A heat-resistant high-adhesion enameled wire for a thermal management system and a preparation method thereof

Abstract

This invention belongs to the field of enameled wire technology, specifically relating to a heat-resistant, high-adhesion enameled wire for a thermal management system, comprising: a circular copper conductor core (1) and four insulating layers coated thereon, wherein a first insulating layer (2) is disposed on the outer surface of the circular copper conductor core (1), and a second insulating layer (3), a third insulating layer (4) and a fourth insulating layer (5) are distributed sequentially from the inside out; wherein the second insulating layer (3) is a tris(2-hydroxyethyl) isocyanurate modified polyesterimide; this invention is based on structurally modified polyamide imide, which greatly improves the adhesion of the enameled wire, and through the design of a multi-layer composite enamel film, it has excellent heat-resistant aging peel retention rate.

Description

Technical Field

[0001] This invention belongs to the field of enameled wire technology, specifically relating to a heat-resistant, high-adhesion enameled wire for thermal management systems and its preparation method, which is particularly suitable for thermal management systems in fields such as new energy vehicles, industrial automation equipment, and power electronic equipment. Background Technology

[0002] Enameled wire is a core conductive component in motors, electrical appliances, and electronic equipment, and its performance directly affects the operational stability and service life of the equipment. With the rapid development of industries such as new energy vehicles and industrial automation, thermal management systems, as key components ensuring reliable operation of equipment in high-temperature environments, place higher demands on the performance of enameled wire.

[0003] When the thermal management system is working, the internal temperature can usually reach 150~200℃, accompanied by continuous vibration. Traditional enameled wires have the following defects: First, they have insufficient heat aging resistance. Under long-term high temperature environment, the insulation layer is prone to aging and cracking, which leads to a decrease in breakdown voltage and causes short circuit faults. Second, they have poor adhesion. Under vibration conditions, the insulation layer is easy to peel off from the conductor core, affecting the conductivity stability. Third, it is difficult to balance mechanical properties and insulation properties. Some high-temperature resistant enameled wires have problems such as high brittleness and weak bending resistance.

[0004] To address the aforementioned issues, existing technologies improve the performance of enameled wires by modifying the insulating varnish formulation or optimizing the preparation process. For example, high-temperature resistant resins such as polyimide and polyetheretherketone are used as the insulating substrate, or nanoparticles are added to improve the material's heat resistance and mechanical properties. However, existing technologies still have shortcomings: the heat aging resistance of single resin substrates is limited, nanoparticles are prone to agglomeration leading to uneven performance, and the interfacial bonding strength between the insulation layer and the conductor core still needs to be improved, making it difficult to meet the stringent operating requirements of thermal management systems.

[0005] Therefore, developing an enameled wire that combines excellent heat aging resistance, high adhesion, and good overall performance, as well as a simple and easily mass-producible preparation method, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing enameled wires, such as insufficient heat aging resistance and poor adhesion, and to provide a heat-resistant, high-adhesion enameled wire for thermal management systems that has excellent heat aging peel retention rate, high adhesion, and also has good refrigerant resistance, so as to meet the needs of thermal management systems in new energy vehicles, industrial automation equipment, power electronic equipment and other fields for higher heat exchange efficiency and safety.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A heat-resistant, aging-resistant, and highly adhesive enameled wire for a thermal management system includes: a circular copper conductor core and four insulating layers coated thereon, wherein a first insulating layer is disposed on the outer surface of the circular copper conductor core, and a second, third, and fourth insulating layer are distributed sequentially from the inside out. The first insulating layer is a polyamide-imide modified in situ with a titanate coupling agent, used to improve the interfacial bonding between the insulating layer and the copper conductor; the second insulating layer is a tris(2-hydroxyethyl) isocyanurate-modified polyesterimide, and its cross-linked structure is shown in the following schematic diagram: ; Both the third and fourth insulating layers are made of polyamide-imide materials; The proportion of the first insulating layer to the total thickness of the four insulating layers shall not exceed 10%, and the proportion of the second insulating layer to the total thickness of the four insulating layers shall not be less than 40%. The heat-resistant, high-adhesion enameled wire exhibits a heat-resistant peeling retention rate of ≥75% after heat aging at 175℃ for 4 hours.

