A method for preparing aluminum-based enameled wire for automobiles

Abstract

The invention discloses a method for preparing an aluminum-based enameled wire for automobiles, belongs to the technical field of enameled wire preparation, and is used to solve the technical problem in the prior art that the bending resistance and corona resistance of the enameled wire need to be further improved. The method specifically comprises the following steps: coating a wear-resistant and anti-corona paint on the surface of an enameled wire blank and curing the paint to obtain the aluminum-based enameled wire; after the enameled wire blank and the polyamic acid-type wear-resistant and anti-corona paint are prepared by the invention, the anhydride groups of the polyamic acid end-capping are combined with the amino groups on the surface of the enameled wire blank by low-temperature curing; and during the process of annealing the conductor at high temperature, a polyimide reaction in the polyamic acid chain segments in the wear-resistant and anti-corona paint is simultaneously carried out, thereby optimizing the conductor material and making the paint surface and the conductor material tightly combined, thereby finally preparing a high-performance aluminum-based enameled wire.

Description

Technical Field

[0001] The invention relates to the technical field of enameled wires, and in particular to a method for preparing aluminum-based enameled wires for automobiles. 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 development of power electronic technology and new insulating materials, corona-resistant and bend-resistant enameled wires will continue to move towards higher temperature resistance and longer life. For example, the prior art CN101127262B discloses a method for manufacturing aluminum enameled wire, particularly a method for manufacturing aluminum enameled wire using ultrasonic cleaning. The method comprises the following steps: first, the drawn aluminum wire is mechanically cleaned, and then ultrasonically cleaned in a liquid. The wire obtained in the previous step is mechanically scrubbed again, rinsed with clean water, and then mechanically scrubbed again. The aluminum wire obtained in the previous step is softened and then dried. The dried aluminum wire obtained in the previous step is painted and then dried to obtain the aluminum enameled wire. The manufacturing of the aluminum enameled wire, especially the continuous scrubbing, has the characteristics of good cleaning effect, wide application range, cleanliness and environmental protection. The obtained enameled wire is not easy to fall off.

[0004] However, the above patent content is to mechanically wipe the aluminum after wire drawing, then ultrasonically clean it, and then paint and cure the surface to obtain aluminum enameled wire. However, no pretreatment is performed to optimize the crystal form of the aluminum, resulting in the conductive performance and bending resistance of the finally prepared aluminum enameled wire to be further improved. Moreover, the aluminum wire is only mechanically cleaned without optimizing its surface structure, which will eventually lead to weak bonding with the paint surface, causing the paint surface to fall off during use, and then causing defects in the paint surface structure, so that the anti-corona performance and scratch resistance of the aluminum enameled wire need to be further improved. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing aluminum-based enameled wire for automobiles, so as to solve the technical problem in the prior art that the bending resistance and corona resistance of the enameled wire need to be further improved.

[0006] The purpose of the present invention can be achieved by the following technical solution: A method for preparing aluminum-based enameled wire for automobiles, comprising the following steps:

[0007] S1. Add an aluminum ingot into a spray refining furnace. After the aluminum ingot is melted under a nitrogen atmosphere, use nitrogen to blow a modified refining agent into the melt. After stirring for 10-15 minutes, let it stand for 20 minutes, and then inject the melt into a mold to obtain a modified aluminum alloy ingot.

[0008] S2, continuously rolling the modified aluminum alloy ingot and then drawing it to obtain an enameled wire substrate;

[0009] S3, performing surface modification on the enameled wire substrate to obtain an enameled wire blank;

[0010] S4. Coating a wear-resistant and anti-corona paint on the surface of the enameled wire blank and curing the paint to obtain an aluminum-based enameled wire.

[0011] Furthermore, in step S1, the temperature of the injection refining furnace is 710-730°C, and the ratio of the aluminum ingot to the modified refining agent is 80-100g:1g;

[0012] Furthermore, in step S2, the preparation method of the enameled wire substrate is: the modified aluminum alloy ingot is continuously rolled at 450-500°C to obtain an aluminum rod, which is then quenched at 21-24°C and 360-400kPa, and drawn at a rate of 8-10m / s to obtain an enameled wire substrate with a diameter of 0.8-1.0mm.

[0013] Furthermore, in step S1, the preparation method of the modified refining agent is:

[0014] A1. Add graphene, boric acid and deionized water to a reactor and stir at room temperature for 10-15 minutes to obtain a composite dispersion;

[0015] A2. Add the composite dispersion to a reactor, add the modifying liquid to the reactor while stirring, adjust the pH of the reaction system to 8-10 with a saturated sodium hydroxide aqueous solution, and transfer the reaction liquid to a stainless steel reactor. After sealing the stainless steel reactor, transfer the stainless steel reactor to a muffle furnace at a temperature of 150-160° C., perform a hydrothermal reaction for 10-12 hours, and perform post-treatment to obtain modified graphene;

[0016] A3. Use an atomizer to atomize the modification liquid to obtain an atomized liquid, spray the atomized liquid onto the surface of the modified graphene in the reactor, and continuously stir the modified graphene during the spraying process. After the spraying is completed, post-process to obtain a modified refining agent.

[0017] The reaction principle for preparing the modified refining agent is as follows: under alkaline conditions, boric acid and cerium trichloride heptahydrate are hydrolyzed to introduce a gel structure on the modified graphene, and a boron-cerium structure is formed after drying to obtain the modified graphene. Finally, after the modification liquid is atomized, potassium chloride and magnesium chloride intercalation structures are formed on the modified graphene to finally prepare the modified refining agent.

