A mine-used flame-retardant cross-linked polyethylene insulated power cable

Abstract

The application belongs to the technical field of cables, and discloses a mine-used flame-retardant crosslinked polyethylene insulated power cable.The power cable comprises a cable core, a protective layer, a mica layer and a sheath layer.The sheath layer is formed by extruding crosslinked polyethylene composite material outside the mica layer.The crosslinked polyethylene composite material is prepared by crosslinking, mixing and extruding processes with high-density polyethylene as a base material and auxiliary materials such as a synergistic flame-retardant functional agent.The synergistic flame-retardant functional agent can act as a crosslinking agent to melt and crosslink polymerize with the high-density polyethylene matrix, which can not only improve the mechanical strength of the material, but also introduce nitrogen, phosphorus and sulfur ternary flame-retardant elements in the structure of the synergistic flame-retardant functional agent into the crosslinked polyethylene molecular chain, thereby greatly enhancing the flame-retardant performance of the material.

Description

Technical Field

[0001] This invention belongs to the field of cable technology, specifically relating to a flame-retardant cross-linked polyethylene insulated power cable for mining. Background Technology

[0002] As the global mining industry accelerates its transformation towards intelligent and automated operations, mining power cables, as the core carrier of power transmission for underground equipment, directly affect the safety and efficiency of mine production. Firstly, due to the unique environment of mines, traditional cable materials (such as polyvinyl chloride) are prone to aging and failure under high temperatures, mechanical stress, and chemical corrosion, leading to risks such as short circuits and leakage, posing a hidden danger to mine safety. With the continuous development of materials science, cross-linked polyethylene (XLPE), with its excellent heat resistance, superior mechanical properties, and good chemical corrosion resistance and electrical properties, has become the optimal choice for the sheathing material of mining power cables.

[0003] Despite its numerous advantages, cross-linked polyethylene (XLPE) remains inherently flammable, with an oxygen index of only 17.4%. It can ignite in the event of a fire or electrical fault, and the large amount of molten material released during combustion can ignite surrounding combustibles, exacerbating the fire and threatening mine safety. Therefore, flame-retardant modification of XLPE has become a key technological direction in the industry. Existing technologies generally improve the flame-retardant properties of XLPE by adding flame retardants, such as inorganic flame retardants like magnesium hydroxide and aluminum hydroxide, as well as organophosphorus and halogenated flame retardants. However, inorganic flame retardants have inherent interface problems with the XLPE matrix, requiring large amounts to achieve good flame-retardant effects, which can negatively impact the material's mechanical properties. Halogenated flame retardants produce significant toxic gas pollution during combustion and are gradually being phased out. Phosphorus-based flame retardants also suffer from poor flame-retardant performance when used alone. Therefore, this invention provides a cross-linked polyethylene insulated power cable that addresses the problems existing in the prior art. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a flame-retardant cross-linked polyethylene insulated power cable for mining.

[0005] In a first aspect, the present invention provides a flame-retardant cross-linked polyethylene insulated power cable for mining, comprising, from the inside out, a cable core, a sheathing layer, a mica layer, and a protective sheath. The sheath layer is formed by extruding cross-linked polyethylene composite material and covering it on the outside of the mica layer; The cross-linked polyethylene composite material comprises the following raw materials measured in parts by weight: The composition includes 65-85 parts high-density polyethylene, 5-15 parts compatibilizer, 10-20 parts elastomer, 0.1-0.3 parts initiator, 2-5.5 parts synergistic flame retardant, 4-8 parts filler, 0.5-1 part antioxidant, and 0.5-1.5 parts lubricant. The method for manufacturing the power cable includes the following steps: The first step is to twist 10-20 copper wires into a core, then extrude polyvinyl chloride to cover the surface of the core to form an insulating protective layer. Next, use aluminum-plastic composite tape to wrap around the surface of the insulating protective layer, and then twist 3-4 fiber cores wrapped with aluminum-plastic composite tape to form a cable core. The second step is to wrap non-woven fabric around the outside of the cable core to form a lining layer. Then, wrap mica around the outside of the lining layer to form a mica layer. Finally, use an extrusion device to extrude cross-linked polyethylene composite material onto the outside of the mica layer to form a sheath layer.

