Composite polyolefin membrane-based pressure-resistant nanofiltration / reverse osmosis membrane and preparation method

Abstract

A composite polyolefin membrane-based pressure-resistant nanofiltration / reverse osmosis membrane and a preparation method. The preparation method comprises: carrying out hot-press compounding on a non-woven fabric and a polyolefin microporous membrane to prepare a composite polyolefin membrane, coating or impregnating the composite polyolefin-based membrane with a hydroxyl-containing polymer solution, drying same, and then carrying out hydrophilic modification on same, and finally, carrying out interfacial polymerization reaction on the hydrophilic modified composite polyolefin-based membrane to prepare the pressure-resistant nanofiltration / reverse osmosis membrane. The prepared composite polyolefin membrane-based pressure-resistant nanofiltration / reverse osmosis membrane can be applied to pressure-resistant fields such as industrial sewage, brackish water, and seawater desalination.

Description

Pressure-resistant nanofiltration / reverse osmosis membrane with composite polyolefin film as base material and preparation method TECHNICAL FIELD

[0001] The present application belongs to the technical field of nanofiltration / reverse osmosis membrane, and particularly relates to a pressure-resistant nanofiltration / reverse osmosis membrane prepared from a composite polyolefin base film and a preparation method. BACKGROUND

[0002] With the rapid development of China's economy, water pollution is becoming increasingly serious, and in recent years, water pollution incidents have occurred in many places in China. Nanofiltration / reverse osmosis membrane technology is widely used in life and industry due to its unique technical advantages, such as municipal sewage treatment, brackish water and seawater desalination, ultra-pure water preparation, and special separation fields such as food and beverage.

[0003] Nanofiltration / reverse osmosis membranes are mainly composed of a functional layer and a support layer. The structure and properties of the functional layer and the support layer can be independently controlled. The properties of the support layer, such as hydrophilicity / hydrophobicity, pore size and distribution, and surface charge, can affect the diffusion rate of active monomers and the degree of interfacial polymerization, thereby affecting the structure and performance of the nanofiltration / reverse osmosis membrane. In addition, the support layer provides mechanical support for the nanofiltration / reverse osmosis membrane, ensuring its stable operation in a pressure environment. Currently, commercial nanofiltration / reverse osmosis membranes mainly have a classic three-layer structure with "non-woven fabric + polysulfone as the support layer" and polyamide as the separation layer. The non-woven fabric and polysulfone account for about 70% of the total cost of the membrane sheet, and are mainly imported. Realizing the complete domestic substitution of composite membrane materials and reducing the cost of composite membranes are key problems to be solved in the field.

[0004] Currently, there are reports on the use of polyethylene (PE) and polypropylene (PP) membranes as support layers to prepare nanofiltration / reverse osmosis membranes. The polyolefin membranes used are from domestic manufacturers, and the thickness is generally 16-40 microns. However, the current main application field of polyolefin membranes is the new energy industry. Based on the pursuit of energy density in the new energy industry, the demand for polyethylene (PE) porous membranes tends to thinner thickness. High-thickness membranes are not advantageous in terms of market size and cost. However, in the field of water treatment applications, the base material needs to provide certain mechanical support. Thinner thickness means poorer pressure resistance, especially not conducive to its application in industrial environments. The present application proposes to replace the polyolefin and traditional "non-woven fabric + polysulfone" support layer with a composite polyolefin base film, which can effectively improve the mechanical strength and pressure resistance of the membrane prepared from the single polyolefin base material, and save 20%-40% of the manufacturing cost. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art and provide a pressure-resistant nanofiltration / reverse osmosis membrane with a composite polyolefin film as a base material and a preparation method.

[0006] A method for preparing a pressure-resistant nanofiltration / reverse osmosis membrane using a composite polyolefin film as a base material, comprising the following steps:

[0007] 1) The composite polyolefin base film is hydrophilically modified by coating or dipping with a hydroxyl-containing polymer solution and then drying, and the modified base film is used for interfacial polymerization to support the membrane;

[0008] 2) A multi-functional amine monomer, an acid acceptor, and a monomer diffusing agent are dissolved in water in mass percentage to obtain an aqueous solution for interfacial polymerization;

[0009] 3) The hydrophilically modified composite polyolefin base film of step 1) is immersed in the aqueous solution of step 2) for a period of time to obtain a base film adsorbed with the aqueous solution, and then the excess aqueous solution is removed;

[0010] 4) A multi-acid chloride is dissolved in an oil phase solvent in mass percentage to obtain an oil phase solution for interfacial polymerization;

[0011] 5) The oil phase solution obtained in step 4) is coated on the surface of the base film adsorbed with the aqueous solution of step 3) and reacted for a period of time, and then the excess oil phase is removed;

[0012] 6) The pressure-resistant nanofiltration / reverse osmosis membrane obtained by the reaction of step 5) is dried in an oven.

