A halogen-free flame-retardant cable with enhanced performance and its preparation method

Abstract

The present invention relates to the field of cables, and discloses a reinforced halogen-free flame-retardant cable and a preparation method thereof. The reinforced halogen-free flame-retardant cable comprises a conductor core, an insulating layer, a shielding layer, and a sheath layer which are arranged in sequence from inside to outside. The sheath layer material comprises low-density polyethylene, ethylene-vinyl acetate copolymer, modified graphene oxide, modified mesoporous silica, a lubricant, a plasticizer, and a light stabilizer. The modified graphene oxide is prepared by grafting a hexachlorocyclotriphosphazene derivative and graphene oxide. The hexachlorocyclotriphosphazene derivative uses 2-allylphenol, sodium hydroxide, hexachlorocyclotriphosphazene, 4,4'-diaminodiphenylmethane, and DOPO as raw materials. The modified mesoporous silica is prepared by loading iron oxide on mesoporous silica and grafting an antioxidant with 3-mercaptopropylmethyldimethoxysilane. The present invention adds modified graphene oxide and modified mesoporous silica, endowing the cable with excellent mechanical properties, flame-retardant properties, and aging resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of cables, and particularly relates to a reinforced halogen-free flame-retardant cable and a preparation method thereof. Background Art

[0002] With the rapid development of the economic society, the application and demand of the cable industry in various fields are increasing continuously. Cable materials are an important part of cables. Cable materials containing halogen flame retardants will generate a large amount of thick smoke and harmful gases when burning, thereby increasing the risk of fire rescue. Therefore, halogen-free, low-smoke and flame-retardant cables have become an important direction for material preparation. As the first layer of barrier of the cable, the material for making the sheath layer should have good heat resistance and flame-retardant properties to play a protective role.

[0003] Traditional cable sheath layers are made of polyolefins. Although they have high dielectric strength, their flame retardancy, aging resistance, etc. are poor. In order to improve the flame retardant performance of cable materials in the prior art, a large amount of inorganic flame retardants are often added. Currently, the commonly used small molecule structure flame retardants mainly include: halogen-containing flame retardants, phosphorus-based flame retardants, silicon-based flame retardants, nitrogen-based flame retardants, and composite flame retardants, etc. Since the small molecule flame retardants have poor compatibility with the materials, they will reduce the mechanical properties of the materials, and will also make the viscosity, compatibility, and flexibility of the polymer materials poor. In addition, in the prior art, non-reactive cyclotriphosphazene derivatives are introduced into the sheath layer material by physical blending, there is a problem of migration and exudation, and the stability of the properties of the obtained products is generally poor; and in the actual application process, the cable materials have to withstand the action of thermal aging, and their mechanical properties are faced with a serious aging threat. The conventional method is to add anti-aging agents, but the anti-aging agents are easy to migrate in the base material, resulting in a decrease in the aging resistance of the base material, and other properties such as corrosion resistance and mechanical strength will be affected by the aging effect and decrease, affecting the service life of the cable. Summary of the Invention

[0004] In order to solve the deficiencies mentioned in the above background art, the purpose of the present invention is to provide a reinforced halogen-free flame-retardant cable and a preparation method thereof, which endow the cable with excellent mechanical properties, flame retardant properties and aging resistance through the addition of modified graphene oxide and modified mesoporous silica.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A reinforced halogen-free flame-retardant cable includes a conductor core, an insulating layer, a shielding layer, and a sheath layer arranged in sequence from inside to outside. The sheath layer is prepared by extruding the sheath layer material around the shielding layer through an extrusion device. The sheath layer material includes the following components in parts by weight: 60-70 parts of low-density polyethylene, 20-35 parts of ethylene-vinyl acetate copolymer, 5-10 parts of modified graphene oxide, 2-5 parts of modified mesoporous silica, 1-3 parts of lubricant, 1-2 parts of plasticizer, and 0.1-0.5 parts of light stabilizer;

[0007] The modified graphene oxide is prepared by grafting a hexachlorocyclotriphosphazene derivative onto graphene oxide through a chemical reaction, wherein the hexachlorocyclotriphosphazene derivative is prepared using 2-allylphenol, sodium hydroxide, hexachlorocyclotriphosphazene, 4,4'-diaminodiphenylmethane, and DOPO as raw materials; the modified mesoporous silica is prepared by loading iron oxide particles using mesoporous silica as a carrier and further grafting antioxidant N-(4-anilinophenyl) maleimide using 3-mercaptopropylmethyldimethoxysilane.

