High-strength double-grid-surface AGM diaphragm and preparation method thereof

Abstract

The invention provides a high-strength double-net-grain-surface AGM diaphragm and a preparation method thereof. The preparation method comprises the following steps: conveying mixed slurry into a wedge-shaped forming area formed by a first forming net and a second forming net which relatively rotate up and down before convergence through a headbox; in the forming area, the mixed slurry is subjected to vacuum dehydration on the back side of a first forming net in the descending direction and is mechanically carded on the net surface of a second forming net in the ascending direction, so that fibers are directionally arranged, and the asymmetric pretreatment of the mixed slurry is realized; and the mixed slurry subjected to asymmetric pretreatment runs to the rear part of a vacuum dehydration section along with the two nets, is clamped by the two joined nets to enter a squeezing part for squeezing dehydration, and is dried to obtain the high-strength double-net-grain-surface AGM diaphragm. According to the scheme, the thickness uniformity, the overall strength and the porosity of the diaphragm are remarkably improved, meanwhile, it is ensured that the two faces of the diaphragm have the same lines and structures, absorption and distribution of electrolyte are more uniform, and the longitudinal tensile strength of the diaphragm is high.

Description

Technical Field

[0001] This invention relates to the field of lead-acid battery separator material technology, and in particular to a high-strength double-textured AGM separator and its preparation method. Background Technology

[0002] With the continuous development of the lead-acid battery industry, the performance of AGM separators, as the "third electrode" of the battery, directly affects the battery's capacity, cycle life, and other performance characteristics.

[0003] In related technologies, AGM separators are generally prepared using a wet papermaking process. During the production process, the forming web is mainly formed by a combination of vacuum dehydration on the front side and gravity stacking on the back side. This results in an overly dense fiber distribution on the front side of the separator, while the fiber structure on the back side is relatively loose. Consequently, the mechanical properties, pore distribution, and electrolyte retention capacity of the front and back sides of the separator are unbalanced during use, which in turn has an adverse effect on the overall stability of the battery performance.

[0004] Furthermore, during the production process, there is significant lateral flow of the slurry in the headbox, which reduces the longitudinal arrangement of fibers and results in a disordered fiber distribution. This not only makes the separator prone to low longitudinal tensile strength during battery assembly and cycling, but also affects its overall structural uniformity, thereby reducing the durability and dimensional stability of the separator during cyclic use.

[0005] Therefore, there is an urgent need to provide a high-strength double-textured AGM membrane and its preparation method. Summary of the Invention

[0006] This invention provides a high-strength double-textured AGM membrane and its preparation method, which can solve the problems of significant differences in structure between the two sides, disordered fiber distribution, and poor longitudinal strength of existing AGM membranes.

[0007] In a first aspect, the present invention provides a method for preparing a high-strength double-textured AGM membrane, the method comprising the following steps: (1) Coarse glass fiber, fine glass fiber, organic fiber and water are mixed and decomposed to obtain a mixed slurry; (2) The mixed slurry is conveyed to the forming area through a headbox; wherein the forming area is the area formed by the first forming mesh and the second forming mesh rotating relative to each other before they merge, and a wedge-shaped area is formed between the first forming mesh and the second forming mesh; (3) In the forming area, the mixed slurry is vacuum dewatered on the back side of the downward first forming mesh, and mechanically combed on the surface of the upward second forming mesh to make the fibers oriented, so as to achieve asymmetric pretreatment of the mixed slurry. (4) The mixed slurry after the asymmetric pretreatment runs with the first forming net and the second forming net to the back of the vacuum dewatering section, and is clamped by the first forming net and the second forming net to enter the pressing section for pressing and dewatering. After drying, the high-strength double-textured AGM diaphragm is obtained.

[0008] Preferably, in step (1), the diameter of the coarse glass fiber is 0.1~1μm, the diameter of the fine glass fiber is 2~5μm, and the length is 1~10mm; the organic fiber is polypropylene fiber, polyethylene fiber, polyethylene terephthalate fiber, or core-sheath bicomponent fiber.

