A vertical flow filter element and method of making the same

Abstract

The application relates to the technical field of filtering devices, in particular to a vertical flow filtering element and a preparation method thereof. The vertical flow filtering element comprises a liquid inlet guide screen, a filtrate guide screen and a filtering layer. A first adhesive layer is arranged between the liquid inlet surface of the filtering layer and the liquid inlet guide screen. The first adhesive layer is a thermosetting glue, the viscosity of which is not less than 10000 cps at room temperature, and at least one temperature point exists in the range of 45 DEG C to 150 DEG C, so that the viscosity of the first adhesive layer is not higher than 1000 cps. The scheme can improve the adhesive performance between the liquid inlet guide screen and the filtering layer, so that the membrane can better maintain the integrity and filtering performance of the membrane in the processes of preparation, processing, use and storage.

Description

Technical Field

[0001] This application relates to the field of filtration device technology, specifically to a vertical flow filter element and its preparation method. Background Technology

[0002] In the biomedical field, filtration devices are needed to separate products in order to extract compounds of specific molecular weights. Membrane separation methods include radial flow filtration and vertical flow filtration. Vertical flow filtration refers to a filtration method where the liquid flow direction is perpendicular to the filtration direction. It utilizes the shear force generated on the surface of the filter medium by the liquid flow, causing the liquid to pass through the filter medium as it flows along the flow path. Simultaneously, the flowing liquid can further carry large molecules that were previously blocked by the filter medium forward, thus separating the filtrate (containing the large molecules) and the concentrate.

[0003] A membrane cartridge is a commonly used filter element in vertical flow filtration. Its typical structure includes a filtrate unit and an inlet unit stacked sequentially, along with a housing to secure the structure. The filtrate unit comprises a filter layer-channel-filter layer structure, while the inlet unit is a screen with channels. When the liquid to be filtered flows through the screen, shear force forces the liquid through the filter layers, thus retaining large molecules within the screen, achieving separation and concentration.

[0004] The filter layer plays a crucial role in the separation process described above. Among various filter layer materials, cellulose materials are widely used in many applications due to their excellent hydrophilicity. In existing technologies, cellulose membranes are often encapsulated with silicone rubber, which bonds the cellulose membrane and the screen together. However, in practical applications, silicone rubber has poor adhesion to the cellulose membrane, easily leading to processing defects during the manufacturing of the filter assembly, thus affecting the quality and yield of the filter assembly. Summary of the Invention

[0005] In order to improve the yield rate of membrane pack processing and to better maintain the integrity and filtration performance of the membrane pack during preparation, processing, use and storage, this application provides a vertical flow filter element and its processing method.

[0006] The vertical flow filter element has at least one inlet end and at least one outlet end, and specifically includes the following components:

[0007] A liquid inlet guiding screen, wherein the liquid inlet guiding screen has at least one first liquid inlet hole and at least one first filter hole;

[0008] A filtrate guiding screen, wherein the filtrate guiding screen has at least one second inlet hole and at least one second filtrate hole;

[0009] The filter layer has an inlet surface and an outlet surface;

[0010] The inlet guide screen and the filtrate guide screen are stacked alternately, and there is a filter layer between adjacent inlet guide screens and filtrate guide screens; the inlet surface of the filter layer faces the adjacent inlet guide screen, the outlet surface of the filter layer faces the adjacent filtrate guide screen, an inlet flow channel is formed between the inlet surfaces of two adjacent filter layers, and a filtrate flow channel is formed between the outlet surfaces of two adjacent filter layers.

[0011] A first adhesive layer is provided between the filter layer and the inlet guide screen to seal and isolate the first filtrate hole and the filtrate flow channel. The inlet surface of the filter layer has an average SEM pore size of not less than 200 nm, specifically, it can have an average pore size of 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 800 nm, 10000 nm, 1200 nm, 1500 nm, or 2000 nm. The first adhesive layer is a thermosetting adhesive with a thermosetting temperature of not more than 150 °C. The adhesion of the first adhesive layer at room temperature is not less than 10000 cps, and when the first adhesive layer is heated to within the range of 45 °C to 150 °C, there is at least one temperature point where the adhesion of the first adhesive layer is not more than 1000 cps.

