Composite flame-retardant cable sheath material for middle-high voltage cable and preparation method of composite flame-retardant cable sheath material

Abstract

The invention relates to the field of cable sheath materials, in particular to a composite flame-retardant cable sheath material for medium and high voltage cables and a preparation method thereof, and aims to solve the problem that the safety of an electric power system is seriously threatened due to the fact that an existing cable sheath material belongs to a flammable material and is difficult to meet the high fireproof requirement. The nitrided phytic acid chelated barium compound and the boron-containing silica sol are reasonably compounded to serve as the composite flame retardant, both the nitrided phytic acid chelated barium compound and the boron-containing silica sol have excellent flame retardant performance, the composite flame retardant is added into the cable sheath material, and under the two synergistic flame retardant effects, the flame retardant performance of the cable sheath material can be remarkably improved; according to the cable sheath material, the fire occurrence and diffusion risks are effectively reduced, the safety and reliability of a cable system are improved, and the preparation process of the cable sheath material is simple and controllable, is suitable for industrial large-scale production, and has a good application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cable sheath materials, in particular to a composite flame-retardant cable sheath material for medium and high voltage cables and a preparation method thereof. BACKGROUND

[0002] As a key equipment for power transmission, medium and high voltage cables are widely used in urban power grids, rail transit, energy and chemical industries. However, due to the high working voltage, once a short circuit or overload occurs, it is easy to cause a fire. However, the traditional cable sheath material is flammable, which often cannot meet the high fireproofing requirements, which poses a serious threat to the safety of the power system. Therefore, it is of great significance to develop a composite flame-retardant cable sheath material for medium and high voltage cables and a preparation method thereof for improving the safety and stability of the power system.

[0003] In view of the above technical defects, a solution is proposed. SUMMARY

[0004] In order to overcome the above technical problems, the purpose of the present application is to provide a composite flame-retardant cable sheath material for medium and high voltage cables and a preparation method thereof, which solves the problem that the existing cable sheath material is flammable and cannot meet the high fireproofing requirements, which poses a serious threat to the safety of the power system.

[0005] The purpose of the present application can be realized by the following technical solutions: In a first aspect, the present application provides a composite flame-retardant cable sheath material for medium and high voltage cables, comprising the following components by weight: polyethylene resin 72-76 parts, ethylene-vinyl acetate copolymer 21-25 parts, composite flame-retardant material 1.5-5.5 parts, lubricant 0.5-1.1 parts, plasticizer 4-8 parts, antioxidant 1-3 parts, ultraviolet absorber 0.3-0.5 parts and light stabilizer 0.6-1 part; The composite flame-retardant material comprises a nitrogenated phytic acid chelated barium compound and a boron-containing silica sol. The nitrogenated phytic acid chelated barium compound is prepared by the following steps: Step a1: phytic acid solution and 2-bromoethanol are added to a three-necked flask equipped with a stirrer, a thermometer and a gas inlet tube, nitrogen is introduced for protection, stirring is carried out at a temperature of 20-25 DEG C and a stirring speed of 200-300 r / min for 10-20 min, then the temperature is raised to 130-140 DEG C and the stirring is continued for 3-5 h, after the reaction is completed, the reaction product is cooled to room temperature, and then placed in a vacuum drying oven and dried at a temperature of 50-60 DEG C for 3-5 h to obtain brominated phytic acid; Step a2: the brominated phytic acid, 5-amino tetrazole, triethylamine and ethanol solution are added into a three-necked flask equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser, and then nitrogen is introduced for protection, and the reaction is stirred at a temperature of 20-25 DEG C and a stirring speed of 200-300 r / min for 10-20 min, and then the temperature is increased to the refluxing temperature, and the reaction is continuously stirred for 3-5 h, and then the reaction product is cooled to room temperature, and then vacuum filtration is carried out, and the filtrate is rotary evaporated to remove the solvent, and then washed with anhydrous ethanol for 3-5 times, and then placed in a vacuum drying oven, and dried at a temperature of 60-70 DEG C for 2-3 h to obtain the nitrogenated phytic acid; Step a3: the nitrogenated phytic acid and deionized water are added into a three-necked flask equipped with a stirrer, a thermometer, a gas inlet tube and a constant pressure dropping funnel, and then nitrogen is introduced for protection, and the reaction is stirred at a temperature of 20-25 DEG C and a stirring speed of 200-300 r / min for 20-30 min, and then the temperature is increased to 80-85 DEG C, and the reaction is continuously stirred for 3-5 min, and then the barium chloride solution is added drop by drop while stirring, and the dropping speed is controlled to be 1-3 drops / s, and after the addition is completed, the reaction is continuously stirred for 4-6 h, and then the reaction product is cooled to room temperature, and then vacuum filtration is carried out, and the filter cake is washed with distilled water for 3-5 times, and then placed in a vacuum drying oven, and dried at a temperature of 60-70 DEG C for 5-6 h to obtain the nitrogenated phytic acid barium chelate compound.

[0006] As a preferred embodiment of the present application, the use amount ratio of the phytic acid solution and 2-bromoethanol in step a1 is 20 g:1.2-3.5 g.

[0007] As a preferred embodiment of the present application, the mass fraction of the phytic acid solution in step a1 is 60-70%.

[0008] As a preferred embodiment of the present application, the use amount ratio of the brominated phytic acid, 5-amino tetrazole, triethylamine and ethanol solution in step a2 is 10 g:0.7-1.9 g:40-50 mmol:70-80 mL.

