Preparation method of fireproof flame-retardant cable

Abstract

The invention discloses a preparation method of a fireproof flame-retardant cable, and relates to the field of power transmission and distribution line equipment. The preparation method comprises the following steps: performing ultrasonic radiation on organic bentonite to strip an interlayer structure, and then inserting rubber and acrylic acid into the interlayer structure of the bentonite in sequence to form a loose three-dimensional network structure. After mixing and adding phenyl phosphorus dichloride, cooking to generate an organic phosphorus flame-retardant compound and polymerizing. And then heating and drying bentonite to reduce the interplanar spacing, so that silicon oxide is generated, the structure is compact, the air contact surface is reduced, and the flame-retardant and fireproof effects are achieved. In addition, the composite bentonite and the alumina trihydrate are mixed as a filler to prepare the flame-retardant fireproof aerogel layer, the alumina trihydrate absorbs heat and is dehydrated when encountering high temperature, the temperature rise rate is slowed down, water is released to swell, the composite bentonite wraps, extends and is carbonized to prevent the combustible part from being in contact with combustion-supporting gas, and the flame-retardant effect is achieved. The cable prepared by the invention has fireproof and flame-retardant effects.

Description

Technical Field

[0001] The present invention relates to the technical field of transmission and distribution line equipment, and specifically to a preparation method of a fireproof and flame-retardant cable. Background Art

[0002] Current flame-retardant wires and cables only have the function of high-temperature flame retardancy and cannot prevent fire. Generally, mica tapes are wound outside the conductor or insulation layer. When such a cable is in a high-temperature environment, although the mica tape is not affected by high temperature, the conductive conductor inside the mica tape is melted due to high temperature, resulting in the interruption of the line, and the insulation layer will also melt and even catch fire; in addition, the mica tape is easily dragged during the erection of wires and cables, resulting in mechanical damage, so that it cannot play the role of fire prevention and insulation.

[0003] Existing fireproof cables are either complex in structure, high in cost, or complex in manufacturing process, and have extremely high requirements for installation and laying, while their fireproof performance is not ideal. How to simplify the process and improve the fireproof performance of cables while reducing material and production costs is of great significance. Organobentonite has many excellent properties, such as good thermal stability, high char residue, large reserves, and low production cost. However, due to its own structure, bentonite has a small interlayer spacing and is prone to agglomeration in the polymer matrix. In addition, the flame-retardant effect of bentonite is general and cannot meet the requirements of fireproof materials. However, there are a large number of exchangeable cations between the layers of bentonite, which provides the necessary conditions for modification. Mixing the modified organobentonite with aluminum trihydroxide to prepare an aerogel layer as a fireproof and flame-retardant layer, based on this idea, the present invention provides a fireproof and flame-retardant cable and its preparation method. Summary of the Invention

[0004] The purpose of the present invention is to provide a fireproof and flame-retardant cable and its preparation method to solve the problems existing in the prior art.

[0005] To solve the above technical problems, the present invention provides the following technical solution: A fireproof and flame-retardant cable, the cable from the inside to the outside is successively an insulating cable core, a modified aerogel layer, a stainless steel layer, and an outer sheath layer.

[0006] Further, the modified aerogel layer is prepared by mixing organobentonite and aluminum trihydroxide.

[0007] Further, the organobentonite is obtained by ultrasonic treatment of bentonite, reacting with rubber and acrylic acid to generate an organophosphorus-based flame retardant and polyacrylic acid, and then accumulating by heating.

