A kind of polyimide composite film insulated copper busbar and preparation method thereof

Abstract

The invention relates to a polyimide composite film insulated copper busbar and a preparation method thereof, belonging to the technical field of copper busbars. The invention comprises the following steps: obtaining a polyimide composite film insulated copper busbar through precision wrapping, high-temperature sintering, mechanical bending, laser head stripping, vacuum heat treatment, standing and inspection; combining a boric acid crosslinking agent with a fluorinated polyimide to obtain a polyimide oligomer; combining the polyimide oligomer with a hydroxylated multi-walled carbon nanotube to obtain a modified polyimide; and mixing the modified polyimide with polytetrafluoroethylene to obtain a polyimide composite film. In the technical scheme of the invention, combining the boric acid crosslinking agent with the fluorinated polyimide not only improves the interface adhesion of the polyimide composite film, but also enhances its thermal stability, hydrolysis resistance and mechanical properties; combining the polyimide oligomer with the hydroxylated multi-walled carbon nanotube further improves the wear resistance and mechanical properties of the polyimide composite film, thereby improving the comprehensive properties of the polyimide composite film as a whole.

Description

Technical Field

[0001] The invention belongs to the technical field of copper busbars, and in particular relates to a polyimide composite film insulated copper busbar and a preparation method thereof. Background Art

[0002] As the key conductor in the new energy battery pack, copper / aluminum busbars need to be completely adjusted and upgraded in terms of current carrying, high temperature resistance, insulation, voltage resistance, and lightweight. The external insulation of copper / aluminum busbars mostly adopts PVC dipping molding process or ceramic / mica tape wrapping process. The dipping process is limited by its own process, the thickness uniformity is not easy to control, the finished product is heavy, and mold assistance is required, and the cost is relatively high; the single layer thickness of ceramic / mica tape is relatively thick, and due to its own material limitations, a large amount of debris is easily generated during processing, and the weight of the finished product is also large. Polyimide is a material with excellent comprehensive performance. It is a type of polymer material containing imide rings on the main chain. It has excellent heat resistance, low temperature resistance, solvent resistance, self-lubrication and flame retardancy. Applying it to the external insulation of copper / aluminum busbars can effectively improve the various performance and requirements of copper / aluminum busbars.

[0003] Polyimide composite film coated copper / aluminum busbars still has the following defects: 1) Polyimide has poor hydrolysis resistance and will absorb water and swell in a high humidity environment, which will cause a significant decrease in the mechanical properties of the polyimide composite film; 2) Polyimide mostly uses diphenylene amine or phthalic anhydride as the basic monomer, and has a large molecular chain rigidity, and its toughness is difficult to meet the requirements; 3) Glue is usually applied on both or one side of polyimide to improve the performance of polyimide composite film, but the interface adhesion between polyimide and the glue material is poor, which leads to a decrease in the adhesion with the copper / aluminum busbar, affecting the final performance of the product. Summary of the invention

[0004] The object of the present invention is to provide a polyimide composite film insulated copper busbar and a preparation method thereof. A boric acid crosslinking agent is combined with a fluorinated polyimide to obtain a polyimide oligomer; the amine group in 3-aminophenylboronic acid can be combined with the carboxyl group in the fluorinated polyimide, and the 3-aminophenylboronic acid is grafted to both ends of the fluorinated polyimide, which can not only improve the interfacial adhesion of the polyimide composite film, but also improve its thermal stability, chemical stability and high temperature resistance, and also provide reaction sites for subsequent reactions. The fluorinated polyimide has a fluorine-containing group (trifluoromethyl), which is beneficial to reducing the dielectric constant of the polyimide composite film and can improve the hydrolysis resistance of the polyimide composite film; the polyimide oligomer is combined with a hydroxylated multi-walled carbon nanotube to obtain to modified polyimide; not only the dispersibility of hydroxylated multi-walled carbon nanotubes is improved and their agglomeration is prevented, but also the mechanical properties of the polyimide composite film are improved, and the wear resistance and wettability of the polyimide composite film are enhanced; the modified polyimide is mixed with polytetrafluoroethylene to obtain a polyimide composite film; the interface adhesion between polyimide and polytetrafluoroethylene is further improved, and the adhesion between the polyimide composite film and the conductor is enhanced; the polyimide composite film is wrapped around the surface of the conductor, and subjected to high-temperature sintering, mechanical bending, laser stripping and vacuum heat treatment, finally a polyimide composite film insulated copper bus is obtained, which can improve the high temperature resistance, thermal stability, mechanical properties and wear resistance of the insulated copper bus, and the obtained insulated copper bus has good comprehensive performance.

