Preparation method of five-membered copolymer high-tg polyimide film

Abstract

The application discloses a preparation method of a five-element copolymer high-Tg polyimide film, which comprises the following steps: first, raw materials PDA, PMDA, M-TOLIDINE, ODA and S-BPDA are weighed according to proportions; PMDA is divided into three parts of dianhydride monomer A, dianhydride monomer B and dianhydride monomer C; PDA is dissolved in an organic solvent to obtain a diamine monomer solution; the dianhydride monomer A is added into the diamine monomer solution to obtain a mixed solution through stirring and mixing reaction; then, the M-TOLIDINE is added into the mixed solution to perform stirring and mixing reaction, and then the dianhydride monomer C is added into the mixed solution to perform stirring and mixing reaction; then, the ODA is added into the mixed solution to perform stirring and mixing reaction, and then the dianhydride monomer B is added into the mixed solution to perform stirring and mixing reaction; finally, the S-BPDA is added into the mixed solution to adjust the viscosity, and then the PAA is obtained through stirring and mixing reaction under a cold water bath condition; the PAA is coated on a glass plate, and then high-Tg polyimide film is obtained through thermal imidization under temperature rising. The high-Tg polyimide film produced by the application has good heat resistance and high heat dimensional stability, and promotes the application of the polyimide film product in the field of flexible display substrates.

Description

Technical Field

[0001] The invention belongs to the technical field of polyimide films, and in particular relates to a method for preparing a five-component copolymerized high-Tg polyimide film. Background Art

[0002] Since its introduction, polyimide (PI) has been widely synthesized and applied in microelectronic devices, thin films, and adhesives due to its excellent mechanical properties, high thermal stability, low dielectric constant, and ease of processing. However, in the rapidly developing field of flexible display substrates, there is an urgent need to develop polyimides (PI) with high heat resistance and thermal dimensional stability. This is because the actual processing temperature during flexible display device processing is generally around 400-500°C, which places higher requirements on the glass transition temperature (Tg) of PI used as a flexible substrate. For example, polyimide used in AMOLED flexible substrates generally requires a temperature above 430°C. For PI used in flexible printed circuit boards, a higher Tg value is preferred. A Tg above 400°C significantly improves the packaging performance of flexible printed circuit boards and expands their application areas.

[0003] The glass transition temperature (GTT) of existing polyimide films generally does not exceed 400°C. Polyimide films are ideal cover materials for advanced flexible AMOLED displays. If low-Tg polyimide films are used on cover panels for extended periods, they can creep after prolonged static or dynamic bending, failing to maintain excellent structural stability. Conventional methods for preparing high-Tg polyimide films, however, struggle to achieve a high Gt due to the rigidity of the PI molecular chain and the difficulty of thermal stretching. This severely impacts the polyimide film's heat resistance and high thermal dimensional stability. Summary of the Invention

[0004] In response to the above-mentioned shortcomings, the present invention discloses a method for preparing a five-component copolymer high-Tg polyimide film, which produces a high-Tg polyimide film with good heat resistance and high thermal dimensional stability, and promotes the application of polyimide film products in the field of flexible display substrates.

[0005] The present invention is achieved by adopting the following technical solutions:

[0006] A method for preparing a five-component copolymer high-Tg polyimide film comprises the following steps:

[0007] (1) Weigh the raw materials according to the molar ratio of p-phenylenediamine (PDA), pyromellitic dianhydride (PMDA), 4,4'-diamino-2,2'-dimethylbiphenyl (M-TOLIDINE), 4,4'-diaminodiphenyl ether (ODA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA) of (1.0-1.5):(4-5):(2-3):(1.5-1.8):(0.5-3) and place them in an oven for drying respectively; divide pyromellitic dianhydride (PMDA) into three parts: dianhydride monomer A, dianhydride monomer B and dianhydride monomer C, and the mass ratio of dianhydride monomer A, dianhydride monomer B and dianhydride monomer C is 2:3:5;

[0008] p-phenylenediamine (PDA) is dissolved in an organic solvent and stirred to obtain a diamine monomer solution. Dianhydride monomer A is added to the diamine monomer solution and stirred and reacted for 0.5 h to obtain a mixed solution. 4,4'-diamino-2,2'-dimethylbiphenyl (M-TOLIDINE) is then added to the mixed solution and stirred and reacted for 0.5 h. Dianhydride monomer C is then added and stirred and reacted for 0.5 h. 4,4'-diaminodiphenyl ether (ODA) is then added and stirred and reacted for 0.5 h. Dianhydride monomer B is then added and stirred and reacted for 0.5 h. Finally, 3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA) is added to adjust the viscosity, and the mixture is placed in a cold water bath and stirred to obtain a polyamic acid solution (PAA).

