PEEK fiber for water electrolysis hydrogen production diaphragm, diaphragm base cloth and application

Abstract

The invention belongs to the technical field of diaphragm materials for water electrolysis hydrogen production, and particularly relates to a PEEK fiber for a diaphragm for water electrolysis hydrogen production, diaphragm base cloth and application. The PEEK fiber is prepared by adopting a specific cooling and stretching process, and has the advantages of high strength and the like; the base cloth is made of a specific weaving structure and is subjected to shallow sulfonation treatment. The diaphragm prepared from the PEEK fiber and the base cloth has the advantages of high strength, excellent durability and good surface resistance and air tightness, realizes the unification of low resistance, high air tightness, high strength and long service life, and is suitable for being used as a hydrogen production diaphragm of proton exchange membrane water electrolysis hydrogen production equipment; and the diaphragm is also suitable for being used as a hydrogen production diaphragm of alkaline anion exchange membrane water electrolysis hydrogen production equipment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of diaphragm materials for water electrolysis hydrogen production, and particularly relates to a PEEK fiber for water electrolysis hydrogen production diaphragm, a diaphragm base cloth and a use. BACKGROUND

[0002] Water electrolysis hydrogen production is a kind of new energy technology. The diaphragm is a key component in the water electrolysis hydrogen production equipment, which is required to have certain low resistance and high air tightness, so as to provide guarantee for the electrolysis reaction and the preparation and purity of the gas. At present, proton exchange membrane water electrolysis hydrogen production (PEM) mainly adopts perfluorosulfonic acid proton exchange membrane (such as Nafion), but its cost is high, the mechanical strength is insufficient and it is not friendly to the environment. The diaphragm material of alkaline anion exchange membrane water electrolysis hydrogen production (AEM, also known as anion exchange membrane water electrolysis hydrogen production, which combines the advantages of alkaline water electrolysis hydrogen production and proton exchange membrane water electrolysis hydrogen production, is considered to be one of the key routes to realize low-cost and low-energy consumption hydrogen production) is also in exploration, and also faces the challenge of long-term alkaline stability.

[0003] Polyether ether ketone (PEEK) is a special engineering plastic with excellent thermal stability (long-term use temperature > 250℃), chemical stability (acid and alkali resistance, hydrolysis resistance) and flame retardance. Due to the excellent performance of PEEK fiber (including monofilament and multifilament), it has been widely used in high-end fields such as aerospace and industrial filtration. However, it has poor hydrophilicity, and the microstructure of the base cloth is not easy to control, which makes it difficult to balance low resistance and high air tightness.

[0004] Therefore, how to improve the performance applicability of PEEK fiber for water electrolysis hydrogen production diaphragm is one of the problems to be solved and improved in the field at present. SUMMARY

[0005] In view of the above problems, the purpose of the present application is to provide a PEEK fiber for water electrolysis hydrogen production diaphragm, a diaphragm base cloth and a use. The present application comprises the following technical solutions: A PEEK fiber for water electrolysis hydrogen production diaphragm, the preparation method of the PEEK fiber comprises the following steps: Spinning: PEEK resin is dried, melt extruded in a screw extruder to prepare a melt, and the melt is extruded through a spinneret. The fiber extruded by the spinneret passes through a three-section gradient slow cooling device with a total length of 20cm~50cm at a constant speed. The lengths of the upper, middle and lower three sections of the gradient slow cooling device are 5cm~15cm, 10cm~20cm and 5cm~15cm respectively, and the temperatures are 380℃~395℃, 320℃~360℃ and 240℃~290℃ respectively. The time length for the fiber to enter and leave each part of the gradient slow cooling device is 0.1s~0.5s. Then the fiber enters a cooling air box at 20℃~30℃ for solidification to obtain a cooled fiber; The cooled fibers are subjected to graded heat drawing, the first stage of drawing is carried out at 150-180 DEG C, the draw ratio is 2-5 times; the second stage of drawing is carried out at 280-320 DEG C, the draw ratio is 1.2-1.5 times; finally, relaxation heat setting is carried out at 250-280 DEG C, the setting time is 1-3 s, to obtain the PEEK fiber for hydrogen production membrane of water electrolysis.

