Corona-resistant aluminum-based enameled wire and method for manufacturing the same

Abstract

The present application relates to the field of enameled wire processing, and particularly relates to a corona-resistant aluminum-based enameled wire and a preparation method thereof. The corona-resistant aluminum-based enameled wire comprises, from inside to outside, an aluminum-based conductor, a bottom insulating layer, a middle corona-resistant layer and an outer protective layer. The bottom insulating layer is composed of polyimide resin and phenolic epoxy resin, which ensures high insulation and high adhesion. The middle corona-resistant layer is mainly composed of modified polyamide-imide, and nanometer boron nitride is added as a filler, which ensures high mechanical properties and high corona resistance. The outer protective layer is mainly composed of polyimide resin, and silica is added as a filler. Lubricant and antioxidant are also added, which increases the strength and avoids paint film scratches during winding, and plays a good protective effect. Through the synergistic effect of the multi-layer paint film, the present application realizes high mechanical strength and long-term corona resistance of the aluminum-based enameled wire in high-voltage and high-frequency scenarios.

Description

Technical Field

[0001] This invention relates to the field of enameled wire processing, and specifically to a corona-resistant aluminum-based enameled wire and its preparation method. Background Technology

[0002] As a key conductor component in motors and electrical appliances, enameled wire has extremely high requirements for insulation and mechanical properties. Traditional enameled wire is prone to corona breakdown and enamel film cracking under high-voltage electric fields and frequent bending environments. To address this issue, the industry has been gradually advancing the research and development of corona-resistant and bend-resistant enameled wires. In terms of corona resistance, the introduction of high dielectric strength materials such as modified polyimide and fluorinated polymers effectively suppresses partial discharge and improves insulation life. At the same time, the use of a multi-layer composite coating structure improves stability against high-frequency impacts and high-temperature environments. As for bend resistance, by optimizing the flexibility of the enamel film and improving the enameling process, the enameled wire can maintain insulation integrity and is not prone to cracking even at small bending radii.

[0003] With the development of power electronics technology and new insulating materials, anti-corona and bend-resistant enameled wires will continue to advance towards higher temperature resistance and longer lifespan. Currently, my country's enameled wire production mainly focuses on polyester, polyurethane, and polyimide varieties. Among them, polyimide enameled wire enamel is a high-temperature resistant enameled wire enamel with excellent comprehensive performance and is one of the main varieties of high-temperature resistant enameled wire enamels above grade 200 worldwide. It not only maintains high heat resistance, allowing long-term use at 200℃, but also has good mechanical properties, chemical corrosion resistance, and refrigerant resistance. Furthermore, it significantly improves adhesion and flexibility to conductors, while also enhancing abrasion resistance, achieving a good balance in the mechanical properties of the enamel film. However, with technological advancements, the operating environment of polyimide enameled wires is becoming increasingly demanding, especially under high-temperature conditions. Although polyimide is not easily softened, its high dielectric constant makes it prone to forming charge channels and causing breakdown. Summary of the Invention

[0004] To address the problems existing in the prior art, the purpose of this invention is to provide a corona-resistant aluminum-based enameled wire and its preparation method.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] In a first aspect, the present invention provides a corona-resistant aluminum-based enameled wire, comprising an aluminum-based conductor, a bottom insulation layer, an intermediate corona-resistant layer, and an outer protective layer arranged sequentially from the inside to the outside; wherein the coating thickness of the bottom insulation layer is 80-100μm, the coating thickness of the intermediate corona-resistant layer is 30-40μm, and the coating thickness of the outer protective layer is 40-50μm.

[0007] Preferably, the bottom insulating layer comprises the following components in parts by weight:

[0008] 100 parts polyimide resin, 10-15 parts phenolic epoxy resin and 80-120 parts first solvent.

[0009] Preferably, the polyimide resin has a weight-average molecular weight (Mw) of 50,000-80,000; the phenolic epoxy resin is of type F-51 or F-44; and the first solvent is a mixture of N-methylpyrrolidone and N,N-dimethylacetamide in a mass ratio of 6-8:2-4.

