Super-hydrophilic strong-alkali-resistant polyphenylene sulfide diaphragm as well as preparation method and application thereof

Abstract

The invention discloses a super-hydrophilic strong-alkali-resistant polyphenylene sulfide diaphragm as well as a preparation method and application thereof, the super-hydrophilic strong-alkali-resistant polyphenylene sulfide diaphragm comprises polyphenylene sulfide fibers and a hydrophilic layer of a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40-50nm; the polyphenylene sulfide diaphragm is immersed in an alkaline electrolyte for 120 hours, the water contact angle between the polyphenylene sulfide diaphragm and an alkaline wetting solution is not greater than 5 degrees, and the wetting water absorption time between the polyphenylene sulfide diaphragm and the alkaline wetting solution is not greater than 0.1 s; under the working voltage of 1.8 V and the alkaline electrolyte, the hydrogen content in the anode side gas of the alkaline electrolytic cell using the polyphenylene sulfide diaphragm is not higher than 0.5%, and the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with the mass concentration of 30%-50%. The hydrophilic layer of the modified polydopamine polymer is prepared through a simple and convenient process, the alkali-resisting hydrophilicity of the polyphenylene sulfide diaphragm is improved, the problems that the hydrophilic performance of an existing hydrophilic layer in an alkaline electrolytic bath is degraded and unstable are solved, and the super-hydrophilic polyphenylene sulfide diaphragm stably used in the alkaline environment is prepared.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogen production by electrolysis of water, and specifically relates to a super-hydrophilic and alkali-resistant polyphenylene sulfide diaphragm, a preparation method and application thereof. Background Art

[0002] Among the existing water electrolysis technologies, alkaline water electrolysis (AWE) is often used for industrial hydrogen production due to its stability and durability. During alkaline water electrolysis, a diaphragm is usually placed between the electrodes in order to effectively separate the hydrogen and oxygen produced by water electrolysis, improve the purity of hydrogen and ensure the safety of the electrolysis process. The function of the diaphragm is to prevent hydrogen and oxygen from mixing in the electrolyzer, thereby avoiding the risk of explosion and improving the purity of the product.

[0003] In AWE, the diaphragm is usually a porous membrane made of organic or inorganic materials, and is required to have sufficient strength, toughness and durability in strong alkaline electrolytes and high temperatures (usually around 80°C). Research on diaphragms in alkaline water electrolysis also focuses on improving the stability and physical properties of diaphragms in chemical environments.

[0004] In addition, the diaphragm must be highly hydrophilic so that the electrolyte can fully fill its porous structure. If the diaphragm has poor hydrophilicity, the diaphragm cloth will not be fully wetted by the electrolyte, the ion permeability of the diaphragm will deteriorate, and the diaphragm resistance will be further increased, which will eventually lead to a decrease in the electrolysis efficiency of the electrolyzer and a huge waste of electricity and energy. Insufficient hydrophilicity of the diaphragm is one of the biggest challenges facing diaphragms.

[0005] At present, there are many methods such as surface modification and composite materials to improve the hydrophilicity of the diaphragm. For example, patent CN118198649A provides a method for preparing a diaphragm, a diaphragm and a battery thereof, which include the following steps: immersing the diaphragm substrate in a sulfuric acid solution, performing a sulfonation treatment, and obtaining a sulfonated diaphragm; immersing the sulfonated diaphragm in a dopamine solution to form a polydopamine coating layer on the diaphragm surface, and then drying to obtain the diaphragm; the dopamine solution contains sodium borate and dopamine hydrochloride; the scheme also provides a diaphragm and a battery thereof; the diaphragm provided by the scheme has a simple synthesis process, the diaphragm is sulfonated to graft hydrophilic functional groups such as sulfate groups on the diaphragm surface, and then the sulfonated diaphragm is immersed in a dopamine solution, and the dopamine solution has rich functional groups, such as -OH and -NH-, which will significantly improve the hydrophilicity and liquid retention capacity of the diaphragm.

[0006] As for the polyphenylene sulfide diaphragm, it has excellent heat resistance, high mechanical strength and good electrical properties, and is a commonly used alkaline electrolyzer diaphragm material in current commercialization. However, the hydrophilicity of the polyphenylene sulfide diaphragm is poor. Introducing a hydrophilic coating on the surface of the polyphenylene sulfide diaphragm can improve hydrophilicity and ion permeability. For example, patent CN117904870A provides a polyphenylene sulfide fabric for alkaline water electrolysis and a preparation method, and polyphenylene sulfide fabric is obtained by granulating, drying, melt spinning, spinning and weaving the polyphenylene sulfide resin in sequence. Then, dopamine hydrochloride and Tris-HCl buffer solution are used as raw materials to obtain a mixed solution; the polyphenylene sulfide fabric is immersed in the mixed solution to form a layer of polydopamine on the surface of the polyphenylene sulfide fabric. Then, the polyphenylene sulfide fabric is immersed in the reaction solution 1 with mercaptoethylamine as the main raw material and the reaction solution 2 with sulfonic acid and acrylic acid as the main raw materials to obtain a finished product. The polyphenylene sulfide fabric obtained by this scheme has good hydrophilicity and chemical resistance, and therefore has broad application prospects in the field of membrane preparation technology.

[0007] However, the above prior art has limited effect on improving the hydrophilicity of the diaphragm. The introduced polydopamine coating will aggregate in the alkaline environment of the alkaline electrolyzer for a long time, causing the membrane pores of the polydopamine coating to be blocked, affecting the hydrophilicity and ion passing performance of the diaphragm.

[0008] Therefore, how to improve the alkali resistance and hydrophilicity of the polyphenylene sulfide membrane and overcome the problem of hydrophilic performance degradation and instability of the existing hydrophilic layer in the alkaline electrolytic cell environment to obtain a super hydrophilic polyphenylene sulfide membrane that can be used stably in an alkaline environment is an urgent problem to be solved by technicians in this field. Summary of the invention

[0009] In view of the defects existing in the above-mentioned prior art, the present invention provides a super hydrophilic and alkali-resistant polyphenylene sulfide membrane, a preparation method and an application thereof. The polyphenylene sulfide membrane specifically comprises: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40-50nm; the water contact angle between the polyphenylene sulfide membrane and the alkaline wetting liquid is not greater than 5°, and the wetting and water absorption time of the polyphenylene sulfide membrane and the alkaline wetting liquid is not greater than 0.1s; under an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the gas on the anode side of the alkaline electrolytic cell using the polyphenylene sulfide membrane is not higher than 0.5%, wherein the alkaline wetting liquid and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%-50%. The invention prepares a hydrophilic layer of a modified polydopamine polymer through a simple process, improves the alkali-resistant hydrophilicity of a polyphenylene sulfide membrane, overcomes the problem of hydrophilic performance decay and instability of the existing hydrophilic layer in an alkaline electrolytic cell environment, and prepares a super-hydrophilic polyphenylene sulfide membrane that can be stably used in an alkaline environment.

