Silane crosslinked low-smoke halogen-free flame-retardant oil-resistant polyolefin cable material and preparation method thereof

Abstract

The invention discloses a silane-crosslinked low-smoke halogen-free flame-retardant oil-resistant polyolefin cable material and a preparation method thereof. The method comprises the following steps: preparing a bio-based polyesteramide toughening phase which is pre-polymerized by castor oil-based polyamide and poly (butylene adipate-co-terephthalate) and is terminated by itaconic anhydride; the preparation method comprises the following steps: self-assembling phytic acid and melamine to wrap ammonium polyphosphate, so as to prepare supramolecular flame-retardant gel powder; the method comprises the following steps: grafting aramid pulp fibers by using a phosphorus-containing silane coupling agent to prepare a reactive liquid crystal reinforced phase; the preparation method comprises the following steps: blending and banburying the components with a hydrogenated styrene-isoprene-styrene block copolymer, an antioxidant and a peroxide cross-linking agent, carrying out dynamic vulcanization and interface bonding, and carrying out extrusion and electron beam irradiation to finally crosslink. An interpenetrating-topology network structure is formed in the prepared cable material, the crosslinking degree is larger than or equal to 82%, and the cable material is rapid in crosslinking, excellent in oil resistance, low in smoke and free of toxicity and is particularly suitable for super high-rise building hanging cables, deep sea exploration cables and new energy automobile liquid cooling cables.

Description

Technical Field

[0001] This invention belongs to the field of cable material technology, specifically, it relates to a silane cross-linked low-smoke halogen-free flame-retardant oil-resistant polyolefin cable material and its preparation method. Background Technology

[0002] With the widespread application of wires and cables in extreme environments such as hanging systems for super high-rise buildings, deep-sea exploration equipment, and high-power charging piles for new energy vehicles, unprecedentedly stringent requirements have been placed on the comprehensive performance of cable materials: they not only need excellent flame retardancy, low smoke and non-toxicity, and oil resistance, but also extremely high mechanical strength, long-term dimensional stability, and durability and reliability in complex chemical environments.

[0003] Currently, silane cross-linked cable materials based on traditional polyolefin (such as EVA, PE) and metal hydroxide (such as magnesium hydroxide, aluminum hydroxide) flame retardant systems face the following technical bottlenecks when addressing the aforementioned high-end applications: First, traditional wet crosslinking technology relies on hydrolysis and condensation reactions in warm water or steam environments, which suffers from long crosslinking cycles (typically 24-72 hours) and the uniformity of crosslinking being greatly affected by ambient temperature and humidity. In deep-sea high-pressure or extremely dry environments, the reliability and efficiency of this crosslinking mechanism are significantly reduced. While single radiation crosslinking technology can avoid moisture dependence, in highly filled flame-retardant systems, it often leads to material embrittlement or performance degradation due to the poor radiation resistance of the matrix resin and insufficient interfacial stability of the flame retardant, and it is difficult to construct multi-layered stable network structures.

[0004] Secondly, existing halogen-free flame retardant systems typically require large amounts of metal hydroxide fillers (often exceeding 150 parts by weight) to achieve high flame retardancy ratings, leading to severe degradation of the material's mechanical properties, fatigue resistance, and processing fluidity. While phosphorus-nitrogen flame retardants such as ammonium polyphosphate are more efficient, they suffer from poor compatibility with polyolefin matrices, are prone to migration and precipitation, and are susceptible to hydrolysis and pyrolysis during processing. Furthermore, although the introduction of nano-flame retardants helps improve efficiency, their dispersion stability and interfacial compatibility in non-polar polymer matrices and high-shear processing remain industry challenges.

[0005] Furthermore, the application of bio-based materials in the cable industry faces key challenges. While common bio-based polymers (such as PLA) are environmentally friendly, their heat resistance, mechanical strength, and compatibility with highly efficient flame-retardant systems are insufficient, making it difficult to meet the requirements of high-performance cables. Developing bio-based cable materials that combine environmental friendliness with excellent overall performance urgently requires breakthroughs in molecular structure design, interfacial compatibility, and composite reinforcement.

[0006] Furthermore, existing technologies mostly employ single physical blending or single crosslinking methods, making it difficult to construct multi-level, synergistic composite network structures. How to organically combine the flexibility of bio-based materials, the high efficiency of supramolecular flame retardants, the rigidity of nano-reinforcing phases, and the advantages of multiple crosslinking methods to form a stable interpenetrating-topological network structure is a core problem that current technologies have not effectively solved.

[0007] Therefore, there is an urgent need in this field for a completely new technical solution that can fundamentally break through the limitations of existing material systems and process routes, and develop a new generation of cable materials that combine environmental friendliness, high efficiency and flame retardancy, excellent mechanical properties and rapid and reliable cross-linking characteristics through innovative material combinations and synergistic mechanisms. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a silane crosslinked low-smoke halogen-free flame-retardant and oil-resistant polyolefin cable material and its preparation method.

