Halogen-free low-smoke flame-retardant insulating material for low-voltage electric wire and preparation method thereof

Abstract

The application discloses a halogen-free low-smoke flame-retardant insulating material for low-voltage electric wires and a preparation method thereof, and the material comprises the following raw materials in parts by weight: 70-80 parts of low-density polyethylene, 20-30 parts of EVA, 7-10 parts of EVA grafted maleic anhydride, 20-30 parts of modified flame-retardant smoke-suppressing agent, 2-3 parts of antioxidant, 2-3 parts of silicone master batch, 1-2 parts of lubricant, 1.5-2.5 parts of crosslinking aid, and 0.5-0.8 parts of initiator. The insulating material is prepared by compounding the modified flame-retardant smoke-suppressing agent prepared by a specific method with a low-density polyethylene and an EVA resin matrix, and adding other additives, so that the final insulating material not only realizes excellent flame-retardant performance and extremely low smoke production in the premise of not containing halogen, but also has good mechanical properties and electrical insulation, and provides a high-performance insulating material which is excellent in comprehensive performance and environment-friendly for the field of low-voltage electric wires.

Description

Technical Field

[0001] This invention belongs to the field of cable material technology, specifically relating to a halogen-free, low-smoke, flame-retardant insulating material for low-voltage wires and its preparation method. Background Technology

[0002] In recent years, with social development, the application of wires and cables has become increasingly widespread. Simultaneously, the requirements for their flame retardant, mechanical, electrical, and environmental performance have also gradually increased. As a substitute for halogen-containing flame-retardant cable materials, low-smoke halogen-free cable materials have wider applications and are more environmentally friendly; however, their flame retardant and mechanical properties face significant challenges.

[0003] Traditional halogenated polymer insulation materials such as polyvinyl chloride (PVC), while possessing good flame retardancy, release large amounts of dense smoke and highly toxic, corrosive hydrogen halide gases during fires, posing a serious threat to personnel escape and causing secondary corrosion damage to electronic equipment and building structures. Therefore, the development and application of halogen-free, low-smoke flame-retardant cable insulation materials that combine excellent flame retardancy, low smoke emission, and no toxic gas release has become an irreversible development trend and technological consensus within the industry. These materials primarily use polyolefins (such as polyethylene, ethylene-vinyl acetate copolymer, etc.) as the base resin, achieving fire safety through the addition of halogen-free flame retardants. They are widely used in locations with extremely stringent safety requirements, such as airports, subways, high-rise buildings, and data centers.

[0004] To achieve halogen-free flame retardancy in polyolefin materials, the current mainstream technical approach is to fill the matrix resin with a large amount of inorganic hydroxide flame retardants, such as aluminum hydroxide (ATH) and magnesium hydroxide (MDH). These flame retardants release water of crystallization through thermal decomposition, achieving flame retardancy through the dual effects of endothermic cooling and the release of water vapor to dilute the concentration of combustible gases. For example, Chinese patent application CN102875887A discloses a low-smoke halogen-free flame-retardant insulation material for cables, belonging to the field of novel insulation materials technology. To address the problem of poor electrical insulation performance of existing cable insulation materials under wet conditions, a low-smoke halogen-free flame-retardant cable insulation material is provided, comprising the following components in parts by weight: base material: 100.0; inorganic flame retardant: 100.0–200.0; antioxidant: 0.1–8.0; crosslinking sensitizer: 1.0–5.0; radiation resist agent: 0.3–10.0; wherein the base material contains at least polyethylene and ethylene-methacrylic acid copolymer; the inorganic flame retardant contains at least aluminum hydroxide and kaolin; and the radiation resist agent is selected from one or more of ferrocene, 2-amino-5-(p-methoxyphenyl)-1,3,4-thiadiazole lanthanum complex, and 6-benzylaminopurine copper complex. For example, Chinese patent application CN116102815A discloses an irradiated crosslinked high-electrical-performance, low-temperature-resistant, low-smoke, halogen-free insulating material. Its raw materials include: 100 parts of base material, 100-190 parts of low-smoke, halogen-free flame retardant, 0.1-10 parts of flame retardant synergist, 1-10 parts of crosslinking catalyst, 1-10 parts of lubricant, and 0.1-10 parts of composite antioxidant. These parts are by weight. This insulating material uses a crosslinking catalyst and irradiated crosslinking technology to further improve crosslinking efficiency, providing wire and cable products with shorter production cycles and more stable heat resistance and mechanical properties. However, this technology has significant inherent drawbacks: First, to achieve the necessary flame retardant rating, the filler content of ATH or MDH typically needs to reach an extremely high proportion (e.g., exceeding 60% by mass). This severely disrupts the continuity of the polymer matrix, leading to a sharp deterioration in the mechanical properties (such as tensile strength and elongation at break) and processing fluidity of the insulation material, resulting in a rigid and brittle product. Second, the interfacial compatibility between inorganic hydroxides and the non-polar polyolefin matrix is ​​extremely poor. Even with surface treatment improvements, interfacial defects are difficult to avoid at high filler contents. This not only affects mechanical properties but also reduces the material's long-term resistance to damp heat and electrical insulation stability. To overcome these drawbacks, the industry is committed to developing more efficient flame retardant systems, such as using synergistic flame retardant systems based on phosphorus and nitrogen elements, or utilizing the dispersion and nucleation effects of nanomaterials to improve the efficiency of flame retardants and their compatibility with the matrix. However, how to systematically solve the interfacial problem and maintain the material's excellent overall mechanical and electrical properties while improving flame retardant efficiency remains the core challenge facing the current technology. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a halogen-free, low-smoke, flame-retardant insulating material for low-voltage wires and its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A halogen-free, low-smoke, flame-retardant insulation material for low-voltage electrical wires, comprising the following raw materials by weight:

[0008] Low-density polyethylene 70-80 parts, EVA 20-30 parts, EVA grafted maleic anhydride 7-10 parts, modified flame retardant and smoke suppressant 20-30 parts, antioxidant 2-3 parts, silicone masterbatch 2-3 parts, lubricant 1-2 parts, crosslinking aid 1.5-2.5 parts, initiator 0.5-0.8 parts.

