissolution. The solution is filtered. Methanol is added dropwise until no more polysulfone flocs are precipitated. The sample is then washed with methanol until the DMF content in the eluate is less than 1 ppm. The sample is then transferred to a vacuum oven and vacuum dried at 150°C for 24 hours to obtain the polyamide separation layer to be tested.

[0051] Pyrolysis-gas chromatography-mass spectrometry: Gas chromatography-mass spectrometry was performed using a Frontier Lab EGA / PY-3030D pyrolyzer coupled with a Shimadzu GC-MS-QP2020 to detect the peak areas of the fragments. The chromatography column model was DB-5MSUI 30 m x 0.25 mm x 0.25 μm, the pyrolysis temperature was 650 °C, the inlet temperature was 280 °C, the reflux ratio was 50:1, and the gas chromatography temperature ramp was 5 °C / min from 50 °C to 80 °C, 15 °C / min from 80 °C to 300 °C, and 15 min at 300 °C. 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. Dividing the normalized peak area of ​​fragment 212 m / z by the sum of the normalized peak areas of all other fragments gives the percentage of that fragment relative to polyamide, and this method is used to measure the dimer content reported from the samples in the Examples section.

[0052] Yellowness Index Test Method: The nonwoven fabric of the polyamide composite membrane is peeled from the porous support layer, leaving the support layer and polyamide layer. The polyamide layer is placed face down on a glass plate and immersed in a solvent to dissolve and remove the polysulfone. Because residual amines also develop color after oxidation, N,N-dimethylformamide (DMF) is used as the solvent to thoroughly remove the polysulfone and free color-forming impurities. The sample on the glass plate is rinsed with DMF, and methanol is dripped onto the surface of the polyamide separation layer to verify complete removal of the polysulfone. If white polysulfone flocs are precipitated, the sample is washed again with fresh DMF and dripped with methanol until no more polysulfone flocs are precipitated. The sample is then washed with methanol until the DMF content in the eluate is less than 1 ppm. The sample is then transferred to a vacuum oven and vacuum dried at 150°C for 24 hours to obtain a glass plate bearing the polyamide separation layer under test. The yellowness index of the separation layer is determined by measuring the transmittance with a colorimeter. The colorimeter used was a Hunter Lab VIS, and the test method was based on standard ASTM E313C.

[0053] Halogen Atom Content: The sheet is immersed in pure water for cleaning and then dried. The element content on the surface of the dried sheet is tested using an X-ray photoelectron spectrometer (ESCALAB 250Xi, ThermoFischer, USA). The vacuum level in the analysis room is 4x10. -9 The pressure was 1000 kJ / s, the excitation source was an Al Ka ​​line (hv=1486.6 eV), the operating voltage was 14.6 kV, the filament current was 13.5 mA, and 20 cycles of signal accumulation were performed. The test pass energy was 20 eV, the step length was 0.1 eV, and charge correction was performed using the binding energy C1s=284.8 eV as the energy standard to detect the contents of C, N, O, F, Cl, Br, and I. The halogen atom content was the sum of the molar ratios of F, Cl, Br, and I among all the detected elements.

[0054] Example 1 The steps for preparing the polyamide composite membrane are as follows:

[0055] 1) m-phenylenediamine, 4-trifluoromethoxy-m-phenylenediamine, camphorsulfonic acid, triethylamine, and water were mixed to obtain an aqueous solution. The concentrations of each component were 4 wt% m-phenylenediamine, 1 wt% 4-trifluoromethoxy-m-phenylenediamine, 3 wt% camphorsulfonic acid, and 1.5 wt% triethylamine.

[0056] 2) Trimesoyl chloride, trifluoroacetic anhydride, and Isopar G were mixed to obtain an oil phase solution. The concentrations of each component were 0.15 wt% trimesoyl chloride and 0.05 wt% trifluoroacetic anhydride.

[0057] 3) At room temperature (20°C), the cut polysulfone membrane was attached to a frame. The frame was rectangular, measuring 10 cm on each side and approximately 8 mm thick. 20 ml of aqueous solution was poured onto the surface of the polysulfone membrane surrounded by the frame. After waiting for 5 minutes, the aqueous solution inside the frame was discarded and the excess aqueous phase was removed from the surface of the membrane using a rubber roller. 20 ml of oil solution was then poured onto the surface of the polysulfone membrane, and the interfacial polymerization reaction was carried out at 25°C for 1 minute. The excess oil phase was then discarded, and the membrane was placed in a 60°C fan oven for 1 minute of drying. The membrane was then thoroughly rinsed with pure water to obtain a polyamide composite membrane.

