A Y-shaped highly asymmetric polyethersulfone microfiltration membrane and its preparation method

Abstract

The invention discloses a highly asymmetric polyethersulfone microfiltration membrane with a Y-shaped structure and a preparation method thereof. Based on specific solution composition requirements and a double induction process, the invention obtains a PES microfiltration membrane with a Y-shaped cross-sectional structure, wherein the Y-shaped structure has an upper layer of gradient macropores and a lower layer of symmetrical micropores, wherein the upper layer of gradient macropores can accommodate more components to be intercepted, thereby improving the pollution holding performance and service life of the filter membrane, and the lower layer of symmetrical micropores ensures the interception capacity, thereby exerting the ability to remove bacteria and stably intercept pollutants.

Description

Technical Field

[0001] The invention belongs to the technical field of microporous filter membranes, and in particular relates to a highly asymmetric polyethersulfone microfiltration membrane with a Y-shaped structure and a preparation method thereof. Background Art

[0002] Polyethersulfone is one of the most widely used polymer membrane materials, with excellent processability, mechanical stability, physical and chemical stability, and thermal stability. The processed and prepared PES microfiltration membrane has become the preferred membrane material for separation of aqueous solution systems due to its good hydrophilicity, low protein adsorption, high separation efficiency, and application reliability. With the increasing demand and application scenarios for PES microfiltration membranes, the demand for asymmetric PES filter membranes with high dirt holding capacity has become more and more clear. Higher dirt holding capacity means that the filter membrane has a longer service life and can effectively reduce application costs.

[0003] There are two main types of asymmetric PES membranes at this stage, hourglass type and V-type, and their cross-sections both contain a macroporous layer and a small pore retention layer. The hourglass type asymmetric PES membrane is represented by 3M's Micro series membranes. Its patent CN101227965A describes its solution carrier high temperature induced molding process. The effective retention layer is located in the middle of the cross-section. It has high mechanical strength and separation rate, but the macroporous layer above the retention layer is relatively small. As the main area for pollutant absorption, it is relatively small, and the pollutant absorption capacity of this series of PES membranes is small. The V-type structure is a typical structure of a highly asymmetric PES membrane and has an ultra-high pollutant absorption capacity. Patent CN115038510A describes that Millipore has prepared a highly asymmetric membrane with a V-type structure in the form of a three-layer composite. The preparation equipment requirements are harsh and difficult to achieve. Its asymmetric structure is gradually changed from ultra-large pores to small pores, and a very thin macroporous structure is added to the outside of the small pore layer to protect the small pore retention layer. Patent CN117582820A describes the preparation of a PES asymmetric membrane by adding a photocuring agent, and the photoinduced expansion of the pore structure to obtain a highly asymmetric V-shaped structure, which is difficult to control in large-scale production. Patent CN117599616A discloses the preparation of a V-shaped PES membrane using the principle of reverse gelation, and its small pore retention layer is only 1 / 4 of the cross-sectional structure, and the thin effective retention layer makes its application stability retention face challenges.

[0004] In summary, at present, commercial asymmetric PES microfiltration membranes mainly have two structures: funnel-shaped and V-shaped, which have the disadvantages of low dirt holding capacity and poor stability according to their structural characteristics. However, asymmetric PES membranes are required to have high dirt holding capacity and stable and reliable interception capacity at the same time. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a highly asymmetric polyethersulfone microfiltration membrane with a Y-shaped structure and a preparation method thereof, which can effectively avoid the application disadvantages of funnel-shaped and V-shaped structures and have better pollution-receiving performance and interception stability and reliability.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The invention discloses a method for preparing a Y-shaped highly asymmetric polyethersulfone microfiltration membrane, comprising the following steps:

[0008] Preparation of S1 solution: According to weight parts, 10-18 parts of polyethersulfone, 5-20 parts of porogen, 20-40 parts of the first solvent, 10-30 parts of the second solvent, and 15-30 parts of the non-solvent additive are mixed and dissolved; wherein the total content of the second solvent and the non-solvent additive is greater than that of the first solvent, and the surface tension of the second solvent is higher than that of the first solvent by more than 5 dyn / cm;

