Polyimide composite film with high CTI (comparative tracking index) value as well as preparation method and application thereof
By introducing a pyridine ring coordination network and a perfluoroalkyl acrylate protective layer into polyimide films through multilayer structure design and electrospinning technology, the problem of low CTI value of traditional polyimide films is solved, achieving a balance between high CTI value, excellent thermal stability and mechanical properties, making it suitable for high-voltage applications such as 5G communication and new energy vehicles.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-29
- Publication Date
- 2026-04-14
AI Technical Summary
Traditional polyimide films have low CTI values, making it difficult to meet the requirements of high-voltage applications such as 5G communication, new energy vehicles, and high-voltage variable frequency motors. At the same time, methods to improve the CTI value usually come at the cost of sacrificing the film's flexibility or processing performance.
The film employs a multi-layer structure design, comprising a perfluoroalkyl acrylate layer, a nanofiber layer, and a polyimide base layer stacked sequentially. The nanofiber layer is formed by electrospinning, and pyridine rings are introduced into the polyamide backbone to form a stable coordination network. Combined with the perfluoroalkyl acrylate layer as a protective layer, the film's electrical tracking resistance and mechanical properties are improved.
It achieves a CTI value of ≥600V, possesses excellent thermal stability and mechanical properties, while maintaining good flexibility and processing performance, making it suitable for electrical equipment insulation in high-voltage and high-humidity environments.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of polyimide film technology, and more particularly to polyimide composite films with high CTI values for use in 5G communications, new energy vehicles, flexible electronics or motor insulation, and methods for preparing the same. Background Technology
[0002] Polyimide film, as a high-performance polymer material, is widely used in flexible electronics, aerospace, and power electronics as a substrate for flexible printed circuit boards and as an insulating material for various high-temperature motors and electrical appliances due to its excellent heat resistance, high mechanical strength, good electrical insulation properties, corrosion resistance, and flame retardancy. However, with the rapid development of technologies such as 5G communication, new energy vehicles, and high-voltage variable frequency motors, higher requirements are being placed on the tracking resistance of polyimide films.
[0003] CTI (Comparative Tracking Index) is a key indicator of a material's resistance to tracking. Tracking is the process by which a conductive path gradually forms on the surface of a solid insulating material under the combined influence of an electric field and an electrolyte. A high CTI means that the material can better resist leakage and tracking in complex electrical environments such as high voltage and high frequency, ensuring the safe operation of electrical equipment. This is crucial for the insulation protection of electronic components and electrical equipment that operate under high voltage, high humidity, and strong electric field conditions for extended periods. However, the CTI value of traditional polyimide films is typically below 400V, making it difficult to meet the high-voltage requirements of some applications (such as 5G communication, new energy vehicles, and high-voltage variable frequency motors). In the prior art, the main methods to improve the CTI value of polyimide include inorganic filler doping, surface coating treatment and molecular structure modification. However, the properties of polyimide are mutually restrictive, and these methods to improve the CTI value often come at the cost of sacrificing film flexibility or processing performance.
[0004] Therefore, developing a polyimide film that combines high CTI value, excellent thermal stability, good mechanical properties, and suitable processability is of great technical significance and market value. Summary of the Invention
[0005] To address the aforementioned problems, the present invention aims to provide a high CTI value polyimide composite film, its preparation method, and its applications. This polyimide composite film has a CTI value ≥ 600V and exhibits excellent thermal stability and good mechanical properties, thus solving the problem of existing polyimide films being prone to tracking failures under high voltage and high humidity conditions.
[0006] To achieve the above objectives, the first aspect of the present invention provides a high CTI value polyimide composite film with a CTI value ≥ 600V, comprising a first perfluoroalkyl acrylate layer, a nanofiber layer, a polyimide base layer, and a second perfluoroalkyl acrylate layer stacked sequentially. The polyimide base layer is formed by thermal imidization of a polyamic acid solution. The polyamic acid solution is obtained by polycondensation reaction of polymeric monomers in a polar aprotic solvent. The polymeric monomers include aromatic diamine monomers containing pyridine rings and fluorinated dianhydride monomers. The nanofiber layer is formed by electrospinning a mixture of the polyamic acid solution and metal compound nanoparticles.
[0007] The polyimide composite film of this invention comprises a perfluoroalkyl acrylate layer, a nanofiber layer, and a polyimide base layer. Its organic-inorganic alternating multilayer structure can suppress the formation and propagation of electrical tracking through interfacial effects. Furthermore, the polyamic acid solution is obtained by polycondensation of monomers including an aromatic diamine monomer containing a pyridine ring and a fluorinated dianhydride monomer in a polar aprotic solvent. Therefore, a pyridine ring can be introduced into the polyimide backbone. The pyridine ring acts as a coordination site, forming a stable coordination network with metal ions. This not only improves the thermal stability and mechanical properties of the film but also significantly enhances its tracking resistance through the charge dispersion effect of metal ions. Additionally, fluorine atoms provide the film with low dielectric properties. The nanofiber layer, formed by electrospinning a mixture of polyamic acid solution and metal compound nanoparticles, serves as an intermediate layer, creating charge dissipation channels that effectively prevent charge accumulation and improve surface electrical resistance. Simultaneously, the outermost perfluoroalkyl acrylate layer acts as a protective layer, effectively reducing surface energy and improving hydrophobicity, making the film less prone to adsorbing moisture and contaminants, thereby inhibiting the formation of surface tracking. Therefore, through the synergistic effect of the pyridine ring-metal coordination network, the organic-inorganic-organic alternating multilayer structure, and the perfluoroalkyl acrylate protective layer, the intrinsic electrical tracking resistance, thermal stability, and mechanical properties of the film are improved simultaneously, thus solving the problem of balancing high CTI value and comprehensive performance from a mechanistic perspective.
