10kV flame-retardant wire cable

Abstract

The invention relates to the technical field of cables, and provides a 10kV flame-retardant wire cable and a preparation method thereof. The 10kV flame-retardant wire cable comprises a bunched wire core and an outer sheath layer, the outer sheath layer is prepared from the following raw materials in parts by weight: 40 to 50 parts of linear low-density polyethylene, 30 to 40 parts of ethylene-vinyl acetate copolymer, 18 to 20 parts of microencapsulated ammonium polyphosphate, 6 to 8 parts of organic modified nano montmorillonite, 4 to 6 parts of zinc borate, 1 to 2 parts of silane coupling agent, 0.5 to 1 part of antioxidant and 0.4 to 0.6 part of calcium stearate. According to the 10 kV flame-retardant electric wire and cable prepared in the invention, the flame-retardant grade of the flame-retardant electric wire and cable is improved, but the problem that the elongation at break of the material is reduced due to excessive addition of the inorganic flame retardant is solved; and the problems of environmental adaptability and mechanical performance of sheath cracking easily caused by insufficient bending radius of the cable are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of cables, and in particular to a 10kV flame-retardant electric wire and cable. Background Art

[0002] With the acceleration of urbanization and the expansion of power systems, the safety and reliability of 10kV medium-voltage distribution networks, the core carrier of urban energy transmission, are directly related to public safety and economic efficiency. Traditional 10kV power cables pose a risk of flame spread in fire scenarios, potentially causing secondary disasters. In recent years, flame-retardant wire and cable technology has become a hot topic in industry research, but existing products still face technical bottlenecks in terms of flame retardancy, environmental adaptability, and mechanical performance.

[0003] To improve flame retardancy, some products excessively add inorganic flame retardants, causing the material's elongation at break to drop from 200% to 120%. During cable laying, insufficient bending radius can easily cause sheath cracking.

[0004] In order to solve the above technical problems, the present invention proposes a new 10kV flame retardant wire and cable. Summary of the Invention

[0005] The present invention proposes a 10kV flame-retardant wire and cable and a preparation method thereof, which improves the flame retardant grade of the flame-retardant wire and cable, but solves the problem of excessive addition of inorganic flame retardants leading to a decrease in the material's elongation at break; and improves the environmental adaptability and mechanical properties problems of the sheath cracking easily caused by insufficient cable bending radius.

[0006] The technical solutions of the present invention are as follows: In the first aspect, the present invention proposes a 10kV flame-retardant wire and cable, comprising a bundled wire core and an outer sheath layer, wherein the outer sheath layer is composed of the following raw materials in parts by weight: 40-50 parts of linear low-density polyethylene, 30-40 parts of ethylene-vinyl acetate copolymer, 18-20 parts of microencapsulated ammonium polyphosphate, 6-8 parts of organically modified nano-montmorillonite, 4-6 parts of zinc borate, 1-2 parts of silane coupling agent, 0.5-1 part of antioxidant, and 0.4-0.6 part of calcium stearate.

[0007] In the present invention, calcium stearate acts as a lubricant, reducing friction between the polymer melt and the equipment during processing, improving melt fluidity and making the material easier to process and shape. Furthermore, it can also, to a certain extent, prevent the agglomeration of inorganic fillers in the polymer matrix, thereby improving the uniformity of the material.

[0008] As a further technical solution, the preparation method of the microencapsulated ammonium polyphosphate includes: dispersing ammonium polyphosphate in ethyl acetate, adding melamine-formaldehyde prepolymer for ultrasonic emulsification; adding hydrochloric acid to adjust the pH to 3, reacting at 60-70°C for 4-6 hours to form a prepolymer coating layer, filtering and drying to obtain microencapsulated ammonium polyphosphate.

[0009] As a further technical solution, the weight ratio of the ammonium polyphosphate, ethyl acetate and melamine-formaldehyde prepolymer is 90-110:15-25:180-220.

