Low-smoke halogen-free flame-retardant insulated cable

Abstract

The invention discloses a low-smoke halogen-free flame-retardant insulated cable. The preparation process of the cable comprises the following steps: step 1, mixing modified fibers and modified aluminum hydroxide in a mass ratio of 1: (20-40) to obtain a composite flame retardant; 2, adding the high-density polyethylene, the composite flame retardant, the antioxidant and the lubricant into a mixer, and uniformly mixing to obtain a mixture; and 3, adding the mixture into an extruder, melting and extruding to the outside of the conductor to form an insulating jacket, thereby obtaining the cable. The low-smoke halogen-free flame-retardant insulating material has the beneficial effects that the modified fiber and the modified aluminum hydroxide are compounded according to a specific proportion to form the composite flame retardant, and the composite flame retardant is combined with the high-density polyethylene, the antioxidant, the lubricant and the compatilizer to prepare the insulating material, so that the low-smoke halogen-free efficient flame-retardant effects are realized, and meanwhile, the mechanical strength of the cable is enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of cables, and specifically relates to a low-smoke, halogen-free, flame-retardant insulated cable. Background Art

[0002] In the technical field of cables, with the continuous improvement of people's requirements for safety performance and environmental protection, low-smoke, halogen-free, flame-retardant insulated cables have gradually become the focus of research and application.

[0003] Existing cable materials mostly use halogen-containing flame retardants or inorganic fillers such as aluminum hydroxide and magnesium hydroxide to improve their flame retardant properties. However, halogen-containing flame retardants will release a large amount of toxic and harmful gases during combustion, posing a serious threat to personnel safety and the environment. Although traditional inorganic flame retardant fillers have good smoke suppression effects, their large addition amounts are likely to cause a significant decline in the mechanical properties of materials, affecting the mechanical strength and processing performance of cables. In addition, the interfacial bonding between fiber-reinforced materials and the matrix in the existing technology is poor, making it difficult to effectively play a synergistic flame retardant role, and there is a lack of optimized design for the high-temperature resistance of the flame retardant system, resulting in an insufficiently dense carbon layer structure and being unable to effectively inhibit heat transfer and smoke release. At the same time, the imperfect modification process also restricts the further improvement of material properties. For example, problems such as improper coupling agent dosage and insufficient surface treatment are common, making the overall thermal stability of the composite material insufficient.

[0004] Therefore, it is urgent to develop a low-smoke, halogen-free, flame-retardant insulated cable that can not only meet the requirements of high-efficiency flame retardancy but also has good mechanical properties and processing performance to overcome many defects in the existing technology. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the existing technology and provide a low-smoke, halogen-free, flame-retardant insulated cable.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A preparation process for a low-smoke, halogen-free, flame-retardant insulated cable is as follows:

[0008] Step 1: Mix modified fibers and modified aluminum hydroxide in a mass ratio of 1:(20 - 40) to obtain a composite flame retardant;

[0009] Step 2: Add high-density polyethylene, the composite flame retardant, antioxidant, lubricant, and compatibilizer to a mixer and mix evenly to obtain a mixed material;

[0010] Step 3: Add the mixed material to an extruder and melt-extrude it onto the outside of the conductor to form an insulating jacket, thereby obtaining the cable.

[0011] Preferably, the mixture comprises the following components: by weight, 80-100 parts of high-density polyethylene, 60-70 parts of a composite flame retardant, 0.1-0.2 parts of an antioxidant, 0.1-0.2 parts of a lubricant, and 2-3 parts of a compatibilizer.

[0012] Preferably, the preparation process of the modified fiber is as follows:

[0013] A1: Add aramid fiber into phosphoric acid solution, soak for 4-5 min, then bake in an oven at 130 °C for 5-8 min, wash and dry; subsequently transfer it to a mixed solution composed of γ-aminopropyltriethoxysilane, ethanol, and deionized water, raise the temperature to 60-70 °C, react for 1-2 h, after the reaction ends, filter, wash, and dry to obtain silanized fiber;

[0014] A2: Add the modifier into tetrahydrofuran, fully dissolve it, adjust the pH to 5-6, immerse the silanized fiber in it, react in a water bath oscillator at 60 °C for 2-4 h, take out the fiber, wash, and dry it in a vacuum drying oven at 50 °C to obtain the modified fiber.