[0010] In a first aspect, the present invention provides a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane, specifically comprising: a base membrane and a hydrophilic layer, wherein the base membrane is polyphenylene sulfide fiber or sulfonated polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40-50 nm;

[0011] The polyphenylene sulfide diaphragm is immersed in an alkaline electrolyte for 120 hours, and the water contact angle with the alkaline wetting liquid is not greater than 5°, and the wetting and water absorption time of the polyphenylene sulfide diaphragm with the alkaline wetting liquid is not greater than 0.1s;

[0012] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the gas at the anode side of an alkaline electrolytic cell using a polyphenylene sulfide diaphragm is no more than 0.5%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%-50%.

[0013] The super hydrophilic and alkali-resistant polyphenylene sulfide membrane is a polyphenylene sulfide membrane having a water contact angle with an alkaline wetting liquid of no more than 5°.

[0014] The alkaline electrolyzer produces oxygen on the anode side and hydrogen on the cathode side. The function of the diaphragm is to prevent the hydrogen produced by the cathode from mixing with the oxygen produced by the anode. The use of the super-hydrophilic, strong-alkali-resistant polyphenylene sulfide diaphragm of the present invention allows electrolyte ions to pass through, preventing hydrogen and oxygen from interpenetrating, and the hydrogen content in the gas produced on the anode side is not higher than 0.5%.

[0015] Furthermore, the most probable pore size of the hydrophilic layer is not greater than 40 μm. The most probable pore size is the pore size value of the peak value on the pore size differential distribution curve.

[0016] Furthermore, the elements of the hydrophilic layer include C, N, and O, wherein the nitrogen-oxygen ratio of the elements of the hydrophilic layer is 0.8-1.2.

[0017] In a second aspect, the present invention further provides a method for preparing the above-mentioned super-hydrophilic and alkali-resistant polyphenylene sulfide membrane, which specifically comprises the following steps:

[0018] Step S1: performing plasma surface treatment on a base membrane woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers to obtain a pretreated polyphenylene sulfide membrane;

[0019] Step S2: placing the pretreated polyphenylene sulfide membrane of step S1 in a pre-prepared mixed aqueous solution for immersion modification treatment to obtain a polyphenylene sulfide membrane with attached modified polydopamine polymer, and after washing and drying, obtaining a super hydrophilic and alkali-resistant polyphenylene sulfide membrane, wherein the mixed aqueous solution includes dopamine and polyethyleneimine, the mass ratio of dopamine to polyethyleneimine is (1-2): 1, the concentration of dopamine is 2-3 mg / ml, and the weight average molecular weight of polyethyleneimine is not higher than 600.

[0020] Furthermore, step S1 specifically includes:

[0021] Step S11: placing a base film woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers in a plasma treatment chamber, turning on the power supply, evacuating the chamber until the vacuum reaches a threshold, turning on the high-voltage power supply after preheating, setting the discharge frequency to 40-50 kHz, and performing plasma treatment for 5-10 minutes before turning off the power supply;

[0022] Step S12: turning over the base film woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers, and repeating step S11;

[0023] Step S13: repeating steps S11 and S12 until the water absorption time of the base membrane woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers is no more than 0.5 s, thereby obtaining a pretreated polyphenylene sulfide membrane.

[0024] Furthermore, in step S1, the threshold of the vacuum degree is 20-50 Pa, and the preheating temperature is not higher than 50°C.

[0025] When the vacuum reaches the threshold and preheating is carried out, a small amount of air will flow back in the plasma treatment chamber, and the high voltage power supply will excite the oxygen to form an ion state. Plasma surface treatment can improve the hydrophilicity of polyphenylene sulfide fibers, introduce oxygen-containing polar functional groups (e.g., -OH) on the surface of the base film, form multiple active points, and also produce a microscopic rough structure that is a good base for the attachment of the polydopamine layer.

[0026] Furthermore, in step S2, the mixed aqueous solution also includes tris(hydroxymethyl)aminomethane, polyethylene polyamine and a phosphate mixture, and the molar ratio of tris(hydroxymethyl)aminomethane to the phosphate mixture is (20-25):1, the concentration of polyethylene polyamine is 8-15 mg / ml, and the pH of the mixed aqueous solution is 8.5-8.8, wherein the phosphate mixture includes dipotassium hydrogen phosphate and potassium dihydrogen phosphate.

[0027] Further, the polyethylene polyamine is a co-product of ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine. The proportion of each component of the polyethylene polyamine can be adjusted according to the specific application scenario. In addition, the proportion of dipotassium hydrogen phosphate and potassium dihydrogen phosphate in the phosphate mixture can also be adjusted according to the specific application scenario.

[0028] Furthermore, in step S2, the preparation of the mixed aqueous solution specifically includes:

[0029] A tris(hydroxymethylaminomethane) solution and a phosphate buffer solution are prepared respectively with tris(hydroxymethylaminomethane) and a phosphate mixture, and the tris(hydroxymethylaminomethane) solution and the phosphate buffer solution are mixed according to the molar ratio to form an initial mixed aqueous solution, wherein the concentration of the tris(hydroxymethylaminomethane) solution is 50-60 mmol / L;

[0030] Dopamine powder, polyethyleneimine and polyethylene polyamine are added into the initial mixed aqueous solution according to the mass ratio to prepare a mixed aqueous solution.

[0031] Dopamine and polyethyleneimine (low weight average molecular weight) are co-deposited and attached to the surface of the pretreated polyphenylene sulfide separator. Among them, polyethyleneimine undergoes Michael addition, which accelerates the copolymerization with dopamine, reduces the self-polymerization of dopamine, and enhances the stability of polymerization, which can avoid the appearance of aggregates caused by dopamine self-polymerization in a long-term alkaline environment. When dopamine and polyethyleneimine are polymerized and co-deposited, the added polyethylene polyamine can improve the uniformity and adhesion of the hydrophilic coating.

[0032] In addition, the pH value of the mixed aqueous solution is adjusted by using a tris(hydroxymethyl)aminomethane solution and a phosphate buffer solution to promote the polymerization of dopamine and polyethyleneimine.

[0033] Further, in step S2, the soaking modification treatment specifically includes:

[0034] The temperature of the mixed aqueous solution is 20-30°C, and the pretreated polyphenylene sulfide membrane in step S1 is immersed in the mixed aqueous solution for modification for 12-48 hours. During the immersion modification process, oxygen is continuously introduced into the mixed aqueous solution, and the oxygen flow rate is not less than 1 / 20L0 / min, where L0 is the volume of the mixed aqueous solution.