[0008] In a preferred example, the tris(2-hydroxyethyl) isocyanurate-modified polyesterimide is prepared by reacting the following raw materials: The raw materials include: tris(2-hydroxyethyl) isocyanurate, ethylene glycol, terephthalic acid, trimellitic anhydride, and 4,4'-diaminodiphenylmethane, in a molar ratio of 0.16~0.24∶0.64~0.96∶1∶0.24~0.36∶0.2~0.3; the most preferred ratio is 0.2∶0.8∶1∶0.3∶0.25. The reaction was carried out using tetrabutyl titanate as a catalyst at a concentration of 0.1-0.2% of the total mass of the reaction system, and the grafting and crosslinking were carried out at a reaction temperature of 180-210℃.

[0009] In a preferred example, the preparation conditions for the in-situ modified polyamide-imide by the titanate coupling agent are as follows: the amount of titanate coupling agent added is 1.5~2.5% of the total mass of the polyamide-imide prepolymer, and it is added in situ during the prepolymerization stage of polyamide-imide at 100~140℃, reacting simultaneously with the dianhydride and diamine monomers and grafting to the molecular chain ends; the prepolymerization stage is maintained at 1~2h to ensure uniform dispersion and initial bonding of the coupling agent, and then the temperature is gradually increased to 220~240℃ to complete the imidization ring-closure reaction; The glass transition temperature of the first insulating layer is 100~180℃.

[0010] In a preferred example, the third insulating layer is a highly elastic polyamide-imide with a film elongation at break of ≥15%, used to improve the flexibility and abrasion resistance of the film; preferably, it is one of the commercially available models: Allentas 595-36KP, Fuyi 801H-36, and Avit 19902ME31.

[0011] In a preferred example, the fourth insulating layer is a self-lubricating polyamide-imide with a surface dynamic friction coefficient ≤0.3, used to improve the winding processability; preferably, the commercially available model is: Allen-Tass 595-36MBA.

[0012] In a preferred embodiment, the diameter of the circular copper conductor core is 0.60~1.80 mm, and the total thickness of the four insulating layers is 50~120 μm.

[0013] Based on a general inventive concept, another object of the present invention is to provide a method for preparing heat-resistant, high-adhesion enameled wire for the above-mentioned thermal management system, comprising the following steps: The copper conductor is drawn to the target diameter using a die and then subjected to online annealing at a processing speed of 45-150 m / min. Modified polyamide-imide insulating varnish, tris(2-hydroxyethyl) isocyanurate-modified polyesterimide insulating varnish, high-elasticity polyamide-imide insulating varnish, and self-lubricating polyamide-imide insulating varnish are applied sequentially through a coating die. The modified polyamide-imide insulating varnish is applied 1-2 times, the tris(2-hydroxyethyl) isocyanurate-modified polyesterimide insulating varnish is applied 6-14 times, and the high-elasticity polyamide-imide insulating varnish is applied... The amine insulating varnish is applied 4-8 times, and the self-lubricating polyamide-imide insulating varnish is applied 1-2 times, for a total of 12-24 coatings. After each coating, the varnish is placed in an oven at a baking temperature of 150-350℃ to preliminarily dry it. Then, it is baked in a curing zone at a curing temperature of 480-610℃ and cooled to obtain a heat-resistant, high-adhesion enameled wire for the thermal management system. (Within the above process parameters, the varnish film can be fully cured without blistering or cracking defects, meeting the requirements for heat resistance and adhesion performance).

[0014] In a preferred example, the online annealing temperature is 460~600℃.

[0015] Compared with traditional polyesterimide / polyamideimide composite enameled wires, this invention, based on structurally modified polyamideimide, significantly improves the adhesion of the enameled wire. Through a multi-layer composite coating design, it exhibits excellent heat aging peel retention rate. For example, after aging at 175°C for 4 hours, the number of peel twists of the enameled wire can be maintained at more than 75% of that in the unaged state at room temperature. It also takes into account the refrigerant resistance performance. For example, after immersion in R134a refrigerant for 1000 hours, the breakdown voltage retention rate is ≥90%, and no foaming is observed after baking at 160°C for 10 minutes. This can effectively improve the operational safety of automotive thermal management systems.

