Preparation process of high-strength halogen-free flame-retardant electric wire

Abstract

The application relates to the technical field of electric wire materials, in particular to a preparation process of high-strength halogen-free flame-retardant electric wire. The polyolefin flame-retardant microspheres are obtained by adding propylene cyclotriphosphazene, propylene phosphaphenanthrene, methyl methacrylate, peroxide dodecanoyl, polyvinyl alcohol and deionized water. The flame-retardant modified boron nitride nanosheet is obtained by adding hydroxylated boron nitride, gamma-glycidyl ether oxygen propyl trimethoxysilane and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. The high-strength halogen-free flame-retardant protective sleeve is obtained by mixing and reacting ethylene-vinyl acetate copolymer, the polyolefin flame-retardant microspheres, the flame-retardant modified boron nitride nanosheet, an antioxidant and a lubricant. The finished product is obtained by wrapping the high-strength halogen-free flame-retardant protective sleeve around a copper core wire. The finished product prepared by the application has excellent flame-retardant performance and high strength, so the application has a wide application prospect in the technical field of electric wire materials.

Description

Technical Field

[0001] The invention relates to the technical field of wire materials, in particular to a preparation process of high-strength halogen-free flame-retardant wires. Background Art

[0002] In modern society, electrical wires, as a crucial medium for power and information transmission, have permeated every sector, becoming a key element in driving social development and ensuring quality of life. From an energy transmission perspective, electrical wires carry electricity from generators to substations, and then, via a high-voltage power line network, transmit electricity to every corner of cities and villages, powering industrial production. In homes, electrical wires connect a variety of appliances, enabling modern living, such as lighting, refrigeration, and cooking, and improving comfort and convenience. Electrical wires also play an indispensable role in information and communications. Network cables, as a type of electrical wire, are a crucial channel for internet data transmission. They enable people everywhere to communicate and access information in real time, promoting the dissemination and sharing of knowledge. Fiber optic cables, with their high-speed, high-capacity information transmission capabilities, underpin modern communications networks, making video calls and high-definition live streaming possible, bringing people closer together.

[0003] However, during the use of wires, high temperatures generated by overloads, short circuits, and other factors can easily cause fires. Therefore, it is necessary to prepare wires with excellent flame retardancy to effectively prevent the spread of fire when encountering a fire source, reducing the risk of fire and buying valuable time for evacuation and fire rescue. Furthermore, in actual use, wires are easily subjected to various external forces such as stretching, bending, and squeezing. If the wires are not strong enough, they are prone to breakage and damage, causing circuit failures and even safety accidents.

[0004] In order to overcome the defects of the prior art, the present invention provides a preparation process of a high-strength halogen-free flame-retardant electric wire. Summary of the Invention

[0005] The object of the present invention is to provide a preparation process of a high-strength halogen-free flame-retardant electric wire to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A process for preparing a high-strength halogen-free flame-retardant electric wire comprises the following steps:

[0008] Step 1: Mix propylene cyclotriphosphazene, propylene phosphaphenanthrene, methyl methacrylate, and lauroyl peroxide, and ultrasonically disperse for 8-10 minutes to obtain an oil phase; mix polyvinyl alcohol and deionized water, and stir evenly to obtain an aqueous phase; under a nitrogen environment, mix the oil phase and the aqueous phase, stir and disperse for 50-60 minutes, then heat to 70-75°C and react for 7-9 hours. After the reaction, filter, wash, and dry to obtain polyolefin flame retardant microspheres;

[0009] Step 2: adding boron nitride powder to a 4.5-5.5 mol / L sodium hydroxide solution, ultrasonically dispersing for 2-3 hours, and hydrothermally reacting at 180-190° C. for 20-25 hours after uniform dispersion to obtain hydroxylated boron nitride; then adding the hydroxylated boron nitride to a mixed solvent, ultrasonically dispersing for 2-3 hours, adjusting the pH to 4.0-4.5, and then adding γ-glycidyloxypropyltrimethoxysilane, stirring and reacting at 70-75° C. for 20-25 hours. After the reaction is completed, washing with alcohol, filtering, and drying to obtain modified boron nitride nanosheets; adding the modified boron nitride nanosheets and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to N,N-dimethylformamide, performing a ring-opening reaction at 120-130° C. for 5-8 hours, cooling, distilling under reduced pressure, washing, and drying to obtain flame-retardant modified boron nitride nanosheets;

[0010] Step 3: Mix ethylene-vinyl acetate copolymer, polyolefin flame retardant microspheres, and flame retardant modified boron nitride nanosheets, stir and dissolve them at 75-85°C for 20-30 minutes, then heat to 110-120°C and react for 3-4 hours to obtain a premix; then add an antioxidant and a lubricant, continue mixing and reacting for 20-30 minutes, and after the reaction is completed, perform extrusion granulation and melt extrusion to obtain a high-strength halogen-free flame retardant protective sleeve; wrap the high-strength halogen-free flame retardant protective sleeve around the copper core wire to obtain a finished product.