[0008] Preferably, the preparation method of the sheath layer material comprises the following steps: mixing low-density polyethylene, ethylene-vinyl acetate copolymer, modified graphene oxide, modified mesoporous silica, lubricant, plasticizer, and light stabilizer in parts by weight evenly to obtain a mixture, and extruding and molding the mixture in a twin-screw extruder to prepare the sheath layer material.

[0009] Preferably, the preparation method of the modified graphene oxide comprises the following steps:

[0010] (1) Take 2-allylphenol and sodium hydroxide in a reactor, react for 25-40 min under nitrogen protection, then raise the temperature to 60-75 °C and react for 0.5-1 h, and then add hexachlorocyclotriphosphazene and continue to react for 18-24 h. After the reaction is completed, rotary evaporation and drying are carried out to prepare a flame retardant intermediate;

[0011] (2) Take the flame retardant intermediate in a reactor, dissolve it in acetonitrile, raise the temperature to 40-55 °C, add 4,4'-diaminodiphenylmethane and triethylamine, and reflux and react for 6-8 h to prepare component A. Take DOPO dissolved in acetonitrile and add it to component A, place it at 75-90 °C and react for 5-7 h. After the reaction is completed, filtration, washing, and drying are carried out to prepare the hexachlorocyclotriphosphazene derivative;

[0012] (3) Take graphene oxide and ultrasonically disperse it in ethanol to obtain a graphene oxide dispersion. Take deionized water, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and N-hydroxysuccinimide, mix them evenly and add them to the graphene oxide dispersion, then add the hexachlorocyclotriphosphazene derivative, place it at 40-55 °C and stir and react for 4-7 h. After the reaction is completed, centrifugation, washing, and drying are carried out to prepare the modified graphene oxide.

[0013] Preferably, in step (1), the molar ratio of 2-allylphenol, sodium hydroxide, and hexachlorocyclotriphosphazene is 1-1.04:1-1.05:0.27-0.33; in step (2), the molar ratio of the flame retardant intermediate, 4,4'-diaminodiphenylmethane, and DOPO is 1:3-3.3:3-3.5.

[0014] Preferably, the method for preparing the modified mesoporous silica comprises the following steps:

[0015] A. Take cetyltrimethylammonium bromide and sodium hydroxide in a reactor, add deionized water, dissolve by ultrasonic oscillation, place it at 75 - 85 °C and stir and mix for 10 - 20 min, then add tetraethyl orthosilicate and continue stirring and reacting for 2 - 3 h. After the reaction is completed, centrifuge, wash, and dry. Ultrasonically disperse the obtained solid product in a mixed solution of methanol and hydrochloric acid, place it under the condition of cooling reflux at 50 - 65 °C, and vigorously stir for 42 - 48 h to remove the surfactant. After centrifugation, washing, and drying, mesoporous silica is prepared;

[0016] B. Dissolve ferric chloride nonahydrate in ethanol to obtain a mixed solution. Add mesoporous silica and ultrasonically disperse it evenly. Place it at 85 - 95 °C and stir until dry, then place it at 150 - 200 °C and calcine for 1.5 - 2 h. Add the obtained product again into the mixed solution of ferric chloride nonahydrate and ethanol, place it at 85 - 95 °C and stir until dry, then place it at 350 - 400 °C and calcine for 3 - 4 h to prepare functionalized mesoporous silica;

[0017] C. Dissolve N-(4-aminophenyl) maleimide and 3-mercaptopropylmethyldimethoxysilane in acetone. Under nitrogen protection, heat it up to 40 - 50 °C, add triethylamine and stir and react for 4 - 5 h to obtain Component 1. Ultrasonically disperse functionalized mesoporous silica in a mixed solution of ethanol and deionized water, add ammonia water to adjust the pH value of the mixed solution to 9 - 10, heat it up to 55 - 65 °C, add Component 1 and stir and react for 4 - 6 h. After the reaction is completed, centrifuge, wash, and dry to prepare modified mesoporous silica.