[0015] Among them, the preparation process of the modifier is as follows:

[0016] S1: Add 4-bromophenol and sodium hydroxide into anhydrous tetrahydrofuran, raise the temperature to 70-80 °C, reflux and stir in a nitrogen atmosphere for 1-2 h; then slowly dropwise add an anhydrous tetrahydrofuran solution of cyanuric chloride, continue to reflux and stir for 24 h, after the reaction ends, cool to room temperature, filter, and purify to obtain a bromo compound;

[0017] S2: Add the bromo compound into anhydrous tetrahydrofuran, fully dissolve it, cool to -70 °C, slowly dropwise add n-butyllithium, stir for 1-2 h, then add triisopropyl borate, continue to stir for 1-2 h, then raise the temperature to room temperature and stir overnight, rotary evaporate to remove the solvent, and perform post-treatment to obtain a boronic acid compound;

[0018] S3: Add the boronic acid compound into anhydrous tetrahydrofuran, stir to dissolve it, add p-aminobenzaldehyde, adjust the pH to 8-9, raise the temperature to 40-60 °C, stir and react for 12-16 h, after the reaction is completed, cool to room temperature, reduce the pressure to concentrate and remove the solvent, filter with suction, wash, and dry to obtain the modifier.

[0019] In the scheme, 4-bromophenol deprotonates under alkaline conditions to form a more nucleophilic phenoxide anion, which then attacks the chlorine atom in cyanuric chloride, undergoing an aromatic nucleophilic substitution reaction; then n-butyllithium undergoes a lithium-halogen exchange with the bromine atom of the bromo compound to generate a highly reactive aryllithium, which attacks the boron atom of triisopropyl borate to form a borate intermediate, and is then converted into boric acid through hydrolysis (during post-treatment). The specific reaction process is as follows:

[0020]

[0021] Preferably, the raw materials in the bromine-based compound include the following components: by weight, 18-20 parts of 4-bromophenol, 4-5 parts of sodium hydroxide, 10-12 parts of cyanuric chloride, and 200-250 parts of anhydrous tetrahydrofuran.

[0022] Preferably, the raw materials in the boric acid-based compound include the following components: by weight, 10-12 parts of bromine-based compound, 1-2 parts of n-butyllithium, 5-6 parts of triisopropyl borate, and 100-120 parts of anhydrous tetrahydrofuran.

[0023] In the scheme, the unreacted chlorine atoms of cyanuric chloride in the boric acid-based compound undergo an aromatic nucleophilic substitution reaction with p-aminobenzaldehyde to obtain a modifier; the structure of the modifier is as follows:

[0024]

[0025] Preferably, the raw materials in the modifier include the following components: by weight, 25-28 parts of boric acid-based compound, 2-4 parts of p-aminobenzaldehyde, and 80-100 parts of anhydrous tetrahydrofuran.

[0026] In the scheme, the electrophilic phosphorus atom in phosphoric acid attacks the carbonyl carbon atom of the amide group in the aramid fiber molecule, resulting in the cleavage of the amide bond; at the same time, the hydroxyl group of phosphoric acid combines with the carbonyl carbon to form a new phosphorus-containing group; and further reacts with the silanol structure generated by the hydrolysis of the silane coupling agent to obtain silanized fiber. The specific reaction process is as follows:

[0027]

[0028] Preferably, the raw materials in the silanized fiber contain the following components: by weight, 1-2 parts of aramid fiber, 20-30 parts of phosphoric acid solution, 0.1-0.2 parts of γ-aminopropyltriethoxysilane, 100-120 parts of ethanol, and 10-12 parts of deionized water; wherein the mass fraction of the phosphoric acid solution is 3wt%.

[0029] In the scheme, the aldehyde group contained in the modifier further reacts with the amino group of the silanized fiber to obtain modified fiber.

[0030] Preferably, the raw materials in the modified fiber include the following components: by weight, 10-20 parts of modifier, 300-350 parts of tetrahydrofuran, and 100-120 parts of silanized fiber.

