A cross-linked polyethylene insulated flame-retardant power cable

Abstract

This invention relates to the field of cable material technology, specifically to a cross-linked polyethylene insulated flame-retardant power cable. To enhance the mechanical strength and wear resistance of the power cable, this invention uses nano-silica as a reinforcing material filled into the cross-linked polyethylene material. The nano-silica is modified by introducing flame-retardant sulfur and phosphorus elements onto its surface, and by introducing acetophenone, which can improve the breakdown field strength of the cross-linked polyethylene, thus avoiding the tendency of acetophenone to migrate out. Furthermore, this invention introduces an acrylic acid structure with unsaturated double bonds onto the surface of the nano-silica, which can react with the polyethylene material during the cross-linking process, further improving the compatibility between the nano-silica and the cross-linked polyethylene material. This results in a cross-linked polyethylene insulated flame-retardant power cable with excellent wear resistance, flame retardancy, and insulation properties.

Description

Technical Field

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

[0002] Cross-linked polyethylene (XLPE) is a three-dimensional network structure material formed by cross-linking polyethylene. Compared with ordinary polyethylene, it has higher resistance to high temperature and high pressure, as well as higher strength and durability. Therefore, it is often used as a coating material for power cables. However, when using XLPE to prepare cable coatings, the working environment limits its application. XLPE needs to withstand the effects of heat, mechanical force, and various environmental aging factors. Furthermore, during power transmission, cables also face phenomena such as electrical treeing aging, which reduces the breakdown field strength of the material, causing cable failure and rendering the cable unusable. Summary of the Invention

[0003] The purpose of this invention is to provide a cross-linked polyethylene insulated flame-retardant power cable to solve the problems mentioned in the background art.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a cross-linked polyethylene insulated flame-retardant power cable, having the following technical features: the cross-linked polyethylene insulated flame-retardant power cable is composed of an outer cross-linked polyethylene insulation layer and a cable body covering the inner side;

[0005] The cross-linked polyethylene insulation layer, by weight, comprises the following components: 70-86 parts low-density polyethylene, 2.5-4.5 parts cross-linking agent, 0.5-1 part antioxidant, and 18-30 parts insulation modified filler.

[0006] Furthermore, the antioxidant is antioxidant 1010.

[0007] Furthermore, the crosslinking agent is dicumyl peroxide.

[0008] A method for preparing a cross-linked polyethylene insulated flame-retardant power cable includes the following steps:

[0009] S1. Preparation of insulating modified filler;

[0010] S11. Mix nano-silica with nitric acid solution, heat to 80-90℃, react for 4-8 hours, separate the precipitate by centrifugation, wash with deionized water until neutral, disperse the precipitate in formaldehyde, sonicate for 30-45 minutes, add potassium hydroxide under nitrogen atmosphere, heat to 55-60℃, react for 4-8 hours, separate the precipitate by centrifugation, wash with deionized water until neutral, and dry to constant weight to obtain hydroxymethylated nano-silica;

[0011] S12. Under a nitrogen atmosphere, hydroxymethylated nano-silica was dispersed in N,N-dimethylformamide and added dropwise to an N,N-dimethylformamide solution containing triphenyl isocyanate thiophosphate. The temperature was raised to 65-75℃ and the reaction was carried out for 1.5-2 hours. Then, dibutyltin dilaurate was added and the temperature was raised to 85-90℃. The reaction was continued for 4-8 hours. After heating was stopped, the nano-silica was separated by centrifugation and washed 3-5 times with N,N-dimethylformamide. The nano-silica was then vacuum evaporated to constant weight to obtain isocyanate-terminated nano-silica.

[0012] S13. Disperse p-hydroxyacetophenone in toluene, heat to 55-65℃, and then add it dropwise to tri(1,2-epoxy)propyl glycerol for 1-2 hours. After the addition is complete, heat to 70-85℃ and react for 4-8 hours. Then, remove excess solvent by vacuum distillation to obtain the terminal epoxy complex.

