Homopore membrane as well as preparation method and application thereof

Abstract

The invention provides a homoporous membrane and a preparation method and application thereof, and the preparation method comprises the following steps: (1) activating a base membrane to obtain an activated membrane; (2) placing the activated membrane in an electrolytic cell, the electrolytic cell comprising a first compartment and a second compartment, the first compartment comprising a first electrode and an etching solution, and the second compartment comprising a second electrode and a termination solution; the activation film is located between the first compartment and the second compartment, and voltage is applied to the electrolytic tank for etching; and (3) then, etching the membrane obtained in the step (2) in an etching solution to obtain the homoporous membrane. The target pore channel is obtained by utilizing the two-step etching process, the etching reaction conditions at the top end and the bottom end of the pore channel are easy to regulate and control, and the porous membrane has higher permeation flux and lower permeation resistance compared with a cylindrical pore channel with the same porosity, and only needs lower porosity when obtaining the same permeation flux as a cylindrical pore channel membrane; and in the application of protein adsorption, the material also shows higher dynamic binding capacity than a cylindrical pore channel.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology, specifically relating to a uniformly porous membrane, its preparation method, and its application. Background Technology

[0002] Since the 19th century, the biopharmaceutical industry has gradually occupied an important position in the pharmaceutical field, and downstream separation and purification processes greatly affect their pharmaceutical properties. Currently, downstream processes for biopharmaceuticals mainly rely on packed column chromatography. Traditional column chromatography suffers from high mass transfer resistance, long processing times, and low ligand utilization, reducing the activity of biomolecules and limiting production efficiency. Compared to column chromatography, membrane chromatography is more suitable for separating and purifying biomolecules (relative molecular mass Mr > 250,000). The main diffusion mechanism in membrane chromatography is convection diffusion, resulting in low mass transfer resistance and short processing times. It removes impurities while preserving the activity of biomolecules as much as possible, and has been widely proven to be an economical and efficient alternative to traditional column chromatography in the downstream purification steps of biopharmaceuticals, especially for ultra-high molecular weight molecules.

[0003] Currently available commercial membrane chromatography media often suffer from wide pore size distribution, tortuous flow channels, and uneven ligand distribution. This leads to uneven local fluid flow, poor flow distribution, and wide retention time distribution during separation. Early saturation of binding sites in macropores and incomplete utilization of binding sites in micropores or dead-end pores severely affect separation performance and efficiency. Using membranes with narrower pore size distribution or uniformly porous membranes as the base membrane for membrane chromatography offers advantages such as extremely precise selectivity and ultra-fast permeability, potentially effectively solving these problems. Most reported methods for preparing uniformly porous membranes result in columnar pore structures. Due to the limitations of pore shape, columnar pores have lower pore throughput, thus failing to fully utilize the advantages of uniformly porous membrane chromatography media.

[0004] Exploring the pore shape and preparation method with excellent permeability has become a breakthrough point. According to the literature "Atheoretical study of permeability enhancement for ultrafiltration ceramic membranes with conical pores and slippage" (Tran-Duc T, et al., Physics of Fluids, 2019, 31, 022003) and "Enhancing water permeation through aluminamembranes by changing from cylindrical to conical nanopores" (Nalaparaju A, Wang J, et al., Nanoscale, 2019, 11, 9869-9878), conical nanopores have an advantage in permeability over cylindrical nanopores. Existing methods for preparing single-conical nanopore membranes involve placing an alkaline etching solution and a neutral / acidic stop solution on both sides of the core-pore membrane. The etching rate at the core track is higher than that of the bulk film due to its more reactive chemical properties, thus creating a conical channel penetrating the film. However, this method keeps the pore tip in the stop solution for an extended period, making it difficult to effectively enlarge the pore tip size and obtain micron-sized conical channels.

[0005] CN105233700A discloses a method for fabricating a nuclear track etching film, which utilizes the property of obtaining biconical channels by directly etching a nuclear pore film. This method involves immersing an irradiated bilayer film in an etching solution for etching, thereby obtaining single-conical channels on both films. However, this method struggles to guarantee that no etching solution will ever seep into the gap between the bilayer films. If the concentration of the etching solution in the gap is not zero, it will lead to reverse etching, affecting the final shape of the etched channels.

[0006] CN105148738A discloses a method for fabricating a nuclear track etching film with a single conical micropore. By adjusting the energy generated by the accelerator, the range of ions in the film during heavy ion bombardment is greater than 2 / 3 of the film thickness but less than the film thickness, thus controlling the length of the nuclear track damage region and constructing an etching reaction rate gradient. Subsequently, the nuclear pore film is placed in an alkaline etching solution, allowing the etching solution to contact the pore tip, thereby amplifying the pore tip and obtaining a micron-sized conical channel. However, the ion range variable involved in this method is difficult to characterize and control, making it impossible to accurately obtain conical pores of the target size in practical applications.

