Insulating film, method for producing the same, and enameled wire, motor, and vehicle

Abstract

The application provides an insulating film, a preparation method thereof and an enameled wire. The insulating film comprises a block polymer, and the block polymer comprises a polyimide block and a polylactic acid block. The insulating film has a porous structure. The insulating film has excellent low dielectricity, and has excellent mechanical and thermal properties, which helps to improve the performance of a motor.

Description

Technical Field

[0001] This application relates to the field of enameled wire, specifically to insulating films and their preparation methods, as well as enameled wire, motors, and vehicles. Background Technology

[0002] With the rapid development of the global economy and the motor industry, the demand for high-voltage motors (referred to as "high-voltage motors") is increasing. Enamelled wire, as the main conductive material inside the motor, is responsible for transmitting current to the stator and rotor windings. Enamelled wire consists of the conductive material and the insulating film covering its surface. To meet the performance requirements of high-voltage motors, the partial discharge initiation voltage (PDIV) value of the enamelled wire can be increased, meaning the PDIV value of the enamelled wire should be higher than the overshoot voltage during motor operation, ensuring that insulation loss does not occur due to partial discharge. Since the dielectric constant is correlated with the PDIV value, the lower the dielectric constant, the higher the PDIV value. However, currently, it is difficult for the enamelled wire insulation film to meet the low dielectric constant requirements of high-voltage motors, and further research is needed. Summary of the Invention

[0003] In view of the technical problems existing in the background art, this application provides an insulating film and its preparation method, enameled wire, motor and vehicle. The insulating film of this application has excellent low dielectric properties, while also having excellent mechanical and thermal properties, which helps to improve the performance of motors and can be used in high voltage motors of not less than 800V.

[0004] The first aspect of this application discloses an insulating film comprising a block polymer, the block polymer comprising polyimide blocks and polylactic acid blocks; the insulating film having a porous structure.

[0005] This application includes at least the following beneficial effects: the insulating film of this application contains a block polymer formed by polyimide and polylactic acid. Because polylactic acid has good biodegradability, it can degrade in the air to produce CO2, thereby forming a porous structure. This porous structure can communicate with the air, and since the dielectric constant of air is the lowest (close to 1), this further reduces the dielectric constant of the insulating film, better meeting the requirements of high-voltage motors.

[0006] In some embodiments, the porosity of the porous structure is 20% to 80%.

[0007] In some embodiments, the polyimide block is generated by reacting at least a dianhydride monomer and a diamine monomer.

[0008] In some embodiments, the diamine monomer has a hydroxyl group, which can undergo esterification with a carboxyl group in the polylactic acid block.

[0009] In some embodiments, the dianhydride monomer further has a fluorine group;

[0010] And / or, the dianhydride monomer comprises at least one of the following: hexafluoroisopropylphthalic anhydride, 9,9-bis(trifluoromethyl)-2,3,6,7-oxanthracene tetracarboxylic dianhydride, 1,4-bis(3,4-dicarboxytrifluorophenoxy)tetrafluorophenyl dianhydride, 1,4-bis(trifluoromethyl)-2,3,5,6-benzenetetracarboxylic dianhydride, 1,4-difluoropyromellitic dianhydride, and 2,2-bis[4-(3,4-dicarboxytrifluorophenoxy)phenyl]hexafluoropropane dianhydride;

[0011] And / or, the diamine monomer comprises at least one of 3,3'-dihydroxybenzidine, 4,6-diaminoresorcinol dihydrochloride, and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane.

[0012] In some embodiments, the number-average molecular weight of the polyimide blocks is 105,000 to 200,000;

[0013] And / or, the number-average molecular weight of the polylactic acid blocks is 50,000 to 120,000.

[0014] In some embodiments, the insulating film satisfies at least one of the following conditions:

[0015] Under electromagnetic waves with a frequency of 1 kHz, the dielectric constant of the insulating film is 2.01 to 2.28, and the dielectric loss factor is 0.001 to 0.006.

[0016] The tensile strength of the insulating film is 180 MPa to 222 MPa;

[0017] The elongation at break of the insulating film is 190.4% to 211.2%;

[0018] The coefficient of thermal expansion of the insulating film is 60.02ppm / ℃~71.23ppm / ℃.

[0019] A second aspect of this application discloses a method for preparing an insulating film, the method comprising:

[0020] The insulating base film is degraded to obtain the insulating film with a porous structure;

[0021] The insulating base film includes a second block polymer, which includes the polyimide block and the polylactic acid block, wherein the polylactic acid block content in the insulating base film is greater than the polylactic acid block content in the insulating film.

[0022] In some embodiments, the molar ratio of the polyimide block to the polylactic acid block in the second block polymer is 1:(2 to 2.5).

[0023] In some embodiments, a method for preparing the second block polymer includes:

[0024] The diamine monomer and the dianhydride monomer are polymerized in an organic solvent to obtain a polymer slurry;

[0025] The polymer slurry is esterified with polylactic acid to obtain the esterified product;

[0026] The esterified product is subjected to imidization to obtain the second block polymer.

