Halogen-free insulation wire material, method of manufacture and three-layer insulation wire using the same

Abstract

The application discloses a halogen-free insulating wire material in the field of wire and cable insulation materials, a preparation method and a three-layer insulating wire using the material, and raw materials of the three-layer insulating wire include: ethylene-vinyl alcohol copolymer as a main body resin, two kinds of modified flame retardants and various additives are prepared. Among them, the biomimetic layered double hydroxide@polydopamine composite flame retardant is prepared by dispersing magnesium-aluminum layered double hydroxide powder in a buffer solution, adding dopamine hydrochloride to react to form a polydopamine coating layer, and then reacting with hexachlorocyclotriphosphazene to introduce phosphazene groups; the dynamic siloxane network modified aluminum hydroxide is prepared by reacting aluminum hydroxide with a silane coupling agent, and then pre-mixing with a methacrylate crosslinking agent to form a dynamic crosslinking network structure. The three-layer insulating wire using the material includes a wire core and two insulating layers, the insulating layer is made of the above-mentioned halogen-free insulating wire material, has the characteristics of low smoke, halogen-free, high flame retardant, migration resistance and good mechanical properties, and is suitable for cable scenes with high safety requirements.

Description

Technical Field

[0001] This invention relates to the field of wire and cable insulation technology, specifically to a halogen-free insulation wire material, its preparation method, and a three-layer insulation wire using the material. Background Technology

[0002] With the increasing demands for cable safety in fields such as electronics, new energy, and rail transportation, halogen-free insulation materials are gradually becoming a replacement for traditional halogen-containing insulation materials due to their low smoke, halogen-free, and environmentally friendly properties. Traditional halogen-free insulation materials are mostly based on polyolefins (such as ethylene-vinyl acetate copolymer), and achieve flame retardant properties by adding halogen-free flame retardants such as aluminum hydroxide, magnesium hydroxide, or ammonium polyphosphate. However, these materials exhibit significant drawbacks in practical applications: the interfacial bonding between the flame retardant and the matrix is ​​weak, and migration and precipitation are prone to occur during processing or long-term use, leading to a decrease in the material's water resistance and electrical insulation; the limiting oxygen index of a single flame retardant system is limited, requiring the addition of a large amount of flame retardant (usually exceeding 40% of the total material mass) to meet basic flame retardant requirements, which severely sacrifices the material's mechanical properties (such as reduced tensile strength and elongation at break); in addition, traditional flame retardants are prone to decomposition and failure at high temperatures, and the material's heat distortion temperature and aging resistance are difficult to meet the requirements of complex working conditions, especially in scenarios with extremely high safety requirements such as high-voltage wiring harnesses for new energy vehicles and special cables for aerospace, where the comprehensive performance of traditional halogen-free insulation materials can no longer match the needs of practical applications.

[0003] To address these issues, the industry has attempted to improve the compatibility between flame retardants and the matrix through surface modification, such as using silane coupling agents or calcium stearate to encapsulate the flame retardants. However, these methods only partially improve interfacial bonding, and the migration problem of flame retardants remains unresolved. Furthermore, the modification process is complex and costly. Simultaneously, the limitations of a single flame retardant system remain unresolved; achieving high flame retardant ratings still relies on the addition of large amounts of flame retardants, making it difficult to simultaneously achieve optimal material mechanical properties and processing flowability. More importantly, traditional materials exhibit significant debonding issues at the matrix-flame retardant interface under high temperatures or long-term use, easily leading to insulation layer cracking and further limiting their application in high-temperature environments.

[0004] In emerging fields such as new energy vehicles and 5G communication equipment, cables not only need to meet the basic requirements of low smoke and halogen-free insulation, but also need to possess comprehensive properties such as high heat resistance, high flame retardancy, and migration resistance to meet the long-term stable operation requirements under complex working conditions. Traditional halogen-free insulation materials, due to the aforementioned shortcomings, are no longer adequate to meet the market demand for high-performance insulation materials. Therefore, developing a halogen-free insulation wire material that improves flame retardant compatibility, synergistic flame retardant efficiency, and material heat resistance through novel modification technologies has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a halogen-free insulating wire material, a preparation method, and a three-layer insulating wire using the material, which solves the problems of flame retardant migration and precipitation, weak interfacial bonding, low flame retardant efficiency, and insufficient heat resistance of traditional halogen-free insulating materials.

[0006] The present invention achieves the above objectives through the following technical solutions:

[0007] A halogen-free insulating wire material, comprising the following raw materials in parts by weight: Ethylene-vinyl alcohol copolymer: 35-45 parts by weight; Dynamic siloxane network modified aluminum hydroxide: 25-35 parts by weight; Bionic layered double hydroxide@polydopamine composite flame retardant: 15-25 parts by weight; Maleic anhydride-grafted ethylene-octene copolymer: 3-5 parts by weight; Antioxidant 1076: 0.3-0.5 parts by weight; Antioxidant 168: 0.2-0.3 parts by weight; Pentaerythritol stearate: 0.5-1.0 parts by weight; The preparation method of the biomimetic layered double hydroxide@polydopamine composite flame retardant includes: A1, dissolving MgCl2·6H2O and AlCl3·6H2O in deionized water, adding NaOH solution to adjust the pH to 10-11, stirring at 60-62℃ to generate magnesium-aluminum layered double hydroxide precipitate, centrifuging and washing until neutral, drying at 60-62℃, grinding and sieving to obtain magnesium-aluminum layered double hydroxide powder; adding the magnesium-aluminum layered double hydroxide powder to Tris-HCl buffer solution, ultrasonically dispersing, adding dopamine hydrochloride, and stirring at room temperature; A2, after centrifugation, redispersing the precipitate in N,N-dimethylformamide, adding hexachlorocyclotriphosphazene and triethylamine, reacting at 60-62℃; finally washing with N,N-dimethylformamide, vacuum drying at 80-82℃, and grinding through a 600-650 mesh sieve.

