Strong-wind-resistant flame-retardant overhead insulated cable and preparation method thereof

Abstract

The invention relates to the technical field of cables, and particularly discloses a strong-wind-resistant flame-retardant overhead insulated cable and a preparation method thereof. The strong-wind-resistant flame-retardant overhead insulated cable comprises a conductor, an insulating layer, a reinforcing piece, a wrapping layer and a flame-retardant layer which are sequentially arranged from inside to outside, the nominal thickness of the insulating layer is 1.7-2.0 mm, and the insulating layer is prepared from the following raw materials in parts by weight: 40-50 parts of NCO modified SEBS; 20 to 23 parts of atactic polypropylene; 45 to 50 parts of white oil; and 1-2 parts of a lubricant. The nominal thickness of the insulating layer in the aerial insulated cable is far smaller than that of other aerial insulated cables, the aerial insulated cable further has more excellent weather resistance, the reinforcing piece and the flame-retardant layer are matched, the windproof performance and the flame-retardant performance of the cable can be improved on the premise that the weight and the size of the cable are not affected, and the service life of the cable is prolonged. Good safety performance can be kept under the conditions of strong wind and fire disasters.

Description

Technical Field

[0001] This application relates to the technical field of cables, and particularly to a strong-wind-proof and flame-retardant overhead insulated cable and its preparation method. Background Art

[0002] As a common power transmission method, overhead insulated cables are used to transmit electricity by erecting cables in the air. Such cables usually consist of multiple strands of conductors, and the conductors are wrapped with an insulating layer to prevent current leakage. According to different usage environments and safety requirements, overhead insulated cables can be bare or insulated. They are usually fixed on utility poles or iron towers and isolated by insulators to ensure the safety of power transmission. Due to their economy and construction convenience, overhead insulated cables are widely used in power transmission in urban and rural areas, especially in open spaces or high-wind areas.

[0003] The design and manufacturing technologies of traditional overhead insulated cables have a long history and have played an important role in meeting basic power transmission requirements. To improve the durability and safety of cables, technicians have adopted various means. For example, increasing the mechanical strength of the conductor, such as using high-strength steel wires to reinforce the conductor; improving the insulating material, such as using high-performance insulating materials like cross-linked polyethylene (XLPE); adding a protective layer, such as setting a flame-retardant sheath on the outer layer. These measures have improved the wind-proof and flame-retardant properties of the cables to a certain extent, but there are still some deficiencies. Some of the existing overhead insulated cables have certain wind-proof and flame-retardant properties, but in extreme weather conditions, especially in strong-wind weather or fire hazards, they are still easily affected by the external environment, resulting in cable damage, short circuits, and even fires, seriously affecting the stability and safety of power transmission. In addition, the existing protective measures rely on adding additional functional layers, which not only increases the weight and size of the cable, but also may make the installation and maintenance of the cable during high-altitude operations more difficult, reducing its practicality and economic benefits. Therefore, there is an urgent need to develop an overhead insulated cable that can maintain good safety performance under strong-wind and fire conditions. Summary of the Invention

[0004] To solve the above technical problems, this application provides a strong-wind-proof and flame-retardant overhead insulated cable and its preparation method.

[0005] In a first aspect, this application provides a strong-wind-proof and flame-retardant overhead insulated cable, including a conductor, an insulating layer, a strengthening member, a wrapping layer, and a flame-retardant layer arranged in sequence from the inside to the outside. The nominal thickness of the insulating layer is 1.7 - 2.0 mm, and it is made from the following raw materials calculated by weight: 40 - 50 parts of NCO-modified SEBS; 20 - 23 parts of atactic polypropylene; 45 - 50 parts of white oil; 1 - 2 parts of lubricant.

[0006] Preferably, the NCO-modified SEBS is prepared by the following method: S1. Dispersing SEBS with Mn = 10 - 30 MDa in a system containing maleic anhydride and an initiator, raising the temperature for reaction, adding isopropanol for precipitation after cooling to obtain intermediate product A1, blending ethyl acetate with intermediate product A1 and raising the temperature for reaction, adding isopropanol for precipitation after cooling to obtain intermediate product B1; S2. Dispersing intermediate product B1 and NCO with a weight ratio of 6:(5 - 6) in an organic solvent containing a catalyst, reacting for 10 - 15 h under the protection of an inert gas at a temperature of 50 - 70 °C to obtain NCO-modified SEBS.

[0007] By adopting the above technical solution, the present application modifies medium molecular weight SEBS with NCO, introduces double hydrogen bonds into the SEBS cross-linking system, strengthens the intermolecular interaction in the SEBS system, forms a cross-linking network, greatly improves the elongation at break of the material, and the increase in the number of hydrogen bonds brings a trend of enhanced intermolecular force between chains. At this time, the EB cross-linking structure in the SEBS system is more stable, and the material recovery ability after being subjected to a large deformation external force (such as wind force) is further improved. After filling the NCO-modified SEBS with oil and blending it with random polypropylene having an appropriate melt index and high cleanliness, and cooperating with a lubricant, the insulating layer material has excellent extrusion processing performance, mechanical properties and electrical properties. All in all, the insulating layer material of the present application not only has high elasticity, excellent weather resistance and good basic properties, but also realizes a reduction in the nominal thickness of the insulating layer. Compared with the existing nominal thickness of the insulating layer (3.4 mm), it is reduced by as much as 40 - 50%. In the specific embodiment of the present application, NCO is n-butyl isocyanate, which is only for illustrative purposes, and those skilled in the art can replace it according to the actual situation.

