A method for preparing superhydrophilic porous membranes by grafting SiO2 onto polyurethane fiber membranes.

Abstract

The application discloses a method for preparing a super-hydrophilic porous membrane by grafting SiO2 on a polyurethane fiber membrane, and comprises the following steps: preparing a N,N-dimethylformamide / butyl acetate DMF / BuAc solution of polyurethane PU to obtain PU spinning solution; the PU spinning solution is used to prepare a micron porous membrane through an electrostatic spinning device; the porous membrane is placed in a plasma treatment device, a radio frequency source is turned on, and radio frequency power and time are set; a higher chemical activity plasma is used to activate the surface of the porous membrane fiber to form grafted active groups; the surface-activated porous membrane is placed in a mixed solution of ethanol and amino silane for ultrasonic treatment; the porous membrane treated by the amino silane is placed in a mixed solution of ethanol, water and tetraethyl orthosilicate for ultrasonic treatment to obtain a super-hydrophilic porous membrane. The super-hydrophilic porous membrane prepared by the method has excellent comprehensive properties such as moisture absorption, quick drying, oil-repellence under water and oil stain resistance.

Description

Technical Field

[0001] This invention relates to the field of superhydrophilic porous membrane preparation technology, and in particular to a method for preparing superhydrophilic porous membranes by grafting SiO2 onto polyurethane fiber membranes. Background Technology

[0002] In the processes of oil extraction, transportation, and the production of petrochemical products, large amounts of oily wastewater are inevitably generated. If this oily wastewater is released directly into natural water bodies without treatment, it will pollute the environment and pose a threat to ecology and human health. Membrane separation, as an effective technology for treating oily wastewater, has significant advantages in the field of oil-water separation due to its high separation efficiency, low energy consumption, and ease of operation.

[0003] Oil-water separation membranes are mainly classified into two types based on the differences in the affinity of membrane materials for oil and water: superhydrophilic-underwater superoleophobic and superhydrophobic-superoleophilic. Superhydrophilic-underwater superoleophobic separation membranes utilize the superhydrophilicity of the membrane surface, allowing water to permeate through the membrane surface; simultaneously, due to the underwater superoleophobicity of the membrane surface, oil is trapped above the membrane surface and cannot pass through, thus achieving oil and water separation. Superhydrophilic-underwater superoleophobic separation membranes effectively prevent oil droplets and other impurities from adsorbing onto the membrane surface, thereby extending the membrane's service life and improving its utilization rate.

[0004] Polyurethane (PU) porous membranes prepared using electrospinning technology exhibit small pore sizes (maximum pore size less than 2.50 μm, average pore size 1.75 μm) and high porosity (up to 80%), making them suitable for microfiltration (effectively separating particles from 0.1 to 10 μm). Furthermore, PU porous membranes are composed of stacked fibers, with interconnected channels within the membrane. The soft segments of PU are composed of polyols, exhibiting a degree of polarity, allowing water droplets to gradually penetrate from the membrane surface into its interior. However, the limited hydrophilicity of PU porous membranes does not provide underwater oleophobicity. To further enhance hydrophilicity, high surface energy materials are often used for hydrophilic treatment, and a roughened surface is constructed to obtain a superhydrophilic surface, achieving underwater superoleophobicity. Superhydrophilic surface preparation processes include spraying, dip coating, deposition, hydrothermal methods, and self-assembly methods. However, these processes have certain selectivity regarding the substrate and are limited by the size and shape of the substrate, hindering the large-scale production of superhydrophilic materials. In addition, for porous membranes made of stacked fiber layers, a hydrophilic rough surface needs to be constructed on the surface of the fibers in order to achieve superhydrophilic / underwater superoleophobic properties and ensure the existence of pores in the membrane material. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a method for preparing a superhydrophilic porous membrane by grafting SiO2 onto a polyurethane fiber membrane. A hydrophilic rough surface is constructed on the fiber surface of the PU porous membrane to prepare a superhydrophilic / underwater superoleophobic porous membrane that meets the requirements for oily wastewater treatment.

[0006] Technical solution: The present invention describes a method for preparing a superhydrophilic porous membrane by grafting SiO2 onto a polyurethane fiber membrane. The apparatus for preparing the superhydrophilic porous membrane includes an electrospinning apparatus and a plasma treatment apparatus.

[0007] The electrospinning device includes a micro-injection pump and a plastic syringe connected to the micro-injection pump. The front end of the plastic syringe is provided with a metal flat-mouth needle, and the front end of the metal flat-mouth needle is provided with a receiving device. A DC voltage is applied between the metal flat-mouth needle and the receiving device. The PU spinning solution stored in the plastic syringe is ejected from the front end of the metal flat-mouth needle and, under the action of the electric field, overcomes its own surface tension to form a jet that is sprayed onto the receiving device to form a micron-sized porous membrane.