[0010] Preferably, the curing process of the bottom insulating layer includes:

[0011] Polyimide resin and phenolic epoxy resin are added to the first solvent and mixed thoroughly. The mixture is then coated onto the surface of the aluminum-based wire and subjected to a stepped curing process: 80℃ heat treatment for 0.5 hours, 150℃ heat treatment for 1 hour, 250℃ heat treatment for 2 hours, and 300℃ heat treatment for 1 hour. After cooling, the curing is complete.

[0012] Preferably, the intermediate corona-resistant layer comprises the following components by weight:

[0013] 100 parts modified polyamide imide, 3-8 parts nano boron nitride and 50-60 parts second solvent.

[0014] Preferably, the method for preparing the modified polyamide-imide includes:

[0015] S1. Weigh 4-trifluoromethyl-1,2-phenylenediamine (TFMPD) and 3,4-diaminobenzenesulfonamide (DABSA) according to the proportion, and add them to the organic solvent in sequence under ice-water bath conditions and stir thoroughly to obtain a diamine mixture.

[0016] S2. Weigh 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), dry it under vacuum, and add it to the diamine mixture in three portions under nitrogen protection. Each addition is the same amount, and the interval between each addition is 10-20 minutes. After complete addition, stir for 8-16 hours under ice-water bath conditions to obtain the prepolymer mixture.

[0017] S3. Add dehydrating agent and catalyst to the prepolymer mixture in sequence. Stir at room temperature for 1-2 hours, then heat to 80℃ for 1-2 hours, then heat to 100℃ for 2-3 hours. After natural cooling, pour into a large amount of anhydrous ethanol, collect the precipitated solid, and dry to obtain modified polyamide imide.

[0018] Preferably, in S1, the ratio of 4-trifluoromethyl-1,2-phenylenediamine (TFMPD), 3,4-diaminobenzenesulfonamide (DABSA) and organic solvent is (0.4-0.6)g:(1.3-1.5)g:(10-20)mL.

[0019] Preferably, in S1, the organic solvent is at least one of N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMF), and N,N-dimethylacetamide (DMAC).

[0020] Preferably, in S2, the ratio of the mixture of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) and diamine is (3.2-3.4) g:(10-20) mL.

[0021] Preferably, in step S3, the dehydrating agent is acetic anhydride, and the amount added is 2%-8% of the mass of the prepolymer mixture; the catalyst is pyridine, and the amount added is 0.5%-1% of the mass of the prepolymer mixture.

[0022] Preferably, the curing process of the intermediate corona-resistant layer includes:

[0023] The modified polyamide-imide was dissolved in the second solvent, and nano-boron nitride was added. After thorough mixing, it was coated on the surface of the bottom insulating layer. Then, it was treated sequentially at 120℃ for 2-3 hours, at 150℃ for 1-2 hours, at 180℃ for 1-2 hours, and finally at 260-300℃ for 0.5 hours to complete the curing.

[0024] Preferably, the particle size of the nano-boron nitride is 60-80 nm; the second solvent is a mixture of N,N-dimethylacetamide and 1,4-butyrolactone in a mass ratio of 5-7:3-5.

[0025] Preferably, the outer protective layer comprises the following components by weight:

[0026] 100 parts polyimide resin, 5-15 parts nano silica, 2-4 parts lubricant, 0.5-1.5 parts antioxidant and 30-50 parts third solvent.

[0027] Preferably, the polyimide resin has a weight-average molecular weight (Mw) of 50,000-80,000; the nano-silica has a particle size of 80-100 nm; the lubricant is polytetrafluoroethylene micro powder; the antioxidant is antioxidant 1010; and the third solvent is obtained by mixing N,N-dimethylacetamide and toluene in a mass ratio of 7-9:1-3.

[0028] Preferably, the curing process of the outer protective layer includes:

[0029] The polyimide resin is dissolved in a third solvent, and then nano-silica, lubricant, and antioxidant are added in sequence. After being thoroughly mixed, the mixture is coated on the surface of the intermediate corona-resistant layer, and then subjected to a step-curing treatment: 120℃ for 1 hour, 180℃ for 2 hours, 250℃ for 3 hours, and 280℃ for 1 hour to complete the curing.