[0010] As a further technical solution, the preparation method of the melamine-formaldehyde prepolymer comprises: adding formaldehyde solution and deionized water to a reactor, adding triethanolamine while stirring to adjust the pH to 8.5-9.0, heating to 70-75° C., adding melamine, and keeping the temperature to react for 30-40 minutes; then heating to 80-85° C., continuing the reaction for 1.5-2 hours, cooling to 35-40° C., adding urea to neutralize free formaldehyde, and adjusting the pH to 7.0-7.5 to obtain the prepolymer.

[0011] As a further technical solution, the formaldehyde solution is a formaldehyde aqueous solution with a mass concentration of 30-40%, and the weight ratio of the formaldehyde solution, deionized water, triethanolamine and melamine is 90-100:160-180:180-220:2-3.

[0012] As a further technical solution, the preparation method of the organic modified nano-montmorillonite comprises: dispersing sodium montmorillonite in 50-60 ° C hot water and stirring at 1200-1400 rpm for 60-70 minutes, adding hexadecyl trimethylammonium bromide, reacting at 75-85 ° C for 5-7 hours, and centrifuging and washing until there is no Br - , vacuum dried and ground to D50=500nm.

[0013] As a further technical solution, the weight ratio of the sodium montmorillonite, water and hexadecyltrimethylammonium bromide is 9-11:180-220:3.5-4.5.

[0014] As a further technical solution, the silane coupling agent is silane coupling agent KH550; the antioxidants are antioxidant 1010 and antioxidant 168 in a weight ratio of 1:1.

[0015] In addition to modifying the interface between OMMT and the polymer matrix, the silane coupling agent KH550 can also improve the compatibility between other inorganic fillers (such as microencapsulated ammonium polyphosphate and zinc borate) and the polymer matrix to a certain extent, promote the uniform dispersion of inorganic fillers in the matrix, and improve the overall performance of the material.

[0016] The antioxidants are formulated with antioxidant 1010 and antioxidant 168 in a 1:1 weight ratio. Antioxidant 1010 is a hindered phenolic antioxidant that captures free radicals generated during polymer processing and use, terminating free radical chain reactions and thereby slowing the thermal oxidative degradation of the polymer. Antioxidant 168 is a phosphite antioxidant that decomposes the hydroperoxides produced during polymer thermal oxidation, preventing further decomposition and free radical formation. The synergistic effect of these two antioxidants effectively improves the thermal stability of the outer sheath of wires and cables, extending their service life.

[0017] In a second aspect, the present invention provides a method for preparing a 10kV flame-retardant wire and cable, comprising the steps of: The steps include: drying linear low-density polyethylene and ethylene-vinyl acetate copolymer at 75-85°C for 4-5 hours, then adding microencapsulated ammonium polyphosphate, organically modified nano-montmorillonite, zinc borate, silane coupling agent, antioxidant and calcium stearate and stirring at a speed of 700-900rpm for 10-20 minutes; using a twin-screw extruder to extrude and granulate to obtain 10kV flame-retardant wire and cable material, melt-extruding and coating it on the surface of the bundled wire core to form an outer sheath layer of 1.4-1.5mm, and forming a 10kV flame-retardant wire and cable after cooling.

[0018] As a further technical solution, during the extrusion granulation, the temperature of zone 1 of the twin-screw extruder is 155-165°C, the temperature of zone 2 is 170-180°C, the temperature of zone 3 is 180-190°C, the temperature of zone 4 is 185-195°C, and the die head temperature is 175-185°C; the screw speed is 280-320rpm.

[0019] The working principle and beneficial effects of the present invention are: Ammonium polyphosphate (APP) in this invention is a highly effective inorganic flame retardant. However, direct addition can lead to problems such as moisture absorption and poor compatibility with the polymer matrix, which can affect the long-term performance of wires and cables. This invention utilizes microencapsulation technology to treat APP. This involves dispersing APP in ethyl acetate, adding a melamine-formaldehyde prepolymer for ultrasonic emulsification, and reacting under acidic conditions to form a prepolymer coating. This microencapsulated structure effectively prevents direct contact between APP and the external environment, reduces moisture absorption, and improves its dispersibility and stability within the polymer matrix.

