A polyimide film tape and its preparation process

Abstract

This application relates to the field of thin film tapes, and specifically discloses a polyimide thin film tape and its preparation process. A preparation process of a polyimide thin film tape is as follows: S1. Prepare a polyimide thin film; S2. Coat a polymer emulsion: The coating is carried out in two times, and finally a polyimide thin film tape is obtained. In the preparation process of this application, the difficulty of coating the emulsion is relatively low, the polymer emulsion layer is easy to be coated thickly, the layer thickness of the polymer emulsion of the obtained polyimide thin film tape is not less than 15 μm, the bonding effect with the electromagnetic wire is better, and more excellent electromagnetic wire waterproof and electrical insulation effects can be achieved after winding.

Description

Technical Field

[0001] This application relates to the technical field of thin film tapes, and particularly to a polyimide thin film tape and its preparation process. Background Art

[0002] Polyimide has unique physical and chemical properties and is widely used in many fields. In particular, when made into a polyimide thin film tape, it can be used as the main raw material for the protective layer in the electromagnetic wire winding of large motor coils. It has the advantages of good electrical insulation performance, thermodynamic stability, and chemical stability, providing extremely high reliability for the operation of power equipment. This material is not only highly stable but also can withstand extreme environmental conditions, enabling the motor to operate stably under harsh environments such as high temperature, high humidity, and high voltage.

[0003] The preparation process of polyimide thin film can be generally summarized as follows: First, dianhydride and diamine react in a polar solvent to form a precursor polyamic acid, then the polyamic acid solution is cast into a film, stretched, and then imidized to finally obtain the polyimide thin film; while the polyimide thin film tape is a tape obtained by coating a polymer emulsion on the surface of the polyimide thin film and then drying it. During the coating process, the coating temperature needs to be maintained within the range of 310 - 400 °C to make the emulsion in a flowing state for easy coating. The polyimide thin film tape is very dry on the surface at room temperature, but it will melt after high-temperature heating and thermoset with the electromagnetic wire to be coated, thereby sealing the electromagnetic wire and enabling the motor to operate normally in harsh environments such as high temperature and high humidity.

[0004] However, there are some problems in the coating process of polyimide thin film. Its surface tension is relatively low, and currently used emulsions are polyperfluoroethylene propylene emulsion and modified polytetrafluoroethylene emulsion, both of which have low solid content and high water content. This leads to great difficulty in coating the emulsion, it is very difficult to coat a thick emulsion layer, and the emulsion cannot be coated a second time after the first coating. Generally, the thickness does not exceed 10 μm, which results in relatively poor adhesion between the polyimide thin film tape and the electromagnetic wire. After winding, the waterproof and electrical insulation properties of the electromagnetic wire are damaged, greatly affecting the service life and stability of the motor. Summary of the Invention

[0005] In order to solve the above technical problems, this application provides a polyimide thin film tape and its preparation process.

[0006] In a first aspect, the present application provides a preparation process for a polyimide film tape, comprising the following steps: S1. Prepare a polyimide film, and the step of preparing the polyimide film includes the step of reacting a diamine and a dianhydride to prepare a polyamic acid polymer. S2. Coat a polymer emulsion on the polyimide film; in step S2, the coating is carried out in two times. Specifically: First, raise the temperature to the melting temperature of the polymer in the polymer emulsion, carry out a first coating, and dry to obtain a first coated tape with a surface roughness R a > 1.45. Subsequently, carry out a second coating. After coating, raise the temperature by 40 - 50 °C for melting, and finally cool and shape, and dry to obtain a polyimide film tape; the polymer emulsion is one or both of a perfluoroethylene-propylene copolymer emulsion and a modified polytetrafluoroethylene emulsion.

[0007] The specific operation of step S1 is as follows: Dissolve the diamine in N,N-dimethylacetamide. Under nitrogen protection, stir until the diamine is completely dissolved. Add the dianhydride in small amounts and multiple times, and react for 1 h each time after adding the dianhydride. The reaction temperature is 20 °C. When the solid content in the system is greater than 15 wt%, carry out defoaming treatment to obtain a polyamic acid polymer. Subsequently, uniformly coat the prepared polyamic acid polymer on glass, and then send it to an environment at 100 °C and let it stand for 0.5 h, transfer it to an environment at 150 °C and let it stand for 0.5 h, transfer it to an environment at 200 °C and let it stand for 0.5 h, transfer it to an environment at 250 °C and let it stand for 0.5 h, transfer it to an environment at 300 °C and let it stand for 0.5 h, and finally transfer it to an environment at 380 °C and let it stand for 0.5 h. Take it out, and after the temperature drops to 25 °C, demold it in deionized water, and finally place it in an environment at 100 °C and dry it until the system reaches a constant weight to finally obtain a polyimide film. Among them, the weight ratio of the diamine to the dianhydride is 25:27. The number of times of adding the dianhydride can be flexibly selected according to the material dosage. Any commonly used dianhydride in the art can be used. In the specific embodiment of the present application, pyromellitic dianhydride is taken as an example for illustration. Any commonly used equipment in the art such as an oven can be used when gradually raising the temperature, and it can be flexibly adjusted according to different requirements.

[0008] Both the coating in step S1 and the coating in step S2 can be carried out using any commonly used equipment in the art. In the specific embodiment of the present application, a numerical control coater is taken as an example for illustration, and it can be flexibly adjusted according to different requirements.

[0009] The polymer emulsion in step S2 is any one of a perfluoroethylene-propylene copolymer emulsion and a modified polytetrafluoroethylene emulsion. In the specific embodiment of the present application, a modified polytetrafluoroethylene emulsion with a lower solid content is used for illustration, and the temperature during the first coating is 350 - 360 °C.

[0010] By adopting the above technical solution, in the polymer emulsion coating of step S2 of the present application, the coating temperature is first raised to a range substantially equal to the polymer melting temperature of the polymer emulsion, so that the polymer emulsion is preliminarily melted. At this time, the polymer emulsion will adhere to the polyimide film, and the surface is a relatively rough solid molten state. Then, secondary coating is carried out. Since the surface roughness of the polymer emulsion after the first coating is relatively large, the secondary coating can still effectively increase the coating layer thickness of the polymer emulsion. After the secondary coating, the final high-temperature melting is carried out, and a polyimide film tape with a polymer emulsion layer thickness of not less than 15 μm can be obtained. Generally speaking, compared with the single coating in the existing preparation process of polyimide film tape, in the present application, the temperature is raised step by step to carry out secondary coating, which relatively increases the polymer emulsion layer thickness by at least 5 μm, and the adhesion force is increased by more than 4.8 N / 10 mm. And in actual use, multiple coatings can be carried out according to needs until the final polymer emulsion layer thickness requirement is met. During coating, only the coating temperature needs to be maintained the same as the first coating temperature. In the specific implementation manner of the present application, the secondary coating is taken as an example because the secondary coating can already achieve a good polymer emulsion layer thickening effect.

[0011] In summary, the adhesion force of the polyimide film tape prepared by the preparation process of the present application and the firmness with the magnet wire have been significantly improved, thereby improving the performance of its winding magnet wire, and excellent waterproof and electrical insulation effects of the magnet wire can be achieved after winding.