[0008] As a technical solution of the present invention, the amount of pyridine ring in the aromatic diamine monomer containing pyridine ring is 20~50 mol.
[0009] As a technical solution of the present invention, the aromatic diamine monomer containing a pyridine ring is selected from at least one of 2,6-bis(4-aminophenyl)-4-tert-butylpyridine, 2,2'-bis[4-(5-amino-2-pyridoxy)phenyl] sulfone, and 4,4'-diamino-2,2'-bipyridine.
[0010] As a technical solution of the present invention, the fluorinated dianhydride monomer is selected from at least one of 4,4'-(hexafluoroisopropene)phthalic anhydride, 9,9-bis(trifluoromethyl)-2,3,6,7-oxanthracene tetracarboxylic dianhydride and 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride.
[0011] As a technical solution of the present invention, the polymeric monomer further includes a third monomer, wherein the third monomer is selected from at least one of 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane.
[0012] As one technical solution of the present invention, the polar aprotic solvent is selected from N-methylpyrrolidone, N,N-dimethylacetamide, dipropylene glycol dimethyl ether, dimethyl sulfoxide, γ-butyrolactone, tetrahydrofuran, or dimethylformamide.
[0013] As one technical solution of the present invention, the metal compound nanoparticles are selected from at least one of zinc oxide, titanium dioxide, aluminum oxide and silicon dioxide.
[0014] As one technical solution of the present invention, the particle size of the metal compound nanoparticles is 20~100nm.
[0015] As one technical solution of the present invention, the content of the metal compound nanoparticles accounts for 5 to 30 wt.% of the nanofiber layer.
[0016] As one technical solution of the present invention, the thickness of the nanofiber layer is 5~20μm.
[0017] As one technical solution of the present invention, the diameter of the fibers in the nanofiber layer is 100~500nm.
[0018] As one technical solution of the present invention, the thickness of the first perfluoroalkyl acrylate layer and the second perfluoroalkyl acrylate layer is 0.5~2.0μm.
[0019] As one technical solution of the present invention, the water contact angle is greater than 100°. As one technical solution of the present invention, the dielectric constant is ≤2.8 at 10GHz.
[0020] As one technical solution of the present invention, the dielectric loss is ≤0.005.
[0021] As one technical solution of the present invention, Tg≥350℃.
[0022] As one technical solution of the present invention, the coefficient of thermal expansion is ≤45ppm / K.
[0023] As one technical solution of the present invention, the tensile strength is ≥140MPa.
[0024] As one technical solution of the present invention, the first perfluoroalkyl acrylate layer and the second perfluoroalkyl acrylate layer are obtained by thermocuring a solution containing a perfluoroalkyl acrylate copolymer, or the first perfluoroalkyl acrylate layer and the second perfluoroalkyl acrylate layer are obtained by photocuring a solution containing a perfluoroalkyl acrylate copolymer and a siloxane compound.
[0025] A second aspect of this invention provides a method for preparing a high CTI value polyimide composite film, comprising the steps of: (1) Preparation of polyamic acid solution Polyamic acid solution is prepared by polycondensation of monomers in a polar aprotic solvent, wherein the monomers include aromatic diamine monomers containing pyridine rings and fluorinated dianhydride monomers. (2) Preparation of nanofiber layers The polyamic acid solution and metal compound nanoparticles are mixed to obtain a mixture, and the mixture is then used to form a nanofiber layer on a substrate by electrospinning. (3) Preparation of composite layer The polyamic acid solution is cast onto the nanofiber layer and subjected to imidization treatment by heating under an inert atmosphere to remove the matrix and obtain a composite layer. (4) Surface functionalization treatment Perfluoroalkyl acrylate layers are formed on both sides of the composite layer through surface treatment.
[0026] The preparation method of this invention first prepares a polyamic acid solution. A portion of the polyamic acid solution and metal compound nanoparticles are electrospinned to form a nanofiber layer. A portion of the polyamic acid solution is cast onto the nanofiber layer. Upon heating, the polyamic acid solution undergoes imidization, yielding a composite layer consisting of a polyimide base layer and a nanofiber layer comprising the polyamic acid solution and metal compound nanoparticles. That is, the composite layer comprises an organic layer of polyimide, an organic-inorganic layer of polyamic acid and metal compound nanoparticles, and this multilayer structure can suppress the formation and propagation of electrical tracking through interfacial effects. Furthermore, both the polyimide base layer and the nanofiber layer contain polyimide, and pyridine rings are introduced into the polyimide backbone. The polyimide in the nanofiber layer and the polyimide base layer may both have pyridine rings near the surface of the nanofiber layer as coordination sites to form a stable coordination network with metal ions, thus improving the thermal stability, mechanical properties, and resistance to electrical tracking of the film. The two sides of the composite layer are surface-treated to form perfluoroalkyl acrylate layers, which can serve as protective layers to suppress the formation of surface leakage tracking. This preparation method is simple to operate and easy to apply industrially.
[0027] As a technical solution of the present invention, the surface treatment is to form the perfluoroalkyl acrylate layer on both sides of the composite layer by ultraviolet irradiation or thermal crosslinking.
[0028] As one technical solution of the present invention, a solution containing perfluoroalkyl acrylate copolymer is coated on both sides of the composite layer and then thermocured; or, a solution containing perfluoroalkyl acrylate copolymer and siloxane compound is coated on both sides of the composite layer and then photocured by ultraviolet irradiation.
[0029] As one technical solution of the present invention, the concentration of the perfluoroalkyl acrylate copolymer in the solution is 0.5~4.0 wt.%.
[0030] As a technical solution of the present invention, the amount of pyridine ring in the aromatic diamine monomer containing pyridine ring is 20~50 mol.
