High-temperature-resistant cable sheath material and preparation method thereof

Abstract

The invention relates to the field of cable sheath material preparation, in particular to a high-temperature-resistant cable sheath material and a preparation method thereof. The method comprises the following steps: performing vacuum drying on a matrix polymer, a heat-resistant filler and a functional additive, mixing, and adding an interfacial compatibilizer to obtain a premix; carrying out mechanical activation treatment on the premix, carrying out segmented temperature control melt blending extrusion by using a twin-screw extruder, cooling and pelletizing to obtain master batches; after the master batch is subjected to pre-crystallization treatment, the master batch is subjected to melt extrusion through a single-screw extruder and is coated on the surface of a cable conductor to form a sheath layer; and the sheath layer is subjected to segmented heating cross-linking reaction and gradient cooling solidification, and is finally rolled and stored. According to the method, by optimizing the material ratio and process parameters, the high temperature resistance, mechanical strength and stability of the sheath material are enhanced, and the sheath material is suitable for being applied to cables in a high-temperature environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cable sheath material preparation, in particular to a high-temperature-resistant cable sheath material and a preparation method thereof. BACKGROUND

[0002] As an important component of cables, cable sheath materials play a crucial role in protecting the conductors from external environmental damage. In the fields of power transmission, communication, industrial equipment, and others, cables often need to work in high-temperature, high-humidity, or corrosive environments for a long time, so the high-temperature resistance of the sheath material is particularly important. Traditional cable sheath materials are mostly made of polyvinyl chloride, polyethylene, or rubber-based polymers. These materials perform well at room temperature, but they can soften, deform, age, or degrade under high-temperature conditions, leading to a decrease in cable insulation performance and a reduction in service life. For example, polyvinyl chloride sheaths may release harmful gases when the temperature exceeds 80℃, and polyethylene materials can easily oxidize under long-term high-temperature conditions, significantly reducing their mechanical strength. With the development of industrial technology, the demand for cables in high-temperature environments is increasing, such as in the metallurgy, chemical industry, and new energy sectors, which require cable sheaths to withstand long-term operating temperatures above 150℃. In existing technologies, to improve the heat resistance of sheath materials, methods such as adding inorganic fillers (e.g., magnesium hydroxide, aluminum oxide) or using high-performance polymers (e.g., silicone rubber, fluoropolymers) are often used. However, these methods have some limitations. When adding fillers, if the fillers are not uniformly dispersed or have poor compatibility with the base polymer, it can lead to material interface defects, affecting the compactness and mechanical properties of the sheath.

[0003] In terms of preparation process, traditional methods often use simple blending extrusion, which lacks fine control of the material's microstructure. For example, the surface of the filler is not modified, and it can easily agglomerate during the mixing process, reducing the reinforcing effect; unreasonable setting of extrusion process parameters can lead to material degradation or phase separation; if the cross-linking temperature is not accurately controlled, the cross-linking degree will be uneven, affecting the thermal stability and durability of the sheath. Some existing technologies attempt to improve performance through multi-step processing or adding multiple additives, but this increases the complexity of the process and can introduce new problems, such as residual solvents or stress concentration.

[0004] Therefore, there is an urgent need in the field for a high-temperature-resistant cable sheath material preparation method that has excellent comprehensive performance and controllable process, which can ensure the heat resistance of the material while considering processing efficiency, cost-effectiveness, and long-term reliability. SUMMARY

[0005] Based on the above-mentioned problems, the present application provides a high-temperature-resistant cable sheath material and a preparation method thereof, the method comprising: Step (a): the base polymer, heat-resistant filler and functional additives are vacuum dried, then mixed according to the mass ratio, and an interfacial agent is added to obtain a premix; Step (b): the premix of step (a) is put into a high-speed mixer for mechanical activation treatment, and then the treated material is transferred into a twin-screw extruder for segmented temperature control melt blending extrusion. The extruded strip is cooled in a water tank and then drawn and cut into particles to obtain a master batch; Step (c): the master batch of step (b) is pre-crystallized in a constant temperature and humidity environment, and then fed into a single-screw extruder for melt extrusion. The extruded melt is coated on the surface of the cable conductor through a die to form a sheath layer; Step (d): the sheath layer of step (c) is subjected to segmented temperature increasing crosslinking reaction, and after crosslinking is completed, it is cured by gradient cooling, and finally it is wound and stored.