[0009] As a preferred embodiment of the present application, the volume fraction of the ethanol solution in step a2 is 50-70%.

[0010] As a preferred embodiment of the present application, the use amount ratio of the nitrogenated phytic acid, deionized water and barium chloride solution in step a3 is 10 g:50-60 mL:90-100 mL.

[0011] As a preferred embodiment of the present application, the barium chloride solution in step a3 is a solution formed by dissolving barium chloride in deionized water at a ratio of 3-7 g:50-55 mL.

[0012] As a preferred embodiment of the present application, the boron-containing silica sol is prepared by the following steps: The tetraethoxysilane, boric acid and anhydrous ethanol are added to a three-necked flask equipped with a stirrer, a thermometer, a gas inlet tube and a constant-pressure dropping funnel, and nitrogen is introduced for protection. The mixture is stirred at a temperature of 20-25℃ and a stirring speed of 200-300r / min for 10-15min, and then the temperature is raised to 70-75℃ and the stirring is continued for 3-5h. Then the hydrochloric acid solution is added dropwise while stirring, and the dropping speed is controlled at 1-3 drops / s. After the addition is completed, the temperature is raised to 80-85℃ and the stirring is continued for 2-3h. After the reaction is completed, the reaction product is cooled to room temperature to obtain the boron-containing silica sol.

[0013] As a preferred embodiment of the present application, the amounts of the tetraethoxysilane, boric acid, anhydrous ethanol and hydrochloric acid solution are 45-50mL:2-5g:18-20mL:5-5.5mL.

[0014] As a preferred embodiment of the present application, the molar concentration of the hydrochloric acid solution is 0.01-0.05mol / L.

[0015] In a second aspect, the application provides a preparation method of a composite flame-retardant cable sheath material for medium and high voltage cables, comprising the following steps: Step one: the polyethylene resin 72-76 parts, ethylene-vinyl acetate copolymer 21-25 parts, composite flame-retardant material 1.5-5.5 parts, lubricant 0.5-1.1 parts, plasticizer 4-8 parts, antioxidant 1-3 parts, ultraviolet absorber 0.3-0.5 parts and light stabilizer 0.6-1 part are weighed according to the weight parts, and are prepared for use. Step two: the polyethylene resin, ethylene-vinyl acetate copolymer, composite flame-retardant material, lubricant, plasticizer, antioxidant, ultraviolet absorber and light stabilizer are added to a high-speed mixer, and are stirred and mixed at a temperature of 60-80℃ and a stirring speed of 700-1500r / min for 10-30min to obtain a premix. Step three: the premix is added to a twin-screw extruder, and is melt-mixed at a screw rotation speed of 100-150r / min and temperatures of 155-165℃, 165-175℃, 175-185℃, 185-195℃ and 180-190℃ in the five temperature zones along the material conveying direction. After extrusion, water cooling and granulation, the composite flame-retardant cable sheath material for medium and high voltage cables is obtained.

[0016] As a preferred embodiment of the present application, the polyethylene resin is LLDPE 318BJ.

[0017] As a preferred embodiment of the present application, the ethylene-vinyl acetate copolymer is EVA V5110J.

[0018] As a preferred embodiment of the present application, the composite flame-retardant fuel is a mixture of a barium phytate chelate nitride compound and a boron-containing silica sol in a mass ratio of 0.9-3.5:7.

[0019] As a preferred embodiment of the present application, the lubricant is ethylene bis-stearamide.

[0020] As a preferred embodiment of the present application, the plasticizer is epoxidized soybean oil.

[0021] As a preferred embodiment of the present application, the antioxidant is a mixture of antioxidant 1010 and antioxidant 2246-S in a mass ratio of 1-2:0.8.

[0022] As a preferred embodiment of the present application, the ultraviolet absorber is ultraviolet absorber UV-531.

[0023] As a preferred embodiment of the present application, the light stabilizer is light stabilizer Tinuvin 788.

[0024] Compared with the prior art, the present application has the following beneficial effects: The present application mixes polyethylene resin, ethylene-vinyl acetate copolymer, composite flame-retardant fuel, lubricant, plasticizer, antioxidant, ultraviolet absorber and light stabilizer by stirring to obtain a premix, melts and mixes the premix, and then extrudes, water-cools and granulates to obtain a composite flame-retardant cable sheath material for medium and high voltage cables. The present application uses a barium phytate chelate nitride compound and a boron-containing silica sol as a composite flame retardant by reasonable compounding. Both of them have excellent flame-retardant properties. The composite flame retardant is added to the cable sheath material, which can significantly improve the flame-retardant properties of the cable sheath material under the synergistic flame-retardant effect, effectively reduces the risk of fire occurrence and spread, and improves the safety and reliability of the cable system. Moreover, the preparation process of the cable sheath material is simple and controllable, suitable for large-scale industrial production, and has good application prospect.