[0008] In this invention, the preparation of the biomimetic layered double hydroxide@polydopamine composite flame retardant is divided into three stages: First, magnesium ions and aluminum ions undergo a hydrolysis reaction in the alkaline environment of sodium hydroxide solution: magnesium ions combine with hydroxide ions to generate [Mg(OH)6] 4- Octahedral ions, aluminum ions, due to their higher charge, partially replace magnesium ions in the laminations, forming a positively charged layered framework [Mg]. 1-x Al x (OH)2] x+The interlayers balance the charge by adsorbing carbonate ions from the solution (from the partial hydrolysis of sodium hydroxide and aluminum ions), ultimately forming a magnesium-aluminum layered double hydroxide precipitate. Subsequently, the magnesium-aluminum layered double hydroxide powder is mixed with dopamine hydrochloride in a Tris-HCl buffer solution (pH=8.5-8.6). Under alkaline conditions, dopamine undergoes auto-oxidative polymerization: the catechol group in the dopamine molecule is oxidized to a quinone structure in the presence of oxygen, releasing hydrogen free radicals and initiating polymerization to form a poly(c-hydroxyl) containing a catechol / quinone structure. The dopamine layer is tightly coated on the surface of the magnesium-aluminum layered double hydroxide through π-π stacking and hydrogen bonding, forming a core-shell structure of magnesium-aluminum layered double hydroxide@polydopamine. Finally, this core-shell structure reacts with a phosphazene compound in N,N-dimethylformamide solvent: the catechol groups of polydopamine react with hexachlorocyclotriphosphazene to graft phosphorus-containing flame-retardant groups onto the surface of the polydopamine layer, forming a magnesium-aluminum layered double hydroxide@polydopamine@phosphazene composite flame retardant, thereby improving the flame retardant efficiency.

[0009] According to a preferred embodiment of the present invention, the ethylene-vinyl alcohol copolymer was purchased from Sinopec Shanghai Petrochemical Co., Ltd. EVOH-VA28 (VA content 28%, melt flow rate 5g / 10min).

[0010] According to a preferred embodiment of the present invention, the MgCl2·6H2O was purchased from Lianyungang Kelunduo Food Ingredients Co., Ltd. as industrial-grade magnesium chloride hexahydrate (purity ≥99.0%).

[0011] According to a preferred embodiment of the present invention, the AlCl3·6H2O was purchased from Jiangsu Runfeng Synthetic Technology Co., Ltd. as industrial-grade aluminum chloride hexahydrate (purity ≥99.5%).

[0012] According to a preferred embodiment of the present invention, the deionized water is purchased from the ultrapure water system of Jiangsu Jiuwu High-Tech Co., Ltd. (resistivity ≥18.2MΩ·cm).

[0013] According to a preferred embodiment of the present invention, the NaOH solution was purchased from Shandong Binhua Binyang Fuel Chemical Co., Ltd. as a 30% sodium hydroxide solution (industrial grade, impurity content ≤0.01%).

[0014] According to a preferred embodiment of the present invention, the Tris-HCl buffer solution was purchased from Shanghai Yuanye Biotechnology Co., Ltd. as pH 8.5-8.6 Tris-HCl buffer (analytical grade).

[0015] According to a preferred embodiment of the present invention, the dopamine hydrochloride was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. (CAS No. 62-31-7, purity ≥98%).

[0016] According to a preferred embodiment of the present invention, the N,N-dimethylformamide was purchased from Jiangsu Feixiang Chemical Co., Ltd. as industrial-grade N,N-dimethylformamide (purity ≥99.5%).

[0017] According to a preferred embodiment of the present invention, the hexachlorocyclotriphosphazene is purchased from Zhejiang Xin'an Chemical Group Co., Ltd. as industrial-grade hexachlorocyclotriphosphazene (purity ≥98%).

[0018] According to a preferred embodiment of the present invention, the triethylamine was purchased from Jiangsu Tianchen New Material Co., Ltd. as industrial-grade triethylamine (purity ≥ 99.0%).

[0019] According to a preferred embodiment of the present invention, the maleic anhydride-grafted ethylene-octene copolymer was purchased from Shanghai Kingfa Science & Technology Development Co., Ltd. as POE-g-MAH-501 (grafting rate ≥1.2%).

[0020] According to a preferred embodiment of the present invention, the antioxidant 1076 was purchased from Nanjing Milan Chemical Co., Ltd. (antioxidant 1076, CAS No. 2082-79-3, purity ≥98%).

[0021] According to a preferred embodiment of the present invention, the antioxidant 168 is purchased from Nanjing Milan Chemical Co., Ltd. (antioxidant 168 (CAS No. 31570-04-4, purity ≥98%).

[0022] According to a preferred embodiment of the present invention, the pentaerythritol stearate was purchased from Hangzhou Oil & Fat Chemical Co., Ltd. as pentaerythritol stearate (PETS-90, melt flow rate ≤2g / 10min).

[0023] According to a preferred embodiment of the present invention, in step A1, the molar ratio of MgCl2·6H2O and AlCl3·6H2O is (3-4):1; the concentration of NaOH solution is 2-3 mol / L; the stirring time is 2-3 h; the drying time is 12-14 h; the mixture is ground through an 800-820 mesh sieve; the pH of the Tris-HCl buffer solution is 8.5-8.6; the ultrasonic dispersion time is 20-30 min; the concentration of dopamine hydrochloride is 2-3 mg / mL; and the stirring time at room temperature is 24-28 h.

[0024] According to a preferred embodiment of the present invention, in step A2, the amount of hexachlorocyclotriphosphazene is 5-8% of the mass of the magnesium-aluminum layered double hydroxide; the amount of triethylamine is 10-12% of the mass of hexachlorocyclotriphosphazene; the reaction time is 6-8 h at 60-62°C; the final washing with N,N-dimethylformamide is 3-4 times; and the vacuum drying time is 18-20 h at 80-82°C.