[0008] On the premise that the thickness of the insulating layer is greatly reduced, the present application further adds a reinforcing member and a flame retardant layer to the cable structure, so that the wind resistance performance and flame retardant performance can be improved on the premise of maintaining the operability of the cable in high-altitude operations. After test detection, the overall breaking force of the final overhead insulated cable product is not less than 105 KN, and the char height is not more than 0.6 m. Therefore, the strong wind and fire resistant overhead insulated cable of the present application can maintain good safety performance under strong wind and fire conditions.

[0009] Preferably, by weight, the flame retardant layer is prepared from the following raw materials: 48 - 52 parts of SEBS; 20 - 25 parts of low-density polypropylene; 65 - 70 parts of a composite flame retardant; 10 - 12 parts of a compatibilizer; 23 - 28 parts of white oil; 3 - 4 parts of a lubricant.

[0010] Preferably, the composite flame retardant comprises at least two of tris(2-chloroethyl) phosphate, urea-based phosphate, melamine cyanurate, ammonium polyphosphate, and aluminum diethyl phosphinate.

[0011] Preferably, the composite flame retardant comprises melamine cyanurate and aluminum diethyl phosphinate.

[0012] By adopting the above technical solutions, the present application uses high molecular weight SEBS (Mn = 30 - 100 MDa) and white oil with a relatively high viscosity for oil filling, so that the overall mechanical properties of the substrate are maintained well, and ultra-low density polyethylene is blended with it. With the help of a compatibilizer, the interaction force between the two phases is enhanced, and a composite flame retardant system is introduced. Further preferably, a highly efficient composite flame retardant system of melamine cyanurate and aluminum diethyl phosphinate is used, which significantly improves the flame retardant performance of the material, while maintaining a low addition amount, reducing the deterioration of the mechanical properties of the overall material of the flame retardant layer. Therefore, the flame retardant layer material of the present application has excellent mechanical properties, tear resistance, and flame retardant performance.

[0013] Preferably, the weight ratio of melamine cyanurate to aluminum diethyl phosphinate is (1.5 - 1.8):1.

[0014] By adopting the above technical solutions, the present application further controls the weight ratio of melamine cyanurate to aluminum diethyl phosphinate, realizes the maximization of the synergistic effect of the flame retardant system, and further improves the flame retardant performance of the flame retardant layer material of the present application.

[0015] Preferably, the SEBS in the flame retardant layer is also modified with ureidopyrimidinone-type NCO. Specifically: a. Dispersing SEBS with Mn = 30 - 100 MDa in a system containing maleic anhydride and an initiator, heating for reaction, cooling and adding isopropanol for precipitation to obtain intermediate product A2. Blending ethyl acetate with intermediate product A2 and heating for reaction, cooling and adding isopropanol for precipitation to obtain intermediate product B2; b. Dispersing intermediate product B2 and ureidopyrimidinone-type NCO with a weight ratio of 6:(4.8 - 5.0) together in an organic solvent containing a catalyst, reacting for 10 - 15 h under the protection of an inert gas at a temperature of 50 - 70 °C to obtain ureidopyrimidinone-type NCO-modified SEBS.

[0016] By adopting the above technical solutions, the present application modifies SEBS with ureidopyrimidinone-type NCO, introduces quadruple hydrogen bonds into the SEBS crosslinking system, strengthens the intermolecular interaction within the SEBS system, forms a crosslinking network, greatly improves the elongation at break of the material. The increase in the number of hydrogen bonds brings a trend of enhanced intermolecular force between chains, hinders the movement of chain segments, and improves the glass transition temperature of SEBS. After the modified SEBS is added to the body, the heat resistance of the flame retardant layer material of the present application can be further improved.

[0017] Preferably, the ureidopyrimidinone type NCO is prepared by the following method: 2-amino-4-hydroxy-6-methylpyrimidine and hexamethylene diisocyanate are blended, heated and stirred under the protection of inert gas, an extractant is added, the solid is obtained by filtration, washed and dried to obtain the ureidopyrimidinone type NCO.

[0018] By adopting the above technical solution, the present application uses 2-amino-4-hydroxy-6-methylpyrimidine and hexamethylene diisocyanate to prepare ureidopyrimidinone type NCO, which can form quadruple hydrogen bonds in the SEBS system, improve the degree of crosslinking, and thus greatly enhance the fire prevention ability of the flame retardant layer.

[0019] In a second aspect, the present application provides a strong wind resistant and flame retardant overhead insulated cable and a preparation method thereof, including the following steps: I. Making a conductor for standby; II. Extruding an insulating layer outside the conductor; III. Wrapping a reinforcing member outside the insulating layer, and covering a wrapping tape outside the reinforcing member to form a wrapping layer; IV. Extruding a flame retardant layer outside the wrapping layer to obtain the overhead insulated cable.

