Environmentally friendly and highly flame-retardant cable and preparation method thereof

Abstract

The invention relates to the technical field of cable materials and discloses an environmentally friendly and highly flame-retardant cable and a preparation method thereof. The cable comprises a conductive core, an insulating layer and a flame-retardant protective sheath material. The flame-retardant protective sheath material is prepared by mixing, cross-linking and extruding granulation using LLDPE as a base material, supplemented with EVA, a compatibilizer and additives such as nitrogen-phosphorus-silicon modified brucite powder. The nitrogen-phosphorus-silicon modified brucite powder is prepared by chemically bonding triallyl isocyanurate, bis(4-methoxyphenyl)phosphine oxide and the like with hydroxyl groups on the surface of the brucite powder. The combination of the two can enable the cable material to obtain better flame-retardant performance. Simultaneously, siloxane is hydrolyzed to form a Si-O-Si cross-linked structure between the polyethylene matrix, thereby improving interface compatibility and allowing the brucite powder to be evenly "embedded" in the polyethylene system to form a physically cross-linked core, which plays a role in stress absorption and load transmission, and has no secondary pollution to the environment, and is safe and environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of cable materials, in particular to an environmentally friendly and highly flame-retardant cable and a preparation method thereof. Background Art

[0002] As important carriers of power and information transmission, wires and cables are increasingly attracting attention for their safety and environmental performance. With growing environmental awareness, halogen-free flame-retardant materials are becoming the preferred choice for wires and cables across various industries. Polyethylene (PE) is the most commonly used matrix for low-smoke, halogen-free, flame-retardant cables due to its halogen-free molecular structure, low dielectric loss, high insulation performance, and competitive price. According to statistics, electrical fires account for approximately 30% of all fires nationwide, with aging wires accounting for over half of all electrical fires. Conventional cable materials produce large amounts of toxic gases and smoke when burned, posing a serious threat to people's lives, health, and property. Therefore, the development of environmentally friendly, highly flame-retardant cable materials is of great significance.

[0003] The flame retardant properties of common flame retardant cables on the market are mainly improved by adding flame retardants and using flame retardant materials. Commonly used inorganic flame retardants such as magnesium hydroxide and aluminum hydroxide contain more hydroxyl groups on the surface and have greater polarity, while PE is a non-polar molecule, which leads to thermodynamic incompatibility between the two and greatly reduces the mechanical properties of low-smoke halogen-free flame retardant PE composite materials. Due to the incompatibility between PE and flame retardants, it is easy to cause the agglomeration of inorganic particles. At the same time, PE has a high degree of crystallinity, which will lead to the high hardness of cable materials produced by PE-based composite materials, which brings certain difficulties to the actual installation and laying. Patent No. CN118772518A discloses a cable composite material with halogen-free flame retardant functionality and a preparation method thereof. Diatomaceous earth with a surface modified with a nitrogen-phosphorus synergistic reaction-type flame retardant is prepared as an inorganic modifier and added to a high-density polyethylene substrate. The abundant pores exposed by the diatomaceous earth and the synergistic flame retardant of the nitrogen-phosphorus synergistic flame retardant are utilized to enhance the flame retardant properties of the polyethylene cable material. However, the inorganic modifier has poor compatibility with the cable matrix and still has the problem of easy agglomeration. In addition, the flame retardant properties of the diatomaceous earth itself are limited, and the problem of poor flexibility of polyethylene is not improved, which is not conducive to market promotion and application.

[0004] Brucite has attracted considerable attention for its abundant reserves, environmental friendliness, low toxicity, and smoke suppression properties. However, brucite often requires a loading of more than 60% to meet flame retardancy requirements. Such a high loading significantly reduces the material's mechanical and processing properties, making it unsuitable for practical applications. The present invention utilizes the excellent flame retardancy of brucite powder and modifies it with a prepared nitrogen-phosphorus-silicon flame retardant. The siloxane in the flame retardant is similarly compatible with the silane-polyolefin compatibilizer, leveraging the synergistic flame retardancy of brucite powder and nitrogen-phosphorus-silicon. The result is excellent mechanical and flame retardancy, while also increasing the flexibility of the cable material, thus meeting the increasingly stringent application requirements of the wire and cable industry. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art and to provide an environmentally friendly and highly flame-retardant cable and a preparation method thereof, so as to improve the flame retardant properties of the cable material so that it has both excellent mechanical properties and is green, environmentally friendly and pollution-free.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for preparing an environmentally friendly and highly flame-retardant cable is carried out according to the following steps:

[0008] Step (1), adding ultrafine brucite powder and ethanol to a reaction flask, stirring evenly at a speed of 800-1000 r / min, adding a nitrogen-phosphorus-silicon flame retardant modifier, reacting at 60-70° C. for 20-40 minutes, filtering, washing with deionized water, drying and grinding to obtain nitrogen-phosphorus-silicon modified brucite powder.

