A polyimide composite film and its preparation method

Abstract

This invention provides a polyimide composite membrane and its preparation method. The polyimide composite membrane includes a base membrane and a polyimide functional layer disposed on one side of the base membrane; the polyimide functional layer is embedded with a zwitterionic polymer-modified cyclodextrin monomer. This polyimide composite membrane effectively inhibits the adsorption of pollutants on the membrane surface, prevents pollutant deposition on the membrane surface, and further improves the permeation performance of the polyimide composite membrane.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology and relates to a polyimide composite membrane and its preparation method. Background Technology

[0002] As chemical separation technologies continue to develop towards higher efficiency, lower cost, and energy conservation, membrane separation technology, compared to traditional chemical separation technologies, has been widely researched and applied due to its advantages such as lower energy consumption and smaller footprint. Polyamide membranes typically consist of a non-woven fabric support layer, a porous polymer interlayer, and a polyamide separation layer, and are an economical and efficient separation method in the fields of water desalination, ultrapure water production, and wastewater treatment.

[0003] Despite the significant advantages of polyamide membranes, their low hydrophilicity and negative charge make membrane fouling a major challenge in applications. This not only reduces filtrate quality and separation efficiency, but the high sensitivity of the polyamide membrane layer to chlorine also shortens its lifespan. Therefore, inventing a reverse osmosis membrane that can simultaneously enhance antifouling capabilities is of great importance for mitigating membrane fouling and slowing down membrane degradation.

[0004] Cyclodextrin (CD), a cyclic oligosaccharide with a hydrophilic outer shell and a hydrophobic inner cavity, forms a stable host-guest inclusion complex with its unique structure, effectively adsorbing and removing organic pollutants. The external hydrophilic groups of cyclodextrin can enhance membrane hydrophilicity, reduce pollutant adsorption and deposition, and optimize overall permeability performance by regulating membrane structure. 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt (SBMA) is a commonly used ionic polymer, its monomer containing equal amounts of quaternary ammonium salt cations and sulfonate anions. Polymethacryloylethyl sulfobetaine (pSBMA) forms two hydrated layers on its surface, exhibiting stronger hydrophilicity than polymers such as polyethylene glycol. The spacing between its charged groups provides balanced charge and strong hydration capacity, making it widely used in membrane separation, antifouling coatings, and other fields. Summary of the Invention

[0005] To address the technical problems existing in the antifouling technology of reverse osmosis membranes, this invention provides a polyimide composite membrane and its preparation method. The polyimide composite membrane effectively inhibits the adsorption of pollutants on the membrane surface, prevents pollutants from depositing on the membrane surface, and further improves the permeation performance of the polyimide composite membrane.

[0006] To achieve the above-mentioned technical effects, the present invention adopts the following technical solution:

[0007] One objective of this invention is to provide a polyimide composite film, which includes a base film and a polyimide functional layer disposed on one side of the base film;

[0008] The polyimide functional layer is embedded with zwitterionic polymer-modified cyclodextrin monomers.

[0009] As a preferred technical solution of the present invention, the base membrane includes a polysulfone porous ultrafiltration membrane.

[0010] As a preferred technical solution of the present invention, the zwitterionic polymer includes polymethacryloylethyl sulfobetaine.

[0011] And / or, cyclodextrins include any one or a combination of at least two of α-cyclodextrin, β-cyclodextrin, or γ-cyclodextrin.

[0012] A second objective of this invention is to provide a method for preparing a polyimide composite film as provided in one objective, the method comprising:

[0013] A zwitterionic monomer is copolymerized with a monomer containing an epoxy group to obtain a zwitterionic copolymer.

[0014] The cyclodextrin was reacted with the first polyamine to obtain the cyclodextrin intermediate;

[0015] The cyclodextrin intermediate was reacted with a zwitterionic copolymer to obtain a zwitterionic polymer-modified cyclodextrin monomer.

[0016] A solution containing zwitterionic polymer-modified cyclodextrin monomers and a second polyamine is loaded onto one side of a base film, and a polyacrylamide chloride solution is coated onto that side to obtain a polyimide composite film by surface polymerization.

