Polyimide film and preparation method thereof

Abstract

The invention provides a polyimide film and a preparation method thereof, and relates to the technical field of polyimide film preparation. The preparation method of the polyimide film comprises the following steps: adding aromatic diamine and aromatic dianhydride into a polar solvent, and reacting to obtain polyamide acid resin; adding a dispersing agent and carbon black into a polar solvent to obtain slurry; adding the slurry into polyamic acid resin, and then adding aromatic dianhydride to obtain a polyamic acid resin solution B; adding aromatic diamine into the polyamic acid resin solution B to obtain a polyamic acid resin solution C, adding aromatic dianhydride to obtain a polyamic acid resin solution D, and adding an end-capping reagent to obtain a modified polyamic acid resin solution E; performing defoaming, coating and solvent removal treatment on the solution E to obtain a gel film, and performing imidization treatment to obtain a polyimide film; the film prepared by the invention has low water absorption and excellent insulating property.

Description

Technical Field

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

[0002] Polyimide film has excellent mechanical, thermal and electrical properties, so it is widely used in electrical and electronics, microelectronics, aerospace and other fields.

[0003] Black polyimide film is mainly used in the field of circuit board covering. Due to its good shielding performance, it can play a good role in technical confidentiality. At the same time, since black is opaque, it can avoid damage to optical equipment during subsequent processing and testing. However, since the filler that plays a shielding function in black polyimide film is carbon black, carbon black generally reduces the insulation performance of the film. At the same time, since the imide ring in the polyimide film material forms hydrogen bonds with water molecules, the film has a high water absorption rate, which further reduces the insulation performance of the black polyimide film.

[0004] The black polyimide film currently used for covering on the market usually has a water absorption rate of more than 1.5%, and its breakdown voltage is generally below 70V / μm after saturated water absorption, which seriously affects the safety of circuit boards. In addition, a high water absorption rate will also accelerate the hydrolysis of the film, causing the film to rupture and delaminate from the circuit board, reducing the service life. The use of fluorinated monomers can effectively reduce the water absorption rate of the film, but the cost will increase significantly; the use of insulating carbon black can also improve the insulation performance of the film, but it will cause the shielding effect to deteriorate. How to reduce the water absorption rate of the black polyimide film while improving the insulation performance of the film under the premise of controlling costs and maintaining a good shielding effect is of great significance. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a polyimide film and a preparation method thereof, which solves the technical problems of high water absorption and low insulation performance of conventional black polyimide films.

[0006] A method for preparing a polyimide film comprises the following steps:

[0007] (1) In an inert gas atmosphere, an aromatic diamine is added to a polar solvent, and after the aromatic diamine is dissolved, an aromatic dianhydride is added, and the mixture is stirred to react to obtain a polyamic acid resin solution having a viscosity of 30-60 Pa·S;

[0008] (2) adding a dispersant to the polar solvent while stirring, and then adding carbon black, and grinding to obtain a slurry;

[0009] (3) adding the slurry to the polyamic acid resin solution, stirring and then adding aromatic dianhydride to obtain a polyamic acid resin solution B with a viscosity of 100-200 Pa·S;

[0010] (4) dissolving an aromatic diamine in a polar solvent and adding the solution to the polyamic acid resin solution B to obtain a polyamic acid resin solution C having a viscosity of 30-60 Pa·S, adding an aromatic dianhydride after stirring to obtain a polyamic acid resin solution D having a viscosity of 130-200 Pa·S, stirring again, and adding a capping agent to obtain a modified polyamic acid resin solution E;

[0011] (5) The modified polyamic acid resin solution E is subjected to degassing, coating and solvent removal treatments to obtain a gel film, which is then subjected to imidization treatment to obtain a polyimide film.

[0012] Preferably, the aromatic diamines in step (1) and step (4) include one or more of p-phenylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diamino-2,2'-dimethylbiphenyl, 4-aminobenzoic acid 4-aminophenyl ester, 2-(4-aminophenyl)-5-aminobenzoxazole, 2,5-diaminotoluene, 4,4'-diaminobenzanilide and [4-(4-aminobenzoyl)oxyphenyl] 4-aminobenzoate.

[0013] Preferably, the end-capping agent includes one or more of phthalic anhydride, trimellitic anhydride, maleic anhydride and succinic anhydride.

