Method for manufacturing a high voltage cable and high voltage cable

Abstract

The application provides a high-voltage cable preparation method and a high-voltage cable. The preparation method comprises the following steps: preparing modified polyvinyl chloride, wherein the modified polyvinyl chloride comprises polyvinyl chloride and a filler added into the polyvinyl chloride; taking 100 parts by weight of the polyvinyl chloride as a base material, and the filler comprises the following components in parts by weight: 1-2 parts of polyethylene, 2-3 parts of a filler, 2-3 parts of a lubricant and 2-5 parts of a toughening agent; extruding the modified polyvinyl chloride on the outer surface of a smooth metal sheath layer to form a modified polyvinyl chloride sheath, and the modified polyvinyl chloride sheath is bonded to the smooth metal sheath layer; and the smooth metal sheath layer is wrapped on the outer surface of a cable core. The high-voltage cable preparation method can greatly improve the flame-retardant performance of the high-voltage cable.

Description

Technical Field

[0001] This invention relates to the field of power cable technology, and in particular to a method for manufacturing a high-voltage cable and the high-voltage cable itself. Background Technology

[0002] With the rapid development of cities, high-voltage cables play an important role in the power system.

[0003] Currently, high-voltage cables typically have a buffer pad layer and a metal sheath layer sequentially covering the outer surface of the insulation shielding layer of the cable core. In existing high-voltage cables, the metal sheath layer mostly uses corrugated aluminum. Research has found that the structure of the corrugated aluminum sheath has certain defects, which can lead to gap discharge during finished product testing. During the research and development of high-voltage cables, related technologies have proposed using a smooth aluminum sheath to replace the existing corrugated aluminum sheath covering the outer surface of the buffer pad layer, forming a smooth aluminum sheath cable. This increases the contact area between the smooth aluminum sheath and the buffer pad layer, thereby overcoming the gap discharge phenomenon during finished product testing.

[0004] However, existing smooth aluminum-sheathed cables are insufficient to meet the requirements for improving the flame-retardant performance of high-voltage cables. Summary of the Invention

[0005] This invention provides a method for preparing a high-voltage cable and a high-voltage cable that can meet the need for improved flame retardant performance of high-voltage cables.

[0006] In a first aspect, the present invention provides a method for preparing a high-voltage cable, the method comprising:

[0007] A modified polyvinyl chloride (PVC) is prepared, comprising PVC and fillers added to PVC, using 100 parts by weight of PVC as the base material, wherein the filler comprises the following components in parts by weight: 1-2 parts of polyethylene, 2-3 parts of filler, 2-3 parts of lubricant and 2-5 parts of toughening agent.

[0008] The modified polyvinyl chloride is extruded onto the outer surface of a smooth metal sheath to form a modified polyvinyl chloride sheath, which is then bonded to the smooth metal sheath; wherein the smooth metal sheath covers the outer surface of the cable core.

[0009] In some optional embodiments, the preparation of modified polyvinyl chloride specifically includes:

[0010] Using 100 parts by weight of polyvinyl chloride as the base material, the filler is added, wherein the mass ratio of the polyethylene, the filler, the lubricant and the toughening agent in the filler is 1:2:2:4, 1:2:3:3 or 2:3:2:2.

[0011] In some optional embodiments, the step of extruding the modified polyvinyl chloride onto the outer surface of a smooth metal sheath to form a modified polyvinyl chloride sheath specifically includes:

[0012] The modified polyvinyl chloride is extruded onto the outer surface of the smooth metal sheath using an extruder to form the modified polyvinyl chloride sheath.

[0013] During the extrusion process, by adjusting the body heating temperature and the die head heating temperature of the extruder, the extruder is controlled to reach the melting temperature of the modified polyvinyl chloride when extruding the modified polyvinyl chloride.

[0014] In some optional embodiments, the melting temperature of the modified polyvinyl chloride is greater than or equal to 175°C and less than or equal to 185°C.

[0015] The extruder body heating temperature is greater than or equal to 160°C and less than or equal to 180°C, and the extruder head heating temperature is greater than or equal to 180°C or equal to 200°C.

[0016] In some optional embodiments, before extruding the modified polyvinyl chloride onto the outer surface of the smooth metal sheath to form the modified polyvinyl chloride sheath, the preparation method further includes:

[0017] Preparation of polyester hot melt adhesive;

[0018] The polyester hot melt adhesive is extruded onto the outer surface of the smooth metal sheath to form a hot melt adhesive layer, wherein the modified polyvinyl chloride sheath is bonded to the smooth metal sheath through the hot melt adhesive layer.

[0019] In some optional embodiments, the preparation of the polyester hot melt adhesive specifically includes:

[0020] Thermoplastic polyester is subjected to alcoholysis, acetylation, heating and cooling treatments in sequence to form polyester hot melt adhesive.

[0021] In some alternative embodiments, the alcoholysis treatment is an alcoholysis performed by adding an alcoholysis solution to the thermoplastic polyester;

[0022] Based on 100 parts by weight of the thermoplastic polyester, the alcoholysis solution comprises the following components in parts by weight: 20 parts of alcohol solution and 2-3 parts of first catalyst.

[0023] In some optional embodiments, the acetylation process involves adding an acid hydrolysate to the material after the alcoholysis process and heating it until all the material in the acetylation process is dissolved.

[0024] Based on 100 parts by weight of the thermoplastic polyester, the acid hydrolysate comprises the following components in parts by weight: 80 parts acid solution, 4-6 parts second catalyst, and 2-4 parts first antioxidant.

[0025] In some optional embodiments, before extruding the modified polyvinyl chloride onto the outer surface of the smooth metal sheath to form the modified polyvinyl chloride sheath, the preparation method further includes:

[0026] Prepare elastic cushioning materials with semi-conductive properties;

[0027] The elastic buffer material is extruded onto the outer surface of the insulating shielding layer of the cable core to form a semi-conductive elastomer buffer layer, and the smooth metal sheath contacts the insulating shielding layer through the semi-conductive elastomer buffer layer.

[0028] In some optional embodiments, the preparation of the elastic cushioning material with semiconductive properties specifically includes:

[0029] The elastic cushioning material is prepared by mixing the following raw materials in parts by weight: 100 parts of elastomer rubber, 20 parts of rubber-plastic foam material, 35-40 parts of styrene-butadiene rubber, 25-30 parts of filler and reinforcing agent, and 2-5 parts of second antioxidant.

[0030] In some alternative embodiments, the elastomeric rubber is a rubber formed from a copolymer of ethylene, propylene, and non-conjugated dienes, the rubber-plastic foam material is a plastic copolymerized from ethylene and acetic acid, and the filler reinforcing agent is carbon black.

[0031] Secondly, the present invention provides a high-voltage cable manufactured using the preparation method described in any of the preceding claims. The high-voltage cable includes a cable core, the outer surface of which is sequentially covered with a smooth metal sheath and a sheath along its own axial direction. The sheath is a modified polyvinyl chloride (PVC) sheath, which covers the outer surface of the smooth metal sheath and is bonded to it. The modified PVC sheath is made of modified PVC, which includes PVC and fillers added to the PVC.

