Anti-pollution modified polymer filter material, preparation method and application

Abstract

This invention discloses an anti-fouling modified polymer filter media, its preparation method, and its application. The filter media uses high-density polyethylene as a base material and includes maleic anhydride-grafted polyethylene, glass fiber powder, a compounded anti-aging agent, and polytetrafluoroethylene micropowder. Its preparation method includes raw material mixing, melt granulation, molding, vacuum foaming, plasma surface modification, and thermal insulation treatment. This invention significantly improves the filter media's anti-fouling properties, dirt-holding capacity, and service life through the synergistic regulation of the composite formulation system, the formation of a highly interconnected open-pore structure through agent-free vacuum foaming, and the long-term stability ensured by thermal insulation treatment. It is suitable for high-speed filtration of wastewater.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to an anti-fouling modified polymer filter material, its preparation method, and its application. Background Technology

[0002] Filter media is the core component of a high-speed filtration system, and its performance directly determines filtration efficiency and operational stability. Fine suspended solids, colloids, organic matter, and microorganisms contained in circulating wastewater easily form an adsorption layer on the filter media surface, leading to clogging and compaction, thus affecting the continuous operation of the system. Existing filter media mainly include quartz sand, ordinary polymer materials, and ceramics, but all have insufficient compatibility.

[0003] Quartz sand filter media can be made from natural quartz sand with a particle size of 0.5-2mm. However, it has low porosity (≤45%) and a dirt holding capacity of only 3-5kg SS / m³. It has poor surface hydrophilicity, making it easy for pollutants to be adsorbed and caking. It has high density (2.65g / cm³), resulting in high backwashing energy consumption. It also has a short service life, requiring replacement every 2-3 years.

[0004] Ordinary polymer filter media are made of polyethylene or polypropylene with a particle size of 3-5mm. However, they have insufficient mechanical strength and are easily worn and damaged at high flow rates (≥15m / h). Furthermore, the surface pollutants are difficult to clean after being adsorbed. They also have limited corrosion resistance and are prone to aging after long-term contact with chlorinated water. Their dirt holding capacity is only 6-8kg SS / m³.

[0005] Ceramic filter media is made of sintered ceramic materials with a porosity of 60-70%. However, it is brittle, has weak impact resistance, and is easily broken during installation and backwashing. It has a high density (1.8-2.0 g / cm³), resulting in high backwashing water consumption (5-8%). The manufacturing cost is high, about 3-5 times that of ordinary filter media. The surface pore size distribution is uneven, leading to large fluctuations in filtration accuracy.

[0006] In addition, vacuum foaming is a common method for preparing porous materials. Conventional vacuum foaming is mainly used in the fields of polyurethane foam and thermal insulation boards. Its core purpose is to reduce density, weight, and heat insulation. However, its process design does not consider the filtration function requirements of the filter media and has many defects: it only pursues weight reduction and heat insulation, which cannot be adapted to the filtration requirements of HDPE composite filter media; the cells are mostly closed cells with uneven pore size, which cannot achieve both high porosity and high strength; the process parameters are coarse and cannot be compatible with multi-component systems such as glass fiber and PTFE micro powder; the timing of implementation is unreasonable, the cell stability is poor, and it cannot meet the working conditions of high-speed filtration of circulating sewage, making it difficult to use as a filter media preparation process.

[0007] Therefore, developing a modified polymer filter material that is suitable for high-speed filtration of circulating sewage, has high porosity, high strength, anti-fouling properties, long lifespan, and a controllable preparation process has become a pressing technical problem in this field. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the existing technology and provide an anti-fouling modified polymer filter material, its preparation method and application, so as to achieve a comprehensive improvement in the filter material's high porosity, high strength, anti-fouling and long service life.

[0009] To achieve one aspect of the above-mentioned objectives, the present invention adopts the following technical solution: A modified polymer filter material for pollution resistance, wherein the raw materials of the modified polymer filter material include high-density polyethylene (HDPE) as the base material, and added maleic anhydride grafted polyethylene modifier (MAH-g-PE), glass fiber powder, anti-aging agent and polytetrafluoroethylene micro powder. The mass percentages of each component are as follows: HDPE 70-80wt%, preferably 72-78wt%, MAH-g-PE 4-12wt%, preferably 5-10wt%, glass fiber powder 6-14wt%, preferably 8-12wt%, anti-aging agent 1-5wt%, preferably 2-3wt%, and polytetrafluoroethylene micro powder 2-7wt%, preferably 3-5wt%.

