Halogen-free flame-retardant B1-level fire-resistant wire and preparation method thereof

Abstract

The invention relates to the field of wire materials, in particular to a halogen-free flame-retardant B1-level fire-resistant wire and a preparation method thereof. The modified polyethylene resin is obtained by adding polyethylene, a hydrogen peroxide solution and a formic acid solution. And then adding olefin phosphaphenanthrene, trimethylolpropane-tri (3-mercaptopropionate), a mercapto branched unit, epoxy chloropropane, sodium hydroxide and tetramethylammonium bromide, and reacting to obtain the flame-retardant hyperbranched epoxy resin. The preparation method comprises the following steps: adding modified polyethylene resin, flame-retardant hyperbranched epoxy resin, a curing agent, 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, a lubricant and an antioxidant, carrying out a blending reaction, and then carrying out extrusion granulation and melt extrusion to obtain the insulating protective sleeve. And wrapping the copper core wire with the insulating protective sleeve to obtain a finished product. The prepared insulating protective sleeve has good mechanical property, flame retardant property and thermal safety performance, so that the insulating protective sleeve has a wide application prospect in the field of electric wire materials.

Description

Technical Field

[0001] The invention relates to the field of wire materials, in particular to a halogen-free flame-retardant B1-level fire-resistant wire and a preparation method thereof. Background Art

[0002] In the operation system of modern society, although wires look ordinary, they play a vital and irreplaceable role and have extremely great value. In the field of energy transmission, wires are the "high-speed channel" of electricity. Wires can efficiently and stably transmit the huge amount of electricity generated by power plants to every corner of the city. Whether it is high-rise buildings or remote villages, they cannot do without the energy transmission of wires. In the field of industrial automation, wires can also provide power and signal transmission for robots and automated production lines, greatly improving production efficiency and product quality.

[0003] However, traditional halogen-containing flame-retardant wires will release a large amount of toxic and corrosive hydrogen halide gas when burning, which can cause serious damage to the human respiratory tract and eyes, and can also corrode electronic equipment and building structures. Halogen-free flame-retardant wires produce less smoke when burning and do not release toxic hydrogen halide gas, which can buy more time for personnel evacuation and fire rescue, and reduce casualties and property losses in fires. In crowded places such as shopping malls, schools, hospitals, etc., the use of halogen-free flame-retardant wires can greatly improve the level of fire safety. In addition, wires will be subjected to various external forces during installation and use, such as stretching, bending, and extrusion. If the mechanical properties of the wires are not good, they are prone to breakage and damage, resulting in power transmission interruptions and even safety accidents. Therefore, wires with good mechanical properties can withstand greater tension and pressure, are not easy to deform and damage, and ensure the reliability and stability of the power system.

[0004] In order to overcome the defects of the prior art, the present invention provides a halogen-free flame-retardant B1-grade fire-resistant electric wire and a preparation method thereof. Summary of the invention

[0005] The object of the present invention is to provide a halogen-free flame-retardant B1-level fire-resistant electric wire and a preparation method thereof, so as 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 method for preparing a halogen-free flame-retardant B1-grade fire-resistant electric wire comprises the following steps:

[0008] Step 1: Mix polyethylene and xylene, stir and dissolve at 110 - 120°C for 1 - 2 h to obtain a polyethylene solution; then drop 30 - 35 wt% hydrogen peroxide solution and 85 - 90 wt% formic acid solution into the cooled polyethylene solution, and stir and react at 25 - 30°C for 10 - 15 h. After the reaction, wash, precipitate, remove the solvent under vacuum and dry to obtain a modified polyethylene resin;

[0009] Step 2: Mix a flame - retardant hyperbranched polymer, epichlorohydrin, sodium hydroxide, and tetramethylammonium bromide, stir and react at 65 - 70°C for 5 - 6 h. After the reaction, filter by suction, wash, and distill under reduced pressure to obtain a flame - retardant hyperbranched epoxy resin;

[0010] Step 3: Mix the modified polyethylene resin, the flame - retardant hyperbranched epoxy resin, a curing agent, and 9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide, stir and dissolve at 80 - 90°C for 20 - 30 min, then raise the temperature to 120 - 140°C and react for 2 - 3 h to obtain a premixed resin; then add a lubricant and an antioxidant, continue to mix and react for 20 - 30 min. After the reaction, extrude and pelletize, and then melt - extrude to obtain an insulating protective sleeve; wrap the insulating protective sleeve around the copper core wire to obtain the finished product.

