UPE Porous Membrane with High Specific Surface Area, Its Manufacturing Method and Use

Abstract

The present invention provides a high specific surface area UPE porous membrane and its manufacturing method and use, the porous membrane includes a first porous outer surface, a second porous outer surface, and a body located between the first porous outer surface and the second porous outer surface, the body has a non-directional serpentine passage, and the specific surface area of ​​the UPE porous membrane is 35 m 2 / g or more, which is higher than the surface area, the first porous outer surface has several branched continuous first fibers, adjacent continuous first fibers are surrounded to form first pores, the first fibers along the thickness direction are stacked with each other, and the average diameter of the first fibers is 10-60nm, the UPE porous membrane is a symmetric membrane, the high specific surface area UPE porous membrane can be blocked by membrane pores as well as adsorption blocking, has excellent collection performance for nano-scale fine impurities, has high blocking efficiency, and is suitable for application in the field of photoresist filtration, and the preparation method provided by the present invention is convenient, rapid, and effectively prepares and obtains the UPE porous membrane.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane materials, and more specifically, to a UPE porous membrane with a high specific surface area, a manufacturing method thereof, and uses thereof.

Background Art

[0002] A polymer filtration membrane is a film made from an organic polymer polymer based on a certain process, and this film mainly serves for filtration and separation. With the development of the petroleum industry and science and technology, the application fields of polymer filtration membranes have been continuously expanding. Currently, the fields where they have been applied include gas separation, seawater desalination, ultrapure water production, treatment of polluted waste, manufacture of artificial organs, pharmaceuticals, food, agriculture, chemical industry, and other aspects. Depending on the polymer, polymer filtration membranes can be divided into cellulose-based polymer filtration membranes, polyamide-based polymer filtration membranes, polysulfone-based polymer filtration membranes, polyolefin-based polymer filtration membranes, and the like.

[0003] Polyolefin-based polymer filtration membranes mainly refer to olefin-based filtration membranes such as polyethylene filtration membranes and polypropylene filtration membranes. Since they have excellent physical and chemical properties, their application range is very wide. For example, ultra-high molecular weight polyethylene (UPE) filtration membranes are commonly used in fields such as photolithography processing and "wet etching and cleaning" (WEC) applications.

[0004] For example, the Chinese patent "Substrate for Liquid Filter" with application number 201480026006.4 introduces a polyethylene filtration membrane used in the semiconductor lithography field that has excellent collection performance for impurity particles with a size of about 10 to 50 nm, has a long lifespan, and its flux is always relatively stable during long-term use.

[0005] In the field of photoresists, the requirements for the purity of photoresists are strict. This is because a small amount of minute impurities in the photoresist can have a great impact on the quality of lithography, and the products after lithography cannot meet practical requirements. Therefore, when filtering the photoresist with a filter membrane, it is desirable to be able to block and retain various substances (such as particles and metal ions) in the photoresist as much as possible to meet practical requirements. However, in the current market, the blocking efficiency of polyolefin filter membranes for impurity particles in photoresists is average, which also limits the development of polyolefin-based polymer filter membranes to a certain extent.

Summary of the Invention

Problems to be Solved by the Invention

[0006] In view of the deficiencies existing in the prior art, the object of the present invention is to provide a UPE porous membrane with a high specific surface area, its manufacturing method and uses. This UPE porous membrane has a high specific surface area, can block various impurities through its pores, and can also perform adsorption and blocking on impurities. Therefore, it can capture various impurities with high quality and has a high blocking efficiency, especially suitable for application in the field of photoresist filtration.

Means for Solving the Problems

[0007] To achieve the above object, the present invention provides the following technical solution. It includes a first porous outer surface, a second porous outer surface, and a body located between the first porous outer surface and the second porous outer surface, and inside the body is a UPE porous membrane with a high specific surface area having a non-directional meandering passage. The specific surface area of the UPE porous membrane is 35 m 2Above / g, the first porous outer surface contains several dendritic continuous first fibers, and the space between adjacent continuous first fibers surrounds to form a first pore. The first fibers along the thickness direction are stacked on top of each other. The average diameter of the first fibers is 10 - 60 nm. The UPE porous membrane is a symmetric membrane. The polyolefin composition constituting the UPE porous membrane contains at least ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more. A UPE porous membrane with a high specific surface area, including a first porous outer surface, a second porous outer surface, and a body located between the first porous outer surface and the second porous outer surface. There is a non-directional meandering passage in the body. The specific surface area of the UPE porous membrane is above 35 m 2 / g. On the first porous outer surface, there are several dendritic continuous first fibers. The space between adjacent continuous first fibers surrounds to form a first pore. The first fibers along the thickness direction are stacked on top of each other. The average diameter of the first fibers is 10 - 60 nm. The UPE porous membrane is a symmetric membrane, and the polyolefin composition constituting the UPE porous membrane contains at least ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more.

[0008] After performing a specific surface area test on the UPE porous membrane of the present invention by the BET method, the applicants were surprised that the specific surface area of this UPE porous membrane is relatively high, and its specific surface area is 35 m 2 / g or more (the specific surface area of conventional UPE porous membranes is generally 25 - 30 m 2 / g). The specific surface area refers to the total area of a unit mass of material (in the present invention, it refers to the porous membrane). The larger the specific surface area, the larger the total area of a certain mass of UPE porous membrane. Therefore, it is indicated that the UPE porous membrane of the present invention has the following advantages.

[0009] In addition to being able to block impurity substances in the photoresist through the membrane pores, the UPE porous membrane of the present invention can adsorb various impurity substances by acting forces such as VDW (Van der Waals' force). Therefore, the blocking efficiency of the filtration membrane against various impurities is enhanced. At the same time, according to experiments, the UPE porous membrane is slightly negatively charged even when it comes into contact with the material liquid. At this time, it was found that the negatively charged UPE porous membrane has stronger adsorption properties. Well, the advantage of the high specific surface area UPE membrane is that when the charge amount per specific surface area is constant, the total charge of the UPE membrane with a high specific surface area is large, so the adsorption effect is high and the ability to retain impurity substances is strong. In addition to some metal ions and small particle impurities, the organic resin substances, which are the active components in the photoresist, aggregate during processes such as transportation (for example, the active component PMMA resin in KrF photoresist is prone to aggregation, and the active component ketones in I-line / KrF photoresist are also prone to aggregation). These aggregated active resins have a certain impact on the refractive index of light and further affect the stability during the lithography process. The lithography process cannot achieve ideal results. At this time, the charged high specific surface area UPE membrane has a good adsorption effect on all the above-mentioned impurities, guarantees the stability of the lithography process, and realizes an ideal lithography process. Also, when developing a purification (demetalization ion) membrane with high specific surface area UPE as the base membrane material, due to its high specific surface area, the number of graftable functional groups is relatively large, and the metal ion removal rate and lifespan of the membrane after modification with high specific surface area UPE are significantly improved. In special applications, for example, when it is necessary for the functional group to adsorb or exchange ions in the reagent, the high surface area UPE can increase the higher capacity space, so this UPE porous membrane is optimal for various modifications of the base membrane.

[0010] When using high specific surface area UPE as the filtration membrane, it can provide more contact opportunities between the reagent and the membrane, thereby increasing the possibility that impurities in the reagent are blocked by the membrane, further improving the blocking efficiency. At the same time, the high specific surface area UPE porous membrane can provide more pore volume so as to have a larger pollution capacity as a filtration membrane material.

[0011] Meanwhile, in the membrane structure of the UPE porous membrane provided by the present invention, several first fibers exist on the first porous outer surface of the UPE porous membrane. These first fibers exhibit a branched structure, and it has been clarified that they are continuous between the first fibers. The space between adjacent continuous first fibers surrounds each other to form a first pore, and then a porous structure of the membrane is formed. The membrane formed by such a first fiber structure has a relatively high specific surface area. At the same time, in the thickness direction, near the first porous outer surface, the first fibers are stacked on each other and overlapped alternately, which is beneficial for the filtration of impurities and guarantees a high blocking efficiency for impurity particles. On the first porous outer surface, the average diameter of the first fibers is 10 - 60 nm. Such a thickness of the first fibers guarantees that the whole membrane has a high tensile strength while meeting the requirements of actual industrial production. On the other hand, the stability of the first pores formed by the first fibers is relatively strong, and it is not easy to collapse or shrink, thus ensuring the stability of the fluid flow rate.

[0012] In addition, the UPE porous membrane of the present invention is a symmetric membrane. The meaning of symmetry means that the structures of the first porous outer surface and the second porous outer surface on the UPE porous membrane are basically similar or the same. The pore shapes, pore diameters, and pore area ratios on these two outer surfaces are basically similar, and the difference is very small (close to the same). In actual use, either outer surface can be used as the liquid feeding surface (if it is an asymmetric membrane, generally a specific outer surface is required as the liquid feeding surface). Therefore, the related technologies regarding the assembly of the porous membrane in the present invention are simpler, and it is easier to manufacture a higher-quality filter core.

