A large-mesh high-strength water inlet grid and its preparation method

Abstract

The present invention belongs to the technical field of water treatment, and specifically relates to a large-mesh high-strength inlet grid and a preparation method thereof. A large-mesh high-strength inlet grid, a preparation method of the inlet grid: weigh raw materials, the raw materials include a base resin and additives, and the additives include at least one of a lubricant, an antioxidant, a nucleating agent, and a filler; add the weighed raw materials into an extruder, and the extruder melts, mixes, and heats, and then extrudes and forms: after the materials are fully melted and mixed evenly, they pass through a specially designed large-mesh rotating die head and are integrally formed into a grid product, and then through the cooling and winding processes to obtain the inlet grid; wherein, the specific parameters for integrally forming the grid product through the specially designed large-mesh rotating die head include: thickness: 20-50 mil; angle: 30-150°; mesh area: 10-50 mm 2 . The grid of the present application can meet the winding process of the existing spiral wound membrane element, and the grid has the characteristics of low pressure drop, high strength, and high filtration efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, and particularly relates to a large-mesh high-strength inlet grid and a preparation method thereof. Background Art

[0002] As a support material, the inlet grid is widely used in the field of water treatment filtration. In spiral components such as reverse osmosis (RO) and nanofiltration (NF), or planar filtration components such as electrodialysis deionization (EDI), the inlet grid separates the filter membranes to create a raw water channel, and at the same time affects the state of raw water flow for cross-flow filtration.

[0003] In cross-flow filtration, the configuration and surface properties of the inlet grid will affect the performance of the component, such as flux, desalination rate, etc. In the actual operation of pressure-driven membrane components, as the raw water channel, the inlet grid will cause pressure loss due to the steric effect while improving the flow state on the membrane surface. Usually, the difference between the raw water inlet pressure and the concentrated water pressure at the end of the component is called the pressure drop.

[0004] In practical applications, the size of the membrane component is fixed. In water treatment applications, the 8040 membrane element is the mainstream, that is, the diameter of the membrane element is 203.2 mm (80 / 10 inch), and the length is 1016 mm (40 inch). The raw materials for forming the membrane element mainly include filter membranes, inlet grids, and product water grids. The three are sealed under the action of an adhesive to form a basic unit; at a fixed membrane element diameter, different numbers of membrane sheet units need to be encapsulated.

[0005] Generally, the thickness range of the inlet grid used in industrial application membrane elements is 20 - 40 mil. An inlet grid that is too thin cannot provide enough raw water channels, has a large pressure drop, and is prone to fouling; an inlet grid that is too thick has a low effective area of the rolled membrane sheets and limited water production flux. Traditional inlet grids have small mesh holes and a dense design of the warp and weft nodes, which can provide excellent support, but often bring additional raw water resistance, large energy loss, and low net driving force for water production, resulting in high overall energy consumption and operating cost of the membrane element and the membrane system. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the present invention provides a large-mesh high-strength inlet grid and a method for preparing the inlet grid. Further, on the basis of this method, a variety of deformation methods are also provided.

[0007] The technical solution of the present invention is as follows:

[0008] A large-mesh high-strength inlet grid is prepared by the following steps:

[0009] Weigh the raw materials, which include a base resin and additives. The additives include at least one of a lubricant, an antioxidant, a nucleating agent, and a filler.

[0010] Add the weighed raw materials into an extruder. The extruder melts, mixes, and heats them, and then extrudes and forms them: After the materials are fully melted and mixed evenly, they pass through a specially designed rotating die head with large mesh holes and are integrally formed into a grid product. Then, through the cooling and winding processes, an intake grid is obtained.

[0011] Among them, the specific parameters for integrally forming into a grid product through the specially designed rotating die head with large mesh holes include:

[0012] Thickness: 20 - 50 mil; Angle: 30 - 150°; Mesh area: 10 - 50 mm 2 ；

[0013] In multiple embodiments, the temperature for melting, mixing, and heating in the extruder is controlled at 200 - 300 °C.

[0014] Regarding the raw materials: Further, by weight, the base resin is 80 - 110 parts; the lubricant is 0 - 0.5 parts; the antioxidant is 0.1 - 0.5 parts; the nucleating agent is 0 - 5.0 parts; the filler is 0 - 10 parts.

[0015] Further, the base resin includes at least one of PP resin, HDPE resin, PVDF, PFA, and PEEK. The lubricant includes PE wax. The antioxidant includes hindered phenol antioxidants. The filler includes at least one of talcum powder, boron nitride nanosheets, and short cut fibers.

[0016] Further, the raw materials also include a silane coupling agent. The antioxidant includes at least one of antioxidant 1010 and antioxidant 168.

[0017] Regarding the preparation method: Further, when adding the weighed raw materials into the extruder, set different temperature sections of 260 - 320 °C, blend the base resin, and then add the remaining raw materials in the mixing stage. The extruder melts, mixes, and heats them, and then extrudes and forms them: After the materials are fully melted and mixed evenly, they pass through a specially designed rotating die head with large mesh holes and are integrally formed into a grid product. Then, through the cooling and winding processes, an intake grid is obtained.