[0031] As a technical solution of the present invention, the aromatic diamine monomer containing a pyridine ring is selected from at least one of 2,6-bis(4-aminophenyl)-4-tert-butylpyridine, 2,2'-bis[4-(5-amino-2-pyridoxy)phenyl] sulfone, and 4,4'-diamino-2,2'-bipyridine.
[0032] As a technical solution of the present invention, the fluorinated dianhydride monomer is selected from at least one of 4,4'-(hexafluoroisopropene)phthalic anhydride, 9,9-bis(trifluoromethyl)-2,3,6,7-oxanthracene tetracarboxylic dianhydride and 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride.
[0033] As a technical solution of the present invention, the polymeric monomer further includes a third monomer, wherein the third monomer is selected from at least one of 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane.
[0034] As one technical solution of the present invention, the polar aprotic solvent is selected from N-methylpyrrolidone, N,N-dimethylacetamide, dipropylene glycol dimethyl ether, dimethyl sulfoxide, γ-butyrolactone, tetrahydrofuran, or dimethylformamide.
[0035] As one technical solution of the present invention, the metal compound nanoparticles are selected from at least one of zinc oxide, titanium dioxide, aluminum oxide and silicon dioxide.
[0036] As a technical solution of the present invention, the solid-liquid ratio of the polyamic acid solution and the metal compound nanoparticles in step (2) is 15~40mL / g.
[0037] As a technical solution of the present invention, the molar ratio of the pyridine-containing aromatic diamine monomer and the fluorinated dianhydride monomer is 1:1.
[0038] As one technical solution of the present invention, the solid content of the polyamic acid solution is 15-25%.
[0039] As one technical solution of the present invention, the reaction temperature of the polycondensation reaction is 0~10℃ and the time is 5~20h.
[0040] As a technical solution of the present invention, the inert atmosphere is selected from nitrogen or argon.
[0041] As a technical solution of the present invention, the maximum temperature of the imidization treatment is 350~450℃, and the holding time at the maximum temperature is 5~40min.
[0042] As a technical solution of the present invention, the heating adopts a stepped heating method, which includes first heating to 160~240℃ and holding for 15~45 minutes, then heating to 250~350℃ and holding for 15~45 minutes, and continuing to heat to 350~450℃ and holding for 5~40 minutes.
[0043] The third aspect of this invention provides the application of the aforementioned high CTI value polyimide composite film as an insulating material in the fields of 5G communication, new energy vehicles, flexible electronics, or motors. Detailed Implementation The polyimide composite film of this invention has a CTI value ≥ 600V, a dielectric constant ≤ 2.8 at 10GHz, a dielectric loss ≤ 0.005, a Tg ≥ 350℃, a coefficient of thermal expansion ≤ 45ppm / K, and a tensile strength ≥ 140MPa. The polyimide composite film possesses a high CTI value, excellent thermal stability and mechanical properties, and a low dielectric constant, making it suitable for use as an insulating material in fields such as 5G communications, new energy vehicles, flexible electronics, and motors.
[0044] The polyimide composite film of the present invention comprises a first perfluoroalkyl acrylate layer, a nanofiber layer, a polyimide base layer, and a second perfluoroalkyl acrylate layer, which are sequentially stacked.
[0045] The polyimide base layer is formed by thermal imidization of a polyamic acid solution. The polyamic acid solution is obtained by polycondensation of monomers in a polar aprotic solvent. The monomers include aromatic diamine monomers containing pyridine rings and fluorinated dianhydride monomers. Furthermore, the amount of pyridine rings in the aromatic diamine monomers containing pyridine rings is 20-50 mol%, containing sufficient pyridine rings as coordination sites to form a stable coordination network with metal ions. The aromatic diamine monomers containing pyridine rings are selected from at least one of 2,6-bis(4-aminophenyl)-4-tert-butylpyridine, 2,2'-bis[4-(5-amino-2-pyridoxy)phenyl]sulfone, and 4,4'-diamino-2,2'-bipyridine. The fluorinated dianhydride monomer is selected from at least one of 4,4'-(hexafluoroisopropene)phthalic anhydride, 9,9-bis(trifluoromethyl)-2,3,6,7-oxanthracene tetracarboxylic dianhydride, and 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride. The polymerization monomer also includes a third monomer selected from at least one of 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane. The polar aprotic solvent is selected from N-methylpyrrolidone, N,N-dimethylacetamide, dipropylene glycol dimethyl ether, dimethyl sulfoxide, γ-butyrolactone, tetrahydrofuran, or dimethylformamide. The thickness of the polyimide base layer is 20–70 μm.
[0046] The nanofiber layer is formed by electrospinning a mixture of polyamic acid solution and metal compound nanoparticles. The polyamic acid solution is obtained by polycondensation of monomers in a polar aprotic solvent. The monomers include aromatic diamine monomers containing pyridine rings and fluorinated dianhydride monomers. Furthermore, the amount of pyridine ring in the aromatic diamine monomer containing pyridine rings is 20-50 mol%, containing sufficient pyridine rings as coordination sites to form a stable coordination network with the metal ions. The aromatic diamine monomer containing pyridine rings is selected from at least one of 2,6-bis(4-aminophenyl)-4-tert-butylpyridine, 2,2'-bis[4-(5-amino-2-pyridoxy)phenyl]sulfone, and 4,4'-diamino-2,2'-bipyridine. The fluorinated dianhydride monomer is selected from at least one of 4,4'-(hexafluoroisopropene)phthalic anhydride, 9,9-bis(trifluoromethyl)-2,3,6,7-oxanthracene tetracarboxylic dianhydride, and 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride. The polymerization monomer also includes a third monomer selected from at least one of 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane; the addition of the third monomer improves flexibility and impact resistance. The polar aprotic solvent is selected from N-methylpyrrolidone, N,N-dimethylacetamide, dipropylene glycol dimethyl ether, dimethyl sulfoxide, γ-butyrolactone, tetrahydrofuran, or dimethylformamide. The metal compound nanoparticles are selected from at least one of zinc oxide, titanium dioxide, aluminum oxide, and silicon dioxide. The particle size of the metal compound nanoparticles is 20–100 nm. The content of the metal compound nanoparticles accounts for 5–30 wt.% of the nanofiber layer. The thickness of the nanofiber layer is 5–20 μm. The fiber diameter in the nanofiber layer is 100–500 nm.