[0035] During the modified deposition process, oxygen is introduced into the mixed aqueous solution evenly and slowly, which can not only make the oxygen in the solution evenly distributed and make the deposition of the modified polydopamine polymer more uniform, but also accelerate the copolymerization of dopamine and polyethyleneimine, reduce the deposition time, and improve the deposition quality of the hydrophilic coating.

[0036] In a third aspect, the present invention further provides an application of a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane, wherein the super-hydrophilic and alkali-resistant polyphenylene sulfide membrane is applied to an alkaline water electrolysis hydrogen production cell.

[0037] The present invention provides a super-hydrophilic and alkali-resistant polyphenylene sulfide diaphragm, a preparation method and an application thereof, which at least have the following beneficial effects:

[0038] (1) The present invention prepares a hydrophilic layer of a modified polydopamine polymer through a simple process, thereby improving the alkali resistance and hydrophilicity of the polyphenylene sulfide membrane, overcoming the problem of hydrophilic performance degradation and instability of the existing hydrophilic layer in an alkaline electrolytic cell environment, and preparing a super-hydrophilic polyphenylene sulfide membrane that can be stably used in an alkaline environment.

[0039] (2) Plasma surface treatment can improve the hydrophilicity of polyphenylene sulfide fibers, introduce oxygen-containing polar functional groups (e.g., -OH) on the surface of the polyphenylene sulfide fiber base film, form multiple active points, and also produce a microscopic rough structure that is a good substrate for the attachment of the polydopamine layer.

[0040] (3) Dopamine and polyethyleneimine (low weight average molecular weight) are co-deposited and attached to the surface of the pretreated polyphenylene sulfide separator. Among them, polyethyleneimine undergoes Michael addition, which accelerates the copolymerization with dopamine, reduces the self-polymerization of dopamine, and enhances the stability of the polymerization, which can avoid the appearance of aggregates caused by dopamine self-polymerization in a long-term alkaline environment. When dopamine and polyethyleneimine are polymerized and co-deposited, the added polyethylene polyamine can improve the uniformity and adhesion of the hydrophilic coating.

[0041] (4) During the modified deposition process, oxygen is introduced into the mixed aqueous solution evenly and slowly, which can not only make the oxygen in the solution evenly distributed and make the deposition of the modified polydopamine polymer more uniform, but also accelerate the copolymerization of dopamine and polyethyleneimine, reduce the deposition time, and improve the deposition quality of the hydrophilic coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The surface SEM images of the polyphenylene sulfide separator of Example 1 provided by the present invention before and after the alkali resistance test;

[0043] Figure 2 This is an example diagram of the water contact angle of the polyphenylene sulfide membrane of Example 1 provided by the present invention;

[0044] Figure 3 This is an example diagram of the water contact angle of the polyphenylene sulfide membrane of Example 2 provided by the present invention;

[0045] Figure 4 This is an example diagram of the water contact angle of the polyphenylene sulfide membrane of Comparative Example 5 provided by the present invention. DETAILED DESCRIPTION

[0046] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings, and "multiple" generally includes at least two.

[0048] It should also be noted that the term "includes", "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, so that a commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the commodity or device including the elements.

[0049] The existing technology has limited effect on improving the hydrophilicity of the diaphragm. The introduced polydopamine coating will aggregate in the alkaline environment of the alkaline electrolyzer for a long time, causing the membrane pores of the polydopamine coating to be blocked, affecting the hydrophilicity and ion passing performance of the diaphragm.

[0050] Currently, there is still a need to improve the alkali resistance and hydrophilicity of polyphenylene sulfide membranes, overcome the problem of hydrophilic performance degradation and instability of the existing hydrophilic layer in the alkaline electrolytic cell environment, and obtain a super hydrophilic polyphenylene sulfide membrane that can be used stably in an alkaline environment.

[0051] In a first aspect, the present invention provides a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane, specifically comprising: a base membrane and a hydrophilic layer, wherein the base membrane is polyphenylene sulfide fiber or sulfonated polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40-50 nm;

[0052] The polyphenylene sulfide diaphragm is immersed in an alkaline electrolyte for 120 hours, and the water contact angle with the alkaline wetting liquid is not greater than 5°, and the wetting and water absorption time of the polyphenylene sulfide diaphragm with the alkaline wetting liquid is not greater than 0.1s;

[0053] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the gas at the anode side of an alkaline electrolytic cell using a polyphenylene sulfide diaphragm is no more than 0.5%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%-50%.

[0054] The super hydrophilic and alkali-resistant polyphenylene sulfide membrane is a polyphenylene sulfide membrane having a water contact angle with an alkaline wetting liquid of no more than 5°.

[0055] Furthermore, the most probable pore size of the hydrophilic layer is not greater than 40 μm. The most probable pore size is the pore size value of the peak value on the pore size differential distribution curve.

[0056] Furthermore, the elements of the hydrophilic layer include C, N, and O, wherein the nitrogen-oxygen ratio of the elements of the hydrophilic layer is 0.8-1.2.

[0057] In a second aspect, the present invention further provides a method for preparing the above-mentioned super-hydrophilic and alkali-resistant polyphenylene sulfide membrane, which specifically comprises the following steps:

[0058] Step S1: performing plasma surface treatment on a base membrane woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers to obtain a pretreated polyphenylene sulfide membrane;

[0059] Step S2: placing the pretreated polyphenylene sulfide membrane of step S1 in a pre-prepared mixed aqueous solution for immersion modification treatment to obtain a polyphenylene sulfide membrane with attached modified polydopamine polymer, and after washing and drying, obtaining a super hydrophilic and alkali-resistant polyphenylene sulfide membrane, wherein the mixed aqueous solution includes dopamine and polyethyleneimine, the mass ratio of dopamine to polyethyleneimine is (1-2): 1, the concentration of dopamine is 2-3 mg / ml, and the weight average molecular weight of polyethyleneimine is not higher than 600.

[0060] Furthermore, step S1 specifically includes:

[0061] Step S11: placing a base film woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers in a plasma treatment chamber, turning on the power supply, evacuating the chamber until the vacuum reaches a threshold, turning on the high-voltage power supply after preheating, setting the discharge frequency to 40-50 kHz, and performing plasma treatment for 5-10 minutes before turning off the power supply;

[0062] Step S12: turning over the base film woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers, and repeating step S11;

[0063] Step S13: repeating steps S11 and S12 until the water absorption time of the base membrane woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers is no more than 0.5 s, thereby obtaining a pretreated polyphenylene sulfide membrane.

[0064] Furthermore, in step S1, the threshold of the vacuum degree is 20-50 Pa, and the preheating temperature is not higher than 50°C.

