Composite fiber bundle, fiber cloth, prepreg, composite board and battery sealing cover

Abstract

The utility model discloses a composite fiber bundle, fiber cloth, prepreg, a composite board and a battery sealing cover, the composite fiber bundle comprises a plurality of fibers extending along the same direction, and the fibers comprise reinforced fibers, low-melting-point thermoplastic fibers and high-melting-point thermoplastic fibers. And the low-melting-point thermoplastic fibers are relatively low in melting point, so that the low-melting-point thermoplastic fibers are relatively easy to melt in the hot-pressing process after being mixed with the reinforced fibers to form the fiber bundles, the reinforced fibers and the resin matrix are relatively well infiltrated, and the transverse strength of the product and the air tightness of the battery sealing cover are improved. The high-melting-point thermoplastic fibers are high in melting point and cannot be completely molten to lose the structure in the hot-pressing process after being mixed with the reinforced fibers to form the fiber bundles, so that the toughness and strength of the fiber bundles in the hot-pressing process are guaranteed, the fiber bundles cannot be broken in the mold pressing and stretching process, and the structural stability of the product is guaranteed.

Description

Composite fiber bundles, fiber cloth, prepreg, composite boards, battery sealing caps Technical Field

[0001] This utility model relates to the fields of textile and battery technology, specifically to a composite fiber bundle, fiber cloth, prepreg, composite board, and battery sealing cap. Background Technology

[0002] With the increasing demands for energy density and lightweight design of power batteries, power battery sealing covers are gradually moving towards thermoplastic materials. Traditional thermosetting materials have long molding cycles, are brittle, and are prone to hidden cracking. Furthermore, thermosetting materials are not easy to recycle and pose significant environmental risks.

[0003] Currently, thermoplastic materials are mainly prepared using thermoplastic resin-glass fiber prepreg. However, the following major problems exist: On the one hand, thermoplastic resins such as polypropylene (PP) resin have a very high viscosity in the molten state, which makes prepreg preparation of glass fibers poor, especially for woven glass fiber fabrics, making it difficult to completely impregnate them and easily causing local defects that lead to air leakage; on the other hand, after PP resin impregnates glass fibers, the glass fibers are easily torn during the hot pressing of the sheet, resulting in a decrease in local strength or even cracking. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in the related art. Therefore, one objective of this invention is to provide a composite fiber bundle that can improve the wetting effect and ensure the toughness and strength of the fiber bundle during hot pressing.

[0005] Specifically, the first aspect of this utility model provides a composite fiber bundle comprising multiple fibers extending in the same direction, wherein the fibers include reinforcing fibers, low-melting-point thermoplastic fibers, and high-melting-point thermoplastic fibers; the low-melting-point thermoplastic fibers and the high-melting-point thermoplastic fibers are dispersed among the reinforcing fibers; the melting point of the low-melting-point thermoplastic fibers is below 200°C; and the melting point of the high-melting-point thermoplastic fibers is above 240°C.

[0006] Low-melting-point thermoplastic fibers, due to their lower melting point, melt more easily during molding when mixed with reinforcing fibers to form fiber bundles. This allows for better wetting of the reinforcing fibers and resin matrix, improving the transverse strength of the product and the airtightness of the battery sealing cap. High-melting-point thermoplastic fibers, due to their higher melting point, do not completely melt and lose their structure during molding when mixed with reinforcing fibers to form fiber bundles. This ensures the toughness and strength of the fiber bundles during molding, preventing breakage during stretching and guaranteeing the structural stability of the product. In summary, arranging multiple reinforcing fibers, low-melting-point thermoplastic fibers, and high-melting-point thermoplastic fibers along the same extension direction in the same composite fiber bundle ensures that the strength of the composite fiber bundle remains unaffected during the molding process of the battery sealing cap, maintaining structural integrity and good airtightness.

[0007] According to some embodiments of the present invention, the reinforcing fibers, low-melting-point thermoplastic fibers and high-melting-point thermoplastic fibers are arranged in parallel along the same direction.

[0008] According to some embodiments of this utility model, the melting point of the low-melting-point thermoplastic fiber is 120℃-150℃; the low-melting-point thermoplastic fiber includes at least one of polyethylene fiber and polypropylene fiber; the low-melting-point thermoplastic fiber accounts for 5%-15% of the total mass of the composite fiber bundle; the diameter of the low-melting-point thermoplastic fiber is 8μm-12μm.

