UPE porous filtration membrane, its manufacturing method and use

Abstract

A UPE porous filtration membrane, its manufacturing method, and uses, includes a main body having a first outer surface and a second outer surface, respectively, and a non-directional serpentine path formed within the main body. The porous membrane has a PMI average pore size of 2 to 100 nm, the first outer surface having first micropores, and the second outer surface having second micropores, the first micropores exhibiting a lace-like shape and being surrounded by several blocky structures, the second micropores exhibiting a circular shape, the SEM average pore size of the first micropores being larger than the SEM average pore size of the second micropores, the SEM average pore size from the first micropores to the second micropores exhibiting a gradient change, and continuous fibers are formed between the first and second outer surfaces. The UPE porous filtration membrane is used for filtering photoresists and solvents.

Description

[Technical Field]

[0001] The present invention relates to the technical field of membrane materials, and in particular to a UPE porous filtration membrane and its manufacturing method and use. [Background technology]

[0002] Porous polymer membranes are films made from organic polymers and primarily function to filter and separate impurities. Depending on the polymer, porous polymer membranes can be divided into cellulose-based porous polymer membranes, polyamide-based porous polymer membranes, polysulfone-based porous polymer membranes, polyester-based porous polymer membranes, polyolefin-based porous polymer membranes, etc.

[0003] Polyolefin polymer porous membranes mainly include polyethylene porous membranes and polypropylene porous membranes, and polyethylene is available in varieties such as low-density polyethylene (LDPE) (high-pressure polymerization), high-density polyethylene (HDPE) (low-pressure Ziegler catalyst polymerization), linear low-density polyethylene (LLDPE), and ultra-high molecular weight polyethylene (UHMPE) depending on the polymerization method and catalyst. In recent years, ultra-high molecular weight polyethylene (UPE) porous membranes have been widely used in various fields such as battery separators and filtration.

[0004] When applying ultra-high molecular weight polyethylene to battery separators, factors such as battery characteristics and safety require that the ultra-high molecular weight polyethylene porous membrane be given more consideration in terms of its breathability, mechanical properties, heat shrinkability, heat sealing, etc.

[0005] The polyethylene microporous membrane in Chinese patent CN101253232B has a mass average molecular weight of 7×10 5The polyethylene microporous membrane is made of a polyethylene resin having a proportion of the above ultra-high molecular weight polyethylene of 1% by mass or more and a ratio of mass average molecular weight to number average molecular weight of 5 to 300, and has a gradient structure consisting of a coarse-structure layer having an average pore size of more than 0.04 μm and a dense-structure layer having an average pore size of 0.04 μm or less, formed on at least one surface. The polyethylene microporous membrane is used for battery separators, and utilizes a combination of the coarse-structure layer and the dense-structure layer, with the coarse-structure layer being mainly used to increase the amount of electrolyte permeation into the battery separator and the dense-structure layer being used to maintain the structural strength of the battery separator. The battery separator exhibits little change in air permeability when pressurized, rapidly absorbs electrolyte, and can improve battery safety.

[0006] The polyethylene microporous membrane in Chinese patent CN101233176A has a mass average molecular weight of 1×10 6 The microporous membrane is made of a polyethylene resin containing 15% or less of the above-mentioned ultra-high molecular weight polyethylene, and has a dense-structure layer with an average pore size of 0.01 to 0.05 μm and a coarse-structure layer formed on at least one surface and having an average pore size 1.2 to 5.0 times that of the dense-structure layer, with a thickness ratio of the coarse-structure layer / fine-structure layer of 5 / 1 to 1 / 10. Its production method involves extruding a molten mixture of the polyethylene resin and a membrane-forming solvent through a die and cooling to obtain an extrudate, rapidly cooling one side and slowly cooling the other side to form a gel-like sheet, which is then uniaxially stretched at a temperature between the crystal dispersion temperature of the polyethylene resin +10°C and the crystal dispersion temperature +30°C, and after removing the solvent, uniaxially stretching again to obtain a polyethylene microporous membrane.

[0007] This shows that when applying ultra-high molecular weight polyethylene filtration membranes to battery separators, it is necessary to consider performance such as the absorption rate of the electrolyte, and also that due to the operational requirements of the battery separator, the battery separator needs to have high-temperature thermal insulation and blocking function between the positive and negative electrodes, and the battery separator needs to provide a path for lithium ions to pass through for charging and discharging the positive and negative electrodes, etc. However, when applied to the field of membrane filtration, it is necessary to consider performance such as the flux and blocking efficiency of the filtration membrane, but these performances are ignored without considering the environment in which the battery separator is used.

[0008] Furthermore, Chinese patent registration number CN101107063B discloses a multilayer microporous polymer membrane and a method for manufacturing the same. The multilayer microporous polymer membrane has at least two porous layers, each with a different average pore size. The layers with different pore sizes are separated by a porous interface, with the pore sizes of the multiple layers being uniform or gradient. The porous layers form the overall porous body matrix. The polymer material for each layer is ultra-high molecular weight polyethylene. The multilayer microporous polymer membrane has a lace-like aperture structure and a membrane thickness of 20-70 μm. The multilayer microporous polymer membrane is prepared by separately heating and heating the mixture of each layer to obtain a solution, co-extruding the solutions through a mold by shearing to form a bilayer sheet. The bilayer sheet is then cooled and phase-separated, and the microporous structure formed by the pore-forming agent is selectively removed to obtain the bilayer microporous membrane. While the filtration membrane described above has a porous interface, the materials on both sides of the porous interface may usually be different. This inevitably results in flow attenuation and loss at the porous interface during filtration and separation, which to some extent affects the blocking efficiency of the porous filtration membrane.

[0009] In the course of experimental research, the applicant discovered that polyethylene microporous membranes made from ultra-high molecular weight polyethylene also have good effects in photoresist filtration processing. Therefore, the applicant proposed an invention patent with Chinese publication number CN113926322A, which discloses a low-specific surface area UPE porous membrane, which includes a main body and a first porous surface and a second porous surface located on both sides of the main body, the first porous surface and the second porous surface respectively having a number of groove-shaped first pores and second pores, the main body has a three-layer structure, respectively consisting of a pre-filtration layer, a separation layer and a support layer, the average pore size of the separation layer is smaller than that of the pre-filtration layer and the support layer, the groove-shaped first pores and second pores are used to reduce the dead pore volume, making the porous membrane easier to clean and allowing the porous membrane to have a high flow rate. At the same time, the pre-filtration layer provides a large space to accommodate impurities, and the separation layer plays the role of a blocking gel, thereby allowing the porous membrane to have better contamination capacity and filtration speed. In the application process, it is the separation layer that actually plays the role of blocking, and the blocking efficiency of the above-mentioned porous membrane is not very high in the filtration process. Although the porous membrane has a high flow rate, the blocking efficiency of the porous membrane is not very limited by the thickness of the separation layer and the thickness of the entire porous membrane, so there is still room for improvement in the blocking efficiency of the UPE porous membrane in the application of photoresist filtration processing. Summary of the Invention

[0010] An object of the present invention is to provide a UPE porous filtration membrane, a method for producing the same, and uses thereof.