[0018] Furthermore, in step A1, the ratio of graphene, boric acid and deionized water is 1-2 g:0.5-0.8 g:100 mL;

[0019] Furthermore, in step A2, the amount ratio of the composite dispersion liquid and the modifying liquid is 2mL:1-2mL, and the modifying liquid is obtained by mixing cerium trichloride heptahydrate, hexadecyltrimethylammonium bromide and deionized water in an amount ratio of 4-5g:2-3g:50mL, and ultrasonicating for 10-15min; the post-treatment is as follows: after the reaction is completed, the temperature of the reactor is lowered to room temperature, the filter cake is collected by filtering the reactor, and the filter cake is washed 3-5 times with ethanol and deionized water. After that, the filter cake is transferred to a vacuum drying oven at a temperature of 60°C and vacuum dried to constant weight to obtain modified graphene;

[0020] Furthermore, in step A3, the modified graphene and the modifying liquid are used in a ratio of 1-2 g: 10-12 mL, and the modifying liquid is obtained by mixing magnesium chloride, potassium chloride and deionized water in a ratio of 1-2 g: 2-4 g: 30-36 mL, and ultrasonicating for 20-30 minutes. The post-treatment is as follows: transferring the material to a vacuum drying oven at a temperature of 60° C. and vacuum drying to constant weight to obtain a modified refining agent.

[0021] Furthermore, in step S3, the method for preparing the enameled wire blank includes the following steps:

[0022] B1. Add the enameled wire substrate and 3-5 wt% sodium hydroxide aqueous solution into a stirred tank, stir at room temperature for 10-15 minutes, and post-treat to obtain an active substrate;

[0023] B2. Add the activated matrix to a reactor containing silica sol, let it stand for 8-10 minutes, take it out and dry it. Repeat the operation 3-5 times to obtain a modified matrix;

[0024] B3. Add the modified matrix, anhydrous ethanol, deionized water and 3-aminopropyltriethoxysilane into the reactor. After the temperature of the reactor is increased to 40-50°C, use saturated sodium hydroxide aqueous solution to adjust the pH of the reaction system to 8-10. Keep the reaction at this temperature for 30-40 minutes, and then post-treat to obtain the enameled wire blank.

[0025] The reaction principle for preparing the enameled wire blank is as follows: under alkaline conditions, the surface of the enameled wire substrate reacts to produce active free radicals and defects to obtain an active matrix. The surface defects of the active matrix are modified by silica sol to obtain a modified matrix, which is then modified by 3-aminopropyltriethoxysilane under alkaline conditions to finally prepare the enameled wire blank.

[0026] Furthermore, in step B1, the ratio of the enameled wire substrate and the 3-5wt% sodium hydroxide aqueous solution is 1-2g:10-12mL, and the post-treatment is as follows: after stirring, the material is transferred to a vacuum drying oven at a temperature of 60°C and vacuum dried to constant weight to obtain an active substrate;

[0027] Furthermore, in step B2, the ratio of the activated matrix to the silica sol is 1-2 g:5-6 g, and the drying operation is as follows: after standing, the material is transferred to a vacuum drying oven at a temperature of 60° C. and vacuum dried to constant weight;

[0028] Furthermore, in step B3, the amount ratio of the modified matrix, anhydrous ethanol, deionized water and 3-aminopropyltriethoxysilane is 3-4g:10-12mL:5-6mL:0.1-0.2g, and the post-treatment is: after the reaction is completed, the material is transferred to a vacuum drying oven at a temperature of 60°C and vacuum dried to constant weight to obtain an enameled wire blank.

[0029] Furthermore, in step S4, the method for preparing the aluminum-based enameled wire includes the following steps:

[0030] C1. Add terminal aminopropyl silicone oil, 1,12-diaminododecane and N,N-dimethylformamide to a reactor at a temperature of 0-5°C, keep warm and stir until the reactants are completely dissolved, then add 4,4'-oxydiphthalic anhydride to the reactor in three portions. After the addition is complete, raise the temperature of the reactor to 30-50°C, keep warm and react for 2-4 hours, and perform post-treatment to obtain modified polyamic acid;

[0031] C2. Adding modified polyamic acid, composite solvent, thickener, leveling agent and hardener into a stirring tank, and stirring evenly to obtain a wear-resistant and anti-corona paint;

[0032] C3. Applying wear-resistant and anti-corona paint to the surface of the enameled wire blank with a coating thickness of 0.2-0.3 mm, and post-processing to obtain the aluminum-based enameled wire.

[0033] The reaction equation for preparing aluminum-based enameled wire is:

[0034]

[0035] Where: ; ;" ” indicates the enameled wire blank.

[0036] The reaction principle for preparing the aluminum-based enameled wire is as follows: under heating conditions, the aminopropyl-terminated silicone oil reacts with the amino groups on 1,12-diaminododecane and the anhydride groups on 4,4'-oxydiphthalic anhydride to obtain polyamic acid segments embedded with siloxane and long alkane chain segments and terminated with anhydride groups. The segments further react with the amino groups modified on the surface of the enameled wire blank during the low-temperature curing process. Furthermore, under high-temperature conditions of 360-380°C, while the enameled wire blank is annealed, the polyamic acid-based wear-resistant and anti-corona paint undergoes a thermal imidization reaction, thereby further curing to finally prepare the aluminum-based enameled wire.

[0037] Furthermore, in step C1, the amount ratio of terminal aminopropyl silicone oil, 1,12-diaminododecane, N,N-dimethylformamide and 4,4'-oxydiphthalic anhydride is 3.0-3.6g:1.8-2.2g:40-48mL:4.2-4.8g, and the post-treatment is as follows: after the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is transferred to a rotary evaporator, the temperature of the rotary evaporator is increased to 60-80°C, and the modified polyamic acid is obtained by distillation under reduced pressure until no liquid is produced;

[0038] Furthermore, in step C2, the modified polyamic acid, the composite solvent, the thickener, the leveling agent, and the hardener are used in a ratio of 70-80 g: 30-32 g: 2-3 g: 3-5 g: 2-3 g, wherein the composite solvent is obtained by mixing butyl acetate and isopropyl alcohol in a ratio of 18-20 g: 12 g;

[0039] Furthermore, in step C2, the thickener is one or both of polyvinyl alcohol and sodium carboxymethyl cellulose; the leveling agent is one or more of polyether-modified silicone oil and dimethyl silicone oil; and the hardener is one or more of maleic anhydride and diaminodiphenyl ether;

[0040] Furthermore, in step C3, the post-treatment is as follows: the coated material is transferred to an oven, the oven temperature is increased to 40-50°C, and after heat preservation treatment for 1-2 hours, the oven temperature is increased to 360-380°C, and heat preservation treatment is performed for 30-40 minutes to obtain an aluminum-based enameled wire.

