An armoured flame retardant power cable

Abstract

The present application relates to the technical field of flame-retardant cable, in particular to a kind of armored flame-retardant power cable, including conductor, modified insulation layer, inner liner and armored layer, the modified insulation layer is wrapped in conductor outside, the inner liner is wrapped in modified insulation layer outside, the armored layer is wrapped in inner liner outside.The present application is modified to polyphosphoric ammonium, melamine formaldehyde prepolymer in steps, solve the problem that traditional flame-retardant additive is poor with polyethylene base material Compatibility, easy to agglomerate, modified polyphosphoric ammonium effectively reduces the van der waals force between flame retardant particles, avoids the local agglomeration phenomenon that traditional polyphosphoric ammonium directly added easily occurs, while modified melamine formaldehyde prepolymer plays steric hindrance effect to polyphosphoric ammonium particles, so that it is mixed and fused in the process of insulation base material, let flame retardant realize global uniform distribution in insulating layer, no dispersion dead angle.

Description

Technical Field

[0001] This invention relates to the field of flame-retardant cable technology, and specifically to an armored flame-retardant power cable. Background Technology

[0002] In power transmission and distribution systems, cables serve as the core carrier, and their performance directly determines the safety, stability, and reliability of power supply. With the acceleration of urbanization, the expansion of industrial scale, and the increase in various densely populated places (such as subways, airports, high-rise buildings, nuclear power plants, etc.), the application scenarios of power cables are becoming increasingly complex, and the requirements for their comprehensive performance such as flame retardancy, insulation, and mechanical protection are constantly increasing. Armored cross-linked polyethylene (XLPE) flame-retardant power cables have emerged to meet this need.

[0003] In existing technologies, traditional flame retardants are directly added to polyethylene-based insulating substrates. Due to the large differences in molecular structure between the flame retardant and the substrate, poor compatibility leads to agglomeration, resulting in microvoids and microcracks within the insulation layer. On the one hand, these defects reduce the electrical insulation performance of the insulation layer, increasing the risk of leakage and breakdown. On the other hand, the flame retardant performance is too strong in the agglomerated areas, while the flame retardant performance is weak in the non-agglomerated areas, forming a flame retardant weakness. The flame retardant effect of the entire cable is uneven, and the agglomerated flame retardant is prone to precipitation during long-term use, causing the flame retardant performance of the cable to gradually decline. Therefore, in response to the problems mentioned above, this invention proposes an armored flame-retardant power cable. Summary of the Invention

[0004] The purpose of this invention is to provide an armored flame-retardant power cable to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an armored flame-retardant power cable, comprising a conductor, a modified insulation layer, an inner liner, and an armor layer, wherein the modified insulation layer is wrapped around the outside of the conductor, the inner liner is wrapped around the outside of the modified insulation layer, and the armor layer is wrapped around the outside of the inner liner. The modified insulating layer is prepared through the following steps: S1. Add ethylene-vinyl acetate copolymer and modified ammonium polyphosphate to cross-linked polyethylene at 80-90℃, mix for 15-20 min, cool to 40-50℃, add dicumyl peroxide, triallyl isocyanurate and antioxidant, mix for 5-8 min to obtain modified cross-linked polyethylene flame retardant insulation material. S2. The modified cross-linked polyethylene flame-retardant insulating material is melt-blended and extruded. The extrudate is water-cooled, stretched into strips, and granulated. It is then dried with hot air at 60-70℃ for 1-2 hours to obtain modified cross-linked polyethylene flame-retardant insulating granules. S3. Preheat the conductor to 60-80℃, and after preheating, molten and coated modified cross-linked polyethylene flame-retardant insulating particles are extruded onto the outside of the conductor. After cooling, a modified insulating layer is obtained on the surface of the conductor.

[0006] As a preferred embodiment of the present invention, the modified ammonium polyphosphate in step S1 is obtained through the following steps: S11. Add ammonium polyphosphate to the ethanol-water mixture, disperse for 24-30 min, then add dilute hydrochloric acid to adjust the pH to 4-5, raise the temperature to 50-60℃, keep warm and stir, and add tetraethyl orthosilicate dropwise. S12. Simultaneously add vinyltrimethoxysilane, adjust the pH to 8-9 with ammonia, react at a constant temperature for 2-4 hours, filter, wash, and vacuum dry to obtain pretreated ammonium polyphosphate. S13. Disperse the pretreated ammonium polyphosphate in deionized water, heat to 65-75℃, add modified melamine-formaldehyde prepolymer, adjust pH to 5-6 with dilute hydrochloric acid, maintain the temperature for polymerization for 2-3 hours, filter, wash, and vacuum dry to obtain modified ammonium polyphosphate.