[0009] S2 degassing and scraping: scrape the prepared solution on the carrier;

[0010] S3 double induction process: the solution coating is pulled into the steam box with the carrier, and the upper air side and the lower carrier side of the solution coating are induced at the same time; the upper air side of the solution coating is induced by steam with controllable temperature and humidity, the steam temperature is 30-50℃, and the steam relative humidity is 60-90%; the lower carrier side of the solution coating is controlled by carrier temperature induction, and the carrier temperature is 10-20℃ higher than the solution temperature; the induction time is 5-60s;

[0011] S4 solidification: The induced coating enters a coagulation water bath with the carrier to undergo a phase separation process, solidifies into a film, and then is cleaned and dried to obtain a highly asymmetric polyethersulfone microfiltration membrane with a Y-shaped structure.

[0012] As a preferred technical solution, in step S1, the first solvent is one of dimethylacetamide and dimethylformamide, the second solvent is one of N-methylpyrrolidone, 2-pyrrolidone, and dimethyl sulfoxide, the non-solvent additive is one of triethylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, and diethylene glycol monomethyl ether, and the porogen is polyvinyl pyrrolidone.

[0013] As a preferred technical solution, in step S1, the dissolution temperature is 40-80°C and the dissolution time is 3-10h.

[0014] As a preferred technical solution, in step S2, the coating thickness is 200-400 μm.

[0015] As a preferred technical solution, in step S3, the steam temperature is 30°C.

[0016] As a preferred technical solution, in step S4, the temperature of the coagulation water bath is 20-70°C.

[0017] The invention also discloses a high-asymmetric polyethersulfone microfiltration membrane with a Y-shaped structure, which is prepared by the preparation method of the high-asymmetric polyethersulfone microfiltration membrane with a Y-shaped structure.

[0018] As a preferred technical solution, the upper half layer of the Y-shaped highly asymmetric polyethersulfone microfiltration membrane is a macroporous layer with a decreasing pore size gradient, and the lower half layer is a microporous layer with symmetrical pore sizes.

[0019] As a preferred technical solution, the thickness ratio of the macroporous layer to the microporous layer of the Y-shaped highly asymmetric polyethersulfone microfiltration membrane is 1:1.

[0020] The beneficial effects of the present invention are:

[0021] The present invention obtains a PES microfiltration membrane with a Y-shaped cross-sectional structure based on specific solution composition requirements and a double induction process. The Y-shaped structure has an upper layer of gradient macropores and a lower layer of symmetrical small pores. The upper layer of gradient macropores can accommodate more components to be retained, thereby improving the pollution-receiving performance and service life of the filter membrane. The lower layer of symmetrical small pores ensures the retention capacity and exerts the ability to sterilize and stably retain pollutants.

[0022] Therefore, the highly asymmetric polyethersulfone microfiltration membrane of the Y-shaped structure of the present invention can effectively avoid the application disadvantages of the funnel-shaped and V-shaped structures, has better dirt-holding performance and interception stability and reliability, and is more suitable for application scenarios such as separation, purification and concentration of mixed solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0024] Figure 1 is a cross-sectional SEM photograph of the polyethersulfone microfiltration membrane prepared in Example 1;

[0025] Figure 2 is a cross-sectional SEM photograph of the polyethersulfone microfiltration membrane prepared in Example 2;

[0026] Figure 3 is a cross-sectional SEM photograph of the polyethersulfone microfiltration membrane prepared in Example 3;

[0027] Figure 4 This is a cross-sectional SEM photograph of the polyethersulfone microfiltration membrane prepared in Comparative Example 1;

[0028] Figure 5 This is a cross-sectional SEM photograph of the polyethersulfone microfiltration membrane prepared in Comparative Example 2;