[0025] In the process of preparing the cable sheath material, a nitridated phytic acid chelated barium compound is first prepared. The phytic acid is reacted with 2-bromoethanol, the phosphate groups on the phytic acid are esterified with the hydroxyl groups on the 2-bromoethanol, and at the same time, bromine atoms are introduced to obtain brominated phytic acid. The brominated phytic acid is reacted with 5-amino tetrazole, the bromine atoms and the phosphate groups on the brominated phytic acid can both react with the amino groups on the 5-amino tetrazole, thereby introducing a large amount of nitrogen elements into the structure of the phytic acid to obtain nitridated phytic acid. Then, the phosphate groups on the nitridated phytic acid are used to form a chelate with barium ions, thereby grafting the barium ions onto the phytic acid structure to obtain the nitridated phytic acid chelated barium compound. The nitridated phytic acid chelated barium compound contains a large amount of phosphorus elements in the molecular structure, which generates phosphoric acid, metaphosphoric acid and other substances at high temperatures, and the acid catalyzes the polymer to carbonize to form a carbon layer that is heat and oxygen insulated, thereby playing a flame-retardant role. At the same time, the molecular structure of the nitridated phytic acid chelated barium compound contains a large amount of nitrogen elements, and the inert gases such as nitrogen and ammonia generated by the thermal decomposition of the nitrogen elements can dilute the oxygen concentration in the combustion area, thereby playing a flame-retardant role. At the same time, the molecular structure of the nitridated phytic acid chelated barium compound contains a large amount of barium metal ions, which has the ability to catalyze the carbonization of the combustion material, and can form a continuous and dense carbon layer with high graphitization degree and structural stability. Therefore, under the synergistic action of the phosphorus elements, the nitrogen elements and the barium metal ions, the nitridated phytic acid chelated barium compound has excellent flame-retardant properties, and when it is added to the cable sheath material, the cable sheath material can have high flame-retardant effect.

[0026] In the process of preparing the cable sheath material, a boron-containing silica sol is also prepared. The boron-containing silica sol is synthesized by a sol-gel method using tetraethoxysilane as a silicon source and boric acid as a boron source. The boron-containing silica sol forms silicon-boron composite glassy substances at high temperatures, which can be filled into the voids of the carbon layer to significantly improve the oxidation resistance and structural stability of the carbon layer, and can also form a dense ceramic protective layer to effectively block the transfer of heat and oxygen to the inside of the material. When the boron-containing silica sol is added to the cable sheath material, it can inhibit the thermal decomposition and combustion of the high molecular material at high temperatures, slow down the spread of the fire, and significantly improve the flame-retardant properties of the cable sheath material. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical scheme of the present application, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a 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.

[0028] Embodiment 1: This embodiment is a preparation method of a composite flame-retardant cable sheath material for medium and high voltage cables, which comprises the following steps: Step S1: 20 g of a phytic acid solution with a mass fraction of 60%, 1.2 g of 2-bromoethanol were added to a three-necked flask equipped with a stirrer, a thermometer and a gas inlet tube, and protected by nitrogen, and stirred at a temperature of 20°C and a stirring speed of 200 r / min for 10 min, and then the temperature was raised to 130°C and the stirring was continued for 3 h. After the reaction was completed, the reaction product was cooled to room temperature, and then placed in a vacuum drying oven and dried at a temperature of 50°C for 3 h to obtain brominated phytic acid; Step S2: 10 g of brominated phytic acid, 0.7 g of 5-amino tetrazole, 40 mmol of triethylamine and 70 mL of an ethanol solution with a volume fraction of 50% were added to a three-necked flask equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser, and protected by nitrogen, and stirred at a temperature of 20°C and a stirring speed of 200 r / min for 10 min, and then the temperature was raised to reflux and the stirring was continued for 3 h. After the reaction was completed, the reaction product was cooled to room temperature, and then vacuum filtered, the filtrate was rotary evaporated to remove the solvent, and then washed with anhydrous ethanol for 3 times, and then placed in a vacuum drying oven and dried at a temperature of 60°C for 2 h to obtain nitrogenated phytic acid; Step S3: 10 g of nitrogenated phytic acid, 50 mL of deionized water were added to a three-necked flask equipped with a stirrer, a thermometer, a gas inlet tube and a constant pressure dropping funnel, and protected by nitrogen, and stirred at a temperature of 20°C and a stirring speed of 200 r / min for 20 min, and then the temperature was raised to 80°C and the stirring was continued for 3 min, and then 90 mL of barium chloride was added dropwise while stirring, the barium chloride solution was prepared by dissolving 3 g of barium chloride in 50 mL of deionized water, the dropping rate was controlled at 1 drop / s, and after the addition was completed, the stirring was continued for 4 h. After the reaction was completed, the reaction product was cooled to room temperature, and then vacuum filtered, the filter cake was washed with distilled water for 3 times, and then placed in a vacuum drying oven and dried at a temperature of 60°C for 5 h to obtain a nitrogenated phytic acid chelated barium compound; Step S4: 45 mL of tetraethoxysilane, 2 g of boric acid and 18 L of anhydrous ethanol were added to a three-necked flask equipped with a stirrer, a thermometer, a gas inlet tube and a constant pressure dropping funnel, and protected by nitrogen, and stirred at a temperature of 20°C and a stirring speed of 200 r / min for 10 min, and then the temperature was raised to 70°C and the stirring was continued for 3 h, and then 5 mL of a hydrochloric acid solution with a molar concentration of 0.01 mol / L was added dropwise while stirring, the dropping rate was controlled at 1 drop / s, and after the addition was completed, the temperature was raised to 80°C and the stirring was continued for 2 h. After the reaction was completed, the reaction product was cooled to room temperature to obtain a boron-containing silica sol; Step S5: 72 parts by weight of polyethylene resin, 21 parts by weight of ethylene-vinyl acetate copolymer, 1.5 parts by weight of composite flame retardant, 0.5 parts by weight of lubricant, 4 parts by weight of plasticizer, 1 part by weight of antioxidant, 0.3 parts by weight of ultraviolet absorber, and 0.6 parts by weight of light stabilizer were weighed and prepared; the polyethylene resin was LLDPE 318BJ; the ethylene-vinyl acetate copolymer was EVA V5110J; the composite flame retardant was a mixture of barium phytate chelate nitride compound and boron-containing silica sol in a mass ratio of 0.9:7; the lubricant was ethylene bis-stearamide; the plasticizer was epoxy soybean oil; the antioxidant was a mixture of antioxidant 1010 and antioxidant 2246-S in a mass ratio of 1:0.8; the ultraviolet absorber was ultraviolet absorber UV-531; and the light stabilizer was light stabilizer Tinuvin 788; Step S6: The polyethylene resin, ethylene-vinyl acetate copolymer, composite flame retardant, lubricant, plasticizer, antioxidant, ultraviolet absorber, and light stabilizer were added to a high-speed mixer and stirred and mixed at a temperature of 60°C and a speed of 700 r / min for 10 min to obtain a premix; Step S7: The premix was added to a twin-screw extruder and melt-mixed at a screw speed of 100 r / min and temperatures of 155°C, 165°C, 175°C, 185°C, and 180°C in the five temperature zones along the material conveying direction, and then extruded, water-cooled, and pelletized to obtain a composite flame-retardant cable sheath material for medium and high voltage cables.

