A method, apparatus and application for preparing expanded polytetrafluoroethylene (ePTFE) tubular membranes

Abstract

This invention discloses a method, apparatus, and application for preparing expanded polytetrafluoroethylene (ePTFE) membranes. The method includes preparing an ePTFE preform using a uniaxial stretching method; extruding the preform to obtain a base membrane with an inner wall pore size smaller than the outer wall pore size; immersing the base membrane in an aminoglucosyl solution until fully wetted, then removing it; removing the surface solution, immersing it in an acyl chloride solution, and heating it for reaction; subsequently immersing it in an aqueous solution of aminopolysaccharide quaternary ammonium salt, and allowing it to react fully at a certain temperature; washing and drying to obtain a modified ePTFE membrane. The preparation method of this invention results in an inner wall pore size smaller than the outer wall pore size, enabling the membrane to be used for internal pressure filtration, reducing internal wall fouling and energy consumption. Simultaneously, the membrane possesses good hydrophilicity and antibacterial properties, allowing for internal pressure filtration of oil-water emulsions.

Description

Technical Field

[0001] This invention belongs to the field of hydrophilic separation membranes, and specifically relates to a method, apparatus and application of preparing expanded polytetrafluoroethylene tubular membrane. Background Technology

[0002] Uniaxially stretched polytetrafluoroethylene (PTFE) microtubule membranes possess advantages such as high porosity, high mechanical strength, and low cost, making them widely used in membrane separation. However, due to the processing method, the pore diameter of the inner wall of the membrane is much larger than that of the outer wall. To reduce membrane pore clogging by contaminants, external pressure components are often used in applications, resulting in high energy consumption. Furthermore, the membrane's low surface tension and poor surface wettability give it strong hydrophobicity, making it highly susceptible to severe membrane fouling in wastewater treatment, thus hindering its effective performance in water treatment processes.

[0003] In recent years, there have been many methods for preparing polytetrafluoroethylene (PTFE) membranes, mainly focusing on reports of hydrophilic modification of the membrane. No reports have been found on the adjustment of the pore size of the inner wall of the tubular membrane. For example, patent CN103481528B obtains a hydrophilic PTFE hollow tubular membrane by biaxially stretching porous expanded PTFE, then impregnating it with lipid chemicals, and finally drying it at 150°C. The pore size of the inner wall of the tube is larger than that of the outer wall, making it prone to clogging during internal pressure filtration. Patent CN104353370A first blends hydrophilic nano-inorganic particles into PTFE powder and then stretches it to prepare a hydrophilic membrane. However, the nano-inorganic particles are not evenly dispersed, resulting in uneven hydrophilicity on the membrane surface. Furthermore, the hydrophilic membrane lacks antibacterial properties and is easily contaminated by bacteria during application, causing micropore blockage. Patent CN115414801A describes immersing a polytetrafluoroethylene (PTFE) membrane in an organic solvent containing hydrophilic inorganic particles, followed by high-temperature treatment to obtain a hydrophilic membrane. However, the binding strength between the inorganic particles and the membrane is poor, and the hydrophilic effect weakens with prolonged use. Furthermore, these preparation methods result in membranes with limited properties. Actual industrial wastewater typically contains a large number of bacteria, which can easily proliferate on the membrane surface during long-term operation, causing micropore blockage. Therefore, separation membranes with only hydrophilic properties have limited applications. Thus, the development of separation membrane materials with unique structures and properties is urgently needed. Summary of the Invention

[0004] To address the problems existing in the background art, the present invention aims to provide a method, apparatus, and application for preparing expanded polytetrafluoroethylene (ePTFE) tubular membranes. The present invention uses equipment to process ePTFE tubular preforms prepared by uniaxial stretching, first reducing the pore size of the inner wall of the membrane, and then using glucosamine, acyl chloride, and aminopolysaccharide quaternary ammonium salts as raw materials, through a series of chemical reactions, endowing the ePTFE tubular membrane with hydrophilic and antibacterial properties.

