Composite separation membrane as well as preparation method and application thereof

Abstract

The invention discloses a composite separation membrane and a preparation method and application thereof, and belongs to the technical field of separation membranes, and the preparation method comprises the following steps: uniformly mixing a polymer, a solvent, a small molecule additive and a polymer additive according to different proportions to obtain membrane casting solutions with different viscosities; coating a base material with the casting membrane solutions with different viscosities in a blade manner, placing the base material in a solidification solution for solidification, and drying to obtain a composite separation membrane; the membrane casting solution comprises a first membrane casting solution and a second membrane casting solution, and the viscosity of the first membrane casting solution at 50 DEG C is 15000-40000 cp; the viscosity of the second membrane casting solution at the temperature of 50 DEG C is 2000-8000 cp; the viscosity of the third membrane casting solution at the temperature of 50 DEG C is 1000-5000 cp. The composite separation membrane provided by the invention has a multi-layer composite structure, and can effectively separate proteins, viruses and other media while maintaining high filtration efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of separation membranes, and in particular to a composite separation membrane and a preparation method and application thereof. Background Art

[0002] Viruses are usually cultivated using proteins as carriers. After the cultivation is complete, membrane separation technology is required to separate the viruses and proteins for efficient separation. This process requires strict control of the separation accuracy of the separation membrane, and during long-term filtration, it is necessary to ensure that the filtration efficiency of the separation membrane decays slowly.

[0003] The separation membrane needs to have precise pore size control to intercept macromolecular substances to be removed and allow proteins to pass through. At the same time, the separation membrane is required to have good anti-fouling performance and can be reused. After long-term filtration, protein compounds are easily adsorbed on the membrane surface or block the membrane pores to cause membrane pollution, resulting in reduced separation membrane flux, poor filtration effect and other problems. At present, there are few examples of separation membranes that have successfully solved problems such as pollution resistance, protein adsorption resistance, and rapid attenuation of protein flux after long-term filtration. The pollution resistance of separation membranes needs to be solved urgently.

[0004] Patent CN109603569A discloses a film-forming device and method for continuously preparing a composite membrane with a PDMS separation layer. This device prepares the composite membrane by scraping another layer of film on the base membrane; Chinese patent application CN117695862A discloses an acid-resistant polyethersulfone composite membrane and its preparation method. This method also prepares the composite membrane by first preparing a layer of film and then repeating the film coating, which is suitable for use in acidic environments; Patent CN113578061A discloses a method for preparing a composite nanofiltration membrane from a contaminated polyethersulfone ultrafiltration membrane. This method coats a phenolic monomer and a mixed solution containing calcium ions and polyethyleneimine on the polyethersulfone nanofiltration membrane in two steps. This membrane uses environmentally friendly calcium ions as coordination cross-linking ions, and calcium ions can also interact with the humus pollution layer to improve stability. In addition, polyethyleneimine small molecules are introduced to improve the separation efficiency of the selective layer of the composite nanofiltration membrane, realizing the upgrade and recycling of the contaminated polyethersulfone ultrafiltration membrane; Patent CN106823841A discloses a method for preparing a polyethersulfone functional composite separation membrane. This method prepares a polyethersulfone separation membrane carrying amino phosphonic acid functional groups and coats a nanofiltration retention thin layer on the surface of the polyethersulfone separation membrane. The preparation process of this membrane has little harm to human health. The nanofiltration retention layer on the surface of this separation membrane and the internal amino phosphonic acid chelating groups are stable, not easily detached and leached, and it has a high interception efficiency for heavy metals, showing broad application prospects in the field of heavy metal wastewater pollution treatment; Patent CN109289555A discloses a method for preparing an ultrafiltration membrane. This method forms a fouling-resistant layer formed by polyethylene glycol on the separation layer formed by polyethersulfone with carboxyl groups. This membrane has a high interception rate, excellent water flux recovery rate and low water flux decline rate, and has strong anti-fouling properties; Patent CN113893701A discloses a method for preparing a conductive polyethersulfone separation membrane. This method embeds conductive nanoparticles in the polyethersulfone separation membrane to endow the membrane with conductive properties, and this membrane has a high BSA interception rate and flux recovery rate, thus improving the anti-fouling ability; Patent CN103263863A discloses a method for preparing an amphoteric polyethersulfone separation membrane. This method uses plasma treatment to graft acrylic monomers on the surface of the polyethersulfone separation membrane to obtain an amphoteric membrane with amine groups and carboxyl groups on the membrane surface. The hydrophilicity of this membrane is enhanced, improving the anti-fouling performance and water passage performance, thereby improving the filtration efficiency. Moreover, plasma treatment is widely used in grafting applications, with simple operation and simple raw material sources; Patent CN115337790A discloses a method for preparing a superhydrophilic polyethersulfone separation membrane. This method modifies the membrane surface using the characteristics of oxidation, self-polymerization, cross-linking and adhesion of dopamine compounds. The membrane surface has a high porosity, persistent superhydrophilic properties and a low protein interception rate.

