Medium voltage fire resistant cable and method of making same

Abstract

The application discloses a kind of medium voltage fireproof cable and preparation method thereof, it is related to cable technical field.The application is when preparing medium voltage fireproof cable, mica base fire resistance layer is coated on the surface of conductor, copper protective layer is coated on the surface of mica base fire resistance layer, protective sleeve is coated on the surface of copper protective layer;The protective sleeve is prepared by modified polyethylene, modified silicon dioxide, catalyst, plasticizer, lubricant;The modified polyethylene is obtained by grafting 3-amino-1-phenyl-2-pyrazoline-5-ketone after maleic anhydride grafting polyethylene, and diazonium salt reaction, and then reacting with allyl boronic acid;The modified silicon dioxide is obtained by reacting with 3,4-dinitrophenol after polymerization on the surface of silicon dioxide modified by p-hydroxystyrene and vinyltrimethoxysilane, and then reducing, and reacting with 2-((2-nitrobenzyl)thio)ethylamine, and then deprotecting.The medium voltage fireproof cable prepared by the application has good fire resistance and anti-aging performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cables, in particular to a medium-voltage fireproof cable and a preparation method thereof. BACKGROUND

[0002] With the acceleration of urbanization, power cables as the core carrier of energy transmission need to densely pass through building groups and population gathering areas, and are exposed to complex natural environments and external forces for a long time, facing multiple challenges: on the one hand, environmental factors such as high temperature, humidity, and ultraviolet radiation easily lead to the aging and brittleness of the cable sheath, the migration and shedding of traditional flame retardants under long-term thermal oxidation, and the significant attenuation of fireproof performance with service time; on the other hand, the frequent bending of the cable during laying and use easily causes micro-cracks in the sheath and copper protective layer, and the rupture of the sheath molecular chain under long-term ultraviolet radiation leads to a sharp drop in anti-aging performance, resulting in insufficient mechanical strength of the sheath, stress concentration and rupture at the bending part, and accelerated flame spread. Therefore, it is very important to develop a fireproof cable with high fire resistance and long-term ultraviolet aging resistance. SUMMARY

[0003] The purpose of the present application is to provide a medium-voltage fireproof cable and a preparation method thereof to solve the problems in the prior art.

[0004] In order to solve the above technical problems, the present application provides the following technical scheme:

[0005] A preparation method of a medium-voltage fireproof cable, which comprises coating a mica-based fire-resistant layer on the surface of a conductor, coating a copper protective layer on the surface of the mica-based fire-resistant layer, and coating a protective sheath on the surface of the copper protective layer.

[0006] As an optimization, the protective sheath is prepared from modified polyethylene, modified silicon dioxide, a catalyst, a plasticizer, and a lubricant.

[0007] As an optimization, the modified polyethylene is obtained by grafting 3-amino-1-phenyl-2-pyrazoline-5-ketone onto maleic anhydride grafted polyethylene, then reacting with diazonium salt, and then reacting with allyl boronic acid.

[0008] As an optimization, the modified silicon dioxide is obtained by polymerizing p-hydroxystyrene on the surface of vinyltrimethoxysilane-modified silicon dioxide, then reacting with 3,4-dinitrophenol, reducing, then reacting with 2-((2-nitrobenzyl)thio)ethylamine, and then deprotecting.

[0009] As an optimization, the preparation method of the protective sheath is as follows:

[0010] (1) Dissolve dicumyl peroxide in styrene, mix with polyethylene and maleic anhydride in a high-speed mixer, and then extrude in a twin-screw extruder to obtain maleic anhydride grafted polyethylene; react the maleic anhydride grafted polyethylene with 3-amino-1-phenyl-2-pyrazolin-5-one to obtain pretreated polyethylene;

[0011] (2) React 4-chloro-2-nitroaniline, pure water, 2 mol / L hydrochloric acid and sodium nitrite to obtain a diazonium salt; react the pretreated polyethylene with the diazonium salt, and then add thiourea dioxide to obtain a pretreated modified polyethylene;

[0012] (3) Mix the pretreated modified polyethylene, allyl boronic acid, a solvent, tetrakis(triphenylphosphine)palladium, potassium carbonate and tetrabutylammonium bromide, heat to 85-90°C, react for 10-12 h, precipitate with ethanol at 0-5°C, filter, wash and dry to obtain a modified polyethylene;

[0013] (4) React silica and vinyltrimethoxysilane to obtain vinylsilica; react the vinylsilica with p-hydroxystyrene to obtain pretreated silica; react the pretreated silica with phosphorus oxychloride and 3,4-dinitrophenol to obtain pretreated modified silica;

[0014] (5) React the pretreated modified silica, thiourea dioxide and sodium bicarbonate to obtain aminosilica; react the aminosilica with glyoxal and 2-((2-nitrobenzyl)thio)ethylamine to obtain a modified silica precursor, and then irradiate the modified silica precursor to obtain a modified silica;

[0015] (6) Mix the modified polyethylene, the modified silica, a catalyst, a plasticizer, a lubricant in a high-speed mixer at a mass ratio of 1:(0.05-0.07):(0.001-0.002):(0.01-0.02):(0.01-0.02), and then transfer to a twin-screw extruder to obtain a protective sleeve; the mixing temperature is 80-90°C, the screw rotation speed of the twin-screw extruder is 150 r / min, and the heating temperature of each section of the extruder is 180°C, 190°C, 200°C, 200°C, 200°C, 200°C, 200°C and 190°C.

[0016] As optimization, the mass ratio of polyethylene, maleic anhydride, benzoyl peroxide and styrene in step (1) is 1:(0.2-0.3):(0.001-0.002):(0.01-0.02), the screw rotation speed of the double-screw extruder is 150 r / min, and the heating temperatures of the sections of the extruder are 180℃, 190℃, 200℃, 200℃, 200℃, 200℃, 200℃, 190℃; the polyethylene is HE3490-LS; and the mass ratio of the maleic anhydride grafted polyethylene, 3-amino-1-phenyl-2-pyrazolin-5-one, dimethylamino pyridine and dimethylbenzene is 1:(0.3-0.5):(0.5-0.7):(10-12).