[0010] To achieve another aspect of the above-mentioned objective, the present invention also improves the preparation method of the modified polymer filter material, comprising the following steps: (1) The raw materials are uniformly mixed and melt-granulated to obtain composite particles; (2) The composite particles are injection molded to obtain a filter material blank; (3) The modified polymer filter material blank is vacuum foamed at 100-120°C to form a connected porous structure inside the modified polymer filter material blank, thereby obtaining foamed filter material. (4) The foamed filter material is subjected to plasma surface modification treatment in an argon and oxygen atmosphere to improve the surface hydrophilicity and obtain modified filter material; (5) The modified filter material is kept at 80-100℃ and then cooled to obtain the finished modified polymer filter material.

[0011] To achieve another aspect of the above-mentioned objectives, the present invention also provides the application of the modified polymer filter material or the modified polymer filter material prepared by the method as a filter material for wastewater filtration.

[0012] Compared with the prior art, the present invention has the following advantages: This invention addresses the shortcomings of existing polymer filter media foaming processes, which rely on foaming agents and are prone to causing matrix performance degradation and secondary water pollution. Through the synergistic regulation of a composite formulation system, and employing vacuum negative pressure foaming technology without chemical / physical foaming agents, porous filter media with a porosity of 85-92% can be stably prepared without adding any foaming agents. Combined with surface modification and heat insulation treatments, the prepared filter media exhibits excellent performance. Significantly improved dirt holding capacity: The filter material of this invention forms a connected porosity of up to 85-92% through vacuum foaming, with a dirt holding capacity of ≥10kg SS / m³, which is more than 25% higher than that of ordinary polymer filter materials, and the operating cycle is extended by 50%.

[0013] Excellent anti-fouling performance: Through plasma surface modification, the surface contact angle of the filter material is ≤30%, the hydrophilicity is significantly improved, the pollutant adsorption is reduced by 40%, and the backwash recovery rate is ≥95%, effectively avoiding caking and blockage.

[0014] Enhanced mechanical strength: By adding glass fiber powder of a specific particle size for reinforcement, combined with optimized formulation and process, the mechanical strength of the filter media is ≥15MPa, which can adapt to high-speed filtration conditions of 15-30m / h, with an annual wear rate of ≤1% and a service life extended to more than 5 years.

[0015] High backwashing efficiency: The filter media density is only 0.8-0.98g / cm³, and only slight stirring is needed to achieve efficient cleaning during backwashing. The backwashing water consumption is ≤2%, which is significantly lower than existing technologies.

[0016] Strong environmental adaptability: resistant to acids and alkalis (pH 2-12), chlorine corrosion, and excellent anti-aging properties; can operate stably for a long time under complex conditions of circulating sewage discharge.

[0017] Stable filtration accuracy: The effective filtration pore size is controlled between 5-20μm, the SS removal rate is ≥90%, the effluent turbidity is stable at ≤3NTU, and the filtration accuracy fluctuates little.

[0018] Controllable preparation cost: Using conventional polymer materials and modifiers, the preparation process is simple and the cost is only 1 / 3 to 1 / 2 of that of ceramic filter media, which has good prospects for industrialization and promotion. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to these ranges or values, such as values ​​±10% of the endpoint values. For numerical ranges, endpoint values ​​of various ranges, endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Without conflict, the embodiments and features described in this application can be combined with each other.

[0021] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0022] In the modified polymer filter material of the present invention, the raw materials of the modified polymer filter material include high-density polyethylene (HDPE) as the base material, and added maleic anhydride grafted polyethylene modifier (MAH-g-PE), glass fiber powder, anti-aging agent and polytetrafluoroethylene micro powder. The mass percentages of each component are as follows: HDPE 70-80wt%, preferably 72-78wt%, for example 75wt%; MAH-g-PE 4-12wt%, preferably 5-10wt%, for example 8wt%; glass fiber powder 6-14wt%, preferably 8-12wt%, for example 10wt%; anti-aging agent 1-5wt%, preferably 2-3wt%, for example 2.5wt%; and polytetrafluoroethylene micro powder 2-7wt%, preferably 3-5wt%, for example 4wt%.

