A low-smoke halogen-free flame-retardant cable material and a preparation method and cable thereof

Abstract

This application relates to the field of cable material technology, specifically disclosing a low-smoke halogen-free flame-retardant cable material, its preparation method, and the cable thereof. The low-smoke halogen-free flame-retardant cable material comprises the following raw materials: 75-95 parts polypropylene resin; 20-35 parts POE elastomer; 18-30 parts compounded flame retardant; 10-18 parts aluminum hydroxide micropowder; 5-10 parts zinc stearate; 3-7 parts polydimethylsiloxane; 0.8-2.0 parts titanate coupling agent; 0.5-1.5 parts carbon nanotubes; 2.0-4.5 parts antioxidant; 3-6 parts stabilizer; and 1.5-4.0 parts nanoscale reinforcing agent. The cable material of this application improves flame-retardant performance while also maintaining good mechanical properties. The low-smoke halogen-free flame-retardant cable obtained from this cable material possesses excellent safety protection capabilities, minimizing fire risk and secondary hazards.

Description

Technical Field

[0001] This application relates to the field of cable material technology, and more specifically, to a low-smoke halogen-free flame-retardant cable material, its preparation method, and the cable thereof. Background Technology

[0002] Cable materials are a crucial component of cable structures. They not only wrap and protect the internal conductors to ensure that current or signals are not interfered with during transmission, but also provide structural support to adapt to various laying environments, such as underground, underwater, high-altitude, and extreme conditions like high temperatures, humidity, and corrosive environments. In numerous fields, including power systems, communication networks, transportation, and construction engineering, the performance of cable materials directly affects the operational safety, stability, and service life of the entire cable system, making them one of the essential foundational materials for ensuring the normal operation of various infrastructures.

[0003] In related technologies, cable materials are mostly based on high-molecular polymers, such as polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), and cross-linked polyethylene (XLPE). Polyethylene is widely used in medium and low-voltage cable materials due to its excellent electrical insulation properties, good chemical resistance, and low production cost. PVC, on the other hand, is commonly used in the manufacture of various conventional cables due to its good mechanical strength and ease of processing. To meet basic usage requirements, these cable materials typically have added plasticizers, antioxidants, fillers, and other additives to improve their processing performance, aging resistance, and mechanical properties.

[0004] However, existing cable materials generally suffer from poor flame-retardant properties. Under conditions of high temperatures, electrical faults causing heating or discharge, or external fires, cable materials are easily ignited and burn rapidly. During combustion, they may release large amounts of toxic and harmful gases and smoke, which can not only paralyze cable systems and disrupt normal operations in related fields, but also hinder personnel evacuation and fire rescue efforts, posing a serious threat to life and property safety. This problem makes it difficult for existing cable materials to meet the stringent requirements for flame-retardant performance in applications such as buildings, subways, nuclear power plants, and high-rise buildings. Therefore, existing cable materials suffer from poor flame-retardant properties. Summary of the Invention

[0005] To improve the flame retardant properties of cable materials, this application provides a low-smoke halogen-free flame retardant cable material, its preparation method, and the cable thereof.

[0006] The low-smoke halogen-free flame-retardant cable material provided in this application adopts the following technical solution:

[0007] A low-smoke, halogen-free, flame-retardant cable material, comprising the following raw materials in parts by weight:

[0008] 75-95 parts of polypropylene resin;

[0009] 20-35 parts of POE elastomer;

[0010] 18-30 parts of compound flame retardant;

[0011] 10-18 parts of aluminum hydroxide micro powder;

[0012] 5-10 parts zinc stearate;

[0013] 3-7 parts of polydimethylsiloxane;

[0014] Titanate coupling agent 0.8-2.0 parts;

[0015] 0.5-1.5 parts of carbon nanotubes;

[0016] Antioxidant 2.0-4.5 parts;

[0017] Stabilizer 3-6 parts;

[0018] 1.5-4.0 parts of nano-scale reinforcing agent;

[0019] The compound flame retardant is obtained by synergistic compounding and modification of pentaerythritol phosphate, dicyandiamide, and zinc borate.

[0020] By adopting the above technical solution and optimizing the matrix resin composition and flame retardant system, a synergistic improvement in the flame retardant performance and overall performance of the cable material was achieved. From the perspective of the matrix resin, polypropylene resin possesses excellent mechanical strength and electrical insulation, while the addition of POE elastomer (polyolefin elastomer) allows it to form an interpenetrating network structure with polypropylene—the octene segments in the POE elastomer can embed into the gaps between the polypropylene molecular chains, thus alleviating the brittleness of polypropylene and enhancing the material's impact resistance. Furthermore, both are polyolefin materials with good compatibility, avoiding performance fluctuations caused by component differences.

[0021] In terms of the flame retardant system, the compound flame retardant (pentaerythritol phosphate + dicyandiamide + zinc borate) adopts a "phosphorus-nitrogen-boron" synergistic flame retardant mechanism: pentaerythritol phosphate decomposes upon heating to generate phosphoric acid, which can catalyze the dehydration of the matrix resin into char, forming a dense char layer to block heat and oxygen; the inert gases such as ammonia and nitrogen released by the decomposition of dicyandiamide can dilute the concentration of combustible gases in the combustion zone and inhibit free radical chain reactions; zinc borate can generate a glassy substance at high temperature, covering the surface of the char layer, further enhancing the heat insulation and oxygen barrier effect of the char layer. The synergistic effect of the three significantly improves the flame retardant efficiency.

