阅读说明：本技术 一种耐电晕聚酰亚胺薄膜制备方法、耐电晕聚酰亚胺薄膜及其制备系统 (Corona-resistant polyimide film preparation method, corona-resistant polyimide film and preparation system thereof ) 是由 张明玉 刘立柱 张春琪 施泉荣 朱小勇 夏智峰 吴斌 马俊峰 于 2019-10-15 设计创作，主要内容包括：本发明公开了一种耐电晕聚酰亚胺复合薄膜的制备方法。包括滚涂层和中间层,所述滚涂层为聚酰亚胺/无机粒子杂化胶液在中间层两面进行一次或多层辊涂之后亚胺化形成,所述中间层为聚酰亚胺纯层。本发明制备的聚酰亚胺复合薄膜实现了多层耐电晕聚酰亚胺复合薄膜的连续工业化生产,在保证耐电晕性能优异的基础上,力学性能更加优异,适用于大规模工业化连续生产。(The invention discloses a preparation method of a corona-resistant polyimide composite film. The roll coating is formed by imidizing polyimide/inorganic particle hybrid glue solution after one or more layers of roll coating on two sides of the middle layer, and the middle layer is a polyimide pure layer. The polyimide composite film prepared by the invention realizes the continuous industrial production of the multilayer corona-resistant polyimide composite film, has more excellent mechanical properties on the basis of ensuring the excellent corona-resistant performance, and is suitable for large-scale industrial continuous production.)

1. A preparation method of a corona-resistant polyimide film is characterized by comprising the following steps:

(1) adding ODA into a reaction device, adding DMAc to ensure that the solid content is 10-20%, stirring and mixing uniformly, wherein the rotating speed is 500 plus 1500 rpm, after the ODA is completely dissolved in the DMAc, weighing PMDA with the same molar ratio as the ODA, adding the PMDA into the reaction device in batches for multiple times, wherein the PMDA feeding process is about 0.5-1h until the viscosity of the glue solution is increased until the stirrer generates a rod climbing phenomenon, reducing the rotating speed to 50-500 rpm, and continuously stirring for 6-12h to finally obtain a pure PAA glue solution with high molecular weight;

(2) adding ODA into a reaction device, adding DMAc to ensure that the solid content is 10-20%, stirring and mixing uniformly at the rotating speed of 500 plus 1500 rpm, adding 15-30% of the mass of gas-phase alumina powder after the ODA is completely dissolved in the DMAc, stirring uniformly, weighing PMDA with the same molar ratio as the ODA, adding the mixture into the reaction device in batches for multiple times, wherein the PMDA feeding process is about 0.5-1h until the viscosity of the glue solution is increased until the stirrer generates a rod climbing phenomenon, reducing the rotating speed to 50-500 rpm, and continuously stirring for 6-12h to finally obtain glue solution hybridization;

(3) pouring the pure PAA glue solution on a rolling steel belt through storage equipment, uniformly spreading the glue solution on the steel plate according to the required thickness by using a film spreading cutter, and slowly spreading the film at a constant speed;

(4) sending the steel plate paved with the pure PAA glue solution into a preheating furnace, maintaining the temperature at 280 ℃ of 120 ℃ and the retention time for 10-30 minutes, carrying out dehydration cyclization treatment on the pure PAA glue solution, and then peeling a pure film to enter the next step of roller coating; the thickness of the pure film is 10-15 microns;

(5) the hybrid glue solution is coated on the peeled film by roller through a storage device, the thickness of the coating layer of each time is adjusted through pressure and traction force, after the first roller coating, the temperature range of an oven is 120-280 ℃, the retention time is 10-30 minutes, and the thickness of the coating layer is 0.5-5 microns; after the second roller coating, the preheating furnace temperature is 180-; after the third roller coating, preheating the furnace at 200 ℃ and 320 ℃, keeping the furnace for 10-30 minutes, and keeping the thickness of the coating to be 0.5-5 microns; after the fourth roller coating, preheating the furnace at 220 ℃ and 340 ℃, keeping the furnace for 10-30 minutes, and enabling the thickness of the coating to be 0.5-5 microns; after the fifth roller coating, preheating the furnace at 240 ℃ and 350 ℃, staying for 10-30 minutes, and coating thickness is 0.5-5 microns; then the mixture enters an oven at 350 ℃, stays for 60-120 minutes and then is rolled;

wherein, the steps (1) and (2) have no requirement of sequence.

2. The method for preparing a corona-resistant polyimide film as claimed in claim 1, wherein the particle size of the gas phase alumina powder in step (2) is 100-5000 nm.