[0041] The present invention also provides an aluminum-based enameled wire for automobiles, which is prepared by adopting the above-mentioned method for preparing the aluminum-based enameled wire for automobiles.

[0042] The present invention has the following beneficial effects:

[0043] 1. In the modified refining agent prepared by the present invention, the conductive efficiency is improved by constructing a conductive network through the boron structure and cerium dioxide loaded on the graphene surface, wherein the electron-deficient characteristic of boron is electronically bonded with the aluminum matrix to reduce the interface resistance, and the oxygen vacancies of cerium dioxide promote electron migration; at the same time, the graphene intercalation acts as a heterogeneous nucleating agent to refine the grains during the solidification of the aluminum ingot, reduce the scattering of electrons by the grain boundaries, and adsorb hydrogen and oxide impurities during the refining process to reduce lattice defects, and the cerium dioxide particles inhibit crack propagation by pinning the grain boundaries, while the three-dimensional graphene network structure absorbs energy through sheet slip when bending, and during the high-temperature annealing treatment, the three-dimensional graphene network acts as a heat-conducting network to promote the progress of the annealing process and improve the annealing effect, and during the annealing process, the polyimidization reaction forms a rigid-flexible cross-linked structure inside the paint layer, thereby dissipating stress through the elastic deformation of the molecular chain when the material is bent, avoiding interface peeling, thereby improving the material's bending resistance and conductive properties.

[0044] 2. The present invention forms a uniform siloxane transition layer on the surface of the enameled wire blank through surface modification with silica sol and silane coupling agent, filling the microscopic pores of the exposed graphene and the enameled wire substrate and reducing surface defects. The polyamic acid-based wear-resistant and anti-corona paint coated on the surface of the enameled wire blank undergoes a polyimidization reaction during high-temperature annealing to form polyimide segments containing stable six-membered rings. The strong chemical bonds such as carbon-nitrogen bonds and silicon-oxygen bonds of the paint can resist thermal vibrations at high temperatures, maintain the stability of the paint layer structure, and enable the paint layer to maintain excellent performance in high-temperature environments. In terms of insulation performance, silica sol and silane coupling agent modify the surface of the aluminum substrate to form a nanoscale siloxane transition layer, filling the microscopic pores and reducing surface defects. During low-temperature curing, the anhydride groups of the polyamic acid and the amino groups on the substrate surface are covalently bonded to form a continuous, gapless interface, blocking the conductive path. High-temperature annealing further promotes polyimidization, forming a dense cross-linked network, reducing ion migration channels, and improving the insulation properties of the paint layer.

[0045] 3. During the surface modification process of the aluminum-based enameled wire of the present invention, the surface of the enameled wire blank is activated and cleaned by alkali solution to form a microporous structure. After the silica sol fills the pores, it combines with the amino group of the silane coupling agent to form a transition layer. During the low-temperature curing process of the paint surface, the amino group of the silane coupling agent is further chemically bonded to the anhydride group at the end of the polyamic acid, thereby forming a stable covalent bond and enhancing the anchoring effect between the paint layer and the metal. During the high-temperature annealing process, the polyamic acid is converted into polyimide, and a tighter cross-linked structure is formed between the molecular chains. At the same time, a chemical interlock is generated with the aluminum substrate interface to prevent the paint layer from peeling off, thereby significantly improving the scratch resistance of the paint layer on the surface of the aluminum-based enameled wire. Moreover, the paint layer with the siloxane chain segment as the main material forms a continuous and dense insulating film after curing, which reduces local discharge caused by surface defects and reduces the probability of corona generation. The polyimidized paint layer has a higher dielectric strength, and the rigid structure of its molecular chain can resist the damage to the material by electric field stress, thereby improving the material's anti-corona performance. DETAILED DESCRIPTION

[0046] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0047] The silica sol used in the present invention was purchased from Anhui Mingyi Silicon Industry Co., Ltd., with the product number MY-930;

[0048] The aminopropyl-terminated silicone oil used in the present invention was purchased from Anhui Mingyi Silicon Industry Co., Ltd., with the product number MY 1100-1k;

[0049] The aluminum ingots used in the present invention were purchased from Beijing Xingrongyuan Technology Co., Ltd., and the product name is high-purity aluminum ingots for smelting;

[0050] The polyvinyl alcohol used in the present invention was purchased from Shanxi Sanwei Shengtai New Material Technology Co., Ltd., with the item number being 095-50;

[0051] The dimethyl silicone oil used in the present invention was purchased from Shanghai Chuyijia Silicone Materials Co., Ltd. with the product number SH-201.

[0052] Example 1

[0053] This embodiment provides a method for preparing a modified refining agent for preparing aluminum-based enameled wire for automobiles, comprising the following steps:

[0054] Step 1: Preparation of composite dispersion

[0055] Weigh 10.0 g of graphene, 5.0 g of boric acid, and 1000.0 mL of deionized water into a reactor, and stir at room temperature for 10 min to obtain a composite dispersion.

[0056] Step ②: Preparation of modified graphene

[0057] Weigh 40.0 g of cerium trichloride heptahydrate, 20.0 g of hexadecyltrimethylammonium bromide, and 500.0 mL of deionized water, mix, and ultrasonicate for 10 min to obtain a modified solution;

[0058] Weigh: 1000.0 mL of the composite dispersion was added to the reactor, and 500.0 mL of the modified liquid was added to the reactor during stirring. After the addition was completed, the pH of the reaction system was adjusted to 8 using a saturated sodium hydroxide aqueous solution and the reaction liquid was transferred to a stainless steel reactor. After sealing the stainless steel reactor, the stainless steel reactor was transferred to a muffle furnace at a temperature of 150°C for hydrothermal reaction for 10 hours. After the reaction was completed, the temperature of the reactor was lowered to room temperature, and the filter cake was collected by filtration in the reactor. The filter cake was washed 3 times with ethanol and deionized water, and then transferred to a vacuum drying oven at a temperature of 60°C and vacuum dried to constant weight to obtain modified graphene.

