Organic solvent resistant nanofiltration membrane and method of making same

Abstract

The application provides an organic-solvent-resistant nanofiltration membrane and a manufacturing method thereof, and relates to the technical field of nanofiltration membranes. The manufacturing method comprises the following steps: providing a diamine, a dianhydride, an octa-maleimide acid cage silsesquioxane and an aprotic polar solvent; mixing the diamine, the octa-maleimide acid cage silsesquioxane and the aprotic polar solvent and heating to reflux to obtain a first mixture; mixing the first mixture with the dianhydride and reacting to obtain a second mixture; and solidifying the second mixture into a film to obtain the organic-solvent-resistant nanofiltration membrane. The organic-solvent-resistant nanofiltration membrane has a high permeation flux and good organic-solvent resistance.

Description

Technical Field

[0001] This invention relates to the field of nanofiltration membrane technology, and more specifically to an organic solvent-resistant nanofiltration membrane and its manufacturing method. Background Technology

[0002] Solvent-resistant nanofiltration membranes are a novel pressure-driven separation membrane that falls between reverse osmosis and ultrafiltration membranes, finding wide applications in water treatment, textile printing and dyeing, papermaking, food, pharmaceuticals, petrochemicals, and biochemicals. Polyimide, as a high-performance polymer, is widely used in the preparation of solvent-resistant nanofiltration membranes. However, with technological advancements, traditional polyimide nanofiltration membranes can no longer meet the requirements for high permeation flux. Currently, the permeation flux of polyimide solvent-resistant nanofiltration membranes is often improved by adding nanomaterials such as graphene oxide, carbon nanotubes, MOFs, and POSS.

[0003] However, nanomaterials suffer from agglomeration due to their difficulty in uniform dispersion within polyimide nanofiltration membranes. This agglomeration creates defects in the membrane, leading to a deterioration in its solvent resistance. Therefore, there is an urgent need for a polyimide solvent-resistant nanofiltration membrane that can improve both the permeation flux and solvent resistance of polyimide nanofiltration membranes. Summary of the Invention

[0004] The purpose of this invention is to provide a method for manufacturing a nanofiltration membrane resistant to organic solvents.

[0005] Another object of the present invention is to provide an organic solvent resistant nanofiltration membrane with high permeation flux and good organic solvent resistance.

[0006] The technical problem solved by this invention is achieved by the following technical solution:

[0007] A method for manufacturing an organic solvent-resistant nanofiltration membrane includes:

[0008] We provide diamines, dianhydrides, octamaleic acid cage-like silsesquioxanes, and aprotic polar solvents;

[0009] A first mixture was obtained by mixing a diamine, an octamaleic acid cage-like silsesquioxane, and an aprotic polar solvent and heating under reflux.

[0010] The first mixture is mixed with a diacid, and the reaction yields a second mixture; and

[0011] The second mixture was cured into a membrane to obtain an organic solvent-resistant nanofiltration membrane.

[0012] Optionally, in some embodiments of the present invention, curing the second mixture into a film includes:

[0013] A second mixture is deposited on a glass plate to form a thin film;

[0014] The film is immersed in the coagulation solution and then removed and dried; and

[0015] The membrane is heated in a vacuum environment of 100–300°C to form a nanofiltration membrane resistant to organic solvents.

[0016] Optionally, in some embodiments of the invention, the second mixture is deposited by a coating method; and / or

[0017] The coagulant is selected from one or more of distilled water, deionized water, and reverse osmosis water.

[0018] Optionally, in some embodiments of the present invention, the molar ratio of diamine, dianhydride and octameric acid cage-like silsesquioxane is 1:1 to 1.05:0.05 to 0.5.

[0019] Optionally, in some embodiments of the present invention, the heating reflux time is 2 to 4 hours; and / or

[0020] The reaction time to obtain the second mixture by mixing the first mixture with the dihydric anhydride is 6-8 hours.

[0021] Optionally, in some embodiments of the present invention, the temperature of the heating reflux is 100–150°C; and / or

[0022] The temperature at which the first mixture is mixed with the diacid to obtain the second mixture is 0–5 °C.

[0023] Optionally, in some embodiments of the present invention, the thickness of the organic solvent-resistant nanofiltration membrane is 50–300 μm.