[0009] Step (2), placing 70-80 parts of LLDPE, 8-15 parts of EVA, 5-10 parts of silane polyolefin compatibilizer, 2-8 parts of nitrogen, phosphorus and silicon modified brucite powder, 0.5-0.8 parts of antioxidant, 2-3 parts of lubricant and 0.2-0.5 parts of ultraviolet absorber in a mixer, stirring at a speed of 1200-1500r / min for 40-60min to form a uniform mixture, then feeding the mixture into an extruder through a feeding hopper, controlling the extrusion temperature to 260-280°C, the screw speed to 300-350r / min, extruding granulation, placing in warm water for cross-linking, pelletizing, and molding to obtain a flame retardant protective cover material, and then extruding and compounding in the order of conductive core, insulation layer, and flame retardant protective cover material from the inside to the outside to obtain an environmentally friendly and highly flame retardant cable.

[0010] Furthermore, in step (1), the ratio of the ultrafine brucite powder to the nitrogen-phosphorus-silicon flame retardant modifier is 100 g:(90-120) g.

[0011] Furthermore, in step (2), the antioxidant is antioxidant 1010, the lubricant is polyethylene wax, and the ultraviolet absorber is UV-329.

[0012] Furthermore, in step (2), the compression molding temperature is 150-170° C., the pressure is 8-12 MPa, and the time is 10-15 min.

[0013] Furthermore, the preparation method of the nitrogen-phosphorus-silicon flame retardant modifier in step (1) is carried out according to the following steps:

[0014] Step S1. Under a nitrogen atmosphere, triallyl isocyanurate and methanol were added to a reaction flask, stirred evenly, and then bis(4-methoxyphenyl)phosphine oxide was added. The mixture was reacted at 45-60° C. for 5-8 hours, concentrated under reduced pressure, and dichloromethane was added and mixed evenly. Boron tribromide was added dropwise in an ice bath, and the mixture was reacted at 0° C. for 12-24 hours. The mixture was extracted with ethyl acetate and deionized water, and purified by column chromatography (dichloromethane / methanol = 20:1 elution) to obtain a polyhydroxyphosphorus nitrogen intermediate.

[0015] Step S2: Under a nitrogen atmosphere, add the polyhydroxyphosphorus nitrogen intermediate and N,N-dimethylformamide to a reaction flask, stir evenly, add triethylamine and 3-isocyanatepropyltrimethoxysilane, stir and react, and after the reaction is completed, concentrate under reduced pressure, wash with n-pentane, and dry to obtain a nitrogen-phosphorus-silicon flame retardant modifier.

[0016] Furthermore, in step S1, the ratio of triallyl isocyanurate, bis(4-methoxyphenyl)phosphine oxide, and boron tribromide is 1 mol: (3.1-3.5) mol: (6.5-8) mol.

[0017] Furthermore, in step S2, the ratio of the polyhydroxyphosphorus nitrogen intermediate, triethylamine, and 3-isocyanatepropyltrimethoxysilane is 1 mol: (5.5-6.2) mol: (7-8.5) mol.

[0018] Furthermore, in step S2, the reaction temperature is 100-120° C., and the reaction time is 8-16 h.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) Brucite powder itself has certain flame retardant properties. The MgO generated by its thermal decomposition has high activity and heat resistance. It can form a dense protective film on the surface of polyethylene and convert toxic combustible gases such as CO into harmless CO2, thereby reducing the generation of toxic smoke. It has excellent smoke suppression effect, so that even after combustion, the material will not cause secondary pollution to the environment, which is safe and environmentally friendly. Nitrogen-phosphorus-silicon flame retardant can decompose to produce non-combustible gases such as N2 and CO2, which can dilute combustible gases and reduce the oxygen concentration in the combustion area, thereby slowing down the combustion rate. At the same time, it can quickly form an expanding carbon layer at high temperature, isolating oxygen and heat, protecting the polyethylene matrix, and preventing the combustion from continuing, thereby greatly enhancing the flame retardant properties of the cable material. Nitrogen-phosphorus-silicon elements synergize with brucite powder, which can play a role in the condensed phase, promoting the carbonization of polymers, and also remove high-energy free radicals in the combustion area. The combination of the two can achieve better flame retardant effect under lower usage conditions.