[0020] By adopting the above technical solution, the strong wind resistant and flame retardant overhead insulated cable of the present application is provided with a reinforcing layer and a flame retardant layer on the basis of the original overhead insulated cable. Among them, the conductor is made by mixing and stranding steel wire and aluminum wire, effectively improving the breaking force of the conductor. The outer aluminum wire adopts a special-shaped single wire compacted structure to ensure the smoothness of the outside of the conductor, eliminating the conductor shielding structure. The insulation adopts a special elastomer material solution, and further adopts a special elastomer material solution to reduce the thickness of the insulating layer while meeting the electrical performance requirements. At the same time, compared with the traditional cross-linked polyethylene material solution, the density is reduced, further reducing the overall weight of the cable. The reinforcing layer is placed between the insulation and the flame retardant layer to improve the overall tensile strength of the cable. Preferably, the carbon fiber wire has a light texture and high tensile strength, and will not increase the overall weight of the cable. The flame retardant material extruded in the flame retardant layer can effectively improve the flame retardant performance of the cable, ensure good operation of the cable under fire conditions, and thus improve the reliability of the entire cable system.

[0021] In summary, the present application has the following beneficial technical effects: 1. The insulating layer prepared by the present application by using raw materials such as NCO-modified SEBS and random polypropylene significantly improves the elongation at break and recovery ability of the material, and can maintain good mechanical properties even under strong wind conditions, effectively preventing the strong wind resistant and flame retardant overhead insulated cable from being damaged and short-circuited due to wind force. 2. The thickness of the insulating layer of the present application is significantly reduced to 1.7 - 2.0 mm, which is 40 - 50% less than that of the prior art. It not only reduces the overall weight of the strong wind resistant and flame retardant overhead insulated cable, but also improves the construction convenience and economy of the cable, and does not affect its electrical performance and weather resistance at the same time. 3. The flame-retardant layer of this application adopts an efficient composite flame-retardant system, especially the optimal ratio of melamine cyanurate and aluminum diethyl phosphinate, which greatly enhances the flame-retardant performance of the material, ensures the safe operation of the strong-wind-resistant and flame-retardant overhead insulated cable under fire conditions, with a char height not exceeding 0.6 m, and avoids the risk of fire spread. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a cross-sectional view of the strong-wind-resistant and flame-retardant overhead insulated cable of this application.

[0023] Description of the reference numerals: 1, conductor (steel core); 2, conductor (aluminum core); 3, insulating layer; 4, strengthening member; 5, wrapping layer; 6, flame-retardant layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] SOURCE OF MATERIALS Unless otherwise specified, the raw materials used in this application are all commercially available products, specifically: Medium molecular weight SEBS is purchased from Taixiang, with the product number 6154; High molecular chain SEBS is purchased from Taixiang, with the product number 6151; Atactic polypropylene is purchased from Shanghai Petrochemical, with the product number M250E; White oil is purchased from Changzhou Kairun, with the product number 36#; Lubricant A is purchased from Luju Chemistry, with the product number PPA2200; Low density polypropylene is purchased from Mitsui Chemicals, with the product number SP0540; Compatibilizer is purchased from Jiangsu Siruida, with the product number TRD-200SE; Lubricant B is purchased from Chengdu Silike, with the product number LYSI-401; Aluminum diethyl phosphinate is purchased from Qingdao Oprui, with the product number ADP-13; Melamine cyanurate is purchased from Qingdao Oprui; Trichloroethyl phosphate is purchased from Shandong Duoju Chemistry; Ureido phosphate is purchased from Wuhan Jiyesheng, with the CAS number 4861-19-2; Ammonium polyphosphate is purchased from Shandong Zhijia Chemical Industry; Maleic anhydride, benzoyl peroxide, n-butyl isocyanate, dibutyltin dilaurate, xylene, hexamethylene diisocyanate are purchased from Shanghai Aladdin; 1-Amino-4-hydroxy-6-methylpyrimidine is purchased from Shanghai Anyij;

[0025] The following further elaborates on this application in combination with preparation examples, examples and comparative examples.

[0026] Preparation Example 1.1 Preparation method of NCO-modified SEBS, comprising the following steps: S1. Completely dissolve 20 kg of medium molecular weight SEBS in 300 L of xylene at a temperature of 60 °C, raise the temperature to 100 °C, add maleic anhydride and initiator benzoyl peroxide, react for 6 h, after the reaction ends, cool to below 40 °C, add 5 times the volume of isopropanol for precipitation, wash repeatedly 3 times, filter by suction to obtain a yellow flocculent product, then transfer it to a vacuum drying oven at 70 °C and dry for 24 h to obtain intermediate product A1. Completely dissolve it in 100 L of xylene at a temperature of 100 °C, raise the temperature to 140 °C, add 11.2 kg of ethyl acetate for reflux reaction, after 4 h, cool to below 40 °C, add 5 times the volume of isopropanol for precipitation, wash repeatedly 3 times, filter by suction to obtain a yellow flocculent product, then transfer it to a vacuum drying oven at 70 °C and dry for 24 h to obtain intermediate product B1; S2. Completely dissolve 6 kg of intermediate product B1 in 100 L of toluene at a temperature of 60 °C, add 6 kg of n-butyl isocyanate to completely react with the hydroxyl groups, dropwise add 0.2% of the catalyst dibutyltin dilaurate, and react for 10 h under nitrogen protection at a temperature of 70 °C to obtain NCO-modified SEBS.