[0065] Furthermore, in step S2, the mixed aqueous solution also includes tris(hydroxymethyl)aminomethane, polyethylene polyamine and a phosphate mixture, and the molar ratio of tris(hydroxymethyl)aminomethane to the phosphate mixture is (20-25):1, the concentration of polyethylene polyamine is 8-15 mg / ml, and the pH of the mixed aqueous solution is 8.5-8.8, wherein the phosphate mixture includes dipotassium hydrogen phosphate and potassium dihydrogen phosphate.

[0066] Further, the polyethylene polyamine is a co-product of ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine. The proportion of each component of the polyethylene polyamine can be adjusted according to the specific application scenario. In addition, the proportion of dipotassium hydrogen phosphate and potassium dihydrogen phosphate in the phosphate mixture can also be adjusted according to the specific application scenario.

[0067] Furthermore, in step S2, the preparation of the mixed aqueous solution specifically includes:

[0068] A tris(hydroxymethylaminomethane) solution and a phosphate buffer solution are prepared respectively with tris(hydroxymethylaminomethane) and a phosphate mixture, and the tris(hydroxymethylaminomethane) solution and the phosphate buffer solution are mixed according to the molar ratio to form an initial mixed aqueous solution, wherein the concentration of the tris(hydroxymethylaminomethane) solution is 50-60 mmol / L;

[0069] Dopamine powder, polyethyleneimine and polyethylene polyamine are added into the initial mixed aqueous solution according to the mass ratio to prepare a mixed aqueous solution.

[0070] Further, in step S2, the soaking modification treatment specifically includes:

[0071] The temperature of the mixed aqueous solution is 20-30°C, and the pretreated polyphenylene sulfide membrane in step S1 is immersed in the mixed aqueous solution for modification for 12-48 hours. During the immersion modification process, oxygen is continuously introduced into the mixed aqueous solution, and the oxygen flow rate is not less than 1 / 20L0 / min, where L0 is the volume of the mixed aqueous solution.

[0072] In a third aspect, the present invention further provides an application of a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane, wherein the super-hydrophilic and alkali-resistant polyphenylene sulfide membrane is applied to an alkaline water electrolysis hydrogen production cell.

[0073] The present invention provides a super-hydrophilic and alkali-resistant polyphenylene sulfide diaphragm, a preparation method and an application thereof, which at least have the following beneficial effects:

[0074] (1) The present invention prepares a hydrophilic layer of a modified polydopamine polymer through a simple process, thereby improving the alkali resistance and hydrophilicity of the polyphenylene sulfide membrane, overcoming the problem of hydrophilic performance degradation and instability of the existing hydrophilic layer in an alkaline electrolytic cell environment, and preparing a super-hydrophilic polyphenylene sulfide membrane that can be stably used in an alkaline environment.

[0075] (2) Plasma surface treatment can improve the hydrophilicity of polyphenylene sulfide fibers, introduce oxygen-containing polar functional groups (e.g., -OH) on the surface of the polyphenylene sulfide fiber base film, form multiple active points, and also produce a microscopic rough structure that is a good substrate for the attachment of the polydopamine layer.

[0076] (3) Dopamine and polyethyleneimine (low weight average molecular weight) are co-deposited and attached to the surface of the pretreated polyphenylene sulfide separator. Among them, polyethyleneimine undergoes Michael addition, which accelerates the copolymerization with dopamine, reduces the self-polymerization of dopamine, and enhances the stability of the polymerization, which can avoid the appearance of aggregates caused by dopamine self-polymerization in a long-term alkaline environment. When dopamine and polyethyleneimine are polymerized and co-deposited, the added polyethylene polyamine can improve the uniformity and adhesion of the hydrophilic coating.

[0077] (4) During the modified deposition process, oxygen is introduced into the mixed aqueous solution evenly and slowly, which can not only make the oxygen in the solution evenly distributed and make the deposition of the modified polydopamine polymer more uniform, but also accelerate the copolymerization of dopamine and polyethyleneimine, reduce the deposition time, and improve the deposition quality of the hydrophilic coating.

[0078] Embodiment 1:

[0079] In Example 1, the specific steps for preparing the super hydrophilic and alkali-resistant polyphenylene sulfide membrane are as follows:

[0080] Step S1: performing plasma surface treatment on a base membrane woven from polyphenylene sulfide fibers to obtain a pretreated polyphenylene sulfide membrane;

[0081] Among them, step S1 specifically includes: step S11: placing a base film woven from polyphenylene sulfide fibers in a plasma treatment chamber, turning on the power supply, evacuating the chamber until the vacuum degree reaches a threshold value (the threshold value is a preset value, which is 40 Pa in this embodiment 1), preheating (the preheating temperature is 30° C.), turning on the high-voltage power supply, setting the discharge frequency to 45 kHz, and after plasma treatment for 5 minutes, turning off the power supply;

[0082] Step S12: turning over the base film woven from polyphenylene sulfide fibers, and repeating step S11;

[0083] Step S13: Step S11 and Step S12 are repeated again, and the water absorption time of the base membrane woven with polyphenylene sulfide fibers is tested to be 0.4 s, and a pretreated polyphenylene sulfide membrane is obtained.

[0084] Step S2: The pretreated polyphenylene sulfide membrane obtained in step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification to obtain a polyphenylene sulfide membrane with modified polydopamine polymer attached thereto, and after washing and drying, a super hydrophilic and alkali-resistant polyphenylene sulfide membrane is obtained.

[0085] The pre-prepared mixed aqueous solution specifically comprises: mixing dopamine powder and polyethyleneimine according to a mass ratio, adding 1L of deionized water, and preparing a mixed aqueous solution. The mixed aqueous solution includes dopamine and polyethyleneimine, the mass ratio of dopamine to polyethyleneimine is 1:1, the concentration of dopamine is 2mg / ml, and the weight average molecular weight of polyethyleneimine is about 550.

[0086] Soaking modification treatment, specifically including:

[0087] The temperature of the mixed aqueous solution is 25° C. The pretreated polyphenylene sulfide membrane obtained in step S1 is immersed in the mixed aqueous solution for modification for 30 hours. During the immersion modification process, oxygen is continuously introduced into the mixed aqueous solution, and the oxygen flow rate is maintained at 50 ml / min.

[0088] The super hydrophilic alkali-resistant polyphenylene sulfide membrane (such as Figure 1 As shown), specifically comprising: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40nm;

[0089] The polyphenylene sulfide separator was immersed in alkaline electrolyte for 120 h (e.g. Figure 1 As shown), the water contact angle with the alkaline wetting liquid is close to 0° (as shown Figure 2 As shown), the wetting and water absorption time of the polyphenylene sulfide diaphragm and the alkaline wetting liquid is about 0.05s;

[0090] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the gas on the anode side of the alkaline electrolyzer using a polyphenylene sulfide diaphragm is about 0.3%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%;

[0091] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 38 μm.

