A microporous hollow fiber membrane, its preparation method and application

Abstract

The present invention relates to the technical field of polymer thin films, and particularly relates to a microporous hollow fiber membrane, a preparation method thereof and an application thereof. The microporous hollow fiber membrane of the present invention has an inner surface in contact with a protein-containing solution and an outer surface for discharging the filtrate; the cross-section from the inner surface to the outer surface has a gradient pore size structure with an average pore size varying from 70 to 20 nm, and has a bicontinuous network structure; the pores on the inner surface of the hollow fiber membrane are micropores of 0.2 to 3 μm, and the outer surface is micropores of 0.01 to 0.1 μm; the inner diameter of the membrane is 100 to 800 μm, and the wall thickness is 60 to 500 μm. The present invention also provides a preparation method and an application of the microporous hollow fiber filter membrane, which can be applied to virus filtration in the downstream process of biological products, and has the characteristics of high loading capacity and reliable virus retention effect.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer films, and particularly relates to a microporous hollow fiber membrane, a preparation method thereof and an application thereof. Background Art

[0002] Monoclonal antibody (mAb) is one of the biologic macromolecule drugs produced by modern biotechnology for disease diagnosis, treatment and prevention. Compared with proteins, polypeptides, enzymes and cytokines produced by DNA recombinant technology, it is widely recognized and occupies a dominant position in the market.

[0003] mAbs are produced by culturing artificially prepared hybridoma cells and are obtained through separation and purification processes such as clarification, capture, refining, purification and virus filtration, which makes them contaminated with endogenous expression of retroviruses and exogenous viruses such as parvoviruses. Therefore, the virus filtration process is very important in the purification process of mAbs. Due to the physicochemical stability of parvoviruses, membrane filtration using size sieving can more effectively remove viruses. However, due to the small pore size of virus filtration membranes, they usually face the risk of mAb aggregates blocking the pores and even forming a filter cake layer during application, resulting in a decrease in membrane efficiency and the maximum filtration capacity, and an increase in virus filtration costs. In addition, regarding protein aggregates blocking the filter membrane, foreign studies have found that only trace protein aggregates in the size range of 20 - 40 nm, accounting for 1×10 -4 % of the total protein mass in the solution, are sufficient to cause a significant decline in membrane flux during virus filtration.

[0004] Currently, the main materials of existing virus filtration membranes are regenerated cellulose membranes, hydrophilically modified polyvinylidene fluoride (PVDF) and polyethersulfone membranes (PES). In the patent of Asahi Kasei on BioEX series virus filtration membranes (CN201780009989), it is a hollow fiber membrane with a gradient pore cross-section that can retain colloidal gold with a size of 30 - 20 nm and can retain part of the colloidal gold with a size of 15 nm, and this membrane is easily challenged by blockage of unexpected impurities such as protein aggregates with a size of 40 nm or larger. Summary of the Invention

[0005] The present invention overcomes the deficiencies of the prior art, provides a microporous hollow fiber membrane, a preparation method thereof and an application thereof, and provides a microporous hollow fiber filter membrane formed by the thermally induced phase separation method (TIPS) with a gradient pore size ranging from 70 nm to 20 nm from the inner surface to the outer surface of the hollow fiber membrane, which can be used for the retention filtration of 20 - 70 nm viruses, can reduce the probability of membrane blockage and membrane failure during the virus filtration process in the downstream process of biological products, and also has a certain compensatory effect on the failure in the upstream link of virus filtration, improves the virus safety of the filtrate, and has the characteristics of high efficiency and high filtration capacity.

[0006] The present invention provides a microporous hollow fiber membrane, which has an inner surface in contact with a protein-containing solution and an outer surface for discharging filtrate; the cross-section from the inner surface to the outer surface has a gradient pore size structure with an average pore size varying from 70 to 20 nm and has a bicontinuous network structure; the pores on the inner surface of the hollow fiber membrane are micropores with a size of 0.2 to 3 μm, and the outer surface has micropores with a size of 0.01 to 0.1 μm; the inner diameter of the membrane is 100 to 800 μm, and the wall thickness is 60 to 500 μm.

[0007] In some embodiments, the material of the microporous hollow fiber membrane is polyvinylidene fluoride.

[0008] In some embodiments, the pure water flux of the microporous hollow fiber membrane is 20 to 60 L / (m 2 ·h·bar); the bubble point range of the microporous hollow fiber membrane is 1.7 to 3 bar. If the bubble point is too high, due to the too small average pore size, the filtration flux will be small; if the bubble point is too low, due to the existence of macropores in the cross-section, the filtration effect may be poor in practical applications.

[0009] The present invention provides a method for preparing a microporous hollow fiber membrane, comprising:

[0010] Step 1, feeding a core liquid, a casting solution 1 and a casting solution 2 to a three-channel spinneret, and controlling the temperatures of the core liquid, the casting solution 1 and the casting solution 2, the spinning temperature of the spinneret, the flow rate and the spinning rate to extrude a hollow fiber nascent filament; the inner layer channel of the three-channel spinneret is the core liquid channel, the middle layer channel is the casting solution 1 channel; the outer layer channel is the casting solution 2 channel;

[0011] Step 2, after passing through the air gap section, the hollow fiber nascent filament enters a coagulation bath for coagulation and forming, and then is soaked in an extractant for extraction and drying to obtain a microporous hollow fiber membrane;

[0012] Wherein, the core liquid is sebacate, phthalate, adipate, citrate or phosphate; the components of the casting solution 1 are 25 to 40 wt% polyvinylidene fluoride and 60 to 75 wt% solvent d1, and the components of the casting solution 2 are 40 to 60 wt% polyvinylidene fluoride and 40 to 60 wt% solvent d2.

[0013] In some embodiments, the solvent d1 and the solvent d2 are sebacate, phthalate, adipate, citrate or phosphate.

[0014] Further, the sebacate esters are dimethyl sebacate, bis(iso)octyl sebacate, di-n-hexyl sebacate, or di-n-butyl sebacate, etc.; the phthalate esters are dimethyl phthalate, diethyl phthalate, bis(2-ethylhexyl) phthalate (DEHP), or dibutyl phthalate, etc.; the adipate esters are dioctyl adipate, 2-n-hexyl adipate, n-octyl n-decyl adipate, or diethylene glycol monobutyl ether adipate, etc.; the citrate esters are trimethyl citrate, tributyl citrate (TBC), or acetyl tributyl citrate (ATBC), etc.