[0012] Thermosetting adhesives refer to polymeric resin systems that can undergo internal physical or chemical reactions under heating, resulting in irreversible curing. They can be selected from epoxy resins, polyurethanes, phenolic resins, urea-formaldehyde resins, furan resins, or other resins with heat-curing properties. Thermosetting temperature refers to the lowest temperature at which a thermosetting adhesive can undergo a curing reaction. At this temperature, most thermosetting resins can undergo cross-linking reactions under the action of a curing agent to form a cured system, thereby losing their fluidity.

[0013] The first adhesive layer, made of thermosetting adhesive, exhibits increased fluidity with rising temperature. During application, it adheres to the surface of the liquid inlet guide screen. Due to the large pore size of the screen, the first adhesive layer can penetrate into the screen even at low temperatures. In this application, the viscosity of the first adhesive layer at room temperature is specified to be no less than 10,000 cps. Within this viscosity range, the first adhesive layer can spread relatively evenly within the liquid inlet guide screen, achieving good sealing and bonding effects. If a first adhesive layer with excessively low viscosity is used, it cannot solidify on the liquid inlet guide screen, resulting in poor integrity of the prepared filter element. After the liquid inlet guide screen and filter layer are combined, the first adhesive layer is then heated. As the viscosity of the first adhesive layer decreases, it can penetrate into the filter layer through the pores on its surface.

[0014] In this application, because the filter layer itself has two sides with different pore sizes, and generally, since the liquid flows from the inlet guide screen to the filtrate guide screen, the inlet side of the filter layer usually has larger pores than the outlet side. This arrangement can improve the filtration effect, reduce filter cake accumulation, and increase the membrane packing capacity. For the above considerations, an adhesive layer needs to be placed between the inlet guide screen and the filter layer to allow the thermosetting adhesive to penetrate into the filter layer, at least to the surface of the filter layer, thereby achieving fixation and sealing.

[0015] During the above process, the heating temperature should not exceed 150℃. Excessively high temperatures will reduce the permeability of the filter membrane, thereby affecting the filtration effect. Generally, the first adhesive layer with a viscosity below 1000 cps can smoothly penetrate into the pores of the inlet surface of the filter layer under additional negative pressure. After curing, it can bond the filter layer and the inlet guide screen together. On the one hand, the supporting effect of the inlet guide screen improves the mechanical strength of the filter layer itself, making it less prone to damage during preparation. On the other hand, it also reduces the loss and breakage of materials in the process.

[0016] Preferably, the first adhesive layer has at least one temperature point in the range of 60 to 120°C such that the viscosity of the first adhesive layer is between 100 and 1000 cps.

[0017] During the heating and penetration of the thermosetting adhesive into the pores of the filter layer, the adhesive penetrates from the inlet to the outlet of the filter layer perpendicular to its plane, and also diffuses outwards along the plane of the filter layer. In actual production, applying negative pressure to the outlet of the filter layer can enhance the penetration of the thermosetting adhesive into the filter layer. In the above technical solution, a viscosity range of 100–1000 cps is selected, while the temperature is limited to 60–120°C. This chosen application temperature range has minimal impact on the properties of the filter layer itself, and the thermosetting adhesive within this viscosity range has appropriate fluidity, preventing excessive coverage of the filter layer due to excessive fluidity.

[0018] For filter layers with different properties, the optimal thermosetting adhesive will also have different properties. Therefore, based on the above scheme, the adhesive layer has at least one temperature in the range of 60 to 120°C, and its viscosity and the pore area ratio of the filter layer inlet face satisfy the following relationship: y = k1 / ln(2-x), where y is the viscosity of the first adhesive layer at the thermosetting temperature, x is the pore area ratio of the filter layer facing the inlet guide screen, and k1 is a constant with a range of 75 to 300 cps.

[0019] In a more preferred case, when k1 is preferably in the range of 100 to 250 cps, and the thermosetting adhesive used for the first adhesive layer is epoxy resin, the film coating has better integrity.

[0020] Preferably, the filter layer has a pore area ratio ranging from 30% to 60% on the side facing the liquid inlet guide screen.