[0005] The technical solution adopted in this invention is as follows:

[0006] I. A method for preparing expanded polytetrafluoroethylene (ePTFE) tubular membrane, comprising the following steps:

[0007] 1) Polytetrafluoroethylene dispersion resin and lubricating oil are mixed, and expanded polytetrafluoroethylene tube blanks are prepared by stretching method;

[0008] 2) Start the speed controller and heat source controller, and place the expanded polytetrafluoroethylene tube blank into the membrane cavity of the membrane plate;

[0009] 3) Insert the steel wire into one end of the expanded polytetrafluoroethylene tube blank. After the front end of the membrane core enters the expanded polytetrafluoroethylene tube blank, wrap the steel wire around the traction rod and use the rotating traction rod to pull the membrane core out of the expanded polytetrafluoroethylene tube blank to obtain the expanded polytetrafluoroethylene tube membrane.

[0010] 4) Immerse the expanded polytetrafluoroethylene (ePTFE) membrane in glucosamine solution until fully soaked, then remove it.

[0011] 5) Use filter paper to absorb and remove excess solution from the surface of the expanded polytetrafluoroethylene (ePTFE) membrane, then immerse the ePTFE membrane in an acyl chloride solution until fully wetted and then remove it; glucosamine and acyl chloride react on the surface of the ePTFE membrane to form a hydrophilic layer;

[0012] 6) The expanded polytetrafluoroethylene (PTFE) membrane forming the hydrophilic layer is immersed in an amino polysaccharide quaternary ammonium salt solution and removed after complete immersion. The unreacted acyl chloride and amino polysaccharide quaternary ammonium salt react on the surface of the expanded PTFE membrane. After the reaction is complete, the expanded PTFE membrane is washed and dried to finally obtain the hydrophilic PTFE membrane.

[0013] In step 1), the expanded polytetrafluoroethylene tube blank is obtained by uniaxial stretching, with a stretching ratio of 1-4 times and a setting temperature of 350℃-400℃; the mass ratio of polytetrafluoroethylene dispersion resin to lubricating oil is 100:17-100:22.

[0014] The polytetrafluoroethylene dispersion resin used is one of Sichuan Chenguang F204, Japan Daikin F104, and USA DuPont F605, and the lubricant is aviation kerosene.

[0015] In step 2), the diameter of the membrane cavity is 0.5-0.6 mm smaller than the outer diameter of the expanded polytetrafluoroethylene tube blank. The membrane cavity is mainly formed by closing the upper half membrane cavity plate and the lower half membrane cavity plate.

[0016] In step 3), the diameter of the membrane core is 0.3-1 mm larger than the inner diameter of the expanded polytetrafluoroethylene tube blank, and the pulling temperature of the membrane cavity is 180-300℃ when the traction rod is pulled.

[0017] In step 4), the glucosamine solution is either an ethanol solution or an isopropanol solution of glucosamine, and the concentration of the glucosamine solution is 1-10 g / L.

[0018] In step 5), the acyl chloride solution is one of cyclohexane solutions of 1,4-benzoyl chloride, 1,3,5-benzotricarboxylic chloride, and 1,2,4,5-benzotetracarboxylic chloride, and the concentration of the acyl chloride solution is 0.5-3 g / L; the reaction temperature of the glucosamine solution and the acyl chloride solution is 40-90℃.

[0019] In step 6), the aminopolysaccharide quaternary ammonium salt solution is an aqueous solution of aminopolysaccharide quaternary ammonium salt with a concentration of 0.5-1.5 g / L.

[0020] In step 6), the solvent used for washing is deionized water; the drying temperature is 60°C.

[0021] II. An apparatus for preparing expanded polytetrafluoroethylene (ePTFE) tubular membranes:

[0022] like Figure 1 As shown, the device includes a speed controller, a heat source controller, a heatable membrane plate, a traction rod, an operating table, steel wires, and a membrane core.

[0023] The speed controller, heat source controller, membrane plate, and traction rod are all placed on the operating table. The speed controller is connected to the traction rod and is used to control the traction rod to rotate at a preset speed. The heat source controller and the membrane plate are connected by an electric heating rod and are used to control the temperature of the membrane plate by the electric heating rod. The tail end of the steel wire and the front end of the membrane core are fixedly connected.

