Composite insulator core rod and preparation method and system thereof

Abstract

The application relates to the technical field of power equipment insulating materials, and discloses a composite insulator core rod and a preparation method and a preparation system thereof. The composite insulator core rod comprises a core body and a surface barrier layer in situ coated on the outer surface of the core body, the core body is obtained by impregnating a plurality of continuous glass fiber bundles in a resin solution and then solidifying, the surface barrier layer is obtained by impregnating polyester fibers treated by a silane coupling agent in a resin solution and then solidifying, and the resin solution contains an epoxy resin, a curing agent and an internal release agent. The compact barrier layer is formed in situ, so that the long-term moisture resistance and reliability of the composite insulator core rod are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of electrical equipment insulation materials technology, specifically to composite insulator core rods and their preparation methods and systems. Background Technology

[0002] Composite insulators are widely used in power grids due to their advantages such as light weight, high strength, and good resistance to flashover. Their core load-bearing component is a glass fiber reinforced epoxy resin core rod. However, during long-term operation, especially in harsh environments such as high temperature and high humidity (HTHM), moisture from the environment may penetrate the core rod through microcracks or defects on its surface.

[0003] Moisture intrusion leads to two main problems: first, it reduces the interfacial bond strength between the glass fiber and the epoxy resin matrix, resulting in a decrease in mechanical properties (such as flexural and shear strength); second, under the influence of an electric field, the intruding moisture can trigger electrochemical corrosion, i.e., the phenomenon of "acid-induced breakdown," causing the core rod to fracture brittlely from the inside, seriously threatening circuit safety. Traditional core rod protection mainly relies on external silicone rubber skirts and sheaths, but once the sheath is damaged or the end seal fails, the core rod body is directly exposed, and its insufficient moisture resistance becomes apparent.

[0004] In existing technologies, to improve the water resistance of the mandrel, hydrophobic agents are often added to the resin formulation or special wetting agents are used to treat the fibers. However, these methods may affect other properties (such as mechanical strength and processability) or increase costs. There are also solutions that perform surface coating treatment after pultrusion molding, but these have issues with coating adhesion, uniformity, and compatibility with subsequent sheath bonding. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing composite insulator core rods in terms of resistance to moisture intrusion, and provides a composite insulator core rod, its preparation method and preparation system. This invention significantly improves the long-term moisture resistance and reliability of composite insulator core rods by forming a dense barrier layer in situ.

[0006] To achieve the above objectives, the first aspect of the present invention provides a composite insulator core rod, which includes a core body and a surface barrier layer in situ covering the outer surface of the core body. The core body is obtained by impregnating multiple continuous glass fiber bundles with a resin solution and then curing them. The surface barrier layer is obtained by impregnating polyester fibers that have been surface-treated with a silane coupling agent with a resin solution and then curing them. The resin solution contains epoxy resin, curing agent, and internal release agent.

[0007] Preferably, the content of polyester fiber in the material of the surface barrier layer is 1-10 wt%.

[0008] Preferably, the polyester fiber has a diameter of 5-20 μm and a length of 3-10 mm.

[0009] Preferably, the thickness of the surface barrier layer is 0.1-0.5 mm; Preferably, the diameter of the core is 10-100mm.

[0010] Preferably, the ratio of the total weight of the continuous glass fiber bundle to the weight of the polyester fiber is 1:0.0005-0.02.

[0011] A second aspect of the present invention provides a system for preparing a composite insulator core rod, comprising: an impregnation tank, a preforming device, a felt guiding device, a heating and forming mold, and a traction machine; The impregnation tank is used to hold the resin solution. Multiple continuous glass fiber bundles are impregnated in the resin solution through the impregnation tank to obtain multiple impregnated continuous glass fiber bundles. The resin solution contains epoxy resin, curing agent and internal release agent. The felt guide device is used to transport polyester fibers that have been surface-treated with silane coupling agent to the preforming device. In the preforming device, the polyester fibers that have been surface-treated with silane coupling agent are used to wrap multiple continuous glass fiber bundles that have been impregnated from the impregnation tank to obtain intermediate material. The traction machine is used to pull the intermediate material into the heating and forming mold for heating and forming to obtain the composite insulator core rod.