[0018] Preferably, the molar ratio of cetyltrimethylammonium bromide, sodium hydroxide, and tetraethyl orthosilicate in step A is 1 - 1.2: 2.2 - 2.8: 8.1 - 9.6.

[0019] Preferably, the mass ratio of N-(4-aminophenyl) maleimide, 3-mercaptopropylmethyldimethoxysilane, and functionalized mesoporous silica in step C is 0.4 - 1: 0.3 - 0.9: 5 - 10 g.

[0020] Preferably, the lubricant is polyethylene wax or oxidized polyethylene wax; the plasticizer is one or a combination of dioctyl adipate, dimethyl phthalate, dioctyl phthalate, and diisodecyl phthalate; the light stabilizer is one or a combination of light stabilizer 770, light stabilizer 944, and light stabilizer 2020.

[0021] Preferably, the insulating layer uses cross-linked polyethylene or polyethylene as the insulating material; the shielding layer includes a first shielding layer and a second shielding layer. The first shielding layer is made by winding aluminum foil, and the second shielding layer is made by braiding silver-plated copper wires.

[0022] The preparation method of the enhanced halogen-free flame-retardant cable as described above includes the following steps:

[0023] S1. Use a wire drawing machine to stretch the copper rod to obtain copper wires, and then perform annealing treatment to obtain a conductor.

[0024] S2. Strands of no less than two of the conductors are twisted together to obtain a conductor core.

[0025] S3. Use an extruder to extrude and coat an insulating layer on the outer surface of the conductor core.

[0026] S4. Take aluminum foil and wind it around the outer surface of the insulating layer to obtain the first shielding layer, and take silver-plated copper wires and cross-braid them on the outer surface of the first shielding layer to obtain the second shielding layer.

[0027] S5. Extrude and coat a sheath layer on the outer surface of the second shielding layer to prepare the enhanced halogen-free flame-retardant cable.

[0028] Advantages of the present invention:

[0029] The present invention uses 2-allylphenol and sodium hydroxide as raw materials to replace three chlorine atoms in the structure of hexachlorocyclotriphosphazene, and prepares a flame-retardant intermediate with a double bond group introduced into its structure. Then, the flame-retardant intermediate and 4,4'-diaminodiphenylmethane are reacted, so that the remaining three chlorine atoms in the structure of the flame-retardant intermediate undergo a substitution reaction with one end amino group in the structure of 4,4'-diaminodiphenylmethane, thereby introducing an amino group into the structure of the flame-retardant intermediate. Thus, component A with a double bond group and an amino group introduced into its structure is prepared. Then, component A is further grafted with DOPO, so that the double bond group in the structure of component A undergoes an addition reaction with the P-H bond in the structure of DOPO, and a hexachlorocyclotriphosphazene derivative rich in phosphorus and nitrogen elements is prepared, forming a nitrogen-phosphorus synergistic flame-retardant effect, achieving excellent flame-retardant performance and heat resistance. Finally, the obtained hexachlorocyclotriphosphazene derivative and graphene oxide undergo an amidation reaction to prepare modified graphene oxide. Among them, graphene oxide has excellent mechanical properties. Introducing the hexachlorocyclotriphosphazene derivative into the layered structure of graphene oxide endows the material with excellent flame-retardant properties. At the same time, the two are combined through strong chemical bonds, avoiding the problem of migration and exudation of the hexachlorocyclotriphosphazene derivative, ensuring that the material achieves a long-term flame-retardant effect. In addition, the grafting reaction increases the interlayer spacing of graphene oxide, which is beneficial to the dispersion of graphene oxide, and to a certain extent avoids the performance defects caused by the aggregation of graphene oxide.