[0006] Preferably, in step (a), the base polymer is ethylene-vinyl acetate copolymer, the heat-resistant filler is nano magnesium oxide, and the functional additives include antioxidants and ultraviolet absorbers; the mass ratio of the base polymer, the heat-resistant filler and the functional additives is 100:15:3; the interfacial agent is a silane coupling agent, and the addition amount is 1.5wt% of the total mass; The particle size of the nano magnesium oxide is 50-100nm, and it is surface modified by a silane coupling agent before use, and the treatment method is as follows: Disperse the nano magnesium oxide in an ethanol solution, and add 2% of the mass of the nano magnesium oxide of a silane coupling agent; After stirring and refluxing at 60℃ for 2 hours, the solvent is removed by drying.

[0007] Preferably, in step (a), the vacuum drying treatment has the following specific parameters: drying temperature 80℃, vacuum degree -0.1MPa, drying time 4 hours; the mixing process is carried out under the protection of inert gas, the mixing speed is 200rpm, and the mixing time is 30 minutes.

[0008] Preferably, in step (b), the high-speed mixer mechanical activation treatment has the following parameters: mixing temperature 60℃, rotation speed 500rpm, and treatment time 10 minutes; the temperature setting for segmented temperature control melt blending extrusion is as follows: feeding section 150℃, melting section 180℃, mixing section 190℃, and die head section 185℃.

[0009] Preferably, in step (b), the screw rotation speed of the twin-screw extruder is 200rpm, the extrusion pressure is 10MPa; the cooling water temperature of the water tank is controlled at 15℃, the drawing speed is 10m / min, and the cutting length is 3mm; The screw configuration of the twin-screw extruder is combined, at least two groups of reverse meshing block elements are arranged in the mixing section, and the screw length-diameter ratio is 40:1.

[0010] Preferably, the pre-crystallization treatment in step (c) is carried out at a temperature of 100℃ and a relative humidity of 50% for 2 hours; the temperature of the single-screw extruder is set to 160℃ for the feeding section, 170℃ for the compression section, 175℃ for the metering section, and 180℃ for the die section.

[0011] Preferably, the coating process in step (c) is carried out in a pressure control mode, with the die pressure maintained at 15 MPa and the coating speed set to 5 m / min synchronously with the conductor pulling speed; the thickness of the sheath layer is adjusted to 1.5 mm by the die gap.

[0012] Preferably, the step-wise temperature increasing cross-linking reaction in step (d) is carried out as follows: in the first stage, the temperature is increased to 120℃ at a rate of 2℃ / min and maintained for 30 minutes; in the second stage, the temperature is increased to 150℃ at a rate of 1℃ / min and maintained for 60 minutes; the cross-linking agent is dicumyl peroxide, and the addition amount is 0.5% of the mass of the base polymer. The dicumyl peroxide is added in the form of a master batch prepared by dispersing dicumyl peroxide in a low-density polyethylene carrier, with the concentration of dicumyl peroxide in the master batch being 20 wt%.

[0013] Preferably, the gradient cooling mode in step (d) is as follows: first, the temperature is decreased from 150℃ to 80℃ at a rate of 5℃ / min by air cooling; then, the temperature is decreased to room temperature by water cooling at a rate of 10℃ / min; the winding tension is controlled at 50 N, and the winding speed is matched with the extrusion speed.

[0014] Preferably, the application further includes a high-temperature-resistant cable sheath material prepared by the above method.

[0015] Compared with the prior art, the application has the following beneficial effects: This invention, through optimized material composition and process design, exhibits multiple advantages in the preparation of high-temperature resistant cable sheath materials. In terms of material selection, ethylene-vinyl acetate copolymer is used as the matrix polymer, combined with nano-magnesium oxide filler and functional additives, and surface modification is performed using a silane coupling agent to enhance the interfacial compatibility between the filler and the matrix. This design allows for more uniform dispersion of the filler in the polymer, reducing interfacial defects and thus improving the overall density and thermal stability of the sheath material. The introduction of nano-fillers not only improves heat resistance but also endows the material with better mechanical strength, such as tensile strength and abrasion resistance, making the sheath less prone to deformation or cracking under high-temperature environments. Vacuum drying effectively removes moisture and volatile substances from the raw materials, avoiding bubbles or degradation during processing. Mechanical activation treatment improves the initial dispersion state of the materials through high-speed mixing, laying a good foundation for subsequent melt blending. The segmented temperature control design of the twin-screw extruder, combined with the screw configuration of the reverse meshing block element, promotes full melting and mixing of the materials, ensuring uniform distribution of components while preventing material deterioration caused by localized overheating. The water cooling and traction pelletizing process after extrusion, through precise control of water temperature and speed, yields masterbatch with consistent particle size, which is beneficial to the stability of subsequent processing.

