Alkaline electrolytic cell plastic gasket and preparation method and application thereof

Abstract

The invention relates to an alkaline electrolytic cell plastic gasket and a preparation method and application thereof, and belongs to the technical field of alkaline electrolytic cells. The alkaline electrolytic cell plastic gasket provided by the invention is prepared from 40 to 60 parts of polyphenylene sulfide, 8 to 20 parts of modified ethylene propylene diene monomer, 10 to 20 parts of polytetrafluoroethylene, 1 to 3 parts of cross-linking agent, 0.5 to 1.5 parts of catalyst, 1 to 2 parts of silane coupling agent, 10 to 20 parts of filler, 0.3 to 1.5 parts of antioxidant and 0.5 to 1 part of calcium stearate. According to the scheme, through compatibility of the polyphenylene sulfide, the polytetrafluoroethylene and the modified ethylene propylene diene monomer, compatibility of multiphase compositions can be coordinated, higher heat resistance and alkali resistance are achieved, meanwhile, good rebound resilience, sealing performance and mechanical strength are achieved, erosion and impact in a high-temperature alkaline electrolytic bath can be powerfully resisted, and the service life of the electrolytic bath is prolonged. And the service life of the sealing gasket is greatly prolonged.

Description

Technical Field

[0001] This application relates to a plastic gasket for an alkaline electrolytic cell, its preparation method, and its application, belonging to the field of alkaline electrolytic cell technology. Background Technology

[0002] In the chamber of an alkaline electrolyzer, sealing gaskets primarily function to prevent the leakage of alkaline solution and the mixing of hydrogen and oxygen, and are stacked alternately with the electrode plates. Due to prolonged exposure to a high-temperature alkaline environment and the scouring effect of the electrolyte, sealing gaskets are highly susceptible to corrosion and require frequent replacement. Current technologies generally involve nickel plating on existing materials, or using alkali-resistant polymers such as polytetrafluoroethylene (PTFE) and polysulfone (PSU), or rubber materials such as ethylene propylene diene monomer (EPDM) and fluororubber. Inorganic fillers such as fibers can also be added to increase strength. However, both plastic and rubber materials used as the matrix have their drawbacks: those with low alkali resistance have short service lives, while those with good alkali resistance are either too expensive or have poor strength. Therefore, the service life of existing gaskets is generally short (only about two years). Furthermore, the challenges and comprehensive performance requirements for gaskets used in high-temperature alkaline electrolyzers where the temperature is maintained above 100°C are much higher than those for traditional low-temperature electrolyzers. In summary, a gasket with a long lifespan and wide applicability that can be used in the field of alkaline water electrolysis for hydrogen production should possess the following properties: aging resistance, resistance to strong alkaline corrosion, insulation, high strength and impact resistance, good compression resilience for stable sealing, long-term stability above 100°C, and reasonable cost to meet the requirements for extensive use in multi-chamber structures of electrolyzers.

[0003] Polyphenylene sulfide (PPS) possesses excellent high-temperature resistance, chemical resistance, insulation, wear resistance, high mechanical strength, and controllable cost, making it suitable as a base material for gaskets. However, due to its brittle nature, PPS exhibits low impact resistance and insufficient sealing performance, necessitating further modification to ensure long-term use of the gaskets in high-temperature alkaline electrolytic cells. The challenge lies in developing a sealing gasket that maintains the advantages of PPS, such as alkali resistance and heat resistance, while also offering good resilience, aging resistance, impact resistance, and a long service life for use in high-temperature alkaline electrolytic cells. Therefore, this invention is proposed. A search revealed no existing technology employing the combination of PPS, polytetrafluoroethylene (PTFE), and modified EPDM rubber, meeting the specific performance requirements of this application, as a plastic gasket for alkaline electrolytic cells. Summary of the Invention

[0004] To address the aforementioned issues, a plastic gasket for alkaline electrolytic cells, its preparation method, and its application are provided. By combining polyphenylene sulfide, polytetrafluoroethylene, and modified EPDM rubber, the compatibility of the multiphase composition can be coordinated, achieving higher heat resistance and alkali resistance while possessing good resilience, sealing properties, and mechanical strength. This effectively resists erosion and impact in high-temperature alkaline electrolytic cells, significantly extending the service life of the sealing gasket.