[0027] In some embodiments, the organic solvent includes at least one of N,N-dimethylacetamide, N-methylpyrrolidone, m-cresol, and 1,4-butyrolactone;

[0028] And / or, the polymerization treatment temperature is 25°C to 30°C;

[0029] And / or, the polymerization treatment time is 8h to 10h;

[0030] And / or, the viscosity of the polymer slurry is 90,000 cps to 110,000 cps.

[0031] In some embodiments, the esterification process includes:

[0032] The polymer slurry, catalyst, and polylactic acid-containing slurry are mixed to obtain a mixture.

[0033] The dehydrating agent solution is added dropwise to the mixture to carry out an activation reaction, resulting in an activated solution.

[0034] The activated solution was subjected to an esterification reaction to obtain the esterified product.

[0035] In some embodiments, the catalyst comprises one or more of 4-dimethylaminopyridine, pyridine, triethylamine, and N-methylpiperidine;

[0036] And / or, the dehydrating agent comprises one or more of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N,N-dicyclohexylcarbodiimide;

[0037] And / or, the solvent contained in the dehydrating agent solution includes one or more of N,N-dimethylacetamide, N-methylpyrrolidone, m-cresol, and 1,4-butyrolactone;

[0038] And / or, the activation reaction is carried out at a temperature of -2°C to 2°C;

[0039] And / or, the activation reaction takes 20 min to 40 min;

[0040] And / or, the temperature of the esterification reaction is 25°C to 30°C;

[0041] And / or, the esterification reaction takes 8 to 15 hours.

[0042] In some embodiments, the imidization treatment includes: 40 min to 60 min at 70 °C to 90 °C, 20 min to 40 min at 150 °C to 170 °C, and 20 min to 40 min at 240 °C to 260 °C.

[0043] In some embodiments, the degradation treatment includes placing the insulating base film at a temperature of 20°C to 30°C for 10 to 30 days.

[0044] A third aspect of this application provides an enameled wire comprising: a conductor; and the insulating film described in the first aspect of this application, the insulating film covering the outer peripheral surface of the conductor.

[0045] The fourth aspect of this application discloses an electric motor, which includes the enameled wire described in the third aspect of this application.

[0046] In some embodiments, the rated voltage of the motor is not less than 800V.

[0047] The fifth aspect of this application discloses a vehicle comprising the motor described in the fourth aspect of this application.

[0048] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0049] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0050] Figure 1 This illustration shows a schematic flowchart of a method for preparing a block prepolymer membrane according to an embodiment of this application;

[0051] Figure 2 A schematic diagram of an esterification process according to an embodiment of this application is shown. Specific Implementation

[0052] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0053] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0054] The first aspect of this application discloses an insulating film comprising a block polymer, the block polymer comprising polyimide blocks and polylactic acid blocks; the insulating film having a porous structure.

[0055] Polyimide possesses high thermal stability, maintaining its physical and chemical properties at high temperatures. Its decomposition temperature is typically above 400°C, and it does not oxidize or degrade at high temperatures. This characteristic makes it an excellent choice for applications requiring high-temperature operation. Furthermore, polyimide exhibits excellent mechanical strength and toughness, with high tensile strength, flexural strength, and impact strength. It is also an excellent electrical insulating material, demonstrating superior electrical insulation properties and remaining stable under high temperature and high pressure conditions.

[0056] While polyimide is currently used as the insulation film for enameled wires in motors, it has the characteristic of low dielectric constant, but its dielectric constant is around 3.4, which is difficult to meet the requirements of high-voltage motors for low dielectric constant.

[0057] To achieve a lower dielectric constant and excellent mechanical and thermal properties, this application attempts to introduce biodegradable polymers to form a porous structure. Utilizing the fact that these porous structures are interconnected with air, and that air has the lowest dielectric constant (close to 1), the dielectric constant can be further reduced. Polylactic acid (PLA) has good biocompatibility and biodegradability. Under the influence of air and microorganisms, PLA degrades, and the CO2 produced during the degradation process forms a porous structure that is interconnected with air, further reducing the dielectric constant of the insulating film. Therefore, the insulating film of this application possesses both good mechanical properties and an excellent dielectric constant. Furthermore, the final products of PLA degradation are water and carbon dioxide, with no secondary pollution. Moreover, by introducing PLA to form a block polymer, the processing temperature, gloss, and air permeability of the insulating film can be further improved, and it can be produced using various common plastic processing methods, which is quite convenient.

[0058] In some embodiments, the porosity of the porous structure is 20% to 80%. Exemplarily, the porosity of the porous structure is 20%, 40%, 50%, 60%, 80%, etc. Porosity that meets the given conditions can further reduce the dielectric constant, and the structure exhibits strong insulation and voltage withstand properties, making it less prone to damage.

