Porous diaphragm as well as preparation method and preparation system thereof

Abstract

The invention discloses a porous diaphragm as well as a preparation method and a preparation system thereof, and belongs to the technical field of diaphragm preparation. The method comprises the following steps: covering one side of a substrate with first slurry, and / or covering the other side of the substrate with second slurry to obtain a coated substrate; the coating substrate passes through a third space formed between the first steam groove and the second steam groove which are oppositely arranged, so that one side of the coating substrate faces the first steam groove, and the other side of the coating substrate faces the second steam groove; a steam outlet of the first steam tank outputs first non-solvent steam to be in contact with one side of the coating substrate, and a steam outlet of the second steam tank outputs second non-solvent steam to be in contact with the other side of the coating substrate, so that a coating in the coating substrate is preliminarily cured to obtain a preliminarily cured film-forming substrate; and the primary curing film-forming substrate enters a coagulating bath for curing film-forming to obtain the porous diaphragm. The diaphragm prepared in this way inhibits the formation of finger-shaped pores, forms an integrally uniform spongy porous structure, and can be a porous diaphragm with asymmetric two side surfaces.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane preparation, and in particular to a porous membrane and a preparation method and system thereof. Background Art

[0002] Alkaline hydrogen production electrolyzers usually use porous diaphragms as key components to isolate hydrogen and oxygen, and require the diaphragms to have good gas isolation, strong ion transmission capacity, low resistance, etc. However, the porous diaphragms in related technologies are prone to finger-like pore structures on their surfaces, which are prone to form gas transmission channels and may eventually lead to gas leakage. Summary of the invention

[0003] The main purpose of the present invention is to provide a porous diaphragm and a preparation method and system thereof, so as to solve the technical problem that it is difficult to control the morphological growth of the finger-like pores inside the diaphragm and the porous structure on the surface during the phase transfer molding process of the diaphragm.

[0004] To achieve the above object, the present invention provides a method for preparing a porous membrane, comprising the following steps: Covering one side of the substrate with the first slurry, and / or covering the other side of the substrate with the second slurry to obtain a coated substrate; The coated substrate passes through a second space formed between a first steam tank and a second steam tank that are arranged opposite to each other, so that one side of the coated substrate faces the first steam tank and the other side faces the second steam tank; the steam outlet of the first steam tank outputs a first non-solvent steam that contacts one side of the coated substrate, and the steam outlet of the second steam tank outputs a second non-solvent steam that contacts the other side of the coated substrate, so that the coating in the coated substrate is initially cured to obtain a initially cured film-forming substrate; The preliminary cured film-forming substrate enters a coagulation bath to be cured to form a film to obtain the porous diaphragm.

[0005] In some embodiments of the present invention, the temperature range of the first non-solvent vapor and the second non-solvent vapor is 100° C. to 240° C.; The first non-solvent vapor includes water, a water-N-methylpyrrolidone mixture, a water-N,N-dimethylacetamide mixture, a water-dimethyl sulfoxide mixture, a water-dimethylformamide mixture, ethanol, isopropanol, and ethylene glycol; The second non-solvent vapor includes at least one of water, a mixture of water and N-methylpyrrolidone, a mixture of water and N,N-dimethylacetamide, a mixture of water and dimethyl sulfoxide, a mixture of water and dimethylformamide, ethanol, isopropanol, and ethylene glycol; The first slurry and the second slurry both include powder particles, an organic polymer and an organic solvent.

[0006] In some embodiments of the present invention, the first non-solvent vapor outputted from the first steam tank is the ethylene glycol, and the second non-solvent vapor outputted from the second steam tank is the water; And / or, the powder particles include at least one of zirconium oxide, zirconium hydroxide, magnesium oxide, magnesium hydroxide, yttrium oxide, yttrium hydroxide, cerium oxide, cerium hydroxide, titanium oxide, titanium hydroxide, barium sulfate, and carbon; And / or, the organic polymer includes at least one of polysulfone, polyethersulfone, polyphenylsulfone, ethylene vinyl alcohol, polyacrylonitrile, polyvinylidene fluoride, polyimide, polyamide, and polyvinyl pyrrolidone And / or, the organic solvent includes at least one of N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, dimethylacetamide, formylpiperidine, dioxane, and morpholine.

[0007] In some embodiments of the present invention, the organic solvent in the first slurry and / or the second slurry is N-methyl-2-pyrrolidone and dimethylacetamide; And / or, the organic solvent in the first slurry and / or the second slurry is N-methyl-2-pyrrolidone and dimethylacetamide, and the mass percentage of the dimethylacetamide is 30% to 40%.

[0008] In some embodiments of the present invention, the steam amount of the first non-solvent steam in the first steam tank is (5-100) g / min·m, and the steam amount of the second non-solvent steam in the second steam tank is (5-100) g / min·m; And / or, the time for the coated substrate to pass through the second space is 0.1s to 10s.

[0009] And / or, the vertical distance between the steam outlet of the first steam groove and one side of the coating substrate is 3 mm to 50 mm, and the vertical distance between the steam outlet of the second steam groove and the other side of the coating substrate is 3 mm to 50 mm.