[0030] Secondly, the present invention provides a method for preparing a corona-resistant aluminum-based enameled wire, comprising the following steps:

[0031] Take an aluminum-based wire, remove oil from its surface, coat it with a bottom insulation layer, apply a first step curing treatment, coat it with an intermediate corona-resistant layer, apply a second step curing treatment, coat it with an outer protective layer, and apply a third step curing treatment to obtain a corona-resistant aluminum-based enameled wire.

[0032] The beneficial effects of this invention are as follows:

[0033] 1. This invention provides a corona-resistant aluminum-based enameled wire, wherein the surface coating of the enameled wire comprises a bottom insulating layer, a middle corona-resistant layer, and an outer protective layer. Through the synergistic effect of the multiple coating layers, this invention achieves high mechanical strength and long-term corona resistance in high-voltage, high-frequency applications for the aluminum-based enameled wire.

[0034] 2. In this invention, the bottom insulating layer is made of polyimide resin and phenolic epoxy resin composite to ensure high insulation and high adhesion; the middle corona-resistant layer uses modified polyamide-imide as the main material and adds nano boron nitride as filler to ensure high mechanical properties and high corona resistance; the outer protective layer uses polyimide resin as the main material and adds silica as filler, as well as lubricant and antioxidant to increase strength while avoiding scratches on the paint film during winding, thus providing good protection.

[0035] 3. Compared with traditional polyimide enameled wire materials, this invention modifies the composition of the intermediate corona-resistant layer. The intermediate corona-resistant layer uses modified polyamide-imide as the main material. The modified polyamide-imide is prepared by using 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) as the dianhydride and 4-trifluoromethyl-1,2-phenylenediamine (TFMPD) and 3,4-diaminobenzenesulfonamide (DABSA) as diamines. The prepared modified polyamide-imide contains both sulfonamide groups and trifluoromethyl groups. The sulfonamide groups have strong free radical scavenging ability, which can ensure sufficient corona resistance. The trifluoro groups have excellent chemical stability. The two are mixed in a unique ratio, so that the resulting intermediate corona-resistant layer has excellent strength, flexibility, adhesion and corona resistance. Detailed Implementation

[0036] The technical solution of the present invention is illustrated below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0037] To better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. While exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0038] The present invention will be further described below with reference to the following embodiments.

[0039] Example 1

[0040] A corona-resistant aluminum-based enameled wire includes, from the inside out, an aluminum-based conductor, a bottom insulation layer, a middle corona-resistant layer, and an outer protective layer.

[0041] The bottom insulating layer comprises the following components in parts by weight:

[0042] 100 parts polyimide resin (Mw = 56,000), 12 parts phenolic epoxy resin F-51 and 100 parts first solvent; the first solvent is N-methylpyrrolidone and N,N-dimethylacetamide mixed in a mass ratio of 7:3.

[0043] The intermediate corona-resistant layer comprises, by weight, the following components:

[0044] 100 parts modified polyamide imide, 5 parts nano boron nitride (60-80 nm) and 55 parts second solvent; the second solvent is N,N-dimethylacetamide and 1,4-butyrolactone mixed in a mass ratio of 6:4.

[0045] The method for preparing the modified polyamide-imide includes:

[0046] S1. Weigh 0.5g of 4-trifluoromethyl-1,2-phenylenediamine (TFMPD) and 1.4g of 3,4-diaminobenzenesulfonamide (DABSA) according to the ratio, and add them sequentially to 15mL of N-methylpyrrolidone (NMP) under ice-water bath conditions, stirring thoroughly to obtain a diamine mixture.

[0047] S2. Weigh 3.3g of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), dry it under vacuum, and add it to 15mL of diamine mixture in three portions under nitrogen protection. The amount added each time is the same, and the interval between each addition is 15min. After the addition is complete, stir for 12h under ice-water bath conditions to obtain prepolymer mixture.

[0048] S3. Add 5% (by weight) of acetic anhydride and 0.6% (by weight) of pyridine to the prepolymer mixture. Stir at room temperature for 1.5 hours, then heat to 80°C for 1.5 hours, then heat to 100°C for 3 hours. After natural cooling, pour into a large amount of anhydrous ethanol, collect the precipitated solid, and dry to obtain modified polyamide imide.