[0021] (2) The surface-modified brucite powder has a smaller particle size and can be added to polyethylene as a filler to fill the gaps between polyethylene molecular chains, increase the density of the material, and thus improve the mechanical strength of the material; the uniform dispersion of brucite powder in polyethylene can form many tiny stress concentration points, which can disperse stress when subjected to external forces and prevent the material from breaking due to excessive local stress.

[0022] (3) EVA has good flexibility, similar structure to LLDPE, and good compatibility. After blending, it can make up for the lack of toughness of polyethylene; a part of the silicon-oxygen bonds on the surface of the nitrogen-phosphorus-silicon flame retardant modifier can produce chemical bonds with the hydroxyl groups on the surface of the brucite powder, so that the nitrogen-phosphorus-silicon flame retardant modifier exists stably on the surface of the brucite and is not easy to migrate and precipitate; the other part of the silicon-oxygen bonds can be hydrolyzed by the silane polyolefin compatibilizer under warm water conditions, so that a Si-O-Si cross-linked structure is formed between the polyethylene matrix, which improves the interfacial compatibility and makes the brucite powder evenly "embedded" in the polyethylene system to form a physical cross-linked core, which plays a role in stress absorption and load transfer. DETAILED DESCRIPTION

[0023] The present invention is further illustrated below by describing specific implementation methods, but this is not intended to limit the present invention. Those skilled in the art can make various modifications or improvements based on the basic ideas of the present invention, but as long as they do not deviate from the basic ideas of the present invention, they are all within the scope of the present invention.

[0024] Unless otherwise stated, the raw materials and reagents used in this application are commercially available or can be prepared by known methods.

[0025] EVA: Ethylene vinyl acetate copolymer, Taiwan Plastics Corporation.

[0026] LLDPE: linear low-density polyethylene, Sinopec.

[0027] Triallyl isocyanurate, CAS number is 1025-15-6.

[0028] Bis(4-methoxyphenyl)oxide, CAS number is 15754-51-5.

[0029] 3-Isocyanatepropyltrimethoxysilane, CAS number 15396-00-6.

[0030] Preparation of silane polyolefin compatibilizer: EVA:LLDPE raw materials in a mass ratio of 3:7, 3% of dibenzoyl peroxide and 2% of vinyltrimethoxysilane are mixed evenly and poured into a torque rheometer. Melt grafting is carried out at 120°C, the speed is 30r / min, and the reaction time is 15min to obtain material A; after the roller temperature of the double roller is preheated to 120°C, 100g of EVA and 2g of dibutyltin dilaurate are added, mixed evenly, taken out, cooled to room temperature, and crushed to obtain material B; material A and material B are mixed evenly on the double roller in a mass ratio of 95:5 and completely plasticized, and then the roller is lowered and sheet-formed to obtain a silane polyolefin compatibilizer.

[0031] Example 1

[0032] (1) Under nitrogen atmosphere, 65 mmol of triallyl isocyanurate and 260 mL of methanol were added to a reaction flask. After stirring, 208 mmol of bis(4-methoxyphenyl)phosphine oxide was added and the mixture was reacted at 55°C for 6 h. The mixture was concentrated under reduced pressure and mixed evenly. 481 mmol of boron tribromide was added dropwise in an ice bath and the mixture was reacted at 0°C for 16 h. The mixture was extracted with ethyl acetate and deionized water and purified by column chromatography (elution with dichloromethane / methanol = 20:1) to obtain a polyhydroxyphosphorus nitrogen intermediate. The preparation reaction formula is as follows:

[0033]

[0034] (2) Under nitrogen atmosphere, 60 mmol of polyhydroxyphosphorus nitrogen intermediate and 510 mL of N,N-dimethylformamide were added to the reaction flask, stirred evenly, and then 357 mmol of triethylamine and 480 mmol of 3-isocyanate propyltrimethoxysilane were added. The mixture was reacted at 110°C for 12 h, concentrated under reduced pressure, washed with n-pentane, and dried to obtain a nitrogen-phosphorus-silicon flame retardant modifier. The preparation reaction formula is as follows:

[0035]

[0036] (3) Add 10 g of ultrafine brucite powder and 260 mL of ethanol to the reaction flask, stir evenly at a speed of 900 r / min, add 9 g of nitrogen-phosphorus-silicon flame retardant modifier, react at 65 ° C for 30 min, filter, wash with deionized water, dry and grind to obtain nitrogen-phosphorus-silicon modified brucite powder.