[0008] Further, a preparation method of a fireproof and flame-retardant cable includes the following preparation steps: (1) Mix the organo - quaternary - ammonium - salt - intercalated bentonite with deionized water at a mass ratio of 1:1000 - 5000, oscillate it under ultrasonic waves with a frequency of 20 kHz - 120 kHz and a power of 100 W - 1200 W for 10 - 20 min, take the solid, and dry it at 50 °C for 2 h; heat the high - speed mixer to 180 - 200 °C, keep it at a constant temperature for 5 - 15 min, put in 6 - 10 parts of the dried bentonite and 2 parts of butyl rubber, stir at a speed of 600 r / min for 15 - 25 min, continue to stir and cool down to 110 - 120 °C, put in 1 - 5 parts of acrylic acid and continue to stir for 5 - 15 min, then put in 0.05 - 0.25 parts of phenyl dichlorophosphine and 0.08 - 0.2 parts of ammonium persulfate, continue to stir for 20 min, then carry out steam cooking, the cooking temperature is 80 - 100 °C, the cooking time is 4 - 6 h, after the cooking is completed, put it into a glass cup, place it in the heating chamber of a muffle furnace, the heating temperature is 105 °C, and the heating time is 1 - 15 d; after heating, cool it to room temperature to prepare the organic composite bentonite; (2) Immerse polystyrene with a cross - linking degree of 5 - 15% in absolute ethanol for 24 - 48 h, take it out and air - dry it naturally at room temperature for 6 h. Put the air - dried polystyrene and tetrabutyl titanate into a mixed solution of dichloromethane and carbon tetrachloride, heat it to 50 °C, and stir at a speed of 200 - 300 r / min for 12 - 15 h, then lower the temperature to room temperature to obtain the aerogel precursor; (3) Use an extruder to extrude and wrap the aerogel precursor on the insulating cable core, the extrusion temperature is 55 - 65 °C, then place it in a high - pressure closed device, pressurize it to 16 MPa and heat it to 40 - 60 °C, and keep the temperature for 8 - 10 h. After completion, reduce the pressure and temperature to normal pressure and normal temperature to obtain a polystyrene aerogel - layer cable; uniformly mix aluminum trihydrate, organic composite bentonite, polydopamine, vinyltriethoxysilane, and benzyl alcohol, then add 5 - mm agate balls as the ball - milling medium, the ball - to - material ratio is 10:1, put the ball - milling tank on the ball - mill and ball - mill it at a rotation speed of 550 r / min for 15 - 75 min to obtain the filler; uniformly spray the filler on the surface of the polystyrene aerogel - layer cable, then place it in a closed environment at 30 - 40 °C for 3 - 5 h, then heat it to 70 - 80 °C and keep it for 2 - 3 h, and finally heat it to 100 - 120 °C and keep it for 30 - 60 min to obtain the modified aerogel - layer cable; (4) Use a stainless - steel strip to carry out on - line coating and welding on the cable core wrapped with the modified aerogel. After welding, the stainless - steel pipe is subjected to grooving treatment; wrap a sheath layer outside the stainless - steel layer, and its raw materials include the following components in parts by weight: 40 - 50 parts of chlorosulfonated polyethylene, 15 - 25 parts of chlorinated polyethylene, 8 - 16 parts of EVA, 20 - 30 parts of halogen - free low - smoke flame - retardant polyolefin, 1 - 2 parts of vinyltriethoxysilane, and 1 - 2 parts of silane coupling agent KH550.

[0009] Further, the size of the organic bentonite in step (1) is 20 - 200 mesh.

[0010] Further, in step (2), the weight ratio of air-dried low-crosslinking polystyrene, tetrabutyl titanate, dichloromethane, and carbon tetrachloride is 10 - 16:1:20:50.

[0011] Further, in step (3), the mass parts of aluminum trihydrate, organic composite bentonite, polydopamine, vinyltriethoxysilane, and benzyl alcohol are 10 - 20 parts, 5 - 13 parts, 5 - 11 parts, 2 - 4 parts, and 15 - 35 parts respectively.

[0012] Further, in step (3), the weight ratio of the filler to the polystyrene aerogel is 0.5 - 1:1.

[0013] Further, in step (4), the silane coupling agent is silane coupling agent KH550.

[0014] Further, the stainless-steel sheath in step (4) is made by welding and corrugating a stainless-steel strip with a thickness of 0.1 - 0.2 mm, a tensile strength of 520 - 595 MPa, and an elongation rate of 42% - 48%; during welding, a mixed gas of helium and argon with a volume ratio of 1:2 is used for protection; the minimum bending radius of the cable thus produced is 7 - 15 times the diameter of the cable.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention prepares an aerogel layer by mixing organic composite bentonite and inorganic aluminum trihydrate to wrap the cable, so as to achieve the effects of fire prevention and flame retardancy.

