Composite membrane for water electrolysis cell

Abstract

Disclosed in the present invention is a composite membrane for a water electrolysis cell. The composite membrane contains non-woven fabric and polymer resin, the polymer resin being present in one or two sides of the non-woven fabric and partially or completely permeating into the non-woven fabric structure, the non-woven fabric accounting for 20-95% of the weight of the composite membrane, the thickness of the non-woven fabric being 0.20-2.00 mm, the gram weight thereof being 100-400 g / m2, and the density thereof being 0.20-0.50 g / cm3. The composite membrane for a water electrolysis cell of the present invention has the characteristics of high air impermeability, low resistance and high service durability in alkali liquor environments.

Description

Composite diaphragm for water electrolyzer Technical Field

[0001] The invention relates to a composite diaphragm for a water electrolyzer. Background Art

[0002] The diaphragm is the core material of alkaline water electrolyzer hydrogen production equipment. It is installed between the anode and cathode of the water electrolyzer. The diaphragm prevents the mixing of hydrogen produced at the cathode and oxygen produced at the anode, while ensuring that ions pass through the diaphragm quickly, improving electrolysis efficiency.

[0003] There are two main types of diaphragms on the market. One is the polyphenylene sulfide fabric diaphragm (referred to as fabric diaphragm), and the other is a composite diaphragm formed by a porous support material and a polymer resin (referred to as composite diaphragm).

[0004] Fabric separators consist solely of a fabric interwoven with polyphenylene sulfide yarns. During actual use, the long-term compression from the electrolytic cell's two electrodes and the impact of ions passing through can cause the fabric to gradually deform and enlarge its pores, reducing its airtightness. Typically, to ensure mechanical strength and resistance to deformation, the fabric thickness is increased to over 0.7 mm, but this increases the membrane's electrical resistance.

[0005] To address the low air tightness of fabric diaphragms, technicians have developed composite diaphragms formed by combining a porous support material with a polymer resin. For example, Chinese patent CN110869538A discloses a reinforced diaphragm for alkaline hydrolysis. The diaphragm is formed by coating a polymer resin containing inorganic particles on a porous support material with a pore size of 100 to 1000 μm. This is then transformed into a porous composite diaphragm through a phase inversion method. This composite diaphragm has high initial air tightness. However, due to the large pore size of the porous support material and the small contact area with the resin layer, the resin layer easily falls off during long-term use in an alkaline solution environment, resulting in a decrease in the air tightness of the composite diaphragm after use.

[0006] For example, Japanese Patent Publication No. 2020-007574 discloses a diaphragm for alkaline water electrolysis, which is composed of a non-woven fabric support and a polymer resin layer, wherein the non-woven fabric support has a certain gram weight and thickness. However, the overall gram weight of the non-woven fabric is low, and the strength of the resulting composite diaphragm is also relatively low. In addition, the thickness of the non-woven fabric is relatively low, and the non-woven fabric structure is relatively tight, resulting in less penetration of the coating resin, resulting in a small contact area between the non-woven fabric fibers and the resin layer. During long-term use in an alkaline solution environment, the resin layer easily falls off, resulting in reduced airtightness of the composite diaphragm.

[0007] Summary of the Invention

[0008] The object of the present invention is to provide a composite diaphragm for a water electrolyzer which has high air tightness, low electrical resistance and high durability in an alkaline solution environment.

[0009] The technical solution of the present invention is as follows: the composite diaphragm for water electrolyzer of the present invention contains non-woven fabric and polymer resin, the polymer resin is present on one or both sides of the non-woven fabric, and partially or completely penetrates into the non-woven fabric structure, the non-woven fabric accounts for 20-95% of the weight of the composite diaphragm, the thickness of the non-woven fabric is 0.20-2.00 mm, and the gram weight is 100-400 g / m 2 , and the density is 0.20~0.50g / cm 3 .

[0010] The beneficial effects of the present invention are as follows: the composite diaphragm for a water electrolyzer of the present invention has the advantages of high air tightness, low electrical resistance and high durability in an alkaline solution environment. DETAILED DESCRIPTION

[0011] The composite diaphragm for a water electrolyzer of the present invention contains a non-woven fabric and a polymer resin. The polymer resin is present on one or both sides of the non-woven fabric and partially or completely penetrates into the non-woven fabric structure. The non-woven fabric accounts for 20 to 95% of the weight of the composite diaphragm. The thickness of the non-woven fabric is 0.20 to 2.00 mm, and the gram weight is 100 to 400 g / m 2 , and the density is 0.20~0.50g / cm 3 .

[0012] The composite diaphragm of the present invention is obtained by adopting the composite technology of non-woven fabric and polymer resin, and has the advantages of more stable structure, higher air tightness and longer service life, and solves the problems of low air tightness and poor durability of simple non-woven fabric diaphragms.

[0013] The non-woven fabric in the composite diaphragm of the present invention is preferably spunlace non-woven fabric, needle-punched non-woven fabric, papermaking non-woven fabric, hot air non-woven fabric or spunbond non-woven fabric. These non-woven fabrics have good compactness and appropriate surface roughness, which allows the polymer resin to easily penetrate into the non-woven fabric structure and enhance the bonding strength between the resin and the non-woven fabric fibers, and are therefore preferred.

[0014] The non-woven fabric in the composite diaphragm of the present invention is most preferably a spunlace non-woven fabric, which can produce a composite diaphragm with high air tightness, low electrical resistance, and high durability in alkaline environments. When the non-woven fabric is a needle-punched non-woven fabric, although the coarser needles allow for entanglement and reinforcement between fibers, the needle-punched non-woven fabric has a larger pore size and higher surface roughness. The resulting composite diaphragm tends to have a tendency to lose resin during long-term use in alkaline solutions, and is therefore not the most preferred choice. When the non-woven fabric is a papermaking non-woven fabric, due to its lower strength and denser surface, the contact area between the resin and the fibers is smaller, and the resin layer is not easily penetrated. The resulting composite diaphragm tends to have a tendency to lose resin during long-term use in alkaline solutions, and is therefore not the most preferred choice.

[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 are preferred because they do not contain easily decomposable esters, amides, etc., have strong chemical stability, and exhibit excellent durability even in high-temperature, high-concentration alkaline solutions. Considering cost, polysulfone is the most preferred polymer resin of the present invention.

[0016] The composite membrane of the present invention preferably contains hydrophilic inorganic particles, preferably at least one of an oxide or hydroxide of zirconium, bismuth, or cerium. These particles not only enhance the hydrophilicity of the composite membrane but also increase ion permeability and reduce electrical resistance, thereby lowering the operating voltage and cost of the hydrogen production equipment. Zirconia is a more preferred hydrophilic inorganic particle of the present invention, given that the chemical properties and structure of the zirconium oxide surface affect the hydrophilicity of the composite membrane.

