Transparent polyimide film material with corona resistance and preparation method thereof

Abstract

The invention is applicable to the field of preparation of modified polyimide materials, and provides a transparent polyimide film material with corona resistance and a preparation method thereof, the transparent polyimide film material comprises the following raw materials: nano SiO2 particle-N, N-dimethylacetamide dispersion liquid, a diamine monomer, a benzoxazine monomer and a dianhydride monomer; wherein the N, N-dimethylacetamide dispersion liquid contains nano silicon dioxide (the particle size is about 10-20 nm, and the mass fraction is 30 wt% + / -5 wt%). The transparent polyimide film with corona resistance is prepared by uniformly dispersing nano silicon dioxide particles and benzoxazine in a polyimide matrix by adopting an in-situ polymerization method, the film realizes excellent corona resistance of a material, and meanwhile, the preparation method has the advantages of simple process, energy conservation, environmental protection, high efficiency and the like.

Description

Technical Field

[0001] The present invention relates to the field of preparation of modified polyimide materials, in particular to a transparent polyimide film material with corona resistance and a preparation method thereof. Background Art

[0002] Polyimide, a specialty engineering material, is considered one of the best organic polymers with the best overall performance. It can withstand temperatures as high as 400°C and has a long-term operating temperature range of -20°C to 400°C. In addition to excellent thermodynamic properties, it also boasts excellent insulation properties, with a dielectric loss of only 0.004 to 0.007 at 100 Hz. It has been widely used in aerospace and microelectronics.

[0003] Although polyimide (PI) has many advantages in corona-resistant applications, the development of emerging applications such as hybrid electric vehicles, wind turbines, and pulsed power systems has placed higher demands on the corona resistance of films. Polymer-based composite dielectric thin films are considered to be a solution to this application problem, combining the advantages of ceramics and polymers, namely the high dielectric constant of ceramics and the processability and low dielectric loss of polymers. However, due to the surface energy difference between inorganic ceramics and the polymer matrix, dispersibility and compatibility remain major challenges in dielectric nanocomposites. At the same time, the dielectric properties of composite dielectric thin films at high temperatures still need to be improved.

[0004] Benzoxazine is a class of organic compounds with unique structures and properties. Under certain conditions, it has the ability to self-cure. That is, it can be cured into a cross-linked network structure through simple heat treatment. This makes the overall structure of the material more compact and makes the migration of electrons and ions more difficult. This improves the material's ability to withstand high electric fields and reduces the possibility of electrical breakdown. Therefore, it can effectively improve the material's electrical properties, reduce the material's electrical conductivity, enhance the uniformity of the electric field distribution, reduce the possibility of matrix breakdown, and thus improve the material's corona resistance.

[0005] Silicon dioxide itself has high thermal stability and can withstand high temperatures without degradation. When the corona phenomenon occurs, the local electric field intensity is high, which easily leads to material breakdown. Nano-silicon dioxide can form an efficient electric field shielding layer on the polymer surface, helping the material to better resist the breakdown phenomenon caused by corona discharge. This prevents the material from being affected by electrical breakdown. Patent CN 114539576 A discloses a method for preparing PI / SiO2 composite films using in-situ sol doping. In the synthesis process of polyimide, ethyl orthosilicate and nano-silicon dioxide particle precursors are added. However, in this method, although in-situ polymerization solves the technical problem of easy agglomeration of nanoparticles, doping with a single inorganic particle is far less effective than composite fillers in improving corona resistance. Summary of the Invention

[0006] The present invention provides a transparent polyimide film material with corona resistance and a preparation method thereof, aiming to solve the problems of poor dispersibility and compatibility between nano inorganic particles and polymer matrix and poor corona resistance of pure polymer.

[0007] A transparent polyimide film material with corona resistance, comprising the following raw materials:

[0008] Nano-SiO2 particles-N,N-dimethylacetamide (DMAc) dispersion (nanoparticle average particle size of 20nm, mass fraction of 30wt%±5wt%), diamine monomer, benzoxazine monomer and dianhydride monomer;

[0009] The N,N-dimethylacetamide dispersion is denoted as SiO2-DMAc dispersion, which contains nano-silicon dioxide with a particle size of 10-20 nm and a mass fraction of nano-silicon dioxide of 30 wt%±5 wt%.