[0013] The material of each part of the UPE porous membrane in the present invention is uniform, that is, the whole membrane is made of polyethylene material and there is no change in the material. Ultra-high molecular weight polyethylene is abbreviated as UPE and is a thermoplastic engineering plastic with excellent comprehensive performance in a linear structure. The filtration membrane made of ultra-high molecular weight polyethylene has relatively high heat resistance, wear resistance, good mechanical performance, large tensile strength, excellent chemical compatibility, a wide range of applications, and is particularly suitable for application in the photoresist field. The polyolefin composition constituting the UPE porous membrane in the present invention contains at least ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more. This enables the finally manufactured filtration membrane to have relatively large tensile strength and elongation at break, meet the requirements of actual applications, have a wide range of applications, and is particularly suitable for application in the photoresist field. The mass average molecular weight can be obtained by heating and dissolving a sample of the polyethylene filtration membrane in o-dichlorobenzene and measuring it using GPC liquid chromatography under the conditions of a column temperature of 135 °C and a flow rate of 1.0 mL / min.

[0014] Among them, after morphologically evaluating the membrane structure using a scanning electron microscope, the average diameter of the first fiber on the first porous outer surface of the porous membrane can be reused with computer software (such as Matlab, NIS-Elements, etc.), measured manually, or corresponding calculations can be performed. In the process of manufacturing the membrane, in the direction perpendicular to the membrane thickness (if the membrane is in the form of a porous membrane, the direction is the planar direction; if the membrane is in the form of a hollow fiber membrane, the direction is perpendicular to the radial direction), each of its characteristics, such as pore size distribution and fiber thickness, is almost uniform and basically consistent. Therefore, the size of the overall fiber average diameter on the corresponding plane can be reflected by the fiber average diameter of the partial region on the corresponding plane. When actually measuring, first, the outer surface of the membrane is characterized using an electron microscope to obtain a corresponding SEM image. Since the thickness of the fibers on the outer surface of the membrane is almost uniform, a certain area, such as 1 μm 2 (1 μm multiplied by 1 μm) or 25 μm 2(Multiply 5 μm by 5 μm) is selected, and the specific area size is determined according to the actual situation. Further, the diameter size of the fibers in this area is measured by corresponding computer software or manually, and then calculations are performed to obtain an average value, thereby obtaining the average diameter size of the first fibers on this first porous outer surface. Of course, those skilled in the art can also obtain the above parameters by other measuring means, and the above measuring means are only for reference. The pore area ratio of the first pores and the average pore diameter of the first pores on the first porous outer surface can also be obtained according to the above method.

[0015] Furthermore, "continuous" means that, unless torn by an external force, substantially all the fibers are integrally interconnected without the need to connect to each other using another adhesive or the like so that the network-like fibers cannot be separated from each other. At the same time, the continuous network-like fibers are also interconnected with the first porous outer surface and the second porous outer surface.

[0016] As a further improvement of the present invention, the first porous outer surface has several circular first pores, the area ratio of the first pores on the first porous outer surface is 30%-70%, and the average pore diameter of the first pores is 1-150 nm.

[0017] As is well known, factors such as the pore diameter size, quantity, and pore shape of the membrane pores have a great influence on the membrane properties such as the filtration accuracy (blocking efficiency) and flow rate of the membrane.

[0018] The first pores on the first porous outer surface in the present invention have a circular pore structure. Some of the first pores are circular, and some are elliptical. The circular pores on the first porous outer surface result in a high pore volume, enabling the porous membrane to have a high specific surface area. The average pore diameter of the first pores in the present invention is 1 - 150 nm. And due to the non-directional meandering channels inside the membrane body, this porous membrane can effectively capture impurity particles with a particle size of 1 - 150 nm. Its cut-off efficiency is greater than 95%, ensuring the filtration accuracy, fully fulfilling the retention function of unwanted substances, and meeting practical requirements. Also, the area ratio of the first pores on the first porous outer surface (the ratio of the area of the first pores to the area of the corresponding membrane region) is 30% - 70%, which easily guarantees that the whole membrane has a relatively high porosity. This is not only beneficial for the porous membrane to have a relatively high flow rate, making it easy for the fluid to quickly pass through the porous membrane, shortening the filtration time, but also having a relatively high tensile strength, meeting the requirements of practical applications.

[0019] As a further improvement of the present invention, the thickness of the UPE porous membrane is 1 - 30 μm, the porosity of the UPE porous membrane is 45% - 85%, and the surface area inside the membrane per unit membrane area is 0.4 - 0.8.

[0020] Also, a porosity test is conducted on the UPE porous membrane of the present invention. The porosity of the membrane refers to the ratio of the pore volume of the porous membrane to the total volume, and the pores include two types: open pores and closed pores. Common porosity test methods include the mercury intrusion porosimetry method, the density method, and the dry-wet membrane weighing method. Through the tests, the applicants have invented that the porosity of this UPE porous membrane is 45% - 85%, having a relatively high porosity. That is, since this UPE porous membrane has a high specific surface area and a high porosity, it indicates that the UPE porous membrane of the present invention has the following advantages.

[0021] 1. Photoresist has a higher viscosity compared to ordinary chemicals, and it is extremely prone to generating bubbles when filtering the medium. The bubbles have a very significant impact on subsequent processes. The UPE porous membrane with a high specific surface area and high porosity can increase the filtration speed of the photoresist. At the same time, due to the faster exhaust caused by the high porosity (the exhaust speed is faster and it is easier to discharge bubbles), the bubble content in the filtered photoresist is less, which is beneficial for ensuring the quality of the photoresist.

[0022] 2. When applying a filter core at the end of the photoresist, since its outer shell dimensions are generally small, the filtration membrane area filled inside is also generally small (generally not exceeding 2 m 2 ). On the other hand, with the decrease of the membrane pores, if the membrane area cannot increase significantly at the same time, the UPE porous membrane with a high specific surface area and high porosity can achieve a lower pressure (smaller pressure loss) at the same flow rate. Thereby, the high surface area UPE membrane can achieve very small pores (filtering nanoscale impurity particles) for photoresist with a fairly high viscosity, and at the same time can meet the demand of the flow rate (the filtration speed is still fast, the time cost is low, and the economic effect is high).

[0023] If the thickness of the membrane is too small, its mechanical strength will decrease, and at the same time, the filtration time is too short, so effective filtration cannot be carried out. If the thickness of the membrane is too large, the filtration time will be long and the time cost will be too high. The thickness of the UPE porous membrane of the present invention is 1 - 30 μm. The UPE porous membrane not only has high mechanical strength, but also can perform effective filtration, has high filtration efficiency, short filtration time, low time cost, and is suitable for application in the photoresist field.

[0024] When performing filtration, various fluids move along the membrane thickness direction to achieve corresponding filtration. Since all filtration is disposable, the characteristic of the internal surface area of the membrane per unit membrane area is particularly important. The internal surface area of the membrane per unit membrane area means the size of the surface area of the internal area of the membrane on a porous membrane with a certain area. The larger this value is, the larger the internal surface area of the porous membrane is. The internal surface area of the membrane per unit membrane area in the present invention is 0.4 - 0.8, and this value is large. Therefore, (1) the contamination amount of the UPE porous membrane is large, the service life is long, and the economic effect is high; (2) the area through which the fluid passes inside the porous membrane is larger, impurities are relatively easier to block, and the blocking efficiency is improved; (3) when graft-modifying this UPE as the base membrane, the functional groups that need to be grafted are easier to graft onto the internal surface area of the membrane, and each performance of the UPE porous membrane can be further improved, indicating that it is particularly suitable for applications in the photoresist field.

[0025] As a further improvement of the present invention, the specific surface area of the UPE porous membrane is 40 - 80m 2 / g, the porosity of the UPE porous membrane is 50% - 75%, and the thickness of the UPE porous membrane is 5 - 20μm.

[0026] The specific surface area refers to the total area of a unit mass of the material. The larger this value is, the larger the total area of a certain mass of the material is. Preferably, the specific surface area of the UPE porous membrane of the present invention is 40 - 80m 2 / g, indicating that a certain mass of the UPE porous membrane has a large total area. When blocking the fluid, the membrane area in contact with the fluid is large, impurities in the fluid are easily blocked, the blocking efficiency is further improved. At the same time, when using this UPE porous membrane as the base membrane and performing various modification treatments, the contact area between the modifier and the membrane is large, the reaction is sufficient, and various modifications, such as hydrophilic modification of the UPE membrane, can be more easily realized.

[0027] Such a UPE membrane with a high specific surface area can be used as a base membrane for charge modification. On the other hand, even without modification, according to experiments, after the UPE porous membrane comes into contact with the material liquid, it becomes slightly negatively charged. In this case, the negatively charged UPE porous membrane also has a certain adsorption property. Now, the advantage of the high specific surface area UPE membrane is that when the charge amount per unit specific surface area is constant, the total charge of the high specific surface area UPE membrane is large, so the adsorption effect is high and the ability to retain impurity substances is strong.

[0028] Except for some metal ions and particulate impurities, the aggregation of the effective component resin substances in the photoresist (for example, the component PMMA resin in the KrF photoresist is prone to aggregation, and the component ketones in the I-line / KrF photoresist are prone to aggregation) affects the refractive index of light and thus is likely to affect the stability of the lithography process. At this time, the charged high specific surface area UPE membrane all has a good adsorption effect on the above impurities.