[0037] (4) 78g of LLDPE, 8g of EVA, 8g of silane polyolefin compatibilizer, 2g of nitrogen-phosphorus-silicon modified brucite powder, 0.65g of antioxidant 1010, 2.5g of polyethylene wax and 0.3g of UV-329 were placed in a mixer and stirred at a speed of 1400r / min for 50min to form a uniform mixture. The mixture was then fed into an extruder through a feeding hopper, the extrusion temperature was controlled to 270℃, the screw speed was controlled to 320r / min, extruded into pellets, placed in 90℃ warm water for cross-linking for 8h, pelletized and molded at a molding temperature of 160℃, a pressure of 10MPa and a time of 12min to obtain a flame retardant protective sheath material, and then extruded and compounded in the order of copper conductor, polyethylene insulation material and flame retardant protective sheath material from the inside to the outside to obtain an environmentally friendly and highly flame retardant cable.

[0038] Example 2

[0039] (1) Under nitrogen atmosphere, 150 mmol of triallyl isocyanurate and 450 mL of methanol were added to a reaction flask, stirred evenly, and then 465 mmol of bis(4-methoxyphenyl)phosphine oxide was added. The mixture was reacted at 60°C for 5 h, concentrated under reduced pressure, and mixed evenly with dichloromethane. 975 mmol of boron tribromide was added dropwise in an ice bath, and the mixture was reacted at 0°C for 12 h. The mixture was extracted with ethyl acetate and deionized water, and purified by column chromatography (dichloromethane / methanol = 20:1) to obtain a polyhydroxyphosphorus nitrogen intermediate.

[0040] (2) Under nitrogen atmosphere, 130 mmol of polyhydroxyphosphorus nitrogen intermediate and 910 mL of N,N-dimethylformamide were added to the reaction flask, and after stirring evenly, 715 mmol of triethylamine and 910 mmol of 3-isocyanatepropyltrimethoxysilane were added. The mixture was reacted at 120 °C for 8 h, concentrated under reduced pressure, washed with n-pentane, and dried to obtain a nitrogen-phosphorus-silicon flame retardant modifier.

[0041] (3) Add 10 g of ultrafine brucite powder and 200 mL of ethanol to a reaction flask, stir evenly at a speed of 1000 r / min, add 10 g of nitrogen-phosphorus-silicon flame retardant modifier, react at 70 ° C for 20 min, filter, wash with deionized water, dry and grind to obtain nitrogen-phosphorus-silicon modified brucite powder.

[0042] (4) 75g of LLDPE, 10g of EVA, 5g of silane polyolefin compatibilizer, 3.5g of nitrogen-phosphorus-silicon modified brucite powder, 0.8g of antioxidant 1010, 2g of polyethylene wax and 0.5g of UV-329 were placed in a mixer and stirred at a speed of 1500r / min for 40min to form a uniform mixture. The mixture was then fed into an extruder through a feeding hopper, the extrusion temperature was controlled to 280℃, the screw speed was controlled to 350r / min, extruded into pellets, placed in 90℃ warm water for cross-linking for 8h, pelletized and molded at a molding temperature of 170℃, a pressure of 12MPa and a time of 10min to obtain a flame-retardant protective sheath material, and then extruded and compounded in the order of copper conductor, polyethylene insulation material and flame-retardant protective sheath material from the inside out to obtain an environmentally friendly and highly flame-retardant cable.

[0043] Example 3

[0044] (1) Under nitrogen atmosphere, 40 mmol of triallyl isocyanurate and 200 mL of methanol were added to a reaction flask, stirred evenly, and then 140 mmol of bis(4-methoxyphenyl)phosphine oxide was added. The mixture was reacted at 45°C for 8 h, concentrated under reduced pressure, and mixed evenly with dichloromethane. 320 mmol of boron tribromide was added dropwise in an ice bath, and the mixture was reacted at 0°C for 24 h. The mixture was extracted with ethyl acetate and deionized water, and purified by column chromatography (dichloromethane / methanol = 20:1 elution) to obtain a polyhydroxyphosphorus nitrogen intermediate.