[0024] The membrane cavity plate is mainly composed of an upper membrane cavity plate and a lower membrane cavity plate. Several strip grooves with semi-circular cross-sections are opened in the upper and lower membrane cavity plates. The strip grooves are evenly spaced along the width direction of the membrane cavity plate. After the upper and lower membrane cavity plates are closed, the strip grooves in the upper and lower membrane cavity plates form a strip-shaped membrane cavity with a circular cross-section. The membrane cavity is used to place the expanded polytetrafluoroethylene tube blank.

[0025] The application of the hydrophilic polytetrafluoroethylene membrane in the preparation of antibacterial and hydrophilic separation membranes.

[0026] This invention first treats the pores in the inner wall of the PTFE membrane using a self-made device, and then forms hydrophilic groups such as amino, hydroxyl, and carboxyl groups on the surface of the PTFE membrane through a series of chemical reactions, thereby giving the PTFE membrane excellent hydrophilic and antibacterial properties.

[0027] The beneficial effects of this invention are:

[0028] 1. The inner wall pores of the membrane after treatment by the device in the invention are smaller than the outer wall pores, which allows the membrane to be used for internal pressure filtration, reducing membrane inner wall contamination and energy consumption.

[0029] 2. The present invention uses glucosamine solution to completely wet the polytetrafluoroethylene membrane, providing a basis for the uniform hydrophilicity of the membrane; glucosamine and acyl chloride form a stable hydrophilic layer on the membrane surface through an amidation reaction, while the excess acyl chloride can fix the quaternary ammonium salt of aminopolysaccharide on the membrane surface, giving the membrane antibacterial properties.

[0030] 3. The polytetrafluoroethylene membrane prepared by this invention can filter oil-water emulsions by internal pressure method. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the device of the present invention;

[0032] Figure 2 These are morphological images of the outer and inner walls of the membrane in Comparative Example 1 of the present invention;

[0033] Figure 3 These are morphological images of the outer and inner walls of the membrane in Comparative Example 2 of the present invention;

[0034] Figure 4 This is a diagram of the static water contact angle at 0s on the membrane surface in Comparative Example 2 of the present invention;

[0035] Figure 5 This is a diagram of the static water contact angle at 0s on the membrane surface in Embodiment 3 of the present invention.

[0036] Figure 6 This is a graph showing the efficiency of oil-water separation of the membrane obtained in Example 1 of the present invention after 10 consecutive cycles.

[0037] In the diagram: 1. Speed ​​controller; 2. Heat source controller; 3. Upper membrane cavity plate; 4. Lower membrane cavity plate; 5. Membrane cavity; 6. Traction rod; 7. Control panel; 8. Steel wire; 9. Membrane core. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] like Figure 1 As shown, the device includes a speed controller 1, a heat source controller 2, a heatable membrane plate, a traction rod 6, an operating table 7, a steel wire 8, and a membrane core 9. The speed controller 1, the heat source controller 2, the membrane plate, and the traction rod 6 are all placed on the operating table 7. The speed controller 1 is connected to the traction rod 6 and is used to control the traction rod 6 to rotate at a preset speed. The heat source controller 2 is connected to the membrane plate through an electric heating rod and is used to control the temperature of the membrane plate through the electric heating rod. The tail end of the steel wire 8 is fixedly connected to the front end of the membrane core 9.

[0040] The membrane cavity plate is mainly composed of an upper membrane cavity plate 3 and a lower membrane cavity plate 4. Several strip grooves with a semi-circular cross-section are opened in the upper membrane cavity plate 3 and the lower membrane cavity plate 4. The strip grooves are evenly spaced along the width direction of the membrane cavity plate. After the upper membrane cavity plate 3 and the lower membrane cavity plate 4 are closed, the strip grooves in the upper membrane cavity plate 3 and the lower membrane cavity plate 4 form a strip-shaped membrane cavity 5 with a circular cross-section. The membrane cavity 5 is used to place the expanded polytetrafluoroethylene tube blank.