[0009] According to some embodiments of this utility model, the melting point of the high-melting-point thermoplastic fiber is 240℃-350℃; the high-melting-point thermoplastic fiber includes one or more of polyamide fiber, polyetheretherketone fiber, polyimide fiber, polystyrene fiber, and polytetrafluoroethylene fiber; the high-melting-point thermoplastic fiber accounts for 20%-30% of the total mass of the composite fiber bundle; the diameter of the high-melting-point thermoplastic fiber is less than 10μm.

[0010] According to some embodiments of the present invention, the reinforcing fiber includes at least one of glass fiber and carbon fiber.

[0011] The second aspect of this utility model provides a fiber cloth, which includes the composite fiber bundle of the first aspect of this utility model.

[0012] Because it employs the composite fiber bundle of the first aspect of this utility model, the fiber cloth of this utility model has all the advantages of the composite fiber bundle, which will not be elaborated here.

[0013] According to some embodiments of the present invention, the fiber cloth includes a mesh cloth.

[0014] The third aspect of this utility model provides a prepreg comprising a matrix resin and a fiber cloth, wherein the fiber cloth is the same as the fiber cloth of the second aspect of this utility model.

[0015] Because it employs the composite fiber bundle of the first aspect of this invention, the prepreg of this invention possesses all the advantages of the composite fiber bundle, which will not be elaborated further here.

[0016] According to some embodiments of the present invention, the matrix resin includes a thermoplastic resin; the thermoplastic resin includes a thermoplastic resin with a melting point of 150℃-200℃; the thermoplastic resin with a melting point of 150℃-200℃ includes at least one of polypropylene and polyethylene.

[0017] The fourth aspect of this utility model provides a composite board, including a prepreg material layer, wherein the prepreg material layer is formed by curing the prepreg of the third aspect of this utility model.

[0018] Because it employs the composite fiber bundle of the first aspect of this utility model, the composite board of this utility model has all the advantages of the composite fiber bundle, which will not be elaborated here.

[0019] The fifth aspect of this utility model provides a battery sealing cover, the material of which includes a composite board, and the composite board is the same as that of the fourth aspect of this utility model.

[0020] Because it employs the composite fiber bundle of the first aspect of this invention, the battery sealing cover of this invention possesses all the advantages of the composite fiber bundle, which will not be elaborated further here.

[0021] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] The above and / or additional aspects and advantages of this utility model will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0023] Figure 1 is a cross-sectional schematic diagram of an exemplary composite fiber bundle of the present invention.

[0024] Figure 2 is a schematic diagram of an exemplary composite fiber bundle of this utility model.

[0025] Figure 3 is a schematic diagram of another exemplary composite fiber bundle of the present invention.

[0026] Figure 4 is a schematic diagram of the structure of an exemplary battery sealing cover of this utility model.

[0027] Figure 5 is a longitudinal cross-sectional view of the battery sealing cover in Figure 4.

[0028] Figure 6 is a bottom view of the battery sealing cover in Figure 4.

[0029] Figure 7 is a cross-sectional view of Figure 6 along the AA direction.

[0030] Figure 8 is a process flow diagram of the battery sealing cover provided in Example 1.

[0031] Figure 9 is a schematic diagram of the airtightness testing equipment.

[0032] Figure label:

[0033] 100. Composite fiber bundle; 10. Fiber; 11. Reinforcing fiber; 12. Low melting point thermoplastic fiber; 13. High melting point thermoplastic fiber; 200. Battery sealing cap; 210. Sealing surface; 1. First test area; 2. Second test area; 3. Third test area; 4. Fourth test area; 5. Fifth test area; 6. Sixth test area; 7. Seventh test area; 8. Eighth test area; 300. Air tightness testing equipment; 310. Air tightness detector; 320. Pressurized pipeline; 330. Sensor; 340. Return gas pipeline; 350. Limiting device; 360. Battery tray; 370. Power battery cell. Detailed Implementation

[0034] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0035] In the description of this utility model, unless otherwise stated, "a plurality of" means two or more. "Multiple kinds" means two or more. "Multiple roots" means three or more. In this document, the terms "comprising" or "including" are open-ended expressions, meaning they include the contents specified in this utility model but do not exclude other aspects.