[0005] Technical problems to be solved by the present invention: The following defects still exist in the polyimide composite film coated copper busbar / aluminum busbar: 1) The hydrolysis resistance of polyimide is poor, and it will absorb water and swell in a high humidity environment, thereby causing a significant decrease in the mechanical properties of the polyimide composite film; 2) Polyimide mostly uses diphenylene amine or phthalic anhydride as the basic monomer, and has a large molecular chain rigidity, and its toughness is difficult to meet the requirements; 3) Usually, glue is applied on both sides or one side of polyimide to improve the performance of the polyimide composite film, but the interface adhesion between polyimide and the glue material is poor, which leads to a decrease in the adhesion with the copper busbar / aluminum busbar, affecting the final performance of the product.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a polyimide composite film insulated copper busbar comprises the following steps:

[0008] S1: Precision wrapping: Use a high-precision wrapping machine to wrap the film around the conductor surface;

[0009] S2: high temperature sintering: using a high temperature sintering furnace to sinter the conductor in step S1 at high temperature;

[0010] S3: Mechanical bending: bending the conductor in step S2 by a bending machine;

[0011] S4: Laser stripping: using laser equipment to strip the insulation of the conductor end in step S3;

[0012] S5: vacuum heat treatment: placing the conductor in step S4 into a high-temperature vacuum box for vacuum heat treatment;

[0013] S6: taking out the conductor in step S5, and obtaining a polyimide composite film insulated copper busbar after standing and inspecting;

[0014] The film is a polyimide composite film;

[0015] The preparation method of the polyimide composite film comprises the following steps:

[0016] A1: combining a boric acid crosslinker with a fluorinated polyimide to obtain a polyimide oligomer;

[0017] A2: combining polyimide oligomers with hydroxylated multi-walled carbon nanotubes to obtain modified polyimide;

[0018] A3: The modified polyimide is mixed with polytetrafluoroethylene to obtain a polyimide composite film.

[0019] Furthermore, step S1 is specifically as follows:

[0020] Precision wrapping: Use a high-precision wrapping machine to wrap the film on the conductor surface. The film thickness is 0.03-0.06mm, the film width is 3.5-25mm, the wrapping line speed is 0.2-3m / min, the wrapping head speed of the wrapping machine is 100-500rpm, the wrapping film angle is 17-80°, and the wrapping film tension is 100-2000g.

[0021] Furthermore, the conductor is a copper bar or an aluminum bar.

[0022] Furthermore, step S2 is specifically as follows:

[0023] High temperature sintering: The conductor in step S1 is sintered at high temperature using a high temperature sintering furnace, the sintering speed is 0.5-8 m / min, the sintering temperature is 200-300° C. After sintering, the surface of the conductor is rolled using a roller.

[0024] Furthermore, step S3 is specifically as follows:

[0025] Mechanical bending: The conductor in step S2 is bent by a bending machine, and the bending shape is a 90° arc bend or a 90° right-angle bend.

[0026] Further, step S4 is specifically as follows:

[0027] Laser stripping: Use laser equipment to strip the insulation of the conductor end in step S3 to expose the conductive part for later installation and use.

[0028] Furthermore, step S5 is specifically as follows:

[0029] Vacuum heat treatment: Place the conductor in step S4 into a high-temperature vacuum box for vacuum heat treatment at a vacuum pressure of 0.5-100 Pa, a temperature of 65-180° C., and a holding time of 0.5-5 h.

[0030] Furthermore, step A1 is specifically as follows:

[0031] Add the boric acid crosslinking agent into the fluorinated polyimide and stir for 3-5 hours to obtain a polyimide oligomer.

[0032] In the above reaction process, the boric acid crosslinker has an amino group and the fluorinated polyimide has a carboxyl group. The amino group in the boric acid crosslinker can combine with the carboxyl group in the boric acid crosslinker to graft the boric acid crosslinker to both ends of the fluorinated polyimide to obtain a polyimide oligomer.

[0033] Furthermore, the boric acid cross-linking agent is 3-aminophenylboronic acid.

[0034] Furthermore, the mass ratio of the boric acid crosslinking agent to the fluorinated polyimide is 1.5-2.5:0.5-1.5.

[0035] Furthermore, the preparation method of the fluorinated polyimide comprises the following steps:

[0036] The diamine and the dianhydride are added to N,N-dimethylformamide under an argon atmosphere, and then stirred at 0±2° C. for 5-7 hours to obtain a fluorinated polyimide.

[0037] In the above reaction process, the diamine has amino groups at both ends, and the dianhydride has an acid anhydride group. The amino group in the diamine can combine with the acid anhydride in the dianhydride to finally generate a fluorinated polyimide.

[0038] Furthermore, the diamine is 4,4′-(hexafluoroisopropyl)bis(p-phenoxy)diphenylamine.

[0039] Furthermore, the dianhydride is 4,4-hexafluoroisopropyl diphthalic anhydride.

[0040] Furthermore, the mass ratio of the diamine, dianhydride and N,N-dimethylformamide is 1:1:15-20.

[0041] Furthermore, step A2 is specifically as follows:

[0042] The hydroxylated multi-walled carbon nanotubes and the polyimide oligomer in step A1 are added to anhydrous ethanol, and then stirred at 55-65° C. for 3-5 hours, filtered, washed with deionized water, and finally dried at 75-85° C. to obtain a modified polyimide.

[0043] In the above reaction process, the hydroxylated multi-walled carbon nanotubes have hydroxyl groups, and the boric acid crosslinking agent in the polyimide oligomer has boric acid groups. The boric acid groups can combine with the hydroxyl groups on the hydroxylated multi-walled carbon nanotubes, so that the hydroxylated multi-walled carbon nanotubes are grafted into the polyimide oligomer, and finally a modified polyimide is obtained.

[0044] Furthermore, the mass ratio of the hydroxylated multi-walled carbon nanotubes, the polyimide oligomer in step A1, and anhydrous ethanol is 0.4-0.6: 2-2.5, 50-70.

