Insulating material and application thereof

Abstract

The invention relates to the field of insulating materials, and discloses an insulating material and application thereof. The material is characterized by being prepared from the following raw materials in parts by weight: 100 parts of a copolymer of ethylene and at least one C3-C6 straight-chain alpha-olefin, 0.1-2.5 parts of an initiator, 0.1-2 parts of a cross-linking agent, 0-0.5 part of an antioxidant and 0-0.1 part of an acid remover. The insulating material has the beneficial effects of good crosslinking performance, thermal stability and mechanical performance.

Description

Technical Field

[0001] This invention relates to the field of insulating materials, and more specifically to an insulating material and its application. Background Technology

[0002] With the rapid development of industry and the continuous increase in the demand for electricity supply, the voltage level and current carrying capacity of power cables are constantly improving, which makes the performance requirements of cable insulation materials in the power industry increasingly stringent. Currently, the materials used for insulation of 35kV and above cables are mainly cross-linked polyethylene (XLPE) materials with low-density polyethylene (LDPE) as the base material. LDPE has good chemical stability and processability, but as a thermoplastic material, its permissible long-term operating temperature is 70℃, limiting its application in the field of cable insulation. XLPE, on the other hand, is a thermosetting material. By mixing PE with initiators such as organic peroxides, an interconnected cross-linked network is formed through a cross-linking reaction. XLPE can be used at higher temperatures and higher voltages than thermoplastic PE, with a long-term operating temperature reaching 90℃.

[0003] Unlike LDPE, which is synthesized via high-pressure free radical polymerization, linear low-density polyethylene (LLDPE) is synthesized using a low-pressure process through α-olefin copolymerization. This process offers greater advantages in molecular structure control, resulting in higher strength, hardness, and toughness due to the uniformity of the molecular structure. Furthermore, LLDPE exhibits higher crystallinity and superior thermal stability compared to LDPE, effectively enhancing electron current carrying capacity and transmission efficiency. Currently, in the field of power cable insulation, LLDPE is commonly used for low-voltage cable insulation layers via radiation crosslinking and silane crosslinking processes. However, its application in high-voltage cables, where chemical crosslinking with peroxides is employed, remains limited.

[0004] Regarding the aforementioned related technologies, the inventors of this invention have discovered that simply replacing LDPE with LLDPE in existing chemical crosslinking systems is difficult to implement. Furthermore, the processing temperature of LLDPE is typically higher than that of LDPE, leading to difficulties in the processing of the modified system, increasing the likelihood of pre-crosslinking reactions, and generating microgels in the modified material, which affects subsequent cable manufacturing applications. Therefore, an insulating polymer is needed to overcome these shortcomings. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of poor crosslinking performance, thermal stability and mechanical properties in the prior art, and to provide an insulating material and its application.

[0006] To achieve the above objectives, the first aspect of the present invention provides an insulating material, characterized in that, by weight, the material is processed from the following raw materials: 100 parts of a copolymer of ethylene and at least one C3-C6 linear α-olefin, 0.1-2.5 parts of an initiator, 0.1-2 parts of a crosslinking agent, 0-0.5 parts of an antioxidant, and 0-0.1 parts of an acid remover.

[0007] The second aspect of the present invention provides the application of the insulating material described in the first aspect of the present invention in power cables.

[0008] The embodiments of the present invention have at least the following beneficial effects:

[0009] 1. This invention uses linear low-density polyethylene obtained by copolymerization of linear α-olefins as the base material for insulation. The uniformity of the molecular structure enables the material to have high strength, hardness and toughness. At the same time, its high crystallinity and good thermal stability can effectively improve electron current carrying capacity and enhance transmission efficiency.

[0010] 2. The chemically cross-linked polyethylene insulation material for power cables provided by the present invention has a wide processing temperature window, which can prevent the occurrence of pre-cross-linking reaction, reduce the formation of microgels in the modified material, and facilitate subsequent molding and processing.

[0011] 3. In a preferred embodiment, the chemically cross-linked polyethylene insulation material for power cables provided by the present invention utilizes the synergistic effect of the initiator and the cross-linking agent to effectively improve the cross-linking performance of the material, reduce the amount of initiator used and the generation of by-products, and further improve the performance of the material.