[0016] Pre-crystallization is performed under constant temperature and humidity conditions, enabling the masterbatch to form a stable crystal structure and reducing internal stress and shrinkage deformation during coating. During single-screw extrusion coating, pressure control and die design ensure uniform sheath thickness and tight bonding with the conductor, avoiding interfacial voids or uneven thickness. The segmented heating crosslinking reaction uses a progressive temperature curve to ensure uniform action of the crosslinking agent, forming a three-dimensional network structure and significantly improving the crosslinking degree and thermal resistance of the sheath. Gradient cooling, combining air and water cooling, controls the curing rate, reducing internal stress caused by rapid cooling and thus improving the long-term durability and dimensional stability of the sheath. Attached Figure Description

[0017] Figure 1 This is a flowchart of a method for preparing a high-temperature resistant cable sheath material according to the present invention. Detailed Implementation

[0018] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0019] See appendix Figure 1This invention proposes a high-temperature resistant cable sheath material and its preparation method. The invention will be further described below with reference to the embodiments, but the invention is not limited to these embodiments.

[0020] Example 1: A method for preparing a high-temperature resistant cable sheath material includes the following steps: Step (a): The matrix polymer ethylene-vinyl acetate copolymer (EVA, vinyl acetate content 28%), heat-resistant filler nano-magnesium oxide (average particle size 80nm), and functional additives (including antioxidant 1010 and UV absorber UV-531) were subjected to vacuum drying. The vacuum drying parameters were: drying temperature 80℃, vacuum degree -0.1MPa, and drying time 4 hours. Then, the following mass ratios were weighed and mixed: 100 parts of matrix polymer, 15 parts of heat-resistant filler, and 3 parts of functional additives (where the mass ratio of antioxidant to UV absorber was 2:1). Interfacial compatibilizer silane coupling agent KH-550 was added at a rate of 1.5wt% of the total mass. The mixing process was carried out under nitrogen protection using a high-speed mixer at a mixing speed of 200rpm for 30 minutes to obtain a premix.

[0021] Step (b): The premixed material from step (a) is fed into a high-speed mixer for mechanical activation treatment. The parameters are set as follows: mixing temperature 60℃, rotation speed 500 rpm, and treatment time 10 minutes. The treated material is then transferred to a co-rotating twin-screw extruder for segmented temperature-controlled melt blending extrusion. The twin-screw extruder parameters are: screw speed 200 rpm, extrusion pressure 10 MPa; the temperature segments are set as follows: feed section 150℃, melt section 180℃, mixing section 190℃, and die head section 185℃. The screw configuration is a combined type, with two sets of counter-meshing block elements in the mixing section, and the screw length-to-diameter ratio is 40:1. The extruded strip is cooled in a water bath (water temperature 15℃) and then drawn (drawing speed 10 m / min) and pelletized (pellet length 3 mm) to obtain masterbatch.

[0022] Step (c): The masterbatch from step (b) is pre-crystallized in a constant temperature and humidity chamber under the following conditions: temperature 100℃, relative humidity 50%, and processing time 2 hours. Then, it is fed into a single-screw extruder for melt extrusion. The temperature is set in stages: feed section 160℃, compression section 170℃, metering section 175℃, and die section 180℃. The coating process uses a pressure control mode, with the die pressure maintained at 15MPa, and the coating speed synchronized with the cable conductor traction speed at 5m / min. The extruded melt is coated onto the surface of the copper core cable conductor through a T-die to form a sheath layer. The sheath layer thickness is adjusted to 1.5mm by adjusting the die gap.

[0023] Step (d): The sheath layer from step (c) undergoes a segmented temperature-controlled crosslinking reaction. Parameters include: the first stage involves heating to 120°C at a rate of 2°C / min and holding for 30 minutes; the second stage involves heating to 150°C at a rate of 1°C / min and holding for 60 minutes. The crosslinking agent is dicumyl peroxide (DCP), added at 0.5% of the matrix polymer mass. DCP is added in masterbatch form, which is prepared by dispersing DDCP in a low-density polyethylene carrier, with a DCP concentration of 20 wt%. After crosslinking, a gradient cooling method is used for curing: first, air cooling from 150°C to 80°C at a rate of 5°C / min; then water cooling to room temperature (25°C) at a rate of 10°C / min. Finally, the material is wound up and stored, with the winding tension controlled at 50 N and the winding speed matched to the extrusion speed at 5 m / min.