[0011] To achieve the above object, the present invention adopts the following technical solutions.

[0012] A UPE porous filtration membrane, comprising a main body, a first outer surface and a second outer surface formed on both sides of the main body, a non-directional meandering passage formed within the main body, and a PMI average pore size of the porous membrane being 2 to 100 nm; the first outer surface has first micropores, the second outer surface has second micropores, the first micropores are lacy and surrounded by several blocky structures, the second micropores are circular, the SEM average pore diameter of the first micropores is larger than the SEM average pore diameter of the second micropores, and the SEM average pore diameter from the first micropores to the second micropores exhibits a gradient change; A UPE porous filtration membrane having continuous fibers between the first outer surface and the second outer surface.

[0013] The first outer surface and the second outer surface of the present invention are the liquid-feeding surface and the liquid-ejecting surface, respectively, and the first micropores of the present invention are formed by being surrounded by several massive structures and have a lace-like pore shape. Compared with sheet-like or striped structures, the pore wall thickness of the first micropores formed by the massive structure is relatively large, and they can withstand a relatively large amount of pressure when subjected to external stress, making the first micropore structure formed by the massive structure more stable and less likely to collapse, and increasing the strength of the UPE porous filtration membrane pores.

[0014] Furthermore, the first micropores formed by being surrounded by the blocky structure have a lace-like structure, and due to the irregular shape of the blocky structure, a completely closed loop is not formed between adjacent first micropores, and fine openings exist; that is, openings exist between adjacent first micropores, and they may be connected to each other through the fine openings; on the other hand, the pores formed by being surrounded by the sheet-like or stripe-like structure are usually closed pores.

[0015] It was found that when the number of pores, the average pore size, the pore area ratio, and other conditions are all basically the same, the first micropores formed by being surrounded by a block structure have a relatively higher permeation flow rate than the first micropores formed by being surrounded by a sheet-like or stripe-like structure. Analysis showed that when the first micropores are in a closed state, when the fluid to be filtered passes through the first micropores on the first outer surface, due to the existence of surface tension, the fluid to be filtered inevitably forms membrane bubbles on the surfaces of the first micropores, which "block" the first micropores within a short time. Under the action of the continuous flow of the fluid to be filtered, the membrane bubbles burst, thereby opening the first micropores and allowing the fluid to continuously pass through. In the present invention, due to the irregularity of the lumpy structure, it is inevitable that there will be interconnected openings between the first micropores formed by the lumpy structure, and when the membrane bubbles are subjected to an acting force, they can be pulled along the openings to adjacent first micropores, thereby promoting the rupture of the membrane bubbles and reducing to a certain extent the time that the first micropores are "blocked" due to the formation of membrane bubbles, and further improving the permeation rate of the fluid to be filtered through the first micropores per unit time.

[0016] In the present invention, the SEM average pore size from the first micropore to the second micropore exhibits a gradient change, and the SEM average pore size of the first micropore is larger than that of the second micropore, the first micropores exhibit a lacy shape to increase the flow rate, and the second micropores exhibit a circular shape to block impurity particles, thereby ensuring the permeation rate of the porous filtration membrane and improving the blocking efficiency of impurity particles. The SEM average pore size along the thickness of the porous filtration membrane gradually decreases, and the SEM average pore size usually has a certain error range. Generally, the measured SEM pore size will have some pores larger than the SEM average pore size, that is, each segment along the thickness of the porous filtration membrane will inevitably have some "large pores", which may allow impurity particles to pass through. However, because the error range of the SEM average pore size due to process factors and other factors is generally stable, each segment still contains some "large pores." However, because the SEM average pore size of the next segment along the thickness of the porous filtration membrane decreases, the next segment also contains "large pores." The SEM pore size of the "large pores" of the next segment is usually smaller than that of the previous segment, thereby blocking particles that pass through the "large pores" of the previous segment. The SEM average pore size from the first micropore to the second micropore exhibits a gradient change, which can somewhat fulfill the role of multiple segments in the "large pore" region in blocking impurity particles and further improve the blocking efficiency of the porous filtration membrane.

[0017] Unlike traditional composite membranes, which typically have a multi-layer structure and a dense separation layer applied to a microporous support layer or support membrane in a separate process, composite membranes of the present invention often have different materials for the support layer and the skin layer, which can result in a certain flow rate attenuation at the separation surface where the fluid to be filtered transitions due to the difference in materials on both sides. The porous filtration membrane formed from continuous fibers of the present invention does not have a transition separation surface for composite membranes, and further avoids the flow rate attenuation induced by the transition separation surface of traditional composite membranes, thereby improving the cutoff filtration speed of the porous filtration membrane to a certain extent.

[0018] Furthermore, a plurality of thin protrusions are formed on the surface of each of the massive structures, the thin protrusions are connected to each other, grooves are formed between the massive structures, a plurality of sub-holes communicating with the grooves are formed in the massive structures, and the non-directional serpentine passage is formed between each of the grooves.

[0019] In the porous filtration membrane structure provided by the present invention, it is clearly observed that a plurality of fine protrusions are formed on the surface of the bulk structure, and each fine protrusion is connected to each other on the first outer surface. Since the fine protrusions are smaller in volume and length than the bulk structure, during filtration, the fine protrusions usually do not affect the permeation of the fluid to be filtered through the first micropores. That is, although the fine protrusions exist on the surface of the bulk structure, the fine protrusions do not affect the flux of the fluid to be filtered passing through the first micropores.

[0020] When the porous filtration membrane is used for filtering photoresist, the presence of the fine protrusions allows the polymers in the photoresist to be blocked and pulled by the fine protrusions when they enter the first micropores. At the same time, the fine protrusions located between the grooves can also block and pull the polymer impurities that enter the porous filtration membrane, thereby playing a role in pre-filtering the polymer impurities in the photoresist to some extent.

