Low-temperature-resistant and high-toughness cable outer sheath material and preparation method thereof

Abstract

The application belongs to the field of cable materials, and relates to a low-temperature-resistant and high-toughness cable outer sheath material and a preparation method thereof.Raw materials of the outer sheath material include polyolefin elastomer, ethylene-vinyl acetate copolymer, low-density polyethylene, high-density polyethylene, surface-modified magnesium oxide, compounded nucleating agent, bis(2-butoxyethyl) adipate, antioxidant, zinc stearate, paraffin and ethylene bis-stearamide.The surface-modified magnesium oxide is obtained by combined modification of bis(dioctyloxyphosphato) ethylene titanate and gamma-glycidoxypropyltrimethoxysilane; and the active components of the compounded nucleating agent are 2,2'-methylene-bis(4,6-di-tert-butylphenylphosphoric acid) alkaline aluminum and decanedioic acid diphenyl dihydrazide in a weight ratio of 1:1.5-3.The cable outer sheath material prepared by the application has excellent low-temperature resistance and toughness, low change rate of tensile strength and elongation at break after low-temperature treatment, and excellent overall performance.

Description

Technical Field

[0001] This invention belongs to the field of cable materials and relates to a low-temperature resistant and high-toughness cable outer sheath material and its preparation method. Background Technology

[0002] Cable sheath material is a crucial component of power cables, primarily protecting the cable core from mechanical damage, environmental corrosion, and climatic influences. With the widespread application of power cables in cold regions, high-altitude areas, and harsh outdoor environments, higher demands are placed on the low-temperature resistance and toughness of cable sheath materials. Traditional cable sheath materials mainly use single polymers such as polyethylene (PE) and polyvinyl chloride (PVC) as the matrix, which tend to harden and become brittle at low temperatures, leading to sheath cracking and loss of protection for the cable core.

[0003] To improve the low-temperature resistance of cable outer sheath materials, existing technologies often employ the following methods: first, adding flexible components such as polyolefin elastomer (POE) or ethylene-vinyl acetate copolymer (EVA) for blending modification; second, adding plasticizers to lower the glass transition temperature of the material; and third, adding inorganic fillers to improve the mechanical properties and thermal stability of the material. However, these methods have the following technical problems: the polarity differences between resins and fillers are significant, and direct blending easily leads to phase separation, resulting in a decrease in the material's mechanical properties; traditional plasticizers are prone to migration and precipitation during long-term use, leading to material performance degradation, and a significant decrease in toughness after high-temperature aging; inorganic fillers such as nano-magnesium oxide have strong surface polarity, making it difficult to disperse uniformly in a non-polar polyolefin matrix, and they tend to agglomerate, becoming stress concentration points and reducing the material's mechanical properties and low-temperature resistance; improving low-temperature resistance usually requires increasing the proportion of flexible components, but this reduces the material's tensile strength and dielectric strength, making it difficult to achieve a balance between rigidity and toughness.

[0004] Therefore, developing a cable outer sheath material that combines excellent low-temperature resistance, high toughness, and good electrical properties has significant practical application value. Summary of the Invention

[0005] To address the technical problems mentioned in the background art, the present invention provides a low-temperature resistant, high-toughness cable outer sheath material and its preparation method.

[0006] The raw material composition of the low-temperature resistant and high-toughness cable outer sheath material described in this invention is: polyolefin elastomer, ethylene-vinyl acetate copolymer, low-density polyethylene, high-density polyethylene, surface-modified magnesium oxide, compound nucleating agent, bis(2-butoxyethyl) adipic acid, antioxidant, zinc stearate, paraffin wax and ethylene bis-stearamide.

[0007] Furthermore, the surface-modified magnesium oxide was obtained by combining bis(dioctyloxypyrophosphate) ethylene titanate with γ-glycidyl etheroxypropyltrimethoxysilane.