[0009] Preferably, in step (1), the mass ratio of coarse glass fiber, fine glass fiber and organic fiber is (80~90):(5~15):(5~15).

[0010] Preferably, the mixing and dissolving process also includes the step of adding 75% concentrated sulfuric acid, with the acid addition time being 4-5 seconds and the mixing and dissolving time being 5-10 minutes.

[0011] Preferably, in step (1), the concentration of the mixed slurry is 0.3~0.8%.

[0012] Preferably, in step (2), before conveying the mixed slurry to the forming area through the headbox, the position of the inlet section of the second forming mesh is adjusted by changing the vertical height of the drive roller supporting or tensioning the second forming mesh, so as to ensure that the mesh surface of the second forming mesh is consistent with the waterline position of the mixed slurry.

[0013] Preferably, the headbox is located in front of the wedge-shaped area formed before the first forming mesh and the second forming mesh merge.

[0014] Preferably, the first forming wire and the second forming wire are a synchronously operating annular belt structure. In the wedge forming area, the first forming wire and the second forming wire are separated and maintain a predetermined distance. After the vacuum dewatering section downstream of the wedge forming area, the first forming wire and the second forming wire merge to clamp the mixed pulp. In the path up to the press section, the first forming wire and the second forming wire keep in contact and clamp the wet paper web synchronously.

[0015] Preferably, the first formed mesh is a monofilament twill woven mesh structure, wherein the woven mesh structure is formed by warp monofilaments and weft monofilaments interlaced in two-up-one-down arrangements.

[0016] More preferably, the diameter of the weft monofilament is 0.4~0.5mm, and the diameter of the warp monofilament is 0.2~0.3mm.

[0017] Preferably, the second forming net is a monofilament plain weave mesh structure, which is formed by warp monofilaments and weft monofilaments interlaced one above the other.

[0018] More preferably, the diameter of the warp monofilament and the weft monofilament is 0.12~0.15mm.

[0019] Preferably, the pressing section includes a pair of opposing pressure rollers, which are located on the operating back sides of the first forming mesh and the second forming mesh, respectively.

[0020] Preferably, the vacuum dehydration is accomplished using a vacuum water suction device located below the first forming mesh.

[0021] Preferably, in step (3), the drying process includes pre-drying and gradient drying in sequence; wherein the temperature of the pre-drying is 100~110℃, and the temperature of the gradient drying is 110~115℃, 120~125℃, and 110~115℃ in sequence.

[0022] Secondly, embodiments of the present invention also provide a high-strength double-textured AGM membrane, which is prepared by the preparation method described in any one of the first aspects above.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects: In this invention, the prepared mixed slurry is conveyed to a wedge-shaped forming area formed by a first forming mesh and a second forming mesh rotating in opposite directions. Within this forming area, the downward-moving first forming mesh performs back-side vacuum dewatering, while the upward-moving second forming mesh mechanically combs the fibers, causing the fibers to oriented along the direction of the long mesh movement, effectively preventing fiber agglomeration, thereby ensuring a uniform distribution of fibers and microporous structure within the membrane. Subsequently, the mixed slurry travels with the first and second forming meshes to the rear of the vacuum dewatering section, where it is clamped by the converging double meshes for pressing dewatering and drying, resulting in a high-strength double-textured AGM membrane. Thus, during the molding process, the fiber orientation and distribution are fundamentally optimized through the synergistic effect of the first and second molding meshes. This significantly improves the uniformity of the separator thickness, overall strength, and porosity, while ensuring that both sides of the separator have the same texture and structure. This fundamentally avoids the uncertainty of battery performance caused by differences between the two sides, making the absorption and distribution of electrolyte more uniform and improving the mechanical adaptability and reliability of the separator during battery assembly and unwinding. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a diagram of the molding apparatus used in a high-strength double-textured AGM diaphragm provided in an embodiment of the present invention; In the diagram, 100 is the headbox, 200 is the forming area, 201 is the first forming screen, 202 is the second forming screen, 203 is the vacuum dewatering device, 300 is the pressing section, 301 is the pressing section roller, 400 is the finishing roller, and 500 is the forced vacuum device. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] This invention provides a method for preparing a high-strength double-textured AGM membrane, which includes the following steps: (1) Coarse glass fiber, fine glass fiber, organic fiber and water are mixed and decomposed to obtain a mixed slurry; (2) The mixed slurry is conveyed to the molding area 200 through the headbox 100; wherein the molding area 200 is the area formed by the first molding net 201 and the second molding net 202 rotating relative to each other before they merge, and a wedge-shaped area is formed between the first molding net 201 and the second molding net 202. (3) In the forming area 200, the mixed slurry is vacuum dehydrated on the back side of the downward first forming net 201, and mechanically combed on the surface of the upward second forming net 202 to make the fibers oriented, so as to achieve asymmetric pretreatment of the mixed slurry. (4) The mixed slurry after the asymmetric pretreatment runs with the first forming net 201 and the second forming net 202 to the back of the vacuum dewatering section, and is clamped by the first forming net 201 and the second forming net 202 and enters the pressing section 300 for pressing and dewatering. After drying, the high-strength double-textured AGM diaphragm is obtained.