[0010] And / or, the coagulation bath contains a coagulation liquid, and the coagulation liquid includes at least one of water, a water-N-methyl-2-pyrrolidone mixture, a water-dimethylacetamide mixture, a water-dimethyl sulfoxide mixture, a water-dimethylformamide mixture, ethanol, isopropanol, and ethylene glycol.

[0011] In some embodiments of the present invention, the substrate passes through a first space formed between a first coating die and a second coating die that are relatively arranged, the first coating die outputs the first slurry to cover one side of the substrate, and the second coating die outputs the second slurry to cover the other side of the substrate to obtain the coated substrate.

[0012] In some embodiments of the present invention, the first space, the second space and the coagulation bath are located on the same straight line, and a third space formed by the first exhaust slot and the second exhaust slot which are arranged opposite to each other is also provided on the same straight line.

[0013] In some embodiments of the present invention, the first exhaust slot and the second exhaust slot adjust the flow direction of the first non-solvent vapor and the second non-solvent vapor by means of negative pressure.

[0014] The present invention also provides a porous membrane prepared by the method for preparing the porous membrane as described above.

[0015] The present invention also provides a porous membrane preparation system for preparing the porous membrane as described above, wherein the porous membrane preparation system comprises a first coating die head, a first steam tank and a coagulation bath arranged in sequence; The first coating die head is provided with a second coating die head opposite to the first direction, The first steam groove is provided with a second steam groove opposite to the first direction; There is a first space between the first coating die head and the second coating die head for the substrate to pass through, A second space is provided between the first steam groove and the second steam groove for the coating substrate to pass through; The porous membrane preparation system further includes a first exhaust groove, wherein the first exhaust groove is provided with a second exhaust groove opposite to the first direction, and a third space is provided between the first exhaust groove and the second exhaust groove. The first space, the second space, the third space and the coagulation bath are located on the same straight line in the first direction.

[0016] The beneficial effects that can be achieved by the present invention are: In the process of forming the preliminary solidified film-forming substrate, the present invention allows the coating of the coating substrate to contact with the non-solvent vapor, and the non-solvent vapor is numerous high-temperature small droplets, which can help the coating to solidify well, inhibit the growth of the finger-like pore structure on the surface of the diaphragm, and form a uniform sponge-like porous structure on the surface of the diaphragm or even on the whole. In addition, the present invention can also control the pore structure on the surface of the diaphragm by adjusting the steam type and temperature output by the first steam tank and the second steam tank, enrich the performance of the diaphragm, and further inhibit the growth of the finger-like pore structure, so as to form a grid-like porous structure with a strong organic-inorganic bond on the surface of the diaphragm, and obtain a porous structure with a uniform sponge-like shape.

[0017] In an alkaline electrolytic cell, the diaphragm needs to be clamped by the electrode. The rough structure on the electrode surface and the catalyst particles may puncture the diaphragm surface, or tiny compression cracks may be formed on the diaphragm surface due to pressure. These punctured perforations and tiny compression cracks may directly connect to the finger-like pore structure, thereby forming a gas transmission channel, which may eventually lead to gas leakage. The porous diaphragm prepared by the present invention can form a uniform sponge-like porous structure on the diaphragm surface or even on the entire diaphragm. Even if the surface is punctured and microcracks occur, it will not affect the internal structure, thereby increasing the safety of the diaphragm. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0019] Figure 1 Schematic diagram of a porous membrane preparation system according to an embodiment of the present invention.

[0020] Figure 2 It is a schematic diagram of a system for preparing a porous membrane according to another embodiment of the present invention.

[0021] Figure 3 This is a SEM image of the diaphragm of Example 1 of the present invention.

[0022] Figure 4 This is a SEM image of the diaphragm of Example 2 of the present invention.

[0023] Figure 5 This is a SEM image of the diaphragm of Comparative Example 1 of the present invention.

[0024] Figure 6 This is a SEM image of the diaphragm of Example 3 of the present invention.

[0025] Figure 7 This is a SEM image of the diaphragm of Comparative Example 2 of the present invention.

[0026] Figure Number:

[0027] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0028] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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.

[0030] In the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0031] In an alkaline electrolyzer, the diaphragm needs to be clamped by the electrodes. The rough structure of the electrode surface and the catalyst particles will puncture the diaphragm surface, or due to pressure, tiny compression cracks will form on the diaphragm surface. These punctured perforations and tiny compression cracks will directly connect to the finger-like pore structure, thereby forming a gas transmission channel, which may eventually lead to gas leakage.