[0008] Furthermore, the active ingredients of the compound nucleating agent are 2,2′-methylene-bis(4,6-di-tert-butylphenyl phosphate) basic aluminum and sebacate diphenyl dihydrazide in a weight ratio of 1:1.5-3, and also include the carrier silica.

[0009] Further, according to parts by weight, the raw materials for preparing the low-temperature resistant and high-toughness cable outer sheath material are: 5-10 parts polyolefin elastomer, 25-40 parts ethylene-vinyl acetate copolymer, 30-45 parts low-density polyethylene, 10-15 parts high-density polyethylene, 5-8 parts surface-modified magnesium oxide, 1.5-2.2 parts compound nucleating agent, 5-9 parts bis(2-butoxyethyl) adipic acid, 0.1-1 parts antioxidant, 0.2-0.8 parts zinc stearate, 0.5-1.5 parts paraffin wax, and 0.4-0.8 parts ethylene bis-stearamide.

[0010] Furthermore, the weight ratio of the active ingredient to the carrier in the compound nucleating agent is 0.6-1:1. The carrier includes silica.

[0011] Furthermore, the nucleating agent is obtained by mixing and grinding 2,2′-methylene-bis(4,6-di-tert-butylphenylphosphine) basic aluminum, sebacate diphenyldiacylhydrazine, and nano-silica.

[0012] Furthermore, the antioxidant includes at least one of antioxidant 1010 and antioxidant 168.

[0013] Furthermore, the preparation method of surface-modified magnesium oxide includes: dispersing nano-magnesium oxide in toluene, sonicating, adding bis(dioctyloxypyrophosphate) ethylene titanate and mixing, then adding γ-glycidyl etheroxypropyltrimethoxysilane hydrolysate and mixing, adding a catalyst, then heating and reacting, centrifuging, washing and drying to obtain the product.

[0014] Furthermore, the weight ratio of bis(dioctyloxypyrophosphate) ethylene titanate to γ-glycidoxypropyltrimethoxysilane is 1:0.5-1.5.

[0015] Furthermore, the catalyst comprises dibutyltin dilaurate. The amount of catalyst used is 0.05-0.2% of the weight of nano-magnesium oxide. The reaction temperature and time are 80-95℃ for 3-20 hours.

[0016] Furthermore, the hydrolysate of γ-glycidoxypropyltrimethoxysilane is obtained by mixing water and acid, then adding γ-glycidoxypropyltrimethoxysilane and stirring to hydrolyze. The acid includes acetic acid. The weight ratio of γ-glycidoxypropyltrimethoxysilane, water, and acid is 1:5-10:0.01-0.5.

[0017] Furthermore, in preparing the low-temperature resistant, high-toughness cable outer sheath material, surface-modified magnesium oxide is first co-extruded with a portion of low-density polyethylene and a portion of ethylene bis-stearamide to obtain a masterbatch, which is then used to prepare the outer sheath material. The low-density polyethylene constitutes 20%-99% of the total weight of the low-density polyethylene. The ethylene bis-stearamide constitutes 20%-85% of the total weight of the ethylene bis-stearamide.

[0018] This invention also provides a method for preparing a low-temperature resistant, high-toughness cable outer sheath material, comprising the following steps: (1) The surface-modified magnesium oxide is mixed with a portion of low-density polyethylene and a portion of ethylene bis-stearamide, extruded and granulated to obtain the masterbatch; (2) The polyolefin elastomer, ethylene-vinyl acetate copolymer, the balance of low-density polyethylene and high-density polyethylene are heated and mixed in a mixer, and bis(2-butoxyethyl) adipate is sprayed on. The mixture is continued to be mixed and discharged into a sealed container for standing and maturation to obtain the matured material. (3) Place the matured material, masterbatch, compound nucleating agent, antioxidant, zinc stearate, paraffin and the balance of ethylene bis-stearamide in a mixer and mix them to obtain the mixed material. (4) Transfer the kneaded material to an extruder, extrude and granulate to obtain the final product.

