A process for preparing a filter membrane

Abstract

This invention relates to the field of hollow fiber membrane preparation technology, specifically a filter membrane preparation process, comprising: a gelation tank, mounting bases, and guide wheels. Multiple mounting bases are fixedly installed inside the gelation tank, and guide wheels are rotatably mounted on the mounting bases. The guide wheels guide the fiber membrane through the gelation tank. This invention reduces heat loss from the solution in the gelation tank by providing an insulating cover plate. A dividing groove is provided at the bottom of the insulating cover plate, dividing the solution in the gelation tank into two parts. The fiber membrane is formed within the dividing groove, and the volume of the solution in the dividing groove is smaller than that in the gelation tank, which facilitates the adjustment of the solution concentration in the dividing groove and ensures the concentration of the solution in the water body where the fiber membrane is formed, thereby improving the quality of the filter membrane produced in the filter membrane preparation process.

Description

Technical Field

[0001] This invention relates to the field of hollow fiber membrane preparation technology, specifically to a process for preparing a filter membrane. Background Technology

[0002] A filter is a common water treatment device used to treat dyeing and printing wastewater and purify domestic water. Hollow fiber filters are a common type of filter, consisting of hundreds or even thousands of hollow fiber membrane filaments assembled internally. Therefore, their filtration effect is very significant, the water quality can fully meet national discharge standards, and the treated water can be reused as greywater. Hollow fiber membranes can be prepared through various methods such as solution spinning, melt spinning, and phase inversion.

[0003] The phase inversion method involves sending the spinning solution from a storage tank through a metering pump and filter, then extruding it through a spinneret. The spinneret nozzle is annular, resulting in hollow fibers. To prevent fiber deformation, an air supply system provides gas into the hollow core of the fiber. The extruded fibers can then directly enter a gelation tank, be rinsed in a rinsing tank, and finally collected on a roller.

[0004] To modify the interactions between components in hollow fiber membranes, particularly influencing the polymer's aggregation state, thermodynamics, and gel kinetics in solution, and thus adjusting membrane structure and performance, an appropriate amount of polyethylene glycol (PEG) can be added to the gelation bath. When the molecular weight of PEG is between 6000 and 20000, the resulting hollow fiber membranes exhibit varying flux, flow cutoff, and tensile strength. At a molecular weight of 6000, the obtained PES hollow fiber membrane exhibits better performance.

[0005] Because PEG is highly water-soluble, its solubility varies at different temperatures. However, due to the large volume of existing gelation baths, the solution surface dissipates heat quickly, resulting in uneven temperature distribution within the bath and consequently uneven PEG concentration. Furthermore, polyethylene glycol, acting as a catalyst for promoting fiber membrane formation, accumulates around the hollow fiber membrane after it enters the gelation bath. After the membrane leaves the bath, the concentration of polyethylene glycol solution carried on its surface is higher than the average concentration of polyethylene glycol in the bath, leading to a localized decrease in polyethylene glycol concentration. This affects the structural formation of the hollow fiber membrane, ultimately reducing the membrane flux and tensile strength.

[0006] Therefore, a process for preparing filter membranes is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a process for preparing a filter membrane, which ensures the structural performance of the fiber membrane by forming a hollow fiber membrane in a polyethylene glycol solution of a stable concentration, thereby solving the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A process for preparing a filter membrane includes:

[0010] S1: The fiber membrane raw material is fed into the extruder, where it melts and is then introduced into the metering pump.

[0011] S2: Molten fiber membrane raw material enters the spinneret in equal amounts from the metering pump and is extruded from the spinneret. In order to prevent the fibers from collapsing, air is supplied to the hollow part of the extruded fiber membrane by the air supply system.

[0012] S3: The extruded fiber membrane enters the gel tank below after passing through the freezing channel. Polyethylene glycol is added to the gel tank in advance to make the fiber membrane form better.

[0013] S4: The fiber membrane in the gel tank is pulled onto the drum of the take-up machine by the guide wheel.

[0014] Preferably, an insulating cover is fixedly installed on the gel tank, and a partition groove is fixedly installed at the bottom of the insulating cover. A connecting groove is opened on the insulating cover, which divides the gel tank into two parts. A fiber membrane is formed in the partition groove. The partition groove is 15cm wide and 50cm long. A drain hole and a water inlet are opened on the partition groove. A drain unit is provided in the partition groove. The drain unit is driven by the friction between the fiber membrane and the guide wheel. The drain unit exchanges the solution in the partition groove and the gel tank through the drain hole and the water inlet. A cleaning component is provided on the insulating cover, which is used to scrape off the solution on the fiber membrane.