[0014] Preferably, in step (1), the reaction temperature is 30-50° C., the reaction time is 4-6 h; the solid content of the polyamic acid resin solution is 15-19.5 wt %; and the molar ratio of the aromatic dianhydride to the aromatic diamine is 0.97-0.98:1.

[0015] Preferably, in step (2), the dispersant is a block polyester lactone copolymer solution; and the grinding medium in step (2) is zirconium oxide beads.

[0016] Preferably, the aromatic dianhydride in step (1), step (3) and step (4) comprises one or more of pyromellitic dianhydride, 3,3'-4,4'-biphenyltetracarboxylic dianhydride, 4,4'-biphenyl ether dianhydride, bisphenol A type diether dianhydride and 3,3',4,4'-dibenzophenone tetracarboxylic dianhydride.

[0017] Preferably, the polar solvent in step (1), step (2) and step (4) includes one or more of N,N'-dimethylacetamide, N,N'-dimethylformamide, N-methylpyrrolidone and N,N'-dialkylcarboxylic acid amide.

[0018] Preferably, in the step (4), the weight ratio of the polar solvent, the aromatic diamine and the polyamic acid resin solution B is 1:0.01-0.1:100; the weight ratio of the end-capping agent to the polyamic acid resin solution D is 0.01-0.05:100; the weight ratio of the slurry to the polyamic acid resin solution in the step (3) is 1-2.5:51.3-66.7; the weight ratio of the polar solvent, carbon black and the dispersant in the step (2) is 80-90:10-20:1-4.

[0019] The polyimide film is prepared by the above preparation method.

[0020] The above polyimide film is used in the production of electrical and electronic, microelectronics and aerospace products.

[0021] The present invention provides a black polyimide film with low water absorption and high insulation performance and a preparation method thereof. Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention uses a diamine monomer solution to adjust the polyamic acid resin solution, and adjusts the polymer molecular weight distribution by adjusting the viscosity of the resin system, so that the resin molecular weight distribution is more concentrated, and the chain segment arrangement is more uniform and regular, thereby improving the insulation performance of the black polyimide film and reducing the water absorption rate of the black polyimide film.

[0023] 2. Compared with the black polyimide film prepared by the traditional process, the black polyimide film prepared by the present invention can effectively prolong the storage time of the polyamic acid resin solution, prevent the hydrolysis and breakage of the molecular chain, and reduce the binding sites of water molecules, thereby reducing the water absorption rate of the film and improving the insulation performance of the film because the precursor (black polyamic acid resin solution) is treated with a capping agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 GPC test chromatogram of the polyamic acid resin prepared in Example 1.

[0026] Figure 2 GPC test results of the polyamic acid resin prepared in Example 1.

[0027] Figure 3 GPC test chromatogram of the polyamic acid resin prepared in Comparative Example 2.

[0028] Figure 4GPC test results of the polyamic acid resin prepared in Comparative Example 2. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The embodiment of the present application solves the technical problems of high water absorption and low insulation performance of conventional black polyimide films by providing a method for preparing a black polyimide film.

[0031] The technical solution in the embodiment of the present application is to solve the above technical problems, and the overall idea is as follows:

[0032] A method for preparing a black polyimide film comprises the following steps:

[0033] (1) preparing a polyamic acid resin solution;

[0034] (2) preparing black slurry;

[0035] (3) preparing a black polyamic acid resin solution;

[0036] (4) Modification of black polyamic acid resin solution;

[0037] (5) Preparation of black polyimide film.

[0038] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0039] Embodiment 1:

[0040] This embodiment provides a method for preparing a black polyimide film, comprising the following steps:

[0041] (1) Preparation of polyamic acid resin solution: 164 g of DMAC was added to a 500 ml glass flask, followed by 3.24 g of PDA and 14 g of ODA, and the mixture was heated and stirred at 40° C. After the mixture was completely dissolved, 21.15 g of PMDA was gradually added to obtain a polyamic acid resin solution with a viscosity of 30 Pa·s;

[0042] (2) Preparation of black slurry: Take 80g of N,N'-dimethylacetamide, add 1g of polyurethane dispersant, stir evenly, then add 10g of carbon black with a primary particle size of 40nm, high shear dispersion and mixing at 2000rpm, and then grind it at 30℃ for 3h using a sand mill with zirconia beads with a particle size of 2mm as the grinding medium to obtain a black slurry with a carbon black particle size of ≤3μm.