[0049] The outer protective layer comprises the following components by weight:

[0050] The mixture comprises 100 parts polyimide resin (Mw = 68,000), 10 parts nano-silica (80-100nm), 2-4 parts polytetrafluoroethylene micro powder, 1 part antioxidant 1010, and 40 parts third solvent; wherein the third solvent is N,N-dimethylacetamide and toluene mixed in a mass ratio of 8:2.

[0051] The above-mentioned method for preparing corona-resistant aluminum-based enameled wire includes:

[0052] Step 1: Take an aluminum-based wire with a diameter of 1.78mm, use acetone to degrease the surface, and then dry it for later use.

[0053] Step 2: According to the raw material composition of the bottom insulation layer, add polyimide resin and phenolic epoxy resin to the first solvent, mix thoroughly, and then coat it on the surface of the aluminum-based wire with a coating thickness of 90μm. Then perform a stepped curing treatment: heat treatment at 80℃ for 0.5h, heat treatment at 150℃ for 1h, heat treatment at 250℃ for 2h, and heat treatment at 300℃ for 1h. After cooling, the curing is complete.

[0054] Step 3: According to the raw material composition of the intermediate corona-resistant layer, the modified polyamide-imide is dissolved in the second solvent, nano boron nitride is added, and after thorough mixing, it is coated on the surface of the bottom insulating layer with a coating thickness of 35μm. Then, it is treated sequentially at 120℃ for 2h, at 150℃ for 2h, at 180℃ for 2h, and finally at 280℃ for 0.5h to complete the curing.

[0055] Step 4: According to the raw material composition of the outer protective layer, dissolve the polyimide resin in the third solvent, then add nano-silica, polytetrafluoroethylene micro powder and antioxidant in sequence. After mixing thoroughly, coat the coating on the surface of the middle corona-resistant layer with a coating thickness of 45μm. Then perform a step curing treatment: treat at 120℃ for 1h, at 180℃ for 2h, at 250℃ for 3h, and at 280℃ for 1h to complete the curing.

[0056] Step 5: After cutting, winding and packaging, corona-resistant aluminum-based enameled wire is obtained.

[0057] Example 2

[0058] A corona-resistant aluminum-based enameled wire includes, from the inside out, an aluminum-based conductor, a bottom insulation layer, a middle corona-resistant layer, and an outer protective layer.

[0059] The bottom insulating layer comprises the following components in parts by weight:

[0060] 100 parts polyimide resin (Mw = 56,000), 10 parts phenolic epoxy resin F-44, and 80 parts first solvent; the first solvent is N-methylpyrrolidone and N,N-dimethylacetamide mixed in a mass ratio of 6:4.

[0061] The intermediate corona-resistant layer comprises, by weight, the following components:

[0062] 100 parts modified polyamide imide, 3 parts nano boron nitride (60-80nm) and 50 parts second solvent; the second solvent is N,N-dimethylacetamide and 1,4-butyrolactone mixed in a mass ratio of 5:5.

[0063] The preparation method of the modified polyamide imide is the same as that in Example 1.

[0064] The outer protective layer comprises the following components by weight:

[0065] The mixture comprises 100 parts polyimide resin (Mw = 68,000), 5 parts nano-silica (80-100nm), 2 parts polytetrafluoroethylene micro powder, 0.5 parts antioxidant 1010, and 30-50 parts third solvent; wherein the third solvent is N,N-dimethylacetamide and toluene mixed in a mass ratio of 7:3.

[0066] The above-mentioned method for preparing corona-resistant aluminum-based enameled wire includes:

[0067] Step 1: Take an aluminum-based wire with a diameter of 2.2mm, degrease the surface with acetone, and then dry it for later use;

[0068] Step 2: According to the raw material composition of the bottom insulation layer, add polyimide resin and phenolic epoxy resin to the first solvent, mix thoroughly, and then coat it on the surface of the aluminum-based wire with a coating thickness of 80μm. Then perform a stepped curing treatment: heat treatment at 80℃ for 0.5h, heat treatment at 150℃ for 1h, heat treatment at 250℃ for 2h, and heat treatment at 300℃ for 1h. After cooling, the curing is complete.