[0047] The first and second perfluoroalkyl acrylate layers are obtained by thermosetting a solution containing a perfluoroalkyl acrylate copolymer. Alternatively, the first and second perfluoroalkyl acrylate layers are obtained by photocuring a solution containing a perfluoroalkyl acrylate copolymer and a siloxane compound. The thickness of the first and second perfluoroalkyl acrylate layers is 0.5~2.0 μm. The water contact angle is greater than 100°.
[0048] The method for preparing the polyimide composite film of the present invention may include the following steps.
[0049] (1) Preparation of polyamic acid solution Polyamic acid solution is prepared by polycondensation of monomers in a polar aprotic solvent.
[0050] (2) Preparation of nanofiber layers A mixture is prepared by mixing a polyamic acid solution with metal compound nanoparticles, and the mixture is then used to form a nanofiber layer on a matrix by electrospinning.
[0051] (3) Preparation of composite layer A polyamic acid solution was cast onto a nanofiber layer and heated under an inert atmosphere to perform imidization treatment, and the matrix was removed to obtain a composite layer.
[0052] (4) Surface functionalization treatment Perfluoroalkyl acrylate layers are formed on both sides of the composite layer through surface treatment.
[0053] The polymerization monomers include aromatic diamine monomers containing a pyridine ring and fluorinated dianhydride monomers. Further, the aromatic diamine monomer containing a pyridine ring is selected from at least one of 2,6-bis(4-aminophenyl)-4-tert-butylpyridine (DABPy), 2,2'-bis[4-(5-amino-2-pyridoxy)phenyl]sulfone, and 4,4'-diamino-2,2'-bipyridine. The fluorinated dianhydride monomer is selected from at least one of 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA), 9,9-bis(trifluoromethyl)-2,3,6,7-oxanthracene tetracarboxylic dianhydride (6FCDA), and 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride. The polymerization monomer also includes a third monomer selected from at least one of 4,4'-diaminodiphenyl ether (ODA), 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane. The molar ratio of the pyridine-containing aromatic diamine monomer to the fluorinated dianhydride monomer is 1:1. The amount of pyridine ring in the pyridine-containing aromatic diamine monomer is 20-50 mol%, containing sufficient pyridine rings as coordination sites to form a stable coordination network with the metal ions. The reaction temperature of the polycondensation reaction is 0-10 °C, and the time is 5-20 h. The polar aprotic solvent is selected from N-methylpyrrolidone (NMP), N,N-dimethylacetamide, dipropylene glycol dimethyl ether, dimethyl sulfoxide, γ-butyrolactone, tetrahydrofuran, or dimethylformamide. The solid content of the polyamic acid solution is 15-25%.
[0054] In step (2), during the preparation of the nanofiber layer, the metal compound nanoparticles are selected from at least one of zinc oxide, titanium dioxide, aluminum oxide, and silicon dioxide. The solid-liquid ratio of the polyamic acid solution and the metal compound nanoparticles is 15-40 mL / g. The particle size of the metal compound nanoparticles is 20-100 nm. Electrospinning can be performed using conventional methods, which are not the focus of this invention and will not be described in detail here. As an example, the electrospinning voltage can be 10-20 kV, the receiving distance can be 10-20 cm, and the spinning speed can be 0.5-3.0 mL / h. The substrate can be aluminum foil, copper foil, etc.
[0055] In step (3), during the preparation of the composite layer, the inert atmosphere is selected from nitrogen or argon. The maximum temperature for imidization is 350~450℃, and the holding time at the maximum temperature is 5~40min. Heating is performed using a stepped heating method, which includes first heating to 160~240℃ and holding for 15~45min, then heating to 250~350℃ and holding for 15~45min, and finally heating to 350~450℃ and holding for 5~40min. This stepped heating method controls the imidization rate. The substrate can be removed after imidization or before casting the polyamic acid solution onto the nanofiber layer. After casting the polyamic acid solution onto the nanofiber layer, the casting thickness can be controlled by a doctor blade, resulting in a thickness of 30~100μm after imidization.
[0056] In step (4) surface functionalization, the surface treatment involves forming a perfluoroalkyl acrylate layer on both sides of the composite layer by ultraviolet irradiation or thermal crosslinking. Further, a solution containing a perfluoroalkyl acrylate copolymer is coated onto both sides of the composite layer and then thermally cured. The thermal curing temperature is 100~150℃, and the time is 0.5~2.0h. Alternatively, a solution containing a perfluoroalkyl acrylate copolymer and a siloxane compound can be coated onto both sides of the composite layer and then photocured by ultraviolet irradiation. The siloxane compound can be 3-(acryloyloxy)propyltrimethoxysilane or 3-(2,3-epoxypropoxy)propylmethyldiethoxysilane. Photocuring is performed by ultraviolet irradiation with a wavelength of 365nm and an energy density of 400~650mJ / cm². 2 The concentration of the perfluoroalkyl acrylate copolymer in the solution is 0.5~4.0 wt.%. The solution of the perfluoroalkyl acrylate copolymer can be obtained by dissolving the perfluoroalkyl acrylate copolymer in alcohol solvents such as ethanol, propanol, and isopropanol. The perfluoroalkyl acrylate copolymer is prepared by free radical copolymerization of acrylate monomers containing perfluoroalkyl side chains (such as perfluoroethyl acrylate) with one or more other polymerizable monomers. Examples include perfluoroethyl acrylate and methyl methacrylate copolymers, perfluoroethyl acrylate and ethylene copolymers, and perfluoroethyl acrylate and hexadiene copolymers.