[0020] The microencapsulated ammonium polyphosphate (APP) and organically modified nano-montmorillonite (OMMT) in this invention work synergistically in the flame retardant process. APP decomposes at high temperatures to produce acidic substances such as phosphoric acid and metaphosphoric acid, which promote the dehydration and carbonization of the polymer matrix, forming a dense char layer. This char layer acts as a heat and oxygen barrier, and prevents the escape of combustible gases, thereby inhibiting the spread of combustion. Furthermore, OMMT has a layered structure and can migrate to the polymer surface during combustion, interweaving with the char layer produced by the decomposition of APP. This further enhances the density and stability of the char layer and improves the flame retardant effect. The synergistic effect of these two factors increases the oxygen index of the wire and cable, reaching UL94 V-0, without the risk of ignition by molten droplets.

[0021] In addition, zinc borate plays a synergistic role in the flame retardant system. Although Comparative Example 6 shows that zinc borate is not a necessary component for achieving flame retardant performance standards, its addition can further enhance the flame retardant effect. Zinc borate decomposes at high temperatures to produce boric acid and zinc oxide. Boric acid can work together with the acidic substances produced by the decomposition of APP to promote the carbonization of the polymer and increase the yield of the carbon layer; zinc oxide has a certain catalytic effect, which can accelerate the thermal degradation and carbonization process of the polymer, making the carbon layer denser and more stable. In addition, zinc borate can also absorb the heat generated during the combustion process, reducing the temperature of the combustion area, thereby further inhibiting the combustion reaction.

[0022] The organically modified sodium montmorillonite (OMMT) in the present invention increases its interlayer spacing, enabling better dispersion within a polymer matrix. During the preparation process, the sodium montmorillonite is dispersed in hot water and stirred at high shear speed. Hexadecyltrimethylammonium bromide is then added to conduct an ion exchange reaction, inserting organic cations between the montmorillonite layers and improving its compatibility with the polymer matrix. In the outer sheath of wires and cables, OMMT can be evenly dispersed within the polymer matrix, acting as physical crosslinking points and restricting the movement of the polymer molecular chains, thereby increasing the material's tensile strength and elongation at break.

[0023] Furthermore, the addition of the silane coupling agent KH550 further improves the interfacial bonding between OMMT and the polymer matrix. The siloxane groups in the KH550 molecule react with the hydroxyl groups on the OMMT surface, forming chemical bonds. Meanwhile, the organic functional groups on the other end of the KH550 molecule entangle with the polymer matrix, enhancing the interaction between the two. This interfacial modification allows for more efficient stress transfer between OMMT and the polymer matrix, reducing stress concentration at the interface and thus improving the overall mechanical properties of the material, ensuring crack-free bending of the wires and cables. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0025] It should be noted that the linear low-density polyethylene in the present invention, CAS No.: 9002-88-4, MDL No.: MFCD00084423, Product No.: L909897; ethylene-vinyl acetate copolymer, CAS No.: 24937-78-8, MDL No.: MFCD00133996, Product No.: P815474; and ammonium polyphosphate, CAS No.: 68333-79-9, Product No.: A875132, were all purchased from MacLean's reagent.

[0026] In the present invention, the silane coupling agent is silane coupling agent KH550; the antioxidants are antioxidant 1010 and antioxidant 168 in a weight ratio of 1:1.

[0027] Example 1 This embodiment provides a 10kV flame-retardant wire and cable, including a bundled wire core and an outer sheath layer, wherein the outer sheath layer is composed of the following raw materials in parts by weight: 45 parts of linear low-density polyethylene, 35 parts of ethylene-vinyl acetate copolymer, 19 parts of microencapsulated ammonium polyphosphate, 7 parts of organically modified nano-montmorillonite, 5 parts of zinc borate, 1.5 parts of a silane coupling agent, 0.8 parts of an antioxidant, and 0.5 parts of calcium stearate.

