Composite diaphragm for water electrolysis cell

Abstract

This invention provides a composite diaphragm for water electrolysis cells that offers high airtightness, low electrical resistance, and high durability for use in alkaline solution environments. [Solution] This invention discloses a composite diaphragm for a water electrolytic cell, the composite diaphragm comprising a nonwoven fabric and a polymer resin, wherein the polymer resin is present on one or both sides of the nonwoven fabric and partially or completely permeates the structure of the nonwoven fabric, the nonwoven fabric accounts for 20-95% of the weight of the composite diaphragm, has a thickness of 0.20-2.00 mm, and a basis weight of 100-400 g / m². 2 Furthermore, the density is 0.20-0.50 g / cm³. 3 That is the case.

Description

[Technical Field]

[0001] This invention relates to a composite diaphragm for a water electrolytic cell. [Background technology]

[0002] The diaphragm is a core material of the alkaline water electrolysis cell type hydrogen production apparatus and is installed between the anode and cathode of the water electrolysis cell. The placement of the diaphragm prevents mixing of hydrogen produced on the cathode side and oxygen produced on the anode side, while ensuring that ions permeate the diaphragm quickly, thereby improving electrolysis efficiency.

[0003] In the current market, there are mainly two types of diaphragms. One is the polyphenylene sulfide woven diaphragm (abbreviated as woven diaphragm), and the other is the composite diaphragm (abbreviated as composite diaphragm), which is formed by combining a porous support material and a polymer resin.

[0004] The woven diaphragm is composed solely of a fabric made by interweaving polyphenylene sulfide (PPS) threads. During actual use, it is subjected to prolonged pressure from both electrodes of the water electrolysis cell, as well as impacts when ions permeate, causing the fabric to gradually deform and the pore size to expand, resulting in a decrease in the airtightness of the woven diaphragm. Normally, to impart a certain level of mechanical strength to the fabric and make it less prone to deformation, the thickness of the fabric is increased to 0.7 mm or more, but this increases the electrical resistance of the woven diaphragm.

[0005] In view of the problem of low airtightness of fabric diaphragms, technicians have researched and developed composite diaphragms formed by combining a porous support material and a polymer resin. For example, Patent Document 1 (Chinese Patent Application Publication No. 110869538 Specification) discloses a reinforced diaphragm for alkaline decomposition. Specifically, a polymer resin containing inorganic particles is coated on a porous support material with a pore diameter of 100 to 1000 μm, and then a porous composite diaphragm is formed by a phase inversion method. The composite diaphragm has high initial airtightness, but due to the large pore diameter of the porous support material, the contact area between the porous support material and the resin layer is small. During long-term use in an alkaline solution environment, the resin layer is easily peeled off, and as a result, the airtightness of the composite diaphragm after use decreases.

[0006] Furthermore, Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2020-007574) discloses a diaphragm for alkaline water electrolysis. The diaphragm is composed of a nonwoven fabric support and a polymer resin layer, and the nonwoven fabric support has a certain basis weight and thickness. However, since the overall basis weight of the nonwoven fabric is low, the resulting composite diaphragm tends to have low strength. In addition, because the thickness of the nonwoven fabric is relatively small and the structure thereof is relatively dense, the permeation amount of the coated resin is reduced, and the contact area between the nonwoven fabric fibers and the resin layer becomes smaller. As a result, during long-term use in an alkaline solution environment, the resin layer is easily peeled off, and the airtightness of the composite diaphragm decreases. [Prior Art Literature] [Patent Literature]

[0007] [Patent Document 1] Specification of Chinese Patent Application Publication No. 110869538 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2020-007574 [Summary of the Invention] [Problem to be Solved by the Invention]

[0008] An object of the present invention is to provide a composite diaphragm for a water electrolyzer that has high airtightness, low electrical resistance, and high durability for use in an alkaline solution environment. [Means for Solving the Problem]

[0009] The composite diaphragm for a water electrolytic cell of the present invention comprises a nonwoven fabric and a polymer resin, wherein the polymer resin is present on one or both sides of the nonwoven fabric and partially or completely penetrates the structure of the nonwoven fabric, and the nonwoven fabric accounts for 20-95% of the weight of the composite diaphragm, has a thickness of 0.20-2.00 mm, and a basis weight of 100-400 g / m². 2 Furthermore, the density is 0.20-0.50 g / cm³. 3 That is the case. [Effects of the Invention]

[0010] The composite diaphragm for water electrolysis cells of the present invention has the advantages of high airtightness, low electrical resistance, and high durability for use in alkaline solution environments. [Modes for carrying out the invention]

[0011] The composite diaphragm for a water electrolytic cell of the present invention comprises a nonwoven fabric and a polymer resin, wherein the polymer resin is present on one or both sides of the nonwoven fabric and partially or completely penetrates the structure of the nonwoven fabric, and the nonwoven fabric accounts for 20-95% of the weight of the composite diaphragm, has a thickness of 0.20-2.00 mm, and a basis weight of 100-400 g / m². 2 Furthermore, the density is 0.20-0.50 g / cm³. 3 That is the case.

[0012] The composite diaphragm of the present invention is obtained using a composite technology of nonwoven fabric and polymer resin, and has the advantages of a more stable structure, higher airtightness, and longer service life, solving the problems of simple nonwoven fabric diaphragms, which have low airtightness and insufficient durability.

[0013] The nonwoven fabric in the composite diaphragm of the present invention is preferably a spunlace nonwoven fabric, a needle-punched nonwoven fabric, a papermaking nonwoven fabric, a hot-air nonwoven fabric, or a spunbond nonwoven fabric. These nonwoven fabrics have good density and appropriate surface roughness, so that the polymer resin easily penetrates the structure of the nonwoven fabric and improves the adhesive strength between the resin and the nonwoven fabric fibers. Therefore, these nonwoven fabrics are suitable choices.

[0014] In the composite diaphragm of the present invention, the nonwoven fabric is most preferably a spunlace nonwoven fabric, which provides a composite diaphragm with high airtightness, low electrical resistance, and excellent durability in alkaline solution environments. When needle-punched nonwoven fabric is used, the thick needles strengthen the entanglement between fibers, but because the pore size of the nonwoven fabric is large and the surface roughness is high, the resin tends to peel off easily when the resulting composite diaphragm is used in an alkaline solution for a long period of time, and therefore it is not the most preferred option. When papermaking nonwoven fabric is used, the strength of the nonwoven fabric is low and the surface is dense, so the contact area between the resin and fibers is small, the resin layer does not penetrate easily, and the resin tends to peel off easily when the resulting composite diaphragm is used in an alkaline solution for a long period of time, and therefore it is not the most preferred option.

[0015] The polymer resin in the composite diaphragm of the present invention is preferably at least one of polysulfone, polyethersulfone, polyphenylsulfone, polyvinylidene fluoride, polycarbonate, polytetrafluoroethylene, polypropylene, polyphenylene sulfide, polyketone, polyetheretherketone, polyimide, and polyetherimide. Polysulfone, polyethersulfone, and polyphenylsulfone do not contain easily decomposable ester groups, amide groups, etc., in their structure, and therefore have high chemical stability and can exhibit excellent durability even in high-temperature, high-concentration alkaline solutions, making them more preferable choices. Considering cost, polysulfone is the most preferred.