[0021] When thermosetting adhesives are heated, their fluidity increases and their viscosity decreases as the temperature rises before they cure. In a filter layer, the larger the surface pore area ratio of the filter layer, the easier it is for the adhesive to penetrate into the filter layer. The pore area ratio of the filter layer is positively correlated with the minimum viscosity of the thermosetting adhesive.

[0022] After conducting numerous experiments, the applicant discovered that the above formula can better fit the parameters of the experimental results. For filter layers with a larger pore area ratio, the viscosity range of the first adhesive layer that it can accommodate is larger. The formula designed above can be used to calculate the thermosetting adhesive most suitable for the system using the pore area ratio of the filter layer.

[0023] Preferably, the relevant parameters of the liquid inlet guide screen and the viscosity of the thermosetting adhesive at room temperature have the following relationship: y2 = k2d / l, where d is the diameter of a single filament of the liquid inlet guide screen, l is the average distance between two adjacent filaments in the same direction in the liquid inlet guide screen, and k2 is a parameter with a range of 25000 to 150000 cps.

[0024] Thermosetting adhesive needs to be applied to the surface of the inlet guide screen first, and then bonded to the filter layer through methods such as heat melting. Therefore, in addition to being related to the properties of the filter layer, the properties of the thermosetting adhesive are also related to the properties of the inlet guide screen because it needs to be applied to the screen at room temperature. The ratio between the diameter of a single filament of the inlet guide screen and the average distance between two adjacent filaments actually measures the density of the fibers on the surface of the inlet guide screen. When using a sparser inlet guide screen, a thermosetting adhesive with a higher viscosity at room temperature can be used. High-viscosity thermosetting adhesive does not easily spread rapidly along the plane of the inlet guide screen, thus potentially increasing the filtration area of ​​the inlet guide screen and the filter layer. At the same time, the spreading state of the adhesive within the inlet guide screen also helps to improve the sealing and integrity of the membrane package.

[0025] Preferably, the diameter of the single filament of the liquid inlet guide screen is in the range of 50 to 500 μm.

[0026] Preferably, the average distance between two adjacent wires in the same direction in the liquid inlet guide screen is in the range of 50 to 500 μm.

[0027] Preferably, the liquid inlet guide screen has a pore size of 200-800 μm.

[0028] Preferably, the liquid inlet guide screen has a porosity of 25-50%.

[0029] Experiments have shown that the liquid inlet guide screen within the above range is more suitable for bonding with thermosetting adhesives, and has a good limiting effect on the adhesion and diffusion ability of thermosetting adhesives.

[0030] Preferably, a first isolation layer is provided between the filter layer and the liquid inlet guide screen, and the thermosetting adhesive passes through the first isolation layer.

[0031] The first isolation layer serves to support the flow channel, increase the strength of the filter layer, and enhance adhesion. This isolation layer can be made from materials such as non-woven fabric. By adjusting the flow channel through the support layer, viruses, antibodies, or other large protein molecules can pass through, thereby reducing material loss. Furthermore, using the isolation layer and the adhesive layer that permeates it to fix the filter layer helps maintain its flatness, reducing deformation and damage.

[0032] In the above scheme, the first adhesive layer can directly penetrate through the first isolation layer, or a clearance space can be created in the first isolation layer to allow the first adhesive layer to pass through. Since the pore size of the first isolation layer is generally not lower than the surface pore size of the filter layer, it will not hinder the penetration of thermosetting adhesives. On the contrary, the strength of the first isolation layer can provide support for the filter layer.

[0033] The first isolation layer has a hollow area, and the projected area of ​​the hollow area on the plane of the liquid inlet guide screen accounts for 40-95% of the effective area of ​​the liquid inlet guide screen.

[0034] Preferably, the thickness of the first isolation layer is 0.1 to 1 mm.

[0035] In the above technical solution, the effective area refers to the area through which liquid flows through the inlet channel during the filtration process and permeates into the filter layer on one or both sides. After adding the support layer, it is essentially located within the inlet channel. Although the support layer is typically made of materials with large pores, such as non-woven fabric, to reduce its impact on liquid flow, this impact still exists. Designing a perforated area in the support layer can help reduce resistance during the liquid inlet process and improve the filtration effect.