[0017] As a preferred technical solution of the present invention, methacryloyl ethyl sulfobetaine, glycidyl methacrylate and solvent are mixed and dissolved, and an initiator is added to carry out a polymerization reaction under a protective atmosphere to obtain a zwitterionic copolymer.

[0018] As a preferred embodiment of the present invention, the mass ratio of methacryloyl ethyl sulfobetaine, glycidyl methacrylate, and solvent is 2.5–3.0:0.05–0.07:18–23.

[0019] And / or, the polymerization reaction is carried out at a temperature of 50–80°C for a time of 4–8 hours.

[0020] As a preferred technical solution of the present invention, cyclodextrin and an alkaline solution are mixed, and a first polyamine is added to obtain a mixed solution; epichlorohydrin is added dropwise to the mixed solution to react and obtain the cyclodextrin monomer.

[0021] And / or, the molar ratio of the cyclodextrin to the polyamine is 0.005-0.01:0.3-0.4.

[0022] And / or, the molar ratio of the cyclodextrin to epichlorohydrin is 0.005–0.01:0.06–0.12.

[0023] And / or, the first polyamine includes any one or a combination of at least two of ethylenediamine, 1,2-propanediamine, 1,3-propanediamine or 1,4-butanediamine.

[0024] And / or, the base includes any one or at least two combinations of sodium carbonate, potassium carbonate, sodium hydroxide, or potassium hydroxide.

[0025] And / or, the reaction is carried out at a temperature of 50–70°C for a time of 1–2 hours.

[0026] As a preferred technical solution of the present invention, zwitterionic copolymer, cyclodextrin monomer and solvent are mixed and reacted to obtain zwitterionic polymer modified cyclodextrin monomer.

[0027] And / or, the solvent includes deionized water.

[0028] And / or, the reaction temperature is 50–80℃, and the time is 8–16 h.

[0029] As a preferred technical solution of the present invention, the zwitterionic polymer-modified cyclodextrin monomer is dispersed in a second polyamine aqueous solution to obtain a dispersion; the base film is immersed in the dispersion, and after removal, excess dispersion is removed from the surface; a polyacrylamide chloride solution is coated on one side of the base film immersed in the dispersion, and a thermal crosslinking reaction is carried out to obtain the polyimide composite film.

[0030] As a preferred embodiment of the present invention, the second polyamine includes any one of m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, polyetheramine, or polyethyleneimine.

[0031] And / or, the mass fraction of zwitterionic polymer-modified cyclodextrin monomer in the dispersion is 0.1 to 1.0 wt%.

[0032] And / or, the soaking time is 60 to 300 seconds.

[0033] And / or, the polyacryl chloride includes 1,3,5-benzenetricarboxyl chloride.

[0034] And / or, the solvent of the polyacrylamide chloride solution includes any one or a combination of at least two of the following: n-hexane, cyclohexane, n-heptane, n-decane, toluene, Isopar E, or Isopar G.

[0035] And / or, the temperature of the thermal crosslinking reaction is 40–90°C and the time is 60–600 s.

[0036] Compared with the prior art, the present invention has at least the following beneficial effects:

[0037] (1) The present invention provides a polyimide composite membrane and its preparation method. The polyimide composite membrane forms a dense hydration layer with the hydrophilic groups outside the embedded cyclodextrin molecules and the zwitterionic polymer, which can effectively inhibit the adsorption of pollutants on the membrane surface and prevent the deposition of pollutants on the membrane surface.

[0038] (2) The present invention provides a polyimide composite membrane and its preparation method. The polyimide composite membrane further improves the permeability of the polyimide composite membrane through the hydrophobic cavity embedded in the cyclodextrin molecule. Attached Figure Description

[0039] Figure 1 The graphs show the test results of the water contact angle on the surface of the polyimide reverse osmosis membranes provided in Examples 1-6 and Comparative Examples 1 and 2 of this invention.

[0040] Figure 2 The graph shows the test results of flux decay rate and flux recovery rate of the polyimide reverse osmosis membranes provided in Examples 1-6 and Comparative Examples 1 and 2 of this invention.

