High-strength flame-retardant fireproof cable and preparation method thereof

Abstract

The invention relates to the technical field of electric power facilities, in particular to a high-strength flame-retardant fireproof cable and a preparation method thereof. The phosphonitrile flame retardant is prepared by adding phosphonitrilic chloride trimer, phenylphosphonic acid, triethylamine and melamine. Then, 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, the modified carbon nanotubes and the flame-retardant modified halloysite nanotubes are used as main raw materials, and the flame-retardant filler is prepared. The preparation method comprises the following steps: mixing polyolefin, a phosphazene flame retardant, a flame-retardant filler, talcum powder, gum and stearic acid, fully stirring and melting to obtain a sizing material, and carrying out crosslinking, granulation and molding on the sizing material to obtain the cable protection sleeve. And wrapping the outermost layer of the cable with the cable protection sleeve to obtain a finished cable. The finished cable prepared by the invention has good flame retardance and mechanical strength, so that the cable has a wide application prospect in the technical field of electric power facilities.

Description

Technical Field

[0001] The present invention relates to the technical field of power facilities, and specifically to a high-strength flame-retardant and fire-proof cable and a preparation method thereof. Background Art

[0002] Cables are the core carriers of power transmission. They efficiently transmit the electric energy generated by power plants to every corner of the city, providing continuous power for industrial production and residents' lives. Among them, the cable protective sheath on the outer layer of the cable can provide comprehensive protection for the cable. It can resist external physical impacts, chemical corrosions, and harsh natural environments, prevent damage to the insulation layer of the cable, avoid safety accidents such as electric leakage and short circuits, ensure the safe and stable power transmission, and guarantee the normal operation of the entire society. In the information age, cables also play a crucial role. Data cables carry a large amount of information, enabling high-speed connections between computers and communication devices, and promoting the vigorous development of technologies such as the Internet and the Internet of Things. At this time, the cable protective sheath can reduce the influence of external electromagnetic interference on signal transmission and ensure the accuracy and stability of information transmission.

[0003] However, during the use of cables, if high temperatures or electric sparks are generated due to faults such as overload and short circuit, fires may be triggered. Therefore, preparing cables with good flame-retardant performance can slow down the spread speed of flames when a fire breaks out, buy precious time for personnel evacuation and fire fighting and rescue, and greatly reduce the risk of casualties. In addition, during the laying and use of cables, they will be subjected to various external forces, such as stretching, bending, and extrusion. Under some harsh environmental conditions, such as underground, underwater, and at high altitudes, cables may also be subjected to soil pressure, water flow impact, wind force, etc. Therefore, preparing cables with high mechanical strength can withstand these external forces, ensure their normal use in complex environments, extend the service life of the cables, reduce the replacement and maintenance costs, and improve the economic benefits of the cables.

[0004] In order to overcome the defects of the prior art, the present invention provides a high-strength flame-retardant and fire-proof cable and a preparation method thereof. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-strength flame-retardant and fire-proof cable and a preparation method thereof to solve the problems in the prior art.

[0006] To solve the above technical problems, the present invention provides the following technical solutions:

[0007] A preparation method of a high-strength flame-retardant and fire-proof cable, comprising the following steps:

[0008] Step 1: Add hexachlorocyclotriphosphazene and phenylphosphonic acid to acetonitrile. After ultrasonic dispersion until uniform, then add triethylamine dropwise, and stir and react at 55 - 60 °C for 5 - 7 h to obtain phosphonic acid cyclotriphosphazene; add the phosphonic acid cyclotriphosphazene to deionized water, and after ultrasonic dispersion until uniform, obtain a phosphonic acid cyclotriphosphazene solution; add melamine to deionized water, and after ultrasonic dispersion until uniform, obtain a melamine solution, then slowly add the phosphonic acid cyclotriphosphazene solution dropwise. After the addition is completed, react at 80 - 90 °C for 3 - 4 h. After the reaction is completed, filter, wash, and dry to obtain a phosphazene flame retardant;

[0009] Step 2: Add 9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide to N - methylpyrrolidone. After ultrasonic dispersion until uniform, obtain a 9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide solution; then add modified carbon nanotubes and flame - retardant modified halloysite nanotubes to N - methylpyrrolidone. After ultrasonic dispersion until uniform, add the 9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide solution dropwise. After the addition is completed, react at 80 - 85 °C for 6 - 7 h, then raise the temperature to 160 - 170 °C and react for 5 - 6 h. After the reaction is completed, filter, wash, and dry to obtain a flame - retardant filler;

[0010] Step 3: Mix polyolefin, phosphazene flame retardant, flame - retardant filler, talc powder, gum, and stearic acid, and fully stir and melt to obtain a rubber compound. The rubber compound is then cross - linked at 180 - 200 °C for 15 - 20 min, granulated, and molded to obtain a cable sheath; wrap the cable sheath around the outermost layer of the cable to obtain a finished product.