[0019] Further, in step (1), the extrusion temperature is: Zone 1: 130-145℃; Zone 2: 145-155℃; Zone 3: 155-165℃; Zone 4: 160-170℃. Granulation yields particles with a diameter of 1.5-3.5mm as masterbatch.

[0020] Furthermore, in step (2), the temperature for heating and mixing, and for continued mixing, is 50-70°C. The aging process involves allowing the mixture to stand at room temperature for 1-10 hours.

[0021] Furthermore, in step (3), the mixing temperature is 140-170℃. The mixing speed and time are 40-80 rpm and 8-15 minutes.

[0022] Furthermore, the extrusion temperature in step (4) is: Zone 1: 135-150℃; Zone 2: 155-170℃; Zone 3: 170-180℃; Zone 4: 170-180℃.

[0023] The advantages of this invention compared to the prior art are as follows: The low-temperature resistant and high-toughness cable outer sheath material prepared by this invention has a tensile strength of 15.34 MPa and an elongation at break of 455.7%. After treatment at -40℃, the change rate of tensile strength is as low as -3.51% and the change rate of elongation at break is as low as -5.46%. The dielectric strength reaches 21.57 kV / mm. After thermal aging, the change rate of tensile strength is as low as -3.03% and the change rate of elongation is as low as -4.57%. The cable outer sheath material prepared by this invention has excellent low-temperature resistance and toughness. After low-temperature treatment, the change rate of tensile strength and elongation at break is low, and the overall performance is excellent.

[0024] The cable outer sheath material of this invention has excellent performance, high low-temperature resistance and strength, as well as excellent tensile strength and toughness. It has broad application prospects and can be effectively used in wind power cables for wind turbine generators in high-altitude / cold regions, as well as in photovoltaic power stations in high-altitude and cold regions, photovoltaic cables in cold regions, marine cables for ship decks and cold storage ships, and mining cables for low-temperature operations in high-altitude mines and underground mines. It is also suitable for rail transit cables for subways / high-speed railways in cold regions, indoor and outdoor wiring for buildings in northern cold regions, as well as cables for greenhouses, cold chain logistics, agriculture / animal husbandry. Detailed Implementation

[0025] The present invention further describes the technical solution of the present invention through specific embodiments, but these embodiments are not intended to limit the present invention. All methods of the present invention and similar variations thereof should be included in the protection scope of the present invention.

[0026] Unless otherwise specified, all reagents used in the following examples and comparative examples are commercially available.

[0027] Polyolefin elastomer: ENGAGE™ 7447 EL, Dow Chemical.

[0028] Ethylene-vinyl acetate copolymer: EVA Elvax® 265, DuPont, USA.

[0029] Low-density polyethylene: LE 6022, Borealis.

[0030] High-density polyethylene: HE 3366, Borealis.

[0031] Nano silica: AEROSIL® R812, Evonik (formerly Degussa).

[0032] Nano magnesium oxide: average particle size 30nm.

[0033] Antioxidant: Composed of antioxidant 1010 and antioxidant 168 in a weight ratio of 1:1.

[0034] Example 1 The raw materials for preparing the outer sheath material are: 8.5 parts polyolefin elastomer, 30 parts ethylene-vinyl acetate copolymer, 35 parts low-density polyethylene, 12 parts high-density polyethylene, 7 parts surface-modified magnesium oxide, 2 parts compound nucleating agent, 6.5 parts bis(2-butoxyethyl) adipic acid, 0.8 parts antioxidant, 0.5 parts zinc stearate, 1 part paraffin wax, and 0.7 parts ethylene bis-stearamide.

[0035] The compound nucleating agent is obtained by mixing and grinding 2,2′-methylene-bis(4,6-di-tert-butylphenylphosphine) basic aluminum and diphenyl dihydrazide sebacate as active ingredients in a weight ratio of 1:1.5 with nano-silica. The weight ratio of active ingredient to carrier in the compound nucleating agent is 0.7:1.

