Insulating material composition for high voltage cables and method for its preparation and use

Abstract

This invention relates to the field of insulation materials technology, specifically to an insulating material composition for high-voltage cables, its preparation method, and its application. The composition comprises an ionomer matrix with a specific structure, an anhydride-functionalized polyolefin elastomer, and an epoxy-functionalized polyhedral oligomeric silsesquioxane. This invention utilizes a stepwise reactive extrusion process to initiate an in-situ chemical reaction between the anhydride and epoxy groups during melt processing, anchoring molecular-level POSS (Positioning of Optical Stylenes) in the matrix via covalent bonds. Combined with the "intrinsic" space charge suppression capability of the ionomer matrix, this synergistically solves the problems of space charge accumulation and partial discharge under high-voltage direct current electric fields. The resulting material is a non-crosslinked thermoplastic material, exhibiting a partial discharge capacity of ≤5pC and a space charge distortion rate of ≤20% under specific testing conditions. It also demonstrates excellent long-term aging stability and chemical resistance, making it specifically designed for 1000 / 1500VDC high-voltage cables for new energy vehicles.

Description

Technical Field

[0001] This invention relates to the field of insulating materials technology, specifically to insulating material compositions for high-voltage cables, their preparation methods, and applications. Background Technology

[0002] With the advancement of global energy transition goals, the new energy vehicle industry is developing at an unprecedented pace. As the "blood vessels" and "neural network" of new energy vehicles, high-voltage wiring harnesses bear the crucial task of high-power, high-voltage energy transmission and signal exchange between the power battery, drive motor, and electronic control system. Unlike the 12V / 24V low-voltage systems of traditional gasoline vehicles, the electrical platforms of new energy vehicles have generally entered the 400V / 800V era and are rapidly evolving towards 1000V and even 1500V DC high-voltage platforms. This leap in voltage levels has placed revolutionary and far more stringent demands on the performance of high-voltage cable insulation materials than previously understood. Existing material systems are generally facing performance bottlenecks, becoming a key technological shortcoming restricting the safety, reliability, and lightweight development of the entire vehicle.

[0003] Existing high-voltage cable insulation materials mainly include cross-linked polyethylene, thermoplastic polyurethane, silicone rubber, and various modified polyolefins. However, under 1500VDC high-voltage direct current conditions, these materials all exhibit inherent and insurmountable defects:

[0004] First, the core challenge stems from the "space charge effect" under a DC electric field. Under the long-term influence of a high-voltage DC electric field, trace impurities within the insulating material, interface defects, and charges injected by the electrodes gradually accumulate, forming locally concentrated "space charge packets." These charge packets severely distort the original uniform electric field within the material, causing local field strengths in certain areas to be several times higher than the average design field strength. This electric field distortion is the main cause of accelerated insulation aging, the initiation of electrical trees, and ultimately, catastrophic breakdown. While traditional XLPE or polyolefin materials exhibit excellent AC performance, their non-polar structure has limited ability to suppress space charge, making it difficult to meet the long-term reliability requirements of high-voltage DC systems.

[0005] Secondly, the harsh service environment poses a significant challenge to the long-term stability of materials. High-voltage wiring harnesses in new energy vehicles are typically located in complex environments such as engine compartments or chassis, requiring them to withstand high temperatures of 125°C or even 150°C, severe vibrations, and constant exposure to coolant (ethylene glycol / water mixture), battery fluid, oil, cleaning agents, and road salt spray. Various small-molecule additives used to enhance the performance of traditional materials, such as plasticizers, antioxidants, and light stabilizers, are highly susceptible to migration, volatilization, or extraction under the combined effects of high temperatures and chemical media. This loss of additives can lead to a sharp decline in material performance during the later stages of service, such as brittleness, reduced insulation resistance, and surface cracking, posing serious safety hazards.

[0006] To achieve the requirements of halogen-free flame retardancy, wear resistance, and high flexibility in high-voltage wiring harnesses, a large amount of inorganic fillers (such as magnesium hydroxide / aluminum) and functional additives must be added to the polymer matrix. However, these additives naturally present interfacial incompatibility issues with the non-polar polymer matrix. At high filler contents, filler particles are prone to agglomeration, forming micron-sized aggregates; simultaneously, poor interfacial bonding generates numerous micropores within the material. These aggregates and micropores become points of electric field concentration and sources of partial discharge under an electric field, severely deteriorating the material's electrical properties. Furthermore, during extrusion processing, these defects also lead to rough cable surfaces, dimensional instability, and low yield.

[0007] In summary, existing technologies generally remain at the level of "physical blending," that is, simply mixing various resins, fillers, and additives to "piece together" performance. This method cannot fundamentally solve the three core scientific problems of space charge accumulation, additive migration, and interface defects. Therefore, there is an urgent need in this field for a completely new design approach that innovates at the molecular structure and micro-interface level to develop an "endogenous" high-performance insulating material to meet the urgent requirements of next-generation new energy vehicles for the ultimate safety, long lifespan, and lightweight of high-voltage cables. Summary of the Invention

[0008] In view of the shortcomings of the prior art, the purpose of this invention is to provide an insulation material composition for high-voltage cables. By introducing an "ion polymer" as a matrix and working synergistically with "molecular-level filler Epoxy-POSS", it achieves excellent corona resistance and "endogenous" space charge suppression capability, fundamentally solving the core problem of electrical aging under DC electric field.

[0009] Another objective of this invention is to provide a method for preparing an insulating material composition for high-voltage cables, which employs a "one-step, segmented feeding reactive extrusion process" to achieve the industrial feasibility of high-performance materials. This method integrates complex interfacial reactions with efficient dispersion, devolatilization, and filtration, ensuring a high degree of consistency in product quality.