[0059] It should be noted that: pores refer to the interparticle spacing of a material, while "porosity" refers to the percentage of pore volume to the total volume of the material in its natural state. Specifically, the porosity test method for porous structures is as follows: using the solvent immersion method, first weigh the insulating film (m), calculate the film volume based on the polymer density, and record it as V1; after placing the insulating film in 10 mL of deionized water at room temperature for 30 minutes, remove it and measure the volume of the remaining water, recording the reduced water volume as V2. Porosity / % = V2 × 100% / (V1 + V2).

[0060] In some embodiments, the polyimide block is generated by reacting at least a dianhydride monomer and a diamine monomer.

[0061] In some embodiments, the diamine monomer has a hydroxyl group, which can undergo esterification with a carboxyl group in the polylactic acid block.

[0062] In some embodiments, the dianhydride monomer further comprises a fluorine group. Since fluorine has strong electronegativity, the introduction of fluorine can further reduce the dielectric constant of the insulating film and improve its dielectric properties.

[0063] In some embodiments, the fluorinated dianhydride monomer comprises at least one of the following: hexafluoroisopropylphthalic anhydride (6FDA), 9,9-bis(trifluoromethyl)-2,3,6,7-oxanthracene tetracarboxylic dianhydride (6FCDA), 1,4-bis(3,4-dicarboxytrifluorophenoxy)tetrafluorophenyl dianhydride (10FEDA), 1,4-bis(trifluoromethyl)-2,3,5,6-benzenetetracarboxylic dianhydride (P6FDA), 1,4-difluoropyromellitic dianhydride (PF2DA), and 2,2-bis[4-(3,4-dicarboxytrifluorophenoxy)phenyl]hexafluoropropane dianhydride (BFDA), preferably 6FDA and / or 6FCDA. Since fluorine is a strongly electronegative substance, its introduction into the material further reduces the dielectric constant of the material.

[0064] In some embodiments, the diamine monomer includes at least one of 3,3'-dihydroxybenzidine, 4,6-diaminoresorcinol dihydrochloride, and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane.

[0065] Taking 3,3'-dihydroxybenzidine as an example, the block polymer has the structure shown in the following formula:

[0066]

[0067] m, n, and p are integers from 1 to 100, where Ar represents an aromatic group derived from dianhydride monomers.

[0068] The insulating film contains block polymers with the above-mentioned structure, which have both low dielectric constant and excellent mechanical and thermal properties.

[0069] In some embodiments, the number-average molecular weight of the polyimide blocks is 105,000 to 200,000. Exemplarily, the number-average molecular weight of the polyimide blocks is 105,000, 110,000, 120,000, 140,000, 150,000, 160,000, 180,000, or 200,000. The number-average molecular weight of the polyimide blocks, satisfying the given conditions, can both form a suitable amount of porous structure, reducing the dielectric constant, and improve mechanical and thermal properties.

[0070] In some embodiments, the number-average molecular weight of the polylactic acid (PLA) blocks is 50,000 to 120,000. Exemplarily, the number-average molecular weight of the PLA blocks is 50,000, 60,000, 80,000, 100,000, 120,000, etc. A PLA block with a number-average molecular weight that meets the given conditions can form a suitable amount of porous structure, reducing the dielectric constant, and also improving mechanical and thermal properties.

[0071] In some embodiments, the insulating film satisfies at least one of the following conditions: under electromagnetic waves at a frequency of 1 kHz, the dielectric constant of the insulating film is 2.01 to 2.28, and the dielectric loss factor is 0.001 to 0.006; the tensile strength of the insulating film is 180 MPa to 222 MPa; the elongation at break of the insulating film is 190.4% to 211.2%; and the coefficient of thermal expansion of the insulating film is 60.02 ppm / ℃ to 71.23 ppm / ℃.

[0072] For example, under electromagnetic waves with a frequency of 1 kHz, the dielectric constant of the insulating film can be 2.05, 2.08, 2.10, 2.12, 2.15, 2.18, 2.20, 2.22, 2.25, etc., and the dielectric loss factor can be 0.002, 0.003, 0.004, 0.005, etc. Meeting the given conditions for the dielectric constant and dielectric loss factor can improve the PDIV value of the enameled wire, avoiding insulation loss due to partial discharge. Simultaneously, it can also reduce energy loss, lower heat generation, improve insulation performance, reduce electric field concentration, increase signal transmission speed, and reduce electromagnetic interference.

[0073] For example, the tensile strength of the insulating film can be 185MPa, 190MPa, 195MPa, 200MPa, 205MPa, 210MPa, 215MPa, 220MPa, etc. When the tensile strength meets the given conditions, the insulating film has good mechanical properties, can withstand certain mechanical stress and tension, is not easily broken or damaged, is not prone to cracking or deformation during processing operations such as cutting and forming, has good impact resistance, and a long service life.

[0074] For example, the elongation at break of the insulating film can be 193%, 195%, 198%, 200%, 202%, 205%, 208%, 210%, etc. When the elongation at break meets the given conditions, the insulating film can withstand large deformations without breaking when stretched or stressed, thereby improving the durability, impact resistance, and structural stability of the insulating film.