[0016] The composite diaphragm of the present invention preferably contains hydrophilic inorganic particles. The hydrophilic inorganic particles are preferably at least one of zirconium, bismuth, or cerium oxides or hydroxides. The hydrophilic inorganic particles not only improve the hydrophilicity of the composite diaphragm but also enhance ion permeability and reduce electrical resistance, thereby reducing the operating voltage and cost of the hydrogen production apparatus. Considering that both the chemical properties and structure of the zirconium oxide surface affect the hydrophilicity of the composite diaphragm, the hydrophilic inorganic particles of the present invention are more preferably zirconium oxide.

[0017] In the composite diaphragm of the present invention, the weight ratio of polymer resin to hydrophilic inorganic particles is preferably 1:0.5 to 3.5, and more preferably 1:1 to 3. If the proportion of hydrophilic inorganic particles is too high, the content of hydrophilic inorganic particles in the composite diaphragm increases, which reduces the adhesion between the polymer resin and the nonwoven fabric, making the hydrophilic inorganic particles more likely to fall off. This reduces the weight of the composite diaphragm, further increasing the rate of weight loss after 6 months, and in addition, the non-uniformity of the falloff of hydrophilic inorganic particles reduces the airtightness of the composite diaphragm. On the other hand, if the proportion of hydrophilic inorganic particles is too low, the hydrophilicity of the composite diaphragm decreases, increasing its electrical resistance, which in turn increases the voltage during operation of the hydrogen production apparatus, thus increasing operating costs.

[0018] In the composite diaphragm of the present invention, the weight ratio of the nonwoven fabric to the composite diaphragm is 20-95%. If the proportion of nonwoven fabric is less than 20%, the polymer resin content is too high, which not only increases the electrical resistance of the composite diaphragm but also reduces the contact area between the resin and the nonwoven fabric fibers. During use in an alkaline solution environment, powder on the resin surface gradually falls off, and as time passes and due to the differential pressure inside the electrode chamber, the polymer resin layer peels off all at once because the entanglement of the nonwoven fabric is slight, instantly reducing the airtightness of the composite diaphragm and significantly decreasing its breaking strength. If the proportion of nonwoven fabric exceeds 95%, the polymer resin content is too low and cannot perform a reinforcing effect, the initial airtightness of the composite diaphragm remains low, and because the contact area between the small amount of resin and the nonwoven fabric fibers is small, after prolonged use in an alkaline solution environment, a small amount of resin is prone to peeling off, further reducing the airtightness of the composite diaphragm. To obtain a composite diaphragm with high airtightness, low electrical resistance, and high durability in alkaline solution environments, the weight ratio of the nonwoven fabric to the composite diaphragm is preferably 40-80%, and more preferably 55-65%.

[0019] The nonwoven fabric in the composite diaphragm of the present invention has a thickness of 0.20 to 2.00 mm and a basis weight of 100 to 400 g / m². 2 Furthermore, the density of the nonwoven fabric (ratio of basis weight to thickness of the nonwoven fabric) is 0.20-0.50 g / cm³. 3, which is at the same level as that of a nonwoven raw fabric. In the present invention, the nonwoven fabric has a thickness of 0.20 to 2.00 mm and a basis weight of 100 to 400 g / m 2 , and the density (the ratio of the basis weight to the thickness of the nonwoven fabric) is 0.20 to 0.50 g / cm 3 By controlling within the above range, thick bulky nonwoven fabrics which have a large thickness, a small basis weight and a density below the density requirement, and thin dense nonwoven fabrics which have a small thickness, a large basis weight and a density exceeding the density requirement are excluded from the scope of the present invention. This is because these cannot achieve the beneficial effects of the present invention. The nonwoven fabric has a thickness of 0.20 to 2.00 mm and a basis weight of 100 to 400 g / m 2 , but the density of the nonwoven fabric is too low, being 0.20 g / cm 3 When the density is less than the above value, the structure of the nonwoven fabric is loose, the number of fibers per unit volume is small, the intertwining force between fibers is weak and the breaking strength is low. Even if the permeation amount of the polymer resin is large, the contact with the loose fibers is insufficient. When the composite separator is used for a long time in an alkaline solution environment, the resin tends to peel off easily, resulting in decreased durability. On the other hand, when the density is too high, being 0.50 g / cm 3 When the density exceeds the above value, the structure of the nonwoven fabric becomes excessively dense, which not only increases the electrical resistance, but also makes it difficult for the resin to permeate, and the contact area between the resin and the fibers is small, resulting in low adhesion. Therefore, when the composite separator is used for a long time in an alkaline solution environment, the resin tends to peel off easily. Considering comprehensively the air tightness, electrical resistance and durability of the composite separator, the nonwoven fabric in the present invention preferably has a thickness of 0.30 to 0.50 mm and a basis weight of 120 to 300 g / m 2 is preferred, and the density is 0.30 to 0.40 g / cm 3 is preferred.

[0020] The polymer resin in this invention is present on one or both sides of the nonwoven fabric, and partially or completely penetrates the structure of the nonwoven fabric. The penetration depth of the polymer resin is influenced not only by the void distribution of the nonwoven fabric itself, but also by the viscosity of the polymer resin and the coating process. Specifically, this invention can employ a method of coating the surface of the nonwoven fabric with the polymer resin by a single-sided or double-sided coating method, and further penetrating it to a range of 1 / 10 or more of the thickness from the surface to the interior, and preferably penetrating to a range of 1 / 3 or more of the thickness from the surface to the interior. When a low-viscosity polymer resin is selected, the resin has high fluidity, so the entire resin can penetrate the structure of the nonwoven fabric. When a high-viscosity polymer resin is selected, by controlling the process, the resin can be present on one or both sides of the nonwoven fabric, and a portion of the resin can penetrate the structure of the nonwoven fabric. Furthermore, this invention can also employ a method of penetrating the entire structure of the nonwoven fabric with the resin by an immersion rolling method, that is, the resin is present on both surfaces of the nonwoven fabric, and the entire resin penetrates the structure of the nonwoven fabric.

[0021] In the composite diaphragm of the present invention, the surface roughness of the nonwoven fabric is preferably 150 to 800 μm. The surface roughness of the nonwoven fabric in the composite diaphragm is at the same level as that of the raw nonwoven fabric. Surface roughness affects the bonding fastness between the nonwoven fabric and the polymer resin, and further affects the durability of the composite diaphragm. If the surface roughness is too high, the surface of the nonwoven fabric will be uneven, and after the resin is applied, many protruding fibers will be exposed on the surface of the resin layer, making it impossible to form a continuous coating layer on the surface of the nonwoven fabric. When using this composite diaphragm, on the one hand, the fibers exposed on the surface of the resin layer will fall off, and on the other hand, there will be insufficient interaction force between the discontinuous resin layers, and if used for a long period of time in an alkaline solution, the risk of peeling of the resin coating will increase, which is undesirable. If the surface roughness is too low, the surface of the nonwoven fabric will be excessively flat, and after the resin is applied, the interfacial force between the resin layer and the nonwoven fabric layer will be low, and if used for a long period of time in an alkaline solution, the risk of peeling of the resin coating layer will also increase, which is undesirable. In the composite diaphragm of the present invention, it is more preferable that the surface roughness of the nonwoven fabric is 200 to 500 μm.