[0010] A third objective of this invention is to provide an application of an insulating material composition for high-voltage cables used in the preparation of high-voltage cables for new energy vehicles with a rated voltage of 1000VDC or 1500VDC.

[0011] This invention is achieved using the following technical solution:

[0012] The insulation material composition of the high-voltage cable comprises:

[0013] (a) Ionic polymers;

[0014] (b) Anhydride-functionalized polyolefin elastomers;

[0015] (c) Epoxy-functionalized polyhedral oligomeric silsesquioxane (epoxy-functionalized POSS); wherein, based on 100 parts by weight of the polymer matrix composed of components (a) and (b):

[0016] The amount of component (a) is 60-90 parts by weight;

[0017] The amount of component (b) used is 10-40 parts by weight;

[0018] The amount of component (c) used is 1-5 parts by weight; and,

[0019] The ionic polymer (a) is a metal ion neutralizer of ethylene-methacrylic acid copolymer, wherein the content of methacrylic acid is 5-15 wt% and the degree of neutralization is 30-70%.

[0020] The anhydride-functionalized polyolefin elastomer (b) is a maleic anhydride-grafted polyolefin elastomer.

[0021] The anhydride group of component (b) and the epoxy group of component (c) undergo a ring-opening reaction during melt processing to form a covalent bond.

[0022] This invention breaks away from the framework of traditional physical blending, innovating at the molecular structure level. Regarding component (a), this invention creatively selects an ionic polymer as the main matrix. Unlike traditional polyethylene or EVA, the molecular chain of the ionic polymer contains ionic bonds (such as -COO). - M +These ionic bonds aggregate at room temperature to form "ionic clusters." These ionic clusters not only act as physical cross-linking points, endowing the material with excellent toughness and wear resistance, but more importantly, they can form a microscopic Coulomb field within the material, effectively capturing and scattering injected charge carriers, thereby "endogenously" suppressing the accumulation of space charge at the matrix level. This is the fundamental innovation of this invention, distinguishing it from all existing technologies that rely on external fillers to suppress space charge. Regarding components (b) and (c), this invention introduces a pair of polymer additives and functional fillers that can chemically react with each other. This allows the material to form a strong covalent bond interface between the polymer matrix and the functional filler through in-situ reaction during subsequent processing. This chemically bonded interface completely solves the interface defect problem caused by poor physical compatibility in traditional composite materials, anchoring the filler in the matrix like "molecular rivets," thereby maximizing the function of the filler and ensuring the stability of the interface structure during long-term service. This "reactive interface" design is key to achieving ultra-low partial discharge (PD) and high dielectric strength.

[0023] The neutralizing metal ion of the ionic polymer (a) is zinc ion.

[0024] Ethylene-methacrylic acid copolymer, as the main chain, provides polyethylene with excellent insulation and processability. The preferred metal ion is zinc ion (Zn). 2+ ) or sodium ions (Na + This is because the ion clusters formed by these two types of ions have moderate strength, providing sufficient physical crosslinking strength at room temperature while also dissociating at melt processing temperatures, thus ensuring the thermoplastic processability of the material. In a preferred embodiment, the ethylene-methacrylic acid copolymer contains 5-15 wt% methacrylic acid and has an ion neutralization degree of 30-70%.

[0025] The epoxy equivalent (EEW) of the epoxy functionalized POSS(c) is 1200-1600 g / eq.

[0026] Maleic anhydride-grafted polyolefin elastomers (such as POE-g-MAH) play three roles simultaneously: 1) their polyolefin segments are physically compatible with the ionomer matrix, providing excellent flexibility; 2) the maleic anhydride groups provide electrophilic carbonyl carbon sites, while the epoxy groups provide cyclic ether structures capable of nucleophilic ring-opening reactions. At melt processing temperatures, the anhydride groups and epoxy groups undergo ring-opening esterification reactions to form stable ester or ether covalent bonds. The introduction of POSS offers multiple advantages: 1) its size is only 1-3 nm, achieving true nanoscale dispersion; 2) the Si-O cage-like core itself is an excellent insulator; 3) its epoxy functional groups can react with maleic anhydride. In subsequent reactive extrusion processes, the maleic anhydride groups and epoxy groups undergo ring-opening esterification reactions to form stable ester bonds. This chemical reaction firmly anchors the POSS molecule to the POE-g-MAH chain, while the POE-g-MAH is physically entangled with the ionomer matrix, thus constructing an unprecedented ultra-strong interface of "matrix-compensator-filler" covalent bonding. The formation of this interface is the fundamental reason why this invention can obtain ultra-low PD value and high dielectric strength.

[0027] The insulating material composition of the high-voltage cable further comprises a high molecular weight hindered amine light stabilizer with a molecular weight greater than 2000 g / mol.

[0028] Traditional small-molecule stabilizers are prone to migration and volatilization under long-term high temperatures and chemical media, leading to performance degradation in the later stages of material development. This invention utilizes polymeric HALS with a molecular weight far exceeding 2000 g / mol, leveraging its large molecular size to significantly reduce its migration rate within the polymer matrix. The "ion cluster" network in the ionomer matrix physically confines and entangles the large molecular chains of HMW-HALS, further hindering its migration. This dual effect of "large molecular size + network confinement" allows the stabilizer to achieve "quasi-permanent" residence, ensuring excellent resistance to thermo-oxidative and damp-heat aging throughout the cable's entire lifespan. This avoids premature embrittlement and cracking caused by stabilizer migration, a feature unmatched by small-molecule stabilizers.