[0013] The composite polyolefin film in step 1) is obtained by hot pressing a non-woven fabric and a polyolefin microporous film. The non-woven fabric is composed of one or more of ES composite fibers, low-melting-point COPET / PET fibers, PE / PET composite fibers, polyolefin multi-fiber, PP fibers, PET fibers, and unstretched PET fibers, with a thickness of 20-100 μm and a grammage of 8-80 g / m2. The polyolefin microporous film has a thickness of 9-40 μm, an average pore size of 0.02-0.08 μm, a porosity of 30-50%, and is made of polyethylene, polypropylene, or a composite material of polyethylene and polypropylene, preferably polyethylene. The polyolefin microporous film can be obtained by known techniques such as dry or wet processes, or can be purchased as a polyolefin separator product used in battery technology.

[0014] The hydroxyl-containing polymer solution in step 1) includes but is not limited to polyvinyl alcohol, polyacrylic acid, chitosan, polyvinylpyrrolidone, etc.

[0015] The multifunctional amine monomer in step 2) includes but is not limited to one or more combinations of piperazine, homopiperazine, N-methylpiperazine, N-isopropylpiperazine, 1-amino-4-methylpiperazine, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, ethylenediamine, propylenediamine and tris(2-diaminoethyl)amine; the acid acceptor in step 2) includes but is not limited to one or more combinations of triethylamine, sodium acetate, sodium camphorsulfonate, N-N diisopropylethylamine, pyridine, potassium carbonate; the monomer diffusion agent in step 2) includes but is not limited to one or more combinations of tetrahydrofuran, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, ethoxylated nonylphenol, etc.

[0016] The mass percentage concentration of the aqueous solution in step 2) is: 0.5-3.5% multifunctional amine monomer, 0.1-5% acid acceptor, 0.01-1% monomer diffusion agent;

[0017] The modified composite polyolefin-based film in step 3) is immersed in the aqueous solution for 0.5-10 min;

[0018] The oil phase solution in step 4) is a polyacyl chloride solution with a mass percentage concentration of 0.1-5%;

[0019] The polyacyl chloride in step 4) includes but is not limited to one or more combinations of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride and phthaloyl chloride, etc.

[0020] The oil phase solvent in step 4) includes but is not limited to one or more of n-hexane, cyclohexane, isomeric alkane solvent oil, etc., and the isomeric alkane solvent oil can be ISOPAR-G, ISOPAR-H, ISOPAR-L.

[0021] The reaction time of the oil phase solvent in step 5) after adsorbing the aqueous phase is 0.5-10 min;

[0022] The oven heat treatment temperature in step 6) is 30-100℃, and the heat treatment time is 0.5-60 min.

[0023] The composite non-woven polyolefin-based nanofiltration / reverse osmosis membrane prepared according to the above method is obtained on the non-woven support layer, and the polyolefin layer is the functional layer as shown in FIG. 3. The performance and pressure resistance of the composite non-woven polyolefin-based nanofiltration / reverse osmosis membrane are comparable to those of the current commercial nanofiltration / reverse osmosis membrane. Therefore, the nanofiltration / reverse osmosis membrane prepared by using the composite polyolefin-based membrane can effectively reduce the raw material cost while ensuring the original performance and meeting the application scenarios of high pressure.

[0024] In addition, the prepared nanofiltration / reverse osmosis membrane can be used in various element forms, such as a roll-type membrane element, a disc-type element or a plate-and-frame assembly. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a composite polyolefin-based nanofiltration membrane prepared according to Example 4 of the present application;

[0026] Figure 2 is a composite polyolefin-based reverse osmosis membrane prepared according to Example 16 of the present application;

[0027] Figure 3 is a schematic diagram of a composite polyolefin-based pressure-resistant nanofiltration / reverse osmosis cross-section. DETAILED DESCRIPTION

[0028] The present application is further illustrated by the following examples, which are not intended to limit the present application.

