An apparatus and method for continuous production of porous filtration membranes
By setting a receiving tray in the gelation tank, the problem of casting solution overflow and contamination is solved by utilizing the characteristic of spontaneous phase transformation of casting solution in water to form solid particles, thereby improving the cleanliness and stability of the porous filter membrane preparation process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SUZHOU LABORATORY
- Filing Date
- 2026-04-29
- Publication Date
- 2026-07-03
AI Technical Summary
During the preparation of porous filter membranes, the casting solution overflows and contaminates the gel tank and equipment, resulting in membrane surface defects and equipment instability. Existing material receiving methods are difficult to effectively intercept and clean up.
A receiving tray is installed in the gelation tank. Taking advantage of the property that the casting solution spontaneously transforms into solid particles in water and sinks naturally, the particles fall into the receiving tray by gravity, thus avoiding contamination of the membrane surface and equipment.
It effectively avoids contamination of the membrane surface and equipment by the casting solution, improves membrane cleanliness and equipment stability, reduces membrane appearance defects, and enhances the reliability and ease of maintenance of the membrane manufacturing process.
Smart Images
Figure CN122098276B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to an apparatus and method for preparing a filter membrane, and more specifically to an apparatus and method for continuously preparing a porous filter membrane. Background Technology
[0002] In the field of membrane separation technology, porous filter membranes, as a type of polymer semi-permeable membrane, can be classified into microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, forward osmosis membranes, gas separation membranes, and pervaporation membranes, depending on their separation precision and application scenarios. Due to their high-efficiency separation characteristics, these membrane materials have been widely used in many fields such as electronics, pharmaceuticals, beverages, food, chemicals, medical treatment, wastewater treatment, and resource recycling.
[0003] The preparation of porous filter membranes is usually based on the principle of phase transformation. By controlling the phase transformation of the casting solution (such as liquid-liquid phase separation or liquid-solid phase transformation), functional materials with specific pore structures are formed. The general preparation process includes the following steps: (1) preparing the casting solution; (2) uniformly coating the casting solution onto the surface of a substrate such as non-woven fabric and briefly exposing it to air; (3) immersing the coated substrate in a coagulation bath, initiating phase separation through the exchange between solvent and non-solvent, and finally achieving membrane curing. However, in the actual slot coating process, the coating head is usually arranged perpendicular to the substrate for horizontal coating. Once a coating abnormality or abnormal shutdown occurs, the coating head will move horizontally, and the casting solution is easy to overflow from the nozzle of the coating head and drip into the gel tank containing the coagulation bath. Especially in continuous industrial production, the membrane orientation in the gel tank is complex and variable, and the coagulation bath is often in a flowing state, which means that the dripping casting solution may not only contaminate the membrane surface that is being formed, but also easily deposit on the tank wall, tank bottom or roller to form impurities that are difficult to remove.
[0004] To address the aforementioned issues, the applicant initially attempted to place a receiving tray directly below the coating head to collect overflowing solution. However, this method has significant shortcomings: First, because the coating head and the base film are applied in contact, the receiving tray cannot get close enough to the coating area to effectively intercept overflowing solution generated during the coating process. Second, the solution collected by the traditional receiving tray is exposed to air for extended periods, making it prone to solidification and difficult to clean. Furthermore, if casting solution overflowing from the side of the coating head is not promptly handled, it will drip along the edges into the coagulation bath, contaminating and interfering with the membrane and drive rollers below. Therefore, there is an urgent need to optimize and improve the existing receiving method to enhance the cleanliness and continuous stability of the membrane preparation process. Summary of the Invention
[0005] This invention aims to provide an apparatus and method for the continuous preparation of porous filter membranes, which can effectively control the contamination of the gelation tank. Specifically, this invention utilizes the characteristic that the casting solution spontaneously undergoes a phase transformation and forms solid particles after being dropped into water, allowing the material to fall naturally under gravity and accurately land in a receiving tray set in the water, thereby preventing it from continuing to fall and contaminating the filter membrane and equipment rollers in operation.