[0059] Step 3: Preparation of modified refining agent

[0060] Weigh 10.0 g of magnesium chloride, 20.0 g of potassium chloride, and 300.0 mL of deionized water, mix, and ultrasonicate for 20 min to obtain a modified solution.

[0061] Use an atomizer to atomize 100.0 mL of the modification liquid to obtain an atomized liquid, and spray the atomized liquid onto the surface of 10.0 g of modified graphene in the reactor. During the spraying process, the modified graphene is continuously stirred. After the spraying is completed, the material is transferred to a vacuum drying oven at a temperature of 60°C and vacuum dried to a constant weight to obtain a modified refining agent.

[0062] Example 2

[0063] This embodiment provides a method for preparing a modified refining agent for preparing aluminum-based enameled wire for automobiles, comprising the following steps:

[0064] Step 1: Preparation of composite dispersion

[0065] Weigh 20.0 g of graphene, 8.0 g of boric acid, and 1000.0 mL of deionized water into a reactor, and stir at room temperature for 15 min to obtain a composite dispersion.

[0066] Step ②: Preparation of modified graphene

[0067] Weigh 50.0 g of cerium trichloride heptahydrate, 30.0 g of hexadecyltrimethylammonium bromide, and 500.0 mL of deionized water, mix them, and ultrasonicate for 15 minutes to obtain a modified solution.

[0068] Weigh: 1000.0 mL of the composite dispersion was added to the reactor, and 500.0 mL of the modified liquid was added to the reactor during stirring. After the addition was completed, the pH of the reaction system was adjusted to 10 using a saturated sodium hydroxide aqueous solution and the reaction liquid was transferred to a stainless steel reactor. After sealing the stainless steel reactor, the stainless steel reactor was transferred to a muffle furnace at a temperature of 160°C for hydrothermal reaction for 12 hours. After the reaction was completed, the temperature of the reactor was lowered to room temperature, and the filter cake was collected by filtration in the reactor. The filter cake was washed 5 times with ethanol and deionized water, and then transferred to a vacuum drying oven at a temperature of 60°C and vacuum dried to constant weight to obtain modified graphene.

[0069] Step 3: Preparation of modified refining agent

[0070] Weigh 20.0 g of magnesium chloride, 40.0 g of potassium chloride, and 360.0 mL of deionized water, mix, and ultrasonicate for 30 min to obtain a modified solution.

[0071] Use an atomizer to atomize 120 mL of the modification liquid to obtain an atomized liquid, and spray the atomized liquid onto the surface of 20.0 g of modified graphene in the reactor. During the spraying process, the modified graphene is continuously stirred. After the spraying is completed, the material is transferred to a vacuum drying oven at a temperature of 60°C and vacuum dried to constant weight to obtain a modified refining agent.

[0072] Example 3

[0073] This embodiment provides a method for preparing a modified refining agent for preparing aluminum-based enameled wire for automobiles, comprising the following steps:

[0074] Step 1: Preparation of composite dispersion

[0075] 16.0 g of graphene, 7.2 g of boric acid and 1000.0 mL of deionized water were weighed and added into a reactor, and stirred at room temperature for 15 min to obtain a composite dispersion.

[0076] Step ②: Preparation of modified graphene

[0077] Weigh 48.0 g of cerium trichloride heptahydrate, 24.0 g of hexadecyltrimethylammonium bromide, and 500.0 mL of deionized water, mix, and ultrasonicate for 12 minutes to obtain a modified solution;

[0078] Weigh: 1000.0 mL of the composite dispersion was added to the reactor, and 500.0 mL of the modified liquid was added to the reactor during stirring. After the addition was completed, the pH of the reaction system was adjusted to 9 with a saturated sodium hydroxide aqueous solution and the reaction liquid was transferred to a stainless steel reactor. After sealing the stainless steel reactor, the stainless steel reactor was transferred to a muffle furnace at a temperature of 155°C for hydrothermal reaction for 11 hours. After the reaction was completed, the temperature of the reactor was lowered to room temperature, and the filter cake was collected by filtration in the reactor. The filter cake was washed 4 times with ethanol and deionized water, and then transferred to a vacuum drying oven at a temperature of 60°C and vacuum dried to constant weight to obtain modified graphene.

[0079] Step 3: Preparation of modified refining agent

[0080] Weigh 15.0 g of magnesium chloride, 30.0 g of potassium chloride, and 320.0 mL of deionized water, mix, and ultrasonicate for 25 min to obtain a modified solution.

[0081] Use an atomizer to atomize 100.0 mL of the modification liquid to obtain an atomized liquid, and spray the atomized liquid onto the surface of 16.0 g of modified graphene in the reactor. During the spraying process, the modified graphene is continuously stirred. After the spraying is completed, the material is transferred to a vacuum drying oven at a temperature of 60°C and vacuum dried to a constant weight to obtain a modified refining agent.

[0082] Example 4

[0083] This embodiment provides a method for preparing a wear-resistant and anti-corona paint for preparing aluminum-based enameled wire for automobiles, comprising the following steps:

[0084] Step I: Preparation of modified polyamic acid

[0085] Weigh: 30.0g of terminal aminopropyl silicone oil, 18.0g of 1,12-diaminododecane and 400.0mL of N,N-dimethylformamide are added to a reactor at a temperature of 0°C, and stirred until the reactants are completely dissolved. Then, 42.0g of 4,4'-oxydiphthalic anhydride is added to the reactor in three portions. After the addition is completed, the temperature of the reactor is raised to 30°C and the reaction is kept warm for 2h. After the reaction is completed, the temperature of the reactor is lowered to room temperature, and the reaction liquid is transferred to a rotary evaporator. The temperature of the rotary evaporator is raised to 60°C and distilled under reduced pressure until no liquid is produced to obtain a modified polyamic acid.