[0011] Preferably, in Step 1, the reaction molar ratio of hexachlorocyclotriphosphazene, phenylphosphonic acid, and melamine is 1:

[0012] (6.5 - 7.5):8.

[0013] Preferably, in Step 2, when preparing the flame - retardant filler, the reaction mass ratio of modified carbon nanotubes, flame - retardant modified halloysite nanotubes, and 9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide is 1:1:(4 - 5).

[0014] Preferably, the preparation process of the modified carbon nanotubes is as follows: Add multi - walled carbon nanotubes to a mixed solvent, after ultrasonic dispersion until uniform, adjust the pH to 4 - 5, then add it to toluene, stir evenly, and then add silane coupling agent KH560, and reflux and react at 110 - 120 °C for 5 - 6 h. After the reaction is completed, centrifuge, filter, and dry to obtain modified carbon nanotubes.

[0015] Preferably, the reaction mass ratio of multi - walled carbon nanotubes and silane coupling agent KH560 is (8 - 10):1.

[0016] Preferably, the preparation process of the flame-retardant modified halloysite nanotubes is as follows: Add halloysite nanotubes to a mixed solvent, adjust the pH to 4-5 after ultrasonic dispersion, then add silane coupling agent KH792, and reflux at 80-85 °C for 5-6 h after ultrasonic dispersion. After the reaction, centrifuge, wash, and vacuum dry to obtain modified halloysite nanotubes; dissolve the modified halloysite nanotubes and p-methylsulfonylbenzaldehyde in an ethanol solution respectively, then drop the p-methylsulfonylbenzaldehyde solution into the modified halloysite nanotube solution, and reflux at 80-85 °C for 8-9 h. After the reaction, cool, filter, wash with alcohol, and dry to obtain the flame-retardant modified halloysite nanotubes.

[0017] Preferably, the reaction mass ratio of halloysite nanotubes, silane coupling agent KH792, and p-methylsulfonylbenzaldehyde is (8-10):1:(1.0-1.2).

[0018] Preferably, the mixed solvent consists of ethanol and water, and the volume ratio of ethanol to water is 9:(1-2).

[0019] Preferably, in step three, the content of each component of the rubber compound is as follows: by mass, 90-100 parts of polyolefin, 15-25 parts of phosphazene flame retardant, 10-15 parts of flame retardant filler, 8-13 parts of talc powder, 3-5 parts of gum, and 2-3 parts of stearic acid.

[0020] The beneficial effects of the present invention:

[0021] The characteristics of the present invention are that in step one, a phosphazene flame retardant is prepared by adding hexachlorocyclotriphosphazene, phenylphosphonic acid, triethylamine, and melamine. In this step, a substitution reaction between hexachlorocyclotriphosphazene and phenylphosphonic acid occurs first to obtain a phosphonic acid cyclotriphosphazene; then the phosphonic acid cyclotriphosphazene and melamine are mixed to undergo a salt-forming reaction, and finally a phosphazene flame retardant is obtained. The phosphazene flame retardant prepared by a specific step combines multiple flame retardant elements such as phosphorus and nitrogen, and has a good flame retardant effect. Specifically, during the combustion process of the phosphazene flame retardant, the phosphorus-containing component will decompose to produce substances such as metaphosphoric acid and phosphoric acid; these phosphorus-containing compounds will further gasify at high temperatures to form active free radicals, and the active free radicals can participate in reactions with highly active hydrogen free radicals and hydroxyl free radicals generated during the combustion process, thereby interrupting the chain reaction of combustion. Therefore, after adding this phosphazene flame retardant, the combustion rate of the material will be significantly reduced.