[0009] (2) The polyamic acid solution obtained in step (1) is coated on a glass plate, and then the temperature is increased to perform thermal imidization to obtain a high Tg polyimide film.

[0010] Furthermore, the organic solvent in step (1) is any one of N-methylpyrrolidone, dimethylformamide, dimethylacetamide and dimethyl sulfoxide.

[0011] Furthermore, the viscosity of the polyamic acid solution in step (1) is 20,000 mPa·s to 120,000 mPa·s.

[0012] Furthermore, the solid content of the polyamic acid solution in step (1) is 10-20%.

[0013] Furthermore, the temperature of the cold water bath in step (1) is 0-15°C.

[0014] Furthermore, the stirring speed in step (1) is 500 to 2000 r / min.

[0015] Furthermore, in step (1), S-BPDA is finally added to adjust the viscosity, and the mixture is placed in a cold water bath and stirred for reaction for 3 to 8 hours to obtain a polyamic acid solution.

[0016] Furthermore, in step (2), the polyamic acid solution obtained in step (1) is evenly coated on a clean glass plate by an automatic coating machine, and then placed in a forced air drying oven and treated at 160°C for 10 minutes to evaporate and remove the solvent, and then the glass plate is continued to be placed in the forced air drying oven and heated according to the following program to perform a thermal imidization process: from 160°C to 210°C after 30 minutes and kept warm for 5 minutes, from 210°C to 260°C after 30 minutes and kept warm for 5 minutes, and finally raised to 400°C and kept warm for 5 minutes before starting to cool down, and after naturally cooling to room temperature, the glass plate is soaked in 100°C hot water for 20 minutes, and then the film is removed from the glass plate and dried to obtain a high Tg polyimide film.

[0017] Furthermore, the thickness of the high Tg polyimide film in step (2) is 20±5 μm.

[0018] Compared with the existing technology, this technical solution has the following beneficial effects:

[0019] 1. The glass transition temperature of polyimide films is directly related to the flexibility of the molecular chains. Greater molecular chain flexibility leads to lower glass transition temperatures, while greater molecular chain rigidity leads to higher glass transition temperatures. Furthermore, a high Tg is typically caused by the combined effects of backbone rigidity and linearity, along with high chain alignment along the film's plane. Therefore, the present invention utilizes a multi-polymerization method to introduce strong intermolecular interactions within polyimide (PI) molecular chains to synthesize high glass transition temperature (Tg) polyimide films. The resulting high-Tg polyimide films exhibit high tensile strength, elongation at break, and a high Tg, providing a key guarantee for the preparation of high-Tg, high-tensile-strength polyimide films. The present invention uses p-phenylenediamine (PDA) with a rigid structure, pyromellitic dianhydride (PMDA) with a highly symmetrical molecular structure, a diamine monomer containing a biphenyl structure, 4,4'-diamino-2,2'-dimethylbiphenyl (M-tol), and a dianhydride monomer containing a biphenyl structure, 3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA). In order to ensure the successful preparation of the film, an appropriate amount of a diamine monomer containing a flexible ether bond, 4,4'-diaminodiphenyl ether (ODA), is also added.

[0020] 2. The p-phenylenediamine (PDA) used in the present invention is a rigid molecular chain that is conducive to obtaining a higher packing density and can effectively reduce the free volume fraction so that the prepared PI film obtains a higher glass transition temperature; the pyromellitic dianhydride (PMDA) monomer has a typical linear skeleton structure, the molecular chain is highly symmetrical and rigid, and it is easier to form an in-plane orientation to form a complete arrangement, thereby obtaining a lower CTE; the 4,4'-diamino-2,2'-dimethylbiphenyl (M-tol) diamine monomer contains a biphenyl structure. The introduction of the biphenyl structure can increase the elastic modulus of the PI film. The monomer containing the biphenyl structure The molecular chain is straighter and the intermolecular force is stronger. The introduction of the biphenyl structure reduces the single bonds for internal rotation, and the side substituents increase the steric hindrance of molecular movement, making the arrangement of the molecular chain more regular, resulting in the PI film having a high degree of in-plane orientation, which can significantly reduce the thermal expansion coefficient (CTE) of PI; 3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA) also has a biphenyl structure, which can increase the molecular chain length of the prepared PI film, and improve the tensile strength and elongation at break of the film; 4,4'-diaminodiphenyl ether (ODA) contains a flexible ether bond that can improve the elongation at break of the PI film.