[0016] This invention addresses the harsh operating conditions of thermal management systems, including high temperatures of 150-200℃, continuous vibration, and refrigerant corrosion. It overcomes the technical shortcomings of traditional enameled wires, such as insufficient heat aging resistance, poor interfacial adhesion, and the difficulty in simultaneously achieving high-temperature resistance and mechanical / processing properties. Through the synergistic effect of multi-layer functionalized coating structure design and in-situ material modification, a comprehensive improvement in overall performance is achieved, as detailed below: 1. Significantly improved interfacial adhesion strength and enhanced resistance to vibration-induced peeling. Polyamide-imide modified in situ with a titanate coupling agent is used as the first insulating layer for conductor contact. The coupling agent is incorporated into the molecular chain end during the prepolymerization stage of polyamide-imide, constructing a chemical bonding interface between the copper conductor and the organic coating film, significantly enhancing interlayer adhesion. Test results show that the coating film desorption length of the sample of this invention is only 1.2~1.6mm, far lower than that of the comparative sample with an unbalanced coating film thickness ratio. This effectively resists the risk of coating film peeling under continuous vibration conditions of the thermal management system, ensuring conductivity and insulation stability.

[0017] 2. Excellent heat aging resistance, significantly improved long-term reliability at high temperatures. Tris(2-hydroxyethyl) isocyanurate (THEIC) crosslinked modified polyesterimide is used as the core heat-resistant layer (second insulating layer), and its thickness is controlled to account for no less than 40% of the total insulating layer. The thermal stability and structural integrity of the coating film are improved through the triazine ring crosslinking structure. Combined with the multi-layer composite structure of inner and outer polyamide-imide layers, a gradient heat-resistant system is formed. The test results show that the peel retention rate of the sample after heat aging can reach 83-91%, and the peel twisting performance after aging at 175℃ for 4 hours still maintains more than 75% of the room temperature state. This is far superior to conventional polyesterimide systems and schemes with unreasonable thickness ratios. It can effectively inhibit the problems of coating film aging and cracking and adhesion decline under long-term high temperature, and extend the service life under high temperature conditions.

[0018] 3. Excellent performance balance, taking into account both mechanical toughness and processing applicability. Performance synergy is achieved through a layered, differentiated functional design: the third layer uses highly elastic polyamide-imide to enhance the flexibility and wear resistance of the coating film, addressing the shortcomings of traditional high-temperature enameled wires, such as high brittleness and weak bending resistance; the fourth layer uses self-lubricating polyamide-imide to reduce the surface friction coefficient and optimize winding processing performance. While ensuring core heat resistance and adhesion performance, a balance is achieved in mechanical properties, wear resistance, and processing performance, adapting to the processing and service requirements of various windings.

[0019] 4. Excellent resistance to refrigerant corrosion, suitable for special thermal management media environments. The dense cross-linked modified polyesterimide core layer and the multi-layer composite structure work together to give the enameled wire excellent refrigerant resistance. After immersion in typical refrigerant R134a in a thermal management system for 1000 hours, the breakdown voltage retention rate is ≥90%, and no foaming occurs after baking at 160℃ for 10 minutes. It can work stably for a long time in a refrigerant environment, matching the medium conditions required by thermal management systems in fields such as new energy vehicles and industrial automation.

[0020] 5. The preparation process is highly adaptable and has the foundation for large-scale mass production. The preparation process adopts a mature process route of online annealing, multi-coating, and segmented baking and curing. The processing speed ranges from 45 to 150 m / min, and the total number of coatings is 12 to 24. The process parameters are highly compatible with existing enameled wire mass production equipment, and stable production can be achieved without the need for additional special equipment. It has low difficulty in industrialization and has good industrial application value. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the heat-resistant, aging-resistant, and highly adhesive enameled wire for the thermal management system of the present invention. Among them, 1-circular copper conductor inner core, 2-first insulating layer, 3-second insulating layer, 4-third insulating layer, 5-fourth insulating layer. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is further described in conjunction with specific embodiments. However, this invention is not limited to these embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. In this invention, unless otherwise specified, the equipment and raw materials used are commercially available or commonly used in the art. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0023] Example 1

[0024] The enameled wire in this embodiment includes: a circular copper conductor core 1 and four insulating layers coated thereon. The first insulating layer 2 is disposed on the outer surface of the circular copper conductor core 1, and the second insulating layer 3, the third insulating layer 4 and the fourth insulating layer 5 are distributed from the inside to the outside in sequence. The second insulating layer 3 is a tris(2-hydroxyethyl) isocyanurate modified polyesterimide, and its cross-linked structure is shown in the following schematic diagram: ; The raw materials and processes for preparing tris(2-hydroxyethyl) isocyanurate-modified polyesterimide are as follows: Raw materials: composed of tris(2-hydroxyethyl) isocyanurate, ethylene glycol, terephthalic acid, trimellitic anhydride and 4,4'-diaminodiphenylmethane in a molar ratio of 0.2:0.8:1:0.3:0.25; Process: Tetrabutyl titanate is used as a catalyst, with the amount of catalyst being 0.15% of the total mass of the reaction system. The temperature is controlled at 180~210℃ to carry out a stable grafting and cross-linking reaction.

