CN113694745B - UPE porous membrane with high specific surface area and preparation method and application thereof - Google Patents

UPE porous membrane with high specific surface area and preparation method and application thereof Download PDF

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CN113694745B
CN113694745B CN202111084321.0A CN202111084321A CN113694745B CN 113694745 B CN113694745 B CN 113694745B CN 202111084321 A CN202111084321 A CN 202111084321A CN 113694745 B CN113694745 B CN 113694745B
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porous membrane
upe
membrane
surface area
film
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CN113694745A (en
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陈梦泽
吕海江
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Zhang Chunyan
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Priority to PCT/CN2022/118659 priority patent/WO2023040880A1/en
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D71/00Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06Organic material
    • B01D71/26Polyalkenes
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D67/00Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002Organic membrane manufacture
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D69/00Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02ATECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124Water desalination
    • Y02A20/131Reverse-osmosis

Abstract

The invention provides a UPE porous membrane with high specific surface area, a preparation method and application thereof, wherein the porous membrane comprises a first porous outer surface, a second porous outer surface and a main body positioned between the first porous outer surface and the second porous outer surface, and a non-directional tortuous passage is arranged in the main body; the UPE porous membrane has a specific surface area of not less than 35m 2 G, the specific surface area is high; a plurality of continuous first fibers in a branch shape are arranged on the outer surface of the first porous, and first holes are formed between adjacent continuous first fibers in a surrounding manner; the first fibers in the thickness direction are laminated to each other; the average diameter of the first fiber is 10-60nm; the UPE porous membrane is a symmetrical membrane, and the UPE porous membrane with high specific surface area can carry out adsorption and interception besides interception through membrane holes, has excellent capturing performance on nanoscale fine impurities and has high interception efficiency; the method is suitable for being applied to the field of photoresist filtration; the preparation method provided by the invention can conveniently, rapidly and effectively prepare and obtain the UPE porous membrane.

Description

UPE porous membrane with high specific surface area and preparation method and application thereof
Technical Field
The invention relates to the technical field of membrane materials, in particular to a UPE porous membrane with high specific surface area, a preparation method and application thereof.
Background
The polymer filter membrane is a membrane which is made from organic high molecular polymer as raw material according to a certain process and mainly has the function of filtering and separating. With the development of petroleum industry and science and technology, the application field of the polymer filter membrane is expanding, and the currently applied fields include gas separation, sea water desalination, ultrapure water preparation, waste treatment, artificial organ manufacturing, medicine, food, agriculture, chemical industry and the like; depending on the polymer, the polymer filters may be classified into cellulose polymer filters, polyamide polymer filters, polysulfone polymer filters, polyolefin polymer filters, and the like.
Polyolefin polymer filter membranes mainly refer to olefin filter membranes such as polyethylene filter membranes, polypropylene filter membranes and the like, and the polyolefin polymer filter membranes have excellent physical and chemical properties and have wide application range; for example, ultra high molecular weight polyethylene (UPE) filters are commonly used in the fields of photolithography processing and "wet etching and cleaning" (WEC) applications; for example, a polyethylene filter membrane for semiconductor lithography is described in chinese patent application No. 201480026006.4, which has excellent trapping performance for impurity particles of about 10-50nm size, and long service life, and which is relatively stable in flux over a long period of use.
In the field of photoresist, the purity requirement on the photoresist is strict, because a small amount of tiny impurities in the photoresist can have a great influence on the quality of the photoresist, so that the product after the photoetching cannot meet the requirement of practical application; it is desirable to retain as much as possible the various substances (particles, metal ions, etc.) in the photoresist when the photoresist is filtered by the filter membrane, thereby meeting the requirements of practical applications; however, the efficiency of trapping impurity particles in photoresist by polyolefin filter membranes is generally in the market at present, which also limits the development of polyolefin polymer filter membranes to a certain extent.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention aims to provide a UPE porous membrane with high specific surface area, and a preparation method and application thereof; the UPE porous membrane has high specific surface area, can absorb and retain various impurities besides retaining various impurities through membrane holes, so that various impurities can be captured with high quality, and the retention efficiency is high; is particularly suitable for being applied to the field of photoresist filtration.
In order to achieve the above purpose, the present invention provides the following technical solutions: a UPE porous membrane with high specific surface area comprises a first porous outer surface, a second porous outer surface and a main body positioned between the first porous outer surface and the second porous outer surface, wherein the main body is internally provided with a non-directional tortuous path, and the specific surface area of the UPE porous membrane is not less than 35m 2 /g; the first porous outer surface comprises a plurality of branch-shaped continuous first fibers, and first holes are formed between adjacent continuous first fibers in a surrounding mode; the first fibers in the thickness direction are laminated to each other; the average diameter of the first fiber is 10-60nm; the UPE porous membrane is a symmetrical membrane, and the polyolefin composition forming the UPE porous membrane at least comprises ultra-high molecular weight polyethylene with mass average molecular weight of more than 300 ten thousand.
After the specific surface area of the UPE porous membrane of the invention is tested by the BET method, we have surprisingly found that the specific surface area of the UPE porous membrane is higher and is not lower than 35m 2 Per gram (whereas the specific surface area of the prior UPE porous membrane is generally 25-30m 2 The specific surface area is the total area of the unit mass material (porous membrane in the invention), and the larger the specific surface area is, the larger the total area of UPE porous membrane with certain mass is; the UPE porous membrane of the present invention is illustrated to have the following advantages:
1. in addition to trapping the impurity substances in the resist through the membrane Kong Duiguang, the UPE porous membrane can adsorb various impurity substances through Van der Waals forces and other acting forces; thereby improving the interception efficiency of the filter membrane to various impurities; meanwhile, according to the finding after the experiment, the UPE porous membrane is also provided with a trace of negative electricity after being contacted with the feed liquid, and the UPE porous membrane provided with the negative electricity has stronger adsorptivity; then, the UPE film with high specific surface area has the advantages that under the condition that the charge amount carried by the UPE film with high specific surface area is constant, the UPE film with high specific surface area has large total charge, so the adsorption effect is good, and the capability of retaining impurity substances is stronger; in addition to some metal ions and small-particle impurities, the organic resin substances of the active ingredients in the photoresist are agglomerated in the transportation process and the like (for example, PMMA resin of the active ingredients in the KrF photoresist is easy to agglomerate, and ketones of the active ingredients in the I-line/KrF photoresist are also easy to agglomerate), and the agglomerated active resins have a certain influence on the light refractive index, so that the stability of the photoetching process is influenced, and the photoetching process cannot achieve an ideal result; the charged UPE film with high specific surface area has good adsorption effect on the impurities, ensures the stability of the photoetching process and realizes the ideal photoetching process; in addition, when the high specific surface area UPE can be used as a base film material to develop a film for purification (metal ion removal), the high specific surface area UPE has relatively more grafted functional groups, so that the removal rate and the service life of the metal ion in a solvent of the film modified by the high specific surface area UPE are greatly improved; when the functional groups are needed to adsorb or exchange ions in the reagent in special application, the high-surface area UPE can improve higher capacity space, so that the UPE porous membrane is very suitable for various modification of the base membrane;
2. When the UPE with high specific surface area is used as a filtering membrane, more contact opportunities of the reagent and the membrane can be provided, so that the possibility of interception of impurities in the reagent by the membrane is improved, the interception efficiency is further improved, and meanwhile, the UPE porous membrane with high specific surface area can provide more pore volume, so that the UPE porous membrane has larger sewage receiving capacity as a filtering membrane material.