[0058] 4) The polyamide composite membrane was immersed in a sodium carbonate aqueous solution at 70°C and pH 12 for 2 minutes to complete the step of removing the protective reagent, and then thoroughly rinsed with pure water to obtain a polyamide composite membrane from which the protective reagent had been removed.

[0059] 5) The polyamide composite membrane from which the protective reagent had been removed was added to a 0.3 wt% aqueous sodium nitrite solution, and the pH of the system was adjusted to 2.5 with citric acid. A diazotization reaction was carried out at 25°C for 80 seconds to generate a diazonium salt. The resulting solution was added to an alkaline aqueous solution at 20°C whose pH had been adjusted to 10 with sodium hydroxide, and a coupling reaction was carried out for 90 seconds. After the reaction was completed, the sheet was rinsed with pure water, moistened with glycerin, and baked in an oven to obtain a polyamide composite membrane. The performance test results are shown in Table 1.

[0060] Example 2 The steps for preparing the polyamide composite membrane are as follows:

[0061] 1) m-phenylenediamine, 3,5-diaminobenzotrifluoride, camphorsulfonic acid, triethylamine, and water were mixed to obtain an aqueous solution. The concentrations of each component were 1 wt% m-phenylenediamine, 0.1 wt% 3,5-diaminobenzotrifluoride, 6 wt% camphorsulfonic acid, and 3 wt% triethylamine, respectively.

[0062] 2) Trimesoyl chloride, triphenylmethyl chloride, and the non-polar solvent Isopar G were mixed to obtain an oil phase solution. The concentrations of each component were 0.08 wt% trimesoyl chloride and 10 wt% triphenylmethyl chloride.

[0063] 3) At room temperature (20°C), the cut polysulfone membrane was attached to a frame. The frame was rectangular, measuring 10 cm on each side and approximately 8 mm thick. 20 ml of aqueous solution was poured onto the surface of the polysulfone membrane enclosed by the frame. After waiting for 5 minutes, the aqueous solution inside the frame was discarded and the membrane was pressed with a rubber roller to remove excess aqueous phase from the membrane surface. 20 ml of oil solution was then poured onto the surface of the polysulfone membrane, and interfacial polymerization was carried out at 30°C for 5 minutes. The excess oil phase was then discarded, and the membrane was placed in a 110°C fan oven to dry for 2 minutes. The membrane was then thoroughly rinsed with pure water to obtain a polyamide composite membrane.

[0064] 4) The polyamide composite membrane was immersed in a hydrochloric acid solution at 60°C and pH 1 for 2 minutes to complete the step of removing the protective reagent, and then thoroughly rinsed with pure water to obtain a polyamide composite membrane from which the protective reagent had been removed.

[0065] 5) The polyamide composite membrane from which the protective reagent had been removed was added to a 0.1 wt% aqueous potassium nitrite solution, and the pH of the system was adjusted to 3.5 with sulfuric acid. A diazotization reaction was carried out at 4°C for 200 seconds to generate a diazonium salt. The resulting solution was added to a 10°C alkaline aqueous solution whose pH had been adjusted to 8 with triethylamine, and a coupling reaction was carried out for 200 seconds. After the reaction was completed, the sheet was rinsed with pure water, moistened with glycerin, and baked in an oven to obtain a polyamide composite membrane. The performance test results are shown in Table 1.

[0066] Example 3 The steps for preparing the polyamide composite membrane are as follows:

[0067] 1) m-phenylenediamine, 4-chloro-1,3-phenylenediamine, camphorsulfonic acid, triethylamine, and water were mixed to obtain an aqueous solution. The concentrations of each component were 8 wt% m-phenylenediamine, 3 wt% 4-chloro-1,3-phenylenediamine, 1 wt% camphorsulfonic acid, and 0.5 wt% triethylamine.

[0068] 2) Trimesoyl chloride, di-tert-butyl dicarbonate, and a nonpolar solvent, n-hexane, were mixed to obtain an oil phase solution. The concentrations of each component were 0.6 wt% trimesoyl chloride and 2 wt% di-tert-butyl dicarbonate.