[0007] CN105169963A discloses another method for fabricating a nuclear track etching film with single-conical micropores. This method constructs an etching reaction rate gradient by coating one side of the nuclear pore film with an anti-etching coating. The film is then placed in an alkaline etching solution, allowing the etching solution to contact the pore tip, thus amplifying the pore tip and obtaining micron-sized conical channels. However, this method can only gradually increase the etch solution concentration at the pore tip by extending the etching time and enlarging the bottom pore diameter. The top-to-bottom ratio is low and cannot be adjusted simultaneously, making it impossible to obtain conical pores of various sizes and proportions.

[0008] Therefore, developing a method for preparing uniformly porous membranes with highly controllable pore size and structure is of great significance for improving the separation accuracy and efficiency of membrane chromatography in the downstream purification process of biopharmaceuticals. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a uniformly porous membrane, its preparation method, and its application. The uniformly porous membrane is obtained using an asymmetric-symmetric etching reaction. The uniformly porous membrane has micron-sized conical channels, which have higher permeation flux and lower permeation resistance than columnar channels with higher porosity. The preparation method is simple, has good reproducibility, and has good universality.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a method for preparing a uniformly porous membrane, the method comprising:

[0012] (1) The base membrane is activated to obtain an activated membrane;

[0013] (2) Place the activated membrane obtained in step (1) in an electrolytic cell, the electrolytic cell comprising a first compartment and a second compartment, the first compartment comprising a first electrode and an etching solution, and the second compartment comprising a second electrode and a termination solution;

[0014] The activated membrane is located between the first compartment and the second compartment, and is etched by applying voltage to the electrolytic cell;

[0015] (3) The membrane obtained in step (2) is etched in an etching solution to obtain the uniformly porous membrane.

[0016] In the preparation method of the present invention, step (2) is an asymmetric etching reaction, specifically including:

[0017] The activated membrane obtained in step (1) is placed in an electrolytic cell. The first compartment is filled with a mixed etching solution of etchant, and the second compartment is filled with a termination solution. Electrodes are placed in the compartments respectively. It is preferred to apply voltage to the electrodes in DC mode. The first compartment is connected to the negative terminal of the power supply, and the second compartment is connected to the positive terminal of the power supply. Then, it is placed in a water bath for temperature control etching for a period of time before being taken out.

[0018] The proposed preparation method first utilizes an asymmetric etching reaction to obtain the target channel shape, with easily controllable etching reaction conditions at both the top and bottom of the channel. Subsequently, a symmetric etching reaction is used to enlarge the aperture in situ, solving the problem that traditional asymmetric etching reactions struggle to adjust the tip size and cannot obtain micron-sized tapered channels. By adjusting the etching reaction conditions, tapered channels of various sizes can be obtained, reducing the limitations of the etching method on the channel size adjustment range. Furthermore, the preparation method is simple, has good reproducibility, and possesses excellent versatility.

[0019] Preferably, the material of the base film in step (1) includes any one or a combination of at least two of polyethylene terephthalate (PET), polyimide (PI), polycarbonate (PC), polyvinylidene fluoride (PVDF), or polypropylene (PP).

[0020] Preferably, the thickness of the base film is 5-15 μm, for example, it can be 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0021] Preferably, the heavy ion bombardment density of the base film is 1000-1000000 cm⁻¹ -2 For example, it can be 1000cm -2 2000cm -2 10000cm -2 100000cm -2 500000cm -2 800000cm -2 1,000,000cm -2 As well as the specific point values ​​between the above point values, due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

[0022] Preferably, the activation includes ultraviolet irradiation.

[0023] Preferably, the activation method includes: subjecting both sides of the base film to ultraviolet irradiation.

[0024] Preferably, the ultraviolet irradiation time is independently 0.1-2h, for example, it can be 0.1h, 0.5h, 1h, 1.5h, 2h, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0025] Preferably, the first electrode and the second electrode each independently comprise a platinum (Pt) electrode.

[0026] Preferably, the method of placing the activated membrane in the electrolytic cell in step (2) includes: placing the activated membrane between the first compartment and the second compartment, sealing it with a gasket, and fixing it with a clamp.

[0027] Preferably, the etchant in the etching solution in step (2) includes any one or a combination of at least two of sodium hydroxide, potassium hydroxide, sulfuric acid, hydrogen chloride, hydrogen fluoride, sodium hypochlorite, hydrogen peroxide, nitric acid, potassium dichromate, potassium permanganate, or chromium trioxide.

[0028] Preferably, the concentration of the etchant in the etching solution in step (2) is 0.1-10 mol / L, for example, it can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 5 mol / L, 8 mol / L, 10 mol / L, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0029] Preferably, the etching solution in step (2) further includes additives.

[0030] Preferably, the additive includes any one or a combination of at least two of ethanol, methanol, propanol, acetonitrile, N,N-dimethylformamide, tetrahydrofuran, or dimethyl sulfoxide.

[0031] Preferably, the volume fraction of the additive in the etching solution in step (2) is ≤50%, for example, it can be 0%, 1%, 5%, 10%, 15%, 20%, 30%, 40%, 45%, 50%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0032] Preferably, the terminating solution in step (2) includes any one or a combination of at least two of the following: formic acid solution, potassium metabisulfite solution, potassium chloride solution, potassium iodide solution, or water.