[0008] The plasma processing device includes a vacuum chamber, on which a vacuum pump, a radio frequency source and an external gas source are installed. The porous membrane is placed in the vacuum chamber for grafting treatment.

[0009] The method for preparing the superhydrophilic porous membrane includes the following steps:

[0010] Step 1: Prepare a polyurethane (PU) solution of N,N-dimethylformamide / butyl acetate (DMF) / BuAc and stir it at room temperature for 6 h to obtain a PU spinning solution; inject the PU spinning solution into a plastic syringe, turn on the micro-injection pump and DC voltage, and spray the PU spinning solution onto the receiving device under the action of the electric field, forming a porous membrane with a fiber diameter of micrometers on the surface of the receiving device; dry the porous membrane for later use.

[0011] Step 2: Place the porous membrane obtained in Step 1 into a vacuum chamber, and simultaneously close the first and second inlet valves of the external gas source to the vacuum chamber, and turn on the vacuum pump to reduce the vacuum level in the vacuum chamber to below 40 Pa; open the second inlet valve of the gas cylinder and adjust the flow rate of the introduced gas until the vacuum level in the vacuum chamber drops below 40 Pa again; turn on the radio frequency source and set the radio frequency power and time. The radio frequency source glow discharge ionizes the introduced gas to generate plasma. The highly chemically active plasma activates the porous membrane fiber surface to form grafted active groups.

[0012] Step 3: Place the surface-activated porous membrane from Step 2 in a mixed solution of ethanol and aminosilane, sonicate it at room temperature for 20-30 minutes, and add water dropwise; after sonication, remove the porous membrane and air dry it for later use.

[0013] Step 4: Place the porous membrane treated with aminosilane in step 3 in a mixed solution of ethanol, water and tetraethyl orthosilicate, and sonicate it at room temperature for 20-30 minutes. Add ammonia dropwise to adjust the pH of the solution. After sonication, remove the porous membrane and air dry it to obtain a superhydrophilic porous membrane.

[0014] Preferably, the distance between the metal flat-tipped needle and the receiving device is 15-25cm; the surface of the receiving device is covered with tin foil.

[0015] Preferably, the DC voltage in step 1 is 8-14 kV; and the delivery rate of the micro-injection pump is 0.6-1.0 mL / h.

[0016] Preferably, the mass fraction of the PU spinning solution in step 1 is 18~22 wt%, and the volume ratio of N,N-dimethylformamide / butyl acetate is (5~9): (5~1).

[0017] Preferably, in step 2, the gas cylinder is selected from any one of oxygen, nitrogen, and ammonia, and the gas flow rate of the gas cylinder is controlled to be 300~1000 sccm.

[0018] Preferably, the radio frequency power of the radio frequency source in step 2 is 50~300 W and the radio frequency time is 30~180 s.

[0019] Preferably, in step 3, the aminosilane is any one of (3-aminopropyl)triethoxysilane, (3-aminopropyl)trimethoxysilane, and N-(β-aminoethyl)-3-aminopropyltrimethoxysilane; the molar mass of the aminosilane is 0.01~0.03 mol, the volume of ethanol is 6~18 mL, the volume ratio of ethanol to water is 1:(1~3), and the room temperature is 25±5 ℃.

[0020] Preferably, in step 4, the molar mass of tetraethyl orthosilicate is 0.01~0.03 mol, the volume of ethanol is 20~60 mL, the volume ratio of ethanol to water (C2H5OH / H2O) is 2:1, the pH value of the solution system is adjusted by ammonia water to a range of 9~12, and the room temperature is 25±5℃.

[0021] Preferably, the superhydrophilic porous membrane has a micron-sized porous structure; wherein the pore size of the superhydrophilic microporous membrane is distributed in the range of 0.75~2.50 μm, the water absorption rate is 150~300%, the water evaporation rate (Ev) is 0.3~0.4 g / h, the underwater oil contact angle of the superhydrophilic porous membrane is 155~165°, and the underwater oil roll-off angle is 3~8°.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following outstanding advantages:

[0023] 1. The superhydrophilic porous membrane of the present invention uses plasma treatment to graft active groups onto the surface of PU fibers, and then through the coupling effect of the active groups with aminosilane, hydrophilic SiO2 nanoparticles generated by the hydrolysis and condensation of tetraethyl orthosilicate are grafted onto the surface of PU fibers to prepare a superhydrophilic PU porous membrane with a water absorption rate greater than 100%, a water evaporation rate (Ev) greater than 0.18 g / h, an underwater oil contact angle greater than 150°, and an underwater oil roll-off angle less than 10°.