[0007] As a preferred embodiment of the present invention, the modified melamine-formaldehyde prepolymer in step S13 is obtained through the following steps: S131. Heat the melamine-formaldehyde prepolymer to 48-52℃, add dilute hydrochloric acid to adjust the pH to 4-4.5, add citric acid and diethanolamine, react for 60-90 min, and adjust the pH to 7.0-7.5 with sodium hydroxide to obtain modified melamine-formaldehyde intermediate A. S132. Add polyethylene glycol to modified melamine-formaldehyde intermediate A, heat to 63-67℃, stir and react for 2-2.5h, add hydroquinone, stir for 10-15min to obtain modified melamine-formaldehyde intermediate B. S133. Add 3-aminopropyltriethoxysilane and hydroxyethyl acrylate to the modified melamine-formaldehyde intermediate B, and simultaneously add anhydrous ethanol. Stir at 68-72℃ for 3-4 hours, cool to room temperature, and stir for 20-30 minutes to obtain the modified melamine-formaldehyde prepolymer.

[0008] As a preferred embodiment of the present invention, in step S1, the mass ratio of cross-linked polyethylene, ethylene-vinyl acetate copolymer, modified ammonium polyphosphate, dicumyl peroxide, triallyl isocyanurate, and antioxidant is 100:(15-25):(20-30):(0.8-1.5):(1.0-2.0):(0.2-0.5).

[0009] As a preferred embodiment of the present invention, in steps S11 and S12, the mass ratio of ammonium polyphosphate to ethanol-water mixture is 100:(200-300), wherein the mass ratio of ethanol to water is (2-3):1, and the mass ratio of ammonium polyphosphate, tetraethyl orthosilicate, and vinyltrimethoxysilane is 100:(8-15):(5-10).

[0010] As a preferred embodiment of the present invention, the mass ratio of pretreated ammonium polyphosphate, deionized water and modified melamine-formaldehyde prepolymer in step S13 is 100:(150-250):(15-25).

[0011] As a preferred embodiment of the present invention, in step S131, the mass ratio of melamine-formaldehyde prepolymer, citric acid, and diethanolamine is 100:(3-6):(2-4).

[0012] As a preferred embodiment of the present invention, in step S132, the mass ratio of modified melamine-formaldehyde intermediate A, polyethylene glycol, and hydroquinone is 100:(5-8):(0.1-0.3).

[0013] As a preferred technical solution of the present invention, the mass ratio of modified melamine formaldehyde intermediate B, 3-aminopropyltriethoxysilane, hydroxyethyl acrylate and anhydrous ethanol in step S133 is 100:(4-7):(3-5):(80-120).

[0014] As a preferred embodiment of the present invention, the conductor is a multi-strand stranded oxygen-free copper conductor with a stranding pitch ratio of 10-15 and a cross-sectional area of ​​100-300 mm². The modified insulation layer has a thickness of 1.5-3 mm. The inner lining is prepared by extrusion of low-smoke halogen-free flame-retardant polyolefin material with a thickness of 1-2 mm. The armor layer is a steel strip armor layer with a thickness of 0.5-1 mm.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention solves the problems of poor compatibility and easy agglomeration between traditional flame retardant additives and polyethylene-based substrates by stepwise modification of ammonium polyphosphate and melamine-formaldehyde prepolymer. The modified ammonium polyphosphate effectively reduces the van der Waals forces between flame retardant particles, avoiding the local agglomeration phenomenon that easily occurs when traditional ammonium polyphosphate is directly added. At the same time, the modified melamine-formaldehyde prepolymer plays a steric hindrance role on the ammonium polyphosphate particles, so that the flame retardant can be uniformly distributed throughout the insulation layer without any dead zones during the mixing and melting process of the insulating substrate.