[0017] The weight ratio of the polymer resin to the hydrophilic inorganic particles in the composite membrane of the present invention is preferably 1:0.5 to 3.5, more preferably 1:1 to 3. If the proportion of the hydrophilic inorganic particles is too large, the number of hydrophilic inorganic particles in the composite membrane increases, the adhesion between the polymer resin and the non-woven fabric decreases, and the hydrophilic inorganic particles tend to fall off, which reduces the weight of the composite membrane, further increasing the weight loss rate of the composite membrane after 6 months. Furthermore, due to the uneven shedding of the hydrophilic inorganic particles, the airtightness of the composite membrane decreases. If the proportion of the hydrophilic inorganic particles is too small, the hydrophilicity of the composite membrane decreases, the resistance increases, and the voltage during operation of the hydrogen production equipment increases, increasing the operating cost.

[0018] In the composite membrane of the present invention, the proportion of non-woven fabric to the weight of the composite membrane is 20-95%. If the proportion of non-woven fabric is less than 20%, the content of polymer resin in the composite membrane is too high, which not only leads to a high surface resistance of the composite membrane, but also reduces the contact area between the resin and the non-woven fabric fibers. During use in an alkaline solution environment, the surface powder in the resin will gradually fall off. As time goes by and the pressure difference in the electrode chamber acts, the polymer resin layer will fall off in one piece due to the entanglement of only a small amount of non-woven fabric, resulting in an instantaneous reduction in the air tightness of the composite membrane and a significant decrease in the breaking strength. If the proportion of non-woven fabric is higher than 95%, the content of polymer resin in the composite membrane is too low and cannot play a reinforcing role. The initial air tightness of the composite membrane is still low. Moreover, the contact area between the small amount of resin and the non-woven fabric fibers is small. After long-term use in an alkaline solution environment, the small amount of resin is easy to fall off, further reducing the air tightness of the composite membrane. In order to obtain a composite separator with high air tightness, low electrical resistance and high durability in alkaline environment, the proportion of the non-woven fabric in the weight of the composite separator is preferably 40-80%, more preferably 55-65%.

[0019] In the composite diaphragm of the present invention, the thickness of the non-woven fabric is 0.20 to 2.00 mm, and the weight is 100 to 400 g / m 2 , and the density of the non-woven fabric (the ratio of the weight to the thickness of the non-woven fabric) is 0.20-0.50g / cm 3 The thickness, weight and density of the non-woven fabric in the composite membrane are at the same level as those of the non-woven fabric. The present invention controls the thickness of the non-woven fabric to be 0.20-2.00 mm and the weight to be 100-400 g / m 2 At the same time, the density (ratio of non-woven fabric weight to thickness) is required to be 0.20-0.50g / cm 3 Within the range, by such a design, thick bulky non-woven fabrics with larger thickness and smaller gram weight but lower than the density requirement, and thin dense non-woven fabrics with smaller thickness and larger gram weight but higher than the density requirement are excluded from the present invention because they cannot achieve the beneficial effects of the present invention. The thickness of the non-woven fabric is 0.20-2.00 mm, and the gram weight is 100-400 g / m 2 However, if the density of the nonwoven fabric is too small, less than 0.20g / cm 3 If the density is too high, the non-woven fabric will have a sparse structure, a small number of fibers per unit volume, weak inter-fiber entanglement, and low breaking strength. Even if a large amount of polymer resin is infiltrated, the contact with the sparse fibers is insufficient. When the composite diaphragm is used in an alkaline environment for a long time, the resin tends to fall off easily, and the durability becomes poor. If the density is too high, higher than 0.50g / cm 3Otherwise, the structure of the non-woven fabric is too tight, not only the resistance is too high, but also the resin is not easy to penetrate, and the contact area with the fiber is small, the adhesion is low, and the resin tends to fall off easily when the composite membrane is used in an alkaline environment for a long time. Taking into account the airtightness, resistance and durability of the composite membrane, the thickness of the non-woven fabric of the present invention is preferably 0.30-0.50mm, and the weight is preferably 120-300g / m 2 , and the density is preferably 0.30 to 0.40 g / cm 3 .

[0020] The polymer resin of the present invention is present on one or both sides of the non-woven fabric, and partially or completely penetrates into the non-woven fabric structure. When the polymer resin is present in the thickness range inside the non-woven fabric, it is not only related to the distribution of the pores of the non-woven fabric itself, but also to the viscosity of the polymer resin and the coating process. Specifically, the present invention can make the polymer resin cover the surface and penetrate into the range of more than one-tenth of the thickness from the surface, preferably more than one-third of the thickness from the surface by single-sided or double-sided coating. If a polymer resin with low viscosity is selected, due to its high fluidity, the polymer resin can be completely penetrated into the non-woven fabric structure; if a resin with high viscosity is selected, the resin can be present on one or both sides of the non-woven fabric and partially penetrated into the non-woven fabric structure through process control. The present invention can also make the resin run through the entire structure of the non-woven fabric by impregnation, that is, the resin is present on both surfaces of the non-woven fabric and completely penetrated into the non-woven fabric.

[0021] In the composite diaphragm of the present invention, the surface roughness of the non-woven fabric is preferably 150 to 800 μm. The surface roughness of the non-woven fabric in the composite diaphragm is at the same level as that of the non-woven fabric. The surface roughness affects the bonding strength between the non-woven fabric and the polymer resin, and thus affects the durability of the composite diaphragm. If it is too large, the surface of the non-woven fabric is uneven. After coating with resin, many protruding fibers are exposed on the surface of the resin layer, resulting in the inability to form a continuous coating layer on the surface of the non-woven fabric. When the composite diaphragm is used, on the one hand, the fibers exposed on the surface of the resin layer fall off, and on the other hand, there is a lack of mutual force between the discontinuous resin layers. When used in alkaline solution for a long time, the risk of the resin coating falling off will increase, so it is not preferred; if it is too small, the surface of the non-woven fabric is too flat. After coating with resin, the interfacial force between the resin layer and the non-woven fabric layer is low. When used in alkaline solution for a long time, the risk of the resin coating falling off will also increase, so it is not preferred. In the composite diaphragm of the present invention, the surface roughness of the non-woven fabric is more preferably 200 to 500 μm.

