An enameled wire finish, enameled wire, and method of making the same

Abstract

The application discloses the technical field of enameled wire and discloses a modified polyamide-imide enameled wire finish paint, which is prepared from the following components: 1-8 parts of graphene, 1-5 parts of silicon dioxide nanoparticles, 1-5 parts of fluororubber, 1-5 parts of nano-aluminum oxide, 70-95 parts of modified polyamide-imide, 1-10 parts of isopropyl alcohol and 1-10 parts of ethyl acetate; the modified polyamide-imide is obtained by the reaction of polyamide-imide and bisphenol A type epoxy resin. The application not only improves the basic performance of the enameled wire, such as heat resistance and electrical insulation, but also solves the demand for wear resistance and low friction coefficient in a targeted manner, and meanwhile, the chemical corrosion resistance and mechanical strength are enhanced, thereby providing high-quality material selection for high-performance motors and electrical appliances. Through the improved preparation process and material formula, the enameled wire can adapt to more extensive application scenarios, and has important application value in the fields of new energy vehicles and high-efficiency motors.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of enameled wire, in particular to a modified polyamide-imide enameled wire finish, enameled wire and a preparation method thereof. BACKGROUND

[0002] In the field of motors and electrical appliances, enameled wire serves as a key insulating material, and its performance directly affects the efficiency, stability and lifespan of the entire device. Traditional enameled wire is usually composed of a copper or aluminum conductor coated with one or more layers of insulating paint. Such insulating paint not only needs to have good electrical insulation performance, but also should have certain mechanical strength, heat resistance and chemical resistance to adapt to different working environments and conditions.

[0003] In recent years, with the rapid development of new energy vehicles, high-performance motors and electrical appliances, the performance requirements for enameled wire are becoming higher and higher. Especially in high-temperature, high-pressure and high-frequency working environments, the performance of traditional enameled wire has gradually failed to meet the needs of these high-end applications. For example, enameled wire is prone to aging at high temperatures, leading to a decrease in insulation performance; under the action of high-frequency current, traditional insulating materials are easily damaged due to corona discharge. In addition, with the development of devices towards high performance and miniaturization, enameled wire also needs to have better wear resistance and low friction coefficient to reduce wear and heat generation during high-speed operation.

[0004] Chinese invention patent (publication number: CN115926615A, publication date: 2023.04.07) discloses a high wear-resistant polyimide enameled wire paint and a preparation method thereof. The polyimide enameled wire paint includes the following components by weight percentage: fluorine-containing polyimide 40-76 parts; nano-silicon dioxide 10-20 parts; polydimethylsiloxane 0.2-0.9 parts; modified graphene 1-6 parts; nano-calcium carbonate 1-6 parts; by introducing fluorine atoms into polyimide, the wear resistance of polyimide enameled wire paint is improved; by adding nano-silicon dioxide and polydimethylsiloxane in polyimide composite material, the friction performance of polyimide enameled wire paint is improved through the synergistic effect between the two; after mixing and filling nano-calcium carbonate and graphene, the friction and wear performance of polyimide composite material is greatly improved due to the synergistic effect of the two. Through the synergistic effect between the components, the finally prepared polyimide enameled wire paint has high wear resistance. However, the invention does not discuss the heat resistance, electrical insulation, chemical resistance and other aspects of the finish. SUMMARY

[0005] The present application provides a modified polyamide-imide enameled wire finish and a preparation method thereof to overcome the deficiencies of the prior art.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A modified polyamide-imide wire enamel, the wire enamel is prepared from raw materials including:

[0008] Graphene 1-8 parts,

[0009] Silica nanoparticles 1-5 parts,

[0010] Fluorine rubber 1-5 parts,

[0011] Nano-alumina 1-5 parts,

[0012] Modified polyamide-imide 70-95,

[0013] Isopropyl alcohol 1-10 parts,

[0014] Ethyl acetate 1-10 parts;

[0015] The modified polyamide-imide is obtained by reacting polyamide-imide and bisphenol A type epoxy resin.