[0016] 2. This invention modifies ammonium polyphosphate and modified melamine-formaldehyde prepolymer to form a synergistic flame-retardant system integrating an acid source, a carbon source, and a gas source. The efficiency of each flame-retardant component is greatly improved. As an acid source, modified ammonium polyphosphate can continuously release phosphoric acid substances at high temperatures, catalyzing the carbonization of the substrate. As a carbon source and gas source, modified melamine-formaldehyde prepolymer simultaneously releases inert gases such as nitrogen and carbon dioxide at high temperatures, which not only isolates oxygen and heat but also inhibits the spread of flames. The synergistic effect of the two upgrades the flame-retardant system from a single physical flame retardant to a physical and chemical flame retardant, achieving flame retardancy throughout the insulation layer without dead angles, and solving the problem of weak local flame retardant performance of traditional cables. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the preparation process of the modified insulating layer in this invention; Figure 2 This is a schematic diagram of the preparation process of modified ammonium polyphosphate in this invention; Figure 3 This is a schematic diagram of the preparation process of the modified melamine-formaldehyde prepolymer in this invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figures 1-3 This invention provides a technical solution for armored flame-retardant power cables: Example 1:

[0020] An armored flame-retardant power cable, comprising a multi-strand oxygen-free copper conductor with a stranding pitch ratio of 10, a cross-sectional area of ​​100 mm², a modified insulation layer thickness of 1.5 mm, an inner lining layer thickness of 1 mm, and a steel tape armor layer thickness of 0.5 mm. The modified insulating layer is prepared through the following steps: I. Preparation of modified melamine-formaldehyde prepolymer: S131. Take 100g of melamine-formaldehyde prepolymer, heat it to 48℃, adjust the pH of the system to 4.0 with dilute hydrochloric acid, add 3g of citric acid and 2g of diethanolamine, react for 60min, and adjust the pH to 7.0 with sodium hydroxide to obtain modified melamine-formaldehyde intermediate A. S132. Add 5g of polyethylene glycol to 100g of modified melamine-formaldehyde intermediate A, heat to 63℃, stir and react for 2h, add 0.1g of hydroquinone, stir for 10min, and obtain modified melamine-formaldehyde intermediate B. S133. Add 4g of 3-aminopropyltriethoxysilane and 3g of hydroxyethyl acrylate to 100g of modified melamine-formaldehyde intermediate B, and simultaneously add 80g of anhydrous ethanol. Stir and react at 68℃ for 3h, cool to room temperature, and stir for 20min to obtain modified melamine-formaldehyde prepolymer.

[0021] II. Preparation of modified ammonium polyphosphate: S11-S12. Take 100g of ammonium polyphosphate, add 200g of ethanol-water mixture (133g of ethanol, 67g of water), disperse for 24min, then add dilute hydrochloric acid to adjust the pH to 4, heat to 50℃, keep warm and stir, and add 8g of tetraethyl orthosilicate, while adding 5g of vinyltrimethoxysilane. Adjust the pH to 8 with ammonia water, react at constant temperature for 2h, filter, wash, and vacuum dry to obtain pretreated ammonium polyphosphate. S13. Take 100g of pretreated ammonium polyphosphate, disperse it in 150g of deionized water, heat it to 65℃, add 15g of the above modified melamine-formaldehyde prepolymer, adjust the pH to 5 with dilute hydrochloric acid, keep it at the temperature for 2h for polymerization, filter, wash, and vacuum dry to obtain modified ammonium polyphosphate.

[0022] III. Preparation of Modified Insulating Layer: S1. At 80°C, add 15g of ethylene-vinyl acetate copolymer and 20g of the above-mentioned modified ammonium polyphosphate to 100g of cross-linked polyethylene, mix for 15min, cool to 40°C, add 0.8g of dicumyl peroxide, 1.0g of triallyl isocyanurate and 0.2g of antioxidant, mix for 5min to obtain modified cross-linked polyethylene flame retardant insulation material; S2. The above modified cross-linked polyethylene flame-retardant insulation material is melt-blended and extruded. The extrudate is water-cooled, stretched into strips, and granulated. It is then dried with hot air at 60°C for 1 hour to obtain modified cross-linked polyethylene flame-retardant insulation granules. S3. Preheat the above oxygen-free copper conductor to 60°C, and moltenly wrap modified cross-linked polyethylene flame-retardant insulating particles on its outer side. After cooling, a modified insulating layer with a thickness of 1.5 mm is obtained.