[0029] Example 2: This example is a preparation method of a composite flame-retardant cable sheath material for medium and high voltage cables, comprising the following steps: Step S1: 20 g of a 65% mass fraction phytic acid solution and 2.3 g of 2-bromoethanol were added to a three-necked flask equipped with a stirrer, a thermometer, and a gas inlet tube, and protected by nitrogen, and stirred at a temperature of 22°C and a stirring speed of 250 r / min for 15 min, and then the temperature was increased to 135°C and the stirring was continued for 4 h. After the reaction was completed, the reaction product was cooled to room temperature, and then placed in a vacuum drying oven and dried at a temperature of 55°C for 4 h to obtain brominated phytic acid. Step S2: 10 g of brominated phytic acid, 1.3 g of 5-amino tetrazole, 45 mmol of triethylamine, and 75 mL of an ethanol solution with a volume fraction of 60% were added to a three-necked flask equipped with a stirrer, a thermometer, a gas inlet tube, and a reflux condenser, and the reaction was stirred for 15 min at a temperature of 22°C and a stirring rate of 250 r / min under nitrogen protection, and then the reaction was continued to be stirred for 4 h under reflux, and after the reaction was completed, the reaction product was cooled to room temperature, and then vacuum filtration was performed, the filtrate was rotary evaporated to remove the solvent, and then washed with anhydrous ethanol 4 times, and then placed in a vacuum drying oven and dried at a temperature of 65°C for 2.5 h to obtain nitrogenated phytic acid; Step S3: 10 g of nitrogenated phytic acid and 55 mL of deionized water were added to a three-necked flask equipped with a stirrer, a thermometer, a gas inlet tube, and a constant pressure dropping funnel, and the reaction was stirred for 25 min at a temperature of 22°C and a stirring rate of 250 r / min under nitrogen protection, and then the reaction was continued to be stirred for 4 min at a temperature of 82°C, and then 95 mL of barium chloride was added dropwise while stirring, and the barium chloride solution was formed by dissolving 5 g of barium chloride in 52 mL of deionized water, and the dropping rate was controlled at 2 drops / s, and after the addition was completed, the reaction was continued to be stirred for 5 h, and after the reaction was completed, the reaction product was cooled to room temperature, and then vacuum filtration was performed, the filter cake was washed with distilled water 4 times, and then placed in a vacuum drying oven and dried at a temperature of 65°C for 5.5 h to obtain a nitrogenated phytic acid chelated barium compound; Step S4: 48 mL of tetraethoxysilane, 3.5 g of boric acid, and 19 mL of anhydrous ethanol were added to a three-necked flask equipped with a stirrer, a thermometer, a gas inlet tube, and a constant pressure dropping funnel, and the reaction was stirred for 12 min at a temperature of 22°C and a stirring rate of 250 r / min under nitrogen protection, and then the reaction was continued to be stirred for 4 h at a temperature of 72°C, and then 5.2 mL of a 0.03 mol / L hydrochloric acid solution was added dropwise while stirring, and the dropping rate was controlled at 2 drops / s, and after the addition was completed, the reaction was continued to be stirred for 2.5 h at a temperature of 82°C, and after the reaction was completed, the reaction product was cooled to room temperature to obtain a boron-containing silica sol; Step S5: 74 parts by weight of polyethylene resin, 23 parts by weight of ethylene-vinyl acetate copolymer, 3.5 parts by weight of composite flame retardant, 0.8 parts by weight of lubricant, 6 parts by weight of plasticizer, 2 parts by weight of antioxidant, 0.4 parts by weight of ultraviolet absorber and 0.8 parts by weight of light stabilizer are weighed and prepared; the polyethylene resin is LLDPE 318BJ; the ethylene-vinyl acetate copolymer is EVA V5110J; the composite flame retardant is a mixture of barium phytate chelate nitride compound and boron-containing silica sol in a mass ratio of 2.2:7; the lubricant is ethylene bis-stearamide; the plasticizer is epoxy soybean oil; the antioxidant is a mixture of antioxidant 1010 and antioxidant 2246-S in a mass ratio of 1.5:0.8; the ultraviolet absorber is ultraviolet absorber UV-531; and the light stabilizer is light stabilizer Tinuvin 788; Step S6: the polyethylene resin, ethylene-vinyl acetate copolymer, composite flame retardant, lubricant, plasticizer, antioxidant, ultraviolet absorber and light stabilizer are added to a high-speed mixer and stirred and mixed at a temperature of 70°C and a speed of 1100 r / min for 20 min to obtain a premix; Step S7: the premix is added to a twin-screw extruder and melt-mixed at a screw speed of 125 r / min and temperatures of 160°C, 170°C, 180°C, 190°C and 185°C in the five temperature zones along the material conveying direction, and then extruded, water-cooled and pelletized to obtain a composite flame-retardant cable sheath material for medium and high voltage cables.