[0016] First, the organic bentonite is subjected to ultrasonic radiation to generate an interlayer peeling structure under the action of high-frequency mechanical waves. Then, rubber is inserted into the interlayer structure of the bentonite to form a composite material with a nano-dispersion structure. Acrylic acid is inserted into the gaps of the composite material, so that the composite material is infiltrated by acrylic acid to form a loose three-dimensional network structure. After adding phenyl dichlorophosphine and mixing, the bentonite is steamed with high-temperature water vapor. During the steaming process, part of the acrylic acid reacts with phenyl dichlorophosphine to generate an organophosphorus-based flame retardant compound, and the excess acrylic acid monomers are in-situ addition polymerized to obtain polyacrylic acid, which locks the organophosphorus-based flame retardant compound and makes it firmly adhere to the three-dimensional structure of the bentonite, capturing the free radicals generated by the cracking of silicone rubber during combustion, so that the combustion reaction is inhibited and delayed. Then, while drying the bentonite by heating, the crystal plane spacing of the bentonite is reduced, and silicon oxides are generated by itself, cementing the remaining mineral components, so that the bentonite undergoes a condensation and accumulation behavior, and the structure of the composite bentonite tends to be compact, reducing the air contact surface to achieve the effect of flame retardancy and fire prevention; Secondly, the treated composite bentonite is mixed with aluminum trihydrate to prepare a flame-retardant and fire-proof aerogel layer as a filler. When the temperature of the aerogel layer is too high, the aluminum trihydrate will absorb heat and dehydrate, slowing down the rate of temperature rise of the aerogel layer to achieve the flame-retardant effect. In addition, the released water will be absorbed by the surrounding composite bentonite. The swollen bentonite will wrap and extend due to the volume change, and the carbonization blocks the contact between the combustible part and the combustion-supporting gas, further achieving the flame-retardant effect through the synergistic action mechanism with aluminum trihydrate. Detailed implementation mode

[0017] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. 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.

[0018] In order to more clearly illustrate the method provided by the present invention, the following examples are used for detailed description. The test methods for each index of a fire-proof and flame-retardant cable manufactured in the following examples are as follows: Flame retardancy: The sample cables of the examples and the comparative examples are subjected to a flame-retardant test: Keep the sample cable vertical, use a test blowtorch with a flame height of 125 mm and a thermal power of 500 W, burn for 15 s, then stop for 15 s, repeat 5 times, and then observe the burning time of the remaining flame and determine the degree of burn according to the overall appearance after the flame goes out. The above experiment is carried out three times for each cable, and the average value is taken.