[0006] As a preferred embodiment of the present invention, the compatibilizer is maleic anhydride-grafted polyethylene or maleic anhydride-grafted polypropylene; the elastomer is SBS or SEBS; and the initiator is dicumyl peroxide or benzoyl peroxide.

[0007] As a preferred embodiment of the present invention, the synergistic flame retardant is prepared by the following method: Step 1: Add the phosphorus-containing halide compound, dimercaptoethyl sulfide, and N,N-dimethylformamide to the polymerization reactor, purge with nitrogen for protection, start stirring, and mix evenly. Then add triethylamine to the polymerization reactor. After the addition is complete, raise the temperature to 80-100℃, keep it at this temperature and stir for 8-16 hours, then stop heating, separate the solid material, wash and vacuum dry it to obtain the functional agent intermediate. Step 2: Add the functional agent intermediate to 1,4-dioxane, stir and mix evenly, then continue to add the end-capping agent and alkaline catalyst. After the addition is complete, raise the temperature to 70-80℃, keep it warm and stir for 4-8 hours, then separate the product to obtain the synergistic flame retardant functional agent.

[0008] As a preferred embodiment of the present invention, the phosphorus-containing halide compound is prepared by the following method: Diethoxyphosphonic isocyanate and 1,3-dibromo-2-propanol were added to 1,4-dioxane and stirred until a homogeneous reaction solution was formed. Then, an organotin catalyst was added. After the addition was complete, the temperature was raised to 65-75℃ and stirred continuously for 6-9 hours. The solvent was then evaporated to remove the product, which was collected and purified to obtain a phosphorus-containing halide compound.

[0009] As a preferred embodiment of the present invention, the organotin catalyst is any one of dibutyltin diacetate, dibutyltin dilaurate, stannous octoate, methyl thiotin, or octyl thiotin.

[0010] As a preferred embodiment of the present invention, the molar ratio of the phosphorus-containing halide compound and the dimercaptoethyl sulfide is 1:1.1-1.2.

[0011] As a preferred embodiment of the present invention, the alkaline catalyst is potassium carbonate or sodium carbonate.

[0012] As a preferred embodiment of the present invention, the capping agent is glycidyl methacrylate or glycidyl acrylate.

[0013] It should be noted that in the above technical solution, phosphorus-containing halogenated compounds and dithioethyl sulfide are used as reactants. The halogen substituents and mercapto substituents in their structures can undergo continuous substitution reactions under the action of triethylamine to prepare phosphorus-containing macromolecules linked by sulfide bonds. By controlling the ratio of reactants, the end of the structure of the phosphorus-containing macromolecule can be made to be mercapto. Then, under the action of an alkaline catalyst, a capping agent is used to perform ring-opening addition with the end of the phosphorus-containing macromolecule to obtain a macromolecular synergistic flame retardant functional agent with unsaturated alkenyl substituents at the end of the structure.

[0014] The phosphorus-containing halogenated compounds are prepared by amino esterification of isocyanate groups and active hydroxyl substituents in the structures of phosphonic isocyanate and 1,3-dibromo-2-propanol as raw materials under the action of organotin catalysts.

[0015] As a preferred embodiment of the present invention, the filler is any one of calcium carbonate, talc, silicon dioxide or titanium dioxide; the antioxidant is antioxidant 168 or antioxidant 1076; and the lubricant is polyethylene wax.