[0022] The characteristics of the present invention are as follows. In step two, multi-walled carbon nanotubes are modified by adding silane coupling agent KH560 to obtain modified carbon nanotubes with good dispersion performance. Halloysite nanotubes are modified by adding silane coupling agent KH792 to obtain modified halloysite nanotubes with good dispersion performance. Then, the p-toluenesulfonyl benzaldehyde solution and the modified halloysite nanotube solution are mixed to undergo a Schiff base reaction, resulting in flame-retardant modified halloysite nanotubes with both flame retardancy and dispersibility.

[0023] Furthermore, in step two, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, modified carbon nanotubes, and flame-retardant modified halloysite nanotubes are mixed, and a flame-retardant filler is prepared through a stepwise temperature-raising reaction. In this step, first, a nucleophilic addition reaction occurs between the P-H bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and the Schiff base group of the flame-retardant modified halloysite nanotubes, thereby introducing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide onto the surface of the filler. Then, the temperature is raised to carry out a ring-opening reaction between the P-H bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and the epoxy group of the modified carbon nanotubes, and finally, a flame-retardant filler is prepared.

[0024] In step two, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is introduced onto the surfaces of the two fillers. The phosphorus-containing compounds generated by the decomposition of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide have a strong dehydration effect, which can promote the carbonization of organic materials. The flame-retardant modified halloysite nanotubes and the modified carbon nanotubes themselves can also serve as the framework for carbon formation, promoting the formation of a carbon layer. The Schiff base structure may also participate in the carbonization reaction during combustion, forming a relatively dense carbon layer. The carbon layer has good heat insulation and oxygen barrier properties, which can prevent oxygen and heat from transferring into the material interior, and at the same time, can also prevent the combustible gases inside the material from diffusing outward, thereby inhibiting the continuation of combustion. In addition, the modified carbon nanotubes and the flame-retardant modified halloysite nanotubes have a nano-size effect. After being uniformly dispersed in the material, they can form a physical barrier. These nanotubes can prevent the escape of combustible gases and the entry of oxygen, delaying the combustion process. Moreover, the modified carbon nanotubes and the flame-retardant modified halloysite nanotubes have a very high aspect ratio and excellent mechanical properties, such as high strength and high modulus. When they are uniformly dispersed in the matrix material polyolefin of the cable sheath, they can play a role similar to that of steel bars in concrete for reinforcement. These nanotubes can effectively transfer stress and prevent crack propagation, thereby improving the rigidity and deformation resistance of the cable sheath.

[0025] Finally, polyolefin, phosphazene flame retardant, flame retardant filler, talc powder, gum, and stearic acid are mixed and stirred thoroughly until melted to obtain a rubber compound. The rubber compound is then cross-linked, granulated, and molded to obtain a cable protective sleeve. The cable protective sleeve is wrapped around the outermost layer of the cable to obtain a finished cable. In summary, the finished cable prepared by the present invention has good flame retardancy and mechanical strength, and thus has broad application prospects in the technical field of power facilities. Detailed Embodiments

[0026] The following will clearly and completely describe the technical solutions in the present invention in conjunction with the embodiments of the present invention. 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 fall within the scope of protection of the present invention.

[0027] Source of raw materials:

[0028] Multi-walled carbon nanotubes are provided by Shenzhen Lithium You New Energy Technology Co., Ltd. with an inner diameter of 4 nm; halloysite nanotubes are provided by Xi'an Mingchuangda Biotechnology Co., Ltd. with a specification of ≥99%; polyolefin is provided by Shanghai Jinsuda Plastics Co., Ltd. with a model of FY2012E; talc powder is provided by Qingdao Kaiweier Powder Engineering Technology Co., Ltd. with a particle size of 425 mesh; gum is provided by Shandong Aicai Biotechnology Co., Ltd. with a particle size of 100 mesh; by mass fraction, one part is 1 g.

