A method for pre-wetting-replacement treatment of porous substrate for composite diaphragm of alkaline electrolytic water with high solid content inorganic particle-containing organic solvent slurry compounding and composite diaphragm

Abstract

The application discloses a kind of for alkaline electrolytic water composite diaphragm contains inorganic particle organic solvent slurry composite porous substrate ion liquid temporary pre-wetting-miscible replacement processing method and composite diaphragm.Method includes: providing alkali-resistant porous substrate;Make the pre-wetting treatment liquid containing ion liquid enter at least part of the inside of the pore of alkali-resistant porous substrate;Remove excess pre-wetting treatment liquid on surface, so that ion liquid is mainly retained in the inside of pore;Alkali-resistant porous substrate pre-wetted with ion liquid is contacted with inorganic particle-containing organic solvent slurry, and organic solvent in slurry and ion liquid occur miscible, diffusion and / or replacement, and make slurry at least part enter the inside of pore;Again, make ion liquid at least part be replaced or removed and make its residual amount reduce to 50% below initial introduction amount, and form composite layer.Different from ion liquid as permanent functional filler, can improve the continuity and interface stability of organic solvent slurry into pore.

Description

Technical Field

[0001] This invention belongs to the technical fields of porous substrate surface treatment, pore prewetting, organic solvent slurry composite, functional composite membrane and alkaline electrolytic water composite membrane. Specifically, it relates to an ionic liquid prewetting-displacement treatment method for porous substrates with high solids content containing inorganic particles and organic solvent slurry for alkaline electrolytic water composite membrane, as well as the ionic liquid prewetting porous substrate, composite membrane and composite membrane obtained by the method. Background Technology

[0002] Porous substrates are widely used in functional membranes, composite membranes, filter materials, electrochemical membranes, coating support materials, reinforcing meshes, and porous support layers. Common porous substrates include porous membranes, woven meshes, braided meshes, nonwoven fabrics, fiber mats, porous support membranes, or porous support meshes made of materials such as polyphenylene sulfide, polytetrafluoroethylene, polyvinylidene fluoride, polyetheretherketone, glass fiber, and ceramic fiber. For applications such as alkaline water electrolysis composite membranes, the porous substrate also needs to have good alkali resistance and dimensional stability.

[0003] In the process of functional layer lamination, it is usually necessary to introduce a slurry containing organic solvents into the surface and / or pores of a porous substrate. The slurry typically contains organic solvents, inorganic particles, organic binders, dispersants, thickeners, and other functional additives. Typical organic solvents include N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide. For composite membranes and functional composite membranes, high-solids or high-viscosity slurries can improve single-pass film formation efficiency and composite layer density, but they are also more likely to cause bubble blockage at pore inlets, intersections, and dead corners of the porous substrate.

[0004] Porous substrates often contain complex pores, fiber gaps, intersecting fiber nodes, dead zones, and partially closed or semi-closed spaces. When high-solids-content or high-viscosity organic solvent slurries directly contact porous substrates, air within the pores is difficult to expel, easily leading to problems such as air bubble retention, insufficient slurry penetration, unwetted areas, interfacial cavities, and localized debonding after drying. These problems are particularly pronounced in porous substrates with low surface energy or complex pore structures, such as polyphenylene sulfide, polytetrafluoroethylene, and polyvinylidene fluoride.

[0005] In related technologies, methods such as plasma treatment, oxidation treatment, surfactant treatment, solvent prewetting, or coupling agent treatment are often used to improve the wettability between porous substrates and slurries. While these methods can improve the wettability of the outer surface to some extent, their effect on air displacement within the pores is limited. Prewetting with ordinary water, alcohol, or N-methylpyrrolidone may still result in problems such as rapid evaporation, poor retention, insufficient air displacement, discontinuous air displacement with subsequent slurry application, or residual foam affecting slurry composite formation in high-porosity, multi-node, or complex pore structures.

[0006] Therefore, a new method for pretreating porous substrates is needed to form a stable temporary pre-wetting state in the pores of the porous substrate before subsequent lamination with organic solvent-containing slurry, thereby displacing the air in the pores and being mutually dissolved, diffused or replaced by the organic solvent in the slurry during the slurry contact process, thereby promoting the continuous entry of the slurry into the pores and reducing air bubble retention, unwetted areas and interface cavities. Summary of the Invention

[0007] Furthermore, in this invention, the ionic liquid is used only as a temporary pre-wetting, pore venting, and mutual dissolution medium, rather than a permanent functional filler; by controlling the liquid film on the outer surface and controlling the residual amount after post-treatment, the ionic liquid is prevented from clogging the pores for a long time or forming a permanent liquid filling layer.

[0008] The purpose of this invention is to provide a method for the temporary pre-wetting-mutual dissolution and replacement treatment of porous substrates containing inorganic particles and organic solvent slurries for alkaline electrolytic water composite membranes. The method allows the ionic liquid to be used as a temporary pre-wetting and pore-occupying and degassing medium to pre-enter the pores, fiber gaps, intersections, dead corners of pores and / or pore inner walls of the porous substrate. During the subsequent slurry composite process, the ionic liquid is mutually dissolved, diffused and / or replaced by the organic solvent, thereby promoting the continuous entry of the inorganic particle-containing organic solvent slurry into the pores and reducing bubble retention, unwetted areas and interface cavities.