[0011] Preferably, in Step 1, the reaction mass ratio of polyethylene, hydrogen peroxide solution, and formic acid is 10:(3.2 - 3.5):2.

[0012] Preferably, in Step 2, the reaction mass ratio of the flame - retardant hyperbranched polymer, epichlorohydrin, sodium hydroxide, and tetramethylammonium bromide is 5:(10 - 12):3:0.05.

[0013] Preferably, the preparation process of the flame - retardant hyperbranched polymer is as follows:

[0014] S1: Mix 10 - (2,5 - dihydroxyphenyl) - 10H - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide and N,N - dimethylformamide, stir at 80 - 85°C for 30 - 40 min, then add sodium hydroxide and stir for 70 - 80 min, then add 4 - vinylbenzyl chloride, cool to 70 - 75°C and stir and react for 6 - 7 h. After the reaction, filter by vacuum, precipitate, dry under vacuum, wash, and dry and grind to obtain an olefinated phosphaphenanthrene; mix diethanolamine and mercaptopropionic acid, stir and react at 70 - 75°C for 25 - 27 h. After the reaction, distill under reduced pressure to obtain a mercapto - branched unit;

[0015] S2: Mix phosphaphenanthrene olefination, trimethylolpropane tris(3-mercaptopropionate), and dimethyl sulfoxide, and stir and react at 25 - 30 °C for 25 - 30 h. After the reaction, wash, dry, and perform vacuum distillation to obtain an olefinated intermediate product; mix the olefinated intermediate product and dimethyl sulfoxide, fully stir and dissolve, then add a mercapto-branching unit and triethylamine, and stir and react at 50 - 55 °C for 70 - 75 h. After the reaction, wash, dry, and perform vacuum distillation to obtain a flame-retardant hyperbranched polymer.

[0016] More preferably, in step S1, when preparing phosphaphenanthrene olefination, the reaction molar ratio of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, sodium hydroxide, and 4-vinylbenzyl chloride is 1.5:4:(4.0 - 4.5); when preparing the mercapto-branching unit, the reaction molar ratio of diethanolamine and mercaptopropionic acid is 1:(1.2 - 1.4).

[0017] More preferably, in step S2, when preparing the flame-retardant hyperbranched polymer, the reaction molar ratio of phosphaphenanthrene olefination and trimethylolpropane tris(3-mercaptopropionate) is (2.0 - 2.3):1, and the reaction molar ratio of phosphaphenanthrene olefination and the mercapto-branching unit is (2.0 - 2.3):2.

[0018] More preferably, in step three, the content of each component of the insulating protective sleeve raw material is: by mass, 60 - 70 parts of modified polyethylene resin, 20 - 30 parts of flame-retardant hyperbranched epoxy resin, 7 - 15 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 8 - 10 parts of curing agent, 1 - 2 parts of lubricant, 0.5 - 1 part of antioxidant; the curing agent is ethylenediamine, the lubricant is calcium stearate, and the antioxidant is antioxidant 1010.

[0019] The beneficial effects of the present invention:

[0020] The characteristics of the present invention are that in step one, by adding polyethylene, hydrogen peroxide solution, and formic acid solution, a modified polyethylene resin is obtained. In this step, by controlling the reaction mass ratio of polyethylene, hydrogen peroxide solution, and formic acid to be 10:(3.2 - 3.5):2, a modified polyethylene resin modified by epoxidation is obtained. By epoxidizing polyethylene, an epoxy-active olefin resin can be obtained. When the olefin resin is blended with subsequent various substances, due to the presence of similar epoxy groups, it has good blending effects and comprehensive properties.

[0021] The characteristics of the present invention lie in that, in step two, by adding 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, 4-vinylbenzyl chloride, and N,N-dimethylformamide, a substitution reaction occurs to obtain an olefinated phosphaphenanthrene. By adding diethanolamine and mercaptopropionic acid, an amidation reaction occurs to obtain a mercapto-branched unit. Then, using the olefinated phosphaphenanthrene, trimethylolpropane tris(3-mercaptopropionate), and the mercapto-branched unit as the main raw materials, a thiol-ene click reaction occurs to obtain a flame-retardant hyperbranched polymer; then, the flame-retardant hyperbranched polymer, epichlorohydrin, sodium hydroxide, and tetramethylammonium bromide are mixed and reacted to introduce epoxy groups to obtain a flame-retardant hyperbranched epoxy resin.