[0036] The preparation method of surface-modified magnesium oxide includes: dispersing 100g of nano-magnesium oxide in 1000mL of toluene, ultrasonically dispersing at room temperature for 20 minutes, adding 2g of bis(dioctyloxypyrophosphate) ethylene titanate and continuing ultrasonic dispersion for 10 minutes, then adding hydrolysate containing 2g of γ-glycidoxypropyltrimethoxysilane and continuing ultrasonic dispersion for 10 minutes, adding 0.08g of dibutyltin dilaurate, heating to 90℃ and stirring at 100rpm for 5.5 hours, then cooling to room temperature, centrifuging at 5000rpm for 20 minutes, washing the centrifuged precipitate with anhydrous ethanol and water sequentially, and vacuum drying to obtain the product.

[0037] Preparation method of hydrolysate: γ-glycidoxypropyltrimethoxysilane was measured as 2g and then mixed with water and glacial acetic acid in a weight ratio of 1:6:0.05 at 45℃ and 120rpm for 30 minutes.

[0038] Preparation method of outer sheath material: (1) Place 75% low-density polyethylene and 50% ethylene bis-stearamide in a mixer and mix at 140°C and 100 rpm for 5 minutes, maintaining the temperature and speed. Then add surface-modified magnesium oxide in three equal portions, mixing for 5 minutes after each addition. After the addition is complete, continue mixing for 10 minutes to obtain the mixer. Then transfer it to an extruder for extrusion. The extrusion temperature is: Zone 1: 142°C; Zone 2: 150°C; Zone 3: 160°C; Zone 4: 165°C. Then granulate to obtain particles with a particle size of 1.5-3.5 mm as masterbatch. (2) Heat the polyolefin elastomer, ethylene-vinyl acetate copolymer, the balance low-density polyethylene and high-density polyethylene in a mixer to 60°C and mix at 100 rpm for 6 minutes. Spray bis(2-butoxyethyl) adipic acid for 6 minutes. Then continue mixing for 5 minutes while maintaining the speed and temperature. Discharge the material into a sealed container and let it stand at room temperature for 8 hours to mature, thus obtaining the matured material. (3) Place the matured material, masterbatch, compound nucleating agent, antioxidant, zinc stearate, paraffin and the balance of ethylene bis-stearamide in a mixer and mix at 150°C and 60 rpm for 12 minutes to obtain the mixed material. (4) Transfer the internally mixed material to an extruder for extrusion. The extrusion temperature is: Zone 1: 140℃; Zone 2: 165℃; Zone 3: 172℃; Zone 4: 172℃. Then granulate to obtain the final product.

[0039] Example 2 The raw materials for preparing the outer sheath material are: 9 parts polyolefin elastomer, 32 parts ethylene-vinyl acetate copolymer, 40 parts low-density polyethylene, 13 parts high-density polyethylene, 7.5 parts surface-modified magnesium oxide, 2.3 parts compound nucleating agent, 7.2 parts bis(2-butoxyethyl) adipic acid, 0.85 parts antioxidant, 0.6 parts zinc stearate, 1.1 parts paraffin wax, and 0.8 parts ethylene bis-stearamide.

[0040] The compound nucleating agent is obtained by mixing and grinding 2,2′-methylene-bis(4,6-di-tert-butylphenylphosphine) basic aluminum and diphenyl dihydrazide sebacate as active ingredients in a weight ratio of 1:3 with nano-silica. The weight ratio of active ingredient to carrier in the compound nucleating agent is 0.75:1.

[0041] The preparation method of surface-modified magnesium oxide includes: dispersing 100g of nano-magnesium oxide in 1000mL of toluene, ultrasonically dispersing at room temperature for 15 minutes, adding 2.3g of bis(dioctyloxypyrophosphate) ethylene titanate and continuing ultrasonic dispersion for 8 minutes, then adding hydrolysate containing 1.8g of γ-glycidoxypropyltrimethoxysilane and continuing ultrasonic dispersion for 15 minutes, adding 0.075g of dibutyltin dilaurate, heating to 92℃ and stirring at 100rpm for 5 hours, then cooling to room temperature, centrifuging at 5000rpm for 25 minutes, washing the centrifuged precipitate with anhydrous ethanol and water sequentially, and drying under vacuum to obtain the product.