[0005] Regarding the patent for the preparation device and method of the composite separation membrane above, it mainly focuses on the device for preparing a single-layer separation membrane, and there are risks such as easy shedding and instability for the membrane with a modified layer. It does not involve serious loss of separation membrane additives, rapid attenuation of protein filtration flux over a long time, improvement of membrane stability and safety, etc. Therefore, it is of great significance to develop a multi-layer composite separation membrane preparation device and its preparation method to achieve efficient separation and long-term stability of the separation membrane. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a composite separation membrane, its preparation method and application. The present invention can effectively separate media such as proteins and viruses while maintaining a high filtration efficiency.

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

[0008] A preparation method of a composite separation membrane includes the following steps:

[0009] Mix polymers, solvents, small molecule additives and polymer additives evenly in different proportions to obtain casting solutions with different viscosities.

[0010] Scrape the casting solutions with different viscosities on a substrate, place them in a coagulation bath for curing and drying to obtain a composite separation membrane.

[0011] The casting solution includes a first casting solution and a second casting solution. The viscosity of the first casting solution at 50°C is 15000 - 40000 cp; the viscosity of the second casting solution at 50°C is 2000 - 8000 cp.

[0012] The composite separation membrane of the present invention has a multi-layer composite structure, can effectively separate media such as proteins and viruses while maintaining a high filtration efficiency; the combined morphology of the multi-layer composite membrane structure can be adapted to the requirements of different separation systems, avoid blocking of membrane pores, and extend the service life of the separation membrane; in addition, through the in-situ reaction of two or more casting solutions, effective embedding of amphiphilic copolymers into the membrane material in-situ is achieved, effectively solving problems such as serious loss of separation membrane additives, and ensuring the long-term stability of the composite separation membrane during use.

[0013] For the multi-layer membrane of the present invention, by using different casting solution formulations, different membrane layer properties are achieved, and the viscosities of the casting solutions and the thicknesses of each layer are also different. Generally speaking, for the membrane prepared with a high-viscosity casting solution, the membrane structure is denser, the pore size is smaller, the rejection rate is higher, and the mechanical properties are improved; for a thicker membrane, generally the mechanical stability is higher, the fouling capacity is greater, which is more beneficial for long-term protein filtration.

[0014] The composite separation membrane of the present invention can effectively reduce the loss of additives inside the composite membrane. The outer separation membrane has the functions of pre-filtration and increasing the dirt-holding capacity, thereby achieving the goals of anti-fouling, high separation efficiency, slow attenuation of protein flux, and long service life of the separation membrane. In addition, by adding amphiphilic copolymers and controlling the membrane-forming process, the separation membrane has better water flux and hydrophilicity, and effectively reduces protein adsorption. At the same time, through the reaction between the casting solution bodies, effective embedding of the amphiphilic copolymer into the membrane material body is achieved, with simple operation, lower dissolution rate of the prepared separation membrane, and long-term stability can be maintained.

[0015] As a preferred embodiment of the present invention, the composite separation membrane includes a first membrane layer and a second membrane layer arranged in sequence;

[0016] The thickness of the first membrane layer is 50 - 100 μm;

[0017] The thickness of the second membrane layer is 30 - 90 μm.

[0018] As a preferred embodiment of the present invention, the first casting solution includes components with the following mass percentages: 18 - 25% polymer, 40 - 60% solvent, 1 - 15% polymer additive, 12 - 35% small molecule additive;

[0019] The second casting solution includes components with the following mass percentages: 10 - 20% polymer, 40 - 60% solvent, 1 - 15% polymer additive, 12 - 25% small molecule additive.

[0020] As a preferred embodiment of the present invention, the casting solution further includes a third casting solution, and the viscosity of the third casting solution at 50 °C is 1000 - 5000 cp.