[0022] In this step, by adding substances such as 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide and ethanolamine, a flame-retardant hyperbranched epoxy resin with an N-P skeleton is obtained. In this structure, due to the synergistic effect between the nitrogen element and the phosphorus element, during the flame-retardant process, the two cooperate with each other to more effectively inhibit the combustion process of the material. When the material burns, this synergistic effect can reduce the rate and total amount of heat release. At the same addition amount of the flame retardant, compared with the flame-retardant system containing only a single phosphorus element or nitrogen element, the flame-retardant hyperbranched epoxy resin of the present invention can significantly reduce the peak value of the heat release rate. This means that the material will not rapidly release a large amount of heat at the initial stage of combustion, slowing down the development speed of the fire and gaining more time for personnel evacuation and fire extinguishing work.

[0023] Meanwhile, during the entire combustion process, the total amount of heat release will also be significantly reduced. Because the N-P synergistic effect enhances the flame-retardant effect, making the material consume less energy during combustion and reducing the total heat released. Or when reaching the same flame-retardant grade, due to the existence of the N-P synergistic effect, the amount of flame retardant used can be reduced, and the material can still maintain a lower peak value of the heat release rate and total heat release amount. In addition, the large number of terminal groups and internal cavities of the hyperbranched structure ensure the uniform dispersion of the flame-retardant elements N and P in the material. This uniform dispersion enables the flame-retardant effect to be fully exerted in all parts of the material, avoiding abnormal local heat release caused by uneven local flame-retardant element concentration. No matter which part of the material contacts the fire source, it can promptly and effectively inhibit combustion, further reducing the peak value of the heat release rate and the total heat release amount, and improving the overall flame-retardant performance and thermal safety of the material.

[0024] The characteristics of the present invention are as follows. In step three, after premixing and reacting the modified polyethylene resin, flame-retardant hyperbranched epoxy resin, curing agent, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, a premixed resin is obtained; then a lubricant and an antioxidant are added, and after continuous mixing and reaction, extrusion granulation and melt extrusion are carried out to obtain an insulating protective sleeve; the insulating protective sleeve is wrapped around the copper core wire to obtain the finished product. In this step, the modified polyethylene resin, flame-retardant hyperbranched epoxy resin, curing agent, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are premixed and reacted. The P-H bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide reacts with the epoxy bonds of the two resins, and at the same time, the curing agent ethylenediamine begins to function to gradually crosslink the resin system, forming a premixed resin with good dispersion. Then a lubricant and an antioxidant are added, and after continuous mixing and crosslinking reaction, extrusion granulation and melt extrusion are carried out to obtain an insulating protective sleeve. The flame-retardant hyperbranched epoxy resin has both a highly branched structure and a rigid molecular chain, and also has an N-P synergistic flame-retardant structure. Therefore, after effectively blending the epoxy resin and the modified polyethylene resin through a chemical reaction, an insulating protective sleeve with good mechanical properties, flame-retardant properties, and thermal safety properties can be obtained, so it has broad application prospects in the field of wire materials. Specific embodiments

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] Source of raw materials:

[0027] Polyethylene, provided by Shanghai Yiqiang Plastic Technology Co., Ltd., model 1002YB (melting point 110 - 115 °C); by mass fraction, one part is 1 g.

[0028] Example 1: Step one: Mix polyethylene and xylene, stir and dissolve at 120 °C for 2 h to obtain a polyethylene solution; then drop 30 wt% hydrogen peroxide solution and 85 wt% formic acid solution into the cooled polyethylene solution, and stir and react at 30 °C for 15 h. After the reaction, washing, precipitation, vacuum decompression to remove the solvent, and drying are carried out to obtain the modified polyethylene resin; the reaction mass ratio of polyethylene, hydrogen peroxide solution, and formic acid is 10:3.3:2;

