Aging-resistant insulating plastic for laminated busbar and laminated busbar prepared from the same

Abstract

This invention discloses an aging-resistant insulating plastic for laminated busbars and the laminated busbars prepared therefrom, belonging to the technical field of insulating plastic materials. It addresses the technical problem that the electrical strength, volume resistivity, flame retardancy, mechanical properties, and aging resistance of existing aging-resistant insulating plastics suitable for laminated busbars need further improvement. Specifically, it comprises the following components by weight: 100 parts of polyphosphite block TPU, 25-32 parts of epoxy-modified polycarbodiimide, 12-16 parts of composite alumina, and 2-3 parts of additives. This invention uses the synergistic combination of polyphosphite block TPU, epoxy-modified polycarbodiimide, and composite alumina to prepare an insulating layer suitable for laminated busbars, achieving an overall improvement in oxygen index, insulation performance, initial mechanical properties, and performance retention rate after aging, demonstrating a significant comprehensive technical effect.

Description

Technical Field

[0001] This invention relates to the field of insulating plastic materials technology, specifically to an aging-resistant insulating plastic for laminated busbars and the laminated busbars prepared therefrom. Background Technology

[0002] Laminated busbars are electrical connection components formed by stacking multiple layers of conductors and insulation layers in a predetermined order. They are characterized by compact structure, low stray inductance, high current carrying capacity, and high installation efficiency. In the fields of power electronics and energy, laminated busbars are used to connect IGBTs and capacitor banks in high-power converter systems to suppress overvoltage. In the field of information and communication, laminated busbars provide reliable solutions for power transmission in equipment such as cellular communication base stations, large network equipment, telephone switching systems, and large and medium-sized computers. In addition, laminated busbars are also widely used in industrial and special fields, such as welding systems and military equipment systems.

[0003] Currently, the insulation layer of laminated busbars is mostly made of polymer materials such as polyester, polyimide, polyvinyl chloride, polypropylene, and thermoplastic polyurethane. Although these materials have certain insulation or processability, some of them lack sufficient flame retardancy. Under conditions of high temperature, overload, or short-term abnormal heating, they are prone to combustion spread, making it difficult to meet the safety requirements of laminated busbars. Although flame retardants, inorganic fillers, or toughening components can be added to improve certain properties, this often leads to problems such as decreased material compatibility, uneven filler dispersion, and insufficient interfacial bonding, which in turn results in decreased electrical strength, reduced volume resistivity, or deterioration of mechanical properties. Moreover, if only a single additive or a single modification method is used, it is often difficult to simultaneously achieve a balance between flame retardancy, electrical insulation, mechanical properties, and heat and wet aging resistance.

[0004] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide an aging-resistant insulating plastic for laminated busbars and the laminated busbars prepared therefrom. The aim is to develop an aging-resistant insulating plastic suitable for laminated busbars, which, while possessing high electrical strength and volume resistivity, also has good flame retardant properties, mechanical properties, heat aging resistance, and damp heat aging resistance.

[0006] The objective of this invention can be achieved through the following technical solution: an aging-resistant insulating plastic for laminated busbars, comprising the following components by weight: 100 parts of polyphosphate block TPU, 25-32 parts of epoxy-modified polycarbodiimide, 12-16 parts of composite alumina, and 2-3 parts of additives. Among them, polyphosphate block TPU is a block copolymer with alternating hydroxyl-terminated polyphosphate soft segments and urethane hard segments and epoxy-terminated segments. The composite alumina has a core-shell structure in which dopamine-modified alumina is encapsulated by a polyethyleneimine-glutaraldehyde crosslinked gel network.

[0007] Furthermore, epoxy-modified polycarbodiimide is obtained by the following steps: A1. Under an inert gas atmosphere, hexamethylene diisocyanate and catalyst are mixed and stirred. The reaction system is heated to 180-190℃ and kept at this temperature for 10-12 hours. After post-treatment, polycarbodiimide is obtained. The synthesis reaction formula for polycarbodiimide is as follows:

[0008] A2. Under an inert gas atmosphere, polycarbodiimide and toluene are mixed and stirred until the system is dissolved. The reaction system is heated to 70-80℃, glycidyl ether is added to the reaction system, and the reaction is maintained at this temperature for 60-80 min. After post-treatment, epoxy-modified polycarbodiimide is obtained.

[0009] The synthesis reaction formula for epoxy-modified polycarbodiimide is as follows:

[0010] Furthermore, in step A1, the weight ratio of hexamethylene diisocyanate to catalyst is 100:1, the catalyst is 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide, and the post-treatment includes: after the reaction is completed, the reaction system is subjected to negative pressure, and low-boiling substances are removed by vacuum evaporation to obtain polycarbodiimide.

[0011] Furthermore, in step A2, the ratio of polycarbodiimide, toluene, and glycidyl is 5g:50mL:2g. The post-treatment includes: after the reaction is complete, the reaction system is heated to 90°C, and low-boiling substances are removed by vacuum evaporation to obtain epoxy-modified polycarbodiimide.

[0012] Furthermore, the preparation method of polyphosphate block TPU is as follows: under an inert gas atmosphere, hydroxyl-terminated polyphosphate, 1,4-butanediol, catalyst and tetrahydrofuran are mixed and stirred, the reaction system is heated to 50-60℃, diphenylmethylene diisocyanate is added to the reaction system, the reaction is kept at the temperature for 60-80 min, 2-hydroxymethyl-1,3-propanediol is added to the reaction system, the reaction is kept at the temperature for 30-50 min, glycidyl ether is added to the reaction system, the reaction is kept at the temperature for 40-60 min, and after post-treatment, polyphosphate block TPU is obtained.

[0013] The synthesis reaction formula for polyphosphite block TPU is as follows:

[0014] In the formula: ; ; .