[0015] The average diameter of an adult's forearm is 11cm. In order for the worker to be able to pull the fiber membrane onto the guide wheel, the width of the dividing groove is set to at least 11cm. However, in actual operation, the fiber membrane needs to be inserted from one side of the guide wheel to the other side, which requires the worker's arm to move laterally. In order to facilitate the worker's operation, a 4cm operating space is left for the worker, so the width of the dividing groove is set to 15cm.

[0016] To match the production speed of the fiber membrane and ensure that it is not stretched or deformed during winding, the industry standard for winding fiber membranes immediately after exiting the spinneret is 25 cm / min. Since the forming time of the fiber membrane in the gel bath is approximately 2 minutes, the length of the separator is set at 50 cm. This length satisfies the forming requirements of the fiber membrane while minimizing the area of ​​the solution exposed to air, thus reducing heat loss.

[0017] Preferably, the heat-insulating cover plate includes two half-plates slidably mounted on the gel water tank. Sliders are fixedly mounted on both side walls of the two half-plates. Multiple fixing plates are fixedly mounted on both side walls of the gel water tank. The fixing plates are L-shaped and have L-shaped grooves at the beginning. A spring is provided in the long side of the L-shaped groove. A support plate is fixedly mounted on the spring. The sliders slide in the L-shaped grooves. The dividing groove includes U-shaped plates fixedly mounted on the two half-plates respectively. The height of the U-shaped plates is 1 / 3 to 2 / 5h, where h is the height of the gel water tank.

[0018] According to the analysis of "The Influence of Molecular Weight and Concentration of PEG on the Structure and Performance of PES Hollow Fiber Membranes", the water flow rate of fiber membranes is significantly improved when the temperature is between 30° and 40° and the concentration of additive is 5%.

[0019] In a 40°C gel bath, the water temperature is most stable at half the height below the liquid surface, ranging from 34°C to 38°C. The fiber membrane formed at this point yields the best quality. Considering the need for the half-plate to flip on the gel bath, the height of the U-shaped plate cannot exceed half the width of the gel bath. Otherwise, the two U-shaped plates will collide when the half-plate is vertically placed on the gel bath. To ensure the fiber membrane forms in a relatively stable temperature range and that the half-plate can flip smoothly, the height of the U-shaped plate should be less than 2 / 5a and as close as possible to 1 / 2h, where h is the height of the gel bath and a is the width of the gel bath.

[0020] The fixed plate is mounted on the side wall edge of the gelation tank and is L-shaped. An L-shaped groove is opened in the middle of the fixed plate. A slider is fixedly installed on the half plate, allowing the half plate to move along the contour of the fixed plate. When producing fiber membranes, the two half plates are placed horizontally on the top wall of the gelation tank. The half plates are equipped with handles. By pushing the half plates horizontally inward with the handles, the two half plates are closed, reducing the area of ​​the solution exposed to the air and reducing heat loss in the gelation tank. At the same time, the two partitioning tanks cooperate to divide the solution into two parts. The solution in the gelation tank is located below the half plates, while the solution in the partitioning tank is exposed to the air, but its volume is smaller than that of the solution in the gelation tank. This allows the solution in the gelation tank to continuously heat the solution in the partitioning tank, thereby maintaining the temperature in the partitioning tank, and the fiber membrane is formed in the partitioning tank. After production is complete, push the half-plate outwards to move the slider to the corner of the fixed plate, then flip the half-plate to a vertical position. This allows the half-plate to move downwards and align with the gel tank. The divider can then hold items such as additives needed for the next day's production, or cleaning items needed for cleaning the gel tank. When pulling the half-plate out, the heavier portion within the gel tank requires the worker to apply pressure to rotate it to a vertical position. By sliding a handle onto the half-plate, pulling the handle down to the edge while pressing down increases the lever arm for rotating the half-plate, facilitating its installation and removal.

[0021] The spring is installed inside the vertical edge of the fixed plate, and the height of the spring extends to be flush with the top wall of the gel tank. When the half-plate is pulled outward to the corner of the fixed plate, the slider on its side wall is exactly located on the support plate. Since half of the half-plate is located inside the gel tank, and there is a dividing groove on the half-plate inside the gel tank, the half-plate cannot flip over by its own weight, preventing the half-plate from suddenly spinning out of control and causing injury to the worker. At this point, the worker needs to rotate the half-plate downward to flip it to a vertical position. At this time, under the action of the spring, the half-plate cannot slide down the fixed plate quickly, further ensuring the safety of the worker. Moreover, during the slow sliding of the half-plate, the spring is compressed, storing gravitational potential energy, which will make it easier for the worker to pull up the half-plate.