[0025] According to a preferred embodiment of the present invention, the preparation method of the dynamically modified aluminum hydroxide network includes: B1, adding aluminum hydroxide to anhydrous ethanol, ultrasonically dispersing it to prepare a suspension, adding γ-glycidoxypropyltrimethoxysilane, heating to 60-62°C and refluxing, adjusting the pH of the system to 4-5 during the reaction; after the reaction is completed, centrifuging to separate the precipitate, washing it with anhydrous ethanol, vacuum drying it at 80-82°C, and grinding it through a 1000-mesh sieve to obtain powder; B2, premixing the powder with a methacrylate crosslinking agent in a high-speed mixer.

[0026] In this invention, ethylene-vinyl alcohol copolymer is used as the main resin, and the densely distributed hydroxyl groups on its molecular chain are the key active sites for subsequent grafting of modified flame retardants. During the preparation of dynamically modified aluminum hydroxide using a siloxane network, the hydroxyl groups on the surface of aluminum hydroxide undergo a condensation reaction with the epoxy groups of the silane coupling agent under weakly acidic conditions: the epoxy groups of the silane coupling agent are protonated in an acidic environment regulated by hydrochloric acid, enhancing their reactivity with the hydroxyl groups on the surface of aluminum hydroxide. The two then form stable siloxane bonds (Si-O-Si) through dehydration condensation, generating a preliminary siloxane network structure. This network is further crosslinked through premixing with a methacrylate crosslinking agent, forming a three-dimensional network structure that enhances the binding force with the hydroxyl groups of the ethylene-vinyl alcohol copolymer, effectively inhibiting flame retardant migration.

[0027] According to a preferred embodiment of the present invention, the aluminum hydroxide is purchased from industrial-grade aluminum hydroxide (purity ≥99.5%, particle size 2-5μm) from China Aluminum Corporation Henan Luoyang Aluminum Co., Ltd.

[0028] According to a preferred embodiment of the present invention, the anhydrous ethanol is purchased from Jiangsu Suopu Group industrial-grade anhydrous ethanol (purity ≥99.7%, impurity content ≤0.03%).

[0029] According to a preferred embodiment of the present invention, the γ-glycidyl etheroxypropyltrimethoxysilane was purchased from Nanjing Shuguang Silane Chemical Co., Ltd. as silane coupling agent KH560 (CAS No. 2530-83-8, purity ≥98%).

[0030] According to a preferred embodiment of the present invention, the high-speed mixer is an SHR-500 high-speed mixer (speed range 200-1000 rpm) purchased from Jiangsu Fanqun Drying Equipment Factory.

[0031] According to a preferred embodiment of the present invention, in step B1, the aluminum hydroxide particle size is 2-5 μm; the ultrasonic dispersion time is 30-40 min; the mass concentration of the suspension is 25-30%; the mass of γ-glycidyl etheroxypropyltrimethoxysilane is 3-5% of the mass of aluminum hydroxide; the reflux reaction time is 4-5 h; the acid used to adjust the system is hydrochloric acid; the number of washings is 3-4; and the vacuum drying time is 12-14 h.

[0032] According to a preferred embodiment of the present invention, in step B2, the amount of the methacrylate crosslinking agent is 1-2% of the mass of γ-glycidoxypropyltrimethoxysilane; the premixing time is 5-10 min.

[0033] The present invention also provides a method for preparing the halogen-free insulating wire material described above, comprising the following steps: S1. Weigh the dried ethylene-vinyl alcohol copolymer, dynamic siloxane network modified aluminum hydroxide, biomimetic layered double hydroxide@polydopamine composite flame retardant, maleic anhydride grafted ethylene-octene copolymer, antioxidant 1076, antioxidant 168, and pentaerythritol stearate, and add them to a high-speed mixer to premix and obtain a mixture. S2. Then transfer the mixture into a twin-screw extruder, control the processing temperature to 140-170℃, and after the melt is extruded through the die, it is water-cooled and pelletized.

[0034] According to a preferred embodiment of the present invention, in step S1, the premixing speed is 200-300 rpm and the time is 5-10 min.

[0035] According to a preferred embodiment of the present invention, in step S2, the temperature of the feeding section of the twin-screw extruder is 80-82°C, the temperature of the compression section is 150-155°C, the temperature of the metering section is 165-170°C, and the screw speed is 500-600 rpm.

[0036] In this invention, maleic anhydride-grafted ethylene-octene copolymer is used as a compatibilizer. Its anhydride groups undergo esterification with the hydroxyl groups of the ethylene-vinyl alcohol copolymer. In the molten state, the anhydride groups combine with hydrogen atoms of the hydroxyl groups, removing water molecules to form ester bonds. Simultaneously, they form hydrogen bonds with the siloxane groups of the dynamically modified aluminum hydroxide network and the polydopamine hydroxyl groups of the magnesium-aluminum layered double hydroxide@polydopamine@phosphazene, improving the interfacial bonding between components, reducing phase separation, and promoting uniform material dispersion. Antioxidant 1076 captures alkyl free radicals generated during processing and use (such as RO· generated by polymer chain breakage), combining with these free radicals to form stable alkoxy free radicals, inhibiting... Further oxidative degradation of polymer chains; antioxidant 168 decomposes peroxide free radicals (such as ROO·) and converts them into stable alcohols (such as ROH), forming a synergistic antioxidant system with antioxidant 1076, delaying the aging of materials caused by oxidation and extending their service life; pentaerythritol stearate, as a lubricant, interacts with the polar groups of ethylene-vinyl alcohol copolymer and flame retardant through van der Waals forces, reducing the frictional resistance inside the melt, reducing the entanglement between molecular chains, reducing the melt viscosity during processing, promoting the uniform dispersion and melt blending of each component in the twin-screw extruder, and ensuring the mechanical properties and appearance quality of the material after molding.

