Preparation method of high-performance tubular membrane

Abstract

The invention discloses a preparation method of a high-performance tubular membrane, which specifically comprises the following steps: S1, selecting non-woven fabric base materials with different gram weights and thicknesses as an inner layer and an outer layer of a tubular membrane supporting layer respectively, and winding the non-woven fabric base materials into a tubular supporting structure through a winding machine to prepare the tubular membrane supporting layer; s2, adding a polymeric membrane material, a pore-forming agent and an additive into a solvent, stirring until the materials are completely dissolved, filtering, defoaming to prepare a membrane casting solution, and storing the membrane casting solution in a sealed container; s3, uniformly coating the membrane casting liquid on the inner wall of the tubular membrane supporting layer under the action of centrifugal force through a coating head or a coating groove of a closed coating and curing device to prepare a tubular membrane liquid membrane; and S4, immersing the tubular liquid membrane in water or a water phase solution for solidification, and washing with water to obtain the tubular liquid membrane. The double-layer structure design that the inner layer uses the tighter non-woven fabric base material and the outer layer uses the loose non-woven fabric base material not only improves the mechanical strength of the membrane, but also increases the anti-pollution performance of the membrane layer. A dynamic tension control system is introduced in the winding forming process, it is ensured that higher adhesive force is formed between a membrane casting solution and a tubular membrane supporting layer, the risks of membrane layer stripping, falling and failure can be remarkably reduced, and therefore the stability of a membrane assembly is improved, and the service life of the membrane assembly is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of membrane separation, and in particular to a method for preparing a high-performance tubular membrane. Background Art

[0002] In the field of membrane separation technology, tubular membranes have broad application prospects, but the traditional preparation process of tubular membranes has many defects. With the continuous improvement of the requirements of various industries for membrane separation technology, these problems have become increasingly prominent. On the one hand, tubular membranes prepared by traditional processes often face the dilemma of poor adhesion of the membrane layer. In actual use, especially under conditions such as high pressure or fluid impact, the membrane layer is very easy to peel off and fall off, causing the membrane assembly to fail, greatly shortening its service life, and increasing the cost of use and maintenance frequency.

[0003] The traditional process performs poorly in terms of membrane uniformity. Its coating method easily causes inconsistent membrane liquid thickness, which not only makes it difficult to ensure the filtration accuracy of the membrane, but also causes performance fluctuations due to uneven membrane layers when operating in a high-flux, high-shear environment, and cannot stably perform the filtration function. The stability is also unsatisfactory. Traditional tubular membranes are difficult to adapt to complex working conditions such as acid-base environments, pressure fluctuations, and temperature changes, which greatly limits their in-depth application in many fields such as water treatment, industrial wastewater treatment, and sewage regeneration. The mechanical strength and pollution resistance are insufficient to meet the growing needs of complex applications.

[0004] In addition, traditional preparation methods lack careful consideration in the selection and processing of raw materials. For example, the use of non-woven fabric substrates is relatively simple and cannot be optimized for different working conditions.

[0005] The traditional coating process is not perfect and can easily introduce impurities from the air, causing membrane pore size deviation and irregular membrane surface, which seriously reduces the filtration effect and leads to poor chemical stability and anti-pollution performance of the membrane. In summary, a new high-performance tubular membrane preparation method is urgently needed to overcome these technical bottlenecks and meet the urgent demand for high-performance tubular membranes in many fields. Summary of the invention

[0006] The purpose of the present invention is to propose a method for preparing a high-performance tubular membrane, which optimizes the winding and film liquid coating links to solve the problems of poor membrane adhesion, insufficient uniformity, instability, etc. in the traditional tubular membrane preparation process.

[0007] The method for preparing a high-performance tubular membrane of the present invention comprises the following steps: S1. Select non-woven fabric substrates of different weights and thicknesses as the inner layer and the outer layer of the tubular membrane support layer, respectively, and wind the non-woven fabric substrate into a tubular support structure by a winding machine to obtain a tubular membrane support layer; S2: adding polymer membrane material, pore-forming agent and additives into solvent, stirring until completely dissolved, filtering and degassing to obtain casting solution and storing it in a sealed container; S3: passing the casting liquid through a coating head or a coating tank of a closed coating and curing device, and coating the casting liquid evenly on the inner wall of the tubular membrane support layer under the action of centrifugal force to obtain a tubular membrane liquid film; S4: immersing the tubular membrane liquid membrane in water or an aqueous solution for coagulation, and then washing with water to obtain the membrane.