[0075] For example, the coefficient of thermal expansion of the insulating film is 62ppm / ℃, 64ppm / ℃, 65ppm / ℃, 68ppm / ℃, 70ppm / ℃, etc. When the coefficient of thermal expansion meets the given conditions, the insulating film exhibits minimal dimensional change under temperature variations, maintains dimensional stability, reduces thermal deformation, and decreases thermal stress, thereby lowering the risk of material delamination or breakage.

[0076] The second aspect of this application provides a method for preparing the insulating film described in the first aspect of this application, the method comprising: degrading an insulating base film to obtain the insulating film having a porous structure;

[0077] The insulating base film includes a second block polymer, which includes the polyimide block and the polylactic acid block, wherein the polylactic acid block content in the insulating base film is greater than the polylactic acid block content in the insulating film.

[0078] The insulating base film contains polylactic acid (PLA). During degradation, PLA produces CO2, forming a porous structure that is interconnected with air, further reducing the dielectric constant of the insulating film. Furthermore, due to the consumption of PLA, the PLA block content in the insulating film is lower than that in the insulating base film. Therefore, the insulating film prepared using the method of this application exhibits low dielectric properties and excellent mechanical and thermal properties. Moreover, the preparation method is simple, low-cost, and suitable for industrial applications. The features and advantages described for the insulating film in the first aspect also apply to this method, and will not be repeated here.

[0079] It should be noted that the types and characteristics of the polyimide blocks and polylactic acid blocks described in the insulating film mentioned in the first aspect are the same as those of the polyimide blocks and polylactic acid blocks in the insulating base film, and will not be repeated here.

[0080] In some embodiments, the molar ratio of the polyimide block to the polylactic acid block in the second block polymer is 1:(2-2.5). Exemplarily, the molar ratio of the polyimide block to the polylactic acid block in the second block polymer is 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, etc. This allows the insulating film to further possess low dielectric properties and excellent mechanical and thermal properties, making it less prone to brittleness and easier to form into a film.

[0081] In some embodiments, see Figure 1 The method for preparing the second block polymer includes: S100 polymerization treatment, S200 esterification treatment, and S300 imidization treatment. Each step will be described in detail below.

[0082] S100 polymerization processing

[0083] In this step, the diamine monomer and the dianhydride monomer are polymerized in an organic solvent to obtain a polymer slurry. The diamine monomer and the dianhydride monomer react to generate polyamic acid.

[0084] In some embodiments, the organic solvent includes at least one selected from N,N-dimethylacetamide, N-methylpyrrolidone, m-cresol, and 1,4-butyrolactone. The diamine monomer and dianhydride monomer are soluble in the organic solvent under the given conditions, resulting in high polymerization efficiency and yield.

[0085] In some embodiments, the polymerization treatment temperature is 25°C to 30°C. Exemplarily, the polymerization treatment temperature is 26°C, 27°C, 28°C, 29°C, etc. This can further improve the polymerization reaction efficiency and yield.

[0086] In some embodiments, the polymerization treatment time is 8 to 10 hours. For example, the polymerization treatment time is 8.5 hours, 9 hours, 9.5 hours, etc. Therefore, the polymerization reaction can be completed efficiently in a short time, resulting in a high product yield.

[0087] In some embodiments, the viscosity of the polymer slurry is 90,000 cps to 110,000 cps. Exemplarily, the viscosity of the polymer slurry is 92,000 cps, 95,000 cps, 98,000 cps, 100,000 cps, 105,000 cps, etc. When the viscosity of the polymer slurry meets the given conditions, it exhibits good coating performance, easily forms a uniform film, and the film has good surface quality and internal structure, as well as excellent mechanical and thermal properties.

[0088] S200 esterification treatment

[0089] In this step, the polymer slurry is esterified with polylactic acid to obtain an esterified product. The hydroxyl groups in polyamic acid react with the carboxyl groups in polylactic acid to form ester bonds.

[0090] In some embodiments, see Figure 2 The esterification process includes:

[0091] S210 Hybrid

[0092] In this step, the polymer slurry, catalyst, and polylactic acid-containing slurry are mixed to obtain a mixture.

[0093] In some embodiments, the catalyst comprises one or more of 4-dimethylaminopyridine (DMAP), pyridine, triethylamine, and N-methylpiperidine. This results in high reaction efficiency and high product yield.

[0094] In some embodiments, the dehydrating agent comprises one or more of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC) and N,N-dicyclohexylcarbodiimide (DCC). This allows for efficient water removal, improving product yield and purity.

[0095] In some embodiments, the solvent contained in the dehydrating agent solution includes one or more of N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), m-cresol, and 1,4-butyrolactone (GBL), preferably DMAc and / or NMP. This results in good reactant solubility, high reaction efficiency, and high product purity and yield.

[0096] S220 activation

[0097] In this step, a dehydrating agent solution is added dropwise to the mixture to initiate an activation reaction, resulting in an activated solution. This helps to improve the reaction success rate, reaction rate, and reaction yield.