[0021] As a preferred embodiment of the present invention, the third casting solution includes components with the following mass percentages: 15 - 20% polymer, 40 - 60% solvent, 5 - 15% polymer additive, 18 - 35% small molecule additive.

[0022] As a preferred embodiment of the present invention, the composite separation membrane further includes a third membrane layer, the third membrane layer is located on the surface of the second membrane layer away from the first membrane layer, and the thickness of the third membrane layer is 20 - 60 μm.

[0023] As a preferred embodiment of the present invention, the polymer includes at least one of polyethersulfone, sulfonated polyethersulfone, polyvinylidene fluoride, polysulfone, sulfonated polysulfone, polyamide;

[0024] The solvent includes at least one of N-methylpyrrolidone, dimethylformamide, dimethylacetamide, and acetone;

[0025] The small molecule additives include at least one of ethanol, ethylene glycol, propylene glycol, glycerol, triethylene glycol, diethylene glycol, acetone, isopropanol, n-butanol, and n-octanol;

[0026] The polymer additives include at least one of polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, poly(ethylene oxide), sulfonated polyethersulfone, and styrene-maleic anhydride copolymer.

[0027] As a preferred embodiment of the present invention, the coagulation bath is pure water, the temperature of the coagulation bath is 10°C to 50°C, and the curing time in the coagulation bath is 2 to 5 minutes.

[0028] Among them, the interfaces between the first film layer and the second film layer are continuous structures, and the interfaces between the second film layer and the third film layer are continuous structures.

[0029] The present invention also provides a composite separation membrane prepared by the above-mentioned preparation method.

[0030] The present invention also provides an application of the composite separation membrane in the separation of viruses, proteins, pyrogens, or colloids.

[0031] The beneficial effects of the present invention are as follows: The composite separation membrane described in the present invention has a multi-layer composite structure, can effectively separate media such as proteins and viruses while maintaining a high filtration efficiency; the combined morphology of the multi-layer composite membrane structure can meet the requirements of different separation systems, avoid clogging of membrane pores, and extend the service life of the separation membrane; in addition, through the bulk reaction of two or more casting solutions, effective embedding of the amphiphilic copolymer into the bulk of the membrane material is achieved, effectively solving problems such as serious loss of additives in the composite separation membrane, and ensuring the long-term stability of the composite separation membrane during use. Description of the Drawings

[0032] Figure 1 It is a microstructural diagram of the separation membrane prepared in Example 1.

[0033] Figure 2 It is a microstructural diagram of the separation membrane prepared in Example 3. Detailed Embodiments

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0035] In this application, among the technical features described in an open-ended manner, it includes a closed technical solution composed of the listed features, as well as an open technical solution containing the listed features.

[0036] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous, and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0037] In this application, there is no particular limitation on the specific dispersion and stirring treatment methods.

[0038] Unless otherwise specified, the component raw materials or instruments used in each embodiment and comparative example of the present invention are all commercially available raw materials or instruments, and the component raw materials used in each parallel experiment are the same kind.

[0039] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0040] The following examples are provided to facilitate the understanding of the present invention. These examples are not provided to limit the scope of the claims.

[0041] Example 1

[0042] A method for preparing a composite separation membrane, comprising the following steps:

[0043] (1) Mix polyethersulfone, polyvinylpyrrolidone K85, glycerol, ethylene glycol, and dimethylacetamide in a mass ratio of 20:8:12:7:53, and stir for 48 hours in a constant temperature oil bath at 50 °C to prepare a clear and transparent solution. Let it stand for defoaming for 24 hours to obtain a first casting solution with a viscosity of 37259 cp at 50 °C;

[0044] Mix polyethersulfone, polyvinylpyrrolidone K85, propylene glycol, and dimethylacetamide in a mass ratio of 16:5:20:59, and stir for 48 hours in a constant temperature oil bath at 65 °C to prepare a clear and transparent solution. Let it stand for defoaming for 12 hours to obtain a second casting solution with a viscosity of 3321 cp at 50 °C;

[0045] Prepare a clarified and transparent solution by stirring polyethersulfone, polyvinylpyrrolidone K30, glycerol, triethylene glycol, and dimethylacetamide at a mass ratio of 17:5:10:15:53 in a constant-temperature oil bath at 50 °C for 48 hours, and let it stand for defoaming for 12 hours to obtain a third casting solution with a viscosity of 2581 cp at 50 °C.