[0010] Another object of the present invention is to provide a method for preparing a transparent polyimide film material having corona resistance, comprising the following steps:

[0011] S1. Ultrasonic dispersion is performed again on the dispersed SiO2-DMAc dispersion to make it more uniform;

[0012] S2. Add the dispersed SiO2-DMAc dispersion to a clean three-necked flask, add the diamine monomer, then add pure N,N-dimethylacetamide, and mechanically stir (600r / mins-800r / mins) until completely dissolved, then add the benzoxazine monomer, then add pure N,N-dimethylacetamide (DMAc), rinse the addition funnel, and mechanically stir (600r / mins-800r / mins) until completely dissolved, then add the dianhydride monomer in a 1-1.1 molar ratio to the diamine, and then add pure N,N-dimethylacetamide (DMAc), and the sum of the volumes of the pure N,N-dimethylacetamide (DMAc) added should make the actual solid content of the system (the percentage value of the total mass of monomers to the total mass of components) 8%-10%;

[0013] S3. Under the protection of N2 atmosphere, mechanically stir (700 rpm-900 rpm) and react at room temperature for 12 h-24 h to obtain a polyimide acid solution containing two fillers; take the polyimide acid solution (0.15 g-0.20 g) and add 8 ml of pure N,N-dimethylacetamide (DMAc) to dilute it, and mechanically stir (600 rpm-800 rpm) until it is completely dissolved to obtain a transparent polyamic acid solution containing a composite filler;

[0014] S4. The polyamic acid solution obtained in S3 is poured onto a leveled 8cm*8cm glass plate by a solution casting method. The mixture is vacuum treated at 60°C for 1h-2h, 80°C for 1h-2h, and 100°C for 1h-2h, then transferred to a high-temperature blast oven and heat treated by programmed temperature increase, i.e., treated at 150°C for 1-2h and 200°C for 2-3h, then heating is stopped and slowly cooled to room temperature to obtain a polyimide-based cross-linked nanocomposite film material containing 0%-50% mass fraction (wt%) of nanoparticles and 0%-15% mass fraction (wt%) of benzoxazine, and the film thickness is controlled at 15μm-20μm.

[0015] As a further technical solution of the present invention, in step S1, the ultrasonic dispersion setting parameters are: ultrasonic temperature is: 25°C ± 5°C, frequency is: 60-100KHz, and ultrasonic duration is: 30-50 minutes.

[0016] As a further technical solution of the present invention, in step S2, the diamine monomer is one of 4,4-diaminodiphenyl ether (ODA), 4,4'-diaminodiphenylmethane (DAPM), m-phenylenediamine (MPD) and diaminocyclohexane (DCH); the dianhydride monomer is one of bisphenol A diether dianhydride (BPADA), 1,2,3,4-pyromellitic anhydride (BTDA), and 2,3,3',4'-diphenyltetrafluorophthalic anhydride (6FDA).

[0017] As a further technical solution of the present invention, in step S2, the benzoxazine monomer is one of the benzoxazine models CB5110, CB5116, CB5211, CB6600, CB6700, CB6800, CB6900 and CB7170 purchased from Chengdu Keyi Group.

[0018] As a further technical solution of the present invention, in step S2, the molar ratio of the diamine monomer to the dianhydride monomer should be 1:1-1.05.

[0019] As a further technical solution of the present invention, in step S3, under the protection of N2 atmosphere, mechanical stirring is performed at room temperature for 12h-16h; the speed of mechanical stirring and dissolution is selected to be 600r / mins-800r / mins.

[0020] As a further technical solution of the present invention, in step S2, the solid content of the entire reaction system (the percentage value of the total mass of monomers to the total mass of components) is 8%-10%, SiO2-DMA C The mass ratio of SiO2 in the dispersion is 30 wt%±5 wt%, and the mass ratio of the incorporated benzoxazine monomer is 10 wt%±5 wt%.

[0021] As a further technical solution of the present invention, in step S3, the reaction time at room temperature is 12h-16h.

[0022] As a further technical solution of the present invention, in step S3, the speed of mechanical stirring is selected to be 700 r / mins-900 r / mins.

[0023] As a further technical solution of the present invention, in step S4, the doping ratio of the nano-SiO2 particles is 5wt%-30wt%.