[0031] Preferably, the preparation process of the modified aluminum hydroxide is as follows: by weight, 10-12 parts of aluminum hydroxide, 0.05-0.08 parts of titanate coupling agent, and 0.1-0.2 parts of white oil are added to a high-speed mixer and stirred for 5-8 minutes to obtain the modified aluminum hydroxide.

[0032] Advantages of the present invention:

[0033] In the present invention, a composite flame retardant is formed by compounding modified fibers and modified aluminum hydroxide in a specific ratio, and an insulating material is made by combining high-density polyethylene, an antioxidant, a lubricant, and a compatibilizer, achieving the effects of low smoke and halogen-free, and high-efficiency flame retardancy, while enhancing the mechanical strength of the cable. Specifically as follows:

[0034] First: In the solution, the introduction of modified fibers can enhance the adhesion of alumina generated by the decomposition of aluminum hydroxide on the material surface through physical support, promote the formation of a denser and continuous carbon layer, inhibit the release of smoke generated by polymer degradation, and enhance the flame retardancy and smoke suppression effects of the material; at the same time, aramid fibers have the characteristics of high modulus and high strength, can act as a reinforcing phase to bear external loads, reduce the weakening of the mechanical properties of the matrix by the filling of aluminum hydroxide, and improve the mechanical properties of the material.

[0035] Second: In the solution, by modifying the surface of aramid fibers, the introduced modifier contains multiple boric acid groups and triazine ring structures, and has good thermal stability; the synergistic flame retardant effect among phosphorus, nitrogen, boron, and silicon elements can also promote the formation of a dense and hard expanded carbon layer on the fiber, and the generated high-temperature substances such as boron phosphate can further improve the stability of the carbon layer, thereby improving the flame retardant performance of the prepared material. Specific embodiments

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described 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 of the embodiments. All other embodiments obtained by those of ordinary skill in the art without making creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0037] Embodiment 1: The preparation process of a low-smoke and halogen-free flame retardant insulating cable is as follows:

[0038] Step 1: Mix modified fibers and modified aluminum hydroxide in a mass ratio of 1:20 to obtain a composite flame retardant;

[0039] Step 2: Add 80 parts of high-density polyethylene, 60 parts of the composite flame retardant, 0.1 part of antioxidant, 0.1 part of lubricant, and 2 parts of compatibilizer (PE-g-MAH) to a mixer and mix evenly to obtain a mixture;

[0040] Step 3: Add the mixture into an extruder, melt and extrude it onto the outside of the conductor to form an insulating jacket, thereby obtaining a cable;

[0041] Among them, the preparation process of the modified aluminum hydroxide is as follows: Add 10 parts of aluminum hydroxide, 0.05 part of titanate coupling agent, and 0.1 part of white oil into a high-speed mixer, stir for 5 min to obtain the modified aluminum hydroxide;

[0042] Among them, the preparation process of the modified fiber is as follows:

[0043] A1: Add 1 part of aramid fiber into 20 parts of phosphoric acid solution (mass fraction is 3 wt%), soak for 4 min, then bake in an oven at 130 °C for 5 min, wash, and dry; Subsequently, transfer it to a mixed solution composed of 0.1 part of γ-aminopropyltriethoxysilane, 100 parts of ethanol, and 10 parts of deionized water, raise the temperature to 60 °C, react for 1 h, after the reaction ends, filter, wash, and dry to obtain the silylated fiber;

[0044] A2: Add 10 parts of modifier into 300 parts of tetrahydrofuran, fully dissolve it, adjust the pH to 5, immerse 100 parts of the silylated fiber into it, react in a water bath oscillator at 60 °C for 2 h, take out the fiber, wash, and dry it in a vacuum drying oven at 50 °C to obtain the modified fiber;

[0045] Among them, the preparation process of the modifier is as follows:

[0046] S1: Add 18 parts of 4-bromophenol and 4 parts of sodium hydroxide into 80 parts of anhydrous tetrahydrofuran, raise the temperature to 70 °C, reflux and stir for 1 h under a nitrogen atmosphere; Then slowly dropwise add an anhydrous tetrahydrofuran solution of cyanuric chloride (dissolve 10 parts of cyanuric chloride in 120 parts of anhydrous tetrahydrofuran), continue to reflux and stir for 24 h, after the reaction ends, cool to room temperature, filter, and purify to obtain the bromo compound;