[0013] S14. Hydroxyethyl methacrylate is dispersed in toluene. After dispersion for 10-15 min, the initiator azobisisobutyronitrile is added, and dispersion is continued for another 10-15 min to obtain a monomer dispersion. Under a nitrogen atmosphere, it is added dropwise to a solution of N,N-dimethylformamide containing terminal epoxy group complexes. The temperature is raised to 65-75℃, and the reaction is carried out for 6-12 h. Then, the isocyanate-terminated nano-silica and dibutyltin dilaurate prepared in step S12 are added. The temperature is raised to 85-95℃, and the reaction is carried out for 3-4.5 h. After filtration, the mixture is washed 3-4 times with N,N-dimethylformamide and deionized water to obtain the insulating modified filler.

[0014] S2. Mix low-density polyethylene, antioxidant and insulating modified filler prepared in step S1, heat to 150-160℃, melt blend for 15-30 min, cool and pelletize to obtain blend masterbatch;

[0015] S3. Mix the blending masterbatch with the crosslinking agent, heat to 105-120℃, knead for 5-15 minutes, and then extrude and coat the surface of the cable body to obtain a crosslinked polyethylene insulated flame-retardant power cable.

[0016] Furthermore, in step S11, the concentration of the nitric acid solution is 6-8 mol / L; the mass ratio of sodium hydroxide to formaldehyde is 1:(8-12).

[0017] Furthermore, in step S12, the mass ratio of the hydroxymethylated nano silica, triphenyl isocyanate thiophosphate, and dibutyltin dilaurate is 5:(50-80):(0.01-0.05) by weight.

[0018] Furthermore, in step S13, the molar ratio of p-hydroxyacetophenone to glyceryl tri(1,2-epoxy)propyl ether is (0.8-1.1):1 based on molar parts.

[0019] Further, in step S14, the mass ratio of hydroxyethyl methacrylate, azobisisobutyronitrile, terminal epoxy complex, terminal isocyanate group nano silica, and dibutyltin dilaurate is (0.9-1.2):(0.03-0.05):3:(10-15):(0.03-0.05).

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0021] 1. In order to enhance the mechanical strength and wear resistance of power cables, this invention uses nano-silica as a reinforcing material to fill cross-linked polyethylene material. In order to enhance the compatibility between nano-silica and cross-linked polyethylene, this invention modifies nano-silica. First, its surface is oxidized to enhance its surface activity. Then, formaldehyde and sodium hydroxide are reacted to generate hydroxymethyl groups on its surface. Then, triphenyl isocyanate thiophosphate is reacted with it to introduce sulfur and phosphorus elements with flame retardant ability on the surface of nano-silica. Free isocyanate groups are grafted on its surface to ensure that it has sufficient reactivity to participate in the next grafting reaction.

[0022] 2. This invention also prepares an epoxy-terminated complex. First, p-hydroxyacetophenone is reacted with glycerol tri(1,2-epoxy)propyl ether. By controlling the reaction conditions, an epoxy-terminated complex with free epoxy groups is obtained. Acetophenone can improve the breakdown field strength of cross-linked polyethylene and is commonly found in cross-linked polyethylene as a decomposition product of dicumyl peroxide crosslinking agent. However, acetophenone has a small molecular weight and high polarity, resulting in poor compatibility with cross-linked polyethylene. Under long-term use, it will migrate to the surface of cross-linked polyethylene, causing a decline in product performance. Therefore, this invention uses p-hydroxyacetophenone and reacts it with glycerol tri(1,2-epoxy)propyl ether to increase its molecular weight. Furthermore, by introducing alkyl side chains, its compatibility with cross-linked polyethylene is further improved.

