Ultrahigh molecular weight polyethylene filter material and preparation method thereof

Abstract

The invention discloses an ultra-high molecular weight polyethylene filter material and a preparation method thereof, and particularly relates to the field of porous material preparation.The preparation method comprises the steps that chopped polyvinyl alcohol fibers are subjected to hydrophobic modification through a boric acid ethanol solution, a three-dimensional fiber skeleton template is prepared, and plasma surface activation is conducted; dispersing polymer polyethylene powder subjected to degassing treatment and polyvinylpyrrolidone in ethanol to prepare stable slurry, coating a polyvinyl alcohol fiber skeleton with the stable slurry through dipping, and performing low-temperature drying to obtain a composite blank; sintering by adopting a stepped temperature and pressure rising program, so that the polyethylene particles are melted and intertwined to form a three-dimensional porous framework coating the template; leaching with hot deionized water to remove a template blank, and drying at low temperature to obtain a pure high-molecular polyethylene porous material with a controllable pore structure and a shape copied to an original template; the method has the advantages of mild process conditions and uniform product structure, and is suitable for preparation of high-performance porous polymer materials.

Description

Technical Field

[0001] This invention relates to the field of porous material preparation, and more specifically, to an ultra-high molecular weight polyethylene filter material and its preparation method. Background Technology

[0002] Currently, foaming is a commonly used method for preparing porous polymer filter materials. The core of the process lies in introducing and stabilizing a large number of air bubbles into the polymer matrix. The polymer resin and chemical foaming agent, such as azodicarbonamide and other additives, are uniformly mixed in an extruder or internal mixer and heated to a molten state to form a viscous mixture. When the temperature reaches the decomposition range of the foaming agent, the foaming agent rapidly decomposes, releasing a large amount of gas, such as nitrogen or carbon dioxide. These gases form fine and uniformly distributed bubble nuclei in the polymer melt due to supersaturation. Subsequently, under controlled temperature and pressure conditions, these bubble nuclei gradually expand and grow. During this process, the size and density of the bubbles can be controlled to a certain extent by adjusting the processing temperature, pressure, and melt viscosity. Finally, in the curing and shaping stage, when the bubbles grow to the preset size, the melt needs to be rapidly cooled to solidify the polymer, thereby fixing the formed bubble structure and obtaining a preform with a three-dimensional porous structure. The preform is then further processed into filter elements such as sheets or filter cartridges as needed.

[0003] However, in practical use, it still has some drawbacks, such as: 1. Random and uncontrollable structure: The formation and growth of cells have significant thermodynamic randomness, making it difficult to accurately pre-set and manufacture materials with complex programmed structures such as anisotropy and gradient pores; 2. Poor inherent permeability: The resulting cell structure is mostly closed-cell, and effective permeability usually requires subsequent secondary processing, and the cell size distribution is wide with low structural uniformity; 3. Insufficient process stability: The foaming process is extremely sensitive to fluctuations in process parameters, resulting in poor batch-to-batch reproducibility of cell structure and difficulty in ensuring product performance consistency. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, the present invention provides an ultra-high molecular weight polyethylene filter material and its preparation method, and solves the problems mentioned in the background art through the following solution.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an ultra-high molecular weight polyethylene filter material and its preparation method, comprising:

[0006] S1. Template preparation: Short-cut water-soluble polyvinyl alcohol fibers are dispersed in an organic solvent and formed into shape. After drying, a three-dimensional fiber skeleton with uniform structure and controllable pores is obtained. This three-dimensional fiber skeleton serves as the template preform.

[0007] S2. Slurry impregnation and drying: Polyethylene powder is uniformly dispersed in an organic solvent to form a stable slurry of a certain concentration. The slurry is impregnated to fully coat the polyvinyl alcohol fibers. Then, the organic solvent is removed by low-temperature drying to obtain the composite preform.

[0008] S3, Sintering: The dried composite preform is fed into a hot press and sintered under specific conditions; the surface of the high molecular weight polyethylene powder particles melts and diffuses and entangles with each other to form a porous three-dimensional skeleton that encapsulates the template preform.