[0009] To achieve the above objectives, the technical solution provided by the present invention is as follows: A method for preparing a silane crosslinked low-smoke halogen-free flame-retardant and oil-resistant polyolefin cable material includes the following steps: (1) 30-50 parts by weight of castor oil-based polyamide, 20-40 parts by weight of poly(butylene adipate / terephthalate) and 5-10 parts by weight of epoxidized soybean oil are prepolymerized in a reactor at 160-180°C, and then 2-5 parts by weight of itaconic anhydride are added for end-capping to obtain a bio-based polyester amide toughening phase; (2) 10-20 parts by weight of phytic acid and 5-15 parts by weight of melamine are self-assembled in an aqueous phase at 60-80°C to form a supramolecular network; then 50-70 parts by weight of ammonium polyphosphate are dispersed in the network and spray-dried to obtain supramolecular flame retardant gel powder. (3) Disperse 15-25 parts by weight of aramid pulp fiber in a solvent, add 3-8 parts by weight of phosphorus-containing silane coupling agent, and perform surface grafting by ultrasonic-microwave synergistic treatment to obtain a reactive liquid crystal reinforcement phase; (4) The bio-based polyesteramide toughening phase obtained in step (1), the supramolecular flame retardant gel powder obtained in step (2), the reactive liquid crystal reinforcing phase obtained in step (3), 20-30 parts by weight of hydrogenated styrene-isoprene-styrene block copolymer, 1-3 parts by weight of dilauryl thiodipropionate and 0.5-2 parts by weight of dicumyl peroxide crosslinking agent are put into a mixer and subjected to dynamic vulcanization and interfacial bonding reaction at 150-170°C under inert gas protection for 15-25 minutes. The high heat and high shear energy of the mixing process promote the condensation reaction between the alkoxysilane on the surface of the reactive liquid crystal reinforcing phase and the carboxyl group at the end of the bio-based polyesteramide toughening phase. At the same time, the peroxide is decomposed by heat to generate free radicals, which initiate the crosslinking of the residual unsaturated bonds in the hydrogenated styrene-isoprene-styrene block copolymer to obtain a pre-crosslinked composite material.

[0010] (5) The pre-crosslinked composite material obtained in step (4) is granulated by a twin-screw extruder and then extruded onto the conductor by a cable extruder; subsequently, the cable is placed under an electron accelerator and irradiated with an electron beam dose of 5~15Mrad in a nitrogen environment to induce the formation of a topological crosslinking network between polymer chains, thereby obtaining a crosslinked finished cable.

[0011] Furthermore, the amine value of the castor oil-based polyamide in step (1) is 40~60 mgKOH / g. By controlling the amine value of the castor oil-based polyamide, the bio-based polyester amide toughening phase is ensured to have suitable reactivity and molecular chain flexibility, providing an optimized network structure basis for subsequent dynamic vulcanization and electron beam irradiation crosslinking.

[0012] Furthermore, the molar ratio of phytic acid to melamine in step (2) is 1:(2~3). By controlling the molar ratio of phytic acid to melamine within this range, a supramolecular network with an ideal cross-linking density can be formed. This network can effectively encapsulate ammonium polyphosphate particles and also exert excellent char-forming and acid-source catalytic effects during combustion, thereby achieving higher flame retardant efficiency.

[0013] Furthermore, the phosphorus-containing silane coupling agent mentioned in step (3) is (dimethoxyphosphoryl)propyltriethoxysilane. Using (dimethoxyphosphoryl)propyltriethoxysilane as a phosphorus-containing silane coupling agent can simultaneously introduce phosphorus and silane functional groups onto the surface of aramid pulp fibers, thereby improving the interfacial bonding force between the fiber and the matrix and enhancing the overall flame-retardant synergistic effect of the material.

[0014] Furthermore, in the hydrogenated styrene-isoprene-styrene block copolymer described in step (4), the hydrogenation rate of the isoprene unit is greater than 95%. This hydrogenation rate ensures that the elastomer has excellent thermal stability and radiation resistance during dynamic vulcanization, providing a guarantee for the formation of a stable topological crosslinking network.

[0015] Furthermore, the purity of dilaurate thiodipropionate in step (4) is not less than 99%. This purity effectively avoids the interference of impurities on dynamic sulfidation and interfacial bonding reactions, ensuring the smooth progress of the crosslinking reaction and the regularity of the crosslinking network structure.

[0016] Furthermore, the dynamic vulcanization and interfacial bonding reaction described in step (4) is a multi-process synergistic step: First, dicumyl peroxide decomposes upon heating to generate free radicals, initiating crosslinking of residual unsaturated bonds in the hydrogenated styrene-isoprene-styrene block copolymer, forming a dynamic vulcanized rubber phase; second, the phosphorus-containing silane coupling agent grafted onto the surface of the reactive liquid crystal reinforcing phase undergoes a condensation reaction between its alkoxysilane groups and the carboxyl groups at the ends of the bio-based polyesteramide toughening phase under heat and shear, forming a strong "fiber-matrix" interfacial chemical bond. This step constructs a stable initial crosslinking and interfacial structure, laying the foundation for the formation of a uniform and dense topological crosslinking network by subsequent electron beam irradiation.

[0017] Furthermore, the accelerating voltage of the electron beam irradiation in step (5) is 1.5~3.0 MeV. This accelerating voltage can ensure that the high-energy electrons have sufficient penetration depth to achieve uniform cross-linking, and can also avoid excessive degradation of polymer molecular chains due to excessive voltage, thereby optimizing the final performance of the material.

[0018] The present invention also provides a silane crosslinked low-smoke halogen-free flame-retardant and oil-resistant polyolefin cable material, which is prepared by the above-mentioned preparation method. It has an interpenetrating-topological composite network structure composed of bio-based polyesteramide, supramolecular flame-retardant gel and aramid fiber reinforcing phase. This structure endows the material with synergistic performance advantages that are difficult to obtain through conventional physical blending.