[0023] 3. This invention further utilizes the reaction of hydroxyethyl methacrylate with terminal epoxy groups to introduce an acrylic acid structure with unsaturated double bonds, which can react with the polyethylene material during crosslinking to form a crosslinked network structure and improve compatibility. Subsequently, this application further grafts it with isocyanate-terminated nano-silica to prepare an insulating modified filler with good compatibility with polyethylene. This filler is then blended with polypropylene, utilizing its surface acrylic acid structure to react and crosslink with crosslinked polyethylene under the action of a crosslinking agent, thereby preparing a crosslinked polyethylene insulated flame-retardant power cable with good wear resistance, flame retardancy, and insulation properties. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0025] The nano silica used in the embodiments and comparative examples of this invention is DK-SiO2-30 type nano silica provided by Beijing Deco Island Gold Technology Co., Ltd.; the triphenyl isocyanate thiophosphate used is provided by Wuhan Kemike Biomedical Technology Co., Ltd.; the tri(1,2-epoxy)propyl glycerol used is provided by Wuhan Kanos Technology Co., Ltd.; and the hydroxyethyl methacrylate used is provided by Jinan Prahua Chemical Co., Ltd.

[0026] Example 1.

[0027] A method for preparing a cross-linked polyethylene insulated flame-retardant power cable includes the following steps:

[0028] S1. Preparation of insulating modified filler;

[0029] S11. By weight, 10 parts of nano-silica were mixed with 150 parts of nitric acid solution with a concentration of 8 mol / L, heated to 80°C, and reacted for 4 hours. The precipitate was separated by centrifugation, washed with deionized water until neutral, and then dispersed in 80 parts of formaldehyde. After ultrasonic dispersion for 30 minutes, 1 part of potassium hydroxide was added under a nitrogen atmosphere, the temperature was raised to 55°C, and reacted for 4 hours. The precipitate was separated by centrifugation, washed with deionized water until neutral, and then dried to constant weight to obtain hydroxymethylated nano-silica.

[0030] S12. Under a nitrogen atmosphere, 5 parts by weight of hydroxymethylated nano silica were dispersed in N,N-dimethylformamide and added dropwise to a solution of N,N-dimethylformamide containing 50 parts of triphenyl isocyanate thiophosphate. The temperature was raised to 65°C and the reaction was carried out for 1.5 h. Then, 0.01 parts of dibutyltin dilaurate were added and the temperature was raised to 85°C. The reaction was continued for 4 h. After heating was stopped, the nano silica was separated by centrifugation, washed three times with N,N-dimethylformamide, and vacuum evaporated to constant weight to obtain isocyanate-terminated nano silica.

[0031] S13. Disperse 0.8 moles of p-hydroxyacetophenone in toluene by molar amount, heat to 55°C, and then add dropwise to 1 mole of glycerol tri(1,2-epoxy)propyl ether over a period of 1 hour. After the addition is complete, heat to 70°C and react for 4 hours. Then, remove excess solvent by vacuum distillation to obtain the terminal epoxy complex.

[0032] S14. By mass, 0.9 parts of hydroxyethyl methacrylate were dispersed in toluene. After dispersion for 10 min, 0.03 parts of the initiator azobisisobutyronitrile were added, and dispersion was continued for another 10 min to obtain a monomer dispersion. Under a nitrogen atmosphere, the dispersion was added dropwise to a solution of N,N-dimethylformamide containing 3 parts of the terminal epoxy group complex. The temperature was raised to 65°C, and the reaction was carried out for 6 h. Then, 10 parts of the isocyanate-terminated nano-silica prepared in step S12 and 0.03 parts of dibutyltin dilaurate were added. The temperature was raised to 85°C, and the reaction was carried out for 3 h. After filtration, the mixture was washed three times with N,N-dimethylformamide and deionized water to obtain the insulating modified filler.

[0033] S2. By weight, 70 parts of low-density polyethylene, 0.5 parts of antioxidant 1010 and 18 parts of the insulating modified filler prepared in step S1 are mixed, heated to 150°C, melt-blended for 15 minutes, cooled and pelletized to obtain blended masterbatch.