[0042] Preparation method of hydrolysate: γ-glycidoxypropyltrimethoxysilane was measured as 1.8 g, and γ-glycidoxypropyltrimethoxysilane, water and glacial acetic acid were mixed at a weight ratio of 1:7:0.048 at 40℃ and 100 rpm for 25 minutes.

[0043] Preparation method of outer sheath material: (1) Place 70% low-density polyethylene and 60% ethylene bis-stearamide in a mixer and mix at 142°C and 100 rpm for 4 minutes, maintaining the temperature and speed. Then add surface-modified magnesium oxide in three equal portions, mixing for 4 minutes after each addition. After the addition is complete, continue mixing for 12 minutes to obtain the mixer. Then transfer it to an extruder for extrusion. The extrusion temperature is: Zone 1: 142°C; Zone 2: 150°C; Zone 3: 160°C; Zone 4: 165°C. Then granulate to obtain particles with a particle size of 1.5-3.5 mm as masterbatch. (2) Heat the polyolefin elastomer, ethylene-vinyl acetate copolymer, the balance low-density polyethylene and high-density polyethylene in a mixer to 65°C and mix at 100 rpm for 5 minutes. Spray bis(2-butoxyethyl) adipate for 7 minutes. Then continue mixing for 5 minutes while maintaining the speed and temperature. Discharge the material into a sealed container and let it stand at room temperature for 8.5 hours to mature, and obtain the matured material. (3) Place the matured material, masterbatch, compound nucleating agent, antioxidant, zinc stearate, paraffin and the balance of ethylene bis-stearamide in a mixer and mix at 152°C and 60 rpm for 11 minutes to obtain the mixed material. (4) Transfer the internally mixed material to an extruder for extrusion. The extrusion temperature is: Zone 1: 140℃; Zone 2: 165℃; Zone 3: 172℃; Zone 4: 172℃. Then granulate to obtain the final product.

[0044] Comparative Example 1 The difference from Example 1 is that no compound nucleating agent is used: the raw materials for preparing the outer sheath material are: 8.5 parts polyolefin elastomer, 30 parts ethylene-vinyl acetate copolymer, 35 parts low-density polyethylene, 12 parts high-density polyethylene, 7 parts surface-modified magnesium oxide, 6.5 parts bis(2-butoxyethyl) adipic acid, 0.8 parts antioxidant, 0.5 parts zinc stearate, 1 part paraffin wax, and 0.7 parts ethylene bis-stearamide. Everything else is the same.

[0045] Comparative Example 2 The difference from Example 1 is that 2,2′-methylene-bis(4,6-di-tert-butylphenylphosphine) basic aluminum is not used in the compound nucleating agent; instead, the compound nucleating agent is obtained by mixing and grinding diphenyl dihydrazide sebacate as the active ingredient with nano-silica. The weight ratio of the active ingredient to the carrier in the compound nucleating agent is 0.7:1. Everything else is the same.

[0046] Comparative Example 3 The difference from Example 1 is that the compound nucleating agent does not use diphenyl disaccharide sebacate; instead, the compound nucleating agent is obtained by mixing and grinding 2,2′-methylene-bis(4,6-di-tert-butylphenyl phosphate) basic aluminum as the active ingredient with nano-silica. The weight ratio of the active ingredient to the carrier in the compound nucleating agent is 0.7:1. Everything else is the same.

[0047] Comparative Example 4 The difference from Example 1 is that bis(2-butoxyethyl) adipic acid is not used; the raw materials for preparing the outer sheath material are: 8.5 parts polyolefin elastomer, 30 parts ethylene-vinyl acetate copolymer, 35 parts low-density polyethylene, 12 parts high-density polyethylene, 7 parts surface-modified magnesium oxide, 2 parts compound nucleating agent, 0.8 parts antioxidant, 0.5 parts zinc stearate, 1 part paraffin wax, and 0.7 parts ethylene bis-stearamide. Everything else is the same.