[0086] Step II: Preparation of wear-resistant and anti-corona paint

[0087] Weigh 70.0 g of modified polyamic acid, 18.0 g of butyl acetate, 12.0 g of isopropyl alcohol, 2.0 g of polyvinyl alcohol, 3.0 g of dimethyl silicone oil and 2.0 g of maleic anhydride, add them into a stirring tank, and stir evenly to obtain a wear-resistant and anti-corona paint.

[0088] Example 5

[0089] This embodiment provides a method for preparing a wear-resistant and anti-corona paint for preparing aluminum-based enameled wire for automobiles, comprising the following steps:

[0090] Step I: Preparation of modified polyamic acid

[0091] Weigh: 36.0g of terminal aminopropyl silicone oil, 22.0g of 1,12-diaminododecane and 480.0mL of N,N-dimethylformamide are added to a reactor at a temperature of 5°C, and stirred until the reactants are completely dissolved. Then, 48.0g of 4,4'-oxydiphthalic anhydride is added to the reactor in three times. After the addition is completed, the temperature of the reactor is raised to 50°C and the reaction is kept warm for 4 hours. After the reaction is completed, the temperature of the reactor is lowered to room temperature, and the reaction liquid is transferred to a rotary evaporator. The temperature of the rotary evaporator is raised to 80°C and distilled under reduced pressure until no liquid is produced to obtain a modified polyamic acid.

[0092] Step II: Preparation of wear-resistant and anti-corona paint

[0093] Weigh 80.0 g of modified polyamic acid, 20.0 g of butyl acetate, 12.0 g of isopropyl alcohol, 3.0 g of polyvinyl alcohol, 5.0 g of dimethyl silicone oil and 3.0 g of maleic anhydride, add them into a stirring tank, and stir evenly to obtain a wear-resistant and anti-corona paint.

[0094] Example 6

[0095] This embodiment provides a method for preparing a wear-resistant and anti-corona paint for preparing aluminum-based enameled wire for automobiles, comprising the following steps:

[0096] Step I: Preparation of modified polyamic acid

[0097] Weigh: 32.0g of terminal aminopropyl silicone oil, 20.0g of 1,12-diaminododecane and 420.0mL of N,N-dimethylformamide are added to a reactor at a temperature of 3°C, and stirred until the reactants are completely dissolved. Then, 45.0g of 4,4'-oxydiphthalic anhydride is added to the reactor in three portions. After the addition is completed, the temperature of the reactor is raised to 40°C and the reaction is kept warm for 3 hours. After the reaction is completed, the temperature of the reactor is lowered to room temperature, and the reaction liquid is transferred to a rotary evaporator. The temperature of the rotary evaporator is raised to 70°C and distilled under reduced pressure until no liquid is produced to obtain a modified polyamic acid.

[0098] Step II: Preparation of wear-resistant and anti-corona paint

[0099] Weigh 72.0 g of modified polyamic acid, 18.0 g of butyl acetate, 12.0 g of isopropyl alcohol, 2.4 g of polyvinyl alcohol, 4.2 g of dimethyl silicone oil and 2.4 g of maleic anhydride, add them into a stirring tank, and stir evenly to obtain a wear-resistant and anti-corona paint.

[0100] Example 7

[0101] This embodiment provides a method for preparing aluminum-based enameled wire for automobiles, comprising the following steps:

[0102] Step 1: Prepare aluminum alloy ingots

[0103] Weigh: 80.0g of aluminum ingot is added to the injection refining furnace, the temperature of the injection refining furnace is set to 710℃, and after the aluminum ingot is melted in a nitrogen atmosphere, 1.0g of the modified refining agent prepared in Example 1 is blown into the melt using nitrogen. After stirring for 10 minutes, the melt is allowed to stand for 20 minutes and injected into a mold to obtain a modified aluminum alloy ingot.

[0104] Step 2: Prepare the enameled wire substrate

[0105] 60.0 g of modified aluminum alloy ingot was weighed and continuously rolled at 450° C. to obtain an aluminum rod, which was then quenched at 21° C. and 360 kPa and drawn at a rate of 8 m / s to obtain an enameled wire substrate with a diameter of 1.8 mm.

[0106] Step 3: Prepare enameled wire blank

[0107] Weigh 30.0 g of enameled wire substrate and 300.0 mL of 3 wt% sodium hydroxide aqueous solution into a stirred tank and stir at room temperature for 10 min. After stirring, transfer the material to a vacuum drying oven at 60°C and vacuum dry to constant weight to obtain an active substrate.

[0108] Weigh 20.0 g of the activated matrix and add it to a reaction kettle containing 100.0 g of silica sol. After standing for 8 minutes, transfer the material to a vacuum drying oven at 60°C and vacuum dry to constant weight. Repeat this operation 3 times to obtain a modified matrix.

[0109] Weigh: 15.0 g of modified matrix, 50.0 mL of anhydrous ethanol, 30.0 mL of deionized water and 0.5 g of 3-aminopropyltriethoxysilane are added to the reactor. After the temperature of the reactor is raised to 40 ° C, the pH of the reaction system is adjusted to 8 using a saturated sodium hydroxide aqueous solution. The reaction is kept warm for 30-40 minutes. After the reaction is completed, the material is transferred to a vacuum drying oven at a temperature of 60 ° C and vacuum dried to constant weight to obtain an enameled wire blank.

[0110] Step 4: Prepare aluminum-based enameled wire

[0111] The wear-resistant and anti-corona paint prepared in Example 4 was applied to the surface of the enameled wire blank with a coating thickness of 0.2 mm. The coated material was transferred to an oven, the oven temperature was raised to 40°C, and after heat preservation for 1 hour, the oven temperature was raised to 360°C and heat preservation for 30 minutes to obtain an aluminum-based enameled wire.

[0112] Example 8

[0113] This embodiment provides a method for preparing aluminum-based enameled wire for automobiles, comprising the following steps:

[0114] Step 1: Prepare aluminum alloy ingots

[0115] Weigh: 100.0g of aluminum ingot is added to a spray refining furnace, the temperature of the spray refining furnace is set to 730°C, and after the aluminum ingot is melted under a nitrogen atmosphere, 1.0g of the modified refining agent prepared in Example 2 is blown into the melt using nitrogen. After stirring for 15 minutes, the melt is allowed to stand for 20 minutes and injected into a mold to obtain a modified aluminum alloy ingot.