[0029] If the porosity of the membrane is too high, the tensile strength of the membrane is too low, its mechanical performance is poor, the industrial practical value is low, and it cannot meet the market needs. On the other hand, if the porosity of the membrane is too low, it affects the flow rate of the membrane, the filtration speed of the membrane is slow, the filtration time is long, and the time cost is large. On the other hand, if the pollution amount of the membrane is too low and the service life is too short, it is necessary to replace the membrane in a short time, and the economic cost has increased significantly. Preferably, the porosity of the porous membrane in the present invention is 50%-75%. This UPE porous membrane not only has a high tensile strength, but also has a relatively fast filtration speed, a large flow rate, and a relatively high pollution amount. It can block a relatively large number of impurity particles, has a long service life, and a low economic cost.

[0030] Preferably, the thickness of the UPE porous membrane is 5-20 μm. Due to the mutual synergistic effect among the membrane thickness, membrane porosity, and membrane specific surface area, the UPE porous membrane has a high tensile strength, a short filtration time, and a high filtration accuracy, ensuring that it meets practical needs.

[0031] As a further improvement of the present invention, several dendritic continuous second fibers are included in the second porous outer surface, and the space between adjacent continuous second fibers surrounds to form a second pore, and the average diameter of the second fibers is 10 - 60 nm.

[0032] In the membrane structure of the UPE porous membrane provided by the present invention, it is clear that several second fibers also exist on the second porous outer surface of the UPE porous membrane. The shape of the second fibers is almost the same as that of the first fibers, but there is a certain difference in thickness, and the difference is also small, which indicates that the UPE porous membrane of the present invention is a symmetric membrane, and the two outer surface structures of the membrane are very similar. These second fibers also exhibit a dendritic structure, and the second fibers are continuous with each other. Adjacent continuous second fibers also surround each other to form corresponding second pores, and then form the porous structure of the membrane. The membrane formed by such a second fiber structure has a higher specific surface area and a higher porosity. At the same time, in the thickness direction, near the second porous outer surface, the second fibers are also laminated with each other, alternating (interleaving) and overlapping with each other, which is beneficial for the filtration of impurities and ensures that the porous membrane has a high blocking efficiency for impurity particles. On the second porous outer surface, the average diameter of the second fibers is 10 - 60 nm. Such a thickness of the second fibers further ensures that the whole membrane has a higher tensile strength, can meet the requirements of actual industrial production, and the stability of the second pores formed by the second fibers is strong, and it is not easy to collapse or shrink, and then ensures the stability of the fluid flow rate.

[0033] As a further improvement of the present invention, the ratio of the average diameter of the second fibers to the average diameter of the first fibers is 0.7 - 1.5, the second pores are circular pores, and the area ratio of the second pores on the second porous outer surface is 30% - 70%.

[0034] As a further improvement of the present invention, the average pore diameter of the second pores is 1 - 150 nm, and the ratio of the average pore diameter of the second pores to the average pore diameter of the first pores is 0.78 - 1.35.

[0035] As is well known, elements such as the size, quantity, and shape of the pores in the membrane have a significant impact on membrane properties such as the filtration accuracy (blocking efficiency) and flow rate of the membrane. The second pores on the second porous outer surface in the present invention have a circular pore structure, and the shape of the second pores is also approximately the same as that of the first pores, but there is a small difference in the pore diameter. Some of the second pores are circular, and some are elliptical. The circular second pores are relatively likely to produce a higher pore volume, enabling the porous membrane to have a relatively high specific surface area. Also, the area ratio of the second pores on the second porous outer surface (the ratio of the area of the second pores to the area of the corresponding membrane region) is 30% - 70%. This is not only advantageous for the porous membrane to have a large flow rate, but also makes it easier for the fluid to quickly pass through the porous membrane, shortening the filtration time, giving the porous membrane a large tensile strength, and meeting the requirements of actual applications. Thereby, through measurement, the average pore diameter of the second pores is 1 - 150 nm, and the sizes of the average pore diameter of the second pores and the average pore diameter of the first pores are approximately equal. In fact, there is a certain difference, but the difference is small. This UPE porous membrane is a symmetric membrane. Each part of this symmetric membrane has approximately the same characteristics, and its pore structure and fiber structure do not change according to the membrane thickness, further proving that this membrane can exhibit a strong collection ability for impurity particles with a particle size of 1 - 150 nm.

[0036] Also, in the present invention, the ratio of the average diameter of the second fibers to the average diameter of the first fibers is 0.7 - 1.5, and the ratio of the average pore diameter of the second pores to the average pore diameter of the first pores is 0.78 - 1.35. There is a certain difference between the thickness of the second fibers and the thickness of the first fibers, but the difference between the two is small and relatively uniform. There is also a certain difference between the average pore diameter of the second pores and the average pore diameter of the first pores, but the difference is small and relatively uniform. Therefore, this UPE porous membrane is a symmetric membrane, further indicating that the properties of the two outer surfaces of this membrane are basically the same. In actual use, either outer surface of the porous membrane can be used as the liquid supply surface, and the process of using the porous membrane as the filter core is simpler and more economically efficient.

[0037] As a further improvement of the present invention, the ratio between the initial IPA bubble point and the complete IPA foaming point of the UPE porous membrane is 0.4 or more, and the complete IPA foaming point of the UPE porous membrane is 0.2 MPa or more.

[0038] One of the important characteristics of the filtration membrane is the bubble point, and the test method for the bubble point is known in the art. For example, ASTM F316-70 and ANS / ASTM F316-70 (re-approved in 1976) detail the programs for these tests, and these documents are hereby incorporated by reference. The size of the bubble point is related to the size of the pore diameter on the porous membrane. Generally, the larger the pore diameter, the lower the bubble point; the smaller the pore diameter, the higher the bubble point. The bubble point includes the initial bubble point and the complete bubble point. The IPA complete bubble point of the UPE porous membrane of the present invention is 0.2 MPa or more, whereby the pore diameter in the UPE porous membrane is relatively small, and it further passes through the non-directional meandering channels in the membrane body, whereby the porous membrane can exert a good collecting effect on impurity particles with a particle size of 1-150 nm, ensure the filtration accuracy, and exert a sufficient retention effect on undesirable substances.

[0039] The initial bubble point mainly reflects the maximum pore diameter inside the membrane, and the complete bubble point mainly reflects the average pore diameter of the membrane. The ratio between the initial bubble point and the complete bubble point can also reflect the symmetry of the membrane to a certain extent. The smaller the ratio, the greater the asymmetry of the membrane to a certain extent; the larger the ratio, the better the symmetry of the membrane to a certain extent. The ratio of the IPA initial bubble point to the IPA complete bubble point of the UPE porous membrane in the present invention is 0.4 or more, and furthermore, this membrane is a symmetric membrane, and the characteristics such as the size of the pore diameter and the pore distribution inside the membrane body are all similar to the corresponding characteristics on the two outer surfaces of the membrane, and there are no pores with particularly large pore diameters, ensuring the filtration accuracy and filtration speed.

[0040] As a further improvement of the present invention, after the porous membrane is left standing at a temperature of 120°C for 1 hour, its shrinkage rate is 5% or less, the compression rate of the porous membrane is less than 15%, and the pore closure temperature of the porous membrane is higher than 120°C.

[0041] A heat resistance test was conducted on the UPE porous membrane. After leaving the porous membrane of the present invention at 120°C for 1 hour, it was found that the shrinkage rate was 5% or less, indicating that the UPE porous membrane has high thermal stability, and the membrane pores are less likely to shrink or deform even at relatively high temperatures. Thereby, it ensures that the membrane has high blocking efficiency for a long time, the flow rate change during use is small, and the service life is long. Furthermore, it shows that its application range is very wide and it is particularly suitable for application in the photoresist field.

[0042] During the long-term use or processing of a liquid filter, the porous membrane needs to be able to maintain a good porous structure, thereby ensuring efficient blocking efficiency and achieving an excellent trapping effect on impurities. The compression rate of the UPE porous membrane of the present invention is less than 15%. During various processing treatments or the long-term use process of the porous membrane, the membrane pores of the porous membrane are less likely to deform, the porous structure is stable, and furthermore, the porous membrane has a stable flow rate and can ensure the blocking efficiency for a long time. The compression rate in the present invention is obtained from the ratio of the membrane thickness difference before and after pressurization to the membrane thickness before pressurization after pressurizing the UPE porous membrane at 2 MPa for 30 seconds at 70°C, then releasing the pressure and leaving it at 25°C for 30 seconds. In the present invention, when the compression rate of the UPE porous membrane is 15% or more, problems such as excessive pressure change occurring in the porous membrane during the long-term use or processing of the liquid filter, being unable to maintain the original porous structure, unstable water permeability, and abnormal increase in filtration pressure due to pore closure will occur.

[0043] Also, the pore closure temperature of the UPE porous membrane of the present invention is higher than 120°C. When the pore closure temperature of the porous membrane is higher than 120°C, in the vicinity of the relatively high-temperature treatment part or the relatively high-temperature body contact part of the actual heat adhesion process during the processing of the UPE porous membrane, the porosity of the UPE porous membrane is not lost, the water permeability is easily maintained, the desired filtration area can be obtained even after processing, and then the ideal flow rate and blocking efficiency are guaranteed, the porosity of the membrane is stable, and the actual industrialization needs can be met.