[0030] Example 3: This example is a preparation method of a composite flame-retardant cable sheath material for medium and high voltage cables, comprising the following steps: Step S1: 20 g of a 70% mass fraction phytic acid solution and 3.5 g of 2-bromoethanol are added to a three-necked flask equipped with a stirrer, a thermometer and a gas inlet tube, and protected by nitrogen, and stirred at a temperature of 25°C and a stirring speed of 300 r / min for 20 min, and then heated to 140°C and stirred for another 5 h, and then cooled to room temperature, and then placed in a vacuum drying oven and dried at a temperature of 60°C for 5 h to obtain brominated phytic acid; Step S2: 10 g of brominated phytic acid, 1.9 g of 5-amino tetrazole, 50 mmol of triethylamine, and 80 mL of an ethanol solution with a volume fraction of 70% were added to a three-necked flask equipped with a stirrer, a thermometer, a gas inlet tube, and a reflux condenser, and the reaction was stirred for 20 min at a temperature of 25°C and a stirring rate of 300 r / min under nitrogen protection, and then the reaction was continued to be stirred for 5 h under reflux, and after the reaction was completed, the reaction product was cooled to room temperature, and then vacuum filtration was performed, the filtrate was rotary evaporated to remove the solvent, and then washed with anhydrous ethanol for 5 times, and then placed in a vacuum drying oven for drying for 3 h at a temperature of 70°C, to obtain nitrogenated phytic acid; Step S3: 10 g of nitrogenated phytic acid and 60 mL of deionized water were added to a three-necked flask equipped with a stirrer, a thermometer, a gas inlet tube, and a constant pressure dropping funnel, and the reaction was stirred for 30 min at a temperature of 25°C and a stirring rate of 300 r / min under nitrogen protection, and then the reaction was continued to be stirred for 5 min at a temperature of 85°C, and then 100 mL of barium chloride was added dropwise while stirring, and the barium chloride solution was formed by dissolving 7 g of barium chloride in 55 mL of deionized water, and the dropping rate was controlled to be 3 drops / s, and after the dropping was completed, the reaction was continued to be stirred for 6 h, and after the reaction was completed, the reaction product was cooled to room temperature, and then vacuum filtration was performed, the filter cake was washed with distilled water for 5 times, and then placed in a vacuum drying oven for drying for 6 h at a temperature of 70°C, to obtain a nitrogenated phytic acid chelated barium compound; Step S4: 50 mL of tetraethoxysilane, 5 g of boric acid, and 20 mL of anhydrous ethanol were added to a three-necked flask equipped with a stirrer, a thermometer, a gas inlet tube, and a constant pressure dropping funnel, and the reaction was stirred for 15 min at a temperature of 25°C and a stirring rate of 300 r / min under nitrogen protection, and then the reaction was continued to be stirred for 5 h at a temperature of 75°C, and then 5.5 mL of a hydrochloric acid solution with a molar concentration of 0.05 mol / L was added dropwise while stirring, and the dropping rate was controlled to be 3 drops / s, and after the dropping was completed, the reaction was continued to be stirred for 3 h at a temperature of 85°C, and after the reaction was completed, the reaction product was cooled to room temperature, to obtain a boron-containing silica sol; Step S5: polyethylene resin 76 parts, ethylene-vinyl acetate copolymer 25 parts, composite flame retardant 5.5 parts, lubricant 1.1 parts, plasticizer 8 parts, antioxidant 3 parts, ultraviolet absorber 0.5 parts and light stabilizer 1 part are weighed according to weight parts for standby; the polyethylene resin is LLDPE 318BJ; the ethylene-vinyl acetate copolymer is EVA V5110J; the composite flame retardant is a mixture of nitrogenated phytic acid chelated barium compound and boron-containing silica sol in a mass ratio of 3.5:7; the lubricant is ethylene bis-stearamide; the plasticizer is epoxy soybean oil; the antioxidant is a mixture of antioxidant 1010 and antioxidant 2246-S in a mass ratio of 2:0.8; the ultraviolet absorber is ultraviolet absorber UV-531; the light stabilizer is light stabilizer Tinuvin 788; Step S6: the polyethylene resin, ethylene-vinyl acetate copolymer, composite flame retardant, lubricant, plasticizer, antioxidant, ultraviolet absorber and light stabilizer are added to a high-speed mixer, stirred and mixed at a temperature of 80℃ and a speed of 1500r / min for 30min to obtain a premix; Step S7: the premix is added to a twin-screw extruder, melt-mixed at a screw speed of 150r / min and temperatures of 165℃, 175℃, 185℃, 195℃ and 190℃ in the five temperature zones along the material conveying direction, extruded, water-cooled and pelletized to obtain a composite flame-retardant cable sheath material for medium and high voltage cables.