[0023] Example 2:

[0024] An armored flame-retardant power cable, comprising a multi-strand oxygen-free copper conductor with a stranding pitch ratio of 12, a cross-sectional area of ​​175 mm², a modified insulation layer thickness of 2.0 mm, an inner lining layer thickness of 1.5 mm, and a steel tape armor layer thickness of 0.7 mm. The modified insulating layer is prepared through the following steps: I. Preparation of modified melamine-formaldehyde prepolymer: S131. Take 100g of melamine-formaldehyde prepolymer, heat it to 50℃, adjust the pH of the system to 4.2 with dilute hydrochloric acid, add 4.5g of citric acid and 3g of diethanolamine, react for 75min, and adjust the pH to 7.2 with sodium hydroxide to obtain modified melamine-formaldehyde intermediate A. S132. Add 6.5g of polyethylene glycol to 100g of modified melamine-formaldehyde intermediate A, heat to 65℃, stir and react for 2.2h, add 0.2g of hydroquinone, stir for 12min to obtain modified melamine-formaldehyde intermediate B. S133. Add 5.5g of 3-aminopropyltriethoxysilane and 4g of hydroxyethyl acrylate to 100g of modified melamine-formaldehyde intermediate B, and simultaneously add 100g of anhydrous ethanol. Stir and react at 70℃ for 3.5h, cool to room temperature, and stir for 25min to obtain modified melamine-formaldehyde prepolymer.

[0025] II. Preparation of modified ammonium polyphosphate: S11-S12. Take 100g of ammonium polyphosphate, add 250g of ethanol-water mixture (179g ethanol, 71g water), disperse for 27min, then add dilute hydrochloric acid to adjust the pH to 4.5, heat to 55℃, keep warm and stir while adding 11.5g of tetraethyl orthosilicate, and add 7.5g of vinyltrimethoxysilane at the same time. Adjust the pH to 8.5 with ammonia water, react at constant temperature for 3h, filter, wash, and vacuum dry to obtain pretreated ammonium polyphosphate. S13. Take 100g of pretreated ammonium polyphosphate, disperse it in 200g of deionized water, heat it to 70℃, add 20g of the above modified melamine-formaldehyde prepolymer, adjust the pH to 5.5 with dilute hydrochloric acid, keep it at the temperature for 2.5h for polymerization, filter, wash, and vacuum dry to obtain modified ammonium polyphosphate.

[0026] III. Preparation of Modified Insulating Layer: S1. At 85°C, add 20g of ethylene-vinyl acetate copolymer and 25g of the above-mentioned modified ammonium polyphosphate to 100g of cross-linked polyethylene, mix for 17min, cool to 45°C, add 1.15g of dicumyl peroxide, 1.5g of triallyl isocyanurate and 0.35g of antioxidant, mix for 6.5min to obtain modified cross-linked polyethylene flame retardant insulation material; S2. The modified cross-linked polyethylene flame-retardant insulating material is melt-blended and extruded. The extrudate is water-cooled, stretched into strips, and granulated. It is then dried with hot air at 65°C for 1.5 hours to obtain modified cross-linked polyethylene flame-retardant insulating granules. S3. Preheat the above oxygen-free copper conductor to 70°C, and moltenly wrap modified cross-linked polyethylene flame-retardant insulating particles on its outer side. After cooling, a modified insulating layer with a thickness of 2.0 mm is obtained.

[0027] Example 3:

[0028] An armored flame-retardant power cable, comprising a multi-strand oxygen-free copper conductor with a stranding pitch ratio of 13, a cross-sectional area of ​​225 mm², a modified insulation layer thickness of 2.5 mm, an inner lining layer thickness of 1.7 mm, and a steel tape armor layer thickness of 0.8 mm. The modified insulating layer is prepared through the following steps: I. Preparation of modified melamine-formaldehyde prepolymer: S131. Take 100g of melamine-formaldehyde prepolymer, heat it to 51℃, adjust the pH of the system to 4.3 with dilute hydrochloric acid, add 5g of citric acid and 3.5g of diethanolamine, react for 80min, and adjust the pH to 7.4 with sodium hydroxide to obtain modified melamine-formaldehyde intermediate A. S132. Add 7g of polyethylene glycol to 100g of modified melamine-formaldehyde intermediate A, heat to 66℃, stir and react for 2.4h, add 0.25g of hydroquinone, stir for 14min to obtain modified melamine-formaldehyde intermediate B. S133. Add 6g of 3-aminopropyltriethoxysilane and 4.5g of hydroxyethyl acrylate to 100g of modified melamine-formaldehyde intermediate B, and simultaneously add 110g of anhydrous ethanol. Stir and react at 71℃ for 3.8h, cool to room temperature, and stir for 28min to obtain modified melamine-formaldehyde prepolymer.