[0024] Optionally, in some embodiments of the present invention, the diamine is selected from one or more of 4,4'-diaminodiphenyl ether, p-phenylenediamine, and benzidine; and / or

[0025] The dihydric anhydride is selected from one or more of pyromellitic anhydride and maleic anhydride.

[0026] Optionally, in some embodiments of the present invention, the aprotic polar solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0027] In addition, an organic solvent-resistant nanofiltration membrane is prepared by the above-described method for manufacturing an organic solvent-resistant nanofiltration membrane.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] In this invention, the permeation flux of a polyimide nanofiltration membrane resistant to organic solvents is improved by adding octamaleic acid cage-like silsesquioxane to the membrane. Because octamaleic acid cage-like silsesquioxane possesses functional groups capable of reacting with amino groups, it can react with diamine, a raw material used in the preparation of the organic solvent-resistant nanofiltration membrane. This improves the dispersibility of octamaleic acid cage-like silsesquioxane in the membrane, thereby preventing its aggregation. Furthermore, since octamaleic acid cage-like silsesquioxane has a functionality of 8, the intermediate product generated after its reaction with diamine can form crosslinking points in the membrane during the subsequent curing process. The presence of these crosslinking points further enhances the organic solvent resistance of the membrane. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The technical solutions provided by this invention will be described in detail below. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this invention, the term "comprising" means "including but not limited to". The terms "first", "second", etc., are used merely as illustrative and do not impose numerical requirements or establish an order. Various embodiments of this invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of this invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range.

[0032] A method for manufacturing an organic solvent-resistant nanofiltration membrane includes:

[0033] We provide diamines, dianhydrides, octamaleic acid cage-like silsesquioxanes, and aprotic polar solvents;

[0034] A first mixture was obtained by mixing a diamine, an octamaleic acid cage-like silsesquioxane, and an aprotic polar solvent and heating under reflux.

[0035] The first mixture is mixed with a diacid, and the reaction yields a second mixture; and

[0036] The second mixture was cured into a membrane to obtain an organic solvent-resistant nanofiltration membrane.

[0037] Octamaleic acid cage-like silsesquioxane (POSS) is a nanoparticle with eight active functional groups, and its chemical structural formula is as follows:

[0038]

[0039] It is understandable that, since the maleic acid group in the ocmaleamic acid cage-like silsesquioxane can react with the amino group in the diamine, the first mixture obtained includes the intermediate product obtained from the reaction of the diamine and the ocmaleamic acid cage-like silsesquioxane. After the first mixture is mixed with the diacid, the amino group in the intermediate product can react with the diacid to generate polyamic acid. Since the functionality of the ocmaleamic acid cage-like silsesquioxane is 8, the intermediate product can form crosslinking points in the generated polyamic acid when it reacts with the diacid. This crosslinking points are then formed in the organic solvent resistant nanofiltration membrane formed by curing the polyamic acid, thereby improving the organic solvent resistance of the nanofiltration membrane.

[0040] In some embodiments, curing the second mixture into a film includes:

[0041] A second mixture is deposited on a glass plate to form a thin film;

[0042] The film is immersed in the coagulation solution and then removed and dried; and

[0043] The membrane is heated in a vacuum environment of 100–300°C to form a nanofiltration membrane resistant to organic solvents.

[0044] It is understandable that the dried film can be dried by vacuum drying or other methods, and there are no restrictions here. The heating time of the film can be determined according to the thickness of the film and the types of diamine and dianhydride.

[0045] In some embodiments, the second mixture is deposited by a coating method.

[0046] In some embodiments, the coagulant is selected from one or more of distilled water, deionized water, and reverse osmosis water.

[0047] In some embodiments, the molar ratio of diamine, dianhydride, and octamaleic acid cage-like silsesquioxane is 1:1 to 1.05:0.05 to 0.5. When the molar ratio of diamine, dianhydride, and octamaleic acid cage-like silsesquioxane is within the above range, the number of crosslinking points in the organic solvent-resistant nanofiltration membrane is appropriate, which is beneficial to improving the solvent resistance performance of the organic solvent-resistant nanofiltration membrane.

[0048] In some embodiments, the heating reflux time is 2 to 4 hours; the heating reflux temperature is 100 to 150°C.