[0021] The present invention provides sub-pores in the bulk structure, which allow the fluid to be filtered to move into the grooves in the porous filtration membrane through the sub-pores of the bulk structure. This ensures the strength of the bulk structure as a whole compared to a solid bulk structure, while at the same time increasing the flux of the fluid to be filtered permeating into the porous filtration membrane per unit time to a certain extent. At the same time, the sub-pores of the bulk structure usually have small pore diameters, which can play a blocking role to a certain extent against polymer impurities in the photoresist, thereby achieving a certain pre-filtration effect.

[0022] Furthermore, the thickness of the massive structure occupies more than 30% of the porous filtration membrane in the thickness direction, and the area of ​​the sub-pores occupies 5% or more of the surface of the massive structure.

[0023] In the porous filtration membrane structure provided by the present invention, the thickness ratio of the lumpy structures is controlled to be greater than 30%, and the grooves formed between the lumpy structures guide the fluid to be filtered in the thickness direction of the porous filtration membrane, allowing the porous filtration membrane to have a better permeation rate. However, the thickness ratio of the lumpy structures in the thickness direction of the porous filtration membrane should not exceed 60%. If the thickness ratio of the lumpy structures is too large, the thickness of the effective pore layer that actually plays a blocking role will be reduced. Increasing the thickness ratio of the lumpy structures is advantageous for increasing the permeation rate of the fluid to be filtered into the porous filtration membrane, but reducing the thickness of the effective pore layer that blocks will result in a decrease in the actual blocking efficiency of the porous filtration membrane.

[0024] Because the subpores are connected to the channels inside the porous filtration membrane, the area ratio of the subpores to the surface of the bulk structure (i.e., the first outer surface) can be used to characterize the distribution of subpores within the bulk structure to some extent. By controlling the subpore area ratio to be 5% or more, the strength of the first pores can be ensured while providing space for the fluid / photoresist molecules to pass through. This allows most of the fluid to enter the porous filtration membrane through the first micropores, while a small portion of the fluid to be filtered can enter the channels inside the porous filtration membrane through the subpores, thereby increasing the amount of fluid to be filtered permeated within a unit time to some extent. At the same time, the subpore structure also plays a certain pre-filtration role, shielding the macromolecules in the fluid to be filtered, such as photoresist, within the subpore structure. However, the proportion of the area occupied by the sub-pores should not exceed 30%. If the proportion of the area occupied by the sub-pores is too large, it will affect the structural strength of the block structure. When the block structure is subjected to pressure or tension, the spacing between adjacent sub-pores will be too close and the proportion of the sub-pores will be too large, which may cause the sub-pores to collapse.

[0025] Furthermore, the ratio of the SEM average pore size of the first micropores to the SEM average pore size of the second micropores is 10 or more.

[0026] In the porous filtration membrane structure provided by the present invention, the SEM average pore size of the first micropores has a significant effect on the permeation rate of the fluid to be filtered into the porous filtration membrane, and the SEM average pore size of the second micropores has a significant effect on the blocking efficiency of the porous filtration membrane. Therefore, by controlling the ratio of the SEM average pore size of the first micropores to the SEM average pore size of the second micropores to be 10 or more, the porous filtration membrane will have a better permeation rate and also a better blocking efficiency; if the ratio between the two is too small, the difference between the SEM average pore size of the first micropores and the SEM average pore size of the second micropores will not be large. If the SEM average pore size of the first micropores is too small, the SEM average pore size of the second micropores will be small, and although good blocking of the fluid to be filtered will be possible, the porous filtration membrane will not be able to achieve a good permeation rate. Conversely, if the SEM average pore size of the first micropores is too large, the SEM average pore size of the second micropores will be large, and the porous filtration membrane will not be able to adequately block the fluid to be filtered, and ultimately will not be able to achieve both flux and blocking efficiency at the same time.

[0027] The ratio of the SEM average pore size of the first micropores to the SEM average pore size of the second micropores is 30 or less.

[0028] Considering the overall structural strength of the porous filtration membrane, the ratio of the SEM average pore size of the first micropores to the SEM average pore size of the second micropores should not be too large. If the ratio exceeds 30, the pore size of the first micropores will be too large, further reducing the strength of the lamination surface and risking collapse of the first micropores under fluid pressure during filtration. Therefore, by adjusting the appropriate ratio of the SEM average pore size of the first micropores to the SEM average pore size of the second micropores, it is possible to ensure both a high permeation rate and high blocking efficiency.

[0029] The SEM average pore size of the first micropores on the first outer surface of the membrane and the second micropores on the second outer surface can be measured using computer software (e.g., Matlab, NIS-Elements, etc.) or manually after morphologically characterizing the membrane structure using a scanning electron microscope, and then corresponding calculations can be performed. During the membrane manufacturing process, in the direction perpendicular to the membrane thickness, each of its features, such as pore size distribution, is nearly uniform and basically consistent. Therefore, the average pore size of a partial area on the corresponding plane can reflect the overall average pore size on that plane. In actual measurements, the membrane surface is first characterized using an electron microscope, and the corresponding SEM image can be obtained. Since the pores on the membrane surface are nearly uniform, the average pore size can be calculated by dividing the pores by a certain area, e.g., 1 μm 2 (1 μm multiplied by 1 μm) or 25 μm 2 (5 μm multiplied by 5 μm) can be selected, and the specific area size will vary depending on the actual situation. Then, the pore diameters of all the pores on that area can be measured using the corresponding computer software or manually, and then calculated to obtain the average pore diameter of the pores on this surface. Of course, those skilled in the art can also obtain the above parameters by other measurement means, and the above measurement means are for reference only.

[0030] Furthermore, the second micropores have an SEM average pore size of 15 to 80 nm, and the SEM average pore size of the second micropores has a discrete coefficient of 0.5 or less.