[0012] A third aspect of the present invention provides a method for preparing a composite insulator core rod, comprising: Multiple continuous glass fiber bundles are guided through an impregnation tank containing a resin solution and immersed in the resin solution to obtain multiple impregnated continuous glass fiber bundles. Then, the multiple impregnated continuous glass fiber bundles are sent into a preforming device. Then, a felt guide device is used to transport polyester fibers that have been surface-treated with silane coupling agent to the preforming device. In the preforming device, the multiple impregnated continuous glass fiber bundles from the impregnation tank are wrapped with polyester fibers that have been surface-treated with silane coupling agent to obtain intermediate material. Then, under the traction of a traction machine, it enters a thermoforming mold for thermoforming, so that the multiple impregnated continuous glass fiber bundles are cured to obtain the core. At the same time, the polyester fibers that have been surface-treated with silane coupling agent are impregnated with resin solution and cured to obtain a surface barrier layer. Finally, a composite insulator core rod is obtained. The resin solution contains epoxy resin, curing agent, and internal release agent; The temperature for heat forming is 120-180℃.

[0013] Preferably, the curing agent is an acid anhydride-based curing agent; Preferably, the internal release agent is a water-based release agent and / or a natural oil-based release agent.

[0014] Preferably, the weight ratio of epoxy resin, curing agent and internal release agent is 100:70-120:0.75-2.

[0015] Preferably, the traction speed of the traction machine is 0.8-2 m / min.

[0016] The beneficial effects of this invention are: 1. In-situ formation of a dense barrier layer: By introducing polyester fibers during the pultrusion process, a resin-rich, dense layer reinforced with chopped fibers is formed in situ on the core surface. This layer significantly reduces capillary channels or microcracks that may form on the surface of a conventional mandrel due to the continuous arrangement of glass fibers, fundamentally blocking the main pathways for moisture intrusion.

[0017] 2. Excellent water vapor resistance: The surface barrier layer has extremely low porosity and moisture absorption. Tests show that the mandrel prepared according to this invention exhibits an average breakdown voltage increase of approximately 45% and a saturated water absorption rate decrease of approximately 34% after being boiled in water at 100°C for 42 hours. Its long-term mechanical strength retention rate under high humidity conditions is significantly improved.

[0018] 3. Excellent interfacial bonding and mechanical properties: The polyester fibers are cured simultaneously with the core within the mold, enabling chemical bonding and physical interlocking between the surface barrier layer and the internal core. This results in high bonding strength and eliminates the risk of peeling. The addition of chopped polyester fibers enhances surface toughness, avoids the brittleness of pure resin layers, and has minimal impact on the overall axial tensile strength of the mandrel.

[0019] 4. Strong process compatibility and controllable cost: This method is seamlessly integrated into existing pultrusion production lines, requiring only the addition of a felt guiding device without altering the core resin system or adding complex post-processing steps. Polyester fiber felt is inexpensive, resulting in minimal increase in overall manufacturing costs and facilitating industrialization.

[0020] 5. Improve the overall reliability of insulators: The improved moisture resistance of the core rod provides a "second line of defense" for composite insulators. Even if the external silicone rubber sheath is locally damaged, it can effectively delay the erosion of the load-bearing core rod by moisture, which greatly improves the service life and reliability of insulators in harsh environments. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a composite insulator core rod; Figure 2 This is a schematic diagram of the composite insulator core rod preparation system; Figure 3 This is a schematic diagram of the moisture intrusion situation in the insulator core rod of Comparative Example 1; Figure 4 This is a schematic diagram illustrating the water vapor intrusion situation of the composite insulator core rod of the present invention.

[0022] Explanation of reference numerals in the attached figures 1. Core; 2. Surface barrier layer; 3. Impregnation tank; 4. Preforming device; 5. Felt guiding device; 6. Heating and forming mold; 7. Traction machine; 8. Yarn frame. Detailed Implementation

[0023] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0024] 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.

