Insulating material compositions, insulating materials and their preparation methods, insulating materials and their applications

Abstract

This invention relates to the field of insulating materials, and discloses an insulating material composition, an insulating material and its preparation method, an insulating material and its application. The insulating material composition includes: polyethylene, an antioxidant, a crosslinking agent and a nano-additive; wherein the nano-additive has a core-shell structure, and the shell is a porous shell layer; the core of the nano-additive is selected from at least one of silicon dioxide, aluminum oxide, magnesium oxide, titanium oxide and zinc oxide, and the shell of the nano-additive is selected from at least one of cerium oxide, zinc oxide, silicon dioxide and titanium oxide, and the oxides of the core and shell are different. Under the combined action of the nano-additive and other components, the insulating material has good scorch resistance and high processing safety during the preparation of insulating materials; and the prepared insulating material has good thermal stability and high resistivity; overcoming the problem in the prior art that it is difficult to simultaneously achieve thermal stability, scorch resistance and electrical performance.

Description

Technical Field

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

[0002] In modern power transmission and electronic equipment, the performance of insulation materials is crucial to the safety and reliability of the system. Cross-linked polyethylene (XLPE) is widely used in cable insulation materials due to its excellent electrical, mechanical, and processing properties. However, traditional XLPE insulation materials are prone to scorching during high-temperature processing, leading to a decline in material performance and a shortened cable lifespan. Anti-scorching agents are often added to extend the scorching time of the insulation material. However, the introduction of anti-scorching agents reduces the degree of cross-linking in the insulation material, compromising its thermal stability. For example, cable insulation may experience thinning and deformation due to thermal elongation, increasing the risk of short circuits and other faults. Traditional XLPE insulation materials often struggle to balance thermal stability and scorching resistance. For instance, increasing the degree of cross-linking helps improve the thermal stability of XLPE, but it reduces scorching resistance. In actual production, improving scorching resistance while ensuring the degree of cross-linking meets insulation performance requirements is a technical challenge that requires complex formulation adjustments and process optimization.

[0003] To improve thermal stability and scorch resistance, existing technologies mainly improve the performance of insulating materials by adding various additives, changing the structure and type of crosslinking agents, and changing the crosslinking process. However, these methods often have limitations, such as (1) adding heat stabilizers can reduce thermal elongation to a certain extent, but have limited effect on improving scorch resistance; (2) too many additives in the insulating material formulation may affect the electrical insulation performance of the insulating material; (3) changing the type of crosslinking agent may lead to a complex crosslinking process, and have limited effect on improving scorch resistance. It may also have an adverse effect on other properties of the insulating material (such as electrical properties, mechanical properties, etc.), making it difficult to achieve simultaneous optimization of thermal elongation and scorch resistance.

[0004] Therefore, developing an insulating material that simultaneously possesses excellent thermal stability and scorch resistance is a key technological requirement in the current field of insulating materials. Summary of the Invention

[0005] The purpose of this invention is to overcome the difficulty in simultaneously achieving scorch resistance, thermal stability, and electrical performance in insulating materials, and to provide an insulating material composition, an insulating material and its preparation method, an insulating material and its application. This insulating material composition exhibits good scorch resistance and high processing safety during the preparation of insulating materials; and the resulting insulating material has good thermal stability and high resistivity.

[0006] To achieve the above objectives, the first aspect of the present invention provides an insulating material composition, wherein the insulating material composition comprises: polyethylene, an antioxidant, a crosslinking agent, and a nano-additive;

[0007] The nano-additive has a core-shell structure, with the shell being a porous shell layer. The core of the nano-additive is selected from at least one of silicon dioxide, aluminum oxide, magnesium oxide, titanium oxide, and zinc oxide, and the shell of the nano-additive is selected from at least one of cerium oxide, zinc oxide, silicon dioxide, and titanium oxide. The oxides of the core and the shell are different, and the surface of the core of the nano-additive is modified with vinyl groups.

[0008] A second aspect of the present invention provides a method for preparing an insulating material, wherein the method includes:

[0009] S1. Mix the components of the above insulating material composition, excluding the crosslinking agent, to obtain a semi-finished material;

[0010] S2. The semi-finished material is mixed with and absorbed by a crosslinking agent to obtain an insulating material.

[0011] A third aspect of the present invention provides an insulating material prepared by the above method.

[0012] A fourth aspect of the present invention provides an insulating material, wherein the insulating material is cross-linked as described above.

[0013] The fifth aspect of the present invention provides the application of the above-described insulating composition, insulating material or insulating material in cables.

[0014] Through the above technical solutions, the insulating material composition, insulating material and its preparation method, insulating material and its application provided by the present invention have the following beneficial effects.

[0015] The insulating material composition of the present invention contains a core-porous shell structured nano-auxiliary agent. The core is selected from at least one of silicon dioxide, aluminum oxide, magnesium oxide, titanium oxide, and zinc oxide, and the shell is selected from at least one of cerium oxide, zinc oxide, silicon dioxide, and titanium oxide. The oxides of the core and the shell are different. Under the combined action of this nano-auxiliary agent and other components, the insulating material has good scorch resistance and high processing safety during the preparation of insulating materials. Furthermore, the insulating material produced has good thermal stability and high resistivity. This overcomes the problem in the prior art that it is difficult to balance thermal stability, scorch resistance, and electrical performance. 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] The first aspect of the present invention provides an insulating material composition, wherein the insulating material composition comprises: polyethylene, an antioxidant, a crosslinking agent, and a nano-additive;

[0018] The nano-additive has a core-shell structure, with the shell being a porous shell layer. The core of the nano-additive is selected from at least one of silicon dioxide, aluminum oxide, magnesium oxide, titanium oxide, and zinc oxide, and the shell of the nano-additive is selected from at least one of cerium oxide, zinc oxide, silicon dioxide, and titanium oxide. The oxides of the core and the shell are different, and the surface of the core of the nano-additive is modified with vinyl groups.