[0022] There are many factors that affect surface roughness, which are listed as follows: the first is the processing method of the non-woven fabric, the second is the fineness of the non-woven fabric fibers, and the third is the finishing method of the non-woven fabric. When the processing method is needle punching, although the thicker needles make the fibers entangled and reinforced, the pore size of the needle-punched non-woven fabric is larger and the surface roughness is higher. The smaller the fineness of the non-woven fabric fibers, the tighter the fibers are, the tighter the structure of the resulting non-woven fabric is, and the smaller its surface roughness is. If the finishing method of the non-woven fabric is calendering, the surface of the non-woven fabric becomes smooth and the surface roughness becomes smaller. The present invention is not limited by the factors affecting surface roughness. As long as it is controlled within the range of 150 to 800 μm, it is within the scope of protection of the present invention.

[0023] In the composite membrane of the present invention, the average pore size of the nonwoven fabric is preferably 8.0 to 18.0 μm, with pores of 18.0 μm or less preferably accounting for at least 40%. The average pore size of the nonwoven fabric in the composite membrane is comparable to that of the nonwoven fabric. If the average pore size is too small, the polymer resin will have difficulty penetrating the interior of the nonwoven fabric, forming only a coating layer on the outermost surface of the nonwoven fabric, with no penetration from the upper surface of the nonwoven fabric into the thickness. This results in minimal contact area between the resin and the nonwoven fibers, making it susceptible to detachment during long-term use in alkaline solutions. If the average pore size is too large, the nonwoven fabric has a sparse structure, resulting in low airtightness and strength, while also reducing the contact area with the resin and reducing the adhesion of the resin layer. Considering the durability and airtightness of the composite membrane, the average pore size of the nonwoven fabric of the present invention is more preferably 10.0 to 16.0 μm, with pores of 18.0 μm or less preferably accounting for at least 50% of the total pores.

[0024] Many factors influence the average pore size, such as fiber fineness. The finer the fibers, the tighter the fibers are, the smaller the gaps between them, and the smaller and more uniform the pore size of the resulting nonwoven fabric. Another example is the uniformity of the fiber web. By adjusting the processing techniques, such as the speed ratio of the cylinder and doffer, the web can be laid more evenly, thereby improving the uniformity of the pore size of the nonwoven fabric. The present invention is not limited by factors affecting the average pore size; as long as the average pore size is controlled within the range of 8.0 to 18.0 μm, it is within the scope of protection of the present invention.

[0025] The average pore size of the composite diaphragm of the present invention is preferably 0.1 to 5.0 μm, and the surface resistance is preferably 200 mΩ·cm 2Below, the porosity is preferably 50-80%, and the air tightness is preferably that no bubbles are generated within 2 minutes under 700mm water column. If the pore size is too large, the air tightness is low and the electrolysis efficiency is also low; if the pore size is too small, the surface resistance is high and the energy consumption during electrolysis is also high. If the surface resistance is too large, since the hydrogen production equipment operates at a constant current, it will cause the operating voltage to increase, and the energy consumption of the hydrogen production equipment will increase. If the air tightness is too small, not only will the purity of the electrolyzed gas be low, but it will also not be able to adapt to the operation of the high-pressure electrolyzer. Therefore, the average pore size of the composite diaphragm of the present invention is more preferably 0.30-2.0μm, and the surface resistance is more preferably 100mΩ·cm 2 Below, the porosity is more preferably 60 to 70%, and the airtightness is more preferably 1000 mmH2O or more.

[0026] Since the electrolyte circulates in the electrolytic cell during the electrolysis process and gas is generated from the anode and cathode, components such as the composite diaphragm will vibrate in the electrolytic cell. After the composite diaphragm vibrates for a long time in the electrolytic cell and is immersed in hot alkaline solution for a long time, the resin layer will fall off, and the air tightness of the composite diaphragm after operation will be greatly reduced, causing the electrolytic cell to stop operating. Therefore, the present invention ensures the full combination of the non-woven fabric and the resin layer through the specific design and selection of the non-woven fabric. After being immersed in a 30% alkaline solution at 90°C for 6 months, the weight reduction rate of the composite diaphragm of the present invention is preferably less than 5.0%, and the breaking strength retention rate is preferably more than 80%. In order to further ensure the stability of the operation of the composite diaphragm, the weight reduction rate of the composite diaphragm is more preferably less than 3.0%, and the breaking strength retention rate is more preferably more than 90%.

[0027] The preparation method of the composite diaphragm for water electrolyzer of the present invention is as follows:

[0028] (1) Preparation of non-woven fabric: High-temperature resistant short fibers with a diameter of 5 to 20 μm are made into a fiber mesh, which is then reinforced, dried, heat-set, and calendered to obtain non-woven fabric.

[0029] (2) Preparation of polymer resin: 10 to 20 wt% of polymer resin, 5 to 45 wt% of hydrophilic inorganic particles, 0.1 to 15 wt% of a pore-opening agent, and a solvent are prepared into a resin liquid with a viscosity of 300 to 1,000,000 Pa·s, wherein the weight ratio of the polymer resin to the hydrophilic inorganic particles in the resin liquid is 1:0.5 to 3.5.

[0030] (3) Preparation of composite diaphragms: The prepared resin liquid is coated on one or both sides of the non-woven fabric by a scraper method, a rolling method or a slit coating method, or the non-woven fabric is immersed in the resin liquid, and then the non-woven fabric with the resin liquid is immersed in water or a mixture of water and an organic solvent for 10 to 30 minutes to form a polymer porous membrane. The prepared polymer porous membrane is then washed in 2 to 3 water baths to precipitate the residual solvent in the porous membrane, and finally a finished composite diaphragm is obtained.

[0031] The diameter of the high-temperature resistant fiber in step (1) is 5 to 20 μm. Compared with coarse fibers, at the same gram weight, finer fibers have more fibers, a larger specific surface area, and are more tightly entangled with each other. The resulting non-woven fabric has a smaller average pore size, a more uniform pore size distribution, a larger contact area with the resin, and better long-term durability during use. Considering the airtightness and long-term durability of the composite diaphragm, the diameter of the high-temperature resistant fiber is preferably 8 to 12 μm.

[0032] Considering that the composite diaphragm of the present invention is used for a long time at a high temperature of 90°C and in a 30% potassium hydroxide solution, the high-temperature resistant fiber is preferably polypropylene, polyphenylene sulfide or polytetrafluoroethylene fiber. Considering its excellent heat resistance, chemical resistance and stability, polyphenylene sulfide fiber is more preferred.