3. The method for preparing the corona-resistant polyimide film according to claim 1, wherein the pure PAA glue solution is pre-treated before being put into storage equipment for film laying, and the pre-treatment comprises: carrying out impurity removal and bubble removal treatment by using a copper mesh; the hybrid glue solution is put into storage equipment to be pretreated before film paving, and the pretreatment comprises the following steps: and removing impurities and removing bubbles by using a copper net.

4. The corona-resistant polyimide film is characterized by comprising a pure PAA layer positioned in a middle layer, wherein five PAA hybrid layers doped with alumina powder are arranged on the upper surface and the lower surface of the pure PAA layer.

5. The corona resistant polyimide film of claim 1 wherein said pure PAA layer is 10-15 microns thick, each said PAA hybrid layer is 0.5-5 microns thick, and said corona resistant polyimide film is 20-30 microns thick.

6. The corona resistant polyimide film of claim 5 wherein each of said PAA hybrid layers is of equal thickness.

7. The corona resistant polyimide film of claim 1, wherein the alumina powder is a vapor phase alumina powder having a particle size of 100-5000nm and a mass fraction of 15-30%.

8. A corona-resistant polyimide film preparation system is characterized by comprising a horizontally arranged film spreading device and five vertically and serially arranged roller coating devices;

the film paving device comprises a rolling steel belt, first storage equipment arranged above the steel belt, a film paving cutter and a first preheating furnace, wherein the first storage equipment is used for storing pure PAA glue solution;

the roller coating device comprises second storage equipment, a roller coating roller and a second preheating furnace which are arranged in bilateral symmetry; the pure PAA glue solution is poured on a rolling steel belt through the first storage device, is paved through the film paving cutter, is subjected to dehydration and cyclization treatment through the first preheating furnace, and is stripped to form a pure film which enters the adjacent roller coating device; and pouring the hybrid glue solution on the surfaces of the left side and the right side of the pure film through the second storage equipment on the left side and the second storage equipment on the right side, rolling the hybrid glue solution by the roller coating rollers on the left side and the right side, then feeding the hybrid glue solution into an oven, and feeding the hybrid glue solution into the next roller coating device.

9. The corona-resistant polyimide film manufacturing system of claim 8, further comprising an oven and a wind-up roll disposed after the roll coating.

10. The corona resistant polyimide film production system of claim 8, wherein said roll coating apparatus further comprises auxiliary rolls disposed at a head end and/or a tail end of said roll coating apparatus for assisting in introducing or removing a film into or from said auxiliary roll arrangement.

Technical Field

The invention belongs to the technical field of high polymer materials, and particularly relates to a preparation method of a corona-resistant polyimide film, the corona-resistant polyimide film and a preparation system thereof.

Background

Polyimide is a film-type insulating material with the best performance in the world, is commonly called as a gold film, and cannot be used in electronic products such as high-speed trains, missiles, fighters, micro-thinned notebook computers, smart phones, cameras, video cameras and the like. The research report shows that with the rapid development of industries such as high-frequency high-speed communication, intelligent robots, new energy automobiles, rail transit, flexible display and the like, the demand of China for high-performance polyimide films will continue to increase in the coming years, and the demand is expected to reach more than 7500 tons in 2020. However, the current dilemma is that the application of domestic polyimide film local enterprises is mostly limited to the field of low-end insulating materials, and the production of high-performance polyimide films is still blank. For example, polyimide films are widely used for slot insulation of motors because of their excellent properties in insulation. However, in the inverter motor, corona discharge generated by pulse overvoltage can cause the pure polyimide material to age rapidly and break down in a short time, so that the improvement of the corona resistance of the polyimide film is a main way to prolong the service life of the inverter motor.

