Flame-retardant cable and preparation method thereof

Abstract

The invention relates to the technical field of flame-retardant materials, and discloses a flame-retardant cable and a preparation method thereof.The flame-retardant cable is prepared by adding polyethylene, maleic anhydride grafted polyethylene, guanidyl modified polyurethane, epoxidized silane and an antioxidant 1010 into a plastic mixing mill, stirring and mixing to obtain a primary material, then transferring the primary material into an open mill, adding a flame-retardant agent, stirring and mixing to obtain the flame-retardant cable. And adding a vulcanizing agent DCP and an accelerant TMTA, uniformly mixing, adding into an extruder, extruding, putting into a press vulcanizer after extrusion, and cooling to obtain the flame-retardant cable. A guanidyl group in the guanidyl modified polyurethane, a silicon element, a phosphorus element and a sulfur element jointly form a flame-retardant system. In the extrusion process of the open mill, a terminal hydroxyl group of guanidyl modified polyurethane and an epoxy group in epoxidized silane are subjected to a ring-opening addition reaction to generate a new hydroxyl group, the new hydroxyl group further reacts with an anhydride group in maleic anhydride grafted polyethylene, and a cross-linked network is formed between the new hydroxyl group and the anhydride group, so that the connection is tighter, and the mechanical property is improved.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardant materials, in particular to a flame retardant cable and a preparation method thereof. Background Art

[0002] Cables play an important role in people's daily lives and are widely used in communications, electricity, and construction industries. Therefore, improving their flame retardant effect is a key factor. Existing flame retardant cables have the problems of high cost and poor flame retardant effect. Application No. 201710989620.6 discloses an insulated cable and a preparation method thereof, which uses titanium dioxide, sodium silicate, calcium hydroxide, and tributyl citrate to reinforce, prevent aging, and fill rubber, but its flame retardant effect has not been improved. Summary of the invention

[0003] 1. Technical issues to be resolved In view of the deficiencies in the prior art, the present invention provides a flame retardant cable and a preparation method thereof, which has good flame retardant effect and mechanical properties.

[0004] (II) Technical solution To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a flame-retardant cable, comprising the following components by weight: 50-70 parts by weight of polyethylene, 15-20 parts by weight of maleic anhydride grafted polyethylene, 6-10 parts by weight of guanidine-modified polyurethane, 4-8 parts by weight of epoxy silane, 1-2 parts by weight of antioxidant 1010, 1-1.2 parts by weight of vulcanizing agent DCP, and 0.8-1 parts by weight of accelerator TMTA.

[0005] Preferably, the preparation method of the guanidine-modified polyurethane is: (1) adding sulfaguanidine to anhydrous ethanol solvent, stirring and mixing, heating to 70-85°C to completely dissolve it, then continuing to add 2,6-dihydroxybenzaldehyde, stirring and reacting for 10-14 hours, then adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stirring and reacting at 70-80°C for 8-12 hours, washing with anhydrous ethanol and deionized water for 2-3 times respectively after completion, and then drying in a vacuum drying oven at 90-100°C for 10-12 hours to obtain hydroxylated sulfaguanidine; (2) Adding vinylphenyldichlorosilane and 4-hydroxymethyl caged bicyclic phosphate to N,N-dimethylformamide solvent, stirring and dispersing, heating to 85-100°C and reacting for 8-14 hours, filtering after reaction, distilling the filtrate under reduced pressure, washing with distilled water, and drying to obtain vinyl silane; (3) Adding olefinic silane to xylene solvent, stirring to dissolve, continuing to add aqueous hydrogen peroxide solution, stirring and reacting at 22-28° C. for 3-6 hours, standing after completion, extracting, taking out the organic phase, drying, and distilling under reduced pressure to obtain epoxidized silane; (4) Adding epoxidized silane and hydroxylated sulfaguanidine to N,N-dimethylformamide solvent, stirring evenly, and continuously adding boron trifluoride etherate thereto, reacting at 75-90° C. for 15-20 hours, washing with deionized water, distilling under reduced pressure, and drying to obtain a guanidine chain extender; (5) Hexamethylene diisocyanate and polyether polyol are added to a reactor, and then dibutyltin dilaurate catalyst is added to carry out prepolymerization under a nitrogen atmosphere at a temperature of 75-90°C for 3-5 hours. Then a guanidine chain extender is added. After the reaction is completed, the mixture is cooled to room temperature to obtain a guanidine-modified polyurethane.

