WO2023040880A1 - Upe porous membrane having high specific surface area, preparation method therefor, and use thereof - Google Patents

Abstract

The present invention provides a UPE porous membrane having a high specific surface area, a preparation method therefor, and a use thereof. The porous membrane comprises a first porous outer surface, a second porous outer surface, and a main body located between the first porous outer surface and the second porous outer surface. A non-directional tortuous path is provided in the main body. The specific surface area of the UPE porous membrane is not less than 35m²/g, and the specific surface area is high. A plurality of branched and continuous first fibers are provided on the first porous outer surface, and a first hole is formed around adjacent continuous first fibers. The first fibers in the thickness direction are stacked on one another. The first fibers have an average diameter of 10-60 nm. The UPE porous membrane is a symmetric membrane. The UPE porous membrane having a high specific surface area can perform entrapment by means of the membrane holes while also performing entrapment by adsorption, having excellent trapping performance for nano-scale fine impurities and having high entrapment efficiency. The UPE porous membrane is suitable for application in the field of photoresist filtering. The preparation method provided by the present invention can conveniently, quickly, and effectively prepare the UPE porous membrane.

Description

A kind of UPE porous film of high specific surface area and its preparation method and application technical field

The invention relates to the technical field of membrane materials, and more specifically relates to a UPE porous membrane with a high specific surface area and its preparation method and application.

Background technique

Polymer filter membrane is a kind of film made of organic high molecular polymer according to a certain process. The film mainly plays the role of filtration and separation. With the development of petroleum industry and science and technology, the application field of polymer filter membrane is continuously expanding. At present, the application fields include gas separation, seawater desalination, ultrapure water preparation, sewage treatment, artificial organ manufacturing, medicine, food, Agriculture, chemical industry, etc.; according to different polymers, polymer membranes can be divided into cellulose polymer membranes, polyamide polymer membranes, polysulfone polymer membranes, polyolefin polymer membranes filter membrane, etc.

Polyolefin polymer filter membranes mainly refer to polyethylene filter membranes, polypropylene filter membranes and other olefin filter membranes. Due to their excellent physical and chemical properties, they have a wide range of applications; for example, ultra-high molecular weight polyethylene (UPE) Filter membranes are usually used in photolithography processing and "wet etching and cleaning" (WEC) applications; Polyethylene filter membrane, which has excellent trapping performance for impurity particles with a size of about 10-50nm, and has a long service life, and its flux can remain relatively stable during long-term use.

In the field of photoresist, the purity requirements for photoresist are the most stringent, because a small amount of small impurities in photoresist will have a great impact on the quality of photoresist, resulting in photoresist The final product cannot meet the needs of practical applications; therefore, it is hoped that when filtering the photoresist with a filter membrane, various substances (particles, metal ions, etc.) in the photoresist can be intercepted as much as possible, so as to meet Practical application needs; but currently on the market, polyolefin filter membranes have an average interception efficiency for impurity particles in photoresist, which also limits the development of polyolefin polymer filter membranes to a certain extent.

Contents of the invention

In view of the deficiencies in the prior art, the purpose of the present invention is to provide a UPE porous membrane with a high specific surface area and its preparation method and application; , It can also adsorb and intercept impurities, so that various impurities can be captured with high quality, and the interception efficiency is high; it is especially suitable for the field of photoresist filtration.

In order to achieve the above object, the present invention provides the following technical scheme: a UPE porous membrane with high specific surface area, comprising a first porous outer surface, a second porous outer surface and a The main body between the outer surfaces, the main body has a non-directional tortuous passage, the specific surface area of the UPE porous membrane is not less than 35m ² /g; the first porous outer surface includes several branch-shaped continuous The first fiber, the first hole is formed around the adjacent continuous first fiber; the first fiber along the thickness direction is stacked with each other; the average diameter of the first fiber is 10-60nm; the UPE porous membrane is A symmetrical membrane, and the polyolefin composition constituting the UPE porous membrane includes at least ultra-high molecular weight polyethylene with a mass average molecular weight of more than 3 million.

After the specific surface area test of the UPE porous membrane of the present invention by the BET method, we were surprised to find that the specific surface area of the UPE porous membrane is higher, and its specific surface area is not less than ^35m2 /g (while the specific surface area of the existing UPE porous membrane is generally At 25-30m / ^g ), the specific surface area refers to the total area of the unit mass material (the present invention refers to the porous film), and the larger the specific surface area, the larger the total area of the UPE porous film of a certain quality; then Illustrate that the UPE porous membrane of the present invention has the following advantages:

1. In addition to intercepting the impurity substances in the photoresist through the membrane pores, the UPE porous membrane of the present invention can also absorb various impurity substances through van der Waals force and other forces; thereby improving the interception efficiency of the filter membrane for various impurities; At the same time, according to the experiment, it is found that the UPE porous membrane will also be slightly negatively charged after contacting the feed liquid. At this time, the negatively charged UPE porous membrane will have stronger adsorption; then, the advantage of the high specific surface area UPE membrane is that When the amount of charge per unit specific surface area is constant, the total charge carried by the UPE film with high specific surface area is large, so the adsorption effect is good and the ability to retain impurity substances is stronger; except for some metal ions and small particles of impurities, light The active ingredient organic resins in the resist will agglomerate during transportation and other processes (for example, the active ingredient PMMA resin in the KrF photoresist is easy to agglomerate, and the active ingredient ketones in the I-line/KrF photoresist also Easy to agglomerate), these effective resins after agglomeration have a certain impact on the light refractive index, which in turn affects the stability of the photolithography process, and the photolithography process cannot achieve the desired result; at this time, the charged high specific surface area UPE film is on the The above-mentioned impurities all have a good adsorption effect, which ensures the stability of the photolithography process and realizes the ideal photolithography process; in addition, UPE with high specific surface area can also be used as the base film material to develop the membrane for purification (removing metal ions). It has a high specific surface area, so the number of functional groups that can be grafted is relatively large, which greatly improves the removal rate and lifespan of metal ions in solvents for the membrane modified by UPE with high specific surface area; in special applications, if functional groups are required When the group adsorbs or exchanges the ions in the reagent, the high surface area UPE can increase the higher capacity space, so the UPE porous membrane is very suitable for various modifications of the base membrane;

2. When UPE with high specific surface area is used as a filter membrane, it can provide more contact opportunities between the reagent and the membrane, thereby increasing the possibility of impurities in the reagent being intercepted by the membrane, and the retention efficiency is further improved. At the same time, the UPE porous membrane with high specific surface area can provide more The large pore volume makes it have a greater dirt holding capacity as a filter membrane material.

At the same time, in the membrane structure of the UPE porous membrane provided by the present invention, it can be clearly seen that there are some first fibers on the first porous outer surface of the UPE porous membrane, and these first fibers present Branch-like structure, the first fiber is continuous with the first fiber; the adjacent continuous first fibers surround each other to form the first hole, and then form the porous structure of the membrane, through which the first fiber structure is formed The membrane has a higher specific surface area; at the same time, in the thickness direction, near the first porous outer surface, the first fibers are stacked together, interwoven and stacked, which is more conducive to impurities Filtration to ensure a high interception efficiency for impurity particles; on the first porous outer surface, the average diameter of the first fibers is 10-60nm, so that the thickness of the first fibers ensures that the membrane as a whole has a higher tensile strength. The tensile strength can meet the needs of actual industrial production. On the other hand, the first hole formed by the first fiber has strong stability and is 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 symmetrical membrane, which 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 the same. The pore shape, pore size and pore area ratio are basically similar, with little difference (close to the same); in actual use, any outer surface can be used as the liquid inlet surface (if it is an asymmetric membrane, a specific outer surface is generally required can be used as the liquid inlet surface), so related processes such as the assembly of the porous membrane are simpler in the present invention, and it is easier to make a high-quality filter element;

In the present invention, the material of the UPE porous membrane is uniform, that is, the entire membrane is made of polyethylene material, and there is no change in the material; ultra-high molecular weight polyethylene is referred to as UPE, which is a linear structure with excellent Comprehensive performance thermoplastic engineering plastics, the filter membrane made of ultra-high molecular weight polyethylene has high heat resistance, wear resistance, good mechanical properties, high tensile strength, excellent chemical compatibility, and a wide range of applications , is especially suitable for use in the field of photoresist; in the present invention, the polyolefin composition that constitutes the UPE porous membrane includes at least ultra-high molecular weight polyethylene with a mass average molecular weight of more than 3 million; this finally ensures that the filter membrane made It has high tensile strength and elongation at break, can meet the needs of practical applications, has a wide range of applications, and is especially suitable for use in the field of photoresist; it should be noted that the mass average molecular weight can be obtained as follows: filter polyethylene The sample of the film is heated and dissolved in o-dichlorobenzene, and measured by GPC liquid chromatography at a column temperature of 135°C and a flow rate of 1.0mL/min;