[0017] As optimization, the preparation method of the pre-modified polyethylene in step (2) is as follows: 4-chloro-2-nitroaniline, pure water and 2 mol / L hydrochloric acid are mixed in a mass ratio of 1:(25-30):(12-15), cooled to 0-5℃, 0.15 g / mL sodium nitrite aqueous solution is added in an amount of 5-6 times the mass of 4-chloro-2-nitroaniline, and stirring is continued for 40-50 min, and the mixture is stored in the dark at 0-5℃ to obtain a diazonium salt; pretreated polyethylene, pure water and dispersant are mixed at 50℃ for 10-20 min, cooled to 10-15℃, and the diazonium salt is added at a drop rate of 1 mL / min, and after the drop addition is completed, sodium dodecyl sulfate is added, and the reaction is carried out for 2-3 h, and then the temperature is raised to 80-85℃, and thiourea dioxide is added in four portions with an interval of 30 min between each addition, and after the addition is completed, the reaction is continued for 2-3 h, and then the temperature is lowered to 5-10℃, and the mixture is filtered, washed and dried to obtain the pre-modified polyethylene; and the mass ratio of the pretreated polyethylene, pure water, dispersant, diazonium salt, sodium dodecyl sulfate and thiourea dioxide is 1:(10-12):(0.05-0.07):(55-65):(0.01-0.02):(0.5-0.7).

[0018] As optimization, the mass ratio of the pre-modified polyethylene, allyl boronic acid, solvent, tetrakis(triphenylphosphine)palladium, potassium carbonate and tetrabutylammonium bromide in step (3) is 1:(1.3-1.5):(20-30):0.01:(0.5-0.7):(0.02-0.03); and the solvent is a mixture of toluene and N,N-dimethylformamide in a volume ratio of 3:1.

[0019] As optimization, the preparation method of the pre-modified silica in step (4) is as follows: the silica, vinyltrimethoxysilane, anhydrous ethanol, pure water are mixed in a mass ratio of 1:(2-3):(10-12):(10-12), hydrochloric acid is used to adjust the pH to 4, the temperature is raised to 70-80℃ and reacted for 7-8h, then the product is filtered, washed and dried to obtain vinyl silica; the vinyl silica, p-hydroxystyrene, N,N-dimethylformamide, azobisisobutyronitrile are mixed in a mass ratio of 1:(2-3):(20-30):(0.01-0.02), the temperature is raised to 75-85℃ and reacted for 5-6h, then the product is filtered, washed and dried to obtain pre-treated silica; the pre-treated silica, tetrahydrofuran, phosphorus oxychloride, pyridine are stirred at 0-5℃ for 2-3h, after stirring, the product is filtered and dispersed into 0.2g / mL 3,4-dinitrophenol-tetrahydrofuran solution, lithium chloride is added, the temperature is raised to 50-60℃, and the reaction is carried out under nitrogen protection for 10-12h, then the product is filtered, washed and dried to obtain the pre-modified silica; the mass ratio of the pre-treated silica, tetrahydrofuran, phosphorus oxychloride, pyridine, 3,4-dinitrophenol and lithium chloride is 1:(20-30):(1-2):(1-2):(2-3):(0.03-0.05).

[0020] As optimization, the preparation method of the modified silica in step (5) is as follows: the pre-modified silica, thiourea dioxide, 10wt% sodium bicarbonate aqueous solution are mixed in a mass ratio of 1:(0.5-0.7):(20-30), the temperature is raised to 70-80℃, and the reaction is carried out for 5-6h, then the product is filtered, washed and dried to obtain aminosilica; the aminosilica, glyoxal, phosphate buffer solution with a pH of 7.4 are stirred at room temperature for 2-3h, then the product is filtered and added into 0.2g / mL 2-((2-nitrobenzyl)thio)ethylamine-acetonitrile solution, wherein the mass of 2-((2-nitrobenzyl)thio)ethylamine is 2-3 times that of the aminosilica, the reaction is carried out under nitrogen protection and in the dark for 10-12h, then the product is filtered, washed and dried to obtain a modified silica precursor; the modified silica precursor is placed in a quartz reactor and irradiated for 30-40min under the condition of a 365nm ultraviolet light source and a power of 50mW / cm 2 , 0-5℃, then the product is washed and dried to obtain the modified silica.

[0021] As optimization, the preparation method of the 2-((2-nitrobenzyl)thio)ethylamine is: mixing lithium hydroxide, pure water, ethanol and cysteamine hydrochloride in a mass ratio of 1:20:50:3 to obtain a mixed solution, mixing 2-nitrobenzyl bromide with a mass of 4.6 times of lithium hydroxide and ethanol in a mass ratio of 1:20 to obtain a 2-nitrobenzyl bromide solution, adding the 2-nitrobenzyl bromide solution into the mixed solution at a speed of 1 mL / min, stirring at 30-35 DEG C for 40 min after the addition is completed, extracting with dichloromethane, drying with anhydrous sodium sulfate, filtering and concentrating to obtain 2-((2-nitrobenzyl)thio)ethylamine.

[0022] The application further provides a medium-voltage fireproof cable prepared by the preparation method of the medium-voltage fireproof cable.

[0023] Compared with the prior art, the application has the following beneficial effects:

[0024] In the preparation of the medium-voltage fireproof cable, a mica-based fire-resistant layer is coated on the surface of the conductor, a copper protective layer is coated on the surface of the mica-based fire-resistant layer, and a protective sleeve is coated on the surface of the copper protective layer; the protective sleeve is prepared from modified polyethylene, modified silicon dioxide, a catalyst, a plasticizer and a lubricant; the modified polyethylene is prepared from maleic anhydride grafted polyethylene grafted with 3-amino-1-phenyl-2-pyrazoline-5-ketone, reacted with diazonium salt, and then reacted with allyl boronic acid; and the modified silicon dioxide is prepared from p-hydroxystyrene polymerized on the surface of vinyltrimethoxysilane modified silicon dioxide, reacted with 3,4-dinitrophenol, reduced, reacted with 2-((2-nitrobenzyl)thio)ethylamine, and then deprotected.