[0009] To achieve the above objectives, the present invention provides a method for temporary pre-wetting and mutual dissolution replacement treatment of porous substrates with ionic liquids, comprising the following steps:

[0010] Step 1: Provide an alkali-resistant porous substrate with pores, fiber gaps, cross nodes, dead corners of pores and / or inner walls of pores; Step 2: The pre-wetting treatment liquid containing ionic liquid is brought into contact with the alkali-resistant porous substrate and enters at least part of the pores, fiber gaps, cross nodes, dead corners of the channels and / or the inner wall of the pores of the alkali-resistant porous substrate, so that the ionic liquid, as a temporary pre-wetting and pore-occupying exhaust medium, at least partially occupies the gas phase space in the alkali-resistant porous substrate and replaces the air therein. Step 3: Remove excess pre-wetting solution from the outer surface of the alkali-resistant porous substrate, so that the ionic liquid is mainly retained in the pores, fiber gaps, cross nodes, dead corners of the channels and / or the inner walls of the pores; Step four: The alkali-resistant porous substrate pre-wetted with ionic liquid is brought into contact with an organic solvent slurry containing inorganic particles, so that the organic solvent in the organic solvent slurry containing inorganic particles is mutually soluble, diffused and / or replaced with the ionic liquid, and the organic solvent slurry containing inorganic particles enters at least partially into the pores, fiber gaps, cross nodes, dead corners of pores and / or the inner wall of pores of the alkali-resistant porous substrate. Step 5: The alkali-resistant porous substrate after being composited with the slurry is subjected to coagulation, phase transformation, solvent replacement, washing, drying and / or heat treatment, so that the ionic liquid is at least partially replaced or removed, and the slurry containing inorganic particles and organic solvent forms a composite layer on the surface and / or in the pores of the alkali-resistant porous substrate.

[0011] In a preferred embodiment, the ionic liquid is not retained as a permanent functional filler within the pores of the alkali-resistant porous substrate.

[0012] In a preferred embodiment, the alkali-resistant porous substrate is a PPS woven mesh, PPS nonwoven fabric, PTFE porous membrane, PVDF porous membrane, PEEK porous membrane, or a composite porous substrate thereof.

[0013] In a preferred embodiment, the ionic liquid is selected from one or more of choline lactate, choline acetate, 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium lactate, or 1-butyl-3-methylimidazolium acetate.

[0014] In a preferred embodiment, the ionic liquid is liquid at 20 °C to 100 °C, and has a viscosity of 5 mPa·s to 1000 mPa·s at 25 °C; the ionic liquid does not produce macroscopic stratification after being mixed with N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylacetamide or N,N-dimethylformamide at a mass ratio of 1:9 to 9:1 and allowed to stand for 30 min.

[0015] In a preferred embodiment, the pre-wetting treatment solution further includes one or more diluents selected from N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, ethanol, isopropanol, or water.

[0016] In a preferred embodiment, step two is carried out by vacuum-assisted impregnation, pressure-assisted impregnation, circulating injection, filtration penetration, impregnation, spraying, roller coating or scraping; step three is carried out by scraping, air knife blowing, roller pressing, metering roller control of liquid, negative pressure suction, centrifugal liquid removal or a combination thereof.

[0017] In a preferred embodiment, after removing excess pre-wetting liquid from the outer surface, the area of ​​the continuous ionic liquid film on the outer surface of the alkali-resistant porous substrate is less than 10% of the observed area of ​​the outer surface.

[0018] In a preferred embodiment, the solid content of the inorganic particle-containing organic solvent slurry is 40 wt% to 85 wt%; the inorganic particle-containing organic solvent slurry includes inorganic particles of zirconium oxide, titanium oxide, aluminum oxide, barium sulfate, magnesium oxide or magnesium hydroxide, as well as film-forming polymers of polysulfone, polyethersulfone, polyvinylidene fluoride or polyphenylene sulfide.

[0019] In a preferred embodiment, after coagulation, phase inversion, solvent replacement, washing, drying and / or heat treatment, the residual amount of the ionic liquid is reduced to less than 50% of the initial amount introduced, preferably to less than 20% of the initial amount introduced.

[0020] The present invention also provides an alkaline water electrolysis composite membrane, wherein the alkaline water electrolysis composite membrane comprises a composite layer-porous substrate composite structure prepared by the above method.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects: First, the ionic liquid enters the pores of the alkali-resistant porous substrate as a temporary pre-wetting and pore-draining medium, which is beneficial for expelling air from the pores; Second, the ionic liquid undergoes mutual solubility, diffusion, and / or displacement with the organic solvent in the subsequent slurry, which is beneficial for the continuous entry of the high-solids-content inorganic particle organic solvent slurry into the pores; Third, after post-treatment, the ionic liquid is at least partially replaced or removed, which is different from the technical route of using ionic liquid as a permanent functional filler; Fourth, this method is beneficial for reducing the risks of bubble retention, unwetted areas, and uneven composite within the pores, and improving the continuity of composite composite within the pores and the stability of interfacial bonding of the composite membrane. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the process of the porous substrate ionic liquid pre-wetting-displacement treatment method of the present invention, illustrating the process of providing a porous substrate, pre-wetting with an ionic liquid and displacing pore air, compositing with an organic solvent slurry containing inorganic particles, and post-treatment to form a composite structure.