[0045] (2) Under nitrogen atmosphere, 35 mmol of polyhydroxyphosphorus nitrogen intermediate and 245 mL of N,N-dimethylformamide were added to the reaction flask, and after stirring evenly, 217 mmol of triethylamine and 297.5 mmol of 3-isocyanatepropyltrimethoxysilane were added. The mixture was reacted at 100 °C for 16 h, concentrated under reduced pressure, washed with n-pentane, and dried to obtain a nitrogen-phosphorus-silicon flame retardant modifier.

[0046] (3) Add 10 g of ultrafine brucite powder and 300 mL of ethanol to the reaction flask, stir evenly at a speed of 800 r / min, add 10.8 g of nitrogen-phosphorus-silicon flame retardant modifier, react at 60 ° C for 40 min, filter, wash with deionized water, dry and grind to obtain nitrogen-phosphorus-silicon modified brucite powder.

[0047] (4) 80g of LLDPE, 12g of EVA, 10g of silane polyolefin compatibilizer, 5g of nitrogen-phosphorus-silicon modified brucite powder, 0.8g of antioxidant 1010, 3g of polyethylene wax and 0.2g of UV-329 were placed in a mixer and stirred at a speed of 1200r / min for 60min to form a uniform mixture. The mixture was then fed into an extruder through a feeding hopper, the extrusion temperature was controlled to 260℃, the screw speed was controlled to 300r / min, extrusion granulation was carried out, and the mixture was placed in 90℃ warm water for cross-linking for 8h. After pelletizing and molding, the molding temperature was 150℃, the pressure was 8MPa, and the time was 15min to obtain a flame retardant protective sheath material, and then extruded and compounded in the order of copper conductor, polyethylene insulation material, and flame retardant protective sheath material from the inside to the outside to obtain an environmentally friendly and highly flame retardant cable.

[0048] Example 4

[0049] (1) Under nitrogen atmosphere, 100 mmol of triallyl isocyanurate and 420 mL of methanol were added to a reaction flask, stirred evenly, and then 325 mmol of bis(4-methoxyphenyl)phosphine oxide was added. The mixture was reacted at 55°C for 7 h, concentrated under reduced pressure, and mixed evenly with dichloromethane. 720 mmol of boron tribromide was added dropwise in an ice bath, and the mixture was reacted at 0°C for 15 h. The mixture was extracted with ethyl acetate and deionized water, and purified by column chromatography (dichloromethane / methanol = 20:1) to obtain a polyhydroxyphosphorus nitrogen intermediate.

[0050] (2) Under nitrogen atmosphere, 80 mmol of polyhydroxyphosphorus nitrogen intermediate and 680 mL of N,N-dimethylformamide were added to the reaction flask, and after stirring evenly, 472 mmol of triethylamine and 615 mmol of 3-isocyanatepropyltrimethoxysilane were added. The mixture was reacted at 115 °C for 10 h, concentrated under reduced pressure, washed with n-pentane, and dried to obtain a nitrogen-phosphorus-silicon flame retardant modifier.

[0051] (3) Add 10 g of ultrafine brucite powder and 265 mL of ethanol to a reaction flask, stir evenly at a speed of 950 r / min, add 11.5 g of nitrogen-phosphorus-silicon flame retardant modifier, react at 70 ° C for 35 min, filter, wash with deionized water, dry and grind to obtain nitrogen-phosphorus-silicon modified brucite powder.

[0052] (4) 72g of LLDPE, 14g of EVA, 7g of silane polyolefin compatibilizer, 6.5g of nitrogen-phosphorus-silicon modified brucite powder, 0.6g of antioxidant 1010, 2.4g of polyethylene wax and 0.4g of UV-329 were placed in a mixer and stirred at a speed of 1450r / min for 45min to form a uniform mixture. The mixture was then fed into an extruder through a feeding hopper, the extrusion temperature was controlled to 275℃, the screw speed was controlled to 330r / min, extrusion granulation was carried out, and the mixture was placed in 90℃ warm water for cross-linking for 8h. After pelletizing and molding, the molding temperature was 165℃, the pressure was 9MPa, and the time was 12min to obtain a flame retardant protective sheath material, and then extruded and compounded in the order of copper conductor, polyethylene insulation material, and flame retardant protective sheath material from the inside to the outside to obtain an environmentally friendly and highly flame retardant cable.