[0025] The first insulating layer 2 is a polyamide-imide modified in situ with a titanate coupling agent and a glass transition temperature of 120°C. The preparation conditions are as follows: the amount of titanate coupling agent (isopropyltris(dioctylpyrophosphoryloxy)titanate) added is 2.0% of the total mass of the polyamide-imide prepolymer. It is added in situ during the prepolymerization stage of polyamide-imide at 125°C and reacts simultaneously with the dianhydride and diamine monomers and grafted to the molecular chain ends. The temperature is maintained for 1.5 h to ensure uniform dispersion and initial bonding of the coupling agent. Subsequently, the temperature is gradually increased to 230°C to complete the imidization ring-closure reaction. The third insulating layer 4 is a high-elasticity polyamide-imide (Allentas 595-36KP), and the fourth insulating layer is a self-lubricating polyamide-imide (Allentas 595-36MBA). The diameter of the circular copper conductor core is 0.85 mm, the total thickness of the four insulating layers is 76 μm, the thickness of the first insulating layer is 5 μm, and the thickness of the second insulating layer is 45 μm.

[0026] The above-mentioned method for preparing enameled wire includes the following steps: The copper conductor is drawn to the target diameter through a mold and then annealed online at a processing speed of 120 m / min. It is then coated with modified polyamide-imide insulating varnish once, tris(2-hydroxyethyl) isocyanurate modified polyesterimide insulating varnish 12 times, high-elasticity polyamide-imide insulating varnish 5 times, and self-lubricating polyamide-imide insulating varnish once through a coating mold, for a total of 19 coating times. After each coating, it is sent to an oven, where the oven inlet is set to a baking temperature of 280°C to pre-dry the varnish. Then, it is baked in a curing zone at a curing temperature of 580°C. After cooling, the heat-resistant, high-adhesion enameled wire for the thermal management system is obtained.

[0027] The two-stage continuous online annealing process involves the production line being heated in two temperature zones: 530℃ and 510℃ respectively.

[0028] Example 2

[0029] The enameled wire in this embodiment includes: a circular copper conductor core 1 and four insulating layers coated thereon. The first insulating layer 2 is disposed on the outer surface of the circular copper conductor core 1, and the second insulating layer 3, the third insulating layer 4 and the fourth insulating layer 5 are distributed from the inside to the outside in sequence. The second insulating layer 3 is a tris(2-hydroxyethyl) isocyanurate modified polyesterimide, and its cross-linked structure is shown in the following schematic diagram: ; The raw materials and processes for preparing tris(2-hydroxyethyl) isocyanurate-modified polyesterimide are as follows: Raw materials: composed of tris(2-hydroxyethyl) isocyanurate, ethylene glycol, terephthalic acid, trimellitic anhydride and 4,4'-diaminodiphenylmethane in a molar ratio of 0.2:0.8:1:0.3:0.25; Process: Tetrabutyl titanate is used as a catalyst, with the amount of catalyst being 0.15% of the total mass of the reaction system. The temperature is controlled at 180~210℃ to carry out a stable grafting and cross-linking reaction.

[0030] The first insulating layer 2 is a polyamide-imide modified in situ with a titanate coupling agent and a glass transition temperature of 180℃. The preparation conditions are as follows: the amount of titanate coupling agent (isopropyltris(dioctylpyrophosphoryloxy)titanate) added is 2.5% of the total mass of the polyamide-imide prepolymer. It is added in situ during the prepolymerization stage of polyamide-imide at 140℃, reacting simultaneously with the dianhydride and diamine monomers and grafting to the molecular chain ends; the temperature is maintained for 1 hour to ensure uniform dispersion and initial bonding of the coupling agent. Subsequently, the temperature is gradually increased to 240℃ to complete the imidization ring-closure reaction. The third insulating layer 4 is a high-elasticity polyamide-imide (Fuyi 801H-36), and the fourth insulating layer is a self-lubricating polyamide-imide (Allentas 595-36MBA). The diameter of the circular copper conductor core is 1.08 mm, the total thickness of the four insulating layers is 85 μm, the thickness of the first insulating layer is 6 μm, and the thickness of the second insulating layer is 54 μm.