[0031] Comparative Example 1 The present comparative example is a preparation method of a composite flame-retardant cable sheath material for medium and high voltage cables, comprising the following steps: Step S1: polyethylene resin 76 parts, ethylene-vinyl acetate copolymer 25 parts, lubricant 1.1 parts, plasticizer 8 parts, antioxidant 3 parts, ultraviolet absorber 0.5 parts and light stabilizer 1 part are weighed according to weight parts for standby; the polyethylene resin is LLDPE 318BJ; the ethylene-vinyl acetate copolymer is EVA V5110J; the lubricant is ethylene bis-stearamide; the plasticizer is epoxy soybean oil; the antioxidant is a mixture of antioxidant 1010 and antioxidant 2246-S in a mass ratio of 2:0.8; the ultraviolet absorber is ultraviolet absorber UV-531; the light stabilizer is light stabilizer Tinuvin 788; Step S2: the polyethylene resin, ethylene-vinyl acetate copolymer, lubricant, plasticizer, antioxidant, ultraviolet absorber and light stabilizer are added to a high-speed mixer, stirred and mixed at a temperature of 80℃ and a speed of 1500r / min for 30min to obtain a premix; Step S3: the premix was added to a twin-screw extruder, and melt-mixed at a screw rotation speed of 150 r / min and temperatures of 165℃, 175℃, 185℃, 195℃ and 190℃ in the five temperature zones along the material conveying direction, and then extruded, water-cooled and pelletized to obtain the composite flame-retardant cable sheath material for medium and high voltage cables.

[0032] Comparative Example 2 The present comparative example is a preparation method of a composite flame-retardant cable sheath material for medium and high voltage cables, comprising the following steps: Step S1: 50 mL of tetraethoxysilane, 5 g of boric acid and 20 mL of anhydrous ethanol were added to a three-necked flask equipped with a stirrer, a thermometer, a gas inlet tube and a constant-pressure dropping funnel, and protected by nitrogen, and stirred at a temperature of 25℃ and a stirring speed of 300 r / min for 15 min, then heated to 75℃ and continued to stir for 5 h, then 5.5 mL of 0.05 mol / L hydrochloric acid solution was added dropwise while stirring, and the dropping rate was controlled at 3 drops / s, and after the addition was completed, the temperature was raised to 85℃ and the reaction was continued for 3 h, and then the reaction product was cooled to room temperature to obtain a boron-containing silica sol; Step S2: polyethylene resin 76 parts, ethylene-vinyl acetate copolymer 25 parts, boron-containing silica sol 5.5 parts, lubricant 1.1 parts, plasticizer 8 parts, antioxidant 3 parts, ultraviolet absorber 0.5 parts and light stabilizer 1 part were weighed according to the weight parts, and were ready for use; the polyethylene resin was LLDPE 318BJ; the ethylene-vinyl acetate copolymer was EVA V5110J; the lubricant was ethylene bis-stearamide; the plasticizer was epoxy soybean oil; the antioxidant was a mixture of antioxidant 1010 and antioxidant 2246-S in a mass ratio of 2:0.8; the ultraviolet absorber was ultraviolet absorber UV-531; and the light stabilizer was light stabilizer Tinuvin 788; Step S3: the polyethylene resin, ethylene-vinyl acetate copolymer, boron-containing silica sol, lubricant, plasticizer, antioxidant, ultraviolet absorber and light stabilizer were added to a high-speed mixer, and stirred and mixed at a temperature of 80℃ and a speed of 1500 r / min for 30 min to obtain a premix; Step S4: the premix was added to a twin-screw extruder, and melt-mixed at a screw rotation speed of 150 r / min and temperatures of 165℃, 175℃, 185℃, 195℃ and 190℃ in the five temperature zones along the material conveying direction, and then extruded, water-cooled and pelletized to obtain the composite flame-retardant cable sheath material for medium and high voltage cables.