[0016] As a preferred embodiment of the present invention, the cross-linked polyethylene composite material is prepared by the following method: Step S1: Weigh each raw material according to the specified weight proportions to complete the material preparation; Step S2: Add high-density polyethylene, compatibilizer, elastomer, initiator and synergistic flame retardant to a torque rheometer, melt polymerize at 180-200℃ for 5-10 minutes, then cool down and discharge to obtain modified cross-linked polyethylene. Step S3: Add the modified cross-linked polyethylene, filler, antioxidant and lubricant to a high-speed mixer and mix them evenly by mechanical stirring. Then feed the mixture into a twin-screw extruder through a feed hopper. Control the temperature of each zone as follows: Zone 1 190±5℃, Zone 2 200±5℃, Zone 3 210±5℃, Zone 4 210±5℃, Zone 5 220±5℃. The screw speed is 50-60 rpm. Perform melt extrusion granulation to obtain cross-linked polyethylene composite material.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The synergistic flame retardant functional agent prepared by this invention contains unsaturated alkenyl substituents at the end of its structure, thus acting as a crosslinking agent. Under the action of an initiator, it undergoes melt crosslinking polymerization with a high-density polyethylene matrix. On the one hand, this can improve the mechanical strength of the material. On the other hand, it can introduce the ternary flame retardant elements of nitrogen, phosphorus, and sulfur from the synergistic flame retardant functional agent structure into the crosslinked polyethylene molecular chain. Among them, phosphorus and sulfur can act as acid sources, and nitrogen can act as a gas source. When combustion occurs, a dense expanded carbon layer can be rapidly formed on the surface of the material, achieving protection of the material's interior. Therefore, a synergistic effect can be produced, achieving the goal of significantly enhancing the flame retardant performance of the material with a small amount of addition. Detailed Implementation

[0018] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0019] Preparation Example Preparation of synergistic flame retardant functional agents: Step A: Add 0.6g of phosphonic isocyanate and 0.73g of 1,3-dibromo-2-propanol to 1,4-dioxane and stir until a homogeneous reaction solution is formed. Then add 0.01g of dibutyltin dilaurate. After the addition is complete, heat to 70℃ and stir continuously for 8 hours. Evaporate to remove the solvent, collect the product, and purify it to obtain a phosphorus-containing halide compound. Step B: Add 0.8g of phosphorus-containing halogenated compound, 0.35g of dimercaptoethyl sulfide and N,N-dimethylformamide to the polymerization reactor, purge with nitrogen for protection, start stirring, and mix evenly. Then add 0.1g of triethylamine to the polymerization reactor. After the addition is complete, raise the temperature to 85℃, keep it at this temperature and stir for 12 hours, then stop heating, separate the solid material, wash and vacuum dry to obtain the functional agent intermediate. Step C: Add 1.2g of the functional agent intermediate to 1,4-dioxane, stir and mix evenly, then add 0.1g of glycidyl methacrylate and 0.1g of potassium carbonate. After the addition is complete, raise the temperature to 75℃, keep it warm and stir for 6 hours, then separate the product to obtain the synergistic flame retardant functional agent. Example

[0020] Preparation of cross-linked polyethylene composite materials: Step S1: According to the weight parts, 65 parts of high-density polyethylene, 5 parts of maleic anhydride grafted polyethylene, 10 parts of SBS elastomer, 0.1 parts of dicumyl peroxide and 2 parts of synergistic flame retardant are added to a torque rheometer and melt-polymerized at 180°C for 10 minutes. After cooling, the material is discharged to obtain modified cross-linked polyethylene. Step S2: Add modified cross-linked polyethylene, 4 parts calcium carbonate, 0.5 parts antioxidant 168 and 0.5 parts polyethylene wax to a high-speed mixer. After mechanically mixing evenly, feed the mixture into a twin-screw extruder through a feed hopper. Control the temperature of each zone as follows: Zone 1 190℃, Zone 2 200℃, Zone 3 210℃, Zone 4 210℃, Zone 5 220℃. The screw speed is 60 rpm. Perform melt extrusion granulation to obtain cross-linked polyethylene composite material.

[0021] The preparation method of the synergistic flame retardant is shown in the preparation example, and the same applies to the following. Example

[0022] Preparation of cross-linked polyethylene composite materials: Step S1: According to the weight parts, 70 parts of high-density polyethylene, 10 parts of maleic anhydride grafted polypropylene, 15 parts of SBS elastomer, 0.2 parts of benzoyl peroxide and 5 parts of synergistic flame retardant functional agent are added to a torque rheometer and melt-polymerized at 190°C for 8 minutes. After cooling, the material is discharged to obtain modified cross-linked polyethylene. Step S2: Add modified cross-linked polyethylene, 6 parts talc powder, 0.8 parts antioxidant 1076 and 1 part polyethylene wax to a high-speed mixer. After mechanically mixing evenly, feed the mixture into a twin-screw extruder through a feed hopper. Control the temperature of each zone as follows: Zone 1 190℃, Zone 2 200℃, Zone 3 210℃, Zone 4 210℃ and Zone 5 220℃. The screw speed is 60 rpm. Perform melt extrusion granulation to obtain cross-linked polyethylene composite material. Example