[0022] There are many factors influencing surface roughness, as listed below: 1) the processing method of the nonwoven fabric; 2) the fineness of the nonwoven fibers; and 3) the post-processing method of the nonwoven fabric. When the processing method is needle punching, the thick needles strengthen the entanglement between fibers, but needle-punched nonwoven fabrics have large pore sizes and high surface roughness. The smaller the fineness of the nonwoven fibers, the denser the entanglement between fibers becomes, and the denser the structure of the resulting nonwoven fabric, resulting in lower surface roughness. When calendering is used as the post-processing method for nonwoven fabrics, the surface of the nonwoven fabric becomes flatter, and the surface roughness decreases. In this invention, surface roughness is not limited by the influencing factors, and any surface roughness controlled within the range of 150 to 800 μm is considered to fall within the protected range of this invention.

[0023] In the composite diaphragm of the present invention, the average pore size of the nonwoven fabric is preferably 8.0 to 18.0 μm, and preferably 40% or more of the pores in the nonwoven fabric are 18 μm or smaller. The average pore size of the nonwoven fabric in the composite diaphragm is at the same level as that of the raw nonwoven fabric. If the average pore size is too small, the polymer resin does not easily penetrate into the nonwoven fabric, forming a coating layer only on the outermost surface of the nonwoven fabric, and the amount of penetration from the surface to the interior of the nonwoven fabric is small. As a result, the contact area between the resin and the nonwoven fabric fibers becomes very small, and the resin is prone to peeling off when used in an alkaline solution for a long period of time. If the average pore size is too large, the structure of the nonwoven fabric is sparse, which reduces the airtightness and strength of the nonwoven fabric, and reduces the contact area between the nonwoven fabric and the resin, thus decreasing the adhesive strength of the resin layer. Considering the durability and airtightness of the composite diaphragm, the nonwoven fabric of the present invention more preferably has an average pore diameter of 10.0 to 16.0 μm, and more preferably has a pore ratio of 50% or more of pores with a diameter of 18 μm or less.

[0024] Many factors influence the average pore size, such as fiber fineness. The finer the fibers, the more densely interwoven they become, resulting in smaller voids and thus a smaller and more uniform pore size in the resulting nonwoven fabric. The uniformity of the fiber network is also a contributing factor. By adjusting the processing process, including the speed ratio of the cylinder and doffer, the fiber network can be made more uniform, thereby improving the uniformity of the pore size in the nonwoven fabric. In this invention, the average pore size is not limited by the influencing factors, and any pore size controlled within the range of 8.0 to 18.0 μm is considered to fall within the protected range of this invention.

[0025] The composite diaphragm of the present invention preferably has an average pore size of 0.1 to 5.0 μm and a surface resistance of 200 mΩ·cm. 2 The following conditions are preferable: the porosity is preferably 50-80%, and in terms of airtightness, it is preferable that no bubbles are generated within 2 minutes under a 700 mm water column. If the pore size is too large, the airtightness will be low and the electrolysis efficiency will also be low. If the pore size is too small, the area resistance will be high and the energy consumption during water electrolysis will also be high. If the area resistance is too high, the hydrogen production equipment will operate at a constant current, so the operating voltage will be high and the energy consumption of the hydrogen production equipment will increase. If the airtightness is too low, not only will the purity of the generated gas be low, but it will also be unable to meet the operating requirements of the high-pressure electrolytic cell. Therefore, the composite diaphragm of the present invention more preferably has an average pore size of 0.30-2.0 μm and an area resistance of 100 mΩ·cm. 2 It is more preferable that the following conditions are met, with a porosity of 60-70% being more preferable, and an airtightness of 1000 mmH2O or more being more preferable.

[0026] During the electrolysis process, the electrolyte circulates within the electrolytic cell, and gases are generated from the anode and cathode, causing vibrations in components such as the composite diaphragm within the electrolytic cell. Due to prolonged vibration within the electrolytic cell and prolonged immersion in a hot alkaline solution, the resin layer may peel off, significantly reducing airtightness and posing a risk of electrolytic cell shutdown. Therefore, the present invention ensures sufficient bonding between the nonwoven fabric and the resin layer through the specific design and selection of the nonwoven fabric. After immersion in a 30% alkaline solution at 90°C for 6 months, it is preferable that the weight loss rate of the composite diaphragm is 5.0% or less, and the retention rate of tensile strength is 80% or more. To further ensure the operational stability of the composite diaphragm, it is more preferable that the weight loss rate of the composite diaphragm is 3.0% or less, and the retention rate of tensile strength is 90% or more.

[0027] The method for manufacturing the composite diaphragm for water electrolysis cells of the present invention is as follows. (1) Manufacturing of nonwoven fabric: Heat-resistant short fibers with a diameter of 5 to 20 μm are formed into a fiber mesh, and then reinforced, dried, heat-set, and calendered to obtain nonwoven fabric. (2) Production of polymer resin: A resin liquid with a viscosity of 300 to 1,000,000 Pa·s is prepared by mixing 10 to 20% by weight of polymer resin, 5 to 45% by weight of hydrophilic inorganic particles, and 0.1 to 15% by weight of a porosity-opening agent and solvent. The weight ratio of polymer resin to hydrophilic inorganic particles in the resin liquid is 1:0.5 to 3.5. (3) Manufacturing of composite diaphragms: The prepared resin solution is applied to one or both sides of a nonwoven fabric by the doctor blade method, roll press method, or slit coating method, or the nonwoven fabric is immersed in the resin solution. The nonwoven fabric with the resin solution attached is then immersed in water or a mixture of water and an organic solvent for 10 to 30 minutes to form a polymer porous membrane. The resulting polymer porous membrane is further washed in a water bath 2 to 3 times to precipitate any solvent remaining in the porous membrane, and finally a composite diaphragm product is obtained.

[0028] In procedure (1), the diameter of the heat-resistant fibers is 5 to 20 μm. Under the same basis weight, the finer the fibers, the greater the number of fibers. Compared to thicker fibers, finer fibers have a larger specific surface area, resulting in denser inter-fiber entanglement. This leads to a smaller average pore diameter in the resulting nonwoven fabric, a more uniform pore size distribution, increased contact area with the resin, and better long-term durability during use. Considering the airtightness and long-term durability of the composite diaphragm, a diameter of 8 to 12 μm for the heat-resistant fibers is preferable.

[0029] Considering that the composite diaphragm of the present invention will be used for a long period of time in a 30% potassium hydroxide solution at a high temperature of 90°C, polypropylene, polyphenylene sulfide, or polytetrafluoroethylene fibers are preferred as heat-resistant fibers. Polyphenylene sulfide fibers are more preferred considering their excellent heat resistance, chemical resistance, and stability.

