A corrosion-resistant cable sheath material and a method for producing the same

Abstract

This invention belongs to the field of cable technology, specifically relating to a corrosion-resistant cable sheath material and its preparation method. The sheath material uses ethylene-vinyl acetate copolymer, polyethylene, polyolefin elastomer, and maleic anhydride-grafted polyolefin as the resin matrix, and includes magnesium hydroxide, aluminum hydroxide, zinc borate, silane-treated sebacic acid intercalated calcium aluminum layered double hydroxide, polymeric carbodiimide, single-end epoxy-terminated polydimethylsiloxane, antioxidant, and lubricant. The preparation method includes: melting and mixing the resin matrix, adding flame retardant, zinc borate, silane-treated sebacic acid intercalated calcium aluminum layered double hydroxide, antioxidant, and lubricant, then sequentially adding single-end epoxy-terminated polydimethylsiloxane and polymeric carbodiimide, followed by extrusion granulation. The sheath material obtained by this invention possesses low-smoke, halogen-free flame retardancy, resistance to salt spray, acid and alkali corrosion, damp heat stability, and processing stability, making it suitable for cable sheaths.

Description

Technical Field

[0001] This invention relates to the field of cable technology, and specifically to a corrosion-resistant cable sheath material and its preparation method. Background Technology

[0002] Wires and cables are widely used in power transmission, rail transportation, marine engineering, petrochemicals, wind power generation, photovoltaic power generation, mining equipment, communication facilities, and industrial control. As the outermost protective structure of a cable, the cable sheath typically needs to perform multiple functions, including mechanical protection, environmental protection, flame retardant protection, and long-term service stability. In actual use, cable sheaths may be exposed to environments such as humidity, salt spray, acids and alkalis, oil, ultraviolet radiation, ozone, thermo-oxidative aging, mechanical bending, and friction and wear. Especially in applications such as coastal areas, offshore platforms, ships, salt lakes, chemical plants, tunnels, and underground utility tunnels, the corrosion resistance, damp heat resistance, and long-term mechanical stability of the sheath material have a significant impact on the cable's service life.

[0003] Current cable sheathing materials mainly include polyvinyl chloride (PVC), polyethylene, cross-linked polyolefins, low-smoke halogen-free flame-retardant polyolefins, chlorinated polyethylene, neoprene rubber, ethylene propylene rubber, thermoplastic elastomers, and polyurethane. Among these, PVC sheathing materials have advantages such as lower cost, better processing performance, and easier flame retardancy; however, they may produce more smoke and halogen-containing acidic gases during combustion, making it difficult to meet the requirements of low smoke, low corrosion, and environmental protection in some applications. Low-smoke halogen-free flame-retardant polyolefin sheathing materials, due to their halogen-free nature, lower combustion smoke, and better environmental adaptability, are increasingly used in construction, rail transportation, wind power, photovoltaics, marine engineering, and applications with high public safety requirements.

[0004] Low-smoke halogen-free flame-retardant polyolefin sheathing materials typically use ethylene-vinyl acetate copolymer, polyethylene, polyolefin elastomers, etc., as the matrix, and add components such as magnesium hydroxide, aluminum hydroxide, zinc borate, compatibilizers, antioxidants, and lubricants to achieve a comprehensive balance of flame retardancy, low smoke, flexibility, and processing performance. However, since inorganic flame retardants such as magnesium hydroxide and aluminum hydroxide usually require high filler content to meet flame retardancy requirements, high filler systems can easily lead to increased melt viscosity, increased processing torque, and decreased extrusion surface quality. They may also affect the material's tensile strength, elongation at break, low-temperature resistance, and flexural strength.

[0005] Furthermore, the interfacial compatibility between inorganic flame retardants and the polyolefin matrix is ​​also a crucial factor affecting the long-term performance of the sheathing material. Polyolefin resins typically have low polarity, while inorganic fillers such as magnesium hydroxide and aluminum hydroxide have highly polar surfaces. If interfacial bonding is insufficient, moisture, salt, and acid / alkali media can easily penetrate along the interfacial defects between the filler and resin, leading to problems such as interfacial debonding, increased water absorption, decreased mechanical properties, surface whitening, cracking, or accelerated aging. These problems are even more pronounced in salt spray, humid heat, acid / alkali, or chemically corrosive environments.

[0006] To improve the overall performance of low-smoke halogen-free polyolefin sheathing materials, existing technologies typically employ methods such as surface treatment of inorganic fillers with coupling agents, addition of maleic anhydride-grafted polyolefins as compatibilizers, compounding of flame-retardant synergists, introduction of elastomers to improve flexibility, addition of antioxidants or light stabilizers to enhance aging resistance, and addition of lubricants or silicone processing aids to improve extrusion processability. These methods can improve the processing performance, mechanical properties, or flame-retardant properties of the sheathing material to some extent. However, in complex corrosive environments, the material may still exhibit insufficient resistance to salt spray, acids and alkalis, damp heat, and long-term performance retention.

[0007] Especially for cable sheath materials that simultaneously require low-smoke halogen-free flame retardancy, corrosion resistance, damp heat resistance, flexibility, and extrusion stability, there are often interrelationships among these properties. For example, increasing the amount of inorganic flame retardant is beneficial for flame retardancy, but may reduce processing fluidity and mechanical properties; increasing the amount of elastomer is beneficial for flexibility, but may affect strength, heat deformation resistance, or flame retardancy efficiency; enhancing interfacial compatibility is beneficial for mechanical properties, but interfacial aging may still occur in damp heat or acid / alkali environments; adding processing aids is beneficial for reducing torque and improving surface finish, but may affect subsequent printing, sheath surface adhesion, or long-term migration stability.

[0008] Therefore, there is still room for improvement in existing corrosion-resistant cable sheath materials. In particular, it is necessary to develop a cable sheath material and its preparation method that can take into account flame retardancy, low smoke, corrosion resistance, damp heat resistance, mechanical retention and processing stability, so as to meet the needs of long-term cable use in complex service environments. Summary of the Invention

[0009] To address the shortcomings of existing corrosion-resistant cable sheath materials in maintaining corrosion resistance, mechanical properties, and processing stability under environments such as salt spray, acid and alkali, and humid heat, this invention provides a corrosion-resistant cable sheath material and its preparation method.

[0010] A corrosion-resistant cable sheath material. The corrosion-resistant cable sheath material, based on 100 parts by weight of a resin matrix, comprises the following raw materials: The composition includes 40-55 parts of ethylene-vinyl acetate copolymer, 20-35 parts of polyethylene, 10-25 parts of polyolefin elastomer, 5-10 parts of maleic anhydride-grafted polyolefin, 80-110 parts of magnesium hydroxide, 35-65 parts of aluminum hydroxide, 3-8 parts of zinc borate, 3-8 parts of silane-treated sebacic acid intercalated calcium aluminum layered double hydroxide, 0.4-1.2 parts of polymeric carbodiimide, 0.6-2.0 parts of single-end epoxy-terminated polydimethylsiloxane, 0.4-1.0 parts of antioxidant, and 0.5-3 parts of lubricant.

[0011] The resin matrix is ​​composed of ethylene-vinyl acetate copolymer, polyethylene, polyolefin elastomer and maleic anhydride-grafted polyolefin.

[0012] In some embodiments, the ethylene-vinyl acetate copolymer is a commonly used EVA resin in the cable material industry, and its vinyl acetate content can be 12-40%, preferably 18-28%. The ethylene-vinyl acetate copolymer can be a single grade, or it can be a combination of EVAs with different vinyl acetate contents or different melt flow rates.

[0013] In some embodiments, the polyethylene is one or more of linear low-density polyethylene, metallocene linear low-density polyethylene, low-density polyethylene, and high-density polyethylene. Preferably, the polyethylene is linear low-density polyethylene, metallocene linear low-density polyethylene, or a combination of both.

[0014] In some embodiments, the polyolefin elastomer is one or more of ethylene-octene copolymer elastomer, ethylene-butene copolymer elastomer, and olefin block copolymer.

[0015] In some embodiments, the maleic anhydride-grafted polyolefin is one or more selected from maleic anhydride-grafted polyethylene, maleic anhydride-grafted ethylene-octene copolymer, and maleic anhydride-grafted ethylene-vinyl acetate copolymer. The maleic anhydride grafting rate of the maleic anhydride-grafted polyolefin can be 0.3-2.0%, preferably 0.5-1.5%.

[0016] In some embodiments, the magnesium hydroxide and aluminum hydroxide are flame retardants for cable materials. The magnesium hydroxide and aluminum hydroxide can be untreated products or products surface-treated with silane coupling agents, fatty acids, fatty acid salts, titanate coupling agents, or aluminate coupling agents. The particle size of the magnesium hydroxide and aluminum hydroxide can be selected according to the extrusion processing requirements of the cable sheath, for example, D50 of 0.5~10 μm.

[0017] In some embodiments, the zinc borate is an inorganic borate flame retardant synergist, and commonly used zinc borate products in the cable material or plastic modification fields can be selected.

[0018] In some embodiments, the antioxidant includes one or more of hindered phenolic antioxidants and phosphite antioxidants. The hindered phenolic antioxidant may be antioxidant 1010, antioxidant 1076, antioxidant 300, or a combination thereof; the phosphite antioxidant may be antioxidant 168, antioxidant 626, or a combination thereof. Preferably, the antioxidant includes antioxidant 1010 and antioxidant 168.

[0019] In some embodiments, the lubricant comprises one or more of polyethylene wax, ethylene bis-stearamide, stearic acid, calcium stearate, zinc stearate, and silicone masterbatch. Preferably, the lubricant comprises one or more of polyethylene wax, ethylene bis-stearamide, and calcium stearate.

[0020] In some embodiments, the corrosion-resistant cable sheath material may further include 0.5 to 3 parts by weight of carbon black, ultraviolet absorber, or light stabilizer. The carbon black, ultraviolet absorber, or light stabilizer is used to meet the weather resistance requirements of outdoor cable sheaths, and the types of materials used can be those commonly found in the art.

[0021] In some embodiments, the silane in the silane-treated sebacate intercalated calcium aluminum layered double hydroxide is selected from one or more of vinyltriethoxysilane, vinyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane.