[0019] In this invention, the insulating material composition contains a core-porous shell structured nano-auxiliary agent. The core is selected from at least one of silicon dioxide, aluminum oxide, magnesium oxide, titanium oxide, and zinc oxide, and the shell is selected from at least one of cerium oxide, zinc oxide, silicon dioxide, and titanium oxide. The oxides of the core and the shell are different. Under the combined action of this nano-auxiliary agent and other components, the insulating material has good scorch resistance and high processing safety during the preparation of insulating materials. Furthermore, the insulating material produced has good thermal stability and high resistivity.

[0020] Furthermore, the core of the nano-auxiliary is selected from at least one of silicon dioxide, titanium dioxide, and zinc oxide, and the shell of the nano-auxiliary is selected from at least one of cerium oxide, silicon dioxide, and titanium oxide.

[0021] Furthermore, the core of the nano-additive is silicon dioxide, and the shell of the nano-additive is cerium oxide.

[0022] According to a preferred embodiment of the present invention, when a nano-additive with silicon dioxide as the core and cerium oxide as the shell is used, the nano-additive can produce a synergistic effect with polyethylene and antioxidants. The insulating material composition has good scorch resistance during the preparation of insulating materials, and the resulting insulating material has high thermal stability and high resistivity.

[0023] According to the present invention, the average particle size of the nucleus is 10-50 nm, which can be any two values ​​formed by 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 45, 50 nm, or any value within that range.

[0024] According to the present invention, the average thickness of the shell is 5-15 nm, which can be any two values ​​formed by 5, 6, 8, 10, 11, 12, 13, 15 nm, or a value within that range.

[0025] According to the present invention, the aperture of the shell is 2-10 nm, which can be any two values ​​formed by 2, 3, 5, 6, 8, 9, 10 nm, or any value within that range.

[0026] In this invention, the average particle size of the nano-adjuvant is 50-120 nm, which can be any two values ​​from 50, 52, 55, 58, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120 nm, or any value within that range.

[0027] In this invention, when at least one of the particle size of the nano-additive core, the thickness of the shell, and the pore size of the shell meets the above-mentioned ranges, the heat conduction path of the insulating material can be optimized, local overheating can be reduced, and the scorch time can be extended. Furthermore, when both the particle size and the thickness of the shell meet the above-mentioned ranges, the agglomeration tendency of the nano-additive can be reduced, allowing the nano-additive to be uniformly dispersed in the insulating material, avoiding microcracks caused by stress concentration, and improving processing stability. Simultaneously, it facilitates the formation of chemical bonds between the nano-additive and the polyethylene matrix, enhancing the stability of the branched network structure, resulting in an insulating material with higher thermal stability and resistivity.

[0028] Furthermore, the average particle size of the nucleus is 25-35 nm.

[0029] Furthermore, the average thickness of the shell is 8-12 nm.

[0030] Furthermore, the pore size of the shell is 2-5 nm.

[0031] Furthermore, the average particle size of the nano-auxiliary is 55-100 nm.

[0032] In this invention, the PDI of the nano-auxiliary agent is ≤0.2.

[0033] According to the present invention, the grafting density of vinyl groups on the core surface of the nano-auxiliary is 1-5 per nm. 2 .

[0034] Furthermore, the grafting density of vinyl groups on the core surface of the nano-auxiliary is 2-4 per nm. 2 .

[0035] In this invention, the vinyl group refers to a group with an unsaturated carbon-carbon double bond at the end. It can be understood that the vinyl group in this invention can be either CH2=CH‒ or CH2=CR‒, wherein R can be an alkyl group with 1-3 carbon atoms.

[0036] According to a preferred embodiment of the present invention, when the core of the nano-auxiliary is silicon dioxide and the shell of the nano-auxiliary is cerium oxide, the preparation method of the nano-auxiliary includes:

[0037] S1. SiO2 nanoparticles are modified using a vinyl-containing silane coupling agent to obtain modified SiO2 nanoparticles.

[0038] S2. The modified SiO2 nanoparticles are dispersed in ethanol and then hexadecyltrimethylammonium bromide (CTAB) is added. After the first stirring reaction is uniform, a micelle template is formed. A cerium-containing precursor is added and the pH value is adjusted to alkaline before a second stirring reaction is carried out. The resulting product is washed, dried, and then the template agent is removed by solvent extraction to obtain the nano-auxiliary agent.

[0039] The temperature of the first stirring reaction is 40-60℃ and the reaction time is 0.5-4h. The temperature of the second stirring reaction is 40-70℃ and the reaction time is 10-16h.

[0040] According to a preferred embodiment of the present invention, in step S1, the average particle size of the SiO2 nanoparticles is 10-50 nm, preferably 25-35 nm.

[0041] According to a preferred embodiment of the present invention, in step S1, the grafting density of vinyl groups on the surface of the modified SiO2 nanoparticles is 1-5 per nm. 2 The possible values ​​are 1, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.3, 3.5, 3.8, 4, 4.3, 4.5, and 5 units per nm. 2 The range formed by any two values ​​and the values ​​within that range are further preferably 2-4 per nm. 2 .

[0042] According to a preferred embodiment of the present invention, in step S1, the molar ratio of the silane coupling agent (based on vinyl groups) to the SiO2 nanoparticles (based on SiO2) is 0.2-1.2:1, more preferably 0.5-1:1.