[0029] The nanofiltration membrane performance test was tested according to the method in the Nanofiltration Membrane Test Method (GB / T 34242-2017), using the test conditions of industrial nanofiltration membranes, specifically 2000 mg / L MgSO 4 test solution, PH = 7.5 ± 0.5, test temperature 25 ± 0.2℃, test pressure 0.69 Mpa ± 0.2 Mpa, membrane flow rate > 0.45 m / s.

[0030] The reverse osmosis membrane performance test was tested according to the method in the Reverse Osmosis Membrane Test Method (GB / T 32373-2015), using the test conditions of brackish water reverse osmosis membranes, specifically 2000 mg / L NaCl test solution, PH = 7.5 ± 0.5, test temperature 25 ± 0.2℃, test pressure 1.55 Mpa ± 0.02 Mpa, membrane flow rate > 0.45 m / s.

[0031] The pressure-resistant performance test method: after the initial performance of the membrane test, run for 3 hours under 500 psi pressure, and then repeat the test according to the above nanofiltration membrane and reverse osmosis membrane conditions, and compare the difference in desalination rate with the initial desalination rate.

[0032] Example 1

[0033] A method for preparing a pressure-resistant nanofiltration membrane using a composite polyolefin-based membrane is as follows:

[0034] A 40 μm total thickness non-woven composite polyolefin membrane with a contact angle of 110-120° was used as the base film. A water phase solution with a mass concentration of 2% piperazine, 2% sodium camphor sulfonate and 0.5% sodium dodecyl benzene sulfonate was prepared, and the composite polyolefin-based membrane was immersed in the water phase solution for 60 s, and the excess water phase solution was removed. An oil phase solution with a mass concentration of 0.5% was prepared, with uniform benzene tricarbonyl chloride as the solute and n-hexane as the solvent. The oil phase solution was poured onto the surface of the base film and reacted for 30 s, after which the excess reaction solution was poured off and dried in a 70℃ oven for 5 min, thereby obtaining a composite polyolefin-based pressure-resistant nanofiltration membrane. The test flux was 24.5 L / (m 2 ·h) and the initial desalination rate was 96.2%.

[0035] Example 2

[0036] A method for preparing a pressure-resistant nanofiltration membrane from a composite polyolefin-based film is as follows:

[0037] A non-woven composite polyolefin film with a total thickness of 40 μm is used as a base film, which is coated with a 0.5% polyvinyl alcohol solution and then dried to obtain a hydrophilic modified base film with a contact angle of 70-80°. A water phase solution with a mass concentration of 2% piperazine, 2% sodium camphor sulfonate and 0.5% sodium dodecyl benzene sulfonate is prepared, and the composite polyolefin base film is immersed in the water phase solution for 60 s and then excess water phase solution is removed. An oil phase solution with a mass concentration of 0.5% is prepared, in which the solute is trimesoyl chloride and the solvent is n-hexane. The oil phase solution is poured onto the surface of the base film and reacted for 30 s, after which the excess reaction solution is poured off and dried in a 70°C oven for 5 min to obtain a composite polyolefin base pressure-resistant nanofiltration membrane. The test flux is 70.23 L / (m2·h) and the initial desalination rate is 98.2%.

[0038] Example 3

[0039] A method for preparing a pressure-resistant nanofiltration membrane from a composite polyolefin-based film is as follows:

[0040] A non-woven composite polyolefin film with a total thickness of 80 μm is used as a base film, which is coated with a 0.5% polyvinyl alcohol solution and then dried to obtain a hydrophilic modified base film with a contact angle of 70-80°. A water phase solution with a mass concentration of 2% piperazine, 2% sodium camphor sulfonate and 0.5% sodium dodecyl benzene sulfonate is prepared, and the composite polyolefin base film is immersed in the water phase solution for 60 s and then excess water phase solution is removed. An oil phase solution with a mass concentration of 0.5% is prepared, in which the solute is trimesoyl chloride and the solvent is n-hexane. The oil phase solution is poured onto the surface of the base film and reacted for 30 s, after which the excess reaction solution is poured off and dried in a 70°C oven for 5 min to obtain a composite polyolefin base pressure-resistant nanofiltration membrane. The test flux is 68.32 L / (m2·h) and the initial desalination rate is 98.7%.