[0030] The present invention prepares mesoporous silica by using the soft template method, and uses the mesoporous silica as a carrier to load iron oxide to prepare functionalized mesoporous silica. The mesoporous structure of the mesoporous silica can absorb and catalytically carbonize the combustible gas generated by the material. Moreover, it is loaded with iron oxide particles, which have more active sites, stronger catalytic carbonization ability during material combustion, and stronger absorption ability for the combustible gas generated by material combustion. Adding it as a synergist to the matrix can further improve the flame retardancy and mechanical properties of the cable material. At the same time, the present invention grafts the antioxidant N-(4-aminophenyl) maleimide on the surface of the functionalized mesoporous silica by using 3-mercaptopropylmethyldimethoxysilane to prepare modified mesoporous silica, forming a firm bond between N-(4-aminophenyl) maleimide and the functionalized mesoporous silica through chemical bonds, endowing the cable material with excellent aging resistance, and at the same time avoiding the problems of easy volatilization, migration and extraction of the antioxidant during processing or long-term use. Detailed implementation mode

[0031] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the protection scope of the present invention.

[0032] Example 1 A preparation method of modified graphene oxide includes the following steps:

[0033] (1) Take 13.9 g of 2-allylphenol and 4.15 g of sodium hydroxide in a reactor, react for 30 min under nitrogen protection, then heat up to 70 °C and react for 1 h, and then add 10 g of hexachlorocyclotriphosphazene and continue to react for 24 h. After the reaction is completed, rotary evaporation and drying are carried out to prepare a flame retardant intermediate.

[0034] (2) Take 6.41 g of the flame retardant intermediate in a reactor, add 200 mL of acetonitrile to dissolve it, heat up to 50 °C, add 5.97 g of 4,4'-diaminodiphenylmethane and 3 g of triethylamine, and reflux and react for 8 h to prepare component A. Take 6.52 g of DOPO dissolved in 40 mL of acetonitrile and add it to component A, place it at 85 °C and react for 7 h. After the reaction is completed, filtration, washing and drying are carried out to prepare a hexachlorocyclotriphosphazene derivative.

[0035] (3) Take 5 g of graphene oxide and ultrasonically disperse it in 120 mL of ethanol to obtain a graphene oxide dispersion. Take 30 mL of deionized water, 0.02 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and 0.03 g of N-hydroxysuccinimide, mix them evenly, and add them to the graphene oxide dispersion. Then add 0.8 g of hexachlorocyclotriphosphazene derivative, place it at 40 - 55 °C and stir for reaction for 4 - 7 h. After the reaction is completed, centrifuge, wash, and dry to prepare modified graphene oxide.

[0036] Example 2 A method for preparing modified mesoporous silica includes the following steps:

[0037] A. Take 1 g of cetyltrimethylammonium bromide and 0.28 g of sodium hydroxide in a reactor, add 450 mL of deionized water, ultrasonically dissolve it, place it at 80 °C and stir and mix for 15 min. Then add 5.92 g of tetraethyl orthosilicate and continue to stir and react for 2 h. After the reaction is completed, centrifuge, wash, and dry. Ultrasonically disperse the obtained solid product in a mixed solution of methanol and hydrochloric acid, place it under the condition of cooling reflux at 60 °C, and vigorously stir for 48 h to remove the surfactant. After centrifugation, washing, and drying, prepare mesoporous silica.

[0038] B. Take 6 mmol of ferric chloride nonahydrate and dissolve it in 100 mL of ethanol to obtain a mixed solution. Add 4.3 g of mesoporous silica and ultrasonically disperse it evenly. Place it at 95 °C and stir until dry, then calcine it at 195 °C for 2 h. Add the obtained product again to a mixed solution of 6 mmol of ferric chloride nonahydrate and 100 mL of ethanol, place it at 95 °C and stir until dry, then calcine it at 400 °C for 3.5 h to prepare functionalized mesoporous silica.