[0092] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer is characterized. The elements of the hydrophilic layer include C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer is about 1.

[0093] Embodiment 2:

[0094] Based on Example 1, Example 2 adjusts the following parameters.

[0095] Compared with the preparation process of Example 1, step S2 of this embodiment is specifically adjusted as follows:

[0096] The pretreated polyphenylene sulfide membrane obtained in step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification treatment to obtain a polyphenylene sulfide membrane with modified polydopamine polymer attached thereto, and after washing and drying, a super hydrophilic and alkali-resistant polyphenylene sulfide membrane is obtained.

[0097] The pre-prepared mixed aqueous solution specifically includes:

[0098] A tris(hydroxymethylaminomethane) solution and a phosphate buffer solution are prepared respectively with tris(hydroxymethylaminomethane) and a phosphate mixture, and the tris(hydroxymethylaminomethane) solution and the phosphate buffer solution are mixed according to the molar ratio to form an initial mixed aqueous solution, wherein the concentration of the tris(hydroxymethylaminomethane) solution is 50 mmol / L;

[0099] Adding dopamine powder, polyethyleneimine and polyethylene polyamine into the initial mixed aqueous solution according to the mass ratio to prepare a mixed aqueous solution;

[0100] In the mixed aqueous solution, the molar ratio of tris(hydroxymethyl)aminomethane to the phosphate mixture is about 20:1, the concentration of polyethylene polyamine is 10 mg / ml, and the pH of the mixed aqueous solution is about 8.5.

[0101] In this embodiment, the polyethylene polyamine is a co-product of ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine, and the molar ratio of each component is about 1:1:1:1. The molar ratio of dipotassium hydrogen phosphate to potassium dihydrogen phosphate in the phosphate mixture is about 1:1.

[0102] In the mixed aqueous solution, the mass ratio of dopamine to polyethyleneimine is 1:1, the concentration of dopamine is 2 mg / ml, and the weight average molecular weight of polyethyleneimine is about 550.

[0103] Soaking modification treatment, specifically including:

[0104] The temperature of the mixed aqueous solution is 25° C. The pretreated polyphenylene sulfide membrane obtained in step S1 is immersed in the mixed aqueous solution for modification for 30 hours. During the immersion modification process, oxygen is continuously introduced into the mixed aqueous solution, and the oxygen flow rate is maintained at 50 ml / min.

[0105] The super hydrophilic and alkali-resistant polyphenylene sulfide membrane prepared by the above steps specifically comprises: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 42nm;

[0106] The polyphenylene sulfide diaphragm was immersed in alkaline electrolyte for 120 h, and the water contact angle with the alkaline wetting solution was close to 0°. The wetting and water absorption time of the polyphenylene sulfide diaphragm with the alkaline wetting solution was about 0.02 s (e.g. Figure 3 shown);

[0107] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the gas on the anode side of the alkaline electrolyzer using a polyphenylene sulfide diaphragm is about 0.1%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%;

[0108] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 35 μm.

[0109] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer is characterized. The elements of the hydrophilic layer include C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer is about 1.

[0110] Embodiment 3:

[0111] Based on Example 1, Example 3 adjusts the following parameters.

[0112] Compared with the preparation process of Example 1, step S2 of this embodiment is specifically adjusted as follows:

[0113] Step S2: The pretreated polyphenylene sulfide membrane obtained in step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification to obtain a polyphenylene sulfide membrane with modified polydopamine polymer attached thereto, and after washing and drying, a super hydrophilic and alkali-resistant polyphenylene sulfide membrane is obtained.

[0114] The pre-prepared mixed aqueous solution specifically comprises: mixing dopamine powder and polyethyleneimine according to a mass ratio, adding 1L of deionized water, and preparing a mixed aqueous solution. The mixed aqueous solution includes dopamine and polyethyleneimine, the mass ratio of dopamine to polyethyleneimine is 2:1, the concentration of dopamine is 2mg / ml, and the weight average molecular weight of polyethyleneimine is about 550.

[0115] The super hydrophilic and alkali-resistant polyphenylene sulfide membrane prepared by the above steps specifically comprises: a base membrane and a hydrophilic layer, wherein the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 45 nm;

[0116] When the polyphenylene sulfide membrane was immersed in the alkaline electrolyte for 120 h, the water contact angle with the alkaline wetting solution was close to 0°, and the wetting and water absorption time of the polyphenylene sulfide membrane with the alkaline wetting solution was about 0.08 s;

[0117] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the gas on the anode side of the alkaline electrolyzer using a polyphenylene sulfide diaphragm is about 0.3%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%;

[0118] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 40 μm.

[0119] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer is characterized. The elements of the hydrophilic layer include C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer is about 1.

[0120] Embodiment 4:

[0121] Based on Example 1, Example 4 adjusts the following parameters.

[0122] Compared with the preparation process of Example 1, step S2 of this embodiment is specifically adjusted as follows:

[0123] Step S2: The pretreated polyphenylene sulfide membrane obtained in step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification to obtain a polyphenylene sulfide membrane with modified polydopamine polymer attached thereto, and after washing and drying, a super hydrophilic and alkali-resistant polyphenylene sulfide membrane is obtained.

[0124] The pre-prepared mixed aqueous solution specifically comprises: mixing dopamine powder and polyethyleneimine according to a mass ratio, adding 1L of deionized water, and preparing a mixed aqueous solution. The mixed aqueous solution includes dopamine and polyethyleneimine, the mass ratio of dopamine to polyethyleneimine is 1:1, the concentration of dopamine is 3mg / ml, and the weight average molecular weight of polyethyleneimine is about 550.

[0125] The super hydrophilic and alkali-resistant polyphenylene sulfide membrane prepared by the above steps specifically comprises: a base membrane and a hydrophilic layer, wherein the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 45 nm;

[0126] When the polyphenylene sulfide membrane was immersed in the alkaline electrolyte for 120 h, the water contact angle with the alkaline wetting solution was close to 0°, and the wetting and water absorption time of the polyphenylene sulfide membrane with the alkaline wetting solution was about 0.08 s;

[0127] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the gas on the anode side of the alkaline electrolyzer using a polyphenylene sulfide diaphragm is about 0.3%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%;

[0128] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 40 μm.

[0129] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer is characterized. The elements of the hydrophilic layer include C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer is about 1.

[0130] Embodiment 5:

[0131] Based on Example 2, Example 5 adjusts the following parameters.