[0037] The present invention also provides a triple-insulated wire, the triple-insulated wire comprising a core and an insulation layer, wherein the insulation layer is made of the aforementioned halogen-free insulation material or the halogen-free insulation material prepared by the method described above, and the insulation layer is two layers.

[0038] The beneficial effects of this invention are as follows: This invention achieves significant improvements in several key properties in the preparation of halogen-free insulated wire materials and their triple-insulated wires through innovative modified flame retardant design and process optimization.

[0039] In terms of flame retardant performance, the material employs a synergistic system of dynamically modified aluminum hydroxide via a siloxane network and a biomimetic layered double hydroxide@polydopamine composite flame retardant, effectively overcoming the efficiency bottleneck of traditional halogen-free flame retardants. The dynamically modified aluminum hydroxide via a siloxane network forms a dynamic cross-linked structure with the matrix through surface-grafted epoxy groups, which not only inhibits flame retardant migration but also delays material decomposition at high temperatures through the thermal stability of the siloxane network. The biomimetic layered double hydroxide@polydopamine composite flame retardant utilizes the decomposition of interlayer anions in the layered double hydroxide to generate inert gases that dilute oxygen. Simultaneously, the catechol groups in the polydopamine layer form hydrogen bonds with the matrix to enhance interfacial bonding, and the phosphazene groups grafted on its surface release phosphorus-containing free radicals during combustion to terminate the chain reaction. The synergistic effect of these two components allows the material to achieve a high flame retardant rating without the need for excessive flame retardant addition, effectively avoiding the mechanical property degradation caused by excessive flame retardant.

[0040] In terms of interfacial compatibility and migration resistance, the structural design of the two modified flame retardants significantly improves the internal bonding stability of the material. The epoxy groups of the dynamically modified aluminum hydroxide network form covalent cross-links with the matrix resin, while the polydopamine layer of the biomimetic layered double hydroxide@polydopamine composite flame retardant is tightly bonded to the matrix through hydrogen bonds. This dual interfacial interaction effectively inhibits the migration and precipitation of the flame retardant during processing or long-term use. Experiments show that the material's water absorption rate is significantly reduced, while its volume resistivity remains stable. Even after long-term placement in high-temperature and high-humidity environments, the degradation of its insulation and mechanical properties is far lower than that of traditional halogen-free materials, greatly expanding its application range in harsh environments such as humidity and high temperature.

[0041] In terms of processing performance and comprehensive applications, the material preparation method achieves efficient and uniform dispersion of high molecular weight matrix and modified flame retardant through optimized raw material mixing and extrusion process parameters. The precise temperature control and screw speed design of the twin-screw extruder effectively reduces melt viscosity and improves material processing fluidity, making it suitable for high-speed extrusion molding and improving production efficiency compared to traditional processes. The resulting triple-insulated wire exhibits excellent applicability in scenarios with extremely high safety requirements, such as high-voltage wiring harnesses for new energy vehicles and special cables for aerospace, due to the low-smoke, halogen-free, high flame-retardant, and migration-resistant insulation material. It meets stringent safety standards while also taking into account the lightweight and flexibility requirements of cables, providing a high-performance and reliable new material solution for the high-end cable industry. Detailed Implementation

[0042] The following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0043] I. Implementation Examples Example 1 Raw material composition: 40g ethylene-vinyl alcohol copolymer, 30g dynamic siloxane network modified aluminum hydroxide, 20g biomimetic layered double hydroxide@polydopamine composite flame retardant, 4g maleic anhydride grafted ethylene-octene copolymer, 0.4g antioxidant 1076, 0.3g antioxidant 168, 0.8g pentaerythritol stearate.

[0044] Preparation of dynamically modified aluminum hydroxide using a siloxane network: 28g of aluminum hydroxide (purity ≥99.5%) with a particle size of 2-5μm was poured into a beaker, and 100mL of anhydrous ethanol (analytical grade, concentration ≥99.7%) was added. The mixture was dispersed in an ultrasonic disperser (frequency 40kHz, power 500W) for 35min to obtain a uniform aluminum hydroxide suspension (no precipitation observed, moderate viscosity). The suspension was transferred to a 250mL round-bottom flask, fitted with a reflux condenser (with circulating cooling water), and preheated in a 61℃ water bath for 5min. 1.4g of γ-glycidoxypropyltrimethoxysilane (KH560, purity ≥98%) was slowly added dropwise at a rate of approximately 0.5mL / min, while continuously stirring with a magnetic stirrer (speed 300rpm). During the reaction, the pH of the system was adjusted to 4.5 using 1 mol / L hydrochloric acid solution (analytical grade) (measured every 10 min with a pH meter and the amount of hydrochloric acid adjusted accordingly) to maintain a weakly acidic environment to promote the hydrolysis and condensation of silanes. After reflux for 4.5 h, the mixture was allowed to cool naturally to room temperature. The reaction solution was transferred to a 50 mL centrifuge tube and centrifuged at 5000 rpm for 10 min. The supernatant was discarded, and the precipitate was washed three times with anhydrous ethanol (20 mL of anhydrous ethanol was added each time, vortexed for 2 min, and then centrifuged and discarded) to remove residual silane monomers and byproducts. The washed precipitate was transferred to a vacuum drying oven (vacuum degree ≤ -0.09 MPa, temperature 81 °C) and dried for 13 h until constant weight was achieved. The precipitate was then removed and ground for 1 h using a ball mill (agate balls, ball-to-material ratio 10:1). The powder was then passed through a 1000-mesh sieve (sieve aperture 150 μm) to obtain dynamically modified aluminum hydroxide powder with a siloxane network.