[0069] Step 3: According to the raw material composition of the intermediate corona-resistant layer, the modified polyamide-imide is dissolved in the second solvent, nano boron nitride is added, and after thorough mixing, it is coated on the surface of the bottom insulating layer with a coating thickness of 30μm. Then, it is treated sequentially at 120℃ for 2h, at 150℃ for 1h, at 180℃ for 1h, and finally at 260℃ for 0.5h to complete the curing.

[0070] Step 4: According to the raw material composition of the outer protective layer, dissolve the polyimide resin in the third solvent, then add nano-silica, polytetrafluoroethylene micro powder and antioxidant in sequence. After mixing thoroughly, coat the coating on the surface of the middle corona-resistant layer with a coating thickness of 40μm. Then perform a step curing treatment: treat at 120℃ for 1h, at 180℃ for 2h, at 250℃ for 3h, and at 280℃ for 1h to complete the curing.

[0071] Step 5: After cutting, winding and packaging, corona-resistant aluminum-based enameled wire is obtained.

[0072] Example 3

[0073] A corona-resistant aluminum-based enameled wire includes, from the inside out, an aluminum-based conductor, a bottom insulation layer, a middle corona-resistant layer, and an outer protective layer.

[0074] The bottom insulating layer comprises the following components in parts by weight:

[0075] 100 parts polyimide resin (Mw = 56,000), 15 parts phenolic epoxy resin F-51 and 120 parts first solvent; the first solvent is N-methylpyrrolidone and N,N-dimethylacetamide mixed in a mass ratio of 8:2.

[0076] The intermediate corona-resistant layer comprises, by weight, the following components:

[0077] 100 parts modified polyamide imide, 8 parts nano boron nitride (60-80nm) and 60 parts second solvent; the second solvent is N,N-dimethylacetamide and 1,4-butyrolactone mixed in a mass ratio of 7:3.

[0078] The preparation method of the modified polyamide imide is the same as that in Example 1.

[0079] The outer protective layer comprises the following components by weight:

[0080] The mixture comprises 100 parts polyimide resin (Mw = 68,000), 15 parts nano-silica (80-100nm), 4 parts polytetrafluoroethylene micro powder, 1.5 parts antioxidant 1010, and 50 parts third solvent; the third solvent is N,N-dimethylacetamide and toluene mixed in a mass ratio of 9:1.

[0081] The above-mentioned method for preparing corona-resistant aluminum-based enameled wire includes:

[0082] Step 1: Take an aluminum-based wire with a diameter of 2.78mm, use acetone to degrease the surface, and then dry it for later use.

[0083] Step 2: According to the raw material composition of the bottom insulation layer, add polyimide resin and phenolic epoxy resin to the first solvent, mix thoroughly, and then coat it on the surface of the aluminum-based wire with a coating thickness of 100μm. Then perform a stepped curing treatment: heat treatment at 80℃ for 0.5h, heat treatment at 150℃ for 1h, heat treatment at 250℃ for 2h, and heat treatment at 300℃ for 1h. After cooling, the curing is complete.

[0084] Step 3: According to the raw material composition of the intermediate corona-resistant layer, the modified polyamide-imide is dissolved in the second solvent, nano boron nitride is added, and after thorough mixing, it is coated on the surface of the bottom insulating layer with a coating thickness of 40μm. Then, it is treated sequentially at 120℃ for 3h, at 150℃ for 2h, at 180℃ for 2h, and finally at 300℃ for 0.5h to complete the curing.

[0085] Step 4: According to the raw material composition of the outer protective layer, dissolve the polyimide resin in the third solvent, then add nano-silica, polytetrafluoroethylene micro powder and antioxidant in sequence. After mixing thoroughly, coat the coating on the surface of the middle corona-resistant layer with a coating thickness of 50μm. Then perform a step curing treatment: treat at 120℃ for 1h, at 180℃ for 2h, at 250℃ for 3h, and at 280℃ for 1h to complete the curing.

[0086] Step 5: After cutting, winding and packaging, corona-resistant aluminum-based enameled wire is obtained.

[0087] Comparative Example 1

[0088] A corona-resistant intermediate corona-resistant layer for an aluminum-based enameled wire differs from that in Example 1 in that only 4-trifluoromethyl-1,2-phenylenediamine (TFMPD) is used as the diamine in the preparation of the modified polyamide-imide in the composition.