[0034] S3. Mix the blending masterbatch with 2.5 parts of dicumyl peroxide, heat to 105°C, knead for 10 minutes, and then extrude and coat the surface of the cable body to obtain a cross-linked polyethylene insulated flame-retardant power cable.

[0035] Example 2.

[0036] Compared with Example 1, this example increases the amount of p-hydroxyacetophenone added in step S13;

[0037] A method for preparing a cross-linked polyethylene insulated flame-retardant power cable includes the following steps:

[0038] S1. Preparation of insulating modified filler;

[0039] S11. By weight, 10 parts of nano-silica were mixed with 150 parts of nitric acid solution with a concentration of 8 mol / L, heated to 80°C, and reacted for 4 hours. The precipitate was separated by centrifugation, washed with deionized water until neutral, and then dispersed in 80 parts of formaldehyde. After ultrasonic dispersion for 30 minutes, 1 part of potassium hydroxide was added under a nitrogen atmosphere, the temperature was raised to 55°C, and reacted for 4 hours. The precipitate was separated by centrifugation, washed with deionized water until neutral, and then dried to constant weight to obtain hydroxymethylated nano-silica.

[0040] S12. Under a nitrogen atmosphere, 5 parts by weight of hydroxymethylated nano silica were dispersed in N,N-dimethylformamide and added dropwise to a solution of N,N-dimethylformamide containing 50 parts of triphenyl isocyanate thiophosphate. The temperature was raised to 65°C and the reaction was carried out for 1.5 h. Then, 0.01 parts of dibutyltin dilaurate were added and the temperature was raised to 85°C. The reaction was continued for 4 h. After heating was stopped, the nano silica was separated by centrifugation, washed three times with N,N-dimethylformamide, and vacuum evaporated to constant weight to obtain isocyanate-terminated nano silica.

[0041] S13. Disperse 1.1 moles of p-hydroxyacetophenone in toluene by molar amount, heat to 55°C, and then add dropwise to 1 mole of glycerol tri(1,2-epoxy)propyl ether over a period of 1 hour. After the addition is complete, heat to 70°C and react for 4 hours. Then, remove excess solvent by vacuum distillation to obtain the terminal epoxy complex.

[0042] S14. By mass, 0.9 parts of hydroxyethyl methacrylate were dispersed in toluene. After dispersion for 10 min, 0.03 parts of the initiator azobisisobutyronitrile were added, and dispersion was continued for another 10 min to obtain a monomer dispersion. Under a nitrogen atmosphere, the dispersion was added dropwise to a solution of N,N-dimethylformamide containing 3 parts of the terminal epoxy group complex. The temperature was raised to 65°C, and the reaction was carried out for 6 h. Then, 10 parts of the isocyanate-terminated nano-silica prepared in step S12 and 0.03 parts of dibutyltin dilaurate were added. The temperature was raised to 85°C, and the reaction was carried out for 3 h. After filtration, the mixture was washed three times with N,N-dimethylformamide and deionized water to obtain the insulating modified filler.

[0043] S2. By weight, 70 parts of low-density polyethylene, 0.5 parts of antioxidant 1010 and 18 parts of the insulating modified filler prepared in step S1 are mixed, heated to 150°C, melt-blended for 15 minutes, cooled and pelletized to obtain blended masterbatch.

[0044] S3. Mix the blending masterbatch with 2.5 parts of dicumyl peroxide, heat to 105°C, knead for 10 minutes, and then extrude and coat the surface of the cable body to obtain a cross-linked polyethylene insulated flame-retardant power cable.

[0045] Example 3.