[0024] As a further technical solution of the present invention, in step S2, the diamine monomer is one of 4,4-diaminodiphenyl ether (ODA), 4,4'-diaminodiphenylmethane (DAPM), m-phenylenediamine (MPD) and diaminocyclohexane (DCH); the dianhydride monomer is one of bisphenol A diether dianhydride (BPADA), 1,2,3,4-pyromellitic anhydride (BTDA), and 2,3,3',4'-diphenyltetrafluorophthalic anhydride (6FDA).

[0025] Beneficial effects achieved by the present invention:

[0026] The present invention provides a corona-resistant transparent polyimide film material and a preparation method thereof. The present invention adopts an in-situ polymerization method to uniformly disperse nano-silica particles and benzoxazine in a polyimide matrix to prepare a corona-resistant transparent polyimide film. The film achieves excellent corona resistance of the material. At the same time, the preparation method is simple in process and has the advantages of energy saving, environmental protection, and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 IR spectra of the transparent polyimide-based cross-linked nanocomposite thin films prepared in Examples 1 to 6.

[0028] Figure 2 These are DSC graphs of different transparent polyimide-based cross-linked nanocomposite film materials prepared in Examples 1 to 6.

[0029] Figure 3 These are breakdown field strength diagrams of different transparent polyimide-based cross-linked composite film materials prepared in Examples 1 to 6 at room temperature of 25°C.

[0030] Figure 4 This is a breakdown field strength diagram of the transparent polyimide-based cross-linked nanocomposite film material prepared in Examples 1 to 6 at 150°C.

[0031] Figure 5 This is the first SEM image of the corona-resistant polyimide-based cross-linked nanocomposite film material prepared in Example 1.

[0032] Figure 6 This is the second SEM image of the corona-resistant polyimide-based cross-linked nanocomposite film material prepared in Example 1. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0035] An embodiment of the present invention provides a transparent polyimide film material with corona resistance, comprising the following raw materials:

[0036] 30 wt%-SiO2-N,N-dimethylacetamide (DMAc) dispersion (30 wt%-SiO2-DMAc), diamine monomer, benzoxazine monomer, and dianhydride monomer;

[0037] The N,N-dimethylacetamide dispersion is denoted as SiO2-DMAc dispersion, which contains nano-silicon dioxide with a particle size of 10-20 nm and a mass fraction of nano-silicon dioxide of 30 wt%±5 wt%.

[0038] Another object of the present invention is to provide a method for preparing a transparent polyimide film material having corona resistance, comprising the following steps:

[0039] S1. Ultrasonic dispersion is performed again on the dispersed SiO2-DMAc dispersion to make it more uniform;

[0040] S2. Add the dispersed SiO2-DMAc dispersion to a clean three-necked flask, add the diamine monomer, then add pure N,N-dimethylacetamide, and mechanically stir (600r / mins-800r / mins) until completely dissolved, then add the benzoxazine monomer, then add pure N,N-dimethylacetamide (DMAc), rinse the addition funnel, and mechanically stir (600r / mins-800r / mins) until completely dissolved, then add the dianhydride monomer in a 1-1.1 molar ratio to the diamine, and then add pure N,N-dimethylacetamide (DMAc), and the sum of the volumes of the pure N,N-dimethylacetamide (DMAc) added should make the actual solid content of the system (the percentage value of the total mass of monomers to the total mass of components) 8%-10%;

[0041] S3. Under the protection of N2 atmosphere, mechanically stir and react at room temperature for 12h-24h (700r / mins-900r / mins) to obtain a polyimide acid solution containing two fillers; take (0.15g-0.2g) of the polyetheramic acid solution containing two fillers, add 8ml of pure N,N-dimethylacetamide (DMAc) to dilute, and mechanically stir (800r / mins) until completely dissolved to obtain a colorless polyamic acid solution;

[0042] S4. The colorless polyamic acid solution obtained in S3 is poured onto a leveled 8cm*8cm glass plate by a solution casting method. The mixture is vacuum treated at 60°C for 1h-2h, 80°C for 1h-2h, and 100°C for 1h-2h, then transferred to a high-temperature blast oven and heat treated by programmed temperature increase, i.e., treated at 150°C for 1-2h and 200°C for 2-3h, then heating is stopped and slowly cooled to room temperature to obtain a polyimide-based cross-linked nanocomposite film material containing 0%-50% mass fraction (wt%) of nanoparticles and 0%-15% mass fraction (wt%) of benzoxazine, and the film thickness is controlled at 15μm-20μm.