[0012] Preferably, before step S2, the polyimide film prepared in step S1 also needs to be surface-treated. The specific steps are as follows: The polyimide film is completely immersed in an alkali solution with a hydroxide ion concentration of 0.05 - 0.5 mol / L for alkali treatment for 50 - 60 min, washed with water, and then completely immersed in an acid solution with a hydrogen ion concentration of 0.1 - 0.12 mol / L for acid treatment for 8 - 10 min. After taking it out, it is washed with water and dried to obtain the surface-treated polyimide film.

[0013] Preferably, the hydroxide ion concentration of the alkali solution is 0.2 mol / L.

[0014] By adopting the above technical solution, before coating the polymer emulsion on the surface layer of the polyimide film, the present application performs surface treatment on it by immersing it in an alkali solution and an acid solution, introducing a large number of hydrophilic groups into the molecules on the surface layer of the polyimide film, thereby significantly improving the surface roughness, surface tension and wettability of the polyimide film. The dynamic water contact angle is not greater than 51.5°, and the surface roughness R aIt can reach 1.60. Therefore, the surface-treated polyimide film can be fully wetted when coated with a polymer emulsion, greatly reducing the difficulty of coating the emulsion. The layer thickness of the finally obtained polymer emulsion is significantly increased. Therefore, this surface treatment operation can significantly optimize the coating effect, improve the comprehensive performance of the polyimide film tape, and have a better bonding effect with the magnet wire, achieving more excellent waterproof and electrical insulation effects for the magnet wire after winding.

[0015] In the specific embodiments of this application, a sodium hydroxide solution is used as the alkaline solution and a hydrochloric acid solution is used as the acidic solution for illustration. However, this is only a feasible solution. In actual use, those skilled in the art can replace the alkaline solution and acidic solution with different types according to the actual situation.

[0016] Moreover, this application strictly controls the hydroxide ion concentration of the alkaline solution to further optimize the comprehensive performance of the polyimide film tape. If the hydroxide ion concentration is too large or too small, an effective surface treatment effect cannot be achieved, and the improvement of the surface roughness, surface tension, and wettability of the polyimide film is insufficient. And when the hydroxide ion concentration is too large, the surface layer of the polyimide film will be eroded by the excessive alkaline solution, exposing a large number of internal structures. After this part of the internal structure comes into contact with the air, it will promote the generation of cracks in the polyimide film tape, thus damaging the tensile strength of the polyimide film. Experimental data shows that when the hydroxide ion concentration of the alkaline solution is 0.2 mol / L, the dynamic water contact angle of the polyimide film is the smallest, only 42.1°, and at the same time the surface roughness R a can reach 1.64, with significant coatability, and the finally obtained emulsion layer thickness can reach 19.8 μm.

[0017] Preferably, the diamine includes p-phenylenediamine, 4,4'-diaminodiphenyl ether, and 4,4'-diaminobenzanilide with a weight ratio of 3:(3 - 4):(3 - 4).

[0018] After acid-base treatment, a small amount of cracks will appear on the surface of the polyimide film, and the tensile strength will be lost to a certain extent. However, acid-base treatment only reduces the tensile strength of the surface layer of the film. After testing, the tensile strength can still reach more than 150 MPa at this time. However, in order to further improve the practicality of the polyimide film and further optimize its comprehensive performance, this application also performs a certain strengthening treatment on it. By adopting the above technical solution, this application adds a certain amount of 4,4'-diaminobenzanilide to the diamine system composed of p-phenylenediamine and 4,4'-diaminodiphenyl ether, partially replacing 4,4'-diaminodiphenyl ether, balancing the ratio of rigid groups and flexible groups in the system, so that the finally obtained polyimide film has a higher tensile strength, and the tensile strength is increased by more than 18% compared with the film obtained without adding 4,4'-diaminobenzanilide.

[0019] Preferably, in the step of reacting the diamine and the dianhydride to prepare the polyamic acid polymer, PDA-silane coupling agent modified boron nitride with a dosage of 0.1-0.7 wt% of the total amount of the dianhydride and the diamine is further added. Specifically: disperse the PDA-silane coupling agent modified boron nitride in N,N-dimethylacetamide, and perform ultrasonic treatment for 3-6 h to obtain a PDA-silane coupling agent modified boron nitride dispersion liquid. Then mix it evenly with the diamine, and finally add the dianhydride for reaction, coating, and drying to obtain a polyimide film.

[0020] Preferably, the dosage of the PDA-silane coupling agent modified boron nitride is 0.5 wt% of the total amount of the dianhydride and the diamine.

[0021] Preferably, the PDA-silane coupling agent modified boron nitride is prepared by the following method: subject boron nitride to hydroxylation treatment, then disperse it and the silane coupling agent in absolute ethanol, stir and react, filter by suction, wash, and dry to obtain silane coupling agent modified boron nitride. Then disperse the silane coupling agent modified boron nitride, dopamine, and tromethamine in an ethanol aqueous solution, adjust the pH to 8.4-8.6, stir at 75-85 °C for 5.5-6 h, filter by suction, wash until the filtrate is colorless and neutral, take the solid obtained at this time, dry, and grind to obtain the PDA-silane coupling agent modified boron nitride.

[0022] Among them, the specific operation in the preparation method of the PDA-silane coupling agent modified boron nitride is as follows: first, mix a 5 mol / L sodium hydroxide solution and nanoscale boron nitride in a weight ratio of 10:1 evenly, stir magnetically at 80 °C for 48 h, filter the solution by suction, and wash it with deionized water until the filtrate is neutral. Then put the product obtained by suction filtration into a constant temperature drying oven and dry it at 120 °C for 24 h to obtain hydroxylated boron nitride. Subsequently, add the silane coupling agent in a 60 °C water bath, stir to make it hydrolyze fully, disperse the hydroxylated boron nitride in the above solution, and then continue to stir at 60 °C for 3 h, filter by suction and wash, and dry at 90 °C for 12 h to obtain silane coupling agent modified boron nitride, where the dosage of the silane coupling agent is 2 wt% of the total amount of the hydroxylated boron nitride. Then disperse the silane coupling agent modified boron nitride, dopamine, and tromethamine with a weight ratio of 4:0.8:1.2 in a 50 wt% ethanol aqueous solution, adjust the pH to 8.4-8.6, stir at 75-85 °C for 5.5-6 h, filter by suction, wash until the filtrate is colorless and neutral, take the solid obtained at this time, dry at 60 °C for 24 h, and grind to obtain the PDA-silane coupling agent modified boron nitride.

[0023] By adopting the above technical solution, the present application first hydroxylates the surface of nanoscale boron nitride with a strong base, and then grafts a silane coupling agent onto the surface of boron nitride by using the reaction between this part of hydroxyl groups and the silane coupling agent. Subsequently, by using the polymerization reaction of dopamine in an aqueous solution with a pH of 8.4 - 8.6, a layer of PDA (polydopamine) is formed on the surface of boron nitride. The PDA layer and the silane coupling agent can greatly enhance the interfacial adhesion strength between boron nitride and the diamine and dianhydride system, as well as its dispersibility in the system.