[0015] In some embodiments, the core liquid, solvent d1, and solvent d2 are ester organic solvents that are above the melting point T of polyvinylidene fluoride and form a homogeneous solution with polyvinylidene fluoride, and the core liquid and solvent d1, and solvent d1 and solvent d2 cannot both be phthalate esters. m p Above, an ester organic solvent that forms a homogeneous solution with polyvinylidene fluoride, and the core liquid and solvent d1, and solvent d1 and solvent d2 cannot both be phthalate esters.

[0016] Further, the melting point T of the compound formed by 50 wt% polyvinylidene fluoride and 50 wt% solvent d1 m p-d1 satisfies 10°C < T m p -T m p-d1 < 20°C, forming a bicontinuous network structure mainly based on liquid-liquid phase separation.

[0017] The melting point T of the compound formed by 50 wt% polyvinylidene fluoride and 50 wt% solvent d2 m p-d2 satisfies 2°C < T m p -T m p-d2 < 8°C. More preferably, the melting point of solvent d2 is greater than 30°C, and it is easier to form a structure with countless slender micropores distributed in the polymer skeleton.

[0018] The melting point T of the compound formed by 50 wt% polyvinylidene fluoride and 50 wt% core liquid m p-b satisfies 30°C < T m p -T m p-b < 100°C. More preferably, 30°C < T m p -T m p-b < 50°C. At this time, the compatibility between the core liquid and the polymer is better than that between solvent d1 and the polymer, and a loose and porous inner surface can be obtained.

[0019] Further, T m p-d2 -T m p-d1 < 8°C. If the difference between the two is greater than 8°C, there is a risk of stratification during the film-forming process of casting solution 1 and casting solution 2; 10°C < T m p-d1 -T m p-b<40 °C, that is, it is required that the compatibility between the solvent d1 and the core liquid is within a certain range. If it is less than 10 °C, it is not easy to form a loose microporous structure on the inner surface, that is, it is impossible to obtain an average pore diameter higher than that obtained by casting the casting solution 1 alone, and thus it is impossible to achieve a true gradient pore diameter; if it is greater than 40 °C, the compatibility between the core liquid and the solvent d1 is too poor, which is not conducive to the smoothness of the inner surface, and an uneven inner surface may be formed.

[0020] In some embodiments, the temperature range of the core liquid is 60-170 °C, and the flow rate range of the core liquid is 3-30 mL / min; more preferably, 80-140 °C. If the temperature of the core liquid is too low, the inner structure of the membrane close to the core liquid will solidify faster due to contacting the core liquid far below the curing temperature, and the degree of mutual diffusion in the contact area between the core liquid and the casting solution 1 is low. Generally speaking, due to the shortening of the coarsening time of the polymer-poor phase droplets during the liquid-liquid phase separation process, it is not easy to form loose micropores, and thus it is impossible to obtain a membrane with a gradient pore diameter change; if the temperature of the core liquid is too high, during the spinning process, due to the slow solidification and shaping of the nascent membrane filaments in the air gap section, it is not easy to shape and it is not easy to spin continuously and stably.

[0021] The temperature range of the casting solution 1 and the casting solution 2 is 180-240 °C, and the flow rate range of the casting solution 1 and the casting solution 2 is 2-15 mL / min; the spinning temperature range of the spinneret is 180-240 °C. If the spinning temperature is too high, the casting solution is not easy to form due to low viscosity and cannot be spun continuously and stably. If the spinning temperature is too low, due to the too high viscosity of the casting solution, the membrane filaments are easy to break during the spinning process and it is not easy to spin continuously and stably; the coagulation bath is an organic solvent or water that is immiscible with polyvinylidene fluoride below 50 °C; the temperature range of the coagulation bath is 10-50 °C, more preferably 10-35 °C. If the temperature of the coagulation bath is too high, the loose macroporous region with an inner surface pore diameter larger than the average pore diameter of the membrane tends to disappear, and the outer surface pore diameter will increase. In some embodiments, the length range of the air gap section is 10-150 mm, and the spinning rate range is 10-100 m / min. More preferably, the length range of the air gap section is 20-130 mm. If the air gap section is too short, the extruded casting solution enters the low-temperature coagulation bath too fast and the phase separation time is too short, resulting in an overall average pore diameter of the formed hollow fiber cross-section being too small; if the air gap section is too long, due to the increased volatilization degree of the solvent component in the high-temperature casting solution, the pore distribution on the outer surface of the membrane is uneven and the micropores are small, and an air gap section environment control method needs to be used to improve the microstructure of the membrane near the outer surface and the microporous structure of the outer surface.

[0022] In the present invention, no special limitation is imposed on the specific components of the extractant, including but not limited to one or more of ethanol, acetone, and isopropanol.

[0023] An application of a microporous hollow fiber membrane, including the application of the microporous hollow fiber membrane in virus filtration in the downstream process of biological products.

[0024] Furthermore, the microporous hollow fiber membrane can be applied to virus filtration in the downstream purification process of monoclonal antibody biologics.

[0025] Beneficial effects:

[0026] The present invention provides a microporous hollow fiber membrane. When facing protein aggregate impurities of 40 nm or larger, it can filter these impurities by virtue of its own structural characteristics. In theory, the flux and filtration capacity of this membrane in the virus separation process will not be affected. The membrane has a gradient pore size structure with pore sizes varying from 70 to 20 nm, and has a bicontinuous network structure; the pores on the inner surface of the membrane are micropores of 0.2 - 3 μm, and the outer surface has micropores of 0.01 - 0.1 μm; at the same time, the inner diameter of the membrane can be adjusted within 100 - 800 μm, and the wall thickness can be 60 - 500 μm.