[0036] This application also designs a method for fabricating the above-mentioned vertical flow filter element, including the following steps:

[0037] S1 combines the liquid inlet guide screen with the filter layer directly or indirectly;

[0038] S2 applies thermosetting adhesive to the first inlet hole of the liquid inlet guide screen, and uses negative pressure to force the thermosetting adhesive into the liquid inlet guide screen and diffuse it into the filter membrane;

[0039] S3 heats the thermosetting adhesive, causing it to penetrate the filter layer and cure.

[0040] S4 alternately stacks the composite system of filter layer-inlet guide screen-filter layer with filtrate guide screen, and packages and fixes the above combination through the shell to form a vertical flow filter element.

[0041] Preferably, in step S3, while heating, opposing pressures are applied to the liquid inlet guide screen and the filter layer to make them directly or indirectly adhere together.

[0042] Thermosetting adhesive penetrates from the inlet screen side to the inlet surface of the filter layer. Heating and negative pressure enhance the adhesive's flowability and hydrodynamics. A certain degree of negative pressure or pressure perpendicular to the filter layer allows the liquid to penetrate the filter layer surface without significantly affecting its filtration efficiency. Under heating, the viscosity of the first adhesive layer decreases, effectively sealing the gap between the filter layer and the inlet screen, achieving excellent sealing. Furthermore, the thermosetting adhesive exhibits excellent anti-peeling properties after thermosetting.

[0043] During the preparation process, filter layers need to be installed on both sides of the liquid inlet guide screen to form a composite system of filter layer-liquid inlet guide screen-filter layer. The filter layer and the liquid inlet guide screen can be directly attached, or a support layer can be set in the middle to adjust the flow channel and fixation method.

[0044] After curing, the composite system of the filter layer and the liquid inlet guiding screen is then bonded to the filtrate guiding screen. The filter layer and the filtrate guiding screen can be connected by an elastic system located on the surface of the filtrate guiding screen. This connection can be achieved by elastic compression sealing or by using an adhesive system with a certain degree of viscosity for auxiliary bonding.

[0045] The vertical flow filter element prepared by the above process has good integrity, sealing performance and filtration effect.

[0046] In summary, this application aims to provide a membrane package structure with a cellulose-based filter layer. The membrane package uses a thermosetting adhesive with low flowability at high temperatures and high flowability at low temperatures to bond the inlet surface of the filter layer and the inlet guide screen. This allows the thermosetting adhesive to penetrate well into the filter layer, thereby achieving bonding and sealing. The overall structure is stable and has good sealing performance, which has an excellent positive impact on improving the performance and yield of the membrane package. Attached Figure Description

[0047] Figure 1 This is a 10,000x magnified SEM image of the cross-section of the filter layer in Example 1, with the upper side being the liquid inlet surface and the lower side being the liquid outlet surface.

[0048] Figure 2 This is a 1000x magnified SEM image of the inlet surface of the filter layer in Example 1;

[0049] Figure 3 This is a schematic diagram of the overall appearance of the filter element in Example 1;

[0050] Figure 4 This is a schematic diagram of the structure of the liquid inlet guide screen, filter layer, and filtrate guide screen in Example 1.

[0051] In the figure, 1 is the liquid inlet guide screen; 11 is the first liquid inlet hole; 12 is the first filtrate hole; 2 is the filtrate guide screen; 21 is the second liquid inlet hole; 22 is the second filtrate hole; 3 is the filter layer; 33 is the third liquid inlet hole; 34 is the third filtrate hole; 4 is the first support layer; 41 is the hollow area; 5 is the first adhesive layer; 6 is the second support layer; and 7 is the second adhesive layer. Detailed Implementation

[0052] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0054] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0055] In the following embodiments, the SEM average pore size of the inlet or outlet surface of the filter layer, or the SEM average pore size of the cross-section, can be obtained by characterizing the membrane structure using a scanning electron microscope, followed by measurement using computer software (such as Matlab, NIS-Elements, etc.) or manual measurement, and then performing corresponding calculations. In actual measurement, the membrane surface can be characterized first using an electron microscope to obtain the corresponding SEM image. Since the pores on the membrane surface are roughly uniform, a certain area can be selected, for example, 1 μm. 2 (1μm x 1μm) or 25μm 2 (5μm by 5μm), the specific area size depends on the actual situation. Then, use appropriate computer software or manual measurement to determine the diameter of all holes on the area, and then calculate to obtain the average diameter of the holes on the surface. Of course, those skilled in the art can also obtain the above parameters through other measurement methods. The above measurement methods are for reference only.