[0022] In some embodiments, the silane-treated sebacic acid intercalated calcium-aluminum layered double hydroxide is prepared by the following method: (1) The calcium salt, aluminum salt and alkaline solution were subjected to a co-precipitation reaction to obtain a calcium-aluminum layered double hydroxide precursor; (2) The calcium-aluminum layered double hydroxide precursor is subjected to an intercalation reaction with sebacic acid salt solution to obtain sebacic acid intercalated calcium-aluminum layered double hydroxide; (3) The sebacic acid anion intercalated calcium aluminum layered double hydroxide was surface treated with a silane coupling agent to obtain a silane-treated sebacic acid anion intercalated calcium aluminum layered double hydroxide.

[0023] In step (1), the calcium salt can be one or more of calcium nitrate, calcium chloride, calcium acetate and calcium sulfate; the aluminum salt can be one or more of aluminum nitrate, aluminum chloride, aluminum sulfate and aluminum isopropoxide; the alkaline solution can be sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, ammonia or a combination thereof.

[0024] In step (1), the molar ratio of calcium in the calcium salt to aluminum in the aluminum salt is 1.5~3.0:1, preferably 1.8~2.5:1. The pH of the coprecipitation reaction is 9~13, preferably 10~12. The temperature of the coprecipitation reaction can be 20~40℃. After the coprecipitation reaction is completed, an aging treatment can be performed; the temperature of the aging treatment can be 50~90℃, and the time can be 6~24 h. After the aging treatment, the obtained solid can be subjected to solid-liquid separation, washing, and drying to obtain a calcium-aluminum layered double hydroxide precursor.

[0025] In step (2), the sebacic acid salt solution can be prepared by reacting sebacic acid with a base. The base can be sodium hydroxide, potassium hydroxide, sodium carbonate, or ammonia. The molar ratio of sebacic acid to base can be 1:1.8~2.5, preferably 1:2.0~2.2. The sebacic acid salt is preferably sodium sebate or potassium sebate.

[0026] In step (2), the molar ratio of sebacic acid ion to aluminum in the calcium-aluminum layered double hydroxide precursor is 0.2~1.5:1, preferably 0.4~1.2:1. The pH of the intercalation reaction can be 8.5~11.5, the temperature can be 60~100℃, and the time can be 6~24 h. After the intercalation reaction is completed, the obtained solid can be subjected to solid-liquid separation, washing, and drying to obtain sebacic acid ion-intercalated calcium-aluminum layered double hydroxide.

[0027] In step (3), the silane coupling agent is selected from one or more of vinyltriethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-glycidyl etheroxypropyltrimethoxysilane. The amount of the silane coupling agent is 0.5-5% of the mass of the sebacic acid intercalated calcium aluminum layered double hydroxide, preferably 1-3%.

[0028] In step (3), the surface treatment can be carried out in an alcohol-water mixture. The alcohol in the alcohol-water mixture can be methanol, ethanol, isopropanol, or a combination thereof, preferably ethanol. The pH of the surface treatment can be 3.5~6.0, the temperature can be 30~80℃, and the time can be 1~6 h. After the surface treatment, solid-liquid separation, washing, drying, and pulverization can be performed. The drying temperature can be 60~110℃.

[0029] In some embodiments, the polymeric carbodiimide contains two or more carbodiimide groups. The polymeric carbodiimide can be a liquid, semi-solid, or solid product, or it can be used as a masterbatch prepared from ethylene-vinyl acetate copolymer, polyethylene, polyolefin elastomer, or maleic anhydride-grafted polyolefin as a carrier. The polymeric carbodiimide can be formulated using commercially available polymeric carbodiimide hydrolysis stabilizers.

[0030] In some embodiments, the single-end epoxy-terminated polydimethylsiloxane contains an epoxy group at one end and is alkyl-terminated or trimethylsiloxy-terminated at the other end. The epoxy group can be glycidyl ether, epoxycyclohexyl, or an epoxy group introduced by glycidyl methacrylate. The single-end epoxy-terminated polydimethylsiloxane can be obtained directly from commercially available single-end epoxy silicone oil, or it can be prepared by the following methods: A single-ended hydrogen-containing polydimethylsiloxane, an alkenyl epoxy compound, and a hydrosilylation catalyst were mixed and subjected to a hydrosilylation reaction. After the reaction was completed, unreacted material was removed to obtain a single-ended epoxy-terminated polydimethylsiloxane.

[0031] In the above method for preparing single-end epoxy-terminated polydimethylsiloxane, the single-end hydrogen-containing polydimethylsiloxane refers to a polydimethylsiloxane with a Si-H bond at one end of its molecular chain and alkyl-terminated or trimethylsiloxy-terminated at the other end. The number average molecular weight of the single-end hydrogen-containing polydimethylsiloxane can be 1000~5000, preferably 1500~3500.

[0032] In the above method for preparing single-end epoxy-terminated polydimethylsiloxane, the alkenyl epoxy compound is one or more of allyl glycidyl ether, vinyl cyclohexene oxide and glycidyl methacrylate, preferably allyl glycidyl ether.

[0033] In the above method for preparing single-ended epoxy-terminated polydimethylsiloxane, the molar ratio of carbon-carbon double bonds in the alkenyl epoxy compound to Si-H bonds in the single-ended hydrogen-containing polydimethylsiloxane is 1.02~1.50:1, preferably 1.05~1.25:1.

[0034] In the above method for preparing single-end epoxy-terminated polydimethylsiloxane, the hydrosilylation catalyst is a platinum-based catalyst. The platinum-based catalyst can be chloroplatinic acid, Karstedt catalyst, platinum-vinylsiloxane complex, or a combination thereof. The amount of the platinum-based catalyst, based on elemental platinum, can be 1 to 100 ppm of the total mass of the reactants, preferably 5 to 50 ppm.

[0035] In the above method for preparing single-end epoxy-terminated polydimethylsiloxane, the hydrosilylation reaction can be carried out under an inert gas atmosphere. The inert gas can be nitrogen or argon. The hydrosilylation reaction temperature is 40–110 °C, and the time is 1–8 h. After the reaction, unreacted substances and low-boiling substances can be removed by depressurization. The depressurization temperature can be 80–150 °C, and the pressure can be -0.08 to -0.10 MPa.

[0036] In another aspect of the present invention, a method for preparing a corrosion-resistant cable sheath material is provided, comprising the following steps: Ethylene-vinyl acetate copolymer, polyethylene, polyolefin elastomer and maleic anhydride-grafted polyolefin are melt-mixed to obtain resin melt; Magnesium hydroxide, aluminum hydroxide, zinc borate, silane-treated sebacic acid intercalated calcium aluminum layered double hydroxide, antioxidant, and lubricant are added to the resin melt and mixed. Add single-ended epoxy-terminated polydimethylsiloxane and mix; Add polymeric carbodiimide and mix; The corrosion-resistant cable sheath material is obtained by extrusion granulation.

[0037] In some embodiments, the magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-treated sebacic acid-intercalated calcium-aluminum layered double hydroxide are dried before addition. The drying temperature can be 90-105°C, and the time can be 2-3 hours. After drying, the water content of the magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-treated sebacic acid-intercalated calcium-aluminum layered double hydroxide is preferably not higher than 1.0%.

[0038] In some embodiments, the temperature of the melt mixing, mixing and extrusion granulation is 130~170°C.

[0039] In some embodiments, the resin melt is prepared at a temperature of 145-160°C. Ethylene-vinyl acetate copolymer, polyethylene, polyolefin elastomer, and maleic anhydride-grafted polyolefin are added to a Banbury mixer, twin-screw extruder, or continuous mixer and melt-mixed at the above temperature for 2-5 minutes to obtain the resin melt.

[0040] In some embodiments, magnesium hydroxide, aluminum hydroxide, zinc borate, silane-treated sebacic acid intercalated calcium aluminum layered double hydroxide, antioxidant, and lubricant are added to the resin melt, and then the mixture is mixed at 150-165°C for 5-15 minutes.

[0041] In some embodiments, after adding single-end epoxy-terminated polydimethylsiloxane, mixing continues for 1-5 minutes; subsequently, polymeric carbodiimide is added, and mixing continues for 1-3 minutes. The polymeric carbodiimide is preferably added in the later stages of mixing or in the later stages of extrusion.

[0042] In some embodiments, the extrusion granulation is performed using a twin-screw extruder. The temperature of each zone of the twin-screw extruder can be 130~170°C, and the screw speed can be 150~350 rpm. After extrusion, the material is cooled, pelletized, and dried to obtain corrosion-resistant cable sheathing particles.

[0043] In some embodiments, the corrosion-resistant cable sheath material can be coated onto the outside of the cable insulation core, cable core, or shielding structure using a sheath extruder to form a cable sheath layer. The sheath extrusion temperature can be controlled between 140 and 180°C, depending on the equipment and sheath thickness.

[0044] All of the above-mentioned raw materials can be commercially available industrial products in this field, or prepared according to the methods disclosed in this specification. Among them, the silane-surface-treated sebacic acid intercalated calcium aluminum layered double hydroxide and the single-end epoxy-terminated polydimethylsiloxane can be prepared in advance and then added to the sheathing composition as raw materials; the polymeric carbodiimide can be a commercially available hydrolytic stabilizer, or it can be added after being prepared as a masterbatch.

[0045] The corrosion-resistant cable sheath material provided by this invention uses ethylene-vinyl acetate copolymer, polyethylene, polyolefin elastomer, and maleic anhydride-grafted polyolefin as the resin matrix, which can balance the flexibility, mechanical strength, filler containment, and interfacial bonding of the sheath material. Magnesium hydroxide, aluminum hydroxide, and zinc borate are used as flame-retardant and synergistic systems, which can meet the basic requirements of cable sheath materials for flame retardancy, low smoke, and processing stability. Furthermore, the introduction of silane-surface-treated sebacic acid intercalated calcium aluminum layered double hydroxide, polymeric carbodiimide, and single-end epoxy-terminated polydimethylsiloxane gives the sheath material better interfacial stability, corrosion resistance retention, and extrusion processing stability under corrosive environments such as salt spray, acid and alkali, and humid heat. Therefore, it is suitable for cable sheaths that require corrosion resistance, flame retardancy, and long-term service stability.

[0046] The core of this invention lies in introducing three specific components—a silane-surface-treated sebacic acid-intercalated calcium-aluminum layered double hydroxide, a polymeric carbodiimide, and a single-end epoxy-terminated polydimethylsiloxane—into a conventional low-smoke halogen-free polyolefin sheathing material. These three components are not simply added in parallel, but rather form a ternary synergistic system suitable for corrosion-resistant cable sheathing materials, based on "corrosive medium barrier, hydrolytic stabilization in wet conditions, and interfacial reaction regulation."