[0045] Furthermore, the method for preparing hydroxylated multi-walled carbon nanotubes comprises the following steps:

[0046] The multi-walled carbon nanotubes are added to the acid mixture, and then stirred in a water bath at 55-65° C. for 11-13 hours, filtered, washed with deionized water until the pH value of the mixture reaches 6-7, and dried at 75-85° C. to obtain hydroxylated multi-walled carbon nanotubes.

[0047] Furthermore, the mass ratio of the multi-walled carbon nanotubes to the acid mixture is 4.5-5.5:35-45.

[0048] Furthermore, the acid mixture is composed of concentrated sulfuric acid and concentrated nitric acid mixed in a mass ratio of 3:1.

[0049] Furthermore, step A3 is specifically as follows:

[0050] The modified polyimide and 2-dimethylaminoethanol in step A2 are added to deionized water and mixed evenly to obtain system A. The polytetrafluoroethylene dispersion is added to deionized water to obtain system B. Then, system A and system B are mixed, coated on a clean glass plate, and thermal imidization is performed under vacuum conditions to finally obtain a polyimide composite film.

[0051] Furthermore, the mass ratio of the modified polyimide, 2-dimethylaminoethanol and deionized water in step A2 is 14-16: 3-3.5: 250-300.

[0052] Furthermore, the vacuum condition is 0.01-0.03Pa.

[0053] Furthermore, the thermal imidization process is: heating at 75-85°C for 2-4h, heating at 145-155°C for 2-4h, heating at 195-205°C for 1-3h and heating at 295-305°C for 1-3h.

[0054] Beneficial effects of the present invention:

[0055] (1) In the technical scheme of the present invention, a boric acid crosslinking agent is combined with a fluorinated polyimide to obtain a polyimide oligomer; the boric acid crosslinking agent is 3-aminophenylboronic acid, which has both an amino group and a boric acid group. The amino group in 3-aminophenylboronic acid can be combined with the carboxyl group in the fluorinated polyimide. Grafting 3-aminophenylboronic acid to both ends of the fluorinated polyimide can not only improve the interfacial adhesion of the polyimide composite film, but also improve its thermal stability, chemical stability and high temperature resistance. At the same time, the boric acid group in 3-aminophenylboronic acid also provides a reaction site for subsequent reactions, further enhancing the performance of the polyimide composite film; the fluorinated polyimide has a fluorine-containing group (trifluoromethyl), and the trifluoromethyl group with a large spatial volume can The close stacking of polyimide molecular chains can be effectively inhibited, and the fluorine atom has a strong electron-withdrawing ability, which can reduce the molecular polarizability of polyimide. The introduction of trifluoromethyl into polyimide is beneficial to reducing the dielectric constant of the polyimide composite film. At the same time, the fluorine atom has a strong hydrophobicity, which can improve the hydrolysis resistance of the polyimide composite film, and further enhance its toughness and performance stability; the polyimide oligomer is combined with the hydroxylated multi-walled carbon nanotube to obtain a modified polyimide; the hydroxylated multi-walled carbon nanotube is combined with the polyimide oligomer, which not only improves the dispersibility of the hydroxylated multi-walled carbon nanotube, prevents its agglomeration, and improves the mechanical properties of the polyimide composite film, but also enhances the wear resistance and wettability of the polyimide composite film.

[0056] (2) In the technical scheme of the present invention, the modified polyimide is mixed with polytetrafluoroethylene to obtain a polyimide composite film; the modified polyimide is mixed with polytetrafluoroethylene and subjected to thermal imidization to obtain a polyimide composite film, which further improves the interfacial adhesion between polyimide and polytetrafluoroethylene, and also enhances the adhesion between the polyimide composite film and the conductor, effectively improving the insulation performance of the copper busbar / aluminum busbar; through precision wrapping, high-temperature sintering, mechanical bending, laser stripping and vacuum heat treatment, a polyimide composite film insulated copper busbar is finally obtained, which effectively improves the mechanical properties, thermal stability and wear resistance of the insulated copper busbar, and has good comprehensive performance.

[0057] (3) In the technical scheme of the present invention, a boric acid crosslinking agent is combined with a fluorinated polyimide, and then combined with a hydroxylated multi-walled carbon nanotube to obtain a modified polyimide, which is then mixed with polytetrafluoroethylene to obtain a polyimide composite film. The polyimide composite film is wrapped around the surface of the conductor, and subjected to high-temperature sintering, mechanical bending, laser stripping and vacuum heat treatment to finally obtain a polyimide composite film insulated copper busbar. This can not only improve the high temperature resistance, thermal stability and mechanical properties of the insulated copper busbar, but also enhance the performance stability and wear resistance of the insulated copper busbar. At the same time, the interface adhesion between the obtained polyimide composite film and the copper busbar / aluminum busbar is good, and the comprehensive performance of the final product is good. DETAILED DESCRIPTION

[0058] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] The specific parameters of the raw materials used in the present invention are as follows:

[0060] Multi-walled carbon nanotubes, No. NM000482, were provided by Beijing Solaibao Technology Co., Ltd.; 4,4-hexafluoroisopropyl diphthalic anhydride and 4,4′-(hexafluoroisopropyl)bis(p-phenyloxy)diphenylamine were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; 3-aminophenylboric acid was provided by Beijing Inokai Technology Co., Ltd.; polytetrafluoroethylene dispersion was made from 3M Dyneon PTFE TF 5050Z (solid content 60wt%, average particle size 205nm) from the United States.