[0046] (2) At 25 °C and an air humidity of 60%, successively scrape the first casting solution, the second casting solution, and the third casting solution onto a PP substrate at a scraping speed of 1.5 m / min, phase-separate and cure in pure water at 40 °C for 2 minutes, and dry at 50 °C for 15 minutes to obtain a composite separation membrane.

[0047] The composite separation membrane includes a first membrane layer, a second membrane layer, and a third membrane layer arranged in sequence. The thickness of the first membrane layer is 90 μm, the thickness of the second membrane layer is 60 μm, and the thickness of the third membrane layer is 40 μm. Among them, the microstructural diagram of the separation membrane in this example is as Figure 1 described.

[0048] Example 2

[0049] A method for preparing a composite separation membrane includes the following steps:

[0050] (1) Stir polyethersulfone, polyethylene oxide with a molecular weight of 300,000, glycerol, ethylene glycol, and dimethylacetamide at a mass ratio of 20:5:10:15:50 in a constant-temperature oil bath at 70 °C for 48 hours to prepare a clarified and transparent solution, and let it stand for defoaming for 24 hours to obtain a first casting solution with a viscosity of 19631 cp at 50 °C;

[0051] Mix a mixture of polyethersulfone, polyvinylpyrrolidone K90, polyethylene glycol 800, glycerol, and dimethylacetamide at a mass ratio of 15:3:12:15:55, and stir in a constant-temperature oil bath at 65 °C for 48 hours to prepare a clarified and transparent solution, and let it stand for defoaming for 12 hours to obtain a second casting solution with a viscosity of 5321 cp at 50 °C;

[0052] Stir polyethersulfone, polyvinylpyrrolidone K30, sulfonated polyethersulfone, diethylene glycol, and dimethylacetamide at a mass ratio of 17:3:10:20:50 in a constant-temperature oil bath at 50 °C for 48 hours to prepare a clarified and transparent solution, and let it stand for defoaming for 12 hours to obtain a third casting solution with a viscosity of 4581 cp at 25 °C.

[0053] (2) At 30 °C and an air humidity of 50%, successively scrape the first casting solution, the second casting solution, and the third casting solution onto a PTFE substrate at a scraping speed of 2 m / min, stand and cure in pure water at 50 °C for 3 minutes, and dry at 50 °C for 15 minutes to obtain a composite separation membrane.

[0054] The composite separation membrane includes a first membrane layer, a second membrane layer, and a third membrane layer arranged in sequence. The thickness of the first membrane layer is 85 μm, the thickness of the second membrane layer is 60 μm, and the thickness of the third membrane layer is 35 μm.

[0055] Example 3

[0056] A preparation method of a composite separation membrane includes the following steps:

[0057] (1) A mixture of polyethersulfone, polyethylene glycol 2000, diethylene glycol, and dimethylformamide in a mass ratio of 20:15:5:10:50 is stirred in a constant-temperature oil bath at 50 °C for 48 hours to prepare a clear and transparent solution, which is left standing for defoaming for 24 h to obtain a first casting solution with a viscosity of 17559 cp at 50 °C;

[0058] A mixture of polyethersulfone, polyvinylpyrrolidone K30, polyvinyl alcohol, n-butanol, and dimethylacetamide in a mass ratio of 13:5:10:17:55 is stirred in a constant-temperature oil bath at 65 °C for 48 hours to prepare a clear and transparent solution, which is left standing for defoaming for 12 h to obtain a second casting solution with a viscosity of 5295 cp at 50 °C;

[0059] (2) At 25 °C and an air humidity of 45%, the first casting solution and the second casting solution are successively knife-coated on a PET substrate at a knife-coating speed of 1.5 m / min, left standing and cured in pure water at 40 °C for 3 minutes, and dried at 50 °C for 15 min to obtain a composite separation membrane.

[0060] The composite separation membrane includes a first membrane layer and a second membrane layer arranged in sequence. The thickness of the first membrane layer is 90 μm, and the thickness of the second membrane layer is 32 μm. Among them, the microstructural diagram of the separation membrane in this example is as Figure 2 described.