[0032] In view of this, the present invention provides a method for preparing a porous membrane, comprising the following steps: S10, covering one side of the substrate 200 with the first slurry, and / or covering the other side of the substrate 200 with the second slurry, to obtain a coated substrate 300; S20, the coated substrate 300 passes through the second space formed between the first steam tank 102 and the second steam tank 202 which are arranged opposite to each other, so that one side of the coated substrate 300 faces the first steam tank 102, and the other side faces the second steam tank 202; the steam outlet of the first steam tank 102 outputs the first non-solvent steam to contact the one side of the coated substrate 300, and the steam outlet of the second steam tank 202 outputs the second non-solvent steam to contact the other side of the coated substrate 300, so that the coating in the coated substrate 300 is initially cured to obtain a initially cured film-forming substrate; S30, Preliminary Solidification: The film-forming substrate enters the coagulation bath 103 to solidify and form a film to obtain a porous diaphragm.

[0033] In step S10 , the slurry may be coated on one side of the substrate 200 to form a single-sided coating, or the slurry may be coated on both sides of the substrate 200 to form a double-sided coating.

[0034] In some embodiments, the material of the substrate 200 includes at least one of polyphenylene sulfide, polyetheretherketone, and nylon.

[0035] In some embodiments, the thickness of the substrate 200 ranges from 30 μm to 300 μm.

[0036] In some embodiments, the single-side coating thickness of the substrate 200 is 30 μm to 200 μm.

[0037] In some embodiments, the slurry may be coated on a single side or both sides of the substrate 200 by a slot coating device.

[0038] In some embodiments, the slurry may be applied to one side or both sides of the substrate 200 by spraying.

[0039] In step S20, referring to Figure 1 and Figure 2 In the present invention, the coating substrate 300 passes through the second space formed between the first steam tank 102 and the second steam tank 202 which are arranged opposite to each other, so that the coating of the coating substrate 300 contacts the non-solvent vapor, so that the coating is uniformly initially solidified. The non-solvent vapor is numerous high-temperature small droplets, which can help the coating to be well solidified, inhibit the growth of the finger-like pore structure on the surface of the diaphragm, and is conducive to forming a sponge-like porous structure that is uniform on the surface or even on the whole. In addition, the present invention can also control the pore structure on the surface of the diaphragm by adjusting the steam type and temperature output by the first steam tank 102 and the second steam tank 202, enrich the performance of the diaphragm, and further inhibit the growth of the finger-like pore structure, so as to form a grid-like porous structure with a firm organic-inorganic bond on the surface of the diaphragm, and obtain a porous structure with a uniform sponge-like shape.

[0040] In some embodiments, the temperature of the first non-solvent vapor is in the range of 100°C to 240°C, for example, it can be any value in the range of 100°C to 240°C, such as 100°C, 150°C, 180°C, 200°C, 240°C, etc.; the temperature of the second non-solvent vapor is in the range of 100°C to 240°C, for example, it can be any value in the range of 100°C to 240°C, such as 100°C, 150°C, 180°C, 200°C, 240°C, etc. The temperature of the non-solvent vapor is within the above range, which is conducive to suppressing the formation of finger-like pores in the diaphragm and obtaining a porous diaphragm with a uniform sponge-like porous structure.

[0041] In some embodiments, the first non-solvent vapor includes at least one of water, a mixture of water and N-methylpyrrolidone (NMP), a mixture of water and N,N-dimethylacetamide (DMAC), a mixture of water and dimethyl sulfoxide (DMSO), a mixture of water and dimethylformamide (DMF), ethanol, isopropanol, and ethylene glycol. It can be understood that the above are all in a vapor state, and the above types of non-solvent vapor can achieve preliminary curing of the coating in the coated substrate 300.

[0042] In some embodiments, the second non-solvent vapor includes at least one of water, a mixture of water and N-methylpyrrolidone (NMP), a mixture of water and N,N-dimethylacetamide (DMAC), a mixture of water and dimethyl sulfoxide (DMSO), a mixture of water and dimethylformamide (DMF), ethanol, isopropanol, and ethylene glycol. It can be understood that the above are all in a vapor state, and the above types of non-solvent vapor can achieve preliminary curing of the coating in the coated substrate 300.

[0043] In some embodiments, the first non-solvent vapor outputted from the steam outlet of the first steam tank 102 is ethylene glycol, which is in a steam state, and the second solvent outputted from the steam outlet of the second steam tank 202 is water, which is in a water vapor state. In this embodiment, the steam tanks on both sides use different types of non-solvent vapors, so that the diaphragm can obtain a double-sided membrane surface with different properties. For example, the surface of the film on the side in contact with water vapor can form a grid-like porous structure, with strong hydrophilicity and a low bubble contact angle, and the surface of the film on the side in contact with ethylene glycol vapor can achieve a generally dense surface structure, with weak hydrophilicity and a high bubble contact angle, and the films on both sides can present a uniform sponge-like porous structure as a whole, and finger-like holes are not easy to appear in its cross section. The diaphragm obtained in this embodiment can not only form a uniform sponge-like porous structure, but also has hydrophilic and hydrophobic properties on the surface, can be used as a Janus material, and is also convenient for subsequent different modifications on the surface of the diaphragm.

[0044] In some embodiments, the temperature of the ethylene glycol output from the first steam tank 102 is 220°C, and the temperature of the water output from the second steam tank 202 is 180°C.