[0036] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0037] With the increasing demands for energy density and lightweight design of power batteries, power battery sealing covers are gradually moving towards thermoplastic materials. Traditional thermosetting materials have long molding cycles, are brittle, and are prone to hidden cracking. Furthermore, thermosetting materials are not easy to recycle and pose significant environmental risks.

[0038] Currently, thermoplastic materials are mainly prepared using thermoplastic resin-glass fiber prepreg. However, the following major problems exist: On the one hand, thermoplastic resins such as PP resin have very high viscosity in the molten state, which makes prepreg preparation of glass fibers poor, especially for woven glass fiber fabrics, making it difficult to completely impregnate them and easily causing local defects that lead to air leakage; on the other hand, after PP resin impregnates glass fibers, the glass fibers are easily torn during the molding process of the sheet, resulting in a decrease in local strength or even cracking.

[0039] To address the above issues, this invention proposes a composite fiber bundle comprising multiple reinforcing fibers, low-melting-point thermoplastic fibers, and high-melting-point thermoplastic fibers extending in the same direction. Due to their lower melting point, the low-melting-point thermoplastic fibers, when mixed with the reinforcing fibers to form a fiber bundle, melt more easily during molding, resulting in better wetting of the reinforcing fibers and resin matrix, thus improving the lateral strength of the product and the airtightness of the battery seal. The high-melting-point thermoplastic fibers, due to their higher melting point, do not completely melt and lose their structure during molding when mixed with the reinforcing fibers, ensuring the toughness and strength of the fiber bundle during molding and preventing breakage during molding and stretching, thus guaranteeing the structural stability of the product. In summary, by arranging multiple reinforcing fibers, low-melting-point thermoplastic fibers, and high-melting-point thermoplastic fibers in the same composite fiber bundle along the same extension direction, the strength of the composite fiber bundle remains unaffected during the molding process of the battery seal, maintaining structural integrity and good airtightness.

[0040] Specifically, referring to Figure 1, the first aspect of this utility model provides a composite fiber bundle 100, comprising multiple fibers 10 extending in the same direction. The fibers 10 include reinforcing fibers 11, low-melting-point thermoplastic fibers 12, and high-melting-point thermoplastic fibers 13. The low-melting-point thermoplastic fibers 12 and high-melting-point thermoplastic fibers 13 are dispersed among the reinforcing fibers 11. The melting point of the low-melting-point thermoplastic fibers 12 is below 200°C, and the melting point of the high-melting-point thermoplastic fibers 13 is above 240°C.

[0041] In this text, "extending in the same direction" means that the main extension directions of multiple fibers in the composite fiber bundle 100 are the same, all extending along the axial direction of the composite fiber bundle 100. For each fiber, its shape can be straight, wavy, spiral, etc., and the main extension direction of each fiber is the axial direction of the composite fiber bundle 100. Multiple fibers are arranged side by side to form a composite fiber bundle 100.

[0042] In some embodiments, the melting point of the low-melting-point thermoplastic fiber 12 may be 100℃-200℃, 120℃-170℃, 120℃-150℃, or 120℃-130℃. Preferably, the melting point of the low-melting-point thermoplastic fiber 12 is 120℃-150℃.

[0043] In some embodiments, the melting point of the high-melting-point thermoplastic fiber 13 may be 240℃-400℃, 240℃-350℃, 240℃-270℃, or 280℃-350℃. Preferably, the melting point of the high-melting-point thermoplastic fiber 13 is 240℃-350℃.

[0044] In some embodiments, referring to FIG2, reinforcing fiber 11, low-melting-point thermoplastic fiber 12, and high-melting-point thermoplastic fiber 13 are arranged in parallel along the same direction. The parallel arrangement of the three different fibers in the same direction can improve the axial strength and durability of the composite cellulose, and the preparation process of this composite fiber bundle is simple.

[0045] In some embodiments, referring to FIG3, low-melting-point thermoplastic fibers 12 and high-melting-point thermoplastic fibers 13 are wound around reinforcing fibers 11 and extend in the same direction. Fiber bundles formed by winding can also improve wettability and ensure strength and resilience, but due to the thinness of individual fibers, the operation of winding to form bundles is difficult and not very conducive to industrial production.

[0046] In some embodiments, low-melting-point thermoplastic fibers 12 and high-melting-point thermoplastic fibers 13 are uniformly dispersed among the reinforcing fibers 11. The uniform interweaving of low-melting-point thermoplastic fibers 12 and high-melting-point thermoplastic fibers 13 between the reinforcing fibers facilitates the formation of uniform composite fiber bundles, further improving wettability and toughness.