[0043] (3) Preparation of black polyamide acid resin solution: 3.03 g of black slurry was added to the polyamide acid resin solution at a speed of 70 rpm and stirred for 1.5 h. After stirring evenly, 0.5 g of PMDA was added to obtain a high-viscosity black polyamide resin solution B with a viscosity of 100 Pa·s.

[0044] (4) Modification of black polyamic acid resin solution: 0.23 g ODA was dissolved in 2.1 g DMAC, and after it was completely dissolved, it was added dropwise to a high-viscosity black polyamic acid resin solution B. After sufficient reaction, a resin solution C with a viscosity of 30 Pa·s was obtained. Then 0.2 g PMDA was added to adjust the resin viscosity to 130 Pa·s, and then 0.02 g phthalic anhydride was added. After the reaction was complete, a modified black polyamic acid resin solution E was obtained.

[0045] (5) Preparation of black polyimide film: The modified black polyamic acid resin solution was subjected to vacuum degassing treatment, and then coated on a glass plate and dried in a forced air drying oven at 80°C for 30 min to obtain a gel film. The obtained gel film was peeled off and fixed on a metal frame, and placed in an imidization furnace for imidization at 360°C for 25 min to obtain a black polyimide film with a thickness of 12.5 μm.

[0046] Example 2

[0047] This embodiment provides a method for preparing a black polyimide film, comprising the following steps:

[0048] (1) Preparation of polyamic acid resin solution: 176 g of DMAC was added to a 500 ml glass flask, followed by 3.24 g of PDA and 14 g of ODA, and the mixture was heated and stirred at 40° C. After the mixture was completely dissolved, 8.83 g of BPDA was first added, followed by 14.88 g of PMDA, to obtain a polyamic acid resin solution having a viscosity of 45 Pa·s.

[0049] (2) Preparation of black slurry: Take 85g of N,N'-dimethylacetamide, add 2.5g of polyurethane dispersant, stir evenly, add 15g of carbon black with a primary particle size of 40nm, high shear dispersion and mix at 2000rpm, and then grind it at 30℃ for 3h using a sand mill with zirconium oxide beads with a particle size of 2mm as the grinding medium to obtain a black slurry with a carbon black particle size of ≤3μm.

[0050] (3) Preparation of black polyamide acid resin solution: 8.08 g of black slurry was added to the polyamide acid resin solution at a speed of 150 rpm and stirred for 1.5 h. After stirring evenly, 0.3 g of PMDA was added to obtain a high-viscosity black polyamide resin solution B with a viscosity of 145 Pa·s.

[0051] (4) Modification of black polyamic acid resin solution: 0.1 g ODA was dissolved in 2 g DMAC, and after it was completely dissolved, it was added dropwise to a high-viscosity black polyamic acid resin solution B. After sufficient reaction, a resin solution C with a viscosity of 30 Pa·s was obtained. Then 0.3 g PMDA was added thereto to adjust the resin viscosity to 160 Pa·s, and then 0.06 g trimellitic anhydride was added. After the reaction was complete, a modified black polyamic acid resin solution E was obtained.

[0052] (5) Preparation of black polyimide film: The modified black polyamic acid resin solution was subjected to vacuum degassing treatment, and then coated on a glass plate and dried in a forced air drying oven at 80°C for 30 min to obtain a gel film. The obtained gel film was peeled off and fixed on a metal frame, and placed in an imidization furnace for imidization at 360°C for 25 min to obtain a black polyimide film with a thickness of 12.5 μm.

[0053] Example 3

[0054] This embodiment provides a method for preparing a black polyimide film, comprising the following steps:

[0055] (1) Preparation of polyamic acid resin solution: 198 g of DMAC was added to a 500 ml glass flask, followed by 4.25 g of m-Tol and 16 g of ODA, and the mixture was heated and stirred at 40° C. After the mixture was completely dissolved, 5.89 g of BPDA was added first, followed by 17.09 g of PMDA, to obtain a polyamic acid resin solution with a viscosity of 60 Pa·s.