[0043] In step S1 of this embodiment, the ultrasonic dispersion setting parameters are: ultrasonic temperature: 25°C ± 5°C, frequency: 60-100KHz, and ultrasonic duration: 30-50 minutes.

[0044] In step S2 of this embodiment, the diamine monomer is one of 4,4-diaminodiphenyl ether (ODA), 4,4'-diaminodiphenylmethane (DAPM), m-phenylenediamine (MPD) and diaminocyclohexane (DCH); the dianhydride monomer is one of bisphenol A diether dianhydride (BPADA), 1,2,3,4-pyromellitic anhydride (BTDA), and 2,3,3',4'-diphenyltetrafluorophthalic anhydride (6FDA).

[0045] In step S2 of this embodiment, the molar ratio of the diamine monomer to the dianhydride monomer should be 1:1-1.05.

[0046] In step S2 of this embodiment, the benzoxazine monomer is one of the benzoxazine models CB5110, CB5116, CB5211, CB6600, CB6700, CB6800, CB6900 and CB7170 purchased from Chengdu Keyi Group.

[0047] In step S2 of this embodiment, under the protection of N2 atmosphere, the mechanical stirring speed (the stirring speed used when the monomer is dissolved) is selected to be 600 r / mins-800 r / mins.

[0048] In step S2 of this embodiment, the total volume of N,N-dimethylacetamide (DMAc) is sufficient to ensure that the solid content of the system (the percentage of the total mass of the monomers to the total mass of the components) is between 8% and 10%. The SiO2-DMAC dispersion (particle size of 10-20 nm, nano-silica mass fraction of 30 wt% ± 5 wt%) is prepared, and the mass fraction of the benzoxazine monomer incorporated is 10 wt% ± 5 wt%.

[0049] In step S3 of this embodiment, the reaction time at room temperature is 12 h to 16 h.

[0050] In step S3 of this embodiment, the reaction is carried out at room temperature with a mechanical stirring speed of 800 r / mins-1000 r / mins.

[0051] In step S4 of this embodiment, the doping ratio of the nano-SiO 2 particles is 5wt%-30wt%.

[0052] The present invention is further described below with reference to the embodiments.

[0053] Example 1

[0054] Add 0.01 mol of diamine (4,4-diaminodiphenyl ether (ODA)) monomer to a clean three-necked flask, followed by 35 ml of pure N,N-dimethylacetamide (DMAc). Mechanically stir (700 rpm) until completely dissolved. Rinse the addition funnel with 20 ml of pure DMAc. Add 0.01 mol of dianhydride monomer (bisphenol A diether dianhydride (BPADA)), and rinse the reaction apparatus with 40 ml of pure DMAc. Under a nitrogen atmosphere, react at room temperature for 12 hours with mechanical stirring (800 rpm) to obtain a viscous, transparent, and clear polyimide acid solution. After weighing on an electronic balance, a polyimide acid solution (0.15 g) was placed in a sample bottle. 8 ml of N,N-dimethylacetamide (DMAc) was added and mechanically stirred at 600 rpm until completely dissolved. The resulting colorless polyimide acid solution was then poured onto a leveled 8 cm x 8 cm glass plate using a solution casting method. The mixture was vacuum-treated at 60°C for 1.5 hours, 80°C for 1 hour, and 100°C for 1 hour. The mixture was then transferred to a high-temperature forced air oven and heat-treated using a programmed temperature ramp (150°C for 1 hour and 200°C for 2 hours). After stopping heating and slowly cooling to room temperature, a pure polyetherimide film material undoped with nano-silica (SiO2) particles and benzoxazine was obtained. The film thickness ranged from 15 μm to 20 μm.