[0012] 4. The preparation method of chemically cross-linked polyethylene insulation material for power cables provided by the present invention is simple, highly operable, and has low equipment requirements, making it suitable for industrial-scale production. Attached Figure Description

[0013] Figure 1 These are polarized light microscope images of the linear low-density polyethylene raw material (a), the insulating material (b), the insulating material (c), and the insulating material (d) in Example 1;

[0014] Figure 2 The infrared spectra of the linear low-density polyethylene raw material (a), the insulation material (b), the insulation material (c), and the insulation material (d) in Example 1 are shown.

[0015] Figure 3 This is a differential scanning calorimetry curve of the insulating material in Example 2. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] In this invention, linear low-density polyethylene (LLDPE) refers to a polymer with a molecular structure in which ethylene and a small amount of α-olefins are copolymerized on the main chain of polyethylene, and the copolymers have very short comonomer branches.

[0018] In this invention, low-density polyethylene (LDPE) refers to a polymer formed solely from ethylene monomers through high-pressure free radical polymerization.

[0019] As previously stated, the first aspect of the present invention provides an insulating material, characterized in that, by weight, the material is processed from the following raw materials: 100 parts of a copolymer of ethylene and at least one C3-C6 linear α-olefin, 0.1-2.5 parts of an initiator, 0.1-2 parts of a crosslinking agent, 0-0.5 parts of an antioxidant, and 0-0.1 parts of an acid remover.

[0020] In some embodiments of the present invention, preferably, the copolymer has a weight-average molecular weight of 5 × 10⁻⁶. 4 -10×10 4 g / mol.

[0021] In some embodiments of the present invention, preferably, the C3-C6 straight-chain α-olefin is selected from at least one of propylene, 1-butene, 1-pentene or 1-hexene, more preferably 1-butene and / or 1-pentene, and even more preferably 1-butene.

[0022] In some embodiments of the present invention, preferably, the mass ratio of the structural units provided by ethylene to the structural units provided by C3-C6 linear α-olefins in the copolymer is 1:0.05-0.15, more preferably 1:0.09-0.11.

[0023] In some embodiments of the present invention, preferably, the copolymer is linear low-density polyethylene formed by random copolymerization of ethylene and C3-C6 linear α-olefins, with a density of 0.91-0.94 g / cm³. 3 In this invention, the density of the copolymer refers to the density measured at 190°C and under a load of 2.16 kg.

[0024] In some embodiments of the present invention, preferably, the copolymer has a melt index (melt index for short) of 2.5-3.5 g / 10 min at 190°C and a load of 2.16 kg, and a density of 0.918-0.924 g / cm³. 3 .

[0025] In some embodiments of the present invention, preferably, the copolymer has a melt index of 2.7-3.1 g / 10 min and a density of 0.92-0.922 g / cm³ at 190°C and a load of 2.16 kg. 3 This melt flow index range allows insulating materials to achieve a gel content exceeding 80%. This density range allows insulating materials to achieve both good cross-linking properties and mechanical properties.

[0026] In some embodiments of the present invention, preferably, the initiator is selected from organic peroxides, more preferably tert-butyl peroxides, and more preferably at least one selected from bis-tert-butylperoxyisopropylbenzene, 2,5-dimethyl-2,5-bis-(tert-butylperoxy)hexane, and 2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexyne. These three organic peroxides can provide a wider processing window for the insulating material system.

[0027] In some embodiments of the present invention, preferably, the amount of the initiator is 0.2-1.5 parts by weight relative to 100 parts of the copolymer, more preferably 0.3-0.9 parts by weight.

[0028] In some embodiments of the present invention, preferably, the crosslinking agent is selected from multifunctional additives, preferably compounds containing three allyl groups, and more preferably at least one of triallyl isocyanurate and triallyl cyanurate.

[0029] In some embodiments of the present invention, preferably, the amount of the crosslinking agent is 0.2-1 parts by weight, more preferably 0.3-0.7 parts, relative to 100 parts of the copolymer.

[0030] In some embodiments of the present invention, preferably, the antioxidant is a hindered phenolic antioxidant and / or a phosphite antioxidant.

[0031] In some embodiments of the present invention, preferably, the hindered phenolic antioxidant is selected from at least one of 4,4'-thiobis(6-tert-butyl-3-methylphenol), pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. These three hindered phenolic antioxidants can capture free radicals in the insulation system, more effectively preventing the insulation from being oxidized by oxygen.