[0069] 3) At room temperature (20°C), the cut polysulfone membrane was attached to a frame. The frame was rectangular, measuring 10 cm on each side and approximately 8 mm thick. 20 ml of aqueous solution was poured onto the surface of the polysulfone membrane enclosed by the frame. After waiting for 5 minutes, the aqueous solution inside the frame was discarded and the membrane was pressed with a rubber roller to remove excess aqueous phase from the membrane surface. 20 ml of oily solution was then poured onto the surface of the polysulfone membrane, and the interfacial polymerization reaction was carried out at 20°C for 0.5 minutes. The excess oily phase was then discarded, the membrane was placed in a 50°C fan oven, dried for 20 seconds, and thoroughly rinsed with pure water to obtain a polyamide composite membrane.

[0070] 4) The polyamide composite membrane was immersed in a sulfuric acid aqueous solution at 90°C and pH 2 for 0.5 minutes to complete the step of removing the protective reagent, and then thoroughly rinsed with pure water to obtain a polyamide composite membrane from which the protective reagent had been removed.

[0071] 5) The polyamide composite membrane from which the protective reagent had been removed was added to a 0.4 wt% aqueous potassium nitrite solution, and the pH of the system was adjusted to 1.5 with hydrochloric acid. A diazotization reaction was carried out at 35°C for 30 seconds to produce a diazonium salt. The resulting solution was added to a 40°C alkaline aqueous solution whose pH had been adjusted to 11 with sodium carbonate, and a coupling reaction was carried out for 30 seconds. After the reaction was completed, the sheet was rinsed with pure water, moistened with glycerin, and baked in an oven to obtain a polyamide composite membrane. The performance test results are shown in Table 1.

[0072] Example 4 The steps for preparing the polyamide composite membrane are as follows:

[0073] 1) m-phenylenediamine, 5-chloro-1,3-phenylenediamine, camphorsulfonic acid, triethylamine, and water were mixed to obtain an aqueous solution. The concentrations of each component were 4 wt% m-phenylenediamine, 1.5 wt% 5-chloro-1,3-phenylenediamine, 1 wt% camphorsulfonic acid, and 0.5 wt% triethylamine.

[0074] 2) Trimesoyl chloride, 9-fluorenylmethyl chloroformate, and the nonpolar solvent dodecane were mixed to obtain an oil phase solution. The concentrations of each component were 0.1 wt% trimesoyl chloride and 0.01 wt% 9-fluorenylmethyl chloroformate.

[0075] 3) At room temperature (20°C), the cut polysulfone membrane was attached to a frame. The frame was rectangular, measuring 10 cm on each side and approximately 8 mm thick. 20 ml of aqueous solution was poured onto the surface of the polysulfone membrane enclosed by the frame. After waiting for 5 minutes, the aqueous solution inside the frame was discarded and the membrane was pressed with a rubber roller to remove excess aqueous phase from the membrane surface. 20 ml of oil solution was then poured onto the surface of the polysulfone membrane, and the interfacial polymerization reaction was carried out at 20°C for 1.5 minutes. The excess oil phase was then discarded, the membrane was placed in an 80°C fan oven, dried for 50 seconds, and thoroughly rinsed with pure water to obtain a polyamide composite membrane.

[0076] 4) The polyamide composite membrane was immersed in a piperidine aqueous solution at 90°C and pH 12.5 for 0.5 minutes to complete the step of removing the protective reagent, and then thoroughly rinsed with pure water to obtain a polyamide composite membrane from which the protective reagent had been removed.

[0077] 5) The polyamide composite membrane from which the protective reagent had been removed was added to a 0.2 wt% aqueous solution of sodium nitrite, and the pH of the system was adjusted to 2.1 with p-toluenesulfonic acid. A diazotization reaction was carried out at 30°C for 70 seconds to generate a diazonium salt. The resulting solution was added to a 20°C alkaline aqueous solution whose pH had been adjusted to 10 with N,N-dimethylaniline, and a coupling reaction was carried out for 60 seconds. After the reaction was completed, the sheet was rinsed with pure water, moistened with glycerin, and baked in an oven to obtain a polyamide composite membrane. The performance test results are shown in Table 1.