[0027] The present invention provides a method for preparing the microporous hollow fiber membrane. The membrane is prepared by combining the thermally induced phase separation method with a three-channel spinneret. By precisely controlling the formulations in each channel and the spinning process, the microstructure of each region in the membrane structure can be controlled. This preparation process is simple and easy to implement. The logarithmic removal rate of the microporous hollow fiber membrane prepared for colloidal gold of 70 nm, 50 nm, 30 nm, and 20 nm is above 1. It can be applied to virus filtration in the downstream process of biological products, is applicable to high-concentration biopharmaceutical culture solutions, and has the effect of improving virus safety in the biopharmaceutical process in practical applications. Description of the drawings

[0028] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings required for use in the examples. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 It is a schematic diagram of the capture site of colloidal gold by the membrane of the present invention;

[0030] Figure 2 It is a schematic diagram for the preparation of the microporous hollow fiber membrane of the present invention;

[0031] Figure 3 It is the microscopic structure of the cross-section of the microporous hollow fiber membrane formed by the casting solution 1 of Example 1;

[0032] Figure 4 It is the microscopic structure of the cross-section of the microporous hollow fiber membrane formed by the casting solution 2 of Example 1 and Example 2;

[0033] Figure 5 It is the microscopic structure of the inner surface of the microporous hollow fiber membrane of Example 1;

[0034] Figure 6The microstructure of the outer surface of the microporous hollow fiber membrane of Example 1;

[0035] Figure 7 The microstructure of the cross-section of the microporous hollow fiber membrane formed by casting solution 1 of Example 2.

[0036] Explanation of reference numerals: 1 - three-channel spinneret, 2 - inner layer channel, 3 - middle layer channel, 4 - outer layer channel, 5 - air gap section, 6 - hollow fiber nascent filament, 7 - coagulation bath. Detailed implementation manners

[0037] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meanings understood by those skilled in the art for the present invention. In case of conflicts, the definitions in this specification shall prevail.

[0038] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0039] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values (including integers and fractions) within the range.

[0040] In this article, for the sake of concise description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope described in this specification.

[0041] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0042] Conventional instruments and equipment in the art are used in the following examples. For the experimental methods without specific conditions noted in the following examples, they are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following examples. Unless otherwise specified, commercially available products are used, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratios represent weight.

[0043] The following further describes a microporous hollow fiber membrane provided by the present application, its preparation method and application in conjunction with specific examples.

[0044] In currently existing virus filtration membranes, such as a hollow fiber membrane for biopharmaceutical clarification (CN200980137972) from Asahi Kasei, different concentrations of hydrophilic additives are added in different regions in the membrane thickness direction to obtain a hollow fiber membrane with gradually increasing hydrophilicity from one side to the other side, and the membrane has a gradient pore structure (the outer periphery is the smallest pore size region). However, firstly, the hydrophilicity of the inner peripheral region near the inner surface of the membrane in this patent is small. Although the pore size in the inner peripheral region is large, monoclonal antibodies and aggregates to be recovered in the filtered solution will also be adsorbed. The overall hydrophilization of the membrane is more beneficial for application. The beneficial effect of this patent is still reflected by the size sieving effect of the gradient pore size on the filtered substances. Secondly, the formation method of the surface gradient pore size is not clear in this patent. According to the invention content of the patent, this membrane is a hollow fiber membrane prepared by the non-solvent induced phase separation (NIPS) method. When the membrane thickness is 350 - 800 μm as described in it, the thickness is very large for the NIPS method to prepare hollow fiber membranes. Even if the proportion of the hydrophilic component gradually increases from the inside to the outside, the pore size range in the middle region of the actual membrane structure generated during the phase separation and solidification process may not necessarily connect the pore sizes of the inner peripheral and outer peripheral regions to form a gradient pore size. Thirdly, during the forming process of the NIPS method, the concentration of the good solvent in the internal coagulation bath used is above 85% by weight, and it is difficult for the membrane filaments to be solidified and formed during the spinning process, and it is difficult to smoothly draw and collect the filaments.

[0045] Therefore, the present invention provides a method for preparing the membrane that can be used for virus filtration. This method uses the thermally induced phase separation method to prepare the membrane, and the driving force for phase separation comes from the decrease in temperature, rather than the phase separation caused by the exchange of non-solvents (the non-solvent induced phase separation method for preparing membranes). Therefore, when preparing a gradient pore membrane, the wall thickness is not limited, and a gradient pore membrane with a large wall thickness can be prepared; a three-channel spinneret is used to prepare a hollow fiber membrane, and through the selection of the casting solution formula and the core liquid in the three channels and the coordination of various process parameters, the membrane structure can be precisely controlled.

[0046] The performance of the microporous hollow fiber membrane of the present application is characterized by the following method:

[0047] Bubble point test:

[0048] Using a bubble pressure method pore size analysis device, and using the method of internal pressure and saturated n-butanol to displace n-butanol in the pores of the hollow fiber membrane, setting a certain pressure increase rate, upper limit of pressure test, and weight stabilization duration, the bubble point pressure and average pore size of the hollow fiber membrane are measured.

[0049] Pure water flux test:

[0050] Adopting a dead-end filtration method, setting the inlet pressure of pure water at 25 °C to 4 bar, measuring the pure water permeation rate per unit time, per unit pressure, and per unit membrane area, and calculating the pure water flux as follows:

[0051] Pure water flux (L / m 2 ·bar·h) = pure water permeation amount / effective membrane area / filtration duration / inlet pressure

[0052] Colloidal gold retention test:

[0053] Refer to the test method of Patent CN201780009989. Prepare colloidal gold solutions of 70 nm, 50 nm, 30 nm, and 20 nm. Dilute the colloidal gold solutions using distilled water for injection, polyoxyethylene-naphthyl ether (1.59 vol%), and poly(4-styrenesulfonic acid sodium) (0.20 vol%) so that the absorbance of the diluted colloidal gold solution at the maximum absorption wavelength measured by an ultraviolet-visible spectrophotometer is 0.25. Take a membrane with an effective area of 10 cm 2 , under a pressure of 196 kPa, use the membrane to filter 40 mL of each size of the prepared colloidal gold solution. Filter the colloidal gold solutions from large particle size to small particle size in sequence. The absorbance of the obtained filtrate at the maximum absorption wavelength is measured using the above ultraviolet spectrophotometer and recorded as a. The logarithmic removal rate (LRV) of the membrane for colloidal gold is calculated as follows:

[0054] LRV = log 10 (0.25 / a)

[0055] Use an optical microscope to visually detect the cross-section transverse slice of the hollow fiber membrane that has captured colloidal gold particles, and measure the relative position of the captured colloidal gold in the cross-section. The capture site of colloidal gold is as shown in the schematic Figure 1 . It can be seen that the distances from the intercepted positions of colloidal gold of the same size on the circumference to the center of the circle are close, that is, the pore sizes at the same radius on the circumference are uniform, and in practical applications, viruses are not likely to leak.