[0032] In some embodiments of the present invention, preferably, the phosphite antioxidant is selected from at least one of tris[2,4-di-tert-butylphenyl]phosphite and pentaerythritol diphosphite (2,4-di-tert-butylphenol). These two phosphite antioxidants can decompose the hydrogen peroxides formed by partial oxidation in the insulating material, further preventing the chain oxidation reaction from occurring.

[0033] In some embodiments of the present invention, preferably, the amount of antioxidant is 0.05-0.45 parts by weight relative to 100 parts of copolymer, more preferably 0.1-0.3 parts.

[0034] In some embodiments of the present invention, preferably, the deacidifying agent is at least one of hydrotalcite, zinc stearate, and calcium stearate. These three deacidifying agents are more effective in eliminating trace amounts of HCl in the copolymer.

[0035] In some embodiments of the present invention, preferably, the amount of the deacidifying agent is 0.005-0.02 parts by weight relative to 100 parts of the copolymer, more preferably 0.007-0.013 parts by weight.

[0036] In some embodiments of the present invention, preferably, the method for preparing the insulating material includes the following steps:

[0037] S1: The copolymer of ethylene and C3-C6 linear α-olefin, initiator, crosslinking agent, antioxidant and deacidifying agent are first processed to obtain modified mixture;

[0038] S2: The modified mixture is subjected to a second processing treatment to obtain chemically cross-linked polyethylene insulation material for power cables.

[0039] In some embodiments of the present invention, preferably, the first processing step includes mixing, wetting, and cooling.

[0040] In some embodiments of the present invention, preferably, the immersion temperature is 40-80°C, more preferably 50-70°C; and the immersion time is 3-12 hours, more preferably 5-8 hours.

[0041] In some embodiments of the present invention, preferably, the temperature after cooling is 20-30°C.

[0042] In some embodiments of the present invention, preferably, the second processing step includes extrusion and pelletizing.

[0043] In some embodiments of the present invention, preferably, the extrusion step is performed using a twin-screw extruder. The twin-screw extruder enables the copolymer, initiator, crosslinking agent, antioxidant, and deacidifying agent to achieve complete mixing.

[0044] In some embodiments of the present invention, preferably, the extrusion temperature is 130-150°C, more preferably 136-144°C.

[0045] The second aspect of the present invention provides the application of the insulating material described in the first aspect of the present invention in power cables.

[0046] The present invention will be described in detail below through examples. In the following examples, the weight-average molecular weight was determined by gel permeation chromatography; linear low-density polyethylene was a commercially available product of Zhenhai Refining & Chemical Co., Ltd. with the brand name DJM1820; bis(tert-butylperoxyisopropylbenzene) was a commercially available product of analytical grade from Sinopharm Chemical Reagent Co., Ltd.; 4,4'-thiobis(6-tert-butyl-3-methylphenol) was a commercially available product of analytical grade from Sinopharm Chemical Reagent Co., Ltd.; triallyl isocyanurate was a commercially available product of analytical grade from Sinopharm Chemical Reagent Co., Ltd.; hydrotalcite was a commercially available product of Kyowa Chemical Co., Ltd. with the brand name DHT-4A; and high-density polyethylene was a commercially available product of Zhenhai Refining & Chemical Co., Ltd. with the brand name ZH6098.

[0047] Example 1

[0048] Raw material formulation (by weight) for chemically cross-linked polyethylene insulation material for power cables: Linear low-density polyethylene (LLDPE) formed by random copolymerization of ethylene and 1-butene, with a mass ratio of structural units provided by the two being 1:0.1 and a weight-average molecular weight of 7.5 × 10⁻⁶. 4 The density is 0.921 g / cm³ at 190℃ and a load of 2.16 kg. 3 100 parts of the following: melt index 2.8 g / 10 min; 0.8 parts of bis-tert-butylperoxyisopropylbenzene; 0.2 parts of 4,4'-thiobis(6-tert-butyl-3-methylphenol); 0.5 parts of triallyl isocyanurate; and 0.01 parts of hydrotalcite.

[0049] Preparation method: The linear low-density polyethylene, initiator, antioxidant, crosslinking agent and deacidifying agent in the above proportions are mixed evenly and impregnated at 60°C for 6 hours. After cooling to 25°C, a modified mixture is obtained. The modified mixture is extruded and pelletized by twin screw extrusion at 140°C to obtain chemically crosslinked polyethylene insulation material for power cables.

