A polypropylene filter material and a method for producing the same

Abstract

The application relates to the technical field of polypropylene fiber filter materials, and discloses a polypropylene filter material and a preparation method thereof, which comprises the following preparation steps: polypropylene chips are vacuum-dried, then are mixed with composite reinforcing fillers, a compatilizer, a dispersing agent and an antioxidant, are stirred to obtain a blending material; the blending material is extruded into filaments, is bonded and cooled on a screen curtain, then is hot-pressed and is left to stand to obtain the polypropylene filter material. The polypropylene filter material prepared by taking the polypropylene chips as a base material, adding the compatilizer, the dispersing agent and the antioxidant, and then compounding the composite reinforcing fillers has a high filtering effect on sewage, and the polypropylene filter material has high mechanical properties and antibacterial activity, so that the polypropylene filter material is not prone to being blocked during sewage treatment.

Description

Technical Field

[0001] This invention relates to the field of polypropylene fiber filter materials technology, specifically to a polypropylene filter material and its preparation method. Background Technology

[0002] Polypropylene filter material is a filter material made from polypropylene fiber (also known as polypropylene fiber). Its fibers are fine, have a large specific surface area, and have a dense three-dimensional spatial network structure with many irregular channels and small pore size. It is one of the most common filter materials. It has good acid and alkali resistance, moisture resistance and chemical stability, and is widely used in the field of wastewater filtration. Traditional polypropylene filter materials mainly rely on mechanical interception to filter particulate matter, which has poor filtration efficiency and is easily damaged during processing and use. Therefore, it is necessary to develop polypropylene filter materials with high filtration efficiency and high mechanical strength.

[0003] Polypropylene filter materials prepared by adding compatibilizers, dispersants, antioxidants and other additives as the base material have high filtration efficiency. However, polypropylene filter materials made of ultrafine fibers often have low strength and are easily damaged during processing and use, which affects the filtration efficiency of sewage. In addition, they lack antibacterial properties, which makes the polypropylene filter materials easy to clog the filter material during sewage treatment, resulting in a decline in filtration performance. Summary of the Invention

[0004] This invention provides a polypropylene filter material and its preparation method, which solves the problems of polypropylene filter materials being easily damaged and lacking antibacterial properties during processing and use.

[0005] The technical solution of the present invention: A method for preparing a polypropylene filter material includes the following preparation steps: S1. After vacuum drying, polypropylene chips are mixed with composite reinforcing fillers, compatibilizers, dispersants, and antioxidants, and stirred to obtain a blend. S2. The blended material is extruded and spun into fibers, bonded and cooled on a screen, then hot-pressed and left to stand to obtain polypropylene filter material; Among them, the composite reinforcing filler is obtained by mixing and reacting citric acid and ethylenediaminetetraacetic acid, and then mixing and reacting it with composite silica and silane coupling agent; Composite silica is obtained by synthesizing a porous carbon layer on the surface of mesoporous silica and then reacting it with silver nitrate.

[0006] Further, in step S1, the mass ratio of polypropylene chips, composite reinforcing filler, compatibilizer, dispersant, and antioxidant is 100:(15-20):(1-2):(1.5-2.5):(0.5-1).

[0007] Furthermore, in step S1, the vacuum drying temperature is 70-90℃, the drying time is 10-12h, and the vacuum degree is 0.05-0.1MPa.

[0008] Furthermore, in step S1, the stirring speed is 500-600 r / min, and the stirring time is 30-40 min.

[0009] Furthermore, in step S2, the extrusion spinning is carried out in a twin-screw extruder, the extrusion spinning temperature is 260-290℃, the micro-orifice diameter of the spinneret is 0.18-0.22mm, the screw speed is 400-500r / min, and the screw length-to-diameter ratio is (33-45):1.

[0010] Furthermore, in step S2, the hot pressing pressure is 15-25 MPa, and the hot pressing time is 10-15 min.

[0011] Furthermore, the dispersant is selected from stearic acid or glyceryl stearate.

[0012] Furthermore, the antioxidant is selected from any one of antioxidant 1010, antioxidant 168, and antioxidant 1024.

[0013] Furthermore, the compatibilizer is a maleic anhydride-grafted ethylene-vinyl acetate copolymer.