[0044] As a further improvement of the present invention, the blocking efficiency of the UPE porous membrane for impurity particles with a particle size of 1 - 150 nm is greater than 95%. 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 porous membrane with a diameter of 47 mm does not exceed 500 s. The tensile strength of the porous membrane is 20 - 100 MPa, and the elongation at break is 200% - 800%.

[0045] By performing a blocking test on the UPE porous membrane, the porous membrane can achieve a good collection effect on impurity particles with a particle size of 1 - 150 nm. Its blocking efficiency is greater than 95%, ensuring the filtration accuracy, achieving a sufficient retention effect on undesirable substances, and being suitable for application in the photoresist area.

[0046] By performing a flow rate test on the UPE porous membrane, 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 UPE porous membrane with a diameter of 47 mm does not exceed 500 s. The UPE porous membrane has a relatively large flow rate, indicating that the time required for the fluid to pass through the porous membrane is short, the time cost is low, and the economic effect is high. At the same time, it shows that the UPE porous membrane of the present invention is suitable for application in the photoresist field.

[0047] Important indicators for evaluating the mechanical strength of the membrane are the tensile strength and elongation at break of the membrane. Under certain conditions, the greater the tensile strength of the membrane, the better the mechanical strength of this membrane. The tensile strength of the UPE porous membrane in the present invention is 20 - 100 MPa, and the elongation at break is 200% - 800%. The UPE porous membrane of the present invention has relatively large tensile strength and elongation at break, indicating that its mechanical performance is relatively good, its industrial practical value is relatively high, and it can fully meet the market demand.

[0048] The present invention also provides a method for manufacturing a UPE porous membrane with a high specific surface area, including the following steps.

[0049] S1: Add a polyethylene resin to a solvent system composed of Compound A and Compound B, stir and mix them. After uniform mixing, a mixed material is formed. Among them, the polyethylene resin contains at least one ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more. Compound A is a non-solvent for the polyethylene resin, and Compound B is a solvent for the polyethylene resin. The mixed material contains a substance composition in parts by weight of polyethylene resin: 10 - 25 parts, Compound A: 0 - 20 parts, and Compound B: 70 - 90 parts. Compound A is at least one of dimethyl phthalate, dioctyl phthalate, ethylene glycol diacetate, dimethyl carbonate, palm oil, and glyceryl triacetate. Compound B is at least one of paraffin oil, white oil, hydraulic oil, decahydronaphthalene, castor oil extract, and castor oil, and

[0050] S2: Heat and melt-knead the mixed material under the condition of a temperature of 150 - 260 °C to form a casting solution. Then, extrude it through a die to form a liquid film on a carrier. The die extrusion temperature is 200 - 250 °C, and

[0051] S3: Phase-separate and solidify the liquid film in a temperature environment of 15 - 50 °C. The phase-separation solidification time is 2 - 50 s to form a green film. When phase-separating and solidifying, the temperature difference between the carrier side and the air side of the liquid film is 5 - 20 °C. And during the process of phase-separating and solidifying, the carrier side and the air side of the liquid film are converted with each other at least once, and

[0052] S4: Then, perform stretching treatment on the green film and perform the first heat setting after stretching is completed, and

[0053] S5: Use an extracting agent to extract the solvent system and remove the solvent system from the green film to obtain a raw film, and

[0054] S6: Perform the second heat setting on the raw film to manufacture a UPE porous membrane, including.

[0055] As a further improvement of the present invention, the polyethylene resin is composed of ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more, accounting for 65% - 85% by mass, and high-density polyethylene with a mass average molecular weight of 1 million - 2 million, accounting for 15% - 35% by mass and a density of 0.92 - 0.98 g / cm 3 ³.

[0056] As a further improvement of the present invention, in S4, stretching the green film means simultaneously performing transverse stretching and longitudinal stretching on the green film. The temperature during transverse stretching and longitudinal stretching is 60 - 150 °C, the multiple of transverse stretching is 1 - 10 times, and the multiple of longitudinal stretching is 1 - 10 times.

[0057] As a further improvement of the present invention, in S4, after stretching the green film, the ratio of the multiple of longitudinal stretching to the multiple of transverse stretching is 0.8 - 2, the speed of transverse stretching is 5% / s - 100% / s, and the speed of longitudinal stretching is 5% / s - 100% / s.

[0058] As a further improvement of the present invention, in S5, the extracting agent is at least one of dichloromethane, acetone, methanol, ethanol, glycerin, tetrafluoroethane, and isopropanol. The extraction temperature is 5 - 25 °C, and the extraction time is 1 - 5 h.

[0059] As a further improvement of the present invention, the temperature during the first heat setting is 100 - 180 °C, and the time is 20 - 90 s. The temperature during the second heat setting is 10 - 40 °C higher than the temperature during the first heat setting, and the time is 20 - 90 s.

[0060] The present invention forms a slab with pores by a thermally induced phase separation method, stretches and shapes the slab to produce a UPE porous membrane with a high specific surface area. During production, a mixed material is first formed by mixing various materials, and the mixed material includes a polyethylene resin and a corresponding solvent system. Ultra-high molecular weight polyethylene is abbreviated as UPE, which is a thermoplastic engineering plastic with excellent comprehensive properties of a linear structure. The porous membrane made from UPE can have relatively high heat resistance and wear resistance, and also has good mechanical properties, high tensile strength, and a wide application range. The polyethylene resin used in the present invention contains at least one ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more. That is, in the present invention, only one kind of UPE with a mass average molecular weight exceeding 3 million can be used as the film-forming raw material, or they can be compounded. For example, after compounding one kind of UPE with a mass average molecular weight exceeding 3 million and one kind of high-density polyethylene with a mass average molecular weight less than 3 million, it can also be used as the film-forming raw material. Preferably, the polyethylene resin of the present invention is composed of 65% - 85% by mass of ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more, and 15% - 35% by mass of polyethylene with a mass average molecular weight of 1 million - 2 million and a density of 0.92 - 0.98 g / cm 3It is made of high-density polyethylene. The polyethylene resin obtained by compounding ultra-high molecular weight polyethylene and high-density polyethylene is advantageous for obtaining a UPE porous membrane with relatively small pore size, high porosity, and simultaneously high tensile strength compared to the ultra-high molecular weight polyethylene used by single selection. On the other hand, the solvent system may be only compound B. Compound B is a solvent for the polyethylene resin. When the solvent is heated to the boiling temperature of compound B, compound B can completely dissolve the polyethylene resin and form a homogeneous solution. Compound B is at least one of paraffin oil, white oil, hydraulic oil, decahydronaphthalene, castor oil extract, and castor oil. Preferably, the solvent system can be composed of compound A and compound B. Compound A is a non-solvent for the polyethylene resin. When the non-solvent is heated to the boiling point of this compound, this compound cannot dissolve the polyethylene resin to form a homogeneous solution, but can only exert a swelling effect on the polyethylene resin. Compound A is at least one of dimethyl phthalate, dioctyl phthalate, ethylene glycol diacetate, dimethyl carbonate, palm oil, and glyceryl triacetate. The content of compound B in the solvent system is much higher than the content of compound A. Therefore, under the subsequent relatively high temperature action, the polyethylene resin can be sufficiently dissolved and dispersed in the solvent system to ensure that the casting solution has an appropriate solid content.

[0061] Compared with selecting a single solvent as the solvent system, the present invention uses a composite of a solvent and a non-solvent as the corresponding solvent system, and such a solvent system has several advantages as follows.

[0062] 1. Small pores with small pore sizes are likely to appear in the green film formed after the phase separation of the liquid film is completed, and at the same time, many small pores are formed. This is because when the liquid film undergoes liquid-liquid phase separation and solidification (phase separation and solidification by the thermal method) due to temperature changes, diffusion exchange occurs between the non-solvent and the solvent, further improving the phase separation and solidification rate.

[0063] 2. It is easier to form fibers, enabling the UPE porous membrane to have higher tensile strength and good mechanical performance. This is because the faster phase separation rate makes it easier for crystal nuclei to precipitate, and fibers are produced along the crystal nuclei, facilitating fiber formation.

[0064] Of course, if necessary, antioxidants, nucleating agents, fillers, and similar substances can be used as additives in the present invention, thereby further improving certain performance of the UPE porous membrane. The polyethylene resin and the corresponding solvent system (including Compound A and Compound B) can be stirred and mixed at a temperature of 100 - 140°C for 10 - 24 hours to form the corresponding mixture.

[0065] Next, the mixture is put into an extruder and heated and melt-kneaded at a temperature of 150 - 260°C (preferably 200 - 255°C) for 10 - 60 minutes of heating and melt-kneading, ensuring that the polyethylene resin is completely melted in the corresponding solvent system to obtain a casting solution with a uniform and stable shape. The solid content of the casting solution of the present invention is preferably 10% - 20%. If the solid content is too low, the tensile strength of the final membrane is too low, the mechanical strength is poor, and it cannot meet practical requirements. If the solid content is too high, the viscosity of the casting solution is too high, the requirements for the mechanical equipment used are too high, and the production cost is too high, making mass production impossible.

