Sealing gasket material for electrolytic bath and preparation method of sealing gasket material

Abstract

The invention belongs to the field of hydrogen production through water electrolysis, and discloses a sealing gasket material for an electrolytic bath and a preparation method thereof. The PFA can form a three-dimensional network structure in the material, so that the relative slippage between polytetrafluoroethylene molecular chains and the relative movement of glass beads are reduced, and the creep resistance of the material is improved. The added molybdenum disulfide can reduce the friction coefficient of the material, and the material is not easy to stick to a mold and is beneficial to demolding. The hollow glass beads have good compression strength, and can improve the rebound rate of the material and reduce the density of the material. According to the invention, through a sectional sintering process, the heating and cooling rates are controlled, the optimal crystallization range of the material is 55-80%, and the creep resistance is optimal. The sealing gasket can continuously provide reliable sealing and insulation guarantee in a complex and changeable electrolytic bath environment, and a solid foundation is laid for further development of a water electrolysis hydrogen production technology.

Description

Technical Field

[0001] The invention belongs to the field of hydrogen production by electrolysis of water, and particularly relates to a sealing gasket material for an electrolytic cell and a preparation method thereof. Background Art

[0002] As a key material in the core equipment of the electrolyzer, the importance of the sealing gasket is self-evident. It is not only the core component for the electrolyzer to achieve efficient sealing, but also shoulders the important task of isolating the current and ensuring the insulation performance between the electrolysis chambers. The performance of the sealing gasket is directly related to the stability of the internal environment of the electrolyzer, which in turn affects the overall efficiency and safety of the electrolysis hydrogen production process. It is the first line of defense to ensure the reliable operation of the entire electrolysis hydrogen production system.

[0003] In view of the multifunctionality of sealing gaskets in electrolyzers - sealing, insulation and support, the selection of materials and modification technology are particularly important. Modified fluoroplastics, with their excellent corrosion resistance, high temperature resistance and good insulation properties, have become a hot spot for research and application in the field of water electrolysis. Researchers are constantly exploring ways to modify fluoroplastics by chemical or physical means to enhance their mechanical strength, creep resistance and thermal stability, so as to meet the use requirements of electrolyzers under extreme working conditions.

[0004] At present, most of the domestic electrolytic water sealing materials are made of glass fiber, carbon fiber, graphite and other materials as reinforcing fillers filled with polytetrafluoroethylene, which are obtained by molding and sintering. However, in actual applications, these materials are still difficult to completely avoid cold flow and creep under complex working conditions of high temperature, high pressure and frequent start and stop. This material deformation will not only lead to the decline of the sealing performance of the electrolyzer and cause leakage of the tank, but also accelerate the aging of the material, shorten the service life of the electrolyzer, increase maintenance costs, and pose a threat to the long-term stable operation of the electrolytic water hydrogen production system.

[0005] Therefore, future research should focus on developing new high-performance sealing materials, or further optimizing the modification technology of existing materials, such as adopting more advanced composite material design strategies, to significantly improve the resilience, creep resistance and long-term stability of sealing gaskets. At the same time, more efficient processing technology should be explored to ensure that sealing gaskets can continue to provide reliable sealing and insulation protection in the complex and changing electrolyzer environment, laying a solid foundation for the further development of water electrolysis hydrogen production technology. Summary of the invention

[0006] In order to solve the above problems, the primary purpose of the present invention is to provide a sealing gasket material for an electrolytic cell, which is composed of the following raw materials in the following weight percentage ratios:

[0007] Polytetrafluoroethylene: 55%-75%;

[0008] Glass beads: 15%-35%;

[0009] PFA: 5%;

[0010] Molybdenum disulfide: 5%.

[0011] PFA is a copolymer obtained by the polymerization of a small amount of perfluoroalkyl vinyl ether and tetrafluoroethylene, and can be regarded as a modified variety of PTFE. Compared with PTFE, its mechanical properties, electrical properties and chemical corrosion resistance are not inferior, while its melt viscosity and gas permeability are reduced, and its cold flow resistance and folding resistance are greatly improved. It turns the complex fibrous particles of PTFE into spherical particles, greatly improves its fluidity, and can be directly used for plunger extrusion molding.