[0041] In practice, firstly, the expanded PTFE tube blank is placed in the strip groove in the lower half of the membrane cavity plate 4, and then the upper half of the membrane cavity plate 3 is placed on top, so that the outer surface of the expanded PTFE tube blank is squeezed by the membrane cavity 5. After the two half of the membrane cavity plates 3 and 4 are completely closed, the head of the steel wire 8 is inserted from one end of the expanded PTFE tube blank. The steel wire 8 drives the membrane core 9 to move. When the front end of the membrane core 9 enters the expanded PTFE tube blank, the steel wire 8 is wound around the traction rod 6. The rotating traction rod 6 is used to pull the steel wire 8 and the membrane core 9 out of the expanded PTFE tube blank. The membrane core 9 squeezes the inner surface of the expanded PTFE tube blank, and after squeezing, an expanded PTFE tube membrane is obtained. Through the above squeezing steps, a base membrane with an inner wall pore diameter smaller than the outer wall pore diameter can be obtained.

[0042] Specific embodiments of the present invention are as follows:

[0043] This invention uses the invented equipment to process polytetrafluoroethylene tube blanks prepared by uniaxial stretching, first reducing the pore size of the inner wall of the tube membrane, and then using glucosamine, acyl chloride, and aminopolysaccharide quaternary ammonium salt as raw materials, through a series of chemical reactions, endowing the polytetrafluoroethylene microporous membrane with hydrophilic and antibacterial properties.

[0044] Example 1:

[0045] 1) Mix polytetrafluoroethylene dispersion resin (Sichuan Chenguang F204) and aviation kerosene 100:17, set the stretching ratio to 1, and the setting temperature to 350℃. Prepare expanded polytetrafluoroethylene tube blanks by stretching method. The outer diameter of the prepared tube blanks is 6mm and the inner diameter of the tube blanks is 4mm.

[0046] 2) Start the speed controller 1 and heat source controller 2, place the expanded polytetrafluoroethylene tube blank in the membrane cavity 5 of the membrane cavity plate, and then close the upper half membrane cavity plate 3 and the lower half membrane cavity plate 4.

[0047] 3) Insert the steel wire 8 into one end of the expanded polytetrafluoroethylene tube blank. When the front end of the membrane core 9 with a diameter of 4.3 mm enters the expanded polytetrafluoroethylene tube blank, wrap the steel wire 8 around the traction rod 6. Use the traction rod 6 to pull the membrane core 9 out of the expanded polytetrafluoroethylene tube blank at 180°C to obtain the expanded polytetrafluoroethylene tube membrane.

[0048] 4) Immerse the expanded polytetrafluoroethylene (ePTFE) membrane in a 1 g / L glucosamine ethanol solution until fully saturated, then remove it.

[0049] 5) Use filter paper to absorb and remove excess solution from the surface of the expanded polytetrafluoroethylene (ePTFE) membrane. Then, immerse the ePTFE membrane in a cyclohexane solution containing 0.5 g / L 1,4-phthaloyl chloride. Remove the membrane after complete immersion. Glucosamine and 1,4-phthaloyl chloride react fully at 40°C to form a hydrophilic layer.

[0050] 6) The expanded polytetrafluoroethylene (ePTFE) membrane forming the hydrophilic layer is immersed in a 0.5 g / L aqueous solution of amino polysaccharide quaternary ammonium salt. After complete immersion, it is removed. The unreacted 1,4-benzoyl chloride and amino polysaccharide quaternary ammonium salt react fully on the surface of the ePTFE membrane. After the reaction is complete, the ePTFE membrane is deionized, washed, and dried at 60°C to finally obtain the hydrophilic polytetrafluoroethylene membrane.

[0051] Example 2:

[0052] 1) Polytetrafluoroethylene dispersion resin (Daikin F104 from Japan) and aviation kerosene 100:22 were mixed, the stretching ratio was set to 4 times, the setting temperature was 400℃, and expanded polytetrafluoroethylene tube blanks were prepared by stretching method. The outer diameter of the prepared tube blanks was 6mm and the inner diameter of the tube blanks was 4mm.

[0053] 2) Start the speed controller 1 and heat source controller 2, place the expanded polytetrafluoroethylene tube blank in the membrane cavity 5 of the membrane cavity plate, and then close the upper half membrane cavity plate 3 and the lower half membrane cavity plate 4.

[0054] 3) Insert the steel wire 8 into one end of the expanded polytetrafluoroethylene tube blank. After the front end of the membrane core 9 with a diameter of 5mm enters the expanded polytetrafluoroethylene tube blank, wrap the steel wire 8 around the traction rod 6. Use the traction rod 6 to pull the membrane core 9 out of the expanded polytetrafluoroethylene tube blank at 300℃ to obtain the expanded polytetrafluoroethylene tube membrane.