[0041] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims. Detailed Implementation

[0042] The technical solution of this application will be further described below through specific implementation methods.

[0043] This invention provides a polyimide composite film, which includes a base film and a polyimide functional layer disposed on one side of the base film;

[0044] A polyimide functional layer is embedded with a zwitterionic polymer-modified cyclodextrin monomer.

[0045] In this invention, the cyclodextrin molecule has hydrophilic groups on the outside and hydrophobic cavities on the inside. This unique structure enables it to form a stable host-guest structure. The external hydrophilic groups enhance the hydrophilicity of the membrane, effectively reducing the adsorption and deposition of pollutants on the membrane surface. The hydrophobic cavity of the cyclodextrin further optimizes the overall membrane permeability. The two hydration layers formed on the surface of the zwitterionic polymer create a dense hydration layer on the polyimide composite membrane surface, effectively inhibiting the adsorption of pollutants and preventing their deposition.

[0046] In one specific embodiment of the present invention, the base membrane comprises a polysulfone porous ultrafiltration membrane.

[0047] In one specific embodiment of the present invention, the zwitterionic polymer includes polymethacryloylethyl sulfobetaine.

[0048] In one specific embodiment of the present invention, the cyclodextrin includes any one or a combination of at least two of α-cyclodextrin, β-cyclodextrin, or γ-cyclodextrin.

[0049] In one specific embodiment of the present invention, the amount of zwitterionic polymer-modified cyclodextrin monomer embedded in the base film can be adjusted according to the usage environment and permeability requirements of the polyimide composite film, and is not specifically limited here.

[0050] This invention provides a method for preparing a polyimide composite film, the method comprising:

[0051] A zwitterionic monomer is copolymerized with a monomer containing an epoxy group to obtain a zwitterionic copolymer.

[0052] The cyclodextrin was reacted with the first polyamine to obtain the cyclodextrin intermediate;

[0053] The cyclodextrin intermediate was reacted with a zwitterionic copolymer to obtain a zwitterionic polymer-modified cyclodextrin monomer.

[0054] A solution containing zwitterionic polymer-modified cyclodextrin monomers and a second polyamine is loaded onto one side of a base film, and a polyacrylamide chloride solution is coated onto that side to obtain a polyimide composite film by surface polymerization.

[0055] In one specific embodiment of the present invention, methacryloyl ethyl sulfobetaine, glycidyl methacrylate and solvent are mixed and dissolved, and an initiator is added to carry out a polymerization reaction under a protective atmosphere to obtain a zwitterionic copolymer.

[0056] In one specific embodiment of the present invention, the mass ratio of methacryloylethyl sulfobetaine, glycidyl methacrylate, and solvent is 2.5–3.0:0.05–0.07:18–23, such as 2.5:0.05:18, 2.6:0.055:19, 2.7:0.06:20, 2.8:0.062:21, 2.9:0.065:22, or 3.0:0.07:23, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0057] In one specific embodiment of the present invention, the solvent is preferably a mixed solution of methanol and water, wherein the volume ratio of methanol to water is preferably 1:1.

[0058] In one specific embodiment of the present invention, the initiator is preferably 2,2'-azobisisobutyronitrile, but it is not limited to this initiator; other initiators suitable for olefin polymerization reactions are also applicable to the present invention. The amount of initiator added can be adjusted according to the polymerization reaction, and is not further limited here, but is preferably 1% of the mass of the mixed solution.

[0059] In one specific embodiment of the present invention, the polymerization reaction temperature is 50–80°C, and the time is 4–8 hours. The temperature can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C, etc., and the time can be 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, or 8 hours, etc., but is not limited to the listed values; other unlisted values ​​within the above ranges are also applicable.

[0060] In one specific embodiment of the present invention, after the polymerization reaction is completed, the reaction is terminated by an ice bath, and the cooling time can be 2 to 6 hours, preferably 3 hours.