[0019] This invention also provides a cable whose insulation and / or sheath layers are made of the aforementioned silane cross-linked low-smoke halogen-free flame-retardant oil-resistant polyolefin cable material. The cable is used as a hanging cable for ultra-high-rise buildings, a cable for deep-sea exploration equipment, or a liquid-cooled cable for new energy vehicle charging piles. This cable product exhibits significantly superior mechanical strength, flame-retardant safety, and long-term reliability compared to traditional cables in these extreme application environments.

[0020] Compared with the prior art, the present invention has the following beneficial effects: I. This invention constructs a unique "rigid-flexible" interpenetrating-topological composite network structure through silane-mediated interfacial bonding and multiphase synergy. Specifically, the carboxyl groups at the ends of the bio-based toughening phase chemically react with the silane functional groups on the aramid fiber surface, forming a robust "fiber-matrix" interface; the supramolecular flame-retardant gel achieves efficient fixation and synergistic effect of the flame retardant; and the three components form a stable three-dimensional network structure through the synergistic effect of binary crosslinking via "dynamic vulcanization-electron beam irradiation." This structure enables the material to maintain a high bio-based content while overcoming the shortcomings of traditional bio-based materials in terms of strength. The tensile strength is increased by more than 35% compared to Comparative Example 4, and the heat resistance temperature is increased by more than 25°C, achieving a synergistic enhancement of mechanical properties, heat resistance, and dimensional stability.

[0021] II. The "chemical pre-crosslinking-physical irradiation crosslinking" binary synergistic crosslinking mechanism adopted in this invention breaks through the technical limitations of traditional moisture crosslinking. The dynamic vulcanization in step (4) constructs the initial chemical crosslinking points and a strong interface through the condensation reaction of peroxide crosslinking agent and silane, giving the composite material excellent melt strength and processability; the electron beam irradiation in step (5) induces the formation of a permanent and stable CC crosslinking topology network in the solid phase in a short time. This innovative process shortens the crosslinking cycle from the traditional 24-72 hours to the minute level, and the degree of crosslinking is uniform and stable, unaffected by environmental temperature and humidity. It not only significantly improves production efficiency, but also makes the cable products reliable in harsh environments such as deep sea high pressure and extreme dryness.

[0022] III. The supramolecular flame-retardant gel powder designed in this invention forms a molecular-level coating network through the self-assembly of phytic acid and melamine, effectively fixing the ammonium polyphosphate flame retardant within it. This structure not only prevents the flame retardant from direct contact with external moisture and heat, solving the technical problems of easy hydrolysis and pyrolysis, but also exerts excellent char-forming catalytic effect during combustion, producing a "phosphorus-nitrogen" synergistic flame-retardant effect with ammonium polyphosphate. This innovative design enables the achievement of the UL-94 V-0 flame retardant rating with a filler content far below 150 parts, fundamentally avoiding the degradation of material mechanical properties caused by high filler content, and achieving a unity of high-efficiency flame retardancy and excellent comprehensive performance. Detailed Implementation

[0023] The specific embodiments are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise specified, the raw materials and reagents used in the examples are commercially available.

[0024] Example 1 A method for preparing a silane crosslinked low-smoke halogen-free flame-retardant and oil-resistant polyolefin cable material includes the following steps: (1) 50 kg of castor oil-based polyamide (amine value of 50 mg KOH / g), 35 kg of poly(adipic acid / butyl terephthalate) and 8 kg of epoxidized soybean oil were added to a reactor and prepolymerized at 170 °C for 45 minutes; then 4 kg of itaconic anhydride was added and the end-capping reaction was carried out for 30 minutes to obtain a bio-based polyester amide toughening phase. (2) 15 kg of phytic acid and 10 kg of melamine (molar ratio of 1:2.5) were stirred in an aqueous phase at 70 °C for 2 hours to form a supramolecular network; then 60 kg of ammonium polyphosphate was slowly added and dispersed in the network. After stirring for 1 hour, the mixture was spray-dried in a spray drying tower at an inlet temperature of 180 °C and an outlet temperature of 80 °C to obtain supramolecular flame-retardant gel powder. (3) Disperse 20 kg of aramid pulp fiber in 200 kg of ethanol solvent, add 5 kg of (dimethoxyphosphoryl)propyltriethoxysilane, first treat with ultrasound (power 800 W, time 30 minutes), then transfer to microwave reactor (power 600 W, temperature 85 °C) for 20 minutes to complete surface grafting, filter and dry at 80 °C for 4 hours to obtain reactive liquid crystal reinforcement phase; (4) All the bio-based polyester amide toughening phase obtained in step (1), all the supramolecular flame retardant gel powder obtained in step (2), all the reactive liquid crystal reinforcing phase obtained in step (3), 25 kg of hydrogenated styrene-isoprene-styrene block copolymer (isoprene unit hydrogenation rate 96%), 2 kg of dilauryl thiodipropionate (purity 99.5%), and 1.0 kg of dicumyl peroxide were put into a mixer and subjected to dynamic vulcanization and interfacial bonding reaction at 160°C under nitrogen protection for 20 minutes to obtain a pre-crosslinked composite material. (5) The pre-crosslinked composite material obtained in step (4) is melt-extruded at 165°C by a twin-screw extruder, granulated underwater and dried; the granules are extruded onto the conductor at 180°C by a cable extruder to form an insulation layer; then the cable is placed under an electron accelerator and irradiated with an electron beam at an accelerating voltage of 2.0 MeV and a dose of 10 Mrad in a nitrogen environment to obtain the crosslinked finished cable.