[0014] Furthermore, the composite reinforced filler is prepared by the following steps: A1. Mesoporous silica and tannic acid were added to ethanol and stirred until homogeneous. Glucose was added and stirred until homogeneous. The mixture was then filtered, washed, dried, placed in a tube furnace, potassium hydroxide solution was added, nitrogen gas was introduced, and the mixture was carbonized. After cooling to room temperature, the mixture was removed, washed, and dried to obtain modified silica. A2. Add the modified silica to the silver nitrate aqueous solution, sonicate, treat at 100-130 Pa, remove, place in a muffle furnace, calcine at 390-410℃ for 30-35 min, cool to room temperature, and obtain composite silica; A3. Add citric acid to deionized water and stir until the citric acid is completely dissolved. Add ethylenediaminetetraacetic acid and stir evenly. Heat the mixture and add hydrochloric acid. After the reaction is complete, cool to room temperature, filter to remove impurities, collect the filtrate, and obtain the complex. A4. Add composite silica to deionized water and ethanol, stir until homogeneous, add silane coupling agent, stir until the reaction is complete, add the composite, continue stirring and mixing, filter, wash, and dry to obtain composite reinforced filler.

[0015] Furthermore, in the above A1 reaction process, tannic acid contains a large number of phenolic hydroxyl groups, which have good adhesion. As a linker, it allows the carbon precursor glucose to be coated onto the surface of mesoporous silica through tannic acid. After high-temperature carbonization, the glucose decomposes under heat to form a dense carbon layer. Potassium hydroxide, as an activator, decomposes under heat and forms channels on the surface of the dense carbon layer, thereby achieving the synthesis of a porous carbon layer on the surface of mesoporous silica and obtaining composite silica.

[0016] Furthermore, in the A2 reaction process described above, the composite silica contains a porous structure and has high adsorption performance, which can adsorb silver nitrate into the pores of the composite silica. After high-temperature calcination, the silver nitrate decomposes to form nano-silver, thus realizing the formation of nano-silver particles in the pores of the porous carbon on the surface of the composite silica, and obtaining composite silica.

[0017] Furthermore, in the A3 reaction process described above, citric acid is dissolved in deionized water. Under the action of hydrochloric acid as a catalyst, the hydroxyl groups in citric acid undergo an esterification reaction with the carboxyl groups of ethylenediaminetetraacetic acid, resulting in ethylenediaminetetraacetic acid being grafted onto citric acid to obtain a complex.

[0018] Furthermore, during the A4 reaction process described above, the silanol groups generated by the hydrolysis of the silane coupling agent can chemically bond with the hydroxyl groups on the surface of the composite silica, allowing the silane coupling agent to be grafted onto the surface of the composite silica. In addition, the amino groups contained in the silane coupling agent can bond with the oxygen-containing functional groups in the composite through hydrogen bonds to form a cross-linked structure, thereby coating the surface of the composite silica with the composite reinforcing filler.

[0019] Further, in step A1, the mass ratio of mesoporous silica, tannic acid, ethanol, glucose and potassium hydroxide solution is (2-2.5):(0.6-1):(80-90):(3-3.3):(2-2.5).

[0020] Further, in step A2, the mass ratio of modified silica to silver nitrate aqueous solution is (3-4):(30-40).

[0021] Further, in step A3, the mass ratio of citric acid, deionized water, ethylenediaminetetraacetic acid, and hydrochloric acid is (3-3.5):(65-75):(2-2.3):(1-1.5).

[0022] Further, in step A4, the mass ratio of composite silica, ethanol, deionized water, silane coupling agent and composite is (2.5-3):(90-100):(30-40):(1-1.2):(20-30).

[0023] The present invention has the following beneficial effects: (1) In the technical solution of the present invention, a porous carbon layer is synthesized on the surface of mesoporous silica. On the one hand, mesoporous silica, as a porous adsorption matrix, can effectively remove heavy metal ions in sewage and improve the filtration performance of polypropylene filter material for heavy metal ions. On the other hand, the porous carbon layer synthesized on the surface of mesoporous silica has a high specific surface area, which increases the contact area with sewage and improves the filtration performance. Moreover, the porous structure contained in the porous carbon has a high adsorption capacity, which further improves the removal efficiency of heavy metal ions in sewage. In addition, there is a large bonding force between mesoporous silica and porous carbon layer, which can absorb and weaken the impact force of sewage flow on polypropylene filter material for a long time, avoid the filter material from cracking and breaking under the impact force of sewage, and improve the filtration performance and mechanical properties of polypropylene filter material.

[0024] (2) In the technical solution of the present invention, nano-silver particles are formed in the pores of porous carbon on the surface of composite silica. On the one hand, the formed nano-silver particles, as inorganic antibacterial agents, can improve the antibacterial performance of polypropylene filter materials. On the other hand, the composite silica, as a carrier of nano-silver particles, improves the dispersibility of nano-silver particles in polypropylene filter materials. As a supporting skeleton of porous carbon in composite silica, nano-silver particles can absorb and weaken the attraction generated by external forces, and prevent the porous carbon from collapsing under the impact of external forces, thus affecting the filtration efficiency of sewage and the mechanical properties of polypropylene filter materials.