[0045] In some embodiments, the compositions of the first slurry and the second slurry may be different, thereby forming coatings with different compositions on one side and the other side of the substrate 200, thereby enriching the performance of the diaphragm. The compositions of the first slurry and the second slurry may also be the same, thereby forming coatings with the same compositions on one side and the other side of the substrate 200.

[0046] In some embodiments, the first slurry includes powder particles, an organic polymer, and an organic solvent; and the second slurry includes powder particles, an organic polymer, and an organic solvent.

[0047] In some embodiments, the powder particles include at least one of zirconium oxide, zirconium hydroxide, magnesium oxide, magnesium hydroxide, yttrium oxide, yttrium hydroxide, cerium oxide, cerium hydroxide, titanium oxide, titanium hydroxide, barium sulfate, and carbon.

[0048] In some embodiments, the organic solvent includes at least one selected from N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), dimethylformamide, tetrahydrofuran, dimethylacetamide (DMAC), formylpiperidine, dioxane, and morpholine.

[0049] In some embodiments, the organic polymer includes at least one of polysulfone, polyethersulfone, polyphenylsulfone, ethylene vinyl alcohol, polyacrylonitrile, polyvinylidene fluoride, polyimide, polyamide, and polyvinylpyrrolidone.

[0050] The present invention does not limit the weight ratio of the organic solvent, powder particles, and organic polymer in the first slurry and the second slurry, and they can be matched according to actual needs.

[0051] In some embodiments, the organic solvent in the first slurry and / or the second slurry is N-methyl-2-pyrrolidone and dimethylacetamide. A mixed solution of N-methyl-2-pyrrolidone and dimethylacetamide is used as the solvent, and non-solvent steam is used in combination. The miscibility of the organic solvent and non-solvent steam system in the slurry can be reduced, thereby inhibiting the formation of finger-like pores on the surface of the diaphragm, and can even completely inhibit the formation of finger-like pores. A sponge-like porous structure is formed on the surface and inside of the diaphragm, and the grid is clear, which reduces or even eliminates the phenomenon of ceramic powder accumulation on the surface.

[0052] In some embodiments, the mass percentage of dimethylacetamide in the organic solvent formed by the mixture of N-methyl-2-pyrrolidone and dimethylacetamide is 30% to 40%, which is beneficial to reduce the miscibility of the organic solvent and the non-solvent vapor system and inhibit the formation of finger-like pores on the surface of the diaphragm.

[0053] In some embodiments, the steam amount of the first non-solvent steam in the first steam tank 102 is (5~100) g / min·m, which can be 5g / min·m, 10g / min·m, 20g / min·m, 30g / min·m, 40g / min·m, 50g / min·m, 60g / min·m, 70g / min·m, 80g / min·m, 90g / min·m, 100g / min·m, etc., and the steam amount of the second non-solvent steam in the second steam tank 202 is (5~100) g / min·m, which can be 5g / min·m, 10g / min·m, 20g / min·m, 30g / min·m, 40g / min·m, 50g / min·m, 60g / min·m, 70g / min·m, 80g / min·m, 90g / min·m, 100g / min·m, etc. m, etc., which is beneficial to the initial solidification of the coating in the coating substrate 300 and is beneficial to the formation of a uniform sponge-like or grid-like porous structure.

[0054] In some embodiments, the time that the coated substrate 300 passes through the second space is 0.1s~10s, preferably 0.1s~3s, so that the coating and non-solvent vapor in the coated substrate 300 are completely in contact, achieving better initial curing, which is conducive to obtaining an overall uniform sponge-like porous structure, and the sponge-like porous structure is not easily destroyed due to excessive contact time.

[0055] In some embodiments, the vertical distance between the steam outlet of the first steam slot 102 and one side of the coated substrate 300 is 3 mm to 50 mm.

[0056] In some embodiments, the vertical distance between the steam outlet of the second steam slot 202 and the other side of the coated substrate 300 is 3 mm to 50 mm.

[0057] In some embodiments, the vertical distance between the steam outlet of the first steam groove 102 and one side of the coating substrate 300 and the vertical distance between the steam outlet of the second steam groove 202 and the other side of the coating substrate 300 are the same, so that the force on both sides of the coating substrate 300 is more uniform, which is conducive to achieving better preliminary curing, so that the surface of the diaphragm forms an overall uniform grid-like or sponge-like porous structure, and inhibits the formation of finger-like holes.

[0058] In step S30, the initially cured film-forming substrate is immersed in a coagulation bath 103, and the coating is completely cured to obtain a porous diaphragm.

[0059] In some embodiments, the coagulation bath 103 contains a coagulation liquid, and the coagulation liquid includes at least one of water, a mixture of water and N-methyl-2-pyrrolidone (NMP), a mixture of water and dimethylacetamide (DMAC), a mixture of water and dimethyl sulfoxide (DMSO), a mixture of water and dimethylformamide (DMF), ethanol, isopropanol, and ethylene glycol.