[0023] Figure 2 This is a schematic diagram of the structure by which the ionic liquid pre-wetting treatment solution of the present invention enters the pores of a porous substrate and displaces the air within the pores. Figure 2 (a) illustrates the state in which the pre-wetting treatment liquid enters the pores of the porous substrate and displaces the gas phase space. Figure 2 (b) illustrates the state in which an organic solvent slurry containing inorganic particles comes into contact with a porous substrate pre-wetted with an ionic liquid and undergoes mutual dissolution, diffusion and / or displacement.

[0024] Figure 3 This is a schematic diagram illustrating the process by which the organic solvent and ionic liquid in the inorganic particle-containing organic solvent slurry of the present invention undergo mutual solubility, diffusion, and / or displacement, thereby promoting the slurry's entry into the pores. Figure 3 (a) Schematic diagram of the initial pore state of the porous substrate. Figure 3 (b) Schematic diagram of slurry contact and solvent displacement process. Figure 3 (c) Schematic diagram of the state after the slurry enters the pore and forms a continuous internal composite structure.

[0025] Figure 4This diagram illustrates a comparison of bubble retention and pore wetting states between untreated porous substrates and porous substrates treated with ionic liquid pre-wetting and displacement during the slurry lamination process. Figure 4 (a) illustrates a state in an untreated porous substrate where there is significant air retention, air bubbles, or unwetted areas. Figure 4 (b) illustrates the state in which the slurry continuously enters the pores and reduces bubble retention after ionic liquid pre-wetting-displacement treatment.

[0026] Figure 5 This is a comparison of the surface composite states of an untreated sample and a sample pre-wetting-displacement treated with an ionic liquid. Figure 5 (a) is the untreated sample. Figure 5 (b) is a sample pre-wetting-displacement treated with ionic liquid.

[0027] Figure 6 This is a comparison of the composite state of the sample surface after different pre-wetting methods, in which... Figure 6 (a) is the untreated sample. Figure 6 (b) is an NMP-pre-wetted sample. Figure 6 (c) is a sample pre-wetting-displacement treated with ionic liquid.

[0028] Figure 7 This is a comparison diagram of the composite state of sample cross-sections after treatment with different pre-wetting methods. Figure 7 (a) is the untreated sample. Figure 7 (b) is an NMP-pre-wetted sample. Figure 7 (c) is a sample pre-wetting-displacement treated with ionic liquid.

[0029] Explanation of reference numerals in the attached figures The specific structural or unit names corresponding to the various reference numerals in the figures are as follows: 1 represents a porous substrate; 11 represents pores; 12 represents fiber gaps; 13 represents a cross node; 14 represents a dead corner in the pore; 15 represents the inner wall of the pore; 16 represents a composite structure within the pore; 17 represents surface bubbles or pore defects; 18 represents cross-sectional cavities or unfilled defects within the pore; 19 represents the NMP pre-wetting treatment area; 20 represents the ionic liquid pre-wetting-displacement treatment area; 2 represents the pre-wetting treatment liquid; 21 represents the ionic liquid; 22 represents the diluting solvent; 3 represents the gas phase space or air; 4 represents a slurry containing inorganic particles and organic solvents; 41 represents organic solvents; 42 represents inorganic particles; 43 represents film-forming polymers; 5 represents a composite layer; 6 represents ionic liquid pre-wetting of the porous substrate; 7 represents a composite membrane or composite diaphragm; 8 represents bubbles or unwetting areas; 9 represents a continuous liquid film on the outer surface; 10 represents the direction of slurry entry. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the following embodiments are only used to illustrate the technical solutions and effects of the present invention, and are not intended to limit the scope of protection of the present invention. Without departing from the concept of the present invention, those skilled in the art can adjust, replace or combine the porous substrate type, ionic liquid type, diluent solvent, pre-wetting conditions, slurry composition and post-treatment conditions.

[0031] Figure 1 This is a schematic diagram of the overall process flow of the porous substrate ionic liquid pre-wetting-displacement treatment method of the present invention. The diagram clearly shows the complete manufacturing process chain of providing an initial porous substrate 1, using a pre-wetting treatment liquid 2 containing ionic liquid 21 and diluent 22 to wet the substrate and displace and expel the gas phase space or air 3 therein, then introducing an organic solvent slurry containing inorganic particles through deep wetting, and then curing it in the interconnected pores and on the surface of the substrate to form a highly dense composite layer 5 through post-treatment.

[0032] Figure 2 This is a schematic diagram illustrating the microscopic evolution of the pre-wetting treatment liquid 2 as it enters the pores 11 of the porous substrate 1 and displaces the air 3 therein. Figure 2 (a) This illustrates that during the pre-wetting stage, the low surface tension pre-wetting treatment liquid 2 rapidly penetrates into the fiber gap 12 and spreads on the inner wall 15 of the pore under the drive of capillary force, and the air 3 that was originally trapped at the cross node 13 and the dead corner of the pore is discharged upward in the form of bubbles. Figure 2 (b) illustrates the transitional state in which the inorganic particle organic solvent slurry 4 comes into contact with the surface of the porous substrate 6 pre-wetted with ionic liquid during the slurry composite stage, and spontaneous mutual dissolution, cross-interface synergistic diffusion, and significant liquid displacement occur.