[0018] Regarding the coating: Further, the preparation steps also include: After extrusion and forming, apply a coating on the surface of the intake grid: Use a plasma spraying device to spray the coating solution on the intake grid. After spraying, cure the intake grid at 100 - 150 °C for 20 - 60 min to obtain the finished grid.

[0019] Further, the coating solution includes at least one of PTFE, fluorinated solvents, promoters, NMP, FEP, and dispersants.

[0020] Further, the coating solution includes coating solution one and coating solution two.

[0021] Mix PTFE with a fluorinated solvent, stir evenly, add a promoter, and stir to obtain coating solution one.

[0022] Heat NMP to 150 - 180 °C, gradually add FEP, stir, add a promoter, then add a dispersant, stir, and slowly cool the uniformly mixed solution to room temperature at 80 - 100 °C while maintaining stirring to obtain coating solution two.

[0023] Further, after extrusion molding, apply a coating on the surface of the water inlet grid: Use a plasma spraying device to spray coating solution one on the water inlet grid. After spraying, cure the water inlet grid at 100 - 150 °C for 20 - 60 min to obtain a cured grid; Use a plasma spraying device to spray coating solution two on the cured grid. After spraying, cure the water inlet grid at 100 - 150 °C for 20 - 60 min to obtain the finished grid.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. Reduce pressure drop and improve fluidity: Although traditional small - mesh grids have strong support force, due to the small mesh area, the resistance of water flow through the grid is large, which easily generates a high pressure drop, resulting in large energy loss and affecting the water treatment efficiency. The large - mesh water inlet grid designed in the present invention has the mesh area increased to 10 - 50 mm² (the traditional mesh area < 10 mm²), significantly improving the smoothness of water flow, effectively reducing the pressure drop, increasing the net driving force and water production flux of the membrane element, and reducing the operating cost. For example, the water inlet grids prepared in Examples 1 - 6 significantly increase the thickness and mesh area, but show excellent performance in performance tests, with a significant decrease in pressure drop, while maintaining good stiffness and tensile breaking force, and can effectively withstand the winding of spiral membrane modules and high - pressure filtration conditions. In addition, the grid of the present application can meet the winding process of existing spiral - wound membrane elements, which has multiple difficulties, such as: how to balance parameters such as the mesh area and thickness of the grid; how to ensure that the grid has the advantages of low pressure drop, high strength, and high filtration efficiency while balancing multiple parameters of the grid; and comprehensive costs also need to be considered. For example, an increase in thickness will increase costs and may also affect fluidity.

[0026] 2. The present application also optimizes the formulation: The present invention uses a matrix formulated by blending multiple high-performance resins such as PP, HDPE, PVDF, PFA, and PEEK, combined with reinforcing fillers such as boron nitride nanosheets and short-cut fibers, to optimize the mechanical properties of the material, especially the stability under high temperature, high pressure, and corrosive environments. The synergistic effect between different polymers forms a good combination of mechanical properties. The reasonable combination of different materials and fillers forms a microstructure with high crystallinity, improving the overall performance of the material.

[0027] 3. The present invention introduces a polymer into the material and applies a PTFE and / or FEP coating on the material surface through plasma spraying technology, effectively preventing the penetration and erosion of chemical substances into the material matrix. The acid and alkali resistance and hydrolysis resistance are greatly improved.

[0028] 4. The grid prepared through the mesh design, material combination, and coating technology of the present invention exhibits excellent performance in multiple aspects such as mechanical strength, chemical corrosion resistance, heat resistance, biological pollution control, and water flow resistance. It can withstand high temperature, high pressure, and strong acid and alkali environments, can be used as a material for the support structure, and is also suitable for efficient filtration in various water treatment processes such as reverse osmosis (RO) and nanofiltration (NF). Especially for some industrial wastewater treatment conditions with high pollution and high corrosiveness, it can significantly improve the service life and operation efficiency of the equipment.

[0029] The more detailed principle is elaborated in detail in the specific implementation manners in combination with examples and comparative examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention and do not constitute a limitation to the present invention.

[0031] In the drawings:

[0032] Figure 1 is a 20-fold magnified high-definition microscope image of the grid of Comparative Example 1 of the present invention;

[0033] Figure 2 is a 20-fold magnified high-definition microscope image of the grid of Example 1 of the present invention;

[0034] Figure 3 is a 20-fold magnified high-definition microscope image of the grid of Example 2 of the present invention;

[0035] Figure 4 is a reference diagram of the pressure drop test equipment of the present invention. SPECIFIC IMPLEMENTATION MANNERS

[0036] To better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below with reference to the accompanying drawings and specific examples. The experimental methods used below are conventional methods unless otherwise specified, and the materials and reagents used are all commercially available unless otherwise specified.