[0006] Preferably, the mass ratio of sulfaguanidine, 2,6-dihydroxybenzaldehyde and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in (1) is 1:1.6-2:2.1-2.4.

[0007] Preferably, the mass ratio of vinylphenyldichlorosilane to 4-hydroxymethyl caged bicyclic phosphate in (2) is 1:1.4-1.8.

[0008] Preferably, the mass ratio of olefinic silane to hydrogen peroxide in (3) is 1:2.2-2.6.

[0009] Preferably, the mass ratio of epoxysilane, hydroxylated sulfaguanidine and boron trifluoride etherate in (4) is 1.2-1.4:1:0.01-0.03.

[0010] Preferably, the mass ratio of hexamethylene diisocyanate, polyether polyol, dibutyltin dilaurate catalyst and guanidine chain extender in (5) is 1.2-1.5:1:0.02-0.03:0.9-1.4.

[0011] Preferably, the preparation method of the flame-retardant cable comprises the following steps: adding polyethylene, maleic anhydride grafted polyethylene, guanidine modified polyurethane, epoxy silane, and antioxidant 1010 to a plastic refiner, protecting with nitrogen, controlling the temperature to 40-55°C, stirring at a rate of 45-50rpm, stirring and mixing for 20-24min to obtain a preliminary material, then transferring the preliminary material to an open mill, controlling the roller temperature to 50-60°C, then adding a vulcanizing agent DCP and an accelerator TMTA to mix, and then adding the material to an extruder, wherein the barrel temperature of the extruder is set to: 120-130°C for zone 1, 140-150°C for zone 2, 150-160°C for zone 3, 145-155°C for zone 4, and a die head temperature of 155-160°C; after extrusion, placing the material in a flat vulcanizer at a vulcanization temperature of 180-185°C and a vulcanization time of 10-15min; and cooling to obtain a flame-retardant cable.

[0012] 3. Beneficial technical effects The invention provides a method for adding polyethylene, maleic anhydride grafted polyethylene, guanidine modified polyurethane, epoxy silane and antioxidant 1010 into a plasticizer, stirring and mixing to obtain a primary material, then transferring the primary material into an open mixer, then adding a vulcanizing agent DCP and an accelerator TMTA to mix evenly, then adding the materials into an extruder, extruding, placing the materials in a flat vulcanizer after extrusion, and cooling the materials to obtain a flame-retardant cable.

[0013] The invention carries out a condensation reaction between an amino group in sulfaguanidine and an aldehyde group in 2,6-dihydroxybenzaldehyde to generate a double bond and hydrogen in 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, carries out an addition reaction, and introduces a hydroxyl group at the same time, thereby obtaining hydroxylated sulfaguanidine; carries out a substitution reaction between chlorine in vinylphenyldichlorosilane and a hydroxyl group in 4-hydroxymethyl cage-like bicyclic phosphate, introduces an alkenyl group, thereby obtaining alkenylated silane, further carries out a cyclization reaction with an aqueous hydrogen peroxide solution, introduces an epoxy group, thereby obtaining epoxidized silane, further carries out an addition reaction with a hydroxyl group in the hydroxylated sulfaguanidine, thereby obtaining a guanidine chain extender; and carries out prepolymerization between hexamethylene diisocyanate and a polyether polyol under the action of a dibutyltin dilaurate catalyst, and then adds the guanidine chain extender to obtain a guanidine-modified polyurethane.