[0028] The preparation method of microencapsulated ammonium polyphosphate includes: adding a 35% formaldehyde aqueous solution and deionized water into a reactor, adding triethanolamine while stirring to adjust the pH to 8.8, heating to 72°C, adding melamine, and keeping the temperature to react for 35 minutes; then heating to 82°C, continuing the reaction for 1.5 hours, cooling to 38°C, adding urea to neutralize free formaldehyde, and adjusting the pH to 7.2 to obtain a melamine-formaldehyde prepolymer; the weight ratio of the formaldehyde aqueous solution, deionized water, triethanolamine, and melamine is 95:170:200:2.5; Ammonium polyphosphate was dispersed in ethyl acetate and added to melamine-formaldehyde prepolymer for ultrasonic emulsification. Hydrochloric acid was added dropwise to adjust the pH to 3, and the mixture was reacted at 65°C for 5 hours to form a prepolymer coating layer. The mixture was filtered and dried to obtain microencapsulated ammonium polyphosphate. The weight ratio of ammonium polyphosphate, ethyl acetate, and melamine-formaldehyde prepolymer was 110:20:200. The preparation method of organic modified nano-montmorillonite includes: dispersing sodium montmorillonite in 55℃ hot water and stirring at 1300rpm for 65min, adding hexadecyltrimethylammonium bromide, reacting at 80℃ for 6h, centrifuging and washing until there is no Br - , vacuum dried and ground to D50 = 500nm; the weight ratio of sodium montmorillonite, water and hexadecyltrimethylammonium bromide is 10:200:4; The preparation method of the 10kV flame-retardant wire and cable comprises the following steps: Linear low-density polyethylene and ethylene-vinyl acetate copolymer were dried at 80°C for 4.5 hours, and then microencapsulated ammonium polyphosphate, organically modified nano-montmorillonite, zinc borate, silane coupling agent, antioxidant and calcium stearate were added and stirred at a speed of 800 rpm for 15 minutes; a twin-screw extruder was used for extrusion granulation to obtain 10kV flame-retardant wire and cable material. During extrusion granulation, the temperature of the first zone of the twin-screw extruder was 160°C, the temperature of the second zone was 175°C, the temperature of the third zone was 185°C, the temperature of the fourth zone was 190°C, and the temperature of the die head was 180°C; the screw speed was 300 rpm; the cable material was controlled to have an extrusion temperature of 190°C and melt-extruded to coat the surface of the bundled wire core to form a 1.5 mm outer sheath layer, and after cooling, a 10kV flame-retardant wire and cable was formed.

[0029] Example 2 This embodiment provides a 10kV flame-retardant wire and cable, including a bundled wire core and an outer sheath layer, wherein the outer sheath layer is composed of the following raw materials in parts by weight: 40 parts of linear low-density polyethylene, 40 parts of ethylene-vinyl acetate copolymer, 18 parts of microencapsulated ammonium polyphosphate, 6 parts of organically modified nano-montmorillonite, 4 parts of zinc borate, 1 part of a silane coupling agent, 0.5 parts of an antioxidant, and 0.4 parts of calcium stearate.