Research shows that a certain amount of inorganic nanoparticles, typically aluminum oxide, are added into a polyimide matrix, so that the corona resistance of the polyimide matrix can be greatly improved, but with the increase of doping amount, the mechanical property of a composite film is greatly reduced compared with that of a pure polyimide film, and higher doping amount is required to achieve good corona resistance, and the mechanical property of the film is seriously reduced to cause that the film cannot be used, so that the application of the polyimide-based composite film is limited to a certain extent, and in addition, the problem of film property distribution difference caused by uneven dispersion of higher inorganic particle doping amount cannot be solved in time. Corona Resistant (CR-Corona resist) polyimide films Kapton-CR and Kapton-FCR, currently introduced by DuPont, USA, have been widely used in the field of high-speed electric locomotives as the insulation part of traction motors. The film is prepared by hybridizing gas phase aluminum oxide capable of resisting corona corrosion with a polyimide substrate on the basis of testing more than 4000 substances, the film structure is approximately a pure polyimide layer in the middle, polyimide/aluminum oxide composite layers are arranged on the upper and lower parts, and the corona resistance of the film is improved by more than 500 times compared with that of pure polyimide under the action of an alternating electric field of 20kV/mm and 50 Hz. Because domestic products cannot achieve satisfactory effects, the products greatly depend on imported DuPont corona-resistant polyimide films, so that the development of polyimide composite films with excellent corona-resistant corrosion performance and excellent comprehensive performance is realized, and the preparation process is explored, so that the polyimide composite films not only have important theoretical significance, but also have important practical engineering significance and application prospect.

Disclosure of Invention

The invention provides a preparation method of a corona-resistant polyimide film, which adopts a roller coating process to design a pure polyimide layer with a certain thickness in the middle, wherein the upper surface and the lower surface of the pure polyimide layer are both two polyimide/alumina hybrid layers with a certain thickness, and the pure polyimide layer has better corona resistance.

The technical scheme of the invention is as follows:

a preparation method of a corona-resistant polyimide film comprises the following steps:

(1) adding ODA into a reaction device, adding DMAc to ensure that the solid content is 10-20%, stirring and mixing uniformly, wherein the rotating speed is 500 plus 1500 rpm, after the ODA is completely dissolved in the DMAc, weighing PMDA with the same molar ratio as the ODA, adding the PMDA into the reaction device in batches for multiple times, wherein the PMDA feeding process is about 0.5-1h until the viscosity of the glue solution is increased until the stirrer generates a rod climbing phenomenon, reducing the rotating speed to 50-500 rpm, and continuously stirring for 6-12h to finally obtain a pure PAA glue solution with high molecular weight;

(2) adding ODA into a reaction device, adding DMAc to ensure that the solid content is 10-20%, stirring and mixing uniformly at the rotating speed of 500 plus 1500 rpm, adding 15-30% of the mass of gas-phase alumina powder after the ODA is completely dissolved in the DMAc, stirring uniformly, weighing PMDA with the same molar ratio as the ODA, adding the mixture into the reaction device in batches for multiple times, wherein the PMDA feeding process is about 0.5-1h until the viscosity of the glue solution is increased until the stirrer generates a rod climbing phenomenon, reducing the rotating speed to 50-500 rpm, and continuously stirring for 6-12h to finally obtain glue solution hybridization;

(3) pouring the pure PAA glue solution on a rolling steel belt through storage equipment, uniformly spreading the glue solution on the steel plate according to the required thickness by using a film spreading cutter, and slowly spreading the film at a constant speed;

(4) sending the steel plate paved with the pure PAA glue solution into a preheating furnace, maintaining the temperature at 280 ℃ of 120 ℃ and the retention time for 10-30 minutes, carrying out dehydration cyclization treatment on the pure PAA glue solution, and then peeling a pure film to enter the next step of roller coating; the thickness of the pure film is 10-15 microns;

(5) the hybrid glue solution is coated on the peeled film by roller through a storage device, the thickness of the coating layer of each time is adjusted through pressure and traction force, after the first roller coating, the temperature range of an oven is 120-280 ℃, the retention time is 10-30 minutes, and the thickness of the coating layer is 0.5-5 microns; after the second roller coating, the preheating furnace temperature is 180-; after the third roller coating, preheating the furnace at 200 ℃ and 320 ℃, keeping the furnace for 10-30 minutes, and keeping the thickness of the coating to be 0.5-5 microns; after the fourth roller coating, preheating the furnace at 220 ℃ and 340 ℃, keeping the furnace for 10-30 minutes, and enabling the thickness of the coating to be 0.5-5 microns; after the fifth roller coating, preheating the furnace at 240 ℃ and 350 ℃, staying for 10-30 minutes, and coating thickness is 0.5-5 microns; then the mixture enters an oven at 350 ℃, stays for 60-120 minutes and then is rolled;

wherein, the steps (1) and (2) have no requirement of sequence.

Preferably, the particle size of the gas phase alumina powder in the step (2) is 100-5000 nm.

Preferably, the pure PAA glue solution is put into a storage device to be pretreated before film spreading, and the pretreatment comprises the following steps: carrying out impurity removal and bubble removal treatment by using a copper mesh; the hybrid glue solution is put into storage equipment to be pretreated before film paving, and the pretreatment comprises the following steps: and removing impurities and removing bubbles by using a copper net.