[0037] (1) Preparation of large mesh and high-strength water inlet grid

[0038] Method 1:

[0039] This application provides a method for preparing a large-mesh, high-strength water inlet grid, the specific steps of which are as follows:

[0040] 1. Weigh the following raw materials: by weight: 80-110 parts base resin; 0.1-0.5 parts lubricant; 0.1-0.5 parts antioxidant; 0.1-5.0 parts nucleating agent; and 0-10 parts filler. Base resins include PP resin and HDPE resin.

[0041] 2. Add the weighed raw materials into the main material hopper of the extruder, control the melting and mixing heating temperature of the extruder at 200-300℃, and then extrude and shape: after the materials are fully melted and mixed, they pass through a specially designed large-mesh rotary die head to be integrally formed into a grid product, and then go through the cooling and winding process to complete the product preparation.

[0042] Among them, the specific parameters of the grid product formed into a one-piece by a specially designed large mesh rotary die are:

[0043] (1) The grid configuration, including thickness, angle, and mesh area, is of great significance to the pressure drop of the grid and membrane elements.

[0044] The grid configuration of this application:

[0045] Thickness: 20-50mil

[0046] Angle: 30-150°

[0047] Mesh area: 10-50mm 2

[0048] It should be noted that the mesh area of the traditional grid is less than 10mm 2 .

[0049] (2) Grid strength, including grid stiffness and tensile strength, is of great significance for membrane element rolling and high-pressure applications.

[0050] The grid stiffness of the present application is: 0.8-2.8 mN·m; the grid tensile breaking force is: 10-50N.

[0051] Among them, the special large-mesh rotating die head is independently designed and manufactured by Dexing Technology (Suzhou) Co., Ltd. The company number / model of the special large-mesh rotating die head is 3554-C-35, and it can be purchased through the number / model.

[0052] Specific examples and comparative examples are provided below:

[0053] Referring to Table 1, Examples 1-6 and Comparative Examples 1-2 were prepared. The preparation methods of Examples 1-6 refer to Method 1.

[0054] Preparation method of Comparative Example 1: Put the raw materials into the main feeding port of the single-screw extruder. The heating temperature of the extruder screw is set at 250 °C, and then extrusion molding is carried out: the melt passes through the traditional small-mesh rotating die head to form a grid product.

[0055] Preparation method of Comparative Example 2: Put the raw materials into the main feeding port of the single-screw extruder. The heating temperature of the extruder screw is set at 230 °C, and then extrusion molding is carried out: the melt passes through the traditional small-mesh rotating die head to form a grid product.

[0056] The specific parameters of the traditional small-mesh rotating die head are as follows:

[0057] (1) Grid configuration:

[0058] Thickness: 20-40 mil

[0059] Angle: 30-150°

[0060] Mesh area < 10 mm 2

[0061] (2) Grid strength:

[0062] Grid stiffness: 0.8-2.8 mN·m; Grid tensile breaking force: 10-20 N.

[0063] Among them, the traditional small-mesh rotating die head is independently designed and manufactured by Dexing Technology (Suzhou) Co., Ltd. The company number / model of the traditional small-mesh rotating die head is 3554-C-30, and it can be purchased through the number / model.

[0064] Table 1

[0065]

[0066] The manufacturer brands in Table 1 are as follows:

[0067] The manufacturer of PP resin is Formosa Plastics Corporation, Taiwan, China, and the brand is Yungsox 1040;

[0068] The manufacturer of HDPE resin is Shanghai Secco Petrochemical Co., Ltd., and the brand is HD 5502;

[0069] The manufacturer of the PE wax is Honeywell International Inc., and the grade is A-C8;

[0070] The manufacturer of the antioxidant is BASF China, and the grade is Irganox 1010;

[0071] The manufacturer of the nucleating agent is Dongguan Baoxu Chemical Technology Co., Ltd., and the grade is BX NA 900;

[0072] The manufacturer of the filler is Suzhou Youkuang Plastics New Materials Co., Ltd., and the grade is ML-30S400B.

[0073] Next, the products (grids) of Examples 1-6 and Comparative Examples 1-2 are tested, and the testing methods are as follows:

[0074] 1. Thickness test: Using a Mitutoyo thickness gauge, the average thickness of 20 different regions is tested as the grid thickness, with the unit of mil, that is, one thousandth of an inch;

[0075] 2. Angle test: Using a protractor, according to the machine direction of the grid, the values at 3 different positions are tested, and the average value is taken as the grid angle, with the unit of °;

[0076] 3. Mesh area: Under a Keyence high-definition microscope, the computer measures the length a of the mesh warp and weft, and combines the mesh angle α to calculate the mesh area, that is, a 2 × sinα;

[0077] 4. Stiffness test: The grid needs to be left standing in an environment of constant temperature (23±2°C) and constant humidity (50±10%) for 24 hours, and then a stiffness tester is used to test the stiffness value of the grid with reference to the standard GB / T 22364-2018;

[0078] 5. Tensile test: The grid needs to be left standing in an environment of constant temperature (23±2°C) and constant humidity (50±10%) for 24 hours, and then a universal testing machine is used. With reference to the standard GB / T 1040.2-2022 and a tensile speed of 50 mm / min, the tensile breaking force of the grid is tested;

[0079] 6. Pressure drop test: Refer to Figure 4 , using a membrane cell from STERLITECH Corporation, by testing the inlet pressure value p1 and the outlet pressure value p2 of the grid, the pressure drop of the grid at a flow rate of 2 L / min is calculated, that is, Δp = p1 - p2. [[ID=*]]

[0080] The results are shown in Table 2.

