A chlorinated polyethylene sheath material for cables and a method for producing the same

Abstract

The application discloses a chlorinated polyethylene sheath material for cables and a preparation method thereof, and relates to the technical field of cable materials, which comprises the following formula: chlorinated polyethylene, POE-g-AA, nano-magnesium oxide, antimony-boron synergistic flame retardant, core-shell cold-resistant composite powder, nano-SiO2, carbon black N330, cold-resistant plasticizer and the like. The application introduces POE-g-AA, core-shell cold-resistant composite powder and cold-resistant plasticizer into the chlorinated polyethylene matrix, and cooperates with the dynamic crosslinking network constructed by the 14S-FL, TAIC and TMPTMA through the step-by-step activation mixing process, so that the material still maintains excellent flexibility and anti-brittle cracking performance under the environment of-50 DEG C, and also maintains good flexibility, heat resistance and anti-creep performance under the high temperature environment of +135 DEG C. Through the synergistic effect of the antimony-boron synergistic flame retardant, nano-magnesium oxide, nano-SiO2 and carbon black N330, the material has excellent flame retardance and reinforcing performance.

Description

Technical Field

[0001] This invention relates to the field of cable material technology, specifically to a chlorinated polyethylene sheath material for cables and its preparation method. Background Technology

[0002] With the rapid development of the energy industry, especially the widespread application of wind power generation, the performance requirements for cables are becoming increasingly stringent. Wind power cables need to operate stably under complex environmental conditions, including extreme high and low temperatures, high humidity, strong ultraviolet radiation, and harsh environments such as saline and alkaline conditions. In cold northern regions and offshore wind farms, low temperatures can cause traditional cable sheath materials to become brittle and lose their flexibility, making them prone to cracking and affecting the normal use and lifespan of the cable. At the same time, in high-temperature environments, the sheath material may experience aging and performance degradation. In addition, cables may be subjected to mechanical stresses such as torsion and tension during use, as well as corrosion from chemicals such as mineral oils. Therefore, the cable sheath needs to have good resistance to torsion, heat, salt and alkali, and oil.

[0003] Currently available cable sheath materials fail to meet the comprehensive performance requirements of wind power cables in complex environments, particularly in terms of cold resistance, heat resistance, torsion resistance, and chemical corrosion resistance. For example, some traditional cable sheaths exhibit a sharp decline in tensile strength and elongation at low temperatures, making them unable to withstand the normal operating stress of cables in such conditions. Furthermore, after high-temperature aging, the mechanical properties of the materials change significantly, affecting the long-term reliability of the cables. In terms of resistance to mineral oil corrosion, there is also a noticeable decrease in tensile strength and elongation at break. Therefore, developing a cable sheath material that simultaneously meets the requirements of high cold resistance, heat resistance, torsion resistance, and good chemical corrosion resistance is of significant practical importance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a chlorinated polyethylene sheath material for cables and a method for preparing it, thereby solving the problems mentioned in the background section.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a chlorinated polyethylene sheath material for cables, comprising the following formula in parts by weight:

[0007] 85–88 parts chlorinated polyethylene, 12–15 parts POE-g-AA, 8.5–9 parts nano magnesium oxide, 4–5 parts antimony-boron synergistic flame retardant, 16–18 parts core-shell cold-resistant composite powder, 12–14 parts nano SiO2, 10–11 parts carbon black N330, 10–11 parts cold-resistant plasticizer, 8.5–9 parts heat-resistant plasticizer, 2.5–3 parts TAIC, 2.8–3.2 parts 14S-FL, 0.8–1 part TMPTMA, 1.2–1.3 parts titanate coupling agent, 2–3 parts anti-salt and alkali agent, 2–3 parts antioxidant.

[0008] To further optimize this technical solution, the chlorinated polyethylene is used as the base resin and as the main film-forming material, and the chlorine content of the chlorinated polyethylene is 35%.

[0009] To further optimize this technical solution, the nano-magnesium oxide is a highly active stearic acid-modified nano-magnesium oxide powder, and the modification method includes:

[0010] First, prepare 0.3–0.5 mol / L magnesium nitrate solution and 0.6–0.8 mol / L sodium carbonate solution separately, controlling the molar ratio of the two to be 1:1.5–2. Under the condition of 20–25℃, add sodium carbonate solution dropwise to magnesium nitrate solution at a constant rate of 1–2 mL / min, while maintaining a magnetic stirring speed of 500–600 rpm. Keep the reaction pH at 9.0±0.2. After the reaction is completed, let the precipitate stand for 1–2 hours to promote the full formation and growth of crystal nuclei.

[0011] Subsequently, the precipitate was separated by vacuum filtration and washed with deionized water until the conductivity of the filtrate was less than 50 μS / cm to remove soluble impurities. The resulting precursor was dried at 100–105 °C for 10–12 h to obtain basic magnesium carbonate powder.

[0012] Secondly, the dried precursor was placed in a muffle furnace and heated to 450–500°C at a heating rate of 3–5°C / min, and held for 2–3 hours. After decomposition, nano-magnesium oxide powder with a particle size distribution of 20–50 nm was obtained.

[0013] Finally, surface modification was performed by dispersing nano-magnesium oxide in anhydrous ethanol and ultrasonically dispersing for 20–30 min. Separately, a 2 wt% stearic acid ethanol solution was prepared in advance and added dropwise to the magnesium oxide dispersion at 35–40 °C for about 20–30 min. The reaction was then stirred for 1–2 h to allow stearic acid molecules to form an organic coating layer by directional bonding between the carboxyl groups and the hydroxyl groups on the surface of magnesium oxide. After removing the solvent by rotary evaporation, the product was vacuum dried at 70–80 °C for 5–6 h to obtain highly active stearic acid-modified nano-magnesium oxide powder with a specific surface area of ​​about 120 m² / g.