[0053] Example 5

[0054] (1) Under nitrogen atmosphere, 52 mmol of triallyl isocyanurate and 235 mL of methanol were added to a reaction flask. After stirring, 176.8 mmol of bis(4-methoxyphenyl)phosphine oxide was added and the mixture was reacted at 55°C for 6 h. The mixture was concentrated under reduced pressure and mixed with dichloromethane. 390 mmol of boron tribromide was added dropwise in an ice bath and the mixture was reacted at 0°C for 18 h. The mixture was extracted with ethyl acetate and deionized water and purified by column chromatography (elution with dichloromethane / methanol = 20:1) to obtain a polyhydroxyphosphorus nitrogen intermediate.

[0055] (2) Under nitrogen atmosphere, 45 mmol of polyhydroxyphosphorus nitrogen intermediate and 370 mL of N,N-dimethylformamide were added to the reaction flask, and after stirring evenly, 260 mmol of triethylamine and 352 mmol of 3-isocyanatepropyltrimethoxysilane were added. The mixture was reacted at 105 °C for 16 h, concentrated under reduced pressure, washed with n-pentane, and dried to obtain a nitrogen-phosphorus-silicon flame retardant modifier.

[0056] (3) Add 10 g of ultrafine brucite powder and 300 mL of ethanol to a reaction flask, stir evenly at a speed of 850 r / min, add 12 g of nitrogen-phosphorus-silicon flame retardant modifier, react at 65 ° C for 40 min, filter, wash with deionized water, dry and grind to obtain nitrogen-phosphorus-silicon modified brucite powder.

[0057] (4) 75g of LLDPE, 15g of EVA, 9g of silane polyolefin compatibilizer, 8g of nitrogen-phosphorus-silicon modified brucite powder, 0.65g of antioxidant 1010, 3g of polyethylene wax and 0.3g of UV-329 were placed in a mixer and stirred at a speed of 1350r / min for 55min to form a uniform mixture. The mixture was then fed into an extruder through a feeding hopper, the extrusion temperature was controlled to 275℃, the screw speed was controlled to 330r / min, extruded into pellets, placed in 90℃ warm water for crosslinking for 8h, pelletized and molded at a molding temperature of 160℃, a pressure of 10MPa and a time of 15min to obtain a flame retardant protective sheath material, and then extruded and compounded in the order of copper conductor, polyethylene insulation material and flame retardant protective sheath material from the inside to the outside to obtain an environmentally friendly and highly flame retardant cable.

[0058] Comparative Example 1

[0059] 78g of LLDPE, 8g of EVA, 8g of silane polyolefin compatibilizer, 2g of nitrogen-phosphorus-silicon flame retardant modifier (prepared by Example 1), 0.65g of antioxidant 1010, 2.5g of polyethylene wax and 0.3g of UV-329 were placed in a mixer and stirred at a speed of 1400r / min for 50min to form a uniform mixture. The mixture was then fed into an extruder through a feeding hopper, the extrusion temperature was controlled to 270°C, the screw speed was controlled to 320r / min, extrusion granulation was carried out, and the mixture was placed in 90°C warm water for cross-linking for 8h. The mixture was pelletized and molded at a molding temperature of 160°C, a pressure of 10MPa and a time of 12min to obtain a protective sheath material, which was then extruded and compounded in the order of copper conductor, polyethylene insulation material and protective sheath material from the inside to the outside to obtain a cable material.

[0060] Comparative Example 2

[0061] 78g of LLDPE, 8g of EVA, 8g of silane polyolefin compatibilizer, 2g of ultrafine brucite powder, 0.65g of antioxidant 1010, 2.5g of polyethylene wax and 0.3g of UV-329 were placed in a mixer and stirred at a speed of 1400r / min for 50min to form a uniform mixture. The mixture was then fed into an extruder through a feeding hopper, the extrusion temperature was controlled to be 270°C, the screw speed was controlled to be 320r / min, extrusion granulation was carried out, and the mixture was placed in 90°C warm water for cross-linking for 8h. The mixture was pelletized and compression molded at a compression molding temperature of 160°C, a pressure of 10MPa and a time of 12min to obtain a protective sheath material. The copper conductor, polyethylene insulation material and protective sheath material were then extruded and compounded in the order of the inside to the outside to obtain a cable material.