[0023] In the formulation system of this invention, the high-density polyethylene (HDPE) selected is well known in the art. For example, its density can be 0.941–0.960 g / cm³, which is a typical thermoplastic polymer material. Its high melt strength provides a bottom material guarantee for the shaping of the interconnected pore structure and avoids the collapse of the pores.

[0024] In the formulation system of this invention, high-density polyethylene (HDPE) is selected as the core substrate (70-80 wt%). Through its use in conjunction with glass fiber powder in the presence of a compatibility modifier, excellent mechanical properties can be provided. Simultaneously, the glass fiber powder and polytetrafluoroethylene micropowder in the formulation of this invention, under the compatibility modification of maleic anhydride-grafted polyethylene, can form a large number of uniform heterogeneous interfaces with the HDPE matrix. Combined with the vacuum foaming process, these interfaces can provide preferential nucleation sites for cell precipitation, significantly improving the density and uniformity of cell nuclei, replacing the nucleation function of traditional foaming agents, and avoiding problems such as decreased corrosion resistance, deteriorated anti-aging performance, and secondary pollution of circulating wastewater caused by foaming agent residue. This perfectly suits the application scenarios of this invention.

[0025] In the formulation system of this invention, maleic anhydride-grafted polyethylene (MAH-g-PE) is well known in the art as a compatibility modifier. It can not only improve the dispersion uniformity of glass fiber powder and PTFE micro powder in HDPE matrix, avoid filler agglomeration, and ensure the uniform distribution of nucleation sites; at the same time, MAH-g-PE modifier can also effectively control the melt strength of HDPE matrix, so that the cell wall can be precisely broken under critical state during expansion, forming interconnected pores instead of continuous stretching to form closed pores.

[0026] In the formulation system of the present invention, glass fiber powder is selected as a reinforcing agent to solve the problems of insufficient mechanical properties and easy wear and breakage under high flow rate conditions of polymer filter media with high porosity. At the same time, it can also synergistically optimize the vacuum foaming pore-forming effect and ensure filtration accuracy and long-term service stability. In a preferred embodiment, the particle size of the glass fiber powder is 4-20μm, preferably 5-10μm.

[0027] The filter media of this invention boasts a porosity of up to 85-92%, far exceeding that of existing quartz sand, ordinary polymers, and ceramic filter media. However, such ultra-high porosity leads to a significant reduction in the mechanical load-bearing capacity of the matrix. The small particle size of the glass fiber powder gives it an extremely high specific surface area, resulting in stronger interfacial bonding with the HDPE matrix. This allows it to form a uniform, three-dimensional, continuous reinforcing skeleton within the ultra-thin pore walls of the porous matrix. Ultimately, this achieves a filter media mechanical strength ≥15MPa, compressive strength ≥10MPa, and the ability to withstand high-speed water flow impacts of 30m / h with an annual wear rate ≤1%, perfectly solving the core defect of existing ordinary polymer filter media's susceptibility to breakage under high flow rates. Using large-size glass fiber powder or even short-cut glass fibers easily creates stress concentration points in the matrix, leading to pore wall rupture and a significant reduction in the mechanical reinforcement effect, making it unsuitable for the high-porosity structural design of this invention. Meanwhile, the introduction of glass fiber powder can provide a large number of heterogeneous nucleation sites, directly improving the density and uniformity of the cells. The high-density synchronous nucleation significantly compresses the initial spacing between adjacent nuclei. The smaller the spacing, the easier it is for the cells to approach each other during growth and eventually connect to form a through-hole when the wall reaches the critical thickness.

[0028] In the formulation system of the present invention, the addition of polytetrafluoroethylene (PTFE) forms a heterogeneous interface with the HDPE matrix, providing more uniformly distributed preferential nucleation sites for cell precipitation, while also increasing the corrosion resistance of the filter material; the PTFE micro powder is well known in the art, for example, its particle size does not exceed 20 μm, such as 1-20 μm, such as 5, 10 or 18 μm.