[0014] To further optimize this technical solution, the core-shell cold-resistant composite powder includes a core and a shell;

[0015] The core is low-temperature activated vermiculite powder that has been cryogenically treated with liquid nitrogen, with a specific surface area ≥80 m² / g;

[0016] The outer shell is a silane coupling agent coating layer with a thickness of 50–100 nm. The silane coupling agent is a methyl vinyl silane coupling agent and a phenyl modified vinyl silane coupling agent, wherein the mass ratio of the methyl vinyl silane coupling agent and the phenyl modified vinyl silane coupling agent is 7:3.

[0017] To further optimize this technical solution, the preparation steps of the core-shell cold-resistant composite powder are as follows:

[0018] First, natural vermiculite powder with a particle size of 80–120 μm was placed in a liquid nitrogen freezing bath and rapidly frozen at −196℃ for 20–30 min to induce microcracks in the vermiculite flakes and expose more active sites. Subsequently, the frozen vermiculite powder was dried in a vacuum drying oven at 50–60℃ for 3–4 h to remove residual nitrogen and moisture from the surface, yielding low-temperature activated vermiculite powder.

[0019] Next, a silane coupling agent coating solution was prepared by mixing methyl vinyl silane coupling agent and phenyl modified vinyl silane coupling agent at a mass ratio of 7:3, and adding 0.5% platinum catalyst and 0.24% hydrogen-containing silicone oil crosslinking agent (by mass of total adhesive) to adjust the solid content to 19–20 wt%. Low-temperature activated vermiculite powder was added to the coating solution and dispersed at 1800–2000 rpm for 20–30 min using a high-speed shear emulsifier to ensure that the silane coupling agent is uniformly adsorbed on the particle surface.

[0020] Finally, pre-vulcanization is carried out at 85–90℃ for 1–2 hours to form a silane coupling agent coating layer with a thickness of 50–100 nm, thus obtaining a core-shell cold-resistant composite powder.

[0021] To further optimize this technical solution, the antimony-boron synergistic flame retardant is composed of antimony trioxide and zinc borate@MOF framework material, and the mass ratio of antimony trioxide to zinc borate@MOF framework material is 3:2.

[0022] The MOF framework material is ZIF-8, which can be used as a carrier to directionally release zinc borate.

[0023] To further optimize this technical solution, the preparation steps of the antimony-boron synergistic flame retardant are as follows:

[0024] First, take antimony trioxide powder with a particle size of 1–3 μm, place it in a planetary ball mill, and grind it at 400–500 rpm for 1–2 hours;

[0025] Subsequently, MOF-supported zinc borate was prepared by dissolving Zn(NO3)2·6H2O and 2-methylimidazole in methanol at a molar ratio of 1:7–8 and stirring at room temperature for 10–12 h to obtain ZIF-8 crystals with a regular polyhedral structure. The pre-synthesized zinc borate powder was dispersed in an ethanol solution, and then the ZIF-8 suspension was added. The mixture was stirred at 50–60 °C for 3–4 h to allow the zinc borate particles to embed into the MOF framework through electrostatic adsorption and pore confinement. After centrifugation and vacuum drying at 70–80 °C for 10–12 h, zinc borate@MOF framework material was obtained.

[0026] Finally, zinc borate@MOF framework material and antimony trioxide are mixed evenly at a mass ratio of 3:2 to obtain antimony-boron synergistic flame retardant.

[0027] To further optimize this technical solution, the anti-salt and alkali agent includes modified zeolite powder and nano-montmorillonite, with a mass ratio of 3:1 between the zeolite powder and the nano-montmorillonite.

[0028] To further optimize this technical solution, the 14S-FL, TAIC, and TMPTMA form an interpenetrating cross-linked network structure;

[0029] 14S-FL is used as the main crosslinking agent, TAIC as the free radical initiator, and TMPTMA as the co-crosslinking agent. The three form a crosslinking system under thermal initiation conditions, which simultaneously forms C–C covalent bonds and C–O–C bonds between polymer molecular chains to construct an interpenetrating crosslinking network.

[0030] A method for preparing a chlorinated polyethylene sheath material for cables, based on the above-mentioned chlorinated polyethylene sheath material, includes the following preparation steps:

[0031] S1, Nanofiller pretreatment;

[0032] Nano-SiO2, nano-magnesium oxide and titanate coupling agent are mixed at 120℃ for 10 minutes to complete the surface activation treatment and obtain a pretreated mixture.

[0033] S2, low-temperature phase mixing;

[0034] Chlorinated polyethylene is uniformly mixed with core-shell cold-resistant composite powder, POE-g-AA, cold-resistant plasticizer, carbon black N330 and pretreatment mixture at 80–90℃.

[0035] S3, cross-linking agent premixing and activation;

[0036] Add 14S-FL, TAIC and TMPTMA to the rubber compound at 80-90℃;

[0037] S4, Functional Synergistic Blending;

[0038] Crosslinked premixed material is blended with antimony-boron synergistic flame retardant, heat-resistant plasticizer, salt and alkali resistant agent and antioxidant in a screw extruder to obtain functional modified material;

[0039] S5, sheath extrusion vulcanization;

[0040] The functional modified material is formed by extrusion molding, vulcanization temperature is 170–180℃, dynamic reaction is 5–10 minutes, forming a network of interpenetrating C–C and C–O–C bonds, and then cooled and shaped to obtain a cable sheath with stable geometric dimensions.

[0041] S6. Construction of a salt and alkali protective layer;

[0042] After vulcanization, the sheath is impregnated with a 5μm thick perfluoropolyether coating, dried, cured, and aged to improve its salt spray resistance to level 6.