[0081] Table 2

[0082]

[0083] In addition, please refer to Figures 1-3, this application also provides high-definition microscope photos of Comparative Example 1, Example 1, and Example 2 magnified 20 times, from which the differences in the products can be clearly seen.

[0084] Analysis: The inlet grids prepared in Examples 1-6 significantly increased in thickness and mesh area, but showed excellent performance in the performance test, with a significant decrease in pressure drop, while maintaining good stiffness and tensile breaking force.

[0085] (II) Further optimize the preparation method

[0086] Example 7

[0087] In this example, the formulation is optimized, and the specific preparation steps are as follows:

[0088] 1. Weigh the raw materials: By weight, 70 parts of polyvinylidene fluoride (PVDF), 15 parts of perfluoroalkoxy ethylene (PFA), 10 parts of polyetheretherketone (PEEK), 3 parts of boron nitride nanosheets, 5 parts of short cut fibers, 1 part of silane coupling agent (KH550), and antioxidant combination (antioxidant 1010: 0.2 parts, antioxidant 168: 0.3 parts).

[0089] 2. Use a twin-screw extruder and set different temperature zones (260 - 320 °C). First, blend PVDF, PFA, and PEEK at 260 °C, then add boron nitride nanosheets, short cut fibers, and the antioxidant combination at 280 °C during the mixing stage. At the same time, add the silane coupling agent for interfacial enhancement treatment. Control the melting and mixing heating temperature of the extruder at 300 °C, and then extrude and form at 320 °C: After the materials are fully melted and mixed evenly, they pass through a specially designed rotating die head with large mesh holes to form an integral body, and then through the cooling and winding processes to obtain the grid.

[0090] The specific parameters and methods for forming an integral body through the specially designed rotating die head with large mesh holes are the same as those in Method 1.

[0091] Example 8

[0092] In this example, the process is optimized, and the specific preparation steps are as follows:

[0093] 1. Weigh the raw materials: By weight, 70 parts of polyvinylidene fluoride (PVDF), 15 parts of perfluoroalkoxy ethylene (PFA), 10 parts of polyetheretherketone (PEEK), 3 parts of boron nitride nanosheets, 5 parts of short cut fibers, 1 part of silane coupling agent (KH550), and antioxidant combination (antioxidant 1010: 0.2 parts, antioxidant 168: 0.3 parts).

[0094] 2. Extrusion molding: Using a twin-screw extruder, set different temperature zones (260 - 320 °C), blend PVDF, PFA, and PEEK at 260 °C in sequence, then add boron nitride nanosheets, short-cut fibers, and antioxidant combination at 280 °C during the mixing stage. At the same time, add a silane coupling agent for interface strengthening treatment. The melting and mixing heating temperature of the extruder is controlled at 300 °C, and then extrusion molding is carried out at 320 °C: After the materials are fully melted and mixed evenly, they pass through a specially designed rotating die head with large mesh holes and are integrally formed. Then, through the cooling process, a grid is obtained.

[0095] The specific parameters and methods for integral forming through the specially designed rotating die head with large mesh holes are the same as those in 1.

[0096] 3. After extrusion molding, a coating is applied to the material surface through a plasma spraying process. Ensure the uniformity and adhesion of the coating. Specifically: Mix PTFE particles (particle size 0.5 - 1 μm) and a fluorinated solvent in a weight ratio of 1:5, stir evenly, add 1 part of a promoter, and stir to obtain coating solution one. Use a plasma spraying device to spray coating solution one on the grid. Spraying pressure: 0.3 MPa, spraying distance: 20 cm, spraying speed: 0.5 m / s, coating thickness: controlled at 3 - 5 μm. After spraying, place the grid in an oven and cure it at 130 °C for 30 min to obtain the finished grid.

[0097] The finished grid can be further cooled and wound according to requirements.

[0098] Example 9

[0099] In this example, a composite coating is carried out. Different from Example 8, step 3 is as follows:

[0100] 3. After extrusion molding, a composite coating is applied to the material surface through a plasma spraying process. Ensure the uniformity and adhesion of the coating. Specifically: Mix PTFE particles (particle size 0.5 - 1 μm) and a fluorinated solvent in a weight ratio of 1:5, stir evenly, add 1 part of a promoter, and stir to obtain coating solution one. Use a plasma spraying device to spray coating solution one on the grid. Spraying pressure: 0.3 MPa, spraying distance: 20 cm, spraying speed: 0.5 m / s, coating thickness: controlled at 3 - 5 μm. After spraying, place the grid in an oven and cure it at 130 °C for 30 min to obtain the cured grid.