[0019] Oxygen index: The sample cables of the examples and the comparative examples are tested according to the method in GB / T2406-2008 "Test Method for Flammability of Plastics - Oxygen Index Method"; the corresponding standard value is ≥32 according to the standard in JB / T10707-2007; Example 1 (1) Mix the 20-mesh organo-quaternary ammonium salt intercalated bentonite with deionized water at a mass ratio of 1:1000, oscillate for 10 min under ultrasonic waves with a frequency of 20 kHz and a power of 100 W, take the solid, and dry it at 50 °C for 2 h; Heat the high-speed mixer to 180 °C, keep it at a constant temperature for 5 min, put in 6 parts of the dried bentonite and 2 parts of butyl rubber, stir at a speed of 600 r / min for 15 min, continue to stir and cool down to 110 °C, put in 1 part of acrylic acid and continue to stir for 5 min, then put in 0.05 part of phenyl dichloride and 0.08 part of ammonium persulfate, continue to stir for 20 min, and then carry out steam cooking. The cooking temperature is 80 °C and the cooking time is 4 h. After the cooking is completed, put it into a glass cup and place it in the heating chamber of a muffle furnace. The heating temperature is 105 °C and the heating time is 1 d; After heating, cool to room temperature to prepare the organic composite bentonite; (2) Soak polystyrene with a crosslinking degree of 5% in absolute ethanol for 24 h, take it out and air-dry it naturally at room temperature for 6 h. Place the air-dried polystyrene and tetrabutyl titanate in a mixed solution of dichloromethane and carbon tetrachloride. The weight ratio of the air-dried low-crosslinking-degree polystyrene, tetrabutyl titanate, dichloromethane, and carbon tetrachloride is 10:1:20:50. Heat the mixed solution to 50 °C, stir it at a speed of 200 r / min for 12 h, and then cool it down to room temperature to obtain the aerogel precursor. (3) Use an extruder to extrude and wrap the aerogel precursor on the insulated cable core. The extrusion temperature is 55 °C, and then place it in a high-pressure closed device, pressurize it to 16 MPa and heat it to 40 °C, and maintain the temperature for 8 h. After completion, reduce the pressure and temperature to normal pressure and normal temperature to obtain a polystyrene aerogel layer cable. Mix 10 parts, 5 parts, 5 parts, 2 parts, and 15 parts by mass of aluminum trihydrate, organic composite bentonite, polydopamine, vinyltriethoxysilane, and benzyl alcohol, and then add 5 mm agate balls as the ball-milling medium. The ball-to-material ratio is 10:1. Place the ball-milling tank on the ball mill and ball-mill it at a rotation speed of 550 r / min for 15 min respectively to obtain the filler. Spray the filler evenly on the surface of the polystyrene aerogel layer cable, and then place it in a closed environment at 30 °C for 3 h, then heat it to 70 °C and maintain it for 2 h, and finally heat it to 100 °C and maintain it for 30 min to obtain the modified aerogel layer cable. (4) Use a stainless steel strip to conduct on-line coating and welding on the cable core wrapped with the modified aerogel. The welded stainless steel pipe is subjected to grooving treatment. The stainless steel sheath is made by welding and grooving a stainless steel strip with a thickness of 0.1 mm, a tensile strength of 520 MPa, and an elongation rate of 42%. During welding, a mixed gas of helium and argon with a volume ratio of 1:2 is used for protection. The minimum bending radius of the cable obtained is 7 times the diameter of the cable. Wrap a sheath layer outside the stainless steel layer, and its raw materials include the following components in parts by weight: 40 parts of chlorosulfonated polyethylene, 15 parts of chlorinated polyethylene, 8 parts of EVA, 20 parts of halogen-free low-smoke flame-retardant polyolefin, 1 part of vinyltriethoxysilane, and 1 part of silane coupling agent KH550.

[0020] Example 2 (1) Mix the 110-mesh organic quaternary ammonium salt-intercalated bentonite with deionized water at a mass ratio of 1:3000, oscillate it under ultrasonic waves with a frequency of 70 kHz and a power of 650 W for 15 min, take the solid, and dry it at 50 °C for 2 h; heat the high-speed mixer to 190 °C, keep it at a constant temperature for 10 min, put in 8 parts of the dried bentonite and 2 parts of butyl rubber, stir at a speed of 600 r / min for 20 min, continue to stir and cool down to 115 °C, put in 3 parts of acrylic acid and continue to stir for 10 min, then put in 0.15 parts of phenyl dichlorophosphine and 0.14 parts of ammonium persulfate, continue to stir for 20 min, and then carry out steam cooking. The cooking temperature is 90 °C and the cooking time is 5 h. After cooking, put it into a glass cup and place it in the heating chamber of a muffle furnace. The heating temperature is 105 °C and the heating time is 8 d; after heating, cool it to room temperature to prepare the organic composite bentonite. (2) Soak the polystyrene with a crosslinking degree of 10% in absolute ethanol for 36 h, take it out and air-dry it naturally at room temperature for 6 h. Put the air-dried polystyrene and tetrabutyl titanate into a mixed solution of dichloromethane and carbon tetrachloride. The weight ratio of the air-dried low-crosslinking-degree polystyrene, tetrabutyl titanate, dichloromethane, and carbon tetrachloride is 13:1:20:50; heat the mixed solution to 50 °C and stir it at a speed of 250 r / min for 13.5 h, and then cool it down to room temperature to obtain the aerogel precursor. (3) Use an extruder to extrude and wrap the aerogel precursor on the insulated cable core. The extrusion temperature is 60 °C, and then place it in a high-pressure closed device, pressurize it to 16 MPa and heat it to 50 °C, and keep the temperature for 9 h. After completion, reduce the pressure and cool it down to normal pressure and normal temperature to obtain the polystyrene aerogel layer cable; mix 15 parts, 9 parts, 8 parts, 3 parts, and 25 parts of aluminum trihydrate, organic composite bentonite, polydopamine, vinyltriethoxysilane, and benzyl alcohol by mass, and then add 5-mm agate balls as the ball-milling medium. The ball-to-material ratio is 10:1. Put the ball-milling tank on the ball mill and ball-mill it at a rotation speed of 550 r / min for 45 min respectively to obtain the filler; evenly spray the filler on the surface of the polystyrene aerogel layer cable, and then place it in a closed environment at 35 °C for 4 h, then heat it to 75 °C and keep it for 2.5 h, and finally heat it to 110 °C and keep it for 45 min to obtain the modified aerogel layer cable. (4) The cable core wrapped with modified aerogel is coated and welded online with a stainless steel strip. After welding, the stainless steel pipe is subjected to grooving treatment; the stainless steel sheath is made by welding and grooving a stainless steel strip with a thickness of 0.15 mm, a tensile strength of 560 MPa, and an elongation rate of 45%; during welding, a mixed gas of helium and argon with a volume ratio of 1:2 is used for protection; the minimum bending radius of the manufactured cable is 11 times the diameter of the cable; a sheath layer is wrapped outside the stainless steel layer, and its raw materials include the following components in parts by weight: 45 parts of chlorosulfonated polyethylene, 20 parts of chlorinated polyethylene, 12 parts of EVA, 25 parts of halogen-free low-smoke flame-retardant polyolefin, 1.5 parts of vinyltriethoxysilane, and 1.5 parts of silane coupling agent KH550.