[0033] The non-woven fabric in step (1) is preferably hydrophilic treated, i.e., sulfonated in a mixed solution of chromic acid and sulfuric acid at a certain concentration, then washed with water at room temperature, washed with hot water, reduced, ultrasonically washed, dried, calendered, or surface treated with plasma. Considering the durability of the composite diaphragm in alkaline solution, the hydrophilic treatment is more preferably sulfonated.

[0034] The surface resistance of the non-woven fabric is preferably 200.0 mΩ·cm 2 If it is too large, the surface resistance will be higher after coating with resin. Since the hydrogen production equipment works at a constant current, it will cause the operating voltage to increase, which will increase the energy consumption of the hydrogen production equipment. The more preferred value is 100mΩ·cm 2 the following.

[0035] The airtightness of the nonwoven fabric is preferably such that no bubbles are generated within 2 minutes under a 400mm water column, i.e., the airtightness is greater than 400mm water column. If the nonwoven fabric maintains high airtightness, the diaphragm composite fabric can also maintain high airtightness even after being coated with resin. Considering the excellent airtightness and ion permeability of the composite diaphragm fabric, the airtightness of the nonwoven fabric is more preferably greater than 500mm water column pressure.

[0036] The content of the polymer resin in step (2) is 10 to 20% by weight. If the resin content is too high, the viscosity is too high, which makes coating difficult on the one hand, and on the other hand, the resin layer penetrates less into the non-woven fabric, making it difficult to form a continuous resin layer. The composite diaphragm tends to have poor durability in high-temperature alkaline solution; if the resin content is too low, the viscosity is too low, and the bonding strength with the non-woven fabric tends to deteriorate.

[0037] In order to enhance the hydrophilicity, hydrophilic inorganic particles with polar surface are added to the polymer resin. The hydrophilic inorganic particles are not particularly limited, but are preferably oxides or hydroxides of zirconium, bismuth, or cerium with good stability, and zirconium dioxide is more preferred. The concentration of the above-mentioned inorganic particles in the resin solution is preferably 5 to 45% by weight, and more preferably 10 to 30% by weight.

[0038] In addition, in order to increase the porosity of the polymer resin layer, a water-soluble pore-forming promoter, i.e., a pore-opening agent, such as polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), polyvinyl acetate (PVAC) or glycerol, is preferably added when preparing the polymer resin solution. When the polymer resin layer is formed into a film in the subsequent coagulation bath, the pore-opening agent will dissolve in a non-solvent such as water, thereby forming micropores. The concentration of the pore-opening agent directly affects the viscosity of the resin solution, i.e., the adhesion strength of the resin solution to the non-woven fabric. The concentration of the pore-opening agent in the resin solution is preferably 0.1 to 15% by weight, and more preferably 1 to 10% by weight.

[0039] The present invention is further described by the following examples, but the scope of protection of the present invention is not limited to the examples. The physical properties in the examples are measured by the following methods.

[0040]

Testing of non-woven fabric monomers

[0041] First, take a piece of composite diaphragm and soak it in N-methyl-2-pyrrolidone solvent for more than 12 hours to completely dissolve the resin layer, leaving only the non-woven fabric monomer, which is the non-woven fabric in the composite diaphragm of the present invention. Then, soak the non-woven fabric monomer in pure water for 2 minutes, take it out and place it in a constant temperature oven at 60°C to dry for 2 hours, and then test the various physical properties of the non-woven fabric monomer.

[0042] [Method for separating non-woven fabric and hydrophilic inorganic particles in composite membrane]

[0043] First, a composite membrane was taken and immersed in N-methyl-2-pyrrolidone solvent for more than 12 hours to completely dissolve the resin layer and allow the hydrophilic inorganic particles to fall off and precipitate. The non-woven fabric was then removed from the solution and soaked in pure water for 2 minutes. The precipitated hydrophilic inorganic particles in the solution were filtered with filter paper and rinsed twice with pure water. The non-woven fabric and hydrophilic inorganic particles were then dried in a constant temperature oven at 60°C for 2 hours to obtain the non-woven fabric monomer and the hydrophilic inorganic particle monomer.

[0044] [Proportion of non-woven fabric in the weight of composite diaphragm]

[0045] Take 20cm×20cm samples from the left, middle and right sides of the composite diaphragm along its width direction (N=3) and weigh them respectively, which is recorded as M. 左 、M 中 、M 右, and then dissolve, separate and dry the non-woven fabric monomers using the above separation method, and weigh the weight of the non-woven fabric monomers, which is recorded as M1 左 、M1 中 、M1 右 The formula for calculating the proportion of the non-woven fabric in the composite membrane weight of any sample is as follows: weight proportion of non-woven fabric = M1 / M×100%. The weight ratios of the left, middle, and right parts are calculated separately, and then the average value is calculated.

[0046] [The composite diaphragm contains hydrophilic inorganic particles]

[0047] A 0.1g sample of hydrophilic inorganic particles was obtained using the separation method for non-woven fabric and hydrophilic inorganic particles in a composite membrane. Sample preparation: Attach double-sided tape to a sample stage and evenly spread 0.1g of hydrophilic inorganic particles on the stage. The stage was then placed in the sample chamber of an elemental analyzer (Thermoscientific, Model: Apreo 2C). The hydrophilic inorganic particles were scanned under vacuum to determine their constituent elements.

[0048] [Weight ratio of polymer resin to hydrophilic inorganic particles in composite diaphragm]

[0049] Take 20cm×20cm samples from the left, middle and right sides of the composite diaphragm along its width direction (N=3) and weigh them respectively, which is recorded as M. 左 、M 中 、M 右 Then, the above separation method is used to filter, rinse and dry the precipitate to obtain the weight of the hydrophilic inorganic particles, which is recorded as M2 左 、M2 中 、M2 右 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 = M3 / M2. Calculate the weight ratios of the left, middle, and right sides respectively, and then calculate their average value.

[0050]

Surface roughness of non-woven fabric

[0051] Three 20 cm x 20 cm samples (N = 3) were taken from the left, center, and right sides of the composite membrane width. These samples were dissolved, separated, and dried using the aforementioned separation method to obtain the nonwoven fabric. The maximum peak height and maximum valley depth of the surface roughness were automatically measured using a VR-5000 3D profilometer. The sum of the maximum peak height and maximum valley depth was calculated as the maximum height Sz, representing the surface roughness of the nonwoven fabric. Two points were measured on each sample, and the average of the six points for the three samples was calculated.