[0024] Example 2: A method for preparing a high-temperature resistant cable sheath material includes the following steps: Step (a): The matrix polymer ethylene-vinyl acetate copolymer (EVA, vinyl acetate content 25%), heat-resistant filler nano-magnesium oxide (average particle size 50nm), and functional additives (including antioxidant 1076 and UV absorber UV-327) were vacuum dried. The vacuum drying parameters were: drying temperature 80℃, vacuum degree -0.1MPa, and drying time 4 hours. Then, the following mass ratios were weighed and mixed: 100 parts of matrix polymer, 20 parts of heat-resistant filler, and 4 parts of functional additives (where the mass ratio of antioxidant to UV absorber was 1:1). Silane coupling agent KH-570 was added as an interfacial compatibilizer at a rate of 2.0 wt% of the total mass. Before use, the nano-magnesium oxide underwent surface modification treatment with the silane coupling agent: the nano-magnesium oxide was dispersed in anhydrous ethanol solution, and 2% (by mass) of silane coupling agent KH-570 was added. After stirring and refluxing at 60℃ for 2 hours, the solvent was removed by drying. The mixing process was carried out under argon protection, with a mixing speed of 250 rpm and a mixing time of 20 minutes, to obtain a premix.

[0025] Step (b): The premixed material from step (a) is fed into a high-speed mixer for mechanical activation treatment. The parameters are set as follows: mixing temperature 70℃, rotation speed 600 rpm, and treatment time 8 minutes. The treated material is then transferred to a twin-screw extruder for segmented temperature-controlled melt blending extrusion. The twin-screw extruder parameters are: screw speed 250 rpm, extrusion pressure 12 MPa; the temperature segments are set as follows: feed section 155℃, melt section 185℃, mixing section 195℃, and die head section 190℃. The screw configuration has three sets of counter-meshing block elements in the mixing section, and the screw length-to-diameter ratio is 42:1. The extruded strip is cooled in a water bath (water temperature 10℃) and then drawn (drawing speed 12 m / min) and pelletized (pellet length 2 mm) to obtain masterbatch.

[0026] Step (c): The masterbatch from step (b) is pre-crystallized under constant temperature and humidity conditions: temperature 105℃, relative humidity 55%, processing time 1.5 hours. Then it is fed into a single-screw extruder for melt extrusion, with the temperature settings in stages: feed section 165℃, compression section 175℃, metering section 180℃, and die section 185℃. The coating process uses pressure control mode, with the die pressure maintained at 18MPa, and the coating speed synchronized with the conductor traction speed at 6m / min. The sheath layer thickness is adjusted to 2.0mm.

[0027] Step (d): The sheath layer undergoes a segmented temperature-controlled crosslinking reaction. Parameters include: the first stage involves heating to 125°C at 3°C / min and holding for 20 minutes; the second stage involves heating to 155°C at 1.5°C / min and holding for 50 minutes. The crosslinking agent is dicumyl peroxide, added at 0.8% of the matrix polymer mass. The concentration in the DCP masterbatch is 25 wt%. Gradient cooling method: first, air cooling from 155°C to 85°C at a cooling rate of 6°C / min; then water cooling to room temperature at a cooling rate of 12°C / min. The winding tension is controlled at 60 N, and the winding speed is matched to 6 m / min.

[0028] Example 3: A method for preparing a high-temperature resistant cable sheath material includes the following steps: Step (a): The matrix polymer ethylene-vinyl acetate copolymer (EVA, vinyl acetate content 30%), heat-resistant filler nano-magnesium oxide (average particle size 100 nm), and functional additives (including antioxidant 168 and UV absorber UV-9) were vacuum dried. The vacuum drying parameters were the same as in Example 1. Then, the following mass ratios were weighed and mixed: 100 parts matrix polymer, 10 parts heat-resistant filler, and 2 parts functional additives (antioxidant to UV absorber mass ratio 3:1). Interfacial compatibilizer silane coupling agent KH-560 was added at 1.0 wt% of the total mass. The surface modification treatment of the nano-magnesium oxide was the same as in Example 1. The mixing process was carried out under nitrogen protection at a mixing speed of 150 rpm for 40 minutes to obtain a premix.