[0009] S4. Leaching and Drying: The porous three-dimensional framework is immersed in heated deionized water. The dissolution and diffusion of the template embryo are accelerated by gentle stirring. After it is completely leached out, it is dried at low temperature to obtain a pure high-molecular-weight polyethylene powder porous material that replicates the morphology of the original template.

[0010] Preferably, boric acid undergoes a controllable and reversible cross-linking reaction with the hydroxyl groups on the polyvinyl alcohol fiber molecular chain, forming a stable protective film on the fiber surface. This effectively blocks the direct action of organic solvents on the polyvinyl alcohol fiber body, allowing the polyvinyl alcohol fiber to maintain a stable solid state in organic solvent media such as ethanol, without swelling, adhesion, or dissolution.

[0011] Preferably, surface treatment of the three-dimensional fiber skeleton can significantly improve the surface polarity of polyvinyl alcohol fibers, improve their wettability and spreadability to the slurry; form micro-roughness on the fiber surface to provide mechanical anchoring points for the slurry, thereby enhancing the interfacial bonding force between the two phases; ultimately ensure that the slurry uniformly coats the fibers, avoiding cracks or holes caused by poor bonding in subsequent processes, and comprehensively improving the quality of the composite preform.

[0012] Preferably, under the bombardment of high-energy electrons, oxygen dissociates into oxygen atoms, ozone, and various active groups. These active species bombard the polyvinyl alcohol fiber molecular chains, slightly increasing the surface roughness through etching and introducing oxygen-containing polar functional groups. These functional groups greatly enhance the polarity and chemical activity of the fiber surface.

[0013] Preferably, the polyvinylpyrrolidone (PVP) molecule has both a hydrophilic lactam group and a lipophilic methylene segment, which allows it to dissolve well in polar ethanol and anchor to the surface of hydrophobic polyethylene powder through the lipophilic segment. One end of the PVP molecular chain is adsorbed on the surface of the polyethylene powder particles, while the remaining long chain extends into the ethanol solution, forming a polymer coating layer. When two PVP-coated powder particles approach each other, these extended polymer layers physically overlap, generating entropic repulsion, thereby preventing the particles from agglomerating and settling.

[0014] Preferably, in order to reduce energy consumption and cost, after completing the low-temperature drying in step S2, the step of cooling the composite blank to room temperature is omitted, and the blank is directly sintered in step S3 while retaining residual temperature.

[0015] Preferably, by controlling the structure of the three-dimensional fiber skeleton in step S1, a porous polyethylene material with anisotropic or gradient porosity characteristics can be prepared; the anisotropic structure is achieved by directional induction of fiber arrangement; the gradient porosity structure is achieved by layering and forming fibers of different specifications or by controlling the slurry impregnation parameters.

[0016] The technical effects and advantages of this invention are as follows:

[0017] 1. Programmable Structure and High-Fidelity Replication: Through fiber orientation and layered control, the precise construction of complex three-dimensional templates with anisotropy and gradient porosity can be achieved. Furthermore, thanks to stable interface engineering and slurry systems, accurate replication of the template morphology is achieved. 2. Inherent Connectivity and Excellent Uniformity: Originating from the template's own three-dimensional interconnected network, the material naturally possesses highly interconnected porous channels. Combined with optimized slurry dispersion and interface bonding technologies, high connectivity of the pore structure and excellent bulk uniformity are ensured. 3. Batch-to-Batch Consistency and Process Robustness: Through standardized raw material pretreatment, quantitative control of key process parameters, and full-process quality monitoring, high batch-to-batch stability of product performance and excellent process reproducibility are ensured. Detailed Implementation

[0018] Example 1

[0019] S1. Template Preparation: Short-cut water-soluble polyvinyl alcohol (PVA) fibers are dispersed in an organic solvent and formed into a three-dimensional fiber skeleton with uniform structure and controllable pores after drying. This three-dimensional fiber skeleton serves as the template preform. The water-soluble PVA fibers need to undergo hydrophobic modification and surface treatment. The hydrophobic modification involves immersing the PVA fibers in an ethanol solution of boric acid at a concentration of 1%–3%. The PVA fibers are then immersed in the ethanol solution of boric acid for 5–15 minutes to complete the modification and remove them. Boric acid undergoes a controllable and reversible cross-linking reaction with the hydroxyl groups on the PVA fiber molecular chain, forming a stable protective film on the fiber surface. This film effectively blocks the direct action of organic solvents on the PVA fiber body, allowing the PVA fibers to maintain a stable solid state in organic solvent media such as ethanol, without swelling, adhesion, or dissolution.