[0015] Furthermore, the ratio of the hydroxyl-terminated polyphosphite, 1,4-butanediol, catalyst, tetrahydrofuran, 2-hydroxymethyl-1,3-propanediol, and glycidyl is 60g:7-8g:0.1g:500mL:3-5g:10g. The catalyst is dibutyltin dilaurate. The molar amount of diphenylmethylene diisocyanate is 0.55 times the molar amount of hydroxyl in the reaction system. The post-treatment includes: after the reaction is completed, the reaction system is heated to 70-80℃, and low-boiling substances are removed by vacuum evaporation to obtain polyphosphite block TPU.

[0016] Furthermore, the preparation method of hydroxyl-terminated polyphosphite is as follows: under the protection of an inert gas atmosphere, 1,4-butanediol, catalyst, acid-binding agent and tetrahydrofuran are mixed and stirred, the reaction system is cooled to 0-6℃, phosphoryl chloride solution is added dropwise to the reaction system, after the addition is completed, the reaction system is heated to 50-60℃, and the reaction is maintained at this temperature for 6-8 hours. After post-treatment, hydroxyl-terminated polyphosphite is obtained.

[0017] The synthesis reaction formula for hydroxyl-terminated polyphospholipids is as follows:

[0018] Furthermore, the ratio of 1,4-butanediol, catalyst, acid-binding agent, and tetrahydrofuran is 10g:0.1g:5g:70mL. The catalyst is 4-dimethylaminopyridine, the acid-binding agent is potassium carbonate, and the phosphoric acid chloride-containing solution is composed of ethyl dichlorophosphate and malonyl chloride. The molar ratio of ethyl dichlorophosphate, malonyl chloride, and 1,4-butanediol is 1:3:5. The post-treatment includes: after the reaction is complete, the reaction system is cooled to room temperature, filtered, and deionized water is added to the filtrate under stirring. The mixture is stirred and dispersed for 30-50 minutes, filtered, and the filter cake is washed three times with purified water and then dried. The filter cake is transferred to a drying oven at 70-80℃ and dried to constant weight to obtain hydroxyl-terminated polyphosphite.

[0019] Furthermore, the composite alumina is obtained by the following steps: B1. Mix and stir nano-alumina and buffer solution. Add dopamine hydrochloride to the reaction system at room temperature and keep the reaction at this temperature for 4-6 hours. After post-treatment, dopamine-coated alumina is obtained. B2. Mix polyethyleneimine, dopamine-coated alumina, and deionized water, and ultrasonically disperse for 30-50 min. At room temperature, add glutaraldehyde aqueous solution to the reaction system, keep the reaction at room temperature for 5-6 h, and then perform post-treatment to obtain composite alumina.

[0020] Further, in step B1, the ratio of nano-alumina, buffer solution, and dopamine hydrochloride is 3g:10mL:1g, the buffer solution is a 0.1mol / L Tris buffer solution with pH=8.5, and the post-processing includes: after the reaction is complete, filtration is performed, the filter cake is washed three times with purified water and then dried, the filter cake is transferred to a drying oven at a temperature of 60-70℃ and dried to constant weight to obtain dopamine-coated alumina.

[0021] Furthermore, in step B2, the ratio of polyethyleneimine, dopamine-coated alumina, deionized water, and glutaraldehyde aqueous solution is 4-5g:3g:50mL:2-3g, and the mass fraction of the glutaraldehyde aqueous solution is 25%. The post-treatment includes: after the reaction is completed, transferring the reaction solution to a freeze dryer at a temperature of -30℃ for freeze drying to obtain composite alumina.

[0022] The present invention also proposes a laminated busbar based on an aging-resistant insulating plastic, comprising the following steps: S1. Add polyphosphate block TPU, epoxy modified polycarbodiimide, composite alumina and additives to a twin-screw extruder, melt mix for 3-5 minutes, extrude and inject into a molding die, cool and cure to obtain an aging-resistant insulating plastic sheet. S2. According to the design sequence, several copper busbars and aging-resistant insulating plastic sheets are stacked alternately to form a preliminary laminated structure, ensuring that each layer is aligned and avoiding misalignment, to obtain a pre-laminated body. S3. Place the pre-laminated body into a hot press, set the hot pressing temperature to 180-200℃, the hot pressing pressure to 12-15MPa, and hot press for 20-30 minutes. Cool to room temperature while maintaining the pressure to obtain the laminated motherboard blank. S4. Cut the laminated busbar blank according to the design dimensions, and drill holes at the ends or fixed positions for bolt connection to obtain the laminated busbar.

[0023] The present invention has the following beneficial effects: 1. This invention utilizes the synergistic combination of hydroxyl-terminated polyphosphite, polyphosphite-blocked TPU, epoxy-modified polycarbodiimide, and composite alumina. The hydroxyl-terminated polyphosphite system introduces a phosphorus-containing structure, which promotes dehydration and carbonization during combustion, forming a protective layer and thus improving the flame-retardant safety of the interlayer insulation layer in laminated busbars. The polyphosphite-blocked TPU provides a continuous film-forming phase and synergistic support between soft and hard segments, enabling the insulation layer to effectively buffer the thermal expansion differences of the copper busbar and maintain structural integrity after hot-pressing. The epoxy-modified polycarbodiimide inhibits hydrolysis and thermo-oxidative degradation under humid and hot environments. This solution reduces the performance degradation of the insulation layer during long-term operation. Composite alumina, by improving interfacial bonding and increasing intralayer density, reduces the probability of local electric field concentration and defect formation. When used as an interlayer insulation medium for copper busbars, this aging-resistant insulating plastic can not only form a continuous, dense, and well-adhesive insulation layer, but also meet multiple requirements such as flame retardancy, electrical insulation, mechanical support, and resistance to environmental aging. When applied to laminated busbars, this material can improve the reliability, flame retardancy, and service stability of the interlayer insulation of the busbars, and reduce the risk of failure caused by heat, humidity, aging, or local breakdown.