[0014] The guanidine groups in guanidine-modified polyurethane will decompose when heated to generate non-flammable gases such as nitrogen and carbon dioxide, which isolate oxygen and achieve a flame retardant effect. The silicon element contained in it has a large silicon-oxygen bond energy, which can not only absorb more heat, but also absorb heat to produce a glass-like substance that covers the surface of the material to achieve a flame retardant effect. The phosphorus element contained in it can produce phosphoric acid, a strong dehydrating substance, when heated, which can promote the dehydration of the material into carbon and achieve a flame retardant effect. The sulfur element contained in it can release strong acid at high temperature to promote the dehydration of the substrate into carbon, isolate external oxygen and heat sources, thereby achieving a flame retardant effect, and together constitute a flame retardant system.

[0015] During the extrusion process on the mixing mill, the terminal hydroxyl groups of the guanidine-modified polyurethane will undergo a ring-opening addition reaction with the epoxy groups in the epoxy silane to generate new hydroxyl groups which will further react with the anhydride groups in the maleic anhydride-grafted polyethylene to form a cross-linked network between them, making their connections tighter and increasing their mechanical properties. At the same time, the interfacial compatibility between the guanidine-modified polyurethane and polyethylene is improved, making its flame retardant system more evenly distributed in the material. DETAILED DESCRIPTION

[0016] Example 1

[0017] (1) Add 1 g of sulfaguanidine to 50 ml of anhydrous ethanol solvent, stir and mix, heat to 70°C to completely dissolve it, then continue to add 2.4 g of 2,6-dihydroxybenzaldehyde, stir and react for 10 hours, then add 1.5 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir and react at 70°C for 8 hours, wash with anhydrous ethanol and deionized water twice each, and then dry in a vacuum drying oven at 90°C for 10 hours to obtain hydroxylated sulfaguanidine; (2) Add 1 g of vinylphenyldichlorosilane and 2.8 g of 4-hydroxymethyl caged bicyclic phosphate to 60 ml of N,N-dimethylformamide solvent, stir and disperse, heat to 85°C and react for 8 h. After the reaction, filter and vacuum distill the filtrate, wash with distilled water, and dry to obtain vinyl silane; (3) Add 1 g of olefinic silane to 70 ml of xylene solvent, stir to dissolve, continue to add 2.2 g of hydrogen peroxide aqueous solution, stir and react at 22 ° C for 3 h, let stand after completion, extract, take out the organic phase, dry, and distill under reduced pressure to obtain epoxidized silane; (4) Add 1.2 g of epoxidized silane and 1 g of hydroxylated sulfaguanidine to 50 ml of N,N-dimethylformamide solvent, stir evenly, and continue to add 0.01 g of boron trifluoride etherate, react at 75 ° C for 15 h, wash with deionized water, distill under reduced pressure, and dry to obtain a guanidine chain extender; (5) 2.4 g of hexamethylene diisocyanate and 1 g of polyether polyol were added to a reactor, and then 0.04 g of dibutyltin dilaurate catalyst was added to carry out prepolymerization under a nitrogen atmosphere at a temperature of 75 ° C for 3 h. Then 1.8 g of guanidine chain extender was added. After the reaction was completed, the mixture was cooled to room temperature to obtain guanidine-modified polyurethane; (6) Add 50 g of polyethylene, 15 g of maleic anhydride grafted polyethylene, 6 g of guanidine modified polyurethane, 4 g of epoxy silane, and 0.1 g of antioxidant 1010 to a plasticizer, protect with nitrogen, control the temperature to 40 °C, and stir at a rate of 45 rpm. Stir and mix for 20 min to obtain a preliminary material, then transfer the preliminary material to an open mixer, control the roller temperature to 50 °C, then add 0.1 g of vulcanizing agent DCP and 0.08 g of accelerator TMTA to mix, and then add to the extruder. The barrel temperature of the extruder is set to: 120 °C for zone 1, 140 °C for zone 2, 150 °C for zone 3, 145 °C for zone 4, and 155 °C for die head. After extrusion, place it in a flat vulcanizer at a vulcanization temperature of 180 °C and a vulcanization time of 10 min. After cooling, a flame retardant cable is obtained.