[0056] In the following embodiments, the adhesion between the filter layer and the inlet guide screen can be characterized by the following method: After bonding the filter layer and the inlet guide screen, at room temperature, the filter layer and the edge of the first adhesive layer are held together by rubber-tipped tweezers. The filter layer is then pulled away from the inlet guide screen in a direction perpendicular to the filter layer until they separate or the filter layer completely breaks, leaving only the portion with no raised edges. Generally, since the cohesive force of the filter layer is usually less than the adhesive force between the filter layer and the screen during normal bonding, the area of ​​the remaining portion can be used to measure the tightness of the adhesion between the filter layer and the inlet guide screen.

[0057] The viscosities of the first and second adhesive layers were measured using a coaxial double-cylinder rotational viscometer.

[0058] The roughness of the filter layer was measured using a commercially available roughness tester.

[0059] The integrity experiment was conducted using an air diffusion flow test, and the specific experimental method is as follows:

[0060] The prepared filter element was wetted with water, and the inlet end of the element was connected to compressed air. A pressure of 0.1 MPa was applied to the inlet end, and then the air flow rate was measured at the outlet end to evaluate the integrity. The lower the air flow rate, the better the integrity of the membrane envelope.

[0061] In the following embodiments, the filter elements are all fabricated with a membrane area of ​​0.46 m². 2 For filter membrane packs, a gas flow rate of less than or equal to 50 mL / min at the liquid outlet is considered a qualified product. The lower the gas flow rate, the better the integrity.

[0062] Example 1, a vertical flow filter element, refer to Figures 1-4It can be used alone or in combination. Its overall shape is a rectangular membrane package, and it includes the following components:

[0063] Liquid inlet guide screen 1: The liquid inlet guide screen 1 is rectangular, with a first liquid inlet hole 11 and a first liquid filter hole 12 on its two opposite sides. The first liquid inlet hole 11 and the first liquid filter hole 12 are alternately arranged on the same side of the liquid inlet guide screen 1. Generally, the diameter of the first liquid inlet hole 11 is larger than the diameter of the first liquid filter hole 12.

[0064] The filtrate guiding screen 2 is rectangular, and its two opposite sides are provided with a second liquid inlet 21 and a second filtrate hole 22. The first liquid inlet 11 and the second liquid inlet 21 are aligned in a direction perpendicular to the plane where the liquid guiding screen 1 and the filtrate guiding screen 2 are located to form the liquid inlet end of the filter element.

[0065] The inlet guide screen 1 and the filtrate guide screen 2 have the following parameters:

[0066]

[0067] A filter layer 3 is provided between any two adjacent inlet guide screens 1 and filtrate guide screens 2. The filter layer 3 has an inlet surface and an outlet surface, with the inlet surface facing the inlet guide screen 1 and the outlet surface facing the filtrate guide screen 2. An inlet flow channel is formed between the inlet surfaces of adjacent filter layers 3, and a filtrate flow channel is formed between the outlet surfaces of adjacent filter layers 3. The filter layer 3 has a third inlet hole 33 aligned with the first inlet hole 11 and the second inlet hole 21, and a third filtrate hole 34 aligned with the first filtrate hole 12 and the second filtrate hole 22.

[0068] In this embodiment, the filter layer is a single-layer renewable cellulose filter membrane, which can be prepared according to CN115770490A. The prepared filter membrane is as follows: Figure 1 As shown, it has the following parameters:

[0069] Thickness 43.1μm

[0070] The surface roughness at the liquid inlet is 0.29 nm.

[0071] The perforation area of ​​the inlet cavity is 47%.

[0072] PMI aperture 20.1nm

[0073] In this embodiment, a first support layer 4 is provided between the liquid inlet guide screen 1 and the liquid inlet surface of the filter layer 3. The first support layer 4 is a non-woven fabric structure, and a first through hole aligned and connected with the first liquid inlet hole 11 and the second liquid inlet hole 21 and a second through hole aligned and connected with the first filtrate hole 12 and the second filtrate hole 22 are provided on it.