Meanwhile, in the film body structure of the UPE porous film provided by the invention, a plurality of first fibers are clearly seen to exist on the first porous outer surface of the UPE porous film, and the first fibers are in a branch-shaped structure and are continuous with each other; the adjacent continuous first fibers mutually encircle to form first holes, so that a porous structure of the membrane is formed, and the membrane formed by the first fiber structure has higher specific surface area; meanwhile, in the thickness direction, the first fibers are mutually stacked and mutually interweaved near the outer surface of the first porous, so that the filtration of impurities is more facilitated, and the higher interception efficiency of impurity particles is ensured; on the outer surface of the first porous, the average diameter of the first fiber is 10-60nm, so that the first fiber with the thickness ensures that the whole film has higher tensile strength, can meet the requirement of actual industrial production, and on the other hand, the first holes formed by the first fiber have stronger stability and are not easy to collapse or shrink, thereby ensuring the stability of the fluid flow rate;
In addition, the UPE porous membrane of the present invention is a symmetric membrane, and 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 even identical, and the pore shapes, pore sizes and pore area ratios on the two outer surfaces are basically similar, and the differences are very small (close to the same); in practical use, any outer surface can be used as a liquid inlet level (if the membrane is an asymmetric membrane, a specific outer surface is generally required to be used as the liquid inlet level), so that the related processes of assembling the porous membrane and the like are simpler, and the high-quality filter element is easier to prepare;
the UPE porous membrane is uniform in all the materials, namely the whole membrane is made of polyethylene materials, and the materials are not changed; the ultra-high molecular weight polyethylene is UPE for short, is thermoplastic engineering plastic with a linear structure and excellent comprehensive performance, and a filter membrane prepared from the ultra-high molecular weight polyethylene has high heat resistance and wear resistance, good mechanical property, high tensile strength, excellent chemical compatibility and wide application range, and is particularly suitable for being applied to the field of photoresist; the polyolefin composition constituting the UPE porous membrane in the invention at least comprises ultra-high molecular weight polyethylene with mass average molecular weight of more than 300 ten thousand; the method finally ensures that the prepared filter membrane has larger tensile strength and elongation at break, can meet the requirements of practical application, has wide application range, and is particularly suitable for being applied to the field of photoresist; the mass average molecular weight can be obtained as follows: heating and dissolving a sample of a polyethylene filter membrane in o-dichlorobenzene, and measuring the sample by utilizing a GPC liquid chromatograph under the conditions of a column temperature of 135 ℃ and a flow rate of 1.0 mL/min;
The average diameter of the first fiber on the first porous outer surface of the porous membrane can be measured by computer software (such as Matlab, NIS-Elements and the like) or manually after the morphology of the membrane structure is characterized by using a scanning electron microscope, and corresponding calculation is performed; in the preparation process of the membrane, in the direction perpendicular to the membrane thickness (the direction is a plane direction if the membrane is in a porous membrane form and is perpendicular to the radial direction if the membrane is in a hollow fiber membrane form), various characteristics such as pore size distribution, and the fiber thickness is approximately uniform and basically consistent; the overall fiber average diameter size in the corresponding plane can be reflected by the fiber average diameter of the partial region in the plane; in practice, the outer surface of the membrane may be characterized by electron microscopy to obtain a corresponding SEM image, and since the thickness of the fibers on the outer surface of the membrane is substantially uniform, a certain area, e.g., 1 μm, may be selected 2 (1 μm by 1 μm) or 25 μm 2 (5 μm by 5 μm), the specific area size is determined according to the actual situation, and corresponding computer software is usedOr the diameter of the fibers in the region is manually measured, and then an average value is obtained by calculation, so that the average diameter of the first fibers on the first porous outer surface is obtained, and the person skilled in the art can obtain the parameters through other measuring means, wherein the measuring means are only used for reference; the pore area ratio of the first pores on the outer surface of the first pores, and the average pore diameter of the first pores can also be obtained according to the above-described method.
Further, it is understood that "continuous" means that substantially all of the fibers are integrally connected to each other, such as integrally formed, without the use of additional adhesives or the like to connect them to each other, and that the fibers in a network cannot be separated from each other unless torn by an external force. At the same time, the continuous network-like fibers are also interconnected with the first porous outer surface and the second porous outer surface.
As a further improvement of the invention, the first porous outer surface is provided with a plurality of round hole-shaped first holes; the area ratio of the first holes on the outer surface of the first porous is 30-70%; the average pore diameter of the first holes is 1-150nm.
It is known that factors such as the pore size, the number and the shape of the pores of the membrane have great influence on the filtration precision (interception efficiency) of the membrane, the flow rate and other membrane properties;
in the invention, the first holes on the outer surface of the first porous are of a round hole-shaped structure, some first holes are round, some first holes are elliptical, and the round hole-shaped first holes can generate higher pore volume, so that the porous membrane has higher specific surface area; the average pore diameter of the first holes is 1-150nm; the porous membrane can well capture impurity particles with the particle size of 1-150nm through the non-directional tortuous path in the membrane main body, the interception efficiency is more than 95%, the filtering precision is ensured, the sufficient retention effect on undesired substances is achieved, and the requirements of practical application are met; the area ratio of the first holes on the outer surface of the first porous (the ratio of the area of the first holes to the area of the corresponding film) is 30-70%, so that the whole film is easy to ensure to have higher porosity, the porous film is easy to have higher flow velocity, fluid can quickly pass through the porous film, the filtering time is shortened, the tensile strength is higher, and the requirements of practical application are met.
As a further improvement of the present invention, the UPE porous membrane has a thickness of 1-30 μm; the porosity of the UPE porous membrane is 45-85%; the surface area of the membrane interior per unit membrane area is 0.4 to 0.8.
In addition, the UPE porous membrane is subjected to a porosity test, wherein the porosity of the membrane refers to the proportion of the volume of membrane pores of the porous membrane to the total volume, and the membrane pores comprise open pores and closed pores; common porosity testing methods include mercury intrusion, density and dry-wet film weighing; through tests, the UPE porous membrane has the porosity of 45-85% and higher porosity; that is, the UPE porous membrane has high specific surface and high porosity, so that the following advantages are shown in the UPE porous membrane:
1. compared with common chemicals, the photoresist has higher viscosity, bubbles are easy to generate when the photoresist passes through a filtering medium, the bubbles have great influence on the subsequent process, the UPE porous film with high specific surface area and high porosity can enable the filtering speed of the photoresist to be higher, and meanwhile, the photoresist is enabled to be discharged faster (the gas discharge speed is higher and the bubbles are easier to discharge) due to the high porosity, so that the content of the bubbles in the filtered photoresist is less, and the quality of the photoresist is more beneficial to being ensured;
2. For the end-use cartridge of photoresist, its outer dimensions are generally smaller, so the filter area filled inside is also generally smaller (typically not more than 2 m) 2 ) The method comprises the steps of carrying out a first treatment on the surface of the With the decrease of the membrane pores, the UPE porous membrane with high specific surface area and high porosity can realize lower pressure (smaller pressure loss) under the same flow rate under the condition that the membrane area can not be increased greatly, so that the UPE porous membrane with high surface area can realize very small pores (for filtering nano-scale impurity particles) on photoresist with quite viscosity and simultaneously meet the flow rate requirement (the filtering speed is still faster, the time cost is lower and the economic benefit is high);
when the thickness of the film is too small, the mechanical strength of the film is low; meanwhile, as the filtering time is too short, effective filtering cannot be performed; when the thickness of the membrane is too large, the filtering time is too long, and the time cost is too high; the UPE porous membrane has the thickness of 1-30 mu m, ensures that the UPE porous membrane not only has higher mechanical strength, but also can effectively filter, has higher filtering efficiency, shorter filtering time and lower time cost, and is suitable for being applied to the field of photoresist;
when filtering, various fluids move along the film thickness direction so as to realize corresponding filtering and the filtering is disposable, so that the characteristic of the surface area of the inner part of the film per unit film area is particularly important; the surface area of the membrane inside per unit membrane area is the surface area of the membrane inside of a porous membrane with a certain area, and the larger the value is, the larger the surface area of the inside of the porous membrane is; the surface area of the inner part of the membrane with unit membrane area is 0.4-0.8, and the value is larger, so that the UPE porous membrane has the advantages of (1) large sewage receiving amount, long service life and high economic benefit; (2) the area of the fluid passing through the porous membrane is larger, and impurities are relatively easier to intercept, so that the interception efficiency is improved; (3) when the UPE is used as a base membrane for grafting modification, functional groups to be grafted are more easily grafted to the surface area inside the membrane, so that various properties of the UPE porous membrane are further improved; is particularly suitable for being applied to the field of photoresist.
As a further improvement of the 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%; the UPE porous membrane has a thickness of 5-20 μm.
The specific surface area is the total area of the materials with unit mass, and the larger the specific surface area is, which indicates that the materials with certain mass are larger in total area; preferably, the UPE porous film of the present invention has a specific surface area of 40 to 80m 2 /g, illustrating that a UPE porous membrane of a certain mass has a larger total area; when the fluid is trapped, the area of the membrane contacted with the fluid is large, so that impurities in the fluid are more easily trapped, and the trapping efficiency is further improved; meanwhile, when the UPE porous membrane is used as a base membrane and various modification treatments are carried out, the modifier is connected with the membraneThe contact area is large, the reaction is complete, and various modifications, such as hydrophilic modification of a UPE film, are easier to realize;
the UPE film with high specific surface area can be used as a charge modified base film, on the other hand, even if the UPE film is not modified, according to experiments, the UPE porous film can be slightly negatively charged after being contacted with feed liquid, and the UPE porous film with negative charge has certain adsorptivity; then, the UPE film with high specific surface area has the advantages that under the condition that the charge amount carried by the UPE film with high specific surface area is fixed, the UPE film with high specific surface area has large total charge, so the adsorption effect is good, and the capability of retaining impurity substances is stronger;
In addition to some metal ions and particle impurities, the agglomeration of the resin substances as the active ingredient in the photoresist (for example, PMMA resin as the ingredient in the KrF photoresist is easy to agglomerate, and ketones as the ingredient in the I-line/KrF photoresist is easy to agglomerate), has an influence on the light refractive index, and further easily influences the stability of the photolithography process; the charged high specific surface area UPE film has a good adsorption effect on the impurities.