[0031] The PMI cutoff pore size of the porous filtration membrane in the present invention is 2 to 100 nm, the SEM average pore size of the second micropores is 15 to 80 nm, and the discrete coefficient of the SEM average pore size of the second micropores is 0.5 or less. Therefore, even if the SEM average pore size of the second micropores is controlled to 15 to 80 nm, by controlling the distribution uniformity of the SEM average pore size of the second micropores on the second outer surface to a certain extent, it can be seen that the porous filtration membrane can filter impurities with particle sizes smaller than the SEM average pore size. This proves that the smaller the discrete coefficient of the SEM average pore size of the second micropores, the more uniform the SEM average pore size distribution of the second micropores on the second outer surface. Furthermore, the effective PMI cutoff pore size range of the porous filtration membrane can be adjusted by combining the SEM average pore size of the second micropores and the discrete coefficient of the SEM average pore size of the second micropores. For example, in the case of a porous filtration membrane with the test model number UPE-598-1, the SEM average pore diameter of the second micropores was approximately 56.4 nm, the discrete coefficient of the SEM average pore diameter of the second micropores was approximately 0.307, and the effective PMI cutoff pore diameter range of this model number UPE-598-1 porous filtration membrane was measured to be 20 nm.

[0032] The discrete coefficient of the second micropores can be determined by measuring the SEM pore diameter and SEM average pore diameter of the second micropores in the selected area using the above-mentioned method, calculating the average number and standard difference, and finally obtaining the discrete coefficient of the second micropores using the calculated standard difference / average number.

[0033] Furthermore, the pore area ratio of the first outer surface is A1, the pore area ratio of the second outer surface is A2, and the range of A1 / A2 is 1.1 to 1.4.

[0034] Furthermore, A1 is 15-25% and A2 is 12-18%.

[0035] The pore area ratios of the first and second outer surfaces in the present invention can be measured using computer software (e.g., Matlab, NIS-Elements, etc.) or manually after morphologically characterizing the membrane structure using a scanning electron microscope, and then corresponding calculations can be performed. During the membrane manufacturing process, in the direction perpendicular to the membrane thickness, each of its features, such as pore size distribution, is approximately uniform and basically consistent. Therefore, the size of the pore area ratio of a partial area on the corresponding plane can reflect the size of the overall pore area ratio on that plane. In actual measurement, the membrane surface is first characterized using an electron microscope, and the corresponding SEM image can be obtained. Since the pore distribution on the membrane surface is approximately uniform, the pore area ratio can be measured within a certain area, e.g., 1 μm 2 (1 μm multiplied by 1 μm) or 25 μm 2 (5 μm multiplied by 5 μm) can be selected, and the specific area size will vary depending on the actual situation. Then, the area of ​​all holes on that area can be measured using corresponding computer software or manually, and then calculated to obtain the hole area ratio of the first outer surface and the second outer surface. Of course, those skilled in the art can also obtain the above parameters by other measurement means, and the above measurement means are for reference only.

[0036] In the present invention, the pore area ratios of the first outer surface and the second outer surface of the porous filtration membrane are 1.1 to 1.4, with the pore area ratio on the feed surface being larger than that on the discharge surface. The area of ​​the single, lacy-shaped first micropore is much larger than that of the single, circular-shaped second micropore, while the first micropores on the first outer surface primarily serve to increase the permeation flow rate. Maintaining a constant pore area ratio on the first outer surface is advantageous for the fluid to be filtered to quickly penetrate the porous filtration membrane. Preferably, the pore area ratio is controlled to 15 to 25%, ensuring a good permeation rate. If the pore area ratio is too high, the pore walls of the first micropores on the first outer surface of the porous filtration membrane will become thin, potentially causing deformation or collapse of the first micropores when subjected to continued external force. Therefore, the pore area ratio should not be too high.

[0037] By making the pore area ratio of the first outer surface of the porous filtration membrane of the present invention larger than the pore area ratio of the second outer surface, the permeation rate of the fluid to be filtered on the first outer surface side (liquid feed side) becomes somewhat larger than the blocking rate on the second outer surface side (i.e., liquid outflow side). Therefore, during filtration, the liquid feed rate of the porous filtration membrane becomes somewhat larger than the liquid outflow rate, and the liquid located inside the porous filtration membrane is subjected to the pressure of the liquid on the liquid feed side, creating a certain pressure difference between the liquid feed side and the liquid outflow side of the porous filtration membrane, promoting the movement of the fluid to be filtered located inside the porous filtration membrane to the liquid outflow side.

[0038] Furthermore, the pore density of the first outer surface is 0.2 to 6 / μm 2 and the pore density of the second outer surface is 120 to 260 pores / μm 2 is.

[0039] Pore ​​density refers to the number of pores per unit area, and can be determined by, for example, observing a scanning electron microscope image of a predetermined square surface area of ​​the first and second outer surfaces of the porous filtration membrane and calculating the number of pores within the predetermined area. The calculated number of pores within the predetermined square area can be standardized to a specific reference area by a simple ratio, and those skilled in the art can also obtain the above parameters by other measurement means.

[0040] The SEM average pore size of the first micropores of the porous filtration membrane of the present invention is much larger than the SEM average pore size of the second micropores, and the pore density of the first outer surface is much lower than the pore density of the second outer surface. Meanwhile, the SEM average pore size of the first micropores, combined with the pore density, embodies the characteristics of large pore size and sparse distribution, which serves to increase the permeation flow rate, and ensures that the permeation speed of the porous filtration membrane is relatively good while preventing the distribution of the first micropores from being overly dense, thereby improving the strength and stability of the pores on the permeation surface side of the porous filtration membrane and reducing the probability of pore collapse. The SEM average pore size of the second micropores, combined with the pore density, embodies the characteristics of small pore size and dense distribution, which serves as a fine blocking role for the fluid to be filtered, and gives the porous filtration membrane good blocking efficiency.

[0041] Furthermore, the gradient of change in SEM average pore size from the first outer surface to the second outer surface is 10 to 80 nm / μm.

[0042] Furthermore, under conditions of a positive pressure of 0.03 MPa and a temperature of 20°C, the time required for 50 ml of water to pass through a porous filtration membrane with a diameter of 47 mm is 60 to 3000 seconds.

[0043] The porous filtration membrane has a transverse tensile strength of 3.4 to 14.18 MPa, and a longitudinal tensile strength of 4.4 to 14.83 MPa.

[0044] In the present invention, a flow rate test was conducted on the polyethylene flat membrane, and it was found that under the conditions of a pressure of 0.03 MPa and a temperature of 20°C, the time required for 50 ml of water to pass through a 47 mm diameter polyethylene flat membrane was 300-3000 seconds. Here, polyethylene flat membranes can be divided into types such as 2 nm, 5 nm, 10 nm, 20 nm, 50 nm, and 100 nm according to the PMI cutoff pore size, and among them, the time required for the fluid to pass through the UPE porous filtration membrane with a PMI cutoff pore size of 2 nm is the longest. The flow rate test demonstrated that the porous filtration membrane has a high flow rate, the time required for the fluid to pass through the porous filtration membrane is short, the time cost for filtration is low, and high economic benefits can be achieved. It also demonstrated that the porous filtration membrane of the present invention is applicable to the field of photoresist.