[0029] The insulation material composition of the high-voltage cable further comprises a halogen-free flame retardant system containing hypophosphite and magnesium hydroxide surface-treated with aminosilane.

[0030] Hypophosphite, preferably aluminum hypophosphite (AHP), is a highly efficient char-forming flame retardant. Magnesium hydroxide (a-MDH), surface-treated with aminosilane, not only improves compatibility with the polymer matrix but, more importantly, introduces basic sites. During combustion, the acidic substances produced by AHP decomposition react with the basic amino groups on the a-MDH surface at the interface, resulting in acid-base catalysis. This significantly accelerates the dehydration and char formation process of the polymer matrix, allowing for the rapid formation of a dense and robust char layer, thus providing highly efficient heat and oxygen insulation. This synergistic effect of "interfacial catalytic char formation" makes the flame retardant efficiency far superior to a simple physical mixture of two flame retardants. This invention, by adding this flame retardant system to the downstream section of reactive extrusion, effectively avoids the potential interference of its basic amino surface on the upstream anhydride-epoxy reaction.

[0031] The insulation composition of the high-voltage cable may optionally further include a thermally conductive filler, such as spherical boron nitride surface-treated with vinylsilane.

[0032] Spherical boron nitride (BN) inherently possesses advantages such as high thermal conductivity and low dielectric constant. Treatment with vinylsilane primarily improves its interfacial compatibility with the polymer matrix, enhances dispersion, and reduces hygroscopicity. The system of this invention is a non-crosslinked thermoplastic system, independent of silane crosslinking reactions.

[0033] The method for preparing the insulation material composition of the high-voltage cable includes the following steps:

[0034] (1) In the upstream section of the extruder, the polymer matrix (a) and the polymer additive (b) are melted;

[0035] (2) In the midstream section after melting, the epoxy-functionalized polyhedral oligomeric silsesquioxane (c) is added, and at a temperature of 200-230°C, a chemical bonding reaction is initiated between the anhydride group of (b) and the epoxy group of (c);

[0036] (3) Add a halogen-free flame retardant to the downstream section after the chemical bonding reaction.

[0037] The above method is a one-step, segmented feeding reactive extrusion. Traditional "one-pot" mixing leads to interference between various components. The segmented feeding strategy of this invention has a clear scientific logic: First, the matrix resin is melted in the upstream section; second, reactive fillers are added in the midstream section, and in a relatively "pure" environment, the high-temperature zone initiates interfacial chemical bonding reactions to ensure the formation of "molecular rivet" structures; finally, a large amount of halogen-free flame retardant powders are added in the downstream section for dispersion. This process sequence maximizes the efficiency of the interfacial reaction and avoids the physical obstruction of the reaction and excessive absorption of shear heat by a large amount of inorganic flame retardants. At the same time, it efficiently integrates multiple processes such as plasticizing, mixing, dispersion, devolatilization, interfacial reaction, and chemical anchoring into a single extrusion, which is the key to realizing the industrial production of the high-performance materials of this invention.

[0038] The method for preparing the insulating material composition of the high-voltage cable further includes the steps of vacuum degassing the melt and filtering the melt through a filter component with an equivalent pore size of no more than 200 micrometers (e.g., a combination of 120-mesh and 200-mesh filters, with equivalent pore sizes of approximately 125 micrometers and 75 micrometers, respectively) during the melt blending process.

[0039] Vacuum venting is used to remove moisture, air, and trace byproducts that may be generated during the reaction from the raw materials; melt filtration is used to intercept undispersed filler agglomerates and gels. These two steps are essential process guarantees for controlling microscopic defects in materials, thereby obtaining excellent partial discharge performance.

[0040] The application of the insulation material composition of the high-voltage cable is used to prepare high-voltage cables for new energy vehicles with a rated voltage of 1000VDC or 1500VDC.

[0041] The aforementioned high-voltage cable for new energy vehicles includes:

[0042] At least one conductor;

[0043] And an insulating layer covering the outside of the conductor, the insulating layer having a microstructure in which polyhedral oligomeric silsesquioxanes are covalently linked to the polymer chains of the anhydride-functionalized polyolefin elastomer via ester or ether bonds.

[0044] The insulating layer is composed of the insulating material composition of the high-voltage cable described above.

[0045] One of the core aspects of this invention is that during the melt extrusion process, the maleic anhydride group in component (b) undergoes an in-situ ring-opening reaction with the epoxy group in component (c) to form a stable ester bond or ether bond, thereby anchoring the POSS molecule in the form of a covalent bond.

[0046] The reactive extrusion process of this invention is carried out in a reaction zone of 200-230°C. This temperature window is carefully selected: it is sufficient to effectively initiate the anhydride-epoxy ring-opening reaction within a limited residence time, while remaining below the significant thermal decomposition temperature of the major components. Thermogravimetric analysis (TGA) shows that the compositions of this invention exhibit a 5% weight loss temperature above 280°C under a nitrogen atmosphere, demonstrating good thermal stability at processing temperatures up to 230°C, preventing material degradation, discoloration, or bubbling.

[0047] Specifically, the preparation method of the insulation material composition for high-voltage cables includes the following steps:

[0048] 1. Pretreatment of raw materials:

[0049] All raw materials must undergo strict drying pretreatment before use to ensure that the moisture content meets the requirements of the clean process.

[0050] Granule drying: Place the ionomer (A1) and POE-g-MAH (A2) granules in a vacuum oven and dry them continuously for 6 hours at 85±5℃ and absolute pressure ≤10kPa until the moisture content is ≤200ppm.