[0032] Using 100 parts by weight of polyvinyl chloride as the base material, the filler comprises the following components in parts by weight: 1-2 parts of polyethylene, 2-3 parts of filler, 2-3 parts of lubricant and 2-5 parts of toughening agent.

[0033] In some alternative embodiments, the high-voltage cable further includes a hot melt adhesive layer located between the smooth metal sheath and the modified polyvinyl chloride sheath to bond the modified polyvinyl chloride sheath and the smooth metal sheath; the hot melt adhesive layer is an adhesive layer formed by polyester hot melt adhesive, which is a polyester adhesive formed by sequentially subjecting thermoplastic polyester to alcoholysis treatment, acetylation treatment, heat treatment and cooling treatment.

[0034] In some optional embodiments, the outer surface of the cable core is further covered with a semi-conductive buffer layer along its own axis. The semi-conductive buffer layer is a semi-conductive elastomer buffer layer. The cable core includes an insulating shielding layer, and the smooth metal sheath contacts the insulating shielding layer through the semi-conductive elastomer buffer layer.

[0035] This invention provides a method for preparing a high-voltage cable and the high-voltage cable itself. In the preparation method, the mechanical properties of PVC are improved through the modification of PVC, making its mechanical properties closer to those of polyethylene used in the preparation of smooth aluminum sheaths in existing high-voltage cables. This ensures that when the modified PVC is extruded onto the outer surface of a smooth metal sheath to form a modified PVC sheath, the resulting sheath exhibits mechanical properties such as mechanical strength and toughness comparable to those of existing polyethylene sheaths, thus meeting the mechanical performance requirements of high-voltage cables. Simultaneously, since the flame-retardant properties of PVC are far superior to those of polyethylene, the modified PVC sheath also enhances the flame-retardant rating of the high-voltage cable, making it easier for the high-voltage cable to pass the bundled Class A burning test, thereby meeting the requirements for improved flame-retardant performance in high-voltage cables. Attached Figure Description

[0036] 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.

[0037] Figure 1 This is a structural schematic diagram of the manufacturing process of the high-voltage cable provided in this embodiment of the invention. Figure 1 ;

[0038] Figure 2 This is a structural schematic diagram of the manufacturing process of the high-voltage cable provided in this embodiment of the invention. Figure 2 ;

[0039] Figure 3 This is a structural schematic diagram of the manufacturing process of the high-voltage cable provided in this embodiment of the invention. Figure 3 .

[0040] Explanation of reference numerals in the attached figures:

[0041] 100-High voltage cable; 1-Conductor; 2-Semi-conductive resistance band; 3-Conductor shielding layer; 4-Insulation layer; 5-Insulation shielding layer; 6-Semi-conductive elastomer buffer layer; 7-Smooth metal sheath; 8-Hot melt adhesive layer; 9-Modified polyvinyl chloride sheath; 10-Conductive layer. Detailed Implementation

[0042] The terminology used in the embodiments section of this invention is for the purpose of explaining specific embodiments of the invention only, and is not intended to limit the invention.

[0043] High-voltage cables: These are a type of power cable used to transmit power between 66kV and 750kV, and are widely used in power transmission and distribution.

[0044] Generally, the outer surface of the insulation shielding layer of a high-voltage cable core is typically covered by a buffer pad layer and a metal sheath layer, with the insulation shielding layer being the outermost layer of the cable core. Most existing high-voltage cables use a corrugated aluminum sheath as the metal sheath layer, covering the outer surface of the buffer pad layer; this type of high-voltage cable can be called a corrugated aluminum sheathed cable. As described in the background section, analysis of recent corrugated aluminum sheathed cable fault cases over the past decade has revealed numerous instances of burn marks or discharge traces on the surface of the insulation shielding layer, even leading to breakdown. This has attracted significant attention from major power companies.

[0045] Extensive testing by research institutes and testing organizations has revealed that the main reasons for the above phenomenon are as follows:

[0046] First, the quality of the cushioning layer;

[0047] Second, the corrugated aluminum sleeve has structural defects.

[0048] The surface of the corrugated aluminum sheath is mostly spiral-shaped, resulting in a linear contact between the sheath and the buffer strip. This means that they cannot maintain continuous electrical contact. If the corrugated aluminum sheath is not manufactured properly, gaps will appear between the sheath and the buffer strip, which will cause gap discharge during the partial discharge withstand voltage test of the finished corrugated aluminum sheathed cable.

[0049] To overcome the structural defects of corrugated aluminum sheaths, the cable industry began developing smooth aluminum sheathed cables. These cables utilize a smooth aluminum sheath, aiming to increase the contact area between the sheath and the buffer strip through surface contact, thereby overcoming the gap discharge phenomenon that occurs during finished product testing. Currently, these smooth aluminum sheathed cables are being used in small batches and are performing well.

[0050] However, smooth aluminum-sheathed cables are further covered with a sheath on the outer surface of the smooth aluminum sheath. Due to the good hardness and mechanical strength of polyethylene (PE), currently only PE sheath materials can meet the requirements for the production of smooth aluminum sheaths. Therefore, most existing smooth aluminum sheaths are made of polyethylene (hereinafter referred to as PE sheath).

[0051] As the State Grid Corporation of China places increasing emphasis on the flame-retardant performance of high-voltage cables, high-voltage cables laid in tunnels now require a flame-retardant rating of Class B or higher. This increases the difficulty of manufacturing smooth aluminum-sheathed cables with high flame-retardant properties. Therefore, the existing smooth aluminum-sheathed cables have a relatively low flame-retardant rating, making it difficult to meet the requirements for improving the flame-retardant performance of high-voltage cables and failing the Class A bundled combustion test for finished high-voltage cables.

[0052] It should be noted that the flame retardancy rating of cables is generally divided into Class A, Class B, and Class C, with the flame retardancy rating decreasing sequentially from Class A to Class B and Class C. The bundled burning Class A test is a routine test for testing the flame retardancy performance of cables in the prior art. Specific test content can be found in the relevant descriptions in the prior art, and will not be further limited in this embodiment.

[0053] In view of this, the present invention provides a method for preparing a high-voltage cable and a high-voltage cable that can meet the need for improved flame retardant performance of high-voltage cables.

[0054] The following description, in conjunction with the accompanying drawings and embodiments, further elaborates on the preparation method of the high-voltage cable and the structure of the high-voltage cable of the present invention.

[0055] refer to Figure 1 The embodiment of the present invention shown provides a method for manufacturing a high-voltage cable, the method comprising:

[0056] Prepare modified polyvinyl chloride, the modified polyvinyl chloride includes polyvinyl chloride and fillers added to polyvinyl chloride, with 100 parts by weight of polyvinyl chloride as the base material, the filler includes the following components in parts by weight: 1-2 parts of polyethylene, 2-3 parts of filler, 2-3 parts of lubricant and 2-5 parts of toughening agent.

[0057] Modified polyvinyl chloride is extruded onto the outer surface of the smooth metal sheath 7 to form a modified polyvinyl chloride sheath 9, which is then bonded to the smooth metal sheath 7; wherein the smooth metal sheath 7 covers the outer surface of the cable core.