[0028] In embodiments of the present invention, such as Figure 1 As shown, the prepared mixed slurry is conveyed into a wedge-shaped forming region 200 formed by a first forming mesh 201 and a second forming mesh 202 rotating in opposite directions. In this forming region 200, the downward-moving first forming mesh 201 performs back-side vacuum dewatering, while the upward-moving second forming mesh 202 mechanically combs the fibers to orient them along the direction of the long mesh, effectively preventing fiber agglomeration and resulting in a uniform distribution of fibers and microporous structure in the membrane. Subsequently, the mixed slurry travels with the first forming mesh 201 and the second forming mesh 202 to the rear of the vacuum dewatering section, where it is clamped by the converging double meshes for pressing dewatering and drying, resulting in a high-strength double-textured AGM membrane. Thus, during the molding process, the fiber orientation and distribution are fundamentally optimized through the synergistic effect of the first molding mesh 201 and the second molding mesh 202. This significantly improves the uniformity of the separator thickness, overall strength, and porosity, while ensuring that both sides of the separator have the same texture and structure. This fundamentally avoids the uncertainty of battery performance caused by differences between the two sides, making the absorption and distribution of electrolyte more uniform and improving the mechanical adaptability and reliability of the separator during battery assembly and unwinding.

[0029] According to some preferred embodiments, in step (1), the diameter of the coarse glass fiber is 0.1~1μm (for example, it can be 0.1μm, 0.5μm, 0.8μm or 1.0μm), the diameter of the fine glass fiber is 2~5μm (for example, it can be 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm or 5μm), and the length is 1~10mm (for example, it can be 1mm, 2mm, 5mm, 8mm or 10mm); the organic fiber is polypropylene fiber, polyethylene fiber, polyethylene terephthalate fiber or core-sheath type bicomponent fiber.

[0030] According to some preferred embodiments, in step (1), the mass ratio of coarse glass fiber, fine glass fiber and organic fiber is (80~90):(5~15):(5~15) (for example, it can be 80:10:10, 80:15:5, 85:10:5, 90:5:5 or 80:5:15); the mixing and dissolving process also includes the step of adding 75% concentrated sulfuric acid, the acid addition time is 4~5s (for example, it can be 4s or 5s), and the mixing and dissolving time is 5~10min (for example, it can be 5min, 8min or 10min).