[0022] The insulation cover of this invention uses a combination of flip-top and sliding cover installation. In retraction mode, the insulation cover slides to both sides, then flips to a vertical position, and finally slides down to the bottom of the fixed plate. Compared to the flip-top installation method, this reduces the flipping radius by half, making it more labor-saving and convenient. Furthermore, the small-scale flipping does not affect equipment located next to the gel bath. Compared to the sliding cover installation method, this invention can be vertically stored on the side wall of the gel bath, reducing space occupancy.

[0023] Preferably, the drainage unit includes a rotating shaft rotatably mounted on two U-shaped plates, a guide wheel fixedly mounted in the middle of the rotating shaft, fan blades fixedly mounted at both ends of the rotating shaft, drainage holes opened on the side walls of the U-shaped plates, the fan blades facing the drainage holes, multiple fiber membranes passing through the guide wheel, the fan blades rotating by the friction between the fiber membranes and the guide wheel, multiple cylinders fixedly mounted on the U-shaped plates, and the drainage holes and fan blades located inside the cylinders.

[0024] Each U-shaped plate is equipped with a guide wheel located at one end of the U-shaped plate. When two U-shaped plates are engaged, the shafts on the two guide wheels are embedded in the opposite U-shaped plates, and the guide wheels are confined in the middle of the shafts. After the fiber membrane is immersed in the solution, it is wound around the guide wheel and finally exits outside the U-shaped plate. By using a cylinder to wrap the fan blades, the solution output by the fan blades is concentrated at the drain hole, improving the utilization rate of the guide wheel's power, increasing the solution exchange rate inside and outside the U-shaped plate, and preventing liquid from splashing out of the tank.

[0025] By placing rubber pads on the guide rollers to increase the friction between them and the fiber membrane, slippage is prevented, ensuring the rotation frequency of the guide rollers. Utilizing the excess torque at the fiber membrane winding end, the guide rollers are rotated while the fiber membrane pulls them, simultaneously driving the fan blades to rotate. This agitates the solution within the U-shaped plate, accelerating heat exchange between the solution in the U-shaped plate and the solution in the gel bath at the sidewall. This further increases heat exchange while simultaneously replenishing the concentration of additives within the U-shaped plate, ensuring the fiber membrane always forms under optimal conditions.

[0026] Fiber membranes, each 2 mm in diameter and 10 cm in length, are bundled together and propelled forward by friction through a 10 cm diameter guide wheel in a 5% polyethylene glycol solution. The guide wheel has 10 cm diameter fan blades. The task is to calculate whether the friction between the fiber membranes and the fan blades is sufficient to rotate the blades.

[0027] The bending stiffness of the fiber membrane can be estimated as: EI = Et 3 / 12(1-ν 2 )

[0028] Where E represents the elastic modulus, I represents the moment of inertia, t represents the thickness of the fiber membrane, ν represents Poisson's ratio, and Et represents the flexural modulus, which can be estimated as E / 20. Taking the elastic modulus as 5 GPa, the flexural modulus Et of the fiber membrane is approximately 250 MPa.

[0029] Let the frictional force between the fiber membrane and the guide wheel be F, and the curvature of the fiber membrane be k, then we have:

[0030] F = EI × k 3 / 6R, where R represents the radius of curvature of the fiber membrane, which is approximately equal to the radius of the guide wheel.

[0031] Let the radius of curvature of the fiber membrane be r, then we have: r = 1 / k, from which the frictional force F can be calculated:

[0032] F = EI / 6R 2 ≈1.04mN. If the guide wheel guides 5 fiber membranes at the same time, then the frictional force F = 5.04mN.

[0033] The resistance to the flow of water that drives the fan blades in the solution is: F f =1 / 2×ρ×v²×Cd×A, where r is the radius of the fan blade, A is the area of ​​the guide wheel, ρ is the density of the solution, the solution flow velocity is v = 0.0025 m / s, and its viscosity is η.

[0034] The drag coefficient of the fan blades is taken as 0.8, and the density of the solution in region V is 1.05 kg / m³. 2 The viscosity of the solution is 0.001 kg / (m·s), and the diameter of the guide wheel is 10 cm. Then F f =1 / 2×ρ×v 2 ×Cd×A≈3.4×10 -3 N < F = 5.04 × 10 -3 N. Therefore, the five fiber membranes can drive the fan blades to rotate in the solution.

[0035] Due to the limited width of the guide wheel, considering that the spacing between the fiber membranes should be at least 8mm, the width of the partition groove should be 15cm, the thickness of the two fan blades on the rotating shaft should be 2cm, and considering that there is a 1cm gap between each component, the width of the guide wheel should be set to 7cm. Therefore, it is most appropriate to set 5 to 7 fiber membranes on the guide wheel, which can drive the fan blades to rotate without affecting the formation of the fiber membrane.