[0043] In this invention, there is no particular limitation on the specific type of vinyl-containing silane coupling agent. For example, it can be methylpropionyloxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, or vinyltri(β-methoxytriethoxy)silane.

[0044] According to a preferred embodiment of the present invention, step S1 includes: mixing a vinyl-containing silane coupling agent with an alcohol, adjusting the pH to 4-5 for hydrolysis to obtain a hydrolyzed silane coupling agent; stirring and grafting the hydrolyzed silane coupling agent with SiO2 nanoparticles; washing and drying the resulting product to obtain modified SiO2 nanoparticles.

[0045] According to a preferred embodiment of the present invention, the volume ratio of the vinyl-containing silane coupling agent to the alcohol is 1:7-12, preferably 1:8-10.

[0046] In this invention, there is no special limitation on the type of alcohol, such as ethanol and / or methanol.

[0047] In this invention, there are no special limitations on the method of adjusting the pH value to 4-5. For example, 0.1-0.5wt% glacial acetic acid can be used to adjust the pH.

[0048] According to a preferred embodiment of the present invention, the hydrolysis and grafting reaction temperature is 50-70°C, the hydrolysis time is 0.5-2h, and the grafting reaction time is 5-8h.

[0049] In this invention, there are no special limitations on the washing method; for example, alcohol can be used for washing. In this invention, there are no special limitations on the drying conditions; for example, drying can be carried out under vacuum for 9-15 hours.

[0050] According to a preferred embodiment of the present invention, in step S2, the cerium-containing precursor is selected from at least one of cerium ammonium nitrate, cerium chloride, cerium sulfate, and cerium nitrate, preferably cerium ammonium nitrate.

[0051] According to a preferred embodiment of the present invention, in step S2, the molar ratio of CTAB to the cerium-containing precursor (calculated as element Ce) is 1:1-5. When the amounts of template agent and cerium-containing precursor meet the above range, it is beneficial to form a stable micelle template and to reasonably control the mesopore size. More preferably, the molar ratio of CTAB to the cerium-containing precursor (calculated as element Ce) is 1:2-3.

[0052] According to a preferred embodiment of the present invention, in step S2, the amount of the cerium-containing precursor and the modified SiO2 nanoparticles is such that the molar ratio of the cerium-containing precursor (calculated as element Ce) to the modified SiO2 nanoparticles (calculated as SiO2) is 1.5-4.5:1. When the amount of the cerium-containing precursor and the SiO2 nanoparticles meets the above range, it is beneficial to obtain a nano-auxiliary agent with better core particle size and shell thickness. More preferably, the amount of the cerium-containing precursor and the SiO2 nanoparticles is such that the molar ratio of the cerium-containing precursor (calculated as element Ce) to the modified SiO2 nanoparticles (calculated as SiO2) is 2-3:1.

[0053] According to a preferred embodiment of the present invention, in step S2, the pH value is 9-10. When the pH value meets this range, the shell of the prepared nano-auxiliary agent has a better mesoporous structure.

[0054] In this invention, there are no special limitations on the washing method in step S2. For example, alcohol can be used for washing.

[0055] In this invention, there are no special limitations on the drying conditions; for example, drying can be carried out under vacuum conditions for 9-15 hours.

[0056] According to a preferred embodiment of the present invention, in step S2, the solvent extraction method uses a mixture of hydrochloric acid and ethanol (volume ratio of hydrochloric acid to ethanol is 1:8-12) for extraction, the extraction temperature is 55-65℃, the extraction time is 6-8h, and the mixture is centrifuged, washed until neutral, and then vacuum dried.

[0057] According to the present invention, the polyethylene is low-density polyethylene and / or linear low-density polyethylene.

[0058] Furthermore, the polyethylene is low-density polyethylene.

[0059] In this invention, the density of the polyethylene is 0.91-0.93 g / cm³. 3 Preferably, the density of the low-density polyethylene and / or linear low-density polyethylene is 0.917-0.925 g / cm³. 3 .

[0060] According to the present invention, the content of terminal double bonds in the polyethylene / 1000C is 0.2-0.7.

[0061] According to the present invention, the terminal double bond of the polyethylene comprises terminal vinyl and terminal vinylidene, wherein the terminal vinyl content / 1000C is 0.01-0.06.

[0062] According to the present invention, the long branched content / 1000C of the polyethylene is 0.5-0.9.

[0063] In this invention, the long branched chain of polyethylene refers to a branched chain structure with more than 6 carbon atoms.

[0064] According to the present invention, the weight-average molecular branch weight of the polyethylene is 7,000-10,000 g / mol.

[0065] In this invention, the weight-average molecular weight of the polyethylene refers to the relative molecular weight of the branched structure, which can characterize the length of long branches.

[0066] According to the present invention, the weight-average molecular weight of the polyethylene is 120,000-200,000 g / mol.

[0067] In this invention, when at least one of the following parameters of polyethylene—terminal double bond content, terminal vinyl content, long-chain branching degree, weight-average molecular branch weight, and weight-average molecular weight—satisfies the above-mentioned range, it can better produce synergistic effects with other components, especially nano-additives. This insulating material composition has good scorch resistance during the preparation of insulating materials, and the resulting insulating material has good thermal stability and high resistivity.

[0068] Furthermore, the content of terminal double bonds in the polyethylene is 0.45-0.55 per 1000C.

[0069] Furthermore, the terminal double bonds of the polyethylene comprise terminal vinyl groups and terminal vinylidenes, wherein the terminal vinyl content / 1000C is 0.02-0.04.

[0070] Furthermore, the long-chain branched content of the polyethylene is 0.6-0.8 per 1000C.

[0071] Furthermore, the weight-average molecular weight of the polyethylene is 8,000-9,000 g / mol.