[0006] Preferably, in the spinning step, the orifice diameter of the spinneret is 0.1-0.5 mm, and the length-diameter ratio is (3-5):1.

[0007] Preferably, in the spinning step, the PEEK resin drying condition is vacuum drying at 120-150 DEG C for 4-8 h.

[0008] Preferably, in the spinning step, when melt-extruding, the temperature from the screw extruder zone 1 to the die head is 340-395 DEG C.

[0009] A PEEK base fabric for hydrogen production membrane of water electrolysis, which is prepared from the aforementioned PEEK fiber for hydrogen production membrane of water electrolysis, and is subjected to sulfonation treatment, with a sulfonation depth of 0.5 ± 0.4 μm.

[0010] Preferably, the PEEK base fabric is woven in plain weave.

[0011] Preferably, the PEEK base fabric has a surface density of 45 ± 2 g / m 2 , a warp density of 60 ± 5 roots / cm, and a weft density of 55 ± 5 roots / cm.

[0012] Preferably, the PEEK base fabric has a thickness of 55 ± 5 μm.

[0013] Use of the aforementioned PEEK fiber for hydrogen production membrane of water electrolysis or PEEK base fabric for hydrogen production membrane of water electrolysis in the preparation of a hydrogen production membrane for water electrolysis.

[0014] A hydrogen production membrane for water electrolysis, which contains the aforementioned PEEK fiber for hydrogen production membrane of water electrolysis or PEEK base fabric for hydrogen production membrane of water electrolysis.

[0015] Advantages

[0016] The PEEK fiber and base fabric prepared in the application have the advantages of high strength, excellent durability, good surface resistance and air tightness, and realize the unification of low resistance, high air tightness, high strength and long service life. The fiber and base fabric are suitable for use as hydrogen production membranes for both proton exchange membrane water electrolysis hydrogen production equipment and alkaline anion exchange membrane water electrolysis hydrogen production equipment, and thus have the advantage of multiple uses. DETAILED DESCRIPTION

[0017] The technical ideas, schemes, effects, etc. of the present application are described in detail below through specific examples. The examples are merely exemplary illustrations of the present application and are not considered to limit the scope of protection of the present application.

[0018] In the following examples: the PEEK resin used is VESTAKEEP PEEK resin from Evonik, Germany ® 4000G; the perfluorinated sulfonic acid resin used is Nafion ® D520 dispersion (DuPont); the DMSO solution of AEM-1 type polyarylether sulfone anion exchange resin used is selected from Suzhou Zhique Bobo Material Technology Co., Ltd. and Anhui Gushi Hyunyou Technology Co., Ltd. The commercially available PP separator used is a commercially available Celgard 3501 dry process unidirectional stretching polypropylene microporous membrane.

[0019] In the following examples: the gradient slow cooling device used is a gradient slow cooling device divided into upper, middle and lower sections, and each section has an independent heating device. Its main function is to perform staged gradient cooling on the fibers extruded from the spinneret from top to bottom. The heating device used can be a ring-shaped heating plate, a heating tube or a ring-shaped air blowing device. The upper section is immediately adjacent to the spinneret (length 5 cm ~ 15 cm), and the temperature control range can be 380℃ ~ 395℃ (this temperature is slightly lower than or equal to the die temperature of the spinneret, and the main function is to keep warm and prevent the melt stream from cooling rapidly due to a large temperature difference in the environment at the outlet); the middle section immediately below (length 10 cm ~ 20 cm) has a temperature control range of 320℃ ~ 360℃ (this temperature is the typical crystallization temperature range of PEEK, allowing the molecular chains to begin to form crystal nuclei and preliminarily arrange in order under mild conditions); the lower section immediately below or connected to the cooling air box (length 5 cm ~ 15 cm) has a temperature control range of 240℃ ~ 290℃ (this temperature is higher than the glass transition temperature Tg of PEEK, ensuring that the fiber always remains in a high-elastic state before entering the forced cooling air box to avoid glass transition). The total length of the gradient slow cooling device can be 20 cm ~ 50 cm, and the fiber stays in it for about 0.1 s ~ 0.5 s.