[0048] Comparative Example 5 The difference from Example 1 is that an equal weight of nano-magnesium oxide is used to replace the surface-modified magnesium oxide; otherwise, they are the same.

[0049] Comparative Example 6 The difference from Example 1 is that the surface-modified magnesium oxide is not treated with γ-glycidoxypropyltrimethoxysilane. The preparation method of the surface-modified magnesium oxide includes: dispersing 100g of nano-magnesium oxide in 1000mL of toluene, ultrasonically dispersing at room temperature for 20 minutes, adding 2g of bis(dioctyloxypyrophosphate) ethylene titanate and continuing ultrasonic dispersion for 10 minutes, adding 0.08g of dibutyltin dilaurate, heating to 90℃ and stirring at 100rpm for 5.5 hours, then cooling to room temperature, centrifuging at 5000rpm for 20 minutes, washing the centrifuged precipitate with anhydrous ethanol and water sequentially, and vacuum drying to obtain the final product. Everything else is the same.

[0050] Comparative Example 7 The difference from Example 1 is that the surface-modified magnesium oxide does not use bis(dioctyloxypyrophosphate) ethylene titanate treatment. The preparation method of the surface-modified magnesium oxide includes: dispersing 100g of nano-magnesium oxide in 1000mL of toluene, ultrasonically dispersing at room temperature for 20 minutes, adding hydrolysate containing 2g of γ-glycidoxypropyltrimethoxysilane and continuing ultrasonic dispersion for 10 minutes, adding 0.08g of dibutyltin dilaurate, heating to 90℃ and stirring at 100rpm for 5.5 hours, then cooling to room temperature, centrifuging at 5000rpm for 20 minutes, washing the centrifuged precipitate with anhydrous ethanol and water sequentially, and vacuum drying to obtain the final product. Everything else is the same.

[0051] The cable outer sheath materials prepared in the examples and comparative examples were pressed into shape on a flat vulcanizing machine, and their performance was tested. Tensile strength and elongation at break were tested in accordance with GB / T 2951.11-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Cables - Part 11: General Test Methods - Measurement of Thickness and Dimensions - Mechanical Properties Test".

[0052] Retention rate of tensile strength and elongation at break after low-temperature treatment: The test was conducted in accordance with the contents of GB / T 2951.14-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers - Part 14: General Test Methods - Low Temperature Test". Specifically, the sample was treated in a -40℃ low-temperature test chamber for 16 hours; after removal, it was allowed to recover under standard environmental conditions (23±2℃) for 2 hours, and the test was conducted in accordance with the method described in GB / T 2951.11-2008. The change rate of tensile strength and elongation at break was calculated as follows: Change rate = [(Test value after low-temperature treatment - Test value before treatment) / Test value before treatment] × 100%.

[0053] Retention rate of tensile strength and elongation at break after heat aging: The test was conducted in accordance with GB / T 2951.12-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers - Part 12: General Test Methods - Heat Aging Test Method", with an aging temperature of 113℃ and an aging time of 168 hours. Recovery conditions: 16 hours at room temperature. The test was conducted in accordance with the method described in GB / T 2951.11-2008, and the change rate of tensile strength and elongation at break was calculated as follows: Change rate = [(Test value after heat treatment - Test value before heat treatment) / Test value before heat treatment] × 100%.

[0054] Dielectric strength: Tested according to GB / T 1408.1-2016 "Electrical strength test methods for insulating materials - Part 1: Tests at power frequency". Prepare a 1mm thick sample, increase the voltage at a rate of 2kV / s until breakdown, record the breakdown voltage, and use the formula: E=U b / d, where U b Let d be the breakdown voltage (kV) and d be the sample thickness (mm); calculate the dielectric strength. The performance test results are shown in Table 1.