[0072] Furthermore, the weight-average molecular weight of the polyethylene is 160,000-180,000 g / mol.

[0073] According to the present invention, the antioxidant is a hindered phenolic antioxidant and / or an ester antioxidant.

[0074] Furthermore, the antioxidant is a hindered phenolic antioxidant or an ester antioxidant.

[0075] In this invention, when the antioxidant is a hindered phenolic antioxidant or an ester antioxidant, the insulating material made from the above-mentioned insulating material composition has high thermal stability and excellent processing performance.

[0076] In this invention, there is no particular limitation on the specific types of hindered phenolic antioxidants and / or ester antioxidants. For example, the hindered phenolic antioxidant may be selected from at least one of antioxidant 1010, antioxidant 1076, antioxidant BHT, antioxidant GM, antioxidant AO-80, and antioxidant 3114. For example, the ester antioxidant may be selected from at least one of antioxidant 168, antioxidant DLTDP, and antioxidant 626. Preferably, the mass ratio of the hindered phenolic antioxidant to the ester antioxidant is 1:0.5-2.

[0077] According to the present invention, the crosslinking agent is a peroxide crosslinking agent.

[0078] In this invention, there is no particular limitation on the specific type of crosslinking agent, and conventional crosslinking agents in the art can be used. To enable the insulating material to form a more stable three-dimensional crosslinked structure, preferably, the crosslinking agent is selected from at least one of dicumyl peroxide, di-tert-butyl peroxide, dicumyl hydroperoxide, and 2,5-dimethyl-2,5-di-tert-butylperoxide.

[0079] According to the present invention, in the insulating material composition, polyethylene is 100 parts by weight, antioxidant is 0.1-0.5 parts by weight, crosslinking agent is 0.8-1.7 parts by weight, and nano-additive is 0.1-1 parts by weight.

[0080] In this invention, when the content of each component in the insulating material composition meets the above-mentioned range, the insulating material made from the above composition has excellent scorch resistance, and the insulating material made after cross-linking has high electrical properties and thermal stability.

[0081] Furthermore, in the insulating material composition, polyethylene is 100 parts by weight, antioxidant is 0.2-0.4 parts by weight, crosslinking agent is 1.2-1.6 parts by weight, and nano-additive is 0.3-0.6 parts by weight.

[0082] A second aspect of the present invention provides a method for preparing an insulating material, wherein the method includes:

[0083] S1. Mix the components of the above insulating material composition, excluding the crosslinking agent, to obtain a semi-finished material;

[0084] S2. The semi-finished material is mixed with and absorbed by a crosslinking agent to obtain an insulating material.

[0085] According to the present invention, in step S1, the mixing conditions include: the mixing temperature is 120-200℃, and the mixing speed is 150-250rpm.

[0086] Further, in step S1, the mixing conditions include: the mixing temperature is 120-170℃, and the mixing speed is 180-220rpm.

[0087] According to the present invention, in step S2, the crosslinking agent is melted and then mixed with the semi-finished material. For example, the crosslinking agent is melted and then mixed with the semi-finished material by spraying.

[0088] According to the present invention, in step S2, the absorption temperature is 60-80°C and the absorption time is 16-24h.

[0089] Furthermore, in step S2, the absorption temperature is 70-75℃, and the absorption time is 18-20h.

[0090] According to a preferred embodiment of the present invention, step S1 includes:

[0091] 1a. Premix 20-35 wt% polyethylene with nano-additives, and after the first mixing, obtain a premixed material;

[0092] 1b. The premixed material is then mixed with the remaining polyethylene and antioxidant to obtain a semi-finished insulating material.

[0093] In this invention, when a stepwise mixing method is used, the nano-additives achieve efficient dispersion. During the premixing stage, the polyethylene molecular chains form a physical adsorption layer on the surface of the nanoparticles, reducing the tendency for aggregation during subsequent mixing. Adding an antioxidant in step 1b avoids mechanical degradation during the high-shear premixing stage and reduces its volatilization loss during high-temperature processing.

[0094] In this invention, the premixing conditions in step 1a include: a rotation speed of 200-300 rpm and a mixing time of 10-20 min.

[0095] According to the present invention, in step 1a, the conditions for the first mixing include: a temperature of 115-135°C and a rotation speed of 150-250 rpm.

[0096] In this invention, step 1a includes: granulating the material after the first mixing.

[0097] According to the present invention, in step 1b, the conditions for the second mixing include: a temperature of 120-170°C and a rotation speed of 150-250 rpm.

[0098] In this invention, in step 1b, the premixed material is stirred with the remaining polyethylene, and then an antioxidant is added and stirred again before a second mixing process is carried out.

[0099] A third aspect of the present invention provides an insulating material prepared by the above method.

[0100] According to the present invention, the scorching time of the insulating material at 160°C is 7-10 min, preferably 8-10 min.

[0101] A fourth aspect of the present invention provides an insulating material, wherein the insulating material is cross-linked as described above.

[0102] According to the present invention, the crosslinking temperature is 150-180°C, preferably 155-175°C.

[0103] According to the present invention, the thermal decomposition temperature of the insulating material is greater than or equal to 350°C, preferably 380-390°C.

[0104] According to the present invention, the oxidation induction period of the insulating material at 200°C is greater than or equal to 25 min, preferably 30-40 min.

[0105] According to the present invention, the volume resistivity of the insulating material at 70°C and an electric field strength of 20 kV / mm is 7 × 10⁻⁶. 12 Ω•m-13×10 12 Ω•m, preferably 8×10 12 Ω•m-12×10 12 Ω•m.

[0106] The fifth aspect of the present invention provides the application of the above-described insulating composition, insulating material or insulating material in cables.