[0045] The time it takes for water to pass through a porous filtration membrane reflects to some extent the flux of the porous filtration membrane. Based on the structure of the UPE porous filtration membrane of the present application, and on the premise of conducting multiple experiments, the time it takes for water to pass through the porous filtration membrane may be affected by the thickness of the membrane, the pore sizes of the first and second outer surfaces, the proportion of the block structure in the membrane thickness direction, and the common effect of the pore area ratio of the first and second outer surfaces.

[0046] Furthermore, a method for producing the above-mentioned UPE porous filtration membrane includes the following steps S1 to S6. S1: A polyethylene resin is added to a solvent system consisting of compound A and compound B and stirred to mix. After uniform mixing, a mixture with a solid content of 8 to 14% is formed, where the polyethylene resin is an ultra-high molecular weight polyethylene having a mass average molecular weight of 2 to 5 million, compound A is a non-solvent for the polyethylene resin, and compound B is a solvent for the polyethylene resin, with the content of compound A being higher than the content of compound B. S2: The mixture is heated, melted and kneaded at a temperature of 220 to 250°C to form a film-forming liquid, which is then extruded through a die to form a liquid film, and the die extrusion temperature is 180 to 220°C. S3: The liquid film is phase-separated and cured in a temperature environment of 15 to 120°C to form a base film, wherein the ratio of the temperature reduction rate on the second outer surface side to the temperature reduction rate on the first outer surface side is 2 or more, the temperature reduction rate on the second outer surface side is controlled to 20 to 100°C / s, and the temperature reduction rate on the first outer surface side is controlled to 8.5 to 50°C / s. S4: The raw film is subjected to a first heat treatment, and the first heat treatment temperature is controlled to 40 to 100°C to obtain a raw film. S5: The solvent system is extracted with the extraction liquid, and the solvent system is removed from the raw membrane to obtain a formed membrane. S6: The raw membrane is subjected to a second heat treatment, and the temperature of the second heat treatment is controlled to 60 to 120°C to produce an ultra-high molecular weight polyethylene porous membrane.

[0047] In the present invention, the molecular weight of the polyethylene resin is controlled to 2,000,000 to 5,000,000, thereby achieving a low solids content in the membrane casting solution. Furthermore, by utilizing the different phase separation rates on both sides of the membrane, a UPE porous filtration membrane is formed with lace pores on one side and circular pores on the other side. Here, the solids content refers to the content of ultra-high molecular weight polyethylene molecules in the membrane casting solution. In this application, the size of the solids content is controlled by controlling the amount of ultra-high molecular weight polyethylene added and the mass-average molecular weight. Typically, when other conditions, such as phase separation conditions, are kept essentially the same, a membrane casting solution with a low solids content is more likely to form large pores, while a membrane casting solution with a high solids content is more likely to form small pores. In this case, the temperature drop rate on the second outer surface side is controlled to be higher than that on the first outer surface side. The rapid temperature drop and the solid content on the second outer surface side result in dense small pores on the second outer surface. Similarly, the temperature drop rate and the solid content on the first outer surface side result in large pores, which are lace pores, on the first outer surface side.

[0048] Through multiple experiments, it was found that the pore size of the first micropores on the first outer surface and the pore size of the second micropores on the second outer surface may be influenced by the combined effect of factors such as the solid content in the membrane-forming solution and the cooling rate.

[0049] In the present invention, heat-stabilizing is performed before extraction, and stress exists in the base membrane, which may cause shrinkage during extraction. Heat-stabilizing before extraction eliminates as much stress as possible within the base membrane. The primary heat-stabilizing temperature is controlled to 40-100°C. Because the porous filtration membrane contains oily substances, a high heat-stabilizing temperature may pose a safety risk, so the primary heat-stabilizing temperature is preferably 60-80°C. The secondary heat-stabilizing is performed to stabilize the structure of the porous filtration membrane, with lacy holes on one side and circular holes on the other side. The temperature is controlled to 60-120°C. If the temperature is too high, the fibers in the porous filtration membrane may coalesce, further causing pore shrinkage. The secondary heat-stabilizing temperature is preferably 70-100°C.

[0050] Meanwhile, in the course of multiple experiments, the temperature control of the first and second heat treatments may be one of the factors affecting the uniformity of distribution of the first and second micropores on the first and second outer surfaces in a suitable range.

[0051] Furthermore, the mixture comprises the following material composition in parts by weight: Polyethylene resin: 10 to 18 parts Compound A: 50~70 parts Compound B: 15~45 parts The compound A is at least one of dimethyl phthalate, dioctyl adipate, ethylene glycol diacetate, triphenyl phosphate, dicyclohexyl phthalate, glycerol triacetate, and dipropyl carbonate, and the compound B is at least one of paraffin oil, white oil, hydraulic oil, decahydronaphthalene, castor oil extract, castor oil, and acetyl tributyl citrate.

[0052] Furthermore, one side of the liquid film is provided as a liquid-cooled roll, and the temperature of the liquid-cooled roll is set to 5 to 40°C, and the other side of the liquid film is provided as air, and the temperature of the air side is set to 20 to 25°C.

[0053] In the present invention, compound A is a volatile component, and component B is a non-volatile component. By controlling the volatilization environment on both sides of the liquid membrane, the volatilization rate of compound A can be controlled to a certain extent, thereby adjusting the solid content on both sides of the liquid membrane. When the liquid membrane inlet side (i.e., the large pore side) is set on the air side, the membrane-forming liquid is exposed to the air environment, and the membrane-forming liquid volatilizes to a certain extent, the occupancy rate of compound A in the membrane-forming liquid gradually decreases, and the occupancy rate of compound B and polyethylene resin in the membrane-forming liquid gradually increases. At this time, the liquid membrane outlet side (small pore side) is set on the carrier side, and the volatilization environment of the membrane-forming liquid does not reach the liquid membrane inlet side. Furthermore, due to the difference in the volatilization environment between the inlet side and the outlet side, the solid content of the membrane-forming liquid on the inlet side and the outlet side is different. In addition, the difference in the phase separation rate between the inlet side and the outlet side. Under the influence of these various process parameters, a UPE porous asymmetric filtration membrane with lace holes on one side and circular holes on the other side is finally formed. Usually, the phase separation rate on the side with a relatively high solid content is controlled quickly, forming circular holes. The phase separation rate is controlled slowly on the side with a relatively low solid content, forming lace holes.

