A polyimide-polyamideimide film and preparation method thereof

Abstract

The present invention belongs to the field of polymer materials, and specifically relates to a polyimide-polyamide-imide film and a preparation method thereof. The polyimide precursor solution containing an excess of anhydride is mixed with an amino-terminated polyamide-imide solution, and then the polyimide-polyamide-imide film is prepared by coating and heat treatment. The polymer molecule main chain has both amide and imide structures, and the content of polyimide and polyamide-imide is adjusted to achieve the comprehensive performance of low CTE and high elongation of the film material. Compared with the existing technology, the polyimide-polyamide-imide provided by the present invention has high temperature resistance, high dimensional stability and good mechanical strength, and can be applied to fields such as electronic displays and flexible circuit boards.

Description

Technical Field

[0001] The present invention relates to the field of polymer films, and in particular to a method for preparing a polyimide-polyamideimide film. Background Art

[0002] Aromatic polyimide (PI) is a rigid material containing a five-membered imide ring in its molecular backbone. It exhibits excellent high-temperature resistance, mechanical properties, chemical resistance, dimensional stability, insulation properties, radiation resistance, and flame retardancy, making it widely used in aerospace, engineering machinery, weaponry, and microelectronic semiconductors. In the fields of electronic displays and flexible circuit boards, polyimide-based materials with thermal expansion coefficients that match those of different substrates and excellent mechanical properties are gradually becoming one of the main areas of technological development. However, due to their high aromatic ring density, PI materials typically exhibit low expansion, but high modulus and poor flexibility, making it difficult to meet the requirements for a combination of thermal stability and mechanical properties.

[0003] Polyamide-imide (PAI) was first developed as a molding compound by Amoco in the United States in 1972 and commercialized under the Torlon brand in 1976. PAI's molecular backbone contains both amide and imide rings. It combines the performance advantages of both PA and PI, such as high-temperature resistance, corrosion resistance, friction and wear resistance, excellent mechanical properties, and compatibility with a variety of materials. It is a high-performance specialty engineering plastic. PAI materials have broad development prospects in aerospace, military equipment, chemical equipment, electronic devices, and other fields.

[0004] To address the application limitations of the above-mentioned PI materials, introducing amide bonds into the PI molecular chain is an important method for simultaneously maintaining the material's excellent mechanical properties and heat resistance. In the prior art, polyamide-imide materials are prepared by copolymerizing dianhydrides, diamines, and carbonyl compounds to adjust the CTE and optical properties of polyimide films. For example, invention patent CN107428962B mentions that a polyamide-imide precursor containing a first block of aromatic polyimide and a second block of polyamide is prepared by controlling the feeding sequence. The polyamide-imide film prepared from this precursor has better transparency, a lower thermal expansion coefficient, and better heat resistance than polyamide films. Compared with polyimide films, polyamide-imide films have better mechanical properties and less dimensional change. Patent CN110540644A also mentions the preparation of polyamide-imide-polyimide copolymer molding materials by copolymerizing diamine monomers, dianhydride monomers, and trimellitic anhydride chloride, which can improve the processing fluidity and heat resistance of the material. However, the above copolymerization methods cause differences in the polymer chain sequence structure due to factors such as different monomer activities and difficult polymerization processes, which easily cause instability in the final material properties. Moreover, the above methods all use monomers containing trifluoromethyl structures, which are not conducive to the preparation of thin film materials with lower thermal expansion coefficients. Therefore, it is of great significance to achieve the preparation of polyimide films with stable performance, low thermal expansion coefficient, and high mechanical properties. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a polyimide-polyamideimide film with stable performance, low expansion coefficient and high mechanical properties and a preparation method thereof.

[0006] The object of the present invention can be achieved by the following technical solution: A method for preparing a polyimide-polyamide-imide film, comprising the following steps:

[0007] 1) adding an aromatic diamine and an aromatic dianhydride to a polar aprotic solvent protected by nitrogen or an inert gas, stirring and reacting at -20-60° C. for 2-24 hours, controlling the molar ratio of the aromatic diamine to the aromatic dianhydride to be 1:1 to 1:1.2, to obtain a polyimide precursor solution A having a solid content of 10-40 wt % and an apparent viscosity of 1000-50000 cps;

[0008] 2) dissolving the amino-terminated polyamide-imide powder in a polar aprotic solvent to control the solid content to be 10-40 wt % to obtain a polyamide-imide solution B having an apparent viscosity of 1000-50000 cps;

[0009] 3) mixing the polyimide precursor solution A from step 1) and the polyamide-imide solution B from step 2) at a molar ratio of 50:49-99:1 of the solutes of the two, controlling the temperature at 20-80° C. and stirring for 4-12 hours to prepare a blended polyimide precursor-polyamide-imide resin solution;

[0010] 4) The blended polyimide precursor-polyamide-imide resin solution obtained in step 3) is filtered to remove impurities, vacuum degassed, and then coated on a substrate, and then heat-treated to obtain a polyimide-polyamide-imide film.