[0029] II. Preparation of modified ammonium polyphosphate: S11-S12, Take 100g of ammonium polyphosphate, add 275g of ethanol-water mixture (203g ethanol, 72g water), disperse for 28min, then add dilute hydrochloric acid to adjust the pH to 4.8, heat to 58℃, keep warm and stir while adding 13g of tetraethyl orthosilicate, and simultaneously add 8.5g of vinyltrimethoxysilane. Adjust the pH to 8.8 with ammonia water, react at a constant temperature for 3.5h, filter, wash, and vacuum dry to obtain pretreated ammonium polyphosphate; S13. Take 100g of pretreated ammonium polyphosphate, disperse it in 225g of deionized water, heat it to 73℃, add 23g of the above modified melamine-formaldehyde prepolymer, adjust the pH to 5.8 with dilute hydrochloric acid, keep it at the temperature for 2.8h for polymerization, filter, wash, and vacuum dry to obtain modified ammonium polyphosphate.

[0030] III. Preparation of Modified Insulating Layer: S1. At 88℃, add 23g of ethylene-vinyl acetate copolymer and 28g of the above modified ammonium polyphosphate to 100g of cross-linked polyethylene, mix for 19min, cool to 48℃, add 1.3g of dicumyl peroxide, 1.8g of triallyl isocyanurate and 0.4g of antioxidant, mix for 7.5min to obtain modified cross-linked polyethylene flame retardant insulation material; S2. The modified cross-linked polyethylene flame-retardant insulating material is melt-blended and extruded. The extrudate is water-cooled, stretched into strips, and granulated. It is then dried with hot air at 68°C for 1.8 hours to obtain modified cross-linked polyethylene flame-retardant insulating granules. S3. Preheat the above oxygen-free copper conductor to 78°C, and moltenly encapsulate modified cross-linked polyethylene flame-retardant insulating particles on its outer side. After cooling, a modified insulating layer with a thickness of 2.5 mm is obtained.

[0031] Example 4:

[0032] A type of armored flame-retardant power cable, wherein the conductor is a multi-strand oxygen-free copper conductor with a stranding pitch ratio of 15, a cross-sectional area of ​​300 mm², a modified insulation layer thickness of 3 mm, an inner lining layer thickness of 2 mm, and a steel tape armor layer thickness of 1 mm. The modified insulating layer is prepared through the following steps: I. Preparation of modified melamine-formaldehyde prepolymer: S131. Take 100g of melamine-formaldehyde prepolymer, heat it to 52℃, adjust the pH of the system to 4.5 with dilute hydrochloric acid, add 6g of citric acid and 4g of diethanolamine, react for 90min, and adjust the pH to 7.5 with sodium hydroxide to obtain modified melamine-formaldehyde intermediate A. S132. Add 8g of polyethylene glycol to 100g of modified melamine-formaldehyde intermediate A, heat to 67℃, stir and react for 2.5h, add 0.3g of hydroquinone, stir for 15min to obtain modified melamine-formaldehyde intermediate B. S133. Add 7g of 3-aminopropyltriethoxysilane and 5g of hydroxyethyl acrylate to 100g of modified melamine-formaldehyde intermediate B, and simultaneously add 120g of anhydrous ethanol. Stir and react at 72℃ for 4h, cool to room temperature, and stir for 30min to obtain modified melamine-formaldehyde prepolymer.

[0033] II. Preparation of modified ammonium polyphosphate: S11-S12. Take 100g of ammonium polyphosphate, add 300g of ethanol-water mixture (225g ethanol, 75g water), disperse for 30min, then add dilute hydrochloric acid to adjust the pH to 5, heat to 60℃, keep warm and stir, and add 15g of tetraethyl orthosilicate, while adding 10g of vinyltrimethoxysilane. Adjust the pH to 9 with ammonia water, react at constant temperature for 4h, filter, wash, and vacuum dry to obtain pretreated ammonium polyphosphate. S13. Take 100g of pretreated ammonium polyphosphate, disperse it in 250g of deionized water, heat it to 75℃, add 25g of the above modified melamine-formaldehyde prepolymer, adjust the pH to 6 with dilute hydrochloric acid, keep it at the temperature for 3h for polymerization, filter, wash, and vacuum dry to obtain modified ammonium polyphosphate.