[0033] Figure 3 This is a schematic diagram illustrating the process by which the organic solvent 41 in the inorganic particle-containing organic solvent slurry 4 of the present invention undergoes efficient miscibility and displacement with the ionic liquid 21 residing in the pores, guiding the infusion of the solid solution components. Wherein, Figure 3 (a) Schematic diagram of the initial unfilled porous mesh state of porous substrate 1; Figure 3 (b) illustrates the dynamic process in which, under the hydrostatic pressure of the slurry entering direction 10, the organic solvent 41, inorganic particles 42 and film-forming polymer 43 penetrate directly into the slurry and undergo unimpeded mixing and replacement with the pre-stored pre-wetting treatment liquid 2. Figure 3 (c) The slurry completely fills the pores and forms a full shape after curing and removing the liquid, resulting in a continuous and defect-free composite structure 16 inside the pores.

[0034] Figure 4This diagram illustrates a comparison of bubble residue and wetting morphology between untreated porous substrates and porous substrates treated with ionic liquid pre-wetting-displacement during slurry casting and film deposition. Figure 4 (a) It shows that when an untreated porous substrate comes into contact with a high-viscosity slurry, the surface tension prevents a large amount of air 3 from being discharged in time, resulting in a large area of ​​air remaining in the intersection 13, the dead corner of the channel 14, or below the continuous liquid film 9 on the outer surface, forming a large number of bubbles or unwetted areas 8 that are difficult to eliminate. Figure 4 (b) illustrates that after the substrate has been pre-wetted, the internal channels are completely filled with liquid, and the slurry 4 containing inorganic particles and organic solvent can be continuously pushed into the slurry inlet direction 10 along the same fluid path without obstruction, thus completely eliminating the air bridging phenomenon and significantly reducing or eliminating air bubble retention.

[0035] Figure 5 This is a comparative image of the measured surface composite state of an untreated sample and a sample pre-wetting-displacement treated with an ionic liquid. Figure 5 (a) is a surface image of an untreated sample, showing a large number of significant surface bubbles or pores caused by obstructed internal air leakage or uneven slurry spreading.17 Figure 5 (b) is a surface image of the sample pre-wetting-displacement treated with ionic liquid, showing an extremely uniform, flat, and continuous densified composite surface without any macro or micro pores.

[0036] Figure 6 This image shows a comparison of the surface composite state of samples treated with different pre-wetting processes at the same magnification. Figure 6 (a) is the surface of a completely untreated sample, which is covered with large-sized defects; Figure 6 (b) The surface of area 19, which has undergone conventional NMP pre-wetting treatment, shows that although macroscopic defects have been reduced, small pitting still exists in some areas; Figure 6 (c) The surface of the ionic liquid pre-wetting-displacement treatment area 20 of the present invention has achieved a breakthrough improvement in surface flatness and excellent structural integrity.

[0037] Figure 7 The images show a comparison of scanning electron microscope (SEM) images of the cross-sectional microstructure of samples treated with different pre-wetting processes. Figure 7 (a) is the cross section of the untreated sample. Due to severe air blockage, a large number of large-sized cross-sectional cavities or unfilled defects were formed inside the holes, resulting in severe loss of composite components. Figure 7 (b) is a cross-section of a sample pre-wetted by conventional NMP. Although the pores are partially filled, there are still obvious cavity defects in the local deep channels and dead corners. Figure 7(c) is a cross section of a sample pre-wetting-displacement treated with the ionic liquid of the present invention. All pores 11 and fiber gaps 12 inside the entire porous framework are filled with dense functional components, forming a perfect interpenetrating network, and finally constructing a high-quality composite membrane or composite separator 7.

[0038] Test methods Bubble area ratio test: Optical microscopy or scanning image acquisition is performed on the sample after slurry composite, and the proportion of bubble or cavity area to the total observed area is statistically analyzed by image binarization.

[0039] Unwetted area percentage test: The percentage of areas where the slurry has not entered or is obviously blank in optical micrographs or cross-sectional images is statistically analyzed. At least 3 areas are tested for each sample and the average value is taken.

[0040] Pore ​​continuous wetting area ratio test: The area ratio of the slurry continuously entering the pore network of the porous substrate is statistically analyzed to evaluate the continuity of slurry composite.

[0041] Thickness direction wetting depth test: The average depth of the slurry penetrating the porous substrate along the thickness direction is measured using cross-sectional micrographs or scanning electron micrographs.

[0042] Test on the proportion of continuous liquid film area on the outer surface: After removing excess pre-wetting liquid from the outer surface, the proportion of the visible continuous liquid film area to the observed area of ​​the outer surface is statistically analyzed using optical images.

[0043] Ionic liquid residual amount test: Characterized by one or more of the following methods: mass change, elemental analysis, ion chromatography, total organic carbon test, infrared spectroscopy or X-ray photoelectron spectroscopy. The residual amount of ionic liquid is expressed as a percentage of the residual amount after treatment relative to the initial amount introduced.