[0062] Comparative Example 3

[0063] 78g of LLDPE, 8g of EVA, 8g of silane polyolefin compatibilizer, 0.65g of antioxidant 1010, 2.5g of polyethylene wax and 0.3g of UV-329 were placed in a mixer and stirred at a speed of 1400r / min for 50min to form a uniform mixture. The mixture was then fed into an extruder through a feeding hopper, the extrusion temperature was controlled at 270°C, the screw speed was controlled at 320r / min, extrusion granulation was carried out, and the mixture was placed in 90°C warm water for cross-linking for 8h. The mixture was pelletized and molded at a molding temperature of 160°C, a pressure of 10MPa and a time of 12min to obtain a protective sheath material. The copper conductor, polyethylene insulation material and protective sheath material were then extruded and compounded in this order from the inside out to obtain a cable material.

[0064] Tensile strength: According to GB / T1040 standard, a microcomputer-controlled electronic universal testing machine was used to stretch the specimen with a size of 150mm×150mm×2mm and a tensile speed of 200mm / min. The test was repeated 5 times and the average value was taken.

[0065] Notched impact strength: According to GB / T1043 standard, the spline size is 100mm×10mm×4mm, the notch depth is 2mm, the notch shape is V-shaped, the pendulum speed is 2.9m / s, and the test is repeated 5 times to obtain the average value.

[0066] Table 1 Mechanical properties test

[0067]

[0068] From the test results in the table above, it can be seen that with the increase of the content of nitrogen, phosphorus and silicon modified brucite powder, the mechanical properties of the cable material are significantly improved. The tensile strength in Example 4 reaches 45.8 MPa and the impact strength is 21.2 kJ / m 2This is because, on the one hand, the particle size of the surface-modified brucite powder is small and can be added to polyethylene as a filler to fill the gaps between polyethylene molecular chains and increase the density of the material. The uniform dispersion of brucite powder in polyethylene can form many tiny stress concentration points. These stress concentration points can disperse stress when subjected to external forces, preventing the material from breaking due to excessive local stress, thereby improving the mechanical strength of the material. On the other hand, part of the silicon-oxygen bonds on the surface of the nitrogen-phosphorus-silicon flame retardant modifier can chemically bond with the hydroxyl groups on the surface of the brucite powder, making the nitrogen-phosphorus-silicon flame retardant modifier stably present on the surface of the brucite. , not easy to migrate and precipitate; the other part of the silicon-oxygen bond can be hydrolyzed by the silane polyolefin compatibilizer under warm water conditions, so that a Si-O-Si cross-linked structure is formed between the polyethylene matrix, which improves the interface compatibility and makes the brucite powder evenly "embedded" in the polyethylene system to form a physical cross-linked core, which plays a role in stress absorption and load transfer; at the same time, EVA has good flexibility, is similar to LLDPE in structure, and has good compatibility. After blending, it can make up for the performance deficiencies and improve the interaction between the interfaces. When the material is subjected to force, the stress at the interface is more evenly transferred, which increases the elongation at break of the material.

[0069] Limiting oxygen index test: Tested in accordance with GB / T2406.1-2008.

[0070] Vertical burning grade test: Tested in accordance with GB / T2408-1996.

[0071] Table 2 Flame retardant performance test

[0072]

[0073] Brucite powder itself possesses certain flame retardant properties. The MgO produced by its thermal decomposition is highly active and heat-resistant, forming a dense protective film on the polyethylene surface. It also converts toxic combustible gases like CO into harmless CO2, thereby reducing the generation of toxic fumes. This excellent smoke suppression property ensures that even after combustion, the material poses no secondary environmental pollution, making it safe and environmentally friendly. Nitrogen-phosphorus-silicon flame retardants decompose to produce non-combustible gases such as N2 and CO2, which dilute combustible gases and reduce oxygen concentration in the combustion zone, thereby slowing combustion. At high temperatures, they rapidly form an expanding char layer, isolating oxygen and heat, protecting the polyethylene matrix and preventing continued combustion, significantly enhancing the flame retardancy of the cable material. Nitrogen-phosphorus-silicon elements synergize with brucite powder, acting in the condensed phase to promote polymer charring while also removing high-energy free radicals in the combustion zone. The combination of these two elements can achieve better flame retardancy at lower usage levels.