[0029] In the formulation system of the present invention, the anti-aging agent is well known in the art. In one embodiment, the anti-aging agent may be composed of antioxidant 1010 and ultraviolet absorber UV-531 in a mass ratio of 1:2 to 2:1.

[0030] In a preferred embodiment, the modified polymer filter material has an interconnected porous structure with a porosity of 85-92% and an effective filtration pore size of 4-25 μm, preferably 5-20 μm.

[0031] Preferably, the modified polymer filter material has a density of 0.8-0.98 g / cm³.

[0032] Preferably, the modified polymer filter material has a mechanical strength ≥15MPa and a compressive strength ≥10MPa.

[0033] Preferably, the modified polymer filter material can withstand high-speed water flow impacts of 15-30 m / h.

[0034] Preferably, the modified polymer filter material has a dirt holding capacity of ≥10 kg SS / m³.

[0035] Preferably, the backwash recovery rate of the modified polymer filter material is ≥95%.

[0036] Preferably, the modified polymer filter material has a chlorine resistance of 5000 mg / L. h, This invention also improves the preparation method of the above-mentioned modified polymer filter material, comprising the following steps: (1) The raw materials are uniformly mixed and melt-granulated to obtain composite particles; (2) The composite particles are injection molded to obtain a filter material blank; (3) The modified polymer filter material blank is vacuum foamed at 100-120°C to form a connected porous structure inside the modified polymer filter material blank, thereby obtaining foamed filter material. (4) The foamed filter material is subjected to plasma surface modification treatment in an argon and oxygen atmosphere to improve the surface hydrophilicity and obtain modified filter material; (5) The modified filter material is kept at 80-100℃ and then cooled to obtain the finished modified polymer filter material.

[0037] In a preferred embodiment, in step (1), during mixing, raw materials including HDPE substrate, modifier, glass fiber powder, anti-aging agent and polytetrafluoroethylene are added to a mixer and mixed evenly at 120-130°C; preferably, during mixing, the mixture is mixed in the mixer for 15-20 minutes at a mixing speed of 800-1000 r / min to ensure that the materials are evenly dispersed.

[0038] In a preferred embodiment, during step (1), when performing melt granulation, the mixture is fed into a twin-screw extruder and extruded and granulated at an extrusion temperature of 160-180°C and a screw speed of 300-400 r / min to obtain composite particles, preferably with a particle size of 2-3 mm.

[0039] In a preferred embodiment, in step (2), during injection molding, the composite particles are fed into the injection molding machine and molded into a filter material blank under the conditions of injection temperature of 170-190℃ and mold pressure of 5-8MPa. The filter material blank is preferably 5×5×3mm to 8×8×6mm in size, such as cylindrical or square.

[0040] The present invention, through the aforementioned high-speed mixing, twin-screw melt granulation, and high-pressure injection molding pre-processes, is more conducive to preparing filter material preforms with uniform component dispersion and high density. This not only removes large air bubbles in the preform and avoids the formation of local large pores during the foaming process, but also ensures that the content of trace volatiles in the matrix is ​​uniform and controllable. This guarantees that during the subsequent vacuum foaming process, the pores nucleate and grow simultaneously from the surface layer to the core of the filter material preform, avoiding the layered closed-cell structure caused by foaming the surface layer first and then the core layer.

[0041] In step (3) of this invention, the foaming temperature range of 100-120℃ set by this invention precisely matches the Vicat softening critical range of HDPE, allowing the molecular chains of the substrate to enter the transition region of high elasticity to viscous flow. This provides sufficient chain segment mobility to support the nucleation, expansion, and structural shaping of cells, while maintaining sufficient melt strength to prevent collapse and uncontrolled pore size during cell growth. This provides the necessary rheological basis for foaming without foaming agent, and also ensures that the polymer chain segments have sufficient mobility, allowing cells to expand continuously and adjacent cell walls to be stretched to critical thickness and rupture to form interconnected channels. If the foaming temperature is below 100℃, the matrix is ​​too rigid, the cells cannot expand sufficiently, and adjacent cell walls cannot be connected, resulting in isolated closed cells. If the foaming temperature is above 120℃, the matrix viscosity is too low and the melt strength is insufficient, resulting in structural collapse after the cell walls rupture, and the formation of stable interconnected channels.