[0046] Compared with Example 1, this example increases the amount of hydroxyethyl methacrylate added in step S14;

[0047] A method for preparing a cross-linked polyethylene insulated flame-retardant power cable includes the following steps:

[0048] S1. Preparation of insulating modified filler;

[0049] S11. By weight, 10 parts of nano-silica were mixed with 150 parts of nitric acid solution with a concentration of 8 mol / L, heated to 80°C, and reacted for 4 hours. The precipitate was separated by centrifugation, washed with deionized water until neutral, and then dispersed in 80 parts of formaldehyde. After ultrasonic dispersion for 30 minutes, 1 part of potassium hydroxide was added under a nitrogen atmosphere, the temperature was raised to 55°C, and reacted for 4 hours. The precipitate was separated by centrifugation, washed with deionized water until neutral, and then dried to constant weight to obtain hydroxymethylated nano-silica.

[0050] S12. Under a nitrogen atmosphere, 5 parts by weight of hydroxymethylated nano silica were dispersed in N,N-dimethylformamide and added dropwise to a solution of N,N-dimethylformamide containing 50 parts of triphenyl isocyanate thiophosphate. The temperature was raised to 65°C and the reaction was carried out for 1.5 h. Then, 0.01 parts of dibutyltin dilaurate were added and the temperature was raised to 85°C. The reaction was continued for 4 h. After heating was stopped, the nano silica was separated by centrifugation, washed three times with N,N-dimethylformamide, and vacuum evaporated to constant weight to obtain isocyanate-terminated nano silica.

[0051] S13. Disperse 0.8 moles of p-hydroxyacetophenone in toluene by molar amount, heat to 55°C, and then add dropwise to 1 mole of glycerol tri(1,2-epoxy)propyl ether over a period of 1 hour. After the addition is complete, heat to 70°C and react for 4 hours. Then, remove excess solvent by vacuum distillation to obtain the terminal epoxy complex.

[0052] S14. By mass, 1.2 parts of hydroxyethyl methacrylate were dispersed in toluene. After dispersion for 10 min, 0.03 parts of initiator azobisisobutyronitrile were added, and dispersion was continued for another 10 min to obtain a monomer dispersion. Under a nitrogen atmosphere, the dispersion was added dropwise to a solution of N,N-dimethylformamide containing 3 parts of terminal epoxy group complex. The temperature was raised to 65°C, and the reaction was carried out for 6 h. Then, 10 parts of nano-silica with terminal isocyanate groups prepared in step S12 and 0.03 parts of dibutyltin dilaurate were added. The temperature was raised to 85°C, and the reaction was carried out for 3 h. After filtration, the mixture was washed three times with N,N-dimethylformamide and deionized water to obtain the insulating modified filler.

[0053] S2. By weight, 70 parts of low-density polyethylene, 0.5 parts of antioxidant 1010 and 18 parts of the insulating modified filler prepared in step S1 are mixed, heated to 150°C, melt-blended for 15 minutes, cooled and pelletized to obtain blended masterbatch.

[0054] S3. Mix the blending masterbatch with 2.5 parts of dicumyl peroxide, heat to 105°C, knead for 10 minutes, and then extrude and coat the surface of the cable body to obtain a cross-linked polyethylene insulated flame-retardant power cable.

[0055] Example 4.

[0056] Compared with Example 1, this example increases the amount of insulating modified filler added in step S2;

[0057] A method for preparing a cross-linked polyethylene insulated flame-retardant power cable includes the following steps:

[0058] S1. Preparation of insulating modified filler;

[0059] S11. By weight, 10 parts of nano-silica were mixed with 150 parts of nitric acid solution with a concentration of 8 mol / L, heated to 80°C, and reacted for 4 hours. The precipitate was separated by centrifugation, washed with deionized water until neutral, and then dispersed in 80 parts of formaldehyde. After ultrasonic dispersion for 30 minutes, 1 part of potassium hydroxide was added under a nitrogen atmosphere, the temperature was raised to 55°C, and reacted for 4 hours. The precipitate was separated by centrifugation, washed with deionized water until neutral, and then dried to constant weight to obtain hydroxymethylated nano-silica.