[0025] Example 2 A method for preparing a silane crosslinked low-smoke halogen-free flame-retardant and oil-resistant polyolefin cable material includes the following steps: (1) 30 kg of castor oil-based polyamide (amine value of 40 mg KOH / g), 40 kg of poly(adipic acid / butyl terephthalate) and 5 kg of epoxidized soybean oil were added to a reactor and prepolymerized at 160 °C for 60 minutes; then 2 kg of itaconic anhydride was added and the end-capping reaction was carried out for 40 minutes to obtain a bio-based polyester amide toughening phase. (2) 10 kg of phytic acid and 5 kg of melamine (molar ratio of 1:2) were stirred in an aqueous phase at 60 °C for 3 hours to form a supramolecular network; then 50 kg of ammonium polyphosphate was slowly added and dispersed in the network. After stirring for 1.5 hours, the mixture was spray-dried in a spray drying tower at an inlet temperature of 170 °C and an outlet temperature of 75 °C to obtain supramolecular flame-retardant gel powder. (3) Disperse 15 kg of aramid pulp fiber in 150 kg of ethanol solvent, add 3 kg of (dimethoxyphosphoryl)propyltriethoxysilane, first treat with ultrasound (power 600 W, time 40 minutes), then transfer to microwave reactor (power 500 W, temperature 80 °C) for 25 minutes to complete surface grafting, filter and dry at 75 °C for 5 hours to obtain reactive liquid crystal enhancement phase; (4) All the bio-based polyesteramide toughening phase obtained in step (1), all the supramolecular flame retardant gel powder obtained in step (2), all the reactive liquid crystal reinforcing phase obtained in step (3), 20 kg of hydrogenated styrene-isoprene-styrene block copolymer (isoprene unit hydrogenation rate 95%), 1 kg of dilauryl thiodipropionate (purity 99%), and 1.0 kg of dicumyl peroxide were put into a mixer and subjected to dynamic vulcanization and interfacial bonding reaction at 150°C under nitrogen protection for 25 minutes to obtain a pre-crosslinked composite material. (5) The pre-crosslinked composite material obtained in step (4) is melt-extruded at 160°C by a twin-screw extruder, granulated underwater and dried; the granules are extruded onto the conductor at 175°C by a cable extruder to form a sheath layer; then the cable is placed under an electron accelerator and irradiated with an electron beam at an accelerating voltage of 1.5MeV and a dose of 5Mrad in a nitrogen environment to obtain the crosslinked finished cable.

[0026] Example 3 A method for preparing a silane crosslinked low-smoke halogen-free flame-retardant and oil-resistant polyolefin cable material includes the following steps: (1) 45 kg of castor oil-based polyamide (amine value of 60 mg KOH / g), 20 kg of poly(adipic acid / butyl terephthalate) and 10 kg of epoxidized soybean oil were added to a reactor and prepolymerized at 180 °C for 30 minutes; then 5 kg of itaconic anhydride was added and end-capping reaction was carried out for 20 minutes to obtain a bio-based polyester amide toughening phase. (2) 20 kg of phytic acid and 15 kg of melamine (molar ratio of 1:3) were stirred in an aqueous phase at 80 °C for 1.5 hours to form a supramolecular network; then 70 kg of ammonium polyphosphate was slowly added and dispersed in the network. After stirring for 45 minutes, the mixture was spray-dried in a spray drying tower at an inlet temperature of 190 °C and an outlet temperature of 85 °C to obtain supramolecular flame-retardant gel powder. (3) Disperse 25 kg of aramid pulp fiber in 250 kg of ethanol solvent, add 8 kg of (dimethoxyphosphoryl)propyltriethoxysilane, first treat with ultrasound (power 1000 W, time 20 minutes), then transfer to microwave reactor (power 700 W, temperature 90 °C) for 15 minutes to complete surface grafting, filter and dry at 85 °C for 3 hours to obtain reactive liquid crystal enhancement phase; (4) All the bio-based polyesteramide toughening phase obtained in step (1), all the supramolecular flame retardant gel powder obtained in step (2), all the reactive liquid crystal reinforcing phase obtained in step (3), 30 kg of hydrogenated styrene-isoprene-styrene block copolymer (isoprene unit hydrogenation rate 98%), 3 kg of dilauryl thiodipropionate (purity 99.8%), and 1.0 kg of dicumyl peroxide were put into a mixer and subjected to dynamic vulcanization and interfacial bonding reaction at 170°C under nitrogen protection for 15 minutes to obtain a pre-crosslinked composite material; (5) The pre-crosslinked composite material obtained in step (4) is melt-extruded at 170°C by a twin-screw extruder, granulated underwater and dried; the granules are extruded onto the conductor at 185°C by a cable extruder to form an insulation layer; then the cable is placed under an electron accelerator and irradiated with an electron beam at an accelerating voltage of 3.0 MeV and a dose of 15 Mrad in a nitrogen environment to obtain the crosslinked finished cable.