[0101] Heat N-methylpyrrolidone (NMP) to 150 - 180 °C, gradually add fluorinated ethylene propylene (FEP) powder (particle size less than 20 μm), keep stirring at high speed for 30 - 60 min, add 0.5 parts of accelerator, then add 0.2 parts of dispersant (polyvinylpyrrolidone, PVP), stir, and slowly cool the uniformly mixed solution to room temperature at 80 - 100 °C while keeping stirring to obtain coating solution two.

[0102] Use a plasma spraying device to spray coating solution two on the cured grid, spraying pressure: 0.25 MPa, spraying distance: 25 cm, spraying speed: 0.4 m / s, coating thickness: controlled at 2 - 3 μm. After spraying, place the grid material in an oven and cure it at 150 °C for 20 min to obtain the finished grid.

[0103] The remaining steps are the same as those in Example 8.

[0104] Example 10

[0105] In this example, PP resin is added, and the specific preparation steps are as follows: [[ID=q14]]

[0106] 1. Weigh the raw materials: By weight, 60 parts of PP resin, 10 parts of polyvinylidene fluoride (PVDF), 5 parts of perfluoroalkoxy ethylene (PFA), 10 parts of polyetheretherketone (PEEK), 3 parts of boron nitride nanosheets, 5 parts of chopped fibers, 1 part of silane coupling agent (KH550), antioxidant combination (0.2 parts of antioxidant 1010: 0.3 parts of antioxidant 168).

[0107] 2. Use a twin-screw extruder, set different temperature zones (260 - 320 °C), and blend PVDF, PFA, PEEK, and PP resin at 260 °C in sequence. Then, add boron nitride nanosheets, chopped fibers, and antioxidant combination at 280 °C during the mixing stage, and simultaneously add silane coupling agent for interfacial enhancement treatment. Control the melting and mixing heating temperature of the extruder at 300 °C, and then extrude and mold at 320 °C: After the materials are fully melted and mixed evenly, pass through a specially designed rotating die head with large mesh holes to form in one piece, and then go through the cooling and winding processes to obtain the grid.

[0108] The specific parameters and methods for forming in one piece through the specially designed rotating die head with large mesh holes are the same as those in Method 1.

[0109] It should be noted that the processing temperature of pure PP resin is relatively low. To avoid the degradation of PP resin, this application conducts copolymer blending modification on PP resin and sets a specific blending sequence.

[0110] Example 11

[0111] In this embodiment, PP resin and HDPE resin are added, and the specific preparation steps are as follows:

[0112] 1. Weigh the raw materials: By weight, 60 parts of PP resin, 20 parts of HDPE resin, 10 parts of polyvinylidene fluoride (PVDF), 5 parts of perfluoroalkoxy ethylene (PFA), 10 parts of polyetheretherketone (PEEK), 3 parts of boron nitride nanosheets, 5 parts of chopped fibers, 1 part of silane coupling agent (KH550), and antioxidant combination (0.2 parts of antioxidant 1010 and 0.3 parts of antioxidant 168).

[0113] 2. Use a twin-screw extruder and set different temperature zones (260 - 320 °C). First, blend PVDF, PFA, PEEK, PP resin, and HDPE resin at 260 °C. Then, at 280 °C in the mixing stage, add boron nitride nanosheets, chopped fibers, and the antioxidant combination. At the same time, add the silane coupling agent for interface strengthening treatment. Control the melting and mixing heating temperature of the extruder at 300 °C, and then extrude and mold at 320 °C: After the materials are fully melted and mixed evenly, they pass through a specially designed rotating die head with large mesh holes for one-piece molding, and then through the cooling and winding processes to obtain the grid.

[0114] The specific parameters and method for one-piece molding through the specially designed rotating die head with large mesh holes are the same as those in Method 1.

[0115] Example 12

[0116] In this embodiment, polyvinylidene fluoride (PVDF) and perfluoroalkoxy ethylene (PFA) are not added, and the specific preparation steps are as follows:

[0117] 1. Weigh the raw materials: By weight, 60 parts of PP resin, 20 parts of HDPE resin, 10 parts of polyetheretherketone (PEEK), 3 parts of boron nitride nanosheets, 5 parts of chopped fibers, 1 part of silane coupling agent (KH550), and antioxidant combination (0.2 parts of antioxidant 1010 and 0.3 parts of antioxidant 168).

[0118] 2. Use a twin-screw extruder and set different temperature zones (260 - 320 °C). First, blend PEEK, PP resin, and HDPE resin at 260 °C. Then, at 280 °C in the mixing stage, add boron nitride nanosheets, chopped fibers, and the antioxidant combination. At the same time, add the silane coupling agent for interface strengthening treatment. Control the melting and mixing heating temperature of the extruder at 300 °C, and then extrude and mold at 320 °C: After the materials are fully melted and mixed evenly, they pass through a specially designed rotating die head with large mesh holes for one-piece molding, and then through the cooling and winding processes to obtain the grid.