[0016] As preferred, the wire enamel is prepared from raw materials including:

[0017] Graphene 2-4 parts,

[0018] Silica nanoparticles 1-3 parts,

[0019] Fluorine rubber 1-2 parts,

[0020] Nano-alumina 1-3 parts,

[0021] Modified polyamide-imide 75-90,

[0022] Isopropyl alcohol 3-5 parts,

[0023] Ethyl acetate 2-5 parts.

[0024] As preferred, the preparation method of the modified polyamide-imide includes the following steps:

[0025] 1) Pretreatment: dissolving polyamide-imide in an appropriate amount of organic solvent to form a uniform solution;

[0026] 2) Adding epoxy compound: adding bisphenol A type epoxy resin to the polyamide-imide solution, stirring the mixture to ensure that the epoxy resin is completely dissolved and uniformly distributed;

[0027] 3) Adding hardener: slowly adding isocyanate hardener to the mixture, continuing to stir until the mixture becomes uniform; continue to stir the mixture at room temperature for 20-28 hours;

[0028] 4) Post-treatment: After the reaction is completed, the mixture is poured into a large amount of cold water to precipitate the modified polyamide-imide; the precipitate is washed with an appropriate amount of water and organic solvent alternately to remove unreacted substances and by-products, and the precipitate is dried at 60°C to obtain a modified polyamide-imide solid.

[0029] Preferably, the amount of the bisphenol A type epoxy resin added is 5%-20% of the weight of the polyamide-imide.

[0030] Preferably, the amount of the hardener added is calculated according to the equivalent ratio of the bisphenol A type epoxy resin.

[0031] Further, the application also discloses a preparation method of the enameled wire finish, which comprises the following steps:

[0032] 1) Mixing solvent and reinforcing agent: in a clean container, first mix isopropyl alcohol and ethyl acetate, and then stir until completely mixed using a stirrer;

[0033] 2) Adding lubricating and wear-resistant ingredients: slowly add graphene, silicon dioxide nanoparticles, fluororubber and nano-alumina, and disperse using a high-shear mixer to ensure that the fillers are completely dispersed without aggregation;

[0034] 3) Mixing all ingredients: slowly add the modified polyamide-imide into the mixture, and continuously stir using a stirrer to ensure that a uniform solution is formed;

[0035] 4) Cooling and adjusting: cool the mixture to room temperature, and adjust the viscosity if necessary to adapt to the coating process; finally, filter the mixture to remove any undispersed particles or impurities to obtain the finish.

[0036] Preferably, the modified polyamide-imide can be preheated to 50-60°C before being mixed with the mixture.

[0037] Preferably, the stirring speed in step 1 is 450-550 rpm; the dispersion speed of the shear mixer in step 2 is 1500-2500 rpm, and the dispersion time is 10-60 minutes; the stirring speed in step 3 is 500-1500 rpm, and the stirring time is 0.5-1.5 hours.

[0038] Further, the application also discloses an enameled wire with high wear resistance, which is obtained by coating the enameled wire finish on the surface of a copper wire by impregnation.

[0039] Further, the application also discloses a preparation method of the enameled wire, which comprises the following steps:

[0040] 1) Impregnation: impregnate the copper wire in the enameled wire finish, and control the coating thickness by adjusting the copper wire extraction speed and the viscosity of the enameled wire finish;

[0041] 2) Pre-drying: The coated copper wire is left to dry at ambient temperature to allow the solvent to evaporate, for 20-40 minutes;

[0042] 3) Curing process: The pre-dried copper wire is placed in a curing oven for thermal curing, with a curing temperature of 170-185°C and a curing time of 1.5-2.5 hours, to ensure cross-linking and hardening of the coating.