[0050] Examples 2-5

[0051] Unlike Example 1, the weight proportions of raw materials in Examples 2-5 are different, as detailed in Table 1.

[0052] Table 1

[0053]

[0054] Example 6

[0055] The raw material formulation for chemically cross-linked polyethylene insulation material for power cables: linear low-density polyethylene (LLDPE) (LLDPE formed by random copolymerization of ethylene and 1-butene, with a mass ratio of structural units of 1:0.1 and a weight-average molecular weight of 7.5 × 10⁻⁶). 4 The density is 0.921 g / cm³ at 190℃ and a load of 2.16 kg. 3 100 parts of a solution with a melt index of 2.8 g / 10 min, 1.0 part of 2,5-dimethyl-2,5-bis-(tert-butylperoxy)hexane, 0.2 parts of 4,4'-thiobis(6-tert-butyl-3-methylphenol), 0.5 parts of triallyl isocyanurate, and 0.01 parts of hydrotalcite.

[0056] Preparation method: The linear low-density polyethylene, initiator, antioxidant, crosslinking agent and deacidifying agent in the above proportions are mixed evenly and impregnated at 60°C for 6 hours. After cooling to 25°C, a modified mixture is obtained. The modified mixture is extruded and pelletized by twin screw extrusion at 140°C to obtain chemically crosslinked polyethylene insulation material for power cables.

[0057] Example 7

[0058] The raw material formulation for chemically cross-linked polyethylene insulation material for power cables: linear low-density polyethylene (LLDPE) (LLDPE formed by random copolymerization of ethylene and 1-butene, with a mass ratio of structural units of 1:0.1 and a weight-average molecular weight of 7.5 × 10⁻⁶). 4 The density is 0.921 g / cm³ at 190℃ and a load of 2.16 kg. 3 100 parts of 2,5-bis(tert-butylperoxy)-2,5-dimethyl-3-hexyne (in liquid form, 85% by weight mineral oil solution), 0.2 parts of 4,4'-thiobis(6-tert-butyl-3-methylphenol), 0.5 parts of triallyl isocyanurate, and 0.01 parts of hydrotalcite.

[0059] Preparation method: The linear low-density polyethylene, initiator, antioxidant, crosslinking agent and deacidifying agent in the above proportions are mixed evenly and impregnated at 60°C for 6 hours. After cooling to 25°C, a modified mixture is obtained. The modified mixture is extruded and pelletized by twin screw extrusion at 140°C to obtain chemically crosslinked polyethylene insulation material for power cables.

[0060] Example 8

[0061] The raw material formulation for chemically cross-linked polyethylene insulation material for power cables: linear low-density polyethylene (LLDPE) (LLDPE formed by random copolymerization of ethylene and 1-butene, with a mass ratio of structural units of 1:0.1 and a weight-average molecular weight of 7.5 × 10⁻⁶). 4 The density is 0.921 g / cm³ at 190℃ and a load of 2.16 kg. 3 100 parts of the following: melt index 2.8 g / 10 min; 1.0 part of bis-tert-butylperoxyisopropylbenzene; 0.1 part of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; 0.1 part of tris[2,4-di-tert-butylphenyl] phosphite; 0.5 part of triallyl isocyanurate; and 0.01 part of hydrotalcite.

[0062] Preparation method: The linear low-density polyethylene, initiator, antioxidant, crosslinking agent and deacidifying agent in the above proportions are mixed evenly and impregnated at 60°C for 6 hours. After cooling to 25°C, a modified mixture is obtained. The modified mixture is extruded and pelletized by twin screw extrusion at 140°C to obtain chemically crosslinked polyethylene insulation material for power cables.

[0063] Example 9

[0064] The raw material formulation for chemically cross-linked polyethylene insulation material for power cables: linear low-density polyethylene (LLDPE) (LLDPE formed by random copolymerization of ethylene and 1-butene, with a mass ratio of structural units of 1:0.1 and a weight-average molecular weight of 7.5 × 10⁻⁶). 4 The density is 0.921 g / cm³ at 190℃ and a load of 2.16 kg. 3 100 parts of the following: melt index 2.8 g / 10 min; 1.0 part of bis-tert-butylperoxyisopropylbenzene; 0.2 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; 0.2 parts of tris[2,4-di-tert-butylphenyl] phosphite; 0.5 parts of triallyl isocyanurate; and 0.01 parts of hydrotalcite.

