UPE film and preparation method thereof

Abstract

The invention discloses a preparation method of a UPE film and a UPE filter membrane obtained through the preparation method, and belongs to the technical field of membrane materials. According to the preparation method of the UPE film, a solvent and a non-solvent are compounded with ultra-high molecular weight polyethylene, and raw membrane raw materials with rich pore diameters are preset; two times of extraction and stretching treatment in a specific sequence are needed, the interception efficiency and mechanical strength of the product are improved, meanwhile, the content of impurities such as metal ions and / or total organic carbon in the product is greatly reduced, and the obtained UPE film is very suitable for being used as a purification medium of photoresist.

Description

Technical Field

[0001] This application relates to the field of membrane technology, specifically to a method for preparing a UPE thin film and the UPE filter membrane obtained by the method. Background Technology

[0002] Photoresist is a crucial material in the electronics industry for fabricating fine patterns, particularly indispensable in the manufacture of semiconductor chips, display panels, and printed circuit boards. Due to the extremely high purity requirements of photoresist—for example, high levels of metal ions and total organic carbon (TOC) can reduce the quality of the formed fine patterns, thus compromising the yield in semiconductor chip, display panel, and printed circuit board manufacturing—strict, high-precision purification is essential before both production and use. This ensures that the content of metal ions and TOC is controlled to extremely low levels, placing high demands on the purification medium itself. Besides requiring high purification efficiency and good mechanical properties, if the purification medium itself contains even slightly high levels of metal ions or TOC, these impurities may be introduced during the photoresist purification and filtration process. Therefore, the purification medium itself must also have a low impurity content. Currently, existing preparation methods using purification media such as filter membranes are generally insufficient to meet these requirements, necessitating further development of suitable products to suit this application scenario. Summary of the Invention

[0003] The purpose of this application is to overcome the shortcomings of the existing technology and provide a method for preparing UPE films. The method involves pre-setting a film-forming raw material with rich pore size using a solvent- and non-solvent compounded ultra-high molecular weight polyethylene. The method requires two extractions and stretching treatments in a specific order to improve the retention efficiency and mechanical strength of the product, while significantly reducing the content of impurities such as metal ions and / or total organic carbon in the product. The resulting UPE film is very suitable as a purification medium for photoresists.

[0004] To achieve the above objectives, in a first aspect of this application, a method for preparing a UPE thin film is provided, comprising the following steps:

[0005] (1) Polyethylene resin, organic A and organic B are compounded and heated to melt and mix. The resulting liquid film is cooled and solidified to obtain a raw film. The polyethylene resin is ultra-high molecular weight polyethylene resin, organic A is a solvent of polyethylene resin, and organic B is a non-solvent of polyethylene resin.

[0006] (2) An adsorption layer is set on two surfaces of the biofilm, and then the biofilm is subjected to rinsing extraction treatment with an extractant along the thickness direction of the biofilm at an ambient temperature not higher than 30°C for 2-3 hours. The adsorption layer includes activated carbon, the activated carbon includes micropores, the proportion of the micropores in the total pore volume of the activated carbon is a, a≥75% and a / b is 0.025-0.095, b is the rinsing extraction flow rate of the extractant, in mL / min;

[0007] (3) The raw film after the rinsing and extraction treatment is subjected to a first stretching treatment to obtain the treated film;

[0008] (4) A catalytic adsorption layer is provided on both surfaces of the treatment membrane, and then the treatment membrane is immersed in the extractant and irradiated with light. Catalytic adsorption extraction is carried out at an ambient temperature not higher than 30°C. The catalytic adsorption layer includes porous titanium dioxide particles with a porosity ≥15% and an average particle size ≥0.3μm.

[0009] (5) The treated membrane after catalytic adsorption extraction is subjected to a second stretching treatment, then wound up and heat-set to obtain the UPE film.

[0010] UPE (ultra-high molecular weight polyethylene) film is currently a popular product for purification in the semiconductor field. It has advantages such as light weight, high purification efficiency, and high mechanical strength. However, in addition to meeting the above requirements, the purification of photoresist also needs to meet the requirements of small size retention accuracy and low impurity content of the film itself. If the metal ions or total organic carbon carried by it exceed the standard, it may cause secondary pollution during the purification process. Therefore, in the technical solution of this application, in order to balance the low impurity content, retention efficiency, and mechanical strength of the product, when preparing the film by combining ultra-high molecular weight polyethylene resin with organic liquid phase, the solvent and non-solvent of the resin are pre-mixed. This makes the film formed after a certain phase separation more porous, and the gradient pores are formed based on the diffusion exchange reaction of solvent and non-solvent, providing channels for the precipitation of impurities in the raw materials, and also providing the basic structure for the expected mechanical strength and retention efficiency of the subsequent product.

[0011] Through continuous research, the inventors of this application have discovered that the biofilm prepared above, through a two-step adsorption combination of an adsorption layer and a catalytic adsorption layer under specific conditions, can achieve the goal of low heavy metal ions and low total organic carbon in the product composition. First, an adsorption layer of activated carbon with adsorption effect is set on the surface of the biofilm. Then, a first extraction treatment is carried out by scouring extraction (specifically, placing it in an industrial water bed and replacing the fluid phase with the extractant, or using a spray gun, which is not specifically limited here). In this process, since the extractant flows dynamically along the thickness direction of the biofilm, a liquid flow attraction force is generated along the thickness direction. This attraction force, together with the adsorption force of the activated carbon in the adsorption layer, pulls out the impurities in the biofilm and fixes them in the activated carbon, or directly dissolves them in the flowing extractant due to the similar compatibility mechanism. It can also be purified by the adsorption layer before the extractant comes into contact with the biofilm. Compared with traditional adsorption extraction or adsorption treatment, it is more beneficial to avoid the situation where the precipitated impurities under no external force flow back into the biofilm due to local concentration differences. This process can effectively remove most of the impurities in the biofilm along the gradient pores.

[0012] However, in this process, the number of micropores in the activated carbon and the ratio of the number of micropores to the extraction flow rate of the extractant during dynamic rinsing have a significant impact on the impurity removal effect. On the one hand, insufficient micropores in the activated carbon result in insufficient surface adsorption activity, meaning the space available for impurities to be contained is also insufficient. On the other hand, if the flow rate is too low, the resulting attraction is weak and cannot adequately attract impurities from the biofilm. However, if the flow rate is too high, some tiny activated carbon particles in the adsorption layer may detach or even fall into the pores of the biofilm, increasing the impurity content. Furthermore, it has been found that... Even with increased flow rate and higher attractive force, the improvement in adsorption efficiency is still limited when the number of micropores in activated carbon is insufficient. However, when the number of micropores in activated carbon is large and the number of micropores in activated carbon increases synchronously with the scouring and extraction flow rate of the extractant during dynamic scouring, the adsorption efficiency can be effectively improved when the two have an appropriate ratio. Therefore, in this application, it is necessary to dynamically control the proportion of micropores in activated carbon and the ratio of the proportion of micropores in activated carbon to the flow rate of the extractant, taking into account the impurity removal efficiency, the full utilization of activated carbon, and the stability of activated carbon particles.