[0060] In some embodiments, the substrate 200 passes through a first space formed between the first coating die head 101 and the second coating die head 201 that are arranged opposite to each other, and the first coating die head 101 outputs the first slurry to cover one side of the substrate 200, and / or the second coating die head 201 outputs the second slurry to cover the other side of the substrate 200. In this embodiment, the coating die head is used to coat the substrate 200, which can simplify the process and improve production efficiency.

[0061] In some embodiments, the first space, the second space and the coagulation bath 103 are located on the same straight line, and a third space formed by the first exhaust slot 104 and the second exhaust slot 204 disposed opposite to each other is also provided on the same straight line. The exhaust slot can control the flow direction of the non-solvent steam outputted from the steam slot, promote the contact between the non-solvent steam and the coating substrate 300, and finally extract the non-solvent steam. In addition, the contact time between the non-solvent steam and the coating substrate 300 can also be controlled.

[0062] In some embodiments, reference Figure 1 The first exhaust groove 104 and the second exhaust groove 204 can be arranged between the first coating die 101, the second coating die 201 and the first steam groove 102, the second steam groove 202, that is, on the same straight line, the first coating die 101, the first exhaust groove 104, the first steam groove 102 are arranged in sequence, the second coating die 201, the second exhaust groove 204, the second steam groove 202 are arranged in sequence, and the first space, the third space, the second space and the coagulation bath 103 are arranged in sequence. In this embodiment, the substrate 200 passes through the first space of the first coating die head 101 and the second coating die head 201, and the coating is coated on both sides or one side to obtain a coated substrate 300. The coated substrate 300 then continues to pass through the third space formed by the first exhaust slot 104 and the second exhaust slot 204 and the second space formed by the first steam slot 102 and the second steam slot 202. The first exhaust slot 104 and the second exhaust slot 204 can control the flow direction of the non-solvent steam output by the steam slot, so that the non-solvent steam moves in the opposite direction of the movement of the coated substrate 300 and finally enters the first exhaust slot 104 and the second exhaust slot 204, thereby promoting the contact between the non-solvent steam and the coated substrate 300 and controlling the contact time between the non-solvent steam and the coated substrate 300.

[0063] In some embodiments, reference Figure 2The first space, the second space, the third space, and the coagulation bath 103 on the same straight line can also be arranged in sequence as the first space, the second space, the third space, and the coagulation bath 103, that is, on the same straight line, the first coating die head 101, the first steam tank 102, and the first exhaust tank 104 are arranged in sequence, and the second coating die head 201, the second steam tank 202, and the second exhaust tank 204 are arranged in sequence, and the substrate 200 passes through the first space formed by the first coating die head 101 and the second coating die head 201 to obtain a coated substrate 300. The coated substrate 300 passes through the second space formed by the first steam groove 102 and the second steam groove 202 in sequence and comes to the third space formed by the first exhaust groove 104 and the second exhaust groove 204. During this process, the first exhaust groove 104 and the second exhaust groove 204 control the flow direction of the non-solvent steam output by the steam, so that the non-solvent steam moves in the direction of the coating substrate 300 and finally enters the exhaust groove, thereby promoting the contact between the non-solvent steam and the coating substrate 300 and controlling the contact time between the non-solvent steam and the coating substrate 300.

[0064] In some embodiments, the first exhaust slot 104 and the second exhaust slot 204 adjust the flow direction of the first steam and the second steam by negative pressure, and control the contact time between the first steam and the second steam and the coated substrate 300 .

[0065] In some embodiments, the time for the coated substrate 300 to pass through the third space formed between the first exhaust slot 104 and the second exhaust slot 204 is 0.1 s to 3 s.

[0066] The present invention also provides a porous membrane preparation system 100, referring to Figure 1 The porous membrane preparation system 100 includes a first coating die 101, a first steam tank 102 and a coagulation bath 103 which are arranged in sequence. The first coating die 101 is provided with a second coating die 201 opposite to each other in a first direction. The first steam tank 102 is provided with a second steam tank 202 opposite to each other in the first direction. A first space for the substrate 200 to pass through is provided between the first coating die 101 and the second coating die 201. A second space for the coated substrate 300 to pass through is provided between the first steam tank 102 and the second steam tank 202.

[0067] When the porous diaphragm is prepared using the preparation system, the first slurry is loaded into the first coating die 101, and / or the second slurry is loaded into the second coating die 201, so that the substrate 200 passes through the first space, one side of the substrate 200 faces the first coating die 101, and the other side of the substrate 200 faces the second coating die 201, and the first coating die 101 is used to coat one side of the substrate 200 to form a first coating, and the second coating die 201 is used to coat the other side of the substrate 200 to form a second coating. It can be understood that the coating can be formed on only one side of the substrate 200, or the coating can be applied to both sides of the substrate 200.

[0068] The coated substrate 200 is a coating substrate 300. The coating substrate 300 continues to pass through the second space formed between the first steam tank 102 and the second steam tank 202. The first steam tank 102 outputs the first non-solvent vapor to act on one side of the coating substrate 300, and the second steam tank 202 outputs the second non-solvent vapor to act on the other side of the coating substrate 300. The coating substrate 300 is initially cured by the first steam tank 102 and the second steam tank 202 to obtain a initially cured film-forming substrate. The initially cured film-forming substrate is moved to the coagulation bath 103, and is further cured to obtain a porous diaphragm.