[0065] Preparation method: The linear low-density polyethylene, initiator, antioxidant, crosslinking agent and deacidifying agent in the above proportions are mixed evenly and impregnated at 60°C for 6 hours. After cooling to 25°C, a modified mixture is obtained. The modified mixture is extruded and pelletized by twin screw extrusion at 140°C to obtain chemically crosslinked polyethylene insulation material for power cables.

[0066] Example 10

[0067] The raw material formulation for chemically cross-linked polyethylene insulation material for power cables: linear low-density polyethylene (LLDPE) (LLDPE formed by random copolymerization of ethylene and 1-butene, with a mass ratio of structural units of 1:0.1 and a weight-average molecular weight of 7.5 × 10⁻⁶). 4 The density at 190℃ and a load of 2.16 kg is 0.923 g / cm³. 3 100 parts of the following ingredients: melt index 3.3 g / 10 min; 1.0 part of bis-tert-butylperoxyisopropylbenzene; 0.2 parts of 4,4'-thiobis(6-tert-butyl-3-methylphenol); 0.5 parts of triallyl isocyanurate; and 0.01 parts of hydrotalcite.

[0068] Preparation method: The linear low-density polyethylene, initiator, antioxidant, crosslinking agent and deacidifying agent in the above proportions are mixed evenly and impregnated at 50°C for 9 hours. After cooling to 25°C, a modified mixture is obtained. The modified mixture is extruded and pelletized by twin screw extrusion at 145°C to obtain chemically crosslinked polyethylene insulation material for power cables.

[0069] Example 11

[0070] The insulating material was prepared according to the preparation method of Example 1, except that the crosslinking agent used in the formulation was 1,7-octadiene, and a chemically crosslinked polyethylene insulating material was obtained.

[0071] Example 12

[0072] The insulating material was prepared according to the preparation method of Example 1, except that the initiator used in the formulation was dicumyl peroxide, and a chemically cross-linked polyethylene insulating material was obtained.

[0073] Example 13

[0074] The insulating material was prepared according to the preparation method of Example 1, except that the formulation used high-density polyethylene (HDPE) with 1-butene as a comonomer (linear low-density polyethylene formed by random copolymerization of ethylene and 1-butene, with a mass ratio of 1:0.02 for the structural units provided by the two, and a weight-average molecular weight of 15 × 10⁻⁶). 4 The density is 0.95 g / cm³ at 190℃ and a load of 2.16 kg. 3 Crosslinking was performed using a melt index of 0.2 g / 10 min to obtain chemically crosslinked polyethylene insulation material.

[0075] Example 14

[0076] The insulating material was prepared according to the preparation method of Example 1, except that talc was used instead of hydrotalcite in the formulation to obtain chemically cross-linked polyethylene insulating material.

[0077] Example 15

[0078] The insulating material was prepared according to the preparation method of Example 1, except that no antioxidant was added to the formulation, resulting in a chemically cross-linked polyethylene insulating material.

[0079] Comparative Example 1

[0080] The insulating material was prepared according to the preparation method of Example 1, except that the formulation used ethylene homopolymer (weight average molecular weight of 5 × 10⁻⁶). 4 Crosslinking was performed on a product (g / mol, Iranian petrochemical grade 2102TX00) to obtain chemically crosslinked polyethylene insulation material.

[0081] Comparative Example 2

[0082] The insulating material was prepared according to the preparation method of Example 1, except that no crosslinking agent was added to the formulation, resulting in a chemically crosslinked polyethylene insulating material.

[0083] Comparative Example 3

[0084] Unlike Example 1, the formulation uses low-density polyethylene raw material (Iranian petrochemical product with grade 2420H) instead of linear low-density polyethylene, and adds 10 parts of talc powder to obtain cross-linked polyethylene insulation material.

[0085] Test Example 1

[0086] Preparation method of cross-linked polyethylene specimens: The chemically cross-linked polyethylene insulation material for power cables prepared in the examples and comparative examples is placed in a 1 mm thick mold frame. The mold frame is placed in a tablet press for melting and tableting. First, it is pre-melted at 130°C for 10 minutes, then kept at 185°C and 16 MPa for 15 minutes, and finally cooled to room temperature. The resulting sheet is then pressed into standard specimens.