[0089] The intermediate corona-resistant layer comprises, by weight, the following components:

[0090] 100 parts modified polyamide imide, 5 parts nano boron nitride (60-80 nm) and 55 parts second solvent; the second solvent is N,N-dimethylacetamide and 1,4-butyrolactone mixed in a mass ratio of 6:4.

[0091] Methods for preparing modified polyamide imides include:

[0092] S1. Weigh 1.9g of 4-trifluoromethyl-1,2-phenylenediamine (TFMPD) and add it to 15mL of N-methylpyrrolidone (NMP) under ice-water bath conditions. Stir thoroughly to obtain a diamine mixture.

[0093] S2. Weigh 3.3g of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), dry it under vacuum, and add it to 15mL of diamine mixture in three portions under nitrogen protection. The amount added each time is the same, and the interval between each addition is 15min. After the addition is complete, stir for 12h under ice-water bath conditions to obtain prepolymer mixture.

[0094] S3. Add 5% (by weight) of acetic anhydride and 0.6% (by weight) of pyridine to the prepolymer mixture. Stir at room temperature for 1.5 hours, then heat to 80°C for 1.5 hours, then heat to 100°C for 3 hours. After natural cooling, pour into a large amount of anhydrous ethanol, collect the precipitated solid, and dry to obtain modified polyamide imide.

[0095] Comparative Example 2

[0096] A corona-resistant intermediate corona-resistant layer for an aluminum-based enameled wire differs from that in Example 1 in that only 3,4-diaminobenzenesulfonamide (DABSA) is used as the diamine in the preparation of the modified polyamide-imide in the composition.

[0097] The intermediate corona-resistant layer comprises, by weight, the following components:

[0098] 100 parts modified polyamide imide, 5 parts nano boron nitride (60-80 nm) and 55 parts second solvent; the second solvent is N,N-dimethylacetamide and 1,4-butyrolactone mixed in a mass ratio of 6:4.

[0099] Methods for preparing modified polyamide imides include:

[0100] S1. Weigh 1.9g of 3,4-diaminobenzenesulfonamide (DABSA) and add it to 15mL of N-methylpyrrolidone (NMP) under ice-water bath conditions. Stir thoroughly to obtain a diamine mixture.

[0101] S2. Weigh 3.3g of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), dry it under vacuum, and add it to 15mL of diamine mixture in three portions under nitrogen protection. The amount added each time is the same, and the interval between each addition is 15min. After the addition is complete, stir for 12h under ice-water bath conditions to obtain prepolymer mixture.

[0102] S3. Add 5% (by weight) of acetic anhydride and 0.6% (by weight) of pyridine to the prepolymer mixture. Stir at room temperature for 1.5 hours, then heat to 80°C for 1.5 hours, then heat to 100°C for 3 hours. After natural cooling, pour into a large amount of anhydrous ethanol, collect the precipitated solid, and dry to obtain modified polyamide imide.

[0103] To more clearly illustrate the present invention, the performance of the intermediate corona-resistant layer of the enameled wires prepared in Example 1, Comparative Example 1, and Comparative Example 2 was tested and compared. The results are shown in the table below:

[0104]

[0105] As can be seen from the table above, compared with Comparative Example 1 and Comparative Example 2, the intermediate corona-resistant layer of the enameled wire prepared in Example 1 of the present invention can have better peel resistance, heat resistance and corona resistance while ensuring high strength and toughness.