[0044] Example Example 1: Pre-wetting-displacement treatment of PPS woven mesh with imidazolium-based ionic liquids Step 1: Provide an alkali-resistant porous substrate. A polyphenylene sulfide woven mesh is provided as the alkali-resistant porous substrate, and is sequentially cleaned with ethanol and deionized water to remove surface contaminants, followed by drying at 60 °C.

[0045] Step two involves contacting the alkali-resistant porous substrate with a pre-wetting solution containing an ionic liquid. A pre-wetting solution containing an imidazolium-based ionic liquid and a small amount of N-methylpyrrolidone is prepared and then contacted with the polyphenylene sulfide woven mesh.

[0046] Step 3: Allow the pre-wetting solution to enter the pores and displace the air. Place the polyphenylene sulfide woven mesh in the pre-wetting solution for vacuum-assisted impregnation, allowing the ionic liquid to enter the inner walls of the pores and the areas where the wires intersect. This serves as a temporary pre-wetting and pore-occupying exhaust medium, occupying at least a portion of the gas phase space and displacing the air.

[0047] Step 4: Remove excess pre-wetting solution from the outer surface. Excess pre-wetting solution is removed by leaching and light air knife purging, ensuring the ionic liquid remains primarily on the inner walls of the pores and at intersections, and reducing the continuous liquid film on the outer surface.

[0048] Step 5: Contact with the organic solvent slurry containing inorganic particles and allow for mutual solubility and displacement. The resulting ionic liquid pre-wetted polyphenylene sulfide woven mesh is then contacted with the inorganic particle slurry containing N-methylpyrrolidone, allowing the N-methylpyrrolidone to undergo mutual solubility, diffusion, and displacement with the ionic liquid within the pores, promoting the slurry's entry into the pores and the inter-fiber node regions.

[0049] Step six: Post-processing to form a composite layer. After lamination, the resulting material is washed, dried, and heat-treated with N-methylpyrrolidone to at least partially replace or remove the ionic liquid and form a composite layer.

[0050] Table 1

[0051] Example 2: Pre-wetting treatment of PPS nonwoven fabric with choline-based ionic liquids Step 1: Provide an alkali-resistant porous substrate. Use polyphenylene sulfide nonwoven fabric as the alkali-resistant porous substrate.

[0052] Step 2: Prepare a pre-wetting solution containing ionic liquids. Prepare a pre-wetting solution containing choline-based ionic liquids and alcohol-based diluents.

[0053] Step 3: Allow the pre-wetting solution to enter the pores and displace the air. Immerse the polyphenylene sulfide nonwoven fabric in the pre-wetting solution, and use pressure assistance to allow the solution to enter the internal pores of the nonwoven fabric, so that the ionic liquid is distributed on the fiber surface and the inner wall of the pores and displaces some of the air in the pores.

[0054] Step 4: Remove excess pre-wetting solution from the outer surface. Removing excess pre-wetting solution from the surface ensures that the ionic liquid remains primarily within the porous network.

[0055] Step 5: Contact with an organic solvent slurry containing inorganic particles and allow for mutual solubility and displacement. The pre-wetted nonwoven fabric is then contacted with a functional slurry containing N-methylpyrrolidone, allowing the N-methylpyrrolidone to diffuse and displace the ionic liquid, promoting the functional slurry's entry into the nonwoven fabric's pore network.

[0056] Step six: Post-processing. Through solvent replacement, washing, and drying, the ionic liquid is at least partially replaced or removed, forming a composite layer.

[0057] Table 2

[0058] Example 3: Pre-wetting-displacement treatment of PTFE porous membranes with quaternary ammonium salt ionic liquids Step 1: Provide an alkali-resistant porous substrate. A polytetrafluoroethylene (PTFE) porous membrane is provided as the alkali-resistant porous substrate.

[0059] Step 2: Prepare a pre-wetting solution containing an ionic liquid. Prepare a pre-wetting solution containing a quaternary ammonium salt ionic liquid and dimethyl sulfoxide.

[0060] Step 3: Allow the pre-wetting solution to enter the pores and displace the air. An ultrasonic-assisted wetting method is used to allow the pre-wetting solution to enter the pores of the polytetrafluoroethylene porous membrane, so that the ionic liquid occupies at least a portion of the pore space as a temporary pre-wetting medium.

[0061] Step 4: Remove excess pre-wetting solution from the outer surface. Remove excess solution from the membrane surface, ensuring the ionic liquid remains primarily within the pore walls and local channels.

[0062] Step 5: Contact with organic solvent slurry containing inorganic particles and allow for mutual dissolution and displacement. The polytetrafluoroethylene porous membrane pre-wetted with the ionic liquid is then contacted with a slurry containing dimethyl sulfoxide or N-methylpyrrolidone. This allows the ionic liquid within the pores to be gradually diluted and replaced by the organic solvent, improving the continuity of the slurry entering the pores.

[0063] Step six: Post-processing. Through solvent replacement and drying, the ionic liquid is at least partially replaced or removed, forming a composite layer.