[0024] 2. This invention also prepares hydroxyl-terminated polyphosphite through esterification condensation to provide terminal hydroxyl groups for subsequent polyurethane reactions, while simultaneously introducing phosphate ester structures into the molecular chain. This allows the phosphorus-containing structure to be stably introduced into the molecular backbone in the form of chemical bonds. Unlike simple external flame retardant components, it is not easy to migrate and precipitate, and it can promote the dehydration and carbonization of the material when heated or burned, forming a relatively stable barrier layer, thereby improving the oxygen index and flame retardant safety of the material. The polyphosphite block TPU further combines the phosphorus-containing soft segment with the polyurethane hard segment, enabling the material to have both high tensile strength and good toughness. The composite alumina, through dopamine coating and polyethyleneimine / glutaraldehyde crosslinking to construct a surface composite layer, significantly improves the dispersion state and interfacial adhesion ability of inorganic fillers in the matrix, thereby reducing stress concentration and electric field distortion caused by particle agglomeration. A continuous synergistic relationship is formed between the phosphorus-containing matrix, the polyurethane support network, and the highly interfacial compatible inorganic filler, from molecular structure to micro-interface, which improves the oxygen index while maintaining high electrical strength, volume resistivity, and tensile strength.

[0025] 3. This invention also prepares polycarbodiimide with both anti-hydrolysis and interfacial stabilizing effects by catalyzing deoxygenation coupling between isocyanate groups. After epoxy modification, epoxy groups are introduced into its molecular chain to prepare epoxy-modified polycarbodiimide. The polycarbodiimide segments of this component can interact with the acidic degradation products generated during the material aging process, thereby inhibiting further hydrolysis, thermal decomposition, or acid-catalyzed degradation of polyester and polyurethane segments and slowing down the molecular chain breakage rate. At the same time, the active groups it carries are conducive to enhancing its bonding with the polymer matrix and inorganic fillers, reducing the possibility of interfacial debonding, microcrack propagation, and local defect accumulation during aging. The composite alumina further plays the role of shielding heat, blocking oxygen, and stabilizing the interface, forming an aging resistance mechanism in the material through the cooperation of molecular stability, interfacial stability, and structural stability. This makes the material not only have good initial mechanical properties and insulation properties, but also maintain high tensile strength and insulation level after high-temperature aging and damp-heat aging, making it more suitable for use as an interlayer insulation material in the long-term operation of laminated busbars. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the hierarchical structure of the stacked busbar of the present invention; Figure 2 This is a schematic diagram of the structure of the finished laminated busbar of the present invention. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0029] In this application, the nano-alumina particles have a diameter of 30-50 nm and a content of 99.99%. In this application, the molecular weight of polyethyleneimine is 1800, and its content is 98%. In this application, the CAS number of 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide is 707-61-9; In this application, PTMEG-1000 is a polytetrahydrofuran ether diol with a molecular weight of 1000.

[0030] Example 1 This embodiment provides a method for preparing aging-resistant insulating plastic for laminated busbars, which includes the following steps: Step 1: Preparation of hydroxyl-terminated polyphosphite Weigh out 32.6g of ethyl dichlorophosphate and 84.6g of malonyl chloride and add them to a constant-pressure dropping hole under argon protection to obtain phosphoric acid chloride solution for later use; Weigh out 90.1 g of 1,4-butanediol, 0.9 g of 4-dimethylaminopyridine catalyst, 45.1 g of potassium carbonate acid binder, and 630.7 mL of tetrahydrofuran and add them to an argon-protected reaction flask. Stir the mixture and cool the reaction flask to 0°C. Open the constant pressure dropping leak and control the temperature of the reaction flask to be below 15°C. Add a phosphoric acid chloride solution dropwise to the reaction flask. After the addition is complete, heat the reaction flask to 50°C and keep it at that temperature for 6 hours. Cool the reaction flask to room temperature and filter it. Add 2 L of deionized water to the filtrate while stirring and stir to disperse for 30 minutes. Filter the filtrate and wash it three times with purified water. Dry the filter cake in a drying oven at 70°C until it reaches constant weight to obtain hydroxyl-terminated polyphosphite.

[0031] In the reaction, under the catalysis of 4-dimethylaminopyridine, the hydroxyl group at the end of the 1,4-butanediol molecule undergoes nucleophilic addition with the phosphoryl group on the ethyl dichlorophosphate molecule or the acyl group on the malonyl chloride molecule to form a transition intermediate. Subsequently, the chloride ion leaves, generating phosphate ester bonds and ester bonds. The hydrogen chloride generated during the reaction is neutralized by potassium carbonate, thereby promoting the polycondensation reaction to continue towards the product. Controlling the addition of the system at a low temperature in the early stage can suppress excessive local exothermic reactions and reduce the risk of side reactions and gelation. After the addition is completed, raising the temperature and maintaining the temperature is beneficial to increasing the degree of polycondensation and making the reaction more complete. The introduction of phosphate ester structures into the molecular chain allows phosphorus to promote dehydration and carbonization of the material during subsequent combustion, thereby increasing the oxygen index. The ester bond and phosphate ester bond together endow the soft segment with a certain polarity, enabling it to have good interfacial compatibility with the subsequent polyurethane hard segment and inorganic filler. The hydroxyl end group, as the active reactive group of the polyphosphate ester segment, participates in the subsequent isocyanate polymerization, becoming the soft segment backbone in block TPU.