[0024] Then, the present application adds PDA-silane coupling agent modified boron nitride with high interfacial adhesion strength and high dispersibility to the raw materials used for the polyimide film. By utilizing the excellent mechanical strength and chemical stability of boron nitride, supplemented by the sufficient dispersion and adhesion effects of PDA-silane coupling agent modified boron nitride, the overall tensile strength of the polyimide film is significantly improved. The finally obtained polyimide film has uniform internal components and a very high tensile strength, and the tensile strength is increased by more than 15% compared with that of the polyimide film without adding PDA-silane coupling agent modified boron nitride.

[0025] Moreover, the present application also strictly controls the addition amount of PDA-silane coupling agent modified boron nitride to further optimize the mechanical properties of the polyimide film. If the addition amount is too small, the reinforcement effect is insufficient. If the addition amount is too large, although PDA-silane coupling agent modified boron nitride will not form system defects and pores due to agglomeration, an inevitable small part of aggregation of PDA-silane coupling agent modified boron nitride particles will still be generated with an excessive addition amount, which will still promote the generation of cracks in the polyimide film under stress, resulting in a decrease in the mechanical properties of the film. It can be seen from the experimental data that when the dosage of the PDA-silane coupling agent modified boron nitride is 0.5 wt% of the total amount of dianhydride and diamine, the tensile strength of the polyimide film is the highest, reaching 182.9 MPa.

[0026] In the second aspect, the present application provides a polyimide film tape prepared by the above preparation process, and the layer thickness of the polymer emulsion of the polyimide film tape is not less than 15 μm.

[0027] To sum up, the present application has the following beneficial technical effects:

[0028] 1. When the polyimide film of the present application is prepared, it undergoes surface treatment, and a large number of hydrophilic groups are introduced into the molecules on the surface layer, which can be fully wetted when coating the polymer emulsion, greatly reducing the difficulty of coating the emulsion. At the same time, the temperature is increased step by step during coating for secondary coating to increase the layer thickness of the polymer emulsion to more than 15 μm. Therefore, the adhesion of the polyimide film tape of the present application and the firmness with the electromagnetic wire are significantly improved, thereby improving its performance of winding the electromagnetic wire, and excellent waterproof and electrical insulation effects of the electromagnetic wire can be achieved after winding.

[0029] 2. In the preparation process of the present application, the diamine in the polyimide film is prepared from p-phenylenediamine, 4,4'-diaminodiphenyl ether, and 4,4'-diaminobenzanilide. This component balances the ratio of rigid groups and flexible groups in the system, making the finally obtained polyimide film have higher tensile strength. The tensile strength is increased by more than 18% compared with the film obtained without adding 4,4'-diaminobenzanilide.

[0030] 3. PDA-silane coupling agent modified boron nitride is also added to the polyimide film of the present application. It has good interfacial adhesion strength, dispersibility, excellent mechanical strength and chemical stability, and can significantly improve the overall tensile strength of the polyimide film. The tensile strength is increased by more than 15% compared with the polyimide film without adding PDA-silane coupling agent modified boron nitride. Detailed implementation mode

[0031] Material source

[0032] Except for special instructions, the raw materials used in this application are all commercially available products, specifically:

[0033] Boron nitride is purchased from Aladdin Biochemical Technology Co., Ltd., nanoscale;

[0034] The silane coupling agent is purchased from Shanghai Ron Reagent Co., Ltd., model KH-550;

[0035] Dopamine is purchased from Aladdin Biochemical Technology Co., Ltd., CAS No. 62-31-7;

[0036] Tromethamine is purchased from Aladdin Reagent Co., Ltd., CAS No. 77-86-1;

[0037] p-Phenylenediamine is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. and dried before use;

[0038] 4,4'-Diaminodiphenyl ether is purchased from J&K Scientific Ltd. and dried before use;

[0039] N,N-Dimethylacetamide is purchased from Sinopharm Chemical Reagent Co., Ltd. and distilled before use;

[0040] Pyromellitic dianhydride is purchased from J&K Scientific Ltd., purity 99%;

[0041] Modified polytetrafluoroethylene emulsion is purchased from Dongguan Xinshengli Plastic New Material Technology Co., Ltd., solid content 45wt%, CAS No. 62-31-7;

[0042] 4,4'-Diaminobenzanilide is purchased from J&K Scientific Ltd. and dried before use.

[0043] The present application will be further described in detail below in conjunction with Preparation Examples, Examples and Comparative Examples.

[0044] Preparation Example 1

[0045] A preparation method of PDA-silane coupling agent modified boron nitride includes the following steps:

[0046] Mix 1 kg of 5 mol / L sodium hydroxide solution and 0.1 kg of nanoscale boron nitride evenly, stir magnetically at 80 °C for 48 h, filter the solution, wash it with deionized water until the filtrate is neutral, then put the filtered product into a constant-temperature drying oven and dry it at 120 °C for 24 h to obtain hydroxylated boron nitride. Subsequently, add 1 g of silane coupling agent to a water bath at 60 °C, stir to make it hydrolyze fully, take 0.05 kg of hydroxylated boron nitride and disperse it in the above solution, continue to stir at 60 °C for 3 h, filter and wash, dry at 90 °C for 12 h to obtain silane coupling agent modified boron nitride. Then disperse 0.04 kg of silane coupling agent modified boron nitride, 8 g of dopamine and 12 g of tromethamine in 8 kg of 50 wt% ethanol aqueous solution, adjust the pH = 8.4, stir at 85 °C for 6 h, filter, wash until the filtrate is colorless and neutral, take the obtained solid at this time and dry it at 60 °C for 24 h, grind it to obtain PDA-silane coupling agent modified boron nitride.

[0047] Preparation Example 2

[0048] A preparation method of PDA-silane coupling agent modified boron nitride includes the following steps:

[0049] Mix 1 kg of 5 mol / L sodium hydroxide solution and 0.1 kg of nanoscale boron nitride evenly, stir magnetically at 80 °C for 48 h, filter the solution, wash it with deionized water until the filtrate is neutral, then put the filtered product into a constant-temperature drying oven and dry it at 120 °C for 24 h to obtain hydroxylated boron nitride. Subsequently, add 1 g of silane coupling agent to a water bath at 60 °C, stir to make it hydrolyze fully, take 0.05 kg of hydroxylated boron nitride and disperse it in the above solution, continue to stir at 60 °C for 3 h, filter and wash, dry at 90 °C for 12 h to obtain silane coupling agent modified boron nitride. Then disperse 0.04 kg of silane coupling agent modified boron nitride, 8 g of dopamine and 12 g of tromethamine in 8 kg of 50 wt% ethanol aqueous solution, adjust the pH = 8.8, stir at 80 °C for 5.8 h, filter, wash until the filtrate is colorless and neutral, take the obtained solid at this time and dry it at 60 °C for 24 h, grind it to obtain PDA-silane coupling agent modified boron nitride.