[0057] To better illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below with reference to specific embodiments. It should be noted that the methods described below are further explanations of this invention and should not be construed as limiting it.
[0058] Example 1 This embodiment is a polyimide composite film, comprising a first perfluoroalkyl acrylate layer, a nanofiber layer, a polyimide base layer, and a second perfluoroalkyl acrylate layer, stacked sequentially. The thickness of the first and second perfluoroalkyl acrylate layers is 1.0 μm. The thickness of the nanofiber layer is 10 μm, and the fiber diameter in the nanofiber layer is 300 nm. The thickness of the polyimide base layer is 40 μm.
[0059] The preparation method of this polyimide composite film includes the following steps: (1) Preparation of polyamic acid solution Under dry nitrogen protection, 0.1 mol of 2,6-bis(4-aminophenyl)-4-tert-butylpyridine was dissolved in 200 mL of N-methylpyrrolidone. After complete dissolution, 0.1 mol of 4,4'-(hexafluoroisopropene)phthalic anhydride was added in batches. The reaction temperature was controlled at 8 °C and the mixture was stirred for 8 h to obtain a polyamic acid solution with a solid content of 20%.
[0060] (2) Preparation of nanofiber layers Take 50 mL of polyamic acid solution, add 2 g of nano zinc oxide (Dv50 is 30~50 nm), disperse it evenly, and then use electrospinning technology to form a nanofiber layer on the aluminum foil substrate. The spinning voltage is 15 kV, the receiving distance is 15 cm, and the spinning speed is 1 mL / h.
[0061] (3) Preparation of composite layer The remaining polyamic acid solution was cast onto the nanofiber layer, and the thickness was controlled by a doctor blade. Under nitrogen protection, a stepped heating process was performed for imidization: the temperature was raised to 80°C and held for 1 hour, then raised to 120°C and held for 1 hour, then successively raised to 200°C and held for 30 minutes, then raised to 300°C and held for 30 minutes, and finally raised to 400°C and held for 10 minutes. After imidization, the aluminum foil substrate was removed to obtain the composite layer.
[0062] (4) Surface functionalization treatment The composite layer was immersed in a 2 wt.% perfluoroalkyl acrylate copolymer solution (a copolymer of perfluoroethyl acrylate and methyl methacrylate dissolved in ethanol) for 30 min, and then cured at 120 °C for 1 h.
[0063] Example 2 This embodiment is a polyimide composite film, comprising a first perfluoroalkyl acrylate layer, a nanofiber layer, a polyimide base layer, and a second perfluoroalkyl acrylate layer, stacked sequentially. The thickness of the first and second perfluoroalkyl acrylate layers is 1.0 μm. The thickness of the nanofiber layer is 10 μm, and the fiber diameter in the nanofiber layer is 300 nm. The thickness of the polyimide base layer is 40 μm.
[0064] The preparation method of this polyimide composite film includes the following steps: (1) Preparation of polyamic acid solution Under dry nitrogen protection, 0.1 mol of 2,6-bis(4-aminophenyl)-4-tert-butylpyridine was dissolved in 200 mL of N-methylpyrrolidone. After complete dissolution, 0.1 mol of 4,4'-(hexafluoroisopropene)phthalic anhydride and 0.005 mol of 4,4'-diaminodiphenyl ether (ODA) were added in batches. The reaction temperature was controlled at 8 °C and the polycondensation reaction was stirred for 8 h to obtain a polyamic acid solution with a solid content of 20%.
[0065] (2) Preparation of nanofiber layers Take 50 mL of polyamic acid solution, add 2 g of nano titanium dioxide (Dv50 is 50~80 nm), disperse it evenly, and then use electrospinning technology to form a nanofiber layer on the aluminum foil substrate. The spinning voltage is 15 kV, the receiving distance is 15 cm, and the spinning speed is 1 mL / h.
[0066] (3) Preparation of composite layer The remaining polyamic acid solution was cast onto the nanofiber layer, and the thickness was controlled by a doctor blade. Under nitrogen protection, a stepped heating process was performed for imidization: the temperature was raised to 80°C and held for 1 hour, then raised to 120°C and held for 1 hour, then successively raised to 200°C and held for 30 minutes, then raised to 300°C and held for 30 minutes, and finally raised to 400°C and held for 10 minutes. After imidization, the aluminum foil substrate was removed to obtain the composite layer.
[0067] (4) Surface functionalization treatment The composite layer was immersed in a 2 wt.% perfluoroalkyl acrylate copolymer solution (a copolymer of perfluoroethyl acrylate and methyl methacrylate dissolved in ethanol) for 30 min, and then cured at 120 °C for 1 h.
[0068] Example 3 This embodiment is a polyimide composite film, comprising a first perfluoroalkyl acrylate layer, a nanofiber layer, a polyimide base layer, and a second perfluoroalkyl acrylate layer, stacked sequentially. The thickness of the first and second perfluoroalkyl acrylate layers is 1.0 μm. The thickness of the nanofiber layer is 10 μm, and the fiber diameter in the nanofiber layer is 300 nm. The thickness of the polyimide base layer is 40 μm.
[0069] The preparation method of this polyimide composite film includes the following steps: (1) Preparation of polyamic acid solution Under dry nitrogen protection, 0.1 mol of 2,6-bis(4-aminophenyl)-4-tert-butylpyridine was dissolved in 200 mL of N-methylpyrrolidone. After complete dissolution, 0.1 mol of 4,4'-(hexafluoroisopropene)phthalic anhydride was added in batches. The reaction temperature was controlled at 8 °C and the mixture was stirred for 8 h to obtain a polyamic acid solution with a solid content of 20%.