[0030] The preparation method of microencapsulated ammonium polyphosphate includes: adding a 30% formaldehyde aqueous solution and deionized water into a reactor, adding triethanolamine while stirring to adjust the pH to 8.5, heating to 70°C, adding melamine, and keeping the temperature to react for 30 minutes; then heating to 80°C, continuing the reaction for 1.5 hours, cooling to 35°C, adding urea to neutralize free formaldehyde, and adjusting the pH to 7.0 to obtain a melamine-formaldehyde prepolymer; the weight ratio of the formaldehyde aqueous solution, deionized water, triethanolamine, and melamine is 90:160:180:2; Ammonium polyphosphate was dispersed in ethyl acetate and added to melamine-formaldehyde prepolymer for ultrasonic emulsification. Hydrochloric acid was added dropwise to adjust the pH to 3, and the mixture was reacted at 60°C for 4 hours to form a prepolymer coating layer. The mixture was filtered and dried to obtain microencapsulated ammonium polyphosphate. The weight ratio of ammonium polyphosphate, ethyl acetate, and melamine-formaldehyde prepolymer was 90:15:180. The preparation method of organic modified nano-montmorillonite includes: dispersing sodium montmorillonite in 50℃ hot water and stirring at 1200rpm for 60min, adding hexadecyltrimethylammonium bromide, reacting at 75℃ for 5h, centrifuging and washing until there is no Br - , vacuum dried and ground to D50 = 500nm; the weight ratio of sodium montmorillonite, water and hexadecyltrimethylammonium bromide is 9:180:3.5; The preparation method of the 10kV flame-retardant wire and cable comprises the following steps: Linear low-density polyethylene and ethylene-vinyl acetate copolymer were dried at 75°C for 4 hours, and then microencapsulated ammonium polyphosphate, organically modified nano-montmorillonite, zinc borate, silane coupling agent, antioxidant and calcium stearate were added and stirred at a speed of 700 rpm for 10 minutes; a twin-screw extruder was used for extrusion granulation to obtain 10kV flame-retardant wire and cable material. During extrusion granulation, the temperature of the first zone of the twin-screw extruder was 155°C, the temperature of the second zone was 170°C, the temperature of the third zone was 180°C, the temperature of the fourth zone was 185°C, and the temperature of the die head was 175°C; the screw speed was 280 rpm; the cable material was controlled to have an extrusion temperature of 190°C and melt-extruded to coat the surface of the bundled wire core to form a 1.5 mm outer sheath layer, which was then cooled to form a 10kV flame-retardant wire and cable.

[0031] Example 3 This embodiment provides a 10kV flame-retardant wire and cable, including a bundled wire core and an outer sheath layer, wherein the outer sheath layer is composed of the following raw materials in parts by weight: 50 parts of linear low-density polyethylene, 30 parts of ethylene-vinyl acetate copolymer, 20 parts of microencapsulated ammonium polyphosphate, 8 parts of organically modified nano-montmorillonite, 6 parts of zinc borate, 2 parts of silane coupling agent, 1 part of antioxidant, and 0.6 part of calcium stearate.

[0032] The preparation method of microencapsulated ammonium polyphosphate includes: adding a 40% formaldehyde aqueous solution and deionized water into a reactor, adding triethanolamine while stirring to adjust the pH to 9.0, heating to 75°C, adding melamine, and keeping the temperature to react for 40 minutes; then heating to 85°C, continuing the reaction for 2 hours, cooling to 40°C, adding urea to neutralize free formaldehyde, and adjusting the pH to 7.5 to obtain a melamine-formaldehyde prepolymer; the weight ratio of the formaldehyde aqueous solution, deionized water, triethanolamine, and melamine is 100:180:220:3; Ammonium polyphosphate was dispersed in ethyl acetate and added to melamine-formaldehyde prepolymer for ultrasonic emulsification. Hydrochloric acid was added dropwise to adjust the pH to 3, and the mixture was reacted at 70°C for 6 hours to form a prepolymer coating layer. The mixture was filtered and dried to obtain microencapsulated ammonium polyphosphate. The weight ratio of ammonium polyphosphate, ethyl acetate, and melamine-formaldehyde prepolymer was 110:25:220. The preparation method of organic modified nano-montmorillonite comprises: dispersing sodium montmorillonite in 60°C hot water and stirring at 1400 rpm for 70 minutes, adding hexadecyltrimethylammonium bromide, reacting at 85°C for 7 hours, and centrifuging and washing until there is no Br - , vacuum dried and ground to D50 = 500nm; the weight ratio of sodium montmorillonite, water and hexadecyltrimethylammonium bromide is 11:220:4.5; The preparation method of the 10kV flame-retardant wire and cable comprises the following steps: Linear low-density polyethylene and ethylene-vinyl acetate copolymer were dried at 85°C for 5 hours, and then microencapsulated ammonium polyphosphate, organically modified nano-montmorillonite, zinc borate, silane coupling agent, antioxidant and calcium stearate were added and stirred at a speed of 900 rpm for 20 minutes; a twin-screw extruder was used for extrusion granulation to obtain a 10kV flame-retardant wire and cable material. During extrusion granulation, the temperature of the first zone of the twin-screw extruder was 165°C, the temperature of the second zone was 180°C, the temperature of the third zone was 190°C, the temperature of the fourth zone was 195°C, and the temperature of the die head was 185°C; the screw speed was 320 rpm; the cable material was controlled to have an extrusion temperature of 190°C and was melt-extruded and coated on the surface of the bundled wire core to form a 1.5 mm outer sheath layer, which was then cooled to form a 10kV flame-retardant wire and cable.