[0050] Preparation Example 3

[0051] Preparation method of PDA-silane coupling agent modified boron nitride, comprising the following steps:

[0052] Mix 1 kg of 5 mol / L sodium hydroxide solution and 0.1 kg of nano-scale boron nitride evenly, stir magnetically at 80 °C for 48 h, filter the solution by suction and wash it with deionized water until the filtrate is neutral. Subsequently, put the product obtained by suction filtration into a constant temperature drying oven and dry it at 120 °C for 24 h to obtain hydroxylated boron nitride. Then, add 1 g of silane coupling agent to a water bath at 60 °C, stir to make it hydrolyze fully. Take 0.05 kg of hydroxylated boron nitride and disperse it in the above solution, continue to stir at 60 °C for 3 h, filter by suction and wash, dry at 90 °C for 12 h to obtain silane coupling agent modified boron nitride. Subsequently, disperse 0.04 kg of silane coupling agent modified boron nitride, 8 g of dopamine and 12 g of tromethamine in 8 kg of 50 wt% ethanol aqueous solution, adjust the pH = 8.6, stir at 75 °C for 5.5 h, filter by suction, wash until the filtrate is colorless and neutral. Take the solid obtained at this time and dry it at 60 °C for 24 h, grind it to obtain PDA-silane coupling agent modified boron nitride.

[0053] Preparation Example 4

[0054] Preparation method of silane coupling agent modified boron nitride, comprising the following steps:

[0055] Mix 1 kg of 5 mol / L sodium hydroxide solution and 0.1 kg of nano-scale boron nitride evenly, stir magnetically at 80 °C for 48 h, filter the solution by suction and wash it with deionized water until the filtrate is neutral. Subsequently, put the product obtained by suction filtration into a constant temperature drying oven and dry it at 120 °C for 24 h to obtain hydroxylated boron nitride. Then, add 1 g of silane coupling agent to a water bath at 60 °C, stir to make it hydrolyze fully. Take 0.05 kg of hydroxylated boron nitride and disperse it in the above solution, continue to stir at 60 °C for 3 h, filter by suction and wash, dry at 90 °C for 12 h to obtain silane coupling agent modified boron nitride.

[0056] Preparation Example 5

[0057] Preparation method of PDA modified boron nitride, comprising the following steps:

[0058] Disperse 0.04 kg of nano-scale boron nitride, 8 g of dopamine and 12 g of tromethamine in 8 kg of 50 wt% ethanol aqueous solution, adjust the pH = 8.6, stir at 75 °C for 5.5 h, filter by suction, wash until the filtrate is colorless and neutral. Take the solid obtained at this time and dry it at 60 °C for 24 h, grind it to obtain PDA modified boron nitride.

[0059] Example 1.1

[0060] A preparation process of a polyimide film tape, comprising the following steps:

[0061] S1. Prepare a polyimide film: Dissolve 2.5 kg of diamine (1.25 kg of p-phenylenediamine and 1.25 kg of 4,4'-diaminodiphenyl ether) in 50 L of N,N-dimethylacetamide. Under nitrogen protection, stir until the diamine is completely dissolved. Add pyromellitic dianhydride in 9 portions, 0.3 kg of pyromellitic dianhydride each time. React for 1 h after each addition. The reaction temperature is 20 °C. When the solid content in the system is greater than 15 wt%, perform degassing treatment to obtain a polyamic acid polymer. Subsequently, use a numerical control coater to uniformly coat the prepared polyamic acid polymer on glass, and then transfer it to an oven at 100 °C for standing for 0.5 h, then transfer it to an oven at 150 °C for standing for 0.5 h, then transfer it to an oven at 200 °C for standing for 0.5 h, then transfer it to an oven at 250 °C for standing for 0.5 h, then transfer it to an oven at 300 °C for standing for 0.5 h, and finally transfer it to an oven at 380 °C for standing for 0.5 h. Take it out, wait until the temperature drops to 25 °C, then demold it in deionized water, and finally place it in an oven at 100 °C for drying until the system reaches a constant weight. Finally, a polyimide film with a film thickness of 25 μm is prepared, and the surface roughness R a is 1.27, and the dynamic water contact angle is 76.5°;

[0062] S2. Coat the polymer emulsion: First, raise the temperature to 350 °C. Use a numerical control coater to coat a modified polytetrafluoroethylene emulsion on the surface of the polyimide film prepared in step S1, and dry it to obtain a coated tape with a surface roughness R a of 1.46. Subsequently, under the condition of constant temperature, use a numerical control coater to perform secondary coating of the modified polytetrafluoroethylene emulsion. After coating, raise the temperature to 400 °C for melting, cool and shape it after 3 h, and dry it to obtain a polyimide film tape.

[0063] Example 1.2

[0064] A preparation process of a polyimide film tape, comprising the following steps:

[0065] S1. Preparation of polyimide film: Dissolve 2.5 kg of diamine (1.15 kg of p-phenylenediamine and 1.35 kg of 4,4'-diaminodiphenyl ether) in 50 L of N,N-dimethylacetamide. Under nitrogen protection, stir until the diamine is completely dissolved. Add pyromellitic dianhydride in 9 portions, with each portion being 0.3 kg. React for 1 h after each addition. The reaction temperature is 20 °C. When the solid content in the system is greater than 15 wt%, perform defoaming treatment to obtain a polyamic acid polymer. Subsequently, use a numerically controlled coater to uniformly coat the prepared polyamic acid polymer on glass, and then transfer it to an oven at 100 °C and let it stand for 0.5 h, then transfer it to an oven at 150 °C and let it stand for 0.5 h, then transfer it to an oven at 200 °C and let it stand for 0.5 h, then transfer it to an oven at 250 °C and let it stand for 0.5 h, then transfer it to an oven at 300 °C and let it stand for 0.5 h, and finally transfer it to an oven at 380 °C and let it stand for 0.5 h. Take it out, and after the temperature drops to 25 °C, demold it in deionized water. Finally, place it in an oven at 100 °C and dry it until the system reaches a constant weight, and finally obtain a polyimide film with a thickness of 25 μm, with a surface roughness R a of 1.26 and a dynamic water contact angle of 76.9°;

[0066] S2. Coating with polymer emulsion: First, raise the temperature to 355 °C. Coat the surface of the polyimide film prepared in step S1 with a modified polytetrafluoroethylene emulsion using a numerically controlled coater, and dry it to obtain a coated tape with a surface roughness R a of 1.46. Subsequently, under the condition of constant temperature, use a numerically controlled coater to perform secondary coating with the modified polytetrafluoroethylene emulsion. After coating, raise the temperature to 400 °C for melting, cool and shape it after 3 h, and dry it to obtain a polyimide film tape.