When the porosity of the film is too high, the tensile strength of the film is too low, the mechanical property of the film is poor, the industrial practical value is low, and the market demand cannot be met; when the porosity of the membrane is too low, on one hand, the flow rate of the membrane can be influenced, so that the filtration speed of the membrane is slower, the filtration time is longer, and the time cost is higher; on the other hand, the membrane has too low sewage containing amount and too short service life, and the membrane needs to be replaced in a shorter time, so that the economic cost is greatly improved; as the preferential, the porosity of the porous membrane is 50-75%, so that the UPE porous membrane not only has higher tensile strength, but also has higher filtering speed, large flow rate and higher dirt holding capacity, can hold back more impurity particles, has long service life and lower economic cost;
Preferably, the UPE porous membrane has a thickness of 5-20 μm; through the mutual synergistic effect among the film thickness, the film porosity and the film specific surface area, the UPE porous film is ensured to have higher tensile strength, shorter filtering time and higher filtering precision, and the requirements of practical application are met.
As a further improvement of the invention, the second porous outer surface comprises a plurality of continuous second fibers in a branch shape, and second holes are formed between adjacent continuous second fibers in a surrounding manner; the second fibers have an average diameter of 10-60nm.
In the film body structure of the UPE porous film provided by the invention, a plurality of second fibers are clearly seen to exist on the second porous outer surface of the UPE porous film, the shape of the second fibers is approximately the same as that of the first fibers, but the second fibers are different in thickness to some extent, but the difference is also smaller, which also shows that the UPE porous film of the invention is a symmetrical film, and the two outer surface structures of the film are very similar; these second fibers also exhibit a crotch-like structure, the second fibers being continuous with the second fibers; corresponding second holes are formed between adjacent continuous second fibers in a surrounding manner, and then a porous structure of the membrane is formed, so that the membrane formed by the second fiber structure further has higher specific surface area and high porosity; meanwhile, in the thickness direction, the second fibers are mutually stacked and mutually interweaved (staggered) and overlapped near the outer surface of the second porous, so that the filtration of impurities is more facilitated, and the porous membrane has higher interception efficiency on impurity particles; on the second porous outer surface, the average diameter of the second fiber is 10-60nm, so that the second fiber with the thickness further ensures that the whole membrane has higher tensile strength, can meet the requirement of actual industrial production, has stronger stability of the second holes formed through the second fiber, is not easy to collapse or shrink, and further ensures the stability of the fluid flow rate.
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 to 1.5; the second hole is in a round hole shape; the area ratio of the second holes on the outer surface of the second porous is 30-70%.
As a further improvement of the invention, the average pore diameter of the second holes is 1-150nm; the ratio of the average pore diameter of the second holes to the average pore diameter of the first holes is 0.78-1.35.
It is known that factors such as the pore size, the number and the shape of the pores of the membrane have great influence on the filtration precision (interception efficiency) of the membrane, the flow rate and other membrane properties; in the invention, the second holes on the outer surface of the second holes are in a round hole-shaped structure, and the shape of the second holes is almost the same as that of the first holes, but the hole diameters are slightly different; the second holes are round, the second holes are elliptical, and the round holes are easy to generate higher pore volume, so that the porous membrane has higher specific surface area; the area ratio of the second holes on the outer surface of the second porous (the ratio of the area of the second holes to the area of the corresponding film) is 30-70%, which is beneficial to the porous film to have a larger flow rate, is convenient for the fluid to quickly pass through the porous film, shortens the filtration time, ensures that the porous film has a larger tensile strength and meets the requirements of practical application; by measuring that the average pore diameter of the second holes is 1-150nm, the average pore diameter of the second holes is approximately equal to the average pore diameter of the first holes, a certain difference value is realized, and the difference value is smaller, further proves that the UPE porous membrane is a symmetrical membrane, all parts of the symmetrical membrane have approximately the same characteristics, the pore structure and the fiber structure of the symmetrical membrane cannot change along with the thickness of the membrane, and the membrane can have stronger trapping capability on impurity particles with the particle diameter of 1-150nm;
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 to 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 to 1.35, and although the thickness of the second fibers and the thickness of the first fibers are different, the two differences are very small and relatively uniform; the average pore diameter of the second hole is also different from that of the first hole to some extent, but the difference is very small and relatively uniform; thus further illustrating that the UPE porous membrane is a symmetric membrane with substantially identical properties on both outer surfaces of the membrane; when in actual use, any outer surface of the porous membrane can be used as a liquid inlet surface, and the process of manufacturing the porous membrane into the filter element is easier, simpler and more convenient, and the economic benefit is higher.
As a further improvement of the present invention, the ratio between the IPA initial bubble point and the IPA full bubble point of the UPE porous membrane is not less than 0.4; and the IPA complete bubble point of the UPE porous membrane is not lower than 0.2MPa.
One of the important performance characteristics of a filter membrane is the bubble point, which is a test method well known in the art. The procedure for these tests is explained in detail, for example, in ASTM F316-70 and ANS/ASTM F316-70 (re-approval 1976), which are incorporated herein by reference. The bubble point is related to the pore size of the pores on the porous membrane; generally, the larger the pore size of the pores, the lower the bubble point; the smaller the pore diameter of the hole, the higher the bubble point; the bubble point includes an initial bubble point and a full out bubble point; the IPA complete bubble point of the UPE porous membrane is not lower than 0.2MPa, so that the pore diameter in the UPE porous membrane is relatively small, and the UPE porous membrane passes through a non-directional tortuous path in a membrane main body, so that the porous membrane can play a good role in trapping impurity particles with the particle size of 1-150nm, ensure the filtering precision and play a sufficient role in retaining unwanted substances;
The initial bubble point is mainly reflected by the maximum pore size inside the membrane, while the full out bubble point is mainly reflected by the average pore size of the membrane; the ratio between the initial bubble point and the complete bubble point can reflect the symmetry of the membrane to a certain extent, and the smaller the ratio is, the larger the asymmetry of the membrane is, and the larger the ratio is, the better the symmetry of the membrane is; the ratio of the initial bubble point of IPA to the complete bubble point of IPA of the UPE porous membrane is not lower than 0.4, and further shows that the membrane is a symmetrical membrane, the pore size and pore distribution characteristics of the inside of the membrane main body are similar to the corresponding characteristics of the two outer surfaces of the membrane, and no pores with particularly large pore diameters exist to ensure the filtering precision and the filtering speed.
As a further improvement of the present invention, the shrinkage rate of the porous film is not more than 5% after being left for 1 hour at a temperature of 120 ℃; the porous membrane has a compressibility of less than 15%; the pore closing temperature of the porous membrane is higher than 120 ℃.
The heat resistance test is carried out on the UPE porous membrane, after the porous membrane is placed for 1 hour at the temperature of 120 ℃, the shrinkage rate of the porous membrane is not more than 5%, which indicates that the UPE porous membrane has higher heat stability, and the membrane pores are not easy to shrink or deform at higher temperature, thereby ensuring that the membrane has higher interception efficiency for a long time, and the flow rate change is smaller in the use process, the service life is long, and further indicates that the application range of the porous membrane is very wide, and the porous membrane is particularly suitable for the photoresist field;
When the liquid filter is used or processed for a long time, the porous membrane needs to keep a good porous structure, so that high-efficiency interception efficiency is ensured, and excellent trapping effect is achieved on impurities; the UPE porous membrane has the compressibility of less than 15%, which indicates that the membrane pores of the porous membrane are not easy to deform in various processing treatments or long-term use processes of the porous membrane, the porous structure is stable, the stable flow rate of the porous membrane is further ensured, and the interception efficiency can be ensured for a long time; the compression ratio in the present invention is obtained in the following manner: the UPE porous film was pressurized at a temperature of 70℃for 30 seconds under 2MPa, and then left at a release pressure of 25℃for 30 seconds, whereby the compression ratio was obtained from the ratio of the difference in film thickness between before and after the pressurization to the film thickness before the pressurization. In the present invention, if the UPE porous membrane has a compressibility of 15% or more, the following problems may occur: the problem is that the porous membrane is changed to more than necessary degree when the liquid filter is used for a long time or processed, the original porous structure can not be maintained, and the water permeability becomes unstable; and abnormal rise of the filtration pressure caused by closing of the hole.
In addition, the pore closing temperature of the UPE porous membrane is higher than 120 ℃; when the pore closing temperature of the porous membrane is higher than 120 ℃, the porosity of the UPE porous membrane is not lost near a higher temperature treatment part or a higher temperature body contact part of a thermal bonding process during processing of the actual UPE porous membrane, the water permeability is easy to keep, the expected filtering area can be obtained even after processing, the ideal flow rate and interception efficiency are further ensured, the porous performance of the membrane is stable, and the actual industrial requirement is met.
As a further improvement of the invention, the interception efficiency of the UPE porous film on impurity particles with the particle diameter of 1-150nm is more than 95 percent; the time required for 50ml of water to pass through the porous membrane with the diameter of 47mm is not more than 500s under the conditions of the pressure of 0.03MPa and the temperature of 20 ℃; the tensile strength of the porous film is 20-100MPa, and the elongation at break is 200% -800%.