[0029] Step 2: S1: Mix 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide and N,N-dimethylformamide, stir at 85 °C for 40 min, then add sodium hydroxide and stir for 80 min, then add 4-vinylbenzyl chloride, cool down to 75 °C and stir for reaction for 7 h. After the reaction is completed, vacuum filtration, precipitation, vacuum drying, washing, drying and grinding are carried out to obtain olefination phosphaphenanthrene; Mix diethanolamine and mercaptopropionic acid, stir at 75 °C for reaction for 27 h. After the reaction is completed, carry out reduced pressure distillation to obtain a mercapto-branched unit; When preparing olefination phosphaphenanthrene, the reaction molar ratio of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, sodium hydroxide and 4-vinylbenzyl chloride is 1.5:4:4.3; The reaction molar ratio of diethanolamine and mercaptopropionic acid is 1:1.3;

[0030] S2: Mix olefination phosphaphenanthrene, trimethylolpropane tris(3-mercaptopropionate) and dimethyl sulfoxide, stir at 30 °C for reaction for 30 h. After the reaction is completed, washing, drying and reduced pressure distillation are carried out to obtain a double-bonded intermediate; Mix the double-bonded intermediate and dimethyl sulfoxide, fully stir and dissolve, then add the mercapto-branched unit and triethylamine, stir at 55 °C for reaction for 75 h. After the reaction is completed, washing, drying and reduced pressure distillation are carried out to obtain a flame-retardant hyperbranched polymer; When preparing the flame-retardant hyperbranched polymer, the reaction molar ratio of olefination phosphaphenanthrene and trimethylolpropane tris(3-mercaptopropionate) is 2.1:1, and the reaction molar ratio of olefination phosphaphenanthrene and the mercapto-branched unit is 2.1:2;

[0031] S3: Mix the flame-retardant hyperbranched polymer, epichlorohydrin, sodium hydroxide and tetramethylammonium bromide, stir at 70 °C for reaction for 6 h. After the reaction is completed, filtration, washing and reduced pressure distillation are carried out to obtain a flame-retardant hyperbranched epoxy resin; The reaction mass ratio of the flame-retardant hyperbranched polymer, epichlorohydrin, sodium hydroxide and tetramethylammonium bromide is 5:11:3:0.05;

[0032] Step 3: Mix 70 g of modified polyethylene resin, 30 g of flame-retardant hyperbranched epoxy resin, 10 g of ethylenediamine and 15 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir and dissolve at 90 °C for 30 min, then raise the temperature to 140 °C and react for 3 h to obtain a premixed resin; Then add 2 g of calcium stearate and 1 g of antioxidant 1010, continue to mix and react for 30 min. After the reaction is completed, extrusion granulation and melt extrusion are carried out to obtain an insulating protective sleeve; Wrap the insulating protective sleeve around the copper core wire to obtain the finished product.

[0033] Example 2: Step 1: Mix polyethylene and xylene, stir and dissolve at 115 °C for 1.5 h to obtain a polyethylene solution; then drop 30 wt% hydrogen peroxide solution and 85 wt% formic acid solution into the cooled polyethylene solution, and stir and react at 27 °C for 12 h. After the reaction, wash, precipitate, remove the solvent under vacuum and dry to obtain a modified polyethylene resin; the reaction mass ratio of polyethylene, hydrogen peroxide solution and formic acid is 10:3.3:2;

[0034] Step 2: S1: Mix 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide and N,N-dimethylformamide, stir at 82 °C for 35 min, then add sodium hydroxide and stir for 75 min, then add 4-vinylbenzyl chloride, cool down to 72 °C and stir and react for 6.5 h. After the reaction, vacuum filter, precipitate, vacuum dry, wash and dry and grind to obtain olefinated phosphaphenanthrene; mix diethanolamine and mercaptopropionic acid, stir and react at 72 °C for 26 h. After the reaction, carry out vacuum distillation to obtain a mercapto-branched unit; when preparing olefinated phosphaphenanthrene, the reaction molar ratio of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, sodium hydroxide and 4-vinylbenzyl chloride is 1.5:4:4.3; the reaction molar ratio of diethanolamine and mercaptopropionic acid is 1:1.3;