[0027] Preparation Example 1.2 Preparation method of NCO-modified SEBS, comprising the following steps: S1. Completely dissolve 20 kg of medium molecular weight SEBS in 300 L of xylene at a temperature of 60 °C, raise the temperature to 100 °C, add maleic anhydride and initiator benzoyl peroxide, react for 6 h, after the reaction ends, cool to below 40 °C, add 5 times the volume of isopropanol for precipitation, wash repeatedly 3 times, filter by suction to obtain a yellow flocculent product, then transfer it to a vacuum drying oven at 70 °C and dry for 24 h to obtain intermediate product A1. Completely dissolve it in 100 L of xylene at a temperature of 100 °C, raise the temperature to 140 °C, add 11.2 kg of ethyl acetate for reflux reaction, after 4 h, cool to below 40 °C, add 5 times the volume of isopropanol for precipitation, wash repeatedly 3 times, filter by suction to obtain a yellow flocculent product, then transfer it to a vacuum drying oven at 70 °C and dry for 24 h to obtain intermediate product B1; S2. Completely dissolve 6 kg of intermediate product B1 in 100 L of toluene at a temperature of 60 °C, add 5 kg of n-butyl isocyanate to completely react with the hydroxyl groups, dropwise add 0.2% of the catalyst dibutyltin dilaurate, and react for 15 h under nitrogen protection at a temperature of 50 °C to obtain NCO-modified SEBS.

[0028] Preparation Example 2.1 Preparation method of ureidopyrimidinone-type NCO-modified SEBS, comprising the following steps: 1. Completely dissolve high molecular weight SEBS (Mn = 30 - 100 MDa) in 300 L of xylene at a temperature of 60 °C, raise the temperature to 100 °C, add maleic anhydride and initiator benzoyl peroxide, react for 6 h. After the reaction is completed, cool to below 40 °C, add 5 times the volume of isopropanol for precipitation, wash repeatedly 3 times, filter by suction to obtain a yellow flocculent product. Subsequently, transfer it to a vacuum drying oven at 70 °C and dry for 24 h to obtain intermediate product A2. Completely dissolve it in 100 L of xylene at a temperature of 100 °C, raise the temperature to 140 °C, add 11.2 kg of ethyl acetate and react under reflux. After 4 h, cool to below 40 °C, add 5 times the volume of isopropanol for precipitation, wash repeatedly 3 times, filter by suction to obtain a yellow flocculent product. Subsequently, transfer it to a vacuum drying oven at 70 °C and dry for 24 h to obtain intermediate product B2; 2. Blend 2 - amino - 4 - hydroxy - 6 - methylpyrimidine and hexamethylene diisocyanate, raise the temperature to 100 °C under nitrogen protection, stir and react for 16 h, add n - hexane for extraction, filter to obtain a solid, wash with acetone 3 times to remove unreacted hexamethylene diisocyanate, dry, transfer to a vacuum drying oven at 60 °C and dry for 48 h to obtain ureidopyrimidinone - type NCO; Completely dissolve 6 kg of intermediate product B2 in 100 L of toluene at a temperature of 60 °C, add 4.8 kg of ureidopyrimidinone - type NCO to completely react with the hydroxyl groups, dropwise add 0.2% catalyst dibutyltin dilaurate, and react for 15 h under nitrogen protection at a temperature of 60 °C to obtain ureidopyrimidinone - type NCO - modified SEBS.

[0029] Preparation Example 2.2 A preparation method of ureidopyrimidinone - type NCO - modified SEBS, comprising the following steps: 1. Completely dissolve high molecular weight SEBS (Mn = 30 - 100 MDa) in 300 L of xylene at a temperature of 60 °C, raise the temperature to 100 °C, add maleic anhydride and initiator benzoyl peroxide, react for 6 h. After the reaction is completed, cool to below 40 °C, add 5 times the volume of isopropanol for precipitation, wash repeatedly 3 times, filter by suction to obtain a yellow flocculent product. Subsequently, transfer it to a vacuum drying oven at 70 °C and dry for 24 h to obtain intermediate product A2. Completely dissolve it in 100 L of xylene at a temperature of 100 °C, raise the temperature to 140 °C, add 11.2 kg of ethyl acetate and react under reflux. After 4 h, cool to below 40 °C, add 5 times the volume of isopropanol for precipitation, wash repeatedly 3 times, filter by suction to obtain a yellow flocculent product. Subsequently, transfer it to a vacuum drying oven at 70 °C and dry for 24 h to obtain intermediate product B2; 2. Blend 2-amino-4-hydroxy-6-methylpyrimidine and hexamethylene diisocyanate, heat up to 100 °C under nitrogen protection, stir and react for 16 h, add n-hexane for extraction, filter to obtain a solid, wash with acetone 3 times to remove unreacted hexamethylene diisocyanate, dry, transfer to a vacuum drying oven at 60 °C, and dry for 48 h to obtain ureidopyrimidinone-type NCO; completely dissolve 6 kg of intermediate B2 in 100 L of toluene at 60 °C, add 5.0 kg of ureidopyrimidinone-type NCO to completely react the hydroxyl groups, dropwise add 0.2% of the catalyst dibutyltin dilaurate, and react under nitrogen protection at 70 °C for 10 h to obtain ureidopyrimidinone-type NCO-modified SEBS.

