Corona-resistant aluminum-based enameled wire and preparation method thereof

Abstract

The invention relates to the field of enameled wire processing, in particular to a corona-resistant aluminum-based enameled wire and a preparation method thereof. The corona-resistant aluminum-based enameled wire comprises an aluminum-based wire, a bottom insulating layer, a middle corona-resistant layer and an external protective layer which are sequentially arranged from inside to outside, the bottom insulating layer is formed by compounding polyimide resin and novolac epoxy resin, so that high insulativity and high adhesive force are ensured; the middle corona-resistant layer adopts modified polyamide-imide as a main material, and nano boron nitride is added as a filler, so that high mechanical property and high corona resistance are ensured; and the outer protection layer adopts polyimide resin as a main material, silicon dioxide is added as a filler, and a lubricant and an antioxidant are also added, so that the strength is improved, a paint film is prevented from being scratched during winding, and a relatively good protection effect is achieved. Through the synergistic effect of multiple layers of paint films, high mechanical strength and long-acting corona resistance of the aluminum-based enameled wire in a high-voltage and high-frequency scene are achieved.

Description

Technical Field

[0001] The invention relates to the field of enameled wire processing, and in particular to a corona-resistant aluminum-based enameled wire and a preparation method thereof. Background Art

[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 paint film cracking in high-voltage electric fields and frequent bending environments. To solve this pain point, the industry has gradually promoted the research and development of corona-resistant and bend-resistant enameled wire. In terms of corona resistance, the introduction of high dielectric strength materials such as modified polyimide and fluorinated polymer can effectively suppress local discharge and improve insulation life. At the same time, a multi-layer composite coating structure is adopted to improve stability to high-frequency impact and high-temperature environments. In terms of bending resistance, by optimizing the flexibility of the paint film and improving the enameling process, the enameled wire can maintain insulation integrity and is not easy to crack even at a small bending radius.

[0003] With the advancement of power electronics technology and new insulation materials, corona-resistant and flex-resistant enameled wire will continue to advance towards higher temperature resistance and longer lifespan. Currently, my country's enameled wire production primarily focuses on polyester, polyurethane, and polyimide varieties. Polyimide wire enamel, a high-temperature resistant wire enamel with excellent comprehensive properties, is one of the world's leading high-temperature enamels above grade 200. It not only maintains high heat resistance, enabling long-term use at 200°C, but also exhibits excellent mechanical properties, chemical resistance, and refrigerant resistance. It also significantly improves conductor adhesion and flexibility, while also enhancing wear resistance, resulting in a well-balanced mechanical property profile. However, with technological advancements, the operating environments of polyimide enameled wire are becoming increasingly demanding, particularly at high temperatures. While polyimide does not readily soften, its high dielectric constant makes it susceptible to charge channels and breakdown. Summary of the Invention

[0004] In view of the problems existing in the prior art, the object of the present invention is to provide a corona-resistant aluminum-based enameled wire and a preparation method thereof.

[0005] The purpose of the present invention is achieved by adopting the following technical solutions:

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

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

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

[0009] Preferably, the weight average molecular weight (Mw) of the polyimide resin is 50,000-80,000; the model of the novolac epoxy resin is 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] Add polyimide resin and phenolic epoxy resin to the first solvent, mix thoroughly, and then coat them on the surface of the aluminum-based wire. Then perform a step-by-step curing treatment: heat treatment at 80°C for 0.5h, heat treatment at 150°C for 1h, heat treatment at 250°C for 2h, and heat treatment at 300°C for 1h. After cooling, curing is completed.

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

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

[0014] Preferably, the preparation method of the modified polyamide-imide comprises:

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

[0016] S2. Weigh 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and dry it in vacuo. Then, under the protection of nitrogen, add the same amount to the diamine mixture three times, with an interval of 10-20 minutes between each addition. After the addition is complete, stir in an ice-water bath for 8-16 hours to obtain a prepolymer mixture.

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

[0018] Preferably, in S1, the ratio of 4-trifluoromethyl-1,2-phenylenediamine (TFMPD), 3,4-diaminobenzenesulfonamide (DABSA) and the 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 mixed solution of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and diamine is (3.2-3.4) g: (10-20) mL.

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

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

[0023] 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, and then treated at 120°C for 2-3 hours, 150°C for 1-2 hours, 180°C for 1-2 hours, and finally at 260-300°C 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 calculated by weight:

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

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

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

[0029] Dissolve the polyimide resin in the third solvent, then add nano-silica, lubricant, and antioxidant in sequence, mix thoroughly, and then coat it on the surface of the middle corona-resistant layer. Then perform step-curing treatment: 120°C for 1 hour, 180°C for 2 hours, 250°C for 3 hours, and 280°C for 1 hour to complete the curing.