[0025] (3) In the technical solution of the present invention, ethylenediaminetetraacetic acid is grafted onto citric acid. On the one hand, ethylenediaminetetraacetic acid, as a complexing agent, can adsorb and complex heavy metal ions in sewage, thereby further improving the filtration efficiency of polypropylene filter material. On the other hand, citric acid, as a carrier, can load more ethylenediaminetetraacetic acid, thereby increasing the binding sites of heavy metal ions, improving filtration efficiency, and avoiding the limited adsorption capacity of ethylenediaminetetraacetic acid, which is easily saturated and affects the removal rate of heavy metal ions.

[0026] (4) In the technical solution of the present invention, the silane coupling agent is grafted onto the surface of the composite silica, thereby introducing active functional groups on the surface of the composite silica, which is beneficial for the composite to be coated on the surface of the composite silica. The composite is coated on the surface of the composite silica by the silane coupling agent. On the one hand, the composite can adsorb and fix the heavy metal ions adsorbed in the composite silica, preventing the heavy metal ions from being desorbed and redispersed into the sewage during the adsorption process, resulting in incomplete adsorption. On the other hand, the composite forms a cross-linked structure on the surface of the composite silica, which can enhance the mechanical properties of the polypropylene filter material. Moreover, the large number of functional groups contained in the composite can improve the dispersibility of the composite silica in the polypropylene filter material, thereby improving the mechanical properties, filtration performance and antibacterial activity of the polypropylene filter material.

[0027] (5) In the technical solution of the present invention, the polypropylene filter material prepared by using polypropylene chips as the base material, adding compatibilizer, dispersant and antioxidant, and then compounding composite reinforced filler has a high filtration effect on sewage, and the polypropylene filter material has high mechanical properties and antibacterial activity, so that the polypropylene filter material is not easy to clog the filter material during sewage treatment. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] The raw materials used in the embodiments of this invention are shown below, and all reagents used are analytical grade.

[0030] The polypropylene chips, designated PP BH by Lanzhou Port Petrochemical, were purchased from Gansu Lanzhou Port Petrochemical Co., Ltd.

[0031] The dispersant is stearic acid, and the antioxidant is antioxidant 1010.

[0032] The compatibilizer is maleic anhydride-grafted ethylene-vinyl acetate copolymer, brand name 3126, manufactured by Dongguan Sujia Polymer Raw Materials Co., Ltd.

[0033] The mesoporous silica has a particle size of 5 μm and a pore size of 40 nm.

[0034] The silane coupling agent is KH550 (γ-aminopropyltriethoxysilane). Example

[0035] A method for preparing a polypropylene filter material includes the following preparation steps: S1. Polypropylene chips are vacuum dried and then mixed with composite reinforcing filler, maleic anhydride-grafted ethylene-vinyl acetate copolymer, stearic acid, and antioxidant 1010. The mixture is stirred at 500 r / min for 30 min to obtain a blend. The mass ratio of polypropylene chips, composite reinforcing filler, maleic anhydride-grafted ethylene-vinyl acetate copolymer, stearic acid, and antioxidant 1010 is 100:15:1:1.5:0.5. The vacuum drying temperature is 70℃, the drying time is 10 h, and the vacuum degree is 0.05 MPa. S2. The blended material is extruded and spun, bonded and cooled on a screen, then hot-pressed and allowed to stand to obtain polypropylene filter material. The extrusion and spinning are carried out in a twin-screw extruder at a temperature of 260℃, a spinneret orifice diameter of 0.18mm, a screw speed of 400r / min, and a screw length-to-diameter ratio of 33:1. The hot-pressing pressure is 15MPa and the hot-pressing time is 10min.

[0036] The composite reinforced filler is prepared by the following steps: A1. Mesoporous silica and tannic acid were added to ethanol and stirred until homogeneous. Glucose was added, and the mixture was stirred at 70°C for 30 min. After filtration, the mixture was washed three times with deionized water and dried in an oven at 70°C for 10 min. The mixture was then placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 800°C for 4 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain modified silica. The mass ratio of mesoporous silica, tannic acid, ethanol, glucose, and potassium hydroxide solution was 2:0.6:80:3:2. A2. Modified silica was added to a 50 g / L silver nitrate aqueous solution, ultrasonicated at 40 kHz for 20 min, treated at 100 Pa for 1 h, removed, placed in a muffle furnace, calcined at 390 °C for 30 min, and cooled to room temperature to obtain composite silica; the mass ratio of modified silica to silver nitrate aqueous solution was 3:30. A3. Add citric acid to deionized water and stir until the citric acid is completely dissolved. Add ethylenediaminetetraacetic acid and stir evenly. Heat to 70°C and add 36% hydrochloric acid. Stir and react for 20 minutes. Cool to room temperature, filter to remove impurities, and collect the filtrate to obtain the complex. The mass ratio of citric acid, deionized water, ethylenediaminetetraacetic acid, and hydrochloric acid is 3:65:2:1. A4. Add composite silica to deionized water and ethanol, stir evenly, add KH550, stir and react at 70℃ for 30 min, add composite, continue stirring and mixing at 70℃ for 30 min, filter, wash 3 times with deionized water, and dry in an oven at 70℃ for 10 min to obtain composite reinforced filler. The mass ratio of composite silica, ethanol, deionized water, KH550 and the composite is 2.5:90:30:1:20. Example