[0039] C. Take 0.86 g of N-(4-aminophenyl)maleimide and 0.64 g of 3-mercaptopropylmethyldimethoxysilane and dissolve them in 50 mL of acetone. Under nitrogen protection, heat it to 45 °C, add 0.4 g of triethylamine and stir and react for 5 h to obtain Component 1. Take 5 g of functionalized mesoporous silica and ultrasonically disperse it in a mixed solution of 90 mL of ethanol and 20 mL of deionized water. Add ammonia water to adjust the pH value of the mixed solution to 10, heat it to 60 °C, add Component 1 and stir and react for 5 h. After the reaction is completed, centrifuge, wash, and dry to prepare modified mesoporous silica.

[0040] Example 3 A sheath layer material includes the following components in parts by weight:

[0041] 60 parts of low-density polyethylene, 21 parts of ethylene-vinyl acetate copolymer, 5 parts of the modified graphene oxide prepared in Example 1, 2 parts of the modified mesoporous silica prepared in Example 2, 1 part of lubricant polyethylene wax, 1 part of plasticizer dioctyl adipate, 0.2 part of light stabilizer 2020;

[0042] The preparation method of the above-mentioned sheath layer material comprises the following steps: uniformly mixing low-density polyethylene, ethylene-vinyl acetate copolymer, modified graphene oxide, modified mesoporous silica, lubricant, plasticizer and light stabilizer in parts by weight to obtain a mixture, and putting the mixture into a twin-screw extruder for extrusion molding to prepare the sheath layer material.

[0043] A reinforced halogen-free flame-retardant cable includes a conductor core, an insulating layer, a shielding layer, and a sheath layer arranged in sequence from inside to outside. Its preparation method comprises the following steps:

[0044] S1. Using a wire drawing machine to stretch a copper rod to obtain copper wire, and then performing annealing treatment to obtain a conductor;

[0045] S2. Stranding no less than two of the said conductors with each other to obtain a conductor core;

[0046] S3. Using an extruder to extrude and coat an insulating layer on the outer surface of the conductor core;

[0047] S4. Taking aluminum foil to wrap around the outer surface of the insulating layer to obtain a first shielding layer, and taking silver-plated copper wire to cross-weave on the outer surface of the first shielding layer to obtain a second shielding layer;

[0048] S5. Extruding and coating a sheath layer on the outer surface of the second shielding layer to prepare the reinforced halogen-free flame-retardant cable.

[0049] Example 4 A sheath layer material comprises the following components in parts by weight:

[0050] 65 parts of low-density polyethylene, 27 parts of ethylene-vinyl acetate copolymer, 7 parts of modified graphene oxide prepared in Example 1, 4 parts of modified mesoporous silica prepared in Example 2, 2 parts of lubricant oxidized polyethylene wax, 2 parts of plasticizer dimethyl phthalate, 0.3 part of light stabilizer 944;

[0051] The preparation method of the above-mentioned sheath layer material and the preparation method of the reinforced halogen-free flame-retardant cable are the same as those in Example 3.

[0052] Example 5 A sheath layer material comprises the following components in parts by weight:

[0053] 70 parts of low-density polyethylene, 34 parts of ethylene-vinyl acetate copolymer, 10 parts of modified graphene oxide prepared in Example 1, 5 parts of modified mesoporous silica prepared in Example 2, 3 parts of lubricant polyethylene wax, 2 parts of plasticizer dioctyl phthalate, 0.5 part of light stabilizer 770;

[0054] The preparation method of the above-mentioned sheath layer material and the preparation method of the reinforced halogen-free flame-retardant cable are the same as those in Example 3.

[0055] Comparative Example 1 A method for preparing modified mesoporous silica includes the following steps:

[0056] A. Take 1 g of cetyltrimethylammonium bromide and 0.28 g of sodium hydroxide in a reactor, add 450 mL of deionized water, dissolve by ultrasonic oscillation, place at 80 °C and stir and mix for 15 min, then add 5.92 g of tetraethyl orthosilicate and continue to stir and react for 2 h. After the reaction is completed, centrifuge, wash, and dry. Ultrasonically disperse the obtained solid product in a mixed solution of methanol and hydrochloric acid, place under the condition of cooling reflux at 60 °C, and vigorously stir for 48 h to remove the surfactant. After centrifugation, washing, and drying, mesoporous silica is prepared;