[0030] Example 1.1 A preparation method of a strong-wind-proof and flame-retardant overhead insulated cable, comprising the following steps: 1. Pretreat the steel, obtain steel wires with different cross-sections through the drawing process according to the specifications, and then perform heat treatment to improve their strength and toughness. The wire size in this example is 2.40 mm, and the wire tolerance is ±0.01 mm; the tensile strength of the obtained steel wire is not less than 1310 Mpa, the stress value at 1% elongation is not less than 1140 Mpa, and the elongation at break is not less than 3%. And perform galvanizing treatment on the obtained steel wire. The galvanized layer adheres firmly to the steel wire without cracking, and the zinc layer will not produce peeling when rubbed with fingers. The zinc layer quality is 240 g / m 2 ; Take an aluminum rod with a diameter of 9 mm, and draw different sector-shaped cross-section special-shaped aluminum single wires through a sector-shaped wire drawing die according to the specifications. The central angles of the special-shaped single wires corresponding to each layer of sector rings are calculated according to the designed number of special-shaped single wires. The wire drawing must ensure that the corrugated arc surface angles of the special-shaped copper single wires in each layer are the same; Use a stranding machine to strand the steel wire and the special-shaped aluminum single wires in layers, arranged in the order of 1 + 6 + 10 + 14 (from the inner layer to the outer layer, there are 1, 6, 10, and 14 single wires in turn), divided into four layers and subjected to three times of compacting. The compacting of each layer is sequentially allocated: 6 wire reels, 10 wire reels, and 14 wire reels; among them, 1 + 6 is the stranding of steel wires, and the rest of the outer layers are the stranding of aluminum wires; The stranding direction of the single wires is set as S, Z, S from the inside to the outside. The stranding direction of the second outer layer single wire is the Z direction, and the stranding direction of the outermost layer single wire is the S direction; the stranding pitch diameter ratio of the outermost layer single wire does not exceed 13 times; the outer diameter of the conductor obtained in this example is 20.4 ± 0.1 mm; II. Extrude an insulating layer outside the conductor. Specifically: Mix 4 kg of the NCO-modified SEBS prepared in Preparation Example 1.1, 2.3 kg of random polypropylene, 4.5 kg of white oil, and 0.2 kg of lubricant A, and perform melt extrusion using a Φ90 extruder. Along the feeding to discharging direction, the temperatures of the 1st - 6th temperature zones of the extruder are respectively: 150 ± 5 °C, 155 ± 5 °C, 165 ± 5 °C, 170 ± 5 °C, 175 ± 5 °C, and 180 ± 5 °C. The screw speed of the extruder is 25.0 revolutions per minute. The die size is: the core aperture is 23 mm, the die sleeve aperture is 35 mm, and the average linear velocity is 18 ± 0.3 m / min. During the insulating layer extrusion process, it must pass the power frequency spark withstand voltage test, with a test voltage of 25 kV, a nominal insulating thickness of 2.0 mm, and the thickness at the thinnest part not less than 90% of the nominal value - 0.1 mm; III. Wrap a strengthening member outside the insulating layer, and wrap a wrapping tape outside the strengthening member to form a wrapping layer. Specifically: Vertically place 12 carbon fiber filaments outside the insulated wire core as the strengthening member to enhance the tensile strength of the cable. The single - root specification is 12K, and the linear density is 800 g / 1000 m. Overlap - wrap a layer of low - smoke and halogen - free flame - retardant tape outside the strengthening member to play a tightening role and enhance the flame - retardant performance of the cable; IV. Extrude a flame - retardant layer outside the wrapping layer to obtain an aerial insulated cable. Specifically: Mix 4.8 kg of high - molecular - weight SEBS (Mn = 30 - 100 MDa), 2.5 kg of low - density polyethylene, 6.5 kg of composite flame - retardant (3.25 kg of ammonium polyphosphate and 3.25 kg of aluminum diethylphosphinate), 1.0 kg of compatibilizer, 2.8 kg of white oil, and 0.3 kg of lubricant B, and perform melt extrusion using a Φ120 extruder. Along the feeding to discharging direction, the temperatures of the 1st - 10th temperature zones of the extruder are respectively: 130 ± 5 °C, 140 ± 5 °C, 145 ± 5 °C, 150 ± 5 °C, 155 ± 5 °C, 160 ± 5 °C, 170 ± 5 °C, 175 ± 5 °C, 175 ± 5 °C, and 180 ± 5 °C. The screw speed of the extruder is 10.0 revolutions per minute. The core aperture increases by 5 - 8 mm according to the outer diameter of the cable core, control the draw ratio not to exceed 2.5, and the die - matching coefficient is 1.02 - 1.05. The average linear velocity of the production line is 10 ± 0.5 m / min. The nominal thickness of the flame - retardant layer is 1.4 mm, and the thickness at the thinnest part is not less than 80% of the nominal value - 0.2 mm.