[0011] More optimally, in step 1, the preparation process of propylene-containing cyclotriphosphazene is as follows: mixing a vanillin solution and a p-phenylenediamine solution, reflux reacting at 70-75° C. for 9-12 hours, filtering after completion of the reaction, washing, and drying to obtain an intermediate product; adding the intermediate product and triethylamine to tetrahydrofuran, stirring and dissolving to obtain a reaction solution 1; adding hexachlorocyclotriphosphazene to tetrahydrofuran, stirring and dissolving to obtain a reaction solution 2; adding the reaction solution 2 dropwise to the reaction solution 1, heating to 60-65° C. after completion of the dropwise addition, continuing to stir and react for 45-50 hours, cooling, filtering, and distilling under reduced pressure to obtain a hydroxylated cyclotriphosphazene; adding the hydroxylated cyclotriphosphazene, glycidyl acrylate, and a catalyst 4-dimethylaminopyridine to N,N-dimethylformamide, performing a ring-opening reaction at 90-100° C. for 5-8 hours, cooling, distilling under reduced pressure, washing, and drying to obtain a propylene-containing cyclotriphosphazene.

[0012] More optimally, vanillin is dissolved in ethanol solvent to obtain a vanillin solution; p-phenylenediamine is dissolved in ethanol solvent to obtain a p-phenylenediamine solution; when preparing propylene cyclotriphosphazene, the reaction molar ratio of vanillin, p-phenylenediamine, hexachlorocyclotriphosphazene, and glycidyl acrylate is (2.2-2.4):1:0.16:(1.0-1.1).

[0013] More optimally, in step 1, the preparation process of propylene phosphaphenanthrene is as follows: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is added to dichloromethane, stirred to dissolve, and then 2,4-dihydroxybenzaldehyde is added, and the reaction is carried out at 80-85°C for 5-6 hours. After the reaction is completed, the mixture is cooled, rotary evaporated, washed, and dried to obtain hydroxylated phosphaphenanthrene; hydroxylated phosphaphenanthrene, glycidyl acrylate, and catalyst 4-dimethylaminopyridine are added to N,N-dimethylformamide, and a ring-opening reaction is carried out at 90-100°C for 5-8 hours. After the reaction is completed, the mixture is cooled, distilled under reduced pressure, washed, and dried to obtain propylene phosphaphenanthrene.

[0014] More optimally, when preparing propylene phosphaphenanthrene, the reaction molar ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 2,4-dihydroxybenzaldehyde, and glycidyl acrylate is 1:(1.2-1.3):(3-4).

[0015] More optimally, in step 1, when preparing polyolefin flame-retardant microspheres, the content of each component is: by mass, 15-20 parts of propylene cyclotriphosphazene, 15-20 parts of propylene phosphaphenanthrene, 20-25 parts of methyl methacrylate, 1-1.2 parts of lauroyl peroxide, 1-1.2 parts of polyvinyl alcohol, and 130-140 parts of deionized water.

[0016] More optimally, in step 2, the mixed solvent consists of ethanol and deionized water in a volume ratio of (1.0-1.2):2.

[0017] More optimally, in step 2, the reaction mass ratio of γ-glycidyloxypropyltrimethoxysilane, hydroxylated boron nitride, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is (5.0-5.5):1:(5.3-5.8).

[0018] More optimally, in step three, the contents of the components of the high-strength halogen-free flame-retardant protective cover are: in parts by mass, 110-130 parts of ethylene-vinyl acetate copolymer, 12-15 parts of polyolefin flame-retardant microspheres, 7-9 parts of flame-retardant modified boron nitride nanosheets, 3-5 parts of antioxidant, and 3-5 parts of lubricant; the lubricant is calcium stearate, and the antioxidant is antioxidant 1010.

[0019] Beneficial effects of the present invention:

[0020] The present invention is characterized in that, in step 1, two propylene flame retardants, propylene cyclotriphosphazene and propylene phosphaphenanthrene, are first prepared. The process for preparing the propylene cyclotriphosphazene is as follows: first, vanillin and p-phenylenediamine are added as reactants to cause a condensation reaction to obtain a hydroxyl-terminated intermediate product; then, the intermediate product is mixed with hexachlorocyclotriphosphazene to cause a substitution reaction to obtain hydroxylated cyclotriphosphazene; and finally, the hydroxylated cyclotriphosphazene and glycidyl acrylate are subjected to a ring-opening reaction under the action of a catalyst, 4-dimethylaminopyridine, to obtain the propylene cyclotriphosphazene.