[0045] Preparation of biomimetic layered double hydroxide@polydopamine composite flame retardant: 3.8 g MgCl2·6H2O and 1.27 g AlCl3·6H2O (molar ratio 3.8:1) were added to a beaker and dissolved in deionized water to prepare a mixed solution. 400 mL of 2.5 mol / L NaOH solution (analytical grade) was slowly added to the solution while stirring. The pH was adjusted to 10.5 (monitored with a pH meter), and the reaction was maintained at 61℃ with stirring for 2.5 h to generate magnesium-aluminum layered double hydroxide precipitate. The precipitate was transferred to a centrifuge tube, centrifuged at 5000 rpm for 10 min, the supernatant was discarded, and the precipitate was washed with deionized water until neutral (pH test paper test). It was then vacuum dried at 61℃ for 13 h (vacuum degree ≤ -0.09 MPa), and ground through an 810-mesh sieve (sieve aperture 180 μm) to obtain magnesium-aluminum layered double hydroxide powder. The powder was added to Tris-HCl buffer solution (pH=8.6, analytical grade) and ultrasonically dispersed for 25 min (ultrasonic frequency 40 kHz, power 500 W). 0.5 g of dopamine hydrochloride (concentration 2.5 mg / mL, analytical grade) was added, and the mixture was magnetically stirred at room temperature for 26 h (300 rpm). Dopamine underwent auto-oxidative polymerization to form a polydopamine layer coating the surface of the layered double hydroxide. The reaction solution was transferred to a centrifuge tube and centrifuged at 5000 rpm for 10 min. The supernatant was discarded, and the precipitate was redispersed in N,N-dimethylformamide (DMF, analytical grade). 1.2 g of hexachlorocyclotriphosphazene and 0.132 g of triethylamine were added, and the mixture was reacted at 61 °C for 7 h (magnetically stirred, 300 rpm). After the reaction was completed, the precipitate was washed three times with DMF (50 mL DMF was added each time, and the mixture was vortexed for 2 min and then centrifuged to remove the unreacted hexachlorocyclotriphosphazene), dried under vacuum at 81 °C for 19 h (vacuum degree ≤ -0.09 MPa), and ground through a 620 mesh sieve (sieve aperture 100 μm) to obtain a biomimetic layered double hydroxide@polydopamine composite flame retardant.

[0046] Preparation of halogen-free insulated wire material: 40g of ethylene-vinyl alcohol copolymer, 30g of dynamically modified aluminum hydroxide with a siloxane network, 20g of biomimetic layered double hydroxide@polydopamine composite flame retardant, 4g of maleic anhydride-grafted ethylene-octene copolymer, 0.4g of antioxidant 1076, 0.3g of antioxidant 168, and 0.8g of pentaerythritol stearate were added to a high-speed mixer (500mL capacity) and premixed at 250rpm for 7.5min (observing that the material is uniform and free of lumps). The mixture was then transferred to a twin-screw extruder (40:1 L / D ratio), with the feeding section temperature set to 81℃, the compression section temperature to 153℃, the metering section temperature to 168℃, and the screw speed to 550rpm. The melt was extruded through a die and then water-cooled and pelletized (water temperature 25℃) to obtain halogen-free insulated wire material granules.

[0047] Example 2 The specific implementation method is the same as in Example 1, except that 45g of ethylene-vinyl alcohol copolymer, 25g of dynamic siloxane network modified aluminum hydroxide, 15g of biomimetic layered double hydroxide@polydopamine composite flame retardant, 5g of maleic anhydride grafted ethylene-octene copolymer, 0.5g of antioxidant 1076, 0.2g of antioxidant 168, and 1.0g of pentaerythritol stearate are used.

[0048] Preparation of dynamically modified aluminum hydroxide using a siloxane network: 23g of aluminum hydroxide was added to anhydrous ethanol and ultrasonically dispersed for 30min to prepare a suspension with a mass concentration of 25%; 1.15g of γ-glycidoxypropyltrimethoxysilane (5% of the mass of aluminum hydroxide) was added, and the mixture was heated to 60℃ and refluxed for 4h. The pH was adjusted to 4 with hydrochloric acid; the mixture was centrifuged and washed 3 times, vacuum dried at 80℃ for 12h, and ground through a 1000-mesh sieve; it was premixed with 0.0115g of methacrylate crosslinking agent for 5min to obtain dynamically modified aluminum hydroxide using a siloxane network.

[0049] Preparation of biomimetic layered double hydroxide@polydopamine composite flame retardant: 2.8 g MgCl2·6H2O and 0.7 g AlCl3·6H2O were dissolved in deionized water, and 300 mL of 3 mol / L NaOH solution was added to adjust the pH to 10. The mixture was stirred at 60 °C for 2 h to form a precipitate. After centrifugation and washing, the precipitate was dried at 60 °C for 12 h and then ground through an 800-mesh sieve. Tris-HCl buffer solution (pH=8.5) was added and the mixture was ultrasonically dispersed for 20 min. 0.4 g dopamine hydrochloride (concentration 2 mg / mL) was added and the mixture was stirred at room temperature for 24 h. After centrifugation, the mixture was dispersed in N,N-dimethylformamide, and 1.2 g hexachlorocyclotriphosphazene and 0.144 g triethylamine were added. The mixture was reacted at 60 °C for 6 h. After washing three times, the mixture was vacuum dried at 80 °C for 18 h and then ground through a 600-mesh sieve to obtain the biomimetic layered double hydroxide@polydopamine composite flame retardant.

[0050] Preparation of halogen-free insulated wire material: Add each raw material to a high-speed mixer and premix at 200 rpm for 5 min; transfer to a twin-screw extruder with a feeding section temperature of 80°C, a compression section temperature of 150°C, a metering section temperature of 165°C, and a screw speed of 500 rpm. After extrusion, water-cool and pelletize to obtain halogen-free insulated wire material.

[0051] Example 3 The specific implementation method is the same as in Example 1, except that 35g of ethylene-vinyl alcohol copolymer, 35g of dynamic siloxane network modified aluminum hydroxide, 25g of biomimetic layered double hydroxide@polydopamine composite flame retardant, 3g of maleic anhydride grafted ethylene-octene copolymer, 0.3g of antioxidant 1076, 0.25g of antioxidant 168, and 0.5g of pentaerythritol stearate are used.