[0054] The factors that affect the phase separation rate between the inlet and outlet sides in this invention are the medium and the temperature gradient. The inlet side medium is air, and the cooling rate is slower than that of the outlet side. The cooling rate is adjusted adaptively according to the thickness of the porous filtration membrane, for example, the time required to cool from 200°C to 30°C is 3 to 20 seconds, and further, a lacy pore pattern is formed on the inlet side. On the other hand, the outlet side medium is cooled using a liquid-cooled roll, for example, a rapid cooling method is used, for example, the time required to cool from 200°C to 100°C is 1 to 5 seconds, and at the same time, solid matter is added to the outlet side to form a dense circular pore pattern on the outlet side.

[0055] Additionally, the UPE porous filtration membrane is used for photoresist and solvent filtration.

[0056] In the present invention, the large-pore surface (first outer surface) of the porous filtration membrane is used as the liquid-feeding surface, and the small-pore surface (first outer surface) of the porous filtration membrane is used as the liquid-exiting surface, thereby ensuring that the porous filtration membrane has excellent collection performance, permeation speed, and filtration accuracy for impurity particles in the photoresist area, and at the same time, the porous filtration membrane has a high contamination capacity, a long service life, and high economic efficiency. For example, the use of UPE in developer and ultrapure water is mainly in solvents, such as OK73, PGMEA, PGME, and IPA. [Brief explanation of the drawings]

[0057] The present invention will now be further described with reference to the accompanying drawings. [Figure 1] 1 is a scanning electron microscope image of the second outer surface of the ultra-high molecular weight polyethylene porous filtration membrane produced in Example 1, where the magnification is 50K×. [Figure 2] 1 is a scanning electron microscope image of the first outer surface of the ultra-high molecular weight polyethylene porous filtration membrane produced in Example 1, where the magnification is 5Kx. [Figure 3] 1 is a scanning electron microscope image of the second outer surface of the ultra-high molecular weight polyethylene porous filtration membrane produced in Example 6, where the magnification is 20K×. [Figure 4] 1 is a scanning electron microscope image of the first outer surface of the ultra-high molecular weight polyethylene porous filtration membrane produced in Example 6, where the magnification is 5Kx. [Figure 5] FIG. 1 is a further scanning electron micrograph of the first outer surface of the ultra-high molecular weight polyethylene porous filtration membrane produced in Example 6, where the magnification is 20K×. [Figure 6] 1 is a scanning electron microscope image of the cross section of the ultra-high molecular weight polyethylene porous filtration membrane produced in Example 1, where the magnification is 20K×. [Figure 7] FIG. 1 is a schematic diagram of an apparatus for testing the flow rate of the ultra-high molecular weight polyethylene flat membrane of the present invention. [Figure 8] FIG. 1 is a schematic diagram of an apparatus for testing the filtration accuracy (blocking efficiency) of the ultra-high molecular weight polyethylene flat membrane of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0058] The present invention will be described in more detail below with reference to the following examples. Unless otherwise specified, the raw materials and equipment used to manufacture the porous filtration membrane in the following examples can be purchased commercially.

[0059] Example 1 The method for producing a UPE porous filtration membrane includes the following steps S1 to S6. S1: Polyethylene resin is added to a solvent system consisting of compound A and compound B, and stirred and mixed to form a homogeneous mixture, in which compound A is a non-solvent for polyethylene resin and compound B is a solvent for polyethylene resin. The mixture contains 12 parts by mass of polyethylene resin, 62 parts by mass of compound A, and 28 parts by mass of compound B. Here, the polyethylene resin is selected to be ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million, the compound A is selected to be dimethyl phthalate, and the compound B is selected to be paraffin oil. S2: The mixture is placed in an extruder at a temperature of 220-250°C and melt-kneaded for 20 minutes to form a film-forming liquid, which is then extruded through a die to form a liquid film, and the die extrusion temperature is 235°C. S3: The liquid film is placed in different environments to undergo phase separation and hardening. The liquid film side is placed in an air environment, the air side temperature is set to 25°C, a liquid-cooled roll is installed on the other side of the liquid film, the carrier temperature is set to 30°C, the air side temperature reduction rate is 20°C / s, and the carrier side temperature reduction rate is 60°C / s. After the phase separation and hardening are completed, the base film is formed. S4: The raw film is subjected to the first heat treatment, and the first heat treatment temperature is controlled to 60°C to form a green film. S5: The solvent system is extracted using dichloromethane as an extractant, and the solvent system is removed from the raw membrane to obtain a formed membrane. S6: The formed membrane is subjected to a second heat treatment, and the temperature of the second heat treatment is controlled at 80°C to produce a UPE porous filtration membrane. The UPE porous filtration membrane produced in Example 1 is shown in FIGS.

[0060] Examples 2 to 26 The differences between Examples 2 to 26 and Example 1 are the composition ratios of the membrane-forming solutions and the process parameters, as shown in Tables 1-1, 1-2, 1-3, and 1-4. The UPE porous filtration membrane produced in Example 6 is shown in FIGS.

[0061] Comparative Example 1 The difference between Comparative Example 1 and Example 5 is that an equal amount of paraffin oil was selected instead of dimethyl phthalate, and the remaining process parameters are shown in Tables 1 to 5.

[0062] Comparative Examples 2 and 3 The difference between Comparative Examples 2 and 3 and Example 5 is that both sides of the liquid film were cooled under the same environment, and the remaining process parameters are shown in Tables 1 to 5.

[0063] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the mass average molecular weight of the polyethylene resin is 1.5 million. See Tables 1 to 5 for the remaining differences in the process parameters.

[0064] Table 1-1 [Table 1] TIFF2026504154000003.tif159170

[0065] Table 1-2 [Table 2] TIFF2026504154000005.tif29170

[0066] Table 1-3 [Table 3] TIFF2026504154000007.tif29170

[0067] Table 1-4 [Table 4] TIFF2026504154000009.tif28170

[0068] Table 1-5 [Table 5]

[0069] Membrane structure parameter detection The ultra-high molecular weight polyethylene porous filtration membranes produced in Examples 1 to 26 and Comparative Examples 1 to 4 were morphologically characterized using a scanning electron microscope. The first outer surface, second outer surface, and cross section of the ultra-high molecular weight polyethylene porous filtration membrane were selected as the observation objects, and the specific detection and measurement results are shown in Tables 2-1, 2-2, 2-3, and 2-4.