[0013] More preferably, the a / b value is a range of one or any two of the following: 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, 0.085, and 0.095.

[0014] After the first dynamic scouring extraction, the process involves a first stretching treatment of the biofilm. This operation increases the pore size and resin crystallinity in the biofilm, allowing impurities deep within the biofilm to be exposed, and also improves the strength of the biofilm to some extent.

[0015] After this treatment, considering the increased pore size of the biofilm, if dynamic rinsing / activated carbon adsorption is still used, it may cause damage to the biofilm and the risk of secondary pollution. Therefore, the present application proposes to perform a second extraction on the biofilm after the first stretching treatment by static impregnation. During this process, a catalytic adsorption layer is set on the surface of the biofilm. This functional layer contains titanium dioxide, which can act as a catalyst under ultraviolet light to catalytically degrade some organic impurities in the biofilm and is more easily dissolved in the extractant. At the same time, this component is set as a porous structure, which, similar to activated carbon, also has a partial physical adsorption effect. Based on the physical-chemical adsorption effect, the impurities in the biofilm are highly separated. However, the pore size and size of the titanium dioxide particles need to be limited. If the porosity of the particles is too small, its adsorption effect is low, and the products after catalytic degradation may still flow back into the biofilm. If the size is too small, during the impregnation process, the particles may detach from the catalytic adsorption layer due to the adsorption force and fall onto the surface of the biofilm. Both situations will cause secondary pollution.

[0016] After secondary extraction, the impurities in the membrane layer are basically removed. Then, the membrane layer is stretched again, which further improves the product's retention efficiency and ultimately shows ideal purification effect and excellent basic material performance.

[0017] It should be noted that in the preparation method described in this application, the membrane formation in step (2) and the setting of the adsorption layer and the setting of the catalytic adsorption layer in step (4) are carried out in a reversible manner. When the adsorption layer or catalytic adsorption layer is set on the membrane, it can be fixed to the membrane surface in a non-adhesive, interlocking manner. After fixing, there is still space between the membrane and the adsorption / catalytic adsorption layer to allow the extractant to flow. After extraction, the adsorption layer or catalytic adsorption layer can be completely separated from the membrane surface without damaging the membrane. For example, in step (4)... In step (2), an adsorption layer is placed at the bottom in advance, followed by the formation of a biofilm. Then, a second adsorption layer is placed on the side where the biofilm is not superimposed on the adsorption layer. The edge of the composite layer is then fixed with a clamp. After rinsing and extraction, the clamp is released and the adsorption layer is directly separated. Alternatively, after setting the composite layer, adhesive tape can be used to fix the adsorption layer in the non-biofilm area to ensure that the biofilm is wrapped between the two adsorption layers and does not move. Those skilled in the art can also use other methods to set it up, and there are no specific restrictions on this.

[0018] Preferably, the organic compound A includes organic compound A1 and organic compound A2, and |T1-T2|≥30℃, where T1 is the boiling point of organic compound A1 and T2 is the boiling point of organic compound A2.

[0019] As mentioned above, the use of solvents and non-solvents allows ultra-high molecular weight polyethylene to form gradient pores during the film formation process. However, when different organic compounds A are used as solvents for polyethylene resin, and the boiling points of the compounded substances are different, the formation of film pores is affected, resulting in a staged gradient. At this point, the inventors discovered that when two solvents with a large difference in boiling point, preferably greater than 30°C, are used in combination, the pore gradient of the film can be made more uniform, and the uniformity of the proportion of pores of different sizes is higher. This not only ensures that there are enough pore channels for impurities to escape and be discharged during the extraction process, but also allows the product to achieve a better level in terms of low impurity residue, retention performance, and mechanical properties.

[0020] More preferably, the organic compound A includes at least one of paraffin oil, white oil, hydraulic oil, castor oil, or extracts thereof.

[0021] Preferably, the organic compound B includes at least one of dimethyl phthalate, dioctyl adipate, ethylene glycol diacetate, dimethyl carbonate, palm oil, and triacetin.

[0022] In this application, the specific type of organic compound A selected as the solvent is not specifically limited. Any solvent commonly used in the art is acceptable, provided that its solvent properties and low impurity content are guaranteed, and it is not limited to the above-mentioned preferred range. Similarly, the specific type of organic compound B selected as the non-solvent is not specifically limited. Any non-solvent commonly used in the art is acceptable, and it is not limited to the above-mentioned preferred range.

[0023] Preferably, the mass ratio of organic compound A to organic compound B is (1.5 to 4):1.

[0024] Preferably, the ultra-high molecular weight polyethylene has a weight-average molecular weight ≥ 1 million and a molecular weight distribution of 6 to 10.

[0025] The type of ultra-high molecular weight polyethylene used in the film-forming process described in this application is not specifically limited. Its weight-average molecular weight can be one or any two of the following: 1 million, 1.5 million, 2 million, 3 million, and 4 million. The molecular weight distribution can be 6–10, 7–10, 8–10, 6–8, or 6–9. No specific limitation is made in these respects, as long as the type used can ensure that the mechanical strength and retention efficiency of the obtained product meet the standards.

[0026] Preferably, in step (3), the first stretching treatment includes a first transverse stretching treatment and a first longitudinal stretching treatment performed simultaneously. The temperature of the first stretching treatment is 100-110°C, the multiple of the first transverse stretching treatment is 1.5-4 times, and the multiple of the first longitudinal stretching treatment is 1.5-4 times. In step (5), the second stretching treatment includes a second transverse stretching treatment and a second longitudinal stretching treatment performed simultaneously. The temperature of the second stretching treatment is 115-140°C, the multiple of the second transverse stretching treatment is 5-10 times, and the multiple of the second longitudinal stretching treatment is 5-10 times.

[0027] During the stretching process, the crystallinity of the resin in the membrane layer increases, resulting in greater mechanical strength. However, the micropores in the membrane layer also become larger. As mentioned above, the pore structure has a certain impact on the extraction effect. The inventors discovered through experiments that using the above-mentioned optimized gradient stretching conditions during two stretching processes can effectively balance the impurity separation effect and performance improvement effect of the product. Before the catalytic adsorption extraction process, using relatively mild stretching conditions can ensure a slight expansion of the pores inside the membrane layer, which is conducive to the migration of internal impurities, but the surface pores will not be too large. The probability of porous titanium dioxide particles from the catalytic adsorption layer falling into the membrane layer is further reduced, resulting in lower impurity residue after extraction. After the catalytic adsorption extraction process, the treated membrane is stretched under conventional stretching conditions, which can ensure that the product has sufficient mechanical strength and retention efficiency, resulting in better overall performance.

[0028] More preferably, the rate of the first transverse stretching treatment is 5-50% / s, the rate of the first longitudinal stretching treatment is 5-50% / s, the rate of the second transverse stretching treatment is 55-70% / s, and the rate of the second longitudinal stretching treatment is 55-70% / s.