[0132] Compared with the preparation process of Example 2, step S2 of this embodiment is specifically adjusted as follows:

[0133] A pre-prepared mixed aqueous solution comprising:

[0134] A tris(hydroxymethylaminomethane) solution and a phosphate buffer solution are prepared respectively with tris(hydroxymethylaminomethane) and a phosphate mixture, and the tris(hydroxymethylaminomethane) solution and the phosphate buffer solution are mixed according to the molar ratio to form an initial mixed aqueous solution, wherein the concentration of the tris(hydroxymethylaminomethane) solution is 60 mmol / L;

[0135] Adding dopamine powder, polyethyleneimine and polyethylene polyamine into the initial mixed aqueous solution according to the mass ratio to prepare a mixed aqueous solution;

[0136] In the mixed aqueous solution, the molar ratio of tris(hydroxymethyl)aminomethane to the phosphate mixture is about 25:1, and the pH of the mixed aqueous solution is about 8.8.

[0137] The super hydrophilic and alkali-resistant polyphenylene sulfide membrane prepared by the above steps specifically comprises: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40 nm;

[0138] When the polyphenylene sulfide membrane was immersed in the alkaline electrolyte for 120 h, the water contact angle with the alkaline wetting solution was close to 0°, and the wetting and water absorption time of the polyphenylene sulfide membrane with the alkaline wetting solution was about 0.06 s;

[0139] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the gas on the anode side of the alkaline electrolyzer using a polyphenylene sulfide diaphragm is about 0.3%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%;

[0140] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 37 μm.

[0141] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer is characterized. The elements of the hydrophilic layer include C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer is about 1.

[0142] Comparative Example 1:

[0143] Based on Example 1, the following parameters were adjusted in Comparative Example 1.

[0144] Compared with the preparation process of Example 1, step S2 of this comparative example is specifically adjusted as follows:

[0145] Step S2: The pretreated polyphenylene sulfide membrane obtained in step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification treatment to obtain a polyphenylene sulfide membrane with polydopamine polymer attached thereto, and after washing and drying, a polyphenylene sulfide membrane is obtained.

[0146] The pre-prepared mixed aqueous solution specifically comprises: adding dopamine powder to 1L of deionized water according to a mass ratio to prepare a mixed aqueous solution. The mixed aqueous solution includes dopamine, and the concentration of dopamine is 2mg / ml.

[0147] Soaking modification treatment, specifically including:

[0148] The temperature of the mixed aqueous solution is 25° C. The pretreated polyphenylene sulfide membrane obtained in step S1 is immersed in the mixed aqueous solution for modification for 30 hours. During the immersion modification process, oxygen is continuously introduced into the mixed aqueous solution, and the oxygen flow rate is maintained at 50 ml / min.

[0149] The polyphenylene sulfide separator prepared by the above steps specifically comprises: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is polydopamine polymer, and the thickness of the hydrophilic layer is 40nm;

[0150] The polyphenylene sulfide separator was immersed in alkaline electrolyte for 120 h, and the water contact angle with the alkaline wetting solution was close to 20°, and the wetting and water absorption time of the polyphenylene sulfide separator with the alkaline wetting solution was about 0.5 s;

[0151] At an operating voltage of 1.8 V and an alkaline electrolyte, the hydrogen content in the gas on the anode side of the alkaline electrolyzer using a polyphenylene sulfide diaphragm is about 0.5%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%;

[0152] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 45 μm.

[0153] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer was characterized. The elements of the hydrophilic layer included C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer was about 1.5.

[0154] Comparative Example 2:

[0155] This comparative example adopts the polyphenylene sulfide fabric for alkaline water electrolysis prepared in Example 1 of patent CN117904870A.

[0156] Comparative Example 3:

[0157] Based on Example 1, the following parameters were adjusted in Comparative Example 3.

[0158] Compared with the preparation process of Example 1, step S1 is omitted in this comparative example.

[0159] The polyphenylene sulfide separator prepared by the above steps specifically comprises: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40nm;

[0160] When the polyphenylene sulfide separator is immersed in alkaline electrolyte for 120 hours, the water contact angle with the alkaline wetting solution is close to 136°, and the wetting and water absorption time of the polyphenylene sulfide separator with the alkaline wetting solution is greater than 10 seconds;

[0161] At an operating voltage of 1.8 V and an alkaline electrolyte, the hydrogen content in the gas on the anode side of the alkaline electrolyzer using a polyphenylene sulfide diaphragm is about 0.5%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%;

[0162] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 40 μm.

[0163] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer is characterized. The elements of the hydrophilic layer include C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer is about 1.

[0164] Comparative Example 4:

[0165] Based on Example 1, the following parameters were adjusted in Comparative Example 4.

[0166] Compared with the preparation process of Example 1, step S1 of this comparative example is specifically adjusted as follows:

[0167] Step S1 specifically includes: Step S11: placing a base film woven from polyphenylene sulfide fibers in a plasma treatment chamber, turning on the power supply, evacuating the chamber until the vacuum degree reaches a threshold value (the threshold value is a preset value, which is 40 Pa in this embodiment 1), preheating (the preheating temperature is 30° C.), turning on the high-voltage power supply, setting the discharge frequency to 45 kHz, and after plasma treatment for 20 minutes, turning off the power supply;

[0168] Step S12: turning over the base film woven from polyphenylene sulfide fibers, and repeating step S11;

[0169] Step S13: obtaining a pretreated polyphenylene sulfide membrane.

[0170] The polyphenylene sulfide separator prepared by the above steps specifically comprises: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40nm;

[0171] The polyphenylene sulfide separator was immersed in alkaline electrolyte for 120 h, and the water contact angle with the alkaline wetting solution was close to 20°, and the wetting and water absorption time of the polyphenylene sulfide separator with the alkaline wetting solution was about 0.5 s;

[0172] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the gas on the anode side of the alkaline electrolyzer using a polyphenylene sulfide diaphragm is about 0.8%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%;

[0173] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 40 μm.

[0174] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer is characterized. The elements of the hydrophilic layer include C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer is about 1.

[0175] Comparative Example 5:

[0176] Based on Example 1, the following parameters were adjusted in Comparative Example 5.

[0177] Compared with the preparation process of Example 1, step S2 is omitted in this comparative example.

[0178] The polyphenylene sulfide separator prepared by the above steps specifically comprises: a base film, which is polyphenylene sulfide fiber that has been subjected to plasma surface treatment;

[0179] The polyphenylene sulfide separator was immersed in alkaline electrolyte for 120 h, and the contact angle with alkaline wetting solution was close to 136° (e.g. Figure 4 shown);

[0180] At an operating voltage of 1.8 V and an alkaline electrolyte, the hydrogen content in the gas on the anode side of the alkaline electrolytic cell using a polyphenylene sulfide diaphragm is about 0.6%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%.

[0181] Comparative Example 6:

[0182] Based on Example 1, the following parameters were adjusted in Comparative Example 6.