[0052] Preparation of dynamically modified aluminum hydroxide using a siloxane network: 33g of aluminum hydroxide was added to anhydrous ethanol and ultrasonically dispersed for 40min to prepare a suspension with a mass concentration of 30%; 0.99g of γ-glycidoxypropyltrimethoxysilane (3% of the mass of aluminum hydroxide) was added, and the mixture was heated to 62℃ and refluxed for 5h, with the pH adjusted to 5 by hydrochloric acid; the mixture was centrifuged and washed 3 times, vacuum dried at 82℃ for 14h, and ground through a 1000-mesh sieve; it was premixed with 0.0198g of a methacrylate crosslinking agent for 10min to obtain dynamically modified aluminum hydroxide using a siloxane network.

[0053] Preparation of biomimetic layered double hydroxide@polydopamine composite flame retardant: 4.8 g MgCl2·6H2O and 1.2 g AlCl3·6H2O were dissolved in deionized water, and 500 mL of 2 mol / L NaOH solution was added to adjust the pH to 11. The mixture was stirred at 62 °C for 3 h to form a precipitate. After centrifugation and washing, the precipitate was dried at 62 °C for 14 h and then ground through an 820-mesh sieve. Tris-HCl buffer solution (pH=8.6) was added and the mixture was ultrasonically dispersed for 30 min. 0.5 g dopamine hydrochloride (concentration 2 mg / mL) was added and the mixture was stirred at room temperature for 28 h. After centrifugation, the mixture was dispersed in N,N-dimethylformamide, and 1.25 g hexachlorocyclotriphosphazene and 0.125 g triethylamine were added. The mixture was reacted at 62 °C for 8 h. After washing three times, the mixture was vacuum dried at 82 °C for 20 h and then ground through a 650-mesh sieve to obtain the biomimetic layered double hydroxide@polydopamine composite flame retardant.

[0054] Preparation of halogen-free insulated wire material: Add each raw material to a high-speed mixer and premix at 300 rpm for 10 min; transfer to a twin-screw extruder with a feeding section temperature of 82℃, a compression section temperature of 155℃, a metering section temperature of 170℃, and a screw speed of 600 rpm. After extrusion, water-cool and pelletize to obtain halogen-free insulated wire material.

[0055] Comparative Example 1 Take 40g of ethylene-vinyl alcohol copolymer, 30g of unmodified aluminum hydroxide, 20g of biomimetic layered double hydroxide@polydopamine composite flame retardant, 4g of maleic anhydride-grafted ethylene-octene copolymer, 0.4g of antioxidant 1076, 0.3g of antioxidant 168, and 0.8g of pentaerythritol stearate. Preparation steps: Except for replacing the dynamically modified siloxane network aluminum hydroxide with unmodified aluminum hydroxide, the remaining steps are the same as in Example 1.

[0056] Comparative Example 2 Take 40g of ethylene-vinyl alcohol copolymer, 30g of dynamically modified siloxane network aluminum hydroxide, 20g of ordinary aluminum hydroxide, 4g of maleic anhydride-grafted ethylene-octene copolymer, 0.4g of antioxidant 1076, 0.3g of antioxidant 168, and 0.8g of pentaerythritol stearate. Preparation steps: Except for replacing the biomimetic layered double hydroxide@polydopamine composite flame retardant with ordinary aluminum hydroxide, the remaining steps are the same as in Example 1.

[0057] Comparative Example 3 Take 40g of ethylene-vinyl alcohol copolymer, 30g of dynamically modified aluminum hydroxide via a siloxane network, 20g of biomimetic layered double hydroxide@polydopamine composite flame retardant, 0g of maleic anhydride-grafted ethylene-octene copolymer, 0.4g of antioxidant 1076, 0.3g of antioxidant 168, and 0.8g of pentaerythritol stearate. Preparation steps: Except for the 0g amount of maleic anhydride-grafted ethylene-octene copolymer, the remaining steps are the same as in Example 1.

[0058] II. Performance Testing The materials prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance testing according to the following methods: 1. Limiting Oxygen Index (LOI) Test: The test was conducted according to GB / T 2406.2-2009 standard using an HC-2 type oxygen index meter (Nanjing Jiangning Analytical Instrument Factory). Sample dimensions were 150mm × 6.5mm × 3mm, and five samples were used. During the test, the sample was placed horizontally in the combustion chamber, and a mixture of pure oxygen and nitrogen was introduced and ignited from the top. The lowest oxygen concentration (%) at which the sample maintained combustion for just 30 seconds was recorded.

[0059] 2. Vertical Burning Rating (UL94) Test: The test was conducted according to GB / T 18380.11-2022 standard using a CZF-3 vertical burning tester (Shanghai Chengsi Intelligent Technology Co., Ltd.). Sample dimensions were 125mm × 13mm × 3mm, with 5 samples required. Ignition was performed by applying a flame to the lower end of the sample within 1 second. The burning time (s), secondary ignition time (s), and char length (mm) were recorded, and the rating was determined (V-0 / V-1 / V-2).

[0060] 3. Tensile strength and elongation at break test: Instron 5967 universal testing machine (Instron Corporation, USA) was used according to GB / T 1040.2-2006 standard. The sample size was 150mm × 10mm × 4mm, the tensile rate was 50mm / min, and 5 specimens were tested per group. The average value (MPa) was taken.

[0061] 4. Thermogravimetric Analysis (TGA): A Pyris 1 TGA thermogravimetric analyzer (PerkinElmer, USA) was used. The sample mass was approximately 10 mg, the atmosphere was nitrogen (flow rate 50 mL / min), the heating rate was 10 °C / min, and the test range was 30–800 °C. The initial decomposition temperature (Td1, 5% weight loss temperature), the maximum decomposition temperature (Tdmax, maximum weight loss rate temperature), and the char residue at 800 °C (%) were recorded.