[0098] In some embodiments, the activation reaction temperature is -2℃ to 2℃. Exemplarily, the activation reaction temperature is -2℃, -1℃, 0℃, 1℃, 2℃, etc. This results in high activation reaction efficiency.

[0099] In some embodiments, the activation reaction time is 20 min to 40 min. Exemplarily, the activation reaction time is 25 min, 30 min, 35 min, etc. Therefore, the activation reaction efficiency is high.

[0100] S230 esterification

[0101] In this step, the activating solution is subjected to an esterification reaction to obtain an esterified product. The hydroxyl groups react with the carboxyl groups in polylactic acid to form ester bonds.

[0102] In some embodiments, the esterification reaction is carried out at a temperature of 25°C to 30°C. Exemplarily, the esterification reaction temperature is 26°C, 27°C, 28°C, 29°C, etc. This results in high esterification efficiency, high product purity, and high yield.

[0103] In some embodiments, the esterification reaction time is 8 to 15 hours. Exemplarily, the esterification reaction time is 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, etc. This results in high esterification efficiency, high product purity, and high yield.

[0104] S300 imidization treatment

[0105] In this step, the esterification product is imidized to obtain the second block polymer. The amyl acid in the esterification product is cyclized and dehydrated to form a polyimide, ultimately yielding the second block polymer.

[0106] In some embodiments, the imidization treatment includes: 40-60 minutes (e.g., 45, 50, 55 minutes, etc.) at 70°C-90°C (e.g., 75°C, 80°C, 85°C, etc.); 20-40 minutes (e.g., 25, 30, 35 minutes, etc.) at 150°C-170°C (e.g., 155°C, 160°C, 165°C, etc.); and 20-40 minutes (e.g., 25, 30, 35 minutes, etc.) at 240°C-260°C (e.g., 245°C, 250°C, 255°C, etc.). This allows for the efficient preparation of block polymers with high product yield and purity.

[0107] In some embodiments, the imidization treatment time is 20 min to 60 min. Exemplarily, the imidization treatment time is 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, etc. Therefore, block polymers can be prepared efficiently with high product yield and purity.

[0108] In some embodiments, the degradation treatment includes placing the insulating substrate film at a temperature of 20°C to 30°C for 10 to 30 days. This forms a porous structure that meets the given conditions, thereby reducing the dielectric constant of the insulating film.

[0109] A third aspect of this application discloses an enameled wire comprising: a conductor; and the insulating film described in the first aspect of this application, the insulating film covering the outer peripheral surface of the conductor. The enameled wire according to this application has excellent partial discharge initiation voltage, high insulation performance, can avoid partial discharge under high voltage, maintains stable operation, and has a long service life.

[0110] This application discloses a motor in a fourth aspect, the motor comprising the enameled wire described in the third aspect of this application. According to the motor of this application, by applying the aforementioned enameled wire, the partial discharge initiation voltage can be increased, the insulation performance is high, thereby improving the stability and efficiency of motor operation, extending service life, and meeting different rated voltage requirements.

[0111] In some embodiments, the rated voltage of the motor is not less than 800V. The enameled wire according to this application can be used for the aforementioned high rated voltage.

[0112] The fifth aspect of this application discloses a vehicle comprising the motor described in the fourth aspect of this application. According to the vehicle of this application, by applying the aforementioned motor, the vehicle possesses at least the following advantages: it is easier to achieve high power and high torque, resulting in good vehicle acceleration and a wide high-efficiency range; it has low operating current at the same power, reducing line losses; it is compatible with high and low voltage platforms, enabling product serialization; and it has fast charging speed, making fast charging easier to achieve.

[0113] It should be noted that the features and advantages described above for the insulating film also apply to the enameled wire, motor, and vehicle, and will not be repeated here.

[0114] The following will explain the solution of this application with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0115] Example 1

[0116] (1) 3,3'-dihydroxybenzidine (0.1 mol, 21.62 g) and 6FDA (0.105 mol, 46.64 g) were added to DMAc (273 g, 20% solids content), and reacted at 25°C for 10 h until completely dissolved to obtain PI slurry (M n =125864, viscosity is 104587 cps;

[0117] (2) The PI slurry (2g, 0.58mmol) and PLA slurry (M) synthesized in step (1) were mixed together. n =60000, 70.33g, 1.172mmol), DMAP (0.035g, 0.29mmol) were dissolved in a round-bottom flask. EDC (0.018g, 0.116mmol) was dissolved in 10mL-15mL of DMAc. The EDC-containing solution was slowly added dropwise to the reaction system under ice bath conditions. After activating the reaction under ice bath conditions for 30min, the reaction was moved to room temperature. After esterification for 8h, PI-PLA esterified product was obtained, with a molar ratio of polyimide block to polylactic acid block of 1:2.