[0037] A method for preparing a polypropylene filter material includes the following preparation steps: S1. Polypropylene chips are vacuum dried and then mixed with composite reinforcing filler, maleic anhydride-grafted ethylene-vinyl acetate copolymer, stearic acid, and antioxidant 1010. The mixture is stirred at 550 r / min for 35 min to obtain a blend. The mass ratio of polypropylene chips, composite reinforcing filler, maleic anhydride-grafted ethylene-vinyl acetate copolymer, stearic acid, and antioxidant 1010 is 100:18:1.5:2:0.8. The vacuum drying temperature is 80℃, the drying time is 11 h, and the vacuum degree is 0.08 MPa. S2. The blended material is extruded and spun, bonded and cooled on a screen, then hot-pressed and allowed to stand to obtain polypropylene filter material. The extrusion and spinning are carried out in a twin-screw extruder with an extrusion and spinning temperature of 275℃, a spinneret micro-orifice diameter of 0.2mm, a screw speed of 450r / min, and a screw length-to-diameter ratio of 40:1. The hot-pressing pressure is 20MPa and the hot-pressing time is 13min.

[0038] The composite reinforced filler is prepared by the following steps: A1. Mesoporous silica and tannic acid were added to ethanol and stirred until homogeneous. Glucose was added, and the mixture was stirred at 70°C for 30 min. After filtration, the mixture was washed three times with deionized water and dried in a 70°C oven for 10 min. The mixture was then placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 800°C for 4 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in a 70°C oven for 10 min to obtain modified silica. The mass ratio of mesoporous silica, tannic acid, ethanol, glucose, and potassium hydroxide solution was 2.3:0.8:85:3.2:2.3. A2. Modified silica was added to a 50 g / L silver nitrate aqueous solution, ultrasonicated at 40 kHz for 20 min, treated at 120 Pa for 1 h, removed, placed in a muffle furnace, calcined at 400 °C for 33 min, and cooled to room temperature to obtain composite silica; the mass ratio of modified silica to silver nitrate aqueous solution was 3.5:35. A3. Add citric acid to deionized water and stir until the citric acid is completely dissolved. Add ethylenediaminetetraacetic acid and stir evenly. Heat to 70°C and add 36% hydrochloric acid. Stir and react for 20 minutes. Cool to room temperature, filter to remove impurities, and collect the filtrate to obtain the complex. The mass ratio of citric acid, deionized water, ethylenediaminetetraacetic acid, and hydrochloric acid is 3.3:70:2.2:1.3. A4. Add composite silica to deionized water and ethanol, stir evenly, add KH550, stir and react at 70℃ for 30 min, add the composite, continue stirring and mixing at 70℃ for 30 min, filter, wash 3 times with deionized water, and dry in an oven at 70℃ for 10 min to obtain composite reinforced filler; the mass ratio of composite silica, ethanol, deionized water, KH550 and composite is 2.8:95:35:1.1:25. Example

[0039] A method for preparing a polypropylene filter material includes the following preparation steps: S1. Polypropylene chips are vacuum dried and then mixed with composite reinforcing filler, maleic anhydride-grafted ethylene-vinyl acetate copolymer, stearic acid, and antioxidant 1010. The mixture is stirred at 600 r / min for 40 min to obtain a blend. The mass ratio of polypropylene chips, composite reinforcing filler, maleic anhydride-grafted ethylene-vinyl acetate copolymer, stearic acid, and antioxidant 1010 is 100:20:2:2.5:1. The vacuum drying temperature is 90℃, the drying time is 12 h, and the vacuum degree is 0.1 MPa. S2. The blended material is extruded and spun, bonded and cooled on a screen, then hot-pressed and allowed to stand to obtain polypropylene filter material. The extrusion and spinning are carried out in a twin-screw extruder with an extrusion and spinning temperature of 290℃, a spinneret micro-orifice diameter of 0.22mm, a screw speed of 500r / min, and a screw length-to-diameter ratio of 45:1. The hot-pressing pressure is 25MPa and the hot-pressing time is 15min.