[0020] The surface treatment process involves placing the three-dimensional fiber skeleton in a plasma device and performing surface activation under an oxygen atmosphere of 10–30 Pa and a processing power of 50–150 W to obtain a three-dimensional fiber skeleton with enhanced surface polarity and chemical activity. Under the bombardment of high-energy electrons, oxygen dissociates into oxygen atoms, ozone, and various active groups. These active species bombard the polyvinyl alcohol fiber molecular chains, slightly increasing the surface roughness through etching and introducing oxygen-containing polar functional groups. These functional groups greatly enhance the polarity and chemical activity of the fiber surface. Surface treatment of the three-dimensional fiber skeleton can significantly improve the surface polarity of polyvinyl alcohol fibers, improving their wettability and spreadability to slurry. The formation of micro-roughness on the fiber surface provides mechanical anchoring points for the slurry, thereby enhancing the interfacial bonding force between the two phases. Ultimately, this ensures that the slurry uniformly coats the fibers, avoiding cracks or voids caused by poor bonding in subsequent processes, and comprehensively improving the quality of the composite preform.

[0021] S2. Slurry impregnation and drying: Polyethylene powder is uniformly dispersed in an organic solvent to form a stable slurry of a certain concentration. The slurry is impregnated to fully coat the polyvinyl alcohol fibers. Then, the organic solvent is removed by low-temperature drying to obtain the composite preform.

[0022] Before preparing the slurry from high-molecular-weight polyethylene powder, a degassing process is required. The high-molecular-weight polyethylene powder is placed in a vacuum drying oven and dried continuously at 60-80°C for 2-4 hours to remove volatiles and moisture. Ethanol is used as the organic solvent. In the fabrication of the three-dimensional fiber skeleton, the mass ratio of polyvinyl alcohol fiber to ethanol is 1-10:100. In the slurry impregnation and drying steps, the mass ratio of high-molecular-weight polyethylene powder to ethanol is 1-5:10. The slurry preparation method involves adding weighed polyvinylpyrrolidone powder to ethanol to form a homogeneous solvent. The mass of polyvinylpyrrolidone powder is 0.5%-2% of the mass of the added high-molecular-weight polyethylene powder. Polyvinyl chloride (PVP) powder is poured into a homogeneous solution and mechanically stirred for 10–20 minutes to form a stable suspension. The PVP molecule possesses both hydrophilic lactam groups and lipophilic methylene segments, allowing it to dissolve well in polar ethanol while anchoring to the hydrophobic PVP powder surface via the lipophilic segments. One end of the PVP molecular chain adsorbs onto the surface of the PVP powder particles, while the remaining long chains extend into the ethanol solution, forming a polymer coating layer. When two PVP-coated powder particles approach each other, these extended polymer layers physically overlap, generating entropic repulsion, thus preventing particle aggregation and sedimentation.

[0023] S3. Sintering: The dried composite preform is fed into a hot press and sintered under specific conditions. The surface of the high molecular weight polyethylene powder particles melts and diffuses and entangles with each other to form a porous three-dimensional skeleton that encapsulates the template preform. The specific conditions include a specified temperature and a specified pressure. The specified temperature is higher than the melting point of the high molecular weight polyethylene powder but lower than the melting point of the polyvinyl alcohol fiber, i.e., 120℃-150℃. The specified pressure is 5-8MPa. Under the specified conditions, the composite preform is continuously heated for 20-30 minutes. After heating, the temperature and pressure are maintained for 10-30 minutes.

[0024] The sintering process adopts a stepped heating and pressurization procedure. After the low-temperature drying is completed, the temperature is increased to the specified temperature at a rate of 10-15°C / min, and the pressure is increased to the specified pressure at a rate of 0.5-1MPa / min. In order to reduce energy consumption and cost, after the low-temperature drying in step S2 is completed, the step of cooling the composite green body to room temperature is omitted, and the green body is directly sintered in step S3 while retaining residual temperature.