[0033] Comparative Example 1 In this comparative example, microencapsulated ammonium polyphosphate is replaced by ammonium polyphosphate, and the rest is the same as that of comparative example 1, and the preparation steps are the same as that of comparative example 1.

[0034] Comparative Example 2 This comparative example does not contain microencapsulated ammonium polyphosphate, and the rest is the same as that of comparative example 1, and the preparation steps are the same as those of comparative example 1.

[0035] Comparative Example 3 In this comparative example, hexadecyltrimethylammonium bromide is replaced by dioctadecyldimethylammonium chloride, and the rest is the same as in comparative example 1, and the preparation steps are the same as in comparative example 1.

[0036] Comparative Example 4 In this comparative example, the organically modified nano-montmorillonite is replaced by unmodified sodium-montmorillonite, and the rest is the same as in comparative example 1, and the preparation steps are the same as in comparative example 1.

[0037] Comparative Example 5 This comparative example does not contain organically modified nano-montmorillonite, and the rest is the same as that of comparative example 1, and the preparation steps are the same as those of comparative example 1.

[0038] Comparative Example 6 This comparative example does not contain zinc borate, and the rest is the same as that of comparative example 1, and the preparation steps are the same as that of comparative example 1.

[0039] Test Example 1: The following tests were performed on the 10kV flame-retardant wires and cables prepared in Examples 1-3 and Comparative Examples 1-6: Tensile strength and elongation at break: tested in accordance with GB / T2951.21-2008; Bending performance: Take a finished cable section with a length of 1m. The sample surface should be free of defects such as scratches and bubbles. According to the cable outer diameter (D), the bending radius is set to 10D. Fix one end of the cable and bend the other end at a constant speed of 0.1m / s to the set radius. Then return to the initial state. This is considered one cycle. Repeat 100 times. Observe the condition of the cable outer sheath and record it. Limiting oxygen index: tested in accordance with GB / T2406.3-2022; Vertical burning test: refer to UL94 vertical burning test, the sample thickness is 1.6mm, and the flame is applied for 10 seconds; The test results are shown in Table 1 below: Table 1

[0040] Combined with the above, Examples 1-3, through the synergistic effect of microencapsulated ammonium polyphosphate and organically modified nano-montmorillonite, achieved an oxygen index of 33%-36%, a UL94 V-0 rating, and no droplet ignition. Comparative Examples 1-2, lacking APP coating or a flame retardant, showed a significant decrease in flame retardancy. Comparative Example 6, without the addition of zinc borate, maintained a V-0 rating, but the oxygen index dropped to 32%, indicating that zinc borate contributes to the flame retardant synergy but is not essential.

[0041] In addition, Examples 1-3 had a tensile strength of 18.9-21.5 MPa, an elongation at break of 248%-260%, and no cracks after bending, verifying the effectiveness of OMMT reinforcement and KH550 interface modification. Comparative Examples 4-5, where unmodified montmorillonite or the complete removal of OMMT resulted in a 30%-50% decrease in tensile strength and an elongation at break of ≤190%, significantly increasing the risk of sheath cracking. After replacing Comparative Example 3 with dioctadecyl ammonium chloride, the tensile strength increased to 19.8 MPa, but the flame retardant grade dropped to V-1, indicating that long-chain alkyl groups enhance mechanical properties but hinder the diffusion of flame-retardant gases.