[0061] Example 1

[0062] Preparation of polyimide composite film insulated copper busbar, the specific steps are:

[0063] S1: Precision wrapping: A high-precision wrapping machine is used to wrap the film on the surface of the conductor. The film thickness is 0.03mm, the film width is 3.5mm, the wrapping line speed is 0.2m / min, the wrapping head speed of the wrapping machine is 100rpm, the wrapping angle of the film is 17°, and the wrapping tension of the film is 100g. The film is a polyimide composite film and the conductor is an aluminum bar.

[0064] S2: high temperature sintering: the conductor in step S1 is sintered at high temperature in a high temperature sintering furnace, the sintering speed is 0.5 m / min, the sintering temperature is 200°C, and after sintering, the conductor surface is rolled by a roller, the roller surface roughness is 0.1 μm, and the rolling pressure is 80 MPa;

[0065] S3: Mechanical bending: The conductor in step S2 is bent by a bending machine, and the bending shape is a 90° right angle bend;

[0066] S4: Laser stripping: Use laser equipment to strip the insulation of the conductor end in step S3 to expose the conductive part for later installation and use;

[0067] S5: Vacuum heat treatment: Place the conductor in step S4 into a high-temperature vacuum box for vacuum heat treatment at a vacuum pressure of 0.5 Pa, a temperature of 65° C., and a holding time of 5 h;

[0068] S6: taking out the conductor in step S5, and obtaining a polyimide composite film insulated copper busbar after standing and inspecting;

[0069] Preparation of polyimide composite membrane, the specific steps are:

[0070] A1: According to the mass ratio of 3-aminophenylboric acid to fluorinated polyimide being 1.5:0.5, 3-aminophenylboric acid was added to fluorinated polyimide and stirred for 3 hours to obtain a polyimide oligomer;

[0071] The preparation method of fluorinated polyimide comprises the following steps:

[0072] According to the mass ratio of 4,4′-(hexafluoroisopropyl)bis(p-phenyloxy)diphenylamine, 4,4-hexafluoroisopropyl diphthalic anhydride and N,N-dimethylformamide being 1:1:15, 4,4′-(hexafluoroisopropyl)bis(p-phenyloxy)diphenylamine and 4,4-hexafluoroisopropyl diphthalic anhydride are added to N,N-dimethylformamide under argon atmosphere, and then stirred at 2°C for 5 hours to obtain a fluorinated polyimide;

[0073] A2: According to the mass ratio of hydroxylated multi-walled carbon nanotubes, the polyimide oligomer in step A1, and anhydrous ethanol being 0.4:2:50, the hydroxylated multi-walled carbon nanotubes and the polyimide oligomer in step A1 are added to anhydrous ethanol, and then stirred at 55° C. for 3 hours, filtered, washed with deionized water (the mass of deionized water is equal to that of anhydrous ethanol), and finally dried at 75° C. for 24 hours to obtain a modified polyimide;

[0074] The method for preparing hydroxylated multi-walled carbon nanotubes comprises the following steps:

[0075] According to the mass ratio of multi-walled carbon nanotubes to the acid mixture of 4.5:35, the multi-walled carbon nanotubes are added to the acid mixture, and then stirred in a water bath at 55°C for 11 hours, filtered, washed with deionized water until the pH value of the mixture reaches 6, and dried at 75°C for 24 hours to finally obtain hydroxylated multi-walled carbon nanotubes, wherein the acid mixture is composed of concentrated sulfuric acid and concentrated nitric acid mixed in a mass ratio of 3:1;

[0076] A3: According to the mass ratio of the modified polyimide, 2-dimethylaminoethanol and deionized water in step A2 being 14:3:250, the modified polyimide and 2-dimethylaminoethanol in step A2 are added to deionized water and mixed evenly to obtain system A, the polytetrafluoroethylene dispersion is added to deionized water and diluted to 10wt% to obtain system B, and then system A and system B are mixed, coated on a clean glass plate, and thermal imidization is performed at 0.01Pa, and heated at 75°C for 2h, 145°C for 2h, 195°C for 1h, and 295°C for 1h in sequence to finally obtain a polyimide composite film.

[0077] Example 2

[0078] Preparation of polyimide composite film insulated copper busbar, the specific steps are:

[0079] S1: Precision wrapping: A high-precision wrapping machine is used to wrap the film on the surface of the conductor. The film thickness is 0.05mm, the film width is 15mm, the wrapping line speed is 1.5m / min, the wrapping head speed of the wrapping machine is 300rpm, the wrapping angle of the film is 60°, and the wrapping tension of the film is 1000g. The film is a polyimide composite film and the conductor is a copper busbar.