[0119] The specific parameters and method for one-piece molding through the specially designed rotating die head with large mesh holes are the same as those in Method 1.

[0120] Example 13

[0121] In this embodiment, polyvinylidene fluoride (PVDF), perfluoroalkoxy ethylene (PFA), and polyetheretherketone (PEEK) are not added. The specific preparation steps are as follows:

[0122] 1. Weigh the raw materials: By weight, 60 parts of PP resin, 20 parts of HDPE resin, 3 parts of boron nitride nanosheets, 5 parts of short cut fibers, 1 part of silane coupling agent (KH550), and antioxidant combination (0.2 parts of antioxidant 1010 and 0.3 parts of antioxidant 168).

[0123] 2. Use a twin-screw extruder and set different temperature zones (260 - 320 °C). First, blend PEEK, PP resin, and HDPE resin at 260 °C. Then, at 280 °C in the mixing stage, add boron nitride nanosheets, short cut fibers, and the antioxidant combination. At the same time, add the silane coupling agent for interfacial enhancement treatment. Control the melting and mixing heating temperature of the extruder at 300 °C, and then extrude and form at 320 °C: After the materials are fully melted and mixed evenly, they pass through a specially designed rotating die head with large mesh holes to form a single piece, and then through the cooling and winding processes to obtain a grid.

[0124] The specific parameters and methods for forming a single piece through the specially designed rotating die head with large mesh holes are the same as those in Method 1.

[0125] Example 14

[0126] In this embodiment, boron nitride nanosheets are not added. The specific preparation steps are as follows:

[0127] 1. Weigh the raw materials: By weight, 60 parts of PP resin, 20 parts of HDPE resin, 10 parts of polyvinylidene fluoride (PVDF), 5 parts of perfluoroalkoxy ethylene (PFA), 10 parts of polyetheretherketone (PEEK), 5 parts of short cut fibers, 1 part of silane coupling agent (KH550), and antioxidant combination (0.2 parts of antioxidant 1010 and 0.3 parts of antioxidant 168).

[0128] 2. Use a twin-screw extruder and set different temperature zones (260 - 320 °C). First, blend PVDF, PFA, PEEK, PP resin, and HDPE resin at 260 °C. Then, at 280 °C in the mixing stage, add short cut fibers and the antioxidant combination. At the same time, add the silane coupling agent for interfacial enhancement treatment. Control the melting and mixing heating temperature of the extruder at 300 °C, and then extrude and form at 320 °C: After the materials are fully melted and mixed evenly, they pass through a specially designed rotating die head with large mesh holes to form a single piece, and then through the cooling and winding processes to obtain a grid.

[0129] The specific parameters and methods for forming a single piece through the specially designed rotating die head with large mesh holes are the same as those in Method 1.

[0130] Example 15

[0131] In this embodiment, short-cut fibers are not added, and the specific preparation steps are as follows:

[0132] 1. Weigh the raw materials: By weight, 60 parts of PP resin, 20 parts of HDPE resin, 10 parts of polyvinylidene fluoride (PVDF), 5 parts of perfluoroalkoxyethylene (PFA), 10 parts of polyetheretherketone (PEEK), 3 parts of boron nitride nanosheets, 1 part of silane coupling agent (KH550), and antioxidant combination (0.2 parts of antioxidant 1010: 0.3 parts of antioxidant 168).

[0133] 2. Use a twin-screw extruder and set different temperature zones (260 - 320 °C). First, blend PVDF, PFA, PEEK, PP resin, and HDPE resin at 260 °C. Then, add boron nitride nanosheets and the antioxidant combination at 280 °C during the mixing stage. At the same time, add the silane coupling agent for interfacial enhancement treatment. Control the melting and mixing heating temperature of the extruder at 300 °C, and then extrude and mold at 320 °C: After the materials are fully melted and mixed evenly, they pass through a specially designed large-mesh rotary die head for one-piece molding, and then through the cooling and winding processes to obtain a grid.

[0134] The specific parameters and methods for one-piece molding through the specially designed large-mesh rotary die head are the same as those in Method 1.

[0135] The manufacturer's grades for Examples 7 - 15 are as follows:

[0136] PP resin: Formosa Plastics Corporation, Taiwan, China, Yungsox 1040;

[0137] HDPE resin: Shanghai Secco Petrochemical Co., Ltd., HD 5502;

[0138] Polyvinylidene fluoride (PVDF): Arkema, Kynar 740;

[0139] Perfluoroalkoxyethylene (PFA): DuPont, USA, PFA 450HP;

[0140] Polyetheretherketone (PEEK): Victrex, 450G;

[0141] Boron nitride nanosheets: Suzhou Napu Materials Technology Co., Ltd., NS-BN, 98.0% purity;

[0142] Silane coupling agent (KH550): Shanghai Hongshun Biotechnology Co., Ltd., 98.0% purity;

[0143] Both antioxidant 1010 and antioxidant 168 are purchased from BASF China;

[0144] PTFE particles (particle size 0.5 - 1 μm): AGC Chemicals Company, Fluon;

[0145] Fluorinated solvents: 3M Company, Novec 7100 electronic fluorinated liquid;

[0146] Accelerators: 3M Company, Novec FC - 4432;

[0147] N - methylpyrrolidone (NMP) was purchased from Aladdin Reagent, with a purity of 99%;

[0148] Fluorinated ethylene propylene (FEP) powder (particle size less than 20 μm) was purchased from 3M Company, Dyneon;

[0149] Dispersant (polyvinylpyrrolidone, PVP): BASF China, Kollidon 30;

[0150] Chopped fibers: Owens Corning, CS415, chopped length 4 mm.