[0047] The composite fiber bundle 100 of this invention includes at least three types of fibers. Reinforcing fibers 11, low-melting-point thermoplastic fibers 12, and high-melting-point thermoplastic fibers 13 coexist in the same composite fiber bundle. A composite fiber bundle may include 6000-8000 reinforcing fibers 11, 1000-1500 low-melting-point thermoplastic fibers 12, and 2000-3000 high-melting-point thermoplastic fibers 13. For example, a composite fiber bundle may include 6000, 6500, 7000, or 8000 reinforcing fibers 11. A composite fiber bundle may include 1000, 1100, 1200, 1300, 1400, or 1500 low-melting-point thermoplastic fibers 12. A bundle of composite fibers may include 2,000, 2,200, 2,400, 2,600, 2,800 or 3,000 high-melting-point thermoplastic fibers 13.

[0048] In some embodiments, the low-melting-point thermoplastic fiber 12 includes at least one of polyethylene (PE) fiber and polypropylene fiber. These polymer fibers have low melting points; for example, PE fiber has a melting point in the range of approximately 120°C-130°C. When mixed with the reinforcing fiber 11, it melts more easily during molding, allowing for better wetting of the reinforcing fiber 11 and the matrix resin, thus improving the transverse strength and airtightness of the product. PE is preferably high molecular weight polyethylene, which provides the necessary rigidity and bundling properties for the fiber bundles. The number average molecular weight of polyethylene can be between 100,000 g / mol and 200,000 g / mol, for example, 100,000 g / mol, 120,000 g / mol, 140,000 g / mol, 160,000 g / mol, 180,000 g / mol, or 200,000 g / mol.

[0049] In some embodiments, the low-melting-point thermoplastic fiber 12 accounts for 5%-15% of the total mass of the composite fiber bundle 100, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%. Optimizing the content of the low-melting-point thermoplastic fiber 12 within the above range is beneficial to improving the wettability of the reinforcing fiber 11. If the content of the low-melting-point thermoplastic fiber 12 is too low, the effect on improving wettability is not significant; if the content of the low-melting-point thermoplastic fiber 12 is too high, the content of the reinforcing fiber 11 and the high-melting-point thermoplastic fiber 13 will decrease accordingly, which is not conducive to improving the strength of the composite fiber bundle.

[0050] In some embodiments, the diameter of the low-melting-point thermoplastic fiber 12 can be 8μm-12μm, for example, 8μm, 9μm, 10μm, 11μm or 12μm. Here, "diameter" refers to the diameter of a single low-melting-point thermoplastic fiber 12. Excessively fine thermoplastic fibers are difficult to mold, and excessively fine fibers may cause fiber breakage during the loosening and composite spinning process; when the thermoplastic fibers are too coarse, the low-melting-point thermoplastic fibers do not melt easily during subsequent product molding and cannot play a wetting role.

[0051] In some embodiments, the high-melting-point thermoplastic fiber 13 includes one or more of polyamide (PA) fiber, polyetheretherketone (PEEK) fiber, polyimide (PI) fiber, polystyrene (PS) fiber, and polytetrafluoroethylene (PTFE) fiber. These polymers have high melting points; for example, PA fiber has a melting point in the range of approximately 240°C-270°C. The molding process for preparing the battery sealing cap from the composite board involves heating to 200°C-230°C followed by cold pressing. Within this temperature range, the PA fiber does not completely melt and lose its structure, maintaining a certain degree of toughness. This prevents the fiber bundle from breaking during the molding and stretching process, solving the problem of insufficient toughness in glass fiber and ensuring the structural stability of the product.

[0052] In some embodiments, the high-melting-point thermoplastic fiber 13 accounts for 20%-30% of the total mass of the composite fiber bundle 100, for example, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%. Optimizing the content of the high-melting-point thermoplastic fiber 13 within the above range is beneficial to improving the toughness and strength of the composite fiber bundle and maintaining the structural stability of the product. If the content of the high-melting-point thermoplastic fiber 13 is too low, the improvement effect on the toughness and strength of the composite fiber bundle is not significant; if the content of the high-melting-point thermoplastic fiber 13 is too high, the product is difficult to mold.