[0066] Thereafter, through die extrusion (die forming), a flat liquid film is formed on a carrier (the carrier may be a roll or other carrier). The die extrusion temperature in the present invention is 200 - 250°C. Preferably, the highest temperature in the extruder is at least 5°C higher than the die extrusion temperature, ensuring that the temperature of each region of the liquid film during extrusion is approximately the same, which is beneficial for subsequent phase separation and solidification, making the phase separation more uniform, and then an ideal membrane structure can be obtained, ensuring that it is beneficial for the formation of a symmetric membrane.

[0067] Furthermore, the liquid film is placed in a temperature environment of 15 to 50°C for phase separation solidification. At relatively high temperatures, a single uniform solution can be formed between the solvent system and the polyethylene resin. However, as the system temperature decreases, the uniform solution becomes turbid, the polyethylene resin gradually precipitates, and subsequently, a phase separation solidification phenomenon occurs. The phase separation temperatures on both sides of the liquid film in the present invention are relatively low (15 to 50°C), the liquid film is prone to rapid phase separation, and is prone to forming a relatively large number of crystalline films (nanopores and small pores are more likely to form a higher specific surface area), and a relatively large number of pores (high porosity) and fibrillation become more obvious. However, when the solvent system is a combination of a solvent and a non-solvent, in addition to phase separation due to temperature changes and diffusion exchange between the solvent and the non-solvent, the phase separation solidification rate is further accelerated, thereby forming a small pore membrane (the faster the phase separation rate, the smaller the pore diameter formed), that is, the nano-membrane required in the present invention. The UPE porous membrane finally formed by the present invention is a symmetric membrane. To form a symmetric membrane, it is necessary that the degree of phase separation on both sides of the liquid film is basically the same. As a result, the pore structures of the two outer surfaces of the porous membrane are similar, and the fiber structures are similar. As one of the key points of the present invention, the combined action of the two conditions ensures that the structures of the two outer surfaces of the membrane are similar. The first condition is that the temperature difference between the liquid film carrier side (the carrier may be a roll or other carriers) and the liquid film air side is 5 to 20°C. For example, if the temperature of the air side is 20°C, the temperature of the carrier side can be set to 30°C. At this time, since the temperatures on both sides of the liquid film are different and the heat transfer rates on both sides are also different, in that case, the phase separation rates on both sides of the liquid film are different. The second condition is that during the phase separation solidification process, the carrier side and the air side of the liquid film are converted with each other at least once. One conversion means that when the liquid film moves on the carrier, when the liquid film is exchanged from one carrier to another carrier, the two sides of the liquid film are converted with each other. At this time, the original air side of the liquid film becomes the carrier side of the liquid film, and the roller side becomes the air side. The number of transfers is preferably 1 to 3 times. By the mutual conversion of the two sides of the liquid film between the carrier side and the air side, with an appropriate time action, it is ensured that the phase separation on both sides of the liquid film is almost the same, and thereby a symmetric green film can be formed.When performing phase separation curing, the selection of factors such as the high or low temperature of phase separation curing and the time of phase separation curing is extremely important. These factors determine the rate of phase separation curing and ultimately determine whether an ideal membrane structure and a membrane with a desired pore size can be obtained. The phase separation curing time is 2 - 50 s, and since the time is relatively short, it is advantageous for obtaining the UPE porous membrane with the ideal membrane structure required by the applicants.

[0068] After the phase separation of the liquid membrane is completed, a green film is formed. A certain number of pores with a certain pore diameter already appear on the two surfaces of the green film, and the pore diameters on the two surfaces are approximately the same. In order to further obtain the UPE porous membrane with the required membrane pore diameter, the present invention subjects the green film to a stretching treatment. The conventional stretching technique first performs longitudinal stretching and then transverse stretching. However, as a result of research, it has been found that when treating the green film by the conventional stretching technique, the pores on the green film are likely to partially collapse or deform, and ultimately the UPE porous membrane with the required membrane structure cannot be obtained. Therefore, in the present invention, the stretching treatment is performed synchronously, that is, the green film is subjected to transverse stretching and longitudinal stretching simultaneously. The temperature during transverse stretching and longitudinal stretching is 60 - 150 °C, the multiple of transverse stretching is 1 - 10 times, and the multiple of longitudinal stretching is 1 - 10 times. The advantage of such stretching is that not only the required membrane pore diameter of the present invention can be obtained, but also the stretching strength of the membrane is increased, and at the same time, the pores are less likely to collapse or deform, which is ultimately advantageous for obtaining the UPE filtration membrane with the required membrane structure of the present invention. Preferably, the ratio of the longitudinal stretching multiple to the transverse stretching multiple is 0.8 - 2, the transverse stretching speed is 5% / s - 100% / s, and the longitudinal stretching speed is 5% / s - 100% / s, thereby further enhancing the uniformity of the pore diameter inside the membrane and ensuring the symmetry of the membrane.

[0069] After the stretching is completed, the first heat setting is carried out synchronously. The function of the first heat setting is to initially shape the raw film after stretching, ensure that the film pores hardly change, and at the same time remove the internal stress caused by stretching. The temperature during the first heat setting is 100 - 180 °C, and the time is 20 - 90 s. Subsequently, extraction is carried out, and the solvent system is removed from the raw film by the extractant to obtain the original film. The extractant is at least one of dichloromethane, acetone, methanol, ethanol, glycerin, tetrafluoroethane, and isopropanol. The extraction temperature is 5 - 25 °C, and the extraction time is 1 - 5 h. By selecting appropriate extractants and extraction conditions, it is ensured that the solvent system is completely removed from the raw film, and at the same time, the time required for extraction is short. After the extraction is completed, the second heat setting is carried out on the original film. The temperature during the second heat setting is 10 - 40 °C higher than the temperature during the first heat setting. The function of the second heat setting is to remove the internal stress caused by extraction while finally shaping the film pores of the original film, ensure that the film pores hardly change, and obtain a UPE porous membrane with the required pore structure. The UPE porous membrane of the present invention is a symmetric membrane, has a uniform pore size distribution on the membrane, has excellent collection performance for impurity particles, has a high cutoff efficiency, and at the same time has a high specific surface area and a high porosity, with a small pressure loss, and is particularly suitable for applications in the photoresist field.

[0070] As a further improvement of the present invention, there is provided the use of a UPE porous membrane for filtering a photoresist.

[0071] After using this UPE porous membrane as a capsule or a cartridge filter core, due to the high specific surface area and high porosity of the UPE porous membrane, the gas generated during the process of filtering the photoresist is easily discharged, the bubble content in the filtered photoresist is reduced, the bubbles will not have an adverse effect on the properties of the photoresist, and it is ensured that a photoresist with excellent properties can be obtained. Therefore, the UPE porous membrane of the present invention is particularly suitable for application in the field of photoresist filtration. When performing photoresist filtration, any outer surface of this UPE porous membrane can be used as the liquid supply surface, and there is no need to guide to use a specific outer surface as the liquid supply surface to avoid the situation that effective filtration cannot be carried out due to the user's operation error. This UPE porous membrane has excellent collection performance for various impurity particles in the photoresist, has high filtration accuracy, at the same time has a relatively high pollution capacity, has a relatively long service life, and has a high economic effect.

[0072] As a further improvement of the present invention, it includes a center rod and a UPE porous membrane located on the outer periphery of the center rod. The UPE porous membrane is folded to form wrinkles. The wrinkles have a wrinkle valley close to the center rod side and a wrinkle peak on the outer periphery. The UPE porous membrane has an upstream side and a downstream side. The upstream side communicates with the inlet, and the downstream side communicates with the outlet. It is a folded filter core with a UPE porous membrane, and the UPE porous membrane is the UPE porous membrane described in any one of Technical Solutions 1-12. The membrane area of the UPE porous membrane in the folded filter core is 0.1-2 m 2 is.

[0073] When applying a filter core, especially a capsule filter core, at the end of the photoresist, since its outer shell dimensions are generally small, the membrane area filled inside is also generally small. The membrane area of the UPE porous membrane in the capsule filter core is often 0.1-0.6 m 2 is, and the membrane area of the UPE porous membrane in the cartridge filter core is also generally 2 m 2It does not exceed. Compared with the UPE film with low specific surface area and low porosity, the high specific surface area UPE film of the present invention can achieve a lower pressure at the same flow rate due to its high aperture ratio. In this way, the high surface area UPE film can achieve very small pores (filtering nanoparticles) for photoresists with a relatively high viscosity, and at the same time can meet the demand for flow rate, with relatively small pressure loss, and can also obtain a good flow rate when filtering nanoparticles, and has a higher economic effect.