[0061] Example 4

[0062] A preparation method of a composite separation membrane includes the following steps:

[0063] (1) A mixture of polyethersulfone, polyethylene oxide 300,000, glycerol, polyethylene glycol 600, and dimethylacetamide in a mass ratio of 18:2:12:10:58 is stirred in a constant-temperature oil bath at 50 °C for 48 hours to prepare a clear and transparent solution, which is left standing for defoaming for 24 h to obtain a first casting solution with a viscosity of 32108 cp at 50 °C;

[0064] Polysulfone, polyvinylpyrrolidone K90, isopropanol, and N-methylpyrrolidone were mixed at a mass ratio of 13:5:22:60 in a constant-temperature oil bath at 70 °C and stirred for 48 hours to prepare a clear and transparent solution. After standing for 12 hours to remove bubbles, a second casting solution with a viscosity of 4538 cp at 50 °C was obtained.

[0065] Polysulfone, polyvinylpyrrolidone K30, polyethylene glycol 400, ethylene glycol, and di-N-methylpyrrolidone were mixed at a mass ratio of 18:3:10:20:49 in a constant-temperature oil bath at 70 °C and stirred for 48 hours to prepare a clear and transparent solution. After standing for 12 hours to remove bubbles, a third casting solution with a viscosity of 4405 cp at 50 °C was obtained.

[0066] (2) At 25 °C and an air humidity of 60%, the first casting solution, the second casting solution, and the third casting solution were successively blade-coated on a PP substrate at a blade-coating speed of 1.5 m / min, phase-separated and cured in pure water at 45 °C for 3 minutes, and dried at 50 °C for 15 minutes to obtain a composite separation membrane.

[0067] The composite separation membrane includes a first membrane layer, a second membrane layer, and a third membrane layer arranged in sequence. The thickness of the first membrane layer is 83 μm, the thickness of the second membrane layer is 66 μm, and the thickness of the third membrane layer is 35 μm.

[0068] Example 5

[0069] A method for preparing a composite separation membrane includes the following steps:

[0070] (1) Polyethersulfone, polyethylene oxide with a molecular weight of 600,000, glycerol, polyethylene glycol 800, and dimethylacetamide were mixed at a mass ratio of 18:4:10:10:58 in a constant-temperature oil bath at 50 °C and stirred for 48 hours to prepare a clear and transparent solution. After standing for 24 hours to remove bubbles, a first casting solution with a viscosity of 39671 cp at 25 °C was obtained.

[0071] Polyethersulfone, a polymer additive, propylene glycol, and dimethylacetamide were mixed at a mass ratio of 16:5:20:59 in a constant-temperature oil bath at 65 °C and stirred for 48 hours to prepare a clear and transparent solution. After standing for 12 hours to remove bubbles, a second casting solution with a viscosity of 3321 cp at 25 °C was obtained.

[0072] Polyethersulfone, a polymer additive, glycerol, triethylene glycol, and dimethylacetamide were mixed at a mass ratio of 17:5:10:15:53 in a constant-temperature oil bath at 50 °C and stirred for 48 hours to prepare a clear and transparent solution. After standing for 12 hours to remove bubbles, a third casting solution with a viscosity of 2581 cp at 25 °C was obtained.

[0073] (2) At 25 °C and 60% air humidity, the first casting solution, the second casting solution, and the third casting solution were successively knife-coated on a PP substrate at a knife-coating speed of 1.5 m / min, phase-separated and cured in pure water at 45 °C for 3 minutes, and dried at 50 °C for 15 min to obtain a composite separation membrane.

[0074] The separation membrane includes a first membrane layer, a second membrane layer, and a third membrane layer arranged in sequence. The thickness of the first membrane layer is 100 μm, the thickness of the second membrane layer is 50 μm, and the thickness of the third membrane layer is 60 μm.

[0075] Comparative Example 1

[0076] A method for preparing a composite separation membrane includes the following steps:

[0077] (1) Polyethersulfone, polyvinylpyrrolidone K85, glycerol, ethylene glycol, and dimethylacetamide were stirred at a mass ratio of 26:10:11:7:46 in a constant-temperature oil bath at 50 °C for 48 hours to prepare a clear and transparent solution, which was allowed to stand and defoam for 24 h to obtain a first casting solution with a viscosity of 68931 cp at 50 °C;

[0078] Polyethersulfone, polyvinylpyrrolidone K85, propylene glycol, and dimethylacetamide were stirred at a mass ratio of 22:8:20:50 in a constant-temperature oil bath at 65 °C for 48 hours to prepare a clear and transparent solution, which was allowed to stand and defoam for 12 h to obtain a second casting solution with a viscosity of 9076 cp at 50 °C;

[0079] Polyethersulfone, polyvinylpyrrolidone K30, glycerol, triethylene glycol, and dimethylacetamide were stirred at a mass ratio of 21:4:5:10:60 in a constant-temperature oil bath at 50 °C for 48 hours to prepare a clear and transparent solution, which was allowed to stand and defoam for 12 h to obtain a third casting solution with a viscosity of 8501 cp at 50 °C.