[0021] 3. The high Tg polyimide composite film prepared by the present invention has balanced mechanical properties, and the high Tg polyimide film has balanced mechanical properties, with a tensile strength of 187 MPa, an elongation at break of 38.1%, a modulus of 3.6 GPa, and a glass transition temperature of 540°C, and can be used in the field of flexible packaging. DETAILED DESCRIPTION

[0022] The present invention is further illustrated by the following examples, which are not intended to limit the present invention. Specific experimental conditions and methods not specified in the following examples are conventional methods well known to those skilled in the art.

[0023] Example 1: A method for preparing a five-component copolymer high Tg polyimide film, comprising the following steps:

[0024] (1) According to the molar ratio of p-phenylenediamine (PDA), pyromellitic dianhydride (PMDA), 4,4'-diamino-2,2'-dimethylbiphenyl (M-TOLIDINE), 4,4'-diaminodiphenyl ether (ODA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA) of 1.1:4.8:2.8:1.55:0.58, the raw materials (including 1.2250 g of p-phenylenediamine) were weighed and placed in an oven for drying; pyromellitic dianhydride (PMDA) was divided into three parts: dianhydride monomer A, dianhydride monomer B and dianhydride monomer C, and the mass ratio of dianhydride monomer A, dianhydride monomer B and dianhydride monomer C was 2:3:5;

[0025] p-phenylenediamine (PDA) was dissolved in 100 mL of an organic solvent and stirred for 15 min to obtain a diamine monomer solution. Dianhydride monomer A was added to the diamine monomer solution and stirred and reacted for 0.5 h to obtain a mixed solution (no obvious particles were present in the mixed solution, and PDA and PMDA had completely reacted). 4,4'-diamino-2,2'-dimethylbiphenyl (M-TOLIDINE) was then added to the mixed solution and stirred and reacted for 0.5 h (the color of the mixed solution changed from light green to turbid white). Dianhydride monomer C was then added and stirred and reacted for 0.5 h (the color of the solution changed from turbid white to yellow). 4,4'-diaminodiphenyl ether (ODA) was then added and stirred and reacted for 0.5 h. Dianhydride monomer B was then added and stirred and reacted for 0.5 h. Finally, 3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA) was added to adjust the viscosity. The mixture was then placed in a cold water bath and stirred for 6 h to obtain a polyamic acid solution (PAA).

[0026] The organic solvent is dimethylacetamide; the viscosity of the polyamic acid solution is 55000 mPa·s; the solid content of the polyamic acid solution is 20%; the temperature of the cold water bath is 10° C.; and the stirring speed is 1500 r / min.

[0027] (2) The polyamic acid solution obtained in step (1) is evenly coated on a clean glass plate by an automatic coating machine, and then placed in a forced air drying oven and treated at 160°C for 10 minutes to evaporate and remove the solvent. The glass plate is then placed in a forced air drying oven and heated according to the following procedure for thermal imidization: from 160°C to 210°C over 30 minutes and kept warm for 5 minutes, from 210°C to 260°C over 30 minutes and kept warm for 5 minutes, and finally heated to 400°C and kept warm for 5 minutes before cooling. After naturally cooling to room temperature, the glass plate is soaked in 100°C hot water for 20 minutes, and then the film is removed from the glass plate and dried to obtain a high Tg polyimide film; the thickness of the high Tg polyimide film is 15 μm.

[0028] Example 2: A method for preparing a five-component copolymer high Tg polyimide film, comprising the following steps:

[0029] (1) According to the molar ratio of p-phenylenediamine (PDA), pyromellitic dianhydride (PMDA), 4,4'-diamino-2,2'-dimethylbiphenyl (M-TOLIDINE), 4,4'-diaminodiphenyl ether (ODA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA) of 1.09:4.9:2.7:1.6:0.6, the raw materials (including 1.1815 g of p-phenylenediamine) were weighed and placed in an oven for drying; pyromellitic dianhydride (PMDA) was divided into three parts: dianhydride monomer A, dianhydride monomer B and dianhydride monomer C, and the mass ratio of dianhydride monomer A, dianhydride monomer B and dianhydride monomer C was 2:3:5;

[0030] p-phenylenediamine (PDA) was dissolved in 100 mL of an organic solvent and stirred for 15 min to obtain a diamine monomer solution. Dianhydride monomer A was added to the diamine monomer solution and stirred and reacted for 0.5 h to obtain a mixed solution (no obvious particles were present in the mixed solution, and PDA and PMDA had completely reacted). 4,4'-diamino-2,2'-dimethylbiphenyl (M-TOLIDINE) was then added to the mixed solution and stirred and reacted for 0.5 h (the color of the mixed solution changed from light green to turbid white). Dianhydride monomer C was then added and stirred and reacted for 0.5 h (the color of the solution changed from turbid white to yellow). 4,4'-diaminodiphenyl ether (ODA) was then added and stirred and reacted for 0.5 h. Dianhydride monomer B was then added and stirred and reacted for 0.5 h. Finally, 3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA) was added to adjust the viscosity. The mixture was then placed in a cold water bath and stirred for 5 h to obtain a polyamic acid solution (PAA).