[0029] Figure 6This is a cross-sectional SEM photograph of the polyethersulfone microfiltration membrane prepared in Comparative Example 3;

[0030] Figure 7 This is a cross-sectional SEM photograph of the polyethersulfone microfiltration membrane prepared in Comparative Example 6. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0032] The control means for generating the Y-shaped structure of the present invention include specific composition requirements of the solution and dual induction process control:

[0033] The solution composition includes 10-18 parts of polyethersulfone, 5-20 parts of porogen, 20-40 parts of a first solvent, 10-30 parts of a second solvent and 15-30 parts of a non-solvent additive, wherein the total content of the second solvent and the non-solvent additive must be greater than the first solvent content, and the surface tension of the second solvent is at least 5 dyn / cm higher than that of the first solvent.

[0034] The double induction control requires that after the solution is coated on the carrier, the upper air side and the lower carrier side of the solution coating are induced at the same time. The upper air side of the solution coating uses temperature and humidity controllable steam induction, the steam temperature is 30-50℃, and the steam relative humidity is 60-90%; the lower carrier side of the solution coating uses carrier temperature induction control, and the carrier temperature is 10-20℃ higher than the solution temperature; the induction time is 5-60s.

[0035] Based on the above-mentioned specific solution composition requirements and dual induction process, when the solution coating is steam-induced, the water vapor combines with the non-solvent in the solution to induce pores on the coating surface, and as the amount of steam increases, the width and depth of the pores in the upper half of the coating increase. The lower half of the coating maintains a stable solution state under the control of the carrier temperature. After entering the coagulation bath water, a phase inversion solidification process occurs, and the macroporous structure formed by the steam-induced phase separation in the upper half of the layer is immediately formed. The solution in the lower half contains a high proportion of the second solvent and non-solvent. The higher surface tension prompts the two to preferentially exchange with water to undergo liquid-liquid phase separation, and the lower half of the layer solidifies to form a conventional symmetrical small pore structure. Therefore, the cross-sectional structure presents a Y-shaped structure with high asymmetry from top to bottom.

[0036] The calculation methods of pure water flux, bubble point and dirt holding capacity in the following examples and comparative examples are as follows:

[0037] Pure water flux bubble point: Tested in accordance with GB / T32361-2015 "Separation membrane pore size test method bubble point and average flow method".

[0038] Pollution tolerance: TSB challenge solution preparation: Use a measuring cylinder to measure 5L of ultrapure water, add 4L of it into a 10-liter plastic bucket, then weigh 150g of TSB and add it to 4L of water. Stir ultrasonically for 10 minutes to dissolve it, then add the dissolved TSB solution into the pressure vessel, rinse the plastic bucket with the reserved ultrapure water and stir for 5 minutes to mix it evenly.

[0039] The membrane to be tested was cut into membrane pieces with a diameter (d) of 47 mm, and after being moistened, they were loaded into a disc filter and filtered at a constant pressure of 1 bar to filter a volume V of tryptic soy broth (TSB).

[0040] The calculation method is as follows:

[0041]

[0042] The present invention characterizes the dirt holding capacity of the filter membrane by filtering the volume of tryptic soy broth (TSB) at a constant pressure of 1 bar.

[0043] Example 1

[0044] Weigh 40g of dimethylformamide, 15g of 2-pyrrolidone and 30g of diethylene glycol in a stirring tank, then add 15g of polyethersulfone and 10g of polyvinylpyrrolidone (K30) to the stirring tank, keep the casting liquid at 60℃ and stir for 6h. After the casting liquid is stirred completely, pour it into a pressure vessel, evacuate it for 0.5h and put it into a 40℃ constant temperature box, control the film thickness at 210μm, the pulling speed at 2.5m / s, cover the bottom of the liquid film with a 50℃ hot plate, and adjust the humidity in the constant temperature and humidity box to 85%. Use 30℃ steam for atomization induction for 30s, and cure it in a 35℃ water bath to form a film;

[0045] The polyethersulfone microfiltration membrane was obtained by washing and drying.