[0040] The composite reinforced filler is prepared by the following steps: A1. Mesoporous silica and tannic acid were added to ethanol and stirred until homogeneous. Glucose was added, and the mixture was stirred at 70°C for 30 min. After filtration, the mixture was washed three times with deionized water and dried in an oven at 70°C for 10 min. The mixture was then placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 800°C for 4 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain modified silica. The mass ratio of mesoporous silica, tannic acid, ethanol, glucose, and potassium hydroxide solution was 2.5:1:90:3.3:2.5. A2. Modified silica was added to a 50 g / L silver nitrate aqueous solution, ultrasonicated at 40 kHz for 20 min, treated at 130 Pa for 1 h, removed, placed in a muffle furnace, calcined at 410 °C for 35 min, and cooled to room temperature to obtain composite silica; the mass ratio of modified silica to silver nitrate aqueous solution was 4:40. A3. Add citric acid to deionized water and stir until the citric acid is completely dissolved. Add ethylenediaminetetraacetic acid and stir evenly. Heat to 70°C and add 36% hydrochloric acid. Stir and react for 20 minutes. Cool to room temperature, filter to remove impurities, and collect the filtrate to obtain the complex. The mass ratio of citric acid, deionized water, ethylenediaminetetraacetic acid, and hydrochloric acid is 3.5:75:2.3:1.5. A4. Add composite silica to deionized water and ethanol, stir evenly, add KH550, stir and react at 70℃ for 30 min, add the composite, continue stirring and mixing at 70℃ for 30 min, filter, wash 3 times with deionized water, and dry in an oven at 70℃ for 10 min to obtain composite reinforced filler; the mass ratio of composite silica, ethanol, deionized water, KH550 and composite is 3:100:40:1.2:30.

[0041] Comparative Example 1 The only difference between this comparative example and Example 3 is the preparation of the composite reinforcing filler, as detailed below: The composite reinforced filler is prepared by the following steps: A1. Silica particles (5 μm in diameter) and tannic acid were added to ethanol and stirred until homogeneous. Glucose was added, and the mixture was stirred at 70°C for 30 min. After filtration, the mixture was washed three times with deionized water and dried in a 70°C oven for 10 min. The mixture was then placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 800°C for 4 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in a 70°C oven for 10 min to obtain modified silica. The mass ratio of silica particles, tannic acid, ethanol, glucose, and potassium hydroxide solution was 2.5:1:90:3.3:2.5. A2. Modified silica was added to a 50 g / L silver nitrate aqueous solution, ultrasonicated at 40 kHz for 20 min, treated at 130 Pa for 1 h, removed, placed in a muffle furnace, calcined at 410 °C for 35 min, and cooled to room temperature to obtain composite silica; the mass ratio of modified silica to silver nitrate aqueous solution was 4:40. A3. Add citric acid to deionized water and stir until the citric acid is completely dissolved. Add ethylenediaminetetraacetic acid and stir evenly. Heat to 70°C and add 36% hydrochloric acid. Stir and react for 20 minutes. Cool to room temperature, filter to remove impurities, and collect the filtrate to obtain the complex. The mass ratio of citric acid, deionized water, ethylenediaminetetraacetic acid, and hydrochloric acid is 3.5:75:2.3:1.5. A4. Add composite silica to deionized water and ethanol, stir evenly, add KH550, stir and react at 70℃ for 30 min, add the composite, continue stirring and mixing at 70℃ for 30 min, filter, wash 3 times with deionized water, and dry in an oven at 70℃ for 10 min to obtain composite reinforced filler; the mass ratio of composite silica, ethanol, deionized water, KH550 and composite is 3:100:40:1.2:30.

[0042] Comparative Example 2 The only difference between this comparative example and Example 3 is the preparation of the composite reinforcing filler, as detailed below: The composite reinforced filler is prepared by the following steps: A1. Mesoporous silica was added to a 50 g / L silver nitrate aqueous solution, sonicated at 40 kHz for 20 min, treated at 130 Pa for 1 h, removed, placed in a muffle furnace, calcined at 410 °C for 35 min, and cooled to room temperature to obtain composite silica; the mass ratio of mesoporous silica to silver nitrate aqueous solution was 4:40. A2. Add citric acid to deionized water and stir until the citric acid is completely dissolved. Add ethylenediaminetetraacetic acid and stir evenly. Heat to 70°C and add 36% hydrochloric acid. Stir and react for 20 minutes. Cool to room temperature, filter to remove impurities, and collect the filtrate to obtain the complex. The mass ratio of citric acid, deionized water, ethylenediaminetetraacetic acid, and hydrochloric acid is 3.5:75:2.3:1.5. A3. Add composite silica to deionized water and ethanol, stir evenly, add KH550, stir and react at 70℃ for 30 min, add the composite, continue stirring and mixing at 70℃ for 30 min, filter, wash 3 times with deionized water, and dry in an oven at 70℃ for 10 min to obtain composite reinforced filler; the mass ratio of composite silica, ethanol, deionized water, KH550 and composite is 3:100:40:1.2:30.