[0031] The organic solvent is dimethylformamide; the viscosity of the polyamic acid solution is 36000 mPa·s; the solid content of the polyamic acid solution is 18%; the temperature of the cold water bath is 8° C.; the stirring speed is 1200 r / min;

[0032] (2) The polyamic acid solution obtained in step (1) is evenly coated on a clean glass plate by an automatic coating machine, and then placed in a forced air drying oven and treated at 160°C for 10 minutes to evaporate and remove the solvent. The glass plate is then placed in a forced air drying oven and heated according to the following program for thermal imidization: from 160°C to 210°C over 30 minutes and kept warm for 5 minutes, from 210°C to 260°C over 30 minutes and kept warm for 5 minutes, and finally heated to 400°C and kept warm for 5 minutes before cooling. After naturally cooling to room temperature, the glass plate is soaked in 100°C hot water for 20 minutes, and then the film is removed from the glass plate and dried to obtain a high Tg polyimide film; the thickness of the high Tg polyimide film is 20 μm.

[0033] Example 3: A method for preparing a five-component copolymer high Tg polyimide film, comprising the following steps:

[0034] (1) According to the molar ratio of p-phenylenediamine (PDA), pyromellitic dianhydride (PMDA), 4,4'-diamino-2,2'-dimethylbiphenyl (M-TOLIDINE), 4,4'-diaminodiphenyl ether (ODA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA) of 1.2:4.68:2.6:1.6:2.6, the raw materials (including 1.1410 g of p-phenylenediamine) were weighed and placed in an oven for drying; pyromellitic dianhydride (PMDA) was divided into three parts: dianhydride monomer A, dianhydride monomer B and dianhydride monomer C, and the mass ratio of dianhydride monomer A, dianhydride monomer B and dianhydride monomer C was 2:3:5;

[0035] p-phenylenediamine (PDA) was dissolved in 100 mL of an organic solvent and stirred for 15 min to obtain a diamine monomer solution. Dianhydride monomer A was added to the diamine monomer solution and stirred and reacted for 0.5 h to obtain a mixed solution (no obvious particles were present in the mixed solution, and PDA and PMDA had completely reacted). 4,4'-diamino-2,2'-dimethylbiphenyl (M-TOLIDINE) was then added to the mixed solution and stirred and reacted for 0.5 h (the color of the mixed solution changed from light green to turbid white). Dianhydride monomer C was then added and stirred and reacted for 0.5 h (the color of the solution changed from turbid white to yellow). 4,4'-diaminodiphenyl ether (ODA) was then added and stirred and reacted for 0.5 h. Dianhydride monomer B was then added and stirred and reacted for 0.5 h. Finally, 3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA) was added to adjust the viscosity. The mixture was then placed in a cold water bath and stirred for 4 h to obtain a polyamic acid solution (PAA).

[0036] The organic solvent is dimethylformamide; the viscosity of the polyamic acid solution is 25000 mmPa·s; the solid content of the polyamic acid solution is 15%; the temperature of the cold water bath is 10° C.; and the stirring speed is 1600 r / min.

[0037] (2) The polyamic acid solution obtained in step (1) is evenly coated on a clean glass plate by an automatic coating machine, and then placed in a forced air drying oven and treated at 160°C for 10 minutes to evaporate and remove the solvent. The glass plate is then placed in a forced air drying oven and heated according to the following procedure for thermal imidization: from 160°C to 210°C over 30 minutes and kept warm for 5 minutes, from 210°C to 260°C over 30 minutes and kept warm for 5 minutes, and finally heated to 400°C and kept warm for 5 minutes before cooling. After naturally cooling to room temperature, the glass plate is soaked in 100°C hot water for 20 minutes, and then the film is removed from the glass plate and dried to obtain a high Tg polyimide film; the thickness of the high Tg polyimide film is 18 μm.