[0025] Firstly, maleic anhydride is grafted on polyethylene by a melt grafting method, 3-amino-1-phenyl-2-pyrazoline-5-ketone is grafted by the reaction of anhydride and amino group, 4-chloro-2-nitroaniline is prepared into diazonium salt, and then the active hydrogen on 3-amino-1-phenyl-2-pyrazoline-5-ketone is coupled to generate a benzotriazole ring, the structure connected by the nitrogen heterocycle and the benzotriazole stabilizes the ground state structure, excitation state proton transfer dissipates energy, and N-heterocycle conjugation enhances the absorption performance, thereby endowing the material with good light aging resistance; then, the Suzuki coupling reaction of the chlorine on 4-chloro-2-nitroaniline and allyl boronic acid is performed to introduce a double bond;

[0026] The structure connected by the nitrogen heterocycle and the benzotriazole and the schematic diagram of the ultraviolet absorption principle of the structure are as follows: the structure has two tautomers of enol form and ketone form;

[0027]

[0028] Secondly, in the presence of initiator, p-hydroxystyrene is polymerized on the surface of vinyl trimethoxysilane modified silica, so that the surface of silica is modified with phenolic hydroxyl group, and then an ester exchange reaction between 3,4-dinitrophenol and phosphorus oxychloride generates a phosphate structure with good flame retardant performance; then the nitro group on 3,4-dinitrophenol is reduced to amino group, a Schiff base structure is generated by using glutaraldehyde as a crosslinking agent, and 2-((2-nitrobenzyl)thio)ethylamine is grafted, and the ortho-nitrobenzyl structure on 2-((2-nitrobenzyl)thio)ethylamine can be removed under light, thereby releasing the mercapto group;

[0029] Finally, the modified polyethylene, modified silica and the like are mixed and melt-extruded to obtain a protective sleeve, which is coated on the copper protective layer, in the process of melt-extrusion, the double bond on the side chain of the modified polyethylene and the mercapto group on the modified silica are crosslinked to generate a sulfide through a click reaction, and the double bond will also undergo self-polymerization in the presence of a catalyst to generate a more complex crosslinking network, thereby enhancing the mechanical properties of the protective sleeve material; in the modification process, the nitrogen heterocycle, phosphate and Schiff base structures of the polyethylene side chain have good complexing ability to metals, and can form a dense protective layer on the copper protective layer to protect the internal copper protective layer from corrosion; in the modification process, the introduction of nitrogen, phosphorus and sulfur elements can also synergistically flame retard, further improving the flame retardant performance of the material. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] In the following examples and comparative examples, the polyethylene type is HE3490-LS; the dispersing agent is polyvinyl alcohol; the plasticizer is dioctyl adipate; the lubricant is vinyl bis-stearamide; the particle size of the silica is 200 nm; the conductor is annealed copper, purchased from Nanyuan Copper Industry (Dongguan) Co., Ltd.; the mica-based fire-resistant layer is mica tape, purchased from Yangzhou Huidong Cable Material Co., Ltd., with a thickness of 0.2 mm; the copper protective layer is annealed soft copper tape, purchased from Shandong Xiyihua Copper Industry Co., Ltd.

[0032] Example 1:

[0033] A preparation method of a medium-voltage fireproof cable, the preparation method of the medium-voltage fireproof cable comprising the following preparation steps: coating a mica-based fire-resistant layer on the surface of a conductor, coating a copper protective layer on the surface of the mica-based fire-resistant layer, and coating a protective sleeve on the surface of the copper protective layer; the preparation method of the protective sleeve is:

[0034] (1) Dissolve dicumyl peroxide in styrene, mix with polyethylene and maleic anhydride in a high-speed mixer, and then extrude in a twin-screw extruder to obtain maleic anhydride grafted polyethylene; the mass ratio of polyethylene, maleic anhydride, benzoyl peroxide and styrene is 1:0.2:0.001:0.01, the screw rotation speed of the twin-screw extruder is 150 r / min, and the heating temperature of each section of the extruder is 180℃, 190℃, 200℃, 200℃, 200℃, 200℃, 200℃ and 190℃; mix maleic anhydride grafted polyethylene, 3-amino-1-phenyl-2-pyrazolin-5-one, dimethylaminopyridine and dimethylbenzene according to a mass ratio of 1:0.3:0.5:10, and react at 110℃ for 8h to obtain pretreated polyethylene;

[0035] (2) Mix 4-chloro-2-nitroaniline, pure water and 2mol / L hydrochloric acid according to a mass ratio of 1:25:12, cool to 5℃, add 0.15g / mL sodium nitrite aqueous solution with a mass of 5 times that of 4-chloro-2-nitroaniline, continue to stir for 50min, and store in the dark at 5℃ to obtain a diazonium salt; mix the pretreated polyethylene, pure water and dispersant at 50℃ for 20min, cool to 15℃, add the diazonium salt at a drop rate of 1mL / min, add sodium dodecyl sulfate after the drop addition is completed, react for 3h, heat to 85℃, add thiourea dioxide in four portions with an interval of 30min between each addition, continue to react for 3h after the addition is completed, cool to 10℃, filter, wash and dry to obtain pretreated polyethylene; the mass ratio of pretreated polyethylene, pure water, dispersant, diazonium salt, sodium dodecyl sulfate and thiourea dioxide is 1:10:0.05:55:0.01:0.5;

[0036] (3) Mix the pretreated polyethylene, allyl boronic acid, solvent, catalyst, potassium carbonate and tetrabutylammonium bromide, heat to 90℃ and react for 12h, precipitate with 5℃ ethanol, filter, wash and dry to obtain modified polyethylene; the mass ratio of pretreated polyethylene, allyl boronic acid, solvent, tetrakistriphenylphosphine palladium, potassium carbonate and tetrabutylammonium bromide is 1:1.3:20:0.01:0.5:0.02; the solvent is a mixture of toluene and N,N-dimethylformamide in a volume ratio of 3:1;