[0029] The research in this application also found that when the rates of the first transverse stretching treatment and the first longitudinal stretching treatment are relatively slow, the rate of pore expansion during the first stretching treatment is slower, resulting in more uniform membrane pores and improved strength of the treated membrane. Since the strength of the obtained treated membrane is improved compared to the raw membrane, the rates of the second transverse stretching treatment and the second longitudinal stretching treatment can be relatively faster, resulting in higher membrane production efficiency without affecting membrane performance.

[0030] Preferably, in step (2), the thickness ratio of the biofilm to the adsorption layer is 1:(1-3).

[0031] More preferably, in step (2), the ratio of the thickness of the biofilm to the thickness of the adsorption layer is one of 1:1, 1:1.5, 1:2, 1:2.5, 1:3 or any two of them.

[0032] In the scheme described in this application, the thickness of the adsorption layer is not specifically limited. The greater the thickness, the more activated carbon content, the greater the total adsorption capacity, and the better the stability of the adsorption layer during dynamic scouring. However, if the thickness is too large, it is too thick relative to the film, and the adsorption capacity is also excessive relative to the impurities in the film, causing some activated carbon to be unable to play its role, resulting in material waste and increased difficulty in fixing. Therefore, those skilled in the art can adjust the thickness based on actual needs.

[0033] Preferably, in step (2), the proportion of micropores in the total pore volume of the activated carbon is 75-95% (a), and the scouring and extraction flow rate of the extractant is 8-35 mL / min.

[0034] More preferably, the proportion of micropores in the total pore volume of the activated carbon, a, is a value within the range of one or any two of 75%, 78%, 80%, 82%, 85%, 90%, 92%, and 95%, and the scouring extraction flow rate b of the extractant is a value within the range of one or any two of 8 mL / min, 10 mL / min, 12 mL / min, 15 mL / min, 18 mL / min, 20 mL / min, 22 mL / min, 25 mL / min, 28 mL / min, 30 mL / min, and 35 mL / min.

[0035] More preferably, a / b = 0.04 to 0.07;

[0036] More preferably, the proportion of micropores in the total pore volume of the activated carbon is 80-95%;

[0037] More preferably, the scouring extraction flow rate b of the extractant is 15-22 mL / min.

[0038] As mentioned above, in addition to ensuring that the rinsing extraction rate is not too high or too low, the proportion of micropores in the activated carbon in the adsorption layer also needs to be maintained within an appropriate range. When the ratio of the rinsing extraction efficiency to the proportion of micropores is limited, it is further preferred to be within the above range, or when the rinsing extraction rate or the proportion of micropores is within the above range, the impurity separation efficiency during extraction can be further improved, resulting in lower impurity residues in the product. This is suitable for some high-end photoresist purification scenarios with higher impurity requirements.

[0039] Preferably, in step (4), the thickness ratio of the treatment membrane to the catalytic adsorption layer is 1:(1-2).

[0040] More preferably, in step (4), the ratio of the thickness of the treatment membrane to the thickness of the catalytic adsorption layer is one of 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2 or any two of them.

[0041] Since titanium dioxide particles have a high density and mainly function as photocatalysts, the thickness of the catalytic adsorption layer can be set to be thinner than that of the adsorption layer. Those skilled in the art can choose an appropriate thickness of the catalytic adsorption layer based on actual operational needs.

[0042] Preferably, the porosity of the porous titanium dioxide in the catalytic adsorption layer is 15-35%.

[0043] More preferably, the porosity of the porous titanium dioxide in the catalytic adsorption layer is a range of one or any two of 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, and 35%.

[0044] Preferably, the average particle size of the porous titanium dioxide in the catalytic adsorption layer is 0.3–2 μm.

[0045] More preferably, the average particle size of the porous titanium dioxide in the catalytic adsorption layer is one or any two of the following: 0.3 μm, 0.35 μm, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, and 2 μm.

[0046] When porous titanium dioxide particles with the above-mentioned porosity or particle size are selected as the active material of the catalytic adsorption layer, the balance between the structural stability of the particles and the adsorption efficiency of impurities can be further optimized.

[0047] Preferably, the extractant in steps (2) and (4) includes at least one of alkane solvents, alcohol solvents, ether solvents, and ketone solvents.

[0048] More preferably, the extraction temperature during extraction in steps (2) and (4) is 5 to 30°C.

[0049] In a second aspect of this application, a method for preparing the UPE film is also provided.

[0050] Preferably, the TOC leaching amount of the UPE film is ≤0.5ppb and the metal ion precipitation amount is ≤10ppt.

[0051] Preferably, the average PMI pore size of the UPE film is 1–50 nm.

[0052] The UPE film prepared by the method described in this application has high mechanical strength, and the impurity content of the product itself, whether it is the total organic carbon content or the metal ion impurity content, can be kept at an extremely low level, so it will not contaminate the purified product and is fully suitable for the purification of high-requirement photoresists.

[0053] The beneficial effects of this invention are that it provides a method for preparing UPE films, which uses a solvent and non-solvent compounded ultra-high molecular weight polyethylene as a pre-set film-forming raw material with rich pore size. It requires two extractions and stretching treatments in a specific order to improve the retention efficiency and mechanical strength of the product, while significantly reducing the content of impurities such as metal ions and / or total organic carbon in the product. The resulting UPE film is very suitable as a purification medium for photoresists. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0055] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0056] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0057] A method for preparing a UPE thin film includes the following steps:

[0058] (1) Polyethylene resin, organic A and organic B are compounded and heated to melt and mix. The resulting liquid film is cooled and solidified to obtain a raw film. The polyethylene resin is ultra-high molecular weight polyethylene resin, organic A is a solvent of polyethylene resin, and organic B is a non-solvent of polyethylene resin.

[0059] (2) An adsorption layer is set on two surfaces of the biofilm, and then the biofilm is subjected to rinsing extraction treatment with an extractant along the thickness direction of the biofilm at an ambient temperature not higher than 30°C for 2-3 hours. The adsorption layer includes activated carbon, the activated carbon includes micropores, the proportion of the micropores in the total pore volume of the activated carbon is a, a≥75% and a / b is 0.025-0.095, b is the rinsing extraction flow rate of the extractant, in mL / min;

[0060] (3) The raw film after the rinsing and extraction treatment is subjected to a first stretching treatment to obtain the treated film;

[0061] (4) A catalytic adsorption layer is provided on both surfaces of the treatment membrane, and then the treatment membrane is immersed in the extractant and irradiated with light. Catalytic adsorption extraction is carried out at an ambient temperature not higher than 30°C. The catalytic adsorption layer includes porous titanium dioxide particles with a porosity ≥15% and an average particle size ≥0.3μm.

[0062] (5) The treated membrane after catalytic adsorption extraction is subjected to a second stretching treatment, then wound up and heat-set to obtain the UPE film.

[0063] In some embodiments, in step (1), the organic compound A includes at least one of paraffin oil, white oil, hydraulic oil, castor oil, or extracts thereof.