[0078] Example 5 The preparation method of Example 4 was referenced, except as follows:

[0079] In step 1), 5-chloro-1,3-phenylenediamine in the aqueous phase is replaced with 4-trifluoromethoxy-m-phenylenediamine, and the concentrations of each component in the aqueous phase solution after the replacement are 1.5 wt% m-phenylenediamine, 0.5 wt% 4-trifluoromethoxy-m-phenylenediamine, 1 wt% camphorsulfonic acid, and 0.5 wt% triethylamine.

[0080] In step 2), 9-fluorenylmethyl chloroformate in the oil phase was replaced with trifluoroacetic anhydride, and the concentrations of each component in the oil phase solution after the replacement were 0.15 wt% trimesoyl chloride and 0.05 wt% trifluoroacetic anhydride.

[0081] In step 4), the step of removing the protective reagent was changed so that the polyamide composite membrane was immersed in a diethylamine aqueous solution at 40°C and pH 11.5 for 1 minute to complete the step of removing the protective reagent, and then thoroughly rinsed with pure water to obtain a polyamide composite membrane from which the protective reagent had been removed.

[0082] The remaining operations were carried out in the same manner to obtain a polyamide composite membrane, the performance of which was tested and the results are shown in Table 1.

[0083] Comparative Example 1 The preparation method of Example 1 was followed except for the following: 4-trifluoromethoxy-m-phenylenediamine was not added in step 1), and trifluoroacetic anhydride was not added in step 2). The remaining operations were the same as above to obtain a polyamide composite membrane, and the performance test results are shown in Table 1.

[0084] Comparative Example 2 The preparation method of Example 1 was followed, except for the following points: In step 1), 4-trifluoromethoxy-m-phenylenediamine was not added, and the remaining operations were the same to obtain a polyamide composite membrane. The performance test results are shown in Table 1.

[0085] Comparative Example 3 The preparation method of Example 1 was followed except for the following points: In step 2), trifluoroacetic anhydride was not added, and the remaining operations were the same to obtain a polyamide composite membrane. The performance test results are shown in Table 1.

[0086] Comparative Example 4 The preparation method of Example 1 was followed, except for the following points: Step 4) was omitted, and the remaining operations were the same to obtain a polyamide composite membrane. The performance test results are shown in Table 1.

[0087] The sheets were subjected to performance tests, and the results are shown in Table 1.

[0088] [Table 1]

Claims

1. A polyamide composite membrane having a polyamide separation layer on a porous support layer, the polyamide separation layer having the following characteristics: a) the ratio of the response signal integral area of ​​the dimer structure represented by Formula I and Formula II when thermally decomposed at 650°C as measured by GC-MS is 4.5% to 10%; b) a yellowness index of 15 to 40; c) a surface halogen atom content of 0.15 to 1 mol % as measured by XPS.

2. The polyamide composite membrane according to claim 1, wherein the ratio of the response signal integral area of ​​the dimer structure represented by Formula I and Formula II when thermally decomposed at 650°C in a) is 6 to 8%.

3. The polyamide composite membrane according to claim 1 or 2, wherein the yellowness index in b) is 25 to 35.

4. The polyamide composite membrane according to any one of claims 1 to 3, wherein the halogen atom content of the surface in c) is 0.25 to 0.75 mol%.

5. A method for preparing the polyamide composite membrane according to any one of claims 1 to 4, comprising the steps of: Step 1) mixing a halogen atom-containing polyfunctional amine, a polyfunctional amine, and water to obtain an aqueous phase solution; Step 2) mixing an amino-protecting reagent, a polyfunctional acyl chloride, and a non-polar solvent to obtain an oil phase solution; Step 3) of applying the aqueous phase solution onto the base film and then contacting it with the oil phase solution to carry out an interfacial polymerization reaction to obtain a polyamide composite film; Step 4) placing the polyamide composite membrane in an amino deprotection solution to remove the amino protecting reagent; and step 5) adding the polyamide composite membrane from which the amino-protecting reagent has been removed to an aqueous diazotization reagent solution to carry out a diazotization reaction to generate a diazonium salt, which is then coupled under alkaline conditions to obtain a polyamide composite membrane.

6. The preparation method according to claim 5, wherein in step 1), the polyfunctional amine has a functionality of 2 to 4 and is one or more selected from aromatic polyamines and aliphatic polyamines.

7. The preparation method according to claim 6, wherein the aromatic polyamine is one or more selected from m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene, the aliphatic polyamine is one or more selected from ethylenediamine, piperazine, diethylenetriamine, and triethylenetetramine, and the polyfunctional amine is preferably m-phenylenediamine.