[0070] Table 2-1 [Table 6]

[0071] Table 2-2 [Table 7]

[0072] Table 2-3 [Table 8]

[0073] Table 2-4 [Table 9]

[0074] Membrane performance parameter detection The surfaces and cross sections of the UPE porous filtration membranes produced in Examples 1 to 26 and Comparative Examples 1 to 4 were observed using a scanning electron microscope. The UPE porous filtration membranes produced in Examples 1 to 26 included a main body, with a first outer surface and a second outer surface formed on both sides of the main body, with lace-like first micropores formed on the first outer surface and circular second micropores formed on the second outer surface, the SEM average pore size of the first micropores being much larger than the SEM average pore size of the second micropores, and the SEM average pore size from the first micropores to the second micropores exhibiting a gradient change in cross section, with the first outer surface and the second outer surface serving as a liquid inlet surface and a liquid outlet surface, respectively, and a non-directional serpentine passage formed between the first outer surface and the second outer surface. The membrane has several distinct block structures on the liquid-feeding side, with the first micropores surrounded by the block structures. Due to the diversity of the block structures, several interconnected microscopic openings are inevitable between adjacent first micropores. The block structures have several small protrusions extending from their surfaces. The small protrusions are smaller in volume and length than the block structures, and the small protrusions are interconnected with the first outer surface of the UPE porous filtration membrane in cross section. Grooves are formed between the block structures, with multiple sets of grooves interconnected vertically to form a non-directional serpentine path. The block structures also have several sub-holes that communicate with the grooves and the internal non-directional serpentine path. None of the UPE porous filtration membranes obtained in Comparative Examples 1 to 4 were able to achieve the above-mentioned morphology. This suggests that the mass-average molecular weight of the polyethylene resin, the difference in solid content on both sides of the liquid membrane, and the difference in phase separation rate may be crucial factors in forming the UPE porous filtration membrane. However, if the mass-average molecular weight of the ultra-high molecular weight polyethylene is less than 2 million, the formed UPE porous filtration membrane will not have a structure with one side having "lace pores" and the other having round pores.

[0075] 1.1 Water flow velocity test (test equipment shown in Figure 7) Experimental procedure Step 1: After wetting with IPA, the measurement sample (the ultra-high molecular weight polyethylene porous filtration membrane produced in Examples 1 to 26 and Comparative Examples 1 to 4) is attached to a vacuum filtration holder, valve 2 on the vacuum filtration holder is closed, valve 1 is opened, the vacuum pump is started, the pressure is adjusted to a test pressure of 0.03 MPa, and then valve 1 is closed. Step 2: Place 50 ml of test liquid (water) into the plastic measuring cylinder of the vacuum filtration holder, open valve 2, start timing from a certain mark, and stop timing until it reaches another mark. Step 3: When the test is complete, record the value displayed on the stopwatch. When all the test liquid has passed through the filtration membrane, close valve 2 on the holder and remove the sample. The detection results are shown in Table 3.

[0076] Table 3 [Table 10] TIFF2026504154000016.tif87170

[0077] 1.2 Filtration Accuracy Test: The ultra-high molecular weight polyethylene porous filtration membranes produced in Examples 1 to 26 and Comparative Examples 1 to 4 were tested for blocking efficiency. Experimental equipment: Tianjin Luojun particle counter KB-3, Experimental preparation: Assemble the experimental equipment according to Figure 8, ensure the cleanliness of the equipment, use ultrapure water to wash the equipment, take a sample with a diameter of 47 mm, load it into the butterfly filter, and ensure that the assembled filter has good airtightness. Testing Procedure: The challenge liquid was poured into the tank, and while taking care to vent the butterfly filter, the tank was pressurized to 10 kPa and a clean bottle was used to collect the filtrate downstream of the butterfly. The number of particles in the filtrate and the raw solution was measured using a particle counter.

number

[0078] Table 4 [Table 11] TIFF2026504154000019.tif91170

[0079] 1.3 Tensile strength test: The transverse tensile strength and longitudinal tensile strength of the ultra-high molecular weight polyethylene porous filtration membranes produced in Examples 1 to 26 and Comparative Examples 1 to 4 were measured using a universal tensile tester, where the width of the tensile tester was 10 mm, the pitch was 30 mm, and the tensile strength MPa = breaking strength cN / 102 / (average thickness mm*width mm), (1 N = 102 cN, 1 mm = 1000 μm), where the longitudinal tensile strength is the tensile strength along the film winding direction, and the transverse tensile strength is the tensile strength perpendicular to the film winding direction. The test results are shown in Table 5.

[0080] Table 5 [Table 12] TIFF2026504154000021.tif87170

[0081] As can be seen from Table 3, the UPE porous filtration membranes manufactured in Examples 1 to 26 of the present application have a wide range of filtration accuracy, and the UPE porous filtration membranes of different model numbers each have a blocking efficiency of approximately 95% or more for impurity particles of 2 to 100 nm, and have strong impurity particle collection capabilities.Of the UPE porous filtration membranes manufactured in Comparative Examples 1 to 3, the UPE porous membrane of Comparative Example 3 showed a decrease in impurity particle blocking accuracy compared to that comparative example (Example 5).

[0082] As can be seen from Table 4, the UPE porous filtration membranes produced in Examples 1 to 26 of the present application have good flow rates depending on the filtration accuracy, i.e., they can achieve good flow rates while ensuring the efficiency of blocking impurity particles, and are particularly suitable for application in the photoresist field. On the other hand, among the UPE porous filtration membranes produced in Comparative Examples 1 to 3, the UPE porous filtration membranes of Comparative Examples 1 and 2 showed a decrease in flow rate compared to the comparative example (Example 5).

[0083] As can be seen from Table 5, the UPE porous filtration membranes produced in Examples 1 to 26 of the present application have good tensile strength, and among the UPE porous filtration membranes produced in Comparative Examples 1 to 4, the UPE porous filtration membrane produced in Comparative Example 1 exhibited a decrease in tensile strength compared to that comparative example (Example 5), and Comparative Examples 2 and 3 exhibited an increase in tensile strength compared to that comparative example (Example 5). Analysis revealed that the reason for this was the tensile strength Made The tensile strength of Comparative Examples 2 and 3 may be affected by factors such as the solid content of the liquid membrane and the thickness of the membrane. In Comparative Examples 2 and 3, the volatilization environment on both sides of the liquid membrane was improved, the volatile component compound A was reduced to a certain extent, and the content of compound B and polyethylene resin was increased, thereby increasing the solid content to a certain extent, so that the tensile strength of Comparative Examples 2 and 3 was slightly higher than that of the comparative example (Example 5).