[0047] S2: Add 10 parts of the bromo compound into anhydrous tetrahydrofuran, fully dissolve it, cool to -70 °C, slowly dropwise add 1 part of n-butyllithium, stir for 1 h, then add 5 parts of triisopropyl borate, continue to stir for 1 h, then raise the temperature to room temperature and stir overnight, rotary evaporate to remove the solvent, and perform post-treatment to obtain the borate compound;

[0048] S3: Add the borate compound into anhydrous tetrahydrofuran, stir to dissolve it, add p-aminobenzaldehyde, adjust the pH to 8, raise the temperature to 40 °C, stir and react for 12 h, after the reaction is completed, cool to room temperature, concentrate under reduced pressure to remove the solvent, filter with suction, wash, and dry to obtain the modifier.

[0049] Example 2: The preparation process of a low-smoke and halogen-free flame-retardant insulated cable is as follows:

[0050] Step 1: Mix modified fibers and modified aluminum hydroxide with a mass ratio of 1:40 to obtain a composite flame retardant;

[0051] Step 2: Add 100 parts of high-density polyethylene, 70 parts of the composite flame retardant, 0.2 parts of antioxidant, 0.2 parts of lubricant, and 3 parts of compatibilizer (PE-g-MAH) into a mixer and mix evenly to obtain a mixed material;

[0052] Step 3: Add the mixed material into an extruder and melt-extrude it onto the outside of the conductor to form an insulating jacket, obtaining a cable;

[0053] Among them, the preparation process of the modified aluminum hydroxide is as follows: Add 12 parts of aluminum hydroxide, 0.08 parts of titanate coupling agent, and 0.2 parts of white oil into a high-speed mixer, stir for 8 min to obtain modified aluminum hydroxide;

[0054] Among them, the preparation process of the modified fibers is as follows:

[0055] A1: Add 2 parts of aramid fibers into 30 parts of phosphoric acid solution (mass fraction is 3 wt%), soak for 5 min, then bake in an oven at 130 °C for 8 min, wash, and dry; Subsequently, transfer to a mixed solution composed of 0.2 parts of γ-aminopropyltriethoxysilane, 120 parts of ethanol, and 12 parts of deionized water, raise the temperature to 70 °C, react for 2 h, after the reaction, filter, wash, and dry to obtain silanized fibers;

[0056] A2: Add 20 parts of modifier into 350 parts of tetrahydrofuran, fully dissolve it, adjust the pH to 6, immerse 120 parts of silanized fibers into it, react in a water bath oscillator at 60 °C for 4 h, take out the fibers, wash, and dry in a vacuum drying oven at 50 °C to obtain modified fibers;

[0057] Among them, the preparation process of the modifier is as follows:

[0058] S1: Add 20 parts of 4-bromophenol and 5 parts of sodium hydroxide into 100 parts of anhydrous tetrahydrofuran, raise the temperature to 80 °C, reflux and stir in a nitrogen atmosphere for 2 h; Then slowly dropwise add an anhydrous tetrahydrofuran solution of cyanuric chloride (dissolve 12 parts of cyanuric chloride in 150 parts of anhydrous tetrahydrofuran), continue to reflux and stir for 24 h, after the reaction, cool to room temperature, filter, and purify to obtain a bromo compound;

[0059] S2: Add 12 parts of the bromo compound into anhydrous tetrahydrofuran, fully dissolve it, cool to -70 °C, slowly dropwise add 2 parts of n-butyllithium, stir for 2 h, then add 6 parts of triisopropyl borate, continue to stir for 2 h, then raise the temperature to room temperature and stir overnight, rotate to evaporate the solvent, and perform post-treatment to obtain a borate compound;

[0060] S3: Add the borate compound into anhydrous tetrahydrofuran. After stirring and dissolving, add p - aminobenzaldehyde, adjust the pH to 9, raise the temperature to 60 °C, stir and react for 16 h. After the reaction is completed, cool to room temperature, remove the solvent by reduced pressure concentration, filter by suction, wash, and dry to obtain the modifier.