[0064] In some embodiments, the boiling point of the organic compound A is 300 to 600°C, specifically it can be one or any two of the following: 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, and 600°C.

[0065] In some embodiments, the organic compound A includes organic compound A1 and organic compound A2, and |T1-T2|≥30℃, where T1 is the boiling point of organic compound A1 and T2 is the boiling point of organic compound A2.

[0066] In some embodiments, the mass ratio of organic compound A1 to organic compound A2 is (7:3) to (3:7).

[0067] In some embodiments, the organic compound B includes at least one of dimethyl phthalate, dioctyl adipate, ethylene glycol diacetate, dimethyl carbonate, palm oil, and triacetin.

[0068] In some embodiments, the boiling point of organic compound B is 80–400°C.

[0069] It should be noted that the boiling points of organic compound A and organic compound B described in this application were measured under standard atmospheric pressure, i.e., 101°C and 325 kPa.

[0070] In some embodiments, the mass ratio of organic compound A to organic compound B is (1.5 to 4):1, specifically it can be one or any two of the following: 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1.

[0071] In some embodiments, the ultra-high molecular weight polyethylene has a weight-average molecular weight ≥ 1 million and a molecular weight distribution of 6 to 10.

[0072] In some embodiments, the weight-average molecular weight of the ultra-high molecular weight polyethylene is 1 million to 4 million.

[0073] In some embodiments, the mass ratio of the total mass of the polyethylene resin to organic A and organic B is m(polyethylene resin):m(organic A + organic B) = (1:9) to (3:7).

[0074] In some embodiments, the heating and melting compounding is carried out in a screw extruder, the temperature of which is set to 150-260°C, the time to be 10-30 min, and the length-to-diameter ratio of the screw to be (30-70):1.

[0075] In some embodiments, the thickness of the film obtained in step (1) is 0.2 to 35 mm.

[0076] In some embodiments, the thickness ratio of the biofilm to the adsorption layer in step (2) is 1:(1-3).

[0077] In some embodiments, the thickness of the adsorption layer is 0.2 to 105 mm.

[0078] In some embodiments, the temperature during the rinsing and extraction process is 5–30°C, specifically room temperature (25°C).

[0079] In some embodiments, the proportion of micropores in the activated carbon of the adsorption layer to the total pore volume of the activated carbon is 75% to 95%.

[0080] In some embodiments, the specific surface area of ​​the activated carbon in the adsorption layer is 800–1500 m². 2 / g, pore volume is 200~4400cm³ 3 / g, with an average pore size of 0.5–2 nm.

[0081] In some embodiments, the activated carbon in the adsorption layer includes micropores, mesopores, and macropores, wherein the micropore diameter is less than 2 nm, the mesopore diameter is greater than or equal to 2 nm and less than or equal to 50 nm, and the macropore diameter is greater than 50 nm.

[0082] In some embodiments, the average particle size of the activated carbon is 100–500 μm.

[0083] It should be noted that the micropores of the activated carbon described in this application are characterized by the Horvath-Kawazoe (HK) equation after the above tests, representing the proportion of total pore volume. The specific surface area and pore volume of the activated carbon are directly confirmed by nitrogen adsorption-desorption method (using a US-made Gemini VII2390 fully automatic rapid analyzer, nitrogen atmosphere, BET, test temperature 198℃, pore volume taken as Vm). The average particle size is directly confirmed by laser particle size analyzer, and the measured particle size D is... v50 As the average particle size.

[0084] In some embodiments, the adsorption layer also includes an organic resin binder.

[0085] For example, the organic resin binder may be at least one of silicone binders, polyionic liquid binders, and epoxy resin binders. In addition, it may also be a partially rubber-type binder. As long as the binder is insoluble in the extractant, that is, the extractant will not affect the structure of the adsorption layer by dissolving the binder during the impurity extraction process, it is acceptable.

[0086] Specifically, the adhesive may be EP 41S-5 manufactured by Master Bond.

[0087] It should be noted that the adsorption layer described in this application can be a commercially available product or a self-made product, wherein the self-made adsorption layer includes the following preparation steps:

[0088] The activated carbon and organic resin binder are mixed evenly, pressed into a mold, and cured to obtain the adsorption layer.

[0089] In some embodiments, the mass ratio of activated carbon to organic resin binder in the adsorption layer is (95:5) to (90:10).

[0090] In some embodiments, the activated carbon is a self-made product. The activated carbon in the scheme described in this application can also be a commercially available product, and there is no specific limitation on this. When making it in-house, the following steps may be included:

[0091] After crushing, cleaning, and removing impurities from the carbon source, pore-forming agent I is added for hydrothermal carbonization pore-forming treatment to obtain modified powder A;

[0092] The modified powder A was then subjected to steam pore-forming treatment to obtain modified powder B;

[0093] Finally, the modified powder B and pore-forming agent II were heated and mixed, and then calcined to form pores, thus obtaining activated carbon.

[0094] In some embodiments, the carbon source includes, but is not limited to, at least one of asphalt, coconut shell, rice husk, straw, bamboo, and fruit peel.

[0095] In some embodiments, the pore-forming agent I includes at least one of sodium hydroxide and potassium hydroxide, and the mass ratio of the carbon source to the pore-forming agent I is 1:(0.2 to 0.5).

[0096] In some embodiments, the temperature during the hydrothermal carbonization pore-forming treatment is 200–300°C, and the time is 5–10 hours.

[0097] In some embodiments, when the modified powder A undergoes steam pore-forming treatment, the steam is water vapor, the flow rate of the water vapor is 2-3 mL / min, the temperature of the steam pore-forming treatment is 700-800℃, and the time is 30-50 min.

[0098] In some embodiments, the steam perforation process includes a first-stage steam perforation process and a second-stage steam perforation process. The steam flow rate of the first-stage steam perforation process is 2 to 2.5 mL / min, and the time is 5 to 15 min. The steam flow rate of the second-stage steam perforation process is 2.5 to 3 mL / min, and the time is 25 to 35 min.

[0099] In some embodiments, the pore-forming agent II includes at least one of copper chloride, ferric chloride, and aluminum chloride.

[0100] In some embodiments, the mass ratio of the modified powder B to the pore-forming agent II is 1:(0.5-1).

[0101] In some embodiments, the heating and mixing is carried out by liquid phase mixing, wherein the modified powder B and pore-forming agent II are added to the liquid phase and heated to 60-100°C and kept at that temperature for 10-20 hours.

[0102] In some embodiments, the liquid phase may be at least one of an aqueous ethanol solution, an aqueous glycerol solution, or pure water.

[0103] In some embodiments, the calcination pore-forming treatment is carried out in an inert atmosphere, and the temperature during the calcination pore-forming treatment is 400-600°C, and the time is 2-5 hours.

[0104] Steam pore-forming treatment and subsequent calcination pore-forming treatment can effectively ensure the formation of micropores and the realization of gradient pores in activated carbon. In the technical solution of this application, the volume ratio of micropores in the activated carbon can be controlled by the water vapor flow rate gradient during steam pore-forming treatment and the temperature and time during calcination pore-forming treatment. Those skilled in the art can also implement it by changing other parameters or steps based on actual conditions, and no specific limitation is made here.