[0116] Step 2: Prepare the enameled wire substrate

[0117] 80.0 g of modified aluminum alloy ingot was weighed and continuously rolled at 500° C. to obtain an aluminum rod, which was then quenched at 24° C. and 400 kPa and drawn at a rate of 10 m / s to obtain an enameled wire substrate with a diameter of 1.0 mm.

[0118] Step 3: Prepare enameled wire blank

[0119] Weigh 60.0 g of enameled wire substrate and 360.0 mL of 5 wt% sodium hydroxide aqueous solution into a stirred tank and stir at room temperature for 15 min. After stirring, transfer the material to a vacuum drying oven at 60°C and vacuum dry to constant weight to obtain an active substrate.

[0120] Weigh: 40.0 g of the activated matrix was added to a reaction kettle containing 120.0 g of silica sol. After standing for 10 minutes, the material was transferred to a vacuum drying oven at a temperature of 60°C and vacuum dried to constant weight. After repeating this operation 5 times, a modified matrix was obtained;

[0121] Weigh: 20.0 g of modified matrix, 60.0 mL of anhydrous ethanol, 30.0 mL of deionized water and 1.0 g of 3-aminopropyltriethoxysilane were added to the reactor. After the temperature of the reactor was raised to 50 ° C, the pH of the reaction system was adjusted to 10 using a saturated sodium hydroxide aqueous solution. The reaction was kept warm for 40 minutes. After the reaction was completed, the material was transferred to a vacuum drying oven at a temperature of 60 ° C and vacuum dried to constant weight to obtain an enameled wire blank.

[0122] Step 4: Prepare aluminum-based enameled wire

[0123] The wear-resistant and anti-corona paint prepared in Example 5 was applied to the surface of the enameled wire blank with a coating thickness of 0.3 mm. The coated material was transferred to an oven, the oven temperature was raised to 50°C, and the heat treatment was continued for 2 hours. Then, the oven temperature was raised to 380°C and the heat treatment was continued for 40 minutes to obtain an aluminum-based enameled wire.

[0124] Example 9

[0125] This embodiment provides a method for preparing aluminum-based enameled wire for automobiles, comprising the following steps:

[0126] Step 1: Prepare aluminum alloy ingots

[0127] Weigh: 96.0g of aluminum ingot is added to the injection refining furnace, the temperature of the injection refining furnace is set to 720℃, and after the aluminum ingot is melted in a nitrogen atmosphere, 1.0g of the modified refining agent prepared in Example 3 is blown into the melt using nitrogen. After stirring for 12 minutes, the mixture is allowed to stand for 20 minutes and injected into a mold to obtain a modified aluminum alloy ingot.

[0128] Step 2: Prepare the enameled wire substrate

[0129] 72.0 g of modified aluminum alloy ingot was weighed and continuously rolled at 480° C. to obtain an aluminum rod, which was then quenched at 24° C. and 400 kPa and drawn at a rate of 10 m / s to obtain an enameled wire substrate with a diameter of 0.9 mm.

[0130] Step 3: Prepare enameled wire blank

[0131] Weigh 45.0 g of enameled wire substrate and 320.0 mL of 4 wt% sodium hydroxide aqueous solution into a stirred tank and stir at room temperature for 12 min. After stirring, transfer the material to a vacuum drying oven at 60°C and vacuum dry to constant weight to obtain an active substrate.

[0132] Weigh: 30.0 g of the activated matrix was added to a reaction kettle containing 120.0 g of silica sol. After standing for 9 minutes, the material was transferred to a vacuum drying oven at a temperature of 60°C and vacuum dried to constant weight. After repeating this operation 4 times, a modified matrix was obtained;

[0133] Weigh: 18.0 g of modified matrix, 54.0 mL of anhydrous ethanol, 30.0 mL of deionized water and 0.8 g of 3-aminopropyltriethoxysilane were added to the reactor. After the temperature of the reactor was raised to 45 ° C, the pH of the reaction system was adjusted to 9 with saturated sodium hydroxide aqueous solution. The reaction was kept warm for 36 minutes. After the reaction was completed, the material was transferred to a vacuum drying oven at a temperature of 60 ° C and vacuum dried to constant weight to obtain an enameled wire blank.

[0134] Step 4: Prepare aluminum-based enameled wire

[0135] The wear-resistant and anti-corona paint prepared in Example 6 was applied to the surface of the enameled wire blank with a coating thickness of 0.3 mm. The coated material was transferred to an oven, the oven temperature was raised to 45°C, and the heat treatment was continued for 2 hours. Then, the oven temperature was raised to 370°C and the heat treatment was continued for 36 minutes to obtain an aluminum-based enameled wire.

[0136] Comparative Example 1

[0137] The difference between this comparative example and Example 9 is that in step 1, an equal amount of potassium chloride is used to replace the modifying refining agent.

[0138] Comparative Example 2

[0139] The difference between this comparative example and Example 9 is that in step I of the preparation process of the wear-resistant and anti-corona paint used in step IV, the use of terminal aminopropyl silicone oil is omitted.

[0140] Comparative Example 3

[0141] The difference between this comparative example and Example 9 is that the operation of "raising the oven temperature to 370° C. and keeping the oven temperature for 36 minutes" is omitted in step 4.

[0142] Performance testing:

[0143] Referring to the standard GB / T 17737.314-2018 "Coaxial communication cables Part 1-314: Mechanical test methods - Cable bending test", the aluminum-based enameled wires prepared in Examples 7-9 and Comparative Examples 1-3 were subjected to a cyclic bending test, and the number of cycles was recorded.

[0144] The volume resistivity of the aluminum-based enameled wires prepared in Examples 7-9 and Comparative Examples 1-3 was tested with reference to the standard GB / T 3048.2-2007 "Test methods for electrical properties of wires and cables - Part 2: Test for resistivity of metallic materials".

[0145] The anti-corona life, temperature resistance, and scratch resistance of the aluminum-based enameled wires prepared in Examples 7-9 and Comparative Examples 1-3 were tested with reference to the standard GB / T 24122-2009 "Corona-resistant enameled wire varnishes."