[0052]

Average pore size of non-woven fabric

[0053] Samples (N=3) of 20 cm x 20 cm were taken from the left, center, and right sides of the composite membrane along its width. These samples were then dissolved, separated, and dried using the aforementioned separation method to obtain a nonwoven fabric monomer. The pore size of the nonwoven fabric was measured using a capillary flow porometer according to ASTM F316-03. The sample was placed in a sample chamber and moistened with silwick silicone fluid with a surface tension of 15.9 dynes / cm. The bottom clamp of the sample chamber had a porous metal disk insert with a diameter of 2.54 cm and a thickness of 3.175 mm. The top clamp of the sample chamber had a hole with a diameter of 3.175 mm. The average value of the three samples was calculated.

[0054] [Percentage of pore diameters less than 18 μm]

[0055] The same as the test method of the average pore size mentioned above, the sum of the number of pores below 18 μm in the pore size range automatically tested by the system is divided by the total number of all pore sizes, and the percentage calculated is the proportion of pores below 18 μm.

[0056]

Fiber diameter

[0057] Samples (N=3) of 20 cm x 20 cm were taken from the left, center, and right sides of the composite membrane along its width. These samples were dissolved, separated, and dried using the above separation method to obtain a nonwoven fabric. The fibers in the nonwoven fabric were photographed using an electron microscope at 800x magnification. The fiber diameters were directly measured at 30 random locations, and the average value was calculated.

[0058]

Non-woven fabric weight

[0059] Samples of 20 cm × 20 cm were taken from the left, middle and right sides of the composite membrane along its width (N=3), and then dissolved, separated and dried using the above separation method to obtain the non-woven fabric monomer. The mass per unit area of ​​the non-woven fabric was measured according to the test standard GB / T24218.1-2009. The gram weight was calculated as follows: gram weight (g / m 2 ) = dry weight (g) / area (m 2 ), calculate the average value.

[0060]

Thickness of non-woven fabric

[0061] Samples (N=3) of 20 cm x 20 cm were taken from the left, center, and right sides of the composite membrane along its width. These samples were then dissolved, separated, and dried using the aforementioned separation method to obtain the nonwoven fabric. The thickness of the nonwoven fabric was measured in mm according to the test standard GB / T24218.2-2009, and the average value was calculated.

[0062]

Non-woven fabric density

[0063] According to the weight w and thickness d of the non-woven fabric, calculate the density p (g / cm 3 )=[weight w(g / m 2 ) / 10000] / [thickness d(mm) / 10], unit is g / cm 3 , calculate the average value.

[0064]

Airtightness of non-woven fabric

[0065] Samples of 20 cm x 20 cm (N = 3) were taken from the left, center, and right sides of the composite membrane along its width, and dissolved, separated, and dried using the above separation method to obtain a non-woven fabric. Airtightness testing was performed according to the Chinese building materials industry standard JCT 211-2009, and the average value was calculated.

[0066] [Surface resistance of non-woven fabric]

[0067] Samples (N = 3) of 20 cm x 20 cm were taken from the left, center, and right sides of the composite separator width. These samples were then dissolved, separated, and dried using the aforementioned separation method to obtain a nonwoven fabric. The nonwoven fabric's surface resistance was measured according to the People's Republic of China Electronics Industry Standard SJ / T 10171.5-91, "Surface Resistance of Alkaline Battery Separators," and the average value was calculated.

[0068]

Breaking strength of non-woven fabric in warp and weft directions

[0069] Samples (N=3) of 20 cm x 20 cm were taken from the left, center, and right sides of the composite membrane along its width. These samples were dissolved, separated, and dried using the above separation method to obtain a nonwoven fabric. The nonwoven fabric breaking strength was tested according to GB / T 24218.3-2010, and the average value was calculated.

[0070] Porosity of composite diaphragm

[0071] Take 20cm×20cm samples (N=3) from the left, middle and right sides of the composite diaphragm in the width direction, immerse them in anhydrous ethanol (purity above 99.7%) for more than 2 hours, take them out and rinse them twice with deionized water, quickly wipe off the liquid on the surface of the composite diaphragm with filter paper, and then use an electronic molecular balance to accurately weigh the mass M of the wet film, and use a thickness meter to measure the thickness L of the wet membrane. Then vacuum dry it at 60℃ for more than 3 hours, and then accurately weigh the mass M1 of the dry film. The porosity calculation formula is as follows: Porosity = (M-M1) / (ρ·A·L), where ρ is the density of pure water (g / mL) and A is the area of ​​the membrane (cm 2 ), L is the thickness of the membrane in the wet state (cm), M and M1 are the mass of the membrane in the wet state and the dry state (g), respectively, and the average value is calculated.

[0072]

Weight of composite diaphragm

[0073] The composite diaphragm was tested for mass per unit area according to the test standard GB / T 24218.1-2009. The weight was calculated as follows: 2 ) = dry weight (g) / area (m 2 ).

[0074]

Thickness of composite diaphragm

[0075] The thickness of the composite diaphragm is measured in accordance with the test standard GB / T 24218.2-2009, in mm.

[0076]

Average pore size of composite diaphragm

[0077] The pore size of the composite membrane was measured using a capillary flow porometer according to ASTM F316-03. The sample was placed in a sample chamber and moistened with silwick silicone fluid with a surface tension of 15.9 dynes / cm. The bottom fixture of the sample chamber contained a porous metal disk insert with a diameter of 2.54 cm and a thickness of 3.175 mm. The top fixture of the sample chamber contained a hole with a diameter of 3.175 mm. The sample pore size was the average of two measurements.

[0078] [Thickness range of polymer resin penetration into non-woven fabric]

[0079] A cross-section of the composite diaphragm was photographed at 100x magnification using a scanning electron microscope. The composite diaphragm thickness, recorded as D in mm, was directly measured. The depth of polymer resin penetration into the non-woven fabric was then measured as d in mm. This depth is the distance from the polymer resin surface to the interior of the non-woven fabric. Five measurement points were selected for each of the composite diaphragm thickness and polymer resin penetration depth, and the average values ​​were taken. The polymer resin penetration thickness range into the non-woven fabric is the ratio of the polymer resin penetration depth to the composite diaphragm thickness, or d / D.

[0080] Airtightness of composite diaphragm

[0081] Airtightness test is carried out according to the Chinese building materials industry standard JCT 211-2009 [diaphragm asbestos cloth].

[0082]

Surface resistance of composite diaphragm

[0083] The surface resistance of the composite diaphragm is tested according to the test standard of the electronic industry standard SJ / T 10171.5-91 of the People's Republic of China for the surface resistance of alkaline battery diaphragms.

[0084]

Latitude and longitude breaking strength of composite diaphragm

[0085] According to GB / T 24218.3-2010 standard, the breaking strength of the composite diaphragm was tested.