[0058] For example, the smooth metal sheath 7 may include, but is not limited to, a smooth aluminum sheath. It should be noted that, compared to the existing corrugated aluminum sheath, the smooth aluminum sheath mainly refers to an aluminum sheath with a smooth surface.

[0059] Due to the softness and low hardness of polyvinyl chloride (PVC) materials, their mechanical strength and hardness are lower than those of PE materials, making it currently unsuitable for use as a sheath in smooth aluminum-sheathed cables.

[0060] Therefore, in the preparation method of this invention, PVC is modified through the preparation of modified polyvinyl chloride (PVC). The addition of PE in the filler can improve the mechanical strength and hardness of PVC, and the addition of toughening agent can improve the toughness of PVC. Thus, the addition of filler can improve the mechanical properties of PVC, making the mechanical properties of the modified PVC closer to those of the polyethylene used to prepare the smooth aluminum sheath in existing smooth aluminum sheathed cables. When the prepared modified PVC is extruded onto the outer surface of the smooth metal sheath 7 to form the modified PVC sheath 9, the mechanical properties of the formed modified PVC sheath 9, such as mechanical strength and toughness, can reach the mechanical strength and toughness of existing PE sheaths. Therefore, when the modified PVC sheath 9 is applied to the high-voltage cable 100, it can meet the mechanical performance requirements of the sheath in the high-voltage cable 100.

[0061] Meanwhile, since the flame-retardant properties of PVC are far superior to those of PE, this embodiment, by modifying PVC to form a modified PVC sheath 9, can further improve the flame-retardant rating of the high-voltage cable 100. This makes the high-voltage cable 100 of this invention more likely to pass the bundled Class A burning test, thus meeting the requirements for improved flame-retardant performance. The flame-retardant rating of the high-voltage cable 100 of this invention can reach Class B or higher, enabling its application in locations with high flame-retardant ratings, such as tunnels and cable trenches, to prevent fires and improve the safe operation of the power grid.

[0062] It should be noted that in this embodiment, soft PVC can be used as the substrate to prepare and obtain modified polyvinyl chloride by adding fillers.

[0063] The preparation of modified polyvinyl chloride specifically includes:

[0064] Using 100 parts by weight of polyvinyl chloride as the base material, fillers are added, and the mass ratio of polyethylene, filler, lubricant and toughening agent in the filler is 1:2:2:4.

[0065] It should be noted that the above mass ratio can be understood as the mass ratio of polyethylene, filler, lubricant, and toughening agent. That is, the mass ratio of polyethylene, filler, lubricant, and toughening agent in the filler is 1:2:2:4. Experiments have shown that when the mass ratio of polyethylene, filler, lubricant, and toughening agent is 1:2:2:4, the prepared modified polyvinyl chloride has a tensile strength of 23 MPa and a Shore hardness of 57D, which are close to the mechanical properties of PE. Therefore, this invention improves the mechanical properties of PVC by modifying it to prepare modified polyvinyl chloride, increasing the flexural stress of PVC from 3N to 21N, reaching the flexural stress level of PE.

[0066] In some embodiments, the mass ratio of polyethylene, filler, lubricant, and toughening agent in the filler can also be 1:2:3:3, 2:3:2:2, or other ratios. Experiments have shown that when the mass ratio of polyethylene, filler, lubricant, and toughening agent is 2:3:2:2, the prepared modified polyvinyl chloride has a tensile strength of 18 MPa and a Shore hardness of 50 D, which is essentially close to the mechanical properties of PE. Therefore, it can be seen that when the mass ratio of polyethylene, filler, lubricant, and toughening agent in the filler is 1:2:3:3 or 2:3:2:2, the modified PVC prepared in this invention also improves the mechanical properties of PVC, increasing the flexural stress of PVC from 3 N to 18 N. Therefore, the mass ratio of polyethylene, filler, lubricant, and toughening agent in the filler in this invention can include, but is not limited to, 1:2:2:4.

[0067] For example, the filler may include, but is not limited to, nano-calcium carbonate or other nanoscale filler materials. In this application, the material of the filler is not further limited. The lubricant may include, but is not limited to, vinyl bis stearamide (EBS). In some embodiments, the lubricant may also include paraffin wax, PE wax, etc. The toughening agent may include, but is not limited to, acrylonitrile-butadiene-styrene copolymer (ABS) or other thermoplastic polymer structural materials. In this application, the material of the toughening agent is not further limited. Acrylonitrile-butadiene-styrene copolymer is a high-strength, high-toughness, and easily processed thermoplastic polymer structural material, also known as ABS resin, which has the characteristics of high strength and good toughness.

[0068] It should be noted that in the preparation process of modified polyvinyl chloride (PVC), after adding the above-mentioned filler to the flexible PVC substrate and mixing it evenly, modified PVC is formed, thus completing the preparation of modified PVC. In the modified PVC, the above-mentioned filler and PVC substrate exist in a blended form.

[0069] Specifically, modified polyvinyl chloride is extruded onto the outer surface of the smooth metal sheath 7 to form a modified polyvinyl chloride sheath 9, which specifically includes:

[0070] Modified polyvinyl chloride is extruded onto the outer surface of the smooth metal sheath 7 using an extruder to form a modified polyvinyl chloride sheath 9.

[0071] During the extrusion process, by adjusting the heating temperature of the extruder body and the heating temperature of the extruder head, the extruder is controlled to reach the melting temperature of the modified polyvinyl chloride when extruding it, so that the modified polyvinyl chloride can be in a molten state when it is extruded through the extruder.

[0072] In some embodiments, the melt temperature of the modified polyvinyl chloride is greater than or equal to 175°C and less than or equal to 185°C. In this case, the extruder body heating temperature is greater than or equal to 160°C and less than or equal to 180°C, and the extruder head heating temperature is greater than or equal to 180°C or equal to 200°C.

[0073] It should be noted that the heating temperature of the machine body can be divided into several melting ranges. For example, the heating temperature of the machine body can be divided into three melting ranges: the feeding section temperature, the melting section temperature, and the homogenization section temperature. Among them, the feeding section temperature can be greater than or equal to 160℃ or 170℃, the melting section temperature can be greater than or equal to 170℃ or 175℃, and the homogenization section temperature can be greater than or equal to 175℃ or 180℃.

[0074] When the extruder body heating temperature is greater than or equal to 160℃ and less than or equal to 180℃, the modified polyvinyl chloride (PVC) can be melted. This allows the extrusion screw in the extruder to push the modified PVC from the extruder body position into the die head position, whereby the modified PVC is extruded onto the outer surface of the smooth metal sleeve 7 (such as a smooth aluminum sleeve) to form the modified PVC sheath 9. By controlling the extruder body heating temperature and the die head heating temperature, the temperature of the modified PVC during extrusion can be controlled, ensuring that the modified PVC melts during extrusion. This allows the modified PVC to be extruded onto the outer surface of the smooth metal sleeve 7 with a uniform thickness, forming the PVC sheath.