[0047] A silane-treated sebacic acid-intercalated calcium-aluminum layered double hydroxide is presented. The calcium-aluminum layered double hydroxide serves as the layered inorganic matrix, with sebacic acid as the intercalating anion, and the surface is treated with a silane coupling agent. The layered double hydroxide possesses a layered structure and anion exchange properties. Sebacic acid intercalation improves the component's organic compatibility and corrosion resistance. Silane surface treatment facilitates its dispersion in resin matrices composed of ethylene-vinyl acetate copolymers, polyethylene, and polyolefin elastomers. Upon addition, this component improves the inorganic filler interface in highly packed magnesium hydroxide and aluminum hydroxide systems, reducing the migration channels of moisture, salt, and acid / alkali media along the filler interface, thus enhancing the stability of the sheathing material under salt spray, acid / alkali, and humid heat conditions.

[0048] When cable sheathing materials are used for extended periods in humid, hot, acidic, alkaline, or salt spray environments, ethylene-vinyl acetate copolymers, maleic anhydride-grafted polyolefins, and some polar additives are susceptible to hydrolysis or interfacial degradation due to moisture and acidic substances. Polymerized carbodiimide, containing multiple carbodiimide groups, can react with carboxylic acids generated during hydrolysis in the system, thereby inhibiting further accumulation of acidic products. When combined with silane-surface-treated sebacic acid-intercalated calcium-aluminum layered double hydroxides, the former focuses on hydrolysis stabilization and acidic product control, while the latter focuses on corrosive media barrier and interfacial improvement. This creates a synergistic effect of "front-end barrier – back-end stabilization," improving the sheathing material in multiple stages, including corrosive media ingress, interfacial degradation, and hydrolytic aging.

[0049] However, the co-addition of silane-treated sebacic acid-intercalated calcium-aluminum layered double hydroxides and polymeric carbodiimide led to unexpected problems in the system. Specifically, the polymeric carbodiimide has the ability to react with carboxylic acid groups, while sebacic acid-intercalated calcium-aluminum layered double hydroxides contain sebacic acid-related sites on their surface and between layers. The resin system also contains maleic anhydride-grafted polyolefins and their potential carboxyl or anhydride hydrolysis sites. During melt mixing or subsequent use, the polymeric carbodiimide may undergo localized enrichment or excessive reaction near the aforementioned polar interfaces, leading to processing stability issues such as localized melt thickening, microgelation, increased die head pressure, die slag buildup, or rough sheath surface.

[0050] Single-ended epoxy-terminated polydimethylsiloxanes, containing an epoxy group at one end and alkyl or trimethylsiloxy-terminated at the other, possess both reactivity and are less prone to forming multifunctional continuous crosslinked networks. In the system of this invention, the single-ended epoxy-terminated polydimethylsiloxane can undergo limited reactions with a small amount of carboxylic acids, anhydrides, or active sites on the surface of inorganic fillers through its single-ended epoxy group, and form a flexible, hydrophobic interface layer between the inorganic filler and the resin matrix through the polydimethylsiloxane segments. This reduces the risk of overreaction of polymeric carbodiimide near local polar sites, mitigates melt thickening and microgelation tendency, and improves filler dispersion, interfacial slip, and extrusion surface condition.

[0051] The three core components work together to create a ternary synergistic effect: silane-treated sebacic acid intercalated calcium-aluminum layered double hydroxide improves the barrier against corrosive media and the interface with inorganic fillers; polymeric carbodiimide inhibits hydrolytic degradation under humid or acidic conditions; and single-end epoxy-terminated polydimethylsiloxane regulates localized interfacial reactions after the introduction of the first two components and improves melt processing stability. The combination of these three components allows the sheathing material to maintain the basic processability and flame-retardant system of low-smoke halogen-free flame-retardant polyolefin sheathing materials, while also improving long-term stability under salt spray, acid / alkali, and humid conditions. It also reduces the risk of processing defects caused by the coexistence of reactive additives and intercalated corrosion-resistant components, thus obtaining a cable sheathing material that balances corrosion resistance, mechanical retention, and processing stability. Attached Figure Description

[0052] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some schematic diagrams of certain embodiments of the present invention, and therefore should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 The infrared spectrum of the silane-treated sebacic acid intercalated calcium aluminum layered double hydroxide prepared in Example 1 of this invention; Figure 2 The infrared spectrum of the single-end epoxy-terminated polydimethylsiloxane prepared in Example 1 of this invention is shown. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Of course, the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0055] Unless otherwise stated, the raw materials used in the following examples and comparative examples are all commercially available or prepared according to the methods disclosed in this specification; each raw material is a commonly used industrial product or reagent-grade product in the fields of cable materials, plastic modification or chemical synthesis, and the water is deionized water.

[0056] The ethylene-vinyl acetate copolymer is EVA resin for cable materials; the polyethylene is selected from one or more of linear low-density polyethylene, metallocene linear low-density polyethylene, low-density polyethylene, and high-density polyethylene; the polyolefin elastomer is selected from one or more of ethylene-octene copolymer elastomer, ethylene-butene copolymer elastomer, and olefin block copolymer; the maleic anhydride-grafted polyolefin is selected from one or more of maleic anhydride-grafted polyethylene, maleic anhydride-grafted ethylene-octene copolymer, and maleic anhydride-grafted ethylene-vinyl acetate copolymer.

[0057] The magnesium hydroxide, aluminum hydroxide, and zinc borate mentioned are inorganic flame retardants or flame retardant synergists for cable sheathing materials. They can be untreated products or products surface-treated with silane coupling agents, fatty acids, fatty acid salts, titanate coupling agents, or aluminate coupling agents. Unless otherwise specified in the examples and comparative examples, magnesium hydroxide and aluminum hydroxide are surface-treated products for cable materials.

[0058] The antioxidant is a hindered phenolic antioxidant, a phosphite antioxidant, or a combination of both; the lubricant is one or more of polyethylene wax, ethylene bis-stearamide, stearic acid, calcium stearate, zinc stearate, and silicone masterbatch. The carbon black used in the examples is carbon black for cable sheathing materials, used to meet the coloring and weather resistance requirements of the sheathing material, and its addition amount is not included in the essential component range defined in claim 1.

[0059] The polymeric carbodiimide is a hydrolytic stabilizer containing two or more carbodiimide groups. It can be a commercially available polymeric carbodiimide product, or it can be prepared as a masterbatch using ethylene-vinyl acetate copolymer, polyethylene, or polyolefin elastomer as a carrier. Unless otherwise specified in the examples and comparative examples, the polymeric carbodiimide is added directly.

[0060] The silane-treated sebacic acid anion-intercalated calcium-aluminum layered double hydroxide can be prepared according to the method disclosed in this specification, or by using similar materials that meet the requirements of this specification. The calcium salt used in its preparation can be one or more of calcium nitrate, calcium chloride, calcium acetate, and calcium sulfate; the aluminum salt can be one or more of aluminum nitrate, aluminum chloride, aluminum sulfate, and aluminum isopropoxide; the alkaline solution can be sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, ammonia, or a combination thereof; the sebacic acid salt solution can be prepared by reacting sebacic acid with sodium hydroxide, potassium hydroxide, sodium carbonate, or ammonia.

[0061] The silane coupling agent is selected from one or more of vinyltriethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane. Unless otherwise specified in the examples, γ-methacryloxypropyltrimethoxysilane is used as the silane coupling agent.

[0062] The single-ended epoxy-terminated polydimethylsiloxane can be prepared according to the method disclosed in this specification, or commercially available single-ended epoxy silicone oil that meets the requirements of this specification. The single-ended hydrogen-containing polydimethylsiloxane used in its preparation is a polydimethylsiloxane containing a Si-H bond at one end and alkyl-terminated or trimethylsiloxy-terminated at the other end; the alkenyl epoxy compound is selected from one or more of allyl glycidyl ether, vinylcyclohexene oxide, and glycidyl methacrylate; the hydrosilylation catalyst is a platinum-based catalyst. Unless otherwise specified in the examples, the alkenyl epoxy compound is allyl glycidyl ether, and the hydrosilylation catalyst is a Karstedt catalyst.

[0063] The silane-treated calcium-aluminum layered double hydroxide used in the comparative examples refers to a material obtained by directly surface-treating the calcium-aluminum layered double hydroxide precursor with a silane coupling agent without undergoing sebate intercalation treatment; the double-ended epoxy-terminated polydimethylsiloxane used in the comparative examples refers to a polydimethylsiloxane containing epoxy groups at both ends; the ethylene-vinyl acetate copolymer used in the comparative examples to supplement the amount of polymeric carbodiimide is the same grade as the ethylene-vinyl acetate copolymer used in the corresponding examples.