[0029] Step (b): Mechanical activation treatment parameters: mixing temperature 50℃, rotation speed 400 rpm, treatment time 15 minutes. Twin-screw extruder parameters: screw speed 180 rpm, extrusion pressure 8 MPa; temperature segment settings: feed section 145℃, melting section 175℃, mixing section 185℃, die head section 180℃. The screw configuration has a set of reverse meshing block elements in the mixing section, and the screw length-to-diameter ratio is 38:1. Cooling water temperature 20℃, traction speed 8 m / min, pellet length 4 mm.

[0030] Step (c): Pre-crystallization treatment conditions: temperature 95℃, relative humidity 45%, treatment time 2.5 hours. Single screw extruder temperature settings: feed section 155℃, compression section 165℃, metering section 170℃, die section 175℃. Die pressure 12MPa, coating speed 4m / min, sheath layer thickness 1.0mm.

[0031] Step (d): Segmented heating crosslinking reaction: In the first stage, the temperature is increased to 115℃ at a rate of 1℃ / min and held for 40 minutes; in the second stage, the temperature is increased to 145℃ at a rate of 0.5℃ / min and held for 70 minutes. The crosslinking agent DCP is added at 0.3%, and the masterbatch concentration is 15wt%. Gradient cooling: Air cooling from 145℃ to 75℃ at a cooling rate of 4℃ / min; water cooling to room temperature at a cooling rate of 8℃ / min. The winding tension is 40N, and the winding speed is 4m / min.

[0032] Example 4: A method for preparing a high-temperature resistant cable sheath material includes the following steps: Step (a): The matrix polymer is EVA (vinyl acetate content 20%), the heat-resistant filler is nano-magnesium oxide (average particle size 60nm), and the functional additives include antioxidant 1010 and ultraviolet absorber UV-531, with the same mass ratio as in Example 1. Material ratio: 100 parts matrix polymer, 18 parts heat-resistant filler, 3.5 parts functional additives. The interface compatibilizer is silane coupling agent KH-550, added at 1.8wt%. The surface modification treatment of nano-magnesium oxide is the same as in Example 1. Vacuum drying parameters are the same as in Example 1. Mixing speed is 220rpm, and mixing time is 25 minutes.

[0033] Step (b): Mechanical activation treatment: mixing temperature 65℃, rotation speed 550rpm, treatment time 9 minutes. Twin-screw extruder parameters: screw speed 220rpm, extrusion pressure 11MPa; temperature segment settings: feed section 152℃, melting section 182℃, mixing section 192℃, die head section 188℃. Screw configuration is the same as in Example 1. Cooling water temperature 12℃, traction speed 11m / min, pellet length 2.5mm.

[0034] Step (c): Pre-crystallization treatment: temperature 102℃, relative humidity 52%, treatment time 1.8 hours. Single screw extruder temperature settings: feed section 162℃, compression section 172℃, metering section 178℃, die section 182℃. Die pressure 16MPa, coating speed 5.5m / min, sheath layer thickness 1.8mm.

[0035] Step (d): Segmented temperature-increasing crosslinking: In the first stage, the temperature is increased to 122℃ at 2.5℃ / min and held for 25 minutes; in the second stage, the temperature is increased to 152℃ at 1.2℃ / min and held for 55 minutes. The crosslinking agent DCP is added at 0.6%, and the masterbatch concentration is 22wt%. Gradient cooling: Air cooling from 152℃ to 82℃ at a cooling rate of 5.5℃ / min; water cooling to room temperature at a cooling rate of 11℃ / min. The winding tension is 55N, and the winding speed is 5.5m / min.

[0036] Example 5: A method for preparing a high-temperature resistant cable sheath material, comprising the following steps: Step (a): The matrix polymer is EVA (33% vinyl acetate content), the heat-resistant filler is nano-magnesium oxide (average particle size 90nm), and the functional additives include antioxidant 1076 and ultraviolet absorber UV-327, in a mass ratio of 1:1. Material ratio: 100 parts matrix polymer, 12 parts heat-resistant filler, and 2.5 parts functional additives. The interface compatibilizer is silane coupling agent KH-570, added at 1.2wt%. The surface modification treatment of nano-magnesium oxide is the same as in Example 1. Vacuum drying parameters are the same as in Example 1. Mixing speed is 180rpm, and mixing time is 35 minutes.

[0037] Step (b): Mechanical activation treatment: mixing temperature 55℃, rotation speed 450rpm, treatment time 12 minutes. Twin-screw extruder parameters: screw speed 190rpm, extrusion pressure 9MPa; temperature segment settings: feed section 148℃, melting section 178℃, mixing section 188℃, die head section 182℃. Screw configuration is the same as in Example 1. Cooling water temperature 18℃, traction speed 9m / min, pellet length 3.5mm.