[0042] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A 10kV flame-retardant wire and cable, characterized in that: The invention comprises a bundled wire core and an outer sheath layer, wherein the outer sheath layer is composed of the following raw materials in parts by weight: 40-50 parts of linear low-density polyethylene, 30-40 parts of ethylene-vinyl acetate copolymer, 18-20 parts of microencapsulated ammonium polyphosphate, 6-8 parts of organically modified nano-montmorillonite, 4-6 parts of zinc borate, 1-2 parts of a silane coupling agent, 0.5-1 part of an antioxidant, and 0.4-0.6 parts of calcium stearate.

2. A 10kV flame-retardant wire and cable according to claim 1, characterized in that: The preparation method of microencapsulated ammonium polyphosphate comprises: dispersing ammonium polyphosphate in ethyl acetate, adding melamine-formaldehyde prepolymer for ultrasonic emulsification; adding hydrochloric acid to adjust the pH to 3, reacting at 60-70° C. for 4-6 hours to form a prepolymer coating layer, filtering and drying to obtain microencapsulated ammonium polyphosphate.

3. A 10kV flame-retardant wire and cable according to claim 2, characterized in that: The weight ratio of the ammonium polyphosphate, ethyl acetate and melamine-formaldehyde prepolymer is 90-110:15-25:180-220.

4. A 10kV flame-retardant wire and cable according to claim 2, characterized in that: The preparation method of the melamine-formaldehyde prepolymer comprises: adding formaldehyde solution and deionized water into a reaction kettle, adding triethanolamine under stirring to adjust the pH to 8.5-9.0, heating to 70-75° C., adding melamine, and keeping the temperature to react for 30-40 minutes; then heating to 80-85° C., continuing the reaction for 1.5-2 hours, cooling to 35-40° C., adding urea to neutralize free formaldehyde, and adjusting the pH to 7.0-7.5 to obtain the prepolymer.

5. The 10kV flame-retardant wire and cable according to claim 4, characterized in that: The formaldehyde solution is a formaldehyde aqueous solution with a mass concentration of 30-40%, and the weight ratio of the formaldehyde solution, deionized water, triethanolamine and melamine is 90-100:160-180:180-220:2-3.

6. The 10kV flame-retardant wire and cable according to claim 1, characterized in that: The preparation method of the organic modified nano-montmorillonite comprises: dispersing sodium montmorillonite in 50-60°C hot water, stirring at 1200-1400 rpm for 60-70 minutes, adding hexadecyltrimethylammonium bromide, reacting at 75-85°C for 5-7 hours, and centrifuging and washing until there is no Br - , vacuum dried and ground to D50=500nm.

7. The 10kV flame-retardant wire and cable according to claim 6, characterized in that: The weight ratio of the sodium montmorillonite, water and hexadecyltrimethylammonium bromide is 9-11:180-220:3.5-4.

5.

8. The 10kV flame-retardant wire and cable according to claim 1, characterized in that: The silane coupling agent is silane coupling agent KH550; the antioxidants are antioxidant 1010 and antioxidant 168 in a weight ratio of 1:

1.

9. A method for preparing a 10kV flame-retardant wire and cable according to any one of claims 1 to 8, characterized in that the steps include: Linear low-density polyethylene and ethylene-vinyl acetate copolymer are dried at 75-85°C for 4-5 hours, and then microencapsulated ammonium polyphosphate, organically modified nano-montmorillonite, zinc borate, silane coupling agent, antioxidant and calcium stearate are added and stirred at a speed of 700-900 rpm for 10-20 minutes; a 10kV flame-retardant wire and cable material is obtained by extrusion and granulation using a twin-screw extruder, and the material is melt-extruded and coated on the surface of the bundled wire core to form an outer sheath layer of 1.4-1.5 mm, and after cooling, a 10kV flame-retardant wire and cable is formed.

10. The method for preparing a 10kV flame-retardant wire and cable according to claim 1, characterized in that: During the extrusion granulation, the temperature of the first zone of the twin-screw extruder is 155-165° C., the temperature of the second zone is 170-180° C., the temperature of the third zone is 180-190° C., the temperature of the fourth zone is 185-195° C., and the die head temperature is 175-185° C.; the screw speed is 280-320 rpm.

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