[0009] Preferably, the antioxidant is a mixture of antioxidant 1098 and antioxidant 168 in a mass ratio of 2-3:1; the lubricant is a mixture of zinc stearate and ethylene bis-stearamide in a mass ratio of 2-4:1.

[0010] In this invention, a modified flame retardant and smoke suppressant prepared by a specific method is compounded with low-density polyethylene and EVA resin matrix, and other additives are added. As a result, the final insulation material not only achieves excellent flame retardant performance and extremely low smoke production during combustion without the presence of halogens, but also has good mechanical properties and electrical insulation properties. This provides a high-performance insulation material with excellent comprehensive performance and environmental friendliness for the field of low-voltage wires.

[0011] Preferably, the preparation method of the modified flame retardant and smoke suppressant includes the following steps:

[0012] S1. Add montmorillonite to deionized water, then add ammonium molybdate and cerium nitrate, stir well, add ammonia water, adjust the pH, and then carry out a hydrothermal reaction. After the reaction is completed, filter, wash, dry and calcine to obtain composite montmorillonite.

[0013] S2. Add the composite montmorillonite from step S1 to an ethanol aqueous solution, then add γ-glycidoxypropyltrimethoxysilane, stir and react, filter, wash and dry after the reaction is complete to obtain pretreated montmorillonite.

[0014] S3. Add the pretreated montmorillonite from step S2 to toluene, then add 3-(diphenylphosphino)propylamine and triethylamine, and heat the mixture to react. After the reaction is complete, filter, wash and dry to obtain organomontmorillonite.

[0015] S4. Add the organomontmorillonite from step S3 to toluene, then add (1-phenylvinyl)phosphonic acid and p-toluenesulfonic acid, and carry out a constant temperature reaction. After the reaction is completed, filter, wash and dry to obtain the modified flame retardant and smoke suppressant.

[0016] Preferably, in step S1, the mass ratio of montmorillonite, deionized water, ammonium molybdate, and cerium nitrate is 80-90:1000-1300:6-10:14-18, the mass concentration of the ammonia water is 25-28%, and the pH is 9.5-10.

[0017] Preferably, the hydrothermal reaction in step S1 is carried out at a temperature of 110-120°C for 3-5 hours; the calcination is carried out at a temperature of 400-500°C for 1-2 hours.

[0018] In this invention, a hydrothermal method is used to generate molybdenum-cerium composite oxide in situ on montmorillonite. Montmorillonite serves as a carrier, and its large specific surface area provides a platform for loading active components. Its layered structure can form a physical barrier during combustion, providing heat and oxygen insulation. The MoO3 generated after calcination is an excellent condensed-phase catalyst that can promote the dehydration and cross-linking of polymers during combustion to form a dense protective char layer. CeO2 not only has the ability to catalyze char formation, but its surface oxygen vacancies also endow it with the unique ability to catalyze the oxidation of CO and soot particles in the gas phase. The in-situ generated molybdenum-cerium composite oxide, as an active catalytic center, provides a strong foundation for condensed-phase flame retardancy and partial gas-phase smoke suppression in insulating materials.

[0019] Preferably, in step S2, the volume ratio of ethanol to water in the ethanol-water solution is 3-4:1, the mass ratio of the composite montmorillonite to γ-glycidoxypropyltrimethoxysilane is 100:8-12, and the stirring reaction temperature is 55-65℃ for 2-3 hours.

[0020] In this invention, by reacting composite montmorillonite with γ-glycidoxypropyltrimethoxysilane, more reactive epoxy groups are introduced, providing reaction sites for the subsequent introduction of functional substances. Furthermore, γ-glycidoxypropyltrimethoxysilane builds a robust chemical bridge between the inorganic montmorillonite and the organic functional layer, ensuring that the flame-retardant filler does not separate from the polymer matrix in the final insulation material, thereby avoiding a significant decrease in the mechanical properties of the material.

[0021] Preferably, in step S3, the mass ratio of the pretreated montmorillonite, 3-(diphenylphosphino)propylamine, and triethylamine is 100:8-12:2-3, and the heating reaction temperature is 60-70℃ for 3-4 hours.

[0022] In this invention, the epoxy groups on montmorillonite undergo a highly efficient ring-opening addition reaction with the primary amine group of 3-(diphenylphosphino)propylamine through pretreatment, forming a new hydroxyl group and a tertiary amine structure. Typical P in 3-(diphenylphosphino)propylamine... 3+The phosphorus-containing groups in this form introduce the first layer of gas-phase flame retardancy into the modified flame retardant and smoke suppressant. During combustion, the weaker PC bonds break, releasing phosphorus-containing reactive free radicals. These free radicals can efficiently capture highly reactive free radicals such as H· and OH· generated during polymer combustion, thereby interrupting the chain reaction of combustion and acting as a gas-phase flame quencher. At the same time, the newly generated hydroxyl groups also provide sites for the next reaction.