[0018] Example 2

[0019] (1) Add 1.5 g of sulfaguanidine to 70 ml of anhydrous ethanol solvent, stir and mix, heat to 85° C. to completely dissolve it, then continue to add 3 g of 2,6-dihydroxybenzaldehyde, stir and react for 14 hours, then add 3.6 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir and react at 80° C. for 12 hours, wash with anhydrous ethanol and deionized water three times each, and then dry in a vacuum drying oven at 100° C. for 12 hours to obtain hydroxylated sulfaguanidine; (2) Add 2 g of vinylphenyldichlorosilane and 3.6 g of 4-hydroxymethyl caged bicyclic phosphate to 85 ml of N,N-dimethylformamide solvent, stir and disperse, heat to 100 °C and react for 14 h. After the reaction, filter and vacuum distill the filtrate, wash with distilled water, and dry to obtain vinyl silane; (3) Add 1 g of olefinic silane to 90 ml of xylene solvent, stir to dissolve, continue to add 2.6 g of hydrogen peroxide aqueous solution, stir and react at 28 ° C for 6 h, let stand after completion, extract, take out the organic phase, dry, and distill under reduced pressure to obtain epoxidized silane; (4) Add 1.4 g of epoxidized silane and 1 g of hydroxylated sulfaguanidine to 80 ml of N,N-dimethylformamide solvent, stir evenly, and continue to add 0.03 g of boron trifluoride etherate, react at 90° C. for 20 h, wash with deionized water, distill under reduced pressure, and dry to obtain a guanidine chain extender; (5) 3 g of hexamethylene diisocyanate and 2 g of polyether polyol were added to a reactor, and then 0.06 g of dibutyltin dilaurate catalyst was added to carry out prepolymerization under a nitrogen atmosphere at a temperature of 90 ° C for 5 h. Then 2.8 g of guanidine chain extender was added. After the reaction was completed, the mixture was cooled to room temperature to obtain guanidine-modified polyurethane; (6) Add 70 g of polyethylene, 20 g of maleic anhydride grafted polyethylene, 10 g of guanidine modified polyurethane, 8 g of epoxy silane, and 0.2 g of antioxidant 1010 to a plasticizer, protect with nitrogen, control the temperature to 55 °C, and stir at a rate of 50 rpm. Stir and mix for 24 min to obtain a preliminary material, then transfer the preliminary material to an open mixer, control the roller temperature to 60 °C, then add 0.12 g of vulcanizing agent DCP and 0.1 g of accelerator TMTA to mix, and then add to the extruder. The barrel temperature of the extruder is set to: 130 °C for zone 1, 150 °C for zone 2, 160 °C for zone 3, 155 °C for zone 4, and 160 °C for die head. After extrusion, place it in a flat vulcanizer at a vulcanization temperature of 185 °C and a vulcanization time of 15 min. After cooling, a flame retardant cable is obtained.