[0118] (3) The PI-PLA esterification product obtained in step (2) is thermally imidized, coated on a glass plate, and cured successively at 80°C for 50 min; 160°C for 30 min; 250°C for 30 min to form a 25 μm film, wherein the molar ratio of polyimide block to polylactic acid block is 1:2.

[0119] (4) The PI-PLA film prepared in step (3) is placed in air for 10 days to obtain an insulating film with a porous structure.

[0120] Example 2

[0121] (1) Same as step (1) in Example 1;

[0122] (2) The PI slurry (2g, 0.58mmol) and PLA slurry (M) synthesized in step (1) were mixed together. n =80000, 93.76g, 1.172mmol), DMAP (0.035g, 0.29mmol) were dissolved in a round-bottom flask. EDC (0.018g, 0.116mmol) was dissolved in 10mL-15mL of DMAc. The EDC-containing solution was slowly added dropwise to the reaction system under ice bath conditions. After activating the reaction under ice bath conditions for 30min, the reaction was moved to room temperature. After esterification for 12h, PI-PLA esterified product was obtained, with a molar ratio of polyimide block to polylactic acid block of 1:2.

[0123] (3) Same as step (3) in Example 1;

[0124] (4) The PI-PLA film prepared in step (3) is placed in air for 10 days to obtain an insulating film with a porous structure.

[0125] Example 3

[0126] (1) Same as step (1) in Example 1;

[0127] (2) The PI slurry (2g, 0.58mmol) and PLA slurry (M) synthesized in step (1) were mixed together. n =110000, 128.92g, 1.172mmol), DMAP (0.035g, 0.29mmol) were dissolved in a round-bottom flask. EDC (0.018g, 0.116mmol) was dissolved in 10mL-15mL of DMAc. The EDC-containing solution was slowly added dropwise to the reaction system under ice bath conditions. After activating the reaction under ice bath conditions for 30min, the reaction was moved to room temperature. After esterification for 15h, PI-PLA esterified product was obtained, with a molar ratio of polyimide block to polylactic acid block of 1:2.

[0128] (3) Same as step (3) in Example 1;

[0129] (4) The PI-PLA film prepared in step (3) is placed in air for 10 days to obtain an insulating film with a porous structure.

[0130] Example 4

[0131] (1) 3,3'-dihydroxybenzidine (0.1 mol, 21.62 g) and 6FDA (0.105 mol, 46.64 g) were added to DMAc (159 g, 30% solids content), and reacted at 25°C for 10 h until completely dissolved to obtain PI slurry (M n =184597, viscosity is 104587 cps;

[0132] (2) The PI slurry (2g, 0.881mmol) and PLA slurry (M) synthesized in step (1) were mixed together. n =60000, 105.66g, 1.761mol), DMAP (0.0538g, 0.0441mmol) were dissolved in a round-bottom flask. EDC (0.0274g, 0.1762mmol) was dissolved in 10mL-15mL of DMAc. The EDC-containing solution was slowly added dropwise to the reaction system under ice bath conditions. After activating the reaction under ice bath conditions for 30min, the reaction was moved to room temperature. After esterification for 8h, PI-PLA esterified product was obtained, with a molar ratio of polyimide block to polylactic acid block of 1:2.

[0133] (3) Same as step (3) in Example 1;

[0134] (4) The PI-PLA film prepared in step (3) is placed in air for 10 days to obtain an insulating film with a porous structure.

[0135] Example 5

[0136] (1) 3,3'-dihydroxybenzidine (0.1 mol, 21.62 g) and 6FDA (0.105 mol, 46.64 g) were added to DMAc (614 g, 10% solid content), and reacted at 25°C for 10 h until completely dissolved to obtain PI slurry (M n =108123, viscosity is 104587 cps;

[0137] (2) The PI slurry (2g, 2.930mmol) and PLA slurry (M) synthesized in step (1) were mixed together. n=60000, 35.16g, 0.586mmol), DMAP (0.178g, 1.465mmol) were dissolved in a round-bottom flask. EDC (0.091g, 0.586mmol) was dissolved in 10mL-15mL of DMAc. The EDC-containing solution was slowly added dropwise to the reaction system under ice bath conditions. After activating the reaction under ice bath conditions for 30min, the reaction was moved to room temperature. After esterification for 8h, PI-PLA esterified product was obtained, with a molar ratio of polyimide block to polylactic acid block of 1:2.

[0138] (3) Same as step (3) in Example 1;

[0139] (4) The PI-PLA film prepared in step (3) is placed in air for 10 days to obtain an insulating film with a porous structure.

[0140] Example 6

[0141] (1) 3,3'-dihydroxybenzidine (0.1 mol, 21.62 g) and 6FCDA (0.105 mol, 46.64 g) were added to DMAc (273 g, 20% solid content), and reacted at 25 °C for 10 h until completely dissolved to obtain PI slurry (M n =152347, viscosity is 104587 cps;

[0142] (2) Same as step (2) in Example 1, to obtain PI-PLA esterification product, with a molar ratio of polyimide block and polylactic acid block of 1:2;

[0143] (3) Same as step (3) in Example 1;

[0144] (4) The PI-PLA film prepared in step (3) is placed in air for 10 days to obtain an insulating film with a porous structure.