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

[0031] Take the aluminum-based wire, degrease the surface, apply the bottom insulation layer, perform the first step curing treatment, apply the middle corona-resistant layer, perform the second step curing treatment, apply the outer protective layer, and perform the third step curing treatment to obtain the corona-resistant aluminum-based enameled wire.

[0032] The beneficial effects of the present invention are:

[0033] The present invention prepares a corona-resistant aluminum-based enameled wire. The surface paint film of the enameled wire includes a bottom insulating layer, an intermediate corona-resistant layer, and an outer protective layer. Through the synergistic effect of the multiple layers of paint film, the present invention achieves high mechanical strength and long-lasting corona resistance in high-voltage and high-frequency applications.

[0034] 2. In the present invention, the bottom insulating layer is made of a composite of polyimide resin and phenolic epoxy resin to ensure high insulation and high adhesion; the middle corona-resistant layer uses modified polyamide-imide as the main material, with nano-boron nitride added as a filler, to ensure high mechanical properties and high corona resistance; the outer protective layer uses polyimide resin and as the main material, with silicon dioxide added as a filler, and lubricants and antioxidants are also added to increase strength while avoiding scratches on the paint film during winding, thereby achieving better protection effect.

[0035] 3. Compared with traditional polyimide enameled wire materials, the present invention has modified 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'-benzophenonetetracarboxylic 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 group has a strong free radical capture ability and can ensure sufficient corona resistance. The trifluoro group has excellent chemical stability. The two are mixed in a unique ratio, so that the obtained intermediate corona-resistant layer can have excellent strength, flexibility, adhesion and corona resistance. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is described below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not exclude the presence of other method steps before and after the combination step or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the present invention. Changes or adjustments in their relative relationships, without substantially changing the technical content, should also be regarded as the scope of the present invention.

[0037] In order to better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. Although 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 by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

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

[0039] Example 1

[0040] A corona-resistant aluminum-based enameled wire comprises an aluminum-based conductor, a bottom insulating layer, a middle corona-resistant layer and an outer protective layer which are arranged in sequence from the inside to the outside.

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

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

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

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

[0045] The preparation method of the modified polyamide-imide comprises:

[0046] S1. Weigh 0.5 g of 4-trifluoromethyl-1,2-phenylenediamine (TFMPD) and 1.4 g of 3,4-diaminobenzenesulfonamide (DABSA) in proportion, add them sequentially into 15 mL of N-methylpyrrolidone (NMP) in an ice-water bath, and stir thoroughly to obtain a diamine mixture;

[0047] S2. Weigh 3.3 g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and dry it in vacuo. Then, under nitrogen, add the mixture into 15 mL of the diamine mixture three times, with the same amount added each time and an interval of 15 min between each addition. After the mixture is fully added, stir in an ice-water bath for 12 h to obtain a prepolymer mixture.

[0048] S3. Add acetic anhydride in an amount of 5% by mass of the prepolymerization mixture to the prepolymerization mixture, and then add pyridine in an amount of 0.6% by mass of the prepolymerization mixture. After stirring at room temperature for 1.5 hours, heat it to 80°C for 1.5 hours, then heat it at 100°C for 3 hours, cool it naturally, pour it into a large amount of anhydrous ethanol, collect the precipitated solid, and dry it to obtain a modified polyamide-imide.

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

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

[0051] The preparation method of the corona-resistant aluminum-based enameled wire comprises:

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

[0053] Step 2: According to the raw material composition of the bottom insulating layer, polyimide resin and phenolic epoxy resin are added to the first solvent, and after being fully mixed, they are coated on the surface of the aluminum-based wire to a coating thickness of 90 μm, and then subjected to a step-by-step curing treatment: heat treatment at 80° C. for 0.5 h, heat treatment at 150° C. for 1 h, heat treatment at 250° C. for 2 h, and heat treatment at 300° C. for 1 h. After cooling, curing is completed;

[0054] Step 3: Dissolve the modified polyamide-imide in a second solvent according to the raw material composition of the intermediate corona-resistant layer, add nano-boron nitride, mix thoroughly, and then coat the surface of the bottom insulating layer with a coating thickness of 35 μm. Then, treat the layer at 120° C. for 2 h, 150° C. for 2 h, 180° C. for 2 h, and finally at 280° C. for 0.5 h to complete the curing.

[0055] Step 4: Dissolve the polyimide resin in a third solvent according to the raw material composition of the outer protective layer, then add nano-silica, polytetrafluoroethylene powder, and antioxidant in sequence, mix thoroughly, and then apply it on the surface of the middle corona-resistant layer to a coating thickness of 45 μm. Then, perform a step-curing treatment: 120° C. for 1 hour, 180° C. for 2 hours, 250° C. for 3 hours, and 280° C. for 1 hour to complete the curing.