[0043] Compared with the prior art, the present invention provides a chlorinated polyethylene sheath material for cables and a method for preparing it, which has the following beneficial effects:

[0044] This cable uses chlorinated polyethylene (CPE) sheath material and its preparation method. By introducing POE-g-AA, core-shell cold-resistant composite powder, and cold-resistant plasticizer into the CPE matrix, and combining this with a staged activation mixing process and a dynamic cross-linked network constructed with 14S-FL, TAIC, and TMPTMA, the material maintains excellent flexibility and anti-brittleness at -50℃, while significantly improving heat resistance and creep resistance at high temperatures. Through the synergistic effect of antimony-boron synergistic flame retardant, nano-magnesium oxide, nano-SiO2, and carbon black N330, the material exhibits… It possesses excellent flame retardancy and reinforcing properties, with flame retardancy efficiency improved by approximately 40% in saline-alkali environments and salt spray resistance reaching level 6. Combined with anti-salt and alkali agents and a perfluoropolyether coating, the sheath does not crack or experience performance degradation during long-term operation in marine and saline-alkali soil environments. Furthermore, the aging is delayed under the synergistic effect of heat-resistant plasticizers and anti-aging agents. As a result, the sheath material simultaneously possesses high cold resistance, excellent heat resistance, outstanding flame retardancy, good torsion resistance, and salt and alkali corrosion resistance, which can meet the long-term stable use requirements of wind power cables in complex environments in both northern and southern regions and offshore wind farms. Attached Figure Description

[0045] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1This is a schematic flowchart of a method for preparing chlorinated polyethylene sheath material for cables according to the present invention. Detailed Implementation

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0048] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0049] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single embodiment or an embodiment selectively excluded from other embodiments.

[0050] A chlorinated polyethylene sheathing material for cables comprises the following formula in parts by weight:

[0051] 85–88 parts chlorinated polyethylene, 12–15 parts POE-g-AA, 8.5–9 parts nano magnesium oxide, 4–5 parts antimony-boron synergistic flame retardant, 16–18 parts core-shell cold-resistant composite powder, 12–14 parts nano SiO2, 10–11 parts carbon black N330, 10–11 parts cold-resistant plasticizer, 8.5–9 parts heat-resistant plasticizer, 2.5–3 parts TAIC, 2.8–3.2 parts 14S-FL, 0.8–1 part TMPTMA, 1.2–1.3 parts titanate coupling agent, 2–3 parts anti-salt and alkali agent, 2–3 parts antioxidant.

[0052] The chlorinated polyethylene is the base resin and serves as the main film-forming material, and the chlorine content of the chlorinated polyethylene is 35%.

[0053] The nano-magnesium oxide is a highly active stearic acid-modified nano-magnesium oxide powder, and the modification method includes:

[0054] First, prepare 0.3–0.5 mol / L magnesium nitrate solution and 0.6–0.8 mol / L sodium carbonate solution separately, controlling the molar ratio of the two to be 1:1.5–2. Under the condition of 20–25℃, add sodium carbonate solution dropwise to magnesium nitrate solution at a constant rate of 1–2 mL / min, while maintaining a magnetic stirring speed of 500–600 rpm. Keep the reaction pH at 9.0±0.2. After the reaction is completed, let the precipitate stand for 1–2 hours to promote the full formation and growth of crystal nuclei.

[0055] Subsequently, the precipitate was separated by vacuum filtration and washed with deionized water until the conductivity of the filtrate was less than 50 μS / cm to remove soluble impurities. The resulting precursor was dried at 100–105 °C for 10–12 h to obtain basic magnesium carbonate powder.

[0056] Secondly, the dried precursor was placed in a muffle furnace and heated to 450–500°C at a heating rate of 3–5°C / min, and held for 2–3 hours. After decomposition, nano-magnesium oxide powder with a particle size distribution of 20–50 nm was obtained.

[0057] Finally, surface modification was performed by dispersing nano-magnesium oxide in anhydrous ethanol and ultrasonically dispersing for 20–30 min. Separately, a 2 wt% stearic acid ethanol solution was prepared in advance and added dropwise to the magnesium oxide dispersion at 35–40 °C for about 20–30 min. The reaction was then stirred for 1–2 h to allow stearic acid molecules to form an organic coating layer by directional bonding between the carboxyl groups and the hydroxyl groups on the surface of magnesium oxide. After removing the solvent by rotary evaporation, the product was vacuum dried at 70–80 °C for 5–6 h to obtain highly active stearic acid-modified nano-magnesium oxide powder with a specific surface area of ​​about 120 m² / g.

[0058] The core-shell cold-resistant composite powder includes a core and a shell;

[0059] The core is low-temperature activated vermiculite powder that has been cryogenically treated with liquid nitrogen, with a specific surface area ≥80 m² / g;

[0060] The outer shell is a silane coupling agent coating layer with a thickness of 50–100 nm. The silane coupling agent is a methyl vinyl silane coupling agent and a phenyl modified vinyl silane coupling agent, wherein the mass ratio of the methyl vinyl silane coupling agent and the phenyl modified vinyl silane coupling agent is 7:3.

[0061] The preparation steps of the core-shell cold-resistant composite powder are as follows:

[0062] First, natural vermiculite powder with a particle size of 80–120 μm was placed in a liquid nitrogen freezing bath and rapidly frozen at −196℃ for 20–30 min to induce microcracks in the vermiculite flakes and expose more active sites. Subsequently, the frozen vermiculite powder was dried in a vacuum drying oven at 50–60℃ for 3–4 h to remove residual nitrogen and moisture from the surface, yielding low-temperature activated vermiculite powder.

[0063] Next, a silane coupling agent coating solution was prepared by mixing methyl vinyl silane coupling agent and phenyl modified vinyl silane coupling agent at a mass ratio of 7:3, and adding 0.5% platinum catalyst and 0.24% hydrogen-containing silicone oil crosslinking agent (by weight of the total adhesive) to adjust the solid content to 19–20 wt%. Low-temperature activated vermiculite powder was added to the coating solution and dispersed at 1800–2000 rpm for 20–30 min using a high-speed shear emulsifier to ensure uniform adsorption of the silane coupling agent onto the particle surface.

[0064] Finally, pre-vulcanization is carried out at 85–90℃ for 1–2 hours to form a silane coupling agent coating layer with a thickness of 50–100 nm, thus obtaining a core-shell cold-resistant composite powder.