[0067] Example 1.3

[0068] A preparation process of a polyimide film tape, comprising the following steps:

[0069] S1. Preparation of polyimide film: Dissolve 2.5 kg of diamine (1.07 kg of p-phenylenediamine and 1.43 kg of 4,4'-diaminodiphenyl ether) in 50 L of N,N-dimethylacetamide. Under nitrogen protection, stir until the diamine is completely dissolved. Add pyromellitic dianhydride in 9 portions, 0.3 kg each time. React for 1 h after each addition. The reaction temperature is 20 °C. When the solid content in the system is greater than 15 wt%, carry out degassing treatment to obtain a polyamic acid polymer. Subsequently, use a numerically controlled coater to uniformly coat the prepared polyamic acid polymer on glass, then transfer it to an oven at 100 °C and let it stand for 0.5 h, transfer to an oven at 150 °C and let it stand for 0.5 h, transfer to an oven at 200 °C and let it stand for 0.5 h, transfer to an oven at 250 °C and let it stand for 0.5 h, transfer to an oven at 300 °C and let it stand for 0.5 h, and finally transfer to an oven at 380 °C and let it stand for 0.5 h. Take it out, after the temperature drops to 25 °C, demold it in deionized water, and finally place it in an oven at 100 °C and dry it until the system reaches a constant weight, finally obtaining a polyimide film with a film thickness of 25 μm, and the surface roughness R a is 1.27, and the dynamic water contact angle is 76.6°;

[0070] S2. Coating with polymer emulsion: First, raise the temperature to 360 °C. Coat the surface of the polyimide film prepared in step S1 with a modified polytetrafluoroethylene emulsion using a numerically controlled coater, and dry it to obtain a coated tape with a surface roughness R a of 1.47. Subsequently, under the condition of constant temperature, use a numerically controlled coater to perform secondary coating with the modified polytetrafluoroethylene emulsion. After coating, raise the temperature to 400 °C for melting, cool and shape it after 3 h, and dry it to obtain a polyimide film tape.

[0071] Example 2.1

[0072] A preparation process of a polyimide film tape, which is different from Example 1.1 in that: in step S1, the polyimide film also undergoes surface treatment, specifically:

[0073] Completely immerse the polyimide film in a sodium hydroxide solution with a hydroxide ion concentration of 0.5 mol / L for alkali treatment for 50 min. After washing with deionized water, completely immerse it in a hydrochloric acid solution with a hydrogen ion concentration of 0.12 mol / L for acid treatment for 8 min. Take it out, wash it with deionized water, and dry it to obtain a surface-treated polyimide film, and the surface roughness R a is 1.60, and the dynamic water contact angle is 49.8°.

[0074] Example 2.2

[0075] A preparation process of a polyimide film tape, which is different from Example 1.1 in that: in step S1, the polyimide film is also subjected to surface treatment, specifically:

[0076] The polyimide film is completely immersed in a sodium hydroxide solution with a hydroxide ion concentration of 0.05 mol / L for alkali treatment for 60 min, washed with deionized water, and then completely immersed in a hydrochloric acid solution with a hydrogen ion concentration of 0.1 mol / L for acid treatment for 10 min. After taking it out, it is washed with deionized water and dried to obtain the surface-treated polyimide film, and the surface roughness R a is 1.61, and the dynamic water contact angle is 51.4°.

[0077] Example 2.3

[0078] A preparation process of a polyimide film tape, which is different from Example 1.1 in that: in step S1, the polyimide film is also subjected to surface treatment, specifically:

[0079] The polyimide film is completely immersed in a sodium hydroxide solution with a hydroxide ion concentration of 0.3 mol / L for alkali treatment for 55 min, washed with deionized water, and then completely immersed in a hydrochloric acid solution with a hydrogen ion concentration of 0.11 mol / L for acid treatment for 9 min. After taking it out, it is washed with deionized water and dried to obtain the surface-treated polyimide film, and the surface roughness R a is 1.62, and the dynamic water contact angle is 51.1°.

[0080] Example 2.4

[0081] A preparation process of a polyimide film tape, which is different from Example 1.1 in that: in step S1, the polyimide film is also subjected to surface treatment, specifically:

[0082] The polyimide film is completely immersed in a sodium hydroxide solution with a hydroxide ion concentration of 0.02 mol / L for alkali treatment for 50 min, washed with deionized water, and then completely immersed in a hydrochloric acid solution with a hydrogen ion concentration of 0.12 mol / L for acid treatment for 8 min. After taking it out, it is washed with deionized water and dried to obtain the surface-treated polyimide film, and the surface roughness R a is 1.43, and the dynamic water contact angle is 67.1°.

[0083] Example 2.5

[0084] A preparation process of a polyimide film tape, which is different from Example 1.1 in that: in step S1, the polyimide film is also subjected to surface treatment, specifically:

[0085] The polyimide film was completely immersed in a sodium hydroxide solution with a hydroxide ion concentration of 0.6 mol / L for 50 min of alkali treatment. After washing with deionized water, it was completely immersed in a hydrochloric acid solution with a hydrogen ion concentration of 0.12 mol / L for 8 min of acid treatment. After taking it out, it was washed with deionized water and dried to obtain the surface-treated polyimide film, with a surface roughness R a of 1.46 and a dynamic water contact angle of 64.0°.

[0086] Example 3.1

[0087] A preparation process of a polyimide film tape, which is different from Example 2.1 in that: in the surface treatment of step S1, the hydroxide ion concentration of the sodium hydroxide solution is 0.1 mol / L, and the rest are the same as in Example 2.1. For the surface-treated polyimide film, the surface roughness R a is 1.61 and the dynamic water contact angle is 64.0°.

[0088] Example 3.2

[0089] A preparation process of a polyimide film tape, which is different from Example 2.1 in that: in the surface treatment of step S1, the hydroxide ion concentration of the sodium hydroxide solution is 0.2 mol / L, and the rest are the same as in Example 2.1. For the surface-treated polyimide film, the surface roughness R a is 1.64 and the dynamic water contact angle is 42.1°.

[0090] Example 3.3

[0091] A preparation process of a polyimide film tape, which is different from Example 2.1 in that: in the surface treatment of step S1, the hydroxide ion concentration of the sodium hydroxide solution is 0.3 mol / L, and the rest are the same as in Example 2.1. For the surface-treated polyimide film, the surface roughness R a is 1.62 and the dynamic water contact angle is 47.3°.

[0092] Example 3.4

[0093] A preparation process of a polyimide film tape, which is different from Example 2.1 in that: in the surface treatment of step S1, the hydroxide ion concentration of the sodium hydroxide solution is 0.4 mol / L, and the rest are the same as in Example 2.1. For the surface-treated polyimide film, the surface roughness R a is 1.60 and the dynamic water contact angle is 51.0°.

[0094] Example 4.1

[0095] A preparation process of a polyimide film tape, which is different from Example 2.1 in that: in step S1, the diamine used is 0.75 kg of p-phenylenediamine, 1 kg of 4,4'-diaminodiphenyl ether, and 0.75 kg of 4,4'-diaminobenzanilide, and the rest are the same as in Example 2.1.

[0096] Example 4.2

[0097] A preparation process of a polyimide film tape, which is different from Example 2.1 in that: in step S1, the diamine used is 0.75 kg of p-phenylenediamine, 0.75 kg of 4,4'-diaminodiphenyl ether, and 1 kg of 4,4'-diaminobenzanilide, and the rest are the same as in Example 2.1.

[0098] Example 4.3

[0099] A preparation process of a polyimide film tape, which is different from Example 2.1 in that: in step S1, the diamine used is 0.75 kg of p-phenylenediamine, 0.87 kg of 4,4'-diaminodiphenyl ether, and 0.88 kg of 4,4'-diaminobenzanilide, and the rest are the same as in Example 2.1.