[0061] In one specific embodiment of the present invention, the copolymerization equation for methacryloylethyl sulfobetaine and glycidyl methacrylate can be shown as follows:

[0062]

[0063] In one specific embodiment of the present invention, after the reaction is terminated, a white solid is obtained by solid-liquid separation. The white solid is dissolved in water, the precipitate is washed with methanol solvent, and the mixture is freeze-dried to obtain a zwitterionic copolymer.

[0064] In one specific embodiment of the present invention, cyclodextrin and an alkaline solution are mixed, and a first polyamine is added to obtain a mixed solution; epichlorohydrin is added dropwise to the mixed solution to react and obtain the cyclodextrin monomer.

[0065] In one specific embodiment of the present invention, the molar ratio of the cyclodextrin to the polyamine is 0.005-0.01:0.3-0.4, such as 0.005:0.3, 0.006:0.32, 0.007:0.35, 0.008:0.36, 0.009:0.38 or 0.01:0.4, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0066] In one specific embodiment of the present invention, the molar ratio of cyclodextrin to epichlorohydrin is 0.005-0.01:0.06-0.12, such as 0.005:0.06, 0.006:0.07, 0.007:0.08, 0.008:0.09, 0.009:0.10, or 0.01:0.12, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0067] In one specific embodiment of the present invention, the first polyamine includes any one or a combination of at least two of ethylenediamine, 1,2-propanediamine, 1,3-propanediamine or 1,4-butanediamine, preferably ethylenediamine.

[0068] In one specific embodiment of the present invention, the alkali includes any one or at least two combinations of sodium carbonate, potassium carbonate, sodium hydroxide, or potassium hydroxide, preferably potassium hydroxide.

[0069] In one specific embodiment of the present invention, the amount of alkali added and the concentration of the alkali solution can be adjusted according to the reaction situation while maintaining the alkalinity of the reaction system, and are not specifically limited here.

[0070] In one specific embodiment of the present invention, the reaction temperature is 50–70°C, and the reaction time is 1–2 hours. The reaction temperature can be 50°C, 52°C, 55°C, 58°C, 60°C, 62°C, 65°C, 68°C, or 70°C, etc., and the reaction time can be 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours, or 2 hours, etc., but is not limited to the listed values; other unlisted values ​​within the above ranges are also applicable.

[0071] In one specific embodiment of the present invention, after the reaction is completed, the pH of the reaction solution is adjusted to neutral using acid to obtain the cyclodextrin intermediate.

[0072] In one specific embodiment of the present invention, zwitterionic copolymer, cyclodextrin monomer and solvent are mixed and reacted to obtain zwitterionic polymer modified cyclodextrin monomer.

[0073] In one specific embodiment of the present invention, the solvent includes deionized water.

[0074] In one specific embodiment of the present invention, the mass ratio of the zwitterionic copolymer, the cyclodextrin monomer, and water is 0.6–1.0:0.3–0.7:8–12, such as 0.6:0.3:8, 0.7:0.4:9, 0.8:0.5:10, 0.9:0.6:11, or 1.0:0.7:12, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0075] In one specific embodiment of the present invention, the reaction temperature is 50–80°C, and the reaction time is 8–16 hours. The reaction temperature can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C, and the reaction time can be 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, or 16 hours, but is not limited to the listed values; other unlisted values ​​within the above ranges are also applicable.

[0076] In one specific embodiment of the present invention, after the reaction is completed, the reaction solution is dialyzed to obtain zwitterionic polymer-modified cyclodextrin monomers. The dialyzing time can be 48 hours, the molecular weight cutoff is 3500 Da, and deionized water is used as the dialysate.

[0077] In one specific embodiment of the present invention, the structural diagram of the zwitterionic polymer-modified cyclodextrin monomer is shown in the following formula:

[0078]

[0079] In one specific embodiment of the present invention, a zwitterionic polymer-modified cyclodextrin monomer is dispersed in a second polyamine aqueous solution to obtain a dispersion; a base film is immersed in the dispersion, and after removal, excess dispersion on the surface is removed; a polyacrylamide chloride solution is coated on one side of the base film immersed in the dispersion, and a thermal crosslinking reaction is carried out to obtain the polyimide composite film.