[0060] S12. Under a nitrogen atmosphere, 5 parts by weight of hydroxymethylated nano silica were dispersed in N,N-dimethylformamide and added dropwise to a solution of N,N-dimethylformamide containing 50 parts of triphenyl isocyanate thiophosphate. The temperature was raised to 65°C and the reaction was carried out for 1.5 h. Then, 0.01 parts of dibutyltin dilaurate were added and the temperature was raised to 85°C. The reaction was continued for 4 h. After heating was stopped, the nano silica was separated by centrifugation, washed three times with N,N-dimethylformamide, and vacuum evaporated to constant weight to obtain isocyanate-terminated nano silica.

[0061] S13. Disperse 0.8 moles of p-hydroxyacetophenone in toluene by molar amount, heat to 55°C, and then add dropwise to 1 mole of glycerol tri(1,2-epoxy)propyl ether over a period of 1 hour. After the addition is complete, heat to 70°C and react for 4 hours. Then, remove excess solvent by vacuum distillation to obtain the terminal epoxy complex.

[0062] S14. By mass, 0.9 parts of hydroxyethyl methacrylate were dispersed in toluene. After dispersion for 10 min, 0.03 parts of the initiator azobisisobutyronitrile were added, and dispersion was continued for another 10 min to obtain a monomer dispersion. Under a nitrogen atmosphere, the dispersion was added dropwise to a solution of N,N-dimethylformamide containing 3 parts of the terminal epoxy group complex. The temperature was raised to 65°C, and the reaction was carried out for 6 h. Then, 10 parts of the isocyanate-terminated nano-silica prepared in step S12 and 0.03 parts of dibutyltin dilaurate were added. The temperature was raised to 85°C, and the reaction was carried out for 3 h. After filtration, the mixture was washed three times with N,N-dimethylformamide and deionized water to obtain the insulating modified filler.

[0063] S2. By weight, 70 parts of low-density polyethylene, 0.5 parts of antioxidant 1010 and 25 parts of the insulating modified filler prepared in step S1 are mixed, heated to 150°C, melt-blended for 15 minutes, cooled and pelletized to obtain blended masterbatch.

[0064] S3. Mix the blending masterbatch with 2.5 parts of dicumyl peroxide, heat to 105°C, knead for 10 minutes, and then extrude and coat the surface of the cable body to obtain a cross-linked polyethylene insulated flame-retardant power cable.

[0065] Example 5.

[0066] A method for preparing a cross-linked polyethylene insulated flame-retardant power cable includes the following steps:

[0067] S1. Preparation of insulating modified filler;

[0068] S11. By weight, 10 parts of nano-silica were mixed with 150 parts of nitric acid solution with a concentration of 8 mol / L, heated to 90°C, and reacted for 8 hours. The precipitate was separated by centrifugation, washed with deionized water until neutral, and then dispersed in 120 parts of formaldehyde. After ultrasonic dispersion for 30 minutes, 1 part of potassium hydroxide was added under a nitrogen atmosphere, heated to 55°C, and reacted for 4 hours. The precipitate was separated by centrifugation, washed with deionized water until neutral, and then dried to constant weight to obtain hydroxymethylated nano-silica.

[0069] S12. Under a nitrogen atmosphere, 5 parts by weight of hydroxymethylated nano silica were dispersed in N,N-dimethylformamide and added dropwise to an N,N-dimethylformamide solution containing 80 parts of triphenyl isocyanate thiophosphate. The temperature was raised to 75°C and reacted for 2 hours. Then, 0.05 parts of dibutyltin dilaurate were added, the temperature was raised to 90°C, and the reaction was continued for 8 hours. After heating was stopped, the mixture was centrifuged, washed three times with N,N-dimethylformamide, and vacuum evaporated to constant weight to obtain nano silica with terminal isocyanate groups.