[0023] Preparation of cross-linked polyethylene composite materials: Step S1: According to the weight parts, 85 parts of high-density polyethylene, 15 parts of maleic anhydride grafted polypropylene, 20 parts of SBS elastomer, 0.3 parts of benzoyl peroxide and 5.5 parts of synergistic flame retardant functional agent are added to a torque rheometer and melt-polymerized at 200°C for 5 minutes. After cooling, the material is discharged to obtain modified cross-linked polyethylene. Step S2: Add modified cross-linked polyethylene, 8 parts talc powder, 1 part antioxidant 1076 and 1.5 parts polyethylene wax to a high-speed mixer. After mechanically mixing evenly, feed the mixture into a twin-screw extruder through a feed hopper. Control the temperature of each zone as follows: Zone 1 190℃, Zone 2 200℃, Zone 3 210℃, Zone 4 210℃, Zone 5 220℃. The screw speed is 60 rpm. Perform melt extrusion granulation to obtain cross-linked polyethylene composite material.

[0024] Comparative Example 1 The difference between this comparative example and Example 2 is that the synergistic flame retardant is replaced with the small molecule phosphorus-containing flame retardant DOPO, while all other aspects are the same.

[0025] Comparative Example 2 The difference between this comparative example and Example 2 is that the synergistic flame retardant agent is removed; otherwise, they are the same.

[0026] The cross-linked polyethylene composite materials provided in the above embodiments and comparative examples were subjected to performance tests, and the test methods are as follows: (1) Flame retardant performance was tested according to standard GB / T 2406.2-2009; (2) Mechanical properties were tested according to standard GB / T 1040.1-2025.

[0027] The performance test data above are shown in Table 1.

[0028] Table 1 Performance Test Results

[0029] Analysis of the test results shows that the cross-linked polyethylene composite material prepared in the embodiments of the present invention is a flame-retardant material with good flame retardant properties, and also exhibits excellent mechanical properties. Replacing the synergistic flame retardant functional agent with the small-molecule phosphorus-containing flame retardant DOPO results in the cross-linked polyethylene structure lacking the synergistic flame retardant elements nitrogen and phosphorus, leading to a significant decrease in flame retardant performance. Furthermore, the cross-linking effect of the synergistic flame retardant functional agent cannot be utilized, resulting in a certain degree of decrease in the mechanical properties of the material.

[0030] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention, including the best mode, and also to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the present invention.

Claims

1. A flame-retardant cross-linked polyethylene insulated power cable for mining, characterized in that, From the inside out, it includes the cable core, the lining layer, the mica layer, and the sheath layer; The sheath layer is formed by extruding cross-linked polyethylene composite material and covering it on the outside of the mica layer; The cross-linked polyethylene composite material comprises the following raw materials measured in parts by weight: The composition includes 65-85 parts high-density polyethylene, 5-15 parts compatibilizer, 10-20 parts elastomer, 0.1-0.3 parts initiator, 2-5.5 parts synergistic flame retardant, 4-8 parts filler, 0.5-1 part antioxidant, and 0.5-1.5 parts lubricant. The method for manufacturing the power cable includes the following steps: The first step is to twist 10-20 copper wires into a core, then extrude polyvinyl chloride to cover the surface of the core to form an insulating protective layer. Next, use aluminum-plastic composite tape to wrap around the surface of the insulating protective layer, and then twist 3-4 fiber cores wrapped with aluminum-plastic composite tape to form a cable core. The second step is to wrap non-woven fabric around the outside of the cable core to form a lining layer. Then, mica is wrapped around the outside of the lining layer to form a mica layer. Finally, cross-linked polyethylene composite material is extruded and wrapped around the outside of the mica layer using an extrusion device to form a sheath layer. The synergistic flame retardant functional agent is prepared using the following method: Step 1: Add the phosphorus-containing halide compound, dimercaptoethyl sulfide, and N,N-dimethylformamide to the polymerization reactor, purge with nitrogen for protection, start stirring, and mix evenly. Then add triethylamine to the polymerization reactor. After the addition is complete, raise the temperature to 80-100℃, keep it at this temperature and stir for 8-16 hours, then stop heating, separate the solid material, wash and vacuum dry it to obtain the functional agent intermediate. The mass ratio of the phosphorus-containing halide compound to dimercaptoethyl sulfide is 0.8:0.35; Step 2: Add the functional agent intermediate to 1,4-dioxane, stir and mix evenly, then continue to add the end-capping agent and alkaline catalyst. After the addition is complete, raise the temperature to 70-80℃, keep it warm and stir for 4-8 hours, then separate the product to obtain the synergistic flame retardant functional agent. The mass ratio of the functional agent intermediate, the capping agent, and the alkaline catalyst is 1.2:0.1:0.