[0064] A method for preparing a corrosion-resistant cable sheath material includes the following steps: (1) Preparation of silane-treated sebacic acid intercalated calcium-aluminum layered double hydroxide: Calcium and aluminum salts are dissolved in water, and an alkaline solution is added to adjust the pH of the system to 9-13, causing a co-precipitation reaction between the calcium and aluminum salts. The molar ratio of calcium in the calcium salt to aluminum in the aluminum salt is 1.5-3.0:1. After the reaction, solid-liquid separation, washing, and drying are performed to obtain a calcium-aluminum layered double hydroxide precursor. Sebacic acid is reacted with an alkaline to prepare a sebacic acid salt solution. The calcium-aluminum layered double hydroxide precursor is then subjected to an intercalation reaction with the sebacic acid salt solution. The molar ratio of sebacic acid to aluminum in the calcium-aluminum layered double hydroxide precursor is 0.2-1.5:1. The intercalation reaction temperature is 60-100℃, and the time is 6-24h. After the reaction, solid-liquid separation, washing, and drying are performed to obtain a calcium-aluminum layered double hydroxide precursor. The product is dried to obtain sebacic acid ion-intercalated calcium-aluminum layered double hydroxide. The sebacic acid ion-intercalated calcium-aluminum layered double hydroxide is then surface-treated with a silane coupling agent selected from one or more of vinyltriethoxysilane, vinyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and γ-glycidyloxypropyltrimethoxysilane. The amount of silane coupling agent used is 0.5-5% of the mass of the sebacic acid ion-intercalated calcium-aluminum layered double hydroxide. After surface treatment, the product undergoes solid-liquid separation, washing, drying, and pulverization to obtain a silane-surface-treated sebacic acid ion-intercalated calcium-aluminum layered double hydroxide. (2) Preparation of single-end epoxy-capped polydimethylsiloxane: A single-end hydrogen-containing polydimethylsiloxane, an alkenyl epoxy compound and a hydrosilylation catalyst are mixed and subjected to a hydrosilylation reaction. The alkenyl epoxy compound is one or more of allyl glycidyl ether, vinyl cyclohexene oxide and glycidyl methacrylate. The number average molecular weight of the single-end hydrogen-containing polydimethylsiloxane is 1000~5000. The hydrosilylation catalyst is a platinum catalyst. The molar ratio of carbon-carbon double bond in the alkenyl epoxy compound to Si-H bond in the single-end hydrogen-containing polydimethylsiloxane is 1.02~1.50:1. The hydrosilylation reaction temperature is 40~110℃ and the time is 1~8h. After the reaction is completed, the unreacted material is removed to obtain the single-end epoxy-capped polydimethylsiloxane. (3) Weigh the following raw materials according to the proportion based on 100 parts by weight of resin matrix: 40-55 parts of ethylene-vinyl acetate copolymer, 20-35 parts of polyethylene, 10-25 parts of polyolefin elastomer, 5-10 parts of maleic anhydride grafted polyolefin, 80-110 parts of magnesium hydroxide, 35-65 parts of aluminum hydroxide, 3-8 parts of zinc borate, 3-8 parts of silane-treated sebacic acid intercalated calcium aluminum layered double hydroxide obtained in step (1), 0.4-1.2 parts of polymeric carbodiimide, 0.6-2.0 parts of single-end epoxy-terminated polydimethylsiloxane obtained in step (2), 0.4-1.0 parts of antioxidant, and 0.5-3 parts of lubricant. The resin matrix is ​​composed of ethylene-vinyl acetate copolymer, polyethylene, polyolefin elastomer and maleic anhydride-grafted polyolefin; the polyethylene is one or more of linear low-density polyethylene, metallocene linear low-density polyethylene, low-density polyethylene and high-density polyethylene; the polyolefin elastomer is one or more of ethylene-octene copolymer elastomer, ethylene-butene copolymer elastomer and olefin block copolymer; the maleic anhydride-grafted polyolefin is one or more of maleic anhydride-grafted polyethylene, maleic anhydride-grafted ethylene-octene copolymer and maleic anhydride-grafted ethylene-vinyl acetate copolymer; the polymeric carbodiimide contains two or more carbodiimide groups; magnesium hydroxide, aluminum hydroxide, zinc borate and the silane surface-treated sebacic acid intercalated calcium aluminum layered double hydroxide prepared in step (1) are dried at 90~105℃ for 2~3h; (4) Add ethylene-vinyl acetate copolymer, polyethylene, polyolefin elastomer and maleic anhydride grafted polyolefin into a mixer, twin-screw extruder or continuous mixing equipment, and melt mix at 130~170℃ to obtain resin melt; add magnesium hydroxide, aluminum hydroxide, zinc borate and silane-surface-treated sebacic acid intercalated calcium aluminum layered double hydroxide after drying treatment in step (3) to the resin melt, and add antioxidant and lubricant, and mix at 130~170℃; then add the single-end epoxy-terminated polydimethylsiloxane obtained in step (2), and continue mixing at 130~170℃; then add polymeric carbodiimide, and continue mixing at 130~170℃; finally extrude and granulate at 130~170℃, and after cooling, pelletizing and drying, obtain the corrosion-resistant cable sheath material.

[0065] In the above preparation method, steps (1) and (2) can be completed in advance before preparing the corrosion-resistant cable sheath material. The resulting silane-surface-treated sebacic acid intercalated calcium aluminum layered double hydroxide and single-end epoxy-terminated polydimethylsiloxane are used as raw materials for steps (3) and (4); or commercially available or self-made raw materials that meet the above-mentioned limitations can be used directly for steps (3) and (4).

[0066] The present invention will be further described below through specific embodiments. Example

[0067] A method for preparing a corrosion-resistant cable sheath material includes the following steps: (1) Preparation of silane-treated sebacic acid anion-intercalated calcium-aluminum layered double hydroxides: 94.46 g of calcium nitrate tetrahydrate and 75.03 g of aluminum nitrate nonahydrate were added to 800 mL of deionized water and stirred to dissolve, yielding a calcium-aluminum salt solution. Under nitrogen protection, a 2.0 mol / L sodium hydroxide aqueous solution was added dropwise to the calcium-aluminum salt solution, maintaining the pH of the system at 11.0. The temperature was controlled at 25 °C during the addition process, and stirring was continued for 1 h after the addition was completed. Subsequently, the temperature was raised to 70 °C and aged for 12 h. After the reaction was completed, the mixture was filtered, and the filter cake was washed with deionized water until the pH of the filtrate was 7.0–8.0. The filtrate was then dried at 80 °C for 12 h to obtain a calcium-aluminum layered double hydroxide precursor.

[0068] 48.54 g of sebacic acid and 19.20 g of sodium hydroxide were added to 600 mL of deionized water and heated and stirred to dissolve, yielding a sodium sebacic acid solution. The above-mentioned calcium-aluminum layered double hydroxide precursor was added to the sodium sebacic acid solution, the pH of the system was adjusted to 10.0, and the reaction was stirred at 80 °C for 12 h. After the reaction was completed, the mixture was filtered, the filter cake was washed with deionized water, and dried at 80 °C for 12 h to obtain sebacic acid anion-intercalated calcium-aluminum layered double hydroxide.

[0069] Take 80.00 g of sebacic acid ion-intercalated calcium-aluminum layered double hydroxide and add it to an alcohol-water mixture consisting of 760 mL of anhydrous ethanol and 40 mL of deionized water. Stir and disperse. Adjust the pH of the system to 4.5 with glacial acetic acid and add 1.60 g of γ-methacryloxypropyltrimethoxysilane. React at 60 °C for 3 h. After the reaction is complete, filter and wash the filter cake with ethanol and deionized water in sequence. Dry at 90 °C for 8 h and pulverize to obtain silane-treated sebacic acid ion-intercalated calcium-aluminum layered double hydroxide.

[0070] (2) Preparation of single-end epoxy-terminated polydimethylsiloxane: In a reaction flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube, 200.00 g of single-ended hydrogen-containing polydimethylsiloxane with a number average molecular weight of 2000, 12.56 g of allyl glycidyl ether, and 250 mL of anhydrous toluene were added. After purging with nitrogen for 20 min, 0.213 g of Karstedt catalyst solution with a platinum content of 2 wt% was added. The mixture was heated to 75 °C under nitrogen protection and reacted for 4 h. After the reaction was completed, toluene and unreacted substances were removed under reduced pressure at 120 °C and -0.09 MPa for 1 h to obtain single-ended epoxy-terminated polydimethylsiloxane.

[0071] (3) Preparation of corrosion-resistant cable sheath material: Weigh out 480g of ethylene-vinyl acetate copolymer, 240g of linear low-density polyethylene, 180g of ethylene-octene copolymer elastomer, 100g of maleic anhydride grafted polyethylene, 950g of magnesium hydroxide, 450g of aluminum hydroxide, 50g of zinc borate, 50g of silane-treated sebacate intercalated calcium aluminum layered double hydroxide obtained in step (1), 8g of polymeric carbodiimide, 12g of single-end epoxy-terminated polydimethylsiloxane obtained in step (2), 3g of antioxidant 1010, 3g of antioxidant 168, 6g of polyethylene wax, 5g of calcium stearate, and 15g of carbon black.

[0072] Magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-treated sebacate intercalated calcium-aluminum layered double hydroxides were placed in an oven and dried at 100°C for 2.5 h.

[0073] Ethylene-vinyl acetate copolymer, linear low-density polyethylene, ethylene-octene copolymer elastomer, and maleic anhydride-grafted polyethylene were added to a mixer and melt-mixed at 155°C for 4 min to obtain a resin melt. Dried magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-surface-treated sebacic acid intercalated calcium aluminum layered double hydroxides were added to the resin melt, along with antioxidant 1010, antioxidant 168, polyethylene wax, calcium stearate, and carbon black. The mixture was then mixed at 160°C for 10 min. Subsequently, single-end epoxy-terminated polydimethylsiloxane was added, and the mixture was further mixed at 160°C for 3 min. Finally, polymeric carbodiimide was added, and the mixture was further mixed at 160°C for 2 min to obtain a final mixture.

[0074] The mixture is added to a twin-screw extruder for extrusion granulation. The temperatures of the twin-screw extruder from the feeding section to the die head are 130℃, 140℃, 150℃, 160℃, 165℃ and 165℃ respectively, and the screw speed is 220 rpm. The extrudate is cooled, pelletized and dried to obtain corrosion-resistant cable sheath material. Example

[0075] A method for preparing a corrosion-resistant cable sheath material includes the following steps: (1) Preparation of silane-treated sebacic acid anion-intercalated calcium-aluminum layered double hydroxides: 94.46 g of calcium nitrate tetrahydrate and 75.03 g of aluminum nitrate nonahydrate were added to 800 mL of deionized water and stirred to dissolve, yielding a calcium-aluminum salt solution. Under nitrogen protection, a 2.0 mol / L sodium hydroxide aqueous solution was added dropwise, maintaining the pH of the system at 10.0. The temperature was controlled at 25 °C during the dropwise addition, and stirring was continued for 1 h after the addition was completed. Subsequently, the temperature was raised to 60 °C and aged for 24 h. The solution was filtered, and the filter cake was washed with deionized water until the pH of the filtrate was 7.0-8.0. The solution was then dried at 80 °C for 12 h to obtain a calcium-aluminum layered double hydroxide precursor.

[0076] 32.36 g of sebacic acid and 12.80 g of sodium hydroxide were added to 500 mL of deionized water and heated and stirred to dissolve, yielding a sodium sebacic acid solution. The above-mentioned calcium-aluminum layered double hydroxide precursor was added to the sodium sebacic acid solution, the pH of the system was adjusted to 9.0, and the reaction was stirred at 60 °C for 24 h. The mixture was filtered, the filter cake was washed with deionized water, and dried at 80 °C for 12 h to obtain sebacic acid anion-intercalated calcium-aluminum layered double hydroxide.

[0077] Take 80.00 g of sebacic acid ion-intercalated calcium-aluminum layered double hydroxide and add it to an alcohol-water mixture consisting of 760 mL of anhydrous ethanol and 40 mL of deionized water. Stir and disperse. Adjust the pH of the system to 4.5 with glacial acetic acid, add 0.80 g of vinyltriethoxysilane, and react at 30 °C for 6 h. Filter, wash the filter cake with ethanol and deionized water in sequence, dry at 90 °C for 8 h, and pulverize to obtain silane-treated sebacic acid ion-intercalated calcium-aluminum layered double hydroxide.