[0023] Preferably, in step S4, the mass ratio of organomontmorillonite, (1-phenylvinyl)phosphonic acid, and p-toluenesulfonic acid is 100:6.5-9.5:1-2, and the isothermal reaction is carried out at a temperature of 80-90°C for 4-5 hours.

[0024] In this invention, under the catalysis of p-toluenesulfonic acid (a strong acid catalyst), the new hydroxyl group formed in step S3 undergoes a dehydration esterification reaction with (1-phenylvinyl)phosphonic acid to form a phosphonate structure. (1-phenylvinyl)phosphonic acid contains P... 5+ The phosphonate structure is a highly efficient condensed-phase flame retardant group that promotes polymer dehydration and char formation during combustion. It forms a synergistic effect with the inorganic core MoO3 / CeO2, further enhancing the condensed-phase catalytic char formation ability. At the same time, the styrene group it contains can undergo copolymerization reaction with the free radicals of LDPE / EVA during the subsequent peroxide crosslinking process of the insulation material. This "anchors" the entire flame retardant molecule in the crosslinking network in the form of chemical bonds, which not only improves the interfacial compatibility between the modified flame retardant and smoke suppressant and the resin matrix, but also increases the crosslinking density, thereby improving the heat resistance and mechanical properties of the material.

[0025] Preferably, the crosslinking aid is triallyl isocyanurate, and the initiator is dicumyl peroxide.

[0026] This invention also protects a method for preparing a halogen-free, low-smoke, flame-retardant insulating material for low-voltage wires as described above, comprising the following steps:

[0027] Weigh the raw materials according to the formula, add low-density polyethylene, EVA, EVA-grafted maleic anhydride, modified flame retardant and smoke suppressant, antioxidant, silicone masterbatch, and lubricant to a high-speed mixer and mix for 10-15 minutes. Then, feed the mixture through the feed port of a twin-screw extruder. Set the temperatures of the extruder's first to tenth stages to 80-110℃, 130-140℃, 145-155℃, 155-165℃, 160-170℃, 165-175℃, 160-170℃, 155-165℃, 150-160℃, and 155-165℃, and the die temperature to 160-170℃. In the eighth stage of the extruder, inject the mixture of crosslinking aid and initiator into the melt through a metering pump. After the material is melted, mixed, and evenly dispersed, it is extruded into strips through the extruder die, cut into uniform granules by a pelletizer, and dried to obtain the final product.

[0028] In this invention, the mixture of crosslinking aid and initiator is injected via a metering pump in the latter stage (eighth stage) of the twin-screw extruder. This ensures that all solid components are fully mixed and dispersed in the melt before the temperature-sensitive initiator is introduced, minimizing its residence time in the high-temperature zone. This process avoids the significant process risk of pre-crosslinking of materials during extrusion granulation, guaranteeing the stability of the production process and the excellent processability of the final product granules.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The halogen-free, low-smoke, flame-retardant insulation material for low-voltage wires provided by the present invention is compounded with a modified flame retardant and smoke suppressant prepared by a specific method and a low-density polyethylene and EVA resin matrix, and other additives are added at the same time. As a result, the final insulation material not only achieves excellent flame retardant performance and extremely low smoke production under the premise of being halogen-free, but also has good mechanical properties and electrical insulation. By fundamentally reducing the introduction of polar components, eliminating interface defects at the micro level, and constructing a dense cross-linked network at the macro level, the excellent electrical insulation performance of the material is systematically guaranteed, providing a high-performance insulation material with excellent comprehensive performance and environmental friendliness for the field of low-voltage wires.

[0031] (2) The halogen-free low-smoke flame-retardant insulation material for low-voltage wires provided by the present invention loads molybdate with condensed phase catalytic carbonization and cerium oxide with both condensed phase and gas phase catalytic effects onto layered montmorillonite in situ using a hydrothermal method, providing a strong foundation for condensed phase flame retardancy and partial gas phase smoke suppression for the insulation material; subsequently, through a multi-step organic grafting reaction, phosphine functional groups with gas phase free radical quenching effects, phosphonate ester structures that promote carbonization, and vinyl functional groups that can participate in matrix crosslinking reactions are covalently bonded to the surface of composite montmorillonite, so that the modified flame retardant and smoke suppressant prepared achieves the effect that can only be achieved by traditional high-filling inorganic flame retardants with a low addition amount. This low filling significantly reduces the introduction of polar fillers from the source, maintains the high volume resistivity and dielectric strength of the polyolefin matrix to the maximum extent, and also greatly reduces the negative impact on the mechanical properties of the matrix resin.

[0032] (3) The halogen-free, low-smoke, flame-retardant insulation material for low-voltage wires provided by this invention ingeniously integrates diphenylphosphine groups (P) on the same molecular carrier. 3+ morphology) and phosphonate group (P 5+ Two functional groups (in morphology) were used to construct a highly efficient "phosphorus-phosphorus" synergistic flame retardant system. This system utilizes the significant differences in the thermal decomposition behavior and mechanism of action of phosphorus compounds with different valence states: in the initial stage of combustion, the chemically more reactive phosphorus compounds... 3+The radical preferentially decomposes in the gas phase, releasing phosphorus-containing fragments that can efficiently quench H· and OH· free radicals in the flame, thereby inhibiting the chain reaction of combustion and delaying flame spread; as the temperature increases, the thermally more stable P... 5+ Phosphonate structures primarily function in the condensed phase, and their decomposition products strongly catalyze the dehydration of the polymer matrix into char, forming a dense thermal and oxygen-barrier barrier. Through the synergistic effect of these two core flame-retardant mechanisms, their overall flame-retardant efficiency far exceeds the simple superposition of single phosphorus-containing flame retardants, thus achieving excellent flame-retardant performance even at low addition levels. Detailed Implementation

[0033] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] Unless otherwise specified, all chemical reagents and materials in this invention are purchased from the market or synthesized from raw materials purchased from the market.