[0005] This application provides a plastic gasket for an alkaline electrolytic cell, comprising, by weight: 40-60 parts of polyphenylene sulfide, 8-20 parts of modified EPDM rubber, 10-20 parts of polytetrafluoroethylene, 1-3 parts of crosslinking agent, 0.5-1.5 parts of catalyst, 1-2 parts of silane coupling agent, 10-20 parts of filler, 0.3-1.5 parts of antioxidant, and 0.5-1 part of calcium stearate.

[0006] Optionally, the melt index of the polyphenylene sulfide is 120~130 g / 10min.

[0007] Optionally, the modified EPDM rubber is maleic anhydride-grafted EPDM rubber.

[0008] Optionally, the molecular weight of the maleic anhydride-grafted EPDM rubber ranges from 50,000 to 100,000, and the molar percentage of maleic acid monomer in the maleic anhydride-grafted EPDM rubber is 1 to 2 mol.

[0009] Optionally, the polytetrafluoroethylene has a molecular weight range of 3 million to 5 million and a molecular weight distribution of 2 to 4.

[0010] Optionally, the crosslinking agent is one or more of dicumyl peroxide, bis-tert-butyl peroxide, and triallyl cyanurate.

[0011] Optionally, the catalyst is one or more of triallyl isocyanurate, stannous octoate, and dibutyltin dilaurate.

[0012] Optionally, the silane coupling agent is one or more of γ-methacryloxypropyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyl-trimethoxysilane, N-(β-aminoethyl)-γ-aminopropyl-trimethoxysilane, octyl-triethoxysilane, and 3-isocyanate-propyl-triethoxysilane.

[0013] This application provides a method for preparing the above-mentioned alkaline electrolytic cell plastic gasket, the method comprising the following steps: S1. Polyphenylene sulfide, modified EPDM rubber, polytetrafluoroethylene powder, filler, silane coupling agent, antioxidant, and calcium stearate are dry premixed at 60-70℃ for 5-15 minutes to obtain a premix. S2. The premixed material is fed into a twin-screw extruder and melt-blended at 280~320℃ with a screw speed of 100~250rpm. The extrudate is cooled and pelletized to obtain composite granules. S3. The composite granules are compressed and molded, and the pressure is maintained at 20-30MPa for 10-30min at a temperature of 300-320℃. S4. After cooling and demolding, the desired shape is obtained through processing, thus obtaining the alkaline electrolytic cell plastic gasket.

[0014] This application provides the use of the above-described alkaline electrolytic cell plastic gasket or the alkaline electrolytic cell plastic gasket prepared by the above method in alkaline electrolytic cell products.

[0015] The beneficial effects of this application include, but are not limited to: 1. According to the alkaline electrolytic cell plastic gasket, its preparation method, and its application, the present application uses polyphenylene sulfide with a suitable melt index, modified EPDM rubber grafted with maleic anhydride, and polytetrafluoroethylene in synergy. While maintaining the rigidity, heat resistance, and alkali resistance of the polyphenylene sulfide skeleton, the introduction of modified EPDM rubber significantly improves the interfacial compatibility, energy dissipation capacity, and surface friction behavior of the material system. It can introduce local chain segment disturbances, thus making it less prone to brittle fracture propagation under impact loads, which is beneficial for the impact load to be transferred from rigid polyphenylene... The sulfide smoothly transfers to the elastic EPDM rubber, significantly improving its impact resistance and elongation at break. Conversely, the polyphenylene sulfide also provides elastic support and deformation constraint for the modified EPDM rubber, while the EPDM rubber provides elastic recovery for the polyphenylene sulfide. Thus, the polyphenylene sulfide forms a stable load-bearing skeleton in the multiphase system. During compression deformation, it works synergistically with the modified EPDM rubber, both restricting the irreversible flow of the rubber phase and not inhibiting its elastic recovery, thereby significantly improving the resilience and long-term sealing stability of the gasket.

[0016] 2. Based on the alkaline electrolytic cell plastic gasket and its preparation method and application in this application, the EPDM rubber with a suitable molecular weight range is selected in the scheme of this application, and the appropriate molar percentage of maleic acid monomer is limited, which can better match with polyphenylene sulfide and polytetrafluoroethylene. If the molar ratio of maleic acid monomer is too high, the chain segment is too rigid, resulting in poor resilience. If the molar ratio of maleic acid monomer is too low, reversible micro-deformation can occur after being compressed, resulting in deformation under liquid impact and poor sealing performance.