[0024] 2. The preparation process of the superhydrophilic porous membrane of the present invention is short and the reaction temperature is low. The aminosilane and tetraethyl orthosilicate are low in cost and require less material. It also has the characteristics of controllable process, short production cycle and environmental protection, and can realize the mass production of superhydrophilic polyurethane porous membrane.

[0025] 3. The superhydrophilic polyurethane porous membrane prepared by this invention has a micron-sized porous structure and excellent comprehensive properties such as moisture absorption, quick drying, underwater oleophobicity, and oil resistance. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the electrospinning apparatus of the present invention;

[0027] Figure 2 This is a schematic diagram of the plasma treatment device of the present invention;

[0028] Figure 3 This is a scanning electron microscope image of the superhydrophilic porous membrane of Example 1 of the present invention;

[0029] Figure 4 This is a scanning electron microscope image of the superhydrophilic porous membrane of Example 3 of the present invention;

[0030] Figure 5 This is a pore size distribution diagram of the superhydrophilic porous membrane of Embodiment 1 of the present invention;

[0031] Figure 6 This is a pore size distribution diagram of the superhydrophilic porous membrane of Embodiment 3 of the present invention;

[0032] Figure 7 The bar chart shows the water absorption rate of the superhydrophilic porous membranes in Examples 1-5 of this invention.

[0033] Figure 8 This is a diagram showing the underwater oil contact angle of the superhydrophilic porous membrane in Embodiment 4 of the present invention.

[0034] Figure 9 This is a diagram showing the underwater oil contact angle of the superhydrophilic porous membrane in Embodiment 5 of the present invention.

[0035] Figure 10 This is a diagram of underwater oil rolling of the superhydrophilic porous membrane in Example 4 of the present invention;

[0036] Figure 11 This is a diagram of underwater oil rolling of the superhydrophilic porous membrane in Embodiment 5 of the present invention;

[0037] Figure 12 This is a graph showing the water evaporation rate-time curve of the superhydrophilic porous membrane in Example 2 of the present invention.

[0038] Figure 13 This is a graph showing the water evaporation rate-time curve of the superhydrophilic porous membrane in Example 4 of the present invention.

[0039] Figure label:

[0040] 100. Electrospinning apparatus; 1. PU spinning solution; 2. Plastic syringe; 3. Metal flat-tipped needle; 4. Receiving device; 5. DC voltage; 6. Miniature syringe pump; 7. Porous membrane;

[0041] 200. Plasma processing device; 8. Vacuum chamber; 9. External air supply; 10. First air inlet valve; 11. Vacuum pump; 12. Gas cylinder; 13. Radio frequency source; 14. Second air inlet valve. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will be described in conjunction with the accompanying drawings of the embodiments of the present invention. Figure 1-13 The technical solutions of the embodiments of the present invention will be clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0043] like Figure 1 As shown, the apparatus for preparing superhydrophilic porous membranes includes an electrospinning device 100 and a plasma treatment device 200. The electrospinning device 100 includes a micro-injection pump 6 and a plastic syringe 2 connected to the micro-injection pump. The micro-injection pump 6 has a propulsion rate of 0.6–1.0 mL / h. A metal flat-mouth needle 3 is provided at the front end of the plastic syringe 2, and a receiving device 4 is provided at the front end of the metal flat-mouth needle 3. The distance between the metal flat-mouth needle 3 and the receiving device 4 is 15–25 cm. The surface of the receiving device 4 is covered with tin foil. A DC voltage 5 of 8–14 kV is applied between the metal flat-mouth needle 3 and the receiving device 4. The PU spinning solution stored in the plastic syringe 2 is ejected from the front end of the metal flat-mouth needle 3 and, under the action of the electric field, overcomes its own surface tension to form a jet that is sprayed onto the receiving device 4 to form a micron-sized porous membrane 7.