[0032] Step 2: Preparation of polyphosphate block TPU Weigh out 120g of hydroxyl-terminated polyphosphite, 14g of 1,4-butanediol, 0.2g of dibutyltin dilaurate, and 1000mL of tetrahydrofuran and add them to an argon-protected reaction flask. Stir the mixture and heat the flask to 50°C. Calculate the amount of diphenylmethylene diisocyanate to be added based on 0.55 times the total molar amount of hydroxyl groups in the reaction flask and add it to the reaction flask. Keep the reaction temperature high for 60 min. Add 6g of 2-hydroxymethyl-1,3-propanediol to the reaction flask and keep the reaction temperature high for 30 min. Add 20g of glycidyl ether to the reaction flask and keep the reaction temperature high for 40 min. Heat the reaction flask to 70°C and remove low-boiling-point substances by vacuum distillation to obtain polyphosphite block TPU.

[0033] The reaction is a typical polyurethane addition reaction between isocyanate and hydroxyl groups. Hydroxyl-terminated polyphosphite and 1,4-butanediol provide hydroxyl groups, while diphenylmethylene diisocyanate provides isocyanate groups. After nucleophilic addition of hydroxyl groups and isocyanate groups, urethane bonds are formed, which are polyurethane segments. Due to the large molecular weight and soft chain of hydroxyl-terminated polyphosphite, it mainly acts as a soft segment in the polymer. The chain formed by diisocyanate and small molecule butanediol is more inclined to be a hard segment, forming a block TPU structure with microphase separation characteristics of soft and hard segments. 2-hydroxymethyl-1,3-propanediol provides multiple hydroxyl sites, introduces limited branching points, and improves the stability of the molecular network. After the addition of glycidyl, its hydroxyl groups can continue to participate in the reaction of active functional groups, while its epoxy structure can be retained in the side chain or chain end, becoming active sites for subsequent interaction with interfacial functional groups.

[0034] The synergy between soft and hard segments imparts high tensile strength and toughness to the material. The phosphorus-containing soft segments improve flame retardancy, while the polyurethane hard segments ensure molding strength. Moderate branching improves thermal and dimensional stability, which helps prevent significant flow or structural collapse of the film during hot pressing. The epoxy active sites improve the interfacial interaction with polycarbodiimide and composite alumina, making the system denser.

[0035] Step 3: Preparation of epoxy-modified polycarbodiimide Weigh out 100g of hexamethylene diisocyanate and 1g of 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide and add them to an argon-protected reaction flask. Stir the mixture and heat the flask to 180℃. Keep the mixture at this temperature for 10 hours. Then, evacuate the flask to -0.1MPa and remove low-boiling substances by vacuum distillation to obtain polycarbodiimide. Weigh 100g of polycarbodiimide and 1000mL of toluene and add them to an argon-protected reaction flask. Stir until the system is dissolved. Heat the reaction flask to 70℃ and add 40g of glycidyl ether to the reaction flask. Keep the reaction at this temperature for 60min. Heat the reaction flask to 90℃ and apply a negative pressure of -0.1MPa to the reaction flask. Remove low-boiling substances by vacuum distillation to obtain epoxy-modified polycarbodiimide.

[0036] In the reaction, hexamethylene diisocyanate undergoes deoxygenation coupling between isocyanate groups under the catalysis of 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide to form a —N=C=N— type carbodiimide structure, accompanied by the escape of small molecule byproducts. The polycarbodiimide has strong acid capture and hydrolysis resistance. Subsequently, glycidyl ether is added, and its hydroxyl groups undergo addition or end-capping reactions with the active sites on the polycarbodiimide chain to introduce epoxy functional groups into the polycarbodiimide molecule, thereby obtaining epoxy-modified polycarbodiimide.

[0037] Polycarbodiimide is a commonly used anti-hydrolysis stabilizer in polyester and polyurethane systems because it can react with carboxylic acids produced during degradation in the system, thereby consuming acidic substances that catalyze hydrolysis and thermal degradation, and inhibiting the chain process of further acid-catalyzed degradation. After introducing epoxy groups, on the one hand, it can enhance its binding ability with interfaces containing hydroxyl and amine groups, and on the other hand, it can improve its dispersibility and compatibility in TPU matrix, avoiding its existence as a free small molecule or oligomer.

[0038] Step 4: Preparation of composite alumina Weigh out 30g of nano-alumina and 100mL of 0.1mol / L Tris buffer solution (pH=8.5) and add them to a reaction flask. Stir and add 10g of dopamine hydrochloride to the reaction flask at room temperature. Keep the reaction temperature for 4h, filter, wash the filter cake three times with purified water and dry it. Transfer the filter cake to a drying oven at 60℃ and dry it to constant weight to obtain dopamine-coated alumina. Weigh out 40g of polyethyleneimine, 30g of dopamine-coated alumina, and 500mL of deionized water and add them to a reaction flask. Disperse the mixture by sonication for 30min. Fix the reaction flask on an iron stand with a mechanical stirrer. At room temperature, add 20g of 25wt% glutaraldehyde aqueous solution to the reaction flask and keep it at this temperature for 5h. Transfer the reaction solution to a freeze dryer at -30℃ and freeze dry it to obtain composite alumina.

[0039] During the reaction, under Tris buffer solution and weakly alkaline conditions, dopamine hydrochloride undergoes oxidative self-polymerization, forming a polydopamine layer deposited on the surface of nano-alumina. This constructs a coating rich in phenolic hydroxyl groups, amino groups, and aromatic structures on the alumina surface, improving the surface activity of the inorganic particles and providing reaction sites for the subsequent construction of the organic layer. Glutaraldehyde undergoes a condensation reaction with primary and secondary amines in polyethyleneimine to form Schiff bases or related cross-linked structures. Simultaneously, the quinone structures produced after dopamine oxidation can undergo Michaelis addition or Schiff base reactions with amino groups, forming an organic polymer network layer on the outside of the alumina particles. The purpose of freeze-drying is to retain this surface composite structure, reduce particle agglomeration, and maintain a high specific surface area and good redispersibility.