[0012] In the present invention, PFA can form a three-dimensional network structure in the material, reduce the relative slip between polytetrafluoroethylene molecular chains and the relative movement of glass microspheres, and improve the creep resistance of the material. Molybdenum disulfide can reduce the friction coefficient of the material, the material is not easy to stick to the mold, and it is helpful for demolding. The hollow glass microspheres have good compression strength, can improve the material rebound rate, and reduce the material density.

[0013] The mesh number of PTFE is 500-600 mesh.

[0014] The particle size of glass beads is 0.4μm-0.6μm, and the compressive strength exceeds 120MPa.

[0015] The mesh number of molybdenum disulfide is 300-400 mesh.

[0016] Further, the glass microspheres in the present invention adopt modified glass microspheres, and the specific modification method is: the glass microspheres are placed in a high mixer, and then a silane coupling agent is added to anhydrous ethanol to prepare a coupling agent solution, and then injected into the high mixer, premixed at 60°C for 10 minutes, and then the solution is filtered and extracted, and finally the modified glass microspheres are dried at 120°C to remove the residual solvent to obtain modified glass microspheres. Among them, 5g of silane coupling agent is added to every 500mL of anhydrous ethanol. The modification method provided by the present invention can improve the compatibility of glass microspheres with polytetrafluoroethylene, reduce the agglomeration of glass microspheres, and improve the uniformity of dispersion of glass microspheres in polytetrafluoroethylene.

[0017] Another object of the present invention is to claim protection for a method for preparing the above-mentioned electrolytic cell sealing gasket material. The steps include:

[0018] (1) Weigh the raw materials according to the ratio;

[0019] (2) Mixing the raw materials: put the raw materials into a double motion mixer and mix for 10-20 minutes;

[0020] (3) Cold pressing: putting the mixed raw materials into a mold, cold pressing at a pressure of 50-60 MPa, holding the pressure for 20-30 seconds, and demolding to obtain a blank;

[0021] Compared with conventional methods, under the conditions of step (3), the material can be preformed into a blank, and the blank can be demoulded and directly placed in a heating furnace for heating, which has higher heating efficiency.

[0022] (4) Sintering, 20℃-280℃ heating time is 130min, 280℃-315℃ heating time is 35min, 315℃-365℃ heating time is 60min, 365℃ keeping time is 60min, 365℃-100℃, cooling time is 120min.

[0023] As a preferred embodiment of the present invention, the preparation method of the sealing gasket material for the electrolytic cell is as follows:

[0024] According to weight percentage, 55% polytetrafluoroethylene, 35% modified glass beads, 5% PFA, and 5% molybdenum disulfide are put into a double-motion mixer and mixed for 20 minutes; the mixed material is put into a mold, cold-pressed at a pressure of 40 MPa, maintained for 30 seconds, and demolded to obtain a blank; the blank is put into a sintering furnace for heating, and the heating process is as follows: 20°C-280°C heating time is 130 minutes, 280°C-315°C heating time is 35 minutes, 315°C-365°C heating time is 60 minutes, and 365°C is kept for 120 minutes.

[0025] The sintering method provided by the present invention is completely different from the conventional sintering method. The present invention controls the heating and cooling rates through a segmented sintering process. The method can adjust the optimal crystallization range of the material to 55%-80%. Experiments have shown that the material has the best creep resistance within this crystallization range.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) Improved rebound rate

[0028] Resilience is a measure of the ability of a gasket to return to its original shape and size after being compressed. Improving the resilience means that the gasket can better return to its original state after undergoing compression deformation, thereby maintaining a long-term sealing effect. The PFA used in the formulation of the present invention has the characteristics of good elasticity, low density and moderate stiffness. These materials can store energy well when compressed and quickly return to their shape after the pressure is released.

[0029] (2) Improved compression strength

[0030] Compression strength refers to the maximum pressure that a gasket can withstand without being damaged when subjected to compression. Improving the compression strength can ensure that the gasket can still maintain good sealing performance under high pressure. The present invention adds reinforcing fillers, such as modified glass microspheres, molybdenum disulfide, etc., to the gasket material to improve its compressive strength and overall performance.

[0031] (3) Improved creep resistance

[0032] Creep refers to the slow and continuous plastic deformation of a material under a long-term constant load. Improving creep resistance can ensure that the gasket maintains a stable sealing effect during long-term use and reduce leakage problems caused by creep.