[0033] Comparative Example 3 The present comparative example is a preparation method of a composite flame-retardant cable sheath material for medium and high voltage cables, comprising the following steps: Step S1: 20g of a phytic acid solution with a mass fraction of 70%, 3.5g of 2-bromoethanol are added to a three-necked flask equipped with a stirrer, a thermometer and a gas inlet tube, nitrogen is introduced for protection, stirring is carried out at a temperature of 25°C and a stirring rate of 300r / min for 20min, then the temperature is raised to 140°C and stirring is continued for 5h, after the reaction is completed, the reaction product is cooled to room temperature, then placed in a vacuum drying oven and dried at a temperature of 60°C for 5h, to obtain brominated phytic acid; Step S2: 10g of brominated phytic acid, 1.9g of 5-amino tetrazole, 50mmol of triethylamine and 80mL of an ethanol solution with a volume fraction of 70% are added to a three-necked flask equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser, nitrogen is introduced for protection, stirring is carried out at a temperature of 25°C and a stirring rate of 300r / min for 20min, then the temperature is raised to reflux and stirring is continued for 5h, after the reaction is completed, the reaction product is cooled to room temperature, then vacuum filtration is carried out, the filtrate is rotary evaporated to remove the solvent, then washed with anhydrous ethanol for 5 times, then placed in a vacuum drying oven and dried at a temperature of 70°C for 3h, to obtain nitrogenated phytic acid; Step S3: 10g of nitrogenated phytic acid, 60mL of deionized water are added to a three-necked flask equipped with a stirrer, a thermometer, a gas inlet tube and a constant pressure dropping funnel, nitrogen is introduced for protection, stirring is carried out at a temperature of 25°C and a stirring rate of 300r / min for 30min, then the temperature is raised to 85°C and stirring is continued for 5min, then 100mL of barium chloride is added dropwise while stirring, the barium chloride solution is formed by dissolving 7g of barium chloride in 55mL of deionized water, the dropping rate is controlled at 3 drops / s, after the addition is completed, stirring is continued for 6h, after the reaction is completed, the reaction product is cooled to room temperature, then vacuum filtration is carried out, the filter cake is washed with distilled water for 5 times, then placed in a vacuum drying oven and dried at a temperature of 70°C for 6h, to obtain a nitrogenated phytic acid chelated barium compound; Step S4: polyethylene resin 76 parts, ethylene-vinyl acetate copolymer 25 parts, nitrogenated phytic acid chelated barium compound 5.5 parts, lubricant 1.1 parts, plasticizer 8 parts, antioxidant 3 parts, ultraviolet absorber 0.5 parts and light stabilizer 1 part are weighed according to weight parts for standby; the polyethylene resin is LLDPE 318BJ; the ethylene-vinyl acetate copolymer is EVA V5110J; the lubricant is ethylene bis-stearamide; the plasticizer is epoxy soybean oil; the antioxidant is a mixture of antioxidant 1010 and antioxidant 2246-S in a mass ratio of 2:0.8; the ultraviolet absorber is ultraviolet absorber UV-531; the light stabilizer is light stabilizer Tinuvin 788; Step S5: polyethylene resin, ethylene-vinyl acetate copolymer, nitrogenated phytic acid chelated barium compound, lubricant, plasticizer, antioxidant, ultraviolet absorber and light stabilizer were added into a high-speed mixer, stirred and mixed at a temperature of 80℃ and a speed of 1500r / min for 30min to obtain a premix; Step S6: the premix was added into a twin-screw extruder, melt-mixed at a screw speed of 150r / min and temperatures of 165℃, 175℃, 185℃, 195℃ and 190℃ in the five temperature zones along the material conveying direction, extruded, water-cooled and pelletized to obtain the composite flame-retardant cable sheath material for medium and high voltage cables.

[0034] Comparative Example 4 The present comparative example is a preparation method of a composite flame-retardant cable sheath material for medium and high voltage cables, comprising the following steps: Step S1: 50mL of tetraethoxysilane, 5g of boric acid and 20mL of anhydrous ethanol were added into a three-necked flask equipped with a stirrer, a thermometer, a gas inlet tube and a constant-pressure dropping funnel, protected by nitrogen, stirred at a temperature of 25℃ and a stirring speed of 300r / min for 15min, then heated to 75℃ and continued to stir for 5h, then 5.5mL of hydrochloric acid solution with a molar concentration of 0.05mol / L was added dropwise while stirring, the dropping rate was controlled at 3 drops / s, after the addition was completed, the temperature was raised to 85℃ and the reaction was continued for 3h, then the reaction product was cooled to room temperature to obtain a boron-containing silica sol; Step S2: polyethylene resin 76 parts, ethylene-vinyl acetate copolymer 25 parts, composite flame retardant 5.5 parts, lubricant 1.1 parts, plasticizer 8 parts, antioxidant 3 parts, ultraviolet absorber 0.5 parts and light stabilizer 1 part were weighed according to the weight parts, and prepared for use; the polyethylene resin was LLDPE 318BJ; the ethylene-vinyl acetate copolymer was EVA V5110J; the composite flame retardant was a mixture of phytic acid and boron-containing silica sol with a mass ratio of 3.5:7; the lubricant was ethylene bis-stearamide; the plasticizer was epoxy soybean oil; the antioxidant was a mixture of antioxidant 1010 and antioxidant 2246-S with a mass ratio of 2:0.8; the ultraviolet absorber was ultraviolet absorber UV-531; the light stabilizer was light stabilizer Tinuvin 788; Step S3: polyethylene resin, ethylene-vinyl acetate copolymer, composite flame retardant, lubricant, plasticizer, antioxidant, ultraviolet absorber and light stabilizer were added into a high-speed mixer, stirred and mixed at a temperature of 80℃ and a speed of 1500r / min for 30min to obtain a premix; Step S4: the premix is added into the twin-screw extruder, and melt-mixed at a screw rotation speed of 150 r / min and temperatures of 165℃, 175℃, 185℃, 195℃ and 190℃ in the five temperature zones along the material conveying direction, and then extruded, water-cooled and pelletized to obtain the composite flame-retardant cable sheath material for medium and high voltage cables.

[0035] The composite flame-retardant cable sheath materials for medium and high voltage cables of Examples 1-3 and Comparative Examples 1-4 are tested for oxygen index according to the standard of ASTM D2863 and for UL-94 grade according to the standard of ASTM D3801, and the test results are shown in the following table: .

[0036] According to the comparison between Examples 1-3 and Comparative Examples 1-4, it can be seen from the data in the above table that the addition of the composite flame-retardant material containing the nitrogenated barium phytate chelate compound and the boron-containing silica sol to the cable sheath material can significantly improve the flame-retardant performance of the cable sheath material.