[0055] 4) Immerse the expanded polytetrafluoroethylene (ePTFE) membrane in a 10 g / L glucosamine ethanol solution until fully saturated, then remove it.

[0056] 5) Use filter paper to absorb and remove excess solution from the surface of the expanded polytetrafluoroethylene (ePTFE) membrane. Then, immerse the ePTFE membrane in a cyclohexane solution containing 3 g / L of 1,3,5-benzenetricarboxyl chloride. After complete immersion, remove the membrane. Glucosamine and 1,3,5-benzenetricarboxyl chloride react fully at 90°C to form a hydrophilic layer.

[0057] 6) The expanded polytetrafluoroethylene (ePTFE) membrane forming the hydrophilic layer is immersed in a 1.5 g / L aqueous solution of amino polysaccharide quaternary ammonium salt. After complete immersion, it is removed. The unreacted 1,3,5-benzenetriacyl chloride and amino polysaccharide quaternary ammonium salt react fully on the surface of the ePTFE membrane. After the reaction is complete, the ePTFE membrane is deionized, washed, and dried at 60°C to finally obtain the hydrophilic polytetrafluoroethylene membrane.

[0058] Example 3:

[0059] 1) Mix polytetrafluoroethylene dispersion resin (DuPont F605) and aviation kerosene 100:20, set the stretching ratio to 3 times, and the setting temperature to 380℃. Prepare expanded polytetrafluoroethylene tube blanks by stretching method. The outer diameter of the prepared tube blanks is 6mm and the inner diameter of the tube blanks is 4mm.

[0060] 2) Start the speed controller 1 and heat source controller 2, place the expanded polytetrafluoroethylene tube blank in the membrane cavity 5 of the membrane cavity plate, and then close the upper half membrane cavity plate 3 and the lower half membrane cavity plate 4.

[0061] 3) Insert the steel wire 8 into one end of the expanded polytetrafluoroethylene tube blank. After the front end of the membrane core 9 with a diameter of 4.6 mm enters the expanded polytetrafluoroethylene tube blank, wrap the steel wire 8 around the traction rod 6. Use the traction rod 6 to pull the membrane core 9 out of the expanded polytetrafluoroethylene tube blank at 260°C to obtain the expanded polytetrafluoroethylene tube membrane.

[0062] 4) Immerse the expanded polytetrafluoroethylene (ePTFE) membrane in a 5 g / L glucosamine ethanol solution until fully saturated, then remove it.

[0063] 5) Use filter paper to absorb and remove excess solution from the surface of the expanded polytetrafluoroethylene (ePTFE) membrane. Then, immerse the ePTFE membrane in a cyclohexane solution containing 1.5 g / L of 1,3,5-benzenetricarboxyl chloride. After complete immersion, remove the membrane. Glucosamine and 1,3,5-benzenetricarboxyl chloride react fully at 70°C to form a hydrophilic layer.

[0064] 6) The expanded polytetrafluoroethylene (ePTFE) membrane forming the hydrophilic layer is immersed in a 1.0 g / L aqueous solution of amino polysaccharide quaternary ammonium salt. After complete immersion, it is removed. The unreacted 1,3,5-benzenetriacyl chloride and amino polysaccharide quaternary ammonium salt react fully on the surface of the ePTFE membrane. After the reaction is complete, the ePTFE membrane is deionized, washed, and dried at 60°C to finally obtain the hydrophilic polytetrafluoroethylene membrane.

[0065] Example 4:

[0066] 1) Mix polytetrafluoroethylene dispersion resin (DuPont F605) and aviation kerosene 100:22, set the stretching ratio to 2 times, and the setting temperature to 350℃. Prepare expanded polytetrafluoroethylene tube blanks by stretching method. The outer diameter of the prepared tube blanks is 6mm and the inner diameter of the tube blanks is 4mm.

[0067] 2) Start the speed controller 1 and heat source controller 2, place the expanded polytetrafluoroethylene tube blank in the membrane cavity 5 of the membrane cavity plate, and then close the upper half membrane cavity plate 3 and the lower half membrane cavity plate 4.