[0056] (2) Preparation of black slurry: Take 90g of N,N'-dimethylacetamide, add 4g of polyurethane dispersant, stir evenly, add 20g of carbon black with a primary particle size of 40nm, high shear dispersion and mix at 2000rpm, and then grind it at 30℃ for 3h using a sand mill with zirconium oxide beads with a particle size of 2mm as the grinding medium to obtain a black slurry with a carbon black particle size of ≤3μm.

[0057] (3) Preparation of black polyamide acid resin solution: 10.64 g of black slurry was added to the polyamide acid resin solution, the rotation speed was 150 rpm, and the mixture was stirred for 1.5 h. After the mixture was stirred evenly, 0.5 g of BPDA was added to obtain a high-viscosity black polyamide resin solution B with a viscosity of 200 Pa·s.

[0058] (4) Modification of black polyamic acid resin solution: 0.021 g ODA was dissolved in 2.3 g NMP, and after it was completely dissolved, it was added dropwise to a high-viscosity black polyamic acid resin solution B. After sufficient reaction, a resin solution C with a viscosity of 60 Pa·s was obtained. Then 0.4 g PMDA was added thereto to adjust the resin viscosity to 200 Pa·s, and then 0.12 g trimellitic anhydride was added. After the reaction was complete, a modified black polyamic acid resin solution E was obtained.

[0059] (5) Preparation of black polyimide film: The modified black polyamic acid resin solution was subjected to vacuum degassing treatment, and then coated on a glass plate and dried in a forced air drying oven at 80°C for 40 min to obtain a gel film. The obtained gel film was peeled off and fixed on a metal frame, and placed in an imidization furnace for imidization at 360°C for 30 min to obtain a black polyimide film with a thickness of 12.5 μm.

[0060] Comparative Example 1

[0061] (1) Preparation of polyamic acid resin solution: 164 g of DMAC was added to a 500 ml glass flask, followed by 3.24 g of PDA and 14 g of ODA, and the mixture was heated and stirred at 40° C. After the mixture was completely dissolved, 21.2 g of PMDA was gradually added to obtain a polyamic acid resin solution with a viscosity of 42 Pa·s;

[0062] (2) Preparation of black slurry: Take 80g of N,N'-dimethylacetamide, add 2g of polyurethane dispersant, stir evenly, then add 18g of carbon black with a primary particle size of 40nm, high shear dispersion and mixing at 2000rpm, and then grind it at 30℃ for 3h using a sand mill with zirconium oxide beads with a particle size of 2mm as the grinding medium to obtain a black slurry with a carbon black particle size of ≤3μm.

[0063] (3) Preparation of black polyamide acid resin solution: 7.5 g of black slurry was added to the polyamide acid resin solution at a speed of 150 rpm and stirred for 1.5 h. After stirring evenly, 0.5 g of PMDA was added to obtain a high-viscosity black polyamide resin solution with a viscosity of 70 Pa·s.

[0064] (4) Modification of black polyamic acid resin solution: 0.08 g ODA was dissolved in 2.1 g DMAC, and after it was completely dissolved, it was added dropwise to the high-viscosity black polyamic acid resin solution. After sufficient reaction, 0.2 g PMDA was added to adjust the resin viscosity to 70 Pa·s to obtain a black polyamic acid resin solution;

[0065] (5) Preparation of black polyimide film: The black polyamic acid resin solution was subjected to vacuum degassing treatment, and then coated onto a glass plate and dried in a forced air drying oven at 80°C for 30 min to obtain a gel film. The obtained gel film was peeled off and fixed on a metal frame, and then placed in an imidization furnace for imidization at 360°C for 25 min to obtain a black polyimide film with a thickness of 12.5 μm.

[0066] Comparative Example 2

[0067] This comparative example provides a conventional process for preparing a black polyimide film, comprising the following steps:

[0068] (1) Preparation of polyamic acid resin solution: 166.1 g of DMAC was added to a 500 ml glass flask, followed by 3.32 g of PDA and 14 g of ODA, and the mixture was heated and stirred at 40° C. After the mixture was completely dissolved, 21.2 g of PMDA was gradually added to obtain a polyamic acid resin solution with a viscosity of 41 Pa·s;

[0069] (2) Preparation of black slurry: Take 80g of N,N'-dimethylacetamide, add 2g of polyurethane dispersant, stir evenly, then add 18g of carbon black with a primary particle size of 40nm, high shear dispersion and mixing at 2000rpm, and then grind it at 30℃ for 3h using a sand mill with zirconium oxide beads with a particle size of 2mm as the grinding medium to obtain a black slurry with a carbon black particle size of ≤3μm.