[0053] In some embodiments, the diameter of the high-melting-point thermoplastic fiber 13 may be less than 10 μm, such as 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, or 1 μm. When the diameter of the high-melting-point thermoplastic fiber is too large, it will lead to difficulties in spinning and uneven mixing with other fibers; at the same time, the toughness will be reduced during the subsequent molding process, and surface fiber floating will easily occur.

[0054] In some embodiments, the reinforcing fiber 11 includes at least one of glass fiber and carbon fiber. For example, the reinforcing fiber 11 is glass fiber. The linear density of the glass fiber may be 1000tex-1400tex, for example, 1000tex, 1500tex, 2000tex, 2500tex, 3000tex, 3500tex or 1400tex.

[0055] The preparation method of the composite fiber bundle of this invention is simple and can be prepared by the following steps: providing a low-melting-point thermoplastic fiber bundle, a high-melting-point thermoplastic fiber bundle, and a reinforcing fiber bundle; performing a fiber-dispersing treatment on the low-melting-point thermoplastic fiber bundle and the high-melting-point thermoplastic fiber bundle; and adding the low-melting-point thermoplastic fibers and the high-melting-point thermoplastic fibers between the reinforcing fibers during the fiber-opening process to re-form a fiber bundle. Here, "fiber-opening process" refers to the process of dispersing the fiber bundle into monofilaments. "Fiber-dispersing treatment" also refers to the process of dispersing the fiber bundle into monofilaments.

[0056] Low-melting-point thermoplastic fibers, high-melting-point thermoplastic fibers, and reinforcing fibers are combined and drawn together to create composite fiber bundles containing both low-melting-point and high-melting-point thermoplastic fibers. These bundles provide the reinforcing fibers with a certain degree of toughness and enable rapid wetting, ensuring that the reinforcing fibers are quickly impregnated during compression molding. Furthermore, the reinforcing fibers are less prone to cracking or breakage at specific structural points in the product. This differs from the commonly used method of spraying PP particles onto the surface of glass fibers. While PP particle spraying is suitable for unidirectional tape molding, woven fabrics have a large number of cross-linked glass fiber structures, and PP spraying can lead to incomplete particle adhesion.

[0057] The second aspect of this utility model provides a fiber cloth, which includes the composite fiber bundle of the first aspect of this utility model.

[0058] Because it employs the composite fiber bundle of the first aspect of this utility model, the fiber cloth of this utility model has all the advantages of the composite fiber bundle, which will not be elaborated here.

[0059] Composite fiber bundles can be woven into the desired fiber fabric. For example, they can be woven using mechanical manufacturing processes such as rapier looms. Of course, other glass fiber weaving methods or fiber blending methods can also be used.

[0060] In some embodiments, the fiber cloth includes a mesh cloth, such as a checkered cloth.

[0061] In some embodiments, the basis weight of the fiber cloth may be 300 g / m². 2 -350g / m 2 For example, 300g / m 2 310g / m 2 320g / m 2 330g / m 2 340g / m 2 Or 350g / m 2 .

[0062] The third aspect of this utility model provides a prepreg comprising a matrix resin and a fiber cloth, wherein the fiber cloth is the same as the fiber cloth of the second aspect of this utility model.

[0063] Because it employs the composite fiber bundle of the first aspect of this invention, the prepreg of this invention possesses all the advantages of the composite fiber bundle, which will not be elaborated further here.

[0064] In some embodiments, the matrix resin comprises a thermoplastic resin. The thermoplastic resin includes a thermoplastic resin with a melting point of 150°C-200°C. The thermoplastic resin with a melting point of 150°C-200°C includes at least one of polypropylene and polyethylene. Preferably, polypropylene resin is used as the matrix resin, having a melting point of approximately 150°C.

[0065] The method for preparing the prepreg includes the following steps: using a melt hot pressing process or a roll pressing process to combine the fiber cloth with the matrix resin to form a resin fiber prepreg.

[0066] The fourth aspect of this utility model provides a composite board, including a prepreg material layer, wherein the prepreg material layer is formed by curing the prepreg of the third aspect of this utility model.

[0067] Because it employs the composite fiber bundle of the first aspect of this utility model, the composite board of this utility model has all the advantages of the composite fiber bundle, which will not be elaborated here.

[0068] In some embodiments, the thickness of the composite board can be 1.0mm-2.0mm, such as 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm or 2.0mm, more preferably 1.5mm.