[0107] In this invention, a low-density polyethylene with a specific structure, a specific antioxidant composite system, and a core-shell nano-additive with a specific structure are used. Under the synergistic effect of these three, the insulating material made from this insulating material can have high scorch resistance, thermal stability, and high resistivity.

[0108] The present invention will be described in detail below through embodiments.

[0109] In the following embodiments:

[0110] The average thickness of the shell and the average particle size of the core of the nano-adjuvant were estimated using a JEM-2100 transmission electron microscope.

[0111] Pore ​​size and specific surface area of ​​nano-additives: The pore structure parameters of the samples were characterized using an ASAP 2010C nitrogen adsorption / desorption instrument.

[0112] Particle size and polydispersity index of nano-additives: Nanoparticle size and polydispersity index were determined by dynamic light scattering method;

[0113] Vinyl grafting density: After vacuum drying of vinyl-modified SiO2 particles to constant weight, the vinyl content of the sample was tested using a thermogravimetric analyzer. 5-10 mg of sample was placed in an alumina crucible, and the temperature was increased from 25 °C to 800 °C at a rate of 10 °C / min under a nitrogen atmosphere. An equal mass of unmodified SiO2 particles was used as a control group. The difference in mass loss between the modified and unmodified samples within the same temperature range (200-500 °C) was calculated as the vinyl grafting amount (wt%), where the actual mass loss difference was for vinylsilane, converted to the vinyl grafting amount. The vinyl grafting density was then calculated using the formula: grafting density (particles / nm). 2 )= In the formula N A Avogadro's constant: 6.022 × 10⁻⁶ 23 SSA represents the specific surface area of ​​silicon dioxide.

[0114] The content of terminal double bonds and terminal vinyl groups in polyethylene: The types and contents of chemical bonds in LDPE samples were analyzed using FTIR spectroscopy (wavenumbers 400-4000 cm⁻¹). -1 The resolution is 4cm. -1 The number of scans was 32. The total content of terminal double bonds was characterized by the ratio of internal standard peak area, and the content of the two types of terminal double bonds was characterized by the ratio of internal standard peak height, with 2020 cm⁻¹ as the baseline. -1 The combined peak is used as an internal standard, 888cm. -1 and 908cm -1 The absorption peaks at these locations are attributed to vinylidene and terminal vinyl groups, respectively.

[0115] Weight-average molecular weight, long-chain branch content, and weight-average molecular weight of polyethylene: The molecular weight and long-chain branching structure of the polymer were characterized by using a PL220 high-temperature gel permeation chromatograph coupled with a differential refractive index detector, a viscosity detector, and a light scattering detector.

[0116] Thermal decomposition temperature: The thermogravimetric analysis was used to characterize the thermal-oxygen stability of the sample. 5-10 mg of sample was placed in an alumina crucible and the temperature was increased from 25 °C to 700 °C at a heating rate of 10 °C / min in an oxygen atmosphere to test the thermal decomposition temperature of the sample.

[0117] Oxidation induction period: The procedure was performed in accordance with GB / T 19466.6-2009. A differential scanning calorimeter was used to raise the temperature to 200℃ in a nitrogen atmosphere (50 mL / min) at a rate of 20℃ / min. After holding the temperature for 5 min, the temperature was switched to an oxygen atmosphere (50 mL / min). The thermal effect was observed and the oxidation induction period of the sample was calculated under the constant temperature condition of 200℃.

[0118] Thermal elongation: The thermal elongation test was performed in accordance with GB / T 2951.21-2008. The specimen was the 5A type specimen in GB / T1040.2-2022. The test temperature was (200±3)℃, the specimen thickness was (1.0±0.1)mm, a load of 0.2MPa was applied to the bottom of the specimen, and the heat treatment was carried out for 15min.

[0119] Scorch time: The crosslinking behavior of XLPE was studied using a rotorless vulcanizer, referring to GB / T 16584-1996. The test temperature was 160℃. The insulating material was gradually melted and plasticized under the shearing and vibration of the lower mold cavity. When the material was completely plasticized, the crosslinking agent was decomposed by heat to generate free radicals, which promoted the formation of crosslinking network.

[0120] Volume resistivity: The test was conducted in accordance with GB / T 31838.2-2019, with a test temperature of (70±2)℃, a test field strength of 20kV / mm, and a test piece thickness of (0.20±0.02)mm;

[0121] All other raw materials used in the examples and comparative examples were commercially available products;

[0122] In the preparation examples, embodiments, and comparative examples, room temperature refers to 22°C.

[0123] Table 1

[0124]

[0125] Preparation Example 1

[0126] S1. Mix the vinyl-containing silane coupling agent with ethanol at a volume ratio of 1:9, sonicate for 30 minutes, add 0.1 wt% glacial acetic acid to adjust the pH to 4.5, stir at 60°C for 30 minutes, add SiO2 nanoparticles (the molar ratio of vinyl to SiO2 nanoparticles in the silane coupling agent is 0.8:1), stir magnetically at 60°C for 6 hours, collect the particles by centrifugation, wash thoroughly with ethanol, and vacuum dry at 80°C for 12 hours to obtain modified SiO2 nanoparticles.