[0031] The above-mentioned method for preparing enameled wire includes the following steps: The copper conductor is drawn to the target diameter through a mold and then annealed online at a processing speed of 97 m / min. It is then coated with modified polyamide-imide insulating varnish once, tris(2-hydroxyethyl) isocyanurate modified polyesterimide insulating varnish eleven times, high-elasticity polyamide-imide insulating varnish four times, and self-lubricating polyamide-imide insulating varnish once through a coating mold, for a total of 17 coating times. After each coating, it is sent to an oven, where the oven inlet is set to a baking temperature of 330°C to pre-dry the varnish. Then, it is baked in a curing zone at a curing temperature of 590°C. After cooling, the heat-resistant, high-adhesion enameled wire for the thermal management system is obtained.

[0032] The two-stage continuous online annealing process involves the production line being heated in two temperature zones: 550℃ and 540℃ respectively.

[0033] Example 3

[0034] The enameled wire in this embodiment includes: a circular copper conductor core 1 and four insulating layers coated thereon. The first insulating layer 2 is disposed on the outer surface of the circular copper conductor core 1, and the second insulating layer 3, the third insulating layer 4 and the fourth insulating layer 5 are distributed from the inside to the outside in sequence. The second insulating layer 3 is a tris(2-hydroxyethyl) isocyanurate modified polyesterimide, and its cross-linked structure is shown in the following schematic diagram: ; The raw materials and processes for preparing tris(2-hydroxyethyl) isocyanurate-modified polyesterimide are as follows: Raw materials: composed of tris(2-hydroxyethyl) isocyanurate, ethylene glycol, terephthalic acid, trimellitic anhydride and 4,4'-diaminodiphenylmethane in a molar ratio of 0.2:0.8:1:0.3:0.25; Process: Tetrabutyl titanate is used as a catalyst, with the amount of catalyst being 0.15% of the total mass of the reaction system. The temperature is controlled at 180~210℃ to carry out a stable grafting and cross-linking reaction.

[0035] The first insulating layer 2 is a polyamide-imide modified in situ with a titanate coupling agent and a glass transition temperature of 100℃. The preparation conditions are as follows: the amount of titanate coupling agent (isopropyltris(dioctylpyrophosphoryloxy)titanate) added is 1.5% of the total mass of the polyamide-imide prepolymer. It is added in situ during the 100℃ prepolymerization stage of the polyamide-imide and reacts simultaneously with the dianhydride and diamine monomers and grafted to the molecular chain ends. The temperature is maintained for 2 hours to ensure uniform dispersion and initial bonding of the coupling agent. Subsequently, the temperature is gradually increased to 220℃ to complete the imidization ring-closure reaction. The third insulating layer 4 is a high-elasticity polyamide-imide (Avit 19902ME31), and the fourth insulating layer is a self-lubricating polyamide-imide (Allentas 595-36MBA). The diameter of the circular copper conductor core is 1.43 mm, the total thickness of the four insulating layers is 92 μm, the thickness of the first insulating layer is 7 μm, and the thickness of the second insulating layer is 62 μm.

[0036] The above-mentioned method for preparing enameled wire includes the following steps: The copper conductor is drawn to the target diameter through a mold and then annealed online at a processing speed of 60 m / min. It is then coated with modified polyamide-imide insulating varnish twice, tris(2-hydroxyethyl) isocyanurate modified polyesterimide insulating varnish 12 times, high-elasticity polyamide-imide insulating varnish 5 times, and self-lubricating polyamide-imide insulating varnish once through a coating mold, for a total of 20 coatings. After each coating, it is sent to an oven, where the oven inlet is set to a baking temperature of 160°C to pre-dry the varnish. Then, it is baked in a curing zone at a curing temperature of 510°C. After cooling, the heat-resistant, high-adhesion enameled wire for the thermal management system is obtained.

[0037] The two-stage continuous online annealing process involves the production line being heated in two temperature zones: 580℃ and 570℃ respectively.