[0080] In one specific embodiment of the present invention, the zwitterionic polymer-modified cyclodextrin monomer is dispersed in a second polyamine aqueous solution by ultrasound. The ultrasonic dispersion time can be 20–30 min.

[0081] In one specific embodiment of the present invention, the second polyamine includes any one of m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, polyetheramine, or polyethyleneimine.

[0082] In one specific embodiment of the present invention, the mass fraction of the zwitterionic polymer-modified cyclodextrin monomer in the dispersion is 0.1 to 1.0 wt%, such as 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1.0 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0083] In one specific embodiment of the present invention, the soaking time is 60 to 300 seconds, such as 60 seconds, 120 seconds, 180 seconds, 240 seconds or 300 seconds, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0084] In one specific embodiment of the present invention, after impregnation, excess dispersion liquid on the surface of the base film is removed by a rubber roller or a nitrogen gas knife.

[0085] In one specific embodiment of the present invention, the polyacryl chloride includes 1,3,5-benzenetricarboxyl chloride.

[0086] In one specific embodiment of the present invention, the solvent of the polyacrylamide chloride solution includes any one or a combination of at least two of the following: n-hexane, cyclohexane, n-heptane, n-decane, toluene, Isopar E, or Isopar G.

[0087] In one specific embodiment of the present invention, the concentration of the polyacrylamide chloride solution can be 0.1 to 1.0 wt%, such as 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1.0 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0088] In one specific embodiment of the present invention, the temperature of the thermal crosslinking reaction is 40–90°C, and the time is 60–600 s. The thermal crosslinking temperature can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 90°C, etc., and the time can be 60 s, 120 s, 180 s, 240 s, 300 s, 360 s, 420 s, 480 s, 540 s, or 600 s, etc., but is not limited to the listed values; other unlisted values ​​within the above ranges are also applicable.

[0089] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0090] Example 1

[0091] This embodiment provides a method for preparing a polyimide composite film, the method comprising:

[0092] Synthesis of p(SBMA-co-GMA) copolymer:

[0093] Methacryloxyethyl sulfobetaine monomer (SBMA monomer) and glycidyl methacrylate (GMA monomer) were dissolved in a round-bottom flask containing a methanol / water solution (volume ratio = 1:1), wherein the mass ratio of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt (SBMA monomer), glycidyl methacrylate (GMA monomer), and methanol was 2.5:0.05:20. After adding 1% equivalent of the initiator 2,2'-azobisisobutyronitrile (AIBN), the homogeneous solution was degassed under a nitrogen stream for 10 min, followed by reaction at 60 °C for 6 h. The reaction was terminated by cooling in an ice-water bath for 3 h, and a white precipitate was collected. The white precipitate was then redissolved in water and washed with methanol. Finally, the purified p(SBMA-co-GMA) product was obtained by freeze-drying for 24 h.

[0094] EDA-CD synthesis:

[0095] 0.01 mol of γ-cyclodextrin was added to a potassium hydroxide aqueous solution at 50 °C, followed by 0.5 mol of ethylenediamine. 0.10 mol of epichlorohydrin (ECH) was then added dropwise to the mixture while the solution was slowly heated to 60 °C for 1 h. The pH was adjusted to 7 with hydrochloric acid solution to obtain EDA-CD.

[0096] Synthesis of pSBMA-CD:

[0097] p(SBMA-co-GMA) copolymer and EDA-CD were added to deionized water and reacted at 60°C for 12 h. The mass ratio of p(SBMA-co-GMA) copolymer, EDA-CD and deionized water was 1.0:0.5:10. The reaction product was obtained by dialysis for 48 h (molecular weight cutoff 3500 Da, deionized water was used as the dialysis solution).

[0098] Preparation of polyimide composite film:

[0099] An aqueous solution containing 2.5 wt% m-phenylenediamine, 3.0 wt% camphor sulfonic acid, and 1.5 wt% triethylamine was prepared; 0.1 wt% pSBMA-CD was added to the aqueous solution, and the solution was sonicated for 20 min to ensure uniform dispersion.

[0100] An organic phase solution containing 0.12 wt% trimesoyl chloride was prepared using Isopar G isoalkanes as the organic solvent.