[0017] 3. Based on the alkaline electrolytic cell plastic gasket, its preparation method, and its application, the molecular weight range of polytetrafluoroethylene (PTFE) in this application was screened, and the optimal molecular weight range for combination with modified EPDM rubber and polyphenylene sulfide was determined. This optimal range balances impact resistance, elongation at break, resilience, and wear resistance. Since the gasket in this application has comprehensive requirements for the above properties, the selection of the molecular weight range of PTFE is of great significance for obtaining an alkaline electrolytic cell plastic gasket with excellent comprehensive performance. Detailed Implementation

[0018] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments. Unless otherwise specified, the raw materials and reagents in the embodiments of the present application are all purchased through commercial channels.

[0019] Example 1 This embodiment provides a plastic gasket for an alkaline electrolytic cell, comprising, by weight: 50 parts polyphenylene sulfide, 14 parts maleic anhydride-grafted modified EPDM rubber, 15 parts polytetrafluoroethylene (PTFE), 2 parts dicumyl peroxide crosslinking agent, 1.0 part triallyl isocyanurate catalyst, 1.5 parts γ-methacryloyloxypropyltrimethoxysilane silane coupling agent, 15 parts mica powder filler, 0.9 parts antioxidant, and 0.75 parts calcium stearate. The polyphenylene sulfide has a melt index of 124 g / 10min, the maleic anhydride-grafted EPDM rubber has a molecular weight range of 50,000 to 100,000, the maleic anhydride-grafted EPDM rubber contains a maleic acid monomer molar percentage of 1.7 mol%, and the PTFE has a molecular weight range of 3,000,000 to 5,000,000 with a molecular weight distribution of 2.6. The preparation method of this alkaline electrolytic cell plastic gasket includes the following steps: S1. Polyphenylene sulfide, modified EPDM rubber, polytetrafluoroethylene micro powder, filler, silane coupling agent, antioxidant, and calcium stearate are dry premixed at 65°C for 10 min to obtain a premix. S2. The premixed material is fed into a twin-screw extruder and melt-blended at 300°C with a screw speed of 200 rpm. The extrudate is cooled and pelletized to obtain composite granules. S3. The composite granules are compressed and molded, and the pressure is maintained at 25MPa for 20 min at 310℃. S4. After cooling and demolding, the desired shape is obtained through processing, thus obtaining the alkaline electrolytic cell plastic gasket.

[0020] Example 2 This embodiment provides a plastic gasket for an alkaline electrolytic cell, comprising, by weight: 40 parts polyphenylene sulfide, 8 parts maleic anhydride-grafted modified EPDM rubber, 10 parts polytetrafluoroethylene (PTFE), 1 part di-tert-butylperoxyisopropylbenzene crosslinking agent, 0.5 parts dibutyltin dilaurate catalyst, 1 part γ-methacryloyloxypropyltrimethoxysilane silane coupling agent, 10 parts mica powder filler, 0.3 parts antioxidant, and 0.5 parts calcium stearate. The polyphenylene sulfide has a melt index of 127 g / 10min, the maleic anhydride-grafted EPDM rubber has a molecular weight range of 50,000 to 100,000, the maleic anhydride-grafted EPDM rubber contains a maleic acid monomer molar percentage of 1.2 mol%, and the PTFE has a molecular weight range of 3,000,000 to 5,000,000 with a molecular weight distribution of 2.6. The preparation method of this alkaline electrolytic cell plastic gasket includes the following steps: S1. Polyphenylene sulfide, modified EPDM rubber, polytetrafluoroethylene micro powder, filler, silane coupling agent, antioxidant, and calcium stearate are dry premixed at 60°C for 15 minutes to obtain a premix. S2. The premixed material is fed into a twin-screw extruder and melt-blended at 280°C with a screw speed of 100 rpm. The extrudate is cooled and pelletized to obtain composite granules. S3. The composite granules are compressed and molded, and held at 20MPa for 30 min at 300℃. S4. After cooling and demolding, the desired shape is obtained through processing, thus obtaining the alkaline electrolytic cell plastic gasket.