[0038] Comparative Example 1

[0039] In this comparative example, the diameter of the circular copper conductor core is 0.95 mm, the total thickness of the four insulating layers is 81 μm, the thickness of the first insulating layer is 3 μm, and the thickness of the second insulating layer is 29 μm. Processing speed: 105m / min; Inlet temperature: 150℃; Curing temperature: 600℃. Other conditions are the same as in Example 1.

[0040] Comparative Example 2

[0041] In this comparative example, the diameter of the circular copper conductor core is 1.60 mm, the total thickness of the four insulating layers is 100 μm, the thickness of the first insulating layer is 10 μm, and the second insulating layer is polyesterimide, commercially available model is Allentas MT533-43FR, with a thickness of 65 μm. Processing speed 50m / min, inlet temperature 160℃, curing temperature 510℃.

[0042] Other conditions are the same as in Example 1.

[0043] Test Example 1

[0044] The following tests were performed on the enameled wires prepared in Examples 1-3 and Comparative Examples 1-2; (1) Length of paint film desorption Take three specimens approximately 300 mm long, set the distance between reference points to 250 mm, apply axial tension until the specimens break, observe the fracture surface according to the requirements of the rapid tensile test in GB / T4074.3-2024, and measure the varnish desorption length of the two fracture surfaces at this point (i.e., the distance from the fracture surface to the point where the varnish begins to separate from the conductor, the distance of the exposed non-conductor), and take the maximum value of the two as the test result.

[0045] (2) Heat aging peel retention rate (a) For diameters of 1.0 mm (inclusive) and below: Take three specimens with a length of 200 mm. At room temperature, set the marking distance to 150 mm for each specimen. Suspend a weight of the specified mass (500 g). Twist the specimen 6 times. Then, scratch one side of the coating along the axial direction, avoiding damage to the conductor substrate during scratching. Next, twist the specimen in the initial direction and measure the number of twists (including the initial 6 twists) until the coating breaks and the conductor is visually visible. More than 30 twists are considered acceptable. However, if the specimen breaks during twisting, the test must be repeated. For diameters of 1.0 mm (exclusive) and above: Perform the peel test according to GB / T4074.3-2024. Place a straightened specimen on the test equipment specified in GB / T4074.3-2024. The two clamps are located on the same axis and 500 mm apart. One clamp can rotate, while the other cannot, but it can move axially and apply the load specified in GB / T4074.3-2024 to apply tension to twist the specimen. After peeling and twisting, the sample should be checked for loss of adhesion. If the paint film can be peeled off the sample without difficulty (e.g., with a fingernail), even if it cannot be completely separated, it should be considered as a loss of adhesion.

[0046] (b) Referring to (a), take a sample, heat it in a constant temperature bath at 175±5℃ for 4 hours, take it out, and after the sample returns to room temperature, conduct the test according to (a).

[0047] (c) The number of twists obtained in test (b) divided by the number of twists obtained in test (a) is the heat aging peel retention rate.

[0048] (3) Refrigerant resistance The twisted wire was sealed in a sealed container, cured, and then sealed again. A vacuum pump was used to reduce the pressure, and refrigerant was added at the experimentally set temperature to pressurize the container to the set value. Example values ​​are shown in Table 1 below. A 1000-hour aging test was conducted. After the test, the characteristics of the enameled wire were evaluated according to GB / T 4074.5-2024: Electrical Performance Test - Breakdown Voltage.

[0049] Table 1:

[0050] (a) Breakdown voltage retention rate: The breakdown voltage before and after the test was tested according to GB / T 4074.5-2024. Breakdown voltage retention rate = sample value after test / sample value before test × 100%.

[0051] (b) Foaming property: After the sample is treated with refrigerant, it is placed in a constant temperature bath at 160°C and heated for 10 minutes. After the sample temperature returns to room temperature, the film is visually inspected for blistering.

[0052] The test results are shown in Table 2 below. Each sample was tested three times, and the average value was taken. Table 2:

[0053] Test results show that the heat-resistant and high-adhesion enameled wire for the thermal management system provided by this invention has a shorter enamel film desorption distance, exhibiting better adhesion. The heat-resistant aging peeling retention rate is over 80%, the refrigerant resistance is better, the breakdown voltage retention rate is over 90%, and there is no foaming phenomenon.