[0078] (2) Preparation of single-end epoxy-terminated polydimethylsiloxane: In a reaction flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube, 200.00 g of single-ended hydrogen-containing polydimethylsiloxane with a number average molecular weight of 2000, 11.88 g of allyl glycidyl ether, and 250 mL of anhydrous toluene were added. After purging with nitrogen for 20 min, 0.213 g of Karstedt catalyst solution with a platinum content of 2 wt% was added. The mixture was heated to 40 °C under nitrogen protection and reacted for 8 h. After the reaction was completed, toluene and unreacted substances were removed under reduced pressure at 120 °C and -0.09 MPa for 1 h to obtain single-ended epoxy-terminated polydimethylsiloxane.

[0079] (3) Preparation of corrosion-resistant cable sheath material: Weigh out 520g of ethylene-vinyl acetate copolymer, 250g of linear low-density polyethylene, 180g of ethylene-octene copolymer elastomer, 50g of maleic anhydride grafted polyethylene, 850g of magnesium hydroxide, 600g of aluminum hydroxide, 40g of zinc borate, 30g of silane-treated sebacic acid intercalated calcium aluminum layered double hydroxide obtained in step (1), 4g of polymeric carbodiimide, 6g of single-end epoxy-terminated polydimethylsiloxane obtained in step (2), 2.5g of antioxidant 1010, 2.5g of antioxidant 168, 8g of polyethylene wax, 6g of calcium stearate, and 15g of carbon black.

[0080] Magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-treated sebacate intercalated calcium-aluminum layered double hydroxides were placed in an oven and dried at 100°C for 2.5 h.

[0081] Ethylene-vinyl acetate copolymer, linear low-density polyethylene, ethylene-octene copolymer elastomer, and maleic anhydride-grafted polyethylene were added to a mixer and melt-mixed at 155°C for 4 min to obtain a resin melt. Dried magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-surface-treated sebacic acid intercalated calcium aluminum layered double hydroxides were added to the resin melt, along with antioxidant 1010, antioxidant 168, polyethylene wax, calcium stearate, and carbon black. The mixture was then mixed at 160°C for 10 min. Subsequently, single-end epoxy-terminated polydimethylsiloxane was added, and the mixture was further mixed at 160°C for 3 min. Finally, polymeric carbodiimide was added, and the mixture was further mixed at 160°C for 2 min to obtain a final mixture.

[0082] The mixture is added to a twin-screw extruder for extrusion granulation. The temperatures of the twin-screw extruder from the feeding section to the die head are 130℃, 140℃, 150℃, 160℃, 165℃ and 165℃ respectively, and the screw speed is 220 rpm. The extrudate is cooled, pelletized and dried to obtain corrosion-resistant cable sheath material. Example

[0083] A method for preparing a corrosion-resistant cable sheath material includes the following steps: (1) Preparation of silane-treated sebacic acid anion-intercalated calcium-aluminum layered double hydroxides: 141.69 g of calcium nitrate tetrahydrate and 75.03 g of aluminum nitrate nonahydrate were added to 1000 mL of deionized water and stirred to dissolve, yielding a calcium-aluminum salt solution. Under nitrogen protection, a 2.0 mol / L sodium hydroxide aqueous solution was added dropwise, controlling the pH of the system at 12.0. The temperature was controlled at 25 °C during the dropwise addition, and stirring was continued for 1 h after the addition was completed. Subsequently, the temperature was raised to 90 °C and aged for 6 h. The solution was filtered, and the filter cake was washed with deionized water until the pH of the filtrate was 7.0~8.0. The solution was then dried at 80 °C for 12 h to obtain a calcium-aluminum layered double hydroxide precursor.

[0084] 72.81 g of sebacic acid and 28.80 g of sodium hydroxide were added to 700 mL of deionized water and heated and stirred to dissolve, yielding a sodium sebacic acid solution. The above-mentioned calcium-aluminum layered double hydroxide precursor was added to the sodium sebacic acid solution, the pH of the system was adjusted to 11.0, and the reaction was stirred at 100 °C for 6 h. The mixture was filtered, the filter cake was washed with deionized water, and dried at 80 °C for 12 h to obtain sebacic acid anion-intercalated calcium-aluminum layered double hydroxide.

[0085] Take 80.00 g of sebacic acid ion-intercalated calcium-aluminum layered double hydroxide and add it to an alcohol-water mixture consisting of 760 mL of anhydrous ethanol and 40 mL of deionized water. Stir and disperse. Adjust the pH of the system to 4.5 with glacial acetic acid. Add 4.00 g of γ-glycidoxypropyltrimethoxysilane and react at 80 °C for 1 h. Filter, wash the filter cake with ethanol and deionized water in sequence, dry at 90 °C for 8 h, and pulverize to obtain silane-surface-treated sebacic acid ion-intercalated calcium-aluminum layered double hydroxide.

[0086] (2) Preparation of single-end epoxy-terminated polydimethylsiloxane: In a reaction flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube, 200.00 g of single-ended hydrogen-containing polydimethylsiloxane with a number average molecular weight of 2000, 17.12 g of allyl glycidyl ether, and 250 mL of anhydrous toluene were added. After purging with nitrogen for 20 min, 0.213 g of Karstedt catalyst solution with a platinum content of 2 wt% was added. The mixture was heated to 110 °C under nitrogen protection and reacted for 1 h. After the reaction was completed, toluene and unreacted substances were removed under reduced pressure at 120 °C and -0.09 MPa for 1 h to obtain single-ended epoxy-terminated polydimethylsiloxane.

[0087] (3) Preparation of corrosion-resistant cable sheath material: Weigh out 420g of ethylene-vinyl acetate copolymer, 300g of metallocene linear low-density polyethylene, 180g of ethylene-octene copolymer elastomer, 100g of maleic anhydride grafted polyethylene, 1050g of magnesium hydroxide, 380g of aluminum hydroxide, 80g of zinc borate, 80g of silane-treated sebacic acid intercalated calcium aluminum layered double hydroxide obtained in step (1), 12g of polymeric carbodiimide, 20g of single-end epoxy-terminated polydimethylsiloxane obtained in step (2), 4g of antioxidant 1010, 4g of antioxidant 168, 10g of polyethylene wax, 8g of calcium stearate, and 15g of carbon black.

[0088] Magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-treated sebacate intercalated calcium-aluminum layered double hydroxides were placed in an oven and dried at 100°C for 2.5 h.

[0089] Ethylene-vinyl acetate copolymer, metallocene linear low-density polyethylene, ethylene-octene copolymer elastomer, and maleic anhydride-grafted polyethylene were added to a mixer and melt-mixed at 155°C for 4 min to obtain a resin melt. Dried magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-surface-treated sebacic acid intercalated calcium aluminum layered double hydroxides were added to the resin melt, along with antioxidant 1010, antioxidant 168, polyethylene wax, calcium stearate, and carbon black. The mixture was then mixed at 160°C for 10 min. Subsequently, single-end epoxy-terminated polydimethylsiloxane was added, and the mixture was further mixed at 160°C for 3 min. Finally, polymeric carbodiimide was added, and the mixture was further mixed at 160°C for 2 min to obtain a final mixture.

[0090] The mixture is added to a twin-screw extruder for extrusion granulation. The temperatures of the twin-screw extruder from the feeding section to the die head are 130℃, 140℃, 150℃, 160℃, 165℃ and 165℃ respectively, and the screw speed is 220 rpm. The extrudate is cooled, pelletized and dried to obtain corrosion-resistant cable sheath material. Example

[0091] A method for preparing a corrosion-resistant cable sheath material includes the following steps: (1) Preparation of silane-treated sebacic acid anion-intercalated calcium-aluminum layered double hydroxides: 141.69 g of calcium nitrate tetrahydrate and 75.03 g of aluminum nitrate nonahydrate were added to 1000 mL of deionized water and stirred to dissolve, yielding a calcium-aluminum salt solution. Under nitrogen protection, a 2.0 mol / L sodium hydroxide aqueous solution was added dropwise, controlling the pH of the system at 12.0. The temperature was controlled at 25 °C during the dropwise addition, and stirring was continued for 1 h after the addition was completed. Subsequently, the temperature was raised to 90 °C and aged for 6 h. The solution was filtered, and the filter cake was washed with deionized water until the pH of the filtrate was 7.0~8.0. The solution was then dried at 80 °C for 12 h to obtain a calcium-aluminum layered double hydroxide precursor.

[0092] 72.81 g of sebacic acid and 28.80 g of sodium hydroxide were added to 700 mL of deionized water and heated and stirred to dissolve, yielding a sodium sebacic acid solution. The above-mentioned calcium-aluminum layered double hydroxide precursor was added to the sodium sebacic acid solution, the pH of the system was adjusted to 11.0, and the reaction was stirred at 100 °C for 6 h. The mixture was filtered, the filter cake was washed with deionized water, and dried at 80 °C for 12 h to obtain sebacic acid anion-intercalated calcium-aluminum layered double hydroxide.

[0093] Take 80.00 g of sebacic acid ion-intercalated calcium-aluminum layered double hydroxide and add it to an alcohol-water mixture consisting of 760 mL of anhydrous ethanol and 40 mL of deionized water. Stir and disperse. Adjust the pH of the system to 4.5 with glacial acetic acid. Add 4.00 g of γ-glycidoxypropyltrimethoxysilane and react at 80 °C for 1 h. Filter, wash the filter cake with ethanol and deionized water in sequence, dry at 90 °C for 8 h, and pulverize to obtain silane-surface-treated sebacic acid ion-intercalated calcium-aluminum layered double hydroxide.

[0094] (2) Preparation of single-end epoxy-terminated polydimethylsiloxane: In a reaction flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube, 200.00 g of single-ended hydrogen-containing polydimethylsiloxane with a number average molecular weight of 2000, 17.12 g of allyl glycidyl ether, and 250 mL of anhydrous toluene were added. After purging with nitrogen for 20 min, 0.213 g of Karstedt catalyst solution with a platinum content of 2 wt% was added. The mixture was heated to 110 °C under nitrogen protection and reacted for 1 h. After the reaction was completed, toluene and unreacted substances were removed under reduced pressure at 120 °C and -0.09 MPa for 1 h to obtain single-ended epoxy-terminated polydimethylsiloxane.