[0043] The present application uses modified polyamide-imide as the base paint, which can maintain excellent electrical insulation performance in high temperature environment, avoiding performance degradation or failure due to temperature rise. The high heat resistance of modified polyamide-imide ensures that the enameled wire can still maintain structural and functional stability under continuous or intermittent high temperature conditions, thereby prolonging the service life of the enameled wire.

[0044] The graphene and silicon dioxide nanoparticles introduced in the present application not only enhance the wear resistance of the finish, but also effectively reduce the friction coefficient. This feature makes the enameled wire have less energy loss and lower heat generation in high-speed operation or frequent action application scenarios, such as electric vehicle drive motors, while reducing wear and extending the service life.

[0045] The nano-aluminum oxide in the present application as a reinforcing agent not only improves the mechanical strength of the finish, but also enhances the ability to resist chemical corrosion. This allows the enameled wire to be used in harsh chemical environments, such as exposure to acids, bases or other corrosive substances, without being easily damaged, ensuring the safe and stable operation of the motor or electrical appliance.

[0046] The specific solvent system and modification process in the present application can ensure uniform dispersion of fillers and reinforcing agents in the modified polyamide-imide matrix, so that the enameled wire finish has high uniformity and consistency. Optimization of this preparation process ensures that each batch of enameled wire products meets the expected high performance standards, meeting the application requirements of high precision and high reliability.

[0047] The present application not only improves the basic performance of enameled wire, such as heat resistance and electrical insulation, but also specifically addresses the needs of wear resistance and low friction coefficient, while enhancing chemical corrosion resistance and mechanical strength, providing high-quality material options for high-performance motors and electrical appliances. Through improved preparation process and material formulation, this enameled wire can adapt to a wider range of application scenarios, especially in the field of new energy vehicles and high-efficiency motors, which has important application value. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0049] Examples 1-4

[0050] A modified polyamide-imide wire enamel is provided, with a formulation as shown in Table 1.

[0051] The preparation method of the wire enamel is as follows:

[0052] 1) Mix the solvent and enhancer: In a clean container, first mix isopropyl alcohol and ethyl acetate, then use a stirrer to stir until completely mixed, at a stirring speed of 500 rpm for 10 minutes;

[0053] 2) Add the lubricating and wear-resistant ingredients: Slowly add graphene, silicon dioxide nanoparticles, fluororubber, and nano-alumina, and use a high-shear mixer to disperse, at a dispersion speed of 2000 rpm for 30 minutes, to ensure that the fillers are completely dispersed without aggregation;

[0054] 3) Pre-heat the base paint: Pre-heat the modified polyamide-imide to about 50-60°C to reduce its viscosity, facilitating mixing;

[0055] 4) Mix all ingredients: Slowly add the modified polyamide-imide to the mixture, and continue stirring to ensure a uniform solution, at a stirring speed of 1000 rpm for about 1 hour;

[0056] 5) Cool and adjust: Cool the mixture to room temperature, and adjust the viscosity as necessary to adapt to the coating process; finally, filter the mixture to remove any undispersed particles or impurities, obtaining the enamel.

[0057] Examples 6-7

[0058] A modified polyamide-imide wire enamel is provided, with a formulation as shown in Table 4, and the preparation method is the same as that of Example 1.

[0059] Comparative Examples 1-6

[0060] A wire enamel is provided, with a formulation as shown in Table 1, and the preparation method is the same as that of Example 1.

[0061] Comparative Examples 7-9

[0062] A wire enamel is provided, with a formulation as shown in Table 4, and the preparation method is the same as that of Example 1.

[0063] Among them, Comparative Example 9 replaces the solvent with toluene, which is a commonly used solvent in industrial paint, and is widely used for its fast evaporation and good solubility.