[0069] The porous membrane preparation system 100 also includes a first exhaust groove 104, which is provided with a second exhaust groove 204 opposite to the first direction, and a third space is provided between the first exhaust groove 104 and the second exhaust groove 204. The first space, the second space, the third space and the coagulation bath 103 are located on the same straight line in the first direction. The first exhaust groove 104 and the second exhaust groove 204 are used to control the flow of the first steam and the second steam, which not only promotes the contact between the non-solvent steam and the coating substrate 300, but also adjusts the contact time between the first steam and the second steam and the coating substrate 300, thereby affecting the formation of the surface porous structure by flexibly controlling the contact time.

[0070] In some embodiments, continue to refer to Figure 1 The arrangement of the first space, the second space, the third space and the coagulation bath 103 in the porous membrane preparation system 100 in the first direction is the first space formed by the first coating die 101 and the first steam tank 102, the third space formed by the first exhaust tank 104 and the second exhaust tank 204, the second space formed by the first steam tank 102 and the second steam tank 202, and the coagulation bath 103.

[0071] In some embodiments, reference Figure 2The arrangement of the first space, the second space, the third space and the coagulation bath 103 in the porous membrane preparation system 100 in the first direction is the first space formed by the first coating die 101 and the first steam tank 102, the second space formed by the first steam tank 102 and the second steam tank 202, the third space formed by the first exhaust slot 104 and the second exhaust slot 204, and the coagulation bath 103.

[0072] In some embodiments, the vertical distance between the exhaust port of the first exhaust slot 104 and one side of the coating substrate 300 passed through is 1mm ~50mm, preferably 5~15mm, and the vertical distance between the exhaust port of the second exhaust slot 204 and the other side of the coating substrate 300 passed through is 1mm ~50mm, preferably 5mm ~15mm.

[0073] In some embodiments, the vertical distance between the steam outlet of the first steam groove 102 and one side of the coated substrate 300 is 3 mm to 50 mm, preferably 5 mm to 30 mm, and the vertical distance between the steam outlet of the second steam groove 202 and the other side of the coated substrate 300 is 3 mm to 50 mm, preferably 5 mm to 30 mm.

[0074] In some embodiments, the vertical distance between the first exhaust slot 104 and the first coating die 101 is 5 cm to 100 cm, preferably 10 cm to 20 cm, and the vertical distance between the second exhaust slot 204 and the second coating die 201 is 5 cm to 100 cm, preferably 10 cm to 20 cm.

[0075] In some embodiments, the vertical distance between the first exhaust slot 104 and the first steam slot 102 is 5 cm to 100 cm, preferably 15 cm to 20 cm, and the vertical distance between the second exhaust slot 204 and the second steam slot 202 is 5 cm to 100 cm, preferably 15 cm to 20 cm.

[0076] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the following specific embodiments are only used to explain the present invention, and are not used to limit the present invention.

[0077] Example 1 Example 1 Using Figure 1 The porous membrane preparation system shown prepares the porous membrane.

[0078] (1) Introduction to porous membrane systems refer to Figure 1The porous membrane preparation system includes a first coating die head 101, a first exhaust slot 104, a first steam slot 102 and a coagulation bath 103 which are arranged in sequence. The first coating die head 101 is provided with a second coating die head 201 opposite to the first direction, the first exhaust slot 104 is provided with a second exhaust slot 204 opposite to the first direction, and the first steam slot 102 is provided with a second steam slot 202 opposite to the first direction; a first space for the substrate 200 to pass through is provided between the first coating die head 101 and the second coating die head 201, a third space for the coated substrate 300 to pass through is provided between the first exhaust slot 104 and the second exhaust slot 204, and a second space for the coated substrate 300 to pass through is provided between the first steam slot 102 and the second steam slot 202; the first space, the third space, the second space and the coagulation bath 103 are located on the same straight line in the first direction.

[0079] The vertical distance between the exhaust port of the first exhaust slot 104 and the side of the substrate 200 passing through the exhaust port facing the first exhaust slot 104 is 15 mm, the distance between the exhaust port of the second exhaust slot 204 and the other side of the substrate 200 passing through is 15 mm, the vertical distance between the steam outlet of the first steam slot 102 and the side of the substrate 200 passing through the steam outlet facing the first steam slot 102 is 30 mm, and the vertical distance between the steam outlet of the second steam slot 202 and the other side of the substrate 200 passing through is 30 mm. The vertical distance between the first exhaust slot 104 and the first coating die 101 is 20 cm, the vertical distance between the second exhaust slot 204 and the second coating die 201 is 20 cm, the vertical distance between the first exhaust slot 104 and the first steam slot 102 is 50 cm, and the vertical distance between the second exhaust slot 204 and the second steam slot 202 is 50 cm.