[0008] According to the present invention, the non-woven fabric substrate in step S1 has a gram weight of 50 to 300 g / m².

[0009] Furthermore, the gram weight of the inner layer non-woven fabric substrate is 50 to 165 g / m².

[0010] Furthermore, the outer non-woven fabric substrate has a gram weight of 70 to 300 g / m².

[0011] According to the present invention, the thickness of the non-woven fabric substrate in step S1 is 30-100 μm.

[0012] According to the present invention, in step S1, the difference in gram weight between the inner non-woven fabric substrate and the outer non-woven fabric substrate is 40-81.2%.

[0013] According to the present invention, a dynamic tension control winding system is added to the winding machine in step S1, and a tension sensor is introduced to achieve dynamic adjustment of the tension of the non-woven fabric substrate during the winding process.

[0014] Furthermore, the tension adjustment range is 20-100N.

[0015] According to the present invention, the polymer membrane material in step S2 is polyvinylidene fluoride, polyether sulfone, polysulfone, polyvinyl chloride, polyacrylonitrile or cellulose acetate.

[0016] According to the present invention, the solvent in step S2 is one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide.

[0017] According to the present invention, the pore-forming agent in step S2 is polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG) or polyvinyl alcohol.

[0018] According to the present invention, the additive in step S2 is one of nano silicon dioxide, anhydrous lithium chloride, calcium carbonate, zirconium dioxide and aluminum oxide.

[0019] According to the present invention, the mass ratio of the polymer membrane material, the pore-forming agent, the additive and the solvent in step S2 is: 10-30: 5-50: 0.5-2: 85-90.

[0020] According to the present invention, the filter material required for the filtration in step S2 is stainless steel, polytetrafluoroethylene (PTFE) or polypropylene (PP).

[0021] Furthermore, the pore size of the filter is 0.5-10 μm.

[0022] According to the present invention, the sealed container in step S2 is made of stainless steel, polytetrafluoroethylene (PTFE), PET, polyethylene (PE) or polypropylene (PP).

[0023] According to the present invention, the sealed container in step S2 is a sealed barrel, a sealed can or a sealed bottle.

[0024] According to the present invention, the casting solution in step S2 is stored at a temperature of 15 to 50°C.

[0025] According to the present invention, the closed coating and curing device in step S3 keeps the tubular membrane support layer rotating during the coating process.

[0026] Furthermore, the rotation speed is 50-100 rpm.

[0027] According to the present invention, the flow rate of the casting solution in step S3 is 10 to 50 mL / min.

[0028] According to the present invention, the coating thickness in step S3 is 10 to 30 μm.

[0029] According to the present invention, the coating time in step S3 is 1 to 10 seconds.

[0030] According to the present invention, the aqueous phase solution in step S4 is a solvent aqueous solution with a mass concentration of 1 to 50%.

[0031] According to the present invention, the solidification temperature in step S4 is 20 to 40° C., and the solidification time is 30 to 500 seconds.

[0032] Compared with the prior art, the present invention has the following advantages: 1) The adhesion of the membrane layer is significantly improved: the present invention adopts a process of first winding the non-woven fabric substrate into shape and then coating the casting liquid. A dynamic tension control system is introduced during the winding process, which can accurately adjust the tension of the tubular membrane support layer when the casting liquid is coated, ensuring that a stronger adhesion is formed between the casting liquid and the tubular membrane support layer, which can significantly reduce the risk of membrane peeling, shedding and failure, thereby improving the stability and service life of the membrane assembly, especially in applications under high pressure and fluid environments; 2) Enhanced mechanical strength and anti-pollution performance: The double-layer structure design with a tighter non-woven fabric substrate for the inner layer and a loose non-woven fabric substrate for the outer layer not only improves the mechanical strength of the membrane, but also increases the anti-pollution performance of the membrane layer; the difference in gram weight and thickness of the double-layer non-woven fabric substrate can be optimized for different types of pollutants, thereby improving the long-term use effect of the membrane; the inner layer uses a tighter non-woven fabric substrate to enhance the pressure bearing capacity of the membrane, while the outer layer uses a loose non-woven fabric substrate to provide a higher filtration flux, which comprehensively improves the overall performance of the membrane; 3) Improved coating uniformity: During the coating process, the tubular membrane support layer is continuously rotated to ensure uniform distribution of the casting liquid, which can avoid the problems of inconsistent membrane liquid thickness or uneven coating that may occur in traditional processes; this not only ensures the filtration accuracy of the membrane layer, but also improves the mechanical strength and stability of the membrane, allowing the membrane assembly to operate continuously and stably under high flux and high shear force environments, reducing performance fluctuations caused by uneven membrane layers; 4) Applicable to a variety of complex working conditions: The present invention adopts a double-layer winding structure and an optimized membrane layer, so that the prepared tubular membrane can still maintain excellent filtration performance and stability when facing complex working conditions such as acid-base environment, pressure fluctuations, temperature changes, etc.; the chemical corrosion resistance and anti-pollution ability of the membrane component make it have broad application prospects in water treatment, industrial wastewater treatment, sewage regeneration and other fields. DETAILED DESCRIPTION