[0151] The following is a test on the grids of Examples 7 - 15, and the test method is as follows:

[0152] Chemical resistance test:

[0153] 1. Acid - alkali corrosion resistance test:

[0154] Method: Immerse the samples in 10% H2SO4 solution, 10% NaOH solution, and 10% NaCl solution respectively, soak for 7 days at room temperature, and observe the changes in surface and mechanical properties.

[0155] Objective: After soaking, there should be no obvious weight loss and mechanical property degradation in each example (weight loss ≤ 1%, tensile breaking force decrease ≤ 5%).

[0156] 2. Hydrolysis resistance test:

[0157] Method: Immerse the samples in a water bath at 95°C for 72 hours, and detect the tensile breaking force before and after soaking.

[0158] Objective: The change in tensile breaking force of each example ≤ 5%.

[0159] Tensile breaking force: Use a universal testing machine, refer to the standard GB / T 1040.2 - 2022, with a tensile speed of 50 mm / min to test the tensile breaking force of the grids.

[0160] The results are shown in Table 3 and Table 4.

[0161] Table 3 Acid - alkali corrosion resistance test results

[0162]

[0163] Table 4 Hydrolysis Resistance Performance Test Results

[0164]

[0165] Analysis:

[0166] In Example 7, a combination of polyvinylidene fluoride (PVDF), perfluoroalkoxy ethylene (PFA), and polyetheretherketone (PEEK) was used. These high-performance polymers can form a highly crystalline structure in the composite material, having excellent chemical resistance and heat resistance, especially performing well in harsh environments. Example 7 provides a new formulation, and the components are compounded to form a polymer network structure with high crystallinity, effectively enhancing the acid and alkali resistance and hydrolysis resistance of the material. The addition of boron nitride nanosheets further improves the thermal conductivity and mechanical properties of the material, and also enables it to have higher creep resistance and anti-aging properties.

[0167] In Example 8, a plasma spraying process was introduced to form a coating on the material surface. The coating has excellent corrosion resistance and low surface energy, can significantly reduce the surface energy of the material, and make the material more stable in acid and alkali environments. The coating forms a chemical barrier on the material surface, preventing acid and alkali substances from eroding the internal structure of the material. The interaction between the fluorinated solvent and PTFE particles further improves the adhesion and durability of the coating.

[0168] In Example 9, in this example, the composite coating of PTFE and FEP combines the advantages of both. The structure of the composite coating can effectively reduce the generation of micropores on the material surface, thus having higher acid and alkali corrosion resistance and hydrolysis resistance, and a better synergistic effect also appears between the two coatings.

[0169] In Example 10, PP (polypropylene) resin was added to form a multi-polymer blend system, improving the impact resistance and processing performance of the material. The addition of PP resin effectively improves the processing fluidity of the material. At the same time, due to the high impact resistance of PP resin, a tough phase is formed in the material, enhancing the impact toughness and fatigue resistance of the overall structure.

[0170] In Example 11, HDPE (high-density polyethylene) resin was further added to enhance the mechanical properties and chemical resistance of the material. In the new formulation, the synergistic effect of PP resin and HDPE resin forms a more compact polymer network structure. The combination of the high crystallinity of HDPE resin and the toughness of PP resin produces excellent stress cracking resistance and environmental aging resistance. At the same time, the good compatibility between PVDF and HDPE further improves the chemical resistance of the material.

[0171] Examples 11 to 15 demonstrate synergistic effects:

[0172] (1) Synergy between PVDF, PFA and PEEK:

[0173] Synergistic Chemical Stability: PVDF and PFA are both fluoropolymers with excellent chemical stability. The addition of PEEK further enhances the material's heat resistance and acid and alkali resistance. At high temperatures, the crystalline phase formed by these three polymers effectively resists damage to the material structure caused by acid and alkali environments.

[0174] Synergistic mechanical properties: PEEK has high rigidity and fatigue resistance, while PVDF and PFA have good flexibility and impact resistance. The combination of the three makes the material have both high rigidity and good impact toughness.

[0175] (2) Synergistic effect of boron nitride nanosheets and chopped fibers:

[0176] Synergistic reinforcement and thermal conductivity: Chopped fibers, as a mechanical reinforcement phase, disperse stress within the material, improving its tensile strength and impact resistance. Silane coupling agent treatment of boron nitride nanosheets and chopped fibers enhances their surface activity and strengthens their interfacial bonding with the matrix resin, further improving the material's creep resistance and interfacial strength.