[0074] A first adhesive layer 5 is also provided between the liquid inlet guide screen 1 and the filter layer 3. In this embodiment, the first adhesive layer 5 is made of epoxy resin, which can pass through the first support layer 4 and seal and isolate the first filtrate hole 12 and the filtrate flow channel.

[0075] A second support layer 6 is provided between the filter layer 3 and the filtrate guiding screen 2. The first support layer and the second support layer 6 are non-woven fabrics. A hollow area 41 is provided in the middle of the first support layer 4. The hollow area 41 accounts for 90% of the area of ​​the first support layer 4 and is used to improve the filtration effect.

[0076] A second adhesive layer 7 is also provided between the filter layer 3 and the filtrate guiding screen 2. In this embodiment, the second adhesive layer 7 is made of silicone with a viscosity of 20,000 cps. It can pass through the second support layer 6 and seal and isolate the second liquid inlet hole 21 and the liquid inlet channel.

[0077] The method for fabricating the vertical flow filter element in this embodiment includes the following steps:

[0078] S1. Lay out the liquid inlet guide screen;

[0079] S2. Lay the first support layer and filter layer on the liquid inlet guide screen on which the first adhesive layer has been laid, so that the third liquid inlet hole is aligned with the first liquid inlet hole and the third filter hole is aligned with the first filter hole. Apply thermosetting adhesive to the first filter hole and apply negative pressure at the position of the first liquid inlet hole to allow the adhesive to penetrate the liquid inlet guide screen.

[0080] S3. The above system is heated to 60°C, so that the adhesive solution permeates through the first support layer and into the inlet surface of the filter layer along the inlet guide screen, and diffuses outward around the first inlet hole, thereby forming an adhesive ring sealing around the first inlet hole; then the temperature is maintained to cure the first adhesive layer for 24 hours, and the inlet unit is obtained after curing; during the above process, a certain pressure is applied along the thickness direction to press it tightly.

[0081] S4. Lay a second support layer on the filtrate guiding screen and lay a second adhesive layer around the second inlet hole. Then, stack the second support layer with the inlet unit alternately and form an elastic sealing structure by compression.

[0082] In this embodiment, after the membrane pack is mounted on a specific fixture, the stock solution enters a first inlet port through the inlet end and then enters the inlet channel through the first inlet port. During the flow of the liquid in the inlet channel, it will discharge the storage liquid or gas inside the membrane pack through other inlets, producing... Figures 3-4 The reflux liquid shown in the diagram is then sealed at the inlet end where no liquid has entered. The liquid then passes through the filter membrane into the filtrate channel and is discharged through the outlet end to obtain the filtrate. During this process, the virus is trapped by the filter membrane, thereby achieving the virus removal effect of the membrane package.

[0083] In this embodiment, the viscosity of the first adhesive layer at room temperature is 240 cps. During the heating process in step S3, after heating to 60°C, the viscosity of the first adhesive layer was measured to be 23261 cps (average of three measurements).

[0084] In this embodiment and subsequent embodiments, the pore shape of the filter membrane inlet surface is irregular and the depth regions are not obvious, so it is difficult to accurately measure the average pore size. However, it can be clearly seen that the pore size on the surface is significantly greater than 500 nm.

[0085] Example 2: Based on Example 1, different first adhesive layer materials are used for different filter layers, and the parameters shown in Table 2 can be obtained.

[0086] Table 2

[0087]

[0088]

[0089] In this embodiment, the thermosetting adhesives are all epoxy resins, and their properties vary depending on the different substituent groups and molecular weights. For example, using a monomer with a larger conjugated system (such as a biphenyl structure or a fused ring structure) as the intermediate monomer of the epoxy resin can increase the thermosetting temperature of the first adhesive layer, and increasing the molecular weight of the epoxy resin can increase the viscosity of the epoxy resin, etc.

[0090] For adjusting the parameters of the filter layer, refer to CN115770490A to form filter membranes with different inlet porosity and surface roughness.