[0021] Example 3 (1) Mix bentonite intercalated with organic quaternary ammonium salt of 200 mesh with deionized water at a mass ratio of 1:5000, oscillate under ultrasonic waves with a frequency of 120 kHz and a power of 1200 W for 20 min, take the solid, and dry it at 50 °C for 2 h; heat the high-speed mixer to 200 °C, keep it at a constant temperature for 15 min, put in 10 parts of dried bentonite and 2 parts of butyl rubber, stir at a speed of 600 r / min for 25 min, continue to stir and cool down to 120 °C, put in 5 parts of acrylic acid and continue to stir for 15 min, then put in 0.25 parts of phenyl dichlorophosphine and 0.2 parts of ammonium persulfate, continue to stir for 20 min, and then carry out steam cooking. The cooking temperature is 100 °C and the cooking time is 6 h. After cooking is completed, put it into a glass cup and place it in the heating chamber of a muffle furnace. The heating temperature is 105 °C and the heating time is 15 d; after heating, cool it to room temperature to prepare the organic composite bentonite; (2) Soak polystyrene with a crosslinking degree of 15% in absolute ethanol for 48 h, take it out and air-dry it naturally at room temperature for 6 h. Put the air-dried polystyrene and tetrabutyl titanate into a mixed solution of dichloromethane and carbon tetrachloride. The weight ratio of air-dried low-crosslinking-degree polystyrene, tetrabutyl titanate, dichloromethane, and carbon tetrachloride is 16:1:20:50; heat the mixed solution to 50 °C, stir at a speed of 300 r / min for 15 h, and then lower the temperature to room temperature to obtain the aerogel precursor; (3) The aerogel precursor is extruded and wrapped around the insulated cable core by an extruder at an extrusion temperature of 65 °C, and then placed in a high-pressure closed device, pressurized to 16 MPa and heated to 60 °C, and the temperature is maintained for 10 h. After completion, the pressure is reduced and the temperature is lowered to normal pressure and normal temperature to obtain a polystyrene aerogel layer cable; alumina trihydrate, organic composite bentonite, polydopamine, vinyltriethoxysilane, and benzyl alcohol are mixed according to 20 parts, 13 parts, 11 parts, 4 parts, and 35 parts by mass, and then 5 mm agate balls are added as ball-milling media, and the ball-to-material ratio is 10:1. The ball-milling tank is placed on a ball mill and ball-milled at a speed of 550 r / min for 75 min respectively to obtain a filler; the filler is evenly sprayed on the surface of the polystyrene aerogel layer cable, and then placed in a closed environment at 40 °C for 5 h, then heated to 80 °C and maintained for 3 h, and finally heated to 120 °C and maintained for 60 min to obtain a modified aerogel layer cable; (4) The cable core wrapped with the modified aerogel is on-line coated and welded with a stainless steel strip, and the welded stainless steel pipe is subjected to grooving treatment; the stainless steel sheath is made by welding and grooving a stainless steel strip with a thickness of 0.2 mm, a tensile strength of 595 MPa, and an elongation rate of 48%; during welding, a mixed gas of helium and argon with a volume ratio of 1:2 is used for protection; the minimum bending radius of the cable obtained is 15 times the diameter of the cable; a sheath layer is wrapped outside the stainless steel layer, and its raw materials include the following components in parts by weight: 50 parts of chlorosulfonated polyethylene, 25 parts of chlorinated polyethylene, 16 parts of EVA, 30 parts of halogen-free low-smoke flame retardant polyolefin, 2 parts of vinyltriethoxysilane, and 2 parts of silane coupling agent KH550.