[0034] III. Preparation of Modified Insulating Layer: S1. At 90°C, add 25g of ethylene-vinyl acetate copolymer and 30g of the above-mentioned modified ammonium polyphosphate to 100g of cross-linked polyethylene, mix for 20min, cool down to 50°C, add 1.5g of dicumyl peroxide, 2g of triallyl isocyanurate and 0.5g of antioxidant, mix for 8min to obtain modified cross-linked polyethylene flame retardant insulation material; S2. The above modified cross-linked polyethylene flame-retardant insulating material is melt-blended and extruded. The extrudate is water-cooled, stretched into strips, and granulated. It is then dried with hot air at 70°C for 2 hours to obtain modified cross-linked polyethylene flame-retardant insulating granules. S3. Preheat the above oxygen-free copper conductor to 80°C, and moltenly wrap modified cross-linked polyethylene flame-retardant insulating particles on its outer side. After cooling, a modified insulating layer with a thickness of 3 mm is obtained.

[0035] Comparative Example 1: Comparative Example 1 differs from Example 1 in that the modified melamine-formaldehyde prepolymer is replaced with a melamine-formaldehyde prepolymer, while the remaining steps are exactly the same as in Example 1.

[0036] Comparative Example 2: Comparative Example 2 differs from Example 1 in that the modified ammonium polyphosphate is replaced with ammonium polyphosphate, and the remaining steps are exactly the same as in Example 1.

[0037] Comparative Example 3: Comparative Example 3 differs from Example 1 in that the modified insulation layer is replaced with a cross-linked polyethylene flame-retardant insulation layer, while the remaining steps are exactly the same as in Example 1.

[0038] Based on the modified insulation layers and corresponding armored flame-retardant power cables prepared in Examples 1-4 and Comparative Examples 1-3 of this invention, and in accordance with the power cable industry standards (GB / T19666-2019 "General Rules for Flame-Retardant and Fire-Resistant Wires and Cables or Optical Cables" and GB / T3048-2023 "Test Methods for Electrical Performance of Wires and Cables"), basic physical performance, electrical performance, flame-retardant performance, and aging resistance test items were designed. Insulation layer strips (100mm×10mm×actual thickness) and cable section samples (1m / section) were cut according to the standards. All samples were placed in an environment of normal temperature (23±2℃) and relative humidity (50±5)% for 24 hours before testing.

[0039] The basic physical properties of the modified insulation layer were tested using the water displacement method. The density of the modified insulation layer was tested according to GB / T1033.1-2008, the melt flow index was tested according to GB / T3682-2020 at 190℃ / 2.16kg, and the oxygen index of the melt flow index was tested according to GB / T2406.2-2009. The specific test results are shown in Table 1. Table 1

[0040] As can be seen from the data in Table 1, the density of the examples is between 0.94 and 0.95 g / cm³. 3 The overall concentration was higher than the comparative example, which ranged from 0.86 to 0.89 g / cm³. 3 This indicates that the modified insulation layer has better film density and more stable structure. In terms of melt flow index, the examples are 2.1-2.4 g / 10 min, while the comparative examples are only 1.5-1.8 g / 10 min, which shows that the insulation material in the examples has better processing fluidity and is more conducive to extrusion molding. As the core indicator of flame retardancy, the oxygen index of the examples reaches 40.3-41.5%, while the comparative examples are only 32% at most and as low as 28%. Moreover, the oxygen index of Examples 2 and 3 is the best among all groups, proving that the basic flame retardant performance of the modified insulation layer is greatly improved. The synergistic effect of modified ammonium polyphosphate and modified melamine formaldehyde prepolymer significantly improves the flame retardancy of the material.

[0041] The electrical properties of the armored flame-retardant power cable were tested according to GB / T3048.12-2023. The volume resistivity of the armored flame-retardant power cable was tested at 23℃, and the unit was Ω·m. The dielectric strength of the armored flame-retardant power cable was tested using the power frequency withstand voltage method according to GB / T3048.8-2023. The sample was an insulation strip. The power frequency withstand voltage of the armored flame-retardant power cable was tested according to GB / T3048.9-2023. The entire cable sample was immersed in water, a 5kV power frequency voltage was applied, and it was maintained for 1 minute. The results were observed for breakdown. The specific test results are shown in Table 2. Table 2

[0042] As can be seen from the data in Table 2, the volume resistivity of Examples 2 and 3 reaches 1.5 × 10⁻⁶. 14 1.6×10 14 Ω·m, Examples 1 and 4 also maintain 1.2 × 10 14 1.3×10 14 The level is high in Ω·m, while the highest comparative value is only 8.2×10. 13 The insulation and conductivity performance showed significant differences in Ω·m. In terms of dielectric strength, Examples 2 and 3 ranked first with 31kV / mm and 31.5kV / mm respectively, while Example 1 had 28.5kV / mm. Only Example 4 showed a numerical deviation, while the comparative example was significantly lower than the examples. In the power frequency withstand voltage test, all examples passed the 5kV / 1min no breakdown test, while only the comparative example 3 broke down. This fully demonstrates that the modified insulation layer of the present invention can effectively improve the electrical insulation reliability of the cable, and the modification process has qualitatively improved the charge barrier capability and withstand voltage performance of the insulation layer.