[0061] Example 3: The preparation process of a low - smoke and halogen - free flame - retardant insulated cable is as follows:

[0062] Step 1: Mix the modified fiber and modified aluminum hydroxide with a mass ratio of 1:30 to obtain a composite flame retardant.

[0063] Step 2: Add 90 parts of high - density polyethylene, 65 parts of the composite flame retardant, 0.15 part of antioxidant, 0.15 part of lubricant, and 2.5 parts of compatibilizer (PE - g - MAH) into a mixer and mix evenly to obtain a mixture.

[0064] Step 3: Add the mixture into an extruder and melt - extrude it onto the outside of the conductor to form an insulating jacket, thus obtaining the cable.

[0065] Among them, the preparation process of the modified aluminum hydroxide is as follows: Add 11 parts of aluminum hydroxide, 0.06 part of titanate coupling agent, and 0.15 part of white oil into a high - speed mixer, stir for 6 min to obtain the modified aluminum hydroxide.

[0066] Among them, the preparation process of the modified fiber is as follows:

[0067] A1: Add 1.5 parts of aramid fiber into 25 parts of phosphoric acid solution (mass fraction is 3 wt%), soak for 4.5 min, then bake in an oven at 130 °C for 6.5 min, wash, and dry. Subsequently, transfer it into a mixed solution composed of 0.15 part of γ - aminopropyltriethoxysilane, 110 parts of ethanol, and 11 parts of deionized water, raise the temperature to 65 °C, react for 1.5 h. After the reaction is completed, filter, wash, and dry to obtain the silylated fiber.

[0068] A2: Add 15 parts of the modifier into 325 parts of tetrahydrofuran, fully dissolve it, adjust the pH to 5.5, immerse 110 parts of the silylated fiber into it, react in a 60 °C water bath oscillator for 3 h, take out the fiber, wash, and dry it in a 50 °C vacuum drying oven to obtain the modified fiber.

[0069] Among them, the preparation process of the modifier is as follows:

[0070] S1: Add 19 parts of 4-bromophenol and 4.5 parts of sodium hydroxide to 90 parts of anhydrous tetrahydrofuran, raise the temperature to 75 °C, and reflux and stir for 1.5 h under a nitrogen atmosphere; then slowly add dropwise an anhydrous tetrahydrofuran solution of cyanuric chloride (dissolve 11 parts of cyanuric chloride in 135 parts of anhydrous tetrahydrofuran), continue to reflux and stir for 24 h. After the reaction is completed, cool to room temperature, filter, and after purification, obtain a bromine-based compound;

[0071] S2: Add 11 parts of the bromine-based compound to anhydrous tetrahydrofuran, fully dissolve it, cool to -70 °C, slowly add dropwise 1.5 parts of n-butyllithium, stir for 1.5 h, then add 5.5 parts of triisopropyl borate, continue to stir for 1.5 h, then raise the temperature to room temperature and stir overnight, rotary evaporate to remove the solvent, and perform post-treatment to obtain a boric acid-based compound;

[0072] S3: Add the boric acid-based compound to anhydrous tetrahydrofuran, stir to dissolve it, add p-aminobenzaldehyde, adjust the pH to 8.5, raise the temperature to 50 °C, stir and react for 14 h. After the reaction is completed, cool to room temperature, concentrate under reduced pressure to remove the solvent, filter, wash, and dry to obtain a modifier.

[0073] Comparative Example 1: In the composite flame retardant, add modified aluminum hydroxide alone, and the rest is the same as in Example 3, specifically as follows:

[0074] Step 1: Add 90 parts of high-density polyethylene, 65 parts of modified aluminum hydroxide, 0.15 parts of antioxidant, 0.15 parts of lubricant, and 2.5 parts of compatibilizer (PE-g-MAH) to a mixer and mix evenly to obtain a mixture;

[0075] Step 2: Add the mixture to an extruder and melt-extrude it onto the outside of the conductor to form an insulating jacket to obtain a cable;

[0076] Among them, the preparation process of the modified aluminum hydroxide is: add 11 parts of aluminum hydroxide, 0.06 parts of titanate coupling agent, and 0.15 parts of white oil to a high-speed mixer, and stir for 6 min to obtain modified aluminum hydroxide.