[0021] The process for preparing propylene phosphaphenanthrene is as follows: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 2,4-dihydroxybenzaldehyde are first added to produce a nucleophilic addition reaction to obtain hydroxylated phosphaphenanthrene. The hydroxylated phosphaphenanthrene and glycidyl acrylate undergo a ring-opening reaction in the presence of a catalyst, 4-dimethylaminopyridine, to obtain propylene phosphaphenanthrene. Polyolefin flame-retardant microspheres are then prepared using propylene cyclotriphosphazene, propylene phosphaphenanthrene, methyl methacrylate, lauroyl peroxide, polyvinyl alcohol, and deionized water as raw materials.

[0022] The present invention is characterized in that, in step 2, flame-retardant modified boron nitride nanosheets are obtained by adding hydroxylated boron nitride, γ-glycidyloxypropyltrimethoxysilane, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. In this step, hydroxylated boron nitride is first modified with γ-glycidyloxypropyltrimethoxysilane, effectively improving the dispersibility of boron nitride. Then, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is added to react with epoxy groups to introduce a flame retardant, thereby obtaining flame-retardant modified boron nitride nanosheets.

[0023] The present invention is characterized in that, in step three, ethylene-vinyl acetate copolymer, polyolefin flame retardant microspheres, flame retardant modified boron nitride nanosheets, antioxidants and lubricants are mixed and reacted, and after the reaction is completed, the mixture is extruded and granulated and melt-extruded to obtain a high-strength halogen-free flame retardant protective sleeve; the high-strength halogen-free flame retardant protective sleeve is wrapped around the copper core wire to obtain a finished product. The finished product prepared by the present invention has excellent flame retardant properties: on the one hand, the polyolefin flame retardant microspheres and flame retardant modified boron nitride nanosheets have excellent flame retardant properties by introducing flame retardant structures such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 2,4-dihydroxybenzaldehyde, cyclotriphosphazene, and Schiff base; on the other hand, the present invention mixes the two flame retardant materials as raw materials and adds them to the protective sleeve. The polyolefin flame retardant microspheres and flame retardant modified boron nitride nanosheets can cooperate with each other in the material to exert a synergistic flame retardant effect. The microsphere structure creates a physical barrier and disperses heat at the macro level, while the layered boron nitride nanosheets build a barrier network and capture free radicals at the micro level. These interactions effectively inhibit the combustion reaction during combustion, improving the material's flame retardancy and achieving an excellent synergistic flame retardancy.

[0024] The finished product prepared by the present invention has good mechanical strength: the boron nitride nanosheets present a regular layered structure, which can effectively disperse stress when subjected to force, so that the external force is evenly distributed throughout the nanosheet, thereby improving the nanosheet's own ability to resist deformation and damage. In the process of preparing the protective cover, the flame-retardant modified boron nitride nanosheets are evenly dispersed in the ethylene-vinyl acetate copolymer matrix. When the material is subjected to external force, the nanosheets can effectively disperse stress and prevent the expansion of cracks. Because the nanosheets are small in size, they can form a large number of tiny interfaces in the matrix. These interfaces can hinder the movement of dislocations, forcing the material to overcome greater resistance when subjected to force and deformation, thereby effectively improving the strength of the material; therefore, by adding flame-retardant modified boron nitride nanosheets, the present invention can effectively improve the flame retardant properties and mechanical strength of the protective cover at the same time. DETAILED DESCRIPTION

[0025] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0026] Source of raw materials:

[0027] Polyvinyl alcohol, provided by Inner Mongolia Meiguan Environmental Protection Products Co., Ltd., model is industrial grade; boron nitride powder, provided by Qinhuangdao Yinuo High-tech Materials Development Co., Ltd., particle size is 10μm; ethylene-vinyl acetate copolymer, provided by Dongguan Tianming New Materials Co., Ltd., model is 7350M; in terms of mass, one part is 1g.

[0028] Example 1: Step 1: Vanillin solution and p-phenylenediamine solution were mixed, refluxed at 75°C for 12 hours, filtered, washed, and dried to obtain an intermediate product after the reaction was completed; the intermediate product and triethylamine were added to tetrahydrofuran, stirred and dissolved to obtain reaction solution 1; hexachlorocyclotriphosphazene was added to tetrahydrofuran, stirred and dissolved to obtain reaction solution 2; reaction solution 2 was added dropwise to reaction solution 1, and after the addition was completed, the temperature was raised to 65°C, and the stirring reaction was continued for 50 hours. After the reaction was completed, the mixture was cooled, filtered, and distilled under reduced pressure to obtain hydroxylated cyclotriphosphazene; the hydroxylated Cyclotriphosphazene, glycidyl acrylate, and catalyst 4-dimethylaminopyridine are added to N,N-dimethylformamide and a ring-opening reaction is carried out at 100°C for 8 hours. After the reaction, the mixture is cooled, distilled under reduced pressure, washed, and dried to obtain propylene-containing cyclotriphosphazene. Vanillin is dissolved in ethanol to obtain a vanillin solution. p-phenylenediamine is dissolved in ethanol to obtain a p-phenylenediamine solution. When preparing propylene-containing cyclotriphosphazene, the reaction molar ratio of vanillin, p-phenylenediamine, hexachlorocyclotriphosphazene, and glycidyl acrylate is 2.3:1:0.16:1.05.