[0011] Furthermore, the aromatic diamine described in step 1) includes: one or more of phenylenediamine (p-PDA), m-phenylenediamine (m-PDA), 4,4'-diaminodiphenyl sulfone (DDS), benzyldiamine (BDE), 4'-diaminobenzanilide (DABA), 3,3'-dimethyl-4,4'-diaminobiphenyl (o-TLD), 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole (p-BOA), 2-(3-aminophenyl)-5-aminobenzoxazole (m-BOA), 2-(3-aminophenyl)-5-aminobenzimidazole (m-BIA), and 2-(4-aminophenyl)-5-aminobenzimidazole (p-BIA).

[0012] Furthermore, the aromatic dianhydride described in step 1) includes one or more of: 1,2,4,5-pyromellitic dianhydride (PMDA), 3,3'4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3'3,4'-biphenyltetracarboxylic dianhydride (a-BPDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), and 4-p-phenylene-diphenyltrimethylol dianhydride (TAHQ).

[0013] Furthermore, the polar aprotic solvent in step 1) includes one or a combination of two or more of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone;

[0014] In step 2), the polar aprotic solvent includes one or a combination of two or more of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.

[0015] Furthermore, the general formula of the amino-terminated polyamide-imide powder described in step 2) is:

[0016]

[0017] In Formula 1, X is a tetravalent organic group, Y is a divalent organic group, and n is an integer of 1 or greater.

[0018] Furthermore, in Formula 1, X is a tetravalent organic group having 6 to 40 carbon atoms;

[0019] Y is an aromatic group having 6 to 40 carbon atoms.

[0020] Furthermore, in Formula 1, X is an aromatic group or an alicyclic aliphatic group in which the imide group and the -CONH- group are ortho to each other, and the structure of X is one or a combination of two or more;

[0021] The structure of Y is one or a combination of two or more.

[0022] Furthermore, the mass ratio of the polyimide precursor solution A and the polyamide-imide solution B in step 3) is 70:30 to 95:5.

[0023] Furthermore, step 4) filtering and removing impurities is to remove impurities with a particle size greater than 1 μm in the blended resin solution obtained in step 3) by positive pressure filtration.

[0024] Substrates include glass, ceramic, stainless steel or plastic substrates;

[0025] The heat treatment is as follows: heating to 60-120°C at a rate of 0-10°C / min (preferably 2-6°C / min) and soft baking for 20-60 minutes. Then, placing the film in an oven and step-wise heating it to 300-500°C (preferably 380-450°C) removes the solvent and undergoes thermal imidization, while also cross-linking the terminal carboxyl groups, which positively impacts the material's ultimate heat resistance and mechanical properties. After the oven cools to ambient temperature, the film is removed from the oven, demolded by soaking in deionized water at 25-80°C, and dried to obtain a blended polyimide-polyamideimide film.

[0026] Another object of the present invention is to provide a polyimide-polyamideimide film prepared by the method.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention prepares a polyimide-polyamide-imide film by mixing a polyimide precursor solution containing an excess of anhydride with an amino-terminated polyamide-imide solution, followed by coating and heat treatment. This method allows covalent bonds to be incorporated into the polyamide-imide structure on the polyimide molecular backbone, utilizing the intermolecular hydrogen bonding provided by the amide structure to maintain thermal stability while improving the flexibility of the molecular chain and enhancing the toughness of the material. Excess terminal carboxyl groups are also reserved to form crosslinks during high-temperature treatment, further enhancing the material's performance. By adjusting the content of the polyimide precursor and polyamide-imide, the film material achieves the combined properties of low CTE and high elongation.