[0031] In this embodiment of the invention, two types of glass fibers with different diameters are mixed with organic fibers for wet papermaking. The coarse and fine glass fibers have different degrees of beating (22-26° for coarse fibers and 36-40° for fine fibers). The glass fibers with different degrees of beating are mixed into a pulp according to a specific ratio, fed into a descaling machine for descaling, and dispersed with 75% concentrated sulfuric acid by mass. This facilitates the acquisition of a highly dispersed, uniform, and stable mixed pulp. By precisely controlling the ratio of different fibers and the forming process parameters, the low-beating-degree coarse glass fibers serve as the diaphragm skeleton, providing support and strength; the high-beating-degree fine glass fibers act as filler, fully filling the skeleton network. The two fibers, together with the organic fibers, intertwine to form a three-dimensional network, which helps improve the overall performance of the diaphragm.

[0032] According to some preferred embodiments, in step (1), the concentration of the mixed slurry is 0.3~0.8% (for example, it can be 0.3%, 0.5% or 0.8%).

[0033] In this embodiment of the invention, the slurry after dewatering undergoes a slurry preparation and slag removal process to remove heavy impurities, forming a mixed slurry of the aforementioned concentration. This slurry is then stored in a slurry tank for later use. During production, the slurry is lifted to a high-level tank by a high-level slurry pump and then flows smoothly into the subsequent molding stage under gravity. The mixed slurry of the aforementioned concentration has high fluidity. This characteristic, combined with the vacuum dehydration and synergistic combing effect of the first molding mesh 201 and the second molding mesh 202 on the fibers, ensures the uniform distribution of the slurry on the molding mesh. At the same time, it effectively avoids the compression and destruction of the pore structure inside the fibers in the early stage of molding, thereby facilitating the acquisition of a high-performance diaphragm.

[0034] According to some preferred embodiments, in step (2), before the mixed slurry is conveyed to the forming area 200 through the headbox 100, the position of the inlet section of the second forming net 202 is adjusted by changing the vertical height of the drive roller supporting the second forming net 202, so as to ensure that the net surface of the second forming net 202 is consistent with the water line position of the mixed slurry.

[0035] In this embodiment of the invention, before the mixed slurry is conveyed into the forming area 200, the height of the inlet section in front of the second forming net 202 is adjusted by changing the vertical height of the drive roller supporting the second forming net 202. This makes the net surface of the second forming net 202 and the water line of the slurry on the same horizontal line. This allows the second forming net 202 to apply the most effective combing force to the fibers, maximize the longitudinal arrangement ratio of the fibers, thereby improving the longitudinal tensile strength of the diaphragm and significantly reducing structural weak points caused by disordered fiber distribution or agglomeration.

[0036] According to some preferred embodiments, the headbox 100 is located in front of the wedge-shaped region formed by the first forming wire 201 and the second forming wire 202 before they merge; the first forming wire 201 and the second forming wire 202 are synchronously operating annular belt structures. Within the wedge-shaped forming region 200, the first forming wire 201 and the second forming wire 202 are separated and maintain a predetermined distance. Downstream of the wedge-shaped forming region 200, behind the vacuum dewatering section, the first forming wire 201 and the second forming wire 202 merge to clamp the mixed pulp. Along the path up to the press section 300, the first forming wire 201 and the second forming wire 202 remain in contact and clamp the wet paper web synchronously.

[0037] In embodiments of the present invention, such as Figure 1 As shown, the headbox 100 is located at the front end of the forming wire. After the pulp is output from the headbox 100, it contacts the forming wire to begin dewatering and is conveyed forward along the direction of the forming wire's movement. It enters a wedge-shaped area formed by the relative rotation of the second forming wire 202 (located above the first forming wire 201) and the first forming wire 201. In this area, the first forming wire 201 mainly undertakes the dewatering function, while the second forming wire 202 mechanically combs the fibers, orienting them along the direction of the paper machine's movement. This effectively reduces the transverse and oblique distribution of fibers, increases the longitudinal distribution ratio, and directly enhances the longitudinal strength of the diaphragm. At the same time, the second forming wire 202 combs the surface of the pulp to make the diaphragm surface smooth and uniform in texture, reducing the generation of lumps on the diaphragm surface and ensuring the consistency of thickness. Subsequently, behind the vacuum dewatering section, the two forming wires converge and clamp the pulp, subjecting it to symmetrical compression and dewatering from both directions. Finally, it enters the press section 300 and is pressed and shaped by the pressure roller 301 to obtain a wet web with a uniform structure.