[0043] The flame retardant performance of armored flame-retardant power cables was tested according to the Class B flame retardant standard in GB / T19666-2019, using a bundled burning test. Bundle 3.5m long cable samples with a mass of ≤1.5kg per meter. Apply an 870℃ flame with a blowtorch and burn continuously for 40min. After the flame is removed, observe the afterburning time (the time it takes for the sample flame to extinguish itself) and smoldering time. At the same time, test the smoke density and light transmittance according to GB / T17651.2-1998. The specific test results are shown in Table 3. Table 3

[0044] As can be seen from the data in Table 3, Examples 2 and 3 showed the best performance in terms of afterflame and smoldering time, with afterflame lasting only 4-5 seconds and smoldering only 1-2 seconds. Examples 1 and 4 also controlled within 8 seconds and 7 seconds, and 5 seconds and 4 seconds, respectively. In contrast, the comparative examples showed the shortest afterflame time of 25 seconds and the longest of 45 seconds, while the smoldering time reached 18-38 seconds. This indicates that the cables in the examples can quickly extinguish the flame after being exposed to fire, with no risk of continued combustion or smoldering. In terms of smoke density and light transmittance, the examples all exceeded 80%, with Examples 2 and 3 reaching 85-86%, while the comparative examples had a maximum of only 55% and a minimum of 30%. This proves that the modified cables produced very little smoke when burning, with a significant low-smoke effect. Overall, they meet the GB / T19666-2019 Class B flame retardant standard. Moreover, Examples 2 and 3 had the best comprehensive flame retardant and smoke suppression performance, and the synergistic flame retardant effect of the modified system was significant.

[0045] To test the aging resistance of the modified insulation layer, according to GB / T2951.12-2021, the modified insulation layer sample was placed in a constant temperature oven at 135℃ for 7 days for heat aging. After cooling, the tensile strength retention rate and elongation at break retention rate were tested. The calculation formula is as follows: Tensile strength retention rate (%) = (Tensile strength after aging / Tensile strength before aging) × 100% Elongation at break retention rate (%) = (Elongation at break after aging / Elongation at break before aging) × 100% The specific test results are shown in Table 4. Table 4

[0046] As can be seen from the data in Table 4, the modified insulation layer prepared in the embodiments of the present invention has a much better thermal aging stability than the comparative examples. After 7 days of constant temperature thermal aging at 135℃, the performance retention rate is still at a high level. The tensile strength retention rate of Example 3 is 93% and the elongation at break retention rate is 91%, which are the highest among all groups. Example 2 also reaches 92% and 90%, respectively. The retention rates of Examples 1 and 4 are also above 85%. This shows that the mechanical structure of the modified insulation layer can still remain stable after high temperature aging and is not prone to embrittlement or cracking. In contrast, the performance retention rate of the comparative examples is greatly reduced, with the highest tensile strength retention rate being only 70% and the elongation at break retention rate being 65%. The performance retention rate of Comparative Example 3 is even lower, at 55% and 50%, respectively. The mechanical properties are severely degraded after aging. This fully demonstrates that the modification process of the present invention effectively improves the thermal aging resistance of the insulation layer and extends the service life and stability of the cable.