[0051] Powder drying: After premixing the functional filler (B), flame retardant system (C), stabilizing system (D) and additives (E) in a high-speed mixer for 10 minutes, place them in a vacuum oven and dry them continuously for 8 hours at 105±5℃ and absolute pressure ≤10kPa until the moisture content is ≤300ppm.

[0052] 2. One-step reactive extrusion (REX) granulation:

[0053] A co-rotating twin-screw extruder with a length-to-diameter ratio (L / D) ≥ 48 was used, and the material was fed in stages as described above.

[0054] Process parameters:

[0055] Temperature profile: Zone 1-4 (melting zone): 160-190℃; Zone 5-8 (reaction zone): 200-230℃; Zone 9-12 (homogenization and degassing zone): 190-210℃; Die head: 200℃.

[0056] Screw speed: 300-400 rpm.

[0057] Vacuum exhaust: Vacuum ports are set in Zone 8 and Zone 11, with an absolute pressure ≤10kPa.

[0058] Filtration and granulation: After the melt is filtered through a 120 / 200 mesh combined filter screen, it is granulated by an underwater pelletizing system, dried, and then vacuum packaged.

[0059] Compared with the prior art, the beneficial effects of the present invention are:

[0060] (1) This invention achieves "endogenous" space charge suppression by introducing an ionomer matrix and, combined with the "covalent bonding" interface formed by reactive extrusion, eliminates interface defects at the molecular level, thus synergistically solving the two core problems of space charge accumulation and partial discharge. As can be seen from the results of Comparative Examples 1-4, the ionomer, anhydride-functionalized elastomer, and epoxy POSS are all indispensable, and the reaction temperature must reach a threshold to achieve excellent electrical properties.

[0061] (2) By selecting high molecular weight HMW-HALS and utilizing the physical confinement effect of ionomer networks, this invention achieves the "quasi-permanent" retention of stabilizers, fundamentally solving the problem of auxiliary agent migration. The results of Comparative Example 5 show that the use of small molecule HALS leads to a large amount of loss during aging and extraction, resulting in a sharp deterioration in the long-term performance of the material.

[0062] (3) This invention utilizes a reactive extrusion process of "one-step, segmented feeding" combined with vacuum degassing and melt filtration to not only efficiently construct chemical bonding interfaces but also strictly control the microscopic defects of the material. The results of Comparative Example 8 clearly demonstrate that without clean process steps, even with the same formulation, the partial discharge performance of the material will be completely ineffective. Detailed Implementation

[0063] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0064] phr: refers to the number of other components per 100 parts by weight of polymer matrix (A). In this invention, polymer matrix (A) refers to the sum of (A1) ionic polymer and (A2) anhydride-functionalized polyolefin elastomer.

[0065] Neutralization degree: refers to the molar percentage of methacrylic acid groups in the ethylene-methacrylic acid copolymer that are neutralized by metal ions.

[0066] Epoxy equivalent (EEW): refers to the number of grams of epoxy resin or compound containing 1 molar equivalent of epoxy groups, measured in g / eq.

[0067] Space charge distortion rate (η): Measured using the pulsed electroacoustic (PEA) method, its calculation formula is η = (E max –E0) / E0×100%, where E maxE0 is the applied average electric field strength (applied voltage / sample thickness) used to measure the maximum electric field strength inside the material at the measurement time point.

[0068] Partial discharge quantity (PD): In this invention, it specifically refers to the discharge quantity measured after applying a 2250V AC voltage (50Hz) to a 5-meter-long cable sample and stabilizing it for 1 minute under the test conditions specified in the IEC60270 standard, and the unit is pC.

[0069] This invention provides a low-segregation, corona-resistant, and hydrolysis-resistant insulating material for 1000VDC or 1500VDC high-voltage cables in new energy vehicles, prepared from raw materials comprising the following components (phr):

[0070] (A) Polymer matrix 100 phr;

[0071] (B) Functional filler 2-15 phr;

[0072] (C) High-efficiency synergistic halogen-free flame retardant system 30-90 phr;

[0073] (D) Long-term stable system 0.5-3.0 phr;

[0074] (E) Auxiliary processing aids 0.5-2.0 phr.

[0075] In this invention, the polymer matrix (A) is preferably composed of an ionic polymer (A1) and a maleic anhydride-grafted polyolefin elastomer (A2). The ionic polymer (A1) is preferably a zinc or sodium salt of an ethylene-methacrylic acid copolymer, more preferably a zinc salt ionic polymer; wherein the content of the unsaturated carboxylic acid is preferably 5-15 wt%, and the degree of neutralization is preferably 30-70%. The maleic anhydride-grafted polyolefin elastomer (A2) is preferably a maleic anhydride-grafted ethylene-octene copolymer, wherein the grafting rate of maleic anhydride is preferably 0.5-2.0 wt%. This invention does not impose any special restrictions on the source of the ionic polymer and the maleic anhydride-grafted polyolefin elastomer; commercially available products well known to those skilled in the art can be used. In this invention, the amount of the ionic polymer (A1) is preferably 60-90 phr, and the amount of the maleic anhydride-grafted polyolefin elastomer (A2) is preferably 10-40 phr. This invention aims to suppress space charge accumulation by introducing ionic polymers and utilizing their unique ionic cluster physical cross-linking network; while POE-g-MAH serves as a reactive compatibilizer and toughening agent, whose maleic anhydride groups can chemically react with the functional groups on the surface of the functional filler to construct a stable chemical bonding interface.