[0037] (4) Silica, vinyltrimethoxysilane, anhydrous ethanol, pure water were mixed according to the mass ratio of 1:2:10:10, hydrochloric acid was used to adjust the pH to 4, and the reaction was carried out at 80°C for 8h, and then filtered, washed and dried to obtain vinyl silica; vinyl silica, p-hydroxystyrene, N,N-dimethylformamide, azobisisobutyronitrile were mixed according to the mass ratio of 1:2:20:0.01, and the reaction was carried out at 85°C for 6h, and then filtered, washed and dried to obtain pretreated silica; the pretreated silica, tetrahydrofuran, phosphorus oxychloride, pyridine were stirred at 5°C for 3h, after stirring, filtration was carried out and then dispersed into 0.2g / mL 3,4-dinitrophenol-tetrahydrofuran solution, lithium chloride was added, the temperature was raised to 60°C, and the reaction was carried out under nitrogen protection for 12h, and then filtered, washed and dried to obtain pre-modified silica; the mass ratio of pretreated silica, tetrahydrofuran, phosphorus oxychloride, pyridine, 3,4-dinitrophenol, lithium chloride was 1:20:1:1:2:0.03;

[0038] (5) The pre-modified silica, thiourea dioxide, 10wt% sodium bicarbonate aqueous solution were mixed according to the mass ratio of 1:0.5:20, the temperature was raised to 80°C, and the reaction was carried out for 6h, and then filtered, washed and dried to obtain aminosilica; lithium hydroxide, pure water, ethanol, cysteamine hydrochloride were mixed according to the mass ratio of 1:20:50:3 to obtain a mixed solution, 2-nitrobenzyl bromide was mixed according to the mass ratio of 1:20 to obtain a 2-nitrobenzyl bromide solution, the 2-nitrobenzyl bromide solution was added to the mixed solution at a speed of 1mL / min, after the addition was completed, stirring was carried out at 35°C for 40min, dichloromethane extraction, anhydrous sodium sulfate drying, filtration and concentration were carried out to obtain 2-((2-nitrobenzyl)thio)ethylamine; the aminosilica, glyoxal, phosphate buffer solution with a pH of 7.4 were stirred at room temperature for 3h, and then filtered and added to a 0.2g / mL 2-((2-nitrobenzyl)thio)ethylamine-acetonitrile solution, wherein the mass of 2-((2-nitrobenzyl)thio)ethylamine was 2 times that of aminosilica, the reaction was carried out under nitrogen protection for 12h in the dark, and then filtered, washed and dried to obtain a modified silica precursor; the modified silica precursor was placed in a quartz reactor and irradiated at 365nm ultraviolet light source with a power of 50mW / cm 2 , 5°C for 40min, and then washed and dried to obtain modified silica;

[0039] (6) The modified polyethylene, modified silicon dioxide, benzoyl peroxide, plasticizer, lubricant are added into a high-speed mixer in a mass ratio of 1:0.05:0.001:0.01:0.01, and then transferred to a double-screw extruder to be extruded to obtain a protective sleeve; the mixing temperature is 90°C, the screw rotation speed of the double-screw extruder is 150 r / min, and the heating temperature of each section of the extruder is 180°C, 190°C, 200°C, 200°C, 200°C, 200°C, 200°C, 190°C.

[0040] Example 2:

[0041] A preparation method of a medium-voltage fireproof cable, comprising the following preparation steps: coating a mica-based fire-resistant layer on the surface of a conductor, coating a copper protective layer on the surface of the mica-based fire-resistant layer, and coating a protective sleeve on the surface of the copper protective layer; the preparation method of the protective sleeve is as follows:

[0042] (1) After the polyethylene, maleic anhydride and benzoyl peroxide are mixed uniformly in a high-speed mixer after the benzoyl peroxide is dissolved in styrene, the mixture is extruded in a double-screw extruder to obtain maleic anhydride grafted polyethylene; the mass ratio of the polyethylene, maleic anhydride, benzoyl peroxide and styrene is 1:0.25:0.001:0.015, the screw rotation speed of the double-screw extruder is 150 r / min, and the heating temperature of each section of the extruder is 180°C, 190°C, 200°C, 200°C, 200°C, 200°C, 200°C, 190°C; the maleic anhydride grafted polyethylene, 3-amino-1-phenyl-2-pyrazolin-5-one, dimethylamino pyridine and dimethylbenzene are mixed in a mass ratio of 1:0.4:0.6:11, and then reacted at 105°C for 7 h to obtain pretreated polyethylene;

[0043] (2) The 4-chloro-2-nitroaniline, pure water and 2 mol / L hydrochloric acid are mixed in a mass ratio of 1:27:13, cooled to 3°C, and then 0.15 g / mL sodium nitrite aqueous solution with a mass of 5.5 times that of the 4-chloro-2-nitroaniline is added, and the stirring is continued for 45 min; the mixture is stored at 3°C in the dark to obtain a diazonium salt; the pretreated polyethylene, pure water and dispersant are mixed at 50°C for 15 min, cooled to 12°C, and then the diazonium salt is added at a drop rate of 1 mL / min; after the dropwise addition is completed, sodium dodecyl sulfate is added, and the reaction is carried out for 2.5 h; the temperature is increased to 85°C, and then thiourea dioxide is added in four portions with an interval of 30 min between each addition; after the addition is completed, the reaction is continued for 2.5 h; the temperature is decreased to 7°C, and then the mixture is filtered, washed and dried to obtain pretreated polyethylene; the mass ratio of the pretreated polyethylene, pure water, dispersant, diazonium salt, sodium dodecyl sulfate and thiourea dioxide is 1:11:0.06:50:0.01:0.6;

[0044] (3) mixing the pre-modified polyethylene, allyl boronic acid, solvent, catalyst, potassium carbonate, tetrabutylammonium bromide, and then heating to 86°C for 11 hours, precipitating with 3°C ethanol, filtering, washing and drying to obtain the modified polyethylene; the mass ratio of the pre-modified polyethylene, allyl boronic acid, solvent, tetrakis(triphenylphosphine)palladium, potassium carbonate, tetrabutylammonium bromide is 1:1.4:25:0.01:0.6:0.02; the solvent is a mixture of toluene and N,N-dimethylformamide in a volume ratio of 3:1;