[0022] In addition, aluminum hydroxide micro powder, as an inorganic flame retardant, absorbs a large amount of heat when it decomposes (i.e., the "endothermic cooling" effect), while releasing water vapor to dilute flammable gases, forming a "gas phase + condensed phase" dual flame retardant system with the compounded flame retardant; carbon nanotubes, with their high specific surface area and excellent thermal conductivity, can be uniformly dispersed in the matrix, which not only enhances the mechanical strength of the material, but also guides the rapid transfer of heat, avoiding the risk of combustion caused by local high temperature. The overall formula, through the synergy of its components, improves the flame retardant performance while taking into account the mechanical properties of the material.

[0023] Optionally, the compound flame retardant is prepared by the following method:

[0024] A. Mix adipic acid, ethanol, pentaerythritol phosphate, dicyandiamide and deionized water, and adjust the pH of the mixture to 10.0-11.0 with sodium hydroxide solution to obtain a premixed solution;

[0025] B. Add dispersant to the premixed liquid, heat to 50-60℃, stir at 500-600r / min for 20-30min, then add zinc borate, heat to 65-70℃, continue stirring for 3.0-5.0h, and obtain the compound flame retardant after filtration, washing and drying.

[0026] The core of the defined compound flame retardant preparation method, achieved through the above technical solution, lies in the uniform dispersion and interfacial bonding of flame retardant components via process control, providing a structural basis for the synergistic flame retardancy of "phosphorus-nitrogen-boron". In step A, adipic acid, as a dispersant, can form hydrogen bonds with the hydroxyl groups of pentaerythritol phosphate and the amino groups of dicyandiamide through its carboxyl groups, promoting uniform dispersion of the three components in an ethanol-water mixed solvent. Sodium hydroxide solution adjusts the pH to 10.0-11.0, enhancing the solubility of dicyandiamide (which readily dissociates into carbamate ions under alkaline conditions), thus preventing its aggregation. Ethanol, as a co-solvent, reduces the surface tension of pentaerythritol phosphate, further optimizing the dispersion effect.

[0027] In step B, the addition of the dispersant nonylphenol polyoxyethylene ether (a nonionic surfactant) allows its hydrophobic segments to adsorb onto the surface of the flame-retardant component particles, while its hydrophilic segments face the aqueous phase, forming a stable colloidal system. This effectively controls the particle size of the flame-retardant particles (avoiding excessively large particles that lead to uneven dispersion). A reaction temperature of 50-60℃ and a stirring rate of 500-600 r / min ensure sufficient adsorption of the dispersant while preventing premature decomposition of the flame-retardant component due to excessively high temperatures. Adding zinc borate and raising the temperature to 65-70℃ promotes the formation of weak chemical bonds (such as borate ester bonds and aminoboronic acid bonds) between zinc borate and pentaerythritol phosphate and dicyandiamide, enhancing the interfacial bonding between the three and preventing a decrease in flame-retardant performance due to component separation during subsequent processing. Finally, through filtration, washing, and drying, a compound flame retardant with uniform particle size and good dispersibility is obtained, laying the foundation for its efficient application in cable materials.

[0028] Optionally, the mass ratio of adipic acid, ethanol, pentaerythritol phosphate, dicyandiamide and deionized water is (0.1-0.3):(2.0-2.5):1:(0.4-0.8):12.

[0029] By adopting the above technical solution, the above ratio is the key to achieving a balance between the dispersibility and flame retardant efficiency of the compound flame retardant. If the adipic acid dosage is less than 0.1, its dispersing effect on the flame retardant components is insufficient, which easily leads to the aggregation of dicyandiamide and affects the synergistic flame retardant effect; if it is higher than 0.3, the excess adipic acid will compete with pentaerythritol phosphate for reaction sites, reducing the char formation efficiency of the phosphate ester. The dicyandiamide dosage is 0.4-0.8. If it is less than 0.4, the released inert gas is insufficient, and the gas-phase flame retardant effect is weakened; if it is higher than 0.8, the excess dicyandiamide is prone to incomplete carbonization at high temperatures, forming a porous char layer, which reduces the heat insulation effect.

[0030] Optionally, the dispersant is nonylphenol polyoxyethylene ether, and the amount of dispersant added is 4%-8% of the total mass of pentaerythritol phosphate and dicyandiamide.

[0031] By adopting the above technical solution, the dispersant is limited to nonylphenol polyoxyethylene ether, and its dosage is 4%-7% of the total mass of pentaerythritol phosphate and dicyandiamide. The core is to optimize the dispersion stability and interfacial compatibility of flame-retardant particles. As a nonionic surfactant, nonylphenol polyoxyethylene ether is more stable in alkaline systems (less affected by pH fluctuations) compared to ionic surfactants (such as sodium alkyl sulfonate), and can form a thicker adsorption layer with the flame-retardant component particles, effectively preventing particle agglomeration.

[0032] Optionally, the amount of zinc borate added is 10%-18% of the mass of pentaerythritol phosphate.

[0033] Optionally, the antioxidant is a compound of phenolic antioxidants and thioester antioxidants, with a mass ratio of phenolic antioxidants to thioester antioxidants of (1.5-2.5):1.