[0022] Comparative Example 1 The difference between Comparative Example 1 and Example 2 lies in the difference in step (1). Step (1) is changed to: Mix the 110-mesh organic quaternary ammonium salt-intercalated bentonite and deionized water at a mass ratio of 1:3000, oscillate under ultrasonic waves with a frequency of 70 kHz and a power of 650 W for 15 min, take the solid, and dry it at 50 °C for 2 h; heat the high-speed mixer to 190 °C, keep it at a constant temperature for 10 min, put in 8 parts of dried bentonite and 3 parts of acrylic acid, stir at a speed of 600 r / min for 20 min, continue to stir and cool to 115 °C, then put in 0.15 parts of phenyl dichlorophosphine and 0.14 parts of ammonium persulfate, continue to stir for 20 min, and then carry out steam cooking. The cooking temperature is 90 °C and the cooking time is 5 h. After the cooking is completed, it is loaded into a glass cup and placed in the heating chamber of a muffle furnace. The heating temperature is 105 °C and the heating time is 8 d; after heating, cool to room temperature to prepare the organic composite bentonite; the remaining steps are the same as those in Example 2.

[0023] Comparative Example 2 The difference between Comparative Example 2 and Example 2 lies in step (1). Step (1) is changed to: Mix bentonite intercalated with organic quaternary ammonium salt of 110 mesh with deionized water at a mass ratio of 1:3000, oscillate for 15 min under ultrasonic waves with a frequency of 70 kHz and a power of 650 W, take the solid, and dry it at 50 °C for 2 h; Heat the high-speed mixer to 190 °C, keep it at a constant temperature for 10 min, put in 8 parts of dried bentonite and 2 parts of butyl rubber, stir at a speed of 600 r / min for 20 min, continue to stir and cool down to 115 °C, put in 3 parts of acrylic acid and continue to stir for 10 min, then put in 0.15 part of phenyl dichlorophosphine, continue to stir for 20 min, and then carry out steam cooking. The cooking temperature is 90 °C and the cooking time is 5 h. After the cooking is completed, put it into a glass cup and place it in the heating chamber of a muffle furnace. The heating temperature is 105 °C and the heating time is 8 d; After heating, cool it to room temperature to prepare the organic composite bentonite; The remaining steps are the same as those in Example 2.

[0024] Comparative Example 3 The difference between Comparative Example 3 and Example 2 lies in step (1). Step (1) is changed to: Mix bentonite intercalated with organic quaternary ammonium salt of 110 mesh with deionized water at a mass ratio of 1:3000, oscillate for 15 min under ultrasonic waves with a frequency of 70 kHz and a power of 650 W, take the solid, and dry it at 50 °C for 2 h; Heat the high-speed mixer to 190 °C, keep it at a constant temperature for 10 min, put in 8 parts of dried bentonite and 2 parts of butyl rubber, stir at a speed of 600 r / min for 20 min, continue to stir and cool down to 115 °C, put in 3 parts of acrylic acid and continue to stir for 10 min, then put in 0.14 part of ammonium persulfate, continue to stir for 20 min, and then carry out steam cooking. The cooking temperature is 90 °C and the cooking time is 5 h. After the cooking is completed, put it into a glass cup and place it in the heating chamber of a muffle furnace. The heating temperature is 105 °C and the heating time is 8 d; After heating, cool it to room temperature to prepare the organic composite bentonite; The remaining steps are the same as those in Example 2.