[0038] According to some preferred embodiments, the first formed mesh 201 is a monofilament twill woven mesh structure, wherein the woven mesh structure is formed by warp monofilaments and weft monofilaments interlaced in a two-up-one-down manner; the diameter of the weft monofilament is 0.4~0.5mm (for example, it can be 0.4mm, 0.45mm or 0.5mm), and the diameter of the warp monofilament is 0.2~0.3mm (for example, it can be 0.2mm, 0.25mm or 0.3mm).

[0039] According to some preferred embodiments, the second forming net 202 is a monofilament plain weave mesh structure, which is formed by warp monofilaments and weft monofilaments interlaced one over the other; the diameter of the warp monofilaments and weft monofilaments is 0.12~0.15mm (for example, it can be 0.12mm, 0.13mm, 0.14mm or 0.15mm).

[0040] Furthermore, considering that the weave pattern of the forming wire can significantly affect fiber retention, dewatering efficiency, and the surface area and internal structure of the final wet paper web, in this embodiment of the invention, the weave pattern of the forming wire is specifically optimized. Specifically, the second forming wire 202 adopts a warp and weft monofilament twill weave structure, in which the warp and weft monofilaments are arranged obliquely in a continuous two-up-one-down interlacing manner to form an oblique pattern. By controlling the diameter of the warp and weft monofilaments, the resulting woven wire structure not only facilitates rapid water passage and has high drainage performance, but also effectively reduces the lateral flow of fibers, achieving a more uniform dewatering pressure distribution. At the same time, the first forming wire 201 adopts a monofilament plain weave structure, in which the warp and weft monofilaments are arranged in a regular one-up-one-down interlacing manner. By matching and controlling the diameter of the warp and weft monofilaments, the resulting woven wire structure significantly improves the flatness of the wire surface while ensuring drainage efficiency, thereby facilitating better fiber combing and ensuring the flatness of the paper web.

[0041] According to some preferred embodiments, the pressing section 300 includes a pair of opposing pressure rollers, which are respectively located on the operating back sides of the first forming screen 201 and the second forming screen 202; the vacuum dewatering is accomplished by a vacuum suction device 203 disposed below the first forming screen 201.

[0042] In this embodiment of the invention, after the vacuum dewatering section, two forming wires converge and clamp the pulp, and enter the press section 300 to be subjected to symmetrical squeezing and dewatering from two bidirectional pressure rollers. Then, the paper is further decorated by the finishing roller 400, and then undergoes secondary vacuum dewatering by the forced vacuum device 500 to obtain a wet web with a uniform structure.

[0043] According to some preferred embodiments, in step (3), the drying process includes pre-drying and gradient drying in sequence; wherein the temperature of the pre-drying is 100~110℃ (for example, it can be 100℃, 105℃ or 110℃), and the temperature of the gradient drying is 110~115℃ (for example, it can be 100℃, 105℃ or 110℃), 120~125℃ (for example, it can be 120℃, 122℃ or 125℃), and 110~115℃ (for example, it can be 110℃, 110℃ or 115℃).

[0044] In this embodiment of the invention, the wet paper web is first pre-dried and shaped, then continues to enter the drying section for gradient temperature drying, and finally the dried diaphragm product is cut into fixed widths to obtain a double-textured AGM diaphragm.

[0045] This invention also provides a high-strength double-textured AGM membrane, which is prepared using any of the above-described preparation methods.

[0046] In this embodiment of the invention, a first forming mesh and a second forming mesh are used for asymmetric pretreatment during the preparation of the AGM separator, which effectively solves the problem of uneven fiber layer distribution in the traditional forming method, thereby preparing a separator with high strength and uniform texture on both sides. The fiber and microporous structure of the obtained AGM separator are highly uniformly distributed throughout the separator, which not only ensures more uniform absorption and distribution of electrolyte in the battery, but also enables the separator to maintain high porosity while maintaining excellent thickness uniformity. This successfully solves the two contradictory points that the separator cannot simultaneously achieve structural uniformity and stability and maintain high porosity.