[0075] Because smooth aluminum-sheathed cables have slightly worse bending performance than corrugated aluminum-sheathed cables, related technologies use hot melt adhesive to bond the PE sheath to the smooth aluminum sheath to improve its bending performance, and then directly coil it up. Although bonding the PE sheath to the smooth aluminum sheath with hot melt adhesive improves the bending performance of smooth aluminum-sheathed cables, the bending performance of ultra-high voltage, large cross-section smooth aluminum-sheathed cables with an outer diameter of 150mm or more is still not ideal, and the smooth aluminum sheath is prone to wrinkling during production.

[0076] In addition, existing hot melt adhesive substrates are usually ethylene-vinyl acetate copolymers, which can also be called EVA (Ethylene Vinyl Acetate Copolymer) plastic. EVA plastic is easy to bond aluminum materials and PE sheaths. Due to the different formulation system, it is impossible to bond modified polyvinyl chloride sheaths 9 to aluminum materials.

[0077] High-voltage cables 100 with an outer diameter of 150mm or more are typically wound up using a take-up reel. Since the modified PVC sheath 9 possesses mechanical strength and toughness comparable to PE sheaths, the smooth metal sheath 7 does not wrinkle after winding up the high-voltage cable 100 when the reel's diameter is 22 times its outer diameter. However, when the reel's diameter decreases to 21 times or less of the high-voltage cable 100's outer diameter, the smooth metal sheath 7 will still wrinkle after bending.

[0078] Therefore, refer to Figure 2 As shown, before extruding modified polyvinyl chloride onto the outer surface of the smooth metal sheath 7 to form the modified polyvinyl chloride sheath 9, the preparation method further includes:

[0079] Preparation of polyester hot melt adhesive;

[0080] Polyester hot melt adhesive is extruded onto the outer surface of the smooth metal sheath 7 to form a hot melt adhesive layer 8, wherein the modified polyvinyl chloride sheath 9 is bonded to the smooth metal sheath 7 through the hot melt adhesive layer 8.

[0081] It should be noted that this application forms a hot melt adhesive layer 8 by extruding polyester hot melt adhesive onto the outer surface of the smooth metal sheath 7. In this way, the hot melt adhesive layer 8 can tightly bond the modified polyvinyl chloride sheath 9 to the smooth metal sheath 7, such as a smooth aluminum sheath, so that while the modified polyvinyl chloride sheath 9 covers the outer surface of the smooth metal sheath 7, it can also improve the overall bending performance of the high voltage cable 100 of the present invention.

[0082] By modifying the PVC sheath 9 and the hot melt adhesive layer 8, it has been verified that when the diameter of the aforementioned cylinder is reduced to 17 to 14 times the outer diameter of the high-voltage cable 100, the smooth metal sheath 7 of the high-voltage cable 100 does not wrinkle after being coiled. When the diameter of the aforementioned cylinder is reduced to 13 times or less the outer diameter of the high-voltage cable 100, the smooth metal sheath 7 wrinkles after bending.

[0083] Therefore, compared with existing smooth aluminum-sheathed cables, the present invention, through the modification of the polyvinyl chloride sheath 9 and the hot melt adhesive layer 8, can greatly improve the bending performance of the high-voltage cable 100, especially for high-voltage cables 100 with an outer diameter of 150mm or more. This allows the bending performance of high-voltage cables 100 with an outer diameter of 150mm or more to reach a more ideal state. During production, the surface of the smooth metal sheath 7 is less prone to wrinkling, making it possible to use PVC as the sheath material in the production of the high-voltage cable 100. The hot melt adhesive layer 8 covers the outer surface of the smooth aluminum sheath, realizing the production and application of the high-voltage cable 100 of the present invention. Since the modified polyvinyl chloride sheath 9 has better flame retardant properties than the PE sheath, it greatly improves the flame retardant performance of the high-voltage cable 100 of the present invention.

[0084] Specifically, the polyester hot melt adhesive is extruded onto the outer surface of the smooth aluminum sheath to form a hot melt adhesive layer 8, which may include:

[0085] Polyester hot melt adhesive is extruded onto the outer surface of the smooth aluminum sheath using an extruder to form a hot melt adhesive layer 8;

[0086] During the extrusion process, the extruder body heating temperature is greater than or equal to 170℃ and less than or equal to 190℃, while the extruder head heating temperature is greater than or equal to 190℃ or equal to 220℃. This adjustment of the extruder body and head heating temperatures controls the melting temperature of the polyester hot melt adhesive during extrusion. The final melting temperature of the polyester hot melt adhesive is greater than or equal to 190℃ or equal to 210℃.

[0087] It should be noted that, similar to the extrusion process of modified polyvinyl chloride (PVC) using an extruder, the heating temperature of the extruder during the extrusion of polyester hot melt adhesive can also include three melting ranges: the feeding section temperature, the melting section temperature, and the homogenization section temperature. Specifically, the feeding section temperature can be greater than or equal to 170℃ or 175℃, the melting section temperature can be greater than or equal to 175℃ or 185℃, and the homogenization section temperature can be greater than or equal to 185℃ or 190℃.

[0088] By controlling the temperatures of the feeding section, melting section, and homogenization section, the extruder body heating temperature is maintained at 170°C or higher and 190°C or lower. This allows the polyester hot melt adhesive to melt, enabling the extrusion screw to push the adhesive from the extruder body into the die head. The die head then extrudes the polyester hot melt adhesive onto the outer surface of the smooth metal sleeve 7 (e.g., a smooth aluminum sleeve), forming a hot melt adhesive layer 8. By controlling the extruder body and die head heating temperatures, the polyester hot melt adhesive reaches its melting temperature when extruded at the die head, and is then extruded onto the outer surface of the smooth metal sleeve 7 with a uniform thickness, forming the hot melt adhesive layer 8.

[0089] The preparation of polyester hot melt adhesive specifically includes:

[0090] Thermoplastic polyester is subjected to alcoholysis, acetylation, heating and cooling treatments in sequence to form polyester hot melt adhesive.

[0091] In this way, after the thermoplastic polyester is subjected to alcoholysis and acetylation in sequence, the acetylated material is heated during the heating process. As some substances in the material evaporate and the co-condensation reaction continues, a polyester hot melt adhesive will be formed after cooling.

[0092] For example, the thermoplastic polyester may include, but is not limited to, polyethylene terephthalate (PET), which can also be referred to as polyester resin. In some embodiments, the thermoplastic polyester may also be other thermoplastic polyesters, such as polyethersulfone (PES). In this embodiment, the type of thermoplastic polyester is not further limited.

[0093] The alcoholysis treatment involves adding an alcoholysis solution to the thermoplastic polyester.

[0094] Based on 100 parts by weight of thermoplastic polyester, the alcoholysis solution includes the following components in parts by weight: 20 parts of alcohol solution and 2-3 parts of first catalyst.

[0095] It should be noted that the alcohol solution includes, but is not limited to, ethylene glycol, and the first catalyst includes, but is not limited to, catalysts commonly used in thermoplastic polyesters, which are well known to those skilled in the art and are not further limited herein. In this way, the alcohol solution can be used to perform alcoholysis on thermoplastic polyesters (such as PET) to form polyester hot melt adhesive in subsequent processes. Under the catalytic action of the first catalyst, the alcoholysis process of thermoplastic polyesters such as PET can be accelerated, thereby shortening the alcoholysis treatment time.