[0145] Example 7

[0146] (1) Same as step (1) in Example 1;

[0147] (2) Same as step (2) in Example 1;

[0148] (3) Same as step (3) in Example 1;

[0149] (4) The PI-PLA film prepared in step (3) is placed in air for 20 days to obtain an insulating film with a porous structure.

[0150] Example 8

[0151] (1) Same as step (1) in Example 1;

[0152] (2) Same as step (2) in Example 1;

[0153] (3) Same as step (3) in Example 1;

[0154] (4) The PI-PLA film prepared in step (3) is placed in air for 30 days to obtain an insulating film with a porous structure.

[0155] Example 9

[0156] (1) Same as step (1) in Example 1;

[0157] (2) Same as step (2) in Example 1;

[0158] (3) Same as step (3) in Example 1;

[0159] (4) The PI-PLA film prepared in step (3) is placed in air for 40 days to obtain an insulating film with a porous structure.

[0160] Example 10

[0161] (1) Same as step (1) in Example 1;

[0162] (2) The PI slurry (2g, 0.58mmol) and PLA slurry (M) synthesized in step (1) were mixed together. n =60000, 87.6g, 1.46mmol), DMAP (0.035g, 0.29mmol) were dissolved in a round-bottom flask. EDC (0.018g, 0.116mmol) was dissolved in 10mL-15mL of DMAc. The EDC-containing solution was slowly added dropwise to the reaction system under ice bath conditions. After activating the reaction under ice bath conditions for 30min, the reaction was moved to room temperature. After esterification for 8h, PI-PLA esterified product was obtained, in which the molar ratio of polyimide block to polylactic acid block was 1:2.5.

[0163] (3) Same as step (3) in Example 1;

[0164] (4) The PI-PLA film prepared in step (3) is placed in air for 10 days to obtain an insulating film with a porous structure.

[0165] Example 11

[0166] (1) Same as step (1) in Example 1;

[0167] (2) The PI slurry (2g, 0.58mmol) and PLA slurry (M) synthesized in step (1) were mixed together. n=60000, 35.164g, 0.586mmol), DMAP (0.035g, 0.29mmol) were dissolved in a round-bottom flask. EDC (0.018g, 0.116mmol) was dissolved in 10mL-15mL of DMAc. The EDC-containing solution was slowly added dropwise to the reaction system under ice bath conditions. After activating the reaction under ice bath conditions for 30min, the reaction was moved to room temperature. After esterification for 8h, PI-PLA esterified product was obtained, with a molar ratio of polyimide block to polylactic acid block of 1:1.

[0168] (3) Same as step (3) in Example 1;

[0169] (4) The PI-PLA film prepared in step (3) is placed in air for 30 days to obtain an insulating film with a porous structure.

[0170] Example 12

[0171] The difference between Example 13 and Example 1 is that 6FDA is replaced with pyromellitic dianhydride (PMDA).

[0172] Comparative Example 1

[0173] The difference between Comparative Example 1 and Example 1 is that step (2) is omitted, and the PI slurry prepared in step (1) is directly subjected to steps (3) and (4).

[0174] Comparative Example 2

[0175] Purchased PLA (Mn=60000) was cast into a film and left in the air for 10 days to obtain an insulating film.

[0176] Test case

[0177] The insulating films prepared in Examples 1-12 and Comparative Examples 1-2 were subjected to compositional, mechanical, thermal, and dielectric property tests, specifically including dielectric constant (Dk), dielectric loss (Df), tensile strength, elongation at break, and coefficient of thermal expansion (CTE). The test methods are as follows:

[0178] Composition testing: The tests were performed according to the general rules of organic mass spectrometry analysis method JY / T 003-1996.

[0179] Porosity testing method: The solvent immersion method is used for testing. First, the weight m of the insulating film is weighed. Based on the density of the polymer, the volume of the film is calculated and recorded as V1. The insulating film is placed in 10 mL of deionized water at room temperature for 30 min and then removed. The volume of the remaining water is measured and the reduced water volume is recorded as V2. Porosity / % = V2 × 100% / (V1 + V2).

[0180] Tensile strength and elongation at break: tested according to GB / T 1040.3-2006.

[0181] Coefficient of thermal expansion: Measured using a Mettler TMA / SDTA 2+ static thermomechanical analyzer at a temperature range of 50-200℃ and a heating rate of 10℃ / min.

[0182] Dielectric constant and dielectric loss: tested according to GB / T31838.6-2021.

[0183] The results are shown in Table 1. The insulating films prepared in Examples 1-12 showed better performance than those prepared in Comparative Examples 1-2. In Comparative Example 1, the polyimide could not form a porous structure after being placed in air, resulting in a higher dielectric constant, a lower coefficient of thermal expansion, poor heat dissipation, and structural instability. In Comparative Example 2, using only polylactic acid as the insulating film resulted in lower tensile strength and elongation at break, as well as poor kinetic properties. Moreover, the coefficient of thermal expansion was higher, making it prone to cracking or delamination under large temperature differences.