[0100] Example 5.1

[0101] A preparation process of a polyimide film tape, which is different from Example 2.1 in that: in step S1, PDA-silane coupling agent modified boron nitride is also added. Specifically: 5.2 g of PDA-silane coupling agent modified boron nitride prepared in Preparation Example 1 is dispersed in 50 L of N,N-dimethylacetamide, and ultrasonic treatment is carried out for 3 h to obtain a PDA-silane coupling agent modified boron nitride dispersion liquid. Subsequently, it is mixed evenly with 2.5 kg of diamine (1.25 kg of p-phenylenediamine and 1.25 kg of 4,4'-diaminodiphenyl ether). Under nitrogen protection, stirring is carried out until the diamine is completely dissolved. Pyromellitic dianhydride is added in 9 times, 0.3 kg of pyromellitic dianhydride is added each time, and the reaction is carried out for 1 h each time. The reaction temperature is 20 °C. When the solid content in the system is greater than 15 wt%, defoaming treatment is carried out to obtain a polyamic acid polymer, which is coated and dried to obtain a polyimide film.

[0102] Example 5.2

[0103] A preparation process of a polyimide film tape, which is different from Example 2.1 in that: in step S1, PDA-silane coupling agent modified boron nitride is also added. Specifically, 25 g of the PDA-silane coupling agent modified boron nitride prepared in Preparation Example 2 is dispersed in 50 L of N,N-dimethylacetamide, and ultrasonic treatment is carried out for 4.5 h to obtain a PDA-silane coupling agent modified boron nitride dispersion liquid. Subsequently, it is mixed evenly with 2.5 kg of diamine (1.25 kg of p-phenylenediamine and 1.25 kg of 4,4'-diaminodiphenyl ether). Under nitrogen protection, stirring is carried out until the diamine is completely dissolved. Pyromellitic dianhydride is added in 9 portions, 0.3 kg of pyromellitic dianhydride is added each time, and the reaction is carried out for 1 h each time. The reaction temperature is 20 °C. When the solid content in the system is greater than 15 wt%, defoaming treatment is carried out to obtain a polyamic acid polymer, which is coated and dried to obtain a polyimide film.

[0104] Example 5.3

[0105] A preparation process of a polyimide film tape, which is different from Example 2.1 in that: in step S1, PDA-silane coupling agent modified boron nitride is also added. Specifically, 36.4 g of the PDA-silane coupling agent modified boron nitride prepared in Preparation Example 3 is dispersed in 50 L of N,N-dimethylacetamide, and ultrasonic treatment is carried out for 6 h to obtain a PDA-silane coupling agent modified boron nitride dispersion liquid. Subsequently, it is mixed evenly with 2.5 kg of diamine (1.25 kg of p-phenylenediamine and 1.25 kg of 4,4'-diaminodiphenyl ether). Under nitrogen protection, stirring is carried out until the diamine is completely dissolved. Pyromellitic dianhydride is added in 9 portions, 0.3 kg of pyromellitic dianhydride is added each time, and the reaction is carried out for 1 h each time. The reaction temperature is 20 °C. When the solid content in the system is greater than 15 wt%, defoaming treatment is carried out to obtain a polyamic acid polymer, which is coated and dried to obtain a polyimide film.

[0106] Example 5.4

[0107] A preparation process of a polyimide film tape, which is different from Example 2.1 in that: in step S1, PDA-silane coupling agent modified boron nitride is also added. Specifically, 4 g of the PDA-silane coupling agent modified boron nitride prepared in Preparation Example 1 is dispersed in 50 L of N,N-dimethylacetamide, and ultrasonic treatment is carried out for 3 h to obtain a PDA-silane coupling agent modified boron nitride dispersion liquid. Subsequently, it is mixed evenly with 2.5 kg of diamine (1.25 kg of p-phenylenediamine and 1.25 kg of 4,4'-diaminodiphenyl ether). Under nitrogen protection, stirring is carried out until the diamine is completely dissolved. Pyromellitic dianhydride is added in 9 portions, 0.3 kg of pyromellitic dianhydride is added each time, and the reaction is carried out for 1 h each time. The reaction temperature is 20 °C. When the solid content in the system is greater than 15 wt%, defoaming treatment is carried out to obtain a polyamic acid polymer, which is coated and dried to obtain a polyimide film.

[0108] Example 5.5

[0109] A preparation process of a polyimide film tape, which is different from Example 2.1 in that: in step S1, PDA-silane coupling agent modified boron nitride is further added, specifically: 40 g of PDA-silane coupling agent modified boron nitride prepared in Preparation Example 1 is dispersed in 50 L of N,N-dimethylacetamide, and ultrasonic treatment is carried out for 3 h to obtain a PDA-silane coupling agent modified boron nitride dispersion liquid. Subsequently, it is mixed evenly with 2.5 kg of diamine (1.25 kg of p-phenylenediamine and 1.25 kg of 4,4'-diaminodiphenyl ether), and under nitrogen protection, it is stirred until the diamine is completely dissolved. Pyromellitic dianhydride is added in 9 times, 0.3 kg of pyromellitic dianhydride is added each time, and the reaction is carried out for 1 h each time. The reaction temperature is 20 °C. When the solid content in the system is greater than 15 wt%, defoaming treatment is carried out to obtain a polyamic acid polymer, which is coated and dried to obtain a polyimide film.

[0110] Examples 6.1 - 6.4

[0111] A preparation process of a polyimide film tape, which is different from Example 5.1 in that: the addition amounts of PDA-silane coupling agent modified boron nitride are 10 g, 18 g, 26 g, and 34 g respectively, and the rest are the same as Example 5.1.

[0112] Example 7

[0113] A preparation process of a polyimide film tape, which is different from Example 4.1 in that: in step S1, PDA-silane coupling agent modified boron nitride is further added, specifically: 26 g of PDA-silane coupling agent modified boron nitride prepared in Preparation Example 1 is dispersed in 50 L of N,N-dimethylacetamide, and ultrasonic treatment is carried out for 3 h to obtain a PDA-silane coupling agent modified boron nitride dispersion liquid. Subsequently, it is mixed evenly with 2.5 kg of diamine (0.75 kg of p-phenylenediamine, 1 kg of 4,4'-diaminodiphenyl ether, and 0.75 kg of 4,4'-diaminobenzanilide), and under nitrogen protection, it is stirred until the diamine is completely dissolved. Pyromellitic dianhydride is added in 9 times, 0.3 kg of pyromellitic dianhydride is added each time, and the reaction is carried out for 1 h each time. The reaction temperature is 20 °C. When the solid content in the system is greater than 15 wt%, defoaming treatment is carried out to obtain a polyamic acid polymer, which is coated and dried to obtain a polyimide film.