[0027] Example 4 A method for preparing a silane crosslinked low-smoke halogen-free flame-retardant and oil-resistant polyolefin cable material includes the following steps: (1) 35 kg of castor oil-based polyamide (amine value 45 mg KOH / g), 30 kg of poly(adipic acid / butyl terephthalate) and 6 kg of epoxidized soybean oil were added to a reactor and prepolymerized at 165 °C for 50 minutes; then 3 kg of itaconic anhydride was added and end-capping reaction was carried out for 35 minutes to obtain a bio-based polyester amide toughening phase. (2) 12 kg of phytic acid and 8 kg of melamine (molar ratio of 1:2.2) were stirred in an aqueous phase at 65 °C for 2.5 hours to form a supramolecular network; then 55 kg of ammonium polyphosphate was slowly added and dispersed in the network, and after stirring for 1.2 hours, it was spray-dried in a spray drying tower at an inlet temperature of 175 °C and an outlet temperature of 78 °C to obtain supramolecular flame retardant gel powder. (3) 18 kg of aramid pulp fiber was dispersed in 180 kg of ethanol solvent, and 4 kg of (dimethoxyphosphoryl)propyltriethoxysilane was added. The mixture was first ultrasonically treated (power 700 W, time 35 minutes), and then transferred to a microwave reactor (power 550 W, temperature 82 °C) for 22 minutes to complete the surface grafting. The mixture was filtered and dried at 78 °C for 4.5 hours to obtain a reactive liquid crystal enhancement phase. (4) All the bio-based polyesteramide toughening phase obtained in step (1), all the supramolecular flame retardant gel powder obtained in step (2), all the reactive liquid crystal reinforcing phase obtained in step (3), 22 kg of hydrogenated styrene-isoprene-styrene block copolymer (isoprene unit hydrogenation rate 96.5%), 1.5 kg of dilauryl thiodipropionate (purity 99.2%), and 1.0 kg of dicumyl peroxide were put into a mixer and subjected to dynamic vulcanization and interfacial bonding reaction at 155°C under nitrogen protection for 22 minutes to obtain a pre-crosslinked composite material; (5) The pre-crosslinked composite material obtained in step (4) is melt-extruded at 162°C by a twin-screw extruder, granulated underwater and dried; the granules are extruded onto the conductor at 178°C by a cable extruder to form a sheath layer; then the cable is placed under an electron accelerator and irradiated with an electron beam at an accelerating voltage of 1.8 MeV and a dose of 8 Mrad in a nitrogen environment to obtain the crosslinked finished cable.

[0028] Example 5 A method for preparing a silane crosslinked low-smoke halogen-free flame-retardant and oil-resistant polyolefin cable material includes the following steps: (1) 48 kg of castor oil-based polyamide (amine value of 55 mg KOH / g), 25 kg of poly(adipic acid / butyl terephthalate) and 9 kg of epoxidized soybean oil were added to a reactor and prepolymerized at 175 °C for 35 minutes; then 4.5 kg of itaconic anhydride was added and end-capping reaction was carried out for 25 minutes to obtain a bio-based polyester amide toughening phase; (2) 18 kg of phytic acid and 12 kg of melamine (molar ratio of 1:2.8) were stirred in an aqueous phase at 75 °C for 1.8 hours to form a supramolecular network; then 65 kg of ammonium polyphosphate was slowly added and dispersed in the network, and after stirring for 50 minutes, it was spray-dried in a spray drying tower at an inlet temperature of 185 °C and an outlet temperature of 82 °C to obtain supramolecular flame retardant gel powder. (3) 22 kg of aramid pulp fiber was dispersed in 220 kg of ethanol solvent, and 7 kg of (dimethoxyphosphoryl)propyltriethoxysilane was added. The mixture was first ultrasonically treated (power 900 W, time 25 minutes), and then transferred to a microwave reactor (power 650 W, temperature 88 °C) for 18 minutes to complete the surface grafting. The mixture was then filtered and dried at 82 °C for 3.5 hours to obtain a reactive liquid crystal enhancement phase. (4) All the bio-based polyesteramide toughening phase obtained in step (1), all the supramolecular flame retardant gel powder obtained in step (2), all the reactive liquid crystal reinforcing phase obtained in step (3), 28 kg of hydrogenated styrene-isoprene-styrene block copolymer (isoprene unit hydrogenation rate 97.5%), 2.5 kg of dilauryl thiodipropionate (purity 99.7%), and 1.0 kg of dicumyl peroxide were put into a mixer and subjected to dynamic vulcanization and interfacial bonding reaction at 165°C under nitrogen protection for 18 minutes to obtain a pre-crosslinked composite material; (5) The pre-crosslinked composite material obtained in step (4) is melt-extruded at 168°C by a twin-screw extruder, granulated underwater and dried; the granules are extruded onto the conductor at 182°C by a cable extruder to form an insulation layer; then the cable is placed under an electron accelerator and irradiated with an electron beam at an accelerating voltage of 2.5MeV and a dose of 12Mrad in a nitrogen environment to obtain the crosslinked finished cable.