[0068] 3) Insert the steel wire 8 into one end of the expanded polytetrafluoroethylene tube blank. After the front end of the membrane core 9 with a diameter of 4.8 mm enters the expanded polytetrafluoroethylene tube blank, wrap the steel wire 8 around the traction rod 6. Use the traction rod 6 to pull the membrane core 9 out of the expanded polytetrafluoroethylene tube blank at 300°C to obtain the expanded polytetrafluoroethylene tube membrane.

[0069] 4) Immerse the expanded polytetrafluoroethylene (ePTFE) membrane in a 1 g / L glucosamine ethanol solution until fully saturated, then remove it.

[0070] 5) Use filter paper to absorb and remove excess solution from the surface of the expanded polytetrafluoroethylene (ePTFE) membrane. Then, immerse the ePTFE membrane in a cyclohexane solution containing 1.5 g / L of 1,2,4,5-benzenetetracarboxylic acid chloride. After complete immersion, remove the membrane. Glucosamine and 1,2,4,5-benzenetetracarboxylic acid chloride react fully at 60°C to form a hydrophilic layer.

[0071] 6) The expanded polytetrafluoroethylene (ePTFE) membrane forming the hydrophilic layer is immersed in a 0.5 g / L aqueous solution of amino polysaccharide quaternary ammonium salt. After complete immersion, it is removed. The unreacted 1,2,4,5-benzenetetracarboxyl chloride and amino polysaccharide quaternary ammonium salt react fully on the surface of the ePTFE membrane. After the reaction is complete, the ePTFE membrane is deionized, washed, and dried at 60°C to finally obtain the hydrophilic polytetrafluoroethylene membrane.

[0072] Comparative Example 1:

[0073] A 100:20 mixture of polytetrafluoroethylene dispersion resin (DuPont F605) and aviation kerosene was prepared, with a stretching ratio of 3 and a setting temperature of 380℃. The resulting tube blank had an outer diameter of 6 mm and an inner diameter of 4 mm.

[0074] Comparative Example 2:

[0075] Polytetrafluoroethylene dispersion resin (DuPont F605) and aviation kerosene were mixed at a ratio of 100:22, stretched to 2 times, and set at 350℃ to prepare a tube blank with an outer diameter of 6mm and an inner diameter of 4mm. The expanded polytetrafluoroethylene tube blank was placed in the membrane cavity 5 of the membrane cavity plate, and then the upper half membrane cavity plate 3 and the lower half membrane cavity plate 4 were closed. The membrane core 9 with a diameter of 4.6mm was pulled into the tube blank and stretched at 260℃.

[0076] Comparative Example 3:

[0077] Polytetrafluoroethylene (PTFE) dispersion resin (DuPont F605) and aviation kerosene were mixed at a ratio of 100:20, stretched to a ratio of 3, and set at 380℃ to prepare a tube blank with an outer diameter of 6 mm and an inner diameter of 4 mm. The expanded PTFE tube blank was placed in the membrane cavity 5 of the membrane cavity plate, and then the upper half membrane cavity plate 3 and the lower half membrane cavity plate 4 were closed. A membrane core 9 with a diameter of 4.6 mm was pulled into the tube blank and stretched at 260℃. The expanded PTFE membrane was immersed in a 5 g / L glucosamine solution in ethanol, and then immersed in a 1.5 g / L cyclohexane solution of 1,3,5-benzenetricarboxylic acid chloride. After removal, it was fully reacted at 70℃, washed with deionized water, and dried at 60℃.

[0078] Oil-water separation performance test:

[0079] At 0.1% (M 大豆油 / M 水 Soybean oil and 20% Tween-80 (M T-80 / M 大豆油 An oil-water emulsion was prepared using an emulsifier. The oil-water emulsion was then stirred at 10,000 rpm for 0.5 h. The permeation and separation performance of the membrane were studied by an internal pressure cross-flow filtration experiment under a transmembrane pressure of 0.1 MPa. The membrane flux was calculated by equation (1). The oil content in the water was determined by a UV-vis spectrophotometer, and the oil-water separation efficiency was calculated by equation (2).