Through interception test on the UPE porous membrane, the porous membrane can play a good role in capturing impurity particles with the particle size of 1-150nm, the interception efficiency is more than 95%, the filtering precision is ensured, and the porous membrane plays a sufficient role in retaining undesired substances, and is suitable for being applied to the field of photoresist;
by performing a flow rate test on the UPE porous membrane, the time required for 50ml of water to pass through the UPE porous membrane with the diameter of 47mm is not more than 500s under the conditions that the pressure is 0.03MPa and the temperature is 20 ℃; the UPE porous membrane has larger flow rate, the time required by fluid passing through the porous membrane is shorter, the time cost is lower, and the economic benefit is higher, and meanwhile, the UPE porous membrane is suitable for being applied to the photoresist field;
important indexes for evaluating the mechanical strength of the film are the tensile strength and the elongation at break of the film; under certain conditions, the greater the tensile strength of the film, the better the mechanical strength of the film is also demonstrated; the tensile strength of the UPE porous membrane is 20-100MPa, and the elongation at break is 200-800%; the UPE porous membrane disclosed by the invention has the advantages of higher tensile strength and elongation at break, better mechanical property and higher industrial practical value, and can completely meet the market demand.
The invention also provides a preparation method of the UPE porous membrane with high specific surface area, which comprises the following steps:
s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing the polyethylene resin and the solvent system to form a mixed material after uniform mixing; wherein the polyethylene resin at least comprises an ultra-high molecular weight polyethylene with a mass average molecular weight of more than 300 ten thousand; the compound A is a non-solvent of polyethylene resin; the compound B is a solvent for the polyethylene resin; the mixed material comprises the following substances in parts by weight: polyethylene resin: 10-25 parts of a lubricant; compound a:0-20 parts; compound B:70-90 parts; the compound A is at least one of dimethyl phthalate, dioctyl adipate, ethylene glycol diacetate, dimethyl carbonate, palm oil and glyceryl triacetate, and the compound B is at least one of paraffin oil, white oil, hydraulic oil, decalin, castor oil extract and castor oil;
s2: heating, melting and mixing the mixed materials at 150-260 ℃ to form a casting solution, extruding the casting solution through a die head, and forming a liquid film on a carrier; the extrusion temperature of the die head is 200-250 ℃;
s3: carrying out phase-splitting solidification on the liquid film at 15-50 ℃ for 2-50s to form a green film; when the phase-splitting solidification is carried out, the temperature difference between the liquid film carrier side and the liquid film air side is 5-20 ℃; in the phase-splitting solidification process, the carrier side and the air side of the liquid film are at least converted once;
S4: then stretching the green film, and performing first heat setting after stretching;
s5: extracting the solvent system with an extraction liquid to remove the solvent system from the raw film to obtain a raw film;
s6: and performing heat setting on the original film for the second time to obtain the UPE porous film.
As a further improvement of the present invention, the polyethylene resin is composed of 65 to 85 mass% of ultra-high molecular weight polyethylene having a mass average molecular weight of 300 ten thousand or more and 15 to 35 mass% of high density polyethylene having a mass average molecular weight of 100 to 200 ten thousand and a density of 0.92 to 0.98g/cm 3.
As a further improvement of the present invention, the stretching treatment of the green film in S4 means that the green film is simultaneously stretched in the transverse direction and in the longitudinal direction, the temperature at which the transverse direction and the longitudinal direction are stretched is 60-150 ℃, the transverse direction stretching multiple is 1-10 times, and the longitudinal direction stretching multiple is 1-10 times.
As a further improvement of the invention, the raw film is subjected to stretching treatment in S4, and the ratio of the longitudinal stretching multiple to the transverse stretching multiple is 0.8-2; the transverse stretching rate is 5%/s-100%/s, and the longitudinal stretching rate is 5%/s-100%/s.
As a further improvement of the invention, the extract in S5 is at least one of dichloromethane, acetone, methanol, ethanol, glycerol, tetrafluoroethane and isopropanol; the extraction temperature is 5-25 ℃; the extraction time is 1-5h.
As a further improvement of the invention, the temperature is 100-180 ℃ and the time is 20-90s during the first heat setting; the temperature in the second heat setting is 10-40 ℃ higher than that in the first heat setting, and the time is 20-90s.
The invention forms a cast sheet with holes by a thermally induced phase separation method, and then stretches and forms the cast sheet to prepare a UPE porous film with high specific surface area, when the cast sheet is prepared, various materials are mixed to form a mixed material, the mixed material comprises polyethylene resin and a corresponding solvent system, the ultra-high molecular weight polyethylene is called UPE for short, the ultra-high molecular weight polyethylene is thermoplastic engineering plastic with a linear structure and excellent comprehensive performance, and the porous film prepared by UPE has higher heat resistance, wear resistance, good mechanical property, larger tensile strength and wide application range; the polyethylene resin used in the invention at least comprises an ultra-high molecular weight polyethylene with a mass average molecular weight of more than 300 ten thousand, namely, only a UPE with a mass average molecular weight of more than 300 ten thousand can be used as a film forming raw material in the invention, and the polyethylene resin can also be compounded, for example, the UPE with the mass average molecular weight of more than 300 ten thousand and the high-density polyethylene with the mass average molecular weight of less than 300 ten thousand can be used as the film forming raw material after being compounded; preferably, the polyethylene resin of the present invention is composed of 65 to 85 mass% of an ultra-high molecular weight polyethylene having a mass average molecular weight of 300 ten thousand or more and 15 to 35 mass% of an ultra-high molecular weight polyethylene having a mass average molecular weight of 100 to 200 ten thousand and a density of 0.92 to 0.98g/cm 3 Is composed of high density polyethylene; compared with the single polyethylene with ultra-high molecular weight, the polyethylene resin compounded by the ultra-high molecular weight polyethylene and the high-density polyethylene is more beneficial to obtaining UPE porous membranes with relatively smaller pore diameters, high porosity and higher tensile strength; and the solvent system can be only the compound B, wherein the compound B is a solvent of the polyethylene resin, and the solvent means that the compound B can completely dissolve the polyethylene resin to form a homogeneous solution when being heated to the boiling point temperature of the compound B at most; the compound B is at least one of paraffin oil, white oil, hydraulic oil, decalin, castor oil extract and castor oil; preferably, the solvent system is composed of a compound A and a compound B, wherein the compound A is insoluble in the polyethylene resinA non-solvent means that when heated up to the boiling point of such a compound, the compound does not dissolve the polyethylene resin to form a homogeneous solution, but only has a certain swelling effect on the polyethylene resin; the compound A is at least one of dimethyl phthalate, dioctyl adipate, ethylene glycol diacetate, dimethyl carbonate, palm oil and glycerol triacetate; the content of the compound B in the solvent system is far higher than that of the compound A, so that the polyethylene resin can be fully melted and dispersed in the solvent system under the action of the subsequent higher temperature, and the casting solution has proper solid content;
Compared with the method which adopts a single solvent as a solvent system, the method adopts the combination of the solvent and the non-solvent as the corresponding solvent system, and has the following advantages:
1. holes with smaller pore diameters are more likely to appear in a raw film formed after the liquid film phase separation is finished, and meanwhile, the formed holes are more; this is because diffusion exchange occurs between the non-solvent and the solvent while the liquid film undergoes liquid-liquid phase separation solidification (phase separation solidification by a thermal method) due to a change in temperature, thereby further improving the phase separation solidification rate;
2. the fiber is easier to form, so that the UPE porous film is ensured to have higher tensile strength and good mechanical property, because crystal nuclei are easier to separate out due to the acceleration of the phase separation rate, and the fiber is produced along the crystal nuclei, so that the fiber is easier to form;
of course, if desired, additional materials such as antioxidants, nucleating agents, fillers, and the like may be used as additives in the present invention to further enhance a certain property of the UPE porous membrane; the polyethylene resin and the corresponding solvent system (including compound a and compound B) may be stirred and mixed at a temperature of 100-140 ℃ for 10-24 hours, thereby forming the corresponding mixture;
Then, putting the mixed material into an extruder, heating, melting and mixing at the temperature of 150-260 ℃ (preferably 200-255 ℃), and heating, melting and mixing for 10-60min, so as to ensure that the polyethylene resin is completely melted in a corresponding solvent system, and the shape is uniform and stable; the solid content of the casting film liquid is preferably 10-20%, and the excessively low solid content can cause excessively low tensile strength and poor mechanical strength of the final film, so that the requirements of practical application cannot be met; the excessively high solid content can cause excessively high viscosity of the casting solution, excessively high requirements on the mechanical equipment, excessively high production cost and incapability of mass production;
then extruding (die forming) through a die head, and forming a flat liquid film on a carrier (the carrier can be a roller or other carriers), wherein the die head extrusion temperature is 200-250 ℃; preferably, the highest temperature in the extruder is at least 5 ℃ higher than the extrusion temperature of the die head, so that the temperature of each area of the liquid film is basically the same during extrusion, subsequent phase separation solidification is facilitated, phase separation is more uniform, an ideal film structure is obtained, and a symmetrical film is formed;