[0064] Table 3

[0065] Example 4: Pre-wetting treatment of PEEK porous support mesh with ether-bonded ionic liquids Step 1: Provide an alkali-resistant porous substrate. A polyetheretherketone (PEEK) porous support mesh is provided as the alkali-resistant porous substrate and then cleaned and dried.

[0066] Step 2: Prepare a pre-wetting solution containing an ionic liquid. Prepare a pre-wetting solution containing an ether-bonded ionic liquid and N,N-dimethylformamide.

[0067] Step 3: Allow the pre-wetting solution to enter the pores and displace the air. Under vacuum-assisted conditions, allow the pre-wetting solution to enter the mesh, wire intersections, and surface micropore areas of the polyetheretherketone porous support mesh.

[0068] Step 4: Remove excess pre-wetting treatment liquid from the outer surface. Remove excess treatment liquid from the outer surface by draining, rolling, or air knife blowing.

[0069] Step 5: Contact with the slurry containing inorganic particles and organic solvent, allowing for mutual solubility and displacement. The polyether ether ketone porous support mesh, pre-wetted with ionic liquid, is brought into contact with the slurry containing organic solvent. This allows the organic solvent in the slurry to diffuse into the pores and undergo mutual solubility and displacement with the ionic liquid, promoting continuous distribution of the slurry within the pores.

[0070] Step six, post-processing. Washing, solvent replacement, drying, and / or heat treatment are performed to at least partially replace or remove the ionic liquid, forming a composite layer.

[0071] Table 4

[0072] Example 5: Pre-wetting treatment of PVDF porous membrane with hydroxyl-containing ionic liquid Step 1: Provide an alkali-resistant porous substrate. A polyvinylidene fluoride porous membrane is provided as the alkali-resistant porous substrate.

[0073] Step 2: Prepare a pre-wetting solution containing ionic liquids. Prepare a pre-wetting solution containing hydroxyl ionic liquids and alcohol solvents.

[0074] Step 3: Allow the pre-wetting solution to enter the pores and displace the air. Immerse the polyvinylidene fluoride porous membrane in the pre-wetting solution and perform a circulating infusion process to allow the pre-wetting solution to enter the surface channels and internal pores of the porous membrane.

[0075] Step 4: Remove excess pre-wetting solution from the outer surface. Remove excess solution by light purging or rolling, ensuring the ionic liquid is primarily distributed on the inner walls of the pores.

[0076] Step 5: Contact with the organic solvent slurry containing inorganic particles and allow for mutual solubility and displacement. The polyvinylidene fluoride porous membrane pre-wetted with the ionic liquid is then contacted with the slurry containing N-methylpyrrolidone, allowing the organic solvent in the slurry to undergo mutual solubility, diffusion, and / or displacement with the ionic liquid, promoting the slurry's entry into the pores.

[0077] Step six: Post-processing. The ionic liquid is at least partially replaced or removed by washing and drying with N-methylpyrrolidone, forming a composite layer.

[0078] Table 5

[0079] Example 6: Pre-wetting treatment of PPS nonwoven fabric with amide-containing ionic liquid Step 1: Provide an alkali-resistant porous substrate. Use polyphenylene sulfide nonwoven fabric as the alkali-resistant porous substrate.

[0080] Step 2: Prepare a pre-wetting solution containing ionic liquid. Prepare a pre-wetting solution containing amide-based ionic liquid and N,N-dimethylacetamide.

[0081] Step 3: Allow the pre-wetting treatment solution to enter the pores and displace the air. Place the polyphenylene sulfide nonwoven fabric in the pre-wetting treatment solution, and allow the treatment solution to pass through the thickness direction of the nonwoven fabric via filtration and permeation, so that the ionic liquid enters the pores between the fibers and displaces some of the pore air.

[0082] Step 4: Remove excess pre-wetting solution from the outer surface. Remove excess pre-wetting solution from the outer surface using an air knife purging method or a metering roller to control the liquid flow.

[0083] Step 5: Contact with organic solvent slurry containing inorganic particles and allow for mutual solubility and displacement. The pre-wetted polyphenylene sulfide nonwoven fabric is contacted with a functional slurry containing N,N-dimethylacetamide, allowing the organic solvent in the slurry to dissolve and displace the ionic liquid.

[0084] Step six, post-processing. Washing, solvent replacement, drying, and / or heat treatment are performed to at least partially replace or remove the ionic liquid, forming a composite layer.

[0085] Example 7: Pre-wetting treatment of PEEK porous membranes with carboxylate-type ionic liquids Step 1: Provide an alkali-resistant porous substrate. A polyetheretherketone (PEEK) porous membrane is provided as the alkali-resistant porous substrate.

[0086] Step 2: Prepare a pre-wetting solution containing an ionic liquid. Prepare a pre-wetting solution containing a carboxylate-type ionic liquid and a water / alcohol mixed solvent.

[0087] Step 3: Allow the pre-wetting solution to enter the pores and displace the air. Immerse the polyetheretherketone porous membrane in the pre-wetting solution and perform pressure-assisted wetting to allow the solution to enter the internal pores and displace some of the pore air.