[0080]

[0081] Where J is the permeation flux, V is the permeation volume, A is the effective area, and Δt is the test time.

[0082]

[0083] Where R1 is the retention rate during oil-water emulsion separation, and C p C represents the concentration of the filtrate oil. f This represents the original oil-water emulsion concentration.

[0084] Antibacterial performance test:

[0085] The membranes prepared in the examples were placed in culture media containing Escherichia coli and Staphylococcus aureus, and incubated at 37°C for 24 hours. The antibacterial rate was then calculated.

[0086] Table 1 Performance of Polytetrafluoroethylene Tube Membrane

[0087]

[0088]

[0089] As can be seen from Table 1, the polytetrafluoroethylene membrane obtained by the method of the present invention has good hydrophilic properties, and not only has high separation efficiency and anti-fouling performance for oil-water emulsions, but also has good antibacterial properties.

[0090] like Figure 2 These are morphological images of the outer and inner walls of the membrane in Comparative Example 1 of the present invention, as shown. Figure 3 These are morphological images of the outer and inner walls of the membrane in Comparative Example 2 of the present invention, as shown. Figure 4 This is a diagram of the static water contact angle at 0s on the membrane surface in Comparative Example 2 of the present invention. Figure 5 This is a static water contact angle diagram of the membrane surface at 0s in Embodiment 3 of the present invention. Compared with the original polytetrafluoroethylene (PTFE) microtubule membrane, the PTFE microtubule membrane obtained by the present invention has a smaller inner wall pore diameter than the outer wall pore diameter, resulting in a significantly reduced water contact angle on the membrane surface and a significantly increased hydrophilicity of the membrane. Figure 6 The diagram shows the efficiency of oil-water separation of the membrane obtained in Example 3 of this invention after 10 consecutive cycles. The glucosamine solution can completely wet the hydrophobic polytetrafluoroethylene membrane and form a stable hydrophilic layer on the membrane surface through an amidation reaction with acyl chloride. The unreacted acyl chloride can further react with the aminopolysaccharide quaternary ammonium salt, which not only imparts antibacterial properties to the membrane but also improves its hydrophilicity and antifouling properties.

[0091] The invented equipment is used to process polytetrafluoroethylene (PTFE) tube blanks prepared by uniaxial stretching. First, the pore size of the inner wall of the tube membrane is reduced. Then, using glucosamine, acyl chloride, and aminopolysaccharide quaternary ammonium salt as raw materials, a series of chemical reactions are carried out to endow the PTFE microporous membrane with hydrophilic and antibacterial properties. The oil-water emulsion separation efficiency reaches over 99.8%, the flux recovery rate reaches over 99.9%, and the inhibition rate against Escherichia coli reaches over 99.5% and the inhibition rate against Staphylococcus aureus reaches over 94.5%.

[0092] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing expanded polytetrafluoroethylene (ePTFE) tubular membrane, characterized in that, Includes the following steps: 1) Polytetrafluoroethylene dispersion resin and lubricating oil are mixed, and expanded polytetrafluoroethylene tube blanks are prepared by stretching method; 2) Start the speed controller (1) and heat source controller (2) and place the expanded polytetrafluoroethylene tube blank in the membrane cavity (5) of the membrane cavity plate; 3) Insert the steel wire (8) from one end of the expanded polytetrafluoroethylene tube blank. After the front end of the membrane core (9) enters the expanded polytetrafluoroethylene tube blank, wrap the steel wire (8) around the traction rod (6) and use the rotating traction rod (6) to pull the membrane core (9) out of the expanded polytetrafluoroethylene tube blank to obtain the expanded polytetrafluoroethylene tube membrane. 4) Immerse the expanded polytetrafluoroethylene (ePTFE) membrane in glucosamine solution until fully soaked, then remove it. 5) Remove the solution from the surface of the expanded polytetrafluoroethylene (ePTFE) membrane, then immerse the ePTFE membrane in an acyl chloride solution until fully wetted, and then remove it; glucosamine and acyl chloride react on the surface of the ePTFE membrane to form a hydrophilic layer; 6) Immerse the expanded polytetrafluoroethylene (ePTFE) membrane in an amino polysaccharide quaternary ammonium salt solution until fully wetted, then remove it. The acyl chloride and amino polysaccharide quaternary ammonium salt react on the surface of the ePTFE membrane. After the reaction is complete, wash and dry the ePTFE membrane to finally obtain a hydrophilic ePTFE membrane.