[0045] (4) mixing silica, vinyltrimethoxysilane, anhydrous ethanol, pure water in a mass ratio of 1:2.5:11:11, adjusting the pH to 4 with hydrochloric acid, heating to 75°C for 7.5 hours, filtering, washing and drying to obtain vinyl silica; mixing the vinyl silica, p-hydroxystyrene, N,N-dimethylformamide, azobisisobutyronitrile in a mass ratio of 1:2.5:25:0.01, heating to 80°C for 5.5 hours, filtering, washing and drying to obtain pretreated silica; mixing the pretreated silica, tetrahydrofuran, phosphorus oxychloride, pyridine at 3°C for 2.5 hours, after stirring, filtering and dispersing into 0.2g / mL 3,4-dinitrophenol-tetrahydrofuran solution, adding lithium chloride, heating to 55°C, reacting for 11 hours under nitrogen protection, filtering, washing and drying to obtain pre-modified silica; the mass ratio of the pretreated silica, tetrahydrofuran, phosphorus oxychloride, pyridine, 3,4-dinitrophenol, lithium chloride is 1:25:1.5:1.7:2.5:0.04;

[0046] (5) mixing the pre-modified silica, sulfourea dioxide, 10wt% sodium bicarbonate aqueous solution in a mass ratio of 1:0.6:25, heating to 75°C, reacting for 5.5 hours, filtering, washing and drying to obtain aminosilica; mixing lithium hydroxide, pure water, ethanol, cysteamine hydrochloride in a mass ratio of 1:20:50:3 to obtain a mixed solution, mixing 2-nitrobenzyl bromide in a mass ratio of 1:20 to obtain a 2-nitrobenzyl bromide solution, adding the 2-nitrobenzyl bromide solution into the mixed solution at a speed of 1mL / min, after the addition, stirring for 40 minutes at 32°C, extracting with dichloromethane, drying with anhydrous sodium sulfate, filtering and concentrating to obtain 2-((2-nitrobenzyl)thio)ethylamine; mixing aminosilica, glyoxal, phosphate buffer with a pH of 7.4 in a mass ratio of 1:2.5:25 at room temperature for 2.5 hours, filtering and adding into 0.2g / mL 2-((2-nitrobenzyl)thio)ethylamine-acetonitrile solution, wherein the mass of 2-((2-nitrobenzyl)thio)ethylamine is 2.5 times that of aminosilica, reacting for 11 hours under nitrogen protection and avoiding light, filtering, washing and drying to obtain a modified silica precursor; placing the modified silica precursor in a quartz reactor, under the irradiation of a 365nm ultraviolet light source with a power of 50mW / cm2 , 3℃ for 35 min, and then washed and dried to obtain the modified silica;

[0047] (6) The modified polyethylene, modified silica, benzoyl peroxide, plasticizer, and lubricant were added into a high-speed mixer in a mass ratio of 1:0.06:0.001:0.01:0.01, and then transferred into a double-screw extruder to obtain a protective sleeve. The mixing temperature was 85°C, the screw rotation speed of the double-screw extruder was 150 r / min, and the heating temperature of each section of the extruder was 180°C, 190°C, 200°C, 200°C, 200°C, 200°C, 200°C, and 190°C.

[0048] Example 3

[0049] A preparation method of a medium-voltage fireproof cable, the preparation method comprising the following preparation steps: coating a mica-based fireproof layer on the surface of a conductor, coating a copper protective layer on the surface of the mica-based fireproof layer, and coating a protective sleeve on the surface of the copper protective layer; the preparation method of the protective sleeve is as follows:

[0050] (1) The benzoyl peroxide was dissolved in styrene, and then mixed with polyethylene and maleic anhydride in a high-speed mixer to obtain maleic anhydride grafted polyethylene. The mass ratio of polyethylene, maleic anhydride, benzoyl peroxide, and styrene was 1:0.3:0.002:0.02, the screw rotation speed of the double-screw extruder was 150 r / min, and the heating temperature of each section of the extruder was 180°C, 190°C, 200°C, 200°C, 200°C, 200°C, 200°C, and 190°C. The maleic anhydride grafted polyethylene, 3-amino-1-phenyl-2-pyrazolin-5-one, dimethylamino pyridine, and dimethylbenzene were mixed in a mass ratio of 1:0.5:0.7:12, and then reacted at 100°C for 6 h to obtain pretreated polyethylene.

[0051] (2) 4-Chloro-2-nitroaniline, pure water, and 2 mol / L hydrochloric acid were mixed in a mass ratio of 1:30:15, and then cooled to 0°C. 0.15 g / mL sodium nitrite aqueous solution was added in an amount of 6 times the mass of 4-chloro-2-nitroaniline, and then stirred for 40 min. The mixture was stored at 0°C in the dark to obtain a diazonium salt. The pretreated polyethylene, pure water, and dispersant were mixed at 50°C for 10 min, and then cooled to 10°C. The diazonium salt was added at a drop rate of 1 mL / min. After the drop addition was completed, sodium dodecyl sulfate was added, and then reacted for 2 h. The temperature was increased to 80°C, and then thiourea dioxide was added in four portions with an interval of 30 min between each addition. After the addition was completed, the reaction was continued for 2 h. The temperature was then decreased to 5°C, and then the mixture was filtered, washed, and dried to obtain pretreated polyethylene. The mass ratio of the pretreated polyethylene, pure water, dispersant, diazonium salt, sodium dodecyl sulfate, and thiourea dioxide was 1:12:0.07:65:0.02:0.7.