[0088] Step 4: Remove excess pre-wetting solution from the outer surface. Use roller pressing or air knife purging to remove excess solution from the surface, ensuring that the ionic liquid remains mainly on the inner wall of the pores.

[0089] Step 5: Contact with an organic solvent slurry containing inorganic particles and allow for mutual solubility and displacement. The pre-wetted polyetheretherketone porous membrane is contacted with an inorganic particle slurry containing N-methylpyrrolidone or dimethyl sulfoxide, allowing the organic solvent in the slurry to undergo mutual solubility, diffusion, and / or displacement with the ionic liquid.

[0090] Step six, post-processing. Through solvent replacement, washing, drying and / or heat treatment, the ionic liquid is at least partially replaced or removed, forming a composite layer.

[0091] Example 8: Pre-wetting treatment of PTFE porous membranes with sulfonate-type ionic liquids Step 1: Provide an alkali-resistant porous substrate. A polytetrafluoroethylene (PTFE) porous membrane is provided as the alkali-resistant porous substrate.

[0092] Step 2: Prepare a pre-wetting solution containing an ionic liquid. Prepare a pre-wetting solution containing a sulfonate-type ionic liquid and dimethyl sulfoxide.

[0093] Step 3: Allow the pre-wetting solution to enter the pores and displace the air. A combination of vacuum-assisted wetting and ultrasonic-assisted methods is used to allow the pre-wetting solution to enter the internal pores of the polytetrafluoroethylene porous membrane.

[0094] Step 4: Remove excess pre-wetting solution from the outer surface. Remove excess solution from the outer surface by air knife purging or negative pressure suction.

[0095] Step 5: Contact with the organic solvent slurry containing inorganic particles and allow for mutual solubility and displacement. The pre-wetted polytetrafluoroethylene porous membrane is contacted with a slurry containing dimethyl sulfoxide (DMSO), allowing the DMSO in the slurry to dissolve and displace the ionic liquid within the pores.

[0096] Step six: Post-processing. After subsequent washing and heat treatment, at least part of the ionic liquid is replaced or removed, forming a continuous composite structure within the pores.

[0097] Example 9: Comparison of different prewetting methods Step 1: Provide polyphenylene sulfide woven mesh from the same batch as an alkali-resistant porous substrate.

[0098] Step two involves treating the samples using untreated samples, direct pre-wetting with N-methylpyrrolidone, pre-wetting with ethanol, pre-wetting with surfactant, and the temporary pre-wetting-mutual dissolution treatment with ionic liquid described in this invention.

[0099] Step 3: Contact the treated substrate with an inorganic slurry containing N-methylpyrrolidone particles of the same composition.

[0100] Step four: Observe and statistically analyze the slurry's entry into the pores, including the percentage of air bubble area, the percentage of unwetted area, and the percentage of continuously wetted pore area. The results are shown in the table below.

[0101] Table 6

[0102] Example 10: Validation of ionic liquid residue, surface liquid film control, and continuous processing Step 1: Prepare porous substrates with ionic liquid pre-wetting-displacement treatment according to the method in Example 1.

[0103] Step two: After compounding, the ionic liquid is removed through solvent replacement, washing, and drying.

[0104] Step 3: Characterize the residual amount of ionic liquid using one or more of the following methods: mass change, elemental analysis, ion chromatography, total organic carbon test, or X-ray photoelectron spectroscopy.

[0105] Step four shows that, after solvent replacement, washing, and heat treatment, the residual amount of ionic liquid can be reduced to less than 80% of the initial amount introduced, and can be further reduced to less than 50% or less than 20%.

[0106] Table 7

[0107] Continuous verification: Polyphenylene sulfide (PPS) woven mesh is passed sequentially through a pre-wetting treatment tank, metering roller, slurry compounding zone, washing zone, and drying zone in continuous roll form to achieve continuous ionic liquid temporary pre-wetting-mutual dissolution treatment. After metering roller or air knife treatment, the proportion of continuous liquid film area on the outer surface of the substrate can be controlled below 10%, while the pores remain in an effective pre-wetting state.

[0108] Table 8

[0109] Comparative Example Comparative Example 1: Without using ionic liquid pre-wetting, directly compounding organic solvent slurry containing inorganic particles resulted in insufficient air removal near dead corners of pores and fiber intersections, leading to poor continuity of slurry entering the pores.

[0110] Comparative Example 2: After pre-wetting with ionic liquid, without sufficient replacement or washing, the residual amount of ionic liquid is higher than 50% of the initial amount introduced. The channels are occupied by liquid for a long time, which reduces the stability of the composite layer and the compatibility with subsequent electrolytes.

[0111] The results show that the present invention can improve the continuity of high solids content slurry entering the hole through a closed-loop process of temporary pre-wetting, hole venting, mutual dissolution and replacement, and post-treatment removal, while avoiding the residue of ionic liquid as a permanent filler.

[0112] Industrial applicability The porous substrate temporary pre-wetting-mutual dissolution replacement method with ionic liquid provided by this invention is simple and applicable to alkali-resistant porous substrates such as polyphenylene sulfide, polytetrafluoroethylene, polyvinylidene fluoride, and polyetheretherketone, especially suitable for porous support substrates for alkaline electrolytic water composite membranes. This method can be implemented through impregnation, vacuum-assisted impregnation, pressure-assisted impregnation, circulating infusion, filtration permeation, ultrasonic-assisted impregnation, spraying, or roller coating, and is suitable for continuous and large-scale production.