[0055] Table 1: Performance Test Results

[0056] As shown in Table 1 above, the low-temperature resistant and high-toughness cable outer sheath material prepared by this invention has a tensile strength of 15.34 MPa, an elongation at break of 455.7%, and after treatment at -40℃, the change rate of tensile strength is as low as -3.51% and the change rate of elongation at break is as low as -5.46%. The dielectric strength reaches 21.57 kV / mm, and after thermal aging, the change rate of tensile strength is as low as -3.03% and the change rate of elongation is as low as -4.57%. The cable outer sheath material prepared by this invention has excellent low-temperature resistance and toughness, and the change rate of tensile strength and elongation at break is low after low-temperature treatment, resulting in excellent overall performance.

[0057] Compared with Example 1, the tensile strength of Comparative Example 1 decreased from 15.34 MPa to 11.08 MPa, and the rate of change of tensile strength at -40℃ after low-temperature treatment increased from -3.51% in Example 1 to -10.15%. In Comparative Example 1, when the compound nucleating agent was absent, the crystals of polyethylene and other components were coarse and uneven, and secondary crystallization was prone to occur at low temperatures, leading to further grain growth and material embrittlement. At the same time, without the nucleating agent, the crystal structure was imperfect, the interface defects increased, and the tensile strength decreased significantly.

[0058] In Comparative Examples 2 and 3, the composite nucleating agent active ingredient used only one of 2,2′-methylene-bis(4,6-di-tert-butylphenylphosphine) basic aluminum and diphenyl disaccharide sebacate, resulting in reduced tensile strength and elongation at break compared to Example 1. While diphenyl disaccharide sebacate alone improved toughness to some extent, it could not achieve optimal crystal form matching, leading to lower overall nucleation efficiency than the composite system, resulting in inferior strength and low-temperature performance compared to Example 1. Furthermore, 2,2′-methylene-bis(4,6-di-tert-butylphenylphosphine) basic aluminum alone could not sufficiently refine the grains, resulting in limited improvement in material toughness and other properties.

[0059] Compared to Example 1, Comparative Example 4 lacked bis(2-butoxyethyl) adipate. Bis(2-butoxyethyl) adipate molecules can insert into the polymer chains to increase free volume. In Comparative Example 4, the absence of this raw material hindered the movement of molecular chain segments, resulting in a decrease in elongation at room temperature. At low temperatures, the molecular chains froze, and without the lubrication of plasticizers, brittleness increased significantly. After thermal aging, the lack of plasticizers exacerbated thermal oxidative degradation, with an elongation change rate of -34.78%.

[0060] In Comparative Example 5, conventional nano-magnesium oxide was used instead of modified MgO. The surface of the unmodified nano-MgO was highly hydrophilic and agglomerated, making it incompatible with the polyolefin matrix. This resulted in numerous stress concentration points and interfacial defects, which easily led to cracks during stretching. The interfacial stress was even greater at low temperatures, resulting in a significant decrease in mechanical properties and low-temperature resistance.

[0061] In Comparative Examples 6 and 7, only bis(dioctyloxypyrophosphate) ethylene titanate and γ-glycidoxypropyltrimethoxysilane were used. While the single bis(dioctyloxypyrophosphate) ethylene titanate modification improved the compatibility of MgO with the matrix, it lacked the strong interaction between the epoxy groups of the silane and polar components such as EVA, failing to form an amphiphilic structure. Therefore, the interfacial bonding strength was inferior to the composite modification system. Furthermore, while the single γ-glycidoxypropyltrimethoxysilane modification could interact with EVA through the epoxy groups, it lacked the physical entanglement between the long-chain alkyl groups of bis(dioctyloxypyrophosphate) ethylene titanate and the non-polar polyolefin, resulting in insufficient interfacial bonding and overall performance lower than that of the composite modification in Example 1.