[0096] Acetic acidification involves adding an acid hydrolysate to the material after alcoholysis and heating it until all the material in the acetic acidification process is dissolved.

[0097] Based on 100 parts by weight of thermoplastic polyester, the acid hydrolysate includes the following components in parts by weight: 80 parts acid solution, 4-6 parts second catalyst and 2-4 parts first antioxidant.

[0098] It should be noted that the acid solution includes, but is not limited to, oxalic acid, and the second catalyst can be a catalyst commonly used in thermoplastic polyesters, which is well known to those skilled in the art and is not further limited here. The first antioxidant includes, but is not limited to, antioxidant 1010 in the prior art. In this way, the acid solution can acid-hydrolyze the material after alcoholysis treatment, so that subsequent processes such as heating and cooling treatments can be performed to form polyester hot melt adhesive. Under the catalytic action of the second catalyst, the acid-hydrolyze process of the material after alcoholysis treatment can be accelerated, thereby shortening the acid-hydrolyze treatment time. By adding the first antioxidant to the acid hydrolysate, oxidation of the material after alcoholysis treatment during the acid-hydrolyze process can be prevented, avoiding any impact on the formation of the polyester hot melt adhesive.

[0099] It should be noted that the heat treatment mainly refers to continuing to heat the acetic acid-treated material to 220℃-240℃. As some low-molecular-weight substances such as ethylene glycol are evaporated from the material and the co-condensation reaction of thermoplastic polyester continues, a polyester hot melt adhesive will be formed after cooling.

[0100] This invention does not impose particular limitations on the heat treatment and cooling treatment; commonly used heat treatment and cooling treatments in the art can be used to heat and cool the thermoplastic polyester. In related technologies, smooth aluminum-sheathed cables use a tape, such as a buffer water-blocking tape, as a buffer layer, covering the outer surface of the insulation shielding layer of the cable core. This buffer layer is located between the cable core and the smooth aluminum sheath, providing buffer protection for the cable core and longitudinal water blocking. However, the design of the buffer layer in existing smooth aluminum-sheathed cables has the following problems:

[0101] 1. The buffer pad layer is designed to be too thick, resulting in an excessive gap between the smooth aluminum sheath and the insulation shield layer 5 in the existing smooth aluminum sheathed cable, which is not conducive to the tightening of the smooth aluminum sheath and the cable core.

[0102] 2. The buffer water-blocking tape contains water-blocking powder, which will react chemically with the smooth aluminum sheath after absorbing moisture, causing the insulation shielding layer and buffer pad layer to be eroded by discharge, thus reducing the product performance of the smooth aluminum sheath cable.

[0103] Therefore, in some embodiments, reference is made to Figure 2 As shown, before extruding modified polyvinyl chloride onto the outer surface of the smooth metal sheath 7 to form the modified polyvinyl chloride sheath 9, the preparation method further includes:

[0104] Prepare elastic cushioning materials with semi-conductive properties;

[0105] Elastic buffer material is extruded onto the outer surface of the insulating shield layer 5 of the cable core to form a semi-conductive elastomer buffer layer 6, and a smooth metal sheath layer 7 contacts the insulating shield layer 5 through the semi-conductive elastomer buffer layer 6.

[0106] It should be noted that the extrusion of the semiconductive elastomer buffer layer 6 onto the outer surface of the insulating shield layer 5 is performed earlier than the extrusion of the smooth metal sheath 7 onto the outer surface of the insulating shield layer 5. In this embodiment of the invention, a semiconductive elastomer buffer layer 6 is formed by extruding a semiconductive elastic buffer material onto the outer surface of the insulating shield layer 5 of the cable core. Because the semiconductive elastomer buffer layer 6 has a certain degree of elasticity, during the production of the high-voltage cable 100, after the smooth metal sheath 7 passes through the diameter reduction device, the inner diameter of the smooth metal sheath 7 and the semiconductive elastomer buffer layer 6 are connected with a negative clearance fit. The semiconductive elastomer buffer layer 6 can effectively fill the gap between the smooth metal sheath 7 and the insulating shield layer 5, providing longitudinal water resistance while also allowing the smooth metal sheath 7 to tighten onto the outer surface of the insulating shield layer 5, ensuring close contact between the smooth metal sheath 7 and the insulating shield layer 5, and guaranteeing continuous and frequent electrical contact between the smooth metal sheath 7 and the insulating shield layer 5.

[0107] In addition, since the semiconductive elastomer buffer layer 6 is formed by extruding elastic buffer material onto the outer surface of the insulating shield layer 5 of the cable core, rather than by using a buffer water-blocking tape, the embodiment of the present invention can also avoid the chemical reaction between the water-blocking powder and the smooth metal sheath 7 by setting the semiconductive elastomer buffer layer 6, thus ensuring the product performance of the high-voltage cable 100 of the embodiment of the present invention and improving the safe and reliable operation of the high-voltage cable 100 in the power grid system.

[0108] Extensive testing has shown that the use of a semi-conductive elastomer buffer layer 6 in the high-voltage cable 100 solves the problem of electrochemical reaction between the smooth metal sheath 7 and the water-blocking powder, as the semi-conductive elastomer buffer layer 6 does not contain water-blocking powder. This prevents corrosion of the semi-conductive elastomer buffer layer 6 and the insulation shielding layer 5, and improves the service life of the high-voltage cable 100.

[0109] In this embodiment, the elastic buffer material can be extruded onto the outer surface of the insulating shield layer 5 using extrusion equipment such as an extruder to form a semi-conductive elastomer buffer layer 6. Specifically, when the rated voltage of the high-voltage cable 100 is 66kV-110kV, the thickness of the semi-conductive elastomer buffer layer 6 can be greater than or equal to 2.5mm and less than or equal to 3.5mm; when the rated voltage of the high-voltage cable 100 is 220kV, the thickness of the semi-conductive elastomer buffer layer 6 can be greater than or equal to 4.5mm and less than or equal to 6mm; and when the rated voltage of the high-voltage cable 100 is 500kV, the thickness of the semi-conductive elastomer buffer layer 6 can be greater than or equal to 5mm and less than or equal to 7.5mm.

[0110] Specifically, the preparation of elastic cushioning materials with semi-conductive properties includes:

[0111] Mix the following raw materials in parts by weight: 100 parts elastomer rubber, 20 parts rubber-plastic foam material, 35-40 parts styrene-butadiene rubber, 25-30 parts filler and reinforcing agent, and 2-5 parts second antioxidant to prepare an elastic cushioning material.

[0112] It should be noted that styrene-butadiene rubber can also be called polystyrene-butadiene rubber (SBR). The elastomer rubber, rubber-plastic foam material, styrene-butadiene rubber, filler reinforcing agent, and second antioxidant can be mixed (physically blended) and melted in an extrusion device such as an extruder, and then extruded onto the outer surface of the insulating shield layer 5 to form a semi-conductive elastomer buffer layer 6. Due to the presence of the elastomer rubber, rubber-plastic foam material, and styrene-butadiene rubber, the semi-conductive elastomer buffer layer 6 possesses a certain degree of elasticity, effectively filling the gap between the smooth aluminum sleeve layer and the insulating shield layer 5. Simultaneously, the addition of the filler reinforcing agent enhances the strength of the elastic buffer material and the semi-conductive elastomer buffer layer 6, and the addition of the second antioxidant ensures that the elastic buffer material and the semi-conductive elastomer buffer layer 6 possess certain antioxidant properties.