[0065] The antimony-boron synergistic flame retardant is composed of antimony trioxide and zinc borate@MOF framework material, and the mass ratio of antimony trioxide to zinc borate@MOF framework material is 3:2.

[0066] The MOF framework material is ZIF-8, which can be used as a carrier to directionally release zinc borate.

[0067] The preparation steps of the antimony-boron synergistic flame retardant are as follows:

[0068] First, take antimony trioxide powder with a particle size of 1–3 μm, place it in a planetary ball mill, and grind it at 400–500 rpm for 1–2 hours;

[0069] Subsequently, MOF-supported zinc borate was prepared by dissolving Zn(NO3)2·6H2O and 2-methylimidazole in methanol at a molar ratio of 1:7–8 and stirring at room temperature for 10–12 h to obtain ZIF-8 crystals with a regular polyhedral structure. The pre-synthesized zinc borate powder was dispersed in an ethanol solution, and then the ZIF-8 suspension was added. The mixture was stirred at 50–60 °C for 3–4 h to allow the zinc borate particles to embed into the MOF framework through electrostatic adsorption and pore confinement. After centrifugation and vacuum drying at 70–80 °C for 10–12 h, zinc borate@MOF framework material was obtained.

[0070] Finally, zinc borate@MOF framework material and antimony trioxide are mixed evenly at a mass ratio of 3:2 to obtain antimony-boron synergistic flame retardant.

[0071] The salt-alkali resistant agent comprises modified zeolite powder and nano-montmorillonite, wherein the mass ratio of zeolite powder to nano-montmorillonite is 3:1.

[0072] The 14S-FL, TAIC, and TMPTMA form an interpenetrating cross-linked network structure.

[0073] 14S-FL is used as the main crosslinking agent, TAIC as the free radical initiator, and TMPTMA as the co-crosslinking agent. The three form a crosslinking system under thermal initiation conditions, which simultaneously forms C–C covalent bonds and C–O–C bonds between polymer molecular chains to construct an interpenetrating crosslinking network.

[0074] Reference Figure 1 A method for preparing a chlorinated polyethylene sheath material for cables, based on the above-mentioned chlorinated polyethylene sheath material, includes the following preparation steps:

[0075] S1, Nanofiller pretreatment;

[0076] Nano-SiO2, nano-magnesium oxide, and titanate coupling agent are added to a mixer or kneading vessel. The jacket temperature is set to 120℃, the rotor speed to 60–80 rpm, and the vacuum degree to ≤−0.06MPa. The mixture is kept at this temperature for 10 min to maintain the shearing and coupling reaction, allowing an organic interface layer to be formed on the inorganic surface, resulting in pretreated mixture A. After unloading, the mixture is dried at 80℃ for 30 min to remove free volatiles and then stored for later use.

[0077] S2, Low-temperature phase mixing;

[0078] Under a mixer temperature of 90℃, chlorinated polyethylene is first added and plasticized for 2 minutes. Then, core-shell cold-resistant composite powder, POE-g-AA, cold-resistant plasticizer, carbon black N330, and pretreatment mixture A are added sequentially. The mixing speed is 40–60 rpm, and vacuum is applied twice for 20–30 seconds to remove entrained gases. Mixing continues until the torque plateau stabilizes (typically 6–8 minutes). The mixture is then sheeted and cooled to ≤40℃ to obtain compound B. This step completes phase dispersion and flexible phase construction within a low-temperature window, providing a uniform matrix for subsequent crosslinking.

[0079] S3, cross-linking agent premixing and activation;

[0080] Return compound B to the internal mixer or open mixing mill, heat to 80-90℃, add 14S-FL, TAIC, and TMPTMA all at once under dynamic conditions for 3 minutes, rotate at 50-70 rpm, and roll out into sheets to obtain crosslinked premix C.

[0081] S4, Functional Synergistic Blending;

[0082] Crosslinked premix C is co-blended with an antimony-boron synergistic flame retardant, a heat-resistant plasticizer, a salt-alkali resistant agent, and an antioxidant in a Banbury mixer. The antimony-boron synergistic flame retardant is then added uniformly, followed by the heat-resistant plasticizer, salt-alkali resistant agent, and antioxidant in sequence, with a total mixing residence time of 60–120 s. The mixture is then sheeted to obtain the functionally modified material D. This step introduces a flame-retardant / heat-resistant / salt-alkali resistant and long-term stable system without damaging the established crosslinked framework, achieving multifunctional integration.

[0083] S5, sheath extrusion vulcanization;

[0084] A dedicated extrusion production line for cable sheathing is used, with functionally modified material D as the feed source; the barrel temperature range for a single-screw (or co-rotating twin-screw) is 60 / 65 / 70 / 75℃, and the die head temperature is 75℃; the die compression ratio is 2.5–3.5, and the linear speed is 5–20 m / min. After extrusion, it enters a continuous vulcanization section: vulcanization temperature 170–180℃, equivalent vulcanization time 5–8 min (based on sheath thickness and online hardness as verification indicators). The cooling water tank temperature is 20–25℃, and the vacuum degree of the sizing sleeve is −0.02 to −0.04 MPa to complete the control of geometric dimensions and roundness.

[0085] S6. Construction of a salt and alkali protective layer;

[0086] After vulcanization and cooling, the outer surface of the sheath is cleaned and activated (by plasma or ethanol wiping), then impregnated with a perfluoropolyether coating. The coating has a solid content of 8–12 wt%, is impregnated for 60–90 seconds at a lifting speed of 50–100 mm / s, and allowed to stand at room temperature for 10 minutes before drying at 80°C for 20–30 minutes to form a 5 μm (±1 μm) continuous film. After aging for 24 hours (23°C / 50%RH), it is stored in the warehouse. This film, together with the aforementioned anti-salt and alkali agent, forms a synergistic barrier, enabling the sheath to achieve a salt spray resistance rating of 6 and maintain stable mechanical and electrical properties under multi-cycle humid heat / salt and alkali environments.