[0105] In some embodiments, in step (2), the scouring extraction flow rate b of the extractant is 8 to 35 mL / min.

[0106] In some embodiments, the extractant may be at least one of alkane solvents, alcohol solvents, ether solvents, and ketone solvents, specifically at least one of dichloromethane, n-hexane, isopropanol, diethyl ether, and N-methylpyrrolidone.

[0107] In some embodiments, step (3) includes a first stretching treatment and a first longitudinal stretching treatment performed simultaneously. The temperature of the first stretching treatment is 100-110°C, the multiple of the first transverse stretching treatment is 1.5-4 times, and the multiple of the first longitudinal stretching treatment is 1.5-4 times. The rate of the first transverse stretching treatment is 5-50% / s, and the rate of the first longitudinal stretching treatment is 5-50% / s.

[0108] In some embodiments, the treated membrane after the first stretching treatment is further subjected to a pre-forming treatment at a temperature of 80–100°C for a time of 30–90 seconds.

[0109] In some embodiments, the temperature during the catalytic adsorption extraction process in step (4) is 5–30°C.

[0110] In some embodiments, in step (4), the catalytic adsorption extraction process uses ultraviolet light and the processing time is 30 to 60 minutes.

[0111] In some embodiments, the thickness of the catalytic adsorption layer is 0.1–6 mm.

[0112] In some embodiments, the catalytic adsorption layer further comprises an organic resin binder.

[0113] The organic resin binder in the catalytic adsorption layer is similar to that in the adsorption layer, and will not be described again here.

[0114] It should be noted that the catalytic adsorption layer described in this application can be a commercially available product or a self-made product, and includes the following preparation steps:

[0115] The porous titanium dioxide particles and organic resin binder are mixed evenly, pressed into a mold, and cured to obtain the catalytic adsorption layer.

[0116] In some embodiments, the mass ratio of porous titanium dioxide particles to organic resin binder in the catalytic adsorption layer is (95:5) to (90:10).

[0117] In some embodiments, the porous titanium dioxide in the catalytic adsorption layer has a porosity of 15-35% and an average particle size of 0.3-2 μm.

[0118] In some embodiments, the specific surface area of ​​the porous titanium dioxide in the catalytic adsorption layer is 50–120 m². 2 / g, pore volume is 5-30cm³ 3 / g, with an average pore size of 1.5–8 nm.

[0119] It should be noted that the specific surface area and pore volume of the porous titanium dioxide particles were directly confirmed by the BET method (using a BELSORP MAX fully automatic rapid specific surface area and porosity analyzer from Microtrac, Japan, and a Gemini VII2390 from the USA, at a test temperature of -196℃), the pore size was directly confirmed by the HK method (using a BELSORP MAX surface area and porosity analyzer from Microtrac, Japan, at a test temperature of -196℃), and the porosity was directly confirmed by the mercury intrusion porosimetry method.

[0120] In some embodiments, the porous titanium dioxide particles are homemade products. The porous titanium dioxide particles described in this application can also be commercially available products, and there is no specific limitation on this. When making them in-house, the following steps may be included:

[0121] A titanium source precursor was prepared and then dispersed in an organic phase solution containing ammonia for a hydrothermal reaction to obtain the porous titanium dioxide particles.

[0122] In some embodiments, the titanium source precursor is prepared by first mixing an organic titanium source and a pore-forming agent in an aqueous ethanol solution to prepare a suspension solution, and then drying it to form a solid substance.

[0123] The organic titanium source includes at least one of tetrabutyl titanate and isopropyl titanate.

[0124] The pore-forming agent includes at least one of dodecylamine, potassium chloride, and sodium chloride.

[0125] The molar ratio of titanium element to pore-forming agent in the organic titanium source is 1:(0.5-0.8).

[0126] In some embodiments, the ammonia concentration in the organic phase solution containing ammonia water is 0.2 to 0.5 mol / L, and the mass ratio of the solid substance to the volume of the organic phase solution containing ammonia water is 1 g: (10 to 20) mL.

[0127] In some embodiments, the hydrothermal reaction is carried out at a temperature of 150–200°C for a duration of 15–20 hours.

[0128] In the technical solution of this application, the porosity of the self-made porous titanium dioxide particles can be controlled by the amount of pore-forming agent added, while the particle size can be controlled by the content ratio of the titanium source precursor when added to the organic phase. However, it is not limited to this, and those skilled in the art can also control it in other ways.

[0129] In some embodiments, step (5) includes a second stretching process and a second longitudinal stretching process performed simultaneously. The temperature of the second stretching process is 115-140°C, the multiplier of the second transverse stretching process is 5-10 times, the multiplier of the second longitudinal stretching process is 5-10 times, the rate of the second transverse stretching process is 55-70% / s, and the rate of the second longitudinal stretching process is 55-70% / s.

[0130] In some embodiments, the heat setting temperature in step (5) is 60-100°C and the time is 50-150 seconds.

[0131] In some embodiments, the thickness of the UPE film is 5–20 μm.

[0132] In some embodiments, the average PMI pore size of the UPE film is 1–50 nm.

[0133] In some embodiments, the porosity of the UPE film is 30-60%.

[0134] In some embodiments, the tensile strength of the UPE film is ≥5 MPa.

[0135] In some embodiments, the TOC leaching amount of the UPE film is ≤0.5ppb and the metal ion precipitation amount is ≤10ppt.

[0136] The present application is further illustrated below with specific embodiments:

[0137] Example 1

[0138] An embodiment of a UPE thin film and its preparation method thereof, wherein the preparation method includes the following steps:

[0139] (1) Polyethylene resin, organic compound A, and organic compound B are compounded and heated to melt and knead. The resulting liquid film is cooled and solidified to obtain a raw film with a thickness of approximately 2.3 mm. The polyethylene resin is ultra-high molecular weight polyethylene resin, comprising polyethylene resin A with a weight average molecular weight of 4 million and polyethylene resin B with a weight average molecular weight of 1.5 million, with a mass ratio of 7:3 and a molecular weight distribution of 8. The organic compound A is a complex, comprising high-purity No. 15 mineral white oil (boiling point 320℃ under standard conditions) produced by Hebei Wantai and high-purity... The mass ratio of No. 20 mineral white oil (boiling point 355℃ under standard conditions) to organic compounds A and B is 1:1. Organic compound B is dimethyl phthalate, and the mass ratio of organic compound A to organic compound B is 2:1. The mass ratio of polyethylene resin to the total mass of organic compounds A and B is m(polyethylene resin):m(organic compound A + organic compound B) = 2:8. The heating and melting mixing is carried out using a screw extruder with a temperature range of 150-260℃, an extrusion time of 22 minutes, and a screw length-to-diameter ratio of 48:1.