[0086]

Retention rate of composite diaphragm's breaking strength in warp and weft directions

[0087] According to GB / T 24218.3-2010, the initial breaking strength G (the sum of the longitudinal and transverse breaking strengths) of the composite diaphragm is first tested, and then it is placed in a KOH solution with a temperature of 90°C and a concentration of 30wt% and immersed for 6 months. The KOH in the diaphragm is fully washed out, and after drying at 60°C for 2 hours, the breaking strength G1 (the sum of the longitudinal and transverse breaking strengths) of the composite diaphragm is tested again. The calculation formula for the breaking strength retention rate is as follows: Breaking strength retention rate = G1 / G×100%.

[0088]

Weight reduction rate of composite diaphragm

[0089] Take 20cm×20cm samples from the left, middle and right of the composite diaphragm width direction (N=3), weigh them respectively, and record them as M 左 、M 中 、M 右 , calculate the average value as M, then soak it in a KOH solution with a temperature of 90℃ and a concentration of 30wt% for 6 months, wash the KOH in the diaphragm thoroughly, dry it at 60℃ for 2 hours, and weigh it respectively, record it as M1 左 、M1中 、M1 右 The weight reduction rate of the composite separator is calculated as follows: weight reduction rate = (M-M1) / M×100%, and the average value of the three samples is calculated.

[0090] Example 01

[0091] (1) Preparation of non-woven fabric

[0092] The polyphenylene sulfide fiber with a diameter of 9 μm is processed into a spunlace non-woven fabric by opening, blending, carding, laying, spunlace at a maximum pressure of 100 Bar, and drying and shaping. The fabric is then sulfonated and hydrophilically modified in a mixed solution of 300 g / L chromic acid and 500 g / L sulfuric acid at a treatment temperature of 80°C for 12 minutes. After sulfonation, the polyphenylene sulfide spunlace non-woven fabric is washed at room temperature, washed with hot water at 50°C, reduced and cleaned, and ultrasonically washed before drying. It is then calendered at a roller temperature of 180°C and a pressure of 1.2 MPa to form a compact and smooth non-woven fabric.

[0093] (2) Preparation of composite diaphragm

[0094] A resin solution with a viscosity of 15574 Pa·s was prepared by mixing polysulfone resin, zirconium oxide particles, glycerol pore opener, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 15wt%: 20wt%: 1wt%: 64wt%. The solution was then coated on one side of a non-woven fabric. The non-woven fabric was then immersed in a coagulation bath to solidify the polysulfone resin, forming a resin layer on one side of the non-woven fabric. The non-woven fabric was then washed with pure water to obtain a non-woven fabric with a thickness of 0.55 mm and a gram weight of 190 g / m 2 The composite membrane has resin that penetrates into one side of the non-woven fabric and extends within two-thirds of the thickness from the upper surface. The physical properties of the composite membrane for a water electrolyzer of the present invention are shown in Table 1 below.

[0095] Examples 02-03

[0096] The preparation process was the same as that of Example 01, and the specific formula and physical properties are shown in Table 1.

[0097] Example 04

[0098] The spunlace water pressure in Example 01 was adjusted to 140 Bar, and the roller pressure was adjusted to 1.4 MPa. The rest of the preparation process was the same as in Example 01. The specific formula and physical properties are shown in Table 1.

[0099] Example 05

[0100] During the preparation of the non-woven fabric, calendering was not performed. The remaining preparation processes were the same as in Example 01. The specific formulation and physical properties are shown in Table 1.

[0101] Examples 06-08

[0102] The nonwoven fabric and resin solution were prepared as in Example 01. The resin solution was then applied to both sides of the nonwoven fabric, solidified, and washed to produce a composite membrane. The resin in this composite membrane penetrated both sides of the nonwoven fabric, extending from the top surface to within three-quarters of its thickness. The physical properties of this composite membrane are shown in Tables 1 and 2.

[0103] Example 09

[0104] The preparation of the nonwoven fabric was the same as in Example 01. A resin solution with a viscosity of 1760 Pa·s was prepared by mixing polysulfone resin, zirconium oxide particles, glycerol pore opener, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 15 wt%: 10 wt%: 1 wt%: 74 wt%. The resin solution was then incorporated into the entire structure of the nonwoven fabric by dipping and rolling. The nonwoven fabric was then immersed in a coagulation bath to solidify the polysulfone resin and then rinsed with pure water to obtain a nonwoven fabric having a thickness of 0.75 mm and a gram weight of 240 g / m2. 2 The physical properties of the composite diaphragm for water electrolysis cell of the present invention are shown in Table 2 below.

[0105] Example 10

[0106] The preparation process is the same as that of Example 09, and the specific formula and physical properties are shown in Table 2. The physical properties of the composite diaphragm for water electrolyzer of the present invention are shown in Table 2 below.

[0107] Example 11

[0108] The spunlacing process of the nonwoven fabric in Example 01 was replaced with a needle-punching process. The remaining preparation processes were the same as in Example 09. The physical properties of the composite diaphragm for a water electrolyzer of the present invention are shown in Table 2 below.

[0109] Example 12

[0110] During the preparation of the non-woven fabric, no sulfonation hydrophilic modification treatment was performed. The rest of the preparation process was the same as in Example 01. The specific formula and physical properties are shown in Table 2.

[0111] Example 13

[0112] The non-woven fabric was prepared as in Example 06. A resin solution with a viscosity of 1760 Pa·s was prepared using polysulfone resin, zirconium oxide particles, glycerol pore opener, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 15 wt%: 10 wt%: 1 wt%: 74 wt%. The resin solution was then applied to both sides of the non-woven fabric, followed by solidification and washing to produce a composite membrane. The resin permeated both sides of the non-woven fabric, extending from the top surface to within three-quarters of its thickness. The physical properties of the composite membrane are shown in Table 3.

[0113] Example 14

[0114] The non-woven fabric was prepared as in Example 06. A resin solution with a viscosity of 996,500 Pa·s was prepared using a mixture of polysulfone resin, zirconium oxide particles, glycerol pore opener, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 13 wt%: 48 wt%: 1 wt%: 38 wt%. The resin solution was then applied to both sides of the non-woven fabric, followed by solidification and washing to produce a composite membrane. The resin permeated both sides of the non-woven fabric, extending from the top surface to within half of its thickness. The physical properties of the composite membrane are shown in Table 3.