[0029] 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is added to dichloromethane, stirred and dissolved, and then 2,4-dihydroxybenzaldehyde is added. The mixture is reacted at 85°C for 6 hours. After the reaction, the mixture is cooled, rotary evaporated, washed, and dried to obtain hydroxylated phosphaphenanthrene. The hydroxylated phosphaphenanthrene, glycidyl acrylate, and catalyst 4-dimethylaminopyridine are added to N,N-dimethylformamide, and a ring-opening reaction is carried out at 100°C for 8 hours. After the reaction, the mixture is cooled, distilled under reduced pressure, washed, and dried to obtain propyleneated phosphaphenanthrene. When preparing propyleneated phosphaphenanthrene, the reaction molar ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 2,4-dihydroxybenzaldehyde, and glycidyl acrylate is 1:1.25:3.5.

[0030] 20 g of propylene cyclotriphosphazene, 20 g of propylene phosphaphenanthrene, 25 g of methyl methacrylate, and 1.2 g of lauroyl peroxide were mixed and ultrasonically dispersed for 10 minutes to obtain an oil phase; 1.2 g of polyvinyl alcohol and 140 g of deionized water were mixed and stirred to obtain an aqueous phase; the oil phase and the aqueous phase were mixed under a nitrogen atmosphere, stirred and dispersed for 60 minutes, and then heated to 75°C for reaction for 9 hours. After the reaction, the mixture was filtered, washed, and dried to obtain polyolefin flame retardant microspheres;

[0031] Step 2: Add boron nitride powder to 5 mol / L sodium hydroxide solution, ultrasonically disperse for 3 hours, and then hydrothermally react at 190°C for 25 hours to obtain hydroxylated boron nitride; then add hydroxylated boron nitride to a mixed solvent, ultrasonically disperse for 3 hours, adjust the pH to 4.5, add γ-glycidyloxypropyltrimethoxysilane, and stir at 75°C for 25 hours. After the reaction, wash with alcohol, filter, and dry to obtain modified boron nitride nanosheets; the modified boron nitride nanosheets, 9,10-dihydro- 9-Oxa-10-phosphaphenanthrene-10-oxide was added to N,N-dimethylformamide and a ring-opening reaction was carried out at 130°C for 8 hours. After the reaction, the nanosheets were cooled, distilled under reduced pressure, washed, and dried to obtain flame-retardant modified boron nitride nanosheets. The mixed solvent consisted of ethanol and deionized water in a volume ratio of 1.1:2. The reaction mass ratio of γ-glycidyloxypropyltrimethoxysilane, hydroxylated boron nitride, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was 5.3:1:5.6.

[0032] Step 3: Mix 130g of ethylene-vinyl acetate copolymer, 15g of polyolefin flame retardant microspheres, and 9g of flame retardant modified boron nitride nanosheets, stir and dissolve at 85°C for 30 minutes, then heat to 120°C and react for 4 hours to obtain a premix; then add 5g of antioxidant 1010 and 5g of calcium stearate, continue mixing and reacting for 30 minutes, and after the reaction is completed, obtain a high-strength halogen-free flame retardant protective sleeve by extrusion granulation and melt extrusion; wrap the high-strength halogen-free flame retardant protective sleeve around the copper core wire to obtain a finished product.

[0033] Example 2: Step 1: Vanillin solution and p-phenylenediamine solution were mixed and refluxed at 73°C for 10 hours. After the reaction, the mixture was filtered, washed, and dried to obtain an intermediate product. The intermediate product and triethylamine were added to tetrahydrofuran, stirred and dissolved to obtain reaction solution 1. Hexachlorocyclotriphosphazene was added to tetrahydrofuran, stirred and dissolved to obtain reaction solution 2. Reaction solution 2 was added dropwise to reaction solution 1. After the addition was completed, the mixture was heated to 62°C and stirred for 47 hours. After the reaction was completed, the mixture was cooled, filtered, and distilled under reduced pressure to obtain hydroxylated cyclotriphosphazene. Hexachlorocyclotriphosphazene, glycidyl acrylate, and a catalyst, 4-dimethylaminopyridine, were added to N,N-dimethylformamide and subjected to a ring-opening reaction at 95°C for 6 hours. After completion of the reaction, the mixture was cooled, distilled under reduced pressure, washed, and dried to obtain propylene cyclotriphosphazene. Vanillin was dissolved in an ethanol solvent to obtain a vanillin solution. p-phenylenediamine was dissolved in an ethanol solvent to obtain a p-phenylenediamine solution. When preparing propylene cyclotriphosphazene, the reaction molar ratio of vanillin, p-phenylenediamine, hexachlorocyclotriphosphazene, and glycidyl acrylate was 2.3:1:0.16:1.05.