Wherein 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, etc.) or manually after using a scanning electron microscope to characterize the membrane structure, and Carry out corresponding calculations; during the preparation of the membrane, in the direction perpendicular to the thickness of the membrane (if the membrane is in the form of a porous membrane, this direction is the plane direction; if the membrane is in the form of a hollow fiber membrane, then this direction is perpendicular to the radial direction) , its characteristics such as pore size distribution and fiber thickness are roughly uniform and basically consistent; therefore, the average fiber diameter of the overall fiber on the plane can be reflected by the average fiber diameter in some areas on the corresponding plane; in actual measurement When , the outer surface of the membrane can be characterized by an electron microscope first to obtain the corresponding SEM image. Since the fiber thickness on the outer surface of the membrane is roughly uniform, a certain area can be selected, such as 1μm ² (1μm times 1μm) or 25μm ² (5μm multiplied by 5μm), the specific area depends on the actual situation, and then use the corresponding computer software or manually measure the diameter of the fiber in the area, and then calculate and get the average value, so as to obtain the first porous The average diameter of the first fiber on the outer surface, certainly those skilled in the art can also obtain the above-mentioned parameters by other measurement means, and the above-mentioned measurement means are for reference only; the pore area ratio of the first hole on the first porous outer surface, the first The average pore diameter of a hole can also be obtained according to the above method.

In addition, it is understood that "continuous" means that substantially all of the fibers are integrally interconnected, such as formed in one piece, without the use of additional adhesives or the like to interconnect them, unless torn by external force, otherwise the network Fibers cannot be separated from each other. At the same time, the continuous network fibers are also interconnected with the first porous outer surface and the second porous outer surface.

As a further improvement of the present invention, there are several circular first holes on the first porous outer surface; the area ratio of the first holes on the first porous outer surface is 30-70%; The average pore diameter of the first hole is 1-150nm.

It is well known that factors such as the pore size, number and shape of the pores in the membrane will have a greater impact on the filtration accuracy (retention efficiency), flow rate and other membrane properties of the membrane;

In the present invention, the first hole on the first porous outer surface is a circular hole structure, some of the first holes are circular, and some of the first holes are elliptical, and the first hole of the circular hole will produce a higher Pore volume, so that the porous membrane has a higher specific surface area; the average pore diameter of the first hole in the present invention is 1-150nm; The 150nm impurity particles play a good role in trapping, and its interception efficiency is greater than 95%, which ensures the accuracy of filtration, plays a sufficient role in retaining unwanted substances, and meets the needs of practical applications; and the first hole is in the first The area ratio on the porous outer surface (the ratio of the area of the first hole to the area of the corresponding membrane area) is 30-70%, which is easy to ensure that the overall membrane has a high porosity, which is not only conducive to the large flow rate of the porous membrane, but also facilitates The fluid passes through the porous membrane quickly, shortening the filtration time, and also has a large tensile strength, which meets the needs of practical applications.

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

In addition, the porosity test of the UPE porous membrane of the present invention is carried out. The porosity of the membrane refers to the ratio of the membrane pore volume of the porous membrane to the total volume. The membrane pores include two types of open pores and closed pores; commonly used porosity testing methods are: Mercury porosimetry, density method and dry and wet film weighing method; after testing, we found that the porosity of the UPE porous membrane is 45-85%, which has a relatively high porosity; that is, the UPE porous membrane has a high specific surface area At the same time, it also has high porosity, so it shows that the UPE porous membrane of the present invention has the following advantages:

1. Compared with ordinary chemicals, photoresist has a higher viscosity, and it is easy to generate bubbles when it passes through the filter medium, and the bubbles have a great influence on the subsequent process. The UPE porous membrane with high specific surface area and high porosity can make photolithography The filtration speed of the glue is faster, and at the same time, due to the faster exhaust caused by the high porosity (the exhaust rate is faster, it is easier to discharge the air bubbles), which makes the air bubbles in the filtered photoresist less and more It is beneficial to ensure the quality of photoresist;

2. For the photoresist terminal application filter element, the shell size is generally small, so the area of the filter membrane filled inside is generally small (generally no more than 2m ² ); and as the membrane pores decrease, and due to When the membrane area cannot be greatly increased, the UPE porous membrane with high specific surface area and high porosity can achieve lower pressure (lower pressure loss) at the same flow rate, so that the high surface area UPE membrane is relatively viscous. Photoresist can achieve very small pores (filtering nano-scale impurity particles) while meeting flow requirements (filtering speed is still fast, time cost is low, and economic benefits are high);

When the thickness of the membrane is too small, the mechanical strength of the membrane will be low; at the same time, due to the short filtration time, effective filtration cannot be performed; when the thickness of the membrane is too large, the filtration time will be too long, and the time cost will be too high. Large; the thickness of the UPE porous membrane of the present invention is 1-30 μm, which ensures that the UPE porous membrane not only has high mechanical strength, but also can perform effective filtration with high filtration efficiency, short filtration time, and low time cost. Used in the field of photoresist;

During filtration, various fluids move along the direction of membrane thickness to achieve corresponding filtration and filtration is one-time, so the surface area inside the membrane per unit membrane area is particularly important; unit membrane area The internal surface area of the membrane refers to the surface area of the internal area of the membrane on a porous membrane of a certain area. The larger the value, the larger the internal surface area of the porous membrane; The surface area is 0.4-0.8, and its value is relatively large, which shows that ① the UPE porous membrane has a large amount of dirt holding capacity, long service life and high economic benefits; ② the area of fluid passing through the porous membrane is larger, and impurities are relatively easier to intercept. So as to improve the retention efficiency; ③When the UPE is used as the base membrane for graft modification, the functional groups that need to be grafted are more easily grafted to the surface area inside the membrane, thereby further improving the performance of the UPE porous membrane; especially suitable for Photoresist field.

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

The specific surface area refers to the total area of the material per unit mass. The larger the value, the larger the total area of the material with a certain quality; as a preference, the specific surface area of the UPE porous membrane of the present invention is 40-80m ² /g, It shows that the UPE porous membrane with a certain quality has a larger total area; when intercepting the fluid, the membrane area that the fluid contacts is large, and it is easier to intercept impurities in the fluid, further improving the interception efficiency; at the same time, the UPE porous membrane is used as For the base membrane, when performing various modification treatments, the contact area between the modifier and the membrane is large, the reaction is fully and completely, and it is easier to achieve various modifications, such as the hydrophilic modification of UPE membrane;

This kind of UPE membrane with high specific surface area can be used as the base membrane for charge modification. On the other hand, even if it is not modified, according to the experiment, the UPE porous membrane will be slightly negatively charged after contacting the feed liquid. At this time, the negatively charged UPE Porous membranes also have a certain degree of adsorption; then, the advantage of high specific surface area UPE membranes is that under the condition of a certain amount of charge per unit specific surface area, the total charge carried by high specific surface area UPE membranes is large, so the adsorption effect is good. The ability of impurity substances is stronger;

In addition to some metal ions and particle impurities, the agglomeration of active component resins in the photoresist (for example, the component PMMA resin in the KrF photoresist is easy to agglomerate, and the component ketones in the I-line/KrF photoresist are easy to agglomerate. Agglomeration) has an impact on the refractive index of light, and then easily affects the stability of the photolithography process; then at this time, the charged UPE film with a high specific surface area has a good adsorption effect on the above impurities.

When the porosity of the membrane is too high, the tensile strength of the membrane will be too low, its mechanical properties are poor, the industrial practical value is low, and it cannot meet the market demand; and when the porosity of the membrane is too low, on the one hand, it will affect The flow rate of the membrane leads to a slow filtration speed of the membrane, a long filtration time, and a large time cost; on the other hand, the dirt holding capacity of the membrane is too low and the service life is too short, and the membrane needs to be replaced in a short period of time. The economic cost is greatly improved; preferably, the porosity of the porous membrane in the present invention is 50-75%, so that the UPE porous membrane not only has a higher tensile strength, but also has a faster filtration rate, a larger flow rate, and a higher High dirt holding capacity, able to retain more impurity particles, long service life and low economic cost;

Preferably, the thickness of the UPE porous membrane is 5-20 μm; through the mutual synergy between the film thickness, membrane porosity and membrane specific surface area, it is ensured that the UPE porous membrane has a higher tensile strength, which is relatively high. Short filtration time and high filtration accuracy meet the needs of practical applications.