[0035] In this invention, the low-density polyethylene is of the Maoming Petrochemical 2426H grade, the EVA is of the Formosa Plastics 7350M grade, and the montmorillonite has a particle size of 40-75μm.

[0036] Example 1

[0037] A halogen-free, low-smoke, flame-retardant insulation material for low-voltage electrical wires, comprising the following raw materials by weight:

[0038] The composition includes 75 parts low-density polyethylene, 25 parts EVA, 9 parts EVA grafted with maleic anhydride, 25 parts modified flame retardant and smoke suppressant, 2.5 parts antioxidant, 2.5 parts silicone masterbatch, 1.5 parts lubricant, 2 parts crosslinking aid, and 0.7 parts initiator.

[0039] The antioxidant is composed of antioxidant 1098 and antioxidant 168 in a mass ratio of 2.5:1; the lubricant is composed of zinc stearate and ethylene bis-stearamide in a mass ratio of 3:1.

[0040] The preparation method of the modified flame retardant and smoke suppressant includes the following steps:

[0041] S1. Add 85g of montmorillonite to 1200g of deionized water, then add 8g of ammonium molybdate and 16g of cerium nitrate. After stirring evenly, add ammonia water with a mass concentration of 28% to adjust the pH to 10. Then, perform a hydrothermal reaction at 115℃ for 4 hours. After the reaction is completed, filter, wash, dry, and calcine at 450℃ for 1.5 hours to obtain composite montmorillonite.

[0042] S2. Add 100g of composite montmorillonite from step S1 to 1.5L of ethanol aqueous solution (ethanol to water volume ratio of 3.5:1), then add 10g of γ-glycidoxypropyltrimethoxysilane, stir and react at 60℃ for 2.5h, filter, wash and dry after the reaction is complete to obtain pretreated montmorillonite.

[0043] S3. Add 100g of pretreated montmorillonite from step S2 to 1.5L of toluene, then add 10g of 3-(diphenylphosphino)propylamine and 2.5g of triethylamine. React at 65°C under a nitrogen atmosphere for 3.5h. After the reaction is complete, filter, wash and dry to obtain organomontmorillonite.

[0044] S4. Add 100g of organomontmorillonite from step S3 to 1.5L of toluene, then add 8g of (1-phenylvinyl)phosphonic acid and 1.5g of p-toluenesulfonic acid. React at a constant temperature of 85℃ for 4.5h under a nitrogen atmosphere. After the reaction is complete, filter, wash and dry to obtain the modified flame retardant and smoke suppressant.

[0045] A method for preparing a halogen-free, low-smoke, flame-retardant insulation material for low-voltage electrical wires includes the following steps:

[0046] Weigh the raw materials according to the formula, add low-density polyethylene, EVA, EVA-grafted maleic anhydride, modified flame retardant and smoke suppressant, antioxidant, silicone masterbatch, and lubricant to a high-speed mixer and mix for 15 minutes. Then, feed the mixture through the feed port of a twin-screw extruder. Set the temperatures of the extruder's first to tenth stages to 100℃, 135℃, 145℃, 155℃, 165℃, 170℃, 165℃, 160℃, 155℃, and 160℃, and the die temperature to 165℃. In the eighth stage of the extruder, inject the mixture of crosslinking aid and initiator into the melt through a metering pump. After the material is melted, mixed, and dispersed evenly, it is extruded into strips through the extruder die, cut into uniform granules by a pelletizer, and dried to obtain the final product.

[0047] Example 2

[0048] A halogen-free, low-smoke, flame-retardant insulation material for low-voltage electrical wires, comprising the following raw materials by weight:

[0049] 70 parts low-density polyethylene, 30 parts EVA, 10 parts EVA grafted with maleic anhydride, 30 parts modified flame retardant and smoke suppressant, 2 parts antioxidant, 2 parts silicone masterbatch, 1 part lubricant, 1.5 parts crosslinking aid, and 0.5 parts initiator.

[0050] The antioxidant is composed of antioxidant 1098 and antioxidant 168 in a mass ratio of 2:1; the lubricant is composed of zinc stearate and ethylene bis-stearamide in a mass ratio of 2:1.

[0051] The preparation method of the modified flame retardant and smoke suppressant includes the following steps:

[0052] S1. Add 80g of montmorillonite to 1000g of deionized water, then add 6g of ammonium molybdate and 14g of cerium nitrate. After stirring evenly, add 25% ammonia water to adjust the pH to 9.5. Then, perform a hydrothermal reaction at 110℃ for 5 hours. After the reaction is completed, filter, wash, dry, and calcine at 400℃ for 2 hours to obtain composite montmorillonite.

[0053] S2. Add 100g of composite montmorillonite from step S1 to 1.5L of ethanol-water solution (ethanol to water volume ratio of 3:1), then add 8g of γ-glycidoxypropyltrimethoxysilane, stir and react at 55℃ for 3h, filter, wash and dry after the reaction is complete to obtain pretreated montmorillonite.