[0049] When the heating and reflux time and temperature are within the above range, it can ensure that the maleic acid group in the octamamic acid cage-like silsesquioxane can react with the amino group in the diamine to generate an intermediate product, and can also prevent further condensation of the intermediate product, thereby ensuring the formation of crosslinking points in the organic solvent resistant nanofiltration membrane.

[0050] In some embodiments, the time for mixing the first mixture with the diacid to react and obtain the second mixture is 6 to 8 hours; the temperature for mixing the first mixture with the diacid to react and obtain the second mixture is 0 to 5°C.

[0051] In some embodiments, the thickness of the organic solvent-resistant nanofiltration membrane is 50–300 μm.

[0052] In some embodiments, the diamine is selected from one or more of 4,4'-diaminodiphenyl ether, p-phenylenediamine, and benzidine.

[0053] In some embodiments, the dihydric anhydride is selected from one or more of pyromellitic anhydride and maleic anhydride.

[0054] In some embodiments, the aprotic polar solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0055] In addition, an organic solvent-resistant nanofiltration membrane is prepared by the above-described method for manufacturing an organic solvent-resistant nanofiltration membrane.

[0056] Example 1

[0057] This embodiment provides an organic solvent-resistant nanofiltration membrane and its manufacturing method.

[0058] Methods for manufacturing organic solvent-resistant nanofiltration membranes include:

[0059] 1. Provides 4,4'-diaminodiphenyl ether, pyromellitic anhydride, octameric acid cage-like silsesquioxane and N,N-dimethylacetamide, wherein the chemical structure of octameric acid cage-like silsesquioxane is given in the chemical structural formula shown in the specific embodiments.

[0060] 2. Dissolve 1 mol of 4,4'-diaminodiphenyl ether and 0.05 mol of octamaleic acid cage-like silsesquioxane in 250 mL of N,N-dimethylacetamide, heat at 120 °C under reflux for 2 h to obtain the first mixture, and then cool the first mixture to 0 °C.

[0061] 3. Add 1.02 mol of pyromellitic anhydride to the cooled first mixture and stir at 0℃ for 8 h to obtain the second mixture;

[0062] 4. The second mixture is coated onto a glass plate to form a film, and then the film is immersed in deionized water at 25°C. After removal, it is vacuum dried at 25°C for 48 hours.

[0063] 5. The vacuum-dried membrane is vacuum-heated at 120°C for 2 hours, then vacuum-heated at 180°C for 4 hours, and then vacuum-heated at 280°C for 1 hour to obtain an organic solvent-resistant nanofiltration membrane.

[0064] Example 2

[0065] This embodiment provides an organic solvent-resistant nanofiltration membrane and its manufacturing method.

[0066] Methods for manufacturing organic solvent-resistant nanofiltration membranes include:

[0067] 1. Provides benzidine, maleic anhydride, octamaleic acid cage-like silsesquioxane and N,N-dimethylformamide;

[0068] 2. Dissolve 1 mol of benzidine and 0.5 mol of octamaleic acid cage-like silsesquioxane in 300 mL of N,N-dimethylformamide, heat at 100 °C under reflux for 4 h to obtain the first mixture, and then cool the first mixture to 5 °C;

[0069] 3. Add 1.05 mol of maleic anhydride to the cooled first mixture and stir at 5°C for 6 h to obtain the second mixture;

[0070] 4. The second mixture is coated onto a glass plate to form a film, and then the film is immersed in deionized water at 25°C. After removal, it is vacuum dried at 25°C for 48 hours.

[0071] 5. The vacuum-dried membrane is vacuum-heated at 100°C for 4 hours, then at 200°C for 4 hours, and then at 300°C for 1 hour to obtain an organic solvent-resistant nanofiltration membrane.

[0072] Example 3

[0073] This embodiment provides an organic solvent-resistant nanofiltration membrane and its manufacturing method.

[0074] Methods for manufacturing organic solvent-resistant nanofiltration membranes include:

[0075] 1. Provides p-phenylenediamine, pyromellitic anhydride, octamaleic acid cage-like silsesquioxane, and N-methylpyrrolidone;

[0076] 2. Dissolve 1 mol of p-phenylenediamine and 0.02 mol of octamaleic acid cage-like silsesquioxane in 250 mL of N-methylpyrrolidone, heat at 150 °C under reflux for 2 h to obtain the first mixture, and then cool the first mixture to 0 °C.