As a further improvement of the present invention, the second porous outer surface includes several branch-shaped continuous second fibers, and second holes are formed around adjacent continuous second fibers; the second fibers The average diameter is 10-60nm.

In the membrane structure of the UPE porous membrane provided by the present invention, it can be clearly seen that there are also some second fibers on the second porous outer surface of the UPE porous membrane, and the shape of the second fiber is the same as that of the first fiber. The shape of a fiber is approximately the same, but there is a certain difference in thickness, but the difference is also small, which also shows that the UPE porous membrane of the present invention is a symmetrical membrane, and the two outer surfaces of the membrane are very similar in structure; these second fibers It also presents a branch-like structure, the second fiber is continuous with the second fiber; the adjacent continuous second fibers also surround each other to form the corresponding second hole, and then form the porous structure of the membrane, through The membrane formed by the second fiber structure further has higher specific surface area and high porosity; at the same time, in the thickness direction, near the second porous outer surface, the second fibers are also stacked together, Interweaving (staggered) stacking, so that it is more conducive to the filtration of impurities, ensuring that the porous membrane has a higher interception efficiency for impurity particles; on the second porous outer surface, the average diameter of the second fiber is 10-60nm, so that The thick and thin second fibers further ensure that the overall membrane has a high tensile strength, which can meet the needs of actual industrial production, and the second holes formed by the second fibers have strong stability and are not easy to collapse or shrink, thereby ensuring stability of the fluid flow rate.

As a further improvement of the present invention, the ratio of the average diameter of the second fiber to the average diameter of the first fiber is 0.7-1.5; the second hole is circular; the second hole is outside the second hole The area ratio on the surface is 30-70%.

As a further improvement of the present invention, the average pore diameter of the second holes is 1-150 nm; 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 well known that factors such as the aperture size, quantity and shape of the pores of the membrane will have a greater impact on the filtration accuracy (retention efficiency) of the membrane, the membrane properties such as flow velocity; the second pores on the second porous outer surface in the present invention are The shape of the second hole is almost the same as the shape of the first hole, but there is a small difference in the diameter of the hole; some second holes are circular, and some second holes are elliptical. The second hole of the second hole easily produces a higher pore volume, so that the porous membrane has a higher specific surface area; and the area ratio of the second hole on the second porous outer surface (the ratio of the second hole area to the corresponding membrane area area) It is 30-70%, which not only helps the porous membrane to have a larger flow rate, but also facilitates the rapid passage of the fluid through the porous membrane, shortening the filtration time, and also makes the porous membrane have a greater tensile strength to meet the needs of practical applications; with this passage, After measuring the average pore diameter of the second hole is 1-150nm, the average pore diameter of the second hole is approximately equal to the average pore diameter of the first hole, there is actually a certain difference, and the difference is also small, which further proves that the UPE Porous membrane is a symmetrical membrane. All parts of the symmetrical membrane have approximately the same characteristics, and its pore structure and fiber structure will not change with the thickness of the membrane. The membrane can act on impurity particles with a particle size of 1-150nm Strong capture capacity;

In addition, in the present invention, the ratio of the average diameter of the second fiber to the average diameter of the first fiber is 0.7-1.5, and the ratio of the average pore diameter of the second hole to the average pore diameter of the first hole is 0.78-1.35, although the second fiber There is a certain difference between the thickness and the thickness of the first fiber, but the difference between the two is very small and relatively uniform; there is also a certain difference between the average pore diameter of the second hole and the average pore diameter of the first hole, but the difference is small and relatively uniform; thus It is further illustrated that the UPE porous membrane is a symmetrical membrane, and the properties of the two outer surfaces of the membrane are basically the same; in actual use, any outer surface of the porous membrane can be used as the liquid inlet surface, and the The process of the filter element is easier and simpler, and the economic benefit is higher.

As a further improvement of the present invention, 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; the complete bubble point of IPA of the UPE porous membrane is not lower than 0.2MPa.

One of the important performance characteristics of the filter membrane is the bubble point, and the test method of the bubble point is well known in the art. The procedures for these tests are explained in detail, for example, in ASTM F316-70 and ANS/ASTM F316-70 (reapproved 1976), which are hereby incorporated by reference. The size of the bubble point is related to the pore size of the pores on the porous membrane; generally speaking, the larger the pore size, the lower the bubble point; the smaller the pore size, the higher the bubble point; the bubble point includes the initial bubble point and the complete exit Bubble point; the IPA full bubble point of the UPE porous membrane of the present invention is not less than 0.2MPa, thereby illustrating that the aperture in the UPE porous membrane is relatively small, and then passes through the non-directional tortuous passage in the membrane main body, so that the porous membrane can It has a good trapping effect on impurity particles with a particle size of 1-150nm, ensures the accuracy of filtration, and plays a sufficient role in retaining unwanted substances;

The initial bubble point mainly reflects the maximum pore size inside the membrane, while the complete bubble point mainly reflects the average pore size of the membrane; the ratio between the initial bubble point and the complete bubble point can also reflect the symmetry of the membrane to a certain extent, and the higher the ratio Smaller, to a certain extent, the greater the asymmetry of the membrane, the greater the ratio, to a certain extent, the better the symmetry of the membrane; the difference between the initial bubble point of IPA of the UPE porous membrane and the complete bubble point of IPA The ratio between them is not less than 0.4, which further shows that the membrane is a symmetrical membrane. The pore size and pore distribution inside the membrane body are similar to the corresponding features on the two outer surfaces of the membrane, and there is no pore diameter. Extra large holes ensure filtration accuracy and filtration speed.

As a further improvement of the present invention, the shrinkage rate of the porous membrane is not more than 5% after being placed under the condition of 120°C for 1 hour; the compression rate of the porous membrane is less than 15%; the pores of the porous membrane are closed The temperature is higher than 120°C.

The UPE porous membrane was tested for heat resistance. After placing the porous membrane of the present invention at a temperature of 120° C. for 1 hour, it was found that the shrinkage rate was not more than 5%, which indicated that the UPE porous membrane had high thermal stability. , at a higher temperature, the membrane pores are not easy to shrink or deform, so as to ensure that the membrane has a high retention efficiency for a long time, the flow rate changes little during use, and the service life is long, which further shows that its application range is very wide, especially suitable for Used in the field of photoresist;

During long-term use or processing of liquid filters, the porous membrane needs to be able to maintain a good porous structure, thereby ensuring high retention efficiency and excellent trapping of impurities; and the compressibility of the UPE porous membrane of the present invention Less than 15%, indicating that the membrane pores of the porous membrane are not easily deformed during various processing or long-term use of the porous membrane, and the porous structure remains stable, which further ensures that the porous membrane has a stable flow rate and can ensure retention efficiency for a long time; The compressibility in the present invention is obtained in the following manner: pressurize the UPE porous membrane at 2 MPa at a temperature of 70°C for 30 seconds, and then release the pressure at 25°C for 30 seconds. The ratio of the film thicknesses before pressing yields the compressibility. In the present invention, if the compressibility of the UPE porous membrane is more than 15%, the following problems may occur: during long-term use or processing of the liquid filter, the porous membrane undergoes a pressure change more than necessary, and the original porosity cannot be maintained. The quality structure, the water permeability becomes unstable; the filtration pressure is abnormally increased due to the closure of the pores.

In addition, the pore closure temperature of the UPE porous membrane of the present invention is higher than 120°C; Near the high-temperature body contact part, the porosity of the UPE porous membrane will not be lost, and the water permeability can be easily maintained. Even after processing, the expected filtration area can be obtained, and then the ideal flow rate and retention efficiency can be guaranteed. The porosity of the membrane is stable and meets the actual situation. Industrialization needs.

As a further improvement of the present invention, the interception efficiency of the UPE porous membrane to impurity particles with a particle size of 1-150nm is greater than 95%; at a pressure of 0.03MPa and a temperature of 20°C, 50ml of water passes through a porous membrane with a diameter of 47mm The required time is not higher than 500s; the tensile strength of the porous membrane is 20-100MPa, and the elongation at break is 200%-800%.