[0115] Example 15

[0116] The non-woven fabric was prepared as in Example 01. A resin solution with a viscosity of 510 Pa·s was prepared using a polysulfone resin, a glycerol pore opener, and an N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 15 wt%: 1 wt%: 84 wt%. The resin solution was then applied to both sides of the non-woven fabric, solidified, and washed to produce a composite membrane in which the resin was completely permeated throughout the non-woven fabric structure. The physical properties of the composite membrane are shown in Table 3.

[0117] Example 16

[0118] The non-woven fabric was prepared as in Example 01. A resin solution with a viscosity of 830 Pa·s was prepared using polyethersulfone resin, glycerol pore opener, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 15 wt%: 1 wt%: 84 wt%. The resin solution was then applied to both sides of the non-woven fabric, solidified, and washed to produce a composite membrane in which the resin was fully permeated throughout the non-woven fabric structure. The physical properties of the composite membrane are shown in Table 3.

[0119] Example 17

[0120] The non-woven fabric was prepared as in Example 01. A resin solution with a viscosity of 16083 Pa·s was prepared using polyethersulfone resin, zirconium oxide particles, glycerol pore opener, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 15 wt%: 20 wt%: 1 wt%: 64 wt%. The resin solution was then applied to both sides of the non-woven fabric, followed by solidification and washing to produce a composite membrane. The resin permeated both sides of the non-woven fabric, extending from the top surface to within half of its thickness. The physical properties of the composite membrane are shown in Table 3.

[0121] Example 18

[0122] The non-woven fabric was prepared as in Example 01. A resin solution with a viscosity of 2440 Pa·s was prepared using polysulfone resin, cerium dioxide particles, glycerol pore opener, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 15 wt%: 10 wt%: 1 wt%: 74 wt%. The resin solution was then applied to both sides of the non-woven fabric, followed by solidification and washing to produce a composite membrane. The resin permeated both sides of the non-woven fabric, extending from the top surface to within half of its thickness. The physical properties of the composite membrane are shown in Table 3.

[0123] The physical properties of the nonwoven fabrics in each table refer to the physical properties of the composite separators obtained by soaking the composite separator in N-methyl-2-pyrrolidone solvent for at least 12 hours to completely dissolve the resin layer, then drying the nonwoven fabrics in a constant temperature oven at 60°C for 2 hours. The physical properties of the nonwoven fabrics obtained in the present invention and the nonwoven fabrics obtained after dissolving the resin in the composite separators are slightly different, but generally similar.

[0124] Comparative Example 01

[0125] Polyphenylene sulfide fibers with a diameter of 9 μm were opened, blended, carded, laid, spunlaced at a maximum spunlace pressure of 100 Br, and dried to form a spunlace nonwoven fabric. The fabric was then hydrophilically modified by sulfonation in a mixture of 300 g / L chromic acid and 500 g / L sulfuric acid at 80°C for 12 minutes. After sulfonation, the polyphenylene sulfide spunlace nonwoven fabric was washed at room temperature, washed in hot water at 50°C, subjected to reduction cleaning, ultrasonically rinsed, dried, and then calendered to form a compact, smooth nonwoven fabric. The physical properties of the membrane are shown in Table 4 below.

[0126] Comparative Example 02

[0127] (1) Preparation of woven mesh

[0128] The PPS monofilament with a fiber diameter of 60 μm was woven into a woven mesh with a pore size of 0.50 mm to obtain a gram weight of 30 g / m 2 , woven mesh with a thickness of 0.10mm.

[0129] (2) Preparation of composite diaphragm

[0130] A resin solution with a viscosity of 15574 Pa·s was prepared by mixing polysulfone resin, zirconium oxide particles, glycerol pore opener, and N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 15wt%: 20wt%: 1wt%: 64wt%. The solution was then coated on both sides of a woven mesh. The mesh was then immersed in a coagulation bath to solidify the polysulfone resin, forming a resin layer on both sides of the woven mesh. The mesh was then washed with pure water to obtain a woven mesh with a thickness of 0.35 mm and a weight of 240 g / m2. 2The composite membrane has a thin woven mesh and a large pore size. The resin layer in the composite membrane wraps the woven mesh within the resin layer. The physical properties of the composite membrane are shown in Table 4 below.

[0131] Comparative Example 03

[0132] (1) Preparation of papermaking nonwoven fabrics

[0133] Undrawn polyphenylene sulfide yarns (9 μm in diameter) and conventional polyphenylene sulfide fibers were mixed in a weight ratio of 30:70 and processed into a nonwoven fabric through wet blending, web laying, and calendering. The fabric was then hydrophilized by sulfonation in a mixed solution of 300 g / L chromic acid and 500 g / L sulfuric acid at 80°C for 12 minutes. After sulfonation, the polyphenylene sulfide papermaking nonwoven fabric was washed at room temperature, washed with hot water at 50°C, subjected to reduction cleaning, ultrasonically rinsed, and then dried to obtain a hydrophilized papermaking nonwoven fabric. The remaining preparation process was the same as in Example 01. The specific formulation and physical properties are shown in Table 4 below.

[0134] Comparative Example 04

[0135] The water pressure of the spunlace in Example 01 was adjusted to 80 Bar, and the rest of the preparation process was the same as in Example 01. For specific formula and physical properties, please refer to Table 4 below.

[0136] Comparative Example 05

[0137] The water pressure of the spunlace in Example 01 was adjusted to 140 Bar, and the rest of the preparation process was the same as in Example 01. For specific formula and physical properties, please refer to Table 4 below.

[0138] Table 1

[0139] Table 2

[0140] Table 3

[0141] Table 4

[0142] According to the above table,

[0143] (1) It can be seen from Example 01 and Example 02 that, under the same conditions, the fiber diameter and the average pore size of the non-woven fabric of the former are within the preferred range, while the fiber diameter and the average pore size of the non-woven fabric of the latter are larger. Compared with the latter, the air tightness of the non-woven fabric of the former is high. After being immersed in a 30% alkaline solution at 90°C for 6 months, the weight reduction rate of the obtained composite diaphragm is small, that is, the composite diaphragm has high air tightness and high durability in alkaline solution environment.

[0144] (2) It can be seen from Example 01 and Example 03 that, under the same conditions, the fiber diameter and the average pore size of the non-woven fabric of the former are within the preferred range, while the average pore size of the non-woven fabric of the latter is smaller. Compared with the latter, the structure of the non-woven fabric of the former is slightly fluffy, the surface resistance is low, and the resin layer penetrates more fully into the interior of the non-woven fabric. The surface resistance of the obtained composite diaphragm is low, and after being immersed in a 30% alkaline solution at 90°C for 6 months, the weight reduction rate of the composite diaphragm is small, the air tightness is high, and the breaking strength retention rate is also high, that is, the durability for use in an alkaline solution environment is high.