[0183] Compared with the preparation process of Example 1, step S2 of this comparative example is specifically adjusted as follows:

[0184] Step S2: The pretreated polyphenylene sulfide membrane obtained in step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification treatment to obtain a polyphenylene sulfide membrane with modified polydopamine polymer attached thereto, and after washing and drying, a polyphenylene sulfide membrane is obtained.

[0185] The pre-prepared mixed aqueous solution specifically comprises: mixing dopamine powder and polyethyleneimine according to a mass ratio, adding 1L of deionized water, and preparing a mixed aqueous solution. The mixed aqueous solution includes dopamine and polyethyleneimine, the mass ratio of dopamine to polyethyleneimine is 5:1, the concentration of dopamine is 2mg / ml, and the weight average molecular weight of polyethyleneimine is about 550.

[0186] The polyphenylene sulfide separator prepared by the above steps specifically comprises: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40nm;

[0187] When the polyphenylene sulfide membrane was immersed in alkaline electrolyte for 120 h, the water contact angle with the alkaline wetting solution was close to 20°, and the wetting and water absorption time of the polyphenylene sulfide membrane with the alkaline wetting solution was about 0.2 s;

[0188] At an operating voltage of 1.8 V and an alkaline electrolyte, the hydrogen content in the gas on the anode side of the alkaline electrolyzer using a polyphenylene sulfide diaphragm is about 0.5%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%;

[0189] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 45 μm.

[0190] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer was characterized. The elements of the hydrophilic layer included C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer was about 1.5.

[0191] Comparative Example 7:

[0192] Based on Example 1, the following parameters were adjusted in Comparative Example 7.

[0193] Compared with the preparation process of Example 1, step S2 of this comparative example is specifically adjusted as follows:

[0194] Step S2: The pretreated polyphenylene sulfide membrane obtained in step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification treatment to obtain a polyphenylene sulfide membrane with modified polydopamine polymer attached thereto, and after washing and drying, a polyphenylene sulfide membrane is obtained.

[0195] The pre-prepared mixed aqueous solution specifically comprises: mixing dopamine powder and polyethyleneimine according to a mass ratio, adding 1L of deionized water, and preparing a mixed aqueous solution. The mixed aqueous solution includes dopamine and polyethyleneimine, the mass ratio of dopamine to polyethyleneimine is 1:2, the concentration of dopamine is 2mg / ml, and the weight average molecular weight of polyethyleneimine is about 550.

[0196] The polyphenylene sulfide separator prepared by the above steps specifically comprises: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40nm;

[0197] When the polyphenylene sulfide separator is immersed in alkaline electrolyte for 120 hours, the water contact angle with the alkaline wetting solution is close to 136°, and the wetting and water absorption time of the polyphenylene sulfide separator with the alkaline wetting solution is greater than 10 seconds;

[0198] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the gas on the anode side of the alkaline electrolyzer using a polyphenylene sulfide diaphragm is about 0.6%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%;

[0199] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 45 μm.

[0200] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer was characterized. The elements of the hydrophilic layer included C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer was about 1.5.

[0201] Comparative Example 8:

[0202] Based on Example 1, the following parameters were adjusted in Comparative Example 8.

[0203] Compared with the preparation process of Example 1, step S2 of this comparative example is specifically adjusted as follows:

[0204] Step S2: The pretreated polyphenylene sulfide membrane obtained in step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification treatment to obtain a polyphenylene sulfide membrane with modified polydopamine polymer attached thereto, and after washing and drying, a polyphenylene sulfide membrane is obtained.

[0205] The pre-prepared mixed aqueous solution specifically comprises: mixing dopamine powder and polyethyleneimine according to a mass ratio, adding 1L of deionized water, and preparing a mixed aqueous solution. The mixed aqueous solution includes dopamine and polyethyleneimine, the mass ratio of dopamine to polyethyleneimine is 1:1, the concentration of dopamine is 2mg / ml, and the weight average molecular weight of polyethyleneimine is about 3000.

[0206] The polyphenylene sulfide separator prepared by the above steps specifically comprises: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40nm;

[0207] When the polyphenylene sulfide separator is immersed in alkaline electrolyte for 120 hours, the water contact angle with the alkaline wetting solution is close to 136°, and the wetting and water absorption time of the polyphenylene sulfide separator with the alkaline wetting solution is greater than 10 seconds;

[0208] At an operating voltage of 1.8 V and an alkaline electrolyte, the hydrogen content in the gas on the anode side of the alkaline electrolyzer using a polyphenylene sulfide diaphragm is about 0.7%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%;

[0209] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 45 μm.

[0210] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer was characterized. The elements of the hydrophilic layer included C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer was about 1.5.

[0211] Testing process:

[0212] Alkali resistance test: In order to verify the alkali resistance of the diaphragm, the diaphragms prepared in Examples 1-5 and Comparative Examples 1-8 were cut into 2 cm × 2 cm squares and immersed in a 30% KOH solution at 80°C. After 120 hours, a hydrophilicity test, i.e., a contact angle test, was performed. During the test, the alkaline wetting liquid was a KOH solution with a mass concentration of 30%, and 5 μL, i.e., one droplet, was taken to give the contact angle and wetting water absorption time.

[0213] Surface resistance test: The surface resistance test refers to SJ / T 10171-2016 "General test method for basic properties of alkaline battery separators", and the test is carried out in section 4.8 of the area resistance (surface resistance) test item.

[0214] Table 1 Performance comparison table of embodiments and comparative examples

[0215]

[0216]

[0217] The data in Table 1 include the test results obtained from various embodiments and comparative examples of the present invention.

[0218] Among them, from the alkali resistance test, the water contact angle of the diaphragm of Examples 1-5 is close to 0°, and the comparative examples are almost all above 20°. Among them, if there is no plasma surface treatment in Comparative Example 3 and there is no hydrophilic layer in Comparative Examples 5, 7-8 or the polyethyleneimine does not meet the requirements, the water contact angle will even increase to 136°. Similarly, the increase in the water contact angle will also greatly increase the wetting and water absorption time.

[0219] The super-hydrophilic and strong-alkali-resistant polyphenylene sulfide diaphragm is a polyphenylene sulfide diaphragm whose water contact angle with the alkaline wetting liquid is not greater than 5°. The above test results show that the diaphragms prepared in various embodiments for alkaline hydrolysis tanks meet the super-hydrophilic requirements and have excellent gas barrier properties.