[0033] Preferably, the applied voltage in step (2) is a DC voltage.

[0034] Preferably, the etching time in step (2) is 1-5 hours, for example, it can be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0035] Preferably, the applied voltage is 0.1-24V, for example, it can be 0.1V, 0.5V, 1V, 5V, 10V, 15V, 20V, 24V, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0036] Preferably, the etching temperature is 20-40℃, for example, it can be 20℃, 25℃, 30℃, 35℃, 40℃, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0037] Asymmetric etching reaction refers to the process of placing the activated film between an alkaline etching solution and a neutral / acidic stop solution, and carrying out the etching reaction on one side of the activated film.

[0038] The asymmetric etched film is placed in an electrolytic cell containing an etchant and additives. The electrolytic cell is placed in a water bath for temperature control. After symmetric etching for a period of time, the film is removed and placed in a termination solution to terminate the reaction.

[0039] Preferably, the etchant in the etching solution of step (3) includes any one or a combination of at least two of sodium hydroxide, potassium hydroxide, sulfuric acid, hydrogen chloride, hydrogen fluoride, sodium hypochlorite, hydrogen peroxide, nitric acid, potassium dichromate, potassium permanganate, or chromium trioxide.

[0040] Preferably, the concentration of the etchant in the etching solution in step (3) is 0.1-10 mol / L, for example, it can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 5 mol / L, 8 mol / L, 10 mol / L, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0041] Preferably, the etching solution in step (3) further includes additives.

[0042] Preferably, the additive includes any one or a combination of at least two of ethanol, methanol, propanol, acetonitrile, N,N-dimethylformamide, tetrahydrofuran, or dimethyl sulfoxide.

[0043] Preferably, the volume fraction of the additive in the etching solution in step (3) is ≤50%, for example, it can be 0%, 1%, 5%, 10%, 15%, 20%, 30%, 40%, 45%, 50%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0044] Preferably, the etching time in step (3) is 75-125 min, for example, it can be 75 min, 80 min, 90 min, 100 min, 110 min, 120 min, 125 min, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0045] Preferably, the etching temperature in step (3) is 20-40℃, for example, it can be 20℃, 25℃, 30℃, 35℃, 40℃, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0046] Preferably, step (3) further includes a termination step after the etching is completed.

[0047] Preferably, the termination method includes: removing the etched film from the etching solution and placing it in a termination solution to terminate the reaction, thereby obtaining the uniformly porous film.

[0048] Preferably, the terminating solution includes any one or a combination of at least two of the following: formic acid solution, potassium metabisulfite solution, potassium chloride solution, potassium iodide solution, or deionized water.

[0049] In the preparation method of the present invention, step (3) is a symmetrical etching reaction, that is, the film after asymmetrical etching is placed in a uniform etching solution and the etching reaction is carried out simultaneously on both sides of the film.

[0050] Preferably, the preparation method specifically includes:

[0051] (1) The two sides of the base film were activated by ultraviolet irradiation to obtain an activated film;

[0052] The duration of each ultraviolet irradiation is independently 0.1-2 hours;

[0053] (2) Place the activated membrane obtained in step (1) in an electrolytic cell, the electrolytic cell comprising a first compartment and a second compartment, the first compartment comprising a first electrode and an etching solution, and the second compartment comprising a second electrode and a termination solution;

[0054] The activated membrane is located between the first compartment and the second compartment. A voltage of 0.1-24V is applied to the electrolytic cell, and etching is performed at 20-40℃ for 1-5 hours.

[0055] (3) The membrane obtained in step (2) is etched in an etching solution at 20-40°C for 75-125 min, and a termination solution is added to terminate the reaction to obtain the uniformly porous membrane.

[0056] The method provided by this invention is simple and easy to use, and the resulting pore size reaches the micrometer level with a precisely adjustable structure. The transmembrane resistance is lower than that of a cylindrical uniformly porous membrane. By adjusting the asymmetric etching reaction, the target conical hole shape is obtained, reducing the limitation of etching on the pore size adjustment range. Subsequently, a symmetric etching reaction is introduced to achieve in-situ enlargement of the top and bottom hole diameters. By controlling the symmetric etching conditions, the pore size is adjusted, thereby achieving controllable and precise adjustment of the conical hole shape and size. This effectively solves the problems of difficulty in adjusting and enlarging the hole tip size and the inability to obtain micrometer-level pores in the prior art.

[0057] In a second aspect, the present invention provides a uniformly porous membrane, which is prepared by the preparation method described in the first aspect.

[0058] Preferably, the uniformly porous membrane has a channel structure.

[0059] Preferably, the channel structure includes a double-cone structure and / or a single-cone structure.

[0060] Preferably, the pore size of the pore structure is 0.08-4.03 μm, for example, it can be 0.1 μm, 0.2 μm, 0.4 μm, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, 3.2 μm, 3.3 μm, 3.5 μm, 3.8 μm, 4 μm, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0061] In this invention, the pore size is 0.08-4.03μm, which refers to the size of the top hole of the top cone (bottom cone) of the obtained uniformly porous membrane.