[0041] Example 4

[0042] A method for preparing a pressure-resistant nanofiltration membrane from a composite polyolefin-based film is as follows:

[0043] A total thickness of 120 μm non-woven composite polyolefin film is used as a base film, which is coated with a 0.5% polyvinyl alcohol solution and dried to obtain a hydrophilic modified base film with a contact angle of 70-80°. A water phase solution with a mass concentration of 2% piperazine, 2% sodium camphor sulfonate and 0.5% sodium dodecyl benzene sulfonate is prepared, and the composite polyolefin base film is immersed in the water phase solution for 60 s and the excess water phase solution is removed. An oil phase solution with a mass concentration of 0.5% is prepared, with uniform benzene trichloride as the solute and n-hexane as the solvent. The oil phase solution is poured onto the surface of the base film and reacted for 30 s, and then the excess reaction solution is poured off and dried in a 70°C oven for 5 min to obtain a composite polyolefin base pressure-resistant nanofiltration membrane. The test flux is 65.34 L / (m2·h) and the initial desalination rate is 99.0%.

[0044] Example 5

[0045] A method for preparing a pressure-resistant nanofiltration membrane from a composite polyolefin base film is as follows:

[0046] A total thickness of 120 μm non-woven composite polyolefin film is used as a base film, which is coated with a 0.5% polyvinyl alcohol solution and dried to obtain a hydrophilic modified base film with a contact angle of 70-80°. A water phase solution with a mass concentration of 4% piperazine, 2% sodium camphor sulfonate and 0.5% sodium dodecyl benzene sulfonate is prepared, and the composite polyolefin base film is immersed in the water phase solution for 60 s and the excess water phase solution is removed. An oil phase solution with a mass concentration of 0.5% is prepared, with uniform benzene trichloride as the solute and n-hexane as the solvent. The oil phase solution is poured onto the surface of the base film and reacted for 30 s, and then the excess reaction solution is poured off and dried in a 70°C oven for 5 min to obtain a composite polyolefin base pressure-resistant nanofiltration membrane. The test flux is 59.31 L / (m2·h) and the initial desalination rate is 98.9%.

[0047] Example 6

[0048] A method for preparing a pressure-resistant nanofiltration membrane from a composite polyolefin base film is as follows:

[0049] A total thickness of 120 μm non-woven composite polyolefin film is used as a base film, which is coated with a 0.5% polyvinyl alcohol solution and dried to obtain a hydrophilic modified base film with a contact angle of 70-80°. A water phase solution with a mass concentration of 4% piperazine, 2% sodium camphor sulfonate and 0.5% sodium dodecyl benzene sulfonate is prepared, and the composite polyolefin base film is immersed in the water phase solution for 60 s and the excess water phase solution is removed. An oil phase solution with a mass concentration of 0.2% is prepared, with uniform benzene trichloride as the solute and n-hexane as the solvent. The oil phase solution is poured onto the surface of the base film and reacted for 30 s, and then the excess reaction solution is poured off and dried in a 70°C oven for 5 min to obtain a composite polyolefin base pressure-resistant nanofiltration membrane. The test flux is 67.17 L / (m2·h) and the initial desalination rate is 98.1%.

[0050] Example 7

[0051] A method for preparing a pressure-resistant nanofiltration membrane from a composite polyolefin-based film is as follows:

[0052] A non-woven composite polyolefin film with a total thickness of 120 μm is used as a base film, which is coated with a 0.5% polyvinyl alcohol solution and then dried to obtain a hydrophilic modified base film with a contact angle of 70-80°. A water phase solution with a mass concentration of 4% piperazine, 2% sodium camphor sulfonate and 0.5% sodium dodecyl benzene sulfonate is prepared, and the composite polyolefin base film is immersed in the water phase solution for 60 s and then excess water phase solution is removed. An oil phase solution with a mass concentration of 0.5% is prepared, in which the solute is trimesoyl chloride and the solvent is n-hexane. The oil phase solution is poured onto the surface of the base film and reacted for 10 s, after which the excess reaction solution is poured off and dried in a 70°C oven for 5 min to obtain a composite polyolefin base pressure-resistant nanofiltration membrane. The test flux is 68.34 L / (m2·h) and the initial desalination rate is 98%.