[0033] The present invention selects polytetrafluoroethylene with excellent creep resistance as the matrix resin. Through the use of special compression molding sintering process and additives, the creep relaxation rate can be significantly reduced. Secondly, the present invention strictly controls the manufacturing process of the gasket, adopts a segmented sintering process, controls the heating and cooling rates, and adjusts the optimal crystallization range of the material to 55%-80%, so that the material has the best creep resistance within this crystallization range, ensures the uniformity and consistency of the material, and thus reduces the creep problem caused by internal defects of the material.

[0034] (4) Material density decreases

[0035] Reducing the material density can reduce the weight and cost of the gasket while maintaining or improving other properties of the gasket. In addition, materials with lower density usually have better elasticity and resilience, which is beneficial to improving the sealing performance of the gasket.

[0036] The sealing gasket of the present invention has a low-density and high-elastic material. The glass microspheres used in the present invention are hollow glass microspheres, which belong to microporous materials. These materials have lower density and lighter weight while maintaining excellent sealing performance. The existing materials are modified by chemical or physical methods to reduce their density and improve other properties.

[0037] It should be noted that the above-mentioned methods of achieving each effect do not exist in isolation, but are interrelated and mutually influential. In practical applications, it is necessary to comprehensively consider various factors according to specific needs and working conditions to select the most appropriate materials and process solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is the compression-rebound curve of Example 1-3;

[0039] Figure 2 This is a 200-fold magnified microscope photo of the sealing gasket material in Example 3 of the present invention;

[0040] Figure 3 This is a process flow chart of preparing a sealing gasket for an electrolytic cell in Example 4;

[0041] Figure 4 It is the structural diagram of granulation equipment.

[0042] Among them, 1. hopper, 2. tile-shaped paddle, 3. inner shaft, 4. discharge port, 5. barrel, 6. large pulley, 7. small pulley, 8. filter, 9. rotating blade, 10. rotating blade, 11. crushing and mixing box, 12. rotating disk, 13. outer shaft. DETAILED DESCRIPTION

[0043] In order to more clearly illustrate the purpose, technical solutions and advantages of the present disclosure, the embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be understood that the following description of the embodiments is intended to explain and illustrate the overall concept of the present invention, and should not be understood as a limitation of the present invention. In the specification and the drawings, the same or similar figure marks refer to the same or similar parts or components. For the sake of clarity, the drawings are not necessarily drawn to scale, and some well-known parts and structures may be omitted in the drawings. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0044] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0045] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood in specific circumstances.

[0046] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0047] Example 1

[0048] According to the weight percentage, 75% polytetrafluoroethylene, 15% modified glass microspheres, 5% PFA, and 5% molybdenum disulfide were put into a double motion mixer and mixed for 20 minutes; the mixed materials were put into a mold, cold pressed at a pressure of 40MPa, and the pressure was maintained for 30 seconds, and the blank was demolded; the blank was placed in a sintering furnace for heating, and the heating process was as follows: 20℃-280℃ heating time 130min, 280℃-315℃ heating time 35min, 315℃-365℃ heating time 60min, and 365℃ insulation for 120min. After simple processing and appearance size inspection, the material performance was tested.

[0049] Example 2

[0050] According to the weight percentage, 65% polytetrafluoroethylene, 25% modified glass microspheres, 5% PFA, and 5% molybdenum disulfide were put into a double-motion mixer and mixed for 20 minutes; the mixed materials were put into a mold, cold-pressed at a pressure of 40MPa, held for 30 seconds, and demolded to obtain a blank; the blank was placed in a sintering furnace for heating, and the heating process was as follows: 20℃-280℃ heating time 130min, 280℃-315℃ heating time 35min, 315℃-365℃ heating time 60min, and 365℃ insulation for 120min. After simple processing and appearance size inspection, the material properties were tested.

[0051] Example 3

[0052] According to the weight percentage, 55% polytetrafluoroethylene, 35% modified glass microspheres, 5% PFA, and 5% molybdenum disulfide were put into a double-motion mixer and mixed for 20 minutes; the mixed materials were put into a mold, cold-pressed at a pressure of 40MPa, held for 30 seconds, and demolded to obtain a blank; the blank was placed in a sintering furnace for heating, and the heating process was as follows: 20℃-280℃ heating time 130min, 280℃-315℃ heating time 35min, 315℃-365℃ heating time 60min, and 365℃ insulation for 120min. After simple processing and appearance size inspection, the material properties were tested.