[0054] S3. Add 100g of pretreated montmorillonite from step S2 to 1.5L of toluene, then add 8g of 3-(diphenylphosphino)propylamine and 2g of triethylamine. React at 60℃ under a nitrogen atmosphere for 4h. After the reaction is complete, filter, wash and dry to obtain organomontmorillonite.

[0055] S4. Add 100g of organomontmorillonite from step S3 to 1.5L of toluene, then add 6.5g of (1-phenylvinyl)phosphonic acid and 1g of p-toluenesulfonic acid. React at a constant temperature of 80℃ for 5h under a nitrogen atmosphere. After the reaction is complete, filter, wash and dry to obtain the modified flame retardant and smoke suppressant.

[0056] A method for preparing a halogen-free, low-smoke, flame-retardant insulation material for low-voltage electrical wires includes the following steps:

[0057] Weigh the raw materials according to the formula, add low-density polyethylene, EVA, EVA-grafted maleic anhydride, modified flame retardant and smoke suppressant, antioxidant, silicone masterbatch, and lubricant to a high-speed mixer and mix for 15 minutes. Then, feed the mixture through the feed port of a twin-screw extruder. Set the temperatures of the extruder's first to tenth stages to 100℃, 135℃, 145℃, 155℃, 165℃, 170℃, 165℃, 160℃, 155℃, and 160℃, and the die temperature to 165℃. In the eighth stage of the extruder, inject the mixture of crosslinking aid and initiator into the melt through a metering pump. After the material is melted, mixed, and dispersed evenly, it is extruded into strips through the extruder die, cut into uniform granules by a pelletizer, and dried to obtain the final product.

[0058] Example 3

[0059] A halogen-free, low-smoke, flame-retardant insulation material for low-voltage electrical wires, comprising the following raw materials by weight:

[0060] 80 parts low-density polyethylene, 20 parts EVA, 7 parts EVA grafted with maleic anhydride, 20 parts modified flame retardant and smoke suppressant, 3 parts antioxidant, 3 parts silicone masterbatch, 2 parts lubricant, 2.5 parts crosslinking aid, and 0.8 parts initiator.

[0061] The antioxidant is composed of antioxidant 1098 and antioxidant 168 in a mass ratio of 3:1; the lubricant is composed of zinc stearate and ethylene bis-stearamide in a mass ratio of 4:1.

[0062] The preparation method of the modified flame retardant and smoke suppressant includes the following steps:

[0063] S1. Add 90g of montmorillonite to 1300g of deionized water, then add 10g of ammonium molybdate and 18g of cerium nitrate. After stirring evenly, add ammonia water with a mass concentration of 28% to adjust the pH to 10. Then, perform a hydrothermal reaction at 120℃ for 3 hours. After the reaction is completed, filter, wash, dry, and calcine at 500℃ for 1 hour to obtain composite montmorillonite.

[0064] S2. Add 100g of composite montmorillonite from step S1 to 1.5L of ethanol aqueous solution (ethanol to water volume ratio of 4:1), then add 12g of γ-glycidoxypropyltrimethoxysilane, stir and react at 65℃ for 2h, filter, wash and dry after the reaction is completed to obtain pretreated montmorillonite.

[0065] S3. Add 100g of pretreated montmorillonite from step S2 to 1.5L of toluene, then add 12g of 3-(diphenylphosphino)propylamine and 3g of triethylamine. React at 70°C under a nitrogen atmosphere for 3 hours. After the reaction is complete, filter, wash and dry to obtain organomontmorillonite.

[0066] S4. Add 100g of organomontmorillonite from step S3 to 1.5L of toluene, then add 9.5g of (1-phenylvinyl)phosphonic acid and 2g of p-toluenesulfonic acid. React at a constant temperature of 90℃ for 4h under a nitrogen atmosphere. After the reaction is complete, filter, wash and dry to obtain the modified flame retardant and smoke suppressant.

[0067] A method for preparing a halogen-free, low-smoke, flame-retardant insulation material for low-voltage electrical wires includes the following steps:

[0068] Weigh the raw materials according to the formula, add low-density polyethylene, EVA, EVA-grafted maleic anhydride, modified flame retardant and smoke suppressant, antioxidant, silicone masterbatch, and lubricant to a high-speed mixer and mix for 15 minutes. Then, feed the mixture through the feed port of a twin-screw extruder. Set the temperatures of the extruder's first to tenth stages to 100℃, 135℃, 145℃, 155℃, 165℃, 170℃, 165℃, 160℃, 155℃, and 160℃, and the die temperature to 165℃. In the eighth stage of the extruder, inject the mixture of crosslinking aid and initiator into the melt through a metering pump. After the material is melted, mixed, and dispersed evenly, it is extruded into strips through the extruder die, cut into uniform granules by a pelletizer, and dried to obtain the final product.

[0069] Comparative Example 1

[0070] A halogen-free, low-smoke, flame-retardant insulation material for low-voltage electrical wires, comprising the following raw materials by weight:

[0071] The composition includes 75 parts low-density polyethylene, 25 parts EVA, 9 parts EVA grafted with maleic anhydride, 25 parts modified flame retardant and smoke suppressant, 2.5 parts antioxidant, 2.5 parts silicone masterbatch, 1.5 parts lubricant, 2 parts crosslinking aid, and 0.7 parts initiator.

[0072] The antioxidant is composed of antioxidant 1098 and antioxidant 168 in a mass ratio of 2.5:1; the lubricant is composed of zinc stearate and ethylene bis-stearamide in a mass ratio of 3:1.