[0077] Comparative Example 2: Only perform silanization treatment on aramid fibers, and the rest is the same as in Example 3, specifically as follows:

[0078] Step 1: Mix modified fibers and modified aluminum hydroxide with a mass ratio of 1:30 to obtain a composite flame retardant;

[0079] Step 2: Add 90 parts of high-density polyethylene, 65 parts of the composite flame retardant, 0.15 parts of antioxidant, 0.15 parts of lubricant, and 2.5 parts of compatibilizer (PE-g-MAH) to a mixer and mix evenly to obtain a mixture;

[0080] Step 3: Add the mixture into an extruder, melt and extrude it onto the outside of the conductor to form an insulating jacket, thus obtaining a cable.

[0081] Among them, the preparation process of the modified aluminum hydroxide is as follows: Add 11 parts of aluminum hydroxide, 0.06 part of titanate coupling agent, and 0.15 part of white oil into a high-speed mixer, and stir for 6 minutes to obtain modified aluminum hydroxide.

[0082] Among them, the preparation process of the modified fiber is as follows:

[0083] A1: Add 1.5 parts of aramid fiber into 25 parts of phosphoric acid solution (mass fraction is 3wt%), soak for 4.5 minutes, then bake in an oven at 130°C for 6.5 minutes, wash, and dry; then transfer it to a mixed solution composed of 0.15 part of γ-aminopropyltriethoxysilane, 110 parts of ethanol, and 11 parts of deionized water, raise the temperature to 65°C, react for 1.5 hours, after the reaction ends, filter, wash, and dry to obtain modified fiber.

[0084] Comparative Example 3: In the composite flame retardant, add an excessive amount of modified aluminum hydroxide, and the rest is the same as in Example 3, specifically as follows:

[0085] Step 1: Mix the modified fiber and the modified aluminum hydroxide with a mass ratio of 1:60 to obtain a composite flame retardant.

[0086] Step 2: Add 90 parts of high-density polyethylene, 65 parts of the composite flame retardant, 0.15 part of antioxidant, 0.15 part of lubricant, and 2.5 parts of compatibilizer (PE-g-MAH) into a mixer and mix evenly to obtain a mixture.

[0087] Step 3: Add the mixture into an extruder, melt and extrude it onto the outside of the conductor to form an insulating jacket, thus obtaining a cable.

[0088] Among them, the preparation process of the modified aluminum hydroxide is as follows: Add 11 parts of aluminum hydroxide, 0.06 part of titanate coupling agent, and 0.15 part of white oil into a high-speed mixer, and stir for 6 minutes to obtain modified aluminum hydroxide.

[0089] Among them, the preparation process of the modified fiber is as follows:

[0090] A1: Add 1.5 parts of aramid fiber into 25 parts of phosphoric acid solution (mass fraction is 3wt%), soak for 4.5 minutes, then bake in an oven at 130°C for 6.5 minutes, wash, and dry; then transfer it to a mixed solution composed of 0.15 part of γ-aminopropyltriethoxysilane, 110 parts of ethanol, and 11 parts of deionized water, raise the temperature to 65°C, react for 1.5 hours, after the reaction ends, filter, wash, and dry to obtain silanized fiber.

[0091] A2: Add 15 parts of modifier to 325 parts of tetrahydrofuran. After complete dissolution, adjust the pH to 5.5. Immerse 110 parts of silylated fiber into it and react in a 60°C water bath oscillator for 3 h. Take out the fiber, wash it, and dry it in a 50°C vacuum drying oven to obtain modified fiber;

[0092] Among them, the preparation process of the modifier is as follows:

[0093] S1: Add 19 parts of 4-bromophenol and 4.5 parts of sodium hydroxide to 90 parts of anhydrous tetrahydrofuran. Raise the temperature to 75°C and reflux and stir for 1.5 h under a nitrogen atmosphere; then slowly dropwise add an anhydrous tetrahydrofuran solution of cyanuric chloride (dissolve 11 parts of cyanuric chloride in 135 parts of anhydrous tetrahydrofuran), continue reflux and stir for 24 h. After the reaction is completed, cool to room temperature, filter, and after purification, obtain a bromo compound;