[0035] S2: Mix olefinated phosphaphenanthrene, trimethylolpropane tris(3-mercaptopropionate) and dimethyl sulfoxide, stir and react at 27 °C for 27 h. After the reaction, wash, dry and carry out vacuum distillation to obtain a double-bonded intermediate; mix the double-bonded intermediate and dimethyl sulfoxide, fully stir and dissolve, then add the mercapto-branched unit and triethylamine, stir and react at 52 °C for 72 h. After the reaction, wash, dry and carry out vacuum distillation to obtain a flame-retardant hyperbranched polymer; when preparing the flame-retardant hyperbranched polymer, the reaction molar ratio of olefinated phosphaphenanthrene and trimethylolpropane tris(3-mercaptopropionate) is 2.1:1, and the reaction molar ratio of olefinated phosphaphenanthrene and mercapto-branched unit is 2.1:2;

[0036] S3: Mix the flame-retardant hyperbranched polymer, epichlorohydrin, sodium hydroxide and tetramethylammonium bromide, stir and react at 67 °C for 5.5 h. After the reaction, filter, wash and carry out vacuum distillation to obtain a flame-retardant hyperbranched epoxy resin; the reaction mass ratio of the flame-retardant hyperbranched polymer, epichlorohydrin, sodium hydroxide and tetramethylammonium bromide is 5:11:3:0.05;

[0037] Step 3: Mix 70 g of modified polyethylene resin, 30 g of flame-retardant hyperbranched epoxy resin, 10 g of ethylenediamine, and 15 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir and dissolve at 85°C for 25 min, then raise the temperature to 130°C and react for 2.5 h to obtain a premixed resin; then add 2 g of calcium stearate and 1 g of antioxidant 1010, continue to mix and react for 25 min. After the reaction is completed, extrude and pelletize, and then melt-extrude to obtain an insulating protective sleeve; wrap the insulating protective sleeve around the copper core wire to obtain the finished product.

[0038] Example 3: Step 1: Mix polyethylene and xylene, stir and dissolve at 110°C for 1 h to obtain a polyethylene solution; then drop 30 wt% hydrogen peroxide solution and 85 wt% formic acid solution into the cooled polyethylene solution, and stir and react at 25°C for 10 h. After the reaction is completed, wash, precipitate, remove the solvent under vacuum and reduce pressure, and dry to obtain modified polyethylene resin; the reaction mass ratio of polyethylene, hydrogen peroxide solution, and formic acid is 10:3.3:2;

[0039] Step 2: S1: Mix 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide and N,N-dimethylformamide, stir at 80°C for 30 min, then add sodium hydroxide and stir for 70 min, then add 4-vinylbenzyl chloride, cool to 70°C and stir and react for 6 h. After the reaction is completed, vacuum filter, precipitate, vacuum dry, wash, and dry and grind to obtain olefinated phosphaphenanthrene; mix diethanolamine and mercaptopropionic acid, stir and react at 70°C for 25 h. After the reaction is completed, distill under reduced pressure to obtain a mercapto-branched unit; when preparing olefinated phosphaphenanthrene, the reaction molar ratio of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, sodium hydroxide, and 4-vinylbenzyl chloride is 1.5:4:4.3; the reaction molar ratio of diethanolamine and mercaptopropionic acid is 1:1.3;

[0040] S2: Mix olefinated phosphaphenanthrene, trimethylolpropane tris(3-mercaptopropionate), and dimethyl sulfoxide, stir and react at 25°C for 25 h. After the reaction is completed, wash, dry, and distill under reduced pressure to obtain a double-bonded intermediate; mix the double-bonded intermediate and dimethyl sulfoxide, fully stir and dissolve, then add the mercapto-branched unit and triethylamine, stir and react at 50°C for 70 h. After the reaction is completed, wash, dry, and distill under reduced pressure to obtain a flame-retardant hyperbranched polymer; when preparing the flame-retardant hyperbranched polymer, the reaction molar ratio of olefinated phosphaphenanthrene and trimethylolpropane tris(3-mercaptopropionate) is 2.1:1, and the reaction molar ratio of olefinated phosphaphenanthrene and the mercapto-branched unit is 2.1:2;

[0041] S3: Mix the flame - retardant hyperbranched polymer, epichlorohydrin, sodium hydroxide, and tetramethylammonium bromide, and stir - react at 65 °C for 5 h. After the reaction, perform suction filtration, washing, and vacuum distillation to obtain the flame - retardant hyperbranched epoxy resin. The reaction mass ratio of the flame - retardant hyperbranched polymer, epichlorohydrin, sodium hydroxide, and tetramethylammonium bromide is 5:11:3:0.05;

[0042] Step three: Mix 70 g of modified polyethylene resin, 30 g of flame - retardant hyperbranched epoxy resin, 10 g of ethylenediamine, and 15 g of 9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide, stir and dissolve at 80 °C for 20 min, then raise the temperature to 120 °C and react for 2 h to obtain a premixed resin. Then add 2 g of calcium stearate and 1 g of antioxidant 1010, continue to mix and react for 20 min. After the reaction, perform extrusion granulation and melt extrusion to obtain an insulating protective sleeve. Wrap the insulating protective sleeve around the copper core wire to obtain the finished product.