[0074] The beneficial effect of the present invention is that the UPE porous membrane provided by the present invention is a symmetric membrane having a membrane body structure optimized from conventional filter membrane materials, including a first porous outer surface, a second porous outer surface, and a main body located between the first porous outer surface and the second porous outer surface. The specific surface area of the UPE porous membrane is 35 m 2 / g or more. The first porous outer surface contains several branched continuous first fibers. The space between adjacent continuous first fibers surrounds and forms a first pore. The first fibers along the thickness direction are laminated with each other, and the average diameter of the first fibers is 10 - 60 nm. The UPE porous membrane with high specific surface area has excellent collection performance for nanoparticles in the filtration process, can adsorb various fine particle substances, and has a high blocking efficiency. In addition, this UPE porous membrane is particularly suitable for modification as a base membrane, has a high modification effect, and is suitable for application in the field of photoresist filtration. The manufacturing method provided by the present invention can conveniently, quickly, and effectively manufacture the above UPE porous membrane.

Brief Description of the Drawings

[0075]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0076] In order to more clearly explain the overall concept of the present application, the following will be shown in detail as embodiments. Example 1

[0077] The manufacturing method of the high specific surface area UPE porous membrane includes the following steps.

[0078] S1: Add polyethylene resin to the solvent system composed of compound A and compound B and stir and mix. After uniformly mixing, a mixed material is formed. The mixed material includes a substance composition of 12 parts by weight of polyethylene resin, 5 parts by weight of compound A, and 72 parts by weight of compound B. The polyethylene resin consists of ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more and accounting for 83% by mass, and high-density polyethylene with a mass average molecular weight of 1 million to 2 million and a density of 0.92 - 0.98 g / cm 3 and accounting for 17% by mass. Compound A is dioctyl phthalate, and compound B is white oil.

[0079] S2: Heat and melt-knead the mixed material under the condition of a temperature of 215°C to form a casting solution, and then extrude it through a die to form a liquid film on the carrier. The die extrusion temperature is 205°C.

[0080] S3: Set the temperature on the liquid film carrier side to 25 °C, set the air side temperature to 20 °C. After 4 s of phase separation and solidification, both sides of the liquid film are converted, that is, the side originally close to the carrier of the liquid film becomes the side close to the air (the phase separation temperature changes from 25 °C to 20 °C), and the side originally close to the air of the liquid film becomes the side close to the carrier (the temperature changes from 20 °C to 25 °C). Continue the phase separation and solidification for 4 s. After the phase separation and solidification is completed, a green film is formed.

[0081] S4: Then, stretch the green film, and perform transverse stretching and longitudinal stretching simultaneously. The temperature during transverse stretching and longitudinal stretching is 80 °C, the transverse stretching ratio is 3 times, the longitudinal stretching ratio is 3 times, the transverse stretching speed is 20% / s, the longitudinal stretching speed is 20% / s. After the stretching is completed, perform the first heat setting. The temperature during the first heat setting is 130 °C, and the time is 65 s.

[0082] S5: Use an extraction agent to extract the solvent system, remove the solvent system from the green film to obtain a raw film. In S5, the extraction agent is dichloromethane, the extraction temperature is 15 °C, and the extraction time is 3 h.

[0083] S6: Perform the second heat setting on the raw film. The temperature during the second heat setting is 160 °C, and the time is 45 s to produce a UPE porous membrane. Example 2

[0084] The method for manufacturing a UPE porous membrane with a high specific surface area includes the following steps.

[0085] S1: Add polyethylene resin to a solvent system composed of compound A and compound B, stir and mix. After uniform mixing, a mixed material is formed. The mixed material contains a substance composition of 14 parts by weight of polyethylene resin, 8 parts by weight of compound A, and 75 parts by weight of compound B. The polyethylene resin consists of ultra-high molecular weight polyethylene with a mass average molecular weight of more than 3 million and accounting for 80% by mass, and high-density polyethylene with a mass average molecular weight of 1 - 2 million and accounting for 20% by mass and a density of 0.92 - 0.98 g / cm 3 ³. Compound A is ethylene glycol diacetate, and compound B is paraffin oil.

[0086] S2: Heat and melt-knead the mixed material under the condition of a temperature of 220 °C to form a casting film solution, then extrude it through a die to form a liquid film on the carrier, and the die extrusion temperature is 210 °C.

[0087] S3: Set the temperature on the carrier side of the liquid film to 30 °C and the temperature on the air side to 20 °C. After phase separation and solidification for 5 s, both sides of the liquid film are converted, that is, the side originally close to the carrier of the liquid film becomes the side close to the air (the phase separation temperature changes from 30 °C to 20 °C), and the side originally close to the air of the liquid film becomes the side close to the carrier (the temperature changes from 20 to 30 °C). Continue phase separation and solidification. After 10 s of phase separation, both sides of the liquid film are converted again, that is, at this time, the side of the liquid film close to the air changes to the side close to the carrier again (the phase separation temperature changes from 20 °C to 30 °C). On the other hand, at this time, the side of the liquid film close to the carrier changes to the side close to the air again (the phase separation temperature changes from 30 °C to 20 °C). Finally, phase separation is carried out for 5 s. After the completion of phase separation and solidification, a green film is formed.

[0088] S4: Then, perform stretching treatment on the green film, and perform transverse stretching and longitudinal stretching simultaneously. The temperature during transverse stretching and longitudinal stretching is 85 °C. The transverse stretching ratio is 4 times, the longitudinal stretching ratio is 4 times, the transverse stretching speed is 25% / s, and the longitudinal stretching speed is 25% / s. After the stretching is completed, perform the first heat setting. The temperature during the first heat setting is 135 °C, and the time is 60 s.

[0089] S5: Use an extraction agent to extract the solvent system, remove the solvent system from the green film to obtain a raw film. The extraction agent is acetone, the extraction temperature is 20 °C, and the extraction time is 2.5 h.

[0090] S6: Perform the second heat setting on the raw film. The temperature during the second heat setting is 150 °C, and the time is 75 s to manufacture a UPE porous membrane. Example 3

[0091] The manufacturing method of a UPE porous membrane with a high specific surface area includes the following steps.

[0092] S1: Add a polyethylene resin to a solvent system composed of Compound A and Compound B, stir and mix them. After uniform mixing, a mixed material is formed. The mixed material contains a substance composition in parts by weight of polyethylene resin: 16 parts, Compound A: 12 parts, and Compound B: 78 parts. The polyethylene resin consists of ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more accounting for 75% by mass and high-density polyethylene with a mass average molecular weight of 1 - 2 million and a density of 0.92 - 0.98 g / cm 3 consisting of polyethylene resin. Compound A is dimethyl phthalate, and Compound B is hydraulic oil.

[0093] S2: Heat and melt-knead the mixed material under the condition of a temperature of 225 °C to form a casting solution. Then extrude it through a die to form a liquid film on the carrier. The die extrusion temperature is 215 °C.

[0094] S3: Set the temperature on the carrier side of the liquid film to 32 °C and the temperature on the air side to 20 °C. After phase separation and solidification for 6 s, the two sides of the liquid film are converted, that is, the side originally close to the carrier of the liquid film becomes the side close to the air (the phase separation temperature changes from 32 °C to 20 °C), and the side originally close to the air of the liquid film becomes the side close to the carrier (the temperature changes from 20 to 32 °C). Continue phase separation and solidification. After 12 s of phase separation, the two sides of the liquid film are converted again, that is, at this time, the side of the liquid film close to the air changes back to the side close to the carrier again (the phase separation temperature changes from 20 °C to 32 °C). On the other hand, at this time, the side of the liquid film close to the carrier changes back to the side close to the air again (the phase separation temperature changes from 32 °C to 20 °C). Finally, phase separation is carried out for 6 s. After the completion of phase separation and solidification, a green film is formed.

[0095] S4: Then, perform stretching treatment on the green film, and perform transverse stretching and longitudinal stretching simultaneously. The temperature during transverse stretching and longitudinal stretching is 90 °C. The transverse stretching ratio is 4 times, the longitudinal stretching ratio is 5 times. The transverse stretching speed is 40% / s, and the longitudinal stretching speed is 50% / s. After the stretching is completed, perform the first heat setting. The temperature during the first heat setting is 140 °C, and the time is 55 s.

[0096] S5: Use an extraction agent to extract the solvent system, remove the solvent system from the green film to obtain a raw film. The extraction agent is isopropanol, the extraction temperature is 23 °C, and the extraction time is 2 h.

[0097] S6: Heat-set the original film for the second time. The temperature during the second heat-setting is 165 °C, and the time is 60 s to produce a UPE porous membrane. Example 4

[0098] The method for manufacturing a UPE porous membrane with a high specific surface area includes the following steps.

[0099] S1: Add a polyethylene resin to a solvent system composed of Compound A and Compound B, stir and mix. After uniform mixing, a mixed material is formed. The mixed material contains a material composition with parts by weight of polyethylene resin: 18 parts, Compound A: 17 parts, and Compound B: 81 parts. The polyethylene resin consists of ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more and accounting for 72% by mass, and high-density polyethylene with a mass average molecular weight of 1 - 2 million and a density of 0.92 - 0.98 g / cm 3 which consists of high-density polyethylene. Compound A is palm oil, and Compound B is castor oil.

[0100] S2: Heat and melt-knead the mixed material under the condition of a temperature of 235 °C to form a casting solution. Then extrude it through a die to form a liquid film on a carrier. The die extrusion temperature is 225 °C.