[0091] In Examples 1 and 2, the values ​​of k1 calculated according to the formula y = k1 / ln(2-x) and their corresponding experimental results are shown in Table 3. Here, y is the viscosity of the first adhesive layer at the thermosetting temperature, and x is the pore area ratio of the filter layer facing the liquid inlet guide screen.

[0092] Table 3

[0093]

[0094] Example 3: Based on Example 1, different first adhesive layers were further adjusted, as shown in Table 4.

[0095] Table 4

[0096]

[0097]

[0098] The value of k1 is calculated according to the formula y = k1 / ln(2-x).

[0099] The value of k2 is calculated according to the formula y2=k2d / l. Where d is the diameter of a single filament of the liquid inlet guide screen, l is the average distance between two adjacent filaments in the same direction in the liquid inlet guide screen, and y2 is the viscosity of the first adhesive layer at room temperature.

[0100] The values ​​of k1 and k2 and related experimental results are shown in Table 5.

[0101] Table 5

[0102]

[0103] Example 4: Based on Example 1, a double-layer membrane structure is selected for the filter layer, and the parameters of the filter layer are shown in Table 6.

[0104] Table 6

[0105]

[0106] For Example 4, the k1 value and related experimental results are shown in Table 7.

[0107] Table 7

[0108]

[0109] Based on the experimental data from Examples 1-4, it can be seen that, in general, the first adhesive layer needs to have a viscosity of less than 1000 cps at the thermosetting temperature to successfully bond to the filter membrane. The bonding performance is similar for both single-layer and multi-layer filter membranes; however, when the viscosity exceeds 1000 cps at the curing temperature, the adhesion between the adhesive and the filter layer is poor. This not only affects the bonding ability between the filter membrane and the screen but also adversely impacts the integrity of the membrane package.

[0110] Regarding the viscosity of the first adhesive layer at the thermosetting temperature, referring to the formula y = k1 / ln(2-x), it can be seen that when the k1 parameter is selected in the range of 75-300 cps, it has better bonding and sealing effects compared to values ​​outside this range. If the viscosity is too low (Examples 3-8), the first adhesive layer will spread too widely along the plane during construction, affecting the filtration area of ​​the membrane pack. If the viscosity is too high (Examples 3-2, 3-4, etc.), the adhesion will be insufficient to fully bond the filter layer and the inlet guide screen, thus reducing the integrity of the membrane pack. Furthermore, based on the above, when the k1 value is in the range of 100-250 cps, the integrity of the membrane pack is better than other solutions, making it a more preferred technical solution.

[0111] Example 5: Based on Example 1, a different screen is used. The specific parameters of the liquid inlet guide screen are shown in Table 8.

[0112] Table 8

[0113]

[0114] In the corresponding embodiment 5, the calculated k2 value and the spreading of the first adhesive layer are shown in Table 9.

[0115] Table 9

[0116]

[0117] The viscosity of the first adhesive layer at room temperature can be calculated using the formula y2 = k2d / l to obtain an applicable range, with k2 preferably ranging from 25,000 to 150,000 cps. If the viscosity is too high, it will spread too slowly on the inlet guide screen, easily forming uneven areas on the surface of the first adhesive layer, thus affecting the integrity of the membrane coating. Conversely, if the viscosity is too low, the first adhesive layer will spread over an excessively large area on the inlet guide screen, making it difficult to bond with the filter layer and reducing the effective filtration area.