[0034] 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is added to dichloromethane, stirred and dissolved, and then 2,4-dihydroxybenzaldehyde is added. The mixture is reacted at 82°C for 5.5 hours. After the reaction, the mixture is cooled, rotary evaporated, washed, and dried to obtain hydroxylated phosphaphenanthrene. The hydroxylated phosphaphenanthrene, glycidyl acrylate, and catalyst 4-dimethylaminopyridine are added to N,N-dimethylformamide, and a ring-opening reaction is carried out at 95°C for 7 hours. After the reaction, the mixture is cooled, distilled under reduced pressure, washed, and dried to obtain propyleneated phosphaphenanthrene. When preparing propyleneated phosphaphenanthrene, the reaction molar ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 2,4-dihydroxybenzaldehyde, and glycidyl acrylate is 1:1.25:3.5.

[0035] 20 g of propylene cyclotriphosphazene, 20 g of propylene phosphaphenanthrene, 25 g of methyl methacrylate, and 1.2 g of lauroyl peroxide were mixed and ultrasonically dispersed for 9 minutes to obtain an oil phase; 1.2 g of polyvinyl alcohol and 140 g of deionized water were mixed and stirred to obtain an aqueous phase; the oil phase and the aqueous phase were mixed under a nitrogen atmosphere, stirred and dispersed for 55 minutes, and then heated to 73°C for reaction for 8 hours. After the reaction, the mixture was filtered, washed, and dried to obtain polyolefin flame retardant microspheres;

[0036] Step 2: Add boron nitride powder to 5 mol / L sodium hydroxide solution, ultrasonically disperse for 2.5 hours, and then hydrothermally react at 185°C for 23 hours to obtain hydroxylated boron nitride; then add hydroxylated boron nitride to a mixed solvent, ultrasonically disperse for 2.5 hours, adjust the pH to 4.3, add γ-glycidyloxypropyltrimethoxysilane, and stir at 72°C for 23 hours. After the reaction, wash with alcohol, filter, and dry to obtain modified boron nitride nanosheets; the modified boron nitride nanosheets and 9,10-dimethoxysilane are mixed. Hydrogen-9-oxa-10-phosphaphenanthrene-10-oxide was added to N,N-dimethylformamide and a ring-opening reaction was carried out at 125°C for 6 hours. After the reaction, the mixture was cooled, distilled under reduced pressure, washed, and dried to obtain flame-retardant modified boron nitride nanosheets. The mixed solvent consisted of ethanol and deionized water in a volume ratio of 1.1:2. The reaction mass ratio of γ-glycidyloxypropyltrimethoxysilane, hydroxylated boron nitride, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was 5.3:1:5.6.

[0037] Step three: Mix 130g of ethylene-vinyl acetate copolymer, 15g of polyolefin flame retardant microspheres, and 9g of flame retardant modified boron nitride nanosheets, stir and dissolve them at 80°C for 25 minutes, then heat to 115°C and react for 3.5 hours to obtain a premix; then add 5g of antioxidant 1010 and 5g of calcium stearate, continue mixing and reacting for 25 minutes, and after the reaction is completed, obtain a high-strength halogen-free flame retardant protective sleeve by extrusion granulation and melt extrusion; wrap the high-strength halogen-free flame retardant protective sleeve around the copper core wire to obtain a finished product.

[0038] Example 3: Step 1: Vanillin solution and p-phenylenediamine solution were mixed and refluxed at 70°C for 9 hours. After the reaction, the mixture was filtered, washed, and dried to obtain an intermediate product. The intermediate product and triethylamine were added to tetrahydrofuran, stirred and dissolved to obtain reaction solution 1. Hexachlorocyclotriphosphazene was added to tetrahydrofuran, stirred and dissolved to obtain reaction solution 2. Reaction solution 2 was added dropwise to reaction solution 1. After the addition was completed, the mixture was heated to 60°C and stirred for 45 hours. After the reaction was completed, the mixture was cooled, filtered, and distilled under reduced pressure to obtain hydroxylated cyclotriphosphazene. Cyclotriphosphazene, glycidyl acrylate, and a catalyst, 4-dimethylaminopyridine, were added to N,N-dimethylformamide and subjected to a ring-opening reaction at 90°C for 5 hours. After completion of the reaction, the mixture was cooled, distilled under reduced pressure, washed, and dried to obtain propylene-containing cyclotriphosphazene. Vanillin was dissolved in an ethanol solvent to obtain a vanillin solution. p-phenylenediamine was dissolved in an ethanol solvent to obtain a p-phenylenediamine solution. When preparing propylene-containing cyclotriphosphazene, the reaction molar ratio of vanillin, p-phenylenediamine, hexachlorocyclotriphosphazene, and glycidyl acrylate was 2.3:1:0.16:1.05.