then the liquid film is placed in a temperature environment of 15-50 ℃ for split-phase solidification; at a higher temperature, a single homogeneous solution can be formed between the solvent system and the polyethylene resin, and the homogeneous solution becomes turbid along with the reduction of the system temperature, and the polyethylene resin slowly separates out, so that the phase-splitting solidification phenomenon occurs; the phase separation temperature of the two sides of the liquid film is low (15-50 ℃), the liquid film is easy to separate rapidly, more crystal films are formed (nano holes and small holes are easier to form high specific surface area), more holes are easy to form (high porosity) and fibrosis is more obvious; if the solvent system is a combination of solvent and non-solvent, besides the phase separation caused by the change of temperature, the diffusion exchange between the solvent and the non-solvent can further accelerate the phase separation solidification rate, so that a small pore film (the faster the phase separation rate, the smaller the pore diameter of the formed pores) is formed, namely, the nano film required by the invention is formed; the UPE porous membrane finally formed by the invention is a symmetrical membrane, and in order to form the symmetrical membrane, the phase separation degree of the two sides of the liquid membrane is required to be basically the same, so that the membrane 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 invention, the structural similarity of the two outer surfaces of the membrane is ensured by the coaction of two conditions; the first condition is that the temperature difference between the carrier side of the liquid film (the carrier may be a roller or other carrier) and the air side of the liquid film is 5-20 ℃, for example, the temperature of the air side is 20 ℃, then the temperature of the carrier side can be set to 30 ℃, then the two sides of the liquid film are different in temperature, and the heat transfer rates of the two sides are also different, and the split phase rates of the two sides of the liquid film are different; the second condition is that in the phase-splitting solidification process, the carrier side and the air side of the liquid film are mutually converted at least once, wherein the conversion once means that when the liquid film moves on the carrier, the two side surfaces of the liquid film are mutually converted when the liquid film is changed from one carrier to one carrier, and at the moment, the air side of the original liquid film is changed into the carrier side of the liquid film, and the roller side is changed into the air side; the number of transitions is preferably 1-3; through the mutual conversion of the two sides of the liquid film between the carrier side and the air side, under the action of proper time, the split phases of the two sides of the liquid film are basically the same, so that a symmetrical green film can be formed; in the process of phase-splitting solidification, the selection of factors such as the temperature of the phase-splitting solidification and the time of the phase-splitting solidification are extremely critical, and the factors determine the speed of the phase-splitting solidification, and whether the film with an ideal film structure and film hole size can be finally obtained or not; the split-phase curing time is 2-50s, and the time is relatively short, so that UPE porous membrane with ideal membrane structure is obtained;
After the liquid film phase separation is finished, a raw film is formed, a certain number of holes with certain aperture are formed on two surfaces of the raw film, the aperture sizes of the holes on the two surfaces are basically the same, and in order to further obtain a UPE porous film with the required film aperture, the raw film is stretched, and the existing stretching technology is to longitudinally stretch and then transversely stretch; however, it has been found that if the raw film is processed according to the conventional stretching technique, the holes on the raw film are likely to be partially collapsed or deformed, and finally the UPE porous film with the desired film structure cannot be obtained, so that the processing is performed by simultaneous stretching, that is, the raw film is simultaneously stretched transversely and longitudinally, the temperature at the time of transverse stretching and longitudinal stretching is 60-150 ℃, the transverse stretching multiple is 1-10 times, and the longitudinal stretching multiple is 1-10 times. The stretching has the advantages that the pore diameter of the membrane hole required by the invention is obtained, the tensile strength of the membrane is improved, and meanwhile, the hole is not easy to collapse or deform, thereby being beneficial to finally obtaining the UPE filter membrane with the membrane structure required by the invention; preferably, the ratio of the longitudinal stretching multiple to the transverse stretching multiple is 0.8-2, the transverse stretching rate is 5%/s-100%/s, and the longitudinal stretching rate is 5%/s-100%/s, so that the uniformity of the pore diameter of the pores in the membrane is further improved, and the symmetry of the membrane is ensured;
After synchronous stretching, performing primary heat setting, wherein the primary heat setting is used for primarily setting the stretched raw film, ensuring that film holes are basically unchanged, and simultaneously eliminating internal stress generated by stretching; the temperature is 100-180 ℃ and the time is 20-90s during the first heat setting; then extracting, removing the solvent system from the raw film through an extract liquid to obtain a raw film; the extract is at least one of dichloromethane, acetone, methanol, ethanol, glycerol, tetrafluoroethane and isopropanol; the extraction temperature is 5-25 ℃; the extraction time is 1-5h; by selecting proper extractant and extraction conditions, the solvent system is completely removed from the green film, and the time required by extraction is short; after extraction is finished, performing secondary heat setting on the original film, wherein the temperature in the secondary heat setting is 10-40 ℃ higher than that in the primary heat setting, and the secondary heat setting has the effects of eliminating internal stress generated by extraction on one hand, and performing final setting on film holes of the original film on the other hand, so that the film holes are basically unchanged, and a UPE porous film with a required film hole structure is obtained; the UPE porous membrane is a symmetrical membrane, the pore diameters of the pores on the membrane are uniformly distributed, the UPE porous membrane has excellent trapping performance on impurity particles, and the trapping efficiency is high; meanwhile, the porous ceramic material has high specific surface area and high porosity, and has small pressure loss, thus being particularly suitable for being applied to the field of photoresist.
As a further improvement of the present invention, the use of a UPE porous membrane for filtering photoresist;
after the UPE porous membrane is made into a capsule-type or cylinder-type filter element, due to the high specific surface area and high porosity of the UPE porous membrane, gas generated in the photoresist filtering process is easier to discharge, so that the content of bubbles in the filtered photoresist is lower, the adverse effect of the bubbles on the photoresist property is reduced, and the photoresist with excellent property is ensured to be obtained; therefore, the UPE porous membrane is particularly suitable for being applied to the photoresist filtering field; when the photoresist is filtered, any outer surface of the UPE porous membrane can be used as a liquid inlet level, and a specific outer surface is not required to be guided to be used as the liquid inlet level, so that the problem that effective filtration cannot be performed due to misoperation of a user is avoided; the UPE porous membrane has excellent trapping performance on various impurity particles in photoresist and high filtering precision; meanwhile, the sewage treatment device has higher sewage containing amount, longer service life and high economic benefit.
As a further improvement of the present invention, a folded filter cartridge with a UPE porous membrane comprising a central rod and a UPE porous membrane located at the periphery of the central rod, the UPE porous membrane being folded to form pleats having pleat valleys near the side of the central rod and pleat peaks at the periphery, the UPE porous membrane having an upstream side in communication with an inlet and a downstream side in communication with an outlet, characterized in that: the UPE porous membrane is a UPE porous membrane as claimed in any one of claims 1 to 12, and the membrane area of the UPE porous membrane in the folding filter element is 0.1 to 2m 2
For the end application of photoresist, especially for the capsule type filter, the size of the capsule type filter is generally smaller, so that the membrane area filled in the capsule type filter is also generally smaller, and the membrane area of UPE porous membrane in the capsule type filter is mostly 0.1-0.6m 2 While the membrane area of UPE porous membrane in the barrel type filter element is not more than 2m 2 The method comprises the steps of carrying out a first treatment on the surface of the Compared with a UPE film with low specific surface area and low porosity, the UPE film with high specific surface area can realize lower pressure under the same flow rate due to high aperture ratio, so that the UPE film with high specific surface area can realize very small holes (for filtering nano-level particles) on photoresist with quite high viscosity, simultaneously meet the flow rate requirement, has relatively small pressure loss, can obtain good flow rate when filtering nano-level impurity particles, and has higher economic benefit.
The invention has the beneficial effects that: the UPE porous membrane provided by the invention is a symmetrical membrane and has a membrane body knot which is more optimized than the existing filter membrane materialThe structure comprises a first porous outer surface, a second porous outer surface and a main body arranged between the first porous outer surface and the second porous outer surface, wherein the specific surface area of the UPE porous membrane is not less than 35m 2 The first porous outer surface comprises a plurality of branch-shaped continuous first fibers, and first holes are formed between adjacent continuous first fibers in a surrounding mode; the first fibers in the thickness direction are laminated to each other; the average diameter of the first fiber is 10-60nm; the UPE porous membrane with high specific surface area has excellent trapping performance on nanoscale fine impurities in the filtering process, can adsorb various fine particulate matters, and has high trapping efficiency; in addition, the UPE porous membrane is particularly suitable for being used as a base membrane for modification, and has good modification effect; the method is suitable for being applied to the field of photoresist filtration; the preparation method provided by the invention can conveniently, rapidly and effectively prepare and obtain the UPE porous membrane.