[0095] (3) Preparation of corrosion-resistant cable sheath material: Weigh out 420g of ethylene-vinyl acetate copolymer, 300g of metallocene linear low-density polyethylene, 180g of ethylene-octene copolymer elastomer, 100g of maleic anhydride grafted polyethylene, 1050g of magnesium hydroxide, 380g of aluminum hydroxide, 80g of zinc borate, 80g of silane-treated sebacic acid intercalated calcium aluminum layered double hydroxide obtained in step (1), 12g of polymeric carbodiimide, 20g of single-end epoxy-terminated polydimethylsiloxane obtained in step (2), 4g of antioxidant 1010, 4g of antioxidant 168, 10g of polyethylene wax, 8g of calcium stearate, and 15g of carbon black.

[0096] Magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-treated sebacate intercalated calcium-aluminum layered double hydroxides were placed in an oven and dried at 100°C for 2.5 h.

[0097] Ethylene-vinyl acetate copolymer, metallocene linear low-density polyethylene, ethylene-octene copolymer elastomer, and maleic anhydride-grafted polyethylene were added to a mixer and melt-mixed at 155°C for 4 min to obtain a resin melt. Dried magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-surface-treated sebacic acid intercalated calcium aluminum layered double hydroxides were added to the resin melt, along with antioxidant 1010, antioxidant 168, polyethylene wax, calcium stearate, and carbon black. The mixture was then mixed at 160°C for 10 min. Subsequently, single-end epoxy-terminated polydimethylsiloxane was added, and the mixture was further mixed at 160°C for 3 min. Finally, polymeric carbodiimide was added, and the mixture was further mixed at 160°C for 2 min to obtain a final mixture.

[0098] The mixture is added to a twin-screw extruder for extrusion granulation. The temperatures of the twin-screw extruder from the feeding section to the die head are 130℃, 140℃, 150℃, 160℃, 165℃ and 165℃ respectively, and the screw speed is 220 rpm. The extrudate is cooled, pelletized and dried to obtain corrosion-resistant cable sheath material. Example

[0099] A method for preparing a corrosion-resistant cable sheath material includes the following steps: (1) Preparation of silane-treated sebacic acid anion-intercalated calcium-aluminum layered double hydroxides: The silane-treated sebacate intercalated calcium aluminum layered double hydroxide was prepared according to the method of step (1) in Example 1; wherein the silane coupling agent was γ-glycidoxypropyltrimethoxysilane, and the amount was 2.40 g, and the other feed amounts and reaction conditions were the same as in Example 1.

[0100] (2) Preparation of single-end epoxy-terminated polydimethylsiloxane: The single-end epoxy-terminated polydimethylsiloxane was prepared according to step (2) of Example 1; wherein the alkenyl epoxy compound used was glycidyl methacrylate, and the amount was 15.63g, and the remaining feed amounts and reaction conditions were the same as in Example 1.

[0101] (3) Preparation of corrosion-resistant cable sheath material: Weigh out 430g of ethylene-vinyl acetate copolymer, 280g of linear low-density polyethylene, 50g of high-density polyethylene, 160g of ethylene-butene copolymer elastomer, 80g of maleic anhydride-grafted ethylene-vinyl acetate copolymer, 1100g of magnesium hydroxide, 350g of aluminum hydroxide, 70g of zinc borate, 40g of silane-treated sebacate intercalated calcium aluminum layered double hydroxide obtained in step (1), 9g of polymeric carbodiimide, 10g of single-end epoxy-terminated polydimethylsiloxane obtained in step (2), 3g of antioxidant 1010, 4g of antioxidant 168, 8g of polyethylene wax, 4g of zinc stearate, and 15g of carbon black.

[0102] Magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-treated sebacate intercalated calcium-aluminum layered double hydroxides were placed in an oven and dried at 100°C for 2.5 h.

[0103] Ethylene-vinyl acetate copolymer, linear low-density polyethylene, high-density polyethylene, ethylene-butene copolymer elastomer, and maleic anhydride-grafted ethylene-vinyl acetate copolymer were added to a mixer and melt-mixed at 155°C for 4 min to obtain a resin melt. Dried magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-treated sebacic acid-intercalated calcium-aluminum layered double hydroxides were added to the resin melt, along with antioxidant 1010, antioxidant 168, polyethylene wax, zinc stearate, and carbon black. The mixture was then mixed at 160°C for 10 min. Subsequently, single-end epoxy-terminated polydimethylsiloxane was added, and the mixture was further mixed at 160°C for 3 min. Finally, polymeric carbodiimide was added, and the mixture was further mixed at 160°C for 2 min to obtain a final mixture.

[0104] The mixture is added to a twin-screw extruder for extrusion granulation. The temperatures of the twin-screw extruder from the feeding section to the die head are 130℃, 140℃, 150℃, 160℃, 165℃ and 165℃ respectively, and the screw speed is 220 rpm. The extrudate is cooled, pelletized and dried to obtain corrosion-resistant cable sheath material.

[0105] The difference between Comparative Example 1 and Example 1 is that the calcium-aluminum layered double hydroxide precursor is not subjected to intercalation treatment with sebacic acid salt solution.

[0106] The specific preparation method is as follows: (1) Preparation of silane-surface-treated calcium-aluminum layered double hydroxides: 94.46 g of calcium nitrate tetrahydrate and 75.03 g of aluminum nitrate nonahydrate were added to 800 mL of deionized water and stirred to dissolve, yielding a calcium-aluminum salt solution. Under nitrogen protection, a 2.0 mol / L sodium hydroxide aqueous solution was added dropwise to the calcium-aluminum salt solution, maintaining the pH of the system at 11.0. The temperature was controlled at 25 °C during the addition process, and stirring was continued for 1 h after the addition was completed. Subsequently, the temperature was raised to 70 °C and aged for 12 h. After the reaction was completed, the mixture was filtered, and the filter cake was washed with deionized water until the pH of the filtrate was 7.0–8.0. The filtrate was then dried at 80 °C for 12 h to obtain a calcium-aluminum layered double hydroxide precursor.

[0107] Take 80.00 g of calcium-aluminum layered double hydroxide precursor and add it to an alcohol-water mixture consisting of 760 mL of anhydrous ethanol and 40 mL of deionized water. Stir and disperse. Adjust the pH of the system to 4.5 with glacial acetic acid. Add 1.60 g of γ-methacryloxypropyltrimethoxysilane and react at 60 °C for 3 h. After the reaction is complete, filter and wash the filter cake with ethanol and deionized water in sequence. Dry at 90 °C for 8 h and pulverize to obtain silane-treated calcium-aluminum layered double hydroxide.

[0108] (2) Preparation of single-end epoxy-terminated polydimethylsiloxane: Single-ended epoxy-terminated polydimethylsiloxane was prepared according to step (2) of Example 1.

[0109] (3) Preparation of corrosion-resistant cable sheath material: Weigh out 480g of ethylene-vinyl acetate copolymer, 240g of linear low-density polyethylene, 180g of ethylene-octene copolymer elastomer, 100g of maleic anhydride grafted polyethylene, 950g of magnesium hydroxide, 450g of aluminum hydroxide, 50g of zinc borate, 50g of silane surface-treated calcium-aluminum layered double hydroxide obtained in step (1), 8g of polymeric carbodiimide, 12g of single-end epoxy-terminated polydimethylsiloxane obtained in step (2), 3g of antioxidant 1010, 3g of antioxidant 168, 6g of polyethylene wax, 5g of calcium stearate, and 15g of carbon black.

[0110] Magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-treated calcium-aluminum layered double hydroxides were placed in an oven and dried at 100°C for 2.5 hours.

[0111] Ethylene-vinyl acetate copolymer, linear low-density polyethylene, ethylene-octene copolymer elastomer, and maleic anhydride-grafted polyethylene were added to a mixer and melt-mixed at 155°C for 4 min to obtain a resin melt. Dried magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-surface-treated calcium-aluminum layered double hydroxide were added to the resin melt, along with antioxidant 1010, antioxidant 168, polyethylene wax, calcium stearate, and carbon black. The mixture was then mixed at 160°C for 10 min. Subsequently, single-end epoxy-terminated polydimethylsiloxane was added, and the mixture was further mixed at 160°C for 3 min. Finally, polymeric carbodiimide was added, and the mixture was further mixed at 160°C for 2 min to obtain a final mixture.

[0112] The mixture is added to a twin-screw extruder for extrusion granulation. The temperatures of the twin-screw extruder from the feeding section to the die head are 130℃, 140℃, 150℃, 160℃, 165℃ and 165℃ respectively, and the screw speed is 220 rpm. The extrudate is cooled, pelletized and dried to obtain corrosion-resistant cable sheath material.

[0113] The difference between Comparative Example 2 and Example 1 is that: double-ended epoxy-terminated polydimethylsiloxane is used instead of single-ended epoxy-terminated polydimethylsiloxane in Example 1, with the same substitution mass.

[0114] The specific preparation method is as follows: (1) Preparation of silane-treated sebacic acid anion-intercalated calcium-aluminum layered double hydroxides: The silane-treated sebacate intercalated calcium-aluminum layered double hydroxide was prepared according to the method in step (1) of Example 1.

[0115] (2) Preparation of double-ended epoxy-capped polydimethylsiloxane: In a reaction flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube, 200.00 g of hydrogen-terminated polydimethylsiloxane with a number average molecular weight of 2000, 25.11 g of allyl glycidyl ether, and 250 mL of anhydrous toluene were added. After purging with nitrogen for 20 min, 0.225 g of Karstedt catalyst solution with a platinum content of 2 wt% was added. The mixture was heated to 75 °C under nitrogen protection and reacted for 4 h. After the reaction was completed, toluene and unreacted substances were removed under reduced pressure at 120 °C and -0.09 MPa for 1 h to obtain epoxy-terminated polydimethylsiloxane.

[0116] (3) Preparation of corrosion-resistant cable sheath material: Weigh out 480g of ethylene-vinyl acetate copolymer, 240g of linear low-density polyethylene, 180g of ethylene-octene copolymer elastomer, 100g of maleic anhydride grafted polyethylene, 950g of magnesium hydroxide, 450g of aluminum hydroxide, 50g of zinc borate, 50g of silane-treated sebacic acid intercalated calcium aluminum layered double hydroxide obtained in step (1), 8g of polymeric carbodiimide, 12g of double-ended epoxy-terminated polydimethylsiloxane obtained in step (2), 3g of antioxidant 1010, 3g of antioxidant 168, 6g of polyethylene wax, 5g of calcium stearate, and 15g of carbon black.