[0039] 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is added to dichloromethane, stirred and dissolved, and then 2,4-dihydroxybenzaldehyde is added. The mixture is reacted at 80°C for 5 hours. After the reaction, the mixture is cooled, rotary evaporated, washed, and dried to obtain hydroxylated phosphaphenanthrene. The hydroxylated phosphaphenanthrene, glycidyl acrylate, and catalyst 4-dimethylaminopyridine are added to N,N-dimethylformamide, and a ring-opening reaction is carried out at 90°C for 5 hours. After the reaction, the mixture is cooled, distilled under reduced pressure, washed, and dried to obtain propyleneated phosphaphenanthrene. When preparing propyleneated phosphaphenanthrene, the reaction molar ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 2,4-dihydroxybenzaldehyde, and glycidyl acrylate is 1:1.25:3.5.

[0040] 20 g of propylene cyclotriphosphazene, 20 g of propylene phosphaphenanthrene, 25 g of methyl methacrylate, and 1.2 g of lauroyl peroxide were mixed and ultrasonically dispersed for 8 minutes to obtain an oil phase; 1.2 g of polyvinyl alcohol and 140 g of deionized water were mixed and stirred to obtain an aqueous phase; the oil phase and the aqueous phase were mixed under a nitrogen atmosphere, stirred and dispersed for 50 minutes, and then heated to 70°C for reaction for 7 hours. After the reaction, the mixture was filtered, washed, and dried to obtain polyolefin flame retardant microspheres;

[0041] Step 2: Add boron nitride powder to 5 mol / L sodium hydroxide solution, ultrasonically disperse for 2 hours, and then hydrothermally react at 180°C for 20 hours after uniform dispersion to obtain hydroxylated boron nitride; then add hydroxylated boron nitride to a mixed solvent, ultrasonically disperse for 2 hours, adjust the pH to 4.0, and then add γ-glycidyloxypropyltrimethoxysilane, stir and react at 70°C for 20 hours. After the reaction, wash with alcohol, filter, and dry to obtain modified boron nitride nanosheets; modify the boron nitride nanosheets, 9,10-dihydro- 9-Oxa-10-phosphaphenanthrene-10-oxide was added to N,N-dimethylformamide and a ring-opening reaction was carried out at 120°C for 5 hours. After the reaction, the nanosheets were cooled, distilled under reduced pressure, washed, and dried to obtain flame-retardant modified boron nitride nanosheets. The mixed solvent consisted of ethanol and deionized water in a volume ratio of 1.1:2. The reaction mass ratio of γ-glycidyloxypropyltrimethoxysilane, hydroxylated boron nitride, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was 5.3:1:5.6.

[0042] Step 3: Mix 130g of ethylene-vinyl acetate copolymer, 15g of polyolefin flame retardant microspheres, and 9g of flame retardant modified boron nitride nanosheets, stir and dissolve at 75°C for 20 minutes, then heat to 110°C and react for 3 hours to obtain a premix; then add 5g of antioxidant 1010 and 5g of calcium stearate, continue mixing and reacting for 20 minutes, and after the reaction is completed, obtain a high-strength halogen-free flame retardant protective sheath by extrusion granulation and melt extrusion; wrap the high-strength halogen-free flame retardant protective sheath around the copper core wire to obtain a finished product.

[0043] Comparative Example 1: The polyolefin flame retardant microspheres were removed, and the rest were the same as in Example 1, and the specific steps were as follows: Step 1: Add boron nitride powder to 5 mol / L sodium hydroxide solution, ultrasonically disperse for 3 hours, and after uniform dispersion, hydrothermally react at 190°C for 25 hours to obtain hydroxylated boron nitride; then add hydroxylated boron nitride to a mixed solvent, ultrasonically disperse for 3 hours, adjust the pH to 4.5, and then add γ-glycidyloxypropyltrimethoxysilane, stir and react at 75°C for 25 hours. After the reaction, wash with alcohol, filter, and dry to obtain modified boron nitride nanosheets; Flame-retardant modified boron nitride nanosheets were prepared by adding hydroxylated boron nitride nanosheets and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to N,N-dimethylformamide, and a ring-opening reaction was carried out at 130°C for 8 hours. After the reaction, the nanosheets were cooled, distilled under reduced pressure, washed, and dried to obtain flame-retardant modified boron nitride nanosheets. The mixed solvent consisted of ethanol and deionized water in a volume ratio of 1.1:2. The reaction mass ratio of γ-glycidyloxypropyltrimethoxysilane, hydroxylated boron nitride, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was 5.3:1:5.6.

[0044] Step 2: Mix 130g of ethylene-vinyl acetate copolymer and 9g of flame-retardant modified boron nitride nanosheets, stir and dissolve them at 85°C for 30 minutes, then heat to 120°C and react for 4 hours to obtain a premix; then add 5g of antioxidant 1010 and 5g of calcium stearate, continue mixing and reacting for 30 minutes, and after the reaction is completed, obtain a high-strength halogen-free flame-retardant protective sleeve by extrusion granulation and melt extrusion; wrap the high-strength halogen-free flame-retardant protective sleeve around the copper core wire to obtain a finished product.