[0101] The polysulfone PSF ultrafiltration substrate was fixed in an plexiglass frame, and the membrane surface was immersed in an aqueous solution for 120 seconds. Then, excess aqueous monomer solution on the surface of the ultrafiltration substrate membrane was removed using a nitrogen gas knife. After that, it was reacted with an organic phase solution for 60 seconds to remove excess organic phase solution. Then, it was uniformly purged until there was no residual solvent on the membrane surface. Finally, it was placed in an 80°C oven for heat treatment for 5 minutes. After being removed from the oven, it was rinsed with pure water.

[0102] Example 2

[0103] Except for the concentration of pSBMA-CD in the aqueous phase being 0.2 wt% and the ultrasonic dispersion time being 25 min, all other conditions in this embodiment are the same as in Example 1.

[0104] Example 3

[0105] Except for the concentration of pSBMA-CD in the aqueous phase being 0.4 wt% and the ultrasonic dispersion time being 30 min, all other conditions in this embodiment are the same as in Example 1.

[0106] Example 4

[0107] Except for the concentration of pSBMA-CD in the aqueous phase being 0.6 wt% and the ultrasonic dispersion time being 35 min, all other conditions in this embodiment are the same as in Example 1.

[0108] Example 5

[0109] Except for the concentration of pSBMA-CD in the aqueous phase being 0.8 wt% and the ultrasonic dispersion time being 40 min, all other conditions in this embodiment are the same as in Example 1.

[0110] Example 6

[0111] Except for the concentration of pSBMA-CD in the aqueous phase being 1.0 wt% and the ultrasonic dispersion time being 45 min, all other conditions in this embodiment are the same as in Example 1.

[0112] Comparative Example 1

[0113] This comparative example provides a method for preparing a polyamide reverse osmosis membrane, the method comprising:

[0114] A casting solution containing 17 wt% polysulfone was prepared in N,N-dimethylformamide. After stirring evenly, the casting solution was placed in a vacuum oven for 6 hours to remove bubbles. Then, the casting solution was poured and coated onto a polyester nonwoven fabric using an automatic coating machine. After coating, the fabric was immediately immersed in a 25°C deionized water coagulation bath to complete the phase inversion and then placed in pure water to soak for later use.

[0115] An aqueous solution containing 2.5 wt% m-phenylenediamine, 3.0 wt% camphor sulfonic acid, and 1.5 wt% triethylamine was prepared.

[0116] An organic phase solution containing 0.12 wt% trimesoyl chloride was prepared using Isopar G isoalkanes as the organic solvent.

[0117] The polysulfone PSF ultrafiltration substrate was fixed in an plexiglass frame, and the membrane surface was immersed in an aqueous solution for 120 seconds. Then, excess aqueous monomer solution on the surface of the ultrafiltration substrate membrane was removed using a nitrogen gas knife. After that, it was reacted with an organic phase solution for 60 seconds, and the excess organic phase solution was poured off. Then, the membrane was purged evenly until there was no residual solvent on the surface. Finally, it was placed in an 80°C oven for heat treatment for 5 minutes. After being removed from the oven, it was rinsed with pure water.

[0118] Comparative Example 2

[0119] This comparative example provides a method for preparing a polyamide reverse osmosis membrane, the method comprising:

[0120] An aqueous solution containing 2.5 wt% m-phenylenediamine, 3.0 wt% camphor sulfonic acid, and 1.5 wt% triethylamine was prepared; 0.4 wt% γ-CD was added to the aqueous solution, and the solution was sonicated for 30 min to ensure uniform dispersion.

[0121] An organic phase solution containing 0.12 wt% trimesoyl chloride was prepared using Isopar G isoalkanes as the organic solvent.

[0122] The polysulfone PSF ultrafiltration substrate was fixed in an plexiglass frame, and the membrane surface was immersed in an aqueous solution for 120 seconds. Then, excess aqueous monomer solution on the surface of the ultrafiltration substrate membrane was removed using a nitrogen gas knife. After that, it was reacted with an organic phase solution for 60 seconds, and the excess organic phase solution was poured off. Then, the membrane was purged evenly until there was no residual solvent on the surface. Finally, it was placed in an 80°C oven for heat treatment for 5 minutes. After being removed from the oven, it was rinsed with pure water.