[0020] Example 1: PEEK fiber and base fabric and composite separator for PEM hydrogen production separator First part: preparation of PEEK fiber for hydrogen production separator S1 Spinning: PEEK resin with melt flow rate (MFR) of 38 g / 10 min was dried at 140 °C under vacuum for 6 h. The dried PEEK resin was fed into a screw extruder. The temperature settings of the screw extruder were as follows: Zone 1 (feed section) 350 °C, Zone 2 (compression section) 370 °C, Zone 3 (metering section) 385 °C, die and spinneret 390 °C. The melt was extruded through a 390 °C spinneret after metering. The spinneret had a diameter of 0.3 mm and a length to diameter ratio of 4:1. The extruded fiber passed through a gradient cooling device with a total length of 35 cm. The lengths of the upper, middle and lower sections were 10 cm, 15 cm and 10 cm, respectively. The temperatures of the upper, middle and lower sections were 390 °C, 350 °C and 250 °C, respectively. The fiber spent 0.29 s in each section of the gradient cooling device (by controlling the godet, the running speed of the nascent fiber in the gradient cooling device was stabilized at 1.2 m / s). Subsequently, the fiber entered a cooling air box at 25 °C for solidification.

[0021] S2 Drawing and setting: The cooled fiber was subjected to a stepwise thermal drawing. The first drawing was performed at 160 °C with a draw ratio of 2.5. The second drawing was performed at 280 °C with a draw ratio of 1.2. Finally, the fiber was subjected to a relaxation heat setting at 250 °C for 2 s to obtain the PEEK fiber for hydrogen separation membrane.

[0022] The PEEK fiber monofilament prepared by this process had a smooth surface and uniform structure. The diameter of the PEEK fiber monofilament was 25 ± 2 μm, and the strength was 6.8 cN / dtex.

[0023] Second part: Preparation of PEEK fabric for hydrogen separation membrane S3 Fabric preparation: Subsequently, the PEEK fiber monofilament prepared in step S2 was woven on a loom according to the specifications of plain weave, warp density of 60 ends / cm and weft density of 55 ends / cm to obtain a PEEK fabric with an areal density of 45 g / m 2 and a thickness of 55 μm.

[0024] S4 Hydrophilic treatment of fabric (controlled surface sulfonation): The PEEK fabric was immersed in 90 wt% concentrated sulfuric acid and treated by gentle shaking in a constant temperature water bath at 30 °C for 90 s. After treatment, the fabric was immediately removed and repeatedly rinsed with deionized water until the rinse water was neutral. Subsequently, the fabric was completely dried in an oven at 60 °C to obtain a hydrophilic PEEK fabric. The sulfonation layer depth of the hydrophilic PEEK fabric was about 0.8 μm as measured by scanning electron microscopy (SEM) cross-section analysis.

[0025] Third part: Preparation of composite membrane for PEM S5 Composite membrane preparation: The hydrophilic PEEK fabric obtained in step S4 was completely immersed in 12 wt% Nafion ®D520 dispersion (Dupont) for 10 min to ensure full wetting. Then pulled out at a constant speed, the wet film thickness was precisely controlled using a doctor blade, and then dried and cured by programmed temperature, first dried at 80 °C for 1 h, then transferred to a 120 °C vacuum oven for 4 h to completely remove the solvent and form a dense composite structure, obtaining a composite hydrogen production membrane for PEM with a final thickness of 60 ± 3 μm.

[0026] Example 2 A PEEK fiber and substrate for AEM hydrogen production membrane and composite membrane The PEEK fiber and substrate preparation steps of this example are the same as steps S1 to S4 of Example 1, the difference is that the preparation method of S5 composite membrane preparation is: the hydrophilic PEEK substrate obtained in step S4 is completely immersed in a 20 wt% DMSO solution of AEM-1 type polyarylether sulfone anion exchange resin for 10 min. Then pulled out at a constant speed, the wet film thickness was precisely controlled using a doctor blade, and then dried and cured by programmed temperature, dried at 80 °C for 12 h to completely remove the DMSO solvent, obtaining a composite hydrogen production membrane for AEM with a final thickness of 60 ± 3 μm.