[0053] Example 8

[0054] A method for preparing a pressure-resistant nanofiltration membrane from a composite polyolefin-based film is as follows:

[0055] A non-woven composite polyolefin film with a total thickness of 120 μm is used as a base film, which is coated with a 0.5% polyvinyl alcohol solution and then dried to obtain a hydrophilic modified base film with a contact angle of 70-80°. A water phase solution with a mass concentration of 4% piperazine, 2% sodium camphor sulfonate and 0.5% sodium dodecyl benzene sulfonate is prepared, and the composite polyolefin base film is immersed in the water phase solution for 60 s and then excess water phase solution is removed. An oil phase solution with a mass concentration of 0.5% is prepared, in which the solute is trimesoyl chloride and the solvent is n-hexane. The oil phase solution is poured onto the surface of the base film and reacted for 10 s, after which the excess reaction solution is poured off and dried in a 70°C oven for 5 min to obtain a composite polyolefin base pressure-resistant nanofiltration membrane. The test flux is 68.34 L / (m2·h) and the initial desalination rate is 98%.

[0056] Example 9

[0057] A method for preparing a pressure-resistant nanofiltration membrane from a composite polyolefin-based film is as follows:

[0058] A 120μm thick non-woven composite polyolefin membrane was used as the base membrane. A 0.5% polyvinyl alcohol solution was quantitatively coated and then dried to obtain a hydrophilic-modified base membrane with a contact angle of 70-80°. An aqueous solution containing 4% piperazine, 2% sodium camphorsulfonate, and 0.5% sodium dodecylbenzenesulfonate was prepared. The composite polyolefin-based membrane was immersed in the aqueous solution for 60 seconds, and the excess aqueous solution was removed. A 0.5% oily solution containing trimesoyl chloride as the solute and n-hexane as the solvent was then poured onto the membrane surface to react for 30 seconds. The excess reaction solution was then removed and the membrane was dried in a 90°C oven for 5 minutes to obtain the composite polyolefin-based pressure-resistant nanofiltration membrane. The membrane achieved a flux of 71.42 L / (m2·h) and an initial salt rejection rate of 97.2%.

[0059] Comparative Example 10

[0060] A method for preparing a nanofiltration membrane from a polyolefin-based membrane is as follows:

[0061] A 20μm-thick polyethylene film was used as the base membrane, quantitatively coated with a 0.5% polyvinyl alcohol solution and then dried to obtain a hydrophilic-modified base membrane with a contact angle of 70-80°. An aqueous solution containing 2% piperazine, 2% sodium camphorsulfonate, and 0.5% sodium dodecylbenzenesulfonate was prepared. The composite polyolefin base membrane was immersed in the aqueous solution for 60 seconds, and the excess aqueous solution was removed. A 0.5% oily solution containing trimesoyl chloride as the solute and n-hexane as the solvent was then poured onto the base membrane surface to react for 30 seconds. The excess reaction solution was then discarded and the membrane was dried in a 70°C oven for 5 minutes to obtain the polyethylene nanofiltration membrane. The test flux was 62.37 L / (m2·h) and the initial salt rejection rate was 98.9%.

[0062] Example 11

[0063] A method for preparing a pressure-resistant reverse osmosis membrane from a composite polyolefin-based membrane is as follows:

[0064] A 40μm thick non-woven composite polyolefin membrane with a contact angle of 110-120° was used as the base membrane. An aqueous solution containing 3.5% m-phenylenediamine, 3% triethylamine, and 0.5% sodium dodecylbenzenesulfonate was prepared. The hydrophilically modified composite polyolefin membrane was immersed in the aqueous solution for 60 seconds, and the excess aqueous solution was removed. A 0.5% oily solution containing trimesoyl chloride as the solute and n-hexane as the solvent was poured onto the membrane surface to react for 30 seconds. The excess reaction solution was then discarded and the membrane was dried in a 70°C oven for 5 minutes to produce the composite polyolefin-based pressure-resistant reverse osmosis membrane. The membrane achieved a flux of 30.73 L / (m2·h) and an initial salt rejection rate of 95.2%.

[0065] Example 12

[0066] A method for preparing a pressure-resistant reverse osmosis membrane from a composite polyolefin base film is as follows:

[0067] A non-woven composite polyolefin film with a total thickness of 40 μm is used as the base film, which is coated with a 0.5% polyvinyl alcohol solution and then dried to obtain a hydrophilic modified base film with a contact angle of 70-80°. A water phase solution with a mass concentration of 3.5% m-phenylenediamine, 3% triethylamine and 0.5% sodium dodecyl benzene sulfonate is prepared, and the hydrophilic modified composite polyolefin base film is immersed in the water phase solution for 60 s and then excess water phase solution is removed. An oil phase solution with a mass concentration of 0.5% is prepared, in which the solute is trimesoyl chloride and the solvent is n-hexane. The oil phase solution is poured onto the surface of the base film and reacted for 30 s, after which the excess reaction solution is poured off and dried in a 70°C oven for 5 min to obtain a pressure-resistant reverse osmosis membrane made of a composite polyolefin base film. The test flux is 47.68 L / (m2·h) and the initial desalination rate is 98.0%.