[0042] In a preferred embodiment, during vacuum foaming in step (3), the vacuum level is 0.08-0.1 MPa. This high vacuum environment makes the furnace environment pressure much lower than the gas partial pressure inside the HDPE matrix, which is the core driving force for cell nucleation, growth, and wall penetration. On the one hand, in the raw material mixing, melt granulation, and injection molding processes of this invention, the matrix will contain trace amounts of air and trace amounts of low molecular weight volatiles generated by the thermal degradation of polymer chain segments. Under high negative pressure, these substances will quickly and uniformly precipitate from the matrix, forming a large number of stable cell nucleation points, significantly reducing the distance between adjacent cell nuclei, and creating the necessary prerequisite for subsequent cell wall penetration. On the other hand, the continuous negative pressure difference provides stable power for the directional expansion and growth of cell nuclei. Uniform cell growth can be achieved without the decomposition and release of gas by the foaming agent, continuously stretching the walls of adjacent cells to the critical rupture thickness, and finally forming continuous interconnected channels under negative pressure, resulting in a porous structure with high porosity. If the vacuum is too low, the power for bubble expansion is insufficient, and the bubble wall cannot reach the critical rupture state, only closed pores can be formed; if the vacuum is too high, the bubble expansion rate is too fast, which can easily lead to excessive fusion of bubbles and structural collapse, making it impossible to form interconnected pores with uniform pore size.

[0043] In a preferred embodiment, during step (3), the vacuum foaming time is 30-40 minutes. This time range effectively covers the entire process of interconnected pore formation, ensuring complete pore development and structural stability. This guarantees sufficient development of interconnected pores while avoiding excessive pore fusion. If the foaming time is too short, the pores will not develop sufficiently, and the walls of adjacent pores will not be able to break through and connect, resulting in closed pores. If the foaming time is too long, the pores will fuse excessively, forming large-sized through-holes, which will significantly degrade the filtration accuracy and mechanical properties of the filter media.

[0044] In step (4) of the present invention, the foamed filter material is subjected to plasma surface modification treatment. The plasma modification can act on the inner surface of the interconnected pores formed by vacuum foaming to improve the hydrophilicity of the inner and outer surfaces of the filter material, which is beneficial to coupling with the bulk phase modification of MAH-g-PE: MAH-g-PE gives the filter material overall basic hydrophilicity, and plasma surface modification produces a highly hydrophilic layer on the surface. The two work together to enable the filter material to obtain the optimal hydrophilicity at the filtration interface while maintaining the overall structural stability, forming a gradient hydrophilic structure from the inside out. While ensuring the ultra-high hydrophilicity of the filter material filtration interface (contact angle ≤30°), the long-term stability of the overall anti-fouling ability is ensured by the durable basic hydrophilicity provided by MAH-g-PE, thereby improving the high anti-fouling ability and high backwash recovery rate of the filter material.

[0045] In a preferred embodiment, during step (4), the foamed filter material is placed in a plasma treatment device and treated with a mixture of argon and oxygen (volume ratio can be 1:1-4:1, such as 2:1 or 3:1), with a treatment power of 100-150W and a treatment time of 5-10 minutes, to effectively improve the hydrophilicity of the inner and outer surfaces of the filter material. Preferably, the surface contact angle of the modified polymer filter material is ≤30°.

[0046] In step (5) of this invention, the modified filter material is subjected to heat preservation treatment at 80-100℃ to specifically address the problems affecting the service life of the filter material after modification by high-energy bombardment of argon-oxygen plasma on the high-porosity, interconnected porous HDPE matrix. These problems include metastable surface polar groups, residual media in the pores, and micro-internal stress in the matrix. If the temperature is too low, the polar groups will not be thermally stabilized on the surface, and the micro-internal stress will not be fully released; if the temperature is too high, the pores of the high-porosity filter material will easily collapse.