[0029] Example 6 A method for preparing a silane crosslinked low-smoke halogen-free flame-retardant and oil-resistant polyolefin cable material includes the following steps: (1) Preparation of bio-based polyester amide toughening phase: 30 kg of castor oil-based polyamide (amine value of 60 mg KOH / g), 40 kg of poly(adipic acid / butyl terephthalate) and 5 kg of epoxidized soybean oil were added to a reactor and prepolymerized at 180 °C for 30 minutes; then 5 kg of itaconic anhydride was added for end-capping reaction for 20 minutes to obtain bio-based polyester amide toughening phase; (2) Preparation of supramolecular flame retardant gel powder: 20 kg of phytic acid and 15 kg of melamine (molar ratio of 1:3) were stirred in an aqueous phase at 60 °C for 3 hours to form a supramolecular network; then 70 kg of ammonium polyphosphate was slowly added and dispersed in the network, and after stirring for 1.5 hours, it was spray-dried in a spray drying tower at an inlet temperature of 190 °C and an outlet temperature of 75 °C to obtain supramolecular flame retardant gel powder; (3) Preparation of reactive liquid crystal reinforcement phase: 25 kg of aramid pulp fiber was dispersed in 250 kg of ethanol solvent, and 3 kg of (dimethoxyphosphoryl)propyltriethoxysilane was added. The mixture was first ultrasonically treated (power 1000 W, time 20 minutes), and then transferred to a microwave reactor (power 500 W, temperature 90 °C) for 25 minutes to complete the surface grafting. The mixture was filtered and dried at 85 °C for 3 hours to obtain the reactive liquid crystal reinforcement phase. (4) Preparation of pre-crosslinked composite material: All bio-based polyesteramide toughening phases obtained in step (1), all supramolecular flame retardant gel powders obtained in step (2), all reactive liquid crystal reinforcing phases obtained in step (3), 20 kg of hydrogenated styrene-isoprene-styrene block copolymer (isoprene unit hydrogenation rate 98%), 3 kg of dilauryl thiodipropionate (purity 99.8%), and 1.0 kg of dicumyl peroxide are put into a mixer and subjected to dynamic vulcanization and interfacial bonding reaction at 150°C under nitrogen protection for 25 minutes to obtain pre-crosslinked composite material; (5) Cable forming and cross-linking: The pre-cross-linked composite material obtained in step (4) is melt-extruded at 170°C by a twin-screw extruder, granulated underwater and dried; the granules are extruded onto the conductor at 185°C by a cable extruder to form a sheath layer; then the cable is placed under an electron accelerator and irradiated with an electron beam at an accelerating voltage of 3.0 MeV and a dose of 15 Mrad in a nitrogen environment to obtain the cross-linked finished cable.

[0030] Comparative Example 1 (Traditional EVA / PE matrix + metal hydroxide flame retardant) A method for preparing a traditional silane crosslinked low-smoke halogen-free flame-retardant cable material includes the following steps: (1) Put 40kg of EVA (VA content 28%), 30kg of LDPE, 20kg of ethylene-vinylsilane copolymer and 10kg of POE-g-MAH compatibilizer into a mixer and mix at 120°C for 5 minutes. (2) Add 120kg of aluminum hydroxide, 80kg of magnesium hydroxide, 5kg of polyethylene wax, 2kg of zinc stearate, 1kg of antioxidant 1010 and 1kg of antioxidant 168, and continue to mix at 150℃ for 12 minutes. (3) The compound is melt-extruded at 160°C using a twin-screw extruder, granulated underwater and dried to obtain grafted flame retardant; (4) Put 45kg of EVA, 35kg of LDPE, 2kg of dibutyltin dilaurate, 90kg of aluminum hydroxide, 60kg of magnesium hydroxide, 1kg of antioxidant 1010 and 1kg of antioxidant 168 into a mixer and mix them at 150°C for 12 minutes. (5) The mixture is extruded and granulated at 155°C using a twin-screw extruder and then dried to obtain catalytic retardant fuel; (6) Mix 90kg of grafted fuel and 10kg of catalytic fuel, and extrude the mixture onto the conductor using a cable extruder. Then, place the cable in 80℃ warm water for 48 hours to crosslink and obtain the crosslinked finished cable.

[0031] Comparative Example 2 (no supramolecular flame retardant structure, direct physical blending) A method for preparing cable material includes the following steps: (1) 50 kg of castor oil-based polyamide (amine value of 50 mg KOH / g), 35 kg of poly(adipic acid / butyl terephthalate) and 8 kg of epoxidized soybean oil were prepolymerized in a reactor at 170 °C for 45 minutes; then 4 kg of itaconic anhydride was added for end-capping reaction for 30 minutes to obtain a bio-based polyester amide toughening phase; (2) 20 kg of aramid pulp fiber was dispersed in 200 kg of ethanol solvent, and 5 kg of (dimethoxyphosphoryl)propyltriethoxysilane was added. The surface grafting was completed by ultrasonic and microwave synergistic treatment to obtain a reactive liquid crystal reinforcement phase. (3) All the bio-based polyesteramide toughening phase obtained in step (1), all the reactive liquid crystal reinforcing phase obtained in step (2), 60 kg of ammonium polyphosphate (without supramolecular coating), 15 kg of phytic acid, 10 kg of melamine, 25 kg of hydrogenated styrene-isoprene-styrene block copolymer, and 2 kg of dilauryl thiodipropionate were put into a mixer and subjected to dynamic vulcanization reaction at 160°C under nitrogen protection for 20 minutes to obtain the compound. (4) The compound is granulated by a twin-screw extruder and then extruded onto the conductor. Subsequently, it is irradiated with an electron beam at an accelerating voltage of 2.0 MeV and a dose of 10 Mrad to obtain the cross-linked finished cable.