[0062] In this invention, the tapered pores of the uniformly porous membrane have a higher fluid flow rate, enabling faster convective mass transfer and thus achieving higher permeability than traditional cylindrical pores. Furthermore, it also exhibits higher dynamic binding capacity than cylindrical pores in protein adsorption applications.

[0063] Thirdly, the present invention provides an application of the uniformly porous membrane as described in the second aspect in the field of biomolecule purification.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] This invention provides a method for preparing a uniformly porous membrane. First, an asymmetric etching reaction is used to obtain the target pore shape, with easily controllable etching reaction conditions at both the top and bottom of the pores. By adjusting the etching reaction conditions, conical channels of various sizes can be obtained, reducing the limitation of the etching reaction on the pore size adjustment range. Subsequently, a symmetric etching reaction is used to enlarge the pore size in situ, solving the problem that traditional asymmetric etching reactions are difficult to adjust the pore tip size, let alone obtain micron-sized conical channels. The resulting uniformly porous membrane has micron-sized conical channels, including biconical and single-conical channels. The bottom pore size of the single-conical channel is 3.17–7.98 μm, and the top pore size is 1.52–4.03 μm. The single-conical channel has a higher permeation flux and lower permeation resistance than cylindrical channels with the same porosity. It requires only a lower porosity to achieve the same permeation flux as the cylindrical channel membrane, and also exhibits higher dynamic binding capacity in protein adsorption applications. Attached Figure Description

[0066] Figure 1 This is a schematic diagram of the electrolytic cell device for steps (2) and (3) in a specific embodiment of the present invention;

[0067] Wherein, 1-first compartment; 2-second compartment; 3-gasket; 4-activation membrane;

[0068] Figure 2 Scanning electron microscope image of the uniformly porous membrane obtained by the preparation method provided in Example 16 of this invention.

[0069] Wherein 1-top cone bottom hole, 2-top cone top hole (bottom cone top hole), 3-bottom cone bottom hole;

[0070] Figure 3 A scanning electron microscope image of the uniformly porous membrane obtained by the preparation method provided in Example 5 of the present invention;

[0071] Figure 4 This is a scanning electron microscope image of a uniformly porous membrane obtained by the preparation method provided in Comparative Example 1 of the present invention. Detailed Implementation

[0072] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0073] In one specific embodiment, a schematic diagram of the electrolytic cell device used for asymmetric etching in step (2) of the preparation method is shown below. Figure 1As shown, it includes a first compartment 1 and a second compartment 2. An activation membrane 4 is placed between the first compartment and the second compartment, sealed with a gasket 3, and fixed with a clamp. Electrodes are placed in the two compartments respectively. The first compartment is connected to the negative terminal of the power supply and contains an etching solution. The second compartment is connected to the positive terminal of the power supply and contains a termination solution.

[0074] In one specific embodiment, the schematic diagram of the electrolytic cell device in step (3) is the same as that in step (2), the only difference being that step (3) is symmetrical etching, and the first and second compartments are filled with the same etching solution.

[0075] Unless otherwise specified, the experimental materials used in the embodiments and comparative examples of this invention are as follows:

[0076] (1) Base film: PET base film (thickness 15μm, heavy ion bombardment density 6×10⁻⁶) 5 cm -2 (From the Institute of Modern Physics, Chinese Academy of Sciences)

[0077] (2) Etching agent: Weigh out sodium hydroxide (purchased from Shanghai Aladdin Co., Ltd., purity 97%) and dissolve it in water;

[0078] (3) Mixed etching solution: Measure anhydrous ethanol (purchased from Sinopharm Chemical Reagent Beijing Co., Ltd.)

[0079] Mix with etchant to a final volume of 120 mL;

[0080] (4) Termination solution: Weigh KCl (purchased from Shanghai Maclean Co., Ltd.) and HCOOH (purchased from Shanghai Aladdin Co., Ltd.) and dissolve them in water;

[0081] (5) Commercial cylindrical porous membrane: Commercial cylindrical porous membrane (thickness 10μm, heavy ion bombardment density 6×10⁻⁶). 5 cm -2 (From the Institute of Modern Physics, Chinese Academy of Sciences)

[0082] Example 1

[0083] This embodiment provides a uniformly porous membrane and its preparation method, the preparation method specifically including the following steps:

[0084] (1) Place the PET base film in an ultraviolet light box and irradiate each side for 1 hour to activate it, thus obtaining an activated film;

[0085] (2) Place the activated membrane obtained in step (1) in the middle of a two-chamber electrolytic cell. One chamber is filled with an etching solution containing 9 mol / L NaOH (the volume fraction of the additive is 0%), and the other chamber is filled with a termination solution. Place Pt electrodes in the chambers respectively, apply a voltage of 6V to the electrodes in DC mode, and always keep the etching solution side negatively charged. Then place the device in a water bath at 30°C for etching for 1 hour and then take it out.