[0080] The exhaust slots on both sides of the system use negative pressure to force the non-solvent steam output from the two steam slots to move in the opposite direction of the first direction, and exhaust the output non-solvent steam.

[0081] (2) Preparation of porous membrane using porous membrane preparation system S10, 100g of organic solvent N-methyl-2-pyrrolidone (NMP), 20g of organic polymer polysulfone (PSU) and 114g of powdered zirconium oxide are ball-milled and mixed evenly, and vacuum degassing is performed to obtain slurry, and the slurry is filled into the first coating die 101 and the second coating die 201 respectively, and the substrate 200 passes through the first space, and the slurry is coated on both sides of the substrate 200 by the first coating die 101 and the second coating die 201 to obtain a coated substrate 300.

[0082] S20, the coated substrate 300 is passed through the third space and the second space in sequence, the steam outlet of the first steam tank 102 outputs the first non-solvent steam of 220°C ethylene glycol steam at a steam volume of 20 g / min m, and slowly sprays it on one side of the coated substrate 300, the steam outlet of the second steam tank 202 outputs the second non-solvent steam of 180°C water vapor at a steam volume of 60 g / min m, and slowly sprays it on the other side of the coated substrate 300, the non-solvent steam on both sides rises under the negative pressure of the first exhaust slot 104 and the second exhaust slot 204 and is gradually extracted by the exhaust slots, so that the contact time between the coated substrate 300 and the non-solvent steam is 1 s, thereby preliminarily solidifying the slurry on both sides to obtain a preliminarily solidified substrate 200.

[0083] S30, the preliminarily solidified substrate 200 continues to enter the solidification bath 103 whose solidification liquid is water, and the preliminarily solidified substrate 200 is solidified in deionized water to obtain a porous diaphragm.

[0084] Comparative Example 1 Comparative Example 1 prepares a porous diaphragm according to the method of Example 1, but the difference is that the first non-solvent steam output by the first steam tank 102 of Comparative Example 1 is ethylene glycol steam at a temperature of 250°C, and the second non-solvent steam output by the second steam tank 202 is water vapor at 250°C.

[0085] Example 2 Example 2 prepares a porous diaphragm by referring to the method of Example 1, but the difference is that in Example 2, the second steam tank 202 only outputs the second non-solvent steam at 180°C on the side of the substrate 200 facing the second coating die 201 to preliminarily cure the coated coating, and the first steam tank 102 does not output non-solvent steam.

[0086] Example 3 Example 3 A porous diaphragm was prepared by referring to the method of Example 1, except that, in Example 3, 70 g NMP, 30 g DMAC, 20 g PSU, and 114 g zirconium oxide were evenly mixed by ball milling, and vacuum degassing was performed to obtain a slurry, wherein the mass ratio of NMP to DMAC was 7:3, and both the first steam tank 102 and the second steam tank 202 output water vapor at 180° C.

[0087] Comparative Example 2 Comparative Example 2 A porous diaphragm was prepared by referring to the method of Example 3, except that, in Comparative Example 2, the organic solvent in the slurry was replaced with 100 g of NMP, DMAC was not added, and both the first steam tank 102 and the second steam tank 202 output water vapor at 180° C., and the steam volume was 1 g / min m.

[0088] Performance Testing The porous membranes prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were observed using a scanning electron microscope.

[0089] The SEM image of Example 1 is as follows Figure 3 As shown, Figure 3 The left side of the middle shows the surface of the diaphragm formed by the initial curing of ethylene glycol vapor. Figure 3 On the right is the surface of the other side of the diaphragm that has been initially solidified by water vapor. Figure 3 It can be seen that one side of the diaphragm forms an overall uniform sponge-like porous structure, and the other side forms an overall uniform grid-like porous structure.

[0090] The SEM picture of Example 2 is as follows Figure 4 As shown, the diaphragm has an asymmetric structure, the side that does not receive steam shows finger-like pore growth, while the side that receives initial solidification from the steam tank does not show finger-like pore growth.

[0091] The SEM image of Comparative Example 1 is as follows Figure 5 As shown, no grid-like structure or sponge-like porous structure is formed on the surface of the separator because the temperature of the non-solvent vapor is too high, reaching 250°C.

[0092] The SEM picture of Example 3 is as follows Figure 6 As shown, Figure 6 The left side is a cross-sectional view of the diaphragm. Figure 6 On the right is the surface image of the diaphragm. There are no finger-like holes in the cross section, and it is a completely sponge-like structure. The surface presents a grid-like structure with a clear grid and no ceramic powder accumulation on the grid surface.

[0093] The SEM image of Comparative Example 2 is as follows Figure 7 As shown, finger-like holes appeared in the cross section of the diaphragm. In Comparative Example 2, the steam volume was 1 g / min m, and the formation of finger-like holes could not be completely suppressed.