[0038] Example 4: A method for preparing a five-component copolymer high Tg polyimide film, comprising the following steps:

[0039] (1) According to the molar ratio of p-phenylenediamine (PDA), pyromellitic dianhydride (PMDA), 4,4'-diamino-2,2'-dimethylbiphenyl (M-TOLIDINE), 4,4'-diaminodiphenyl ether (ODA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA) of 1.0:4:2:1.5:0.5, the raw materials (including 1.3350 g of p-phenylenediamine) were weighed and placed in an oven for drying; pyromellitic dianhydride (PMDA) was divided into three parts: dianhydride monomer A, dianhydride monomer B and dianhydride monomer C, and the mass ratio of dianhydride monomer A, dianhydride monomer B and dianhydride monomer C was 2:3:5;

[0040] p-phenylenediamine (PDA) was dissolved in 100 mL of an organic solvent and stirred for 15 min to obtain a diamine monomer solution. Dianhydride monomer A was added to the diamine monomer solution and stirred and reacted for 0.5 h to obtain a mixed solution (no obvious particles were present in the mixed solution, and PDA and PMDA had completely reacted). 4,4'-diamino-2,2'-dimethylbiphenyl (M-TOLIDINE) was then added to the mixed solution and stirred and reacted for 0.5 h (the color of the mixed solution changed from light green to turbid white). Dianhydride monomer C was then added and stirred and reacted for 0.5 h (the color of the solution changed from turbid white to yellow). 4,4'-diaminodiphenyl ether (ODA) was then added and stirred and reacted for 0.5 h. Dianhydride monomer B was then added and stirred and reacted for 0.5 h. Finally, 3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA) was added to adjust the viscosity. The mixture was then placed in a cold water bath and stirred for 3 h to obtain a polyamic acid solution (PAA).

[0041] The organic solvent is N-methylpyrrolidone; the viscosity of the polyamic acid solution is 120,000 mPa·s; the solid content of the polyamic acid solution is 10%; the temperature of the cold water bath is 15° C.; and the stirring speed is 500 r / min.

[0042] (2) The polyamic acid solution obtained in step (1) is evenly coated on a clean glass plate by an automatic coating machine, and then placed in a forced air drying oven and treated at 160°C for 10 minutes to evaporate and remove the solvent. The glass plate is then placed in a forced air drying oven and heated according to the following program for thermal imidization: from 160°C to 210°C over 30 minutes and kept warm for 5 minutes, from 210°C to 260°C over 30 minutes and kept warm for 5 minutes, and finally heated to 400°C and kept warm for 5 minutes before cooling. After naturally cooling to room temperature, the glass plate is soaked in 100°C hot water for 20 minutes, and then the film is removed from the glass plate and dried to obtain a high Tg polyimide film; the thickness of the high Tg polyimide film is 25 μm.

[0043] Example 5: A method for preparing a five-component copolymer high Tg polyimide film, comprising the following steps:

[0044] (1) According to the molar ratio of p-phenylenediamine (PDA), pyromellitic dianhydride (PMDA), 4,4'-diamino-2,2'-dimethylbiphenyl (M-TOLIDINE), 4,4'-diaminodiphenyl ether (ODA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA) of 1.5:5:3:1.8:3, the raw materials (including 1.2850 g of p-phenylenediamine) were weighed and placed in an oven for drying; pyromellitic dianhydride (PMDA) was divided into three parts: dianhydride monomer A, dianhydride monomer B and dianhydride monomer C, and the mass ratio of dianhydride monomer A, dianhydride monomer B and dianhydride monomer C was 2:3:5;

[0045] p-phenylenediamine (PDA) was dissolved in 100 mL of an organic solvent and stirred for 15 min to obtain a diamine monomer solution. Dianhydride monomer A was added to the diamine monomer solution and stirred and reacted for 0.5 h to obtain a mixed solution (no obvious particles were present in the mixed solution, and PDA and PMDA had completely reacted). 4,4'-diamino-2,2'-dimethylbiphenyl (M-TOLIDINE) was then added to the mixed solution and stirred and reacted for 0.5 h (the color of the mixed solution changed from light green to turbid white). Dianhydride monomer C was then added and stirred and reacted for 0.5 h (the color of the solution changed from turbid white to yellow). 4,4'-diaminodiphenyl ether (ODA) was then added and stirred and reacted for 0.5 h. Dianhydride monomer B was then added and stirred and reacted for 0.5 h. Finally, 3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA) was added to adjust the viscosity. The mixture was then placed in a cold water bath and stirred for 8 h to obtain a polyamic acid solution (PAA).

[0046] The organic solvent is dimethylformamide; the viscosity of the polyamic acid solution is 60,000 mPa·s; the solid content of the polyamic acid solution is 20%; the temperature of the cold water bath is 0° C.; and the stirring speed is 2000 r / min.

[0047] (2) The polyamic acid solution obtained in step (1) is evenly coated on a clean glass plate by an automatic coating machine, and then placed in a forced air drying oven and treated at 160°C for 10 minutes to evaporate and remove the solvent. The glass plate is then placed in a forced air drying oven and heated according to the following program for thermal imidization: from 160°C to 210°C over 30 minutes and kept warm for 5 minutes, from 210°C to 260°C over 30 minutes and kept warm for 5 minutes, and finally heated to 400°C and kept warm for 5 minutes before cooling. After naturally cooling to room temperature, the glass plate is soaked in 100°C hot water for 20 minutes, and then the film is removed from the glass plate and dried to obtain a high Tg polyimide film; the thickness of the high Tg polyimide film is 22 μm.