[0086] (3) Place the membrane obtained in step (2) into an electrolytic cell containing a mixed etching solution consisting of 9 mol / L etchant and 33% ethanol by volume. Place the electrolytic cell in a water bath to control the temperature. After etching at 30°C for 100 min, remove the membrane and place it in a termination solution to terminate the reaction, thus obtaining the uniformly porous membrane.

[0087] Example 2

[0088] This embodiment provides a uniformly porous membrane and its preparation method, the preparation method specifically including the following steps:

[0089] (1) Place the PET base film in an ultraviolet light box and irradiate each side for 1 hour to activate it, thus obtaining an activated film;

[0090] (2) Place the activated membrane obtained in step (1) in the middle of a two-chamber electrolytic cell. One chamber is filled with an etching solution containing 9 mol / L NaOH, and the other chamber is filled with a termination solution. Place Pt electrodes in the chambers respectively, apply a voltage of 6V to the electrodes in DC mode, and always keep the etching solution side negatively charged. Then place the device in a water bath at 30°C for 5 hours and remove it.

[0091] (3) Place the membrane obtained in step (2) into an electrolytic cell containing a mixed etching solution of 9 mol / L NaOH and 33% ethanol by volume. Place the electrolytic cell in a water bath to control the temperature. After etching at 30°C for 100 min, remove the membrane and place it in a termination solution to terminate the reaction, thus obtaining the uniformly porous membrane.

[0092] Example 3

[0093] This embodiment provides a uniformly porous membrane and its preparation method, the preparation method specifically including the following steps:

[0094] (1) Place the PET base film in an ultraviolet light box and irradiate each side for 1 hour to activate it, thus obtaining an activated film;

[0095] (2) Place the activated membrane obtained in step (1) in the middle of a two-chamber electrolytic cell. One chamber is filled with an etching solution containing 9 mol / L NaOH, and the other chamber is filled with a termination solution. Place Pt electrodes in the chambers respectively, apply a voltage of 6V to the electrodes in DC mode, and always keep the etching solution side negatively charged. Then place the device in a water bath at 20°C for etching for 2.5 hours and then remove it.

[0096] (3) Place the membrane obtained in step (2) into an electrolytic cell containing a mixed etching solution consisting of 9 mol / L etchant and 33% ethanol by volume. Place the electrolytic cell in a water bath to control the temperature. After etching at 30°C for 100 min, remove the membrane and place it in a termination solution to terminate the reaction, thus obtaining the uniformly porous membrane.

[0097] Example 4

[0098] This embodiment provides a uniformly porous membrane and its preparation method, the preparation method specifically including the following steps:

[0099] (1) Place the PET base film in an ultraviolet light box and irradiate each side for 1 hour to activate it, thus obtaining an activated film;

[0100] (2) Place the activated membrane obtained in step (1) in the middle of a two-chamber electrolytic cell. One chamber is filled with an etching solution containing 9 mol / L NaOH, and the other chamber is filled with a termination solution. Place Pt electrodes in the chambers respectively, apply a voltage of 6V to the electrodes in DC mode, and always keep the etching solution side negatively charged. Then place the device in a water bath at 40°C for etching for 2.5 hours and then remove it.

[0101] (3) Place the membrane obtained in step (2) into an electrolytic cell containing a mixed etching solution consisting of 9 mol / L etchant and 33% ethanol by volume. Place the electrolytic cell in a water bath to control the temperature. After etching at 30°C for 100 min, remove the membrane and place it in a termination solution to terminate the reaction, thus obtaining the uniformly porous membrane.

[0102] Example 5

[0103] This embodiment provides a uniformly porous membrane and its preparation method. The difference between the preparation method and that in Embodiment 1 is that the etching time in step (2) is 2.5 h and the volume fraction of the additive ethanol is 33%.

[0104] The morphology of the uniformly porous membrane obtained in Example 5 was characterized using scanning electron microscopy, and the results are as follows: Figure 3 As shown, by Figure 3 It can be seen that the uniformly porous membrane has a single conical channel.

[0105] Example 6

[0106] This embodiment provides a uniformly porous membrane and its preparation method. The only difference between the preparation method and that of Embodiment 1 is that the etching time in step (2) is 2.5 h and the volume fraction of the additive ethanol is 50%.

[0107] Example 7

[0108] This embodiment provides a uniformly porous membrane and its preparation method. The difference between the preparation method and that in Embodiment 1 is that the etching time in step (2) is 2.5 h and the etching voltage is 0 V.

[0109] Example 8

[0110] This embodiment provides a uniformly porous membrane and its preparation method. The difference between the preparation method and that in Embodiment 1 is that the etching time in step (2) is 2.5 h and the etching voltage is 3 V.

[0111] Example 9

[0112] This embodiment provides a uniformly porous membrane and its preparation method. The difference between the preparation method and that in Embodiment 1 is that the etching time in step (2) is 2.5 h and the etching voltage is 9 V.

[0113] Example 10

[0114] This embodiment provides a uniformly porous membrane and its preparation method. The difference between the preparation method and that in Embodiment 1 is that the etching time in step (2) is 2.5 h and the etching time in step (3) is 75 min.