[0046] Figure 1 This is a cross-sectional SEM photograph of the polyethersulfone microfiltration membrane prepared in Example 1. In the figure, it can be seen that a polyethersulfone microfiltration membrane with a Y-shaped cross-sectional structure is obtained. The upper half layer is a macroporous layer with a decreasing pore size gradient, and the lower half layer is a small pore layer with symmetrical pore sizes. The thickness ratio of the macroporous layer to the small pore layer is about 1:1.

[0047] The surface pore size of the prepared polyethersulfone microfiltration membrane is 0.2μm, and the pure water flux of the polyethersulfone microfiltration membrane at 0.7MPa is 31.39ml / cm 2 ·min, the first bubble point pressure is 0.475MPa, and the medium filtration volume representing the pollution holding capacity is 48g / cm 2 .

[0048] Example 2

[0049] 30g of dimethylacetamide, 25g of dimethyl sulfoxide and 20g of dipropylene glycol were weighed in a stirring tank, and then 15g of polyethersulfone and 10g of polyvinylpyrrolidone (K30) were added to the stirring tank, and the casting liquid was kept at 60°C for 8h. After the casting liquid was stirred completely, it was poured into a pressure vessel, vacuumed for 0.5h, and then placed in a 40°C constant temperature box, the film thickness was controlled at 220μm, the pulling speed was 2.5m / s, the bottom of the liquid film was covered with a 60°C hot plate, and the humidity in the constant temperature and humidity box was adjusted to 85%, and 30°C steam was used for atomization induction for 30s, and the film was cured in a 35°C water bath; the polyethersulfone microfiltration membrane was washed and dried.

[0050] Figure 2 This is a cross-sectional SEM photograph of the polyethersulfone microfiltration membrane prepared in Example 2. In the figure, it can be seen that a polyethersulfone microfiltration membrane with a Y-shaped cross-sectional structure is obtained. The upper half layer is a macroporous layer with a decreasing pore size gradient, and the lower half layer is a small pore layer with symmetrical pore sizes. The thickness ratio of the macroporous layer to the small pore layer is about 1:1.

[0051] The surface pore size of the prepared polyethersulfone microfiltration membrane is 0.2μm, and the pure water flux of the polyethersulfone microfiltration membrane at 0.7MPa is 35.44ml / cm 2 ·min, the first bubble point pressure is 0.415MPa, and the medium filtration volume representing the pollution holding capacity is 68g / cm 2 .

[0052] Example 3

[0053] Weigh 30g of dimethylformamide, 10g of N-methylpyrrolidone and 30g of polyethylene glycol 200 in a stirring tank, then add 15g of polyethersulfone and 15g of polyvinylpyrrolidone (K30) to the stirring tank, keep the casting liquid at 60℃ and stir for 6h. After the casting liquid is stirred completely, pour it into a pressure vessel, evacuate it for 0.5h and put it into a 40℃ constant temperature box, control the film thickness at 250μm, the pulling speed at 2.5m / s, cover the bottom of the liquid film with a hot plate at 50℃, adjust the humidity in the constant temperature and humidity box to 85%, use 30℃ steam for atomization induction for 30s, and solidify it in a 35℃ water bath to form a film; wash and dry to obtain a polyethersulfone microfiltration membrane.

[0054] Figure 3 This is a cross-sectional SEM photograph of the polyethersulfone microfiltration membrane prepared in Example 3. In the figure, it can be seen that a polyethersulfone microfiltration membrane with a Y-shaped cross-sectional structure is obtained. The upper half layer is a macroporous layer with a decreasing pore size gradient, and the lower half layer is a small pore layer with symmetrical pore sizes. The thickness ratio of the macroporous layer to the small pore layer is about 1:1.