[0029] Example 1: Step 1: Add hexachlorocyclotriphosphazene and phenylphosphonic acid to acetonitrile, ultrasonically disperse them evenly, then dropwise add triethylamine, and stir and react at 60 °C for 7 h to obtain phosphazene cyclotriphosphazene. Add phosphazene cyclotriphosphazene to deionized water, ultrasonically disperse it evenly to obtain a phosphazene cyclotriphosphazene solution. Add melamine to deionized water, ultrasonically disperse it evenly to obtain a melamine solution, and then slowly dropwise add the phosphazene cyclotriphosphazene solution. After the addition is completed, react at 90 °C for 4 h. After the reaction is completed, filter, wash, and dry to obtain a phosphazene flame retardant; the reaction molar ratio of hexachlorocyclotriphosphazene, phenylphosphonic acid, and melamine is 1:7:8;

[0030] Step 2: Add multi-walled carbon nanotubes to the mixed solvent, ultrasonically disperse them evenly, adjust the pH to 5, then add them to toluene, stir evenly, and then add silane coupling agent KH560. React under reflux at 120 °C for 6 h. After the reaction is completed, centrifuge, filter by suction, and dry to obtain modified carbon nanotubes; the reaction mass ratio of multi-walled carbon nanotubes and silane coupling agent KH560 is 9:1; the volume ratio of ethanol and water in the mixed solvent is 9:1.5;

[0031] The halloysite nanotubes were added to a mixed solvent, and the mixture was ultrasonically dispersed and then the pH was adjusted to 5. The silane coupling agent KH792 was then added, and the mixture was ultrasonically dispersed and then refluxed at 85°C for 6 hours. After the reaction, the mixture was centrifuged, washed, and vacuum-dried to obtain modified halloysite nanotubes. The modified halloysite nanotubes and p-methylsulfonylbenzaldehyde were respectively dissolved in an ethanol solution, and the p-methylsulfonylbenzaldehyde solution was added dropwise to the modified halloysite nanotube solution. The mixture was refluxed at 85°C for 9 hours. After the reaction, the mixture was cooled, filtered, washed with alcohol, and dried to obtain flame-retardant modified halloysite nanotubes. The reaction mass ratio of the halloysite nanotubes, the silane coupling agent KH792, and the p-methylsulfonylbenzaldehyde was 9:1:1.1. The volume ratio of ethanol to water in the mixed solvent was 9:1.5.

[0032] 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is added to N-methylpyrrolidone, and ultrasonically dispersed to obtain a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide solution; modified carbon nanotubes and flame-retardant modified halloysite nanotubes are added to N-methylpyrrolidone, and ultrasonically dispersed to obtain a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide solution; the modified carbon nanotubes and flame-retardant modified halloysite nanotubes are added dropwise to the N-methylpyrrolidone, and the mixture is reacted at 85° C. for 7 h, and then the temperature is raised to 170° C. for 6 h. After the reaction is completed, the mixture is filtered, washed, and dried to obtain a flame-retardant filler; the reaction mass ratio of the modified carbon nanotubes, the flame-retardant modified halloysite nanotubes, and the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 1:1:4.5;

[0033] Step 3: Mix 90g of polyolefin, 15g of phosphazene flame retardant, 10g of flame retardant filler, 8g of talc, 3g of gum, and 2g of stearic acid, stir and melt them thoroughly to obtain a rubber compound, cross-link the rubber compound at 200°C for 20min, granulate, and shape them to obtain a cable protective cover; wrap the cable protective cover to the outermost layer of the cable to obtain a finished product.

[0034] Example 2: Step 1: Hexachlorocyclotriphosphazene and phenylphosphonic acid are added to acetonitrile, ultrasonically dispersed, and then triethylamine is added dropwise. The mixture is stirred at 57°C for 6 hours to obtain phosphonic acid cyclotriphosphazene; phosphonic acid cyclotriphosphazene is added to deionized water, ultrasonically dispersed, and then a phosphonic acid cyclotriphosphazene solution is obtained; melamine is added to deionized water, ultrasonically dispersed, and then a melamine solution is obtained. The phosphonic acid cyclotriphosphazene solution is slowly added dropwise. After the addition is completed, the mixture is reacted at 85°C for 3.5 hours. After the reaction is completed, the mixture is filtered, washed, and dried to obtain a phosphazene flame retardant; wherein the reaction molar ratio of hexachlorocyclotriphosphazene, phenylphosphonic acid, and melamine is 1:7:8;

[0035] Step 2: Add multi-walled carbon nanotubes to the mixed solvent. After ultrasonic dispersion until uniform, adjust the pH to 4.5, then add it to toluene. After stirring evenly, add silane coupling agent KH560, and reflux at 115 °C for 5.5 h. After the reaction, centrifuge, filter, and dry to obtain modified carbon nanotubes; the reaction mass ratio of multi-walled carbon nanotubes to silane coupling agent KH560 is 9:1; the volume ratio of ethanol to water in the mixed solvent is 9:1.5;