[0029] 2. The present invention utilizes aromatic diamine and aromatic dianhydride as raw materials, and controls their ratio and reaction conditions to obtain a polyimide precursor solution A having a solid content of 10-40 wt% and an apparent viscosity of 1000-50,000 cps. Amino-terminated polyamide-imide powder is dissolved in a polar aprotic solvent, controlling the solid content to 10-40 wt%, to obtain a polyamide-imide solution B having an apparent viscosity of 1000-50,000 cps. Controlling the solid content and apparent viscosity yields a resin solution with excellent film-forming properties, reducing defects caused by poor film-forming properties during the material forming process, thereby improving the performance of the film material. The polyimide precursor solution A and the polyamide-imide solution B are mixed and reacted under specific conditions, and then coated and heat-treated to produce a polyimide-polyamide-imide film. Controlling the molar ratio of the two solutes to 50:49-99:1 allows for the retention of excess terminal carboxyl groups, allowing for crosslinking during specific high-temperature treatment processes, further improving the material's performance. The method can prepare polyimide-polyamideimide precursors and films more simply and stably. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Tensile strength at break curves of polyimide-polyamideimide films prepared in Example 1 and Comparative Examples 1 and 2;

[0031] Figure 2 TMA spectra of polyimide-polyamideimide films prepared in Example 1 and Comparative Examples 1 and 2. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] The raw materials used in the present invention are all commercially available products, wherein the amino-terminated polyamide-imide powder is prepared by a method reported in existing literature, such as the method disclosed in patent application CN 105111469 A.

[0034] The amino-terminated polyamide-imide powder can also be prepared by the following method:

[0035] 4,4'-diaminodiphenyl ether, m-phenylenediamine and 1,2,4-trimellitic anhydride chloride are subjected to polycondensation reaction in a molar ratio of 54:49:100, and then spray precipitated and imidized to obtain a polyamide-imide powder having the above general formula I.

[0036] Example 1

[0037] This example achieves the preparation of polyimide-polyamide-imide resin and film by the following method:

[0038] 1. Add 19.47 g of p-PDA and 50.84 g of s-BPDA to a polar aprotic solvent protected by nitrogen or other inert gas, stir and react at 25°C for 8 hours, and control the molar ratio of PDA to s-BPDA to be 1:1.02 to obtain a polyimide precursor solution A with a solid content of 25 wt%;

[0039] 2. A polycondensation reaction was carried out using 17.45 g of m-PDA, 35.24 g of ODA, and 69.48 g of 1,2,4-trimellitic anhydride chloride, followed by spray precipitation and imidization to obtain a polyamide-imide powder. The molar ratio of diamine to chloride was controlled to be 1.02:1. The obtained powder was dissolved in a polar aprotic solvent at 35° C. and stirred for 8 hours to obtain a polyamide-imide solution B with a solid content of 25 wt%;

[0040] 3. The polyimide precursor solution A in step 1 and the polyamide-imide solution B in step 2 were mixed at a molar ratio of 95:5 and stirred at 35° C. for 8 hours to prepare a polyimide precursor-polyamide-imide solution;

[0041] 4. Use a filter membrane with a pore size of 0.3 μm to filter the polyimide precursor-polyamide-imide solution obtained in step 3 by positive pressure, and after vacuum degassing, evenly coat it on a clean substrate with a predetermined thickness, and heat it to 80°C at a rate of 10°C / min for pre-drying for 30 minutes. Then, place it in an oven and heat it stepwise to 400°C to remove the solvent and perform thermal imidization. After the oven temperature cools to ambient temperature, take it out, soak it in deionized water at 80°C for demolding, and dry it to obtain a polyimide-polyamide-imide film.

[0042] Testing of the film's thermal properties revealed a coefficient of thermal expansion (CTE) of 5.088 ppm / K (50°C-250°C), demonstrating thermal stability and a low coefficient of thermal expansion. Mechanical testing of the film revealed excellent mechanical properties, including a tensile strength of 319 MPa, a tensile modulus of 9.5 GPa, and an elongation at break of 24.2%.

[0043] Example 2

[0044] The molar ratio of the solutes of the polyimide precursor solution A and the polyamide-imide solution B in step 3 is 90:10. Other steps are the same as those in Example 1. The purpose is to increase the content of amide-imide in the structure, improve the flexibility of the film material, and maintain good thermal stability.