[0094] S2: Add 11 parts of the bromo compound to anhydrous tetrahydrofuran. After complete dissolution, cool to -70°C, slowly dropwise add 1.5 parts of n-butyllithium, stir for 1.5 h, then add 5.5 parts of triisopropyl borate, continue stirring for 1.5 h, then raise the temperature to room temperature and stir overnight. Rotate and evaporate to remove the solvent, and perform post-treatment to obtain a boronic acid compound;

[0095] S3: Add the boronic acid compound to anhydrous tetrahydrofuran. After stirring and dissolving, add p-aminobenzaldehyde, adjust the pH to 8.5, raise the temperature to 50°C, and stir and react for 14 h. After the reaction is completed, cool to room temperature, concentrate under reduced pressure to remove the solvent, filter with suction, wash, and dry to obtain the modifier.

[0096] Detection test: Prepare dumbbell-shaped specimens (80 mm×10 mm×4 mm) from the mixtures obtained in the examples and comparative examples. According to the standard GB / T1040.1-2008, detect the tensile strength of the material at a tensile speed of 200 mm / min; according to the standard GB / T2406.2-2009, detect the limiting oxygen index (LOI); according to the standard GB / T8323.2-2018, conduct smoke density detection; the obtained data are shown in the following table:

[0097]

[0098] Table 1

[0099] Conclusion: The tensile strength (63.4 - 66.6 MPa), limiting oxygen index (LOI, 42.6% - 45.1%), and smoke density (127 - 131) of Examples 1 to 3 are significantly better than those of the comparative examples, while the performance of Comparative Examples 1 to 3 decreased due to material ratio or process defects:

[0100] In Comparative Example 1, when using modified aluminum hydroxide alone, the lack of the physical support of modified fibers made it impossible to form a dense carbon layer to inhibit smoke release (the smoke density reached 180), and the excessive filling amount of aluminum hydroxide weakened the mechanical properties of the matrix (the tensile strength was only 28.9 MPa);

[0101] In Comparative Example 2, the untreated silanized fibers with a modifier led to the weakening of the interface bonding between the fibers and the matrix, and the insufficient synergistic effect of flame retardant elements (the LOI decreased to 39.9%, and the smoke density increased to 156);

[0102] In Comparative Example 3, the excessive addition of modified aluminum hydroxide (mass ratio 1:60) damaged the structural uniformity of the material, resulting in a decrease in mechanical properties (tensile strength 48.6 MPa) and a reduction in flame retardant efficiency (LOI 35.6%, smoke density 148). In summary, the synergistic effect of modified fibers and aluminum hydroxide effectively achieved the effect of low-smoke and halogen-free, high-efficiency flame retardancy, while enhancing the mechanical strength of the cable.

[0103] In the description of the specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0104] The above content is only an example and illustration of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods to replace them. As long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should fall within the protection scope of the present invention.

Claims

1. A low-smoke, halogen-free flame-retardant insulated cable, characterized in that: The preparation process of the cable is as follows: Step 1: Mix modified fibers and modified aluminum hydroxide with a mass ratio of 1:(20 - 40) to obtain a composite flame retardant; Step 2: Add high-density polyethylene, the composite flame retardant, an antioxidant, a lubricant, and a compatibilizer to a mixer and mix evenly to obtain a mixture; Step 3: Add the mixture to an extruder and melt-extrude it onto the outside of the conductor to form an insulating jacket, thereby obtaining the cable.

2. The low-smoke and halogen-free flame-retardant insulated cable according to claim 1, wherein: The mixture includes the following components: by weight, 80 - 100 parts of high-density polyethylene, 60 - 70 parts of the composite flame retardant, 0.1 - 0.2 parts of the antioxidant, 0.1 - 0.2 parts of the lubricant, and 2 - 3 parts of the compatibilizer.