[0070] S13. Disperse 1.1 moles of p-hydroxyacetophenone in toluene by molar amount, heat to 65°C, and then add dropwise to 1 mole of glycerol tri(1,2-epoxy)propyl ether over a period of 2 hours. After the addition is complete, heat to 85°C and react for 8 hours. Then, remove excess solvent by vacuum distillation to obtain the terminal epoxy complex.

[0071] S14. By mass, 1.2 parts of hydroxyethyl methacrylate were dispersed in toluene. After dispersion for 10 min, 0.05 parts of the initiator azobisisobutyronitrile were added, and dispersion was continued for another 10 min to obtain a monomer dispersion. Under a nitrogen atmosphere, the dispersion was added dropwise to a solution of N,N-dimethylformamide containing 3 parts of terminal epoxy group complex. The temperature was raised to 75°C, and the reaction was carried out for 12 h. Then, 15 parts of the isocyanate-terminated nano-silica prepared in step S12 and 0.05 parts of dibutyltin dilaurate were added. The temperature was raised to 95°C, and the reaction was carried out for 4.5 h. After filtration, the mixture was washed three times with N,N-dimethylformamide and deionized water to obtain the insulating modified filler.

[0072] S2. By weight, 86 parts of low-density polyethylene, 1 part of antioxidant 1010 and 30 parts of the insulating modified filler prepared in step S1 are mixed, heated to 160°C, melt-blended for 15 minutes, cooled and pelletized to obtain blend masterbatch.

[0073] S3. Mix the blending masterbatch with 4.5 parts of dicumyl peroxide, heat to 120°C, knead for 10 minutes, and then extrude and coat the surface of the cable body to obtain a cross-linked polyethylene insulated flame-retardant power cable.

[0074] Comparative Example 1.

[0075] Compared with Example 1, this comparative example did not prepare an insulating modified filler, but instead replaced it with an equal mass of nano-silica material;

[0076] A method for preparing a cross-linked polyethylene insulated flame-retardant power cable includes the following steps:

[0077] S1. By weight, 70 parts of low-density polyethylene, 0.5 parts of antioxidant 1010 and 18 parts of nano silica are mixed, heated to 150°C, melt-blended for 15 minutes, cooled and pelletized to obtain blend masterbatch;

[0078] S2. Mix the blending masterbatch with 2.5 parts of dicumyl peroxide, heat to 105°C, knead for 10 minutes, and then extrude and coat the surface of the cable body to obtain a cross-linked polyethylene insulated flame-retardant power cable.

[0079] Testing: Following the operating procedures of Examples 1-5 and Comparative Example 1, cross-linked polyethylene insulation layers were prepared individually. Samples with a thickness of 4 mm were prepared from the cross-linked polyethylene insulation layers prepared in Examples 1-5 and Comparative Example 1. The abrasion resistance of the samples was tested according to GB 5478-85, and their impact strength was tested according to GB / T1043-93. The dielectric strength of the cross-linked polyethylene insulation layers prepared in Examples 1-5 and Comparative Example 1 was tested according to ASTM D149. After storing the cross-linked polyethylene insulation layers prepared in Examples 1-5 and Comparative Example 1 at 75°C for 30 days, the dielectric strength was tested again. The flame retardant rating of the cross-linked polyethylene insulation layers prepared in Examples 1-5 and Comparative Example 1 was tested according to UL94. The test results are shown in the table below.