[0045] Testing of the film's thermal properties revealed a coefficient of thermal expansion (CTE) of 5.104 ppm / K (50°C-250°C), demonstrating thermal stability and low thermal expansion. Mechanical testing of the film revealed a tensile strength of 316 MPa, a tensile modulus of 9.2 GPa, and an elongation at break of 24.7%, demonstrating superior mechanical properties.

[0046] Example 3

[0047] The molar ratio of the solutes of the polyimide precursor solution A and the polyamide-imide solution B in step 3 is 85:15. Other steps are the same as those in Example 1, and the purpose is to further increase the content of amide-imide in the structure and regulate the mechanical properties and thermal stability of the film material.

[0048] Testing of the film's thermal properties revealed a coefficient of thermal expansion (CTE) of 6.898 ppm / K (50°C-250°C), demonstrating thermal stability and low thermal expansion. Mechanical testing of the film revealed a tensile strength of 313 MPa, a tensile modulus of 8.8 GPa, and an elongation at break of 24.6%, demonstrating superior flexibility.

[0049] Example 4

[0050] The molar ratio of the solutes of the polyimide precursor solution A and the polyamide-imide solution B in step 3 is 80:20. Other steps are the same as those in Example 1, and the purpose is to further increase the content of amide-imide in the structure and regulate the mechanical properties and thermal stability of the film material.

[0051] Testing of the film's thermal properties revealed a coefficient of thermal expansion (CTE) of 7.088ppm / K (50°C-250°C), demonstrating thermal stability and low thermal expansion. Mechanical testing of the film revealed tensile strength of 311MPa, tensile modulus of 8.4GPa, and elongation at break of 23.8%, demonstrating superior flexibility.

[0052] Example 5

[0053] 1. Add 16.45 g of p-PDA, 25.12 g of p-BOA, 25.00 g of p-BIA, and 83.54 g of PMDA to a polar aprotic solvent protected by nitrogen or other inert gas. Stir and react at 25°C for 12 hours. Control the molar ratio of diamine to dianhydride to be 1:1.02 to obtain a polyimide precursor solution A with a solid content of 25 wt%.

[0054] 2. A polycondensation reaction was carried out using 17.45 g of m-PDA, 35.24 g of ODA, and 1,2,4-trimellitic anhydride chloride, followed by spray precipitation and imidization to obtain a polyamide-imide powder. The molar ratio of diamine to chloride was controlled to be 1.02:1. The obtained powder was dissolved in a polar aprotic solvent at 35° C. and stirred for 8 hours to obtain a polyamide-imide solution B with a solid content of 25 wt%;

[0055] 3. The polyimide precursor solution A in step 1 and the polyamide-imide solution B in step 2 were mixed at a molar ratio of 90:10, and stirred at 35° C. for 8 hours to prepare a polyimide precursor-polyamide-imide solution;

[0056] 4. Use a filter membrane with a pore size of 0.3 μm to filter the polyimide precursor-polyamide-imide solution obtained in step 3 by positive pressure, and after vacuum degassing, evenly coat it on a clean substrate with a predetermined thickness, and heat it to 80°C at a rate of 10°C / min for pre-drying for 30 minutes. Then, place it in an oven and heat it stepwise to 400°C to remove the solvent and perform thermal imidization. After the oven temperature cools to ambient temperature, take it out, soak it in deionized water at 80°C for demolding, and dry it to obtain a polyimide-polyamide-imide film.

[0057] Testing of the film's thermal properties revealed a coefficient of thermal expansion (CTE) of 1.068ppm / K (50°C-250°C), demonstrating thermal stability and low thermal expansion. Mechanical testing of the film revealed excellent mechanical properties, including a tensile strength of 316MPa, a tensile modulus of 10.3GPa, and an elongation at break of 23.9%.

[0058] Example 6

[0059] The molar ratio of the solutes of the polyimide precursor solution A and the polyamide-imide solution B in step 3 is 85:15. Other steps are the same as those in Example 5. The purpose is to increase the content of amide-imide in the structure, improve the flexibility of the film material, and maintain good thermal stability.

[0060] Testing of the film's thermal properties revealed a coefficient of thermal expansion (CTE) of 2.107 ppm / K (50°C-250°C), demonstrating thermal stability and low thermal expansion. Mechanical testing of the film revealed a tensile strength of 319 MPa, a tensile modulus of 10.1 GPa, and an elongation at break of 24.4%, demonstrating even superior mechanical properties.