[0033] A method for preparing a high-performance tubular membrane comprises the following steps: S1 Select non-woven fabric substrates of different weights and thicknesses as the inner layer and outer layer of the tubular membrane support layer, respectively, and use a winding machine to wind the non-woven fabric substrate into a tubular support structure to obtain a tubular membrane support layer; S2: adding polymer membrane material, pore-forming agent and additives into solvent, stirring until completely dissolved, filtering and degassing to obtain a casting solution and storing it in a sealed container; S3: passing the casting liquid through a coating head or a coating tank of a closed coating and curing device, and coating the casting liquid evenly on the inner wall of the tubular membrane support layer under the action of centrifugal force to obtain a tubular membrane liquid film; S4: immersing the tubular membrane liquid membrane in water or an aqueous solution for coagulation, and then washing with water to obtain the membrane.

[0034] According to the present invention, the non-woven fabric substrate in step S1 has a gram weight of 50 to 300 g / m².

[0035] According to the present invention, the thickness of the non-woven fabric substrate in step S1 is 30-100 μm.

[0036] According to the present invention, the weight difference between the inner and outer non-woven fabric substrates in step S1 is 40-81.2%.

[0037] According to the present invention, a dynamic tension control winding system is added to the winding machine in step S1, and a tension sensor is introduced to achieve dynamic adjustment of the tension of the non-woven fabric substrate during the winding process.

[0038] The weight of the non-woven fabric substrate can be adjusted as needed. The inner and outer layers of the non-woven fabric substrate are tension-controlled to ensure consistency of density. During the winding process, the tension of the non-woven fabric substrate is dynamically adjusted through the tension control sensor and control system to ensure smooth transition and close fit between non-woven fabric substrates of different weights, forming a support structure with distinct layers.

[0039] Furthermore, the tension adjustment range is 20-100N.

[0040] Furthermore, the inner layer tension is adjusted in the range of 20 to 50N to ensure that the inner non-woven fabric substrate is tightly fitted; the outer layer tension is adjusted in the range of 50 to 100N to ensure that the outer non-woven fabric substrate maintains a certain stability and density during the winding process; in addition, different tension parameters are set according to the properties of different non-woven fabric substrates (such as gram weight, thickness) to ensure that the supporting structure after winding has a consistent density in the direction of water flow scouring and filtration, so as to improve the stability and compression resistance of the tubular membrane.

[0041] According to the present invention, the filter material required for the filtration in step S2 is stainless steel, polytetrafluoroethylene (PTFE) or polypropylene (PP).

[0042] Furthermore, the pore size of the filter is 0.5-10 μm.

[0043] During the filtration process, filters with smaller pore sizes (0.5-2μm) are used to remove fine impurities, such as tiny particles that may exist in the solvent, to ensure the high purity of the membrane liquid; if the membrane liquid is relatively clear or the impurities are larger, filters with larger pore sizes (5-10μm) can be selected.

[0044] According to the present invention, the sealed container in step S2 is made of stainless steel, polytetrafluoroethylene (PTFE), PET, polyethylene (PE) or polypropylene (PP). These materials have good chemical stability and can effectively prevent the solvent from reacting with the container material or the solvent from volatilizing.

[0045] According to the present invention, the sealed container in step S2 is a sealed barrel, a sealed can or a sealed bottle. Ensure that the container can be completely sealed to prevent air and water vapor from contacting the casting solution. For larger batches of casting solution, sealed barrels are often used; for small batches or experimental preparations, sealed bottles are often used.

[0046] According to the present invention, the storage condition of the casting solution in step S2 needs to control the temperature to avoid the quality of the casting solution being reduced, the solvent being volatilized, or the chemical composition of the casting solution being changed. The storage temperature range of the casting solution is 15-50°C.