[0113] For example, the elastomeric rubber may include, but is not limited to, rubber formed from copolymers of ethylene, propylene, and non-conjugated dienes, which may also be referred to as elastomer EPMD. The rubber-plastic foam material may include, but is not limited to, a plastic copolymerized from ethylene and acetate, which may also be referred to as EVA plastic. The reinforcing filler may include, but is not limited to, carbon black. The second antioxidant may include, but is not limited to, antioxidant 168 as known in the art.

[0114] To verify the performance of the elastic buffer material, the following raw materials in parts by weight were mixed: 100 parts of elastomer EPMD, 20 parts of EVA plastic, 40 parts of styrene-butadiene rubber, 30 parts of carbon black, and 5 parts of a second antioxidant. The volume resistivity of the prepared elastic buffer material can reach 10 Ω·m, which can meet the performance requirements of the semiconductive elastomer buffer layer 6 in the high-voltage cable 100.

[0115] refer to Figure 3 As shown, after extruding the modified polyvinyl chloride sheath 9 onto the outer surface of the smooth aluminum sheath, the method for preparing the high-voltage cable of the present invention further includes:

[0116] A conductive layer 10 is formed on the outer surface of the modified polyvinyl chloride sheath 9.

[0117] It should be noted that the conductive layer 10 may include, but is not limited to, a semi-conductive graphite layer. The formation method of the conductive layer 10 can be referred to the relevant description of the high-voltage cable 100 in the prior art. In this embodiment, the formation method of the conductive layer 10 will not be further elaborated.

[0118] refer to Figure 3 As shown, the cable core may include a conductor 1. The outer surface of the conductor 1 is sequentially covered with a semiconducting resistance strip 2, a conductor shielding layer 3, an insulating layer 4, and an insulating shielding layer 5. The conductor 1, the semiconducting resistance strip 2, the conductor shielding layer 3, the insulating layer 4, and the insulating shielding layer 5 together constitute the cable core, with the insulating shielding layer 5 serving as the outermost layer of the cable core. For example, the insulating layer 4 may include, but is not limited to, an insulating layer made of cross-linked polyethylene (XLPE).

[0119] In this embodiment, before extruding the elastic buffer material onto the outer surface of the insulating shielding layer 5, the method for preparing the high-voltage cable in this invention may further include:

[0120] Prepare the cable core.

[0121] It should be noted that the preparation method of the cable core and the materials of each layer in the cable core can be referred to the relevant descriptions of high-voltage cables in the prior art. In this embodiment, the preparation method of the cable core will not be further elaborated. The structure of the high-voltage cable 100 prepared by the high-voltage cable preparation method provided in the embodiment of the present invention is as follows: Figure 3 As shown in the image.

[0122] The method for preparing the high-voltage cable of the present invention will be further described below with reference to specific embodiments.

[0123] Example 1

[0124] refer to Figure 3As shown, the method for manufacturing a high-voltage cable provided in this embodiment may include the following steps:

[0125] 1) Preparation of cable core

[0126] 2) A semi-conductive elastomer buffer layer is formed on the outer surface of the cable core.

[0127] The following raw materials in parts by weight are mixed: 100 parts of elastomer EPMD, 20 parts of EVA plastic, 40 parts of styrene-butadiene rubber, 30 parts of carbon black, and 5 parts of a second antioxidant (antioxidant 168) to prepare an elastic cushioning material.

[0128] The elastic buffer material is extruded onto the outer surface of the insulating shield layer 5 of the cable core using an extrusion device to form a semi-conductive elastomer buffer layer 6. The semi-conductive elastomer buffer layer 6 covers the outer surface of the insulating shield layer 5 and is in close contact with the insulating shield layer 5.

[0129] Among them, the volume resistivity of the elastic buffer material can reach 10 Ω·m.

[0130] 3) A smooth metal sheath 7 is formed on the outer surface of the semiconductive elastomer buffer layer 6.

[0131] The smooth metal sheath 7 can be a smooth aluminum sheath, and the formation method of the smooth aluminum sheath can be referred to the relevant description of the high-voltage cable 100 in the prior art. The cable core covered with the smooth metal sheath 7 is passed through a diameter reduction device so that the smooth metal sheath 7 and the semi-conductive elastomer buffer layer 6 are in a negative clearance fit, and the gap between the aluminum sheath and the cable core is filled by the semi-conductive elastomer buffer layer 6.

[0132] 4) A hot melt adhesive layer 8 is formed on the outer surface of the smooth metal sheath 7.

[0133] Alcohololysis: Alcohololysis is carried out by adding alcoholysis solution to PET. Based on 100 parts by weight of PET, the alcoholysis solution includes the following components in parts by weight: 20 parts of ethylene glycol and 3 parts of the first catalyst.

[0134] Acetic acidification: Add acid hydrolysate to the material after alcoholysis and heat until all the material in the acetic acidification process is dissolved; Based on 100 parts by weight of PET, the acid hydrolysate includes the following components in parts by weight: 80 parts of oxalic acid, 6 parts of the second catalyst and 4 parts of the first antioxidant;

[0135] The material after acetylation is heated to 220℃-240℃ during the heat treatment. As some substances in the material evaporate and the co-condensation reaction continues, polyester hot melt adhesive will be formed after cooling treatment.

[0136] Polyester hot melt adhesive is extruded onto the outer surface of the smooth metal sleeve 7 using an extruder to form a hot melt adhesive layer 8. The modified polyvinyl chloride sheath 9 is bonded to the smooth metal sleeve 7 via the hot melt adhesive layer 8. The extruder body heating temperature is 190℃, and the extruder head heating temperature is 220℃.

[0137] 5) A modified polyvinyl chloride sheath 9 is formed on the outer surface of the hot melt adhesive layer 8.

[0138] Modified polyvinyl chloride was prepared by adding fillers to 100 parts by weight of polyvinyl chloride as the base material. The fillers included the following components in parts by weight: 1 part of polyethylene, 2 parts of filler, 3 parts of lubricant and 3 parts of ABS resin.

[0139] Modified polyvinyl chloride (PVC) is extruded onto the outer surface of a smooth metal sleeve 7 using an extruder to form a modified PVC sheath 9, which is then bonded to the smooth metal sleeve 7. The extruder body heating temperature is 180°C, and the extruder head heating temperature is 200°C.

[0140] Among them, the modified PVC sheath 9 has a tensile strength of 22 MPa, a hardness of 55D, and the PVC bending stress is increased from 3N to 19N.

[0141] 6) A conductive layer 10 is formed on the outer surface of the modified polyvinyl chloride sheath 9.

[0142] It should be noted that after the conductive layer 10 is formed, the high-voltage cable 100 can be formed.