[0114] Example 8.1

[0115] A preparation process of a polyimide film tape, which is different from Example 2.1 in that: in step S1, silane coupling agent modified boron nitride is further added. Specifically, 5.2 g of the silane coupling agent modified boron nitride prepared in Preparation Example 4 is dispersed in 50 L of N,N-dimethylacetamide, and ultrasonic treatment is carried out for 3 h to obtain a silane coupling agent modified boron nitride dispersion liquid. Subsequently, it is mixed evenly with 2.5 kg of diamine (1.25 kg of p-phenylenediamine and 1.25 kg of 4,4'-diaminodiphenyl ether). Under nitrogen protection, stirring is carried out until the diamine is completely dissolved. Pyromellitic dianhydride is added in 9 portions, 0.3 kg of pyromellitic dianhydride is added each time, and the reaction is carried out for 1 h each time. The reaction temperature is 20 °C. When the solid content in the system is greater than 15 wt%, defoaming treatment is carried out to obtain a polyamic acid polymer, which is coated and dried to obtain a polyimide film.

[0116] Example 8.2

[0117] A preparation process of a polyimide film tape, which is different from Example 2.1 in that: in step S1, PDA modified boron nitride is further added. Specifically, 5.2 g of the PDA modified boron nitride prepared in Preparation Example 5 is dispersed in 50 L of N,N-dimethylacetamide, and ultrasonic treatment is carried out for 3 h to obtain a PDA modified boron nitride dispersion liquid. Subsequently, it is mixed evenly with 2.5 kg of diamine (1.25 kg of p-phenylenediamine and 1.25 kg of 4,4'-diaminodiphenyl ether). Under nitrogen protection, stirring is carried out until the diamine is completely dissolved. Pyromellitic dianhydride is added in 9 portions, 0.3 kg of pyromellitic dianhydride is added each time, and the reaction is carried out for 1 h each time. The reaction temperature is 20 °C. When the solid content in the system is greater than 15 wt%, defoaming treatment is carried out to obtain a polyamic acid polymer, which is coated and dried to obtain a polyimide film.

[0118] Comparative Example 1

[0119] It is different from Example 1.1 in that in step S2, it is a one-time coating. Specifically, the temperature is first raised to 410 °C, and a modified polytetrafluoroethylene emulsion is coated on the surface of the polyimide film prepared in step S1 by a numerically controlled coater, dried to obtain a single-layer coated tape with a surface roughness R a of 1.14. After 3 h, it is cooled and shaped, and dried to obtain a polyimide film tape.

[0120] Performance testing

[0121] 1. Film thickness test: A non-contact film thickness tester is used to measure the thickness of the polymer emulsion layer in step S2 in the examples and comparative examples;

[0122] 2. Mechanical property test: Take the polyimide films obtained in Step S1 of the examples and comparative examples, cut them into 5 dumbbell-shaped specimens for each group with a standard cutter on a punching machine, install the specimens on the fixture of a universal tensile testing machine, and set the tensile rate to 10 mm / min for testing. After the test is completed, read the tensile strength and calculate the average value;

[0123] 3. Adhesion strength test: Take the polyimide film tapes in the examples and comparative examples, cut them into a size of 150 mm × 10 mm, wipe the side coated with the polymer emulsion layer clean with benzene alcohol and white cotton fabric, then place a 150 mm × 10 mm × 1.0 mm copper sheet on the tape, stack them neatly, place them on the pressing surface of a sample preparation device at a temperature of 360 ± 2 °C, keep the pressure applied at 1 × 10 5 Pa, press for 1.0 min to obtain specimens. A total of 5 specimens are prepared for each example or comparative example for standby; Test the specimens prepared above with a tensile testing machine with a measuring range of 5 - 10 kg and an accuracy of 0.02 N. Peel the tape at both ends of the specimen by about 40 mm by hand, then clamp the two peeled ends on the upper and lower clamps with a clamp of 50 mm respectively, and conduct a 180° peeling test at a speed of 300 mm / min. Test 5 specimens and record the highest value. Adhesion force (N / 10 mm) = tensile force × 10 / 10 mm.

[0124] Table 1 Performance detection table

[0125] Group Thickness of polyimide film tape / μm Tensile strength / MPa Example 1.1 15.2 179.2 Example 1.2 15.3 179.8 Example 1.3 15.3 179.7 Example 2.1 18.3 154.1 Example 2.2 18.0 154.7 Example 2.3 18.2 154.2 Example 2.4 16.5 160.7 Example 2.5 16.7 132.6 Example 3.1 18.4 154.7 Example 3.2 19.8 154.6 Example 3.3 18.2 154.4 Example 3.4 18.5 154.3 Example 4.1 18.3 182.3 Example 4.2 18.2 187.6 Example 4.3 18.4 184.9 Example 5.1 18.6 177.5 Example 5.2 18.7 177.4 Example 5.3 18.6 177.3 Example 5.4 18.6 162.6 Example 5.5 18.7 162.0 Example 6.1 18.7 178.4 Example 6.2 18.7 178.2 Example 6.3 18.7 182.9 Example 6.4 18.6 177.8 Example 7.1 18.6 165.6 Example 7.2 18.6 165.9 Comparative Example 1 9.7 175.4

[0126] Data analysis:

[0127] As can be seen from Table 1, the surface roughness R of the polyimide films in Examples 1.1 - 1.3 after one-time coating is a 1.46, the final thickness of the polymer emulsion layer obtained is 15.2 - 15.3 μm, and the adhesion force can reach 14.4 - 14.5 N / 10 mm, which proves that in this application, the temperature is increased step by step for secondary coating. The surface roughness of the polymer emulsion after coating at the one-time coating temperature of this application is relatively large. Therefore, the secondary coating can still effectively increase the coating layer thickness of the polymer emulsion, and the thickness of the polymer emulsion layer is relatively increased by at least 5 μm. The adhesion force of the polyimide film tape and the firmness with the electromagnetic wire are both significantly improved, thereby improving the performance of its wrapped electromagnetic wire. After wrapping, it can achieve excellent electromagnetic wire waterproof and electrical insulation effects;

[0128] Examples 2.1-3.4 are different from Example 1.1 in that before coating the polymer emulsion on the surface layer of the polyimide film, the present application performs surface treatment on it, immersing it in an alkaline solution and an acid solution respectively, introducing a large number of hydrophilic groups into the molecules on the surface layer of the polyimide film, thereby significantly improving the surface roughness, surface tension and wettability of the polyimide film. The dynamic water contact angle is not greater than 51.5°, and the surface roughness R a can reach more than 1.60. Therefore, the polyimide film after surface treatment can be fully wetted when coating the polymer emulsion, greatly reducing the difficulty of coating the emulsion. The layer thickness of the finally obtained polymer emulsion is significantly increased to 16.5-19.8 um, and the adhesion can be increased to 14.9-16.2 N / 10 mm. Therefore, the operation of surface treatment can significantly optimize the coating effect, increase the layer thickness of the polymer emulsion layer by layer, thereby improving the adhesion of the polyimide film tape;