[0053] Figure 1 The figure shows the pressure rebound curve of the embodiment of the present invention. The figure shows that the material is loaded with a load of 30MPa in a slow and uniform manner. After reaching 30MPa, the load is removed in a slow and uniform manner. The thickness of the material at this time is recorded, which is the rebound thickness. It can be seen from the figure that the three embodiment materials have good rebound performance, among which the material of embodiment 3 is the best.

[0054] Figure 2 The photo is a 200-fold magnified microscope photo of the material of the present invention. From the photo, it can be seen that the glass microbeads and molybdenum disulfide are evenly dispersed in the polytetrafluoroethylene, and the structure of the glass microbeads is not destroyed.

[0055] Example 4

[0056] The polytetrafluoroethylene, glass microbeads, PFA, molybdenum disulfide and organic solvent in Example 1 are placed together in a mixing device for mixing, so that the solvent and the materials are fully mixed.

[0057] Put the mixed wet ingredients into Figure 4 The granulation is carried out in a granulation equipment. The mixed wet material containing solvent is fed from the hopper 1 into the crushing and mixing box 11. In the crushing and mixing box 11, the cutter disc drives the rotating blade 9 on the cutter disc to rotate at a high speed, exerting impact force on the wet material falling in, repeatedly breaking up and crushing the wet material in blocks to achieve full mixing. A pair of inclined rotating blades 10 are installed at the bottom of the cutter disc. When rotating with the cutter disc, an upward force is exerted on the material, so that the material flows circumferentially under the circumferential force of the rotating blade 9 and also flows axially under the axial force of the bottom blade, so that the material is mixed more evenly. The fully mixed material with the required particle diameter is continuously discharged from the filter screen 8.

[0058] The material discharged through the screen of the crushing and mixing box 11 falls into the barrel 5. The rotating turntable working surface exerts friction on the material. The material rolls under the action of the friction force. The material unites and adheres to each other to form granules. When the granules roll, they are also affected by the centrifugal force. When the granules are away from the rotation center of the turntable, they are affected by the tile-shaped paddle 2. The granules return to the turntable working surface. The material continues to unite and adhere on the surface of the granules, and the volume of the granules continues to increase. The force of the tile-shaped paddle 2 on the granules can be adjusted by adjusting the rotation angle of the tile-shaped paddle 2. When the component force of the centrifugal force of the granules is not less than the force of the tile-shaped paddle 2 on the granules, the granules are separated from the turntable working surface and discharged from the discharge port 4 to complete the granulation. The volume density and average particle size of the granulated material can be adjusted and controlled by controlling the rolling time of the turntable and the angle of the tile-shaped paddle 2.

[0059] After that, the organic solvent in the polytetrafluoroethylene resin must be evaporated and then it is sintered, and finally the polytetrafluoroethylene granules can be obtained by screening.

[0060] The prepared material was placed in a mold, cold-pressed at a pressure of 40 MPa, held for 30 seconds, and demolded to obtain a blank; the blank was placed in a sintering furnace for heating, and the heating process was as follows: 20°C-280°C heating time for 130 minutes, 280°C-315°C heating time for 35 minutes, 315°C-365°C heating time for 60 minutes, and 365°C insulation for 120 minutes.

[0061] Ordinary polytetrafluoroethylene powder has very poor fluidity, so it is difficult to add it evenly when adding it to the mold. The powder added to the mold must be pounded evenly by hand, which is time-consuming and labor-intensive, and the production efficiency is extremely low. For thinner gasket products, the uneven flow of powder in the mold often leads to uneven density, porosity, cracking and other problems during the molding process, affecting product performance.

[0062] Advantages of polytetrafluoroethylene after modification and granulation:

[0063] 1. Advantages of strong fluidity: Compared with powder materials, especially in summer, due to the high temperature, the powder materials themselves will be sticky, and it is more troublesome to mold and discharge them, and they need to be refrigerated. Granulated materials can be operated at room temperature, with fast discharge speed, improved work efficiency, and saved labor costs. In addition, the good fluidity can be better reflected when molding products with relatively thin wall thickness (sealing gasket products).

[0064] 2. Density uniformity advantage: The density uniformity of finished products produced from powder materials is much higher.