[0064] Table 1

[0065] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Modified polyamide-imide 84.5 83.5 83.5 84 83.5 / / 86 87.5 86.5 86.5 Polyamide-imide / / / / / 93 84.5 / / / / Graphene 3 4 3 3 3 / 3 3 / 3 3 Silica nanoparticles 2 2 3 2 2 / 2 2 2 / 2 Fluororubber 1.5 1.5 1.5 2 1.5 / 1.5 / 1.5 1.5 1.5 Nano-alumina 2 2 2 2 3 / 2 2 2 2 / Isopropyl alcohol 4 4 4 4 4 4 4 4 4 4 4 Ethyl acetate 3 3 3 3 3 3 3 3 3 3 3

[0066] Preparation of experimental samples

[0067] The enamel wire topcoats obtained from Examples 1-5 and Comparative Examples 1-6 were coated on the surface of copper wires by dipping method to obtain coated copper wires, and then the coated copper wires were tested for various performance tests.

[0068] The preparation method of the coated copper wire is as follows:

[0069] 1) Dipping: dip the copper wire in the enamel wire topcoat, and control the coating thickness by adjusting the extraction speed of the copper wire and the viscosity of the enamel wire topcoat;

[0070] 2) Pre-drying: place the coated copper wire at ambient temperature for drying to volatilize the solvent, and place for about 30 minutes;

[0071] 3) Curing treatment: place the pre-dried copper wire in a curing oven for heat curing, with a curing temperature of 180°C and a curing time of about 2 hours, to ensure cross-linking and hardening of the coating.

[0072] Experiment 1

[0073] Purpose of the experiment: test the performance of the coated copper prepared using the enamel wire topcoats of Examples 1-5 and Comparative Examples 1-6, and the test results are shown in Table 2.

[0074] Test items:

[0075] 1. Heat resistance test: test the retention rate (%) of the insulation layer after heating each group of samples at 180°C for 72 hours.

[0076] 2. Electrical insulation performance test: use a high-voltage electrical tester to test and record the insulation breakdown strength of each group of samples.

[0077] 3. Abrasion resistance test: use an abrasion tester to determine the number of abrasion cycles of the sample under specific conditions.

[0078] 4. Friction coefficient test: use a friction coefficient tester to measure the dynamic friction coefficient under standard conditions.

[0079] 5. Mechanical strength test: measure the tensile strength and elongation of each group of samples at room temperature by a tensile testing machine.

[0080] 6. Chemical stability test: measure the mass change rate after immersing the sample in a specific chemical reagent for a certain period of time.

[0081] Table 2

[0082] Test item Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Heat resistance 98% 99% 97% 98% 98.5% 90% 92% 95% 98% 98% 95% Electrical insulation (kV / mm) 30 32 29 31 31 12 17 30 27 30 30 Wear resistance (thousands of times) 5 5.5 4.8 5.2 5 3.1 5 4.5 4.2 4.1 5 Friction coefficient 0.05 0.045 0.05 0.048 0.05 0.74 0.05 0.06 0.065 0.065 0.05 Tensile strength (MPa) 350 360 340 350 355 210 350 350 300 320 310 Elongation (%) 15 16 14 15 15.5 6.5 15 15 10 11 11 Chemical stability -0.5% -0.4% -0.6% -0.5% -0.4% -1.2% -1.1% -0.5% -0.5% -0.5% -1.7%

[0083] Referring to Table 2, it can be seen from Example 1 and Comparative Example 2 that the modified polyamide-imide can provide better heat resistance, chemical resistance and electrical insulation of the topcoat; from Example 1 and Comparative Example 3 that the fluororubber can reduce the friction coefficient of the topcoat and improve the wear resistance; from Example 1 and Comparative Example 4 that the graphene can improve the mechanical properties and wear resistance of the topcoat; from Example 1 and Comparative Example 5 that the silica nanoparticles have certain influence on the wear resistance, friction coefficient and mechanical strength; and from Example 1 and Comparative Example 6 that the nano-alumina can improve the mechanical strength, thermal stability and chemical stability of the topcoat.