[0045] Comparative Example 2: The polyolefin flame retardant microspheres and flame retardant modified boron nitride nanosheets are removed, and the rest are the same as Example 1. The specific steps are as follows: Step 1: 130g of ethylene-vinyl acetate copolymer is stirred and dissolved at 85°C for 30 minutes, then heated to 120°C for reaction for 4 hours, and then 5g of antioxidant 1010 and 5g of calcium stearate are added, and the mixing reaction is continued for 30 minutes. After the reaction is completed, it is extruded and granulated, and melt-extruded to obtain a protective sheath; the protective sheath is wrapped around the copper core wire to obtain a finished product.

[0046] Oxygen index test: Referring to GB / T 2406.2-2009 "Plastics - Determination of Combustion Behavior by Oxygen Index Method - Part 2: Room Temperature Test", the protective covers prepared in the examples or comparative examples of the present invention were used as samples with a sample size of 90 × 10 × 4 mm, and the oxygen index value was recorded.

[0047] Vertical burning test (UL-94): referring to ASTM D 3801, the flame retardancy rating of the sample was determined using the FFT008 instrument. The protective cover prepared in the embodiment or comparative example of the present invention was used as the sample. The sample size was 120×13×4 mm.

[0048] Mechanical properties test: Referring to GB / T 1040.2-2022 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics," the protective covers prepared in the examples or comparative examples of the present invention were used as specimens with a size of 160 × 10 × 4 mm. The tensile strength was recorded. The results are shown in the following table:

[0049]

[0050] Conclusion: The dosages used in Examples 1 to 3 remain unchanged, and only some reaction parameters are modified. The experimental data show that there is no significant fluctuation in the performance of the samples.

[0051] Comparative Example 1: The polyolefin flame retardant microspheres were removed, and the rest were the same as in Example 1. From the experimental data, it can be seen that compared with Example 1, the oxygen index was reduced to 24.9%, and the flame retardant grade became V-1. The reason for this is that the polyolefin flame retardant microspheres contain a variety of flame retardant structures such as cyclotriphosphazene, Schiff base and other flame retardant structures, so they have excellent flame retardant properties. Therefore, after removing them, the oxygen index is reduced and the flame retardant grade is changed to V-1.

[0052] Comparative Example 2: The polyolefin flame retardant microspheres and flame retardant modified boron nitride nanosheets were removed, and the rest was the same as Example 1. From the experimental data, it can be seen that compared with Example 1, the oxygen index was reduced to 21.7%, the flame retardant grade was changed to V-2, and the tensile strength was reduced to 16.3 MPa. The reasons were analyzed as follows: Comparative Example 2 further removed the flame retardant modified boron nitride nanosheets on the basis of Comparative Example 1, so the flame retardant performance was further reduced. In addition, the boron nitride nanosheets uniformly dispersed in the ethylene-vinyl acetate copolymer matrix can effectively disperse stress and prevent crack expansion, thereby improving the strength of the material. Therefore, the tensile strength decreased significantly after removing them.

[0053] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include," "comprise," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0054] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A process for preparing a high-strength halogen-free flame-retardant electric wire, characterized by: The following steps are involved: Step 1: Mix propylene cyclotriphosphazene, propylene phosphaphenanthrene, methyl methacrylate, and lauroyl peroxide, and ultrasonically disperse for 8-10 minutes to obtain an oil phase; mix polyvinyl alcohol and deionized water, and stir evenly to obtain an aqueous phase; under a nitrogen environment, mix the oil phase and the aqueous phase, stir and disperse for 50-60 minutes, then heat to 70-75°C and react for 7-9 hours. After the reaction, filter, wash, and dry to obtain polyolefin flame retardant microspheres; Step 2: adding boron nitride powder to a 4.5-5.5 mol / L sodium hydroxide solution, ultrasonically dispersing for 2-3 hours, and hydrothermally reacting at 180-190° C. for 20-25 hours after uniform dispersion to obtain hydroxylated boron nitride; then adding the hydroxylated boron nitride to a mixed solvent, ultrasonically dispersing for 2-3 hours, adjusting the pH to 4.0-4.5, and then adding γ-glycidyloxypropyltrimethoxysilane, stirring and reacting at 70-75° C. for 20-25 hours. After the reaction is completed, washing with alcohol, filtering, and drying to obtain modified boron nitride nanosheets; adding the modified boron nitride nanosheets and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to N,N-dimethylformamide, performing a ring-opening reaction at 120-130° C. for 5-8 hours, cooling, distilling under reduced pressure, washing, and drying to obtain flame-retardant modified boron nitride nanosheets; Step 3: Ethylene-vinyl acetate copolymer, polyolefin flame retardant microspheres, and flame retardant modified boron nitride nanosheets are mixed, stirred and mixed at 75-85° C. for 20-30 minutes, and then heated to 110-120° C. for reaction for 3-4 hours to obtain a premix; an antioxidant and a lubricant are then added, and the mixture is mixed and reacted for 20-30 minutes. After the reaction is completed, the mixture is extruded and granulated, and then melt-extruded to obtain a high-strength halogen-free flame retardant protective cover; A high-strength halogen-free flame-retardant protective sheath is wrapped around the copper core wire to obtain a finished product; the contents of the components of the high-strength halogen-free flame-retardant protective sheath are: in parts by mass, 110-130 parts of ethylene-vinyl acetate copolymer, 12-15 parts of polyolefin flame-retardant microspheres, 7-9 parts of flame-retardant modified boron nitride nanosheets, 3-5 parts of antioxidant, and 3-5 parts of lubricant; the lubricant is calcium stearate, and the antioxidant is antioxidant 1010.