[0220] The present invention provides a super-hydrophilic and alkali-resistant polyphenylene sulfide diaphragm, a preparation method and an application thereof, which at least have the following beneficial effects:

[0221] (1) The present invention prepares a hydrophilic layer of a modified polydopamine polymer through a simple process, thereby improving the alkali resistance and hydrophilicity of the polyphenylene sulfide membrane, overcoming the problem of hydrophilic performance degradation and instability of the existing hydrophilic layer in an alkaline electrolytic cell environment, and preparing a super-hydrophilic polyphenylene sulfide membrane that can be stably used in an alkaline environment.

[0222] (2) Plasma surface treatment can improve the hydrophilicity of polyphenylene sulfide fibers, introduce oxygen-containing polar functional groups (e.g., -OH) on the surface of the polyphenylene sulfide fiber base film, form multiple active points, and also produce a microscopic rough structure that is a good substrate for the attachment of the polydopamine layer.

[0223] (3) Dopamine and polyethyleneimine (low weight average molecular weight) are co-deposited and attached to the surface of the pretreated polyphenylene sulfide separator. Among them, polyethyleneimine undergoes Michael addition, which accelerates the copolymerization with dopamine, reduces the self-polymerization of dopamine, and enhances the stability of the polymerization, which can avoid the appearance of aggregates caused by dopamine self-polymerization in a long-term alkaline environment. When dopamine and polyethyleneimine are polymerized and co-deposited, the added polyethylene polyamine can improve the uniformity and adhesion of the hydrophilic coating.

[0224] (4) During the modified deposition process, oxygen is introduced into the mixed aqueous solution evenly and slowly, which can not only make the oxygen in the solution evenly distributed and make the deposition of the modified polydopamine polymer more uniform, but also accelerate the copolymerization of dopamine and polyethyleneimine, reduce the deposition time, and improve the deposition quality of the hydrophilic coating.

[0225] Although preferred embodiments of the present invention have been described, additional changes and modifications may be made to these embodiments by those skilled in the art once the basic inventive concepts are known. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A super hydrophilic and alkali-resistant polyphenylene sulfide diaphragm, characterized in that: Specifically include: Basement membrane and hydrophilic layer, the basement membrane is polyphenylene sulfide fiber or sulfonated polyphenylene sulfide fiber, the hydrophilic layer is modified polydopamine polymer, and the thickness of the hydrophilic layer is 40-50nm; The polyphenylene sulfide diaphragm is immersed in an alkaline electrolyte for 120 hours, and the water contact angle with the alkaline wetting liquid is not greater than 5°, and the wetting and water absorption time of the polyphenylene sulfide diaphragm with the alkaline wetting liquid is not greater than 0.1s; At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the gas at the anode side of an alkaline electrolytic cell using a polyphenylene sulfide diaphragm is no more than 0.5%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%-50%.

2. The super hydrophilic and alkali-resistant polyphenylene sulfide membrane according to claim 1, characterized in that: The most probable pore size of the hydrophilic layer is no greater than 40 μm.

3. The super hydrophilic and alkali-resistant polyphenylene sulfide membrane according to claim 2, characterized in that: The elements of the hydrophilic layer include C, N, and O, wherein the nitrogen-oxygen ratio of the elements of the hydrophilic layer is 0.8-1.

2.

4. A method for preparing the super-hydrophilic and alkali-resistant polyphenylene sulfide membrane according to any one of claims 1 to 3, characterized in that: The specific steps include: Step S1: performing plasma surface treatment on a base membrane woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers to obtain a pretreated polyphenylene sulfide membrane; Step S2: placing the pretreated polyphenylene sulfide membrane of step S1 in a pre-prepared mixed aqueous solution for immersion modification treatment to obtain a polyphenylene sulfide membrane with attached modified polydopamine polymer, and after washing and drying, obtaining a super hydrophilic and alkali-resistant polyphenylene sulfide membrane, wherein the mixed aqueous solution includes dopamine and polyethyleneimine, the mass ratio of dopamine to polyethyleneimine is (1-2): 1, the concentration of dopamine is 2-3 mg / ml, and the weight average molecular weight of polyethyleneimine is not higher than 600.

5. The method for preparing a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane according to claim 4, characterized in that: Step S1 specifically includes: Step S11: placing a base film woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers in a plasma treatment chamber, turning on the power supply, evacuating the chamber until the vacuum reaches a threshold, turning on the high-voltage power supply after preheating, setting the discharge frequency to 40-50 kHz, and performing plasma treatment for 5-10 minutes before turning off the power supply; Step S12: turning over the base film woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers, and repeating step S11; Step S13: repeating steps S11 and S12 until the water absorption time of the base membrane woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers is no more than 0.5 s, thereby obtaining a pretreated polyphenylene sulfide membrane.

6. The method for preparing a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane according to claim 5, characterized in that: In step S1, the threshold of the vacuum degree is 20-50 Pa, and the preheating temperature is not higher than 50°C.

7. The method for preparing a super hydrophilic and alkali-resistant polyphenylene sulfide membrane according to claim 4, characterized in that: In step S2, the mixed aqueous solution also includes tris(hydroxymethyl)aminomethane, polyethylene polyamine and a phosphate mixture, and the molar ratio of tris(hydroxymethyl)aminomethane to the phosphate mixture is (20-25):1, the concentration of polyethylene polyamine is 8-15 mg / ml, and the pH of the mixed aqueous solution is 8.5-8.8, wherein the phosphate mixture includes dipotassium hydrogen phosphate and potassium dihydrogen phosphate.

8. The method for preparing a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane according to claim 7, characterized in that: In step S2, the preparation of the mixed aqueous solution specifically includes: A tris(hydroxymethylaminomethane) solution and a phosphate buffer solution are prepared respectively with tris(hydroxymethylaminomethane) and a phosphate mixture, and the tris(hydroxymethylaminomethane) solution and the phosphate buffer solution are mixed according to the molar ratio to form an initial mixed aqueous solution, wherein the concentration of the tris(hydroxymethylaminomethane) solution is 50-60 mmol / L; Dopamine powder, polyethyleneimine and polyethylene polyamine are added into the initial mixed aqueous solution according to the mass ratio to prepare a mixed aqueous solution.

9. The method for preparing a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane according to claim 4, characterized in that: In step S2, the soaking modification treatment specifically includes: The temperature of the mixed aqueous solution is 20-30°C, and the pretreated polyphenylene sulfide membrane in step S1 is immersed in the mixed aqueous solution for modification for 12-48 hours. During the immersion modification process, oxygen is continuously introduced into the mixed aqueous solution, and the oxygen flow rate is not less than 1 / 20L0 / min, where L0 is the volume of the mixed aqueous solution.

10. An application of a super hydrophilic and alkali-resistant polyphenylene sulfide diaphragm, characterized in that: The super-hydrophilic and alkali-resistant polyphenylene sulfide membrane as claimed in any one of claims 1 to 3 is applied to an alkaline water electrolysis hydrogen production cell.

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