[0115] Example 11

[0116] This embodiment provides a uniformly porous membrane and its preparation method. The difference between the preparation method and that in Embodiment 1 is that the etching time in step (2) is 2.5 h and the etching time in step (3) is 125 min.

[0117] Example 12

[0118] This embodiment provides a uniformly porous membrane and its preparation method. The difference between the preparation method and that in Embodiment 1 is that the etching time in step (2) is 2.5 h and the etching temperature in step (3) is 20 °C.

[0119] Example 13

[0120] This embodiment provides a uniformly porous membrane and its preparation method. The difference between the preparation method and that in Embodiment 1 is that the etching time in step (2) is 2.5 h and the etching temperature in step (3) is 40 °C.

[0121] Example 14

[0122] This embodiment provides a uniformly porous membrane and its preparation method. The only difference between the preparation method and that of Embodiment 1 is that the etching time in step (2) is 2.5 h and the volume fraction of the additive in the etching solution in step (3) is 0%.

[0123] Example 15

[0124] This embodiment provides a uniformly porous membrane and its preparation method. The only difference between the preparation method and that of Embodiment 1 is that the etching time in step (2) is 2.5 h and the volume fraction of the additive in the etching solution in step (3) is 50%.

[0125] Example 16

[0126] This embodiment provides a uniformly porous membrane and its preparation method. The difference between the preparation method and that of Embodiment 1 is that the etching time in step (2) is 2.5 hours.

[0127] The morphology of the uniformly porous membrane obtained in Example 16 was characterized using scanning electron microscopy, and the results are as follows: Figure 2 As shown, by Figure 2 It is known that the uniformly porous membrane has a double conical pore structure.

[0128] Comparative Example 1

[0129] This comparative example provides a uniformly porous membrane and its preparation method. The difference between the preparation method and Example 1 is that the etching time in step (2) is 2.5 h, and step (3) is omitted.

[0130] The morphology of the uniformly porous membrane obtained in Comparative Example 1 was characterized using scanning electron microscopy, and the results are as follows: Figure 4 As shown, the nanoscale portion cannot be displayed.

[0131] Comparative Example 2

[0132] This comparative example provides a uniformly porous membrane and its preparation method. The difference between the preparation method and Example 1 is that step (2) is omitted, and the activated membrane obtained in step (1) is directly subjected to step (3), and the etching time of step (3) is 200 min.

[0133] The pore size of the uniformly porous membranes provided in Examples 1-16, the porosity of the uniformly porous membrane provided in Example 5, the commercial cylindrical porous membrane with cylindrical channels, and the uniformly porous membrane provided in Comparative Example 2, as well as the pure water permeation resistance were tested.

[0134] (1) Pore size measurement: The pore size of the membrane was analyzed using a scanning electron microscope. Membrane samples were cut to 1cm × 1cm size, adhered to a conductive adhesive surface, and sputter-coated with gold before testing at a magnification of 1K. Three to five different planar and cross-sectional positions were randomly selected for observation. ImageJ software was used to process the electron microscope images, and the pore size was measured and recorded.

[0135] (2) Porosity testing: The porosity of the uniformly porous membrane was analyzed using a scanning electron microscope. Membrane samples were cut to 1cm × 1cm size, adhered to a conductive adhesive surface, and sputter-coated with gold before testing at a magnification of 1K. Three to five different planar and cross-sectional locations were randomly selected for observation. ImageJ software was used to process the electron microscope images, measure the pore size and thickness, calculate the volume of a single pore, and count the number of pores per unit membrane area.

[0136] The porosity of a uniformly porous membrane is calculated using the following formula:

[0137]

[0138] Among them, V 单孔 V represents the volume of a single hole. 膜 This represents the total volume of the uniformly porous membrane;

[0139] (3) Pure water permeation resistance test: The pure water permeation resistance of the composite membrane was tested using a self-made dead-end device. The effective volume of the membrane chamber was 13 mL, and the effective membrane area was 4.52 cm². 2 The feed liquid was deionized water, the constant flux washing and filtration mode was used, the test flux was 0.5~8.5mL / min, and the test temperature was 25℃.

[0140] (4) Protein dynamic binding capacity test: The test membrane was cut into circles with a diameter of 16 mm. Six membrane sheets (0.01 mL) were placed in a self-made chromatography apparatus and connected to the AKTA Prime Plus chromatography system for detection. The absorbance at 280 nm, conductivity, and system pressure were monitored and recorded using the AKTA system. Proteins of different molecular weights were used as test proteins. The test protein solutions included 5 mg / mL BSA (5 mL) and 1 mg / mL BBTI (2 mL). The protocol for a single run is as follows:

[0141] First, inject the protein solution into the system without connecting the chromatography apparatus. Rinse the system with 10 mM Tris-HCl buffer (pH 6) until the UV absorbance stabilizes, and record the maximum absorbance value A. max Then connect the chromatographic apparatus and equilibrate the system with 10 mM Tris-HCl buffer (pH 6) until the UV absorbance reaches a stable level. Inject 5 wt% acetone aqueous solution into the system and wash the system with 10 mM Tris-HCl buffer (pH 6) until the UV absorbance of the sample reaches a stable level. Record the volume at which the peak begins to elute as V. delay .