[0027] Example 3 Performance test of hydrogen production membrane The following comparative examples of membranes were simultaneously explored and tested in the performance test of hydrogen production membrane: (1) PEM hydrogen production membrane of Comparative Example 1: The hydrogen production membrane of this comparative example was prepared by basically the same method as Example 1, the only difference being that no sulfonation treatment was performed (step S4 was omitted).

[0028] (2) AEM hydrogen production membrane of Comparative Example 1: The hydrogen production membrane of this comparative example was prepared by basically the same method as Example 2, the only difference being that no sulfonation treatment was performed (step S4 was omitted).

[0029] (3) SPEEK homogeneous membrane of Comparative Example 2: a homogeneous membrane prepared according to the method of the reference. The preparation method is as follows: SPEEK resin (sulfonated PEEK resin) preparation: 10 g of VESTAKEEP® 4000G PEEK resin was slowly added to 100 mL of 98 wt% concentrated sulfuric acid, and the reaction was continuously mechanically stirred at 50 °C oil bath for 3 h. After the reaction was completed, the mixture was poured into a large amount of ice water to precipitate a yellow fibrous precipitate, which was washed repeatedly with deionized water until the water phase was neutral. The obtained solid was dried at 60 °C under vacuum for 48 h, obtaining a SPEEK resin with a sulfonation degree (DS) of about 60%.

[0030] Membrane formation: Dry SPEEK resin was dissolved in DMF (dimethylformamide) to prepare a 15 wt% casting solution. After degassing, the solution was cast on a flat glass plate and slowly dried in an oven at 80 °C for 24 h, followed by vacuum treatment at 100 °C for 6 h. After cooling, the homogeneous membrane with a thickness of about 60 ± 3 pm was peeled off.

[0031] (4) PP separator of Comparative Example 3: Commercially available PP separator, Celgard 3501 dry-laid uniaxially stretched polypropylene microporous membrane was directly used as a comparative sample.

[0032] (5) PEM hydrogen production separator of Comparative Example 4: The hydrogen production separator of this comparative example was prepared by the same method as in Example 1, except that the gradient slow cooling device was not used in step S1. After the melt stream left the spinneret (390 °C), it was directly exposed to room temperature air and immediately entered the 25 °C cooling air box for quenching. The obtained filament surface was slightly whitened, and the skin-core structure was visible under a microscope. Its diameter was the same as that of Example 1, but the strength was only 5.2 cN / dtex.

[0033] (6) AEM hydrogen production separator of Comparative Example 4: The hydrogen production separator of this comparative example was prepared by the same method as in Example 2, except that the gradient slow cooling device was not used in step S1. After the melt stream left the spinneret (390 °C), the upper, middle and lower three sections of the slow cooling device were 300 °C, 300 °C and 250 °C, respectively, and then the fiber entered the 25 °C cooling air box for solidification. The obtained filament surface was slightly whitened, and the skin-core structure was visible under a microscope. Its diameter was the same as that of Example 1, but the strength was only 5.2 cN / dtex.

[0034] The following indicators were tested and compared in the performance test of the hydrogen production separator: (1) Area resistance: AC impedance method was used, PEM WE simulation environment was 0.5 M H2SO4 solution, 80 °C. AEM WE simulation environment was 1 M KOH solution, 60 °C. The resistance value of a certain area of the separator at a frequency of 1 kHz was measured by an electrochemical workstation. The difference between the blank solution resistance without the separator and the resistance of the separator was calculated to obtain the area resistance of the separator, unit: Ω·cm 2 .

[0035] (2) Gas tightness: tested by differential pressure method, expressed in unit of millimeters of water column (mm H2O), indicating the comprehensive ability of the separator to block hydrogen and oxygen. The higher the value, the better the barrier performance of the separator to hydrogen and oxygen.

[0036] (3) Tensile strength: tested according to standard GB / T 3923.1-2013 Textiles - Determination of tensile resistance - Part 1 : determination of breaking force and elongation at break (strip method). The membrane sample was cut into a specified size, and the breaking force was measured on a universal material testing machine, and the tensile strength (unit: MPa) was calculated.