[0143] Example 2

[0144] refer to Figure 3 As shown, the method for manufacturing a high-voltage cable provided in this embodiment may include the following steps:

[0145] 1) Preparation of cable core

[0146] 2) A semi-conductive elastomer buffer layer is formed on the outer surface of the cable core.

[0147] The following raw materials in parts by weight are mixed: 100 parts of elastomer EPMD, 20 parts of EVA plastic, 40 parts of styrene-butadiene rubber, 30 parts of carbon black, and 5 parts of a second antioxidant to prepare an elastic cushioning material.

[0148] The elastic buffer material is extruded onto the outer surface of the insulation shielding layer 5 of the cable core using an extrusion device to form a semi-conductive elastomer buffer layer 6. The smooth metal sheath 7 is in close contact with the insulation shielding layer 5 through the semi-conductive elastomer buffer layer 6.

[0149] Among them, the volume resistivity of the elastic buffer material can reach 10 Ω·m.

[0150] 3) A smooth metal sheath 7 is formed on the outer surface of the semiconductive elastomer buffer layer 6.

[0151] The smooth metal sheath 7 can be a smooth aluminum sheath, and the formation method of the smooth aluminum sheath can be referred to the relevant description of the high-voltage cable 100 in the prior art. The cable core covered with the smooth metal sheath 7 is passed through a diameter reduction device so that the smooth metal sheath 7 and the semi-conductive elastomer buffer layer 6 are in a negative clearance fit, and the gap between the aluminum sheath and the cable core is filled by the elastomer.

[0152] 4) A hot melt adhesive layer 8 is formed on the outer surface of the smooth metal sheath 7.

[0153] Alcohololysis: Alcohololysis is carried out by adding alcoholysis solution to PET. Based on 100 parts by weight of PET, the alcoholysis solution includes the following components in parts by weight: 20 parts of ethylene glycol and 2 parts of the first catalyst.

[0154] Acetic acidification: After the alcoholysis treatment is completed, acid hydrolysate is added to the material and heated until all the material in the acetic acidification treatment is dissolved; based on 100 parts by weight of PET, the acid hydrolysate includes the following components in parts by weight: 80 parts of oxalic acid, 4 parts of the second catalyst and 2 parts of the first antioxidant;

[0155] The material after acetylation is heated to 220℃-240℃ during the heat treatment. As some substances in the material evaporate and the co-condensation reaction continues, polyester hot melt adhesive will be formed after cooling treatment.

[0156] Polyester hot melt adhesive is extruded onto the outer surface of the smooth metal sleeve 7 using an extruder to form a hot melt adhesive layer 8. The modified polyvinyl chloride sheath 9 is bonded to the smooth metal sleeve 7 via the hot melt adhesive layer 8. The extruder body heating temperature is 170℃, and the extruder head heating temperature is 190℃.

[0157] 5) A modified polyvinyl chloride sheath 9 is formed on the outer surface of the hot melt adhesive layer 8.

[0158] Modified polyvinyl chloride was prepared by adding fillers to 100 parts by weight of polyvinyl chloride as the base material. The fillers included the following components in parts by weight: 2 parts of polyethylene, 3 parts of filler, 2 parts of lubricant and 2 parts of ABS resin.

[0159] Modified polyvinyl chloride (PVC) is extruded onto the outer surface of a smooth metal sleeve 7 using an extruder to form a modified PVC sheath 9, which is then bonded to the smooth metal sleeve 7. The extruder body heating temperature is 160°C, and the extruder head heating temperature is 180°C.

[0160] Among them, the modified PVC sheath 9 has a tensile strength of 21 MPa, a hardness of 56, and the PVC bending stress is increased from 3 N to 18 N.

[0161] 6) A conductive layer 10 is formed on the outer surface of the modified polyvinyl chloride sheath 9.

[0162] It should be noted that after the conductive layer 10 is formed, the high-voltage cable 100 can be formed.

[0163] Based on the above, this embodiment of the invention also provides a high-voltage cable 100, which is manufactured using any of the above-described manufacturing methods. (See reference) Figure 3 As shown, the high-voltage cable 100 includes a cable core, the outer surface of which is sequentially covered with a smooth metal sheath 7 and a sheath along its own axial direction. The sheath is a modified polyvinyl chloride sheath 9, which covers the outer surface of the smooth metal sheath 7 and is bonded to it. The modified polyvinyl chloride sheath 9 is made of modified polyvinyl chloride, which includes polyvinyl chloride and fillers added to the polyvinyl chloride.

[0164] The base material is 100 parts by weight of polyvinyl chloride, and the filler includes the following components in parts by weight: 1-2 parts of polyethylene, 2-3 parts of filler, 2-3 parts of lubricant and 2-5 parts of toughening agent.

[0165] By modifying the PVC sheath 9, the flame retardant rating of the high-voltage cable 100 can be improved, making it easier for the high-voltage cable 100 of the present invention to pass the Class A burning test of high-voltage cable 100 bundled, thus meeting the requirements of the high-voltage cable 100 for improved flame retardant performance. This allows the high-voltage cable 100 of the present invention to be used in places with high flame retardant ratings, such as tunnels and cable trenches, to avoid fires and improve the safe operation of the power grid.

[0166] The mass ratio of polyethylene, filler, lubricant and toughening agent in the filler is 1:2:2:4, 1:2:3:3 or 2:3:2:2.

[0167] It should be noted that the composition, proportion, and preparation process of the filler in the modified PVC, the preparation process of the modified PVC sheath 9, the structure of the smooth metal sheath 7, and the structure of the cable core can be referred to the relevant descriptions above, and will not be repeated here. Furthermore, since the high-voltage cable 100 is manufactured using the high-voltage cable manufacturing method described in the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the manufacturing methods described in the above embodiments, and will not be elaborated upon here.

[0168] refer to Figure 3As shown, the high-voltage cable 100 also includes a hot melt adhesive layer 8, which is located between the smooth metal sheath 7 and the modified polyvinyl chloride (PVC) sheath 9 to bond the modified PVC sheath 9 and the smooth metal sheath 7. The hot melt adhesive layer 8 is a polyester hot melt adhesive layer, which is formed by sequentially subjecting thermoplastic polyester to alcoholysis, acetylation, heat treatment, and cooling treatment. In this way, the hot melt adhesive layer 8 can tightly bond the modified PVC sheath 9 and the smooth metal sheath 7, such as a smooth aluminum sheath, together. This not only achieves the coverage of the modified PVC sheath 9 on the outer surface of the smooth metal sheath 7, but also improves the overall bending performance of the high-voltage cable 100.

[0169] It should be noted that the preparation process of the polyester hot melt adhesive and the formation method of the hot melt adhesive layer 8 can be referred to the relevant descriptions above, and will not be repeated here.