[0052] (3) mixing the pre-modified polyethylene, allyl boronic acid, solvent, catalyst, potassium carbonate, tetrabutylammonium bromide, and heating to 85°C for 10h, precipitating with ethanol at 0°C, filtering, washing and drying to obtain the modified polyethylene; the mass ratio of the pre-modified polyethylene, allyl boronic acid, solvent, tetratrisphenylphosphine palladium, potassium carbonate, tetrabutylammonium bromide is 1:1.5:30:0.01:0.7:0.03; the solvent is a mixture of toluene and N,N-dimethylformamide in a volume ratio of 3:1;

[0053] (4) mixing silica, vinyltrimethoxysilane, anhydrous ethanol, pure water in a mass ratio of 1:3:12:12, adjusting the pH to 4 with hydrochloric acid, heating to 70°C for 7h, filtering, washing and drying to obtain vinyl silica; mixing the vinyl silica, p-hydroxystyrene, N,N-dimethylformamide, azobisisobutyronitrile in a mass ratio of 1:3:30:0.02, heating to 75°C for 5h, filtering, washing and drying to obtain pretreated silica; stirring the pretreated silica, tetrahydrofuran, phosphorus oxychloride, pyridine at 0°C for 2h, after stirring, filtering and dispersing into 0.2g / mL 3,4-dinitrophenol-tetrahydrofuran solution, adding lithium chloride, heating to 50°C, reacting for 10h under nitrogen protection, filtering, washing and drying to obtain pre-modified silica; the mass ratio of the pretreated silica, tetrahydrofuran, phosphorus oxychloride, pyridine, 3,4-dinitrophenol, lithium chloride is 1:30:2:2:3:0.05;

[0054] (5) mixing the pre-modified silica, sulfourea dioxide, 10wt% sodium bicarbonate aqueous solution in a mass ratio of 1:0.7:30, heating to 70°C, reacting for 5h, filtering, washing and drying to obtain aminosilica; mixing lithium hydroxide, pure water, ethanol, cysteamine hydrochloride in a mass ratio of 1:20:50:3 to obtain a mixed solution, mixing 2-nitrobenzyl bromide in a mass ratio of 1:20 to obtain a 2-nitrobenzyl bromide solution, adding the 2-nitrobenzyl bromide solution to the mixed solution at a speed of 1mL / min, after the addition is completed, stirring at 30°C for 40min, extracting with dichloromethane, drying with anhydrous sodium sulfate, filtering and concentrating to obtain 2-((2-nitrobenzyl)thio)ethylamine; stirring the aminosilica, glyoxal, phosphate buffer with a pH of 7.4 in a mass ratio of 1:3:30 at room temperature for 2h, filtering and adding to a 0.2g / mL 2-((2-nitrobenzyl)thio)ethylamine-acetonitrile solution, wherein the mass of 2-((2-nitrobenzyl)thio)ethylamine is 3 times that of the aminosilica, reacting for 10h under nitrogen protection in the dark, filtering, washing and drying to obtain a modified silica precursor; placing the modified silica precursor in a quartz reactor, under the irradiation of a 365nm ultraviolet light source with a power of 50mW / cm 2, 0 ℃ for 30 min, and then washed and dried to obtain the modified silica;

[0055] (6) Modified polyethylene, modified silica, benzoyl peroxide, plasticizer, lubricant were added into a high-speed mixer at a mass ratio of 1:0.07:0.002:0.02:0.02, and then transferred to a twin-screw extruder to obtain a protective sleeve. The mixing temperature was 80 ℃, the screw rotation speed of the twin-screw extruder was 150 r / min, and the heating temperature of each section of the extruder was 180 ℃, 190 ℃, 200 ℃, 200 ℃, 200 ℃, 200 ℃, 200 ℃, and 190 ℃.

[0056] Comparative Example 1:

[0057] The preparation method of the medium-voltage fireproof cable of Comparative Example 1 was different from that of Example 2 in that the polyethylene was not modified, specifically, steps (1)-(3) were not included, and step (6) was modified as follows: polyethylene, modified silica, benzoyl peroxide, plasticizer, and lubricant were added into a high-speed mixer at a mass ratio of 1:0.06:0.001:0.01:0.01, and then transferred to a twin-screw extruder to obtain a protective sleeve. The mixing temperature was 85 ℃, the screw rotation speed of the twin-screw extruder was 150 r / min, and the heating temperature of each section of the extruder was 180 ℃, 190 ℃, 200 ℃, 200 ℃, 200 ℃, 200 ℃, 200 ℃, and 190 ℃. The remaining steps were the same as those of Example 2.

[0058] Comparative Example 2:

[0059] The preparation method of the medium-voltage fireproof cable of Comparative Example 2 was different from that of Example 2 in that the silica was not modified, specifically, steps (4)-(5) were not included, and step (6) was modified as follows: modified polyethylene, silica, benzoyl peroxide, plasticizer, and lubricant were added into a high-speed mixer at a mass ratio of 1:0.06:0.001:0.01:0.01, and then transferred to a twin-screw extruder to obtain a protective sleeve. The mixing temperature was 85 ℃, the screw rotation speed of the twin-screw extruder was 150 r / min, and the heating temperature of each section of the extruder was 180 ℃, 190 ℃, 200 ℃, 200 ℃, 200 ℃, 200 ℃, 200 ℃, and 190 ℃. The remaining steps were the same as those of Example 2.

[0060] Comparative Example 3:

[0061] The preparation method of the medium voltage fireproof cable of Comparative Example 3 is different from that of Example 2 in that the pre-modified silicon dioxide is not subjected to the next step of modification, specifically, step (5) is not included, and step (6) is modified as follows: the modified polyethylene, the pre-modified silicon dioxide, the benzoyl peroxide, the plasticizer, and the lubricant are added into a high-speed mixer in a mass ratio of 1:0.06:0.001:0.01:0.01 for mixing, and then are transferred to a double-screw extruder for extrusion to obtain a protective sleeve; the mixing temperature is 85°C, the screw rotation speed of the double-screw extruder is 150 r / min, and the heating temperature of each section of the extruder is 180°C, 190°C, 200°C, 200°C, 200°C, 200°C, 200°C, and 190°C. The other steps are the same as those of Example 2.

[0062] Test Example 1

[0063] Test of fireproof performance:

[0064] Test method: The fireproof cables prepared in the examples and comparative examples are subjected to fireproof test according to the standard GB / T 19216.11-2003, and the flame temperature is 950°C.

[0065] Test of anti-aging performance:

[0066] Test method: The fireproof test is performed according to the test method of the test of fireproof performance after standard aging treatment for 720h according to the standard GB / T 16422.2-2014. The results are shown in Table 1.