[0006] First, the present invention provides an apparatus for continuous preparation of porous filter membranes, comprising: a coating head (1), which includes a nozzle (8) for coating a continuously moving base membrane (2) with casting liquid in the horizontal direction, and a gel tank (7) for phase inversion of the coated base membrane (2), the gel tank (7) containing a coagulation bath liquid; wherein the coated base membrane (2) enters the gel tank (7) in the vertical direction and is turned by a turning bottom roller (5) so that the base membrane (2) continues to move at an angle greater than 0° with the entry direction; at least one receiving tray (4) is provided below the turning bottom roller (5) in the gel tank (7); the projection of the extension line of the base membrane (2) entering the gel tank (7) in the vertical direction on the horizontal plane falls into the non-edge area of the receiving tray (4) so that the receiving tray (4) receives the solid particles formed after phase inversion of the casting liquid dripped from the nozzle (8) to the liquid surface of the gel tank (7).
[0007] As a preferred method, the position of the coating head (1) is fixed, or the coating head (1) has a certain horizontal displacement when the machine is turned on or off and when the coating is working.
[0008] As a preferred method, the at least one receiving tray (4) is to cover the horizontal displacement of the nozzle (8) in the horizontal direction. As a preferred method, the movement path of the coated base film (2) in the gel tank (7) includes at least a section located below the receiving tray (4), which partially overlaps with the horizontal position.
[0009] As a preferred method, the distance between the receiving tray (4) and the water surface of the gel tank (7) is 0.01-1 meter. Preferably, this distance is 0.3-0.5 meters.
[0010] As a preferred method, the distance between the receiving tray (4) and the base film (2) at the same horizontal height is 0.005 m to 0.5 m. Preferably, the distance is 0.1 m to 0.2 m.
[0011] As a preferred method, the liquid inside the gel tank (7) is either in a static state or in a flowing state; and / or, the flow rate in the flowing state is 0.01 - 0.2 m / s.
[0012] As a preferred method, the device further includes a back concave roller (3) having a concave point (9) corresponding to the nozzle (8) so that the nozzle (8) and the base film (2) come into contact at the concave point (9).
[0013] As a preferred method, the material of the receiving tray (4) is resistant to polar solvents; preferably, the material is stainless steel.
[0014] As a preferred method, the receiving tray (4) is made of a material resistant to polar solvents; and / or, the receiving tray (4) has a bottom edge with complete or incomplete sidewalls on the bottom edge; and / or, the sidewalls are permeable or impermeable structures.
[0015] Secondly, the present invention also provides a method for continuous preparation of porous filter membrane using the above-mentioned device. The coating head (1) is used to coat the continuously moving base membrane (2) with casting liquid in the horizontal direction. The coated base membrane (2) enters the gel tank (7) in the vertical direction and is turned by the bottom roller (5) so that the base membrane (2) continues to move at an angle greater than 0° with the entry direction. The casting liquid that is not coated on the base membrane (2) drips into the gel tank (7) and the solid particles formed after phase transformation are received by the receiving tray (4).
[0016] As a preferred method, the solid particles are removed when there is a possibility of overflow of solid particles in the receiving tray (4) or when the coagulation bath liquid in the gel tank (7) is discharged.
[0017] As a preferred embodiment, the porous filter membrane is one of the following: microfiltration membrane, ultrafiltration membrane, nanofiltration membrane, reverse osmosis membrane, forward osmosis membrane, gas separation membrane, and pervaporation membrane. Preferably, the material of the porous filter membrane is selected from one or a blend of two or more of cellulose lipids, polysulfones, polyolefins, and fluorinated materials.
[0018] Compared with the prior art, the present invention has the following beneficial effects:
[0019] Firstly, this invention cleverly utilizes the characteristic that the casting solution rapidly transforms into solid particles upon dripping into water and naturally sinks. This allows for the precise interception and collection of any abnormally overflowing solution in the receiving tray, completely preventing it from continuing to fall or spreading with the fluid and contaminating the forming membrane surface and the drive roller shaft. This design not only significantly reduces membrane appearance defects and performance degradation caused by casting solution dripping, but also effectively prevents the deposition of solid impurities on the tank walls and bottom, greatly improving the cleanliness of the gelation tank and the long-term stability of the equipment operation.