[0040] The composite alumina structure improves the uniformity of alumina dispersion in the polymer, reducing stress concentration points and electric field distortion points caused by inorganic particle agglomeration. The surface organic coating layer enhances the interfacial adhesion between the alumina and the TPU matrix, improving tensile properties and strength retention after aging. Alumina itself is a high-resistivity inorganic insulating filler and helps to form thermal and oxygen barriers at high temperatures, thus having a positive effect on electrical strength, volume resistivity, and oxygen index. Moreover, the polydopamine and polyethyleneimine crosslinking layers can promote the formation of a more continuous char layer and inorganic shielding layer during combustion, thereby improving the flame retardant effect.

[0041] Step 5: Prepare aging-resistant insulating plastic Antioxidant 245, antioxidant 168, ethylene bis-stearamide, sodium stearate, and dioctyl phthalate were mixed evenly in a weight ratio of 4:3:2:3:6 to obtain the additive. Weigh out the following components by weight: 100 parts of polyphosphate block TPU, 25 parts of epoxy-modified polycarbodiimide, 12 parts of composite alumina, and 2 parts of additives. Add these components to a twin-screw extruder. Set the temperatures of the six temperature zones of the twin-screw extruder to 185℃, 190℃, 190℃, 190℃, 195℃, and 195℃ respectively. Melt and mix for 3 minutes, then extrude and inject the mixture into the molding die. Set the extrusion injection pressure to 3MPa. Cool and cure to obtain an aging-resistant insulating plastic sheet with a thickness of 0.3mm.

[0042] Example 2 This embodiment provides a method for preparing aging-resistant insulating plastic for laminated busbars, which includes the following steps: Step 1: Preparation of hydroxyl-terminated polyphosphite Weigh out 32.6g of ethyl dichlorophosphate and 84.6g of malonyl chloride and add them to a constant-pressure dropping hole under argon protection to obtain phosphoric acid chloride solution for later use; Weigh out 90.1 g of 1,4-butanediol, 0.9 g of 4-dimethylaminopyridine catalyst, 45.1 g of potassium carbonate acid binder, and 630.7 mL of tetrahydrofuran and add them to an argon-protected reaction flask. Stir the mixture and cool the reaction flask to 3°C. Open the constant pressure dropping leak and control the temperature of the reaction flask to be below 15°C. Add a phosphoric acid chloride solution dropwise to the reaction flask. After the addition is complete, heat the reaction flask to 55°C and keep it at that temperature for 7 hours. Cool the reaction flask to room temperature and filter it. Add 2 L of deionized water to the filtrate while stirring and stir to disperse for 40 minutes. Filter the filtrate and wash it three times with purified water. Dry the filter cake in a drying oven at 75°C until it reaches constant weight to obtain hydroxyl-terminated polyphosphite.

[0043] Step 2: Preparation of polyphosphate block TPU Weigh out 120g of hydroxyl-terminated polyphosphite, 15g of 1,4-butanediol, 0.2g of dibutyltin dilaurate, and 1000mL of tetrahydrofuran and add them to an argon-protected reaction flask. Stir the mixture and heat the flask to 55°C. Calculate the amount of diphenylmethylene diisocyanate to be added based on 0.55 times the total molar amount of hydroxyl groups in the reaction flask and add it to the reaction flask. Keep the reaction temperature high for 70 min. Add 8g of 2-hydroxymethyl-1,3-propanediol to the reaction flask and keep the reaction temperature high for 40 min. Add 20g of glycidyl ether to the reaction flask and keep the reaction temperature high for 50 min. Heat the reaction flask to 75°C and remove low-boiling-point substances by vacuum distillation to obtain polyphosphite block TPU.

[0044] Step 3: Preparation of epoxy-modified polycarbodiimide Weigh out 100g of hexamethylene diisocyanate and 1g of 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide and add them to an argon-protected reaction flask. Stir the mixture and heat the reaction flask to 185℃. Keep the reaction at this temperature for 11 hours. Then, evacuate the reaction flask to -0.1MPa and remove low-boiling substances by vacuum distillation to obtain polycarbodiimide. Weigh 100g of polycarbodiimide and 1000mL of toluene and add them to an argon-protected reaction flask. Stir until the system is dissolved. Heat the reaction flask to 75℃ and add 40g of glycidyl ether to the reaction flask. Keep the reaction at this temperature for 70min. Heat the reaction flask to 90℃ and apply a negative pressure to -0.1MPa. Remove low-boiling-point substances by vacuum distillation to obtain epoxy-modified polycarbodiimide.

[0045] Step 4: Preparation of composite alumina Weigh out 30g of nano-alumina and 100mL of 0.1mol / L Tris buffer solution with pH=8.5 and add them to the reaction flask. Stir and add 10g of dopamine hydrochloride to the reaction flask at room temperature. Keep the reaction temperature for 5h, filter, wash the filter cake three times with purified water and dry it. Transfer the filter cake to a drying oven at 65℃ and dry it to constant weight to obtain dopamine-coated alumina. Weigh out 45g of polyethyleneimine, 30g of dopamine-coated alumina, and 500mL of deionized water and add them to a reaction flask. Disperse the mixture by sonication for 40min. Fix the reaction flask on an iron stand with a mechanical stirrer. At room temperature, add 25g of 25wt% glutaraldehyde aqueous solution to the reaction flask and keep it at this temperature for 5.5h. Transfer the reaction solution to a freeze dryer at -30℃ and freeze dry it to obtain composite alumina.

[0046] Step 5: Prepare aging-resistant insulating plastic Antioxidant 245, antioxidant 168, ethylene bis-stearamide, zinc stearate, and dibutyl phthalate were mixed evenly in a weight ratio of 4:3:2:3:6 to obtain the additive. Weigh out the following components by weight: 100 parts of polyphosphate block TPU, 28 parts of epoxy-modified polycarbodiimide, 14 parts of composite alumina, and 2.5 parts of additives. Add these components to a twin-screw extruder. Set the temperatures of the six temperature zones of the twin-screw extruder to 185℃, 190℃, 190℃, 190℃, 195℃, and 195℃ respectively. Melt and mix for 4 minutes, then extrude and inject the mixture into the molding die. Set the extrusion injection pressure to 4MPa. Cool and cure to obtain an aging-resistant insulating plastic sheet with a thickness of 0.5mm.