[0020] Example 3

[0021] (1) Add 1.25 g of sulfaguanidine to 60 ml of anhydrous ethanol solvent, stir and mix, heat to 77.5°C to completely dissolve it, then continue to add 2.7 g of 2,6-dihydroxybenzaldehyde, stir and react for 12 hours, then add 2.55 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir and react at 75°C for 10 hours, wash with anhydrous ethanol and deionized water twice each, and then dry in a vacuum drying oven at 95°C for 11 hours to obtain hydroxylated sulfaguanidine; (2) Add 1.5 g of vinylphenyldichlorosilane and 3.2 g of 4-hydroxymethyl caged bicyclic phosphate to 72.5 ml of N,N-dimethylformamide solvent, stir and disperse, heat to 92.5 °C and react for 11 h. After the reaction, filter and vacuum distill the filtrate, wash with distilled water, and dry to obtain vinyl silane; (3) Add 1 g of olefinic silane to 80 ml of xylene solvent, stir to dissolve, continue to add 2.4 g of hydrogen peroxide aqueous solution, stir and react at 25 ° C for 5 h, let stand after completion, extract, take out the organic phase, dry, and distill under reduced pressure to obtain epoxidized silane; (4) Add 1.3 g of epoxidized silane and 1 g of hydroxylated sulfaguanidine to 65 ml of N,N-dimethylformamide solvent, stir evenly, and continue to add 0.02 g of boron trifluoride etherate, react at 82 °C for 17.5 h, wash with deionized water, distill under reduced pressure, and dry to obtain a guanidine chain extender; (5) 2.7 g of hexamethylene diisocyanate and 1.5 g of polyether polyol were added to a reactor, and then 0.05 g of dibutyltin dilaurate catalyst was added to carry out prepolymerization under a nitrogen atmosphere at a temperature of 82.5 °C for 4 h. Then 2.3 g of guanidine chain extender was added. After the reaction was completed, the mixture was cooled to room temperature to obtain guanidine-modified polyurethane. (6) Add 60 g of polyethylene, 17.5 g of maleic anhydride grafted polyethylene, 8 g of guanidine modified polyurethane, 6 g of epoxy silane, and 0.15 g of antioxidant 1010 to a plasticizer, protect with nitrogen, control the temperature to 45 °C, and stir at a rate of 48 rpm. Stir and mix for 22 min to obtain a preliminary material, then transfer the preliminary material to an open mixer, control the roller temperature to 55 °C, then add 0.11 g of vulcanizing agent DCP and 0.09 g of accelerator TMTA to mix, and then add to the extruder. The barrel temperature of the extruder is set to: 125 °C for zone 1, 145 °C for zone 2, 155 °C for zone 3, 150 °C for zone 4, and 157.5 °C for die head. After extrusion, place it in a flat vulcanizer at a vulcanization temperature of 182.5 °C and a vulcanization time of 12.5 min. After cooling, a flame retardant cable is obtained.

[0022] Comparative Example 1 (1) 60 g of polyethylene, 17.5 g of maleic anhydride grafted polyethylene, 6 g of epoxidized silane, and 0.15 g of antioxidant 1010 were added to a plasticizer, and nitrogen protection was used. The temperature was controlled at 45 °C and the stirring rate was 48 rpm. The mixture was stirred and mixed for 22 min to obtain a preliminary material. The preliminary material was then transferred to an open mixer, and the roller temperature was controlled at 55 °C. Then, 0.11 g of a vulcanizing agent DCP and 0.09 g of an accelerator TMTA were added and mixed. The mixture was then added to an extruder. The barrel temperature of the extruder was set to: 125 °C for zone 1, 145 °C for zone 2, 155 °C for zone 3, 150 °C for zone 4, and 157.5 °C for die head. After extrusion, the mixture was placed in a flat vulcanizer at a vulcanization temperature of 182.5 °C and a vulcanization time of 12.5 min. After cooling, a flame-retardant cable was obtained.