[0145] (3) It can be seen from Example 01 and Example 04 that, under the same conditions, the thickness and density of the former non-woven fabric are within the preferred range. Compared with the latter, the structure of the former non-woven fabric is slightly fluffy, the surface resistance is low, the polymer resin penetrates more fully into the interior of the non-woven fabric, the contact area with the fiber is larger, the adhesion strength of the resin layer is higher, and after being immersed in a 30% alkaline solution at 90°C for 6 months, the composite diaphragm has a high breaking strength retention rate, that is, it has high durability in an alkaline environment.

[0146] (4) It can be seen from Example 01 and Example 05 that under the same conditions, the thickness, density and surface roughness of the non-woven fabric of the former are within the preferred range. Compared with the latter, after being immersed in a 30% alkaline solution at 90°C for 6 months, the composite diaphragm has a small weight reduction rate, high air tightness and high breaking strength retention rate, that is, it has high durability in an alkaline solution environment.

[0147] (5) It can be seen from Examples 06 to 08 that, under the same conditions, the proportion of the non-woven fabric in the overall weight of the composite diaphragm in Example 06 is within the preferred range. Compared with Examples 07 and 08, after being immersed in a 30% alkaline solution at 90°C for 6 months, the composite diaphragm in Example 06 has a small weight reduction rate, high air tightness, and high breaking strength retention rate, that is, it has high durability in an alkaline solution environment.

[0148] (6) It can be seen from Example 09 and Example 10 that, under the same conditions, the gram weight of the non-woven fabric of the former is within the preferred range. Compared with the latter, the resistance of the composite diaphragm obtained by the former is small, and the energy consumption of the equipment during use is low.

[0149] (7) It can be seen from Example 10 and Example 11 that, under the same conditions, the latter is a needle-punched non-woven fabric. Since the needles for needle punching are relatively thick, the surface roughness of the processed non-woven fabric is high, the pore size is large, and the air tightness is low. Compared with the latter, the composite diaphragm obtained by resin impregnation of the former has a small weight reduction rate, high air tightness, and high breaking strength retention rate after being immersed in a 30% alkaline solution at 90°C for 6 months, that is, it has high durability in an alkaline solution environment.

[0150] (8) It can be seen from Example 01 and Example 12 that, under the same conditions, the non-woven fabric of the former is subjected to sulfonation hydrophilic treatment. Compared with the latter, since the resin in the former is more easily penetrated into the hydrophilic treated non-woven fabric, the resin coating is not easy to fall off. After being immersed in a 90°C, 30% alkaline solution for 6 months, the breaking strength retention rate of the composite diaphragm is slightly higher, that is, the durability of the composite diaphragm in the alkaline solution environment is high.

[0151] (9) As can be seen from Example 06 and Example 13, under the same conditions, the weight ratio of the polymer resin to the hydrophilic inorganic particles in the former is within a more preferred range, and the sheet resistance of the composite diaphragm obtained in the former is lower than that in the latter. (10) As can be seen from Example 06 and Example 14, under the same conditions, the weight ratio of the polymer resin to the hydrophilic inorganic particles in the latter is greater, and the composite diaphragm in the latter has a greater weight loss rate and a lower breaking strength retention rate after immersion in a 30% alkaline solution at 90°C for 6 months than the former.

[0152] (11) It can be seen from Example 13 and Example 15 that under the same conditions, the latter does not add hydrophilic inorganic particles, and the resistance of the composite diaphragm obtained by the latter is higher than that of the former.

[0153] (12) It can be seen from Example 01 and Comparative Example 01 that, under the same conditions, the former is a composite diaphragm formed by non-woven fabric and resin, while the latter is a single non-woven fabric. Compared with the latter, the former has higher air tightness and better durability in long-term use.

[0154] (13) It can be seen from Example 06 and Comparative Example 02 that, under the same conditions, the proportion of the base fabric in the latter to the overall weight of the composite diaphragm is too low. Compared with the former, the composite diaphragm obtained by the latter has low air tightness and low breaking strength retention, that is, poor durability.

[0155] (14) It can be seen from Example 01 and Comparative Example 03 that, under the same conditions, the composite diaphragm obtained by the latter using a papermaking non-woven fabric with too high a density and too small a thickness as a base fabric has a high weight reduction rate, low air tightness, and low breaking strength retention rate compared with the former, that is, poor durability.

[0156] (15) It can be seen from Example 01 and Comparative Example 04 that, under the same conditions, the gram weight in the latter is too low, and the density ratio of gram weight to thickness is also too low. Compared with the former, the composite diaphragm obtained from the latter has poor air tightness and low breaking strength retention, that is, poor durability.

[0157] (16) It can be seen from Example 01 and Comparative Example 05 that, under the same conditions, the gram weight in the latter is higher, and the density ratio of gram weight to thickness is also too high. Compared with the former, the resistance of the composite diaphragm obtained in the latter is too high, that is, the energy consumption of the equipment operation is too large.

Claims

1. A composite diaphragm for a water electrolyzer, characterized in that: The composite diaphragm contains non-woven fabric and polymer resin, the polymer resin exists on one side or both sides of the non-woven fabric, and partially or completely penetrates into the non-woven fabric structure, the non-woven fabric accounts for 20-95% of the weight of the composite diaphragm, the thickness of the non-woven fabric is 0.20-2.00 mm, and the gram weight is 100-400 g / m 2 , and the density is 0.20~0.50g / cm 3 .

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

3. The composite diaphragm for a water electrolyzer 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 electrolyzer according to claim 3, characterized in that: The polymer resin is polysulfone resin.

5. The composite diaphragm for a water electrolyzer according to claim 1, characterized in that: The composite diaphragm contains hydrophilic inorganic particles, and the hydrophilic inorganic particles are at least one of oxides or hydroxides of zirconium, bismuth, and cerium.

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

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

5.

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

9. The composite diaphragm for a water electrolyzer 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 electrolyzer according to claim 9, characterized in that: The pore sizes of the nonwoven fabric are less than 18 μm, accounting for more than 40%.

11. The composite diaphragm for a water electrolyzer according to claim 1 or 2, characterized in that: After being immersed in a 30% alkaline solution at 90° C. for 6 months, the weight reduction rate of the composite separator is 5.0% or less.

12. The composite diaphragm for a water electrolyzer according to claim 1 or 2, characterized in that: After being immersed in a 30% alkaline solution at 90° C. for 6 months, the breaking strength retention rate of the composite separator is above 80%.

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