[0084] The UPE porous filtration membranes produced in Comparative Examples 1 to 4 have difficulty in achieving both high membrane flux and high blocking efficiency, whereas the UPE porous filtration membranes produced in Examples 1 to 26 of the present application have good membrane flux while achieving high blocking accuracy, and at the same time have good tensile strength, making them suitable for use in the photoresist field.

[0085] Although the preferred embodiments of the present invention have been described in detail above, it should be understood that after reading the above description of the present invention, those skilled in the art can make various changes or modifications to the present invention, the equivalents of which are also encompassed within the scope defined by the claims appended hereto.

Claims

1. A UPE porous filtration membrane comprising a main body, a first outer surface and a second outer surface formed on opposite sides of the main body, and a non-directional serpentine path formed within the main body, wherein the porous membrane has a PMI average pore size of 2 to 100 nm, the first outer surface has first micropores, the second outer surface has second micropores, the first micropores are lacy and surrounded by several block structures, the second micropores are circular, the SEM average pore size of the first micropores is larger than the SEM average pore size of the second micropores, and the SEM average pore size from the first micropores to the second micropores exhibits a gradient change, A UPE porous filtration membrane, characterized in that the portion between the first outer surface and the second outer surface is made of continuous fibers.

2. The UPE porous filtration membrane described in claim 1, characterized in that a plurality of fine protrusions are formed on the surface of each of the massive structures, each of the fine protrusions is connected to each other, grooves are formed between the massive structures, a plurality of sub-holes communicating with the grooves are formed in the massive structures, and the non-directional serpentine passage is formed between each of the grooves.

3. 2. The UPE porous filtration membrane according to claim 1, wherein the thickness of the block structure occupies a proportion of more than 30% of the thickness of the porous filtration membrane in the thickness direction.

4. 3. The UPE porous filtration membrane according to claim 2, wherein the area ratio of the sub-pores along the surface of the block structure is 5% or more.

5. 2. The UPE porous filtration membrane according to claim 1, wherein the SEM average pore size of the first micropores / the SEM average pore size of the second micropores is 10 or more.

6. The UPE porous filtration membrane according to claim 1, characterized in that the SEM average pore diameter of the second micropores is 15 to 80 nm, and the discrete coefficient of the SEM average pore diameter of the second micropores is 0.5 or less.

7. The UPE porous filtration membrane according to claim 1, characterized in that the pore area ratio of the first outer surface is A1, the pore area ratio of the second outer surface is A2, the A1 / A2 value range is 1.1 to 1.4, and A1 is 15 to 25%.

8. The pore density of the first outer surface is 0.2 to 6 / μm ２ and the pore density of the second outer surface is 120 to 260 pores / μm ２ 8. The UPE porous filtration membrane according to claim 7,

9. 2. The UPE porous filtration membrane according to claim 1, wherein the gradient of change in SEM average pore size from the first outer surface to the second outer surface is 4 to 30 nm / μm.

10. The time required for 50 ml of water to pass through a porous filtration membrane with a diameter of 47 mm under conditions of a positive pressure of 0.03 MPa and a temperature of 20°C is 60 to 3000 seconds. The UPE porous filtration membrane according to claim 1, characterized in that the transverse tensile strength of the porous filtration membrane is 3.4 to 14.18 MPa, and the longitudinal tensile strength of the porous filtration membrane is 4.4 to 14.83 MPa.

11. A method for producing a UPE porous filtration membrane according to any one of claims 1 to 10, comprising the following steps S1 to S6: S1: A polyethylene resin is added to a solvent system consisting of compound A and compound B, and the mixture is stirred and mixed to form a mixture with a solid content of 8-14% after uniform mixing, wherein the polyethylene resin is an ultra-high molecular weight polyethylene having a mass average molecular weight of 2 million to 5 million, compound A is a non-solvent for the polyethylene resin, and compound B is a solvent for the polyethylene resin, and the content of compound A is higher than the content of compound B; S2: The mixture is heated, melted and kneaded at a temperature of 220 to 250°C to form a film-forming liquid, which is then extruded through a die to form a liquid film; S3: The liquid film is subjected to phase separation and curing in a temperature environment of 15 to 120°C to form a base film, wherein the phase separation rates on both sides of the film are different, the ratio of the temperature decrease rate on the second outer surface side to the temperature decrease rate on the first outer surface side is 2 or more, the temperature decrease rate on the second outer surface side is controlled to 20 to 100°C / s, and the temperature decrease rate on the first outer surface side is controlled to 8.5 to 50°C / s; S4: The raw film is subjected to a first heat treatment, and the first heat treatment temperature is controlled to 40 to 100°C to form a raw film; S5: Extracting the solvent system with the extraction liquid, removing the solvent system from the raw membrane, and obtaining a formed membrane; S6: A manufacturing method characterized by subjecting the formed film to a second heat-stabilizing step, controlling the temperature of the second heat-stabilizing step to 60 to 120°C, and producing an ultra-high molecular weight polyethylene porous film.

12. The mixture comprises a polyethylene resin, compound A, and compound B in the following parts by weight: Polyethylene resin: 10 to 18 parts Compound A: 50 to 70 parts Compound B: 15 to 45 parts 12. The method for producing a UPE porous filtration membrane according to claim 11, wherein compound A is at least one of dimethyl phthalate, dioctyl adipate, ethylene glycol diacetate, triphenyl phosphate, dicyclohexyl phthalate, glycerol triacetate, and dipropyl carbonate, and compound B is at least one of paraffin oil, white oil, hydraulic oil, decahydronaphthalene, castor oil extract, castor oil, and acetyl tributyl citrate.

13. The method for producing a UPE porous filtration membrane according to claim 12, characterized in that one side of the liquid membrane is provided as a liquid-cooled roll, and the temperature of the liquid-cooled roll is set to 5 to 40°C, and the other side of the liquid membrane is provided as air, and the temperature of the air side is set to 20 to 25°C.

14. 11. Use of the UPE porous filtration membrane according to any one of claims 1 to 10, characterized in that the UPE porous filtration membrane is used for photoresist and solvent filtration.

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