[0025] S4. Leaching and Drying: The porous three-dimensional framework is immersed in heated deionized water. The dissolution and diffusion of the template embryo are accelerated by gentle stirring. After it is completely leached out, it is dried at low temperature to obtain a pure porous high-molecular-weight polyethylene powder material that replicates the morphology of the original template. By controlling the structure of the three-dimensional fiber framework in step S1, porous high-molecular-weight polyethylene materials with anisotropic or gradient porosity characteristics can be prepared. The anisotropic structure is achieved by directional induction of fiber arrangement. The gradient porosity structure is achieved by layering and forming fibers of different specifications or by controlling the slurry coating parameters.

[0026] Example 2

[0027] In the template preparation step, no hydrophobic modification or surface treatment is performed on the polyvinyl alcohol fibers. The short-cut water-soluble polyvinyl alcohol fibers are dispersed in an organic solvent and formed into shape. After drying, a three-dimensional fiber skeleton with uniform structure and controllable pores is obtained. This three-dimensional fiber skeleton serves as the template preform. Other operations are the same as in Example 1.

[0028] Example 3

[0029] In the slurry impregnation and drying steps, high molecular weight polyethylene powder is uniformly dispersed in an organic solvent to form a stable slurry of a certain concentration. The slurry is then impregnated to fully coat the polyvinyl alcohol fibers. Subsequently, the organic solvent is removed by low-temperature drying to obtain a composite preform. The slurry preparation method is as follows: the weighed high molecular weight polyethylene powder is poured into an ethanol solution and mechanically stirred for 10 to 20 minutes to form a stable suspension slurry. Other operations are the same as in Example 1.

[0030] Example 4

[0031] In the template preparation step, short-cut water-soluble polyvinyl alcohol fibers are dispersed in an organic solvent and formed into shape. After drying, a three-dimensional fiber skeleton with uniform structure and controllable pores is obtained. This three-dimensional fiber skeleton serves as the template preform. The organic solvent is ethanol, and the mass ratio of polyvinyl alcohol fibers to ethanol is 10-20:100. Other operations are the same as in Example 1.

[0032] Example 5

[0033] In the template preparation step, short-cut water-soluble polyvinyl alcohol fibers are dispersed in an organic solvent and formed into shape. After drying, a three-dimensional fiber skeleton with uniform structure and controllable pores is obtained. This three-dimensional fiber skeleton serves as the template preform. The organic solvent is ethanol, and the mass ratio of polyvinyl alcohol fibers to ethanol is 20-30:100. Other operations are the same as in Example 1.

[0034] Example 6

[0035] In the template preparation step, short-cut water-soluble polyvinyl alcohol fibers are dispersed in an organic solvent and formed into shape. After drying, a three-dimensional fiber skeleton with uniform structure and controllable pores is obtained. This three-dimensional fiber skeleton serves as the template preform. The organic solvent is ethanol, and the mass ratio of polyvinyl alcohol fibers to ethanol is 30-40:100. Other operations are the same as in Example 1.

[0036] Example 7

[0037] In the template preparation step, short-cut water-soluble polyvinyl alcohol fibers are dispersed in an organic solvent and formed into shape. After drying, a three-dimensional fiber skeleton with uniform structure and controllable pores is obtained. This three-dimensional fiber skeleton serves as the template preform. The organic solvent is ethanol, and the mass ratio of polyvinyl alcohol fibers to ethanol is 40-50:100. Other operations are the same as in Example 1.

[0038] Example 8

[0039] In the slurry impregnation and drying steps, high molecular weight polyethylene powder is uniformly dispersed in an organic solvent to form a stable slurry of a certain concentration. The slurry is then impregnated to fully coat the polyvinyl alcohol fibers. Subsequently, the organic solvent is removed by low-temperature drying to obtain a composite preform. The mass ratio of high molecular weight polyethylene powder to ethanol in the slurry is 6-8:10, and other operations are the same as in Example 1.