[0037] (4) Strength retention rate after 2000h: the calculation formula is: Strength retention rate (%) = (average tensile strength of the sample after aging / average tensile strength of the sample before aging) x 100%. Each data point is the average value of at least 5 parallel samples.

[0038] (5) Fenton test: according to the commonly used method in the literature, the membrane sample was immersed in a 4 ppm Fe 2+ solution of 3% H2O2 at 80°C for 24 hours. The oxidative weight loss rate was calculated by testing the change in dry weight of the sample before and after the test, to evaluate the oxidation resistance of the membrane in the PEM anode harsh environment.

[0039] (6) Ion exchange capacity (IEC) retention rate: the IEC values of the membrane before and after the durability test were tested according to the standard method (such as titration method), and the retention rate was calculated to evaluate the stability of the functional groups in the AEM membrane in the alkaline environment.

[0040] The performance of different membranes under two hydrogen production method conditions (PEM simulation condition (0.5M H2SO4, 80°C) and AEM simulation condition (1M KOH, 60°C)) was tested respectively. The results are shown in Tables 1 and 2, respectively.

[0041] Table 1 Performance of different membranes under PEM simulation conditions

[0042] Table 2 Performance of different membranes under AEM simulation conditions

[0043] N / A: The material of Comparative Example 3 itself does not have ion exchange function, and is not suitable for determining ion exchange capacity (IEC) and its retention rate.

[0044] Comparing the data of the comparative example with that of Comparative Example 4, it can be clearly found that the air tightness (>8000 mm H2O) and mechanical strength (above 43 MPa) of the PEEK fiber, base cloth and composite membrane prepared by using the three-gradient slow cooling process are significantly better than those of the sample without slow cooling process (air tightness ~5000 mm H2O, strength below 33 MPa). This proves that the slow cooling process can eliminate internal stress and micro defects, and build a more dense and strong PEEK skeleton structure. At the same time, the surface resistance of Comparative Example 4 is also higher than that of the embodiment, which may be due to the uneven fiber structure affecting the uniform impregnation of the resin and the formation of ion transmission channels.

[0045] All PEEK membrane samples (Examples 1, 2, Comparative Examples 1, 4) exhibit air tightness (>8000 mm H2O) far exceeding that of Comparative Examples 2 and 3, which indicates that the plain weave structure and the design of specific warp and weft density successfully build a dense and stable high-strength PEEK skeleton layer with excellent gas barrier ability.

[0046] In the PEM environment (Table 1), the present application (Example 1) significantly reduces the surface resistance by 50% compared with Comparative Example 1 by surface sulfonation of the base cloth, without sacrificing air tightness and mechanical strength. In the AEM environment (Table 2), it is also observed that the surface resistance of the present application (Example 2) is reduced by about 46% compared with Comparative Example 1, and the air tightness remains at the same extremely high level. This proves that the surface sulfonation treatment can effectively improve the interfacial hydrophilicity and ion transmission efficiency in both acidic and alkaline environments, without damaging the inherent density of the PEEK skeleton layer.

[0047] Compared with Comparative Example 2 (SPEEK homogeneous membrane), in two test environments, the membrane of the present application has more than 4 times higher air tightness (>8000 vs less than 1800) and about 70-80% higher mechanical strength (Example 1: 0.19 vs 0.15; Example 2: 0.22 vs 0.18) under similar surface resistance, which strongly proves that the composite structure of "specifically treated high-strength PEEK skeleton + surface functional layer" achieves a performance balance that homogeneous materials cannot achieve, and solves the industry problem.

[0048] Compared with Comparative Example 3 (commercial PP), the present application not only has an absolute advantage in chemical stability, but also has much higher air tightness than the commercial PP membrane (>8000 vs about 3200-3500), showing comprehensive performance advantages throughout the life cycle.

[0049] By comparison with Comparative Example 4, it is proved that the three-gradient slow cooling process adopted in the present application is not a routine step, but a key and necessary technical feature to achieve high-performance separator. It ensures that the PEEK skeleton can fully exert its material potential, thus producing a synergistic effect with the surface functional layer, and finally obtaining a composite separator with excellent comprehensive performance.