[0038] Step (c): Pre-crystallization treatment: temperature 98℃, relative humidity 48%, treatment time 2.2 hours. Single screw extruder temperature settings: feed section 158℃, compression section 168℃, metering section 173℃, die section 178℃. Die pressure 14MPa, coating speed 4.5m / min, sheath layer thickness 1.2mm.

[0039] Step (d): Segmented temperature-increasing crosslinking: In the first stage, the temperature is increased to 118℃ at a rate of 1.5℃ / min and held for 35 minutes; in the second stage, the temperature is increased to 148℃ at a rate of 0.8℃ / min and held for 65 minutes. The crosslinking agent DCP is added at 0.4%, and the masterbatch concentration is 18wt%. Gradient cooling: Air cooling from 148℃ to 78℃ at a cooling rate of 4.5℃ / min; water cooling to room temperature at a cooling rate of 9℃ / min. The winding tension is 45N, and the winding speed is 4.5m / min.

[0040] Comparative Example 1: A method for preparing a high-temperature resistant cable sheath material includes the following steps: Step (a): The matrix polymer, heat-resistant filler, and functional additives are the same as in Example 1, but without the addition of an interfacial compatibilizer. Material ratio: 100 parts matrix polymer, 15 parts heat-resistant filler, and 3 parts functional additives. Vacuum drying and mixing parameters are the same as in Example 1.

[0041] Step (b): Mechanical activation treatment and twin-screw extrusion process are the same as in Example 1.

[0042] Step (c): Pre-crystallization treatment and single-screw extrusion coating are the same as in Example 1.

[0043] Step (d): The segmented crosslinking and cooling processes are the same as in Example 1.

[0044] Comparative Example 2: A method for preparing a high-temperature resistant cable sheath material includes the following steps: Step (a): The material proportions and mixing are the same as in Example 1, but the heat-resistant filler has not undergone surface modification treatment. Step (b): In the twin-screw extrusion process, the temperature settings are incorrect: 130°C in the feeding section, 160°C in the melting section, 170°C in the mixing section, and 165°C in the die head section, with the rest being the same as in Example 1.

[0045] Step (c): The pre-crystallization treatment temperature was too high, at 120°C, with a relative humidity of 60%, and a treatment time of 1 hour. Single-screw extrusion was performed in the same manner as in Example 1.

[0046] Step (d): During the crosslinking reaction, the heating rate was too fast: in the first stage, the temperature was increased to 120°C at 5°C / min and held for 10 minutes; in the second stage, the temperature was increased to 150°C at 3°C / min and held for 20 minutes. The cooling process was the same as in Example 1.

[0047] Comparative Example 3: A method for preparing a high-temperature resistant cable sheath material, comprising the following steps: Step (a): In the material formulation, the amount of heat-resistant filler was too low, at 5 parts, the amount of functional additive was 1 part, and no antioxidant was added. The amount of interface compatibilizer added was 0.5 wt%. The mixing process was the same as in Example 1.

[0048] Step (b): The mechanical activation treatment time was too short, 2 minutes. The twin-screw extruder screw speed was too low, 100 rpm, and the extrusion pressure was 5 MPa. The cooling water temperature was 25℃, and the traction speed was 5 m / min.

[0049] Step (c): No pre-crystallization treatment was performed. The single-screw extrusion die pressure was too low, at 5 MPa, and the coating speed was 10 m / min.

[0050] Step (d): No crosslinking agent was added. Cooling was direct water cooling, without gradient cooling. Winding tension was 100N.

[0051] The performance of the cable sheath materials prepared in Examples 1 to 5 and Comparative Examples 1 to 3 was tested, and the results are shown in Tables 1 and 2.

[0052] Table 1: Material Proportioning Table (parts by weight) Table 2: Performance Test Results Table 1 lists the key material ratio differences between the various embodiments and comparative examples. Combined with the performance test results in Table 2, it can be seen that: Examples 1 to 5 all employed the complete technical solution defined in this invention, including appropriate amounts of heat-resistant filler (10-20 parts), functional additives (2-4 parts), and interface compatibilizers (1.0-2.0 wt%), and all heat-resistant fillers underwent surface modification treatment. Correspondingly, their performance test results all exhibited excellent and balanced comprehensive performance: heat distortion temperature all exceeded 185℃, tensile strength exceeded 17.0 MPa, and elongation at break exceeded 320%, especially with a performance retention rate exceeding 92% after long-term heat aging at 200℃. This indicates that within the proportion range set by this invention, the components work synergistically to effectively improve the material's heat resistance, mechanical properties, and thermal stability.