[0036] Add halloysite nanotubes to the mixed solvent. After ultrasonic dispersion until uniform, adjust the pH to 4.5, then add silane coupling agent KH792, and ultrasonic disperse evenly and reflux at 82 °C for 5.5 h. After the reaction, centrifuge, wash, and vacuum dry to obtain modified halloysite nanotubes; dissolve the modified halloysite nanotubes and p-toluenesulfonyl benzaldehyde in ethanol solution respectively, then drop the p-toluenesulfonyl benzaldehyde solution into the modified halloysite nanotube solution, and reflux at 82 °C for 8.5 h. After the reaction, cool, filter, wash with alcohol, and dry to obtain flame-retardant modified halloysite nanotubes; the reaction mass ratio of halloysite nanotubes, silane coupling agent KH792, and p-toluenesulfonyl benzaldehyde is 9:1:1.1; the volume ratio of ethanol to water in the mixed solvent is 9:1.5;

[0037] Add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to N-methylpyrrolidone, and ultrasonic disperse evenly to obtain a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide solution; then add the modified carbon nanotubes and flame-retardant modified halloysite nanotubes to N-methylpyrrolidone, ultrasonic disperse evenly and then drop the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide solution. After dropping, react at 82 °C for 6.5 h, then raise the temperature to 165 °C and react for 5.5 h. After the reaction, filter, wash, and dry to obtain flame-retardant filler; the reaction mass ratio of modified carbon nanotubes, flame-retardant modified halloysite nanotubes, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 1:1:4.5;

[0038] Step 3: Mix 90 g of polyolefin, 15 g of phosphazene flame retardant, 10 g of flame-retardant filler, 8 g of talc powder, 3 g of gum, and 2 g of stearic acid, stir and melt thoroughly to obtain a rubber compound. The rubber compound is crosslinked at 190 °C for 17 min, granulated, and molded to obtain a cable sheath; wrap the cable sheath around the outermost layer of the cable to obtain the finished product.

[0039] Example 3: Step 1: Add hexachlorocyclotriphosphazene and phenylphosphonic acid to acetonitrile. After ultrasonic dispersion, add triethylamine dropwise, and stir and react at 55 °C for 5 h to obtain phosphazene cyclotriphosphazene. Add phosphazene cyclotriphosphazene to deionized water, and obtain a phosphazene cyclotriphosphazene solution after ultrasonic dispersion. Add melamine to deionized water, and obtain a melamine solution after ultrasonic dispersion. Then slowly add the phosphazene cyclotriphosphazene solution. After the addition, react at 80 °C for 3 h. After the reaction, filter, wash, and dry to obtain a phosphazene flame retardant. The reaction molar ratio of hexachlorocyclotriphosphazene, phenylphosphonic acid, and melamine is 1:7:8;

[0040] Step 2: Add multi-walled carbon nanotubes to the mixed solvent. After ultrasonic dispersion, adjust the pH to 4, then add it to toluene. After stirring evenly, add silane coupling agent KH560, and reflux and react at 110 °C for 5 h. After the reaction, centrifuge, filter, and dry to obtain modified carbon nanotubes. The reaction mass ratio of multi-walled carbon nanotubes and silane coupling agent KH560 is 9:1; the volume ratio of ethanol and water in the mixed solvent is 9:1.5;

[0041] Add halloysite nanotubes to the mixed solvent. After ultrasonic dispersion, adjust the pH to 4, then add silane coupling agent KH792, and ultrasonically disperse evenly and reflux and react at 80 °C for 5 h. After the reaction, centrifuge, wash, and vacuum dry to obtain modified halloysite nanotubes. Dissolve the modified halloysite nanotubes and p-methylsulfonylbenzaldehyde in ethanol solution respectively, then add the p-methylsulfonylbenzaldehyde solution dropwise to the modified halloysite nanotubes solution, and reflux and react at 80 °C for 8 h. After the reaction, cool, filter, wash with alcohol, and dry to obtain flame retardant modified halloysite nanotubes. The reaction mass ratio of halloysite nanotubes, silane coupling agent KH792, and p-methylsulfonylbenzaldehyde is 9:1:1.1; the volume ratio of ethanol and water in the mixed solvent is 9:1.5;