[0073] The preparation method of the modified flame retardant and smoke suppressant includes the following steps:

[0074] S1. Add 100g of montmorillonite from step S1 to 1.5L of ethanol-water solution (ethanol to water volume ratio of 3.5:1), then add 10g of γ-glycidoxypropyltrimethoxysilane, stir and react at 60℃ for 2.5h, filter, wash and dry after the reaction is complete to obtain pretreated montmorillonite.

[0075] S2. Add 100g of pretreated montmorillonite from step S1 to 1.5L of toluene, then add 10g of 3-(diphenylphosphino)propylamine and 2.5g of triethylamine. React at 65°C under a nitrogen atmosphere for 3.5h. After the reaction is complete, filter, wash and dry to obtain organomontmorillonite.

[0076] S3. Add 100g of organomontmorillonite from step S2 to 1.5L of toluene, then add 8g of (1-phenylvinyl)phosphonic acid and 1.5g of p-toluenesulfonic acid. React at a constant temperature of 85℃ for 4.5h under a nitrogen atmosphere. After the reaction is complete, filter, wash and dry to obtain the modified flame retardant and smoke suppressant.

[0077] A method for preparing a halogen-free, low-smoke, flame-retardant insulation material for low-voltage electrical wires includes the following steps:

[0078] Weigh the raw materials according to the formula, add low-density polyethylene, EVA, EVA-grafted maleic anhydride, modified flame retardant and smoke suppressant, antioxidant, silicone masterbatch, and lubricant to a high-speed mixer and mix for 15 minutes. Then, feed the mixture through the feed port of a twin-screw extruder. Set the temperatures of the extruder's first to tenth stages to 100℃, 135℃, 145℃, 155℃, 165℃, 170℃, 165℃, 160℃, 155℃, and 160℃, and the die temperature to 165℃. In the eighth stage of the extruder, inject the mixture of crosslinking aid and initiator into the melt through a metering pump. After the material is melted, mixed, and dispersed evenly, it is extruded into strips through the extruder die, cut into uniform granules by a pelletizer, and dried to obtain the final product.

[0079] Compared with Example 1, this comparative example did not introduce molybdenum-cerium composite oxide into the modified flame retardant and smoke suppressant.

[0080] Comparative Example 2

[0081] A halogen-free, low-smoke, flame-retardant insulation material for low-voltage electrical wires, comprising the following raw materials by weight:

[0082] The composition includes 75 parts low-density polyethylene, 25 parts EVA, 9 parts EVA grafted with maleic anhydride, 25 parts modified flame retardant and smoke suppressant, 2.5 parts antioxidant, 2.5 parts silicone masterbatch, 1.5 parts lubricant, 2 parts crosslinking aid, and 0.7 parts initiator.

[0083] The antioxidant is composed of antioxidant 1098 and antioxidant 168 in a mass ratio of 2.5:1; the lubricant is composed of zinc stearate and ethylene bis-stearamide in a mass ratio of 3:1.

[0084] The preparation method of the modified flame retardant and smoke suppressant includes the following steps:

[0085] S1. Add 85g of montmorillonite to 1200g of deionized water, then add 8g of ammonium molybdate and 16g of cerium nitrate. After stirring evenly, add ammonia water with a mass concentration of 28% to adjust the pH to 10. Then, perform a hydrothermal reaction at 115℃ for 4 hours. After the reaction is completed, filter, wash, dry, and calcine at 450℃ for 1.5 hours to obtain composite montmorillonite.

[0086] S2. Add 100g of composite montmorillonite from step S1 to 1.5L of ethanol aqueous solution (ethanol to water volume ratio of 3.5:1), then add 10g of γ-glycidoxypropyltrimethoxysilane, stir and react at 60℃ for 2.5h, filter, wash and dry after the reaction is complete to obtain pretreated montmorillonite.

[0087] S3. Add 100g of pretreated montmorillonite from step S2 to 1.5L of toluene, then add 10g of 3-(diphenylphosphino)propylamine and 2.5g of triethylamine. React at 65℃ under a nitrogen atmosphere for 3.5h. After the reaction is complete, filter, wash and dry to obtain the modified flame retardant and smoke suppressant.

[0088] A method for preparing a halogen-free, low-smoke, flame-retardant insulation material for low-voltage electrical wires includes the following steps:

[0089] Weigh the raw materials according to the formula, add low-density polyethylene, EVA, EVA-grafted maleic anhydride, modified flame retardant and smoke suppressant, antioxidant, silicone masterbatch, and lubricant to a high-speed mixer and mix for 15 minutes. Then, feed the mixture through the feed port of a twin-screw extruder. Set the temperatures of the extruder's first to tenth stages to 100℃, 135℃, 145℃, 155℃, 165℃, 170℃, 165℃, 160℃, 155℃, and 160℃, and the die temperature to 165℃. In the eighth stage of the extruder, inject the mixture of crosslinking aid and initiator into the melt through a metering pump. After the material is melted, mixed, and dispersed evenly, it is extruded into strips through the extruder die, cut into uniform granules by a pelletizer, and dried to obtain the final product.

[0090] Compared to Example 1, this comparative example did not introduce (1-phenylvinyl)phosphonic acid into the modified flame retardant and smoke suppressant.