[0053] Comparative Example 1 did not contain an interfacial compatibilizer. Although other components were the same as in Example 1, all performance indicators showed a significant decrease, especially the performance retention rate after thermal aging, which was only 75%. This indicates that the lack of an interfacial compatibilizer leads to poor interfacial adhesion between the matrix polymer and the filler, low stress transfer efficiency, and that interfacial defects are more likely to become the starting point of performance degradation during thermal aging, thus verifying the indispensable role of the interfacial compatibilizer in the system of this invention.

[0054] Although an interfacial compatibilizer was added in Comparative Example 2, the heat-resistant filler was not surface-modified, and the processing temperature was improperly set. Its performance test results, especially the heat distortion temperature and tensile strength, were significantly lower than those of Example 1. This indicates that the unmodified filler has poor dispersibility in the matrix and is prone to agglomeration. Furthermore, the improper processing temperature prevents sufficient melt blending, leading to internal defects in the material and thus impairing the performance of the final product.

[0055] Comparative Example 3 exhibits several defects deviating from the core principles of this invention: the amount of heat-resistant filler is too low (5 parts), functional additives are insufficient and antioxidants are missing, the amount of interfacial compatibilizer is insufficient, and key process steps are missing or parameters are inappropriate. Its test results are the worst among all samples, with a heat distortion temperature of only 150℃, a tensile strength of 8.0 MPa, and a performance retention rate as low as 60% after heat aging. This fully demonstrates that the material ratio range and process parameters determined in this invention are necessary conditions for achieving excellent high-temperature resistance; the absence or weakening of any key element will lead to a significant decrease in performance.

[0056] The technical effects of the present invention can be further quantified from the performance data in Table 2: Regarding heat resistance, using heat distortion temperature as an indicator, all examples (185-205℃) were significantly higher than the comparative examples (150-170℃). Example 2, due to the use of a higher proportion of heat-resistant filler (20 parts), achieved the highest heat distortion temperature of 205℃, demonstrating the positive impact of filler dosage on heat resistance. However, the dosage must be within a reasonable range to ensure processability and mechanical properties.

[0057] In terms of mechanical properties, the tensile strength (17.0-20.0 MPa) and elongation at break (320-380%) of Examples 1-5 remained at a high level, demonstrating a good balance between strength and toughness. However, the comparative examples showed varying degrees of deterioration in mechanical properties due to the aforementioned reasons. For example, Comparative Example 1 had the lowest tensile strength and elongation at break due to poor interfacial adhesion; Comparative Example 3 had the worst mechanical properties due to insufficient filler reinforcement and numerous processing defects.

[0058] Regarding long-term thermal stability, the performance retention rate after aging at 200℃ for 168 hours is a key indicator for evaluating the material's high-temperature resistance. Examples 1-5 all exhibited performance retention rates exceeding 92%, indicating stable material structure and excellent resistance to long-term thermal oxidation. In contrast, Comparative Examples 1-3 all had performance retention rates below 75%, with Comparative Example 3 at only 60%, suggesting that its composition and processing cannot meet the requirements for long-term high-temperature use.

[0059] In summary, through systematic comparison of the embodiments and comparative examples, the preparation method of the high-temperature resistant cable sheath material provided by the present invention has been fully verified. Through specific material composition, filler surface modification, and optimized processing technology (including mechanical activation, segmented temperature-controlled extrusion, pre-crystallization, segmented cross-linking, and gradient cooling), a cable sheath material with high heat resistance, excellent mechanical properties, and outstanding long-term thermal stability can be prepared, with significant technical effects.

[0060] The above embodiments demonstrate the superior effects of the present invention, while the comparative examples show a significant decrease in performance due to improper processes or proportions. The present invention is not limited to the above embodiments; any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-temperature resistant cable sheath material, characterized in that, Includes the following steps: Step (a): Vacuum dry the matrix polymer, heat-resistant filler and functional additives, then weigh and mix them according to the mass ratio, and add an interfacial compatibilizer to obtain a premix; Step (b): The premixed material from step (a) is put into a high-speed mixer for mechanical activation treatment. The treated material is then transferred to a twin-screw extruder for segmented temperature-controlled melt blending and extrusion. The extruded strip is cooled in a water tank and then pulled and pelletized to obtain masterbatch. Step (c): The masterbatch from step (b) is pre-crystallized in a constant temperature and humidity environment, and then fed into a single screw extruder for melt extrusion. The extruded melt is coated onto the surface of the cable conductor through a die to form a sheath layer. Step (d): Perform a segmented heating crosslinking reaction on the sheath layer from step (c). After crosslinking is completed, cure it using a gradient cooling method, and finally roll it up and store it.