[0106] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0107] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A corona-resistant aluminum-based enameled wire, characterized in that, It includes, from the inside out, an aluminum-based conductor, a bottom insulation layer, a middle corona-resistant layer, and an outer protective layer; The bottom insulating layer comprises the following components in parts by weight: 100 parts of the first polyimide resin, 10-15 parts of the phenolic epoxy resin and 80-120 parts of the first solvent; The intermediate corona-resistant layer comprises, by weight, the following components: 100 parts modified polyamide-imide, 3-8 parts nano boron nitride, and 50-60 parts second solvent; The outer protective layer comprises the following components by weight: 100 parts of second polyimide resin, 5-15 parts of nano silica, 2-4 parts of lubricant, 0.5-1.5 parts of antioxidant and 30-50 parts of third solvent; The method for preparing the modified polyamide-imide includes: S1. Weigh 4-trifluoromethyl-1,2-phenylenediamine and 3,4-diaminobenzenesulfonamide according to the proportion, and add them to an organic solvent in sequence under ice-water bath conditions, stirring thoroughly to obtain a diamine mixture. S2. Weigh out 3,3',4,4'-benzophenone tetracarboxylic dianhydride, dry it under vacuum, and add it to the diamine mixture in three portions under nitrogen protection. The amount added each time is the same, and the interval between each addition is 10-20 minutes. After complete addition, stir for 8-16 hours under ice-water bath conditions to obtain the prepolymer mixture. S3. Add dehydrating agent and catalyst to the prepolymer mixture in sequence. Stir at room temperature for 1-2 hours, then heat to 80℃ for 1-2 hours, then heat to 100℃ for 2-3 hours. After natural cooling, pour into a large amount of anhydrous ethanol, collect the precipitated solid, and dry to obtain modified polyamide imide.

2. The corona-resistant aluminum-based enameled wire according to claim 1, characterized in that, The first polyimide resin has a weight-average molecular weight of 50,000-80,000; the phenolic epoxy resin is of type F-51 or F-44; the first solvent is a mixture of N-methylpyrrolidone and N,N-dimethylacetamide in a mass ratio of 6-8:2-4.

3. The corona-resistant aluminum-based enameled wire according to claim 1, characterized in that, The boron nitride nanoparticles have a particle size of 60-80 nm; the second solvent is a mixture of N,N-dimethylacetamide and 1,4-butyrolactone in a mass ratio of 5-7:3-5.

4. The corona-resistant aluminum-based enameled wire according to claim 1, characterized in that, The second polyimide resin has a weight-average molecular weight of 50,000-80,000; the nano-silica has a particle size of 80-100 nm; the lubricant is polytetrafluoroethylene micro powder; the antioxidant is antioxidant 1010; and the third solvent is obtained by mixing N,N-dimethylacetamide and toluene in a mass ratio of 7-9:1-3.

5. The corona-resistant aluminum-based enameled wire according to claim 1, characterized in that, In S1, the ratio of 4-trifluoromethyl-1,2-phenylenediamine, 3,4-diaminobenzenesulfonamide and organic solvent is (0.4-0.6)g:(1.3-1.5)g:(10-20)mL.

6. The corona-resistant aluminum-based enameled wire according to claim 1, characterized in that, In S2, the ratio of the mixture of 3,3',4,4'-benzophenone tetracarboxylic dianhydride and diamine is (3.2-3.4) g:(10-20) mL.

7. The corona-resistant aluminum-based enameled wire according to claim 1, characterized in that, In S3, the dehydrating agent is acetic anhydride, and the amount added is 2%-8% of the mass of the prepolymer mixture; the catalyst is pyridine, and the amount added is 0.5%-1% of the mass of the prepolymer mixture.

8. A method for preparing the corona-resistant aluminum-based enameled wire according to claim 1, characterized in that, Includes the following steps: Step 1: Take the aluminum-based wire after surface degreasing, coat the bottom insulation layer, and perform the first step curing treatment: 80℃ heat treatment for 0.5h, 150℃ heat treatment for 1h, 250℃ heat treatment for 2h, and 300℃ heat treatment for 1h. Step 2: Apply an intermediate corona-resistant layer and perform a second step curing treatment: treat at 120℃ for 2-3 hours, at 150℃ for 1-2 hours, at 180℃ for 1-2 hours, and finally at 260-300℃ for 0.5 hours. Step 3, then apply an external protective layer and perform a third step curing treatment: 120℃ for 1 hour, 180℃ for 2 hours, 250℃ for 3 hours, and 280℃ for 1 hour; Step 4: After cutting, winding and packaging, corona-resistant aluminum-based enameled wire is obtained.

9. The method for preparing a corona-resistant aluminum-based enameled wire according to claim 8, characterized in that, The coating thickness of the bottom insulating layer is 80-100μm, the coating thickness of the middle corona resistant layer is 30-40μm, and the coating thickness of the outer protective layer is 40-50μm.

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