[0055] The surface pore size of the prepared polyethersulfone microfiltration membrane is 0.2μm, and the pure water flux of the polyethersulfone microfiltration membrane at 0.7MPa is 23.81ml / cm 2 ·min, the first bubble point pressure is 0.547MPa, and the medium filtration volume representing the pollution holding capacity is 45g / cm 2 .

[0056] Comparative Example 1

[0057] Weigh 50g of dimethylformamide, 5g of 2-pyrrolidone and 30g of diethylene glycol in a stirring tank, then add 15g of polyethersulfone and 10g of polyvinylpyrrolidone (K30) to the stirring tank, keep the casting liquid at 60℃ and stir for 6h. After the casting liquid is stirred completely, pour it into a pressure vessel, evacuate it for 0.5h and put it into a 40℃ constant temperature box, control the film thickness at 210μm, the pulling speed at 2.5m / s, cover the bottom of the liquid film with a hot plate at 50℃, adjust the humidity in the constant temperature and humidity box to 85%, use 30℃ steam for atomization induction for 30s, and solidify it in a 35℃ water bath to form a film; wash and dry to obtain a polyethersulfone microfiltration membrane.

[0058] Figure 4 This is a cross-sectional SEM photograph of the polyethersulfone microfiltration membrane prepared in Comparative Example 1. In the figure, it can be seen that a polyethersulfone microfiltration membrane with a Y-shaped cross-sectional structure is obtained. The upper half layer is a large pore layer with a decreasing pore size gradient, and the lower half layer is a small pore layer with symmetrical pore sizes. However, the large pore layer accounts for a small area, and the membrane flow rate and pollution absorption performance are poor.

[0059] The surface pore size of the prepared polyethersulfone microfiltration membrane is 0.1 μm, and the pure water flux of the polyethersulfone microfiltration membrane at 0.7 MPa is 14.8 ml / cm 2 ·min, the first bubble point pressure is 0.572MPa, and the medium filtration volume representing the pollution holding capacity is 15g / cm 2 .

[0060] Comparative Example 2

[0061] Weigh 40g of N-methylpyrrolidone, 15g of 2-pyrrolidone and 30g of diethylene glycol in a stirring tank, then add 15g of polyethersulfone and 10g of polyvinylpyrrolidone (K30) to the stirring tank, keep the casting liquid at 60℃ and stir for 6h. After the casting liquid is stirred completely, pour it into a pressure vessel, evacuate it for 0.5h and put it into a 40℃ constant temperature box, control the film thickness at 210μm, the pulling speed at 2.5m / s, cover the bottom of the liquid film with a hot plate at 50℃, adjust the humidity in the constant temperature and humidity box to 85%, use 30℃ steam for atomization induction for 30s, and solidify it in a 35℃ water bath to form a film; wash and dry to obtain a polyethersulfone microfiltration membrane.

[0062] Figure 5 This is a cross-sectional SEM photograph of the polyethersulfone microfiltration membrane prepared in Comparative Example 2. In the figure, it can be seen that a polyethersulfone microfiltration membrane with a Y-shaped cross-sectional structure is obtained. The upper half layer is a large pore layer with a decreasing pore size gradient, and the lower half layer is a small pore layer with symmetrical pore sizes. However, the large pore layer accounts for a small area, and the membrane flow rate and pollution absorption performance are poor.

[0063] The surface pore size of the prepared polyethersulfone microfiltration membrane is 0.2μm, and the pure water flux of the polyethersulfone microfiltration membrane at 0.7MPa is 19.09ml / cm 2 ·min, the first bubble point pressure is 0.531MPa, and the medium filtration volume representing the pollution holding capacity is 18g / cm 2 .