[0043] Comparative Example 3 The only difference between this comparative example and Example 3 is the preparation of the composite reinforcing filler, as detailed below: The composite reinforced filler is prepared by the following steps: A1. Mesoporous silica and tannic acid were added to ethanol and stirred until homogeneous. Glucose was added, and the mixture was stirred at 70°C for 30 min. After filtration, the mixture was washed three times with deionized water and dried in an oven at 70°C for 10 min. The mixture was then placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 800°C for 4 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain modified silica. The mass ratio of mesoporous silica, tannic acid, ethanol, glucose, and potassium hydroxide solution was 2.5:1:90:3.3:2.5. A2. Add citric acid to deionized water and stir until the citric acid is completely dissolved. Add ethylenediaminetetraacetic acid and stir evenly. Heat to 70°C and add 36% hydrochloric acid. Stir and react for 20 minutes. Cool to room temperature, filter to remove impurities, and collect the filtrate to obtain the complex. The mass ratio of citric acid, deionized water, ethylenediaminetetraacetic acid, and hydrochloric acid is 3.5:75:2.3:1.5. A3. Add modified silica to deionized water and ethanol, stir evenly, add KH550, stir and react at 70℃ for 30 min, add the composite, continue stirring and mixing at 70℃ for 30 min, filter, wash 3 times with deionized water, and dry in an oven at 70℃ for 10 min to obtain the composite reinforced filler; the mass ratio of modified silica, ethanol, deionized water, KH550 and composite is 3:100:40:1.2:30.

[0044] Comparative Example 4 The only difference between this comparative example and Example 3 is the preparation of the composite reinforcing filler, as detailed below: The composite reinforced filler is prepared by the following steps: A1. Mesoporous silica and tannic acid were added to ethanol and stirred until homogeneous. Glucose was added, and the mixture was stirred at 70°C for 30 min. After filtration, the mixture was washed three times with deionized water and dried in an oven at 70°C for 10 min. The mixture was then placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 800°C for 4 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain modified silica. The mass ratio of mesoporous silica, tannic acid, ethanol, glucose, and potassium hydroxide solution was 2.5:1:90:3.3:2.5. A2. Modified silica was added to a 50 g / L silver nitrate aqueous solution, ultrasonicated at 40 kHz for 20 min, treated at 130 Pa for 1 h, removed, placed in a muffle furnace, calcined at 410 °C for 35 min, and cooled to room temperature to obtain composite silica; the mass ratio of modified silica to silver nitrate aqueous solution was 4:40. A3. Add composite silica to deionized water and ethanol, stir evenly, add KH550, stir and react at 70℃ for 30 min, add ethylenediaminetetraacetic acid, continue stirring and mixing at 70℃ for 30 min, filter, wash 3 times with deionized water, and dry in an oven at 70℃ for 10 min to obtain composite reinforcing filler; the mass ratio of composite silica, ethanol, deionized water, KH550 and ethylenediaminetetraacetic acid is 3:100:40:1.2:30.

[0045] Comparative Example 5 The only difference between this comparative example and Example 3 is the preparation of the composite reinforcing filler, as detailed below: The composite reinforced filler is prepared by the following steps: A1. Mesoporous silica and tannic acid were added to ethanol and stirred until homogeneous. Glucose was added, and the mixture was stirred at 70°C for 30 min. After filtration, the mixture was washed three times with deionized water and dried in an oven at 70°C for 10 min. The mixture was then placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 800°C for 4 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain modified silica. The mass ratio of mesoporous silica, tannic acid, ethanol, glucose, and potassium hydroxide solution was 2.5:1:90:3.3:2.5. A2. Modified silica was added to a 50 g / L silver nitrate aqueous solution, ultrasonicated at 40 kHz for 20 min, treated at 130 Pa for 1 h, removed, placed in a muffle furnace, calcined at 410 °C for 35 min, and cooled to room temperature to obtain composite silica; the mass ratio of modified silica to silver nitrate aqueous solution was 4:40. A3. Add citric acid to deionized water and stir until the citric acid is completely dissolved. Add ethylenediaminetetraacetic acid and stir evenly. Heat to 70°C and add 36% hydrochloric acid. Stir and react for 20 minutes. Cool to room temperature, filter to remove impurities, and collect the filtrate to obtain the complex. The mass ratio of citric acid, deionized water, ethylenediaminetetraacetic acid, and hydrochloric acid is 3.5:75:2.3:1.5. A4. Add composite silica to deionized water and ethanol, stir evenly, and stir at 70℃ for 30 min. Add the composite material, and continue stirring and mixing at 70℃ for 30 min. After filtration, wash three times with deionized water, and dry in an oven at 70℃ for 10 min to obtain the composite reinforcing filler. The mass ratio of composite silica, ethanol, deionized water and composite material is 4.2:100:40:30.