8. The preparation method according to any one of claims 5 to 7, wherein the concentration of the polyfunctional amine in the aqueous phase solution is 1 to 8 wt%, preferably 1.5 to 3.5 wt%.

9. In step 1), the halogen atom-containing polyfunctional amine is one or more selected from 4-trifluoromethoxy-m-phenylenediamine, 3,5-diaminobenzotrifluoride, 4-chloro-1,3-phenylenediamine, and 5-chloro-1,3-phenylenediamine, and is preferably 4-trifluoromethoxy-m-phenylenediamine; The preparation method according to any one of claims 5 to 8, wherein the concentration of the halogen atom-containing polyfunctional amine in the aqueous phase solution is preferably 0.1 to 3 wt%, preferably 1 to 2.5 wt%.

10. In step 2), the polyfunctional acyl chloride has a functionality of 2 or more, preferably 2 to 3, and is one or more selected from terephthaloyl chloride, isophthaloyl dichloride, naphthalene-2,6-dicarboyl chloride, trimesoyl chloride, 1,3,5-cyclohexanetricarbonyl chloride, 1,2,4-cyclobutanetricarbonyl chloride, etc., and is preferably trimesoyl chloride; The preparation method according to any one of claims 5 to 9, wherein the concentration of the polyfunctional acyl chloride in the oil phase solution is preferably 0.08 to 0.6 wt%, preferably 0.1 to 0.3 wt%.

11. In step 2), the amino-protecting reagent is one or more selected from the group consisting of trifluoroacetic anhydride, di-tert-butyl dicarbonate, triphenylmethyl chloride, and 9-fluorenylmethyl chloroformate; The preparation method according to any one of claims 5 to 10, wherein the concentration of the amino-protected reagent in the oil phase solution is preferably 0.01 to 10 wt%, preferably 0.05 to 2 wt%.

12. In step 4), when the amino-protecting reagent is trifluoroacetic anhydride and / or 9-fluorenylmethyl chloroformate, the amino-deprotecting solution is an alkaline aqueous solution having a pH in the range of 11.5 to 12.5, preferably, the alkali is one or more of sodium hydroxide, sodium carbonate, piperidine, and diethylamine, the removal temperature is 40 to 90°C, and the removal time is 0.5 to 2 minutes; The preparation method according to any one of claims 5 to 11, wherein when the amino-protecting reagent is di-tert-butyl dicarbonate and / or triphenylmethyl chloride, the amino-deprotecting solution is an acidic aqueous solution having a pH in the range of 1 to 2, preferably employing one or more of hydrochloric acid, sulfuric acid, acetic acid, and trifluoroacetic acid as the acid, the removal temperature is 60 to 90°C, and the removal time is 0.5 to 2 minutes.

13. The diazotization reagent in step 5) is nitrous acid, preferably a mixture of an alkali metal salt of nitrous acid (e.g., sodium nitrite, potassium nitrite) and an organic acid and / or an inorganic acid, preferably the organic acid is selected from citric acid, p-toluenesulfonic acid, and tartaric acid, preferably citric acid, and the inorganic acid is selected from hydrochloric acid, sulfuric acid, and phosphoric acid, preferably sulfuric acid; The preparation method according to any one of claims 5 to 12, wherein the concentration of the alkali metal salt of nitrous acid in the aqueous diazotization reagent solution is preferably 0.1 to 0.4 wt%, and the pH value when an acid is added is 1.5 to 3.

5.

14. The preparation method according to any one of claims 5 to 13, wherein the diazotization reaction in step 5) is carried out at a temperature of 4 to 35°C, preferably 20 to 30°C, for a time of 30 to 200 s, preferably 60 to 120 s.

15. The coupling reaction of step 5) is carried out at a temperature of 10 to 40°C, preferably 20 to 30°C, for a time of 30 to 200 seconds, preferably 60 to 120 seconds; Preferably, during the reaction, the pH value of the system is adjusted to 8 to 11, preferably 9 to 10, with alkali; The preparation method according to any one of claims 5 to 14, characterized in that the alkali used for adjusting the pH is preferably selected from organic alkali and / or inorganic alkali, the organic alkali being selected from triethylamine, N,N-dimethylaniline, preferably triethylamine, and the inorganic alkali being selected from sodium carbonate, sodium hydroxide, preferably sodium hydroxide.

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