[0070] (3) Preparation of black polyamide acid resin solution: 7.5 g of black slurry was added to the polyamide acid resin solution at a speed of 150 rpm and stirred for 1.5 h. After stirring evenly, 0.6 g of PMDA was added to obtain a high-viscosity black polyamide resin solution with a viscosity of 68 Pa·s.

[0071] (4) Preparation of black polyimide film: The black polyamic acid resin solution was subjected to vacuum degassing treatment, and then coated onto a glass plate and dried in a forced air drying oven at 80°C for 30 min to obtain a gel film. The obtained gel film was peeled off and fixed on a metal frame, and then placed in an imidization furnace for imidization at 360°C for 25 min to obtain a black polyimide film with a thickness of 12.5 μm.

[0072] Comparative Example 3

[0073] (1) Preparation of polyamic acid resin solution: 176 g of DMAC was added to a 500 ml glass flask, followed by 3.24 g of PDA and 14 g of ODA, and the mixture was heated and stirred at 40° C. After the mixture was completely dissolved, 8.83 g of BPDA was first added, followed by 14.8 g of PMDA, to obtain a polyamic acid resin solution with a viscosity of 50 Pa·s.

[0074] (2) Preparation of black slurry: Take 80g of N,N'-dimethylacetamide, add 2g of polyurethane dispersant, stir evenly, then add 18g of carbon black with a primary particle size of 40nm, high shear dispersion and mixing at 2000rpm, and then grind it at 30℃ for 3h using a sand mill with zirconium oxide beads with a particle size of 2mm as the grinding medium to obtain a black slurry with a carbon black particle size of ≤3μm.

[0075] (3) Preparation of black polyamide acid resin solution: 8.08 g of black slurry was added to the polyamide acid resin solution at a speed of 150 rpm and stirred for 1.5 h. After stirring evenly, 0.3 g of PMDA was added to obtain a high-viscosity black polyamide resin solution with a viscosity of 145 Pa·s.

[0076] (4) Modification of black polyamic acid resin solution: 0.07 g ODA was dissolved in 2 g DMAC, and after it was completely dissolved, it was added dropwise to the high-viscosity black polyamic acid resin solution. After sufficient reaction, 0.3 g PMDA was added to adjust the resin viscosity to 145 Pa·s to obtain a black polyamic acid resin solution;

[0077] (5) Preparation of black polyimide film: The black polyamic acid resin solution was subjected to vacuum degassing treatment, and then coated onto a glass plate and dried in a forced air drying oven at 80°C for 30 min to obtain a gel film. The obtained gel film was peeled off and fixed on a metal frame, and then placed in an imidization furnace for imidization at 360°C for 25 min to obtain a black polyimide film with a thickness of 12.5 μm.

[0078] Comparative Example 4

[0079] This comparative example provides a conventional process for preparing a black polyimide film, comprising the following steps:

[0080] (1) Preparation of polyamic acid resin solution: 178 g of DMAC was added to a 500 ml glass flask, followed by 3.31 g of PDA and 14 g of ODA, and the mixture was heated and stirred at 40° C. After the mixture was completely dissolved, 8.83 g of BPDA was first added, followed by 14.8 g of PMDA, to obtain a polyamic acid resin solution having a viscosity of 49 Pa·s.

[0081] (2) Preparation of black slurry: Take 80g of N,N'-dimethylacetamide, add 2g of polyurethane dispersant, stir evenly, then add 18g of carbon black with a primary particle size of 40nm, high shear dispersion and mixing at 2000rpm, and then grind it at 30℃ for 3h using a sand mill with zirconium oxide beads with a particle size of 2mm as the grinding medium to obtain a black slurry with a carbon black particle size of ≤3μm.

[0082] (3) Preparation of black polyamide acid resin solution: 8.08 g of black slurry was added to the polyamide acid resin solution at a speed of 150 rpm and stirred for 1.5 h. After stirring evenly, 0.4 g of PMDA was added to obtain a high-viscosity black polyamide resin solution with a viscosity of 146 Pa·s.