[0025] Comparative Example 4 The difference between Comparative Example 4 and Example 2 lies in step (1). Step (1) is changed to: Mix bentonite intercalated with organic quaternary ammonium salt of 110 mesh with deionized water at a mass ratio of 1:3000, oscillate for 15 min under ultrasonic waves with a frequency of 70 kHz and a power of 650 W, take the solid, and dry it at 50 °C for 2 h; Heat the high-speed mixer to 190 °C, keep it at a constant temperature for 10 min, put in 8 parts of dried bentonite and 2 parts of butyl rubber, stir at a speed of 600 r / min for 20 min, continue to stir and cool down to 115 °C, put in 3 parts of acrylic acid and continue to stir for 10 min, then put in 0.15 part of phenyl dichlorophosphine and 0.14 part of ammonium persulfate, continue to stir for 20 min, then carry out steam cooking, the cooking temperature is 90 °C, the cooking time is 5 h, after the cooking is completed, put it into a constant temperature drying oven, dry it at 50 °C for 5 h to prepare organic composite bentonite; The remaining steps are the same as those in Example 2.

[0026] Comparative Example 5 The difference between Comparative Example 5 and Example 2 lies in step (3). Step (3) is changed to: Use an extruder to extrude and wrap the aerogel precursor on the insulated cable core, the extrusion temperature is 60 °C, then place it in a high-pressure closed device, pressurize to 16 MPa and heat up to 50 °C, and keep the temperature for 9 h. After completion, reduce the pressure and cool down to normal pressure and normal temperature to obtain a polystyrene aerogel layer cable; Mix organic composite bentonite, polydopamine, vinyltriethoxysilane, and benzyl alcohol in mass fractions of 15 parts, 9 parts, 8 parts, 3 parts, and 25 parts respectively, then add 5 mm agate balls as ball milling media, the ball-to-material ratio is 10:1, put the ball milling tank on the ball mill and ball mill at a rotation speed of 550 r / min for 45 min respectively to obtain a filler; Spray the filler evenly on the surface of the polystyrene aerogel layer cable, then place it in a closed environment at 35 °C for 4 h, then heat up to 75 °C and keep it for 2.5 h, and finally heat up to 110 °C and keep it for 45 min to obtain a modified aerogel layer cable; The remaining steps are the same as those in Example 2.

[0027] Effect Example The following Table 1 gives the performance analysis results of a fireproof and flame-retardant cable using Examples 1 to 3 and Comparative Examples 1 to 5 of the present invention.

[0028] Table 1 From the comparison of the experimental data on the flame retardancy and oxygen index between the examples and the comparative examples, it can be found that in the present invention, organic bentonite is subjected to ultrasonic radiation to generate an interlayer exfoliated structure under the action of high-frequency mechanical waves, and then rubber is inserted into the interlayer structure of bentonite to form a composite material with a nano-dispersed structure. Acrylic acid is inserted into the gaps of the composite material, so that the composite material is infiltrated by acrylic acid to form a loose three-dimensional network structure. After adding phenyl dichlorophosphine and mixing, the bentonite is steamed with high-temperature water vapor. During the steaming process, part of the acrylic acid reacts with phenyl dichlorophosphine to generate an organophosphorus-based flame retardant compound, and the excess acrylic acid monomer is in-situ addition polymerized to obtain polyacrylic acid, which locks the organophosphorus-based flame retardant compound and makes it firmly adhere to the three-dimensional structure of bentonite, capturing the free radicals generated by the pyrolysis during the combustion of silicone rubber, so that the combustion reaction is inhibited and delayed. Then, while drying the bentonite by heating, the crystal plane spacing of the bentonite is reduced, and silicon oxides are generated by itself, cementing the remaining mineral components, so that the bentonite undergoes a condensation and accumulation behavior, and the structure of the composite bentonite tends to be compact, reducing the air contact surface to achieve the effect of flame retardancy and fire prevention. The present invention uses the treated composite bentonite and aluminum trihydroxide to be mixed as fillers to prepare a flame-retardant and fire-proof aerogel layer. When the temperature of the aerogel layer is too high, the aluminum trihydroxide will absorb heat and dehydrate, slowing down the rate of temperature rise of the aerogel layer to achieve the flame retardant effect. In addition, the released water will be absorbed by the surrounding composite bentonite. The bentonite that absorbs and swells covers and extends due to its volume change, and carbonizes to block the contact between the combustible part and the combustion-supporting gas. The aerogel prepared in this way makes the cable have the effect of fire prevention and flame retardancy.