[0047] Specifically, on the one hand, during the heat preservation treatment, the trace oxygen in the air atmosphere can assist the hydrophilic groups such as hydroxyl and carboxyl groups introduced by the plasma to complete the end group stabilization and avoid group relaxation and failure; thus, the basic hydrophilic layer of MAH-g-PE and the plasma high hydrophilic layer together form a dual guarantee of continuous hydrophilicity of the filter interface, so that the filter material maintains stable anti-fouling performance under long-term high flow rate impact and frequent backwashing conditions. On the other hand, after the vacuum foaming and plasma surface modification treatment of the present invention, trace amounts of reactive gaseous media and condensed water vapor will be trapped in the interconnected pores of the high-porosity filter material. These can be effectively removed by the heat insulation treatment of the present invention. Without heat insulation removal, some effective filtration channels may be directly blocked, resulting in a decrease in the actual effective porosity of the filter material and the dirt holding capacity failing to meet the design requirement of ≥10kg SS / m³. At the same time, the pore size distribution is disordered, and the effective filtration pore size deviates from the design range of 5-20μm, resulting in an SS removal rate of less than 90%, an unstable effluent turbidity of ≤3NTU, and a filtration accuracy fluctuation far exceeding ±0.5NTU, which cannot meet the stable operation requirements of high-speed filtration. On the other hand, after vacuum foaming, the porous filter material is bombarded by high-energy plasma, which generates a small amount of internal stress in the matrix. The heat preservation treatment of this invention can effectively eliminate this internal stress. At the same time, the treatment temperature is much lower than the thermal oxidation decomposition temperature of HDPE, so it will not cause oxidation and deterioration to the matrix, modifier, glass fiber powder and other components. Without heat preservation treatment, the internal stress will be continuously released under the conditions of high and low flow rate alternation, hydraulic impact and temperature fluctuation during filtration and backwashing, which will cause the filter material to shrink in size, warp and deform, and even collapse of the cell wall and breakage of the connecting channels. This will directly cause a significant decrease in the mechanical strength and compressive strength of the filter material, making it unable to withstand the impact of high-speed water flow of 15-30m / h, with an annual wear rate far exceeding 1%, and the service life shortened from ≥5 years to less than 3 years.

[0048] In a preferred embodiment, during step (5), the modified filter material is kept at 80-100°C for 2-3 hours and then cooled to room temperature to obtain the finished filter material.

[0049] The present invention also provides the application of the modified polymer filter material as a filter material for sewage filtration, which can withstand the impact of high-speed water flow of 15-30m / h during filtration.

[0050] The present invention will be further illustrated below with examples / comparative examples, but it should not be construed as the present invention being limited thereto.

[0051] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in this technical field can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0052] Example 1 The preparation method of the modified polymer filter material in this embodiment is as follows: 1. Formulation: By weight percentage, high-density polyethylene (HDPE) 75%, maleic anhydride grafted polyethylene (MAH-g-PE) 8%, glass fiber powder with a particle size of 5-10μm 10%, compound anti-aging agent (antioxidant 1010 and UV-531 mixed in a 1:1 ratio) 2.5%, polytetrafluoroethylene (PTFE) micro powder 4.5%.

[0053] 2. Preparation method: a. Raw material mixing: Add each component in the above formula to a high-speed mixer and mix for 18 minutes at 125°C and 900 r / min.

[0054] b. Melt granulation: The mixture is fed into a twin-screw extruder and melt-extruded at 170°C and a screw speed of 350 r / min. The resulting composite granules are then granulated to obtain a particle size of 2.5 mm.

[0055] c. Molding and processing: The composite granules are fed into the injection molding machine and injection molded into a square filter material blank with dimensions of 6×6×4mm at 180℃ and mold pressure of 6.5MPa.

[0056] d. Vacuum foaming: The filter material blank is placed in a vacuum foaming furnace and foamed for 35 minutes at 110℃ and a vacuum degree of 0.09MPa to form a connected porous structure.

[0057] e. Surface modification: The foamed filter material is placed in a plasma treatment device and treated for 8 minutes at a power of 125W using a 3:1 volume ratio of argon and oxygen mixed gas.

[0058] f. Heat preservation treatment: The surface-modified filter material is placed in a 90℃ atmospheric pressure air oven and dried for 2.5 hours. After cooling, the finished filter material is obtained.