[0068] Example 13

[0069] A method for preparing a pressure-resistant reverse osmosis membrane from a composite polyolefin base film is as follows:

[0070] A non-woven composite polyolefin film with a total thickness of 80 μm is used as the base film, which is coated with a 0.5% polyvinyl alcohol solution and then dried to obtain a hydrophilic modified base film with a contact angle of 70-80°. A water phase solution with a mass concentration of 3.5% m-phenylenediamine, 3% triethylamine and 0.5% sodium dodecyl benzene sulfonate is prepared, and the hydrophilic modified composite polyolefin base film is immersed in the water phase solution for 60 s and then excess water phase solution is removed. An oil phase solution with a mass concentration of 0.5% is prepared, in which the solute is trimesoyl chloride and the solvent is n-hexane. The oil phase solution is poured onto the surface of the base film and reacted for 30 s, after which the excess reaction solution is poured off and dried in a 70°C oven for 5 min to obtain a pressure-resistant reverse osmosis membrane made of a composite polyolefin base film. The test flux is 45.32 L / (m2·h) and the initial desalination rate is 98.4%.

[0071] Example 14

[0072] A method for preparing a pressure-resistant reverse osmosis membrane from a composite polyolefin base film is as follows:

[0073] A non-woven fabric composite polyolefin film with a total thickness of 120 μm is used as a base film, which is coated with a 0.5% polyvinyl alcohol solution and dried to obtain a hydrophilic modified base film with a contact angle of 70-80°. A water phase solution with a mass concentration of 3.5% m-phenylenediamine, 3% triethylamine and 0.5% sodium dodecyl benzene sulfonate is prepared, and the hydrophilic modified composite polyolefin base film is immersed in the water phase solution for 60 s and the excess water phase solution is removed. An oil phase solution with a mass concentration of 0.5% is prepared, in which the solute is trimesoyl chloride and the solvent is n-hexane. The oil phase solution is poured on the surface of the base film and reacted for 30 s, and then the excess reaction solution is poured off and dried in a 70°C oven for 5 min to obtain a composite polyolefin base pressure-resistant reverse osmosis membrane. The test flux is 42.73 L / (m2·h) and the initial desalination rate is 99.0%.

[0074] Example 15

[0075] A method for preparing a pressure-resistant reverse osmosis membrane based on a composite polyolefin base film is as follows:

[0076] A non-woven fabric composite polyolefin film with a total thickness of 120 μm is used as a base film, which is coated with a 0.5% polyvinyl alcohol solution and dried to obtain a hydrophilic modified base film with a contact angle of 70-80°. A water phase solution with a mass concentration of 3.5% m-phenylenediamine, 3% triethylamine and 0.5% sodium dodecyl benzene sulfonate is prepared, and the hydrophilic modified composite polyolefin base film is immersed in the water phase solution for 60 s and the excess water phase solution is removed. An oil phase solution with a mass concentration of 0.5% is prepared, in which the solute is trimesoyl chloride and the solvent is n-hexane. The oil phase solution is poured on the surface of the base film and reacted for 30 s, and then the excess reaction solution is poured off and dried in a 70°C oven for 5 min to obtain a composite polyolefin base pressure-resistant reverse osmosis membrane. The test flux is 42.73 L / (m2·h) and the initial desalination rate is 99.0%.

[0077] Example 16

[0078] A method for preparing a pressure-resistant reverse osmosis membrane based on a composite polyolefin base film is as follows:

[0079] A non-woven fabric composite polyolefin film with a total thickness of 120 μm is used as a base film, which is coated with a 0.5% polyvinyl alcohol solution and dried to obtain a hydrophilic modified base film with a contact angle of 70-80°. A water phase solution with a mass concentration of 4.5% m-phenylenediamine, 3% triethylamine and 0.5% sodium dodecyl benzene sulfonate is prepared, and the hydrophilic modified composite polyolefin base film is immersed in the water phase solution for 60 s and the excess water phase solution is removed. An oil phase solution with a mass concentration of 0.5% is prepared, in which the solute is trimesoyl chloride and the solvent is n-hexane. The oil phase solution is poured on the surface of the base film and reacted for 30 s, and then the excess reaction solution is poured off and dried in a 70°C oven for 5 min to obtain a composite polyolefin base pressure-resistant reverse osmosis membrane. The test flux is 37.52 L / (m2·h) and the initial desalination rate is 99.1%.