[0076] In this invention, the functional filler (B) preferably comprises epoxy-functionalized polyhedral oligomeric silsesquioxane (Epoxy-POSS) (B1) and spherical boron nitride (v-BN) (B2) treated with vinylsilane. The Epoxy-POSS (B1) is preferably a commercially available or custom-made product with an epoxy functional group equivalent (EEW) in the range of 1300-1400 g / eq. The v-BN (B2) is preferably spherical boron nitride with a D50 particle size of 1-5 μm, and its surface is preferably treated with vinyltrimethoxysilane or vinyltriethoxysilane at an amount of 0.5-1.5 wt% of the boron nitride mass. This invention does not impose any particular restriction on the source of the functional filler; it can be commercially available or prepared using conventional methods in the art. In this invention, the amount of Epoxy-POSS (B1) is preferably 1-5 phr, and the amount of v-BN (B2) is preferably 1-10 phr. Epoxy-POSS, as a molecular-level filler, aims to fundamentally solve the problems of filler dispersion and interfacial bonding by reacting its epoxy groups with the matrix to form chemical anchoring points; v-BN is used to improve the thermal conductivity of materials and help suppress space charge.

[0077] In this invention, the highly efficient synergistic halogen-free flame retardant system (C) preferably comprises hypophosphite (C1) and ultrafine magnesium hydroxide (a-MDH) (C2) with a special surface treatment. The hypophosphite (C1) is preferably aluminum hypophosphite (AHP) or aluminum diethylphosphite (DEAP), more preferably aluminum hypophosphite. The a-MDH (C2) is preferably ultrafine magnesium hydroxide with a D50 particle size of 0.8-1.5 μm, and its surface is preferably deeply chemically modified with an aminosilane (such as γ-aminopropyltriethoxysilane). This invention does not impose any special restrictions on the source of each component of the flame retardant system. In this invention, the amount of hypophosphite (C1) is preferably 10-40 phr, and the amount of a-MDH (C2) is preferably 20-60 phr. This invention, through the combination of two flame retardants, aims to achieve a highly efficient halogen-free flame retardant effect by utilizing their synergistic effect of interfacial catalytic char formation and physical barrier during combustion.

[0078] In this invention, the long-lasting stable system (D) preferably comprises a high molecular weight hindered amine light stabilizer (HMW-HALS) (D1) and a composite antioxidant (D2). The HMW-HALS (D1) is preferably a polymeric hindered amine light stabilizer with a molecular weight greater than 2500 g / mol. The composite antioxidant (D2) is preferably a mixture of a hindered phenolic antioxidant and a phosphite antioxidant. The auxiliary processing aid (E) is preferably a lubricant such as erucamide or ethylene bis-stearamide (EBS). This invention does not impose any special restrictions on the source of the stabilizer and auxiliary agents. In this invention, the amount of HMW-HALS (D1) is preferably 0.2-1.5 phr. HMW-HALS aims to solve the problem of easy migration and volatilization of traditional small molecule stabilizers in long-term high-temperature or chemical media environments, thereby ensuring the performance stability of the insulating material throughout its entire life cycle.

[0079] The insulating material composition provided by this invention organically combines an ionomer matrix with endogenous space charge suppression capability, a reactive additive system that can form chemical bonding interfaces during processing, a highly efficient and synergistic halogen-free flame retardant system, and a long-term stable system, and is prepared through a one-step reactive extrusion process. This systematically solves the comprehensive technical problems of existing high-voltage DC cable insulation materials in terms of corona resistance, aging resistance, flame retardancy, and processing performance. It provides a brand-new technical solution with industrialization prospects for preparing high-voltage cables for new energy vehicles that meet the requirements of 1500VDC rating, thin wall, lightweight, and long life.

[0080] This invention employs a highly efficient dry chemical grafting process for surface treatment of ultrafine magnesium hydroxide, the steps of which are as follows:

[0081] (1) Raw material preparation and pretreatment:

[0082] Magnesium hydroxide: Ultrafine magnesium hydroxide powder with a D50 particle size of 1.2 μm was selected. It was placed in a forced-air drying oven and dried at 110℃ for 4 hours to remove the physical water adsorbed on the surface and ensure that its surface hydroxyl groups have high reactivity.

[0083] Treatment agent solution: γ-aminopropyltriethoxysilane (APTES) was selected as the treatment agent. A hydrolysis activation solution was prepared in a beaker according to the ratio of treatment agent: anhydrous ethanol: deionized water = 10:90:1 (weight ratio). A small amount of glacial acetic acid was added as a hydrolysis catalyst (0.5% of the mass of APTES), and the mixture was magnetically stirred at room temperature for 30 minutes to ensure complete hydrolysis of the silane, generating highly active silanol (Si-OH) groups.

[0084] (2) High-speed blending and surface grafting:

[0085] The pre-dried magnesium hydroxide powder is fed into a high-speed mixer with jacketed heating / cooling function.

[0086] Turn on the stirrer and set the speed to 1200 rpm. Use the intense friction between the material particles to allow the system temperature to rise naturally to 95℃.

[0087] Using a peristaltic pump or atomizing nozzle, slowly and evenly spray the hydrolyzed APTES activation solution into the high-speed tumbling magnesium hydroxide powder over 30 minutes. The amount of treatment agent (based on pure APTES) is 0.8%-1.5% of the mass of magnesium hydroxide.

[0088] After the spraying is complete, continue stirring at high speed at 105℃ for 30 minutes to promote the dehydration condensation reaction between the silanol groups and the hydroxyl groups on the surface of magnesium hydroxide, forming stable Mg-O-Si chemical bonds.