[0036] Furthermore, the water inlet channel is located in the middle of the U-shaped plate.

[0037] The U-shaped plate is made of 6061 aluminum alloy, which has good thermal conductivity. The closer the two water inlets are, the more efficient the solution circulation within the U-shaped plate. However, if the two water inlets are combined into one unit, the circulation effect will be reduced. Theoretically, the closer the two water inlets are, the more efficient the solution circulation within the U-shaped plate. However, when the distance between the water inlets is too small, the gap between them is prone to breakage. Since the U-shaped plate is immersed in the solution, its stress is almost zero. Therefore, we only need to consider the factors of aging of the U-shaped plate and the metal's contraction or expansion due to temperature changes. Since the coefficient of expansion and the coefficient of contraction of 6061 aluminum alloy are 11.8 μm / m℃ and 11.8 μm / m℃ respectively, a 1 cm gap between the two water inlets can meet the solution circulation requirements within the partition plate while ensuring the stability of the gap between the two water inlets.

[0038] When the solution is discharged from the drain hole, the solution in the gel tank enters from the middle of the U-shaped plate. Since the drain hole is located at both ends of the U-shaped plate, the solution can also accelerate the diffusion of the solution in the U-shaped plate to both ends when it enters from the inlet tank, thereby accelerating the solution exchange rate inside the U-shaped plate.

[0039] Compared to agitating a scattered solution, the fan blades conduct the solution within the two U-shaped plates, allowing the solution to drain out of the U-shaped plates more quickly. This is more conducive to heat exchange and replenishment of the solution concentration within the U-shaped plates. Moreover, because the production speed of the fiber membrane is relatively slow, the rotation speed of the guide wheel is also relatively slow. If sufficient flow of water is desired near the fiber membrane, the relatively sealed small space formed by the two U-shaped plates is even more necessary.

[0040] Preferably, the partitioning tank and the gel water tank are independent of each other, and the partitioning tanks are combined by splicing. A sealing strip is fixedly installed at the splice of the partitioning tanks. A cleaning component is provided on the heat-insulating cover plate. The cleaning component is used to scrape off the solution on the fiber membrane and return the solution to the gel tank.

[0041] The U-shaped plate does not have drainage holes or water inlets for solution exchange with the gel water tank, and only the solution inside the U-shaped plate is needed for forming the fiber membrane, while the solution inside the gel water tank is water.

[0042] The specific operation is as follows: First, add water at an appropriate temperature to the gel water tank. After lifting the heat-insulating cover plate from the fixed plate and flipping it to a horizontal position, immerse the U-shaped plate in the water and push the two half plates inward to close the two U-shaped plates. At this time, the U-shaped plates are filled with water. Calculate the water volume when the two U-shaped plates are closed and add 5% additive to it. One of the U-shaped plates has a groove with the same outline at the joint, while the other U-shaped plate has a locking block that matches the groove at the joint. A sealing strip is also set on the groove to ensure the sealing effect when the U-shaped plates are joined.

[0043] The solution concentration inside the U-shaped plate is ensured by the cleaning components on the heat-insulating cover. Therefore, it is only necessary to ensure the temperature balance inside the U-shaped plate by using fan blades and to accelerate the heat exchange between the solution on the side wall of the U-shaped plate and the solution in the gel water tank to meet the production requirements of the fiber membrane.

[0044] Compared to U-shaped plates with drainage holes, U-shaped plates without drainage holes require less additives and have higher additive utilization. However, because they cannot exchange water with the gel bath, the temperature of the solution in the U-shaped plate without drainage holes differs more from that in the U-shaped plate with drainage holes. Furthermore, due to the lack of replenishment of the solution in the gel bath, the concentration of additives is also lower, resulting in lower stability of fiber membrane formation compared to U-shaped plates with drainage holes.

[0045] Preferably, the cleaning component includes fixed posts respectively fixedly installed on the two heat-insulating cover plates. Each of the two fixed posts has a sliding groove. A scraper is slidably installed in the two fixed posts through the sliding groove. The scraper is divided into upper and lower parts. A circular hole is opened on the scraper. The diameter of the circular hole is larger than the diameter of the fiber membrane. Two semi-circular rubber rings are fixedly installed in the circular hole. When the two scrapers are closed, the semi-circular rubber rings are in an interference fit with the fiber membrane.

[0046] The solution on the fiber membrane is scraped off by an interference fit between a semi-circular rubber ring and the fiber membrane.