[0025] Furthermore, the technical solutions provided in the various embodiments of the present invention can be combined with each other, but only if they are feasible to those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0026] The first aspect of the present invention provides a method such as Figure 1 The composite insulator core shown includes a core 1 and a surface barrier layer 2 in situ covering the outer surface of the core 1. The core 1 is obtained by impregnating multiple continuous glass fiber bundles with a resin solution and then curing them. The surface barrier layer 2 is obtained by impregnating polyester fibers that have been surface treated with a silane coupling agent with a resin solution and then curing them. The resin solution contains epoxy resin, curing agent, and internal release agent.

[0027] Preferably, the content of polyester fiber in the material of the surface barrier layer 2 is 1-10 wt% (based on the total weight of the material of the surface barrier layer 2 being 100 wt%).

[0028] The polyester fiber in this invention is a chopped polyester fiber with a diameter of 5-20 μm and a length of 3-10 mm.

[0029] The surface barrier layer 2 of the present invention is formed in situ on the outer surface of the core 1. In the surface barrier layer 2, polyester fibers treated with silane coupling agent are uniformly dispersed in the epoxy resin matrix to form a dense interface without exposed continuous fibers. The thickness of the surface barrier layer 2 is 0.1-0.5 mm. The surface barrier layer 2 mainly serves as an isolation layer. The thickness should not be too large, as excessive thickness will affect the mechanical properties of the composite insulator core rod.

[0030] In this invention, the specific number of continuous glass fiber bundles is selected according to the diameter of the core 1. Continuous glass fiber bundles with different linear densities can be selected. Preferably, the diameter of the core 1 in the composite insulator core rod of this invention is 10-100 mm.

[0031] In a preferred embodiment of the present invention, the ratio of the total weight of all continuous glass fiber bundles to the weight of polyester fibers in the composite insulator core rod is 1:0.0005-0.02.

[0032] The second aspect of the present invention provides Figure 2 The composite insulator core rod preparation system shown includes: an impregnation tank 3, a preforming device 4, a felt guiding device 5, a heating and forming mold 6, and a traction machine 7; The impregnation tank 3 is used to hold the resin solution. Multiple continuous glass fiber bundles are impregnated in the resin solution through the impregnation tank 3 to obtain multiple impregnated continuous glass fiber bundles. The resin solution contains epoxy resin, curing agent and internal release agent. The felt guide device 5 is used to transport polyester fibers that have been surface treated with silane coupling agent to the preforming device 4. In the preforming device 4, the polyester fibers that have been surface treated with silane coupling agent are used to wrap multiple continuous glass fiber bundles that have been impregnated from the impregnation tank 3 to obtain intermediate material. The traction machine 7 is used to pull the intermediate material into the heating and forming mold 6 for heating and forming to obtain the composite insulator core rod.

[0033] The guide felt device 5 can uniformly and stably transport the polyester fibers treated with silane coupling agent to the preforming device 4, thereby guiding and controlling the tension of the polyester fibers treated with silane coupling agent.

[0034] Furthermore, the preparation system also includes a yarn rack 8, from which multiple bundles of continuous glass fiber yarn are drawn out and combed in a concentrated manner to obtain multiple combed continuous glass fiber bundles, which are then guided through an impregnation tank 3 containing a resin solution.

[0035] A third aspect of the present invention provides a method for preparing a composite insulator core rod, comprising: Multiple continuous glass fiber bundles are guided through an impregnation tank 3 containing a resin solution, where they are fully impregnated to obtain multiple impregnated continuous glass fiber bundles. These bundles are then fed into a preforming device 4. A tension- and position-adjustable guide mat device 5 transports polyester fibers treated with a silane coupling agent to the preforming device 4. In the preforming device 4, the polyester fibers treated with the silane coupling agent continuously and smoothly wrap the multiple impregnated continuous glass fiber bundles from the impregnation tank 3, wrapping them together to form a general outline and prevent material displacement. The intermediate material is then pulled into the heating and forming mold 6 by the traction machine 7 for heating and forming, so that multiple impregnated continuous glass fiber bundles are cured to obtain the core 1. At the same time, the polyester fibers that have been surface treated with silane coupling agent are impregnated with resin solution and cured (under the pultrusion traction force and the extrusion action of the heating and forming mold 6, the polyester fibers surface treated with silane coupling agent are carried and embedded into the surface layer of the continuous glass fiber bundle, and the polyester fibers are fully impregnated, mixed and cured by part of the epoxy resin carried by the impregnated continuous glass fiber bundle), to obtain the surface barrier layer 2. Finally, it is pulled out at a uniform speed by the traction machine 7 and cut to a set length to finally obtain the composite insulator core rod.