[0080]

[0081] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a cross-linked polyethylene insulated flame-retardant power cable, characterized in that, Includes the following steps: S1. Preparation of insulating modified fillers; S11. Mix nano-silica with nitric acid solution, heat to 80-90℃, react for 4-8 hours, centrifuge to separate the precipitate, wash with deionized water until neutral, disperse the precipitate in formaldehyde, sonicate for 30-45 minutes, add potassium hydroxide under nitrogen atmosphere, heat to 55-60℃, react for 4-8 hours, centrifuge to separate the precipitate, wash with deionized water until neutral, and dry to constant weight to obtain hydroxymethylated nano-silica; S12. Under a nitrogen atmosphere, hydroxymethylated nano-silica was dispersed in N,N-dimethylformamide and added dropwise to an N,N-dimethylformamide solution containing triphenyl isocyanate thiophosphate. The temperature was raised to 65-75℃ and the reaction was carried out for 1.5-2 hours. Then, dibutyltin dilaurate was added and the temperature was raised to 85-90℃. The reaction was continued for 4-8 hours. After heating was stopped, the nano-silica was separated by centrifugation, washed 3-5 times with N,N-dimethylformamide, and then vacuum evaporated to constant weight to obtain isocyanate-terminated nano-silica. S13. Disperse p-hydroxyacetophenone in toluene, heat to 55-65℃, and then add it dropwise to tri(1,2-epoxy)propyl glycerol for 1-2 hours. After the addition is complete, heat to 70-85℃ and react for 4-8 hours. Then, remove excess solvent by vacuum distillation to obtain the terminal epoxy complex. S14. Hydroxyethyl methacrylate is dispersed in toluene. After dispersion for 10-15 min, the initiator azobisisobutyronitrile is added, and dispersion is continued for another 10-15 min to obtain a monomer dispersion. Under a nitrogen atmosphere, the dispersion is added dropwise to a solution of N,N-dimethylformamide containing an epoxy-terminated complex. The temperature is raised to 65-75℃, and the reaction is carried out for 6-12 h. Then, the isocyanate-terminated nano-silica and dibutyltin dilaurate prepared in step S12 are added. The temperature is raised to 85-95℃, and the reaction is carried out for 3-4.5 h. After filtration, the mixture is washed 3-4 times with N,N-dimethylformamide and deionized water to obtain the insulating modified filler. S2. Mix low-density polyethylene, antioxidant and insulating modified filler prepared in step S1, heat to 150-160℃, melt blend for 15-30 min, cool and pelletize to obtain blend masterbatch; S3. Mix the blending masterbatch with the crosslinking agent, heat to 105-120℃, knead for 5-15 minutes, and then extrude and coat the cable body surface to obtain crosslinked polyethylene insulated flame-retardant power cable. The cross-linked polyethylene insulated flame-retardant power cable consists of an outer cross-linked polyethylene insulation layer and a cable body covering the inner side. The cross-linked polyethylene insulation layer, by weight, comprises the following components: 70-86 parts low-density polyethylene, 2.5-4.5 parts cross-linking agent, 0.5-1 part antioxidant, and 18-30 parts insulation modifying filler. In step S12, the mass ratio of the hydroxymethylated nano-silica, triphenyl isocyanate thiophosphate, and dibutyltin dilaurate is 5:(50-80):(0.01-0.05) by weight. In step S14, the mass ratio of hydroxyethyl methacrylate, azobisisobutyronitrile, terminal epoxy complex, terminal isocyanate group nano silica, and dibutyltin dilaurate is (0.9-1.2):(0.03-0.05):3:(10-15):(0.03-0.05).

2. The method for preparing a cross-linked polyethylene insulated flame-retardant power cable according to claim 1, characterized in that: The antioxidant is antioxidant 1010.

3. The method for preparing a cross-linked polyethylene insulated flame-retardant power cable according to claim 1, characterized in that: The crosslinking agent is dicumyl peroxide.

4. The method for preparing a cross-linked polyethylene insulated flame-retardant power cable according to claim 1, characterized in that: In step S11, the concentration of the nitric acid solution is 6-8 mol / L; the mass ratio of potassium hydroxide to formaldehyde is 1:(8-12).

5. The method for preparing a cross-linked polyethylene insulated flame-retardant power cable according to claim 1, characterized in that: In step S13, the molar ratio of p-hydroxyacetophenone to glyceryl tri(1,2-epoxy)propyl ether is (0.8-1.1):1 based on molar parts.

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