[0034] Optionally, the polypropylene resin has a melt index of 2-4 g / min; the POE elastomer is a polyolefin elastomer with an octene content of 15%-25%, and the melt index of the POE elastomer is 5-8 g / 10min.

[0035] Optionally, the nano-scale reinforcing agent is a mixture of nano-titanium dioxide and nano-talc powder, with a mass ratio of (1.0-1.8):1, and the particle size of the nano-scale reinforcing agent is 60-120 nm.

[0036] By adopting the above technical solution, the nano-reinforcing agent is limited to a mixture of nano-silica and nano-calcium carbonate (mass ratio 1.0-1.8:1) with a particle size of 60-120 nm. The core lies in improving the mechanical and flame-retardant properties of the material through the "reinforcing effect" of nanoparticles. Nano-silica has a high specific surface area and high hardness. Its surface hydroxyl groups can form hydrogen bonds with polypropylene molecular chains. When uniformly dispersed in the matrix, it can effectively prevent stress concentration (when the material is under stress, nano-silica can disperse stress and avoid crack propagation), significantly improving the tensile strength and rigidity of the material. Nano-calcium carbonate has good dispersibility and low cost advantages. After its surface is modified with a coupling agent (in synergy with titanate coupling agents), it can form a tight interfacial bond with polypropylene, enhancing the impact resistance of the material.

[0037] Secondly, this application also provides a method for preparing a low-smoke halogen-free flame-retardant cable material, employing the following technical solution:

[0038] A method for preparing a low-smoke halogen-free flame-retardant cable material includes the following steps:

[0039] S1. Mix polypropylene resin, POE elastomer, aluminum hydroxide micro powder, zinc stearate, polydimethylsiloxane, titanate coupling agent, carbon nanotubes, antioxidant, stabilizer and nanoscale reinforcing agent evenly to obtain a mixture.

[0040] S2. Add the mixture to a twin-screw extruder and melt-blend at 180-200℃ and 90-120MPa pressure for 1-2 hours to form a melt blend.

[0041] S3. Add a compound flame retardant to the melt blend, and continue to melt blend for 1-2 hours at 170-190℃ and 90-120MPa pressure. Then, extrude the mixture through a mold and cool and solidify it to obtain a low-smoke halogen-free flame retardant cable material.

[0042] By adopting the above technical solution, and through stepwise melt blending and process parameter control, uniform dispersion and synergistic performance of each component can be achieved. Step S1 first mixes the base resin, inorganic flame retardant, and additives, which can ensure the uniform dispersion of non-flame retardant components (such as polypropylene, POE, and antioxidants). If the compounded flame retardant is added first, its organic components (such as pentaerythritol phosphate) may compete with the additives (such as antioxidants) for adsorption, resulting in uneven dispersion of the additives. Uniformly mixed materials can reduce the risk of component separation during subsequent melt blending.

[0043] The process parameters for step S2 (175-200℃, 90-120MPa, 1.2-2.2h) are designed based on the melting characteristics of the matrix resin and inorganic additives: 175-200℃ is the optimal melting temperature for polypropylene (the melting point of polypropylene is about 160-170℃), which can ensure that polypropylene melts completely and does not undergo thermal degradation; the pressure of 90-120MPa can promote melt flow and enhance the uniformity of component mixing; the time of 1.2-2.2h can ensure that inorganic additives (such as aluminum hydroxide and nano-reinforcing agents) are fully dispersed in the matrix.

[0044] After adding the compound flame retardant in step S3, the temperature is lowered to 170-195℃ (below the decomposition temperature of the compound flame retardant to avoid premature decomposition and inactivation). Continued melt blending for 1.2-1.8 hours ensures the compound flame retardant is uniformly dispersed in the melt and forms a synergistic flame retardant system with the inorganic flame retardant. After extrusion molding and cooling / curing, the microstructure of the material is fixed, preventing internal stress caused by excessively rapid cooling (which affects the material's mechanical properties). The overall process, through stepwise mixing and precise temperature and pressure control, ensures uniform dispersion of all material components, fully leveraging their synergistic effects to ultimately improve both flame retardant performance and overall performance.

[0045] Thirdly, this application also provides a low-smoke halogen-free flame-retardant cable, which uses the aforementioned low-smoke halogen-free flame-retardant cable material as the insulation layer and / or insulation layer.

[0046] The aforementioned low-smoke halogen-free flame-retardant cable possesses excellent safety protection capabilities, minimizing fire risks and secondary hazards. Because the insulation and / or sheath layers contain a phosphorus-nitrogen-boron composite flame-retardant system and aluminum hydroxide micropowder, the cable is not only difficult to ignite under high temperatures, electrical faults, or external fire attacks, but also does not release halogen-containing toxic gases during combustion. The halogen-free nature of the material avoids corrosion and damage to the human respiratory tract from toxic gases and also prevents corrosion and damage to equipment. Simultaneously, the material generates very little smoke during combustion and has high light transmittance (e.g., in the example, the minimum light transmittance during combustion is ≥60%), maintaining clear rescue routes and visibility during a fire, thus buying valuable time for personnel evacuation and fire rescue. It is particularly suitable for densely populated or highly enclosed environments such as subways, high-rise buildings, and nuclear power plants.