[0057] B. Take 0.86 g of N-(4-aminophenyl) maleimide and 0.64 g of 3-mercaptopropylmethyldimethoxysilane and dissolve them in 50 mL of acetone. Under nitrogen protection, heat to 45 °C, add 0.4 g of triethylamine and stir and react for 5 h to obtain Component 1. Take 5 g of mesoporous silica and ultrasonically disperse it in a mixed solution of 90 mL of ethanol and 20 mL of deionized water, add ammonia water to adjust the pH value of the mixed solution to 10, heat to 60 °C, add Component 1 and stir and react for 5 h. After the reaction is completed, centrifuge, wash, and dry to prepare modified mesoporous silica.

[0058] Comparative Example 2 A method for preparing modified mesoporous silica includes the following steps:

[0059] A. Take 1 g of cetyltrimethylammonium bromide and 0.28 g of sodium hydroxide in a reactor, add 450 mL of deionized water, dissolve by ultrasonic oscillation, place at 80 °C and stir and mix for 15 min, then add 5.92 g of tetraethyl orthosilicate and continue to stir and react for 2 h. After the reaction is completed, centrifuge, wash, and dry. Ultrasonically disperse the obtained solid product in a mixed solution of methanol and hydrochloric acid, place under the condition of cooling reflux at 60 °C, and vigorously stir for 48 h to remove the surfactant. After centrifugation, washing, and drying, mesoporous silica is prepared;

[0060] B. Take 6 mmol of ferric chloride nonahydrate and dissolve it in 100 mL of ethanol to obtain a mixed solution. Add 4.3 g of mesoporous silica and ultrasonically disperse it evenly. Place at 95 °C and stir until dry, then place at 195 °C and calcine for 2 h. Add the obtained product to the mixed solution of 6 mmol of ferric chloride nonahydrate and 100 mL of ethanol again, place at 95 °C and stir until dry, then place at 400 °C and calcine for 3.5 h to prepare modified mesoporous silica.

[0061] Comparative Example 3 A sheath layer material includes the following components in parts by weight:

[0062] 70 parts of low-density polyethylene, 34 parts of ethylene-vinyl acetate copolymer, 10 parts of graphene oxide, 5 parts of modified mesoporous silica prepared in Example 2, 3 parts of lubricant polyethylene wax, 2 parts of plasticizer dioctyl phthalate, 0.5 part of light stabilizer 770;

[0063] The preparation method of the above sheath layer material and the preparation method of the enhanced halogen-free flame-retardant cable are the same as those in Example 3.

[0064] Comparative Example 4 A sheath layer material comprises the following components in parts by weight:

[0065] 70 parts of low-density polyethylene, 34 parts of ethylene-vinyl acetate copolymer, 10 parts of modified graphene oxide prepared in Example 1, 5 parts of modified mesoporous silica prepared in Comparative Example 1, 3 parts of lubricant polyethylene wax, 2 parts of plasticizer dioctyl phthalate, 0.5 part of light stabilizer 770;

[0066] The preparation method of the above sheath layer material and the preparation method of the enhanced halogen-free flame-retardant cable are the same as those in Example 3.

[0067] Comparative Example 5 A sheath layer material comprises the following components in parts by weight:

[0068] 70 parts of low-density polyethylene, 34 parts of ethylene-vinyl acetate copolymer, 10 parts of modified graphene oxide prepared in Example 1, 5 parts of modified mesoporous silica prepared in Comparative Example 2, 3 parts of lubricant polyethylene wax, 2 parts of plasticizer dioctyl phthalate, 0.5 part of light stabilizer 770;

[0069] The preparation method of the above sheath layer material and the preparation method of the enhanced halogen-free flame-retardant cable are the same as those in Example 3.

[0070] Performance testing

[0071] The sheath layer materials prepared in Examples 3-5 and Comparative Examples 3-5 were subjected to performance testing: the tensile properties were tested using a universal mechanical testing machine according to the standard of GB / T 1040.2-2022, and the change rates of the tensile strength and elongation at break were tested after aging at 110 °C for 48 h and 72 h. The impact strength was tested according to the standard of GB / T 1843-2008, and the tear strength was tested according to the standard of GB / T 529-2008; the flame retardant performance was tested by the limiting oxygen index test and the vertical burning test, and the data results are shown in Table 1.