[0140] (2) An adsorption layer with a thickness of 4.6 mm and an area size consistent with the raw film is set on each of the two surfaces of the raw film, which can just cover the surface of the raw film. When setting it up, the first adsorption layer is placed on the bed surface of the industrial water bed and perpendicular to the outlet. Then the raw film is placed, and the second adsorption layer is placed on the other side of the raw film to form a "sandwich structure". The composite structure is fixed with a fixing clamp. Then the water bed is turned on along the thickness direction of the raw film at an ambient temperature of 25°C. The extractant dichloromethane flows out at the outlet (the flow direction is perpendicular to the plane of the raw film). The height of the extractant outlet of the water bed is set to cover the raw film and the adsorption layer. The flow rate is kept constant. The extractant is used for flushing and extraction treatment for 3 hours. The adsorption layer includes activated carbon. The activated carbon includes micropores. The proportion of the micropores in the total pore volume of the activated carbon is a. b is the flushing and extraction flow rate of the extractant in mL / min. The specific parameters are shown in Table 1.

[0141] The adsorption layer is a self-made product, and its preparation includes the following steps:

[0142] 1g of dried coconut shell was crushed, washed with pure water, and then desiliconized with 30% sodium hydroxide solution. After washing twice with pure water, potassium hydroxide pore-forming agent I was added at a mass ratio of 1:0.3 between coconut shell and pore-forming agent I. 200mL of water was added to prepare a mixture. The mixture was placed in a sealed reaction vessel and heated to 220℃ for 8 hours. After washing twice with pure water and drying, modified powder A was obtained.

[0143] The modified powder A was then placed in a closed reactor for steam pore-forming treatment. The temperature was raised to 750°C, and water vapor was first introduced at a flow rate of 2.2 mL / min and kept at that temperature for 10 min. Then the flow rate was increased to 2.8 mL / min and kept at that temperature for 30 min. After drying, modified powder B was obtained.

[0144] Finally, 1g of modified powder B was mixed with pore-forming agent II copper chloride in 200mL of glycerol aqueous solution (V:V = 50:50) at a mass ratio of 1:0.8 and heated to 70℃ for 15h. Then, the resulting mixture was directly calcined at 500℃ for 4h under an inert atmosphere to create pores. It was washed once with ethanol and once with pure water and dried to obtain activated carbon. The porosity data of the activated carbon are shown in Table 1.

[0145] Activated carbon and Master Bond's EP 41S-5 were mixed at a mass ratio of 9:1, pressed into a mold, and cured to obtain an adsorption layer.

[0146] (3) Remove the fixing clamp, remove the adsorption layer, and perform a first stretching treatment on the biofilm after the rinsing and extraction treatment. Then, heat it to 85°C and pre-shape it for 60 seconds to obtain a treated membrane with a thickness of 0.76 mm. The first stretching treatment includes a first transverse stretching treatment and a first longitudinal stretching treatment performed simultaneously. The temperature of the first stretching treatment is 105°C, the multiplication factor of the first transverse stretching treatment is 2 times, and the multiplication factor of the first longitudinal stretching treatment is 1.5 times. The rate of the first transverse stretching treatment is 50% / s, and the rate of the first longitudinal stretching treatment is 37.5% / s.

[0147] (4) A catalytic adsorption layer with a thickness of 1.5 mm is set on each of the two surfaces of the treatment membrane. The size and setting method are the same as those of the adsorption layer in step (2). Then the treatment membrane is directly immersed in the same extractant as in step (2). The extractant is placed in a transparent glass jar that can transmit light. Ultraviolet light is applied and catalytic adsorption extraction is performed at an ambient temperature of 25°C for 60 min. The catalytic adsorption layer includes porous titanium dioxide particles. The porosity and average particle size of the porous titanium dioxide are shown in Table 1.

[0148] The catalytic adsorption layer is a self-made product, and the preparation method is as follows:

[0149] First, isopropyl titanate, dodecylamine, and potassium chloride are mixed in a molar ratio of 1:0.5:0.05. Then, a suspension is prepared by adding the mixture to an ethanol-water solution (V:V = 50:50) at a mass ratio of 1 g:100 mL. The mixture is then dried to form a solid.

[0150] Subsequently, 10g of solid material was placed into 150mL of an ethanol aqueous solution containing ammonia (concentration 0.3mol / L) (V:V = 20:80), mixed evenly, and transferred to a closed reaction vessel. The mixture was heated to 180℃ and kept at that temperature for 15h. The solid and liquid were separated, and the obtained solid was washed once with pure water and once with ethanol, and then dried to obtain the porous titanium dioxide particles.

[0151] Porous titanium dioxide particles were mixed with Master Bond's EP 41S-5 at a mass ratio of 9:1, then molded, pressed, and cured to obtain an adsorption layer.

[0152] (5) The treated membrane after catalytic adsorption extraction is subjected to a second stretching treatment, wound up, and heat-set at 80°C for 100s to obtain the UPE film; the second stretching treatment includes a second transverse stretching treatment and a second longitudinal stretching treatment performed simultaneously. The temperature of the second stretching treatment is 120°C, the multiple of the second transverse stretching treatment is 8 times, the multiple of the second longitudinal stretching treatment is 6.3 times, the rate of the second transverse stretching treatment is 70% / s, and the rate of the second longitudinal stretching treatment is 55% / s.

[0153] The product was tested for thickness, porosity, and pore size. The results showed that the product had a thickness of 15 μm and a porosity of 45%. The average pore size of the PMI is shown in Table 2.

[0154] Example 2

[0155] An embodiment of a UPE film and its preparation method differs from Embodiment 1 in that the polyethylene resin has a weight-average molecular weight of 1 million, the organic compound A is a composite comprising high-purity No. 20 mineral white oil (boiling point 355°C under standard conditions) produced by Hebei Wantai and USP castor oil (boiling point 313°C under standard conditions) produced by Maclean, with a mass ratio of 1:1, the temperature of the first stretching treatment in step (3) is 100°C, the multiple of the first transverse stretching treatment is 1.5 times, the multiple of the first longitudinal stretching treatment is 1.5 times, the rate of the first transverse stretching treatment is 5%, and the rate of the second longitudinal stretching treatment is 5%.

[0156] Example 3

[0157] An embodiment of a UPE film and its preparation method differs from Embodiment 1 only in that the organic compound A is a composite material comprising high-purity No. 15 mineral white oil (boiling point 320°C under standard conditions) produced by Hebei Wantai and USP castor oil (boiling point 313°C under standard conditions) produced by Maclean, with a mass ratio of 1:1.

[0158] Example 4

[0159] An embodiment of a UPE film and its preparation method differs from Embodiment 1 only in that the temperature of the second stretching treatment in step (5) is 130°C, the multiple of the second transverse stretching treatment is 5 times, the multiple of the second longitudinal stretching treatment is 6.4 times, the rate of the second transverse stretching treatment is 55% / s, and the rate of the second longitudinal stretching treatment is 70% / s.

[0160] Examples 5-13, Comparative Examples 1-4

[0161] A UPE thin film and its preparation method differ from Example 1 in that the operating conditions in steps (2) and (4) are different, which also makes the parameters of the activated carbon in the adsorption layer and the porous titanium dioxide particles in the catalytic adsorption layer different, as shown in Table 1.