[0080] (2) At 25 °C and 60% air humidity, the first casting solution, the second casting solution, and the third casting solution were successively knife-coated on a PP substrate at a knife-coating speed of 1.5 m / min, phase-separated and cured in pure water at 40 °C for 2 minutes, and dried at 50 °C for 15 min to obtain a composite separation membrane.

[0081] The composite separation membrane includes a first membrane layer, a second membrane layer, and a third membrane layer arranged in sequence. The thickness of the first membrane layer is 93 μm, the thickness of the second membrane layer is 58 μm, and the thickness of the third membrane layer is 35 μm.

[0082] Comparative Example 2

[0083] A method for preparing a composite separation membrane includes the following steps:

[0084] (1) Prepare a clear and transparent solution by stirring polyethersulfone, polyvinylpyrrolidone K85, glycerol, ethylene glycol, and dimethylacetamide at a mass ratio of 17:8:15:5:55 in a constant-temperature oil bath at 50 °C for 48 hours. Let it stand for defoaming for 24 hours to obtain a first casting solution with a viscosity of 14653 cp at 50 °C;

[0085] Prepare a clear and transparent solution by stirring polyethersulfone, polyvinylpyrrolidone K85, propylene glycol, and dimethylacetamide at a mass ratio of 12:5:25:58 in a constant-temperature oil bath at 65 °C for 48 hours. Let it stand for defoaming for 12 hours to obtain a second casting solution with a viscosity of 1896 cp at 50 °C;

[0086] Prepare a clear and transparent solution by stirring polyethersulfone, polyvinylpyrrolidone K30, glycerol, triethylene glycol, and dimethylacetamide at a mass ratio of 10:5:15:10:60 in a constant-temperature oil bath at 50 °C for 48 hours. Let it stand for defoaming for 12 hours to obtain a third casting solution with a viscosity of 1528 cp at 50 °C.

[0087] (2) At 25 °C and an air humidity of 60%, sequentially scrape the first casting solution, the second casting solution, and the third casting solution onto the PP substrate at a scraping speed of 1.5 m / min, phase-separate and cure in pure water at 40 °C for 2 minutes, and dry at 50 °C for 15 minutes to obtain a composite separation membrane.

[0088] The composite separation membrane includes a first membrane layer, a second membrane layer, and a third membrane layer arranged in sequence. The thickness of the first membrane layer is 82 μm, the thickness of the second membrane layer is 55 μm, and the thickness of the third membrane layer is 25 μm.

[0089] Comparative Example 3

[0090] A method for preparing a composite separation membrane, comprising the following steps:

[0091] (1) Prepare a clear and transparent solution by stirring polyethersulfone, polyvinylpyrrolidone K85, glycerol, ethylene glycol, and dimethylacetamide at a mass ratio of 20:8:12:7:53 in a constant-temperature oil bath at 50 °C for 48 hours. Let it stand for defoaming for 24 hours to obtain a first casting solution with a viscosity of 37259 cp at 50 °C;

[0092] Prepare a clear and transparent solution by stirring polyethersulfone, polyvinylpyrrolidone K85, propylene glycol, and dimethylacetamide at a mass ratio of 16:5:20:59 in a constant-temperature oil bath at 65 °C for 48 hours. Let it stand for defoaming for 12 hours to obtain a second casting solution with a viscosity of 3321 cp at 50 °C;

[0093] Prepare a clear and transparent solution by stirring polyethersulfone, polyvinylpyrrolidone K30, glycerol, triethylene glycol, and dimethylacetamide at a mass ratio of 17:5:10:15:53 in a constant-temperature oil bath at 50°C for 48 hours. Let it stand for defoaming for 12 hours to obtain a third casting solution with a viscosity of 2581 cp at 50°C.

[0094] (2) At 25°C and an air humidity of 60%, successively scrape the first casting solution, the second casting solution, and the third casting solution onto a PP substrate at a scraping speed of 1.5 m / min, phase-separate and cure in pure water at 40°C for 2 minutes, and dry at 50°C for 15 minutes to obtain a composite separation membrane.