[0055] Example 2

[0056] 1.2g of the prepared N,N-dimethylacetamide (DMAc) containing nano-silica particles (SiO2) with a uniform mass fraction of 30% was recorded as 30wt%-SiO2-DMAc solution, which was taken out with a rubber dropper and placed in a sample dissolving bottle for ultrasonic dispersion to make it more uniform. The ultrasonic dispersion setting parameters were: ultrasonic temperature: 25℃, frequency: 60KHz, and ultrasonic duration: 45 minutes; 1.2g of 30wt%-SiO2-DMAc dispersion was added to a clean three-necked flask, and then the sample dissolving bottle was rinsed with 20ml of pure N,N-dimethylacetamide (DMAc), and then added in sequence. 2.0 g of 4,4-diaminodiphenyl ether (ODA) was added, followed by 15 ml of DMAc, which was added to rinse the addition funnel. Mechanical stirring (700 rpm) was performed until the diamine monomer was completely dissolved. 0.36 g of benzoxazine monomer (model CB6600, purchased from Chengdu Keyi Co., Ltd.) was then added, followed by 20 ml of neat DMAc, which was added to rinse the addition funnel. Mechanical stirring (700 rpm) was performed until the benzoxazine monomer was completely dissolved. Finally, 5.2 g of dianhydride (bisphenol A diether dianhydride (BPADA)) was added, followed by 40 ml of neat DMAc, which was added to rinse the reaction apparatus. Under an N2 atmosphere, the resulting reaction system containing the composite filler was mechanically stirred (700 rpm) until complete dissolution. The mixture was allowed to react at room temperature for 14 hours, yielding a viscous, transparent, and clear polyimide acid solution containing both fillers. 0.15 g of the reaction solution was placed in a sample dissolution bottle and weighed using an electronic balance. 8 ml of N,N-dimethylacetamide (DMAc) was then added and mechanically stirred at 800 rpm until completely dissolved. The resulting colorless polyimide acid solution was then poured onto a leveled 8 cm*8 cm glass plate using a solution casting method. The mixture was then vacuum-treated at 60°C for 1 hour, 80°C for 1 hour, and 100°C for 1.5 hours. The mixture was then transferred to a high-temperature forced air oven and heat-treated using a programmed temperature ramp (150°C for 1 hour, 200°C for 2 hours). After stopping heating and slowly cooling to room temperature, a polyimide-based dielectric nanocomposite film material with a thickness of 15 μm-20 μm was obtained.

[0057] Example 3

[0058] 2.4g of the prepared N,N-dimethylacetamide (DMAc) containing nano-silica particles (SiO2) with a uniform mass fraction of 30% was recorded as 30wt% SiO2-DMAc solution, which was taken out with a rubber dropper and placed in a sample dissolving bottle for ultrasonic dispersion to make it more uniform. The ultrasonic dispersion setting parameters were: ultrasonic temperature: 25℃, frequency: 60KHz, and ultrasonic duration: 45 minutes; 2.4g of 30wt%-SiO2-DMAc dispersion was added to a clean three-necked flask, and then the sample dissolving bottle was rinsed with 20ml of pure N,N-dimethylacetamide (DMAc), and then added in sequence. 2.0 g of 4,4-diaminodiphenyl ether (ODA) was added, followed by 15 ml of DMAc, which was then added to rinse the addition funnel. Mechanical stirring (700 rpm) was performed until the diamine monomer was completely dissolved. 0.36 g of benzoxazine monomer (model CB6600, purchased from Chengdu Keyi Co., Ltd.) was then added, followed by 20 ml of neat DMAc, which was then added to rinse the addition funnel. Mechanical stirring (700 rpm) was performed until the benzoxazine monomer was completely dissolved. Finally, 5.2 g of dianhydride (bisphenol A diether dianhydride (BPADA)) was added, followed by 40 ml of neat DMAc, which was then added to rinse the reaction apparatus. Under an N2 atmosphere, the resulting reaction system containing the composite filler was mechanically stirred (800 rpm) until complete dissolution. The mixture was allowed to react at room temperature for 14 hours, yielding a viscous, transparent, and clear polyimide acid solution containing both fillers. 0.15g of polyimide acid solution was placed in a sample dissolution bottle and weighed using an electronic balance. 8ml of N,N-dimethylacetamide (DMAc) was then added and mechanically stirred at 800r / mins until completely dissolved. The resulting colorless polyimide acid solution was poured onto a leveled 8cm*8cm glass plate using a solution casting method. The mixture was then vacuum-treated at 60°C for 1 hour, 80°C for 1 hour, and 100°C for 1.5 hours. The mixture was then transferred to a high-temperature forced air oven and heat-treated using a programmed temperature ramp, i.e., at 150°C for 1 hour and 200°C for 2 hours. After stopping heating and slowly cooling to room temperature, a polyimide-based dielectric nanocomposite film material with a thickness of 15μm-20μm was obtained.