[0036] In this invention, the resin solution contains epoxy resin, curing agent, and internal release agent.

[0037] In this invention, the temperature for heat forming is 120-180℃.

[0038] The curing agent described in this invention is an acid anhydride curing agent; the internal release agent is a water-based release agent and / or a natural oil-based release agent.

[0039] In one specific embodiment, the curing agent used in this invention is methyltetrahydrophthalic anhydride HK-021, and the internal release agent is natural oil-based MR-3908.

[0040] The method for preparing the composite insulator core rod of the present invention is to use a pultrusion process. In the heated molding die 6, the epoxy resin undergoes rapid gelation and curing. At the same time, the polyester fiber with the outer silane coupling agent surface treatment is compacted by the die pressure. The fiber is fully mixed with the epoxy resin and cured, and then integrated with the inner core 1.

[0041] In a preferred embodiment, the weight ratio of epoxy resin, curing agent, and internal release agent is 100:70-120:0.75-2.

[0042] The traction speed of the traction machine 7 is 0.8-2 m / min.

[0043] More specifically, the aforementioned heating forming mold 6 is a three-section heating forming mold, wherein the temperature of the first section of heating forming is 120-140℃, the temperature of the second section is 140-180℃, and the temperature of the third section is 140-180℃.

[0044] In this invention, for ease of coating, a polyester fiber felt surface-treated with a silane coupling agent is actually used. This silane coupling agent-treated polyester fiber felt can be homemade or commercially available. The silane coupling agent content in the felt is 0.1-0.5 wt%. In a specific embodiment, the silane coupling agent-treated polyester fiber felt used in this invention is commercially available from Changzhou Baosheng New Material Technology Co., Ltd., specifically the PSM series of polyester surface felt / organic surface felt, with a unit area mass of 25-60 g / m². 2 .

[0045] The present invention will be described in detail below through embodiments. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0046] The following examples are as follows Figure 2 The pultrusion system shown includes an impregnation tank 3, a preforming device 4, a felt guide device 5, a thermoforming die 6, a traction machine 7, and a yarn frame 8; the thermoforming die 6 is a three-section thermoforming die.

[0047] The resin solution used in the following examples was obtained by mixing bisphenol A type epoxy resin, an anhydride curing agent (methyltetrahydrophthalic anhydride HK-021), and an internal release agent (natural oil-based MR-3908). The weight ratio of bisphenol A type epoxy resin, anhydride curing agent, and internal release agent was 100:100:1. The polyester fiber felt surface-treated with silane coupling agent was purchased from Changzhou Baosheng New Material Technology Co., Ltd., polyester surface felt / organic surface felt PSM series. In this silane coupling agent surface-treated polyester fiber felt, the content of silane coupling agent was 0.1-0.5wt%, and the unit area mass was 25 g / m². 2 The polyester fiber felt is made by randomly laying out polyester fibers through needle punching. The polyester fibers used are short-cut polyethylene terephthalate (PET) fibers (6mm in length and 15μm in diameter).