[0047] In summary, this application has the following beneficial effects:

[0048] 1. This application employs a matrix composition of polypropylene resin and POE elastomer, combined with a compound flame-retardant system consisting of pentaerythritol phosphate, dicyandiamide, and zinc borate. Through a phosphorus-nitrogen-boron synergistic flame-retardant mechanism, combined with the heat-absorbing and cooling effect of aluminum hydroxide micropowder and the dilution effect of water vapor, a dual flame-retardant system is formed. Specifically, the compound flame retardant catalyzes the dehydration of the matrix resin into char and forms a glassy protective layer on the material surface, blocking heat and oxygen transfer. When the aluminum hydroxide micropowder decomposes upon heating, it absorbs a large amount of heat, lowering the temperature of the combustion zone, while simultaneously releasing water vapor to dilute the concentration of flammable gases. The synergistic effect of these two components significantly improves the flame-retardant performance of the cable material, effectively inhibiting rapid combustion under high temperatures, electrical faults, or external fire attacks, reducing the release of toxic and harmful gases, and meeting the application requirements of buildings, subways, nuclear power plants, and other applications with strict flame-retardant performance requirements.

[0049] 2. This application preferably uses a composite additive system composed of nano-scale reinforcing agents and carbon nanotubes. The nano-scale reinforcing agent is a mixture of nano-titanium dioxide and nano-talc powder, and its performance is optimized by precisely controlling the parameters of each raw material (e.g., controlling the octene content of the POE elastomer to 15%-25%, and the particle size of the nano-scale reinforcing agent to 60-120nm). The nano-scale reinforcing agent, with its high specific surface area, can disperse stress concentration under stress through a reinforcing effect, improving the tensile strength and impact resistance of the material. Carbon nanotubes have excellent thermal conductivity, guiding the uniform transfer of heat within the material and avoiding the risk of combustion caused by localized high temperatures. Simultaneously, the flexible segments of the POE elastomer can be embedded in the gaps between polypropylene molecular chains, alleviating the brittleness of polypropylene. This design allows the cable material to improve its flame retardant performance while maintaining excellent mechanical and electrical insulation properties, avoiding problems such as material brittleness and decreased insulation performance caused by the addition of flame retardants in traditional flame-retardant modification.

[0050] 3. The preparation method of this application adopts a stepwise melt blending process. First, polypropylene resin, POE elastomer, aluminum hydroxide micro powder, and additives are mixed evenly and then melt blended. Then, a compounded flame retardant is added and melt blending continues. Key process parameters are controlled simultaneously (melting temperature of 180-200℃ in the first step, 170-190℃ in the second step, melting pressure of 90-120MPa for both steps, and blending time of 1-2 hours for each step). The stepwise mixing method avoids competitive adsorption between the compounded flame retardant and antioxidants, preventing uneven dispersion of additives. The relatively low melting temperature in the second step prevents premature decomposition of the compounded flame retardant at high temperatures, ensuring its flame-retardant activity. The specific melting pressure and blending time promote full diffusion of each component in the melt, achieving uniform dispersion. This process design not only improves the stability and controllability of the production process but also ensures the uniformity of the final product's performance, reduces the risk of quality fluctuations in industrial production, and facilitates large-scale mass production. Detailed Implementation

[0051] The present application will be further described in detail below with reference to the embodiments.

[0052] Preparation example of compound flame retardants

[0053] Preparation Example 1

[0054] The compound flame retardant was prepared using the following method:

[0055] A. Mix 0.1 kg adipic acid, 2.0 kg ethanol, 1 kg pentylenetetrazol phosphate, 0.4 kg dicyandiamide and 12 kg deionized water, and adjust the pH of the mixture to 10.0-11.0 with sodium hydroxide solution to obtain a premixed solution;

[0056] B. Add 0.056 kg of nonylphenol polyoxyethylene ether dispersant to the premixed liquid, heat to 50°C, stir at 500 r / min for 20 min, then add 0.1 kg of zinc borate, heat to 65°C, continue stirring for 3.0 h, and obtain the compound flame retardant after filtration, washing, and drying.

[0057] Preparation Example 2

[0058] The compound flame retardant was prepared using the following method:

[0059] A. Mix 0.2 kg adipic acid, 2.2 kg ethanol, 1 kg pentylenetetrazol phosphate, 0.6 kg dicyandiamide and 12 kg deionized water, and adjust the pH of the mixture to 10.0-11.0 with sodium hydroxide solution to obtain a premixed solution;

[0060] B. Add 0.096 kg of nonylphenol polyoxyethylene ether dispersant to the premixed liquid, heat to 55°C, stir at 550 r / min for 25 min, then add 0.14 kg of zinc borate, heat to 68°C, continue stirring for 4.0 h, and obtain the compound flame retardant after filtration, washing, and drying.

[0061] Preparation Example 3

[0062] The compound flame retardant was prepared using the following method:

[0063] A. Mix 0.3 kg adipic acid, 2.5 kg ethanol, 1 kg pentylenetetrazol phosphate, 0.8 kg dicyandiamide and 12 kg deionized water, and adjust the pH of the mixture to 10.0-11.0 with sodium hydroxide solution to obtain a premixed solution;

[0064] B. Add 0.144 kg of nonylphenol polyoxyethylene ether dispersant to the premixed liquid, heat to 60°C, stir at 600 r / min for 30 min, then add 0.18 kg of zinc borate, heat to 70°C, continue stirring for 5.0 h, and obtain the compound flame retardant after filtration, washing, and drying.