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

[0057] Example 2

[0058] A corona-resistant aluminum-based enameled wire comprises an aluminum-based conductor, a bottom insulating layer, a middle corona-resistant layer and an outer protective layer which are arranged in sequence from the inside to the outside.

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

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

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

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

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

[0066] The preparation method of the corona-resistant aluminum-based enameled wire comprises:

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

[0068] Step 2: According to the raw material composition of the bottom insulating layer, polyimide resin and phenolic epoxy resin are added to the first solvent, and after being fully mixed, they are coated on the surface of the aluminum-based wire to a coating thickness of 80 μm, and then subjected to a step-by-step curing treatment: heat treatment at 80° C. for 0.5 h, heat treatment at 150° C. for 1 h, heat treatment at 250° C. for 2 h, and heat treatment at 300° C. for 1 h. After cooling, curing is completed;

[0069] Step 3: Dissolve the modified polyamide-imide in a second solvent according to the raw material composition of the intermediate corona-resistant layer, add nano-boron nitride, mix thoroughly, and then coat the surface of the bottom insulating layer with a coating thickness of 30 μm. Then, treat the mixture at 120° C. for 2 h, 150° C. for 1 h, 180° C. for 1 h, and finally at 260° C. for 0.5 h to complete the curing.

[0070] Step 4: Dissolve the polyimide resin in a third solvent according to the raw material composition of the outer protective layer, then add nano-silica, polytetrafluoroethylene powder, and antioxidant in sequence, mix thoroughly, and then apply it on the surface of the middle corona-resistant layer to a coating thickness of 40 μm. Then, perform a step-curing treatment: 120° C. for 1 hour, 180° C. for 2 hours, 250° C. for 3 hours, and 280° C. for 1 hour to complete the curing.

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

[0072] Example 3

[0073] A corona-resistant aluminum-based enameled wire comprises an aluminum-based conductor, a bottom insulating layer, a middle corona-resistant layer and an outer protective layer which are arranged in sequence from the inside to the outside.

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

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

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

[0077] 100 parts of modified polyamide-imide, 8 parts of nano-boron nitride (60-80 nm) and 60 parts of a second solvent; the second solvent is a mixture of N,N-dimethylacetamide and 1,4-butyrolactone 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 in parts by weight:

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

[0081] The preparation method of the corona-resistant aluminum-based enameled wire comprises:

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

[0083] Step 2: According to the raw material composition of the bottom insulating layer, polyimide resin and phenolic epoxy resin are added to the first solvent, and after being fully mixed, they are coated on the surface of the aluminum-based wire to a coating thickness of 100 μm, and then subjected to a step-by-step curing treatment: heat treatment at 80° C. for 0.5 h, heat treatment at 150° C. for 1 h, heat treatment at 250° C. for 2 h, and heat treatment at 300° C. for 1 h. After cooling, curing is completed;

[0084] Step 3: Dissolve the modified polyamide-imide in a second solvent according to the raw material composition of the intermediate corona-resistant layer, add nano-boron nitride, mix thoroughly, and then coat the surface of the bottom insulating layer with a coating thickness of 40 μm. Then, treat the mixture at 120° C. for 3 h, 150° C. for 2 h, 180° C. for 2 h, and finally at 300° C. for 0.5 h to complete the curing.

[0085] Step 4: Dissolve the polyimide resin in a third solvent according to the raw material composition of the outer protective layer, then add nano-silica, polytetrafluoroethylene powder, and antioxidant in sequence, mix thoroughly, and then apply it on the surface of the middle corona-resistant layer to a thickness of 50 μm. Then, perform a step-curing treatment: 120° C. for 1 hour, 180° C. for 2 hours, 250° C. for 3 hours, and 280° C. for 1 hour to complete the curing.

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

[0087] Comparative Example 1

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

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

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

[0091] The preparation method of modified polyamide-imide comprises:

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

[0093] S2. Weigh 3.3 g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and dry it in vacuo. Then, under nitrogen, add the mixture into 15 mL of the diamine mixture three times, with the same amount added each time and an interval of 15 min between each addition. After the mixture is fully added, stir in an ice-water bath for 12 h to obtain a prepolymer mixture.

[0094] S3. Add acetic anhydride in an amount of 5% by mass of the prepolymerization mixture to the prepolymerization mixture, and then add pyridine in an amount of 0.6% by mass of the prepolymerization mixture. After stirring at room temperature for 1.5 hours, heat it to 80°C for 1.5 hours, then heat it at 100°C for 3 hours, cool it naturally, pour it into a large amount of anhydrous ethanol, collect the precipitated solid, and dry it to obtain a modified polyamide-imide.

[0095] Comparative Example 2

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

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

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

[0099] The preparation method of modified polyamide-imide comprises:

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

[0101] S2. Weigh 3.3 g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and dry it in vacuo. Then, under nitrogen, add the mixture into 15 mL of the diamine mixture three times, with the same amount added each time and an interval of 15 min between each addition. After the mixture is fully added, stir in an ice-water bath for 12 h to obtain a prepolymer mixture.