[0050] More importantly, in the long-term durability test (strength retention rate after 2000h), the sample of Comparative Example 2 swelled, became brittle and even broke in both acidic and alkaline environments, with a strength retention rate of less than 60%. This is because the entire structure is composed of sulfonated polymers, and the hydrophilic sulfonic acid group absorbs a large amount of water, leading to plasticization and accelerating chemical degradation. However, the present application benefits from the non-sulfonated PEEK core layer, which maintains excellent chemical stability and mechanical integrity, with a strength retention rate of more than 90%.

[0051] As can be seen, although the skilled in the art usually chooses to increase the sulfonation degree of the material (such as Comparative Example 2) to improve the hydrophilicity and reduce the resistance of the material, this will inevitably lead to a decrease in mechanical properties and durability. The present application surprisingly achieves the unification of low resistance, high air tightness, high strength and long life through the composite structure of high-strength PEEK skeleton (ring cooling process to ensure durability) + extremely thin surface sulfonated layer (to ensure conductivity).

Claims

1. A PEEK fiber for a diaphragm for hydrogen production by water electrolysis, characterized by, The preparation method of the PEEK fiber comprises the following steps: spinning: drying the PEEK resin, melt extruding in a screw extruder to prepare a melt, and extruding the melt through a spinneret; the fiber extruded by the spinneret passes through a three-section gradient slow cooling device with a total length of 20-50 cm at a constant speed; the lengths of the upper, middle and lower three sections of the gradient slow cooling device are 5-15 cm, 10-20 cm and 5-15 cm respectively, and the temperatures thereof are 380-395℃, 320-360℃ and 240-290℃ respectively; the time length for the fiber to enter and leave each section of the gradient slow cooling device is 0.1-0.5 s; then the fiber enters a cooling air box at 20-30℃ to be solidified to obtain a cooled fiber; drawing and setting: the cooled fiber is subjected to staged heat drawing, the first stage drawing is carried out at 150-180℃, and the drawing multiple is 2-5 times; the second stage drawing is carried out at 280-320℃, and the drawing multiple is 1.2-1.5 times; finally, relaxation heat setting is carried out at 250-280℃, and the setting time is 1-3 s, to obtain the PEEK fiber for hydrogen production by water electrolysis.

2. The PEEK fiber for a diaphragm of a water electrolysis hydrogen generator according to claim 1, characterized by, In the spinning step, the aperture of the spinneret is 0.1-0.5 mm, and the aspect ratio is (3-5):

1.

3. The PEEK fiber according to claim 1, wherein, In the spinning step, the drying conditions of the PEEK resin are vacuum drying at 120-150℃ for 4-8 h.

4. The PEEK fiber according to claim 1, wherein, In the melt extrusion, the temperature of the screw extruder from the first zone to the head is 340-395℃.

5. A PEEK-based cloth for a hydrogen production diaphragm for water electrolysis, characterized by, The PEEK fabric is prepared from the PEEK fiber for hydrogen production by water electrolysis according to any one of claims 1 to 4, and the PEEK fabric is subjected to sulfonation treatment, and the sulfonation depth is 0.5 ± 0.4 μm.

6. The PEEK-based cloth for water electrolysis hydrogen production diaphragm according to claim 5, characterized in that, The PEEK fabric is plain woven.

7. The PEEK-based cloth for water electrolysis hydrogen production diaphragm according to claim 5, characterized in that, The PEEK fabric has a surface density of 45 ± 2 g / m², a warp density of 60 ± 5 roots / cm, and a weft density of 55 ± 5 roots / cm.

8. The PEEK-based cloth for water electrolysis hydrogen production diaphragm according to claim 5, characterized in that, The PEEK fabric has a thickness of 55 ± 5 μm.

9. Use of the PEEK fiber for hydrogen production by water electrolysis according to any one of claims 1 to 4 or the PEEK fabric for hydrogen production by water electrolysis according to any one of claims 6 to 8 in the preparation of a membrane for hydrogen production by water electrolysis.

10. A separator for hydrogen production by water electrolysis, characterized by, The membrane contains the PEEK fiber for hydrogen production by water electrolysis according to any one of claims 1 to 4 or the PEEK fabric for hydrogen production by water electrolysis according to any one of claims 6 to 8.

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