[0127] S2. Modified SiO2 particles and ethanol were mixed at a mass ratio of 1:150 and ultrasonically treated for 30 minutes. Hexadecyltrimethylammonium bromide solution (0.1 mol / L) was added, and the mixture was stirred for the first time at 60°C for 2 hours to form a micelle template. Cerium ammonium nitrate solution (0.1 mol / L) was added dropwise. The molar ratio of cerium ammonium nitrate (calculated as element Ce) to SiO2 nanoparticles (calculated as element SiO2) was 2:1, and the molar ratio of CTAB to cerium ammonium nitrate (calculated as element Ce) was 1:2. Ammonia was added to adjust the pH to 10. The mixture was stirred for the second time at 60°C for 10 hours. The product was collected by centrifugation and washed thoroughly with ethanol. After drying, the template agent was removed by solvent extraction (volume ratio of hydrochloric acid and ethanol was 1:10) to obtain SiO2-CeO2 nano-auxiliary agent N-1.

[0128] The test results of nano-additive N-1 are shown in Table 2.

[0129] Preparation Example 2

[0130] The nano-auxiliary agent was prepared according to the method of Preparation Example 1, except that in step S2, the amount of cerium source and SiO2 nanoparticles was such that the molar ratio of cerium ammonium nitrate (calculated as elemental Ce) to SiO2 nanoparticles was 1.5:1.

[0131] The test results of nano-additive N-2 are shown in Table 2.

[0132] Preparation Example 3

[0133] The nano-auxiliary agent was prepared according to the method of Preparation Example 1, except that in step S2, the amount of cerium source and SiO2 nanoparticles was such that the molar ratio of cerium ammonium nitrate (calculated as elemental Ce) to SiO2 nanoparticles was 5:1, and the reaction was stirred at 60°C for 16 h.

[0134] The test results of nano-additive N-3 are shown in Table 2.

[0135] Preparation Example 4

[0136] The nano-auxiliary agent was prepared according to the method of Preparation Example 1, except that in step S2, the amount of template agent CTAB and cerium source was such that the molar ratio of CTAB to cerium ammonium nitrate (calculated as element Ce) was 1:4, the micelle reaction temperature was 80°C, and the reaction time was 4 h.

[0137] The test results of nano-additive N-4 are shown in Table 2.

[0138] Preparation Example 5

[0139] The nano-auxiliary agent was prepared according to the method of Preparation Example 1, except that in step S2, the amount of cerium source and SiO2 nanoparticles was such that the molar ratio of cerium ammonium nitrate (calculated as element Ce) to SiO2 nanoparticles was 4:1, the amount of template agent CTAB and cerium source was such that the molar ratio of CTAB to cerium ammonium nitrate (calculated as element Ce) was 1:4, the micelle reaction temperature was 80°C, and the reaction time was 4 h.

[0140] The test results of nano-additive N-5 are shown in Table 2.

[0141] Preparation Example 6

[0142] The nano-auxiliary agent was prepared according to the method of Preparation Example 1, except that in step S1, the molar ratio of silane coupling agent (based on vinyl groups) to SiO2 nanoparticles (based on SiO2) was 1.2:1.

[0143] The test results of nano-additive N-6 are shown in Table 2.

[0144] Preparation Example 7

[0145] The nano-auxiliary agent was prepared according to the method of Preparation Example 1, except that in step S1, the molar ratio of silane coupling agent (based on vinyl groups) to SiO2 nanoparticles (based on SiO2) was 2:1, and the grafting reaction was carried out under magnetic stirring at a temperature of 40°C for 8 hours.

[0146] The test results of nano-additive N-7 are shown in Table 2.

[0147] Preparation Example 8

[0148] The nano-auxiliaries were prepared according to the method of Preparation Example 1, except that the cerium ammonium nitrate solution in step S2 was replaced with tetrabutyl titanate solution, and the pH was adjusted to 10.

[0149] The test results of nano-additive N-8 are shown in Table 2.

[0150] Preparation Example 9

[0151] The nano-auxiliary agent was prepared according to the method of Preparation Example 1, except that the SiO2 nanoparticles in step S1 were replaced with nano-ZnO particles, and the pH was adjusted to 5.5. In step S2, the pH was adjusted to 9.

[0152] The test results of nano-additive N-9 are shown in Table 2.

[0153] Comparative Preparation Example 1

[0154] The nano-auxiliaries were prepared according to the method of Preparation Example 1, except that in step S2, the template agent solution was replaced with sodium dodecyl sulfate (SDS), the molar ratio of SDS to cerium ammonium nitrate (calculated as element Ce) was reduced to 1:6 (to prevent the formation of micelle templates), the pH was adjusted to 11 with ammonia, the reaction temperature was 80°C, the reaction time was 10 h, and the template was not removed by solvent extraction.

[0155] The test results of nano-additive DN-1 are shown in Table 2.

[0156] Comparative Preparation Example 2

[0157] The nano-auxiliary agent was prepared according to the method of Preparation Example 1, except that step S1 was omitted, that is, the nano-auxiliary agent was SiO2@mCeO2 nano-auxiliary agent.

[0158] The test results of nano-additive DN-2 are shown in Table 2.

[0159] Comparative preparation example 3

[0160] The nano-additives were prepared according to the method of Preparation Example 1, except that the SiO2@mCeO2 nano-additives prepared in Comparative Preparation Example 2 were subjected to a silane coupling reaction.

[0161] The test results of nano-additive DN-3 are shown in Table 2.

[0162] Table 2

[0163]

[0164] Example 1

[0165] Insulation material composition: 100 parts by weight of polyethylene A, 0.3 parts by weight of antioxidant (the mass ratio of antioxidant 1010 to antioxidant 168 is 1:1), 1.6 parts by weight of crosslinking agent, and 0.5 parts by weight of nano-additive N-1.

[0166] Insulating material preparation method:

[0167] (1a) 20-35 wt% of low-density polyethylene and nano-additives are premixed in a high-speed mixer and then fed into the feed port of a twin-screw extruder for melt mixing (first mixing). After water cooling and air drying, the mixture is granulated to obtain the premixed material. The high-speed mixer speed is 200 rpm, the mixing time is 15 min, the temperatures of each zone of the extruder are 115, 120, 120, 125, 125, 130, 135, and 135 °C, and the extruder speed is 200 rpm.