[0047] According to the present invention, the closed coating and curing device in step S3 keeps the tubular membrane support layer rotating during the coating process.

[0048] Furthermore, the rotation speed is 50-100 rpm.

[0049] This speed range can ensure the uniformity of the casting liquid coating, ensure consistent coating thickness, and avoid uneven thickness of the film liquid.

[0050] According to the present invention, the closed coating and curing device in step S3 can achieve precise control of coating, so that the film layer is coated in a closed environment, avoiding contamination, and further improving the uniformity of the membrane pore size and the surface flatness. Example 1

[0051] The weight of the inner non-woven fabric is 50g / m², the thickness is 30μm, the weight of the outer non-woven fabric is 70g / m², the thickness is 60μm, and the weight difference between the inner and outer layers is 40%. The inner layer is a fine non-woven fabric to enhance support, and the outer layer is a loose non-woven fabric to provide a higher filtration flux.

[0052] Using a winder, the tensions of the inner and outer nonwoven fabric substrates were set to 20N and 50N, respectively.

[0053] Preparation of membrane solution: 85 g of N,N-dimethylformamide was used as solvent, 10 g of PVDF was used as membrane material, 5 g of polyvinyl pyrrolidone (PVP) was used as pore former and 0.5 g of nano-silica was used as additive. The above materials were mixed and dissolved, filtered through a stainless steel filter with a pore size of 1 μm, and prepared into membrane solution after degassing. The prepared membrane solution was stored in a polyethylene (PE) sealed barrel at 15°C.

[0054] The membrane liquid is poured into a closed coating and curing device, the rotation speed is set to 50 rpm, the coating thickness is controlled at 10 μm, the flow range of the coating membrane liquid is controlled at 10 mL / min, the coating time is 2 seconds, and the inner wall of the tubular membrane support layer after winding is evenly coated to obtain a tubular membrane liquid film; immersed in a 1% mass concentration N, N-dimethylformamide aqueous solution for coagulation (temperature at 20°C, time 30 seconds), and then washed with water to obtain a high-performance tubular membrane product. Example 2

[0055] The weight of the inner non-woven fabric is 100g / m², the thickness is 60μm, the weight of the outer non-woven fabric is 150g / m², the thickness is 85μm, and the weight difference between the inner and outer layers is 50%. The inner layer is a fine non-woven fabric to enhance support, and the outer layer is a loose non-woven fabric to provide a higher filtration flux.

[0056] Using a winder, the tension of the inner and outer nonwoven fabric substrates was set to 40N and 80N, respectively.

[0057] Preparation of membrane solution: 87 g of N-methylpyrrolidone as solvent, 15 g of polyethersulfone as membrane material, 30 g of polyethylene glycol (PEG) as pore former and 1 g of anhydrous lithium chloride as additive are mixed and dissolved, filtered through a polytetrafluoroethylene (PTFE) filter with a pore size of 5 μm, and prepared into membrane solution after degassing; the prepared membrane solution is stored in a polytetrafluoroethylene (PTFE) sealed barrel at 30°C.

[0058] The membrane liquid was poured into a closed coating and curing device, the rotation speed was set to 80rpm, the coating thickness was controlled at 20μm, the flow range of the coating membrane liquid was controlled at 30mL / min, the coating time was 6 seconds, and the inner wall of the wound tubular membrane support layer was evenly coated to obtain a tubular membrane liquid film; it was immersed in deionized water for coagulation, the water phase temperature was 30℃, and the coagulation time was controlled at 300 seconds. After washing with water, a high-performance tubular membrane product was obtained. Example 3

[0059] The weight of the inner nonwoven fabric is 165g / m², the thickness is 90μm, the weight of the outer nonwoven fabric is 300g / m², the thickness is 100μm, and the weight difference between the inner and outer layers is 81.8%. The inner layer is a fine nonwoven fabric to enhance support, and the outer layer is a loose nonwoven fabric to provide a higher filtration flux.

[0060] Using a winder, the tension of the inner and outer nonwoven fabric substrates was set to 50N and 100N, respectively.

[0061] Preparation of membrane liquid: 90 g of dimethyl sulfoxide as solvent, 30 g of polyacrylonitrile as membrane material, 50 g of polyvinyl alcohol as pore former and 2 g of aluminum oxide as additive are mixed and dissolved, filtered through a polypropylene (PP) filter with a pore size of 10 μm, and prepared into membrane liquid after degassing; the prepared membrane liquid is stored in a polypropylene (PP) sealed barrel at 50°C.