2. The method for preparing a high-temperature resistant cable sheath material as described in claim 1, characterized in that, The matrix polymer in step (a) is an ethylene-vinyl acetate copolymer, the heat-resistant filler is nano-magnesium oxide, and the functional additives include antioxidants and ultraviolet absorbers; the mass ratio of the matrix polymer, heat-resistant filler, and functional additives is 100:15:3; the interfacial compatibilizer is a silane coupling agent, added at 1.5 wt% of the total mass; The nano-magnesium oxide has a particle size of 50-100 nm and undergoes surface modification treatment with a silane coupling agent before use. The treatment method is as follows: Nano-magnesium oxide was dispersed in an ethanol solution, and 2% by mass of a silane coupling agent was added. After stirring and refluxing at 60°C for 2 hours, the solvent is removed by drying.

3. The method for preparing a high-temperature resistant cable sheath material as described in claim 1, characterized in that, The vacuum drying process described in step (a) has the following specific parameters: drying temperature 80℃, vacuum degree -0.1MPa, drying time 4 hours; the mixing process is carried out under inert gas protection, the mixing speed is 200rpm, and the mixing time is 30 minutes.

4. The method for preparing a high-temperature resistant cable sheath material as described in claim 1, characterized in that, The mechanical activation treatment of the high-speed mixer described in step (b) is set with the following parameters: mixing temperature 60℃, rotation speed 500rpm, and processing time 10 minutes; the temperature settings for the segmented temperature-controlled melt blending extrusion are: feeding section 150℃, melting section 180℃, mixing section 190℃, and die head section 185℃.

5. The method for preparing a high-temperature resistant cable sheath material as described in claim 1, characterized in that, The twin-screw extruder described in step (b) has a screw speed of 200 rpm, an extrusion pressure of 10 MPa, a water tank cooling water temperature of 15℃, a traction speed of 10 m / min, and a pellet length of 3 mm. The twin-screw extruder has a combined screw configuration, with at least two sets of counter-meshing block elements in the mixing section, and the screw length-to-diameter ratio is 40:

1.

6. The method for preparing a high-temperature resistant cable sheath material as described in claim 1, characterized in that, The pre-crystallization treatment described in step (c) is performed under the following conditions: temperature 100℃, relative humidity 50%, and treatment time 2 hours. The temperature segments for melt extrusion of the single screw extruder are set as follows: feeding section 160℃, compression section 170℃, metering section 175℃, and die section 180℃.

7. The method for preparing a high-temperature resistant cable sheath material as described in claim 1, characterized in that, The coating process described in step (c) adopts a pressure control mode, with the die head pressure maintained at 15MPa, and the coating speed and conductor traction speed set synchronously to 5m / min; the sheath layer thickness is adjusted to 1.5mm through the die head gap.

8. The method for preparing a high-temperature resistant cable sheath material as described in claim 1, characterized in that, The segmented temperature-increasing crosslinking reaction described in step (d) has the following parameters: in the first stage, the temperature is increased to 120°C at a rate of 2°C / min and held for 30 minutes; in the second stage, the temperature is increased to 150°C at a rate of 1°C / min and held for 60 minutes; the crosslinking agent is dicumyl peroxide, and the amount added is 0.5% of the mass of the matrix polymer. The dicumyl peroxide is added in the form of a masterbatch, which is made by dispersing dicumyl peroxide in a low-density polyethylene carrier, and the concentration of dicumyl peroxide in the masterbatch is 20 wt%.

9. The method for preparing a high-temperature resistant cable sheath material as described in claim 1, characterized in that, The gradient cooling method described in step (d) is as follows: first, the temperature is reduced from 150°C to 80°C by air cooling at a rate of 5°C / min; then, the temperature is cooled to room temperature by water at a rate of 10°C / min; the winding tension is controlled at 50N, and the winding speed is matched with the extrusion speed.

10. A high-temperature resistant cable sheath material, characterized in that, It is prepared by the method for preparing a high-temperature resistant cable sheath material according to any one of claims 1-9.

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