[0080] S2: high temperature sintering: the conductor in step S1 is sintered at high temperature in a high temperature sintering furnace, the sintering speed is 4 m / min, the sintering temperature is 250°C, and after sintering, the conductor surface is rolled with a roller, the roller surface roughness is 0.3 μm, and the rolling pressure is 90 MPa;

[0081] S3: Mechanical bending: The conductor in step S2 is bent by a bending machine, and the bending shape is a 90° arc bend;

[0082] S4: Laser stripping: Use laser equipment to strip the insulation of the conductor end in step S3 to expose the conductive part for later installation and use;

[0083] S5: Vacuum heat treatment: Place the conductor in step S4 into a high-temperature vacuum box for vacuum heat treatment at a vacuum pressure of 60 Pa, a temperature of 120° C., and a holding time of 3 h;

[0084] S6: taking out the conductor in step S5, and obtaining a polyimide composite film insulated copper busbar after standing and inspecting;

[0085] Preparation of polyimide composite membrane, the specific steps are:

[0086] A1: According to the mass ratio of 3-aminophenylboric acid to fluorinated polyimide being 2:1, 3-aminophenylboric acid was added to fluorinated polyimide and stirred for 4 hours to obtain a polyimide oligomer;

[0087] The preparation method of fluorinated polyimide comprises the following steps:

[0088] According to the mass ratio of 4,4′-(hexafluoroisopropyl)bis(p-phenyloxy)diphenylamine, 4,4-hexafluoroisopropyl diphthalic anhydride and N,N-dimethylformamide being 1:1:18, 4,4′-(hexafluoroisopropyl)bis(p-phenyloxy)diphenylamine and 4,4-hexafluoroisopropyl diphthalic anhydride are added to N,N-dimethylformamide under argon atmosphere, and then stirred at 0°C for 6 hours to obtain a fluorinated polyimide;

[0089] A2: According to the mass ratio of hydroxylated multi-walled carbon nanotubes, the polyimide oligomer in step A1, and anhydrous ethanol being 0.5:2.3:60, the hydroxylated multi-walled carbon nanotubes and the polyimide oligomer in step A1 are added to anhydrous ethanol, and then stirred at 60° C. for 4 hours, filtered, washed with deionized water (the mass of deionized water is equal to that of anhydrous ethanol), and finally dried at 80° C. for 24 hours to obtain a modified polyimide;

[0090] The method for preparing hydroxylated multi-walled carbon nanotubes comprises the following steps:

[0091] According to the mass ratio of multi-walled carbon nanotubes to the acid mixture of 5:40, the multi-walled carbon nanotubes are added to the acid mixture, and then stirred in a water bath at 60°C for 12 hours, filtered, washed with deionized water until the pH value of the mixture reaches 6.5, and dried at 80°C for 24 hours to finally obtain hydroxylated multi-walled carbon nanotubes, wherein the acid mixture is composed of concentrated sulfuric acid and concentrated nitric acid mixed in a mass ratio of 3:1;

[0092] A3: According to the mass ratio of the modified polyimide, 2-dimethylaminoethanol and deionized water in step A2 being 15:3.3:280, the modified polyimide and 2-dimethylaminoethanol in step A2 are added to deionized water and mixed evenly to obtain system A, the polytetrafluoroethylene dispersion is added to deionized water and diluted to 10wt% to obtain system B, and then system A and system B are mixed, coated on a clean glass plate, and thermal imidization is carried out at 0.02Pa, and heated at 80°C for 3h, 150°C for 3h, 200°C for 2h, and 300°C for 2h in sequence to finally obtain a polyimide composite film.

[0093] Example 3

[0094] Preparation of polyimide composite film insulated copper busbar, the specific steps are:

[0095] S1: Precision wrapping: A high-precision wrapping machine is used to wrap the film on the conductor surface. The film thickness is 0.06mm, the film width is 25mm, the wrapping line speed is 3m / min, the wrapping head speed of the wrapping machine is 500rpm, the wrapping angle is 80°, and the wrapping tension is 2000g. The film is a polyimide composite film and the conductor is an aluminum bar.

[0096] S2: high temperature sintering: the conductor in step S1 is sintered at high temperature in a high temperature sintering furnace, the sintering speed is 8 m / min, the sintering temperature is 300°C, and after sintering, the conductor surface is rolled with a roller, the roller surface roughness is 0.4 μm, and the rolling pressure is 100 MPa;

[0097] S3: Mechanical bending: The conductor in step S2 is bent by a bending machine, and the bending shape is a 90° right angle bend;

[0098] S4: Laser stripping: Use laser equipment to strip the insulation of the conductor end in step S3 to expose the conductive part for later installation and use;

[0099] S5: Vacuum heat treatment: Place the conductor in step S4 into a high-temperature vacuum box for vacuum heat treatment at a vacuum pressure of 100 Pa, a temperature of 180° C., and a holding time of 0.5 h;

[0100] S6: taking out the conductor in step S5, and obtaining a polyimide composite film insulated copper busbar after standing and inspecting;

[0101] Preparation of polyimide composite membrane, the specific steps are:

[0102] A1: 3-aminophenylboric acid was added to fluorinated polyimide at a mass ratio of 2.5:1.5, and stirred for 5 hours to obtain a polyimide oligomer;

[0103] The preparation method of fluorinated polyimide comprises the following steps:

[0104] According to the mass ratio of 4,4′-(hexafluoroisopropyl)bis(p-phenyloxy)diphenylamine, 4,4-hexafluoroisopropyl diphthalic anhydride and N,N-dimethylformamide being 1:1:20, 4,4′-(hexafluoroisopropyl)bis(p-phenyloxy)diphenylamine and 4,4-hexafluoroisopropyl diphthalic anhydride are added to N,N-dimethylformamide under argon atmosphere, and then stirred at -2°C for 7h to obtain a fluorinated polyimide;