[0087] Example 1:

[0088] 85 parts chlorinated polyethylene, 15 parts POE-g-AA (acrylic acid grafting), 9 parts nano magnesium oxide, 5 parts antimony-boron synergistic flame retardant, 18 parts core-shell cold-resistant composite powder, 12 parts nano SiO2 (gas phase method), 10 parts carbon black N330 (DBP absorption value 102cm³ / 100g), 10 parts cold-resistant plasticizer (dioctyl adipate), 9 parts heat-resistant plasticizer (trioctyl trimellitate), 3 parts TAIC (tracene propyl isocyanurate), 2.8 parts 14S-FL (di(tert-butylperoxypropylbenzene)benzene), 0.8 parts TMPTMA (trimethylolpropane trimethacrylate), 1.2 parts titanate coupling agent (NDZ-201), 3 parts salt and alkali resistant agent, 2 parts antioxidant (RD+4010NA).

[0089] The chlorinated polyethylene is the base resin and the main film-forming material, with the model number CPE 135B. The chlorinated polyethylene has a chlorine content of 35%.

[0090] The nano-magnesium oxide is a highly active stearic acid-modified nano-magnesium oxide powder, and the modification method includes:

[0091] First, prepare 0.5 mol / L magnesium nitrate solution and 0.8 mol / L sodium carbonate solution separately, controlling the molar ratio of the two to be 1:1.5. Under the condition of 25℃, add sodium carbonate solution dropwise to magnesium nitrate solution at a constant rate of 2 mL / min, while maintaining magnetic stirring speed of 600 rpm. Keep the reaction pH at 9.0±0.2. After the reaction is completed, let the precipitate stand for 2 hours to promote the full formation and growth of crystal nuclei.

[0092] Subsequently, the precipitate was separated by vacuum filtration and washed with deionized water until the conductivity of the filtrate was less than 50 μS / cm to remove soluble impurities. The resulting precursor was dried at 105 °C for 12 h to obtain basic magnesium carbonate powder.

[0093] Secondly, the dried precursor was placed in a muffle furnace and heated to 500°C at a heating rate of 5°C / min, and held for 3 hours. After decomposition, nano-magnesium oxide powder with a particle size distribution of 20–50 nm was obtained.

[0094] Finally, surface modification was performed by dispersing nano-magnesium oxide in anhydrous ethanol and ultrasonically dispersing for 30 min. Separately, a 2 wt% stearic acid ethanol solution was prepared in advance and added dropwise to the magnesium oxide dispersion at 40 °C for about 30 min. The reaction was then stirred for 2 h to allow stearic acid molecules to form an organic coating layer by directional bonding between the carboxyl groups and the hydroxyl groups on the surface of magnesium oxide. After removing the solvent by rotary evaporation, the product was vacuum dried at 80 °C for 6 h to obtain highly active stearic acid-modified nano-magnesium oxide powder with a specific surface area of ​​about 120 m² / g.

[0095] The core-shell cold-resistant composite powder includes a core and a shell;

[0096] The core is low-temperature activated vermiculite powder that has been cryogenically treated with liquid nitrogen, with a specific surface area ≥80 m² / g;

[0097] The outer shell is a silane coupling agent coating layer with a thickness of 50–100 nm. The silane coupling agent is a methyl vinyl silane coupling agent and a phenyl modified vinyl silane coupling agent, wherein the mass ratio of the methyl vinyl silane coupling agent and the phenyl modified vinyl silane coupling agent is 7:3.

[0098] The preparation steps of the core-shell cold-resistant composite powder are as follows:

[0099] First, natural vermiculite powder with a particle size of 80–120 μm was placed in a liquid nitrogen freezing bath and rapidly frozen at −196℃ for 30 min to induce microcracks in the vermiculite flakes and expose more active sites. Subsequently, the frozen vermiculite powder was dried in a vacuum drying oven at 60℃ for 4 h to remove residual nitrogen and moisture from the surface, yielding low-temperature activated vermiculite powder.

[0100] Next, a silane coupling agent coating solution was prepared by mixing methyl vinyl silane coupling agent and phenyl modified vinyl silane coupling agent at a mass ratio of 7:3, and adding 0.5% platinum catalyst and 0.24% hydrogen-containing silicone oil crosslinking agent (by weight of the total adhesive) to adjust the solid content to 19–20 wt%. Low-temperature activated vermiculite powder was added to the coating solution and dispersed at 1800–2000 rpm for 20–30 min using a high-speed shear emulsifier to ensure uniform adsorption of the silane coupling agent onto the particle surface.

[0101] Finally, pre-vulcanization was carried out at 90℃ for 2 hours to form a silane coupling agent coating layer with a thickness of 50–100 nm, thus obtaining a core-shell cold-resistant composite powder.

[0102] The antimony-boron synergistic flame retardant is composed of antimony trioxide and zinc borate@MOF framework material, and the mass ratio of antimony trioxide to zinc borate@MOF framework material is 3:2.

[0103] The MOF framework material is ZIF-8, which can be used as a carrier to directionally release zinc borate.

[0104] The preparation steps of the antimony-boron synergistic flame retardant are as follows:

[0105] First, antimony trioxide powder with a particle size of 1–3 μm was placed in a planetary ball mill and ground at 500 rpm for 2 hours.

[0106] Subsequently, MOF-supported zinc borate was prepared by dissolving Zn(NO3)2·6H2O and 2-methylimidazole in methanol at a molar ratio of 1:8 and stirring at room temperature for 12 h to obtain ZIF-8 crystals with a regular polyhedral structure. The pre-synthesized zinc borate powder was dispersed in an ethanol solution, and then the ZIF-8 suspension was added. The mixture was stirred at 60 °C for 4 h to allow the zinc borate particles to embed into the MOF framework through electrostatic adsorption and pore confinement. After centrifugation and vacuum drying at 80 °C for 12 h, zinc borate@MOF framework material was obtained.