[0056] Average pore size test of the membranes formed by casting solutions 1 and 2:

[0057] The hollow fiber membranes 1 and 2 were prepared using the casting solutions 1 and 2 respectively, and the microstructures of the inner and outer surfaces of the membranes were adjusted to be close to the forming structures at the corresponding positions of the casting solutions of the membranes. The average pore sizes of the membranes formed by the two casting solutions were measured. The average pore size of membrane 1 was in the range of 0.045 - 0.05 μm, and the average pore size of membrane 2 was in the range of 0.019 - 0.022 μm.

[0058] Melting point determination method:

[0059] The melting point T of the polyvinylidene fluoride of the present invention m p and the melting point T of the compound formed by 50 wt% polyvinylidene fluoride and 50 wt% solvent d1 m p-d1 and the melting point T of the compound formed by 50 wt% polyvinylidene fluoride and 50 wt% solvent d2 m p-d2 and the melting point T of the compound formed by 50 wt% polyvinylidene fluoride and 50 wt% core liquid m p-b The melting points were determined using differential scanning calorimetry (DSC) at a cooling rate of 5 °C / min.

[0060] Example 1

[0061] 30 wt% of polyvinylidene fluoride and 70 wt% of tributyl citrate were stirred and mixed evenly at 220 °C using a screw extruder or a high-temperature stirring kettle to obtain casting solution 1; 45 wt% of polyvinylidene fluoride and 55 wt% of dicyclohexyl phthalate were mixed evenly at 220 °C using a screw extruder or a high-temperature stirring kettle to obtain casting solution 2.

[0062] The casting solution 1, the casting solution 2, and dimethyl sebacate as the core liquid at 130 °C were respectively metered by a melt metering pump and supplied to a three-channel spinneret plate at 225 °C for extrusion. As Figure 2 shown, the extruded liquid entered the coagulation bath water at 20 °C to be cooled and formed into hollow fibers after passing through a 100 mm air gap section.

[0063] Among them, the flow rates of the casting solution 1 and the casting solution 2 were 6.2 mL / min and 7.9 mL / min respectively, the flow rate of the core liquid was 9 mL / min, and the spinning rate was 40 m / min.

[0064] The residual chemical reagents in the hollow fibers were fully extracted with ethanol and dried to obtain microporous hollow fiber membranes.

[0065] The cross-sectional microstructure of the microporous hollow fiber membrane formed by the casting solution 1 is as Figure 3 shown, and the cross-sectional microstructure of the microporous hollow fiber membrane formed by the casting solution 2 is as Figure 4 shown.

[0066] The microstructure of the inner surface of the prepared microporous hollow fiber membrane is as Figure 5As shown, the microstructure of the outer surface of the membrane is as follows Figure 6 As shown, the inner diameter of the microporous hollow fiber membrane is 400 μm, the wall thickness is 120 μm, and the bubble point tested by the liquid-liquid method is 1.8 bar. The pure water flux of the microporous hollow fiber membrane is 38 L / (m 2 ·h·bar). The logarithmic rejection rate of the microporous hollow fiber membrane for colloidal gold with a diameter of 70 nm is 6, the logarithmic rejection rate for colloidal gold with a diameter of 50 nm is 6, the logarithmic rejection rate for colloidal gold with a diameter of 30 nm is 1.4, and the logarithmic rejection rate for colloidal gold with a diameter of 20 nm is 1.2. The membrane slices that filtered the colloidal gold solutions of the aforementioned four particle sizes were observed under an optical microscope for the particle retention area, which was within the range Figure 1 shown, and no serious deviation occurred. The pure water flux of the microporous hollow fiber membrane after retaining colloidal gold was tested to be 38 L / (m 2 ·h·bar).

[0067] Example 2

[0068] 33 wt% of polyvinylidene fluoride and 67 wt% of diphenyl carbonate were stirred and mixed evenly at 220 °C using a screw extruder or a high-temperature stirring kettle to obtain casting solution 1; 48 wt% of polyvinylidene fluoride and 52 wt% of dicyclohexyl phthalate were mixed evenly at 220 °C using a screw extruder or a high-temperature stirring kettle to obtain casting solution 2.

[0069] Casting solution 1, casting solution 2, and dimethyl sebacate as the core liquid at 120 °C were respectively metered by a melt metering pump and supplied to a three-channel spinneret plate at 225 °C for extrusion. The extruded liquid passed through a 100-mm air gap section and then entered a coagulation bath water at 20 °C for cooling and forming to form hollow fibers.

[0070] Among them, the flow rates of casting solution 1 and casting solution 2 were 6.2 mL / min and 7.9 mL / min respectively, the flow rate of the core liquid was 9 mL / min, and the spinning rate was 40 m / min.

[0071] Ethanol was used to fully extract the residual chemical reagents in the hollow fibers and dried to obtain the microporous hollow fiber membrane.

[0072] The cross-sectional microstructure of the microporous hollow fiber membrane formed by casting solution 1 is as Figure 7 shown, and the cross-sectional microstructure of the microporous hollow fiber membrane formed by casting solution 2 is as Figure 4 shown. The prepared hollow fiber membrane has an inner diameter of 400 μm, a wall thickness of 120 μm, and a bubble point tested by the liquid-liquid method of 2.3 bar. The pure water flux of the hollow fiber membrane is 33 L / (m 2·h·bar). The logarithmic removal rate of the hollow fiber membrane for colloidal gold with a diameter of 70 nm is 6, for colloidal gold with a diameter of 50 nm is 6, for colloidal gold with a diameter of 30 nm is 2, and for colloidal gold with a diameter of 20 nm is 2. The membrane slices that filtered the colloidal gold solutions of the aforementioned four particle sizes were observed under an optical microscope for the particle retention area, which conformed to Figure 1 the range shown, and no serious deviation occurred. The pure water flux of the microporous hollow fiber membrane after retaining colloidal gold was 33 L / (m 2 ·h·bar).

[0073] Example 3

[0074] 30 wt% of polyvinylidene fluoride and 70 wt% of tributyl citrate were stirred and mixed evenly at 220 °C using a screw extruder or a high-temperature stirring kettle to obtain casting solution 1; 48 wt% of polyvinylidene fluoride and 52 wt% of dibutyl sebacate were mixed evenly at 220 °C using a screw extruder or a high-temperature stirring kettle to obtain casting solution 2.