[0047] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. An armored flame-retardant power cable, characterized in that, It includes a conductor, a modified insulation layer, an inner liner layer, and an armor layer, wherein the modified insulation layer is wrapped around the outside of the conductor, the inner liner layer is wrapped around the outside of the modified insulation layer, and the armor layer is wrapped around the outside of the inner liner layer; The modified insulating layer is prepared through the following steps: S1. Add ethylene-vinyl acetate copolymer and modified ammonium polyphosphate to cross-linked polyethylene at 80-90℃, mix for 15-20 min, cool to 40-50℃, add dicumyl peroxide, triallyl isocyanurate and antioxidant, mix for 5-8 min to obtain modified cross-linked polyethylene flame retardant insulation material. S2. The modified cross-linked polyethylene flame-retardant insulating material is melt-blended and extruded. The extrudate is water-cooled, stretched into strips, and granulated. It is then dried with hot air at 60-70℃ for 1-2 hours to obtain modified cross-linked polyethylene flame-retardant insulating granules. S3. Preheat the conductor to 60-80℃, and after preheating, molten modified cross-linked polyethylene flame-retardant insulating particles are extruded and wrapped on the outside of the conductor. After cooling, a modified insulating layer is obtained wrapped on the surface of the conductor. The modified ammonium polyphosphate in step S1 is obtained through the following steps: S11. Add ammonium polyphosphate to the ethanol-water mixture, disperse for 24-30 min, then add dilute hydrochloric acid to adjust the pH to 4-5, raise the temperature to 50-60℃, keep warm and stir, and add tetraethyl orthosilicate dropwise. S12. Simultaneously add vinyltrimethoxysilane, adjust the pH to 8-9 with ammonia, react at a constant temperature for 2-4 hours, filter, wash, and vacuum dry to obtain pretreated ammonium polyphosphate. S13. Disperse the pretreated ammonium polyphosphate in deionized water, heat to 65-75℃, add modified melamine-formaldehyde prepolymer, adjust pH to 5-6 with dilute hydrochloric acid, keep warm for 2-3 hours for polymerization, filter, wash, and vacuum dry to obtain modified ammonium polyphosphate. The modified melamine-formaldehyde prepolymer in step S13 is obtained through the following steps: S131. Heat the melamine-formaldehyde prepolymer to 48-52℃, add dilute hydrochloric acid to adjust the pH to 4-4.5, add citric acid and diethanolamine, react for 60-90 min, and adjust the pH to 7.0-7.5 with sodium hydroxide to obtain modified melamine-formaldehyde intermediate A. S132. Add polyethylene glycol to modified melamine-formaldehyde intermediate A, heat to 63-67℃, stir and react for 2-2.5h, add hydroquinone, stir for 10-15min to obtain modified melamine-formaldehyde intermediate B. S133. Add 3-aminopropyltriethoxysilane and hydroxyethyl acrylate to the modified melamine-formaldehyde intermediate B, and add anhydrous ethanol at the same time. Stir at 68-72℃ for 3-4 hours, cool to room temperature, and stir for 20-30 minutes to obtain the modified melamine-formaldehyde prepolymer. In step S1, the mass ratio of cross-linked polyethylene, ethylene-vinyl acetate copolymer, modified ammonium polyphosphate, dicumyl peroxide, triallyl isocyanurate, and antioxidant is 100:(15-25):(20-30):(0.8-1.5):(1.0-2.0):(0.2-0.5). In steps S11 and S12, the mass ratio of ammonium polyphosphate to ethanol-water mixture is 100:(200-300), wherein the mass ratio of ethanol to water is (2-3):1, and the mass ratio of ammonium polyphosphate, tetraethyl orthosilicate, and vinyltrimethoxysilane is 100:(8-15):(5-10). In step S13, the mass ratio of pretreated ammonium polyphosphate, deionized water, and modified melamine-formaldehyde prepolymer is 100:(150-250):(15-25).

2. The armored flame-retardant power cable according to claim 1, characterized in that, In step S131, the mass ratio of melamine-formaldehyde prepolymer, citric acid, and diethanolamine is 100:(3-6):(2-4).

3. The armored flame-retardant power cable according to claim 1, characterized in that, In step S132, the mass ratio of modified melamine-formaldehyde intermediate A, polyethylene glycol, and hydroquinone is 100:(5-8):(0.1-0.3).

4. The armored flame-retardant power cable according to claim 1, characterized in that, In step S133, the mass ratio of modified melamine formaldehyde intermediate B, 3-aminopropyltriethoxysilane, hydroxyethyl acrylate, and anhydrous ethanol is 100:(4-7):(3-5):(80-120).

5. The armored flame-retardant power cable according to claim 1, characterized in that, The conductor is a multi-strand stranded oxygen-free copper conductor with a stranding pitch ratio of 10-15 and a cross-sectional area of ​​100-300 mm². 2 The modified insulation layer has a thickness of 1.5-3 mm, the inner liner is made by extrusion of low-smoke halogen-free flame-retardant polyolefin material, and the inner liner has a thickness of 1-2 mm. The armor layer is a steel strip armor layer, and the armor layer has a thickness of 0.5-1 mm.

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