[0030] In procedure (1), it is preferable that the nonwoven fabric is obtained by hydrophilic processing. After sulfonation processing in a mixed solution of chromic acid and sulfuric acid at a certain concentration, the surface of the nonwoven fabric is treated by washing with room temperature water, hot water washing, reductive washing, ultrasonic washing, drying and calendering, or by plasma method. Considering the durability of the composite diaphragm in alkaline solution, sulfonation processing is more preferable as the hydrophilic processing.

[0031] The surface resistance of the nonwoven fabric is 200.0 mΩ·cm. 2 The following is preferable. If it is too large, the area resistance of the resin-coated nonwoven fabric will also increase, and since the hydrogen production device operates at a constant current, this will cause an increase in the operating voltage, and the energy consumption of the hydrogen production device tends to increase. Area resistance of 100 mΩ·cm 2 The following is more preferable:

[0032] The airtightness of the nonwoven fabric is preferably such that no bubbles are generated within 2 minutes under a 400 mm water column condition, i.e., the airtightness exceeds 400 mm water column. If the nonwoven fabric has high airtightness, the resin-coated diaphragm composite fabric can also maintain high airtightness. Considering that the composite diaphragm combines excellent airtightness and ion permeability, it is more preferable that the airtightness of the nonwoven fabric is 500 mm water column or higher.

[0033] The polymer resin content in step (2) is 10-20% by weight. If the resin content is too high, the viscosity becomes excessive, making coating difficult. Furthermore, the amount of resin layer that penetrates into the nonwoven fabric decreases, making it difficult to form a continuous resin layer, which tends to reduce the durability of the composite diaphragm in high-temperature alkaline solutions. On the other hand, if the resin content is too low, the viscosity becomes insufficient, which tends to reduce the adhesive strength between the resin and the nonwoven fabric.

[0034] To improve hydrophilicity, hydrophilic inorganic particles with polar surfaces are added to the polymer resin. The hydrophilic inorganic particles are not particularly limited, but oxides or hydroxides of zirconium, bismuth, or cerium, which have excellent stability, are preferred, and zirconium dioxide is more preferred. The concentration of inorganic particles in the resin liquid is preferably 5 to 45% by weight, and more preferably 10 to 30% by weight.

[0035] Furthermore, in order to improve the porosity of the polymer resin layer, it is preferable to add a water-soluble pore-forming accelerator (i.e., a pore-opening agent) when preparing the polymer resin liquid. Examples of pore-opening agents include polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyvinyl acetate (PVAC), or glycerin. When the polymer resin layer is formed in the subsequent solidification bath, the pore-opening agent dissolves in a non-solvent such as water, thereby forming micropores. The concentration of the pore-opening agent directly affects the viscosity of the resin liquid, i.e., the adhesion strength of the resin liquid to the nonwoven fabric. The concentration of the pore-opening agent in the resin liquid is preferably 0.1 to 15% by weight, and more preferably 1 to 10% by weight. [Examples]

[0036] The present invention will be further illustrated by the following examples, but the scope of protection of the present invention is not limited by these examples. The physical properties in the examples are measured by the following methods.

[0037] [Measurement of nonwoven fabric alone] First, one composite diaphragm is taken and immersed in an N-methyl-2-pyrrolidone solvent for more than 12 hours to completely dissolve the resin layer, leaving only the nonwoven fabric (this nonwoven fabric is the nonwoven fabric in the composite diaphragm of the present invention). Next, the nonwoven fabric is immersed in pure water for 2 minutes and removed, dried in a 60°C constant temperature oven for 2 hours, and then the physical properties of each item of the nonwoven fabric are measured.

[0038] [Method for separating nonwoven fabric and hydrophilic inorganic particles in a composite diaphragm] First, one composite membrane is taken and immersed in N-methyl-2-pyrrolidone solvent for more than 12 hours to completely dissolve the resin layer and remove and precipitate the hydrophilic inorganic particles. Next, the nonwoven fabric is removed from the solution and immersed in pure water for 2 minutes. The hydrophilic inorganic particles precipitated in the solution are filtered through filter paper, washed twice with pure water, and both are dried in a 60°C constant temperature oven for 2 hours to obtain the nonwoven fabric alone and the hydrophilic inorganic particles alone.

[0039] [Weight percentage of nonwoven fabric in the composite diaphragm] Samples measuring 20cm x 20cm were taken from three locations (left, center, and right) along the width of the composite diaphragm (N=3), and the weight of each sample was measured. 左 M 中 M 右 This is how it is written. Dissolve, separate, and dry using the above separation method to obtain individual nonwoven fabrics, and measure the weight of each to obtain M1 左 M1 中 M1 右 This is how it is written. As an arbitrary sample, the weight percentage of nonwoven fabric in the composite diaphragm is calculated using the following formula: Weight percentage of nonwoven fabric = M1 / M × 100%. After calculating the weight ratios of the left, center, and right parts, calculate the average value.

[0040] [Confirmation of the presence or absence of hydrophilic inorganic particles in the composite diaphragm] Approximately 0.1 g of inorganic particles are collected from the hydrophilic inorganic particles obtained by the separation method of nonwoven fabric and hydrophilic inorganic particles in a composite membrane. Sample preparation: Double-sided tape is attached to the sample stage, and 0.1 g of hydrophilic inorganic particles are uniformly spread on the sample stage. Then, the sample stage is placed in the sample chamber of an elemental analyzer (Thermoscientific Thermo Fisher, model number: Apreo 2C), and the hydrophilic inorganic particles are scanned under vacuum. The constituent elements of the hydrophilic inorganic particles are confirmed from the scan results.

[0041] [Weight ratio of polymer resin to hydrophilic inorganic particles in the composite membrane] Samples measuring 20cm x 20cm were taken from three locations (left, center, and right) along the width of the composite diaphragm (N=3), and the weight of each sample was measured. 左 M 中 M 右 This is how it is written. Next, the precipitate is filtered, washed, and dried using the separation method described above to obtain the weight of hydrophilic inorganic particles, and M2 左 M2 中 M2 右 This is how it is written. The weight of the polymer resin is M3 左 =(M 左 -M1 左 -M2 左 ), M3 中 =(M 中 -M1 中 -M2 中 ), M3 右 =(M 右 -M1 右 -M2 右 ) The weight ratio of polymer resin to inorganic particles is M3 / M2. After calculating the weight ratios of the left, middle, and right parts respectively, the average value is calculated.

[0042] [Surface roughness of nonwoven fabric] Three 20cm x 20cm samples (N=3) were taken from three locations (left, center, and right) along the width direction of the composite diaphragm. These samples were then dissolved, separated, and dried using the separation method described above to obtain individual nonwoven fabrics. The maximum peak height and maximum valley depth of the surface roughness were automatically measured using a 3D contour measuring instrument VR-5000. The sum of the obtained maximum peak height and maximum valley depth was defined as the maximum hardness Sz (i.e., the surface roughness of the nonwoven fabric). Two measurements were taken for each sample, and the average value of the six points from the three samples was calculated.