[0047] To more clearly illustrate the technical solution and advantages of the present invention, the following describes in detail a high-strength double-textured AGM membrane and its preparation method through several embodiments.

[0048] Example 1: (1) High-alkali coarse glass fiber (diameter 0.6μm), high-alkali coarse glass fiber (diameter 2.2μm), organic fiber (diameter 2D, PET / PET sheath-core type bicomponent fiber (sheath melting point 120℃, core melting point 200℃) were added to water and mixed and dissolved for 9 min to prepare slurries with different degrees of dissolution (coarse fiber 26°, fine fiber 40°). Then, they were mixed and added to deionized water containing 75% concentrated sulfuric acid (acid concentration 2.5%) for 10 s to disperse and obtain a mixed slurry with a concentration of 0.8%. Then, water was added to prepare a mixed sizing slurry with a concentration of 3.2‰ and the mixed sizing slurry was stored in a slurry tank for later use. The mass ratio of coarse glass fiber, coarse glass fiber and organic fiber was 85:10:5. (2) Adjust the position of the inlet section of the second forming screen by changing the vertical height of the drive roller supporting the second forming screen, so as to ensure that the screen surface of the second forming screen is consistent with the water line of the mixed slurry, and pass the mixed slurry through the headbox at a speed of 55m. 3 The slurry flow rate is / h and it is delivered to the wedge-shaped forming area formed by the first forming net and the second forming net rotating in opposite directions before they merge; wherein, the speed of the long net is 6.5m / min; the first forming net is a monofilament twill woven net structure formed by two upper and one lower interlacing warp monofilaments (diameter of 0.4mm) and weft monofilaments (diameter of 0.2mm); the second forming net is a monofilament plain woven net structure formed by one upper and one lower interlacing warp monofilaments (diameter of 0.12mm) and weft monofilaments (diameter of 0.12mm). (3) In the forming area, the mixed slurry is vacuum dewatered on the back side of the first forming mesh going downwards, and mechanically combed on the surface of the second forming mesh going upwards, so that the fibers are oriented and arranged in a direction, so as to achieve asymmetric pretreatment of the mixed slurry. (4) The mixed slurry after asymmetric pretreatment runs with the first forming net and the second forming net to the back of the vacuum dewatering section, and is clamped by the first forming net and the second forming net to enter the pressing section for pressing and dewatering. Then, it is first pre-dried at 100°C, and then dried at 110°C, 120°C and 115°C in sequence to obtain a high-strength double-textured AGM diaphragm.

[0049] In this embodiment, the thickness of the fabricated double-textured AGM separator is 1.45 mm (20 kPa), the process capability index (cpk) for thickness is 1.32, and the basis weight is 160 g / m³. 2 With a diameter of 1.3 mm, longitudinal strength of 1.3 KN / m, transverse strength of 0.8 KN / m, and porosity of 91%, it has high porosity and high tensile strength, which can adapt to the stretching during battery assembly and has good stability and consistency inside the battery.