[0146] The breakdown voltage of the aluminum-based enameled wires prepared in Examples 7-9 and Comparative Examples 1-3 was tested with reference to the standard HG / T 3330-2012 “Determination of the breakdown strength of insulating paint films”. Specific data are shown in Table 1.

[0147] Table 1 - Performance test data of each sample

[0148]

[0149] Data Analysis:

[0150] Comparing and analyzing the data in Table 1, it can be found that the aluminum-based enameled wire prepared by the present invention has a cyclic bending number of 3.43 million times and a volume resistivity of the internal conductor of 2.0×10 -8 Ω·cm, the paint surface anti-corona life is 86h, the temperature index is 246, the paint surface scraping average pressure is 24.2N and the breakdown voltage is 18.2kV, all of which are better than the comparative example;

[0151] After comparing and analyzing the data in Table 1, we found that:

[0152] The bending resistance and electrical conductivity of the aluminum-based enameled wire prepared in Comparative Example 1 were significantly reduced, indicating that in the modified refining agent used in Example 9 for preparing the aluminum-based enameled wire, the boron structure and cerium dioxide loaded on the graphene surface improved the electrical conductivity by constructing a conductive network, wherein the electron-deficient property of boron electronically bonds with the aluminum matrix to reduce the interface resistance, and the oxygen vacancies of cerium dioxide promote electron migration; at the same time, the graphene intercalation acts as a heterogeneous nucleating agent to refine the grains during the solidification of the aluminum ingot, reducing the scattering of electrons by the grain boundaries, and adsorbs hydrogen and oxide impurities during the refining process to reduce lattice defects, and the cerium dioxide particles suppress crack propagation by pinning the grain boundaries, while the three-dimensional graphene network absorbs energy by sheet slip when bending, and during the high-temperature annealing treatment, the three-dimensional graphene network acts as a heat-conducting network to promote the progress of the annealing process and improve the annealing effect, thereby improving the electrical conductivity and mechanical properties of the material;

[0153] The high temperature resistance and breakdown voltage performance of the aluminum-based enameled wire prepared in Comparative Example 2 decreased significantly, indicating that the polyamic acid-based wear-resistant and anti-corona paint of Example 9, by introducing a siloxane structure into the molecular chain segment, is tightly arranged by the intermolecular force of the paint to form a continuous and non-porous paint film, thereby blocking electron migration and leakage channels. At the same time, the chemical inertness of siloxane makes it less likely to undergo polarization or charge accumulation under an electric field, thereby reducing the risk of partial discharge. Moreover, the strong resistance to thermal vibration of the silicon-oxygen bond maintains structural stability at high temperatures, thereby avoiding molecular chain breakage or decomposition, thereby significantly improving high temperature resistance and insulation performance.

[0154] The anti-corona performance of the aluminum-based enameled wire prepared in Comparative Examples 2-3 was significantly reduced, indicating that the paint layer with siloxane segments as the main material formed a continuous and dense insulating film after curing, reducing partial discharge caused by surface defects and the probability of corona generation. In addition, the paint layer after polyimide treatment has a higher dielectric strength, and the rigid structure of its molecular chain can resist the damage to the material caused by electric field stress, thereby improving the anti-corona performance of the material.

[0155] The bending resistance of the aluminum-based enameled wire prepared in Comparative Example 3 was significantly reduced, indicating that during the high-temperature annealing process in Example 9, the polyimidization reaction formed a rigid-flexible cross-linked structure inside the paint layer, which in turn dispersed the stress through the elastic deformation of the molecular chain when the material was bent, avoiding interface peeling, thereby improving the bending resistance of the material;

[0156] The temperature resistance and insulation performance of the aluminum-based enameled wire prepared in Comparative Example 3 decreased significantly, indicating that during the high-temperature annealing process of Example 9, the polyamic acid-based wear-resistant and anti-corona paint coated underwent polyimidization reaction during high-temperature annealing to form polyimide segments containing stable six-membered rings. The strong chemical bonds such as carbon-nitrogen bonds and silicon-oxygen bonds can resist thermal vibrations at high temperatures, maintaining the stability of the paint layer structure. The high-temperature annealing further promotes polyimidization, forming a dense cross-linked network, reducing ion migration channels, and improving the insulation of the paint layer. In addition, the synergistic effect of cerium dioxide and boron structure suppresses electric field concentration, reduces the risk of local breakdown, and thus improves the high-temperature resistance and insulation performance of the paint surface.

[0157] The scratch resistance of the aluminum-based enameled wire prepared in Comparative Example 3 is significantly reduced, indicating that during the low-temperature curing process of the paint surface of the aluminum-based enameled wire prepared in Example 9, the amino group of the silane coupling agent is further chemically bonded to the anhydride group at the end of the polyamic acid paint, thereby forming a stable covalent bond and enhancing the anchoring effect between the paint layer and the metal. During the high-temperature annealing process, the polyamic acid is converted into polyimide, and a tighter cross-linked structure is formed between the molecular chains. At the same time, chemical interlocking is generated with the aluminum substrate interface to prevent the paint layer from peeling off, thereby significantly improving the scratch resistance of the paint layer on the surface of the aluminum-based enameled wire.

[0158] Finally, the present invention loads boron structure and cerium dioxide on the surface of graphene by a gel method, and intercalates potassium chloride and magnesium chloride into the graphene by atomized dispersion to obtain a modified refining agent. The modified refining agent is used as an additive in the process of aluminum ingot refining to optimize the structure of the aluminum ingot, thereby obtaining a modified aluminum alloy ingot. The modified aluminum alloy ingot is used as a raw material to obtain an enameled wire substrate through rolling and drawing.