Through the interception test of UPE porous membrane, it is found that the porous membrane can play a good role in trapping the impurity particles with a particle size of 1-150nm, and its interception efficiency is greater than 95%, which ensures the accuracy of filtration and plays a sufficient role. Retention of unwanted substances, suitable for use in the field of photoresist;

Through the flow rate test of UPE porous membrane, under the condition of pressure of 0.03MPa and temperature of 20℃, the time required for 50ml of water to pass through the UPE porous membrane with a diameter of 47mm is not more than 500s; it shows that the UPE porous membrane has a large The flow rate, the time required for the fluid to pass through the porous membrane is shorter, the time cost is lower, and the economic benefit is higher. It also shows that the UPE porous membrane of the present invention is suitable for use in the field of photoresist;

The important index for evaluating the mechanical strength of the membrane is exactly the tensile strength and elongation at break of the membrane; under certain conditions, the greater the tensile strength of the membrane, the better the mechanical strength of the membrane; in the present invention, the UPE porous The tensile strength of the film is 20-100MPa, and the elongation at break is 200%-800%; it shows that the UPE porous membrane of the present invention has larger tensile strength and elongation at break, and its mechanical properties are better, and it has industrial practical value. High, fully able to meet market demand.

The present invention also provides a kind of preparation method of the UPE porous membrane of high specific surface area, comprises the following steps:

S1: Add polyethylene resin to the solvent system composed of compound A and compound B, stir and mix, and mix uniformly to form a mixed material; wherein the polyethylene resin includes at least one ultra-high molecular weight polyethylene with a mass average molecular weight of more than 3 million ; Compound A is a non-solvent for polyethylene resin; Compound B is a solvent for polyethylene resin; The mixed material includes the following components by weight: polyethylene resin: 10-25 parts; 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 , the compound B is at least one of paraffin oil, white oil, hydraulic oil, decahydronaphthalene, castor oil extract, castor oil;

S2: Heat, melt and knead the mixed materials at a temperature of 150-260°C to form a casting solution, and then extrude through a die to form a liquid film on the carrier; the extrusion temperature of the die is 200-250°C;

S3: The liquid film is phase-separated and solidified at a temperature of 15-50°C, and the phase-separated solidification time is 2-50s to form a green film; during the phase-separated solidification, the liquid film carrier side and the liquid film air The temperature difference between the sides is 5-20°C; and during the phase-separation solidification process, the carrier side and the air side of the liquid film are mutually transformed at least once;

S4: Then stretch the raw film, and perform the first heat setting after stretching;

S5: extracting the solvent system with the extract, so that the solvent system is removed from the raw film to obtain the original film;

S6: heat-setting the original film for the second time to obtain a UPE porous film.

As a further improvement of the present invention, the polyethylene resin consists of 65-85% by mass of ultra-high molecular weight polyethylene with a mass-average molecular weight of more than 3 million and 15-35% by mass of ultra-high molecular weight polyethylene with a mass-average molecular weight of 1-2 million and a density of 0.92-0.98g/cm3 high-density polyethylene composition.

As a further improvement of the present invention, stretching the raw film in S4 refers to simultaneously stretching the raw film transversely and longitudinally. The temperature during transverse stretching and longitudinal stretching is 60-150°C. The multiple is 1-10 times, and the longitudinal stretching multiple is 1-10 times.

As a further improvement of the present invention, in S4, the raw film is stretched, and the ratio of the longitudinal stretching ratio to the transverse stretching ratio is 0.8-2; the transverse stretching rate is 5%/s-100%/s, and the longitudinal stretching The elongation rate is 5%/s-100%/s.

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

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

In the present invention, a cast sheet with holes is formed by a thermally induced phase separation method, and then the cast sheet is stretched and formed to prepare a UPE porous membrane with a high specific surface area. During the preparation, various materials are firstly mixed to form a mixed material , the mixed material includes polyethylene resin and corresponding solvent system. Ultra-high molecular weight polyethylene is referred to as UPE. It is a thermoplastic engineering plastic with a linear structure and excellent comprehensive properties. The porous film made of UPE can have higher Heat resistance, wear resistance, and good mechanical properties, high tensile strength, wide application range; the polyethylene resin used in the present invention includes at least one ultra-high molecular weight polyethylene with a mass average molecular weight of more than 3 million , that is, in the present invention, only one UPE with a mass average molecular weight of more than 3 million can be used as a film-forming raw material, and it can also be compounded, for example, a UPE with a mass average molecular weight of more than 3 million and a UPE with a mass average molecular weight of less than 3 million High-density polyethylene is compounded as a film-forming raw material; preferably, the polyethylene resin of the present invention is composed of 65-85 mass % of ultra-high molecular weight polyethylene with a mass-average molecular weight of more than 3 million and 15-35 mass % of mass-average Composed of high-density polyethylene with a molecular weight of 1-2 million and a density of 0.92-0.98g/cm ³ ; compared to a single ultra-high-molecular-weight polyethylene, such a composite of ultra-high-molecular-weight polyethylene and high-density polyethylene The resulting polyethylene resin is more conducive to obtaining a UPE porous membrane with relatively small pore size, high porosity, and high tensile strength; and the solvent system can only be compound B, which is a solvent for polyethylene resin, and the solvent is It means that when heated to the boiling point of compound B at most, compound B can completely dissolve polyethylene resin to form a homogeneous solution; compound B is paraffin oil, white oil, hydraulic oil, decahydronaphthalene, castor oil extract, castor oil at least one of them; preferably, the solvent system can be composed of compound A and compound B, wherein compound A is a non-solvent for polyethylene resin, and non-solvent means that when heated to the boiling point of this compound at most, the compound does not It cannot dissolve polyethylene resin to form a homogeneous solution, but can only have a certain swelling effect on polyethylene resin; compound A is dimethyl phthalate, dioctyl adipate, ethylene glycol diacetate, dicarbonate At least one of methyl ester, palm oil, and triacetin; the content of compound B in the solvent system is much higher than that of compound A, so as to ensure that the polyethylene resin can be fully melted and dispersed in the solvent under the action of subsequent high temperature In the system, the casting solution has a suitable solid content;

Compared with selecting a single solvent as the solvent system, the present invention uses the compounding of solvent and non-solvent as the corresponding solvent system. Such a solvent system has the following advantages:

1. Holes with smaller pore sizes are more likely to appear in the raw film formed after the phase separation of the liquid film, and more small holes are formed at the same time; this is because the liquid film is undergoing liquid-liquid phase separation and solidification due to temperature changes (through heat phase-separation solidification) while diffusion exchange occurs between the non-solvent and the solvent, thereby further improving the phase-separation solidification rate;

2. It is easier to form fibers and fibers are easier to form, so as to ensure that the UPE porous membrane has higher tensile strength and good mechanical properties. This is because due to the accelerated phase separation rate, the crystal nuclei are easier to precipitate, and the fibers are Crystal nucleus production, which makes it easier to form fibers;

Of course, if desired, other substances such as antioxidants, nucleating agents, fillers and similar substances can be used as additives of the present invention, thereby further improving a certain performance of UPE porous membrane; polyethylene resin and corresponding solvent system (comprising compound A and compound B) can be stirred and mixed for 10-24 hours at a temperature of 100-140°C to form a corresponding mixed material;

Then put the mixed material into the extruder and heat, melt and knead at a temperature of 150-260°C (preferably 200-255°C), and heat, melt and knead for 10-60min, so as to ensure that the polyethylene resin is completely melted in the corresponding In the solvent system, uniform in shape, stable casting solution; the solid content of the casting solution of the present invention is preferably 10-20%, if the solid content is too low, the tensile strength of the final film will be too low and the mechanical strength will be poor , cannot meet the needs of practical applications; if the solid content is too high, the viscosity of the casting film solution will be too high, the requirements for the mechanical equipment used will be too high, the production cost will be too high, and mass production will not be possible;

Then through the die extrusion (die forming), on the carrier (the carrier can be a roll or other carrier) to form a plate-shaped liquid film, the die extrusion temperature 200-250 ° C among the present invention; as preferably, the extruder The highest temperature inside the die is at least 5°C higher than the extrusion temperature of the die head, so as to ensure that the temperature of each area of the liquid film is basically the same during extrusion, which is beneficial to the subsequent phase separation and solidification, and the phase separation is more uniform, and then an ideal film structure can be obtained. Facilitate the formation of symmetrical membranes;