1.

2. The mining flame-retardant cross-linked polyethylene insulated power cable according to claim 1, characterized in that, The compatibilizer is maleic anhydride-grafted polyethylene or maleic anhydride-grafted polypropylene; the elastomer is SBS or SEBS; and the initiator is dicumyl peroxide or benzoyl peroxide.

3. The mining flame-retardant cross-linked polyethylene insulated power cable according to claim 1, characterized in that, The phosphorus-containing halide compound was prepared by the following method: Diethoxyphosphonic isocyanate and 1,3-dibromo-2-propanol were added to 1,4-dioxane and stirred until a homogeneous reaction solution was formed. Then an organotin catalyst was added. After the addition was complete, the temperature was raised to 65-75℃ and stirred continuously for 6-9 hours. The solvent was then evaporated to remove the product, which was collected and purified to obtain a phosphorus-containing halide compound. The mass ratio of the phosphonodiesterate diethoxyisocyanate, 1,3-dibromo-2-propanol, and dibutyltin dilaurate is 0.6:0.73:0.

01.

4. A flame-retardant cross-linked polyethylene insulated power cable for mining as described in claim 3, characterized in that, The organotin catalyst is any one of dibutyltin diacetate, dibutyltin dilaurate, stannous octoate, methyl thiotin, or octyl thiotin.

5. A flame-retardant cross-linked polyethylene insulated power cable for mining as described in claim 1, characterized in that, The molar ratio of the phosphorus-containing halide compound and the dimercaptoethyl sulfide is 1:1.1-1.

2.

6. A flame-retardant cross-linked polyethylene insulated power cable for mining as described in claim 1, characterized in that, The alkaline catalyst is potassium carbonate or sodium carbonate.

7. A flame-retardant cross-linked polyethylene insulated power cable for mining as described in claim 1, characterized in that, The capping agent is glycidyl methacrylate or glycidyl acrylate.

8. A flame-retardant cross-linked polyethylene insulated power cable for mining as described in claim 1, characterized in that, The filler is any one of calcium carbonate, talc, silica, or titanium dioxide; the antioxidant is antioxidant 168 or antioxidant 1076; and the lubricant is polyethylene wax.

9. A flame-retardant cross-linked polyethylene insulated power cable for mining as described in claim 1, characterized in that, The cross-linked polyethylene composite material is prepared by the following method: Step S1: Weigh each raw material according to the specified weight proportions to complete the material preparation; Step S2: Add high-density polyethylene, compatibilizer, elastomer, initiator and synergistic flame retardant to a torque rheometer, melt polymerize at 180-200℃ for 5-10 minutes, then cool down and discharge to obtain modified cross-linked polyethylene. Step S3: Add the modified cross-linked polyethylene, filler, antioxidant and lubricant to a high-speed mixer and mix them evenly by mechanical stirring. Then feed the mixture into a twin-screw extruder through a feed hopper. Control the temperature of each zone as follows: Zone 1 190±5℃, Zone 2 200±5℃, Zone 3 210±5℃, Zone 4 210±5℃, Zone 5 220±5℃. The screw speed is 50-60 rpm. Perform melt extrusion granulation to obtain cross-linked polyethylene composite material.

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