[0069] The method for preparing the composite board includes the following steps: using a melt-pressing or roll-pressing method to laminate multiple layers of the prepreg into a composite board. The number of prepreg layers can be 4 to 10, for example, 4, 6, 8, or 10 layers.

[0070] The fifth aspect of this utility model provides a battery sealing cover, the material of which includes a composite board, and the composite board is the same as that of the fourth aspect of this utility model.

[0071] Because it employs the composite fiber bundle of the first aspect of this invention, the battery sealing cover of this invention possesses all the advantages of the composite fiber bundle, which will not be elaborated further here.

[0072] In some embodiments, the battery sealing cover has the structure shown in Figures 4-7. The area of ​​the battery sealing cover 200 may be 2m². 2 -3m 2 For example, 2m 2 2.2m 2 2.4m 2 2.6m 2 2.8m 2 or 3m 2 The depth H can be 200mm-500mm, for example, 200mm, 300mm, 400mm or 500mm.

[0073] The battery sealing cap can be prepared from the composite sheet through hot melting and molding. Before preparing the battery sealing cap, the composite sheet is cut to a specified size, which is 15%-25% larger than the top surface of the sealing cap, for example, 20% larger. Then, the cut composite sheet is heated until the surface thermoplastic resin (matrix resin and low-melting-point thermoplastic fibers) reaches a molten state. Heating can be performed using methods such as continuous heating in a tunnel furnace, oven, or infrared irradiation. The heating temperature can be 200℃-250℃, for example, 200℃, 210℃, 220℃, 230℃, 240℃, or 250℃, which is 30℃-50℃ higher than the melting point of the surface thermoplastic resin itself. The heating time can be 150s-300s, for example, 150s, 200s, 250s, or 300s, depending on whether the surface thermoplastic resin reaches a molten state.

[0074] After heating, the molten composite material sheet is transferred to a mold using a fixture (process equipment). During the transfer, the composite sheet is stretched on all four sides on the fixture to ensure that the thermoplastic fibers in the composite fiber bundle remain straight. This is because the rigidity of thermoplastic fibers is inconsistent with that of glass fibers, causing the thermoplastic fibers to bend easily when heated and exhibit abnormal surface fiber protrusions after cooling. Therefore, the transfer is performed in a stretched state. The transfer can be carried out using a robotic arm or manually, ensuring complete conformity between the composite sheet and the mold.

[0075] The temperature of the mold surface can be between 60℃ and 90℃, for example, 60℃, 70℃, 80℃ or 90℃, so as to ensure that the thermoplastic resin can be demolded smoothly after curing, and not to cause internal stress due to the temperature being too low, which would lead to fiber breakage.

[0076] After transferring the composite sheet into the mold, the molding machine is turned on for compression molding. A 1000T-2000T molding machine is generally selected, with a pressure of around 1500T. The molding speed needs to be relatively slow; too high a speed will cause the fibers to break. During the molding process, the fibers undergo two bends, as shown in Figure 5. The glass fibers are contained within molten thermoplastic fibers, making them less prone to breakage. Furthermore, at the molding temperature, the high-melting-point thermoplastic fibers do not melt, retaining a certain strength and toughness. This ensures that reinforcing fibers remain after the two bends, thus guaranteeing the strength and thickness at the bends and preventing excessive fiber tearing.

[0077] The fibers at the bend of the battery sealing cover exist in three states:

[0078] First, because the heating temperature exceeds the melting point of the low-melting-point thermoplastic fiber, the low-melting-point thermoplastic fiber melts and impregnates the reinforcing fiber, enhancing the resin's wettability to the fiber; the cavity in the middle of the fiber is reduced, enhancing the airtightness level.

[0079] Second, the two bends cause the reinforcing fibers to be stretched and broken. Fiber aggregation will occur in the first test area 1, the second test area 2, the third test area 3, and the fourth test area 4 shown in Figure 6. However, since the low-melting-point thermoplastic resin used in this application can flow to other locations after melting, the uniformity of the thickness of the entire product is ensured, overcoming the problem of poor fiber flow and increased thickness at the bend in traditional products.

[0080] Third, since the heating temperature does not reach the melting temperature of high-melting-point thermoplastic fibers, their structure does not change. However, at high temperatures, the rigidity of high-melting-point thermoplastic fibers decreases and their toughness increases, enabling them to be effectively stretched to ensure the integrity of the structure. This makes it less likely for fibers to break on the surface, reducing damage and tearing.