[0062] The prepared membrane liquid is poured into a closed coating and curing device, the rotation speed is set to 100 rpm, the coating thickness is controlled at 30 μm, the flow range of the coating membrane liquid is controlled at 50 mL / min, the coating time is 10 seconds, and the inner wall of the wound tubular membrane support layer is evenly coated to obtain a tubular membrane liquid film; it is immersed in a 50% mass concentration dimethyl sulfoxide aqueous solution for solidification (temperature is 40°C, time is 500 seconds), and then washed with water to obtain a high-performance tubular membrane product.

Claims

1. A method for preparing a high-performance tubular membrane, characterized in that: The following steps are involved: S1. Select non-woven fabric substrates of different weights and thicknesses as the inner layer and the outer layer of the tubular membrane support layer, respectively, and wind the non-woven fabric substrate into a tubular support structure by a winding machine to obtain a tubular membrane support layer; S2: adding polymer membrane material, pore-forming agent and additives into solvent, stirring until completely dissolved, filtering and degassing to obtain casting solution and storing it in a sealed container; S3: passing the casting liquid through a coating head or a coating tank of a closed coating and curing device, and coating the casting liquid evenly on the inner wall of the tubular membrane support layer under the action of centrifugal force to obtain a tubular membrane liquid film; S4: immersing the tubular membrane liquid membrane in water or an aqueous solution for coagulation, and then washing with water to obtain the membrane.

2. The preparation method according to claim 1, characterized in that: The non-woven fabric substrate in step S1 has a gram weight of 50 to 300 g / m²; Furthermore, the gram weight of the inner non-woven fabric substrate is 50 to 165 g / m²; the gram weight of the outer non-woven fabric substrate is 70 to 300 g / m²; and the gram weight difference between the inner non-woven fabric substrate and the outer non-woven fabric substrate is 40 to 81.2%.

3. The preparation method according to claim 1, characterized in that: The thickness of the non-woven fabric substrate in step S1 is 30-100 μm.

4. The preparation method according to claim 1, characterized in that: In step S1, a dynamic tension control winding system is added to the winding machine, and a tension sensor is introduced to achieve dynamic adjustment of the tension of the non-woven fabric substrate during the winding process; Furthermore, the tension adjustment range is 20-100N.

5. The preparation method according to claim 1, characterized in that: The polymer membrane material in step S2 is polyvinylidene fluoride, polyether sulfone, polysulfone, polyvinyl chloride, polyacrylonitrile or cellulose acetate; the solvent in step S2 is one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide; the pore former in step S2 is polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG) or polyvinyl alcohol; the additive in step S2 is one of nano silicon dioxide, anhydrous lithium chloride, calcium carbonate, zirconium dioxide and aluminum oxide; the mass ratio of the polymer membrane material, pore former, additive and solvent in step S2 is: 10-30: 5-50: 0.5-2: 85-90.

6. The preparation method according to claim 1, characterized in that: The filter material required for the filtration in step S2 is stainless steel, polytetrafluoroethylene (PTFE) or polypropylene (PP); Furthermore, the pore size of the filter is 0.5 to 10 μm; The material of the sealed container in step S2 is stainless steel, polytetrafluoroethylene (PTFE), PET, polyethylene (PE) or polypropylene (PP); The sealed container in step S2 is a sealed barrel, a sealed can or a sealed bottle; According to the present invention, the casting solution in step S2 is stored at a temperature of 15 to 50°C.

7. The preparation method according to claim 1, characterized in that: In step S3, the closed coating and curing device keeps the tubular membrane support layer rotating during the coating process; Furthermore, the rotation speed is 50-100 rpm.

8. The preparation method according to claim 1, characterized in that: The flow rate of the casting solution in step S3 is 10 to 50 mL / min; the coating thickness in step S3 is 10 to 30 μm; and the coating time in step S3 is 1 to 10 seconds.

9. The preparation method according to claim 1, characterized in that: The aqueous phase solution in step S4 is a solvent aqueous solution with a mass concentration of 1 to 50%; the coagulation temperature in step S4 is 20 to 40° C., and the coagulation time is 30 to 500 seconds.

10. A high-performance tubular membrane prepared by the preparation method according to any one of claims 1 to 9.