[0043] [Average pore size of nonwoven fabrics] Three 20cm x 20cm samples (N=3) were taken from three locations (left, center, and right) along the width direction of the composite diaphragm. These samples were then dissolved, separated, and dried using the separation method described above to obtain a nonwoven fabric. The pore size of the nonwoven fabric was measured using a capillary flow porometer according to the ASTM F316-03 standard. The samples were placed in a sample chamber and moistened with Silwick silicone fluid with a surface tension of 15.9 dynes / cm. A porous metal disc insert with a diameter of 2.54cm and a thickness of 3.175mm was provided in the bottom clamp of the sample chamber, and a hole with a diameter of 3.175mm was provided in the top clamp of the sample chamber. The average value of the three samples was calculated.

[0044] [Percentage of pores with a diameter of 18 μm or less] Similar to the average pore size test method described above, the total number of pores with a diameter of 18 μm or less within the pore size range automatically measured by the system is divided by the total number of pores of all sizes, and the resulting percentage is taken as the proportion of pores with a diameter of 18 μm or less.

[0045] [Fiber diameter] Three 20cm x 20cm samples were taken from the left, center, and right sides along the width direction of the composite diaphragm (N=3). These samples were then dissolved, separated, and dried using the separation method described above to obtain a single nonwoven fabric. The fibers in the nonwoven fabric were photographed using an electron microscope (magnification 800x), and the diameter of the fibers was directly measured. Measurements were taken at 30 random locations, and the average value was calculated.

[0046] [Balance weight of nonwoven fabric] Three 20cm x 20cm samples (N=3) were taken from the left, center, and right sides along the width direction of the composite diaphragm. These samples were then dissolved, separated, and dried using the separation method described above to obtain the nonwoven fabric. The unit weight of the nonwoven fabric was measured according to the test standard GB / T 24218.1-2009. The formula for calculating the basis weight is as follows: basis weight (g / m²). 2 )=Weight (g) / Area (m 2 ), and then calculate the average value.

[0047] [Thickness of nonwoven fabric] Three 20cm x 20cm samples (N=3) were taken from the left, center, and right sides along the width direction of the composite diaphragm. These samples were then dissolved, separated, and dried using the separation method described above to obtain a single nonwoven fabric. The thickness of the nonwoven fabric was measured (in mm) according to the test standard GB / T 24218.2-2009, and its average value was calculated.

[0048] [Density of nonwoven fabric] Based on the basis weight w and thickness d of the nonwoven fabric, the density ρ (unit: g / cm³) of the nonwoven fabric can be calculated using the following formula. 3 Calculate the values ​​and then calculate the average value. ρ(g / cm 3 )=[Grain weight w(g / m 2 ) / 10000] / [thickness d(mm) / 10].

[0049] [Airtightness of nonwoven fabrics] Three 20cm x 20cm samples (N=3) were taken from the left, center, and right sides along the width direction of the composite diaphragm. These samples were then dissolved, separated, and dried using the separation method described above to obtain individual nonwoven fabrics. An airtightness test was conducted in accordance with the Chinese building materials industry standard JCT 211-2009, and the average value was calculated.

[0050] [Area resistance of nonwoven fabrics] Three 20cm x 20cm samples (N=3) were taken from the left, center, and right sides along the width direction of the composite diaphragm. These samples were then dissolved, separated, and dried using the separation method described above to obtain a nonwoven fabric. The area resistance of the nonwoven fabric was measured and its average value was calculated based on the Chinese Electronics Industry Standard SJ / T 10171.5-91 "Standard for Area Resistance Testing of Diaphragms for Alkaline Storage Batteries".

[0051] [Break strength in the warp and weft directions of nonwoven fabrics] Three 20cm x 20cm samples (N=3) were taken from the left, center, and right sides along the width direction of the composite diaphragm. These samples were then dissolved, separated, and dried using the separation method described above to obtain a single nonwoven fabric. The breaking strength of the nonwoven fabric was measured according to standard GB / T 24218.3-2010, and its average value was calculated.

[0052] [Porthosis of composite diaphragms] Three 20cm x 20cm samples (N=3) were taken from the left, center, and right sides along the width of the composite diaphragm, and immersed in anhydrous ethanol (purity 99.7% or higher) for at least two hours. After removal, the samples were washed twice with pure water, and the liquid on the surface of the composite diaphragm was quickly and lightly wiped off using filter paper. The mass M of the wetted diaphragm was accurately weighed using an electronic analytical balance, and the thickness L of the wetted diaphragm was measured using a thickness gauge. Next, the diaphragm was vacuum dried at 60°C for at least three hours, and the mass M1 of the dried diaphragm was accurately weighed. The formula for calculating the porosity is as follows: Porosity = (M - M1) / (ρ·A·L). Here, ρ is the density of pure water (g / mL), and A is the area of ​​the diaphragm (cm²). 2 ), L is the thickness of the wet diaphragm (cm), and M and M1 are the masses of the wet and dry diaphragms (g), respectively. Calculate their average values.

[0053] [Balance of composite diaphragm] The unit area weight of the composite diaphragm is measured according to the test standard GB / T 24218.1-2009. The formula for calculating the basis weight is as follows: basis weight (g / m²) 2 )=Dry weight (g) / Area (m 2 ).

[0054] [thickness of the composite diaphragm] The thickness of the composite diaphragm is measured according to the test standard GB / T 24218.2-2009 (unit: mm).

[0055] [Average pore size of composite diaphragm] The pore size of the composite diaphragm is measured using a capillary flow porometer in accordance with the ASTM F316-03 standard. The sample is placed in the sample chamber and moistened with Silwick silicone fluid with a surface tension of 15.9 dynes / cm. A metal disc insert with a diameter of 2.54 cm and a thickness of 3.175 mm is attached to the bottom clamp of the sample chamber, and a hole with a diameter of 3.175 mm is made in the top clamp of the sample chamber. The average of two measurements is taken as the pore size of the sample.

[0056] [The range of thickness of polymer resin that has penetrated the nonwoven fabric] A scanning electron microscope is used to photograph a cross-section of the composite diaphragm (magnification 100x), and the thickness of the composite diaphragm is directly measured and defined as D (unit: mm). Next, the thickness of the polymer resin that has permeated the nonwoven fabric is measured and defined as d (unit: mm) (this thickness is the distance from the surface of the polymer resin to the inside of the nonwoven fabric). Five measurement points are selected for each, and the thickness of the composite diaphragm and the thickness of the polymer resin that has permeated the nonwoven fabric are measured, and the average value is calculated. The range of the thickness of the polymer resin that has permeated the nonwoven fabric is the ratio of the thickness of the polymer resin that has permeated the nonwoven fabric to the thickness of the composite diaphragm (d / D).

[0057] [Airtightness of composite diaphragms] An airtightness test will be conducted based on the Chinese building materials industry standard JCT 211-2009, "Divider Asbestos Fabric" standard.

[0058] [Area resistance of composite diaphragm] The area resistance of the composite diaphragm is measured according to the Chinese Electronics Industry Standard SJ / T 10171.5-91, "Standard for Area Resistance Testing of Diaphragms for Alkaline Storage Batteries."

[0059] [Resistant fracture strength of composite diaphragms in the longitudinal direction] The rupture strength of the composite diaphragm is measured according to standard GB / T 24218.3-2010.