[0043] Comparative example 1: Remove the modification step of the polyethylene resin, and the rest is the same as in Example 1. The specific steps are as follows: Step one: S1: Mix 10 - (2,5 - dihydroxyphenyl) - 10H - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide and N,N - dimethylformamide, stir at 85 °C for 40 min, then add sodium hydroxide and stir for 80 min, then add 4 - vinylbenzyl chloride, cool down to 75 °C and stir - react for 7 h. After the reaction, perform vacuum suction filtration, precipitation, vacuum drying, washing, and drying and grinding to obtain olefinated phosphaphenanthrene. Mix diethanolamine and mercaptopropionic acid, stir - react at 75 °C for 27 h. After the reaction, perform vacuum distillation to obtain a mercapto - branched unit. When preparing olefinated phosphaphenanthrene, the reaction molar ratio of 10 - (2,5 - dihydroxyphenyl) - 10H - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide, sodium hydroxide, and 4 - vinylbenzyl chloride is 1.5:4:4.3; the reaction molar ratio of diethanolamine and mercaptopropionic acid is 1:1.3;

[0044] S2: Mix olefinated phosphaphenanthrene, trimethylolpropane - tris(3 - mercaptopropionate), and dimethyl sulfoxide, stir - react at 30 °C for 30 h. After the reaction, perform washing, drying, and vacuum distillation to obtain a double - bond intermediate product. Mix the double - bond intermediate product and dimethyl sulfoxide, fully stir and dissolve, then add the mercapto - branched unit and triethylamine, stir - react at 55 °C for 75 h. After the reaction, perform washing, drying, and vacuum distillation to obtain the flame - retardant hyperbranched polymer. When preparing the flame - retardant hyperbranched polymer, the reaction molar ratio of olefinated phosphaphenanthrene and trimethylolpropane - tris(3 - mercaptopropionate) is 2.1:1, and the reaction molar ratio of olefinated phosphaphenanthrene and the mercapto - branched unit is 2.1:2;

[0045] S3: Mix the flame retardant hyperbranched polymer, epichlorohydrin, sodium hydroxide and tetramethylammonium bromide, stir and react at 70°C for 6 hours, and after the reaction, filter, wash and distill under reduced pressure to obtain a flame retardant hyperbranched epoxy resin; the reaction mass ratio of the flame retardant hyperbranched polymer, epichlorohydrin, sodium hydroxide and tetramethylammonium bromide is 5:11:3:0.05;

[0046] Step 2: Mix 70g of polyethylene resin, 30g of flame-retardant hyperbranched epoxy resin, 10g of ethylenediamine, and 15g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir and dissolve at 90°C for 30min, then heat to 140°C and react for 3h to obtain a premixed resin; then add 2g of calcium stearate and 1g of antioxidant 1010, continue mixing and reacting for 30min, and after the reaction is completed, extrusion granulation and melt extrusion are performed to obtain an insulating protective sleeve; wrap the insulating protective sleeve around the copper core wire to obtain a finished product.

[0047] Comparative Example 2: The flame retardant hyperbranched epoxy resin is removed, and the rest is the same as Example 1, and the specific steps are as follows: Step 1: polyethylene and xylene are mixed, and stirred and dissolved at 120° C. for 2 hours to obtain a polyethylene solution; then 30wt% hydrogen peroxide solution and 85wt% formic acid solution are added dropwise to the cooled polyethylene solution, and stirred and reacted at 30° C. for 15 hours. After the reaction is completed, the modified polyethylene resin is obtained by washing, precipitation, vacuum decompression and solvent removal, and drying; the reaction mass ratio of polyethylene, hydrogen peroxide solution, and formic acid is 10:3.3:2;

[0048] Step 2: Mix 70g of modified polyethylene resin, 10g of ethylenediamine, and 15g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir and dissolve at 90°C for 30min, then heat to 140°C and react for 3h to obtain a premixed resin; then add 2g of calcium stearate and 1g of antioxidant 1010, continue mixing and reacting for 30min, and after the reaction is completed, extrusion granulation and melt extrusion are performed to obtain an insulating protective sleeve; wrap the insulating protective sleeve around the copper core wire to obtain a finished product.