[0105] A2: According to the mass ratio of hydroxylated multi-walled carbon nanotubes, the polyimide oligomer in step A1, and anhydrous ethanol being 0.6:2.5:70, the hydroxylated multi-walled carbon nanotubes and the polyimide oligomer in step A1 are added to anhydrous ethanol, and then stirred at 65° C. for 5 hours, filtered, washed with deionized water (the mass of deionized water is equal to that of anhydrous ethanol), and finally dried at 85° C. for 24 hours to obtain a modified polyimide;

[0106] The method for preparing hydroxylated multi-walled carbon nanotubes comprises the following steps:

[0107] According to the mass ratio of multi-walled carbon nanotubes to the acid mixture of 5.5:45, the multi-walled carbon nanotubes are added to the acid mixture, and then stirred in a water bath at 65°C for 13 hours, filtered, washed with deionized water until the pH value of the mixture reaches 7, and dried at 85°C for 24 hours to finally obtain hydroxylated multi-walled carbon nanotubes, wherein the acid mixture is composed of concentrated sulfuric acid and concentrated nitric acid mixed in a mass ratio of 3:1;

[0108] A3: According to the mass ratio of the modified polyimide, 2-dimethylaminoethanol and deionized water in step A2 being 16:3.5:300, the modified polyimide and 2-dimethylaminoethanol in step A2 are added to deionized water and mixed evenly to obtain system A, the polytetrafluoroethylene dispersion is added to deionized water and diluted to 10wt% to obtain system B, and then system A is mixed with system B, coated on a clean glass plate, and thermal imidization is carried out at 0.03Pa, and heated at 85°C for 4h, 155°C for 4h, 205°C for 3h and 305°C for 3h in sequence to finally obtain a polyimide composite film.

[0109] Comparative Example 1

[0110] The difference between this comparative example and Example 3 is that when preparing the polyimide composite film, the mass of 3-aminophenylboric acid and the like in step A1 is replaced by boric acid, and the remaining steps and raw materials are the same as those in Example 3.

[0111] Comparative Example 2

[0112] The difference between this comparative example and Example 3 is that when preparing the polyimide composite film, the mass of 4,4′-(hexafluoroisopropyl)bis(p-phenyloxy)diphenylamine in step A1 is replaced by 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and the remaining steps and raw materials are synchronized with Example 3.

[0113] Comparative Example 3

[0114] The difference between this comparative example and Example 3 is that when preparing the polyimide composite film, 3-aminophenylboric acid is not added, the fluorinated polyimide is directly combined with the hydroxylated multi-walled carbon nanotubes, and the remaining steps and raw materials are synchronized with Example 3;

[0115] Preparation of polyimide composite membrane, the specific steps are:

[0116] A1: According to the mass ratio of hydroxylated multi-walled carbon nanotubes, fluorinated polyimide and anhydrous ethanol being 0.6:2.5:70, hydroxylated multi-walled carbon nanotubes and fluorinated polyimide are added to anhydrous ethanol, and then stirred at 65°C for 5 hours, filtered, washed with deionized water (the mass of deionized water is equal to that of anhydrous ethanol), and finally dried at 85°C for 24 hours to obtain modified polyimide;

[0117] The preparation method of fluorinated polyimide comprises the following steps:

[0118] According to the mass ratio of 4,4′-(hexafluoroisopropyl)bis(p-phenyloxy)diphenylamine, 4,4-hexafluoroisopropyl diphthalic anhydride and N,N-dimethylformamide being 1:1:20, 4,4′-(hexafluoroisopropyl)bis(p-phenyloxy)diphenylamine and 4,4-hexafluoroisopropyl diphthalic anhydride are added to N,N-dimethylformamide under argon atmosphere, and then stirred at -2°C for 7h to obtain a fluorinated polyimide;

[0119] The method for preparing hydroxylated multi-walled carbon nanotubes comprises the following steps:

[0120] According to the mass ratio of multi-walled carbon nanotubes to the acid mixture of 5.5:45, the multi-walled carbon nanotubes are added to the acid mixture, and then stirred in a water bath at 65°C for 13 hours, filtered, washed with deionized water until the pH value of the mixture reaches 7, and dried at 85°C for 24 hours to finally obtain hydroxylated multi-walled carbon nanotubes, wherein the acid mixture is composed of concentrated sulfuric acid and concentrated nitric acid mixed in a mass ratio of 3:1;

[0121] A2: According to the mass ratio of the modified polyimide, 2-dimethylaminoethanol and deionized water in step A1 being 16:3.5:300, the modified polyimide and 2-dimethylaminoethanol in step A1 are added to deionized water and mixed evenly to obtain system A, the polytetrafluoroethylene dispersion is added to deionized water and diluted to 10wt% to obtain system B, and then system A is mixed with system B, coated on a clean glass plate, and thermal imidization is carried out at 0.03Pa, and heated at 85°C for 4h, 155°C for 4h, 205°C for 3h and 305°C for 3h in sequence to finally obtain a polyimide composite film.

[0122] Comparative Example 4

[0123] The difference between this comparative example and Example 3 is that when preparing the polyimide composite film, the mass of hydroxylated multi-walled carbon nanotubes in step A2 is replaced by multi-walled carbon nanotubes, and the remaining steps and raw materials are the same as those in Example 3.