[0065] Preparation Example 4

[0066] The compound flame retardant differs from that in Preparation Example 1 in that zinc borate was not added in step B of this preparation example. Specifically, step B is as follows: 0.056 kg of nonylphenol polyoxyethylene ether dispersant was added to the premixed solution, the temperature was raised to 50°C, and the mixture was stirred at a rate of 500 r / min for 20 min. The temperature was then raised to 65°C, and stirring was continued for 3.0 h. After filtration, washing, and drying, the compound flame retardant was obtained.

[0067] Example

[0068] Example 1

[0069] A low-smoke, halogen-free flame-retardant cable material, the raw material composition and dosage of which are shown in Table 1, wherein the melt index of polypropylene resin is 2 g / min; the POE elastomer is a polyolefin elastomer with 15% octene content; the melt index of the POE elastomer is 5 g / 10 min; the compound flame retardant is the compound flame retardant of Preparation Example 1; the aluminum hydroxide micro powder has a particle size of 2 μm; the nano-reinforcing agent is a mixture of nano-titanium dioxide and nano-talc powder in a mass ratio of 1:1; the antioxidant is a compound of phenolic antioxidant and thioester antioxidant in a mass ratio of 1.5:1, wherein the phenolic antioxidant is antioxidant 1076 and the thioester antioxidant is antioxidant DLTP; and the stabilizer is a calcium-zinc composite stabilizer.

[0070] A low-smoke, halogen-free flame-retardant cable material, the preparation method of which is as follows:

[0071] S1. Mix polypropylene resin, POE elastomer, aluminum hydroxide micro powder, zinc stearate, polydimethylsiloxane, titanate coupling agent, carbon nanotubes, antioxidant, stabilizer and nanoscale reinforcing agent evenly to obtain a mixture.

[0072] S2. Add the mixture to a twin-screw extruder and melt-blend at 180°C and 90MPa pressure for 1 hour to form a melt blend.

[0073] S3. Add a compound flame retardant to the melt blend, continue to melt blend at 170℃ and 90MPa pressure for 1 hour, then extrude through a mold, and obtain a low-smoke halogen-free flame retardant cable material after cooling and solidification.

[0074] A low-smoke halogen-free flame-retardant cable comprises, from the inside out: a conductor, an insulation layer, a shielding layer, and a sheath layer. The specifications and materials of each component are as follows:

[0075] The conductor is made of multi-strand annealed soft copper wire, with a diameter of 0.25mm for each strand and a total of 36 strands. The nominal cross-sectional area of ​​the conductor is 1.5mm². 2 The DC resistance is ≤13.7Ω / km (at 20℃), ensuring that the cable has excellent conductivity and meets the requirements of medium and low voltage power transmission.

[0076] The insulation layer is extruded from the low-smoke halogen-free flame-retardant cable material prepared above. The average thickness of the insulation layer is 0.8 mm, and the minimum thickness is not less than 0.7 mm. The insulation layer is free of defects such as pinholes and bubbles. This material endows the insulation layer with excellent electrical insulation properties, with a volume resistivity ≥1×10⁻⁶. 14 It has a dielectric loss tangent of ≤0.005 Ω·cm (at 20℃) and low smoke halogen-free flame retardant properties, which can effectively prevent current leakage and avoid electrical accidents.

[0077] The shielding layer is located outside the insulation layer and is made of tin-plated copper wire braided with a braiding density of ≥80% and a wire diameter of 0.12mm. The shielding layer can effectively suppress external electromagnetic interference and prevent the internal electric field of the cable from radiating outward, ensuring that the cable can still stably transmit signals or power in complex electromagnetic environments (such as industrial plants, subway tunnels, etc.).

[0078] The sheath layer is also extruded using the low-smoke halogen-free flame-retardant cable material prepared in Example 1 above. The average thickness of the sheath layer is 1.2 mm, and the minimum thickness is not less than 1.0 mm. The surface of the sheath layer is smooth, without cracks or impurities. This material gives the sheath layer good mechanical strength and environmental resistance, with a tensile strength ≥12 MPa and an elongation at break ≥150%, and can resist external physical impact, abrasion, and mild chemical corrosion.

[0079] Example 2

[0080] A low-smoke, halogen-free flame-retardant cable material, the raw material composition and dosage of which are shown in Table 1, wherein the melt index of polypropylene resin is 3 g / min; the POE elastomer is a polyolefin elastomer with 20% octene content; the melt index of the POE elastomer is 6 g / 10 min; the compound flame retardant is the compound flame retardant of Preparation Example 1; the aluminum hydroxide micro powder has a particle size of 4 μm; the nano-reinforcing agent is a mixture of nano-titanium dioxide and nano-talc powder with a mass ratio of 1.5:1; the antioxidant is a compound of phenolic antioxidant and thioester antioxidant with a mass ratio of 2:1, wherein the phenolic antioxidant is antioxidant 1076 and the thioester antioxidant is antioxidant DLTP; and the stabilizer is a calcium-zinc composite stabilizer.