[0029] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be construed as limiting the claimed claim.

Claims

1. A method for preparing a fire-retardant cable, characterized in that: The method comprises the following preparation steps: (1) 110 mesh organic quaternary ammonium salt intercalated bentonite and deionized water were mixed at a mass ratio of 1:3000, and oscillated under ultrasonic wave with a frequency of 70kHz and a power of 650W for 15 minutes. The solid was taken and dried at 50°C for 2 hours. The high-speed mixer was heated to 190°C and kept at a constant temperature for 10 minutes. 8 parts of dried bentonite and 2 parts of butyl rubber were added and stirred at a speed of 600r / min for 20 minutes. The mixture was stirred and cooled to 115°C. 3 parts of acrylic acid were added and stirred for 10 minutes. Subsequently, 0.15 parts of phenylphosphine dichloride and 0.14 parts of ammonium persulfate were added and stirred for 20 minutes. The mixture was then steamed at a temperature of 90°C for 5 hours. After the steaming was completed, the mixture was put into a glass cup and placed in the heating chamber of a muffle furnace at a heating temperature of 105°C for 8 days. The mixture was cooled to room temperature after heating to prepare an organic composite bentonite. (2) Soaking polystyrene with a cross-linking degree of 10% in anhydrous ethanol for 36 hours, taking it out and air-drying it at room temperature for 6 hours, placing the air-dried polystyrene and tetrabutyl titanate in a mixed solution of dichloromethane and carbon tetrachloride, wherein the weight ratio of the air-dried low cross-linking polystyrene, tetrabutyl titanate, dichloromethane and carbon tetrachloride is 13:1:20:50; heating the mixed solution to 50°C, stirring it at a speed of 250 r / min for 13.5 hours, and then lowering the temperature to room temperature to obtain an aerogel precursor; (3) The aerogel precursor is extruded onto the insulating cable core by an extruder at a temperature of 60°C, and then placed in a high-pressure sealed device, pressurized to 16 MPa and heated to 50°C, and maintained at the temperature for 9 hours. After completion, the pressure is reduced and the temperature is cooled to normal pressure and temperature to obtain a polystyrene aerogel layer cable; trihydrate alumina, organic composite bentonite, polydopamine, vinyl triethoxysilane and benzyl alcohol are mixed in 15, 9, 8, 3 and 25 parts by weight, and then 5 mm agate balls are added as ball milling media with a ball-to-material ratio of 10:

1. The ball mill jar is placed in a ball mill and ball milled at a speed of 550 r / min for 45 minutes to obtain a filler; the filler is evenly sprayed on the surface of the polystyrene aerogel layer cable, and then placed in a sealed environment at 35°C for 4 hours, then heated to 75°C for 2.5 hours, and finally heated to 110°C for 45 minutes to obtain a modified aerogel layer cable; (4) The cable core coated with modified aerogel is coated and welded online with a stainless steel strip, and the stainless steel tube after welding is corrugated; the stainless steel sheath is made by welding and corrugating a stainless steel strip with a thickness of 0.15 mm, a tensile strength of 560 MPa, and an elongation of 45%; during welding, a mixed gas of helium and argon with a volume ratio of 1:2 is used for protection; the minimum bending radius of the obtained cable is 11 times the diameter of the cable; a sheath layer is wrapped around the stainless steel layer, and its raw materials include the following components by weight: 45 parts of chlorosulfonated polyethylene, 20 parts of chlorinated polyethylene, 12 parts of EVA, 25 parts of halogen-free low-smoke flame-retardant polyolefin, 1.5 parts of vinyl triethoxysilane, and 1.5 parts of silane coupling agent KH550.

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