[0031] Example 1.2 A preparation method of a strong - wind - resistant and flame - retardant aerial insulated cable, comprising the following steps: 1. Pretreat the steel, and obtain steel wires with different cross-sections through the drawing process according to the specifications. Then, perform heat treatment to improve their strength and toughness. The size of the steel wires in this embodiment is 2.40 mm, and the wire tolerance is ±0.01 mm. The tensile strength of the obtained steel wires is not less than 1310 Mpa, the stress value at 1% elongation is not less than 1140 Mpa, and the elongation at break is not less than 3%. Then, perform galvanizing treatment on the obtained steel wires. The galvanized layer adheres firmly to the steel wire without cracking, and no peeling will occur when the zinc layer is rubbed with fingers. The zinc layer quality is 240 g / m 2 ; Take an aluminum rod with a diameter of 9 mm, and draw special-shaped aluminum single wires with different sector cross-sections through a sector wire drawing die according to the specifications. The central angles of the special-shaped single wires corresponding to each layer of sector rings are calculated according to the designed number of special-shaped single wires. The wire drawing must ensure that the corrugated arc surface angles of the special-shaped copper single wires in each layer are the same; Use a stranding machine to strand the steel wires and special-shaped aluminum single wires in layers, arranged in the order of 1 + 6 + 10 + 14 (from the inner layer to the outer layer, there are 1, 6, 10, and 14 single wires in sequence), divided into four layers and subjected to three compactings. The compaction of each layer is allocated as follows: 6 wire reels, 10 wire reels, and 14 wire reels; among them, 1 + 6 is the stranding of steel wires, and the remaining outer layers are the stranding of aluminum wires; The stranding direction of the single wires is set as S, Z, S from the inside to the outside. The stranding direction of the second outer layer of single wires is the Z direction, and the stranding direction of the outermost layer of single wires is the S direction; the stranding pitch diameter ratio of the outermost layer of single wires does not exceed 13 times; the outer diameter of the conductor obtained in this embodiment is 20.4 ± 0.1 mm; II. Extrude an insulating layer outside the conductor. Specifically: Mix 5 kg of NCO-modified SEBS prepared in Preparation Example 1.2, 2.0 kg of random polypropylene, 5 kg of white oil, and 0.1 kg of lubricant A, and perform melt extrusion using a Φ90 extruder. Along the feeding to discharging direction, the temperatures of the 1st - 6th temperature zones of the extruder are respectively: 150 ± 5 °C, 155 ± 5 °C, 165 ± 5 °C, 170 ± 5 °C, 175 ± 5 °C, and 180 ± 5 °C. The screw speed of the extruder is 25.0 revolutions per minute. The die size is: the die core aperture is 23 mm, the die sleeve aperture is 35 mm, and the average linear speed is 18 ± 0.3 m / min. During the extrusion of the insulating layer, it must pass through the power frequency spark withstand voltage test, the test voltage is 25 kV, the nominal thickness of the insulation is 1.7 mm, and the thickness of the thinnest part is not less than 90% of the nominal value - 0.1 mm; III. Wrap a reinforcing member outside the insulating layer, and wrap a wrapping tape outside the reinforcing member to form a wrapping layer. Specifically: Vertically place 12 carbon fiber filaments with a single specification of 12K and a linear density of 800 g / 1000 m outside the insulated wire core as the reinforcing member to improve the tensile strength of the cable. Overlap and wrap a layer of low-smoke and halogen-free flame retardant tape outside the reinforcing member to play a tightening role and improve the flame retardant performance of the cable; IV. Extrude the flame-retardant layer outside the wrapping layer to obtain an overhead insulated cable. Specifically: 5.2 kg of high molecular weight SEBS (Mn = 30 - 100 MDa), 2.0 kg of low density polyethylene, 7.0 kg of composite flame retardant (3.5 kg of urea-based phosphate and 3.5 kg of melamine cyanurate), 1.2 kg of compatibilizer, 2.3 kg of white oil, and 0.4 kg of lubricant B are mixed and melt-extruded using a Φ120 extruder. Along the direction from feeding to discharging, the temperatures of the 1st - 10th temperature zones of the extruder are respectively: 130 ± 5 °C, 140 ± 5 °C, 145 ± 5 °C, 150 ± 5 °C, 155 ± 5 °C, 160 ± 5 °C, 170 ± 5 °C, 175 ± 5 °C, 175 ± 5 °C, and 180 ± 5 °C. The screw speed of the extruder is 10.0 revolutions per minute. The die core aperture increases by 5 - 8 mm according to the outer diameter of the cable core. Control the draw ratio not to exceed 2.5, and the die matching coefficient is 1.02 - 1.05. The average linear speed of the production line is 10 ± 0.5 m / min. The nominal thickness of the flame-retardant layer is 1.4 mm, and the thickness at the thinnest part is not less than 80% of the nominal value - 0.2 mm.

[0032] Examples 2.1 - 2.6 A preparation method of a strong wind-resistant and flame-retardant overhead insulated cable, which is different from Example 1.1 in that: in step IV, the composition of the composite flame retardant is different, as shown in Table 1 specifically, and the rest are the same as Example 1.1.

[0033] Table 1 Composition of the composite flame retardant in Examples 2.1 - 2.6 Group Compound flame retardant composition Example 1.1 3.25 kg of ammonium polyphosphate and 3.25 kg of aluminum diethylphosphinate Example 2.1 3.25 kg of ammonium polyphosphate and 3.25 kg of tris(2-chloroethyl) phosphate Example 2.2 3.25 kg of tris(2-chloroethyl) phosphate and 3.25 kg of aluminum diethylphosphinate Example 2.3 3.25 kg of melamine cyanurate and 3.25 kg of aluminum diethylphosphinate Example 2.4 3.25 kg of melamine cyanurate and 3.25 kg of ammonium polyphosphate Example 2.5 3.25 kg of urea phosphate and 3.25 kg of ammonium polyphosphate Example 2.6 3.25 kg of melamine cyanurate and 3.25 kg of tris(2-chloroethyl) phosphate Example 3.1 A preparation method of a strong wind-resistant and flame-retardant overhead insulated cable, which is different from Example 2.3 in that: in step IV, the weight ratio of melamine cyanurate to aluminum diethylphosphinate is 1.5:1, the dosage of melamine cyanurate is 3.9 kg, and the dosage of aluminum diethylphosphinate is 2.6 kg, and the rest are the same as Example 2.3.