[0162] The differences between Example 5 and Example 1 include: the temperature of the first stretching treatment in step (3) is 110°C, the multiple of the first transverse stretching is 4 times, the multiple of the first longitudinal stretching is 4 times, the rate of the first transverse stretching treatment is 50% / s, the rate of the first longitudinal stretching treatment is 50% / s, the temperature of the second stretching treatment in step (5) is 140°C, the multiple of the second transverse stretching treatment is 10 times, the multiple of the second longitudinal stretching treatment is 10 times, the rate of the second transverse stretching treatment is 70% / s, and the rate of the second longitudinal stretching treatment is 70% / s.

[0163] The differences between Example 9 and Example 1 include: the polyethylene resin has a weight-average molecular weight of 900,000, the molecular weight distribution of the polyethylene resin is 5, the temperature of the first stretching treatment in step (3) is 130°C, the first stretching treatment includes a first transverse stretching treatment followed by a first longitudinal stretching treatment, the first transverse stretching multiple is 6 times, the first longitudinal stretching multiple is 8 times, the first transverse stretching rate is 60% / s, the first longitudinal stretching rate is 80% / s, the temperature of the second stretching treatment in step (5) is 145°C, the second stretching treatment includes a second transverse stretching treatment followed by a second longitudinal stretching treatment, the second transverse stretching multiple is 4 times, the second longitudinal stretching multiple is 4 times, the second transverse stretching rate is 40%, and the second longitudinal stretching rate is 40%.

[0164] Example 14

[0165] A UPE film and its preparation method differ from Example 1 in that the activated carbon is a commercially available product, produced by Guangdong Huayi Activated Carbon Co., Ltd., with micropores accounting for 85% of the total porosity.

[0166] Example 15

[0167] A UPE thin film and its preparation method differ from Example 1 in that the porous titanium dioxide particles are commercially available products. AR-grade porous micron-sized titanium dioxide produced by Nangong Jiuxin New Material Technology Co., Ltd. has a porosity of 22% and an average particle size of 1.5 μm.

[0168] Comparative Example 5

[0169] A UPE film and its preparation method differ from Example 1 in that step (2) is as follows: the film is placed on the surface of an industrial water bed and perpendicular to the outlet. Then, the water bed is turned on along the thickness direction of the film at an ambient temperature of 25°C. The extractant dichloromethane flows out at the outlet (the flow direction is perpendicular to the film plane). The height of the extractant outlet of the water bed is set to cover the film. The flow rate is kept constant. The extractant is used for rinsing and extraction treatment for 3 hours.

[0170] Comparative Example 6

[0171] A UPE film and its preparation method differ from Example 1 only in that step (4) is: the treated film is directly immersed in the same extractant as in step (2) for 60 min.

[0172] Comparative Example 7

[0173] A UPE thin film and its preparation method, the preparation method comprising the following steps:

[0174] (1) Polyethylene resin, organic compound A, and organic compound B are compounded and heated to melt and knead. The resulting liquid film is cooled and solidified to obtain a raw film with a thickness of approximately 2.3 mm. The polyethylene resin is an ultra-high molecular weight polyethylene resin, comprising polyethylene resin A with a weight average molecular weight of 4 million and polyethylene resin B with a weight average molecular weight of 1.5 million, with a mass ratio of 7:3 and a molecular weight distribution of 8. The organic compound A is a complex, comprising high-purity No. 15 mineral white oil (boiling point 320℃ under standard conditions) produced by Hebei Wantai and high-purity... The mass ratio of No. 20 mineral white oil (boiling point 355℃ under standard conditions) to organic compounds A and B is 1:1. Organic compound B is dimethyl phthalate, and the mass ratio of organic compound A to organic compound B is 2:1. The mass ratio of polyethylene resin to the total mass of organic compounds A and B is m(polyethylene resin):m(organic compound A + organic compound B) = 2:8. The heating and melting mixing is carried out using a screw extruder with a temperature range of 150-260℃, an extrusion time of 22 minutes, and a screw length-to-diameter ratio of 48:1.

[0175] (2) The raw film is subjected to a first stretching treatment, and then heated to 85°C for a pre-formed film for 60 seconds to obtain a treated film; the first stretching treatment includes a first transverse stretching treatment and a first longitudinal stretching treatment performed simultaneously, the temperature of the first stretching treatment is 105°C, the multiple of the first transverse stretching treatment is 2 times, and the multiple of the first longitudinal stretching treatment is 1.5 times; the rate of the first transverse stretching treatment is 50% / s, and the rate of the first longitudinal stretching treatment is 37.5% / s.

[0176] (3) The treatment membrane is subjected to a second stretching treatment, which includes a second transverse stretching treatment and a second longitudinal stretching treatment performed simultaneously. The temperature of the second stretching treatment is 120°C, the multiple of the second transverse stretching treatment is 8 times, the multiple of the second longitudinal stretching treatment is 6.3 times, the rate of the second transverse stretching treatment is 70% / s, and the rate of the second longitudinal stretching treatment is 55% / s.

[0177] (4) The membrane was directly immersed in dichloromethane for extraction for 4 hours and then dried.

[0178] (5) Rewind and heat set at 80°C for 100 seconds to obtain the UPE film.

[0179] Table 1

[0180]

[0181]

[0182] Example 1

[0183] To verify the performance of the UPE film described in this application, the following tests were conducted on the various embodiments and comparative products:

[0184] (1) Refer to the test method in section

[0137] of CN113351033B manual and use the same device to test the water flow rate;

[0185] (2) Tensile strength was tested using a universal tensile testing machine;

[0186] (3) Referring to the CN113351033B manual

[0148] section, a particle counter and rinsing test device were used to test the retention accuracy of Examples 1, 6-15 and Comparative Examples 1-7. The particle size of the test medium was 2nm.

[0187] (4) Cut the products obtained from each embodiment and comparative example to 0.2m. 2 The effective filtration area is used as the filter element, and then it is rinsed with ultrapure water. The rinsing volume is controlled at 20L and the rinsing speed is controlled at 500mL / min. The downstream filtrate is tested for total organic carbon (TOC) (testing instrument: total organic carbon analyzer) to determine the TOC dissolution of the product.

[0188] (5) Cut the products obtained from each embodiment and comparative example to 0.2m. 2The effective filtration area was used as the filter element, and then it was soaked in 0K73 detection reagent (a mixed solvent of propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate in a mass ratio of 7:3) for 24 hours. Then, the total content of metal ions in the mixed solvent was detected by an ICPMS (Agilent 7850, gas flow rate 0.5L / min, power 1150W) instrument (based on common contaminating metal ions in photoresist, sodium ions, potassium ions, lithium ions, transition metal ions, aluminum ions, magnesium ions, calcium ions, gallium ions, indium ions, germanium ions, tin ions, and lead ions were selected for observation).