[0044] like Figure 2As shown, the plasma processing device 200 includes a vacuum chamber 8, on which a vacuum pump 11, a radio frequency source 13, and an external gas source are installed. The external gas source includes external air 9 and a gas cylinder 12, which stores any one of oxygen, nitrogen, or ammonia. The external air 9 is connected to the vacuum chamber 8 through a first inlet valve 10, and the gas cylinder is connected to the vacuum chamber 8 through a second inlet valve 14. During operation, the porous membrane 7 is fixed inside the vacuum chamber 8, and the first and second inlet valves 10 and 14 of the external gas source are closed. The vacuum pump 11 is then turned on to reduce the vacuum level inside the vacuum chamber 8 to below 40 Pa. The second inlet valve 14 of the gas cylinder 12 is then opened, and the gas flow rate of the gas cylinder 12 is controlled to be 300~1000 sccm until the vacuum level inside the vacuum chamber 8 drops below 40 Pa again. The radio frequency source 13 is then turned on, with a radio frequency power of 50~300 W and a radio frequency duration of 30~180 s. The radio frequency source glow discharge ionizes the introduced gas to generate plasma, and the highly chemically active plasma is activated on the surface of the porous membrane 7 fiber to form grafted active groups.

[0045] Example 1:

[0046] The present invention discloses a method for preparing a superhydrophilic porous membrane by grafting SiO2 onto a polyurethane fiber membrane, comprising the following steps:

[0047] Step 1: Preparation of PU spinning solution 1. 1.222 g of polymer PU was added to 6 ml of DMF / BuAc solution (volume ratio 7:3). The solution was magnetically stirred for 6 h at room temperature (25±5℃) to obtain PU spinning solution 1 with a mass fraction of 18 wt%. PU spinning solution 1 was injected into a plastic syringe 2. The distance between the metal flat-tipped needle 3 and the receiving device 4 was 15 cm. The propulsion rate of the micro-injection pump 6 was 0.6 mL / h. A DC voltage 5 of 12 kV was applied between the metal flat-tipped needle 3 and the receiving device 4. The micro-injection pump 6 was turned on, and the PU spinning solution was sprayed into the receiving device under the action of the electric field. Under the action of the electric field, the PU spinning solution overcame its own surface tension to form a jet stream. As the solvent evaporated, the jet stream solidified to form a porous membrane 7 with micron-sized fibers. The porous membrane 7 was dried and set aside for later use.

[0048] Step 2: Place the porous membrane 7 obtained in Step 1 into the vacuum chamber 8, and simultaneously close the first inlet valve 10 and the second inlet valve 14 of the external gas source connected to the vacuum chamber 8, and turn on the vacuum pump 11 to reduce the vacuum degree in the vacuum chamber 8 to below 40 Pa; open the second inlet valve 14 of the gas cylinder 12 and control the flow rate of nitrogen gas to 500 sccm, and wait for the vacuum degree in the vacuum chamber 8 to drop below 40 Pa again; turn on the radio frequency source 13 with a radio frequency power of 200 W and a radio frequency time of 60 s. The radio frequency source glow discharge ionizes the nitrogen gas to generate plasma. The highly chemically active plasma activates the porous membrane 7 fiber surface to form grafted active groups, thus obtaining a porous membrane 7 with fiber surface activation.

[0049] Step 3: Add 0.01 mol of (3-aminopropyl)triethoxysilane (KH550) to a 6 mL ethanol solution. Place the surface-activated porous membrane 7 in the mixed solution and sonicate it at room temperature of 25±5 ℃ for 20 min. Add 18 mL of water dropwise. After sonication, remove the porous membrane and air dry it for later use.

[0050] Step 4: Add 0.02 mol of tetraethyl orthosilicate to a C2H5OH / H2O solution with a volume ratio of 2:1 (where the volume of C2H5OH is 40 ml). Place the KH550 surface-activated porous membrane 7 in the mixed solution and sonicate it at room temperature of 25±5℃ for 25 min. Add ammonia dropwise to adjust the pH of the solution to 9. After sonication, remove the porous membrane and air dry it to obtain the superhydrophilic polyurethane porous membrane.

[0051] Example 2:

[0052] The present invention discloses a method for preparing a superhydrophilic porous membrane by grafting SiO2 onto a polyurethane fiber membrane, comprising the following steps:

[0053] Step 1: Preparation of PU spinning solution 1. 1.382 g of polymer PU was added to 6 ml of DMF / BuAc solution (volume ratio 6:4). The solution was magnetically stirred for 6 h at room temperature (25±5℃) to obtain PU spinning solution 1 with a mass fraction of 20 wt%. PU spinning solution 1 was injected into a plastic syringe 2. The distance between the metal flat-tipped needle 3 and the receiving device 4 was 18 cm. The micro-injection pump 6 was driven at a rate of 0.8 mL / h. A DC voltage 5 of 14 kV was applied between the metal flat-tipped needle 3 and the receiving device 4. The micro-injection pump 6 was turned on, and the PU spinning solution was sprayed into the receiving device under the action of the electric field. Under the action of the electric field, the PU spinning solution overcame its own surface tension to form a jet stream. As the solvent evaporated, the jet stream solidified to form a porous membrane 7 with micron-sized fibers. The porous membrane 7 was dried and set aside for later use.