[0047] After the two halves are joined, the distance between the two fixed posts is equal to the width of the scraper. The lower part of the scraper is inserted between the two fixed posts, pressing each fiber membrane into the semi-circular rubber ring. Then, the upper part of the scraper is inserted into the groove. Because the diameter of the semi-circular rubber ring is smaller than the diameter of the fiber membrane, as the fiber membrane is rolled up, the semi-circular rubber ring scrapes off the solution from the surface of the fiber membrane, and the solution flows back into the U-shaped plate, ensuring the concentration of the additives. This prevents the solution carried on the fiber membrane from contaminating subsequent rinsing processes. Furthermore, utilizing the elasticity of the semi-circular rubber ring, it does not damage the fiber membrane when scraping off fiber membranes of different diameters.

[0048] This is one of the reasons why existing gel water tanks are so large. In a small gel water tank, the overall concentration of polyethylene glycol changes more significantly as the fiber membrane continuously moves in and out, which also increases the heat dissipation area of ​​the gel water tank.

[0049] Preferably, the scraper is hollow inside, the semi-circular rubber ring is located in the inner wall of the scraper away from the U-shaped plate, the U-shaped plate extends to the bottom of the fixed column, and the semi-circular plate is provided with a guide groove for recovering the solution.

[0050] The solution on the fiber membrane is scraped off directly by a semi-circular rubber ring located on the inner wall of the scraper away from the U-shaped plate. The scraped solution falls directly into the U-shaped plate, preventing it from drying on the scraper or other components, maximizing solution recycling, and further ensuring that the additive concentration in the U-shaped plate remains unchanged. This also prevents the solution from accumulating along the scraper on the insulation cover, where the evaporation of the solution would form solid or liquid polyethylene glycol. Liquid polyethylene glycol is quite viscous, while solid polyethylene glycol is waxy and difficult to clean.

[0051] Preferably, the ratio of the diameter of the cylinder to the diameter of the fan is 1.2.

[0052] To evaluate the ratio of the blade diameter to the cylinder diameter using the flow coefficient, assuming the water flow rate is Q, the cylinder diameter is D, the blade diameter is d, the thrust coefficient is Kt, and the flow coefficient is Cq, the following formula applies:

[0053] For reference, Cq=Q / (π×D) 2 ×sqrt(2g×h)), F=Kt×ρ×π / 4×d 2 ×N 2 The thrust coefficient Kt is set to 2.5.

[0054] Based on the parameters above,

[0055] When the diameter ratio is 1.0, Cq = 0.054; when the diameter ratio is 1.2, Cq = 0.057.

[0056] When the diameter ratio is 1.5, Cq = 0.032; when the diameter ratio is 1.8, Cq = 0.046.

[0057] When the diameter ratio is 2.4, Cq = 0.033; when the diameter ratio is 3.2, Cq = 0.030. The higher the flow coefficient, the higher the drainage efficiency. Therefore, under the conditions of this invention, the drainage efficiency is highest when the diameter ratio of the cylinder to the fan blade is 1.2.

[0058] Preferably, a flap is rotatably installed on the gel water tank, the distance between the flap and the U-shaped plate is 1cm, the flap has rounded corners, and the fiber membrane extends out from both sides of the flap.

[0059] After the fiber membrane is fully threaded onto the guide wheel, the solution exposed to the air is covered by a flap to further reduce heat loss in the gel bath.

[0060] The average diameter of an adult's finger is 1 cm, and the diameter of the fiber membrane is 2 mm. Without affecting the entry and exit of the fiber membrane from the gel water tank, the worker's finger can be inserted between the flap and the separating groove. Without affecting the entry and exit of the fiber membrane from the gel water tank, it is beneficial to control the rotation of the flap.

[0061] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0062] 1. A process for preparing a filter membrane, wherein the structural properties of the fiber membrane are ensured by forming a hollow fiber membrane in a polyethylene glycol solution of stable concentration. The temperature and concentration distribution of the solution in a gel bath are continuously adjusted. A separator is set in the gel bath to divide the solution into two parts. The solution in the gel bath is located under an insulating cover, while the separator is exposed to air. The fiber membrane is formed within the separator. The solution in the gel bath is heated by the solution in the separator, and the two solutions exchange heat, ensuring that the polyethylene glycol solution in direct contact with the hollow fiber membrane remains at a stable concentration, thereby improving the quality of the filter membrane produced by this process.

[0063] 2. To further ensure the structural performance of the fiber membrane during the forming process, a cleaning component is installed on the gel tank. After the fiber membrane passes through the separator, the solution on the surface of the fiber membrane is scraped off, allowing the solution to flow back into the separator. The drainage component thoroughly mixes the solution flowing back into the separator and maintains the solution concentration in the separator. This also prevents the solution carried on the fiber membrane from contaminating the subsequent rinsing process. At the same time, it avoids the solution from accumulating on the insulation cover along the scraper and evaporating into stains that are difficult to clean, thereby reducing the material and labor costs of the filter membrane preparation process.