[0046] The performance of the polypropylene filter materials prepared in Examples 1-3 and Comparative Examples 1-5 was tested.

[0047] Mechanical property testing: The polypropylene filter material prepared above was cut into strips of 30mm×5mm with a thickness of 2mm. The breaking strength of the samples was determined using a UTM-Q422 universal tensile tester according to ASTM standard D882-02.

[0048] Filtration performance test: The polypropylene filter material prepared above was tightly attached to the inside of the Buchner funnel. 100 mL of sewage was taken and filtered under a pressure of 0.4 MPa, so that the sewage passed through the filter material prepared above and was discharged from the bottom of the funnel. The filtrate was collected. The heavy metal content in the sewage was M0. Metal ion detection: The metal ions in the supernatant were detected according to the "Test Method for Sludge of Urban Wastewater Treatment Plant (CJT221-2005)". After digestion treatment, the content of metal ions (M1) in the supernatant was determined by flame atomic emission spectrophotometry and inductively coupled plasma atomic emission spectrometry. The heavy metal removal efficiency (%) was calculated; heavy metal removal efficiency = (M0-M1) / M0×100%.

[0049] Antibacterial performance test: Polypropylene filter material was cut into 2cm×2cm test samples, autoclaved, and then placed in 10mL of a solution with a concentration of 1×10⁻⁶. 6 The bacterial culture was incubated at 37°C with shaking for 12 hours in a CFU / mL E. coli culture, and then diluted 1×10⁻⁶. 5 Then, the mixture was evenly spread on the surface of the solid culture medium using an "L"-shaped stick. The number of colonies in the culture medium was recorded after 12 hours, and the antibacterial rate was calculated.

[0050] As shown in Table 1 below.

[0051] Table 1 Performance testing of polypropylene filter materials prepared in Examples 1-3 and Comparative Examples 1-5 Example 1 40.5 65.6 92.6 99.7 Example 2 41.6 66.3 93.4 99.8 Example 3 40.2 65.2 92.1 99.6 Comparative Example 1 33.6 44.1 75.7 97.2 Comparative Example 2 29.6 38.5 70.3 97.4 Comparative Example 3 37.9 48.2 83.6 88.3 Comparative Example 4 30.2 40.7 73.2 82.3 Comparative Example 5 31.7 41.2 74.8 83.7 As can be seen from the data in Table 1, the polypropylene filter materials prepared in Examples 1-3 have high filtration performance, mechanical strength and antibacterial properties.

[0052] In Comparative Example 1, when mesoporous silica was replaced with a composite reinforcing filler prepared from silica particles and added to the polypropylene filter material, its filtration performance and mechanical strength decreased. This demonstrates that mesoporous silica, as a porous adsorption matrix, can effectively remove heavy metal ions from wastewater, improve the filtration performance of the polypropylene filter material for heavy metal ions, and that the strong bonding force between the mesoporous silica and the porous carbon layer can absorb and weaken the long-term impact force of wastewater flow on the polypropylene filter material, preventing the filter material from cracking and breaking under the impact force of wastewater, thus improving the filtration performance and mechanical properties of the polypropylene filter material.

[0053] In Comparative Example 2, when the modified silica was replaced with a composite reinforcing filler prepared from mesoporous silica and added to the polypropylene filter material, its filtration performance and mechanical strength decreased. This demonstrates that the porous carbon layer synthesized on the surface of mesoporous silica has a high specific surface area, increasing the contact area with sewage and improving filtration performance. Furthermore, the porous structure of the porous carbon has a high adsorption capacity, further improving the removal efficiency of heavy metal ions in sewage. In addition, the strong bonding force between the mesoporous silica and the porous carbon layer can absorb and weaken the long-term impact force of sewage flow on the polypropylene filter material, preventing the filter material from cracking and breaking under the impact force of sewage, thus improving the filtration performance and mechanical properties of the polypropylene filter material.

[0054] In Comparative Example 3, when the composite silica was replaced with a composite reinforced filler prepared from modified silica and added to the polypropylene filter material, its filtration performance, mechanical strength, and antibacterial properties decreased. This demonstrates that the formation of nano-silver particles in the pores of porous carbon on the surface of the composite silica, acting as an inorganic antibacterial agent, can improve the antibacterial properties of the polypropylene filter material. Furthermore, the composite silica acts as a carrier for the nano-silver particles, improving their dispersibility within the polypropylene filter material. In addition, the nano-silver particles, as a supporting framework for the porous carbon in the composite silica, can absorb and weaken the attraction generated by external forces, preventing the porous carbon from collapsing under external impact, thus affecting the filtration efficiency of wastewater and the mechanical properties of the polypropylene filter material.