[0142] Inject the protein solution into the system and rinse the system with 10 mM Tris-HCl buffer (pH 6) until the UV absorbance reaches a stable level. Then elute the protein and regenerated membrane with 10 mM Tris-HCl buffer (pH 6) + 1 M NaCl. Record the UV absorbance value as 10% A. max Solution volume V 10％ The dynamic binding capacity of the membrane can be calculated using the following formula:

[0143]

[0144] Where C is the concentration of the test protein solution, M protein S represents the relative molecular mass of the protein being tested, and S represents the surface area of ​​the test membrane, including the pore wall area and the membrane surface area.

[0145] The specific test results of the pore size of the uniformly porous membranes provided in Examples 1-16 and Comparative Example 1 are shown in Table 1; where " / " indicates that the uniformly porous membrane is a single conical pore without a top cone bottom hole; the test results of the porosity and pure water permeation resistance of the uniformly porous membrane provided in Example 5, the commercial cylindrical pore membrane with cylindrical pores, and the uniformly porous membrane provided in Comparative Example 2 are shown in Table 2; the test results of the protein dynamic binding capacity of the uniformly porous membrane provided in Example 5, the commercial cylindrical pore membrane with cylindrical pores, and the uniformly porous membrane provided in Comparative Example 2 are shown in Table 3.

[0146] Table 1

[0147]

[0148]

[0149] Table 2

[0150]

[0151]

[0152] Table 3

[0153]

[0154]

[0155] As can be seen from the comparison of Examples 1-15 and Comparative Example 1, the uniform porous film preparation method, through ingenious design, modulates the channel shape and channel size in two different etching processes, respectively, to obtain micron-sized single conical channels and asymmetric double conical channels, thereby reducing the limitation of the channel size adjustment range of the traditional etching method and realizing the precise control of conical channels.

[0156] As can be seen from the comparison between Examples 1-2 and Example 16 in Table 1, in the uniform pore film etching reaction, the asymmetric time is extended, and the diameter of the top cone bottom hole that directly contacts the stop liquid remains basically unchanged, and the etching reaction progresses slowly here; the top cone becomes larger as the asymmetric etching time increases; the bottom cone bottom hole directly contacts the high-concentration etching liquid, so the pore size increases significantly.

[0157] As can be seen from the comparison between Examples 3-4 and Example 16, increasing the asymmetric etching temperature in the uniform pore film etching reaction increases the etching reaction rate constant, accelerates the etching reaction, and the pore size increases with the increase of etching temperature.

[0158] As can be seen from the comparison between Examples 5-6 and Example 16, increasing the volume ratio of the asymmetric etching reaction additive in the uniform pore film etching reaction reduces the surface energy of the etching solution in contact with the film surface, increases the spreading ability of the etching solution on the film surface, promotes the etching reaction, and the pore size also increases accordingly.

[0159] As can be seen from the comparison between Examples 7-9 and Example 16, in the uniform pore film etching method, due to the high etching concentration and large volume, the solvent diffusion effect is strong, the ion migration enhancement effect and solution heating effect caused by voltage increase are not obvious, and increasing the asymmetric etching reaction voltage does not have a significant impact on the pore shape and size.

[0160] A comparison of Examples 10-11 and Example 16 shows that the symmetrical etching reaction in the uniform pore film etching reaction amplifies the channel size in situ without changing the channel shape, and the size of each position of the channel increases with the increase of the etching reaction time.

[0161] A comparison of Examples 12-13 and Example 16 shows that increasing the symmetrical etching temperature in the uniform pore film etching reaction increases the etching reaction rate constant, accelerates the etching reaction, and the pore size increases with the increase of etching temperature.

[0162] A comparison of Examples 14-15 and Example 16 shows that in the uniform pore film etching reaction, increasing the volume ratio of the additive in the symmetric process reduces the surface energy of the etching solution in contact with the film surface, increases the spreading ability of the etching solution on the film surface, promotes the etching reaction, and the pore size also increases accordingly.

[0163] As shown in Table 2, compared with cylindrical pore membranes with higher porosity, the uniform pore membrane provided by the present invention exhibits lower flow resistance.

[0164] Table 3 shows that there is no significant difference in the adsorption capacity of conical and cylindrical channels for large protein molecules. This is because BSA, with a molecular weight of 66 kDa, exhibits significant steric hindrance during adsorption, shielding the influence of the pores. However, there is a significant difference in the adsorption capacity of conical and cylindrical channels for small protein molecules. Conical channels show a higher adsorption capacity for BBTI, possibly because the inclined pore walls of conical channels are more conducive to the adsorption of small protein molecules than the vertical pore walls of cylindrical channels.