[0021] Example 3 This embodiment provides a plastic gasket for an alkaline electrolytic cell, comprising, by weight: 60 parts polyphenylene sulfide, 20 parts maleic anhydride-grafted modified EPDM rubber, 20 parts polytetrafluoroethylene (PTFE), 3 parts triallyl cyanurate crosslinking agent, 1.5 parts stannous octoate catalyst, 2 parts γ-methacryloyloxypropyltrimethoxysilane silane coupling agent, 20 parts mica powder filler, 1.5 parts antioxidant, and 1 part calcium stearate. The polyphenylene sulfide has a melt index of 128 g / 10min, the maleic anhydride-grafted EPDM rubber has a molecular weight range of 50,000 to 100,000, the maleic anhydride-grafted EPDM rubber has a molar percentage of maleic acid monomer of 1.9 mol%, and the PTFE has a molecular weight range of 3,000,000 to 5,000,000 with a molecular weight distribution of 2.6. The preparation method of this alkaline electrolytic cell plastic gasket includes the following steps: S1. Polyphenylene sulfide, modified EPDM rubber, polytetrafluoroethylene micro powder, filler, silane coupling agent, antioxidant, and calcium stearate are dry premixed at 70°C for 5 minutes to obtain a premix. S2. The premixed material is fed into a twin-screw extruder and melt-blended at 320°C with a screw speed of 250 rpm. The extrudate is cooled and pelletized to obtain composite granules. S3. The composite granules are compressed and molded, and the pressure is maintained at 30MPa for 10 minutes at 320℃. S4. After cooling and demolding, the desired shape is obtained through processing, thus obtaining the alkaline electrolytic cell plastic gasket.

[0022] Example 4 This embodiment is basically the same as Example 1, except that the melt index of polyphenylene sulfide is 143 g / 10min.

[0023] Example 5 This embodiment is basically the same as Example 1, except that the melt index of polyphenylene sulfide is 112 g / 10min.

[0024] Example 6 This embodiment is basically the same as Example 1, except that the molecular weight of the EPDM rubber is in the range of 150,000 to 250,000 and the molar percentage of maleic acid monomer is 3.6 mol.

[0025] Example 7 This embodiment is basically the same as that of Embodiment 1, except that the molecular weight of the EPDM rubber is in the range of 20,000 to 50,000 and the molar percentage of maleic acid monomer is 0.7 mol.

[0026] Example 8 This embodiment is basically the same as Embodiment 1, except that the molecular weight of polytetrafluoroethylene is in the range of 1 million to 2 million, and the molecular weight distribution is 2.2.

[0027] Example 9 This embodiment is basically the same as Embodiment 1, except that the molecular weight of polytetrafluoroethylene is in the range of 8 million to 10 million, and the molecular weight distribution is 5.7.

[0028] Comparative Example 1 This comparative example is basically the same as Example 1, except that it does not contain EPDM rubber.

[0029] Comparative Example 2 This comparative example is basically the same as Example 1, except that the EPDM rubber is unmodified EPDM rubber.

[0030] Comparative Example 3 This comparative example is basically the same as Example 1, except that it does not contain polytetrafluoroethylene.

[0031] Test Example 1 The performance of the alkaline electrolytic cell plastic gasket materials obtained in the examples and comparative examples was tested. In order to meet the requirements of the gaskets' resistance to high temperature of 80°C and strong alkali corrosion, the gasket materials to be tested were accelerated aged in the following way: a 30wt% potassium hydroxide aqueous solution was prepared, and the sample was completely immersed in the strong alkali solution. After sealing the container, it was placed in a constant temperature oven and kept at 80°C for 240 hours. After the treatment, it was taken out and cleaned. Then, the cleaned sample was placed in a vacuum drying oven at 35°C and dried. Then, the performance of the gasket material after accelerated aging was tested. The results are shown in Table 1 below.

[0032] Impact resistance: The notched impact strength of the cantilever beam was tested according to GB / T 1843-2008; Elongation at break: The elongation at break is tested according to GB / T 1040.2-2022. Since gaskets often need a certain interference fit, they need to have good elastic polar strain capacity to maintain a good sealing effect.