[0101] S3: Set the temperature on the carrier side of the liquid film to 35 °C and the temperature on the air side to 25 °C. After phase separation and solidification for 15 s, the two sides of the liquid film are converted, that is, the side originally close to the carrier of the liquid film becomes the side close to the air (the phase separation temperature changes from 35 °C to 25 °C), and the side originally close to the air of the liquid film becomes the side close to the carrier (the temperature changes from 25 to 35 °C). Continue phase separation and solidification for 15 s. After the completion of phase separation and solidification, a green film is formed.

[0102] S4: Then, perform stretching treatment on the green film, simultaneously perform transverse stretching and longitudinal stretching. The temperature during transverse stretching and longitudinal stretching is 80 °C. The transverse stretching ratio is 6 times, the longitudinal stretching ratio is 5 times. The transverse stretching speed is 60% / s, and the longitudinal stretching speed is 50% / s. After the stretching is completed, perform the first heat-setting. The temperature during the first heat-setting is 145 °C, and the time is 50 s.

[0103] S5: Extract the solvent system using an extractant, remove the solvent system from the raw film to obtain a primary film. In S5, the extractant is glycerin, the extraction temperature is 10 °C, and the extraction time is 4 h.

[0104] S6: Thermally shape the primary film for the second time. The temperature during the second thermal shaping is 170 °C and the time is 65 s to produce a UPE porous membrane. Example 5

[0105] A method for manufacturing a UPE porous membrane with a high specific surface area includes the following steps.

[0106] S1: Add a polyethylene resin to a solvent system composed of Compound A and Compound B and stir and mix. After uniformly mixing, a mixed material is formed. The mixed material includes a substance composition by weight parts of polyethylene resin: 20 parts, Compound A: 2 parts, and Compound B: 84 parts. The polyethylene resin consists of ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more accounting for 70% by mass and high-density polyethylene with a mass average molecular weight of 1 - 2 million and a density of 0.92 - 0.98 g / cm 3 ³ consisting of 30% by mass. Compound A is glyceryl triacetate, and Compound B is decahydronaphthalene.

[0107] S2: Heat and melt-knead the mixed material under the condition of a temperature of 245 °C to form a casting solution, and then extrude it through a die to form a liquid film on a carrier. The die extrusion temperature is 230 °C.

[0108] S3: Set the temperature on the liquid film carrier side to 40 °C, set the air side temperature to 25 °C. After 9 s of phase separation and solidification, both sides of the liquid film are converted, that is, the side originally close to the carrier of the liquid film becomes the side close to the air (the phase separation temperature changes from 40 °C to 25 °C), and the side originally close to the air of the liquid film becomes the side close to the carrier (the temperature changes from 25 °C to 40 °C). Continue the phase separation and solidification. After 18 s of phase separation, both sides of the liquid film are converted again, that is, at this time, the side of the liquid film close to the air changes to the side close to the carrier again (the phase separation temperature changes from 20 °C to 40 °C). On the other hand, at this time, the side of the liquid film close to the carrier changes to the side close to the air again (the phase separation temperature changes from 40 °C to 25 °C). Finally, phase separation is carried out for 9 s. After the phase separation and solidification are completed, a green film is formed.

[0109] S4: Then, stretch the green film, and perform transverse stretching and longitudinal stretching simultaneously. The temperature during transverse stretching and longitudinal stretching is 110 °C. The transverse stretching ratio is 6 times, the longitudinal stretching ratio is 6 times, the transverse stretching speed is 60% / s, and the longitudinal stretching speed is 60% / s. After the stretching is completed, perform the first heat setting. The temperature during the first heat setting is 150 °C, and the time is 45 s.

[0110] S5: Use an extracting agent to extract the solvent system, remove the solvent system from the green film to obtain a raw film. The extracting agent is ethanol, the extraction temperature is 8 °C, and the extraction time is 4.5 h.

[0111] S6: Perform the second heat setting on the raw film. The temperature during the second heat setting is 180 °C, and the time is 50 s to manufacture a UPE porous membrane. Example 6

[0112] The method for manufacturing a UPE porous membrane with a high specific surface area includes the following steps.

[0113] S1: Add a polyethylene resin to a solvent system composed of compound A and compound B, stir and mix them. After uniformly mixing, a mixed material is formed. The mixed material contains a substance composition of 22 parts by weight of polyethylene resin and 89 parts by weight of compound B. Compound B is a castor oil extract. The polyethylene resin consists of ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more accounting for 65% by mass, and high-density polyethylene with a mass average molecular weight of 1 - 2 million and a density of 0.92 - 0.98 g / cm 3 consisting of

[0114] S2: Heat and melt-knead the mixed material under the condition that the temperature is 255 °C to form a casting solution. Then extrude it through a die to form a liquid film on a carrier. The die extrusion temperature is 245 °C,

[0115] S3: Set the temperature on the carrier side of the liquid film to 50 °C and the temperature on the air side to 30 °C. After phase separation and solidification for 24 s, both sides of the liquid film are converted, that is, the side originally close to the carrier of the liquid film becomes the side close to the air (the phase separation temperature changes from 50 °C to 30 °C), and the side originally close to the air of the liquid film becomes the side close to the carrier (the temperature changes from 30 °C to 50 °C). Continue phase separation and solidification for 24 s. After the completion of phase separation and solidification, a green film is formed.

[0116] S4: Then, perform stretching treatment on the green film, simultaneously perform transverse stretching and longitudinal stretching. The temperature during transverse stretching and longitudinal stretching is 120 °C. The transverse stretching ratio is 9 times, and the longitudinal stretching ratio is 9 times. The transverse stretching speed is 80% / s, and the longitudinal stretching speed is 80% / s. After the stretching is completed, perform the first heat setting. The temperature during the first heat setting is 160 °C, and the time is 40 s.

[0117] S5: Use an extraction agent to extract the solvent system and remove the solvent system from the green film to obtain a raw film. The extraction agent is isopropanol, the extraction temperature is 13 °C, and the extraction time is 3.5 h.

[0118] S6: Perform the second heat setting on the raw film. The temperature during the second heat setting is 170 °C, and the time is 80 s to manufacture a UPE porous membrane.

[0119] One: Structural characteristics

[0120] The UPE porous membranes obtained in each example were morphologically characterized using a scanning electron microscope, and then the desired data were obtained. The specific results are as shown in the following table. JPEG0007713266000001.jpg73149JPEG0007713266000002.jpg44150

[0121] As is clear from the above table, in the UPE porous membranes manufactured in Examples 1 to 6 of the present invention, there are appropriate numbers and appropriate pore diameters of first pores on the first porous outer surface, and appropriate numbers and appropriate pore diameters of second pores on the second porous outer surface. The existence of such a structure guarantees the stability of the first pores and the second pores, making shrinkage and collapse less likely to occur. Therefore, it is advantageous for ensuring that the membrane has a stable flow rate and that the flow rate change of the membrane during use is small. Moreover, with a relatively large flow rate, it facilitates the rapid passage of the fluid through the porous membrane, shortens the filtration time, and has a relatively large tensile strength to meet the requirements of actual applications. At the same time, the tensile strength of the film can be further increased to meet the requirements of industrialization. The pore distribution on the first porous outer surface and the pore distribution on the second porous outer surface are relatively similar, indicating that this UPE porous membrane is a symmetric membrane. JPEG0007713266000003.jpg55152

[0122] All the UPE porous membranes manufactured in Examples 1 to 6 of the present invention have relatively high specific surface area, internal surface area per membrane area, high porosity, and appropriate thickness, which are advantageous for subsequent photoresist filtration and can obtain a photoresist with excellent performance.

[0123] Performance Characteristics

[0124] Water flow rate test (the test apparatus is as shown in Figure 5)

[0125] Experimental Procedure

[0126] Step 1: Attach the test sample after IPA wetting to the bracket for vacuum filtration, close valve 2 on the vacuum filtration holder, open valve 1, start the vacuum pump, adjust the pressure to the test pressure of 0.03 MPa, and then close valve 1.

[0127] Step 2: Pour 50 ml of the test liquid (water) into the plastic graduated cylinder of the bracket for vacuum filtration, open valve 2, start timing from a certain scale, and stop timing until another scale.

[0128] Step 3: When the test is completed, record the value displayed on the stopwatch. If all the test liquid has passed through the filter membrane, close valve 2 on the bracket and take out the sample.

[0129] Use a universal tensile testing machine to test the tensile strength and elongation at break of each sample. JPEG0007713266000004.jpg52152

[0130] All the UPE porous membranes manufactured in Examples 1 to 6 of the present invention have a large filtration rate, low time cost, and at the same time have a large tensile strength and elongation at break, can meet the requirements of various assembly and processing, and can realize full-scale industrialization.

[0131] Filtration accuracy test: The test of the blocking efficiency for the filter membrane obtained in each example was carried out.

[0132] Experimental equipment: Tianjin Logan particle counter KB-3

[0133] Experimental preparation: Assemble the experimental device according to Figure 6, ensure the cleanliness of the device, wash the device with ultrapure water, collect a sample with a diameter of 47 mm, mount it on a butterfly filter, and ensure that the assembled filter has good airtightness.