[0065] Comparative Example

[0066] Pure polytetrafluoroethylene was used to prepare a sealing material by the same molding, sintering and curing, and controlled cooling process parameters as in Example 1, and the material properties were tested.

[0067] Table 1 Experimental data of each embodiment and comparative example

[0068]

[0069] It can be seen from the above table that the materials of Examples 1-3 have good compression strength, rebound rate, creep rate, and lower density compared with the comparative example.

[0070] Table 2 Performance comparison between the product of the present invention and commercially available products

[0071]

[0072]

[0073] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A sealing gasket material for an electrolytic cell, characterized in that: It is composed of the following raw materials in weight percentage: Polytetrafluoroethylene: 55%-75%; Glass beads: 15%-35%; PFA: 5%; Molybdenum disulfide: 5%.

2. The electrolytic cell sealing gasket material according to claim 1, characterized in that: The mesh size of polytetrafluoroethylene is 500-600 mesh, and the mesh size of molybdenum disulfide is 300-400 mesh.

3. The electrolytic cell sealing gasket material according to claim 1, characterized in that: The particle size of glass beads is 0.4μm-0.6μm.

4. The electrolytic cell sealing gasket material according to claim 1, characterized in that: The glass microspheres are modified glass microspheres.

5. The electrolytic cell sealing gasket material according to claim 1, characterized in that: The modification method of the modified glass microspheres is as follows: placing the glass microspheres in a high-speed mixer, then adding a silane coupling agent to anhydrous ethanol to prepare a coupling agent solution, then injecting the solution into the high-speed mixer, premixing at 60° C. for 10 minutes, then filtering and extracting the solution, and finally drying the glass microspheres at 120° C. to remove the residual solvent to obtain the modified glass microspheres.

6. The material according to claim 5, characterized in that Add 5 g of silane coupling agent to every 500 mL of anhydrous ethanol.

7. A method for preparing a sealing gasket material for an electrolytic cell, characterized in that the steps include: Step S1. Weigh each raw material according to the ratio; Step S2. Mix the raw materials: put the raw materials into a double motion mixer and mix for 10-20 minutes; Step S3: cold pressing, putting the mixed raw materials into a mold, cold pressing at a pressure of 50-60 MPa, holding the pressure for 20-30 seconds, and demolding to obtain a blank; Step S4. sintering, 20°C-280°C heating time 130 min, 280°C-315°C heating time 35 min, 315°C-365°C heating time 60 min, 365°C insulation 60 min, 365°C-100°C, cooling time 120 min.

8. The method for preparing a sealing gasket material for an electrolytic cell according to claim 7, characterized in that: According to weight percentage, 55% polytetrafluoroethylene, 35% modified glass beads, 5% PFA, and 5% molybdenum disulfide are put into a double-motion mixer and mixed for 20 minutes; the mixed material is put into a mold, cold-pressed at a pressure of 40 MPa, maintained for 30 seconds, and demolded to obtain a blank; the blank is put into a sintering furnace for heating, and the heating process is as follows: 20°C-280°C heating time is 130 minutes, 280°C-315°C heating time is 35 minutes, 315°C-365°C heating time is 60 minutes, and 365°C is kept for 120 minutes.

9. The method for preparing a sealing gasket material for an electrolytic cell according to claim 7, characterized in that: The preparation process includes granulation between step S2 and step S3.

10. The method for preparing a sealing gasket material for an electrolytic cell according to claim 9, characterized in that: The specific method of granulation is as follows: the mixed wet material is put into the granulation equipment for granulation, the mixed wet material containing solvent is fed into the crushing and mixing box 11 from the hopper 1, in the crushing and mixing box 11, the cutter disc drives the rotating blade 9 on the cutter disc to rotate at a high speed, exerts impact force on the wet material falling in, and the blocky wet material is repeatedly broken up and crushed by the rotating blade 10 to achieve full mixing, and the fully mixed material with the required particle diameter is continuously discharged from the filter screen 8, and then falls into the barrel 5, the material continues to unite and bond on the surface of the particle body, and the volume density and average particle size of the granulated material are adjusted and controlled by controlling the rolling time of the turntable and the angle of the tile-shaped paddle 2; the organic solvent in the polytetrafluoroethylene resin is evaporated and then sintered, and finally the polytetrafluoroethylene granulated material can be obtained by screening.

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