[0033] Resilience: The compression set test is conducted according to GB / T 7759.1-2015. The compression set is used to characterize the resilience performance. The smaller the compression set, the better the resilience, and the better the gasket's sealing performance. It is also less likely to break or crack.

[0034] Wear resistance: The wear resistance is tested according to GB / T 3960-2016 and the wear rate is calculated. Since the gasket needs to face the impact and loss of the liquid in the channel, it also needs to have a certain wear resistance.

[0035] Table 1. Performance test results of plastic gasket materials in alkaline electrolytic cells of the examples and comparative examples.

[0036] As shown in Table 1, the proposed solution, by introducing maleic anhydride-grafted EPDM rubber in synergistic combination with polyphenylene sulfide and polytetrafluoroethylene (PTFE), and optimizing and screening the molecular weight of PTFE, the molecular weight of maleic anhydride-grafted EPDM rubber, the molar percentage of maleic acid monomer, and the melt index of PTFE, results in alkaline electrolytic cell plastic gaskets with good high-temperature resistance, strong alkali corrosion resistance, good resilience, sealing properties, and mechanical strength. These properties effectively resist erosion and impact in high-temperature alkaline electrolytic cells, significantly extending the service life of the gaskets, and demonstrating a clear advantage over current nickel-plated metal gaskets.

[0037] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A plastic gasket for an alkaline electrolytic cell, characterized in that, By weight, it includes: 40-60 parts polyphenylene sulfide, 8-20 parts modified EPDM rubber, 10-20 parts polytetrafluoroethylene, 1-3 parts crosslinking agent, 0.5-1.5 parts catalyst, 1-2 parts silane coupling agent, 10-20 parts filler, 0.3-1.5 parts antioxidant, and 0.5-1 part calcium stearate.

2. The alkaline electrolytic cell plastic gasket according to claim 1, characterized in that, The melt index of the polyphenylene sulfide is 120~130 g / 10min.

3. The alkaline electrolytic cell plastic gasket according to claim 1, characterized in that, The modified EPDM rubber is maleic anhydride-grafted EPDM rubber.

4. The alkaline electrolytic cell plastic gasket according to claim 3, characterized in that, The molecular weight range of the maleic anhydride-grafted EPDM rubber is 50,000 to 100,000, and the molar percentage of maleic acid monomer in the maleic anhydride-grafted EPDM rubber is 1 to 2 mol.

5. The alkaline electrolytic cell plastic gasket according to claim 1, characterized in that, The polytetrafluoroethylene has a molecular weight range of 3 million to 5 million and a molecular weight distribution of 2 to 4.

6. The alkaline electrolytic cell plastic gasket according to claim 1, characterized in that, The crosslinking agent is one or more of dicumyl peroxide, bis-tert-butyl peroxide, and triallyl cyanurate.

7. The alkaline electrolytic cell plastic gasket according to claim 1, characterized in that, The catalyst is one or more of triallyl isocyanurate, stannous octoate, and dibutyltin dilaurate.

8. The alkaline electrolytic cell plastic gasket according to claim 1, characterized in that, The silane coupling agent is one or more of γ-methacryloxypropyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyl-trimethoxysilane, N-(β-aminoethyl)-γ-aminopropyl-trimethoxysilane, octyl-triethoxysilane, and 3-isocyanate-propyl-triethoxysilane.

9. The method for preparing the alkaline electrolytic cell plastic gasket according to any one of claims 1 to 8, characterized in that, The preparation method includes the following steps: S1. Polyphenylene sulfide, modified EPDM rubber, polytetrafluoroethylene powder, filler, silane coupling agent, antioxidant, and calcium stearate are dry premixed at 60-70℃ for 5-15 minutes to obtain a premix. S2. The premixed material is fed into a twin-screw extruder and melt-blended at 280~320℃ with a screw speed of 100~250rpm. The extrudate is cooled and pelletized to obtain composite granules. S3. The composite granules are compressed and molded, and the pressure is maintained at 20-30MPa for 10-30 min at a temperature of 300-320℃. S4. After cooling and demolding, the desired shape is obtained through processing, thus obtaining the alkaline electrolytic cell plastic gasket.

10. The application of the alkaline electrolytic cell plastic gasket as described in any one of claims 1 to 8 or the alkaline electrolytic cell plastic gasket obtained by the preparation method as described in claim 9 in alkaline electrolytic cell products.

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