[0061] Example 7

[0062] The molar ratio of the solutes of the polyimide precursor solution A and the polyamide-imide solution B in step 3 is 80:20. Other steps are the same as those in Example 5, and the purpose is to further increase the content of amide-imide in the structure and regulate the mechanical properties and thermal stability of the film material.

[0063] Testing of the film's thermal properties revealed a coefficient of thermal expansion (CTE) of 2.947 ppm / K (50°C-250°C), demonstrating thermal stability and low thermal expansion. Mechanical testing of the film revealed tensile strength of 309 MPa, tensile modulus of 9.8 GPa, and elongation at break of 24.2%, demonstrating superior flexibility.

[0064] Example 8

[0065] The molar ratio of the solutes of the polyimide precursor solution A and the polyamide-imide solution B in step 3 is 75:25. Other steps are the same as those in Example 5, and the purpose is to further increase the content of amide-imide in the structure and regulate the mechanical and thermal stability of the film material.

[0066] Testing of the film's thermal properties revealed a coefficient of thermal expansion (CTE) of 3.245 ppm / K (50°C-250°C), demonstrating thermal stability and low thermal expansion. Mechanical testing of the film revealed a tensile strength of 311 MPa, a tensile modulus of 9.4 GPa, and an elongation at break of 23.6%, demonstrating superior flexibility.

[0067] Comparative Example 1

[0068] Example 1 was repeated, except that in step 3, the molar ratio of the two solutes was 100:0.

[0069] The thermal properties of the film were tested and the coefficient of thermal expansion (CTE) was 4.643ppm / K (50°C -250°C). Compared with Examples 1-4, the thermal stability and low expansion coefficient were better. The mechanical properties test results of the film were as follows: tensile strength of 334MPa, tensile modulus of 10.2GPa, and elongation at break of 20.3%. Compared with Examples 1-4, the elongation at break was lower. The introduction of the amide-imide structure, in view of the effect of intermolecular hydrogen bonds, can not only improve the elongation at break of the film material, but also effectively regulate the thermal expansion coefficient of the polyimide film material, providing ideas for the polyimide film to be suitable for substrate materials with different thermal expansion properties.

[0070] Comparative Example 2

[0071] Example 1 was repeated, except that in step 3, the molar ratio of the two solutes was 0:100.

[0072] Testing of the film's thermal properties revealed a coefficient of thermal expansion (CTE) of 50.31 ppm / K (50°C-250°C). Compared to Examples 1-8, this lower coefficient of thermal expansion is significantly higher, significantly enhancing the thermal stability of the polyimide film. By increasing the amide-imide content, films with varying thermal expansion levels can be prepared. Mechanical performance testing of the film revealed a tensile strength of 155 MPa, a tensile modulus of 5.5 GPa, and an elongation at break of 28.6%. Compared to Examples 1-8, the introduction of the amide-imide structure into the polyimide structure resulted in a synergistic effect between the hydrogen bonding interactions of the amide bonds of PAI and the rigid backbone of PI, allowing the material to maintain both thermal stability and good mechanical properties.

[0073] like Figure 1 Shown are the tensile strength at break curves of the polyimide-polyamide-imide films prepared in Example 1 and Comparative Examples 1 and 2. The figure shows that the introduction of the amide-imide structure, due to the effect of intermolecular hydrogen bonds, can not only improve the elongation at break of the film material, but also effectively regulate the thermal expansion coefficient of the polyimide film material, providing ideas for the application of polyimide films to substrate materials with different thermal expansion properties.

[0074] like Figure 2 Shown are TMA spectra of polyimide-polyamideimide films prepared in Example 1 and Comparative Examples 1 and 2. As can be seen from the figure, the introduction of the amide-imide structure into the polyimide structure synergizes the hydrogen bonding interactions of the amide bonds of PAI and the rigid backbone of PI, enabling the material to retain both good mechanical properties and thermal stability.

[0075] Comparative Example 3

[0076] Example 5 was repeated, except that in step 3, the molar ratio of the two solutes was 100:0.

[0077] Thermal performance testing of the film revealed a coefficient of thermal expansion (CTE) of 1.031 ppm / K (50°C-250°C), demonstrating ultra-low thermal expansion. Mechanical performance testing of the film revealed tensile strength of 335 MPa, tensile modulus of 10.5 GPa, and elongation at break of 21.6%. Compared to Examples 5-8, the introduction of an amide-imide structure into the polyimide structure effectively modulates the CTE to accommodate the expansion of the glass substrate, providing insights into the development of highly heat-resistant, high-strength, and ultra-low thermal expansion PI substrate materials.