[0087] Melt index was determined according to GB / T 3682.1-2018 under a load of 2.16 kg and a temperature of 190℃; density was determined according to GB / T 1033.2; tensile strength and elongation at break were determined according to GB / T 1040.2-2022 using type II dumbbell plates and a stretching speed of 250 mm / min; elongation at heat extension load and permanent deformation after cooling were determined according to GB / T2951.21-2008; gel content was determined according to JB / T 10437-2004; and volume resistivity was determined according to GB / T 1410-2006.

[0088] Differential scanning calorimetry test method: Cut 5-10 mg of sample from the sample to be tested and place it in an aluminum crucible. The experiment is conducted in an N2 atmosphere at a rate of 50 mL / min, and the heating and cooling rates are both maintained at 10 °C / min.

[0089] Polarizing microscope test method: Cut the sample to be tested into a thin slice and place it between two glass slides. Place the glass slide with the sample in the hot stage. Set the heating rate of the hot stage to 20℃ / min. After heating to 210℃, hold for 5min. Then cool to room temperature at a cooling rate of 20℃ / min. Observe the crystal morphology with a polarizing microscope using a magnification of 10×50 (eyepiece×objective).

[0090] Infrared spectroscopy testing method: The hot-pressing temperature during sample preparation is 210℃, and the scanning wavenumber range is 4000-400cm⁻¹. -1 .

[0091] The performance test results of the samples in the examples and comparative examples are shown in Table 2.

[0092] Table 2

[0093]

[0094] As can be seen from Table 2, the chemically cross-linked polyethylene insulation materials for power cables prepared in each embodiment exhibit higher tensile strength, elongation at break, and volume resistivity compared to the comparative example, and also have excellent thermal elongation properties and higher gel content.

[0095] Furthermore, a comparison of Examples 1, 2, and 3 shows that the thermal elongation properties of the insulating material of the present invention are significantly improved with the increase of the amount of bis-tert-butylperoxyisopropylbenzene, and the gel content is significantly increased, proving that the prepared polymer has a high degree of crosslinking.

[0096] As can be seen from the comparison of Examples 2, 4 and 5, the thermal elongation properties and gel content of the insulating material of the present invention are significantly improved with the increase of the amount of triallyl isocyanurate.

[0097] The comparison of Examples 2, 6, and 7 shows that the crosslinking performance of the insulating material of the present invention varies with the type of initiator. At the same dosage ratio, bis-tert-butylperoxyisopropylbenzene has the greatest promoting effect on the crosslinking reaction. Furthermore, the addition of antioxidants further improves the crosslinking efficiency.

[0098] Figure 1 Images (a), (b), (c), and (d) are polarized light microscope images of the linear low-density polyethylene raw material in Example 1 and the insulating materials prepared in Examples 1-3, respectively. Figure 1It can be seen that with the addition of the initiator bis-tert-butylperoxyisopropylbenzene, the amorphous portion (black part in the figure) increases, indicating that the linear low-density polyethylene forms a good three-dimensional cross-linked network structure, which is beneficial to improving the cross-linking performance. Other embodiments also show certain amorphous regions, indicating that they have a cross-linked structure.

[0099] Figure 2 These are the infrared spectra of the linear low-density polyethylene raw material in Example 1 and the insulating materials prepared in Examples 1-3. The polyethylene raw material contains a large number of methylene structures located at 1450 cm⁻¹. -1 and 720cm -1 The response peaks belong to the -CH2- bending vibration peak and the rocking vibration peak, respectively. Furthermore, the linear low-density polyethylene structure also contains many short hydrocarbon side chains terminated with methyl groups, located at 1373 cm⁻¹. -1 and 1081cm -1 The response peaks were attributed to the bending and rocking vibration peaks of -CH3, respectively. The infrared spectrum of the cross-linked material was basically consistent with that of the uncross-linked material, indicating that the molecular structure of cross-linked polyethylene is mainly composed of methylene and methyl groups. Notably, the cross-linked material showed a peak at 965 cm⁻¹. -1 A new response appeared at 965 cm⁻¹, which is attributed to the rocking vibration peak of the methylene group. This is due to carbon-carbon bonding during the crosslinking process of polyethylene, and the peak value increases with increasing initiator dosage. Insulating materials prepared in other embodiments showed a peak at 965 cm⁻¹. -1 A corresponding response peak also appeared at the location, indicating that a cross-linked structure was introduced into linear low-density polyethylene.