[0040] Table 1

[0041] Fiber coating uniformity Open porosity Porosity variation coefficient between batches (%) Structural radial uniformity (%) Example 1 96 83 2 95 Example 2 71 71 9 67 Example 3 83 79 5 81

[0042] Example 1 describes a complete hydrophobic modification and surface treatment process for polyvinyl alcohol (PVA) fibers. The hydrophobic modification forms a protective film on the fiber surface, preventing swelling or adhesion in organic solvents and maintaining fiber morphological stability. The surface treatment enhances the polarity and chemical activity of the fiber surface, improving the wettability and spreadability of the slurry. It also increases surface roughness, providing mechanical anchoring points and ensuring uniform fiber coating. Polyvinylpyrrolidone (PVP) is used as a dispersant in the slurry to ensure its stability, prevent aggregation and sedimentation of polyethylene powder particles, and ensure a uniform coating. The surface treatment also enhances the interfacial bonding between the fiber and the slurry, preventing cracks or voids. A stepped heating and pressurization process is used for sintering, reducing internal stress. The cooling step is omitted, and direct hot pressing reduces the risk of thermal deformation. The internal pore structure uniformity is 95%, resulting from the uniformity of the template structure and the uniform coating of the slurry. The surface treatment ensures a tight bond between the slurry and the fiber. During sintering, the polyethylene powder melts uniformly, forming a stable three-dimensional skeleton with a consistent pore distribution.

[0043] Example 2 involved hydrophobic modification and surface treatment of polyvinyl alcohol (PVA) fibers, resulting in low uniformity of slurry coating. PVA fibers are prone to swelling and adhesion in organic solvents, leading to an unstable fiber skeleton structure, poor slurry wettability, and inability to uniformly coat the fibers. This resulted in an increased and uneven average slurry thickness of 15 μm. The product porosity decreased to 75% because fiber swelling altered the original pore structure of the template. During slurry coating and hot pressing, fiber deformation caused pore blockage or expansion, making it impossible to accurately replicate the designed pores. The deviation rate from the design dimensions was as high as 10%, due to poor fiber swelling and bonding. Unmodified PVA fibers exhibited significant dimensional changes in organic solvents, easily shrinking or deforming during sintering, leading to discrepancies between product dimensions and design. Fiber swelling resulted in an uneven template structure, incomplete slurry coating, and a chaotic pore distribution after hot pressing, potentially exhibiting locally dense or sparse areas, resulting in poor overall uniformity.

[0044] In Example 3, no PVP dispersant was used in the slurry preparation. Hydrophobic modification and surface treatment were performed, resulting in better slurry coating uniformity than in Example 2 but worse than in Example 1. The lack of PVP dispersant led to slurry instability, causing polyethylene powder particles to easily agglomerate and settle, resulting in uneven slurry coating and uneven average slurry thickness. The product porosity deviated from the design value because slurry agglomeration may block some pores or cause local defects. However, the fiber template itself had a uniform structure, so the porosity reduction was not as significant as in Example 2, with a deviation rate of 5% from the design size. Due to uneven slurry coating, local stress concentration occurred during sintering, leading to slight deformation or cracks. However, the fiber template was well-treated, reducing dimensional changes to some extent. The internal pore structure uniformity was 80%. Because slurry agglomeration affected the uniform formation of the polyethylene skeleton, the pore structure roughly replicated the template, but there were localized agglomerated particles causing anomalies, resulting in lower uniformity than in Example 1. Conclusion

[0045] Table 2

[0046] Example 1 Example 5 Example 6 Example 7 Example 8 Polyvinyl alcohol fiber to ethanol mass ratio 10-20：100 20-30：100 30-40：100 40-50：100 1-10：100 Polyethylene powder to ethanol mass ratio 1-5：10 1-5：10 1-5：10 1-5：10 6-8：10

[0047] Table 3

[0048] Example 1 Example 5 Example 6 Example 7 Example 8 Morphology fidelity (%) 92 84 77 63 71 Bulk density (g / cm³) 0.26 0.32 0.41 0.51 0.55 Compressive strength 3.7 5.3 6.8 8.4 12.3 Interconnected porosity 82 78 72 65 60 Drying stress defect rate 3 5 8 15 4 Aperture distribution dispersion 11 19 23 37 16 Radial density variation coefficient 8 12 17 26 21