[0064] Comparative Example 3

[0065] Weigh 40g of dimethylformamide, 15g of 2-pyrrolidone and 30g of diethylene glycol in a stirring tank, then add 15g of polyethersulfone and 10g of polyvinylpyrrolidone (K30) to the stirring tank, keep the casting liquid at 60℃ and stir for 6h. After the casting liquid is stirred completely, pour it into a pressure vessel, evacuate it for 0.5h and put it into a 40℃ constant temperature box, control the film thickness at 250μm, the pulling speed at 2.5m / s, cover the bottom of the liquid film with a hot plate at 50℃, adjust the humidity in the constant temperature and humidity box to 85%, use 30℃ steam for atomization induction for 80s, and solidify it in a 35℃ water bath to form a film; wash and dry to obtain a polyethersulfone microfiltration membrane.

[0066] Figure 6 This is a cross-sectional SEM photograph of the polyethersulfone microfiltration membrane prepared in Comparative Example 3. It can be seen in the figure that a polyethersulfone microfiltration membrane with a symmetrical structure is obtained, the steam induction is excessive, the overall pore size is too large, and the retention accuracy is low.

[0067] The surface pore size of the prepared polyethersulfone microfiltration membrane is 0.4μm, and the pure water flux of the polyethersulfone microfiltration membrane at 0.7MPa is 52.76ml / cm 2 ·min, the first bubble point pressure is 0.32MPa, and the medium filtration volume representing the pollution holding capacity is 30g / cm 2 .

[0068] Comparative Example 4

[0069] Weigh 55g of dimethylacetamide and 20g of dipropylene glycol in a stirring tank, then add 15g of polyethersulfone and 10g of polyvinylpyrrolidone (K30) to the stirring tank, keep the casting solution at 60℃ and stir for 8h. After the casting solution is completely stirred, pour it into a pressure vessel, evacuate it for 0.5h, put it into a 40℃ constant temperature box, control the film thickness at 220μm, and the pulling speed at 2.5m / s. The bottom of the liquid film is covered with a hot plate at 60℃. At the same time, the humidity in the constant temperature and humidity box is adjusted to 85%, and 30℃ steam is used for atomization induction for 30s, and the film is cured in a 35℃ water bath; wash and dry to obtain a polyethersulfone microfiltration membrane.

[0070] The surface pore size of the prepared polyethersulfone microfiltration membrane is 0.65μm, and the pure water flux of the polyethersulfone microfiltration membrane at 0.7MPa is 55.68ml / cm 2 ·min, the first bubble point pressure is 0.238MPa, and the medium filtration volume representing the pollution holding capacity is 34g / cm 2 .

[0071] Comparative Example 5

[0072] 30g of dimethylacetamide, 25g of dimethyl sulfoxide and 20g of dipropylene glycol were weighed in a stirring tank, and then 15g of polyethersulfone and 10g of polyvinylpyrrolidone (K30) were added to the stirring tank, and the casting solution was kept at 60°C and stirred for 8h. After the casting solution was completely stirred, it was poured into a pressure vessel, vacuumed for 0.5h, and then placed in a 40°C constant temperature box, the film thickness was controlled at 220μm, the pulling speed was 2.5m / s, and the humidity in the constant temperature and humidity box was adjusted to 85%, and 30°C steam was used for atomization induction for 30s, and the film was cured in a 35°C water bath; the polyethersulfone microfiltration membrane was obtained by washing and drying.

[0073] The surface pore size of the prepared polyethersulfone microfiltration membrane is 0.15μm, and the pure water flux of the polyethersulfone microfiltration membrane at 0.7MPa is 40ml / cm 2 ·min, the first bubble point pressure is 0.325MPa, and the medium filtration volume representing the pollution holding capacity is 28g / cm 2 .

[0074] Comparative Example 6

[0075] Weigh 40g of dimethylformamide, 15g of 2-pyrrolidone and 30g of diethylene glycol in a stirring tank, then add 15g of polyethersulfone and 10g of polyvinylpyrrolidone (K30) to the stirring tank, keep the casting liquid at 60℃ and stir for 6h. After the casting liquid is stirred completely, pour it into a pressure vessel, evacuate it for 0.5h and put it into a 40℃ constant temperature box, control the film thickness at 210μm, the pulling speed at 2.5m / s, cover the bottom of the liquid film with a hot plate at 50℃, adjust the humidity in the constant temperature and humidity box to 85%, use 60℃ steam for atomization for 30s, and solidify it in a 35℃ water bath to form a film; wash and dry to obtain a polyethersulfone microfiltration membrane.