[0059] Example 2 The difference from Example 1 lies in the following adjustments to the formula and some process parameters: Formula: HDPE 80%, MAH-g-PE 5%, glass fiber powder 8%, compound anti-aging agent 2%, PTFE micro powder 5%.

[0060] Preparation method: Mixing temperature 120℃, mixing time 20min; twin-screw extrusion temperature 160℃, screw speed 400r / min; injection molding into a 5×5×3mm square preform; vacuum foaming parameters: 100℃, vacuum degree 0.1MPa, foaming time 40min; plasma treatment: power 100W, time 10min; heat preservation treatment: drying at 80℃ for 3h.

[0061] The rest is the same as in Example 1.

[0062] Example 3 The difference from Example 1 lies in the following adjustments to the formula and some process parameters: Formula: HDPE 70%, MAH-g-PE 10%, glass fiber powder 12%, compound anti-aging agent 3%, PTFE micro powder 5%.

[0063] Preparation method: Mixing temperature 130℃, mixing time 15min; twin-screw extrusion temperature 180℃, screw speed 300r / min; injection molding into 8×8×6mm cylindrical preform; vacuum foaming parameters: 120℃, vacuum degree 0.08MPa, foaming for 30min; plasma treatment: power 150W, time 5min; heat preservation treatment: drying at 100℃ for 2h.

[0064] The rest is the same as in Example 1.

[0065] The performance testing method is as follows:

[0066] The performance test results are as follows:

[0067] Comparative Example 1 The only difference from Example 1 is that the glass fiber powder is replaced with large-particle glass fiber powder with a particle size of 20-30μm, while the addition amount remains 10%.

[0068] The rest is the same as in Example 1.

[0069] Results Comparison - Comparative Example 1 vs Example 1: When the glass fiber powder particle size increased from 5-10 μm to 20-30 μm, the porosity decreased from 89.5% to 78.6%, and the proportion of interconnected pores decreased from 94% to 75%. This indicates that small-particle-size glass fiber powder (5-10 μm) provides a higher density of heterogeneous nucleation sites, achieving refinement of pores and optimization of interconnected pore structure.

[0070] Comparative Example 2 The difference from Example 1 is that: (1) 2 wt% of azodicarbonamide (AC) chemical foaming agent is added on the basis of the formulation of Example 1.

[0071] (2) The vacuum foaming step d of Example 1 is adjusted as follows: the preform after injection molding of the mixture is placed in the molding foaming mold and foamed at 200°C for 15 minutes (AC foaming agent decomposes to produce gas).

[0072] The remaining steps are the same as in Example 1.

[0073] Results Comparison - Comparative Example 2 vs. Example 1: After foaming with AC chemical foaming agent, the proportion of interconnected pores was only 72% (94% in Example 1), and the closed-pore rate was as high as 28%. Furthermore, foaming agent residue led to a decrease in the corrosion resistance and aging resistance of the filter media, resulting in a service life of only 2.5 years. The foaming agent-free vacuum foaming technology of this invention utilizes vacuum negative pressure to drive the directional and synchronous growth of foam pores, forming a highly interconnected open-pore structure. This eliminates residual contamination at its source and significantly extends the service life.

[0074] Comparative Example 3 The difference from Example 1 is that the heat preservation treatment step f is omitted, i.e., the plasma surface modification is followed by natural cooling to room temperature. The remaining steps are the same as in Example 1.

[0075] Results Comparison - Comparative Example 3 vs. Example 1: After omitting the heat preservation treatment, the initial contact angle was 26°, but after 30 days of aging, the contact angle sharply rebounded to 58°, an increase of 32° (Example 1 only rebounded by 2°); the dirt holding capacity decreased from 12.5 kg / m³ to 8.5 kg / m³, and the service life was shortened from >6 years to <2.5 years. This indicates that the heat preservation treatment plays an irreplaceable role in stabilizing the hydrophilic polar groups introduced by the plasma, removing residual media in the pores, and eliminating micro-internal stress, and is the key process for achieving long-lasting hydrophilicity and high filtration accuracy in this invention.