[0078] Example 9

[0079] A method for preparing a polyimide-polyamide-imide resin and a film comprises the following steps:

[0080] 1) BDE and BTDA were added to N-methylpyrrolidone protected by nitrogen or other inert gas, and stirred at -20°C for 2 hours to achieve a molar ratio of diamine to anhydride of 1:1.07, thereby obtaining a polyimide precursor solution A having a solid content of 10 wt % and an apparent viscosity of 1000 cps;

[0081] 2) dissolving the amino-terminated polyamide-imide powder in N-methylpyrrolidone to control the solid content to 10 wt % to obtain a polyamide-imide solution B having an apparent viscosity of 1000 cps;

[0082] 3) The polyimide precursor solution A in step 1) and the polyamide-imide solution B in step 2) were mixed at a mass ratio of 50:49 of the solutes thereof, the temperature was controlled at 20° C., and the mixture was stirred for 12 hours to prepare a polyimide precursor-polyamide-imide resin solution;

[0083] 4) removing impurities with a particle size greater than 1 μm from the resin solution obtained in step 3) by positive pressure filtration, and evenly coating the solution on a clean substrate with a predetermined thickness after vacuum degassing. The solution was then heated to 60° C. at a rate of 1° C. / min and soft-baked for 20 min. The solution was then placed in an oven and heated in a stepwise manner to a certain temperature to remove the solvent and perform thermal imidization. After the oven temperature was cooled to ambient temperature, the solution was removed from the oven, demolded by soaking in deionized water at 25° C., and dried to obtain a polyimide-polyamideimide film.

[0084] The thermal properties of the film were tested and the thermal expansion coefficient CTE was 21.095ppm / K (50℃-250℃), which shows thermal stability and low expansion coefficient. The mechanical properties test results of the film are as follows: tensile strength is 259MPa, tensile modulus is 5.1GPa, elongation at break is 31%, and the mechanical properties are good.

[0085] Example 10

[0086] A method for preparing a polyimide-polyamide-imide resin and a film comprises the following steps:

[0087] 1) m-phenylenediamine, 4,4'-diaminodiphenyl ether, and pyromellitic dianhydride were added to N-methylacetamide protected by nitrogen or other inert gas, and stirred at 60° C. to react for 24 hours, controlling the molar ratio of diamine to anhydride to be 1:1.2 to obtain a polyimide precursor solution A having a solid content of 40 wt % and an apparent viscosity of 50,000 cps;

[0088] 2) dissolving amino-terminated polyamide-imide powder in N-methylacetamide to control the solid content to 40 wt % to obtain a polyamide-imide solution B having an apparent viscosity of 50,000 cps;

[0089] 3) The polyimide precursor solution A from step 1) and the polyamide-imide solution B from step 2) were mixed at a mass ratio of 99:1 of the solute molar ratio of the two, and the mixture was stirred at 80° C. for 4 hours to prepare a polyimide precursor-polyamide-imide resin solution;

[0090] 4) removing impurities with a particle size greater than 1 μm from the resin solution obtained in step 3) by positive pressure filtration, and evenly coating the solution on a clean substrate with a predetermined thickness after vacuum degassing. The solution was then heated to 120° C. at a rate of 8° C. / min and soft-baked for 60 min. The solution was then placed in an oven and heated in a stepwise manner to a certain temperature to remove the solvent and perform thermal imidization. After the oven temperature was cooled to ambient temperature, the solution was removed from the oven, demolded by soaking in deionized water at 80° C., and dried to obtain a polyimide-polyamideimide film.

[0091] Testing of the film's thermal properties revealed a coefficient of thermal expansion (CTE) of 16.894 ppm / K (50°C-250°C), similar to that of copper, making it suitable for use in flexible copper-clad laminates. Mechanical testing of the film revealed excellent mechanical properties, with a tensile strength of 242 MPa, a tensile modulus of 5.9 GPa, and an elongation at break of 20%.

[0092] The above description of the embodiments is intended to facilitate understanding and application of the present invention by those skilled in the art. It is apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without inventive effort. Therefore, the present invention is not limited to the embodiments herein. Improvements and modifications made by those skilled in the art based on the disclosure of this application without departing from the scope and spirit of this application are within the scope of this application.