[0048] Example 1 Multiple bundles of continuous glass fiber yarn (using 2400Tex alkali-free glass fiber direct yarn) are drawn from the yarn rack 8 and carded together to obtain multiple continuous glass fiber bundles after carding. These carded continuous glass fiber bundles are then guided through the resin impregnation tank 3, where they are fully impregnated with the resin solution to obtain multiple impregnated continuous glass fiber bundles. These impregnated continuous glass fiber bundles are then fed into the preforming device 4. Finally, the polyester fiber felt, which has undergone silane coupling agent surface treatment, is conveyed to the preforming device 4 using an adjustable tension and position guide felt device 5. In the preforming device 4, polyester fibers treated with a silane coupling agent are used to continuously and smoothly wrap multiple impregnated continuous glass fiber bundles from the impregnation tank 3, forming a general outline and preventing material displacement, thus obtaining intermediate material. This intermediate material is then pulled into the heating mold 6 by the traction machine 7 for heating and forming. The first stage of heating and forming has a temperature of 135°C, the second stage 155°C, and the third stage 145°C. The traction speed of the traction machine 7 is 0.8 km / h. The flow rate is m / min to solidify multiple impregnated continuous glass fiber bundles to obtain core 1. At the same time, polyester fibers treated with silane coupling agent are impregnated with resin solution and cured (under the extrusion force of pultrusion and the extrusion action of heating molding die 6, the polyester fibers treated with silane coupling agent are carried and embedded into the surface layer of continuous glass fiber bundle, and the polyester fibers are fully impregnated, mixed and cured by part of the epoxy resin carried by the impregnated continuous glass fiber bundle), to obtain surface barrier layer 2. Finally, it is pulled out at a uniform speed by traction machine 7 and cut to a set length to finally obtain composite insulator core rod.

[0049] The composite insulator core rod obtained in this embodiment includes a load-bearing core 1 and a surface barrier layer 2 in situ covering the outer surface of the core 1. The core 1 is obtained by impregnating multiple continuous glass fiber bundles with a resin solution and then curing them, and has a diameter of 50 mm. The surface barrier layer 2 is obtained by impregnating polyester fiber felt, which has been surface-treated with a silane coupling agent, with a resin solution and then curing it. The polyester fiber content in the material of the surface barrier layer 2 is 10 wt%. The surface barrier layer 2 is formed in situ on the outer surface of the core 1. In the surface barrier layer 2, the polyester fiber is uniformly dispersed in the epoxy resin matrix, and the polyester fiber and the epoxy resin matrix form a dense interface without exposed continuous fibers. The thickness of the surface barrier layer 2 is about 0.2 mm. In this composite insulator core rod, the ratio of the total weight of the continuous glass fiber bundles to the weight of the polyester fiber is 1:0.001.

[0050] Comparative Example 1 The method of Example 1 is implemented, except that the polyester fibers without silane coupling agent surface treatment are used to coat the multiple impregnated continuous glass fiber bundles from the impregnation tank 3. The multiple impregnated continuous glass fiber bundles are directly put into the heating and forming mold 6 under the action of the traction machine 7 for heating and forming to obtain the insulator core rod.

[0051] Test Example 1 The composite insulator core rod of Example 1 and the insulator core rod of Comparative Example 1 were tested according to the water diffusion test method specified in GB / T 19519-2014 (boiling water at 100℃ for 42 hours), and their average breakdown voltage was measured. The test results show that the average breakdown voltage of the composite insulator core rod of the present invention is about 45% higher than that of the insulator core rod of Comparative Example 1. Meanwhile, after 1000 hours of accelerated aging at 85% relative humidity and 50℃, the bending strength retention rate of the core rod of the present invention is as high as 92%, while that of Comparative Example 1 is only 78%. Furthermore, the saturated water absorption rate was measured according to GB / T 1462-2005. The composite insulator core rod of Example 1 was 0.31%, while that of the insulator core rod of Comparative Example 1 was 0.47%, representing a decrease in saturated water absorption rate of about 34%.

[0052] The moisture intrusion conditions of the two were compared. A schematic diagram of moisture intrusion in the insulator core rod of Comparative Example 1 is shown below. Figure 3 As shown, due to the weak fiber / resin interface on the surface, and because the core rod is formed by continuous fiber pultrusion, moisture easily penetrates the interior along it. A schematic diagram of moisture intrusion in the composite insulator core rod of this invention is shown below. Figure 4 As shown, its surface barrier layer 2 is dense and has no axial conduction channels formed by continuous glass fibers; the content of epoxy resin matrix in the surface barrier layer 2 is much higher than that in the core 1. The higher the epoxy resin content, the more obvious the barrier effect on water vapor; moreover, the polyester fibers in the surface barrier layer 2 are short-cut fibers and randomly arranged, which effectively block and disrupt the intrusion path of water vapor, making it easier to hinder water vapor conduction and protect the internal core 1.