[0168] (1b) The premix is ​​stirred with the remaining polyethylene, and then an antioxidant is added and stirred again. After a second mixing, the mixture is extruded by a twin-screw extruder, water-cooled, air-dried, and granulated to obtain a semi-finished insulating material. The temperatures of each zone of the extruder are 120, 125, 130, 140, 150, 160, 165, and 170°C, and the extruder speed is 200 rpm.

[0169] (2) After the crosslinking agent is melted, it is sprayed into the post-absorption shaking tank and mixed thoroughly with the semi-finished material. Then the material in the shaking tank is introduced into the heat preservation tank for full absorption. The absorption temperature is 75℃ and the heat preservation time is 20h. After cooling, the insulating material is obtained.

[0170] Examples 2-9

[0171] The insulating material was prepared according to the method of Example 1. The difference was that the nano-additive N-1 was replaced with N-2 to N-9 in sequence.

[0172] Example 10

[0173] The insulating material was prepared according to the method of Example 1. The difference was that polyethylene A was replaced with polyethylene B.

[0174] Example 11

[0175] The insulating material was prepared according to the method of Example 1. The difference was that polyethylene A was replaced with polyethylene C.

[0176] Example 12

[0177] The insulating material was prepared according to the method of Example 1. The difference is that the polyethylene A was 100 parts by weight, the antioxidant was 0.2 parts by weight (the mass ratio of antioxidant 1010 to antioxidant 168 was 1:1), the crosslinking agent was 1.6 parts by weight, and the nano-additive N-1 was 0.2 parts by weight.

[0178] Example 13

[0179] The insulating material was prepared according to the method of Example 1. The difference was that the amount of polyethylene A was 100 parts by weight, the amount of antioxidant was 0.6 parts by weight (the mass ratio of antioxidant 1010 to antioxidant 168 was 1:1), the amount of crosslinking agent was 1.6 parts by weight, and the amount of nano-additive N-1 was 0.05 parts by weight.

[0180] Example 14

[0181] The insulating material was prepared according to the method of Example 1. The difference was that polyethylene A was replaced with polyethylene B, and nano-additive N-1 was replaced with N-5.

[0182] Example 15

[0183] The insulating material was prepared according to the method of Example 1. The difference was that polyethylene A was replaced with polyethylene B, and nano-additive N-1 was replaced with N-8.

[0184] Example 16

[0185] The insulating material was prepared according to the method of Example 1. The difference was that antioxidant 1010 was 0.3 parts by weight and antioxidant 168 was not present.

[0186] Example 17

[0187] Insulation material composition: 100 parts by weight of polyethylene A, 0.3 parts by weight of antioxidant (the mass ratio of antioxidant 1010 to antioxidant 168 is 1:1), 1.6 parts by weight of crosslinking agent, and 0.5 parts by weight of nano-additive N-1.

[0188] Insulating material preparation method:

[0189] (1) Low-density polyethylene, nano-additives and antioxidants are melt-blended, water-cooled and air-dried and then granulated to obtain semi-finished material. The temperatures of each zone of the extruder are 120, 125, 130, 140, 150, 160, 165 and 170℃, and the extruder speed is 200 rpm.

[0190] (2) After the crosslinking agent is melted, it is sprayed into the post-absorption shaking tank and mixed thoroughly with the semi-finished material. Then the material in the shaking tank is introduced into the heat preservation tank for full absorption. The absorption temperature is 75℃ and the heat preservation time is 20h. After cooling, the insulating material is obtained.

[0191] Example 18

[0192] The insulating material was prepared according to the method of Example 1. The difference was that polyethylene A was replaced with polyethylene D.

[0193] Comparative Example 1

[0194] The insulating material was prepared according to the method of Example 1. The difference was that nano-additive N-1 was replaced with nano-additive DN-1.

[0195] Comparative Example 2

[0196] The insulating material was prepared according to the method of Example 1. The difference was that nano-additive N-1 was replaced with nano-additive DN-2.

[0197] Comparative Example 3

[0198] The insulating material was prepared according to the method of Example 1. The difference was that nano-additive N-1 was replaced with nano-additive DN-3.

[0199] Comparative Example 4

[0200] The insulating material was prepared according to the method in Example 1. The difference was that no nano-additives were added.

[0201] Comparative Example 5

[0202] The insulating material was prepared according to the method in Example 1. The difference was that the nano-additive N-1 was replaced with nano-silica (particle size D50 of 50 nm).

[0203] Comparative Example 6

[0204] The insulating material was prepared according to the method in Example 1. The difference was that the nano-additive N-1 was replaced with cerium oxide (particle size D50 of 50 nm).

[0205] Comparative Example 7

[0206] The insulating material was prepared according to the method of Example 1. The difference was that the composition of the insulating material was as follows: 100 parts by weight of polyethylene A, 0.3 parts by weight of antioxidant (the mass ratio of antioxidant 1010 to antioxidant 168 was 1:1), 1.6 parts by weight of crosslinking agent, 0.3 parts by weight of nano-silica, and 0.2 parts by weight of cerium oxide.

[0207] Test Example 1

[0208] The scorch time of the insulation materials in the test examples and comparative examples is shown in Table 3.