[0034] Example 3.2 A preparation method of a strong wind-resistant and flame-retardant overhead insulated cable, which is different from Example 2.3 in that: in step IV, the weight ratio of melamine cyanurate to aluminum diethylphosphinate is 1.65:1, the dosage of melamine cyanurate is 4.05 kg, and the dosage of aluminum diethylphosphinate is 2.45 kg, and the rest are the same as Example 2.3.

[0035] Example 3.3 A preparation method of a strong wind-resistant and flame-retardant overhead insulated cable, which is different from that of Example 2.3 in that: in Step IV, the weight ratio of melamine cyanurate to aluminum diethyl phosphinate is 1.8:1, the dosage of melamine cyanurate is 4.18 kg, and the dosage of aluminum diethyl phosphinate is 2.32 kg, and the rest are the same as those in Example 2.3.

[0036] Example 3.4 A preparation method of a strong wind-resistant and flame-retardant overhead insulated cable, which is different from that of Example 2.3 in that: in Step IV, the weight ratio of melamine cyanurate to aluminum diethyl phosphinate is 2:1, the dosage of melamine cyanurate is 4.33 kg, and the dosage of aluminum diethyl phosphinate is 2.17 kg, and the rest are the same as those in Example 2.3.

[0037] Examples 4.1 - 4.2 A preparation method of a strong wind-resistant and flame-retardant overhead insulated cable, which is different from that of Example 3.1 in that: in Step IV, SEBS is respectively replaced with the ureido pyrimidinone type NCO-modified SEBS prepared in Preparation Examples 2.1 - 2.2, and the rest are the same as those in Example 3.1.

[0038] Comparative Example 1 It is different from Example 1.1 in that: in Step II, all the NCO-modified SEBS prepared in Preparation Example 1.1 are replaced with medium molecular weight SEBS, and the rest are the same as those in Example 1.1.

[0039] Comparative Example 2 It is different from Example 1.1 in that: in Step II, all the NCO-modified SEBS prepared in Preparation Example 1.1 are replaced with medium molecular weight SEBS, the nominal insulation thickness is 3.4 mm, and the rest are the same as those in Example 1.1.

[0040] Performance testing The overall breaking force and char height of the overhead insulated cables prepared in the examples and comparative examples were detected, and the test results were recorded in Table 2.1, and a comprehensive test was carried out on the group with the best test results, and the test items and results were recorded in Table 2.2.

[0041] Table 2.1 Test results (1) According to the above results, Example 4.2 A comprehensive test was carried out.

[0042] Table 2.2 Test results (2) Data analysis: As can be seen from Table 2.1, the overall breaking force of the aerial insulated cable in Examples 1.1 - 1.2 of this application is 105 - 106 kN, the charring height is 0.59 - 0.6 m, and at the same time, the nominal thickness of the insulation layer is only 1.7 - 2.0 mm, which proves that this application can improve the wind resistance and flame retardancy of the cable on the premise of maintaining the operability of the cable in high-altitude operations, and can maintain good safety performance under strong wind and fire conditions.

[0043] The difference between Examples 2.1 - 2.6 and Example 1.1 is that this application replaces the components of the composite flame retardant. The results show that the charring height of Example 2.3 is significantly lower than that of other examples, which proves that this application further optimizes the efficient composite flame retardant system of melamine cyanurate and aluminum diethyl phosphinate, significantly improves the flame retardancy of the material, while maintaining a low addition amount and reducing the deterioration of the mechanical properties of the overall flame retardant layer material. Therefore, the flame retardant layer material of this application has excellent mechanical properties, tear resistance and flame retardancy.

[0044] The difference between Examples 3.1 - 3.4 and Example 2.3 is that this application replaces the dosage ratio of melamine cyanurate and aluminum diethyl phosphinate. The results show that the charring heights of Examples 3.1 - 3.3 are significantly lower than those of Example 2.3 and Example 3.4, which proves that this application further controls the weight ratio of melamine cyanurate and aluminum diethyl phosphinate, realizes the maximization of the flame retardant system synergistic effect, and further improves the flame retardancy of the flame retardant layer material of this application.

[0045] The difference between Examples 4.1 - 4.2 and Example 3.1 is that the SEBS in the flame retardant layer of this application is also modified with ureidopyrimidinone - type NCO. The results show that the overall breaking force of the cable has increased and the charring height has also been reduced, which proves that this application uses ureidopyrimidinone - type NCO to modify SEBS, introduces quadruple hydrogen bonds into the SEBS cross - linking system, strengthens the intermolecular interaction within the SEBS system, forms a cross - linked network, greatly improves the elongation at break of the material, and the increase in the number of hydrogen bonds brings a trend of enhanced intermolecular force between chains, hinders the movement of chain segments, and increases the glass transition temperature of SEBS. After the modified SEBS is added, the heat resistance of the flame retardant layer material of this application can be further improved.