[0089] (3) Curing and post-processing:

[0090] The grafted powder was transferred to an oven and aged at 120°C for 2 hours to ensure complete chemical reaction and thoroughly remove reaction byproducts (ethanol) and residual moisture.

[0091] After the curing process is completed, the powder is cooled to room temperature and deagglomerated by air jet milling or light grinding to obtain aminosilane-modified magnesium hydroxide (a-MDH) product with uniform surface coating and excellent dispersibility.

[0092] For hexagonal boron nitride, this invention employs a wet solvent process for surface treatment to ensure the uniformity and integrity of the silane coating. The steps are as follows:

[0093] (1) Raw material preparation and pretreatment:

[0094] Hexagonal boron nitride (BN): Hexagonal boron nitride powder with a D50 particle size of 3μm was selected. It was dried in a vacuum oven at 120℃ for 6 hours before use.

[0095] Treatment agent: Vinyltriethoxysilane (VTES) was selected as the treatment agent.

[0096] (2) Dispersion and hydrolysis:

[0097] A 95% aqueous ethanol solution was added as the reaction medium to a three-necked flask equipped with a mechanical stirrer, a reflux condenser, and a dropping funnel.

[0098] Start stirring and slowly add the pre-dried hexagonal boron nitride powder into the solvent to form a suspension. Then, turn on the ultrasonic disperser for 30 minutes to completely break up the BN aggregates and fully expose its surface active sites.

[0099] VTES was dissolved in a small amount of ethanol and slowly added dropwise to the BN suspension over 30 minutes using a dropping funnel. The amount of VTES used was 1% of the mass of hexagonal boron nitride. After the addition was complete, the mixture was stirred at room temperature for 1 hour to allow the VTES to hydrolyze in situ in the presence of water.

[0100] (3) Grafting reaction:

[0101] The three-necked flask was placed in a constant-temperature oil bath and heated to 82°C, where it was reacted for 5 hours. Heating promotes the condensation reaction between the silanol groups generated by the hydrolysis of VTES and the hydroxyl groups or other active sites on the BN surface, forming covalent bonds.

[0102] (4) Washing and drying:

[0103] After the reaction is complete, stop heating and allow the system to cool to room temperature.

[0104] The suspension is separated by centrifugation or filtration to collect the solid product.

[0105] The filter cake was washed multiple times with anhydrous ethanol to thoroughly remove unreacted silanes, hydrolyzed self-polymers, and byproducts.

[0106] The washed solid product was placed in a vacuum oven and dried at 80°C for 12 hours until constant weight was achieved.

[0107] (5) Post-processing:

[0108] The dried powder was sieved to obtain a free-flowing vinylsilane-modified hexagonal boron nitride (v-BN) product.

[0109] Raw materials used in the examples and comparative examples:

[0110]

[0111] Test method:

[0112]

[0113] Raw material pretreatment:

[0114] All raw materials must undergo drying pretreatment before use to ensure that the moisture content meets the requirements of the clean process.

[0115] Granule drying: Place the ionomer (A1) and POE-g-MAH (A2) granules in a vacuum oven and dry them continuously for 6 hours at 85°C and absolute pressure ≤10kPa until the moisture content is ≤200ppm.

[0116] Powder drying: The functional filler (B), flame retardant system (C), stabilizing system (D) and additive (E) are premixed in a high-speed mixer for 10 minutes, and then placed in a vacuum oven and dried continuously for 8 hours at 105°C and absolute pressure ≤10kPa until the moisture content is ≤300ppm.

[0117] To further illustrate the present invention, the following embodiments will be described in detail.

[0118] Example 1

[0119] Formulation (phr): (A) Total polymer matrix 100phr, of which A1: 80phr; A2: 20phr; (B) B1: 2phr; B2: 5phr; (C) C1: 25phr; C2: 45phr; (D) D1: 0.8phr; D2: 1.0phr; (E) E: 0.5phr.

[0120] Preparation method:

[0121] (1) In the upstream section (Zone1) of the extruder, the pretreated polymer matrix (A1, A2) is added and melted through the main feed port;

[0122] (2) In the midstream section (Zone5) after melting, pretreated functional fillers (B1, B2) are added through the first side feed port, and chemical bonding reaction between maleic anhydride and epoxy groups is initiated in the reaction zone of Zone5-8;

[0123] (3) In the downstream section (Zone9) after the chemical bonding reaction, pretreated halogen-free flame retardant (C1, C2), stabilizer (D) and additive (E) are added through the second side feed port.

[0124] A co-rotating twin-screw extruder with an L / D ratio of 48 was used. The process parameters were set as follows: Temperature profile settings: Zone 1: 170℃, Zone 2: 180℃, Zone 3: 185℃, Zone 4: 190℃; Zones 5-8 (reaction zone): 225℃; Zone 9: 210℃, Zone 10: 205℃, Zone 11: 200℃, Zone 12: 200℃; Die head: 200℃. The screw speed was 350 rpm. Vacuum ports were set in Zones 8 and 11, with an absolute pressure ≤10 kPa. The melt was filtered through a 120 / 200 mesh combined filter and then granulated by an underwater pelletizing system.

[0125] Example 2

[0126] Formulation (phr): (A) Polymer matrix total 100phr, of which A1: 60phr; A2: 40phr; the rest are the same as in Example 1.

[0127] Preparation method: The preparation conditions are exactly the same as those in Example 1.

[0128] Example 3

[0129] Formulation (phr): (A) Polymer matrix total 100phr, of which A1: 75phr; A2: 25phr; B1: 2phr; B2: 8phr; C1: 35phr; C2: 55phr; the rest are the same as in Example 1.