[0072] Table 1 Test results of sample performance

[0073]

[0074] As can be seen from the data in Table 1, the sheath layer materials prepared in Examples 3-5 of the present invention have excellent mechanical properties, flame retardant properties and aging resistance. Among them, in Comparative Example 3, graphene oxide was not modified, and the measured mechanical properties were lower than those in Examples 3-5. This may be due to the agglomeration of graphene oxide, which leads to the reduction of its mechanical properties. And due to the lack of grafting of hexachlorocyclotriphosphazene derivatives, its flame retardant properties are worse than those in Examples 3-5. In Comparative Example 4, the modified mesoporous silica added did not carry iron oxide, and the measured mechanical properties and flame retardant properties were slightly worse than those in Examples 3-5, indicating that the loading of iron oxide can be used as a synergist to further improve the flame retardant and mechanical properties of the material. In Comparative Example 5, the modified mesoporous silica added was not grafted with anti-aging agent, resulting in poor dispersibility, and the measured mechanical properties were lower than those in Examples 3-5. The change rates of tensile strength and elongation at break were significantly different from those in Examples 3-5, indicating that the grafting of anti-aging agent can endow the material with excellent aging resistance.

[0075] In the description of this specification, the descriptions referring to the terms "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0076] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A reinforced halogen-free flame-retardant cable, characterized in that: The invention comprises a conductor core, an insulating layer, a shielding layer and a sheath layer which are sequentially arranged from the inside to the outside. The sheath layer is prepared by pulling out a sheath layer material from the periphery of the shielding layer through an extrusion device. The sheath layer material comprises the following components in parts by weight: 60 to 70 parts of low-density polyethylene, 20 to 35 parts of ethylene-vinyl acetate copolymer, 5 to 10 parts of modified graphene oxide, 2 to 5 parts of modified mesoporous silica, 1 to 3 parts of lubricant, 1 to 2 parts of plasticizer and 0.1 to 0.5 parts of light stabilizer. The modified mesoporous silica is prepared by using mesoporous silica as a carrier to load iron oxide particles, and further using 3-mercaptopropylmethyldimethoxysilane to graft an antioxidant N-(4-anilinophenyl)maleimide; The preparation method of the modified graphene oxide comprises the following steps: (1) 2-allylphenol and sodium hydroxide are placed in a reactor, reacted for 25-40 minutes under nitrogen protection, then heated to 60-75°C for 0.5-1 hour, and then hexachlorocyclotriphosphazene is added to continue the reaction for 18-24 hours. After the reaction is completed, the flame retardant intermediate is prepared by rotary evaporation and drying; (2) Put the flame retardant intermediate in a reactor, add acetonitrile to dissolve it, raise the temperature to 40-55°C, add 4,4'-diaminodiphenylmethane and triethylamine to reflux for 6-8h to prepare component A, dissolve DOPO in acetonitrile and add it to component A, and react at 75-90°C for 5-7h. After the reaction is completed, filter, wash and dry to prepare a hexachlorocyclotriphosphazene derivative; (3) ultrasonically dispersing graphene oxide in ethanol to obtain a graphene oxide dispersion, mixing deionized water, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide evenly and adding the mixture to the graphene oxide dispersion, then adding a hexachlorocyclotriphosphazene derivative, stirring and reacting at 40-55°C for 4-7h, and after the reaction is completed, centrifuging, washing and drying to obtain modified graphene oxide; In the step (1), the molar ratio of 2-allylphenol, sodium hydroxide and hexachlorocyclotriphosphazene is 1-1.04:1-1.05:0.27-0.33; and in the step (2), the molar ratio of the flame retardant intermediate, 4,4'-diaminodiphenylmethane and DOPO is 1:3-3.3:3-3.

5.