[0053] The results above show that the present invention significantly improves the resistance to water vapor intrusion of composite insulator core rods through a simple and efficient process modification. The average breakdown voltage of the core rods prepared by the present invention is significantly improved and the saturated water absorption rate is significantly reduced after boiling in water at 100°C for 42 hours. The mechanical strength retention rate under long-term high humidity environment is greatly improved, which is of great significance for ensuring the safe and stable operation of transmission lines.

[0054] It should be understood that any parts not described in detail in this specification belong to the prior art.

[0055] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A composite insulator core rod, characterized in that, The composite insulator core rod includes a core (1) and a surface barrier layer (2) that is in situ wrapped around the outer surface of the core (1). The core (1) is obtained by impregnating multiple continuous glass fiber bundles with resin solution and then curing them. The surface barrier layer (2) is obtained by impregnating polyester fibers that have been surface treated with silane coupling agent with resin solution and then curing them. The resin solution contains epoxy resin, curing agent, and internal release agent.

2. The composite insulator core rod according to claim 1, characterized in that, The content of polyester fiber in the material of the surface barrier layer (2) is 1-10 wt%.

3. The composite insulator core rod according to claim 1 or 2, characterized in that, Polyester fibers have a diameter of 5-20μm and a length of 3-10mm.

4. The composite insulator core rod according to claim 1, characterized in that, The thickness of the surface barrier layer (2) is 0.1-0.5 mm; The diameter of the core (1) is 10-100mm.

5. The composite insulator core rod according to claim 1, characterized in that, The ratio of the total weight of the continuous glass fiber bundle to the weight of the polyester fiber is 1:0.0005-0.

02.

6. A system for preparing a composite insulator core rod, characterized in that, include: Impregnation tank (3), preforming device (4), felt guiding device (5), heating molding mold (6), and traction machine (7); The impregnation tank (3) is used to hold the resin solution. Multiple continuous glass fiber bundles are impregnated in the resin solution through the impregnation tank (3) to obtain multiple impregnated continuous glass fiber bundles. The resin solution contains epoxy resin, curing agent and internal release agent. The felt guide device (5) is used to transport the polyester fibers treated with silane coupling agent to the preforming device (4). In the preforming device (4), the polyester fibers treated with silane coupling agent are used to wrap multiple continuous glass fiber bundles after impregnation from the impregnation tank (3) to obtain intermediate material. The traction machine (7) is used to pull the intermediate material into the heating and forming mold (6) for heating and forming to obtain the composite insulator core rod.

7. A method for preparing a composite insulator core rod, characterized in that, include: Multiple continuous glass fiber bundles are guided through an impregnation tank (3) containing resin solution and impregnated in the resin solution to obtain multiple impregnated continuous glass fiber bundles. Then, the multiple impregnated continuous glass fiber bundles are sent into a preforming device (4). Then, a polyester fiber treated with silane coupling agent is transported to the preforming device (4) using a felt guide device (5). In the preforming device (4), the multiple impregnated continuous glass fiber bundles from the impregnation tank (3) are wrapped with polyester fiber treated with silane coupling agent to obtain intermediate material. Then, under the traction of a traction machine (7), the material enters a heating molding mold (6) for heating molding to solidify the multiple impregnated continuous glass fiber bundles and obtain a core (1). At the same time, the polyester fiber treated with silane coupling agent is impregnated with resin solution and solidified to obtain a surface barrier layer (2). Finally, a composite insulator core rod is obtained. The resin solution contains epoxy resin, curing agent, and internal release agent; The temperature for heat forming is 120-180℃.

8. The preparation method according to claim 7, characterized in that, The curing agent is an acid anhydride-based curing agent; The internal release agent is a water-based release agent and / or a natural oil-based release agent.

9. The preparation method according to claim 7 or 8, characterized in that, The weight ratio of epoxy resin, curing agent, and internal release agent is 100:70-120:0.75-2.

10. The preparation method according to claim 7 or 8, characterized in that, The traction speed of the traction machine (7) is 0.8-2 m / min.

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