[0083] (5) Preparation of black polyimide film: The black polyamic acid resin solution was subjected to vacuum degassing treatment, and then coated onto a glass plate and dried in a forced air drying oven at 80°C for 30 min to obtain a gel film. The obtained gel film was peeled off and fixed on a metal frame, and then placed in an imidization furnace for imidization at 360°C for 25 min to obtain a black polyimide film with a thickness of 12.5 μm.

[0084] Comparative Example 5

[0085] This embodiment provides a method for preparing a black polyimide film, comprising the following steps:

[0086] (1) Preparation of polyamic acid resin solution: 198 g of DMAC was added to a 500 ml glass flask, followed by 4.25 g of m-Tol and 16 g of ODA, and the mixture was heated and stirred at 40° C. After the mixture was completely dissolved, 5.89 g of BPDA was added first, followed by 16.8 g of PMDA, to obtain a polyamic acid resin solution with a viscosity of 45 Pa·s.

[0087] (2) Preparation of black slurry: Take 80g of N,N'-dimethylacetamide, add 2g of polyurethane dispersant, stir evenly, then add 18g of carbon black with a primary particle size of 40nm, high shear dispersion and mixing at 2000rpm, and then grind it at 30℃ for 3h using a sand mill with zirconium oxide beads with a particle size of 2mm as the grinding medium to obtain a black slurry with a carbon black particle size of ≤3μm.

[0088] (3) Preparation of black polyamide acid resin solution: 9 g of black slurry was added to the polyamide acid resin solution at a speed of 150 rpm and stirred for 1.5 h. After stirring evenly, 0.5 g of BPDA was added to obtain a high-viscosity black polyamide resin solution with a viscosity of 145 Pa·s.

[0089] (4) Modification of black polyamic acid resin solution: 0.07 g ODA was dissolved in 2.4 g NMP, and after it was completely dissolved, it was added dropwise to the high-viscosity black polyamic acid resin solution. After sufficient reaction, 0.3 g PMDA was added to adjust the resin viscosity to 145 Pa·s to obtain a black polyamic acid resin solution;

[0090] (5) Preparation of black polyimide film: The black polyamic acid resin solution was subjected to vacuum degassing treatment, and then coated onto a glass plate and dried in a forced air drying oven at 80°C for 40 min to obtain a gel film. The obtained gel film was peeled off and fixed on a metal frame, and placed in an imidization furnace for imidization at 360°C for 30 min to obtain a black polyimide film with a thickness of 12.5 μm.

[0091] Comparative Example 6

[0092] This comparative example provides a conventional process for preparing a black polyimide film, comprising the following steps:

[0093] (1) Preparation of polyamic acid resin solution: 200 g of DMAC was added to a 500 ml glass flask, followed by 4.25 g of m-Tol and 16 g of ODA, and the mixture was heated and stirred at 40° C. After the mixture was completely dissolved, 5.89 g of BPDA was added first, followed by 16.8 g of PMDA, to obtain a polyamic acid resin solution with a viscosity of 45 Pa·s.

[0094] (2) Preparation of black slurry: Take 80g of N,N'-dimethylacetamide, add 2g of polyurethane dispersant, stir evenly, then add 18g of carbon black with a primary particle size of 40nm, high shear dispersion and mixing at 2000rpm, and then grind it at 30℃ for 3h using a sand mill with zirconium oxide beads with a particle size of 2mm as the grinding medium to obtain a black slurry with a carbon black particle size of ≤3μm.

[0095] (3) Preparation of black polyamide acid resin solution: 9 g of black slurry was added to the polyamide acid resin solution at a speed of 150 rpm and stirred for 1.5 h. After stirring evenly, 0.5 g of BPDA was added to obtain a high-viscosity black polyamide resin solution with a viscosity of 145 Pa·s.

[0096] (4) Preparation of black polyimide film: The modified black polyamic acid resin solution was subjected to vacuum degassing treatment, and then coated on a glass plate and dried in a forced air drying oven at 80°C for 40 min to obtain a gel film. The obtained gel film was peeled off and fixed on a metal frame, and placed in an imidization furnace for imidization at 360°C for 30 min to obtain a black polyimide film with a thickness of 12.5 μm.

[0097] The properties of the black polyimide films prepared in the above-mentioned Examples 1-3 and Comparative Examples 1-6 were tested. The test methods are shown in Table 1, and the results are shown in Table 2.