2. The reinforced halogen-free flame-retardant cable according to claim 1, characterized in that: The preparation method of the sheath layer material comprises the following steps: uniformly mixing parts by weight of low-density polyethylene, ethylene-vinyl acetate copolymer, modified graphene oxide, modified mesoporous silica, a lubricant, a plasticizer and a light stabilizer to obtain a mixture, and extruding the mixture into a twin-screw extruder to prepare the sheath layer material.

3. The reinforced halogen-free flame-retardant cable according to claim 1, characterized in that: The preparation method of the modified mesoporous silica comprises the following steps: A. Take hexadecyltrimethylammonium bromide and sodium hydroxide in a reactor, add deionized water, dissolve with ultrasonic vibration, place at 75-85°C and stir for 10-20 minutes, then add tetraethyl orthosilicate and continue stirring for 2-3 hours. After the reaction is completed, centrifuge, wash and dry, ultrasonically disperse the obtained solid product in a mixed solution of methanol and hydrochloric acid, place under cooling reflux conditions at 50-65°C, stir vigorously for 42-48 hours to remove the surfactant, centrifuge, wash and dry to prepare mesoporous silica; B. Dissolve ferric chloride nonahydrate in ethanol to obtain a mixed solution, add mesoporous silica to disperse evenly by ultrasonication, stir at 85-95°C until dry, and then calcine at 150-200°C for 1.5-2h, add the obtained product to the mixed solution of ferric chloride nonahydrate and ethanol again, stir at 85-95°C until dry, and then calcine at 350-400°C for 3-4h to prepare functionalized mesoporous silica; C. Take N-(4-anilinophenyl)maleimide and 3-mercaptopropylmethyldimethoxysilane and dissolve them in acetone. Heat the temperature to 40-50°C under nitrogen protection, add triethylamine and stir to react for 4-5 hours to obtain component one. Take functionalized mesoporous silica and ultrasonically disperse it in a mixed solution of ethanol and deionized water, add ammonia water to adjust the pH value of the mixed solution to 9-10, heat the temperature to 55-65°C, add component one and stir to react for 4-6 hours. After the reaction is completed, centrifuge, wash and dry to prepare modified mesoporous silica.

4. The reinforced halogen-free flame-retardant cable according to claim 3, characterized in that: In the step A, the molar ratio of hexadecyltrimethylammonium bromide, sodium hydroxide and tetraethyl orthosilicate is 1-1.2:2.2-2.8:8.1-9.

6.

5. The reinforced halogen-free flame-retardant cable according to claim 3, characterized in that: In the step C, the mass ratio of N-(4-anilinophenyl)maleimide, 3-mercaptopropylmethyldimethoxysilane and functionalized mesoporous silica is 0.4-1:0.3-0.9:5-10 g.

6. The reinforced halogen-free flame-retardant cable according to claim 1, characterized in that: The lubricant is polyethylene wax or oxidized polyethylene wax; the plasticizer is one or more combinations of dioctyl adipate, dimethyl phthalate, dioctyl phthalate, and diisodecyl phthalate; the light stabilizer is one or more combinations of light stabilizer 770, light stabilizer 944, and light stabilizer 2020.

7. The reinforced halogen-free flame-retardant cable according to claim 1, characterized in that: The insulating layer uses cross-linked polyethylene or polyethylene as the insulating material; the shielding layer includes a first shielding layer and a second shielding layer, the first shielding layer is made of aluminum foil wrapping, and the second shielding layer is made of silver-plated copper wire weaving.

8. A method for preparing a reinforced halogen-free flame-retardant cable according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Using a wire drawing machine to draw the copper rod to obtain a copper wire, and then annealing the wire to obtain a conductor; S2, twisting at least two of the conductors together to obtain a conductor core; S3, using an extruder to extrude an insulating layer on the outer surface of the conductor core; S4, wrap aluminum foil around the outer surface of the insulation layer to obtain a first shielding layer, and cross-weave silver-plated copper wire on the outer surface of the first shielding layer to obtain a second shielding layer; S5. Extruding a sheath layer on the outer surface of the second shielding layer to prepare a reinforced halogen-free flame-retardant cable.

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