[0020] Secondly, the structural design of this device fully considers the potential horizontal displacement of the coating head, the diverse fluid states within the gelation tank, and the complex membrane orientation that may occur during actual production. The receiving tray horizontally covers the area where the coating head may overflow and is positioned below the coagulation bath surface. This avoids the problem of receiving tray failure caused by its inability to get close to the coating area, as is common with traditional receiving trays, and also solves the drawback of overflow solidifying in the air and being difficult to clean. This method achieves automatic and continuous collection of overflow without the need for external power or complex control, significantly improving the reliability and maintenance convenience of continuous membrane fabrication processes, and has outstanding practicality and promotional value. Attached Figure Description
[0021] Figure 1 The apparatus for continuous preparation of porous filter membranes provided by the present invention comprises: 1-coating head, 2-base membrane, 3-backside concave roller, 4-receiving tray, 5-turning bottom roller, 6-large bottom roller, 7-gel tank, 8-nozzle, and 9-concave point. Detailed Implementation
[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.
[0023] Example 1
[0024] like Figure 1 As shown, the apparatus for continuous preparation of porous filter membranes provided by the present invention includes a coating head 1, a back concave roller 3, a receiving tray 4, a steering bottom roller 5, a large bottom roller 6, and a gelation tank 7. The coating head 1 and the back concave roller 3 are positioned above the liquid surface of the gelation tank 7, while the receiving tray 4, the steering bottom roller 5, and the large bottom roller 6 are positioned below the liquid surface of the gelation tank 7. The coating head 1 has a nozzle 8 at its front end, and the back concave roller 3 has recesses 9. The recesses 9 correspond to the nozzle 8 to achieve contact between the nozzle and the base membrane 2 at the recesses, thereby coating the casting solution onto the vertically moving base membrane 2. A steering roller 5 is provided below the back concave roller 3, and the side of the steering roller 5 that contacts the base film 2 of the back concave roller 3 is vertically aligned to enable vertical movement of the coated base film 2. The steering roller 5 is used to change the vertical movement of the coated base film 2 to an inclined downward left movement, and then reverses again at the large bottom roller 6 to satisfy the multi-directional movement of the base film 2 in the gel tank 7 to fully meet the phase inversion requirements. A single receiving tray 4 is provided below the steering roller 5 and on the right side of the base film 2 that is moving inclined downward left. The distance between the receiving tray and the liquid surface of the gel tank 7 is 0.5 meters, and the distance between the receiving tray and the base film 2 at the same horizontal height is 0.1 meters. The projection of the extension line of the base film 2 entering the gel tank vertically onto the horizontal plane falls within the non-edge area of the receiving tray.
[0025] In this embodiment, the position of the coating head 1 is movable. When the machine is stopped, the distance between the nozzle and the base film 2 is 0.2 meters. During operation, the nozzle 8 contacts the base film 2. In case of an abnormal shutdown, the coating head 1 moves from the operating position to the stopped position. The horizontal length of the receiving tray is 0.5 meters, and the nozzle 9 covering the spray head 1 is also horizontally displaced. The gel tank 7 is externally connected to a pump to ensure that the internal coagulation bath liquid is in a micro-flow state with a flow velocity of 0.05 m / s. A filter screen sidewall is provided on the bottom edge of the receiving tray 4, with a filter screen aperture of 0.1 cm, which can trap solid particles dripping into the receiving tray 4 while allowing water to pass through.