[0130] Preparation method: The preparation conditions are exactly the same as those in Example 1.

[0131] Example 4

[0132] Formula (phr): exactly the same as in Example 1.

[0133] Preparation method: Except for adjusting the process parameters to a reaction zone temperature of 210℃ and a screw speed of 450rpm, the other preparation conditions are exactly the same as in Example 1.

[0134] Comparative Example 1

[0135] Formulation (phr): Substitute matrix (EBA / LLDPE blend): 80 phr; A2: 20 phr; other components and dosages are the same as in Example 1.

[0136] Preparation method: The preparation conditions are exactly the same as those in Example 1.

[0137] Comparative Example 2

[0138] Formula (phr): A1: 80 phr; pure POE (Engage8200): 20 phr; other components and dosages are the same as in Example 1.

[0139] Preparation method: The preparation conditions are exactly the same as in Example 1.

[0140] Comparative Example 3

[0141] Formulation (phr): Inert POSS (SO1458): 2 phr replacing B1; other components and dosages are the same as in Example 1.

[0142] Preparation method: The preparation conditions are exactly the same as those in Example 1.

[0143] Comparative Example 4

[0144] Formula (phr): exactly the same as in Example 1.

[0145] Preparation method: Except for adjusting the process parameters to a reaction zone temperature of 180℃ (lower than the effective initiation temperature of the reaction), the other preparation conditions are exactly the same as in Example 1.

[0146] Comparative Example 5

[0147] Formulation (phr): HALS770: 0.8 phr replacing D1; other components and dosages are the same as in Example 1.

[0148] Preparation method: The preparation conditions are exactly the same as those in Example 1.

[0149] Comparative Example 6

[0150] Formula (phr): LDPE: 70phr; EVA: 30phr; Magnesium hydroxide (untreated with amine): 120phr; Composite antioxidant (Irganox B225): 1.0phr; DCP (diisopropylbenzene peroxide): 1.8phr.

[0151] Process: (1) Premix all raw materials in a high-speed mixer for 10 minutes. (2) Add the mixture to a twin-screw extruder for granulation from the main feed port. The processing temperature is controlled below 130℃ throughout the process to prevent premature decomposition of DCP. (3) Press the obtained granules at 180℃ on a flat vulcanizing machine and crosslink them for 15 minutes to prepare 2mm thick test samples.

[0152] Comparative Example 7

[0153] Formulation (phr): SMA resin (XIRANSZ26150): 1.5 phr replacing A2 (POE-g-MAH) (Note: to roughly match the molar amount of acid anhydride); A1: 98.5 phr; the remaining components and amounts are the same as in Example 1.

[0154] Preparation method: The preparation conditions are exactly the same as those in Example 1.

[0155] Comparative Example 8

[0156] Formula (phr): exactly the same as in Example 1.

[0157] Preparation method: The preparation conditions are the same as in Example 1, but the vacuum degassing steps in Zone 8 and Zone 11 are omitted, and the melt filter screen in front of the die head is removed.

[0158] The test data for Examples 1-4 and Comparative Examples 1-8 are shown in Table 1.

[0159] Table 1: Test data of Examples 1-4 and Comparative Examples 1-8

[0160]

[0161] Table 1 shows that, compared with Example 1 and Comparative Example 6, the traditional crosslinking system of Comparative Example 6, while exhibiting higher tensile strength, completely fails in core electrical properties: PD value > 20 pC, space charge distortion rate as high as 38.2%, and poor resistance to chemical media. This demonstrates that simple crosslinking physical blending cannot solve the core problems under high voltage DC conditions. Data from Comparative Examples 1, 2, and 3 demonstrate the necessity of the synergistic effect of the three elements of this invention: "ionomer matrix, anhydride functionalized bridge, and epoxy POSS reaction point." The absence of any one of these elements significantly deteriorates the electrical properties. Comparative Example 4 demonstrates that a reaction temperature of 200-230°C is a necessary condition for forming an effective chemical bonding interface. Data from Comparative Example 7 shows that even using the same reactive interface approach, replacing the flexible POE-g-MAH with rigid SMA resin significantly reduces the material's flexibility, and the PD and space charge properties are also significantly worse than in Example 1. This proves that the selection of a specific flexible compatibilizer in this invention has special technical effects and is not a simple equivalent substitution. The data from Comparative Example 8 are highly convincing: with the exact same formulation, the PD value soared to >20 pC simply by eliminating vacuum degassing and precision filtration. Notably, its space charge distortion rate is similar to that of Example 1. This clearly demonstrates that the space charge suppression capability is primarily determined by the intrinsic chemical structure of the ionomer, while the partial discharge performance is extremely sensitive to microscopic defects (such as bubbles and impurities) introduced during processing. The data from Comparative Example 5 further confirms that the use of small-molecule stabilizers leads to significant loss during long-term aging, directly resulting in a precipitous drop in mechanical properties after thermal aging and material brittleness. Although its resistivity retention rate remains at 90%, the failure of mechanical properties poses a more fatal safety hazard to the cable. The HMW-HALS+ ion cluster confinement system of this invention fundamentally solves this problem.

[0162] Application Example 1

[0163] Material source: Insulating material particles prepared in Example 1.

[0164] Cable fabrication: A precision extrusion production line is used to coat the material onto a 50mm² conductor, with the insulation thickness controlled at 1.2mm. The conductor is preheated to 100℃, and the extrusion temperature is 170-205℃. The cable is then vacuum sizing and multi-stage warm water cooling. Test data from Application Example 1 are shown in Table 2.