[0098] Table 1 Performance test methods of polyimide films

[0099]

[0100] Table 2 Performance test results of the prepared polyimide film

[0101]

[0102]

[0103] As can be seen from Table 2, the water absorption rate of the polyimide film prepared by the method of the present invention is significantly lower than that of the polyimide film prepared by the traditional process, and the insulation performance is significantly improved, which can meet the use in the covering field, and the tensile strength, modulus and elongation at break of the former are also improved to varying degrees. The preparation method of the present invention has a simple operation process and strong feasibility, and has a significant improvement effect on the comprehensive properties of the film including the thermal expansion coefficient, and has potential application value in the field of industrial production.

[0104] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0105] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a polyimide film, characterized in that: The steps include: (1) In an inert gas atmosphere, an aromatic diamine is added to a polar solvent, and after the aromatic diamine is dissolved, an aromatic dianhydride is added, and the mixture is stirred to react to obtain a polyamic acid resin solution having a viscosity of 30-60 Pa·S; (2) adding a dispersant to the polar solvent while stirring, and then adding carbon black, and grinding to obtain a slurry; (3) adding the slurry to the polyamic acid resin solution, stirring and then adding aromatic dianhydride to obtain a polyamic acid resin solution B with a viscosity of 100-200 Pa·S; (4) dissolving an aromatic diamine in a polar solvent and adding the solution to the polyamic acid resin solution B to obtain a polyamic acid resin solution C having a viscosity of 30-60 Pa·S, adding an aromatic dianhydride after stirring to obtain a polyamic acid resin solution D having a viscosity of 130-200 Pa·S, stirring again, and adding a capping agent to obtain a modified polyamic acid resin solution E; (5) The modified polyamic acid resin solution E is subjected to degassing, coating and solvent removal treatments to obtain a gel film, which is then subjected to imidization treatment to obtain a polyimide film.

2. The method for preparing a polyimide film according to claim 1, characterized in that: The aromatic diamines in step (1) and step (4) include one or more of p-phenylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diamino-2,2'-dimethylbiphenyl, 4-aminobenzoic acid 4-aminophenyl ester, 2-(4-aminophenyl)-5-aminobenzoxazole, 2,5-diaminotoluene, 4,4'-diaminobenzanilide and [4-(4-aminobenzoyl)oxyphenyl] 4-aminobenzoate.

3. The method for preparing a polyimide film according to claim 1, characterized in that: The end-capping agent includes one or more of phthalic anhydride, trimellitic anhydride, maleic anhydride and succinic anhydride.

4. The method for preparing a polyimide film according to claim 1, characterized in that: In the step (1), the reaction temperature is 30-50° C., and the reaction time is 4-6 hours; the solid content of the polyamic acid resin solution is 15-19.5 wt %; and the molar ratio of the aromatic dianhydride to the aromatic diamine is 0.97-0.98:

1.

5. The method for preparing a polyimide film according to claim 1, characterized in that: In the step (2), the dispersant is a block polyester lactone copolymer solution; and the grinding medium in the step (2) is zirconium oxide beads.

6. The method for preparing a polyimide film according to claim 1, characterized in that: The aromatic dianhydride in step (1), step (3) and step (4) includes one or more of pyromellitic dianhydride, 3,3'-4,4'-biphenyltetracarboxylic dianhydride, 4,4'-biphenyl ether dianhydride, bisphenol A type diether dianhydride and 3,3',4,4'-dibenzophenone tetracarboxylic dianhydride.

7. The method for preparing a polyimide film according to claim 1, characterized in that: The polar solvent in step (1), step (2) and step (4) includes one or more of N,N'-dimethylacetamide, N,N'-dimethylformamide, N-methylpyrrolidone and N,N'-dialkylcarboxylic acid amide.

8. The method for preparing a polyimide film according to claim 1, characterized in that: In the step (4), the weight ratio of the polar solvent, the aromatic diamine and the polyamic acid resin solution B is 1:0.01-0.1:100; the weight ratio of the end-capping agent to the polyamic acid resin solution D is 0.01-0.05:100; the weight ratio of the slurry to the polyamic acid resin solution in the step (3) is 1-2.5:51.3-66.7; the weight ratio of the polar solvent, carbon black and the dispersant in the step (2) is 80-90:10-20:1-4.

9. The polyimide film obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the polyimide film according to claim 9 in the production of electrical and electronic, microelectronic and aerospace products.

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