Preferably, the polyimide film comprises a pure PAA layer positioned in the middle layer, and five PAA hybrid layers doped with alumina powder are arranged on the upper surface and the lower surface of the pure PAA layer.

Preferably, the thickness of the pure PAA layer is 10-15 microns, the thickness of each PAA hybrid layer is 0.5-5 microns, and the thickness of the corona-resistant polyimide film is 20-30 microns.

Preferably, the thickness of each PAA hybrid layer is equal.

Preferably, the alumina powder is gas phase alumina powder with the particle size of 100-5000nm and the mass fraction of 15-30%.

A corona-resistant polyimide film preparation system comprises a horizontally arranged film laying device and five vertically and serially arranged roller coating devices;

the film paving device comprises a rolling steel belt, first storage equipment arranged above the steel belt, a film paving cutter and a first preheating furnace, wherein the first storage equipment is used for storing pure PAA glue solution;

the roller coating device comprises second storage equipment, a roller coating roller and a second preheating furnace which are arranged in bilateral symmetry;

the pure PAA glue solution is poured on a rolling steel belt through the first storage device, is paved through the film paving cutter, is subjected to dehydration and cyclization treatment through the first preheating furnace, and is stripped to form a pure film which enters the adjacent roller coating device; and pouring the hybrid glue solution on the surfaces of the left side and the right side of the pure film through the second storage equipment on the left side and the second storage equipment on the right side, rolling the hybrid glue solution by the roller coating rollers on the left side and the right side, then feeding the hybrid glue solution into an oven, and feeding the hybrid glue solution into the next roller coating device.

Preferably, the coating device further comprises an oven and a winding roller which are arranged after the roller coating.

Preferably, the roll coating device further comprises auxiliary rolls, and the auxiliary rolls are arranged at the head end and/or the tail end of the roll coating device and are used for assisting in introducing or leading out the film from the auxiliary roll arrangement.

Compared with the prior art, the invention has the following beneficial effects:

in conclusion, the novel corona-resistant polyimide composite film is designed by adopting a roller coating process, wherein the middle of the polyimide composite film is a pure polyimide layer with a certain thickness, and the upper surface and the lower surface of the polyimide composite film are hybrid layers of polyimide/alumina with a certain thickness. The middle pure layer maintains the excellent mechanical property of the composite film on one hand, and forms an interlayer interface with the hybrid layer to enhance the dielectric property of the composite film on the other hand; the hybrid layers positioned on the two surfaces are used as protective layers containing aluminum oxide to resist the damage of corona to protect the thin film from penetrating damage to cause insulation failure, and the process of using roller coating to lay layers can also solve the problem of difference of performance distribution of the thin film caused by uneven dispersion of inorganic particles in the thin film.

Of course, it is not necessary for any product in which the invention is practiced to achieve all of the above-described advantages at the same time.

Drawings

FIG. 1 is a schematic diagram of a system for producing corona resistant polyimide films;

FIG. 2 is a schematic diagram of a process for forming a corona resistant polyimide film;

FIG. 3 is a schematic representation of the non-uniform dispersion of inorganic particles in a monolayer matrix;

FIG. 4 is a schematic representation of the uniform dispersion of inorganic particles in a multi-layer matrix;

FIG. 5 is a schematic diagram of a corona discharge process, wherein FIG. 5(a) is a single layer film and FIG. 5(b) is a multilayer film.

Detailed Description

The invention is further explained by the following specific embodiments in combination with the attached drawings. It should be understood that these examples are only for illustrating the present invention and are not intended to limit the scope of the present invention. In practice, the invention will be understood to cover all modifications and variations of this invention provided they come within the scope of the appended claims.