[0064] 3. To further ensure the structural performance of the fiber membrane during the forming process, when the gel tank and the separator are exchanging solutions, the solution enters from the middle of the separator, diffuses to both sides of the separator, and is discharged. This allows the solution replenished from the gel tank into the separator to fully contact the fiber membrane. Moreover, since the middle of the separator corresponds to the center of the gel tank, the temperature in the center of the gel tank is the most stable, i.e., the solution concentration is the most stable. Therefore, it can be ensured that the solution replenished into the separator is at a stable concentration, thereby further improving the quality of the filter membrane processed by this preparation process. Attached Figure Description

[0065] Figure 1 This is an overall structural diagram of the present invention;

[0066] Figure 2 for Figure 1 A half-section view;

[0067] Figure 3 for Figure 2 Enlarged view of the structure at point A;

[0068] Figure 4 This is a diagram showing the state of the insulation cover being pushed to the corner of the fixed plate.

[0069] Figure 5 This is a diagram showing the state of the insulation cover when it is placed vertically on the side wall of the gel water tank.

[0070] In the diagram: 1. Gel water tank; 2. Fixing plate; 3. Half plate; 4. U-shaped plate; 5. Fan blade; 501. Rotating shaft; 502. Guide wheel; 6. Fixing column; 7. Scraper; 701. Round hole; 702. Semi-circular rubber ring; 8. Cylinder; 9. Flip plate; 201. Slider; 202. Support plate; 203. Spring; 401. Drain hole; 402. Water inlet tank. Detailed Implementation

[0071] The aspects and features of this disclosure, as well as the methods for implementing these aspects and features, will be apparent; however, this disclosure is not limited to the embodiments disclosed below and can be implemented in various forms. These embodiments are provided to assist those skilled in the art in fully understanding this disclosure, and this disclosure is limited only to the scope of the appended claims.

[0072] Example 1: Drainage holes 401 are provided on the U-shaped plate 4. Please refer to [link / reference]. Figures 1 to 5 This invention provides a process for preparing a filter membrane, the technical solution of which is as follows:

[0073] Four fixing plates 2 are fixed to both sides of the gel water tank 1 by bolts. The fixing plates 2 are L-shaped and made of Q235 steel. The two ends of two half plates 3 are respectively installed on the two fixing plates 2 located on the long side of the gel water tank 1. The half plates 3 move within the fixing plates 2 by sliders 201 on the side wall. The sliders 201 are located in the middle of the half plates 3. The dimensions of the gel water tank 1 are 120×45×75cm, so the width of the half plates 3 is 22.5cm. A connecting groove with a length of 15cm and a width of 4cm is opened in the middle of the insulation cover. A spring 203 is installed in the long side of each fixing plate 2. A support plate 202 is placed on the top of each spring 203. The width of the support plate 202 is equal to the inner diameter of the fixing plate 2. The guide wheel 502 has a rotating shaft 501 set on the U-shaped plate 4. Each rotating shaft 501 has a guide wheel 502 set on it. The guide wheel 502 is set 10cm away from the end of the U-shaped plate 4. Two fan blades 5 are also glued to each rotating shaft 501. The fixing post 6 is welded to the half plate 3. The distance between the two fixing posts 6 is 12cm. The width of the groove opened on the fixing post 6 is 5mm. The scraper 7 is installed between the two fixing posts 6.

[0074] Before production begins, a solution for adjusting the membrane structure is prepared in gelation tank 1, which has a volume of 405L. 384.5L of 40°C warm water is added to gelation tank 1, along with 20kg of polyethylene glycol additive. The mixture is stirred until dissolved. Holding the handle on half-plate 3, half-plate 3 is lifted from the side wall of gelation tank 1. Due to the spring 203, lifting is relatively effortless until the slider 201 on half-plate 3 moves to the corner position of the fixed plate 2. Half-plate 3 is then pushed into gelation tank 1, causing it to rotate. Once the L-shaped plate is in a horizontal position, it is immersed in the solution in the gel tank 1. Similarly, the above operation is repeated on the other half plate 3 of the gel tank 1 to adjust it to a horizontal position. The worker moves to the middle of the two half plates 3 and brings the two half plates 3 together towards the middle of the gel tank 1 so that the two U-shaped plates 4 are interlocked. During this period, the rotating shaft 501 inside the two U-shaped plates 4 is embedded in the opposite U-shaped plate 4. There is a limit block on the rotating shaft 501 so that the guide wheel 502 is always located in the middle of the rotating shaft 501. Finally, the scraper 7 is installed into the two fixed columns 6.