[0047] Example 3 This embodiment provides a method for preparing aging-resistant insulating plastic for laminated busbars, which includes the following steps: Step 1: Preparation of hydroxyl-terminated polyphosphite Weigh out 32.6g of ethyl dichlorophosphate and 84.6g of malonyl chloride and add them to a constant-pressure dropping hole under argon protection to obtain phosphoric acid chloride solution for later use; Weigh out 90.1 g of 1,4-butanediol, 0.9 g of 4-dimethylaminopyridine catalyst, 45.1 g of potassium carbonate acid binder, and 630.7 mL of tetrahydrofuran and add them to an argon-protected reaction flask. Stir the mixture and cool the reaction flask to 6°C. Open the constant pressure dropping leak and control the temperature of the reaction flask to be below 15°C. Add a phosphoric acid chloride solution dropwise to the reaction flask. After the addition is complete, heat the reaction flask to 60°C and keep it at that temperature for 8 hours. Cool the reaction flask to room temperature and filter it. Add 2 L of deionized water to the filtrate while stirring and stir to disperse for 50 minutes. Filter the filtrate and wash it three times with purified water. Dry the filter cake and transfer it to a drying oven at 80°C to dry it to constant weight to obtain hydroxyl-terminated polyphosphite.

[0048] Step 2: Preparation of polyphosphate block TPU Weigh out 120g of hydroxyl-terminated polyphosphite, 16g of 1,4-butanediol, 0.2g of dibutyltin dilaurate, and 1000mL of tetrahydrofuran and add them to an argon-protected reaction flask. Stir the mixture and heat the flask to 60℃. Calculate the amount of diphenylmethylene diisocyanate to be added based on 0.55 times the total molar amount of hydroxyl groups in the reaction flask and add it to the reaction flask. Keep the reaction temperature high for 80min. Add 10g of 2-hydroxymethyl-1,3-propanediol to the reaction flask and keep the reaction temperature high for 50min. Add 20g of glycidyl ether to the reaction flask and keep the reaction temperature high for 60min. Heat the reaction flask to 80℃ and remove low-boiling-point substances by vacuum distillation to obtain polyphosphite block TPU.

[0049] Step 3: Preparation of epoxy-modified polycarbodiimide Weigh out 100g of hexamethylene diisocyanate and 1g of 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide and add them to an argon-protected reaction flask. Stir the mixture and heat the reaction flask to 190℃. Keep the reaction at this temperature for 12 hours. Then, evacuate the reaction flask to -0.1MPa and remove low-boiling substances by vacuum distillation to obtain polycarbodiimide. Weigh 100g of polycarbodiimide and 1000mL of toluene and add them to an argon-protected reaction flask. Stir until the system is dissolved. Heat the reaction flask to 80℃ and add 40g of glycidyl ether to the reaction flask. Keep the reaction at this temperature for 80min. Heat the reaction flask to 90℃ and apply a negative pressure of -0.1MPa to the reaction flask. Remove low-boiling substances by vacuum distillation to obtain epoxy-modified polycarbodiimide.

[0050] Step 4: Preparation of composite alumina Weigh out 30g of nano-alumina and 100mL of 0.1mol / L Tris buffer solution (pH=8.5) and add them to a reaction flask. Stir and add 10g of dopamine hydrochloride to the reaction flask at room temperature. Keep the reaction temperature for 6h, filter, wash the filter cake three times with purified water and dry it. Transfer the filter cake to a drying oven at 70℃ and dry it to constant weight to obtain dopamine-coated alumina. Weigh out 50g of polyethyleneimine, 30g of dopamine-coated alumina, and 500mL of deionized water and add them to a reaction flask. Disperse the mixture by sonication for 50min. Fix the reaction flask on an iron stand with a mechanical stirrer. At room temperature, add 30g of 25wt% glutaraldehyde aqueous solution to the reaction flask and keep it at this temperature for 6h. Transfer the reaction solution to a freeze dryer at -30℃ and freeze dry to obtain composite alumina.

[0051] Step 5: Prepare aging-resistant insulating plastic Antioxidant 245, antioxidant 168, ethylene bis-stearamide, calcium stearate, and diisobutyl phthalate were mixed evenly in a weight ratio of 4:3:2:3:6 to obtain the additive. Weigh out the following components by weight: 100 parts of polyphosphate block TPU, 32 parts of epoxy-modified polycarbodiimide, 16 parts of composite alumina, and 3 parts of additives. Add these components to a twin-screw extruder. Set the temperatures of the six temperature zones of the twin-screw extruder to 185℃, 190℃, 190℃, 190℃, 195℃, and 195℃ respectively. Melt and mix for 5 minutes, then extrude and inject the mixture into the molding die. Set the extrusion injection pressure to 5MPa. Cool and cure to obtain an aging-resistant insulating plastic sheet with a thickness of 0.5mm.

[0052] Example 4 This embodiment provides a method for preparing a laminated busbar, specifically including the following steps: S1. According to the design sequence, several copper busbars and several aging-resistant insulating plastic sheets prepared in Example 1 are stacked alternately to form a preliminary laminated structure, ensuring that each layer is aligned and avoiding misalignment, to obtain a pre-laminated body. S3. Place the pre-laminated body into a hot press, set the hot pressing temperature to 180℃, the hot pressing pressure to 12MPa, and hot press for 20 minutes. Cool to room temperature while maintaining the pressure to obtain the laminated motherboard blank. S4. Cut the laminated busbar blank according to the design dimensions, and drill holes at the ends or fixed positions for bolt connection to obtain the laminated busbar.