Drawings
FIG. 1 is a Scanning Electron Microscope (SEM) image of the outer surface of a first porous on a UPE porous membrane prepared in example 6, with magnification of 10K×;
FIG. 2 is a further enlarged Scanning Electron Microscope (SEM) image of the first porous outer surface of the UPE porous membrane prepared in example 6, wherein the magnification is 50K×;
FIG. 3 is a Scanning Electron Microscope (SEM) image of the second porous outer surface of the UPE porous membrane prepared in example 6, wherein the magnification is 10K×;
FIG. 4 is a further enlarged Scanning Electron Microscope (SEM) image of the second porous outer surface of the UPE porous membrane prepared in example 1, wherein the magnification is 50K×;
FIG. 5 is a schematic diagram of an apparatus for flow rate testing of UPE porous membranes of the present invention;
FIG. 6 is a schematic diagram of an apparatus for testing filtration accuracy (rejection efficiency) of a UPE porous membrane of the present invention.
Detailed Description
In order to more clearly illustrate the general concepts of the present application, the following detailed description is given by way of example. Example 1 a method for preparing a UPE porous membrane with high specific surface area comprising the steps of:
s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing the polyethylene resin and the solvent system to form a mixed material after uniform mixing; the mixed material comprises the following substances in parts by weight: polyethylene resin: 12 parts; compound a:5 parts; compound B:72 parts;
The polyethylene resin is prepared from 83 mass% of ultra-high molecular weight polyethylene with mass average molecular weight of more than 300 ten thousand and 17 mass% of polyethylene with mass average molecular weight of 100-200 ten thousand and density of 0.92-0.98g/cm 3 Is composed of high density polyethylene; the compound A is dioctyl adipate and the compound B is white oil;
s2: heating, melting and mixing the mixed materials at 215 ℃ to form a casting solution, extruding the casting solution through a die head, and forming a liquid film on a carrier; the die extrusion temperature is 205 ℃;
s3: setting the temperature of the liquid film carrier side to 25 ℃, setting the temperature of the air side to 20 ℃, and after 4s of phase separation and solidification, converting the two sides of the liquid film, namely changing the side of the liquid film originally close to the carrier into the side close to the air (changing the phase separation temperature from 25 ℃ to 20 ℃), changing the side of the liquid film originally close to the air into the side close to the carrier (changing the temperature from 20 to 25 ℃), and continuing the phase separation and solidification for 4s; after the split-phase solidification is finished, forming a green film;
s4: then stretching the green film, and simultaneously performing transverse stretching and longitudinal stretching, wherein the temperature of the transverse stretching and the longitudinal stretching is 80 ℃, the transverse stretching multiple is 3 times, the longitudinal stretching multiple is 3 times, the transverse stretching rate is 20%/s, and the longitudinal stretching rate is 20%/s; after the stretching is finished, performing primary heat setting, wherein the temperature of the primary heat setting is 130 ℃ and the time is 65s;
S5: extracting the solvent system with an extraction liquid to remove the solvent system from the raw film to obtain a raw film; s5, extracting solution is dichloromethane; the extraction temperature is 15 ℃; the extraction time is 3h;
s6: and (3) performing secondary heat setting on the original film, wherein the temperature is 160 ℃ and the time is 45s during the secondary heat setting, so as to prepare the UPE porous film.
Example 2 a method for preparing a UPE porous membrane with high specific surface area comprising the steps of:
s1: will be polymerizedAdding vinyl resin into a solvent system consisting of a compound A and a compound B, stirring and mixing the vinyl resin and the solvent system to form a mixed material after uniform mixing; the mixed material comprises the following substances in parts by weight: polyethylene resin: 14 parts; compound a:8 parts; compound B:75 parts; the polyethylene resin is prepared from 80 mass% of ultra-high molecular weight polyethylene with mass average molecular weight of 300 ten thousand or more, 20 mass% of mass average molecular weight of 100-200 ten thousand and density of 0.92-0.98g/cm 3 Is composed of high density polyethylene; the compound A is ethylene glycol diacetate, and the compound B is paraffin oil;
s2: heating, melting and mixing the mixed materials at 220 ℃ to form a casting solution, extruding the casting solution through a die head, and forming a liquid film on a carrier; the die extrusion temperature is 210 ℃;
S3: setting the temperature of the liquid film carrier side to 30 ℃, setting the temperature of the air side to 20 ℃, carrying out phase separation and solidification for 5 seconds, converting the two sides of the liquid film, namely, changing the side of the liquid film originally close to the carrier into the side close to the air (the phase separation temperature is changed from 30 ℃ to 20 ℃), changing the side of the liquid film originally close to the carrier into the side close to the carrier (the temperature is changed from 20 ℃ to 30 ℃), continuing phase separation and solidification, carrying out phase separation for 10 seconds, converting the two sides of the liquid film again, namely, changing the side of the liquid film which is now close to the carrier into the side close to the carrier again (the phase separation temperature is changed from 20 ℃ to 20 ℃), and finally carrying out phase separation again for 5 seconds; after the split-phase solidification is finished, forming a green film;
s4: then stretching the green film, and simultaneously performing transverse stretching and longitudinal stretching, wherein the temperature of the transverse stretching and the longitudinal stretching is 85 ℃, the transverse stretching multiple is 4 times, the longitudinal stretching multiple is 4 times, the transverse stretching rate is 25%/s, and the longitudinal stretching rate is 25%/s; after the stretching is finished, performing primary heat setting, wherein the temperature of the primary heat setting is 135 ℃ and the time is 60s;
s5: extracting the solvent system with an extraction liquid to remove the solvent system from the raw film to obtain a raw film; the extract is acetone; the extraction temperature is 20 ℃; the extraction time is 2.5h;
S6: and (3) performing secondary heat setting on the original film, wherein the temperature is 150 ℃ and the time is 75 seconds during the secondary heat setting, so as to prepare the UPE porous film.
Example 3 a method for preparing a UPE porous membrane with high specific surface area comprising the steps of:
s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing the polyethylene resin and the solvent system to form a mixed material after uniform mixing; the mixed material comprises the following substances in parts by weight: polyethylene resin: 16 parts; compound a:12 parts; compound B:78 parts; the polyethylene resin is prepared from 75 mass% of ultra-high molecular weight polyethylene with a mass average molecular weight of more than 300 ten thousand and 25 mass% of polyethylene with a mass average molecular weight of 100-200 ten thousand and a density of 0.92-0.98g/cm 3 Is composed of high density polyethylene; the compound A is dimethyl phthalate, and the compound B is hydraulic oil;
s2: heating, melting and mixing the mixed materials at 225 ℃ to form a casting solution, extruding the casting solution through a die head, and forming a liquid film on a carrier; the die extrusion temperature is 215 ℃;
s3: setting the temperature of the liquid film carrier side to be 32 ℃, setting the temperature of the air side to be 20 ℃, carrying out phase separation and solidification for 6s, converting the two sides of the liquid film, namely, changing the side of the liquid film originally close to the carrier into the side close to the air (the phase separation temperature is changed from 32 ℃ to 20 ℃), changing the side of the liquid film originally close to the carrier into the side close to the carrier (the temperature is changed from 20 ℃ to 32 ℃), continuing phase separation and solidification, carrying out phase separation for 12s, converting the two sides of the liquid film again, namely, changing the side of the liquid film at the moment close to the carrier into the side close to the carrier again (the phase separation temperature is changed from 20 ℃ to 32 ℃), changing the side close to the carrier into the side of the liquid film at the moment again (the phase separation temperature is changed from 32 ℃) and finally carrying out phase separation for 6s; after the split-phase solidification is finished, forming a green film;
S4: then stretching the green film, and simultaneously performing transverse stretching and longitudinal stretching, wherein the temperature of the transverse stretching and the longitudinal stretching is 90 ℃, the transverse stretching multiple is 4 times, the longitudinal stretching multiple is 5 times, the transverse stretching rate is 40%/s, and the longitudinal stretching rate is 50%/s; carrying out primary heat setting after stretching, wherein the temperature is 140 ℃ and the time is 55s when the primary heat setting is carried out;
s5: extracting the solvent system with an extraction liquid to remove the solvent system from the raw film to obtain a raw film; the extract is isopropanol; the extraction temperature is 23 ℃; the extraction time was 2h.
S6: and (3) performing secondary heat setting on the original film, wherein the temperature is 165 ℃ and the time is 60s during the secondary heat setting, and thus the UPE porous film is prepared.