[0074] Comparative Example 1 uses a single nitrogen-phosphorus-silicon synergistic flame retardant. Since the load transfer effect of brucite powder cannot be utilized, the mechanical properties and flame retardant properties are reduced to varying degrees. At the same time, the small molecule flame retardant has problems such as migration and precipitation, resulting in poor overall flame retardant properties of the material. The brucite powder in Comparative Example 2 has not been surface-modified, has poor compatibility with the polyethylene matrix, and has interface problems, which prevents the advantages of brucite powder from being effectively utilized, resulting in a slight decrease in mechanical properties. Comparative Example 3 does not contain nitrogen-phosphorus-silicon flame retardant and brucite powder, and has the worst mechanical and flame retardant properties.

[0075] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing an environmentally friendly and highly flame-retardant cable, characterized in that: The preparation method is carried out according to the following steps: Step (1), adding ultrafine brucite powder and ethanol to a reaction flask, stirring at a speed of 800-1000 r / min, adding nitrogen, phosphorus and silicon flame retardant modifier, reacting at 60-70° C. for 20-40 minutes, filtering, washing with deionized water, drying and grinding to obtain nitrogen, phosphorus and silicon modified brucite powder; Step (2), placing 70-80 parts by weight of LLDPE, 8-15 parts of EVA, 5-10 parts of silane polyolefin compatibilizer, 2-8 parts of nitrogen-phosphorus-silicon modified brucite powder, 0.5-0.8 parts of antioxidant, 2-3 parts of lubricant and 0.2-0.5 parts of ultraviolet absorber in a mixer, stirring at a speed of 1200-1500 r / min for 40-60 minutes to form a uniform mixture, then feeding the mixture into an extruder through a feeding hopper, controlling the extrusion temperature to 260-280°C and the screw speed to 300-350 r / min, extruding and granulating, placing in warm water for cross-linking, pelletizing, and molding to obtain a flame-retardant protective sheath material, and then extruding and compounding in the order of conductive core, insulation layer, and flame-retardant protective sheath material from the inside out to obtain an environmentally friendly and highly flame-retardant cable; The preparation method of the nitrogen-phosphorus-silicon flame retardant modifier in step (1) is carried out according to the following steps: Step S1: Under a nitrogen atmosphere, triallyl isocyanurate and methanol are added to a reaction flask, stirred evenly, and then bis(4-methoxyphenyl)phosphine oxide is added. The mixture is reacted at 45-60° C. for 5-8 hours, concentrated under reduced pressure, and mixed evenly with dichloromethane. Boron tribromide is added dropwise in an ice bath, and the mixture is reacted at 0° C. for 12-24 hours. The mixture is extracted with ethyl acetate and deionized water, and purified by column chromatography to obtain a polyhydroxyphosphorus nitrogen intermediate. Step S2: under a nitrogen atmosphere, adding a polyhydroxyphosphorus nitrogen intermediate and N,N-dimethylformamide to a reaction flask, stirring evenly, adding triethylamine and 3-isocyanatepropyltrimethoxysilane, stirring to react, and after the reaction is completed, concentrating under reduced pressure, washing with n-pentane, and drying to obtain a nitrogen-phosphorus-silicon flame retardant modifier; In step S1, the ratio of triallyl isocyanurate, bis(4-methoxyphenyl)phosphine oxide, and boron tribromide is 1 mol: (3.1-3.5) mol: (6.5-8) mol; In the step S2, the ratio of the polyhydroxyphosphorus nitrogen intermediate, triethylamine, and 3-isocyanatepropyltrimethoxysilane is 1 mol: (5.5-6.2) mol: (7-8.5) mol.

2. The method for preparing an environmentally friendly and highly flame-retardant cable according to claim 1, characterized in that: In the step (1), the ratio of the ultrafine brucite powder to the nitrogen-phosphorus-silicon flame retardant modifier is 100 g: (90-120) g.

3. The method for preparing an environmentally friendly and highly flame-retardant cable according to claim 1, characterized in that: In step (2), the antioxidant is antioxidant 1010, the lubricant is polyethylene wax, the ultraviolet absorber is UV-329, the conductive wire core is a copper conductor, and the insulating layer is a polyethylene insulating material.

4. The method for preparing an environmentally friendly and highly flame-retardant cable according to claim 1, characterized in that: In step (2), the compression molding temperature is 150-170° C., the pressure is 8-12 MPa, and the time is 10-15 min.

5. The method for preparing an environmentally friendly and highly flame-retardant cable according to claim 1, characterized in that: In step S2, the reaction temperature is 100-120° C., and the reaction time is 8-16 hours.

6. An environmentally friendly and highly flame-retardant cable, characterized in that: The method is obtained by the preparation method according to any one of claims 1 to 5.

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