[0084] Experiment Two

[0085] Purpose of the experiment: to test the compatibility of the modified polyamide-imide with graphene, silica nanoparticles and fluororubber and the improvement of the interfacial bonding capacity, and the test results are shown in Table 3.

[0086] The experimental group is the coated copper wire prepared by using Example 1, and the control group is the coated copper wire prepared by using Comparative Example 2.

[0087] Test items:

[0088] 1. Compatibility test: dynamic light scattering (DLS) and transmission electron microscopy (TEM) are used to evaluate the dispersion state of the fillers in the modified polyamide-imide, analyze the particle size distribution and dispersion uniformity.

[0089] 2. Interfacial bonding capacity test: infrared spectroscopy (FTIR) is used to analyze the possible chemical bonding between the modified polyamide-imide and the fillers.

[0090] Table 3

[0091] Test item Control group Experimental group Particle size distribution (DLS) Wide distribution, multi-modal Narrow distribution, single-modal Dispersion uniformity (TEM) Uneven dispersion Uniform dispersion Chemical bonding (FTIR) No obvious characteristic peak New characteristic peak appears

[0092] Referring to Table 3, the FTIR results show that there is chemical bonding between the modified polyamide-imide and the fillers, and the experimental group shows a narrower particle size distribution and more uniform dispersion, indicating that the modified polyamide-imide can better compatible with the fillers.

[0093] Experiment Three

[0094] Purpose of the experiment: to test the improvement effect of isopropyl alcohol and ethyl acetate mixed as a solvent on the film-forming properties of the paint film, and the test results are shown in Table 4.

[0095] Test items (film-forming property test):

[0096] 1. Drying time test: Record the time from application to complete dryness.

[0097] 2. Levelness test: Evaluate the levelness of the paint film by visual inspection and optical microscope observation.

[0098] 3. Adhesion test: Test the adhesion of the paint film by cross-cut method.

[0099] 4. Hardness test: Evaluate the hardness of the paint film by pencil hardness test method.

[0100] Table 4

[0101] Example 1 Example 6 Example 7 Comparative Example 7 Comparative Example 8 Comparative Example 9 Modified polyamide-imide 84.5 83.5 83.5 84.5 84.5 84.5 Graphene 3 4 3 3 3 3 Silica nanoparticles 2 2 3 2 2 2 Fluororubber 1.5 1.5 1.5 1.5 1.5 1.5 Nano-alumina 2 2 2 2 2 2 Isopropyl alcohol 4 3 3.5 7 / / Ethyl acetate 3 4 3.5 / 7 / Toluene / / / / / 7 Drying time (minutes) 15 16 15 30 20 25 Coat film smoothness Excellent Excellent Excellent Good Medium Good Adhesion (0-5 level) 5 5 5 3 4 3 Hardness (pencil hardness) 2H 2H 2H HB F H

[0102] Referring to Table 4, the drying times of the examples are all shorter than the comparative examples, indicating that the mixed solvent of isopropyl alcohol and ethyl acetate has a significant advantage in accelerating drying. The levelness of the paint film of the examples continues to be optimal, and the results of Comparative Example 9, although better than Comparative Examples 7 and 8, are comparable to Comparative Example 7, indicating that the toluene solvent, although it can provide good solvency, is not superior to the mixed solvent system of isopropyl alcohol and ethyl acetate in forming high-quality paint films. The results show that the adhesion of the examples is the highest, and Comparative Example 9 is comparable to Comparative Example 7, which further confirms the special effect of the isopropyl alcohol and ethyl acetate mixture in promoting good bonding between the paint film and the substrate. The hardness of the paint film of the examples is the highest, and the hardness of Comparative Example 9 is between Comparative Example 7 and the examples, indicating that the contribution of toluene solvent to hardness is less than that of the mixed solvent of isopropyl alcohol and ethyl acetate.