[0046] The difference between Comparative Example 1 and Example 1.1 is that in this application, the NCO-modified SEBS in the insulating layer is replaced by SEBS. The results show that the overall breaking force of the cable is greatly reduced, and at the same time, the charring height also increases. This proves that by using NCO to modify medium molecular weight SEBS in this application, double hydrogen bonds are introduced into the SEBS cross-linking system, strengthening the intermolecular interaction within the SEBS system, forming a cross-linked network, greatly improving the elongation at break of the material. The increase in the number of hydrogen bonds brings a trend of enhanced intermolecular force between chains. At this time, the EB cross-linking structure within the SEBS system is more stable, and the material's recovery ability after being subjected to a large deformation external force (such as wind force) is further improved.

[0047] The difference between Comparative Example 2 and Example 1.1 is that in this application, the NCO-modified SEBS in the insulating layer is replaced by SEBS, and at the same time, the nominal thickness of the insulating layer is changed to the existing 3.4 mm. However, the results show that the overall breaking force of the cable is still lacking, and the charring height is also slightly higher than that of Example 1.1. Moreover, Comparative Example 2 also increases the weight and size of the cable, which may make the installation and maintenance of the cable during high-altitude operations more difficult. This further verifies that the overhead insulated cable of this application can maintain good safety performance under strong wind and fire conditions without affecting its own size and weight.

[0048] The embodiments of this specific implementation manner are all preferred embodiments of this application, and do not limit the protection scope of this application accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. A strong wind resistant flame retardant overhead insulated cable, characterized in that: The invention comprises a conductor, an insulating layer, a reinforcing member, a wrapping layer and a flame retardant layer which are arranged in sequence from the inside to the outside. The insulating layer has a nominal thickness of 1.7-2.0 mm and is prepared from the following raw materials calculated by weight: 40-50 parts of NCO modified SEBS; 20-23 parts of random polypropylene; 45-50 parts of white oil; and 1-2 parts of lubricant.

2. The strong wind proof flame retardant overhead insulated cable according to claim 1, characterized in that: The NCO modified SEBS is prepared by the following method: S1, dispersing SEBS with Mn=10-30MDa in a system containing maleic anhydride and an initiator, heating the system for reaction, cooling the system and adding isopropanol for precipitation to obtain an intermediate product A1, blending ethyl acetate with the intermediate product A1 and heating the system for reaction, cooling the system and adding isopropanol for precipitation to obtain an intermediate product B1; S2. Disperse the intermediate product B1 and NCO in a weight ratio of 6:(5-6) in an organic solvent containing a catalyst, and react them for 10-15 hours at a temperature of 50-70° C. under the protection of an inert gas to obtain NCO-modified SEBS.

3. The strong wind proof flame retardant overhead insulated cable according to claim 1, characterized in that: The flame retardant layer is made of the following raw materials in parts by weight: 48-52 parts of SEBS; 20-25 parts of low-density polypropylene; 65-70 parts of composite flame retardant; 10-12 parts of compatibilizer; 23-28 parts of white oil; and 3-4 parts of lubricant.

4. The strong wind proof flame retardant overhead insulated cable according to claim 3, characterized in that: The composite flame retardant includes at least two of trichloroethyl phosphate, urea-based phosphate, melamine cyanurate, ammonium polyphosphate and diethyl aluminum phosphinate.

5. The strong wind proof flame retardant overhead insulated cable according to claim 4, characterized in that: The composite flame retardant comprises melamine cyanurate and aluminum diethylphosphinate.

6. The strong wind resistant flame retardant overhead insulated cable according to claim 5, characterized in that: The weight ratio of the melamine cyanurate to aluminum diethylphosphinate is (1.5-1.8):

1.

7. The strong wind proof flame retardant overhead insulated cable according to claim 3, characterized in that: The SEBS in the flame retardant layer is also modified by ureido-pyrimidone-type NCO, specifically: a. Disperse SEBS with Mn=30-100 MDa in a system containing maleic anhydride and an initiator, heat the mixture to react, add isopropanol to precipitate after cooling, and obtain intermediate product A2; blend ethyl acetate with intermediate product A2 and heat the mixture to react, add isopropanol to precipitate after cooling, and obtain intermediate product B2; b. Disperse the intermediate product B2 and ureidopyrimidone-type NCO in a weight ratio of 6:(4.8-5.0) in an organic solvent containing a catalyst, and react for 10-15 hours at a temperature of 50-70°C under the protection of an inert gas to obtain ureidopyrimidone-type NCO-modified SEBS.

8. The strong wind resistant flame retardant overhead insulated cable according to claim 6, characterized in that: The ureido-pyrimidone-type NCO is prepared by the following method: 2-amino-4-hydroxy-6-methylpyrimidine and hexamethylene diisocyanate are mixed, heated and stirred under the protection of inert gas for reaction, an extractant is added, a solid is obtained by filtration, and the solid is washed and dried to obtain ureidopyrimidone type NCO.

9. A method for preparing the strong wind resistant flame retardant overhead insulated cable according to any one of claims 1 to 8, characterized in that: The following steps are involved: I. Make conductors and keep them ready for use; II. Extruding an insulating layer on the outside of the conductor; III. Wrapping the reinforcement member outside the insulating layer, and wrapping the wrapping tape around the outside of the reinforcement member to form a wrapping layer; IV. Extruding a flame retardant layer on the outside of the wrapping layer to obtain an overhead insulated cable.

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