[0023] Comparative Example 2 (1) Add 1.25 g of sulfaguanidine to 60 ml of anhydrous ethanol solvent, stir and mix, heat to 77.5°C to completely dissolve it, then continue to add 2.7 g of 2,6-dihydroxybenzaldehyde, stir and react for 12 hours, then add 2.55 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir and react at 75°C for 10 hours, wash with anhydrous ethanol and deionized water twice each, and then dry in a vacuum drying oven at 95°C for 11 hours to obtain hydroxylated sulfaguanidine; (2) Add 1.5 g of vinylphenyldichlorosilane and 3.2 g of 4-hydroxymethyl caged bicyclic phosphate to 72.5 ml of N,N-dimethylformamide solvent, stir and disperse, heat to 92.5 °C and react for 11 h. After the reaction, filter and vacuum distill the filtrate, wash with distilled water, and dry to obtain vinyl silane; (3) Add 1 g of olefinic silane to 80 ml of xylene solvent, stir to dissolve, continue to add 2.4 g of hydrogen peroxide aqueous solution, stir and react at 25 ° C for 5 h, let stand after completion, extract, take out the organic phase, dry, and distill under reduced pressure to obtain epoxidized silane; (4) Add 1.3 g of epoxidized silane and 1 g of hydroxylated sulfaguanidine to 65 ml of N,N-dimethylformamide solvent, stir evenly, and continue to add 0.02 g of boron trifluoride etherate, react at 82 °C for 17.5 h, wash with deionized water, distill under reduced pressure, and dry to obtain a guanidine chain extender; (5) 2.7 g of hexamethylene diisocyanate and 1.5 g of polyether polyol were added to a reactor, and then 0.05 g of dibutyltin dilaurate catalyst was added to carry out prepolymerization under a nitrogen atmosphere at a temperature of 82.5 °C for 4 h. Then 2.3 g of guanidine chain extender was added. After the reaction was completed, the mixture was cooled to room temperature to obtain guanidine-modified polyurethane. (6) Add 60 g of polyethylene, 17.5 g of maleic anhydride grafted polyethylene, 8 g of guanidine modified polyurethane, and 0.15 g of antioxidant 1010 to a plasticizer, protect with nitrogen, control the temperature to 45 °C, and stir at a rate of 48 rpm. Stir and mix for 22 min to obtain a preliminary material, then transfer the preliminary material to an open mixer, control the roller temperature to 55 °C, then add 0.11 g of vulcanizing agent DCP and 0.09 g of accelerator TMTA to mix, and then add to the extruder. The barrel temperature of the extruder is set to: 125 °C for zone 1, 145 °C for zone 2, 155 °C for zone 3, 150 °C for zone 4, and 157.5 °C for die head. After extrusion, place it in a flat vulcanizer at a vulcanization temperature of 182.5 °C and a vulcanization time of 12.5 min. After cooling, a flame retardant cable is obtained.

[0024] The limiting oxygen index of the material was tested using an oxygen index meter, and the combustion grade of the material was tested using a horizontal and vertical combustion instrument. The test results are shown in Table 1.

[0025] Table 1: Flame retardancy tests.

[0026]

[0027] As can be seen from Table 1, Examples 1-3 of the present invention have better flame retardant effects than Comparative Examples 1-2. Examples 1-3 have better flame retardant effects than Comparative Examples 1-2 because Examples 1-3 contain guanidine groups, silicon elements, phosphorus elements, and sulfur elements flame retardant systems, while Comparative Example 1 only contains silicon elements flame retardant systems, and Comparative Example 2 lacks epoxysilane flame retardant substances compared to Example 1, so the flame retardant effect is not as good as that of Examples 1-3.

[0028] Tensile properties: Tensile strength and elongation at break were measured according to JIS K6251. The test results are shown in Table 2.

[0029] Table 2: Tensile properties tested.

[0030]

[0031] As shown in Table 2, compared with Comparative Examples 1-2, Examples 1-3 of the present invention have better mechanical properties. Because compared with Comparative Examples 1-2, in the process of extrusion on the open mill, the terminal hydroxyl groups of the guanidine-modified polyurethane of Examples 1-3 react with the epoxy groups in the epoxidized silane to generate new hydroxyl groups, which react with the anhydride groups in the maleic anhydride-grafted polyethylene to form a cross-linked network, making them more closely connected and increasing their mechanical properties, while Comparative Example 1 lacks guanidine-modified polyurethane, and Comparative Example 2 lacks epoxidized silane, making its contact network less tight than that of Examples 1-3, so the mechanical properties are lower than those of Examples 1-3.