[0062] 5. Volume resistivity test: According to GB / T 1410-2006 standard, a ZC-8 type high resistance meter (Shanghai No. 6 Electric Meter Factory) was used. The sample size was 100mm×100mm×3mm. After the surface was polished smooth, it was clamped between the electrodes. A DC voltage of 100V was applied, and after stabilizing for 1 minute, the resistance value (Ω) was measured and converted into volume resistivity (ρv, Ω·cm).

[0063] 6. Breakdown Field Strength Test: Following GB / T 1408.1-2016 standard, a BDJC-50kV breakdown tester (Beijing Beiguang Precision Instrument Equipment Co., Ltd.) was used. The sample thickness was 3mm, the voltage ramp rate was 1kV / s, and the electrode spacing was 2mm. The breakdown voltage value (kV / mm) was recorded.

[0064] 7. Migration Resistance Test: Cut the sample into 50mm×50mm×3mm pieces, immerse them in deionized water (500mL), remove them after 72h, blot the surface moisture with filter paper, and dry them in an 80℃ vacuum drying oven for 24h until constant weight. Calculate the mass change rate (%) = [(mass after drying - initial mass) / initial mass] × 100%. Simultaneously, take 10mL of the immersion solution and use ICP-OES (Thermo Fisher Scientific iCAP RQ) to detect Al. 3+ Mg 2+ Cl - Ion concentration (mg / L).

[0065] 8. Performance test results: Table 1: Performance test results of each embodiment and comparative example

[0066] As shown in Table 1, Examples 1-3 of this invention effectively solved the problems of flame retardant migration and precipitation, weak interfacial bonding, low flame retardant efficiency, and insufficient heat resistance of traditional halogen-free insulating materials by optimizing the design of key components. The specific analysis is as follows: In Examples 1-3, the introduction of dynamically modified aluminum hydroxide with a siloxane network significantly inhibited the migration and precipitation of flame retardants. Comparative Example 1 (unmodified aluminum hydroxide) showed better migration resistance (mass change rate 3.5 ± 0.5%, Al content in immersion solution). 3+ The concentration (1.5 ± 0.2 mg / L) was significantly higher than that of Example 1 (mass change rate 0.8 ± 0.1%). 3+The concentration was 0.2 ± 0.05 mg / L. This is because the dynamic siloxane network forms a dense cross-linked structure on the aluminum hydroxide surface through siloxane bonds (Si-O-Si), which enhances the interfacial bonding between the flame retardant and the matrix, and also hinders the migration and diffusion of flame retardant molecules through steric hindrance. The migration amount in Examples 2 and 3 was further reduced (mass change rate 1.2 ± 0.2%, 1.8 ± 0.3%), indicating that the migration inhibition effect continues to improve with the increase of modified aluminum hydroxide content.

[0067] The problem of weak interfacial bonding was effectively improved by adding maleic anhydride-grafted ethylene-octene copolymer (POE-g-MAH). The tensile strength (13.5 ± 0.5 MPa) and elongation at break (200 ± 9%) of Comparative Example 3 (without POE-g-MAH) were significantly lower than those of Example 1 (18.2 ± 1.1 MPa, 280 ± 15%). This is because the anhydride groups of POE-g-MAH undergo esterification with the hydroxyl groups of EVOH, simultaneously forming hydrogen bonds on the flame retardant surface, significantly enhancing the interfacial bonding between the components. In Examples 1-3, the POE-g-MAH content increased from 4 g (Example 1) to 5 g (Example 2) and then decreased to 3 g (Example 3). Although the tensile strength and elongation at break fluctuated slightly, they remained at a high level (>15 MPa, >220%), indicating that an appropriate amount of compatibilizer can effectively improve interfacial bonding.

[0068] The low flame retardant efficiency is addressed through the synergistic effect of the biomimetic layered double hydroxide@polydopamine composite flame retardant. The LOI (29.3 ± 0.3%) and UL94 rating (V-1) of Comparative Example 2 (ordinary aluminum hydroxide) are lower than those of Example 1 (LOI 32.5 ± 0.3%, V-0). This is because the biomimetic flame retardant synergistically retards flames through multiple mechanisms: the interlayer anion decomposition of the layered double hydroxide generates an inert gas that dilutes oxygen; the catechol / quinone structure of polydopamine is tightly bonded to the matrix via hydrogen bonds and promotes char formation; and the phosphazene groups of hexachlorocyclotriphosphazene release phosphorus-containing free radicals during combustion to terminate the chain reaction. In Examples 1-3, the content of the composite flame retardant was increased from 20g to 25g (Example 3), and the LOI increased from 32.5% to 30.8% (Note: In Example 3, the LOI decreased slightly due to the reduction of EVOH content, but it was still higher than that of the comparative example). The UL94 rating remained V-0, indicating that the synergistic flame retardant efficiency of the composite flame retardant was significantly better than that of the single flame retardant.

[0069] The problem of insufficient heat resistance was improved through the synergistic effect of dynamic siloxane modification and biomimetic flame retardant. The initial decomposition temperature (Td1365±8℃) and maximum decomposition temperature (Tdmax428±8℃) of Comparative Example 1 (unmodified aluminum hydroxide) were lower than those of Example 1 (Td1385±5℃, Tdmax450±5℃), and the char residue at 800℃ (22.1±1.1%) was also significantly lower than that of Example 1 (28.5±1.2%). This is because the introduction of the dynamic siloxane network improved the thermal stability of the flame retardant and delayed its decomposition at high temperatures; at the same time, the layered structure and phosphorus-containing groups of the biomimetic flame retardant formed a more stable char layer at high temperatures, further inhibiting the decomposition of the material. In Examples 1-3, as the content of modified aluminum hydroxide and composite flame retardant increased, Td1, Tdmax and char residue all showed an upward trend (Td1 372±7℃, Tdmax 435±7℃, char residue 25.3±0.8% in Example 3), indicating that the thermal stability of the material is enhanced with the optimization of the flame retardant system.