[0102] S3. Add acetic anhydride in an amount of 5% by mass of the prepolymerization mixture to the prepolymerization mixture, and then add pyridine in an amount of 0.6% by mass of the prepolymerization mixture. After stirring at room temperature for 1.5 hours, heat it to 80°C for 1.5 hours, then heat it at 100°C for 3 hours, cool it naturally, pour it into a large amount of anhydrous ethanol, collect the precipitated solid, and dry it to obtain a modified polyamide-imide.

[0103] In order to more clearly illustrate the present invention, the performance of the middle corona-resistant layer of the enameled wire prepared in Example 1, Comparative Example 1 and Comparative Example 2 was tested and compared, and the results are shown in the following table:

[0104]

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

[0106] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0107] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A corona-resistant aluminum-based enameled wire, characterized in that: It includes an aluminum-based conductor, a bottom insulation layer, a middle corona-resistant layer and an outer protective layer arranged in sequence from the inside to the outside; The bottom insulating layer comprises the following components in parts by weight: 100 parts of a first polyimide resin, 10-15 parts of a novolac epoxy resin, and 80-120 parts of a first solvent; Wherein, the intermediate corona-resistant layer comprises the following components calculated by weight: 100 parts of modified polyamide-imide, 3-8 parts of nano-boron nitride and 50-60 parts of a second solvent; The outer protective layer comprises the following components in parts by weight: 100 parts of a second polyimide resin, 5-15 parts of nano-silicon dioxide, 2-4 parts of a lubricant, 0.5-1.5 parts of an antioxidant and 30-50 parts of a third solvent.

2. The corona-resistant aluminum-based enameled wire according to claim 1, characterized in that: The weight average molecular weight of the first polyimide resin is 50,000-80,000; the model of the novolac epoxy resin is 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 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.

4. The corona-resistant aluminum-based enameled wire according to claim 1, characterized in that: The weight average molecular weight of the second polyimide resin is 50,000-80,000; the particle size of the nano-silica is 80-100 nm; the lubricant is polytetrafluoroethylene powder; the antioxidant is antioxidant 1010; and the third solvent is a mixture of 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: The preparation method of the modified polyamide-imide comprises: S1. Weigh 4-trifluoromethyl-1,2-phenylenediamine and 3,4-diaminobenzenesulfonamide in proportion, add them to an organic solvent in an ice-water bath, and stir thoroughly to obtain a diamine mixture; S2. Weigh 3,3',4,4'-benzophenonetetracarboxylic dianhydride, dry it in vacuum, and then add it to the diamine mixture in three times under the protection of nitrogen, with the same amount added each time and the interval between each addition being 10-20 minutes. After it is fully added, stir it in an ice-water bath for 8-16 hours to obtain a prepolymer mixture; S3. Add a dehydrating agent and a catalyst to the prepolymer mixture in sequence, stir at room temperature for 1-2 hours, heat it to 80°C for 1-2 hours, then heat it at 100°C for 2-3 hours, cool it naturally, pour it into a large amount of anhydrous ethanol, collect the precipitated solid, and dry it to obtain a modified polyamide-imide.

6. The corona-resistant aluminum-based enameled wire according to claim 5, characterized in that: In the 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.

7. The corona-resistant aluminum-based enameled wire according to claim 5, characterized in that: In the S2, the ratio of the mixed solution of 3,3',4,4'-benzophenonetetracarboxylic dianhydride and diamine is (3.2-3.4) g: (10-20) mL.

8. The corona-resistant aluminum-based enameled wire according to claim 5, characterized in that: In said S3, the dehydrating agent is acetic anhydride, and the added amount is 2%-8% of the mass of the prepolymerization mixture; the catalyst is pyridine, and the added amount is 0.5%-1% of the mass of the prepolymerization mixture.

9. A method for preparing the corona-resistant aluminum-based enameled wire according to claim 1, characterized in that: The following steps are involved: Step 1: Take the aluminum-based wire after surface degreasing, apply the bottom insulation layer, and perform the first step curing treatment: heat treatment at 80°C for 0.5h, heat treatment at 150°C for 1h, heat treatment at 250°C for 2h, and heat treatment at 300°C for 1h; Step 2: apply an intermediate corona-resistant layer and perform a second step curing treatment: 2-3 hours at 120°C, 1-2 hours at 150°C, 1-2 hours at 180°C, and finally 0.5 hours at 260-300°C. Step 3: After coating the outer protective layer, perform a third step curing treatment: 120°C for 1 hour, 180°C for 2 hours, 250°C for 3 hours, and 280°C for 1 hour; Step 4: After shearing, winding and packaging, the corona-resistant aluminum-based enameled wire is obtained.

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

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