[0077] 3. Add 1 mol of pyromellitic anhydride to the cooled first mixture and stir at 0℃ for 8 h to obtain the second mixture;

[0078] 4. The second mixture is coated onto a glass plate to form a film, and then the film is immersed in deionized water at 25°C. After removal, it is vacuum dried at 25°C for 48 hours.

[0079] 5. The vacuum-dried membrane is then vacuum-heated at 150°C for 24 hours to obtain an organic solvent-resistant nanofiltration membrane.

[0080] Comparative Example

[0081] This comparative example provides an organic solvent-resistant nanofiltration membrane and its manufacturing method.

[0082] Methods for manufacturing organic solvent-resistant nanofiltration membranes include:

[0083] 1. Provides 4,4'-diaminodiphenyl ether, pyromellitic anhydride, and N,N-dimethylacetamide;

[0084] 2. Dissolve 1 mol of 4,4'-diaminodiphenyl ether and 1 mol of pyromellitic anhydride in 250 mL of N,N-dimethylacetamide and stir at 0 °C for 8 h to obtain a mixture;

[0085] 3. Coat the mixture onto a glass plate to form a film, then immerse the film in deionized water at 25°C, and remove it to vacuum dry at 25°C for 48 hours;

[0086] 4. The vacuum-dried membrane is vacuum-heated at 120°C for 2 hours, then vacuum-heated at 180°C for 4 hours, and then vacuum-heated at 280°C for 1 hour to obtain an organic solvent-resistant nanofiltration membrane.

[0087] The water flux and Na2SO4 rejection rate of the organic solvent-resistant nanofiltration membranes in Examples 1-3 and the comparative examples were tested, and the results are shown in Table 1.

[0088] Table 1

[0089] experimental group Example 1 Example 2 Example 3 Comparative Example <![CDATA[Sodium sulfate rejection rate (%)]]> 90 92 86 72 Flux (L / m2·h) 56 53 49 45

[0090] As can be seen from the data in Table 1, compared with the prior art, the present invention significantly improves the small molecule rejection rate and permeation flux of the organic solvent resistant nanofiltration membrane by introducing octamaleic acid cage-like silsesquioxane. Therefore, the present invention has significant progress compared with the prior art.

[0091] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for producing an organic solvent-resistant nanofiltration membrane sheet, characterized by comprising: The method comprises: providing a diamine, a dianhydride, an octa-maleimide acid cage silsesquioxane, and an aprotic polar solvent; mixing the diamine, the octa-maleimide acid cage silsesquioxane, and the aprotic polar solvent and heating to reflux to obtain a first mixture; mixing the first mixture with the dianhydride to obtain a second mixture; and curing the second mixture into a film to obtain the organic solvent resistant nanofiltration membrane.

2. The production method according to claim 1, characterized by The curing the second mixture into a film comprises: depositing the second mixture on a glass plate to form a thin film; immersing the thin film in a coagulation liquid and taking out to dry; and heating the thin film under vacuum at 100-300°C to form the organic solvent resistant nanofiltration membrane.

3. The production method according to claim 2, characterized by The depositing the second mixture is by a coating method; and / or The coagulation liquid is selected from one or more of distilled water, deionized water, and reverse osmosis water.

4. The production method according to claim 1, characterized by The diamine, the dianhydride, and the octa-maleimide acid cage silsesquioxane are in a molar ratio of 1:1-1.05:0.05-0.

5.

5. The production method according to claim 1, characterized by The heating to reflux is for 2-4 h; and / or The mixing the first mixture with the dianhydride to obtain a second mixture is for 6-8 h.

6. The production method according to claim 1, characterized by The heating to reflux is at a temperature of 100-150°C; and / or The mixing the first mixture with the dianhydride to obtain a second mixture is at a temperature of 0-5°C.

7. The production method according to claim 1, wherein The organic solvent resistant nanofiltration membrane has a thickness of 50-300 µm.

8. The production method according to claim 1, characterized by The diamine is selected from one or more of 4,4'-diaminodiphenyl ether, p-phenylenediamine, and biphenyl diamine; and / or The dianhydride is selected from one or more of pyromellitic dianhydride and maleic anhydride.

9. The production method according to claim 1, characterized by The aprotic polar solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

10. An organic solvent resistant nanofiltration membrane, characterized in that, The organic solvent resistant nanofiltration membrane is prepared by the method of any one of claims 1-9.

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