[0070] (2) Preparation of nanofiber layers Take 50 mL of polyamic acid solution, add 2 g of nano zinc oxide (Dv50 is 30~50 nm), disperse it evenly, and then use electrospinning technology to form a nanofiber layer on the aluminum foil substrate. The spinning voltage is 15 kV, the receiving distance is 15 cm, and the spinning speed is 1 mL / h.
[0071] (3) Preparation of composite layer The remaining polyamic acid solution was cast onto the nanofiber layer, and the thickness was controlled by a doctor blade. Under nitrogen protection, a stepped heating process was performed for imidization: the temperature was raised to 80°C and held for 1 hour, then raised to 120°C and held for 1 hour, then successively raised to 200°C and held for 30 minutes, then raised to 300°C and held for 30 minutes, and finally raised to 400°C and held for 10 minutes. After imidization, the aluminum foil substrate was removed to obtain the composite layer.
[0072] (4) Surface functionalization treatment The composite layer was immersed in an ethanol solution of perfluoroalkyl acrylate copolymer and 3-(acryloyloxy)propyltrimethoxysilane (the content of perfluoroalkyl acrylate copolymer in the ethanol solution was 2 wt.%, the perfluoroalkyl acrylate copolymer was a copolymer of perfluoroethyl acrylate and methyl methacrylate, and the molar ratio of perfluoroalkyl acrylate copolymer and 3-(acryloyloxy)propyltrimethoxysilane was 1:1) for 30 min, and then irradiated with ultraviolet light (wavelength, energy density of 365 nm, 500 mJ / cm). 2 Curing occurs under the following conditions.
[0073] Example 4 This embodiment is a polyimide composite film, comprising a first perfluoroalkyl acrylate layer, a nanofiber layer, a polyimide base layer, and a second perfluoroalkyl acrylate layer, stacked sequentially. The thickness of the first and second perfluoroalkyl acrylate layers is 1.5 μm. The thickness of the nanofiber layer is 15 μm, and the fiber diameter in the nanofiber layer is 450 nm. The thickness of the polyimide base layer is 35 μm.
[0074] The preparation method of this polyimide composite film includes the following steps: (1) Preparation of polyamic acid solution Under dry nitrogen protection, 0.1 mol of 2,2'-bis[4-(5-amino-2-pyridinoxy)phenyl] sulfone was dissolved in 220 mL of N,N-dimethylacetamide. After complete dissolution, 0.1 mol of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride was added in batches. The reaction temperature was controlled at 10 °C and the mixture was stirred for 6 h to obtain a polyamic acid solution with a solid content of 25%.
[0075] (2) Preparation of nanofiber layers Take 80 mL of polyamic acid solution, add 3 g of nano zinc oxide (Dv50 is 30~50 nm), disperse it evenly, and then use electrospinning technology to form a nanofiber layer on the aluminum foil substrate. The spinning voltage is 20 kV, the receiving distance is 18 cm, and the spinning speed is 2 mL / h.
[0076] (3) Preparation of composite layer The remaining polyamic acid solution was cast onto the nanofiber layer, and the thickness was controlled by a doctor blade. Under argon protection, a stepped heating process was performed for imidization: the temperature was raised to 100℃ and held for 2 hours, then successively raised to 250℃ and held for 20 minutes, and finally raised to 450℃ and held for 20 minutes. After imidization, the aluminum foil substrate was removed to obtain the composite layer.
[0077] (4) Surface functionalization treatment The composite layer was immersed in a 3 wt.% perfluoroalkyl acrylate copolymer solution (a copolymer of perfluoroethyl acrylate and hexadiene dissolved in isopropanol) for 20 min, and then cured at 110 °C for 2 h.
[0078] Example 5 This embodiment is a polyimide composite film, comprising a first perfluoroalkyl acrylate layer, a nanofiber layer, a polyimide base layer, and a second perfluoroalkyl acrylate layer, stacked sequentially. The thickness of the first and second perfluoroalkyl acrylate layers is 2.0 μm. The thickness of the nanofiber layer is 15 μm, and the fiber diameter in the nanofiber layer is 150 nm. The thickness of the polyimide base layer is 40 μm.
[0079] The preparation method of this polyimide composite film includes the following steps: (1) Preparation of polyamic acid solution Under dry nitrogen protection, 0.1 mol of 2,6-bis(4-aminophenyl)-4-tert-butylpyridine was dissolved in 200 mL of N-methylpyrrolidone. After complete dissolution, 0.1 mol of 4,4'-(hexafluoroisopropene)phthalic anhydride was added in batches. The reaction temperature was controlled at 5 °C and the mixture was stirred for 15 h to obtain a polyamic acid solution with a solid content of 18%.
[0080] (2) Preparation of nanofiber layers Take 60 mL of polyamic acid solution, add 2 g of nano zinc oxide (Dv50 is 20~45 nm), disperse it evenly, and then use electrospinning technology to form a nanofiber layer on the aluminum foil substrate. The spinning voltage is 12 kV, the receiving distance is 13 cm, and the spinning speed is 2 mL / h.
[0081] (3) Preparation of composite layer The remaining polyamic acid solution was cast onto the nanofiber layer, and the thickness was controlled by a doctor blade. Under nitrogen protection, a stepped heating process was performed for imidization: the temperature was raised to 100°C and held for 2 hours, then successively raised to 200°C and held for 30 minutes, then raised to 300°C and held for 30 minutes, and finally raised to 380°C and held for 25 minutes. After imidization, the aluminum foil substrate was removed to obtain the composite layer.
[0082] (4) Surface functionalization treatment The composite layer was immersed in a 4 wt.% perfluoroalkyl acrylate copolymer solution (a copolymer of perfluoroethyl acrylate and methyl methacrylate dissolved in ethanol) for 30 min, and then cured at 100 °C for 1 h.