[0091] Comparative Example 3

[0092] A halogen-free, low-smoke, flame-retardant insulation material for low-voltage electrical wires, comprising the following raw materials by weight:

[0093] The composition includes 75 parts low-density polyethylene, 25 parts EVA, 9 parts EVA grafted with maleic anhydride, 25 parts modified flame retardant and smoke suppressant, 2.5 parts antioxidant, 2.5 parts silicone masterbatch, 1.5 parts lubricant, 2 parts crosslinking aid, and 0.7 parts initiator.

[0094] The antioxidant is composed of antioxidant 1098 and antioxidant 168 in a mass ratio of 2.5:1; the lubricant is composed of zinc stearate and ethylene bis-stearamide in a mass ratio of 3:1.

[0095] The preparation method of the modified flame retardant and smoke suppressant includes the following steps:

[0096] S1. Add 85g of montmorillonite to 1200g of deionized water, then add 8g of ammonium molybdate and 16g of cerium nitrate. After stirring evenly, add ammonia water with a mass concentration of 28% to adjust the pH to 10. Then, perform a hydrothermal reaction at 115℃ for 4 hours. After the reaction is completed, filter, wash, dry, and calcine at 450℃ for 1.5 hours to obtain composite montmorillonite.

[0097] S2. Add 100g of composite montmorillonite from step S1 to 1.5L of ethanol aqueous solution (ethanol to water volume ratio of 3.5:1), then add 10g of γ-glycidoxypropyltrimethoxysilane, stir and react at 60℃ for 2.5h, filter, wash and dry after the reaction is complete to obtain pretreated montmorillonite.

[0098] S3. Add 100g of pretreated montmorillonite from step S2 to 1.5L of toluene, then add 8g of (1-phenylvinyl)phosphonic acid and 2.5g of triethylamine. React at 65°C under a nitrogen atmosphere for 3.5h. After the reaction is complete, filter, wash and dry to obtain the modified flame retardant and smoke suppressant.

[0099] A method for preparing a halogen-free, low-smoke, flame-retardant insulation material for low-voltage electrical wires includes the following steps:

[0100] Weigh the raw materials according to the formula, add low-density polyethylene, EVA, EVA-grafted maleic anhydride, modified flame retardant and smoke suppressant, antioxidant, silicone masterbatch, and lubricant to a high-speed mixer and mix for 15 minutes. Then, feed the mixture through the feed port of a twin-screw extruder. Set the temperatures of the extruder's first to tenth stages to 100℃, 135℃, 145℃, 155℃, 165℃, 170℃, 165℃, 160℃, 155℃, and 160℃, and the die temperature to 165℃. In the eighth stage of the extruder, inject the mixture of crosslinking aid and initiator into the melt through a metering pump. After the material is melted, mixed, and dispersed evenly, it is extruded into strips through the extruder die, cut into uniform granules by a pelletizer, and dried to obtain the final product.

[0101] Compared with Example 1, this comparative example did not introduce 3-(diphenylphosphine)propylamine into the modified flame retardant and smoke suppressant.

[0102] Comparative Example 4

[0103] A halogen-free, low-smoke, flame-retardant insulation material for low-voltage electrical wires, comprising the following raw materials by weight:

[0104] The composition includes 75 parts low-density polyethylene, 25 parts EVA, 9 parts EVA grafted with maleic anhydride, 25 parts modified flame retardant and smoke suppressant, 2.5 parts antioxidant, 2.5 parts silicone masterbatch, 1.5 parts lubricant, 2 parts crosslinking aid, and 0.7 parts initiator.

[0105] The antioxidant is composed of antioxidant 1098 and antioxidant 168 in a mass ratio of 2.5:1; the lubricant is composed of zinc stearate and ethylene bis-stearamide in a mass ratio of 3:1.

[0106] The preparation method of the modified flame retardant and smoke suppressant includes the following steps:

[0107] S1. Add 85g of montmorillonite to 1200g of deionized water, then add 8g of ammonium molybdate and 16g of cerium nitrate. After stirring evenly, add ammonia water with a mass concentration of 28% to adjust the pH to 10. Then, perform a hydrothermal reaction at 115℃ for 4 hours. After the reaction is completed, filter, wash, dry, and calcine at 450℃ for 1.5 hours to obtain composite montmorillonite.

[0108] S2. Add 100g of composite montmorillonite from step S1 to 1.5L of ethanol aqueous solution (ethanol to water volume ratio of 3.5:1), then add 10g of γ-glycidoxypropyltrimethoxysilane, stir and react at 60℃ for 2.5h, filter, wash and dry after the reaction is complete to obtain modified flame retardant and smoke suppressant.

[0109] A method for preparing a halogen-free, low-smoke, flame-retardant insulation material for low-voltage electrical wires includes the following steps:

[0110] Weigh the raw materials according to the formula, add low-density polyethylene, EVA, EVA-grafted maleic anhydride, modified flame retardant and smoke suppressant, antioxidant, silicone masterbatch, and lubricant to a high-speed mixer and mix for 15 minutes. Then, feed the mixture through the feed port of a twin-screw extruder. Set the temperatures of the extruder's first to tenth stages to 100℃, 135℃, 145℃, 155℃, 165℃, 170℃, 165℃, 160℃, 155℃, and 160℃, and the die temperature to 165℃. In the eighth stage of the extruder, inject the mixture of crosslinking aid and initiator into the melt through a metering pump. After the material is melted, mixed, and dispersed evenly, it is extruded into strips through the extruder die, cut into uniform granules by a pelletizer, and dried to obtain the final product.