[0059] Example 4

[0060] 3.6g of the prepared N,N-dimethylacetamide (DMAc) containing nano-silica particles (SiO2) with a uniform mass fraction of 30% was recorded as 30wt% SiO2-DMAc solution, which was taken out with a rubber dropper and placed in a sample dissolving bottle for ultrasonic dispersion to make it more uniformly dispersed. The ultrasonic dispersion setting parameters were: ultrasonic temperature: 25℃, frequency: 60KHz, and ultrasonic duration: 45 minutes; 3.6g of 30wt%-SiO2-DMAc dispersion was added to a clean three-necked flask, and then the sample dissolving bottle was rinsed with 20ml of pure N,N-dimethylacetamide (DMAc), and then added in sequence. 2.0 g of 4,4-diaminodiphenyl ether (ODA) was added, followed by 15 ml of DMAc, which was added to rinse the addition funnel. Mechanical stirring (700 rpm) was performed until the diamine monomer was completely dissolved. 0.36 g of benzoxazine monomer (model CB6600, purchased from Chengdu Keyi Co., Ltd.) was then added, followed by 20 ml of neat DMAc. The addition funnel was rinsed and mechanical stirring (700 rpm) was performed until the benzoxazine monomer was completely dissolved. Finally, 5.2 g of dianhydride (bisphenol A diether dianhydride (BPADA)) was added, followed by 40 ml of neat DMAc, which was added to rinse the reaction apparatus. Under an N2 atmosphere, the resulting reaction system containing the composite filler was mechanically stirred (800 rpm) until complete dissolution. The mixture was allowed to react at room temperature for 14 hours, yielding a viscous, transparent, and clear polyimide acid solution containing both fillers. 0.15g of polyimide acid solution was placed in a sample dissolution bottle and weighed using an electronic balance. 8ml of N,N-dimethylacetamide (DMAc) was then added and mechanically stirred at 800r / mins until completely dissolved. The resulting colorless polyimide acid solution was poured onto a leveled 8cm*8cm glass plate using a solution casting method. The mixture was vacuum-treated at 60°C for 1h, 80°C for 1h, and 100°C for 1.5h. The mixture was then transferred to a high-temperature forced air oven and heat-treated using a programmed temperature ramp, i.e., at 150°C for 1h and 200°C for 2h. After stopping heating and slowly cooling to room temperature, a polyimide-based dielectric nanocomposite film material with a thickness of 15μm-20μm was obtained.

[0061] Example 5

[0062] 4.8 g of the prepared 30 wt% SiO2-DMAc solution containing 30% N,N-dimethylacetamide (DMAc) with uniform dispersion was taken out with a rubber-tipped pipette and placed in a sample dissolving bottle for ultrasonic dispersion to make the dispersion more uniform. The ultrasonic dispersion parameters were set as follows: ultrasonic temperature: 25°C, frequency: 60 kHz, and ultrasonic duration: 45 minutes. 4.8 g of the 30 wt% SiO2-DMAc dispersion was added to a clean three-necked flask, and the sample dissolving bottle was rinsed with 20 ml of pure N,N-dimethylacetamide (DMAc), and then 2. 0g of 4,4-diaminodiphenyl ether (ODA) was added, followed by 15ml of DMAc, which was then added to rinse the addition funnel. Mechanical stirring (700 r / min) was performed until the diamine monomer was completely dissolved. Once the diamine monomer was completely dissolved, 0.36g of benzoxazine monomer (model CB6600, purchased from Chengdu Keyi Co., Ltd.) was added, followed by 20ml of neat DMAc, which was then added to rinse the addition funnel. Mechanical stirring (700 r / min) was performed until the benzoxazine monomer was completely dissolved. Finally, 5.2g of dianhydride (bisphenol A diether dianhydride (BPADA)) was added, followed by 40ml of neat DMAc, which was then added to rinse the reaction apparatus. Under an N2 atmosphere, the resulting reaction system containing the composite filler was mechanically stirred (800 r / min) until complete dissolution. The mixture was allowed to react at room temperature for 14 hours, yielding a viscous, transparent, and clear polyimide acid solution containing both fillers. After weighing on an electronic balance, 0.15g of polyimide acid solution was placed in a sample dissolution bottle. 8ml of N,N-dimethylacetamide (DMAc) was then added and mechanically stirred at 800r / mins until completely dissolved. The resulting colorless polyimide acid solution was poured onto a leveled 8cm*8cm glass plate using a solution casting method. The mixture was then vacuum-treated at 60°C for 1 hour, 80°C for 1 hour, and 100°C for 1.5 hours. The mixture was then transferred to a high-temperature forced air oven and heat-treated using a programmed temperature ramp (150°C for 1 hour, 200°C for 2 hours). After stopping heating and slowly cooling to room temperature, a polyimide-based dielectric nanocomposite film material with a thickness of 15μm-20μm was obtained.