[0123] The performance of the polyamide reverse osmosis membranes prepared in Examples 1-6 and Comparative Examples 1 and 2 was tested, and the results are shown in Table 1.

[0124] Test method: The feed solution is a 2000ppm sodium chloride aqueous solution with a pH of 7.0±0.5, an operating pressure of 225psi (1.55MPa), and an operating temperature of 25±1℃. For antifouling performance testing, protein was used as the turbidity agent in the antifouling test, and water flux was measured according to GB / T 32373-2015 Reverse Osmosis Membrane Test Method.

[0125] Table 1

[0126] Experimental group name Flux (LMH) NaCl retention rate (%) Comparative Example 1 44.56 99.07 Comparative Example 2 49.51 98.43 Example 1 53.42 98.95 Example 2 55.97 99.30 Example 3 61.22 99.35 Example 4 62.38 99.21 Example 5 60.72 99.18 Example 6 58.93 99.04

[0127] The hydrophilicity of the polyamide reverse osmosis membranes prepared in Examples 1-6 and Comparative Examples 1 and 2 was tested using a contact angle tester, and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that in Examples 1-6, as the loading of pSBMA-CD increases, the water contact angle on the surface of the amide reverse osmosis membrane becomes smaller, and the hydrophilicity is better, indicating that its surface hydration layer is denser and its antifouling performance is better. In Example 3, the loading of pSBMA-CD is the same as that of γ-CD in Comparative Example 2. The hydrophilicity of the polyamide reverse osmosis membrane surface in Example 3 is better than that in Comparative Example 2. Comparative Example 1 has no pSBMA-CD or γ-CD loaded, and its surface hydrophilicity is the worst.

[0128] The flux decay rate and flux recovery rate of the polyamide reverse osmosis membranes prepared in Examples 1-6 and Comparative Examples 1 and 2 were tested. The test method was as follows: the reverse osmosis membrane was pre-pressurized with pure water for 30 minutes. The initial flux J0 was recorded at this time. A model contaminant (BSA) at a concentration of 500 ppm was added to the pure water solution. The immediate flux J after membrane fouling was recorded. t Once the contamination reached a stable state, the experimental cleaning and recovery tests were stopped: the membrane surface was rinsed with pure water (without pressure), and the flux J after rinsing was recorded. c .

[0129] Flux Decay Rate: FDR(%) = (J0 - J t ) / J 0* 100%

[0130] Flux recovery rate: FRR (%) = J c / J 0* 100%

[0131] The result is as follows Figure 2 As shown, from Figure 2 As can be seen from the comparative examples, with the increase of pSBMA-CD loading, the flux decay rate decreases and the recovery rate increases in the examples. The flux recovery rate of Example 3 reaches 96%, indicating that its antifouling performance is significantly improved. Within the polyamide membrane, the incorporation of pSBMA-CD effectively inhibits the adsorption of pollutants on the membrane surface and prevents pollutant deposition on the membrane surface.

[0132] The applicant declares that the detailed structural features of the present invention are illustrated through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components selected in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0133] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0134] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0135] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A polyimide composite film, characterized in that, The polyimide composite film includes a base film and a polyimide functional layer disposed on one side of the base film; The polyimide functional layer is embedded with zwitterionic polymer-modified cyclodextrin monomers; The preparation method of the polyimide composite film includes the following steps: A zwitterionic monomer is copolymerized with a monomer containing an epoxy group to obtain a zwitterionic copolymer. Cyclodextrin and an alkaline solution were mixed, and a first polyamine was added to obtain a mixed solution; epichlorohydrin was added dropwise to the mixed solution, and the reaction yielded the cyclodextrin monomer; The cyclodextrin monomer is reacted with the zwitterionic copolymer to obtain a zwitterionic polymer-modified cyclodextrin monomer. A solution containing zwitterionic polymer-modified cyclodextrin monomers and a second polyamine is loaded onto one side of a base film, and a polyacrylamide chloride solution is coated onto that side. A thermal crosslinking reaction is then carried out to obtain the polyimide composite film.