[0075] Casting solution 1, casting solution 2, and diethyl phthalate as the core liquid at 120 °C were respectively metered by a melt metering pump and supplied to a three-channel spinneret for extrusion at a temperature of 225 °C. The extruded liquid passed through a 100-mm air gap section and then entered the coagulation bath water at a temperature of 20 °C for cooling and forming to form hollow fibers.

[0076] Among them, the flow rates of casting solution 1 and casting solution 2 were 6.2 mL / min and 7.9 mL / min respectively, the flow rate of the core liquid was 9 mL / min, and the spinning rate was 40 m / min.

[0077] The residual chemical reagents in the hollow fibers were fully extracted with ethanol and dried to obtain a microporous hollow fiber membrane.

[0078] The prepared hollow fiber membrane had an inner diameter of 400 μm, a wall thickness of 120 μm, and a liquid-liquid method test bubble point of 2.2 bar. The pure water flux of the hollow fiber membrane was 34 L / (m 2 ·h·bar). The logarithmic removal rate of the hollow fiber membrane for colloidal gold with a diameter of 70 nm is 6, for colloidal gold with a diameter of 50 nm is 6, for colloidal gold with a diameter of 30 nm is 2, and for colloidal gold with a diameter of 20 nm is 1.8. The membrane slices that filtered the colloidal gold solutions of the aforementioned four particle sizes were observed under an optical microscope for the particle retention area, which conformed to Figure 1 the range shown, and no serious deviation occurred. The pure water flux of the membrane after retaining colloidal gold was 34 L / (m 2 ·h·bar).

[0079] Example 4

[0080] Using a screw extruder or a high-temperature stirring kettle, 33 wt% of polyvinylidene fluoride and 67 wt% of diphenyl carbonate were stirred and mixed evenly at 210 °C to obtain casting solution 1; using a screw extruder or a high-temperature stirring kettle, 48 wt% of polyvinylidene fluoride and 52 wt% of dicyclohexyl phthalate were mixed evenly at 210 °C to obtain casting solution 2.

[0081] Casting solution 1, casting solution 2, and dimethyl sebacate as the core liquid at 120 °C were respectively metered by a melt metering pump and supplied to a three-channel spinneret plate at 225 °C for extrusion. The extruded liquid passed through a 70-mm air gap section and then entered the coagulation bath water at 20 °C for cooling and forming to form hollow fibers.

[0082] Among them, the flow rates of casting solution 1 and casting solution 2 were 6.2 mL / min and 7.9 mL / min respectively, the flow rate of the core liquid was 9 mL / min, and the spinning rate was 40 m / min.

[0083] Ethanol was used to fully extract the residual chemical reagents in the hollow fibers, and then dried to obtain a microporous hollow fiber membrane.

[0084] The prepared hollow fiber membrane had an inner diameter of 400 μm, a wall thickness of 120 μm, and a liquid-liquid method test bubble point of 2.6 bar. The pure water flux of the hollow fiber membrane was 27 L / (m 2 ·h·bar). The logarithmic rejection rate of the hollow fiber membrane for colloidal gold with a diameter of 70 nm was 6, the logarithmic rejection rate for colloidal gold with a diameter of 50 nm was 6, the logarithmic rejection rate for 30-nm colloidal gold was 2, and the logarithmic rejection rate for 20-nm colloidal gold was 2. The membrane slices that filtered the colloidal gold solutions of the aforementioned four particle sizes were observed under an optical microscope for the particle retention area, which met the Figure 1 range shown, and no serious deviation occurred. The pure water flux of the microporous hollow fiber membrane after testing the retained colloidal gold was 26 L / (m 2 ·h·bar).

[0085] Example 5

[0086] Using a screw extruder or a high-temperature stirring kettle, 33 wt% of polyvinylidene fluoride and 67 wt% of tributyl citrate were stirred and mixed evenly at 220 °C to obtain casting solution 1; using a screw extruder or a high-temperature stirring kettle, 48 wt% of polyvinylidene fluoride and 52 wt% of dibutyl sebacate were mixed evenly at 220 °C to obtain casting solution 2.

[0087] Casting solution 1, casting solution 2, and diethyl phthalate as the core liquid at 120 °C were respectively metered by a melt metering pump and supplied to a three-channel spinneret plate at 200 °C for extrusion. The extruded liquid passed through a 100-mm air gap section and then entered the coagulation bath water at 20 °C for cooling and forming to form hollow fibers.

[0088] Among them, the flow rates of the casting solution 1 and the casting solution 2 are 6.2 mL / min and 7.9 mL / min respectively, the flow rate of the core fluid is 9 mL / min, and the spinning rate is 40 m / min.

[0089] Use ethanol to fully extract the residual chemical reagents in the hollow fiber, and dry to obtain the microporous hollow fiber membrane.

[0090] The prepared hollow fiber membrane has an inner diameter of 400 μm, a wall thickness of 120 μm, and a bubble point of 3 bar measured by the liquid-liquid method. The pure water flux of the hollow fiber membrane is 20 L / (m 2 ·h·bar). The logarithmic rejection rate of the hollow fiber membrane for colloidal gold with a diameter of 70 nm is 6, the logarithmic rejection rate for colloidal gold with a diameter of 50 nm is 6, the logarithmic rejection rate for colloidal gold with a diameter of 30 nm is 2, and the logarithmic rejection rate for colloidal gold with a diameter of 20 nm is 1.8. Cut the membrane that has filtered the colloidal gold solutions of the aforementioned four particle sizes, and observe the particle retention area under an optical microscope, which conforms to Figure 1 the range shown, and no serious deviation occurs. The pure water flux of the membrane after testing for retaining colloidal gold is 16 L / (m 2 ·h·bar).

[0091] Example 6

[0092] Use a screw extruder or a high-temperature stirring kettle to stir and mix 33 wt% of polyvinylidene fluoride and 67 wt% of tributyl citrate evenly at 220 °C to obtain the casting solution 1; use a screw extruder or a high-temperature stirring kettle to mix 48 wt% of polyvinylidene fluoride and 52 wt% of dicyclohexyl phthalate evenly at 220 °C to obtain the casting solution 2.

[0093] After the casting solution 1, the casting solution 2 and dimethyl sebacate as the core fluid at 120 °C are respectively metered by a melt metering pump, they are supplied to a three-channel spinneret plate at 225 °C for extrusion. As Figure 2 shown, the extruded liquid enters the coagulation bath water at 20 °C to cool and form a hollow fiber after passing through a 100 mm air gap section.