[0107] Finally, zinc borate@MOF framework material and antimony trioxide are mixed evenly at a mass ratio of 3:2 to obtain antimony-boron synergistic flame retardant.

[0108] The salt-alkali resistant agent comprises modified zeolite powder and nano-montmorillonite, wherein the mass ratio of zeolite powder to nano-montmorillonite is 3:1.

[0109] The chlorinated polyethylene sheath material for cables is prepared according to the following steps:

[0110] S1, Nanofiller pretreatment;

[0111] Nano-SiO2, nano-magnesium oxide, and titanate coupling agent are added to a mixer or kneading vessel. The jacket temperature is set to 120℃, the rotor speed to 80 rpm, and the vacuum degree to ≤−0.06MPa. The mixture is kept at this temperature for 10 min to maintain the shearing and coupling reaction, thereby obtaining an organic interface layer on the inorganic surface, resulting in pretreated mixture A. After unloading, the mixture is dried at 80℃ for 30 min to remove free volatiles and then stored for later use.

[0112] S2, Low-temperature phase mixing;

[0113] Under a mixer temperature of 90℃, chlorinated polyethylene was first added and plasticized for 2 minutes. Then, core-shell cold-resistant composite powder, POE-g-AA, cold-resistant plasticizer, carbon black N330, and pretreatment mixture A were added sequentially. The mixer speed was 60 rpm, and vacuum was applied twice for 30 seconds to remove entrained gases. Mixing continued until the torque plateau stabilized (8 minutes). The mixture was then sheeted and cooled to ≤40℃ to obtain compound B. This step completes phase dispersion and flexible phase construction within a low-temperature window, providing a uniform matrix for subsequent crosslinking.

[0114] S3, cross-linking agent premixing and activation;

[0115] Return compound B to the internal mixer or open mixing mill, heat to 80-90℃, add 14S-FL, TAIC, and TMPTMA all at once under dynamic conditions for 3 minutes, rotate at 50-70 rpm, and roll out into sheets to obtain crosslinked premix C.

[0116] S4, Functional Synergistic Blending;

[0117] Crosslinked premix C is co-blended with an antimony-boron synergistic flame retardant, a heat-resistant plasticizer, a salt-alkali resistant agent, and an antioxidant in a Banbury mixer. The antimony-boron synergistic flame retardant is then added uniformly, followed by the heat-resistant plasticizer, salt-alkali resistant agent, and antioxidant in sequence, with a total mixing residence time of 60–120 s. The mixture is then sheeted to obtain the functionally modified material D. This step introduces a flame-retardant / heat-resistant / salt-alkali resistant and long-term stable system without damaging the established crosslinked framework, achieving multifunctional integration.

[0118] S5, sheath extrusion vulcanization;

[0119] A dedicated extrusion production line for cable sheathing is used, with functionally modified material D as the feed source; the barrel temperature range for a single screw (or co-rotating twin screw) is 60 / 65 / 70 / 75℃, and the die head temperature is 75℃; the die compression ratio is 2.5–3.5, and the linear speed is 5–20 m / min. After demolding, it enters the continuous vulcanization section: vulcanization temperature 170–180℃, equivalent vulcanization time 5–8 min (based on sheath thickness and online hardness as verification indicators). The cooling water tank temperature is 20–25℃, and the vacuum degree of the sizing sleeve is −0.02 to −0.04 MPa to complete the control of geometric dimensions and roundness. S6, Construction of the salt and alkali protective layer;

[0120] After vulcanization and cooling, the outer surface of the sheath is cleaned and activated (by plasma or ethanol wiping), then impregnated with a perfluoropolyether coating. The coating has a solid content of 8–12 wt%, is impregnated for 90 seconds at a lifting speed of 100 mm / s, and allowed to stand at room temperature for 10 minutes before drying at 80°C for 30 minutes to form a 5 μm (±1 μm) continuous film. After aging for 24 hours (23°C / 50%RH), it is stored in the warehouse. This film, together with the aforementioned salt and alkali resistance agent, forms a synergistic barrier, enabling the sheath to achieve a salt spray resistance rating of 6 and maintain stable mechanical and electrical properties under multi-cycle humid heat / salt and alkali environments.

[0121] Example 2:

[0122] 88 parts chlorinated polyethylene, 12 parts POE-g-AA (acrylic acid grafting), 8.5 parts nano magnesium oxide, 4 parts antimony-boron synergistic flame retardant, 16 parts core-shell cold-resistant composite powder, 14 parts nano SiO2 (gas phase method), 10 parts carbon black N330 (DBP absorption value 102cm³ / 100g), 11 parts cold-resistant plasticizer (dioctyl adipate), 8.5 parts heat-resistant plasticizer (trioctyl trimellitate), 2.5 parts TAIC (tracene propyl isocyanurate), 3.2 parts 14S-FL (di(tert-butylperoxypropylbenzene)benzene), 1 part TMPTMA (trimethylolpropane trimethacrylate), 1.3 parts titanate coupling agent (NDZ-201), 2 parts salt and alkali resistant agent, 2 parts antioxidant (RD+4010NA).

[0123] The formulation and preparation method of the chlorinated polyethylene sheath material for cables are the same as in Example 1.

[0124] Using Examples 1 and 2 as test objects, the performance of chlorinated polyethylene sheathing material for cables was tested and compared with the national standard, as shown in Table 1.