[0062] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low-temperature resistant, high-toughness cable outer sheath material, characterized in that, The raw materials, by weight, are: 5-10 parts polyolefin elastomer, 25-40 parts ethylene-vinyl acetate copolymer, 30-45 parts low-density polyethylene, 10-15 parts high-density polyethylene, 5-8 parts surface-modified magnesium oxide, 1.5-2.2 parts compound nucleating agent, 5-9 parts bis(2-butoxyethyl) adipic acid, 0.1-1 part antioxidant, 0.2-0.8 parts zinc stearate, 0.5-1.5 parts paraffin wax, and 0.4-0.8 parts ethylene bis-stearamide; Among them, the surface-modified magnesium oxide was obtained by combining bis(dioctyloxypyrophosphate) ethylene titanate with γ-glycidyl etheroxypropyltrimethoxysilane. The active ingredients of the compound nucleating agent are 2,2′-methylene-bis(4,6-di-tert-butylphenylphosphine) basic aluminum and sebacate diphenyl dihydrazide in a weight ratio of 1:1.5-3, and also include the carrier silica.

2. The low-temperature resistant, high-toughness cable outer sheath material according to claim 1, characterized in that, The weight ratio of active ingredient to carrier in the compound nucleating agent is 0.6-1:

1.

3. The low-temperature resistant, high-toughness cable outer sheath material according to claim 1, characterized in that, Antioxidants include at least one of antioxidant 1010 and antioxidant 168.

4. The low-temperature resistant, high-toughness cable outer sheath material according to claim 1, characterized in that, The coupling agent used in the preparation of surface-modified magnesium oxide is a titanate coupling agent.

5. The low-temperature resistant, high-toughness cable outer sheath material according to claim 1, characterized in that, The preparation method of surface-modified magnesium oxide includes: dispersing nano-magnesium oxide in toluene, sonicating, adding bis(dioctyloxypyrophosphate) ethylene titanate and mixing, then adding γ-glycidyl etheroxypropyltrimethoxysilane hydrolysate and mixing, adding catalyst, then heating and reacting, centrifuging, washing and drying to obtain the product.

6. The low-temperature resistant, high-toughness cable outer sheath material according to claim 5, characterized in that, The weight ratio of bis(dioctyloxypyrophosphate) ethylene titanate to γ-glycidoxypropyltrimethoxysilane is 1:0.5-1.

5.

7. The low-temperature resistant, high-toughness cable outer sheath material according to claim 5, characterized in that, The catalyst includes dibutyltin dilaurate, and the reaction temperature and time are 80-95℃ for 3-20 hours.

8. The low-temperature resistant, high-toughness cable outer sheath material according to claim 5, characterized in that, The hydrolysate of γ-glycidoxypropyltrimethoxysilane is obtained by mixing water and acid, then adding γ-glycidoxypropyltrimethoxysilane and stirring to hydrolyze.

9. The low-temperature resistant, high-toughness cable outer sheath material according to claim 5, characterized in that, In preparing the low-temperature resistant and high-toughness cable outer sheath material, surface-modified magnesium oxide is co-extruded with a portion of low-density polyethylene and a portion of ethylene bis-stearamide to obtain a masterbatch, which is then used to prepare the outer sheath material.

10. A method for preparing a low-temperature resistant, high-toughness cable outer sheath material according to any one of claims 1-9, characterized in that, Includes the following steps: (1) The surface-modified magnesium oxide is mixed with a portion of low-density polyethylene and a portion of ethylene bis-stearamide, extruded and granulated to obtain the masterbatch; (2) The polyolefin elastomer, ethylene-vinyl acetate copolymer, the balance of low-density polyethylene and high-density polyethylene are heated and mixed in a mixer, and bis(2-butoxyethyl) adipate is sprayed on. The mixture is continued to be mixed and discharged into a sealed container for standing and maturation to obtain the matured material. (3) Place the matured material, masterbatch, compound nucleating agent, antioxidant, zinc stearate, paraffin and the balance of ethylene bis-stearamide in a mixer and mix them to obtain the mixed material. (4) Transfer the kneaded material to an extruder, extrude and granulate to obtain the final product.

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