[0053] Example 5 This embodiment provides a method for preparing a laminated busbar, specifically including the following steps: S1. According to the design sequence, several copper busbars and several aging-resistant insulating plastic sheets prepared in Example 2 are stacked alternately to form a preliminary laminated structure, ensuring that each layer is aligned and avoiding misalignment, to obtain a pre-laminated body. S3. Place the pre-laminated body into a hot press, set the hot pressing temperature to 190℃, the hot pressing pressure to 13.5MPa, and hot press for 25 minutes. Cool to room temperature while maintaining the pressure to obtain the laminated motherboard blank. S4. Cut the laminated busbar blank according to the design dimensions, and drill holes at the ends or fixed positions for bolt connection to obtain the laminated busbar.

[0054] Example 6 This embodiment provides a method for preparing a laminated busbar, specifically including the following steps: S1. According to the design sequence, several copper busbars and several aging-resistant insulating plastic sheets prepared in Example 3 are stacked alternately to form a preliminary laminated structure, ensuring that each layer is aligned and avoiding misalignment, to obtain a pre-laminated body. S3. Place the pre-laminated body into a hot press, set the hot pressing temperature to 200℃, the hot pressing pressure to 15MPa, and hot press for 30 minutes. Cool to room temperature while maintaining the pressure to obtain the laminated motherboard blank. S4. Cut the laminated busbar blank according to the design dimensions, and drill holes at the ends or fixed positions for bolt connection to obtain the laminated busbar.

[0055] Comparative Example 1 The difference between this comparative example and Example 6 is that the preparation process of the aging-resistant insulating plastic sheet used is different. Step 1 is omitted, and hydroxyl-terminated polyphosphite in step 2 is replaced by an equal weight of PTMEG-1000.

[0056] Comparative Example 2 The difference between this comparative example and Example 6 is that the preparation process of the aging-resistant insulating plastic sheet used is different; step 3 is omitted, and epoxy-modified polycarbodiimide is not added in step 5.

[0057] Comparative Example 3 The difference between this comparative example and Example 6 is that, in the preparation process of the aging-resistant insulating plastic sheet, the dopamine-coated alumina in step 4 is used to replace the composite alumina in step 5 in an equal amount.

[0058] Comparative Example 4 The difference between this comparative example and Example 6 is that in the preparation process of the aging-resistant insulating plastic sheet used, ethyl dichlorophosphate in step 1 is replaced by an equimolar amount of malonyl chloride.

[0059] Performance testing: The tensile strength of the aging-resistant insulating plastic sheet specimens used in Examples 4-6 and Comparative Examples 1-4 was determined in accordance with the standard GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets". The electrical strength of the aging-resistant insulating plastic sheet specimens used in Examples 4-6 and Comparative Examples 1-4 was determined in accordance with the standard GB / T 1408.1-2016 "Electrical strength test method for insulating materials - Part 1: Test at power frequency". The volume resistivity of the aging-resistant insulating plastic sheet samples used in Examples 4-6 and Comparative Examples 1-4 was determined in accordance with the standard GB / T 31838.2-2019 "Dielectric and resistive properties of solid insulating materials - Part 2: Resistive properties (DC method) - Volume resistivity and volume resistivity". The oxygen index of the laminated busbar samples prepared in Examples 4-6 and Comparative Examples 1-4 was determined in accordance with the standard GB / T 2406.2-2009 "Determination of Combustion Behavior by Oxygen Index Method for Plastics - Part 2: Room Temperature Test". The tensile strength of the aging-resistant insulating plastic sheet samples used in Examples 4-6 and Comparative Examples 1-4 after heat aging (150℃, 168h) was determined in accordance with the standard GB / T 7141-2008 "Test Method for Thermal Aging of Plastics". The tensile strength of the aging-resistant insulating plastic sheet samples used in Examples 4-6 and Comparative Examples 1-4 was determined according to the standard GB / T 2423.50-2025 "Environmental Testing - Part 2: Test Methods - Test Cy: Constant Damp Heat - Accelerated Testing of Components". The specific test data are shown in Table 1 below.

[0060] Table 1 - Performance Test Data of Samples ; Data Analysis: Comparative analysis of the data in Table 1 above shows that the electrical strength of the aging-resistant insulating plastic sheet samples prepared in this invention reaches 30.3-30.6 kV / mm, and the volume resistivity reaches 1.11-1.15 × 10⁻⁶ kV / mm. 15 The tensile strength reached 44.9-45.3 MPa in Ω·cm, 42.2-43.6 MPa after heat aging, and 35.8-36.6 MPa after damp heat aging. The oxygen index of the prepared laminated busbar samples reached 31.9-32.3%. All performance test data are superior to those of the comparative example, indicating that the present invention, by forming a polymer matrix with phosphorus-containing polyphosphate segments and polyurethane segments, enables the material to simultaneously possess intrinsic flame retardancy, good film-forming properties, and high mechanical support. The introduction of epoxy-modified polycarbodiimide improves the system's ability to inhibit thermo-oxidative degradation and wet hydrolysis, and slows down molecular chain breakage and interfacial instability. At the same time, by modifying the alumina with organic composite surfaces, its dispersibility and interfacial bonding in the matrix are enhanced, reducing stress concentration and local electric field distortion caused by agglomeration, thereby improving electrical strength and volume resistivity. Combined with melt blending and hot-pressing lamination processes, each functional component forms a dense, stable insulating layer inside the material that is suitable for busbar structures. Through the synergistic effect of molecular structure, interfacial structure, and molding structure, the overall improvement of oxygen index, insulation performance, initial mechanical properties, and performance retention rate after aging is achieved, demonstrating a significant comprehensive technical effect.