[0054] The above embodiments are merely preferred embodiments of the present invention. Any simple modifications, alterations, and substitutions made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A heat-resistant aging-resistant high-adhesion enameled wire for a thermal management system, characterized by, include: A circular copper conductor core (1) and four insulating layers coated thereon, wherein the first insulating layer (2) is disposed on the outer surface of the circular copper conductor core (1), and the second insulating layer (3), the third insulating layer (4) and the fourth insulating layer (5) are distributed sequentially from the inside to the outside. The first insulating layer (2) is a polyamide-imide modified in situ with a titanate coupling agent, and the second insulating layer (3) is a polyesterimide modified with tris(2-hydroxyethyl) isocyanurate. The molecular formula diagram of its crosslinking structure is shown below: ； Both the third insulating layer (4) and the fourth insulating layer (5) are made of polyamide-imide materials; The proportion of the first insulating layer to the total thickness of the four insulating layers shall not exceed 10%, and the proportion of the second insulating layer to the total thickness of the four insulating layers shall not be less than 40%.

2. The heat-resistant aging and high adhesion enameled wire for a thermal management system according to claim 1, characterized by, The tris(2-hydroxyethyl) isocyanurate-modified polyesterimide is prepared by reacting the following raw materials: The raw materials include: tris(2-hydroxyethyl) isocyanurate, ethylene glycol, terephthalic acid, trimellitic anhydride and 4,4'-diaminodiphenylmethane, in a molar ratio of 0.16~0.24∶0.64~0.96∶1∶0.24~0.36∶0.2~0.3; The reaction was carried out using tetrabutyl titanate as a catalyst, with the amount of catalyst being 0.1~0.2% of the total mass of the reaction system, and the reaction temperature being 180~210℃.

3. The heat management system resistant heat-ageing high adhesion enameled wire according to claim 1, characterized in that, The preparation conditions for the in-situ modified polyamide-imide by the titanate coupling agent are as follows: the amount of titanate coupling agent added is 1.5~2.5% of the total mass of the polyamide-imide prepolymer, and it is added in situ during the prepolymerization stage of polyamide-imide at 100~140℃. It reacts simultaneously with the dianhydride and diamine monomers and is grafted to the molecular chain end. After holding at this temperature for 1~2h, the temperature is gradually increased to 220~240℃ to complete the imidization ring-closure reaction.

4. The heat management system with heat-resistant aging high adhesion enameled wire according to claim 1, characterized in that, The third insulating layer (4) is a highly elastic polyamide-imide with a film elongation at break of ≥15%.

5. The heat-resistant, high-adhesion enameled wire for the thermal management system according to claim 1, characterized in that, The fourth insulating layer (5) is a self-lubricating polyamide-imide with a surface dynamic friction coefficient ≤0.

3.

6. The heat management system with heat-ageing resistant high adhesion enameled wire according to claim 1, characterized in that, The diameter of the circular copper conductor core (1) is 0.60~1.80mm, and the total thickness of the four insulating layers is 50~120μm.

7. The heat management system resistant heat aged high adhesion enameled wire according to claim 1, characterized by, The heat-resistant, high-adhesion enameled wire exhibits a heat-resistant peeling retention rate of ≥75% after heat aging at 175℃ for 4 hours.

8. A method of manufacturing a heat-resistant, high-adhesion enameled wire for a thermal management system according to any one of claims 1 to 7, characterized by, Includes the following steps: The copper conductor is drawn to the target diameter using a die and then subjected to online annealing at a processing speed of 45~150m / min. Modified polyamide-imide insulating varnish, tris(2-hydroxyethyl) isocyanurate-modified polyesterimide insulating varnish, high-elasticity polyamide-imide insulating varnish, and self-lubricating polyamide-imide insulating varnish are applied sequentially through a coating die. The modified polyamide-imide insulating varnish is applied 1~2 times, the tris(2-hydroxyethyl) isocyanurate-modified polyesterimide insulating varnish 6~14 times, the high-elasticity polyamide-imide insulating varnish 4~8 times, and the self-lubricating polyamide-imide insulating varnish 1~2 times, for a total of 12~24 coatings. After each coating, the conductor is placed in an oven with a baking temperature of 150~350℃ at the oven inlet to initially dry the varnish. It then passes through a curing zone at a curing temperature of 480~610℃ and is baked. After cooling, a heat-resistant, high-adhesion enameled wire for the thermal management system is obtained.

9. The preparation method according to claim 8, characterized in that, The temperature for online annealing is 460~600℃.

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