[0117] Magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-treated sebacate intercalated calcium-aluminum layered double hydroxides were placed in an oven and dried at 100°C for 2.5 h.

[0118] Ethylene-vinyl acetate copolymer, linear low-density polyethylene, ethylene-octene copolymer elastomer, and maleic anhydride-grafted polyethylene were added to a mixer and melt-mixed at 155°C for 4 min to obtain a resin melt. Dried magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-treated sebacic acid-intercalated calcium-aluminum layered double hydroxides were added to the resin melt, along with antioxidant 1010, antioxidant 168, polyethylene wax, calcium stearate, and carbon black. The mixture was then mixed at 160°C for 10 min. Subsequently, double-ended epoxy-terminated polydimethylsiloxane was added, and the mixture was further mixed at 160°C for 3 min. Finally, polymeric carbodiimide was added, and the mixture was further mixed at 160°C for 2 min to obtain a final mixture.

[0119] The mixture is added to a twin-screw extruder for extrusion granulation. The temperatures of the twin-screw extruder from the feeding section to the die head are 130℃, 140℃, 150℃, 160℃, 165℃ and 165℃ respectively, and the screw speed is 220 rpm. The extrudate is cooled, pelletized and dried to obtain corrosion-resistant cable sheath material.

[0120] The difference between Comparative Example 3 and Example 1 is that no polymeric carbodiimide was added, and an equal amount of ethylene-vinyl acetate copolymer was used to make up the difference.

[0121] The specific preparation method is as follows: (1) Preparation of silane-treated sebacic acid anion-intercalated calcium-aluminum layered double hydroxides: The silane-treated sebacate intercalated calcium-aluminum layered double hydroxide was prepared according to the method in step (1) of Example 1.

[0122] (2) Preparation of single-end epoxy-terminated polydimethylsiloxane: Single-ended epoxy-terminated polydimethylsiloxane was prepared according to step (2) of Example 1.

[0123] (3) Preparation of corrosion-resistant cable sheath material: Weigh out 488g of ethylene-vinyl acetate copolymer, 240g of linear low-density polyethylene, 180g of ethylene-octene copolymer elastomer, 100g of maleic anhydride grafted polyethylene, 950g of magnesium hydroxide, 450g of aluminum hydroxide, 50g of zinc borate, 50g of silane-treated sebacic acid intercalated calcium aluminum layered double hydroxide obtained in step (1), 12g of single-end epoxy-terminated polydimethylsiloxane obtained in step (2), 3g of antioxidant 1010, 3g of antioxidant 168, 6g of polyethylene wax, 5g of calcium stearate, and 15g of carbon black.

[0124] Magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-treated sebacate intercalated calcium-aluminum layered double hydroxides were placed in an oven and dried at 100°C for 2.5 h.

[0125] Ethylene-vinyl acetate copolymer, linear low-density polyethylene, ethylene-octene copolymer elastomer, and maleic anhydride-grafted polyethylene were added to a mixer and melt-mixed at 155°C for 4 min to obtain a resin melt. Dried magnesium hydroxide, aluminum hydroxide, zinc borate, and silane-surface-treated sebacic acid intercalated calcium aluminum layered double hydroxides were added to the resin melt, along with antioxidant 1010, antioxidant 168, polyethylene wax, calcium stearate, and carbon black. The mixture was then mixed at 160°C for 10 min. Subsequently, single-end epoxy-terminated polydimethylsiloxane was added, and the mixture was further mixed at 160°C for 3 min to obtain a final mixture.

[0126] The mixture is added to a twin-screw extruder for extrusion granulation. The temperatures of the twin-screw extruder from the feeding section to the die head are 130℃, 140℃, 150℃, 160℃, 165℃ and 165℃ respectively, and the screw speed is 220 rpm. The extrudate is cooled, pelletized and dried to obtain corrosion-resistant cable sheath material.

[0127] I. Sample Preparation The corrosion-resistant cable sheathing material particles obtained in Examples 1-5 and Comparative Examples 1-3 were dried at 70°C for 4 hours. The dried granules were placed in a flat vulcanizing machine or a sheet press and pressed into sheets. The sheet pressing temperature was 165°C, the preheating time was 3 minutes, the hot pressing pressure was 10 MPa, and the hot pressing time was 5 minutes. Subsequently, the sheets were cold-pressed to room temperature at a pressure of 10 MPa to obtain sheets with thicknesses of 1.0 mm and 3.0 mm.

[0128] The 1.0mm sheet was used for tensile properties, mechanical properties after salt spray, mechanical properties after acid and alkali immersion, mechanical properties after damp heat, and water absorption testing; the 3.0mm sheet was used for oxygen index, smoke density, and pH / conductivity testing of combustion gases. After cutting, the samples were conditioned for 24 hours in an environment of 23℃ and 50% relative humidity.

[0129] Examples 1-5 are samples of the present invention containing silane-surface-treated sebacic acid intercalated calcium aluminum layered double hydroxide, polymeric carbodiimide, and single-end epoxy-terminated polydimethylsiloxane; in Comparative Example 1, the calcium aluminum layered double hydroxide precursor was not treated with sebacic acid for intercalation; in Comparative Example 2, double-end epoxy-terminated PDMS was used instead of single-end epoxy-terminated PDMS; in Comparative Example 3, polymeric carbodiimide was not added, and an equal amount of EVA resin was used to make up the difference.

[0130] II. Testing Methods 1. Tensile property testing The tensile strength and elongation at break of the specimens were tested according to GB / T 2951.11-2008. Five specimens were tested in each group, and the average value was taken.

[0131] 2. Mechanical retention rate after salt spray aging Tensile test specimens were cut from 1.0 mm sheets and subjected to salt spray treatment. The salt solution was a 5 wt% NaCl aqueous solution with a pH of 6.5–7.2. The test temperature was 35 °C, and the salt spray treatment time was 336 h. After the salt spray treatment, the specimens were rinsed with deionized water to remove surface salt and then placed in an environment at 23 °C and 50% relative humidity for 24 h to equilibrate. Tensile strength and elongation at break were then tested, and retention rate was calculated.

[0132] 3. Mechanical retention rate after acid and alkali immersion Tensile specimens were immersed in hydrochloric acid aqueous solution (pH=3) and sodium hydroxide aqueous solution (pH=10), respectively, at 60℃ for 168 hours. The total mass of specimens placed in each 100 mL of solution did not exceed 5 g, and the immersion solution was replaced every 48 hours. After immersion, the specimen surface was rinsed with deionized water and placed in an environment of 23℃ and 50% relative humidity for 24 hours to equilibrate before testing the tensile strength and calculating the retention rate.

[0133] 4. Mechanical retention rate after damp heat aging Referring to GB / T 2423.3-2016 Steady-state damp heat test method, the tensile specimens were placed in a damp heat environment with a temperature of 85℃ and a relative humidity of 85% for 336 hours. After treatment, the specimens were placed in an environment with a temperature of 23℃ and a relative humidity of 50% for 24 hours to equilibrate, and then the tensile strength and elongation at break were tested, and the retention rate was calculated.

[0134] 5. Water absorption rate test A sheet-like sample measuring 50mm × 50mm × 1.0mm was dried at 70℃ to constant weight, and its initial mass m0 was recorded. The sample was then immersed in a 5wt% NaCl aqueous solution at 60℃ for 168 hours. After immersion, the sample was wiped dry with lint-free paper, and its mass m1 was recorded. The water absorption rate was calculated using the following formula: Water absorption rate / % = (m1-m0) / m0 × 100%.

[0135] Three samples were tested in each group, and the average value was taken.

[0136] 6. Oxygen Index Test According to GB / T 2406.2-2009, the limiting oxygen index of the test specimen was tested, and the oxygen index before aging and after 336 hours of damp heat aging were recorded.

[0137] 7. Smoke density test The smoke density of the samples was tested using the single-chamber method according to GB / T 8323.2-2008, and the maximum smoke density Ds,max was recorded. Three samples were tested in each group, and the average value was taken.

[0138] 8. Combustion gas pH and conductivity testing The pH and conductivity of the combustion gas absorbent liquid of the sample were tested according to the relevant methods in GB / T 17650.2 to evaluate the corrosiveness of the combustion gas. Three samples were tested in each group, and the average value was taken.

[0139] 9. Processing stability test During the granulation process in the examples and comparative examples, the die pressure was recorded after the twin-screw extruder had been running stably for 30 minutes. A torque rheometer was used to test the equilibrium torque of each sample at 160°C and 60 rpm. A 200-mesh melt filter was used to test the filtration pressure rise over 30 minutes, and filter residue was collected to calculate the melt filter residue content. The surface condition of the extruded strip was observed.

[0140] III. Test Results Table 1 Initial performance, low smoke flame retardancy and processing stability Example 1 12.9 286 33.5 118 5.9 1.6 42 8.6 0.7 42 smooth Example 2 12.4 292 32.8 126 5.8 1.8 40 8.2 0.6 39 smooth Example 3 13.2 268 34.1 112 5.9 1.5 46 9.1 0.9 55 smooth Example 4 12.1 318 32.9 124 5.8 1.8 41 8.4 0.7 45 smooth Example 5 13.5 252 34.4 109 5.9 1.5 47 9.3 0.9 58 Basic smooth Comparative Example 1 12.2 263 33.2 121 5.8 1.7 43 8.7 0.8 49 Basic smooth Comparative Example 2 12.7 241 33.4 120 5.8 1.7 57 11.8 2.4 165 Slight pockmarks Comparative Example 3 12.6 274 33.3 122 5.8 1.7 41 8.5 0.7 44 smooth Table 2 Corrosion resistance, moisture retention and water absorption Example 1 0.82 91.5 89.7 90.8 92.1 90.2 88.9 32.7 Example 2 0.95 88.6 86.4 87.9 89.0 87.6 85.8 31.9 Example 3 0.78 92.3 88.5 91.6 92.8 90.7 87.1 33.2 Example 4 0.89 89.8 90.6 88.7 90.4 88.5 89.3 32.0 Example 5 0.84 90.9 85.8 90.2 91.5 89.8 84.9 33.4 Comparative Example 1 1.36 80.4 74.8 78.6 81.2 79.1 73.9 31.6 Comparative Example 2 0.91 87.5 76.2 86.8 88.1 84.3 72.8 32.1 Comparative Example 3 1.08 82.6 78.3 80.9 83.4 75.2 68.6 30.8 Examples 1-5 all employed three core components: silane-surface-treated sebacic acid intercalated calcium-aluminum layered double hydroxide, polymeric carbodiimide, and single-end epoxy-terminated polydimethylsiloxane. As shown in Table 1, Examples 1-5 exhibited an oxygen index of 32.8%-34.4%, smoke density (Ds,max) of 109-126, combustion gas pH of 5.8-5.9, and electrical conductivity of 1.5-1.8 μS / mm, indicating that the addition of these three core components did not compromise the fundamental properties of the low-smoke halogen-free flame-retardant system.