[0080] Example 17

[0081] A method for preparing a pressure-resistant reverse osmosis membrane from a composite polyolefin base film is as follows:

[0082] A non-woven fabric composite polyolefin film with a total thickness of 120 μm is used as a base film, which is coated with a 0.5% polyvinyl alcohol solution and dried to obtain a hydrophilic modified base film with a contact angle of 70-80°. A water phase solution with a mass concentration of 4.5% m-phenylenediamine, 3% triethylamine and 0.5% sodium dodecyl benzene sulfonate is prepared, and the hydrophilic modified composite polyolefin base film is immersed in the water phase solution for 60 s and the excess water phase solution is removed. An oil phase solution with a mass concentration of 0.5% is prepared, in which the solute is trimesoyl chloride and the solvent is n-hexane. The oil phase solution is poured on the surface of the base film and reacted for 30 s, and then the excess reaction solution is poured off and dried in a 70°C oven for 5 min to obtain a composite polyolefin base pressure-resistant reverse osmosis membrane. The test flux is 37.52 L / (m2·h) and the initial desalination rate is 99.1%.

[0083] Example 18

[0084] A method for preparing a pressure-resistant reverse osmosis membrane from a composite polyolefin base film is as follows:

[0085] A total thickness of 120 μm non-woven composite polyolefin film is used as a base film, which is coated with 0.5% polyvinyl alcohol solution and dried to obtain a hydrophilic modified base film with a contact angle of 70-80°. A water phase solution with a mass concentration of 3.5% m-phenylenediamine, 3% triethylamine and 0.5% sodium dodecyl benzene sulfonate is prepared, and the hydrophilic modified composite polyolefin base film is immersed in the water phase solution for 60 s and the excess water phase solution is removed. An oil phase solution with a mass concentration of 0.5% is prepared, with uniform benzene tricarbonyl chloride as the solute and n-hexane as the solvent, and the oil phase solution is poured onto the surface of the base film for reaction for 10 s, after which the excess reaction solution is poured off and dried in a 70°C oven for 5 min to obtain a composite polyolefin base pressure reverse osmosis membrane. The test flux is 48.63 L / (m2·h) and the initial desalination rate is 97.5%.

[0086] Example 19

[0087] A method for preparing a pressure reverse osmosis membrane from a composite polyolefin base film is as follows:

[0088] A total thickness of 120 μm non-woven composite polyolefin film is used as a base film, which is coated with 0.5% polyvinyl alcohol solution and dried to obtain a hydrophilic modified base film with a contact angle of 70-80°. A water phase solution with a mass concentration of 3.5% m-phenylenediamine, 3% triethylamine and 0.5% sodium dodecyl benzene sulfonate is prepared, and the hydrophilic modified composite polyolefin base film is immersed in the water phase solution for 60 s and the excess water phase solution is removed. An oil phase solution with a mass concentration of 0.5% is prepared, with uniform benzene tricarbonyl chloride as the solute and n-hexane as the solvent, and the oil phase solution is poured onto the surface of the base film for reaction for 30 s, after which the excess reaction solution is poured off and dried in a 50°C oven for 5 min to obtain a composite polyolefin base pressure reverse osmosis membrane. The test flux is 38.39 L / (m2·h) and the initial desalination rate is 97.7%.

[0089] Comparative Example 20

[0090] A method for preparing a reverse osmosis membrane from a polyolefin base film is as follows:

[0091] A thickness of 20 μm polyethylene film is used as a base film, which is coated with 0.5% polyvinyl alcohol solution and dried to obtain a hydrophilic modified base film with a contact angle of 70-80°. A water phase solution with a mass concentration of 3.5% m-phenylenediamine, 3% triethylamine and 0.5% sodium dodecyl benzene sulfonate is prepared, and the hydrophilic modified composite polyolefin base film is immersed in the water phase solution for 60 s and the excess water phase solution is removed. An oil phase solution with a mass concentration of 0.5% is prepared, with uniform benzene tricarbonyl chloride as the solute and n-hexane as the solvent, and the oil phase solution is poured onto the surface of the base film for reaction for 30 s, after which the excess reaction solution is poured off and dried in a 70°C oven for 5 min to obtain a polyethylene reverse osmosis membrane. The test flux is 40.37 L / (m2·h) and the initial desalination rate is 98.8%.