[0095] The composite separation membrane includes a first membrane layer, a second membrane layer, and a third membrane layer arranged in sequence. The thickness of the first membrane layer is 63 μm, the thickness of the second membrane layer is 39 μm, and the thickness of the third membrane layer is 18 μm.

[0096] Comparative Example 4

[0097] A method for preparing a composite separation membrane includes the following steps:

[0098] (1) Prepare a clear and transparent solution by stirring polyethersulfone, polyvinylpyrrolidone K85, glycerol, ethylene glycol, and dimethylacetamide at a mass ratio of 20:8:12:7:53 in a constant-temperature oil bath at 50°C for 48 hours. Let it stand for defoaming for 24 hours to obtain a first casting solution with a viscosity of 37259 cp at 50°C;

[0099] Prepare a clear and transparent solution by stirring polyethersulfone, polyvinylpyrrolidone K85, propylene glycol, and dimethylacetamide at a mass ratio of 16:5:20:59 in a constant-temperature oil bath at 65°C for 48 hours. Let it stand for defoaming for 12 hours to obtain a second casting solution with a viscosity of 3321 cp at 50°C;

[0100] Prepare a clear and transparent solution by stirring polyethersulfone, polyvinylpyrrolidone K30, glycerol, triethylene glycol, and dimethylacetamide at a mass ratio of 17:5:10:15:53 in a constant-temperature oil bath at 50°C for 48 hours. Let it stand for defoaming for 12 hours to obtain a third casting solution with a viscosity of 2581 cp at 50°C.

[0101] (2) At 25°C and an air humidity of 60%, successively scrape the first casting solution, the second casting solution, and the third casting solution onto a PP substrate at a scraping speed of 1.5 m / min, phase-separate and cure in pure water at 40°C for 2 minutes, and dry at 50°C for 15 minutes to obtain a composite separation membrane.

[0102] The composite separation membrane includes a first membrane layer, a second membrane layer, and a third membrane layer arranged in sequence. The thickness of the first membrane layer is 53 μm, the thickness of the second membrane layer is 50 μm, and the thickness of the third membrane layer is 55 μm.

[0103] Comparative Example 5

[0104] A method for preparing a composite separation membrane includes the following steps:

[0105] (1) Polyethersulfone, polyvinylpyrrolidone K85, glycerol, ethylene glycol, and dimethylacetamide are mixed at a mass ratio of 20:8:12:7:53 and stirred in a constant-temperature oil bath at 50 °C for 48 hours to prepare a clear and transparent solution. After standing for 24 hours to remove bubbles, a first casting solution with a viscosity of 37259 cp at 50 °C is obtained.

[0106] (2) At 25 °C and an air humidity of 60%, the first casting solution, the second casting solution, and the third casting solution are sequentially blade-coated on a PP substrate at a blade-coating speed of 1.5 m / min, phase-separated and cured in pure water at 40 °C for 2 minutes, and dried at 50 °C for 15 minutes to obtain a separation membrane.

[0107] The thickness of the separation membrane is 96 μm.

[0108] Two layers of the separation membranes are stacked.

[0109] Comparative Example 6

[0110] A method for preparing a composite separation membrane includes the following steps:

[0111] (1) Polyethersulfone, polyvinylpyrrolidone K85, glycerol, ethylene glycol, and dimethylacetamide are mixed at a mass ratio of 20:8:12:7:53 and stirred in a constant-temperature oil bath at 50 °C for 48 hours to prepare a clear and transparent solution. After standing for 24 hours to remove bubbles, a first casting solution with a viscosity of 37259 cp at 50 °C is obtained.

[0112] (2) At 25 °C and an air humidity of 60%, the first casting solution, the second casting solution, and the third casting solution are sequentially blade-coated on a PP substrate at a blade-coating speed of 1.5 m / min, phase-separated and cured in pure water at 40 °C for 2 minutes, and dried at 50 °C for 15 minutes to obtain a separation membrane.

[0113] The thickness of the separation membrane is 190 μm.

[0114] Test Example

[0115] Pure water flux: The water permeability of the membrane was tested by the dead-end filtration method using an ultrafiltration cell. Nitrogen was applied at a pressure of 1 bar for pre-pressurization for 10 minutes, and the water flux (J1) was calculated by Equation (1).