[0124] Comparative Example 5

[0125] The difference between this comparative example and Example 3 is that, when preparing the polyimide composite film, the hydroxylated multi-walled carbon nanotubes are first combined with the fluorinated polyimide and then combined with 3-aminophenylboronic acid, and the remaining steps and raw materials are the same as those of Example 3;

[0126] Preparation of polyimide composite membrane, the specific steps are:

[0127] A1: According to the mass ratio of hydroxylated multi-walled carbon nanotubes, fluorinated polyimide and anhydrous ethanol being 0.6:2.5:70, hydroxylated multi-walled carbon nanotubes and fluorinated polyimide are added to anhydrous ethanol, and then stirred at 65°C for 5 hours, filtered, washed with deionized water (the mass of deionized water is equal to that of anhydrous ethanol), and finally dried at 85°C for 24 hours to obtain modified polyimide;

[0128] The preparation method of fluorinated polyimide comprises the following steps:

[0129] According to the mass ratio of 4,4′-(hexafluoroisopropyl)bis(p-phenyloxy)diphenylamine, 4,4-hexafluoroisopropyl diphthalic anhydride and N,N-dimethylformamide being 1:1:20, 4,4′-(hexafluoroisopropyl)bis(p-phenyloxy)diphenylamine and 4,4-hexafluoroisopropyl diphthalic anhydride are added to N,N-dimethylformamide under argon atmosphere, and then stirred at -2°C for 7h to obtain a fluorinated polyimide;

[0130] The method for preparing hydroxylated multi-walled carbon nanotubes comprises the following steps:

[0131] According to the mass ratio of multi-walled carbon nanotubes to the acid mixture of 5.5:45, the multi-walled carbon nanotubes are added to the acid mixture, and then stirred in a water bath at 65°C for 13 hours, filtered, washed with deionized water until the pH value of the mixture reaches 7, and dried at 85°C for 24 hours to finally obtain hydroxylated multi-walled carbon nanotubes, wherein the acid mixture is composed of concentrated sulfuric acid and concentrated nitric acid mixed in a mass ratio of 3:1;

[0132] A2: according to the mass ratio of 3-aminophenylboric acid to the modified polyimide in step A1 being 2.5:1.5, 3-aminophenylboric acid is added to the modified polyimide in step A1, and stirred for 5 hours to obtain a polyimide oligomer;

[0133] A3: According to the mass ratio of the polyimide oligomer, 2-dimethylaminoethanol and deionized water in step A2 being 16:3.5:300, the polyimide oligomer and 2-dimethylaminoethanol in step A2 are added to deionized water and mixed evenly to obtain system A, the polytetrafluoroethylene dispersion is added to deionized water and diluted to 10wt% to obtain system B, and then system A and system B are mixed, coated on a clean glass plate, and thermal imidization is carried out at 0.03Pa, and heated at 85°C for 4h, 155°C for 4h, 205°C for 3h and 305°C for 3h in sequence to finally obtain a polyimide composite film.

[0134] The polyimide composite films prepared in Examples 1-3 and Comparative Examples 1-5 are now tested for tensile strength, elongation at break, hydrolysis resistance and breakdown voltage; the tensile strength and elongation at break of the polyimide composite films prepared in Examples 1-3 and Comparative Examples 1-5 are tested on a universal testing machine at a tensile rate of 10 mm / min; the polyimide composite films prepared in Examples 1-3 and Comparative Examples 1-5 are placed in a vacuum oven, dried at 120°C for 10 hours, the mass of the film is obtained, and then placed in deionized water at 80°C for 72 hours, the film is taken out, dried at 80°C for 8 hours, and then placed in a vacuum oven, dried at 120°C for 10 hours, the mass of the film is obtained again, the hydrolysis percentage of the film after hydrolysis is calculated, and its hydrolysis resistance is tested; the breakdown voltage test is performed according to GB / T 1408.2-2016. The test results are shown in Table 1 below:

[0135] Table 1 Performance parameters of polyimide composite films obtained in Examples 1-3 and Comparative Examples 1-5

[0136]

[0137] It can be seen from the data in Table 1 above that, by comparing Comparative Examples 1-2 with Example 3, it can be seen that the mass of 3-aminophenylboric acid and the like in step A1 is replaced with boric acid or the mass of 4,4′-(hexafluoroisopropyl)bis(p-phenyloxy)diphenylamine and the like in step A1 is replaced with 2,2-bis[4-(4-aminophenoxy)phenyl]propane to prepare a polyimide composite film, and the test results are worse than those in Example 3, indicating that the fluorinated polyimide prepared by combining 4,4′-(hexafluoroisopropyl)bis(p-phenyloxy)diphenylamine with 4,4-hexafluoroisopropyl diphthalic anhydride can effectively improve the hydrolysis resistance of the polyimide composite film, and the tensile strength, elongation at break, breakdown voltage and hydrolysis resistance of the polyimide composite film can be well improved by combining 3-aminophenylboric acid with the fluorinated polyimide;

[0138] From the comparison between Comparative Examples 3-4 and Example 3, it can be seen that when no 3-aminophenylboric acid is added or the mass of the hydroxylated multi-walled carbon nanotubes in step A2 is replaced by multi-walled carbon nanotubes, and finally a polyimide composite film is prepared, the test results are worse than those of Example 3, indicating that combining 3-aminophenylboric acid with fluorinated polyimide and then combining it with hydroxylated multi-walled carbon nanotubes to obtain a modified polyimide can improve the interfacial adhesion between the modified polyimide and polytetrafluoroethylene, and further improve the mechanical properties, insulation properties and hydrolysis resistance of the polyimide composite film;