[0042] Add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to N-methylpyrrolidone, and obtain a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide solution after ultrasonic dispersion. Then add the modified carbon nanotubes and flame retardant modified halloysite nanotubes to N-methylpyrrolidone, and after ultrasonic dispersion, add the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide solution dropwise. After the addition, react at 80 °C for 6 h, then raise the temperature to 160 °C and react for 5 h. After the reaction, filter, wash, and dry to obtain a flame retardant filler. The reaction mass ratio of the modified carbon nanotubes, flame retardant modified halloysite nanotubes, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 1:1:4.5;

[0043] Step 3: Mix 90 g of polyolefin, 15 g of phosphazene flame retardant, 10 g of flame retardant filler, 8 g of talc powder, 3 g of gum, and 2 g of stearic acid. After fully stirring and melting, a rubber compound is obtained. The rubber compound is then cross-linked at 180 °C for 15 min, granulated, and molded to obtain a cable sheath; the cable sheath is wrapped around the outermost layer of the cable to obtain a finished product.

[0044] Comparative Example 1: Remove the phosphazene flame retardant, and the rest is the same as in Example 1. The specific steps are as follows: Step 1: Add multi-walled carbon nanotubes to the mixed solvent, adjust the pH to 5 after ultrasonic dispersion, then add it to toluene, stir evenly, and then add silane coupling agent KH560. React at 120 °C under reflux for 6 h. After the reaction, centrifuge, filter, and dry to obtain modified carbon nanotubes; the reaction mass ratio of multi-walled carbon nanotubes to silane coupling agent KH560 is 9:1; the volume ratio of ethanol to water in the mixed solvent is 9:1.5;

[0045] Add halloysite nanotubes to the mixed solvent, adjust the pH to 5 after ultrasonic dispersion, then add silane coupling agent KH792, and ultrasonically disperse evenly and react at 85 °C under reflux for 6 h. After the reaction, centrifuge, wash, and vacuum dry to obtain modified halloysite nanotubes; dissolve the modified halloysite nanotubes and p-toluenesulfonylbenzaldehyde in an ethanol solution respectively, and then drop the p-toluenesulfonylbenzaldehyde solution into the modified halloysite nanotube solution, and react at 85 °C under reflux for 9 h. After the reaction, cool, filter, wash with alcohol, and dry to obtain flame retardant modified halloysite nanotubes; the reaction mass ratio of halloysite nanotubes, silane coupling agent KH792, and p-toluenesulfonylbenzaldehyde is 9:1:1.1; the volume ratio of ethanol to water in the mixed solvent is 9:1.5;

[0046] Add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to N-methylpyrrolidone, and obtain a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide solution after ultrasonic dispersion; then add the modified carbon nanotubes and flame retardant modified halloysite nanotubes to N-methylpyrrolidone, ultrasonically disperse evenly, and then drop the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide solution. After dropping, react at 85 °C for 7 h, then raise the temperature to 170 °C and react for 6 h. After the reaction, filter, wash, and dry to obtain a flame retardant filler; the reaction mass ratio of the modified carbon nanotubes, flame retardant modified halloysite nanotubes, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 1:1:4.5;

[0047] Step 2: Mix 90 g of polyolefin, 10 g of flame retardant filler, 8 g of talc, 3 g of gum, and 2 g of stearic acid, and fully stir and melt to obtain a rubber compound. The rubber compound is then crosslinked at 200 °C for 20 min, granulated, and molded to obtain a cable protective sleeve; the cable protective sleeve is wrapped around the outermost layer of the cable to obtain a finished product.