[0032] Comparative Example 3 (single cross-linking method, electron beam irradiation only) A method for preparing cable material includes the following steps: (1)~(3) are the same as steps (1)~(3) in Example 1; (4) All the bio-based polyesteramide toughening phase obtained in step (1), all the supramolecular flame retardant gel powder obtained in step (2), all the reactive liquid crystal reinforcing phase obtained in step (3), and 25 kg of hydrogenated styrene-isoprene-styrene block copolymer (without adding dicumyl peroxide and dilaurate thiodipropionate) are put into a mixer and mixed at 160°C for 20 minutes (without dynamic vulcanization) to obtain the mixture. (5) The compound is granulated by a twin-screw extruder and then extruded onto the conductor. Subsequently, it is irradiated with an electron beam at an accelerating voltage of 2.0 MeV and a dose of 10 Mrad to obtain the cross-linked finished cable.

[0033] Comparative Example 4 (alternative elastomer matrix, without bio-based / liquid crystal enhancement synergy) A method for preparing cable material includes the following steps: (1) Preparation of supramolecular flame retardant gel powder: Same as step (2) in Example 1; (2) 60 kg of hydrogenated styrene-butadiene-styrene block copolymer (SEBS), 25 kg of polyolefin elastomer (POE), all the supramolecular flame retardant gel powder obtained in step (1), 1 kg of antioxidant, and 2 kg of lubricant were put into a mixer and mixed at 160°C for 20 minutes (dynamic vulcanization was not performed because the traditional matrix could not effectively carry out this reaction). (3) The compound is granulated by a twin-screw extruder and then extruded onto the conductor. Subsequently, it is irradiated with an electron beam at an accelerating voltage of 2.0 MeV and a dose of 10 Mrad to obtain the cross-linked finished cable.

[0034] Performance comparison tests were conducted on Examples 1-6 and Comparative Examples 1-4, and the test methods are as follows: 1. Degree of crosslinking (GB / T 2951.11 or ASTM D2765) Weigh a certain mass of the cross-linked sample, reflux extract it in a suitable solvent (such as xylene) for a specified time, take out the insoluble matter, dry and weigh it, and calculate the mass percentage of the insoluble matter as the degree of cross-linking.

[0035] 2. Limiting Oxygen Index (GB / T 2406 or ASTM D2863) The sample is vertically fixed in the combustion chamber, an oxygen-nitrogen mixture is introduced, the top of the sample is ignited, and the minimum percentage of oxygen concentration that can support the continuous combustion of the material is determined.

[0036] 3. Tensile strength and elongation at break (GB / T 1040 or ISO 527) Prepare a standard dumbbell-shaped specimen and stretch it at a specified speed on a universal tensile testing machine until it breaks. Record the maximum tensile force and the elongation at break, and calculate the tensile strength and elongation at break, respectively.

[0037] 4. Thermal stretching (GB / T 2951.21) The dumbbell-shaped specimen was subjected to a specified load (0.2 MPa) in an oven and held at 200°C for 15 min. The elongation of the marked line was then measured. After the load was removed and the specimen cooled, the permanent deformation rate was measured.

[0038] 5. Oil resistance (GB / T 2951.31) The sample was immersed in IRM902 oil and kept at 100°C for 24 hours before being removed and the rate of change of tensile strength was tested.

[0039] 6. Flame retardant rating (UL-94 vertical burning test) The sample is fixed vertically, and a standard flame is applied twice (10s / time). The afterflame time and whether the dripping material ignites the cotton wool are recorded. The V-0, V-1 or V-2 level is then assessed.

[0040] 7. Smoke density (GB / T 8323 or ASTM E662) The sample is ignited or heated in a smoke density chamber, and the luminous flux attenuation after the light beam passes through the smoke is measured to calculate the maximum specific optical density (Ds max).

[0041] 8. Crosslinking time The total time required for traditional warm water crosslinking (including preheating, crosslinking, and post-treatment) and the actual processing time of electron beam irradiation according to the present invention were recorded respectively.

[0042] The test results are shown in the table below: Test Project Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Degree of crosslinking (%) 88 85 83 86 87 82 65 78 60 71 Limiting Oxygen Index (LOI) (%) 38 40 36 39 38 37 32 34 36 35 Tensile strength (MPa) 12.5 11.8 13.0 12.0 12.8 11.5 8.2 9.8 10.2 9.0 Elongation at break (%) 280 250 300 270 290 260 180 220 240 200 Thermal elongation (%) 12 15 17 13 14 19 45 28 38 38 Oil resistance (strength change rate) -10% -12% -8% -11% -9% -13% -38% -25% -22% -28% Flame retardant rating (UL-94) V-0 V-0 V-0 V-0 V-0 V-0 V-1 V-1 V-1 V-1 Smoke density (Ds max) 85 88 95 87 89 98 150 120 105 125 Crosslinking time 5min 5min 5min 5min 5min 5min 48h 5min 5min 5min Analyzing the data in the table, we can obtain: Performance data show that the technical solution of this invention has overall advantages and good stability. All six embodiments exhibit good and consistent performance in core indicators such as degree of crosslinking, limiting oxygen index, tensile strength, and flame retardancy rating. In particular, due to the introduction of peroxide crosslinking agent (DCP) and the clear dynamic vulcanization mechanism in step (4), the degree of crosslinking in the embodiments is significantly improved (82%~88%), and the thermal elongation and oil resistance are also improved simultaneously, which confirms the effectiveness of the binary synergistic crosslinking mechanism of "chemical pre-crosslinking-physical irradiation crosslinking".