Then place the liquid film at a temperature of 15-50°C for phase-separation curing; at higher temperatures, a single homogeneous solution can be formed between the solvent system and the polyethylene resin, and as the system temperature decreases, The homogeneous solution will become turbid, the polyethylene resin will slowly precipitate, and then the phase separation and solidification phenomenon will occur; the phase separation temperature on both sides of the liquid film in the present invention is relatively low (15-50 ° C), and the liquid film is easy to phase separation quickly , forming more crystal film (nanopore, small hole is easier to form high specific surface area), easy to form more holes (high porosity) and more obvious fibrosis; and if the solvent system is a solvent and non-solvent Combination, then in addition to the temperature change leading to phase separation, the diffusion exchange between the solvent and the non-solvent will further accelerate the phase separation solidification rate, thereby forming a small-pore membrane (the faster the phase separation rate, the smaller the hole diameter formed), Promptly form the nanomembrane needed by the present invention; The UPE porous membrane that the present invention finally forms is a kind of symmetric membrane, and in order to form symmetric membrane, just require the degree of phase separation on both sides of the liquid membrane to be substantially the same, so that the The film pore structure of the two outer surfaces of the porous membrane is similar, and the fiber structure is similar; as one of the key points of the present invention, the structure of the two outer surfaces of the membrane is guaranteed to be similar by the joint action of two conditions; the first condition is that the liquid film The temperature difference between the carrier side (the carrier can be a roller or other carriers) and the air side of the liquid film is 5-20°C, for example, the temperature of the air side is 20°C, then the temperature of the carrier side can be set to 30°C, at this time, since the temperature on both sides of the liquid film is different, and the heat transfer rate on both sides is also different, the phase separation rate on both sides of the liquid film is different at this time; the second condition is that the phase separation and solidification During the process, the carrier side and the air side of the liquid film are mutually changed at least once, and a change means that when the liquid film moves on the carrier, when the liquid film is changed from one carrier to another, the two sides of the liquid film are changed. Mutual transformation, at this time, the air side of the original liquid film becomes the carrier side of the liquid film, and the roller side becomes the air side; the number of transformations is preferably 1-3 times; through the interaction between the carrier side and the air side on both sides of the liquid film Transformation, under the action of appropriate time, so as to ensure that the phase separation on both sides of the liquid film is basically the same, so that a symmetrical raw film can be formed; when performing phase separation curing, the temperature of phase separation curing and the time of phase separation curing The selection of other factors is extremely critical. These factors determine the speed of phase separation curing, and whether the film with ideal membrane structure and membrane hole size can be obtained in the end; the phase separation curing time is 2-50s, which is relatively short. , so as to obtain the UPE porous membrane with the ideal membrane structure we need;

After the phase separation of the liquid film is completed, the raw film is formed. A certain number of holes with a certain pore size have appeared on the two surfaces of the raw film, and the pore sizes of the holes on the two surfaces are basically the same. In order to further obtain the required membrane pore size UPE porous membrane, the present invention stretches the raw film, the current existing stretching technology is to stretch longitudinally first, and then stretch transversely; but after research, it is found that if the raw film is stretched according to the conventional stretching During processing, the pores on the raw film are prone to partial collapse or deformation, and finally the UPE porous membrane with the required film structure cannot be obtained. Therefore, in the present invention, the processing is carried out by synchronous stretching, that is, the raw film is stretched transversely and longitudinally at the same time. Stretching, the temperature during transverse stretching and longitudinal stretching is 60-150°C, the transverse stretching ratio is 1-10 times, and the longitudinal stretching ratio is 1-10 times. The benefit of stretching like this is exactly not only obtained the required membrane pore diameter of the present invention, has improved the tensile strength of membrane, simultaneously hole is not easy to collapse or deform, is beneficial to finally obtaining the UPE filter membrane of membrane structure required by the present invention; As Preferably, the ratio of the longitudinal stretch ratio to the transverse stretch ratio is 0.8-2, the transverse stretch rate is 5%/s-100%/s, and the longitudinal stretch rate is 5%/s-100%/s, thereby further Improve the uniformity of the hole diameter in the membrane and ensure the symmetry of the membrane;

After the synchronous stretching, the first heat setting is carried out. The function of the first heat setting is to carry out preliminary shaping of the raw film after stretching, so as to ensure that the pores of the film will not change basically, and at the same time eliminate the internal stress caused by stretching; The temperature during the first heat setting is 100-180°C, and the time is 20-90s; then extraction is carried out, and the solvent system is removed from the raw film through the extract to obtain the original film; the extract is dichloromethane, acetone, methanol At least one of , ethanol, glycerol, tetrafluoroethane and isopropanol; the extraction temperature is 5-25°C; the extraction time is 1-5h; by selecting the appropriate extraction agent and extraction conditions, the solvent system is guaranteed It is completely removed from the raw film, and the time required for extraction is relatively short; after the extraction, the original film is subjected to a second heat setting, and the temperature of the second heat setting is 10 times higher than that of the first heat setting. -40℃, the function of the second heat setting is to eliminate the internal stress caused by extraction on the one hand, and to finalize the membrane pores of the original membrane on the other hand, so as to ensure that the membrane pores will basically not change and obtain the required membrane pore structure. UPE porous membrane; the UPE porous membrane of the present invention is a symmetrical membrane, the pore size distribution on the membrane is uniform, it has excellent trapping performance for impurity particles, and the interception efficiency is high; it has high specific surface area and high porosity at the same time, and the pressure loss is low. Small, especially suitable for application in the field of photoresist.

As a further improvement of the present invention, a kind of purposes of UPE porous membrane, described UPE porous membrane is used for filtering photoresist;

After the UPE porous membrane is made into a capsule or cartridge filter element, due to the high specific surface area and high porosity of the UPE porous membrane, the gas generated in the process of filtering the photoresist is easier to discharge, so that the filtered photoresist In the glue, the bubble content is lower, thereby reducing the bad influence of bubbles on the properties of the photoresist, ensuring that the photoresist with excellent properties is obtained; therefore, the UPE porous membrane of the present invention is particularly suitable for use in the field of photoresist filtration; in When performing photoresist filtration, any outer surface of the UPE porous membrane can be used as the liquid inlet surface, and there is no need to guide a specific outer surface as the liquid inlet surface, which avoids the failure of effective filtration due to user's operation errors ; The UPE porous membrane has excellent trapping performance for various impurity particles in the photoresist, and has high filtration accuracy; at the same time, it has a high dirt holding capacity, a long service life, and high economic benefits.

As a further improvement of the present invention, a pleated filter element with a UPE porous membrane includes a central rod and a UPE porous membrane positioned on the periphery of the central rod, the UPE porous membrane is folded to form pleats, and the pleats have pleats near the central rod side. The valley and the pleated peaks of the periphery, the UPE porous membrane has an upstream side and a downstream side, the upstream side communicates with the inlet, and the downstream side communicates with the outlet, and the UPE porous membrane is any one of claims 1-12. The UPE porous membrane mentioned above, the membrane area of the UPE porous membrane in the pleated filter element is 0.1-2m ² .

For photoresist terminal application filter elements, especially capsule filter elements, the shell size is generally small, so the membrane area filled inside is generally small, and the membrane area of UPE porous membrane in capsule filter elements is mostly 0.1- 0.6m ² , and the membrane area of the UPE porous membrane in the cartridge filter element generally does not exceed 2m ² ; compared with the UPE membrane with low specific surface area and low porosity, the high specific surface area UPE membrane of the present invention can realize Lower pressure at the same flow rate, so that the high surface area UPE membrane can achieve very small pores (filtering nano-scale particles) for photoresists with considerable viscosity, while meeting the flow requirements, the pressure loss is relatively small, and filtering nanometer A good flow rate can be obtained even when the level of impurity particles is high, and the economic benefit is higher.

Beneficial effects of the present invention: the UPE porous membrane provided by the present invention is a symmetrical membrane, which has a more optimized membrane structure compared with existing filter membrane materials, including a first porous outer surface, a second porous outer surface The surface and the main body between the first porous outer surface and the second porous outer surface, the specific surface area of the UPE porous membrane is not less than 35m ² /g, and the first porous outer surface includes several branch-shaped continuous The first fiber, the first hole is formed around the adjacent continuous first fiber; the first fiber along the thickness direction is stacked with each other; the average diameter of the first fiber is 10-60nm; the UPE porous membrane with high specific surface area is in During the filtration process, it has excellent trapping performance for nano-scale fine impurities, can adsorb various fine particles, and has high retention efficiency; in addition, the UPE porous membrane is particularly suitable for modification as a base membrane, and the modification effect is good; suitable for applications In the field of photoresist filtration; the preparation method provided by the invention can conveniently, quickly and effectively prepare the above-mentioned UPE porous membrane.