[0177] Example 7-Example 9:

[0178] Microcrystalline structure: PVDF, PFA and PEEK gradually crystallize at different temperatures to form a multi-level crystalline structure.

[0179] Coating structure: The PTFE and FEP composite coatings in Examples 8 and 9 form a dense microstructure on the surface of the material, which prevents the penetration of moisture and chemical reagents and improves the chemical corrosion resistance and hydrolysis resistance of the material.

[0180] Example 10-Example 11:

[0181] Polymer blend structure: The addition of PP and HDPE resins changes the material's microphase distribution, forming a dispersed, nested structure. The intertwining of polymer chains at the blend interface enhances the material's toughness and creep resistance, thereby enhancing its chemical and hydrolysis resistance.

[0182] Fiber-reinforced network: The chopped fibers form a randomly distributed reinforcement network in the material, which works together with the boron nitride nanosheets in the matrix to further enhance the material’s chemical and hydrolysis resistance.

[0183] Example 12-Example 15:

[0184] Degradation of the polymer crystalline phase: With the removal of high-performance polymers (such as PVDF, PFA, and PEEK), the crystallinity of the material decreases, and the internal microstructure becomes unstable. Both chemical resistance and heat resistance decrease.

[0185] Lack of fillers: After removing boron nitride nanosheets or short-cut fibers, the performance of the material decreases, indicating that these fillers play an important reinforcing role in the composite material.

[0186] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than a limitation on the protection scope of the present invention. Any simple modification or equivalent replacement of the technical solution of the present invention by those of ordinary skill in the art shall not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A large-mesh high-strength water inlet grid, characterized in that, The intake grid is prepared through the following steps: Weigh the raw materials, which include a base resin and additives. The additives include at least one of a lubricant, an antioxidant, a nucleating agent, and a filler. Add the weighed raw materials into an extruder. The extruder melts, mixes, and heats them, and then extrudes them into a shape: After the materials are fully melted and mixed evenly, they pass through a specially designed rotating die head with large mesh holes and are integrally formed into a grid product. Then, through the cooling and winding processes, the intake grid is obtained. After extrusion molding, apply a coating on the surface of the intake grid: Use a plasma spraying device to spray the coating solution on the intake grid. After spraying, cure the intake grid at 100 - 150 °C for 20 - 60 min to obtain the finished grid. Among them, the specific parameters for integrally forming a grid product through the specially designed rotating die head with large mesh holes include: Thickness: 20 - 50 mil; Angle: 30 - 150°; Mesh area: 10 - 50 mm 2 ; The base resin includes at least one of PP resin, HDPE resin, PVDF, PFA, and PEEK. The lubricant includes PE wax. The antioxidant includes a hindered phenol antioxidant. The filler includes at least one of talcum powder, boron nitride nanosheets, and short cut fibers. The coating solution includes coating solution one and coating solution two. Mix PTFE with a fluorinated solvent, stir evenly, add a promoter, and stir to obtain coating solution one. Heat NMP to 150 - 180 °C, gradually add FEP, stir, add a promoter, then add a dispersant, stir, and slowly cool the uniformly mixed solution to room temperature at 80 - 100 °C while maintaining stirring to obtain coating solution two.

2. The large-mesh high-strength water inlet grid according to claim 1, wherein, By weight, 80 - 110 parts of the base resin; 0 - 0.5 parts of the lubricant; 0.1 - 0.5 parts of the antioxidant; 0 - 5.0 parts of the nucleating agent; 0 - 10 parts of the filler.

3. The large-mesh high-strength water inlet grid according to claim 1, characterized in that The temperature control for the extrusion and melting mixing and heating of the extruder is at 200 - 300 °C.

4. The large-mesh high-strength water inlet grid according to claim 1, characterized in that The raw materials also include a silane coupling agent. The antioxidant includes at least one of antioxidant 1010 and antioxidant 168.

5. The large-mesh high-strength water inlet grid according to claim 1, wherein, When adding the weighed raw materials into the extruder, set different temperature sections at 260 - 320 °C, blend the base resin, and then add the remaining raw materials in the mixing stage. The extruder melts, mixes, and heats them, and then extrudes them into a shape: After the materials are fully melted and mixed evenly, they pass through a specially designed rotating die head with large mesh holes and are integrally formed into a grid product. Then, through the cooling and winding processes, the intake grid is obtained.

6. The large-mesh high-strength water inlet grid according to claim 1, characterized in that, After extrusion molding, apply a coating on the surface of the intake grid: Use a plasma spraying device to spray coating solution one on the intake grid. After spraying, cure the intake grid at 100 - 150 °C for 20 - 60 min to obtain the cured grid; Use a plasma spraying device to spray coating solution two on the cured grid. After spraying, cure the intake grid at 100 - 150 °C for 20 - 60 min to obtain the finished grid.

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