3. A low-smoke and halogen-free flame-retardant insulated cable according to claim 1, characterized in that: The preparation process of the modified fibers is as follows: A1: Add aramid fibers to a phosphoric acid solution, soak for 4 - 5 min, then bake in an oven at 130 °C for 5 - 8 min, wash, and dry; subsequently transfer to a mixed solution composed of γ-aminopropyltriethoxysilane, ethanol, and deionized water, raise the temperature to 60 - 70 °C, react for 1 - 2 h, after the reaction ends, filter, wash, and dry to obtain silanized fibers; A2: Add the modifier to tetrahydrofuran, fully dissolve it, adjust the pH to 5 - 6, immerse the silanized fibers in it, react in a 60 °C water bath oscillator for 2 - 4 h, take out the fibers, wash, and dry in a 50 °C vacuum drying oven to obtain modified fibers.

4. The low-smoke halogen-free flame-retardant insulated cable according to claim 3, wherein: The raw materials in the silanized fibers contain the following components: by weight, 1 - 2 parts of aramid fibers, 20 - 30 parts of phosphoric acid solution, 0.1 - 0.2 parts of γ-aminopropyltriethoxysilane, 100 - 120 parts of ethanol, and 10 - 12 parts of deionized water; the mass fraction of the phosphoric acid solution is 3 wt%.

5. A low-smoke and halogen-free flame-retardant insulated cable according to claim 3, characterized in that: The raw materials in the modified fibers include the following components: by weight, 10 - 20 parts of the modifier, 300 - 350 parts of tetrahydrofuran, and 100 - 120 parts of silanized fibers.

6. The low-smoke halogen-free flame-retardant insulated cable according to claim 1, characterized in that: The preparation process of the modified aluminum hydroxide is as follows: by weight, add 10 - 12 parts of aluminum hydroxide, 0.05 - 0.08 parts of titanate coupling agent, and 0.1 - 0.2 parts of white oil to a high-speed mixer, and stir for 5 - 8 min to obtain modified aluminum hydroxide.

7. The low-smoke halogen-free flame-retardant insulated cable according to claim 3, wherein: The preparation process of the modifier is as follows: S1: Add 4-bromophenol and sodium hydroxide to anhydrous tetrahydrofuran, raise the temperature to 70 - 80 °C, reflux and stir in a nitrogen atmosphere for 1 - 2 h; then slowly dropwise add an anhydrous tetrahydrofuran solution of cyanuric chloride, continue reflux and stir for 24 h, after the reaction ends, cool to room temperature, filter, and purify to obtain a bromine-based compound; S2: Add the bromine-based compound to anhydrous tetrahydrofuran, fully dissolve it, cool to -70 °C, slowly dropwise add n-butyllithium, stir for 1 - 2 h, then add triisopropyl borate, continue to stir for 1 - 2 h, then raise the temperature to room temperature and stir overnight, rotary evaporate to remove the solvent, and perform post-treatment to obtain a boric acid-based compound; S3: Add the borate compound into anhydrous tetrahydrofuran, stir to dissolve it, then add p-aminobenzaldehyde, adjust the pH to 8 - 9, raise the temperature to 40 - 60 °C, stir and react for 12 - 16 h. After the reaction is completed, cool to room temperature, remove the solvent by reduced pressure concentration, filter by suction, wash, and dry to obtain the modifier.

8. A low-smoke halogen-free flame-retardant insulated cable according to claim 7, characterized in that: The raw materials in the bromide compound include the following components: by weight, 18 - 20 parts of 4-bromophenol, 4 - 5 parts of sodium hydroxide, 10 - 12 parts of cyanuric chloride, and 200 - 250 parts of anhydrous tetrahydrofuran.

9. A low-smoke halogen-free flame-retardant insulated cable according to claim 7, characterized in that: The raw materials in the borate compound include the following components: by weight, 10 - 12 parts of the bromide compound, 1 - 2 parts of n-butyllithium, 5 - 6 parts of triisopropyl borate, and 100 - 120 parts of anhydrous tetrahydrofuran.

10. A low-smoke and halogen-free flame-retardant insulated cable according to claim 7, characterized in that: The raw materials in the modifier include the following components: by weight, 25 - 28 parts of the borate compound, 2 - 4 parts of p-aminobenzaldehyde, and 80 - 100 parts of anhydrous tetrahydrofuran.

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