Example 4 a method for preparing a UPE porous membrane with high specific surface area comprising the steps of:
s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing the polyethylene resin and the solvent system to form a mixed material after uniform mixing; the mixed material comprises the following substances in parts by weight: polyethylene resin: 18 parts; compound a:17 parts; compound B:81 parts;
the polyethylene resin is prepared from 72 mass% of ultra-high molecular weight polyethylene with mass average molecular weight of more than 300 ten thousand and 28 mass% of polyethylene with mass average molecular weight of 100-200 ten thousand and density of 0.92-0.98g/cm 3 Is composed of high density polyethylene; the compound A is palm oil, and the compound B is castor oil;
s2: heating, melting and mixing the mixed materials at 235 ℃ to form a casting solution, extruding the casting solution through a die head, and forming a liquid film on a carrier; the extrusion temperature of the die head is 225 ℃;
s3: setting the temperature of the liquid film carrier side to 35 ℃, setting the temperature of the air side to 25 ℃, carrying out phase separation and solidification for 15s, and then converting the two sides of the liquid film, namely, changing the side of the liquid film originally close to the carrier into the side close to the air (changing the phase separation temperature from 35 ℃ to 25 ℃), changing the side of the liquid film originally close to the air into the side close to the carrier (changing the temperature from 25 to 35 ℃), and continuing the phase separation and solidification for 15s; after the split-phase solidification is finished, forming a green film;
s4: then stretching the raw film, and simultaneously performing transverse stretching and longitudinal stretching, wherein the temperature of the transverse stretching and the longitudinal stretching is 80 ℃, the transverse stretching multiple is 6 times, the longitudinal stretching multiple is 5 times, the transverse stretching rate is 60%/s, and the longitudinal stretching rate is 50%/s; after the stretching is finished, performing primary heat setting, wherein the temperature of the primary heat setting is 145 ℃ and the time is 50s;
s5: extracting the solvent system with an extraction liquid to remove the solvent system from the raw film to obtain a raw film; s5, extracting liquid is glycerol; the extraction temperature is 10 ℃; the extraction time was 4h.
S6: and (3) performing secondary heat setting on the original film, wherein the temperature is 170 ℃ and the time is 65s during the secondary heat setting, so as to prepare the UPE porous film.
Example 5 a method for preparing a UPE porous membrane with high specific surface area comprising the steps of:
s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing the polyethylene resin and the solvent system to form a mixed material after uniform mixing; the mixed material comprises the following substances in parts by weight: polyethylene resin: 20 parts; compound a:2 parts; compound B:84 parts;
the polyethylene resin is prepared from 70 mass% of ultra-high molecular weight polyethylene with mass average molecular weight of more than 300 ten thousand and 30 mass% of polyethylene with mass average molecular weight of 100-200 ten thousand and density of 0.92-0.98g/cm 3 Is composed of high density polyethylene; the compound A is glyceryl triacetate, and the compound B is decalin;
s2: heating, melting and mixing the mixed materials at 245 ℃ to form a casting solution, extruding the casting solution through a die head, and forming a liquid film on a carrier; the extrusion temperature of the die head is 230 ℃;
s3: setting the temperature of the liquid film carrier side to 40 ℃, setting the temperature of the air side to 25 ℃, carrying out phase separation and solidification for 9 seconds, converting the two sides of the liquid film, namely, changing the side of the liquid film originally close to the carrier into the side close to the air (the phase separation temperature is changed from 40 ℃ to 25 ℃), changing the side of the liquid film originally close to the carrier into the side close to the carrier (the temperature is changed from 25 ℃ to 40 ℃), continuing phase separation and solidification, continuing phase separation for 18 seconds, converting the two sides of the liquid film, namely, changing the side of the liquid film which is now close to the carrier into the side close to the carrier again (the phase separation temperature is changed from 25 ℃ to 40 ℃), changing the side close to the carrier into the side close to the carrier again (the phase separation temperature is changed from 40 ℃), and finally carrying out phase separation for 9 seconds; after the split-phase solidification is finished, forming a green film;
S4: then stretching the raw film, and simultaneously performing transverse stretching and longitudinal stretching, wherein the temperature of the transverse stretching and the longitudinal stretching is 100 ℃, the transverse stretching multiple is 6 times, the longitudinal stretching multiple is 6 times, the transverse stretching rate is 60%/s, and the longitudinal stretching rate is 60%/s; carrying out primary heat setting after stretching, wherein the temperature is 150 ℃ and the time is 45s;
s5: extracting the solvent system with an extraction liquid to remove the solvent system from the raw film to obtain a raw film; the extract is ethanol; the extraction temperature is 8 ℃; the extraction time was 4.5h.
S6: and (3) performing secondary heat setting on the original film, wherein the temperature is 180 ℃ and the time is 50s during the secondary heat setting, so as to prepare the UPE porous film.
Example 6 a method for preparing a UPE porous membrane with high specific surface area comprising the steps of:
s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing the polyethylene resin and the solvent system to form a mixed material after uniform mixing; the mixed material comprises the following substances in parts by weight: polyethylene resin: 22 parts; compound B:89 parts; the compound B is castor oil extract;
the polyethylene resin is prepared from 65 mass% of ultra-high molecular weight polyethylene with mass average molecular weight of more than 300 ten thousand and 35 mass% of polyethylene with mass average molecular weight of 100-200 ten thousand and density of 0.92-0.98g/cm 3 Is composed of high density polyethylene;
s2: heating, melting and mixing the mixed materials at 255 ℃ to form a casting solution, extruding the casting solution through a die head, and forming a liquid film on a carrier; the extrusion temperature of the die head is 245 ℃;
s3: setting the temperature of the liquid film carrier side to 50 ℃, setting the temperature of the air side to 30 ℃, and after phase separation and solidification for 24 seconds, converting the two sides of the liquid film, namely, changing the side of the liquid film originally close to the carrier into the side close to the air (changing the phase separation temperature from 50 ℃ to 30 ℃), changing the side of the liquid film originally close to the air into the side close to the carrier (changing the temperature from 30 ℃ to 50 ℃), and continuing phase separation and solidification for 24 seconds; after the split-phase solidification is finished, forming a green film;
s4: then stretching the raw film, and simultaneously performing transverse stretching and longitudinal stretching, wherein the temperature of the transverse stretching and the longitudinal stretching is 120 ℃, the transverse stretching multiple is 9 times, the longitudinal stretching multiple is 9 times, the transverse stretching rate is 80%/s, and the longitudinal stretching rate is 80%/s; carrying out primary heat setting after stretching, wherein the temperature is 160 ℃ and the time is 40s when the primary heat setting is carried out;
s5: extracting the solvent system with an extraction liquid to remove the solvent system from the raw film to obtain a raw film; the extract is isopropanol; the extraction temperature is 13 ℃; the extraction time was 3.5h.
S6: and (3) performing secondary heat setting on the original film, wherein the temperature is 170 ℃ and the time is 80s during the secondary heat setting, so as to prepare the UPE porous film.
And (3) a step of: structural characterization
Performing morphology characterization on the UPE porous film obtained in each embodiment by using a scanning electron microscope, and then obtaining required data;
the specific results are shown in the following table:
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as can be seen from the above table, in the UPE porous membranes prepared in examples 1 to 6 of the present invention, the first porous outer surface has a suitable number of first holes with a suitable pore diameter, and the second porous outer surface has a suitable number of second holes with a suitable pore diameter; the existence of the structure is beneficial to ensuring the stability of the first holes and the second holes, and is not easy to shrink or collapse, so that the stable flow rate of the membrane is ensured, and the change of the flow rate of the membrane is small in the use process; the porous membrane has a large flow velocity, is convenient for fluid to pass through the porous membrane quickly, shortens the filtering time, has large tensile strength and meets the requirements of practical application; meanwhile, the tensile strength of the film can be further improved, and the requirement of industrialization is met; the pore distribution on the first porous outer surface is relatively similar to the pore distribution on the second porous outer surface, also indicating that the UPE porous membrane is a symmetric membrane.
The UPE porous membranes prepared in the embodiments 1-6 have higher specific surface area and surface area of the membrane inside per unit membrane area, high porosity and proper thickness, and are beneficial to subsequent photoresist filtration, so that the photoresist with excellent performance is obtained.
Performance characteristics
Water flow rate test (test device as shown in FIG. 5)
Experimental procedure
Step one: the IPA wet sample to be tested is arranged on a support for decompression filtration, a valve 2 on the decompression filtration support is closed, a valve 1 is opened, a vacuum pump is started, and after the pressure is regulated to be 0.03MPa, the valve 1 is closed.
Step two: filling 50ml of test liquid (water) into a plastic measuring cylinder of a support for decompression filtration, opening a valve 2, starting timing from one scale to the other scale, and stopping timing;
step three: after the test is completed, the value displayed by the stopwatch is recorded, when all the test liquid passes through the filter membrane, the valve 2 on the bracket is closed, and the sample is taken out.
Testing the tensile strength and the elongation at break of each sample by using a universal tensile testing machine;
sample preparation Flow rate/s Tensile Strength/MPa Elongation at break/%
Example 1 406 60 400
Example 2 300 45 550
Example 3 217 65 350
Example 4 148 55 450
Example 5 80 50 500
Example 6 30 40 600
The UPE porous membranes prepared in the embodiments 1-6 have higher filtering speed and lower time cost; simultaneously has larger tensile strength and elongation at break, can meet the requirements of various assembly and processing, and really realize industrialization.
And (3) testing the filtering precision: the filtration membranes obtained in each example were tested for interception efficiency.
Experimental facilities: tianjin root particle counter KB-3; experiment preparation: the experimental device was assembled according to fig. 6, ensuring the device was clean, and rinsed with ultrapure water; a sample with a diameter of 47mm is taken and placed in the butterfly filter, so that the air tightness of the assembled filter is ensured to be good.
The experimental steps are as follows: pouring the challenge liquid into a storage tank, paying attention to the exhaust of a butterfly filter, pressurizing to 10kPa, and taking out the butterfly downstream filtrate by using a clean bottle; the number of particles in the filtrate and stock solutions was measured with a particle counter.