[0094] Among them, the flow rates of the casting solution 1 and the casting solution 2 are 9.3 mL / min and 11.9 mL / min respectively, the flow rate of the core fluid is 13.5 mL / min, and the spinning rate is 60 m / min.

[0095] Use ethanol to fully extract the residual chemical reagents in the hollow fiber, and dry to obtain the microporous hollow fiber membrane.

[0096] The microporous hollow fiber membrane has an inner diameter of 400 μm, a wall thickness of 120 μm, and a bubble point of 2.3 bar measured by the liquid-liquid method. The pure water flux of the microporous hollow fiber membrane is 32 L / (m2 ·h·bar). The logarithmic removal rate of the microporous hollow fiber membrane for colloidal gold with a diameter of 70 nm is 6, for colloidal gold with a diameter of 50 nm is 6, for colloidal gold with a diameter of 30 nm is 2, and for colloidal gold with a diameter of 20 nm is 1.8. The membrane slices that filtered the colloidal gold solutions of the aforementioned four particle sizes were observed in the particle retention area under an optical microscope, which conformed to Figure 1 the range shown, and no serious deviation occurred. The pure water flux of the microporous hollow fiber membrane after retaining colloidal gold was 31 L / (m 2 ·h·bar).

[0097] Example 7

[0098] 33 wt% of polyvinylidene fluoride and 67 wt% of tributyl citrate were stirred and mixed evenly at 220 °C using a screw extruder or a high-temperature stirring kettle to obtain casting solution 1; 48 wt% of polyvinylidene fluoride and 52 wt% of dicyclohexyl phthalate were mixed evenly at 220 °C using a screw extruder or a high-temperature stirring kettle to obtain casting solution 2.

[0099] Casting solution 1, casting solution 2, and dimethyl sebacate as the core liquid at 120 °C were respectively metered by a melt metering pump and supplied to a three-channel spinneret plate at 225 °C for extrusion. As Figure 2 shown, the extruded liquid entered the coagulation bath water at 20 °C through a 100 mm air gap section for cooling and forming to form hollow fibers.

[0100] Among them, the flow rates of casting solution 1 and casting solution 2 were 4.7 mL / min and 5.9 mL / min respectively, the flow rate of the core liquid was 6.75 mL / min, and the spinning rate was 30 m / min.

[0101] Ethanol was used to fully extract the residual chemical reagents in the hollow fibers, and after drying, a microporous hollow fiber membrane was obtained.

[0102] The microscopic structure of the cross-section of the microporous hollow fiber membrane formed by casting solution 1 was as Figure 3 shown, and the microscopic structure of the cross-section of the microporous hollow fiber membrane formed by casting solution 2 was as Figure 4 shown.

[0103] The microscopic structure of the inner surface of the prepared microporous hollow fiber membrane was as Figure 5 shown, and the microscopic structure of the outer surface of the membrane was as Figure 6 shown. The inner diameter of the microporous hollow fiber membrane was 400 μm, the wall thickness was 120 μm, and the bubble point measured by the liquid-liquid method was 2 bar. The pure water flux of the microporous hollow fiber membrane was 36 L / (m 2·h·bar). The logarithmic rejection rate of the microporous hollow fiber membrane for colloidal gold with a diameter of 70 nm is 6, for colloidal gold with a diameter of 50 nm is 6, for colloidal gold with a diameter of 30 nm is 2, and for colloidal gold with a diameter of 20 nm is 1.8. The membrane slices that filtered the colloidal gold solutions of the aforementioned four particle sizes were observed under an optical microscope for the particle retention area, which conformed to Figure 1 as shown in the range, and no serious deviation occurred. The pure water flux of the microporous hollow fiber membrane after retaining colloidal gold was 36 L / (m 2 ·h·bar).

[0104] Example 8

[0105] 33 wt% of polyvinylidene fluoride and 67 wt% of tributyl citrate were stirred and mixed evenly at 220 °C using a screw extruder or a high-temperature stirring kettle to obtain casting solution 1; 48 wt% of polyvinylidene fluoride and 52 wt% of dicyclohexyl phthalate were mixed evenly at 220 °C using a screw extruder or a high-temperature stirring kettle to obtain casting solution 2.

[0106] Casting solution 1, casting solution 2, and dimethyl sebacate as the core liquid at 60 °C were respectively metered by a melt metering pump and supplied to a three-channel spinneret plate at 225 °C for extrusion. The extruded liquid passed through a 100-mm air gap section and then entered the coagulation bath water at 20 °C for cooling and forming to form hollow fibers.

[0107] Among them, the flow rates of casting solution 1 and casting solution 2 were 6.2 mL / min and 7.9 mL / min respectively, the flow rate of the core liquid was 9 mL / min, and the spinning rate was 40 m / min.

[0108] Ethanol was used to fully extract the residual chemical reagents in the hollow fibers, and then dried to obtain the microporous hollow fiber membrane.

[0109] The prepared hollow fiber membrane had an inner diameter of 400 μm, a wall thickness of 120 μm, and a liquid-liquid method test bubble point of 2.4 bar. The pure water flux of the hollow fiber membrane was 29 L / (m 2 ·h·bar). The logarithmic rejection rate of the hollow fiber membrane for colloidal gold with a diameter of 70 nm is 6, for colloidal gold with a diameter of 50 nm is 6, for colloidal gold with a diameter of 30 nm is 2, and for colloidal gold with a diameter of 20 nm is 1.8. The membrane slices that filtered the colloidal gold solutions of the aforementioned four particle sizes were observed under an optical microscope for the particle retention area, which conformed to Figure 1 as shown in the range, and no serious deviation occurred. The pure water flux of the membrane after retaining colloidal gold was 26 L / (m 2 ·h·bar).

[0110] Example 9

[0111] Using a screw extruder or a high-temperature stirring kettle, 33 wt% of polyvinylidene fluoride and 67 wt% of tributyl citrate are stirred and mixed evenly at 230 °C to obtain casting solution 1; using a screw extruder or a high-temperature stirring kettle, 48 wt% of polyvinylidene fluoride and 52 wt% of dicyclohexyl phthalate are mixed evenly at 230 °C to obtain casting solution 2.