[0063] Example 6

[0064] 6.0 g of the prepared 30 wt% SiO2-DMAc solution containing 30% N,N-dimethylacetamide (DMAc) with uniform dispersion was taken out with a rubber-tipped pipette and placed in a sample dissolving bottle for ultrasonic dispersion to make the dispersion more uniform. The ultrasonic dispersion parameters were set as follows: ultrasonic temperature: 25°C, frequency: 60 kHz, and ultrasonic duration: 45 minutes. 6.0 g of the 30 wt% SiO2-DMAc dispersion was added to a clean three-necked flask, and the sample dissolving bottle was rinsed with 20 ml of pure N,N-dimethylacetamide (DMAc), and then 2. 0g of 4,4-diaminodiphenyl ether (ODA) was added, followed by 15ml of DMAc, which was then added to rinse the addition funnel. Mechanical stirring (700 r / min) was performed until the diamine monomer was completely dissolved. Once the diamine monomer was completely dissolved, 0.36g of benzoxazine monomer (model CB6600, purchased from Chengdu Keyi Co., Ltd.) was added, followed by 20ml of neat DMAc, which was then added to rinse the addition funnel. Mechanical stirring (700 r / min) was performed until the benzoxazine monomer was completely dissolved. Finally, 5.2g of dianhydride (bisphenol A diether dianhydride (BPADA)) was added, followed by 40ml of neat DMAc, which was then added to rinse the reaction apparatus. Under an N2 atmosphere, the resulting reaction system containing the composite filler was mechanically stirred (800 r / min) until complete dissolution. The mixture was allowed to react at room temperature for 14 hours, yielding a viscous, transparent, and clear polyimide acid solution containing both fillers. After weighing on an electronic balance, 0.15g of polyimide acid solution was placed in a sample dissolution bottle, followed by the addition of 8ml of N,N-dimethylacetamide (DMAc). Mechanical stirring was performed at 800r / mins until complete dissolution. The resulting colorless polyimide acid solution was poured onto a leveled 8cm*8cm glass plate using a solution casting method. The mixture was then vacuum-treated at 60°C for 1 hour, 80°C for 1 hour, and 100°C for 1.5 hours. The mixture was then transferred to a high-temperature forced air oven and heat-treated using a programmed temperature ramp (150°C for 1 hour, 200°C for 2 hours). After stopping heating and slowly cooling to room temperature, a polyimide-based dielectric nanocomposite film material with a thickness of 15μm-20μm was obtained.

[0065] As can be seen from the above, the present invention uses an in-situ polymerization method to first prepare an N,N-dimethylacetamide (DMAc) dispersion of nano-silica (SiO2) (particle size of about 10-20nm, mass fraction of 30wt%±5wt%), then ultrasonically disperse it, add it to the reaction system, and then add monomers. After mechanical stirring under the protection of N2 atmosphere at room temperature, a transparent, colorless and viscous polyetheramic acid solution containing different nano-silica (SiO2) particles is obtained. The temperature is programmed to heat it to prepare a polyetherimide-based dielectric nanocomposite film material containing different nano-silica particles and benzoxazine doping ratios.

[0066] The infrared spectra of the transparent polyimide-based cross-linked nanocomposite film prepared in Examples 1 to 6 are as follows: Figure 1 shown.

[0067] The DSC graphs of different transparent polyimide-based cross-linked nanocomposite film materials prepared in Examples 1 to 6 are as follows: Figure 2 shown.

[0068] The breakdown field strength of different transparent polyimide-based cross-linked composite film materials prepared in Examples 1 to 6 at room temperature 25°C is shown in FIG. Figure 3 shown.

[0069] The breakdown field strength of the transparent polyimide-based cross-linked nanocomposite film materials prepared in Examples 1 to 6 at 150°C is shown in FIG. Figure 4 shown.