[0048] Comparative Example 2: Remove the flame retardant filler, and the rest is the same as in Example 1. The specific steps are as follows: Step 1: Add hexachlorocyclotriphosphazene and phenylphosphonic acid to acetonitrile, ultrasonically disperse evenly, and then dropwise add triethylamine, and stir and react at 60 °C for 7 h to obtain phosphazene cyclotriphosphazene; add phosphazene cyclotriphosphazene to deionized water, ultrasonically disperse evenly to obtain a phosphazene cyclotriphosphazene solution; add melamine to deionized water, ultrasonically disperse evenly to obtain a melamine solution, and then slowly dropwise add the phosphazene cyclotriphosphazene solution. After the addition is completed, react at 90 °C for 4 h. After the reaction is completed, filter, wash, and dry to obtain a phosphazene flame retardant; the reaction molar ratio of hexachlorocyclotriphosphazene, phenylphosphonic acid, and melamine is 1:7:8;

[0049] Step 2: Mix 90 g of polyolefin, 15 g of phosphazene flame retardant, 8 g of talc, 3 g of gum, and 2 g of stearic acid, and fully stir and melt to obtain a rubber compound. The rubber compound is then crosslinked at 200 °C for 20 min, granulated, and molded to obtain a cable protective sleeve; the cable protective sleeve is wrapped around the outermost layer of the cable to obtain a finished product.

[0050] Detection test:

[0051] Tensile strength test: Use the cable protective sleeve prepared by the present invention as a specimen, and conduct a tensile test on the specimen with reference to the standard of GB / T 1040.1-2006 to test the tensile strength of the specimen.

[0052] Limiting oxygen index test: Use the cable protective sleeve prepared by the present invention as a specimen, and record the oxygen index value with reference to the standard of GB / T2406-1993.

[0053] Vertical burning test: Use the cable protective sleeve prepared by the present invention as a specimen, with reference to the standard of ASTM D635-77. Move the externally applied flame to the lower end of the specimen to ignite for 10 s, remove the externally applied flame and record the burning time of the specimen with flame. If the specimen extinguishes within 30 s, then it is necessary to apply the flame to the lower end of the specimen again for 10 s. Finally, remove the heat source and record the burning duration of the specimen with flame and without flame. Determine the vertical burning test grade according to the test record results. The results are as follows in the table:

[0054] Tensile strength / MPa Limiting oxygen index / % Combustion rating Example 1 26.8 39 V-0 Example 2 26.4 38 V-0 Example 3 26.3 38 V-0 Comparative example 1 25.9 27 V-2 Comparative example 2 21.7 30 V-1

[0055] Conclusion: The dosages in Examples 1 to 3 remain unchanged, and only some reaction parameters are modified. From the experimental data, it can be seen that the performance of the specimens does not show obvious fluctuations.

[0056] Comparative Example 1: The phosphazene flame retardant 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 tensile strength decreased to 25.9 MPa, the limiting oxygen index decreased to 27%, and the combustion rating became V-2. The reason is analyzed as follows: The phosphazene flame retardant prepared in the present invention will decompose into various phosphorus-containing flame retardant materials during the high-temperature combustion process, so it can effectively slow down the combustion rate of the material. Therefore, after removing it, the limiting oxygen index decreases and the combustion rating becomes V-2.

[0057] Comparative Example 2: The flame retardant filler 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 tensile strength decreased to 21.7 MPa, the limiting oxygen index decreased to 30%, and the combustion rating became V-1. The reason is analyzed as follows: The flame retardant filler prepared in the present invention can form a dense carbon layer, thereby preventing oxygen and heat from transferring to the interior of the material, and at the same time, it can also prevent the combustible gas inside the material from diffusing outward, inhibiting the continuation of combustion. Therefore, after removing it, the limiting oxygen index decreases and the combustion rating becomes V-1; in addition, the nanotubes in the flame retardant filler can effectively transfer stress and prevent the propagation of cracks, thereby improving the rigidity and anti-deformation ability of the cable sheath. Therefore, after removing it, the tensile strength decreases.