[0184] Table 1

[0185]

[0186] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0187] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. An electric motor, characterized in that, The rated voltage of the motor is not less than 800 V, and the motor includes: enameled wire, the enameled wire including: conductor; An insulating film covering the outer peripheral surface of the conductor, the insulating film comprising a block polymer comprising: polyimide blocks and polylactic acid blocks; The insulating film has a porous structure; Under electromagnetic waves with a frequency of 1 kHz, the dielectric constant of the insulating film is 2.01~2.28; The tensile strength of the insulating film is 180 MPa ~ 222 MPa; The polyimide block is generated by reacting at least a dianhydride monomer and a diamine monomer, wherein the diamine monomer has a hydroxyl group, and the hydroxyl group can undergo an esterification reaction with the carboxyl group in the polylactic acid block; The method for preparing the insulating film includes: The insulating base film is degraded to obtain the insulating film with a porous structure; The insulating base film includes a second block polymer, which includes polyimide blocks and polylactic acid blocks. The number-average molecular weight of the polyimide blocks is 105,000 to 200,000. The number-average molecular weight of the polylactic acid blocks is 60,000 to 120,000. The method for preparing the second block polymer includes: The diamine monomer and the dianhydride monomer are polymerized in an organic solvent to obtain a polymer slurry; The polymer slurry is esterified with polylactic acid to obtain the esterified product; The esterification product was subjected to imidization to obtain the second block polymer; The imidization treatment includes: 70℃~90℃ for 40 min~60 min, 150℃~170℃ for 20 min~40 min, and 240℃~260℃ for 20 min~40 min. The degradation treatment includes placing the insulating base film at a temperature of 20℃~30℃ for 10 days to 30 days.

2. The motor according to claim 1, characterized in that, The porosity of the porous structure is 20% to 80%.

3. The motor according to claim 1, characterized in that, The dianhydride monomer further has a fluorine group; And / or, the dianhydride monomer comprises at least one of the following: hexafluoroisopropylphthalic anhydride, 9,9-bis(trifluoromethyl)-2,3,6,7-oxanthracene tetracarboxylic dianhydride, 1,4-bis(3,4-dicarboxytrifluorophenoxy)tetrafluorophenyl dianhydride, 1,4-bis(trifluoromethyl)-2,3,5,6-benzenetetracarboxylic dianhydride, 1,4-difluoropyromellitic dianhydride, and 2,2-bis[4-(3,4-dicarboxytrifluorophenoxy)phenyl]hexafluoropropane dianhydride; And / or, the diamine monomer comprises at least one of 3,3'-dihydroxybenzidine, 4,6-diaminoresorcinol dihydrochloride, and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane.

4. The motor according to claim 1, characterized in that, The insulating film satisfies at least one of the following conditions: Under electromagnetic waves with a frequency of 1 kHz, the dielectric loss factor of the insulating film is 0.001~0.006; The tensile strength of the insulating film is 180 MPa ~ 222 MPa; The elongation at break of the insulating film is 190.4%~211.2%; The coefficient of thermal expansion of the insulating film is 60.02 ppm / ℃ to 71.23 ppm / ℃.

5. The motor according to claim 1, characterized in that, The molar ratio of the polyimide block and the polylactic acid block in the second block polymer is 1:(2~2.5).

6. The motor according to claim 1, characterized in that, The organic solvent includes at least one of N,N-dimethylacetamide, N-methylpyrrolidone, m-cresol, and 1,4-butyrolactone. And / or, the polymerization treatment temperature is 25°C to 30°C; And / or, the polymerization process takes 8 h to 10 h; And / or, the viscosity of the polymer slurry is 90,000 cps to 110,000 cps.

7. The motor according to claim 1, characterized in that, The esterification process includes: The polymer slurry, catalyst, and polylactic acid-containing slurry are mixed to obtain a mixture. The dehydrating agent solution is added dropwise to the mixture to carry out an activation reaction, resulting in an activated solution. The activated solution was subjected to an esterification reaction to obtain the esterified product.

8. The motor according to claim 7, characterized in that, The catalyst comprises one or more of 4-dimethylaminopyridine, pyridine, triethylamine, and N-methylpiperidine; And / or, the dehydrating agent comprises one or more of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N,N-dicyclohexylcarbodiimide; And / or, the solvent contained in the dehydrating agent solution includes one or more of N,N-dimethylacetamide, N-methylpyrrolidone, m-cresol, and 1,4-butyrolactone; And / or, the activation reaction is carried out at a temperature of -2°C to 2°C; And / or, the activation reaction takes 20 min to 40 min; And / or, the temperature of the esterification reaction is 25°C to 30°C; And / or, the esterification reaction takes 8 h to 15 h.

9. A vehicle, characterized in that, include: The motor according to any one of claims 1-8.

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