[0054] Step 2: Place the porous membrane 7 obtained in Step 1 into the vacuum chamber 8, and simultaneously close the first inlet valve 10 and the second inlet valve 14 of the external gas source connected to the vacuum chamber 8, and turn on the vacuum pump 11 to reduce the vacuum degree in the vacuum chamber 8 to below 40 Pa; open the second inlet valve 14 of the gas cylinder 12 and control the oxygen gas flow rate to 800 sccm, and wait for the vacuum degree in the vacuum chamber 8 to drop below 40 Pa again; turn on the radio frequency source 13 with a radio frequency power of 100 W and a radio frequency time of 120 s. The radio frequency source glow discharge ionizes the oxygen to generate plasma. The highly chemically active plasma activates the porous membrane 7 fiber surface to form grafted active groups, thus obtaining a porous membrane 7 with fiber surface activation.

[0055] Step 3: Add 0.02 mol of (3-aminopropyl)trimethoxysilane (KH540) to 12 mL of ethanol solution, place the surface-activated porous membrane 7 in the mixed solution, sonicate at room temperature of 25±5 ℃ for 25 min, and add 24 mL of water dropwise. After sonication, remove the porous membrane and air dry it for later use.

[0056] Step 4: Add 0.01 mol of tetraethyl orthosilicate to a C2H5OH / H2O solution with a volume ratio of 2:1 (where the volume of C2H5OH is 20 ml). Place the KH540 surface-activated porous membrane 7 in the mixed solution and sonicate it at room temperature of 25±5℃ for 20 min. Add ammonia dropwise to adjust the pH of the solution to 10. After sonication, remove the porous membrane and air dry it to obtain the superhydrophilic polyurethane porous membrane.

[0057] Example 3:

[0058] The present invention discloses a method for preparing a superhydrophilic porous membrane by grafting SiO2 onto a polyurethane fiber membrane, comprising the following steps:

[0059] Step 1: Preparation of PU spinning solution 1. 1.581 g of polymer PU was added to 6 ml of DMF / BuAc solution (volume ratio 8:2). The solution was magnetically stirred for 6 h at room temperature (25±5℃) to obtain PU spinning solution 1 with a mass fraction of 22 wt%. PU spinning solution 1 was injected into a plastic syringe 2. The distance between the metal flat-tipped needle 3 and the receiving device 4 was 20 cm. The micro-injection pump 6 was driven at a rate of 0.6 mL / h. A DC voltage 5 of 14 kV was applied between the metal flat-tipped needle 3 and the receiving device 4. The micro-injection pump 6 was turned on, and the PU spinning solution was sprayed into the receiving device under the action of the electric field. Under the action of the electric field, the PU spinning solution overcame its own surface tension to form a jet stream. As the solvent evaporated, the jet stream solidified to form a porous membrane 7 with micron-sized fibers. The porous membrane 7 was dried and set aside for later use.

[0060] Step 2: Place the porous membrane 7 obtained in Step 1 into the vacuum chamber 8, and simultaneously close the first inlet valve 10 and the second inlet valve 14 of the external gas source connected to the vacuum chamber 8, and turn on the vacuum pump 11 to reduce the vacuum degree in the vacuum chamber 8 to below 40 Pa; open the second inlet valve 14 of the gas cylinder 12 and control the gas flow rate of ammonia to 1000 sccm, and wait for the vacuum degree in the vacuum chamber 8 to drop below 40 Pa again; turn on the radio frequency source 13 with a radio frequency power of 100 W and a radio frequency time of 180 s, and use the radio frequency source glow discharge to ionize the ammonia to generate plasma. The highly chemically active plasma activates the porous membrane 7 fiber surface to form grafted active groups, thus obtaining a porous membrane 7 with fiber surface activation.

[0061] Step 3: Add 0.03 mol of N-(β-aminoethyl)-3-aminopropyltrimethoxysilane (KH792) to 18 mL of ethanol solution. Place the surface-activated porous membrane 7 in the mixed solution and sonicate it at room temperature of 25±5 °C for 30 min. Add 54 mL of water dropwise. After sonication, remove the porous membrane and air dry it for later use.