[0116] J1 = V / (A·Δt) (1)

[0117] In the formula, J1 is the pure water flux of the membrane, L / (m 2 ·h·bar); V is the volume of pure water permeating through the membrane within Δt time, L; A is the effective filtration area of the membrane, m 2 ; Δt is the test time, h.

[0118] Protein adsorption amount: Soak a membrane with a certain area in a bovine serum albumin solution with a certain concentration and volume. The protein in the solution will be adsorbed by the ultrafiltration membrane on the membrane surface or in the membrane pores. Test the concentration of bovine serum albumin before and after soaking, and calculate the mass of the adsorbed protein.

[0119] Long-term IVIG permeation attenuation test: Adopt the dead-end filtration method of an ultrafiltration cup to test the IVIG flux of the membrane. Apply a pressure of 3 bar with nitrogen for continuous testing for 3 h, and record relevant data every 10 min. The IVIG flux (J2) is calculated by formula (2).

[0120] J2 = V / (A·Δt) (2)

[0121] In the formula, J2 is the pure water flux of the membrane, L / (m 2 ·h·bar); V is the volume of pure water permeating through the membrane within Δt time, L; A is the effective filtration area of the membrane, m 2 ; Δt is the test time, h.

[0122] Table 1

[0123]

[0124] As can be seen from Table 1, the composite separation membrane described in the present invention has a multi-layer composite structure and can effectively separate media such as proteins and viruses while maintaining a high filtration efficiency.

[0125] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a composite separation membrane, characterized in that, It includes the following steps: Mix the polymer, solvent, small molecule additive and polymer additive evenly in different proportions to obtain casting solutions with different viscosities; Doctor the casting solutions with different viscosities on a substrate, cure them in a coagulation bath, and dry them to obtain a composite separation membrane; The casting solution includes a first casting solution and a second casting solution. The viscosity of the first casting solution at 50°C is 15,000 - 40,000 cp; the viscosity of the second casting solution at 50°C is 2,000 - 8,000 cp.

2. The composite separation membrane according to claim 1, wherein The composite separation membrane includes a first membrane layer and a second membrane layer arranged in sequence; The thickness of the first membrane layer is 80 - 100 μm; The thickness of the second membrane layer is 50 - 90 μm.

3. The preparation method of the composite separation membrane according to claim 1, characterized in that, The first casting solution includes components with the following mass percentages: 18 - 25% polymer, 40 - 60% solvent, 1 - 15% polymer additive, 12 - 35% small molecule additive; the second casting solution includes components with the following mass percentages: 10 - 20% polymer, 40 - 60% solvent, 1 - 15% polymer additive, 12 - 25% small molecule additive.

4. The preparation method of the composite separation membrane according to claim 1, characterized in that, The casting solution further includes a third casting solution, and the viscosity of the third casting solution at 50°C is 1,000 - 5,000 cp.

5. The preparation method of the composite separation membrane according to claim 4, characterized in that, The third casting solution includes components with the following mass percentages: 15 - 20% polymer, 40 - 60% solvent, 5 - 15% polymer additive, 18 - 35% small molecule additive.

6. The preparation method of the composite separation membrane according to claim 5, wherein The separation membrane further includes a third membrane layer, the third membrane layer is located on the surface of the second membrane layer away from the first membrane layer, and the thickness of the third membrane layer is 20 - 60 μm.

7. The preparation method of the composite separation membrane according to any one of claims 1 to 6, characterized in that, The polymer includes at least one of polyethersulfone, sulfonated polyethersulfone, polyvinylidene fluoride, polysulfone, sulfonated polysulfone, polyamide; The solvent includes at least one of N-methylpyrrolidone, dimethylformamide, dimethylacetamide, acetone; The small molecule additive includes at least one of ethanol, ethylene glycol, propylene glycol, glycerol, triethylene glycol, diethylene glycol, acetone, isopropanol, n-butanol, n-octanol; The polymer additive includes at least one of polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, poly(ethylene oxide), sulfonated polyethersulfone, styrene-maleic anhydride copolymer; 8. The preparation method of the composite separation membrane according to claim 1, characterized in that, The coagulation bath is pure water, the temperature of the coagulation bath is 10°C - 50°C, and the curing time in the coagulation bath is 2 - 5 minutes.

9. A composite separation membrane, characterized in that, It is prepared by using the preparation method according to any one of claims 1 - 8.

10. Application of the composite separation membrane according to claim 9 in the separation of viruses, proteins, pyrogens or colloids.

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