[0170] refer to Figure 3 As shown, the outer surface of the cable core is also covered with a semi-conductive buffer layer along its own axis. The semi-conductive buffer layer is a semi-conductive elastomer buffer layer 6. The cable core includes an insulating shield layer 5, and the smooth metal sheath 7 is in contact with the insulating shield layer 5 through the semi-conductive elastomer buffer layer 6. Due to the elasticity of the semi-conductive elastomer buffer layer 6, during the production process of the high-voltage cable 100, the semi-conductive elastomer buffer layer 6 can effectively fill the gap between the smooth metal sheath 7 and the insulating shield layer 5. This not only achieves longitudinal water blocking but also allows the smooth metal sheath 7 to tighten onto the outer surface of the insulating shield layer 5, ensuring close contact between the smooth metal sheath 7 and the insulating shield layer 5, and guaranteeing continuous and frequent electrical contact between the smooth metal sheath 7 and the insulating shield layer 5.

[0171] It should be noted that the rated voltage of the high-voltage cable 100 of the present invention can be greater than or equal to 66kV and less than or equal to 550kV.

[0172] The high-voltage cable 100 provided by this invention utilizes PVC as the sheath material, which not only greatly improves the flame-retardant properties of the high-voltage cable 100, but also ensures that the smooth metal sheath 7 does not wrinkle after bending the upper coil, exhibiting good bending performance. Furthermore, it enhances the safe and reliable operation of the high-voltage cable 100 in power grid systems.

[0173] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0174] In the description of this invention, it should be understood that the terms “comprising” and “having” as used herein, and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, display structure, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or device.

[0175] Unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0176] 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for manufacturing a high-voltage cable, characterized in that, include: A modified polyvinyl chloride (PVC) is prepared, comprising PVC and fillers added to PVC, using 100 parts by weight of PVC as the base material, wherein the filler comprises the following components in parts by weight: 1-2 parts of polyethylene, 2-3 parts of filler, 2-3 parts of lubricant and 2-5 parts of toughening agent. The modified polyvinyl chloride is extruded onto the outer surface of a smooth metal sheath to form a modified polyvinyl chloride sheath, which is bonded to the smooth metal sheath; wherein the smooth metal sheath covers the outer surface of the cable core. Before extruding the modified polyvinyl chloride onto the outer surface of the smooth metal sheath to form the modified polyvinyl chloride sheath, the preparation method further includes: Preparation of polyester hot melt adhesive; The polyester hot melt adhesive is extruded onto the outer surface of the smooth metal sheath to form a hot melt adhesive layer, wherein the modified polyvinyl chloride sheath is bonded to the smooth metal sheath through the hot melt adhesive layer; The preparation of the polyester hot melt adhesive specifically includes: Thermoplastic polyester is subjected to alcoholysis and acetylation treatment in sequence. The acetylated material is heated during the heating treatment. As some low molecular weight substances in the material are evaporated and the co-condensation reaction continues, after cooling treatment, polyester hot melt adhesive is formed. The alcoholysis treatment is carried out by adding an alcoholysis solution to the thermoplastic polyester; Based on 100 parts by weight of the thermoplastic polyester, the alcoholysis solution comprises the following components in parts by weight: 20 parts of alcohol solution and 2-3 parts of first catalyst; The acetylation process involves adding an acid hydrolysate to the material after the alcoholysis process and heating it until all the material in the acetylation process is dissolved. Based on 100 parts by weight of the thermoplastic polyester, the acid hydrolysate comprises the following components in parts by weight: 80 parts acid solution, 4-6 parts second catalyst, and 2-4 parts first antioxidant.

2. The preparation method according to claim 1, characterized in that, The preparation of modified polyvinyl chloride specifically includes: Using 100 parts by weight of polyvinyl chloride as the base material, the filler is added, wherein the mass ratio of the polyethylene, the filler, the lubricant and the toughening agent in the filler is 1:2:2:4, 1:2:3:3 or 2:3:2:

2.

3. The preparation method according to claim 2, characterized in that, The process of extruding the modified polyvinyl chloride onto the outer surface of a smooth metal sheath to form a modified polyvinyl chloride sheath specifically includes: The modified polyvinyl chloride is extruded onto the outer surface of the smooth metal sheath using an extruder to form the modified polyvinyl chloride sheath. During the extrusion process, by adjusting the body heating temperature and the die head heating temperature of the extruder, the extruder is controlled to reach the melting temperature of the modified polyvinyl chloride when extruding the modified polyvinyl chloride.

4. The preparation method according to claim 3, characterized in that, The melting temperature of the modified polyvinyl chloride is greater than or equal to 175°C and less than or equal to 185°C. The extruder body heating temperature is greater than or equal to 160°C and less than or equal to 180°C, and the extruder head heating temperature is greater than or equal to 180°C or equal to 200°C.

5. The preparation method according to any one of claims 1-4, characterized in that, Before extruding the modified polyvinyl chloride onto the outer surface of the smooth metal sheath to form the modified polyvinyl chloride sheath, the preparation method further includes: Prepare elastic cushioning materials with semi-conductive properties; The elastic buffer material is extruded onto the outer surface of the insulating shielding layer of the cable core to form a semi-conductive elastomer buffer layer, which covers the insulating shielding layer and the smooth metal sheath.

6. The preparation method according to claim 5, characterized in that, The preparation of the elastic cushioning material with semi-conductive properties specifically includes: The elastic cushioning material is prepared by mixing the following raw materials in parts by weight: 100 parts of elastomer rubber, 20 parts of rubber-plastic foam material, 35-40 parts of styrene-butadiene rubber, 25-30 parts of filler and reinforcing agent, and 2-5 parts of second antioxidant.

7. The preparation method according to claim 6, characterized in that, The elastomer rubber is a rubber formed from a copolymer of ethylene, propylene and non-conjugated diene, the rubber-plastic foam material is a plastic copolymerized from ethylene and acetic acid, and the filler and reinforcing agent is carbon black.

8. A high-voltage cable, characterized in that, The high-voltage cable is prepared by the preparation method described in any one of claims 1-7. The high-voltage cable includes a cable core, and the outer surface of the cable core is sequentially covered with a smooth metal sheath and a sheath along its own axial direction. The sheath is a modified polyvinyl chloride sheath, and the modified polyvinyl chloride sheath covers the outer surface of the smooth metal sheath and is bonded to the smooth metal sheath. The modified polyvinyl chloride sheath is made of modified polyvinyl chloride, which includes polyvinyl chloride and fillers added to the polyvinyl chloride; Using 100 parts by weight of polyvinyl chloride as the base material, the filler comprises the following components in parts by weight: 1-2 parts of polyethylene, 2-3 parts of filler, 2-3 parts of lubricant and 2-5 parts of toughening agent.

9. The high-voltage cable according to claim 8, characterized in that, It also includes a hot melt adhesive layer, which is located between the smooth metal sleeve and the modified polyvinyl chloride sheath to bond the modified polyvinyl chloride sheath and the smooth metal sleeve; the hot melt adhesive layer is an adhesive layer formed by polyester hot melt adhesive, which is a polyester adhesive formed by sequentially subjecting thermoplastic polyester to alcoholysis treatment, acetylation treatment, heat treatment and cooling treatment.

10. The high-voltage cable according to claim 9, characterized in that, The outer surface of the cable core is also covered with a semi-conductive elastomer buffer layer along its own axis. The cable core includes an insulating shielding layer, and the smooth metal sheath contacts the insulating shielding layer through the semi-conductive elastomer buffer layer.

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