[0049] Detection test:

[0050] Flame retardant performance test: referring to GB / T 2406.2-2009 "Determination of combustion behavior of plastics by oxygen index method Part 2: Room temperature test", the insulating protective cover prepared by the present invention is used as a sample with a sample size of 90×10×4 mm, and the oxygen index value is recorded.

[0051] 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 insulating protective cover prepared by the present invention was used as a sample with a sample size of 160×10×4 mm, and the tensile strength was recorded.

[0052] Heat release performance test: Referring to GB 31247-2014 "Classification of the burning performance of cables and optical cables" and GB / T 31248-2014 "Test methods for flame spread, heat release and smoke production characteristics of cables or optical cables under fire conditions", the finished wire prepared by the present invention was used as a specimen, and the heat release performance during specimen combustion was characterized by testing the peak heat release rate and the total heat release. The results are shown in the following table:

[0053]

[0054] Conclusion: The dosages of Examples 1-3 remain unchanged, and only some reaction parameters are modified. From the experimental data, it can be seen that there are no obvious fluctuations in the performance of the specimens.

[0055] Comparative Example 1: The modification step of the polyethylene resin was removed, and the rest was the same as in Example 1. From the experimental data, it can be seen that compared with Example 1, the oxygen index decreased to 30.1%, the tensile strength decreased to 27.1 MPa, the peak heat release rate increased to 16.7 kW, and the total heat release within 1200 s of exposure to fire increased to 10.5 MJ. The reason for the analysis is that after removing the modification step of the polyethylene resin, it is difficult for the polyethylene resin, the flame-retardant hyperbranched epoxy resin, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to be fully wetted and dispersed during the mixing process, resulting in a tendency for the components to aggregate together rather than being evenly dispersed throughout the system. Therefore, a phase separation structure will be formed inside the material due to poor compatibility, and these phase interfaces are likely to become stress concentration points when stressed, leading to a decrease in the mechanical properties of the material. In addition, since the flame-retardant structure cannot be evenly dispersed in the system, it cannot fully exert its flame-retardant effect, and uneven local flame-retardant element concentrations will also cause abnormal heat release, resulting in a decrease in the flame-retardant performance and heat release performance.

[0056] Comparative Example 2: The flame-retardant hyperbranched epoxy resin was removed, and the rest was the same as in Example 1. From the experimental data, it can be seen that compared with Example 1, the oxygen index decreased to 25.6%, the tensile strength decreased to 21.5 MPa, the peak heat release rate increased to 18.9 kW, and the total heat release within 1200 s of exposure to fire increased to 11.9 MJ. The reason for the analysis is that the flame-retardant hyperbranched epoxy resin has both a highly branched structure and a rigid molecular chain, as well as an N-P synergistic flame-retardant structure. Therefore, it has good mechanical properties, flame-retardant properties, and thermal safety properties. So after removing it, the oxygen index decreased, the tensile strength decreased, the peak heat release rate increased, and the total heat release within 1200 s of exposure to fire increased.

[0057] It should be noted that in this text, relational terms such as first and second are only used 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 "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0058] Finally, it should be noted that the above are only 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 foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a halogen-free flame-retardant B1-level fire-resistant electric wire, characterized in that: It includes the following steps: Step 1: Mix polyethylene and xylene, stir and dissolve at 110 - 120°C for 1 - 2 h to obtain a polyethylene solution; then drop 30 - 35 wt% hydrogen peroxide solution and 85 - 90 wt% formic acid solution into the cooled polyethylene solution, and stir and react at 25 - 30°C for 10 - 15 h. After the reaction, wash, precipitate, remove the solvent under vacuum and dry to obtain a modified polyethylene resin; Step 2: Mix a flame - retardant hyperbranched polymer, epichlorohydrin, sodium hydroxide, and tetramethylammonium bromide, stir and react at 65 - 70°C for 5 - 6 h. After the reaction, filter by suction, wash, and distill under reduced pressure to obtain a flame - retardant hyperbranched epoxy resin; Step 3: Mix the modified polyethylene resin, the flame - retardant hyperbranched epoxy resin, a curing agent, and 9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide, stir and dissolve at 80 - 90°C for 20 - 30 min, then raise the temperature to 120 - 140°C and react for 2 - 3 h to obtain a premixed resin; then add a lubricant and an antioxidant, continue to mix and react for 20 - 30 min. After the reaction, extrude and pelletize, and melt - extrude to obtain an insulating protective sleeve; wrap the insulating protective sleeve around the copper core wire to obtain the finished product.