[0076] Figure 7 This is a cross-sectional SEM photograph of the polyethersulfone microfiltration membrane prepared in Comparative Example 6. In the figure, it can be seen that a polyethersulfone microfiltration membrane with a Y-shaped cross-sectional structure is obtained. The upper half layer is a large pore layer with a decreasing pore size gradient, and the lower half layer is a small pore layer with symmetrical pore sizes. However, the large pore layer area accounts for a small proportion, and the membrane flow rate and pollution absorption performance are poor.

[0077] The surface pore size of the prepared polyethersulfone microfiltration membrane is 0.2μm, and the pure water flux of the polyethersulfone microfiltration membrane at 0.7MPa is 20.37ml / cm 2 ·min, the first bubble point pressure is 0.375MPa, and the medium filtration volume representing the pollution holding capacity is 20g / cm 2 .

[0078] The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or changes made by those skilled in the art based on the present invention are within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A highly asymmetric polyethersulfone microfiltration membrane with a Y-shaped structure, characterized in that: The preparation method of the Y-shaped highly asymmetric polyethersulfone microfiltration membrane comprises the following steps: Preparation of S1 solution: According to weight parts, 10-18 parts of polyethersulfone, 5-20 parts of porogen, 20-40 parts of the first solvent, 10-30 parts of the second solvent, and 15-30 parts of the non-solvent additive are mixed and dissolved; wherein the total content of the second solvent and the non-solvent additive is greater than that of the first solvent, and the surface tension of the second solvent is higher than that of the first solvent by more than 5 dyn / cm; S2 degassing and scraping: scrape the prepared solution on the carrier; S3 double induction process: the solution coating is pulled into the steam box with the carrier, and the upper air side and the lower carrier side of the solution coating are induced at the same time; the upper air side of the solution coating is induced by steam with controllable temperature and humidity, the steam temperature is 30-50℃, and the steam relative humidity is 60-90%; the lower carrier side of the solution coating is controlled by carrier temperature induction, and the carrier temperature is 10-20℃ higher than the solution temperature; the induction time is 5-60s; S4 curing: The induced coating enters the coagulation water bath with the carrier to undergo a phase separation process, solidifies into a film, and then washes and dries to obtain a Y-shaped highly asymmetric polyethersulfone microfiltration membrane; In step S1, the first solvent is one of dimethylacetamide and dimethylformamide, the second solvent is one of N-methylpyrrolidone, 2-pyrrolidone, and dimethyl sulfoxide, the non-solvent additive is one of triethylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, and diethylene glycol monomethyl ether, and the porogen is polyvinyl pyrrolidone; The upper half layer of the prepared Y-shaped highly asymmetric polyethersulfone microfiltration membrane is a macroporous layer with a decreasing pore size gradient, and the lower half layer is a microporous layer with symmetrical pore size. The thickness ratio of the macroporous layer to the microporous layer is 1:

1.

2. The Y-shaped highly asymmetric polyethersulfone microfiltration membrane according to claim 1, characterized in that: In step S1, the dissolution temperature is 40-80°C and the dissolution time is 3-10h.

3. The Y-shaped highly asymmetric polyethersulfone microfiltration membrane according to claim 1, characterized in that: In step S2, the coating thickness is 200-400 μm.

4. The Y-shaped highly asymmetric polyethersulfone microfiltration membrane according to claim 1, characterized in that: In step S3, the steam temperature is 30°C.

5. The Y-shaped highly asymmetric polyethersulfone microfiltration membrane according to claim 1, characterized in that: In step S4, the temperature of the coagulation water bath is 20-70°C.

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