[0062] Step 4: Add 0.03 mol of tetraethyl orthosilicate to a C2H5OH / H2O solution with a volume ratio of 2:1 (where the volume of C2H5OH is 60 ml). Place the KH792 surface-activated porous membrane 7 in the mixed solution and sonicate it at room temperature of 25±5℃ for 30 min. Add ammonia dropwise to adjust the pH of the solution to 12. After sonication, remove the porous membrane and air dry it to obtain the superhydrophilic polyurethane porous membrane.

[0063] Example 4:

[0064] The present invention discloses a method for preparing a superhydrophilic porous membrane by grafting SiO2 onto a polyurethane fiber membrane, comprising the following steps:

[0065] Step 1: Preparation of PU spinning solution 1. 1.239 g of polymer PU was added to 6 ml of DMF / BuAc solution (volume ratio 9:1). The solution was magnetically stirred for 6 h at room temperature (25±5℃) to obtain PU spinning solution 1 with a mass fraction of 18 wt%. PU spinning solution 1 was injected into a plastic syringe 2. The distance between the metal flat-tipped needle 3 and the receiving device 4 was 18 cm. The micro-injection pump 6 was used at a propulsion rate of 1.0 mL / h. A DC voltage 5 of 10 kV was applied between the metal flat-tipped needle 3 and the receiving device 4. The micro-injection pump 6 was turned on, and the PU spinning solution was sprayed onto the receiving device under the action of the electric field. Under the action of the electric field, the PU spinning solution overcame its own surface tension to form a jet stream. As the solvent evaporated, the jet stream solidified to form a porous membrane 7 with micron-sized fibers. The porous membrane 7 was dried and set aside for later use.

[0066] Step 2: Place the porous membrane 7 obtained in Step 1 into the vacuum chamber 8, and simultaneously close the first inlet valve 10 and the second inlet valve 14 of the external gas source connected to the vacuum chamber 8, and turn on the vacuum pump 11 to reduce the vacuum degree in the vacuum chamber 8 to below 40 Pa; open the second inlet valve 14 of the gas cylinder 12 and control the oxygen gas flow rate to 300 sccm, and wait for the vacuum degree in the vacuum chamber 8 to drop below 40 Pa again; turn on the radio frequency source 13 with a radio frequency power of 50 W and a radio frequency time of 180 s. The radio frequency source glow discharge ionizes the oxygen to generate plasma. The highly chemically active plasma activates the porous membrane 7 fiber surface to form grafted active groups, thus obtaining a porous membrane 7 with fiber surface activation.

[0067] Step 3: Add 0.01 mol of (3-aminopropyl)triethoxysilane (KH550) to 12 mL of ethanol solution, place the surface-activated porous membrane 7 in the mixed solution, sonicate at room temperature of 25±5 ℃ for 20 min, and add 12 mL of water dropwise. After sonication, remove the porous membrane and air dry it for later use.

[0068] Step 4: Add 0.01 mol of tetraethyl orthosilicate to a C2H5OH / H2O solution with a volume ratio of 2:1 (where the volume of C2H5OH is 40 ml). Place the KH550 surface-activated porous membrane 7 in the mixed solution and sonicate it at room temperature of 25±5℃ for 30 min. Add ammonia dropwise to adjust the pH of the solution to 11. After sonication, remove the porous membrane and air dry it to obtain the superhydrophilic polyurethane porous membrane.

[0069] Example 5:

[0070] The present invention discloses a method for preparing a superhydrophilic porous membrane by grafting SiO2 onto a polyurethane fiber membrane, comprising the following steps:

[0071] Step 1: Preparation of PU spinning solution 1. 1.373 g of polymer PU was added to 6 ml of DMF / BuAc solution (volume ratio 5:5). The solution was magnetically stirred for 6 h at room temperature (25±5℃) to obtain PU spinning solution 1 with a mass fraction of 20 wt%. PU spinning solution 1 was injected into a plastic syringe 2. The distance between the metal flat-tipped needle 3 and the receiving device 4 was 20 cm. The micro-injection pump 6 was driven at a rate of 0.8 mL / h. A DC voltage 5 of 8 kV was applied between the metal flat-tipped needle 3 and the receiving device 4. The micro-injection pump 6 was turned on, and the PU spinning solution was sprayed into the receiving device under the action of the electric field. Under the action of the electric field, the PU spinning solution overcame its own surface tension to form a jet stream. As the solvent evaporated, the jet stream solidified to form a porous membrane 7 with micron-sized fibers. The porous membrane 7 was dried and set aside for later use.