[0048] Comparative Example 1: Preparation of PMDA-PDA-ODA-M-tol-PI film, specifically comprising the following steps:

[0049] S1: 1.2480 g of PDA was weighed and dissolved in 100 mL of dimethylacetamide to obtain a homogeneous and transparent solution of diamine; after stirring at 1500 r / min for 15 minutes, 2.3000 g of PMDA was added and the reaction continued for 0.5 hour, followed by the addition of 6.1284 g of M-TOLIDINE and stirring at 1500 r / min for 15 minutes, followed by the addition of 5.7000 g of PMDA, followed by the addition of 3.4663 g of ODA and stirring at 1500 r / min for 15 minutes, followed by the addition of 4.0001 g of PMDA; 0.5859 g of PMDA was then added to adjust the solution viscosity, and the mixture was reacted in an ice-water bath at 10°C for 6 hours to obtain a PMDA-PDA-ODA-M-tol polyamic acid solution;

[0050] S2: A PMDA-PDA-ODA-M-tol polyamide acid solution with a solid content of 20% was evenly coated on a glass plate, placed in a forced air drying oven, heated from 160 °C to 210 °C over 30 min and kept warm for 5 min, then heated from 210 °C to 260 °C over 30 min and kept warm for 5 min, finally heated to 400 °C and kept warm for 5 min before starting to cool down, naturally cooled to room temperature, soaked the glass plate in hot water for 20 minutes, and then removed from the glass plate. The thickness of the resulting PMDA-PDA-ODA-M-tol-PI film was approximately 20 μm.

[0051] Comparative Example 2: Preparation of PMDA-S-BPDA-PDA-ODA-PI film, specifically comprising the following steps:

[0052] S1: 3.0865 g of PDA was weighed and dissolved in 100 mL of dimethylacetamide to obtain a homogeneous and transparent solution of diamine; after stirring at 1500 r / min for 15 minutes, 5.7000 g of PMDA was added and the reaction continued for 0.5 hour, followed by the addition of 5.0352 g of ODA and stirring at 1500 r / min for 15 minutes. 5.5000 g of PMDA was then added, and the remaining PMDA was added to adjust the solution viscosity. The mixture was reacted in an ice-water bath at 10°C for 6 hours to obtain a PMDA-S-BPDA-PDA-ODA polyamic acid solution. The viscosity of the prepared PAA solution was 40,000 mPa·s.

[0053] S2: The PMDA-S-BPDA-PDA-ODA polyamic acid solution with a solid content of 20% was uniformly coated on a glass plate, and placed in a blast drying oven. The temperature was increased from 160 °C to 210 °C in 30 min and kept for 5 min, increased from 210 °C to 260 °C in 30 min and kept for 5 min, and finally increased to 400 °C and kept for 5 min, and then the temperature began to decrease. The glass plate was naturally cooled to room temperature, soaked in hot water for 20 minutes, and then the film was taken off from the glass plate. The thickness of the obtained PMDA-S-BPDA-PDA-ODA-PI film was about 20 μm.

[0054] Comparative Example 3: Preparation of PMDA-S-BPDA-PDA-M-tol-PI film, specifically including the following steps:

[0055] S1: 3.0419 g of PDA was dissolved in 100 mL of dimethylacetamide to obtain a uniform transparent diamine solution. After stirring at 1500 r / min for 15 minutes, 5.5700 g of PMDA was added and reacted for 0.5 h, and then 5.9715 g of M-TOLIDINE was added, stirred at 1500 r / min for 15 minutes, and then 5.5800 g of PMDA was added as a viscosity solution. The remaining PMDA was added as a viscosity solution and reacted for 6 h in an ice water bath at 10 °C. A PMDA-S-BPDA-PDA-M-tol polyamic acid solution was prepared. The viscosity of the prepared PAA solution was 15000 mpa·s;

[0056] S2: The PMDA-S-BPDA-PDA-ODA polyamic acid solution with a solid content of 20% was uniformly coated on a glass plate, and placed in a blast drying oven. The temperature was increased from 160 °C to 210 °C in 30 min and kept for 5 min, increased from 210 °C to 260 °C in 30 min and kept for 5 min, and finally increased to 400 °C and kept for 5 min, and then the temperature began to decrease. The glass plate was naturally cooled to room temperature, soaked in hot water for 20 minutes, and then the film was taken off from the glass plate. The thickness of the obtained PMDA-S-BPDA-PDA-ODA-PI film was about 20 μm.