[0037] In the description of the present specification, the description referring to the terms "one embodiment", "an example", "a specific example" and the like means 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 application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0038] The above is only an example and description of the present application, and those skilled in the art can make various modifications or supplements or use similar ways to replace the described specific embodiments, as long as they do not deviate from the invention or exceed the scope defined in the present application, which shall be within the protection scope of the present application.

Claims

1. A composite flame-retardant cable jacket material for medium and high voltage cables, characterized in that, The following components by weight parts are included: polyethylene resin 72-76 parts, ethylene-vinyl acetate copolymer 21-25 parts, composite flame retardant 1.5-5.5 parts, lubricant 0.5-1.1 parts, plasticizer 4-8 parts, antioxidant 1-3 parts, ultraviolet absorber 0.3-0.5 parts, and light stabilizer 0.6-1 part; The composite flame retardant includes a nitrogenated phytic acid chelated barium compound and a boron-containing silica sol. The nitrogenated phytic acid chelated barium compound is prepared by the following steps: Step a1: stirring phytic acid solution and 2-bromoethanol, cooling the reaction product after the reaction, and then drying to obtain brominated phytic acid; Step a2: stirring brominated phytic acid, 5-amino tetrazole, triethylamine, and ethanol solution, cooling the reaction product after the reaction, vacuum filtration, rotary evaporation of the filtrate, and then washing and drying to obtain nitrogenated phytic acid; Step a3: stirring nitrogenated phytic acid and deionized water, adding barium chloride solution dropwise, continuing to stir, cooling the reaction product after the reaction, vacuum filtration, washing and drying the filter cake to obtain the nitrogenated phytic acid chelated barium compound.

2. A composite flame retardant cable jacket material for medium and high voltage cables according to claim 1, characterized in that, The amount ratio of the phytic acid solution and 2-bromoethanol in step a1 is 20g:1.2-3.5g; the mass fraction of the phytic acid solution is 60-70%.

3. A composite flame retardant cable jacket material for medium and high voltage cables according to claim 1, characterized in that, The amount ratio of the brominated phytic acid, 5-amino tetrazole, triethylamine, and ethanol solution in step a2 is 10g:0.7-1.9g:40-50mmol:70-80mL; the volume fraction of the ethanol solution is 50-70%.

4. A composite flame retardant cable jacket material for medium and high voltage cables according to claim 1, characterized in that, The amount ratio of the nitrogenated phytic acid, deionized water, and barium chloride solution in step a3 is 10g:50-60mL:90-100mL; the barium chloride solution is a solution formed by dissolving barium chloride in deionized water at 3-7g:50-55mL.

5. A composite flame retardant cable jacket material for medium and high voltage cables according to claim 1, characterized in that, The boron-containing silica sol is prepared by the following steps: Stirring tetraethoxysilane, boric acid, and anhydrous ethanol, adding hydrochloric acid solution dropwise, continuing to stir, and cooling the reaction product after the reaction to obtain the boron-containing silica sol.

6. A composite flame retardant cable jacket material for medium and high voltage cables according to claim 5, characterized in that, The amount ratio of the tetraethoxysilane, boric acid, anhydrous ethanol, and hydrochloric acid solution is 45-50mL:2-5g:18-20mL:5-5.5mL; the molar concentration of the hydrochloric acid solution is 0.01-0.05mol / L.

7. A process for the production of a composite flame-retardant cable sheath material for medium- and high-voltage cables as claimed in any of claims 1 to 6, characterized in that The following steps are included: Step one: weighing polyethylene resin 72-76 parts, ethylene-vinyl acetate copolymer 21-25 parts, composite flame retardant 1.5-5.5 parts, lubricant 0.5-1.1 parts, plasticizer 4-8 parts, antioxidant 1-3 parts, ultraviolet absorber 0.3-0.5 parts, and light stabilizer 0.6-1 part by weight parts, and reserving; Step two: adding polyethylene resin, ethylene-vinyl acetate copolymer, composite flame retardant, lubricant, plasticizer, antioxidant, ultraviolet absorber, and light stabilizer into a high-speed mixer, stirring and mixing at a temperature of 60-80℃ and a speed of 700-1500r / min for 10-30min to obtain a premix; Step three: the premix is added into the twin-screw extruder, melt-mixed at screw rotation speed of 100-150 r / min, temperature of five temperature zones along the material conveying direction is 155-165℃, 165-175℃, 175-185℃, 185-195℃, 180-190℃ respectively, extruded, water-cooled, and pelletized to obtain the composite flame-retardant cable sheath material for medium and high voltage cable.

8. A process for the preparation of a composite flame retardant cable jacketing material for medium and high voltage cables according to claim 7, characterized in that, The polyethylene resin is LLDPE 318BJ; The ethylene-vinyl acetate copolymer is EVA V5110J; The composite flame-retardant agent is a mixture of nitrogenated phytate chelated barium compound and boron-containing silica sol in a mass ratio of 0.9-3.5:7; The lubricant is ethylene bis-stearamide; The plasticizer is epoxidized soybean oil; The antioxidant is a mixture of antioxidant 1010 and antioxidant 2246-S in a mass ratio of 1-2:0.8; The ultraviolet absorber is ultraviolet absorber UV-531; The light stabilizer is light stabilizer Tinuvin 788.