[0141] As shown in Table 2, the tensile strength retention rates after salt spray in Examples 1-5 were 88.6%-92.3%, after damp heat were 87.6%-90.7%, and after acid and alkali immersion were all above 87%, which is better than Comparative Examples 1 and 3 overall. This indicates that the addition of the three core components can improve the mechanical properties under salt spray, acid and alkali, and damp heat environments. Example 1 is the median preferred formulation, with a relatively balanced initial mechanical properties, water absorption, corrosion resistance retention, and processing stability. In Example 2, the core component dosage was lower, the water absorption was slightly higher, and the corrosion resistance retention was slightly lower, but it was still better than the comparative examples lacking a specific core structure. In Example 3, the core component dosage was higher, the water absorption was lower, and the flame retardant performance was better, but the torque and die head pressure were slightly higher. Example 4 is a more flexible formulation with a higher elongation at break. Example 5 is a formulation with higher polyethylene and higher flame retardant filler, with higher tensile strength and oxygen index, but a relatively lower elongation at break.

[0142] In Comparative Example 1, the calcium-aluminum layered double hydroxide precursor was not treated with sebacic acid but directly subjected to silane surface treatment. Compared with Example 1, the initial tensile strength, oxygen index, smoke density, and processing stability of Comparative Example 1 did not change significantly, indicating that ordinary silane treatment of calcium-aluminum layered double hydroxides does not significantly damage the basic properties; however, its 5% NaCl water absorption rate increased from 0.82% to 1.36%, the tensile strength retention rate after salt spray decreased from 91.5% to 80.4%, and the tensile strength retention rate after damp heat decreased from 90.2% to 79.1%. The above results indicate that the sebacic acid intercalation structure plays an important role in reducing brine absorption and improving performance retention after salt spray and damp heat, and ordinary silane treatment of calcium-aluminum layered double hydroxides cannot achieve the same effect.

[0143] In Comparative Example 2, double-ended epoxy-terminated PDMS was used instead of single-ended epoxy-terminated PDMS. Compared with Example 1, the water absorption rate, oxygen index, and smoke density of Comparative Example 2 did not change significantly, indicating that the hydrophobicity of the PDMS segments and the low-smoke halogen-free flame-retardant system were basically retained. However, its equilibrium torque increased from 42 N·m to 57 N·m, the die head pressure increased from 8.6 MPa to 11.8 MPa, the 30-minute filtration pressure rise increased from 0.7 MPa to 2.4 MPa, the melt filtration residue increased from 42 mg·kg⁻¹ to 165 mg·kg⁻¹, and slight pitting appeared on the extruded surface. The above results indicate that although double-ended epoxy-terminated PDMS is structurally similar to single-ended epoxy-terminated PDMS, the double-ended reactivity is more likely to cause local thickening or microgelation, and cannot effectively solve the interfacial overreaction problem caused by the co-addition of the first two core components.

[0144] Comparative Example 3 did not include polymeric carbodiimide, and the remainder was made up with an equal amount of EVA resin. Compared with Example 1, Comparative Example 3 showed little difference in initial tensile strength, elongation at break, oxygen index, and processing stability. However, the retention rate of tensile strength after hygrothermal treatment decreased from 90.2% to 75.2%, the retention rate of elongation at break after hygrothermal treatment decreased from 88.9% to 68.6%, and the oxygen index after hygrothermal treatment decreased from 32.7% to 30.8%. These results indicate that polymeric carbodiimide plays an important role in hydrolytic stability and performance retention under hygrothermal conditions. Relying solely on silane-treated sebacic acid intercalated calcium aluminum layered double hydroxides and single-end epoxy-capped PDMS is insufficient to adequately suppress resin phase and interface degradation caused by hygrothermal aging.

[0145] In summary, Examples 1-5, compared to Comparative Examples 1-3, exhibit more balanced overall performance in terms of water absorption, mechanical retention after salt spray, mechanical retention after acid and alkali immersion, mechanical retention after wet heat, and processing stability. Comparative Example 1 demonstrates that the sebacic acid intercalation structure plays an important role in salt spray resistance and corrosion resistance; Comparative Example 3 demonstrates that the polymeric carbodiimide plays an important role in wet heat hydrolysis stability; Comparative Example 2 demonstrates that single-end epoxy-capped PDMS can better balance interfacial reaction control and processing stability compared to double-end epoxy-capped PDMS.

[0146] Therefore, the silane-treated sebacic acid intercalated calcium aluminum layered double hydroxide, the polymeric carbodiimide, and the single-ended epoxy-terminated polydimethylsiloxane form a ternary synergistic effect of "corrosion medium barrier - hydrolysis stabilization - interface reaction regulation" in the system of this invention, so that the obtained corrosion-resistant cable sheath material can maintain low smoke halogen-free flame retardant properties while also having good corrosion resistance retention, humid heat stability and extrusion processing stability.

[0147] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A corrosion-resistant cable sheath material, characterized in that, Based on 100 parts by weight of the resin matrix, it comprises the following raw materials: 40-55 parts of ethylene-vinyl acetate copolymer, 20-35 parts of polyethylene, 10-25 parts of polyolefin elastomer, 5-10 parts of maleic anhydride-grafted polyolefin, 80-110 parts of magnesium hydroxide, 35-65 parts of aluminum hydroxide, 3-8 parts of zinc borate, 3-8 parts of silane-treated sebacic acid intercalated calcium aluminum layered double hydroxide, 0.4-1.2 parts of polymeric carbodiimide, 0.6-2.0 parts of single-end epoxy-terminated polydimethylsiloxane, 0.4-1.0 parts of antioxidant, and 0.5-3 parts of lubricant; The resin matrix is ​​composed of ethylene-vinyl acetate copolymer, polyethylene, polyolefin elastomer and maleic anhydride-grafted polyolefin.

2. The corrosion-resistant cable sheath material according to claim 1, characterized in that, The polyethylene is one or more of linear low-density polyethylene, metallocene linear low-density polyethylene, low-density polyethylene, and high-density polyethylene; the polyolefin elastomer is one or more of ethylene-octene copolymer elastomer, ethylene-butene copolymer elastomer, and olefin block copolymer; the maleic anhydride-grafted polyolefin is one or more of maleic anhydride-grafted polyethylene, maleic anhydride-grafted ethylene-octene copolymer, and maleic anhydride-grafted ethylene-vinyl acetate copolymer.

3. A corrosion-resistant cable sheath material according to claim 1, characterized in that, The silane-treated sebacic acid anion-intercalated calcium-aluminum layered double hydroxide was prepared by the following steps: (1) The calcium salt, aluminum salt and alkaline solution were subjected to a co-precipitation reaction to obtain a calcium-aluminum layered double hydroxide precursor; (2) The calcium-aluminum layered double hydroxide precursor is subjected to an intercalation reaction with sebacic acid salt solution to obtain sebacic acid intercalated calcium-aluminum layered double hydroxide; (3) The sebacic acid anion intercalated calcium aluminum layered double hydroxide was surface treated with a silane coupling agent to obtain a silane-treated sebacic acid anion intercalated calcium aluminum layered double hydroxide.

4. The corrosion-resistant cable sheath material according to claim 3, characterized in that, The molar ratio of calcium in the calcium salt to aluminum in the aluminum salt is 1.5~3.0:1; the pH of the coprecipitation reaction is 9~13.

5. The corrosion-resistant cable sheath material according to claim 3, characterized in that, In the intercalation reaction, the molar ratio of sebacic acid ion to aluminum in the calcium-aluminum layered double hydroxide precursor is 0.2~1.5:1; the temperature of the intercalation reaction is 60~100℃, and the time is 6~24h.

6. The corrosion-resistant cable sheath material according to claim 3, characterized in that, The silane coupling agent is selected from one or more of vinyltriethoxysilane, vinyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane and γ-glycidyloxypropyltrimethoxysilane; the amount of silane coupling agent used is 0.5-5% of the mass of sebacic acid intercalated calcium aluminum layered double hydroxide.

7. A corrosion-resistant cable sheath material according to claim 1, characterized in that, The single-ended epoxy-terminated polydimethylsiloxane was prepared by the following steps: A single-ended hydrogen-containing polydimethylsiloxane, an alkenyl epoxy compound, and a hydrosilylation catalyst were mixed and subjected to a hydrosilylation reaction. After the reaction was completed, unreacted material was removed to obtain a single-ended epoxy-terminated polydimethylsiloxane.

8. The corrosion-resistant cable sheath material according to claim 7, characterized in that, The alkenyl epoxy compound is one or more of allyl glycidyl ether, vinyl cyclohexene oxide, and glycidyl methacrylate; the single-ended hydrogen-containing polydimethylsiloxane has a number average molecular weight of 1000-5000; and the hydrosilylation catalyst is a platinum-based catalyst.

9. The corrosion-resistant cable sheath material according to claim 7, characterized in that, The molar ratio of carbon-carbon double bonds in the alkenyl epoxy compound to Si-H bonds in the single-ended hydrogen-containing polydimethylsiloxane is 1.02~1.50:1; the hydrosilylation reaction is carried out at a temperature of 40~110℃ for 1~8 h.

10. A method for preparing the corrosion-resistant cable sheath material according to any one of claims 1 to 9, characterized in that, Includes the following steps: Ethylene-vinyl acetate copolymer, polyethylene, polyolefin elastomer and maleic anhydride-grafted polyolefin are melt-mixed to obtain resin melt; Magnesium hydroxide, aluminum hydroxide, zinc borate, silane-treated sebacic acid intercalated calcium aluminum layered double hydroxide, antioxidant, and lubricant are added to the resin melt and mixed. Add single-ended epoxy-terminated polydimethylsiloxane and mix; Add polymeric carbodiimide and mix; The corrosion-resistant cable sheath material is obtained by extrusion granulation.

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