2. The polyimide composite film according to claim 1, characterized in that, The base membrane includes a polysulfone porous ultrafiltration membrane.

3. The polyimide composite film according to claim 1, characterized in that, The zwitterionic polymer includes polymethacryloylethyl sulfobetaine; And / or, the cyclodextrin includes any one or a combination of at least two of α-cyclodextrin, β-cyclodextrin, or γ-cyclodextrin.

4. A method for preparing a polyimide composite film according to any one of claims 1-3, characterized in that, The preparation method includes: A zwitterionic monomer is copolymerized with a monomer containing an epoxy group to obtain a zwitterionic copolymer. Cyclodextrin and an alkaline solution were mixed, and a first polyamine was added to obtain a mixed solution; epichlorohydrin was added dropwise to the mixed solution, and the reaction was carried out to obtain the cyclodextrin monomer; the cyclodextrin monomer was reacted with the zwitterionic copolymer to obtain a zwitterionic polymer-modified cyclodextrin monomer; A solution containing zwitterionic polymer-modified cyclodextrin monomers and a second polyamine is loaded onto one side of a base film, and a polyacrylamide chloride solution is coated onto that side. A thermal crosslinking reaction is then carried out to obtain the polyimide composite film.

5. The preparation method according to claim 4, characterized in that, Methacryloxyethyl sulfobetaine, glycidyl methacrylate, and a solvent were mixed and dissolved, and an initiator was added to carry out a polymerization reaction under a protective atmosphere to obtain a zwitterionic copolymer.

6. The preparation method according to claim 5, characterized in that, The mass ratio of methacryloylethyl sulfobetaine, glycidyl methacrylate, and solvent is 2.5~3.0:0.05~0.07:18~23; And / or, the polymerization reaction is carried out at a temperature of 50~80℃ for a time of 4~8 h.

7. The preparation method according to claim 4, characterized in that, The molar ratio of the cyclodextrin to the polyamine is 0.005~0.01:0.3~0.4; And / or, the molar ratio of the cyclodextrin to epichlorohydrin is 0.005~0.01:0.06~0.12; And / or, the first polyamine includes any one or a combination of at least two of ethylenediamine, 1,2-propanediamine, 1,3-propanediamine or 1,4-butanediamine; And / or, the base includes any one or at least two combinations of sodium carbonate, potassium carbonate, sodium hydroxide, or potassium hydroxide; And / or, the reaction is carried out at a temperature of 50-70°C for 1-2 hours.

8. The preparation method according to claim 4, characterized in that, The zwitterionic copolymer, cyclodextrin monomer, and solvent are mixed and reacted to obtain the zwitterionic polymer-modified cyclodextrin monomer. And / or, the solvent includes deionized water; And / or, the reaction is carried out at a temperature of 50-80°C for a time of 8-16 h.

9. The preparation method according to claim 4, characterized in that, The zwitterionic polymer-modified cyclodextrin monomer is dispersed in a second polyamine aqueous solution to obtain a dispersion; the base film is immersed in the dispersion, and after removal, excess dispersion is removed from the surface; a polyacrylamide chloride solution is coated on one side of the base film immersed in the dispersion, and a thermal crosslinking reaction is carried out to obtain the polyimide composite film.

10. The preparation method according to claim 9, characterized in that, The second polyamine includes any one of m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, polyetheramine, or polyethyleneimine; And / or, the mass fraction of the zwitterionic polymer-modified cyclodextrin monomer in the dispersion is 0.1~1.0 wt%; And / or, the soaking time is 60~300 s; And / or, the polyacryl chloride includes 1,3,5-benzenetricarboxyl chloride; And / or, the solvent of the polyacrylamide chloride solution includes any one or a combination of at least two of the following: n-hexane, cyclohexane, n-heptane, n-decane, toluene, Isopar E, or Isopar G; And / or, the temperature of the thermal crosslinking reaction is 40~90℃ and the time is 60~600 s.

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