2. The preparation method of a halogen-free flame-retardant B1-class fire-resistant electric wire according to claim 1, characterized in that: In Step 1, the reaction mass ratio of polyethylene, hydrogen peroxide solution, and formic acid is 10:(3.2 - 3.5):

2.

3. The preparation method of a halogen-free flame-retardant B1-class fire-resistant electric wire according to claim 1, wherein: In Step 2, the reaction mass ratio of the flame - retardant hyperbranched polymer, epichlorohydrin, sodium hydroxide, and tetramethylammonium bromide is 5:(10 - 12):3:0.

05.

4. The preparation method of a halogen-free flame-retardant B1-level fire-resistant electric wire according to claim 3, characterized in that: The preparation process of the flame - retardant hyperbranched polymer is as follows: S1: Mix 10 - (2,5 - dihydroxyphenyl) - 10H - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide and N,N - dimethylformamide, stir at 80 - 85°C for 30 - 40 min, then add sodium hydroxide and stir for 70 - 80 min, then add 4 - vinylbenzyl chloride, cool to 70 - 75°C and stir and react for 6 - 7 h. After the reaction, filter by vacuum, precipitate, dry under vacuum, wash, and dry and grind to obtain an olefinated phosphaphenanthrene; mix diethanolamine and mercaptopropionic acid, stir and react at 70 - 75°C for 25 - 27 h. After the reaction, distill under reduced pressure to obtain a mercapto - branched unit; S2: Mix the olefinated phosphaphenanthrene, trimethylolpropane - tris(3 - mercaptopropionate), and dimethyl sulfoxide, stir and react at 25 - 30°C for 25 - 30 h. After the reaction, wash, dry, and distill under reduced pressure to obtain a double - bond - containing intermediate; mix the double - bond - containing intermediate and dimethyl sulfoxide, fully stir and dissolve, then add the mercapto - branched unit and triethylamine, stir and react at 50 - 55°C for 70 - 75 h. After the reaction, wash, dry, and distill under reduced pressure to obtain the flame - retardant hyperbranched polymer.

5. The preparation method of a halogen-free flame-retardant B1-level fire-resistant electric wire according to claim 4, characterized in that: In step S1, when preparing the olefination phosphaphenanthrene, the reaction molar ratio of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, sodium hydroxide, and 4-vinylbenzyl chloride is 1.5:4:(4.0-4.5); when preparing the mercapto-branched unit, the reaction molar ratio of diethanolamine and mercaptopropionic acid is 1:(1.2-1.4).

6. The preparation method of a halogen-free flame-retardant B1-class fire-resistant electric wire according to claim 4, characterized in that: In step S2, when preparing the flame-retardant hyperbranched polymer, the reaction molar ratio of the olefination phosphaphenanthrene and trimethylolpropane tris(3-mercaptopropionate) is (2.0-2.3):1, and the reaction molar ratio of the olefination phosphaphenanthrene and the mercapto-branched unit is (2.0-2.3):

2.

7. The preparation method of a halogen-free flame-retardant B1-level fire-resistant electric wire according to claim 1, wherein: In step three, the content of each component of the insulating protective sleeve raw material is as follows: in terms of mass parts, 60-70 parts of modified polyethylene resin, 20-30 parts of flame-retardant hyperbranched epoxy resin, 7-15 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 8-10 parts of curing agent, 1-2 parts of lubricant, and 0.5-1 part of antioxidant; the curing agent is ethylenediamine, the lubricant is calcium stearate, and the antioxidant is antioxidant 1010.

8. A halogen-free flame-retardant B1-class fire-resistant electric wire, characterized in that, Prepared by the preparation method according to any one of claims 1-7.

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