Description of drawings

Fig. 1 is the scanning electron microscope (SEM) picture of the first porous outer surface on the UPE porous membrane that embodiment 6 prepares, and wherein magnification is 10K *;

Fig. 2 is the further enlarged scanning electron microscope (SEM) picture of the first porous outer surface on the UPE porous membrane prepared in Example 6, wherein the magnification is 50K ×;

Fig. 3 is the scanning electron microscope (SEM) picture of the second porous outer surface on the UPE porous membrane that embodiment 6 prepares, and wherein magnification is 10K *;

Fig. 4 is the further enlarged scanning electron microscope (SEM) figure of the second porous outer surface on the UPE porous membrane prepared in Example 1, wherein the magnification is 50K ×;

Fig. 5 is the device schematic diagram of UPE porous membrane flow velocity test of the present invention;

Fig. 6 is a schematic diagram of the device for testing the filtration accuracy (retention efficiency) of the UPE porous membrane of the present invention.

Detailed ways

In order to illustrate the overall concept of the present application more clearly, the following will be described in detail in the form of examples.

A kind of preparation method of the UPE porous membrane of embodiment 1 high specific surface area, comprises the following steps:

S1: Add polyethylene resin to the solvent system composed of compound A and compound B, stir and mix, and mix uniformly to form a mixed material; the mixed material includes the following components by weight: polyethylene resin: 12 parts; compound A: 5 parts; Compound B: 72 parts;

The polyethylene resin is composed of 83% by mass of ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more and 17% by mass of high-density polyethylene with a mass average molecular weight of 1 to 2 million and a density of 0.92 to 0.98 g/cm ³ ; Compound A is dioctyl adipate, and Compound B is white oil;

S2: Heat, melt and knead the mixed materials at a temperature of 215°C to form a casting liquid, and then extrude through a die to form a liquid film on the carrier; the extrusion temperature of the die is 205°C;

S3: Set the temperature on the carrier side of the liquid film to 25°C, and the temperature on the air side to 20°C. After 4 seconds of phase separation and solidification, the two sides of the liquid film will change, that is, the side of the liquid film that was originally close to the support becomes the side close to the air. side (phase separation temperature changed from 25°C to 20°C), and the side of the liquid film that was close to the air changed to the side close to the carrier (temperature changed from 20°C to 25°C), and the phase separation curing continued for 4 seconds; the phase separation curing ended After that, the biofilm is formed;

S4: Then stretch the raw film, and carry out transverse stretching and longitudinal stretching at the same time, the temperature during transverse stretching and longitudinal stretching is 80°C, the transverse stretching ratio is 3 times, and the longitudinal stretching ratio is 3 times , the transverse stretching rate is 20%/s, and the longitudinal stretching rate is 20%/s; the first heat setting is carried out after the stretching is completed, and the temperature during the first heat setting is 130°C, and the time is 65s;

S5: Extract the solvent system with the extract, so that the solvent system is removed from the raw film to obtain the original film; the extract in S5 is dichloromethane; the extraction temperature is 15°C; the extraction time is 3h;

S6: The original film is heat-set for the second time, the temperature of the second heat-setting is 160° C., and the time is 45 s to prepare a UPE porous film.

Embodiment 2 A kind of preparation method of the UPE porous membrane of high specific surface area, comprises the following steps:

S1: Add polyethylene resin to the solvent system composed of compound A and compound B, stir and mix, and mix uniformly to form a mixed material; the mixed material includes the following components by weight: polyethylene resin: 14 parts; compound A: 8 parts ; Compound B: 75 parts; Polyethylene resin consists of 80% by mass of ultra-high molecular weight polyethylene with a mass average molecular weight of more than 3 million and 20% by mass of ultrahigh molecular weight polyethylene with a mass average molecular weight of 1 to 2 million and a density of 0.92 to 0.98 g/cm ³ high-density polyethylene composition; Compound A is ethylene glycol diacetate, and Compound B is paraffin oil;

S2: Heat, melt and knead the mixed materials at a temperature of 220°C to form a casting solution, and then extrude through a die to form a liquid film on the carrier; the extrusion temperature of the die is 210°C;

S3: Set the temperature on the carrier side of the liquid film to 30°C, and the temperature on the air side to 20°C. After 5 seconds of phase separation and solidification, the two sides of the liquid film will change, that is, the side of the liquid film that was originally close to the carrier becomes the side close to the air. side (the phase separation temperature changes from 30°C to 20°C), and the side of the liquid film that was originally close to the air changes to the side close to the carrier (temperature changes from 20 to 30°C), and continues to separate and solidify. After 10 seconds of phase separation, The two sides of the liquid film change again, that is, the side of the liquid film that is close to the air at this time becomes the side close to the carrier again (the phase separation temperature changes from 20°C to 30°C), and the side of the liquid film that is close to the carrier at this time side, change to the side close to the air again (phase separation temperature changes from 30°C to 20°C), and finally separate phase for 5s; after phase separation and curing, a green film is formed;

S4: Then stretch the raw film, and carry out transverse stretching and longitudinal stretching at the same time. The temperature during transverse stretching and longitudinal stretching is 85°C, and the transverse stretching ratio is 4 times, and the longitudinal stretching ratio is 4 times. , the transverse stretching rate is 25%/s, and the longitudinal stretching rate is 25%/s; the first heat setting is carried out after the stretching is completed, and the temperature during the first heat setting is 135°C, and the time is 60s;

S5: extracting the solvent system with the extract, so that the solvent system is removed from the raw film to obtain the original film; the extract is acetone; the extraction temperature is 20°C; the extraction time is 2.5h;

S6: The original film is heat-set for the second time, the temperature of the second heat-setting is 150° C., and the time is 75 s to prepare a UPE porous film.

Embodiment 3 A kind of preparation method of the UPE porous membrane of high specific surface area, comprises the following steps:

S1: Add polyethylene resin to the solvent system composed of compound A and compound B, stir and mix, and mix uniformly to form a mixed material; the mixed material includes the following components by weight: polyethylene resin: 16 parts; compound A: 12 parts; compound B: 78 parts; polyethylene resin consists of 75% by mass of ultra-high molecular weight polyethylene with a mass average molecular weight of more than 3 million and 25% by mass of ultrahigh molecular weight polyethylene with a mass average molecular weight of 1 to 2 million and a density of 0.92 to 0.98g /cm ³ of high-density polyethylene; compound A is dimethyl phthalate, and compound B is hydraulic oil;

S2: Heat, melt and knead the mixed materials at a temperature of 225°C to form a casting solution, and then extrude through a die to form a liquid film on the carrier; the extrusion temperature of the die is 215°C;

S3: Set the temperature on the carrier side of the liquid film to 32°C, and the temperature on the air side to 20°C. After phase separation and solidification for 6 seconds, the two sides of the liquid film will change, that is, the side of the liquid film that was originally close to the carrier becomes the side close to the air. side (phase separation temperature changed from 32°C to 20°C), and the side of the liquid film that was close to the air changed to the side close to the carrier (temperature changed from 20°C to 32°C), and continued phase separation solidification. After 12 seconds of phase separation, The two sides of the liquid film change again, that is, the side of the liquid film that is close to the air at this time becomes the side close to the carrier again (the phase separation temperature changes from 20°C to 32°C), and the side of the liquid film that is close to the carrier at this time side, change to the side close to the air again (phase separation temperature changes from 32°C to 20°C), and finally separate phase for 6s; after phase separation and curing, a green film is formed;

S4: Then stretch the raw film, and carry out transverse stretching and longitudinal stretching at the same time, the temperature during transverse stretching and longitudinal stretching is 90°C, the transverse stretching ratio is 4 times, and the longitudinal stretching ratio is 5 times , the transverse stretching rate is 40%/s, and the longitudinal stretching rate is 50%/s; after the stretching, the first heat setting is carried out, and the temperature during the first heat setting is 140°C, and the time is 55s;

S5: extracting the solvent system with the extract, so that the solvent system is removed from the raw film to obtain the original film; the extract is isopropanol; the extraction temperature is 23° C.; the extraction time is 2 h.

S6: The original film is heat-set for the second time. During the second heat-setting, the temperature is 165° C. and the time is 60 s to prepare a UPE porous film.