[0050] Example 2: (1) High-alkali coarse glass fiber (0.6 μm in diameter) and high-alkali coarse glass fiber (2.2 μm in diameter) were added to water and mixed and dissolved for 9 min to prepare slurries with different degrees of dissolution (coarse fiber 26°, fine fiber 40°). Then, they were mixed and added to deionized water containing 75% concentrated sulfuric acid (acid concentration of 2.5%) for 10 s to disperse and obtain a mixed slurry with a concentration of 0.8%. Then, water was added to prepare a mixed sizing slurry with a concentration of 3.2‰. The mixed sizing slurry was stored in a slurry storage tank for later use. The mass ratio of coarse glass fiber, coarse glass fiber and organic fiber was 65:35. (2) Adjust the position of the inlet section of the second forming screen by changing the vertical height of the drive roller supporting the second forming screen, so as to ensure that the screen surface of the second forming screen is consistent with the water line of the mixed slurry, and pass the mixed slurry through the headbox at a speed of 55m. 3 The slurry flow rate is / h and it is delivered to the wedge-shaped forming area formed by the first forming net and the second forming net rotating in opposite directions before they merge; wherein, the speed of the long net is 5.2m / min; the first forming net is a monofilament twill woven net structure formed by two upper and one lower interlacing warp monofilaments (diameter of 0.5mm) and weft monofilaments (diameter of 0.3mm); the second forming net is a monofilament plain woven net structure formed by one upper and one lower interlacing warp monofilaments (diameter of 0.15mm) and weft monofilaments (diameter of 0.15mm). (3) In the forming area, the mixed slurry is vacuum dewatered on the back side of the first forming mesh going downwards, and mechanically combed on the surface of the second forming mesh going upwards, so that the fibers are oriented and arranged in a direction, so as to achieve asymmetric pretreatment of the mixed slurry. (4) The mixed slurry after asymmetric pretreatment runs with the first forming net and the second forming net to the back of the vacuum dewatering section, and is clamped by the first forming net and the second forming net to enter the pressing section for pressing and dewatering. Then, it is first pre-dried at 100°C, and then dried at 110°C, 120°C and 115°C in sequence to obtain a high-strength double-textured AGM diaphragm.

[0051] In this embodiment, the prepared double-textured AGM separator has a thickness of 1.1 mm (10 kPa), a thickness cpk of 1.35, and a basis weight of 155 g / m³. 2 The membrane has a diameter of 0.95 mm, a longitudinal strength of 0.95 kN / m, a transverse strength of 0.6 kN / m, a porosity of 93.5%, and a smooth surface without protrusions.

[0052] Example 3: Example 3 is basically the same as Example 1, except that in step (2), both the first and second forming nets are monofilament plain weave net structures formed by warp monofilaments (0.15mm in diameter) and weft monofilaments (0.15mm in diameter) interlaced one above the other.

[0053] In this embodiment, the thickness of the prepared double-textured AGM separator is 1.42 (20 kPa), the thickness cpk is 1.48, and the basis weight is 162 g / m³. 2 The longitudinal strength is 1.39 KN / m, the transverse strength is 0.90 KN / m, and the porosity is 91.5%.

[0054] Example 4: Example 4 is basically the same as Example 1, except that both the first forming net and the second forming net adopt a monofilament twill weave structure.

[0055] In this embodiment, the prepared double-textured AGM separator has a thickness of 1.46 (20 kPa), a thickness cpk of 1.37, and a basis weight of 159 g / m³. 2 The membrane has a longitudinal strength of 1.35 KN / m, a transverse strength of 0.83 KN / m, a porosity of 91.3%, and fiber aggregation and protrusions on its surface.

[0056] Comparative Example 1: Comparative Example 1 is basically the same as Example 1, except that in steps (2) and (3), the mixed slurry is passed through a headbox at a speed of 55m. 3 The slurry flow rate is 6.5 m / min, which is delivered to the forming area formed by the first forming screen. In the forming area, the mixed slurry is vacuum dewatered on the back side of the first forming screen.

[0057] In this comparative example, the prepared AGM membrane had a thickness of 1.45 mm (20 kPa), a thickness cpk of 0.98, and a basis weight of 158 g / m³. 2 The membrane has a diameter of 0.56 mm, a longitudinal strength of 0.9 KN / m, a transverse strength of 0.56 KN / m, a porosity of 90%, and protrusions on its surface.

[0058] Comparative Example 2: Comparative Example 2 is basically the same as Example 1, except that in steps (2) and (3), the mixed slurry is passed through a headbox at a speed of 55m. 3 The slurry flow rate is 5.2 m / min, which is delivered to the forming area formed by the first forming screen. In the forming area, the mixed slurry is vacuum dewatered on the back side of the first forming screen.