[0061] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. An aging-resistant insulating plastic for laminated busbars, characterized by, It includes the following components by weight: 100 parts of polyphosphate block TPU, 25-32 parts of epoxy-modified polycarbodiimide, 12-16 parts of composite alumina, and 2-3 parts of additives; Among them, polyphosphate block TPU is a block copolymer with alternating hydroxyl-terminated polyphosphate soft segments and urethane hard segments and epoxy-terminated segments. The composite alumina has a core-shell structure in which dopamine-modified alumina is encapsulated by a polyethyleneimine-glutaraldehyde crosslinked gel network.

2. The anti-aging insulating plastic for laminated busbar according to claim 1, characterized in that, Epoxy-modified polycarbodiimide is obtained by the following steps: A1. Under an inert gas atmosphere, hexamethylene diisocyanate and catalyst are mixed and stirred. The reaction system is heated to 180-190℃ and kept at this temperature for 10-12 hours. After post-treatment, polycarbodiimide is obtained. A2. Under an inert gas atmosphere, polycarbodiimide and toluene are mixed and stirred until the system is dissolved. The reaction system is heated to 70-80℃, glycidyl ether is added to the reaction system, and the reaction is maintained at this temperature for 60-80 min. After post-treatment, epoxy-modified polycarbodiimide is obtained.

3. The aging-resistant insulating plastic for laminated busbars according to claim 2, characterized in that, In step A1, the weight ratio of hexamethylene diisocyanate to catalyst is 100:1, and the catalyst is 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide; in step A2, the ratio of polycarbodiimide, toluene, and glycidyl is 5g:50mL:2g.

4. The aging-resistant insulating plastic for laminated busbars according to claim 1, characterized in that, The preparation method of polyphosphate block TPU is as follows: Under the protection of an inert gas atmosphere, hydroxyl-terminated polyphosphate, 1,4-butanediol, catalyst and tetrahydrofuran are mixed and stirred. The reaction system is heated to 50-60℃. Diphenylmethylene diisocyanate is added to the reaction system and the reaction is maintained at this temperature for 60-80 min. 2-hydroxymethyl-1,3-propanediol is added to the reaction system and the reaction is maintained at this temperature for 30-50 min. Glycidyl ether is added to the reaction system and the reaction is maintained at this temperature for 40-60 min. After post-treatment, polyphosphate block TPU is obtained.

5. The aging-resistant insulating plastic for laminated busbars according to claim 4, characterized in that, The ratio of the hydroxyl-terminated polyphosphite, 1,4-butanediol, catalyst, tetrahydrofuran, 2-hydroxymethyl-1,3-propanediol, and glycidyl is 60g:7-8g:0.1g:500mL:3-5g:10g. The catalyst is dibutyltin dilaurate, and the molar amount of diphenylmethylene diisocyanate is 0.55 times the molar amount of hydroxyl groups in the reaction system.

6. The aging-resistant insulating plastic for laminated busbars according to claim 4, characterized in that, The preparation method of hydroxyl-terminated polyphosphite is as follows: under the protection of an inert gas atmosphere, 1,4-butanediol, catalyst, acid-binding agent and tetrahydrofuran are mixed and stirred. The reaction system is cooled to 0-6℃, and a phosphoric acid chloride solution is added dropwise to the reaction system. After the addition is completed, the reaction system is heated to 50-60℃ and kept at this temperature for 6-8 hours. After post-treatment, hydroxyl-terminated polyphosphite is obtained.

7. The aging-resistant insulating plastic for laminated busbars according to claim 6, characterized in that, The ratio of 1,4-butanediol, catalyst, acid-binding agent, and tetrahydrofuran is 10g:0.1g:5g:70mL. The catalyst is 4-dimethylaminopyridine, the acid-binding agent is potassium carbonate, and the phosphoric acid chloride-containing solution is composed of ethyl dichlorophosphate and malonyl chloride, with a molar ratio of ethyl dichlorophosphate, malonyl chloride, and 1,4-butanediol of 1:3:

5.

8. The aging-resistant insulating plastic for laminated busbars according to claim 6, characterized in that, Composite alumina is obtained through the following steps: B1. Mix and stir nano-alumina and buffer solution. Add dopamine hydrochloride to the reaction system at room temperature and keep the reaction at this temperature for 4-6 hours. After post-treatment, dopamine-coated alumina is obtained. B2. Mix polyethyleneimine, dopamine-coated alumina, and deionized water, and ultrasonically disperse for 30-50 min. At room temperature, add glutaraldehyde aqueous solution to the reaction system, keep the reaction at room temperature for 5-6 h, and then perform post-treatment to obtain composite alumina.

9. The aging-resistant insulating plastic for laminated busbars according to claim 8, characterized in that, In step B1, the ratio of nano-alumina, buffer solution, and dopamine hydrochloride is 3g:10mL:1g, and the buffer solution is a 0.1mol / L Tris buffer solution with pH=8.5; in step B2, the ratio of polyethyleneimine, dopamine-coated alumina, deionized water, and glutaraldehyde aqueous solution is 4-5g:3g:50mL:2-3g, and the mass fraction of the glutaraldehyde aqueous solution is 25%.

10. A laminated busbar made of aging-resistant insulating plastic according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Add polyphosphate block TPU, epoxy modified polycarbodiimide, composite alumina and additives to a twin-screw extruder, melt mix for 3-5 minutes, extrude and inject into a molding die, cool and cure to obtain an aging-resistant insulating plastic sheet. S2. According to the design sequence, several copper busbars and aging-resistant insulating plastic sheets are stacked alternately to form a preliminary laminated structure, ensuring that each layer is aligned and avoiding misalignment, to obtain a pre-laminated body. S3. Place the pre-laminated body into a hot press, set the hot pressing temperature to 180-200℃, the hot pressing pressure to 12-15MPa, and hot press for 20-30 minutes. Cool to room temperature while maintaining the pressure to obtain the laminated motherboard blank. S4. Cut the laminated busbar blank according to the design dimensions, and drill holes at the ends or fixed positions for bolt connection to obtain the laminated busbar.

Images