[0139] By comparing Comparative Example 5 with Example 3, it can be seen that the test results of the polyimide composite film prepared by first combining hydroxylated multi-walled carbon nanotubes with fluorinated polyimide and then combining them with 3-aminophenylboric acid are worse than those of Example 3, indicating that first combining 3-aminophenylboric acid with fluorinated polyimide and then combining it with hydroxylated multi-walled carbon nanotubes can better improve the mechanical properties and stability of the polyimide composite film, and improve its insulation properties and hydrolysis resistance.

[0140] It can be seen from Table 1 above that the polyimide composite films prepared in Examples 1-3, compared with the polyimide composite films prepared in Comparative Examples 1-5, are prepared by combining a boric acid crosslinker with a fluorinated polyimide, and then combining it with a hydroxylated multi-walled carbon nanotube to obtain a modified polyimide, and mixing the modified polyimide with polytetrafluoroethylene to obtain a polyimide composite film, which meets the test performance requirements, while the polyimide composite films prepared in Comparative Examples 1-5 do not meet the performance requirements. This shows that the polyimide composite film prepared by the present invention not only has good mechanical properties and stability, but also has good hydrolysis resistance and insulation properties, and its comprehensive performance is good.

[0141] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0142] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing a polyimide composite film insulated copper busbar, characterized in that: The following steps are involved: S1: Precision wrapping: Use a high-precision wrapping machine to wrap the film around the conductor surface; S2: high temperature sintering: using a high temperature sintering furnace to sinter the conductor in step S1 at high temperature; S3: Mechanical bending: bending the conductor in step S2 by a bending machine; S4: Laser stripping: using laser equipment to strip the insulation of the conductor end in step S3; S5: vacuum heat treatment: placing the conductor in step S4 into a high-temperature vacuum box for vacuum heat treatment; S6: taking out the conductor in step S5, and obtaining a polyimide composite film insulated copper busbar after standing and inspecting; The film is a polyimide composite film; The preparation method of the polyimide composite film comprises the following steps: A1: combining a boric acid crosslinker with a fluorinated polyimide to obtain a polyimide oligomer; A2: combining polyimide oligomers with hydroxylated multi-walled carbon nanotubes to obtain modified polyimide; A3: Mixing the modified polyimide with polytetrafluoroethylene to obtain a polyimide composite membrane; The boric acid cross-linking agent is 3-aminophenylboronic acid.

2. The method for preparing a polyimide composite film insulated copper busbar according to claim 1, characterized in that: Step S1 is specifically as follows: Precision wrapping: Use a high-precision wrapping machine to wrap the film on the conductor surface. The film thickness is 0.03-0.06mm, the film width is 3.5-25mm, the wrapping line speed is 0.2-3m / min, the wrapping head speed of the wrapping machine is 100-500rpm, the wrapping film angle is 17-80°, and the wrapping film tension is 100-2000g.

3. The method for preparing a polyimide composite film insulated copper busbar according to claim 2, characterized in that: The conductor is a copper bar or an aluminum bar.

4. The method for preparing a polyimide composite film insulated copper busbar according to claim 1, characterized in that: Step A1 is specifically as follows: Add the boric acid crosslinking agent into the fluorinated polyimide and stir for 3-5 hours to obtain a polyimide oligomer.

5. The method for preparing a polyimide composite film insulated copper busbar according to claim 4, characterized in that: The preparation method of the fluorinated polyimide comprises the following steps: The diamine and the dianhydride are added to N,N-dimethylformamide under an argon atmosphere, and then stirred at 0±2° C. for 5-7 hours to obtain a fluorinated polyimide.

6. The method for preparing a polyimide composite film insulated copper busbar according to claim 1, characterized in that: Step A2 is specifically as follows: The hydroxylated multi-walled carbon nanotubes and the polyimide oligomer in step A1 are added to anhydrous ethanol, and then stirred at 55-65° C. for 3-5 hours, filtered, washed with deionized water, and finally dried at 75-85° C. to obtain a modified polyimide.

7. The method for preparing a polyimide composite film insulated copper busbar according to claim 6, characterized in that: The preparation method of the hydroxylated multi-walled carbon nanotubes comprises the following steps: The multi-walled carbon nanotubes are added to the acid mixture, and then stirred in a water bath at 55-65° C. for 11-13 hours, filtered, washed with deionized water until the pH value of the mixture reaches 6-7, and dried at 75-85° C. to obtain hydroxylated multi-walled carbon nanotubes.

8. The method for preparing a polyimide composite film insulated copper busbar according to claim 1, characterized in that: Step A3 is specifically as follows: The modified polyimide and 2-dimethylaminoethanol in step A2 are added to deionized water and mixed evenly to obtain system A. The polytetrafluoroethylene dispersion is added to deionized water to obtain system B. Then, system A and system B are mixed, coated on a clean glass plate, and thermal imidization is performed under vacuum conditions to finally obtain a polyimide composite film.

9. A polyimide composite film insulated copper busbar prepared by the preparation method according to any one of claims 1 to 8.

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