Claims

1. A modified polymer filter material for pollution resistance, characterized in that, The modified polymer filter material comprises high-density polyethylene (HDPE) as the base material, and added maleic anhydride grafted polyethylene modifier (MAH-g-PE), glass fiber powder, anti-aging agent and polytetrafluoroethylene micro powder. The mass percentages of each component are as follows: HDPE 70-80wt%, preferably 72-78wt%, MAH-g-PE 4-12wt%, preferably 5-10wt%, glass fiber powder 6-14wt%, preferably 8-12wt%, anti-aging agent 1-5wt%, preferably 2-3wt%, and polytetrafluoroethylene micro powder 2-7wt%, preferably 3-5wt%.

2. The modified polymer filter material according to claim 1, characterized in that, The modified polymer filter material has an internal interconnected porous structure with a porosity of 85-92% and a pore size distribution in the range of 1-60μm, with an effective filtration pore size in the range of 5-20μm.

3. The modified polymer filter material according to claim 1 or 2, characterized in that, The modified polymer filter material has a mechanical strength ≥15MPa and a compressive strength ≥10MPa; and / or The glass fiber powder has a particle size of 5-10 micrometers; and / or The anti-aging agent is composed of antioxidant 1010 and ultraviolet absorber UV-531 in a mass ratio of 1:2-2:1; and / or The particle size of the polytetrafluoroethylene micropowder does not exceed 20 μm; and / or The modified polymer filter media has a density of 0.8-0.98 g / cm³, a dirt holding capacity of ≥10 kg SS / m³, a backwash recovery rate of ≥95%, and a chlorine resistance of up to 5000 mg / L. h.

4. The method for preparing the modified polymer filter material according to any one of claims 1-3, comprising the following steps: (1) The raw materials are uniformly mixed and melt-granulated to obtain composite particles; (2) The composite particles are injection molded to obtain a filter material blank; (3) The modified polymer filter material blank is vacuum foamed at 100-120°C to form a connected porous structure inside the modified polymer filter material blank, thereby obtaining foamed filter material. (4) The foamed filter material is subjected to plasma surface modification treatment in an argon and oxygen atmosphere to improve the surface hydrophilicity and obtain modified filter material; (5) The modified filter material is kept at 80-100℃ and then cooled to obtain the finished modified polymer filter material.

5. The method according to claim 4, characterized in that, In step (1), during mixing, raw materials including HDPE substrate, modifier, glass fiber powder, anti-aging agent, and polytetrafluoroethylene micro powder are added to a mixer and mixed evenly at 120-130°C; preferably, during mixing, the mixture is mixed in the mixer for 15-20 minutes at a mixing speed of 800-1000 r / min to ensure uniform dispersion of the materials; and / or In step (1), during melt granulation, the mixture is fed into a twin-screw extruder. Under the conditions of extrusion temperature of 160-180℃ and screw speed of 300-400r / min, composite particles are obtained by extrusion and pelletizing, with a preferred particle size of 2-3mm.

6. The method according to claim 4 or 5, characterized in that, In step (2), during injection molding, the composite particles are fed into the injection molding machine and molded into a filter material blank under the conditions of injection temperature of 170-190℃ and mold pressure of 5-8MPa. The filter material blank is preferably 5×5×3mm to 8×8×6mm in size.

7. The method according to any one of claims 4-6, characterized in that, In step (3), during vacuum foaming, the modified polymer filter material preform is foamed for 30-40 minutes at 100-120℃ and a vacuum degree of 0.08-0.1MPa.

8. The method according to any one of claims 4-7, characterized in that, In step (4), during modification, the foamed filter material is placed in a plasma treatment device, using a mixture of argon and oxygen (volume ratio 3:1), with a treatment power of 100-150W and a treatment time of 5-10min to improve surface hydrophilicity; preferably, the surface contact angle of the modified filter material is ≤30°.

9. The method according to any one of claims 4-8, characterized in that, In step (5), during the heat preservation treatment, the modified filter material is kept at 80-100℃ for 2-3 hours, and then cooled to room temperature to obtain the finished filter material.

10. The application of the modified polymer filter material according to claim 1 or the modified polymer filter material prepared by the method according to claim 4 as a filter material for wastewater filtration.

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