[0209] Test Example 2

[0210] The insulating materials of the examples and comparative examples were crosslinked to prepare insulating materials. Specifically, the preparation process of the sheet-like insulating material samples included three stages: pressure preheating, pressure crosslinking, and cooling. For pressure preheating, molds of different thicknesses were placed in a flat vulcanizing machine, and the insulating material was placed between two layers of polyester film for pressing. Pre-crosslinking was performed at 130°C for 5 minutes, with the pressure gradually increased from 0 MPa to 15 MPa, applied every 1 minute. For pressure crosslinking, the pre-crosslinked sample was pressurized at 180°C and 15 MPa for 15 minutes. Cooling was then performed by cooling the crosslinked sample with circulating water at 15 MPa for 5 minutes. The cooled sample was then placed in a vacuum oven at 70°C for degassing and stress relief treatment for 24 hours.

[0211] The test results of thermal decomposition temperature, oxidation induction period, thermal elongation and volume resistivity of the insulating material are shown in Table 3.

[0212] Table 3

[0213]

[0214] As can be seen from the results in Table 3, the insulating material composition provided in the embodiments of the present invention has good scorch resistance. Furthermore, using the preferred embodiment of the present invention, i.e., using the preferred nano-additives provided by the present invention, the scorch time is above 9 minutes. In addition, the insulating material composition provided by the present invention has good thermal stability and high resistivity. Using the preferred embodiment of the present invention, the thermal decomposition temperature is above 380℃, and the volume resistivity is greater than 11 × 10⁻⁶. 12 Ω•m, as can be seen from the comparison with the comparative example, the insulating material composition prepared by adding the nano-additives provided by the present invention has good scorch resistance, as well as good thermal stability and high resistivity.

[0215] 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 composition, characterized in that, The insulating material composition includes: polyethylene, antioxidant, crosslinking agent and nano-additives; The nano-additive has a core-shell structure, and the shell is a porous shell layer. The core of the nano-additive is selected from at least one of silicon dioxide, aluminum oxide, magnesium oxide, titanium oxide and zinc oxide, and the shell of the nano-additive is selected from at least one of cerium oxide, zinc oxide, silicon dioxide and titanium oxide. The oxides of the core and the shell are different, and the surface of the core of the nano-additive is modified with vinyl groups. In the insulating material composition, polyethylene is 100 parts by weight, antioxidant is 0.1-0.5 parts by weight, crosslinking agent is 0.8-1.7 parts by weight, and nano-additive is 0.1-1 parts by weight.

2. The insulating composition according to claim 1, wherein, The core of the nano-additive is selected from at least one of silicon dioxide, titanium dioxide, and zinc oxide, and the shell of the nano-additive is selected from at least one of cerium oxide, silicon dioxide, and titanium oxide. And / or, the average particle size of the nucleus is 10-50 nm; And / or, the average thickness of the shell is 5-15 nm; And / or, the pore size of the shell is 2-10 nm; Or, the average particle size of the nano-adjuvant is 50-120 nm; And / or, the grafting density of vinyl groups on the core surface of the nano-adjuvant is 1-5 per nm. 2 .

3. The insulating composition according to claim 1 or 2, wherein, The polyethylene is low-density polyethylene and / or linear low-density polyethylene; And / or, the content of terminal double bonds in the polyethylene is 0.2-0.7 per 1000C; And / or, the terminal double bonds of the polyethylene comprise terminal vinyl groups and terminal vinylidenes, wherein the terminal vinyl content / 1000C is 0.01-0.06; And / or, the long-branched content of the polyethylene is 0.5-0.9 per 1000C; And / or, the weight-average molecular weight of the polyethylene is 7,000-10,000 g / mol; And / or, the weight-average molecular weight of the polyethylene is 120,000-200,000 g / mol.

4. The insulating composition according to claim 1 or 2, wherein, The antioxidant is a hindered phenolic antioxidant and / or an ester antioxidant; And / or, the crosslinking agent is a peroxide crosslinking agent.

5. A method for preparing an insulating material, characterized in that, The method includes: S1. Mix the components of the insulating material composition according to any one of claims 1-4, excluding the crosslinking agent, to obtain a semi-finished material; S2. The semi-finished material is mixed with and absorbed by a crosslinking agent to obtain an insulating material.

6. The method according to claim 5, wherein, In step S1, the mixing conditions include: the mixing temperature is 120-200℃, and the mixing speed is 150-250rpm. And / or, in step S2, the crosslinking agent is melted and then mixed with the semi-finished material; And / or, in step S2, the absorption temperature is 60-80℃ and the absorption time is 16-24h.

7. The method according to claim 5 or 6, wherein, Step S1 includes: 1a. After premixing and first kneading 20-35 wt% polyethylene with nano-additives, a premixed material is obtained; 1b. The premixed material is then mixed with the remaining polyethylene and antioxidant to obtain a semi-finished insulating material.

8. The method according to claim 7, wherein, In step 1a, the conditions for the first mixing include: a temperature of 115-135℃ and a rotation speed of 150-250 rpm. And / or, in step 1b, the conditions for the second mixing include: a temperature of 120-170°C and a rotation speed of 150-250 rpm.

9. An insulating material made by the method according to any one of claims 5-8.

10. An insulating material, characterized in that, It is made from the insulating material described in claim 9 after cross-linking.

11. The insulating material according to claim 10, wherein, The crosslinking temperature is 150-180℃.

12. The insulating material according to claim 10, wherein, The thermal decomposition temperature of the insulating material is greater than or equal to 350°C. And / or, the oxidation induction period of the insulating material at 200°C is greater than or equal to 25 min; And / or, the volume resistivity of the insulating material at 70°C and an electric field strength of 20 kV / mm is 7 × 10⁻⁶. 12 Ω•m-13×10 12 Ω•m.

13. The use of the insulating composition according to any one of claims 1-4, the insulating material according to claim 9, or the insulating material according to any one of claims 10-12 in cables.

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