2. The method for preparing an expanded polytetrafluoroethylene (ePTFE) membrane according to claim 1, characterized in that: In step 1), the expanded polytetrafluoroethylene tube blank is obtained by uniaxial stretching, with a stretching ratio of 1-4 times and a setting temperature of 350℃-400℃; the mass ratio of polytetrafluoroethylene dispersion resin to lubricating oil is 100:17-100:

22.

3. The method for preparing an expanded polytetrafluoroethylene (ePTFE) membrane according to claim 1, characterized in that: In step 2), the diameter of the membrane cavity (5) is 0.5-0.6 mm smaller than the outer diameter of the expanded polytetrafluoroethylene tube blank.

4. The method for preparing an expanded polytetrafluoroethylene (ePTFE) membrane according to claim 1, characterized in that: In step 3), the diameter of the membrane core (9) is 0.3-1 mm larger than the inner diameter of the expanded polytetrafluoroethylene tube blank, and the temperature of the membrane cavity (5) is 180-300℃ when the traction rod (6) pulls it.

5. The method for preparing an expanded polytetrafluoroethylene (ePTFE) membrane according to claim 1, characterized in that: In step 4), the glucosamine solution is either an ethanol solution or an isopropanol solution of glucosamine, and the concentration of the glucosamine solution is 1-10 g / L.

6. The method for preparing an expanded polytetrafluoroethylene (ePTFE) membrane according to claim 1, characterized in that: In step 5), the acyl chloride solution is one of cyclohexane solutions of 1,4-benzoyl chloride, 1,3,5-benzotricarboxylic chloride, and 1,2,4,5-benzotetracarboxylic chloride, and the concentration of the acyl chloride solution is 0.5-3 g / L; the reaction temperature of the glucosamine solution and the acyl chloride solution is 40-90℃.

7. The method for preparing an expanded polytetrafluoroethylene (ePTFE) membrane according to claim 1, characterized in that: In step 6), the aminopolysaccharide quaternary ammonium salt solution is an aqueous solution of aminopolysaccharide quaternary ammonium salt with a concentration of 0.5-1.5 g / L.

8. The method for preparing an expanded polytetrafluoroethylene (ePTFE) membrane according to claim 1, characterized in that: In step 6), the solvent used for washing is deionized water; the drying temperature is 60°C.

9. An apparatus for preparing expanded polytetrafluoroethylene (ePTFE) tubular membranes for implementing the preparation method according to any one of claims 1 to 8, characterized in that: It includes a speed controller (1), a heat source controller (2), a membrane chamber plate, a traction rod (6), an operating table (7), a steel wire (8), and a membrane core (9); The speed controller (1), heat source controller (2), membrane plate and traction rod (6) are all placed on the operating table (7); the speed controller (1) is connected to the traction rod (6), and the speed controller (1) is used to control the traction rod (6) to rotate at a preset speed; the heat source controller (2) and the membrane plate are connected by an electric heating rod, and the heat source controller (2) is used to control the temperature of the membrane plate; the tail end of the steel wire (8) and the front end of the membrane core (9) are fixedly connected; The membrane cavity plate is mainly composed of an upper membrane cavity plate (3) and a lower membrane cavity plate (4). Several strip grooves with a semi-circular cross-section are opened in the upper membrane cavity plate (3) and the lower membrane cavity plate (4). Each strip groove is evenly spaced along the width direction of the membrane cavity plate. After the upper membrane cavity plate (3) and the lower membrane cavity plate (4) are closed, the strip grooves in the upper membrane cavity plate (3) and the lower membrane cavity plate (4) form a strip-shaped membrane cavity (5) with a circular cross-section. The membrane cavity (5) is used to place the expanded polytetrafluoroethylene tube blank.

10. The application of the hydrophilic polytetrafluoroethylene membrane obtained by the preparation method according to any one of claims 1-8, characterized in that: The application of the hydrophilic polytetrafluoroethylene membrane in the preparation of antibacterial and hydrophilic separation membranes.

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