[0113] This invention is particularly applicable to the composite processing of slurries containing organic solvents such as N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide. It is especially suitable for slurries with high solids content or high viscosity organic solvents. It can be used to improve the continuity of pore wetting in porous substrates, reduce bubble retention, unwetted areas and interface cavities, and improve the uniformity and stability of the interfacial contact between the subsequent composite layer and the porous substrate.

Claims

1. A method for temporary pre-wetting-mutual dissolution and displacement treatment of porous substrates containing inorganic particles and organic solvent slurry for alkaline water electrolysis composite membranes, characterized in that, Includes the following steps: Step 1: Provide an alkali-resistant porous substrate with pores, fiber gaps, cross nodes, dead corners of pores and / or inner walls of pores; Step 2: The pre-wetting treatment liquid containing ionic liquid is brought into contact with the alkali-resistant porous substrate and enters at least part of the pores, fiber gaps, cross nodes, dead corners of the channels and / or the inner wall of the pores of the alkali-resistant porous substrate, so that the ionic liquid, as a temporary pre-wetting and pore-occupying exhaust medium, at least partially occupies the gas phase space in the alkali-resistant porous substrate and replaces the air therein. Step 3: Remove excess pre-wetting liquid from the outer surface of the alkali-resistant porous substrate, so that the area of ​​the continuous ionic liquid film on the outer surface accounts for less than 10% of the observed area of ​​the outer surface, and the ionic liquid is mainly retained in the pores, fiber gaps, cross nodes, dead corners of the channels and / or the inner wall of the pores. Step four: The alkali-resistant porous substrate pre-wetted with ionic liquid is brought into contact with an organic solvent slurry containing inorganic particles, so that the organic solvent in the organic solvent slurry containing inorganic particles is mutually soluble, diffused and / or replaced with the ionic liquid, and the organic solvent slurry containing inorganic particles enters at least partially into the pores, fiber gaps, cross nodes, dead corners of pores and / or the inner wall of pores of the alkali-resistant porous substrate. Step 5: The alkali-resistant porous substrate after being composited with slurry is subjected to coagulation, phase transformation, solvent replacement, washing, drying and / or heat treatment, so that the ionic liquid is at least partially replaced or removed, and the slurry containing inorganic particles and organic solvent forms a composite layer on the surface and / or in the pores of the alkali-resistant porous substrate. After step five, the residual amount of the ionic liquid is reduced to less than 50% of the initial amount introduced, and the ionic liquid is not retained in the pores of the alkali-resistant porous substrate as a permanent functional filler.

2. The method according to claim 1, characterized in that, The alkali-resistant porous substrate is PPS woven mesh, PPS nonwoven fabric, PTFE porous membrane, PVDF porous membrane, PEEK porous membrane or a composite porous substrate thereof.

3. The method according to claim 1, characterized in that, The ionic liquid is selected from one or more of choline lactate, choline acetate, 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium lactate, or 1-butyl-3-methylimidazolium acetate.

4. The method according to claim 1, characterized in that, The ionic liquid is liquid at 20 °C to 100 °C, and has a viscosity of 5 mPa·s to 1000 mPa·s at 25 °C. The ionic liquid does not produce macroscopic stratification after being mixed with N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylacetamide or N,N-dimethylformamide at a mass ratio of 1:9 to 9:1 and allowed to stand for 30 min.

5. The method according to claim 1, characterized in that, The pre-wetting treatment solution also includes one or more diluents selected from N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, ethanol, isopropanol, or water.

6. The method according to claim 1, characterized in that, Step two is carried out by vacuum-assisted impregnation, pressure-assisted impregnation, circulating injection, filtration penetration, impregnation, spraying, roller coating or scraping; Step three is carried out by scraping, air knife purging, roller pressing, metering roller control liquid, negative pressure suction, centrifugal liquid removal or a combination thereof.

7. The method according to claim 1, characterized in that, After step three, the area of ​​the continuous ionic liquid film on the outer surface of the alkali-resistant porous substrate is less than 10% of the observed area on the outer surface.

8. The method according to claim 1, characterized in that, The solid content of the inorganic particle-containing organic solvent slurry is 40 wt% to 85 wt%; the inorganic particle-containing organic solvent slurry includes inorganic particles of zirconium oxide, titanium oxide, aluminum oxide, barium sulfate, magnesium oxide or magnesium hydroxide, as well as film-forming polymers of polysulfone, polyethersulfone, polyvinylidene fluoride or polyphenylene sulfide.

9. The method according to claim 1, characterized in that, After step five, the residual amount of the ionic liquid is reduced to less than 50% of the initial amount introduced, preferably to less than 20% of the initial amount introduced.

10. An alkaline water electrolysis composite membrane, characterized in that, The composite layer-porous substrate composite structure prepared by the method of any one of claims 1 to 9, wherein the composite layer is at least partially inserted into the pores, fiber gaps, cross nodes, dead corners of the channels and / or the inner walls of the pores of the alkali-resistant porous substrate.

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