[0070] The SEM image of the corona-resistant polyimide-based cross-linked nanocomposite film material prepared in Example 1 is as follows: Figures 5 and 6 shown.

[0071] It should be noted that, in this document, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article, or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0072] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A transparent polyimide film material with corona resistance, characterized in that: Including the following ingredients: N,N-dimethylacetamide dispersion, diamine monomer, benzoxazine monomer, and dianhydride monomer; The N,N-dimethylacetamide dispersion is denoted as SiO2-DMAc dispersion, which contains nano-silicon dioxide with a particle size of 10-20 nm and a mass fraction of nano-silicon dioxide of 30 wt%±5 wt%.

2. The method for preparing a transparent polyimide film material with corona resistance according to claim 1, characterized in that: The following steps are involved: S1. Ultrasonic dispersion of SiO2-DMAc dispersion to make it more uniform; S2. Add the dispersed SiO2-DMAc dispersion to a clean three-necked flask, add diamine monomer, then add pure N,N-dimethylacetamide, stir mechanically until completely dissolved, then add benzoxazine monomer, then add pure N,N-dimethylacetamide, rinse the addition funnel, stir mechanically until completely dissolved, then add dianhydride monomer in a 1-1.1 molar ratio to diamine, then add pure N,N-dimethylacetamide. The total volume of pure N,N-dimethylacetamide added should make the actual solid content of the system 8%-10%; S3. Under the protection of N2 atmosphere, mechanically stir and react at room temperature for 12h-24h to obtain a polyimide acid solution containing two fillers; take the polyimide acid solution containing two fillers and add 8ml of pure N,N-dimethylacetamide to dilute it, and mechanically stir until it is completely dissolved to obtain a transparent polyamic acid diluted solution doped with composite fillers; S4. The diluted polyamic acid solution obtained in S3 is poured onto a leveled 8cm*8cm glass plate by solution casting, and vacuum treated at 60℃ for 1h-2h, 80℃ for 1h-2h, and 100℃ for 1h-2h, then transferred to a high-temperature blast oven and heat treated by programmed temperature, i.e., 150℃ for 1-2h, 200℃ for 2-3h, then cooled to room temperature after stopping heating to obtain a polyimide-based cross-linked nanocomposite film material, and the film thickness is controlled at 15μm-20μm.

3. The method for preparing a transparent polyimide film material with corona resistance according to claim 2, characterized in that: In step S1 , the ultrasonic dispersion setting parameters are: ultrasonic temperature: 25° C.±5° C., frequency: 60-100 KHz, and ultrasonic duration: 30-50 minutes.

4. The method for preparing a transparent polyimide film material with corona resistance according to claim 2, wherein: In step S2, the diamine monomer is one of 4,4-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, m-phenylenediamine and diaminocyclohexane; the dianhydride monomer is one of bisphenol A diether dianhydride, 1,2,3,4-pyromellitic anhydride and 2,3,3',4'-diphenyltetrafluorophthalic anhydride.

5. The method for preparing a transparent polyimide film material with corona resistance according to claim 2, characterized in that: In step S2, the benzoxazine monomer is one of CB5110, CB5116, CB5211, CB6600, CB6700, CB6800, CB6900 and CB7170.

6. The method for preparing a transparent polyimide film material with corona resistance according to claim 2, characterized in that: In step S2, the molar ratio of the diamine monomer to the dianhydride monomer should be 1:1-1.

05.

7. The method for preparing a transparent polyimide film material with corona resistance according to claim 2, characterized in that: In step S2, the mass fraction of the added benzoxazine monomer is 10 wt%±5 wt%.

8. The method for preparing a transparent polyimide film material with corona resistance according to claim 2, characterized in that: In step S2, under the protection of N2 atmosphere, the speed of mechanical stirring to dissolve the monomer is selected to be 600r / mins-800r / mins.

9. The method for preparing a transparent polyimide film material with corona resistance according to claim 2, characterized in that: In step S3, under the protection of N2 atmosphere, the reaction time at room temperature is 12h-16h; in step S3, the speed of mechanical stirring is selected to be 700r / mins-900r / mins.

10. The method for preparing a transparent polyimide film material with corona resistance according to claim 2, characterized in that: In step S4, the doping ratio of the nano-SiO2 particles is 5wt%-30wt%.

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