[0055] In Comparative Example 4, when the composite reinforced filler prepared by replacing the complex with ethylenediaminetetraacetic acid (EDTA) was added to the polypropylene filter material, its filtration performance, mechanical strength, and antibacterial properties decreased. This demonstrates that EDTA grafted onto citric acid can load a larger amount of EDTA, thereby increasing the binding sites for heavy metal ions, improving filtration efficiency, and avoiding the limited adsorption capacity of EDTA, which easily becomes saturated and affects the removal rate of heavy metal ions. Furthermore, the complex formed by EDTA grafted onto citric acid forms a cross-linked structure on the surface of the composite silica, which can enhance the mechanical properties of the polypropylene filter material. In addition, the large number of functional groups contained in the complex can improve the dispersibility of the composite silica in the polypropylene filter material, thereby improving the mechanical properties, filtration performance, and antibacterial activity of the polypropylene filter material.

[0056] In Comparative Example 5, when KH550 was replaced by composite reinforced filler prepared with composite silica, the filtration performance, mechanical strength, and antibacterial properties of the polypropylene filter material decreased. This demonstrates that the composite material, through silane coupling agent coating on the surface of composite silica, forms a cross-linked structure on the surface of composite silica, which can enhance the mechanical properties of the polypropylene filter material. Furthermore, the large number of functional groups contained in the composite material can improve the dispersibility of composite silica in the polypropylene filter material, thereby improving the mechanical properties, filtration performance, and antibacterial activity of the polypropylene filter material.

[0057] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0058] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing a polypropylene filter material, characterized in that, The preparation steps include the following: S1. After vacuum drying, polypropylene chips are mixed with composite reinforcing fillers, compatibilizers, dispersants, and antioxidants, and stirred to obtain a blend. S2. The blended material is extruded and spun into fibers, bonded and cooled on a screen, then hot-pressed and left to stand to obtain polypropylene filter material; The composite reinforced filler is prepared by the following steps: A1. Mesoporous silica and tannic acid were added to ethanol and stirred until homogeneous. Glucose was added and stirred until homogeneous. The mixture was then filtered, washed, dried, placed in a tube furnace, potassium hydroxide solution was added, nitrogen gas was introduced, and the mixture was carbonized. After cooling to room temperature, the mixture was removed, washed, and dried to obtain modified silica. A2. Add the modified silica to the silver nitrate aqueous solution, sonicate, treat at 100-130 Pa, remove, place in a muffle furnace, calcine at 390-410℃ for 30-35 min, cool to room temperature, and obtain composite silica; A3. Add citric acid to deionized water and stir until the citric acid is completely dissolved. Add ethylenediaminetetraacetic acid and stir evenly. Heat to 70°C and add 36% hydrochloric acid. Stir and react for 20 minutes. Cool to room temperature, filter to remove impurities, collect the filtrate, and obtain the complex. The mass ratio of citric acid, deionized water, ethylenediaminetetraacetic acid, and hydrochloric acid is (3-3.5):(65-75):(2-2.3):(1-1.5). A4. Add composite silica to deionized water and ethanol, stir evenly, add silane coupling agent, stir and react at 70℃ for 30 min, add composite, continue stirring and mixing at 70℃ for 30 min, filter, wash and dry to obtain composite reinforced filler; The mass ratio of the composite silica, ethanol, deionized water, silane coupling agent and composite is (2.5-3):(90-100):(30-40):(1-1.2):(20-30).

2. The method for preparing a polypropylene filter material according to claim 1, characterized in that, In step A1, the mass ratio of the mesoporous silica, tannic acid, ethanol, glucose and potassium hydroxide solution is (2-2.5):(0.6-1):(80-90):(3-3.3):(2-2.5).

3. The method for preparing a polypropylene filter material according to claim 1, characterized in that, In step A2, the mass ratio of the modified silica to the silver nitrate aqueous solution is (3-4):(30-40).

4. The method for preparing a polypropylene filter material according to claim 1, characterized in that, In step S1, the mass ratio of the polypropylene chips, composite reinforcing filler, compatibilizer, dispersant, and antioxidant is 100:(15-20):(1-2):(1.5-2.5):(0.5-1); In step S1, the vacuum drying temperature is 70-90℃, the drying time is 10-12h, and the vacuum degree is 0.05-0.1MPa.

5. The method for preparing a polypropylene filter material according to claim 1, characterized in that, In step S2, the extrusion spinning is carried out in a twin-screw extruder, with an extrusion spinning temperature of 260-290℃, a spinneret micro-orifice diameter of 0.18-0.22mm, a screw speed of 400-500r / min, and a screw length-to-diameter ratio of (33-45):

1.

6. The method for preparing a polypropylene filter material according to claim 1, characterized in that, In step S2, the hot pressing pressure is 15-25 MPa and the hot pressing time is 10-15 min.

7. A polypropylene filter material prepared by the method of any one of claims 1-6.