[0159] The enameled wire substrate is further activated by alkaline solution, the surface of the material is modified by silica sol, and the amino groups on the surface of the material are modified by a silane coupling agent to obtain an enameled wire blank. After the surface of the enameled wire blank is coated with a polyamic acid-based wear-resistant and anti-corona paint with a siloxane segment as the main material, the anhydride groups of the polyamic acid end-capping are combined with the amino groups on the surface of the enameled wire blank through low-temperature curing. During the process of annealing the conductor at high temperature, the polyimide reaction in the polyamic acid segment in the wear-resistant and anti-corona paint is simultaneously carried out, thereby optimizing the conductor material and making the paint surface and the conductor material tightly bonded, and finally preparing a high-performance aluminum-based enameled wire.

[0160] The above are merely examples and explanations of the structure of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing aluminum-based enameled wire for automobiles, characterized in that: The following steps are involved: S1. Add an aluminum ingot into a spray refining furnace. After the aluminum ingot is melted under a nitrogen atmosphere, use nitrogen to blow a modified refining agent into the melt. After stirring for 10-15 minutes, let it stand for 20 minutes, and then inject the melt into a mold to obtain a modified aluminum alloy ingot. S2, continuously rolling the modified aluminum alloy ingot and then drawing it to obtain an enameled wire substrate; S3, performing surface modification on the enameled wire substrate to obtain an enameled wire blank; S4, coating the surface of the enameled wire body with a wear-resistant and anti-corona paint and curing the paint to obtain an aluminum-based enameled wire; The preparation method of the modified refining agent is: A1. Add graphene, boric acid and deionized water to a reactor and stir at room temperature for 10-15 minutes to obtain a composite dispersion; A2. The composite dispersion was added to a reactor, and a modifying liquid was added to the reactor during stirring. After the addition was completed, a saturated aqueous sodium hydroxide solution was used to adjust the pH of the reaction system to 8-10, and the reaction liquid was transferred to a stainless steel reactor. After the stainless steel reactor was sealed, the stainless steel reactor was transferred to a muffle furnace at a temperature of 150-160° C., and a hydrothermal reaction was carried out for 10-12 hours. The modified graphene was obtained by post-treatment, wherein the modifying liquid was obtained by mixing cerium trichloride heptahydrate, hexadecyltrimethylammonium bromide and deionized water in a ratio of 4-5 g:2-3 g:50 mL and ultrasonicating for 10-15 minutes; A3. Use an atomizer to atomize the modification liquid to obtain an atomized liquid, spray the atomized liquid onto the surface of the modified graphene in the reactor, and continuously stir the modified graphene during the spraying process. After the spraying is completed, post-process to obtain a modified refining agent, wherein the modification liquid is obtained by mixing magnesium chloride, potassium chloride and deionized water in a dosage ratio of 1-2g:2-4g:30-36mL, and ultrasonicating for 20-30min.

2. The method for preparing an aluminum-based enameled wire for automobiles according to claim 1, wherein: In step S1, the temperature of the spray refining furnace is 710-730°C, and the ratio of the aluminum ingot to the modified refining agent is 80-100g:1g. In step S2, the enameled wire substrate is prepared by continuously rolling the modified aluminum alloy ingot at 450-500°C to obtain an aluminum rod, then quenching it at 21-24°C and 360-400kPa, and drawing it at a rate of 8-10m / s to obtain an enameled wire substrate with a diameter of 0.8-1.0mm.

3. The method for preparing an aluminum-based enameled wire for automobiles according to claim 1, wherein: In step A1, the ratio of graphene, boric acid and deionized water is 1-2 g: 0.5-0.8 g: 100 mL; in step A2, the ratio of the composite dispersion and the modifying liquid is 2 mL: 1-2 mL; in step A3, the ratio of the modified graphene and the modifying liquid is 1-2 g: 10-12 mL.

4. The method for preparing an aluminum-based enameled wire for automobiles according to claim 1, wherein: In step S3, the method for preparing the enameled wire blank includes the following steps: B1. Add the enameled wire substrate and 3-5 wt% sodium hydroxide aqueous solution into a stirred tank, stir at room temperature for 10-15 minutes, and post-treat to obtain an active substrate; B2. Add the activated matrix to a reactor containing silica sol, let it stand for 8-10 minutes, take it out and dry it. Repeat the operation 3-5 times to obtain a modified matrix; B3. Add the modified matrix, anhydrous ethanol, deionized water and 3-aminopropyltriethoxysilane into the reactor. After the temperature of the reactor is increased to 40-50°C, use saturated sodium hydroxide aqueous solution to adjust the pH of the reaction system to 8-10. Keep the reaction at this temperature for 30-40 minutes, and then post-treat to obtain the enameled wire blank.

5. The method for preparing an aluminum-based enameled wire for automobiles according to claim 4, characterized in that: In step B1, the enameled wire substrate and 3-5wt% sodium hydroxide aqueous solution are used in a ratio of 1-2g:10-12mL; in step B2, the activated substrate and silica sol are used in a ratio of 1-2g:5-6g; in step B3, the modified substrate, anhydrous ethanol, deionized water and 3-aminopropyltriethoxysilane are used in a ratio of 3-4g:10-12mL:5-6mL:0.1-0.2g.

6. The method for preparing an aluminum-based enameled wire for automobiles according to claim 1, wherein: In step S4, the method for preparing the aluminum-based enameled wire includes the following steps: C1. Add terminal aminopropyl silicone oil, 1,12-diaminododecane and N,N-dimethylformamide to a reactor at a temperature of 0-5°C, keep warm and stir until the reactants are completely dissolved, then add 4,4'-oxydiphthalic anhydride to the reactor in three portions. After the addition is complete, raise the temperature of the reactor to 30-50°C, keep warm and react for 2-4 hours, and perform post-treatment to obtain modified polyamic acid; C2. Adding modified polyamic acid, composite solvent, thickener, leveling agent and hardener into a stirring tank, and stirring evenly to obtain a wear-resistant and anti-corona paint; C3. Applying wear-resistant and anti-corona paint to the surface of the enameled wire blank with a coating thickness of 0.2-0.3 mm, and post-processing to obtain the aluminum-based enameled wire.

7. An aluminum-based enameled wire for automobiles, characterized in that: The automotive aluminum-based enameled wire is prepared by the method for preparing an automotive aluminum-based enameled wire according to any one of claims 1 to 6.

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