[0083] Comparative Example 1 This comparative example is a polyimide composite film comprising a first perfluoroalkyl acrylate layer, a nanofiber layer, a polyimide base layer, and a second perfluoroalkyl acrylate layer, stacked sequentially. The thickness of the first and second perfluoroalkyl acrylate layers is 1.0 μm. The thickness of the nanofiber layer is 10 μm, and the fiber diameter in the nanofiber layer is 300 nm. The thickness of the polyimide base layer is 40 μm.
[0084] The preparation method of this polyimide composite film includes the following steps: (1) Preparation of polyamic acid solution Under dry nitrogen protection, 0.1 mol of diethyltoluenediamine was dissolved in 200 mL of N-methylpyrrolidone. After complete dissolution, 0.1 mol of 4,4'-(hexafluoroisopropene)phthalic anhydride was added in batches. The reaction temperature was controlled at 8 °C and the polycondensation reaction was stirred for 8 h to obtain a polyamic acid solution with a solid content of 20%.
[0085] (2) Preparation of nanofiber layers Take 50 mL of polyamic acid solution, add 2 g of nano zinc oxide (Dv50 is 30~50 nm), disperse it evenly, and then use electrospinning technology to form a nanofiber layer on the aluminum foil substrate. The spinning voltage is 15 kV, the receiving distance is 15 cm, and the spinning speed is 1 mL / h.
[0086] (3) Preparation of composite layer The remaining polyamic acid solution was cast onto the nanofiber layer, and the thickness was controlled by a doctor blade. Under nitrogen protection, a stepped heating process was performed for imidization: the temperature was raised to 80°C and held for 1 hour, then raised to 120°C and held for 1 hour, then successively raised to 200°C and held for 30 minutes, then raised to 300°C and held for 30 minutes, and finally raised to 400°C and held for 10 minutes. After imidization, the aluminum foil substrate was removed to obtain the composite layer.
[0087] (4) Surface functionalization treatment The composite layer was immersed in a 2 wt.% perfluoroalkyl acrylate copolymer solution (a copolymer of perfluoroethyl acrylate and methyl methacrylate dissolved in ethanol) for 30 min, and then cured at 120 °C for 1 h.
[0088] Comparative Example 2 This comparative example is a polyimide composite film comprising a first perfluoroalkyl acrylate layer, a nanofiber-polyimide composite layer, and a second perfluoroalkyl acrylate layer, sequentially stacked. The thickness of the first and second perfluoroalkyl acrylate layers is 1.0 μm. The thickness of the nanofiber-polyimide composite layer is 50 μm.
[0089] The preparation method of this polyimide composite film includes the following steps: (1) Preparation of polyamic acid solution Under dry nitrogen protection, 0.1 mol of 2,6-bis(4-aminophenyl)-4-tert-butylpyridine was dissolved in 200 mL of N-methylpyrrolidone. After complete dissolution, 0.1 mol of 4,4'-(hexafluoroisopropene)phthalic anhydride was added in batches. The reaction temperature was controlled at 8 °C and the mixture was stirred for 8 h to obtain a polyamic acid solution with a solid content of 20%.
[0090] (2) Preparation of nanofiber-polyimide composite layer Take a polyamic acid solution, add 2g of nano-zinc oxide (Dv50 of 30~50nm), disperse evenly, and then spin it on an aluminum foil substrate using electrospinning technology. The spinning voltage is 15kV, the receiving distance is 15cm, and the spinning speed is 1mL / h. Under nitrogen protection, perform a stepwise heating process for imidization: heat to 80℃ and hold for 1h, then heat to 120℃ and hold for 1h, then successively heat to 200℃ and hold for 30min, then heat to 300℃ and hold for 30min, and finally heat to 400℃ and hold for 10min. After imidization, remove the aluminum foil substrate to obtain the composite layer.
[0091] (3) Surface functionalization treatment The composite layer was immersed in a 2 wt.% perfluoroalkyl acrylate copolymer solution (a copolymer of perfluoroethyl acrylate and methyl methacrylate dissolved in ethanol) for 30 min, and then cured at 120 °C for 1 h.
[0092] Performance tests were conducted on the polyimide composite films of Examples 1-5 and Comparative Examples 1-2, and the results are shown in Table 1.
[0093] Table 1. Performance of polyimide composite films of Examples 1-5 and Comparative Examples 1-2
[0094] As shown in Table 1, the present invention uses a polyamic acid solution obtained by polycondensation of a monomer comprising an aromatic diamine monomer containing a pyridine ring and a fluorinated dianhydride monomer. A nanofiber layer formed by electrospinning a mixture of the polyamic acid solution and metal compound nanoparticles is used as an intermediate layer, supplemented by a polyimide base layer formed by thermal imidization of the polyamic acid solution. The resulting polyimide composite film has a high CTI value, better heat resistance, mechanical properties and a low dielectric constant, thus effectively solving the problem of electrical tracking failure that easily occurs in existing polyimide films under high voltage and high humidity application environments.
[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A high CTI value polyimide composite film, characterized in that, The product has a CTI value ≥ 600V and comprises a first perfluoroalkyl acrylate layer, a nanofiber layer, a polyimide base layer, and a second perfluoroalkyl acrylate layer, which are sequentially stacked. The polyimide base layer is formed by thermal imidization of a polyamic acid solution. The polyamic acid solution is obtained by polycondensation reaction of polymeric monomers in a polar aprotic solvent. The polymeric monomers include aromatic diamine monomers containing pyridine rings and fluorinated dianhydride monomers. The nanofiber layer is formed by electrospinning a mixture of the polyamic acid solution and metal compound nanoparticles.