Claims

1. A method for preparing a polyimide-polyamideimide film, characterized in that: The following steps are involved: 1) adding an aromatic diamine and an aromatic dianhydride to a polar aprotic solvent protected by nitrogen or an inert gas, stirring and reacting at -20-60° C. for 2-24 hours, controlling the molar ratio of the aromatic diamine to the aromatic dianhydride to be 1:1-1:1.2, to obtain a polyimide precursor solution A having a solid content of 10-40 wt % and an apparent viscosity of 1000-50000 cps; 2) dissolving amino-terminated polyamide-imide powder in a polar aprotic solvent to control the solid content to 10-40 wt % to obtain a polyamide-imide solution B having an apparent viscosity of 1000-50000 cps; The general formula of the amino-terminated polyamide-imide powder is: ； Formula 1; In Formula 1, X is a trivalent organic group, Y is a divalent organic group, and n is an integer greater than 1; 3) mixing the polyimide precursor solution A from step 1) and the polyamide-imide solution B from step 2) in a molar ratio of 50:49-99:1 of the solutes of the two, controlling the temperature at 20-80° C. and stirring for 4-12 hours to prepare a blended polyimide precursor-polyamide-imide resin solution; 4) The blended polyimide precursor-polyamide-imide resin solution obtained in step 3) is filtered to remove impurities, vacuum degassed, and then coated on a substrate, followed by heat treatment to obtain a polyimide-polyamide-imide film.

2. The method for preparing a polyimide-polyamideimide film according to claim 1, wherein: The aromatic diamine described in step 1) includes one or more of p-phenylenediamine (p-PDA), m-phenylenediamine (m-PDA), 4,4'-diaminodiphenyl sulfone (DDS), benzyldiamine (BDE), 4,4'-diaminobenzanilide (DABA), 3,3'-dimethyl-4,4'-diaminobiphenyl (o-TLD), 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole (p-BOA), 2-(3-aminophenyl)-5-aminobenzoxazole (m-BOA), 2-(3-aminophenyl)-5-aminobenzimidazole (m-BIA), and 2-(4-aminophenyl)-5-aminobenzimidazole (p-BIA).

3. The method for preparing a polyimide-polyamideimide film according to claim 1, wherein: The aromatic dianhydride described in step 1) includes one or more of: 1,2,4,5-pyromellitic dianhydride (PMDA), 3,3'4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3'3,4'-biphenyltetracarboxylic dianhydride (a-BPDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), and 4-p-phenylene-diphenyltrimethylol dianhydride (TAHQ).

4. The method for preparing a polyimide-polyamideimide film according to claim 1, wherein: Step 1) wherein the polar aprotic solvent comprises N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone in one or a combination of two or more; In step 2), the polar aprotic solvent includes one or a combination of two or more of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.

5. The method for preparing a polyimide-polyamideimide film according to claim 1, wherein: In formula 1, X is a trivalent organic group having 6 to 40 carbon atoms; Y is an aromatic group having 6 to 40 carbon atoms.

6. The method for preparing a polyimide-polyamideimide film according to claim 1 or 5, characterized in that: In Formula 1, X is an aromatic group or an alicyclic aliphatic group in which the imide group and the -CONH- group are ortho to each other, and the structure of X is one or a combination of two or more; The structure of Y is one or a combination of two or more.

7. The method for preparing a polyimide-polyamideimide film according to claim 1, characterized in that: The mass ratio of the polyimide precursor solution A and the polyamide-imide solution B in step 3) is 70:30 to 95:

5.

8. The method for preparing a polyimide-polyamideimide film according to claim 1, wherein: Step 4) Filtration and impurity removal is to remove impurities with a particle size greater than 1 μm in the blended resin solution obtained in step 3) by positive pressure filtration. Substrates include glass, ceramic, stainless steel or plastic substrates; The heat treatment comprises the following steps: heating the film to 60-120°C at a rate of 0-10°C / min, soft baking the film for 20-60 minutes, then placing the film in an oven and heating the film in a stepwise manner to 300-500°C to remove the solvent and perform thermal imidization. After the oven temperature is cooled to ambient temperature, the film is taken out, soaked in deionized water at 25-80°C for demolding, and dried to obtain a blended polyimide-polyamideimide film.

9. A polyimide-polyamideimide film prepared by the method according to any one of claims 1 to 8.

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