[0094] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a porous diaphragm, characterized in that: The following steps are involved: Covering one side of the substrate with the first slurry, and / or covering the other side of the substrate with the second slurry to obtain a coated substrate; The coated substrate passes through a second space formed between a first steam tank and a second steam tank that are arranged opposite to each other, so that one side of the coated substrate faces the first steam tank and the other side faces the second steam tank; the steam outlet of the first steam tank outputs a first non-solvent steam that contacts one side of the coated substrate, and the steam outlet of the second steam tank outputs a second non-solvent steam that contacts the other side of the coated substrate, so that the coating in the coated substrate is initially cured to obtain a initially cured film-forming substrate; The preliminary cured film-forming substrate enters a coagulation bath to be cured to form a film to obtain the porous diaphragm.

2. The method for preparing a porous diaphragm according to claim 1, characterized in that: The temperature range of the first non-solvent vapor and the second non-solvent vapor is 100° C. to 240° C.; The first non-solvent vapor includes water, a water-N-methylpyrrolidone mixture, a water-N,N-dimethylacetamide mixture, a water-dimethyl sulfoxide mixture, a water-dimethylformamide mixture, ethanol, isopropanol, and ethylene glycol; The second non-solvent vapor includes at least one of water, a mixture of water and N-methylpyrrolidone, a mixture of water and N,N-dimethylacetamide, a mixture of water and dimethyl sulfoxide, a mixture of water and dimethylformamide, ethanol, isopropanol, and ethylene glycol; The first slurry and the second slurry both include powder particles, an organic polymer and an organic solvent.

3. The method for preparing a porous diaphragm according to claim 2, characterized in that: The first non-solvent vapor outputted by the first steam tank is the ethylene glycol, and the second non-solvent vapor outputted by the second steam tank is the water; And / or, the powder particles include at least one of zirconium oxide, zirconium hydroxide, magnesium oxide, magnesium hydroxide, yttrium oxide, yttrium hydroxide, cerium oxide, cerium hydroxide, titanium oxide, titanium hydroxide, barium sulfate, and carbon; And / or, the organic polymer includes at least one of polysulfone, polyethersulfone, polyphenylsulfone, ethylene vinyl alcohol, polyacrylonitrile, polyvinylidene fluoride, polyimide, polyamide, and polyvinyl pyrrolidone And / or, the organic solvent includes at least one of N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, dimethylacetamide, formylpiperidine, dioxane, and morpholine.

4. The method for preparing the porous diaphragm according to claim 3, characterized in that: The organic solvent in the first slurry and / or the second slurry is N-methyl-2-pyrrolidone and dimethylacetamide; And / or, the organic solvent in the first slurry and / or the second slurry is N-methyl-2-pyrrolidone and dimethylacetamide, and the mass percentage of the dimethylacetamide is 30% to 40%.

5. The method for preparing the porous membrane according to claim 1, characterized in that: The steam volume of the first non-solvent steam in the first steam tank is (5-100) g / min·m, and the steam volume of the second non-solvent steam in the second steam tank is (5-100) g / min·m; and / or, the time for the coated substrate to pass through the second space is 0.1s to 10s; And / or, the vertical distance between the steam outlet of the first steam groove and one side of the coating substrate is 3 mm to 50 mm, and the vertical distance between the steam outlet of the second steam groove and the other side of the coating substrate is 3 mm to 50 mm; And / or, the coagulation bath contains a coagulation liquid, and the coagulation liquid includes at least one of water, a water-N-methyl-2-pyrrolidone mixture, a water-dimethylacetamide mixture, a water-dimethyl sulfoxide mixture, a water-dimethylformamide mixture, ethanol, isopropanol, and ethylene glycol.

6. The method for preparing a porous diaphragm according to any one of claims 1 to 5, characterized in that: The substrate passes through a first space formed between a first coating die and a second coating die that are arranged opposite to each other, the first coating die outputs the first slurry to cover one side of the substrate, and the second coating die outputs the second slurry to cover the other side of the substrate to obtain the coated substrate.

7. The method for preparing a porous diaphragm according to claim 6, characterized in that: The first space, the second space and the coagulation bath are located on the same straight line, and a third space formed by the first exhaust slot and the second exhaust slot which are arranged opposite to each other is also provided on the same straight line.

8. The method for preparing the porous membrane according to claim 7, characterized in that: The first exhaust slot and the second exhaust slot adjust the flow directions of the first non-solvent vapor and the second non-solvent vapor by means of negative pressure.

9. A porous membrane prepared by the method for preparing a porous membrane according to any one of claims 1 to 8.

10. A porous membrane preparation system for preparing the porous membrane according to claim 9, characterized in that: The porous membrane preparation system comprises a first coating die head, a first steam tank and a coagulation bath which are arranged in sequence; The first coating die head is provided with a second coating die head opposite to the first direction, The first steam groove is provided with a second steam groove opposite to the first direction; There is a first space between the first coating die head and the second coating die head for the substrate to pass through, A second space is provided between the first steam groove and the second steam groove for the coating substrate to pass through; The porous membrane preparation system further includes a first exhaust groove, wherein the first exhaust groove is provided with a second exhaust groove opposite to the first direction, and a third space is provided between the first exhaust groove and the second exhaust groove. The first space, the second space, the third space and the coagulation bath are located on the same straight line in the first direction.

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