[0081] Due to the influence of two types of thermoplastic fibers, the battery sealing cover molding process resulted in a structurally intact product with no scratches or cracks on the surface, ensuring the product's airtightness rating.

[0082] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0083] Example 1

[0084] The battery sealing cover is manufactured according to the process flow diagram shown in Figure 8. The specific steps are as follows.

[0085] The composite fiber bundle is made of alkali-free E-glass fiber TEX1200, PE fiber (8μm in diameter), and PA fiber (10μm in diameter), which are mixed into a composite fiber bundle using a spinning machine. The mass ratio of the three fibers is PE fiber:PA fiber:glass fiber 10:20:70.

[0086] PE fiber bundles are prepared by spinning using ultra-high molecular weight PE fiber (number average molecular weight of 1,200,000 g / mol) as raw material. The PE fiber bundles are then subjected to surface treatment and fiber separation treatment. The melting point of ultra-high molecular weight PE is 135℃-145℃.

[0087] PA fiber is a high-heat-resistant PA fiber with a melting point of 315℃-325℃. It is prepared into PA fiber bundles using a spinning process. The PA fiber bundles undergo surface treatment followed by a fiber-loosening process.

[0088] The three types of fiber bundles were combined into a unidirectional composite fiber bundle using a rapier loom. PA and PE fibers were evenly dispersed among the glass fibers at the root level, as shown in Figure 1-2. The three fibers were arranged parallel to each other in the same direction. The composite fiber bundles were then mixed and woven into a fiber cloth. The woven fiber cloth was a mesh fabric with a basis weight of 350 g / cm³. 3 ;

[0089] The fiber cloth is made from thermoplastic PP through dry melt rolling to prepare a mesh prepreg, with a single layer of prepreg thickness of about 0.3 mm. The single layers of prepreg are mixed and laid up to a total thickness of 1.5 mm, and PP mixed glass fiber composite board is prepared by melt rolling.

[0090] The composite panels were heated and melted in a tunnel furnace for 180 seconds at 200°C. They were then transferred by a robotic arm to a mold in a hydraulic press (1500T, actual pressure 1100T). The molding time was 3 minutes.

[0091] After molding and edge trimming, a battery sealing cap is obtained. Three parallel samples (sample 1, sample 2, and sample 3) are made to test the product's airtightness level, dimensions, and appearance.

[0092] Comparative Example 1

[0093] PP unidirectional tape prepreg (made by impregnating alkali-free E glass fiber with PP thermoplastic resin) was laid up, and then molded in the same equipment and mold according to the process of Example 1 to obtain the battery sealing cap. Three samples (sample 4, sample 5, and sample 6) were made in parallel to test the airtightness level, product size, and appearance of the product.

[0094] Product-level testing

[0095] (1) Air tightness test

[0096] Test equipment: Adekair airtightness testing equipment, as shown in Figure 9. The airtightness testing equipment 300 includes an airtightness detector 310, a pressurization line 320, a sensor 330, a return air line 340, a limiting device 350, a battery tray 360, a power battery cell 370, and a battery sealing cover 200. The battery tray 360 and the battery sealing cover 200 are fastened using conventional bolt fastening with silicone foam.

[0097] Test Method: After fixing the battery sealing cover, click the "System Menu" on the airtightness testing equipment to enter the interface, and then set the parameters: inflation time 70s (pressure set to 15Kpa, inflating the sealing cover cavity to 2.5KPa through the pre-drilled hole on the test fixture), pressure stabilization time 60s (the system automatically adjusts the system pressure to maintain the system pressure at 2.5-3KPa), test time 120s (stop pressurization and automatic system adjustment). Under an air pressure of 2.0-3.0KPa, a leakage rate ≤5cc / min indicates good airtightness. Three parallel tests were performed. The test results are shown in Table 1 below.

[0098] Table 1

[0099]

[0100] Results and Discussion:

[0101] The composite board of Example 1 provides a large amount of resin and thermoplastic fibers, ensuring the integrity of the main structure and fibers of the product, and reducing the voids in the glass fiber bundles, effectively improving the airtightness of the sample. Its airtightness reaches the airtightness level of thermosetting resins. In contrast, the composite board of Comparative Example 1 experienced extensive glass fiber breakage during molding, resulting in unpredictable surface damage and a severe decrease in airtightness, with some parts even showing serious leakage.