[0059] In this comparative example, the prepared AGM membrane had a thickness of 1.1 mm (10 kPa), a thickness cpk of 1.05, and a basis weight of 153 g / m³. 2 The membrane has a diameter of 0.5 mm, a longitudinal strength of 0.8 KN / m, a transverse strength of 0.5 KN / m, a porosity of 91.5%, and small protrusions on the surface of the membrane caused by fiber aggregation.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-strength double-textured AGM membrane, characterized in that, The preparation method includes the following steps: (1) Coarse glass fiber, fine glass fiber, organic fiber and water are mixed and decomposed to obtain a mixed slurry; (2) The mixed slurry is conveyed to the forming area through a headbox; wherein the forming area is the area formed by the first forming mesh and the second forming mesh rotating relative to each other before they merge, and a wedge-shaped area is formed between the first forming mesh and the second forming mesh; (3) In the forming area, the mixed slurry is vacuum dewatered on the back side of the downward first forming mesh, and mechanically combed on the surface of the upward second forming mesh to make the fibers oriented, so as to achieve asymmetric pretreatment of the mixed slurry. (4) The mixed slurry after the asymmetric pretreatment runs with the first forming net and the second forming net to the back of the vacuum dewatering section, and is clamped by the first forming net and the second forming net to enter the pressing section for pressing and dewatering. After drying, the high-strength double-textured AGM diaphragm is obtained.

2. The preparation method according to claim 1, characterized in that, In step (1), the diameter of the coarse glass fiber is 0.1~1μm, the diameter of the fine glass fiber is 2~5μm, and the length is 1~10mm; the organic fiber is polypropylene fiber, polyethylene fiber, polyethylene terephthalate fiber, or core-sheath bicomponent fiber.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of coarse glass fiber, fine glass fiber, and organic fiber is (65~85):(10~35):(0~5); and / or The mixing and dissolving process also includes the step of adding 75% concentrated sulfuric acid, with the acid addition time being 4-5 seconds and the mixing and dissolving time being 5-10 minutes.

4. The preparation method according to claim 1, characterized in that, In step (1), the concentration of the mixed slurry is 0.3~0.8%.

5. The preparation method according to claim 1, characterized in that, In step (2), before conveying the mixed slurry to the molding area through the headbox, the following steps are also included: The position of the inlet section of the second forming mesh is adjusted by changing the vertical height of the drive roller supporting the second forming mesh, so as to ensure that the mesh surface of the second forming mesh is aligned with the water line of the mixed slurry.

6. The preparation method according to claim 1, characterized in that, The headbox is located in front of the wedge-shaped area formed before the first and second forming nets converge; and / or The first forming wire and the second forming wire are a synchronously operating annular belt structure. In the wedge forming area, the first forming wire and the second forming wire are separated and maintain a predetermined distance. After the vacuum dewatering section downstream of the wedge forming area, the first forming wire and the second forming wire merge to clamp the mixed pulp. In the path up to the press section, the first forming wire and the second forming wire keep in contact and clamp the wet paper web synchronously.

7. The preparation method according to claim 1, characterized in that, The first formed mesh is a monofilament twill woven mesh structure, which is formed by warp monofilaments and weft monofilaments interlaced in two-up-one-down arrangements; Preferably, the diameter of the weft monofilament is 0.4~0.5mm, and the diameter of the warp monofilament is 0.2~0.3mm.

8. The preparation method according to claim 1, characterized in that, The second forming net is a monofilament plain weave mesh structure, which is formed by warp monofilaments and weft monofilaments interlaced one above the other; Preferably, the diameter of the warp monofilament and the weft monofilament is 0.12~0.15mm.

9. The preparation method according to claim 1, characterized in that, In step (3), the drying process includes pre-drying and gradient drying in sequence; wherein the temperature of the pre-drying is 100~110℃, and the temperature of the gradient drying is 110~115℃, 120~125℃, and 110~115℃ in sequence.

10. A high-strength double-textured AGM separator, characterized in that, It is prepared by any one of the preparation methods according to claims 1 to 9.

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