[0112] Casting solution 1, casting solution 2 and dimethyl sebacate as the core liquid at 120 °C are respectively metered by a melt metering pump and then supplied to a three-channel spinneret plate at 225 °C for extrusion. The extruded liquid passes through a 100-mm air gap section and then enters a coagulation bath water at 50 °C for cooling and forming to form hollow fibers.

[0113] Among them, the flow rates of casting solution 1 and casting solution 2 are 6.2 mL / min and 7.9 mL / min respectively, the flow rate of the core liquid is 9 mL / min, and the spinning rate is 40 m / min.

[0114] Use ethanol to fully extract the residual chemical reagents in the hollow fibers and dry them to obtain a microporous hollow fiber membrane.

[0115] The inner diameter of the prepared hollow fiber membrane is 400 μm, the wall thickness is 120 μm, and the bubble point tested by the liquid-liquid method is 2.2 bar. The pure water flux of the hollow fiber membrane is 58 L / (m 2 ·h·bar). The logarithmic rejection rate of the hollow fiber membrane for colloidal gold with a diameter of 70 nm is 5, the logarithmic rejection rate for colloidal gold with a diameter of 50 nm is 5, the logarithmic rejection rate for 30-nm colloidal gold is 1.5, and the logarithmic rejection rate for 20-nm colloidal gold is 1.2. The membrane slices that have filtered the colloidal gold solutions of the aforementioned four particle sizes are observed under an optical microscope for the particle retention area, which conforms to Figure 1 the range shown, and no serious deviation occurs. The pure water flux of the membrane after testing the retained colloidal gold is 50 L / (m 2 ·h·bar).

[0116] Example 10

[0117] Using a screw extruder or a high-temperature stirring kettle, 40 wt% of polyvinylidene fluoride and 60 wt% of tributyl citrate are stirred and mixed evenly at 220 °C to obtain casting solution 1; using a screw extruder or a high-temperature stirring kettle, 50 wt% of polyvinylidene fluoride and 50 wt% of dicyclohexyl phthalate are mixed evenly at 220 °C to obtain casting solution 2.

[0118] Casting solution 1, casting solution 2 and dimethyl sebacate as the core liquid at 120 °C are respectively metered by a melt metering pump and then supplied to a three-channel spinneret plate at 225 °C for extrusion, as Figure 2The extruded liquid enters the coagulation bath water at 20 °C through a 100-mm air gap section for cooling and forming, resulting in hollow fibers.

[0119] Among them, the flow rates of casting solution 1 and casting solution 2 are 6.2 mL / min and 7.9 mL / min respectively, the flow rate of the core liquid is 9 mL / min, and the spinning rate is 40 m / min.

[0120] Ethanol is used to fully extract the residual chemical reagents in the hollow fibers, and after drying, a microporous hollow fiber membrane is obtained.

[0121] The inner diameter of the microporous hollow fiber membrane is 400 μm, the wall thickness is 120 μm, and the bubble point tested by the liquid-liquid method is 2.6 bar. The pure water flux of the microporous hollow fiber membrane is 30 L / (m 2 ·h·bar). The logarithmic rejection rate of the microporous hollow fiber membrane for colloidal gold with a diameter of 70 nm is 6, the logarithmic rejection rate for colloidal gold with a diameter of 50 nm is 6, the logarithmic rejection rate for colloidal gold with a diameter of 30 nm is 3.5, and the logarithmic rejection rate for colloidal gold with a diameter of 20 nm is 2. The membrane slices that have filtered the colloidal gold solutions of the aforementioned four particle sizes are observed under an optical microscope for the particle retention area, which conforms to Figure 1 the range shown, and no serious deviation occurs. The pure water flux of the microporous hollow fiber membrane after testing for retaining colloidal gold is 27 L / (m 2 ·h·bar).

[0122] Example 11

[0123] A screw extruder or a high-temperature stirring kettle is used to stir and mix 28 wt% of polyvinylidene fluoride and 72 wt% of tributyl citrate evenly at 220 °C to obtain casting solution 1; a screw extruder or a high-temperature stirring kettle is used to mix 43 wt% of polyvinylidene fluoride and 67 wt% of dicyclohexyl phthalate evenly at 220 °C to obtain casting solution 2.

[0124] Casting solution 1, casting solution 2, and dimethyl sebacate as the core liquid at 120 °C are respectively metered by a melt metering pump and supplied to a three-channel spinneret for extrusion at 225 °C. As Figure 2 shown, the extruded liquid enters the coagulation bath water at 20 °C through a 100-mm air gap section for cooling and forming, resulting in hollow fibers.

[0125] Among them, the flow rates of casting solution 1 and casting solution 2 are 6.2 mL / min and 7.9 mL / min respectively, the flow rate of the core liquid is 9 mL / min, and the spinning rate is 40 m / min.

[0126] Ethanol is used to fully extract the residual chemical reagents in the hollow fibers, and after drying, a microporous hollow fiber membrane is obtained.

[0127] The inner diameter of the microporous hollow fiber membrane is 400 μm, the wall thickness is 120 μm, and the bubble point measured by the liquid-liquid method is 1.8 bar. The pure water flux of the microporous hollow fiber membrane is 49 L / (m 2 ·h·bar). The logarithmic rejection rate of the microporous hollow fiber membrane for colloidal gold with a diameter of 70 nm is 6, the logarithmic rejection rate for colloidal gold with a diameter of 50 nm is 5, the logarithmic rejection rate for colloidal gold with a diameter of 30 nm is 1.2, and the logarithmic rejection rate for colloidal gold with a diameter of 20 nm is 1. The membrane slices that have filtered the colloidal gold solutions of the aforementioned four particle sizes are observed under an optical microscope for the particle retention area, which conforms to Figure 1 the range shown, and no serious deviation occurs. The pure water flux of the microporous hollow fiber membrane after testing the retention of colloidal gold is 49 L / (m 2 ·h·bar).

[0128] Comparative Example 1

[0129] Based on Example 1, casting solution 1 is not used, and only the core liquid and casting solution 2 are used to prepare the hollow fiber membrane.

[0130] The prepared hollow fiber membrane has an inner diameter of 400 μm, a wall thickness of 60 μm, and a bubble point measured by the liquid-liquid method of 2.2 bar. The pure water flux of the central fiber membrane is 40 L / (m 2 ·h·bar). Its logarithmic rejection rate for colloidal gold can basically reach the same level, but the pure water flux of the membrane after testing the retention of colloidal gold is only 12 L / (m 2 ·h·bar).