[0102] (2) Product appearance and edge thickness test

[0103] Thickness tests were performed at one test location on each of the eight test areas (shown by dashed boxes) of the product shown in Figure 6. The eight test areas are: Test Area 1, Test Area 2, Test Area 3, Test Area 4, Test Area 5, Test Area 6, Test Area 7, and Test Area 8. The corresponding eight test locations are: Test Location 1, Test Location 2, Test Location 3, Test Location 4, Test Location 5, Test Location 6, Test Location 7, and Test Location 8. All eight test locations are located on the sealing surface 210 of the battery sealing cover (shown by dashed boxes in Figure 5). An edge thickness within the range of 3.0 ± 0.5 mm ensures a good seal on the assembly surface after product assembly. The test results are shown in Table 2.

[0104] Table 2

[0105]

[0106] Results and Discussion:

[0107] The composite board of Example 1 showed no edge defects during molding, and the product edge thickness was uniform, meeting the requirements. In contrast, the composite board of Comparative Example 1 exhibited severe fiber enrichment at the four corners (i.e., test positions 1-4) during molding. After rapid solidification on the PP resin surface, flow was difficult, resulting in a thickness tolerance of over 1mm on the sealing surface. This severely affected the product's appearance and yield, and also caused assembly difficulties and poor airtightness.

[0108] In summary, by arranging multiple reinforcing fibers, low-melting-point thermoplastic fibers, and high-melting-point thermoplastic fibers in the same composite fiber bundle along the same extension direction, the strength of the composite fiber bundle can be maintained without affecting the structure during the molding process of the battery sealing cover, ensuring structural integrity and good airtightness.

[0109] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0110] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A composite fiber bundle, characterized in that, It includes multiple fibers extending in the same direction, the fibers including reinforcing fibers, low-melting-point thermoplastic fibers and high-melting-point thermoplastic fibers; the low-melting-point thermoplastic fibers and the high-melting-point thermoplastic fibers are dispersed among the reinforcing fibers; The low-melting-point thermoplastic fiber has a melting point below 200°C; the high-melting-point thermoplastic fiber has a melting point above 240°C.

2. The composite fiber bundle according to claim 1, characterized in that, The reinforcing fibers, low-melting-point thermoplastic fibers, and high-melting-point thermoplastic fibers are arranged in parallel along the same direction.

3. The composite fiber bundle according to claim 1, characterized in that, The melting point of the low-melting-point thermoplastic fiber is 120℃-150℃; the low-melting-point thermoplastic fiber includes at least one of polyethylene fiber and polypropylene fiber; the low-melting-point thermoplastic fiber accounts for 5%-15% of the total mass of the composite fiber bundle; the diameter of the low-melting-point thermoplastic fiber is 8μm-12μm.

4. The composite fiber bundle according to claim 1, characterized in that, The high-melting-point thermoplastic fiber has a melting point of 240℃-350℃; the high-melting-point thermoplastic fiber includes one or more of polyamide fiber, polyetheretherketone fiber, polyimide fiber, polystyrene fiber, and polytetrafluoroethylene fiber; the high-melting-point thermoplastic fiber accounts for 20%-30% of the total mass of the composite fiber bundle; the diameter of the high-melting-point thermoplastic fiber is less than 10μm.

5. The composite fiber bundle according to claim 1, characterized in that, The reinforcing fiber includes at least one of glass fiber and carbon fiber.

6. A fiber cloth, characterized in that, The composite fiber bundle includes any one of claims 1-5.

7. The fiber cloth according to claim 6, characterized in that, The fiber cloth includes a mesh cloth.

8. A prepreg, characterized in that, It includes a matrix resin and a fiber cloth, wherein the fiber cloth is the fiber cloth as described in claim 6 or 7.

9. The prepreg according to claim 8, characterized in that, The matrix resin includes a thermoplastic resin; the thermoplastic resin includes a thermoplastic resin with a melting point of 150℃-200℃; the thermoplastic resin with a melting point of 150℃-200℃ includes at least one of polypropylene and polyethylene.

10. A composite board, characterized in that, It includes a prepreg material layer, which is formed by curing the prepreg as described in claim 8 or 9.

11. A battery sealing cover, characterized in that, The battery sealing cover is made of a composite board, which is the composite board described in claim 10.

Images