[0072] Step 2: Place the porous membrane 7 obtained in Step 1 into the vacuum chamber 8, and simultaneously close the first inlet valve 10 and the second inlet valve 14 of the external gas source connected to the vacuum chamber 8, and turn on the vacuum pump 11 to reduce the vacuum degree in the vacuum chamber 8 to below 40 Pa; open the second inlet valve 14 of the gas cylinder 12 and control the flow rate of nitrogen gas to 1000 sccm, and wait for the vacuum degree in the vacuum chamber 8 to drop below 40 Pa again; turn on the radio frequency source 13 with a radio frequency power of 200 W and a radio frequency time of 120 s, and use the radio frequency source glow discharge to ionize the nitrogen gas to generate plasma. The highly chemically active plasma activates the porous membrane 7 fiber surface to form grafted active groups, thus obtaining a porous membrane 7 with fiber surface activation.

[0073] Step 3: Add 0.03 mol of (3-aminopropyl)trimethoxysilane (KH540) to 12 mL of ethanol solution, place the surface-activated porous membrane 7 in the mixed solution, sonicate at room temperature of 25±5 ℃ for 30 min, and add 36 mL of water dropwise. After sonication, remove the porous membrane and air dry it for later use.

[0074] Step 4: Add 0.02 mol of tetraethyl orthosilicate to a C2H5OH / H2O solution with a volume ratio of 2:1 (where the volume of C2H5OH is 60 ml). Place the KH540 surface-activated porous membrane 7 in the mixed solution and sonicate it at room temperature of 25±5℃ for 20 min. Add ammonia dropwise to adjust the pH of the solution to 10. After sonication, remove the porous membrane and air dry it to obtain the superhydrophilic polyurethane porous membrane.

[0075] Experimental results:

[0076] Scanning electron microscope (SEM) images and pore size distribution diagrams of the superhydrophilic polyurethane porous membranes prepared in Examples 1 and 3 of this invention (e.g., ...) Figure 3-6 As shown in the scanning electron microscope (SEM) images, the superhydrophilic polyurethane porous membrane is composed of micron-sized fiber porous membranes grafted with SiO2 particles on the surface, and the SiO2 particles do not block the pores of the polyurethane porous membrane. The pore size distribution of the superhydrophilic polyurethane porous membrane is 0.75–2.50 μm. Therefore, the prepared superhydrophilic polyurethane porous membrane has a rough surface and excellent pore size distribution.

[0077] The bar charts showing the water absorption rates of the superhydrophilic polyurethane porous membranes prepared in Examples 1-5 of this invention (e.g.) Figure 7 As shown in the figure, the water absorption rate of the superhydrophilic polyurethane porous membrane is 150-300%; the water evaporation-time curves of the superhydrophilic polyurethane porous membranes prepared in Examples 2 and 4 of this invention (as shown in the figure) Figure 12-13 As shown in the figure, the water evaporation rate (Ev) of the superhydrophilic polyurethane porous membrane is 0.3~0.4 g / h, indicating that the superhydrophilic polyurethane porous membrane prepared by the present invention has excellent moisture absorption and quick-drying properties.

[0078] The underwater oil contact angle diagram and underwater oil rolling diagram of the superhydrophilic polyurethane porous membranes prepared in Examples 4 and 5 of this invention (e.g.) Figure 8-11 As shown in the figure, the underwater oil contact angle of the superhydrophilic polyurethane porous membrane is 155-165°, and the roll-off angle of the superhydrophilic polyurethane porous membrane is 3-10°, indicating that the superhydrophilic polyurethane porous membrane prepared by the present invention has excellent underwater oleophobic and anti-oil properties.