[0165] Table 2: Test data from Application Example 1

[0166]

[0167] Application Example 2

[0168] Material source: Insulating material particles prepared in Example 3.

[0169] Cable fabrication: The fabrication method is the same as in Application Example 1. Test data for Application Example 2 are shown in Table 3.

[0170] Table 3: Test data from Application Example 2

[0171]

[0172] Application Comparative Example 1

[0173] Material source: Insulating material particles prepared using Comparative Example 1.

[0174] Cable fabrication: The fabrication method is the same as in Application Example 1. The test data for Application Comparative Example 1 are shown in Table 4.

[0175] Table 4: Test data for application comparison example 1

[0176]

[0177] Application Comparative Example 2

[0178] Material source: Insulating material particles prepared using Comparative Example 4.

[0179] Cable fabrication: The fabrication method is the same as in Application Example 1. Test data for Application Comparative Example 2 are shown in Table 5.

[0180] Table 5: Test data for application comparison example 2

[0181]

[0182] As shown in Tables 2-5, the excellent material properties directly translate into qualified final product performance. Application Example 1 successfully incorporated the advantages of the material from Example 1, such as low PD, low space charge, high CTI, and high reliability, into the final cable product. The failures of Comparative Examples 1 and 2 strongly demonstrate the integrity and indivisibility of the technical solution of this invention. Without the ionomer matrix, the core electrical performance and aging resistance of the cable cannot meet the standards; without the reactive extrusion process, the PD performance of the cable is unstable and unqualified. This indicates that only by combining the specific material system proposed in this invention with a specific preparation process can a qualified cable meeting the stringent requirements of the 1500VDC rating be manufactured. Application Example 2, using a high flame-retardant formulation, successfully achieved excellent results in the most stringent Cat.A bundled burning test, proving that this technical platform can meet the specific performance requirements of different application scenarios through formulation adjustments. The failures of Comparative Examples 1 and 2 strongly demonstrate the integrity and indivisibility of the technical solution of this invention.

Claims

1. An insulating material composition for a high-voltage cable, characterized in that, It includes: (a) Ionic polymers; (b) Anhydride-functionalized polyolefin elastomers; (c) Epoxy-functionalized polyhedral oligomeric silsesquioxanes; It also includes a halogen-free flame retardant system, which contains hypophosphite and magnesium hydroxide surface-treated with aminosilane; It also contains a high molecular weight hindered amine light stabilizer with a molecular weight greater than 2000 g / mol; Wherein, based on 100 parts by weight of the polymer matrix composed of components (a) and (b): The amount of component (a) is 60-90 parts by weight; The amount of component (b) used is 10-40 parts by weight; The amount of component (c) used is 1-5 parts by weight; and, The ionic polymer (a) is a metal ion neutralizer of ethylene-methacrylic acid copolymer, wherein the content of methacrylic acid is 5-15 wt% and the degree of neutralization is 30-70%. The anhydride-functionalized polyolefin elastomer (b) is a maleic anhydride-grafted polyolefin elastomer. The anhydride group of component (b) and the epoxy group of component (c) undergo a ring-opening reaction during melt processing to form a covalent bond. The method for preparing the insulation material composition of the high-voltage cable includes the following steps: (1) In the upstream section of the extruder, the ionomer (a) and the anhydride-functionalized polyolefin elastomer (b) are melted; (2) In the midstream section after melting, the epoxy-functionalized polyhedral oligomeric silsesquioxane (c) is added, and at a temperature of 200-230°C, a chemical bonding reaction is initiated between the anhydride group of (b) and the epoxy group of (c); (3) In the downstream section after the chemical bonding reaction, add a halogen-free flame retardant system and a high molecular weight hindered amine light stabilizer; It also includes steps such as vacuum degassing of the melt and filtration of the melt through a filter screen with a pore size of no more than 200 micrometers during the melt blending process.

2. The insulating material composition for high-voltage cables according to claim 1, characterized in that, The neutralizing metal ion of the ionic polymer (a) is zinc ion.

3. The insulating material composition for high-voltage cables according to claim 1, characterized in that, The epoxy equivalent of the epoxy-functionalized polyhedral oligomeric silsesquioxane (c) is 1200-1600 g / eq.

4. A method for preparing an insulating material composition for a high-voltage cable according to any one of claims 1-3, characterized in that, Includes the following steps: (1) In the upstream section of the extruder, the ionomer (a) and the anhydride-functionalized polyolefin elastomer (b) are melted; (2) In the midstream section after melting, the epoxy-functionalized polyhedral oligomeric silsesquioxane (c) is added, and at a temperature of 200-230°C, a chemical bonding reaction is initiated between the anhydride group of (b) and the epoxy group of (c); (3) In the downstream section after the chemical bonding reaction, add a halogen-free flame retardant system and a high molecular weight hindered amine light stabilizer; It also includes steps such as vacuum degassing of the melt and filtration of the melt through a filter screen with a pore size of no more than 200 micrometers during the melt blending process.

5. The application of an insulating material composition for a high-voltage cable according to any one of claims 1-3, characterized in that, Used to manufacture high-voltage cables for new energy vehicles with a rated voltage of 1000VDC or 1500VDC.

6. The application of the insulating material composition for high-voltage cables according to claim 5, characterized in that, The aforementioned high-voltage cable for new energy vehicles includes: At least one conductor; And an insulating layer covering the outside of the conductor, the insulating layer having a microstructure in which polyhedral oligomeric silsesquioxanes are covalently linked to the polymer chains of the anhydride-functionalized polyolefin elastomer via ester or ether bonds. The insulating layer is composed of the insulating material composition of the high-voltage cable according to any one of claims 1-3.

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