Embodiment 4 A kind of preparation method of the UPE porous membrane of high specific surface area, comprises the following steps:

S1: Add polyethylene resin to the solvent system composed of compound A and compound B, stir and mix, and mix uniformly to form a mixed material; the mixed material includes the following components by weight: polyethylene resin: 18 parts; compound A: 17 parts; Compound B: 81 parts;

The polyethylene resin is composed of 72% by mass of ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more and 28% by mass of high-density polyethylene with a mass average molecular weight of 1 to 2 million and a density of 0.92 to 0.98 g/cm ³ ; Compound A is palm oil, and Compound B is castor oil;

S2: Heat, melt and knead the mixed materials at a temperature of 235°C to form a casting liquid, and then extrude through a die to form a liquid film on the carrier; the extrusion temperature of the die is 225°C;

S3: Set the temperature on the carrier side of the liquid film to 35°C, and the temperature on the air side to 25°C. After 15 seconds of phase separation and solidification, the two sides of the liquid film will change, that is, the side of the liquid film that was originally close to the carrier becomes the side close to the air. side (phase separation temperature changed from 35°C to 25°C), and the side of the liquid film that was close to the air changed to the side close to the carrier (temperature changed from 25°C to 35°C), and the phase separation curing continued for 15 seconds; the phase separation curing ended After that, the biofilm is formed;

S4: Then stretch the raw film, and carry out transverse stretching and longitudinal stretching at the same time. The temperature during transverse stretching and longitudinal stretching is 80°C, the transverse stretching ratio is 6 times, and the longitudinal stretching ratio is 5 times. , the transverse stretching rate is 60%/s, and the longitudinal stretching rate is 50%/s; the first heat setting is carried out after the stretching is completed, and the temperature during the first heat setting is 145°C, and the time is 50s;

S5: Extracting the solvent system with the extract, so that the solvent system is removed from the raw film to obtain the original film; the extract in S5 is glycerol; the extraction temperature is 10° C.; the extraction time is 4 hours.

S6: The original film is heat-set for the second time, the temperature for the second heat-setting is 170° C., and the time is 65 s to prepare a UPE porous film.

Embodiment 5 A kind of preparation method of the UPE porous membrane of high specific surface area, comprises the following steps:

S1: Add polyethylene resin to the solvent system composed of compound A and compound B, stir and mix, and mix uniformly to form a mixed material; the mixed material includes the following components by weight: polyethylene resin: 20 parts; compound A: 2 parts; Compound B: 84 parts;

The polyethylene resin is composed of 70% by mass of ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more and 30% by mass of high-density polyethylene with a mass average molecular weight of 1 to 2 million and a density of 0.92 to 0.98 g/cm ³ ; The compound A is triacetin, and the compound B is decahydronaphthalene;

S2: Heat, melt and knead the mixed materials at a temperature of 245°C to form a casting liquid, and then extrude through a die to form a liquid film on the carrier; the extrusion temperature of the die is 230°C;

S3: Set the temperature on the carrier side of the liquid film to 40°C, and the temperature on the air side to 25°C. After 9 seconds of phase separation and solidification, the two sides of the liquid film will change, that is, the side of the liquid film that was originally close to the carrier becomes the side close to the air. side (phase separation temperature changed from 40°C to 25°C), and the side of the liquid film that was originally close to the air changed to the side close to the carrier (temperature changed from 25 to 40°C), and continued phase separation solidification. After 18s of phase separation, The two sides of the liquid film change again, that is, the side of the liquid film that is close to the air at this time becomes the side close to the carrier again (the phase separation temperature changes from 25°C to 40°C), and the side of the liquid film that is close to the carrier at this time The side becomes the side close to the air again (the phase separation temperature changes from 40°C to 25°C), and finally, after phase separation for 9s; after the phase separation and curing is completed, a green film is formed;

S4: Then stretch the raw film, and carry out transverse stretching and longitudinal stretching at the same time. The temperature during transverse stretching and longitudinal stretching is 100°C, the transverse stretching ratio is 6 times, and the longitudinal stretching ratio is 6 times. , the transverse stretching rate is 60%/s, and the longitudinal stretching rate is 60%/s; the first heat setting is carried out after the stretching is completed, and the temperature during the first heat setting is 150°C, and the time is 45s;

S5: extracting the solvent system with the extract, so that the solvent system is removed from the raw film to obtain the original film; the extract is ethanol; the extraction temperature is 8° C.; the extraction time is 4.5 h.

S6: The original film is heat-set for the second time, the temperature for the second heat-setting is 180° C., and the time is 50 s to prepare a UPE porous film.

Embodiment 6 A kind of preparation method of the UPE porous membrane of high specific surface area, comprises the following steps:

S1: Add polyethylene resin to the solvent system composed of compound A and compound B, stir and mix, and mix uniformly to form a mixed material; the mixed material includes the following components by weight: polyethylene resin: 22 parts; compound B: 89 parts ; Compound B is castor oil extract;

The polyethylene resin is composed of 65% by mass of ultra-high molecular weight polyethylene with a mass average molecular weight of 3 million or more and 35% by mass of high-density polyethylene with a mass average molecular weight of 1 to 2 million and a density of 0.92 to 0.98 g/cm ³ ;

S2: Heat, melt and knead the mixed materials at a temperature of 255°C to form a casting solution, and then extrude through a die to form a liquid film on the carrier; the extrusion temperature of the die is 245°C;

S3: Set the temperature on the carrier side of the liquid film to 50°C, and the temperature on the air side to 30°C. After 24 seconds of phase separation and solidification, the two sides of the liquid film will change, that is, the side of the liquid film that was originally close to the carrier becomes the side close to the air. side (phase separation temperature changed from 50°C to 30°C), and the side of the liquid film that was close to the air changed to the side close to the carrier (temperature changed from 30°C to 50°C), and continued phase separation curing for 24s; phase separation curing After the end, a raw film is formed;

S4: Then stretch the raw film, and carry out transverse stretching and longitudinal stretching at the same time, the temperature during transverse stretching and longitudinal stretching is 120°C, the transverse stretching ratio is 9 times, and the longitudinal stretching ratio is 9 times , the transverse stretching rate is 80%/s, and the longitudinal stretching rate is 80%/s; after the stretching, the first heat setting is carried out, and the temperature during the first heat setting is 160°C, and the time is 40s;

S5: extracting the solvent system with the extract, so that the solvent system is removed from the raw film to obtain the original film; the extract is isopropanol; the extraction temperature is 13° C.; the extraction time is 3.5 h.

S6: The original film is heat-set for the second time, the temperature of the second heat-setting is 170° C., and the time is 80 s to prepare a UPE porous film.

1: Structural characterization

The UPE porous membrane obtained by each embodiment is characterized by scanning electron microscope, and then obtains required data; Concrete results are as follows:

As can be seen from the above table, in the UPE porous membrane prepared in Examples 1-6 of the present invention, the first porous outer surface has an appropriate number of first holes with an appropriate pore diameter, and the second porous outer surface has an appropriate number and an appropriate pore diameter. The second hole; the existence of such a structure is beneficial to ensure the stability of the first hole and the second hole, and it is not easy to shrink or collapse, so as to ensure that the membrane has a stable flow rate. During use, the membrane flow rate changes little; And it has a large flow rate, which is convenient for the fluid to pass through the porous membrane quickly, shortens the filtration time, and has a large tensile strength to meet the needs of practical applications; at the same time, it can further improve the tensile strength of the membrane to meet the needs of industrialization; The pore distribution on the first porous outer surface is relatively similar to the pore distribution on the second porous outer surface, which also shows that the UPE porous membrane is a symmetrical membrane.

The UPE porous membranes prepared in Examples 1-6 of the present invention all have higher specific surface area and surface area inside the membrane per unit membrane area, high porosity and suitable thickness, which are beneficial to subsequent photoresist filtration and obtain excellent performance. Photoresist.

performance characteristics

Water flow rate test (test device as shown in Figure 5)

Experimental procedure

Step 1: Put the sample to be tested after wetting with IPA on the support for decompression filtration, close valve 2 on the decompression filter holder, open valve 1, start the vacuum pump, adjust the pressure to the test pressure of 0.03MPa, and then close the valve 1.

Step 2: Put 50ml of test liquid (water) into the plastic measuring cylinder of the support for decompression filtration, open the valve 2, start timing from a certain scale, and stop at another scale;

Step 3: After the test, record the value displayed by the stopwatch. When all the test liquid passes through the filter membrane, close the valve 2 on the bracket and take out the sample.

Test the tensile strength and elongation at break of each sample with a universal tensile testing machine;

sample	Velocity/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 Examples 1-6 of the present invention all have a relatively high filtration rate and low time cost; meanwhile, they have relatively high tensile strength and elongation at break, which can meet various assembly and processing requirements , to truly realize industrialization.

Filtration accuracy test: the interception efficiency test is carried out on the filter membrane obtained in each example.

Experimental equipment: Tianjin Logan Particle Counter KB-3; Experimental preparation: Assemble the experimental device according to Figure 6, ensure that the device is clean, and rinse the device with ultra-pure water; take a sample with a diameter of 47 mm and install it in a butterfly filter. Make sure that the assembled filter is airtight.