[0103] The above description of the examples of the present application enables those skilled in the art to implement or use the present application by means of the above description of the disclosed examples. Various modifications to these examples will be apparent to those skilled in the art. The general principles defined herein can be implemented in other examples without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the examples shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A modified polyamide-imide wire enameled topcoat, characterized in that: The topcoat is prepared from the raw materials of the following components: 1-8 parts of graphene, 1-5 parts of silicon dioxide nanoparticles, 1-5 parts of fluororubber, 1-5 parts of nano-alumina, 70-95 parts of modified polyamide-imide, 1-10 parts of isopropyl alcohol, 1-10 parts of ethyl acetate; The preparation method of the modified polyamide-imide comprises the following steps: 1) Pretreatment: dissolve polyamide-imide in an appropriate amount of organic solvent to form a uniform solution; 2) Adding epoxy compound: Add bisphenol A epoxy resin to the polyamide-imide solution and stir to ensure that the epoxy resin is completely dissolved and evenly distributed; 3) Add hardener: Slowly add isocyanate hardener and continue stirring until the mixture becomes homogeneous. Continue stirring the mixture at room temperature and allow it to react for 20-28 hours. 4) Post-treatment: After the reaction is completed, the mixture is poured into a large amount of cold water to promote the precipitation of modified polyamide-imide; the mixture is washed alternately with appropriate amounts of water and organic solvent to remove unreacted substances and by-products, and the precipitate is dried at 60°C to obtain a modified polyamide-imide solid; The added amount of the bisphenol A epoxy resin is 5%-20% of the weight of the polyamide-imide; the added amount of the hardener is calculated based on the equivalent ratio of the bisphenol A epoxy resin.

2. The wire enameled topcoat according to claim 1, characterized in that: The topcoat is prepared from the raw materials of the following components: 2-4 parts of graphene, 1-3 parts of silicon dioxide nanoparticles, 1-2 parts of fluororubber, 1-3 parts of nano-alumina, 75-90 parts of modified polyamide-imide, 3-5 parts of isopropyl alcohol, 2-5 parts of ethyl acetate.

3. The method for preparing the wire enameled topcoat according to any one of claims 1 to 2, characterized in that: The steps include: 1) In a clean container, first combine isopropyl alcohol and ethyl acetate, then use a blender to stir until thoroughly mixed; 2) Slowly add graphene, silica nanoparticles, fluororubber, and nano-alumina and disperse them using a high shear mixer to ensure that the fillers are completely dispersed without aggregation; 3) Slowly add the modified polyamide-imide and stir continuously with a stirrer to ensure a uniform mixture; 4) Cool the mixture to room temperature and adjust the viscosity if necessary to suit the coating process; finally, filter the mixture to remove any undispersed particles or impurities to obtain the topcoat.

4. The method for preparing the wire enameled topcoat according to claim 3, wherein: The modified polyamide-imide is preheated to 50-60° C. before being added.

5. The method for preparing the wire enameled topcoat according to claim 3, wherein: In step 1, the stirring speed is 450-550 rpm; in step 2, the dispersion speed of the shear mixer is 1500-2500 rpm, and the dispersion time is 10-60 minutes; in step 3, the stirring speed is 500-1500 rpm, and the stirring time is 0.5-1.5 hours.

6. A highly wear-resistant enameled wire, characterized in that: The enameled wire topcoat according to any one of claims 1 to 2 is applied to the surface of a copper wire by an immersion method to obtain a highly wear-resistant enameled wire.

7. The method for preparing the enameled wire according to claim 6, characterized in that: The preparation method comprises the following steps: 1) Dipping: Dip the copper wire into the wire enameled topcoat and control the coating thickness by adjusting the copper wire extraction speed and the viscosity of the wire enameled topcoat. 2) Pre-drying: Place the coated copper wire at ambient temperature to dry for 20-40 minutes to allow the solvent to evaporate; 3) Curing treatment: Place the pre-dried copper wire in a curing oven for heat curing at a temperature of 170-185°C for 1.5-2.5 hours to ensure crosslinking and hardening of the coating.