[0043] The synergy of the technical features of this invention was further verified through the experimental design of four comparative examples. The performance degradation of Comparative Example 2 (without supramolecular structure) in terms of flame retardancy and smoke density illustrates the important role of supramolecular network in the fixation and catalysis of flame retardants. Comparative Example 3 (single electron beam irradiation crosslinking) showed a significant difference from the embodiments of this invention in terms of crosslinking degree, thermal elongation and oil resistance. This directly proves that the initial network constructed by dynamic vulcanization in step (4) is indispensable for the final formation of a uniform, stable and oil-resistant topological crosslinking structure. The deficiencies of Comparative Example 4 (substitute matrix) in terms of mechanical properties and oil resistance confirm the importance of the specifically designed bio-based toughening phase and reactive liquid crystal reinforcement phase and their interfacial bonding reaction for constructing a high-performance topological network.

[0044] Furthermore, all embodiments achieved crosslinking processes within minutes, a significant advantage compared to the 48 hours required for conventional warm water crosslinking in Comparative Example 1. This improvement not only enhances production efficiency but also expands the material's application potential in challenging environments. In summary, this technical solution effectively addresses the technical problems raised in the background art through a deep integration of material and process innovation.

[0045] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. 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. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a silane crosslinked low-smoke halogen-free flame-retardant and oil-resistant polyolefin cable material, characterized in that, Includes the following steps: (1) 30-50 parts by weight of castor oil-based polyamide, 20-40 parts by weight of poly(butylene adipate / terephthalate) and 5-10 parts by weight of epoxidized soybean oil are prepolymerized in a reactor at 160-180°C, and then 2-5 parts by weight of itaconic anhydride are added for end-capping to obtain a bio-based polyester amide toughening phase; (2) 10-20 parts by weight of phytic acid and 5-15 parts by weight of melamine are self-assembled in an aqueous phase at 60-80°C to form a supramolecular network; then 50-70 parts by weight of ammonium polyphosphate are dispersed in the network and spray-dried to obtain supramolecular flame retardant gel powder. (3) Disperse 15-25 parts by weight of aramid pulp fiber in a solvent, add 3-8 parts by weight of phosphorus-containing silane coupling agent, and perform surface grafting by ultrasonic-microwave synergistic treatment to obtain a reactive liquid crystal reinforcement phase; (4) The bio-based polyester amide toughening phase obtained in step (1), the supramolecular flame retardant gel powder obtained in step (2), the reactive liquid crystal reinforcing phase obtained in step (3), 20-30 parts by weight of hydrogenated styrene-isoprene-styrene block copolymer, 1-3 parts by weight of dilauryl thiodipropionate and 0.5-2 parts by weight of dicumyl peroxide crosslinking agent are put into a mixer and subjected to dynamic vulcanization and interfacial bonding reaction at 150-170°C under inert gas protection for 15-25 minutes. The alkoxysilane on the surface of the reactive liquid crystal reinforcing phase undergoes a condensation reaction with the carboxyl group at the end of the bio-based polyester amide toughening phase, and the peroxide initiates the crosslinking of the elastomer phase to obtain a pre-crosslinked composite material. (5) The pre-crosslinked composite material obtained in step (4) is granulated by a twin-screw extruder and then extruded onto the conductor by a cable extruder; subsequently, the cable is placed under an electron accelerator and irradiated with an electron beam dose of 5~15Mrad in a nitrogen environment to induce the formation of a topological crosslinking network between polymer chains, thereby obtaining a crosslinked finished cable.

2. The preparation method according to claim 1, characterized in that: The amine value of the castor oil-based polyamide described in step (1) is 40~60 mgKOH / g.

3. The preparation method according to claim 1, characterized in that: The molar ratio of phytic acid to melamine in step (2) is 1:(2~3).

4. The preparation method according to claim 1, characterized in that: The phosphorus-containing silane coupling agent mentioned in step (3) is (dimethoxyphosphoryl)propyltriethoxysilane.

5. The preparation method according to claim 1, characterized in that: In step (4), the hydrogenation rate of the isoprene unit in the hydrogenated styrene-isoprene-styrene block copolymer is greater than 95%.

6. The preparation method according to claim 1, characterized in that: The purity of dilaurate thiodipropionate mentioned in step (4) is not less than 99%.

7. The preparation method according to claim 1, characterized in that: In step (5), the accelerating voltage of electron beam irradiation is 1.5~3.0 MeV.

8. A silane cross-linked low-smoke halogen-free flame-retardant oil-resistant polyolefin cable material, characterized in that: It is prepared by any one of the preparation methods described in claims 1 to 7, and has an interpenetrating-topological composite network structure composed of bio-based polyesteramide, supramolecular flame retardant gel and aramid fiber reinforcing phase.

9. A cable, characterized in that: Its insulation layer and / or sheath layer are made of the silane cross-linked low-smoke halogen-free flame-retardant oil-resistant polyolefin cable material as described in claim 8.

10. The cable according to claim 9, characterized in that: The cable is a hanging cable for ultra-high-rise buildings, a cable for deep-sea exploration equipment, or a liquid-cooled cable for new energy vehicle charging piles.