[0081] A low-smoke, halogen-free flame-retardant cable material, the preparation method of which is as follows:

[0082] S1. Mix polypropylene resin, POE elastomer, aluminum hydroxide micro powder, zinc stearate, polydimethylsiloxane, titanate coupling agent, carbon nanotubes, antioxidant, stabilizer and nanoscale reinforcing agent evenly to obtain a mixture.

[0083] S2. Add the mixture to a twin-screw extruder and melt-blend at 190°C and 105MPa pressure for 1.5 hours to form a melt blend.

[0084] S3. Add a compound flame retardant to the melt blend, continue to melt blend at 180℃ and 105MPa pressure for 1.5h, then extrude it through a mold, and obtain a low-smoke halogen-free flame retardant cable material after cooling and solidification.

[0085] Example 3

[0086] A low-smoke, halogen-free flame-retardant cable material, the raw material composition and dosage of which are shown in Table 1, wherein the melt index of polypropylene resin is 4 g / min; the POE elastomer is a polyolefin elastomer with 25% octene content; the melt index of the POE elastomer is 8 g / 10 min; the compound flame retardant is the compound flame retardant of Preparation Example 1; the aluminum hydroxide micro powder has a particle size of 6 μm; the nano-reinforcing agent is a mixture of nano-titanium dioxide and nano-talc powder with a mass ratio of 1.8:1; the antioxidant is a compound of phenolic antioxidant and thioester antioxidant with a mass ratio of 2.5:1, wherein the phenolic antioxidant is antioxidant 1076 and the thioester antioxidant is antioxidant DLTP; and the stabilizer is a calcium-zinc composite stabilizer.

[0087] A low-smoke, halogen-free flame-retardant cable material, the preparation method of which is as follows:

[0088] S1. Mix polypropylene resin, POE elastomer, aluminum hydroxide micro powder, zinc stearate, polydimethylsiloxane, titanate coupling agent, carbon nanotubes, antioxidant, stabilizer and nanoscale reinforcing agent evenly to obtain a mixture.

[0089] S2. Add the mixture to a twin-screw extruder and melt-blend at 200℃ and 120MPa pressure for 2 hours to form a melt blend.

[0090] S3. Add a compound flame retardant to the melt blend, continue to melt blend at 190℃ and 120MPa pressure for 2 hours, then extrude it through a mold, and obtain a low-smoke halogen-free flame retardant cable material after cooling and solidification.

[0091] Table 1. Raw material composition and dosage (kg) of cable materials in Examples 1-3

[0092]

[0093] Example 4

[0094] A composite flame-retardant cable material, which differs from Example 1 in that the composite flame retardant used in this example is the same as the composite flame retardant used in Preparation Example 2.

[0095] Example 5

[0096] A composite flame-retardant cable material, which differs from Example 1 in that the composite flame retardant used in this example is the same as the composite flame retardant used in Preparation Example 3.

[0097] Example 6

[0098] A composite flame-retardant cable material, which differs from Example 1 in that the nano-scale reinforcing agent in this example is nano-titanium dioxide.

[0099] Comparative Example

[0100] Comparative Example 1

[0101] A composite flame-retardant cable material, which differs from Example 1 in that no POE elastomer is added in this comparative example, and polypropylene resin is used instead.

[0102] Comparative Example 2

[0103] A composite flame-retardant cable material, which differs from Example 1 in that an equal amount of triphenyl phosphate is used instead of the compound flame retardant in this comparative example.

[0104] Comparative Example 3

[0105] A composite flame-retardant cable material, which differs from Example 1 in that the flame retardant used in this comparative example is the same as the flame retardant used in Preparation Example 4.

[0106] Comparative Example 4

[0107] A composite flame-retardant cable material differs from Example 1 in that no nano-level reinforcing agent is added in this comparative example, and polypropylene resin is used instead.

[0108] Performance testing

[0109] The performance of the composite flame-retardant cable materials prepared in Examples 1-6 and Comparative Examples 1-4 was tested, and the test results are shown in Table 2.

[0110] Table 2 Test Results

[0111]

[0112] The limiting oxygen index (LOI) is an important indicator for evaluating the flame retardant performance of materials. It represents the minimum oxygen concentration at which a material can sustain combustion in a mixture of oxygen and nitrogen. A higher LOI indicates that the material is less flammable, and vice versa. The LOI values ​​of Examples 1-6 range from 44.1% to 47.3%, significantly higher than the 21.9%-37.4% of the comparative examples. This difference clearly demonstrates the advantages of the technical solution in this application in improving flame retardant performance.

[0113] Comparative Example 2 used triphenyl phosphate (a single phosphorus-based flame retardant) instead of the "pentaerythritol phosphate + dicyandiamide + zinc borate" compound flame retardant in this application. Its LOI value was only 21.9%, which was only half of that of Example 1 (44.3%). This comparison fully demonstrates that the "gas phase + condensed phase" dual flame retardant mechanism of the compound flame retardant system is more efficient. The single phosphorus-based flame retardant can only form a condensed phase flame retardant barrier by catalyzing the dehydration of the matrix resin to form char, but the resulting char layer structure is loose and easily permeable, resulting in limited flame retardant effect. In the compound flame retardant system, pentaerythritol phosphate catalyzes the formation of char to form a basic barrier. Dicyandiamide decomposes upon heating to release inert gases such as ammonia and nitrogen, which can dilute the concentration of combustible gases in the combustion zone and inhibit free radical chain combustion reactions, thus achieving gas-phase flame retardancy. Zinc borate generates B2O3 glassy substance at high temperatures, which can fill the micropores and gaps in the char layer, enhancing the density and heat and oxygen insulation capabilities of the char layer. The flame retardant barrier formed by the synergistic effect of the three is more stable and efficient, significantly improving the LOI value of the material.