[0134] Experimental procedure: Pour the test liquid into the tank, pay attention to the exhaust of the butterfly filter, pressurize it up to 10 kPa, catch the downstream filtrate of the butterfly using a clean bottle, and test the number of particles in the filtrate and the stock solution with a particle counter.

[0135] JPEG0007713266000005.jpg1783

[0136] Where: η───Blocking efficiency, %, n0───Number of particles in the stock solution, average value of 5 sets of counts, number, n1───Number of particles in the filtrate, average value of 5 sets of counts, number

[0137] The test results of the blocking efficiency of each example are as follows. JPEG0007713266000006.jpg76164

[0138] As is clear from the above table, the UPE porous membranes produced in Examples 1 to 6 of the present invention have high filtration accuracy, and their blocking efficiencies are all 95% or more. They have a strong collection ability for impurity particles (for example, standard gold particle impurities), meet the actual industrialization requirements, and are particularly suitable for application in the photoresist field.

[0139] After the samples obtained in Examples 1 to 6 were fabricated on the filter core (membrane area 1.3 m 2 ), first wet the membrane pieces with IPA, then flow the filter core at a constant flow rate using deionized water at 20 °C, test the pressure before and after the deionized water flows through the filter core, and obtain the pressure loss of the corresponding filter core. JPEG0007713266000007.jpg38152

[0140] As is clear from the above table, after manufacturing the filter core using the UPE porous membrane of the present invention, the pressure loss during filtration is small. Therefore, when filtering nanoscale impurity particles, it still has a relatively fast filtration speed, ensuring high economic efficiency, and is particularly suitable for application to the filtration of high-viscosity photoresist.

[0141] What has been described above is merely a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions belonging to the idea of the present invention fall within the protection scope of the present invention. It should be pointed out that for those skilled in the art of this technology, some improvements and refinements can be made without departing from the principle of the present invention, and these improvements and refinements should also be regarded as falling within the protection scope of the present invention.

Claims

1. A high specific surface area UPE porous membrane including a first porous outer surface, a second porous outer surface, and a body located between the first porous outer surface and the second porous outer surface, wherein the body has a non-directional meandering passage, and The specific surface area of the UPE porous membrane is 35 m ２ / g or more, the first porous outer surface includes several dendritic continuous first fibers, and the space between adjacent continuous first fibers surrounds to form a first pore, and the first fibers along the thickness direction are laminated with each other, and the average diameter of the first fibers is 10 - 60 nm, the UPE porous membrane is a symmetric membrane, and the polyolefin composition constituting the UPE porous membrane contains at least ultra-high molecular weight polyethylene having a mass average molecular weight of 3 million or more, the ratio between the IPA initial bubble point and the IPA complete foaming point of the UPE porous membrane is 0.4 or more, and the IPA complete foaming point of the UPE porous membrane is 0.2 MPa or more. A high specific surface area UPE porous membrane characterized by this.

2. The first porous outer surface has several circular first pores, and the area ratio of the first pores on the first porous outer surface is 30% - 70%, and the average pore diameter of the first pores is 1 - 150 nm. The high specific surface area UPE porous membrane according to Claim 1, characterized by this.

3. The thickness of the UPE porous membrane is 1 - 30 μm, the porosity of the UPE porous membrane is 45% - 85%, and the surface area inside the membrane per unit membrane area is 0.4 - 0.

8. The high specific surface area UPE porous membrane according to Claim 1, characterized by this.

4. The specific surface area of the UPE porous membrane is 40 - 80 m ２ / g, the porosity of the UPE porous membrane is 50% - 75%, and the thickness of the UPE porous membrane is 5 - 20 μm. The UPE porous membrane with a high specific surface area according to claim 3, characterized by this.

5. The second porous outer surface includes several dendritic continuous second fibers, and the space between adjacent continuous second fibers surrounds to form a second pore, and the average diameter of the second fibers is 10 - 60 nm. The high specific surface area UPE porous membrane according to Claim 1, characterized by this.

6. The ratio of the average diameter of the second fibers to the average diameter of the first fibers is 0.7 - 1.5, the second pores are circular, and the area ratio of the second pores on the second porous outer surface is 30% - 70%. The high specific surface area UPE porous membrane according to Claim 5, characterized by this.

7. The average pore diameter of the second pores is 1 - 150 nm, and the ratio of the average pore diameter of the second pores to the average pore diameter of the first pores is 0.78 - 1.

35. The high specific surface area UPE porous membrane according to Claim 5, characterized by this.

8. After the UPE porous membrane is left standing for 1 hour under the condition that the temperature is 120 °C, its shrinkage rate is 5% or less, the compression rate of the UPE porous membrane is less than 15%, and the pore closing temperature of the UPE porous membrane is higher than 120 °C. The UPE porous membrane with a high specific surface area according to claim 1, characterized in that.

9. The blocking efficiency of the UPE porous membrane against impurity particles with a particle size of 1 - 150 nm is greater than 95%, 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 flow through a porous membrane with a diameter of 47 mm does not exceed 500 s, The tensile strength of the UPE porous membrane is 20 - 100 MPa, and the elongation at break is 200% - 800%. The UPE porous membrane with a high specific surface area according to claim 1, characterized in that.

10. S1: Add a polyethylene resin to a solvent system composed of compound A and compound B and stir and mix. After uniformly mixing, a mixed material is formed. Among them, the polyethylene resin contains at least one ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more. Compound A is a non-solvent for the polyethylene resin, and compound B is a solvent for the polyethylene resin. The mixed material contains a substance composition in parts by weight of polyethylene resin: 10 - 25 parts, compound A: 0 - 20 parts, and compound B: 70 - 90 parts. Compound A is at least one of dimethyl phthalate, dioctyl phthalate, ethylene glycol diacetate, dimethyl carbonate, palm oil, and glyceryl triacetate. Compound B is at least one of paraffin oil, white oil, hydraulic oil, decahydronaphthalene, castor oil extract, and castor oil. S2: Heat and melt-knead the mixed material under the condition of a temperature of 150 - 260 °C to form a casting solution. Then, extrude it through a die to form a liquid film on a carrier. The die extrusion temperature is 200 - 250 °C. S3: Phase-separate and solidify the liquid film in a temperature environment of 15 - 50 °C. The phase-separating and solidifying time is 2 - 50 s to form a green film. When phase-separating and solidifying, the temperature difference between the carrier side and the air side of the liquid film is 5 - 20 °C, and during the process of phase-separating and solidifying, the carrier side and the air side of the liquid film are converted with each other at least once. S4: Then, perform stretching treatment on the green film and perform the first heat setting after the stretching is completed. S5: Use an extraction agent to extract the solvent system and remove the solvent system from the green film to obtain a raw film. S6: Secondarily thermosetting the original film to produce a UPE porous membrane, the method for producing a high specific surface area UPE porous membrane according to any one of claims 1-9, characterized by including this.

11. The polyethylene resin is composed of ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more and accounting for 65% - 85% by mass, and high-density polyethylene with a mass average molecular weight of 1 - 2 million and a density of 0.92 - 0.98 g / cm ３ which is characterized in that it consists of the high-density polyethylene as described in claim 10, and is a method for manufacturing a UPE porous membrane with a high specific surface area.

12. In S4, stretching the green film, simultaneously performing transverse stretching and longitudinal stretching on the green film, the temperature during transverse stretching and longitudinal stretching is 60 - 150 °C, the multiple of transverse stretching is 1 - 10 times, and the multiple of longitudinal stretching is 1 - 10 times, the method for producing a high specific surface area UPE porous membrane according to claim 10, characterized by this.

13. In S4, stretching the green film, the ratio of the multiple of longitudinal stretching to the multiple of transverse stretching is 0.8 - 2, the speed of transverse stretching is 5% / s - 100% / s, and the speed of longitudinal stretching is 5% / s - 100% / s, the method for producing a high specific surface area UPE porous membrane according to claim 12, characterized by this.

14. In S5, the extraction agent is at least one of dichloromethane, acetone, methanol, ethanol, glycerin, tetrafluoroethane, isopropanol, the extraction temperature is 5 - 25 °C, and the extraction time is 1 - 5 h, the method for producing a high specific surface area UPE porous membrane according to claim 10, characterized by this.

15. The temperature during the first thermosetting is 100 - 180 °C, the time is 20 - 90 s, the temperature during the second thermosetting is 10 - 40 °C higher than the temperature during the first thermosetting, and the time is 20 - 90 s, the method for producing a high specific surface area UPE porous membrane according to claim 10, characterized by this.

16. The UPE porous membrane is used for filtering photoresist, the use of the high specific surface area UPE porous membrane according to any one of claims 1-9, characterized by this.

17. Including a center rod and a UPE porous membrane located on the outer periphery of the center rod, the UPE porous membrane is folded to form wrinkles, the wrinkles have a trough near the center rod side and a peak on the outer periphery, the UPE porous membrane has an upstream side and a downstream side, the upstream side communicates with the inlet, and the downstream side communicates with the outlet, a folded filter core with a UPE porous membrane. The membrane area of the UPE porous membrane in the foldable filter core is 0.1 - 2 m ２ The foldable filter core with a UPE porous membrane according to any one of claims 1 - 9, characterized in that it is so.

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