[0067] Table 1

[0068] Continuous power supply time (min) Continuous power supply time after aging (min) Example 1 194 Example 1 190 Example 2 197 Example 2 194 Example 3 197 Example 3 195 Comparative Example 1 174 Comparative Example 1 131 Comparative Example 2 153 Comparative Example 2 143 Comparative Example 3 181 Comparative Example 3 175

[0069] It can be found from the experimental data of Examples 1-3 and Comparative Examples 1-3 in Table 1 that the coating prepared in the application has good fireproof performance and anti-aging performance.

[0070] The fireproof and anti-aging performance of Examples 1-3 is better than that of Comparative Examples 1-3, which indicates that, in the presence of the initiator, the p-hydroxystyrene is polymerized on the surface of the silicon dioxide modified by vinyltrimethoxysilane, so that the phenolic hydroxyl group is modified on the surface of the silicon dioxide, and then the ester exchange reaction between 3,4-dinitrophenol and phosphorus oxychloride generates a phosphate structure with good flame retardant performance; the introduction of nitrogen element, phosphorus element, and sulfur element in the modification process can also synergistically retard flame, and further improve the flame retardant performance of the material.

[0071] Maleic anhydride is grafted on polyethylene by melt grafting method, 3-amino-1-phenyl-2-pyrazolin-5-ketone is grafted by reaction of anhydride and amino group, 4-chloro-2-nitroaniline is prepared into diazonium salt, and then coupling reaction occurs between the active hydrogen on 3-amino-1-phenyl-2-pyrazolin-5-ketone and the diazonium salt, and then reduction reagent is used for reduction and cyclization to generate benzotriazole ring, the structure of the connected nitrogen heterocycle and benzotriazole is stabilized by ground state structure, excited state proton transfer dissipates energy, and N-heterocycle conjugation enhances absorption performance, thereby endowing the material with good anti-photoaging performance.

[0072] Test Example 2

[0073] Test of corrosion resistance:

[0074] Test method: after the surface of a 120mm*50mm*0.5mm copper plate is polished, cleaned and dried, the protective sleeve material is wrapped on the copper plate, the copper plate is placed in a 5wt% sodium chloride solution at 25°C, and 2 / 3 of the length of each copper plate is immersed in the sodium chloride solution, the immersion time is 600h, and the appearance of the steel plate is observed. The results are shown in Table 2.

[0075] Table 2

[0076] Appearance Appearance Example 1 No change Comparative Example 1 Frothing Example 2 No change Comparative Example 2 Slight frothing Example 3 No change Comparative Example 3 Slight frothing

[0077] From the comparison of the experimental data of Examples 1-3 and Comparative Examples 1-3 in Table 2, it can be found that the coating prepared by the present application has good corrosion resistance.

[0078] The corrosion resistance of Examples 1-3 is better than that of Comparative Examples 1-3, which shows that during the modification process, the nitrogen heterocycle, phosphate ester and Schiff base structure of the polyethylene side chain have good complexing ability to metal, and can form a dense protective layer on the copper protective layer to protect the internal copper protective layer from corrosion.

[0079] It is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the examples should be regarded as exemplary and non-limiting in any respect, and the scope of the present application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application. Any mark in the claims should not be regarded as limiting the involved claims.

Claims

1. A method for the production of a medium voltage fire resistant cable, characterized in that, The surface of the conductor is coated with a mica-based refractory layer, the surface of the mica-based refractory layer is coated with a copper protective layer, and the surface of the copper protective layer is coated with a protective sleeve; The protective sleeve is prepared from modified polyethylene, modified silicon dioxide, a catalyst, a plasticizer and a lubricant; The modified polyethylene is obtained by grafting 3-amino-1-phenyl-2-pyrazolin-5-ketone onto maleic anhydride grafted polyethylene, then reacting with diazonium salt, and then reacting with allyl boronic acid; The modified silicon dioxide is obtained by polymerizing p-hydroxystyrene on the surface of vinyltrimethoxysilane modified silicon dioxide, then reacting with 3,4-dinitrophenol, reducing, then reacting with 2-((2-nitrobenzyl)thio)ethylamine, and then deprotecting; The preparation method of the protective sleeve is as follows: (1) Dissolve dicumyl peroxide in styrene, mix polyethylene and maleic anhydride in a high-speed mixer, and then extrude in a twin-screw extruder to obtain maleic anhydride grafted polyethylene; then react the maleic anhydride grafted polyethylene with 3-amino-1-phenyl-2-pyrazolin-5-ketone to obtain pretreated polyethylene; (2) React 4-chloro-2-nitroaniline, pure water, 2 mol / L hydrochloric acid and sodium nitrite to obtain diazonium salt; then react the pretreated polyethylene with the diazonium salt, and then add thiourea dioxide to obtain pretreated polyethylene; (3) Mix the pretreated polyethylene, allyl boronic acid, solvent, tetrakis(triphenylphosphine)palladium, potassium carbonate and tetrabutylammonium bromide, heat to 85-90°C for 10-12 hours, precipitate in 0-5°C ethanol, filter, wash and dry to obtain modified polyethylene; (4) React silicon dioxide and vinyltrimethoxysilane to obtain vinylsilica; then react the vinylsilica with p-hydroxystyrene to obtain pretreated silicon dioxide; then react the pretreated silicon dioxide with phosphorus oxychloride and 3,4-dinitrophenol to obtain pretreated silicon dioxide; (5) React the pretreated silicon dioxide, thiourea dioxide and sodium bicarbonate to obtain aminosilica; then react the aminosilica with glyoxal and 2-((2-nitrobenzyl)thio)ethylamine to obtain a modified silicon dioxide precursor, and then irradiate the modified silicon dioxide precursor to obtain modified silicon dioxide; (6) Mix the modified polyethylene, modified silicon dioxide, catalyst, plasticizer and lubricant in a high-speed mixer at a mass ratio of 1:(0.05-0.07):(0.001-0.002):(0.01-0.02):(0.01-0.02), and then transfer to a twin-screw extruder to obtain the protective sleeve; the mixing temperature is 80-90°C, the screw rotation speed of the twin-screw extruder is 150 r / min, and the heating temperature of each section of the extruder is 180°C, 190°C, 200°C, 200°C, 200°C, 200°C, 200°C and 190°C.