2. The high CTI value polyimide composite film according to claim 1, characterized in that, Includes at least one of the following features (1) to (16): (1) The amount of pyridine ring in the aromatic diamine monomer containing the pyridine ring is 20~50 mol% (2) The aromatic diamine monomer containing a pyridine ring is selected from at least one of 2,6-bis(4-aminophenyl)-4-tert-butylpyridine, 2,2'-bis[4-(5-amino-2-pyridoxy)phenyl] sulfone and 4,4'-diamino-2,2'-bipyridine; (3) The fluorinated dianhydride monomer is selected from at least one of 4,4'-(hexafluoroisopropene) phthalic anhydride, 9,9-bis(trifluoromethyl)-2,3,6,7-oxanthracene tetracarboxylic dianhydride and 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride; (4) The polymer monomer further includes a third monomer selected from at least one of 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane; (5) The polar aprotic solvent is selected from N-methylpyrrolidone, N,N-dimethylacetamide, dipropylene glycol dimethyl ether, dimethyl sulfoxide, γ-butyrolactone, tetrahydrofuran or dimethylformamide; (6) The metal compound nanoparticles are selected from at least one of zinc oxide, titanium dioxide, aluminum oxide and silicon dioxide; (7) The particle size of the metal compound nanoparticles is 20~100nm; (8) The content of the metal compound nanoparticles accounts for 5~30 wt.% of the nanofiber layer. (9) The thickness of the nanofiber layer is 5~20μm; (10) The diameter of the fibers in the nanofiber layer is 100~500nm; (11) The thickness of the first perfluoroalkyl acrylate layer and the second perfluoroalkyl acrylate layer is 0.5~2.0 μm; (12) The water contact angle is greater than 100°; (13) Dielectric constant ≤ 2.8 at 10 GHz; (14) Dielectric loss ≤ 0.005; (15) Tg ≥ 350℃; (16) Coefficient of thermal expansion ≤ 45 ppm / K; (17) Tensile strength ≥140MPa.
3. The high CTI value polyimide composite film according to claim 1, characterized in that, The first perfluoroalkyl acrylate layer and the second perfluoroalkyl acrylate layer are obtained by thermocuring a solution containing a perfluoroalkyl acrylate copolymer, or by photocuring a solution containing a perfluoroalkyl acrylate copolymer and a siloxane compound.
4. A method for preparing a high CTI value polyimide composite film, characterized in that, Including the following steps: (1) Preparation of polyamic acid solution Polyamic acid solution is prepared by polycondensation of monomers in a polar aprotic solvent, wherein the monomers include aromatic diamine monomers containing pyridine rings and fluorinated dianhydride monomers. (2) Preparation of nanofiber layers The polyamic acid solution and metal compound nanoparticles are mixed to obtain a mixture, and the mixture is then used to form a nanofiber layer on a substrate by electrospinning. (3) Preparation of composite layer The polyamic acid solution is cast onto the nanofiber layer and subjected to imidization treatment by heating under an inert atmosphere to remove the matrix and obtain a composite layer. (4) Surface functionalization treatment Perfluoroalkyl acrylate layers are formed on both sides of the composite layer through surface treatment.
5. The method for preparing a high CTI value polyimide composite film according to claim 4, characterized in that, The surface treatment involves forming the perfluoroalkyl acrylate layer on both sides of the composite layer by ultraviolet irradiation or thermal crosslinking.
6. The method for preparing a high CTI value polyimide composite film according to claim 5, characterized in that, A solution containing perfluoroalkyl acrylate copolymer is coated onto both sides of the composite layer and then thermocured; or a solution containing perfluoroalkyl acrylate copolymer and siloxane compound is coated onto both sides of the composite layer and then photocured by ultraviolet irradiation.
7. The method for preparing a high CTI value polyimide composite film according to claim 6, characterized in that, The concentration of the perfluoroalkyl acrylate copolymer in the solution is 0.5~4.0 wt.%.
8. The method for preparing a high CTI value polyimide composite film according to claim 5, characterized in that, Includes at least one of the following features (1) to (13): (1) The amount of pyridine ring in the aromatic diamine monomer containing the pyridine ring is 20~50 mol%; (2) The pyridine-containing aromatic diamine monomer is selected from at least one of 2,6-bis(4-aminophenyl)-4-tert-butylpyridine, 2,2'-bis[4-(5-amino-2-pyridoxy)phenyl] sulfone, and 4,4'-diamino-2,2'-bipyridine; (3) The fluorinated dianhydride monomer is selected from at least one of 4,4'-(hexafluoroisopropene)phthalic anhydride, 9,9-bis(trifluoromethyl)-2,3,6,7-oxanthracene tetracarboxylic dianhydride, and 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride; (4) The polymer monomer further includes a third monomer selected from at least one of 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane; (5) The polar aprotic solvent is selected from N-methylpyrrolidone, N,N-dimethylacetamide, dipropylene glycol dimethyl ether, dimethyl sulfoxide, γ-butyrolactone, tetrahydrofuran or dimethylformamide; (6) The metal compound nanoparticles are selected from at least one of zinc oxide, titanium dioxide, aluminum oxide and silicon dioxide; (7) The solid-liquid ratio of the polyamic acid solution and the metal compound nanoparticles in step (2) is 15~40mL / g; (8) The molar ratio of the pyridine-containing aromatic diamine monomer to the fluorinated dianhydride monomer is 1:1; (9) The solid content of the polyamic acid solution is 15-25%; (10) The reaction temperature of the polycondensation reaction is 0~10℃ and the time is 5~20h; (11) The inert atmosphere is selected from nitrogen or argon; (12) The maximum temperature of the imidization treatment is 350~450℃, and the holding time at the maximum temperature is 5~40min; (13) The heating adopts a stepped heating method, which includes first heating to 160~240℃ and holding for 15~45min, then heating to 250~350℃ and holding for 15~45min, and then heating to 350~450℃ and holding for 5~40min.
9. The application of the high CTI value polyimide composite film according to any one of claims 1 to 3 as an insulating material in the fields of 5G communication, new energy vehicles, flexible electronics or motors.