The existing methods for producing the composite film mainly comprise four methods, including a direct tape casting method, a pulling method, an ion exchange method and a tape casting layer laying method. The direct tape casting method for preparing the monolayer hybrid film has the advantages of simple process and continuous industrial production, and the polyimide composite film in China is produced by adopting the method at present, but has the defect that the integral performance of the film is influenced due to uneven particle dispersion in the film matrix, and the overall performance is greatly different compared with the similar products abroad. The aluminum oxide films are prepared on two sides of the film by using the pulling method, and the method has the advantages that the uniform aluminum oxide film can be prepared on the film, the corona resistance of the film is improved, but the inorganic film is easy to crack and peel when the surface is stressed, and the adhesion performance is poor. The composite layer is prepared on the surface of the film by adopting an ion exchange method, and the composite layer has the advantages of good cohesiveness and certain improvement of the performance of the film, has the defect that the composite layer is too thin to achieve satisfactory dielectric performance, and the hydrolysis time prepared in the early stage needs to be increased if a thicker composite layer is obtained, but the mechanical performance of the film is seriously reduced if the hydrolysis time is too long. The three-layer composite film can be prepared by adopting a tape-casting layer-paving method, the comprehensive performance of the film is also improved, but the dispersion of inorganic particles is difficult to solve, in addition, the thickness of each layer in the preparation method is difficult to control, and the continuous production of the composite film is difficult to realize by the process, so the industrial production is difficult to realize. But the method shows the feasibility of layer-by-layer compounding, and has certain reference value for the roller coating process designed by people. The preparation method provided by the patent combines the advantages of the methods, provides a process of roller coating for multiple times, and prepares the multilayer composite film under the condition of keeping the advantages of the four methods and avoiding the disadvantages of the four methods. The process flow of the preparation method is shown in figure 3, and the existing composite technology is combined, the middle pure layer is prepared by a tape casting method, and then the multilayer composite film is prepared by controlling a series of roll coating process parameters such as roll coating speed, solid content, pre-curing temperature and the like. In technical terms, the research is an innovative technology on the original preparation process and has feasibility.

The problem of uneven dispersion of inorganic particles in the film is solved by a method of multiple roller coating. Dispersion problems can ultimately affect the corona resistance of the film. In the conventional process, the inorganic particles are easily agglomerated in the prepared matrix, so that the inorganic particles cannot be uniformly dispersed, and the dispersion effect of the obtained matrix inorganic particles in the powder is shown in fig. 3. This patent adopts the roller coat successive layer to spread the membrane, sees from the individual layer, and the particle dispersion of each layer all has inhomogeneous phenomenon, has realized the whole dispersion of inorganic particle in the film evenly through the stack layer upon layer in the technology, and dispersion effect is as shown in figure 4. The unification of local unevenness and overall evenness is realized.

By using a roller coating layer compounding process, the corona resistance of the compound film is improved by using inorganic particles to form a dense corona protection layer in a three-dimensional space inside the film. As shown in fig. 5, the single-layer film has an inorganic particle agglomeration problem, so that the pure polyimide is exposed too early to cause premature exposure in a place without particle protection due to uneven inorganic particle distribution in a three-dimensional space, thereby causing premature corona breakdown (fig. 5(a)), while the film prepared by the roll coating multi-layer composite process has an agglomeration problem in each single layer, the dense protective layer is formed on the whole due to layer-by-layer stacking, thereby preventing premature exposure of the pure polyimide, forming a relatively good corona protective layer (fig. 5(b)), and improving the corona resistance of the film on the whole.

The following embodiments may employ a corona resistant polyimide film production system, see fig. 1, comprising a horizontally disposed film-laying device and five vertically serially disposed roll-coating devices;

the film paving device comprises a rolling steel belt 2, first storage equipment arranged above the steel belt, a film paving cutter 3 and a first preheating furnace, wherein the first storage equipment is used for storing pure PAA glue solution;

the roller coating device comprises second storage equipment, a roller coating roller 5 and a second preheating furnace which are arranged in bilateral symmetry; for convenience of description, the first storage facility and the second storage facility will be hereinafter referred to as the storage facility 1; the first preheating furnace and the second preheating furnace are collectively called preheating furnace 4;

the pure PAA glue solution is poured on a rolling steel belt 2 through the first storage device, is paved through the film paving cutter 3, is subjected to dehydration and cyclization treatment through the first preheating furnace, and is stripped to form a pure film which enters the adjacent roller coating device; and pouring the hybrid glue solution on the surfaces of the left side and the right side of the pure film through the second storage equipment on the left side and the second storage equipment on the right side, rolling the hybrid glue solution by the roller coating rollers on the left side and the right side, then feeding the hybrid glue solution into an oven, and feeding the hybrid glue solution into the next roller coating device.

Further, the device also comprises an oven 601 and a wind-up roll 602 which are arranged after the roll coating.

Further, the roll coating device further comprises an auxiliary roll 603, and the auxiliary roll 603 is arranged at the head end and/or the tail end of the roll coating device and is used for assisting in introducing or leading out the film from the auxiliary roll.

With continued reference to fig. 1, to enable the production of multilayer corona resistant polyimide films, five roll coating apparatuses arranged vertically in series may be increased to 10 roll coating apparatuses arranged in series, several of which may be selected to produce a corresponding number of layers of film.