2. A process for the production of a medium voltage fire resistant cable according to claim 1, characterized in that, The mass ratio of polyethylene, maleic anhydride, dicumyl peroxide and styrene in step (1) is 1:(0.2-0.3):(0.001-0.002):(0.01-0.02), the screw rotation speed of the double-screw extruder is 150 r / min, and the heating temperatures of the sections of the extruder are 180℃, 190℃, 200℃, 200℃, 200℃, 200℃, 200℃, 190℃; the polyethylene is HE3490-LS; and the mass ratio of the maleic anhydride grafted polyethylene and 3-amino-1-phenyl-2-pyrazolin-5-one is 1:(0.3-0.5).

3. A process for the preparation of a medium voltage fire resistant cable according to claim 1, characterized in that, The preparation method of the pre-modified polyethylene in step (2) is as follows: 4-chloro-2-nitroaniline, pure water and 2 mol / L hydrochloric acid are mixed in a mass ratio of 1:(25-30):(12-15), cooled to 0-5℃, 0.15 g / mL sodium nitrite aqueous solution is added in an amount of 5-6 times the mass of 4-chloro-2-nitroaniline, and stirring is continued for 40-50 min, and the mixture is stored in the dark at 0-5℃ to obtain a diazonium salt; pretreated polyethylene, pure water and a dispersant are mixed at 50℃ for 10-20 min, cooled to 10-15℃, and the diazonium salt is added at a drop rate of 1 mL / min, and after the drop addition is completed, sodium dodecyl sulfate is added, and the mixture is reacted for 2-3 h, then heated to 80-85℃, and thiourea dioxide is added in four portions with an interval of 30 min between each addition, and after the addition is completed, the mixture is continuously reacted for 2-3 h, then cooled to 5-10℃, filtered, washed and dried to obtain the pre-modified polyethylene. The mass ratio of pretreated polyethylene, pure water, dispersant, diazonium salt, sodium dodecyl sulfate and thiourea dioxide is 1:(10-12):(0.05-0.07):(55-65):(0.01-0.02):(0.5-0.7).

4. A process for the preparation of a medium voltage fire resistant cable according to claim 1, characterized in that, The mass ratio of the pre-modified polyethylene, allyl boronic acid, solvent, tetrakis(triphenylphosphine)palladium, potassium carbonate and tetrabutylammonium bromide in step (3) is 1:(1.3-1.5):(20-30):0.01:(0.5-0.7):(0.02-0.03); and the solvent is a mixture of toluene and N,N-dimethylformamide in a volume ratio of 3:

1.

5. A process for the preparation of a medium voltage fire resistant cable according to claim 1, characterized in that, The preparation method of the pre-modified silica in step (4) is as follows: mixing silica, vinyltrimethoxysilane, anhydrous ethanol, and pure water according to a mass ratio of 1: (2-3): (10-12): (10-12), adjusting pH to 4 by using hydrochloric acid, heating to 70-80 DEG C and reacting for 7-8 h, filtering, washing, and drying to obtain vinyl silica; mixing the vinyl silica, p-hydroxystyrene, N, N-dimethylformamide, and azobisisobutyronitrile according to a mass ratio of 1: (2-3): (20-30): (0.01-0.02), heating to 75-85 DEG C and reacting for 5-6 h, filtering, washing, and drying to obtain pretreated silica; stirring the pretreated silica, tetrahydrofuran, phosphorus oxychloride, and pyridine at 0-5 DEG C for 2-3 h, filtering after stirring, and dispersing into 0.2 g / mL 3, 4-dinitrophenol-tetrahydrofuran solution, adding lithium chloride, heating to 50-60 DEG C, and reacting for 10-12 h under nitrogen protection, filtering, washing, and drying to obtain the pre-modified silica; the mass ratio of the pretreated silica, tetrahydrofuran, phosphorus oxychloride, pyridine, 3, 4-dinitrophenol, and lithium chloride is 1: (20-30): (1-2): (1-2): (2-3): (0.03-0.05).

6. A process for the preparation of a medium voltage fire resistant cable according to claim 1, characterized in that, The preparation method of the modified silica in step (5) is as follows: mixing the pre-modified silica, thiourea dioxide and 10wt% sodium bicarbonate aqueous solution according to the mass ratio of 1:(0.5-0.7):(20-30), heating to 70-80℃, and reacting for 5-6h, then filtering, washing and drying to obtain aminosilica; mixing the aminosilica, glyoxal and phosphate buffer solution with pH of 7.4 according to the mass ratio of 1:(2-3):(20-30) at room temperature for 2-3h, filtering and adding to a 0.2g / mL 2-((2-nitrobenzyl)thio)ethylamine-acetonitrile solution, wherein the mass of 2-((2-nitrobenzyl)thio)ethylamine is 2-3 times that of the aminosilica, and reacting for 10-12h under nitrogen protection and away from light, then filtering, washing and drying to obtain a modified silica precursor; placing the modified silica precursor in a quartz reactor, irradiating under a 365nm ultraviolet light source with a power of 50mW / cm 2 at 0-5℃ for 30-40min, and washing and drying to obtain the modified silica.

7. A method of manufacturing a medium voltage fire resistant cable according to claim 6, characterized in that, The preparation method of the 2-((2-nitrobenzyl)thio)ethylamine is as follows: mixing lithium hydroxide, pure water, ethanol, and cysteamine hydrochloride according to a mass ratio of 1:20:50:3 to obtain a mixed solution, mixing 2-nitrobenzyl bromide and ethanol according to a mass ratio of 1:20 to obtain a 2-nitrobenzyl bromide solution, adding the 2-nitrobenzyl bromide solution into the mixed solution at a speed of 1 mL / min, stirring for 40 min at 30-35 DEG C after the addition is completed, extracting with dichloromethane, drying with anhydrous sodium sulfate, filtering, and concentrating to obtain 2-((2-nitrobenzyl)thio)ethylamine.

8. A medium voltage fire resistant cable prepared according to the preparation method of the medium voltage fire resistant cable in any one of claims 1-7.

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