Experimental steps: pour the challenge liquid into the storage tank, pay attention to the exhaust of the butterfly filter, pressurize to 10kPa, use a clean bottle to receive the filtrate downstream of the butterfly; use a particle counter to test the number of particles in the filtrate and the original solution.

Interception efficiency:

In the formula: η───interception efficiency, %; n0───the number of particles in the stock solution, the average of 5 groups of counts, pcs; n1───the number of particles in the filtrate, the average of 5 groups of counts, pcs.

The interception efficiency test results of each example are as follows:

As can be seen from the above table, the UPE porous membranes prepared in Examples 1-6 of the present invention have relatively high filtration accuracy, and their interception efficiencies are all above 95%, and have strong trapping of impurity particles (such as standard gold particle impurities) Ability to meet the actual industrial needs, especially suitable for application in the field of photoresist.

After making the sample obtained in Examples 1-6 into a filter core (with a membrane area of 1.3m ² ), first wet the membrane with IPA, and then pass through the filter core with deionized water at a certain flow rate at 20°C. Test the pressure before and after the deionized water flows through the filter element, so as to obtain the pressure loss of the corresponding filter element.

sample	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

It can be seen from the above table that after the filter element is made of the UPE porous membrane of the present invention, the pressure loss during filtration is small, thereby ensuring that when filtering nano-scale impurity particles, it still has a faster filtration speed and high economic benefits; it is especially suitable for application For high viscosity photoresist filtration.

The above descriptions are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions under the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principles of the present invention should also be regarded as the protection scope of the present invention.

Claims (18)

1. A UPE porous membrane with high specific surface area, comprising a first porous outer surface, a second porous outer surface and a main body between the first porous outer surface and the second porous outer surface, the main body has a non- Directional tortuous pathway, characterized by:

   The specific surface area of the UPE porous membrane is not less than 35m ² /g;

   The first porous outer surface includes several branch-shaped continuous first fibers, and first holes are formed around adjacent continuous first fibers; the first fibers along the thickness direction are stacked with each other; the The average diameter of the first fibers is 10-60 nm;

   The UPE porous membrane is a symmetrical membrane, and the polyolefin composition constituting the UPE porous membrane at least includes ultra-high molecular weight polyethylene with a mass average molecular weight of more than 3 million.
2. A kind of UPE porous membrane with high specific surface area according to claim 1, it is characterized in that: there are a plurality of circular hole-shaped first holes on the first porous outer surface; The area ratio of the outer surface of the hole is 30-70%; the average pore diameter of the first hole is 1-150nm.
3. The UPE porous membrane with high specific surface area according to claim 1, characterized in that: the thickness of the UPE porous membrane is 1-30 μm; the porosity of the UPE porous membrane is 45-85%; the unit membrane area The internal surface area of the membrane is 0.4-0.8.
4. A UPE porous membrane with high specific surface area according to claim 3, characterized in that: the specific surface area of the UPE porous membrane is ^40-80m2 /g; the porosity of the UPE porous membrane is 50-75% ; The thickness of the UPE porous membrane is 5-20 μm.
5. The UPE porous membrane with high specific surface area according to claim 1, characterized in that: the second porous outer surface includes several branch-shaped continuous second fibers, and the adjacent continuous second Second holes are formed around the fibers; the average diameter of the second fibers is 10-60 nm.
6. The UPE porous membrane with high specific surface area according to claim 5, characterized in that: the ratio of the average diameter of the second fiber to the average diameter of the first fiber is 0.7-1.5; the second hole is a circle Pore shape; the area ratio of the second hole on the second porous outer surface is 30-70%.
7. A kind of UPE porous membrane of high specific surface area according to claim 5, it is characterized in that: the average pore diameter of described second hole is 1-150nm; The average pore diameter of described second hole and the average pore diameter of first hole The ratio is 0.78-1.35.
8. The UPE porous membrane of a kind of high specific surface area according to claim 1, is characterized in that: the ratio between the IPA initial bubble point of described UPE porous membrane and the IPA complete bubble point is not less than 0.4; Described UPE porous membrane The IPA complete bubble point of the membrane is not lower than 0.2MPa.
9. A UPE porous membrane with high specific surface area according to claim 1, characterized in that: the shrinkage of the porous membrane is not more than 5% after the porous membrane is placed under the condition of 120° C. for 1 hour; The compression ratio is less than 15%; the pore closure temperature of the porous membrane is higher than 120°C.
10. A kind of UPE porous membrane of high specific surface area according to claim 1, is characterized in that:

    The interception efficiency of the UPE porous membrane to impurity particles with a particle size of 1-150nm is greater than 95%;

    At a pressure of 0.03MPa and a temperature of 20°C, the time required for 50ml of water to pass through a porous membrane with a diameter of 47mm is no more than 500s;

    The tensile strength of the porous membrane is 20-100 MPa, and the elongation at break is 200%-800%.
11. The preparation method of the UPE porous membrane of a kind of high specific surface area as described in any one of claims 1 to 10, comprises the following steps:

    S1: Add polyethylene resin to the solvent system composed of compound A and compound B, stir and mix, and mix uniformly to form a mixed material; wherein the polyethylene resin includes at least one ultra-high molecular weight polyethylene with a mass average molecular weight of more than 3 million ; Compound A is a non-solvent for polyethylene resin; Compound B is a solvent for polyethylene resin;

    The mixed material comprises the following components by weight: polyethylene resin: 10-25 parts; 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 glycerol triacetate, and the compound B is At least one of paraffin oil, white oil, hydraulic oil, decalin, castor oil extract, castor oil;

    S2: Heat, melt and knead the mixed materials at a temperature of 150-260°C to form a casting solution, and then extrude through a die to form a liquid film on the carrier; the extrusion temperature of the die is 200-250°C;

    S3: The liquid film is phase-separated and solidified at a temperature of 15-50°C, and the phase-separated solidification time is 2-50s to form a green film; during the phase-separated solidification, the liquid film carrier side and the liquid film air The temperature difference between the sides is 5-20°C; and during the phase-separation solidification process, the carrier side and the air side of the liquid film are mutually transformed at least once;

    S4: Then stretch the raw film, and perform the first heat setting after stretching;

    S5: extracting the solvent system with the extract, so that the solvent system is removed from the raw film to obtain the original film;

    S6: heat-setting the original film for the second time to obtain a UPE porous film.
12. A method for preparing a UPE porous membrane with a high specific surface area according to claim 11, wherein the polyethylene resin is composed of 65-85% by mass of ultra-high molecular weight polyethylene with a mass average molecular weight of more than 3 million and 15-35% by mass of high-density polyethylene with a mass-average molecular weight of 1-2 million and a density of 0.92-0.98 g/cm ³ .
13. The preparation method of a UPE porous membrane with a high specific surface area according to claim 11, characterized in that: stretching the raw film in S4 refers to performing transverse stretching and longitudinal stretching on the raw film at the same time, and transverse stretching The temperature during stretching and longitudinal stretching is 60-150°C, the transverse stretching ratio is 1-10 times, and the longitudinal stretching ratio is 1-10 times.
14. The preparation method of a UPE porous membrane with high specific surface area according to claim 13, characterized in that: in S4, the raw film is stretched, and the ratio of the longitudinal stretch ratio to the transverse stretch ratio is 0.8-2; The transverse stretching rate is 5%/s-100%/s, and the longitudinal stretching rate is 5%/s-100%/s.
15. The preparation method of a UPE porous membrane with a high specific surface area according to claim 11, wherein the extract in S5 is dichloromethane, acetone, methanol, ethanol, glycerol, tetrafluoroethane and isopropyl At least one of the alcohols; the extraction temperature is 5-25°C; the extraction time is 1-5h.
16. A method for preparing a UPE porous membrane with a high specific surface area according to claim 11, characterized in that: the temperature during the first heat setting is 100-180°C, and the time is 20-90s; The temperature is 10-40°C higher than the temperature during the first heat setting, and the time is 20-90s.
17. The use of a UPE porous membrane with a high specific surface area according to any one of claims 1-10, characterized in that: the UPE porous membrane is used for filtering photoresist.
18. A kind of pleated filter core with UPE porous membrane according to any one of claims 1-10, comprising a central rod and a UPE porous membrane positioned at the periphery of the central rod, the UPE porous membrane is folded to form pleats, and the pleats have The pleat valley on the central rod side and the pleat peak on the periphery, the UPE porous membrane has an upstream side and a downstream side, the upstream side communicates with the inlet, and the downstream side communicates with the outlet, it is characterized in that: the UPE porous membrane is The UPE porous membrane according to any one of claims 1-12, wherein the membrane area of the UPE porous membrane in the pleated filter element is 0.1-2m ² .

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