[0057] Comparative Example 4: Preparation of S-BPDA-PDA-ODA-M-tol-PI film, specifically including the following steps:

[0058] S1: 1.0510 g of PDA was weighed and dissolved in 100 mL of dimethylacetamide to obtain a homogeneous and transparent solution of diamine; after stirring at 1500 r / min for 15 minutes, 2.8002 g of S-BPDA was added and the reaction continued for 0.5 hour, followed by the addition of 5.1579 g of M-TOLIDINE, stirring at 1500 r / min for 15 minutes, and the addition of 6.5003 g of S-BPDA; then 2.9191 g of ODA was added, followed by the addition of 0.9970 g of S-BPDA. The remaining S-BPDA was added to adjust the viscosity of the solution, and the reaction was carried out in an ice-water bath at 10°C for 6 hours to obtain an S-BPDA-PDA-ODA-M-tol polyamic acid solution. The viscosity of the prepared PAA solution was 25000 mPa·s;

[0059] S2: A 20% solid content S-BPDA-PDA-ODA-M-tol polyamide acid solution was evenly coated on a glass plate, placed in a forced air drying oven, heated from 160 °C to 210 °C over 30 min and kept warm for 5 min, then heated from 210 °C to 260 °C over 30 min and kept warm for 5 min, finally heated to 400 °C and kept warm for 5 min before cooling, naturally cooling to room temperature, soaking the glass plate in hot water for 20 minutes, and then removing the film from the glass plate. The thickness of the obtained S-BPDA-PDA-ODA-M-tol-PI film was about 20 μm.

[0060] Comparative Example 5: Preparation of PMDA-ODPA-PDA-M-tol-ODA-PI film, specifically comprising the following steps:

[0061] S1: 1.1209 g PDA was weighed and dissolved in 100 mL dimethylacetamide to obtain a homogeneous transparent solution of diamine; after stirring at 1500 r / min for 15 minutes, 2.9098 g ODPA was added and the reaction continued for 0.5 hour, and then 5.5009 g M-TOLIDINE was added, and the mixture was stirred at 1500 r / min for 15 minutes, and 5.1038 g ODPA was added and the reaction continued for 0.5 hour; then 2.6715 g ODA was added and stirred at 1500 r / min for 15 minutes, and then 4.6189 g PMDA was added; the remaining PMDA was added to adjust the solution viscosity, and the mixture was reacted in an ice-water bath at 10°C for 6 hours to obtain PMDA-ODPA-PDA-M-ol-ODA polyamic acid solution. The viscosity of the prepared PAA solution was 15000 mPa·s;

[0062] S2: A PMDA-ODPA-PDA-M-ol-ODA polyamide acid solution with a solid content of 20% was evenly coated on a glass plate, placed in a forced air drying oven, heated from 160 °C to 210 °C over 30 min and kept warm for 5 min, then heated from 210 °C to 260 °C over 30 min and kept warm for 5 min, finally heated to 400 °C and kept warm for 5 min before starting to cool down, naturally cooled to room temperature, soaked the glass plate in hot water for 20 minutes, and then removed from the glass plate. The thickness of the obtained PMDA-ODPA-PDA-M-ol-ODAPI film was about 20 μm.

[0063] Comparative Example 6: Preparation of BPDA-ODPA-PDA-ODA-M-Tol-PI film, specifically comprising the following steps:

[0064] S1: Weigh 1.0338 g of PDA and dissolve it in 100 mL of dimethylacetamide to obtain a uniform and transparent solution of diamine; after stirring at 1500 r / min for 15 minutes, add 2.9098 g of ODPA and continue to react for 0.5 hour, then continue to add 5.0738 g of M-TOLIDINE, stir at 1500 r / min for 15 minutes, add 7.0319 g of ODPA, then add 2.8715 g of ODA and stir at 1500 r / min for 15 minutes, and then add 4.0189 g of S-BPDA; then add the remaining S-BPDA to adjust the solution viscosity, and react in an ice-water bath at 10°C for 6 hours to obtain a BPDA-ODPA-PDA-ODA-M-Tol polyamic acid solution;

[0065] S2: A BPDA-ODPA-PDA-ODA-M-Tol polyamide acid solution with a solid content of 20% was evenly coated on a glass plate, placed in a forced air drying oven, heated from 160 °C to 210 °C over 30 min and kept warm for 5 min, then heated from 210 °C to 260 °C over 30 min and kept warm for 5 min, finally heated to 400 °C and kept warm for 5 min before starting to cool down, naturally cooled to room temperature, soaked the glass plate in hot water for 20 minutes, and then removed from the glass plate. The thickness of the obtained BPDA-ODPA-PDA-ODA-M-Tol-PI film was about 20 μm.