[0129] The surface roughness R of the polyimide film in Examples 2.4-2.5 a is significantly lower than that in Examples 2.1-2.3, the dynamic water contact angle is significantly larger than that in Examples 2.1-2.3, and the adhesion is also significantly lower than that in Examples 2.1-2.3. The tensile strength of Example 2.5 also has obvious defects. In Examples 3.1-3.4, it can also be clearly seen that the polyimide film in Example 3.2 has the largest surface roughness and the smallest dynamic water contact angle, proving that the present application further optimizes the comprehensive performance of the polyimide film tape by strictly controlling the concentration of hydroxide ions in the alkaline solution. If the concentration of hydroxide ions is too large or too small, effective surface treatment effects cannot be achieved, and the improvement of the surface roughness, surface tension and wettability of the polyimide film is insufficient. And when the concentration of hydroxide ions is too large, the surface layer of the polyimide film will be eroded by excessive alkaline solution, exposing a large number of internal structures. After this part of the internal structure contacts the air, it will promote the generation of cracks in the polyimide film tape, thereby damaging the tensile strength of the polyimide film;

[0130] The tensile strength of the polyimide film in Examples 4.1-4.3 is significantly higher than that in Example 2.1, proving that the present application adds a certain amount of 4,4'-diaminobenzanilide to the diamine system composed of p-phenylenediamine and 4,4'-diaminodiphenyl ether, partially replacing 4,4'-diaminodiphenyl ether, balancing the ratio of rigid groups and flexible groups in the system, so that the finally obtained polyimide film has higher tensile strength;

[0131] The tensile strength of the polyimide films in Examples 5.1 - 6.4 is significantly higher than that in Example 2.1, which proves that the PDA-silane coupling agent modified boron nitride with high interfacial adhesion strength and high dispersibility is added to the raw materials used for the polyimide films in this application. By utilizing the excellent mechanical strength and chemical stability of boron nitride, and supplemented by the sufficient dispersion and adhesion effects of the PDA-silane coupling agent modified boron nitride, the overall tensile strength of the polyimide film is significantly improved. The finally obtained polyimide film has uniform internal components and a very high tensile strength, and the tensile strength is increased by more than 15% compared with the polyimide film without the addition of the PDA-silane coupling agent modified boron nitride;

[0132] Moreover, the tensile strength of the polyimide films in Examples 5.4 - 5.5 is significantly lower than that in Example 5.1, and the tensile strength of the polyimide film in Example 6.3 is higher than that of other examples, which proves that by strictly controlling the addition amount of the PDA-silane coupling agent modified boron nitride in this application, the mechanical properties of the polyimide film are further optimized. If the addition amount is too small, the reinforcing effect is insufficient. If the addition amount is too large, although the PDA-silane coupling agent modified boron nitride will not form system defects and pores due to agglomeration, the excessive addition amount will still cause inevitable small part aggregation of the PDA-silane coupling agent modified boron nitride particles, which will still promote the generation of cracks after the polyimide film is stressed, resulting in the decline of the mechanical properties of the film;

[0133] The difference between Example 7 and Example 2.1 is that a certain amount of 4,4'-diaminobenzanilide and the PDA-silane coupling agent modified boron nitride are added simultaneously, and the tensile strength of the finally obtained film is significantly improved, which proves that while balancing the ratio of rigid groups and flexible groups in the system in this application, the PDA-silane coupling agent modified boron nitride with high interfacial adhesion strength, high dispersibility and reinforcing effect is added, which can further improve the tensile strength of the polyimide film, and its comprehensive improvement rate is much greater than the simple superposition of the improvement rates of adding a single component;

[0134] The tensile strength of the polyimide films in Examples 8.1 - 8.2 is significantly lower than that in Example 5.1, which proves that both the PDA layer and the silane coupling agent can greatly enhance the interfacial adhesion strength between boron nitride and the diamine and dianhydride system and its dispersibility in the system, and significantly improve the overall tensile strength of the polyimide film;

[0135] The thickness of the polymer emulsion layer in Comparative Example 1 is only 9.7 um, and the adhesion is only 9.6 N / 10 mm. It is proved that the temperature is increased step by step in this application for secondary coating. The surface roughness of the polymer emulsion after coating at the primary coating temperature in this application is relatively large. Therefore, the secondary coating can still effectively increase the coating layer thickness of the polymer emulsion. Compared with the traditional preparation process of forming by one-time coating, the thickness of the polymer emulsion layer can be relatively increased by more than 5 um, and the adhesion is increased by more than 4.8 N / 10 mm.

[0136] The embodiments of this specific implementation manner are all preferred embodiments of this application, and do not limit the protection scope of this application accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. A preparation process of a polyimide film tape, comprising the following steps: S1. Prepare a polyimide film. The steps for preparing the polyimide film include the step of reacting a diamine and a dianhydride to prepare a polyamic acid polymer. S2. Coat a polymer emulsion on the polyimide film. It is characterized in that: in step S2, the coating is carried out in two times, specifically: First, raise the temperature to the melting temperature of the polymer in the polymer emulsion, perform a primary coating, and dry it to obtain a surface roughness R a > 1.45 of a layer of coated tape. Subsequently, perform a secondary coating. After the coating, raise the temperature by 40 - 50 °C for melting, and finally cool and shape it, and dry it to obtain a polyimide film tape; the polymer emulsion is one or both of a perfluoroethylenepropylene copolymer emulsion or a modified polytetrafluoroethylene emulsion; Before step S2, the polyimide film prepared in step S1 also needs to be surface-treated. The specific steps are as follows: Completely immerse the polyimide film in an alkali solution with a hydroxide ion concentration of 0.2 mol / L for alkali treatment for 50 - 60 min. After washing with water, then completely immerse it in an acid solution with a hydrogen ion concentration of 0.1 - 0.12 mol / L for acid treatment for 8 - 10 min. Take it out, wash with water, and dry to obtain the surface-treated polyimide film; In the step of reacting the diamine and the dianhydride to prepare the polyamic acid polymer, PDA-silane coupling agent-modified boron nitride with a dosage of 0.5 wt% of the total amount of the dianhydride and the diamine is also added. Specifically: Disperse the PDA-silane coupling agent-modified boron nitride in N,N-dimethylacetamide, and carry out ultrasonic treatment for 3 - 6 h to obtain a PDA-silane coupling agent-modified boron nitride dispersion liquid. Then mix it evenly with the diamine, and finally add the dianhydride for reaction, coat, and dry to obtain the polyimide film.

2. The preparation process of a polyimide film tape according to claim 1, characterized in that: The diamine includes p-phenylenediamine, 4,4'-diaminodiphenyl ether, and 4,4'-diaminobenzanilide with a weight ratio of 3:(3 - 4):(3 - 4).

3. The preparation process of a polyimide film tape according to claim 1, characterized in that: The PDA-silane coupling agent-modified boron nitride is prepared by the following method: Hydroxylate boron nitride, then disperse it and a silane coupling agent in absolute ethanol, stir and react, carry out suction filtration, washing, and drying to obtain the silane coupling agent-modified boron nitride. Then disperse the silane coupling agent-modified boron nitride, dopamine, and tromethamine in an ethanol aqueous solution, adjust the pH to 8.4 - 8.6, stir at 75 - 85 °C for 5.5 - 6 h, carry out suction filtration, washing until the filtrate is colorless and neutral, take the obtained solid at this time, dry, and grind to obtain the PDA-silane coupling agent-modified boron nitride.

4. A polyimide film tape prepared by the preparation process of the polyimide film tape according to any one of claims 1-3, characterized in that: The layer thickness of the polymer emulsion of the polyimide film tape is not less than 15 μm.