[0114] Comparative Example 3 used a "zinc borate-free compound flame retardant" (i.e., the flame retardant in Preparation Example 4), and its LOI value was 25.4%, far lower than the 44.3% of Example 1. This difference confirms the crucial role of zinc borate in the compound flame retardant system. Without zinc borate, the phosphorus-nitrogen flame retardant system formed solely by pentaerythritol phosphate and dicyandiamide, while capable of generating a char layer and releasing inert gas, cannot fill the micropores of the char layer. Oxygen can still permeate through these micropores to the combustion zone, leading to the failure of the flame retardant barrier and a significant decrease in the LOI value. This further illustrates the necessity of zinc borate in perfecting the flame retardant system and improving its flame retardant efficiency.

[0115] Comparative Example 1, which removed the POE elastomer and replaced it with an equal amount of polypropylene resin, had an LOI value of 37.4%, lower than the 44.3% of Example 1. This difference indicates that the POE elastomer has an auxiliary optimizing effect on the flame retardant performance of the material. POE elastomer and polypropylene resin both belong to the polyolefin family and have good compatibility. Its octene segments can embed into the gaps between polypropylene molecular chains to form an interpenetrating network structure. This structure allows the compounded flame retardant to be more evenly dispersed in the matrix, avoiding insufficient flame retardant content in local areas due to flame retardant agglomeration, thus forming "weak points" in combustion. Without the POE elastomer, the polypropylene molecular chains are relatively tightly arranged, making it easy for the flame retardant to agglomerate in the matrix. This results in excessively low flame retardant concentrations in local areas, leading to a decrease in the overall LOI value and affecting the flame retardant performance of the material.

[0116] The LOI values ​​of Examples 2 and 3 were 46.5% and 47.3%, respectively, slightly higher than that of Example 1. This trend is due to the increased dosage of the compound flame retardant and aluminum hydroxide micropowder, resulting in a stronger synergistic flame retardant effect of "phosphorus-nitrogen-boron" and a stronger "endothermic cooling" effect of aluminum hydroxide micropowder. When aluminum hydroxide micropowder decomposes upon heating, it absorbs a large amount of heat, reducing the temperature of the combustion zone, and simultaneously releases water vapor to dilute the concentration of combustible gases. This synergistic effect with the compound flame retardant system further enhances the flame retardant effect. However, judging from the data increase, the LOI value of Example 3 only increased by 3 percentage points compared to Example 1, indicating a limited increase. This suggests that the technical solution of this application can achieve a high flame retardant standard for the material within the range of 18-30 parts of compound flame retardant and 10-18 parts of aluminum hydroxide micropowder, without the need to excessively increase the amount of flame retardant. This ensures flame retardant performance while avoiding negative impacts on the mechanical properties of the material due to excessive addition of flame retardant.

[0117] In existing technologies, the addition of flame retardants to cable materials often leads to a decline in mechanical properties and material embrittlement. This application effectively addresses this issue through the synergistic effect of POE elastomer and nano-scale reinforcing agents. The tensile strength of Examples 1-5 is between 28.3-29.5 MPa, and the elongation at break is between 388-397%, significantly higher than the mechanical properties of Comparative Example 1 (without POE elastomer) and Comparative Example 4 (without nano-scale reinforcing agents). After removing the POE elastomer, Comparative Example 1 exhibits a tensile strength of only 18.4 MPa, only 65% ​​of Example 1 (28.3 MPa), and an elongation at break of 284%, only 72% of Example 1 (392%). This difference fully demonstrates the toughening effect of POE elastomer—the octene segments of POE elastomer possess excellent flexibility, and when embedded in the gaps between polypropylene molecular chains, they form a flexible "interpenetrating network." This network retains the original rigidity of polypropylene resin while enhancing the material's toughness, effectively alleviating the material embrittlement problem caused by the addition of flame retardants and preventing a significant decline in mechanical properties.

[0118] Comparative Example 4, by removing the nano-scale reinforcing agent and replacing it with an equal amount of polypropylene resin, showed a tensile strength of 20.6 MPa and an elongation at break of 307%, both lower than Example 1. This comparison demonstrates that the nano-scale reinforcing agent can enhance the mechanical properties of materials through stress dispersion. The nano-scale reinforcing agent has an extremely high specific surface area; when uniformly dispersed in the matrix, it can disperse stress concentration during material stress, preventing crack generation and propagation, thereby improving tensile strength and elongation at break. Example 6, by replacing the composite nano-scale reinforcing agent of "nano-titanium dioxide + nano-talc" with single nano-titanium dioxide, showed a tensile strength of 22.3 MPa and an elongation at break of 331%, still lower than Example 1. This difference indicates that the composite nano-scale reinforcing agent has a superior reinforcing effect. Nano-titanium dioxide has high hardness, significantly improving the rigidity and tensile strength of the material; nano-talc has a sheet-like structure, enhancing the toughness and impact resistance of the material. The synergistic effect of the two can achieve a balance between the rigidity and toughness of the material, avoiding the "one-sided" problem when using single nanoparticles for reinforcement, further optimizing the mechanical properties of the material.