2. The process for preparing a high-strength halogen-free flame-retardant electric wire according to claim 1, characterized in that: In step 1, the preparation process of propylene cyclotriphosphazene is as follows: mixing a vanillin solution and a p-phenylenediamine solution, reflux reacting at 70-75° C. for 9-12 hours, filtering after the reaction, washing, and drying to obtain an intermediate product; adding the intermediate product and triethylamine to tetrahydrofuran, stirring and dissolving to obtain a reaction solution 1; adding hexachlorocyclotriphosphazene to tetrahydrofuran, stirring and dissolving to obtain a reaction solution 2; adding the reaction solution 2 dropwise to the reaction solution 1, heating to 60-65° C. after the addition is completed, continuing to stir and react for 45-50 hours, cooling, filtering, and distilling under reduced pressure to obtain a hydroxylated cyclotriphosphazene; adding the hydroxylated cyclotriphosphazene, glycidyl acrylate, and catalyst 4-dimethylaminopyridine to N,N-dimethylformamide, performing a ring-opening reaction at 90-100° C. for 5-8 hours, cooling, distilling under reduced pressure, washing, and drying to obtain a propylene cyclotriphosphazene.

3. The process for preparing a high-strength halogen-free flame-retardant electric wire according to claim 2, characterized in that: Vanillin is dissolved in an ethanol solvent to obtain a vanillin solution; p-phenylenediamine is dissolved in an ethanol solvent to obtain a p-phenylenediamine solution; when preparing propylene cyclotriphosphazene, the reaction molar ratio of vanillin, p-phenylenediamine, hexachlorocyclotriphosphazene, and glycidyl acrylate is (2.2-2.4):1:0.16:(1.0-1.1).

4. The process for preparing a high-strength halogen-free flame-retardant electric wire according to claim 1, characterized in that: In step 1, the preparation process of propylene phosphaphenanthrene is as follows: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is added to dichloromethane, stirred to dissolve, and then 2,4-dihydroxybenzaldehyde is added, and the reaction is carried out at 80-85°C for 5-6 hours. After the reaction is completed, the mixture is cooled, rotary evaporated, washed, and dried to obtain hydroxylated phosphaphenanthrene; hydroxylated phosphaphenanthrene, glycidyl acrylate, and catalyst 4-dimethylaminopyridine are added to N,N-dimethylformamide, and a ring-opening reaction is carried out at 90-100°C for 5-8 hours. After the reaction is completed, the mixture is cooled, distilled under reduced pressure, washed, and dried to obtain propylene phosphaphenanthrene.

5. The process for preparing a high-strength halogen-free flame-retardant electric wire according to claim 4, characterized in that: When preparing propylene phosphaphenanthrene, the reaction molar ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 2,4-dihydroxybenzaldehyde and glycidyl acrylate is 1:(1.2-1.3):(3-4).

6. The process for preparing a high-strength halogen-free flame-retardant electric wire according to claim 1, characterized in that: In step 1, when preparing polyolefin flame-retardant microspheres, the contents of the components are as follows: by mass: 15-20 parts of propylene cyclotriphosphazene, 15-20 parts of propylene phosphaphenanthrene, 20-25 parts of methyl methacrylate, 130-140 parts of deionized water, 1-1.2 parts of polyvinyl alcohol, and 1-1.2 parts of lauroyl peroxide.

7. The process for preparing a high-strength halogen-free flame-retardant electric wire according to claim 1, characterized in that: In step 2, the mixed solvent consists of ethanol and deionized water in a volume ratio of (1.0-1.2):

2.

8. The process for preparing a high-strength halogen-free flame-retardant electric wire according to claim 1, characterized in that: In step 2, the reaction mass ratio of γ-glycidyloxypropyltrimethoxysilane, hydroxylated boron nitride, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is (5.0-5.5):1:(5.3-5.8).

9. A high-strength halogen-free flame-retardant electric wire, characterized in that: Prepared according to the preparation process according to any one of claims 1 to 8.

Images