[0165] The applicant declares that the present invention illustrates a uniformly porous membrane, its preparation method, and its application through the above embodiments. However, the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing an isotropic membrane, characterized by, The preparation method comprises: (1) activating a base film to obtain an activated film; (2) placing the activated film obtained in step (1) in an electrolytic cell, the electrolytic cell comprising a first compartment and a second compartment, the first compartment comprising a first electrode and an etching solution, and the second compartment comprising a second electrode and a termination solution; the activated film is located between the first compartment and the second compartment, and a voltage is applied to the electrolytic cell for etching; (3) etching the film obtained in step (2) in an etching solution to obtain the uniform pore film.

2. The production method according to claim 1, characterized by, The material of the base film in step (1) comprises any one or a combination of at least two of polyethylene terephthalate, polyimide, polycarbonate, polyvinylidene fluoride or polypropylene; Preferably, the thickness of the base film is 5-15 μm; Preferably, the base film has a heavy ion bombardment density of 1000-1000000 cm -2 .

3. The production method according to claim 1 or 2, characterized by, The activation comprises ultraviolet irradiation; Preferably, the method of the activation comprises separately irradiating two faces of the base film with ultraviolet light; Preferably, the time of the ultraviolet irradiation is independently 0.1-2 h.

4. The production method according to any one of claims 1 to 3, characterized by, The first electrode and the second electrode each independently comprise a platinum electrode; Preferably, the method of placing the activated film in the electrolytic cell in step (2) comprises placing the activated film between the first compartment and the second compartment, sealing with a gasket and fixing with a clamp; Preferably, the etchant in the etching solution in step (2) comprises any one or a combination of at least two of sodium hydroxide, potassium hydroxide, sulfuric acid, hydrogen chloride, hydrogen fluoride, sodium hypochlorite, hydrogen peroxide, nitric acid, potassium dichromate, potassium permanganate or chromium trioxide; Preferably, the concentration of the etchant in the etching solution in step (2) is 0.1-10 mol / L; Preferably, the etching solution in step (2) further comprises an additive; Preferably, the additive comprises any one or a combination of at least two of ethanol, methanol, propanol, acetonitrile, N, N-dimethylformamide, tetrahydrofuran or dimethyl sulfoxide; Preferably, the volume fraction of the additive in the etching solution in step (2) is ≤50%; Preferably, the termination solution in step (2) comprises any one or a combination of at least two of formic acid solution, potassium metabisulfite solution, potassium chloride solution, potassium iodide solution or water.

5. The method of any one of claims 1-4, wherein, The voltage applied in step (2) is direct current voltage; Preferably, the etching time in step (2) is 1-5 h; Preferably, the applied voltage is 0.1-24 V; Preferably, the etching temperature is 20-40℃.

6. The method of any one of claims 1-5, wherein, The etchant in the etching solution in step (3) comprises any one or a combination of at least two of sodium hydroxide, potassium hydroxide, sulfuric acid, hydrogen chloride, hydrogen fluoride, sodium hypochlorite, hydrogen peroxide, nitric acid, potassium dichromate, potassium permanganate or chromium trioxide; Preferably, the concentration of the etchant in the etching solution in step (3) is 0.1-10 mol / L; Preferably, the etching solution in step (3) further comprises an additive; Preferably, the additive comprises any one or a combination of at least two of ethanol, methanol, propanol, acetonitrile, N, N-dimethylformamide, tetrahydrofuran or dimethyl sulfoxide; Preferably, the volume fraction of the additive in the etching solution in step (3) is ≤50%. Preferably, the etching in step (3) is performed for 75-125 min. Preferably, the etching in step (3) is performed at a temperature of 20-40℃. Preferably, the etching in step (3) is followed by a termination step. Preferably, the termination method comprises: taking the etched membrane out of the etching solution, and placing it in a termination solution to terminate the reaction, thereby obtaining the uniform pore membrane. Preferably, the termination solution comprises any one or a combination of at least two of formic acid solution, potassium pyrosulfite solution, potassium chloride solution, potassium iodide solution, or deionized water.

7. The production method according to claim 5 or 6, characterized by, The preparation method specifically comprises: (1) activating two surfaces of the base membrane by ultraviolet irradiation, thereby obtaining an activated membrane; The time of the ultraviolet irradiation is independently 0.1-2 h. (2) placing the activated membrane obtained in step (1) in an electrolytic cell, wherein the electrolytic cell comprises a first compartment and a second compartment, the first compartment comprises a first electrode and an etching solution, and the second compartment comprises a second electrode and a termination solution; The activated membrane is located between the first compartment and the second compartment, a voltage of 0.1-24 V is applied to the electrolytic cell, and etching is performed at 20-40℃ for 1-5 h; (3) etching the membrane obtained in step (2) in the etching solution at 20-40℃ for 75-125 min, and adding a termination solution to terminate the reaction, thereby obtaining the uniform pore membrane.

8. An isotropic membrane characterized by, The uniform pore membrane is prepared by the preparation method of any one of claims 1-7.

9. The uniform pore membrane according to claim 8, wherein, The uniform pore membrane has a pore structure. Preferably, the pore structure comprises a double cone structure and / or a single cone structure. Preferably, the pore size of the pore structure is 0.08-4.03 μm.

10. Use of the uniform pore membrane of claim 8 or 9 in the field of biological macromolecule purification.

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