[0058] It should be noted that in this article, 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 "include", "comprise" or any other variation thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0059] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used 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 modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a high-strength flame-retardant and fire-proof cable, characterized in that: The following steps are involved: Step 1: adding hexachlorocyclotriphosphazene and phenylphosphonic acid to acetonitrile, ultrasonically dispersing them uniformly, then adding triethylamine dropwise, and stirring at 55-60° C. for 5-7 hours to obtain phosphonic acid cyclotriphosphazene; adding phosphonic acid cyclotriphosphazene to deionized water, ultrasonically dispersing them uniformly to obtain a phosphonic acid cyclotriphosphazene solution; adding melamine to deionized water, ultrasonically dispersing them uniformly to obtain a melamine solution, then slowly adding the phosphonic acid cyclotriphosphazene solution dropwise, reacting at 80-90° C. for 3-4 hours after the addition is completed, filtering, washing, and drying to obtain a phosphazene flame retardant; Step 2: adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to N-methylpyrrolidone, and ultrasonically dispersing the mixture to obtain a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide solution; then adding modified carbon nanotubes and flame-retardant modified halloysite nanotubes to N-methylpyrrolidone, and ultrasonically dispersing the mixture to obtain a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide solution, and reacting the mixture at 80-85° C. for 6-7 hours after the addition is completed, and then raising the temperature to 160-170° C. for 5-6 hours. After the reaction is completed, filtering, washing, and drying the mixture to obtain a flame-retardant filler; Step 3: Mix polyolefin, phosphazene flame retardant, flame retardant filler, talc, gum, and stearic acid, stir and melt to obtain a rubber compound, cross-link the rubber compound at 180-200° C. for 15-20 minutes, granulate, and form to obtain a cable protective cover; wrap the cable protective cover to the outermost layer of the cable to obtain a finished product.

2. The preparation method of a high-strength flame-retardant and fire-proof cable according to claim 1, characterized in that: In step 1, the reaction molar ratio of hexachlorocyclotriphosphazene, phenylphosphonic acid, and melamine is 1:(6.5-7.5):

8.

3. The preparation method of a high-strength flame-retardant and fire-proof cable according to claim 1, wherein: In step 2, when preparing the flame retardant filler, the reaction mass ratio of the modified carbon nanotubes, the flame retardant modified halloysite nanotubes, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 1:1:(4-5).

4. The preparation method of a high-strength flame-retardant and fire-proof cable according to claim 3, wherein: The preparation process of modified carbon nanotubes is as follows: multi-walled carbon nanotubes are added to a mixed solvent, ultrasonically dispersed and then the pH is adjusted to 4-5, then added to toluene, stirred evenly and then silane coupling agent KH560 is added, refluxed at 110-120 ° C for 5-6 hours, and after the reaction is completed, the modified carbon nanotubes are obtained by centrifugation, filtration and drying.

5. The preparation method of a high-strength flame-retardant and fire-proof cable according to claim 4, characterized in that: The reaction mass ratio of multi-walled carbon nanotubes and silane coupling agent KH560 is (8-10):

1.

6. The preparation method of a high-strength flame-retardant and fire-proof cable according to claim 3, characterized in that: The preparation process of flame-retardant modified halloysite nanotubes is as follows: adding halloysite nanotubes to a mixed solvent, ultrasonically dispersing them uniformly, adjusting the pH to 4-5, adding a silane coupling agent KH792, ultrasonically dispersing them uniformly, and reflux reacting at 80-85°C for 5-6 hours. After the reaction is completed, the modified halloysite nanotubes are centrifuged, washed, and vacuum-dried to obtain the modified halloysite nanotubes; the modified halloysite nanotubes and p-methylsulfonylbenzaldehyde are respectively dissolved in an ethanol solution, and the p-methylsulfonylbenzaldehyde solution is dropwise added to the modified halloysite nanotube solution, reflux reacting at 80-85°C for 8-9 hours. After the reaction is completed, the flame-retardant modified halloysite nanotubes are obtained by cooling, filtering, washing with alcohol, and drying.

7. The preparation method of a high-strength flame-retardant and fire-proof cable according to claim 6, characterized in that: The reaction mass ratio of halloysite nanotubes, silane coupling agent KH792, and 4-methylsulfonylbenzaldehyde is (8 - 10):1:(1.0 - 1.2).

8. The preparation method of a high-strength flame-retardant and fire-proof cable according to claim 4 or 6, characterized in that: The mixed solvent consists of ethanol and water, and the volume ratio of ethanol to water is 9:(1 - 2).

9. The preparation method of a high-strength flame-retardant and fire-proof cable according to claim 1, characterized in that: In step three, the component contents of the rubber compound are as follows: in terms of mass parts, 90 - 100 parts of polyolefin, 15 - 25 parts of phosphazene flame retardant, 10 - 15 parts of flame retardant filler, 8 - 13 parts of talc powder, 3 - 5 parts of gum, and 2 - 3 parts of stearic acid.

10. A high-strength flame-retardant and fire-proof cable, characterized in that, Prepared by the preparation method according to any one of claims 1 - 9.