Interception efficiency:
wherein: η -interception efficiency,%; n 0-number of particles in stock solution, average of 5 counts, one; n 1-number of particles in filtrate, average of 5 counts.
The interception efficiency test results for each example are as follows:
as shown in the table, the UPE porous membranes prepared in the embodiments 1-6 have larger filtration precision, the interception efficiency is more than 95%, the UPE porous membranes have stronger interception capability on impurity particles (such as standard gold particle impurities), and the UPE porous membranes meet the actual industrial requirements and are particularly suitable for being applied to the field of photoresist.
After the samples prepared in examples 1 to 6 were made into a filter cartridge (membrane area: 1.3m 2), the membrane was wetted with IPA, and deionized water was passed through the filter cartridge at a certain flow rate at 20 c, and the pressures of the deionized water before and after passing through the filter cartridge were measured, thereby obtaining pressure losses corresponding to the filter cartridge.
Sample preparation Pressure loss
Example 1 20KPa@2L/min
Example 2 14KPa@4L/min
Example 3 34KPa@20L/min
Example 4 29KPa@20L/min
Example 5 25KPa@20L/min
Example 6 20KPa@20L/min
The table shows that after the UPE porous membrane is used for preparing the filter element, the pressure loss is smaller during filtration, so that the filter element still has higher filtration speed and high economic benefit when nano-scale impurity particles are filtered; is particularly suitable for filtering high-viscosity photoresist.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above examples, and all technical solutions belonging to the concept of the present invention belong to the protection scope of the present invention. It should be noted that modifications and adaptations to the present invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be within the scope of the present invention.

Claims (17)

1. A UPE porous membrane of high specific surface area comprising a first porous outer surface, a second porous outer surface, and a body between the first porous outer surface and the second porous outer surface, the body having a non-directional tortuous passageway therein, characterized in that:
The UPE porous membrane has a specific surface area of not less than 35m 2 /g;
The first porous outer surface comprises a plurality of branch-shaped continuous first fibers, and first holes are formed between adjacent continuous first fibers in a surrounding mode; the first fibers in the thickness direction are laminated to each other; the average diameter of the first fiber is 10-60nm;
the area ratio of the first holes on the outer surface of the first porous is 30-70%;
the second porous outer surface comprises a plurality of branch-shaped continuous second fibers, and second holes are formed between adjacent continuous second fibers in a surrounding mode; the average diameter of the second fiber is 10-60nm;
the area ratio of the second holes on the outer surface of the second porous is 30-70%;
the UPE porous membrane is a symmetrical membrane, and the polyolefin composition forming the UPE porous membrane at least comprises ultra-high molecular weight polyethylene with mass average molecular weight of more than 300 ten thousand.
2. A high specific surface area UPE porous membrane according to claim 1, characterized in that: the first porous outer surface is provided with a plurality of round hole-shaped first holes; the average pore diameter of the first holes is 1-150nm.
3. A high specific surface area UPE porous membrane according to claim 1, characterized in that: the thickness of the UPE porous film is 1-30 mu m; the porosity of the UPE porous membrane is 45-85%; the surface area of the membrane interior per unit membrane area is 0.4 to 0.8.
4. A high specific surface area UPE porous membrane according to claim 3, characterized in that: the specific surface area of the UPE porous membrane is 40-80m 2 /g; porosity of the UPE porous film50-75%; the UPE porous membrane has a thickness of 5-20 μm.
5. A high specific surface area UPE porous membrane according to claim 1, characterized in that: the ratio of the average diameter of the second fibers to the average diameter of the first fibers is 0.7 to 1.5; the second hole is in a round hole shape.
6. A high specific surface area UPE porous membrane according to claim 1, characterized in that: the average pore diameter of the second holes is 1-150nm; the ratio of the average pore diameter of the second holes to the average pore diameter of the first holes is 0.78-1.35.
7. A high specific surface area UPE porous membrane according to claim 1, characterized in that: the ratio between the initial bubble point of IPA and the complete bubble point of IPA of the UPE porous membrane is not lower than 0.4; and the IPA complete bubble point of the UPE porous membrane is not lower than 0.2MPa.
8. A high specific surface area UPE porous membrane according to claim 1, characterized in that: the shrinkage rate of the porous membrane is not more than 5% after the porous membrane is placed for 1 hour under the condition that the temperature is 120 ℃; the porous membrane has a compressibility of less than 15%; the pore closing temperature of the porous membrane is higher than 120 ℃.
9. A high specific surface area UPE porous membrane according to claim 1, characterized in that:
the interception efficiency of the UPE porous membrane to impurity particles with the particle size of 1-150nm is more than 95%;
the time required for 50ml of water to pass through the porous membrane with the diameter of 47mm is not more than 500s under the conditions of the pressure of 0.03MPa and the temperature of 20 ℃;
the tensile strength of the porous film is 20-100MPa, and the elongation at break is 200% -800%.
10. A method of preparing a UPE porous membrane of high specific surface area according to any one of claims 1 to 9, comprising the steps of:
s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing the polyethylene resin and the solvent system to form a mixed material after uniform mixing; wherein the polyethylene resin at least comprises an ultra-high molecular weight polyethylene with a mass average molecular weight of more than 300 ten thousand; the compound A is a non-solvent of polyethylene resin; the compound B is a solvent for the polyethylene resin;
the mixed material comprises the following substances in parts by weight: polyethylene resin: 10-25 parts of a lubricant; compound a:0-20 parts; compound B:70-90 parts;
the compound A is at least one of dimethyl phthalate, dioctyl adipate, ethylene glycol diacetate, dimethyl carbonate, palm oil and glyceryl triacetate, and the compound B is at least one of paraffin oil, white oil, hydraulic oil, decalin, castor oil extract and castor oil;
S2: heating, melting and mixing the mixed materials at 150-260 ℃ to form a casting solution, extruding the casting solution through a die head, and forming a liquid film on a carrier; the extrusion temperature of the die head is 200-250 ℃;
s3: carrying out phase-splitting solidification on the liquid film at 15-50 ℃ for 2-50s to form a green film; when the phase-splitting solidification is carried out, the temperature difference between the liquid film carrier side and the liquid film air side is 5-20 ℃; in the phase-splitting solidification process, the carrier side and the air side of the liquid film are at least converted once;
s4: then stretching the green film, and performing first heat setting after stretching;
s5: extracting the solvent system with an extraction liquid to remove the solvent system from the raw film to obtain a raw film;
s6: and performing heat setting on the original film for the second time to obtain the UPE porous film.
11. The method for preparing the UPE porous membrane with the high specific surface area according to claim 10, which is characterized in that: the polyethylene resin consists of 65-85 mass% of ultra-high molecular weight polyethylene with the mass average molecular weight of more than 300 ten thousand and 15-35 mass% of polyethylene with the mass average molecular weight of 100-200 ten thousand and the densityIs 0.92-0.98g/cm 3 Is composed of high density polyethylene.
12. The method for preparing the UPE porous membrane with the high specific surface area according to claim 10, which is characterized in that: and S4, stretching the raw film, namely, simultaneously stretching the raw film transversely and longitudinally, wherein the temperature of the transverse stretching and the longitudinal stretching is 60-150 ℃, the transverse stretching multiple is 1-10 times, and the longitudinal stretching multiple is 1-10 times.
13. The method for preparing a UPE porous membrane with high specific surface area according to claim 12, wherein the method comprises the following steps: s4, stretching the raw film, wherein the ratio of the longitudinal stretching multiple to the transverse stretching multiple is 0.8-2;
the transverse stretching rate is 5%/s-100%/s, and the longitudinal stretching rate is 5%/s-100%/s.
14. The method for preparing the UPE porous membrane with the high specific surface area according to claim 10, which is characterized in that: the extraction liquid in S5 is at least one of dichloromethane, acetone, methanol, ethanol, glycerol, tetrafluoroethane and isopropanol, and the extraction temperature is 5-25 ℃; the extraction time is 1-5h.
15. The method for preparing the UPE porous membrane with the high specific surface area according to claim 10, which is characterized in that: the temperature is 100-180 ℃ and the time is 20-90s during the first heat setting; the temperature in the second heat setting is 10-40 ℃ higher than that in the first heat setting, and the time is 20-90s.
16. Use of a UPE porous membrane of high specific surface area according to any one of claims 1-9, characterized in that: the UPE porous membrane is used for filtering photoresist.
17. A folded filter cartridge with a UPE porous membrane of high specific surface area according to any one of claims 1-9 comprising a central rod and a UPE porous membrane at the periphery of the central rod, the UPE porous membrane folded to form A pleat having valleys near a central rod side and peaks at an outer periphery, the UPE porous membrane having an upstream side in communication with an inlet and a downstream side in communication with an outlet, characterized in that: the UPE porous membrane is a UPE porous membrane with high specific surface area as in any one of claims 1-9, and the membrane area of the UPE porous membrane in the folded filter element is 0.1-2m 2
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