[0060] [Retention rate of fracture strength in the longitudinal direction of composite diaphragms] Based on standard GB / T 24218.3-2010, the initial breaking strength G (sum of breaking strengths in the warp and weft directions) of the composite diaphragm is first measured. Next, the diaphragm is immersed in a 30 wt% KOH solution at 90°C for 6 months, removed, the KOH in the diaphragm is thoroughly washed off, and after drying at 60°C for 2 hours, the breaking strength G1 (sum of breaking strengths in the warp and weft directions) of the composite diaphragm is measured. The formula for calculating the breaking strength retention rate is as follows: Breaking strength retention rate = G1 / G × 100%.

[0061] [Weight reduction rate of composite diaphragm] Samples measuring 20cm x 20cm were taken from three locations (left, center, and right) along the width of the composite diaphragm (N=3), and the weight of each sample was measured. 左 M 中 M 右 This is expressed as follows, and the average value is denoted as M. Next, the test sample is immersed in a 30 wt% KOH solution at 90°C for 6 months, the KOH in the membrane is thoroughly washed off, and after drying at 60°C for 2 hours, the weight of each sample is measured and M1 is obtained. 左 M1 中 M1 右 This is expressed as follows, and the average value is taken as M1. The formula for calculating the weight loss rate of the composite diaphragm is as follows: Weight loss rate = (M - M1) / M × 100%, and the average value of the three samples is calculated.

[0062] Example 01 (1) Manufacturing of nonwoven fabrics Polyphenylene sulfide fibers with a diameter of 9 μm are opened, blended, carded, web laid down, spunlace processed at a maximum pressure of 100 Bar, and then dried and heat-set to obtain a spunlace nonwoven fabric. Next, this fabric is subjected to sulfonation and hydrophilization modification in a mixed solution of 300 g / L chromic acid and 500 g / L sulfuric acid at a temperature of 80°C for 12 minutes. After the sulfonation treatment, the polyphenylene sulfide spunlace nonwoven fabric is washed with room temperature water, 50°C hot water, reductive washing, and ultrasonic water washing, dried, and then calendered at a roll temperature of 180°C and a pressure of 1.2 MPa to obtain a dense and flat nonwoven fabric.

[0063] (2) Manufacturing of composite diaphragms A resin solution with a viscosity of 15574 Pa·s was prepared by mixing polysulfone resin, zirconium oxide particles, glycerin pore-opening agent, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 15 wt%:20 wt%:1 wt%:64 wt%. This resin solution was coated onto one side of a nonwoven fabric, and the fabric was immersed in a solidification bath to solidify the polysulfone resin, forming a resin layer on one side of the nonwoven fabric. After washing with pure water, the fabric was made to a thickness of 0.55 mm and a basis weight of 190 g / m². 2 A composite diaphragm is obtained, in which the resin penetrates one side of the nonwoven fabric and is distributed over a range of 2 / 3 of the thickness from the upper surface to the interior. The parameters and physical properties of the composite diaphragm for water electrolysis cell of the present invention are shown in Table 1.

[0064] Examples 02-03 The manufacturing process is the same as in Example 01, and the specific formulation and physical properties are shown in Table 1.

[0065] Example 04 In Example 01, the spunlace water pressure was adjusted to 140 Bar and the roll pressure to 1.4 MPa. The other manufacturing processes were the same as in Example 01, and the specific formulation and physical properties are shown in Table 1.

[0066] Example 05 In the manufacturing process of the nonwoven fabric, calendering was omitted, and the other manufacturing processes were the same as in Example 01. The specific formulation and physical properties are shown in Table 1.

[0067] Examples 06-08 The nonwoven fabric was manufactured and the resin solution was prepared in the same manner as in Example 01. The resin solution was then coated onto both sides of the nonwoven fabric, solidified, and washed to obtain a composite diaphragm. In this composite diaphragm, the resin penetrated both sides of the nonwoven fabric and was distributed over a 3 / 4 range in the thickness direction from the top surface to the interior. The parameters and physical properties of the composite diaphragm are shown in Tables 1 and 2.

[0068] Example 09 The nonwoven fabric was manufactured in the same manner as in Example 01, by mixing polysulfone resin, zirconium oxide particles, glycerin porolithizer, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 15 wt%:10 wt%:1 wt%:74 wt% to prepare a resin solution with a viscosity of 1760 Pa·s. The resin solution was then permeated into the entire structure of the nonwoven fabric using a one-dip, one-nip method, and the polysulfone resin was solidified by immersion in a solidification bath. After that, it was washed with pure water to obtain a thickness of 0.75 mm and a basis weight of 240 g / m². 2 A polymer porous composite diaphragm is obtained. The parameters and physical properties of the composite diaphragm for water electrolysis cells of the present invention are shown in Table 2.

[0069] Example 10 The manufacturing process is the same as in Example 09, and the specific formulation and physical properties are shown in Table 2. The parameters and physical properties of the composite diaphragm for water electrolysis cells of the present invention are shown in Table 2.

[0070] Example 11 In Example 01, the spunlace processing of the nonwoven fabric was changed to needle punching, and the other manufacturing processes were the same as in Example 09. The parameters and physical properties of the composite diaphragm for water electrolysis cells of the present invention are shown in Table 2.

[0071] Example 12 In the manufacturing process of the nonwoven fabric, no sulfonation hydrophilization treatment was performed, and the other manufacturing processes were the same as in Example 01. The specific formulation and physical properties are shown in Table 2.

[0072] Example 13 The nonwoven fabric was manufactured in the same manner as in Example 06, by mixing polysulfone resin, zirconium oxide particles, glycerin pore-opening agent, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 15 wt%:10 wt%:1 wt%:74 wt% to prepare a resin solution with a viscosity of 1760 Pa·s. This resin solution was coated onto both sides of the nonwoven fabric, solidified, and washed to obtain a composite diaphragm. The resin in the composite diaphragm penetrates both sides of the nonwoven fabric and is distributed over a 3 / 4 range in the thickness direction from the top surface to the interior. The parameters and physical properties of the composite diaphragm are shown in Table 3.

[0073] Example 14 The nonwoven fabric was manufactured in the same manner as in Example 06, by mixing polysulfone resin, zirconium oxide particles, glycerin pore-opening agent, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 13 wt%:48 wt%:1 wt%:38 wt% to prepare a resin solution with a viscosity of 996,500 Pa·s. This resin solution was coated onto both sides of the nonwoven fabric, solidified, and washed to obtain a composite diaphragm. In this composite diaphragm, the resin penetrates both sides of the nonwoven fabric and is distributed over a range of half the thickness from the top surface to the interior. The parameters and physical properties of the composite diaphragm are shown in Table 3.

[0074] Example 15 The nonwoven fabric was manufactured in the same manner as in Example 01, by mixing polysulfone resin, glycerin porolithizer, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 15 wt%:1 wt%:84 wt% to prepare a resin solution with a viscosity of 510 Pa·s. This resin solution was coated onto both sides of the nonwoven fabric, solidified, and washed to obtain a composite diaphragm, in which the resin had completely penetrated into the interior of the nonwoven fabric structure. The parameters and physical properties of the composite diaphragm are shown in Table 3.