[0111] Compared with Example 1, this comparative example did not introduce 3-(diphenylphosphino)propylamine and (1-phenylvinyl)phosphonic acid into the modified flame retardant and smoke suppressant.

[0112] The performance of the halogen-free, low-smoke, flame-retardant insulating materials obtained in Examples 1-3 and Comparative Examples 1-4 was tested as follows: The flame-retardant insulating granules prepared in each group were molded at 10 MPa and 135°C for 5 min, and then held at 15 MPa and 175°C for 15 min in a flat vulcanizing machine to obtain test samples. The performance of the samples was tested according to the standard GB / T 32129-2015 "Halogen-free, low-smoke, flame-retardant cable materials for wires and cables". The test results are shown in Table 1 below.

[0113] Table 1

[0114]

[0115] As can be seen from Table 1 above, the halogen-free low-smoke flame-retardant insulation material prepared by this invention has good mechanical properties, as well as excellent flame-retardant and electrical properties, and has good application prospects.

[0116] The above description is a further detailed explanation of the present invention in conjunction with specific implementation examples. It should not be considered that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the protection scope of the present invention.

[0117] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A halogen-free, low-smoke, flame-retardant insulating material for low-voltage electrical wires, characterized in that, By weight, it includes the following ingredients: Low-density polyethylene 70-80 parts, EVA 20-30 parts, EVA grafted with maleic anhydride 7-10 parts, modified flame retardant and smoke suppressant 20-30 parts, antioxidant 2-3 parts, silicone masterbatch 2-3 parts, lubricant 1-2 parts, crosslinking aid 1.5-2.5 parts, initiator 0.5-0.8 parts; The preparation method of the modified flame retardant and smoke suppressant includes the following steps: S1. Add montmorillonite to deionized water, then add ammonium molybdate and cerium nitrate, stir well, add ammonia water, adjust the pH, then carry out hydrothermal reaction, filter, wash, dry and calcine to obtain composite montmorillonite. S2. Add the composite montmorillonite to an aqueous ethanol solution, then add γ-glycidoxypropyltrimethoxysilane and stir to react, thus obtaining pretreated montmorillonite. S3. Add the pretreated montmorillonite to toluene, then add 3-(diphenylphosphino)propylamine and triethylamine, and heat the mixture to obtain organomontmorillonite; S4. Add organomontmorillonite to toluene, then add (1-phenylvinyl)phosphonic acid and p-toluenesulfonic acid, and carry out a constant temperature reaction to obtain a modified flame retardant and smoke suppressant.

2. The halogen-free, low-smoke, flame-retardant insulation material for low-voltage wires according to claim 1, characterized in that, The antioxidant is a mixture of antioxidant 1098 and antioxidant 168 in a mass ratio of 2-3:1; the lubricant is a mixture of zinc stearate and ethylene bis-stearamide in a mass ratio of 2-4:

1.

3. The halogen-free, low-smoke, flame-retardant insulation material for low-voltage wires according to claim 1, characterized in that, In step S1, the mass ratio of montmorillonite, deionized water, ammonium molybdate, and cerium nitrate is 80-90:1000-1300:6-10:14-18, the mass concentration of ammonia water is 25-28%, and the pH is 9.5-10.

4. The halogen-free, low-smoke, flame-retardant insulation material for low-voltage wires according to claim 1, characterized in that, The hydrothermal reaction in step S1 is carried out at a temperature of 110-120℃ for 3-5 hours; the calcination is carried out at a temperature of 400-500℃ for 1-2 hours.

5. The halogen-free, low-smoke, flame-retardant insulation material for low-voltage wires according to claim 1, characterized in that, In step S2, the volume ratio of ethanol to water in the aqueous ethanol solution is 3-4:1, the mass ratio of the composite montmorillonite to γ-glycidoxypropyltrimethoxysilane is 100:8-12, and the stirring reaction temperature is 55-65℃ for 2-3 hours.

6. The halogen-free, low-smoke, flame-retardant insulation material for low-voltage wires according to claim 1, characterized in that, In step S3, the mass ratio of the pretreated montmorillonite, 3-(diphenylphosphino)propylamine, and triethylamine is 100:8-12:2-3, and the heating reaction temperature is 60-70℃ for 3-4 hours.

7. The halogen-free, low-smoke, flame-retardant insulation material for low-voltage wires according to claim 1, characterized in that, In step S4, the mass ratio of organomontmorillonite, (1-phenylvinyl)phosphonic acid, and p-toluenesulfonic acid is 100:6.5-9.5:1-2, and the isothermal reaction is carried out at a temperature of 80-90°C for 4-5 hours.

8. The halogen-free, low-smoke, flame-retardant insulation material for low-voltage wires according to claim 1, characterized in that, The crosslinking aid is triallyl isocyanurate, and the initiator is dicumyl peroxide.

9. A method for preparing a halogen-free, low-smoke, flame-retardant insulating material for low-voltage wires as described in any one of claims 1-8, characterized in that, Includes the following steps: Weigh the raw materials according to the formula, add low-density polyethylene, EVA, EVA grafted maleic anhydride, modified flame retardant and smoke suppressant, antioxidant, silicone masterbatch, and lubricant to a high-speed mixer and mix for 10-15 minutes. Then, through the feed port of a twin-screw extruder, inject the mixture of crosslinking aid and initiator into the melt through a metering pump in the eighth section of the extruder. After the material is melted, mixed, and dispersed evenly, it is extruded into strips through the extruder die, cut into uniform granules by a pelletizer, and dried to obtain the final product.

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