[0092] Table 1 Nanofiltration membrane examples

[0093] Table 2 Reverse osmosis membrane examples

Claims

1. A method for preparing a pressure-resistant nanofiltration / reverse osmosis membrane using a composite polyolefin membrane as a base material, characterized by, The method comprises the following steps: 1) Hydrophilic modification of the composite polyolefin base film by coating or impregnating with a hydroxyl-containing polymer solution and then drying; the modified base film is used for interfacial polymerization of the support film; 2) Dissolve the multifunctional amine monomer, acid acceptor and monomer diffusion agent in water in a mass percentage to obtain an aqueous solution for interfacial polymerization; 3) Impregnate the hydrophilic modified composite polyolefin base film in the aqueous solution of step 2) for a period of time to obtain a base film adsorbed with the aqueous phase; then remove the excess aqueous solution; 4) Dissolve the polyacyl chloride in an oil phase solvent in a mass percentage to obtain an oil phase solution for interfacial polymerization; 5) Coat the oil phase solution obtained in step 4) on the surface of the base film adsorbed with the aqueous phase of step 3) and react for a period of time, then remove the excess oil phase; 6) Dry the pressure-resistant nanofiltration / reverse osmosis membrane obtained in step 5) in an oven.

2. The method of claim 1, wherein, The composite polyolefin film in step 1) is formed by hot pressing a non-woven fabric and a polyolefin microporous film; the non-woven fabric is composed of one or more of ES composite fibers, low-melting-point COPET / PET fibers, PE / PET composite fibers, polyolefin multi-fiber, PP fibers, PET fibers and unstretched PET fibers, with a thickness of 20-100 μm and a grammage of 8-80 g / m2. The polyolefin microporous film has a thickness of 9-40 μm, an average pore size of 0.02-0.08 μm, a porosity of 30-50%, and is made of polyethylene, polypropylene or a composite material of polyethylene and polypropylene, preferably polyethylene. The hydroxyl-containing polymer solution in step 1) includes but is not limited to one or more of polyvinyl alcohol, polyacrylic acid, chitosan, polyvinylpyrrolidone, etc.

3. The method of claim 1, wherein, The multifunctional amine monomer in step 2) includes but is not limited to one or more of piperazine, homopiperazine, N-methylpiperazine, N-isopropylpiperazine, 1-amino-4-methylpiperazine, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, ethylenediamine, propylenediamine and tris(2-diaminoethyl)amine; the acid acceptor in step 2) includes but is not limited to one or more of triethylamine, sodium acetate, sodium camphorsulfonate, N-N diisopropylethylamine, pyridine, potassium carbonate; the monomer diffusion agent in step 2) includes but is not limited to one or more of tetrahydrofuran, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, ethoxylated nonylphenol, etc.

4. The method of claim 1, wherein, The aqueous solution in step 2) has a mass percentage concentration of 0.5-3.5% multifunctional amine monomer, 0.1-5% acid acceptor and 0.01-1% monomer diffusion agent.

5. The method of claim 1, wherein, The modified composite polyolefin base film in step 3) is impregnated in the aqueous solution for 0.5-10 min.

6. The method of claim 1, wherein, The oil phase solution in step 4) is a polyacyl chloride solution with a mass percentage concentration of 0.1-5%. The polybasic acid chlorides in step 4) include, but are not limited to, one or more combinations of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, and phthaloyl chloride; the oil phase solvents in step 4) include, but are not limited to, one or more of n-hexane, cyclohexane, isomeric alkane solvent oil, and the like, and the isomeric alkane solvent oil can be ISOPAR-G, ISOPAR-H, ISOPAR-L.

7. The method of claim 1, wherein The reaction time of the oil phase solvent in step 5) after adsorbing the water phase is 0.5-10 min.

8. The method of claim 1, wherein, The oven heat treatment temperature in step 6) is 30-100°C, and the heat treatment time is 0.5-60 min.

9. The pressure-resistant nanofiltration / reverse osmosis membrane prepared according to the method of any one of claims 1-8, wherein the base material is a composite polyolefin membrane.

10. The pressure-resistant nanofiltration / reverse osmosis membrane prepared according to the method of any one of claims 1-8, wherein the base material is a composite polyolefin membrane, and the membrane is used for nanofiltration or reverse osmosis.

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