[0049] Morphological fidelity measures the accuracy with which the final porous polyethylene material replicates the initial polyvinyl alcohol fiber template in three dimensions. High fidelity indicates successful transfer of the designed template pore structure to the final product. Bulk density is the mass of material per unit volume, encompassing both the material's solid structure and internal pores. For the same material, lower bulk density generally indicates higher porosity and a lighter weight. Compressive strength is the material's ability to resist deformation and failure under compressive force, determining the mechanical reliability of porous materials in practical applications; insufficient strength can lead to functional impairment. Interconnected porosity is the percentage of the volume of interconnected pores in the material; pores must be interconnected to function properly. For applications such as filtration, adsorption, and electrode materials, high interconnected porosity is key to achieving efficient permeation and transport. The drying stress defect rate is the percentage of products in a batch that exhibit defects such as cracks, warping, and splitting due to internal stress concentration during slurry drying or subsequent processes. Processes with high defect rates cannot be scaled up, and product performance cannot be guaranteed. Dispersion reflects pore size distribution; lower dispersion indicates more uniform pore sizes, while higher dispersion indicates inconsistent pore sizes and a wide distribution range. The radial density variation coefficient reveals the density difference from the outer surface to the internal center point of the material. When the fiber skeleton is too dense, the pores in the fiber network become very small and tortuous, forming a high-resistance permeation path. During the impregnation process, high-viscosity slurries, under capillary action and external pressure, do not fully penetrate into the core area. The polyethylene powder they carry is deposited and coated on the outer fiber surface, blocking the channels to the interior. A dense layer of slurry and fibers forms on the outside of the filter material, while the interior remains an unfilled, relatively loose fiber network.

[0050] In Example 1, the mass ratio of polyvinyl alcohol fiber to ethanol is 10-20:100, which is a moderate ratio and a low fiber concentration. The template itself has large pores, making it easy for the slurry to penetrate and replicate the macroscopic morphology of the template well. At the same time, it has complete modification operations, surface treatment operations, and a stable slurry system. The fiber skeleton is stable and the interface bonding is good. Therefore, the various properties are balanced, the morphology fidelity is high, the structure is relatively uniform, and the defect rate is low.

[0051] In Example 5, the fiber-to-ethanol ratio was increased to 20-30:100, resulting in increased fiber density. This made the internal structure of the template more complex, and some micropores may not have been completely filled by the slurry, leading to a decrease in morphological fidelity and interconnected porosity. The increased fiber quantity slightly increased the risk of uneven shrinkage during drying and hot pressing. Therefore, the defect rate and structural uniformity indicators, namely interconnected porosity and drying stress defect rate, were slightly worse than in Example 4. More fibers and PE formed more support points, thus improving the compressive strength.

[0052] In Example 6, the fiber ratio was further increased, exacerbating the negative effects. The high-density fiber skeleton significantly increased the difficulty of slurry penetration and distribution, easily causing uneven local encapsulation or pore blockage, resulting in a significant decrease in morphological fidelity and interconnected porosity. During drying and hot pressing, internal stress was more likely to concentrate, leading to an increased defect rate and significantly worse structural uniformity. Its advantage is a higher solids content, thus further improving bulk density and compressive strength.

[0053] Example 7 illustrates a case of excessively high fiber content. The overly dense template severely hinders the flow and penetration of the slurry, resulting in significant distortion of the replicated morphology, low morphology fidelity, and blockage of numerous pores. The extremely high solids content and complex structure generate enormous internal stress during processing, leading to a sharp increase in drying defect rate. The product is highly prone to cracking or deformation, and exhibits the worst internal structural uniformity. Its only advantage is that its mechanical strength continues to improve due to the high material density.

[0054] In Example 8, the slurry concentration was increased. The high solids content of the slurry resulted in high viscosity and poor fluidity, making it difficult to fully penetrate into the fine pores of the template. Instead, it formed an excessively thick coating layer on the fiber surface. This led to insufficient fine structure of the template, low morphological fidelity and interconnected porosity. The excessively thick slurry layer also resulted in greater shrinkage stress during drying, which easily led to defects and caused obvious density differences from the outside to the inside, with a high radial density variation coefficient. However, its most significant feature was that the extremely high PE content formed a very dense and robust PE skeleton. Therefore, the bulk density and compressive strength were the highest among all examples, making it closer to a high-strength porous solid material.