[0070] In summary, Examples 1-3 comprehensively address the key performance defects of traditional halogen-free insulating materials by using dynamic siloxane network modification to inhibit flame retardant migration, POE-g-MAH to improve interfacial bonding, and biomimetic flame retardants to synergistically enhance flame retardant efficiency and thermal stability, thus exhibiting superior overall performance.

[0071] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A halogen-free insulating wire material, characterized in that, The ingredients include the following parts by weight: Ethylene-vinyl alcohol copolymer: 35-45 parts by weight; Dynamic siloxane network modified aluminum hydroxide: 25-35 parts by weight; Bionic layered double hydroxide@polydopamine composite flame retardant: 15-25 parts by weight; Maleic anhydride-grafted ethylene-octene copolymer: 3-5 parts by weight; Antioxidant 1076: 0.3-0.5 parts by weight; Antioxidant 168: 0.2-0.3 parts by weight; Pentaerythritol stearate: 0.5-1.0 parts by weight; The preparation method of the biomimetic layered double hydroxide@polydopamine composite flame retardant includes: A1, dissolving MgCl2·6H2O and AlCl3·6H2O in deionized water, adding NaOH solution to adjust the pH to 10-11, stirring at 60-62℃ to generate magnesium-aluminum layered double hydroxide precipitate, centrifuging and washing until neutral, drying at 60-62℃, grinding and sieving to obtain magnesium-aluminum layered double hydroxide powder; adding the magnesium-aluminum layered double hydroxide powder to Tris-HCl buffer solution, ultrasonically dispersing, adding dopamine hydrochloride, stirring at room temperature; A2, after centrifugation, redispersing the precipitate in N,N-dimethylformamide, adding hexachlorocyclotriphosphazene and triethylamine, reacting at 60-62℃; finally washing with N,N-dimethylformamide, vacuum drying at 80-82℃, grinding and passing through a 600-650 mesh sieve; The preparation method of the dynamically modified aluminum hydroxide network includes: B1, adding aluminum hydroxide to anhydrous ethanol, ultrasonically dispersing it into a suspension, adding γ-glycidoxypropyltrimethoxysilane, heating to 60-62℃ and refluxing, adjusting the pH of the system to 4-5 with hydrochloric acid during the reaction; after the reaction is completed, centrifuging to separate the precipitate, washing it with anhydrous ethanol, drying it under vacuum at 80-82℃, and grinding it through a 1000-mesh sieve to obtain powder; B2, premixing the powder with a methacrylate crosslinking agent in a high-speed mixer.

2. The halogen-free insulating wire material according to claim 1, characterized in that, In step A1, the molar ratio of MgCl2·6H2O and AlCl3·6H2O is (3-4):1; the concentration of NaOH solution is 2-3 mol / L; the stirring time is 2-3 h; the drying time is 12-14 h; the mixture is ground through an 800-820 mesh sieve; the pH of the Tris-HCl buffer solution is 8.5-8.6; the ultrasonic dispersion time is 20-30 min; the concentration of dopamine hydrochloride is 2-3 mg / mL; and the stirring time at room temperature is 24-28 h.

3. The halogen-free insulating wire material according to claim 1, characterized in that, In step A2, the amount of hexachlorocyclotriphosphazene used is 5-8% of the mass of magnesium aluminum layered double hydroxide; the amount of triethylamine used is 10-12% of the mass of hexachlorocyclotriphosphazene; the reaction time is 6-8 hours at 60-62°C; the final washing with N,N-dimethylformamide is 3-4 times; and the vacuum drying time is 18-20 hours at 80-82°C.

4. The halogen-free insulating wire material according to claim 1, characterized in that, In step B1, the aluminum hydroxide particle size is 2-5 μm; the ultrasonic dispersion time is 30-40 min; the mass concentration of the suspension is 25-30%; the mass of γ-glycidyl etheroxypropyltrimethoxysilane is 3-5% of the mass of aluminum hydroxide; the reflux reaction time is 4-5 h; the acid used to adjust the system is hydrochloric acid; the number of washings is 3-4; and the vacuum drying time is 12-14 h.

5. The halogen-free insulating wire material according to claim 1, characterized in that, In step B2, the amount of the methacrylate crosslinking agent is 1-2% of the mass of γ-glycidoxypropyltrimethoxysilane; the premixing time is 5-10 min.

6. A method for preparing a halogen-free insulating wire material according to any one of claims 1-5, characterized in that, step... include: S1. Weigh the dried ethylene-vinyl alcohol copolymer, dynamic siloxane network modified aluminum hydroxide, biomimetic layered double hydroxide@polydopamine composite flame retardant, maleic anhydride grafted ethylene-octene copolymer, antioxidant 1076, antioxidant 168, and pentaerythritol stearate, and add them to a high-speed mixer to premix and obtain a mixture. S2. Then transfer the mixture into a twin-screw extruder, control the processing temperature to 140-170℃, and after the melt is extruded through the die, it is water-cooled and pelletized.

7. The preparation method according to claim 6, characterized in that, In step S1, the premixing speed is 200-300 rpm and the time is 5-10 min.

8. The preparation method according to claim 6, characterized in that, In step S2, the temperature of the feeding section of the twin-screw extruder is 80-82℃, the temperature of the compression section is 150-155℃, the temperature of the metering section is 165-170℃, and the screw speed is 500-600 rpm.

9. A triple-insulated wire, characterized in that, The triple-insulated wire comprises a core and an insulation layer. The insulation layer is made of the halogen-free insulation material as described in any one of claims 1-5 or the halogen-free insulation material prepared by the method described in any one of claims 6-8. The insulation layer is two layers.

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