[0189] (6) The average PMI pore size of the prepared UPE film was measured by a PMI pore size tester.

[0190] The test results are shown in Table 2.

[0191] Table 2

[0192]

[0193] The test results show that the UPE film prepared by the method described in this application has ideal performance, fast filtration speed, and high tensile strength. Examples 1 and 6-15 show a retention efficiency of more than 95% for impurities with a particle size of 2 nm. Most importantly, the product has extremely low impurity residue, with a total organic carbon content of no more than 0.5 ppb and a metal ion content of no more than 10 ppt. This is mainly due to the use of two adsorption layers based on different working principles to remove impurities during the preparation process, and to avoid the introduction of new impurities. In contrast, the method described in Comparative Example 7, after two stretching treatments, only uses a simple extractant for impregnation extraction, resulting in high TOC and metal ion impurity content. In the schemes described in Comparative Examples 5 and 6, an adsorption layer is set in the first extraction treatment and a catalytic adsorption layer is set in the second extraction treatment, respectively. Although the impurity content is lower than that of the product in Comparative Example 7, it still does not meet the standard. Meanwhile, a comparison of Comparative Examples 1-4 with the products of the Examples shows that in the first extraction process, if the micropore content of activated carbon in the adsorption layer and the flow rate of the extractant cannot be balanced, the impurity removal effect will be affected. In the second extraction process, if the porous titanium dioxide particles in the catalytic adsorption layer have too few pores, they cannot exert the ideal adsorption-catalysis effect; if the particle size is too small, they may also detach and cause secondary contamination of the membrane layer during the extraction process, resulting in excessive impurity content.

[0194] As can be seen from Examples 1-4, when two solvents with a large difference in boiling point are selected for compounding during the film preparation process, the filtration speed of the product can be effectively improved while maintaining a low impurity content. As can be seen from Examples 5-15, when the ratio of the micropore ratio a of activated carbon in the adsorption layer used in the preparation process to the flow rate b of the extractant is preferably in the range of 0.04-0.07, or a is preferably 80-95% and b is preferably 15-22 mL / min, the impurity content of the product can be further reduced, making the product applicable to high-precision photoresist purification scenarios with more stringent impurity content requirements.

Claims

1. A method for preparing a UPE thin film, characterized in that, Includes the following steps: (1) Polyethylene resin, organic A and organic B are compounded and heated to melt and mix. The resulting liquid film is cooled and solidified to obtain a raw film. The polyethylene resin is ultra-high molecular weight polyethylene resin, organic A is a solvent of polyethylene resin, and organic B is a non-solvent of polyethylene resin. (2) An adsorption layer is set on two surfaces of the biofilm, and then the biofilm is subjected to rinsing extraction treatment with an extractant along the thickness direction of the biofilm at an ambient temperature not higher than 30°C for 2-3 hours. The adsorption layer includes activated carbon, the activated carbon includes micropores, the proportion of the micropores in the total pore volume of the activated carbon is a, a≥75% and a / b is 0.025-0.095, b is the rinsing extraction flow rate of the extractant, in mL / min; (3) The raw film after the rinsing and extraction treatment is subjected to a first stretching treatment to obtain the treated film; (4) A catalytic adsorption layer is provided on both surfaces of the treatment membrane, and then the treatment membrane is immersed in the extractant and irradiated with light. Catalytic adsorption extraction is carried out at an ambient temperature not higher than 30°C. The catalytic adsorption layer includes porous titanium dioxide particles with a porosity ≥15% and an average particle size ≥0.3μm. (5) The treated membrane after catalytic adsorption extraction is subjected to a second stretching treatment, then wound up and heat-set to obtain the UPE film.

2. The method for preparing the UPE thin film as described in claim 1, characterized in that, The organic compound A includes organic compound A1 and organic compound A2, and |T1-T2|≥30℃, where T1 is the boiling point of organic compound A1 and T2 is the boiling point of organic compound A2.

3. The method for preparing the UPE thin film as described in claim 2, characterized in that, The organic compound A includes at least one of paraffin oil, white oil, hydraulic oil, castor oil or its extracts, and the organic compound B includes at least one of dimethyl phthalate, dioctyl adipate, ethylene glycol diacetate, dimethyl carbonate, palm oil, and triacetin, and the mass ratio of the organic compound A to the organic compound B is (1.5-4):

1.

4. The method for preparing the UPE thin film as described in claim 1, characterized in that, The ultra-high molecular weight polyethylene has a weight-average molecular weight ≥ 1 million and a molecular weight distribution of 6 to 10.

5. The method for preparing the UPE thin film as described in claim 1, characterized in that, In step (3), the first stretching treatment includes a first transverse stretching treatment and a first longitudinal stretching treatment performed simultaneously. The temperature of the first stretching treatment is 100-110℃, the multiplier of the first transverse stretching treatment is 1.5-4 times, and the multiplier of the first longitudinal stretching treatment is 1.5-4 times. In step (5), the second stretching treatment includes a second transverse stretching treatment and a second longitudinal stretching treatment performed simultaneously. The temperature of the second stretching treatment is 115-140℃, the multiplier of the second transverse stretching treatment is 5-10 times, and the multiplier of the second longitudinal stretching treatment is 5-10 times.

6. The method for preparing the UPE thin film as described in claim 5, characterized in that, The rate of the first transverse stretching treatment is 5-50% / s, the rate of the first longitudinal stretching treatment is 5-50% / s, the rate of the second transverse stretching treatment is 55-70% / s, and the rate of the second longitudinal stretching treatment is 55-70% / s.

7. The method for preparing the UPE thin film as described in claim 1, characterized in that, In step (2), the thickness ratio of the biofilm to the adsorption layer is 1:(1-3); the proportion of micropores in the total pore volume of the activated carbon is 75-95%; and the scouring and extraction flow rate of the extractant is 8-35 mL / min.

8. The method for preparing the UPE thin film as described in claim 7, characterized in that, The a / b ratio is 0.04 to 0.07; and / or, the proportion of micropores in the total pore volume of the activated carbon is 80% to 95% (a); and / or, the scouring and extraction flow rate of the extractant is 15 to 22 mL / min (b).

9. The method for preparing the UPE thin film as described in claim 1, characterized in that, In step (4), the thickness ratio of the treatment membrane to the catalytic adsorption layer is 1:(1-2); the porosity of the porous titanium dioxide in the catalytic adsorption layer is 15-35%, and / or the average particle size of the porous titanium dioxide in the catalytic adsorption layer is 0.3-2 μm.

10. The method for preparing the UPE thin film as described in claim 1, characterized in that, The extractant in steps (2) and (4) includes at least one of alkane solvents, alcohol solvents, ether solvents, and ketone solvents, and the extraction temperature during extraction is 5 to 30°C.

11. The UPE film prepared by the method according to any one of claims 1 to 10.

12. The UPE film as described in claim 11, characterized in that, The TOC leaching amount of the UPE film is ≤0.5ppb and the metal ion precipitation amount is ≤10ppt; the average pore size of the PMI of the UPE film is 1-50nm.

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