[0055] Secondly: In the embodiments disclosed in this invention, only the structures involved in the embodiments disclosed in this invention are involved. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0056] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A super high molecular weight polyethylene filter material and its preparation method, characterized in that, include: S1. Template preparation: Short-cut water-soluble polyvinyl alcohol fibers are dispersed in an organic solvent and formed into shape. After drying, a three-dimensional fiber skeleton with uniform structure and controllable pores is obtained. This three-dimensional fiber skeleton serves as the template blank. S2. Slurry impregnation and drying: Polyethylene powder is uniformly dispersed in an organic solvent to form a stable slurry of a certain concentration. The slurry is impregnated to fully coat the polyvinyl alcohol fibers. Then, the organic solvent is removed by low-temperature drying to obtain the composite preform. S3. Sintering: The dried composite green body is fed into a hot press and sintered under specific conditions; the surface of the high molecular weight polyethylene powder particles melts and diffuses and entangles with each other to form a porous three-dimensional skeleton that encapsulates the template green body. S4. Leaching and Drying: The porous three-dimensional framework is immersed in heated deionized water. The dissolution and diffusion of the template blank are accelerated by gentle stirring. After it is completely leached out, it is dried at low temperature to obtain a pure high-molecular-weight polyethylene powder porous material that replicates the morphology of the original template.

2. The ultra-high molecular weight polyethylene filter material and its preparation method according to claim 1, characterized in that: The water-soluble polyvinyl alcohol fiber needs to undergo hydrophobic modification and surface treatment. The hydrophobic modification involves immersing the fiber in an ethanol solution of boric acid at a concentration of 1% to 3% for 5 to 15 minutes to complete the modification and remove the fiber.

3. The ultra-high molecular weight polyethylene filter material and its preparation method according to claim 2, characterized in that: The surface treatment operation involves placing the three-dimensional fiber skeleton in a plasma device and performing surface activation under an oxygen atmosphere of 10–30 Pa and a processing power of 50–150 W to obtain a three-dimensional fiber skeleton with enhanced surface polarity and chemical activity.

4. The ultra-high molecular weight polyethylene filter material and its preparation method according to claim 1, characterized in that: Before the high molecular weight polyethylene powder is made into a slurry, a degassing process is required. The high molecular weight polyethylene powder is placed in a vacuum drying oven and dried continuously at 60-80°C for 2-4 hours to remove volatiles and moisture from the high molecular weight polyethylene powder.

5. The ultra-high molecular weight polyethylene filter material and its preparation method according to claim 1, characterized in that: The organic solvent is ethanol. In the fabrication of the three-dimensional fiber skeleton, the mass ratio of polyvinyl alcohol fiber to ethanol is 1-10:

100. In the slurry dipping and drying steps, the mass ratio of high molecular weight polyethylene powder to ethanol is 1-5:

10.

6. The ultra-high molecular weight polyethylene filter material and its preparation method according to claim 1, characterized in that: The slurry preparation method is as follows: weighed polyvinylpyrrolidone powder is added to ethanol to form a homogeneous solvent. The mass of polyvinylpyrrolidone powder is 0.5% to 2% of the mass of added high molecular weight polyethylene powder. The weighed high molecular weight polyethylene powder is poured into the homogeneous solution and mechanically stirred for 10 to 20 minutes to form a stable suspension slurry.

7. The ultra-high molecular weight polyethylene filter material and its preparation method according to claim 1, characterized in that: The specific conditions include a specified temperature and a specified pressure. The specified temperature is higher than the melting point of the high molecular weight polyethylene powder and lower than the melting point of the polyvinyl alcohol fiber, i.e., 120℃-150℃. The specified pressure is 5-8MPa. Under the specified conditions, the composite preform is continuously heated for 20-30 minutes. After heating, the temperature and pressure are maintained for 10-30 minutes.

8. The ultra-high molecular weight polyethylene filter material and its preparation method according to claim 1, characterized in that: The sintering step adopts a stepped heating and pressurization program. After the low-temperature drying is completed, the temperature is increased to the specified temperature at a rate of 10-15°C / min, and the pressure is increased to the specified pressure at a rate of 0.5-1MPa / min.