[0125] Table 1 Performance Comparison Table

[0126] Test Project Example 1 Example 2 GB / T 33606-2017 GB / T 29631-2013 Test Standards Tensile strength (MPa) 15.3 16 ≥10 ≥10 2951.11-2008 Elongation at break (%) 488 410 ≥300 ≥250 2951.11-2008 Hardness (Shore A) 67 69 -- -- GB / T 531.1-2008 Elongation retention rate (%) at -50℃ for 4 hours 120 90 ≥30 ≥30 2951.14-2008 -50℃ low temperature shock No cracks No cracks No cracks No cracks 2951.14-2008 Aging at 135℃ for 168 hours: 2951.12-2008 Elongation change rate (%) -14 -21 ≤-40 ≤-30 Intensity change rate (%) 18 25 ≤-30 ≤-30 100℃×24h oil immersion: GB / T 2951.21-2008 Intensity change rate (%) -4.5 -4.5 ≤-40 ≤-40 Elongation change rate (%) -13 -10 ≤-40 ≤-40 JB / T 10696.7-2007 Tear strength (N / mm) 7.9 6.5 ≥5 ≥5 JB / T 10696.7-2007 Dynamic torsional fatigue (-50℃) >3800 times >3800 times 2000 2000 GB / T 29631-20213 5% salt spray test (500h) Level 6 Level 6 - Level 6 GB / T 2423.18-2000

[0127] As shown in Table 1, the test results demonstrate that the chlorinated polyethylene sheath material for cables in this embodiment exhibits outstanding comprehensive performance: its tensile strength reaches 15.3 MPa, and its elongation at break is as high as 488%, both significantly exceeding the requirements of current standards. At -50℃, the elongation retention rate reaches 120%, and no cracks are observed during low-temperature impact, proving the material's excellent cold resistance and low-temperature toughness. Under 135℃×168h heat aging conditions, the elongation and strength change rates are -14% and 18%, respectively, far below the standard limits, demonstrating excellent heat aging stability. After immersion in mineral oil at 100℃×24h, the strength change rate is only -4.5%, and the elongation change rate is -13%, showing good oil resistance. In terms of mechanical properties, the tear strength reaches 7.9 N / mm, and the dynamic torsional fatigue test exceeds 3800 cycles at -40℃, significantly exceeding the standard requirement of 2000 cycles, ensuring the long-term reliability of the material under complex stress environments. Furthermore, after a 500-hour salt spray test at 5% concentration, the sheath surface achieved a grade 6 rating, indicating that the material possesses excellent resistance to salt and alkali and corrosion. In summary, the sheath material of Example 1 simultaneously achieves high cold resistance, excellent heat resistance, good oil resistance, outstanding flame retardancy, and outstanding mechanical durability, fully meeting the long-term stable use requirements of wind power cables in extreme environments.

[0128] Meanwhile, in field tests of wind power cables conducted at the Zhangbei wind farm, the sheath material of this invention withstood over 3000 bending cycles at -45℃ without cracking, fully verifying its excellent cold resistance. Furthermore, after being buried in saline-alkali soil for 18 months, the volume change rate was less than 2%, significantly better than the national standard requirement of ≤5%, indicating its superior salt and alkali resistance and long-term stability. Regarding key performance aspects, the glass transition temperature (Tg) of the sheath material of this invention, as determined by DSC testing, is -68℃, far lower than the Tg ≥ -25℃ of traditional chlorinated polyethylene sheaths, demonstrating a significant advantage in maintaining flexibility under low-temperature conditions. Its torsional resistance also achieved a breakthrough, reaching 20,000 cycles in ±180° dynamic torsional fatigue testing, twice the national standard requirement (10,000 cycles), fully demonstrating the material's high reliability and application value under extreme service conditions.

[0129] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A chlorinated polyethylene sheathing material for cables, characterized in that, The formula includes the following parts by weight: 85–88 parts chlorinated polyethylene, 12–15 parts POE-g-AA, 8.5–9 parts nano magnesium oxide, 4–5 parts antimony-boron synergistic flame retardant, 16–18 parts core-shell cold-resistant composite powder, 12–14 parts nano SiO2, 10–11 parts carbon black N330, 10–11 parts cold-resistant plasticizer, 8.5–9 parts heat-resistant plasticizer, 2.5–3 parts TAIC, 2.8–3.2 parts 14S-FL, 0.8–1 part TMPTMA, 1.2–1.3 parts titanate coupling agent, 2–3 parts anti-salt and alkali agent, 2–3 parts antioxidant.

2. The chlorinated polyethylene sheath material for cables according to claim 1, characterized in that, The chlorinated polyethylene is the base resin and serves as the main film-forming material. The chlorine content of the chlorinated polyethylene is 35%.

3. The chlorinated polyethylene sheathing material for cables according to claim 1, characterized in that, The nano-magnesium oxide is a highly active stearic acid-modified nano-magnesium oxide powder, and the modification method includes: First, prepare 0.3–0.5 mol / L magnesium nitrate solution and 0.6–0.8 mol / L sodium carbonate solution separately, controlling the molar ratio of the two to be 1:1.5–2. Under the condition of 20–25℃, add sodium carbonate solution dropwise to magnesium nitrate solution at a constant rate of 1–2 mL / min, while maintaining a magnetic stirring speed of 500–600 rpm. Keep the reaction pH at 9.0±0.

2. After the reaction is completed, let the precipitate stand for 1–2 hours to promote the full formation and growth of crystal nuclei. Subsequently, the precipitate was separated by vacuum filtration and washed with deionized water until the conductivity of the filtrate was less than 50 μS / cm to remove soluble impurities. The resulting precursor was dried at 100–105 °C for 10–12 h to obtain basic magnesium carbonate powder. Secondly, the dried precursor was placed in a muffle furnace and heated to 450–500°C at a heating rate of 3–5°C / min, and held for 2–3 hours. After decomposition, nano-magnesium oxide powder with a particle size distribution of 20–50 nm was obtained. Finally, surface modification was performed by dispersing nano-magnesium oxide in anhydrous ethanol and ultrasonically dispersing for 20–30 min. Separately, a 2 wt% stearic acid ethanol solution was prepared in advance and added dropwise to the magnesium oxide dispersion at 35–40 °C for about 20–30 min. The reaction was then stirred for 1–2 h to allow stearic acid molecules to form an organic coating layer by directional bonding between the carboxyl groups and the hydroxyl groups on the surface of magnesium oxide. After removing the solvent by rotary evaporation, the product was vacuum dried at 70–80 °C for 5–6 h to obtain highly active stearic acid-modified nano-magnesium oxide powder with a specific surface area of ​​about 120 m² / g.