[0066] Experimental Example: Films were prepared according to the methods described in Examples 1 to 5 and Comparative Examples 1 to 6, and all films were tested for mechanical properties, water absorption, and glass transition temperature. The specific results are shown in Table 1. The high Tg polyimide films prepared according to Examples 1 to 5 of the present invention were all about 20 μm thick and had glass transition temperatures of 511.37 to 544.11°C, both higher than those of the comparative examples. This indicates that the high Tg polyimide films of the present invention have good thermal stability and high temperature resistance. The films obtained by the present invention have good mechanical properties, high tensile strength and elongation at break, with an elastic modulus of 3.6 to 4.2 GPa, a tensile strength of 187 to 201 MPa, and an elongation at break of 38.1 to 45.5%.

[0067] Table 1 Performance test results of films prepared by different methods

[0068]

[0069] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing a five-component copolymer high Tg polyimide film, characterized in that: The following steps are involved: (1) Weigh the raw materials according to the molar ratio of p-phenylenediamine, pyromellitic dianhydride, 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diaminodiphenyl ether and 3,3',4,4'-biphenyltetracarboxylic dianhydride of (1.0-1.5):(4-5):(2-3):(1.5-1.8):(0.5-3) and place them in an oven for drying respectively; divide pyromellitic dianhydride into three parts: dianhydride monomer A, dianhydride monomer B and dianhydride monomer C, and the mass ratio of dianhydride monomer A, dianhydride monomer B and dianhydride monomer C is 2:3:5; p-phenylenediamine is dissolved in an organic solvent and stirred to obtain a diamine monomer solution. Dianhydride monomer A is added to the diamine monomer solution and stirred and reacted for 0.5 h to obtain a mixed solution. 4,4'-diamino-2,2'-dimethylbiphenyl is first added to the mixed solution and stirred and reacted for 0.5 h. Dianhydride monomer C is then added and stirred and reacted for 0.5 h. 4,4'-diaminodiphenyl ether is then added and stirred and reacted for 0.5 h. Dianhydride monomer B is then added and stirred and reacted for 0.5 h. Finally, 3,3',4,4'-biphenyltetracarboxylic dianhydride is added to adjust the viscosity, and the mixture is placed in a cold water bath and stirred to obtain a polyamic acid solution. (2) The polyamic acid solution obtained in step (1) is coated on a glass plate, and then the temperature is increased to perform thermal imidization to obtain a high Tg polyimide film.

2. The method for preparing a five-component copolymer high Tg polyimide film according to claim 1, wherein: The organic solvent in step (1) is any one of N-methylpyrrolidone, dimethylformamide, dimethylacetamide and dimethyl sulfoxide.

3. The method for preparing a five-component copolymer high Tg polyimide film according to claim 1, wherein: The viscosity of the polyamic acid solution in step (1) is 20,000 mPa·s to 120,000 mPa·s.

4. The method for preparing a five-component copolymerized high Tg polyimide film according to claim 1, wherein: The solid content of the polyamic acid solution in step (1) is 10-20%.

5. The method for preparing a five-component copolymerized high Tg polyimide film according to claim 1, wherein: The temperature of the cold water bath in step (1) is 0-15°C.

6. The method for preparing a five-component copolymerized high Tg polyimide film according to claim 1, wherein: The stirring speed in step (1) is 500-2000 r / min.

7. The method for preparing a five-component copolymerized high Tg polyimide film according to claim 1, wherein: In step (1), 3,3',4,4'-biphenyltetracarboxylic dianhydride is finally added to adjust the viscosity, and then the mixture is placed in a cold water bath and stirred for reaction for 3 to 8 hours to obtain a polyamic acid solution.

8. The method for preparing a five-component copolymerized high Tg polyimide film according to claim 1, wherein: In step (2), the polyamic acid solution obtained in step (1) is evenly coated on a clean glass plate by an automatic coating machine, and then placed in a blast drying oven and treated at 160°C for 10 minutes to evaporate and remove the solvent. The glass plate is then placed in a blast drying oven and heated according to the following program to perform a thermal imidization process: from 160°C to 210°C after 30 minutes and kept warm for 5 minutes, from 210°C to 260°C after 30 minutes and kept warm for 5 minutes, and finally raised to 400°C and kept warm for 5 minutes before cooling. After naturally cooling to room temperature, the glass plate is soaked in 100°C hot water for 20 minutes, and then the film is removed from the glass plate and dried to obtain a high Tg polyimide film.

9. The method for preparing a five-component copolymer high Tg polyimide film according to claim 1, wherein: The thickness of the high Tg polyimide film in step (2) is 20±5 μm.

10. The five-component copolymer high Tg polyimide film obtained by the preparation method according to any one of claims 1 to 9.

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