[0075] During fiber membrane production, the produced fiber membrane has an outer diameter of 2mm and an inner diameter of 1.2mm. The extruder is started, and the fiber membrane raw material is added. The extruder pushes the molten fiber membrane raw material into a metering pump, which then guides an equal amount of molten fiber membrane into the spinneret. Air is supplied to the spinneret. The molten fiber membrane raw material flowing out of the spinneret undergoes preliminary shaping through a cooling channel and enters the gel water tank 1 below. At this point, the worker picks up the fiber membrane and winds it around the two guide wheels 502 inside the U-shaped plate 4, pulling the fiber membrane through the circular hole 701 on the scraper 7. The diameter of the circular hole 701 is 3mm, while the semi-circular rubber ring 7... The diameter of 02 is 1mm. When the fiber membrane passes through the scraper 7, the solution on the surface of the fiber membrane can be continuously scraped off by the two semi-circular rubber rings 702. The scraped solution enters the U-shaped plate 4 and is mixed by the fan blade 5 before being discharged into the gel tank 1. This ensures that the solution concentration in the gel tank 1 is maintained between 4% and 5%. During this period, the fiber membrane drives the guide wheel 502 to rotate, which in turn drives the fan blade 5 fixed on the rotating shaft 501 to rotate. Under the slow rotation of the fan blade 5, the solution inside the U-shaped plate 4 exchanges with the solution in the gel tank 1, ensuring that the temperature and concentration of the solution in the U-shaped plate 4 are within the set range.

[0076] After production is completed, push half plate 3 to the outside of gel tank 1 to separate the two U-shaped plates 4. First, push the slider 201 on one half plate 3 to the corner of the fixed plate 2 so that the slider 201 is located on the support plate 202 on the spring 203. Since half plate 3 is still half inside gel tank 1, half plate 3 cannot move downwards. Also, because it is inside gel tank 1 and there are U-shaped plates 4, half plate 3 cannot flip over by its own weight. At this time, the worker holds the handle and slowly pushes half plate 3 downwards. With the support of the springs 203 on both sides of gel tank 1, half plate 3 slowly descends until it is vertical. At this time, the compressive force of the springs 203 on both sides of gel tank 1 is equal to the weight of half plate 3, reducing the pulling force required when the worker lifts half plate 3 next time.

[0077] In the second embodiment, the U-shaped plate 4 does not have drainage holes 401, and the two U-shaped plates 4 are interlocked and independent of the gel water tank 1.

[0078] The L-shaped baffle does not have a drain hole 401 for exchanging solution with the gel tank 1, and only the solution in the U-shaped plate 4 is required for forming the fiber membrane, while the solution in the gel tank 1 is water.

[0079] First, add water at 30° to 40° to the gel tank 1. Then, lift one half-plate 3 from the fixed plate 2 and flip it to a horizontal position. At this time, the U-shaped plate 4 is immersed in the water. Repeat the above operation with the other half-plate 3 and push the two half-plates 3 into the gel tank 1 to close the two U-shaped plates 4. At this time, the U-shaped plates 4 are filled with water. The combined volume of the two U-shaped plates 4 is 2.4L. If 5% additive is added, 0.12Kg of polyethylene glycol needs to be added. A sealing strip is also set on the groove to ensure the sealing effect when the two U-shaped plates 4 are joined.

[0080] The solution concentration in the U-shaped plate 4 is ensured by the scraper 7 on the half plate 3. Therefore, it is only necessary to ensure the temperature balance in the U-shaped plate 4 by the fan blade 5 and accelerate the heat exchange between the solution on the side wall of the U-shaped plate 4 and the solution in the gel water tank 1 to meet the production requirements of the fiber membrane.

[0081] Compared to the U-shaped plate 4 with drainage holes 401, the U-shaped plate 4 without drainage holes 401 requires less additives and has a higher utilization rate of additives. However, since it cannot exchange with the water in the gel tank 1, the temperature of the solution in the U-shaped plate 4 without drainage holes 401 is significantly different from that in the U-shaped plate 4 with drainage holes 401. Furthermore, due to the lack of replenishment of the solution in the gel tank 1, the concentration of additives is also lower, resulting in lower stability of fiber membrane formation compared to the U-shaped plate 4 with drainage holes 401.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate and facilitate those skilled in the art to understand the technical solutions of the present invention, and are not intended to limit them; modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the inventive motivation of the present invention.