[0100] Figure 3 This is a differential scanning calorimetry (DSC) curve of the insulating material prepared in Example 2. During the heating process, a significant endothermic peak appears at approximately 125°C, indicating the melting behavior of the linear low-density polyethylene (LDPE) base material; an exothermic peak appears in the range of approximately 170-210°C, attributed to the crosslinking reaction of the material. A clear boundary exists between the melting peak and the crosslinking peak, indicating that the material has a wide processing window. Differential scanning calorimetry curves of other examples are shown below. Figure 3 The similarity indicates that both have a relatively wide processing window.

[0101] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An insulating material, characterized in that, The material is made from the following raw materials in parts by weight: 100 parts of copolymer of ethylene and at least one C3-C6 linear α-olefin, 0.1-2.5 parts of initiator, 0.1-2 parts of crosslinking agent, 0-0.5 parts of antioxidant, and 0-0.1 parts of deacidifying agent.

2. The insulating material according to claim 1, wherein, The copolymer has a weight-average molecular weight of 5 × 10⁻⁶. 4 -10×10 4 g / mol.

3. The insulating material according to claim 1 or 2, wherein, The C3-C6 straight-chain α-olefin is selected from at least one of propylene, 1-butene, 1-pentene and 1-hexene, more preferably 1-butene and / or 1-pentene, and even more preferably 1-butene.

4. The insulating material according to any one of claims 1-3, wherein, In the copolymer, the mass ratio of the structural units provided by ethylene to the structural units provided by C3-C6 linear α-olefins is 1:0.05-0.15, preferably 1:0.09-0.

11.

5. The insulating material according to any one of claims 1-4, wherein, The copolymer is a linear low-density polyethylene formed by random copolymerization of ethylene and C3-C6 straight-chain α-olefins, with a density of 0.91-0.94 g / cm³ at 190°C and a load of 2.16 kg. 3 ; Preferably, the copolymer has a melt index of 2.5-3.5 g / 10 min at 190°C and a load of 2.16 kg, more preferably 2.7-3.1 g / 10 min; and a density of 0.918-0.924 g / cm³. 3 More preferably, it is 0.920-0.922 g / cm³. 3 .

6. The insulating material according to any one of claims 1-5, wherein, The initiator is selected from organic peroxides, preferably peroxides containing tert-butyl groups, and more preferably at least one of bis-tert-butylperoxyisopropylbenzene, 2,5-dimethyl-2,5-bis-(tert-butylperoxy)hexane, and 2,5-bis(tert-butylperoxy)-2,5-dimethyl-3-hexyne. Preferably, the amount of the initiator is 0.2-1.5 parts by weight relative to 100 parts of the copolymer, more preferably 0.3-0.9 parts by weight.

7. The insulating material according to any one of claims 1-6, wherein, The crosslinking agent is selected from polyfunctional substances, preferably compounds containing three allyl groups, and more preferably at least one of triallyl isocyanurate and triallyl cyanurate. Preferably, the amount of the crosslinking agent is 0.2-1 parts by weight, more preferably 0.3-0.7 parts, relative to 100 parts of the copolymer.

8. The insulating material according to any one of claims 1-7, wherein, The antioxidant is a hindered phenolic antioxidant and / or a phosphite antioxidant; Preferably, the hindered phenolic antioxidant is selected from at least one of 4,4'-thiobis(6-tert-butyl-3-methylphenol), pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. Preferably, the phosphite antioxidant is selected from at least one of tris[2,4-di-tert-butylphenyl] phosphite and bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite; Preferably, the amount of antioxidant is 0.05-0.45 parts by weight relative to 100 parts of copolymer, more preferably 0.1-0.3 parts.

9. The insulating material according to any one of claims 1-8, wherein, The acid remover is at least one of hydrotalcite, zinc stearate, and calcium stearate; Preferably, the amount of the deacidifying agent is 0.005-0.02 parts by weight relative to 100 parts of the copolymer, more preferably 0.007-0.013 parts by weight.

10. The insulating material according to any one of claims 1-9, wherein, The processing methods include mixing, impregnation, cooling, extrusion, and optional pelleting; Preferably, the immersion temperature is 40-80℃, more preferably 50-70℃; the immersion time is 3-12h, more preferably 5-8h; Preferably, the temperature after cooling is 20-30°C; Preferably, the extrusion temperature is 130-150°C, more preferably 136-144°C.

11. The use of the insulating material according to any one of claims 1-10 in power cables.

Images