[0079] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a superhydrophilic porous membrane by grafting SiO2 onto a polyurethane fiber membrane, characterized in that: The apparatus for preparing superhydrophilic porous membranes includes an electrospinning apparatus (100) and a plasma treatment apparatus (200). The electrospinning device (100) includes a micro-injection pump (6) and a plastic syringe (2) connected to the micro-injection pump. A metal flat needle (3) is provided at the front end of the plastic syringe (2). A receiving device (4) is provided at the front end of the metal flat needle (3). A DC voltage (5) is applied between the metal flat needle (3) and the receiving device (4). The PU spinning liquid (1) stored in the plastic syringe (2) is ejected from the front end of the metal flat needle (3) and overcomes its own surface tension under the action of the electric field to form a jet that is sprayed onto the receiving device (4) to form a micron-sized porous membrane (7). The plasma processing device (200) includes a vacuum chamber (8), on which a vacuum pump (11), a radio frequency source (13) and an external gas source are provided. The porous membrane (7) is placed in the vacuum chamber (8) for grafting treatment. The method for preparing the superhydrophilic porous membrane includes the following steps: Step 1: Prepare a polyurethane (PU) N,N-dimethylformamide / butyl acetate DMF / BuAc solution and stir it at room temperature for 6 h to obtain PU spinning solution (1); inject the PU spinning solution (1) into a plastic syringe (2), turn on the micro injection pump (6) and DC voltage (5), and spray the PU spinning solution onto the receiving device under the action of the electric field, and form a porous membrane (7) with a fiber diameter of micrometers on the surface of the receiving device. Dry the porous membrane (7) for later use. Step 2: Place the porous membrane (7) obtained in Step 1 into a vacuum chamber (8), and simultaneously close the first inlet valve (10) and the second inlet valve (14) of the external gas source of the vacuum chamber (8), and turn on the vacuum pump (11) to reduce the vacuum degree in the vacuum chamber (8) to below 40 Pa; open the second inlet valve (14) of the gas cylinder (12), adjust the flow rate of the introduced gas, and wait for the vacuum degree in the vacuum chamber (8) to drop below 40 Pa again; turn on the radio frequency source (13) and set the radio frequency power and time. The radio frequency source glow discharge ionizes the introduced gas to generate plasma. The plasma with high chemical activity is activated on the fiber surface of the porous membrane (7) to form grafted active groups. Step 3: Place the surface-activated porous membrane (7) from step 2 in a mixed solution of ethanol and aminosilane, sonicate it at room temperature for 20-30 min, and add water dropwise; after the sonication is completed, take out the porous membrane and let it dry for later use. Step 4: Place the porous membrane treated with aminosilane in step 3 in a mixed solution of ethanol, water and tetraethyl orthosilicate, and sonicate it at room temperature for 20-30 min. Add ammonia dropwise to adjust the pH of the solution. After sonication, remove the porous membrane (7) and air dry it to obtain a superhydrophilic porous membrane. The superhydrophilic porous membrane has a micron-sized porous structure; the pore size of the superhydrophilic microporous membrane is distributed in the range of 0.75~2.50μm, the water absorption rate is 150~300%, and the water evaporation rate is 0.3~0.4 g / h; the underwater oil contact angle of the superhydrophilic porous membrane is 155~165°, and the underwater oil roll-off angle is 3~8°.

2. The method for preparing a superhydrophilic porous membrane by grafting SiO2 onto a polyurethane fiber membrane according to claim 1, characterized in that, The distance between the metal flat needle (3) and the receiving device (4) is 15-25cm; the surface of the receiving device (4) is covered with tin foil.

3. The method for preparing a superhydrophilic porous membrane by grafting SiO2 onto the surface of a polyurethane fiber membrane according to claim 1, characterized in that, The DC voltage (5) mentioned in step 1 is 8-14 kV; the propulsion rate of the micro-injection pump (6) is 0.6-1.0 mL / h.

4. The method for preparing a superhydrophilic porous membrane by grafting SiO2 onto a polyurethane fiber membrane according to claim 1, characterized in that, In step 1, the mass fraction of PU spinning solution (1) is 18~22wt%, and the volume ratio of N,N-dimethylformamide / butyl acetate is (5~9):(5~1).

5. The method for preparing a superhydrophilic porous membrane by grafting SiO2 onto a polyurethane fiber membrane according to claim 1, characterized in that, In step 2, the gas cylinder (12) can be any one of oxygen, nitrogen or ammonia, and the gas flow rate of the gas cylinder (12) is controlled to be 300~1000 sccm.

6. The method for preparing a superhydrophilic porous membrane by grafting SiO2 onto a polyurethane fiber membrane according to claim 1, characterized in that, The radio frequency power of the radio frequency source (13) mentioned in step 2 is 50~300 W and the radio frequency time is 30~180 s.

7. The method for preparing a superhydrophilic porous membrane by grafting SiO2 onto a polyurethane fiber membrane according to claim 1, characterized in that, In step 3, the aminosilane is any one of (3-aminopropyl)triethoxysilane, (3-aminopropyl)trimethoxysilane, and N-(β-aminoethyl)-3-aminopropyltrimethoxysilane; the molar mass of the aminosilane is 0.01~0.03 mol, the volume of ethanol is 6~18 mL, the volume ratio of ethanol to water is 1:(1~3), and the room temperature is 25±5℃.

8. The method for preparing a superhydrophilic porous membrane by grafting SiO2 onto a polyurethane fiber membrane according to claim 1, characterized in that, In step 4, the molar mass of tetraethyl orthosilicate is 0.01~0.03 mol, the volume of ethanol is 20~60 mL, the volume ratio of ethanol to water is 2:1, the pH value of the solution system is adjusted to 9~12 with ammonia, and the room temperature is 25±5℃.

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