[0119] Examples 2 and 3 show an increase in the amount of compound flame retardant and aluminum hydroxide micropowder compared to Example 1, but the tensile strength (29.2-29.5 MPa) and elongation at break (388-397%) remain close to those of Example 1, without a significant decrease. This phenomenon is attributed to the synergistic effect of the stepwise melt blending process and titanate coupling agent of this application. The stepwise melt blending process first mixes and melt-blends polypropylene resin, POE elastomer, aluminum hydroxide micropowder, and additives to ensure uniform dispersion of non-flame retardant components before adding the compound flame retardant and continuing melt blending. This avoids competitive adsorption between the compound flame retardant and antioxidants, preventing uneven dispersion of additives from affecting mechanical properties. At the same time, the titanate coupling agent can enhance the interfacial compatibility between inorganic powders such as aluminum hydroxide micropowder and nano-scale reinforcing agents and the organic matrix, reducing the damage to the mechanical properties of materials caused by inorganic powder agglomeration, ultimately achieving the effect of "enhanced flame retardant performance without decreased mechanical properties".

[0120] In summary, through the technical solutions of this application, Examples 1-6 simultaneously achieve the goals of "high flame retardancy (LOI≥44%)" and "high mechanical properties (tensile strength≥28MPa, elongation at break≥388%)", fully meeting the application requirements of applications such as buildings, subways, and nuclear power plants that have strict requirements for the flame retardancy and mechanical properties of cable materials.

[0121] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A low-smoke, halogen-free flame-retardant cable material, characterized in that, The raw materials include the following parts by weight: 75-95 parts of polypropylene resin; 20-35 parts of POE elastomer; 18-30 parts of compound flame retardant; 10-18 parts of aluminum hydroxide micro powder; 5-10 parts zinc stearate; 3-7 parts of polydimethylsiloxane; Titanate coupling agent 0.8-2.0 parts; 0.5-1.5 parts of carbon nanotubes; Antioxidant 2.0-4.5 parts; Stabilizer 3-6 parts; 1.5-4.0 parts of nano-scale reinforcing agent; The compound flame retardant was prepared by the following method: A. Mix adipic acid, ethanol, pentaerythritol phosphate, dicyandiamide and deionized water, and adjust the pH of the mixture to 10.0-11.0 with sodium hydroxide solution to obtain a premixed solution; B. Add dispersant to premixed liquid, heat to 50-60℃, stir at 500-600r / min for 20-30min, then add zinc borate, heat to 65-70℃, continue stirring for 3.0-5.0h, and obtain compound flame retardant after filtration, washing and drying. The mass ratio of adipic acid, ethanol, pentaerythritol phosphate, dicyandiamide, and deionized water is (0.1-0.3):(2.0-2.5):1:(0.4-0.8):12; the amount of zinc borate added is 10%-18% of the mass of pentaerythritol phosphate. The nanoscale reinforcing agent is a mixture of nano-titanium dioxide and nano-talc.

2. The low-smoke halogen-free flame-retardant cable material according to claim 1, characterized in that: The dispersant is nonylphenol polyoxyethylene ether, and the amount of dispersant added is 4%-8% of the total mass of pentaerythritol phosphate and dicyandiamide.

3. The low-smoke halogen-free flame-retardant cable material according to claim 1, characterized in that: The antioxidant is a compound of phenolic antioxidants and thioester antioxidants, with a mass ratio of phenolic antioxidants to thioester antioxidants of (1.5-2.5):

1.

4. The low-smoke halogen-free flame-retardant cable material according to claim 1, characterized in that: The polypropylene resin has a melt index of 2-4 g / min; the POE elastomer is a polyolefin elastomer with an octene content of 15%-25%, and the melt index of the POE elastomer is 5-8 g / 10min.

5. The low-smoke halogen-free flame-retardant cable material according to claim 1, characterized in that, The nanoscale reinforcing agent is a mixture of nano-titanium dioxide and nano-talc powder, with a mass ratio of (1.0-1.8):1, and the particle size of the nanoscale reinforcing agent is 60-120 nm.

6. A method for preparing a low-smoke halogen-free flame-retardant cable material according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Mix polypropylene resin, POE elastomer, aluminum hydroxide micro powder, zinc stearate, polydimethylsiloxane, titanate coupling agent, carbon nanotubes, antioxidant, stabilizer and nanoscale reinforcing agent evenly to obtain a mixture. S2. Add the mixture to a twin-screw extruder and melt-blend at 180-200℃ and 90-120MPa pressure for 1-2 hours to form a melt blend. S3. Add a compound flame retardant to the melt blend, continue to melt blend at 170-190℃ and 90-120MPa pressure for 1-2 hours, then extrude it through a mold, and obtain a low-smoke halogen-free flame retardant cable material after cooling and solidification.

7. A low-smoke halogen-free flame-retardant cable, characterized in that, The low-smoke halogen-free flame-retardant cable material described in any one of claims 1-6 is used as the insulation layer and / or sheath layer.

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