[0075] Example 16 The nonwoven fabric was manufactured in the same manner as in Example 01, by mixing polyethersulfone resin, glycerin porolithizer, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 15 wt%:1 wt%:84 wt% to prepare a resin solution with a viscosity of 830 Pa·s. This resin solution was coated onto both sides of the nonwoven fabric, solidified, and washed to obtain a composite diaphragm, in which the resin had completely penetrated into the interior of the nonwoven fabric structure. The parameters and physical properties of the composite diaphragm are shown in Table 3.

[0076] Example 17 The nonwoven fabric was manufactured in the same manner as in Example 01, by mixing polyethersulfone resin, zirconium oxide particles, glycerin pore-opening agent, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 15 wt%:20 wt%:1 wt%:64 wt% to prepare a resin solution with a viscosity of 16083 Pa·s. This resin solution was coated onto both sides of the nonwoven fabric, solidified, and washed to obtain a composite diaphragm. In the composite diaphragm, the resin penetrates both sides of the nonwoven fabric and is distributed in a range of half the thickness from the top surface to the interior. The parameters and physical properties of the composite diaphragm are shown in Table 3.

[0077] Example 18 The nonwoven fabric was manufactured in the same manner as in Example 01, by mixing polysulfone resin, cerium oxide particles, glycerin porolithizer, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 15 wt%:10 wt%:1 wt%:74 wt% to prepare a resin solution with a viscosity of 2440 Pa·s. This resin solution was coated onto both sides of the nonwoven fabric, solidified, and washed to obtain a composite diaphragm. In this composite diaphragm, the resin penetrates both sides of the nonwoven fabric and is distributed over a range of half the thickness from the top surface to the interior. The parameters and physical properties of the composite diaphragm are shown in Table 3.

[0078] The physical properties of the nonwoven fabrics shown in each table are data obtained by measuring the nonwoven fabric alone. Specifically, the composite diaphragm is immersed in an N-methyl-2-pyrrolidone solvent for more than 12 hours to completely dissolve the resin layer, and then dried in a constant temperature oven at 60°C for 2 hours to obtain the nonwoven fabric alone. The physical properties of the nonwoven fabric alone are measured and recorded in the table. In this invention, although there are some differences between the physical properties of the nonwoven fabric raw material and the physical properties of the nonwoven fabric alone, they are at an equivalent level.

[0079] Comparative Example 01 Polyphenylene sulfide fibers with a diameter of 9 μm were opened, blended, carded, web laid down, spunlace processed at a maximum spunlace pressure of 100 Bar, dried, and heat-set to obtain a spunlace nonwoven fabric. Next, the fabric was subjected to sulfonation and hydrophilization modification in a mixed solution of 300 g / L chromic acid and 500 g / L sulfuric acid at a temperature of 80°C for 12 minutes. After the sulfonation treatment, the polyphenylene sulfide spunlace nonwoven fabric was washed with room temperature water, 50°C hot water, reductive washing, and ultrasonic water washing, dried, and then calendered to obtain a dense and flat nonwoven fabric. The physical properties of the diaphragm are shown in Table 4.

[0080] Comparative Example 02 (1) Manufacturing of woven mesh Using polyphenylene sulfide monofilaments with a fiber diameter of 60 μm, a woven mesh with a pore size of 0.50 mm was produced, with a basis weight of 30 g / m². 2 A woven mesh with a thickness of 0.10 mm is obtained.

[0081] (2) Manufacturing of composite diaphragms A resin solution with a viscosity of 15574 Pa·s was prepared by mixing polysulfone resin, zirconium oxide particles, glycerin pore-opening agent, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 15 wt%:20 wt%:1 wt%:64 wt%. This resin solution was coated onto both sides of a woven mesh, and the mesh was immersed in a solidification bath to solidify the polysulfone resin, forming a resin layer on both sides of the woven mesh. After washing with pure water, the mesh was made to a thickness of 0.35 mm and a basis weight of 240 g / m². 2 A composite diaphragm is obtained. Because the woven mesh is thin and has a large pore size, the composite diaphragm has a form in which the woven mesh is encased inside the resin layer. The parameters and physical properties of the composite diaphragm are shown in Table 4.

[0082] Comparative Example 03 (1) Manufacturing of papermaking nonwoven fabrics Undrawn polyphenylene sulfide yarn with a diameter of 9 μm and ordinary polyphenylene sulfide fibers are mixed in a weight ratio of 30:70. A nonwoven fabric is obtained through wet blending, web laydown, and calendering processes. Next, the fabric is subjected to sulfonation and hydrophilization modification in a mixed solution of 300 g / L chromic acid and 500 g / L sulfuric acid at a temperature of 80°C for 12 minutes. After the sulfonation treatment, the polyphenylene sulfide papermaking nonwoven fabric is washed with room temperature water, 50°C hot water, reductive washing, and ultrasonic water washing, and then dried to obtain a hydrophilic papermaking nonwoven fabric. Other manufacturing processes are the same as in Example 01, and the specific formulation and physical properties are shown in Table 4.

[0083] Comparative Example 04 In Example 01, the spunlace water pressure was adjusted to 80 Bar, and the other manufacturing processes were the same as in Example 01. The specific formulation and physical properties are shown in Table 4.

[0084] Comparative Example 05 In Example 01, the spunlace water pressure was adjusted to 140 Bar, and the other manufacturing processes were the same as in Example 01. The specific formulation and physical properties are shown in Table 4.

[0085] [Table 1]

[0086] [Table 2]

[0087] [Table 3]

[0088] [Table 4]

[0089] According to Tables 1 to 4, (1) Observing from Example 01 and Example 02, under equivalent conditions, the fiber diameter and average pore size of the nonwoven fabric of the former are within a favorable range, while the fiber diameter and average pore size of the nonwoven fabric of the latter are slightly larger. Therefore, compared to the latter, the former has higher airtightness of the nonwoven fabric, a smaller weight loss rate of the composite diaphragm after immersion in a 30% alkaline solution at 90°C for 6 months, and high airtightness of the composite diaphragm, indicating superior durability for use in an alkaline solution environment.

[0090] (2) From Examples 01 and 03, it was found that under equivalent conditions, the fiber diameter and average pore diameter of the nonwoven fabric of the former were within a favorable range, while the average pore diameter of the nonwoven fabric of the latter was slightly smaller. Compared to the latter, the structure of the nonwoven fabric of the former was slightly bulkier, the area resistance was lower, the resin layer penetrated sufficiently into the interior of the nonwoven fabric, the area resistance of the resulting composite diaphragm was lower, the weight loss rate after immersion in a 30% alkaline solution at 90°C for 6 months was smaller, the airtightness was higher, and the rupture strength retention rate was also higher, meaning that it had superior durability for use in an alkaline solution environment.

[0091] (3) From Examples 01 and 04, it was found that under equivalent conditions, the thickness and density of the former nonwoven fabric are within a favorable range. Compared to the latter, the former has a bulkier nonwoven fabric structure, lower surface resistance, sufficient penetration of the polymer resin into the nonwoven fabric, a larger contact area with the fibers, higher adhesion strength of the resin layer, and a high retention rate of the rupture strength of the composite diaphragm after immersion in a 30% alkaline solution at 90°C for 6 months, indicating superior durability in an alkaline solution environment.