[0032] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A flame retardant cable, characterized in that: The invention comprises the following components by weight: 50-70 parts by weight of polyethylene, 15-20 parts by weight of maleic anhydride grafted polyethylene, 6-10 parts by weight of guanidine modified polyurethane, 4-8 parts by weight of epoxy silane, 1-2 parts by weight of antioxidant 1010, 1-1.2 parts by weight of vulcanizing agent DCP, and 0.8-1 parts by weight of accelerator TMTA; The preparation method of the guanidine-modified polyurethane is as follows: (1) adding sulfaguanidine to anhydrous ethanol solvent, stirring and mixing, heating to 70-85°C to completely dissolve it, then continuing to add 2,6-dihydroxybenzaldehyde, stirring and reacting for 10-14 hours, then adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stirring and reacting at 70-80°C for 8-12 hours, washing with anhydrous ethanol and deionized water for 2-3 times respectively after completion, and then drying in a vacuum drying oven at 90-100°C for 10-12 hours to obtain hydroxylated sulfaguanidine; (2) Adding vinylphenyldichlorosilane and 4-hydroxymethyl caged bicyclic phosphate to N,N-dimethylformamide solvent, stirring and dispersing, heating to 85-100°C and reacting for 8-14 hours, filtering after reaction, distilling the filtrate under reduced pressure, washing with distilled water, and drying to obtain vinyl silane; (3) Adding olefinic silane to xylene solvent, stirring to dissolve, continuing to add aqueous hydrogen peroxide solution, stirring and reacting at 22-28° C. for 3-6 hours, standing after completion, extracting, taking out the organic phase, drying, and distilling under reduced pressure to obtain epoxidized silane; (4) Adding epoxidized silane and hydroxylated sulfaguanidine to N,N-dimethylformamide solvent, stirring evenly, and continuously adding boron trifluoride etherate thereto, reacting at 75-90° C. for 15-20 hours, washing with deionized water, distilling under reduced pressure, and drying to obtain a guanidine chain extender; (5) Hexamethylene diisocyanate and polyether polyol are added to a reactor, and then dibutyltin dilaurate catalyst is added to carry out prepolymerization under a nitrogen atmosphere at a temperature of 75-90°C for 3-5 hours. Then a guanidine chain extender is added. After the reaction is completed, the mixture is cooled to room temperature to obtain a guanidine-modified polyurethane.

2. The flame-retardant cable according to claim 1, characterized in that: The mass ratio of sulfaguanidine, 2,6-dihydroxybenzaldehyde and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in (1) is 1:1.6-2:2.1-2.

4.

3. The flame-retardant cable according to claim 1, characterized in that: The mass ratio of vinylphenyldichlorosilane to 4-hydroxymethyl caged bicyclic phosphate in (2) is 1:1.4-1.

8.

4. The flame-retardant cable according to claim 1, characterized in that: The mass ratio of olefinic silane to hydrogen peroxide in (3) is 1:2.2-2.

6.

5. The flame retardant cable according to claim 1, characterized in that: The mass ratio of epoxide silane, hydroxylated sulfaguanidine and boron trifluoride ether in (4) is 1.2-1.4:1:0.01-0.

03.

6. The flame retardant cable according to claim 1, characterized in that: The mass ratio of hexamethylene diisocyanate, polyether polyol, dibutyltin dilaurate catalyst and guanidine chain extender in (5) is 1.2-1.5:1:0.02-0.03:0.9-1.

4.

7. A method for preparing a flame-retardant cable according to any one of claims 1 to 6, characterized in that: The preparation method of the flame-retardant cable comprises the following steps: adding polyethylene, maleic anhydride grafted polyethylene, guanidine modified polyurethane, epoxy silane and antioxidant 1010 into a plasticizer, protecting with nitrogen, controlling the temperature to 40-55°C, stirring at a rate of 45-50rpm, stirring and mixing for 20-24min to obtain a primary material, then transferring the primary material into an open mixer, controlling the roller temperature to 50-60°C, then adding a vulcanizing agent DCP and an accelerator TMTA to mix, and then adding the material into an extruder, wherein the barrel temperature of the extruder is set to: 120-130°C for zone 1, 140-150°C for zone 2, 150-160°C for zone 3, 145-155°C for zone 4, and a die head temperature of 155-160°C, and after extrusion, placing the material in a flat vulcanizer at a vulcanization temperature of 180-185°C and a vulcanization time of 10-15min, and cooling to obtain a flame-retardant cable.

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