Claims

1. A process for preparing a filter membrane, comprising: S1: The fiber membrane raw material is fed into the extruder, where it melts and is then introduced into the metering pump. S2: Molten fiber membrane raw material enters the spinneret in equal amounts from the metering pump and is extruded from the spinneret. In order to prevent the fibers from collapsing, air is supplied to the hollow part of the extruded fiber membrane by the air supply system. S3: The extruded fiber membrane enters the gel water tank (1) below after passing through the freezing channel. Polyethylene glycol is added to the gel water tank (1) in advance to make the fiber membrane better formed. S4: The fiber membrane in the gel tank (1) is pulled onto the drum of the take-up machine by the guide wheel (502); The features are as follows: a heat-insulating cover plate is fixedly installed on the gel water tank (1), a partition groove is fixedly installed at the bottom of the heat-insulating cover plate, a connecting groove connected to the partition groove is opened on the heat-insulating cover plate, the partition groove divides the gel water tank (1) into two parts, a fiber membrane is formed in the partition groove, the width of the partition groove is 15cm and the length is 50cm, a drain hole (401) and a water inlet groove (402) are opened on the partition groove, a drain unit is provided in the partition groove, the drain unit is driven by the friction between the fiber membrane and the guide wheel (502), the drain unit exchanges the solution in the partition groove and the gel water tank (1) through the drain hole (401) and the water inlet groove (402), a cleaning component is provided on the heat-insulating cover plate, the cleaning component is used to scrape off the solution on the fiber membrane; The heat-insulating cover plate includes two half plates (3) that are slidably installed on the gel water tank (1). Slider (201) is fixedly installed on both sides of the two half plates (3). Multiple fixing plates (2) are fixedly installed on both sides of the gel water tank (1). The fixing plate (2) is L-shaped. The fixing plate (2) has an L-shaped groove. A spring (203) is provided in the long side of the L-shaped groove. A support plate (202) is fixedly installed on the spring (203). The slider (201) slides in the L-shaped groove. The partition groove includes a U-shaped plate (4) that is fixedly installed on the two half plates (3). The height of the U-shaped plate (4) is less than 2 / 5a and closest to 1 / 2h, where h is the height of the gel water tank (1) and a is the width of the gel water tank (1). The drainage unit includes two rotating shafts (501) rotatably installed in the partition groove. The two rotating shafts (501) are respectively installed on two U-shaped plates (4). The guide wheel (502) is fixedly installed in the middle of the rotating shaft (501). Fan blades (5) are fixedly installed at both ends of the rotating shaft (501). The drainage hole (401) is opened on the side wall of the U-shaped plate (4). The fan blades (5) face the drainage hole (401). Multiple fiber membranes pass through the guide wheel (502). The guide wheel (502) is driven by the friction between the fan blades (5) and the fiber membranes. The guide wheel (502) guides 5 to 7 fiber membranes at a time. Multiple cylinders (8) are fixedly installed on the U-shaped plate (5), and the cylinders (8) correspond one-to-one with the fan blades (5). The drainage hole (401) and the fan blades (5) are both located inside the cylinders (8).

2. The process for preparing a filter membrane according to claim 1, characterized in that: The water inlet trough (402) is located in the middle of the U-shaped plate (4). The U-shaped plate (4) is made of 6061 aluminum alloy. There are two water inlet troughs (402), and the interval between the two water inlet troughs (402) is 1 cm.

3. The process for preparing a filter membrane according to claim 1, characterized in that: A flap (9) is rotatably installed on the gel water tank (1). The distance between the flap (9) and the U-shaped plate (4) is 1cm. The flap (9) has rounded corners, and the fiber membrane passes through both sides of the flap (9).

4. The process for preparing a filter membrane according to claim 1, characterized in that: The cleaning component includes fixed posts (6) fixedly installed on the two heat-insulating cover plates respectively. Each of the two fixed posts (6) has a sliding groove. A scraper (7) is slidably installed in the two fixed posts (6) through the sliding groove. The scraper (7) is divided into upper and lower parts. A circular hole (701) is opened on the scraper (7). The diameter of the circular hole (701) is larger than the diameter of the fiber membrane. Two semi-circular rubber rings (702) are fixedly installed in the circular hole (701). When the two scrapers (7) are closed, the semi-circular rubber rings (702) are interference-fitted with the fiber membrane.

5. The process for preparing a filter membrane according to claim 4, characterized in that: The scraper (7) is hollow inside. The semi-circular rubber ring (702) is located in the inner wall of the scraper (7) away from the U-shaped plate (4). The U-shaped plate (4) extends to the bottom of the fixed column (6). A guide groove for recovering the solution is opened on the half plate (3).

6. The process for preparing a filter membrane according to claim 1, characterized in that: The ratio of the diameter of the cylinder (8) to the diameter of the fan blade (5) is 1.2.

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