[0092] (4) Based on the results of Examples 01 and 05, under equivalent conditions, the thickness, density, and surface roughness of the former nonwoven fabric are within a favorable range. Therefore, compared to the latter, the former shows a smaller weight loss rate of the composite diaphragm after immersion in a 30% alkaline solution at 90°C for 6 months, higher airtightness, and higher retention of breaking strength, meaning it has superior durability for use in an alkaline solution environment.

[0093] (5) Based on Examples 06 to 08, under equivalent conditions, the weight ratio of the nonwoven fabric in Example 06 to the composite diaphragm is within a favorable range. Therefore, compared to Examples 07 and 08, Example 06 showed a smaller weight loss rate, higher airtightness, and higher rupture strength retention, indicating superior durability in an alkaline solution environment.

[0094] (6) From Examples 09 and 10, it was found that under equivalent conditions, the basis weight of the former nonwoven fabric was within a favorable range, and therefore, compared to the latter, the former had a smaller surface resistance of the composite diaphragm and lower energy consumption of the hydrogen production equipment.

[0095] (7) From Examples 10 and 11, it was observed that under equivalent conditions, the latter was a needle-punched nonwoven fabric, and because the needles used in the needle punch were thick, the resulting nonwoven fabric had a high surface roughness, a large pore size, and low airtightness. Compared to the latter, the former showed a smaller weight loss rate of the composite diaphragm after immersion in a 30% alkaline solution at 90°C for 6 months, high airtightness, and high retention of breaking strength, indicating superior durability in an alkaline solution environment.

[0096] (8) From Examples 01 and 12, it was found that under equivalent conditions, the former nonwoven fabric was obtained by sulfonated hydrophilic processing, and compared to the latter, the former allowed the resin to penetrate the nonwoven fabric more easily, making the resin coating layer less likely to peel off, and the retention rate of breaking strength after immersion in a 30% alkaline solution at 90°C for 6 months was slightly higher, meaning that it had superior durability for use in an alkaline solution environment.

[0097] (9) From Examples 06 and 13, it was found that under equivalent conditions, the weight ratio of the polymer resin to hydrophilic inorganic particles in the former was within a more favorable range, and therefore the area resistance of the composite diaphragm was lower in the former compared to the latter.

[0098] (10) From Examples 06 and 14, it was found that under equivalent conditions, the latter had a larger weight ratio of polymer resin to hydrophilic inorganic particles, and therefore, compared to the former, the latter had a larger weight loss rate of the composite diaphragm after immersion in a 30% alkaline solution at 90°C for 6 months and a lower fracture strength retention rate.

[0099] (11) From Examples 13 and 15, it was found that under equivalent conditions, the latter does not contain hydrophilic inorganic particles, and therefore the electrical resistance of the composite diaphragm is higher in the latter compared to the former.

[0100] (12) Comparing Example 01 and Comparative Example 01, under equivalent conditions, the former is a composite diaphragm made of nonwoven fabric and resin, while the latter is a single nonwoven fabric. Therefore, it was found that the former has higher airtightness and superior durability during long-term use compared to the latter.

[0101] (13) From Example 06 and Comparative Example 02, it was found that under equivalent conditions, the weight ratio of the base fabric to the composite diaphragm was too low in the latter, resulting in lower airtightness of the composite diaphragm and lower rupture strength retention compared to the former, i.e., inferior durability.

[0102] (14) Comparing Example 01 and Comparative Example 03, it was found that under equivalent conditions, the latter used a papermaking nonwoven fabric that was too dense and too thin. As a result, compared to the former, the latter had a higher weight loss rate of the composite diaphragm, lower airtightness, lower breaking strength retention, and thus inferior durability.

[0103] (15) From Example 01 and Comparative Example 04, it was found that under equivalent conditions, the basis weight of the latter was too low, the specific density of basis weight to thickness was also too low, and compared to the former, the airtightness of the composite diaphragm of the latter was poor, the rupture strength retention rate was low, and that is, it was inferior in durability.

[0104] (16) From Example 01 and Comparative Example 05, it was found that under equivalent conditions, the latter had a higher basis weight and a higher specific density of basis weight to thickness. Compared to the former, the latter had a higher electrical resistance of the composite diaphragm, meaning that the energy consumption of the hydrogen production equipment was excessive.

Claims

1. A composite diaphragm comprising a nonwoven fabric and a polymer resin, wherein the polymer resin is present on one or both sides of the nonwoven fabric and partially or completely permeates the structure of the nonwoven fabric, the nonwoven fabric accounts for 20-95% of the weight of the composite diaphragm, has a thickness of 0.20-2.00 mm, and a basis weight of 100-400 g / m². ２ Furthermore, the density is 0.20 to 0.50 g / cm³. ３ A composite diaphragm for a water electrolysis cell, characterized by the following features.

2. The composite diaphragm for a water electrolytic cell according to claim 1, characterized in that the nonwoven fabric is a spunlace nonwoven fabric.

3. The composite diaphragm for a water electrolytic cell according to claim 1, characterized in that the polymer resin is at least one of polysulfone, polyethersulfone, polyphenylsulfone, polyvinylidene fluoride, polycarbonate, polytetrafluoroethylene, polypropylene, polyphenylene sulfide, polyketone, polyetheretherketone, polyimide, and polyetherimide.

4. The composite diaphragm for a water electrolytic cell according to claim 3, characterized in that the polymer resin is a polysulfone resin.

5. The composite diaphragm for a water electrolytic cell according to claim 1, characterized in that the composite diaphragm contains hydrophilic inorganic particles, and the hydrophilic inorganic particles are at least one of zirconium, bismuth, cerium oxide, or hydroxide.

6. The composite diaphragm for a water electrolytic cell according to claim 5, characterized in that the hydrophilic inorganic particles are zirconium oxide.

7. The composite diaphragm for a water electrolytic cell according to claim 1 or 5, characterized in that the weight ratio of polymer resin to hydrophilic inorganic particles in the composite diaphragm is 1:0.5 to 3.

5.

8. The composite diaphragm for a water electrolytic cell according to claim 1 or 2, characterized in that the surface roughness of the nonwoven fabric is 150 to 800 μm.

9. The composite diaphragm for a water electrolytic cell according to claim 1 or 2, characterized in that the average pore size of the nonwoven fabric is 8.0 to 18.0 μm.

10. The composite diaphragm for a water electrolytic cell according to claim 9, characterized in that the nonwoven fabric has a pore size of 18 μm or less, with a proportion of 40% or more.

11. The composite diaphragm for a water electrolytic cell according to claim 1 or 2, characterized in that the weight loss rate after immersion in a 30% alkaline solution at 90°C for 6 months is 5.0% or less.

12. The composite diaphragm for a water electrolytic cell according to claim 1 or 2, characterized in that the composite diaphragm retains a fracture strength of 80% or more after being immersed in a 30% alkaline solution at 90°C for 6 months.

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