[0026] Example 2
[0027] Based on the apparatus provided in Example 1, this embodiment provides a method for continuous preparation of porous ultrafiltration membranes, wherein the ultrafiltration membrane is polysulfone, and pure water is contained in the gelation tank 7 as the coagulation bath liquid. The specific steps are as follows:
[0028] The coating head 1 uses a nozzle to apply casting solution to a continuously moving nonwoven fabric base membrane 2 in a horizontal direction. The coated base membrane 2 then enters the gel tank 7 vertically and is turned by a bottom roller 5, causing it to continue moving at an angle to the lower left. When the coating head 1 overflows or stops abnormally, the casting solution at the nozzle 9 drips into the pure water in the gel tank 7 below, undergoing a phase transformation to form solid particles. These particles then fall vertically into the receiving tray 4 below under gravity, preventing them from falling again or being disturbed by the water circulation inside the tank, thus avoiding adhesion and contamination of the membrane or rollers. This results in a intact porous ultrafiltration membrane.
[0029] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. An apparatus for continuous preparation of porous filter membranes, characterized in that, include: The coating head (1) includes a nozzle (8) for applying casting liquid to a continuously moving base film (2) in a horizontal direction, and a gel tank (7) for phase inversion of the coated base film (2), the gel tank (7) containing a coagulation bath liquid; wherein the coated base film (2) enters the gel tank (7) in a vertical direction and is turned by a turning bottom roller (5) so that the base film (2) continues to move at an angle greater than 0° with the entry direction; at least one receiving tray (4) is provided below the turning bottom roller (5) in the gel tank (7); the projection of the extension line of the base film (2) entering the gel tank (7) in a vertical direction on the horizontal plane falls into the non-edge area of the receiving tray (4) so that the receiving tray (4) receives the solid particles formed after phase inversion of the casting liquid dripped from the nozzle (8) to the liquid surface of the gel tank (7).
2. The apparatus according to claim 1, characterized in that, The position of the coating head (1) is fixed, or the coating head (1) has a certain horizontal displacement when the machine is turned on or off and when the coating is working; and / or the at least one receiving tray (4) is to cover the horizontal displacement of the nozzle (8) in the horizontal direction.
3. The apparatus according to claim 2, characterized in that, The distance between the receiving tray (4) and the water surface of the gel tank (7) is 0.01-1 meter; and / or, the distance between the receiving tray (4) and the base film (2) at the same horizontal height is 0.005-0.5 meters.
4. The apparatus according to claim 2, characterized in that, The movement path of the coated base film (2) in the gel tank (7) includes at least one section located below the receiving tray (4).
5. The apparatus according to claim 1, characterized in that, The liquid inside the gel tank (7) is either in a static state or in a flowing state; and / or, the flow rate in the flowing state is 0.01-0.2 m / s.
6. The apparatus according to claim 1, characterized in that, The device also includes a back concave roller (3), which has a concave point (9) corresponding to the nozzle (8) so that the nozzle (8) and the base film (2) can contact each other at the concave point (9).
7. The apparatus according to claim 1, characterized in that, The receiving tray (4) is made of a material resistant to polar solvents; and / or, the receiving tray (4) has a bottom edge with a complete or incomplete sidewall; and / or, the sidewall is a permeable or impermeable structure.
8. A method for continuous preparation of porous filter membranes using the apparatus described in claim 1, characterized in that, The casting liquid is applied to the continuously moving base film (2) in the horizontal direction using the coating head (1). The coated base film (2) enters the gel tank (7) in the vertical direction and is turned by the bottom roller (5) so that the base film (2) continues to move at an angle greater than 0° with the direction of entry. The casting liquid that is not coated on the base film (2) drips into the gel tank (7) and the solid particles formed after phase transformation are received by the receiving tray (4).
9. The method according to claim 8, characterized in that, The solid particles are removed when there is a possibility of overflow of solid particles in the receiving tray (4) or when the coagulation bath liquid in the gel tank (7) is discharged.
10. The method according to claim 8, characterized in that, The porous filter membrane is one of the following: microfiltration membrane, ultrafiltration membrane, nanofiltration membrane, reverse osmosis membrane, forward osmosis membrane, gas separation membrane, and pervaporation membrane.