[0131] Comparative Example 2

[0132] Based on Example 2, casting solution 1 is not used, and only the core liquid and casting solution 2 are used to prepare the hollow fiber membrane.

[0133] The prepared hollow fiber membrane has an inner diameter of 400 μm, a wall thickness of 60 μm, and a bubble point measured by the liquid-liquid method of 2.4 bar. The pure water flux of the central fiber membrane is 35 L / (m 2 ·h·bar). Its logarithmic rejection rate for colloidal gold can basically reach the same level, but the pure water flux of the membrane after testing the retention of colloidal gold is only 7 L / (m 2 ·h·bar).

[0134] Comparative Example 3

[0135] Based on Example 10, the composition of casting solution 2 is 70 wt% polyvinylidene fluoride and 30 wt% dicyclohexyl phthalate, and other conditions are the same.

[0136] The prepared hollow fiber membrane has an inner diameter of 400 μm, a wall thickness of 120 μm, and a bubble point measured by the liquid-liquid method of 4.7 bar. The pure water flux of the central fiber membrane is 12 L / (m2 ·h·bar). The logarithmic rejection rate of the microporous hollow fiber membrane for colloidal gold with a diameter of 70 nm is 6, for colloidal gold with a diameter of 50 nm is 5, for colloidal gold with a diameter of 30 nm is 4, and for colloidal gold with a diameter of 20 nm is 3. However, the pure water flux of the membrane after testing for intercepting colloidal gold is only 4 L / (m 2 ·h·bar).

[0137] Comparative Example 4

[0138] Based on Example 11, the composition of the casting solution in Group 1 is 22 wt% polyvinylidene fluoride and 82 wt% tributyl citrate, and other conditions are the same.

[0139] The inner diameter of the prepared hollow fiber membrane is 400 μm, the wall thickness is 120 μm, and the bubble point tested by the liquid-liquid method is 1.4 bar. The pure water flux of the central fiber membrane is 65 L / (m 2 ·h·bar). The logarithmic rejection rate of the microporous hollow fiber membrane for colloidal gold with a diameter of 70 nm is 4, for colloidal gold with a diameter of 50 nm is 3, for colloidal gold with a diameter of 30 nm is 0.9, and for colloidal gold with a diameter of 20 nm is <1. However, the pure water flux of the membrane after testing for intercepting colloidal gold is only 65 L / (m 2 ·h·bar).

[0140] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.

Claims

1. A microporous hollow fiber membrane, characterized in that, It has an inner surface that contacts a protein-containing solution and an outer surface that discharges filtrate; the cross-section from the inner surface to the outer surface has a gradient pore size structure with an average pore size varying from 70 to 20 nm and has a bicontinuous network structure; the pores on the inner surface of the hollow fiber membrane are micropores of 0.2 to 3 μm, and the outer surface is micropores of 0.01 to 0.1 μm; The inner diameter of the membrane is 100 to 800 μm, and the wall thickness is 60 to 500 μm; The pure water flux of the microporous hollow fiber membrane is 20 - 60 L / (m 2 ·h·bar); the bubble point range of the microporous hollow fiber membrane is 1.7 - 3 bar.

2. A microporous hollow fiber membrane according to claim 1, wherein The material of the microporous hollow fiber membrane is polyvinylidene fluoride.

3. A method for preparing the microporous hollow fiber membrane according to any one of claims 1 to 2, characterized in that, It includes: Step 1, feeding a core liquid, casting solution 1, and casting solution 2 to a three-channel spinneret, and controlling the temperatures of the core liquid, casting solution 1, and casting solution 2, the spinning temperature of the spinneret, the flow rates, and the spinning speed to extrude hollow fiber nascent filaments; the inner layer channel of the three-channel spinneret is the core liquid channel, the middle layer channel is the casting solution 1 channel; the outer layer channel is the casting solution 2 channel; Step 2, the hollow fiber nascent filaments enter a coagulation bath through an air gap section for coagulation and forming, and then are soaked in an extractant for extraction and dried to obtain a microporous hollow fiber membrane; Among them, the core liquid is sebacate, phthalate, adipate, citrate, or phosphate; the composition of the casting solution 1 is 25 to 40 wt% polyvinylidene fluoride and 60 to 75 wt% solvent d1, and the composition of the casting solution 2 is 40 to 60 wt% polyvinylidene fluoride and 40 to 60 wt% solvent d2; The solvents d1 and d2 are sebacate, phthalate, adipate, citrate, or phosphate.

4. The preparation method of the microporous hollow fiber membrane according to claim 3, characterized in that, The core liquid, solvent d1, and solvent d2 are ester organic solvents that are above the melting point T of polyvinylidene fluoride and form a homogeneous solution with polyvinylidene fluoride. mp ​ 5. The method for preparing a microporous hollow fiber membrane according to claim 3, characterized in that, The melting point of the compound formed by 50 wt% polyvinylidene fluoride and 50 wt% solvent d1 is T mp-d1 , the melting point of the compound formed by 50 wt% polyvinylidene fluoride and 50 wt% solvent d2 is T mp-d2 , the melting point of the compound formed by 50 wt% polyvinylidene fluoride and 50 wt% core liquid b is T mp-b , the T mp-b , T mp-d1 and T mp-d2 satisfy T mp-d2 - T mp-d1 < 8 °C, 10 °C < T mp-d1 - T mp-b < 40 °C.

6. The method for preparing a microporous hollow fiber membrane according to claim 3, wherein The temperature range of the core liquid is 60 to 170 °C, and the flow rate range of the core liquid is 3 to 30 mL / min; the temperature ranges of the casting solution 1 and casting solution 2 are 180 to 240 °C, and the flow rate ranges of the casting solution 1 and casting solution 2 are 2 to 15 mL / min; the spinning temperature is 180 to 240 °C.

7. The method for preparing the microporous hollow fiber membrane according to claim 3, characterized in that, The coagulation bath is an organic solvent or water that is immiscible with polyvinylidene fluoride below 50 °C; the temperature range of the coagulation bath is 10 to 50 °C; the length range of the air gap section is 10 to 150 mm, and the spinning speed range is 10 to 100 m / min.

8. Use of the microporous hollow fiber membrane according to any one of claims 1 to 2, characterized in that It includes the application of the microporous hollow fiber membrane to virus filtration in the downstream process of biological products.

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