4. The chlorinated polyethylene sheath material for cables according to claim 1, characterized in that, The core-shell cold-resistant composite powder includes a core and a shell; The core is low-temperature activated vermiculite powder that has been cryogenically treated with liquid nitrogen, with a specific surface area ≥80 m² / g; The outer shell is a silane coupling agent coating layer with a thickness of 50–100 nm. The silane coupling agent is a methyl vinyl silane coupling agent and a phenyl modified vinyl silane coupling agent, wherein the mass ratio of the methyl vinyl silane coupling agent and the phenyl modified vinyl silane coupling agent is 7:

3.

5. The chlorinated polyethylene sheath material for cables according to claim 4, characterized in that, The preparation steps of the core-shell cold-resistant composite powder are as follows: First, natural vermiculite powder with a particle size of 80–120 μm was placed in a liquid nitrogen freezing bath and rapidly frozen at −196℃ for 20–30 min to induce microcracks in the vermiculite flakes and expose more active sites. Subsequently, the frozen vermiculite powder was dried in a vacuum drying oven at 50–60℃ for 3–4 h to remove residual nitrogen and moisture from the surface, yielding low-temperature activated vermiculite powder. Next, a silane coupling agent coating solution was prepared by mixing methyl vinyl silane coupling agent and phenyl modified vinyl silane coupling agent at a mass ratio of 7:3, and adding 0.5% platinum catalyst and 0.24% hydrogen-containing silane coupling agent (by weight of the total adhesive) to adjust the solid content to 19–20 wt%. Low-temperature activated vermiculite powder was added to the coating solution and dispersed at 1800–2000 rpm for 20–30 min using a high-speed shear emulsifier to ensure uniform adsorption of the silane coupling agent onto the particle surface. Finally, the mixture is premixed at 85–90℃ for 1–2 hours to form a silane coupling agent coating layer with a thickness of 50–100 nm, thus obtaining a core-shell cold-resistant composite powder.

6. The chlorinated polyethylene sheathing material for cables according to claim 1, characterized in that, The antimony-boron synergistic flame retardant is composed of antimony trioxide and zinc borate@MOF framework material, with the mass ratio of antimony trioxide to zinc borate@MOF framework material being 3:

2. The MOF framework material is ZIF-8, which can be used as a carrier to directionally release zinc borate.

7. The chlorinated polyethylene sheath material for cables according to claim 6, characterized in that, The preparation steps of the antimony-boron synergistic flame retardant are as follows: First, take antimony trioxide powder with a particle size of 1–3 μm, place it in a planetary ball mill, and grind it at 400–500 rpm for 1–2 hours; Subsequently, MOF-supported zinc borate was prepared by dissolving Zn(NO3)2·6H2O and 2-methylimidazole in methanol at a molar ratio of 1:7–8 and stirring at room temperature for 10–12 h to obtain ZIF-8 crystals with a regular polyhedral structure. The pre-synthesized zinc borate powder was dispersed in an ethanol solution, and then the ZIF-8 suspension was added. The mixture was stirred at 50–60 °C for 3–4 h to allow the zinc borate particles to embed into the MOF framework through electrostatic adsorption and pore confinement. After centrifugation and vacuum drying at 70–80 °C for 10–12 h, zinc borate@MOF framework material was obtained. Finally, zinc borate@MOF framework material and antimony trioxide are mixed evenly at a mass ratio of 3:2 to obtain antimony-boron synergistic flame retardant.

8. The chlorinated polyethylene sheathing material for cables according to claim 1, characterized in that, The salt-alkali resistant agent comprises modified zeolite powder and nano-montmorillonite, wherein the mass ratio of zeolite powder to nano-montmorillonite is 3:

1.

9. The chlorinated polyethylene sheathing material for cables according to claim 1, characterized in that, The 14S-FL, TAIC, and TMPTMA form an interpenetrating cross-linked network structure; 14S-FL is used as the main crosslinking agent, TAIC as the free radical initiator, and TMPTMA as the co-crosslinking agent. The three form a crosslinking system under thermal initiation conditions, which simultaneously forms C–C covalent bonds and C–O–C bonds between polymer molecular chains to construct an interpenetrating crosslinking network.

10. A method for preparing a chlorinated polyethylene sheath material for cables, comprising preparing the material based on the chlorinated polyethylene sheath material according to any one of claims 1-9, characterized in that, The preparation steps include the following: S1, Nanofiller pretreatment; Nano-SiO2, nano-magnesium oxide and titanate coupling agent are mixed at 120℃ for 10 minutes to complete the surface activation treatment and obtain a pretreated mixture. S2, Low-temperature phase mixing; Chlorinated polyethylene is uniformly mixed with core-shell cold-resistant composite powder, POE-g-AA, cold-resistant plasticizer, carbon black N330 and pretreatment mixture at 80–90℃. S3, cross-linking agent premixing and activation; Add 14S-FL, TAIC and TMPTMA to the rubber compound at 80-90℃; S4, Functional Synergistic Blending; Crosslinked premixed material is blended with antimony-boron synergistic flame retardant, heat-resistant plasticizer, salt and alkali resistant agent and antioxidant in a screw extruder to obtain functional modified material; S5, sheath extrusion vulcanization; The functional modified material is formed by extrusion molding, vulcanization temperature is 170–180℃, dynamic reaction is 5–10 minutes, forming a network of interpenetrating C–C and C–O–C bonds, and then cooled and shaped to obtain a cable sheath with stable geometric dimensions. S6. Construction of a salt and alkali protective layer; After vulcanization, the sheath is impregnated with a 5μm thick perfluoropolyether coating, dried, cured, and aged to improve its salt spray resistance to level 6.

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