[0118] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A vertical flow filtration element, comprising the following components: a feed flow guide screen having at least one first feed flow hole and at least one first filtrate flow hole; a filtrate flow guide screen having at least one second feed flow hole and at least one second filtrate flow hole; a filter layer disposed between the feed flow guide screen and the filtrate flow guide screen, the filter layer having a feed flow surface and a filtrate flow surface; the feed flow guide screen and the filtrate flow guide screen are alternately stacked, and each has a filter layer between adjacent feed flow guide screen and filtrate flow guide screen; the feed flow surface of the filter layer faces the adjacent feed flow guide screen, and the filtrate flow surface of the filter layer faces the adjacent filtrate flow guide screen; the feed flow channel is formed between the feed flow surfaces of adjacent filter layers, and the filtrate flow channel is formed between the filtrate flow surfaces of adjacent filter layers; characterized in that: a first adhesive layer is provided between the filter layer and the feed flow guide screen, for sealing and isolating the first filtrate flow hole and the filtrate flow channel, and the feed flow surface of the filter layer has a SEM average pore size of no less than 200 nm; the first adhesive layer is a thermosetting adhesive having a thermosetting temperature of no higher than 150°C; the viscosity of the first adhesive layer at room temperature is no less than 10,000 cps, and the first adhesive layer has at least one temperature point within the range of 45°C to 150°C, at which the viscosity of the first adhesive layer is no higher than 1,000 cps, and the first adhesive layer has at least one temperature point within the range of 60°C to 120°C, at which the viscosity of the first adhesive layer is within the range of 100 cps to 1,000 cps; the first adhesive layer has at least one temperature within the range of 60°C to 120°C, at which the viscosity of the first adhesive layer and the filter layer pore area ratio on the side facing the feed flow guide screen satisfy the following relationship: y=k1 / ln(2-x), wherein y is the viscosity of the first adhesive layer at the thermosetting temperature, x is the pore area ratio of the filter layer on the side facing the feed flow guide screen, and k1 is a constant within the range of 75 to 300 cps.

2. A vertical flow filter element according to claim 1, wherein the filter layer has a pore area ratio on the side facing the feed flow guide screen within the range of 30% to 60%.

3. A vertical flow filter element according to claim 1, wherein the filter layer has a surface tension on the side of the feed flow surface within the range of 50 to 80 mN / m.

4. A vertical flow filter element according to claim 1, wherein the filter layer has a roughness on the side of the filtrate flow surface within the range of 0.1 to 0.5 μm.

5. A vertical flow filter element according to claim 1 wherein, the feed flow guide screen has the following relationship between the relevant parameters and the viscosity of the first adhesive layer at room temperature: y2=k2d / l, wherein y2 is the viscosity of the first adhesive layer at room temperature, d is the diameter of the monofilament of the feed flow guide screen, l is the average distance between two adjacent monofilaments of the feed flow guide screen, and k2 is a parameter within the range of 25,000 to 150,000 cps.

6. A vertical flow filter element according to claim 5, wherein, the diameter of the monofilament of the feed flow guide screen is within the range of 50 to 500 μm.

7. A vertical flow filter element according to claim 5 wherein, the average distance between two adjacent monofilaments of the feed flow guide screen is within the range of 50 to 500 μm.

8. A vertical flow filter element according to claim 5 wherein, the feed flow guide screen has a pore size within the range of 200 to 800 μm.

9. A vertical flow filter element according to claim 5 wherein, the feed flow guide screen has a porosity within the range of 25% to 50%.

10. A vertical flow filter element according to claim 1 wherein, a first isolation layer is provided between the filter layer and the feed flow guide screen, and the thermosetting adhesive penetrates the first isolation layer.

11. A vertical flow filter element according to claim 10, wherein, The first isolation layer has a hollowed-out area, and a projection area of the hollowed-out area on a plane of the liquid inlet flow guide screen accounts for 40-95% of an effective area of the liquid inlet flow guide screen.

12. A vertical flow filter element according to claim 10 wherein, The first isolation layer has a thickness of 0.1-1 mm.

13. A vertical flow filter element according to claim 1 wherein, The filter layer is a cellulose filter layer.

14. The method of making a vertical flow filter element according to any one of claims 1 to 13, characterized in that, At least comprising the following steps: S1, directly or indirectly combining the liquid inlet flow guide screen with the filter layer; S2, attaching the thermosetting glue to the first liquid inlet hole position on the liquid inlet flow guide screen, making the thermosetting glue enter the liquid inlet flow guide screen and diffuse to the filter membrane through negative pressure; S3, heating the thermosetting glue to make the thermosetting glue permeate the filter layer and solidify; S4, alternately stacking the filter layer-liquid inlet flow guide screen-filter layer composite system with the filtrate flow guide screen, and packaging and fixing the above combination through a shell to form a vertical flow filter element.

15. The method of making a vertical flow filter element according to claim 14, wherein, In step S3, while heating, opposite pressure is applied to the liquid inlet flow guide screen and the filter layer to make them directly or indirectly adhere to each other.

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